Teses / dissertações sobre o tema "Rats Physiology"
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1
Hohl, Rodrigo. "Padronização de um modelo de indução de overreaching em ratos : desenvolvimento e perspectivas de investigação em natação e esteira". [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314733.
Resumo:
Orientador: Denise Vaz de MacedoTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-08T20:10:55Z (GMT). No. of bitstreams: 1 Hohl_Rodrigo_D.pdf: 822844 bytes, checksum: fd38d4c98d17c89e25fcfd09540ba103 (MD5) Previous issue date: 2007
Resumo: O empirismo do treinamento pode levar a um desequilíbrio entre estímulo da atividade motora e tempo de recuperação do esforço. Como conseqüência o atleta pode experimentar um estado agudo de fadiga e queda de desempenho denominado de overreaching, revertido em poucos dias. A persistência desta situação de desequilíbrio pode levar a um quadro crônico de sensação de fadiga acompanhado de queda de desempenho denominado de síndrome do overtraining (OTS), que pode durar semanas ou meses. O objetivo deste trabalho foi padronizar um protocolo controlado e reprodutível de treinamento em ratos que contivesse um período de desequilíbrio entre o estímulo do exercício e o tempo de recuperação que gerasse queda de desempenho. Há duas formas de exercício em ratos amplamente utilizadas na literatura: a natação e a corrida em esteira. Os primeiros dois capítulos deste trabalho descrevem a padronização de um teste de desempenho em natação, reprodutível ao longo do crescimento animal, para ser utilizado em estudos longitudinais. Para isso, precisávamos considerar o empuxo sofrido pelo animal no meio líquido e validamos (Capítulo I) um aparato de medição de volume para animais vivos e conscientes (AMV). No capítulo II apresentamos os dados da comparação da reprodutibilidade de dois testes de desempenho até a exaustão na natação durante os cinco primeiros meses de vida dos ratos. Um teste com adição de cargas ajustadas de acordo com o porcentual da massa corporal (MC) e outro com cargas constantes (CC). Utilizando o AMV constatamos que a densidade dos animais não variava e, como conseqüência, o teste MC diminuía o tempo de exaustão conforme os ratos aumentavam a massa durante o crescimento, enquanto o teste CC mantinha o tempo de exaustão ao longo do tempo. Paralelamente, iniciamos os estudos com exercício em esteira. No Capítulo III apresentamos um protocolo de 11 semanas, onde o desequilíbrio entre exercício e recuperação foi determinado pelo aumento das sessões diárias nas três últimas semanas em 2, 3 e 4 vezes, com diminuição no tempo de recuperação entre elas. Selecionamos no final desse treinamento dois grupos de ratos, aqueles que apresentaram baixo desempenho (BD) e aqueles que apresentaram aumento ou manutenção do desempenho (AD). Embora ambos os grupos tenham apresentado uma diminuição da massa corporal durante o aumento da freqüência de treinamento, o grupo BD precisou de uma semana a mais de repouso para voltar a aumentar a massa, sem modificar o desempenho. No Capítulo IV comparamos quatro grupos de ratos obtidos desse protocolo (Controle (CO), Treinados (T), BD e AD) em análises no sangue (glutamina, glutamato, alanina e hemograma) e músculo (citrato sintase (CS), lactato desidrogenase e glicogênio). Comparando BD com T e AD observamos: (1) diminuição da concentração plasmática de glutamina e aumento na de glutamato, com valores semelhantes aos do grupo CO; (2) diminuição da capacidade oxidativa (CS) e manutenção dos estoques de glicogênio; (3) leucocitose. Em vista das diferenças encontrada entre os grupos BD e AD, concluímos que o protocolo de treinamento de indução de overreaching representa uma ferramenta metodológica importante, que pode auxiliar no desvendamento dos mecanismos causadores da queda de desempenho nos estados de overreaching/OTS
Abstract: The empirical training can lead to an imbalance between the motor activity stress and recovery. As consequence, the athlete can try an acute state of fatigue and performance decrement called overreaching, reverted in a few days. This continuous unbalance can lead to a chronic fatigue state called as overtraining syndrome (OTS), that may last weeks or months. Our goal was to standardize a controlled and reproducible training protocol in rats that contained an unbalance period between exercise stress and recovery with performance decrement. Two forms of exercise is widely used for rats training in literature: swimming and treadmill running. Chapters I and II describe an adequate standardization for workload in swimming tests when applied to longitudinal studies with sedentary rats. Therefore, considering the rats' buoyance, we validate (Chapter I) an apparatus for measuring conscientious living rat body volume (AMV). In chapter II, we evaluated two types of swimming tests with overload in sedentary rats: one with the load adjusted according to percentage of body weight (BW) and another one with constant load (CL) over time. Through the AMV, we found that the rats' density did not vary significantly, as consequence, MC test showed performance decrement as the rats had their mass increased, while CC test maintained performance along rats growth. In time, we initiate the studies with treadmill exercise. In Chapter III, we present an eleven weeks training protocol where the unbalance between exercise stress and recovery was determined by the increase of the daily sessions in 2, 3 and 4 times in the last three weeks, reducing the recovery time between sessions. We selected two groups of rats in the end of the training protocol, those that presented low performance (BD) and those that presented performance increase or maintenance (AD). Although both groups (AD and BD) showed corporal mass reduction during the increase of the daily frequency, BD group return to increase the mass one week later than AD group, without modifying the performance. In Chapter IV, we compare four groups of rats after the eleven weeks training protocol (Control (CO), Trained (T), AD and BD) in blood (glutamine, glutamate, alanine and hematological variables) and muscle analyses (citrate synthase (CS), lactate dehydrogenase and glycogen). Comparing BD with AD and T groups, we observe: (1) reduction of the glutamine plasma concentration and increase of glutamate, with similar CO values; (2) reduction of the oxidative capacity (CS) and maintenance of the glycogen stores; (3) leucocitosys. We conclude that the training protocol induces the rats to overreaching and it represents a relevant methodological tool in overreaching / OTS metabolical mechanisms research envolved in performance decrement
Doutorado
Fisiologia
Doutor em Biologia Funcional e Molecular
2
Feng, Tian Bin. "The effects of clomiphene citrate on ovarian function in rats". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28984.
Resumo:
In the present study, the effects of clomiphene citrate (CC) on ovulation, ovarian growth and ovarian steroidogenesis were examined. Ovulation in rats in response to PMSG was completely blocked by administration of three daily treatments of 1.0 mg CC/rat, but was restored by administration of hCG as a preovulatory LH surge substitute. When the number of treatment days was reduced to two days, 1.0 mg of CC enhanced ovulation in response to PMSG, whereas treatment for one day with the same dose of CC did not affect ovulation. The effects of CC on ovulation appear to be dose-dependent.
The effects of CC on ovarian growth were similar to the effects of CC on ovulation. The ovarian growth induced by PMSG was inhibited by high doses of CC, while a lower dose had no effect. The inhibition of ovarian growth in terms of ovarian weight by a high dose of CC was restored by hCG given as a preovulatory LH surge. Treatment duration with CC appears to have an important influence on ovarian growth. Three daily treatments with high doses of CC significantly inhibited ovarian growth. However, when the number of treatment days was reduced from three to two, the opposite results were obtained in that CC significantly stimulated ovarian growth.
The effects of CC on ovarian steroidogenesis in response to PMSG were dose-dependent. A higher dose of CC significantly stimulated estradiol-17β biosynthesis. Clomiphene citrate did not show any inhibitory effects on progesterone production. Progesterone production was stimulated by hCG in CC
treated rats. Lower doses of CC stimulated progesterone and androgen production. Further studies on this are necessary.
Histological examination of the ovary revealed that CC selectively inhibited the development of nondominant follicles. The dominant follicles were unaffected as for they were able to develop to the mature stage.
These results suggest that the effects of CC on ovulation, ovarian growth and ovarian steroidogenesis are dose-dependent and affected by treatment duration. Clomiphene citrate is assumed to exert its action via a gonadotropic mechanism.Medicine, Faculty of
Obstetrics and Gynaecology, Department of
Graduate
3
Chura, Lindsay R. "The effect of chronic and acute maternal stress on expression of placental barrier genes in the rat /". Connect to online version, 2006. http://ada.mtholyoke.edu/setr/websrc/pdfs/mhc/2006/143.pdf.
4
Van, Wageningen Gerhard Derek. "The crossed mesostriatal pathway and circling behaviour in rats". Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/21152.
Resumo:
Bibliography: pages 326-345.Rats with unilateral 6-OHDA lesions of the nigrostriatal (NS) projection display motor asymmetry in the form of rotational behaviour. The rotation is in the direction ipsilateral with respect to the lesioned side (Ungerstedt 1979). The nett ipsilateral rotations decrease with time, from 1 week to about a month. This decrease has been interpreted as recovery from the lesion-induced motor asymmetry (Glick and Cox 1978). Pritzel et al. (1983) have ascribed the recovery from motor asymmetry to increased activity of a crossed NS projection, which is spared by the ipsilateral lesion. The present study has defined the size and anatomical path of this crossed projection, and has examined its involvement in the behavioural recovery of rats from lesion-induced motor asymmetry. The anatomy of the crossed projection was investigated in male Long-Evans rats using retrograde HRP tract tracing from deposition sites in the striatum.
5
Lee, Ronald Duane. "The synthesis of 2-((E)-1'-propenyl)-(E)-2-pentenoic acid and its metabolism and pharmacokinetics in rats". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26437.
Resumo:
The anticonvulsant drug valproic acid (VPA) is extensively metabolized with 16 metabolites identified in man. Of interest are the unsaturated metabolites which appear to be responsible for the observed secondary antiepileptic activity and/or idiosyncratic hepatotoxicity. A study by Abbott et al . (1986) has shown 2-((E)-1'-propenyl)-(E)-2-pentenoic acid ((E,E)-2,3'-diene VPA) to be a major unsaturated metabolite of VPA. Acheampong (1985) demonstrated that an isomeric mixture of 2,3'-diene VPA prevented pentylenetetrazole-induced seizures in mice and had 60% the potency of VPA. Research on (E,E)-2,3'-diene VPA is limited even though the diene appears to be a contributor to the secondary antiepileptic effect. Available synthesis of 2,3'-diene VPA result in two or more isomers with very low yields as shown by Acheampong and Abbott (1985). The object of this work was, therefore, to synthesize (E,E)-2,3'-diene VPA in sufficient quantity and isomeric purity for metabolic and pharmacokinetic studies in rats.
Synthesis of (E,E)-2,3'-diene VPA was achieved by the alkylation of ethyl (Z)-2-pentenoate to afford ethyl 2-(l'-hydroxypropyl)-(E)-2-pentenoate. Dehydration using
methanesulfonyl chloride and potassium hydride gave the ethyl ester of (E,E)-2,3'-diene VPA. Hydrolysis of the ester in 1 N NaOH afforded an 81.2% pure sample of (E,E)- 2,3'-diene VPA as determined by GCMS and NMR. A second method was used to unequivocally synthesize (E,E)-2,3' - diene VPA whereby an O-trimethylsilylketene acetal was oxidized via a hydride abstractor to yield two isomers of 2,3'-diene VPA plus the starting material (E)-3-ene VPA. The identity of the products were determined by GCMS with the major isomer being (E,E)-2,3'-diene VPA.
In the metabolism studies, Wistar rats were given 100 mg/kg i.p. of (E,E)-2,3'-diene VPA and bile and urine collected for 24 hours. GCMS analysis revealed three metabolites present in both bile and urine. These were reduction products of (E,E)-2,3'-diene VPA metabolism and consisted of the monounsatured (E)-3-ene VPA and (E)-2-ene VPA plus the fully saturated VPA. These results suggest that trace levels of (E)-3-ene VPA observed after VPA dosing may not be a direct metabolic product of VPA itself but rather a reduced metabolite of (E,E)-2,3'-diene VPA. All polar metabolites are yet to be identified.
For the pharmacokinetic studies, two doses, 20 and 100 mg/kg of (E,E)-2,3'-diene VPA were administered i.v. to Wistar rats and the plasma concentration vs time decline curve determined using GCMS analysis of the plasma samples. The bile duct of these animals was then cannulated and the study repeated. A comparison between the elimination rate constant (KE), clearance (C1), and volume of distribution (Vd) between the bile duct intact and cannulated rats for both dose groups revealed no significant differences (p>0.1). A comparison of the KE, Vd, and C1 between dosage groups of both bile duct intact and cannulated rats revealed no significant difference (p>0.08-0.7).
Therefore, extensive enterohepatic recirculation was not apparent and the elimination of (E,E)-2,3'-diene VPA appeared to be dose-independent. The diene seems to follow a simple one-compartment model with a half-life of 35.9±8.9 (S.D.) minutes and a large volume of distribution of 0.95±0.22 (S.D.) L/kg.
In vitro protein binding studies revealed that (E,E)-2,3'-diene VPA saturates plasma proteins between concentrations of 30 - 600 ug/mL. The percent of (E,E)-2,3'-diene VPA bound decreases from 92.1% to 28.7% as the concentration of diene increases suggesting concentration-dependent protein binding.
The synthesis of (E,E)-2,3'-diene VPA in substantial quantities has allowed metabolic and pharmacokinetic studies to be performed in rats. Preliminary studies showed that (E,E)-2,3' -diene VPA was metabolically reduced to monounsaturated and saturated products. Pharmacokinetic data appear to indicate a potential for the diene to accumulate in the central nervous system. Further studies are required to determine the contribution of (E,E)-2,3'-diene VPA to the secondary antiepileptic activity of VPA.Pharmaceutical Sciences, Faculty of
Graduate
6
Anand, Uma. "Target derived influences on primary afferent neurons in rats". Thesis, King's College London (University of London), 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283305.
7
Walker, Celia Gillian Rowena. "Dietary and metabolic regulation of leptin in rats". Thesis, The University of Sydney, 2005. https://hdl.handle.net/2123/28031.
Resumo:
Obesity has become one of the most prevalent health concerns of developed countries. Consequently metabolic research in recent years has focussed on the control of body weight, causes of obesity, and possible preventative measures. Body weight is usually maintained through a series of hormonal and neuronal actions which respond to changes in energy balance. The adipose tissue hormone leptin plays an important role in the regulation of body weight, by decreasing appetite and increasing energy expenditure through a number of central and peripheral effects. Basal leptin levels are raised proportionately to adiposity but leptin levels are also acutely altered by nutritional state.
Because of the importance of this hormone in body weight homeostasis it is necessary to understand how it is regulated.
8
Courtois, Frédérique J. "Residual erectile capacity of paraplegic rats". Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74335.
Resumo:
This series of studies was designed to investigate the residual erectile capacity of paraplegic rats. Results from human studies suggest that erectile capacity in paraplegic men may be maintained following psychogenic, but not reflexogenic, stimulation. Using an animal model to overcome methodological difficulties associated with human studies, reflexogenic stimulation was defined as local stimulation of the genitals, and psychogenic stimulation as stimulation of a key central structure. Results from higher CNS stimulation showed that electrical stimulation of the medial preoptic area of the hypothalamus reliably triggers penile responses in rats and elicits penile responses as a post-stimulation effect. Optimal stimulation parameters were identified and used to maximize the effect on spinal animals. The effect of central stimulation was then compared to that of local stimulation to examine whether truly sexual responses were elicited. Results demonstrated that central stimulation elicits primarily erectile responses with a few urine-marking responses. The two stimulation sources were then used to test the residual erectile capacity of paraplegic rats whose lesions interrupted the L6-S1 fibers. Results showed that a high proportion of animals (85%) indeed maintain erectile responses to central stimulation but lose reflex activity from the genital area. These results support the hypothesis under study and are discussed in terms of the neural substrates of erection and their implication at the human level.
9
Andalib, Ali. "Relationship between a trial fibrillation and hypertension in rats". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83962.
Resumo:
The importance of hypertension as a risk factor for the development of AF is well recognized. Despite this leading importance, the role of essential hypertension in providing a substrate for AF is incompletely understood. The present study was undertaken to investigate the possibility of having rats as an adequate animal model for the relationship between hypertension and AF in man and to elucidate the role of hypertension as a risk factor for AF. The results of this study show that structural remodeling especially in the form of increased amount of interstitial fibrosis seems to be the major contributing factor to the AF sustainability. Although it can be concluded that hypertension could accelerate the accumulation of fibrosis which occurs during the normal process of aging, a clear relationship between hypertension and AF in this rat model was not found. Further work in the other animal models of hypertension would be interesting.
10
Amoni, Matthew. "The effects of magnesium treatment on short-term changes in heart rate variability, ventricular function and lipid profile in streptozotocin-induced diabetic rats". Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/24459.
Resumo:
INTRODUCTION: Diabetes mellitus is a major and rapidly growing worldwide health problem, causing mortality largely in developing countries such as South Africa. Diabetes induces life threatening cardiovascular complications including cardiac autonomic neuropathy, ventricular dysfunction and dyslipidaemia, which are dependent on the duration and severity of the diabetes. Most complications are identified at a late, irreversible stage following long-standing diabetes; therefore, early detection and treatment of cardiovascular complications may reverse impairments and improve outcomes. The early treatment of diabetic complications remains ineffective, as the associated underlying features, such as electrolyte disturbances, are poorly understood. A key electrolyte disturbance in diabetes is hypomagnesaemia, which is also an independent cardiovascular risk factor. However, the effects of magnesium (Mg²⁺) supplementation are unclear. Therefore, this study investigated the effects of Mg²⁺ treatment on the early manifestations of streptozotocin (STZ)-induced diabetic cardiac complications. METHODS: Adult male Wistar rats were treated once with STZ (50 mg/kg, i.p.) or vehicle (citrate), and daily for seven days with MgSO4 (270 mg/kg, i.p.) or saline. Blood glucose and body weight were monitored daily. On the eighth day, in vivo tail-pulse plethysmography was recorded for analysis of heart rate variability (HRV), a marker of cardiac autonomic function. Ex vivo, Langendorff-based left ventricular (LV) pressure-volume parameters were measured using an intraventricular balloon. Other hearts were stained with Masson's trichrome and haematoxylin and eosin for histological analysis. Cardiac tissue Mg²⁺ concentration as well as plasma lipid- and Mg²⁺ levels were measured by colorimetric assays. RESULTS: Diabetes reduced heart rate and increased the low-frequency (LF)/high-frequency (HF) power ratio. Mg²⁺ treatment prevented theses diabetes-induced changes in heart rate and in the low-frequency (LF)/high-frequency (HF) power ratio (p < 0.05, n = 9/group). In addition, Mg²⁺ restored orthostatic stress induced changes in heart rate, and LF/HF ratio in diabetic rats (p < 0.05, n = 9/group). In isolated hearts, Mg²⁺ reversed the diabetes-induced decrease in LV end-diastolic elastance (p < 0.05, n = 6/group) and the right shift of end diastolic equilibrium volume intercept from 49 ± 6 μ L to 25 ± 5 μL (p < 0.05, n = 6/group), without altering LV developed pressure or end systolic elastance. Diabetes significantly increased plasma triglyceride, total cholesterol and blood glucose (p < 0.05, n = 7/group), and significantly decreased body weight (p < 0.05, n ≥ 16/group) compared to control, but these changes were not prevented by Mg²⁺ treatment. Neither diabetes nor Mg²⁺ treatment altered plasma- and tissue Mg²⁺ levels. Histologically, diabetes and Mg²⁺ treatment also did not alter cardiomyocyte size or the amount of interstitial collagen in myocardial tissue. CONCLUSION: These results show that Mg²⁺ treatment attenuates diabetes-induced autonomic dysfunction and improves LV diastolic distensibility in short-term diabetes. However, the diabetic metabolic disturbances of hyperglycaemia and dyslipidaemia, the changes in cardiac microstructure or the plasma- and cardiac tissue Mg²⁺ levels were uninfluenced by Mg²⁺ treatment. This suggests that Mg²⁺ exerted its beneficial effects independent of these factors, highlighting the underling mechanisms remain to be clarified. The Mg²⁺ levels not measured in this study by which changes could have been mediated was intracellularly; an aspect that should be further explored in future studies. Furthermore, whether these effects would be translatable to chronic diabetes is an important next question. Thus, the results of this study suggest that Mg²⁺ may have a modulatory role in treating early diabetic cardiovascular complications, but future studies will need to clarify the underlying mechanisms.
11
Scott, Trevor Robert. "The identification, purification and characterization of the fetal rat liver glutathione S-transferase isoenzyme YcYfetus". Doctoral thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/27171.
Resumo:
This study has examined the expression of the glutathione S-transferases (GSH S-T) in fetal rat livers in order to provide more information about the role played by this important group of enzymes in the fetus. The study commenced with an examination of the subunit composition of adult and fetal rat liver GSH S-T using affinity chromatography followed by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. Adult livers contained four major GSH S-T subunits. An additional and previously unidentified subunit was detected in fetal livers. This subunit, which differed from that found in rat placenta, had a Mᵣ of approximately 25 500. Densitometric measurements suggest that the newly detected subunit accounts for as much as 26% of the GSH S-T in fetal livers. The novel fetal isoenzyme comprising this subunit was purified using a combination of affinity chromatography, carboxymethyl-cellulose column chromatography and chromatofocusing. The six major basic rat liver GSH S-T were purified for reference and comparative purposes. The fetal isoenzyme is composed of two non-identical subunits, namely, subunit Yc (Mᵣ 28 000) and the fetal subunit referred to as 'Yfetus'· The enzyme which I have termed GSH S-transferase Yc Y fetus has an isoelectric point of approximately 8.65 and has GSH S-T activity towards a number of substrates. Significantly, the fetal isoenzyme has one of the highest glutathione peroxidase activities yet described for the purified rat liver GSH S-T towards the model substrate, cumene hydroperoxide. Kinetic studies reveal that the fetal isoenzyme has a catalytic efficiency for the peroxide substrate which is four fold higher than that of the adult rat liver isoenzyme, GSH S-T YcYc. The in vitro effect of the GSH S-T substrate and teratogen, acrolein, on this fetal isoenzyme was investigated and compared with acrolein's effect on some of the adult rat liver GSH S-T isoenzymes in the standard 1-chloro-2,4-dinitrobenzene assay. Surprisingly, acrolein was identified as a non-competitive inhibitor of the GSH S-T. Exposure to acrolein in various guises could therefore result in inhibition of the fetal isoenzyme and its subsequent failure in inhibiting lipid peroxidation. Inhibitor studies were performed to look at the effect of acrolein, as well as other substrate and non-substrate ligands, on the glutathione peroxidase activity of GSH S-T YcY fetus and YcYc. The glutathione peroxidase activity of the fetal isoenzyme was far less susceptible to acrolein inhibition than the YcYc isoenzyme and the fetal isoenzyme was found to retain significant glutathione peroxidase activity despite saturating concentrations of non-substrate ligand. This study suggests that the fetal isoenzyme serves a specific function in protecting fetuses against the possible teratogenic effects of organic peroxides.
12
Wickens, Nicolas John. "Histopathological changes in male wistar rats maintained on a water-based sutherlandia frutescens extract". Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/4742.
Resumo:
In this study a standardized 46 week chronic drinking water toxicity protocol was used to elucidate the toxic potential of Sutherlandia frutescens (S. frutescens) using histopathologic, morphometric and transmission electron microscopic analysis. The histopathologic changes in the duodenum, heart, kidney, liver, lung, pancreas and spleen of male Wistar rats were evaluated. Fifty-four rats were randomly divided into four groups: Group 1 – Normal diet control (ND control), n=7, Group 2 – Normal diet + plant extract (ND + p), n=9, Group 3 – High fat diet control (HFD control), n=19Group 4 – High fat diet + p (HFD + p), n=19In the high fat group male Wistar rats were fed ±55 g/day of a specialised high fat diet over a 46 week period to induce obesity and an insulin resistant state. The treatment groups (groups 2 and 4) received a dose concentration of a tea extract of the S. frutescens plant in their drinking water daily. This study showed that the consumption of S. frutescens significantly reduces weight gain in male Wistar rats on a chronic high fat diet (p≤0.001 vs. HFD control group). S. frutescens appears to propagate periportal and centrilobular glycogen storage in rat hepatocytes in the experimental groups as exemplified by a significantly (p≤0.0001 vs. control groups) increased incidences of Periodic Acid Schiff (PAS) positive staining S. frutescens also reduced intracellular lipid accumulation as made evident by the significantly lower incidence of epicardial adipose tissue (EAT), hepatic steatosis and pancreatic interstitial fat. Obesity was associated with increased fibrotic lesions such as myocardial perivascular fibrosis, centrilobular hepatic fibrosis and pancreatic periductal fibrosis. Obesity associated hypertension contributed to the widespread and significant increase in the average lesion severity of arterial congestion in all organs in the HFD control group. Pulmonary infection was equally prevalent in all rats. Despite the complex histopathology in all groups, differences in the control groups, such as, the presence of a conservative polymorphonuclear leukocyte (PMNL) infiltration, substantial intra-alveolar oedema and focal arterial wall hypertrophy in the control groups was highly suggestive of Sendai viral infection. However histopathologic evidence, in the treatment groups, suggested chronic recurrent viral infection with superimposed Mycoplasma pulmonis (M. pulmonis) bacterial infection. The impact of advanced suppurative pulmonary infection was widespread and exemplified by increased lesion incidences of spontaneous murine progressive cardiomyopathy (MCP) and spontaneous chronic progressive nephropathy (CPN) among others. In conclusion S. frutescens administered for 46 weeks to male Wistar rats significantly lowered intracellular lipid accumulation and obesity associated myocardial, renal, hepatobiliary, pulmonary and pancreatic histopathology. Moreover, duodenal, cardiovascular, hepatobiliary, pulmonary, renal, pancreatic and splenic tissue did not show histopathologic evidence of direct plant extract associated toxicity or carcinogenicity.
13
Aboalgasm, Hamida. "The effects of magnesium administration on cardiac ventricular function, heart rate variability, and myocardial morphological changes in a chronic diabetes disease model in rats". Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29579.
Resumo:
Introduction:
Diabetes mellitus (DM) is a leading cause of morbidity and mortality all over the world, and the main cause of the mortality is cardiovascular complications. Such diabetic cardiovascular complications include coronary heart disease, cardiac autonomic neuropathy and ventricular dysfunction. Furthermore, DM is associated with electrolyte disturbances such as those involving potassium, calcium and magnesium (Mg2+). Among these electrolyte disturbances hypomagnesemia is common in diabetes and is associated with increased cardiovascular risk. Recent evidence has shown that Mg2+ supplementation can prevent cardiac autonomic dysfunction and improve ventricular compliance in acute DM. However, the underlying mechanisms of Mg2+ action and Mg2+ effects in chronic DM are unknown. Therefore, the present study explored the effects of Mg2+ administration and its possible mechanisms of action in chronic streptozotocin (STZ) induced diabetic rats.
Methods:
Adult male Wistar rats were injected intraperitoneally (i.p) once with either STZ (50 mg/Kg body weight) or the STZ vehicle (citrate buffer). The rats were then injected i.p once daily with either magnesium sulphate (MgSO4; 270 mg/Kg body weight) or the MgSO4 vehicle (normal saline) for 28 consecutive days. Blood glucose and body weight were measured throughout the period of the study. On day 28 of the experiments, in-vivo heart rate variability (HRV) parameters were measured to assess cardiac autonomic function using tail pulse plethysmography. Orthostatic stress was induced by tilting the animals from flat position to 70° head-up position. Ex-vivo hemodynamic and electrocardiograph (ECG) measurements were performed on a Langendorff perfusion system. Histological studies of ventricular tissue were performed using haematoxylin-eosin and Masson’s trichrome staining. Western blot analyses of the cardiac autonomic presynaptic marker (synaptophysin) and of the mitochondrial marker of oxidative stress (ATP5A) were performed on right atrial tissue. Plasma Mg2+ concentration was measured using automated photometric assays.
Results:
STZ treatment significantly increased the blood glucose level and decreased the body weight, and these STZ effects were not prevented by Mg2+ treatment. Diabetes decreased the root mean square differences of successive normal-to-normal intervals (RMSSD) and increased the low frequency (LF) /high frequency (HF) power ratio, which are both indicative of abnormal HRV. These diabetes effects on HRV parameters were significantly prevented by Mg2+ treatments (P < 0.05, STZ+Mg vs. STZ). DM also reduced both the heart rate and orthostatic stress-induced tachycardia, and these effects were reversed by Mg2+ treatment (P < 0.05, STZ+Mg vs. STZ). DM also decreased the left ventricular (LV) developed pressure and the maximal rate of LV pressure increase (+dP/dt), and these diabetic effects were prevented by Mg2+ treatment (P < 0.05, STZ+Mg vs. STZ). DM also decreased the maximal rate of LV pressure decline (-dP/dt) and the rate pressure product, but these parameters were not improved by Mg2+ treatment. DM and Mg2+ treatment did not affect the ECG waveforms and the coronary flow rate in all groups. Histologically, there were no differences in ventricular cardiomyocyte width or in the extent of interstitial fibrosis in all groups. Western blot analysis qualitatively showed a decrease in the expression of synaptophysin in DM that was prevented by Mg2+ treatment. Neither DM nor Mg2+ treatment altered ATP5A expression. The plasma Mg2+ concentration was not altered by DM or Mg2+ treatment.
Conclusion:
This study showed that Mg2+ treatment prevented cardiac autonomic dysfunction and improved hemodynamic function impairment in chronic DM. Based on the expression of synaptophysin, the mechanism through which Mg2+ improved cardiac autonomic function could involve the prevention of synaptic degradation in diabetes. The effects of Mg2+ on hemodynamic impairment in diabetes seemed to be unrelated to the Mg2+ effects on the cardiac histological structure or on the changes in coronary perfusion. Moreover, the overall effects of Mg2+ in diabetes were independent of its effects on the blood glucose level or the alteration of plasma Mg2+ level. Thus, Mg2+ treatment may have long-lasting therapeutic effects on ventricular dysfunction and cardiac autonomic impairment in chronic diabetes, but further studies are needed to explore the precise underlying mechanisms.
14
Ho, Sze-ngar Sara, e 何思雅. "Synaptic modulation by 5-hydroxytryptamine in the rat hypothalamic paraventricular nucleus". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B3194341X.
15
Gwayi, Noluzuko. "The effects of melatonin on the testis, epididymis and sperm physiology of the Wistar rat". Thesis, Rhodes University, 2001. http://hdl.handle.net/10962/d1005366.
Resumo:
Melatonin is a product of the pineal gland and is postulated to play an antigonadotropic role in the reproductive system of mammals. The reproductive system of non-seasonally breeding mammals is believed to be not as responsive to melatonin treatment as that of seasonally breeding mammals. Recently, there has been increasing support from in vivo and in vitro studies, for the hypothesis that melatonin has negative effects on sperm physiology, especially on sperm motility. High and/or low seminal concentrations of melatonin have been associated with abnormalities in human sperm motility and concentration. In this study, I examined the effects of melatonin on the testis, epididymis and sperm physiology, using in vivo and in vitro experiments, in a non-seasonally breeding mammal. Treatment, in vivo, with exogenous melatonin for six weeks did not inhibit testosterone production or spermatogenesis, nor did it affect the mass of the testes and epididymides at dissection, the concentration the morphology of speimatozoa. However, melatonin in vivo had a small, but significant negative effect on sperm motility and sperm motility index. In vitro incubation of spermatozoa Fith melatonin reduced the percentage (%) of forward progressive movement (fpm), increased the % reduction in fpm, reduced the vigor or quality of sperm motility, reduced the sperm motility index, and delayed and/or prolonged the transition of one pattern of sperm motility to the subsequent patterns. Melatonin increased the pH of the culture medium, and the increased pH, and the ethanol utilized as a solvent for melatonin, both negatively affected all the sperm motility parameters that were assessed in my study. The effects of ethanol increased with time, and the effects of pH increased with both time and increasing pH. Melatonin in vitro did not inhibit capacitation and the acrosome reaction, but it delayed the onset and the progression of capacitation and the acrosome reaction. These results suggest that while melatonin did not inhibit spermatogenesis in the Wistar rat, it may influence sperm motility. Therefore, the presence of high concentrations of melatonin in the reproductive fluids may inhibit sperm motility. With further detailed research, melatonin may have a potential use as a contraceptive drug.
16
He, Ying 1972 Apr 20. "Impacts of metabolic stress-induced malnutrition and oxidative stress on biochemical changes in the slow- and fast-twitch skeletal muscles of rats". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33774.
Resumo:
To assess the changes in glycolysis of skeletal muscles within metabolic stress and to test whether metabolic stress-induced oxidative stress and malnutrition were associated with these changes, slow- (soleus) and fast-twitch extensor digitorum longus (EDL) muscles were studied in zymosan-induced critically ill, pair-fed and control rats for 7 days. Thiobarbituric acid reactive species (TBARS) concentrations were increased in both stressed and pair-fed rats. In slow-twitch muscle, the fructose-1,6-bisphosphate (F-1,6-P2)/fructose-6-phosphate (F-6-P) ratio was decreased in stressed rats and was not altered with increased food intake. F-1,6-P2/F-6-P ratio in soleus was correlated with both TBARS and muscle dry weight. In EDL, the F-1,6-P2/F-6-P was unaffected and neither oxidative stress nor muscle weight correlated with the ratio. In conclusion, metabolic stress-induced oxidative stress and malnutrition influenced glycolytic slowdown only in slow-twitch muscle.
17
Amevor, Solomon Francis. "Renal physiology and aluminum biokinetics : studies in laboratory rats and human subjects /". [S.l.] : [s.n.], 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10972.
18
Creamer, Katherine. "Characterization of the modulatory effects of neurosteroids on dorsal raphe neurons in a non anaesthetized rats preparation". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101842.
Resumo:
Dorsal raphe nucleus (DRN) neurons projects to widespread areas throughout the brain and are involved in many physiological functions and neuropsychiatric disorders. In particular, DRN serotonin (5-HT) neurons are thought to be implicated in major depressive disorder (MDD) as are steroid hormones. Therefore, the aim of this thesis was to assess the effects of some neurosteroids on DRN neurons in non-anaesthetized rats. Initially, we examined electrophysiological properties of dorsal raphe cells across the sleep---wake cycle in non-anaethetized rats. In this first study we characterized six distinct neuronal populations in the DRN based on spike waveform and firing pattern. We then examined the effects of DHEA-S and testosterone (T) on the firing properties of DRN neuronal populations previously characterized. We observed that most populations exhibited an initial decrease in firing activity following one week of treatment. However, there was a great variability in responses across the populations.
19
Fayyad, Tariq Hasan. "Is Mitochondrial Development Impaired in Hyperoxic Rats and does this Underpin the Blunting of the Acute Hypoxic Ventilatory Response?" Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1496145386683819.
20
張永魁 e Yongkui Zhang. "Functional development of otolith afferents in postnatal rats". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242716.
21
Wieczerzak, Krystyna Blanka. "Sensorimotor Analysis of Oxaliplatin Treated Rats". Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1432856752.
22
Ryan, Collen. "Glucose and glycogen metabolism during prolonged swimming and recovery in rats". Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7812.
Resumo:
In order to assess glucose dynamics and the pathways (direct and gluconeogenic) by which muscle and liver glycogen is synthesized during and following prolonged submaximal exercise, twelve-hour-fasted catheterized rats were infused intravenously with ($\sp3$H-6) -glucose (or ($\sp3$H-3) -glucose) and either (i) NaH$\sp $CO$\sb3,$ (ii) ($\sp $C-U) -lactate or (iii) ($\sp $C-1) -glucose (three gluconeogenic tracers) throughout two-hour basal, four-hour swim (or rest) and three-hour postexercise recovery periods. During recovery, rats were infused with either saline, lactic acid or glucose. Arterial blood samples were taken throughout the protocols. Liver and three muscles (soleus, white and red gastrocnemii) were excised and assessed for total and radiolabelled glycogen content. The results indicate that: (1) While plasma glucose concentrations are maintained during the prolonged swim owing to matched doubling of both glucose production (R$\sb{\rm a}$) and clearance (MCR), glucose increases during the recovery period as the fall in R$\sb{\rm a}$ lags behind that of MCR and the rate of gluconeogenesis remains elevated. (2) Despite increases in direct glycogenesis during prolonged swimming, glycogen is significantly depleted in white and red gastrocnemii. Glyconeogenesis contributes at least 20-25% to glycogen repletion during fasted recovery. The source of this gluconeogenic substrate appears to be lactate which is formed locally in the muscles (as traced by recycled $\sp $C-glucose). Although not required to elicit muscle gluconeogenic activity, high lactate levels enhance glyconeogenesis, especially in the postexercise period. (3) There is a high turnover of soleus glycogen at rest. The soleus does not respond to prolonged swimming but rather to the availability of substrate (glucose) to synthesize its glycogen almost entirely via the direct route. (4) Glyconeogenesis is the primary pathway of hepatic glycogen synthesis. While glucose infusion is the most potent stimulus of glycogenesis, the combined effects of lactate and exercise appear synergistic in the formation of liver glycogen.
23
Wang, Qian. "Substrates for muscle glyconeogenesis during prolonged swimming and recovery in rats". Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/10224.
Resumo:
The goal of this work was to initiate a systematic investigation of the possible substrates for muscle glyconeogenesis under physiological circumstances--during recovery from prolonged submaximal exercise. The hypothesis was that amino acids mobilized from possibly increased body protein breakdown (in particular muscle protein degradation), or glycerol liberated from catabolism of body fat (especially intramuscular fat) during and after exercise might serve as substrates for muscle glyconeogenesis after exercise. In order to assess whole body protein breakdown, muscle myofibrillar protein degradation during and after exercise as well as to determine the incorporation of putative substrates into muscle glycogen during postexercise recovery, twelve-hour-fasted rats were infused intravenously with: (a) $\sp $C-U-urea, (b) $\sp $C-U-threonine (a representative of gluconeogenic amino acids) and $\sp3$H-6-glucose, and (c) $\sp $C-U-glycerol and $\sp3$H-6-glucose throughout two-hour basal, four-hour swim (or rest) and three-hour postexercise recovery periods. Arterial blood samples were taken every hour. Soleus, white and red gastrocnemius muscles were excised and assessed for 3-methylhistidine (3-MH) and tyrosine contents as well as for total and radiolabelled glycogen contents at the end of the postexercise recovery. The results indicate that: (1) whole body protein breakdown and muscle myofibrillar protein degradation increase significantly during and after prolonged swimming in white and red gastrocnemii as evidenced by an increased rate of urea production and increased 3-MH level in blood and in these muscles, respectively; (2) glyconeogenic amino acids released from increased body proteolysis appear to serve as substrates for glyconeogenesis after exercise in at least red gastrocnemius muscle, as demonstrated by the fact that nearly 11% of the label arising from $\sp $C-U-threonine and incorporated into muscle glycogen could be accounted for by muscle glyconeogenesis; and (3) circulating glycerol does not play a role in muscle glyconeogenesis. (Abstract shortened by UMI.)
24
Tomie, Jo-Anne B., e University of Lethbridge Faculty of Arts and Science. "Cognitive behavior of rats with thalamic lesions". Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 1994, 1994. http://hdl.handle.net/10133/60.
Resumo:
The objective of this thesis was to test the idea that medial thalamic nuclei are part of a "memory circuit" in the brain. Rats received lesions of the anterior (ANT) or medial dorsal (MD) thalamic nuclei and were tested on two spatial tasks, a nonspatial configural task, and spontaneous and amphetamine-induced acitivity. The thalamic rats were impaired on the spatial and conifural tasks, ans some of the thalamic groups were slightly hyperactive after administration of amphertamine. The deficits were not large and could not be unequivocally attributed to the ANT or MD damage. The results question the role of the ANT or MD in the behaviors studied. It is suggested that the deficits obtained after thalamic damage may be nonspecific and it is concluded that the results do not support the notion that thalamic structures have a primary role in memory.xi, 187 leaves : ill., plates ; 29 cm.
25
何禮昌 e Lai-cheong Ho. "Effects of green tea on ovariectomized rats". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31970540.
26
Sylvester, Christopher John. "A Demonstration of Photoresponsiveness in Laboratory Rats using Whole Animal and Neuroendocrine Approaches". W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539626097.
27
Belkaid, Wiam 1983. "Micropatterning of hippocampal neurons : characterization and implications for studying synaptogenesis". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111597.
Resumo:
During development of the nervous system, formation of specific connections between nerve cells depends on the stability of growing axons to reach appropriate target cells and form synapses. In culture, hippocampal neurons form numerous synapses by developing axonal and dendritic extensions. To elucidate principles of neuronal signaling and network establishment, creation of neuronal networks in which connectivity and pathways can be experimentally controlled is of great interest. In the present study we used a microcontact printing technique to control and study neurite outgrowth of hippocampal neurons in vitro. My preliminary results show that hippocampal neurons follow the microcontact printed pattern of poly-D-lysine (PDL). In doing so, neurons retain their morphology with normal subcellular distribution of various cell adhesion and synaptic molecules. However, the distribution of various axonal or dendrite components is altered. Hence we have developed a system in which isolated axons and dendrites align with inputs from very few neurons. With this technique we intend to study axon-dendrite communications on a spatially restricted and defined substrate.
28
陳遠儀 e Yuen-yee Roxanne Chan. "Studies on receptor-mediated uptake of transferrin and iron acquisition by rabbit reticulocytes and a rat hepatoma cell line". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31207571.
29
Symons, Lawrence André. "A behavioural examination of the intramodal and intemodal consequences of long-term tactile restriction by vibrissae removal in rats". Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28134.
Resumo:
Despite the extensive work done on the neural consequences of tactile restriction very little is known about the behavioural consequences of this manipulation. In the present investigation, an assessment was made of the effects of early, long-term tactile restriction by bilateral removal of the mystacial vibrissae on the subsequent somatosensory capacities of rats (i.e. the intramodal consequences) as well as its effects on visual and spatial capacities (i.e. the intermodal consequences). As well, rearing environment (enriched vs. normal) and type of surgery (vibrissae removal by cauterization of follicles or by plucking) were examined to determine specific factors that might influence the effect of early, long-term vibrissae removal.
Five tasks were used to assess these effects. The first two tasks assessed the intermodal consequences of vibrissae removal. Visual competence was assessed by measuring the habituation of orientation to repeated visual stimuli and the
dishabituation to subtle changes in these stimuli. A version of the Morris (1981) water maze was used to assess the rats' spatial abilities.
The results of these two tasks revealed limited evidence for intermodal effects. In terms of habituation to visual orientation, rats that had had their vibrissae removed by cauterization and were subsequently reared with daily access to an enriched environment required more trials to habituate to the presentation of repeated visual stimuli. As well, these rats were the only group to dishabituate to a subtle change in the stimuli. No effect of vibrissae removal was found in the spatial task, and environmental enrichment during development enhanced performance on this task, apparently through increased attention to distal cues by rats reared in this condition.
The remaining three tasks assessed the motoric and somatosensory effects of tactile restriction. No effect was found on the performance of the Puzzle Latch Box test in which the rats were required to manipulate various latches to obtain a food reward. As well, no significant effect was observed in reactions to the tying of pieces of wire to the rats' wrists. However, early, long-term vibrissae removal (by cauterization of follicles or by plucking) attenuated orientation to contacts of the mystacial pad itself. This effect was dissociated from tactile reactivity; all rats exhibited eye-flinch responses to taps on this area.
These results suggest that early, long-term tactile restriction has significant behavioural consequences for the
somatosensory system as well as the visual system. These data also provide limited evidence for theories of modality interdependence as well as yielding basic information concerning the role of the mystacial vibrisse in the behaviour of the rat.Arts, Faculty of
Psychology, Department of
Graduate
30
Morgan, Michael J. "Stimulation-produced analgesia in the formalin and tail-flick tests : a comparison of brainstem and fore-brain sites in the rat". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65408.
31
Panenic, Robert. "TTX-induced disuse of mammalian skeletal muscle". Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59523.
Resumo:
Previous reports of the effects of tetrodotoxin (TTX)-induced muscular disuse have demonstrated alterations in muscle force, speed, and fatiguability that might suggest changes in the quality of contractile proteins. These studies were extended to the effects of TTX-induced disuse on the Ca$ sp{2+}$-activation characteristics of myofibrillar ATPase of the rat gastrocnemius. Atrophic responses after TTX treatment were as previously reported with a significant decrease in left gastrocnemius weight (g) compared to the control-pump (C) group (1.25 $ pm$ 0.04 for C vs 0.72 $ pm$ 0.04 for TTX, X $ pm$ SEM, p $ leq$ 0.01). Myofibrillar protein yield (mg$ cdot$g$ sp{-1}$ wet weight) was also depressed (92.8 $ pm$ 4.6 for C vs 70.3 $ pm$ 3.7 for TTX; p $ leq$ 0.01). Maximum ATPase of myofibrils (nmol Pi$ cdot$mg$ sp{-1} cdot$min$ sp{-1}$) was decreased (424 $ pm$ 46 for C vs 199 $ pm$ 27 for TTX, p $ leq$ 0.01). Furthermore, the Hill n which reflects the cooperative aspects of Ca$ sp{2+}$-activation of the myofibrillar ATPase was significantly depressed (1.58 $ pm$ 0.07 for C vs 1.29 $ pm$ 0.09 for TTX; p $ leq$ 0.05) after TTX treatment. The results of the present study suggest that muscle perturbations that result from TTX-induced disuse are at least partially related to changes in the myofibrillar fraction.
32
黎振航 e Chun-hong Lai. "Functional properties of otolith neurons in the vestibular nucleus of young and adult rats during off-vertical axis rotation". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31212372.
33
李克楷 e Huk-kai Paul Lee. "Corticosteroid effects on serotonergic function: a study on the acute and chronic effects of corticosteroids onserotonin uptake and binding in rat synaptosomes and bloodplatelets". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1985. http://hub.hku.hk/bib/B31230519.
34
黃景祥 e King-chong Stephen Joseph Huang. "Biophysical and biochemical studies of anion secretion in the rat epididymis". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31232231.
35
黎錦明 e Kam-ming Lai. "Structure and function of 5'-nucleotidase of the rat brain". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1991. http://hub.hku.hk/bib/B31232280.
36
Zhao, Hang, e 趙航. "Melatonin receptors in the rat uterus". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31241384.
37
Li, Li, e 李莉. "Melatonin receptors in the rat epididymis". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31238907.
38
Li, Chuan, e 李川. "Spatial coding of gravitational input to the vestibuloolivary pathway and its refinement in development". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B31539609.
39
Ma, Chun-wai, e 馬俊偉. "Change in perineuronal net of rat vestibular nuclear neurons in development and in injury". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B45010328.
40
Cameron, Angus Crawford. "The control of physiological programmed cell death : apoptosis". Thesis, The University of Sydney, 1991. http://hdl.handle.net/2123/4751.
41
Dorrell, Helen Mary. "An investigation of the neurohumoural involvement in the antinociceptive effects of microelectrostimulation in rats". Thesis, University of East London, 1992. http://roar.uel.ac.uk/1247/.
42
Wong, Wing-man Miranda, e 黃詠雯. "Effects of Hawthorn extract on blood pressure in anesthetized rats". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31972305.
43
Stump, Craig Stephan. "Hindlimb muscle glucose uptake and metabolism in rats exposed to simulated microgravity". Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185927.
Resumo:
Over the last 30 years data from manned spaceflight missions have indicated that microgravity affects a number of physiological systems including the skeletal muscles. The purpose of the experiments in this dissertation was to examine the influence of 14 days of simulated microgravity on insulin and exercise stimulated glucose utilization in rat hindlimb muscles. To accomplish this aim, male Sprague-Dawley rats (250-325 g) were suspended in a head down position (SUS) so that one or both hindlimbs were non-weight bearing. The results from hindlimb perfusion experiments indicated that glucose uptake rates for the entire hindquarter at both submaximally and maximally stimulating insulin concentrations were significantly higher (p ≤ 0.05) in the SUS rats (77% and 15%, respectively) than the cage control rats (CC), suggesting increases in insulin sensitivity and responsiveness. Insulin sensitivity for ¹⁴C glucose incorporation into glycogen was also increased for the soleus (SOL), plantaris (PL), and extensor digitorum longus (EDL) muscles in the SUS rats. When the suspended (SUS-E) and control (CC-E) rats were exposed to acute treadmill exercise at 80-90% of VO₂ max, hindlimb glucose uptake and its incorporation into glycogen in the absence of insulin were higher in the PL, EDL, and white gastrocnemius (GW) muscles from the SUS-E rats. However, hindlimb muscle responses to insulin appeared to be impaired after exercise for the SUS-E rats when compared to the CC-E rats, especially in the SOL muscle. To examine the influence of non-weight bearing per se on muscles during simulated microgravity, rats were suspended with the left hindlimb non-weight bearing (NWB) and the right hindlimb bearing 20% of pre-suspension body mass (WB). The results indicated that ³H 2-deoxyglucose uptake was significantly higher for the SOL, PL, EDL and GW muscles (21-80%), at a maximally stimulating insulin concentration, in both SUS-NWB and SUS-WB hindlimbs despite the prevention of SOL and PL muscle mass losses in the SUS-WB hindlimbs. Collectively, the results from this dissertation indicate that the suspension of the rat with hindlimbs non-weight bearing leads to enhanced muscle responses to insulin for glucose uptake and metabolism, and suggest that systemic influences may be involved. In addition, exercise induced glucose and glycogen utilization increase to a greater extent in the hindlimb muscles of suspended rats when compared to their controls; but, there was evidence that muscle responses to insulin were attenuated with exercise in the suspended animals.
44
D'Asti, Esterina 1984. "Maternal dietary fat intake alters the neonatal stress response and metabolic profile in the offspring : participation of the endocannabinoid system?" Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111554.
Resumo:
Endocannabinoids are products of phospholipid-derived arachidonic acid that regulate hypothalamus-pituitary-adrenal axis activity. We hypothesize that differences in the quality and quantity of maternal dietary fat will modulate the neonatal phospholipid arachidonic acid content of the brain affecting the stress response via differences in endocannabinoid concentration of stress-activated brain areas. Dams were fed a 5% (C) or 300.10 fat diet rich in either n-6 (C, HF) or n-3 (HFF) fat during the perinatal period. PND4-5 HFF milk displays a reduced n-6/n-3 ratio compared to C and HF milk. PND10 hypothalamic and hippocampal PL AA levels are reduced in HFF pups relative to C and HF offspring; and predict endocannabinoid levels in a region-specific manner. In all pups pre-treated with an endocannabinoid receptor antagonist (AM251) or an inhibitor of the endocannabinoid degradative enzyme (URB597), basal and stress-induced ACTH secretion dose-dependently increased. Moreover, HFF pups exhibited a tendency towards reduced AM251 sensitivity under stressful conditions. These data suggest that the nature of perinatal dietary fat can differentially influence neonatal brain arachidonic acid levels and their endocannabinoid derivatives; and endocannabinoid signaling may be altered between diet groups since pups exhibit differences in sensitivity to endocannabinoid receptor blockade.
45
Lu, Xiaodong, e n/a. "Contribution of the perirhinal cortex to the firing properties of hippocampal pyramidal neurons". University of Otago. Department of Psychology, 2007. http://adt.otago.ac.nz./public/adt-NZDU20080128.154906.
Resumo:
The hippocampus appears to carry out spatial memory processing and navigation. As one of the inputs to the hippocampus originates in the perirhinal cortex and the spatial behaviour is affected by lesion of the perirhinal cortex, this structure may be critical for the functioning of hippocampal place cells. To investigate this hypothesis, the firing properties of hippocampal place cells were compared between control rats and rats with perirhinal cortex lesions.
Rats were randomly assigned to control and lesion groups. Animals from both groups received recording electrode implantation and the lesion group rats received bilateral perirhinal cortex lesions. In experiment 1, the control and lesioned rats moved freely in an open field. In experiment 2, the control and lesion rats ran for reward in a linear track with either horizontal or vertical grating pattern stimulation along both sidewalls. These two experiments examined the spatial firing and movement-related firing properties of the control and lesion groups; and the theta-related firing properties of the two groups. In addition, experiment 2 investigated the influence of optic flow on these properties between the two groups. In experiment 3, the control and lesion rats were passively moved in the linear track with either a horizontal or vertical grating pattern on both sidewalls. This experiment examined the spatial firing and movement-related firing properties and also investigated the influences of optic flow, motor efferent and proprioceptive information on the firing properties of the control and lesion groups� place cells.
The perirhinal cortex lesion affected the spatial firing properties of hippocampal place cells. The place field size in the lesion group was significantly reduced compared to the control group in both open field and linear track experiments. The lesion also altered the movement-related firing properties. The positive relationship between the animal�s movement speed and place cell�s firing rate was disrupted by the perirhinal cortex lesion whether the animals freely ran in the open field or in the linear track. In the open field study, the perirhinal cortex lesion altered the theta-related firing pattern, and the lesion disrupted phase precession in the linear track experiment. Phase precession is that when a rat passes through the place field, the firing of the cell advances progressively and systematically across the phase of the theta cycle from a late to an early phase of the cycle. The lesion also induced poorer theta "quality" of the EEG recorded at the hippocampal fissure. Optic flow affected the spatial firing of hippocampal place cells. The place field size was smaller in both the control and lesion group when the animals received vertical grating pattern stimulation compared to the horizontal grating condition. Change in the levels of optic flow stimulation did not, however, influence the relationship between the animal�s movement speed and place cell�s firing rate in the control group. When the animals were passively moved in a linear track, many of the place cells of both the groups stopped firing. The remaining cells from the control and lesion groups still displayed a place field. The cells in the control group lost the positive relationship between the animal�s movement speed and place cell�s firing rate.
The perirhinal cortex lesion affected the spatial, movement- related and theta-related firing properties of hippocampal place cells. Change of optic flow had a subtle effect on the movement-related firing properties of the place cells. The PrhC lesion therefore disrupted motor efferent and proprioceptive input to the HPC rather than visual sensory information. Motor efferent / proprioceptive or vibrissae information may be conveyed from related cortex to the perirhinal cortex. This information may then project from the perirhinal cortex to the hippocampus directly or indirectly via the entorhinal cortex. Future studies could investigate the relationship between whisker stimulation and hippocampal place cell firing properties and further examine the possible role of motor efferent / proprioceptive signals in the firing of these cells.
46
Sun, Bing, e 孫冰. "Vestibular influence on central cardiovascular regulation in the rat: functional and anatomical aspects". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244774.
47
古永亮 e Wing-leung Marcel Koo. "The modulating action of verapamil on the gastric effects of cold-restraint stress in rats". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1987. http://hub.hku.hk/bib/B31230891.
48
Heron, Marcia Indranee. "Effect of hyperthyroidism and hypothyroidism on coronary microvascular geometry in neonatal and adult rats". Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/9470.
Resumo:
The coronary microvascular response during pathological growth is important for the maintenance of adequate myocardial oxygenation. The aim of this research was to examine the coronary microvascular response to hyperthyroidism. Capillary geometry was examined in hyperthyroid, hypothyroid, and hypo-hyperthyroid adult male Sprague Dawley rats. Heart rates increased in hyperthyroid and hypo-hyperthyroid rats but decreased in hypothyroid rats compared to control. Adult-onset hyperthyroidism increased absolute and relative heart mass, whereas hypothyroidism decreased these parameters. In hypo-hyperthyroid rats, heart mass increased compared to hypothyroid rats and relative heart mass increased compared to control. Capillary numerical density was maintained in hyperthyroid and hypo-hyperthyroid rats despite increased LV mass, suggesting capillary proliferation. Hypothyroid rats had a larger than expected increase in capillary numerical density compared to control. In hyperthyroid rats, the area of tissue surrounding an individual capillary (capillary domain) decreased for proximal capillaries, whereas in hypothyroid rats domain areas decreased in both proximal and distal regions compared to control. All groups had shorter capillary segment lengths in proximal and distal regions relative to control. PCNA labelling of endothelial cells was significantly increased only in hypo-hyperthyroid rats. These data suggest that both adult-onset hyper- and hypothyroidism induced capillary proliferation. The effect of altered thyroid hormone status on the developing coronary microvasculature was examined in neonatal rats. Long-term effects of neonatal-onset hyper- and hypothyroidism on coronary microvascular geometry and cardiac function were examined in a subset of adult rats in which euthyroidism had been re-established. Neonatal-onset hyperthyroidism enhanced maturation, while hypothyroidism attenuated maturation. Serum T$\sb3$ levels and heart rates increased in hyperthyroid but decreased in hypothyroid rats compared to control. After discontinuing treatment, heart rates were similar between control and previously hypothyroid rats. Occasionally, heart rates remained elevated in previously hyperthyroid rats compared to control. Hyperthyroidism produced ventricular hypertrophy while hypothyroidism slowed cardiac growth. Both neonatal thyroid conditions induced a long-term deficit in LV growth after euthyroidism was re-established. Capillary and arteriolar numerical density, as well as proximal and distal capillary segment lengths, were maintained in hyperthyroid rats despite LV hypertrophy suggesting enhancement of capillary and arteriolar proliferation. Total arteriolar length was greater in hyperthyroid than control rats. With hypothyroidism, capillary numerical density was either maintained or increased compared to control. Total arteriolar length was significantly lower in hypothyroid rats suggesting slowed arteriolar growth. After cessation of treatment, total arteriolar length in previously hyperthyroid rats did not change despite increased LV mass. Previously hyperthyroid rats had increased RV and LV systolic pressure, LV developed and end-diastolic pressure, and +(dP/dt)max (P 0.05). An increased percentage of small arterioles (i.e. 10-30$\mu$m) was observed in previously hypothyroid rats. (Abstract shortened by UMI.)
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Kong, Wuyi. "Absorption and distribution of epidermal growth factor in the gastrointestinal tract of suckling rats". Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186231.
Resumo:
Suckling rats show a low level of synthesis of epidermal growth factor (EGF) and obtain this important polypeptide from maternal milk. Thus, this study was performed to characterize how and where in the gastrointestinal tract the absorption of rat-EGF (rEGF) occurs and to which organs it is delivered. Although radiolabeled EGF transferred to the liver by the ileum was significantly higher than that by the jejunum, the total amounts of immunoreactive and receptor-binding active ¹²⁵I-rEGF in the liver were significantly higher from jejunal than from ileal absorption. These results indicate that the ileum degrades most of the ¹²⁵I-rEGF during absorption, whereas the jejunum absorbs more intact ¹²⁵I-rEGF. Higher numbers of EGF receptors were found in the brush border membranes of jejunum than that of the ileum, suggesting that the larger amounts of intact EGF delivered by the jejunum to the liver may be due to a higher capacity of EGF receptors in the jejunum. Liver and intestine were the main organs taking up the radioactivity after intrafemoral vein ¹²⁵I-rEGF administration. The degradation rates of EGF in the liver, intestine and pancreas were significantly lower in suckling as opposed to adult rats. In suckling rats intact rEGF was secreted by the liver into the bile and by the enterocytes into the lumen of the intestine. The competitive effects of unlabeled rEGF were found at both sides of the small intestine and at the circulatory side of the liver, submandibular glands, pancreas, and other organs, indicating a receptor-related uptake of EGF from the lumen and circulation of these organs in suckling rats. The results indicate that after absorption maternal milk-EGF stays mainly in the digestive system during the suckling period. The amount of EGF in each organ may remain relatively stable on a daily basis since EGF is absorbed continuously from the jejunum in suckling rats and is distributed and circulated in the digestive system by hepatico-enteric, entero-enteric, and perhaps pancreatico-enteric circulations; in this way, EGF accelerates the growth of the digestive system.
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Insel, Nathan. "Physiology of the medial frontal cortex during decision-making in adult and senescent rats". Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/196140.
Resumo:
Convergent evidence suggests that the dorsal medial prefrontal cortex (dmPFC) makes an important contribution to goal-directed action selection. The dmPFC is also part of a network of brain regions that becomes compromised in old age. It was hypothesized that during decision-making, some process of comparison takes place in the dmPFC between the representation of available actions and associated values, and that this process is changed with aging. These hypotheses were tested in aged and young adult rats performing a novel 3-choice, 2-cue decision task. Neuron and local field potential activity revealed that the dmPFC experienced different states during decision and outcome phases of the task, with increased local inhibition and oscillatory (gamma and theta) activity during cue presentation, and increased excitatory neuron activity (among regular firing neurons) at goal zones. Although excitatory and inhibitory activity appeared anti-correlated over phases of the decision task, cross-correlations and the prominent gamma oscillation revealed that excitation and inhibition were highly correlated on the millisecond scale. This "micro-scale" coupling between excitation and inhibition was altered in aged rats and the observed changes were correlated with changes in decision and movement speeds of the aged animals, suggesting a putative mechanism for age-related behavioral slowing. With respect to decision-making, both aged and young adult rats learned over multiple days to follow the rewarded cue in the 3-choice, 2-cue task. Support for the hypothesis that the dmPFC simultaneously represents alternative actions was not found; however, neuron activity selective for particular goal zones was observed. Interestingly, goal-selective neural activity during the decision period was more likely to take place on error trials, particularly on high-performing sessions and when rats exhibited a preference for a particular feeder. A possible interpretation of these patterns is that goal representations in the dmPFC might have sometimes overruled learned habits, which are likely to be involved in following the correct cue and which are known to be supported by other brain regions. These results describe fundamental properties of network dynamics and neural coding in the dmPFC, and have important implications for the neural basis of processing speed and goal-directed action.