Gotowa bibliografia na temat „Plasma lactate concentration”

Some of the initial biochemical findings, obtained from 141 randomly-selected cases of acute hyperglycaemia (admission plasma glucose >20 mmol/L) were examined. When viewed in terms of their initial plasma bicarbonate concentration, three groups were identifiable. Plasma concentrations of free fatty acids (FFA), acetone and the sum of 3-hydroxybutyrate (3OHB) and lactate were different between these groups. However, there were no differences in plasma glucose or lactate concentrations. It was further observed that the relationship between the plasma FFA/albumin molar ratio, and ketone concentration could be described by a rectangular hyperbola, and the initial anion gap was linearly related to the sum of the 3OHB and lactate concentrations.

Abstract Measurement of lactate concentrations in cerebrospinal fluid (CSF) has been suggested as part of the investigation of inborn errors of the electron transport chain, but little information exists regarding the reference range in children or the relationship between CSF and plasma concentrations. In 39 children without bacterial meningitis, diabetes, or recent seizures, we determined that the median (range) lactate concentrations in CSF and plasma collected concurrently were 1.4 (0.8–2.2) and 1.5 (0.6–2.3) mmol/L; the regression equation was CSF lactate = (0.38 ± 0.06) plasma lactate + 0.83 (r2 = 0.14). In 8 of 11 (73%) children with electron transport chain defects, CSF lactate was ≥3.0 mmol/L; however, 2 of these 8 had a normal plasma lactate concentration. CSF lactate was also increased in 2 children with nonketotic hyperglycinemia. The finding that CSF lactate concentrations may be increased despite a normal plasma lactate value in children with electron transport chain defects is an important clue to the diagnosis of these disorders.

In the present study the microdialysis technique was evaluated in an isolated autoperfused dog fat pad. Concentrations of glucose, lactate, and glycerol were measured in interstitial fluid by microdialysis and simultaneously in arterial and adipose venous plasma. Adipose tissue blood flow was measured by both133Xe washout and timed weighing of venous blood. Metabolite concentrations in adipose venous plasma calculated from interstitial and arterial metabolite concentrations and133Xe washout were positively correlated with measured venous concentrations (glucose: r = 0.95, lactate: r = 0.92, glycerol: r = 0.81). Calculated and measured venous plasma concentrations did not differ for either glucose or lactate, but for glycerol, calculated concentration was on average 76% of measured concentration. Metabolite exchanges (Fick’s principle) calculated from interstitial metabolite concentrations were positively correlated with measured exchanges only for lactate ( r = 0.69). In conclusion, metabolite concentrations in adipose venous plasma can be calculated from microdialysis measurements with greater accuracy for glucose and lactate than for glycerol. The precision, however, is too low to allow calculation of metabolite exchange when arteriovenous metabolite differences are low.

The precise mechanism responsible for the increase in plasma lactate concentration during exercise in humans is not known. We have used dichloroacetate to test the hypothesis that a limitation in pyruvate dehydrogenase activity is responsible for the rise in plasma lactate. Dichloroacetate stimulates the activity of pyruvate dehydrogenase, which is normally the regulatory enzyme in the oxidation of glucose when tissue oxygenation is adequate. Six subjects were studied twice according to a randomized, crossover protocol, involving one test with saline infusion and another with dichloroacetate infusion. Exercise load on a bicycle ergometer was increased progressively until exhaustion. Blood samples were drawn each minute throughout exercise and periodically throughout 120 min of recovery. Dichloroacetate significantly lowered the lactate concentration during exercise performed at less than 80% of the average maximal O2 consumption. The peak concentration of lactate at exhaustion was not affected by dichloroacetate treatment, but dichloroacetate did lower lactate concentration throughout recovery. These results suggest that a limitation in pyruvate dehydrogenase activity contributes to the increase in plasma lactate during submaximal exercise and recovery.

Rates of lactate uptake into giant sarcolemmal vesicles were determined in vesicles collected from rat muscles at rest and immediately after 10 min of intense muscle contraction. This contraction period reduced muscle glycogen rapidly by 37–82% in all muscles examined ( P < 0.05) except the soleus muscle (no change P > 0.05). At an external lactate concentration of 1 mM lactate, uptake into giant sarcolemmal vesicles was not altered ( P > 0.05), whereas at an external lactate concentration of 20 mM, the rate of lactate uptake was increased by 64% ( P < 0.05). Concomitantly, the plasma membrane content of monocarboxylate transporter (MCT)1 was reduced slightly (−10%, P < 0.05), and the plasma membrane content of MCT4 was reduced further (−25%, P < 0.05). In additional studies, the 10-min contraction period increased the plasma membrane GLUT4 ( P < 0.05) while again reducing MCT4 (−20%, P < 0.05) but not MCT1 ( P > 0.05). These studies have shown that intense muscle contraction can increase the initial rates of lactate uptake, but only when the external lactate concentrations are high (20 mM). We speculate that muscle contraction increases the intrinsic activity of the plasma membrane MCTs, because the increase in lactate uptake occurred while plasma membrane MCT4 was decreased and plasma membrane MCT1 was reduced only minimally, or not at all.

The primary aim of this thesis was to develop a better understanding of the physiology and perceptual responses associated with the performance of continuous (CE) and intermittent exercise (IE) in patients with moderate chronic obstructive pulmonary disease (COPD). A secondary aim was to examine factors that could potentially limit exercise tolerance in COPD patients, particularly in relation to the dynamics of the cardiovascular system and muscle metabolism. The results of the four studies conducted to achieve these aims are presented in this thesis. In Study 1, the physiological, metabolic and perceptual responses to an acute bout of IE and CE were examined in 10 individuals with moderate COPD. Each subject completed an incremental exercise test to exhaustion on a cycle ergometer. Subjects then performed IE (1 min exercise: 1 min rest ratio) and CE tests at 70% of peak power in random order on separate days. Gas exchange, heart rate, plasma lactate concentration, ratings of breathlessness, inspiratory capacity and the total amount of work completed were measured during each exercise test. Subjects were able to complete a significantly greater amount of work during IE (71 ± 32 kJ) compared with CE (31 ± 24 kJ). Intermittent exercise was associated with significantly lower values for oxygen uptake, expired ventilation and plasma lactate concentration when compared with CE. Subjects also reported a significantly lower rating of breathlessness during IE compared to CE. The degree of dynamic lung hyperinflation (change in end-expiratory lung volume) was lower during IE (0.23 ± 0.07 L) than during CE (0.52 ± 0.13 L). The results suggest that IE may be superior to CE as a mode of training for patients with COPD. The greater amount of total work performed and the lower measured physiological responses attained with intermittent exercise could potentially allow greater training adaptations to be achieved in individuals with more limited lung function. The purpose of Study 2 was to compare the adaptations to 8 wk of supervised intermittent and continuous cycle ergometry training, performed at the same relative intensity and matched for total work completed, in patients with COPD. Nineteen subjects with moderate COPD were stratified according to age, gender, and pulmonary function, and then randomly assigned to either an IE (1 min exercise: 1 min rest ratio) or CE training group. Subjects trained 3 d per week for 8 wk and completed 30 min of exercise. Initial training intensity, i.e., the power output applied during the CE bouts and during the exercise interval of the IE bouts, was determined as 50% of the peak power output achieved during incremental exercise and was increased by 5% each week after 2 wk of training. The total amount of work performed was not significantly different (P=0.74) between the CE (750 ± 90 kJ) and IE (707 ± 92 kJ) groups. The subjects who performed IE (N=9) experienced significantly lower levels of perceived breathlessness and lower limb fatigue during the exercise-training bouts than the group who performed CE (N=10). However, exercise capacity (peak oxygen uptake) and exercise tolerance (peak power output and 6-min walk distance) improved to a similar extent in both training groups. During submaximal constant-load exercise, the improved (faster) phase II oxygen uptake kinetic response with training was independent of exercise mode. Furthermore, training-induced reductions in submaximal exercise heart rate, carbon dioxide output, expired ventilation and blood lactate concentrations were not different between the two training modes. Exercise training also resulted in an equivalent reduction for both training modes in the degree of dynamic hyperinflation observed during incremental exercise. Thus, when total work performed and relative intensity were the same for both training modes, 8 wk of CE or IE training resulted in similar functional improvements and physiological adaptations in patients with moderate COPD. Study 3 examined the relationship between exercise capacity (peak oxygen uptake) and lower limb vasodilatory capacity in 9 patients with moderate COPD and 9 healthy age-matched control subjects. While peak oxygen uptake was significantly lower in the COPD patients (15.8 ± 3.5 mL·min-1·kg-1) compared to the control subjects (25.2 ± 3.5 mL·kg-1·min-1), there were no significant differences between groups in peak calf blood flow or peak calf conductance measured 7 s post-ischemia. Peak oxygen uptake was significantly correlated with peak calf blood flow and peak conductance in the control group, whereas there was no significant relationship found between these variables in the COPD group. However, the rate of decay in blood flow following ischemia was significantly slower (p less than 0.05) for the COPD group (-0.036 ± 0.005 mL·100 mL-1·min-1·s-1) when compared to the control group (-0.048 ± 0.015 mL·100 mL-1·min-1·s-1). The results of this study suggest that the lower peak exercise capacity in patients with moderate COPD is not related to a loss in leg vasodilatory capacity. Study 4 examined the dynamics of oxygen uptake kinetics during high-intensity constant-load cycling performed at 70% of the peak power attained during an incremental exercise test in 7 patients with moderate COPD and 7 healthy age-matched controls. The time constant of the primary component (phase II) of oxygen uptake was significantly slower in the COPD patients (82 ± 8 s) when compared to healthy control subjects (44 ± 4 s). Moreover, the oxygen cost per unit increment in power output for the primary component and the overall response were significantly higher in patients with COPD than in healthy control subjects. A slow component was observed in 5 of the 7 patients with COPD (49 ± 11 mL·min-1), whereas all of the control subjects demonstrated a slow component of oxygen uptake (213 ± 35 mL·min-1). The slow component comprised a significantly greater proportion of the total oxygen uptake response in the healthy control group (18 ± 2%) than in the COPD group (10 ± 2%). In the COPD patients, the slow component amplitude was significantly correlated with the decrease in inspiratory capacity (r = -0.88, P less than 0.05; N=5), indicating that the magnitude of the slow component was larger in individuals who experienced a greater degree of dynamic hyperinflation. This study demonstrated that most patients with moderate COPD are able to exercise at intensities high enough to elicit a slow component of oxygen uptake during constant-load exercise. The significant correlation observed between the slow component amplitude and the degree of dynamic hyperinflation suggests that the work of breathing may contribute to the slow component in patients with COPD.

The primary aim of this thesis was to develop a better understanding of the physiology and perceptual responses associated with the performance of continuous (CE) and intermittent exercise (IE) in patients with moderate chronic obstructive pulmonary disease (COPD). A secondary aim was to examine factors that could potentially limit exercise tolerance in COPD patients, particularly in relation to the dynamics of the cardiovascular system and muscle metabolism. The results of the four studies conducted to achieve these aims are presented in this thesis. In Study 1, the physiological, metabolic and perceptual responses to an acute bout of IE and CE were examined in 10 individuals with moderate COPD. Each subject completed an incremental exercise test to exhaustion on a cycle ergometer. Subjects then performed IE (1 min exercise: 1 min rest ratio) and CE tests at 70% of peak power in random order on separate days. Gas exchange, heart rate, plasma lactate concentration, ratings of breathlessness, inspiratory capacity and the total amount of work completed were measured during each exercise test. Subjects were able to complete a significantly greater amount of work during IE (71 ± 32 kJ) compared with CE (31 ± 24 kJ). Intermittent exercise was associated with significantly lower values for oxygen uptake, expired ventilation and plasma lactate concentration when compared with CE. Subjects also reported a significantly lower rating of breathlessness during IE compared to CE. The degree of dynamic lung hyperinflation (change in end-expiratory lung volume) was lower during IE (0.23 ± 0.07 L) than during CE (0.52 ± 0.13 L). The results suggest that IE may be superior to CE as a mode of training for patients with COPD. The greater amount of total work performed and the lower measured physiological responses attained with intermittent exercise could potentially allow greater training adaptations to be achieved in individuals with more limited lung function. The purpose of Study 2 was to compare the adaptations to 8 wk of supervised intermittent and continuous cycle ergometry training, performed at the same relative intensity and matched for total work completed, in patients with COPD. Nineteen subjects with moderate COPD were stratified according to age, gender, and pulmonary function, and then randomly assigned to either an IE (1 min exercise: 1 min rest ratio) or CE training group. Subjects trained 3 d per week for 8 wk and completed 30 min of exercise. Initial training intensity, i.e., the power output applied during the CE bouts and during the exercise interval of the IE bouts, was determined as 50% of the peak power output achieved during incremental exercise and was increased by 5% each week after 2 wk of training. The total amount of work performed was not significantly different (P=0.74) between the CE (750 ± 90 kJ) and IE (707 ± 92 kJ) groups. The subjects who performed IE (N=9) experienced significantly lower levels of perceived breathlessness and lower limb fatigue during the exercise-training bouts than the group who performed CE (N=10). However, exercise capacity (peak oxygen uptake) and exercise tolerance (peak power output and 6-min walk distance) improved to a similar extent in both training groups. During submaximal constant-load exercise, the improved (faster) phase II oxygen uptake kinetic response with training was independent of exercise mode. Furthermore, training-induced reductions in submaximal exercise heart rate, carbon dioxide output, expired ventilation and blood lactate concentrations were not different between the two training modes. Exercise training also resulted in an equivalent reduction for both training modes in the degree of dynamic hyperinflation observed during incremental exercise. Thus, when total work performed and relative intensity were the same for both training modes, 8 wk of CE or IE training resulted in similar functional improvements and physiological adaptations in patients with moderate COPD. Study 3 examined the relationship between exercise capacity (peak oxygen uptake) and lower limb vasodilatory capacity in 9 patients with moderate COPD and 9 healthy age-matched control subjects. While peak oxygen uptake was significantly lower in the COPD patients (15.8 ± 3.5 mL·min-1·kg-1) compared to the control subjects (25.2 ± 3.5 mL·kg-1·min-1), there were no significant differences between groups in peak calf blood flow or peak calf conductance measured 7 s post-ischemia. Peak oxygen uptake was significantly correlated with peak calf blood flow and peak conductance in the control group, whereas there was no significant relationship found between these variables in the COPD group. However, the rate of decay in blood flow following ischemia was significantly slower (p less than 0.05) for the COPD group (-0.036 ± 0.005 mL·100 mL-1·min-1·s-1) when compared to the control group (-0.048 ± 0.015 mL·100 mL-1·min-1·s-1). The results of this study suggest that the lower peak exercise capacity in patients with moderate COPD is not related to a loss in leg vasodilatory capacity. Study 4 examined the dynamics of oxygen uptake kinetics during high-intensity constant-load cycling performed at 70% of the peak power attained during an incremental exercise test in 7 patients with moderate COPD and 7 healthy age-matched controls. The time constant of the primary component (phase II) of oxygen uptake was significantly slower in the COPD patients (82 ± 8 s) when compared to healthy control subjects (44 ± 4 s). Moreover, the oxygen cost per unit increment in power output for the primary component and the overall response were significantly higher in patients with COPD than in healthy control subjects. A slow component was observed in 5 of the 7 patients with COPD (49 ± 11 mL·min-1), whereas all of the control subjects demonstrated a slow component of oxygen uptake (213 ± 35 mL·min-1). The slow component comprised a significantly greater proportion of the total oxygen uptake response in the healthy control group (18 ± 2%) than in the COPD group (10 ± 2%). In the COPD patients, the slow component amplitude was significantly correlated with the decrease in inspiratory capacity (r = -0.88, P less than 0.05; N=5), indicating that the magnitude of the slow component was larger in individuals who experienced a greater degree of dynamic hyperinflation. This study demonstrated that most patients with moderate COPD are able to exercise at intensities high enough to elicit a slow component of oxygen uptake during constant-load exercise. The significant correlation observed between the slow component amplitude and the degree of dynamic hyperinflation suggests that the work of breathing may contribute to the slow component in patients with COPD.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Physiotherapy and Exercise Science
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Infections in critically ill patients are a problem for the healthcare system and at any one time, 70 % of all intensive care unit (ICU) patients are treated with antibiotics. Antibiotics bind toproteins in the blood, but only unbound drug can diffuse over capillary membranes and bindto the targeted receptor. Standard protein binding percentages for antibiotics have been developed from studies on healthy volunteers and dosing regimens for patients are adapted accordingly. The determination of the total concentration of antibiotics in patients’ bloodsamples is, based on the standard percentages, ordinarily representative for the pharmacological effect of the antibiotic. However, certain conditions that are common incritically ill patients can alter protein binding percentages, resulting in a larger or smaller unbound fraction. This in turn can result in toxicity or therapeutic failure. The aim of this project was to develop an analytical method for the determination of the unbound concentration of the Beta-Lactam antibiotics cefotaxime, flucloxacillin, cloxacillin and piperacillin in plasma. A method was successfully developed using ultrafiltration for the extraction of unbound analytes and ultra high performance liquid chromatography tandem mass spectrometry, UHPLC-MS/MS, for their quantification. The method was partly validated according to the European Medicines Agency’s guidelines on bioanalytical method validation.
Kritiskt sjuka patienter med infektioner är en börda för sjukvården och 70 % av alla patienter på intensivvårdsavdelningar är ordinerade antibiotika. Antibiotika binder till proteiner i blodet, men enbart den icke-proteinbundna (fria) fraktionen kan diffundera över kapillära membran och binda till receptorer. Standardproteinbindningsgrad för olika antibiotika har utvecklats från studier på friska frivilliga och doseringen av läkemedlen är anpassade därefter. Den totala koncentrationen av antibiotika i patienters blod är vanligen representativ för den farmakologiska effekten. Dock kan vissa sjukdomar påverka proteinbindningsgraden vilket resulterar i en större eller mindre mängd fria antibiotika i blodcirkulationen. Det här kan i sintur resultera i toxicitet eller otillräcklig effekt av läkemedlet. Syftet med det här projektet var att utveckla en analytisk metod för att bestämma den fria koncentrationen av Beta-Lactam antibiotikan cefotaxim, flukloxacillin, kloxacillin och piperacillin i plasma. En metod utvecklades med ultrafiltrering för extraktion av den fria fraktionen och högupplösande vätskekromatografi och tandem masspektrometri, UHPLCMS/MS, för kvantifiering av analyterna. Metoden validerades delvis enligt den Europeiska Läkemedelsmyndighetens riktlinjer för bioanalytisk metodvalidering.

This thesis contains two studies. The first study consisted of a prospective, randomized, clinical trial involving twenty-five client-owned dogs with intracranial disease. Each dog was randomly assigned to receive propofol or isoflurane for maintenance of anesthesia, without premedication. All dogs received propofol IV to effect, were intubated and mechanically ventilated (end-tidal carbon dioxide [ETCO2] 30-35 mmHg). Temperature and cardiac output were measured pre- and post-magnetic resonance imaging (MRI). Scores for mentation, neurological status, maintenance, and recovery were obtained. Pulse oximetry, end tidal gases, arterial blood pressure (AP), heart rate (HR) and requirements for dopamine administration to maintain mean AP > 60 mmHg were recorded throughout anesthesia. Cardiac index was higher, while HR was lower, with propofol in dogs younger than 5 years. Dogs receiving isoflurane were 14.7 times more likely to require dopamine. Sedation and maintenance scores and temperature were not different. Mean and diastolic AP were higher in the propofol group. Recovery scores were better with propofol. Change in neurological score from pre- to post-anesthesia was not different between treatments. In the second study, blood and CSF were collected from 11 dogs with intracranial disease after MRI (Group ID-MRI), in 10 healthy dogs post-MRI (Group H-MRI), and in 39 healthy dogs after induction of anesthesia (Group H-Anesth). Groups ID-MRI and H-MRI were induced to anesthesia with propofol, IV to effect, and maintained on isoflurane or propofol. Dogs in H-Anesth were premedicated with acepromazine and hydromorphone, induced with propofol or thiopental, IV to effect, and maintained on isoflurane. Neurologic scores (NS) and sedation scores (SS) were assessed pre-anesthesia in ID-MRI dogs. There was a tendency for higher cerebrospinal fluid lactate (CSFL) in ID-MRI than H-MRI or H-Anesth (p = 0.12). There was agreement between CSFL and plasma lactate (PL) in ID-MRI dogs (p = 0.007), but not in H-MRI (p = 0.45) or H-Anesth (p = 0.15). Of the ID-MRI dogs, those with worse NS had higher CSFL (r2 = 0.44). Propofol showed some advantages to isoflurane in this patient population for maintenance of blood pressure and recovery. The results of the second study warrant further investigation.
OVC Pet Trust

Inborn errors of galactose metabolism—galactose is principally found as free lactose in dairy products. Three inborn errors of galactose metabolism are recognized: (1) galactokinase deficiency (‘galactose diabetes’)—a very rare condition which impairs the assimilation of dietary galactose such that the free sugar and its metabolites appear in plasma and urine; (2) classical galactosaemia (galactose-1-phosphate uridylyltransferase deficiency)—the commonest (1/47 000 births) and most important disorder. High concentrations of galactose in the plasma and tissues lead to aberrant glycosylation of glycoproteins and other glycoconjugates, including lipids. The principal manifestations are a bactericidal defect associated with neonatal Escherichia coli sepsis; failure to thrive; and—in older patients—growth retardation, mental retardation, renal Fanconi’s syndrome, jaundice, and hepatosplenomegaly: without exclusion of lactose and galactose, death with cirrhosis is the rule. (3) Uridine diphosphate galactose-4´-epimerase deficiency—a rare but often harmless disorder which may be identified by neonatal screening. Rarely, cataract, sensorineural deafness and impaired psychomotor development with hepatorenal features of classical galactosaemia occur, with favourable responses to the galactose exclusion diet. Pentosuria—essential pentosuria is an asymptomatic, autosomal recessive trait affecting glucuronate metabolism, principally found in Ashkenazi Jews. Disorders of pyruvate metabolism—deficiency of the pyruvate dehydrogenase complex is the most common inherited disorder with lactic acidaemia, most often due to deficiency of the E1α‎ subunit inherited as a dominant X-linked character. Presentation is with overwhelming neonatal acidosis; moderate lactic acidosis with progressive neurological features; or—in male children and young adults—an indolent neurological course without overt acidosis but with episodes of cerebellar ataxia induced by carbohydrate administration. Pyruvate carboxylase deficiency causes lactate/pyruvate acidosis with a necrotizing encephalopathy resembling Wernicke’s encephalopathy. Hypoglycaemia may complicate intercurrent infections and starvation.

<em>Abstract.</em>—Urban streams typically have increased flows, high suspended sediment concentrations, and reduced water quality during rainstorms as a result of changes within the watershed related to human activity. In the 6-month periods from May through October of 2001 and 2002, water quality was monitored continuously at five sites along Rapid Creek within Rapid City, South Dakota. Water quality samples were collected for eight base flows (nonevents) and eight storm events. Blood samples were collected from wild adult brown trout <em>Salmo trutta </em>during base flow conditions and six of eight storm events to determine if storm events could elicit physiological stress responses. Blood samples were also collected 24, 48, and 96 h after each storm event had started. Water monitoring results showed significant increases in runoff volume and peak flows during storm events. Water quality parameters exceeding South Dakota’s water quality criteria for a coldwater fishery were total suspended solids and temperature. Plasma concentrations of cortisol and lactate, during and after storm events, were not significantly different than those measured during base flow conditions. Plasma glucose values were lower during storm events than during nonevent periods. These observations were compared to those predicted by a suspended sediment dose–response model developed for adult salmonids. The dose–response model overpredicted the severity of the effects of increased total suspended sediment on the brown trout during stormwater runoff events.

Abstract.—To provide a synthesis of the physiological responses to otter-trawl capture in spiny dogfish <em>Squalus acanthias</em>, blood values from trawled individuals were evaluated against values from minimally stressed dogfish caught rapidly by hook and line (control). Values and analyses from published studies are considered along with those from the most expansive set of blood samples taken from dogfish captured by both methods to date. Significant impacts of trawling on dogfish blood physiology were reflected in all parameters excluding log plasma protein. Parameters for whole-blood acid–base status (pH, significant decrease; pO₂, 45% decrease; pCO₂, 82% increase), and the metabolite lactate anion (125% increase) were most perturbed relative to differences induced by the capture methods in other parameters. The concentrations of sera monovalent electrolytes (Na⁺, K⁺, Cl^-) and glucose were significantly elevated by trawling, but not to the magnitude seen in other studies related to capture stress in fish. Significant elevations in hematocrit and reductions in blood urea nitrogen (BUN) concentrations were also observed subsequent to trawling. Overall, this capture method incited marked changes in blood physiology relative to values in minimally stressed dogfish. However, previous studies demonstrating high rates of posttrawl dogfish survival indicate that such changes are resolvable in this species prior to lethal consequences.

In the 1970's, when platelet concentrates (PC) were stored in "first generation" plastic containers at 22°C, many showed a fall in pH.In vivo viability was well maintained as pH fell from the starting level, 7.1, to 6.2 but was progressively lost below thatlevel. pH after a storage interval correlated with the platelet count in the PC, the higher the count, the lower the pH after storage. Since 30-50% of PC might have pH below 6.2 after 3 days of storage, shelflife was severely limited.We now have "second generation" containers which allow storage for 7 days without significant fall in pH.Superior pH maintenance results from increased oxygen transport through the walls of the container thuspreventing platelet hypoxia within. Under all circumstances which we have examined, PC, pH correlates inversely with lactate concentration. The superiority of the "second generation" containers results from the lower rate of glycolysis within them due to the Pasteur effect. Like many cells, the platelet has a baseline rate of lactate production which is increased up to 8 times if oxidative metabolism is interrupted by hypoxia. For any container, there is an inverse relationship between PC pCL and platelet count since each platejlet |as a fixed oxygen demand. In "first generation" containers, the pO2 approached zero with platelet counts, 1.0-1.5 × 106 /mm3 , a range commonly seen in practice. At platelet counts above thatlevel, the platelets would have an increasing oxygendebt. The greater the oxygen debt is, the greater will be the rate of lactate production per platelet and, therefore, the rate of pH fall. An ideal "second generation" container will have oxygen permeability twice thgt 05 a "first generation" container such that platelets will begin to have an oxygen debt at platelet count, 2.4 × 106/mm3 , a level rarely seen in practice. In "second generation" containers, there is a continuing, linear production of lactate in spite of adequate oxygen supply. The major buffer in plasma for the hydrogen ion accompanying lactate production is bicarbonate. As lactate is produced, bicarbonate is consumed and pH remains stable until bicarbonate is completely depleted.Thereafter, pH falls precipitously.However, there is adequate bicarbonate in the 50 ml of plasma used as medium for the PC to buffer the baseline production of lactate for seven days.This is the major reason why storage for sevendays is now satisfactory.With knowledge of the oxygen transport capability of a container and measurement of pO2 within the container, we can calculate the rate of oxygen consumptionduring storage, 1.1 nmol/min/109 platelets. Knowing the rates of oxygen consumption and lactate production and the predicted rate of ATP synthesis from ADP for each type of metabolism we calculated that 85% ofATP regeneration is from oxidative metabolism. When we contrasted the rate of glucose consumption with the rate of lactate production, we were surprised that the slope of the regression line was exactly 0.5 suggesting that two moles of lactate were produced for each mole of glucose utilized and that there must be a prominent substrate for oxidative metabolism other than glucose. Recent work in our laboratory suggests fatty acid as such a substrate.There is much to be learned about storage in "secondgeneration" containers. At the onset of storage 70% of the platelets have a discoid appearance whereas after seven days only 30% do with most of the rest being spheres. Furthermore, 5-10% of cells are "leaf-shaped", elongated tubules, or ring forms. In addition, many studies have described reduced platelet function in vitro after storage. There is a 20-50% reduction in the maximal extent of aggregation with high ADP concentrations and the concentrations of single agonists which produce 50% of maximal response are increased after storage. However, we have been encouraged to find that the response to these agents was reduced much less when they were used a pairs. Finally, there is concern that trace bacterial contamination at the time of phlebotomy might allow enough proliferation to produce sepsis in recipients. Further research should improve our understanding inthese areas and the safety and efficacy of platelets after storage.

Leukocyte poor platelet concentrates (PC), containing less than 10 leukocytes, prepared from buffycoats can be stored in normal PVC bags for 7 days at 22°C without deterioration of the pH. We assumed that a low number of leukocytes present in the PC, is a critical factor to maintain the pH. To test this hypothesis increasing amounts of leukocytes were added to four groups of three PC with comparable plasma volumes (mean 58.6 ± 0.8 (SD) ml) and platelet concentrations (1.01 ± 0.04×109 /ml). Group I had a leukocyte concentration of 0.14±0.048×106 /ml, group II 1.96±0.09×106 /ml, group III 5.53±0.98×106 /ml, and group IV 13.0±0.93×106 /ml. The PC were stored in normal PVC bags for 7 days at 22°C. Measurements in vitro were performed at day 0, 2, 5 and 7.The initial mean pH value was 7.12±0.02 (SD) for all PC and dropped to 6.89, 6.85, 6.77 and 6.61 for group I to IV respectively, at day 7. A significant correlation (Spearman rank test) between low pH values and high leukocytes was found. The same significant positive correlation was observed between high leukocyte concentrations and high glucose consumption and high lactate production and LDH release during storage.These results show that the amount of leukocytes in PC has a significant contribution to the detrimental effect on pH during platelet storage. It is therefore important to prepare PC with a leukocyte count lower than 10 . Moreover the risk of alloimmunisation against HLA antigens will be diminished.

TFP is a lipophilic antipsychotic drug. The drug will first encounter with cell membrane when adding it into a cell suspension. The effect of TFP on plasma membrane of the gel-filtered human platelet was investigated by : 1) scanning electron microscopy (SEM); 2) measuring theleakiness of marker enzymes and compound; 3) estimating its solubility in membrane. The cells were suspended in the modified Tyrode's buffer containing 0.1% dextrose, 0.2% of bovine serum albumin and without calcium. The SEM study showed that platelet changed shape from disc to ellipsoid in 10 μM TFP.,Increasingthe TFP concentration from 20 μM to 50 μM resulted in changing thecell from ellipsoid to sphere with a wavy surface. The drug did not cause any significant change in the cell volume. TFPof 70 μM caused platelet becoming a round ball shape with a spongy-like cell surface. 100 μM TFP caused more than 90% of cells to lyse and to agglutinate with each other. The time courseof morphological change of the TFP-affected platelets showed that the cellsswelled into irregular shape within 2 min. Apparent leakiness of serotonin was observed at 20 μM TFP, while the leakages of both lactate dehydrogenase and acid hydrolase were found at 40 μM TFP. The TFP uptake study showed that platelet was permeable to TFP by simple diffusion. The partition coefficient of TFP in platelet membrane was estimated to be 1 x 104. These results indicate that TFP molecules are solubilized in membrane. The extent in perturbation of the membrane structure depends on concentration of the drug used. (This research was supported by a grant from the National Science Council of the Republic of China.)

Feverfew (Tanacetum parthenium) is used for prophylaxis of migraine and it had been suggested that the plant may have antithrombotic potential. We have prepared extracts from the leaves of feverfew and have demonstrated inhibition of 14C-5HT secretion in platelet-rich plasma induced by the phorbol ester PMA, l-oleoyl-2-acetyl-sn-glycerol (OAG), arachidonic acid, the thromboxane analogue U46619, adrenaline, collagen and ADP. The effects of a solution of parthenolide (an∝-methylenebutyro-lactone isolated from feverfew) were determined in parallel. Both feverfew extract (FE) and parthenolide inhibited 14C-5HT release in a concentration-dependent manner and the effectiveness depended on the nature of the aggregating agent used. Both FE and parthenolide were most effective as inhibitors of the secretion induced by PMA and OAG. When we compared the concentrations of FE and parthenolide which gave 50% inhibition of secretion for all the agents tested, a good correlation was found (r= 0.936). Further studies showed that feverfew extract and parthenolide inhiMt release of β-thromboglobulin from platelets as well as 14C-5HT. FE did not cause liberation of LDH. Inhibition of secretion by FE appears to be irreversible since washing platelets after treatment did not restore secretory activity.The structure of parthenolide suggests that it can alkylate sulphydryl (SH) groups. When agents containing SH groups (e.g. cysteine) were added to FE, anti-secretory activity was reduced. We also obtained a considerable decrease in the number of acid-soluble SH groups in platelets treated with feverfew extract or parthenolide at concentrations which inhibit secretion. However there was a less marked decrease in the number of acid-insoluble SH groups. FE itself does not induce formation of disulphide-linked proteins but such proteins were formed when platelets were activated in the presence of FE, probably as a result of decreased glutathione levels.We conclude that parthenolide or parthenolide-like compounds are responsible for the anti-secretory effects of FE, and that alkylation of sulphydryl groups in platelets may be involved.