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1
Pourkomailian, B. "Osmoregulation in Staphylococcus aureus." Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593300.
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Osmoregulation in Staphylococcus aureus has been studied. Glycine betaine was found to act as an osmoprotectant by stimulating specific growth rate and salt tolerance of osmotically stressed S. aureus cells. The accumulation of this compatible solute was accomplished via two constitutive Na+ dependant transport systems, a high-affinity system (Km = 3μM; Vmax = 26nmol. min-1 mg total protein-1) and a low-affinity system (Km = 133μM; Vmax = 155 nmol. min-1 mg total protein-1). The high-affinity system is specific for glycine betaine and its activity is not greatly stimulated by osmotic pressure. The low-affinity sytem transports proline and proline analogues and its activity is stimulated by increases in external osmolarity. Proline transport is achieved via two similar systems. Through transposon mutagenesis it was demonstrated that the low-affinity glycine betaine transport system and the low-affinity proline transport system are the same system. The low-affinity system is the major system responsible for the accumulation of glycine betaine. This is the more important system for the osmoregulation strategy of S. aureus. All three transport systems have been demonstrated to be subject to feedback regulation. The internal compatible solute concentration dictates the level of activity of the transport systems. A mutant has been isolated that lacks the low-affinity system and the high-affinity proline transport system.
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Paradis, Hilje K. "Osmoregulation in uncontrolled diabetes mellitus." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7568.
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In this thesis we studied the influence of osmotic loading on vasopressin secretion and water intake in experimentally-induced diabetes mellitus, in the insulin deprived state as well as when treated with insulin, in order to investigate whether the osmotic drive for vasopressin release and thirst is altered in the diabetic state. Four dogs were used for the experiments to be reported. They were infused with hypertonic sodium sulfate to investigate the influence of osmotic loading on water intake and vasopressin secretion in the control, insulin-treated diabetic and diabetic conditions. Forty-eight hours of insulin depletion did not produce a change in the basal plasma vasopressin levels, even though there was a significant increase in plasma osmolality. In addition, forty-eight hours of insulin depletion did not alter the sensitivity of the osmoreceptors controlling vasopressin release and thirst. The effect of the diabetic condition on the osmotic threshold is subject to interpretation of the data. If glucose is considered an osmotically effective solute in the diabetic state, there is an upward resetting of the osmostat for vasopressin release and thirst, and a downward or leftward shift of the osmostat when glucose is not considered to be effective osmotically. The results of the present study provide evidence that the osmotic sensitivity of vasopressin release and thirst is not affected by the presence or absence of insulin. However, whether there is a true resetting of the osmostat for vasopressin release and thirst in the diabetic state depends on the assumption mode concerning glucose permeability.
3
Phillips, Elizabeth M. G. "Osmoregulation and thirst in cirrhosis." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308018.
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Evbuomwan, I. O. "Osmoregulation in ovarian hyperstimulation syndrome (OHSS)." Thesis, University of Newcastle upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246609.
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Morgan, John David. "Energetic aspects of osmoregulation in fish." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25121.pdf.
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Brooks, Steven John. "The osmoregulation of selected gammarid amphipods." Thesis, Nottingham Trent University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272439.
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Al-Hadi, T. A. A. "Osmoregulation in the crab Carcinus maenas." Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374249.
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Hu, Chien-an Andy. "Osmoregulation and proline biosynthesis in plants /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487843688956923.
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Guo, Ruoquan. "Osmoregulation in Australian bass, Macquaria novemaculeata." Thesis, Queensland University of Technology, 1997.
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10
Kaenjak, Anisa Wilkinson Brian J. "Osmoregulation in coagulase-positive and coagulase-negative staphylococci." Normal, Ill. Illinois State University, 1993. http://wwwlib.umi.com/cr/ilstu/fullcit?p9416856.
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Thesis (Ph. D.)--Illinois State University, 1993.Title from title page screen, viewed March 6, 2006. Dissertation Committee: Brian J. Wilkinson (chair), Herman E. Brockman, H. Tak Cheung, Radheshyam K. Jayaswal, Robert L. Preston. Includes bibliographical references (leaves 162-176) and abstract. Also available in print.
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Campbell, Peter J. "Osmoregulation in the prawn Palaemon longirostris (Caridea, Palaemonidae)." Thesis, University of Plymouth, 1988. http://hdl.handle.net/10026.1/2644.
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Salinity tolerance, and several aspects of osmoregulation, ionic regulation and permeability were measured for Palaemon longirostris at three temperatures (4, 12 & 20°C). Influence of ontogenetic stage on salinity tolerance and osmoregulation was investigated by testing separately individuals sorted, using carapace length, into 'small' (10-18mm), 'medium' (18-24mm), 'large' (>24mm) and 'ovigerous' (>24mm) size groupings. Effect of seasonal acclimatization on salinity tolerance and osmoregulation was taken into account by comparing responses of summer- with winter-collected prawns. Irrespective of temperature and size, summer Palaemon longirostris were extremely euryhaline and had >90% survival in various salinities from 0.5-34 º/oo . For summer prawns, survival in 43 º/oo was reduced, particularly at 4°C. Salinity tolerance of winter prawns was generally less than that of summer individuals, this difference being marked at salinity extremes in combination with low temperature. Over the salinity range 0.5-34 º/oo , prawns were very efficient hyper-hypo-osmoregulators at each temperature. At 43 º/oo, blood osmolalities tended towards the isosmotic, indicating that osmoregulation was breaking down. There was no clear effect of prawn size or season on osmoregulation, however, low temperature appeared to be disruptive. Transfer of prawns from 14 º/oo to either 5 º/oo or 34 º/oo, and from 1 º/oo to 34 º/oo, resulted in a new steady blood osmolality within 6-12h. Transfer from 34 º/oo to 1 º/oo , caused blood osmolality to drop significantly within 12h, and a new equilibrium was not reached until 72h. The inorganic ions sodium, chloride, potassium, calcium and magnesium accounted for >94% of total blood osmolality over the salinity range 0.5-34 º/oo . There was no consistent effect of temperature on the regulation of these ions.
12
Perrott, M. N. "The Renin-Angiotensin System and osmoregulation in fish." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233470.
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Rosendale, Andrew J. "Importance of Facilitative Urea Transporters in Anuran Osmoregulation." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1313089167.
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Vijaranakul, Uriwan Jayaswal Radheshyam K. "Osmoregulation in staphylococcus aureus characterization of NaCl-sensitive mutants /." Normal, Ill. Illinois State University, 1997. http://wwwlib.umi.com/cr/ilstu/fullcit?p9804938.
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Thesis (Ph. D.)--Illinois State University, 1997.Title from title page screen, viewed June 13, 2006. Dissertation Committee: Radheshyam K. Jayaswal (chair), Brian J. Wilkinson, Mathew J. Nadakavukaren, Herman E. Brockman, Alan J. Katz. Includes bibliographical references and abstract. Also available in print.
15
Park, Simon Fearon. "The biochemistry and genetics of osmoregulation in Escherichia coli." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254420.
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Armstrong-Buisseret, Lindsay Katherine. "The biochemistry and genetics of osmoregulation in Staphylococcus aureus." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387279.
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Wood, Nicholas James. "The role of proline in osmoregulation by a streptomycete." Thesis, University of Warwick, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319812.
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18
Martin, Lincoln. "Growth Hormone Mediated Regulation of Osmoregulation in Euryhaline Teleosts." Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/27486.
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Within the multitude of fish species that exist on our planet, there are a certain number that possess the unique ability to live in both freshwater (FW) and seawater (SW) environments. This ability, known as euryhalinity, is limited to a relatively small number of species, thus making it a prime target for scientific research into osmoregulation, due to the uniqueness of this ability. It has been shown previously that growth hormone (GH) plays an important role in regulating this ability, and in this work, Atlantic salmon (Salmo salar) and Rainbow trout (Oncorhynchus mykiss) were used as models to examine the expression of specific osmoregulatory genes in response to SW transfer and GH exposure, and to examine the signaling mechanisms used by GH to facilitate any changes. We found that GH utilizes specific cell signaling pathways to facilitate the transition between FW and SW in both Rainbow trout and Atlantic salmon.
19
Grierson, Christal Elizabeth. "The role of angiotensin II in osmoregulation in teleost fish." Thesis, University of St Andrews, 1991. http://hdl.handle.net/10023/15054.
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An osmoregulatory role for angiotensin II was investigated in the euryhaline European eel Anguilla anguilla L., plaice (Pleuronectes platessa) and dab (Limanda limanda). 1. Ile5 - and val5 -AII increased blood pressure in all species. Ile5 -AII produced a greater effect than val5 - AII, at equal concentrations, in eels, however in plaice and dab, this trend was reversed. Papaverine reduced blood pressure, followed by recovery to control in all cases. 2. Both AII sequences increased drinking rates except ile5 -AII in dab. ile5 -AII again proved more potent than val5-AII in eels and val5 - was greater than ile5- AII in flatfish. Papaverine increased drinking in all species. Captopril had no effect on eel or dab drinking rates, but reduced those of plaice. 3. 1.0nM and 10.0nM AII increased ANP release from isolated eel myocytes, except from FW atria. At 1.0nM, ventricular release was greater than atrial, however at 10.0nM, AII ANP secretion was similar in both types of myocyte. In all cases ANP release was greater from SW than FW myocytes. 4. Tissue/plasma ratios revealed greatest binding in SW eel liver. Tissue receptor specific binding was also greatest in FW eel liver membranes, however in SW tissues gill was slightly greater than liver. A FW eel liver membrane radioreceptor assay was developed. Binding was optimal at 22°C, 25mM calcium, protein concentration of 700ug, 125I-AII concentration of 25pM and an incubation period of 60 minutes. 6. Initial FW eel liver binding studies indicated two receptor classes with Kd=1. 5x10-11M and 2.46x10-10. However subsequent studies reveal Kd =3.31x10-8M in FW liver and Kd=1.09x10-7M in SW liver preparations. 7. 125I-ile5 -AII produced greater binding than 125I-val5 -AII in eel liver preparations. 125I-val5 -AII produced greater binding in flatfish membranes. Investigations of 125I-ile5 -AII displacement from FW eel liver membranes revealed peptide potencies in the following order, sar-AII > ile5-AII > 5-8AII > ile5-AI > val5-AI > ile4-AIII > val4-AIII > bradykinin > 1-4AII.
20
Tierney, Mary Louise. "Endocrine control of osmoregulation in the euryhaline eel, Anguilla anguilla." Thesis, University of St Andrews, 1993. http://hdl.handle.net/10023/14936.
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1. Groups of eels, Anguilla anguilla, were adapted from freshwater (FW) to seawater, (SW) for periods of 90 - 300 mins. maximum (acute transfer), 0 - 7 days (chronic transfer), or for more than 14 days (longterm seawater transfer). 2. Acute SW transfer led to a decline in blood pressure, an elevation in plasma osmolality and chloride concentration, an immediate "reflex" drinking response and a non-significant increase in plasma angiotensin II (AH) concentration. 3. Administration of papaverine to FW adapted eel caused hypotension, with subsequent recovery of blood pressure, elevation in the drinking rate and plasma All concentration, and a decline in plasma osmolality. Captopril alone had no effect on blood pressure, drinking rate, osmolality or All concentration, but was successful in partially blocking the papaverine-induced blood pressure recovery and increase in AH concentration, with complete inhibition of the drinking. 4. Administration of papaverine to SW adapted eel caused hypotension, with partial recovery of blood pressure, increased drinking rate, plasma All concentration and plasma osmolality. Captopril alone caused a sustained decrease in blood pressure, inhibition of basal SW drinking and a reduction in plasma All concentration, with change in plasma osmolality. Administration of captopril prior to papaverine was successful in partially blocking the papaverine-induced recovery in blood pressure, increase in drinking, plasma All concentration, and plasma osmolality. 5. Chronic SW transfer led to a general decline in blood pressure, increase in plasma electrolyte concentration, elevation in drinking rate after 4-5 days, an increase in plasma All concentration, and a rise in Na+-K+-ATPase, all leading to long term SW values. 6. Plasma arginine vasotocin concentrations were unchanged in long term-FW and SW adapted fish, with a small transitory rise after 4 days in SW. 7. Cortisol plasma concentrations were similar in both long term- FW and SW- adapted fish, with a rise observed 1 day after transfer to SW. 8. Metabolic clearance rates (MCR) and blood production rates (BPR) were significantly elevated in long term SW adapted fish and during chronic SW adaptation, compared to the FW levels. Binding of 125I-AII to gill (filaments and lamellae), brain (cerebellum and medulla oblongata), kidney (head and caudal), and liver was observed in long term FW and SW adapted fish and 6 day SW transfer animals, with significant increase observed in binding in the caudal kidney and cerebellum and medulla oblongata between the FW group and 6 day SW transfer group.
21
Veillette, Philip A., and n/a. "Osmoregulatory physiology of salmon intestine : developmental and endocrine regulation." University of Otago. Department of Zoology, 2005. http://adt.otago.ac.nz./public/adt-NZDU20070315.163047.
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The parr-smolt transformation is a life-history strategy that has evolved in salmon to prepare migratory juveniles for oceanic survival. A necessary adjustment for homeostasis is an increase in the uptake of fluid by the intestine, which will continuously replace the loss of body water in a salty environment. Vertebrate corticosteroids regulate hydromineral balance. Cortisol mediates adaptive changes in fish intestine, but much remains to be learned about the sites of action and participation of other endocrine signals.
To begin, I asked whether the numerous extensions of the salmonid intestine, pyloric caeca, are osmoregulatory sites? Fluid uptake rate and Na⁺, K⁺-ATPase activity (ion pump that drives solute and water transport) were measured on isolated caeca of chinook salmon (Oncorhynchus tshawytscha) after 9-10 days or 6 months residence in seawater, following transfer from fresh water. Na⁺, K⁺- ATPase and fluid uptake were concurrently elevated after seawater adaptation. Short-term cortisol implants in the peritoneal cavity of freshwater salmon increased circulating cortisol to high physiological concentrations and caused similar elevations in Na⁺, K⁺-ATPase activity and fluid uptake.
Tissue culture of intestine from freshwater-adapted sockeye salmon (Oncorhynchus nerkca) was used to assess potential direct effects of cortisol. Cortisol exposure maintained Na⁺, K⁺-ATPase activity above that of control explants and, in some cases, similar to levels before culture. A response was specific for the corticoid cortisol, elicited within 2 days, and dose-dependent over a physiological range.
Next, seasonal changes in endogenous Na⁺, K⁺-ATPase activity and tissue responsiveness to cortisol were determined for chinook salmon maintained in fresh water. There were pronounced increases in endogenous enzyme activity in summer for both intestinal regions, in underyearlings and yearlings. In pyloric caeca, a significant positive response of Na⁺, K⁺-ATPase activity to cortisol, in vitro, was restricted to the months preceding increases in endogenous Na⁺, K⁺-ATPase and the month afterward.
Several experiments were conducted in which chinook salmon were implanted with ovine growth hormone (5 (mu)g/g body weight), cortisol (50 (mu)g/g body weight), or both. Cortisol implants significantly elevated plasma cortisol concentrations and stimulated Na⁺, K⁺-ATPase activity in either caeca or posterior intestine, or both, after 7 and 14 days. Although growth hormone increased plasma cortisol concentrations after 14 days, no interaction occurred between cortisol and growth hormone on Na⁺, K⁺-ATPase activity.
The effect of insulin-like growth factor I on Na⁺, K⁺-ATPase activity was examined in tissue-cultured intestine of chinook salmon. Prior to culture, salmon were implanted with or without ovine growth hormone (5 (mu)g/g body weight) for 7 days. Intestinal explants were then exposed to recombinant human insulin-like growth factor I (rhIGF-I) for 3 or 6 days in culture. In caeca, rhIGF-I (0.01-1.0 (mu)g/ml) significantly maintained Na⁺, K⁺-ATPase activity above controls (0 (mu)g rhIGF-I /ml) in a dose-dependent manner, regardless of whether the fish were pretreated with growth hormone in vivo. The posterior intestine was not responsive to rhIGF-I.
These results demonstrate pyloric caeca are a major osmoregulatory site, evidenced by tissue responsiveness to cortisol (and IGF-I) and stimulation of functional changes indicative of parr-smolt transformation.
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Gray, C. J. "Renal and cardiovascular effects of angiotensin II in the rainbow trout." Thesis, University of Hull, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375609.
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李詠欣 and Wing-yan Lee. "Regulation of genes involved in cellular osmotic regulation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31223011.
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Manison, Nicholas Frederick. "Ion channel activity and signalling in the Fucus rhizoid." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285958.
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Schamber, Kristopher Cody. "Tachykinin NK3R protein levels in the PVN of rats following an osmotic challenge." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1407489691&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Bolin, Greta M. Burggren Warren W. "Incubation humidity as an environmental stressor on the osmoregulatory developmental program of the chicken, Gallus gallus domesticus." [Denton, Tex.] : University of North Texas, 2009. http://digital.library.unt.edu/permalink/meta-dc-11055.
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Lee, Wing-yan. "Regulation of genes involved in cellular osmotic regulation /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21301165.
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El, Missiry M. A. "Membrane sulphydryl groups in the control of water and ion balance in the red blood cell of the eel Anguilla anguilla L." Thesis, University of Bath, 1986. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374600.
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Rönsch, Hendrik. "Untersuchungen zum Einfluss der Osmoregulation auf die Aminosäureproduktion mit Corynebacterium glutamicum." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961195681.
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Fridman, Sophie. "The ontogeny of osmoregulation in the Nile tilapia (Oreochromis niloticus L.)." Thesis, University of Stirling, 2011. http://hdl.handle.net/1893/3080.
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In recent times, diminishing freshwater resources, due to the rapidly increasing drain of urban, industrial and agricultural activities in combination with the impact of climate change, has led to an urgent need to manage marine and brackish water environments more efficiently. Therefore the diversification of aquacultural practices, either by the introduction of new candidate species or by the adaptation of culture methods for existing species, is vital at a time when innovation and adaptability of the aquaculture industry is fundamental in order to maintain its sustainability. The Nile tilapia (Oreochromis niloticus, Linnaeus, 1758), which has now been spread well beyond its natural range, dominates tilapia aquaculture because of its adaptability and fast growth rate. Although not considered to be amongst the most salt tolerant of the cultured tilapia species, the Nile tilapia still offers considerable potential for culture in low-salinity water. An increase in knowledge of the limits and basis of salinity tolerance of Nile tilapia during the sensitive early life stages and the ability to predict responses of critical life-history stages to environmental change could prove invaluable in improving larval rearing techniques and extend the scope of this globally important fish species. The capability of early life stages of the Nile tilapia to withstand variations in salinity is due to their ability to osmoregulate, therefore the ontogeny of osmoregulation in the Nile tilapia was studied from spawning to yolk-sac absorption after exposure to different experimental conditions ranging from freshwater to 25 ppt. Eggs were able to withstand elevated rearing salinities up to 20 ppt, but transfer to 25 ppt induced 100% mortality by 48 h post-fertilisation. At all stages embryos and larvae hyper-regulated at lower salinities and hypo-regulated at higher salinities, relative to the salinity of the external media. Osmoregulatory capacity increased during development and from 2 days post-hatch onwards remained constant until yolk-sac absorption. Adjustments to larval osmolality, following abrupt transfer from freshwater to experimental salinities (12.5 and 20 ppt), appeared to follow a pattern of crisis and regulation, with whole-body osmolality for larvae stabilising at c. 48 h post-transfer for all treatments, regardless of age at time of transfer. Age at transfer to experimental salinities (7.5 – 20 ppt) had a significant positive effect on larval ability to osmoregulate; larvae transferred at 8 dph maintained a more constant range of whole body osmolality over the experimental salinities tested than larvae at hatch. Concomitantly, survival following transfer to experimental salinities increased with age. There was a significant effect (GLM; p < 0.05) of salinity of incubation and rearing media on the incidence of gross larval malformation that was seen to decline over the developmental period studied. It is well established that salinity exerts a strong influence on development and growth in early life stages of fishes therefore the effects of varying low salinities (0 - 25 ppt) on hatchability, survival, growth and energetic parameters were examined in the Nile tilapia during early life stages. Salinity up to 20 ppt was tolerable, although reduced hatching rates at 15 and 20 ppt suggest that these salinites may be less than optimal. Optimum timing of transfer of eggs from freshwater to elevated salinities was 3-4 h post-fertilisation, following manual stripping and fertilisation of eggs, however increasing incubation salinity lengthened the time taken to hatch. Salinity was related to dry body weight, with larvae in salinities greater than 15 ppt displaying, at hatch, a significantly (GLM: p < 0.05) lower body weight but containing greater yolk reserves than those in freshwater or lower salinities. Survival at yolk-sac absorption displayed a significant (GLM; p < 0.05) inverse relationship with increasing salinity and mortalities were particularly heavy in the higher salinities of 15, 20 and 25 ppt. Mortalities occurred primarily during early yolk-sac development yet stabilised from 5 dph onwards. Salinity had a negative effect on yolk absorption efficiency (YAE). Salinity-related differences in oxygen consumption rates were not detectable until 3 days post-hatch; oxygen consumption rates of larvae in freshwater between days 3 – 6 post-hatch were always significantly higher (GLM p < 0.05) than those in 7.5, 15, 20 and 25 ppt, however, on day 9 post-hatch this pattern was reversed and freshwater larvae had a significantly lower QO2 than those in elevated salinities. Salinity had a significant inverse effect on larval standard length, with elevated salinities producing shorter larvae from hatch until 6 dph, after which time there was no significant differences between treatments. Salinity had a significant effect on whole larval dry weight, with heavier larvae in elevated salinities throughout the yolk-sac period (GLM; p < 0.05). The ability of the Nile tilapia to withstand elevated salinity during early life stages is due to morphological and ultrastructural modifications of extrabranchial mitochondria-rich cells (MRCs) that confer an osmoregulatory capacity before the development of the adult osmoregulatory system. A clearly defined temporal staging of the appearance of these adaptive mechanisms, conferring ability to cope with varying environmental conditions during early development, was evident. Ontogenetic changes in MRC location, 2-dimensional surface area, density and general morphological changes were investigated in larvae incubated and reared in freshwater and brackish water (15 ppt) from hatch until yolk-sac absorption using Na+/K+-ATPase immunohistochemistry with a combination of microscope techniques. The pattern of MRC distribution was seen to change during development under both treatments, with cell density decreasing significantly on the body from hatch to 7 days post-hatch, but appearing on the inner opercular area at 3 days post-hatch and increasing significantly (GLM; p < 0.05) thereafter. Mitochondria-rich cells were always significantly (GLM; p < 0.05) denser in freshwater than in brackish water maintained larvae. In both freshwater and brackish water, MRCs located on the outer operculum and tail showed a marked increase in size with age, however, cells located on the abdominal epithelium of the yolk-sac and the inner operculum showed a significant decrease in size (GLM; p < 0.05) over time. Mitochondria-rich cells from brackish water maintained larvae from 1 day post-hatch onwards were always significantly larger (GLM; p < 0.05) than those maintained in freshwater. Preliminary scanning electron microscopy studies revealed structural differences in chloride cell morphology that varied according to environmental conditions. Mitochondria-rich cell morphology and function are intricately related and the plasticity or adaptive response of this cell to environmental changes is vital in preserving physiological homeostasis and contributes to fishes’ ability to inhabit diverse environments. Yolk-sac larvae were transferred from freshwater at 3 days post-hatch to 12.5 and 20 ppt and sampled at 24 and 48 h post-transfer. The use of scanning electron microscopy allowed a quantification of MRC, based on the appearance and surface area of their apical crypts, resulting in a reclassification of ‘sub-types’ i.e. Type I or absorptive, degenerating form (surface area range 5.2 – 19.6 μm2), Type II or active absorptive form (surface area range 1.1 – 15.7 μm2), Type III or differentiating form (surface area range 0.08 – 4.6 μm2) and Type IV or active secreting form (surface area range 4.1 – 11.7 μm2). In addition, the crypts of mucous cells were discriminated from those of MRCs based on the presence of globular extensions and similarly quantified.
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Pichereau, Vianney. "Osmoregulation chez sinorhizobium meliloti ; diversite des modes d'action des osmoprotecteurs exogenes." Rennes 1, 1998. http://www.theses.fr/1998REN10182.
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La bacterie du sol sinorhizobium meliloti adopte une reponse d'osmoprotection par des solutes exogenes tout a fait atypique. Cette bacterie peut utiliser en tant qu'osmoprotecteur l'ectoine, le saccharose, la glycine betaine (gb) ou le dimethylsulfoniopropionate (dmsp). Cependant, a l'exception du dmsp, s. Meliloti a la possibilite de cataboliser activement ces molecule, meme lorsqu'elle est soumise a contrainte hyperosmotique. Ainsi, l'ectoine et le saccharose ne sont a aucun moment accumules par la bacterie, ces molecules n'agissent donc pas d'elles-memes, mais permettent a la bacterie d'augmenter de facon spectaculaire les teneurs intracellulaires en osmolytes endogenes. La gb apparait quant a elle accumulee transitoirement par la bacterie osmotiquement stressee. 31 proteines de stress osmotique ont ete mises en evidence, et groupees en trois classes, en fonction du caractere precoce ou tardif, et du caractere transitoire ou durable de leur induction osmotique. Les sequences n-terminales de deux d'entre-elles ont ete obtenues. La premiere montre des homologies significatives avec ycif, proteine d'escherichia coli de fonction inconnue. La seconde a ete identifiee sans ambiguite comme etant la superoxyde dismutase, enzyme essentielle dans le metabolisme du stress oxydatif des organismes vivants. Par ailleurs, les resultats obtenus montrent que les osmoprotecteurs non accumules (ectoine, saccharose) stimulent la synthese de certaines proteines de stress tandis qu'a l'inverse, les osmoprotecteurs accumules (gb, dmsp) contribuent a reduire la synthese de ces proteines. Les resultats presentes suggerent fortement la coexistence de deux voies distinctes d'osmoprotection par des solutes exogenes chez s. Meliloti. Les possibles implications ecophysiologiques de ces resultats sont egalement discutees.
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Daloso, Danilo de Menezes. "Role of sucrose for tobacco guard cell osmoregulation: osmolyte or substrate?" Universidade Federal de Viçosa, 2013. http://www.locus.ufv.br/handle/123456789/9919.
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Fundação de Amparo à Pesquisa do Estado de Minas Gerais
A papel da sacarose em CG foi investigado através da caracterização de plantas de Tabaco transgênicas superexpressando a isoforma 3 do gene sacarose sintase (NtSuSy3) sob controle do promotor KST1 bem como por experimentos de análise de fluxo metabólico utilizando fragmentos epidérmicos enriquecidos com CG (EF) durante abertura estomática induzida pela luz. As plantas NtSuSy3 mostraram aumentos na condutância estomática, fotossíntese e nas taxas de transpiração a nível foliar e de planta inteira. As alterações observadas no metabolismo de CG das plantas transgênicas são discutidas no texto. Observou-se uma redução nos níveis de sacarose em diferentes experimentos de abertura estomática induzida pela luz, enquanto que os níveis de sacarose no meio não foram alterados, sugerindo que a sacarose foi degradada no simplasto de CG. A análise via LC-qTOF-MS de experimentos com EF submetidos a NaH13C03 durante abertura estomática induzida pela luz mostraram um enriquecimento de 13 C em sacarose, malato, fumarate e glutamins. As possíveis funções exercidas por esses metabólitos são discutidas no texto. Em conjunto, os dados desse trabalho sugerem que a degradação da sacarose no simplasto de CG pode ser um mecanismo importante para a abertura estomática de Tabaco induzida pela luz.
A characterization of transgenic tobacco plants overexpressing potato sucrose synthase 3 gene (NtSuSy3) under control of KST1 promoter was performed in order to analyze the role of sucrose metabolism on GC osmoregulation. Also, we performed a metabolic flux analysis in guard cell enriched epidermal fragment (EF) of Nicotiana tabacum in order to investigate changes in GC metabolism during stomatal aperture light-induced. NtSuSy3 plants showed higher stomatal conductance, transpiration rate, whole plant transpiration, and net photosynthetic rate than wild type (WT). Several changes in GC metabolism were observed in transgenic plants are discussed in the text. In different stomatal aperture light-induced experiments, it was observed a decrease in sucrose content, while no changes were detected in the sugar content in the medium; suggesting that the sugars decreased observed is due to breakdown and not efflux of GC. Using a feeding strategy in EF submitted to NaH13C03 followed by LC-qTOF-MS analysis, a 13 C-enrichment in sucrose, malate, fumarate and glutamine were observed. The possible function of these metabolites for GC osmoregulation are discussed in the text. Taken together, the data showed here provide evidence for another role of sucrose for GC osmoregulation. Our data suggest that sucrose breakdown, not just sucrose accumulation, can be performed to induce stomatal opening in tobacco.
O autor não aprersentou título em portuguẽs. A data de aprovação foi aleatória devido não constar na tese. Tese enviada pela secretaria do curso por e-mail, em 28-03-17.
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Ulrich, Paul N. "Sensitivity of molluscs to temperature, osmotic shock, and infection by protozoa implications for temperate and polar bivalves /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 267 p, 2007. http://proquest.umi.com/pqdlink?did=1251900721&Fmt=7&clientId=79356&RQT=309&VName=PQD.
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Lee, Hoi-yi Vien, and 李凱怡. "The role of secretin in mediating the osmoregulatory functions of angiotensin II." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43703707.
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Lee, Hoi-yi Vien. "The role of secretin in mediating the osmoregulatory functions of angiotensin II." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43703707.
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Schoorlemmer, Gerhardus H. M. "Body fluid regulation during water deprivation, role of solute balance in osmoregulation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24038.pdf.
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Berk, Benjamin-Andreas. "Brain-derived neurotrophic factor-induzierte neuroprotektive Osmoregulation der Müller-Gliazelle der Rattenretina." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-170385.
Full textAbstract:
Einleitung: Die Ausbildung eines Netzhautödems ist eine Hauptursache für die Verschlechterung des Sehvermögens bei ischämisch-hypoxischen und inflammatorischen Netzhauterkrankungen. Neben der erhöhten Permeabilität der Blut-Retina-Schranke trägt eine Wasserakkumulation in Netzhautzellen zur Ausbildung eines Netzhautödems bei. Müllerzellen regulieren die retinale Ionen- und Osmohomöostase, indem sie einen transzellulären Ionen- und Wassertransport vermitteln. Zudem kontrollieren Müllerzellen die Größe des Extrazellularraumes, indem sie bei neuronaler Aktivität eine Zellkörperschwellung – ausgelöst durch eine Verkleinerung der extrazellulären Osmolarität – verhindern. Unter pathologischen Bedingungen ist die Volumenregulation gestört, sodass Müllerzellen bei Hypoosmolarität anschwellen. Diese Müllerzellschwellung und eine Glutamat-induzierte Schwellung retinaler Neurone tragen zur Ausbildung eines zytotoxischen Netzhautödems bei. Neuroprotektive Faktoren wie BDNF (brain-derived neurotrophic factor) und bFGF (basic fibroblast growth factor) stimulieren das Überleben retinaler Neurone und verzögern so die retinale Degeneration. Zielstellung: Es war zu zu ermitteln, ob BDNF die zytotoxische Schwellung von Müller- und Bipolarzellen der Rattennetzhaut verhindert. Material und Methoden: Es wurden Netzhautschnitte und isolierte Müller- und Bipolarzellen von 55 adulten Long-Evans-Ratten (durchschnittlich 8-15 Zellen pro Versuchsreihe) verwendet. Eine osmotische Schwellung von Müller- und Bipolarzellen wurde durch eine Superfusion der Schnitte oder der Zellen mit einer 60%igen hypoosmolaren Lösung in Ab- oder Anwesenheit von Bariumchlorid induziert. Die maximale Querschnittsfläche von Müller- und Bipolarzellsomata wurde vor und nach einer vierminütigen Superfusion mit einem konfokalen Laserscanningmikroskop aufgezeichnet. Die nach der Superfusion ermittelte Querschnittsfläche wurde zu den anfänglich gemittelten Kontrollwerten in Beziehung gesetzt und prozentual als Mittelwert mit Standardfehler bestimmt. Mit Hilfe des Prism-Statistikprogramms (Graphpad) wurden die Ergebnisse mittels einem one-way ANOVA Test und einem nachfolgenden Bonferroni\'s multiple comparison Test sowie durch einen Mann-Whitney U Test statistisch analysiert. Ergebnisse: Bei Anwesenheit von BDNF wurde die osmotische Schwellung von Müllerzellen konzentrationsabhängig sowohl in Netzhautschnitten als auch in isolierten Zellen inhibiert. Ebenso inhibierte BDNF konzentrationsabhängig die Schwellung von Bipolarzellen in Netzhautschnitten, jedoch nicht in isolierten Zellen. In Schnitten von postischämischen Netzhäuten bewirkte BDNF eine Schwellungsinhibition von Müllerzellen, nicht aber von Bipolarzellen. Mit pharmakologischen Blockern wurde die durch BDNF induzierte Signalkaskade untersucht. Die BDNF-Schwellungsinhibition von Müllerzellen wurde durch eine Aktivierung von TrkB bewirkt. Die TrkB-Aktivierung führte in Müllerzellen zu einer Transaktivierung von FGF-Rezeptoren sowie zu einer Aktivierung einer glutamatergen-purinergen Signalkaskade, von der bekannt ist, dass sie die osmotische Müllerzellschwellung unterdrückt. Da bFGF die osmotische Müllerzellschwellung inhibiert, wird die Transaktivierung der FGF-Rezeptoren wahrscheinlich durch eine BDNF-induzierte Freisetzung von bFGF aus Müllerzellen vermittelt. Die Ergebnisse lassen vermuten, dass BDNF indirekt auf Bipolarzellen wirkt, indem es eine Freisetzung von Faktoren wie bFGF aus Müllerzellen induziert. Schlussfolgerungen: Die Schwellungsinhibition von Müller- und Bipolarzellen könnte ein neuroprotektiver Mechanismus von BDNF in der Netzhaut darstellen. Während BDNF direkt TrkB auf Müllerzellen aktiviert, ist die Inhibition der Bipolarzellschwellung indirekt und durch die Ausschüttung von glialen Faktoren wie bFGF vermittelt. Der Verlust des Effektes von BDNF auf die Bipolarzellschwellung in ischämischen Netzhäuten könnte darauf zurückzuführen sein, dass gliotische Müllerzellen keine glialen Faktoren mehr in Reaktion auf BDNF freisetzen. Der Verlust des glialen Einflusses auf die Bipolarzellvolumenhomöostase könnte zur Neurodegeneration in der ischämischen Netzhaut beitragenIntroduction: Tissue edema is a major blinding complication of ischemic-hypoxic and inflammatory retinal diseases. In addition to the hyperpemeability of the blood-retinal barrier, water accumulation in retinal cells resulting in cellular swelling may contribute to the development of retinal edema. Müller glial cells regulate the retinal ion and water homeostasis by allowing transcellular ion and water fluxes. During neuronal activity Müller cells control the extracellular space volume by autocrine inhibition of cellular swelling caused by the reduction of extracellular osmolarity. However, under pathological conditions, Müller cells are not capable to regulate their volume so that they swell rapidly under hypoosmolarity. The osmotic swelling of Müller glial cells and the glutamate induced swelling of retinal neurons contribute to the development of cytotoxic retinal edema. Various neuroprotective factors including brain-derived neurotrophic factor (BDNF) and basic fibroblast growth factor (bFGF) stimulate the survival of retinal neurons and thus delay the retinal degeneration. Objective: The objective of the study is to determine whether BDNF inhibits the osmotic swelling of Müller and bipolar cells of the rat retina. Material and Methods: Retinal slices and freshly isolated Müller and bipolar cells of 55 adult Long-Evans rats (in average 8-15 cells per trial) were used. Osmotic swelling of Müller and bipolar cells was induced by superfusion of retinal slices or isolated cells with a 60% hypoosmotic extracellular solution in the absence or presence of barium chloride. The maximal cross-sectional area of Müller and bipolar cell somata was recorded before and after a four minute-long superfusion by using a laser scanning microscope. To determine the extent of cell soma swelling, the cross-sectional area of the cell body extent after superfusion was related to the former averaged cross-sectional area. Results were given as means with standard error as percent values. Statistical analysis was made with Prism (Graphpad) and the significance was determined by the One-way ANOVA test followed by Bonferroni\'s multiple comparison test and the Mann-Whitney U test, respectively. Results: We found that BDNF inhibits dose-depending the osmotic swelling of Müller cells in retinal slices and of isolated cells. BDNF also inhibited dose-depending the osmotic swelling of bipolar cells in retinal slices; however, it did not inhibit the osmotic swelling in isolated bipolar cells. In slices of postischemic retinas, BDNF inhibited the swelling of Müller cells but not the swelling of bipolar cells. The BDNF induced signal transduction cascade was examined by simultaneous administration of blocking agents with the receptor agonists in the hypoosmotic solution. The BDNF-induced inhibition of the osmotic Müller cell swelling was mediated by activation of TrkB. Activation of TrkB in Müller cells results in transactivation of FGF receptors and in an activation of a glutamatergic-purinergic signal transduction cascade which is known to inhibit the osmotic swelling of the cells. Since bFGF also inhibits the osmotic swelling of Müller cells, it can be assumed that the transactivation of FGF receptors is mediated by a BDNF-induced release of bFGF from Müller cells. The results suggest that the effect of BDNF on bipolar cells is indirect by inducing a subsequent release of glial factor from Müller cells such as bFGF. Conclusion: The results show that BDNF inhibits the osmotic swelling of Müller and bipolar cells. The inhibition of cytotoxic cell swelling may contribute to the neuroprotective action of BDNF in the retina. While BDNF acts directly in Müller cells, the BDNF-induced inhibition of the bipolar cell swelling is indirect and mediated by the release of glial factors such as bFGF from Müller cells. The abrogation of the BDNF-induced inhibition of the osmotic bipolar cell swelling in the postischemic retina could be explained with the impairment of the release of glial factors by Müller cells. The abrogation of the Müller cell-mediated regulation of the bipolar cell volume could contribute to the neuronal degeneration in the ischemic retina
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Birrell, Lynne M. "Osmoregulation in glass eels and elvers of the European eel, Anguilla anguilla." Thesis, University of St Andrews, 1999. http://hdl.handle.net/10023/14934.
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Glass eels of the European eel migrate from coastal waters inland to freshwater as part of the catadromous lifecycle. The osmotic challenge faced at this time is augmented by their large surface area to volume ratio, and by the fact that the migration may only be completed after several attempts, due to the effects of tide and river flow. Glass eels and elvers developed normally when maintained in waters of differing salinity over a six month period. Drinking rates increased with environmental acclimation salinity (from 0.072 +/- 0.023 mul/g/h to 0.698 +/- 0.099 mul/g/h in FW and SW respectively), and freshwater acclimated fish exhibited a rapid drinking response upon contact with seawater. These accounts of dipsogenic behaviour are similar to those previously reported for adult eels. Results obtained from determinations of branchial Na+K+ATPase activities were more equivocal. Only after nearly five months were activities higher in SW (508.52 +/- 99.76 nmoles/Spairs gills/h) as compared to FW fish (151.65 +/- 8.9 nmoles/5pairs gills/h). Following the transfer of FW acclimated fish to SW there was a trend towards increased Na+K+ATPase activity after seven days post-transfer, which reached a significant peak after two months post-transfer. A transient increase in whole body cortisol content was noted following the transfer of fish from freshwater (388.02 + 90.38 pg/g) to seawater (6268.44 +/- 773.14 pg/g). However, it was not possible to ascertain that this was due to a direct effect of environmental salinity change. There were no clear changes in interrenal cell morphology between salinity groups, although the cells did appear reduced in size with time, regardless of environmental salinity. Total body Na+ content increased with time, and was higher in SW (58.66 +/- 1.66 mumoles/g) as compared to FW reared fish (44.85 +/-1.01 mumoles/g).
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Tervonen, V. (Virpi). "Salmon cardiac peptide (sCP): a new model for natriuretic peptide biology." Doctoral thesis, University of Oulu, 2001. http://urn.fi/urn:isbn:9514264932.
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Abstract
Natriuretic peptide hormones secreted from the heart are important in
maintaining
the volume and electrolyte balance and in regulation of blood pressure. The
secretion of natriuretic peptides is stimulated by myocyte stretch and paracrine
factors. However, the intracellular actions of these stimuli and the cellular and
molecular mechanisms involved in the processing and secretion of natriuretic
peptides are still largely unknown. In this study, a new model for studies of the
natriuretic peptide system was developed using a novel natriuretic peptide from
salmon.
Salmon (Salmo salar) maintains its water and salt
homeostasis despite the volume gain in fresh water and electrolyte gain in sea
water. Thus, salmon is an ideal model to study the mechanisms regulating the
extracellular volume and salt balance, like natriuretic peptides. Furthermore,
comparative studies revealing the common characteristics in phylogenetically
distinct species suggest the importance of these factors in the regulation of the
natriuretic peptide system.
A novel natriuretic peptide, salmon cardiac peptide (sCP), was cloned from
salmon
heart. Distribution of sCP was studied in a variety of vertebrates and its
physiological effects were examined in in vitro and
in vivo experiments in salmon and rats. The storage and
release of sCP was studied using a salmon ventricle perfusion system and by
analysing the molecular forms of stored and secreted forms. Factors modulating
the secretion and circulating concentration of sCP, and cardiac peptide and sCP
mRNA level in salmon were examined as well.
The biosynthesis of sCP is strictly restricted to the heart. sCP is stored
in
myocytes in the prohormone form, while the secreted form is a 29-amino acid
peptide in salmon. Mechanical load on isolated salmon ventricle and volume
overload in intact salmon induced a rapid release of sCP. Exposure to
hyperosmotic environment decreased the plasma sCP level. sCP increased diuresis
and natriuresis, as well as relaxed preconstricted arteries from salmon and rats.
Thus the storage, processing and release of sCP resembles those of mammalian ANP.
The circulating level of sCP in salmon was markedly upregulated at increased
temperatures. Upregulation resulted from decreased elimination rather than
increased secretion of sCP, providing the first direct evidence that elimination
is used for the regulation of the natriuretic peptide system. In conclusion, sCP
is a promising model for studying the general factors regulating the cardiac
natriuretic peptides.
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Brinkmann, Inge. "Charakterisierung eines nicht selektiven Kationenkanals in Epithelzellen des Pansens von Schafen : Bedeutung für die Osmoregulation der Pansenflüssigkeit /." Berlin : Mensch- & -Buch-Verl, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015522696&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Tong, Hoi-yee, and 唐凱怡. "Molecular study of the regulation of osmotic response element-binding protein." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841562.
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Al-Barazanji, K. A. "The renin-angiotensin system and renal and endocrine function in the rat." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378010.
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Zhi, Hui. "Alternative activation of HOG pathway under hyperosmotic stress and analysis of salt-tolreance in saccharomyces cerevisiae." HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1430.
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Wei, Ling. "Experimental study of growth and protein dynamics in yeast Hog1 mutants under osmotic stress." HKBU Institutional Repository, 2011. http://repository.hkbu.edu.hk/etd_ra/1282.
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Tong, Hoi-yee. "Molecular study of the regulation of osmotic response element-binding protein." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42841562.
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Crombie, Hazel Janet. "Control mechanisms of Na'+-K'+-ATPase mediated branchial ion exchange in cod, Gadus morhua." Thesis, University of Stirling, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386643.
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Sonntag, Svenja Rebecca [Verfasser]. "Osmoregulation der Tight Junctions in Zellen und Nephronabschnitten des inneren Nierenmarks / Svenja Rebecca Sonntag." Kiel : Universitätsbibliothek Kiel, 2019. http://d-nb.info/1188636235/34.
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Cieluch, Ude. "Ontogeny of osmoregulatory functions and structures of three decapod crustaceans from the North Sea." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972621083.
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Zarate, Jacques. "The role of osmolyte transporters and heat shock proteins in adaptation of Atlantic salmon to selected stressors /." View online ; access limited to URI, 2006. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3248247.
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Robinson, Kevin Peter. "The role of the skin of early post-hatch turbot (Scophthalmus maximus L.) in osmoregulation." Thesis, University of Stirling, 1996. http://hdl.handle.net/1893/21433.
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To date, the structural significance of the skin of fish larvae in osmoregulation has received little attention and the evidence for salt secretion by cutaneous chloride cells is based largely on morphological observations. Thus, in the present study, a combination of microscopical and electrophysiological techniques were utilised to determine the role of the skin of early post-hatch turbot larvae in osmoregulation. A number of specialised structural features were revealed in the skin of the turbot larva with electron microscopy which would appear to provide some protection against the high osmotic and ionic gradients tending to dehydrate and salt load the body tissue and fluids. In the heterogenous epidermis, consisting of both transporting and non-transporting cells, only the shallow junctions between chloride cells and accessory cells were believed to permit ion influx and/or water loss via the paracellular pathway; the extensive junctions between adjacent pavement cells and pavement cells and neighbouring chloride cells effectively occluding the passage of ions and water through the extracellular space. Chloride cells were revealed in the skin and prebranchial epithelium of the turbot larva from hatching, but accessory cells, and thus "leaky" junctions, were only observed in association with the closely juxtaposed chloride cells in the prebranchial epithelium which, although densely packed, represented just a small area of the otherwise "tight" skin. Water and ion permeation through the external plasma membrane of the superficial pavement cells might further be impeded by the extracellular glycocalyx coat observed in TEM. In addition, the large numbers of mucous cells, which were a characteristic feature of the skin of the turbot larva, may produce a protective mucus coating of low permeability. The apparent "tightness" of the skin was reflected by the measurements of diffusional water permeability (Pdiff) from early stage larvae which suggested that the larvae of turbot were relative impermeable to water compared with the gills of adults. Nevertheless, the rates of water turnover were still sufficiently high that a net osmotic loss of water must be replaced by water uptake through drinking. The observation that the Pdiff of early stage turbot larvae increased with development substantiates earlier supposition that the drinking rates of larvae are a direct function of the permeability of the larva to water. A study of the chronology of chloride cell development utilising specific fluorochromes and electron microscopy revealed that the prebranchial chloride cells, which closely resembled the chloride cells described in the branchial epithelium of juveniles, were both numerous and well equipped to participate in active salt extrusion in turbot larvae even at hatching. In view of the early hypertrophy and proliferation of the prebranchial cells, their rapid increase in Na+,K+-ATPase binding sites, and the subsequent degeneration of the cutaneous chloride cells observed with larval development, it was concluded that the prebranchial chloride cells are the primary site for active ion excretion shortly after yolksac absorption. The potential importance of the cutaneous chloride cells in salt extrusion was also considered, but in view of the apparent lack of accessory cell associations and the small number of apical pits observed in SEM and TEM sections, questions were raised as to the significance of these cells in ion excretion. Measurements of the trans epithelial electrical potential (TEP) from early stage turbot using intracellular micro electrode techniques confirmed that the larvae of turbot maintain ionic gradients by the active extrusion of ions that enter into the body cavity down electrical or chemical gradients. The TEP was found to be largely the result of a Na+ diffusion potential with an additive electrogenic potential due to CI- transport, which was somehow functionally connected to Na+,K+ -ATPase. Furthermore, the concentration of Na+ in the external bathing medium was found to have a direct regulatory influence on the rate of CI- secretion, suggesting that the active secretion of Cl across the skin must be coupled to Na+. These conclusions are consistent with the current theories proposed for salt extrusion by the chloride cells in the adult teleost.