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PubMed1981

The role of proline in osmoregulation in Salmonella typhimurium and Escherichia coli.

Previously we demonstrated that high intracellular proline levels conferred enhanced osmotolerance on Salmonella typhimurium. Stimulation of growth rate under conditions of osmotic inhibition could be brought about either by the addition of proline to the culture media or by mutations which result in proline over-production. Here, we report that there is a novel proline transport system in S. typhimurium which is activated in media of elevated osmolarity. this conclusion is based on the observation that putP- proP- double mutants, which lack both of the known proline permeases are resistant in minimal medium to the toxic proline analogues 3,4-dehydro-D, L-proline and L-azetidine-2-carboxylate. However, they regain sensitivity to the analogues in media of elevated osmolarity. Selecting resistance to 3,4-dehydro-D, L-proline in media of elevated osmolarity, we obtained mutants of putP- proP- strains which lack the osmotically activated proline permease. In these strains, exogenous proline could no longer alleviate osmotic inhibition.

Biological Transport↗
PubMed1977

The coxal glands of geophilomorpha (chilopoda): organs of osmoregulation.

The organs terminating at the coxal pores of the tug-legs of Geophilomorpha are not repugnatorial glands, but possess typical transport epithelia with deep apical and basal infolding of the cell membranes, between which numerous large mitochondria are located. Many transport vesicles are found in the basal region but fewer in the apical cytoplasm. The apex is characterized by bundles of longitudinally oriented microtubules, sparse endoplasmic reticulum and free ribosomes. Single neurosecretory axons with synaptoid areas are scattered among the cells. It is suggested that the coxal organs have a diuretic function in moist habitats and an antidiuretic effect in arid environments. The "switch-over" is evidently controlled by a neuroendocrine mechanism.

Animals↗
PubMed1993

Osmoregulation of the fatty acid receptor gene fadL in Escherichia coli.

The fadL gene of Escherichia coli codes for an outer membrane protein that is involved in the uptake of long-chain fatty acids. Uptake is regulated by environmental osmolarity, and decreases when the cells are grown under conditions of high osmolarity. A temperature-sensitive mutant that requires fatty acid for growth at 42 degrees C was unable to grow at the high temperature even in the presence of fatty acid if the medium contained 10% sucrose. Promoter activity of the fadL gene in vivo was repressed by high osmolarity in a FadR repressor null mutant. Furthermore, in vitro transcription of the fadL gene was strongly repressed by the addition of OmpR and EnvZ proteins. The results of gel retardation and DNase I protection experiments indicated that OmpR, after incubation with the protein kinase EnvZ, specifically binds to at least four sites around the fadL promoter, two upstream and two downstream from the transcriptional start site. These results suggest that transcription of the fadL gene is osmotically regulated by the OmpR-EnvZ two-component system.

Bacterial Outer Membrane Proteins↗
PubMed1987

Osmoregulation in Escherichia coli by accumulation of organic osmolytes: betaines, glutamic acid, and trehalose.

It has been shown previously that externally added glycine betaine is accumulated in Escherichia coli in response to the external osmotic strength. Here we have shown, by using nuclear magnetic resonance spectroscopy and radiochemical methods, that E. coli growing in a glucose-mineral medium of elevated osmotic strength generated with NaCl, had the same capacity to accumulate proline betaine and glycine betaine. Its capacity to accumulate gamma-butyrobetaine was, however, 40 to 50% lower. Accordingly, externally added proline betaine and glycine betaine stimulated aerobic growth of osmotically stressed cells equally well, and they were more osmoprotective than gamma-butyrobetaine. In cells grown at an osmotic strength of 0.64, 1.01, or 1.47 osmolal, respectively, the molal cytoplasmic concentration of the two former betaines corresponded to 29, 38, or 58% of the external osmotic strength. Nuclear magnetic resonance spectroscopy revealed that trehalose and glutamic acid were the only species of organic osmolytes accumulated in significant amounts in cells grown under osmotic stress in glucose-mineral medium without betaines. Their combined molal concentration in the cytoplasm of cells grown at 1.01 osmolal corresponded to 27% of the external osmotic strength.

Amino Acids↗
PubMed1985

Osmoregulation of renal papillary cells.

Element concentrations were determined in various extra- and intracellular compartments of the rat renal papilla in antidiuresis and after furosemide-induced diuresis using electron microprobe analysis to elucidate further how the cells adapt osmotically to different osmolalities. In antidiuresis and diuresis the sum of intracellular cations (sodium and potassium), accompanying anions and urea was insufficient in both cases to provide cell osmolalities similar to those in extracellular compartments. This finding provides further evidence that the papillary cells achieve osmoadaptation to widely differing extracellular electrolyte concentrations mainly by varying the cellular concentrations of osmotically-active substances other than urea and electrolytes.

Animals↗
PubMed1980

Serum arginine-vasotocin (AVT) and afferent and central control of osmoregulation in conscious Pekin ducks.

In conscious Pekin ducks adapted either to fresh water or to hypertonic saline (1.9%) as drinking fluid, urinary excretion, salt gland secretion and the serum concentration of radioimmunoassayable arginine-vasotocin (AVT) were examined with regard to their afferent and central control. The experiments were carried out under conditions of water diuresis, osmotic diuresis or supraorbital salt gland secretion, which were induced by continuous infusions of appropriate solutions. Temporary bilateral vagus blockade caused rises in AVT serum concentration accompanied by antidiuresis in hydrated ducks and by inhibition of salt gland secretion in salt-stressed ducks. Rostral brainstem cooling caused decreases of AVT serum concentration and water diuresis in ducks under osmotic diuresis and reduction of AVT serum concentration and inhibition of salt gland secretion in salt-stressed ducks. Cerebral osmotic stimulation in hydrated ducks by intracarotid injection or by intracerebroventricular microinfusion of hypertonic NaCl solutions caused antidiuretic reactions associated with rises of AVT serum concentration.

Animals↗
PubMed1979

Hypothalamic temperature and osmoregulation in the Pekin duck.

The temperature of the anterior and middle hypothalamus of conscious Pekin ducks was altered with chronically implanted thermodes. Both urine formation and salt secretion by the supraorbital glands were influenced by hypothalamic cooling. When osmotic diuresis was induced by continuous intravenous infusion of 1.2 ml . min-1 of 293 mosm . kg-1 mannitol in H2O solution, hypothalamic cooling increased urine flow rate at reduced urine osmolality and unchanged osmolal excretion rate. The degree of this cold induced diuresis increased with cooling intensity. Additional ADH administration by continuous infusion at a supramaximal dose abolished the diuretic effect of hypothalamic cooling. When water diuresis was induced by intragastric continuous infusion of 1.2 ml . min-1 of distilled water, hypothalamic cooling enhanced the diuresis, but hypothalamic warming had equivocal effects. The diuretic effects of hypothalamic cooling suggest an inhibition of endogeneous ADH release by lowering hypothalamic temperature. When the salt glands of salt adapted ducks were stimulated by continuous intravenous infusion of 0.2 ml . min-1 of 800 mosm . kg-1 NaCl in H2O solution, hypothalamic cooling reduced the salt gland secretion rate to an extent depending on cooling intensity. It is concluded that the activities of those integrative and/or efferent hypothalamic neurons, which mediate the hormonal control of renal water absorption and the nervous control of salt secretion by the supraorbital gland, depend on their own temperature.

Animals↗
PubMed1983

A central mechanism of action for taurine: osmoregulation, bivalent cations, and excitation threshold.

A postulated zinc-taurine complex, with a zinc affinity intermediate between that for glutamic acid dehydrogenase and the calcium binding protein(s), provides an explanation for a series of seemingly unrelated biochemical and physiological effects of taurine. The proposed complex suggests a central mechanism for the action of taurine, such as a bicarbonate and pH dependent influence on calcium and zinc movements (and vice versa), the osmoregulatory role of taurine, and its effect on the excitation threshold.

Animals↗
PubMed1992

Plasma osmolality, osmoregulation and prognosis after head injury.

108 Patients with severe brain damage were examined for the course of plasma osmolality. In addition plasma values of Na+, K+, glucose and blood urea nitrogen (BUN) were measured simultaneously by auto-analyzer. The clinical status was registered daily by using a modified Glasgow coma scale. Outcome of the injured patients was registered by using the Glasgow outcome scale. 60 patients survived, 48 died, 39 of brain damage and 9 of secondary diseases, such as infection or embolism. Sustained severe brain damage is generally followed by disturbances of metabolic regulation. Quite often the osmotic regulation is disturbed. In most cases these disturbances are of hyperosmolar nature, their extent and duration being correlated to the prognosis. Hyposmolar deregulation occurs less frequently, and occasionally lead to peracute brain oedema (e.g. SIADH-syndrome). These dysregulations are interpreted as disturbances of the central function of the diencephalon, in lethal cases even as "hypothalamic death". Blood osmolality measurements should therefore be made early in states of acute cerebral disease to help establish a prognosis, control the treatment of water imbalance and to determine contra-indications to osmotherapy.

Adolescent↗
PubMed1975

DDT: short term effects on osmoregulation in black surfperch (Embiotoca jacksoni).

DDT injected intraperitoneally into black surfperch caused substantial increases in plasma osmotic concentration only at doses much larger than are likely to be encountered in nature. Increased plasma concentrations were below those tolerated by fish adapted to high salinities. Death of marine teleosts from DDT poisoning probably involves factors other than simply osmoregulatory failure.

Animals↗
PubMed1989

Analysis and DNA sequence of the osmoregulated treA gene encoding the periplasmic trehalase of Escherichia coli K12.

The treA gene of Escherichia coli K12 codes for a periplasmic trehalase that is induced by growth at high osmolarity. The position of treA within a cloned chromosomal DNA fragment was identified by subcloning of restriction fragments and analysis of the gene product in minicells. The nucleotide sequence of the treA coding region as well as its upstream control region was determined. The treA gene consists of 1695 bp encoding 565 amino acids. The amino-terminus of the mature trehalase was found to begin with the amino acid Glu at position 31 of the open reading frame. The first 30 amino acids resemble a typical signal sequence, consistent with trehalase being a secreted periplasmic enzyme. Two previously isolated phoA fusions to the osmA gene were transferred by homologous recombination on to a treA-containing plasmid and found to be within treA. Analysis of the hybrid genes and their gene products aided the localization of treA and the determination of its direction of transcription within the cloned chromosomal segment. The treA-phoA fusions encoded hybrid proteins which could be found in the periplasm. We found that at high osmolarity the normal pathway for the uptake and utilization of trehalose is blocked. Therefore, the function of the periplasmic trehalase is to provide the cell with the ability to utilize trehalose at high osmolarity by splitting it into glucose molecules that can subsequently be taken up by the phosphotransferase-mediated uptake system.

Amino Acid Sequence↗
PubMed1999

Osmoregulation and the Genetic Induction of Glycerol-3-phosphate Dehydrogenase by NaCl in the Euryhaline Yeast Debaryomyces hansenii.

: In the yeasts Saccharomyces cerevisiae and Debaryomyces hansenii, glycerol-3-phosphate dehydrogenase (NAD+-GPD) is believed to be the enzyme controlling the synthesis of glycerol in osmotically challenged cells. Consistent with this concept, immunoblot analyses demonstrated quantitative increases in NAD+-GPD 30 minutes after the addition of NaCl to actively growing D. hansenii cells; Northern blot analyses showed increases in GPD-messenger RNA within 15 minutes after the addition of salt. There appears to be an upper limit of salt concentration above which the cells appear to be less responsive. The results we describe support the concept of transcriptional regulation of NAD+-GPD in D. hansenii.

Journal Article↗