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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The lamellar spacing dl of purple membrane (PM) multilayer systems was investigated with neutron diffraction as a function of temperature and of the level of hydration. The observed large T-dependent variations of dl indicate that PM is partially dehydrated when cooled below a "hydration water freezing point". This phenomenon is reversible, but a hysteresis is observed when PM is rehydrated upon reheating. The hydration water remaining bound to the membrane below about 240 K is non-freezing. Its amount was found to be hnf=0.24(+/-0.02) g 2H2O/g BR for all samples equilibrated at room temperature in the presence of 2H2O vapour at >/=84% r.h. It is evident, that the dehydration/rehydration behaviour of PM is strongly correlated with the temperature-dependent behaviour of the dynamical structure factor. Above the well-known "dynamical transition" announcing the onset of localized diffusive molecular motions between 190 K and 230 K, a second dynamical transition is caused by the temperature-induced rehydration of the PM starting near 255 K. This is also correlated with the deviation from a pure Arrhenius law of the rate-limiting process in the photocycle, known to occur upon cooling beyond the ice point into the same temperature region. Our results suggest that the phenomenon of dehydration and rehydration induced by cooling and reheating, respectively, is a general property of biological membranes.
J Mol Biol 1998 Apr 03
PMID:Dehydration of biological membranes by cooling: an investigation on the purple membrane. 953 82

The expression of several Arabidopsis thaliana senescence-associated genes (SAGs) in attached and/or detached leaves was compared in response to age, dehydration, darkness, abscisic acid, cytokinin, and ethylene treatments. Most of the SAGs responded to most of the treatments in a similar fashion. Detachment in darkness and ethylene were the strongest inducers of both SAGs and visible yellowing. Detachment in light was also a strong inducer of SAGs, but not of visible yellowing. The other treatments varied more in their effects on individual SAGs. Responses were examined in both older and younger leaves, and generally were much stronger in the older ones. Individual SAGs differed from the norms in different ways, however, suggesting that their gene products play a role in overlapping but not identical circumstances. Some SAGs responded quickly to treatments, which may indicate a direct response. Others responded more slowly, which may indicate an indirect response via treatment-induced senescence. Four new SAGs were isolated as part of this work, one of which shows strong similarity to late embryogenesis-abundant (Lea) genes.
Plant Mol Biol 1998 Jun
PMID:A comparison of the expression patterns of several senescence-associated genes in response to stress and hormone treatment. 961 13

Cholera caused by toxigenic Vibrio cholerae is a major public health problem confronting developing countries, where outbreaks occur in a regular seasonal pattern and are particularly associated with poverty and poor sanitation. The disease is characterized by a devastating watery diarrhea which leads to rapid dehydration, and death occurs in 50 to 70% of untreated patients. Cholera is a waterborne disease, and the importance of water ecology is suggested by the close association of V. cholerae with surface water and the population interacting with the water. Cholera toxin (CT), which is responsible for the profuse diarrhea, is encoded by a lysogenic bacteriophage designated CTXPhi. Although the mechanism by which CT causes diarrhea is known, it is not clear why V. cholerae should infect and elaborate the lethal toxin in the host. Molecular epidemiological surveillance has revealed clonal diversity among toxigenic V. cholerae strains and a continual emergence of new epidemic clones. In view of lysogenic conversion by CTXPhi as a possible mechanism of origination of new toxigenic clones of V. cholerae, it appears that the continual emergence of new toxigenic strains and their selective enrichment during cholera outbreaks constitute an essential component of the natural ecosystem for the evolution of epidemic V. cholerae strains and genetic elements that mediate the transfer of virulence genes. The ecosystem comprising V. cholerae, CTXPhi, the aquatic environment, and the mammalian host offers an understanding of the complex relationship between pathogenesis and the natural selection of a pathogen.
Microbiol Mol Biol Rev 1998 Dec
PMID:Epidemiology, genetics, and ecology of toxigenic Vibrio cholerae. 984 73

The incidence of certain ageing sequelae such as lung and cardiovascular disease and cataract are higher in smokers than in non-smokers. We recently proposed that certain components of mainstream cigarette smoke can react with plasma and extracellular matrix proteins to form covalent adducts with many of the properties of advanced glycation endproducts (AGE). AGEs have been implicated previously in the pathogenesis of the end-organ complications of diabetes and ageing, including cataract, atherosclerosis and renal insufficiency. In these circumstances, AGEs arise in vivo from the non-enzymatic reaction of reducing sugars with amino groups. Over time the initial Schiff base and Amadori products that form gradually undergo dehydration and rearrangement to produce reactive, carbonyl containing compounds with characteristic fluorescence and covalent crosslinking properties. Recent studies indicate that in smokers, tobacco-derived AGEs accumulate on plasma low density lipoprotein (LDL), structural proteins present within the vascular wall, and the lens proteins of the eye. These data point to a new and significant source of Maillard products in the human environment, significantly broaden the role of Maillard chemistry in pathological processes, and provide new insight into the pathogenesis of atherosclerosis and other diseases associated with tobacco usage.
Cell Mol Biol (Noisy-le-grand) 1998 Nov
PMID:Advanced glycation endproducts and cigarette smoking. 984 84

Major intrinsic proteins (MIPs) are a family of channel proteins that are mainly represented by aquaporins in plants. These are divided into TIPs (tonoplast intrinsic proteins) and PIPs (plasma membrane intrinsic proteins) according to their subcellular localization. Homologues to PIPs and TIPs were isolated from the desiccation-tolerant resurrection plant Craterostigma plantagineum by two approaches: firstly, a cDNA library constructed from RNA of dehydrated C. plantagineum leaves was screened with an Arabidopsis thaliana Ath-PIP1b cDNA probe and, secondly, a cDNA library was screened differentially to isolate early drought-induced transcripts. According to sequence homologies the isolated cDNA clones were grouped as follows: Cp-PIPa, Cp-PIPb, Cp-PIPc and Cp-TIP. Cp-PIPa, Cp-PIPc and Cp-TIP transcript accumulation was regulated by dehydration and abscisic acid (ABA). Within the Cp-PIPa group transcripts were regulated either by drought only or by drought and ABA, indicating that ABA-dependent and -independent signal transduction pathways lead to Cp-PIPa expression. Comparison of Cp-PIPa expression in detached leaves and in whole plants suggested the involvement of a signal transmitted in the whole plant in response to drought. Cp-PIPb transcript levels were constitutive in all organs tested. Antibodies raised against a Cp-PIPA protein recognized a polypeptide with an apparent molecular mass of 28 kDa. Using these antibodies it was shown that both Cp-PIPA and Cp-PIPB proteins were localized to the plasma membrane. The role of different members of the MIP group in the dehydration response is discussed.
Plant Mol Biol 1998 Dec
PMID:Desiccation- and abscisic acid-responsive genes encoding major intrinsic proteins (MIPs) from the resurrection plant Craterostigma plantagineum. 986 15

Many anurans have excellent dehydration tolerance that allows endurance of the loss of up to 50-60% of total body water. One of the effects of severe dehydration is circulatory impairment due the reduced volume and increased viscosity of blood, which leads to organ hypoxia. The rehydration situation, therefore, involves a reoxygenation of tissues that may include elements of oxidative stress that resemble the injury in post-ischemic reperfusion of mammalian organs. The role of endogenous defenses against oxygen radicals in the tolerance of severe dehydration by leopard frogs, Rana pipiens, was investigated by monitoring the activities of antioxidant enzymes and glutathione levels (reduced GSH and oxidized GSSG) in leg muscle and liver of control, 50%-dehydrated, and fully rehydrated frogs. The maximal activities of muscle catalase and liver glutathione peroxidase, measured per mg soluble protein, increased significantly by 52 and 74%, respectively, after dehydration whereas muscle superoxide dismutase and glutathione reductase activities responded oppositely, decreasing by 32 and 35%, respectively. Enzyme activities returned to control levels after full rehydration. Hepatic GSH and GSSG increased early in the rehydration process (30% recovery of total body water), but returned to control levels after full recovery. A similar trend was observed for liver GSSG. The elevation of antioxidant defenses against peroxides during dehydration could provide protection against post-hypoxic oxyradical stress during rehydration. Indeed, analysis of one product of lipid peroxidation, thiobarbituric acid reactive substances, in frog tissues gave no indication of oxidative stress during the dehydration/rehydration cycle.
Mol Cell Biochem 1998 Dec
PMID:Role of antioxidant defenses in the tolerance of severe dehydration by anurans. The case of the leopard frog Rana pipiens. 987 57

Through the high-resolution structure of the gramicidin A channel in lamellar phase lipids and the characterization of specific ion peptide interactions, fundamental principles for ion channel selectivity and conductance efficiency are illustrated with atomic resolution detail. Delocalized cation binding in the first turn of the helix reduces the unfavorable entropy contribution upon binding. Stepwise dehydration minimizes the energy barrier for cation entry and provides valence selectivity in this channel. Three or more water molecules in the monovalent cation binding site result in flexibility in the cation solvation environment causing weak cation size selectivity. Lack of cation induced structural modification avoids the formation of a significant energy barrier, thus permitting efficient cation transport.
J Mol Biol 1999 Feb 05
PMID:Cation transport: an example of structural based selectivity. 992 80

The present study describes the differential rostro-caudal patterning of angiotensinogen (AoGen) and AT1A receptor mRNAs in the rat SFO using specific and validated oligodeoxynucleotide probes for in situ hybridization. Highest levels of AoGen-specific gene expression were observed in the rostral region of the SFO with gradually decreasing intensity towards the caudal region of this sensory circumventricular organ lacking blood-brain barrier function. AoGen-related hybridization signals proved to be specifically prominent above cells in lateral aspects of the SFO, surrounding septal venules. Maximal expression of the AT1A receptor-specific gene, on the other hand, could be detected in the neuron-enriched, ventro-medial core region and dorsal annulus of the SFO, with low-intensity hybridization signals in its rostral and caudal parts. Water deprivation for 48 h, leading to extracellular hypertonic hypovolemia with elevated circulating AngII concentrations within the physiological range, caused a significant increase in AoGen-specific hybridization signals in the rostral and medial SFO regions. AT1A receptor gene expression and AngII receptor binding were markedly stimulated in the medial and caudal regions of the SFO (core and annulus) as compared to euhydrated animals. These data indicate, that mild dehydration differentially up-regulates AoGen- and AT1A receptor-specific mRNA formation as well as AT1 receptor binding in distinct regions of the SFO, and supports the involvement of different cellular subgroups in the expression of two major components of the central nervous renin-angiotensin system in this sensory circumventricular organ.
Brain Res Mol Brain Res 1999 Feb 05
PMID:Differential regulation of angiotensinogen and AT1A receptor mRNA within the rat subfornical organ during dehydration. 993 78

The neurohypophysial hormone, arginine vasotocin (AVT), plays an important role in the osmoregulation of birds. After a prolonged period of water deprivation, plasma osmolality and plasma concentration of AVT are elevated. In this study, the effects of short term dehydration were examined in laying hens by measuring plasma osmolality, plasma levels of potassium, sodium and AVT and hypothalamic concentrations of mRNA encoding AVT during 8 h of water deprivation. Plasma osmolality increased significantly after at 6 h of water deprivation. Plasma sodium levels, however, did not change. Plasma potassium concentrations gradually decreased during dehydration. Plasma AVT levels and hypothalamic AVT mRNA levels increased significantly after 8 h. The results of this study demonstrate that depriving chickens of water results first in an increase in plasma osmolality followed by increases in AVT levels in plasma and AVT mRNA levels in the hypothalamus. The data indicate that the synthesis of AVT in the magnocellular neurons in the hypothalamus is activated soon after the animals are deprived of water. This indicates that both de novo synthesized AVT as well as AVT stored in the neurohypophysis are available to meet the increasing demands for the hormone during osmotic stress.
Comp Biochem Physiol A Mol Integr Physiol 1998 Nov
PMID:Effects of short-term dehydration on plasma osmolality, levels of arginine vasotocin and its hypothalamic gene expression in the laying hen. 997 22

Targeted disruption of mineralocorticoid receptor (MR) gene results in pseudohypoaldosteronism type I with failure to thrive, severe dehydration, hyperkalemia, hyponatremia, and high plasma levels of renin, angiotensin II, and aldosterone. In this study, mRNA expression of the different components of the renin-angiotensin system (RAS) were evaluated in liver, lung, heart, kidney and adrenal gland to assess their response to a state of extreme sodium depletion. Angiotensinogen, renin, angiotensin-I converting enzyme, and angiotensin II receptor (AT1 and AT2) mRNA expressions were determined by Northern blot and RT-PCR analysis. Furthermore, in situ hybridization and immunohistochemistry allowed us to identify the cell types involved in the variation of the RAS component expression. In the heterozygous mice (MR+/-), compared with wild-type mice (MR+/+), there was no significant variation of any mRNA of the RAS components. In MR knockout mice (MR-/-), compared with wild-type mice, there were significant increases in the expression level of several RAS components. In the liver, angiotensinogen and AT1 receptor mRNA expressions were moderately stimulated. In the kidney, renin mRNA was increased up to 10-fold and in situ hybridization showed a marked recruitment of renin-producing cells; however, the levels of angiotensin-I converting enzyme mRNA and AT1 mRNA were not changed. Interestingly, in adrenal gland, renin expression was also strongly up-regulated in a thickened zona glomerulosa, whereas AT1 mRNA expression remained unchanged. Altogether, these results demonstrate that in the MR knockout mice model, RAS component expressions are differentially altered, renin being the most stimulated component. Angiotensinogen and AT1 in the liver are also increased, but the other elements of the RAS are not affected.
Mol Endocrinol 1999 Feb
PMID:Effects of mineralocorticoid receptor gene disruption on the components of the renin-angiotensin system in 8-day-old mice. 997 59


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