Water intake and 24-hour blood pressure monitoring in a patient with nephrogenic diabetes insipidus caused by a novel mutation of the vasopressin V2R gene.
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A 47-year-old man presented with polydipsia, which had had since childhood, and recent onset of hypertension. Genetic analysis proved that he had nephrogenic diabetes insipidus caused by a novel mutation (deletion of 6 amino acids between G107 and C112) in the vasopressin V2 receptor gene. Results of 24-hour blood pressure monitoring disclosed a greater dipping pattern and greater blood pressure variability during waking hours than in male patients with only essential hypertension. This characteristic blood pressure profile may result from daily occurrence of free water depletion, as further observation indicated that water deprivation was associated with a reduction in blood pressure. (+info)
Structure and characterization of the mouse UT-A gene (Slc14a2).
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The movement of urea across plasma membranes is modulated by facilitated urea transporter proteins. These proteins are the products of two closely related genes, termed UT-A (Slc14a2) and UT-B (Slc14a1). By genomic library screening and P1 artificial chromosome "shotgun" sequencing, we have determined the structure of the mouse UT-A gene. The gene is >300 kb in length, contains 24 exons, and has 2 distinct promoters. Flanking the 5'-region of the gene is the UT-Aalpha promoter that regulates transcription of UT-A1 and UT-A3. The second promoter, termed UT-Abeta, is present in intron 13 and regulates transcription of UT-A2. cAMP agonists (100 microM dibutryl cAMP, 25 microM forskolin, 0.5 mM IBMX) increased the activity of a 2.2-kb UT-Aalpha promoter construct 6.2-fold [from 0.026 +/- 0.003 to 0.160 +/- 0.004, relative light units (RLU)/microg protein] and a 2.4-kb UT-Abeta promoter construct 9.5-fold (from 0.020 +/- 0.002 to 0.190 +/- 0.043 RLU/microg protein) above that in untreated controls. Interestingly, only the UT-Abeta promoter contained consensus sequences for CREs and deletion of these elements abolished cAMP sensitivity. Increasing the tonicity of culture medium from 300 to 600 mosmol/kg H(2)O with NaCl caused a significant increase (from 0.060 +/- 0.004 to 0.095 +/- 0.010 RLU/microg protein) in UT-Aalpha promoter activity but had no effect on the UT-Abeta promoter. A tonicity-responsive enhancer was identified in UT-Aalpha and is suggested to be responsible for mediating this effect. Levels of UT-A2 and UT-A3 mRNA were increased in thirsted mice compared with control animals, indicating that the activities of both promoters are likely to be elevated during prolonged antidiuresis. (+info)
Episodes of water deprivation enhance daily hypertonic NaCl intake in rats.
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Water and 1.8% NaCl intake was recorded daily in adult male rats (N = 6) submitted to four water deprivations plus four sodium appetite tests, each at the end of each 7-day interval, or in controls (non-deprived, N = 6). Water deprivation was achieved by removing water and 1.8% NaCl for 24 h. Water was then offered for 2 h. At the end of this period, 1.8% NaCl was also offered in addition to water (sodium appetite test). Average daily 1.8% NaCl intake was enhanced from 5.2 +/- 1.0 to 15.7 +/- 2.5 ml from the first to the fifth week in the experimental group and was unchanged in the control group. Daily water intake was not altered in either group. Thus, repeated episodes of water deprivation enhance daily NaCl intake. (+info)
Identification and characterization of a novel freezing inducible gene, li16, in the wood frog Rana sylvatica.
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The wood frog Rana sylvatica survives for weeks during winter hibernation with up to 65% body water frozen as ice. Natural freeze tolerance includes both seasonal and freeze-induced molecular adaptations that control ice formation, deal with long-term ischemia, regulate cell volume changes, and protect macromolecules. This report identifies and characterizes a novel freeze-inducible gene, li16, that codes for a protein of 115 amino acids. Northern blot analysis showed that li16 transcript levels rose quickly during freezing to reach levels 3.7-fold higher than control values after 24 h; immunoblotting showed a parallel 2.4-fold rise in Li16 protein. Regulatory influences on gene expression were assessed. Nuclear runoff assays confirmed that freezing initiated an increase in the rate of li16 transcription, and analysis of signal transduction pathways via in vitro incubation of liver slices implicated a cGMP-mediated pathway in li16 expression. Gene and protein expression in liver was also strongly stimulated by anoxia exposure, whereas the gene was less responsive to dehydration stress. The strong response of li16 to both freezing and anoxia, and the rapid down-regulation of the gene when oxygen was reintroduced, suggest that the Li16 protein may play a role in ischemia resistance during freezing. (+info)
Inhibition of thermal tachypnoea in rabbits following exposure to cold and water deprivation.
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1. Rabbits were clipped and exposed in turn to four environmental conditions: control (C), cold exposure (CE), water deprivation (WD) and water deprivation and cold exposure together (WD/CE). 2. Following each type of treatment, the rabbits were exposed for 1 hr to an ambient temperature (Ta) of 35 degrees C. During this time, respiratory frequency (RF), rectal temperature (Tre), activity and oxygen consumption (V02) were recorded. 3. It was found that under both cold exposure and water deprivation conditions, the mean respiratory frequency during the first 30 min of heat exposure was reduced when compared with controls. This was associated with a delay in the onset of thermal tachypnoea. Under conditions of water deprivation and cold exposure together, the mean respiratory frequency was further reduced and the length of the delay was increased. 4. Previous cold exposure led to an increase in the V02 measured at 35 degrees C, whereas the V02, after water deprivation and water deprivation and cold exposure together were not significantly different from the control. 5. Neither the initial Tre nor the change in the Tre during the course of the heat exposure were significantly different from the controls under any of the experimental conditions. 6. It is concluded that both water deprivation and previous cold exposure cause a block to panting in the heat and that the blocking mechanisms involved are closely interrelated. It is also concluded that neither the metabolic rate of the animal nor its initial or final Tre are important factors in determing the degree to which thermal tachypnoea is inhibited. (+info)
Proliferation and osmotic tolerance of renal inner medullary epithelial cells in vivo and in cell culture.
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Renal inner medullary (IM) cells survive interstitial osmolality that ranges from 600 to 1,700 mosmol/kgH2O or more. In contrast, much smaller acute changes killed the cells previously studied in tissue culture, such as mouse IM collecting duct 3 (mIMCD3) cells, that are immortalized with SV40 and proliferate rapidly. Proliferation and DNA replication sensitize mIMCD3 cells to hypertonicity. In the present studies, we observed that proliferating cells were scarce in rat IM. Then, we prepared passage 2 mouse IM epithelial (p2mIME) cells. They have a much lower incidence of DNA replication than do mIMCD3 cells. p2mIME cells survive much greater acute increases in NaCl than do mIMCD3 cells and also tolerate significantly greater acute increases of urea and of NaCl plus urea, but still not to levels as high as occur in vivo. We conclude that immortalization and continued DNA replication account for part of the previously observed difference in osmotic tolerance between IM cells in vivo and in cell culture but that other factors must also be involved. (+info)
Structural-functional correlations in the kidneys and observations of colon and cloacal morphology in certain Australian birds.
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1. Variations in renal microstructure between the zebra finch and Senegal dove were consistent with their relative renal concentrating abilities (urine/plasma ratios of 2-8 and 1-7, respectively). Compared with dove kidneys, those of the finch contained a higher fraction of mammalian-type nephrons (with Henle's loops), and a lower fraction of reptilian-type nephrons (without loops). 2. Singing honeyeaters concentrated their urine almost as well as zebra finches, although honeyeater kidneys were less specialized (fewer mammalian-type nephrons). Such findings emphasize the need to clarify other osmoregulatory parameters. 3. No significant microstructural differences were found in the kidneys of domesticated as compared with those of wild zebra finches. Hence, osmoregulatory differences between tame and wild birds must be related to physiological factors rather than morphological. 4. Thickness of the renal medulla seemed to be directly correlated with urine concentrating ability. However, certain inconsistencies obscure this relationship such that its resolution will require further research. 5. Histological features of the mucosae of the colon and cloaca are described. The galah and kookaburra displayed a mammalian (non-villous) pattern of mucosal organization. Zebra finches, singing honeyeaters, and particularly emus, possessed colonic and cloacal villi and hence an increased surface area per volume in this region of the gut. This raises the possibility that the colon and cloaca are involved in uring concentration and osmoregulatory activities in these species. (+info)
Some central mechanisms of thirst in the dog.
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Measurements of water intake were made on a population of trained conscious dogs of both sexes prepared with chronic third ventricle cannulae. 2. Injection of 100 ng angiotensin II into the third ventricle lead to a prompt stimulation of drinking, the mean water intake over a 5 min period being 503 +/- 89 ml. (n=6) compared with controls. This dipsogenic effect of angiotensin II was abolished by prior central administration of 10 mug saralasin acetate or 100 ng atropine. 3. Injection of 1 mug carbachol into the third ventricle produced a small, variable increase in drinking. 4. Injection of 0-2 ml. 5% NaCl into the third ventricle stimulated drinking, a response that was not affected by prior administration of 10 mug saralasin acetate or 100 ng atropine. 5. Following a 24 hr period of water deprivation there was an increase in plasma osmolality and plasma-renin activity. The drinking following this period of water deprivation was not affected by prior control administration of either 10 mug saralasin acetate or 100 ng atropine. 6. In two acute dogs, intracarotid infusion of 125I angiotensin II was not followed by significant appearance of radioactivity in the third ventricle or cisterna magna c.s.f. 7. The relevance of these results to the control of water intake is discussed. (+info)