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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Numerous community drinking water sources have elevated levels of both sodium and lead. Recently reported studies have indicated that elevated levels of sodium in drinking water may be a facter in the development of elevated blood pressure. The question of how elevated levels of lead may affect sodium induced elevated blood pressure is addressed. The hypothesis is developed which states that elevated levels of lead exposure will not interact with sodium to enhance the development of renin angiotensin aldosterone related hypertension but in fact may even diminish the effects of exposure to elevated amounts of sodium on blood pressure through a depression of plasma renin activity.
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PMID:Does exposure to elevated levels of lead enhance sodium induced hypertension? 51 19

Physical and chemical considerations permit the division of the near-surface regolith on Mars into at least six zones of distinct microenvironments. The zones are euphotic, duricrust/peds, tempofrost, permafrost, endolithic, and interfacial/transitional. Microenvironments vary significantly in temperature extremes, mean temperature, salt content, relative pressure of water vapor, UV and visible light irradiance, and exposure to ionizing radiation events (100 Mrad) and oxidative molecular species. From what is known of the chemistry of the atmosphere and regolith fines (soil), limits upon the aqueous chemistry of soil pastes may be estimated. Heat of wetting could reach 45 cal/g dry soil; initial pH is indeterminate between 1 and 10; ionic strength and salinity are predicted to be extremely high; freezing point depression is inadequate to provide quantities of liquid water except in special cases. The prospects for biotic survival are grim by terrestrial standards, but the extremes of biological resiliency are inaccessible to evaluation. Second-generation in situ experiments which will better define Martian microenvironments are clearly possible. Antarctic dry valleys are approximations to Martian conditions, but deviate significantly by at least half-a-dozen criteria.
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PMID:Chemical and physical microenvironments at the Viking landing sites. 52 49

The role of specialized regions of insect rectal papillae in the regulation of water and ion uptake is well documented. Although the apparatus for active uptake of water or ions is located in various cell membranes, the absorbed molecules must first pass through the cuticle which lines the rectal epithelium. Most cuticle (e.g. abdominal) has been shown to be permeable only to molecules soluble in wax, and to be impermeable to water and ions. Obviously if such cuticle lined the rectum, absorption of water and ions would be severely restricted. The present freeze-fracture and lanthanum tracer study was undertaken to investigate in more detail both the morphological features of the rectal papillae cuticle which could be responsible for its anomalous permeability and the various cell membranes involved in this transport. It has been suggested from permeability studies that the anomalous permeability of rectal papillae cuticle could be due to the lack of a complete wax layer over the surface of the rectal cuticle. The present study strongly supports this suggestion. Thus, the freeze-fracture micrographs have shown that a surface layer of the cuticle reacts during fracturing like a lipid bilayer. However, in rectal papilla cuticle this surface bilayer is interrupted at each epicuticular depression by areas of different fracturing behaviour. These discontinuities in the surface bilayer probably allow the rectal contents to contact directly the true cuticular matrix. They could, therefore, explain the case with which water and ions penetrate the rectal cuticle and so gain access to the underlying epithelial cells. Although similar discontinuities are present on some of the rectal cuticle surface external to the rectal papillae, they appear to be filled in by plugs of lipid-like material. The lateral plasma membranes of the rectal papillae cells are generally considered to be the main site of active transport. The present lanthanum tracer and freeze-fracture study has shown that the lateral plasma membranes contain 3 distinct differentiations. Septate junctions are present at the apical and basal surfaces of the epithelial layer; a further membrane differentiation is found adjacent to the septate junctions; and thirdly, an array of short, variable length, non-anastomosing linear structures covers most of the lateral plasma membrane surface. These latter structures, unlike known types of cell junctions do not show equivalent arrays in apposing membranes even when the lateral plasma membranes of adjacent cells are closely apposed. The possible function of these structures is discussed.
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PMID:Rectal papillae in Musca domestica: the cuticle and lateral membranes. 52 79

The effects of various cations on the water unit activity were studied by recording unitary discharges in the superior laryngeal nerve fibers of the rabbit. Chloride salts of Li+, Na+, K+, Cs+ depressed the water response, while sulfate salts of Li+, Na+, NH4+, K+ facilitated it. Cations were less effective in stimulating action than anions. The depression of the water response in the laryngeal nerve has been thought to be caused by permeation of the stimulating anions through the receptor membrane and/or by destruction of the water structure on the membrane surface induced by adsorbed anions (SHINGAI, 1977 a). In order to differentiate these two possible actions of anions, the effects of benzenesulfonate and trichloroacetate were examined, because these anions were expected to be impermeant through the receptor membrane and to have a water structure-breaking effect. These anions showed no effect on the water response in concentrations below 320 mM. Measurements of the viscosity and the density of the electrolyte solutions showed that benzenesulfonate had a strong water structure-breaking effect. These results suggested that impermeant anions having water structure-breaking actions do not influence the excitability of the water receptor and that the depression of the water response by anions in the stimulating solution is caused by a hyperpolarization generated by permeation of the anions through the receptor membrane.
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PMID:Physicochemical study of receptive mechanism of laryngeal water fibers in the rabbit. 53 47

The separate administration of mercuric chloride (HgCl2) and sodium selenate (Na2SeO4) to male rats in drinking water or a combined administration of both (50 ppm Hg, 15 ppm Se) caused different signs of toxicity over a 22 week period. The HgCl2 group showed histopathological and ultrastructural lesions as evidenced by periportal fatty degeneration and cell necrosis in the liver and tubular necrosis with proteinaceous casts in the kidney. The Na2SeO4 group showed the most severe depression of growth and food and water consumption, but no pathological changes were seen in the liver or kidney. Simultaneous administration of both toxicants produced a protective effect on weight loss and histopathology. These effects were associated with the formation of electron dense nuclear inclusions in kidney proximal tubule cells and similar electron dense formations in the reticuloendothelial cell cytoplasm and in the extracellular space of Disse in the liver. These formations were shown to contain both Se and Hg by energy dispersive X-ray microanalysis. The basis of the protective interaction of these two elements appears to result from an alteration of the chemical form or association of the mercury and selenium.
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PMID:Effects of separate and combined chronic mercuric chloride and sodium selenate administration in rats: histological, ultrastructural, and x-ray microanalytical studies of liver and kidney. 54 21

The oral administration of phenylbutazone at a dose rate of approximately 10 mg per kg per day for seven to 14 days resulted in the development of signs of toxicity in seven of eight ponies treated. Clinical signs included anorexia, depression and abdominal oedema. Blood biochemical determinations showed a decrease in total plasma protein and calcium concentrations with an increase in urea concentration. These changes were considered indicative of water retention. Three of the ponies died during treatment following the development of shock. Shock was considered to arise from the submucosal oedema of the large intestine observed on necropsy. Oral ulceration was also found in these animals. In two ponies intravenous administration of phenylbutazone (4.0 mg per kg) for seven days was studied. In one of these ponies a marked decrease in total plasma protein concentration occurred.
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PMID:Phenylbutazone toxicity in ponies. 55 15

Male rats (N = 27) were given initial experience with escapable shock, equivalent amounts of inescapable shock, or no shock. Measures were then obtained in the ensuing 15 hours on food intake, water intake, number of cage crossings, and weight change for all groups. Following this, animals were tested on an escape task. Inescapably shocked animals showed significant decreases in food and water consumption in comparison to both nonshocked and escapably shocked control rats. Weight gains were significantly decreased by exposure to shock irrespective of the availability of a coping response. Consistency of these findings with proposals suggesting that exposure to inescapable shock leads to a state of animal depression (learned helplessness) is discussed and compared to alternative stress explanations.
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PMID:The applicability of inescapable shock as a source of animal depression. 55 62

1. The influence of partial hepatectomy on urinary concentrating ability and renal tissue sodium was determined in conscious rats deprived of water for 24 h. In comparison with a sham operation, partial hepatectomy resulted in: a) a 50% reduction in free-water reabsorption, urinary osmolality, and osmolal urine-to-plasma ratio; b) depression of free-water reabsorption at similar levels of osmolal clearance above 200 microliter/min per ml of GFR during the infusion of hypertonic NaCl and vasopressin; and c) a 30% reduction in sodium content of the renal papilla and outer medulla. 2. The renal response to an intravenous water load (2.5% glucose infused to 2.5% of body wt at 0.4 ml/min) was determined in sham-operated and partially hepatectomized, conscious rats. By 60 min after the water load, both groups had excreted practically all of the load. However, during and for 30 min after the infusion in the partially hepatectomized group, the percent of the water load excreted, urine flow, and free-water clearance were significantly reduced while urinary osmolality and osmolal urine-to-plasma ratio were significantly elevated. 3. These experiments demonstrate that shortly after partial removal of the liver the renal concentrating ability is defective and the excretion of a water load is not grossly impaired.
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PMID:Concentration and dilution of the urine in partially hepatectomized, conscious rats. 56 70

1. Measurements of milk secretion, mammary oxygen consumption and blood flow, cardiac output and blood pressure have been made in lactating goats exposed to a thermoneutral environment and to two levels of cold stress which were sufficient to raise total body oxygen consumption by an average of 18 and 46% above that in a thermoneutral environment. 2. Mammary blood flow and oxygen consumption were not appreciably affected by the milder cold stress but fell to 63 and 70%, respectively, of their thermoneutral value in the moderately cold environment. Resistance to blood flow through the udder was increased by this level of cold stress and the gland took a smaller fraction of an increased cardiac output. 3. Both levels of cold exposure caused a reduction in milk secretion, to 80 and 40% of its thermoneutral value in the mild and moderate cold respectively. The amount of milk secreted per unit volume of blood flowing through the gland decreased as the severity of the cold stress increased. 4. Voluntary food intake was not affected by the change in environmental temperature but the intake of water was reduced to 55% of the thermoneutral value during mild cold exposure and to 40% of the thermoneutral value during the moderate cold stress. 5. It is concluded that a reduction in blood flow to the mammary gland could be one of several possible mechanisms underlying the depression of milk secretion during cold exposure.
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PMID:Effect of cold exposure on mammary circulation oxygen consumption and milk secretion in the goat. 56 44

A single administration of ifenprodil at the doses of 100, 200 and 400 mg/kg (p.o.), and 50 and 100 mg/kg (i.m.) produced a moderate CNS depression in rats, such as, sedation, ptosis, systemic muscle relaxation and decrease in motor activity. These symptoms appeared dose-dependently and persisted for about 4 hours following administration. In a direct physical dependence test, 5 groups of rats were fed the ifenprodil-admixed food together with drinking water ad libitum for 24 hours daily for 53 approximately 103 days (mean ifenprodil intake, 43--240 mg/kg/day), on the gradedly increased dosage schedule with a dosage level of 0.5 vs. 1 mg/g food to 4 mg/g food. In the natural withdrawal following administration, no significant withdrawal signs were observed in any group. In a substitution test either for phenobarbital or morphine, no suppression of withdrawal signs during the period of cross-administration of ifenprodil and no maintenance of dependence were observed. In a physical dependence-producing test, the rats fed ifenprodil never manifested withdrawal signs such as diarrhea, "wet shakes", sudden loss of body weight as in the levallorphan precipitation test. Ifenprodil apparently has no physical dependence liability.
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PMID:[Physical dependence liability test of ifenprodil in rats (author's transl)]. 56 49


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