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S Thomas

Publications and source records attributed to S Thomas.

At least 775 records · Page 43Linked to original sources
PubMed1969

Influence of prehydration on the changes in renal tissue composition induced by water diuresis in the rat.

1. The composition of renal tissue was determined in rats before and immediately after intravenous infusion of dextrose (2.5 g/100 ml.) in amounts sufficient to administer a positive fluid load of 4% body weight over 2 hr. The rats were classified into three groups, according to the preinfusion urine osmolality: hydropaenia, normal and moderately diuretic (over 2400, 800-1500 and below 800 mu-osmoles/g H(2)O, respectively).2. In non-infused rats, the steepness of the corticomedullary osmolal gradient varied, due to differences in both water and solute (sodium and urea) contents, and was related to urinary osmolality. Whereas differences in medullary and papillary solute contents occurred between all three groups, papillary water content was significantly higher only in the moderately diuretic animals.3. Dextrose infusion caused the induction of water diuresis, the lowest urinary osmolalities being produced in the previously moderately diuretic animals.4. Dextrose infusion caused a considerable reduction in the steepness of the corticomedullary osmolal gradient in all rats, particularly in the previously hydropaenic animals, due to changes in both solute (sodium and urea) and water contents. Whereas reductions in medullary and papillary solute contents occurred in all three groups, there was no further increase in papillary water content from the already high values seen in the noninfused diuretic animals.5. Thus, dextrose infusion largely abolished any previous differences in tissue water content, whereas significant, though small, differences in osmolal (particularly urea) content persisted.6. These data are discussed in terms of changes and differences in endogenous antidiuretic hormone (A.D.H.) release.7. Changes in the magnitude and direction of the urinary-papillary urea concentration difference are discussed in terms of passive transport, with probable A.D.H.-induced changes in nephron urea permeability.

Animals↗
PubMed1968

Effects of water diuresis and osmotic (mannitol) diuresis on urinary solute excretion by the conscious rat.

1. The time course and extent of changes in urinary flow and in the outputs of urea, Na(+), K(+), and NH(4) (+) over a period of 7(1/2) hr in conscious rats during water and osmotic (mannitol) diuresis were determined, and compared with spontaneous changes in non-diuretic animals.2. In non-diuretic rats, a morning rise and subsequent decline in urinary osmolal, sodium, potassium and ammonium outputs occurred, possibly attributable to circadian rhythms.3. Water diuresis was accompanied by (i) a rapid increase in urea excretion during the phase of increasing urine flow, followed by a fall in later periods to values similar to those in non-diuresis, (ii) a slower increase in sodium output, continuing after the establishment of the constant water load, (iii) unchanged potassium excretion, but slightly increased ammonium outputs.4. Mannitol diuresis was accompanied by (i) a rapid increase in urea outputs which subsequently fell but remained significantly higher, (ii) a steep rise in sodium and potassium outputs to values which remained far higher than those in non-diuretic and water diuretic animals.5. The changes in mannitol diuresis are considered to result mainly from decreased tubular reabsorption, due to the lowered intraluminal sodium, potassium and urea concentrations and increased intratubular fluid flow. Some of the acute increase in urea excretion may be due to washout of medullary urea into the tubular fluid.6. In water diuresis, some of the changes in solute excretion may similarly result from altered tubular reabsorption, perhaps influenced by suppression of anti-diuretic hormone (A.D.H.). In addition, the slower changes in sodium output may be related to several consequences of change in body fluid volume.

Ammonia↗
PubMed1968

The time course of changes in renal tissue composition during mannitol diuresis in the rat.

1. The time course and extent of changes in the composition of renal tissue slices in osmotic diuresis were determined by sacrificing groups of rats before and during the intravenous infusion of mannitol (15 g/100 ml.) for up to 7(1/2) hr.2. Very rapid changes in tissue water and solute contents occurred within 15 min, preceding the times of maximal diuresis, with little subsequent change even up to 7(1/2) hr.3. The main changes were:(a) an increase in water content in all slices, particularly the papilla; (b) a very profound decrease in papillary and medullary urea content in the first 15 min, with a small, but significant, further decrease, subsequently; (c) a small, but significant, rapid decrease in papillary sodium, and small non-significant increases in the outer medulla and cortex. Subsequent changes in any segment were small and non-significant; (d) apart from small changes in the first 15 min ammonium and potassium contents remained fairly constant.4. The rates of change in papillary and urinary urea concentrations were similar, so that after 30 min, any differences between tip and urinary concentrations were small and non-significant.5. The findings are discussed in terms of factors influencing counter-current mechanisms. It is concluded that altered medullary blood flow is mainly responsible for the rapid changes in medullary composition.6. The relation between papillary and urinary urea concentrations is explicable in terms of passive handling, with equilibration across a freely permeable collecting duct membrane.

Ammonia↗
PubMed1968

The time course of changes in renal tissue composition duruig water diuresis in the rat.

1. The time course and extent of changes in the composition of renal tissue slices in water diuresis were determined by sacrificing groups of rats before and during the intravenous infusion of dextrose (2.5 g/100 ml.) in amounts sufficient to administer over 2 hr, and subsequently to maintain for up to 7(1/2) hr, a positive fluid load of 4% body weight.2. The corticomedullary osmolal gradient characteristic of the nondiuretic rats was progressively dissipated until, at 7(1/2) hr, only papillary tip concentrations were higher than those of other segments.3. The changes in individual constituents followed different time courses: (i) an increase in water content in all segments, particularly the papilla, was almost complete by 1 hr, preceding the maximal increases in urine flow; (ii) a marked decrease in papillary and medullary urea content in the first hour was followed by a slower, progressive decrease leading to an almost complete dissipation of the urea gradient by 7(1/2) hr; (iii) small, non-significant decreases in sodium content occurred in all segments in the first hr, followed by a further small, progressive decrease in papillary sodium content; (iv) changes in ammonium and potassium concentrations were mainly related to those in water content, since the contents of these solutes showed only small changes.4. By 2 hr, differences in the rates of decline of osmolal and urea concentrations in urine and papilla led to urinary concentrations significantly lower than papillary values. The steep papilla-urine urea concentration difference became smaller, but remained significant even at 7(1/2) hr.5. The findings are discussed in terms of changes in countercurrent mechanisms, particularly as influenced by anti-diuretic hormone.6. The development of papilla/urine urea concentration ratio greater than unity is also considered in terms of passive transport with changes in membrane permeability.

Ammonia↗
PubMedDate not supplied

Prognostic value of a normal or nonspecific initial electrocardiogram in acute myocardial infarction.

CONTEXT: Although previous studies have suggested that normal and nonspecific initial electrocardiograms (ECGs) are associated with a favorable prognosis for patients with acute myocardial infarction (AMI), their independent predictive value for mortality has not been examined. OBJECTIVE: To compare in-hospital mortality among patients with AMI who have normal or nonspecific initial ECGs with that of patients who have diagnostic ECGs. DESIGN, SETTING, AND PATIENTS: Multihospital observational study in which 391 208 patients with AMI met the study criteria between June 1994 and June 2000 and had ECGs that were normal (n = 30 759), nonspecific (n = 137 574), or diagnostic (n = 222 875; defined as ST-segment elevation or depression and/or left bundle-branch block). A logistic regression model was constructed using a propensity score for ECG findings and data on demographics, medical history, diagnostic procedures, and therapy to determine the independent prognostic value of a normal or nonspecific initial ECG. MAIN OUTCOME MEASURES: In-hospital mortality; composite outcome of in-hospital death and life-threatening adverse events. RESULTS: In-hospital mortality rates were 5.7%, 8.7%, and 11.5% while the rates of the composite of mortality and life-threatening adverse events were 19.2%, 27.5%, and 34.9% for the normal, nonspecific, and diagnostic ECG groups, respectively. After adjusting for other predictor variables, the odds of mortality for the normal ECG group was 0.59 (95% confidence interval [CI], 0.56-0.63; P<.001) and for the nonspecific group was 0.70 (95% CI, 0.68-0.72; P<.001), compared with the diagnostic ECG group. CONCLUSION: In this large cohort of patients with AMI, patients presenting with normal or nonspecific ECGs did have lower in-hospital mortality rates than those of patients with diagnostic ECGs, yet the absolute rates were still unexpectedly high.

Aged↗
PubMedDate not supplied

ACE, PAI-1, decorin and Werner helicase genes are not associated with the development of renal disease in European patients with type 1 diabetes.

BACKGROUND: Genetic factors are involved in the development of diabetic nephropathy in Type 1 diabetes. We have examined the association of four candidate genes, angiotensin converting enzyme (ACE): insertion/deletion (I/D) polymorphism, plasminogen activator inhibitor-1 (PAI-1): 4G/5G polymorphism, decorin: 179/183/185 polymorphism and Werner syndrome helicase: C/R polymorphism, with the presence of diabetic nephropathy in Type 1 diabetic patients. METHODS: 175 Type 1 diabetic patients with albuminuria (59 with microalbuminuria and 116 with macroalbuminuria) were compared with 136 Type 1 diabetic patients with normoalbuminuria and duration of disease longer than 15 years (mean+/-SD: 25+/-8 years). 200 non-diabetic subjects were also studied as background population. RESULTS: We found no association in the polymorphism of the four genes examined between patients with and without diabetic nephropathy and the control subjects. CONCLUSIONS: The genes studied are unlikely to be involved in the susceptibility to nephropathy in Type 1 diabetic patients.

Adult↗