PubMed Health⌕ Search

Biomedical subjects

B Stanton

Publications and source records attributed to B Stanton.

87 records · Page 5Linked to original sources
PubMed1985

Ultrastructure of rat initial collecting tubule. Effect of adrenal corticosteroid treatment.

This study examines the effects of adrenalectomy and physiological replacement of mineralocorticoids and glucocorticoids on the cellular ultrastructure of the rat initial collecting tubule (late distal tubule). Animals were adrenalectomized (ADX) and for 10 d received by osmotic minipump either: vehicle, aldosterone (0.5 micrograms X 100 g-1 X d-1), aldosterone (2.0 micrograms X 100 g-1 X d-1), dexamethasone (1.2 micrograms X 100 g-1 X d-1), or aldosterone (0.5 micrograms X 100 g-1 X d-1) with dexamethasone (1.2 micrograms X 100 g-1 X d-1). Radioimmunoassay revealed that the low dose of aldosterone restored plasma aldosterone to control levels. The higher dose of aldosterone increased plasma levels by threefold. Morphometric techniques were used to measure membrane length of individual principal and intercalated cells in each condition. The basolateral membrane length of principal cells decreased by 35% in ADX animals. Low dose aldosterone replacement (0.5 micrograms X 100 g-1 X d-1) in ADX animals maintained membrane length at control values; at a higher level of aldosterone (2.0 micrograms X 100 g-1 X d-1) membrane length increased by 111% compared with control. Dexamethasone treatment, at a level that restored glomerular filtration rate to normal, had no effect on cellular ultrastructure. Combined aldosterone and dexamethasone replacement had no greater effect on basolateral membrane length than aldosterone alone. The length of the luminal membrane of the principal cell type was not affected by ADX or hormone treatment. Intercalated cell membrane length was not affected by ADX or hormone replacement. Thus, chronic aldosterone levels have an important, selective effect on the basolateral membrane of the principal cell. The correlation between these morphological results and the steroid hormone effects on renal electrolyte excretion, reported in the companion paper (15), suggests that basolateral membrane length is an important factor controlling the rate of sodium and potassium transport by the initial collecting tubule.

Adrenal Cortex Hormones↗
PubMed1985

The urban volunteer programme in Dhaka: a community based primary health care and research initiative.

In response to a recognition that existing health facilities could not adequately reach the poorer sections of Dhaka city, the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) established the Urban Volunteer Programme in 1981. This paper describes the primary health care and research activities of this program and suggests that such an approach can be and should be used in other urban areas of developing countries.

Adult↗
PubMed1984

Cellular ultrastructure of Amphiuma distal nephron: effects of exposure to potassium.

The cellular ultrastructure of the renal distal nephron of the salamander, Amphiuma means, was examined by electron-microscopic and stereological techniques before and after exposure to potassium in the ambient environment. The distal nephron of Amphiuma is composed of three ultrastructurally distinct segments: early distal (or diluting segment), late distal, and collecting tubule. The early distal tubule structurally resembles the mammalian thick ascending limb of Henle's loop. Large renin-like granules are present in the smooth muscle cells of the afferent arteriole in the vicinity of the early distal tubule, suggesting the presence of a rudimentary juxtaglomerular apparatus. Late distal tubules are composed of one large cell type characterized by extensive basal membrane invaginations, often extending to the luminal membrane. Collecting tubules contain principal and intercalated cells that are ultrastructurally similar to cells of the mammalian cortical collecting tubule. Exposure to potassium had no effect on the ultrastructure of early distal cells but led to a sharp increase in the basolateral membrane surface density of principal cells in the collecting tubule (1.17 +/- 0.08-1.63 +/- 0.13 micron2/micron3). Potassium adaptation leads to a similar structural response in the mammalian collecting tubule. Since Amphiuma collecting tubules can be isolated and perfused in vitro and impaled with ion- and voltage-sensitive microelectrodes, the observed structural adaptation suggests that the collecting tubule may be a useful preparation to study the cellular mechanisms of potassium adaptation.

Animals↗
PubMed1983

Inhibitory effect of epinephrine on renal potassium secretion: a micropuncture study.

The effect of epinephrine on renal potassium excretion was examined in the rat. In group I KCl was infused acutely to increase plasma K (PK) by 2.0 meq/liter; urinary K excretion (UKV) rose by 1.22 mueq/min. In group II rats, which received a similar dose of KCl but with epinephrine, the increase in PK (delta = 0.8 meq/liter, P less than 0.001) was blunted and UKV was reduced (delta = 0.23 mueq/min, P less than 0.001). To determine whether the reduction in UKV resulted from the smaller increase in PK or from a direct action of epinephrine on renal K transport, a third group of animals received a lower dose of KCl. Despite similar PK levels, the epinephrine group excreted significantly less K in the urine (0.61 vs. 0.93 mueq/min). In group IV propranolol was infused with KCl; UKV was modestly increased. The effects of epinephrine on UKV were unrelated to changes in glomerular filtration rate, urine flow, or UNaV. Micropuncture results showed that at comparable PK levels epinephrine had no direct effect on K secretion by the distal tubule but indirectly inhibited K secretion in this nephron segment by reducing PK. In addition, epinephrine reduced K addition at tubular sites beyond the late distal tubule, most likely in the collecting tubule.

Animals↗
PubMed1983

Influence of acute potassium loading on renal phosphate transport in the rat kidney.

UNLABELLED: This study examined 1) whether potassium-induced depression of phosphate excretion is a parathyroid hormone-dependent phenomenon, and 2) whether such stimulation of tubular phosphate reabsorption capacity involves increased phosphate reabsorption in the distal tubule. Potassium was infused into intact rats (25 mumol X min-1 X kg-1) during stepwise addition of phosphate to the infusion and led to a significant drop in phosphate excretion; this effect was abolished in thyroparathyroidectomized (TPTX) animals. In intact rats the maximal tubular Pi reabsorption per milliliter of glomerular filtrate (max TRPi/ml GF) was significantly higher in the potassium group (2.54 +/- 0.06 mumol/ml GF) compared with the control group (2.31 +/- 0.06 mumol/ml GF) (means +/- SE). In TPTX rats no difference in max TRPi/ml GF was observed: 3.44 +/- 0.07 and 3.49 +/- 0.07 mumol/ml GF during potassium and sodium infusion, respectively. Free-flow micropuncture was carried out on superficial distal tubules of intact rats and fluid samples were analyzed for [3H]inulin and phosphorus (electron microprobe). Phosphorus delivery into the distal tubule was similar in control and potassium-loaded rats. Whereas net phosphorus reabsorption along the distal tubule was absent in the control group, intravenous potassium administration stimulated distal phosphorus reabsorption. CONCLUSION: potassium stimulates renal phosphate reabsorption capacity, an effect that is abolished after TPTX. The potassium effect on phosphate occurs along the distal tubule.

Animals↗
PubMed1975

Collision behavior of young drivers. Impact of the change in the age of majority.

A comparison of the number of collisions experienced by young male drivers in London, Ontario, before and after the reduction in the legal age for drinking and purchasing alcoholic beverages from 21 to 18, indicated that the change in the law led to an increase in the collision involvement of young drivers.

Accidents, Traffic↗
PubMedDate not supplied

Equivocal test results and prognostic staging uncertainties in the evaluation of patients with cancer of the prostate.

In the staging of cancer, equivocal test results may occur in subjectively evaluated imaging procedures whose interpretations raise the possibility of metastases but are too uncertain to rule in or rule out metastatic spread, and in tests whose repetitions in the same patient yield conflicting results about dissemination. We assessed the frequency and prognostic correlates of test results giving equivocal evidence of disseminated (Stage IV) disease in an inception cohort of 280 patients receiving initial treatment for prostatic cancer between 1973-76. Among tests used for clinical staging, lymphangiograms (equivocal in 28 percent of tested patients), bone scans (equivocal in 25 percent of tested patients), and bone radiographs (equivocal in 20 percent of tested patients) most frequently yielded interpretations that equivocally suggested metastatic spread. Eighty-three (45 percent) of the 185 patients without clear-cut dissemination (Stages I-III) had at least one equivocal test result that suggested dissemination and that remained unresolved at the time of selection of therapy. Five-year survival (30 percent) for the 20 patients with local extracapsular spread (Stage III) and multiple equivocal results suggesting dissemination was identical to that for patients with clear-cut dissemination. In contrast, other patients with equivocal dissemination in Stages I-III had survival rates similar to those patients in the same stage and lacking equivocal dissemination. Unresolved equivocal staging results frequently complicate management decisions for patients with prostatic cancer. Survival analyses aid these decisions by demonstrating that equivocal findings of dissemination are prognostically unimportant unless they are multiple and occur in the context of unequivocal extracapsular spread.

Acid Phosphatase↗