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Biomedical subjects

J B Coelho

Publications and source records attributed to J B Coelho.

24 records · Page 2Linked to original sources
PubMedDate not supplied

Changes in glomerulotubular dimensions, single nephron glomerular filtration rates and the renin-angiotensin system in hypothyroid rats.

Glomerular diameters (GD) and lengths of attached proximal convoluted tubules (TPL) were measured in nephrons dissected from the superficial (S), intermediate and juxtamedullary (JM) cortex (7-15 each) of acid-macerated kidneys of weight-matched (E) euthyroid and (H) hypothyroid (2-6 months after radioiodine treatment or thyroidectomy) male Sherman-Wistar rats. Incoordination of growth in H rats was evident in a more marked retardation in kidney than in total body growth. A similar incoordination of microstructural growth was evident in maintenance or GD within normal limits with respect to body weight while attached TPL fell 23% on the average below control values relative to body weight. These changes affected the total nephron population uniformly. As a result, GD/TPL in all nephrons increased significantly (p less than 0.01), by 27% in S and by 29% in JM nephrons. The glomerulotubular dimensional imbalance was associated with a marked and uniformly distributed reduction in single nephron glomerular filtration rate (ferrocyanide method), by 36% in S and JM nephrons. Plasma renin activity fell within normal limits while plasma renin substrate was decreased to 56% of control values. These findings are construed as evidence that growth retardation in hypothyroid rats affects the parenchyma of the kidney (and perhaps other viscera) more than the vasculature.

Angiotensin II↗
PubMedDate not supplied

Ellepsis and akairial disproportion in the hypothyroid rat.

Renal structural and functional changes observed in rats during hypothyroidism have been employed to illustrate the concepts of "ellepsis" and "akairia" that have emerged from the work of Cournand and Richards. Ellepsis--the inadequate homeostatic response--is evident in the failure of corrective adjustments in glomerular filtration rate to prevent the excessive natriuresis and detrimental salt loss typical of this disorder in the rat but not in man. A slowing in overall bodygrowth is associated with an inappropriate (akairial) disproportion in the growth of glomeruli and tubules. Comparison of the changes in body weight, glomerular diameters, and tubular lengths in euthyroid and hypothyroid (radioiodine) littermates showed that glomeruli continued to grow in proportion to total body weight following administration of radioiodine while tubular growth almost ceased. Since disproportional failure of pulmonary growth has also been observed in these studies (0.829 +/- SEM 0.040 g in hypothyroid rats as compared with 1.14 +/- 0.034 g in euthyroid weight-matched controls), it may be profitable to look for abnormalities in respiratory homeostasis in the hypothyroid rat.

Animals↗
PubMedDate not supplied

Glomerulotubular dimensional readjustments during compensatory renal hypertrophy in the hypothyroid rat.

Although growth of tubules is arrested and that of glomeruli retarded by hypothyroidism in rats, unilateral nephrectomy has been found to elicit a vigorous compensatory hypertrophy of the hypothyroid kidney. Microdissection and measurement of the dimensions of glomeruli and proximal convoluted tubules taken from the kidney removed first and from the hypertrophic contralateral organ removed two to three weeks later, disclosed a "normalization" of the typical glomerulotubular dimensional imbalance as a result of greater tubular than glomerular growth. A somewhat more striking but qualitatively identical response was observed in 9 euthyroid animals. Glomerular filtration rate and maximal glucose reabsorptive capacity (Tm(G)) increased in both euthyroid and hypothyroid animals in accord with the structural shifts.

Adaptation, Physiological↗