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Biomedical subjects

N Farman

Publications and source records attributed to N Farman.

101 records · Page 6Linked to original sources
PubMed1978

Binding of aldosterone to cytoplasmic and nuclear receptors of the urinary bladder epithelium of Bufo marinus.

Binding of aldosterone to cytoplasmic and nuclear sites in urinary bladder epithelia of Bufo marinus (Dominican variant) is saturable and dependent upon steroid concentration. Scatchard analysis of specific cytoplasmic binding yielded a maximal binding capacity (N) of 14.5 X 10(-14) mol/mg protein and an apparent equilibrium dissociation constant (Kd) of 1.4 X 10(-8) M. Since Scatchard analysis of specific nuclear binding was complex, this binding was resolved by a computer-generated cirve-fitting technique which analyzed total aldosterone bound. Nuclear binding was resolved into three sites: a nonsaturable site that was linearly dependent upon aldosterone concentration, and two saturable sites (types I and II). Type I sites had relatively low capacity for aldosterone (N = 31 +/- 1 X 10(-14) mol/mg DNA) and high affinity (Kd = 2.5 +/- 0.5 X 10(-9 M); tffininty (Kd = 8.6 +/- 1.7 X 10(-7) M). Competition for [3H]aldosterone binding by dexamethasone, corticosterone, cortisol, progesterone, testosterone, and 17 beta-estradiol demonstrated that type I nuclear sites have higher affinity for aldosterone than for other steroids. The findings are consistent with the inference that the type I site is the mineralocorticoid receptor.

Aldosterone↗
PubMed1978

Aldosterone receptor occupancy and sodium transport in the urinary bladder of Bufo marinus.

The concentration dependence of binding of [3H]aldosterone to cytoplasmic and nuclear receptors was evaluated in urinary bladder epithelial cells of Colombian toads. One class of specific sites (sensitive to displacement by excess aldosterone) was detected in the cytosol. However, two classes of specific nuclear [3H]aldosterone binding sites were evident. In the nucleus, high-affinity (Kd = 2.7 X 10(-9) M), low-capacity (N = 15 X 10(-14) mol/mg DNA) sites (type I) were completely saturated at approximately 4 X 10(-8) M aldosterone, a concentration which gave a maximal increase in short-circuit current (SCC). Occupancy of low-affinity (Kd = 4.6 X 10(-7) M), high-capacity sites (N = 150 X 10(-14) mol/mg DNA) (type II) occurred at higher steroid concentrations and did not correlate with further increase in SCC. Binding parameters of Colombian and Dominican variants of Bufo marinus were compared. In both variants, the SCC increase elicited by aldosterone correlated with accumulation of type I complexes in the nucleus, but the relationship was markedly nonlinear. Various alternatives were considered as the basis for a curvilinear dependence of the increment in Na+ transport on abundance of nuclear type I complexes.

Aldosterone↗
PubMed1977

Number of glomeruli in normal and hypertrophied kidneys of mice and guinea-pigs.

1. In mice and guinea-pigs, the number of glomeruli was counted in kidneys during normal growth and in hypertrophy induced by unilateral nephrectomy. 2. In mice, the number of glomeruli increased sharply during the first 2 weeks in life, and more slowly afterwards. Unilateral nephrectomy, when performed during this period of natural increase, induced the formation of supplementary nephrons in the contralateral kidney. 3. In guinea-pigs, the number of glomeruli was almost complete at birth. No evidence of a supplementary increase in the number of nephrons was found in hypertrophied kidneys following unilateral nephrectomy. 4. These results, together wit previous data obtained in the rat, suggest that the ability to induce new nephrons after unilateral nephrectomy in different species would depend more on the state of kidney maturity at birth than on differences in the renal mechanisms which lead to hypertrophy.

Age Factors↗
PubMed1975

Ultrastructural and histochemical study of the adrenal medulla in normal and cold-stressed Syrian hamsters.

The effect of 24 and 48 hours' cold stress on the hamsters' adrenomedullary follicles and on the medullary ATPase activity was studied by light and electron microscopy. Only norepinephrine cells were depleted after this stress, and exocytosis seemed to be the mechanism involved in the release of catecholamine. Follicles containing these cells expanded and their lumina became narrow. A few other cellular and follicular changes also occurred and are described. ATPase activity was apparent in control organs along the endothelial linings, in neural elements and macrophages, and in approximately 40% of the linings of follicular lumina. Cold stress did not alter this pattern. These results have been compared with previous findings and the possible functions of the follicular lumina are discussed. It is concluded that they are unlikely sites for catecholamine storage or release.

Adenosine Triphosphatases↗
PubMed1975

Abnormal relationship between sodium excretion and hypertension in spontaneously hypertensive rats.

Inulin clearance, single nephron glomerular filtration rate (SNGFR), Na and K excretion were studied following an acute saline infusion in spontaneously hypertensive (Okamoto strain) rats (SH). 1. Hypertonic saline load: experiments were performed in adult and young SH rats. As compared to control normotensive Wistar rats (NI), the sodium excretion rose much less following the load in SH. During the 75 min following the beginning of the load, adult SH excreted 15 degrees (NT: 58%) and young SH 9%(NT = 38%) of the sodium load (P less than 0.01 in both cases). Cin were similar in SH and NT during control period, and a similar increase was observed following the load. The superficial to juxtamedullary SNGFR ratio was 0.80 plus or minus 0.05 in 5 non diuretic adult SH, a value not different from that found in normal rats, and 0.87 plus or minus 0.07 in 3 salt loaded SH, indicating that no significant intrarenal GFR redistribution occurs in SH following an acute hypertonic saline load. 2. Following an isotonic saline load, the results were not different: the percentage of the sodium load excreted was 44 plus or minus 5% and 10 plus or minus 2% in NT and SH adult rats respectively. The possibility that the observed defect in sodium excretion of SH rats involves distal tubular function is suggested by the pattern of evolution in Na and K excretion.

Age Factors↗