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Biomedical subjects

Z Iqbal

Publications and source records attributed to Z Iqbal.

At least 73 records · Page 4Linked to original sources
PubMed1987

The effects of postoperative factors on serum thyroid hormones and rat liver nuclear 3,5,3'-triiodothyronine receptor concentrations in surgical models of uremia and regenerating liver.

We have determined the individual effects of postoperative fasting, surgical/anesthetic factors, acute uremia (AU), and regenerating liver (RL) on nucleoplasmic (NP; 0.15 M KCl-extractable) and chromatin-bound (CB; 0.4 M KCl-extractable) rat liver T3 receptors. AU and RL rats were studied 24 h after bilateral nephrectomy (blood urea nitrogen, 128 +/- 13 mg/dl) or two thirds hepatectomy, respectively. The effects of postoperative fasting were assessed by comparison of normal rats (N) with control rats (N6) pair-fed to match the caloric intake of the AU and RL rats. Surgical/anesthetic effects were determined by comparison of N6 rats with sham-operated pair-fed rats (S6). The effects of AU or RL were obtained by comparison with S6 controls. Changes in mean body weight attributable to fasting (N6-N), surgical/anesthetic effects (S6-N6), acute uremia (AU-S6), and regenerating liver (RL-S6) were: -17.3 (P less than 0.001), -4.0 (P = NS), -4.5 (P less than 0.05), and -1.0 g/24 h (P = NS), respectively. Changes in mean serum T4 (N, 5.3 +/- 1.3 micrograms/dl) were: -1.0 (P = NS), -0.6 (P = NS), -0.9 (P less than 0.05), and -1.0 micrograms/dl (P less than 0.05), respectively. Changes in mean serum T3 (N, 53 +/- 23 ng/dl) were: -8 (P = NS), -18 (P less than 0.05), -10 (P = NS), and -14 ng/dl (P less than 0.05), respectively. The NP and CB receptor pools of the AU and RL rats were not significantly different from those of age-matched N rats (NP, 25 +/- 5 fmol/mg DNA; CB, 405 +/- 134 fmol/mg DNA). Chronically uremic (CU) rats 2 weeks after five sixths nephrectomy (blood urea nitrogen, 36 +/- 2 mg/dl) did not exhibit significant change in their extractable receptor pools. Complete starvation for 24 h (NO) or 72 h (NOO) generally resulted in marked reductions in receptor concentrations compared to those in age-matched N rats fed ad libitum: NP pool (N, 31 +/- 17 fmol/mg DNA): NO-N, -40% (P = NS); NOO-N, -59% (P less than 0.01); CB pool (N, 303 +/- 105 fmol/mg DNA): NO-N, -19% (P less than 0.05); NOO-N, -41% (P less than 0.001). These studies indicate that severe AU, moderate CU, and LR have relatively little effect on solubilized rat liver nuclear receptor concentrations. In contrast, complete starvation is a potent depressant of both nuclear receptor pools. In the surgical models of AU and LR, postoperative fasting was the primary cause of weight loss.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Polyamines appear to be second messengers in mediating Ca2+ fluxes and neurotransmitter release in potassium-depolarized synaptosomes.

High potassium (50 mM) depolarization induces a rapid (less than 15 sec) increase in the levels of the polyamines putrescine, spermidine and spermine and their rate-regulating synthetic enzyme ornithine decarboxylase in synaptosomes from rat cerebral cortex. The ornithine decarboxylase inhibitor alpha-difluoromethylornithine blocked the K+-stimulated increase in enzyme activity and polyamines and also suppressed the increase in 45Ca2+ influx and efflux and the Ca2+-dependent release of GABA and norepinephrine. Added putrescine attenuated or negated the effects of alpha-difluoromethylornithine. These results suggest that enhanced polyamine synthesis is required for potassium depolarized stimulation of synaptic function.

Animals↗
PubMed1980

Calmodulin in mammalian nerve.

Calmodulin, a calcium-dependent regulatory protein has been isolated from mammalian nerve. The protein has similarities to the calcium-binding protein earlier shown to be transported at a fast rate in the nerve fibers. The implication is that calmodulin, which has been shown to be involved in various key cellular processes, may have a relation to axoplasmic transport.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1980

Uptake of Vinca alkaloids into mammalian nerve and its subcellular components.

Three Vinca alkaloids, vinblastine (VLB), vincristine (VCR), and vindesine (VDS), were recently found to affect axoplasmic transport to different degrees, with VCR the most potent. The uptake of these three species by desheathed cat sciatic nerves in vitro was determined by using tritium-labeled derivatives. In a sucrose medium, the uptake of VCR was found to be three to four times greater than that of VLB and VDS, which is in accord with the neurotoxicity of VCR. Uptake of VCR was dependent on Ca2+ concentration in the medium. Removal of Ca2+ from the incubation medium reduced the uptake of VCR, without having much effect on VLB or VDS uptake. The uptake of all three Vinca agents into nerve in a saline medium was about 50% of that in a sucrose medium, and elimination of Ca2+ from the saline incubation medium did not result in any significant change in uptake. High Ca2+ concentrations (100 mM) in the incubation medium, which cause a block of axoplasmic transport, did not change the total uptake of the Vinca alkaloids to any significant degree. The amount of labeled alkaloid found in the soluble fraction was, however, decreased by 50%. There was an increase in the amount present in the particulate fraction, caused, most likely, by an aggregation of vinca-binding components. The amount of VCR associated with tubulin-containing components isolated by gel filtration of the soluble fraction increased twofold when the nerves were exposed to a high-Ca2+ medium, as might be expected of a microtubule disassembly. Exposure of the nerve to low temperatures (0 degrees-4 degrees C) for 90 min did not show any effect on the total uptake of Vinca alkaloids.

Animals↗
PubMed1976

DNA repair synthesis in guinea pig pancreatic slices following in vitro exposure to N-nitrosomethylurethane.

The incorporation of thymidine into DNA in the presence of hydroxyurea (HU) by guinea pig pancreatic slices following exposure to N-nitrosomethylurethane (NMUT) was used to follow DNA repair synthesis. HU was used to suppress normal replicative DNA synthesis. Slices from the duodenal segment of the pancreas were exposed for periods of 15 to 90 min to NMUT at concentrations of 2 to 20 mM, then incubated in tritiated thymidine ([H3]-TdR) free of carcinogen, and radioactivity in DNA was determined. NMUT induced a a dose- and time-dependent increase in HU-insensitive thymidine incorporation. This stimulated incorporation, which could be attributed to repair synthesis, occurred immediately following the treatment and was largely complete within 3 h.

Animals↗