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Biomedical subjects

S Khan

Publications and source records attributed to S Khan.

At least 397 records · Page 22Linked to original sources
PubMed1988

Analysis of bacterial flagellar rotation.

Bacterial flagella have rotary motors at their base; embedded in the cytoplasmic membrane and powered by transmembrane ion gradients instead of ATP. Assays have been developed to measure the torque output of individual motors over a wide regime of load, to correlate the energizing proton flux with rotation speed and relate through genetic analysis motor structure to function. These assays promise substantial advances in understanding mechanochemical coupling in these motors. Here, I summarize the present status of our understanding of energy transduction in bacterial flagella and compare this with the case for muscle.

Bacteria↗
PubMed1988

Effect of hexacarbons on selected lipids in developing rat brain and peripheral nerves.

The effects of neurotoxic solvents, i.e. 2,5-hexanedione (2,5-HD), 2,5-hexanediol (2,5-HDiol) and the non-neurotoxic solvent, 2,4-hexanedione (2,4-HD) (500 mg/kg body wt./day, i.p.), have been studied on the lipid composition of brain and sciatic nerves in weanling rats. Five-day-old rats were administered a solvent daily for 21 days. Clinical signs of peripheral neuropathy appeared in 2,5-HD and 2,5-HDiol treated groups. Absolute weights of brain, spleen, thymus significantly decreased with 2,5-HD. Cholesterol content in whole brain homogenates and myelin was significantly reduced with 2,5-HD and 2,5-HDiol treatment. There was also a significant reduction in ubiquinone content of brain with 2,5-HD and 2,5-HDiol treatment. On exposure to neurotoxic chemicals to weanling rats, significant alteration in lipid profile was observed in the brain, which may be one of the key factors in the development of neuropathy.

Animals↗
PubMed1988

In vivo determinations of labelling index of metastatic colorectal carcinoma and normal colonic mucosa using intravenous infusions of bromodeoxyuridine.

In vivo determination of the labelling index of metastatic colon carcinoma was performed in 14 patients following intravenous infusion of bromodeoxyuridine (BrdU), at doses of 100 and 50 mg/M2. No toxicity was seen. Labelled cells were detected by an immunohistochemical technique using a monoclonal antibody to BrdU. Labelling was uniform and highly specific with good preservation of morphology. Labelling index values ranged from 15.0-40.6% for metastatic lesions and 3.6%-20% for normal colonic mucosa, with mean values of 24% and 11%, respectively. This represents a useful new method for in vivo labelling index determination in solid tumors.

Bromodeoxyuridine↗
PubMed1988

Comparison of the inhibitory effects of some compounds present in crude oils on rat platelet aggregation: role of intra- and extra- cellular calcium.

In vitro addition of some representative aliphatic, aromatic or heterocyclic compounds present in petroleum crude oils to washed rat platelets resulted in a concentration-dependent inhibition of aggregation induced by ADP or thrombin. Increasing concentration of extracellular Ca2+ did not alter the pattern of inhibition. ADP-induced intracellular Ca2+ mobilization was unaffected by most of the compounds tested. However, Ca2+ uptake was significantly inhibited when platelets were preincubated with these agents. This suggests that some components of crude oil may inhibit platelet aggregation by bringing about alterations in the platelet plasma membrane.

Adenosine Diphosphate↗
PubMed1988

Ontogeny and cellular origin of an interleukin-1-like factor in the reproductive tract of the male rat.

We have recently isolated an interleukin-1 (IL-1)-like factor from the rat testis, which originates from the seminiferous tubules and is a protein with an MW of 17,000 and a pI of 5-6. This paper reports on the appearance of the IL-1-like factor during postnatal development and investigates its cellular origin further. IL-1 activity was measured by a murine thymocyte proliferation assay. Very low IL-1 activity was present in culture medium conditioned by seminiferous tubules from rats aged 10 or 20 days. From 30 days of age, increasing amounts were detected, reaching a maximum level in adult animals (60-90 days). No IL-1 activity was found in medium conditioned by peritubular cells. Sertoli cell-enriched seminiferous tubules obtained from experimentally cryptorchid or from prenatally irradiated rats produced much higher levels of IL-1 activity than did those obtained from intact testes. IL-1 activity was detected in efferent duct fluid after ligation of the efferent ducts for 24 h, indicating that the IL-1-like factor was secreted into the tubular lumen. Low levels of IL-1 activity were detected in extracts of epididymal tissue and epididymal sperm, whereas ejaculated seminal plasma, seminal vesicle fluid and extracts of seminal vesicles (together with the coagulating glands) and ventral and dorsolateral prostate lacked IL-1 activity. Instead, seminal plasma inhibited testicular IL-1 activity dose-dependently without affecting cell viability in the thymocyte cultures. Although its biological function remains to be defined, our results indicate that the testicular IL-1-like factor is produced by Sertoli cells and that its appearance during development coincides with the initiation of active spermatogenesis in the rat testis.

Animals↗
PubMed1988

Characterization of a novel anti-peptide antibody that recognizes a specific conformation of the platelet-derived growth factor receptor.

Two site-specific anti-peptide antibodies (AbP1 and AbP2) were raised against the platelet-derived growth factor (PDGF) receptor. These two sites correspond to amino acid residues 977 through 988 (peptide 1) and 932 through 947 (peptide 2) of the murine PDGF receptor. Both antibodies recognized human and murine PDGF receptors in immunoprecipitation and immunoblotting analyses. None of the antibodies was directed to phosphotyrosine. One of the antibodies (AbP2) showed unusual antigen recognition specificity. This antibody specifically recognized the tyrosine-phosphorylated PDGF receptor and not the unphosphorylated native receptor, suggesting that recognition by this antibody requires a specific conformation that is induced by PDGF-stimulated autophosphorylation.

Animals↗
PubMed1988

Early post-pneumonectomy bronchial stump fistula.

Bronchial stump fistula occurred on the seventh postoperative day in a 45-year-old man who underwent right pneumonectomy for T2N2M0 adenocarcinoma of the lung. It was attributable to ventilator-related barotrauma during treatment of ARDS from multiple pulmonary emboli. A frequently lethal complication, its presentation, management and prevention in the early postoperative period are discussed.

Adenocarcinoma↗
PubMed1987

The hepatotoxic potential of a Prudhoe Bay crude oil: effect on mouse liver weight and composition.

The hepatotoxic properties of a Prudhoe Bay Crude Oil (PBCO) were evaluated in mice. Administration of PBCO (5.0 ml/kg body wt, daily for 2 days) to mice resulted in an increase in (i) liver wet and dry weight, (ii) hepatic total proteins, RNA, glycogen and total lipids, and (iii) individual lipids such as cholesterol, triglycerides and phospholipids. Hepatic protein biosynthesis, determined in vivo by administration of L-[14C]leucine was increased in PBCO exposed mice. The rate of 3H incorporation from 3H2O was significantly enhanced in liver fatty acids, cholesterol, triglycerides and thus ultimately in total lipids. Also, an increase in 3H incorporation was noticed in hepatic glycogen after PBCO administration. The results suggest that PBCO may induce hepatotoxicity by altering the intermediary metabolism of biochemical constituents.

Animals↗
PubMed1987

Expression of the protooncogenes c-myc, c-fos, and c-fms in acute myelocytic leukemia at diagnosis and in remission.

RNA transcript levels of the protooncogenes c-myc, c-fos, and c-fms were measured in bone marrow cells obtained from patients with acute myelocytic leukemia at diagnosis or in complete remission. As controls, normal bone marrow cells were studied. The c-myc RNA levels are significantly higher in acute myelocytic leukemia cells at diagnosis than in remission or in normal marrow cells. In most instances the high c-myc RNA levels are a reflection of the high proportion of immature cells present in leukemic marrows. The bone marrow cells of several patients contain extremely high levels of c-myc RNA, levels which cannot be accounted for by the proportion of immature cells present in the bone marrow. The leukemic cells of patients with morphologically indistinguishable leukemias manifest different patterns of c-myc, c-fos, and c-fms expression. This observation is consistent with differences in behavior of leukemic cells even among patients with the same French-American-British type of leukemia. The normal-appearing bone marrow cells of some acute myelocytic leukemia patients in complete remission differ from normal bone marrow cells in having slightly higher c-myc RNA levels, as well as in the pattern of expression of c-fos and c-fms. The possible use of protooncogene expression patterns to subdivide the French-American-British categories of acute myelocytic leukemia into subtypes with greater prognostic significance is discussed.

Bone Marrow↗
PubMed1987

Effectiveness of a Prudhoe Bay crude oil and its aliphatic, aromatic and heterocyclic fractions in inducing mortality and aryl hydrocarbon hydroxylase in chick embryo in ovo.

Prudhoe Bay crude oil (PBCO) and its aliphatic, aromatic and heterocyclic fractions were tested on the developing chick embryo for (i) embryotoxicity (ii) their ability to induce hepatic and renal cytochrome P450 levels as well as hepatic, renal and pulmonary aryl hydrocarbon hydroxylase activities. On the basis of its concentration in PBCO, the aromatic fraction was responsible for most of the embryotoxicity as well as for the enzyme inducing ability. The NOS fraction constituted less than 7% (w/v) of PBCO but, on a weight equivalent basis, was roughly as potent as the aromatic fraction in causing embryotoxicity and in inducing cytochrome P450 levels and aryl hydrocarbon hydroxylase. The aliphatic fraction was found to be essentially inactive. The results are consistent with the concept that elevation of aryl hydrocarbon hydroxylase levels by certain components of PBCO may lead to increased embryotoxicity.

Animals↗
PubMed1987

Differing patterns of proto-oncogene expression in immature and mature myeloid cells.

Comparisons of the level of proto-oncogene expression in neoplastic cells and in normal cells are being made to determine the role of these genes in neoplastic development. Recent papers have reported that leukemic cells differ from normal cells in having higher c-myc RNA levels. One problem in interpreting these data is that leukemic and normal cell populations differ in the proportion of immature cells present in each. The studies described here, using chronic phase chronic myelogenous leukemia (CML) cells, compared the level of proto-oncogene expression in immature and mature myeloid cells. Substantial differences in the level and pattern of expression were found with the immature cells containing higher c-myc RNA levels and the mature cells containing higher histone H3 RNA levels. c-fos RNA levels parallel the distribution of monocytes. While the c-myc RNA level in the CML cell population as a whole is similar to that in normal marrow cell populations and less than that in the bone marrow cells of patients with acute myelogenous leukemia (AML), c-myc RNA levels in subpopulations of immature chronic phase CML myeloid cells approximate that found in AML cells. Additionally, the studies described here suggest that the presence of high c-myc and c-fos RNA levels in light density immature cells may be a unique characteristic of acute myeloid leukemic cells.

Adult↗
PubMed1987

The influence of Bavistin and Calixin on CO2-evolution and the major nutrient status (NPK) of the soil.

An application of Bavistin (5 mg kilogram of soil) and Calixin (1.5 mg per kilogram of soil) significantly enhanced the microbial activity, as well as availability, of NH(4)(+)-N and P in the soil, while NO(2)(-)-NO(3)(-)-N and available K were found to decrease. During incubation, decreases in CO(2)-evolution were observed initially up to 21 days, with an increase up to 42 days, and, thereafter, a fall in both treatments.

Journal Article↗
PubMed1987

Embryotoxic evaluation of a Prudhoe Bay crude oil in rats.

The embryotoxic potential of a Prudhoe Bay crude oil (PBCO) was investigated in rats. PBCO was administered orally to pregnant rats as (i) a single dose on various gestation days, (ii) a single variable dose on gestation day 6, or (iii) as daily doses from day 6 to day 17 of pregnancy. PBCO administered during the earlier stages of pregnancy (day 3, 6 or 11) but not during the later stages, affected the reproductive performance of pregnant rats by significantly increasing the number of resorptions including fetal death and by decreasing the fetal weight. A dose-dependent increase in fetomortality was also observed. Multiple exposure to low levels of crude oil also caused a significant reduction in maternal body weight besides other embryotoxic changes.

Administration, Oral↗
PubMed1987

Urea stibamine: an improved method of preparation and its antileishmanial activity.

An improved method for preparation of urea stibamine was developed. The crude p-acetylaminophenyl stibonic acid (II) prepared was purified by dissolving it in Na2CO3 solution, whererin acid (II) dissolved leaving behind the impurities. Acid (II) was directly combined with urea without hydrolyzing the acetyl group to give urea stibamine. Biological activity of the drug in vitro as well as in vivo was also studied. The drug had no inhibitory effect on growth, respiration, incorporation of radiolabeled precursors into promastigotes of L. donovani, and on transformation of amastigotes to promastigotes. In infected hamster, the effect of the drug was highly significant in vivo., as it removed the parasitic burden completely.

Animals↗
PubMed1987

The role of heme metabolism during the induction of hepatic and renal cytochrome P-450 levels and drug-metabolizing enzymes in rats by a Prudhoe Bay crude oil.

Administration of Prudhoe Bay crude oil (PBCO) to rats resulted in a dose-related increase in liver weight; rapid and marked increase in the activity of hepatic delta-aminolevulinate synthetase, the initial and rate-limiting enzyme in the heme biosynthetic pathway; rapid decline in the activity of hepatic heme oxygenase, the rate-limiting enzyme of heme catabolism; and more gradual increase in the levels of hepatic cytochrome P-450 and some mixed-function oxidase activities such as benzo[a]pyrene hydroxylase and 7-ethoxyresorufin-O-deethylase. PBCO treatment also increased renal cytochrome P-450 levels and mixed-function oxidase activities; however, delta-aminolevulinate synthetase and heme oxygenase activities were unchanged. This suggests that different regulatory mechanism(s) may be involved in renal heme metabolism and induction of monoxygenase system.

5-Aminolevulinate Synthetase↗
PubMed1987

Effect of a Prudhoe Bay crude oil on hepatic and placental drug metabolism in rats.

Administration of a Prudhoe Bay crude oil (PBCO) to pregnant rats resulted in induction of hepatic microsomal P-450 levels and various monooxygenases in a dose-dependent manner. The activities of aniline hydroxylase, benzo[a]pyrene hydroxylase, aminopyrine-N-demethylase, ethoxyresorufin-O-deethylase, and pentoxyresorufin-O-depentylase were increased 2-3-fold, 12-15-fold, 1.4-1.8-fold, 20-24-fold, and 6-8-fold, respectively, on gestation day 18, when a single dose of PBCO (5-10 mL/kg body weight, p.o.) had been administered 24 h earlier. Glutathione-S-transferase, UDPG transferase, and DT-diaphorase activities were also increased; however, maximum induction was noticed when crude oil was given 72 h earlier. Repeated exposure (day 6-day 17, daily) of crude oil at lower levels was able to produce similar induction patterns in enzyme systems at day 18 of gestation. The xenobiotic-metabolizing enzyme systems were also induced transplacentally: treatment of pregnant rats with PBCO induced both placental and fetal hepatic enzyme systems. Liver microsomal P-450 contents, benzo[a]pyrene hydroxylase, and ethoxyresorufin-O-deethylase activities were increased 2-fold, 2-3-fold, and 10-12-fold, respectively in 18-day-old fetuses. Similar trends were noticed in placenta. Activities of phase II enzymes such as glutathione-S-transferase, UDPG transferase, and DT-diaphorase were also significantly elevated. It is suggested that crude oil induces maternal hepatic drug metabolism and that some of its constituents (mainly aromatic hydrocarbons) and (or) their metabolites pass through the placenta and thus induce drug-metabolizing enzymes transplacentally. The practical importance of the results in relation to human and environmental health is also discussed.

Animals↗
PubMed1986

Mechanisms of petroleum hydrocarbon toxicity: studies on the response of rat liver mitochondria to Prudhoe Bay crude oil and its aliphatic, aromatic and heterocyclic fractions.

The effect of Prudhoe Bay crude oil (PBCO) and its different fractions [aliphatic, aromatic, heterocyclic (NOS)] on the bioenergetic functions of isolated rat liver mitochondria were studied. A DMSO extract of PBCO inhibited state 3 respiration (in the presence of ADP) with either succinate or beta-hydroxybutyrate as substrate. The ascorbate-TMPD dependent state 3 respiration was not affected. Succinate dehydrogenase and beta-hydroxybutyrate dehydrogenase activities were also lost in the presence of the PBCO extract suggesting that inhibition of state 3 respiration may be due to blockage of the electron transport chain. Stimulation of state 4 respiration (in the absence of ADP) and of the oligomycin sensitive ATPase activity by the PBCO extract was observed. Fractionation of PBCO indicated that the aromatic fraction was mainly responsible for its inhibitory effects. By comparison, the heterocyclic fraction had weak inhibitory properties while the aliphatic fraction was essentially inactive. It is concluded that the aromatic components of PBCO inhibit mitochondrial respiration and oxidative phosphorylation mainly through impairment of the mitochondrial membrane and inhibition of beta-hydroxybutyrate and succinate dehydrogenase supported electron transfer activities of the respiratory chain.

Adenosine Triphosphatases↗