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M Ali

Publications and source records attributed to M Ali.

At least 307 records · Page 17Linked to original sources
PubMed1988

Isolation of transketolase from rabbit liver and comparison of some of its kinetic properties with transketolase from other sources.

1. Rabbit liver transketolase activity was purified 56-fold using the following steps: ammonium sulfate precipitation, chromatography on DEAE-Sephadex A-25, concentration through an Amicon ultrafiltration cell and rechromatography on DEAE-Sephadex A-25. 2. The enzyme showed an optimum PH for activity at 7.8-8.0. 3. The optimum temperature was around 40 degrees C and the activation energy calculated from the Arrhenius plot was found to be 11.4 kcal/mole. 4. The molecular weight of the enzyme, as determined by gel filtration, was found to be approximately 162,000, while the content of thiamin diphosphate was between 1.8 and 2 mumole per mole protein. 5. Addition of thiamin diphosphate and magnesium chloride did not influence the activity. 6. From the kinetic studies of the enzyme, the Km values for xylulose-5-phosphate, ribose-5-phosphate and fructose-6-phosphate were 3.8 x 10(-5) M, 9.5 x 10(-5) M and 1.1 x 10(-2) M, respectively.

Animals↗
PubMed1988

Nasopharyngeal carcinoma in Saudi Arabia: a retrospective study of 166 cases treated with curative intent.

A retrospective review was performed of the medical records of 166 adult patients with biopsy-proven carcinomas of the nasopharynx treated with curative intent at King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia. All patients were treated between June 1975 and December 1985 using megavoltage therapy equipment. Most patients presented with advanced nodal disease: 23 patients (13.9%) were N0, 16 patients (9.6%) were N1, 29 patients (17.5%) were N2, and 98 patients (59%) were N3. The overwhelming majority of patients had nonkeratinizing lesions (158/166). At the time of analysis, mean follow-up time was 24.2 months (range 2-108). Actuarial curves are presented for local/regional control as a function of T-stage and N-stage and for survival and time to development of distant metastases as a function of N-stage. At 4 years local/regional control was 70% for T1 lesions, 59% for T2 lesions, 30% for T3 lesions, and 35% for T4 lesions. There was little correlation between local/regional control and N-stage being about 50% at 4 years for all nodal subgroups. Only six patients exhibited an isolated first failure in the regional nodes alone, whereas 60 patients failed initially at the primary site (either alone or in conjunction with a simultaneous nodal failure). The development of distant metastases correlated to some extent with nodal disease ranging from 20% at 4 years for T1/T2 N0 patients to 70% for patients who initially presented with N3 disease. Survival data was more difficult to obtain due to cultural biases in a medically unsophisticated patient population. True survival curves are bounded by calculating actuarial curves in two ways: death as the failure endpoint and death plus lost-with-active-disease as failure endpoints. In terms of the latter curves, at 4 years "survival" ranged from 39% for patients with T1/T2 N0 lesions to 23% for patients with N3 lesions.

Adult↗
PubMed1988

Measles vaccination and childhood mortality in rural Bangladesh.

To ascertain whether measles vaccination was associated with reduced mortality rates in rural Bangladeshi children, the authors conducted a case-control study in four contiguous areas, two of which had participated in an intensive measles vaccination program which began in the spring of 1982. Cases were 536 children who had died in the four-area region at the age of 10-60 months between April 1982 and December 1984. Two age- and sex-matched controls were selected from the four-area region for each case; each control had survived at least through the date of death of the matched case. Measles vaccination was associated with a 36% (95% confidence interval 21%-48%) proportionate reduction in the overall rate of death and a 57% (95% confidence interval 43%-67%) reduction in the rate of deaths directly attributed to measles or ascribed to diarrhea, respiratory illness, or malnutrition. The association of measles vaccination and reduced mortality remained unchanged after the authors restricted controls to children who had survived at least one year after the deaths of their matched cases. Moreover, children vaccinated in 1982 exhibited a sustained reduction in the rate of death in 1983 and 1984. The authors concluded that measles vaccination was associated with a pronounced and sustained reduction in the rate of death among children in this study.

Bangladesh↗
PubMed1988

Mukhzan-e-Ayurveda.

Explore the source record for details and available documents.

History, Modern 1601-↗
PubMed1988

Comparative study of collecting tubules and vasopressin binding capacity in the renal medulla of developing hypothyroid rat.

The effects of congenital hypothyroidism on both the structure and function of the renal medulla were studied by comparing, in 1-month old rats, the structural features of collecting tubules with the capacity of vasopressin to bind membrane preparations and the related adenylate cyclase activation. With the exception of a reduced caliber, hypothyroidism had no effect on the density, total number, distribution of tubules according to epithelial thickness, or on the number of epithelial cells, or their area. The binding capacity of vasopressin and the related adenylate cyclase activation were equally reduced by about 50%, without changes in (i) the basal or guanylyl-imidodiphosphate (Gpp(NH)p)-stimulated adenylate cyclase activities, (ii) the apparent dissociation constant (KD) of labelled vasopressin from its specific receptor or (iii) the apparent activation constant (Kact) of vasopressin for adenylate cyclase. Taken together, these results clearly demonstrate that congenital hypothyroidism exerts a direct influence on the developing responsiveness of the renal medulla, mainly by reducing the density of active hormone receptors per cell, instead of reducing cell number or cell membrane area.

Adenylyl Cyclases↗
PubMed1987

Uncoupling between the insulin-receptor cycle and the cellular degradation of the hormone in cultured foetal hepatocytes. Effect of drugs and temperature that inhibit insulin degradation.

Sequential changes in the numbers of cell-surface receptors induced by a transitory exposure to insulin in cultured 18-day foetal-rat hepatocytes were investigated in the presence of drugs and at a temperature of 22 degrees C, which inhibit cellular insulin degradation. Chloroquine (70 microM) and monensin (3 microM) did not greatly change the initial rate of internalization of cell-surface receptor sites after exposure to 10 nM-insulin, but led to a steady state after 20 min, which represented 40% of the initial binding, compared with 5 min and 60% in the absence of the drug. Moreover, these drugs strongly decreased the proportion of receptor sites recovered at the cell surface after subsequent removal of the hormone. They were ineffective when insulin was not present. The removal of monensin together with the hormone allowed partial restoration of cell-surface receptor sites and degradation of cell-associated insulin to start again at the initial speed, indicating a reversible effect of the drug. During this phase, the drug concentration-dependence for the two effects showed that receptor recycling was restored with concentrations of monensin not as low as for insulin degradation. The effect of vinblastine (50-100 microM) was similar to that of chloroquine and monensin, whereas no modification in the internalization and recovery processes was observed in the presence of bacitracin concentrations (1-3 mM) that inhibit insulin degradation by 70%. A temperature of 22 degrees C did not prevent the receptor internalization, but had a slowing effect on the recycling process, which appeared to vary in experiments where insulin degradation remained inhibited. The present study shows that the process of insulin degradation mediated by receptor endocytosis is not a prerequisite for insulin-receptor recycling in cultured foetal hepatocytes.

Animals↗
PubMed1987

Interaction of RNA with transformed glucocorticoid receptor. I. Isolation and purification of the RNA.

The glucocorticoid receptor (GR) from mouse AtT-20 pituitary tumor cells, when transformed using a variety of in vitro protocols, yields a DNA-binding RNA-containing 6 S form. In order to better understand the physiological role of RNA interaction with the transformed GR, we have isolated and purified the putative RNA from AtT-20 cells. [3H]Triamcinolone acetonide-labeled cytosolic GR was transformed, using Sephadex G-25 filtration, to yield the RNA-containing 6 S GR. The transformed 6 S GR was separated on DEAE-cellulose into the 4 S GR (eluting at about 100 mM KCl) while its associated RNA eluted at 0.30-0.45 M KCl. The addition of only these RNA fractions to the 4 S GR can reconstitute 6 S GR as shown on 5-20% sucrose gradients. RNA (0.3-0.45 M KCl fractions) was further purified by hydroxylapatite chromatography, and the bound RNA (eluted at approximately 70 mM PO4(-2)) was then loaded onto preparative 5-20% sucrose gradients to separate RNA on the basis of size (sedimentation rate). A uniform class of RNA sedimenting at 4 S was obtained and then adsorbed to oligo(dT)-cellulose columns. The unbound fraction (poly(A-)) was capable of shifting 4 S GR to 6 S. Using these chromatographic procedures about 90% of the cellular RNA, incapable of reconstituting the 6 S GR from the 4 S form, was eliminated. The 4 S GR was covalently cross-linked with the purified RNA (termed PIVB RNA) using formaldehyde. The resulting cross-linked GR X RNA complexes were shown to sediment at the density of ribonucleoprotein (1.38 g/cm3) in CsCl gradients and at the 6 S position in high salt sucrose gradients. The hydrolysis of PIVB RNA with ribonuclease A prevented the formation of high salt-resistant ribonucleoprotein complexes, indicating that the GR may be in close contact with PIVB RNA. Electrophoresis of the PIVB RNA on 5% agarose-formaldehyde-denaturing gels yielded one major band with a molecular size of approximately 75 bases. It thus appears that an endogenous 4 S RNA (PIVB RNA) of about 25 kDa specifically interacts with the monomeric 4 S GR to yield the 6 S GR.

Animals↗
PubMed1987

Interaction of RNA with transformed glucocorticoid receptor. II. Identification of the RNA as transfer RNA.

An endogenous RNA (designated as PIVB RNA), which is capable of associating with the 4 S glucocorticoid receptor (GR) to generate the 6 S form, has been purified from AtT-20 cells (Ali, M., and Vedeckis, W. V. (1987) J. Biol. Chem., 262, 6771-6777). We describe here the physiochemical properties, GR-RNA interaction characteristics, and the chemical identification of PIVB RNA. 32P-Labeled PIVB RNA was similar to transfer RNA (tRNA) in its sedimentation coefficient (4 S) on sucrose gradients, electrophoretic mobility on formaldehyde-agarose gels, and receptor binding characteristics. The amino acid acceptor activity of PIVB RNA displayed a typical tRNA-dependent saturation curve and was 2-3-fold higher than that of homologous rabbit liver tRNA when tested using rabbit liver aminoacyl-tRNA synthetase. The purified [3H] aminoacyl-PIVB complex was also capable of binding to the 4 S GR to generate the 6 S form. The analysis of PIVB RNA on an acrylamide-urea sequencing gel revealed that it contained a major tRNA of 76 nucleotides and other minor tRNA species of 74 and 78 nucleotides. The identity of the tRNA present in the PIVB RNA was indirectly deduced by analyzing the 3H-amino acids, liberated from the [3H]aminoacyl-PIVB RNA (tRNA) complex, and subsequent analysis on an amino acid analyzer. PIVB RNA mainly contained tRNAArg (51.8%), tRNALys (17.1%), and tRNAHis (9.2%) which together accounted for 78% of the total PIVB tRNA. The remaining 22% of tRNA was contributed by threonine, valine, aspartic acid, alanine, and phenylalanine tRNAs. The GR displayed no species specificity, and tRNA samples from mouse, cow, rabbit, yeast, and Escherichia coli can bind to the mouse 4 S GR to generate the 6 S form. However, PIVB RNA did not affect the sedimentation profiles of albumin, chymotrypsinogen, and histone, indicating that PIVB RNA does not bind to all proteins. Thus, there may exist some specificity both at the level of protein (GR) and the selection of RNA (tRNA). The GR binding to PIVB RNA occurred at low (nM) receptor concentration, and PIVB RNA showed limited capacity to shift 4 S GR to the 6 S form. 22.4 X 10(-11) mol of PIVB RNA can completely shift 4.8 X 10(-13) mol of 4 S GR to 6 S. That is, PIVB RNA has to be in a 500-600-fold excess over the amounts of GR to observe a stable 6 S GR X RNA complex on sucrose gradients. These results conclusively demonstrate that the transformed GR specifically binds to endogenous tRNA.

Amino Acids↗
PubMed1987

The glucocorticoid receptor protein binds to transfer RNA.

The glucocorticoid receptor from mouse AtT-20 cells exists in three forms: the untransformed receptor (9.1S; Mr of 319,000), a large oligomeric molecule that does not bind to DNA; the transformed receptor (4S; Mr of 96,000), which is formed by dissociation of untransformed receptor after steroid binding and which binds to DNA to modulate gene expression; and an intermediate size receptor (6S; Mr of 132,000), which also binds to DNA and contains a bound small RNA molecule. This RNA species has now been purified and identified as transfer RNA (tRNA). The three tRNA's for the basic amino acids accounted for about 78% of the total amino acid-accepting activity [arginine (52%), lysine (17%), and histidine (9%)], while the remaining 22% was represented by six other tRNA species. This tRNA-binding activity of the glucocorticoid receptor may reflect post-transcriptional mechanisms of regulating gene expression, such as alterations in the translational efficiency of or the modulation of the stability of hormone-induced proteins.

Animals↗
PubMed1987

Prostaglandin associated mortality following intravenous injection of catfish epidermal secretions in rabbits.

Toxicity of soluble protein extracts from epidermal gel secretions of the catfish, Arius thalassinus, was examined in rabbits. Intravenous injections containing doses as low as 2 mg protein/kg body weight caused mortality in all animals tested. An increase in plasma levels of thromboxane B2 (TXB2) and of 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) were observed following injections. Both the mortality and prostaglandin release were prevented by pretreatment of rabbits with either indomethacin or hydrocortisone. A similar indomethacin sensitive induction of prostaglandin release was noted following the in vitro treatment of arterial tissue sections with gel. Lethality appears to result from gel substances stimulating phospholipase activity to yield arachidonic acid, which is then metabolized to give toxic levels of prostaglandins.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

A potent inhibitor of thrombin stimulated platelet thromboxane formation from unprocessed tea.

A ninhydrin positive compound (L2) from commercially available unfermented dry green tea (Thea sinesis) leaves is found to be a potent inhibitor of thrombin-stimulated thromboxane formation in rabbit whole blood. Its potency is compared with caffeine, a member of the methylxanthines family. Both caffeine and L2 inhibit thromboxane formation in whole blood in a dose dependent fashion. L2 inhibition when calculated as I50 by a dose response curve is found to be more than 40 fold stronger than caffeine as an inhibitor of thromboxane formation. A concentration of L2 as low as 50 microM, suppresses thromboxane formation (by 84%) whereas a concentration of 5000 microM is necessary to achieve the same inhibition with caffeine. The potent inhibitory effect of L2 on the TXB2 production maybe of benefit in the treatment of vascular disease.

Animals↗
PubMed1987

Comparative study of the developmental patterns of vasopressin, glucagon, angiotensin II, and alpha 1-adrenergic receptors in the liver of developing and adult hypothyroid rats.

The effects of propylthiouracil (PTU) treatment on vasopressin, angiotensin II, glucagon and alpha 1-adrenergic receptors in both developing and adult rats were studied in liver membrane preparations by measuring the binding of the following ligands: [3H][8-lysine]vasopressin, [3H]Sar-angiotensin II, [125I]glucagon and [3H]prazosin, and in the case of glucagon, by measuring adenylate cyclase activation. Whatever the ligand used, in young as well as in adult animals, PTU treatment led to a similar reduction (about 50%) in the maximal number of binding sites (Bmax), without significant changes in the apparent dissociation constant (KD) of labeled hormone for its specific receptor. In normal adult animals, thyroxine treatment, i.e. hyperthyroidism, had an opposite effect on the Bmax (25-50% increase), without changes in the KD. In developing PTU-treated rats, the abnormalities completely disappeared after therapy with increasing physiological doses of thyroxine; consequently they were directly related to thyroid deficiency and not to toxic effects of PTU. Moreover, the abnormalities resulting from induced hypothyroidism were reversible. In developing and adult hypothyroid rats, neither basal, NaF-, nor Gpp(NH)p-stimulated adenylate cyclase activities were significantly affected. Glucagon-sensitive adenylate cyclase activity seemed to be slightly increased (by about 15%), without changes in the apparent activation constant (Kact). These results are considered in parallel with findings on plasmatic glucagon and vasopressin levels, compared with similar previous reports related to renal vasopressin receptors, and discussed with respect to unpublished observations concerning hepatic responsiveness to glycogenolytic hormones in young and adult rats with induced hypothyroidism.

Adenylyl Cyclases↗