Transcarboxylase. X. Assembly of active transcarboxylase from its inactive subunits and incorporation of the biotin-carboxyl carrier protein.
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Biotin↗
Biomedical subjects
F Ahmad
Publications and source records attributed to F Ahmad.
Alteration in the amino acid content of yeast during growth under various nutritional conditions.
Yeast cells grown under optimal and suboptimal concentrations of biotin were analyzed for the amino acid content of their soluble pool and cellular protein. Optimally grown yeast cells exhibited a maximum amino acid content after 18 hr of growth. Biotin-deficient cells were depleted of all amino acids at 26 and 43 hr, with alanine, arginine, aspartate, cysteine, glutamate, isoleucine, leucine, lysine, methionine, serine, threonine, and valine being present in less than half the concentration observed in biotin-optimal cells. At early time intervals, the amino acid pool of biotin-deficient yeast contained lower concentrations of all amino acids except alanine. After more prolonged incubation, several amino acids accumulated in the pool of biotin-deficient yeast, but citrulline and ornithine accumulated to appreciable levels. The addition of aspartate to the growth medium resulted in a decrease in the amino acid content of biotin-optimal cells but caused a marked increase in the concentration of amino acids in biotin-deficient cells. The pools of biotin-deficient yeast grown in the presence of aspartate displayed a marked reduction in every amino acid with the exception of aspartate itself. These data provide evidence that the amino acid content of yeast cells and their free amino acid pools are markedly affected by biotin deficiency as well as by supplementation with aspartate, indicating that aspartate plays a major role in the nitrogen economy of yeast under both normal as well as abnormal nutritional conditions.
Amino Acids↗
Nicotinic acid biosynthesis in prototrophs and tryptophan auxotrophs of Saccharomyces cerevisiae.
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Amidohydrolases↗
Thermostability of Bacillus cereus penicillinase.
Williams, Daniel H., III (Hahnemann Medical College, Philadelphia, Pa.), A. Bondi, A. G. Moat, and F. Ahmad. Thermostability of Bacillus cereus penicillinase. J. Bacteriol. 91:257-261. 1966.-The extracellular penicillinase of Bacillus cereus, strain 13-10, exhibited an unusual thermostability. Whereas it was completely and irreversibly inactivated by heating at 70 C, it retained considerable activity when heated at 100 C for 30 min. The active enzyme remaining was completely stable to further heating at temperatures from 40 to 100 C for as long as 1 hr. Preparations of the enzyme heated to 100 C possessed pH (7.0) and temperature (37 C) optima identical with the unheated enzyme. Furthermore, both enzyme preparations exhibited identical combining capacity for the substrate (penicillin G), suggesting that the two preparations had similar hydrolytic properties. Our findings suggest that heating of penicillinase at 100 C results in the formation of a protein complex which is resistant to further denaturation by heat and other agents. Addition of certain metal ions to the enzyme solution before heat treatment increased the stability to heat at 100 C by virtue of their ability to induce complex formation. Pectin was shown to decrease thermostability, presumably by preventing aggregation of proteins present in the enzyme preparations. The well-known stabilizing effect of gelatin may be attributed to its role in enhancing complex formation.
Bacillus cereus↗
Aminoimidazole ribonucleotide carboxylase. Partial purification and properties.
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Animals↗
Effect of age on the binding of lectin 125I-PHA-B to pancreatic islets of rat in vitro and stimulation of some cellular events.
Agaricus bisporus lectin (PHA-B) stimulates insulin release in vitro. The stimulation is associated with increased conversion of proinsulin to insulin in the isolated islets of Langerhans of rats. Both these functions are directly proportional to the binding of I125 PHA-B, which is more marked in the islets from younger rats. The lectin binding to islets is not affected by glucose concentration in the medium.
Agaricus↗
Effect of some novel synthetic analogues of CCK-4 on insulin and glucagon secretion.
The biologic activities of three synthetic analogues of CCK-4 (Trp-Met-Asp-Phe-NH2) in which (i) the C-terminal residue Phe was N-methylated (peptide I); (ii) the C-terminal Phe residue was N-methylated and Ser is substituted for Met in position 2 (peptide II); (iii) Pro was substituted for Trp in position 1 and the C-terminal amino nitrogen was methylated (peptide III), have been described. Peptides I and II have been found to inhibit the release of both insulin and glucagon, while peptide III was found to be a potent releasing agent for insulin and an inhibitor for glucagon.
Amino Acid Sequence↗
Insulin like activity in (-) epicatechin.
Water extract of the bark of plant of Pterocarpus marsupium Roxb is used as an antidiabetic drug in indigenous medicine in India. (-) Epicatechin, its active principle, has been found to be insulinogenic. The present in vitro study reports some insulin like activities of (-) epicatechin. Like insulin, (-) epicatechin stimulates oxygen uptake in fat cells and tissue slices of various organs, increases glycogen content of rat diaphragm in dose-dependent manner with corresponding increase in U14-C glucose uptake, and inhibits theophylline induced lipolysis in isolated fat pads in dose-dependent manner. Experiments on competitive binding of 125I-insulin and (-) epicatechin to liver cell plasma membrane indicate that insulin does not share binding site with (-) epicatechin. (-) Epicatechin at a concentration of up to 1 mM does not effect the release of glucagon from the islets in vitro. Thus, (-) epicatechin has insulinogenic as well as insulin like properties.
Adipose Tissue↗
Selective stimulation of insulin secretion by CCK-4 analogues having N-terminal modifications.
Synthetic analogues of CCK-4 in which Trp was replaced by D-Pro (peptide I), Thz (peptide II) and delta Pro (peptide III) have been studied for their insulin and glucagon releasing activities from the islets of Langerhans in vitro. Peptide I has been found to be the most potent insulin releaser among the three analogues and its activity is comparable to that of CCK-4. Unlike CCK-4, its three analogues (peptides I-III) do not stimulate the release of glucagon with basal concentration of glucose in the medium. However, with increasing glucose concentration, all the three analogues potentiate the glucose stimulus for insulin release.
Animals↗
Insulin and glucagon releasing activity of coleonol (forskolin) and its effect on blood glucose level in normal and alloxan diabetic rats.
Colenol, a diterpenoid isolated from the roots of Coleus forskohlii stimulates the release of insulin and glucagon from the islets both in vitro and in vivo. Colenol-stimulated release of glucagon from islets in vitro is much more pronounced as compared to that of insulin. Glucose concentration of 5.6 mM in the medium is required for the colenol stimulation of insulin release. Feeding of coleonol to alloxan diabetic rats cause 36.5% increase in blood glucose level as compared to alloxan diabetic control. Oral feeding of coleonol for 7 days to normal rats causes increase in blood glucose, serum insulin, glucagon and free fatty acid levels with corresponding increase in glucose-6-phosphatase activity and depletion of liver glycogen. Predominant stimulation of A-cells by coleonol is suggested for the above effects.
Animals↗
Primary prevention of violence against women.
The best mechanisms to prevent violence against women were reviewed in a critical appraisal conducted by the University Health Network Women's Health Program. Several promising primary interventions were identified. These included: educational and policy-related interventions to change social norms, early identification of abuse by health and other professionals, programs and strategies to empower women, safety and supportive resources for victims of abuse, and improved laws and access to the criminal justice system. The policy recommendations emerging from this analysis are presented.
Female↗
Association between cerebral structural abnormalities and dermatoglyphic ridge counts in schizophrenia.
Dermatoglyphic ridge counts (1) reflect ontogenic processes during the second trimester of pregnancy and (2) can be influenced by some of the factors that also affect cerebral development. Therefore, the demonstration of an association between dermatoglyphic and cerebral structural measures in patients with schizophrenia would give credence to the view that the structural brain abnormalities associated with this disorder have their origin early in development. Twenty-eight male subjects with schizophrenia and 19 male controls underwent magnetic resonance imaging (MRI) and dermatoglyphic analysis. The pattern of association between the ab-ridge count and nine MRI features was dissimilar in cases and controls for two measures. Associations between dermatoglyphic features, on the one hand, and the frontal CSF (r = .54, P = .004) and fourth ventricular volume (r = .38, P = .05), on the other, were larger in the cases versus the controls (test for interaction, P = .08 and P = .06, respectively). These findings, while in need of replication, support the view that the cerebral structural abnormalities found in patients with schizophrenia are the result of an early pathologic process affecting the development of fetal ectodermal structures.
Adult↗
Localization of a gene responsible for arrhythmogenic right ventricular dysplasia to chromosome 3p23.
BACKGROUND: Arrhythmogenic right ventricular dysplasia (ARVD), a familial cardiomyopathy occurring with a prevalence of 1 in 5000, is characterized by replacement of myocytes with fatty and fibrous tissue. Clinical manifestations include structural and functional abnormalities of the right ventricle and arrhythmias, leading to a sudden death rate of 2.5% per year. Four loci have been mapped, but no gene has been identified as yet. METHODS AND RESULTS: We identified a large family of >200 members with ARVD segregating as an autosomal dominant trait affecting 10 living individuals. The diagnosis of ARVD was based on international diagnostic criteria including history, physical examination, ECG, echocardiogram, right ventricular angiogram, endomyocardial biopsy, and 24-hour ambulatory ECG. Blood was collected for DNA from 149 family members. Analysis of 257 polymorphic microsatellite markers by genetic linkage excluded previously known loci for ARVD and identified a novel locus at 3p23. Analysis of an additional 20 markers further defined the region. A peak logarithm of the odds score of 6.91 was obtained with marker D3S3613 at theta=0% recombination. Haplotype analysis identified a shared region between markers D3S3610 and D3S3659 of 9. 3 cM. CONCLUSIONS: A novel locus for ARVD has been mapped to 3p23 and the region narrowed to 9.3 cM. Identification of the gene will allow genetic screening and a specific diagnosis for a disease with protean nonspecific findings. It should also provide insight fundamental to understanding cardiac chamber-specific gene expression and/or the mechanism of myocyte apoptosis observed in this disease.
Adult↗