Nicotinic acid inhibits thromboxane synthesis in platelets

The formation of thromboxane A₂ by phospholipase A₂ in rat platelets is inhibited by nicotinic acid. The synthesis of PGE₂ and PGF_2α is increased.Nicotinic acid inhibits collagen-induced aggregation in rat platelets.     

Mycoplasma Phosphoenolpyruvate-Dependent Sugar Phosphotransferase System: Purification and Characterization of Enzyme I

The Mycoplasma phosphoenolpyruvate-dependent sugar phosphotransferase system consists of three components: a membrane-bound enzyme II, a soluble phosphocarrier protein (HPr), and a soluble enzyme I. The soluble enzyme I was purified by ammonium sulfate fractionation; Bio-Gel P-10 gel filtration; acid precipitation; diethylaminoethyl-Bio-Gel A; and Bio-Gel HTP column chromatography. The enzyme I was shown to be homogeneous by electrophoresis in a pH 8.9 non-sodium dodecyl sulfate gel and by isoelectric focusing. Whereas the protein moved as a single component in both the non-sodium dodecyl sulfate gel and isoelectric focusing, on sodium dodecyl sulfate gels, it moved as three subcomponents. The molecular weights of the three subunits, alpha, beta, and gamma, were 44,500, 62,000 and 64,500, respectively. The holoprotein moved as a single component, in the region of 220,000 daltons, in a Bio-Gel A 0.5-agarose column. The molar ratio of subunits was estimated to be 2alpha:1beta:1gamma. The elution characteristics on a diethylaminoethyl column at pH 7.4 and 6.8, acid precipitation data, and amino acid composition indicated that the protein is acidic. Isoelectric focusing occurred at pH 4.8. N-terminal amino acids determined by the dansyl chloride method indicated that glycine, alanine, and tyrosine are N-terminal amino acids of the three subunits. Although the protein was stable for at least 14 months at -20 degrees C, it was irreversibly inactivated by the thiol reagent N-ethyl-maleimide.     

The Role of Estrogens as a Risk Factor for Stroke in Postmenopausal Women

The estrogen component in oral contraceptives is generally thought to increase the risk of stroke in users as compared with controls. If this were true, an increased risk for stroke also should be seen among postmenopausal women using estrogens as compared with nonusers. To test this hypothesis, the charts of 198 postmenopausal patients who had had strokes were compared with those of 396 controls for estrogen use and for the associated risk factors of diabetes, hypertension and coronary artery disease. The difference between estrogen use in the study population versus controls proved not significant, and the use of estrogens did not significantly influence the distribution of the above risk factors. We concluded that the use of estrogens in physiological replacement doses does not increase the risk of stroke in postmenopausal women.     

Thermophilic mycoflora of cigarettes and cured tobacco leaves

Nine species of thermophilic fungi were obtained from retailed packets of imported and locally manufactured brands of cigarettes and from cured tobacco leaves. They include known human pathogens such asThermoascus aurantiacus Miehesensu Apinis,Mucor pusillus Lindt andMucor miehei Cooney and Emerson. Chaetomium thermophile La Touche,Humicola insolens Cooney and Emerson,Thermoascus crustaeus (Apinis and Chesters) Stolk andMucor miehei have not been previously reported on tobacco products.Fewer species were obtained from foreign cigarettes than from locally manufactured brands. A mean moisture content of 19% was recorded for imported cigarettes and 37% for Nigerian brands. The potential health hazards posed to man by the unrestricted use of tobacco products are discussed.     

Comparison of pyloric ligation and pyloric cuff techniques for collecting gastric secretion in the rat.

A comparison was made between two methods for collecting gastric secretion in the rat. The two included a pyloric ligation technique and a snare-type pyloric cuff which was surgically implanted 2 weeks before the collection was initiated. It was hypothesized that the surgical trauma associated with pyloric ligation would inhibit gastric secretion and thus yield smaller gastric samples with this procedure as compared to the cuff technique. No differences in volume of gastric secretion or total acid output were observed between the two methods.     

Rapid physiological assays for nutrient demand by the plankton. I. Nitrogen

Three assays for nitrogen demand were compared on samples ofnatural plankton and on green and blue-green algal species inculture. The most reliable guide was selective luxury uptakeof nitrogen by the plankton after enrichment with a 10-to-1(wt/wt) mixture of inorganic N and P. Ammonium transport capacity,measured either directly (cultures) or by V_max for uptake ofthe NH₄⁺ analogue methylammonium (lakewaters), was generallyhigh in lakewaters with low dissolved inorganic N-to-P ratiosand in N-deficient cultures of green algae. By contrast, transportcapacity was much reduced in both natural and cultured populationsof heterocystous blue-green algae growing under conditions oflow combined inorganic nitrogen. Ammonium enhancement assays(heterotrophic CO₂, fixation after NH₄⁺ enrichment) were conductedat monthly intervals on eutrophic Lake Rotorua. There was astrong, negative correlation between this indicator of N deficiencyand dissolved inorganic N-to-P ratios below a threshold of 6:1.Ammonium enhancement was not, however, a reliable indicatorof combined inorganic N-demand by populations of heterocystousblue-green algae. All three assays provided strong evidenceof a persistent shortage of nitrogen relative to phosphorusfor algal production in Lake Rotorua.     

The Yale Affiliated Hospital Program in Internal Medicine

In July, 1975, the Departments of Internal Medicine at the Yale University School of Medicine and eight community hospitals in southern and western Connecticut formed the Yale Affiliated Hospital Program (YAHP) in Internal Medicine. The YAHP provides a planned and focused program of continuing education for medical staff and housestaff at the affiliated hospitals. Six formats for the over 1,000 rounds, lectures, and conferences given annually are used. The members of the YAHP also cooperate in housestaff and faculty recruiting, evaluation of quality of care and evaluation of the process of continuing medical education itself. This report summarizes the organization, goals and future plans of the YAHP.     

Flexibility of the pyrrolidine ring in proline peptides

A survey of over 50 crystal structures indicates that both imino acid and peptide derivatives of proline populate ring conformers consistent with the torsional potentials about single bonds. In both cases, lower barriers for rotation about C? N bonds relative to those about C? C bonds favor smaller values for dihedral angles about the former bonds. In peptides a minimum in the torsional potential about C? N bonds occurs at zero dihedral angle, further favoring small angles. The pyrrolidine-ring dihedral angles of the proline compounds in the solid state obey a cyclopentane-type pseudorotation function. Thus the puckering of the five-membered ring can be quantitatively described by two parameters. Consistent with small dihedral angles about C? N bonds, C^β and/or C^γ are puckered out of the mean plane of the ring in nearly all of the nonstrained compounds. Utilizing the consistent force-field method of Lifson and coworkers [see A. Warshel, M. Levitt, and S. Lifson (1970) J. Mol. Spectrosc. 33 , 84] the intramolecular energy of five proline peptides was minimized with respect to all internal coordinates. In addition, the energy surface near minima was explored by constraining a particular dihedral angle and reminimizing the energy with respect to all remaining variables. In linear peptides two types of pyrrolidine-ring conformers have identical predicted energies. In the cyclic dipeptide cyclo (Pro-Gly) one of the ring conformers is favored by about 3 kcal/mol, while the cyclic tripeptide cyclo(Pro-Gly-Gly) favors the other conformer by a comparable margin. In agreement with observations in the solid state and in solution, C^β and/or C^γ are puckered in the predicted conformers. A correlation between proline Φ and the details of the puckered conformation was predicted and found to match precisely conformers observed in crystals. For the diamides N-acetyl-L -proline-N′-methyl-amide and N-acetyl-L -proline-N′,N′-dimethylamide (AcProMe₂A) 30% and 60% cis acetyl peptide bonds were predicted in good agreement with observations in nonpolar solvents for the respective compounds. The conformational distributions with respect to proline Ψ are also in accord with experimental observations. For AcProMe₂A, a model for a -Pro-Pro-sequence in a peptide chain, this study is the first to predict stable conformers for proline Ψ either ca. ?50° or 140° for both cis and trans peptides.     

Quinine-induced agranulocytosis: toxic effect of quinine bisulphate on bone marrow cultures in vitro.

In a case of quinine-induced agranulocytosis marrow culture studies confirmed the inhibitory effect on the patient''s cells of equivalent therapeutic plasma concentrations of quinine. Similar concentrations had no effect on normal marrow cells. Quinidine, the stereoisomer of quinine, had no effect on either cells from the patient or normal cells. The results encourage the use of in-vitro bone marrow cultures for identifying drugs responsible for agranulocytosis.