Structure determination of the 2:1 derivatives of copper(I) bromide and iodide with bis(diphenylphosphino)methane. A simple structural scheme for the formation of (CuX)nLm species

The structures of the complexes (CuX)₂DPM (X = Br, I; DMP = bis(diphenylphosphino)methane) were determined from three dimensional X-ray data collected by counter methods. The iodine derivative crystallizes in the space group Pbca with eight units in a cell defined by a = 17.128(9), b = 18.306(9) c, = 16.508 (8) Å. The structure was refined by the least-squares method to a final R factor of 0.054 for 1336 non-zero independent reflections. The bromine derivative crystallizes in the space group P2₁/c with eight units in a cell defined by a = 23.707(1), b = 17.805(9), c = 16.991(1) Å, β = 136.10(5)°. The final least-squares refinement, based on 2489 non-zero independent reflections, gave an R factor of 0.074.Both the compounds have similar structures with a centrosymmetric (CuX)₄ core, in which two copper atoms have a tetrahedral geometry, while the other two are trigonal.The above structures are compared with those already reported for other compounds (CuX)_nL_m and a single scheme is proposed to rationalize the different geometries of the (CuX)_n core on the basis of steric and electronic effects.     

Phenotypic dissections of the Blastocladiella emersonii zoospore's developmental choice

A developmentally homogeneous neural crest cell population has been used to assay the role of environmental factors in regulating crest cell differentiation. If cultured on tissue culture plastic, virtually all of the cells of this population differentiate into melanocytes. In contrast, when these cells are cultured for 3 or more days on substrata “conditioned” by somite fibroblasts, the proportion of cells undergoing melanogenesis decreased and the proportion expressing formaldehyde-induced fluorescence (FIF), characteristic of catecholamine-containing cells, increased. For a limited period of culture on somite-conditioned substrata, some cells in the population exhibit both pigment granules and fluorescence. Collagen-coated substrata decreased the number of cells that formed pigment but did not stimulate FIF. In contrast, optimum doses of exogenous cellular fibronectin mimicked the effect of somite-conditioned substrata, suppressing melanogenesis and promoting FIF. Glycosaminoglycan-derivatized substrata (i.e., hyaluronic acid, various chondroitin sulfate preparations, and heparin) did not alter the differentiative homogeneity of the cultured crest cell populations. The choice and expression of phenotype by some members of a cultured crest cell population can, therefore, be affected by environmental stimuli provided in the form of certain substrate-attached macromolecules. We suggest that optimal concentrations of some extracellular matrix components produced by embryonic tissue and normally encountered by migrating crest cells may elicit the expression of FIF in crest cells that would otherwise follow a different developmental pathway.     

The determination of purine levels in human and mouse plasma

Variable levels of acetic anhydride have been recommended for addition to one of two reagents used in the glyoxylic acid method for the determination of tryptophan. For use of this reagent immediately after preparation it was shown that a minimum of 16% (v/v) of acetic anhydride should be included in the formulation to obtain near-maximum sensitivity. It was further demonstrated that reagent formulations with and without acetic anhydride changed with exposure to light. The observed changes are manifest as changes in the relative sensitivities of the assay. Several modifications are recommended to improve the sensitivity and stability of the acetic anhydride-containing reagent in this assay.     

Hormones and liver mitochondria: Influence of growth hormone,thyroxine, testosterone,and insulin on thermotropic effects of respiration and fatty acid composition of membranes

The effects of hypophysectomy and subsequent administration of growth hormone, thyroxine, insulin, and testosterone were examined in rat liver for the relationship between the thermotropic effects on State 3 respiration (ADP induced) and fatty acid composition of the phospholipid fraction of intact mitochondria as well as of inner membrane vesicles. The Arrhenius profile for energy-linked (succinate) State 3 respiration of mitochondria from hypophysectomized rats lacked the discontinuity at 23.5 °C seen with mitochondria from normal rats. After injections of the hormones the discontinuity representing the transition temperature from gel to liquid crystalline state of lipids occurred at different temperatures: 18.5 °C for growth hormone, 26.0 °C for thyroxine, 19.5 °C for growth hormone + thyroxine, 27.6 °C for insulin, and 25.3 °C for testosterone. The energy of activation between 37.5 and 23.5 °C was 1.9 times greater for hypophysectomy than for controls. Growth hormone was the most effective in restoring the energy of activation to normal, above as well as below transition temperature. The effect of thyroxine appears to be due to a larger stimulation of the State 4 respiration than that of growth hormone, insulin, or testosterone, especially at higher temperatures. Phospholipids extracted from intact mitochondria or inner membrane vesicles of hypophysectomized rats contained less arachidonic acid (20:4) and more linoleic acid (18:2) than those of normal rats. In addition, the contents of some of the minor fatty acids were also changed. Calculated unsaturation index showed an 18.8 and 14.9% depletion in unsaturation in whole mitochondria and inner membranes, respectively. Among the different hormones used to treat the hypophysectomized rats, growth hormone was the most effective in restoring the transition temperature and fatty acid composition to normal levels and increasing the gain in body weight. Although the other hormones increased total unsaturation index to some extent, some of the individual fatty acids were affected differently. Good correlation exists between the unsaturation index of mitochondrial fatty acids and transition temperature of State 3 respiration. These results strongly suggest a role for the hormones, particularly growth hormone, in the control of mitochondrial membrane fluidity of hypophysectomized rat liver, through fatty acid composition of phospholipids.     

Multiple forms of amylase in leaf extracts: electrophoretic transfer of the enzyme forms into amylose-containing polyacrylamide gels

A method for the analysis of multiple forms of glucan-degrading enzymes is described. The procedure consists of the separation of the proteins by electrophoresis or isoelectric focusing in glucan-free polyacrylamide gels followed by the nondenaturing electrophoretic transfer into a second polyacrylamide layer which contains immobilized glucans. The method combines the resolving power of electrophoretic separations in glucan-free media with the sensitivity of amylase activity detection in amylose-containing polyacrylamide gels. The procedure is especially useful when samples containing low amylase activity, but a large number of multiple enzyme forms, are to be analyzed.     

Application of the imidate procedure to α-d-galactosyltion

Using the imidate procedure, 2,3,4,6-tetra-O-benzyl-1-O-(N-methylacetimidoyl)-β-d-galactopyranose was condensed with various monosaccharides to provide, in good yield and with high stereoselectivity, α-linked disaccharides.     

Block by phencyclidine of acetylcholine and barium induced adrenal catecholamine secretion

Activation of the sympathetic system by phencyclidine (PCP) should result in catecholamine release from the adrenals. However, adrenalectomy does not reduce PCP-induced hypertension. In an attempt to rectify this inconsistency, the direct effects of PCP on the bovine adrenal medulla were examined. At (3×10^?6M), PCP reduced the acetylcholine-(ACh)-induced catecholamine release by 50%. Surprisingly, barium-induced secretion of catecholamines was also reduced by PCP. ACh-induced catecholamine release was not altered by 10^?3M 4-aminopyridine (4 AP), the potassium channel blocker. Thus, calcium antagonist actions of PCP and consequent block of catecholamine secretion from adrenal medulla may explain the lack of effect of adrenalectomy on PCP-induced hypertension. Possible contributions of calcium and/or potassium channel blockade to other manifestations of PCP overdosage are discussed.     

Fractionation and molecular-weight determination of large polypeptides by gel filtration in guanidiniun chloride

The interaction of several N-acetyl-d-glucosamine analogs and of sialyl lactose with the lectin wheat germ agglutinin was studied by nuclear magnetic resonance. N-²H₃-acetyl-d-gluocosamine was synthesized and found to displace the N-acetyl methyl signal toward its free chemical shift in N-acetylglucosamine and N-acetylneuraminic acid demonstrating common binding sites for the latter two compounds. The N-acetyl methyl signal of the α-methylglucoside of N-acetylglucosamine could be titrated but a 3-deoxy analog could not, the latter exhibiting very weak binding and demonstrating the importance of the 3-OH group in the binding process. Sialyl lactose (an N-acetylneuraminic acid analog) was rather tightly bound to the lectin. N-F₃-acetyl-d-glucosamine was synthesized and its binding to the lectin was studied at pH 4, 4.5, 5.1 by ¹⁹F NMR. The two anomers were found to bind with nearly equal K_d′s but exhibited a pH and anomer dependent Δ (total bound chemical shift). The -CF₃ analog was found to bind considerably stronger to the lectin than the -CH₃ compound. The clear resolution of the α and β anomers of this molecule make it a very useful probe of the lectin binding site.     

Influence of increasing levels of β-glucanase on the productive value of barley diets for broiler chickens

The influence on the productive value of diets for broiler chickens based on barley harvested at two stages of ripeness, when including β-glucanase in increasing amounts, was evaluated in a production experiment over three weeks. Feed consumption and live weight increased (P < 0.001) and feed conversion was improved (P < 0.001) by including β-glucanase in the diets. Dry matter content of excreta increased significantly as a result of β-glucanase inclusion. Broiler chickens receiving diets based on barley harvested at combine ripeness were slightly heavier (P < 0.05) at three weeks than those fed on barley harvested at early yellow ripeness.     

The chemical-transformation products of 1,6-dibromo-1,6-dideoxygalactitol and 1,2:5,6-dianhydrogalactitol in aqueous solution

After hydrolysis of 1,6-dibromo-1,6-dideoxygalactitol (1) and 1,2:5,6-dianhydrogalactitol (2), 11 compounds were isolated, three of them as tritylated derivatives. Their structures were established on the basis of chemical evidence and, for four compounds, by X-ray diffraction. The main product of the hydrolysis of 1 was 3,6-anhydro-1-bromo-1-deoxy-dl-galactitol; the end-products of the hydrolysis of 2 were 1,5-anhydro-dl-galactitol, 2,5-anhydro-dl-altritol, and galactitol.