The use of different oils for the cultivation ofStreptomyces cinnamonensis

The addition of 2–4% oils to the synthetic fermentation medium used for the cultivation ofStreptomyces cinnamonensis increased the production of monensin three times on the average. When the amount of the added oil was lower than 2% and higher than 4% the production sharply decreased. The maximal production preceded the maximal consumption of individual fatty acids of the added oils, the content of oleic acid decreasing most pronouncedly.     

The effect of glucose on cellobiose uptake and β-D-glucosidase activity inStreptomyces granaticolor

Glucose inhibits the inducible synthesis of β-D-glucosidase inStreptomyces granaticolor. Neither cAMP nor cGMP influence the inhibitory effect of glucose. Glucose also inhibits the inducible synthesis of the cellobiose uptake system but has no effect on its activity. This may be the mechanism underlying glucose inhibition of induction of β-D-glucosidase inS.granaticolor.     

Invertase immobilization via its carbohydrate moiety

After periodate oxidation of its glycosidic component, invertase was covalently bound onto three types of modified solid supports: glycidyl methacrylate, styrene-divinylbenzene copolymers, and bead cellulose. Direct reaction of the invertase aldehyde groups that were formed with amino groups of the support and use of the modified Ugi reaction have been employed as immobilization procedures. Apart from binding methods, the important effects of the buffer, support, conditions of periodate oxidation, and the length of the spacer on the activity of the enzyme conjugate have been investigated. Superior conjugate activity was obtained, via modified Ugi reaction, by the immobilization of a suitably oxidized invertase to a styrene-divinylbenzene copolymer having free amino groups.     

Dion tomasellii (Zamiaceae), a new species with two varieties from western Mexico

Dion tomasellii sp. nov. occurs with an interrupted distribution from Guerrero to central Sonora. It is characterized by falcate to subfalcate leaflets. The populations from Sonora and northern Sinaloa are segregated asD. tomasellii var.sonorense on the basis of their narrower and glaucous leaflets.     

2-Bromoethyl glycosides in glycoside synthesis: preparation of glycoproteins containing alpha-L-Fuc-(1----2)-D-Gal and beta-D-Gal-(1----4)-D-GlcNAc

The applicability of 2-bromoethyl glycosides in carbohydrate synthesis is demonstrated by the synthesis of glycosides of alpha-L-Fuc-(1----2)-D-Gal and beta-D-Gal-(1----4)-D-GlcNAc. The bromoethyl aglycon was transformed into the methoxycarbonylethylthioethyl spacer, which allowed coupling of the sugars to proteins (BSA and KLH).     

Reaction of ethyl 2-amino-4,6-O-benzylidene-2-deoxy-d-gluconate with acetylenic esters

Ethyl 2-amino-4,6-O-benzylidene-2-deoxy-d-gluconate adds to acetylenic esters to give sugar enaminones. The following acetylene derivatives have been employed: methyl propiolate, ethyl phenylpropiolate, and dimethyl acetylenedicarboxylate (6). With compound 6, the reaction leads to a mixture of the expected enaminone and the isomeric oxazolidine derivative. The structures and configurations of the new compounds were studied by spectroscopic and chemical methods.     

Modulatory effect of zinc on the proliferative response of murine spleen cells to polyclonal T cell mitogens

To study the effect of zinc on the proliferative response to polyclonal T cell mitogens, spleen cells from C57BL/6 mice were cultured with or without ZnCl2 and stimulated with graded doses of concanavalin A or phytohemagglutinin. Addition of 10(-4) M ZnCl2 inhibited proliferation whereas 10(-5) to 10(-6) M ZnCl2 did not modify the response to suboptimal doses of mitogen but increased DNA synthesis in cultures stimulated with high doses of mitogen (10 or 20 micrograms/ml of concanavalin A and 10 or 25 microliters/ml of phytohemagglutinin) which are supraoptimal for C57BL/6 mice, and inhibited proliferation in cultures of spleen cells from animals of this strain, low responder to T cell mitogens. In contrast, supplementation with ZnCl2 did not enhance the response to mitogen of spleen cells from high responder BALB/c mice. The enhancing effects of ZnCl2 on the proliferative response of C57BL/6 cells were not observed following depletion of adherent cells or in cultures supplemented with 5 X 10(-5) M 2-mercaptoethanol, both conditions capable of abrogating the inhibitory effect of high mitogen doses on the response of C57BL/6 cells.     

Short term regulation by lysine of ornithine decarboxylase activity in Dictyostelium discoideum

A transitory increase in ornithine decarboxylase activity has been observed soon after food removal from Dictyostelium discoideum amoeba. This increase can be prevented by supplementation of the differentiation buffer with the 11 amino acids known for their ability to retard the development of this slime mold. Lysine can replace the amino acid mixture with an apparent inhibition constant of 50 micromolar. This inhibition by lysine, which was only observed in vivo, took place within 5 min and was readily reversed upon lysine removal.     

Contribution of histones H2A and H2B to the folding of nucleosomal DNA

We have studied the structural properties of nucleosomal particles deficient in histones H2A and H2B produced by modification of histone amino groups with dimethylmaleic anhydride [Jordano, J., Montero, F., & Palacián, E. (1984) Biochemistry (preceding paper in this issue)]. Digestion with DNase I of residual particles containing only 15% of the original H2A . H2B complement produces only discrete DNA fragments no longer than 70 nucleotides. As compared with the original nucleosomes, thermal denaturation of the residual particles shows a decrease from 140 to about 90 in the number of nucleotide base pairs per particle that melt at the highest temperature transition as well as a drop in the temperature of this transition. Circular dichroism spectra of the residual particles give ellipticity values around 275 nm, much higher than those corresponding to the control nucleosomes, which appears to indicate a loss in the compact DNA tertiary structure. When regeneration of the modified amino groups of the residual particles takes place in the presence of the complementary fraction containing histones H2A and H2B, but not in its absence, nucleosomal particles with the structural properties of the original nucleosomes are reconstituted. Therefore, the structural change observed in the residual particles can be assigned to the lack of histones H2A and H2B and not to the modified amino groups of the histones present in the residual particles. The results are consistent with the stabilization by histones H2A and H2B of a DNA length of 50-70 base pairs per nucleosome.