Exoglucanases fromZea mays L. seedlings: their role inβ-D-glucan hydrolysis and their potential role in extension growth

Exoglucanases of corn seedlings were examined and evaluated in terms of their participation in the hydrolysis of cell-wall β-D-glucan and their possible role in extension growth. An exo-β-1,3-glucanase (EC 3.2.1.58), a component of the protein dissociated from isolated wall by use of high salt solutions, was purified using gel-filtration and ion-exchange chromatography. The purified enzyme hydrolyzed a number of polymeric and oligosaccharide substrates, including those of mixedlinkage, and their direct conversion to monosaccharide was evidence that the enzyme was capable of hydrolyzing both β1–4 and β1–3 linkages. The enzyme was considerably more active toward glucan that had been previously hydrolyzed by a cell-wall endo-β-D-glucanase. Similarly, the capacity of the purified exo-β-D-glucanase to degrade isolated wall was enhanced by more than 60% when the wall had been previously treated with the endoenzyme. The exo-β-D-glucanase did not exhibit growth-promoting properties nor was its activity, measured in vivo, enhanced by auxin. Another glucanase was obtained from the soluble fraction of seedling homogenates. It functioned strictly as a β-glucosidase and did not appear to participate in the hydrolysis of wall β-D-glucan.     

Partial deglycosylation of blood-group-specific glycoproteins.

The time course for the partial deglycosylation of blood-group-specific glycoproteins from human ovarian-cyst fluids with 0.25 M-H2SO4/acetic acid and 6 M-HCl in methanol was studied. Either reagent readily removed about 80% of the carbohydrate from the glycoproteins to leave non-diffusible glycopeptides that contain N-acetylgalactosamine as the predominant sugar. Some changes in amino acid distribution were observed during the deglycosylation, which were attributed to an accelerated break-up of the nonglycosylated regions of the parent glycoprotein. The N-acetylgalactosaminyl-peptides isolated were judged to be polydisperse by gel filtration, and ion-exchange chromatography divided the glycopeptide population into several fractions with differing amino acid compositions. A Lumbricus terrestris hexosaminidase preparation was successful in removing almost all the remaining sugar from the glycopeptides, but caused further rupture of the peptide. When a per O-acetylated glycoprotein was treated with the H2SO4/acetic acid reagent the glycopeptide contained, in addition to N-acetylgalactosamine, about 50% of the sialic acid present in the parent glycoprotein, indicating that most of this sugar is located near the peptide end of the carbohydrate chains.     

Nearest-neighbor and next-nearest-neighbor effects in the proton NMR spectra of the oligoribonucleotides ApGpX and CpApX

The variable-temperature proton nmr spectra of the oligoribonucleotides in the series CpApX and the series ApGpX, X = A, G, C, U, together with the parent dimers CpA and ApG have been measured. A complete analysis of all the nonexchangeable base proton resonances and ribose H-1′ proton resonances was made. The presence of trends in the shielding abilities of the various bases at both the nearest-neighbor and next-nearest-neighbor positions were identified. The observed shieldings could be used to predict the chemical shifts of protons in related systems. Based on the empirical results from ribodinucleoside monophosphates, the temperature-dependent behavior of the J_1′2′ coupling constants of the triribonucleotides suggested that the compounds in the CpApX series stacked from the 5′-end to the 3′-end, while those in the ApGpX series stacked from the 3′-end to the 5′-end.     

Cell free synthesis of some storage protein subunits by polyribosomes and RNA isolated from developing seeds of pea (Pisum sativum L.)

Polyribosomes which have template activity in the wheat germ system have been isolated from developing pea seeds. Some of the translation products have identical mobilities to the vicilin and legumin subunits by SDS-PAGE. Certain products were specifically immunoprecipitated with antisera prepared against purified vicilin and legumin fractions. Various RNA fractions including poly A-rich RNA have also been isolated from polyribosomes and shown to direct the synthesis of polyripeptides whose properties are similar to the storage protein subunits. The results are discussed in relationship to other investigations with seed storage protein biosynthesis in vitro.Abbreviations DTT dithiothreitol - SDS-PAGE SDS-polyacrylamide gel electrophoresis - TCA tricarboxylic acid     

A generalized diffusion model for growth and dispersal in a population

A reaction-diffusion model is presented in which spatial structure is maintained by means of a diffusive mechanism more general than classical Fickian diffusion. This generalized diffusion takes into account the diffusive gradient (or gradient energy) necessary to maintain a pattern even in a single diffusing species. The approach is based on a Landau-Ginzburg free energy model. A problem involving simple logistic kinetics is fully analyzed, and a nonlinear stability analysis based on a multi-scale perturbation method shows bifurcation to non-uniform states.Part of this work was done while at the Mathematical Institute, Oxford University as a Senior Visiting Fellow supported by the Science Research Council of Great Britain under grant GR/B31378     

Oncofetal antigen-I (OFA-I) relative antigenicity on melanoma cells

Summary The oncofetal antigen-I (OFA-I) has been defined as an immunogenic antigen that is expressed on human cancer cells and is cross reactive with fetal brain tissue. Quantitative variations in the expression of OFA-I among different cultured melanoma cell lines were determined by absorption techniques based on functionally monospecific anti-OFA-I serum. Allo-antibodies were removed by absorption with lymphoblasts autologous to an OFA-I-positive target cell. Functional monospecificity toward OFA-I was confirmed by complete absorption with a specimen of fetal brain but not by liver from the same fetus.Of 14 melanoma cell lines tested, two did not express OFA-I, whereas 12 expressed the antigen to varying degrees. Five of the cell lines were highly antigenic, and serum absorbed with 5×10⁵ of any of these cell lines could reduce the anti-OFA-I titer (1 : 96) at least four-fold. OFA-I was detected on biopsied melanomas autologous to the antigenic cultured cells. The ability to select highly antigenic cell lines could be useful in further attempts to characterize OFA-I and to monitor tumor immunity in vitro. Antigenic cell lines may improve the response of patients treated in trials of immunotherapy.     

Induction by progesterone of a sexual dimorphism of estrogen uptake by anterior pituitary cells in situ

Summary The effects of progesterone pretreatment on in vivo ³H-estrogen uptake by five anterior pituitary cell types was analyzed by means of a quantitative autoradiographic-immunocytochemical technique. Male and female rats castrated for 14 days show nuclear concentration of label in all five cell types one h after injection of ³H-estradiol, whether progesterone treated or not. The order of labeling intensity is gonadotropes lactotropes = somatotropes > thyrotropes = corticotropes. Progesterone treatment induces a dramatic sexual dimorphism in estrogen uptake; it significantly increases ³H-estrogen uptake in all female cell types. In males, progesterone decreases uptake in gonadotropes while not altering uptake in other cell types.Supported by PHS grant HD 12173 and Research Career Development Award HD 00243. Portions of these data were presented at the American Association of Anatomists meeting, Omaha, 1980I wish to acknowledge Mr. Sing Kung Lau for his excellent technical assistance and Dr. P. Rodier for her advice and assistance with the statistical analyses. I also wish to thank Dr. A.F. Parlow and NIAMDD for antisera against rLH, hFSH, rPRL and rTSH and Dr. Peter Petrusz, University of North Carolina, for antisera against bGH and h endorphin     

Prostaglandin E1 effects on resting and cholinergically stimulated lower esophageal sphincter pressure in cats

Intraluminal esophageal manometry with a sleeve catheter was used to compare the magnitude of decrease in lower esophageal spincter (LES) pressure produced by an arterial or venous infusion of prostaglandin E₁ in cats. Arterial PGE₁ produced significantly lower LES pressures than venous PGE₁ (p < 0.05). Maximal decrease of 75% in basal LES pressure occurred with an associated 15% decrease in systolic blood pressure. The site of action of PGE₁ in producing LES hypotension was studied by injection of either edrophonium, or bethanechol during the maximal PGE₁ effects. Bethanechol, which acts directly on sphincteric smooth muscle, produced an increase in LES pressure during both saline and PGE₁ infusion, while the increases in LES pressure seen with edrophonium during saline infusion were blocked during the PGE₁ infusion. From these studies, we conclude that PGE₁ produces LES hypotension in the cat by an inhibitory effect on the cholinergic pathway responsible for maintaining LES tone. These studies pharmacologically reproduce the LES pressure abnormality previously reported in the cat during acid-induced esophagitis and support the hypothesis that PGE₁ may be involved in the pathogenesis of acute acid-induced lower esophageal sphincter abnormalities.