Comparative studies of seed proteins of the genusArtocarpus with respect to lectins

Proteins from two species of the genusArtocarpus (A. integrifolia L. andA. incisa L.) were compared by ammonium sulphate fractionation, molecular sieve chromatography and SDS-polyacrylamide gel electrophoresis, with special attention to the lectins. The protein content and hemagglutinating activity were markedly different in the two seeds. The protein pattern obtained by both molecular sieve chromatography and SDS-polyacrylamide gel electrophoresis were quite different. The only similarities found were the elution volume of the lectins in the Sephadex G-100 column and the lectin bands (11 500 and 15 000 daltons) in SDS-polyacrylamide gel electrophoresis.     

Simple computer method for evaluation of lateral diffusion coefficients from fluorescence photobleaching recovery kinetics.

A method is presented for the analysis of fluorescence photobleaching recovery curves. Based on the simplified kinetic expression of Yguerabide, J., J.A. Schmidt, and E.E. Yguerabide (1982, Biophys. J., 40:69-75), a linearization procedure is described that permits unequivocal determination of all diffusion parameters. The presence of additional membrane flow or multiple diffusion coefficients can easily be detected by this method, and simple corrections for the presence of these alternative recovery processes can be made by the use of a regular mini-computer. The validity of the method is tested on simulated recovery curves, varying the contribution of flow, multiple diffusion coefficients, and statistical noise due to counting error.     

Salt-dependent conformational transitions in the self-complementary deoxydodecanucleotide d(CGCAATTCGCG): Evidence for hairpin formation

Differential scanning calorimetry (DSC), temperature-dependent uv-absorption spectroscopy, and temperature-dependent CD were used to monitor and characterize the salt-dependent, thermally induced structural transitions in the deoxydodecanucleotide d(CGCGAATTCGCG). At the high oligomer concentrations required for DSC, the calorimetric scans revealed a single, monophasic transition curve at all salt concentrations. Based on previous nmr melting studies under similar conditions, we conclude that these monophasic transitions correspond to the cooperative duplex-to-single-strand conversion of the dodecamer. By contrast, at the lower oligomer concentrations used for the spectroscopic studies, the shapes of the uv and CD melting curves were found to depend on the concentration of the added salt. At high salt (≥0.1M Na⁺), a single, monophasic transition curve was observed. At lower salt (?0.01M Na⁺), the CD and uv melting curves exhibit biphasic behavior. Based on the concentration dependence, the enthalpy, and the cooperativity of each transition in the biphasic curve, we conclude that at low salt and low oligomer concentrations, the dodecamer melts in a sequential manner involving initial disruption of a duplex structure and subsequent disruption of a hairpin structure.     

Mixtures of gramicidin and lysophosphatidylcholine from lamellar structures

It is shown by ³¹P-NMR and freeze-fracture electron microscopy that in aqueous dispersions of mixtures of gramicidin and palmitoyllysophosphatidylcholine lamellar structures are formed which contain four lysophosphatidylcholine molecules per gramicidin monomer.     

Interferon affects intracellular calmodulin levels

Interferon lowers calmodulin levels in two cell lines sensitive to its antiproliferative effect. Further, in synchronized cells, interferon strongly inhibits the increase in calmodulin observed when control cells enter the S phase, and concomitantly inhibits DNA synthesis. Calmodulin has been implicated in the control of cell proliferation and an increase in this protein seems to be necessary for the progression of cells into the S phase of the cell cycle. Therefore, the effect of interferon on calmodulin content might constitute part of the molecular mechanism by which interferon inhibits DNA synthesis.     

Comparison of various atmospheric conditions for isolation and subcultivation of Mycoplasma hyorhinis from cell cultures

The efficiency of aerobic incubation was compared with incubation under various oxygen and carbon dioxide conditions for the isolation and subcultivation of three strains of Mycoplasma hyorhinis from VERO-cell cultures and subcultivation of three laboratory strains. Under anaerobic conditions with a low oxidation-reduction potential (at or below -115 mV) as obtained in jars, with catalysts, containing mixtures of 5%-10% CO2 in H2, very poor or no growth of any of the six M. hyorhinis strains was observed. When traces of oxygen were present (that is, under conditions with higher oxidation-reduction potentials, e.g. when omitting the catalyst in the above gas mixtures or in 5% CO2 + 95% N2) isolation from cell cultures was successful in most tests, but subcultivation of these primary isolates was seldom possible under these semi-anaerobic conditions. However, in most cases these primary isolates could be subcultivated aerobically, although aerobic conditions were unsatisfactory for isolation in about half of the experiments. Isolation of M. hyorhinis was optimal in 5% O2 + 95% N2, under which condition the isolates could also always be subcultivated. Isolation failed occasionally when 5% O2 + 5% CO2 + 90% N2 was used, thus indicating that 5% CO2 was slightly inhibitory. 5% CO2 in air and 10% CO2 either in air, H2 or N2 were also inadequate for isolation from cell cultures. In contrast to the findings with these cell culture-adapted M. hyorhinis strains, the laboratory strains could be subcultivated easily under all conditions tested except those with an oxidation-reduction potential at or below -115 mV; 100% CO2 was inhibitory for all 6 strains. Our findings may partly explain why M. hyorhinis is often considered "non-cultivable" on artificial media once adapted to cell cultures. The findings emphasize the need to employ also a micro-aerophilic condition (5% O2 in 95% N2) in the examination of cell cultures for mycoplasma.     

Inactivation of haemolysin production in Escherichia coli by transposon insertion results in loss of virulence

A haemolytic E. coli strain is nephropathogenic for mice. Mutagenesis by transposon insertion resulted in mutants with altered haemolytic activity.Reduction or elimination of the haemolytic activity is accompanied with loss of virulence. It is shown that this loss of virulence is due to altered haemolytic activity and not caused by the transposon insertion itself.     

Selection of Wine Yeasts for Growth and Fermentation in the Presence of Ethanol and Sucrose

To optimize the conversion of carbohydrates to ethanol, strains of several Saccharomyces species were examined for the ability to grow and ferment in a range of sucrose and ethanol concentrations. A total of 632 wine yeasts, most of them isolated from wineries in Andalusia and Extremadura, southwestern Spain, were subjected to screening and selection. Growth and fermentative capacity in different ethanol and sucrose concentrations varied from one strain to another. There was no correlation between growth and fermentative capacity. The best 35 strains grew in 15% ethanol and fermented in 18% ethanol. Ethanol accumulated, although at a reduced rate, after the cells stopped growing. Most yeast strains were highly fermentative in 50% sucrose. Some of them effectively utilized the carbohydrates of the culture, yielding final ethanol concentrations of > 14%. Of the 35 selected strains, 16 were promising for genetic analysis and breeding because of their capacity to sporulate. These strains were homothallic, and their spores were viable. The meiotic products analyzed so far were also homothallic.     

Cyclic AMP, cyclic GMP and glucose utilization by diabetic rat fat cells

Fat cells from epididymal adipose tissue from normal and streptozotocin-diabetic rats were studied to determine glucose utilization and cyclic nucleotide levels. Diabetic rat fat cells present a higher cAMP content (P less than 0.05) compared with controls. Addition of insulin decreases within 10-min incubation the cAMP content in both normal and diabetic cells (P less than 0.05). However, the value obtained in the latter remains by 25% higher than that of normal cells not exposed to insulin. No changes in cGMP were detected. Pretreatment of the diabetic animals during two days with propranolol (1 mg kg body wt-1 day-1) induces the decrease to normal levels of the fat cell cAMP content. However, it persists the impairment on glucose utilization observed in fat cells from diabetic animals. It seems that the increase in the intracellular amount of cAMP found in fat cells from diabetic rats is not involved, at least directly, to the impaired glucose utilization found in the diabetic state. Furthermore, through an unknown mechanism, pretreatment with propranolol can induce a drop in fat tissue cAMP toward normal values without normalizing glucose utilization.     

Secondary structure features of ribosomal RNA species within intact ribosomal subunits and efficiency of RNA-protein interactions in thermoacidophilic (Caldariella acidophila, Bacillus acidocaldarius) and mesophilic (Escherichia coli) bacteria

Ribosomal subunits of Caldariella acidophila (max.growth temp., 90 degrees C) have been compared to subunits of Bacillus acidocaldarius (max. growth temp., 70 degrees C) and Escherichia coli (max. growth temp., 47 degrees C) with respect to (a) bihelical content of rRNA; (b) G . C content of bihelical domains and (c) tightness of rRNA-protein interactions. The principal results are as follows. Subunits of C. acidophilia ribosomes (Tm = 90-93 degrees C) exhibit considerable thermal tolerance over their B. acidocaldarius (Tm = 77 degrees C) and E. coli counterparts (Tm = 72 degrees C). Based on the "melting' hyperchromicities of the intact ribosomal subunits a 51-55% fraction of the nucleotides appears to participate in hydrogen-bonded base pairing regardless of ribosome source, whereas a larger fraction, 67-70%, appears to be involved in hydrogen bonding in the naked rRNA species. The G . C content of bihelical domains of both free and ribosome-bound rRNA increases with increasing thermophily; based on hyperchromicity dispersion spectra of intact subunits and free rRNA, the bihelical parts of C. acidophila rRNA are estimated to contain 63-64% G . C, compared to 58.5% G . C for B. acidocaldarius and 55% G . C for E. coli. The increment of ribosome Tm values with increasing thermophily is greater than the increase in Tm for the free rRNA, indicating that within ribosomes bihelical domains of the thermophile rRNA species are stabilized more efficiently than their mesophile counterparts by proteins or/ and other component(s). The efficiency of the rRNA-protein interactions in the mesophile and thermophile ribosomes has been probed by comparing the releases, with LiCl-urea, of the rRNA species from the corresponding ribosomal subunits stuck to a Celite column through their protein moiety; it has been established that the release of C. acidophila rRNA from the Celite-bound ribosomes occurs at salt-urea concentrations about 4-fold higher than those required to release rRNA from Celite-bound E. coli ribosomes. Compared to E. coli the C. acidophila 50 and 30 S ribosomal subunits are considerably less susceptible to treatment designed to promote ribosome unfolding through depletion of magnesium ions.