Cell-density-dependent Changes in the Metabolism of Chloronema Cell Cultures: I. Relationship between Cell Density and Enzymic Activities

In the growing chloronema cell suspension cultures of the moss Funaria hygrometrica Hedw., activities of several enzymes have been found to be cell-density-dependent. Cyclic nucleotide phosphodiesterase (cNPDE), nitrate reductase (NR), and protein kinase showed highest activity at a low cell density (1 to 2 milligrams per milliliter) while indoleacetic acid (IAA) oxidase and peroxidase were highest at a high cell density (>10 milligrams per milliliter). 3′-Nucleotidase and the glycolytic enzymes (aldolase, hexokinase, phosphofructokinase, phosphoglucoisomerase, pyruvate kinase, and triose phosphate isomerase) showed no significant dependence on the cell density. Alternatively, if the NR and peroxidase activities were determined as a function of time in batch cultures, their levels were maximal 60 to 70 and 320 hours after subculture, respectively, the corresponding cell densities being 1 to 2 and 23 milligrams per milliliter. The relationship between cell density and NR and peroxidase activities is the same, whether these enzymes are measured in batch cultures during a growth cycle or in the cells cultured at different initial inoculum densities for a constant time. Conventionally enzymic changes have been correlated with growth phases; however, it is felt that the pattern of enzymic activities can also be interpreted as cell-density-dependent.     

Growth rate and oxygen regulate the interactions of group B Streptococcus with polarized respiratory epithelial cells

We investigated growth conditions that regulate the ability of group B Streptococcus (GBS) to attach to, invade, and translocate through polarized human respiratory epithelial cells (RECs). GBS grown in a chemostat at a fast cell mass doubling time (t(d) = 1.8 h), invaded RECs from both the apical and basolateral surfaces in higher numbers compared with those held at a t(d) = 11 h. With the exception of adherence from the basolateral surface, GBS reached peak adherence to, invasion of, and translocation through RECs when held at the fast t(d) with 15% dissolved oxygen compared with 0% dissolved oxygen. Growth rate and oxygen level strongly influence the interaction of GBS with polarized RECs and likely GBS pathogenicity.     

Analysis of time-dependent recovery from beryllium toxicity following chelation therapy and antioxidant supplementation

Efforts have been made to minimize the toxic effect caused by beryllium. Adult cyclic rats of Sprague Dawley strain were administered a bolus dose of 50mg/kg beryllium nitrate intramuscularly. The chelation therapy with glutathione (GSH), dimercapto propane sulfonic acid (DMPS)+ selenium (Se) and D-Penicillamine (DPA) + Se was given for 3 days followed by a rest of 1,3 and 7 days respectively. The results revealed a significant fall in the blood sugar level, serum alkaline phosphatase activity, serum proteins. A significant rise in the transaminases i.e. aspartate aminotranferase and alanine aminotranferase pattern is indicative of leakage of enzymes from liver resulting in alterations in the cell permeability. A rise in the hepatic lipid peroxidation activity is a direct indication of oxidative damage resulting in free radical generation. Results of the distribution studies by atomic absorption spectrophotometry reveal an increased concentration of beryllium in liver and kidney followed by lung and uterus. The relative ability of 3 chelating agents to act as antagonists for acute beryllium poisoning have been examined in liver, kidney, lungs and uterus. The appreciable change in the beryllium concentration in various organs is duration-dependent during the entire period being highly significant after 7 days rest. From the biochemical assays, and distribution studies it can be assumed that DPA+Se was the most effective therapeutic agent followed by DMPS+Se and GSH. Thus it can be concluded that DPA+Se is a better therapeutic agent as compared to DMPS+Se and GSH.     

Populations Microbiennes Des Bois

Resumé Les auteurs ont étudié la composition chimique (N, substances humiques, lignine) de copeaux de bois blanc exposés à l'air libre depuis 2 à 10 ans, ainsi que leur type de peuplement fongique. En l'absence de lignivore, le pH, les taux de lignine et d'N s'élèvent et il se forme des quantités modérées d'humus à forte capacité d'échange. Dans le cas contraire, on voit apparaître, en abondance, des substances humiques peu condensées et la matière organique subit une évolution rappelant celle du mor.Avec la collaboration technique de Melle. M. Clet.Kononova, dans sa monographie⁵, signale de Troussov (1916) une étude que nous n'avons pas eu en mains.     

Studies of esterase 6 in Drosophila melanogaster. XVIII. Biochemical differences between the slow and fast allozymes

Most natural populations of Drosophila melanogaster are polymorphic for two major electrophoretic variants at the esterase-6 locus. The frequency of the EST 6F allozyme is greatest in populations in warmer latitudes, whereas the EST 6S allozyme is predominant in colder latitudes. Latitudinal clines in electromorph frequencies are found on three continents. Purified preparations of the allozymes have been characterized for their pH optimum, substrate specificity, organophosphate inhibition, alcohol activation, thermal stability, and kinetic parameters. These and previous analyses of the EST 6 allozymes reveal that the two variants have differences in their physical and kinetic properties that may provide a basis for the selective maintenance of the polymorphisms and an explanation of the clinal variation observed in natural populations.      

Selection for egg production on part records

Summary Responses from four generations of index selection for egg production to 280 days of age in four White Leghorn populations have been presented. A pedigreed randombred population derived from one of the lines was reared with the selected lines to measure the environmental trend. The magnitude of total as well as average response although varying from population to population was positive in all the lines studied. Close correspondence between predicted and realized gains indicated that natural selection, genotype environmental interactions and environmental fluctuations were unimportant during the course of selection. Realized heritabilities agreed fairly well with the estimated heritabilities in at least three out of four populations studied. Probable reasons for variable and insufficient response were investigated.     

A novel esterase from Bacillus subtilis (RRL 1789): purification and characterization of the enzyme

An esterase (EC 3.1.1.1) produced by an isolated strain of Bacillus subtilis RRL 1789 exhibited moderate to high enantioselectivity in the kinetic resolution of several substrates like aryl carbinols, hydroxy esters, and halo esters. The enzyme named as B. subtilis esterase (BSE), was purified to >95% purity with a specific activity of 944 U/mg protein and 12% overall yield. The purified enzyme is approximately 52 kDa monomer, maximally activity at 37 degrees C and pH 8.0 and fairly stable up to 55 degrees C. The enzyme does not exhibit the phenomenon of interfacial activation with tributyrin and p-nitrophenyl butyrate beyond the saturation concentration. The enzyme showed preference for triacyglycerols and esters of p-nitrophenol with short chain fatty acid. Presence of Ca2+ ions increases the activity of enzyme by approximately 20% but its presence does not have any influence on the thermostability of the enzyme. The enzyme is not a metalloprotein and belongs to the family of serine proteases. The N-terminal amino acid sequence of BSE determined, as Met-Thr-Pro-Glu-Iso-Val-Thr-Thr-Glu-Tyr-Gly- revealed similarity with the N-terminal amino acid sequence of p-nitrobenzylesterase of B. subtilis.     

Effects of cyanobacterial extracellular products and gibberellic acid on salinity tolerance in Oryza sativa L

The XI International Rotifer Symposium was held during 11–18 March, 2006 at the National Autonomous University of Mexico Campus Iztacala located at the North Mexico City (Mexico). These triennial international meetings, first organized in Austria by Late Ruttner-Kolisko in September 1976, are gradually becoming the focal point of discussion and collaboration from rotifer workers across the world. The present XI symposium was attended by 125 participants from 20 nations. During this meeting, different themes of rotifer research from morphology to molecular biology were considered. In addition, there were four invited lectures and four workshops covering different themes of the symposium. During the last 30 years, rotifer research has witnessed gradual shift from the conventional morphological taxonomy to molecular and evolutionary systematics. While the basic rotifer ecological studies continue today, applied areas such as ecotoxicology and aquaculture have taken key roles in the recent meetings. The international rotifer meetings provide ample opportunities not only for exchange of ideas and recent research, but also for material and in establishing inter-personal relationships. Over the last 30 years, the number of participants attending the rotifer meetings has increased.