An improved method for cell and spore counts during aerobic cultivation of crystal toxin producingBacillus sphaericus

Summary A simple improved method including sonication treatment is proposed to determine accurate cell and spore counts forBacillus sphaericus, a microorganism which can form cell aggregates. Sonication (10 watt power output) for 40 seconds after dilution of culture broth was effective in dispersing clumps of cells and spores without disruption. This improved method gave approximately 2 times higher cell and spore counts compared with the conventional counting methods (without sonication).     

Nod signal-induced plasma membrane potential changes in alfalfa root hairs are differentially sensitive to structural modifications of the lipochitooligosaccharide

Lipochitooligosaccharide Nod signals are important determinants of host specificity in the Rhizobium -legume symbiosis. The most rapid response of plant cells to the R. meliloti Nod signal NodRm-IV(C16:2,S) reported so far is the depolarization of the plasma membrane potential in alfalfa root hairs. In order to investigate whether this response may be part of a specific signal transduction cascade involved in the nodulation process, its specificity was studied with respect to host-specific modifications of the lipochitooligosaccharide. Five different Nod factors displaying different degrees of activity in inducing root hair deformation or cortical cell divisions on alfalfa were tested. The ability of the Nod factors to elicit plasma membrane depolarization correlated well with their activity in the bioassays. Removal of the sulfate group (NodRm-IV(C16:2)) led to inactivation of the Nod factor. An increase in the length of the chitooligosaccharide backbone (NodRm-V(C16:2,S)) or saturation of the acyl chain (NodRm-IV(C16:0,S)) resulted in severely reduced activity. In contrast, the O -acetyl group at the non-reducing terminus in NodRm-IV(Ac,C16:2,S), which confers substantially higher activity in long-term bioassays, did not enhance plasma membrane depolarization significantly in comparison with the non- O -acetylated factor. Thus, the rapid plasma membrane response is differentially sensitive to various structural motifs of the lipochitooligosaccharide. These data suggest that the different substituents modifying the basic Nod factor structure may have distinct functions, not all of them contributing to the interaction with a putative receptor in root hair cells. However, the overall specificity of the membrane depolarization for the cognate Nod factors raises the possibility that it is involved in a Nod signal transduction pathway.     

The calcium hypothesis of cystic fibrosis

Data have been presented which suggests that various CF cell types show evidence of alterations in calcium homeostasis. The significance of these observations and the exact nature of the putative calcium defect in CF remains to be elucidated. It must also be determined whether this possible defect is primary, or is secondary or tertiary to some more basic lesion. The data reviewed suggests that altered calcium homeostasis may play some focal role in the aetiology or the pathogenesis of CF.     

The structural basis of the multiple forms of human complement component C4

cDNA clones of human complement components C4A and C4B alleles were prepared from mRNA obtained from the liver of a donor heterozygous at both loci. cDNA from one C4A allele was sequenced to give the derived complete amino acid sequence of 1722 amino acid residues of the C4 single chain precursor molecule and the estimated sequences of the three peptide chains of secreted C4. Comparison with partial sequences of a second C4A allele and a C4B allele has led to the tentative identification of some class differences in nucleotide sequences between C4A and C4B and of allelic differences between C4A alleles in this highly polymorphic system.     

Normal and mutant human β-globin pre-mRNAs are faithfully and efficiently spliced in vitro

Human β-globin mRNA precursors (pre-mRNAs) synthesized in vitro from a bacteriophage SP6 promoter/β-globin gene fusion are accurately and efficiently spliced when added to a HeLa cell nuclear extract. Under optimal conditions, the first intervening sequence (IVS 1) is removed by splicing in up to 90% of the input. pre-mRNA. Splicing requires ATP and in its absence the pre-mRNA is neither spliced nor cleaved at splice junctions. Splicing does not require that the pre-mRNA contain a correct 5′ or 3′ end, a 3′ poly A tail, or a 5′-terminal cap structure. However, capping of the pre-mRNA significantly affects the specificity of in vitro processing. In the absence of a cap approximately 30%–40% of the pre-mRNA is accurately spliced, and a number of aberrantly cleaved RNAs are also detected. In contrast, capped pre-mRNAs are spliced more efficiently and produce fewer aberrant RNA species. The specificity of splice-site selection in vitro was tested by analyzing pre-mRNAs that contain β-thalassemia splicing mutations in IVS 1. Remarkably, these mutations cause the same abnormal splicing events in vitro and in vivo. The ability to synthesize mutant pre-mRNAs and study their splicing in a faithful in vitro system provides a powerful approach to determine the mechanisms of RNA splice-site selection.     

Brain Infarction and Hemorrhage in Young and Middle-aged Adults

Of 131 young (17 to 44 years) and middle-aged (45 to 55 years) adults who had brain infarction or hemorrhage, the most common etiologic factors were rheumatic heart disease, migraine and oral contraceptive use among the younger group. In contrast, atherosclerotic, hypertensive and diabetes-associated cerebrovascular were the most common causes in the middle-aged group. Patients who have a stroke before age 45 should have prompt, complete laboratory and radiologic testing to define a possible treatable cause.     

Beta-2 microglobulin types in mice of wild origin

To determine the distribution of beta-2 microglobulin (B2m) alleles in wild mice we have typed mice derived from natural populations in Europe, North Africa, South America, and East Asia. Mus musculus domesticus mice from Germany, France, Italy, and Peru were all B2m ^a as were most from the United Kingdom. M.m. musculus mice from Denmark and Czechoslovakia, several stocks of M.m. molossinus from Japan, and M.m. castaneus from China, Thailand, and the Philippines were of B2m ^b type. This is consistent with the notion that C57BL/6 may have obtained some of its genes, including B2m, from Eastern mice. A BgII restriction site characteristic of B2m ^b was also found in mice from Czechoslovakia and Japan, confirming that B2m ^b is a naturally occurring allele of B2m. A new type of ₂m ( ₂m^w1) was found in four stocks of M. spretus from Portugal, Spain, and Morocco. This molecule differs in apparent size and charge from the a and b types. ₂m^w2 was found together with ₂ ma in one stock of M.m. domesticus (brevirostris) from Morocco. ₂m^w3 and ₂m^w4 were found in a few M. m. bactrianus from Pakistan. In all cases tested, these new ₂m molecules associate with class I histocompatibility antigens.Abbreviations used in this paper ₂m beta-2 microglobulin - B2m gene for beta-2 microglobulin - IEF isoelectric focusing - SDS-PAGE polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate - MHC major histocompatibility complex - T. E. Tris-EDTA buffer     

Life-related aspects of stellar evolution

It is generally thought that the Universe started with a big explosion (Big Bang) approximately 15 billion years ago. Hydrogen and helium were formed within the first few minutes, while all the other chemical elements are the by-products of stellar evolution that are added to the interstellar medium through the supernova explosions of the larger stars. Carbon, Oxygen, Hydrogen and Nitrogen, which constitute about 98% of the biomass of the Earth, are also among the most abundant chemical elements in the Universe. A seemingly unique combination of the fundamental laws and constants of the Universe made possible the origin and subsequent slow evolution of life.