Acyl-CoA-binding protein from cow. Binding characteristics and cellular and tissue distribution.

Hydroxyl radicals (OH.) in free solution react with scavengers at rates predictable from their known second-order rate constants. However, when OH. radicals are produced in biological systems by metal-ion-dependent Fenton-type reactions scavengers do not always appear to conform to these established rate constants. The detector molecules deoxyribose and benzoate were used to study damage by OH. involving a hydrogen-abstraction reaction and an aromatic hydroxylation. In the presence of EDTA the rate constant for the reaction of scavengers with OH. was generally higher than in the absence of EDTA. This radiomimetic effect of EDTA can be explained by the removal of iron from the detector molecule, where it brings about a site-specific reaction, by EDTA allowing more OH. radicals to escape into free solution to react with added scavengers. The deoxyribose assay, although chemically complex, in the presence of EDTA appears to give a simple and cheap method of obtaining rate constants for OH. reactions that compare well with those obtained by using pulse radiolysis.     

Neural network detects errors in the assignment of mRNA splice sites.

The use of databanks in genetic research assumes reliability of the information they contain. Currently, error-detection in the manually or electronically entered data contained in the nucleotide sequence databanks at EMBL, Heidelberg and GenBank at Los Alamos is limited. We have used a subset of sequences from these databanks to train neural networks to recognize pre-mRNA splicing signals in human genes. During the training on 33 human genes from the EMBL databank seven genes appeared to disturb the learning process. Subsequent investigation revealed discrepancies from the original published papers, for three genes. In four genes, we found wrongly assigned splicing frames of introns. We believe this to be a reflection of the fact that splicing frames cannot always be unambiguously assigned on the basis of experimental data. Thus incorrect assignment appear both due to mere typographical misprints as well as erroneous interpretation of experiments. Training on 241 human sequences from GenBank revealed nine new errors. We propose that such errors could be detected by computer algorithms designed to check the consistency of data prior to their incorporation in databanks.     

Saint Lucia revisited

The eastern Caribbean island of Saint Lucia is now famous in parasitological history as the setting for a major programme of schistosomiasis control'. Perhaps less well-known are the island's effective control of many intestinal parasites, and elimination of malaria, such that the current patterns of mortality and other demographic indicators now resemble those of industrialized countries. More recently, the island has become the focus for another community-based health programme as the Caribbean region again comes to grips with Aedes aegypti and its recently imported relative, Aedes albopictus, important vectors of yellow fever and dengue viruses (see Box 1).     

Alterations in cell surface galactosyltransferase activity during limb chondrogenesis in brachypod mutant mouse embryos

The autosomal mutation brachypod (bpH/bpH) in the mouse affects the development of precartilage mesenchymal condensation in the limb-bud. We have previously shown that this defect is localized to the expression of terminal N-acetylglucosamine (GlcNAc) glycoproteins in the plasma membrane (Elmer and Wright, '83). The present study is focused on cell surface galactosyltransferase (GalTase), an ectoenzyme that transfers galactose to its GlcNAc substrate. Purified plasma membrane preparations derived from wild-type (+/+), heterozygote (+/bpH) and brachypod (bpH/bpH) embryonic mouse limb cells were assayed for GalTase activity during in vitro and in utero chondrogenesis using High-Performance Liquid Chromatography (HPLC). On embryonic day E12, prior to overt expression of the mutant gene, no significant difference in GalTase activity was observed. By the third day in culture, all major chondrogenic elements of the autopod were present in +/+ and +/bpH embryos, whereas the mutant autopods were markedly deficient in staining and appeared consistently shorter. The accumulation of alcianophilic cartilage matrix in the wild-type was accompanied by a 29% increase in GalTase activity, which reflected the net change (29%) observed during development from days E12 to E13 in utero. The GalTase activity for the in utero E13 mutant (13%) was significantly different from control. In culture, day E12 mutant autopods actually decreased in their GalTase level by 3 days so that the activity was reduced to only 57% of the wild-type. Though GalTase activity in the heterozygote showed an intermediate expression, optical image analysis did not reveal consistent differences in cartilage development when compared to +/+, arguing against a gene-dosage effect at the gross anatomical level. These data indicate that an increase in plasma membrane GalTase activity is a natural developmental event that occurs during limb-bud chondrogenesis and a decrease in GalTase activity contributes to the dysmorphogenesis in brachypod limb-buds.     

Predictive model of conjugative plasmid transfer in the rhizosphere and phyllosphere.

A computer simulation model was used to predict the dynamics of survival and conjugation of Pseudomonas cepacia (carrying the transmissible recombinant plasmid R388:Tn1721) with a nonrecombinant recipient strain in simple rhizosphere and phyllosphere microcosms. Plasmid transfer rates were derived for a mass action model, and donor and recipient survival were modeled as exponential growth and decay processes or both. Rate parameters were derived from laboratory studies in which donor and recipient strains were incubated in test tubes with a peat-vermiculite solution or on excised radish or bean leaves in petri dishes. The model predicted donor, recipient, and transconjugant populations in hourly time steps. It was tested in a microcosm planted with radish seeds and inoculated with donor and recipient strains and on leaf surfaces of radish and bean plants also growing in microcosms. Bacteria were periodically enumerated on selective media over 7 to 14 days. When donor and recipient populations were 10(6) to 10(8) CFU/g (wet weight) of plant or soil, transconjugant populations of about 10(1) to 10(4) were observed after 1 day. An initial rapid increase and a subsequent decline in numbers of transconjugants in the rhizosphere and on leaf surfaces were correctly predicted.     

Proteins transferred to nitrocellulose for use as immunogens

Proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and were eluted efficiently from the gel by transfer to nitrocellulose paper. The protein-bearing nitrocellulose was solubilized with dimethyl sulfoxide and used as an immunogen in rabbits. Polyclonal antibodies to the proteins were generated.     

Fluid balance in exercise dehydration and rehydration with different glucose-electrolyte drinks

After exercise dehydration (3% of body weight) the restoration of water and electrolyte balance was followed in 6 male subjects. During a 2 h rest period after exercise, a drink of one of four solutions was given as 9 X 300 ml portions at 15 min intervals: control (C-drink), high potassium (K-drink), high sodium (Na-drink) or high sugar (S-drink). An exercise test (submaximal and supramaximal work) was performed before dehydration and after rehydration. Dehydration reduced plasma volume by 16%, a process reversed on resting even before fluid ingestion began, due to release of water accumulated in the muscles during exercise. After 2 h rehydration, plasma volume was above the initial resting value with all 4 drinks. The final plasma volumes after the Na-drink (+14%) and C-drink (+9%) were significantly higher than after the K- and S-drinks. The Na-drink favoured filling of the extracellular compartment, whereas the K- and S-drinks favoured intracellular rehydration. In spite of the higher than normal plasma volume after rehydration, mean heart rate during the submaximal test was 10 bpm higher after rest and rehydration than in the initial test, and was not different between the drinks. The amount of work which could be performed in the supramaximal test (105% VO2max) was 20% less after exercise dehydration and subsequent rest and rehydration than before. This reduction was similar for all drinks, and may be due to a decreased muscle glycogen content (70% of initial) at the time of the second test.