SCE variability in lymphocytes and fibroblasts

Summary To determine whether the sister chromatid exchange (SCE) distributions obtained in lymphocytes and fibroblasts from different individuals are comparable, a controlled study was set up. Peripheral blood and skin biopsies were taken on the same day from five individuals living for years under the same environmental conditions. All samples were treated in the same fashion, and the SCEs were scored in 50 metaphases of peripheral blood lymphocytes and of skin fibroblasts in an early and in a late passage. A repeat blood sample was taken from the same five indivuduals 1 year later. Based on the results obtained in this first part of the study, five randomly chosen healthy blood donors were sampled at different times and studied in the same fashion. Each chromosome was identified, and the SCE scores were tabulated per chromosome over 50 metaphases. The statistical analysis consisted of fitting log linear models to these scores and examining the best fit by determining the exceedance probabilities (observed significance level). For lymphocytes, the results indicated that the SCE distributions depended only on the chromosome examined, and not on BrdU-exposure time, individuals, or time of sampling. Treatment with ethyl methane sulfonate (EMS) increased the number of SCEs proportionally on all chromosomes. Analysis of the SCE scores on lymphocytes and fibroblasts of the five individuals and on their low and high passage fibroblast cultures revealed the necessity of including higher order interactions in order to fit a suitable model to the data. Therefore comparison of the SCE scores of lymphocytes with those of fibroblasts or comparison of scores on fibroblasts from different individuals could not be done. In practice, to compare samples or individuals, it suffices to score the SCE on a limited number of chromosomes (e.G., the A group) of 50 metaphases.     

Existence and function of a receptor for immunoglobulin A on human eosinophils

The existence of receptors for immunoglobulin A on human eosinophils is demonstrated by flow cytofluorometry. Between 5 and 60% of eosinophils purified from peripheral blood of hypereosinophilic patients are able to bind monomeric serum IgA. The addition of antihuman IgA antibodies to surface IgA-bearing eosinophils induces the exocytosis of peroxidase contained in the granules suggesting a cell activation due to IgA receptors. The inhibition of antiparasitic cytotoxicity by eosinophils preincubated with IgA under a polymeric form only, indicates the low affinity of IgA receptors as well as their participation in the effector function of eosinophils.     

The Boer goat. II. Growth, nutrient requirements, carcass and meat quality

Growth rates of Boer goats were generally lower than sheep and, under favorable nutritional conditions, weight gains of more than 200 g per day were obtained, against values of up to 176 g per day under extensive subtropical conditions. Lactation and pregnancy had a marked effect on ME intake, and the latter had an improved feed conversion ratio (6.06 kg/kg) in comparison to that of virgin does (10.96 kg/kg). Below 6% crude protein in the diet, feed intake is reduced and has negative effects on birth weights, growth and milk production. Little information is available on mineral requirements of goats. The carcass of Boer goats is generally leaner, less compact and has different carcass proportions than sheep. The relatively high collagen contents with lower solubility of Boer goat meat, has meant that the eating quality has been regarded as inferior to that of lamb and mutton. Breeding holds the key to improving tenderness of goat meat; different slaughtering techniques can be used as well. Boer goats have high potential as meat animals when yielding three kid crops in 2 years and when fed to gain more than 200 g/day.     

Incorporation of hexose nucleoside analogues into oligonucleotides: synthesis, base-pairing properties and enzymatic stability.

Oligonucleotides containing 1-(2,4-dideoxy-beta-D-erythro-hexopyranosyl)thymine (2) and 1-(3,4-dideoxy-beta-D-erythro-hexopyranosyl)thymine (3) were synthesized on a solid support using the phosphoramidite approach. The properties of these oligonucleotides were compared with the earlier reported characteristics of oligonucleotides containing 1-(2,3-dideoxy-beta-D-erythro-hexopyranosyl) thymine (1). The order in enzymatic stability of end-substituted oligonucleotides is 3 greater than 1 much greater than 2. The hybridization properties of the modified oligonucleotides are in reverse order: 2 much greater than 1 greater than 3.     

Differences in human chemosensory evoked potentials to olfactory and somatosensory chemical stimuli presented to left and right nostrils

The aim of the present study was to determine whether the recordingof chemosensory evoked potentials (CSEP) in healthy subjects(n = 11) can be helpful in differentiating the olfactory ortrigeminal component possessed by odorants. By recording fromseveral positions on the surface of the skull it was attemptedto ascertain whether different generators are responsible forCSEP associated with the different sensory components of odorants.Birhinal stimulation was used in order to establish an interactionbetween the stimulated side and the stimulated sensory channel.The four substances carbon dioxide, menthol, hydrogen sulphideand vanillin were tested. EEG was recorded from eight positions. The CSEPs' topographical distribution revealed differences inthe location of maximum amplitudes following stimulation withdifferent types of stimulants. Largest amplitudes always appearedat the vertex when trigeminal stimulants (menthol, carbon dioxide)were presented, whereas olfactory substances (vanillin, hydrogensulphide) elicited maximal amplitudes at parietal and centralsites. This suggests that at least two neuronal populationsare involved in the cortical generation of CSEP. Another interestingfinding was that the evoked potentials differed in relationto the stimulated side. Generally, responses to carbon dioxide,menthol and hydrogen sulphide had shorter latencies and smalleramplitudes after stimulation of the left nostril. In contrast,after stimulation with vanillin latencies were shorter and amplitudestended to be smaller after stimulation of the right side. Sincevanillin was the only substance which always evoked pleasantand positive associations, it was assumed that the differencesin CSEP after stimulation of the two nostrils are related tothe different processing of emotional information within thetwo hemispheres.     

NH(4)-Excreting Azospirillum brasilense Mutants Enhance the Nitrogen Supply of a Wheat Host

Spontaneous ethylenediamine-resistant mutants of Azospirillum brasilense were selected on the basis of their excretion of NH(4). Two mutants exhibited no repression of their nitrogenase enzyme systems in the presence of high (20 mM) concentrations of NH(4). The nitrogenase activities of these mutants on nitrogen-free minimal medium were two to three times higher than the nitrogenase activity of the wild type. The mutants excreted substantial amounts of ammonia when they were grown either under oxygen-limiting conditions (1 kPa of O(2)) or aerobically on nitrate or glutamate. The mutants grew well on glutamate as a sole nitrogen source but only poorly on NH(4)Cl. Both mutants failed to incorporate [C]methylamine. We demonstrated that nitrite ammonification occurs in the mutants. Wild-type A. brasilense, as well as the mutants, became established in the rhizospheres of axenically grown wheat plants at levels of > 10 cells per g of root. The rhizosphere acetylene reduction activity was highest in the preparations containing the mutants. When plants were grown on a nitrogen-free nutritional medium, both mutants were responsible for significant increases in root and shoot dry matter compared with wild-type-treated plants or with noninoculated controls. Total plant nitrogen accumulation increased as well. When they were exposed to a N(2)-enriched atmosphere, both A. brasilense mutants incorporated significantly higher amounts of N inside root and shoot material than the wild type did. The results of our nitrogen balance and N enrichment studies indicated that NH(4)-excreting A. brasilense strains potentially support the nitrogen supply of the host plants.     

Tumour invasion: effects of cell adhesion and motility

Metastasis is the major cause of failure in cancer therapy. Recent studies of the molecular cell biology of the metastatic process have provided new insights into the mechanisms of cell-cell adhesion, cell-substrate adhesion and cell motility that underly invasion by tumour cells. In this review, Van Roy and Mareel discuss the role of proteins with invasion-promoting and invasion-suppressing functions in metastasis.     

A goal programming network for linear programming

Tank and Hopfield have shown that networks of analog neurons can be used to solve linear programming (LP) problems. We have re-examined their approach and found that their network model frequently computes solutions that are only suboptimal or that violate the LP problem's constraints. As their approach has proven unreliable, we have developed a new network model: the goal programming network. To this end, a network model was first developed for goal programming problems, a particular type of LP problems. From the manner the network operates on such problems, it was concluded that overconstrainedness, which is possibly present in an LP formulation, should be removed, and we have provided a simple procedure to accomplish this.