Antigenic determinants expressed by human C4 allotypes; a study of 325 families provides evidence for the structural antigenic model

The antigenic determinants of human C4 have been defined by human IgG antisera, Rodgers (Rg) and Chido (Ch), in hemagglutination-inhibition assays (HAI). Eight (2 Rg and 6 Ch) are of high frequency, > 90% , and 1, WH, is of low frequency, 15 %. The phenotypic combinations are complex; generally, C4A expresses Rg, and C4B has Ch, but reverse antigenicities have been established both by HAI and by sequence data of selected C4 allotypes. A study of 325 families provides data on the antigenic expression of each C4 allotype and demonstrates strong associations. A structural model for the antigenic determinants of C4 proteins has been proposed and is completely supported by the family material. Of the 16 possible antigenic combinations for C4 proteins, only 3 are undetected. A new Ch combination has been recorded in two French families. The reported sequence variation within the C4d region can account for the antigenic determinants but leaves the location of electrophoretic variation in C4 still unclear.     

Stretch activated ion channels in ventricular myocytes

Patch-clamp recordings from ventricular myocytes of neonatal rats identified ionic channels that open in response to membrane stretch caused by negative pressures (1 to 6 cm Hg) in the electrode. The stretch response, consisting of markedly increased channel opening frequency, was maintained, with some variability, during long (>40 seconds) stretch applications. The channels have a conductance averaging 120 pS in isotonic KCl, have a mean reversal potential 31 mV depolarized from resting membrane potential, and do not require external Ca⁺⁺ for activation. The channels appear to be relatively non-selective for cations. Since they are gated by physiological levels of tension, stretch-activated channels may represent, a cellular control system wherein beat-to-beat tension and/or osmotic balance modulate a portion of membrane conductance.Abbreviations SACs stretch-activated channels - HEPES 4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid     

Copper absorption in young men fed adequate and low zinc diets

Copper absorption was measured at two levels of dietary zinc in six healthy young men who were confined to a metabolic unit for a 75 d study of zinc utilization. A diet of conventional foods was fed, providing either 16.5 or 5.5 mg zinc and 1.3 mg copper daily. Copper absorption was determined by feeding⁶⁵Cu, a stable isotope of copper, once during the 16.5 mg Zn diet and near the beginning and end of the 5.5 mg Zn diet. Apparent copper absorption averaged 48.1% when the 16.5 mg Zn diet was fed. This was significantly higher than the averages of 37.2 and 38.5% when the 5.5 mg Zn diet was fed. Absorption also differed significantly among subjects. Fecal copper did not differ between diets or among subjects. All subjects were in positive copper balance at both levels of dietary zinc. These results suggest that a dietary zinc intake slightly above the Recommended Dietary Allowance of 15 mg/d does not increase fecal copper loss and does not interfere with copper absorption.     

Overwintering and growth regulator treatment effects on celery (Apium graveolens L.) flowering and seed production

Celery (Apium graveolens L.) plants cv. Jason overwintered in a polythene tunnel flowered earlier and grew taller than similar plants given a 10-week cold-treatment at 5°C prior to transplanting in the same tunnel in mid-February. However, there was no significant difference in the yield of seeds obtained from both treatments, plants grown at a density of 4m^-2 yielded less seeds than those at 2m^-2, though the yield per unit area was slightly higher from the high density treatment. Treatment with 100 mgl^-1 GA₃ applied twice just prior to flowering and during anthesis increased flower stalk, flower pedicel and stamen length but delayed flower opening and seed ripening and decreased seed set and seed yield. Treatment with a mixture of 1000 mgl^-1 GA₄ and GA₇ plus 1000 mgl^-1 ethephon on three occasions during seed ripening decreased seed yield and reduced seed germination though those seeds capable of germinating were less dormant than seeds from untreated plants. The size distribution of seeds was unaffected by any treatment other than the preseeding spray with GA₃ which reduced the percentage of medium-size seeds.     

Induction of embryogenicTriticum aestivum L. calli. I. Quantification of genotype and culture medium effects

Somatic embryo (embryoid) formation from immature-embryo-derived calli was quantified in replicated experiments involving 10Triticum aestivum L. genotypes. Several published media formulations, which had previously been optimized for wheat tissue culture, were tested for each genotype. Embryos from each plant were randomly assigned to each medium. Percentage precocious germination of immature embryos and mean percentage scutellar callus per explant were recorded. Embryoids per callus were determined by microscopic examination at 28 and 56 days. There were highly significant differences among genotypes, media, and individual plants from which explants were taken. A medium based on double the Murashige and Skoog (MS) inorganic salt concentration was significantly better than other media. Inclusion of all MS vitamins appeared essential for optimal response. Two genotypes were tested in a second experiment where both 3,6-dichloro-o-anisic acid (9.05 M) and 6-furfurylaminopurine (0.46 M) were substituted for 2,4-dichlorophenoxyacetic acid (4.52 M) in either double or normal MS medium. This substitution significantly increased embryoid formation at 28 days. Additions of either 6-furfurylaminopurine or coconut water increased precocious germination of both embryo explants and embryoids.This study was supported in part by NASA-Ames Cooperative Agreement No. NCC2-139. Contribution of the Utah Agricultural Experiment Station, Utah State University, Logan, UT, Journal Paper No. 3358.     

The effect of food consumption on sodium and water balance in the predaceous diving beetle,Dytiscus verticalis

Summary Sodium and water balance ofDytiscus verticalis in fresh water were investigated under three feeding regimes: unfed, and fed a diet either low or high in sodium chloride. Unfed sodium influx was 0.13 and sodium efflux was 0.74 moles/100 gwm·h. These values are low in comparison with most freshwater animals. The electrical potential difference across the integument in artificial soft water (ASW) was about 150 mV smaller than the potential necessary to maintain sodium balance in the absence of active transport. However, sodium influx did not show saturation kinetics over an external concentration range of 91 to 1725 M. Unfed beetles failed to arrest net sodium loss to baths that were initially distilled water or ASW, even when bath sodium concentrations reached 75–298 M. The long-term rate of net sodium loss ranged from 0.61 to 4.4 moles/100 gwm·h for four sets of animals. Beetles decreased sodium efflux during a period of fasting. During subsequent feeding, beetles fed a high sodium diet (HSD) increased sodium efflux while beetles fed a low sodium diet (LSD) maintained low rates of sodium efflux. HSD fed beetles increased body sodium and hemolymph sodium concentration, and expanded extracellular fluid, relative to LSD fed beetles. Thus beetles cannot achieve sodium balance in fresh water without dietary sodium input, although they are able to regulate sodium loss.Abbreviations gwm grams wet mass - ASW artificial soft water - DW distilled water - HSD high sodium diet - LSD low sodium diet - ECF extracellular fluid volume     

A flexible method to align large numbers of biological sequences

Summary A method for the alignment of two or more biological sequences is described. The method is a direct extension of the method of Taylor (1987) incorporating a consensus sequence approach and allows considerable freedom in the control of the clustering of the sequences. At one extreme this is equivalent to the earlier method (Taylor 1987), whereas at the other, the clustering approaches the binary method of Feng and Doolittle (1987). Such freedom allows the program to be adapted to particular problems, which has the important advantage of resulting in considerable savings in computer time, allowing very large problems to be tackled. Besides a detailed analysis of the alignment of the cytochrome c superfamily, the clustering and alignment of the PIR sequence data bank (3500 sequences approx.) is described.     

pH Dependence of Histidine Affinity for Blood-Brain Barrier Carrier Transport Systems for Neutral and Cationic Amino Acids

The effects of pH (3.5-7.5) on the brain uptake of histidine by the blood-brain barrier (BBB) carriers for neutral and cationic amino acids were tested, in competition with unlabeled histidine, arginine, or phenylalanine, with the single-pass carotid injection technique. Cationic amino acid ( [14C]arginine) uptake was increasingly inhibited by unlabeled histidine as the pH of the injection solution decreased. In contrast, the inhibitory effect of unlabeled histidine on neutral amino acid ( [14C]phenylalanine) uptake decreased with decreasing pH. Brain uptake indices with varying histidine concentrations indicated that the neutral form of histidine inhibited phenylalanine uptake whereas the cationic form competed with arginine uptake. Since phenylalanine decreased [14C]histidine uptake at all pH values whereas arginine did not, it was concluded that the cationic form of histidine had an affinity for the cationic carrier, but was not transported by it. We propose that the saturable entry of histidine into brain is, under normal physiological circumstances, mediated solely by the carrier for neutral amino acids.     

Structural Features of Human Monoamine Oxidase A Elucidated from cDNA and Peptide Sequences

Monoamine oxidase (MAO), an important enzyme for the degradation of amine neurotransmitters, has been implicated in neuropsychiatric illness. The amino acid sequence for one form of the enzyme, MAO-A, has been deduced from human cDNA clones and verified against proteolytic peptides. The covalent binding site for the flavin adenine dinucleotide (FAD) cofactor is near the C-terminal region. The presence of features characteristic of the ADP-binding fold suggests that the N-terminal region is also involved in the binding of FAD. These cDNAs should facilitate the study of the structure, function, and intracellular targeting of MAO, as well as the analysis of its expression in normal and pathological states.     

Effects on growth and sporulation of inactivation of a Bacillus subtilis gene (ctc) transcribed in vitro by minor vegetative cell RNA polymerases (E-sigma 37, E-sigma 32)

Summary The E-³⁷ gene ctc was inactivated by a site-specific insertion into the Bacillus subtilis chromosome. The resulting mutation inhibited sporulation by 95% at elevated temperatures (48° C). If the ctc ^- mutation is placed in a strain that carries a mutation in the closely linked but distinct spoVC gene, ctc now affects both growth and sporulation at elevated temperatures. Growth of the ctc ^- spoVC285 strain was transiently inhibited when exponentially growing cultures were shifted from 37° C to 48° C. A similar, but less pronounced growth lag, was also seen in a B. subtilis strain carrying only the spoVC-285 mutation. This finding suggests that both the ctc and spoVC products function in vegetatively growing B. subtilis.