Metabolic cost of sodium transport in toad urinary bladder

Summary The metabolic cost of active sodium transport was determined in toad bladder at different gradients of transepithelial potential, , by continuous and simultaneous measurements of CO₂ production and of transepithelial electric current. Amiloride was used to block active sodium transport in order to assess the nontransport-linked, basal, production of CO₂ and the passive permeability of the tissue. From these determinations active sodium transport,J _Na, and suprabasal CO₂ production, , were calculated. Since large transients inJ _Na and frequently accompanied any abrupt change in , steady state conditions were carefully defined.Some 20 to 40 min were required after a change in before steady state of transport activity and of CO₂ production were achieved. The metabolic cost of sodium transport proved to be the same whether the bladder expended energy moving sodium against a transepithelial electrical potential grandient of +50 mV or whether sodium was being pulled through the active transport pathway by an electrical gradient of –50 mV. In both cases the value of the ratio averaged some 20 sodium ions transported per molecule of CO₂ produced.When the Na pump was blocked by 10^–2 m ouabain, the perturbations of the transepithelial electrical potential did not elicit changes ofJ _Na nor, consequently, of .The independence of the ratio from over the range ±50 mV indicates a high degree of coupling between active sodium transport and metabolism.     

The B-chromosome system of the grasshopper Eyprepocnemis plorans subsp. plorans (Charpentier)

Supernumerary chromosomes of two types have been observed in the grasshopper Eyprepocnemis plorans subsp. plorans. One of these (the B-type) is similar in size to an S autosome; the other is smaller (B-type). Both are telocentric and mitotically stable. The frequencies of individuals with the B-type supernumeraries in five natural populations were 56, 56, 70, 71 and 30 per cent respectively. The equivalent levels of the B-type supernumerary were 0, 0, 13, 3 and 0 per cent respectively. Because of the relative infrequency of the B-type only the B-type has been studied in detail. In males with 1B, anaphase I segregation of X and B was random in four populations but non-random in that from Otivar. Here the B was distinctive in having a secondary constriction near the centromere. A study of chiasma frequency among A-chromosomes revealed that the B-type supernumerary increases significantly both the mean chiasma frequency and the between-cell variance. A comparison of body morphometrics failed to reveal any effect of these B-chromosomes on the exophenotype.     

HLA antigens in a sample of the Spanish population: Common features among Spaniards,Basques, and Sardinians

Summary Frequencies of recently described HLA-A,-B (antigens or splits) and HLA-C and HLA-DR antigens are studied in a 450 normal Spaniards sample. The linkage disequilibria are also calculated. HLA-DR7 is more frequent than in any other population studied. Aw30-B18 and Aw33-B14 associations are common and specific Spanish, Basque, and Sardinian HLA features. A11-B27 association is found in our Spanish sample and also in Basques.HLA-Bw4,-Bw6 antigens are analyzed by family mating and segregation and also using unrelated individuals. It shows a good fit as a genetic system. HLA-B antigens are included either in Bw4 or Bw6 according to expectations from other Caucasoid population results. The possibility of a common and North African origen (Iberians) for Spaniards, Basques, and Sardinians is discussed on the basis of presently available HLA data.     

Grain size,sucrose level and starch accumulation in developing rice grain

Five rices (Oryza sativa L.) differing in final grain size were studied at the midmilky stage to determine if any factor could be identified which might limit rate of starch accumulation. Only UDP glucose pyrophosphorylase activity increased with increasing grain size. Detached rice panicles incubated in liquid medium containing 1% sucrose and 0.1% glutamine, in addition to minerals and vitamins, produced grains similar to those on intact plants. Sucrose level (0–1.5%) in the medium determined the extent of dry matter and starch accumulation and influenced physiological development of the ripening grains. Chemical and enzymic composition of the grain were similar to previously reported levels in grains of intact panicles analysed at regular intervals after anthesis. Addition of 3-P glycerate or K⁺ to the medium did not improve dry matter accumulation in the developing grain.     

Cytogenetics of the chinese giant salamander,Andrias davidianus (Blanchard): the evolutionary significance of cryptobranchoid karyotypes

Cytogenetic aspects of the cryptobranchid salamander Andrias davidianus of western China have been studied, including chromosome number and morphology, C-band patterns, meiosis, and the chromosomal localization of ribosomal 5S RNA genes. Our data regarding chromosome number (2n=60) and general chromosome morphology largely confirm the results of Morescalchi et al. (1977). The karyotype consists of 16 pairs of macrochromosomes that decrease gradually in relative length to 14 pairs of microchromosomes. Telocentric chromosomes are a conspicuous feature of the karyotype, representing more than half the genome. Differential staining reveals that all of the chromosomes, except four pairs of microchromosomes, have C-band heterochromatin in their centromeric regions, the amount varying irrespective of chromosome size. Faint bands of interstitial and telomeric C-band heterochromatin are found in mitotic chromosomes but are not seen in meiotic preparations. In C-banded mitotic preparations from a female, one of the smallest macrochromosome pairs is heteromorphic in respect to C-band heterochromatin and centromere position. In situ hybridization of an iodinated 5S RNA probe to meiotic chromosome preparations reveals that this repeated gene is clustered near the telomeric region of chromosome 7, a medium size telocentric, a location corresponding to a band of heterochromatin. Studies of spermatocytes indicate that the process of meiosis in A. davidianus closely resembles that of more advanced salamanders, and that the microchromosomes are meiotically stable. The significance of microchromosomes and chromosome morphology in the reorganization of salamander genomes during evolution is discussed on the basis of cytogenetic data available for A. davidianus and various other primitive and advanced salamanders.     

Sequence of the S-layer gene of Thermus thermophilus HB8 and functionality of its promoter in Escherichia coli.

The nucleotide sequence of the slpA gene, which is responsible for the synthesis of the S-layer protein of Thermus thermophilus HB8, is described. This gene is transcribed as a unit in which the coding region is preceded by a 127-base-long leader mRNA sequence. The promoter region is also recognized by the RNA polymerase of Escherichia coli because of the presence of homologous -35 and -10 boxes. Homologies with other promoters from Thermus spp. are also presented.     

Effects of Feeding and Drinking on Acetylcholine Release in the Nucleus Accumbens, Striatum, and Hippocampus of Freely Behaving Rats

Extracellular levels of acetylcholine (ACh) were measured in the nucleus accumbens (NAC), striatum (STR), and hippocampus (HIPP) using microdialysis in 30-min intervals before, during, and after free-feeding in 20-h food-deprived rats. The effects on ACh in the NAC and STR were also observed in response to water intake in 20-h water-deprived animals. Neostigmine was used in the perfusate to improve ACh recovery. Basal ACh was sensitive to tetrodotoxin and low calcium, and therefore largely neuronal in origin. Feeding caused a 38% increase in extracellular ACh in the NAC and no change in the STR or HIPP. Dopamine was also increased in the NAC (48%) and to a lesser extent in the STR (21%) following feeding. Drinking caused 18-20% increases in ACh release in both the NAC and STR. In a separate experiment, ACh release in the NAC was monitored in 10-min intervals during free-feeding; ACh increased in the interval immediately following maximal food intake. These results suggest a site-specific increase in ACh release following feeding that cannot be solely attributed to the activation associated with this behavior.     

Clonally related IgM rheumatoid factors undergo affinity maturation in the rheumatoid synovial tissue.

Using hybridoma technology we established a panel of human monoclonal rheumatoid factors (RF) from the synovial tissues of two patients with rheumatoid arthritis (RA), and one patient with polyarticular juvenile RA. Nucleotide sequence analysis of the V regions of these RF indicates that two independently derived antibodies from one of the RA patients are clonally related. One of these antibodies appears to be close to germ-line configuration, whereas the other has accumulated a total of 36 substitutions in both H and L chains. Measurements of the affinity for human IgG of the two RF show that the extensively mutated RF has 100-fold higher affinity for IgG than the RF close to germline. These findings indicate that IgM RF in RA can undergo affinity maturation and suggest that certain RF may be the product of an Ag-driven immune response.