Determination of intracellular volume and internal solute concentrations of the green alga Chlorococcum submarinum

A method is described for measuring the cell volume of the unicellular green alga Chlorococcum submarinum, which depends on measurements of bromide concentration before and after disruption of the cells by ammonium hydroxide. Simultaneous equations are derived, which along with direct determination of cell water weight, allow the calculation of the intracellular volume in three different ways. The volumes calculated are in agreement indicating the validity of the method. The cell volumes and internal concentrations of glycerol, proline, potassium and sodium were determined for algae adapted to three salinities, 0.1, 0.5 and 1.0 M NaCl. The results showed that glycerol was the major internal solute and that the total measured solutes balanced the external osmotic pressure at all three salinities.Abbreviations DMSO dimethyl sulphoxide - Hepes N-[2-hydroxyethyl]piperazine-N-2-ethane sulfonic acid - TCA trichloroacetic acid - Tris tris[hydroxymethyl]aminoethane     

Passive and active transport properties of a gill model, the cultured branchial epithelium of the freshwater rainbow trout (Oncorhynchus mykiss)

Branchial epithelia of freshwater rainbow trout were cultured on permeable supports, polyethylene terephthalate membranes ("filter inserts"), starting from dispersed gill epithelial cells in primary culture. Leibowitz L-15 media plus foetal bovine serum and glutamine, with an ionic composition similar to trout extracellular fluid, was used. After 6 days of growth on the filter insert with L-15 present on both apical and basolateral surfaces, the cultured preparations exhibited stable transepithelial resistances (generally 1000-5000 ohms cm2) typical of an electrically tight epithelium. Under these symmetrical conditions, transepithelial potential was zero, and unidirectional fluxes of Na+ and Cl- across the epithelium and permeability to the paracellular marker polyethylene glycol-4000 (PEG) were equal in both directions. Na+ and Cl- fluxes were similar to one another and linearly related to conductance (inversely related to resistance) in a manner indicative of fully conductive passive transport. Upon exposure to apical fresh water, transepithelial resistance increased greatly and a basolateral-negative transepithelial potential developed. At the same time, however, PEG permeability and unidirectional effluxes of Na+ and Cl- increased. Thus, total conductance fell, and ionic fluxes and paracellular permeability per unit conductance all increased greatly, consistent with a scenario whereby transcellular conductance decreases but paracellular permeability increases upon dilution of the apical medium. In apical fresh water, there was a net loss of ions from the basolateral to apical surfaces as effluxes greatly exceeded influxes. However, application of the Ussing flux ratio criterion, in two separate series involving different methods for measuring unidirectional fluxes, revealed active influx of Cl- against the electrochemical gradient but passive movement of Na+. The finding is surprising because the cultured epithelium appears to consist entirely of pavement-type cells.     

MappingTNNC1, the Gene That Encodes Cardiac Troponin I in the Human and the Mouse

We have mapped the TNNC1 gene, whose protein product is the cardiac TnI protein. TnI is one of the proteins that makes up the troponin complex, which mediates the response of muscle to calcium ions. The human TNNC1 locus had been assigned to a large region of chromosome 19, and we have refined the mapping position to the distal end of the chromosome by amplification of DNAs from a chromosome 19 mapping panel. We have also mapped the mouse Tnnc1 locus, by following the segregation of an intron sequence through DNAs from the European Interspecific Backcross. Tnnc1 maps close to the centromere on mouse chromosome 7.     

Protein-to-wet weight relationships in supragingival plaques from caries-prone tooth surfaces.

The ratio of protein to wet weight in unpooled samples of supragingival plaques from sound and carious tooth surfaces was studied. Protein was assayed by a procedure developed for the study, in order to achieve a sensitivity of 1 microgram with minimum effects upon quantitation from protein composition and nonprotein components. Ratios of protein to wet weight in plaque specimens from caries-free surfaces were almost equally distributed into two main categories of 9.4% and 6.5%. Corresponding values for specimens from carious surfaces were 9.1% and 5.0%. The occurrence of high and of low values among samples from each type of surface indicated that the plaques differed quantitatively in protein, water, or a nonprotein component, possibly extracellular polysaccharide. Although compositional differences between plaques from the two types of surfaces were indicated by the lower ratios of 6.5% from noncarious and 5.0% from carious surfaces, they were not indicated by the higher ratio values, which were similar. These results suggest either that protein-to-wet weight ratios are not related to caries, or that the ratio values are related to caries for some but not all types of plaques.     

Micronutrient status of the rice plant

Summary Soil solution Zn, Cu, Mn and Fe concentrations which were monitored throughout the growing season were found to be representative for flooded rice culture. Plant Zn, Cu, Mn and Fe contents of top, middle and bottom leaves as well as whole plants were also measured periodically throughout the growing season. These data were found to be within reported ranges for rice plants grown on flooded soils. Simple regression analyses were performed between plant micronutrient contents for each plant part sampled and the corresponding soil solution values. Results showed that the most promising portions of the rice plant to sample for accurate assessment of plant response to changes in soil solution micronutrient concentration as a function of time are as follows: (a) for Zn, bottom leaf; (b) for Cu, top or bottom leaf, whole plant; (c) for Mn, top leaf and (d) for Fe, bottom leaf or whole plant. re]19750915