The relationship of flagellar length to sexual signalling in Chlamydomonas

The flagella of Chlamydomonas reinhardi are required for the initiation of mating between opposite mating type gametes. It has been suggested that flagellar length is a crucial factor in a cell's ability to transmit and receive the sexual signals necessary for fusion. Mating type + (mt⁺) cells of gam-5, a mutant which is characterized by variable length, paralyzed flagella, were mated with wild-type, mt⁻ cells. Activation of the mating structures of the gam-5 gametes, and therefore successful signalling, was demonstrated for cells with flagella as short as 1.5 μm (less than 1/6 normal length). Because this mutant displays aberrant axonemal structures, and because various mutants with other defects in axonemal structure are also able to mate, it seems likely that the flagellar membrane may provide the main conduit for gametic sexual signals.     

Connective tissue activation. XXI

Summary The quantitative radiochemical methodology described in this report allows a major increase in information generation, increased experimental flexibility, improved statistical control, and increased diversity of information per culture. Other advantages relate to economies of technical time, supplies, cells, and test materials per individual culture. Microcultures of human synovial cells incorporate [¹⁴C]glucosamine into hyaluronic acid that accumulated primarily in the media and to a lesser extent in the cell mass. CTAP-I (from lymphoid cells), CTAP-III (from human platelets), PGE₂, dibutyryl cAMP, and poly(I)·poly(C) markedly stimulated hyaluronate synthesis, whereas cortisol, cycloheximide, and tunicamycin inhibited stimulated synthesis. Time studies with cycloheximide indicated that translation, essential for the activation of synovial cells, was completed by 17 h postexposure to CTAP-I. Tunicamycin also seemed to inhibit CTAP-I induced activation primarily by interpering with translation; however, tunicamycin also caused modest post-translational inhibition of hyaluronate synthesis in activated adult human synovial cells. Study supported by U.S. Public Health Service Grant AM-10728, the Michigan Chapter of the Arthritis Foundation, and Michigan Memorial-Phoenix Project Grant No. 517.     

D614G Spike Mutation Increases SARS CoV-2 Susceptibility to Neutralization

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The lack of genotoxicity of sodium fluoride in a battery of cellular tests

In a comprehensive assessment of genotoxicity, sodium fluoride was evaluated in a battery of cellular tests providing different genetic end points and biotransformation capabilities. The tests included the following: rat hepatocyte primary culture/DNA repair assay, Salmonella typhimurium histidine locus reversion assay, adult rat liver epithelial cell/hypoxanthine guanine phosphoribosyl transferase mutation assay, and sister chromatid exchange in two target cell types, human peripheral blood lymphocytes and Chinese hamster ovary cells. Negative findings were made in all assays, indicating that sodium fluoride is not genotoxic in these assays.Abbreviations ARL adult rat liver epithelial cell - CHO Chinese hamster ovary cell - HGPRT hypoxanthineguanine phosphoribosyl transferase - HPBL human peripheral blood lymphocyte - HPC hepatocyte primary culture - SCE sister chromatid exchange     

Sex differences in the biotransformation of 2-acetylaminofluorene in cultured rat hepatocytes

Sex-related differences in susceptability to 2-acetylaminofluorene (2-AAF) hepatocarcinogenicity and in vivo biotransformation of 2-AAF have been observed. In order to determine the contribution of hepatocytes to these differences, 2-AAF biotransformation was investigated in monolayer cultures of hepatocytes freshly isolated from male and female F-344 rats.In cultured hepatocytes from both sexes, ring and N-hydroxylated, deacetylated and conjugated metabolites were formed. The half-life of 2-AAF was similar at concentrations of 5×10^–6 and 10^–5 M; however, at 10^–4 M a slower rate was observed in cultures from males. Although the total formation of aqueous metabolites was similar, the ratio of sulfate to glucuronide conjugates of 2-AAF formed by hepatocytes from male and female rats differed. Sulfate conjugates predominated in hepatocytes from male rats, whereas in females, glucuronides predominated. The demonstration of sex-dependent variations in the rate of metabolism at a high concentration of 2-AAF and in conjugation provides evidence that in vivo differences are a function, at least in part, of the biotransformation characteristics of hepatocytes.Abbreviations 2-AAF 2-acetylaminofluorene - 2AF 2-aminofluorene - WME Williams Medium E.     

Evidence of Phenotypic Plasticity in the Response of <Emphasis Type="Italic">Fagopyrum esculentum</Emphasis> to Population Density and Sowing Date

Phenotypic plasticity is an important attribute that enables plants to survive across a range of environments. We conducted two experiments to investigate the plasticity of architectural traits and biomass ratios for Fagopyrum esculentum Moench in response to population density and sowing date. These included (1) inter-planting distances of 5, 10, 15, or 20 cm; and (2) sowing on 25 July, 1 August, 5 August, or 10 August. Many traits exhibited phenotypic plasticity that was coupled with changes in plant size. However, variations in leaf/mass ratio from either experiment, as well as leaf/root ratios in response to sowing date, were independent of size. When coefficients of variation were computed, some consistency was found in the magnitude of trait plasticity for both density and sowing date. For each experiment, leaf/root ratios, leaf/mass ratios, and stem/mass ratios were most plastic. Although this suggests that biomass ratios could be more responsive to environmental changes, a wide array of traits should be considered if we are to fully understand the mechanism for these phenomena.