Spatio‐temporal variation of salt marsh seedling establishment in relation to the abiotic and biotic environment

Contrary to our expectations, soil salinity and moisture explained little of the spatial variation in plant establishment in the upper intertidal marsh of three southern California wetlands, but did explain the timing of germination. Seedlings of 27 species were identified in 1996 and 1997. The seedlings were abundant (maximum densities of 2143/m² in 1996 and 1819/m² in 1997) and predominantly annual species. CCAs quantified the spatial variation in seedling density that could be explained by three groups of predictor variables: (1) perennial plant cover, elevation and soil texture (16% of variation), (2) wetland identity (14% of variation) and (3) surface soil salinity and moisture (2% of variation). Increasing the spatial scale of analysis changed the variables that best predicted patterns of species densities. Timing of germination depended on surface soil salinity and, to a lesser extent, soil moisture. Germination occurred after salinity had dropped below a threshold or, in some cases, after moisture had increased above a critical level. Between 32% and 92% of the seedlings were exotic and most of these occurred at lower soil salinity than native species. However, Parapholis incurva and Mesembryanthemum nodiflorum were found in the same environments as the native species. In 1997, the year of a strong El Niño/Southern Oscillation event with high rainfall and sea levels, the elevation distribution of species narrowed and densities of P. incurva and other exotic species decreased but densities of native and rare species did not change. The ‘regeneration niche’ of wetland plant communities includes the effects of multiple abiotic and biotic factors on both the spatial and temporal variations in plant establishment.     

Chlamydia isopodii sp. n., an obligate intracellular parasite of Porcellio scaber

In an ultrastructural study of the hepatopancreas of Porcellio scaber, an obligate intracellular parasite, Chlamydia, was noted in the epithelial cells. Although the infection was found to extend the entire length of the hepatopancreas, it was most extensive in the glandular region. Indirect immunofluorescence testing revealed no cross-reactivity with either lymphogranuloma venereum or psittacosis antisera.     

A human NK and K cell subset shares with cytotoxic T cells expression of the antigen recognized by antibody OKT8

The antigen recognized by monoclonal antibody OKT8 is expressed on the cell membrane of 30 to 50% of human NK/K cells. The reactivity of OKT8 with NK/K cells was determined by indirect methods (treatment of the effector cells with OKT8 antibody and complement (C) and separation of OKT8(+) and (-) effector cell populations by fluorescence-activated cell sorting or by rosetting techniques) and, at single cell level, by C-dependent lysis of effector NK cells that bind and kill K562 targets. Analysis by indirect immunofluorescence (flow cytofluorometry) of lymphocyte subpopulations mediating NK/K cytotoxic activity and deprived of OKT8(+) T cells reveals that the NK/K cell subset bears OKT8 antigen at a density lower than that present on cytotoxic T cells. The OKT8 antigen on NK/K cells is trypsin- and pronase-sensitive, but it is resynthesized by the same effector cells during 24 hr of culture at 37 degrees C. OKT8 antibody does not inhibit NK killing, and, on a per cell basis, OKT8(+) cells within the NK/K subset mediate the same level of cytotoxic activity as OKT8(-) NK/K cells. Analogous results were obtained by using anti-Leu-2a, an antibody with the same specificity as OKT8 on cytotoxic/suppressor T cells, but not when OKT5 was used, which might identify a distinct epitope on the same antigenic molecule. The possible significance of these findings in understanding the cell lineage of NK/K cells is discussed.     

Dependence of cytoplasmic calcium transients on the membrane potential in isolated nerve endings of the guinea pig

The relation of changes in internal, free Ca2+, measured with arsenazo III, to the membrane potential, measured with the cyanine dye di-S-C2(5) or 86Rb+ distribution ratio, was studied in isolated guinea pig cortical nerve endings. Depolarization of the plasma membrane with veratridine or gramicidin as well as addition of ionophore A23187 led to an increase in cytosolic Ca2+. Only the response to veratridine was inhibited by tetrodotoxin. The dependence of the depolarization-induced increase in intraterminal, free Ca2+ on the membrane potential between about -50 to 0 mV was sigmoidal. A maximal increase in cytosolic Ca2+ was reached when the membrane potential was depolarized from the resting level, about -64 mV, to about -40 mV. These results show that in isolated nerve endings the activation of voltage-sensitive Ca2+ channels concomitantly leads to an increase in cytosolic, free Ca2+. Comparison of the results of the present study with the previous electrophysiological observations indicate that Ca2+ channels in synaptosomes, presynaptic nerve terminals of the squid giant synapse and cardiac cells have essentially similar voltage dependency.     

Objective test for food sensitivity in asthmatic children: increased bronchial reactivity after cola drinks.

Ten asthmatic children with a history of cough and wheeze after drinking a cola drink performed histamine inhalation tests before and 30 minutes after a drink of Pepsi-Cola, soda water, and water on three separate study days. There was no significant change in baseline peak expiratory flow after any of the three drinks. Sensitivity to histamine was increased after the cola drink (p less than 0.005) but was not significantly different after soda water or water. The detection of change in sensitivity to histamine appears to be a simple and effective method of testing for food sensitivity in asthma.     

Growth of acetotrophic,methane-producing bacteria in a pH auxostat

Three acetotrophicMethanosarcina species, which included marine, nonmarine, and thermophilic strains, were grown on acetate in a 10-liter pH auxostat. Specific growth rates and molar growth yields were constant throughout growth. Cell yields were up to 18-fold greater than previously reported. These properties of the pH auxostat indicate that it is a preferred culture method for the biochemical study of methanogenesis from acetate.     

Analysis of the antigenic and immunogenic properties of protein M of the influenza virus by an immunoenzyme method

A test system permitting the detection of influenza virus protein M at a concentration of 0.1-0.5 ng/ml in ELISA has been developed. The use of this system made it possible to detect influenza viruses A and B directly in crude virus-containing material and clinical samples obtained from influenza patients. During the outbreak of influenza in the spring of 1983 ELISA was successfully used for the rapid diagnosis of influenza, and some of its advantages in comparison with the conventional immunofluorescence test were thus demonstrated. To overcome difficulties arising from the low immunogenic potency of protein M, in the process of obtaining diagnostic sera and ascitic fluids the animals were immunized with the conjugate of protein M and polyelectrolite, which ensured considerable activation of humoral immune response.