Longevity of Salmonella typhimurium in Tilapia aurea and water from pools fertilized with swine waste.

Salmonella typhimurium declined rapidly when inoculated into Tilapia aurea culture pools fertilized with fresh swine waste. Within the water column, a 95% decline of viable cells occurred during the first 6 h. Isolation of viable salmonellae was possible at 16 days post-inoculation, but not at 32 days. Similarly, salmonellae could be detected in the viscera and epithelium of T. aurea at 16 days, although not at 32 days. Salmonellae were not isolated from the fish flesh, nor was there evidence of septicemic infection.     

Bacterial Activity Associated with the Decomposition of Woody Substrates in a Stream Sediment

Ground bark and heartwood from Alnus rubra and Pseudotsuga menziesii were added to a muddy sediment from a small Oregon stream and incubated in situ. Carbon dioxide and methane production rates were increased by all amendments, the biggest increase being shown with A. rubra wood. Except for sediment amended with A. rubra wood, nitrogen fixation rates from all treatments (including the control) were approximately 0.1 nmol/g per h throughout the 6-month study period. Contrary to expectations, neither bark had a noticeable adverse effect on microbial activity, but the A. rubra wood promoted nitrogen fixation. These results help to explain the faster rate of decomposition of A. rubra wood in water compared with that of P. menziesii described in the literature. The uptake kinetics of glucose (V_max) did not follow the same pattern as gas evolution.     

Identification of a monoclonal antibody that specifically recognizes corneal and skeletal keratan sulfate. Monoclonal antibodies to cartilage proteoglycan

Monoclonal antibodies were raised against proteoglycan core protein isolated after chondroitinase ABC digestion of human articular cartilage proteoglycan monomer. Characterization of one of the monoclonal antibodies (1/20/5-D-4) indicated that it specifically recognized an antigenic determinant in the polysaccharide structure of both corneal and skeletal keratan sulfate. Enzyme immunoassay analyses indicated that the mouse monoclonal IgG1 recognized keratan sulfate in native proteoglycan aggregate and proteoglycan monomer preparations isolated from hyaline cartilages of a wide variety of animal species (human, monkey, cow, sheep, chicken, and shark cartilage). The 1/20/5-D-4 monoclonal antibody did not recognize antigenic determinants on proteoglycan isolated from Swarm rat chondrosarcoma. This finding is consistent with several biochemical analyses showing the absence of keratan sulfate in proteoglycan synthesised by this tissue. A variety of substructures isolated after selective cleavage of bovine nasal cartilage proteoglycan (Heineg?rd, D., and Axelsson, J. (1977) J. Biol. Chem. 252, 1971-1979) were used as competing antigens in radioimmunoassays to characterize the specificity of the 1/20/5-D-4 immunoglobulin. Substructures derived from the keratan sulfate attachment region of the proteoglycan (keratan sulfate peptides) showed the strongest inhibition. Both corneal and skeletal keratan sulfate peptides as competing antigens in radioimmunoassays showed similar inhibition when compared on the basis of their glucosamine content. Therefore, the 1/20/5-D-4 monoclonal antibody appears to recognize a common determinant in their polysaccharide moieties. Chemical desulfation of the keratan sulfate reduced the antigenicity of the glycosaminoglycan. The antibody did not recognize determinants present in dermatan sulfate, heparin, heparin sulfate, or hyaluronic acid.     

Heritable fragile sites on human chromosomes. X. New folate-sensitive fragile sites: 6p23, 9p21, 9q32, and 11q23

Four new folate-sensitive fragile sites are documented at 6p23, 9p21, 9q32, and 11q23. These have all been shown to be heritable except for the one at 9p21, which has been seen only in a single individual. As with the other autosomal fragile sites, these appear to be innocuous in heterozygotes.     

Barriers to the radial diffusion of ions in maize roots

Summary The water-extractable and ion-exchangeable fractions of the free space of maize roots for sodium ions has been determined. The free space of whole roots, excised roots and isolated stelar and cortical tissues, has been compared and the results examined for any evidence of a barrier between the cortex and the stele. Similarly the free space of whole roots and excised roots, from which the epidermal and outer cortical cells have been removed by shaving, has been compared and the results examined for any evidence of an epidermal barrier.Whole roots gave a free space value some 20% lower than excised roots. It was calculated that this difference could be accounted for if the cortical tissues only were considered in estimating the whole root value, that is if the stele was considered as participating in the excised root but not in the whole root. Samples in which isolated cortical and stelar material were measured together, or separately and the value calculated, gave similar values to those obtained for excised roots. These results are interpreted as evidence that a barrier to free diffusion exists between the cortical and the stelar tissues at or near the endodermis. Shaving both whole and excised roots increased the free space by about 35%. However, as this value was similar for both, it was concluded that the increase was due to the contribution of damaged cortical cells and does not indicate that the epidermis is an effective barrier to the diffusive entry of sodium ions into the root.     

Phloem transport of 14C-labelled assimilates in Ricinus

Summary Exudate can be obtained from incisions made in the bark of the stem of actively growing Ricinus plants. ¹⁴C-labelled assimilates from a fed leaf are rapidly detected in the exudate. This movement was both acropetal and basipetal from the fed leaf, at rates of over 100 cm h^-1. Estimated rates within intact plants were 80–84 cm h^-1.In contrast with xylem sap obtained from the same plant, the exudate obtained had an alkaline pH (8.2), a high dry matter content (10–12.5%), high sugar content (8–10%) which was predominantly sucrose; high potassium content (60–80 mM) and low calcium content (0.5–1.0 mM).It is concluded, on the basis of the present evidence, that the exudate is a true sample of the sieve tube sap undergoing translocation.     

Sea urchin egg fertilization studied with a fluorescent probe (ANS)

The rates of intracellular DNA synthesis at various temperatures between 39 ° and 31 °C were determined in hamster fibroblasts and HeLa cells by measuring average amounts of ³H-thymidine incorporated per cell in S phase per unit of time. The energy of activation and Q₁₀ for intracellular DNA synthesis were calculated from the slopes of the relative rates of DNA synthesis in HeLa cells and hamster fibroblasts vs. time, plotted on Arrhenius coordinates. In both cell types the incorporation of thymidine into DNA is characterized by an energy of activation of 21 000 calories/mole and a Q₁₀ of 2.94. The absolute rates of DNA synthesis were determined in hamster cells at various temperatures, with values ranging from 1.44 to 0.60 × 10^?14 g DNA/ min/cell at 39 ° to 31 °C, respectively. The length of the S phase of the hamster cell was calculated over a 39 ° to 31 °C range, and found to be 5.0 to 11.9 h, respectively. It is concluded that the S phase length is partly determined by the rate of temperature-dependent DNA synthesis.     

Grey seals, Halichoerus grypus, of the Dee Estuary and observations on a characteristic skin lesion in British seals

Grey seals on the West Hoyle Bank feed on a variety of fish and have a high incidence of dermal lesions, often associated with emaciation and nematode parasite infection. Corynebacterium phocae has been isolated from an active lesion. The significance of large numbers of seals in the Dee Estuary bearing lesions is discussed and the occurrence of seals with lesions elsewhere in British waters is reviewed. No evidence was found to associate the dermal lesions with any environmental factor and it is probable that lesions develop as a result of infection of minor wounds.     

Isolation of ouabain-resistant human diploid fibroblasts

Seventeen clones resistant to the cytotoxic action of ouabain were isolated in culture by direct selection from 5 independent strains of diploid human fibroblasts. Resistant clones were recovered at frequencies on the order of 10^?7 per wild type cell selected from populations treated with the mutagen EMS, but no resistant cells were detected among 10⁸ unmutagenized cells. Most selected clones remained ouabain-resistant following further propagation in the absence of drug. The growth of wild type cells was inhibited by 50% at ouabain concentrations of 2–5 × 10^?8 M, while resistant clones required 15–180 fold higher drug concentrations to cause equivalent inhibition. Ouabain-resistant clones showed increased resistance of K+ transport function to ouabain inhibition that paralleled their increased resistance to growth inhibition. Initial experiments suggest that under selective conditions the resistant diploid fibroblasts differ significantly from wild type in binding of ³H-ouabain per unit surface area. The ouabain-resistant cells were similar to wild type in transport properties unrelated to ouabain inhibition. Resistant cells had normal karyotypes and senesced with a lifespan similar to control clones. The ouabain-resistant phenotypes of these diploid human fibroblast isolates apparently reflect point mutations that specifically affect the Na+/K+ transport ATPase with respect to ouabain-binding and/or response to bound ouabain.