The response of several murine embryonal carcinoma cell lines to stimulation of differentiation by alpha-difluoromethylornithine

In an attempt to better establish the relationship between polyamine levels and the differentiation of embryonal carcinoma cells, we have examined the ability of alpha-difluoromethylornithine (DFMO), a known inducer of differentiation in one embryonal carcinoma cell line, to stimulate the differentiation of embryonal carcinoma cells from a variety of cell lines. Differentiation was monitored using a variety of criteria including morphological alterations and changes in biochemical and antigenic parameters. Depending on their response to difluoromethylornithine, three classes of cell lines could be identified, those which 1) differentiate extensively, 2) differentiate poorly, and 3) fail to differentiate. Three different classes of embryonal carcinoma cell lines reflect differential changes in polyamine levels resulting from inhibition of ornithine decarboxylase enzyme activity by DFMO. The specific cell lines which exhibit large decreases in both ornithine decarboxylase activity and polyamine levels also show extensive differentiation. The cell lines which show only moderate decreases in enzyme activity and polyamines differentiate poorly while the cell lines which fail to respond to DFMO in that polyamines do not drop below the threshold level necessary to induce differentiation fail to differentiate. These studies suggest that decreases in intracellular polyamines induce EC cell differentiation in vitro.     

Immobilisation of organelles and actin bundles in the cortical cytoplasm of the alga Chara corallina Klein ex. Wild

The mechanism by which sub-cortical actin bundles and membranous organelles are immobilised in the cortical cytoplasm of the alga Chara was studied by perfusing cells with a solution containing 1% Triton X-100. Light and scanning electron microscopy and the release of starch grains and chlorophyll-protein complexes indicated that the detergent extensively solubilised the chloroplasts. However, the sub-cortical actin bundles remained in situ even though they were originally separated from the plasma membrane by the chloroplasts. A fibrous layer between chloroplasts and plasma membrane became readily visible after detergent extraction of the cells and could be released by low-ionic-strength ethylenediaminetetraacetic acid, thioglycollate and trypsin. The same treatments applied to cells not subject to detergent extraction released the membrane-bound organelles and actin bundles and no fibrous meshwork was visible on subsequent extraction with Triton. It is, therefore, concluded that a detergent-insoluble cortical cytoskeleton exists and contributes to the immobility of the actin and cortical organelles in the cells.Abbreviation EDTA ethylenediaminetetraacetic acid     

Local names for vascular plants in the John Crow mountains,Jamaica

Local names of vascular plants, accompanied by botanical specimens, were collected in the John Crow Mountains, Portland Parish, Jamaica. Each of the names was volunteered by one local informant; many were independently corroborated by others. We recorded 91 names of forest trees and shrubs, 20 names of climbers, and 33 names of other plants. The uneven distribution of local names among different categories of plants is discussed. The names are mostly of English origin, with a scattering from Spanish, Amerindian and West African languages. Many names are not listed in the standard floras; 20 names are apparently hitherto unrecorded in print. The same name was often found to be applied to a different species from the usage given in the floras, showing the variation in vernacular names from one part of the island to another.     

Schistosoma mansoni: complexity of antigenic and nonantigenic surface polypeptides

Two-dimensional gel analysis of the surface polypeptides of the schistosomula stage of Schistosoma mansoni resolved a complex pattern of approximately 20 polypeptides. The majority of these were identified as immunogenic since they were immunoprecipitated with antisera from chronically infected mice and from mice vaccinated with irradiated cercariae. However, several major surface polypeptides were not immunoprecipitated by sera from infected or immune mice and were presumed to be nonantigenic.     

Meiotic Gene Conversion Mutants in SACCHAROMYCES CEREVISIAE . I. Isolation and Characterization of pms1-1 and pms1-2

The pms1 mutants, isolated on the basis of sharply elevated meiotic prototroph frequencies for two closely linked his4 alleles, display pleiotropic phenotypes in meiotic and mitotic cells. Two isolates carrying recessive mutations in PMS1 were characterized. They identify a function required to maintain low postmeiotic segregation (PMS) frequencies at many heterozygous sites. In addition, they are mitotic mutators. In mutant diploids, spore viability is reduced, and among survivors, gene conversion and postmeiotic segregation frequencies are increased, but reciprocal exchange frequencies are not affected. The conversion event pattern is also dramatically changed in multiply marked regions in pms1 homozygotes. The PMS1 locus maps near MET4 on chromosome XIV. The PMS1 gene may identify an excision-resynthesis long patch mismatch correction function or a function that facilitates correction tract elongation. The PMS1 gene product may also play an important role in spontaneous mitotic mutation avoidance and correction of mismatches in heteroduplex DNA formed during spontaneous and UV-induced mitotic recombination. Based on meiotic recombination models emphasizing mismatch correction in heteroduplex DNA intermediates, this interpretation is favored, but alternative interpretations involving longer recombination intermediates in the mutants are also considered.     

Biosynthesis of the beta-lactam antibiotic, thienamycin, by Streptomyces cattleya

Radioactive- and stable isotope-containing substrates were used to identify the biosynthetic precursors of the beta-lactam antibiotic, thienamycin, in Streptomyces cattleya. Acetate is utilized by the organism to form C(6) and C(7) of the beta-lactam ring. The two carbons of the hydroxyethyl group attached to C(6) are both derived from the methyl of methionine. The cysteaminyl side chain attached to C(2) is derived from cysteine. Selective inhibition of thienamycin and cephamycin C biosynthesis has been achieved either through the addition of metabolic inhibitors or through manipulation of the growth medium. These results suggest that the two beta-lactam antibiotics, thienamycin and cephamycin C, are formed by different biosynthetic pathways.     

Analysis of the direct effects of prostaglandins on human sperm function

Time-exposure photomicrography and interspecies in-vitro fertilization procedures have been used to examine the influence of prostaglandins on human sperm function. An analysis of variance indicated that the presence of PGs in the incubation media was associated with a significant increase in sperm velocity and the frequency of sperm head rotation, although there were no differences between individual PGs in the degree of stimulation observed. Changes in the penetrating ability of human spermatozoa were detected after exposure to PGs, particularly PGE-1 and PGE-2. PGE-2 induced a sustained increase in penetration rates at all doses of greater than 8.4 micrograms/ml, while exposure to PGE-1 gave a bell-shaped dose-response curve which exhibited a peak between 8.4 and 33.3 micrograms/ml and progressively fell to reach control levels at the maximum concentration tested of 270 micrograms/ml. A combination of PGE-2 and PGE-1 produced a dose-response curve similar to that for PGE-1 alone, while exposure to PGF-2 alpha was without effect. Seminal extracts containing predominantly 19-hydroxy PGE-1, or equal amounts of 19-hydroxy PGE-1 + 2 induced a slight, but significant, rise in penetration rates while a combination of PGs representing the major components of human seminal plasma was without significant effect. We conclude that certain prostaglandins may have a direct action on the functional competence of human spermatozoa.     

Ram-induced growth of ovarian follicles and gonadotrophin inhibition in anoestrous ewes

Southdown ewes in mid-seasonal anoestrus were exposed to rams for 0 h (control group), 2 h, 24 h, 40 h, 3 days, 10 days or 20 days. Serial blood samples were then taken to determine LH and FSH levels. Ewes with greater than 24 h ram exposure were ovariectomized immediately after bleeding, and all follicles greater than 1 mm diameter were dissected from the ovaries and measured. LH basal concentrations and pulse frequency increased significantly within 2 h of ram introduction, but by 24 h fell, and then remained low. FSH concentrations fell within 2 h of ram introduction and remained low. Control group ewes (isolated) had no follicles greater than 4 mm diameter, whereas all ewes exposed to rams had large follicles, with CL or preovulatory follicles present at 40 h after ram introduction. Ram introduction was also associated with follicle recruitment (antrum formation to less than 2 mm). Follicular recruitment and development to the large follicle stage therefore occurred during a period of low plasma gonadotrophin levels and suppressed LH pulsing.