Effects of Cellulolytic Ruminal Bacteria and of Cell Extracts on Germination of Euonymus americanus L. Seeds

In past attempts, the experimental germination of the seeds of Euonymus americanus L. in vitro has had little success. However, treatment of seeds with ruminal fluid containing viable microflora has been successful in stimulating germination. In the presence of the cellulolytic ruminal bacterium, Clostridium cellobioparum ATCC 15832, seeds of E. americanus were stimulated to germinate. Subsequent studies were designed to determine whether the bacterium synthesized a cellulolytic enzyme responsible for initiating germination. The cell-free endocellulase from C. cellobioparum induced germination of the seeds. To support the hypothesis that the endocellulase from C. cellobioparum was responsible for triggering germination, a 1,4-beta-d-glucan glucanohydrolase (EC 3.2.1.4) from Penicillum funiculosum was used to treat the seeds. In addition, no germination was obtained from seeds treated with a commercial exocellulase enzyme. Also, Ruminococcus flavefaciens FD-1 was found to initiate germination of E. americanus seeds. Thus, cellulase activity is indicated in the degradation of the testa of the seed, allowing imbibition and germination.     

Diversity of the mouse T cell receptor Cγ1 gene: structural analysis in C57BL/Ka

We have isolated an unusual T cell receptor chain cDNA clone (7.1) from a library made from RNA derived from adult thymus of C57BL/Ka mice. This cDNA clone corresponds to the appropriately processed C1 constant region exons preceded by 1.5 kb of J-C1 intron. The 7.1 coding region is extremely homologous to the C1 gene of BALB/c mice, differing at the protein level by a single deletion (alanine 139) and a single substitution. This latter change eliminates the sole N-linked sugar attachment site, providing a basis for strain-specific glycosylation patterns. The J-C1 intronic region contains two DNA segments (termed J1 and J2) that are highly reminiscent of joining (J) segments; both have potentially functional recombination and donor splice sequences flanking an open reading frame. Northern analysis suggests that 7.1 may be derived from a large, variable region-containing precursor.     

Effects of temperature and moisture during incubation on carcass composition of hatchling snapping turtles (Chelydra serpentina)

Summary Flexible-shelled eggs of common snapping turtles (Chelydra serpentina) were incubated on each of two substrates (vermiculite, sand) at each of three temperatures (26.0°C, 28.5°C, 31.0°C) and three moisture regimes (wet, intermediate, dry). Embryos developing in cool, wet environments mobilized the largest amounts of protein from their yolk and attained the largest size before hatching, whereas turtles developing in warm, dry environments mobilized the smallest quantities of protein and were the smallest in body size at hatching. Embryos on wet substrates mobilized more lipid from their yolk than did embryos on dry media, but ambient temperature had no demonstrable influence on patterns of lipid mobilization. The total reserve of neutral lipid available in residual yolk plus carcass to sustain neonates in the interval prior to the beginning of feeding was largest in hatchlings from dry environments and smallest in animals from wet environments, but was unaffected by temperature during incubation. Hydration of tissues in hatchlings was higher when incubation was in cool, moist conditions than when incubation was in warm, dry settings, thereby indicating that some of the effects of moisture and temperature on mobilization of nutrients by embryos may be mediated by differences in intracellular water. Patterns of response to temperature and moisture recorded for turtles emerging from eggs on sand were similar to those recorded for hatchlings on vermiculite, so no important conclusion would have been affected by incubating eggs on one medium instead of the other.     

Differential amplification of antifreeze protein genes in the pleuronectinae

Summary The organization of antifreeze protein (AFP) genes in the yellowtail flounder was investigated by Southern blotting and the characterization of clones from a genomic library. This flounder, like the closely related winter flounder, has a set of 10–12 linked but irregularly spaced AFP genes. However, it lacks the tandemly amplified set of 20 such genes that are present in the winter flounder. DNA sequence analysis of a tandemly repeated gene from winter flounder showed that it can code for one of the two most abundant AFP components in the serum. Consistent with this higher AFP gene dosage, the peak serum AFP level in midwinter was 9 mg/ml in the winter flounder and only 4 mg/ml in the yellowtail flounder. A recent amplification of the AFP gene in the winter flounder lineage might be responsible for the higher serum AFP levels in this fish. This increase in gene dosage might have helped the winter flounder colonize the ice-laden, shallow-water niche that it currently occupies along the east coast of North America. Genomic Southern blotting of two other righteye flounders, the smooth flounder and the American plaice, illustrates another example of a differential amplification of AFP genes that correlates with a species' exposure to ice.     

Conopy architecture of Larrea tridentata (DC.) Cov., a desert shrub: foliage orientation and direct beam radiation interception

Summary At sites in the United States, creosote bushes (Larrea tridentata (DC.) Cov.) orient foliage clusters predominantly toward the southeast. Foliage of bushes at the southernmost distribution extreme in Mexico shows no predominant orientation. Clusters at all sites are inclined between 33° and 71° from the horizontal. Inclinations are steeper in the drier and hotter Mojave Desert than in the Chihuahuan Desert. Individual leaflets, though not measured, appear more randomly oriented than foliage clusters. In several populations studied, branches were shorter in the southeastern sectors of the crown, reducing self-shading early in the morning. Measurements of direct beam radiation interception by detached branches, using digital image processing, indicated that foliage clusters oriented toward the southeast exhibited less self-shading during spring mornings than clusters oriented northeast. This effect was not apparent at the summer solstice. This type of canopy architecture may tend to minimize self-shading during the morning hours when conditions are more favorable for photosynthesis, resulting in an improved daily water use efficiency.     

N5-Formyltetrahydrofolate counteracts methotrexate toxicity in tobacco cell culture

N5-Formyltetrahydrofolate (leucovorin) counteracted methotrexate toxicity in suspension cultures of Nicotiana tabacum var. Xanthi. Methotrexate at 50 nM inhibited growth of the tobacco cell cultures by 87%. Leucovorin at 200 uM reduced growth inhibition in methotrexate-treated cultures to 37%, but only if exogenous adenine and thymidine were simultaneously provided. In the absence of leucovorin, neither adenine plus thymidine, nor adenine plus thymidine plus methionine gave appreciable relief from methotrexate toxicity. Uptake of radioactive methotrexate at 50 nM was linear for at least 7 h. Uptake of methotrexate appeared to be saturable, with a K_m of 50 uM and a V_max of 1 nmol h^–1 g^–1 fresh weight. Leucovorin showed competitive inhibition of methotrexate uptake, having a K_i of 400 uM.Abbreviations ade adenine - MS Murashige and Skoog - MTX methotrexate - thd thymidine     

Fumarate reductase of Escherichia coli: an investigation of function and assembly using in vivo complementation

Recombinant plasmids which carried portions of the Escherichia coli frd operon were constructed and their expression examined by in vivo complementation of E. Coli MI 1443. This strain lacked a chromosomal frd operon and was unable to grow anaerobically on glycerol and fumarate. Introduction of all four fumarate reductase subunits into E. coli MI1443 was essential for the restoration of growth. The FRD A, FRD B dimer (but neither subunit alone) was active in the benzyl viologen oxidase assay. Both FRD C and FRD D were required for membrane association of fumarate reductase and for the oxidation of reduced quinone analogues. Introduction into E. coli MI1443 of the frdABC and frdD genes on two separate plasmid vectors failed to restore anaerobic growth on glycerol and fumarate. Thus separation of the DNA coding for the FRD C and FRD D proteins affected the ability of fumarate reductase to assemble into a functional complex.     

Characterization of the postacrosomal sheath of bovine spermatozoa

A purified head fraction was prepared from bovine epididymal spermatozoa and was utilized to identify the solubility characteristics and major polypeptide components of the postacrosomal sheath. Sperm heads extracted in nonionic-detergent-containing or high-salt-containing solutions retained an intact postacrosomal sheath, but it was readily solubilized by high pH extraction solutions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a major polypeptide of 58,000 daltons (58-kD) in the high pH extract solution. Antibodies to the 58-kD polypeptide specifically reacted with the postacrosomal segment by immunofluorescence and by electron microscopic immunohistochemistry were shown to bind the postacrosomal sheath. We conclude that this 58-kD polypeptide is a constituent of the postacrosomal sheath and that its distribution is restricted to the postacrosomal segment.     

Circadian and seasonal rhythms of 5-HT receptor subtypes, membrane anisotropy and 5-HT release in hippocampus and cortex of the rat.

Specific serotonin binding (5-HT1, 5-HT1A, and 5-HT2 subtypes) and membrane anisotropy were measured at 2 h intervals over a 24 h period in the hippocampus and cortex of Wistar WU rats, housed under a 12 h light-dark cycle, with lights on at 07.00. All experiments were performed both in March and December. In the hippocampus significant circadian rhythms could be ascertained for 5-HT1 binding sites in March and December while for 5-HT1A (subtype of 5-HT1) binding sites the circadian rhythm was only significant in March. The membrane anisotropy also showed significant variations only in March. Circadian rhythms were also found in the cortex for 5-HT1 (December) and 5-HT2 (March and December) binding sites as well as for the membrane anisotropy (December). A correlation was found between membrane anisotropy and 5-HT1 and 5-HT2 binding sites in hippocampus and cortex, respectively. A circadian rhythmicity was also observed for serotonin release as measured by in vivo voltammetry in both brain areas. The results obtained on the diurnal variations of serotonin receptor subtypes and serotonin release and the probable inverse relationship of these two parameters may be relevant in understanding the coupling of pre- and postsynaptic activity.