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1.
Summary The sequence of the synthesis and transport of the organic matrix of spicules has been elucidated in the gorgonian Leptogorgia virgulata by use of 3H-aspartic acid as the tracer in electron-microscopic autoradiography. The entire process of matrix synthesis and transport takes approximately 2 h. It seems that the protein moiety of the organic matrix is synthesized in the RER prior to 5 min following the initial 10 min incubation in the tracer. At the 5 min chase the label is moving from the RER to the Golgi complexes where the carbohydrate moiety of the matrix is presumed to be synthesized. At the 5 to 15 min chases the label is transported out of the Golgi complexes via Golgi vesicles. This phase continues for 30 min. From 60 to 120 min the 3H-aspartic acid moves to the spicules. After 120 min the majority of the label has moved into the spicules. Silver grain counts over both multivesicular and electron-dense bodies remain at relatively low and constant levels over 4 h indicating that neither organelle is involved in the synthesis and transport of the organic matrix.Contribution No 512; Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, Columbia, South Carolina 29208, USA  相似文献   
2.
Replication of X chromosomes in complete moles   总被引:1,自引:0,他引:1  
Summary DNA replication patterns of X chromosomes in complete hydatidiform moles were studied using cultured fibroblasts from three 46,XX moles resulting from duplication of a haploid sperm, and from a 46,XY mole originating from dispermy. Control cultures included skin fibroblasts from an adult woman and a female fetus as well as PB lymphocytes from an adult woman. Cultures were treated with 5-bromodeoxyuridine for the last 2–4h of the S phase, and the chromosome slides prepared were stained by the Hoechst 33258-Giemsa procedure. Each of the three XX moles studied revealed one early-replicating and one late-replicating X chromosomes, while the XY mole revealed one early-replicating X chromosome. DNA replication patterns of molar X chromosomes were similar to those of adult and fetal fibroblasts, but different from those in adult lymphocytes. These findings indicate that DNA replication kinetics of molar fibroblasts are tissue-specific rather than origin- or developmental-stage specific.  相似文献   
3.
Whole cells of Chlorella vulgaris and Clostridium butyricum were co-immobilized in 2% agar gel. NADP was suitable as an electron carrier. The rate of hydrogen evolution increased with increasing NADP concentration. The optimum conditions for hydrogen evolution were pH 7.0 and 37°C. The immobilized C. vulgaris-NADP-immobilized Cl. butyricum system continuously evolved hydrogen at a rate of 0.29–1.34 μmol/h per mg Chl for 6 days. On the other hand, the system without NADP evolved only a trace amount of hydrogen.  相似文献   
4.
1. Catch is a mechanism found in many molluscan smooth muscles in which tension is maintained at relatively low energy cost. 2. Paramyosin forms the core of thick filaments. In catch muscle paramyosin concentrations are high and the thick filaments are relatively long. 3. The mechanism of catch is not understood, but the consensus is that tension during catch is borne by slowly-cycling cross-bridge attachments to actin. 4. Stimulation by acetylcholine increases intracellular Ca2+ and initiates a contraction characterized by a relatively rapid cross-bridge cycling. Reduction of Ca2+ can lead to relaxation or catch. Relaxation occurs only when a second neurotransmitter, serotonin, is present. 5. The catch state is released by serotonin, via activation of adenylate cyclase, increased levels of cAMP and phosphorylation of one or more contractile proteins, possibly paramyosin. Other targets for phosphorylation are discussed. 6. The contractile cycle of catch muscles, therefore, is controlled by both Ca2+ and cAMP.  相似文献   
5.
Aim To estimate the rate of adaptive radiation of endemic Hawaiian Bidens and to compare their diversification rates with those of other plants in Hawaii and elsewhere with rapid rates of radiation. Location Hawaii. Methods Fifty‐nine samples representing all 19 Hawaiian species, six Hawaiian subspecies, two Hawaiian hybrids and an additional two Central American and two African Bidens species had their DNA extracted, amplified by polymerase chain reaction and sequenced for four chloroplast and two nuclear loci, resulting in a total of approximately 5400 base pairs per individual. Internal transcribed spacer sequences for additional outgroup taxa, including 13 non‐Hawaiian Bidens, were obtained from GenBank. Phylogenetic relationships were assessed by maximum likelihood and Bayesian inference. The age of the most recent common ancestor and diversification rates of Hawaiian Bidens were estimated using the methods of previously published studies to allow for direct comparison with other studies. Calculations were made on a per‐unit‐area basis. Results We estimate the age of the Hawaiian clade to be 1.3–3.1 million years old, with an estimated diversification rate of 0.3–2.3 species/million years and 4.8 × 10?5 to 1.3 × 10?4 species Myr?1 km?2. Bidens species are found in Europe, Africa, Asia and North and South America, but the Hawaiian species have greater diversity of growth form, floral morphology, dispersal mode and habitat type than observed in the rest of the genus world‐wide. Despite this diversity, we found little genetic differentiation among the Hawaiian species. This is similar to the results from other molecular studies on Hawaiian plant taxa, including others with great morphological variability (e.g. silverswords, lobeliads and mints). Main conclusions On a per‐unit‐area basis, Hawaiian Bidens have among the highest rates of speciation for plant radiations documented to date. The rapid diversification within such a small area was probably facilitated by the habitat diversity of the Hawaiian Islands and the adaptive loss of dispersal potential. Our findings point to the need to consider the spatial context of diversification – specifically, the relative scale of habitable area, environmental heterogeneity and dispersal ability – to understand the rate and extent of adaptive radiation.  相似文献   
6.
7.
A respiration-deficient (RD) mutant was isolated from the petite-negative, salt-tolerant yeast Zygosaccharomyces rouxii. One strain among sixteen glycerol-non-utilizing mutants exhibited vigorous liberation of CO2 but no uptake of O2. Furthermore, this strain lacked cytochrome aa3 and had a reduced level of cytochrome b. The few mitochondria found in cells of this strain contained few or no cristae. Salt tolerance and intracellular accumulation of glycerol by the RD strain were almost equal to that of the wild-type strain in media containing NaCl up to 2.5 M. In media with more than 3 M NaCl, the growth of the RD mutant was retarded and the intracellular accumulation of glycerol was depressed in spite of ample production.  相似文献   
8.
A feruloylated arabinoxylan trisaccharide inhibited IAA-stimulatedelongation of cells in rice lamina joints. The de-esterifiedcompound, an arabinoxylan trisaccharide, did not inhibit suchelongation. This is the first report that feruloylated arabinoxylanfragments are involved in the regulation of plant growth. (Received September 18, 1991; Accepted January 13, 1992)  相似文献   
9.
Effects of dnats genes on the replication of plasmids in Bacillus subtilis   总被引:1,自引:0,他引:1  
An essential region (2.3 kb) for the replication of a low-copy-number plasmid, pBS-2, has been identified and cloned into plasmid pHV60 in Bacillus subtilis. The resultant plasmid, pKW1, and two other plasmids, pC194 (medium copy number) and pTP5 (high copy number), were examined by double radio-labelling and gel electrophoresis to determine which host functions are required for their replication in B. subtilis. Replication of pKW1 requires the functions of most dna genes, in particular dnaB, C, E, F, G and H; pC194 requires only dnaG and H; and pTP5 requires dnaE, F, G and H. Thus dnaG and dnaH are required for the replication of all three plasmids tested, even though each plasmid showed a different spectrum of dependency on other host functions. Because of its greater dependence on host functions and its low copy number, pKW1 should be a useful model with which to investigate the function of host genes in the replication of DNA in B. subtilis. pKW1 should also be a useful shuttle vector for cloning of genes in B. subtilis in cases when high gene dosage might be a problem.  相似文献   
10.
The N-terminal amino acid sequence of sweet potato cytochromec oxidase subunit II polypeptide was determined. Comparisonsbetween the sequence and amino acid sequences deduced from thenucleotide sequences of other higher plant subunit II genesindicate a post-translational clevage of N-terminal extensionpart. 1Present address: Institute of Low Temperature Science, HokkaidoUniversity, Sapporo, 060 Japan. (Received June 13, 1989; Accepted September 8, 1989)  相似文献   
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