Replication of X chromosomes in complete moles

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.     

Hydrogen evolution by co-immobilized Chlorella vulgaris and Clostridium butyricum cells

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.     

Area and the rapid radiation of Hawaiian Bidens (Asteraceae)

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.     

Protein kinase A inhibitors enhance radiation-induced apoptosis

In addition to a role for de novo protein synthesis in apoptosis we have previously shown that activation of a protein phosphatase or loss of activity of a kinase is also important in radiation-induced apoptosis in human cells [Baxter, and Lavin (1992): J Immunol 148:149–1954]. We show here that some inhibitors of protein kinases exacerbate radiation-induced apoptosis in the human cell line BM13674. The specific protein kinase A inhibitor isoquinoline sulfonamide (20 μM) gave rise to significantly increased levels of apoptosis at 2–6 h postirradiation compared to values after radiation exposure only. The same concentration of isoquinolinesulfonamide, which was effective in increasing apoptosis, reduced activity markedly. A 66% inhibition of cyclic AMP-dependent protein kinase A activity occurred in unirradiated cells at this concentration of H89 and activity was reduced to 58% in irradiated cells. Calphostin C, a specific inhibitor of protein kinase C, at a concentration of 0.1 μM, which caused 68% inhibition of enzyme activity in irradiated cells, failed to enhance the level of radiation-induced apoptosis. Other kinase inhibitors did not lead to an additional increase in apoptosis over and above that observed after irradiation. The results obtained here provide further support for an important role for modification of existing proteins during radiation-induced apoptosis.     

Salt tolerance and glycerol accumulation of a respiration-deficient mutant isolated from the petite-negative, salt-tolerant yeast Zygosaccharomyces rouxii

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.     

Inhibition of Auxin-Stimulated Elongation of Cells in Rice Lamina Joints by a Feruloylated Arabinoxylan Trisaccharide

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)     

Study of insulin response to oral glucose load after acute and chronic glycemic control in type 2 diabetic subjects

To investigate whether correction of fasting hyperglycemia per se improves the insulin secretion in type 2 diabetic subjects, plasma insulin response to 75 g oral glucose load has been studied after acute and chronic normalization of fasting plasma glucose levels in 7 overt type 2 diabetic subjects. For the acute normalization of elevated fasting plasma glucose levels, an artificial endocrine pancreas was employed. Although fasting plasma glucose concentrations were normalized before the oral glucose challenge, insulin response to oral glucose was not improved compared to those without normalization of fasting plasma glucose levels. After 1-3 month control of hyperglycemia, the insulin response to glucose in the subjects was significantly improved compared to those without treatments. Results indicate that chronic metabolic control is essential for the improvement of insulin response to glucose in type 2 diabetic subjects, and also suggest that the impaired insulin secretion in type 2 diabetes is not due to hyperglycemia per se, but due to the metabolic derangements which lead to chronic hyperglycemia.     

N-Terminal Amino Acid Sequence and Processing Site of Sweet Potato Cytochrome c Oxidase Subunit II

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)