Hormonal induction of steroid sulphatase in the mouse

By comparing steroid sulphatase levels per se, and also ratios to alpha-galactosidase, in 6 sets of mice - normal females, entire and castrated males both with and without exogenous testosterone administration - we obtained support for the contention that induction of this enzyme is in part controlled by male hormones.     

Subcutaneous transposition of the spleen enhances the survival rate following 90% hepatectomy in rats

Summary The effects of subcutaneous transposition of the spleen (STS) on the survival rate following 90% hepatectomy were investigated in rats. The survival rate was significantly higher in the STS group than in the non-STS group. Light microscopy enabled us to note that congestion in the terminal portal veins and sinusoids occurred either slightly earlier or to a higher degree in the non-STS group.     

Domain of E. coli DNA polymerase I showing sequence homology to T7 DNA polymerase

Escherichia coli contains three DNA polymerases that differ in their size, ability to interact with accessory proteins and biological function. Monomeric DNA polymerase I (Pol I) has a relative molecular mass (Mr) of 103,000 (103K) and is involved primarily in the repair of damaged DNA and the processing of Okazaki fragments; polymerase II is of Mr 120K, and polymerase III has a Mr of 140K, is responsible for the replication of the DNA chromosome and is just one of several proteins that are required for replication. DNA polymerases from bacteriophage as well as those of eukaryotic viral and cellular origin also differ with respect to their size and the number of associated proteins that are required for them to function in replication. However, the template-directed copying of DNA is identical in all cases. The crystal structure of the large proteolytic fragment of Pol I shows that it consists of two domains, the larger of which contains a deep crevice whose dimensions are such that it can bind duplex DNA. The T7 polymerase consists of two subunits, the 80K gene 5 protein and the host-encoded 12K thioredoxin of E. coli. We show here that there is an amino acid sequence homology between at least eight polypeptide segments that form the large cleft in the Klenow fragment and polypeptides in T7 DNA polymerase gene 5 protein, suggesting that this domain evolved from a common precursor. The parts of the Pol I and T7 DNA polymerase molecules that bind the DNA substrate appear to share common structural features, and these features may be shared by all of these varied DNA polymerases.     

The effects of vitamin A nutritional status on glutathione levels and microsomal lipid peroxidation in rat lung

Summary In vitamin A-deficient rats, the glutathione level in lung was diminished and microsomal lipid peroxidation much increased. In vitamin A-loaded animals, however, both were depressed below control. Thus vitamin A protection against lipid peroxidation is independent of glutathione.Acknowledgments. We thank Dr L. Y. Y. Fong and Mr David Y. H. Woo for preparing the animals used in this research, for retinol determinations and for valuable discussions, and also the China Medical Board of New York and the University of Hong Kong for the award of a Fellowship to V.P.     

Actin microfilament dynamics in locomoting cells

The dynamic behaviour of actin filaments has been directly observed in living, motile cells using fluorescence photoactivation. In goldfish epithelial keratocytes, the actin microfilaments in the lamellipodium remain approximately fixed relative to the substrate as the cell moves over them, regardless of cell speed. The rate of turnover of actin subunits in the lamellipodium is remarkably rapid. Cell movement is directly and tightly coupled to the formation of new actin filaments at the leading edge.     

Oriential orchid (Cymbidium pumilum) attracts drones of the Japanese honeybee (Apis cerana japonica) as pollinators

The discovery that drones of the Japanese honeybee (Apis cerana japonica) pollinate the oriental orchid (Cymbidium pumilum) is reported. Drones are attracted to the orchid flower aroma mainly during their mating flights in April through May. Some drones cluster on the flower racemes and others insert their heads deep into the flowers. Drones with pollinia on their scutellum visit other orchids, which facilitates pollination. Individual workers and swarming colonies are also strongly attracted by the flower aroma, but the allopatric western honeybee (Apis mellifera) is not attracted.     

'Pseudo' domains in phage-encoded DNA methyltransferases

5-Cytosine-DNA-methyltransferases, which are found in many organisms ranging from bacteriophages to mammals, transfer a methyl group from S-adenosylmethionine to the carbon-5 of a cytosine residue in specific DNA target sequences. Some phage-encoded methyltransferases methylate more than one sequence: these enzymes contain several independent target-recognizing domains each responsible for recognizing a different site. The amino-acid sequences of these multispecific methyltransferases reveal that some enzymes in addition carry domains that do not contribute to the enzymes' methylation potential, but strongly resemble previously identified target-recognizing domains. Here we show that introducing defined amino-acid alterations into these inactive domains endows these enzymes with additional methylation specificities. Gel retardation analysis demonstrates that these novel methylation specificities correlate with the acquisition of additional DNA-binding potential of the proteins.     

DNA in wheat seeds from European archaeological sites

We have used hybridization analysis to detect ancient DNA in wheat seeds collected from three archaeological sites in Europe and the Middle East. One of these samples, carbonizedT. spelta dated to the first millennium BC, has yielded PCR products after amplification with primers directed at the leader regions of the HMW (high molecular weight) glutenin alleles. Sequences obtained from these products suggest that the DNA present in the Danebury seeds is chemically damaged, as expected for ancient DNA, and also indicate that it should be possible to study the genetic variability of archaeological wheat by ancient DNA analysis. Finally, we describe a PCR-based system that enables tetraploid and hexaploid wheats to be distinguished.