The role of oxygen availability in the embryonation of Heterakis gallinarum eggs.

The importance of oxygen availability in the embryonation of the infective egg stages of the gastrointestinal nematode parasite Heterakis gallinarum was studied in the laboratory. Unembryonated H. gallinarum eggs were kept under either aerobic conditions by gassing with oxygen, or anaerobic conditions by gassing with the inert gas nitrogen, under a range of constant temperatures. Oxygenated eggs embryonated at a rate influenced by temperature. Conversely, eggs treated with nitrogen showed no embryonation although when these eggs were transferred from nitrogen to oxygen gas after 60 days of treatment, embryonation occurred. This demonstrated that oxygen is an essential requirement for H. gallinarum egg development, although undeveloped eggs remain viable, even after 60 days in low oxygen conditions. The effects of climate on the biology of free-living stages studied under constant laboratory conditions cannot be applied directly to the field where climatic factors exhibit daily cycles. The effect of fluctuating temperature on development was investigated by including an additional temperature group in which H. gallinarum eggs were kept under daily temperature cycles between 12 and 22°C. Cycles caused eggs to develop significantly earlier than those in the constant mean cycle temperature, 17°C, but significantly slower than those in constant 22°C suggesting that daily temperature cycles had an accelerating effect on H. gallinarum egg embryonation but did not accelerate to the higher temperature. These results suggest that daily fluctuations in temperature influence development of the free-living stages and so development cannot be accurately predicted on the basis of constant temperature culture.     

A new species of Galearis (Orchidinae: Orchidaceae) from Sichuan,China

A new species, Galearis huanglongensis Q.W.Meng & Y.B.Luo, is described and illustrated. It is similar to Galearis cyclochila (Franch. & Sav.) Soó and Galearis diantha (Schltr.) P.F.Hunt, but differs in having a short spur, two elliptical lateral stigma lobes and distinctly separated bursicles. This new species is known only from the type locality, the Huanglong Valley, Songpan County, western Sichuan, China, growing amongst mosses under alpine shrubs at an elevation of about 3000 m. Based on two years of observations of its population size, the species was categorized as critically endangered CR (B1a, B2a) according to the World Conservation Union (IUCN) Red List Categories and Criteria, Version 3.1. The micromorphology of pollinia and seeds was observed by scanning electron microscopy and compared with that of G. cyclochila and G. diantha. The results supported G. huanglongensis Q.W.Meng & Y.B.Luo as a new species. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 689–695.     

Dominant lethal studies in male mice after exposure to 2.45 GHz microwave radiation

Adult male mice had the lower halves of their bodies exposed in a waveguide system to 2.45 GHz microwave radiation for 30 min. The half body dose-rate of 43 W kg-1 had been shown in a previous study [7] to deplete severely the heat-sensitive stages of sperm production. The males were mated at intervals to adult hybrid females over the following 8-10 weeks. There was no significant reduction in post-implantation survival, suggesting that the microwave exposure did not have a mutagenic effect on the male germ cells. However, pregnancy rate was significantly reduced in weeks 3, 4, 5 and 6; reaching a minimum of about 10% of the control value in weeks 4 and 5. The occurrence of low values in weeks 4 and 5 correlated well with the expected reductions in sperm count due to the pattern of depletion of the spermatogenic epithelium of the testes. Thus it was concluded that the reduced pregnancy rate resulted from reduced male fertility. Pre-implantation survival can also be affected by reduced sperm count [8] and was significantly reduced in this study but it correlated less well with the anticipated heat response. A further study is in progress looking at the contribution of sperm count and sperm abnormality to the results.     

Soluble di- and aminopeptidases in Escherichia K-12. Dispensible enzymes.

As part of a study of the peptidase content of Escherichia coli K-12, two peptidase-deficient amino acid auxotrophs isolated and characterized by Miller as pepD- (strain CM17) and pepD- pepN- pepA- pepB- pepQ- (strain CM89) were examined for the presence of several peptidases previously obtained from strain K-12 in this laboratory. The soluble fraction of each mutant was found to lack the broad-specificity strain K-12 dipeptidase DP and the strain CM89 fraction also lacked activity characteristic of the strain K-12 aminopeptidases AP, L, and OP; like strain CM17, strain CM89 contained the tripeptide-specific aminopeptidase TP. Strain CM89 (but not CM17) appeared to contain little if any activity attributable to the ribosome-bound aminopeptidase I of strain K-12. Whereas loss of DP, AP, OP, and aminopeptidase I activity may be attributed to the pepD-, pepB-, pepN-, and pepA- mutations, respectively, the reason for the loss of L activity remains uncertain. Grown responses of strain CM89 in liquid media containing di- or tripeptides were in accord with absence of enzymes catalyzing rapid hydrolysis of dipeptides. In synthetic liquid media supplemented with the required amino acids per se or with peptone, cultures of both CM strains grew more slowly than strain K-12 and produced smaller cell-yields than those produced by strain K-12.     

Inhibitors of inosinate dehydrogenase

Inosinate dehydrogenase (IMP-dehydrogenase) from Chinese Hamster Ovary cells was found to be inhibited by two types of inhibitors. One type of inhibitor binds competitively at IMP-binding site and other type at NAD-binding site of the enzyme. Some new inhibitors of both classes have been illustrated here and their inhibition constants and type of inhibition determined. NAD-analog of tiazofurin was found to bind with both the sites and this type of inhibitors were found to be non-competitive with IMP and NAD.