Effects of prenatal X-irradiation: studies on the mechanism of X-irradiation-induced inhibition of microsomal enzyme development in rat liver

Exposure of pregnant rats to 25 R of x-irradiation on the fourteenth gestation day has produced in the male offspring an impairment of the development of the hepatic microsomal enzyme system which metabolizes hexobarbital. However, irradiation did not suppress the increase of enzyme activity brought about by the administration of chemical inducers (pheno-barbital). Actinomycin, on the other hand, inhibited to varying degrees both the ontogenic and phenobarbital-induced increases in enzyme activity. The effects on the enzyme system have been supported by in vivo measurements of the duration of hexobarbital hypnosis. The ontogenic increase in enzyme activity is hormone-dependent, while that following phenobarbital administration is independent of hormonal regulation as evidenced by the response in hypophysectomized or sexually immature animals. It is concluded from these results that the inhibitory effect of x-irradiation on the hepatic enzyme system is mediated through an action on the hormonal regulation of enzyme activity. Evidence for this hypothesis is discussed.     

Preliminary observations on the interstitial fauna of the south-west coast of India

Summary This paper presents the preliminary observations on the interstitial fauna of the south-west coast of India, made during the course of 1963–1964. Observations were made at four stations representing different ecological habitats. The influence of some factors, such as wave action, grain size, temperature and salinity on the fauna was studied. The occurrence, seasonal abundance and the nature of distribution of the different groups on the intertidal zone, were also studied at the four stations.     

Effect of soil solarization on nodulation,infection by mycorrhizal fungi and yield of cowpea

Solarization of soil was found beneficial for plant growth in cowpea under field conditions. Root nodulation, infection by mycorrhizal fungi and yield were higher in plants grown in solarized soil. These increases were to the extent of 104.7, 20.0 and 23.7 per cent respectively when compared to control treatment without solarization.     

Analysis of Vibrio cholerae O139 Bengal Isolated from Different Geographical Areas Using Macrorestriction DNA Analysis

Vibrio cholerae O139 isolated from different countries, as well as from different locations within a country, were examined using macrorestriction DNA analysis to determine the clonality of the O139 strains. NotI digests of genomic DNA of representative strains from Nepal, India, Bangladesh, China, Thailand, and Malaysia revealed very similar but not identical patterns. Examinations of the banding patterns generated by pulsed-field gel electrophoresis of strains isolated within countries revealed complete homogeneity. These results further reiterate the spread of an identical clone of V. cholerae O139 although it appears that genetic polymorphism among the O139 strains is becoming apparent.     

Random amplified polymorphic DNA analysis of root-nodulating bacterial strains from Arachis hypogaea with physiological characteristics of both fast and slow growers

N. MATHAN, M. PARANI, A. PARIDA AND S. NAIR. 1996. Strains of root-nodulating bacteria isolated from Arachis hypogaea showed physiological characteristics of both fast and slow growers. Random amplified polymorphic DNA (RAPD) markers showed most of the genotypes could be identified using one or two primers; however, cluster analysis based on the number of bands shared by the genotypes showed a homogenous cluster. These strains were halotolerant in nature and have potential for use in saline soil.     

PCR-based DNA markers linked to a gall midge resistance gene, Gm4t, has potential for marker-aided selection in rice

Rice DNAs from a gall midge resistant variety, Abhaya, a susceptible variety, Tulsi and their F₃ progeny were screened using 500 random primers in conjunction with bulked-segregant analysis in a polymerase chain reaction (PCR) with a view to detecting random amplified polymorphic DNAs (RAPDs) linked to the gene, Gm4t, which confers resistance to gall midge, a dipteran insect pest of rice. A total of 454 primers were able to produce a distinct amplification pattern, and 3695 bands/loci were amplified between the phenotypically different parents. Of these, 304 bands were polymorphic between the parents, with 19 being phenotypespecific. One of these primers, E20, amplified 2 bands, E20₅₇₀ and E20₅₈₃, which are tightly linked to resistance and susceptibility, respectively. These specific bands were cloned and sequenced, and a 94% sequence homology was found between the two fragments. Two specific 20-mer oligonucleotides were synthesized, based on the sequence information of E20₅₈₃, for use in PCR amplification directly from genomic DNAs. These PCR primers were able to amplify phenotype-specific bands, a 583-bp fragment in susceptible F₃ lines and a 570-bp fragment in resistant F₃ lines that had been derived from a cross between the parents, indicating their potential and utility for marker-aided selection of the Gm4t gene in rice. Its use would facilitate the early and efficient selection of resistant genes in plant breeding programmes and even in those areas where the insect is not known to occur. These phenotype-specific bands are single-copy sequences and are being mapped to ascertain their chromosomal location in rice.     

The need for standardised broad scale bioassay testing: A case study using the red alga Laurencia rigida

Two major problems associated with biofouling studies are the lack of broad scale testing and failure to use consistent standards among different assays or studies. To address these issues the activity of two biologically active natural products, elatol and deschloroelatol, isolated from the marine red alga Laurencia rigida, and three commonly used biocides, Nopcocide N-96?, Irgarol 1051? and Sea-Nine 211?, was compared, in a broad spectrum of bioassays. The activity of the different compounds varied substantially among different bioassay tests. Elatol and deschloroelatol had a narrow range of activity with strongest effects against invertebrate larvae. Both compounds were highly toxic. However, neither compound had strong activity against marine bacteria or the common epiphyte Ulva lactuca. Irgarol 1051 also had a narrow range of activity, only affecting algal settlement strongly. Nopcocide N-96 and Sea-Nine 211 had moderate to strong activity across the spectrum of bioassays, viz. growth of marine bacteria (Vibrio fischeri, Serratia sp.), inhibition of settlement of macroalgae (Ulva lactuca), toxicity (Balanus amphitrite), and inhibition of settlement of invertebrate larvae (Balanus amphitrite, Bugula neritina). Based on the results it is proposed that Sea-Nine 211, because of its broad spectrum activity, be used as a standard for comparative assessments of the antifouling activity of marine natural products and analogues.     

Effect of carbon sources on the synthesis of pectinase by Aspergilli

The synthesis of pectinase is investigated using six species of Aspergillus, with five media differing either in their carbon sources or level of carbon source(s). Five of the six species used, synthesized appreciable amounts of pectinase in the media containing sugars. Pectinase synthesis was highest for A. niger, NCIM 548, with all the sugar containing media. A. foetidus, NCIM 510, was the only one among the organisms studied, that responded well to the medium containing pectin in the absence of additional sugars supplied in the medium.