Population genetics of glyoxalase I (GLO) polymorphism in India

Phenotype and gene frequency data are presented on the glyoxalase I (GLO) polymorphism in seven endogamous caste groups: Jat Sikh, Ramdasia Sikh, Ramgarhia Sikh, Khatri, Brahmin and Bania of Patiala district, and Jat Sikh of Faridkot district of Punjab, North-West India. Apparently, there is considerable heterogeneity in the frequency distribution of the GLO1 gene that varies from 0.168 in Bania to 0.287 in Brahmin. However, these differences are not statistically significant, and the overall GLO1 frequency in Punjab is well within the North Indian range.     

P1 plasmid replication. Role of initiator titration in copy number control

The copy number control locus incA of unit copy plasmid P1 maps in a region containing nine 19 base-pair repeats. Previous results from studies in vivo and in vitro indicated that incA interacts with the plasmid-encoded RepA protein, which is essential for replication. It has been proposed that the repeat sequences negatively control copy number by sequestering the RepA protein, which is rate-limiting for replication. Our results lend further support to this hypothesis. Here we show that the repeats can be deleted completely from P1 miniplasmids and the deletion results in an approximately eightfold increase in plasmid copy number. So, incA sequences are totally dispensable for replication and have only a regulatory role. The copy number of incA-deleted plasmids can be reduced if incA sequences are present in trans or are reincorporated at two different positions in the plasmid. This reduction in copy number is not due to lowered expression of the repA gene in the presence of incA. We show that one repeat sequence is sufficient to bind RepA and can reduce the copy number of incA-deleted plasmids. When part of the repeat was deleted, it lost its ability to bind as well as influence copy number. These results show a strong correlation between the capacity of incA repeats to bind RepA protein both in vivo and in vitro, and the function of incA in the control of copy number.     

Effect of centchroman on tubal transport and preimplantation embryonic development in rats

A single oral administration of centchroman (1.25 mg/kg) to adult female rats within 24 h of mating induced slight acceleration in the rate of transport of embryos through the oviducts. The compound did not seem to produce any deleterious effect on preimplantation embryonic development since well organized and apparently normal embryos were collected from the genital tract up to Day 12 of pregnancy. The recovery rate of embryos from centchroman-treated rats was, however, significantly reduced after Day 4 of pregnancy. There was some stimulation in the rate of cleavage of embryos and morula to blastocyst transformation, but retardation in the shedding of the zona pellucida. The rate of blastocyst formation was not altered when 6-8-cell embryos collected from the oviducts of control rats were transferred to the uteri of control or centchroman-treated females. A delay in zona shedding was observed in the centchroman-treated recipients.     

Protection from quinidine or physostigmine against in vitro inhibition by sarin of acetylcholinesterase activity

We have studied the relative effectiveness of quinidine and physostigmine in protecting against the inhibition of acetylcholinesterase (AChE) by sarin, an organophosphate (OP) compound. The protective effects of these compounds were studied in vitro in both synaptosomal and soluble samples obtained from various regions of sarin-administered or control isolated, perfused canine brain. Although AChE activities in the sarin-administered brain were substantially lower than in the control brain, we observed regional differences in the AChE activity in both. The AChE in the control brain and the AChE remaining in sarin-administered brain had different susceptibilities to inhibition from OP compounds in vitro and, therefore, have different properties. Quinidine partially protected AChE from the inhibitory effects of sarin in vitro possibly by altering the sarin binding sites. Addition of sarin to physostigmine-treated control brain samples allowed partial recovery of the AChE activity. The protective effects of quinidine or physostigmine were lost when samples from sarin-administered brain were treated in vitro with these compounds and then again exposed to sarin. Therefore, both quinidine and physostigmine provided partial protection against the inhibitory effects of sarin in vitro if they were added prior to sarin.     

Transposon mutagenesis in Azospirillum brasilense: isolation of auxotrophic and Nif- mutants and molecular cloning of the mutagenized nifDNA

Summary We report the successful mutagenesis of Azospirillum brasilense 29710 Rif Sm with transposon Tn5. The narrow host-range plasmid pGS9 (p15A replicon), which possesses broad host-range N-type transfer genes, was used as the suicide vehicle to deliver Tn5 in Azospirillum. Out of 900 colonies tested, 0.8% proved to be auxotrophic. One mutant altered in indoleacetic acid (auxin) biosynthesis was isolated and, in addition, three mutants completely defective in nitrogen fixation (nif) were obtained. All the mutants tested contained a single copy of Tn5 integrated randomly in the genome. The Tn5-mutagenized EcoRI fragments were cloned from the three Nif^- mutants. Physical analysis of cloned DNA showed that Tn5 was present on a different EcoRI fragment in each case, ranging in size from 15–17 kb. The nitrogenase structural genes (nifHDK) in A. brasilense 29710 Rif Sm were localized on a 6.7 kb EcoRI fragment. We found that Tn5 is not inserted in the nifHDK genes in the Nif^- mutants reported here. Site-directed mutagenesis using the cloned, Tn5-containing DNA from mutant Nif27(pMS188), produced a large number of Nif^- transconjugants of the A. brasilense 29710 Rif wild-type strain, showing the linkage between Tn5 insertion and the Nif^- phenotype. This is the first time that transposon-mutagenized auxotrophic, Nif^- and other mutants have been available for genetic analysis in Azospirillum. This should greatly facilitate the cloning and mapping of genes involved in nitrogen fixation as well as in many other phenotypic characteristics of Azospirillum.     

A Possible Role for Indoleacetic Acid, Low Temperature, and Phospholipid Metabolism in the Induction of GA(3) Responsiveness in GA(3) Insensitive (Rht3-Containing) Dwarf Wheat Aleurone

Preincubation of dwarf, Rht3-containing deembryonated seed for 4 hours in 342 nanomolar indoleacetic acid (IAA) induced maximum sensitivity to GA₃. In addition, the 4-hour IAA pretreatment caused a 2-fold increase in total phospholipids which coincided identically on a temporal basis with the induced GA₃ sensitivity. Changes in absolute levels of individual phospholipids and their acyl groups were recorded and compared with the changes observed in several Rht-containing aleurone tissues which were induced to develop GA₃ sensitivity by exposure to low temperature (5°C). Several distinct similarities between all tissues were recorded as they develop GA₃ sensitivity. One parameter, the percentage phospholipid composition, was quite similar in all tissues after they had become maximally sensitive to GA₃, suggesting that there is at least one membrane phospholipid composition which is particularly responsive to GA₃. The results indicate that (a) the basis of the GA₃ insensitivity of the Rht mutation resides in an aberrant phospholipid/fatty acid composition and/or metabolism; (b) exposure to low temperature (5°C) for 20 hours or longer, or 342 nanomolar IAA for 4 hours or longer reverses or corrects the genetic lesion, enabling the tissue to adopt a GA₃ responsive membrane composition. Finally, an hypothesis is discussed which indicates that IAA may play a controlling role in the mobilization of endospermal reserves, at least in Rht3-containing wheat aleurone.     

Lymphopoiesis in the nude fetal thymus following sympathectomy

This study was carried out to examine the innervation of the nude fetal thymus during ontogeny and to see if lymphopoietic activity would occur within these thymic lobes in the absence of sympathetic neuronal input. Fetal thymic rudiments from nu/nu mice were removed and examined for galoxylic acid-induced histofluorescence to detect the catecholaminergic nerves. Some of these lobes were organ cultured for 5 to 7 days in the presence of deoxyguanosine to eliminate any existing lymphoid cells within the rudiments. Such "nonlymphoid" thymic rudiments were implanted into the anterior eye chambers of syngenic BALB/c mice (heterozygous) from which cervical sympathetic ganglia and part of the sympathetic chain had been surgically removed (right side) one week earlier. The left side was only sham operated. The thymic implants were allowed to grow for up to 21 days on both sides; they were then removed and examined by histofluorescence, immunofluorescence, and light microscopy. The results indicate for the first time that the nude fetal thymus is innervated by sympathetic nerves and that following sympathectomy the nude thymus is able to sustain lymphopoietic activity and generate lymphoid cells which have characteristics present on thymocytes during in vivo development in normal mice, such as binding to peanut agglutinin and expression of Thy-1 antigen. The relationship between the presence of sympathetic inhibitory influence and the thymic atrophy seen in the nude mice during ontogeny, is being investigated.     

Differential induction of chromosome puffs in two cell types of Melanagromyza obtusa

The patterns of puffing activity in polytene nuclei of salivary gland (SG) and midgut (MG) tissues of Melanagromyza obtusa have been studied after heat shock (HS), 2-4-dinitrophenol (DNP) or benzamide treatment. This study has revealed that HS and DNP treatments induced the same set of puffs but in a tissue-specific pattern. Benzamide treatment was found ineffective in inducing puffing activity. Some HS genes were also found to be more or less active during normal development, indicating some function in the normal metabolism of the cells.     

Yeast fatty acid synthase: structure to function relationship

The yeast fatty acid synthase is a multifunctional enzyme composed of two nonidentical subunits in an alpha 6 beta 6 complex that is active in synthesizing fatty acids. The seven catalytic activities required for fatty acid synthesis are divided between the alpha and beta subunits such that the alpha 6 beta 6 complex has six complements of each activity. It has been proposed that these are organized into six centers for fatty acid synthesis. There are different opinions regarding the operation of these centers in the alpha 6 beta 6 complex, on view being that they are functionally independent and the other proposes half-sites activity for the complex. We have attempted to distinguish between these proposals by the most direct method of active site titration, i.e., quantitation of fatty acyl product in the absence of turnover. This was accomplished by using p-nitrophenyl thioacetate and thiophenyl malonate (in place of the coenzyme A analogues) as substrates along with NADPH, thereby depriving the yeast synthase of coenzyme A required to release product as fatty acyl coenzyme A. The amount of fatty acyl product formed was quantitated by gas-liquid chromatography, as well as by direct estimation of radioactivity in the product when p-nitrophenyl thio [1-14C] acetate was used as a substrate. In both cases, a stoichiometry of close to six was found for mole of fatty acid synthesized per mole of alpha 6 beta 6 complex. This indicates that there are six functional centers for fatty acid synthesis in the multifunctional yeast alpha 6 beta 6 fatty acid synthase and that these centers operate independently.(ABSTRACT TRUNCATED AT 250 WORDS)