Influence of tea and coffee beverages on prostacyclin synthesis by the rat aorta

Influences of 2.5 and 5% (w/v) aqueous tea and coffee beverages administered ad lib. to rats for two weeks on PGI2 synthesis by the rat thoracic aorta in vitro were investigated using a rat platelet antiaggregatory bioassay and HPLC methods. The 2.5% beverages did not affect PGI2 synthesis; however, the 5% beverages significantly decreased PGI2 synthesis. The observed decreases were significantly abolished in presence of exogenous arachidonic acid suggesting a beverage-induced inhibition of precursor release. The ability of the beverages to inhibit PGI2 synthesis may partly contribute towards better understanding of the biochemical mechanisms underlying some of the beverages-induced actions in vivo.     

Linear and non-linear regression analysis of genotype X environment interactions in pearl millet

Summary Regression analysis was computed on the grain yield of 15 single cross F₁ hybrids of pearl millet (Pennisetum typhoides (Burm.) S. & H.) evaluated in 20 environments at 19 sites in India to assess the nature of genotype X environment interactions. Linear, quadratic, cubic, twoand three-intersecting straight line models were examined for fit. The interactions of six hybrids viz. MH 110, MH 113, MH 114, MH 115, MH 120 and MBH 110 were explained by the linear regression model. The response of the remaining nine hybrids was largely non-linear. The two and three-intersecting straight line models fit better than the quadratic and cubic models and explained non-linearity of response. The two-intersecting straight line models fit for 6 hybrids MH 106, MH 107, MH 112, MH 116, MH 117 and BJ 104. The response of MH 109 was best explained by a three-intersecting straight line model, but there still existed a significant remainder variation. The truncation of environmental range by assuming moving division points was more efficient than the fixed division points for the segmental regression models. The stability of hybrid varieties on the best fitting model has been discussed.     

Bacteria of public health significance in blackcurrant juice

A total of 192 samples of blackcurrant juice were investigated for hygienic quality and drug resistance. The average aerobic bacteria in 1 ml of the blackcurrant juice was 4.8 x 10(8) and the average MPN was 8.4 x 10(2) coliform/100 ml. The percentage of the samples contaminated with coliform bacteria was 23.4. The incidence of Escherichia coli, Klebsiella, Pseudomonas aeruginosa, Staphylococcus aureus and faecal streptococci were 19.8, 9.9, 29.2, 14.0 and 18.2%, respectively. Biochemical and serological studies showed that 10.5% of total Escherichia coli were enteropathogenic E. coli. Of sixty strains tested against six antibacterial drugs, 57% were resistant to one or more of the drugs. The incidence of resistance to ampicillin, chloramphenicol, sulphonamide, streptomycin, tetracyline and gentamycin was 40.0, 25.0, 43.3, 18.3, 20.0 and 8.3%, respectively.     

Calcium and the mechanical properties of soybean hypocotyl cell walls: Possible role of calcium and protons in cell-wall loosening

The role of calcium in the mechanical strength of isolated cell walls of soybean (Glycine max (L.) Merr. cv. Wayne) hypocotyls has been investigated, using the Instron technique to measure the plastic extensibility (PEx) of methanol-boiled, bisected hypocotyl sections and epidermal strips, and atomic absorption spectroscopy to measure wall calcium. Plastic extensibility was closely correlated with the growth rate of intact soybean hypocotyls. Removal of calcium from isolated cell walls by ethylene glycol-bis(2-aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA) or low pH increased PEx, while addition of calcium decreased PEx; both effects were reversible. The amount of calcium removed and the increase in PEx at pH 4.5 were strongly dependent upon the chelating ability of the buffer anion. There was a direct correlation between the amount of calcium removed from the wall by EGTA or acid and the increase in PEx. Removal of up to 60% of the calcium increased PEx of half-section up to two fold, but further loss of calcium caused a much greater increase in PEx. With epidermal strips, PEx increased only when calcium was reduced below a threshold. At pH 3.5, there was an additional increase in PEx after a lag of about 2 h; this additional increase may be the result of acid-induced cleavage of a different set of load-bearing bonds. We conclude that calcium bridges are part of the load-bearing bonds in soybean hypocotyl cell walls, and that breakage of these crosslinks by apoplastic acid participates in wall loosening. Acid-induced solubilization of wall calcium may be one mechanism involved in wall loosening of dicotyledonous stems.Abbreviations EGTA ethylene glycol-bis(2-aminoethyl ether)-N,N,N,N-tetraacetic acid - PEx Instron plastic extensibility     

Ca2+ transport and Ca2+-dependent ATP hydrolysis by Golgi vesicles from lactating rat mammary glands.

Ca2+ transport across mammary-gland Golgi membranes was measured after centrifugation of the membrane vesicles through silicone oil. In the presence of 2.3 microM free Ca2+ the vesicles accumulated 5.8 nmol of Ca2+/mg of protein without added ATP, and this uptake was complete within 0.5 min. In the presence of 1 mM-ATP, Ca2+ was accumulated at a linear rate for 10 min after the precipitation of intravesicular Ca2+ with 10 mM-potassium oxalate. ATP-dependent Ca2+ uptake exhibited a Km of 0.14 microM for Ca2+ and a Vmax. of 3.1 nmol of Ca2+/min per mg of protein. Ca2+-dependent ATP hydrolysis exhibited a Km of 0.16 microM for Ca2+ and a Vmax. of 10.1 nmol of Pi/min per mg of protein. The stoichiometry between ATP-dependent Ca2+ uptake and Ca2+-stimulated ATPase varied between 0.3 and 0.7 over the range 0.03-8.6 microM-Ca2+. Both Ca2+ uptake and Ca2+-stimulated ATPase were strongly inhibited by orthovanadate, which suggests that the major mechanism by which Golgi vesicles accumulate Ca2+ is through the action of the Ca2+-stimulated ATPase. However, Ca2+ uptake was also decreased by the protonophore CCCP (carbonyl cyanide m-chlorophenylhydrazone), indicating that it may occur by other mechanisms too. The effect of CCCP may be related to the existence of transmembrane pH gradients (delta pH) in these vesicles: the addition of 30 microM-CCCP reduced delta pH from a control value of 1.06 to 0.73 pH unit. Golgi vesicles also possess a Ca2+-efflux pathway which operated at an initial rate of 0.5-0.57 nmol/min per mg of protein.     

Effect of taurine on arterial, uterine and cardiac PGI2 and TXA2 synthesis in the rat

The influence of taurine (in drinking water for 6 weeks) on PGI₂ and TXA₂ synthesis by some female rat organs was investigated using radioimmunoassay and platelet antiaggregatory bioassay. Taurine 100 and 200 mg/kg/day increased aortic PGI₂ release from 0.59 ± 0.04 (control) to 0.85 ± 0.05 and 1.01 ± 0.06 ng/mg, respectively and that by the myometrium from 0.24 ± 0.02 (control) to 0.38 ± 0.01 and 0.50 ± 0.04 ng/mg wet tissue, respectively (P < 0.05, n = 6). It did not affect PGI₂ and TXA₂ production in the heart or TXA₂ in the aorta. Taurine 200 mg/kg depressed uterine TXA₂ synthesis from 148.6 ± 9.8 (control) to 85.4 ± 6.8 pg/mg (P < 0.05, n = 6). Furthermore taurine 0.4 and 0.8 mM in vitro stimulated PGI₂ released by the myometrial and aortic tissues from pregnant rats. The stimulant effect of taurine on PGI₂ may be related to its antioxidant effect whereas its inhibitory effect on uterine TXA₂ may result from direction of synthesis towards PGI₂. It is concluded that endogenous taurine may participate in regulation of PGs synthesis and that prostanoids may contribute to its known actions. On broad basis, taurine-induced release of PGI₂ may prove of potential value in those ailments characterised by deficiency in PGI₂ release.     

Detection and characterization of a glutenin subunit with unusual high Mr at the Glu-A1 locus in hexaploid wheat

A hexaploid wheat landrace collected from the Baluchistan province of Pakistan was found to possess a novel high-molecular-weight glutenin subunit (HMW-GS). The subunit has a very slow electrophoretic mobility as revealed by SDS-PAGE, and its molecular weight is comparable to that of the highest molecular weight glutenin subunit (2.2 encoded in the D-genome) reported so far in hexaploid wheat varieties and landraces of Japanese origin. Evidence obtained from (PCR) gene amplification studies using the primers specific for Glu-1 loci proved that the gene coding for this novel subunit belongs to the Glu-A1 locus located on the long arm of chromosome 1A. Digestion of the amplified gene (PCR product) with restriction enzymes indicated that the novel gene differs from prevailing Glu-A1 alleles (null, 1 and 2^*) by an extra DNA fragment of approximately 600 base pairs. The results also indicated that the novel subunit is most probably a derivative of subunit 2^* that has very likely incorporated the 600-bp fragment following a process of unequal crossing over. The present findings were further substantiated by reserved phase high performance liquid chromatography (RP-HPLC) analysis.     

Indigenous Arbuscular Mycorrhizal Fungi Associated with Acacia albida Del. in Different Areas of Senegal

The influences of seasons, plant age, and physicochemical properties of the soil on surface and deep biological arbuscular mycorrhizal fungus parameters associated with Acacia albida were assessed in different areas of Senegal. More indigenous arbuscular mycorrhizal propagules were found in the localities of the Sudano-Guinean zone (Djinaki and Kabrousse) than in those of the Sahelian zone (Louga and Diokoul), and species belonging to the genera Glomus, Gigaspora, Acaulospora, and Sclerocystis prevailed. The numbers of total and viable spores increased more during the rainy season than during the dry season (about 108% more total spores and 262% more viable spores). Similarly, both total and viable spores were more prevalent around young Acacia trees than old trees. However, the intensities of root colonization did not differ in each ecoclimatic zone.     

Field evaluation of a model of photothermal flowering responses in a world lentil collection

A model to predict flowering time in diverse lentil genotypes grown under widely different photothermal conditions was developed in controlled environments. The present study evaluated that model with a world germ plasm collection of 369 accessions using two field environments in Syria and two in Pakistan. Photoperiod alone accounted for 69% of the variance in 1/f, the reciprocal of time (d) from sowing to flower. In contrast, temperature alone did not account for a significant proportion of variation in flowering time due to the exposure of plants to supra-optimal temperatures in the late-sown Syrian trial. With the model mean pre-flowering values of photoperiod and temperature combined additively to account for 90.3% of the variance of 1/f over accessions. The correlation of field-derived estimates of temperature sensitivity of accessions to glass-house-derived estimates was significant at P = 0.05, but the equivalent correlation for estimates of photoperiodic sensitivity was higher at P < 0.01. Flowering in the field was better measured as time from sowing to 50% plants in flower rather than time to first bloom or its node number. Dissemination of the lentil crop following domestication in West Asia to the lower latitudes such as Ethiopia and India has depended on selection for intrinsic earliness and reduced sensitivity to photoperiod. Movement from West Asia to the higher latitudes accompanied by spring sowing has resulted in a modest reduction in photoperiod sensitivity and an increase in temperature sensitivity.     

Assessment of cytoplasmic differences of near-isonuclear male-sterile lines in pearl millet

Four near-isonuclear polycytoplasmic versions of 81A and two of Pb 402A male-sterile lines of pearl millet (Pennisetum typhoides) were used in factorial matings with five inbred male testers in different combinations in three sets. The cytoplasmic differences were studied for several agronomic traits using mean values and general combining effects (gca) of male-sterile lines, and specific combining ability effects of hybrids. The fertility/ sterility behaviour of different male-sterile lines in crosses with common male parents was also studied. Significant differences among near-isonuclear polycytoplasmic lines were observed in mean values for a few traits such as plant height, leaf length and peduncle length, but the differences for combining ability were more pronounced. The A₃ cytoplasm was a better general combiner than the A₂ cytoplasm for grain yield and both A₂ and A₃ cytoplasms were better general combiners for leaf length and peduncle length. In addition, superiority of A₃ cytoplasm for gca was observed for plant height and ear characters over the A₂ cytoplasm in set II. A differential behaviour of cytoplasms, both in combination with a common pollinator and across pollinators, was observed for several traits. The results provide evidence for the distinctiveness of different cytoplasmic sources in pearl millet and for the influence of cytoplasmic factors on the phenotypic expression of nuclear genes. A diversification of male sterility sources in the breeding of pearl millet hybrids is suggested.