A differential medium for the enumeration of homofermentative and heterofermentative lactic Acid bacteria

A medium was developed for the differential enumeration of homofermentative and heterofermentative lactic acid bacteria. Essential components of the medium included fructose (14 mM), KH(2)PO(4) (18 mM), bromcresol green (as a pH indicator), and other nutrients to support growth. In agar medium, homofermentative colonies were blue to green, while heterofermentative colonies remained white. A total of 21 Lactobacillus, Pediococcus, Leuconostoc, and Streptococcus species were correctly classified with the medium.     

Control of wild carrot somatic embryo development by antioxidants : a probable mode of action of 2,4-dichlorophenoxyacetic Acid

As we previously reported for glutathione (GSH), both ascorbic acid (AA) and vitamin E were observed to suppress wild carrot (Daucus carota L.) somatic embryogenesis with little concomitant effect on biomass. Endogenous concentrations of AA were lower during embryo development than during cell proliferation, exhibiting a temporal pattern nearly identical to that of GSH. GSSG (oxidized GSH) reductase was found to be considerably more active in proliferating than in developing cultures, whereas no difference was evident in the case of dehydroascorbate (DHA) reductase. Both GSH and AA concentrations in these cells are governed by 2,4-D. These results show that redox status is a strong determinant of proliferative versus developmental growth and indicate that the mode of action of 2,4-D in this system may be explained at least in part by its influence on endogenous antioxidant levels.     

Gibberellic Acid effects on greening in pea seedlings

The effect of gibberellic acid (GA) on light-induced greening of etiolated pea plants (Pisum sativum [L.] cultivars Alaska and Progress) was characterized. Progress, a GA-deficient dwarf of Alaska, was found to accumulate chlorophyll and light harvesting chlorophyll protein associated with photosystem II (LHC-II) more rapidly than Alaska, Alaska treated with GA, or Progress treated with GA. A slightly lower chlorophyll content was noted after 24 hours of light induced greening for Alaska treated with GA relative to untreated Alaska. GA-treated Progress, Alaska, and GA-treated Alaska all gave essentially identical patterns for LHC-II accumulation. Similar patterns of LHC-II mRNA induction were found in all four treatments indicating that differences in mRNA induction did not cause differences in LHC-II accumulation. Chlorophyll and LHC-II accumulation in each treatment followed the same patterns of accumulation and a significant correlation (at the 0.01 level of significance) was found between chlorophyll and LHC-II content. Since Progress treated with GA accumulated LHC-II and chlorophyll in a manner similar to that of Alaska, it is clear that GA alters the process of greening either directly or indirectly.     

Effect of zearalenone and estradiol benzoate on serum concentrations of LH, FSH and prolactin in ovariectomized gilts

Six ovariectomized gilts were given zearalenone (Z), estradiol benzoate (EB) or vehicle in a replicated 3 x 3 Latin square design. Zearalenone was added to 2.3 kg of a corn-soybean ration at a dose of 1 mg Z/kg body weight; EB was given intramuscularly at 0.1 mg EB/kg body weight. Control gilts received vehicle solvent for both Z and EB. Blood samples were collected from indwelling jugular cannulas at 6-h intervals for 48 h before Z, EB or vehicle was given. After treatment, blood samples were drawn at 6-h intervals for an additional 84 h. Serum concentrations of luteinizing hormone (LH) decreased (P<0.001) from 4.67 ng/ml to 0.29 ng/ml within 6 h of EB. From 54 to 84 h after EB, serum concentrations of LH rose to 15.60 ng/ml (P<0.001). Serum concentrations of LH were reduced (P<0.001) in a similar pattern after Z (3.70 ng/ml to 0.49 ng/ml), but a rise in serum LH was not observed 54 to 84 h after Z (1.30 ng/ml). Serum concentrations of LH remained unchanged (P=0.55) in gilts given vehicle. Serum concentrations of follicle stimulating hormone (FSH) were suppressed (P<0.03) at 6 h in EB (19.10 vs 11.35 ng/ml) and Z gilts (16.16 vs 11.41 ng/ml) but remained unchanged in vehicle gilts. Serum concentrations of FSH did not change in EB or Z gilts during the next 36 h. These data indicate that the suppressive action of Z on serum concentrations of LH and FSH was similar to that of EB, while the biphasic stimulatory effect of EB for LH was not manifested by Z.     

A comparison of three models for the diffusion of oxygen in electrolyte solutions

Diffusion of oxygen through aqueous solutions is of great importance in biological systems. In this work, three models for the diffusion of oxygen through aqueous salt solutions are compared. One model uses mole fraction as the driving force (Fick's Law) and another uses chemical potential. The third model uses the gradient in oxygen activity as the driving force. This new model was chosen because of the availability of oxygen electrodes which directly measure oxygen activity in aqueous solution. These models have been used to reevaluate the technique of measuring O(2) diffusivities. We show that Pick's Law diffusion coefficients do not vary strongly with salt concentration as was erroneously reported in the literature. In addition, we compare the predicted O(2) fluxes of the three models over a wide range in O(2) concentrations. For oxygen concentrations of biological interest, the three models give identical predictions of the flux.     

Inhibitory Effects of Methylcellulose on Cellulose Degradation by Ruminococcus flavefaciens

Highly methylated, long-chain celluloses strongly inhibited cellulose degradation by several species of cellulolytic bacteria of ruminal origin. Specifically, the inhibitory effects of methylcellulose on the growth of Ruminococcus flavefaciens FD1 were concentration dependent, with complete inhibition at 0.1% (wt/vol). However, methylcellulose did not inhibit growth on cellobiose or cellulooligosaccharides. Mixtures of methylated cellulooligosaccharides having an average degree of polymerization of 6.7 to 9.5 inhibited cellulose degradation, but those with an average degree of polymerization of 1.0 to 4.5 did not. Similar inhibitory effects by methylcellulose and, to a lesser extent, by methyl cellulooligosaccharides were observed on cellulase activity, as measured by hydrolysis of p-nitrophenyl-beta-d-cellobioside. R. flavefaciens cultures hydrolyzed cellulooligosaccharides to cellobiose and cellotriose as final end products. Cellopentaose and cellohexaose were cleaved to these end products, but cellotetraose was also formed from cellohexaose. Methylcellulose did not inhibit hydrolysis of cellulooligosaccharides. These data are consistent with the presence of separate cellulase (beta-1,4-glucanase) and cellulodextrinase activities in R. flavefaciens.     

Effect of incubation conditions, inhibitors, 2-mercaptoethanol and testosterone on RNA synthesis in ram spermatozoa

In vitro studies on RNA synthesis using washed ram spermatozoa were carried out by measuring the incorporation of (3)H-uridine into RNA. Penicillin-G (100 mug/ml medium) was added to prevent contamination by microorganisms. Spermatozoa were quickly separated from seminal plasma by washing twice in Tris-HCl buffer (at pH 7.2) and centrifuged at 1,000 g for 5 min. Washed spermatozoa were then diluted to 1 10 , 1 20 or 1 40 (v/v) by the same buffer system (containing 400 mg% glucose) and were incubated in air at 37 degrees C for 1, 2 and 4 h. Results indicated that the rate of RNA synthesis was maximal at 1 40 semenbuffer dilution (5-8 x 10(7) spermatozoa/ml) and increased linearly up to 4 h of incubation. The rate of RNA synthesis at 1 40 dilution also increased linearly as the dose of exogenous glucose substrate was increased up to 400 mg%. Denaturation of the ram spermatozoa by 1% HgCl(2) caused almost complete inhibition of RNA synthesis that amounted to 97% of the control samples. Incubation of spermatozoa with 50, 100 or 200 mug/ml chloramphenicol also inhibited uridine incorporation by 86 to 94%, while equivalent doses of cycloheximide did not. On the other hand, the incorporation of (3)H-uridine into the RNA of ram spermatozoa was significantly enhanced by graded doses of 2-mercaptoethanol (0.2, 0.4 and 0.8 muM) and of testosterone (15 and 30 mug/ml). The results of this study indicate RNA synthesis, mainly of mitochondrial origin, by mature ram sperm. The data also suggest a role for intracellular cyclic adenosine monophosphate in the regulation of sperm RNA synthesis.     

Effect of extraction and subsequent addition of manganese ions on photooxidation of chlorophyll P(680) in the photosystem II preparations

Effect of reversible removal of Mn on the amplitude of photoinduced absorbance changes (ΔA) related to photooxidation of chlorophyll P(680) in pea oxygen -- evolving photosystem 2 (PS(2)) preparations has been studies. It is shown that after complete removal of Mn the amplitude of ΔA is increased by a factor of 7--8 and it is decreased again to the initial value upon subsequent addition of MnCl(2). This reactivation needs four Mn atoms per one reaction centre (RC) of PS(2). In the presence of 3 μM MgCI(2) the reactivation requires two Mn atoms per RC of PS2. The obtained data confirm our earlier conclusion that a four-atomic Mn centre functions in the donor side of PS(2); two of them can be replaced by either Mg(2+) or other divalent metals.