Lectin recognition of host-like saccharide motifs in streptococcal cell wall polysaccharides

Viridans streptococci that participate in the microbial colonizationof teeth have cell wall polysaccharides composed of linear phosphodiester-linkedhexa- or heptasaccharide repeating units, each containing ahost-like disaccharide motif, either Galß1     

Determinants of the high-methionine trait in wild and exotic germplasm may have escaped selection during early cultivation of maize

The 18 kDa high-methionine δ-class zein gene from maize has been cloned, and its regulation, structure, and map position studied. These studies have shown that (i) zein genes may also contain tryptophan and lysine codons, (ii) the 18 kDa and the related 10 kDa zein gene are coordinately regulated, but their products accumulate to different levels in a genotype-dependent manner, (iii) the duplication of δ-zein genes probably involved unequal crossing over, (iv) no copy correction in either direction has occurred from teosinte to modern corn, and (v) the duplication of of the 18 kDa zein gene probably occurred before the tetraploidization of a progenitor chromosome. The work shows that important nutritional quality determinants like the high-methionine seed proteins are abundant in several exotic and wild corn varieties and low in most of the inbreds screened. The lack of a selectable phenotype for such quality traits during initial domestication and breeding of corn would have eliminated cis and trans regulatory determinants from the germplasm used in modern corn breeding. Examples of the high-methionine δ-class zeins shown here may be generally applicable in explaining the low nutritional quality of most present-day corn grown.     

Purification of rabbit liver phosphofructokinase and its properties under simulatingin vivo conditions

Phosphofructokinase (EC 2.7.1.11) from rabbit liver was purified to homogeneity. Preincubation of enzyme results in nonlinearity of enzyme activity with enzyme concentration. Therefore K_0.5 of enzyme for fructose 6 phosphate in the absence or presence of fructose 2,6 bisphosphate or polyethylene glycol or in the presence of both was determined at physiological concentrations of its various effectors by taking the initial rate obtained by adding the enzyme last. They decrease the K_0.5 value from 4.1 mM to about 0.2mM. The K_0.5 of enzyme for fructose 2,6 bisphosphate was also determined under the above conditions. It is about 4.3ΜM. Transient kinetics of phosphofructokinase at varying concentrations of enzyme in the presence of fructose 2,6 bisphosphate or polyethylene glycol or in the presence of both were studied. It was found that although they decrease t_1/2 i.e. the time to reach half the maximal steady rate by about 5–8 fold, it was about constant at varying concentrations of the enzyme. These results indicate that fructose 2,6 bisphosphate and polyethylene glycol decrease K_0.5 of the enzyme for fructose 6 phosphate not by associating the enzyme to higher aggregates, but by a different mechanism.     

Intracellular glycosidases of human colon Bacteroides ovatus B4-11.

Activity of various glycosidases in the intracellular enzyme fraction of Bacteroides ovatus B4-11 was investigated. During 120 h of incubation at 37 degrees C, ca. 30% of the crude hemicellulose was hydrolyzed by an intracellular enzyme fraction of strain B4-11. Xylose was the major sugar released from crude hemicellulose. Glycosidases (alpha-1,6-glucosidase, alpha-1,4-glucosidase, beta-1,4-glucosidase, and beta-1,4-xylosidase) were induced in B. ovatus B4-11 by crude hemicellulose and heteroxylan. When B. ovatus B4-11 was grown on either crude hemicellulose or heteroxylan, the predominant enzyme in the intracellular enzyme fraction was beta-1,4-xylosidase.     

Kinetics of succinic dehydrogenase inhibition by methyl parathion and its recovery by oximes and L-cysteine in hepatopancreas of Lamellidens marginalis

Effects in vitro of methyl parathion on some kinetic constants of succinic dehydrogenase (SDH) in hepatopancreas of freshwater mussel, L. marginalis were studied. Altered pH vs. specific activity curves for SDH demonstrated significant inhibition by methyl parathion in buffered acidic, neutral and alkaline ranges. At high pH ranges IC50 (12.5 microM) of methyl parathion did not cause 50% inhibition enzyme as it did at neutral and acidic pHs. Activation energies (delta E) were found to be increased suggesting decreased efficiency of enzyme in presence of methyl parathion. Non-competitive inhibition with respect to activation by succinate was indicated by decreased maximal velocity (V) without change in Michaelis Menten constant (Km). Pyridine-2-aldoxime (25 microM), pyridine-4-aldoxime (15 microM) and L-cysteine (40 microM) neutralized the inhibition of SDH by methyl parathion (12.5 microM). The kinetic data suggests that inhibition of SDH by methyl parathion was pH and temperature independent.     

Long-chain acyl-coenzyme A synthetase from rat brain microsomes. Kinetic studies using [1-14C]docosahexaenoic acid substrate

The activation of docosahexaenoic acid by rat brain microsomes was studied using an assay method based on the extraction of unreacted [1-14C]docosahexaenoic acid and the insolubility of [1-14C]docosahexaenoyl-CoA in heptane. This reaction showed a requirement for ATP, CoA, and MgCl2 and exhibited optimal activity at pH 8.0 in the presence of dithiothreitol and when incubated at 45 degrees C. The apparent Km values for ATP (185 microM), CoA (4.88 microM), MgCl2 (555 microM) and [1-14C]docosahexaenoic acid (26 microM) were determined. The presence of bovine serum albumin or Triton X-100 in the incubation medium caused a significant decrease in the Km and Vm values for [1-14C]docosahexaenoic acid. The enzyme was labile at 45 degrees C (t1/2:3.3 min) and 37 degrees C (t1/2:26.5 min) and lost 36% of its activity after freezing and thawing. The transition temperature (Tc) obtained from Arrhenius plot was 27 degrees C with the activation energies of 74 kJ/mol between 0 degrees C and 27 degrees C and 30 kJ/mol between 27 degrees C and 45 degrees C. [1-14C]Palmitic acid activation in rat brain and liver microsomes showed apparent Km values of 25 microM and 29 microM respectively, with V values of 13 and 46 nmol X min-1 X mg protein-1. The presence of Triton X-100 (0.05%) in the incubation medium enhanced the V value of the liver enzyme fourfold without affecting the Km value. Brain palmitoyl-CoA synthetase, on the other hand, showed a decreased Km value in the presence of Triton X-100 with unchanged V. The Tc obtained were 25 degrees C and 28 degrees C for brain and liver enzyme with an apparent activation energy of 109 and 24 kJ/mol below and above Tc for brain enzyme and 86 and 3.3 kJ/mol for liver enzyme. The similar results obtained for the activation of docosahexaenoate and palmitate in brain microsomes suggest the possible existence of a single long-chain acyl-CoA synthetase. The differences observed in the activation of palmitate between brain and liver microsomes may be due to organ differences. Fatty acid competition studies showed a greater inhibition of labeled docosahexaenoic and palmitic acid activation in the presence of unlabeled unsaturated fatty acids. The Ki values for unlabeled docosahexaenoate and arachidonate were 38 microM and 19 microM respectively for the activation of [1-14C]docosahexaenoate. In contrast, the competition of unlabeled saturated fatty acids for activation of labeled docosahexaenoate is much less than that for activation of labeled palmitate.(ABSTRACT TRUNCATED AT 400 WORDS)     

Distribution, endogamy, and isolation of Malas of Chittoor district, Andhra Pradesh, India

This study investigates the distribution of Malas, a scheduled caste population of Andhra Pradesh, their isolates in different eco-cultural zones, and their endogamy and isolation by marriage district. The Malas, formerly "untouchables," occupy the lowest status in the Hindu hierarchy. The sample consists of 10% of Malas from 10% of the villages in 2 taluks of Chitoor district of Andhra Pradesh. 6 Mala populations--Tangala, Maladasari, Pakanati, Rampala, Murikinati, and Bommanati--live in the area. These populations show a regionality in their distribution, with very little overlapping even when 2 populations inhabit the same village. Of 885 marriages in the 6 endogamous populations, all but 3 have been contracted between individuals belonging to the same Mala group. The 3 exogamous marriages took place between Mala men and women from another caste. Such small exceptions to the general rule do not mean that the Mala populations are not breeding isolates; these 6 populations satisfy Wright's island model. The high incidence of matings between closely related populations also contributes to their genetic and breeding isolation. Consanguineous marriages range from 26.76 to 38.75%. The distance between the birth place of spouses in miles, called marriage distance, shows a range from 7.72 to 15.71 miles. Lower values mean higher population densities. Groups within each population are isolated by distance and form small overlapping Mendelian populations, approaching a stepping stone model with continuous variation of genetic traits between adjacent groups of people.     

In vitro flowering and pod formation from cotyledons of groundnut (Arachis hypogaea L.)

Summary The response of groundnut cotyledons to the presence of various growth regulators in concentrations from 0.1 to 5 mg/l has been studied in detail using several genotypes of groundnut on two different media. Cotyledons with embryo axis, cultured on Blaydes' medium with cytokinins, produced shoots, in the axils of which 2–7 flower buds could be seen. The frequency of flower bud induction in general increased with increasing concentrations of cytokinins, the optimal levels being 3 mg/l of KN or 4 mg/l of BAP. Cotyledons without embryo axis, cultured on Blaydes' medium with BAP (0.5 mg/l), produced a cluster of flower buds directly, ranging in number from 8–28, without any vegetative growth. Excised embryo axes cultured on the same medium gave plantlets without flower buds. The growth regulators IAA, NAA, GA₃ and ABA failed to induce flower buds in independent treatments. However, lower concentrations of IAA and NAA in combination with cytokinins exerted a positive influence on flowering. The blooming of the flower buds was facilitated on media supplemented with low concentrations of cytokinins. Six percent of the induced flowers resulted in gynophore development and ultimately formed pods when cultured under complete dark conditions in modified MS medium supplemented with kinetin.     

Cryosurgery of the monkey (macaque) prostate. II. Apparent immunopathologic alterations following cryostimulation.

Previous investigation of the development of humoral immunologic responsiveness following cryostimulation of the monkey prostate up to 30 days postoperatively disclosed low to modest titres of antibodies to prostatic tissue antigens. In the present study, the possible occurrence and predominance of a cellular response and its ensuing immunopathologic effects on the prostate and other accessory sexual glands of these animals, not initially examined, together with further serologic evaluation and correlation of this cellular response with the presence of antiprostatic antibodies, has been made 41 to 90 days following freezing. A reduction in the size of the prostate observed following freezing was accompanied by what were suggestive of immunopathologic alterations. Alterations occurred principally in the caudal lobe, and were characterized by what appeared to be specific periacinar foci of lymphocytic infiltrates. These lymphocytes were observed to infiltrate onto the acinar epithelial cells with subsequent separation of epithelial cells from the basal lamina and epithelial cell destruction. Other observed alterations in the prostate consisting of stromal fibrosis, periodic presence of inflammatory cells, proliferation of regenerating glands, and squamous metaplasia were in consonance with previous histologic studies of the prostate following cryosurgery by others. Antiprostatic antibodies were present in only one of the seven animals evaluated at the time which these observations were made. The present preliminary observations provide evidence suggestive of the development of a specific cellular immunologic response following cryosurgery of the prostate. Fending confirmation of the study of a larger series of animals, these observations may be of potential significance in providing an explanation of reported cases of eradication of human prostatic carcinomas following cryotherapy.