Evidence for Plasmid Linkage of Raffinose Utilization and Associated alpha-Galactosidase and Sucrose Hydrolase Activity in Pediococcus pentosaceus

The ability to ferment the trisaccharide raffinose was linked with the presence of plasmid DNA in three strains of Pediococcus pentosaceus. Parental strains showed associated inducible alpha-galactosidase and sucrose hydrolase activities when grown in alpha-galactosides and sucrose, respectively. Derivative strains of PPE1.0, PPE2.0, and PPE5.0, which had lost 30-, 28-, and 23-megadalton plasmids, respectively, had no alpha-galactosidase or sucrose hydrolase activity.     

Microbial-invertebrate interactions and potential for biotechnology

Conclusion As the interactions between marine invertebrates and their bacterial commensals and symbionts are better understood, the application of biotechnology will enhance both environmental and economic benefit. In the immediate future, marine bacteria, either selected or genetically engineered, will play a significant role in enhancing the development of selected invertebrates in aquaculture and in the field. Luck may also favor discovery of mechanisms to suppress the development of biofouling species, perhaps by making it possible to coat submerged surfaces with bacterial films designed to repell larvae and/or interfere with larval morphogenesis. In any case, the future is appealing.     

Ontogenetic development of corticotropin-releasing factor (CRF)-containing neural elements in the brain of the chicken during incubation and after hatching

Summary In chicken embryos of different ages and in young chickens after hatching, neural elements reacting with antibodies generated against synthetic ovine corticotropin-releasing factor (CRF) were studied by means of the peroxidase-anti-peroxidase (PAP) technique at the lightmicroscopic level. CRF-immunoreactivity was first observed in perikarya located in the periventricular part of the hypothalamus on the 14th day of the incubation period. CRF-containing neural elements were detected on the same day of incubation in the external zone of the median eminence, but not in all investigated animals. In extrahypothalamic sites, immunoreactive perikarya were demonstrable in the central gray of the mesencephalon on the 15th day of incubation. Furthermore, immunoreactive cells appeared in other brain regions such as nucleus accumbens and dorsomedial nucleus of the thalamus after hatching. The present observations provide information regarding the functional development of the hypothalamo-hypophyseal-adrenal axis in the chick embryo.     

Clastogen-induced chromosomal breakage as a marker for first trimester prenatal diagnosis of Fanconi anemia

Summary Using cultured trophoblast cells obtained by chorionic villus biopsy, we diagnosed Fanconi anemia (FA) in two pregnancies and excluded it in eight pregnancies at risk for the syndrome. Baseline chromosomal breakage and breakage induced by diepoxybutane (DEB) were analyzed. Increased breakage was used as a marker for the syndrome. Our results were unambiguous and provide a reliable method for prenatal detection of FA in the first trimester of pregnancy.     

The anthranilate aggregate of Escherichia coli: kinetics of inhibition by tryptophan of phosphoribosyltransferase

The kinetic mechanism of the phosphoribosyltransferase reaction is shown to be rapid equilibrium random bi bi with an enzyme-anthranilate-pyrophosphate abortive complex. We present a rate equation that not only predicts the observed kinetic patterns but also accommodates the fact that feedback inhibition is partial, even though tryptophan (Ki = 0.5 microM) and phosphoribosylpyrophosphate (Km = 50 microM) are competitive. Neither ligand completely abolishes the effect of the other. Instead, the binding of one ligand leads to a mutual elevation in the dissociation constant of the opposing ligand by a factor of two to three. Tryptophan inhibition is noncompetitive with respect to anthranilate (Km = 0.58 microM) and does not diminish the rate of interconversion of ternary complexes. Tryptophan cooperativity, with respect to the inhibition of phosphoribosyltransferase, conforms to the concerted Monod-Wyman-Changeux formulation (kinetic Hill coefficient = 2), whereas tryptophan as an inhibitor of anthranilate synthase more closely conforms to a Koshland model of sequential cooperativity with a kinetic Hill coefficient of 1.4. The aggregate contains only one class of tryptophan sites. Thus the first tryptophan molecule bound to the aggregate maximally inhibits both phosphoribosyltransferase active centers and one of the two anthranilate synthase catalytic sites. The remaining anthranilate synthase subunit thereupon is converted into a form with less (but not zero) affinity for chorismate and a greater affinity for a second molecule of tryptophan.