Plasmid transfer between Pseudomonas spp. within epilithic films in a rotating disc microcosm

Abstract A microcosm using rotating slate discs in a chemostat was used to study bacterial population dynamics and genetic interactions in river epilithon. Populations of all introduced donor and recipient Pseudomonas spp. decreased with time but all the bacteria survived better on the slate discs than in the liquid phase. Conjugal transfer of an epilithic plasmid encoding mercury resistance (pQM1) occured with transfer frequencies of 1.4 × 10⁻⁶ to 3.6 × 10⁻³ per recipient, which were about 100-fold lower than in standard membrane filter mating experiments.     

Induction and amplification of T-lymphocyte proliferative responses to periodate and soybean agglutinin by human adult vascular endothelial cells

Human mononuclear phagocyte (M phi) populations were compared to adult human endothelial cells (HEC) for their respective abilities to influence the proliferative responses of purified human T lymphocytes to the mitogenic agents Na-m-periodate (IO-4), soybean agglutinin (SBA), or allogeneic cells. HEC and M phi were both capable of inducing proliferative responses of allogeneic T lymphocytes in mixed-lymphocyte culture. Under low cell density culture conditions, purified T-lymphocyte proliferative responses to IO-4 or SBA could be restored by addition of syngeneic M phi or HEC. At higher cell density culture conditions, proliferation of T cells to IO-4 could be amplified more by HEC than M phi. T-lymphocyte proliferative responses to SBA were amplified by addition of HEC but were suppressed by addition of M phi. These findings indicate that human adult HEC are unique and potent accessory cells for T lymphocytes. Furthermore, these findings demonstrate that accessory cell functions of HEC can be discriminated from those of M phi.     

Species differences in the metabolism of benzoic acid by isolated hepatocytes and kidney tubule fragments

The metabolism of benzoic acid to hippuric acid and benzoyl glucuronide has been studied in viable hepatocytes and renal tubule fragments from two species of omnivores (rat, hamster) and two species of carnivores (ferret, dog). Hippuric acid formation was detected in hepatocytes and tubules from omnivores but was not detectable in hepatocytes from the two carnivore species. High levels of hippuric acid were produced in the tubules from the carnivores. A small amount of glucuronidation occured in hepatocytes of all these species tested and in the carnivores this reaction was the predominant pathway of benzoic acid metabolism. These results indicated that the marked species differences in patterns of benzoic acid conjugation are related to differences in the ability of liver and kidney cells to carry out glycine and glucuronic acid conjugation.     

Aryl mono-oxygencise activity in hepatic microsomes isolated by isoelectric precipitation

The activity of the aryl mono-oxygenase (AMO) system has been compared in hepatic microsomes isolated by precipitation at pH 5.4 and by conventional centrifugation. “Acid” microsomes were shown to contain comparable levels of AMO activity, when measured on a per gram of liver basis, in control and induced rat liver and in human liver. Acid microsomes from control rat liver possess extra nonmicrosomal protein that appears to be cytoplasmic in origin.     

Bioassaying Putative RNA-Binding Motifs in a Protein Encoded by a Gene That Influences Courtship and Visually Mediated Behavior in Drosophila: In Vitro Mutagenesis of Nona

The no-on-transient-A (nonA) gene of Drosophila melanogaster influences vision, courtship song, and viability. The nonA-encoded polypeptide is inferred to bind single-stranded nucleic acids. Although sequence-analysis of NONA implies that it belongs to a special interspecific family of this protein type, it does contain two classical RNA recognition motifs (RRM). Their behavioral significance was assayed by generating transgenic strains that were singly or multiply mutated within the relatively N-terminal motif (RRM1) or within RRM2. Neither class of mutation affected NONA binding to polytene chromosomes. The former mutations led to extremely low viability, accompanied by diminished adult longevities that were much worse than for a nonA-null mutant, implying that faulty interpolypeptide interactions might accompany the effects of the amino-acid substitutions within RRM1. All in vitro-mutated types caused optomotor blindness and an absence of transient spikes in the electroretinogram. Courtship analysis discriminated between the effects of the mutations: the RRM2-mutated type generated song pulses and trains that tended to be mildly mutant. These phenotypic abnormalities reinforce the notion that nonA''s ubiquitous expression has its most important consequences in the optic lobes, the thoracic ganglia, or both, depending in part on the nonA allele.