Inositol lipid-mediated signalling in response to endothelin and ATP in the mammalian testis

Molecular and Cellular Biochemistry - The testis is a complex organ in which local control is achieved by signalling between its constituent cells. Herein we describe the responses of cultured rat...     

Applications of DNA shuffling to pharmaceuticals and vaccines

DNA shuffling is a practical process for directed molecular evolution which uses recombination to dramatically accelerate the rate at which one can evolve genes. Single and multigene traits that require many mutations for improved phenotypes can be evolved rapidly. DNA shuffling technology has been significantly enhanced in the past year, extending its range of applications to small molecule pharmaceuticals, pharmaceutical proteins, gene therapy vehicles and transgenes, vaccines and evolved viruses for vaccines, and laboratory animal models.     

Phonotaxis in the painted reed frog (Hyperolius marmoratus)

Summary A detailed study was conducted of the three-dimensional accuracy of phonotaxis by femaleHyperolius marmoratus. This analysis involved videotape recordings of phonotactic approaches to an elevated loudspeaker through a three-dimensional grid. Females readily resolved the sound source elevation, but the jump error angles describing the precision of approach were considerably greater in this three-dimensional analysis than in the more conventional two-dimensional ground approach analysis. Extensive use was made of visual cues in elevated phonotactic approach and lateral head scanning prior to jumps, often accompanied by vertical changes in head orientation, was frequent. The ability of such small anurans to localize a sound source in both the horizontal and vertical plane is remarkable.On leave from the Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853, USA     

Specificity of the spermidine requirement for the replication of phi X174 DNA be cell-free extracts of Escherichia coli

A new experimental approach for assessing the biological significance of spermidine interactions in isolated systems is applied to the stimulation by spermidine of the conversion of phi X174 virion DNA to its replicative form by cell-free extracts of Escherichia coli. At 2.5 mM Mg2+, spermidine activated the reaction 20-fold. Varying the spermidine concentration affected both the rate and extent of this DNA synthetic reaction without altering the nature of the reaction products. We evaluated the biological significance of the spermidine requirement by measuring reaction rates in the presence of a homologous series of spermidine analogs of known activity in vivo. There was a lack of specificity, in that all of these analogs were capable of efficiently substituting for spermidine in stimulating the reaction rate. The relevance of this in vitro spermidine stimulation to Escherichia coli chromosome replication in vivo is discussed in light of the results obtained with the spermidine analogs.     

Central neural peptides and catecholamines in spontaneous and DOCA/salt hypertension

Hypothalamic and neurophypophyseal levels of catecholamines and peptides were measured in spontaneous and deoxycorticosterone (DOCA)/salt hypertension. Catecholamines, norepinephrine, epinephrine and dopamine were measured by electrochemical detection while the peptides, vasopressin, oxytocin, luteinizing hormone-releasing hormone (LHRH), the enkephalins and somatostatin (SRIF) were measured by radioimmunoassay. Blood pressure was significantly elevated in both groups as compared to their controls. Marked changes in central neural peptides were observed in the SHR, while no differences were seen in DOCA/salt hypertension. Hypothalamic vasopressin, oxytocin, LHRH and SRIF were significantly decreased. In the posterior pituitary, enkephalins were increased twofold in the SHR. With regard to catecholamines, there was no change in hypothalamic content. However, a dramatic decrease in neurohypophyseal dopamine was observed in SHR. Plasma levels of vasopressin were significantly elevated in both types of hypertension while oxytocin was increased only in the DOCA/salt model. These result show that (1) a wide spectrum of neuroendocrine changes are associated with genetic hypertension, (2) there are CNS differences between DOCA/salt and spontaneous hypertension, and (3) central aminergic changes may be involved in th neuroendocrine alterations seen in the SHR.     

A redescription of the Middle Cambrian wormAmiskwia sagittiformis Walcott from the Burgess Shale of British Columbia

Amiskwia sagittiformis Walcott is redescribed on the basis of the five available specimens. The dorsoventrally compressed body consists of a head bearing a pair of prominent tentacles and a trunk with lateral and caudal fins. A gut with subterminal openings, cerebral ganglia, nerve cords, blood vessels and muscles have been identified with varying degrees of confidence. An active pelagic mode of life is considered probable. The rejection by earlier workers of this worm from the arrow-worms (Chaetognatha) is confirmed, but their identification of it as a nemertean (Nemertea) cannot be supported owing to the absence of critical data. The systematic position ofA. sagittiformis remains unresolved.     

6-Hydroxydopamine produces a weight increase in toads

A large increase in body weight occurred after injection of 6-hydroxydopamine (6-OHDA, 100 mg kg-1) into the iliac lymph sac of toads. The body weight increase was apparently due to retention of fluid and only occurred when toads could not avoid contact of their ventral skin with water. Lower doses of 6-OHDA (25 or 50 mg kg-1) did not cause a weight increase although they were sufficient to eliminate fluorescence from peripheral adrenergic nerves. A peripheral injection of 6-OHDA did not affect the appearance of central aminergic nerves. Removal of the pituitary and median eminence did not affect the weight increase. Although the primary action of 6-OHDA in upsetting water balance in toads has not been revealed by this study, it is clearly not related to the chemical sympathectomy of adrenergic nerves.