Adrenoceptor regulation of canine skeletal muscle blood flow during carbon monoxide hypoxia.

We questioned whether carbon monoxide hypoxia (COH) would affect peripheral blood flow by neural activation of adrenoceptors to the extent we had found in other forms of hypoxia. We studied this problem in hindlimb muscles of four groups of anesthetized dogs (untreated, alpha 1-blocked, alpha 1 + alpha 2-blocked, and beta 2-blocked). Cardiac output increased, but hindlimb blood flow (QL) and resistance (RL) remained at prehypoxic levels during COH (O2 content reduced 50%) in untreated animals. When activity in the sciatic nerve was reversibly cold blocked, QL doubled and RL decreased 50%. These changes with nerve block were the same during COH, suggesting that neural activity to hindlimb vasculature was not increased by COH. In animals treated with phenoxybenzamine (primarily alpha 1-blocked), RL dropped (approximately 50%) during COH, an indication that catecholamines played a significant role in maintaining tone to skeletal muscle. Animals with both alpha 1 + alpha 2-adrenergic blockade (phenoxybenzamine and yohimbine added) did not survive COH. RL was higher in beta 2-block than in the untreated group during COH, but nerve cooling indicated that beta 2-adrenoceptor vasodilation was accomplished primarily by humoral means. The above findings demonstrated that adrenergic receptors were important in the regulation of QL and RL during COH, but they were not activated by sympathetic nerve stimulation to the limb muscles.     

Risk of Infection with Leishmania spp. in the Canine Population in the Netherlands

The dog is the main reservoir of Leishmania infantum, the causative agent of visceral leishmaniasis (VL) in humans in Southern Europe. In order to identify the risk of dogs from a Leishmania non-endemic area traveling to a Leishmania -endemic area becoming infected and the risk of transmitting infection to humans in non-endemic areas an investigation was performed, in which the results of a questionnaire were combined with the results of a serologic survey.     

Metabolism of phenols by Ochromonas danica

Abstract This study investigated the catabolic potential of a eukaryotic alga to degrade one of the most common organic pollutants, phenol. The alga, Ochromonas danica (993/28), was selected for study after screening for its heterotrophic capabilities. The catabolic versatility of the alga was elucidated by incubating with a variety of phenolic compounds. The alga removed phenol, all the cresol isomers and 3,4-xylenol from its incubation media, with phenol being removed more rapidly than any of its methylated homologues. Consequently, the alga was found to have a greater specificity for phenol than for o - or p -cresols. This study shows that O. danica could catabolize phenol and its methylated homologues.     

The effect of cross-links on the conformational dynamics of duplex DNA.

The base pair lifetimes and apparent dissociation constants of a 21 base DNA hairpin and an analog possessing a disulfide cross-link bridging the 3'- and 5'-terminal bases were determined by measuring imino proton exchange rates as a function of exchange catalyst concentration and temperature. A comparison of the lifetimes and apparent dissociation constants for corresponding base pairs of the two hairpins indicates that the cross-link neither increases the number of base pairs involved in fraying nor alters the lifetime, dissociation constant, or the opened structure from which exchange occurs for the base pairs that are not frayed. The cross-link does, however, stabilize the frayed penultimate base pair of the stem duplex. Significantly, it appears that the disulfide cross-link is more effective at preventing fraying of the penultimate base pair than is the 5 base hairpin loop. Because this disulfide cross-link can be incorporated site specifically, and does not adversely affect static or dynamic properties of DNA, it should prove very useful in studies of nucleic acid structure and function.     

Ribonucleic Acid Polymerase in Allomyces arbuscula

Three distinct species of ribonucleic acid (RNA) polymerase were resolved from Allomyces arbuscula by diethylaminoethyl-cellulose chromatography and characterized as to ionic strength and divalent cation preference. alpha-Amanitin specifically inhibited enzyme II; neither rifampin nor cycloheximide had any effect on the three enzymes. RNA polymerase was isolated from three stages of the diploid life cycle: the hyphal growth stage, mycelia in the process of forming sporangia, and the mitospores. The same three enzyme species could be resolved from each stage. Thus, there is no evidence from this work that RNA polymerase plays a major role in the control of development.