Narrow- and Broad-Host-Range Symbiotic Plasmids of Rhizobium spp. Strains That Nodulate Phaseolus vulgaris

Agrobacterium transconjugants containing symbiotic plasmids from different Rhizobium spp. strains that nodulate Phaseolus vulgaris were obtained. All transconjugants conserved the parental nodulation host range. Symbiotic (Sym) plasmids of Rhizobium strains isolated originally from P. vulgaris nodules, which had a broad nodulation host range, and single-copy nitrogenase genes conferred a Fix⁺ phenotype to the Agrobacterium transconjugants. A Fix⁻ phenotype was obtained with Sym plasmids of strains isolated from P. vulgaris nodules that had a narrow host range and reiterated nif genes, as well as with Sym plasmids of strains isolated from other legumes that presented single nif genes and a broad nodulation host range. This indicates that different types of Sym plasmids can confer the ability to establish an effective symbiosis with P. vulgaris.     

Benzo[a]pyrene metabolism and induction of enzyme-altered foci in regenerating rat liver

The metabolism of benzo[a]pyrene (BP) in regenerating rat liver and the induction of enzyme-altered foci (EAF) in the liver of partially hepatectomized rats, treated with BP and promoted with 2-acetylaminofluorene (2-AAF)/CCl4 was investigated. The aim was to examine factors that might be of importance for the tumorigenicity of BP in the regenerating rat liver, such as cytochrome P-450 activity and glutathione levels. In regenerating rat liver, obtained 18 h after partial hepatectomy (PH), the amount of microsomal cytochrome P-450 was reduced by 20% whereas the level of glutathione was elevated by 15% and the cytosolic glutathione transferase activity towards chlorodinitrobenzene and (+/-)-7 beta,8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydro-BP (BPDE) was unaffected. Microsomes from these animals had a reduced capacity to activate (-)-trans-7,8-dihydroxy-7,8-dihydro-BP (BPD) to DNA-binding products but the pattern of BP metabolites was similar to that observed with control rat liver microsomes. Treatment of rats with 3-methylcholanthrene (MC, 50 mg/kg body wt.) increased cytochrome P-450 levels and glutathione transferase activity towards both substrates. Regenerating livers from these animals retained their cytochrome P-450 level and enzymatic activity towards BP and BPD. Regenerating rat liver microsomes from MC-treated animals were about 35 times more efficient in activating BPD than microsomes from uninduced, partially hepatectomized animals. Intraperitoneal administration of BP (50 mg/kg body wt.) 18 h after PH induced EAF in rats subsequently promoted with 2-AAF/CCl4. Pretreatment of rats with MC 66 h before PH and 84 h before BP administration, increased the number of EAF. In accordance with results by Tsuda et al. (Cancer Res., 40 (1980) 1157-1164), these studies demonstrate that BP is tumorigenic in regenerating rat liver, despite a reduced ability of the liver to activate this compound. Furthermore, MC, an inducer of certain cytochrome P-450 species ("aryl hydrocarbon hydroxylase"), potentiates the effect of BP.     

Cardiovascular responses to intrathecal administration of arginine vasopressin in rats

Arginine vasopressin (AVP) has been localized in numerous extrahypothalamic brain regions and in the spinal cord. The results of intracerebroventricular AVP injections and microinjection of AVP into the brain stem suggest that this peptide, acting centrally at higher levels, may influence cardiovascular function. No function for the AVP occurring at spinal levels has been reported. In this study we report that AVP, in picomole quantities, increased arterial blood pressure and integrated heart rate in a dose-dependent manner following intrathecal application to the thoracic region in the rat. This response was not blocked by intravenous administration of the AVP antagonist d(CH₂)₅-d-Tyr-VAVP. These results suggest that AVP, acting within the spinal cord, may alter neural outflow regulating blood pressure and heart rate.     

Management of a harem breeding colony of rhesus monkeys to reduce trauma-related morbidity and mortality

A management procedure was developed for a harem breeding colony of rhesus monkeys to reduce trauma-related injuries and deaths resulting from the periodic removal of pregnant monkeys for research and their subsequent return to the population. Lower morbidity and mortality rates, a reduced mean conception interval, and a higher mean conception rate occurred when monkeys were maintained in permanent harems to which returning females were reintroduced compared to new social groups formed from aggregates of unfamiliar animals.     

Permeability of the boundary layers of Bdellovibrio bacteriovorus 109J and its bdelloplasts to small hydrophilic molecules.

Measurements of the sucrose-permeable and -impermeable volumes during Bdellovibrio bacteriovorus attack on Escherichia coli or Pseudomonas putida showed that the volume of the bdelloplast increased over that of the substrate cell. Although the pattern of the increase differed with the two organisms, the volumes reached maximum at about 60 min into the bdellovibrio growth cycle. By this time, the cytoplasmic membranes of the attacked cells were completely permeable to sucrose. The kinetics of increase in sucrosepermeable volumes were similar to the kinetics of attachment and penetration (Varon and Shilo, J. Bacteriol. 95:744-753, 1968). These data show that the original cytoplasmic and periplasmic compartmentalization of the substrate cell ceases to exist with respect to small hydrophilic molecules during bdellovibrio attack. In contrast, the effective pore size of the outer membrane of the substrate cell to small oligosaccharides remains unaltered during bdelloplast formation as was shown by direct measurements of its exclusion limits. The major porin protein of E. coli, OmpF, was recoverable from the bdelloplast outer membrane fraction until the onset of lysis. The Braun lipoprotein was removed from the bdelloplast wall early, and OmpA was lost in the terminal part of the bdellovibrio growth cycle.     

High affinity, calcium-stimulated adenosine triphosphatase activity in the particulate fraction of rat pancreatic acini

Adenosine triphosphatase activity which is Mg2+-dependent and stimulated by submicromolar concentrations of Ca2+ (as Ca . ATP) was identified in the total particulate fraction of rat pancreatic acini. Half-maximal activity (V0.5) is obtained at 100.1 +/- 6 nM Ca . ATP with a Hill coefficient of 2.2 +/- 0.1 (mean +/- S.E.; n = 4). Maximal activity was 75 +/- 19 pmol of Pi released from ATP minute-1 microgram of membrane protein-1 (mean +/- S.E.; n = 7). High affinity Ca2+-ATPase activity was unaffected by ouabain, Na+, K+, La3+, and added calmodulin. Activity was slightly reduced by ruthenium red (0.1 mM) and by oligomycin (80 micrograms/ml) but was reduced almost 50% by the phenothiazine derivative fluphenazine in a dose-related and Ca2+-dependent manner. Hydrolysis of p-nitrophenyl phosphate was 9% of the rate of ATP hydrolysis and was independent of Ca2+ concentration. However, ADP, GTP, UTP, and ITP were hydrolyzed at 76-93% the rate that ATP was hydrolyzed with V0.5 values and Hill coefficients similar to those of Ca . ATP. We conclude that rat pancreatic acini contain an enzyme for active Ca2+ translocation: ATPase activity that is Mg2+-dependent and stimulated by submicromolar concentrations of Ca . ATP. Substrate hydrolysis appears to involve positive cooperative interactions of multiple ligand-binding sites and may be regulated in part by calmodulin.