Simultaneous measurement of O2 radicals and pulmonary vascular reactivity in rat lung

The role of endogenous radicals in the regulation of pulmonary vascular tone was evaluated by simultaneous measurement of pulmonary artery pressure and lung radical levels during exposure of isolated rat lungs to varying inspired O2 concentrations (0-95%) and angiotensin II. Lung radical levels, measured "on-line" using luminol and lucigenin-enhanced chemiluminescence, decreased in proportion to the degree of alveolar hypoxia. Radical levels fell during hypoxia before the onset of pulmonary vasoconstriction and promptly returned to basal levels with restoration of normoxic ventilation. Mild alveolar hypoxia (10% O2), which failed to decrease chemiluminescence, did not trigger pulmonary vasoconstriction. Although chemiluminescence tended to decrease more as the hypoxic response strengthened, there was not a simple correlation between the magnitude of the change in chemiluminescence induced by hypoxia and the strength of the hypoxic pressor response. Normoxic chemiluminescence was largely inhibited by superoxide dismutase but not catalase. Superoxide dismutase also increased normoxic pulmonary vascular tone and the strength of the pressor response to hypoxia and angiotensin II. Thus the predominant activated O2 species in the lung, during normoxia, was the superoxide anion or a closely related substance. Alteration of endogenous radical levels can result in changes in vascular tone. It remains uncertain whether the decrease in lung radical production during hypoxia caused pulmonary vasoconstriction or was merely associated with hypoxic ventilation.     

Muscle fibre types and metabolism in post-larval and adult stages of notothenioid fish

Summary A histochemical study was carried out on muscle fibre types in the myotomes of post-larval and adult stages of seven species of notothenioid fish. There was little interspecific variation in the distribution of muscle fibre types in post-larvae. Slow fibres (diameter range 15–60 m) which stained darkly for succinic dehydrogenase activity (SDHase) formed a superficial layer 1–2 fibres thick around the entire lateral surface of the trunk. In all species a narrow band of very small diameter fibres (diameter range 5–62 m), with only weak staining activity, occurred between the skin and slow fibre layer. These have the characteristics of tonic fibres found in other teleosts. The remainder of the myotome was composed of fast muscle fibres (diameter range 9–75 m), which stain weakly for SDHase, -glycerophosphate dehydrogenase, glycogen and lipid. Slow muscle fibres were only a minor component of the trunk muscles of adult stages of the pelagic species Champsocephalus gunnari and Pseudochaenichthys georgianus, consistent with a reliance on pectoral fin swimming during sustained activity. Of the other species examined only Psilodraco breviceps and Notothenia gibberifrons had more than a few percent of slow muscle in the trunk (20%–30% in posterior myotomes), suggesting a greater involvement of sub-carangiform swimming at cruising speeds. The ultrastructure of slow fibres from the pectoral fin adductor and myotomal muscles of a haemoglobinless (P. georgianus) and red-blooded species (P. breviceps), both active swimmers, were compared. Fibres contained loosely packed, and regularly shaped myofibrils numerous mitochondria, glycogen granules and occasional lipid droplets. Mitochondria occupied >50% of fibre volume in the haemoglobinless species P. georgianus, each myofibril was surrounded by one or more mitochondria with densely packed cristae. No significant differences, however, were found in mean diameter between fibres from red-blooded and haemoglobinless species. The activities of key enzymes of energy metabolism were determined in the slow (pectoral) and fast (myotomal) muscles of N. gibberifrons. In contrast to other demersal Antarctic fish examined, much higher glycolytic activities were found in fast muscle fibres, probably reflecting greater endurance during burst swimming.     

Stabilization of a HemA-LacZ hybrid protein against proteolysis during carbon starvation in atp mutants of Salmonella typhimurium.

Transposon insertions that stabilize the beta-galactosidase activity of a HemA-LacZ hybrid protein following carbon starvation were mapped to the atp operon of Salmonella typhimurium. This effect is similar to that seen with nuo mutants defective in the energy-conserving type I NADH dehydrogenase. Insertions in several other genes, including such highly pleiotropic mutants as rpoS, polA, and hfq, were isolated with the same phenotypic screen, but they do not affect the beta-galactosidase activity of HemA-LacZ. All of these mutants act indirectly to alter the colony color of many different fusion strains on indicator plates.     

Media alternatives for the collection, culture and freezing of mouse and cattle embryos

The replacement of biological products in media for the collection, culture and freezing of mammalian embryos was studied. To test the hypothesis that chemically defined surfactants can replace bovine serum albumin (BSA) or serum in embryo media, morula-stage mouse and cattle embryos were collected, cultured, and/or frozen in the surfactant compound, VF5. Collection efficiency of mouse and cattle embryos did not differ whether the medium contained serum or surfactant. In addition, morula-stage mouse and cattle embryos developed and hatched at similar rates in culture media containing either BSA or surfactant. Although the freeze/thaw survival and development in culture of bovine embryos was not significantly different in any of the media, there was a significantly lower hatching rate of mouse embryos frozen with serum or surfactant than with cryoprotectant alone or with cryoprotectant plus albumin-free serum. However, the absence of serum or surfactant in embryo freezing media resulted in embryo loss, presumably due to stickiness. The data suggest that serum can be replaced by a chemically defined surfactant in mouse and cattle embryo transfer systems for the collection, culturing and freezing of embryos. It is likely that the beneficial effects of serum are due to its surfactant properties.     

The isolation of Ant1, a transposable element from Aspergillus niger

A transposable element has been isolated from the industrially important fungus Aspergillus niger (strain N402). The element was identified as an insertion sequence within the coding region of the nitrate reductase gene. It had inserted at a TA site and appeared to have duplicated the target site upon insertion. The isolated element was found to be 4798 by in length and contained 37-bp inverted, imperfect, terminal repeats (ITRs). The sequence of the central region of the element revealed an open reading frame (designated ORF1) which showed similarity, at the amino acid level, to the transposase of the Tc1/mariner class of DNA transposons. Another sequence within the central region of the element showed similarity to the 3 coding and downstream untranslated region of the amyA gene of A. niger. Sequence homology and structural features indicate that this element, which has been named Ant1 (A. niger transposon 1), is related to the Tc1/mariner group of DNA transposons. Ant1 is apparently present as a single copy in strain N402 of A. niger.     

Isolation of Race-and Cultivar-Specific Elicitors from Intercellular Fluids of Compatible Interactions of Pseudomonas syringae pv. pisi and Pea

Intercellular fluids obtained by an in vacuo infiltration technique from compatible race-cultivar interactions of five races of Pseudomonas syringae pv. pisi and pea induced extensive light brown necrotic (hypersensitive type of) lesions in resistant but not susceptible cultivars. In susceptible cultivars the intercellular fluids induced extetensive water soaking symptoms. The intercellular fluids elicited intermediate reactions in pea cultivars of moderate resistance. The intensity of the light brown necrotic reactions in pea appears to be positively correlated with the degree of resistance.     

Hydrogen-using bacteria in a methanogenic acetate enrichment culture

A rcher , D.B. 1984. Hydrogen-using bacteria in a methanogenic acetate enrichment culture. Journal of Applied Bacteriology 56 , 125–129.
In a study of the anaerobic utilization of acetate, an enrichment culture of sewage sludge organisms was initiated with calcium acetate as the sole carbon and energy source. A mixed bacterial population became established from which 14 anaerobic species were isolated. Two of the isolates were methanogenic bacteria but only one of these, Methanosarcina barkeri , utilised acetate as an energy source in axenic culture. The other methanogenic isolate, a Methanobacterium sp., utilised H₂/CO₂ but not acetate. A third methanogen, which was morphologically identical to Methanothrix soehngenii , was detected in the enrichment but was not obtained in monoculture. 2-Bromoethanesulphonate, a specific inhibitor of methanogenesis. completely inhibited the enrichment at a concentration of 10 μmol/1. Addition of H₂ formate or methanol to the enrichment did not affect the rate of methanogenesis. An H₂-utilizing Desulfovibrio sp. was also isolated from the enrichment.     

Thermodynamics of antibody-antigen reactions. 2. The binding of bivalent synthetic random coil antigens to antibodies having different antigen precipitating properties

The objects of this study were the equine IgG and IgG(T) classes of antibodies with immunologic specificity for the dinitrophenyl group and bivalent antigens consisting of linear poly(ethylene glycol) polymers which terminated at both ends in dinitrophenyl groups. Complex formation between antibodies of both classes and one of several sharp fractions of antigen having number average molecular weights in the range 25 000 to 75 000 were studied by measuring the light scattered from solutions containing equimolar amounts (approximately 5 x 10(-6) mol/L) of one of the antibodies and one size fraction of antigen, and variable amounts of monovalent hapten. The data were analyzed in the context of a model that accounted for the formation of linear and cyclic complexes of all extents of aggregation. Two parameters in addition to the intrinsic antibody-dinitrophenyl group association constant were found to be necessary in the assumed equilibrium model to account for the behavior of the system. One of these accounted for the looses in configuration entropy that resulted when a random-coil polymer became bound at one end to a space-occupying antibody. The other was a ring closure factor for the formation of cyclic complexes. Ring closure factors for the formation of larger cyclic complexes (present in only small amounts under the conditions studied) were related to the ring closure factor for the formation of the smallest, which was found to increase as antigen size decreased, and for each antigen size to be consistently higher for IgG(T) antibody than for IgG antibody. Comparison of the theoretically estimated values of the two parameters within their measured values indicated that the average conformation of IgG antibodies in solution is open ("T" shaped) but the average inter-Fab are angle in IgG(T) antibodies is approximately 60 degrees or less.