The preparation of a sarcolemmal fraction from evacuated muscle slices

A novel procedure is described for preparing a plasma membrane fraction from skeletal muscle (i.e., sarcolemma). The procedure entails evacuating the myoplasm from muscle slices as a preliminary step to homogenization and fractionation. The evacuated muscle slices are composed of a stroma-containing sarcolemma, which is then homogenized and fractionated, utilizing a sequence of differential and discontinuous sucrose density gradient centrifugations. On the basis of electron microscopy, selective enzyme markers and α-bungarotoxin binding in innervated and denervated muscles, the fraction most enriched with sarcolemma is recovered from the 0.5/0.7 M interface of a discontinuous sucrose gradient.     

Cytochrome P-450 lowering effect of alkyl halides,correlation with decrease in arachidonic acid

Treatment of male rats with carbon tetrachloride, bromotrichloromethane, chloroform, 1,2-dibromoethane, 1-bromo-2-chloroethane, and 1,2-dibromo-3-chloropropane results in a decrease in cytochrome P-450 content and alterations in the relative content of fatty acids in hepatic microsomes. A high correlation was found between the loss of cytochrome P-450, the decrease in arachidonic acid (r=0.93), and the increases in linoleic (r=?0.91) and oleic acids (r=?0.89).     

Radiation activation of respiration inBacillus cereus T spores

The effects of gamma-irradiation on glucose oxidase activity were studied inBacillus cereus T spores. Radiation was found to activate oxidase in native spores. This activation was greatly enhanced when irradiated spores were subsequently heat-activated. Although activation by heat alone was 1.6 times that by radiation alone, the combined treatment with both radiation and heating resulted in a 12-fold enhancement of oxidase activity over that obtainable by optimum heat activation. Activation by combined treatment of gamma-rays and heat depended on the presence of exchangeable calcium during heating but not during irradiation.     

Anomalies physio-morphologiques de la souche virosée (Bali 1) d'Allomyces arbuscula

An escape reaction of the hyphae from virus-containing strain Bali 1 of A. arbuscula was detected when intra- and interspecific Allomyces cultures were opposed on solid media. Hyphae of this virus-containing strain proliferate into witch-broom structures only detectable on solid media in which bunches of rhizoid-like structures remain more superficial than those of the control cultures, suggesting that metabolism of the Bali 1 strain is altered into a more aerobic type.     

Distribution and properties of NADPH-linked aldehyde reductases from rat brain synaptosomes

Studies on the subcellular distribution of NADPH-linked aldehyde reductase from rat brain showed that 10% of the total reductase activity is located in the mitochondrial-synaptosomal fraction. There are differences in the percentages of reductase activity found in the synaptosomes compared to cytosol in various regions of the brain. The NADPH-linked aldehyde reductase from the synaptosomal fraction exhibited a nonlinear Lineweaver-Burk plot. This nonlinearity is due to the presence of two distinct aldehyde reductases, which can be distinguished by Michealis constants forp-nitrobenzaldehyde of 4.1×10^–5 M and 2.6×10^–6 M. The two NADPH-linked aldehyde reductases isolated from synaptosomes were further characterized according to pH optima, andK _i values for inhibition by barbiturates. In addition regional distributions for the two enzymes were determined. TheK _i values for pentobarbital for the highK _m enzyme and the lowK _m enzyme were estimated to be 2×10^–5 M and 6×10^–5 M, respectively. It was concluded from the above studies that the lowK _m reductase is probably responsible for 3,4-dihydroxyphenylglycoaldehyde (derived from norepinephrine) reduction in brain and a role of the highK _m enzyme for protection of neurons from high concentrations of chemically reactive aldehydes was proposed.This work was supported in part by Grants from the National Institute of Mental Health, MH 18948 from the University of Colorado Council on Research and Creative Work and by an MBS Program Grant #081-39.This work was performed in partial fulfillment of the requirements for the Ph. D. thesis.     

Location of Lyb-2 on mouse chromosome 4

TheLyb-2 locus responsible for the B-lymphocyte alloantigen system Lyb-2 is located on chromosome 4 at a distance of 20.6±4.9 map units fromPgm-2. A three-point cross indicated the orderLyb-2: Mup-1b Pgm-2.     

Separation of urine proteins on the anion-exchange resin mono QTM

Proteins excreted in urine due to renal failure were separated on Mono Q^TM, a new strong anion exchanger designed for fast high-resolution protein separations. The separation procedure was divided into two steps. The first step involved removal of low-molecular- weight substances by rapid desalting on a Sephadex G-25 Superfine column. In the second step, the total protein fraction (3–6 ml) was loaded onto the Mono Q column with the aid of a superloop. The proteins were adsorbed onto the top of the ion-exchanger column and gradually displaced by a combined pH and salt gradient in 40 min. The choice of ion exchanger and initial operating conditions were based on data obtained from electrophoretic titration curve experiments. Identification of separated proteins was achieved by fused rocket electrophoresis and sodium dodecyl sulphate-polyacrylamide gel electrophoresis, respectively.     

Increased Neopterin Levels in Brains of Patients with Human Immunodeficiency Virus Type 1 Infection

Postmortem levels of native neopterin (D-erythro-neopterin) were measured in cerebral cortical samples from 44 human immunodeficiency virus type 1-infected and eight uninfected, nonneurological control patients. Cerebral cortical gray and white matter neopterin levels for the controls ranged from 0.5 to 7.2 pmol/mg of protein in contrast to neopterin levels in brains of the virus-infected patients, which frequently were more than threefold and occasionally more than 30-fold higher than mean control levels. Cortical neopterin levels did not correlate with severity of the acquired immunodeficiency syndrome dementia complex, but subcortical levels correlated with the presence of active human immunodeficiency virus type 1 infection, as reflected by pathological evidence of multinucleated giant cell encephalitis. Evidence of opportunistic cytomegalovirus infections in approximately 25% of the human immunodeficiency virus type 1-infected patients was associated with enhanced levels of neopterin in frontal cortex.     

Effects of nitrogen limitation on species replacement dynamics during early secondary succession on a semiarid sagebrush site

Summary A soil nitrogen (N) availability gradient was induced on a disturbed sagebrush site in northwestern Colorado by fertilizing with nitrogen (high available N), applying sucrose (low available N), and applying neither nitrogen nor sucrose (control). Species composition was studied for 3 years. At the end of the study, N concentration of aboveground tissue of 3 major species was determined. The rate of species replacement was most rapid on plots receiving the sucrose treatment and was slowest on plots receiving the N treatment. Early-seral dominats had greater tissue N concentrations when availability of the resource was high but lower tissue N concentrations when available soil N became limited. Midseral dominants displayed the opposite pattern. These results suggest that the supply of available soil N, and therefore the dynamics of N incorporation in perennial plant tissue, is a primary mechanism in controlling the rate of secondary succession within this semiarid ecosystem.