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.     

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.     

Factors affecting the reproductive success of the crab spider Misumenoides formosipes: the covariance between juvenile and adult traits

Summary To examine the importance of covariance between stages in traits related to foraging, we quantified the relationships between reproductive success and sizerelated variability in weight gain in juvenile and adult instars of the crab spider Misumenoides formosipes (Araneae: Thomisidae). Prereproductive weight and fecundity are both highly correlated with carapace width, a linear measure of size which does not change within an instar. In field populations, adult females with larger carapaces gain more weight and are more likely to reproduce than females with smaller carapaces. The growth rate of spiders fed ad libitum in the laboratory is unrelated to size, suggesting that size-related differences in the field are due to variation in prey-capture success. Adult females with a carapace width less than 3.4 mm comprised 22% of the population, but were never found to reproduce. Of the individuals that did reproduce, a 17% increase in carapace width resulted in a 100% increase in fecundity. Juvenile stages must be examined to understand adult foraging and reproductive success, because the net weight gained by juvenile instars determines adult size. The final weight gained by spiders in the antepenultimate and penultimate instars explained nearly all the variation in carapace width in the penultimate and adult instars, respectively. We found that constraints on foraging in late juvenile stages are different from the adult stage. Penultimate foraging behavior differs from that of adults, because of constraints on foraging in the period preceding ecdysis. Additionally, in both late juvenile instars, carapace width had little or no effect on the final weight gained within the instar suggesting that factors that affect foraging are different between the juvenile and adult stages. These analyses stress the fact that to fully understand the effects of foraging on reproductive success, we must examine stage-specific constraints throughout an organism's life history.     

Using replicate observations in observer agreement studies with binary assessments.

By introducing replicate observations into observer agreement studies, one can obtain better measures of observer agreement than heretofore possible. New methodology based on the analysis of latent variables allows a separation of within- and between-observer variation for binary measures of assessment among pairs of observers. Maximum likelihood estimation and hypothesis testing are discussed. The methodology is illustrated using data on the assessment of dysplasia by pathologists.     

Preliminary results from the self-regulatory treatment of high-medication-consumption headache

Data are presented from a prospective clinical replication series of ten consecutive high-medication headache patients who presented for nondrug treatment of their headaches. For the first eight, an attempt was made to withdraw the patients from medication, with the assistance of relaxation training, prior to entering a comprehensive self-regulatory treatment program. For the last two, drug withdrawal accompanied the treatment. Six of the ten patients showed clinically significant reductions in headache activity, which held up over follow-ups of up to 12 months. Psychological tests provide some discrimination between success and failures.This research was supported in part by a grant from NINDS, No. NS-23340. Appreciation is expressed to Dr. Kenneth A. Appelbaum and Ms. Denise Michultka for their roles in this study.     

Transforming growth factor-beta: Its effect on phenotype reexpression by dedifferentiated chondrocytes in the presence and absence of osteogenin

Summary The single and combined actions of transforming growth factor (TGF)-beta and osteogenin were evaluated with regard to induction of colony formation and reexpression of the differentiated phenotype by dedifferentiated rabbit articular chondrocytes in soft agarose under serum-free conditions. TGF-beta alone did not promote colony formation and induced accumulation of proteoglycans and type II collagen at significantly lower levels than those induced by osteogenin. Although synergism between these two growth factors occurred with respect to the induction of colony formation, their joint action on reexpression of the differentiated phenotype was additive. Complex interactions between the two growth factors may explain the latter phenomenon.