Search PubMed⌕ Search

Biomedical subjects

R L Warner

Publications and source records attributed to R L Warner.

72 records · Page 4Linked to original sources
PubMed1982

Pyridine nucleotide specificity of barley nitrate reductase.

NADPH nitrate reductase activity in higher plants has been attributed to the presence of NAD(P)H bispecific nitrate reductases and to the presence of phosphatases capable of hydrolyzing NADPH to NADH. To determine which of these conditions exist in barley (Hordeum vulgare L. cv. Steptoe), we characterized the NADH and NADPH nitrate reductase activities in crude and affinity-chromatography-purified enzyme preparations. The pH optima were 7.5 for NADH and 6 to 6.5 for the NADPH nitrate reductase activities. The ratio of NADPH to NADH nitrate reductase activities was much greater in crude extracts than it was in a purified enzyme preparation. However, this difference was eliminated when the NADPH assays were conducted in the presence of lactate dehydrogenase and pyruvate to eliminate NADH competitively. The addition of lactate dehydrogenase and pyruvate to NADPH nitrate reductase assay media eliminated 80 to 95% of the NADPH nitrate reductase activity in crude extracts. These results suggest that a substantial portion of the NADPH nitrate reductase activity in barley crude extracts results from enzyme(s) capable of converting NADPH to NADH. This conversion may be due to a phosphatase, since phosphate and fluoride inhibited NADPH nitrate reductase activity to a greater extent than the NADH activity. The NADPH activity of the purified nitrate reductase appears to be an inherent property of the barley enzyme, because it was not affected by lactate dehydrogenase and pyruvate. Furthermore, inorganic phosphate did not accumulate in the assay media, indicating that NADPH was not converted to NADH. The wild type barley nitrate reductase is a NADH-specific enzyme with a slight capacity to use NADPH.

Journal Article↗
PubMed1982

Characteristics of a Nitrate Reductase in a Barley Mutant Deficient in NADH Nitrate Reductase.

A barley (Hordeum vulgare L.) mutant, nar1a (formerly Az12), deficient in NADH nitrate reductase activity is, nevertheless, capable of growth with nitrate as the sole nitrogen source. In an attempt to identify the mechanism(s) of nitrate reduction in the mutant, nitrate reductase from nar1a was characterized to determine whether the residual activity is due to a leaky mutation or to the presence of a second nitrate reductase. The results obtained indicate that the nitrate reductase in nar1a differs from the wild-type enzyme in several important aspects. The pH optima for both the NADH and the NADPH nitrate reductase activities from nar1a were approximately pH 7.7, which is slightly greater than the pH 7.5 optimum for the NADH activity and considerably greater than the pH 6.0 to 6.5 optimum for the NADPH activity of the wild-type enzyme. The nitrate reductase from nar1a exhibits greater NADPH than NADH activity and has apparent K(m) values for nitrate and NADH that are approximately 10 times greater than those of the wild-type enzyme. The nar1a nitrate reductase has apparent K(m) values of 170 micromolar for NADPH and 110 micromolar for NADH. NADPH, but not NADH, inhibited the enzyme at concentrations greater than 50 micromolar.Unlike that of the wild-type, the nitrate reductase from nar1a did not bind to blue dextran-Sepharose. The nar1a enzyme did bind to Affi Gel Blue, but recoveries were low. The NADH and NADPH nitrate reductase activities of nar1a were not separated by affinity chromatography. The nitrate reductase in nar1a is a different enzyme than the wild-type NADH nitrate reductase and appears to be a NAD(P)H-bispecific enzyme.

Journal Article↗
PubMed1981

Nitrate Utilization by Nitrate Reductase-deficient Barley Mutants.

Two nitrate reductase-deficient barley mutants were studied for growth on nitrate and ammonium sources of nitrogen and for resistance to chlorate. Although nitrate reductase-deficient mutants in some species are chlorate-resistant (unable to reduce chlorate to chlorite), the barley mutants used in these studies when grown on nitrate and treated with chlorate were only slightly more resistant to chlorate than the control. When grown to maturity on vermiculite supplemented with either nitrate or ammonium nutrient solutions, the mutants produced as much dry weight and reduced nitrogen per plant as the control. The in vivo and in vitro nitrate reductase activities in the roots and shoots of the mutants grown on nitrate were consistently less than 10% of the control. To avoid the possibility that the mutants received reduced nitrogen from microbial sources, excised embryos were cultured under sterile conditions. Again the mutants were capable of growth and reduced nitrogen accumulation with nitrate as the sole source of nitrogen. In spite of the low apparent nitrate reductase activity, the nitrate reductase-deficient mutants are capable of substantial nitrate reduction.

Journal Article↗
PubMed1980

The effect of adrenal glands on ovulation in Japanese quail (Coturnix coturnix japonica).

Adrenal involvement in ovulation has been demonstrated for several mammalian species and has recently come under scrutiny in birds. Complete adrenalectomy causes severe system imbalances; therefore, it was decided to evaluate the effect of unilateral adrenalectomy on ovulation in coturnix. Since no mortality occurred among 59 hens recovering from anesthesia following hemiadrenalectomy, systemic imbalances appeared to be tolerable. Hen-day egg production of adrenalectomized hens was significantly (P greater than .05) lower than that of sham operated and unoperated controls. Adrenalectomized birds exhibited their lowest rate of lay (18.7%) on the second day following treatment. The amount of time that hemiadrenalectomy preceded oviposition on the day of treatment influenced the occurrence of an ovulation. When adrenalectomy occurred 5 to 7.5 hr prior to oviposition, 86.7% of the birds failed to ovulate that day, compared with 27.8% of controls. This difference was highly significant. When adrenalectomy occurred less than 2.5 hr prior to oviposition, 92.3% of the birds ovulated on that day, but failed to ovulate on the next day. Subsequent to the period of adrenal insufficiency, hens resumed normal egg production. It was concluded that the adrenals directly influence daily ovulations in Coturnix, exerting an effect on hormonal events leading to ovulation.

Adrenal Glands↗
PubMed1977

Effects of perinatal estrogen on mouse mammary response to corticoids in vitro.

Effects of three adrenal corticoids on in vitro mammary differentiation were compared in neonatally estrogenized (E) and uninjected control (N) BALB/c Crgl female mice. E mice were injected with 10 microgram of 17 beta-estradiol on each of the first 5 days of life. At 4 weeks of age, all mice were pretreated with 1 microgram 17beta-estradiol and 1 mg progesterone for 9 consecutive days. Groups of 10 or more entire mammary glands then were organ-cultured for 5 days at 37 degree C on chemically defined medium in 95% O2/5% CO2 with various combinations of hormones: mammotropin (M), somatotropin (S), insulin (I), thyroxine (T); and corticosterone (B), aldosterone (A), or cortisol (F). Differentiation followed a quantitative pattern of MSIT less than BMSIT less than AMSIT less than FMSIT for both E and N tissues. E tissues formed more alveoli and more lobules in vitro than N tissues with each of the corticoids tested. These findings may have pathologic significance.

Adrenal Cortex Hormones↗
PubMed1975

Effects of age at carcinogen administration and exposure as neonates to 17beta-estradiol on subsequent gland-pair distribution of murine mammary dysplasias.

The distribution of mammary dysplasias in 7,12-dimethylbenz[a]anthracene (DMBA)-treated BALB/c female mice differed with respect to the position of mammary gland pairs. The time of life when DMBA was given affected the incidence of lesions more than it did their distribution. Giving neonates injections of 49 mug 17beta-estradiol for the first 5 days of life resulted in increased numbers of dysplasia after DMBA administration at certain ages, but there was no consistent effect on gland-pair distribution of dysplasias at those ages. Possible reasons for differential gland-pair growth and occurrence of dysplasia are discussed.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1975

Effects of exposure of neonatal mice to 17beta-estradiol on subsequent age-incidence and morphology of carcinogen-induced mammary dysplasia.

Mice exposed to estrogens as neonates developed more mammary dysplasias and had different morphologic types of dysplasias than did normal animals when both groups were exposed to a carcinogen: 1) before puberty, 2) during active mammary growth, 3) or at 6 months of age (the time when spontaneous dysplasias begin to appear in normal animals). The relative percentages of various morphologic types of dysplasias differed in hosts that received different treatments. The significance for subsequent patterns of mammary disease caused by exposure of neonates to 17beta-estradiol was discussed.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1969

Inheritance of nitrate reductase activity in Zea mays L.

Since the F(1) hybrid (B14 x Oh43) had been shown to have a higher (heterotic) level of nitrate reductase activity than either inbred parent (B14 or Oh43), studies were undertaken to determine the mode of inheritance. Standard methods for determining Mendelian inheritance were used to study segregation for level of nitrate reductase activity of individual plants. The genetic material used was the inbreds B14 and Oh43, F(1), F(1) backcrossed to both parents, F(2), F(3), and F(4) generations of the cross B14 x Oh43. The plant material was grown in the field and in growth chambers. It was shown that the maize inbreds B14 and Oh43 differ at two loci that control the level of nitrate reductase activity. Each inbred is homozygous for a dominant or partially dominant allele at one locus and homozygous recessive at a second locus. The locus at which B14 carries a dominant allele carries the recessive allele in Oh43. Oh43 has both a higher in vivo rate of synthesis of nitrate reductase and higher in vivo and in vitro loss of enzyme activity (decay) than B14. Thus, the rates of both enzyme synthesis and decay are factors governing the level of nitrate reductase activity in corn. The data suggest that the heterotic level of nitrate reductase activity in the F(1) hybrid is the result of inheritance of qualities that gives it "intermediate" rates of enzyme synthesis and decay.

Crosses, Genetic↗
PubMedDate not supplied

Neutrophil depletion and chemokine response after liver ischemia and reperfusion.

Neutrophils play a major role in the hepatic microvasculature following liver ischemia and reperfusion (I/R). Leukocyte cytokine chemoattractants (chemokines) are produced by neutrophils and cause neutrophil activation in I/R injury. We examined the role of neutrophils in the production of chemokines in the liver and lung inflammatory response following liver I/R. C57BL/6 mice were subjected to partial liver ischemia for 90 min. Four groups of animals were included: sham group, sham group with neutrophil depletion, ischemic control group, and ischemic control with neutrophil depletion. We evaluated at 3 h liver injury measurements, serum macrophage inflammatory protein-2 (MIP-2) and macrophage inflammatory protein-1 alpha (MIP-1alpha) chemokines, liver and lung tissue myeloperoxidase (MPO), and liver and lung histology. Statistical analysis included analysis of variance (ANOVA), and Student-Newman-Keuls and Kruskal-Wallis multiple comparison Z-value tests. Ischemic controls showed a significant increase in liver enzyme levels along with statistically significant higher liver and lung MPO activity values than the rest of the other groups (p < .05). MIP-2 values were higher in the ischemic control group when compared to the ischemic neutrophil depleted group. MIP-1alpha levels showed opposite results, being significantly lower (p < .05) in the ischemic control as compared to the neutrophil-depleted group. Improved liver and lung histopathological features were observed in the ischemic neutrophil depleted group when compared to the ischemic control group. Our study confirmed the key role of neutrophils in liver I/R injury and appeared to suggest some relationship between neutrophils and the production of certain chemokines, such as MIP-1alpha, which had an inverse relationship in the absence of neutrophils. Further studies will confirm the validity of these preliminary observations.

Animals↗