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Biomedical subjects

S A Russell

Publications and source records attributed to S A Russell.

46 records · Page 3Linked to original sources
PubMed1976

Nitrogen fixation associated with grasses in Oregon.

Nitrogen fixation associated with both natural grasslands and grain crops of Oregon was studied using the acetylene-reduction assay. A number of the grasses collected has some acetylene-reducing activity. Agrostis tenuis Sibth. had substantially greater activity than any of the other species, with a mean rate estimated at 37 g N2 fixed per hectare per day. Assuming 100 days of activity, about 3 kg of N2 would be fixed per hectare per year. This quantity of nitrogen may be important in the maintenance of this species under natural conditions. Nitrogen-fixing microorganisms were isolated from the root surfaces of some of the grasses. Cultures of Bacillus macerans, Bacillus polymyxa, and Enterobacter cloacoa were isolated from wheat roots as were two cultures which have not been assigned a specific taxonomic classification. Strains of N2-fixing Bacillus species and Gram-negative aerobic bacteria were isolated from Festuca and Agrostis.

Acetylene↗
PubMed1975

Energy State and Dinitrogen Fixation in Soybean Nodules of Dark-grown Plants.

Dark treatment of 25-day-old greenhouse-grown plants of inoculated soybean (Glycine max var. Chippewa) for 1 day reduced ATP by 70%, sucrose by 60%, total adenosine phosphates by 60%, ATP/ADP ratio by 55%, nitrogenase activity by 50%, and energy charge by 15% in nodules. The close correlation between nitrogenase activity and these energy parameters indicates that they may play a major role in regulating dinitrogen fixation in the symbiotic system.

Journal Article↗
PubMed1973

Reduction of acetylene and hydrazine with a molybdenum-glutathione complex.

Crystalline preparations of a molybdenum-glutathione complex catalyze the reduction of acetylene to ethylene in the presence of borohydride. The reaction proceeds at rates up to 6 mol of C(2)H(2) produced per min per mol of bound Mo, which is 4% of the activity of a quantity of nitrogenase with an equivalent amount of Mo. The activity of the complex is enhanced 100-fold by ATP, but the addition of ADP has no effect. Stimulation in activity by GTP is about the same as that by ATP, and the effects of CTP or UTP are considerably less. Inhibition of acetylene-reduction activity by the addition of 32 mM orthophosphate was 14%, by 32 mM pyrophosphate 62%, by 0.2 atm of O(2) 65%, and by 0.5 atm of CO 12%; 0.5 atm of H(2) had no effect. The molybdenum-glutathione complex also catalyzes the reduction of hydrazine to ammonia in a reaction that is dependent upon borohydride. The reaction is enhanced about 7-fold by ATP and proceeds at a rate of 2 mol of NH(3) produced per min per mol of bound Mo.

Journal Article↗
PubMed1970

Purification and some properties of a non-haem iron protein from the bacteroids of soya-bean (Glycine max Merr) nodules.

A non-haem iron protein was isolated from an extract of soya-bean nodule bacteroids by a procedure including protamine sulphate and heat precipitation followed by chromatography on DEAE-cellulose. The purified protein contains non-haem iron and acid-labile sulphur and exhibits a spectrum with a rather broad absorption shoulder in the region 380-440nm and a more prominent peak at 280nm. From sedimentation-velocity measurements an apparent s(20,w) value of 1.3S was calculated. The protein functions as an electron carrier between the reducing system of illuminated chloroplast fragments and nitrogenase from nodule bacteroids, but it failed to function as a cofactor for the photochemical reduction of NADP in the presence of spinach chloroplasts. Also, it is inactive as a cofactor in the enzymic degradation of pyruvate to acetyl phosphate and CO(2) in the presence of a ferredoxin-free extract of Clostridium pasteurianum. Repeated freezing, storage and thawing of the non-haem iron protein resulted in a marked loss of activity in the photochemical acetylene-reduction assay. A major portion of the activity that was lost was restored as a result of treatment with sodium sulphide, mercaptoethanol and ferrous ammonium sulphate.

Bacterial Proteins↗
PubMed1969

B12 coenzyme-dependent ribonucleotide reductase in Rhizobium species and the effects of cobalt deficiency on the activity of the enzyme.

This investigation revealed that the ribonucleotide reductases in extracts of Rhizobium leguminosarum, R. trifolii, R. phaseoli, R. japonicum, and R. meliloti 3DOal (ineffective in nitrogen fixation) are dependent upon B(12) coenzyme for activity. Rhizobium and certain Lactobacillus species are the only two groups of organisms known to contain B(12) coenzyme-dependent ribonucleotide reductases. Extracts of cobalt-deficient R. meliloti cells assayed in the presence of optimum B(12) coenzyme showed a 5- to 10-fold greater ribonucleotide reductase activity than comparable extracts from cells grown on a complete medium. Furthermore, cobalt-deficient cells were abnormally elongated and contained reduced contents of deoxyribonucleic acid. The addition of purified deoxyribonucleosides to cobalt-deficient cultures of R. meliloti failed to alleviate deficiency symptoms.

Alcohol Oxidoreductases↗
PubMed1968

Purification and Some Properties of the Nitrogenase From Soybean (Glycine max Merr.) Nodules.

The nitrogenase system in cell-free extracts of soybean nodule bacteroids was fractionated into 2 components by use of protamine sulfate or polypropylene glycol precipitation followed by chromatography on DEAE-cellulose. Iron and molybdenum were concentrated in 1 fraction and iron in the other. Combination of fractions resulted in a striking stimulation in activity relative to the activity of individual fractions. The effect of different proportions of the 2 fractions on specific activities was studied. The ratios of the rates of reduction of acetylene and N(2) by extracts or fractions of different purities were relatively constant. Extracts or fractions retained most of their nitrogenase activities when stored in liquid N(2).

Journal Article↗
PubMedDate not supplied

Attending physician coverage in a teaching hospital's emergency department: effect on malpractice.

It seems self-evident that the establishment of 24-hour per day attending physician coverage in a teaching hospital's emergency department would enhance risk management. However, prior to this study, little investigation had been done to corroborate the effects of full-time emergency department attending physician coverage. In a retrospective study from a large teaching hospital's emergency department, malpractice claims filed for 1985-1987 (part-time attending physician coverage) were analyzed and compared to those for 1987-1989 (full-time attending physician coverage). A total of 98 claims were filed; these data were derived from 466,862 patient visits. Attending physician presence increased from 6000 hours per year in 1985-1987 to 26,280 hours per year in 1987-1989. There was an 18.5% decrease in claims filed, and a 70.1% decrease in disbursements for the first 2 years after the introduction of full-time attending physician coverage as compared with the preceding 2 years. These findings suggest that full-time attending physician coverage in the emergency department is associated with improved risk management.

Emergency Service, Hospital↗
PubMedDate not supplied

Skeletal abnormalities in Meckel syndrome.

Meckel syndrome is an autosomal recessive condition with a wide phenotypic variation. The most consistent features are cystic kidneys and intrahepatic bile duct anomalies, frequently accompanied by central nervous system (CNS) malformations and polydactyly. Approximately one sixth of all cases also show skeletal anomalies. We present two cases, siblings born to a consanguineous couple, in whom there was a striking curvature and shortening of the long bones in addition to cystic kidneys, CNS abnormalities, and polydactyly. Histological examination of the long bones in the second affected sibling showed mid-diaphysial ectopic cartilaginous growth plates differentiating the long bone changes from other skeletal dysplasias with similar radiological features.

Bile Ducts, Intrahepatic↗