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Biomedical subjects

R A Scott

Publications and source records attributed to R A Scott.

At least 145 records · Page 8Linked to original sources
PubMed1985

Kinetics of dithionite reduction of the heme nonapeptide of cytochrome c.

The kinetics of dithionite reduction of the oxidized heme nonapeptide fragment of horse heart cytochrome c have been measured as a function of ionic strength at pH 7 and pH 9 by the stopped-flow technique. Dithionite concentration dependences indicate that the radical anion monomer, SO2-., is the active reductant. The pH 7 ionic strength dependence suggests that the heme peptide is reacting as a negatively charged molecule (its overall charge is calculated to be -1). Comparison of these results with the known rate of dithionite reduction of cytochrome c indicates that the heme nonapeptide has substantially greater inherent reactivity than cytochrome c, perhaps due to the greater accessibility of the heme.

Animals↗
PubMed1985

[4Fe-4S]-cluster-depleted Azotobacter vinelandii ferredoxin I: a new 3Fe iron-sulfur protein.

Fe(CN)6(-3) oxidation of the aerobically isolated 7Fe Azotobacter vinelandii ferredoxin I, (7Fe)FdI, is a degradative reaction. Destruction of the [4Fe-4S] cluster occurs first, followed by destruction of the [3Fe-3S] cluster. At a Fe(CN)6(-3)/(7Fe)FdI concentration ratio of 20, the product is a mixture of apoprotein and protein containing only a [3Fe-3S] cluster, (3Fe)FdI. This protein mixture, after partial purification, has been characterized by absorption, CD, magnetic CD, and EPR and Fe x-ray absorption spectroscopies. EPR and magnetic CD spectra provide strong evidence that the [3Fe-3S] cluster in (3Fe)FdI is essentially identical in structure to that in (7Fe)FdI. Analysis of the extended x-ray absorption fine structure (EXAFS) of (3Fe)FdI finds Fe scattering at an average Fe...Fe distance of approximately equal to 2.7 A. The structure of the oxidized [3Fe-3S] cluster in solutions of oxidized (3Fe)FdI, and, by extension, of oxidized (7Fe)FdI, is thus different from that obtained by x-ray crystallography on oxidized (7Fe)FdI. Possible interpretations of this result are discussed.

Azotobacter↗
PubMed1983

Iron-sulfur stoichiometry and structure of iron-sulfur clusters in three-iron proteins: evidence for [3Fe-4S] clusters.

Beef heart aconitase contains 3Fe clusters in its inactive and 4Fe clusters in its active form. The fully active form can be restored from the inactive one by insertion of Fe(2+), whereas S(2-) is not required. Chemical analyses for iron and labile sulfide yield Fe/S(2-) ratios of 0.66-0.74 for the inactive and 0.90-1.03 for the active form. Sulfane sulfur (S(0)) was not detected. We propose on the basis of these data that the inactive form may arise from the active one by loss of one iron only per cluster with the sulfur remaining as S(2-) in a [3Fe-4S] structure. Measurements by extended x-ray absorption fine structure (EXAFS) spectroscopy on the 3Fe form of aconitase yield a Fe..S distance of 2.24 A and a Fe..Fe distance of 2.71 A. This Fe..Fe distance is in agreement with that obtained by EXAFS on ferredoxin II of Desulfovibrio gigas, another 3Fe protein, but disagrees with Fe..Fe distances observed for the 3Fe cluster of Azotobacter vinelandii ferredoxin I by x-ray diffraction-namely, 4.1 A. We suggest that this difference may be due to the presence of a [3Fe-3S] structure in the Azotobacter ferredoxin I crystals vs. a [3Fe-4S] structure in liquid or frozen solutions of aconitase. The [3Fe-3S] cluster has been shown to have a relatively flat twist-boat structure, whereas a [3Fe-4S] cluster could be expected to essentially maintain the compact structure of the [4Fe-4S] cluster. This would explain the differences in Fe..Fe distances. Two possible structural models for a [3Fe-4S] cluster are discussed.

Aconitate Hydratase↗
PubMed1982

Retropharyngeal tendinitis.

We report a case of retropharyngeal tendinitis. A brief review of the literature, as well as extensive differential diagnosis, is presented. Retropharyngeal tendinitis should be a prime diagnostic consideration in patients who present with acute cervical pain, retropharyngeal calcium deposition, and prevertebral soft tissue swelling.

Adult↗
PubMed1981

Extended x-ray absorption fine structure of copper in cytochrome c oxidase: Direct evidence for copper-sulfur ligation.

The copper x-ray fluorescence excitation spectrum of cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) has been recorded in the 245-270 K range. The beat pattern observed in the extended x-ray absorption fine structure can be accounted for only by postulating a combination of sulfur and nitrogen (or oxygen) ligands to the copper. The average Cu-S distance is 2.27 +/- 0.02 A and the average Cu-N (or Cu-O) distance is 1.97 +/- 0.02 A. The amplitudes require ca, 1-1.5 sulfurs and 2 nitrogens (or oxygens) per copper. The distribution of sulfur ligands between Cu(A) and Cu(B) sites is not known, although there is some evidence that two sulfur atoms are bound to Cu(A).

Journal Article↗
PubMed1981

Effects of age on lipogenesis and lipolysis in lean and obese swine.

The effects of age on lipogenic and lipolytic activities in several breeds of swine were investigated. Females from a contemporary line and genetically selected populations of lean and obese pigs were utilized. Subcutaneous adipose tissue samples were taken from the shoulder area of nonfasted animals at 28-day intervals from 3 to 6 months of age for determination of in vitro lipogenic, lipolytic and acetyl CoA carboxylase activities. There were no significant differences between the breeds in the in vitro lipogenic rates measured in tissue slices with 14 C-glucose as substrate, except at 6 months of age, when the rate was higher in the obese than in the lean animal. However, the trend each months was obese greater than contemporary greater than lean. Lipogenic activity was greatest in all breeds at 4 months of age. Acetyl CoA carboxylase activity closely paralleled the lipogenic activity. The in vitro unstimulated lipolytic rate measured in tissue slices by the release of fatty acids to the incubation medium was similar for all breeds and decreases with age. Lipogenesis appears to be more important than unstimulated lipolysis in regulating backfat thickness in the breeds of swine examined.

Aging↗
PubMed1980

Effects of intravenous infusions of glucose, lactate, propionate or acetate on the induction of lipogenesis in bovine adipose tissue.

Crossbred steers (seven to nine per treatment) fed a pelleted alfalfa hay diet were biopsied (preinfusion) to obtain subcutaneous adipose tissue (SAT). Five days later a continuous intravenous infusion was begun of either 0.9% NaCl, glucose (2.75 moles/day), DL-lactate (5.5 moles/day of L-lactate), propionate (5.5 moles/day) or acetate (8.25 moles/day); after infusion for 14 days, a second biopsy sample of SAT was obtained. Glucose and DL-lactate infusion increased acetyl-CoA carboxylase activity about 12-fold compared to preinfusion activity of 5.3 +/- 4.2 nmoles/minute/g of wet weight. Glucose infusion induced activities of fatty acid synthetase (2.6 fold) and NADP+-malate dehydrogenase (7-fold) relative to preinfusion activities of 26.8 +/- 5.2 and 30.3 +/- 15.5 nmoles/minute/g of wet weight, respectively. Glucose, DL-lactate and propionate infusion increased NADP-isocitrate dehydrogenase activity 20-30% compared to preinfusion activity. Activity of NAD-malate dehydrogenase was not altered by any infusion treatment (P > 0.05). Activity of ATP-citrate lyase was decreased 48% by lactate infusion. Glucose, lactate and propionate infusion increased the rates of lactate and glucose incorporation into fatty acids in SAT incubated in vitro three to fourfold over preinfusion incorporation rates. Increased availability of glucose or gluconeogenic precursors may be responsible for induction of lipogenesis in steers fed high concentrate diets.

Acetates↗
PubMed1978

Magnetic susceptibility studies of laccase and oxyhemocyanin.

The magnetic susceptibility of Rhus vernicifera laccase has been remeasured over the temperature range 5-260 K. In contrast to our previous results [Solomon, E.I., Dooley, D. M., Wang R.-H., Gray, H.B., Cerdonio, M., Mogno, F. & Romani, G. L. (1975) J. Am. Chem. Soc. 98, 1029-1031] linear chi versus T-1 behavior was observed. The susceptibility of Limulus polyphemus oxyhemocyanin has also been measured in the range 5-260 K. Only weak paramagnetism, attributable to dissolved oxygen and a small amount of paramagnetic impurities, was observed. Analysis of the data establishes a lower limit of 550 cm-1 for J, consistent with our earlier work. The temperature dependence of the susceptibility of laccase is quantitatively accounted for by the presence of two paramagnetic copper ions (types 1 and 2) per enzyme molecule. Curie law behavior at low temperatures rules out significant interaction between the two coppper types, indicating that these redox centers are well separated (several angstroms) and are not connected by bridging ligands. Formulation of the type 3 site as binuclear Cu(II) requires J greater than or equal to 500 cm-1.

Animals↗
PubMed1976

Locomotory energetics in a marsupial (Antechinomys spenceri) and a rodent (Notomys alexis).

Steady state oxygen consumption was compared in a rodent Notomys alexis and a marsupial Antechinomys spenceri. The marsupial was found to diverge from predicted eutherian energic patterns. N. alexis appears to use energy storage as a significant part of the step cycle before becoming bipedal. Aerobic scope and heat storage during running are similar in both species.

Animals↗
PubMed1976

Cellular gluconeogenesis by lactating bovine mammary tissue.

The gluconeogenic capacity of mammary tissue of lactating cow was investigated by incubating mammary tissue slices with alanine, glutamate, lactate, pyruvate, or glycerol in conjunction with acetate and glucose (10mM or 1 mM). In no case was any substrate incorporated into glucose per se. In lactose synthesis, glucose was the major source of carbon although glycerol also was incorporated into lactose. Alanine, glutamate, lactate, or pyruvate were not incorporated into lactose at optimum (10 mM) or suboptimum (1 mM) concentrations of glucose. Activity of glucose-6-phosphatase was negligible in mammary tissue, less than 1% of the activity in liver or kidney tissue from the same cows. Pyruvate carboxylase, phosphoenolpyruvate carboxykinase, and fructose-1,6-diphosphatase were in cow mammary tissue, but the activities were lower than in liver. Gluconeogenic substrates were not converted to glucose regardless of whether the incubation contained an optimum (10 mM) or a suboptimum (1 mM) glucose concentration. Consistent with the inability of cow mammary tissue to convert gluconeogenic metabolites to glucose is the virtual absence of glucose-6-phosphatase and the lack of excess gluconeogenic substrates available to the intact mammary gland of lactating cow.

Animals↗
PubMed1975

Progressive rubella panencephalitis. Late onset after congenital rubella.

In children with congenital rubella infection the deficits remain stable; neurologic deterioration after the first few years of life is not believed to occur. We have encountered three patients with a definite or presumptive diagnosis of congenital rubella, in whom a progressive neurologic illness developed that began in the second decade and was characterized by spasticity, ataxia, intellectual deterioration, and seizures. High antibody titers to rubella virus in serum and spinal fluid were present in two, and all had increased cerebrospinal-fluid protein and gamma globulin. Extensive attempts to recover a virus from brain and body fluids were unsuccessful. The brains of two patients showed a widespread, progressive, subacute panencephalitis mainly affecting white matter. These data suggest that rubella virus may be a cause of progressive panencephalitis.

Adolescent↗
PubMed1975

Studies in burns. XIII. Effects of a topical lipid on burned subjects and their wounds.

We evaluated ethyl linoleate (ethyl, (9, 12)-cic, cis-octadecadienoate), a naturally occurring cutaneous water-holding lipid, for its water-holding metabolic, healing and toxic properties in groups of unburned and burned rabbits and its toxic potentials in this species and mice. The lipid appears to reduce evaporative water loss in full-thickness burned rabbits. Associated with this effect is a proportional and related lowering of metabolic heat production. The topical application of the lipid at any time after burn appears to be associated with a significant healing in lesions that, histologically at least, would be interpreted as fullthickness. The material is highly toxic if applied daily to mice or rabbits. The details of the toxic effect (s) are being studied. The commerical-grade material (75 percent pure) contains a derivative of ricinoleci acid and chronic exposure of the EL to air may result in the formation of peroxides and epoxides. These materials exert well-defined toxicity. The obvious potential uses of this agent in treating human burn lesions need not be emphasized, but it does need to be stated categorically that, at present, (Feb 1974), the toxicity has not been defined enough for use except in experiments.

Administration, Topical↗