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Biomedical subjects

M J Nelson

Publications and source records attributed to M J Nelson.

At least 73 records · Page 4Linked to original sources
PubMed1984

Carbon monoxide-dependent methyl coenzyme M methylreductase in acetotrophic Methosarcina spp.

Cell extracts of acetate-grown Methanosarcina strain TM-1 and Methanosarcina acetivorans both contained CH3-S-CoM methylreductase activity. The methylreductase activity was supported by CO and H2 but not by formate as electron donors. The CO-dependent activity was equivalent to the H2-dependent activity in strain TM-1 and was fivefold higher than the H2-dependent activity of M. acetivorans. When strain TM-1 was cultured on methanol, the CO-dependent activity was reduced to 5% of the activity in acetate-grown cells. Methanobacterium formicicum grown on H2-CO2 contained no CO-dependent methylreductase activity. The CO-dependent methylreductase of strain TM-1 had a pH optimum of 5.5 and a temperature optimum of 60 degrees C. The activity was stimulated by the addition of MgCl2 and ATP. Both acetate-grown strain TM-1 and acetate-grown M. acetivorans contained CO dehydrogenase activities of 9.1 and 3.8 U/mg, respectively, when assayed with methyl viologen. The CO dehydrogenase of acetate-grown cells rapidly reduced FMN and FAD, but coenzyme F420 and NADP+ were poor electron acceptors. No formate dehydrogenase was detected in either organism when grown on acetate. The results suggest that a CO-dependent CH3-S-CoM methylreductase system is involved in the pathway of the conversion of acetate to methane and that free formate is not an intermediate in the pathway.

Acetates↗
PubMed1984

A comparison of computed tomography and radionuclide scanning for detection of brain metastases in small cell lung cancer.

Neurologic history and examination, radionuclide brain scans (RN), and computed tomographic brain scans (CT) were performed at diagnosis and sequentially in 153 consecutive patients with small cell lung cancer (SCLC) to assess the sensitivity and accuracy of these screening methods and to determine whether the early detection of brain metastases influences survival. CT scans (sensitivity, 98%; positive predictive accuracy, 98%) were superior to RN scans (sensitivity, 71%; positive predictive accuracy, 86%) in patients with or without neurologic signs or symptoms. However, CT scans were positive in only 6% of asymptomatic patients at diagnosis and 13% of asymptomatic patients after systemic therapy. Brain metastases detected by CT scan were the sole site of extensive-stage disease in 6% of patients at diagnosis. Despite the enhanced ability of CT scans to detect asymptomatic lesions, survival after therapeutic cranial irradiation was similar for asymptomatic and symptomatic patients. The results suggest that CT brain scans should be used routinely in SCLC patients with neurologic signs or symptoms, at diagnosis (when treatment decisions are based on stage), and at six-month intervals in patients with prior brain metastases and in whom erratic follow-up is likely.

Actuarial Analysis↗
PubMed1983

Alveolar bone necrosis and tooth loss. a rare complication associated with herpes zoster infection of the fifth cranial nerve.

Eleven case reports involving herpes zoster infection associated with alveolar bone necrosis and tooth loss were reviewed in order to develop a patient profile for this rare combination of physical findings. The clinical course of a 56-year-old white woman with herpes zoster infection of the fifth cranial nerve and related alveolar bone necrosis, tooth loss, and oroantral fistula development is reported. The etiology and management of herpes zoster infection associated with destructive oral sequelae are discussed.

Alveolar Process↗
PubMed1983

Metal and sulfur composition of iron-molybdenum cofactor of nitrogenase.

The sulfur content of N-methylformamide solutions of cofactor from Clostridium pasteurianum nitrogenase has been determined to be 11.9 (+/- 0.9) mol per mol of molybdenum. This number was determined radiochemically, using iron-molybdenum cofactor isolated from molybdenum-iron protein from bacteria grown on 35SO4. A total of 3.2 (+/- 0.2) mol of sulfur per mol of molybdenum was found to be present in cysteine and methionine, probably arising from contaminating proteins not intrinsic to the cofactor. Combined with accumulated evidence that is discussed, these results lead to an updated stoichiometry of MoFe6S8 or 9, not MoFe6S4 as previously thought, for this cluster.

Bacterial Proteins↗
PubMed1982

Calmodulin-dependent spectrin kinase activity in resealed human erythrocyte ghosts.

Membrane protein phosphorylation has been studied in resealed human erythrocyte ghosts by measuring the incorporation of 32P into spectrin and band 3. Norepinephrine- and Ca2+-stimulated phosphate incorporation was diminished in ghosts depleted of calmodulin. Ghosts prepared with endogenous calmodulin showed Ca2+- and norepinephrine-stimulated protein phosphorylation only when the ghosts had been resealed in the presence of (gamma-32P)ATP. Ghosts resealed with or without calmodulin in the presence of unlabeled ATP showed no net gain or loss of 32P when exposed to norepinephrine or a Ca2+-specific ionophore. These observations suggest that Ca2+ and norepinephrine stimulation of membrane protein phosphorylation is mediated by calmodulin-dependent spectrin kinase activity, and not by increased turnover of spectrin ATPase or by inhibition of phosphospectrin phosphatase.

Calcimycin↗
PubMed1982

Cholinergic stimulation of glucose transport in human erythrocytes.

The effects of cholinergic stimulation on glucose equilibrium exchange rate have been studied in human erythrocytes. Carbamylcholine increases in V of equilibrium exchange by 20% but has no significant effect on Km. The cholinergic effect is abolished by the muscarinic antagonist atropine or by alterations in intracellular calcium concentrations induced by the calcium ionophore A23187.

Atropine↗
PubMed1981

Calmodulin-dependent spectrin kinase activity in human erythrocytes.

Membrane protein phosphorylation has been studied in intact human erythrocytes and in resealed erythrocyte ghosts by measuring the incorporation of 32P into band 2 of spectrin. alpha-Adrenergic agonists and Ca+2 stimulate 32P-phosphate incorporation, an effect inhibited by trifluoperazine and diminished in resealed ghosts depleted of calmodulin. Ghosts prepared with endogenous calmodulin or resealed around purified calmodulin exhibit norepinephrine- and Ca+2-stimulated phosphorylation only in the presence of [gamma-32P]-ATP. Ghosts resealed with or without calmodulin in the presence of unlabelled ATP show no net gain or loss of 32P in membrane proteins when exposed to norepinephrine or calcium stimulation. These observations suggest that calcium and norepinephrine stimulation of membrane protein phosphorylation is mediated by calmodulin-dependent spectrin kinase activity, rather than by increased turnover by spectrin ATPase or by inhibition of phosphospectrin phosphatase.

Adenosine Triphosphate↗
PubMed1980

Evidence that calcium acts as an intracellular messenger for adrenergic responses in human erythrocytes.

Adrenergic stimulation of membrane protein phosphorylation has been studied in human erythrocytes. The adrenergic enhancement in phosphorylation of band 2 could be mimicked by the calcium-specific ionophore A23187 in the presence of 10 micron extracellular calcium. Experiments with the potassium ionophore, valinomycin, showed that potassium efflux was not the primary effector of the response. Trifluoperazine, an inhibitor of the Ca2+-dependent regulatory protein, calmodulin, inhibited phosphorylation stimulation by either norepinephrine or the calcium ionophore. The norepinephrine response was observed in the absence of extracellular calcium, implicating Ca2+ released from cellular bound pools in mediating the response.

Calcimycin↗
PubMed1980

Preparation of a novel 13C-labelled heme protein.

Protohemin chloride 90% enriched with 13C in the terminal carbons of the 2-nd and 4-position vinyl side-chains has been synthesized. The 13C-NMR spectrum of carboxymyoglobin reconstituted with the 13C-enriched hemin revealed two signals of nearly equal intensity at 117.6 and 113.4 ppm downfield of tetramethylsilane. The inequivalence of these vinyl carbons must reflect differences in environment imposed by the protein.

Animals↗
PubMed1979

Adrenergic stimulation of membrane protein phosphorylation in human erythrocytes.

Adrenergic modification of membrane protein phosphorylation was studied in intact human erythrocytes. Micromolar norepinephrine increased 32P incorporation into Band 2 by 70%, and into Band 3 by 40%. Phosphorylation levels observed with a series of specific agonists and antagonists suggest that an alpha-adrenergic receptor is involved in this effect. The mechanism of linkage between this receptor and protein phosphorylation does not appear to involve modulation of intracellular concentrations of ATP, cyclic AMP, or cyclic GMP.

1-Methyl-3-isobutylxanthine↗
PubMed1978

A multidisciplinary study on bancroftian filariasis in Jakarta.

A study on bancroftian filariasis in Jakarta has indicated that one person in one year could be exposed to 223,000 bites of Culex pipens fatigans and to 1,941 infective-stage larvae of Wuchereria bancrofti. Blood surveys with 20 mm3 samples revealed a microfilaria rate of 6%. Although some cases of hydrocele (4% of 272 males examined) were found, there was little evidence of severe filarial disease in either males or females. Amongst wild-caught mosquitoes only 0.3% contained infective larvae, but much higher levels of vectorial competence were established under laboratory conditions. High daily vector mortality (30%) coupled with noticeable improvements in standards of living could have been important factors preventing an increase in endemicity.

Adolescent↗
PubMed1976

Control of Culex pipiens fatigans(W) by the larvivorous fish Poecillia reticulata and by removal of debris from the breeding habitat.

Twice weekly removal of floating debris from two polluted ponds in Bangkok resulted in 75% reduction of immature populations of C.p. fatigans for seven weeks. Subsequent introduction of the guppy Poecilia reticulata at 10 fish per m2 further reduced the aquatic population to 2% of the pretreatment level during 12 weeks. When debris removal was discontinued, partial recovery of the larval density was observed. When fish were introduced in a plot without prior debris removal, there was no reduction of the mosquito population, and when only part of the debris was removed from one plot, the reduction was immediate.

Animals↗
PubMed1976

Observations on the breeding habitats of Aedes aegypti (L.) in Jakarta, Indonesia.

A one-year study was done of the breeding habitats of Aedes aegypti (L.) and of the water storage habits of the inhabitants in four crowded districts of urban Jakarta. Immature mosquitoes were found in or near houses in containers of relatively clean water used for drinking or bathing purposes. An average of 185 containers were found per 100 houses, of which 60 were positive for Aedes immatures, resulting in a Container Index of 32%. The mean potential water storage capacity per house was 173 liters of which only 92 liters of water was actually being stored at any one time. Water jars were the most common containers found, but bak mandi (cuboidal or oblong concrete reservoirs) held more water per container. Total water storage per house in bak mandi was twice that of water jars and ten times that of drums, which were uncommon. Ant traps and other miscellaneous containers were unimportant for either water storage or mosquito production. A mean of 0.93 pupae per house was found, pupal production indoors being ten times than outdoors. Indoor water jars produced more pupae per house than all other containers combined. The infestation rate of covered containers was significantly higher than that of uncovered containers, perhaps because loose-fitting lids allowed entrance of gravid females to the attractive darkened interior of the container.

Aedes↗