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Biomedical subjects

J Green

Publications and source records attributed to J Green.

At least 559 records · Page 31Linked to original sources
PubMed1985

Protein B of soluble methane monooxygenase from Methylococcus capsulatus (Bath). A novel regulatory protein of enzyme activity.

An understanding of the mechanism of biological methane oxidation has been hampered by the lack of purified proteins. We describe here a purification protocol for the previously uncharacterized protein B of the soluble methane monooxygenase from the obligate methanotroph Methylococcus capsulatus (Bath). Soluble methane monooxygenase is a multicomponent enzyme consisting of a hydroxylase component, protein A, a reductase component, protein C, and protein B. All three proteins are required for monooxygenase activity. Protein B proves to be a low molecular weight (16,000) single subunit protein devoid of prosthetic groups. The protein is a powerful regulator of soluble methane monooxygenase activity, possessing the capacity to convert the enzyme from an oxidase to an oxygenase. Proteins A and C together catalyze the reduction of molecular oxygen to water, a reaction prevented by protein B. The uncoupling of soluble methane monooxygenase in this manner displays a number of novel features. First, the product of the uncoupled reaction is water, and second, the uncoupling is independent of substrate. Free hydrogen peroxide is not an intermediate in the reduction of oxygen by the incomplete methane monooxygenase enzyme complex. Finally, electron transfer can occur between protein C and protein A in the absence of protein B and protein B prevents the steady-state transfer of electrons in the absence of an oxidizable substrate, such as methane. It is demonstrated that oxygen reduction occurs at the active site of the hydroxylase component, protein A. A unifying mechanism, describing the interaction of the three proteins of soluble methane monooxygenase, is proposed.

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

Copper ions as inhibitors of protein C of soluble methane monooxygenase of Methylococcus capsulatus (Bath).

Copper(I), copper(II) and silver ions have been shown to be potent inhibitors of purified soluble methane monooxygenase (MMO) of Methylococcus capsulatus (Bath). A weaker inhibition has been observed with zinc and cadmium ions. Proteins A and B of soluble MMO are unaffected by copper but protein C is rapidly and irreversibly inhibited. The site of copper inhibition has been shown to be primarily at the iron-sulphur centre of protein C with a secondary effect at the FAD centre when the copper(II):protein C ratio is high. Copper appears to bring about the inhibition of soluble MMO by interacting with protein C to disrupt the protein structure causing, firstly, the loss of the iron-sulphur centre, preventing the transfer of electrons from protein C to protein A, and secondly, the loss of FAD preventing the protein from accepting electrons from NADH. Inhibition and spectral data are provided to support this thesis. The inactivation of protein C is associated with the tight binding of four Cu atoms to each protein C molecule. These data extend our knowledge of how copper, which is known to have a key role in the cellular location of MMO, interacts with and rapidly and irreversibly inactivates the soluble form of this enzyme.

Binding Sites↗
PubMed1985

Interactions between T helper cells and dendritic cells during the rat mixed lymphocyte reaction.

This paper describes the interactions between dendritic cells (DC) and T helper (Th) cells in the rat mixed lymphocyte reaction (MLR). Th blasts that are actively proliferating were generated in a 5 d primary MLR; resting Th memory cells were derived from a 10-12 d MLR. The DC were purified from thoracic duct lymph derived from rats whose mesenteric lymph nodes had been removed. The results show that DC are the major stimulators in the primary MLR and also for the restimulation of Th blasts and Th memory cells. Th blasts rapidly formed large clusters when cultured with DC but not with Ia+ macrophages or B cells. This interaction was not dependent on a major histocompatibility complex (MHC) difference between the T blasts and the DC. Con A-activated T and B blasts also formed clusters when cultured with DC. Th memory cells formed small clusters with DC, but, in a different assay in which clusters are dispersed, we detected an antigen-specific interaction between Th memory cells and DC. The monoclonal antibodies W3/25 (anti-rat CD4) and MRC OX-6 (anti-MHC class II) blocked proliferation in the primary MLR and also inhibited the restimulation of Th memory cells. However, the restimulation of Th blasts in a secondary MLR was only blocked by MRC OX-6. These results suggest that there are different requirements for the restimulation of T blasts than for the activation of primary or memory Th cells. W3/25 and MRC OX-6 did not affect the clustering of T blasts with DC but they both inhibited the antigen-specific binding of Th memory cells to DC. The data suggest that the CD4 (W3/25) antigen is involved in antigen-specific interactions between Th cells and DC.

Animals↗
PubMed1985

Decay B--> psi X.

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Journal Article↗
PubMed1985

Induction of a sustained fibrinolytic response by BRL 26921 in vitro.

The role of thrombus-binding in the fibrinolytic response to the acylated streptokinase.plasminogen activator complex, BRL 26921, has been examined using human plasma clots, radiolabelled with 125I-fibrin, in vitro. When clots were briefly exposed to BRL 26921, washed and returned to homologous plasma, lysis continued for up to 3 hours and attained approximately 25% of that lysis achieved by incubating with BRL 26921 for 5 hours. This continuing lysis was potentiated by return of exposed clots to alpha 2-antiplasmin-depleted plasma, or buffer and is attributed to an initial uptake of BRL 26921 rather than the binding of exogenous plasmin that was observed for streptokinase and high concentrations of urokinase. The sustained lysis is not explained by transfer of loosely-associated surface material or by dissociation of agent from the clot with reuptake from a dilute systemic pool. The response can be attributed, at least in part, to specific fibrin binding, mediated by kringles 1-4, for a low-molecular weight plasminogen (Val442) variant was less active.

Anistreplase↗
PubMed1985

Successful parenteral penicillin therapy of established Lyme arthritis.

In a double-blind placebo-controlled trial carried out from 1980 to 1982, 20 patients with established Lyme arthritis were assigned treatment with 2.4 million U of intramuscular benzathine penicillin weekly for three weeks (total, 7.2 million U) and 20 patients received saline. Seven of the 20 penicillin-treated patients (35 per cent) had complete resolution of arthritis soon after the injections and have remained well during a mean follow-up period of 33 months. In contrast, all 20 patients given placebo continued to have attacks of arthritis (P less than 0.02). In 1983, of 20 patients treated with intravenous penicillin G, 20 million U a day for 10 days, 11 (55 per cent) had complete resolution of arthritis and have remained well since. As compared with nonresponders, penicillin-responsive patients in both studies were more likely to have previously received antibiotics for erythema chronicum migrans (P less than 0.02) and less likely to have been given intraarticular corticosteroids during or at the conclusion of parenteral therapy (P less than 0.1). The Lyme spirochete was not cultured from synovium or joint fluid. We conclude that established Lyme arthritis can often be treated successfully with parenteral penicillin. However, neither of the regimens that we tested is uniformly effective, and further experience will be needed to determine the optimal course of therapy.

Adult↗
PubMed1985

Acylated derivatives of streptokinase-plasminogen activator complex as thrombolytic agents in a dog model of aged venous thrombosis.

A procedure is described for the establishment of experimental clots, aged in vivo for 72 hr, in the jugular vein of beagle dogs. Two acylated derivatives of streptokinase-human (lys) plasminogen activator complex with greatly differing deacylation rates under physiological conditions were compared as thrombolytic agents in the model. These were BRL 26921 (deacylation half-life, 40 min) and BRL 33575 (deacylation half-life c. 17 hr). The pharmacokinetic clearance rate of BRL 33575 from the circulation was studied and gave a clearance half-life of about 7 hr. BRL 33575 was found to be the superior agent in lysing 72 hr aged clots, being effective at a single bolus dose of 420 micrograms/kg or in three equal divided doses of 140 micrograms/kg given at 12 hr intervals. The single dose regime gave moderate systemic plasminogen activation, and the effect was significantly reduced with the divided dose regime. Infusion of freshly formed streptokinase-human plasminogen activator complex at 420 micrograms/kg over 15 hr gave little thrombolysis despite marked systemic plasminogen activation.

Animals↗
PubMed1985

Molecular archaeology of the mitochondrial genome.

We develop a stepwise model for the net transfer of nucleic acid sequences between non-homologous genomes. This model is then used to explain the two major patterns in the evolutionary history of mitochondrial genomes: the gross reduction of the number of genes, and the subsequent acquisition of introns.

Base Sequence↗
PubMed1985

Primary hyperparathyroidism in familial multiple endocrine neoplasia type I. Long-term follow-up of serum calcium levels after parathyroidectomy.

Serum calcium levels were analyzed after one or more explorations for primary hyperparathyroidism in familial multiple endocrine neoplasia type I. These data covered all 85 operations (performed in many hospitals) on 61 of 62 members from 14 kindreds. After 61 initial operations, there were high rates of persistent or recurrent hypercalcemia (54 percent) and chronic hypocalcemia (10 percent). These rates contrast with lower postoperative rates of hypercalcemia (4 to 16 percent) or chronic hypocalcemia (1 to 8 percent) in large series of primary hyperparathyroidism. Persistent or recurrent hypercalcemia after initial exploration decreased only modestly in patients who underwent surgery after 1975 versus before 1975 (46 versus 63 percent). The rate for long-term remission of hypercalcemia after initial parathyroidectomy was higher after a diagnosis of parathyroid hyperplasia was made (as opposed to adenoma) (57 versus 30 percent, p less than 0.05) and after removal of three or more glands (as opposed to removal of two and a half or less) (70 versus 34 percent, p less than 0.01). Following 24 reoperations, there were also high rates of persistent or recurrent hypercalcemia (46 percent) and chronic hypocalcemia (25 percent). After surgery in unselected patients with primary hyperparathyroidism, recurrent hypercalcemia (as opposed to persistent hypercalcemia) is distinctly uncommon; however, it was frequent in familial multiple endocrine neoplasia type I, with total recurrences increasing from 21 percent at five years to 41 percent at 10 years in patients who showed a normocalcemic interval after surgery. The data indicate that the occurrence of persistent or recurrent hypercalcemia after parathyroidectomy in familial multiple endocrine neoplasia type I remains frequent. Although recurrent hypercalcemia may be characteristic of the response to any technique of parathyroidectomy in familial multiple endocrine neoplasia type I and not preventable, persistent hypercalcemia can be decreased by preoperative recognition of the specific familial cause, involvement of an experienced surgical team, and histologic confirmation of the identification of three or more parathyroid glands.

Actuarial Analysis↗
PubMed1985

Psychological support and counselling for patients with acquired immune deficiency syndrome (AIDS).

The growing numbers of patients with the acquired immune deficiency syndrome (AIDS) in England had led to the development of a counselling service for patients, their sexual partners, contacts, and others. The nature of the counselling is described with reference to the primary qualitative issues arising from diagnosis. The necessity for preventative education for patients and those at risk is stressed, and guidelines for low risk sexual activities are outlined.

Acquired Immunodeficiency Syndrome↗