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Biomedical subjects

C Freeman

Publications and source records attributed to C Freeman.

At least 91 records · Page 5Linked to original sources
PubMed1987

Kidney transplant recipients with long incubation-positive antiglobulin-negative T cell crossmatches.

Low-affinity, cold-reactive antibodies easily removed by washing were not detected by the antiglobulin technique but killed T lymphocytes when washing was omitted, incubation was prolonged, and cytotoxic tests were incubated at room temperature or at 4 degrees C. These antibodies were present in approximately 25% of sera from dialysis patients. Only a subset of such sera (22%) reacted with autologous lymphocytes. The majority (86%) appeared to detect non-HLA antigens. A small number (14%) detected class I HLA antigens. Two patients transplanted with antiglobulin-negative, T-warm-negative crossmatch results, but positive cytotoxicity after a 2-hr incubation without washing, rapidly lost their grafts (less than 1 month) due to rejection. Their sera contained antibodies against non-HLA alloantigens expressed on lymphocytes and platelets, but not on granulocytes or erythrocytes. Two other patients with positive autoantibody tests exhibiting similar crossmatches with the current serum were transplanted recently. Both of them retain their grafts with good function at one month. In two other cases, the recipients were unreactive against the donor in current serum but displayed an antiglobulin-negative, 2-hr cytotoxicity-positive pattern in a previously drawn serum specimen. One patient continues to have stable renal function after 10 months. The other patient lost the transplant as a result of renal artery thrombus thought not to be immunologic in origin. Work is continuing to define the specificity and determine the clinical relevance of such cold-reactive antibodies.

Autoantibodies↗
PubMed1986

Human liver sulphamate sulphohydrolase. Determinations of native protein and subunit Mr values and influence of substrate agylcone structure on catalytic properties.

Human sulphamate sulphohydrolase was purified at least 20,000-fold to homogeneity from liver with a three-step four-column procedure, which consisted of a concanavalin A-Sepharose/Blue A agarose coupled step, and Bio-Gel HT step and then a CM-Sepharose step. The procedure was also used to purify enzyme from kidney and placenta. The subunit Mr of liver, kidney and placenta sulphamate sulphohydrolase was assessed to be 56,000 by using SDS/polacrylamide-gel electrophoresis. The native protein Mr of enzyme from all three tissue sources was assessed by gel-permeation chromatography to be approx. 120,000 on Sephacryl S-300 and 100,000 on Fractogel TSK. It is probable that the native enzyme results from dimerization of subunits. Kinetic parameters (km and kcat.) of human liver sulphamate sulphohydrolase were determined with a variety of substrates matching structural aspects of the physiological substrates in vivo, namely heparin and heparan sulphate. More structurally complex substrates, in which several aspects of the aglycone structure of the natural substrate were maintained, are turned over up to 372000 times faster than the monosaccharide substrate 2-sulphaminoglucosamine. Aglycone structures that influence substrate binding and/or enzyme activity were penultimate-residue C-6 carboxy and C-2 sulphate ester groups and a post-penultimate 2-sulphaminoglucosamine residue. The C-4 hydroxy group of the 2-sulphaminoglucosamine under enzymic attack is involved in binding of substrate to enzyme. The presence of C-6 sulphate ester on the non-reducing end 2-sulphaminoglucosamine stimulates sulphamate bond hydrolysis and substrate affinity if the adjacent monosaccharide residue is idose or 2-sulphoidose, but strongly inhibits hydrolysis if the adjacent monosaccharide residue is iduronic acid. Sulphamate sulphohydrolase is an exoenzyme, since activity toward internal sulphamate bonds was not detected. The effect of incubation pH on enzyme activity towards the variety of substrates evaluated was complex and dependent on substrate aglycone structure. The presence of aglycone C-2 sulphate ester and aglycone C-6 carboxy groups and C-6 sulphate ester groups on the 2-sulphaminoglucosamine residue under attack considerably affect the pH response. Structurally complex substrates had two pH optima. Incubation temperature and buffer ionic strength markedly influenced pH optima and enzyme activity. Cu2+ and SO4(2-)ions are potent inhibitors of enzyme activity.

Catalysis↗
PubMed1985

Psychotherapy for bulimia: a controlled study.

A psychotherapy study for bulimia is described. The preliminary results of a random allocation control trial comparing cognitive behaviour therapy, behaviour therapy and group psychotherapy with a waiting list control are presented. The results of the first 60 subjects in active treatment are shown. They indicate that all three treatments are effective in dramatically reducing the behavioural symptoms of the bulimia syndrome. There is evidence that cognitive therapy has a greater effect on symptoms of depression and self-esteem. No evidence is yet available on the longterm outcome of the three treatments.

Adolescent↗
PubMed1984

Intracranial ependymomas and ependymoblastomas.

Nineteen cases of intracranial ependymal tumors were reviewed to examine the prognostic factors influencing survival of the patients with this disease. The two most important predictive factors in relation to survival status were a histologic grade of tumors and a presence of hydrocephalus. The clinicopathological correlation in this study has supported the view of two distinct ependymal tumors; more curable ependymomas and highly malignant ependymoblastomas .

Adolescent↗
PubMed1983

Phenytoin II: in vitro-in vivo bioequivalence standard for 100-mg phenytoin sodium capsules.

A bioequivalence study was undertaken using an oral solution, a fast-dissolving capsule and a slow-dissolving phenytoin sodium capsule. The AUC, tmax and Cmax correlated with in vitro dissolution data. The results of the present studies substantiate the presence of two types of phenytoin sodium products on the market. On the basis of these studies, in vitro specifications for fast- and slow-dissolving phenytoin sodium capsules as well as the in vivo bioequivalence requirements for these two types of products are recommended.

Capsules↗
PubMed1983

Acetyl CoA:alpha-glucosaminide N-acetyl transferase: partial purification from human liver.

The lysosomal enzyme acetyl CoA:alpha-glucosaminide N-acetyltransferase (GNAT) was shown to be an integral membrane protein requiring high concentrations of the detergent Triton X-100 for maximal solubilization. Using a concentration dependent Triton X-100 solubilization procedure and Concanavalin A-Sepharose affinity chromatography, GNAT was purified 50-fold with a yield of 45%. GNAT activity was separated from N-acetyltransferase activity toward glucosamine 6-phosphate, an alternative non-lysosomal pathway for glucosamine metabolism. GNAT was different from other lysosomal enzymes which bound to Concanavalin A-Sepharose in that both alpha-methylmannoside and Triton X-100 were required for elution of enzyme activity. GNAT activity, which bound to Concanavalin A-Sepharose, required at least one other component which did not bind for maximal expression of enzyme activity and for storage stability. Phospholipids and glycolipids, such as phosphatidylethanolamine, phosphatidylcholine, phosphatidylglycerol, sphingomyelin and gangliosides, and bovine serum albumin allowed expression of enzyme activity and storage stability similar to the component(s) which did not bind to Concanavalin A-Sepharose.

Acetyltransferases↗
PubMed1983

Cellular location of N-acetyltransfer activities toward glucosamine and glucosamine-6-phosphate in cultured human skin fibroblasts.

The intracellular location in normal human cultured skin fibroblasts of the N-acetyltransferase activities that transfer the acetyl group from acetyl-CoA to the 2-amino group of glucosamine and glucosamine-6-phosphate have been investigated. Organelles have been separated using a combination of differential centrifugation and free flow electrophoresis. The intracellular distribution of the enzyme involved in the N-acetyltransfer to glucosamine and an alpha-glucosaminide disaccharide indicated that this enzyme activity concentrates mainly with lysosomal organelles whereas the activity associated with N-acetyltransferase to glucosamine-6-phosphate is non-lysosomal. It is proposed that acetyl-CoA: alpha-glucosaminide N-acetyltransferase may be used as a convenient enzyme marker of lysosomal organelle membranes.

Acetyltransferases↗
PubMed1981

Effect of nerve activity on transport of nerve growth factor and dopamine beta-hydroxylase antibodies in sympathetic neurones.

The effect of nerve activity on the uptake and retrograde transport of nerve growth factor (NGF) and dopamine beta-hydroxylase (DBH) antibodies was studied by injecting 125I-labelled NGF and anti-DBH into the anterior eye chamber of guinea-pigs. Decentralization of the ipsilateral superior cervical ganglion (SCG) had no significant effect on the retrograde transport of either NGF or anti-DBH. Phenoxybenzamine produced a 50% increase in anti-DBH but not NGF accumulation and this effect was prevented by prior decentralization. This demonstrates that NGF is taken up independently of the retrieval of synaptic vesicle components.

Adrenergic Fibers↗
PubMed1981

Induction of complement receptor expression in cell lines derived from human undifferentiated lymphomas. II. Characterization of the induced complement receptors and demonstration of the simultaneous induction of EBV receptor.

We have studied the specificity of complement receptors induced by theophylline in 2 cell lines derived from undifferentiated lymphomas, one of Burkitt's type, and compared it to that of complement receptors in other cell types. Both C3b and C3d receptors were induced. The induced C3b receptor differed from the C3b receptor of mature normal lymphocytes, polymorphonuclear leukocytes and the cells of a nodular lymphoma in 2 respects. Firstly, it bound C3b much less avidly (by a factor of several hundred-fold) and secondly, we were unable to demonstrate C4b binding. EBV receptors were induced at the same time as complement receptors, and permitted the conversion of a greater fraction of cells to EBNA positivity after experimental infection with EBV. The induction of receptors was not associated with a change in the fluidity of the plasma membranes and our data do not favor a different orientation of induced receptors within the membrane as compared to receptors of other cell types--a potential explanation for the different specificities. Our findings are consistent with the possibility that the complement receptors of lymphocyte precursors differ from these of mature lymphocytes.

Binding, Competitive↗
PubMed1979

Single case study. Complementary effects of phenelzine and psychotherapy in long term treatment of depression.

A case report is described wherein the monoamine oxidase inhibitor phenelzine was administered for 10 months at different doses. Drug treatment in the initial part of the study was double blind. Weekly psychotherapy was instituted at the point of symptomatic recovery. At a reduced dose, in month 3, the patient experienced a relapse in depression. While platelet monoamine oxidase inhibition was greater than 80 per cent the patient was well, but at the point of relapse, inhibition was 14 per cent. Clinical ratings at relapse (Beck and SCL-90 scales) revealed greater readiness by the patient to report psychological discomfort compared with the original interview. The combined effects of psychotherapy and pharmacotherapy were felt to be responsible for this change. However, psychotherapy in this form and duration did not prevent relapse, which depended upon maintaining an adequate dose of phenelzine.

Adult↗