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Biomedical subjects

G MacDonald

Publications and source records attributed to G MacDonald.

At least 55 records · Page 3Linked to original sources
PubMed1985

(TAA)n within sequences flanking several intrachromosomal variant surface glycoprotein genes in Trypanosoma brucei.

In Trypanosoma brucei telomeric copies of intrachromosomal variant surface glycoprotein (VSG) genes are produced through a gene conversion mechanism and are expressed if the telomere is or becomes transcriptionally activated. We have analyzed a sequence that occurs 1 to 1.5 kb 5' to several intrachromosomal VSG genes. This flanking sequence has three distinct sections: a 5' section containing 5 to 116 TAA or TAA-like tandem repeats; a moderately conserved sequence with an alternating GT characteristic; and a highly conserved 3' sequence that is largely alternating TA. Restriction mapping data and the location of this sequence suggest that it occurs at or near the 5' gene conversion boundary. This sequence, however, is not 5' to all VSG genes. These data suggest that this flanking sequence alone is not sufficient for VSG gene expression but that it may function in gene conversion for many, but not all, VSG genes.

Animals↗
PubMed1985

Role of etoposide-based chemotherapy in the treatment of patients with refractory or relapsing germ cell tumors.

Forty-nine patients with metastatic germ cell tumors were treated with etoposide 100 mg/m2 and cisplatin 20 mg/m2 intravenously each day for five days as "salvage" chemotherapy. Forty-seven patients had received standard induction regimens for metastatic germ cell tumors before receiving etoposide and cisplatin. Four patients were treated after surgical resection of a single site of relapse (Group I). Forty-five patients had measurable or evaluable disease at the time of treatment. In 17 patients with evaluable disease who had either achieved a prior complete remission or received no prior cisplatin (Group II), eight (47 percent) complete and four (24 percent) partial remission were observed. In 28 patients who had never achieved a prior complete remission (Group III), no complete and five (18 percent) partial responses were observed. Seven of 21 patients in Groups I and II and none of 28 patients in Group III remain alive and free of disease. Assuming prior treatment with cisplatin-based chemotherapy, these data and a review of the published experience with similar salvage regimens for patients with relapsing or refractory germ cell tumors suggest that combination chemotherapy based on etoposide and cisplatin is effective primarily in those patients who achieved a prior complete remission. Such therapy is ineffective in the absence of a prior complete remission probably because the patients have tumors that are largely resistant to cisplatin. Observed responses are probably due to etoposide alone. Investigational therapies should be pursued in those patients whose disease is refractory to current induction regimens.

Agranulocytosis↗
PubMed1985

Preoperative laparoscopic localization of the nonpalpable testis.

Laparoscopic examination was performed successfully on 14 patients with 17 nonpalpable testes. The procedure was successful in determining the location in 16 of 17 nonpalpable testes, and this information was beneficial for selecting the subsequent operative approach. Laparoscopy was safe in the younger child (10 patients were 3 years old or less and 7 patients were less than 2 years old), and it added an insignificant increase in operative time.

Child, Preschool↗
PubMed1985

Antigen-antibody analyses in neurocysticercosis.

In this report we show that there are 37 polypeptides of larval Taenia solium which react with antibodies from humans with neurocysticercosis. Six of these 37 polypeptides are recognized by antibodies present in the sera of both patients and control individuals. Thus, a minimum of 31 antigens are specific for cysticerci. We describe herein the antigens more frequently recognized by the patients, and the immunoglobulin classes favored in antibody production against each of the cysticercal antigens. It was found that there are 10 major polypeptides with molecular weights of 200,000, 64,000, 62,000-61,000, 53,000, 45,000, 41,000, 36,000-35,000, 30,000 and 16,000 daltons. About 65% of the larval components found to be antigenic are glycoproteins with oligosaccharide chains containing N-acetyl-D-glycosamine and alpha-D-galactose. These results suggest that the sugar moieties of glycoproteins may play a role in the antigenicity of larval T. solium. Based on these observations polypeptides with molecular weights of 64,000, 53,000, and 32,000-30,000 daltons are probably the best choice as sources of antigen to develop an optimal immunological test for the serological diagnosis of neurocysticercosis.

Antibodies↗
PubMed1984

Monoclonal antibodies to the Ca2+ + Mg2+-dependent ATPase of sarcoplasmic reticulum identify polymorphic forms of the enzyme and indicate the presence in the enzyme of a classical high-affinity Ca2+ binding site.

In order to determine whether polymorphic forms of the Ca2+ + Mg2+-dependent ATPase exist, we have examined the cross-reactivity of five monoclonal antibodies prepared against the rabbit skeletal muscle sarcoplasmic reticulum enzyme with proteins from microsomal fractions isolated from a variety of muscle and nonmuscle tissues. All of the monoclonal antibodies cross-reacted in immunoblots against rat skeletal muscle Ca2+ + Mg2+-dependent ATPase but they cross-reacted differentially with the enzyme from chicken skeletal muscle. No cross-reactivity was observed with the Ca2+ + Mg2+-dependent ATPase of lobster skeletal muscle. The pattern of antibody cross-reactivity with a 100,000 dalton protein from sarcoplasmic reticulum and microsomes isolated from various muscle and nonmuscle tissues of rabbit demonstrated the presence of common epitopes in multiple polymorphic forms of the Ca2+ + Mg2+-dependent ATPase. One of the monoclonal antibodies prepared against the purified Ca2+ + Mg2+-dependent ATPase of rabbit skeletal muscle sarcoplasmic reticulum was found to cross-react with calsequestrin and with a series of other Ca2+-binding proteins and their proteolytic fragments. Its cross-reactivity was enhanced in the presence of EGTA and diminished in the presence of Ca2+. Its lack of cross-reactivity with proteins that do not bind Ca2+ suggests that it has specificity for antigenic determinants that make up the Ca2+-binding sites in several Ca2+-binding proteins including the Ca2+ + Mg2+-dependent ATPase.

Animals↗
PubMed1980

Efficacy of nifedipine in the treatment of angina pectoris and chronic airways obstruction.

Twenty patients suffering from angina pectoris with co-existing fixed or labile airways obstruction, were administered fortnightly treatment periods of nifedipine or matching placebo over an 8-week period. Maintenance treatment for their airways obstruction continued throughout this period. Nifedipine was found to be an effective drug in controlling their angina, and did not have an adverse effect on the airways obstruction. Both systolic and diastolic BP was reduced over a 90-min period after administration of a single dose of nifedipine.

Adult↗
PubMed1976

Cytidine diphosphate diglyceride of bovine brain. Positional distribution of fatty acids and analysis of major molecular species.

A method is described for the isolation of CDP-diglyceride from bovine brain. Yields of the product ranged from 9.2-15.5 mumol per kilogram of tissue, which corresponds to about 1% of the level of phosphatidic acid. Mild alkaline hydrolysis of the product gave three water-soluble phosphate esters which had the same electrophoretic mobilities as CMP, CDP-glycerol and glycerol 3-phosphate. The liponucleotide was quantitatively hydrolysed by CDP-diglyceride hydrolase from Escherichia coli to phosphatidic acid and CMP. No dCMP was recovered in enzymatic or alkaline hydrolysates and it is concluded there can be little or no dCDP-diglyceride in bovine brain. Brain CDP-diglyceride was similar to phosphatidylinositol in that in both lipids stearate was the major saturated fatty acid and arachidonate the most abundant unsaturated fatty acid. This differed significantly from the fatty acid patterns of other metabolically related phospholipids, phosphatidic acid and cardiolipin. Brain CDP-diglyceride was hydrolysed with phospholipase C from Clostridium welchii with the liberation of the diglyceride moiety in high yield. Treatment of the diglyceride with pancreatic lipase showed CDP-diglyceride with the asymmetric distribution of fatty acids characteristic of most mammalian phospholipids, saturated fatty acids being found mostly at position 1 and polyunsaturated fatty acids at position 2. The derived diglyceride acetates were separated into different molecular species by argentation thin-layer chromatography. These analyses showed that 1-stearoyl, 2-arachidonoyl was the major species of brain CDP-diglyceride.

Animals↗
PubMed1975

Isolation and characterization of cytidine diphosphate diglyceride from beef liver.

Cytidine diphosphate diglyceride was isolated from beef liver by a combination of silicic acid column, DEAE-cellulose column, and this layer chromatography. The product (5.8 to 17.4 mumol/kg of liver) contained cytidine/phosphate/fatty acids in the molar proportions 1.05/2.0/2.05 (theoretical, 1.0/2.0/2.0) (average for three preparations). The liponucleotide was split quantitatively by a partially purified hydrolase from Escherichia coli, specific for CDP-diglyceride, (Raetz, C. R. H., Hirschberg, C. B., Dowhan, W., Wickner, W. T., and Kennedy, E. P. (1972) J. Biol. Chem. 247, 2245-2247) into phosphatidic acid and a water-soluble nucleotide that was chromatographically identical with CMP. No dCMP was located in these hydrolysates. The liver liponucleotide was more effective than a synthetic preparation of CDP-diglyceride in promoting the formation of phosphatidylinositol with guinea pig brain microsomes. The fatty acid composition of CDP-diglyceride was compared with metabolically related phospholipids from beef liver. The liponucleotide had a similar composition to phosphatidylinositol, characterized by a high level of stearate and with arachidonate as the major unsaturated fatty acid. The content of arachidonate in both lipids was significantly higher than that in phosphatidic acid. The profile of fatty acids of cardiolipin was quite unlike that of CDP-diglyceride. These findings suggest several alternatives for the metabolic origins of beef liver CDP-diglyceride: (a) CDP-diglyceride is formed from an atypical pool of phosphatidic acid, (b) the enzyme is selective for arachidonoyl-containing species of phosphatidic acid, (c) the liponucleotide may also be derived from phosphatidylinositol by the back-reaction of CDP-diglyceride: inositol phosphatidyltransferase.

Animals↗