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Biomedical subjects

D Graham

Publications and source records attributed to D Graham.

At least 127 records · Page 7Linked to original sources
PubMed1984

Chemical properties, distribution, and physiology of plant and algal carbonic anhydrases.

Plant carbonic anhydrases (CAs) have a range of molecular weights (MW). Among flowering plants, dicotyledons with C3 photosynthesis have two isoenzymes of 140-250K each with 6 subunits, while monocotyledons have two isoenzymes of 42-45K. Plant and animal CAs have a similar amino acid content, subunit size and zinc content, suggesting they are homologous proteins, although the higher plant CAs have no esterase activity and are not strongly inhibited by sulfonamides. Algal CAs vary widely in MW and some are highly sensitive to sulfonamides like the animal enzymes. The two plant isoenzymes, from the chloroplast and cytosol, can be separated by gradient polyacrylamide gel electrophoresis and subsequently visualized by enzymic H+ ion production. In plants, CAs probably facilitate diffusion of CO2 to the site of photosynthetic fixation; they may also have a role in pH regulation, in the use of bicarbonate by aquatic plants and in concentrating inorganic carbon within the chloroplast.

Carbonic Anhydrases↗
PubMed1983

Photoaffinity-labelling of the glycine receptor of rat spinal cord.

The irreversible incorporation upon ultraviolet illumination of the glycine receptor antagonist, [3H]strychnine, into synaptic membrane fractions of rat spinal cord has been investigated. The specificity of this photoaffinity-labelling reaction for the glycine receptor was demonstrated by the following results: (a) the Kd value (9.7 nM) of the glycine-displaceable irreversible incorporation of [3H]strychnine was similar to the previously reported Kd of [3H]strychnine binding to the glycine receptor; (b) pre-illumination of the membranes with unlabelled strychnine led to a corresponding reduction in the number, but not the affinity, of reversible glycine-displaceable [3H]strychnine binding sites; (c) the ultraviolet light-induced incorporation into the membranes of [3H]strychnine was inhibited by different glycine receptor agonists; other neurotransmitter substances had little or no effect. Also, [3H]strychnine alone was shown to be stable upon illumination with ultraviolet light; this suggests that photocrosslinking of [3H]strychnine may require energy transfer from specific groups of its high-affinity receptor binding site. Upon sodium dodecyl sulphate/polyacrylamide gel electrophoresis a single labelled polypeptide with a relative molecular mass of 48000 was revealed from spinal cord membranes photoaffinity-labelled with [3H]strychnine. Spinal cord membranes photoaffinity-labelled with the gamma-aminobutyric acid receptor ligand [3H]flunitrazepam, however, gave a single polypeptide with a relative molecular mass of 5- 0000. Treatment of membranes, labelled with [3H]strychnine, by endoglycosidase H did not alter the relative molecular mass of the 48000-Mr labelled polypeptide. Trypsin treatment, on the other hand, successively produced major fragments of relative molecular masses of 42000 and 37000. Also, even after extensive treatment with trypsin or chymotrypsin, greater than or equal to 90% of the radioactivity incorporated into the labelled membranes remained membrane-associated. It is concluded that the strychnine binding site of the glycine receptor is located on a protease-inaccessible, i.e. probably hydrophobic domain of the 48000-Mr subunit.

Affinity Labels↗
PubMed1983

The natural disease course of ankylosing spondylitis.

One hundred fifty war veterans with ankylosing spondylitis were entered into a prospective study in 1947. In 1957, 142 were traced, and they have been reviewed periodically. Eighty-one of these patients were still alive in 1980. Information was obtained from 67 (83%) of the survivors and 51 were reexamined. This report is based on the clinical findings in these 51 patients, who have a mean disease duration of 38 years. Forty-seven (92%) were functioning well. The disease in 21 (41%) had progressed to cause severe spinal restriction. Of those, 12 had peripheral joint involvement early in their course and 9 had iritis. Seventy-four percent of the patients who had mild spinal restriction after 10 years did not progress to having more severe restriction. Eighty-one percent of the patients who had severe spinal restriction in 1980 were severely restricted within the first 10 years. Hips that were normal after 10 years of disease did not become diseased subsequently. This study suggests that a predictable pattern of ankylosing spondylitis emerges within the first 10 years of the disease.

Adult↗
PubMed1982

Identification of polypeptides associated with a putative neuronal nicotinic acetylcholine receptor.

Polypeptides involved in the binding of the nicotinic acetylcholine receptor ligand alpha-bungarotoxin (Mr = 8,000) to neuronal membranes were identified by three independent methods: (i) 125I-alpha-bungarotoxin bound to membrane fractions or to monolayer cultures of chick retina was cross-linked to its binding site by using glutaraldehyde, or the photoactivatable bifunctional reagent N-succinimidyl-6-(4'-azido-2'-nitrophenylamino)hexanoate. Electrophoretic analysis of the cross-linked membrane proteins revealed 125I-alpha-bungarotoxin-polypeptide adducts of apparent Mr = 63,000, 43,000, and 33,000. (ii) Affinity purification of the alpha-bungarotoxin binding protein from detergent extracts of [35S]methionine-labeled retina cultures identified one major polypeptide with an Mr = 57,000. (iii) Indirect immunoprecipitation from detergent extracts of [35S]methionine-labeled rat pheochromocytoma cells (PC 12) gave evidence for a specific co-precipitation of alpha-bungarotoxin with three polypeptides (Mr = 57,000, 34,000, and 25,000). The data suggest that polypeptides of Mr - 57,000, 35,000, and 25,000 (+/- 3,000) are located at or close to the alpha-bungarotoxin binding domain of the putative neuronal nicotinic acetylcholine receptor.

Animals↗
PubMed1982

Purification by affinity chromatography of the glycine receptor of rat spinal cord.

The glycine receptor of rat spinal cord was solubilized with the nonionic detergent Triton X-100 and subsequently purified by affinity chromatography on aminostrychnine-agarose and wheat germ agglutinin-Sepharose. An overall purification of 1950-fold was achieved. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and mercaptoethanol revealed three glycine receptor-associated polypeptides of Mr = 48,000, 58,000, and 93,000. [3H]Strychnine was incorporated irreversibly into the Mr = 48,000 polypeptide upon UV-illumination. The dissociation constant (KD) of [3H]strychnine binding to the purified glycine receptor was 9.3 +/- 0.6 nM. The glycine receptor agonists glycine, beta-alanine, and taurine inhibited the binding of [3H]strychnine to the purified receptor. Gel filtration and sedimentation in sucrose/H2O and sucrose/D2O gradients gave a Stokes radius of 7.7 nm, a partial specific volume of 0.780 +/- 0.005 ml/g and a sedimentation coefficient s20,w of 8.2 +/- 0.2 S for the purified glycine receptor. From these data, a molecular weight of 246,000 +/- 6,000 was calculated for the glycine receptor protein.

Affinity Labels↗
PubMed1982

Avermectin B1a inhibits the binding of strychnine to the glycine receptor of rat spinal cord.

The anthelmintic drug, avermectin B1a, has been reported to interfere with gamma-aminobutyric acid-mediated chloride conductance. Also, enhancement of diazepam binding to mammalian brain membranes by avermectin B1a has led to the suggestion that avermectin B1a interacts with the 'benzodiazepine receptor-gamma-aminobutyric acid receptor-chloride ionophore' complex. Here we report an interaction of avermectin B1a with the glycine receptor. The binding of the glycine receptor antagonist, strychnine, to both membranes and solubilized receptor from rat spinal cord, was inhibited by avermectin B1a with Ki values of 1.3 microM and 3.6 microM, and Hill coefficients of 0.46 and 0.62, respectively.

Animals↗
PubMed1982

Amniotic fluid.

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Amniocentesis↗
PubMed1982

Sonographic findings in abdominal pregnancy.

The sonographic findings in four cases of abdominal pregnancy are described and compared with similar cases reported in the literature. The findings include demonstration of an empty uterus adjacent to the bladder, absence of myometrium around the fetus, unusual fetal lie, poor definition of the placenta, and relative oligohydramnios.

Adult↗