Search PubMed⌕ Search

Biomedical subjects

M B Smith

Publications and source records attributed to M B Smith.

At least 181 records · Page 10Linked to original sources
PubMed1977

Effect of specific trifluoroacetylation of individual cytochrome c lysines on the reaction with cytochrome oxidase.

We have prepared three different cytochrome c derivatives, each containing a single specifically trifluoroacetylated lysine at residues 13, 55, and 99, respectively. The only modification that affected cytochrome c oxidase (EC 1.9.3.1) activity was that of lysine-13 at the top of the heme crevice. Trifluoroacetylation of lysine-13 increased the apparent Michaelis constant fivefold compared to that of native cytochrome c, but did not affect the maximum velocity. Trifluoroacetylation of lysine-55 at the left side of the cytochrome c molecule did not affect cytochrome oxidase activity in any way, nor did trifluoroacetylation of lysine-99 at the rear of the cytochrome c molecule. This indicates that the cytochrome oxidase binding site on cytochrome c involved only the front of the cytochrome c molecule and those lysines immediately surrounding the heme crevice.

Animals↗
PubMed1977

Comparative teratogenicity of selected glucocorticoids applied ocularly in mice.

Three glucocorticoids (dexamethasone, hydrocortisone, and prednisolone), were ocularly applied to pregnant CD-1 mice on days 10-13 of gestation. The drug concentrations were various multiples of the common therapeutic dose levels and were applied to both eyes in 1 microliter drops five times a day. Eighteen-day fetuses were examined for malformations. A significant increase in the incidence of cleft palate was observed in fetuses treated with each of these glucocorticoids. There appeared to be a dose related effect on cleft palate width among fetuses from both dexamethasone and prednisolone treated dams. The incidence of sex organ anomalies, although lower than the incidence of cleft palate, also showed a positive dose relationship. Analysis of variance was used to compare the teratogenic effects of these glucocorticoids ocularly applied in equipotent anti-inflammatory concentrations. Our results indicate that dexamethasone produces a higher incidence of cleft palate, than either of the other two drugs when given in equipotent concentrations. It appears that the teratogenic potency of these ocularly applied glucocorticoids cannot be predicted on the basis of anti-inflammatory potency.

Abnormalities, Drug-Induced↗
PubMed1976

The incidence of glucose-6-phosphate dehydrogenase deficiency in a population of Greek, Italian and Yugoslav origin in Australia.

Cord blood from 2,220 male babies of Greek, Italian and Yugoslav origin, born consecutively over a four-year period at The Royal Women's Hospital, Melbourne, were screened by enzyme electrophoresis for glucose-6-phosphate dehydrogenase (G6PD) deficiency. The group comprised 1,220 babies of Greek, 600 of Italian and 400 of Yugoslav origin. G6PD deficiency occurred most commonly in the group of Greek babies, and 4-6% of these babies were deficient, while G6PD deficiency was detected in 1-2% of Italian and 0-3% of Yugoslav babies. These percentages are similar to those reported in Greece, Italy and Yugoslavia, and give some indication of the incidence of G6PD deficiency in people of Mediterranean origin in Australia.

Australia↗
PubMed1976

An enzyme kinetics and 19F nuclear magnetic resonance study of selectively trifluoroacetylated cytochrome c derivatives.

The reaction of cytochrome c with ethyl thioltrifluoroacetate was carried out under conditions which led to the selective trifluoroacetylation of a small number of the 19 lysines. The mixture of derivatives was separated by ion-exchange chromatography and four different derivatives with well-resolved 19F nuclear magnetic resonance (NMR) spectra were obtained. Peptide mapping techniques indicated that one of these derivatives contained a single trifluoroacetyl group at lysine 22, and another derivative was singly labeled at lysine 25. The trifluoroacetylated lysine 22 derivative was fully active toward both succinate-cytochrome c reductase (EC 1.3.99.1) and cytochrome oxidase (EC 1.9.3.1) white the trifluoroacetylated lysine 25 derivative was fully active toward the reductase, but had a threefold greater Michaelis constant in the cytochrome oxidase reactin. This supports the hypothesis that the cytochrome oxidase binding site is located in the heme cervice region, and that Lys-25 is important in the binding. 19FNMR spectra of the cytochrome c derivatives bound to phospholipid vesicles were obtained. The reasonably narrow line widths (35-65 Hz) and good sensitivity of the trifluoroacetyl resonances indicated that they might be useful probes for the interaction of cytochrome c with intact mitochondria.

Arginine↗
PubMed1975

Thermal transitions in the low-density lipoprotein and lipids of the egg yolk of hens.

1. Differential sanning calorimetry and light-scattering have been used to investigate temperature-dependent transitions in low-density lipoprotein and in lipids from hens' egg yolk. Yolks of different fatty acid composition were obtained by varying the dietary lipid and by adding methyl sterculate to the hen's diet. 2. Lipoprotein solutions in 50 percent glycerol/water gave characteristic melting curves between -25 degrees C and 50 degrees C, and on cooling showed increases in light-scattering between 10 degrees C and -20 degrees C. The temperatures at which major changes occurred depended on the proportions of saturated and unsaturated fatty acids. 3. The thermal transitions in the intact lipoprotein in glycerol solution were reversible, but with marked hysteresis. Lipid extracted from the lipoprotein did not show temperature hystersis but the transition heats and melting curves similar to those of the intact lipoprotein. The results support the hypothesis of a "lipid-core" structure for low-density lipoproteins. 4. Scanning calorimetry of egg-yolk lecithins indicated a strong dependence of transition temperature on water content in the rane 3 percent-20 percent water. A rise in the mid-temperature of the liquid-crystalline to gel transition as the water content is lowered on freezing may be the primary event in the irreversible gelation of egg yolk and aggregation of lipoprotein.

Animals↗
PubMed1975

The detection of glucose-6-phosphate dehydrogenase deficiency in mediterraneans by comparative quantitative enzyme electrophoresis.

Glucose-6-phosphate dehydrogenase (G6PD) can be easily isolated from haemolysates by cellulose acetate electrophoresis, and heterozygous (as well as hemizygous and homozygous) G6PD deficiency can be readily detected if the activity of the enzyme is determined densitometrically after electrophoresis and expressed as a ratio of the activity of a second enzyme, 6-phosphogluconate dehydrogenase (6PGD), which is isolated at the same time and whose activity is similarly determined. A method is presented here, together with the results of a recent survey in which 400 babies of Greek origin were tested for G6PD deficiency by the method. An overall incidence of 4-3% was found in the group; 2-9% of the males were completely G6PD deficient and 5-2% of the females were heterozygous for the deficiency.

Australia↗