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Biomedical subjects

G M Smith

Publications and source records attributed to G M Smith.

At least 217 records · Page 12Linked to original sources
PubMed1981

Comparison of three methods for the purification of the delta haemolysin of Staphylococcus aureus.

Three methods for the purification of Staphylococcus aureus delta haemolysin were compared (Kantor et al., 1972; Kreger et al., 1971; Heatley, 1971). The products of these purifications from the culture supernatant of S. aureus strain RN25 were compared by electrophoresis, amino acid analysis, amino-terminal sequence analysis and thin-layer chromatography. The method of Heatley (1971) was found to be superior in terms of recovery and purity of the product. Delta haemolysin prepared by the method of Kreger et al. (1971) could not be sequenced successfully prior to treatment aimed at the removal of the N-formyl group at the amino-terminus. Delta haemolysin appears to exist in two distinct molecular forms, one with N-formylmethionine and the other with un-formylated methionine in the amino-terminal position. The former polypeptide species is purified preferentially by the method of Kreger et al. (1971). Thin-layer chromatography of the products of each method of purification revealed that they were all heterogeneous, although the major component from the product of the method of Heatley (1971) represented not less than 70% of the product.

Aluminum Oxide↗
PubMed1981

Effects of 6-[p-(4-phenylacetylpiperazin-1-yl)phenyl]-4,5-dihydro-3(2H)pyridazinone (CCI 17810) and aspirin on platelet aggregation and adhesiveness.

1. The effects of 6-[p-(4-phenylacetylpiperazin-1-yl)]-4,5-dihydro-3(2H)pyridazinon (CCI 17810) on platelet aggregation and adhesiveness have been investigated and compared with those of aspirin. 2. In vitro, CCI 17810 was a potent inhibitor of the aggregation of human platelets induced by collagen, adenosine 5'-diphosphate (ADP) (primary response), thrombin and arachidonic acid, with EC50 values in the range 0.5 to 10 micrograms/ml. The second phase of the response to adrenaline was blocked by concentrations in the range 15 to 25 micrograms/mg. Platelets from rats, rabbits and dogs were as sensitive as human platelets to the effects of CCI 17810. Aspirin was nearly as effective as CCI 17810 against collagen, and adrenaline but about 10 times less active against arachidonic acid; it did not inhibit the primary response to ADP and was only a weak inhibitor of thrombin-induced aggregation. 3. In mice, single oral doses of CCI 17810 in the range 12.5 to 100 mg/kg inhibited collagen-induced thrombocytopenia. Arachidonic acid-induced mortality was markedly reduced by 10 mg/kg and possibly slightly reduced by 1 mg/kg. Aspirin was considerably less active than CCI 17810 in inhibiting collagen-induced thrombocytopenia but was almost as active as CCI 17810 in reducing arachidonic acid-induced mortality. 4. In vitro, CCI 17810 reduced the adhesiveness of human platelets to glass beads (retention of platelets in glass bead columns). Single oral doses of CCI 17810 in the range 25 to 200 mg/kg reduced mouse platelet adhesiveness; rat platelet adhesiveness was reduced by doses in the range 12.5 to 100 mg/kg. Aspirin (20 or 200 mg/kg) slightly increased mouse platelet adhesiveness.

Adenosine Diphosphate↗
PubMed1981

Effect of Soybean Casein Digest Agar Lot on Number of Bacillus stearothermophilus Spores Recovered.

In recent years it has become increasingly apparent that Bacillus stearothermophilus spores are affected by various environmental factors that influence the performance of the spores as biological indicators. One environmental factor is the recovery medium. The effect of different lots of commercial soybean casein digest agar on the number of colony-forming units per plate was examined in two series of experiments: (i) several lots of medium from two manufacturers were compared in single experiments, and (ii) paired media experiments with four lots of medium were carried out and yielded three-point survivor curves. The results demonstrate that commercial soybean casein digest agar is variable on a lot-to-lot basis. The variation was lowest when recovering unheated or minimally heated spores and increased greatly with the severity of heating.

Journal Article↗
PubMed1980

Erythroid differentiation of clonal Rauscher erythroleukemia cells in response to erythropoietin or dimethyl sulfoxide.

Clonal lines of Rauscher erythroleukemia cells exhibited selective responses to two inducers of differentiation, erythropoietin and dimethyl sulfoxide. There were substantial quantitiative differences between clones that reponded to both inducers. Several clones differentiated only in response to erythropoietin. Erythropoietin stimulated cell proliferation and differentiation whereas dimethyl sulfoxide inhibited proliferation, suggesting dissimilar modes of action.

Animals↗
PubMed1980

Three-dimensional molecular modeling and drug design.

A discussion of drug-receptor theory is used to show that the three-dimensional structure, or shape, of molecules is important for biological activity. The computer-assisted molecular modeling system at Merck is described, and it is shown that this system is useful for generating and storing molecular structures, determining preferred conformation, comparing molecular shapes, and computing molecular properties. Applications of the system to the study of anti-inflammatory drugs, somatostatin-like compounds, and dihydrofolate reductase inhibitors are summarized.

Animals↗
PubMed1980

Identification of N,N-dimethylproline as the N-terminal blocking group of Crithidia oncopelti cytochrome c557.

The N-terminal tryptic peptide of Crithidia oncopelti cytochrome c557 X-Pro-Me3Lys-Ala-Arg in which X represents an unknown N-terminal blocking group was characterized by electrophoresis at pH 2 and by 1H and 13C nuclear magnetic resonance. 1H-NMR spectra of the tryptic peptide suggested that the blocking group X was N,N-dimethylproline although the electrophoretic mobility of the peptide suggested a larger molecular weight. The peptides X-Pro-Me3Lys and X-Pro were generated by treatment of the tryptic peptide with thermolysin and carboxypeptidase and the free blocking group X was prepared by acid hydrolysis. Comparison of the 1H-NMR spectra of these peptides with spectra of synthetic N,N-dimethylproline and N,N-dimethylprolylproline demonstrated that the blocking group was indeed N,N-dimethylproline. The 13C-NMR spectrum of the tryptic peptide was consistent with this conclusion although unambiguous assignments to all resonances could not be obtained because of the small amount of material available. The origin of the dimethylproline blocking group is discussed.

Animals↗
PubMed1980

The effect of heparin on cardiovascular and metabolic parameters following burn shock in guinea pigs.

The effect of heparin intravenous (IV) infusion (1,200 IV/kg day) on the cardiovascular and metabolic responses to scalding was studied. The burn was produced by immersing an anesthetized guinea pig into 100 degrees C water for 3 seconds, resulting in a full-skin-thickness burn that covered 50% of the body surface area. We found that heparin-treated animals had lower cardiac outputs and carotid artery temperatures 24 hours after the burn than did control animals receiving saline. Heart rates and mean arterial blood pressures did not differ in the heparin-plus-saline and saline-infused animals. The hematocrits and plasma protein concentrations decreased similarly in both groups 8 and 24 hours after the burn. Free fatty acid levels were increased in heparin treated animals, whereas glucose concentrations were comparable. The 48 hour mortality was higher in the heparin-treated group. It appears that in our model, heparin was not of benefit in the immediate recovery after a full-skin-thickness burn.

Animals↗
PubMed1979

Proton nuclear magnetic resonance studies of Rhodospirillum rubrum cytochrome.

Rhodospirillum rubrum cytochrome c2 was studied by proton nuclear magnetic resonance at 220 MHz. Assignments were made to the resonances of heme c by double-resonance techniques and by temperature-dependence studies. The aromatic resonances of Trp-62 and Tyr-70 of ferrocytochrome c2 were identified by spin-decoupling experiments. The resonances of the Met-91 methyl group of the ferri- and ferrocytochromes were assigned by saturation-transfer experiments. The assignments are compared to those made for cytochromes c. A pH titration showed that the methionine methyl resonance of ferricytochrome c2 shifted with a pK of 6.25 and disappeared above pH 9. No histidine CH resonances that titrated normally over the neutral pH range were observed in the spectrum of either oxidation state of the protein. The possible origins of the ionizations at pH 6.25 and 9 are discussed.

Cytochrome c Group↗
PubMed1979

Pain of first-trimester abortion: its quantification and relations with other variables.

Among 2,299 patients on whom first-trimester abortions were performed after administration of local anesthesia, 97 per cent reported experiencing some degree of pain. Independent ratings of the pain severity were obtained from the patients and also from the doctors and counselors who observed them. Although the rating procedures used by patients from those used by doctors and counselors, the three sources agreed significantly in evaluating pain levels of individual patients. Data from all three sources indicated that pain produced during the abortion procedure tended to be minor in severity. The ranking of relative painfulness of the eight stages of the aborton procedure based on average ratings obtained from doctors was nearly identical to that based on average ratings obtained from counselors. (Patients did not rate the separate stages.) On average, the patients rated the pain as being less than earache or toothache, but more than headache or bachache. The youngest patients experienced the most pain, and the oldest experienced the least. Both gestational age and cervical dilatation were related to pain in a curvilinear fashion, i.e., for both variables, patients in extreme categories experienced more pain than those in intermediate categories. Preprocedure fearfulness was positively related to intraoperative pain. No support was found for the expectation that oral administration of 5 mg. of diazepam reduces pain during this procedure.

Abortion, Induced↗
PubMed1979

The release of prostaglandin E2 from the skin of the plaice, Pleuronectes platessa L.

1 A fungal extract which produces a cutaneous hypersensitivity reaction in the plaice, Pleuronectes platessa L., was incubated in vitro with the skin of this teleost fish. Samples of incubation media were assayed for smooth muscle stimulating activity. 2 Prostaglandin E2 was identified by bioassay, thin-layer chromatography, ultraviolet absorption spectroscopy and gas chromatography--mass spectrometry. Release from challenged skin was maximum after 60 min incubation. 3 Analysis of the fatty acid composition of plaice skin showed that although arachidonic acid was present (3% of total fatty acids), the precursor of prostaglandin E3, eicosapentaenoic acid contributed 9% of total. 4 Indomethacin (50 mg/kg i.p) did not inhibit the erythema induced by the fungal extract, whilst a dose of 1 mg/kg maximally inhibited prostaglandin release from skin on incubation in vitro. 5 It is concluded that prostaglandins do not have an exclusive role in the mediation of the hypersensitivity reaction.

Animals↗