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Biomedical subjects

M Smith

Publications and source records attributed to M Smith.

At least 793 records · Page 44Linked to original sources
PubMed1992

[Drainage of the erectile organs in the rat].

The retro-pubic veinous circle of the male rat was investigated on the both sides: anatomic and functional aspect. The dorsal vein of penis in the male rat run into a retro-pubic veinous circle. This circle receive the anterior vesical veins too. The internal pudendal vein and the anastomotic vein begin in this circle, and go together to the iliac vein. From the retro-pubic veinous circle, there is a triangular circulation between the internal pudendal vein, the anastomotic vein and the iliac vein. Angiographies performed on rats in vivo, indicates that the anastomotic vein is effical for the drainage of the retro-pubic circle only if the flow of the penis dorsal vein is sufficient. These conclusions are proved by experimentation on dead rats.

Animals↗
PubMed1992

Functional improvement in geriatric trauma patients admitted to a dedicated rehabilitation hospital.

A retrospective study was undertaken of trauma patients over 55 years of age who were admitted to a rehabilitation hospital during an 18-month period. Significant risk factors for poorer in-hospital improvement in functional independent measures were male sex, having an offspring listed as next of kin, pre-injury diabetes mellitus and/or dementia, and number of co-morbidities. Being married was found to be protective.

Activities of Daily Living↗
PubMed1992

[To plead for the introduction of a new psycho-oncology in France].

Psycho-oncology is a new discipline which considers the problem of psychological distress of cancer patients in a different manner to that of classical psychoanalysis. It is symptomatic, practical, scientific, and widely used on an international scale. It provides fresh clarification and the latest practical techniques in many areas: treatment of side-effects subsequent to radio- or chemotherapy, problems connected with life "after", risk factors, psychosocial interventions for normal stress reactions, treatment of anxiety and depressive syndromes, etc. This approach has been adopted to only a limited extent in France and deserves wider diffusion.

Combined Modality Therapy↗
PubMed1992

Effect of exercise on uterine activity in the patient in preterm labor.

Preterm labor patients are at risk for physiologic complications associated with long-term bed rest. Although conditioning exercise programs are recommended for patients confined to bed rest, no studies have been reported that have evaluated the effects of exercise on uterine activity in women with preterm labor. A pilot study with 10 women was conducted to evaluate the short-term effects of exercise with a protocol involving pretesting and posttesting of uterine activity. The results indicated minimal changes in the frequency of uterine contractions after exercise. Future research is recommended with larger and more diverse samples to evaluate both short- and long-term effects of exercise throughout high-risk pregnancies.

Adult↗
PubMed1992

Use of a ligand-screening procedure to study the interaction of S. cerevisiae alpha 2 repressor with its operator sequence.

A simple and rapid screening procedure was developed to study the interaction of the S. cerevisiae alpha 2 repressor with its operator sequence. An E. coli expression vector was constructed in which the alpha 2 coding sequence was placed under control of the lac promoter. Bacterial colonies containing this vector could be lysed and assayed directly for binding of wild-type and mutant operator sequences when grown on nitrocellulose filters. alpha 2 assayed in this way showed the same sequence specificity as determined in vivo. Pools of mutant alpha 2 repressors in which the codons for Arg185 or Ser181 in the homeodomain region were randomized were created by cassette mutagenesis. These pools of mutants were screened with the wild-type operator sequence to determine allowed amino acid substitutions at each position. Results suggest that both Arg185 and Ser181 have a role in high affinity operator binding.

Amino Acid Sequence↗
PubMed1992

DH11S: an Escherichia coli strain for preparation of single-stranded DNA from phagemid vectors.

A new E. coli strain DH11S [mcrA delta(mrr-hsdRMS-mcrBC) delta(lac-proAB) delta(rec1398) deoR rpsL srl- thi-/F'proAB+ lacIqZ delta M 15] has been constructed. Transformation of DH11S competent cells with any of several different phagemid vectors [pSPORT1, pBluescript II SK(+), pGEM11Zf(+)] results in the production of highly purified single-stranded DNAs upon the addition of M13KO7 helper phage. Contamination by double-stranded DNAs was observed with all the other studied strains (XL1-Blue, JM109, DH5 alpha F'IQ). The optimal yield of single-stranded DNA production was obtained when glycerol stocks made from stationary phase cells or single colonies from overnight ampicillin plates of DH11S containing the phagemid vector were infected with M13KO7 helper phage using a wide range (1 to 100) of multiplicities of infection. Five different pSPORT1 clones containing cDNA inserts of various lengths (0.3 kb to 2.0 kb) were compared using these four different bacterial strains. The use of strain DH11S results in the best yields and quality of single-stranded DNA. Therefore, DH11S appears to be the best all-around host for various applications that require single-stranded DNA such as DNA sequencing, in vitro mutagenesis and construction of subtractive cDNA libraries.

Coliphages↗
PubMed1992

Assay of endopeptidase-24.11 activity in plasma applied to in vivo studies of endopeptidase inhibitors.

We developed a fluorometric assay for endopeptidase-24.11 (EC 3.4.24.11) in human plasma. Substrate [glutaryl-Ala-Ala-Phe-amidomethylcoumarin(AMC)] was incubated with plasma (20 microL, 30 min, pH 7.6) with (control) or without the endopeptidase-24.11 inhibitor phosphoramidon. Further incubation with aminopeptidase M released free AMC. Within-assay CVs were 4.5% and 8.6%, respectively, at 3.31 and 0.27 nmol of AMC released per milliliter per minute. The between-assay CV was 10.4% at 0.31 nmol/mL per minute and the detection limit was 0.05 nmol/mL per minute. A highly skewed distribution of endopeptidase-24.11 in 41 normal samples was found, ranging from 0.12 to 6.84 nmol/mL per minute (median = 0.44). Mean endopeptidase-24.11 concentrations were significantly higher in hypertensive subjects (0.68 nmol/mL per minute) than in normotensive subjects (0.34 nmol/mL per minute; P less than 0.05). Compared with placebo administration, the oral endopeptidase-24.11 inhibitor UK 79300 significantly inhibited the plasma enzyme at doses of 100 mg (twice daily). Although in normotensive subjects the enzyme was unaffected with doses of 25 mg, the same dose (25 mg) inhibited the plasma enzyme in hypertensive subjects. No activity was detected in sheep plasma, but addition of exogenous endopeptidase-24.11 to sheep plasma in vitro allowed in vivo assessment of the effect of infused endopeptidase-24.11 inhibitor SCH 39370.

Amino Acid Sequence↗
PubMed1991

NMR study of the structural characteristics of variants of yeast iso-1-cytochrome c in which unvaried aromatic residues have been substituted.

The structures of variants of yeast iso-1-cytochrome c, in which the previously unchanged Tyr48 and Tyr48 + Trp59 have been replaced by Phe, have been characterised by NMR. The NMR data indicated that the structures of the variant cytochromes c are very similar to the wild-type protein. In particular, the heme environment and interactions of the heme macrocycle were shown to be preserved. The observation of chemical shift differences have allowed for the assessment of conformational changes. The substitution of Trp59 by Phe may have caused a small conformational change, a manifestation of which is the observed chemical shift differences at His39, Val57 and Tyr74. The structural basis for the reduction in redox potential accompanying the amino acid substitutions is discussed and the proposal made that the changes in potential are a direct consequence of the side chain properties and do not result primarily from conformational changes.

Amino Acids↗
PubMed1991

Characterization of the solubilized charybdotoxin receptor from bovine aortic smooth muscle.

Monoiodotyrosine ([125I]ChTX) binds with high affinity to a single class of receptors present in bovine aortic smooth muscle sarcolemmal membranes that are functionally associated with the high-conductance Ca(2+)-activated K+ channel [maxi-K channel; Vázquez, J., et al. (1989) J. Biol. Chem. 265, 20902-20909]. Cross-linking experiments carried out with this preparation in the presence of [125I]ChTX and disuccinimidyl suberate indicate specific incorporation of radioactivity into a protein of Mr 35,000. The smooth muscle ChTX receptor can be solubilized in active form in the presence of selected detergents. Treatment of membranes with digitonin releases about 50% of the ChTX binding sites. The solubilized receptor retains the same biochemical and pharmacological properties that are characteristic of toxin interaction with membrane-bound receptors. The solubilized receptor binds specifically to wheat germ agglutinin-Sepharose resin, suggesting that it is a glycoprotein. Functional ChTX binding sites can also be solubilized in 3-[(3-cholamidopropyl)dimethylamino]-1-propanesulfonate (CHAPS). Sucrose density gradient centrifugation of either digitonin or CHAPS extracts indicates that the ChTX receptor has a high apparent sedimentation coefficient (s20,w = 23 and 18 S, respectively). Cross-linking experiments indicate that the appearance of the 35-kDa membrane protein correlates with ChTX binding activity after both wheat germ agglutinin-Sepharose and sucrose density gradient centrifugation steps. Given the high apparent sedimentation coefficient of the ChTX receptor, the 35-kDa membrane protein may be a subunit of a higher molecular weight complex which forms the maxi-K channel in smooth muscle sarcolemma.

Animals↗
PubMed1991

Enhancing protein engineering capabilities by combining mutagenesis and semisynthesis.

If site-directed mutagenesis could be used to facilitate protein semisynthesis, then structural engineering goals should be achieved that are unattainable by either technique alone. We tested this possibility by mutating Ser65 of yeast cytochrome c to methionine, creating a new site for CNBr cleavage. Fragments obtained by cleaving there were found to refold cooperatively, bringing together the breakpoint termini and leading to efficient autocatalytic peptide bond synthesis. Structurally modified fragments may be substituted for natural ones. Generally, naturally occurring sites are unsuitable for autocatalytic religation, for reasons briefly discussed, and thus the power of this new approach lies in the freedom to choose sites, including enzymatic ones, that are appropriate to the semisynthetic goals.

Amino Acid Sequence↗
PubMed1991

Prevention of postmenopausal osteoporosis. A comparative study of exercise, calcium supplementation, and hormone-replacement therapy.

BACKGROUND: Osteoporosis among older women is a major public health problem. We studied the effects of three approaches to the prevention of osteoporosis in women with low bone density. METHODS: One hundred twenty postmenopausal women (mean [+/- SD] age, 56 +/- 4) who were selected because they had low forearm bone density were enrolled in a double-blind, placebo-controlled, randomized study comparing the effects of an exercise regimen (exercise group, n = 41), exercise plus dietary calcium supplementation (exercise-calcium group, n = 39), and exercise plus continuous replacement of estrogen and progesterone (exercise-estrogen group, n = 40). Periodically during the two-year study period, we measured the women's bone density at three forearm sites, measured indexes of calcium metabolism, and recorded symptom scores. A comparison group of 42 women (mean age, 55.5 +/- 3.1) with normal bone density was also followed for two years. RESULTS: Significant bone loss in the distal forearm occurred in the group with normal bone density (control group) and the exercise group (change, -2.7 percent and -2.6 percent of the base-line value per year, respectively). Bone loss at the distal forearm site was significantly lower in the exercise-calcium group (-0.5 percent of the base-line value per year), and bone density increased at this site in the exercise-estrogen group (+2.7 percent of the base-line value per year). Bone loss at the median forearm site was significantly lower in the exercise-calcium group (-1.3 percent of the base-line value per year) than in the exercise group (-2.4 percent), and bone density at this site increased significantly in the exercise-estrogen group (+0.8 percent of the base-line value per year). Breast tenderness occurred in 47 percent of the women in the exercise-estrogen group but in only 20 percent in the other two treatment groups. Vaginal bleeding occurred at some time in 52 percent of the women who had not had a hysterectomy in the exercise-estrogen group, as compared with 11 percent and 12.5 percent, respectively, in the exercise and exercise-calcium groups. CONCLUSIONS: In postmenopausal women with low bone density, bone loss can be slowed or prevented by exercise plus calcium supplementation or estrogen-progesterone replacement. Although the exercise-estrogen regimen was more effective than exercise and calcium supplementation in increasing bone mass, it also caused more side effects.

Bone Density↗
PubMed1991

Platelet activation by a synthetic hydrophobic polymer, polymethylmethacrylate.

Platelets adhere to artificial surfaces in the initial stage of thrombus formation, but the subsequent steps in signal transduction that lead to platelet activation by artificial surfaces are not understood. When 0.325-micron diameter beads composed of a hydrophobic polymer, polymethylmethacrylate (PMMA), were added to gel-filtered aequorin-loaded platelets suspended in media containing Ca2+, the platelets aggregated; addition of fibrinogen was not required. Platelet aggregation was preceded by an increase in cytoplasmic Ca2+ and was accompanied by phosphorylation of the 47-Kd substrate of protein kinase C (PKC), 5-hydroxytryptamine (5-HT) release, and accumulation of phosphatidic acid. All these effects were partially inhibited by apyrase and aspirin. Monoclonal antibodies (MoAbs) 7E3 and M148 and the synthetic peptides RGDS and fibrinogen gamma chain fragment 400-411, all of which bind to the platelet fibrinogen receptor glycoprotein IIb-IIIa (GPIIb-IIIa) and inhibit fibrinogen binding, prevented PMMA-induced aggregation but did not inhibit the Ca2+ increase. Chymotrypsin-treated platelets aggregated after addition of fibrinogen, but not PMMA. We conclude that platelets interact initially with PMMA at membrane sites other than those required for fibrinogen binding, leading to activation of membrane phospholipases and PKC, an increase in cytoplasmic Ca2+, release of 5-HT, ADP, and fibrinogen from storage granules, and to platelet aggregation.

Adenosine Diphosphate↗
PubMed1991

Gabaculine-resistant glutamate 1-semialdehyde aminotransferase of Synechococcus. Deletion of a tripeptide close to the NH2 terminus and internal amino acid substitution.

Glutamate 1-semialdehyde aminotransferase (GSA-AT) is the last enzyme in the C5 pathway converting glutamate into the tetrapyrrole precursor delta-aminolevulinate in plants, algae, and several bacteria. Sequence analysis of the genes encoding GSA-AT in barley, Synechococcus, and Escherichia coli revealed 50-70% similarity in the primary structures of the proteins. The enzyme is inhibited rapidly by gabaculine when added in approximately stoichiometric amounts with the enzyme. A gabaculine-tolerant Synechococcus strain, GR6, was found to produce a GSA-AT less sensitive to the inhibitor. Accordingly, the mutant gene was isolated and sequenced. In comparison with the wild-type gene it contains a deletion of nine nucleotides (position 12-20) and a guanine to adenine substitution (position 743). This resulted in the loss of the amino acids serine, proline, and phenylalanine (position 5-7) close to the NH2 terminus of the enzyme and an exchange of Met-248 for isoleucine in the middle of the polypeptide chain. Wild-type and mutant GSA-AT were expressed in E. coli and purified close to homogeneity. Although the specific activity of the mutant GSA-AT was only one-fifth of the wild type, it displayed a 100-fold increased resistance to gabaculine. Peaks in the absorption spectrum of the purified recombinant GSA-ATs at 335 and 417 nm are typical of a transaminase containing a B6 cofactor. Incubation with substrate and with inhibitor induced spectral changes characteristic of other gabaculine-sensitive, B6-requiring enzymes.

Amino Acids↗
PubMed1991

Functional complementation of ataxia-telangiectasia group D (AT-D) cells by microcell-mediated chromosome transfer and mapping of the AT-D locus to the region 11q22-23.

The hereditary human disease ataxia-telangiectasia (AT) is characterized by phenotypic complexity at the cellular level. We show that multiple mutant phenotypes of immortalized AT cells from genetic complementation group D (AT-D) are corrected after the introduction of a single human chromosome from a human-mouse hybrid line by microcell-mediated chromosome transfer. This chromosome is cytogenetically abnormal. It consists primarily of human chromosome 18, but it carries translocated material from the region 11q22-23, where one or more AT genes have been previously mapped by linkage analysis. A cytogenetically normal human chromosome 18 does not complement AT-D cells after microcell-mediated transfer, whereas a normal human chromosome 11 does. We conclude that the AT-D gene is located on chromosome 11q22-23.

Ataxia Telangiectasia↗
PubMed1991

Change in charge of an unvaried heme contact residue does not cause a major change of conformation in cytochrome c.

The structure of the Ala38 variant of yeast iso-1-cytochrome c, in which the previously unchanged Arg38 has been replaced, has been characterised by NMR. The NMR data indicate that the structure of the Ala38 variant is very similar to that of the wild type protein. In particular, the heme environment and interactions of the heme macrocycle are shown to be preserved. Analysis of the chemical shift perturbations to the resonances of Ile35 is shown to be consistent with the change in charge at position 38. The only significant area of conformational change detected was at residues 39 and 58, close to the site of modification. Therefore the redox potential change accompanying the modification [1988, Biochemistry 28, 3188-3197] appears to be a direct consequence of the altered side-chain of residue 38 and not a result of secondary conformational changes induced by the modification.

Alanine↗