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Biomedical subjects

S Smith

Publications and source records attributed to S Smith.

At least 541 records · Page 30Linked to original sources
PubMed1994

Physical and genetic mapping at the ATA/ATC locus on chromosome 11q22-23.

Genetic heterogeneity in ataxia-telangiectasia (A-T) points to four different genes responsible for this disease. The two major A-T genes, ATA and ATC, were localized by genetic analysis close to each other on chromosome 11q22-23, prompting efforts of positional cloning. Essential steps in positional cloning are long-range cloning of the genomic region of interest, and derivation of highly polymorphic markers that would allow further reduction of the interval carrying the A-T gene. We constructed genomic contigs across the D11S611-D1S424 region harbouring the ATA and ATC genes in yeast artificial chromosome (YAC) vectors. These contigs were used as a fine mapping tool and enabled us to localize along the A-T region, eight microsatellite markers generated randomly by genome mapping centres. In addition, we used specific YAC clones to generate five new microsatellite markers based on polymorphic CA repeats. Recombination mapping based on Israeli A-T families indicates that the ATC gene is distal to the locus D11S1817. Further linkage analysis using these markers is expected to reduce the major A-T locus considerably to a size appropriate for cosmid cloning and identification of transcribed sequences.

Ataxia Telangiectasia↗
PubMed1994

The Saskatchewan Clinical Stroke Prevention Project: design.

The Saskatchewan Clinical Stroke Prevention Project aims to examine the process and impact of incorporating enhanced stroke prevention into the routine clinical practice of family physicians. Twenty-four physicians in three practices in Saskatchewan are participating in a staged series of educational interventions over two years to enhance their management of smoking, transient ischemic attack/stroke, atrial fibrillation and hypertension. The components of each intervention include a seminar, printed materials, a one-to-one case discussion or "academic detailing," a self-documented chart audit and changes to the office system. Patients for whom this intervention is targeted are those 55 to 75 years of age presenting for a periodic health examination with one or more of the four main risk factors for stroke. Intervention will consist of counselling on relevant risk factors by the doctor and nurse teams, supported by appropriate patient education materials. Patient follow-up will be carried out according to clinical indications and will be done at least 3, 6, 12 and 24 months after entry into the study. Evaluation comprises measures of the process of implementing change in preventive practice as well as of the impact of such change. The former includes semi-structured interviews and focus groups with physicians, support staff and patients. The latter includes an assessment of knowledge, attitudes and charted practice before and after intervention.

Adult↗
PubMed1994

The animal fatty acid synthase: one gene, one polypeptide, seven enzymes.

The animal fatty acid synthase comprises two multifunctional polypeptide chains, each containing seven discrete functional domains, juxtaposed head-to-tail such that two separate centers for fatty acid assembly are formed at the subunit interface. The kinetics and specificities of the component enzymes are well adapted to ensure that, at each of the two centers, the iterative condensation of an acetyl moiety with successive malonyl moieties and complete reduction of the beta-keto intermediates normally results in the formation of palmitic acid as the major product. Nevertheless, utilization of alternative substrates and alternative chain-terminating mechanisms can extend the range of products to include branched-chain, odd carbon-numbered, and shorter chain-length fatty acids. The potential of this multifunctional form of molecular architecture for the elaboration of more complex natural products has been further exploited in microorganisms that, by the use of different fatty acid synthase "modules" that perform variable beta-carbon processing at successive elongation steps, generate a structurally diverse family of polyketides retaining keto, hydroxyl, enoyl, or alkyl functions at specific positions in the carbon chain.

Amino Acid Sequence↗
PubMed1994

Hematocrit levels and physiologic factors in relationship to cardiovascular risk in Tecumseh, Michigan.

OBJECTIVE: To investigate the relationship between hematocrit, blood pressure and other known cardiovascular risk factors. DESIGN: The Tecumseh Blood Pressure Study includes a cohort of subjects of average age 29.5 years (346 male, 277 female) who reside in Tecumseh, Michigan, USA. METHODS: The body weight; home, work and clinic blood pressures; hematocrit level, plasma renin activity, baseline and mentally stimulated plasma catecholamines level; and fasting glucose, insulin and lipids levels were obtained. Since menstruation and childbearing affect the hematocrit, results are presented only for males. The males in Tecumseh were divided into tertiles of hematocrit (group I < or = 43.25, group II 43.26-45.2 and group III > 45.2%). RESULTS: Higher hematocrit levels were significantly related to higher blood pressures at home, at work and in the clinic, although all of the values measured were within the normotensive range (128/79 mmHg clinic blood pressure in group III). The metabolic factors weight, cholesterol, triglycerides, insulin and glucose levels were significantly elevated in group III. The weight affected only the relationship of hematocrit to plasma insulin levels and not the other variables including the blood pressure. Groups II and III showed signs of sympathetic overactivity; their plasma renin levels, heart rates and norepinephrine levels after mental stimulation were elevated. CONCLUSIONS: Although the relationship of blood pressure to the hematocrit level was previously known, in Tecumseh hematocrit is also found to be associated with several other cardiovascular risk factors and with signs of a hypersympathetic state. We intend to evaluate prospectively the relative prognostic significance of a higher hematocrit level versus the other associated risk factors.

Adult↗
PubMed1993

Surveillance for pregnancy and birth rates among teenagers, by state--United States, 1980 and 1990.

PROBLEM/CONDITION: In the United States in 1990, there were an estimated 1 million pregnancies and 521,826 births among women ages 15-19 years. Rates of teenage pregnancy and birth rates by state in 1990 exceeded those in most developed countries. An estimated 95% of teenage pregnancies are unintended (i.e., they occur sooner than desired or are not wanted at any time). REPORTING PERIOD COVERED: This report summarizes and reviews surveillance data for pregnancies, abortions, and births among women ages 15-19, 15-17, and 18-19 years reported by CDC for 1980 and 1990. DESCRIPTION OF SYSTEM: Data for births and abortions were reported to state health departments and other health agencies and sent to CDC. The data from each state included the total number of births and abortions by age and race/ethnicity. RESULTS: Data in this report indicate that pregnancy rates by state among U.S. teenagers ages 15-19 years have changed little since 1980. Moreover, many states have reported increases in birth rates that are probably related to concurrent decreases in abortion rates. Pregnancy rates range from 25 to 75 per 1,000 for 15- to 17-year-olds and from 92 to 165 per 1,000 for 18- to 19-year-olds. INTERPRETATION: States with low rates of teenage pregnancy or birth may have developed and used prevention strategies directed at the needs of both younger and older teenagers; these programs may serve as models for other states where birth rates have remained high or have increased since 1980. ACTIONS TAKEN: CDC will continue to conduct surveillance of and analyze data for pregnancies, abortions, and births among teenagers to monitor progress toward national goals and to assist in targeting program efforts for reducing teenage pregnancy.

Abortion, Legal↗
PubMed1993

Construction of a cDNA encoding the multifunctional animal fatty acid synthase and expression in Spodoptera frugiperda cells using baculoviral vectors.

A cDNA encoding the 2505-residue multifunctional rat fatty acid synthase has been constructed and expressed as a catalytically active protein in Spodoptera frugiperda (Sf9) cells using Autographa californica nuclear polyhedrosis virus (baculovirus). The 7.5 kb cDNA was engineered by the amplification and sequential splicing together of seven fragments contained in overlapping cDNAs that collectively spanned the entire rat fatty acid synthase coding sequence. The full-length cDNA was cloned into a baculoviral transfer vector and used together with linearized baculoviral DNA to co-transfect Sf9 cells. Recombinant viral clones were purified and identified by Western blotting. The recombinant fatty acid synthase was expressed maximally 2 days after infection of the Sf9 cells, constituting up to 20% of the soluble cytoplasm, and could be conveniently separated from the insect host fatty acid synthase by high-performance anion-exchange chromatography. The catalytic properties of the purified recombinant fatty acid synthase are indistinguishable from those of the best preparations of the natural protein obtained from rat liver. These results indicate that, in the insect cell host, all seven catalytic components of the 2505-residue recombinant fatty acid synthase fold correctly, the acyl-carrier-protein domain is appropriately phosphopantetheinylated post-translationally, and the multifunctional polypeptide forms catalytically competent dimers. Thus the baculoviral system appears to be well suited for the expression of specific fatty acid synthase mutants that can be used to explore the mechanism by which the seven domains of this multifunctional homodimer co-operate in the biosynthesis of fatty acids.

Amino Acid Sequence↗
PubMed1993

Construction, expression, and characterization of a mutated animal fatty acid synthase deficient in the dehydrase function.

The location of the dehydrase domain in the multifunctional animal fatty acid synthase has been determined by engineering a fatty acid synthase mutant deficient in dehydrase activity. A full-length fatty acid synthase cDNA encoding a mutated histidine residue (His878-->Ala) was constructed and expressed in insect Sf9 cells using a baculoviral vector. The mutated recombinant fatty acid synthase retained all partial activities of the multifunctional complex except the dehydrase and was unable to synthesize fatty acids. beta-Hydroxybutyryl moieties were formed by the mutant fatty acid synthase from acetyl-CoA, malonyl-CoA, and NADPH and slowly released as the CoA thioester, confirming that this protein cannot perform the dehydration reaction. This finding points to an important catalytic role for His878 in the dehydration reaction and establishes that the dehydrase domain is located immediately adjacent to the carboxyl terminus of the transferase domain. Examination of the completed domain map for the animal fatty acid synthase indicates that the catalytic domains are clustered in two groups separated by a central structural core: the ketoacyl synthase, malonyl/acetyltransferase, and dehydrase in the amino-terminal half and the enoyl reductase, ketoreductase, acyl carrier protein, and thioesterase in the carboxyl-terminal half. A model is proposed in which the two centers for acyl chain initiation, elongation and termination, are formed by the cooperation of the three amino-terminal domains of one subunit with the four carboxyl-terminal domains of the other subunit.

Alanine↗
PubMed1993

Evidence against a relationship between fatty acid ethyl ester synthase and the Pi class glutathione S-transferase in humans.

Recently, Bora et al. (Bora, P. S., Bora, N. S., Wu, X., and Lange, L. G. (1991) J. Biol. Chem. 266, 16774-16777) reported the cloning and expression of a human fatty acid ethyl ester synthase III (FAEES-III) cDNA that has only four amino acid substitutions compared with human glutathione S-transferase (GST) GSTP1-1, and, when expressed in MCF-7 cells, the protein has both FAEES and GST activities. By site-directed mutagenesis of a GSTP1 cDNA, we have constructed a clone that encodes the FAEES-III protein described by Bora et al. (1991). The recombinant FAEES-III protein was expressed in Escherichia coli and has been shown to be devoid of FAEES and GST activities. The recombinant FAEES-III protein does not bind to a glutathione agarose affinity matrix, presumably because two of the substituted amino acids, Trp-39-->Cys and Gln-52-->Glu, are thought to contribute to the GST glutathione binding site. One of the base substitutions in the FAEES-III cDNA encodes an extra SacI site not found in the GSTPI cDNA. Polymerase chain reaction amplification of human genomic DNA has identified the GSTPI gene, but no DNA from the proposed FAEES gene with a diagnostic SacI site has been detected. Evaluation of the hybridization pattern of HindIII genomic restriction fragments has identified fragments that contain the GSTPI gene and a pseudogene (Board et al. 1992), and there do not appear to be any hybridizing fragments that could contain the FAEES-III gene. Our results do not provide any evidence in support of a relationship between FAEES-III and GST, and the cDNA reported by Bora et al. (1991) may have resulted from a cloning artifact.

Acyltransferases↗
PubMed1993

Characterization of fatty acid synthase monomers restrained from reassociating by immobilization to a solid support.

The controversial question as to whether the ketoreductase activity of the animal fatty acid synthase is lost on dissociation of the homodimer has been addressed by using immobilized subunits which cannot reassociate under the conditions of assay. Ketoreductase activity, assessed with the model substrate S-acetoacetyl-N-acetylcysteamine, was identical in immobilized monomers and dimers, exhibiting normal Michaelis-Menten kinetics with Km values in the millimolar range. When acetoacetyl-CoA was used as a substrate, however, biphasic kinetics were observed in the case of the dimer, with estimated Km values in the micro- and milli-molar ranges, but only the high-Km reaction was observed with the monomer. Thus when the ketoreductase activities of the monomer and dimer are assessed with acetoacetyl-CoA at concentrations sufficient to saturate only the low-Km reaction, it appears that the ketoreductase activity towards acetoacetyl-CoA is lost upon dissociation. Reduction of acetoacetyl-CoA via the low-Km pathway is CoA-dependent, indicating that acetoacetyl-CoA can react with the dimer by two mechanisms: a high-Km pathway analogous to that utilized by model substrates and a low-Km pathway in which substrate and product are transferred between acyl-CoA and acyl-enzyme forms. The results indicate that the ketoreductase activity per se is unaffected by subunit dissociation and are consistent with a model in which the transfer of substrate from CoA ester to the acyl-carrier-protein domain necessitates juxtaposition of the transferase active-site serine residue of one subunit and the phosphopantetheine moiety of the adjacent subunit.

Catalysis↗
PubMed1993

p53 Mutation and MDM2 amplification in human soft tissue sarcomas.

The p53 and MDM2 genes were analyzed in 24 human soft tissue sarcomas (11 malignant fibrous histiocytomas and 13 liposarcomas). Alterations of p53, consisting of point mutations, deletions, or overexpression, were detected in one-third (8 of 24) of the sarcomas. MDM2 gene amplification was detected in another 8 tumors, but no tumor contained an alteration of both genes. Monoclonal antibodies reactive with the human MDM2 gene product were developed, and immunohistochemical analysis revealed nuclear localization and overexpression of MDM2 in those tumors with amplified MDM2 genes. These data support the hypothesis that p53 and MDM2 genetic alterations are alternative mechanisms for inactivating the same regulatory pathway for suppressing cell growth.

Animals↗
PubMed1993

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Ill-Housed Persons↗
PubMed1993

Immunohistochemical identification of leucocyte populations in normal tissue and inflamed synovium of the rabbit.

A panel of monoclonal antibodies which recognizes well-defined markers of rabbit leucocytes has been used in an immunohistochemical survey of normal rabbit spleen, thymus, and liver, and of inflamed synovial tissue. The results demonstrate that these antibodies are well suited for the identification of leucocytes in frozen sections of rabbit tissues and that T lymphocytes, macrophages, and neutrophils can be readily distinguished. Antibodies to CD44 differentiate between medullary and cortical thymocytes, with the cortical cells being almost entirely negative for this marker. Antibodies to RLA class II show that periportal lymphocytes in the liver express RLA-DR but not RLA-DQ. The type A cells of the synovial lining from inflamed joint tissue are stained by antibodies that recognize macrophages in a manner similar to that found in the human synovial lining.

Animals↗
PubMed1993

Animal models of early osteoarthritis: their use for the evaluation of potential chondroprotective agents.

Medial meniscectomy was undertaken in adult merino sheep and after 16 weeks exercise each group was administered five weekly intra-articular injections of saline, pentosan polysulphate (PPS), hyaluronic acid (HA) or a combination of PPS + HA. Gait analysis and x-rays were undertaken before and after drug treatment. At sacrifice (26 weeks), joints were examined for gross pathological and histochemical changes. Only the PPS-treated group showed an improvement in gait, with low radiological and histology scores. The HA-treated group showed similar but less significant changes to these parameters.

Animals↗
PubMed1993

The metabolic response of articular cartilage to abnormal mechanical loading induced by medial or lateral meniscectomy.

The effects of medial versus lateral meniscectomy on articular cartilage (AC) of adult sheep was investigated. In vitro incorporation of 35S into proteoglycans (PGs) and their release into media was used to assess cartilage metabolism. Lateral meniscectomy produced higher loss of PGs from AC and lower 35S-PG biosynthesis than for AC from medial meniscectomized joints. These findings were consistent with the proposed role of the lateral meniscus in joint mechanics.

Animals↗