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Biomedical subjects

G Turner

Publications and source records attributed to G Turner.

At least 181 records · Page 10Linked to original sources
PubMed1992

Calcium influx into neurons can solely account for cell contact-dependent neurite outgrowth stimulated by transfected L1.

We have used monolayers of control 3T3 cells and 3T3 cells expressing transfected human L1 as a culture substrate for rat PC12 cells and rat cerebellar neurons. PC12 cells and cerebellar neurons extended longer neurites on human L1 expressing cells. Neurons isolated from the cerebellum at postnatal day 9 responded equally as well as those isolated at postnatal day 1-4, and this contrasts with the failure of these older neurons to respond to the transfected human neural cell adhesion molecule (NCAM). Human L1-dependent neurite outgrowth could be blocked by antibodies that bound to rat L1 and, additionally, the response could be fully inhibited by pertussis toxin and substantially inhibited by antagonists of L- and N-type calcium channels. Calcium influx into neurons induced by K+ depolarization fully mimics the L1 response. Furthermore, we show that L1- and K+(-)dependent neurite outgrowth can be specifically inhibited by a reduction in extracellular calcium to 0.25 microM, and by pretreatment of cerebellar neurons with the intracellular calcium chelator BAPTA/AM. In contrast, the response was not inhibited by heparin or by removal of polysialic acid from neuronal NCAM both of which substantially inhibit NCAM-dependent neurite outgrowth. These data demonstrate that whereas NCAM and L1 promote neurite outgrowth via activation of a common CAM-specific second messenger pathway in neurons, neuronal responsiveness to NCAM and L1 is not coordinately regulated via posttranslational processing of NCAM. The fact that NCAM- and L1-dependent neurite outgrowth, but not adhesion, are calcium dependent provides further evidence that adhesion per se does not directly contribute to neurite outgrowth.

3T3 Cells↗
PubMed1992

Regulation of Aspergillus nidulans penicillin biosynthesis and penicillin biosynthesis genes acvA and ipnA by glucose.

Expression of the Aspergillus nidulans penicillin biosynthesis genes acvA and ipnA, encoding delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase and isopenicillin N synthetase, respectively, was analyzed. The intergenic region carrying the divergently oriented promoters was fused in frame in both orientations to Escherichia coli lacZ and E. coli uidA reporter genes. Each construct permits simultaneous expression studies of both genes. Transformants of A. nidulans carrying a single copy of either plasmid integrated at the chromosomal argB locus were selected for further investigations. Expression of both genes was directed by the 872-bp intergenic region. ipnA- and acvA-derived gene fusions were expressed from this region at different levels. ipnA had significantly higher expression than did acvA. Glucose specifically reduced the production of penicillin and significantly repressed the expression of ipnA but not of acvA gene fusions. The specific activities of isopenicillin N synthetase, the gene product of ipnA, and acyl coenzyme A:6-aminopenicillanic acid acyltransferase were also reduced in glucose-grown cultures.

Acyltransferases↗
PubMed1992

Experience with direct molecular diagnosis of fragile X.

The utility of the pfxa3 probe for direct molecular diagnosis of the fragile X (FRAXA) has been established. This probe detects amplification of an unstable DNA element consisting of variable length CCG repeats. The size of the amplified fragment is correlated with phenotype and was determined using PstI digested DNA in family members. In 35 families with the fragile X, there was correspondence in 183 cases between the presence of an amplified unstable element and the presence of the fragile X chromosome independently determined by cytogenetics, position in the pedigree, or linked DNA markers flanking the fragile X. There was also correspondence in 124 cases between the presence of the normal 1.0 kb PstI fragment and absence of the fragile X chromosome independently determined by linked flanking markers. Six additional families considered to be isolated cases of 'fragile X' had been diagnosed before recognition of FRAXD. The pfxa3 probe confirmed the cytogenetic diagnosis in three families, the other three being rediagnosed as non-fragile X. A further two families had consistent expression of a different folate sensitive fragile site, FRAXE, close to FRAXA but not associated with fragile X syndrome and not detectable with the pfxa3 probe. Subsequent referrals were received from additional family members or from members of new families for whom carrier status had not been predetermined by linked markers. Direct pfxa3 diagnosis for the 135 females within these 222 additional cases was confirmed by dosage analysis with the control probe pS8.(ABSTRACT TRUNCATED AT 250 WORDS)

Artifacts↗
PubMed1992

Genes for the biosynthesis of beta-lactam compounds in microorganisms.

Rapid progress has recently been made in the characterization of genes and gene clusters involved in the biosynthesis of beta-lactam antibiotics such as penicillins, cephalosporins and cephamycins. The biosynthetic pathways are found in a wide range of microorganisms, including fungi, actinomycetes and Gram-negative bacteria. Comparisons of gene sequences (particularly the genes encoding isopenicillin N synthetase) and gene organization in these different microorganisms have led to proposals about the evolution of this group of pathways, and how they might have been transferred from prokaryotes to eukaryotes. The isolation and characterization of the genes encoding ACV (tripeptide) synthetase, the first step in the beta-lactam biosynthetic pathway, have revealed the presence of three partly repeated domains, most likely responsible for the recognition, adenylation and activation of the three amino acid precursors of the penams and cephems. This has confirmed their classification as peptide synthetases, distantly related to enzymes responsible for the synthesis of peptide antibiotics in Bacillus brevis and other bacteria and fungi.

Actinomycetaceae↗
PubMed1992

Black American folk medicine health care beliefs: implication for nursing plans of care.

Even in this age of information, some African Americans equate good health with luck or success. An illness or disease, viewed as undesirable, may be equated with bad luck, chance, fate, poverty, domestic turmoil, or unemployment, and in such case, Black Americans will consult a physician only after attempts with home remedies have failed. It is important for the nurse when working with Black patients, remember that when this patient enters the traditional bio-medical health care delivery system, it is best to assume that all known and available cultural home remedies have been tried. According to Bloch (1976), some Black Americans believe that the nurse should recognize cultural medical practices and the western medical remedies based on these beliefs. It is essential that the nurse determine whether these home remedies will interact or interfere with orthodox medical approaches. If home remedies are found to be efficacious or neutral. they may be kept at the patient's bedside. However, if they are found to be harmful, the nurse should assist the patient in developing an understanding about the remedies' dangers. With an emphasis on education, the patient can be navigated toward modern medical preventive techniques and cures, and the nurse may observe and judge the variety and efficacy of age-old culturally entrenched health care practices. Future studies may just substantiate the science behind the folklore.

Black or African American↗
PubMed1992

Fragile-X syndrome: unique genetics of the heritable unstable element.

The fragile site at Xq27.3 is an unstable microsatellite repeat, p(CCG)n. In fragile-X syndrome pedigrees, this sequence exhibits variable amplification, the length of which correlates with fragile-site expression. There is a direct relationship between increased p(CCG)n copy number and propensity for instability: individuals having large amplifications exhibit somatic variation due to increased instability. The instability of the p(CCG)n repeat, when transmitted through affected pedigrees, explains the unusual segregation patterns of fragile-X phenotype, referred to as the Sherman paradox. All individuals of fragile-X genotype were found (where testing was possible) to have a parent with amplified p(CCG)n repeat, indicating that few, if any, cases of fragile-X syndrome are not familial.

Blotting, Southern↗
PubMed1991

New X-linked syndrome of mental retardation, gynecomastia, and obesity is linked to DXS255.

We describe 14 males from 3 successive generations in a family who have X-linked mental retardation (XLMR), obesity, gynecomastia, speech difficulties, emotional lability, tapering fingers, and small feet. Linkage analysis using markers spread along the X chromosome demonstrated a gene localisation close to the centromere. Maximum lod scores for markers near the centromere, all at theta = 0.00, were 1.36 for DXS72, and 1.46 for DXYS1. The closest flanking markers which showed recombination were DXS84 and DXS94, defining the physical localisation within Xp21.1-q22. DXS255 was fully informative with lod-1 confidence interval for theta of 0.00-0.12. Clinical findings and linkage data in this family distinguish it from the Börjeson-Forssman-Lehmann syndrome and other previously described XLMR syndromes.

Adolescent↗
PubMed1991

Smith-Fineman-Myers syndrome in two brothers.

We report on 2 brothers with a distinctive facial appearance, severe mental retardation, short stature, cryptorchidism, asplenia in one, dramatic failure to thrive, early hypotonia, and later hypertonia all suggestive of the Smith-Fineman-Myers syndrome. All 5 of the reported cases have been males, suggesting X-linked inheritance.

Abnormalities, Multiple↗
PubMed1991

Purification and characterization of two endopolygalacturonases from Sclerotinia sclerotiorum.

The endopolygalacturonase (EC 3.2.1.15) enzyme produced in vitro by Sclerotinia sclerotiorum were found to consist of numerous isoforms covering a broad pI range. Two of the isoforms, labelled PG2 and PG3, were purified using gel-filtration chromatography, isoelectric focusing and anion-exchange chromatography. The pIs of PG2 and PG3 were, respectively, 4.8 and 4.9. Their molecular weights were similar. Both enzymes hydrolysed 0.9% of the bonds in reaching a 50% reduction in viscosity. However, their enzymic parameters were different. Their amino acid compositions differed only in the aspartic acid-asparagine content. The N-terminal sequences differed at the fourth amino acid only. PG2 and PG3 exhibited a high level of glycosylation compared to a similar enzyme isolated from Aspergillus niger. Antibody raised against PG3 was shown to crossreact with PG2, but not with the enzyme purified from Aspergillus niger.

Amino Acid Sequence↗
PubMed1991

Localisation of the MRX3 gene for non-specific X linked mental retardation.

A family is described with five affected males segregating a new gene for non-specific X linked mental retardation (MRX). Linkage analysis localised the gene at Xq28-qter. The maximum lod score was 2.89 with DXS52 (St14) at theta = 0.0. A recombinant was observed with DXS304 (U6.2) defining the proximal limit to the localisation. No evidence for linkage was determined using markers at several points along the remainder of the X chromosome, including the regions known to contain MRX1 and MRX2. This delineates the third gene for non-specific X linked mental retardation, MRX3.

Adult↗
PubMed1991

Non-specific X linked mental retardation.

Non-specific X linked mental retardation (MRX) is mental retardation in persons of normal physical appearance who have no recognisable features apart from a characteristic pedigree. Review of published reports shows that there is clinical variability in the degree of mental retardation within families and genetic heterogeneity, based on gene localisation, between families. We propose a classification based on genetic localisation and a set of minimal clinical features that should be recorded in the hope of identifying possible specific phenotypes.

Genetic Linkage↗
PubMed1991

Accuracy of growth hormone measurements.

The availability of high quality reagents and new methodology have contributed to overall improvements in the performance of immunoassays of human growth hormone in recent years. Discrepancies between superficially similar methods do occur as a result of the heterogeneous nature of the hormone itself. However, there is also evidence of incorrect standardisation in widely used, commercially available assays. Careful interpretation of growth hormone assays is still required, therefore, especially when results from different laboratories are being compared.

Genetic Variation↗
PubMed1991

Renal insufficiency and secondary hyperparathyroidism in elderly patients.

Glomerular filtration rate (GFR) is frequently reduced in elderly people. However, the effect of this on mineral metabolism in this population has received little attention. GFR, serum intact parathyroid hormone (PTH) and vitamin D metabolites were measured in 37 patients admitted to hospital for various reasons. In 20 patients with GFR greater than 50 mL/min, an elevated serum intact PTH concentration (greater than 5.4 pmol/L) was found in two, while in 17 patients with GFR less than 50 mL/min PTH was elevated in 13. One of this group was hypercalcaemic and presumed to have primary hyperparathyrodism. Adjusted calcium was normal in all other patients. Two patients had a low serum 25-hydroxyvitamin D concentration (less than 9 nmol/L) suggesting vitamin D insufficiency while a further five had a reduced 1,25-dihydroxyvitamin D concentration, four of these having a GFR less than 50 mL/min. We conclude that hyperparathyrodism is common in hospitalized elderly patients, particularly in those with mild to moderate renal insufficiency. This may contribute to bone mineral loss in such patients.

Aged↗
PubMed1991

Preceptorship programs: a public relations tool.

This article discusses the components and benefits of the public relations model, as developed by Black and Sharp (1983), and the use of this model in the development and implementation of a successful preceptorship program at Columbus College in Columbus, Georgia.

Education, Nursing, Baccalaureate↗
PubMed1990

The multifunctional peptide synthetase performing the first step of penicillin biosynthesis in Penicillium chrysogenum is a 421,073 dalton protein similar to Bacillus brevis peptide antibiotic synthetases.

The nucleotide sequence of the Penicillium chrysogenum Oli13 acvA gene encoding delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase, which performs the first step in penicillin biosynthesis, has been determined. The acvA gene contains an open reading frame of 11,238 bp encoding a protein of 3746 amino acids with a predicted mol. wt of 421,073 dalton. Three domains within the protein of approximately 570 amino acids have between 38% and 43% identity with each other and share similarity with two antibiotic peptide synthetases from Bacillus brevis as well as two other enzymes capable of performing ATP-pyrophosphate exchange reactions. The acvA gene is located close to the pcbC gene encoding isopenicillin N synthetase, the enzyme for the second step of beta-lactam biosynthesis, and is transcribed in the opposite orientation to it. The intergenic region of 1107 bp from which the acvA and pcbC genes are divergently transcribed has also been sequenced.

Amino Acid Sequence↗