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Biomedical subjects

S M Wilson

Publications and source records attributed to S M Wilson.

At least 73 records · Page 4Linked to original sources
PubMed1998

The rapid diagnosis of isoniazid and rifampicin resistance in Mycobacterium tuberculosis--a molecular story.

Isoniazid and rifampicin resistance are assayed phenotypically by the resistance ratio, absolute concentration or proportion methods. Assay methods are often difficult to standardise and the World Health Organization (WHO) Global Programme on Drug Resistance is attempting to produce standardised drug resistance data worldwide. Broth-based methods are faster than solid media systems, and a commercial radiometric system, the Bactec 460, is arguably the fastest method and permits testing to be completed within 7-14 days; however, this method is expensive and requires disposal of radioactive material. Novel phenotypic methods that utilise mycobacteriophages have shown promise. Other molecular detection systems require knowledge of the genes encoding the drug target (the inhA/mabA, katG, oxyR and ahpC genes for isoniazid; rpoB for rifampicin) and the mutations producing resistance. These genotypic methods are limited in that not all resistance mechanisms are known, but advanced assays for rifampicin resistance that use gene sequencing, heteroduplex analysis, solid-phase hybridisation or single-strand conformation polymorphism analysis are becoming available.

Base Sequence↗
PubMed1998

Comparison of three molecular assays for rapid detection of rifampin resistance in Mycobacterium tuberculosis.

Multidrug-resistant Mycobacterium tuberculosis (MDR-TB) is an emerging problem of great importance to public health, with higher mortality rates than drug-sensitive TB, particularly in immunocompromised patients. MDR-TB patients require treatment with more-toxic second-line drugs and remain infectious for longer than patients infected with drug-sensitive strains, incurring higher costs due to prolonged hospitalization. It is estimated that 90% of United Kingdom rifampin-resistant isolates are also resistant to isoniazid, making rifampin resistance a useful surrogate marker for multidrug resistance and indicating that second- and third-line drugs to which these isolates are susceptible are urgently required. Resistance in approximately 95% of rifampin-resistant isolates is due to mutations in a 69-bp region of the rpoB gene, making this a good target for molecular genotypic diagnostic methods. Two molecular assays, INNO-LiPA Rif.TB (Innogenetics, Zwijndrecht, Belgium) and MisMatch Detect II (Ambion, Austin, Tex.), were performed on primary specimens and cultures to predict rifampin resistance, and these methods were compared with the resistance ratio method. A third method, the phenotypic PhaB assay, was also evaluated in comparison to cultures in parallel with the genotypic assays. In an initial evaluation 16 of 16, 15 of 16, and 16 of 16 rifampin-resistant cultures (100, 93.8, and 100%, respectively), were correctly identified by line probe assay (LiPA), mismatch assay, and PhaB assay, respectively. Subsequently 38 sputa and bronchealveolar lavage specimens and 21 isolates were received from clinicians for molecular analysis. For the 38 primary specimens the LiPA and mismatch assay correlated with culture and subsequent identification and susceptibility tests in 36 and 38 specimens (94.7 and 100%), respectively. For the 21 isolates submitted by clinicians, both assays correlated 100% with routine testing.

Antibiotics, Antitubercular↗
PubMed1998

Osteopontin inhibits inducible nitric oxide synthase activity in rat vascular tissue.

We tested the hypothesis that osteopontin (OPN) can inhibit the induction of inducible nitric oxide synthase (iNOS) in vascular tissue. iNOS activity was induced in rat thoracic aortas by incubation of the tissue with lipopolysaccharide (LPS) and measured by conversion of L-[3H]arginine to L-[3H]citrulline. Addition of >/=1 nM recombinant OPN protein significantly reduced the LPS-induced increase in iNOS activity. Western blotting and the RT-PCR were used to determine the effect of LPS with and without OPN on tissue levels of iNOS protein and RNA, respectively. LPS resulted in an increase in iNOS protein and RNA, whereas OPN dose-dependently reduced tissue levels of iNOS activity, protein, and RNA. Mutated OPN proteins, in which the integrin-binding RGD amino acid sequence was deleted or mutated to RGE, resulted in complete and partial loss, respectively, of the ability of OPN to inhibit LPS-induced iNOS activity, implicating integrin binding in the effect. These results indicate that OPN can prevent induction of iNOS in vascular tissue.

Animals↗
PubMed1998

Persistent desensitisation of the beta 2 adrenoceptors expressed by cultured equine sweat gland epithelial cells.

Adrenaline, forskolin and ATP all evoked accumulation of cyclic AMP in equine sweat gland epithelial cells, although the response to adrenaline was more transient than that to forskolin and ATP. Cells preincubated in adrenaline (10 micromol l-1, 32 min) showed essentially complete, homologous desensitisation, and this phenomenon reversed slowly (half-time 6.3+/-0.9 h). After 10 min of recovery from preincubation in adrenaline, isobutylmethylxanthine (IBMX, 5 mmol l-1) had no effect upon the desensitisation and the cells showed no loss of sensitivity to ATP and forskolin. After 10 h, however, the persistent desensitisation was partially reversed by IBMX and the cells showed reduced responses to ATP and forskolin. Increased phosphodiesterase activity may thus contribute to the persistent desensitisation. Experiments using forskolin-preincubated (100 micromol l-1, 32 min) cells suggested that increased cytosolic cyclic AMP levels did not underlie the initial loss of sensitivity to adrenaline but that this second messenger may initiate the series of events leading to the generalised loss of sensitivity seen after 10 h.

1-Methyl-3-isobutylxanthine↗
PubMed1997

Neoral compared to Sandimmune is associated with a decrease in histologic severity of rejection in patients undergoing primary liver transplantation.

BACKGROUND: In a randomized, controlled study we investigated the clinical efficacy of the microemulsion formulation of cyclosporine (Neoral) in comparison with Sandimmune (SIM) in the treatment of patients who underwent primary orthotopic liver transplantation (OLT). METHODS: In total, 33 patients were randomized in a double-blind fashion before undergoing primary OLT to receive either Neoral or SIM. All 33 patients initially received intravenous cyclosporine, but as soon as it was tolerated, the oral study drug was initiated (median time, 3.6 days) and 17 patients received Neoral and 16 SIM (for both drugs, 10 mg/kg/day). Both groups were comparable with regard to age, sex, etiology of chronic liver disease, and hepatic biochemical profile. Episodes of rejection were diagnosed histologically and characterized as mild, moderate, or severe using criteria from the National Institute of Diabetes and Digestive and Kidney Diseases. RESULTS: Patients were followed for 1 year. Four patients in each group were discontinued prematurely. The reason for discontinuation of cyclosporine was drug-related complications in two of the NEO patients and in three of the SIM group; the other three were non-drug-related. Rejection episodes occurred in 9 of 17 patients (52.90%) in the Neoral group and in 9 of 16 patients (56.3%) in the SIM group. The total number of rejection episodes in each group was 14. However, in evaluating the severity of rejection histologically, nine episodes of rejection were characterized as moderate/ severe in the SIM group compared with only three in the Neoral group (P=0.027). Five of the nine moderate/severe rejection episodes in the SIM group occurred within the first 2 weeks after transplant. In contrast, moderate/severe rejection did not occur in the Neoral group in this early period. Two patients in the SIM group and no patients in the Neoral group required treatment with OKT3 for steroid-resistant rejection. There were no differences in mean doses or trough levels when comparing the two study groups. The incidence of adverse effects was similar in the two groups. CONCLUSIONS: Neoral is a safe and efficacious drug in the treatment of primary OLT patients. Given comparable doses of cyclosporine in each group over 1 year, there was no significant difference in the total number of rejection episodes between study groups. However, patients treated with Neoral had a lower incidence of moderate/severe histologic rejection and were free of steroid-resistant rejection when compared with SIM-treated patients.

Adult↗
PubMed1997

ras mutation and expression of the ras-regulated genes osteopontin and cathepsin L in human esophageal cancer.

As part of our ongoing studies to characterize molecular alterations in a well-defined series of surgically resected esophageal cancers, we examined the expression of 2 ras-regulated genes, whose products (osteopontin and cathepsin L) previously were shown to be associated with tumor invasion and metastasis. RNA was extracted from primary esophageal tumors (adenocarcinomas, 19; squamous-cell carcinomas, 6) and matched histologically normal esophageal mucosa from the distant resection margin. Northern analysis was used to quantitate RNA, relative to an 18S rRNA control, and immunohistochemistry to assess the tissue distribution of osteopontin. In addition, H-, K- and N-ras mutations were studied in the same tissues using PCR and hybridization with allele (mutant)-specific oligonucleotide probes. We demonstrated a K-ras mutation (codon 12, GTT) in one esophageal adenocarcinoma. The ras-regulated gene osteopontin was over-expressed in 100% of squamous-cell carcinomas and in 58% of adenocarcinomas relative to matched normal esophageal mucosa. Patterns of immunoreactivity for osteopontin protein also varied between squamous-cell carcinomas (tumor cell staining) and adenocarcinomas (predominantly tumor-infiltrating macrophages). Expression of cathepsin L also varied with esophageal tumor histology, with over-expression in 58% of primary esophageal adenocarcinomas and 33% of squamous-cell cancers.

Adenocarcinoma↗
PubMed1997

Immunoglobulin molecules are present in early-generated neuronal populations in the rat cerebral cortex and retina.

Immunoglobulin-like antigens have been identified in neuronal subsets restricted to deeper layers of the developing mammalian cerebral cortex. The pattern is suggestive of selective uptake of immunoglobulin (Ig) from serum or synthesis of Ig or a molecule with Ig-like motifs. To distinguish between these alternatives, biochemical, immunocytochemical, and birthdating analyses were conducted. In neonatal rat cerebral cortex, immunoglobulin-like immunoreactivity was chiefly in subplate neurons, marginal zone neuropil, and processes spanning the cortical plate. Isolated staining was also observed within the ventricular zone. Although most staining in the cortical plate was absent several days after birth, subplate neuron staining persisted until the end of the second postnatal week. Quantitative immunoassays showed that the antigen concentration dropped from 130 ng/mg in cortical cytosol at birth to approximately 80 ng/mg by postnatal day 7 (P7) and remained low thereafter. Two Ig-immunoreactive polypeptides with mobilities similar to heavy and light chains of serum IgG, were identified by Western blotting. The larger band was purified, partially sequenced by Edman degradation, and found to match rat IgG heavy chain. Bromodeoxyuridine birthdating and anti-IgG double-labeling studies showed that most of the Ig-containing cells were early-generated neurons. Outside of the cortex, transient IgG staining was also detected in neurons of the retina and cerebellum. These studies suggest that subplate and other early-generated neurons selectively take up Ig from serum. The IgG may then either be degraded or lost from the central nervous system (CNS) during developmentally regulated cell death.

Amino Acid Sequence↗
PubMed1997

Life satisfaction among low-income rural youth from Appalachia.

The purpose of this study was to examine the relative strength of objective, subjective, and congruency variables as predictors of life satisfaction among low-income youth from rural areas. A 10-year longitudinal survey of low-income, rural youth from Appalachia (n = 322) was conducted to explore these issues. Although support was provided for variables representing all three types of life satisfaction predictors, the strongest of these were subjective variables such as self-perceptions about goal attainment in jobs, overall goal attainment in life, and self-esteem. Another set of consistent predictors of life satisfaction, congruence variables, were concerned with the extent to which low-income you believed that they had fulfilled their own aspirations in terms of formal education, proximity to their childhood homes, and number of children, Finally, some of the objective variables consisting of family of origin's SES, community size, and marital status also were predictive of life satisfaction. In general, the life satisfaction of low-income, rural youth seemed to be influenced more extensively by personal meanings shaped within a particular cultural context rather than by traditional objective measures of life circumstances.

Adolescent↗
PubMed1997

Purine and pyrimidine nucleotide receptors in the apical membranes of equine cultured epithelia.

1. The short circuit current (ISC) technique was used to quantify electrolyte transport by equine cultured sweat gland epithelia. Adenosine 5'-triphosphate (ATP) and certain related compounds, caused transient increases in ISC when added to the apical solution. The order of potency was uridine triphosphate (UTP) > ATP > ADP > > AMP = adenosine. 2. The responses to apical nucleotides were due to chloride and bicarbonate secretion and were reduced in pertussis toxin-treated cells. P2-receptors sensitive to uridine 5'-triphosphate (UTP), that interact with inhibitory G proteins, therefore appear to be present in the apical membrane. 3. Responses to ATP and UTP were reduced in cells loaded with BAPTA, a calcium chelator. BAPTA attenuated the response to ATP more than the response to UTP suggesting that these nucleotides may not act via a common pathway. 4. Cross-desensitization experiments indicated that two populations of UTP-sensitive receptor were present. One was sensitive to UTP and ATP, whereas the second was sensitive only to UTP. Uridine diphosphate appeared to activate the ATP-insensitive receptor population selectively. 5. These data suggest that apical pyrimidinoceptors may be expressed by these cells. The physiological role of these receptors is unknown but they may allow the autocrine regulation of epithelial function.

Adenosine↗
PubMed1997

An improved colorimetric PCR-based method for detection and differentiation of Entamoeba histolytica and Entamoeba dispar in feces.

The epidemiological implications of the recent separation of "Entamoeba histolytica" into two separate species, pathogenic E. histolytica sensu stricto and commensal E. dispar, will not become apparent without methods of distinguishing between them which are applicable to large numbers of specimens. We have modified a PCR-based method to produce such a technique which may be completed in 1 day while still identifying 10(-1) E. histolytica and 1 to 10 E. dispar trophozoites per g of feces when present separately and 10 E. histolytica and 100 E. dispar trophozoites per g in the presence of 10(6) trophozoites per g of the other species. Applied to fecal specimens from 18 patients from which E. histolytica or E. dispar had been grown and identified to the species level by hexokinase isoenzyme analysis, the method in every case yielded the correct result. Positive and negative results are easily distinguished by eye, and we are now applying this technique to a large-scale epidemiological study of amebiasis in the eastern Mediterranean region.

Animals↗
PubMed1997

A mere exposure effect for transformed three-dimensional objects: effects of reflection, size, or color changes on affect and recognition.

If the mere exposure effect is based on implicit memory, recognition and affect judgments should be dissociated by experimental variables in the same manner as other explicit and implicit measures. Consistent with results from recognition and picture naming or object decision priming tasks (e.g., Biederman & E.E. Cooper, 1991, 1992; L.A. Cooper, Schacter, Ballesteros, & Moore, 1992), the present research showed that recognition memory but not affective preference was impaired by reflection or size transformations of three-dimensional objects between study and test. Stimulus color transformations had no effect on either measure. These results indicate that representations that support recognition memory code spatial information about an object's left-right orientation and size, whereas representations that underlie affective preference do not. Insensitivity to surface feature changes that do not alter object form appears to be a general characteristic of implicit memory measures, including the affective preference task.

Analysis of Variance↗