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Biomedical subjects

B Scott

Publications and source records attributed to B Scott.

At least 19 recordsLinked to original sources
PubMed2003

Molecular analysis of two cytochrome P450 monooxygenase genes required for paxilline biosynthesis in Penicillium paxilli, and effects of paxilline intermediates on mammalian maxi-K ion channels.

The gene cluster required for paxilline biosynthesis in Penicillium paxilli contains two cytochrome P450 monooxygenase genes, paxP and paxQ. The primary sequences of both proteins are very similar to those of proposed cytochrome P450 monooxygenases from other filamentous fungi, and contain several conserved motifs, including that for a haem-binding site. Alignment of these sequences with mammalian and bacterial P450 enzymes of known 3-D structure predicts that there is also considerable conservation at the level of secondary structure. Deletion of paxP and paxQ results in mutant strains that accumulate paspaline and 13-desoxypaxilline, respectively. These results confirm that paxP and paxQ are essential for paxilline biosynthesis and that paspaline and 13-desoxypaxilline are the most likely substrates for the corresponding enzymes. Chemical complementation of paxilline biosynthesis in paxG (geranygeranyl diphosphate synthase) and paxP, but not paxQ, mutants by the external addition of 13-desoxypaxilline confirms that PaxG and PaxP precede PaxQ, and are functionally part of the same biosynthetic pathway. A pathway for the biosynthesis of paxilline is proposed on the basis of these and earlier results. Electrophysiological experiments demonstrated that 13-desoxypaxilline is a weak inhibitor of mammalian maxi-K channels (Ki=730 nM) compared to paxilline (Ki=30 nM), indicating that the C-13 OH group of paxilline is crucial for the biological activity of this tremorgenic mycotoxin. Paspaline is essentially inactive as a channel blocker, causing only slight inhibition at concentrations up to 1 microM.

Amino Acid Sequence↗
PubMed2001

Elimination of ergovaline from a grass-Neotyphodium endophyte symbiosis by genetic modification of the endophyte.

The fungal endophytes Neotyphodium lolii and Neotyphodium sp. Lp1 from perennial ryegrass (Lolium perenne), and related endophytes in other grasses, produce the ergopeptine toxin ergovaline, among other alkaloids, while also increasing plant fitness and resistance to biotic and abiotic stress. In the related fungus, Claviceps purpurea, the biosynthesis of ergopeptines requires the activities of two peptide synthetases, LPS1 and LPS2. A peptide synthetase gene hypothesized to be important for ergopeptine biosynthesis was identified in C. purpurea by its clustering with another ergot alkaloid biosynthetic gene, dmaW. Sequence analysis conducted independently of the research presented here indicates that this gene encodes LPS1 [Tudzynski, P., Holter, K., Correia, T., Arntz, C., Grammel, N. & Keller, U. (1999) Mol. Gen. Genet. 261, 133-141]. We have cloned a similar peptide synthetase gene from Neotyphodium lolii and inactivated it by gene knockout in Neotyphodium sp. Lp1. The resulting strain retained full compatibility with its perennial ryegrass host plant as assessed by immunoblotting of tillers and quantitative PCR. However, grass-endophyte associations containing the knockout strain did not produce detectable quantities of ergovaline as analyzed by HPLC with fluorescence detection. Disruption of this gene provides a means to manipulate the accumulation of ergovaline in endophyte-infected grasses for the purpose of determining the roles of ergovaline in endophyte-associated traits and, potentially, for ameliorating toxicoses in livestock.

Base Sequence↗
PubMed2001

Differential production of IL-12, IFN-alpha, and IFN-gamma by mouse dendritic cell subsets.

Dendritic cells (DC) not only stimulate T cells effectively but are also producers of cytokines that have important immune regulatory functions. In this study we have extended information on the functional differences between DC subpopulations to include differences in the production of the major immune-directing cytokines IL-12, IFN-alpha, and IFN-gamma. Splenic CD4(-)8(+) DC were identified as the major IL-12 producers in response to microbiological or T cell stimuli when compared with splenic CD4(-)8(-) or CD4(+)8(-) DC; however, all three subsets of DC showed similar IL-12 regulation and responded with increased IL-12 p70 production if IL-4 was present during stimulation. High level CD8 expression also correlated with extent of IL-12 production for DC isolated from thymus and lymph nodes. By using gene knockout mice we ruled out any role for CD8alpha itself, or of priming by T cells, on the superior IL-12-producing capacity of the CD8(+) DC. Additionally, CD8(+) DC were identified as the major producers of IFN-alpha compared with the two CD8(-) DC subsets, a finding that suggests similarity to the human plasmacytoid DC lineage. In contrast, the CD4(-)8(-) DC produced much more IFN-gamma than the CD4(-)8(+) or the CD4(+)8(-) DC under all conditions tested.

Animals↗
PubMed2001

The effects of restraint stress on the neuropathogenesis of Theiler's virus infection: I. Acute disease.

Restraint stress was found to have a profound effect on the acute phase of Theiler's virus infection. Increased mortality rates were observed in restrained CBA mice infected with the BeAn strain of Theiler's virus. In addition, restrained mice developed higher CNS viral titers than infected/nonrestrained mice. Thymic atrophy was observed in both infected and uninfected restrained mice. Decreased microgliosis, perivascular cuffing, and astrocytosis were observed in restrained mice compared to nonrestrained infected mice at 7 days postinfection. Restraint-stressed mice also developed decreased numbers of lymphocytes and increased numbers of neutrophils in the blood. The mechanism proposed for these alterations involves stress-induced corticosterone, which causes immunosuppression, decreased trafficking of inflammatory cells in the CNS, and, consequently, increased viral replication.

Acute Disease↗
PubMed2001

Genetic susceptibility to MS: a second stage analysis in Canadian MS families.

Four published genome screens have identified a number of markers with increased sharing in multiple sclerosis (MS) families, although none has reached statistical significance. One hundred and five markers previously identified as showing increased sharing in Canadian, British, Finnish, and American genome screens were genotyped in 219 sibling pairs ascertained from the database of the Canadian Collaborative Project on Genetic Susceptibility to MS (CCPGSMS). No markers examined met criteria for significant linkage. Markers located at 5p14 and 17q22 were analyzed in a total of 333 sibling pairs and attained mlod scores of 2.27 and 1.14, respectively. The known HLA Class II DRB1 association with MS was confirmed (P<0.0001). Significant transmission disequilibrium was also observed for D17S789 at 17q22 (P=0.0015). This study highlights the difficulty of searching for genes with only mild-to-moderate effects on susceptibility, although large effects of specific loci may still be present in individual families. Future progress in the genetics of this complex trait may be helped by (1) focussing on more ethnically homogeneous samples, (2) using an increased number of MS families, and (3) using transmission disequilibrium analysis in candidate regions rather than the affected relative pair linkage analysis.

Canada↗
PubMed2001

Epichloë endophytes: fungal symbionts of grasses.

Recent developments have increased our understanding of the evolution of mutualistic associations between Epichloë endophytes and their grass hosts. Most of the asexual species appear to be interspecific hybrids. Although endophytes form compatible associations with their natural hosts, transfers to other hosts elicit a range of incompatible reactions. Recently, the genes involved in the synthesis of the secondary metabolites ergot alkaloids and indole-diterpenes, which confer protective benefits on the association, have been cloned.

Ascomycota↗
PubMed2001

Prevalence, incidence and prospective risk factors for eating disorders.

OBJECTIVE: To examine the prevalence, incidence and prospective risk factors for eating disorders (ED) among young adult females. METHOD: Using a prospective design, a randomly selected sample of 1157 females (18-30 years) from the general population was examined with questionnaires for establishing ED diagnoses, self-esteem, body concern, coping and perceived social support. RESULTS: The prevalence of ED was 3.2% and the 2-year first-time incidence was 0.0105 (n=8). Subjects in the extended incidence group (n=34) reported significantly lower self-esteem and perceived social support, and higher body concern and relative use of escape-avoidance coping, at the onset of the study in 1997, compared to controls (n=643). Furthermore, they reported a significant increase in body concern and relative use of escape-avoidance coping, and a significant decrease in self-esteem compared to controls from 1997 to 1999. CONCLUSION: These factors may be considered as risk factors for later development of ED among young adult women.

Adaptation, Psychological↗
PubMed2001

Molecular cloning and genetic analysis of an indole-diterpene gene cluster from Penicillium paxilli.

The indole-diterpene paxilline is a potent tremorgenic mammalian mycotoxin and a known inhibitor of maxi-K ion channels. The gene cluster responsible for paxilline biosynthesis in Penicillium paxilli was identified by mapping four large plasmid-induced chromosome deletions. The cluster is predicted to lie within a 50 kb region of chromosome Va and to contain 17 genes, including a geranylgeranyl pyrophosphate (GGPP) synthase (paxG), two FAD-dependent monooxygenases (paxM and N), two cytochrome P450 monooxygenases (paxP and Q), a dimethylallyltryptophan (DMAT) synthase (paxD) and two possible transcription factors (paxR and paxS), which contain a Zn(II)2Cys6 DNA-binding motif. Targeted replacement of paxG confirmed that it is essential for paxilline biosynthesis but dispensable for growth. The GGPP for primary metabolism is predicted to be provided by a second GGPP synthase (ggs1) that was cloned, sequenced and mapped to chromosome IV. Semi-quantitative reverse transcriptase-polymerase chain reaction analysis demonstrated that the expression of paxG, paxM and paxP in submerged liquid cultures of P. paxilli increased dramatically with the onset of paxilline biosynthesis. In contrast, the expression of beta-tubulin (tub2) and ggs1 was not induced. This is the first description of the molecular cloning and genetic analysis of an indole-diterpene gene cluster.

Alkyl and Aryl Transferases↗
PubMed2001

The tripeptide feG reduces endotoxin-provoked perturbation of intestinal motility and inflammation.

Lipopolysaccharide (LPS)-induced intestinal endotoxaemia perturbs motility and causes activation and influx of inflammatory cells into the muscle tissue. Because rat submandibular gland peptide T (SGP-T; Thr-Asp-Ile-Phe-Glu-Gly-Gly), its carboxyl-terminal fragment tripeptide, FEG (Phe-Glu-Gly) and its D-isomeric analogue, feG, modulate intestinal anaphylactic reactions, we examined whether these peptides also modulate LPS-induced intestinal endotoxaemia in conscious rats. The disruption of the fasting pattern of intestinal MMCs (migrating motor complexes), induced by intravenous LPS (20 microg kg-1) injection, was prevented by all three peptides. The extravasation of leucocytes into the peritoneal cavity and increased expression of the activation marker CD18 on mesenteric tissue leucocytes (18 h after intraperitoneal injection of LPS) were reduced by orally administered feG, which also significantly decreased the number of intestinal tissue leucocytes expressing the integrin CD18. We conclude that feG attenuates both the immediate (intestinal motility) and late ( approximately 18 h) inflammatory reactions provoked by endotoxaemia.

Animals↗
PubMed2001

Enumeration of non-communicable disease in rural South Africa by electronic data linkage and capture-recapture techniques.

Non-communicable diseases (NCDs) are becoming increasingly common and important in developing countries, yet their enumeration is problematic. We have attempted to enumerate NCD patients in a rural district of KwazuluNatal, South Africa, using the techniques of electronic data linkage and capture-recapture (CR). We examined four major NCDs (hypertension, diabetes, asthma and epilepsy). Basic patient details were recorded onto EpiInfo software over a 6-week period, from the main hospital clinic at Hlabisa, as well as the 10 outlying peripheral health clinics. Using electronic data linkage of lists from the main hospital, the peripheral clinics, and repeat prescription cards, a district NCD register was produced of 2455 patients. The mean age was 51 +/- 16 years (1 SD) and 76% were female. Of the total NCD patients, 62% had hypertension (age 57 +/- 12 years, 82% female), 16% epilepsy (age 35 +/- 17 years, 49% female), 13% asthma (age 45 +/- 19 years, 60% female) and 12% diabetes (age 54 +/- 13 years, 61% female). Estimated population crude prevalence rates for known NCD cases on the register were 7.4% for hypertension, epilepsy 0.2%, asthma 0.2% and diabetes 0.2%. We also attempted a CR analysis to assess completeness of data, by comparing overlap between patients attending peripheral clinics, and the central Hlabisa Hospital clinic. Matching by name, age, and diagnosis proved feasible, but there was little overlap, and CR calculations were invalid because of the relative independence of sources. We conclude that NCDs are common in rural Africa, and that a simple NCD district register is a potentially feasible and inexpensive option. Capture-recapture analysis is feasible, but requires suitable lists with acceptable overlap of patients.

Adolescent↗
PubMed2001

Measuring the negative mood component of stress experiences: description and psychometric properties of a short adjective check-list of stress responses.

Negative Mood (NM) is a 19-items adjective check-list developed to assess negative mood and stress responses. The items of the scale reflect dimensions such as depressed mood, anxiety, anger and time urgency. The data were collected from four different samples, two random population samples and two smaller selective samples. The psychometric properties of the NM showed high internal consistency (Cronbach's Alpha). When analysed with principal components analysis, three factors emerged, anxiety/depression, time pressure, and anger. The factors emerged in all four samples, within samples and between gender. The NM factors were tested for convergent and discriminative validity by correlating them with other more established measures of different aspects of negative mood. The results showed high convergent and discriminative validity for two of the NM factors, i.e., anxiety/depression, and anger, whereas the results for the third factor, time pressure, were more ambiguous. This scale has proven to be useful in capturing some vital dimensions of negative affect across different kinds of populations.

Adult↗
PubMed2001

Multifocal streptococcal pyomyositis complicated by acute compartment syndrome: case report.

A 5-year-old girl sought treatment for pyrexia of unknown origin. Despite prompt surgical drainage of a streptococcal septic arthritis of the ankle joint, her condition deteriorated. Multifocal pyomyositis was subsequently diagnosed. This was complicated by acute compartment syndrome in three extremities. With aggressive surgical and medical management, the child made a complete recovery. Orthopaedic clinicians in nontropical areas must familiarize themselves with this rare, potentially life-threatening, but eminently curable disease.

Acute Disease↗
PubMed2001

The emotional effects of tooth loss in a group of partially dentate people: a quantitative study.

This study investigated the reactions to tooth loss in a partially dentate group of 100 people using a questionnaire-based method. Partially dentate people who experienced difficulties in accepting their tooth loss were more likely to feel less confident, restrict food choice, enjoy food less, avoid laughing in public and avoid forming close relationships than those people who had no difficulties accepting tooth loss. Also, they were more likely to feel that they had not been adequately prepared for the effects that tooth loss had on their confidence, daily living activities and appearance.

Activities of Daily Living↗
PubMed2000

Tumor-specific CD4+ T cells have a major "post-licensing" role in CTL mediated anti-tumor immunity.

A number of tumor studies have indicated a link between CD4 help and the magnitude and persistence of CTL activity; however, the mechanisms underlying this have been largely unclear. To evaluate and determine the mechanisms by which CD4(+) T cells synergize with CD8(+) T cells to prevent tumor growth, we used the novel technique of monitoring in vivo CTL by labeling target cells with CFSE. This approach was supported by the direct visualization of CTL using peptide-MHC tetramers to follow tumor-specific T cells. The data presented demonstrate that while cotransfer of Ag-specific CD4(+) T cells was not required for the generation of CTLs, because adoptive transfer of CD8(+) T cells alone was sufficient, CD4(+) T cells were required for the maintenance of CD8(+) T cell numbers. Our data suggest that there is a correlation among the number of CD8(+) T cells, in vivo CTL function, and IFN-gamma production, with no evidence of a partial or nonresponsive phenotype among tetramer-positive cells. We also show that CD4(+) T cells are required for CD8(+) T cell infiltration of the tumor.

Adoptive Transfer↗
PubMed2000

The emotional effects of tooth loss: a preliminary quantitative study.

AIM: To establish how widespread the emotional effects of tooth loss are. METHOD: A questionnaire, distributed to 100 edentulous people undergoing routine prosthetic care in the Department of Prosthetic Dentistry at Guy's, King's and St Thomas' Dental Institute (GKT), was used to explore the emotional effects of tooth loss. RESULTS: Ninety four people completed the questionnaire of whom 42 stated that they had experienced difficulties in accepting the loss of their teeth. In comparison with people who had no difficulties in accepting the situation, these people were: more likely to feel less confident about themselves; more likely to feel inhibited in carrying out everyday activities; and less able to accept the inevitable change in facial shape which occurs following the loss of teeth. Additionally, they took longer to come to terms with their tooth loss (All these differences were statistically significant). Just over three-quarters of the people who were unprepared for the loss of their teeth, felt that an explanation from the dentist prior to dental extractions would have helped. CONCLUSION: The impact that tooth loss can have on people and their lives should not be underestimated. In this study it affected 45% of the participants.

Activities of Daily Living↗
PubMed2000

Mirrorless lasing from mesostructured waveguides patterned by soft lithography

Mesostructured silica waveguide arrays were fabricated with a combination of acidic sol-gel block copolymer templating chemistry and soft lithography. Waveguiding was enabled by the use of a low-refractive index (1.15) mesoporous silica thin film support. When the mesostructure was doped with the laser dye rhodamine 6G, amplified spontaneous emission was observed with a low pumping threshold of 10 kilowatts per square centimeter, attributed to the mesostructure's ability to prevent aggregation of the dye molecules even at relatively high loadings within the organized high-surface area mesochannels of the waveguides. These highly processible, self-assembling mesostructured host media and claddings may have potential for the fabrication of integrated optical circuits.

Journal Article↗