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Biomedical subjects

S Mitchell

Publications and source records attributed to S Mitchell.

At least 55 records · Page 3Linked to original sources
PubMed2001

Microleakage of tetric ceram/excite and Ariston pHc/Ariston liner.

PURPOSE: To investigate the microleakage associated with a hybrid resin-based composite, Tetric Ceram, bonded with the single component dentin bonding agent Excite and Ariston pHc bonded with Ariston Liner. Ariston pHc bonded with Excite and Tetric Ceram bonded with Prime and Bond NT were used as controls. MATERIALS AND METHODS: Twenty-four extracted human premolars and molars were randomly assigned to four groups. Group 1: cavities were bonded with Excite and filled with Tetric Ceram. Group 2: cavities were bonded with Ariston Liner and filled with Ariston pHc. Group 3, control: cavities were bonded with Prime & Bond NT and filled with Tetric Ceram. Group 4, control: cavities were bonded Excite and filled with Ariston pHc. Cavities were cut in both the buccal and lingual surfaces. Half of each preparation was in enamel and the other was in cementum/dentin. The teeth were thermocycled at 15 degrees C for 2 s, 35 degrees C for 28 s and 45 degrees C for 2 s for 5,000 cycles after which the restorations were examined microscopically for leakage using procion brilliant red as a marker. SEM microphotographs were prepared from dye-labeled and non dye-labeled areas to illustrate the micromorphology of the systems. RESULTS: None of the groups showed microleakage at the enamel margins. All groups showed microleakage at the gingival margins. At the gingival margin there was a significant difference between the groups (Kruskal-Wallis ANOVA, P= 0.1111.). Ariston pHc/Ariston Liner showed significantly lower microleakage scores than the other groups (Dunn's Multiple Comparison test). SEM showed that in non-dye labeled areas, Ariston pHc/Ariston Liner was in close apposition to the deeper dental tissues. The "total etch" technique resulted in a zone of demineralization. Debonding occurred at or near the top of the hybrid layer in >95% of specimens.

Acid Etching, Dental↗
PubMed2001

Clinical evaluation of Prime & Bond 2.1 for treating cervical dentin hypersensitivity.

PURPOSE: To evaluate the effectiveness of a "one-bottle" dentin adhesive for reducing or eliminating hypersensitivity in exposed cervical dentin. MATERIALS AND METHODS: Eight patients with hypersensitive teeth were enrolled in this clinical trial. The hypersensitive teeth included a total of 22 premolars and anterior teeth with exposed cervical dentin that was sensitive to cold or other stimuli. A single layer of Prime & Bond 2.1, an acetone-based "one-bottle" adhesive, was applied to the cervical dentin and was light-cured. Sensitivity to compressed air and cold stimuli was determined immediately before and after treatment, and at periods ranging to 24 wks after treatment. Patient responses to the stimuli were timed, and were also evaluated by the use of a visual analogue scale. RESULTS: Application of a single coat of Prime & Bond 2.1 significantly reduced cervical dentin hypersensitivity to both compressed air and cold stimuli immediately after treatment. The reduction in hypersensitivity remained significant at 24 wks after treatment.

Acetone↗
PubMed2000

The influence of relative resistance and urea-supplementation on deliberate infection with Teladorsagia circumcincta during winter.

The consequences for lambs of infection over the winter with Teladorsagia circumcincta were quantified by deliberate, trickle infection of selected animals at 7 months of age. Infected and control uninfected animals were each allocated into four groups, relatively resistant animals on a normal diet, relatively resistant animals on an isocaloric diet supplemented with urea, and relatively susceptible animals on the same two diets. Resistance and susceptibility was assessed by faecal egg counts following natural infection during the summer preceding the deliberate infection. During the deliberate infection egg counts remained low and most parasites recovered at necropsy were inhibited larvae. Nonetheless, infection reduced weight gain, decreased albumin and fructosamine concentrations and provoked a noticeable pepsinogen and eosinophil response. As most larvae were inhibited these responses may have been largely a consequence of immuno-inflammatory responses in the host rather than the direct action of parasites themselves. Relatively resistant animals on the supplemented diet allowed fewer larvae to establish and had higher fructosamine concentrations, higher albumin concentrations and decreased pepsinogen responses. Therefore, a combination of relatively resistant sheep and nutritional supplementation appears most efficient at controlling infection.

3-Hydroxybutyric Acid↗
PubMed2000

The influence of age on the variation among sheep in susceptibility to natural nematode infection.

A longitudinal study of faecal nematode egg counts was made in naturally infected Scottish Blackface sheep over two grazing seasons to 75 weeks of age. Although egg counts were lower in the second grazing season the variation among animals was greater. Egg counts were repeatable from 3 months of age. The repeatability of faecal egg counts within and between grazing seasons was about 0.3. Animals with lower than average egg counts in the first grazing season tended to have lower than average egg counts in the second grazing season. Therefore lambs with relatively low faecal egg counts after 3 months of age are likely to retain their advantage in the following year.

Aging↗
PubMed2000

Human 3'-phosphoadenosine 5'-phosphosulfate synthetase 1 (PAPSS1) and PAPSS2: gene cloning, characterization and chromosomal localization.

Sulfae conjugation is an important pathway in the metabolism of a large number of exogenous and endogenous compounds. These reactions are catalyzed by sulfotransferase (SULT) enzymes that utilize 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as a sulfate donor. PAPS is synthesized from ATP and inorganic sulfate by PAPS synthetase (PAPSS). Two separate PAPSS cDNAs, PAPSS1 and PAPSS2, have been identified in human tissues. We have cloned and characterized the genes for human PAPSS1 and PAPSS2 to make it possible to study the pharmacogenomics of these enzymes. Both genes consisted of 12 exons with virtually identical exon-intron splice junction locations. All splice junctions conformed to the "GT-AG" rule. The total length of PAPSS1 was approximately 108 kb, while that of PAPSS2 was greater than 37 kb. The 5'-flanking region of PAPSS1 did not include a TATA box sequence near the site of transcription initiation, but PAPSS2 had a TATA motif located 21 bp upstream from the site of transcription initiation. Northern blot analysis showed that the major PAPSS1 and PAPSS2 transcripts were approximately 2.7 and 4.2 kb in length, respectively. PAPSS1 mapped to human chromosome band 4q24 while PAPSS2 mapped to 10q22-23 by fluorescence in situ hybridization analysis. Cloning and structural characterization of PAPSS1 and PAPSS2 will make it possible to perform molecular genetic and pharmacogenomic studies of these important enzymes in humans.

Blotting, Northern↗
PubMed2000

Cutting edge: lipoxins rapidly stimulate nonphlogistic phagocytosis of apoptotic neutrophils by monocyte-derived macrophages.

Lipoxins (LX) are lipoxygenase-derived eicosanoids generated during inflammation. LX inhibit polymorphonuclear neutrophil (PMN) chemotaxis and adhesion and are putative braking signals for PMN-mediated tissue injury. In this study, we report that LXA4 promotes another important step in the resolution phase of inflammation, namely, phagocytosis of apoptotic PMN by monocyte-derived macrophages (Mphi). LXA4 triggered rapid, concentration-dependent uptake of apoptotic PMN. This bioactivity was shared by stable synthetic LXA4 analogues (picomolar concentrations) but not by other eicosanoids tested. LXA4-triggered phagocytosis did not provoke IL-8 or monocyte chemoattractant protein-1 release. LXA4-induced phagocytosis was attenuated by anti-CD36, alphavbeta3, and CD18 mAbs. LXA4-triggered PMN uptake was inhibited by pertussis toxin and by 8-bromo-cAMP and was mimicked by Rp-cAMP, a protein kinase A inhibitor. LXA4 attenuated PGE2-stimulated protein kinase A activation in Mphi. These results suggest that LXA4 is an endogenous stimulus for PMN clearance during inflammation and provide a novel rationale for using stable synthetic analogues as anti-inflammatory compounds in vivo.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Decreased HLA-A expression in prostate cancer is associated with normal allele dosage in the majority of cases.

A comparison has been made of the phenotypic expression of MHC class I antigens with the corresponding HLA-A genotype in 15 cases of benign prostatic hyperplasia (BPH) and 34 cases of primary locally invasive prostatic carcinoma. Expression of class 1 protein, detected by immunocytochemistry, was partially or completely lost in approximately 90% of the tumours examined. Comparative genomic analysis of the beta2 microglobulin (beta2m) gene and 15 individual HLA-A haplotypes using a polymerase chain reaction (PCR)-based method demonstrated abnormal gene dosage in the minority of cases: homozygous deletion of the beta2m locus was detected in one case and HLA-A allele in two cases (HLA-A1 and HLA-A2, respectively), representing approximately 8% of the population studied. This first comparative study of gene dosage and expression of class 1 protein reported for prostate cancer reveals that deletion is not the cause of the partial or complete loss seen in the majority of cases. This raises the possibility, in the future, for novel selective immunomodulatory therapeutic strategies which stimulate a clinically significant re-expression of class 1 protein and associated cytotoxic T-cell response.

Alleles↗
PubMed2000

Contractile behavior of smooth muscle actin-containing osteoblasts in collagen-GAG matrices in vitro: implant-related cell contraction.

The contraction of connective tissue cells may facilitate their production and maintenance of extracellular matrix architecture and can benefit healing through wound closure. However, aberrant cell contraction can result in pathological contracture. Implants may stimulate this process leading to contracture of the surrounding fibrous capsule. In the case of compliant porous matrices used for tissue engineering the cell contraction may cause the constriction of pores and the distortion of the implant. The objective of this study was to determine if osteoblasts expressed a specific muscle actin, alpha-smooth muscle actin (SMA), that could provide for their contraction. Immunohistochemistry revealed the presence of SMA in some cells in all of three human and three canine trabecular bone specimens. The majority of the cells of an osteoblastic cell line, MC3T3-E 1, also expressed this actin isoform in two-dimensional culture and when seeded into a collagen-glycosaminoglycan (GAG) matrix. These SMA-containing cells were found to cause contraction of the collagen-GAG analog of extracellular matrix. These findings demonstrate that osteoblasts can display contractile behavior that might help to explain the mechanism by which they impart architecture to bone matrix, including that at implant interfaces. An understanding of this process could also guide the development of matrices for bone tissue engineering.

3T3 Cells↗
PubMed2000

Phenotypic and genotypic characterization of commonly used human prostatic cell lines.

OBJECTIVE: To investigate and catalogue systematically the phenotypic and genotypic characteristics of the commonly used prostatic cell lines using immunocytochemistry and polymerase chain reaction (PCR) of hypervariable sequences within the genome to provide a 'fingerprint' characteristic of each cell line. Materials and methods Malignant (LNCaP, LNCaP-r, PC-3, DU-145) and benign immortalized prostatic cell lines (PNT-1A, PNT-1B, BPH-1) were grown on four-well slides, fixed and subjected to indirect streptavidin-biotin immunocytochemistry. Twenty-three antibodies were used in the following groups: cytoskeletal elements: cytokeratins (CK)-5, -7, -8, -14 (two), -16, -18, -19 (three), -20, vimentin and desmin; MUC1 (three); cell adhesion molecules (E-cadherin, alpha-beta-and gamma-catenin); and prostatic associated proteins: prostate specific antigen (PSA), prostatic acid phosphatase (PAP) and androgen receptor (AR). For the PCR, genomic DNA was extracted from the cell lines and from SKOV3 and MCF7 (positive controls). PCR was performed on three variable regions which were then sequenced: AR exon 1 (CAG repeat polymorphism), and two areas of microsatellite instability (MSI): AR exon 8 and hypoxanthine-guanine phosphoribosyl transferase (HPRT) exon 3. RESULTS: All cell lines were CK-8/18 positive and most also expressed CK-7 and -19. Heterogeneous CK-20 expression was detected for the first time in prostatic cell lines. All lines were positive for vimentin and negative for desmin. MUC1 was expressed in one malignant (DU-145) and all immortalized cell lines. E-cadherin expression was low or absent in three lines: PNT1A, 1B and PC-3. Only PC-3 failed to express alpha-catenin; beta- and gamma-catenin were expressed by all lines. PSA, PAP and AR were only expressed by LNCaP and LNCaP-r. On PCR, the CAG repeat lengths in exon 1 of the AR ranged from 19 to 27. Three pairs of cell lines had the same exon 1 CAG repeat length: LNCaP/PC-3 (26 repeats), BPH-1/DU-145 (19 repeats) and PNT1 A/1B (20 repeats). Exon 8 sequences were identical except for LNCaP, which showed a single base mutation, and HPRT exon 3 sequences were all identical. There was no evidence of generalized MSI in any of the cell lines examined. CONCLUSIONS: The cell lines studied fell into three broad groups according to their phenotypic characteristics: (i) prostatic marker positive (LNCaP and LNCaP-r); (ii) high expression of most antigens (DU-145, PC-3 and BPH-1); and (iii) low or absent expression of most antigens (PNT1 A and 1B). Each of the cell lines derived from PC could be identified on the basis of exon 1 and 8 AR sequence variability. DU145 and BPH-1 had identical profiles of the three areas studied, but these cell lines are easily distinguished by their different phenotypic characteristics. PNT1A and 1B had identical genetic and similar phenotypic profiles, which is unsurprising given that they are subclones derived from the same parental line. Even so, these were separable on the basis of CK-19 immunostaining. Using a combination of geno- and phenotypic markers it was possible to derive a 'fingerprint' for each of the cell lines assessed, which will allow meaningful comparison between similar cell lines held in other laboratories.

Cadherins↗
PubMed2000

Current patterns of referral in breast disease.

The aim was to audit symptomatic referrals to this breast unit in 1998, in order to ascertain the main diagnosis in relation to age, and thereby identify the percentage and age of patients who were reassured and discharged without investigation. 3199 general practitioner referrals were seen in 1998. Of these, 8.7% (n=274) were diagnosed as cancer and 91.3% (n=2925) were given a non-malignant diagnosis. In those under 40 years, only 18 patients of the 1231 seen were diagnosed with cancer, and only one of these was younger than 30 years (29 years). Twenty-seven per cent (n=333) of women under 40 were diagnosed as normal, and of these 14% (n=174) had no investigation. We confirm the recommendations of the guidelines issued by the Department of Health, that in younger women without discrete lumps or family history, clinical examination and reassurance is adequate. This audit should therefore empower general practitioners, to confidently reassure the younger patient, without a discrete lump.

Journal Article↗
PubMed2000

An evaluation of peer-led STD/HIV prevention work in a public sex environment.

This paper describes an independent evaluation of a peer-led STD/HIV prevention intervention conducted by Gay Men Fighting AIDS (GMFA) in a public sex environment (PSE). A variety of quantitative and qualitative research methods were employed to collect data on the intervention process as well as its outcomes. The main aim of the intervention was the distribution of condoms and safer sex literature to PSE users. During a five-month period, over 100,000 condoms and 2,200 safer sex information packs were distributed by GMFA volunteers to the PSE users. Condom provision was identified as the most needed health promotion activity in PSEs in a survey of gay and bisexual men (n = 688) conducted by the evaluators. Data collected showed that condoms provided by GMFA, as well as from other sources, were being used in the PSE. The peer-led focus of the intervention was acceptable to the PSE users. In addition, high levels of commitment and input from the volunteers contributed considerable added value to the intervention. The evaluation found that GMFA was successful in reaching the target population and addressing their needs and demands.

Adolescent↗
PubMed2000

Recurrent blastomycosis of the central nervous system: case report and review.

Although blastomycosis of the central nervous system (CNS) occurs in approximately 4% of patients with blastomycosis, recurrent CNS blastomycosis is very rare. We review the clinical features, treatment, and outcome of 4 previously reported cases. We also report a case of recurrent CNS blastomycosis successfully treated with surgery and liposomal amphotericin B after an inadequate response to amphotericin B therapy. This treatment may be an alternate approach for management of similar cases.

Amphotericin B↗
PubMed2000

Sensory neural processing in work-related upper limb disorders.

Pain in the upper limb is a common complaint in adults, and is often attributed to or exacerbated by occupational activities. In many patients there is no demonstrable pathology in the neck or arm to account for the symptom, and this has prompted the hypothesis that such cases might arise through abnormal neural processing of sensory information with a lowering of pain thresholds. In this paper we review the evidence in support of this theory and suggest directions for future research.

Adult↗
PubMed2000

[Not Available].

Explore the source record for details and available documents.

History, 19th Century↗
PubMed2000

Marginal leakage of filled dentin adhesives used with wet and dry bonding techniques.

PURPOSE: To evaluate the effect of wet and dry bonding on microleakage of Class V restorations bonded with three filled bonding agents. MATERIALS AND METHODS: Sixty extracted human premolar and molar teeth were randomly assigned to five groups for bonding with OptiBond Solo, PermaQuick PQI, Prime & Bond NT (one coat), Prime & Bond NT (two coats) and Prime & Bond 2.1, as a control material. Cavities were cut in both the buccal and lingual surfaces. Half of each preparation was in enamel and the other was in cementum/dentin. The cavities were restored with resin-based composite after the application of dentin bonding agents using a wet and dry technique for each material. The teeth were stored in distilled water for 6 days at 37 degrees C, thermocycled, and the restorations examined microscopically for leakage using Procion Brilliant Red as a marker. RESULTS: All groups showed microleakage at both the enamel and dentin margins. At the gingival margin, there was a significant difference between the groups for wet bonding (P = 0.0349) but not for dry bonding (P = 0.9983) (Kruskal-Wallis test). There was no significant difference between the groups at the enamel margin (wet bonding: P = 0.9999, dry-bonding: P = 0.9304) (Kruskal-Wallis test). The wet-bonding technique was compared with the dry-bonding technique for each material at both the gingival and enamel margins and no significant differences were observed (in all cases P > 0.5) (Mann-Whitney U-test).

Analysis of Variance↗
PubMed1999

Genome duplications and other features in 12 Mb of DNA sequence from human chromosome 16p and 16q.

Several publicly funded large-scale sequencing efforts have been initiated with the goal of completing the first reference human genome sequence by the year 2005. Here we present the results of analysis of 11.8 Mb of genomic sequence from chromosome 16. The apparent gene density varies throughout the region, but the number of genes predicted (84) suggests that this is a gene-poor region. This result may also suggest that the total number of human genes is likely to be at the lower end of published estimates. One of the most interesting aspects of this region of the genome is the presence of highly homologous, recently duplicated tracts of sequence distributed throughout the p-arm. Such duplications have implications for mapping and gene analysis as well as the predisposition to recurrent chromosomal structural rearrangements associated with genetic disease.

Animals↗
PubMed1999

A Simple Model for Estimating Mean Monthly Stream Temperatures After Riparian Canopy Removal.

/ The removal of riparian vegetation along small streams affects the thermal regime of the stream and consequently the biota within it. A simple regression model for mean monthly temperature after riparian canopy removal, based on conditions prior to removal, is presented. The model is determined to have an accuracy of +/-2 degrees C 95% of the time over the temperature range 0.7-17 degrees C. The regression also predicts a switching point at 3 degrees C, below which postharvesting temperatures are colder than prior to harvest. The ability to predict postharvest stream temperatures based on preharvest air temperatures is also evaluated. Management implications of thermal effects due to riparian removal are discussed.KEY WORDS: Stream temperature; Temperature model; Prediction; Air temperature; Thermal change; Riparian canopy removalhttp://link.springer-ny.com/link/service/journals/00267/bibs/24n1p77.html

Journal Article↗