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Biomedical subjects

D Lewis

Publications and source records attributed to D Lewis.

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

Intimin-specific immune responses prevent bacterial colonization by the attaching-effacing pathogen Citrobacter rodentium.

The formation of attaching and effacing (A/E) lesions on gut enterocytes is central to the pathogenesis of enterohemorrhagic (EHEC) Escherichia coli, enteropathogenic E. coli (EPEC), and the rodent pathogen Citrobacter rodentium. Genes encoding A/E lesion formation map to a chromosomal pathogenicity island termed the locus of enterocyte effacement (LEE). Here we show that the LEE-encoded proteins EspA, EspB, Tir, and intimin are the targets of long-lived humoral immune responses in C. rodentium-infected mice. Mice infected with C. rodentium developed robust acquired immunity and were resistant to reinfection with wild-type C. rodentium or a C. rodentium derivative, DBS255(pCVD438), which expressed intimin derived from EPEC strain E2348/69. The receptor-binding domain of intimin polypeptides is located within the carboxy-terminal 280 amino acids (Int280). Mucosal and systemic vaccination regimens using enterotoxin-based adjuvants were employed to elicit immune responses to recombinant Int280alpha from EPEC strain E2348/69. Mice vaccinated subcutaneously with Int280alpha, in the absence of adjuvant, were significantly more resistant to oral challenge with DBS255(pCVD438) but not with wild-type C. rodentium. This type-specific immunity could not be overcome by employing an exposed, highly conserved domain of intimin (Int388-667) as a vaccine. These results show that anti-intimin immune responses can modulate the outcome of a C. rodentium infection and support the use of intimin as a component of a type-specific EPEC or EHEC vaccine.

Adhesins, Bacterial↗
PubMed2001

Performance of the applied biosystems ViroSeq human immunodeficiency virus type 1 (HIV-1) genotyping system for sequence-based analysis of HIV-1 in pediatric plasma samples.

The ViroSeq HIV-1 Genotyping System is a commercially available, integrated sequence-based system for analysis of human immunodeficiency virus type 1 (HIV-1) drug resistance. We evaluated the performance of this system by analyzing HIV-1 in pediatric plasma samples. Plasma samples from children 4 months to 17 years of age were obtained from a clinical trial protocol (PACTG 377). Children in PACTG 377 were randomized to four treatment arms, including different combinations of antiretroviral drugs. HIV-1 genotyping was performed using samples collected prior to antiretroviral therapy (baseline) and at the time of virologic failure. Performance of the genotyping system was compared in three university laboratories. A total of 196 samples were analyzed, including 135 baseline and 61 failure samples. Plasma volumes ranged from 0.05 to 0.5 ml, and viral loads ranged from 1,084 to 3,484,991 copies/ml. PCR products suitable for sequencing were obtained for 192 of the 196 samples. Complete sequences for protease and reverse transcriptase were obtained for all of these 192 samples. For 180 samples, data were obtained from both DNA strands for the entire region analyzed. There was no evidence of sample cross-contamination based on phylogenetic analysis of HIV-1 sequences. Performance of the genotyping system was similar in three laboratories. This genotyping system performs well for analysis of HIV-1 in pediatric plasma samples, including those with low volume and low viral load. The availability of this system should facilitate studies of HIV-1 drug resistance.

Adolescent↗
PubMed2001

GABA transporter-1 mRNA in the prefrontal cortex in schizophrenia: decreased expression in a subset of neurons.

OBJECTIVE: Within the prefrontal cortex of schizophrenic subjects, alterations in markers of gamma-aminobutyric acid (GABA) neurotransmission, including decreased immunoreactivity for the GABA membrane transporter GAT-1, may be most prominent in a subset of inhibitory neurons. In the present study, the authors sought to determine whether the alterations in GAT-1 protein could be attributed to a reduction in GAT-1 mRNA expression. METHOD: Tissue sections containing prefrontal cortex area 9 from 10 matched pairs of schizophrenic and comparison subjects were processed for in situ hybridization histochemistry with (35)S-oligonucleotide probes for GAT-1 mRNA. RESULTS: In the schizophrenic subjects, the relative density of labeled neurons was 21%-33% lower in layers 1-5 of the prefrontal cortex but was unchanged in layer 6. In contrast, cellular levels of GAT-1 mRNA expression, as reflected in grain density per labeled neuron, did not differ by more than 11% between subject groups in any layer. These findings indicate that GAT-1 mRNA expression is relatively unaltered in the majority of prefrontal cortex GABA neurons in schizophrenic subjects but is reduced below a detectable level in a subset of GABA neurons. Furthermore, the magnitude and laminar pattern of these results were strikingly similar to those found in a previous study of mRNA expression for the synthesizing enzyme of GABA, glutamic acid decarboxylase(67), in the same subjects. CONCLUSIONS: Both GABA synthesis and reuptake appear to be altered at the level of gene expression in a subset of GABA neurons, and the resulting changes in GABA neurotransmission may contribute to prefrontal cortex dysfunction in schizophrenia.

Adult↗
PubMed2001

Identifying research priorities on infections in older adults: proceedings of an interdisciplinary workshop.

BACKGROUND: Infections pose a substantial burden to the health of older adults. In this report, we describe the proceedings of a workshop to formulate and prioritize research questions about infections in older adults using an interdisciplinary approach. METHODS: Researchers from four sectors (basic science, clinical sciences, health services and epidemiology/determinants of health) and representatives from various Canadian local, provincial, and federal stakeholder groups were invited to a two-day workshop. Five multi-disciplinary groups and stakeholders from each of three healthcare settings (long term, acute care and community) discussed research priorities for each of the settings. Five to ten research questions were identified for each setting. RESULTS: The research questions proposed ranged from risk factors and outcomes for different infections to the effect of nutrition on infection and the role of alternative and complementary medicine in treating infections. Health service issues included barriers to immunization, prolongation of hospital length of stay by infection, use of care paths for managing infections, and decision-making in determining the site of care for individuals with infections. Clinical questions included risk factor assessment for infection, the effectiveness of preventative strategies, and technology evaluation. Epidemiologic issues included the challenge of achieving a better understanding of respiratory infections in the community and determining the prevalence of colonization with multi-resistant bacteria. CONCLUSIONS: The questions are of direct relevance to researchers in a wide variety of fields. Bringing together a multi-disciplinary group of researchers to frame and prioritize research questions about aging is feasible, participants valued the opinions of people working in other areas.

Journal Article↗
PubMed2001

Working with women in secure environments.

1. Women's adverse experiences as patients in secure and other mental health services appear to reflect sexism in wider social and historical contexts. 2. A Women's Service Development Group in a medium secure unit in the United Kingdom has made improvements in services for female patients, including an independent advocacy and befriending service, a Well-Woman Clinic, and other gender-sensitive activities. 3. In general, services were evaluated positively by women. Some dissatisfaction primarily was related to activities, issues concerning seclusion, and the lack of a day area for women only. 4. Women had mixed views about their contact with male staff and patients. Because of this, policies and services in this and related areas should account for individual needs.

Adult↗
PubMed2000

Detailed characterization of the cooperative mechanism of Ca(2+) binding and catalytic activation in the Ca(2+) transport (SERCA) ATPase.

Expression of heterologous SERCA1a ATPase in Cos-1 cells was optimized to yield levels that account for 10-15% of the microsomal protein, as revealed by protein staining on electrophoretic gels. This high level of expression significantly improved our characterization of mutants, including direct measurements of Ca(2+) binding by the ATPase in the absence of ATP, and measurements of various enzyme functions in the presence of ATP or P(i). Mutational analysis distinguished two groups of amino acids within the transmembrane domain: The first group includes Glu771 (M5), Thr799 (M6), Asp800 (M6), and Glu908 (M8), whose individual mutations totally inhibit binding of the two Ca(2+) required for activation of one ATPase molecule. The second group includes Glu309 (M4) and Asn796 (M6), whose individual or combined mutations inhibit binding of only one and the same Ca(2+). The effects of mutations of these amino acids were interpreted in the light of recent information on the ATPase high-resolution structure, explaining the mechanism of Ca(2+) binding and catalytic activation in terms of two cooperative sites. The Glu771, Thr799, and Asp800 side chains contribute prominently to site 1, together with less prominent contributions by Asn768 and Glu908. The Glu309, Asn796, and Asp800 side chains, as well as the Ala305 (and possibly Val304 and Ile307) carbonyl oxygen, contribute to site 2. Sequential binding begins with Ca(2+) occupancy of site 1, followed by transition to a conformation (E') sensitive to Ca(2+) inhibition of enzyme phosphorylation by P(i), but still unable to utilize ATP. The E' conformation accepts the second Ca(2+) on site 2, producing then a conformation (E' ') which is able to utilize ATP. Mutations of residues (Asp813 and Asp818) in the M6/M7 loop reduce Ca(2+) affinity and catalytic turnover, suggesting a strong influence of this loop on the correct positioning of the M6 helix. Mutation of Asp351 (at the catalytic site within the cytosolic domain) produces total inhibition of ATP utilization and enzyme phosphorylation by P(i), without a significant effect on Ca(2+) binding.

Adenosine Triphosphate↗
PubMed2000

The effect of orthodontic referral guidelines: a randomised controlled trial.

OBJECTIVE: To develop and evaluate the effectiveness of referral guidelines for the referral of orthodontic patients to consultant and specialist practitioner orthodontists. DESIGN: Single centre randomised controlled trial with random allocation of referral guidelines for orthodontic treatment to general dental practitioners. SETTING: Hospital orthodontic departments and specialist orthodontic practices in Manchester and Stockport. SUBJECTS: General dental practitioners and the patients they referred for orthodontic treatment. MAIN OUTCOME MEASURE: Appropriateness of referral, defined as whether the patient was accepted for orthodontic treatment. RESULTS: The referral guidelines did not reduce the number of inappropriate referrals. CONCLUSIONS: Referral guidelines for orthodontic referrals did not influence the behaviour of the general dental practitioners. More research into the optimum methods of dissemination and implementation of referral guidelines for use in the general dental service is needed.

Adolescent↗
PubMed2000

Distinct epidemiological patterns of Norwalk-like virus infection.

Norwalk-like viruses (NLV) are important economically as a cause of both sporadic gastroenteritis in the community and large outbreaks in hospitals and other institutional settings. Despite the description of several antigenic types relatively little is known about the epidemiology of these individual types. NLVs were detected by electron microscopy in faecal specimens from 706 outbreaks of gastroenteritis that represented 68% of all outbreaks of non-bacterial gastroenteritis. These outbreaks took place in the counties of West and North Yorkshire and Humberside during six winter seasons between July 1992 and June 1998. NLV strains from 671 outbreaks were typed by antigen capture enzyme linked immunosorbent assays (ELISA) based on antisera made to recombinant virus-like particles of three antigenically distinct NLVs; Norwalk (NV), Mexico (MXV) and Grimsby (GRV) viruses. GRV was the predominant strain for five of the six winter seasons and overall was associated with 61% of NLV outbreaks. MXV was responsible for a single epidemic peak in the winter of 1993/94 but was also observed at other times throughout the study period. NV was only associated with two outbreaks in 1994 that were epidemiologically linked. Strains from the remaining 32% of outbreaks were non-reactive in all three ELISA. Thus, a single NLV antigenic type seems to have predominated during the period 1992 to 1998 in the UK.

Adult↗
PubMed2000

Manipulation of gold nanoparticles in liquid environments using scanning force microscopy

Precise and controlled manipulation of individual gold nanoparticles (deposited on a Si/SiO2 surface) in liquid environments using the tip of a scanning force microscope is reported for the first time. Experiments were performed in deionized water and in ethanol as a prototype for an organic solvent. Analysis of the amplitude signal of the cantilever before and during manipulation reveals that the particles are pushed across the surface, similar to the manipulation of nanoparticles in air.

Journal Article↗
PubMed2000

Particle mass emission rates from current-technology, light-duty gasoline vehicles.

Now that the U.S. Environmental Protection Agency has promulgated new National Ambient Air Quality Standards for PM2.5, work will begin on generating the data required to determine the sources of ambient PM2.5 and the magnitude of their contributions to air pollution. This paper summarizes the results of an Environmental Research Consortium program, carried out under the auspices of the U.S. Council for Automotive Research. The program focused on particulate matter (PM) emissions from representative, current-technology, light-duty gasoline vehicles produced by DaimlerChrysler Corp., Ford Motor Co., and General Motors Corp. The vehicles, for the most part taken from the manufacturer's certification and durability fleets, were dynamometer-tested using the three-phase Federal Test Procedure in the companies' laboratories. The test fleet was made up of a mixture of both low-mileage (2K-35K miles) and high-mileage (60K-150K miles) cars, vans, sport utility vehicles, and light trucks. For each vehicle tested, PM emissions were accumulated over 4 cold-start tests, which were run on successive days. PM emission rates from the entire fleet (22 vehicles total) averaged less than 2 mg/mile. All 18 vehicles tested using California Phase 2 reformulated gasoline had PM emission rates less than 2 mg/mile at both low and high mileages.

Air Pollution↗
PubMed2000

Ultrastructural localization of sulfated and unsulfated keratan sulfate in normal and macular corneal dystrophy type I.

Keratan sulfate (KS) proteoglycans are of importance for the maintenance of corneal transparency as evidenced in the condition macular corneal dystrophy type I (MCD I), a disorder involving the absence of KS sulfation, in which the cornea becomes opaque. In this transmission electron microscope study quantitative immuno- and histochemical methods have been used to examine a normal and MCD I cornea. The monoclonal antibody, 5-D-4, has been used to localize sulfated KS and the lectin Erythrina cristagalli agglutinin (ECA) to localize poly N -acetyllactosamine (unsulfated KS). In normal cornea high levels of sulfated KS were detected in the stroma, Bowman's layer, and Descemet's membrane and low levels in the keratocytes, epithelium and endothelium. Furthermore, in normal cornea, negligible levels of labeling were found for N -acetyllactosamine (unsulfated KS). In the MCD I cornea sulfated KS was not detected anywhere, but a specific distribution of N -acetyllactosamine (unsulfated KS) was evident: deposits found in the stroma, keratocytes, and endothelium labeled heavily as did the disrupted posterior region of Descemet's membrane. However, the actual cytoplasm of cells and the undisrupted regions of stroma revealed low levels of labeling. In conclusion, little or no unsulfated KS is present in normal cornea, but in MCD I cornea the abnormal unsulfated KS was localized in deposits and did not associate with the collagen fibrils of the corneal stroma. This study has also shown that ECA is an effective probe for unsulfated KS.

Adult↗
PubMed2000

Epithelial barrier function and ultrastructure of gelatinous drop-like corneal dystrophy.

PURPOSE: Recently, mutations in the M1S1 gene have been identified as responsible for gelatinous drop-like corneal dystrophy (GDLD). How the abnormal M1S1 gene product causes GDLD is not known, although evidence suggests that it may compromise corneal epithelial function. This investigation attempted to determine the effect of the abnormal M1S1 gene product by assessing epithelial barrier function and epithelial ultrastructure in GDLD corneas. METHODS: Epithelial barrier function was assessed on the basis of fluorescein uptake. The method used a modified slit-lamp fluorophotometer. High-resolution scanning electron and atomic force microscopy was used to investigate the amyloid deposits and epithelial cell structure. RESULTS: Epithelial permeability was orders of magnitude higher in GDLD corneas than normal. The structure of the amyloid deposits was characterized, and clear abnormalities in epithelial morphology and cell junctions were observed. CONCLUSIONS: The high epithelial permeability observed in GDLD corneas was directly correlated with abnormalities in epithelial structure, including irregular cell junctions. This suggests that the abnormal M1S1 gene product may affect epithelial cell junctions resulting in increased cell permeability in GDLD corneas.

Adult↗
PubMed2000

Molecular detection and epidemiology of Sapporo-like viruses.

Sapporo-like viruses (SLVs) are associated with acute gastroenteritis in humans. Due to a limited supply of available reagents for diagnosis, little is known about the incidence and pathogenicity of these viruses. We have developed a first-generation generic reverse transcriptase (RT) PCR assay based on a single primer pair targeting the RNA polymerase gene. With this assay, 55 (93%) of the 59 stool specimens collected in a 10-year period of time (1988 to 1998) and containing typical caliciviruses by electron microscopy tested positive and could be confirmed by Southern hybridization. By phylogenetic analysis, most SLV strains could be classified into one of the three recently described genotypes. However, three samples clustered separately, forming a potential new genotype. We sequenced the complete capsid gene of one of the strains in this cluster: Hu/SLV/Stockholm/97/SE. Alignment of the capsid sequences showed 40 to 74% amino acid identity among strains of the different clusters. Phylogenetic analysis of the aligned sequences confirmed the placing of Hu/SLV/Stockholm/97/SE into a new distinct genetic cluster. This is the first report on the development of a broadly reactive RT-PCR assay for the detection of SLVs.

Adult↗
PubMed2000

Three children with a syndrome of obesity and overgrowth, atypical psychosis, and seizures: a problem in neuropsychopharmacology.

Three children presented with a complex syndrome of atypical psychotic and extremely immature behavior, obesity and overgrowth, borderline retardation, and seizures (prominent in two). Weight overgrowth exceeded height overgrowth and was stratospheric (up to 8 SD above mean). Obesity seemed related to lack of satiety. The cases fit no known condition: hypothalamic damage, Sotos' syndrome, and Prader-Willi syndrome were excluded. Empirical treatment with anticonvulsants (carbamazepine and acetazolamide) together with psychotropic agents (selective serotonin reuptake inhibitors and risperidone) controlled seizures, improved behavior, and stopped weight gain in each patient. We have not found this syndrome previously described. The etiology is unknown: perinatal encephalopathy could be a factor in the two patients with prominent seizures; in the third, familial major affective disorder is implicated. Medication responses suggest a low-serotonin state underlying the lack of satiety, an imbalance of serotonin and noradrenergic modulation in the hypothalamus, and epileptogenic disorders (or affective disorder responsive to anticonvulsants in one case) involving these same systems.

Anticonvulsants↗
PubMed2000

How can you protect yourself from employee dishonesty?

BACKGROUND: Forty percent of dental offices have been or will be embezzled by an employee. OVERVIEW: As employers, dentists need to prescreen applicants diligently, as well as take strong, proactive roles in the monitoring of all business aspects of their practices. PRACTICE IMPLICATIONS: To make their offices embezzlement-proof, dentists need to take responsibility for both implementing and monitoring strict accounting and banking procedures.

Financial Audit↗