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Biomedical subjects

P Lewis

Publications and source records attributed to P Lewis.

At least 37 records · Page 2Linked to original sources
PubMed2001

Vagus nerve stimulation: analysis of device parameters in 154 patients during the long-term XE5 study.

PURPOSE: To determine the effect of changes in device settings and duty cycle (on and off times) on the efficacy of vagus nerve stimulation (VNS) for refractory epilepsy. In the long-term XE5 study of VNS for intractable epilepsy, the median reduction in seizure frequency improved significantly after 1 year of follow-up. A central question is whether device changes improve efficacy. We analyzed the effects of device parameter changes on seizure frequency in 154 subjects who completed the study and who had complete data for analysis. METHODS: Retrospective analysis of device changes during the XE5 long-term study of VNS. During the XE5 long-term follow-up study, the subject's device settings were modified within a Food and Drug Administration (FDA)-approved range of output current, pulse duration, frequency, on time, and off time. Significant changes in device settings occurred after 3 months. We investigated the relationship between percentage reduction in seizures and changes in device parameters between the 3- and 12-month visits. Within-group comparisons were performed for those who continued on standard on/off cycle of 30 s on and 5 min off, and those with the most common off times of 3, 1.8, and < 1.1 min. RESULTS: Output current, pulse duration, frequency, and off time changed significantly between the 3- and 12-month long-term follow-ups. For the group as a whole, changes in device settings were not correlated with an improvement in efficacy. However, a significant improvement in efficacy occurred in a subgroup whose off time was reduced to < or = 1.1 min. In this group, the median reduction in seizures improved from 21% before the change in off time, to 39% after the change in off time (Wilcoxon Signed-Rank, p = 0.011). The responder rate (> 50% reduction in seizures) also significantly improved from 19 to 35% (McNemar's test, p = 0.046). CONCLUSIONS: The data from this retrospective analysis indicate that device changes were not the primary determinant of increased efficacy at 12 months of long-term follow-up. In general, patients who remained on the original settings of 30 s on and 5 min off continued to respond or improve in their response over the 1-year period. However, some patients may benefit from reductions in off time (increases in duty cycle). In a subgroup initially resistant to VNS, a change in off time to < or = 1.1 min off did result in significant improvements in efficacy.

Double-Blind Method↗
PubMed2001

Inflammatory eye, skin, and bowel disease in spondyloarthritis: genetic, phenotypic, and environmental factors.

OBJECTIVE: To explore the nature of the interrelationship between inflammatory disease of the spine/joints, skin, eye, and bowel [i.e., ankylosing spondylitis (AS), psoriasis, iritis, inflammatory bowel disease (IBD)]. METHODS: The study used 4 approaches: (1) analysis of the prevalence of secondary disorders within the AS individual (chi-square and matched pair analysis); (2) study of the temporal relationship between the onset of the different conditions; (3) evaluation of the prevalence of disease among first degree relatives; and (4) influence of secondary disorders on outcome of AS. RESULTS: 1. Among 3287 patients with AS, more than expected had either spondylitis associated with multiple co-disorders or pure AS (with no co-diseases); fewer than expected had AS plus a single co-disease (chi-square = 32.2, p < 0.001). In a matched pair analysis, patients with AS and a secondary disorder were more likely to have an additional concomitant disease, e.g., IBD-AS (n = 335) patients had a higher prevalence of iritis [45.4% vs 36.7%; OR 1.4 (1.1-2.0)] or psoriasis [23.9% vs 14.3%; OR 1.9 (1.3-2.8)] than controls. 2. Among our database subjects, the symptomatic onset of the spinal disease precedes or is contemporaneous with gut, skin, and eye involvement (matched pair t test, p < 0.001). 3. Patients with multiple disorders predict the highest prevalence of co-diseases (i.e., psoriasis, IBD, iritis, or AS) within family members, followed by those AS patients with only IBD, psoriasis, or iritis in descending order. 4. Both psoriasis and IBD increase severity in terrms of function and disease activity of AS in the patient. Radiological change is greatest for those AS subjects with iritis. CONCLUSION: There is a striking overlap within patients and family members of rheumatological, dermatological, and gastroenterological diseases. The susceptibility genes of these co-disorders appear to overlap with each other and with AS: 1. A patient with 2 inflammatory conditions is at an increased risk of developing an additional related inflammatory disorder. 2. Those with enteropathic spondylarthritis would appear to carry the greatest genetic load in terms of first degree relatives developing inflammatory conditions (including psoriasis and iritis that are not seen in the index IBD-AS patient). 3. The secondary disorders do not precede AS (arguing against psoriasis and IBD allowing for an environmental conduit to pathogenic triggers in AS). The susceptibility factors for these inflammatory conditions may be additive or have a synergistic effect on each other. There is evidence for a shared gene hypothesis.

Age of Onset↗
PubMed2000

Rabies virus entry at the neuromuscular junction in nerve-muscle cocultures.

Early events in rabies virus entry into neurons were investigated in chick spinal cord-muscle cocultures. Rabies virus (CVS strain) was adsorbed to the surface of cells in the cold. At times up to 10 min of warming to 37 degrees C, virus was most intensely localized to dense swellings on the myotube surface. Texas Red-labeled alpha-bungarotoxin, which binds to nicotinic acetylcholine receptors, colocalized precisely with virus at the densities identifying these regions as neuromuscular junctions. Rabies virus also colocalized in the junctions with synapsin I, a marker for synaptic vesicles. The endosome tracers Lucifer Yellow, Texan Red-dextran, and rhodamine-wheat germ agglutinin were added to the cultures at the end of the virus adsorption period and the cultures were warmed. At 10 min, rabies virus and tracers colocalized at neuromuscular junctions and nerve terminals. At 30 min, rabies virus and tracers showed more intense fluorescence over nerve fibers and nerve cell bodies. At 60 min, nerve terminals, nerve fibers, and nerve cell bodies showed intense fluorescence and colocalization for rabies virus and tracers. LysoTracker Red, a marker for acidic compartments, colocalized with rabies virus at nerve-muscle contacts. These findings show that in nerve-muscle cocultures, the neuromuscular junction is the major site of entry into neurons. Colocalization of virus and endosome tracers within nerve terminals indicates that virus resides in an early endosome compartment, some of which are acidified. The progressive increase of virus and tracers in nerve fibers and nerve cell bodies over time is consistent with retrograde transport of endocytosed virus from the motor nerve terminal.

Animals↗
PubMed2000

Molecular characterization and pathogenesis of transmissible gastroenteritis coronavirus (TGEV) and porcine respiratory coronavirus (PRCV) field isolates co-circulating in a swine herd.

TGEV replicates in intestinal enterocytes and causes diarrhea in young pigs. PRCV, a spike (S) gene deletion mutant of TGEV with an altered respiratory tissue tropism, causes mild or subclinical respiratory infections. Comparisons of TGEV and PRCV strains suggest that tropism and pathogenicity are influenced by the S gene and ORF3, respectively. Recently, outbreaks of TGE of reduced virulence were reported in the field. We investigated a similar suspect TGEV outbreak of reduced virulence in nursery pigs from a swine herd in the Midwest. A TGEV strain (BW021898B) was isolated in swine testicular cells from gut contents of a diarrheic pig and three PRCV strains (BW126, BW154, BW155) were isolated from nasal swabs from normal TGEV-seronegative sentinel pigs in contact with the diarrheic pigs. Sequence analysis of the TGEV isolate in the partial S gene and ORF3/3a and ORF3-1/3b revealed high homology with enteropathogenic TGEV strains. Gnotobiotic pig inoculation and histopathological results revealed that this TGEV isolate retained virulence even though in the field outbreak the diarrheal disease was of reduced severity. Sequence analysis of the S gene deletion region of the three PRCV isolates revealed identical deletions between nt 105-752, which differ from deletions previously reported among PRCV strains. The three PRCV isolates had variable sequence changes in ORF 3/3a and ORF 3-1/3b, affecting the ORF size and amino acid sequence. Thus, sequence analysis and pathogenicity studies indicate that this TGEV isolate resembles other enteropathogenic TGEV strains. Therefore, the reduced severity of TGE observed in this herd may be due to the ongoing PRCV infections, which induce antibodies cross-reactive with TGEV and result in decreased disease severity. The results outlined in this study highlight the need to monitor the molecular epidemiology of TGEV/PRCV strains with sensitive differential diagnostic assays, followed by sequence analysis of the critical regions to identify changes and pathogenicity studies to confirm the disease potential of the TGEV isolates.

Amino Acid Sequence↗
PubMed2000

Prospective long-term study of vagus nerve stimulation for the treatment of refractory seizures.

PURPOSE: To determine the long-term efficacy of vagus nerve stimulation (VNS) for refractory seizures. VNS is a new treatment for refractory epilepsy. Two short-term double-blind trials have demonstrated its safety and efficacy, and one long-term study in 114 patients has demonstrated a cumulative improvement in efficacy at 1 year. We report the largest prospective long-term study of VNS to date. METHODS: Patients with six or more complex partial or generalized tonic-clonic seizures enrolled in the pivotal EO5 study were prospectively evaluated for 12 months. The primary outcome variable was the percentage reduction in total seizure frequency at 3 and 12 months after completion of the acute EO5 trial, compared with the preimplantation baseline. Subjects originally randomized to low stimulation (active-control group) were crossed over to therapeutic stimulation settings for the first time. Subjects initially randomized to high settings were maintained on high settings throughout the 12-month study. RESULTS: The median reduction at 12 months after completion of the initial double-blind study was 45%. At 12 months, 35% of 195 subjects had a >50% reduction in seizures, and 20% of 195 had a >75% reduction in seizures. CONCLUSIONS: The efficacy of VNS improves during 12 months, and many subjects sustain >75% reductions in seizures.

Electric Stimulation Therapy↗
PubMed2000

Sonic hedgehog regulates growth and morphogenesis of the tooth.

During mammalian tooth development, the oral ectoderm and mesenchyme coordinate their growth and differentiation to give rise to organs with precise shapes, sizes and functions. The initial ingrowth of the dental epithelium and its associated dental mesenchyme gives rise to the tooth bud. Next, the epithelial component folds to give the tooth its shape. Coincident with this process, adjacent epithelial and mesenchymal cells differentiate into enamel-secreting ameloblasts and dentin-secreting odontoblasts, respectively. Growth, morphogenesis and differentiation of the epithelium and mesenchyme are coordinated by secreted signaling proteins. Sonic hedgehog (Shh) encodes a signaling peptide which is present in the oral epithelium prior to invagination and in the tooth epithelium throughout its development. We have addressed the role of Shh in the developing tooth in mouse by using a conditional allele to remove Shh activity shortly after ingrowth of the dental epithelium. Reduction and then loss of Shh function results in a cap stage tooth rudiment in which the morphology is severely disrupted. The overall size of the tooth is reduced and both the lingual epithelial invagination and the dental cord are absent. However, the enamel knot, a putative organizer of crown formation, is present and expresses Fgf4, Wnt10b, Bmp2 and Lef1, as in the wild type. At birth, the size and the shape of the teeth are severely affected and the polarity and organization of the ameloblast and odontoblast layers is disrupted. However, both dentin- and enamel-specific markers are expressed and a large amount of tooth-specific extracellular matrix is produced. This observation was confirmed by grafting studies in which tooth rudiments were cultured for several days under kidney capsules. Under these conditions, both enamel and dentin were deposited even though the enamel and dentin layers remained disorganized. These studies demonstrate that Shh regulates growth and determines the shape of the tooth. However, Shh signaling is not essential for differentiation of ameloblasts or odontoblasts.

Animals↗
PubMed2000

When is reduced-compression bandaging safe and effective?

During a one-year period 44 patients were treated with reduced-compression bandaging in the vascular unit at a district general hospital. Twenty patients with venous ulcers were referred from community leg ulcer clinics because they could not tolerate standard compression bandaging (group 1). A further 24 patients had mixed aetiology leg ulcers (group 2), and high-compression bandaging was not attempted because of significant peripheral vascular disease (ankle brachial pressure index < 0.8). Forty-two patients tolerated reduced-compression bandaging without discomfort or skin pressure changes. Healing was achieved in 32 patients (13 in group 1 and 19 in group 2). All non-healed ulcers were considered smaller at the time of final follow-up, and had less exudate. Reduced-compression bandaging has been shown to be effective and well tolerated by patients with venous ulcers who cannot comply with high-compression bandaging. With close supervision, it is safe to use in patients with significant peripheral vascular disease.

Adult↗
PubMed2000

Outcomes of weight-based heparin dosing based on literature guidelines and institution individualization.

STUDY OBJECTIVE: To determine whether unfractionated heparin is optimally dosed using published weight-based guidelines. DESIGN: Six-month, prospective study. SETTING: University hospital. PATIENTS: Ninety-six patients in the weight-based unfractionated heparin-dosing group 1 (WBHD1; 37 men; mean age 66.9 +/- 15.1 years; mean weight 80.1 +/- 20.6 kg) and 68 patients in the WBHD2 (25 men; mean age 68.2 +/- 15.6 years; mean weight 82.0 +/- 19.6 kg). INTERVENTIONS: The WBHD1 received a 100-U/kg intravenous bolus followed by an 18-U/kg/hour continuous intravenous infusion. After 3 months, the protocol was modified, and the WBHD2 received a 90-U/kg bolus followed by a 16-U/kg/hour continuous infusion for 3 months. MEASUREMENTS AND MAIN RESULTS: Activated partial thromboplastin times (aPTTs), frequency of bleeding episodes that required blood transfusions, and the number of recurrent thromboembolic events were collected from both groups after 3 months on the study. In the WBHD1, 24 hours after starting heparin, 38.5% of patients had therapeutic aPTTs, and at 48 hours, 54.3% were therapeutic. In the WBHD2, 42.6% and 51.4% of patients had therapeutic aPTTs at 24 and 48 hours, respectively. There was no statistical difference between the WBHD1 and WBHD2 in the percentage of patients with therapeutic aPTTs. CONCLUSIONS: Weight-based heparin dosing resulted in low percentages of patients with therapeutic aPTTs. The use of weight alone to dose heparin may not be adequate to optimize therapy.

Aged↗
PubMed2000

A suicide prevention advisory group at an academic medical center.

During a 15-month period, there were seven suicides among patients who were in active treatment or who had been seen recently by providers in the Department of Psychiatry of Tripler Army Medical Center, Honolulu, Hawaii. As a result, a Suicide Prevention Advisory Group was formed to identify possible causes and make recommendations aimed at improving the identification and treatment of suicidal patients. The group made 11 specific recommendations. No known suicides occurred during the 22 months after the implementation of the Suicide Prevention Advisory Group's recommendations.

Academic Medical Centers↗
PubMed2000

The impact of race on freedom from prostate-specific antigen failure in prostate cancer patients treated with definitive radiation therapy.

Many studies have reported that African-American men have the highest incidence and mortality rates for prostate cancer in the United States. A retrospective analysis of 607 patients treated with definitive radiation therapy was performed at the University of California San Francisco and its affiliated hospitals between 1987 and 1995. The patient population analyzed included African-American, Caucasian, and Asian men with AJCC T1-T3 disease. Race, Gleason score, pretreatment prostate-specific antigen levels, stage, and treatment delivery were all evaluated. The percent free from PSA failure at 48 months for African-American, Caucasian, and Asian men were 53%, 59%, and 53%, respectively. There was no difference among the three races or for any of the pairwise comparisons. Gleason score and stage of disease were each independent predictors of outcome, but race was not associated with remaining free from PSA failure. These results are similar to those recently reported in the literature from centers of excellence across the United States.

Adenocarcinoma↗
PubMed2000

Variant Alzheimer's disease with spastic paraparesis and cotton wool plaques is caused by PS-1 mutations that lead to exceptionally high amyloid-beta concentrations.

We describe 3 new families affected by Alzheimer's disease with spastic paraparesis. In affected individuals, including the earliest known patient with this clinical syndrome, neuropathological examination revealed large "cotton wool" plaques similar to those we have previously described in a Finnish family. In the families in which DNA was available, presenilin-1 mutations were observed. Transfection of cells with these mutant genes caused exceptionally large increases in secreted Abeta42 levels. Furthermore, brain tissue from individuals with this syndrome had very high amyloid-beta concentrations. These findings define the molecular pathogenesis of an important subgroup of Alzheimer's disease and have implications for the pathogenesis of the disease in general.

Alzheimer Disease↗