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Biomedical subjects

L Williams

Publications and source records attributed to L Williams.

At least 19 recordsLinked to original sources
PubMed2006

Role of resynchronisation therapy and implantable cardioverter defibrillators in heart failure.

The worldwide prevalence of heart failure is increasing in part because of an aging population. In the developed world, heart failure affects 1%-2% of the general population, accounting for 5% of adult hospital admissions. There is now convincing evidence supporting the beneficial effects of cardiac resynchronisation therapy for the treatment of heart failure. Numerous observational studies, as well as a series of randomised controlled trials, have shown the safety, efficacy, and long term benefits for patients with chronic systolic heart failure who have broad QRS complexes and refractory symptoms despite optimal medical therapy. These studies have consistently found statistically significant improvements in quality of life, New York Heart Association functional class, exercise tolerance, and left ventricular reverse remodelling. Recent evidence suggests that the benefit may at least in part be because of a reduction in mechanical dysynchrony.

Cardiac Pacing, Artificial↗
PubMed2005

The neurotransmitters glycine and GABA stimulate glucagon-like peptide-1 release from the GLUTag cell line.

The incretin hormone, glucagon-like peptide-1 (GLP-1) is released from intestinal L-cells following food ingestion. Its secretion is triggered by a range of nutrients, including fats, carbohydrates and proteins. We reported previously that Na(+)-dependent glutamine uptake triggered electrical activity and GLP-1 release from the L-cell model line GLUTag. However, whereas alanine also triggered membrane depolarization and GLP-1 secretion, the response was Na+ independent. A range of alanine analogues, including d-alanine, beta-alanine, glycine and l-serine, but not d-serine, triggered similar depolarizing currents and elevation of intracellular [Ca2+], a sensitivity profile suggesting the involvement of glycine receptors. In support of this idea, glycine-induced currents and GLP-1 release were blocked by strychnine, and currents showed a 58.5 mV shift in reversal potential per 10-fold change in [Cl-], consistent with the activation of a Cl(-)-selective current. GABA, an agonist of related Cl- channels, also triggered Cl- currents and secretion, which were sensitive to picrotoxin. GABA-triggered [Ca2+]i increments were abolished by bicuculline and partially impaired by (1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid (TPMPA), suggesting the involvement of both GABA(A) and GABA(C) receptors. Expression of GABA(A), GABA(C) and glycine receptor subunits was confirmed by RT-PCR. Glycine-triggered GLP-1 secretion was impaired by bumetanide but not bendrofluazide, suggesting that a high intracellular [Cl-] maintained by Na(+)-K(+)-2Cl- cotransporters is necessary for the depolarizing response to glycine receptor ligands. Our results suggest that GABA and glycine stimulate electrical activity and GLP-1 release from GLUTag cells by ligand-gated ion channel activation, a mechanism that might be important in responses to endogenous ligands from the enteric nervous system or dietary sources.

Action Potentials↗
PubMed2005

Fluorescence in situ hybridisation analysis of chromosomal aberrations in gastric tissue: the potential involvement of Helicobacter pylori.

In this series of experiments, a novel protocol was developed whereby gastric cells were collected using endoscopic cytology brush techniques, and prepared, such that interphase fluorescence in situ hybridization (FISH) could be performed. In total, 80 distinct histological samples from 37 patients were studied using four chromosome probes (over 32,000 cells analysed). Studies have previously identified abnormalities of these four chromosomes in upper GI tumours. Using premalignant tissues, we aimed to determine how early in Correa's pathway to gastric cancer these chromosome abnormalities occurred. Aneuploidy of chromosomes 4, 8, 20 and 17(p53) was detected in histologically normal gastric mucosa, as well as in gastritis, intestinal metaplasia, dysplasia and cancer samples. The levels of aneuploidy increased as disease severity increased. Amplification of chromosome 4 and chromosome 20, and deletion of chromosome 17(p53) were the more common findings. Hence, a role for these abnormalities may exist in the initiation of, and the progression to, gastric cancer. Helicobacter pylori infection was determined in premalignant tissue using histological analysis and PCR technology. Detection rates were comparable. PCR was used to subtype H. pylori for CagA status. The amplification of chromosome 4 in gastric tissue was significantly more prevalent in H. pylori-positive patients (n=7) compared to H. pylori-negative patients (n=11), possibly reflecting a role for chromosome 4 amplification in H. pylori-induced gastric cancer. The more virulent CagA strain of H. pylori was associated with increased disease pathology and chromosomal abnormalities, although numbers were small (CagA+ n=3, CagA- n=4). Finally, in vitro work demonstrated that the aneuploidy induced in a human cell line after exposure to the reactive oxygen species (ROS) hydrogen peroxide was similar to that already shown in the gastric cancer pathway, and may further strengthen the hypothesis that H. pylori causes gastric cancer progression via an ROS-mediated mechanism.

Aged↗
PubMed2005

The role of cardiac resynchronization therapy in heart failure.

The worldwide prevalence of heart failure is increasing in part due to an ageing population. In the developed world, heart failure affects 1-2% of the general population, accounting for 5% of adult hospital admissions. There is now convincing evidence supporting the beneficial effects of cardiac resynchronization therapy for the treatment of heart failure. Numerous observational studies, as well as a series of randomised controlled trials, have demonstrated the safety, efficacy, and long-term benefits for patients with chronic systolic heart failure who have broad QRS complexes and refractory symptoms despite optimal medical therapy. These studies have consistently demonstrated statistically significant improvements in quality of life, NYHA functional class, exercise tolerance, and left ventricular reverse remodeling. Recent evidence suggests that the benefit may at least in part be due to a reduction in mechanical dyssynchrony.

Equipment Design↗
PubMed2004

Glutamine potently stimulates glucagon-like peptide-1 secretion from GLUTag cells.

AIMS/HYPOTHESIS: Glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) are secreted from enteroendocrine L cells in response to nutrient ingestion. As glutamine is an important metabolic fuel for the gut, the aim of this study was to investigate the effect of glutamine on the GLP-1-secreting cell line, GLUTag. METHODS: GLP-1 release was measured following incubation of GLUTag cells under a range of conditions. Single cells were studied by electrophysiology, calcium imaging and cytosolic ATP measurement using recombinant luciferase. RESULTS: Glutamine was a more potent GLP-1 secretagogue than glucose or other amino acids, increasing GLP-1 release 7.1+/-0.7-fold ( n=19) at 10 mmol/l, with an estimated median effective concentration of between 0.1 and 1 mmol/l. Glutamine (10 mmol/l) induced a sodium-dependent inward current of 3.2+/-1.2 pA per cell ( n=9), which triggered membrane depolarisation and an increase in intracellular calcium. Asparagine and alanine produced electrophysiological and calcium changes that were at least as large as those caused by glutamine, but they were less effective GLP-1 secretagogues, suggesting that glutamine also potentiates secretion downstream of the calcium signal. This was confirmed by measuring secretion in the presence of 30 mmol/l KCl + diazoxide, or in alpha-haemolysin-permeabilised cells. Glutamine increased cytosolic ATP, but was less effective than glucose. CONCLUSIONS/INTERPRETATION: Glutamine acts as a trigger and potentiator of GLP-1 release, consistent with its role as the major metabolic fuel for the gut. The results suggest that nutritional agents like glutamine might have beneficial effects in diabetes and obesity.

Adenosine Triphosphate↗
PubMed2004

Streptococcus pneumoniae and Streptococcus pyogenes isolated from a paediatric population in Great Britain and Ireland: the in vitro activity of telithromcycin versus comparators.

OBJECTIVES: To investigate the antimicrobial susceptibility profiles of clinical isolates of Streptococcus pneumoniae and Streptococcus pyogenes, isolated from children within Great Britain and Ireland (Northern Ireland and Eire), with particular reference to the new oral ketolide telithromycin. To determine the distribution of macrolide resistance genes within the erythromycin resistant population. METHODS: MICs were determined using NCCLS microbroth dilution methodology and macrolide resistance mechanisms were investigated using PCR. RESULTS: Penicillin susceptibility was found to be 92.6% in S. pneumoniae isolates ( n=831; 3.7% intermediate, MIC 0.12-1 mg/l, 3.7% resistant, MIC >2.0 mg/l) and 100% in S. pyogenes isolates (n=1333) 8.8% of S. pneumoniae and 2.5% of S. pyogenes isolates demonstrated erythromycin-A resistance (EryA(R)). One hundred percent of S. pneumoniae and 99.8% of S. pyogenes isolates were susceptible to telithromycin (MIC<or=1.0 mg/l). Of the 73 EryA(R) S. pneumoniae isolates tested, 55 (75.3%) were mef (A) positive, 17 (23.3%) erm (B) positive and one isolate (1.4%) was positive for both mechanisms. Of the 34 isolates of EryA(R) S. pyogenes tested, 23 (67.6%) were erm (A) subclass erm (TR) positive, 4 (11.8%) erm (B) and 7 (20.6%) mef (A) positive. CONCLUSIONS: This paper presents baseline data on penicillin and macrolide resistance in S. pneumoniae and S. pyogenes isolates in the paediatric population of Great Britain and Ireland. Telithromycin, recently approved for the treatment of community acquired respiratory tract infections (CARTI) in patients over 12 years of age throughout the European community, demonstrated high in vitro activity against these pathogens, including EryA(R) strains.

Child↗
PubMed2003

Cervical spine injuries to children under 11: should we use radiography more selectively in their initial assessment?

OBJECTIVES: To assess the effectiveness of cervical spine radiography in injured children under 11 years old, and suggest improvements. METHODS: Retrospective survey of radiographs and accident and emergency records for children examined during a one year period in a large teaching hospital. RESULTS: No cervical spine fractures occurred in this age group during the year. The recorded clinical findings did not always justify radiography. CONCLUSIONS: Clinical examination appears undervalued by those assessing injured children and is poorly recorded. Radiography can be used more selectively. Initial assessment using a single lateral projection can be followed in doubtful cases by cross sectional imaging.

Age Distribution↗
PubMed2003

Efficacy and tolerability of fixed-dose combinations of telmisartan plus HCTZ compared with losartan plus HCTZ in patients with essential hypertension.

Telmisartan, an angiotensin II receptor blocker, is an effective once-daily antihypertensive agent available either alone or in fixed-dose combination with hydrochlorothiazide (HCTZ). This multicentre, prospective, randomised, open-label, blinded-endpoint (PROBE) study assessed the efficacy and safety of six weeks' treatment with telmisartan 40 mg/HCTZ 12.5 mg (n = 199) and telmisartan 80 mg/HCTZ 12.5 mg (n = 200) versus losartan 50 mg/HCTZ 12.5 mg (n = 198) in patients with mild to moderate essential hypertension. During the last six hours of the dosing interval, telmisartan 40 mg/HCTZ 12.5 mg and telmisartan 80 mg/HCTZ 12.5 mg reduced mean ambulatory diastolic blood pressure (DBP) to a greater extent than losartan 50 mg/HCTZ 12.5 mg (treatment differences 1.8 mmHg [p < 0.05] and 2.5 mmHg [p < 0.001], respectively). Telmisartan 80 mg/HCTZ 12.5 mg also lowered mean 24-hour DBP by 2.3 mmHg more than losartan 50 mg/HCTZ 12.5 mg (p < 0.001). Telmisartan 40 mg/HCTZ 12.5 mg and telmisartan 80 mg/HCTZ 12.5 mg produced greater reductions in ambulatory systolic blood pressure versus losartan 50 mg/HCTZ 12.5 mg of 2.5 mmHg and 3.4 mmHg, respectively, during the last six hours of the dosing interval (p < 0.05), and of 2.1 mmHg and 3.4 mmHg, respectively, over the entire 24-hour dosing interval (p < 0.05). All treatments were well tolerated.

Adult↗
PubMed2003

The adjunctive effect of telmisartan in patients with hypertension uncontrolled on current antihypertensive therapy.

This prospective, double-blind, randomised, parallel-group, multicentre study assessed the adjunctive effect of telmisartan monotherapy versus placebo in controlling blood pressure during the last six hours of the 24-hour dosing period. After a two-week run-in phase, 375 patients with essential hypertension uncontrolled on existing therapy were randomised to either placebo or telmisartan (40 mg uptitrated to 80 mg after four weeks, if needed) for eight weeks. Ambulatory blood pressure monitoring (ABPM) was conducted at randomisation (baseline) and treatment end. The change from baseline in diastolic blood pressure (DBP) over the last six hours (primary endpoint) was significantly greater with telmisartan than placebo (adjusted mean treatment difference in favour of telmisartan: -3.7 mmHg, 95% confidence interval (CI) -5.5, -1.9 mmHg, p < or = 0.001, n = 350), as was the reduction in 24-hour DBP (adjusted mean treatment difference: -5.0 mmHg, 95% CI -6.5, -3.5 mmHg, p < or = 0.001). Telmisartan also reduced mean systolic blood pressure significantly more than placebo over the last six hours and the entire 24-hour dosing interval. Responder rates (ABPM DBP, seated DBP, and overall [seated SBP/DBP]) at 8 weeks were significantly higher with telmisartan than with placebo (p < or = 0.01). All treatments were well tolerated. When added to existing antihypertensive regimens, telmisartan offers additional effectiveness while maintaining placebo-like tolerability.

Adult↗
PubMed2002

A rapid test for detection of mite allergens in homes.

BACKGROUND: International guidelines recommend allergen avoidance for asthma management, but do not include making assessments of allergen exposure. Mite allergen exposure cannot be assumed, especially in geographical regions where climatic conditions vary. OBJECTIVE: To develop a rapid test that would enable consumers to detect mite allergen in the home. METHODS: A lateral flow test using gold labelled antibody for mite group 2 allergen was developed as part of a detection kit incorporating the MITEST dust sampling device. Dust samples were assayed by ELISA for group 1 and group 2 allergens and by using the rapid test. The tests were compared as indices of mite allergen exposure. RESULTS: There was a good correlation between group 1 and group 2 levels by ELISA (n = 349, r = 0.60, P < 0.001). In a multi-centre study of 65 homes (263 dust samples) in five countries, there was a strong correlation between ELISA and the rapid test. Most samples with high scores in the test (43/48, 90%) contained > 1 microg/m2 group 2 allergen, whereas most low samples contained < 1 microg/m2 (50/64, 78%). Differences between mean group 2 levels of samples that scored low (0.28 microg/m2), medium (1.68 microg/m2) or high (3.18 microg/m2) on the test were highly significant (P 0.007 to < 0.001). CONCLUSIONS: A simple rapid test has been developed that detects mite allergen in the home within 10 min. The mite screening test should educate consumers about allergen exposure and encourage compliance with allergen-avoidance procedures. This technology has applications for the detection of other common environmental allergens.

Allergens↗
PubMed2002

Clinical results using biochemotherapy as a standard of care in advanced melanoma.

Phase II studies of biochemotherapy in metastatic melanoma patients have reported response rates of 47-63%. Even though these were highly selected patients, we were intrigued by these promising response rates and began using this regimen as standard care in advanced melanoma patients. We report the results of the first 65 patients with AJCC stage IV melanoma (n = 57) or unresectable stage III (n = 8) melanoma treated with concurrent biochemotherapy at Memorial Hospital. Treatment was repeated every 3 weeks and patients were assessed for antitumour effects after every other cycle. The overall response rate among the 63 patients evaluable for response was 29% (three complete responses, 15 partial responses). The median duration of responses was 3.7 months. The response rate among previously treated and previously untreated patients was 6% and 38%, respectively. The estimated median survival for all patients was 8.5 months; the median survival for previously untreated patients was 9.2 months. Tumour response did not correlate with survival. Our experience, which is a retrospective evaluation, does not provide support for the routine use of biochemotherapy as standard treatment. The low response rate among previously treated patients indicates that biochemotherapy is not useful as second-line therapy.

Adolescent↗
PubMed2001

Urinary 11-dehydro-thromboxane B(2) and coagulation activation markers measured within 24 h of human acute ischemic stroke.

The aim of this study was to determine the extent of change in platelet and coagulation markers in the acute phase of ischemic stroke and to assess the utility of marker measurement in stroke subtype classification. Urinary 11-dehydro-thromboxane B(2) (11-dTXB2), a marker of in vivo platelet activation, and markers of coagulation activation, including prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT), and fibrinogen, were measured in 25 patients with ischemic stroke within 24 h of onset of symptoms. Marker levels in patients with ischemic stroke were compared with those in 19 age-matched controls who had not taken aspirin for at least 2 weeks before sampling and 25 healthy controls. Median marker levels were significantly increased in stroke over those in age-matched controls for fibrinogen (344 vs. 289 mg/dl; P=0.030), F1+2 (1.40 vs. 0.80 nmol/l; P=0.003), and TAT (6.65 vs. 2.20 microg/l; P<0.0001). Median marker levels for seven patients with cardioembolic stroke and 18 with non-cardioembolic stroke were not significantly different for any marker test. Eight patients taking aspirin at the time of the stroke had significantly lower 11-dTXB2 values than patients not taking aspirin (964 vs. 4,314 pg/mg of creatinine; P=0.007). Stroke patients not taking aspirin had significantly higher 11-dTXB2 concentration than age-matched controls (4,314 vs. 1,788 pg/mg of creatinine; P=0.006). Coagulation and platelet activation markers are increased in the acute phase of stroke regardless of the clinical mechanism. This finding suggests that the markers may not be useful for predicting clinical subtype of ischemic stroke in the acute phase.

Acute Disease↗
PubMed2001

Two phases of chromatin decondensation during dedifferentiation of plant cells: distinction between competence for cell fate switch and a commitment for S phase.

Cellular dedifferentiation is the major process underlying totipotency, regeneration, and formation of new stem cell lineages in multicellular organisms. In animals it is often associated with carcinogenesis. Here, we used tobacco protoplasts (plant cells devoid of cell wall) to study changes in chromatin structure in the course of dedifferentiation of mesophyll cells. Using flow cytometry and micrococcal nuclease analyses, we identified two phases of chromatin decondensation prior to entry of cells into S phase. The first phase takes place in the course of protoplast isolation, following treatment with cell wall degrading enzymes, whereas the second occurs only after protoplasts are induced with phytohormones to re-enter the cell cycle. In the absence of hormonal application, protoplasts undergo cycles of chromatin condensation/decondensation and die. The ubiquitin proteolytic system was found indispensable for protoplast progression into S phase, being required for the second but not the first phase of chromatin decondensation. The emerging model suggests that cellular dedifferentiation proceeds by two functionally distinct phases of chromatin decondensation: the first is a transitory phase that confers competence for cell fate switch, which is followed, under appropriate conditions, by a second proteasome-dependent phase representing a commitment for the mitotic cycle. These findings might have implications for a wide range of dedifferentiation-driven cellular processes in higher eukaryotes.

Base Sequence↗
PubMed2001

Primary commissure pioneer neurons in the brain of the grasshopper Schistocerca gregaria: development, ultrastructure, and neuropeptide expression.

The bilaterally paired primary commissure pioneer neurons in the median domain of the grasshopper brain are large, descending interneurons that uniquely express the TERM-1 antigen, even in the adult. After pioneering the primary interhemispheric brain commissure, these neurons extend TERM-1-immunoreactive collaterals into most parts of the brain except the mushroom bodies. In this report, the authors show that the TERM-1 antigen is located in the cell body cytoplasm of these neurons and not on the membranes. Screening with antisera to insect neuropeptides reveals that an antiserum recognizing peptides of the leucokinin family labels the cell body cytoplasm of the primary commissure neurons. Leucokinin-related peptides are known to modulate motility of visceral muscle, play a role in diuresis, and are likely to be neuromodulators in the insect nervous system. The primary commissure neurons differ ultrastructurally from median neurosecretory cells in that their cell body cytoplasm is more extensive, contains high numbers of mitochondria and extensive endoplasmic reticulum, but does not contain neurosecretory granules. In the adult, the cell somata are enveloped by multiple glia membranes and associated trophospongia. According to these ultrastructural characteristics, the primary commissure pioneers are not classical neurosecretory cells.

Animals↗
PubMed2001

Effects of 2 inhaled corticosteroids on growth: results of a randomized controlled trial.

OBJECTIVE: To compare the long-term effect of treatment with fluticasone propionate or beclomethasone dipropionate on growth in asthmatic children. DESIGN: Prospective, multicenter, randomized, double-blind, parallel-group study. SETTING: Children requiring regular treatment with inhaled corticosteroids and with a sexual maturity rating of Tanner stage 1 (prepubertal). PATIENTS: Three hundred forty-three children aged 4 to 11 years with asthma. The growth population (excluding patients with protocol violations likely to affect growth measurements) included 277 patients. INTERVENTIONS: Fluticasone propionate or beclomethasone dipropionate, both at a dosage of 200 microg administered twice daily via a dry powder inhaler (Diskhaler) for 12 months. MAIN OUTCOME MEASURES: Growth velocity, lung function, and serum and urinary cortisol levels. RESULTS: The adjusted mean growth velocity in the fluticasone group was significantly greater than that in the beclomethasone group (5.01 [SE, 0.14] vs 4.10 [SE, 0.15] cm/y; difference, 0.91 cm; 95% confidence interval, 0.63-1.20 cm; P<.001). Both treatments improved lung function, with significant differences in favor of fluticasone. Adverse events were similar in both groups, and there were no significant differences in effect on serum and urinary cortisol levels. CONCLUSIONS: The more favorable risk-benefit ratio of fluticasone indicates that this agent is preferable to beclomethasone for the long-term treatment of children with asthma, especially if moderate doses are required.

Androstadienes↗
PubMed2001

Time courses of left and right amygdalar responses to fearful facial expressions.

Despite the many studies highlighting the role of the amygdala in fear perception, few have examined differences between right and left amygdalar responses. Using functional magnetic resonance imaging (fMRI), we examined neural responses in three groups of healthy volunteers (n = 18) to alternating blocks of fearful and neutral faces. Initial observation of extracted time series of both amygdalae to these stimuli indicated more rapid decreases of right than left amygdalar responses to fearful faces, and increasing magnitudes of right amygdalar responses to neutral faces with time. We compared right and left responses statistically by modeling each time series with (1) a stationary fit model (assuming a constant magnitude of amygdalar response to consecutive blocks of fearful faces) and (2) an adaptive model (no assumptions). Areas of significant sustained nonstationarity (time series points with significantly greater adaptive than stationary model fits) were demonstrated for both amygdalae. There was more significant nonstationarity of right than left amygdalar responses to neutral, and left than right amygdalar responses to fearful faces. These findings indicate significant variability over time of both right and left amygdalar responses to fearful and neutral facial expressions and are the first demonstration of specific differences in time courses of right and left amygdalar responses to these stimuli.

Adult↗