A wormer's eye view.
A report on the thirteenth international Caenorhabditis elegans meeting, University of California, Los Angeles, USA, 22-26 June 2001.
Animals↗
Biomedical subjects
A G Fraser
Publications and source records attributed to A G Fraser.
Roles for 147 embryonic lethal genes on C.elegans chromosome I identified by RNA interference and video microscopy.
Early embryonic development involves complex events such as the regulation of cell division and the establishment of embryonic polarity. To identify genes involved in these events, we collected four-dimensional time-lapse video recordings of the first three cell divisions and analysed terminal phenotypes after RNA interference of 147 embryonic lethal genes previously identified in a systematic screen of Caenorhabditis elegans chromosome I. Over half gave defects in early processes such as meiosis, the assembly or position of the first mitotic spindle, cytokinesis, and proper nuclear positioning. For some phenotypic classes, the majority of genes are involved in a shared biochemical process. In addition, we identified loss-of-function phenotypes for genes of unknown function, but for which homologues exist in other organisms, shedding light on the function of these uncharacterized genes. When applied to the whole genome, this approach should identify the vast majority of genes required for early cell processes, paving the way for a greatly improved understanding of these processes and their regulation at the molecular level.
Animals↗
Differentiation between pathologic and physiologic left ventricular hypertrophy by tissue Doppler assessment of long-axis function in patients with hypertrophic cardiomyopathy or systemic hypertension and in athletes.
To identify new echocardiographic indexes of long-axis function that might differentiate between pathologic and physiologic left ventricular (LV) hypertrophy, we compared 60 subjects with different types of LV hypertrophy (group I: 15 patients with hypertrophic cardiomyopathy, group II: 15 patients with systemic hypertension, and group III: 30 athletes) with 20 normal subjects (group IV). The peak velocities of mitral annular motion at 4 sites were measured from the apex by tissue Doppler echocardiography. There were no differences in mean age and global ejection fraction between groups. Groups I and II had lower long-axis systolic and early diastolic velocities than the athletes (p <0.01) for all 4 sites. The best differentiation of pathologic from physiologic hypertrophy was provided by a mean systolic annular velocity <9 cm/s (sensitivity 87%, specificity 97%). Heterogeneity of annular velocities discriminated between group I and group II. Thus, long-axis systolic and early diastolic velocities are decreased in patients with pathologic hypertrophy, but preserved in athletes. These simple new echocardiographic parameters can differentiate between pathologic and physiologic hypertrophy.
Adult↗
Prospective study of routine perioperative transesophageal echocardiography for elective valve replacement: clinical impact and cost-saving implications.
Transesophageal echocardiography (TEE) is widely used during heart valve replacement operations, but its clinical impact and cost-saving profile have not been studied prospectively for this indication. We investigated the clinical benefits and cost-savings of routine TEE for elective valve replacement at a regional tertiary center. We prospectively studied 300 patients (140 men; mean age [+/-SD], 66 +/- 9 years) undergoing aortic valve, mitral valve, or double-valve replacements. Transesophageal echocardiography with a biplane (in 161 patients) or a multiplane probe was performed before and after surgery. We assessed whether the TEE findings changed the operation or the postoperative treatment and the cost of TEE either as an extension of a preexisting service or as a new development. In 2 patients undergoing aortic valve replacement, significant mitral regurgitation on TEE led to additional mitral valve replacement, and in 1 patient undergoing mitral valve replacement, aortic regurgitation also required aortic valve replacement. Immediate reoperation (dehisced mitral valve prosthesis) and delayed extubation (suspected obstruction of an aortic valve prosthesis) were prompted by postoperative TEE. Extending an existing TEE service to routine intraoperative use saved up to $109 (US) per patient per year. Routine intraoperative TEE can provide major clinical benefit to a small proportion of patients undergoing elective valve replacement, and this can lead to cost savings, but only if the service can be provided without major capital investment.
Aged↗
Assessment of left ventricular long axis contraction can detect early myocardial dysfunction in asymptomatic patients with severe aortic regurgitation.
OBJECTIVE: To identify variables that could be applied at rest to diagnose subclinical ventricular dysfunction in asymptomatic patients with severe aortic regurgitation. DESIGN: Cross sectional study. PATIENTS: Left ventricular long axis contraction was studied using tissue Doppler and M mode echocardiography in 21 patients with no symptoms (New York Heart Association (NYHA) functional class </= 2a) but severe aortic regurgitation (jet area/left ventricular outflow tract area > 40%). MAIN OUTCOME MEASURES: Left ventricular ejection fraction (LVEF) at baseline and peak exercise (Weber protocol), cardiopulmonary function, and left ventricular long axis function at rest (peak systolic velocity and excursion of the mitral annulus). RESULTS: In 11 patients, ejection fraction increased or did not change (from mean (SD) 55 (5)% to 58 (4)%, p < 0.05) (group I); in 10 patients it decreased by > 5% (from 54 (4)% to 42 (5)%, p < 0.001) (group II). Exercise ejection fraction was < 50% in all patients in group II. At rest, there were no differences between the groups in ejection fraction, left ventricular diameter indices, wall stress, and short axis contraction. However, patients in group II had reduced long axis contraction compared with group I: peak systolic velocity 8.6 (0.6) v 11.9 (2.2) cm/s (p < 0.001); excursion 11 (2) v 14 (2) mm (p < 0.01). A resting velocity of < 9.5 cm/s was the best indicator of poor exercise tolerance (sensitivity 90%, specificity 100%). CONCLUSIONS: Markers of reduced long axis contraction may provide simple and reliable indices of subclinical left ventricular dysfunction in asymptomatic patients with severe aortic regurgitation.
Adult↗
Subclinical right ventricular dysfunction in cystic fibrosis. A study using tissue Doppler echocardiography.
Patients with severe cystic fibrosis can develop cor pulmonale, but little is known about the function of the right ventricle (RV) early in the disease. We hypothesized that such patients might have subclinical RV dysfunction, detectable by tissue Doppler echocardiography, and related to the severity of lung disease. We studied 21 clinically stable patients (Group 1), five patients with severe lung disease (Group 2), and 23 age-matched healthy subjects. Patients had impaired RV systolic function. The mean (SD) systolic velocities of the RV free wall were 8.9 (1.7) cm/s in Group 1, 7.7 (1.0) in Group 2, and 10.8 (1.9) in healthy subjects (p < 0.001). The velocities of the tricuspid annulus were less in patients (p < 0.0001). Patients had a greater isovolumic relaxation time (p < 0.001), indicating RV diastolic dysfunction. RV wall thickness was greater in patients (0.4 [0.1] versus 0.3 [0.1] cm/m(2), p < 0.01). RV systolic function was related to C-reactive protein (r = - 0.66, p < 0.001) and FEV(1) (r = 0.62, p = 0.003) and diastolic function to interleukin-6 (r = 0.64, p < 0.005). Patients with cystic fibrosis have subclinical RV dysfunction, which correlates with the severity of lung disease. Tissue Doppler echocardiography provides a quantifiable indicator useful for detection and monitoring of disease progression.
Adult↗
Effectiveness of specific RNA-mediated interference through ingested double-stranded RNA in Caenorhabditis elegans.
BACKGROUND: In Caenorhabditis elegans, injection of double-stranded RNA (dsRNA) results in the specific inactivation of genes containing homologous sequences, a technique termed RNA-mediated interference (RNAi). It has previously been shown that RNAi can also be achieved by feeding worms Escherichia coli expressing dsRNA corresponding to a specific gene; this mode of dsRNA introduction is conventionally considered to be less efficient than direct injection, however, and has therefore seen limited use, even though it is considerably less labor-intensive. RESULTS: Here we present an optimized feeding method that results in phenotypes at least as strong as those produced by direct injection of dsRNA for embryonic lethal genes, and stronger for genes with post-embryonic phenotypes. In addition, the interference effect generated by feeding can be titrated to uncover a series of hypomorphic phenotypes informative about the functions of a given gene. Using this method, we screened 86 random genes on consecutive cosmids and identified functions for 13 new genes. These included two genes producing an uncoordinated phenotype (a previously uncharacterized POU homeodomain gene, ceh-6, and a gene encoding a MADS-box protein) and one gene encoding a novel protein that results in a high-incidence-of-males phenotype. CONCLUSIONS: RNAi by feeding can provide significant information about the functions of an individual gene beyond that provided by injection. Moreover, it can be used for special applications for which injection or the use of mutants is sometimes impracticable (for example, titration, biochemistry and large-scale screening). Thus, RNAi by feeding should make possible new experimental approaches for the use of genomic sequence information.
Animals↗
Functional genomic analysis of C. elegans chromosome I by systematic RNA interference.
Complete genomic sequence is known for two multicellular eukaryotes, the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster, and it will soon be known for humans. However, biological function has been assigned to only a small proportion of the predicted genes in any animal. Here we have used RNA-mediated interference (RNAi) to target nearly 90% of predicted genes on C. elegans chromosome I by feeding worms with bacteria that express double-stranded RNA. We have assigned function to 13.9% of the genes analysed, increasing the number of sequenced genes with known phenotypes on chromosome I from 70 to 378. Although most genes with sterile or embryonic lethal RNAi phenotypes are involved in basal cell metabolism, many genes giving post-embryonic phenotypes have conserved sequences but unknown function. In addition, conserved genes are significantly more likely to have an RNAi phenotype than are genes with no conservation. We have constructed a reusable library of bacterial clones that will permit unlimited RNAi screens in the future; this should help develop a more complete view of the relationships between the genome, gene function and the environment.
Animals↗
Presumed laryngo-pharyngeal reflux: investigate or treat?
A review of a combined gastroenterology and laryngology clinic was conducted to determine the effectiveness of treatment and the predictive value of clinical findings and investigations. Data were collected prospectively. Investigations were performed according to clinical criteria. Patients with symptoms suspected to be due to laryngopharyngeal reflux (based on a positive oesophageal pH test and/or changes on videolaryngoscopy consistent with posterior laryngitis) were treated with omeprazole for at least two to three months. There were 87 patients; the most common symptoms were cough (38 per cent) and hoarseness (36 per cent); 77 per cent had some symptoms suggestive of gastro-oesophageal reflux. Sixty-seven patients were given omeprazole. A good response to laryngo-pharyngeal symptoms was seen in 37 patients (55 per cent). The presence of reflux symptoms was not a predictor of a good response. Increasing severity of oesophageal acid exposure over the 24 hours of pH testing was associated with a better symptom response (Spearman rank correlation, p = 0.01). Posterior laryngitis was not associated with the response to treatment, although there was a trend towards an association between improvement in laryngitis (after treatment) and improvement in symptoms (p = 0.08). The response to proton pump inhibitors was lower than other published results. Oesophageal pH monitoring may have a role in predicting which patients will respond to proton pump inhibitors. This study does not support the decision to treat with anti-secretory therapy, based only on the presence of posterior laryngitis.
Anti-Ulcer Agents↗
Bleeding peptic ulcers: audit of eradication treatment for H pylori.
AIMS: To determine the outcomes after presentation with bleeding peptic ulcer and to assess the implementation of H. pylori testing, treatment and follow-up testing. METHODS: Case notes and endoscopy records of patients presenting to Auckland Hospital between 1993-95 were reviewed. Patients were recalled for interview and urea breath test. RESULTS: Mean follow-up after presentation was three years. Eighty-nine patients were reviewed; 62% were confirmed as H. pylori positive, although 20% had no biopsies. H. pylori eradication treatment was given to 49 patients. Thirty-five patients had a definite treatment success; eight were failures (eradication rate of 81%) and six received treatment without proof of H. pylori by biopsy. Forty patients received acid suppression only. Twelve patients had biopsy evidence of H. pylori, and a further nine were proven H. pylori positive at follow-up by urea breath test (initial tests had been negative or not performed). Nine patients had a rebleed; seven were confirmed H pylori positive either at presentation, or by follow-up breath test or endoscopic biopsies. CONCLUSIONS: The incidence of H. pylori in patients with bleeding peptic ulcer is underestimated and many infected patients do not receive eradication treatment. Rebleeding is largely preventable if more attention is given to diagnosis and treatment of H. pylori and follow-up of treatment with a urea breath test.
Anti-Bacterial Agents↗
Caenorhabditis elegans inhibitor of apoptosis protein (IAP) homologue BIR-1 plays a conserved role in cytokinesis.
BACKGROUND: Inhibitor of apoptosis proteins (IAPs) suppress apoptotic cell death in several model systems and are highly conserved between insects and mammals. All IAPs contain at least one copy of the approximately 70 amino-acid baculovirus IAP repeat (BIR), and this domain is essential for the anti-apoptotic activity of the IAPs. Both the marked structural diversity of IAPs and the identification of BIR-containing proteins (BIRPs) in yeast, however, have led to the suggestion that BIRPs might play roles in other, as yet unidentified, cellular processes besides apoptosis. Survivin, a human BIRP, is upregulated 40-fold at G2-M phase and binds to mitotic spindles, although its role at the spindle is still unclear. RESULTS: We have identified and characterised two Caenorhabditis elegans BIRPs,BIR-1 and BIR-2; these proteins are the only BIRPs in C. elegans. The bir-1 gene is highly expressed during embryogenesis with detectable expression throughout other stages of development; bir-2 expression is detectable only in adults and embryos. Overexpression of bir-1 was unable to inhibit developmentally occurring cell death in C. elegans and inhibition of bir-1 expression did not increase cell death. Instead, embryos lacking bir-1 were unable to complete cytokinesis and they became multinucleate. This cytokinesis defect could be partially suppressed by transgenic expression of survivin, the mammalian BIRP most structurally related to BIR-1, suggesting a conserved role for BIRPs in the regulation of cytokinesis. CONCLUSIONS: BIR-1, a C. elegans BIRP, is probably not involved in the general regulation of apoptosis but is required for embryonic cytokinesis. We suggest that BIRPs may regulate cytoskeletal changes in diverse biological processes including cytokinesis and apoptosis.
Amino Acid Sequence↗
Long-term follow-up of the management of benign oesophageal strictures at Auckland Hospital 1990-1994.
AIMS: To audit the success of endoscopic dilatation treatment for oesophageal stricture, to determine any predictive factors for multiple dilatations and to compare data with a previous series from the same department. METHODS: The endoscopy records of 121 consecutive patients with benign oesophageal strictures undergoing endoscopic dilatation were reviewed at Auckland Hospital from 1990 to 1994. RESULTS: Two hundred and thirty-eight procedures were performed with no recorded technical failures and minimal morbidity. The follow-up period from presentation ranged from 18 to 77 months (median 47 months) and the symptom-free period after the last dilatation ranged from 6 to 77 months (median 47 months). One hundred and nineteen patients had been followed for 12 months or more since their last dilatation. Sixty-three patients (52%) required only one dilatation, 44 (36%) patients required two to three dilatations and 14 (12%) patients required more than three dilatations. There was a trend for patients treated with omeprazole to require fewer dilatations than patients treated with H2-receptor antagonists (p = 0.07). Patients with tight strictures (< 11 mm) and Barrett's oesophagus required more dilatations. CONCLUSIONS: Oesophageal dilatation for benign peptic strictures is a safe and effective procedure.
Adult↗
Morphologic analysis of a strand recovered from a prosthetic mitral valve: No evidence of fibrin.
We report the first morphologic analysis of a linear mobile structure (strand) detected by transesophageal echocardiography on a bioprosthetic mitral valve and then recovered at surgery. Electron microscopy showed it to consist of a sparsely cellular component, with extracellular amorphous or fibrillary areas. Collagen was largely responsible for the fibrillary appearance.
Echocardiography, Transesophageal↗
Reproducibility of pulsed wave tissue Doppler echocardiography.
Four hundred and eighty paired recordings obtained from 16 patients (55 +/- 10 yrs; 10 men, 6 women) were analyzed to determine the reproducibility of both acquiring and measuring myocardial velocities recorded by tissue Doppler echocardiography. To assess intraobserver variability, 1 observer recorded and measured the data twice, from the same patients, and to assess interobserver variability, patients were examined by 2 independent observers. For the left ventricle, intraobserver reproducibility was higher when assessing long-axis velocities (+/- 10% to 16%) than short-axis velocities (+/- 14% to 24%). For the right ventricle, intraobserver reproducibility was high for the tricuspid annulus (+/- 9% to 15%), but unsatisfactory for the right ventricular anterior wall (+/- 21% to 25%). The highest interobserver reproducibilities were obtained for systolic and diastolic velocities of the lateral mitral annulus (+/- 9% to 17%) and systolic velocity of the tricuspid annulus (+/-13%). Interobserver reproducibility of the ratio of early-to-late peak diastolic velocities was very low for all investigated sites (+/- 20% to 52%). With the use of current techniques and software, reproducibility of acquiring and measuring tissue Doppler echocardiography is suboptimal for both systolic and diastolic myocardial velocities.
Echocardiography, Doppler↗
Programmed cell death in C. elegans.
Genetic screens in the hermaphrodite nematode worm Caenorhabditis elegans resulted in the identification of the basal conserved machinery of apoptosis, arguably the single most important finding for our understanding of cell death. The last two years have seen enormous progress in the elucidation of the molecular interactions that lie at the heart of this conserved machinery, along with major insights both into how cell death is activated in the worm and into the mechanism of recognition and engulfment of the cell corpses. In this review, I set out the current models of cell death regulation and execution in C. elegans, focussing in particular on the similarities between cell death in C. elegans and vertebrates. Finally, I attempt to highlight key areas for future progress in cell death research in C. elegans and explore additional ways in which the worm can be used to understand the regulation of cell death in mammals.
Animals↗
Gastric juice ascorbic acid is related to Helicobacter pylori infection but not ethnicity.
BACKGROUND: Maori and Pacific Island ethnic groups in New Zealand have a high risk for gastric cancer. Low levels of gastric juice ascorbic acid (vitamin C) have been suggested to be a risk factor for gastric cancer. Previous studies have shown that gastric juice ascorbic acid may be independently associated with both ethnicity and Helicobacter pylori infection. This study aimed to examine the interrelationship between H. pylori and ethnicity in New Zealand. METHODS: Gastric juice was collected into 70% perchloric acid preservative and stored at -80 degrees C. Ascorbic acid was analysed by high-performance liquid chromatography using ion-pair chromatography and electrochemical detection. Inflammation and atrophy was graded from biopsies from multiple sites in the antrum and body. Gastric juice was collected from 89 patients during routine endoscopy. RESULTS: There was a wide range of measured gastric juice ascorbic acid from 0.001 to 410 microg/mL. The median concentration of ascorbic acid for H. pylori-negative patients was 1.78 microg/mL (n = 57) and 0.12 microg/mL (n = 32) for H. pylori-positive patients (P = 0.001). Gastric juice ascorbic acid concentration was not associated with age, endoscopic diagnosis or intestinal metaplasia, but was significantly associated with the degree of acute inflammation (P = 0.01) and the presence of atrophy (P = 0.04). The median ascorbic acid concentration for European patients was 0.92 microg/mL (n = 44) and 0.09 microg/mL (n = 38) for Maori and Pacific Island ethnic groups combined (P = 0.1). Multiple step-wise regression analysis showed that only H. pylori infection was a significant factor for predicting ascorbic acid concentrations (r2 = 0.12). CONCLUSIONS: This study has confirmed that gastric juice ascorbic acid concentration is lower in the presence of H. pylori infection.
Adult↗
Mobile echoes on prosthetic valves are not reproducible. Results and clinical implications of a multicentre study.
AIMS: To test the hypothesis that inter-observer variability accounts for the wide variation in reported prevalences of fibrin strands on prosthetic heart valves and to develop criteria for their identification and reporting. METHODS AND RESULTS: A videotape with 30 sequences of prosthetic heart valves imaged by transoesophageal echocardiography and showing abnormalities such as strands, microbubbles, and spontaneous echocardiographic contrast, was assessed in 13 European and three American centres. There were three duplicated examples, unbeknown to the observers. Definitions and reported prevalence rates of the abnormalities were analysed, and inter- and intra-observer agreement estimated with the kappa statistic. Mobile echoes were identified in 40 to 80% of the sequences on the tape. The reported prevalence of mobile echoes correlated with the time spent reporting the tape. There was moderate inter-observer agreement for the identification of any mobile echoes (kappa = 0.38), but no agreement for their labelling (kappa = 0.22), in spite of similar definitions. Intra-observer reproducibility was good (agreement in 76% of the reduplicated sequences). CONCLUSIONS: The true prevalence and potential significance of mobile echoes on prosthetic heart valves cannot be assessed unless inter-observer consensus on echocardiographic criteria for identifying such echoes is reached.
Adult↗
Helicobacter pylori treatment and antibiotic susceptibility: results of a five-year audit.
BACKGROUND: Helicobacter pylori eradication treatment has been a rapidly evolving field. Audit of treatment results provides reassurance that trial data can be translated into routine clinical practice. METHODS: Data were collected prospectively over five years. Patients were given four different treatment regimens over the audit period 'standard' triple therapy, two types of clarithromycin-based treatment or ranitidine, amoxycillin and metronidazole. Eradication was proven by a urea breath test at least four weeks after completing treatment. RESULTS: Eradication treatment for H. pylori was given to 665 patients; 89% had follow-up data. H. pylori eradication was significantly associated with treatment type (p<0.0001) and smoking (p=0.04) by univariate analysis, but was not associated with sex, age, alcohol consumption, endoscopic diagnosis, recent treatment with anti-secretory drugs or NSAIDs. By logistic regression analysis, only treatment type was significant (p=0.0001). H. pylori culture and sensitivities were available for 255 patients. Metronidazole resistance was shown for 84 isolates (32%) and clarithromycin resistance for 18 isolates (6.8%). Metronidazole resistance was significantly associated with younger age (p=0.02), ethnicity (p=0.02), female sex (p=0.02), and year of endoscopy (p=0.04), but was not associated with clarithromycin resistance. Clarithromycin resistance was not associated with age, sex, or ethnicity. Metronidazole resistance significantly affected H. pylori eradication for regimens containing metronidazole without clarithromycin. Eradication with metronidazole without clarithromycin was achieved in 90% of sensitive strains but only 55% of resistant strains (p<0.001). Metronidazole resistance was not significantly associated with treatment failure when metronidazole was combined with clarithromycin. Eradication with metronidazole and clarithromycin was achieved in 86% of sensitive strains and 78% of resistant strains (p=0.42). CONCLUSION: Treatment type and antibiotic susceptibility are the most important determinants of treatment success.
Adolescent↗