Role of the CLOCK protein in the mammalian circadian mechanism

The mouse Clock gene encodes a bHLH-PAS protein that regulates circadian rhythms and is related to transcription factors that act as heterodimers. Potential partners of CLOCK were isolated in a two-hybrid screen, and one, BMAL1, was coexpressed with CLOCK and PER1 at known circadian clock sites in brain and retina. CLOCK-BMAL1 heterodimers activated transcription from E-box elements, a type of transcription factor-binding site, found adjacent to the mouse per1 gene and from an identical E-box known to be important for per gene expression in Drosophila. Mutant CLOCK from the dominant-negative Clock allele and BMAL1 formed heterodimers that bound DNA but failed to activate transcription. Thus, CLOCK-BMAL1 heterodimers appear to drive the positive component of per transcriptional oscillations, which are thought to underlie circadian rhythmicity.

Mutagenesis and mapping of a mouse gene, Clock, essential for circadian behavior

In a search for genes that regulate circadian rhythms in mammals, the progeny of mice treated with N-ethyl-N-nitrosourea (ENU) were screened for circadian clock mutations. A semidominant mutation, Clock, that lengthens circadian period and abolishes persistence of rhythmicity was identified. Clock segregated as a single gene that mapped to the midportion of mouse chromosome 5, a region syntenic to human chromosome 4. The power of ENU mutagenesis combined with the ability to clone murine genes by map position provides a generally applicable approach to study complex behavior in mammals.

Positional cloning of the mouse circadian clock gene

We used positional cloning to identify the circadian Clock gene in mice. Clock is a large transcription unit with 24 exons spanning approximately 100,000 bp of DNA from which transcript classes of 7.5 and approximately 10 kb arise. Clock encodes a novel member of the bHLH-PAS family of transcription factors. In the Clock mutant allele, an A-->T nucleotide transversion in a splice donor site causes exon skipping and deletion of 51 amino acids in the CLOCK protein. Clock is a unique gene with known circadian function and with features predicting DNA binding, protein dimerization, and activation domains. CLOCK represents the second example of a PAS domain-containing clock protein (besides Drosophila PERIOD), which suggests that this motif may define an evolutionarily conserved feature of the circadian clock mechanism.

Functional identification of the mouse circadian Clock gene by transgenic BAC rescue

As a complementary approach to positional cloning, we used in vivo complementation with bacterial artificial chromosome (BAC) clones expressed in transgenic mice to identify the circadian Clock gene. A 140 kb BAC transgene completely rescued both the long period and the loss-of-rhythm phenotypes in Clock mutant mice. Analysis with overlapping BAC transgenes demonstrates that a large transcription unit spanning approximately 100,000 base pairs is the Clock gene and encodes a novel basic-helix-loop-helix-PAS domain protein. Overexpression of the Clock transgene can shorten period length beyond the wild-type range, which provides additional evidence that Clock is an integral component of the circadian pacemaking system. Taken together, these results provide a proof of principle that "cloning by rescue" is an efficient and definitive method in mice.

Development of a disease specific questionnaire to measure health related quality of life in patients with chronic liver disease

BACKGROUND AND AIMS

To develop and assess a disease specific instrument for measuring health related quality of life (HRQL) in patients with chronic liver disease (CLD).

METHODS

Based on responses from 60 patients with chronic liver disease, from 20 liver experts, and from a Medline search of the literature, items potentially affecting the HRQL of these patients were identified. A separate sample of 75 patients identified which items they found problematic and rated their importance. Results were explored using factor analysis; domains were chosen and items placed within domains. Redundant questions were eliminated and the final questionnaire was pretested in 10 patients. Using this instrument, HRQL was assessed in a further 133 patients with various types and stages of liver disease.

RESULTS

Patients, experts, and the literature search identified 156 items of potential importance. Of these, 35 proved important to over 50% of 75 respondents in the item reduction sample. The factor analysis suggested six domains. After eliminating redundancies, the Chronic Liver Disease Questionnaire (CLDQ) included 29 items in the following domains: fatigue, activity, emotional function, abdominal symptoms, systemic symptoms, and worry. In pretesting, patients found the CLDQ clear and easy to complete in 10 minutes. In another 133 patients, the CLDQ showed a gradient between patients without cirrhosis, Child's A cirrhosis, and those with Child's B or C cirrhosis. CLDQ has evidence for moderate reliability at six months and seems to be responsive.

CONCLUSION

The CLDQ is short, easy to administer, produces both a summary score and domain scores, and correlates with the severity of liver disease.

Meta-analysis of respiratory rehabilitation in chronic obstructive pulmonary disease

BACKGROUND

Respiratory rehabilitation is increasingly recognised as an important part of the management of patients with chronic obstructive pulmonary disease (COPD). The widespread application of such programmes should be preceded by evidence of directly attributable improvements in function. We assessed the effect of respiratory rehabilitation on exercise capacity and health-related quality of life (HRQL) in patients with COPD.

METHODS

We carried out a meta-analysis of randomised controlled trials of respiratory rehabilitation in patients with COPD that assessed functional or maximal exercise capacity, HRQL, or both. Respiratory rehabilitation was defined as exercise training (for at least 4 weeks) with or without education, psychological support, or both. The most commonly used measure for HRQL was the chronic respiratory questionnaire, in which responses were presented on a 7-point scale. The control groups received no rehabilitation. Within each trial and for each outcome an effect size was calculated; the effect sizes were then pooled by a random-effects model. The overall effect of treatment was compared with its minimum clinically important difference (MCID)--defined as the smallest difference perceived as important by the average patient.

FINDINGS

We included 14 trials. Significant improvements were found for all the outcomes. For two important features of HRQL, dyspnoea and mastery, the overall treatment effect was larger than the MCID: 1.0 (95% CI 0.6-1.5) and 0.8 (0.5-1.2), respectively, compared with an MCID of 0.5. For functional exercise capacity (6-min walk test), the overall effect was 55.7 m (27.8-92.8), and for maximum exercise capacity (incremental cycle ergometer test), 8.3 W (2.8-16.5). Functional exercise capacity showed heterogeneity that could not be explained by the sensitivity analyses.

INTERPRETATION

Respiratory rehabilitation relieves dyspnoea and improves the control over COPD. These improvements are clinically important. The value of the improvement in exercise capacity is not clear. Respiratory rehabilitation is an effective part of care in patients with COPD.

A CLOCK polymorphism associated with human diurnal preference

A single nucleotide polymorphism located in the 3' flanking region of the human CLOCK gene was investigated as a predictor of diurnal preference in a population-based random sample of 410 normal adults. Morningness-eveningness preferences were determined using the 19-item Home-Ostberg questionnaire. Subjects carrying one of the two CLOCK alleles, 3111C, had a significantly lower mean Horne-Ostberg score. The distribution of scores was clearly shifted toward eveningness for these subjects. The score difference was independent of age, sex and ethnic heritage, thus making population stratification effects unlikely to explain this difference. These subjects had a substantial 10- to 44-minute delay in preferred timing for activity or sleep episodes. We suggest that the identified polymorphism or another tightly linked polymorphism within the CLOCK gene or its regulatory elements may be responsible for the finding.

Molecular genetics of circadian rhythms in mammals

Recent gene discovery approaches have led to a new era in our understanding of the molecular basis of circadian oscillators in animals. A conserved set of genes in Drosophila and mammals (Clock, Bmal1, Period, and Timeless) provide a molecular framework for the circadian mechanism. These genes define a transcription-translation-based negative autoregulatory feedback loop that comprises the core elements generating circadian rhythmicity. This circadian core provides a focal point for understanding how circadian rhythms arise, how environmental inputs entrain the oscillatory system, and how the circadian system regulates its outputs. The addition of molecular genetic approaches to the existing physiological understanding of the mammalian circadian system provides new opportunities for understanding this basic life process.

Corticosteroid treatment for sepsis: a critical appraisal and meta-analysis of the literature

OBJECTIVE

To determine the effect of corticosteroid therapy on morbidity and mortality in patients with sepsis.

DATA SOURCES

We searched for published and unpublished research using MEDLINE, EMBASE, and the Science Citation Index, manual searching of Index Medicus, citation review of relevant primary and review articles, personal files, and contact with primary investigators.

STUDY SELECTION

From a pool of 124 potentially relevant articles, duplicate independent review identified nine relevant, randomized, controlled trials of corticosteroid therapy in sepsis and septic shock among critically ill adults.

DATA EXTRACTION

In duplicate, independently, we abstracted key data on population, intervention, outcome, and methodologic quality of the randomized controlled trials.

DATA SYNTHESIS

Corticosteroids appear to increase mortality in patients with overwhelming infection (relative risk 1.13, 95% confidence interval 0.99 to 1.29), and have no beneficial effect in the subgroup of patients with septic shock (relative risk 1.07, 95% confidence interval 0.91 to 1.26). Studies with the highest methodologic quality scores also suggest a trend toward increased mortality overall (relative risk 1.10, 95% confidence interval 0.94 to 1.29). A similar trend was observed for patients with septic shock (relative risk 1.12, 95% confidence interval 0.95 to 1.32). No difference in secondary infection rates was demonstrated in corticosteroid-treated patients with sepsis or septic shock. However, there was a trend toward increased mortality from secondary infections in patients receiving corticosteroids (relative risk 1.70, 95% confidence interval 0.70 to 4.12). The occurrence rate of gastrointestinal bleeding was increased slightly in the treatment group (relative risk 1.17, 95% confidence interval 0.79 to 1.73).

CONCLUSIONS

Current evidence provides no support for the use of corticosteroids in patients with sepsis or septic shock, and suggests that their use may be harmful. These trials underscore the need for future methodologically rigorous trials evaluating new immune-modulating therapies in well-defined critically ill patients with overwhelming infection.

Maximizing oxygen delivery in critically ill patients: a methodologic appraisal of the evidence

OBJECTIVE

To systemically review the effect of interventions designed to achieve supraphysiologic values of cardiac index, oxygen delivery (DO2), and oxygen consumption (VO2) in critically ill patients.

DATA SOURCES

Computerized bibliographic search of published research, citation review of relevant articles, and contact with primary investigators.

STUDY SELECTION

We included all randomized clinical trials of adult intensive care unit (ICU) patients that evaluated interventions (fluids, inotropes, and vasoactive drugs) designed to achieve supraphysiologic values of cardiac index, DO2, and/or VO2. Independent review of 64 articles identified seven relevant studies of 1,016 patients.

DATA EXTRACTION

We abstracted data on the population, interventions, outcomes, and methodologic quality of the studies by duplicate independent review. Agreement was high (weighed kappa 0.73); differences were resolved by consensus.

DATA SYNTHESIS

Targeting therapy to achieve supraphysiologic end points in critically ill patients is associated with a nonstatistically significant trend toward decreased mortality rates (relative risk 0.86, 95% confidence intervals 0.62 to 1.20). For the two studies in which supraphysiologic goals were initiated preoperatively, the relative risk was 0.20 (95% confidence intervals 0.07 to 0.55). This value differed significantly from the combined estimate of the remaining studies, in which the intervention was started after ICU admission (relative risk 0.98, 95% confidence intervals 0.79 to 1.22; p<.01). However, there are several methodologic problems with the primary studies. In no trials were caregivers or outcome assessors blinded to treatment allocation. Only three of seven trials analyzed patients according to the group to which they were allocated. None adequately controlled for cointerventions, and there was considerable crossover between groups (patients in the control group achieved the goals of the intervention group and vice versa).

CONCLUSIONS

Interventions designed to achieve supraphysiologic goals of cardiac index, DO2, and VO2 did not significantly reduce mortality rates in all critically ill patients. However, there may be a benefit in those patients in which the therapy is initiated preoperatively. Methodologic limitations weaken the inferences that can be drawn from these studies and preclude any evidence-based clinical recommendations.

Mammalian circadian autoregulatory loop: a timeless ortholog and mPer1 interact and negatively regulate CLOCK-BMAL1-induced transcription

We report the cloning and mapping of mouse (mTim) and human (hTIM) orthologs of the Drosophila timeless (dtim) gene. The mammalian Tim genes are widely expressed in a variety of tissues; however, unlike Drosophila, mTim mRNA levels do not oscillate in the suprachiasmatic nucleus (SCN) or retina. Importantly, hTIM interacts with the Drosophila PERIOD (dPER) protein as well as the mouse PER1 and PER2 proteins in vitro. In Drosophila (S2) cells, hTIM and dPER interact and translocate into the nucleus. Finally, hTIM and mPER1 specifically inhibit CLOCK-BMAL1-induced transactivation of the mPer1 promoter. Taken together, these results demonstrate that mTim and hTIM are mammalian orthologs of timeless and provide a framework for a basic circadian autoregulatory loop in mammals.

Dexamethasone suppression tests in antidepressant treatment of melancholia. The process of normalization and test-retest reproducibility

Pilot studies suggest that changes in response to the dexamethasone suppression test (DST) in melancholic patients receiving antidepressants might represent a laboratory marker of clinical progress. We performed weekly DSTs in 31 hospitalized patients with major depressive disorder, primary and endogenous subtypes, during drug-free and subsequent treatment periods. Most nonsuppressors had progressive normalization of DST responses in conjunction with clinical improvement, DST normalization usually preceded or coincided with good clinical response, and failure to normalize was often associated with poorer clinical outcome. Occasional patients with baseline dexamethasone suppression become nonsuppressive after withdrawal from medication, but the DST has no apparent value as a serial marker in patients with well-documented normal DST findings. Our results extend the construct validity of the DST as a state-related marker in nonsuppressors and suggest future clinical applications.

Simple sequence repeats as a source of quantitative genetic variation

Most traits in biological populations appear to be under stabilizing selection, which acts to eliminate quantitative genetic variation. Yet, virtually all measured traits in biological populations continue to show significant quantitative genetic variation. The paradox can be resolved by postulating the existence of an abundant, though unspecified, source of mutations that has quantitative effects on phenotype, but does not reduce fitness. Does such a source actually exist? We propose that it does, in the form of repeat-number variation in SSRs (simple sequence repeats, of which the triplet repeats of human neurodegenerative diseases are a special case). Viewing SSRs as a major source of quantitative mutation has broad implications for understanding molecular processes of evolutionary adaptation, including the evolutionary control of the mutation process itself.

The diabetes network internet-based physical activity intervention: a randomized pilot study

OBJECTIVE

Because of other competing priorities, physical activity (PA) is seldom addressed in a consistent way in either primary care or diabetes education. This 8-week pilot study evaluated the short-term benefits of an Internet-based supplement to usual care that focused on providing support for sedentary patients with type 2 diabetes to increase their PA levels.

RESEARCH DESIGN AND METHODS

A total of 78 type 2 diabetic patients (53% female, average age 52.3 years) were randomized to the Diabetes Network (D-Net) Active Lives PA Intervention or an Internet information-only condition. The intervention condition received goal-setting and personalized feedback, identified and developed strategies to overcome barriers, received and could post messages to an on-line "personal coach," and were invited to participate in peer group support areas. Key outcomes included minutes of PA per week and depressive symptomatology.

RESULTS

There was an overall moderate improvement in PA levels within both intervention and control conditions, but there was no significant improvement in regard to condition effects. There was substantial variability in both site use and outcomes within the intervention and control conditions. Internal analyses revealed that among intervention participants, those who used the site more regularly derived significantly greater benefits, whereas those in the control condition derived no similar benefits with increased program use.

CONCLUSIONS

Internet-based self-management interventions for PA and other regimen areas have great potential to enhance the care of diabetes and other chronic conditions. We conclude that greater attention should be focused on methods to sustain involvement with Internet-based intervention health promotion programs over time.

Bipolar outcome in the course of depressive illness. Phenomenologic, familial, and pharmacologic predictors

Twenty percent of a cohort of 206 outpatient depressives with no past bipolar history switched during prospective observation. These 41 probands developed manic periods on the average of 6.4 years (median 4, range 1-25) after their first depressive episode. The change in polarity occurred throughout the life span, but was most common in adolescence and early adulthood. The following variables were found useful in predicting this outcome: onset less than or equal to 25 years, bipolar family history, loaded pedigrees, precipitation by childbirth, hypersomnic-retarded phenomenology, and pharmacologically-mobilized hypomania. Although the respective sensitivities of these findings were relatively low (32-71%), their specificities ranged from 69% to 100% for bipolar outcome; the diagnostic specificity of any 3 of these variables when combined was 98%. When compared with nonbipolar depression, bipolar disorder was seldom chronologically secondary to nonaffective psychiatric disorders. These findings suggest that many young depressives with lethargy and oversleeping are not manifesting a "neurotic" disorder, but rather a precursor of primary bipolar affective disorder. Finally, a psychotically depressed adolescent or young adult with positive bipolar family history should be observed for eventual bipolar outcome, especially when the clinical presentation is that of stupor.

Relationship between acute morphine and the course of PTSD in children with burns

OBJECTIVE

To investigate the relationship between the dose of morphine administered during a child's hospitalization for an acute burn and the course of posttraumatic stress disorder (PTSD) symptoms over the 6-month period following discharge from the hospital.

METHOD

Twenty-four children admitted to the hospital for an acute burn were assessed twice with the Child PTSD Reaction Index: while in the hospital and 6 months after discharge. The Colored Analogue Pain Scale was also administered during the hospitalization. All patients received morphine while in the hospital. The mean dose of morphine (mg/kg/day) was calculated for each subject through chart review.

RESULTS

The Pearson product moment correlation revealed a significant association between the dose of morphine received while in the hospital and a 6-month reduction in PTSD symptoms. Children receiving higher doses of morphine had a greater reduction in PTSD symptoms over 6 months.

CONCLUSIONS

This study suggests the possibility that acute treatment with morphine can secondarily prevent PTSD. This result is discussed in terms of the possible effect of morphine on fear conditioning and the consolidation of traumatic memory.

High-level expression of a recombinant antibody from myeloma cells using a glutamine synthetase gene as an amplifiable selectable marker

We report a method for introducing a glutamine synthetase (GS) selectable marker into myeloma cells in which transfectants are selected by growth in a glutamine-free medium. Vector amplification can subsequently be selected using the specific inhibitor of GS, methionine sulphoximine (MSX). Using this system, DNA sequences encoding a chimeric B72.3 IgG4 antibody were expressed from hCMV-MIE promoters in NSO myeloma cells. A cell line was isolated after a single round of selection for vector amplification which contains approximately 4 copies of the vector, secretes 10-15 pg/cell/day cB72.3 antibody during exponential growth and can accumulate 560 mg/l antibody in a fed-batch air-lift fermentation system. Productivity is stable in the absence of MSX selection.

Energy expenditure during front crawl swimming: predicting success in middle-distance events

Male (n = 25) and female (n = 14) competitive swimmers were studied during tethered (breaststroke) and free (front crawl) swimming to determine the validity of calculating exercise oxygen uptake (VO2) from expired gas samples taken immediately after the activity. Based on a single 20-s recovery VO2, the swimmers' VO2 max was correlated with performance in a 400-yd (365.8-m) front crawl swim. The best predictors of VO2 max for trained swimmers were lean body weight and stroke index (r = 0.97). The single best predictor of performance in the 365.8-m front crawl swim was the distance per stroke (r = 0.88), whereas the combination of distance per stroke and VO2 max (ml/kg LBW/min) correlated 0.97 with performance in the swim. This study demonstrates that it is possible to accurately determine the VO2 during maximal and submaximal swimming using a single, 20-s expired gas collection taken immediately after a 4-7 min swim. These findings demonstrate the importance of stroke technique on the energy cost and variations in performance during competitive swimming.

Central venous catheter replacement strategies: a systematic review of the literature

OBJECTIVE

To evaluate the effect of guidewire exchange and new-site replacement strategies on the frequency of catheter colonization and infection, catheter-related bacteremia, and mechanical complications in critically ill patients.

DATA SOURCES

We searched for published and unpublished research by means of MEDLINE and Science Citation Index, manual searching of Index Medicus, citation review of relevant primary and review articles, review of personal files, and contact with primary investigators.

STUDY SELECTION

From a pool of 151 randomized, controlled trials on central venous catheter management, we identified 12 relevant randomized trials of catheter replacement over a guidewire or at a new site.

DATA EXTRACTION

In duplicate and independently, we abstracted data on the population, intervention, outcome, and methodologic quality.

DATA SYNTHESIS

As compared with new-site replacement, guidewire exchange is associated with a trend toward a higher rate of catheter colonization (relative risk 1.26, 95% confidence interval 0.87 to 1.84), regardless of whether patients had a suspected infection. Guidewire exchange is also associated with trends toward a higher rate of catheter exit-site infection (relative risk 1.52, 95% confidence interval 0.34 to 6.73) and catheter-related bacteremia (relative risk 1.72, 95% confidence interval 0.89 to 3.33). However, guidewire exchange is associated with fewer mechanical complications (relative risk 0.48, 95% confidence interval 0.12 to 1.91) relative to new-site replacement. Exchanging catheters over guidewires or at new sites every 3 days is not beneficial in reducing infections, compared with catheter replacement on an as-needed basis.

CONCLUSIONS

Guidewire exchange of central venous catheters may be associated with a greater risk of catheter-related infection but fewer mechanical complications than new-site replacement. More studies on scheduled vs. as-needed replacement strategies using both techniques are warranted. If guidewire exchange is used, meticulous aseptic technique is necessary.

Decline in ICU adverse events, nosocomial infections and cost through a quality improvement initiative focusing on teamwork and culture change

BACKGROUND

Nosocomial infections occur in approximately 10% of patients in intensive care units (ICUs). Several studies have shown that a quality improvement initiative can reduce nosocomial infections, mortality, and cost.

CONTEXT

Our hospital is located in Northern Mississippi and has a 28 bed Medical-Surgical ICU unit with 95% occupancy. We joined the ICU collaborative with the IMPACT initiative of the Institute of Healthcare Improvement (IHI) in October 2002. A preliminary prospective before (fiscal year (FY) 2001-2) and after (FY 2003) hypothesis generating study was conducted of outcomes resulting from small tests of change in the management of ICU patients.

KEY MEASURES FOR IMPROVEMENT

Nosocomial infection rates, adverse events per ICU day, average length of stay, and average cost per ICU episode.

STRATEGY FOR CHANGE

Four changes were implemented: (1) physician led multidisciplinary rounds; (2) daily "flow" meeting to assess bed availability; (3) "bundles" (sets of evidence based best practices); and (4) culture changes with a focus on the team decision making process.

EFFECTS OF CHANGE

Between baseline and re-measurement periods, nosocomial infection rates declined for ventilator associated pneumonia (from 7.5 to 3.2 per 1000 ventilator days, p = 0.04) and bloodstream infections (from 5.9 to 3.1 per 1000 line days, p = 0.03), with a downward trend in the rate of urinary tract infections (from 3.8 to 2.4 per 1000 catheter days, p = 0.17). There was a strong downward trend in the rates of adverse events in the ICU as well as the average length of stay per episode. From FY 2002 to FY 2003 the cost per ICU episode fell from $3406 to $2973.

LESSONS LEARNED

A systematic approach through collaboration with IHI's IMPACT initiative may have contributed to significant improvements in care in the ICU setting. Multidisciplinary teams appeared to improve communication, and bundles provided consistency of evidence based practices. The flow meetings allowed for rapid prioritization of activity and a new decision making culture empowered team members. The impact of these changes needs to be assessed more widely using rigorous study designs.

Genome-wide epistatic interaction analysis reveals complex genetic determinants of circadian behavior in mice

Genetic heterogeneity underlies many phenotypic variations observed in circadian rhythmicity. Continuous distributions in measures of circadian behavior observed among multiple inbred strains of mice suggest that the inherent contributions to variability are polygenic in nature. To identify genetic loci that underlie this complex behavior, we have carried out a genome-wide complex trait analysis in 196 (C57BL/6J X BALB/cJ)F(2) hybrid mice. We have characterized variation in this panel of F(2) mice among five circadian phenotypes: free-running circadian period, phase angle of entrainment, amplitude of the circadian rhythm, circadian activity level, and dissociation of rhythmicity. Our genetic analyses of these phenotypes have led to the identification of 14 loci having significant effects on this behavior, including significant main effect loci that contribute to three of these phenotypic measures: period, phase, and amplitude. We describe an additional locus detection method, genome-wide genetic interaction analysis, developed to identify locus pairs that may interact epistatically to significantly affect phenotype. Using this analysis, we identified two additional pairs of loci that have significant effects on dissociation and activity level; we also detected interaction effects in loci contributing to differences of period, phase, and amplitude. Although single gene mutations can affect circadian rhythms, the analysis of interstrain variants demonstrates that significant genetic complexity underlies this behavior. Importantly, most of the loci that we have detected by these methods map to locations that differ from the nine known clock genes, indicating the presence of additional clock-relevant genes in the mammalian circadian system. These data demonstrate the analytical value of both genome-wide complex trait and epistatic interaction analyses in further understanding complex phenotypes, and point to promising approaches for genetic analysis of such phenotypes in other mammals, including humans.

Impaired gastric emptying in mechanically ventilated, critically ill patients

OBJECTIVE

To measure gastric emptying in critically ill patients using an acetaminophen absorption model and determine which variables are associated with impaired gastric emptying.

DESIGN

A prospective, cohort study.

SETTING

A medical/surgical ICU at a tertiary care hospital: Hamilton General Hospital, Hamilton, Ontario.

PATIENTS AND PARTICIPANTS

We recruited 72 mechanically ventilated patients expected to remain in the ICU for more than 48 h. Our results were compared to those in healthy volunteers.

INTERVENTION

Within 48 h of admission to the ICU, 1.6 g acetaminophen suspension were administered via a nasogastric tube into the stomach. Blood samples were drawn a t = 0, 30, 60, 90, and 120 min for measurement of plasma acetaminophen levels determined by the enzymatic degradation method.

MEASUREMENTS AND RESULTS

Maximal concentration of acetaminophen was 94.1 (75.3) mumol/l compared to 208.4 (33.1) mumol/l in a control population (p < 0.0001). The time to reach the maximal concentration was 105 min (60-180) compared to 30 min (15-90) in controls (p < 0.0001). The area under the time-acetaminophen concentration curve t = 120 was 9301 (7343) mumol/min per l compared to 11644 (1336) mumol/min per l in the controls (p = 0.28). The variables associated with delayed gastric emptying were age, sex and use of opioids for analgesia and sedation.

CONCLUSIONS

Gastric emptying is delayed in critically ill patients. The important consequences of this phenomenon include intolerance to enteral nutrition and gastric colonization. Strategies to minimize the use of narcotics may improve gastric emptying. Studies to examine the effect of gastrointestinal prokinetic agents on gastric emptying are needed.

Novel reverse transcription loop-mediated isothermal amplification for rapid detection of foot-and-mouth disease virus

Speed is paramount in the diagnosis of foot-and-mouth disease (FMD) and simplicity is required if a test is to be deployed in the field. The development of a one-step, reverse transcription loop-mediated amplification (RT-LAMP) assay enables FMD virus (FMDV) to be detected in under an hour in a single tube without thermal cycling. A fragment of the 3D RNA polymerase gene of the virus is amplified at 65 degrees C in the presence of a primer mixture and both reverse transcriptase and Bst DNA polymerase. Compared with real-time RT-PCR, RT-LAMP was consistently faster, and ten copies of FMDV transcript were detected in twenty-two minutes. Amplification products were detected by visual inspection, agarose gel electrophoresis, or in real-time by the addition of a fluorescent dye. The specificity of the reaction was demonstrated by the absence of amplification of RNA from other viruses that cause vesicular diseases and from that of genetically related picornaviruses. Diagnostic sensitivity was validated by the amplification of reference FMDV strains and archival material from field cases of FMD. In comparison with the performance of the established diagnostic TaqMan assay, RT-LAMP appears to be sensitive, rapid, specific, and cost-effective, with the potential for field deployment and use by developing countries for FMDV surveillance.