Functional diversification of the nematode mbd2/3 gene between Pristionchus pacificus and Caenorhabditis elegans

Abstract Background Several members of the Methyl-Binding Domain protein family link DNA methylation with chromatin remodeling complexes in vertebrates. Amongst the four classes of MBD proteins, MBD2/3 is the most highly conserved and widespread in metazoans. We have previously reported that an mbd2/3 like gene (mbd-2) is encoded in the genomes of the nematodes Pristionchus pacificus, Caenorhabditis elegans and Caenorhabditis briggsae. RNAi knock-down of mbd-2 in the two Caenorhabditis species results in varying percentages of lethality. Results Here, we report that a general feature of nematode MBD2/3 proteins seems to be the lack of a bona fide methyl-binding domain. We isolated a null allele of mbd-2 in P. pacificus and show that Ppa-mbd-2 mutants are viable, fertile and display a fully penetrant egg laying defect. This egg laying defect is partially rescued by treatment with acetylcholine or nicotine suggesting a specific function of this protein in vulval neurons. Using Yeast-two-hybrid screens, Ppa-MBD-2 was found to associate with microtubule interacting and vesicle transfer proteins. Conclusion These results imply that MBD2/3 proteins in nematodes are more variable than their relatives in insects and vertebrates both in structure and function. Moreover, nematode MBD2/3 proteins assume functions independent of DNA methylation ranging from the indispensable to the non-essential.</p

Does bronchial thermodilution allow estimation of cardiac output?

Objective: Transcapillary heat transfer after injections of cold saline into the right atrium generates bronchial thermodilution curves resembling those observed in the aorta. Under the assumption that no indicator is lost or gained within the pulmonary capillary bed and changes in blood temperature are instantaneously recorded in the bronchial system, we tested the hypothesis that flow rates calculated from bronchial temperature-time curves are similar to those from aortic curves. Design: Comparative study of two cardiac output estimates in five dogs. Setting: Research laboratory for Experimental Anaesthesiology. Interventions: Cardiac output was decreased (repeated withdrawal of blood) and increased (infusion of colloids or dobutamine) in order to study a wide range of cardiac outputs. Measurements and results: Thermistors were placed in a bronchiole (wedge position) and in the ascending aorta of anaesthetized dogs. Bronchial and aortic thermodilution curves were recorded after injection of 5 mi ice-cord saline into the right atrium. We found that bronchial thermodilution yields flow estimates similar to those from aortic curves. Correlation between the two now estimates was acceptable (r = 0.84) with a mean difference between the two of less than 2 %. Conclusion: We conclude that the Stewart-Hamilton equation may be extended to bronchial temperature-time curves for estimations of cardiac output. At this time, however, we do not advocate bronchial thermistors as suitable and less invasive alternatives to pulmonary arterial catheters for routine cardiac output measurements in patients

Carbon monoxide: toxic molecule with antiinflammatory and cytoprotective properties

Carbon monoxide arises during incomplete combustion of organic material, is incorporated into the circulation via the lungs and displaces oxygen from hemoglobin. Consecutively, symptoms of intoxication such as headache, vertigo, nausea, seizures and coma may result in a dose dependent fashion. Carbon monoxide is however also generated endogenously during heme degradation catalysed by heme oxgenase enzymes. The isoform hemeoxygenase-1 is inducible by oxidative stress and may mediate cytoprotection mainly attributable to endogenously produced carbon monoxide. Exogenous applied carbon monoxide has also been shown to confer protection in experimental studies. Meanwhile, in addition to the toxicological properties, antiinflammatory and cytoprotective effects of carbon monoxide have moved into the focus of scientific interest

Breathing variability during propofol/remifentanil procedural sedation with a single additional dose of midazolam or s-ketamine: a prospective observational study

Purpose Regulation of spontaneous breathing is highly complex and may be influenced by drugs administered during the perioperative period. Because of their different pharmacological properties we hypothesized that midazolam and s-ketamine exert different effects on the variability of minute ventilation (MV), tidal volume (TV) and respiratory rate (RR). Methods Patients undergoing procedural sedation (PSA) with propofol and remifentanil received a single dose of midazolam (1–3 mg, n = 10) or s-ketamine (10–25 mg, n = 10). We used non-invasive impedance-based respiratory volume monitoring to record RR as well as changes in TV and MV. Variability of these three parameters was calculated as coefficients of variation. Results TV and MV decreased during PSA to a comparable extent in both groups, whereas there was no significant change in RR. In line with our hypothesis we observed marked differences in breathing variability. The variability of MV (– 47.5% ± 24.8%, p = 0.011), TV (– 42.1% ± 30.2%, p = 0.003), and RR (– 28.5% ± 29.3%, p = 0.011) was significantly reduced in patients receiving midazolam. In contrast, variability remained unchanged in patients receiving s-ketamine (MV + 16% ± 45.2%, p = 0.182; TV +12% ± 47.7%, p = 0.390; RR +39% ± 65.2%, p = 0.129). After termination of PSA breathing variables returned to baseline values. Conclusions While midazolam reduces respiratory variability in spontaneously breathing patients undergoing procedural sedation, s-ketamine preserves variability suggesting different effects on the regulation of spontaneous breathing

Variations in respiratory rate do not reflect changes in tidal volume or minute ventilation after major abdominal surgery

Monitoring of postoperative pulmonary function usually includes respiratory rate and oxygen saturation measurements. We hypothesized that changes in postoperative respiratory rate do not correlate with changes in tidal volume or minute ventilation. In addition, we hypothesized that variability of minute ventilation and tidal volume is larger than variability of respiratory rate. Respiratory rate and changes in tidal volume and in minute ventilation were continuously measured in 27 patients during 24 h following elective abdominal surgery, using an impedance-based non-invasive respiratory volume monitor (ExSpiron, Respiratory Motion, Waltham, MA, US). Coefficients of variation were used as a measure for variability of respiratory rate, tidal volume and minute ventilation. Data of 38,149 measurements were analyzed. We found no correlation between respiratory rate and tidal volume or minute ventilation (r2 = 0.02 and 0.01). Mean respiratory rate increased within the first 24 h after abdominal surgery from 13.9 ± 2.5 to 16.2 ± 2.4 breaths/min (p = 0.008), while tidal volume and minute ventilation remained unchanged (p = 0.90 and p = 0.18). Of interest, variability of respiratory rate (0.21 ± 0.06) was significantly smaller than variability of tidal volume (0.37 ± 0.12, p < 0.001) and minute ventilation (0.41 ± 0.12, p < 0.001). Changes in postoperative respiratory rate do not allow conclusions about changes in tidal volume or minute ventilation. We suggest that postoperative alveolar hypoventilation may not be recognized by monitoring respiratory rate alone. Variability of respiratory rate is smaller than variability in tidal volume and minute ventilation, suggesting that adaptations of alveolar ventilation to metabolic needs may be predominately achieved by variations in tidal volume

Between-trial heterogeneity in ARDS research

Purpose Most randomized controlled trials (RCTs) in patients with acute respiratory distress syndrome (ARDS) revealed indeterminate or conflicting study results. We aimed to systematically evaluate between-trial heterogeneity in reporting standards and trial outcome. Methods A systematic review of RCTs published between 2000 and 2019 was performed including adult ARDS patients receiving lung-protective ventilation. A random-effects meta-regression model was applied to quantify heterogeneity (non-random variability) and to evaluate trial and patient characteristics as sources of heterogeneity. Results In total, 67 RCTs were included. The 28-day control-group mortality rate ranged from 10 to 67% with large non-random heterogeneity (I2 = 88%, p < 0.0001). Reported baseline patient characteristics explained some of the outcome heterogeneity, but only six trials (9%) reported all four independently predictive variables (mean age, mean lung injury score, mean plateau pressure and mean arterial pH). The 28-day control group mortality adjusted for patient characteristics (i.e. the residual heterogeneity) ranged from 18 to 45%. Trials with significant benefit in the primary outcome reported a higher control group mortality than trials with an indeterminate outcome or harm (mean 28-day control group mortality: 44% vs. 28%; p = 0.001). Conclusion Among ARDS RCTs in the lung-protective ventilation era, there was large variability in the description of baseline characteristics and significant unexplainable heterogeneity in 28-day control group mortality. These findings signify problems with the generalizability of ARDS research and underline the urgent need for standardized reporting of trial and baseline characteristics

Cell salvage in burn excisional surgery

Background: Hemostasis during burn surgery is difficult to achieve, and high blood loss commonly occurs. Bleeding control measures are limited, and many patients require allogeneic blood transfusions. Cell salvage is a well-known method used to reduce transfusions. However, its evidence in burns is limited. Therefore, this study aimed to examine the feasibility of cell salvage during burn surgery. Study design and methods: A prospective, observational study was conducted with 16 patients (20 measurements) scheduled for major burn surgery. Blood was recovered by washing saturated gauze pads with heparinized saline, which was then processed using the Cell Saver. Erythrocyte concentrate quality was analyzed by measuring hemoglobin, hematocrit, potassium, and free hemoglobin concentration. Microbial contamination was assessed based on cultures at every step of the process. Differences in blood samples were tested using the Student's t-test. Results: The red blood cell mass recovered was 29 ± 11% of the mass lost. Patients’ preoperative hemoglobin and hematocrit levels were 10.5 ± 1.8 g/dL and 0.33 ± 0.05 L/L, respectively. The erythrocyte concentrate showed hemoglobin and hematocrit levels of 13.2 ± 3.9 g/dL and 0.40 ± 0.11 L/L thus showing a concentration effect. The potassium level was lower in the erythrocyte concentrate (2.5 ± 1.5 vs. 4.1 ± 0.4 mmol/L, p < 0.05). The free hemoglobin level was low (0.16 ± 0.21 μmol/L). All cultures of the erythrocyte concentrate showed bacterial growth compared to 21% of wound cultures. Conclusion: Recovering erythrocytes during burn excisional surgery using cell salvage is possible. Despite strict sterile handling, erythrocyte concentrates of all patients showed bacterial contamination. The consequence of this contamination remains unclear and should be investigated in future studies