Continuous peripheral nerve blocks for analgesia of ventilated critically ill patients with multiple trauma: a prospective randomized study

BACKGROUND

Sedation of ventilated critically ill trauma patients requires high doses of opioids and hypnotics. We aimed to compare the consumption of opioids and hypnotics, and patient outcomes using sedation with or without continuous regional analgesia (CRA).

METHODS

Multiple trauma-ventilated patients were included. The patients were randomized to receive an intravenous analgesia (control group) or an addition of CRA within 24h of admission. A traumatic brain injury (TBI) patients group was analyzed. The primary endpoint was the cumulative consumption of sufentanil at 2 days of admission. Secondary endpoints were cumulative and daily consumption of sufentanil and midazolam, duration of mechanical ventilation, intensive care unit (ICU) stay, and safety of CRA management.

RESULTS

Seventy six patients were analyzed: 40 (67.5% males) in the control group and 36 (72% males) in the CRA group, respectively. The median [IQR] Injury Severity Score was 30.5 [23.5-38.5] and 26.0 [22.0-41.0]. The consumption of sufentanil at 48h was 725 [465-960] μg/48h versus 670 [510-940] μg/48h (p = 0.16). Daily consumption did not differ between the groups except on day 1 when consumption of sufentanil was 360 [270-480] μg vs. 480 [352-535] μg (p = 0.03). Consumptions of midazolam did not differ between the groups. No difference was noted between the groups according to the secondary endpoints.

CONCLUSIONS

CRA does not decrease significantly sufentanil and midazolam consumption within the first 5 days after ICU admission in multiple trauma-ventilated patients. The use of peripheral nerve blocks in heavily sedated and ventilated trauma patients in the ICU seems safe.

Prevalence and prognostic value of left ventricular late gadolinium enhancement in patients with idiopathic outflow tract ventricular arrhythmias

Background

Patients with idiopathic outflow tract ventricular arrhythmias (OTVAs) and structurally normal heart by ECG and echocardiogram often undergo cardiac magnetic resonance (CMR) study to evaluate for presence of concealed myocardial abnormalities with late gadolinium enhancement (LGE). However, the clinical impact of incidental LGE finding in the left ventricle (LV) in patients with idiopathic OT-VAs is unclear. Accordingly, the aim of the present study was to investigate the prevalence, characteristics and prognostic significance of isolated LV LGE in a large population of patients with OTVA undergoing CMR.

Methods

A total of 364 consecutive patients (43±16 years, 53% male) with OTVA and negative routine diagnostic work-up were included. All patients underwent a CMR study with LGE imaging for detection of scar/replacement fibrosis. Presence of LGE was correlated with long term major adverse cardiovascular events including sudden cardiac death (SCD), resuscitated cardiac arrest and nonfatal documented sustained ventricular tachycardia.

Results

Isolated LGE in the LV was identified in 15 patients (4%), typically involving the inferolateral wall (11 cases, 73%) and having a median extension of 3 (2–5)% of the LV mass. All cases showed a midmyocardial/subepicardial distribution consistent with a possible prior myocarditis. Patients with incidental finding of LV-LGE were older (55±13 years vs. 42±16 years; p<0.01) and were more frequently males (80% vs. 51%; p=0.03). After a median follow-up of 69 (47–98) months, none of the patients in the LV-LGE group and 1 patient (0.3%) in the non-LGE group (p=1.0) experienced the composite end-point which consisted in an episode of sustained VT with hypotension and dizziness. The patient subsequently underwent effective radiofrequency ablation of the VT from the right ventricular outflow tract.

Conclusion

In this large CMR study, isolated LV scar was found in 4% of patients with idiopathic OT-VAs, was small in size with distribution consistent with prior myocarditis. The LGE abnormality did not portend a negative prognosis.

Funding Acknowledgement

Type of funding source: None

Prognostic value of non-ischemic ring-like left ventricular scar pattern in patients with apparently idiopathic ventricular arrhythmias: a CMR imaging study

Background

The presence of left ventricular (LV) late gadolinium enhancement (LGE) at cardiac magnetic resonance (CMR) has been correlated to life-threatening arrhythmic events in patients with apparently idiopathic ventricular arrhythmias (VAs). Aim of the present study was to investigate the prognostic significance of a specific LV-LGE phenotype characterized by a subepicardial/midmyocardial “ring-like” pattern of fibrosis.

Methods

Out of a total of 518 consecutive patients with apparently idiopathic VAs who underwent CMR study, 79 (15%) had evidence of LV-LGE. Of these, 23 (4%) patients had LV LGE with ring-like pattern, defined as subepicardial or midmyocardial LGE involving at least 3 contiguous segments in the same slice (group A), while 56 (11%) patients had LV LGE with no ring-like pattern (group B). The remaining 439 patients had no LGE (group C). The end-point of the study was a composite SCD, resuscitated cardiac arrest and nonfatal episodes of ventricular fibrillation or documented sustained ventricular tachycardia.

Results

Group A patients were more frequently males compared to groups B and C (96% vs. 79% vs. 52%; p<0.01) and had more frequently a family history of SCD and/or cardiomyopathy (30% vs. 11% vs. 5%; p<0.01). All patients in Group A showed VAs with a predominant RBBB morphology vs. 38 (68%) patients in Group B and 65 (15%) in Group C (p<0.01). During a follow-up of 63±39 months, the composite outcome occurred in 13 patients (57%) in Group A vs. 11 (20%) in Group B and 2 (1%) in Group C (p<0.01).

Conclusion

In patients with apparently idiopathic VAs, a nonischemic LV-LGE with a ring-like pattern at CMR is associated with a high rate of malignant arrhythmic events during follow-up.

Funding Acknowledgement

Type of funding source: None

P2853Contemporary reporting of acute complications from implantable cardioverter defibrillator surgery

Background

Defibrillator placement carries an inherent risk to the patient. Traditionally, major adverse events defined as cardiac arrest, tamponnade, pneumothorax, infection requiring re-operation, MI and CVA within 30 days are reported to occur between 3 and 4%. Minor complications such as heamatomae or lead dislodgement are reported between 8 and 13%. Novel lead technologies, protocolised programming and reduced use of Heparin bridging have been reported to reduce adverse outcomes. However, patients are still typically monitored in hospital for 24 hours to mitigate these risks. There is little evidence that discharge delay is effective yet incurs significant additional costs.

Purpose

We sought to evaluate the frequency and timing of adverse events relating to defibrillator surgery (ICD and CRT-D) at a large Canadian tertiary care center (UOHI).

Methods

We retrospectively reviewed all patients who received a defibrillator placed from 1st April 2013 to 31st March 2018 inclusive. Patient comorbidities were extracted from the hospital electronic medical record (EMR) system. Device related information and complications were extracted from UOHI PaceartTM system and EMR and cross referenced with physician remuneration databases.

Results

A total of 2221 procedures were performed on 2153 patients (78% male, mean age 65 years). The majority (60%) of defibrillator implants were de novo, with 884 (40%) pulse generator replacements/ upgrades and 868 (39%) defibrillators had CRT capability. Patients were routinely discharged within 24 hours of ICD surgery. Post-operative follow up ≥30 days was complete in 97% patients. Major adverse events occurred within 30 days in 9 patients (0.4%); 9 (100%) were infection requiring re-operation. An additional 32 patients (1.5%) required repeat interventions or readmission within 30 days of implant, most commonly due to lead dislodgement. Only 2 patients required readmission within 24 hours of surgery (0.1%). All procedure-related adverse events during clinical follow up (≤5 years) were 131 (5.9%) occurring in 122 patients. There were no apparent predictors of adverse events in this cohort.

Conclusion(s)

Contemporary risks to patients undergoing defibrillator surgery are considerably lower than that reported in 2010. The risk of infection appears constant despite increased antibiosis. Patients receiving an ICD or CRT-D can safely be discharged within 24 hours if no complications are apparent.

Acknowledgement/Funding

None

The Influence of Arm Positioning on Ultrasonic Visualization of the Subclavian Vein: An Anatomical Ultrasound Study in Healthy Volunteers

We hypothesized that placing the arm in 90° abduction, through 90° flexion and 90° external rotation, could improve ultrasound visualization of the subclavian vein. In 49 healthy volunteers, a single operator performed a view of the subclavian vein in neutral position and abduction position. A second blinded operator measured the cross-sectional area of the subclavian vein. Abduction position increased the cross-sectional area of the subclavian vein from 124 ± 46 (mean ± SD) to 162 ± 58 mm (P = 0.001). An increase of the cross-sectional area of ≥50% was observed in 41% volunteers (95% confidence interval, 27%-56%, n = 20); this technique offers an alternative approach (maybe safer) for ultrasound-guided catheterization of the subclavian vein.

Complications of endovenous lasers

Endovenous laser ablation (EVLA) and radiofrequencey ablation have become the procedures of choice for the treatment of superficial venous insufficiency. Their minimally invasive technique and safety profile when compared with operative saphenectomy have led to this change. As EVLA has replaced saphenectomy as the procedure of choice, the distribution of complications has changed. We evaluated the most common and most devastating complications in the literature including burns, nerve injury, arterio-venous fistula (AVF), endothermal heat-induced thrombosis and deep venous thrombosis. The following review will discuss the most frequently encountered complications of treatment of superficial venous insufficiency using EVLA. The majority of the complications described can be avoided with the use of good surgical technique and appropriate duplex ultrasound guidance. Overall, EVLA has an excellent safety profile and should be considered among the first line for treatment of superficial venous reflux.

Acute renal failure in the State of Qatar: presentation and outcome

Despite major improvements in health care, acute renal failure is still one of the main prognostic factors in terms of patient mortality and long-term morbidity. This cohort prospective study to evaluate the patterns and outcomes of renal failure in Qatar was performed between January and June 2005. Of the 213 patients followed prospectively from referral to the end of their hospitalization, 66.7% were males and 33.3% females. Their overall mean age was 60 years; the majority were referred from critical care units. Comorbidity was present in 87% of all patients. Volume depletion, hypotension, and sepsis were the main predisposing factors for renal failure. Eighty three patients (39%) needed renal replacement treatment and 130 (61%) were treated conservatively. The majority of critical care patients needed dialysis. Overall mortality was 23.9%, 7% needed chronic dialysis, and 69.1% were discharged with normal or mild renal impairment. This study showed that acute renal failure was a major factor affecting patient mortality in Qatar. Early treatment of predisposing factors may improve overall patient outcomes.

Early graft function and carboxyhemoglobin level in liver transplanted patients

INTRODUCTION

Heme-Oxygenase-1 catalyzes hemoglobin into bilirubin, iron, and carbon monoxide, a well known vasodilator. Heme-Oxygenase-1 expression and carbon monoxide production as measured by blood carboxyhemoglobin levels, increase in end stage liver disease patients. We hypothesized that there may be a correlation between carboxyhemoglobin level and early graft function in patients undergoing liver transplant surgeries.

METHODS

In a descriptive retrospective study, 39 patients who underwent liver transplantation between the year 2005 and 2006 at KFSH&RC, are included in the study. All patients received general anesthesia with isoflurane in 50% oxygen and air. Levels of oxyhemoglobin, carboxyhemoglobin and methemoglobin concentration in percentage were recorded at preoperative time, anhepatic phase, end of surgery, ICU admission and 24 hr after surgery. The level of lactic acid, prothrombin time (PT), partial thrombin time (PTT), serum total bilirubin and ammonia were also recorded at ICU admission and 24 hr after surgery. The numbers of blood units transfused were recorded.

RESULTS

39 patients were included in the study with 13/39 for living donor liver transplant (LDLT) compared to 26/39 patients scheduled for deceased donor liver transplant (DDLT). The mean age was 35.9 +/- 16.9 years while the mean body weight was 60.3 +/- 20.9 Kg. Female to male ratio was 21/18. The median packed red blood cell (PRBC) units was 4 (Rang 0-40). There was a significant increase in carboxyhemoglobin level during the anhepatic phase, end of surgery and on ICU admission compared with preoperative value (p<0.005). However, there was insignificant changes in methemoglobin level and significant decrease in oxyhemoglobin levels throughout the study period compared to the preoperative value (p<0.005). The changes in carboxyhemoglobin level on ICU admission and 24 hrs postoperatively were positively correlated with the changes in serum total bilirubin and prothrombin time (R = 0.35, 0.382, 0.325 and 0.31) respectively p<0.05) but not with the changes in serum lactic acid. The same strong correlation was found when analysing LDLT and DDLT patients separately between carboxyhemoglobin concentration and PT and total bilirubin while still the correlation with lactic acid was weak. There was no correlation between average perioperative carboxyhemoglobin concentration during different timing of measurements and average units of transfused blood (R = -0.02) p>0.05.

CONCLUSION

The changes in carboxyhemoglobin level significantly correlate with the Changes in graft functions particularly prothrombin time and serum total bilirubin and may be used as an early, rapid and simple test for early evaluation of graft function.

Dynamic three-dimensional spiral computed tomographic cysto-urethrography: a novel technique for evaluating post-traumatic posterior urethral defects

OBJECTIVE

To present a new method of identifying the anatomy of posterior urethral distraction defects (PUDDs) using three-dimensional spiral computed tomography/cysto-urethrography (CTCUG), as conventional two-dimensional CUG can give a false interpretation of the exact anatomy.

PATIENTS AND METHODS

Twenty-one patients presenting with a PUDD were assessed between February 2001 and October 2002. All patients initially underwent combined ascending and micturating CUG (ACUG), followed by CTCUG analysed using special software. In this technique all soft-tissue densities were subtracted from the volume of interest leaving only high-density images, i.e. pelvic bony structure and the contrast medium-filled bladder and urethra. The images were taken over a sequence and 36 different images viewed by 'roll and spin' techniques, each of which had a different plane of vision. Images were supplied as static CT films and as a movie on a compact disk using a computer program.

RESULTS

The technique allows one CT image to be viewed from 36 different angles both dynamically and statically, allowing the surgeon the unique opportunity to view the PUDD through several planes and precisely identify its anatomy. By comparing the data obtained with this technique to those obtained by conventional ACUG, and each in relation to the operative findings, the following aspects could be more thoroughly evaluated by CTCUG: the location of the distraction injury, the length of the distraction defect, the degree and direction of urethral end-alignment, the relation of the ectopic bony fragments and bone callus to the urethra, and the presence of various pathological defects, e.g. fistulae, false passages and diverticulae.

CONCLUSION

With CTCUG, both static and dynamic images can be obtained, allowing the easier staging of a PUDD and thus better surgical planning and consequently better results from reconstruction.

Comparative evaluation of the nuclear matrix protein, fibronectin, urinary bladder cancer antigen and voided urine cytology in the detection of bladder tumors

PURPOSE

We evaluate the diagnostic efficacy of nuclear matrix protein-22 (NMP22, Matritech, Newton, Massachusetts), fibronectin and urinary bladder cancer antigen (UBC, IDL Biotech, Borlange, Sweden) compared with voided urine cytology in the detection of bladder cancer.

MATERIALS AND METHODS

A total of 168 patients provided a single voided urine sample for NMP22, fibronectin an ideal monoclonal for urinary bladder cancer and cytology before cystoscopy. Cystoscopy was done for all patients as the reference standard for identification of bladder cancer. Biopsy of any suspicious lesion was performed for histopathological examination. Of the 168 cases 100 were histologically diagnosed as bladder cancer, whereas the remaining 68 had benign urological disorders. A group of 47 healthy volunteers were also enrolled in this study. Voided urine was evaluated by NMP22, fibronectin and UBC, and their values were expressed relative to mg. creatinine.

RESULTS

The optimal threshold values for NMP22, fibronectin and UBC were calculated by receiver operator characteristics curves as 27 units per mg. creatinine, 198 mg./mg. creatinine and 13 ng./mg. creatinine, respectively. The levels and positive rates of the 3 parameters were significantly higher in the malignant group compared to either the benign group or normal controls. Of the entire group NMP22, fibronectin and UBC were positive in 93.2%, 91% and 68.2%, respectively in bladder cancer cases with positive cytology. Moreover, these positive rates were significantly higher in bilharzial bladder cancer cases (58.8%, 67.5%, 58.8%, respectively) compared to nonbilharzial cases (35.6%, 36.3%, 31.1%). Overall sensitivity and specificity were 85% and 91.3% for NMP22, 83% and 82.6% for fibronectin, 67% and 80.8% for UBC and 44% and 100% for voided urine cytology. Combined sensitivity of voided urine cytology with the 3 biomarkers together was higher than either combined sensitivity of voided urine cytology with 1 of the biomarkers or than that of the biomarker alone.

CONCLUSIONS

Our data indicate that NMP22 and fibronectin had superior sensitivities compared to UBC and voided urine cytology, while NMP22 and voided urine cytology had the highest specificities. The combined use of markers increased the sensitivity of cytology from 44% to 95.3%. The higher sensitivities of markers in bilharzial than nonbilharzial bladder cancer highlight their clinical use in screening patients with urinary bilharziasis.

Associations between family history of asthma, bronchopulmonary dysplasia, and childhood asthma in very low birth weight children

Very low birth weight (VLBW) infants are at risk for childhood wheezing and asthma, as are children with a family history of asthma. Family history of asthma may also be associated with premature labor and, among VLBW infants, with bronchopulmonary dysplasia (BPD) and chronic lung disease (CLD) of prematurity. This study targeted all neonates with birth weight <1,501 g who were admitted to seven perinatal centers in Wisconsin and Iowa between August 1, 1988 and June 30, 1991. Comprehensive information was collected for 723 of the 1,007 30-day survivors, and for 106 full-term controls. A representative subgroup of 257 VLBW children was contacted at age 5 years to ascertain bronchodilator and/or steroid use and diagnosis of asthma. Some evidence of an association between family history of asthma and premature birth was found, but it was not associated with neonatal BPD/CLD or BPD/CLD severity. Among BPD/CLD indicators, radiographic evidence of BPD at age 25-35 days was most strongly associated with bronchodilator use up to age 2 years (odds ratio (OR) = 10.1, 95% confidence interval (CI) 4.07-25.2) and with asthma between ages 2 years and 5 years (OR = 4.83, 95% CI 2.18-10.7). Among children without radiographic evidence of BPD, family history of asthma was associated with childhood asthma and bronchodilator use.

Association of tocolytic therapy with antenatal steroid administration and infant outcomes. Newborn Lung Project

The use of tocolytic agents to halt premature labor is controversial. We examine a database on very low-birth-weight infants born following the onset of premature labor (n = 540) for association between tocolytic and antenatal steroid therapy, and to assess neonatal and childhood outcomes following combined therapy. Data are from a multicenter regionally based study of all infants below 1501 g at seven neonatal intensive care units (NICUs) in Wisconsin and Iowa, born August 1, 1988 through June 30, 1991. Infant outcomes analyzed are death in the first 30 days, respiratory distress syndrome (RDS), and intraventricular hemorrhage (IVH). Fewer deliveries occurred within 12 hours of labor onset with tocolytics (61 vs. 75% without). A strong association between tocolytic therapy and antenatal steroid administration was found [adjusted odds ratio OR = 5.7, 95% confidence interval CI: (3.3, 10.0)]. Tocolytics were associated with lower mortality in the first 30 days [OR = 0.29, CI: (0.15, 0.56)]. Joint administration of tocolytics and antenatal steroids versus neither was associated with lower incidence of the combined outcome of respiratory distress syndrome (RDS) or death [OR = .30, CI: (0.15, 0.60)] and grade III-IV IVH or death [OR = 0.35, CI: (0.14, 0.98)]. Tocolytic therapy alone was not associated with IVH grade III-IV [OR = 1.0, CI: (0.57, 1.9)] among survivors.

Evaluation of criteria for chronic lung disease in surviving very low birth weight infants. Newborn Lung Project

Criteria in common use for the diagnosis of chronic lung disease of prematurity or bronchopulmonary dysplasia in the neonatal period have not been sufficiently compared and validated against indicators of later respiratory complications. In this study of all 680 infants < or = 1500 gm birth weight admitted to six perinatal centers August 1, 1988, to July 31, 1990, 524 were alive and had no major congenital anomalies at 5 years old. Of 419 who had given permission to release their names and addresses, 272 were located and participated in a follow-up study. The following diagnostic criteria for bronchopulmonary dysplasia and chronic lung disease of prematurity were used during the initial hospitalization: (1) use of supplemental oxygen on day 30 of life, (2) a comprehensive bronchopulmonary dysplasia severity score applied at 25 to 35 days of life developed by a clinician panel to adjust for practice variation in ventilatory support and blood gases, (3) use of supplemental oxygen on day 30 of life with radiographic evidence consistent with bronchopulmonary dysplasia between days 25 and 35 of life, (4) radiographic evidence consistent with bronchopulmonary dysplasia alone, and (5) use of supplemental oxygen at 36 weeks' postconceptional age. These criteria were assessed against use of bronchodilators or steroids during the first 2 years of life, diagnosis of asthma, and hospitalizations for respiratory causes up to age 5. Although all criteria were significantly associated with all the outcomes, radiographic evidence was most predictive. These results indicate that, during a period when 21% of neonates were exposed to antenatal steroids, 24% received surfactant and 9% received postnatal corticosteroids, radiographic evidence was more predictive of long-term respiratory outcome than other commonly used criteria.

Purification and characterization of an extracellular (1 --> 6)-beta-glucanase from the filamentous fungus Acremonium persicinum

An endo-(1 --> 6)-beta-glucanase has been isolated from the culture filtrates of the filamentous fungus Acremonium persicinum and purified by (NH4)2SO4 precipitation followed by anion-exchange and gel-filtration chromatography. SDS/PAGE of the purified enzyme gave a single band with an apparent molecular mass of 42.7 kDa. The enzyme is a non-glycosylated, monomeric protein with a pI of 4.9 and pH optimum of 5.0. It hydrolysed (1 --> 6)-beta-glucans (pustulan and lutean), initially yielding a series of (1 --> 6)-beta-linked oligoglucosides, consistent with endo-hydrolytic action. Final hydrolysis products from these substrates were gentiobiose and gentiotriose, with all products released as beta-anomers, indicating that the enzyme acts with retention of configuration. The purified enzyme also hydrolysed Eisenia bicyclis laminarin, liberating glucose, gentiobiose, and a range of larger oligoglucosides, through the apparent bydrolysis of (1 --> 6)-beta- and some (1 --> 3)-beta-linkages in this substrate. K(m) values for pustulan, lutean and laminarin were 1.28, 1.38, and 1.67 mg/ml respectively. The enzyme was inhibited by N-acetylimidazole, N-bromosuccinimide, dicyclohexylcarbodi-imide, Woodward's Reagent K, 2-hydroxy-5-nitrobenzyl bromide, KMnO4 and some metal ions, whereas D-glucono-1,5-lactone and EDTA had no effect.

The relation of maternal complications to outcomes in very low birthweight infants in an era of changing neonatal care

We examine the relation of key neonatal outcomes to pregnancy complications and to the use of antenatal steroids and investigate whether there is evidence of recent change in this relation. Complete information on pregnancy and neonatal course was available for 749 out of 949 singleton births without major congenital anomalies below 1501 g admitted to seven regional neonatal intensive care units between August 1, 1988 and June 30, 1991. Mortality was highest in infants born after labor with spontaneous rupture of fetal membranes of less than 24 hours duration (odds ratio [OR] = 1.6, 95% confidence interval [1.0, 2.6]). Spontaneous rupture of membranes of over 24 hours duration was associated with decreased risk of respiratory distress syndrome (OR = 0.42, [0.28, 0.64]) and decreased risk of patent ductus arteriosus (OR = 43, [0.28, 0.66]). Pregnancy induced hypertension was associated with increased risk of respiratory distress syndrome in those born at less than 20 weeks' gestation (OR = 6.0, [2.0, 17]). Labor with or without rupture of membranes of short duration was associated with increased risk of intraventricular hemorrhage (OR = 1.9, [1.2, 2.5]). These associations were not different in early versus late time periods of the study. Antenatal steroids were associated with dramatically reduced risk of mortality (OR = 0.20, [0.09, 0.50] ), respiratory distress syndrome (OR = 0.52, [0.32, 0.85]), and intraventricular hemorrhage (OR = 0.37, [0.21-0.65]).

Stereochemical course of glucan hydrolysis by barley (1-->3)- and (1-->3, 1-->4)-beta-glucanases

The stereochemical course of hydrolysis of Laminaria digitata laminarin and barley (1-->3, 1-->4)-beta-glucan by barley (1-->3)-beta-glucanase (E.C. 3.2.1.39) isoenzyme GII and (1-->3, 1-->4)-beta-glucanase (EC 3.2.1.73) isoenzyme EII, respectively, has been determined by 1H-NMR. Both enzymes catalyse hydrolysis with retention of anomeric configuration (e-->e) and may therefore operate via a double displacement mechanism. We predict that all other members of Family 17 of beta-glycosyl hydrolases also follow this stereochemical course of hydrolysis.

Comparison of native and mutant proteins provides a sequence-specific assignment of the cysteinyl ligand proton NMR resonances in the 2[Fe4S4] ferredoxin from Clostridium pasteurianum

A sequence-specific assignment is presented for the eight low-field paramagnetically shifted cysteinyl ligand proton NMR resonances in the 2[Fe4S4] ferredoxin from Clostridium pasteurianum. The assignment is based upon comparison of chemical shifts in 1D and 2D NMR spectra of native oxidized protein and those of three mutants. The mutant proteins G12A and G41A were designed to produce minor local structural changes (hence small chemical shift perturbations) in either cluster I (glycine 12 to alanine) or in cluster II (glycine 41 to alanine). Observed chemical shift changes in spectra of the double mutant G12,41A support the interpretation. The comparison is aided by structural models derived from the crystal structure of the related ferredoxin from Peptococcus aerogenes. Each of the eight low-field resonances is assigned to a beta-proton from a different cysteinyl ligand, and so connectivities established from previous TOCSY and HMQC data allow assignment of all 24 cysteinyl ligand protons.

A new radiographic scoring system for bronchopulmonary dysplasia. Newborn Lung Project

OBJECTIVES

To develop a simple, clinically meaningful radiographic score for bronchopulmonary dysplasia (BPD). To investigate its reliability, validity, and usefulness and to compare it to the Edwards score.

WORKING HYPOTHESIS

Our radiographic scoring of BPD is reliable, correlates with respiratory support, and provides a necessary standardization in comparing severity of respiratory disease between hospitals.

STUDY DESIGN

Prospective cohort study.

PATIENT SELECTION

The study included all neonates (n = 366) with birth weight below 1501 g admitted to 7 neonatal intensive care units, who had chest radiographs taken at age 25-35 days.

METHODOLOGY

A simple radiographic scoring system was developed. Scores ranging from 0 to 6 were assigned based on standard radiographs and descriptors of degree of abnormality. All radiographs taken between days 25 and 35 of age (n = 1087) were graded by a radiologist and a neonatologist. Radiographs from a stratified random sample of 37 neonates (10%) were also scored by the method of Edwards (n = 128 radiographs). A respiratory support index was constructed for days 25-35 and correlated with the radiographic score.

RESULTS

Between-reader correlation was r = 0.87 for our score and r = 0.88 for the Edwards score. The two scores correlated with each other at r = 0.94. The respiratory support index correlated with our radiographic score at r = 0.75 overall, and r = 0.56 to 0.88 within hospitals. Higher postnatal corticosteroid use was found at the hospitals with the lower correlations.

CONCLUSIONS

Our radiographic scoring is reliable, valid, and gives results similar to the Edwards score. Radiographs play a standardizing role in assessing severity of BPD between hospitals.

Tris(N,N-dialkyldithiocarbamato-S,S')thiotungsten(VI) Complexes and the X-Ray Crystal Structure of [WS(S2CNEt2)3]BF4

The orange, diamagnetic compounds [WS(S2CNR2)3]X(R = Me, X- = BF4-, BPh4-;R = Et, X- =BF4-) were prepared by reacting WSCl4 and Me3SiS2CNR2 in dichloromethane, followed by metathesis with NaX in methanol. The compounds were characterized by elemental analysis, infrared and variable-temperature 1H n.m.r. spectroscopy and X-ray crystallography. Crystals of [WS(S2CNEt2)3] BF4 were monoclinic, space group P21/a with a 12.293(1), b 17.229(5), c 14.257(2) Ǻ,β 113.69(1)°, V 2765(2) Ǻ3 and Dc = 1.796 g cm-3 for Z = 4. The structure was solved by the Patterson method and refined by a full-matrix least-squares procedure, 3961data being used, to a conventional R value of 0.039 ( Rw = 0.040). The seven-coordinate cation possesses a pentagonal-bipyramidal geometry; the terminal thio ligand [W=S 2.127(2)Ǻ] occupies an axial position, a unique dithiocarbamate ligand spans the other axial position and an equatorial position while the two other dithiocarbamate ligands occupy the four remaining equatorial sites.

Determination of the solution structure of neuropeptide K by high-resolution nuclear magnetic resonance spectroscopy

1H NMR chemical shift assignments for neuropeptide K (NPK) and neurokinin A (NKA) have been determined at 600 MHz in 28% trifluoroethanol/water solution. Two-dimensional NMR techniques were used to assign proton resonances, and interproton distances were estimated from the observed nuclear Overhauser effects (NOEs). These distances were used as constraints in a simulated annealing protocol within the program XPLOR to generate structures consistent with experimental data. NPK forms a regular amphipathic alpha-helical structure from Asp 3, terminating at Gly 18. Slowly exchanging amide protons identified in this region are likely to be involved in hydrogen bonds to stabilize the helix. The remainder of the molecule displays many sequential NOEs, with some i-(i + 2) contacts, but little further evidence of defined secondary conformation. NKA displays strong sequential connectivities between amide protons from Thr 3 to Met 10, and some i-(i + 2) connectivities suggestive of a series of dynamic turns in equilibrium. A comparison of the tail region of NPK with the related peptide homologue, neurokinin A, in the same solvent system, indicates that both show increasing order when trifluoroethanol is titrated into water solution, with the appearance of sequential NOEs between backbone amide protons. Differences between the corresponding spans of primary sequence appear to be minimal. The clear finding that NPK adopts a well-defined helix in its N-terminal half and is relatively disordered in the C-terminal half, which includes the entire NKA sequence, may have important implications for understanding the increased selectivity of NPK over NKA for one class of neurokinin receptor.

Preparation of lipid emulsions by pressure extrusion

Lipid emulsions consisting of a surface monolayer of phospholipid enclosing a core of neutral lipids have been prepared by repeated extrusion through polycarbonate filters of defined pore size. Particle size, as measured by photon correlation spectroscopy, decreases on successive passes through a 100 nm filter, reaching a near constant value (130-150 nm) after 4 passes. A corresponding decrease in the standard deviation of the particle size distribution occurs during this process. The recovery of lipids, especially of cholesterol and cholesterol ester, is improved if the emulsion is sonicated before extrusion through filters. [31P]-NMR and fluorescence techniques are used to confirm that the resulting structures are emulsions rather than lipid bilayers.

Conformational analysis of cyproheptadine hydrochloride

A nuclear magnetic resonance and theoretical study on the conformations and molecular flexibility of cyproheptadine hydrochloride (1) is reported. In the 1H NMR spectrum of 1 in CDCl3, two conformational forms are observed to occur in an approximate ratio of 1:4. In both forms, NOE and coupling constant measurements suggested that the terminal N-methyl group is equatorial. NOE experiments identified the more populated conformer (labeled D) as similar to the form seen in the X-ray crystal structure of cyproheptadine. The other form observed (A) may in principle be converted to D via either inversion of the central ring (T(inv)) or concerted nitrogen (N(inv)) and piperidine ring inversion (P(inv)). Chemical-exchange peaks in the 400-MHz 2D NOESY/chemical-exchange spectrum suggested that the latter mechanism is responsible for interconversion between the two forms. A theoretical study of the various interconversion processes using both molecular mechanics (MM2) and molecular orbital (AM1) approaches is also reported.

Morpheus: a conformation-activity relationships and receptor modeling package

Our molecular modeling software package, MORPHEUS, allows the study of the interactions between biologically active molecules and their receptors. The package is capable of exploring the multidimensional conformational space accessible to each molecule of the data set under study. By specifying distance constraints or hypothetical receptor binding points, the package is able to filter the biologically accessible conformations of each active compound and deduce a three-dimensional model of the binding sites consistent with the properties of the agonists (or antagonists) under scrutiny. The electrostatic potentials in the environment of a putative binding site can also be investigated using the MORPHEUS package. The molecular modeling module CRYS-X, which is written in FORTRAN 77 for IBM PC machines, is capable of building, displaying and manipulating molecules.

Caveat Regarding the Use of Substituent Parameters in Statistical Analyses of Molecular Properties. I. The Interdependence of Field, Resonance, Electronegativity and Polarizability Effects

lt is shown that several frequently employed electronegativity ( α1), field ( σF) and resonance ( σR) parameters are substantially interdependent for most of the commonly used substituents. Substituents are shown to belong to two categories, In which the first atom of the group is a first row (FR) or non-first row (NFR) atom, The degree, of interdependence of the three parameters increases markedly when the two substituent types are treated separately, although it is found that, for NFR groups, σF and σx alone are highly correlated, in contrast to FR groups, where σR contributes significantly to the interdependence equations. The disparate behaviour of FR and NFR substituent types is partly reconciled by the inclusion of a polarizability parameter (σx). Evidence is presented which indicates that σF is the parameter which is constitutionally dependent on the other three, although the dependence seems not to be completely causative, but partially fortuitous. Implications for the quantitative analysis of molecular processes at positions close to the substituent where electronegativity and polarizability effects are believed to operate, are discussed.