Hunting or habitat? Drivers of waterbird abundance and community structure in agricultural wetlands of southern India.

The relative impacts of hunting and habitat on waterbird community were studied in agricultural wetlands of southern India. We surveyed wetlands to document waterbird community, and interviewed hunters to document hunting intensity, targeted species, and the motivations for hunting. Our results show that hunting leads to drastic declines in waterbird diversity and numbers, and skew the community towards smaller species. Hunting intensity, water spread, and vegetation cover were the three most important determinants of waterbird abundance and community structure. Species richness, density of piscivorous species, and medium-sized species (31-65 cm) were most affected by hunting. Out of 53 species recorded, 47 were hunted, with a preference for larger birds. Although illegal, hunting has increased in recent years and is driven by market demand. This challenges the widely held belief that waterbird hunting in India is a low intensity, subsistence activity, and undermines the importance of agricultural wetlands in waterbird conservation.

A pictorial review of imaging in paediatric stroke.

Stroke is recognised as an important disease in adults. Paediatric stroke is less understood, yet still an important cause of morbidity and mortality, with an incidence of 5 per 100 000 children and is one of the top 10 leading causes of death in children. In adults the vast majority of strokes are ischaemic, whereas in children haemorrhage makes up half the cases. The incidence of neonatal stroke is much higher, at up to 45 per 100 000 population; however, the underlying causes are less understood. This paper acts as a guide to the different causes of stroke with the key differences on imaging discussed.

Does elastography reduce the need for thyroid FNAs?

OBJECTIVE: Ultrasound elastography (USE) assesses lesion stiffness by evaluating tissue distortion in response to stress; it is emerging as a potentially useful tool to augment the ultrasound characterisation of thyroid nodules. The aim of this study was to assess the accuracy of USE examination of thyroid nodules compared with pathological outcome, especially to determine whether USE could reliably detect benign nodules and reduce the numbers of ultrasound guided fine needle aspiration cytology (USgFNAC). DESIGN: Over a three-year period, thyroid nodules were initially characterised by B-mode ultrasound (US) findings. Where USgFNAC was indicated by clinical concern and/or the sonographic appearances, the lesion was then subjected to USE by an experienced operator prior to the USgFNAC. PATIENTS: 147 thyroid nodules were examined by USE and USgFNAC in 146 patients. MEASUREMENTS: The elastographic appearance was subjectively categorized at the time of the examination (soft, intermediate or hard) and subsequently compared with the cytological/histological outcome. RESULTS: A total of 122 nodules were non-neoplastic, 5 nodules were benign neoplasms, 10 nodules had indeterminate cytology and 10 were malignant neoplasms. The sensitivity of USE for malignancy was 90.0%, specificity was 79.6%, PPV was 24.3%, NPV was 99.1% and accuracy was 80.3%. CONCLUSION: Thyroid nodules that are soft at USE have a high likelihood of being non-neoplastic and subjective USE assessment of thyroid nodules by an experienced operator can be a useful means of avoiding USgFNAC for benign nodules. In contrast, we suggest that all nodules that are intermediate or hard on USE undergo USgFNAC.

Investigation of subarachnoid haemorrhage: does the buck stop with CT?

BACKGROUND AND AIM: In patients suspected of having a subarachnoid haemorrhage (SAH), a normal CT should be followed by lumbar puncture (LP) to detect xanthochromia. We studied the practice of performing a LP following a normal CT in patients with a clinical suspicion of SAH in a District General Hospital. We aimed to assess whether patients were being fully investigated for SAH and whether standards were being met. METHODS: This was a prospective study aiming to improve the patient's care by implementing the best practice. We initially recorded CT and LP results of patients with suspected SAH (phase 1) and presented the results to the referring clinicians. After a period of time, data was re-collected to study any change in practice (phase 2). RESULTS: In phase 1, 36 of 61 patients (59.0%) with a normal CT had a subsequent LP compared to 67/104 (64.4%) in the second phase (p = 0.51). In the first phase, xanthochromia was detected in 1 of 36 patients (2.8%) who had a LP following a normal CT, compared to 1 of 67 patients (1.5%) in the second phase (p = 1.0). CONCLUSION: Approximately a third of patients with symptoms of SAH in both study periods did not undergo LP following a normal CT scan. This is an important finding, as it is known that a normal CT does not exclude the diagnosis of SAH and by not proceeding to LP, patients have not been fully investigated for a SAH.

Early versus delayed laparoscopic cholecystectomy for acute cholecystitis: a prospective randomized trial.

BACKGROUND: The role of laparoscopic cholecystectomy for acute cholecystitis is not yet clearly established. The aim of this prospective randomized study was to evaluate the safety and feasibility of laparoscopic cholecystectomy for acute cholecystitis and to compare the results with delayed cholecystectomy. METHODS: Between January 2001 and November 2002, 40 patients with a diagnosis of acute cholecystitis were assigned randomly to early laparoscopic cholecystectomy within 24 h of admission (early group, n = 20) or to initial conservative treatment followed by delayed laparoscopic cholecystectomy, 6 to 12 weeks later (delayed group, n = 20). RESULTS: There was no significant difference in the conversion rates (early, 25% vs delayed, 25%), operating times (early, 104 min vs delayed, 93 min), postoperative analgesia requirements (early, 5.3 days vs delayed, 4.8 days), or postoperative complications (early, 15% vs delayed, 20%). However, the early group had significantly more blood loss (228 vs 114 ml) and shorter hospital stay (4.1 vs 10.1 days). CONCLUSIONS: Early laparoscopic cholecystectomy for acute cholecystitis is safe and feasible, offering the additional benefit of a shorter hospital stay. It should be offered to patients with acute cholecystitis, provided the surgery is performed within 72 to 96 h of the onset of symptoms.

Identifying three-phase induction motor faults using artificial neural networks

This paper presents an artificial neural network (ANN) based technique to identify faults in a three-phase induction motor. The main types of faults considered are overload, single phasing, unbalanced supply voltage, locked rotor, ground fault, over-voltage and under-voltage. Three-phase currents and voltages from the induction motor are used in the proposed approach. A feedforward layered neural network structure is used. The network is trained using the backpropagation algorithm. The trained network is tested with simulated fault current and voltage data. Fault detection is attempted in the no fault to fault transition period. Off-line testing results on a 3 HP induction motor model show that the proposed ANN based method is effective in identifying various types of faults.

Extracorporeal life support outcome for 128 pediatric patients with respiratory failure.

PURPOSE: The aim of this study was to describe a single-center experience with pediatric extracorporeal life support (ECLS) and to determine variables predictive of outcome in pediatric patients, both before the institution of ECLS and while on support. METHODS: From October 1985 to September 1998 the authors supported 128 children with severe acute hypoxemic respiratory failure(n = 121, Pao2/FIo2 ratio = 58+/-29) or acute hypercarbic respiratory failure (n = 7, Paco2 = 128+/-37), despite maximal conventional ventilation. Mode of access included venoarterial bypass (VA, n = 64), venovenous bypass (VV, n = 53), and VV to VA bypass (n = 11). The techniques used included lung rest, pulmonary physiotherapy, diuresis to dry weight using hemofiltration if needed, minimal anticoagulation, and optimal systemic oxygen delivery. RESULTS: The median age was 1.4 years (range, 2 weeks to 17 years). The mean duration of ECLS was 288+/-240 hours (range, 4 to 1148 hours or 0.2 to 47.8 days). Lung compliance increased from 0.32+/-0.02 mL/cm H2O/kg to 0.59+/-0.03 mL/cm H2O/kg in survivors, but only increased from 0.34+/-0.02 mL/cm H2O/kg to 0.35+/-0.02 mL/cm H2O/kg in nonsurvivors (P<.002 comparing change between survivors and nonsurvivors). Mean body weight decreased from 9%+/-2% over dry weight to 4%+/-2% in survivors, whereas in nonsurvivors the mean body weight increased from 25%+/-5% over dry weight to 35%+/-7% (P<.001). Outcome results by diagnosis were pneumonia, 73%; acute respiratory distress syndrome, 67%; and airway support, 60%, with overall lung recovery occurring in 77%, and hospital survival in 71%. Multivariate logistic regression modelling of patients with hypoxemic respiratory failure found the only pre-ECLS variable significantly associated with outcome to be pH (P<.05). Variables during the course of ECLS significantly associated with decreased survival were the presence of creatinine greater than 3.0 (P<.01), the need for inotropes (P<.04), failure to return the patient to dry weight (P<.04), and lung compliance that did not improve significantly. (P<.01). CONCLUSIONS: ECLS provides life support in severe respiratory failure in children, allowing time for injured lungs to recover. Pre-ECLS predictors, such as pH and variables during ECLS, such as presence of renal failure, improvement in compliance, return to dry weight, and the need for inotropes on ECLS, may be useful for predicting outcome.

Extracorporeal life support in pulmonary failure after trauma.

OBJECTIVE: To present a series of 30 adult trauma patients who received extracorporeal life support (ECLS) for pulmonary failure and to retrospectively review variables related to their outcome. METHODS: In a Level I trauma center between 1989 and 1997, ECLS with continuous heparin anticoagulation was instituted in 30 injured patients older than 15 years. Indication was for an estimated mortality risk greater than 80%, defined by a PaO2: FIO2 ratio less than 100 on 100% FIO2, despite pressure-mode inverse ratio ventilation, optimal positive end-expiratory pressure, reasonable diuresis, transfusion, and prone positioning. Retrospective analysis included demographic information (age, gender, Injury Severity Score, injury mechanism), pulmonary physiologic and gas-exchange values (pre-ECLS ventilator days [VENT days], PaO2:FIO2 ratio, mixed venous oxygen saturation [SvO2], and blood gas), pre-ECLS cardiopulmonary resuscitation, complications of ECLS (bleeding, circuit problems, leukopenia, infection, pneumothorax, acute renal failure, and pressors on ECLS), and survival. RESULTS: The subjects were 26.3+/-2.1 years old (range, 15-59 years), 50% male, and had blunt injury in 83.3%. Pulmonary recovery sufficient to wean the patient from ECLS occurred in 17 patients (56.7%), and 50% survived to discharge. Fewer VENT days and more normal SvO2 were associated with survival. The presence of acute renal failure and the need for venoarterial support (venoarterial bypass) were more common in the patients who died. Bleeding complications (requiring intervention or additional transfusion) occurred in 58.6% of patients and were not associated with mortality. Early use of ECLS (VENT days < or = 5) was associated with an odds ratio of 7.2 for survival. Fewer VENT days was independently associated with survival in a logistic regression model (p = 0.029). Age, Injury Severity Score, and PaO2:FIO2 ratio were not related to outcome. CONCLUSION: ECLS has been safely used in adult trauma patients with multiple injuries and severe pulmonary failure. In our series, early implementation of ECLS was associated with improved survival. Although this may represent selection bias for less intractable forms of acute respiratory distress syndrome, it is our experience that early institution of ECLS may lead to improved oxygen delivery, diminished ventilator-induced lung injury, and improved survival.

Colonic H-K-ATPase beta-subunit: identification in apical membranes and regulation by dietary K depletion.

P-type ATPases require both alpha- and beta-subunits for functional activity. Although an alpha-subunit for colonic apical membrane H-K-ATPase (HKcalpha) has been identified and studied, its beta-subunit has not been identified. We cloned putative beta-subunit rat colonic H-K-ATPase (HKcbeta) cDNA that encodes a 279-amino-acid protein with a single transmembrane domain and sequence homology to other rat beta-subunits. Northern blot analysis demonstrates that this HKcbeta is expressed in several rat tissues, including distal and proximal colon, and is highly expressed in testis and lung. HKcbeta mRNA abundance is upregulated threefold compared with normal in distal colon but not proximal colon, testis, or lung of K-depleted rats. In contrast, Na-K-ATPase beta1 mRNA abundance is unaltered in distal colon of K-depleted rats. Na depletion, which also stimulates active K absorption in distal colon, does not increase HKcbeta mRNA abundance. Western blot analyses using a polyclonal antibody raised to a glutathione S-transferase-HKcbeta fusion protein established expression of a 45-kDa HKcbeta protein in both apical and basolateral membranes of rat distal colon, but K depletion increased HKcbeta protein expression only in apical membranes. Physical association between HKcbeta and HKcalpha proteins was demonstrated by Western blot analysis performed with HKcbeta antibody on immunoprecipitate of apical membranes of rat distal colon and HKcalpha antibody. Tissue-specific upregulation of this beta-subunit mRNA in response to K depletion, localization of its protein, its upregulation by K depletion in apical membranes of distal colon, and its physical association with HKcalpha protein provide compelling evidence that HKcbeta is the putative beta-subunit of colonic H-K-ATPase.

An approach to the treatment of severe adult respiratory failure.

OBJECTIVES: The purpose of this article is to evaluate outcome in adult patients with severe respiratory failure managed with an approach using (1) limitation of end inspiratory pressure, (2) inverse ratio ventilation, (3) titration of PEEP by SvO2, (4) intermittent prone positioning, (5) limitation of FiO2, (6) diuresis, (7) transfusion, and (8) extracorporeal life support (ECLS) if patients failed to respond. PATIENTS AND METHODS: This study was designed as a retrospective review in the intensive care unit of a tertiary referral hospital. One-hundred forty-one consecutive patients with hypoxic (n = 135) or hypercarbic (n = 6) respiratory failure referred for consideration of ECLS between 1990 and 1996. Overall, initial PaO2/FiO2 (P/F) ratio was 75+/-5 (median = 66). RESULTS: Lung recovery occurred in 67% of patients and 62% survived. Forty-one patients improved without ECLS (83% survived); 100 did not and were supported with ECLS (54% survived). Survival was greater in patients cannulated within 12 hours of arrival (59%) compared with those cannulated after 12 hours (40%, P < .05). Multiple logistic regression identified age, duration of mechanical ventilation before transfer, four or more dysfunctional organs, and the requirement for ECLS as independent predictors of mortality. CONCLUSIONS: An approach that emphasizes lung protection and early implementation of extracorporeal life support is associated with high rates of survival in patients with severe respiratory failure.

Matrices of paired substitutions show the effects of tRNA D/T loop sequence on Drosophila RNase P and 3'-tRNase processing.

Drosophila RNase P and 3'-tRNase endonucleolytically process the 5' and 3' ends of tRNA precursors. We examined the processing kinetics of normal substrates and the inhibitory effect of the tRNA product on both processing reactions. The product is not a good RNase P inhibitor, with a KI approximately 7 times greater than the substrate KM of approximately 200 nM and is a better inhibitor of 3'-tRNase, with a KI approximately two times the KM of approximately 80 nM. We generated matrices of substitutions at positions G18/U55 and G19/C56 (two contiguous universally conserved D/T loop base pairs) in Drosophila tRNAHis precursors. More than half the variants display a significant reduction in their ability to be processed by RNase P and 3'-tRNase. Minimal substrates with deleted D and anticodon stems could be processed by RNase P and 3'-tRNase much like full-length substrates, indicating that D/T loop contacts and D arm/enzyme contacts are not required by either enzyme. Selected tRNAs that were poor substrates for one or both enzymes were further analyzed using Michaelis-Menten kinetics and by structure probing. Processing reductions arise principally due to an increase in KM with relatively little change in Vmax, consistent with the remote location of the sequence and structure changes from the processing site for both enzymes. Local changes in variant tRNA susceptibility to RNase T1 and RNase A did not coincide with processing disabilities.

CCAAT displacement protein (CDP/cut) recognizes a silencer element within the lactoferrin gene promoter.

Expression of neutrophil secondary granule protein (SGP) genes is coordinately regulated at the transcriptional level, and is disrupted in specific granule deficiency and leukemia. We analyzed the regulation of SGP gene expression by luciferase reporter gene assays using the lactoferrin (LF) promoter. Reporter plasmids were transiently transfected into non-LF-expressing hematopoietic cell lines. Luciferase activity was detected from reporter plasmids containing base-pair (bp) -387 to bp -726 of the LF promoter, but not in a -916-bp plasmid. Transfection of a -916-bp plasmid into a LF-expressing cell line resulted in abrogation of the silencing effect. Sequence analysis of this region revealed three eight-bp repetitive elements, the deletion of which restored wild-type levels of luciferase activity to the -916-bp reporter plasmid. Electrophoretic mobility shift assay and UV cross-linking analysis identified a protein of approximately 180 kD that binds to this region in non-LF-expressing cells but not in LF-expressing cells. This protein was identified to be the CCAAT displacement protein (CDP/cut). CDP/cut has been shown to downregulate expression of gp91-phox, a gene expressed relatively early in the myeloid lineage. Our observations suggest that the binding of CDP/cut to the LF silencer element serves to suppress basal promoter activity of the LF gene in non-LF-expressing cells. Furthermore, overexpression of CDP/cut in cultured myeloid stem cells blocks LF expression upon granulocyte colony-stimulating factor-induced neutrophil maturation without blocking phenotypic maturation. This block in LF expression may be due, in part, to the persistence of CDP/cut binding to the LF silencer element.

Extracorporeal life support for 100 adult patients with severe respiratory failure.

OBJECTIVE: The authors retrospectively reviewed their experience with extracorporeal life support (ECLS) in 100 adult patients with severe respiratory failure (ARF) to define techniques, characterize its efficacy and utilization, and determine predictors of outcome. SUMMARY BACKGROUND DATA: Extracorporeal life support maintains gas exchange during ARF, providing diseased lungs an optimal environment in which to heal. Extracorporeal life support has been successful in the treatment of respiratory failure in infants and children. In 1990, the authors instituted a standardized protocol for treatment of severe ARF in adults, which included ECLS when less invasive methods failed. METHODS: From January 1990 to July 1996, the authors used ECLS for 100 adults with severe acute hypoxemic respiratory failure (n = 94): paO2/FiO2 ratio of 55.7+/-15.9, transpulmonary shunt (Qs/Qt) of 52+/-22%, or acute hypercarbic respiratory failure (n = 6): paCO2 84.0+/-31.5 mmHg, despite and after maximal conventional ventilation. The technique included venovenous percutaneous access, lung "rest," transport on ECLS, minimal anticoagulation, hemofiltration, and optimal systemic oxygen delivery. RESULTS: Overall hospital survival was 54%. The duration of ECLS was 271.9+/-248.6 hours. Primary diagnoses included pneumonia (49 cases, 53% survived), adult respiratory distress syndrome (45 cases, 51 % survived), and airway support (6 cases, 83% survived). Multivariate logistic regression modeling identified the following pre-ECLS variables significant independent predictors of outcome: 1) pre-ECLS days of mechanical ventilation (p = 0.0003), 2) pre-ECLS paO2/FiO2 ratio (p = 0.002), and 3) age (years) (p = 0.005). Modeling of variables during ECLS showed that no mechanical complications were independent predictors of outcome, and the only patient-related complications associated with outcome were the presence of renal failure (p < 0.0001) and significant surgical site bleeding (p = 0.0005). CONCLUSIONS: Extracorporeal life support provides life support for ARF in adults, allowing time for injured lungs to recover. In 100 patients selected for high mortality risk despite and after optimal conventional treatment, 54% survived. Extracorporeal life support is extraordinary but reasonable treatment in severe adult respiratory failure. Predictors of survival exist that may be useful for patient prognostication and design of future prospective studies.

Characteristics of an albumin dialysate hemodiafiltration system for the clearance of unconjugated bilirubin.

Extraction of protein bound liver failure toxins, such as unconjugated bilirubin, short chain fatty acids, and aromatic amino acids has been reported using hemodiafiltration with albumin in the dialysate, but the characteristics of such a system have not been described. Therefore, bilirubin clearance using albumin dialysate hemodiafiltration was evaluated in the setting of different dialysate albumin concentrations, varying temperature and pH. An in vitro continuous hemodiafiltration circuit was used with single pass countercurrent dialysis. Unconjugated bilirubin was added to bovine blood and filtered across a polyalkyl sulfone (PAS) hemofilter using matched filtration and dialysate flow rates. The serial bilirubin content was measured and first order clearance kinetics verified. The clearance rate constants were calculated for three dialysate groups of different albumin concentration at constant temperature and pH (group 1: 10 g/dl albumin, n = 5; 2 g/dl albumin, n = 5; normal saline, n = 5), and three groups of different temperature and pH at constant albumin dialysate concentration (group 2: pH = 7.0, temperature = 20 degrees C, n = 5; pH = 7.5, temperature = 20 degrees C, n = 5; pH = 7.0, temperature = 40 degrees C, n = 5). Comparisons were made with ANOVA and Tukey post hoc analysis. When albumin was used in the dialysate, the 2 g/dl group cleared bilirubin 3.1 times faster than saline alone (p = 0.001), and the 10 g/dl group was superior to both (p = 0.001). There were no measurable differences between the 2 g/dl groups at the various temperatures tested (p = 0.08), but the clearance was less at a pH of 7.5 (p = 0.015). The clearance of unconjugated bilirubin is greatly enhanced with the use of albumin containing dialysates when compared to traditional crystalloid hemodiafiltration, is greater at lower pH, and seems to be unaffected by temperature.

Total respiratory support with tidal flow extracorporeal circulation in adult sheep.

A novel pressure gated tidal flow extracorporeal circulation (TF ECC) device was developed, and it was hypothesized that it could provide total respiratory support in apneic adult sheep without adverse hemodynamic or cardiac effects. The circuit consisted of a single lumen cannula, computer driven tubing occluders gated by circuit pressure, a nonocclusive peristaltic blood pump, a spiral coiled membrane lung, and a heat exchanger. Six paralyzed, anesthetized adult sheep were instrumented and TF ECC was instituted via cannulation of the right atrium. Total respiratory support was provided by the circuit during an apneic period of 6 hours. Echocardiography was performed with the animal instrumented (baseline) and after 2 hours of TF ECC. Circuit blood tidal volume was 172.6 +/- 18.0 cc, resulting in a TF ECC flow of 71.1 +/- 10.1 cc/kg/min. At the end of the study period, PaCO2 was 35.5 +/- 7.6 mmHg, paO2) was 91.2 +/- 30.6 mmHg, and pulmonary artery oxygen saturation (SPAO2) was 95 +/- 5%. Hemodynamic stability was maintained with no significant differences at baseline and after 6 hours in mean arterial pressure, mean pulmonary artery pressure, or heart rate noted. Echocardiographic evaluation showed preserved fractional shortening of the left ventricular (LV) septal-lateral dimension (baseline 32.4 +/- 11.4%; 2 hours 34.8 +/- 8.4%). This study demonstrates TF ECC provides total respiratory support without adverse hemodynamic effects, and preserved LV function.

Prolonged extracorporeal life support (ECLS) for varicella pneumonia.

OBJECTIVE: To review the institutional experience of a national tertiary referral center for extracorporeal life support (ECLS) in severe varicella pneumonia. DATA SOURCES: Hospital records and ECLS flow sheets. STUDY SELECTION: All pediatric (nonneonatal) and adult patients who were treated for varicella pneumonia with ECLS at the University of Michigan Medical Center between 1986 and 1995. DATA EXTRACTION: Diagnosis of varicella pneumonia was made by history of recent exposure to chickenpox, progressive dyspnea, fever, a characteristic diffuse, vesicular rash, and a supporting chest roentgenogram. Indications for ECLS included a shunt fraction of > 30% or PaO2/FlO2 ratio of < 80 despite maximal conventional therapy, which included aggressive diuresis, blood transfusions to optimize oxygen-carrying capacity, pressure-controlled/inverse-ratio ventilation, and intermittent prone positioning. DATA SYNTHESIS: Between 1986 and 1995, 191 patients were referred for ECLS. Among these patients, there were 51 (27%) cases of viral pneumonia, of which nine cases were due to acute varicella-zoster infection. Intravenous acyclovir was administered to eight of the nine patients. Of the nine patients, two patients improved using conventional ventilator management, and seven patients underwent ECLS. Overall survival on ECLS was 71% (5/7). The mean (+/-SD) alveolar-arterial oxygen gradient and PaO2/FlO2 ratio were 533 +/- 101 torr (71.3 +/- 13.5 kPa) and 67 +/- 24, respectively. The median duration of mechanical ventilation before ECLS and the subsequent duration of ECLS were 4 and 12.8 days, respectively. One of the deaths was from progressive right heart failure secondary to pulmonary hypertension and the other death was from overwhelming Pseudomonas sepsis. CONCLUSIONS: Early recognition of imminent pulmonary failure and rapid institution of ECLS are critical in the successful management of severe, life-threatening varicella pneumonia.

Extracorporeal life support for cardiovascular support in adults.

The authors retrospectively reviewed their institution's experience with extracorporeal life support (ECLS) for adult cardiovascular failure to determine efficacy and further indications for its use. From 1985 to 1996, venoarterial ECLS was used in 27 adult patients. Indications for ECLS included post cardiotomy cardiac failure, primary myocardial failure, bridge to transplant, and emergency cardiopulmonary resuscitation. The average age was 38.7 +/- 2.7 years and duration of support was 164.0 +/- 26.8 hr. Overall cardiovascular recovery from ECLS was 44%, and hospital survival was 30%. Late deaths were due to multisystem organ failure. Best results were obtained in patients whose processes were reversible during a short duration of ECLS (< 91.6 +/- 33.3 hr. The worst results were obtained in post cardiotomy patients who underwent prolonged support with ECLS. Evaluation of physiologic parameters during the first 30-48 hr of support showed marked improvements from values before ECLS. Because of its relative ease of deployment and its rapid correction of acute physiologic derangements, ECLS can be used as a temporary means of support to determine extent and reversibility of organ dysfunction. Longer term support should include consideration of other mechanical assist devices. The authors no longer consider bridge to transplant an indication for ECLS due to relative donor unavailability.

Sequence and structure requirements for Drosophila tRNA 5'- and 3'-end processing.

Eukaryotic tRNAs are processed at their 5'- and 3'- ends by endonucleases RNase P and 3'-tRNase, respectively. We have prepared substrates for both enzymes, separated the activities from a Drosophila extract, and designed variant tRNAs to assess the effects of sequence and structure on processing. Mutations affect these reactions in similar ways; thus, RNase P and 3'-tRNase probably require similar substrate structures to maintain the catalytic fit. RNase P is more sensitive to substrate substitutions than 3'-tRNase. In three of the four stems, one substitution prevents both processing reactions while the opposite one has less effect; anticodon stem substitutions hardly affect processing, and double substitution intended to restore base pairing also restore processing to the wild type rate. Structure probing suggests that tRNA misfolding sometimes coincides with reduced processing. In other cases, processing inhibition probably results from specific unfavorable stem appositions leading to local helix deformation. A single T loop substitution disrupts the tertiary D-T loop interaction and reduces processing. We have thus begun mapping tRNA processing determinants on the global, local, and tertiary structure levels.