WAVES - The Lucile Packard Children's Hospital Pediatric Physiological Waveforms Dataset

WAVES is a large, single-center dataset comprising 9 years of high-frequency physiological waveform data from patients in intensive and acute care units at a large academic, pediatric medical center. The data comprise approximately 10.6 million hours of 1 to 20 concurrent waveforms over approximately 50,364 distinct patient encounters. The data have been de-identified, cleaned, and organized to facilitate research. Initial analyses demonstrate the potential of the data for clinical applications such as non-invasive blood pressure monitoring and methodological applications such as waveform-agnostic data imputation. WAVES is the largest pediatric-focused and second largest physiological waveform dataset available for research.

ECG-I Phenotyping of Persistent AF Based on Driver Burden and Distribution to Predict Response to Pulmonary Vein Isolation (PHENOTYPE-AF)

BACKGROUND

This prospective trial sought to phenotype persistent AF based on AF mechanisms using ECGI mapping to determine whether this would predict long term freedom from arrhythmia after pulmonary vein isolation (PVI).

METHODS

Patients with persistent AF of < 2 years duration underwent cryoballoon PVI. ECGI mapping was performed prior to PVI to determine potential drivers (PDs) defined as rotational activations completing ≥ 1.5 revolutions or focal activations. The co-primary end point was the association between (1) PD burden (defined as the number of PD occurrences) and (2) PD distribution (defined as the number of segments on an 18 segment model of the atria harbouring PDs) with freedom from arrhythmia at 1 year follow up.

RESULTS

Of 100 patients, 97 completed follow up and 52 (53.6%) remained in sinus rhythm off antiarrhythmic drugs. Neither PD burden nor PD distribution predicted freedom from arrhythmia (HR 1.01, 95% CI 0.99 - 1.03, p = 0.164; and HR 1.04, 95% CI 0.91 - 1.17, p = 0.591 respectively). Otherwise, the burden of rotational PDs, rotational stability, and the burden of PDs occurring at the pulmonary veins and posterior wall all failed to predict arrhythmia recurrence (all p > 0.10).

CONCLUSIONS

AF mechanisms as determined using ECGI mapping do not predict outcome after PVI for persistent AF. Further studies using different methodologies to characterise AF mechanisms are warranted. (NCT03394404) This article is protected by copyright. All rights reserved.

Feasibility of the use of different types of enzymatically treated cellulosic fibres for polylactic acid (PLA) recycling

In the present study, the potential use of cellulosic microfibers (CMFs) extracted from hemp fiber (HF) and pulp and paper solid waste (mixed sludge (MS), deinked sludge (DS)) as a reinforcing agent in novel bio composite materials produced from recycled Polylactic acid (rPLA) was investigated. CMFs were extracted and treated using physicochemical method followed by enzymatic treatment with laccase and cellulase. The effects of CMFs concentrations (1.5, 3 and 6% w/w) and fiber size (75 μm-1.7 mm) on the mechanical properties (impact and tensile) and biodegradability of the biocomposite samples were investigated. A modified interfacial adhesion between rPLA matrix and the three fibers used, was clearly observed through mechanical tests due to alkali and enzymatic treatments. The use of different types of enzymatically treated cellulosic fibers for polylactic acid (PLA) recycling was assessed by Scaning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The combined physicochemical and enzymatic treatments led to a considerable size reduction of the cellulosic fibers (HF, MS and DS) resulting in the enhanced interfacial adhesion between rPLA matrix and fibers. The biocomposite obtained with rPLA with HF gave the most favorable values for Young's modulus (324.53 ± 3.10 MPa, p-value 0.03), impact strength (27.61 ± 2.94 kJ/m², p-value 0.01) and biodegradation rate (1.97%).

An Analysis of Hospital Mortality After Cardiac Operations in Children With Down Syndrome

Children with Down syndrome (DS) have lower mortality compared to nonsyndromic (NS) children after atrioventricular septal defect (AVSD) repair. Limited data exist regarding hospital mortality and utilization after other congenital heart disease (CHD) operations in DS. We compared hospital mortality and utilization after CHD operations in both populations and hypothesized that the survival benefit in children with DS is not consistent across CHD lesions. The Texas Inpatient Public Use Datafile was queried for all patients <18 years old undergoing operations for CHD between 1999 and 2016. Hospital mortality, length-of-stay and charges were compared between DS and NS groups, stratified by CHD operation using mixed-effects multivariable analyses and propensity score matching analyses adjusting for prematurity, low birth weight, age, and sex. Over the 18-year period, 2841 cases with DS underwent CHD operations compared to 25,063 NS cases. The most common types of interventions performed in DS were AVSD repair, isolated ventricular septal defect (VSD) repair and tetralogy of Fallot (TOF) repair. By multivariable analyses, DS was associated with lower mortality after isolated AVSD repair (RR 0.40 [IQR 0.20-0.79]), and higher hospital mortality after bidirectional Glenn anastomosis (BDG) (RR 5.17 [IQR 2.10-12.77]) and TOF/pulmonary atresia repair (RR 9.71 [IQR 2.16-43.68]) compared to NS children. Similar results were noted using propensity score matching. Children with DS had lower mortality after AVSD repair than NS children, but higher mortality after operations for BDG and TOF/pulmonary atresia. Further study is needed to determine if the presence of pulmonary hypertension in DS modifies the association between DS and mortality depending on cardiac lesion.

Impact of pulmonary vein isolation on mechanisms sustaining persistent atrial fibrillation: Predicting the acute response

BACKGROUND

Noninvasive mapping identifies potential drivers (PDs) in atrial fibrillation (AF). We analyzed the impact of pulmonary vein isolation (PVI) on PDs and whether baseline PD pattern predicted termination of AF.

METHODS

Patients with persistent AF less than 2 years underwent electrocardiographic imaging mapping before and after cryoballoon PVI. We recorded the number of PD occurrences, characteristics (rotational wavefronts ≥ 1.5 revolutions or focal activations), and distribution using an 18-segment atrial model.

RESULTS

Of 100 patients recruited, PVI terminated AF in 15 patients; 21.3% ± 9.1% (8.7 ± 4.8) of PDs occurred at the pulmonary veins (PVs) and posterior wall. PVI had no impact on PD occurrences outside the PVs and posterior wall (33.2 ± 12.9 vs 31.6 ± 12.5; P = .164), distribution over the remaining 13 segments (9 [8-11] vs 9 [8-10]; P = .634), the proportion of PDs that was rotational (82.9% ± 9.7% vs 83.6% ± 10.1%; P = .496), or temporal stability (2.4 ± 0.4 vs 2.4 ± 0.5 rotations; P = .541). Fewer focal PDs (area under the curve, 0.683; 95% CI, 0.528-0.839; P = .024) but not rotational PDs (P = .626) predicted AF termination with PVI.

CONCLUSIONS

PVI did not have a global impact on PDs outside the PVs and posterior wall. Although fewer focal PDs predicted termination of AF with PVI, the burden of rotational PDs did not. It is accepted though not all PDs are necessarily real or important. Outcome data are needed to confirm whether noninvasive mapping can predict patients likely to respond to PVI.

Drug-Eluting Stents Compared With Bare Metal Stents for Stenting the Ductus Arteriosus in Infants With Ductal-Dependent Pulmonary Blood Flow

There have been no clinical studies evaluating the use of drug-eluting stents (DES) versus bare metal stents (BMS) for infants who underwent ductus arteriosus (DA) stent placement for ductal-dependent pulmonary blood flow (PBF). We aimed to compare the use of second-generation (fluoropolymer-coated everolimus) DES to BMS in infants who underwent DA stenting for ductal-dependent PBF. A retrospective study of infants who underwent DA stenting for ductal-dependent PBF from January 2004 to March 2018 at a single tertiary care pediatric hospital was performed. Of 94 infants identified, 71 (46 BMS and 25 DES) met inclusion criteria. Baseline characteristics of the DES and BMS cohorts were comparable. The patent lumen to stent diameter on subsequent angiographic evaluation was 81% in DES as compared with 50% in BMS group; p = 0.01. There were 2 deaths early in our experience, both in the BMS group. Unplanned reinterventions were less in the DES group (3, 12% patients) compared with the BMS group (13, 28%), p = 0.03. Pulmonary artery size as assessed using Nakata and pulmonary artery symmetry index was comparable in both the groups. There was no difference in infection rates between the groups. On multivariate analysis, prematurity, BMS, and lower oxygen saturations at discharge were associated with subsequent unplanned reintervention (p = 0.01, 0.03 and 0.03, respectively). In conclusion, our clinical experience suggests that in infants who underwent DA stenting for ductal-dependent PBF, (fluoropolymer-coated everolimus eluting) DES results in less luminal loss and lower unplanned reintervention for cyanosis as compared with BMS implantation.

Transposition of the great arteries: When echocardiography does not match the clinical picture

Aortopulmonary window (APW) is a rare form of congenital heart disease seen in isolation or with complex cardiac lesions. APW has been associated with other cardiac defects such as interrupted aortic arch and Tetralogy of Fallot, but few cases have been reported of APW associated with transposition of the great arteries (TGA). In a newborn with TGA and intact ventricular septum, diagnosis of APW requires a high index of suspicion. This article reviews the literature on TGA with APW and illustrates the importance of additional evaluation in neonates with TGA when oxygen saturation and PaO2 do not match predicted clinical values.

Predictive value of oxygenation index for outcomes in left-sided congenital diaphragmatic hernia

BACKGROUND & OBJECTIVES

Congenital Diaphragmatic Hernia (CDH) is associated with significant morbidity and mortality. This study compares the efficacy of the highest oxygenation index in the first 48 h (HiOI) versus current prenatal indices to predict survival and morbidity.

METHODS

Medical records of 50 prenatally diagnosed, isolated, left-sided CDH patients treated from January 2011 to April 2016 were reviewed. Data abstracted included HiOI, lung to head ratio (LHR), observed to expected total fetal lung volume (O/E TFLV), percent liver herniation (%LH), 6 month survival, respiratory support at discharge, ventilator days and length of stay. Data were analyzed using parametric and nonparametric tests and regression analyses as appropriate.

RESULTS

HiOI was associated with significantly increased LOS (p<0.001), respiratory support at discharge (p<0.001), greater ventilator days (p=0.001) and higher odds of death (p=0.004) with risk of death increasing by 5% for every one-unit increase in OI. HiOI was statistically a better predictor of LOS than O/E TFLV (p=0.007) and %LH (p=0.02).

CONCLUSIONS

In isolated, left-sided CDH patients, HiOI is associated with higher mortality, greater length of stay, more ventilator days and increased respiratory support at discharge. HiOI is a better predictor of length of stay than O/E TFLV and %LH.

TYPE OF STUDY

Retrospective Study LEVEL OF EVIDENCE: II.

The impact of fetal endoscopic tracheal occlusion in isolated left-sided congenital diaphragmatic hernia on left-sided cardiac dimensions

OBJECTIVES

Fetal endoscopic tracheal occlusion (FETO) is offered to fetuses with congenital diaphragmatic hernia (CDH) and severe lung hypoplasia to promote lung growth and may secondarily affect left heart growth. The effects of FETO on left heart hypoplasia (LHH) are not described post-CDH repair.

METHODS

A retrospective analysis was performed for fetuses with left-sided CDH who underwent FETO and severity-matched controls from 2007 to 2016 at our institution. Echocardiographic, ultrasound, and MRI data were reviewed. Left heart dimensions were assessed prenatally and postnatally. Primary clinical outcome evaluated was death.

RESULTS

Twelve FETO patients and 18 controls were identified. Fetal LHH was noted in both groups and worsened after FETO. Postnatal mitral valve dimensions were larger in the FETO group pre-CDH repair (P = .03). Post-CDH repair, mitral valve and left ventricular dimensions were not significantly different between groups (P = .79 and P = .63 respectively) while FETO aortic valve dimensions were smaller (P = .04). Extracorporeal membrane oxygenation use was lower in the FETO group. No associations were found between left heart dimensions and outcomes.

CONCLUSION

Although increased lung growth was seen after FETO, fetal LHH persisted with relative normalization seen post-repair. Persistent LHH post-FETO could be secondary to a small contribution of pulmonary venous return to the fetal left heart and increased intrathoracic pressures post-FETO.

Fetal left-sided cardiac structural dimensions in left-sided congenital diaphragmatic hernia - association with severity and impact on postnatal outcomes

OBJECTIVES

Fetuses with congenital diaphragmatic hernia (CDH) demonstrate varying degrees of left heart hypoplasia. Our study assesses the relationship between fetal left-sided cardiac structural dimensions, lung size, percentage liver herniation, lung-to-head ratio, postnatal left-sided cardiac structural dimensions, and postnatal outcomes.

METHODS

We performed a retrospective cohort study of fetuses with left-sided CDH who had prenatal echocardiographic, ultrasound, and magnetic resonance imaging examinations at our institution between January 2007 and March 2015. Postnatal outcomes assessed include use of inhaled nitric oxide (iNO), use of extracorporeal membrane oxygenation, and death.

RESULTS

Fifty-two fetuses with isolated left-sided CDH were included. Multivariate logistic regression models indicated that smaller fetal aortic valve z-score was associated with postnatal use of iNO (p = 0.03). Fetal mitral valve z-score correlated with lung-to-head ratio (p = 0.04), postnatal mitral valve z-score correlated with percent liver herniation (p = 0.03), and postnatal left ventricular end-diastolic dimension z-score correlated with liver herniation <20% (p = 0.04).

CONCLUSION

We identified associations between smaller fetal left-sided cardiac structural dimensions and classic CDH indices. Smaller aortic valve z-score was associated with iNO use; however, left heart dimensions showed no association with extracorporeal membrane oxygenation or mortality. Further study into the impact of left-sided hypoplasia on outcomes in CDH is worthy of evaluation in a larger, prospective study. © 2017 John Wiley & Sons, Ltd.

Analysis of pulmonary non-tuberculous mycobacterial infections after lung transplantation

PURPOSE

Non-tuberculous mycobacteria (NTM) are important pathogens in lung transplant recipients. This study describes the spectrum of NTM respiratory tract infections and examines the association of NTM infections with lung transplant complications.

METHODS

Data from 208 recipients transplanted from November 1990 to November 2005 were analyzed. Follow-up data were available to November 2010. Lung infection was defined by bronchoalveolar lavage, sputum, or blood cultures in the appropriate clinical setting. All identified NTM respiratory tract infections were tabulated. The cohort of patients with NTM lung infections (NTM+) were compared to the cohort without infection (NTM-). Univariate and multivariate analysis was performed to determine characteristics associated with NTM infection. Survival analyses for overall survival and development of bronchiolitis obliterans syndrome (BOS) were also performed.

RESULTS

In total, 52 isolates of NTM lung infection were identified in 30 patients. The isolates included Mycobacterium abscessus (46%), Mycobacterium avium complex (MAC) (36%), Mycobacterium gordonae (9%), Mycobacterium chelonae (7%), and Mycobacterium fortuitum (2%), with multiple NTM isolates seen on 3 different occasions. The overall incidence was 14%, whereas cumulative incidences at 1, 3, and 5 years after lung transplantation were 11%, 15%, and 20%, respectively. Comparisons between the NTM+ and NTM- cohorts revealed that NTM+ patients were more likely to be African-American and have cytomegalovirus mismatch. Although no difference was seen in survival, the NTM+ cohort was more likely to develop BOS (80% vs. 58%, P = 0.02). NTM+ infection, however, was not independently associated with development of BOS by multivariate analysis.

CONCLUSION

With nearly 20 years of follow-up, 14% of lung recipients develop NTM respiratory tract infections, with M. abscessus and MAC more commonly identified. M. gordonae was considered responsible for nearly 10% of NTM infections. Although survival of patients with NTM infections is similar, a striking difference in BOS rates is present in the NTM+ and NTM- groups.

Solid-substrate bioprocessing of cow dung for the production of carboxymethyl cellulase by Bacillus halodurans IND18

The production of carboxymethyl cellulase (CMCase) by Bacillus halodurans IND18 under solid substrate fermentation (SSF) using cow dung was optimized through two level full factorial design and second order response surface methodology (RSM). The central composite design (CCD) was employed to optimize the vital fermentation parameters, such as pH of the substrate, concentration of nitrogen source (peptone) and ion (sodium dihydrogen phosphate) sources in medium for achieving higher enzyme production. The optimum medium composition was found to be 1.46% (w/w) peptone, 0.095% (w/w) sodium dihydrogen phosphate and pH 8.0. The model prediction of 4210IU/g enzyme activity at optimum conditions was verified experimentally as 4140IU/g. The enzyme was active over a broad temperature range (40-60±1°C) and pH (7.0-9.0) with maximal activity at 60±1°C and pH 8.0. This study demonstrated the potential of cow dung as novel substrate for CMCase production.

Screening of agro-industrial wastes for citric acid bioproduction by Aspergillus niger NRRL 2001 through solid state fermentation

BACKGROUND

The citric acid (CA) industry is currently struggling to develop a sustainable and economical process owing to high substrate and energy costs. Increasing interest in the replacement of costly synthetic substrates by renewable waste biomass has fostered research on agro-industrial wastes and screening of raw materials for economical CA production. The food-processing industry generates substantial quantities of waste biomass that could be used as a valuable low-cost fermentation substrate. The present study evaluated the potential of different agro-industrial wastes, namely apple pomace (AP), brewer's spent grain, citrus waste and sphagnum peat moss, as substrates for solid state CA production using Aspergillus niger NRRL 2001.

RESULTS

Among the four substrates, AP resulted in highest CA production of 61.06 ± 1.9 g kg(-1) dry substrate (DS) after a 72 h incubation period. Based on the screening studies, AP was selected for optimisation studies through response surface methodology (RSM). Maximum CA production of 312.32 g kg(-1) DS was achieved at 75% (v/w) moisture and 3% (v/w) methanol after a 144 h incubation period. The validation of RSM-optimised parameters in plastic trays resulted in maximum CA production of 364.4 ± 4.50 g kg(-1) DS after a 120 h incubation period.

CONCLUSION

The study demonstrated the potential of AP as a cheap substrate for higher CA production. This study contributes to knowledge about the future application of carbon rich agro-industrial wastes for their value addition to CA. It also offers economic and environmental benefits over traditional ways used to dispose off agro-industrial wastes.

Breast MR Imaging: What the Radiologist Needs to Know

Magnetic resonance imaging (MRI) of the breast is being performed more frequently to improve primary and recurrent tumor detection, characterization, and response to therapy. Sensitivity of this test approaches 90% and the specificity ranges from 37% to 100%. We present a concise tutorial for the general radiologist with a pictorial review of common lesions identified with breast MRI.

Enhanced solid-state citric acid bio-production using apple pomace waste through surface response methodology

AIMS

  To evaluate the potential of apple pomace (AP) supplemented with rice husk for hyper citric acid production through solid-state fermentation by Aspergillus niger NRRL-567. Optimization of two key parameters, such as moisture content and inducer (ethanol and methanol) concentration was carried out by response surface methodology.

METHODS AND RESULTS

  In this study, the effect of two crucial process parameters for solid-state citric acid fermentation by A. niger using AP waste supplemented with rice husk were thoroughly investigated in Erlenmeyer flasks through response surface methodology. Moisture and methanol had significant positive effect on citric acid production by A. niger grown on AP (P < 0·05). Higher values of citric acid on AP by A. niger (342·41gkg(-1) and 248·42gkg(-1) dry substrate) were obtained with 75% (v/w) moisture along with two inducers [3% (v/w) methanol and 3% (v/w) ethanol] with fermentation efficiency of 93·90% and 66·42%, respectively depending upon the total carbon utilized after 144h of incubation period. With the same optimized parameters, conventional tray fermentation was conducted. The citric acid concentration of 187·96gkg(-1) dry substrate with 3% (v/w) ethanol and 303·34gkg(-1) dry substrate with 3% (v/w) methanol were achieved representing fermentation efficiency of 50·80% and 82·89% in tray fermentation depending upon carbon utilization after 120h of incubation period.

CONCLUSIONS

  Apple pomace proved to be the promising substrate for the hyper production of citric acid through solid-state tray fermentation, which is an economical technique and does not require any sophisticated instrumentation.

SIGNIFICANCE AND IMPACT OF THE STUDY

  The study established that the utilization of agro-industrial wastes have positive repercussions on the economy and will help to meet the increasing demands of citric acid and moreover will help to alleviate the environmental problems resulting from the disposal of agro-industrial wastes.

Clostridium difficile colitis in lung transplantation

PURPOSE

Clostridium difficile colitis (CDC) is the most common nosocomial infection of the gastrointestinal tract in patients with recent antibiotic use or hospitalization. Lung transplant recipients receive aggressive antimicrobial therapy postoperatively for treatment and prophylaxis of respiratory infections. This report describes the epidemiology of CDC in lung recipients from a single center and explores possible associations with bronchiolitis obliterans syndrome (BOS), a surrogate marker of chronic rejection.

METHODS

Patients were divided into those with confirmed disease (CDC+) and those without disease (CDC-) based on positive C. difficile toxin assay. Because of a bimodal distribution in the time to develop CDC, the early postoperative CDC+ group was analyzed separately from the late postoperative CDC+ cohort with respect to BOS development.

RESULTS

Between 1990 and 2005, 202 consecutive patients underwent 208 lung transplantation procedures. Of these, 15 lung recipients developed 23 episodes of CDC with a median follow-up period of 2.7 years (range, 0-13.6). All patients with confirmed disease had at least 1 of the following 3 risk factors: recent antibiotic use, recent hospitalization, or augmentation of steroid dosage. Of the early CDC+ patients, 100% developed BOS, but only 52% of the late CDC+ patients developed BOS, either preceding or following infection.

CONCLUSION

CDC developed in 7.4% of lung transplant patients with identified risk factors, yielding a cumulative incidence of 14.7%. The statistical association of BOS development in early CDC+ patients suggests a relationship between early infections and future chronic lung rejection.

Effects of Short-Term Training on Sensory and Motor Function in Severed Nerves of Long-Term Human Amputees

Much has been studied and written about plastic changes in the CNS of humans triggered by events such as limb amputation. However, little is known about the extent to which the original pathways retain residual function after peripheral amputation. Our earlier, acute study on long-term amputees indicated that central pathways associated with amputated peripheral nerves retain at least some sensory and motor function. The purpose of the present study was to determine if these functional connections would be strengthened or improved with experience and training over several days time. To do this, electrodes were implanted within fascicles of severed nerves of long-term human amputees to evaluate the changes in electrically evoked sensations and volitional motor neuron activity associated with attempted phantom limb movements. Nerve stimulation consistently resulted in discrete, unitary, graded sensations of touch/pressure and joint-position sense. There was no significant change in the values of stimulation parameters required to produce these sensations over time. Similarly, while the amputees were able to improve volitional control of motor neuron activity, the rate and pattern of change was similar to that seen with practice in normal individuals on motor tasks. We conclude that the central plasticity seen after amputation is most likely primarily due to unmasking, rather than replacement, of existing synaptic connections. These results also have implications for neural control of prosthetic limbs.

Acute peripheral nerve recording characteristics of polymer-based longitudinal intrafascicular electrodes

We examined the recording characteristics of two different types of polymer-based longitudinal intrafascicular electrodes (LIFEs) in peripheral nerve: single-stranded (s-polyLIFEs) and multistranded (m-polyLIFEs). Recordings were also made from Pt-Ir wire-based electrodes (PtIrLIFEs) as a control. The electrodes were implanted in either tibial or medial gastrocnemius branches of the rabbit sciatic nerve, and in the sciatic nerve of rats. Recorded neural activity induced by manually elicited afferent neural activity showed that both polyLIFE versions performed comparably to PtIrLIFEs.

Residual function in peripheral nerve stumps of amputees: implications for neural control of artificial limbs

PURPOSE

It is not known whether motor and sensory pathways associated with a missing or denervated limb remain functionally intact over periods of many months or years after amputation or chronic peripheral nerve transection injury. We examined the extent to which activity on chronically severed motor nerve fibers could be controlled by human amputees and whether distally referred tactile and proprioceptive sensations could be induced by stimulation of sensory axons in the nerve stumps.

METHODS

Amputees undergoing elective stump procedures were invited to participate in this study. Longitudinal intrafascicular electrodes were threaded percutaneously and implanted in severed nerves of human amputees. The electrodes were interfaced to an amplifier and stimulator system controlled by a laptop computer. Electrophysiologic tests were conducted for 2 consecutive days after recovery from the surgery.

RESULTS

It was possible to record volitional motor nerve activity uniquely associated with missing limb movements. Electrical stimulation through the implanted electrodes elicited discrete, unitary, graded sensations of touch, joint movement, and position, referring to the missing limb.

CONCLUSIONS

These findings indicate that both central and peripheral motor and somatosensory pathways retain significant residual connectivity and function for many years after limb amputation. This implies that peripheral nerve interfaces could be used to provide amputees with prosthetic limbs that have more natural feel and control than is possible with current myoelectric and body-powered control systems.

Fabrication and characteristics of an implantable, polymer-based, intrafascicular electrode

We describe new manufacturing techniques and physical properties of an improved polymer-based longitudinal intrafascicular electrode (polyLIFE). Modifications were made to correct: (1) poor metal film adhesion and fatigue resistance, (2) inconsistent insulation adhesion and control over recording/stimulation zone length, and (3) insufficient tensile strength for clinical use. Metal adhesion was significantly improved by both plasma treatment and fiber rotation (about the long axis) during metal deposition. Fatigue resistance was improved by reduction in sputtering energy (time x power) combined with long axis rotation, resulting in thin metal films that were 250 times more resistant to cyclic bending fatigue. Insulation adhesion was enhanced with the application of an adhesion-promoting silicone (MED2-4013, Nusil), while the recording/stimulation zone length was controlled to 1 +/- 0.2mm (mean +/- S.D.). The polyLIFE was made more robust by the inclusion of three individually metallized fibers, improving its tensile strength by a factor of 4 while producing minimal changes to its overall stiffness. However, the metallized fiber redundancy did not significantly affect fatigue resistance. The manufacturing changes described in this study enable the construction of more mechanically robust polyLIFEs, which should provide greater success when chronically implanted in peripheral nerves.

Implementation of the STOP protocol for Stroke Prevention in Sickle Cell Anemia by using duplex power Doppler imaging

PURPOSE

To compare the results of the nonduplex ultrasonography (US) Stroke Prevention Trial in Sickle Cell Anemia (STOP) with those of transcranial duplex power Doppler US by using the STOP protocol and to correlate abnormal transcranial Doppler findings with magnetic resonance (MR) imaging and MR angiographic findings.

MATERIALS AND METHODS

One hundred twenty-five asymptomatic patients aged 2-16 years with sickle cell anemia or sickle cell-beta thalassemia were examined by using transcranial duplex power Doppler US with a 2.5-MHz transducer and classified according to STOP criteria. The results were compared with those obtained in the nonduplex STOP study. Eight of 10 patients with abnormal results, as well as one who had normal results and a subsequent stroke, were examined with MR imaging and MR angiography.

RESULTS

Ten (8.0%) patients were judged to have abnormal findings by using the duplex Doppler US and STOP criteria compared with 9.4% of patients in the nonduplex US STOP study. Of the eight patients with abnormal transcranial Doppler US results who underwent MR imaging and MR angiography, six had abnormal MR imaging findings and all eight had abnormal MR angiographic findings.

CONCLUSION

The STOP protocol can be reproduced by using duplex power Doppler US. Abnormal results with the STOP criteria strongly suggest vascular abnormality.

What's new in the treatment of cerebrovascular disease?: an endovascular perspective

Surgical therapy currently allows for the correction of many pathologic conditions affecting the vasculature of the central nervous system. Recent advances in technology have given the cerebrovascular specialist further options in the minimally invasive sphere. Endovascular techniques, complimentary to surgery in some conditions, are poised to replace conventional open surgery in others. A review of current interventional radiological procedures for the treatment and prevention of ischemic and hemorrhagic stroke are herewith presented.

Evidence that metabolically active synaptosomes lack functional cyclic AMP-dependent protein kinase

Cyclic adenosine monophosphate (cAMP)-mediated signal transduction was evaluated in synaptosomes prepared from rat brain cortex. Adenylate cyclase was responsive to known adenylate cyclase stimulators including peptides (CRH and VIP), catecholamines (norepinephrine and isoproterenol) and ligands that directly stimulate adenylate cyclase (forskolin). Cyclic AMP accumulation also increased approximately 2 to 3-fold, but none of the agonists was able significantly to activate cyclic AMP-dependent protein kinase (A-kinase) in cortical synaptosomes. However, in parallel studies with slices prepared from rat brain cortex, adenylate cyclase activity, cAMP accumulation and A-kinase activity were all stimulated by CRH, VIP, norepinephrine, isoproterenol and forskolin. These data suggest that, in intact synaptosomes, either the cellular machinery which facilitates binding of cAMP to the regulatory subunit of A-kinase is missing or the cAMP produced by adenylate cyclase is not accessible to A-kinase.

Effects of adrenalectomy on CRH regulation of ACTH release: adenylate cyclase activity, cyclic AMP-dependent protein kinase activity and ACTH release

Corticotropin releasing hormone (CRH) stimulation of ACTH release and cyclic AMP-mediated events involved in the control of ACTH release were compared in sham-operated and adrenalectomized rats. CRH-stimulated adenylate cyclase activity was decreased in pituitary homogenates from adrenalectomized animals. CRH-stimulated cyclic AMP accumulation was essentially abolished and CRH-stimulated cyclic AMP-dependent protein kinase (A-kinase) activity was decreased in freshly prepared anterior pituitary cells from adrenalectomized animals. Basal and CRH-stimulated ACTH release was elevated in these cells. Since ACTH release is increased in adrenalectomized rats despite the down regulation of CRH-linked pituitary mechanisms, we speculate that the site of action of disinhibition by corticosterone of ACTH release (or synthesis) following adrenalectomy is distal to the generation of cyclic AMP and/or that non-CRH mediated mechanisms assume a greater role in ACTH regulation following adrenalectomy.

Neuroendocrine correlates of sustained stress: the activity-stress paradigm

Rats sacrificed after 4 days in the activity-stress paradigm or after 4 days of food restriction had significantly elevated levels of plasma corticosterone as compared to control rats. The approximately 5 fold increase in corticosterone in the stressed treatment groups was consistently found in all experiments. ACTH levels were elevated in activity-stress and food-restricted groups in some experiments but these increases were not statistically significant. Prolactin levels were significantly elevated in food-restricted group rats as compared to controls or activity-stress group animals in one experiment but this finding was not repeated in further experiments. In a second series of experiments, rats from activity-stressed and food-restricted treatment groups and controls were exposed to an acute stressor for 15 min prior to sacrifice to assess the effects of prior sustained stress on hormonal responses to an acute stressor. Exposure to 15 min of immobilization or intermittent footshock immediately prior to sacrifice increased plasma levels of corticosterone, ACTH and prolactin in control, food-restricted and activity-stressed rats. Generally, hormonal responses to the acute stress were similar in all treatment groups. However, in two experiments where the resting levels of corticosterone were especially elevated in the activity-stress group, the acute stress-induced rise in corticosterone was less than that seen for the other two treatment groups. In another experiment, administration of dexamethasone suppressed acute stress-evoked levels of ACTH and corticosterone in control, activity-stressed and food-restricted rats. Thus, rats exposed to 4 days of sustained stress were found to have consistently elevated resting levels of corticosterone.(ABSTRACT TRUNCATED AT 250 WORDS)

cAMP-dependent protein kinase and lipolysis in rat adipocytes. III. Multiple modes of insulin regulation of lipolysis and regulation of insulin responses by adenylate cyclase regulators

The relationship between cAMP-dependent protein kinase (A-kinase) activity ratios and lipolysis in the presence of insulin was compared to the standard relationship between these two parameters established with a variety of adenylate cyclase modulators (Honnor, R. C., Dhillon, G., and Londos, C. (1985) J. Biol. Chem. 260, 15130-15138). Three phases of insulin action were observed. First, when tested in control cells exhibiting A-kinase activity ratios up to approximately 0.25, insulin inhibition of lipolysis could be accounted for by the decrease in A-kinase activity. Second, in cells exhibiting A-kinase activity ratios greater than 0.3, the decrease in kinase activity by insulin did not account for the decrease in lipolysis. Finally, as the A-kinase activity ratio approached 0.6 the insulin effect on lipolysis was lost. The data suggest that protein phosphatase activation accounts for the cAMP-independent insulin action. Moreover, the insulin effect not accounted for by a decrease in A-kinase activity appears to be elicited only upon elevation of A-kinase activity. The method by which cells were stimulated determined the IC50 for insulin inhibition of: 1) A-kinase activity ratios, 2) lipolysis explained by the decrease in A-kinase activity ratios, and 3) lipolysis not explained by a decrease in A-kinase activity ratios. For all three parameters, cells stimulated by lipolytic hormones were approximately 5 times more sensitive to insulin than cells stimulated by incubation in a ligand-free environment achieved with adenosine deaminase; insulin IC50 values were approximately 120 and 600 pM, respectively. Such data establish a link between insulin actions in modifying cAMP concentrations and in modifying events apparently independent of changes in cAMP. It is proposed that the receptors and regulatory components associated with adipocyte adenylate cyclase are associated also with components of the insulin response system separate from cyclase.

cAMP-dependent protein kinase and lipolysis in rat adipocytes. I. Cell preparation, manipulation, and predictability in behavior

With the use of -cAMP/+cAMP activity ratios of cAMP-dependent protein kinase (A-kinase) in fat cell extracts as an index of cellular cAMP concentrations, it is apparent from both the current literature and from data presented in this paper that classical cell isolation procedures yield cells whose behavior is unpredictable from day to day. Herein, procedures are described for isolating adipocytes, preparing cytosolic extracts, and assaying A-kinase that result in kinase activity ratios in isolated cells equal to those in the fat pad from which cells are derived, approximately 0.05. An important modification in the procedure is the inclusion of 200 nM exogenous Ado in all cell manipulation media, and the data indicate that variable removal of contaminating endogenous Ado accounts for unpredictable results with standard cell isolation techniques. A further benefit of Ado inclusion is greatly reduced cell lysis. Acute removal of Ado with adenosine deaminase results in rapid elevation of A-kinase activity ratios and lipolysis which, in fasted animals, equals that achieved with lipolytic hormones. Cells from fed animals exhibit poor predictability in behavior. Moreover, A-kinase activity ratios exhibit seasonal tendencies in response to Ado removal, with cells isolated in spring being more activated than cells isolated later in the year. The information and procedures in this paper form the basis for succeeding papers on the regulation of adipocyte metabolism by hormones.

cAMP-dependent protein kinase and lipolysis in rat adipocytes. II. Definition of steady-state relationship with lipolytic and antilipolytic modulators

The steady-state relationship between the activation state of cAMP-dependent protein kinase (A-kinase) and lipolysis has been defined quantitatively. A-kinase activation was assessed by measuring the ( +/- cAMP) activity ratio in adipocyte extracts, and lipolysis was determined by measuring glycerol release from cells. Both processes were stimulated either by incubating cells in a ligand-free environment achieved with adenosine deaminase or by addition of lipolytic hormones. A response spectrum was obtained with a variety of adenylate cyclase stimulators and inhibitors, both receptor- and nonreceptor-mediated. Regardless of the ligands used to manipulate adipocyte activity, lipolysis varied from nil to maximal as the A-kinase activity ratio varied from approximately 0.05 to 0.3-0.35. These data provide a quantitative description of the steady-state relationship between A-kinase activity and lipolysis and indicate that the various lipolytic and antilipolytic agents tested act on the lipolytic process exclusively by altering adenylate cyclase activity and, thus, cellular cAMP concentrations. The data reveal also that transient "peaking" of cAMP, as measured by A-kinase activity ratios, is not an inherent feature of adipocyte metabolism. Moreover, the concentration requirements for lipolytic hormone action are critically dependent on the ambient concentration of antilipolytic agents, and t concentration requirements for antilipolytic agents are dependent on the extent to which cells are stimulated. The data in this paper provide the basis for assessing the relationship between A-kinase activity ratio and lipolysis in the presence of insulin (Londos, C., Honnor, R. C., and Dhillon, G. S. (1985) J. Biol. Chem. 260, 15139-15145).

Bioconversion of wheat straw and wheat straw components into single-cell protein

Several fungi (Aspergillus niger, A. terreus, Cochliobolus specifer, Myrothecium verrucaria, Rhizoctonia solani, Spicaria fusispora, Penicillium sp., and Gliocladium sp.) were isolated from decomposing wheat straw and tested for their ability to utilize whole straw and its components, holocellulose (hemicellulose and cellulose) and cellulose, for the production of single-cell protein (SCP). It was found that C. specifer was the most efficient fungus for protein synthesis with the three substrates. Using potassium nitrate as N source in mixtures of 0.04 g N/g substrate (0.04% wt./vol.) at pH 4.5, it was found that incubation periods of 3, 4, and 5 days were optimal for protein production on cellulose and holocellulose fractions, and whole straw, respectively. Whole native straw was found to be the most recalcitrant to bioconversion into SCP; however, protein production was almost doubled when the lignin component was removed using a mixture of sodium chlorite and acetic acid.