Dust grains fall from Saturn's D-ring into its equatorial upper atmosphere.

The sizes of Saturn's ring particles range from meters (boulders) to nanometers (dust). Determination of the rings' ages depends on loss processes, including the transport of dust into Saturn's atmosphere. During the Grand Finale orbits of the Cassini spacecraft, its instruments measured tiny dust grains that compose the innermost D-ring of Saturn. The nanometer-sized dust experiences collisions with exospheric (upper atmosphere) hydrogen and molecular hydrogen, which forces it to fall from the ring into the ionosphere and lower atmosphere. We used the Magnetospheric Imaging Instrument to detect and characterize this dust transport and also found that diffusion dominates above and near the altitude of peak ionospheric density. This mechanism results in a mass deposition into the equatorial atmosphere of ~5 kilograms per second, constraining the age of the D-ring.

Chemical interactions between Saturn's atmosphere and its rings.

The Pioneer and Voyager spacecraft made close-up measurements of Saturn's ionosphere and upper atmosphere in the 1970s and 1980s that suggested a chemical interaction between the rings and atmosphere. Exploring this interaction provides information on ring composition and the influence on Saturn's atmosphere from infalling material. The Cassini Ion Neutral Mass Spectrometer sampled in situ the region between the D ring and Saturn during the spacecraft's Grand Finale phase. We used these measurements to characterize the atmospheric structure and material influx from the rings. The atmospheric He/H2 ratio is 10 to 16%. Volatile compounds from the rings (methane; carbon monoxide and/or molecular nitrogen), as well as larger organic-bearing grains, are flowing inward at a rate of 4800 to 45,000 kilograms per second.

Herpes simplex encephalitis occurring after chemotherapy, surgery, and stereotactic radiotherapy for medulloblastoma.

Reactivation of latent herpes simplex virus (HSV) in the trigeminal ganglion most commonly gives rise to recurrent herpes labialis and rarely to herpes simplex encephalitis. The mechanisms underlying reactivation of latent trigeminal HSV are complex. Here we report the case history of a 25-year-old woman who developed a fatal, bilateral necrotizing destructive temporal lobe lesion following surgical removal of a cerebellar medulloblastoma and combined radiotherapy and chemotherapy for recurrent tumor. Neuropathologic examination of the brain revealed minimal inflammatory changes, but immunohistochemistry was positive for HSV protein, and HSV deoxyribonucleic acid (DNA) was recovered from formalin-fixed paraffin-embedded brain tissue. The temporal proximity of the surgery, chemotherapy, and radiotherapy to the onset of disease suggests that these factors may have acted as triggers that precipitated conversion of latent HSV to overt HSV.

Microspectrophotometric analysis of respiratory pigments using a novel fibre optic dip probe in microsamples.

A microspectrophotometer system to monitor the reduction of mitochondrial respiratory pigments in cell extracts and permeabilized cells has been developed. The novel optical fibre set-up uses visible spectrophotometry to measure the reduction of mitochondrial electron carriers. The basis of the system is an Ocean Optics S1000 spectrometer, a broadband tungsten based light source, input and output coupling fibre optics and a fibre optic dip-probe which requires less than 20 microl of sample for analysis. The spectral range of the system is from 250 to 850 nm with a spectral resolution of 0.5 nm. Data are presented for the reduction of purified cytochrome c by the reducing agent sodium dithionite and the reduction of cytochrome c by isolated mitochondria using sodium succinate as substrate. Reduction of cytochrome c by digitonin permeabilized cultured mouse cells, C2C12, is also shown. The effect of temperature on cytochrome c reduction in these assays is also demonstrated. The optical design of the probe system is optimized to maintain maximum light throughput and spectral resolution. The key features of the system are small sample size, front-end adaptability, high sensitivity and fast multispectral acquisition which are essential for observing these biological reactions in vivo.

Paired ventricular pacing: an alternative therapy for postoperative junctional ectopic tachycardia in congenital heart disease.

Junctional ectopic tachycardia (JET) is one of the most life-threatening postoperative arrhythmias in children with congenital heart disease, and medical management is difficult. Paired ventricular pacing (PVP) may provide a safe alternative mode of management. We evaluated the safety and efficacy of PVP for the management of postoperative JET in patients with congenital heart disease. A retrospective collection of data was done from 1981-1995. PVP was successfully tried in five postoperative patients (age range: 37 days to 22 years, median: 10 months). Onset of JET was 3-60 hours (mean +/- SD, 19 +/- 23 hours) postoperatively. The maximal JET rate was 261 +/- 39 beats/min. PVP was used as the first line of management in three patients and was successful in all patients. It resulted in an instantaneous increase in blood pressure from 66 +/- 9 to 94 +/- 15 mmHg (42% increase) and was required for 12 +/- 14 hours (range 2-36 hours). No complications were noted. Therefore, in our experience, this is a safe alternative modality for the control of postoperative JET.

The formation of respiratory chain complexes in mitochondria is under the proteolytic control of the m-AAA protease.

Yta10p (Afg3p) and Yta12p (Rcal1p), members of the conserved AAA family of ATPases, are subunits of the mitochondrial m-AAA protease, an inner membrane ATP-dependent metallopeptidase. Deletion of YTA10 or YTA12 impairs degradation of non-assembled inner membrane proteins and assembly of respiratory chain complexes. Mutations of the proteolytic sites in either YTA10 or YTA12 have been shown to inhibit proteolysis of membrane-integrated polypeptides but not the respiratory competence of the cells, suggesting additional activities of Yta10p and Yta12p. Here we demonstrate essential proteolytic functions of the m-AAA protease in the biogenesis of the respiratory chain. Cells harbouring proteolytically inactive forms of both Yta10p and Yta12p are respiratory deficient and exhibit a pleiotropic phenotype similar to Deltayta10 and Deltayta12 cells. They show deficiencies in expression of the intron-containing mitochondrial genes COX1 and COB. Splicing of COX1 and COB transcripts is impaired in mitochondria lacking m-AAA protease, whilst transcription and translation can proceed in the absence of Yta10p or Yta12p. The function of the m-AAA protease appears to be confined to introns encoding mRNA maturases. Our results reveal an overlapping substrate specificity of the subunits of the m-AAA protease and explain the impaired assembly of respiratory chain complexes by defects in expression of intron-containing genes in mitochondria lacking m-AAA protease.

Fetal tissue typing in anticipation of neonatal heart transplantation.

BACKGROUND: Hypoplastic left heart syndrome is among the most common major congenital cardiac anomalies. Fetuses with this anomaly survive but require either reconstructive surgery or heart transplantation postnatally. CASE: A woman whose fetus was diagnosed with hypoplastic left heart syndrome underwent funipuncture for fetal tissue typing. The fetus then was listed for heart transplantation. Once an ABO-compatible donor heart was procured, the fetus was delivered and immediately underwent transplantation. CONCLUSION: In candidates for neonatal heart transplantation, fetal tissue typing allows the search for an ABO-compatible donor heart to begin earlier. This approach minimizes the morbidity associated with postnatal waiting and allows transplantation to take place while the neonate is less immunocompetent.

Atrially based pericardial tunnel for central pulmonary artery construction.

Discontinuity of central intrapericardial pulmonary arteries requires reconstruction of a pulmonary artery confluence before cavopulmonary connection, whether this connection be by bidirectional Glenn or Fontan procedure. Reconstruction of the central pulmonary arteries has previously been described using material of poor or no growth potential. A method is described for central pulmonary artery reconstruction that provides growth potential and is based on previous experience with Fontan lateral tunnel construction.

Rapid safe central venous access in children and adults undergoing open cardiac operations.

A technique is described for percutaneous placement of central venous catheters under direct vision in children and adults undergoing open heart operations. The method is reliable, rapid, and safe, and avoids blind attempts at obtaining vascular access.

Emboli from an extraluminal blood flow hollow fiber oxygenator with and without an arterial filter during cardiopulmonary bypass in a pig model.

The effect of an arterial filter on visceral emboli was quantified with autologous indium-111 labeled platelets (INPLT) during cardiopulmonary bypass (CPB) in Yorkshire pigs. Biodistribution of INPLT was determined in 12 control pigs (30-35 kg, unoperated control [n = 6] and sham operated control [n = 6]). CPB was carried out with (n = 6) and without (n = 6) an arterial filter in 12 pigs at a flow rate of 2.5-3.5 L/min. Platelets labeled with In-111 tropolone (650-780 microCi) were injected intravenously 24 hr before CPB. All pigs were systemically heparinized (activated coagulation time > 400 sec); CPB was instituted with a roller pump, an extraluminal blood flow oxygenator (Bentley Univox, 1.8 m2), and an arterial filter (0.25 m2) and continued for 3 hr. Platelet kinetics, pooling, and counts were monitored by a Geiger probe and a Coulter counter. The thrombi in the oxygenator and arterial filter and emboli in viscera and brain were imaged with a gamma camera and measured with an ion chamber and gamma counter. Percentage of INPLT (mean +/- SD) in organs, tissues, and components of the circuit in four groups of pigs was calculated. Flow cytometry with antibodies to CD61 (GPIIIa) and CD62P (GMP-140: control) of porcine platelets was carried out with blood samples taken before, during, and after CPB for estimation of circulating platelet aggregates and platelet microparticles. Pulmonary, renal, cardiac, and cerebral emboli in pigs undergoing CPB with and without a filter were similar (p < 0.1). The amount of filter adherent thrombi was small (0.04 +/- 0.01%); oxygenator adherent thrombus in both groups was similar (p < 0.1). Emboli were found in the cerebral medulla, hippocampus, and posterior cerebral cortex in both groups. During CPB, the arterial filter functioned minimally as a trap for platelet thrombi detached from the oxygenator and circulating emboli. Flow cytometry of blood demonstrated the shift of equilibria from single platelets to platelet aggregates and microparticles during CPB and their gradual reversal to single platelets after CPB; the loosely adherent emboli disaggregated and further shifted these equilibria to single platelets and smaller aggregates, probably through the action of endogenous nitric oxide and prostacyclin. The emboli were trapped in organs and tissues and microparticles were sequestered by the reticuloendothelial system.

Reduction of neutrophil margination by L-arginine during hypothermic cardiopulmonary bypass in a pig model.

Nitric oxide generation by L-arginine (2 mg/kg/min) infusion during cardiopulmonary bypass (CPB) increases blood flow to all organs and reduces cytokine induced organ damage by reducing the level of marginating neutrophils (Ns). The N-trapping in the oxygenator (OX), arterial filter (AF), cardiotomy reservoir (CR), and N-margination were quantified with indium 111 labeled autologous neutrophils (INN) in nine groups of 40 Yorkshire pigs (30-35 kg). Cardiopulmonary bypass (180 min or 90 min CPB, 90 min reperfusion) was carried out at 2.5-3.5 L/min and at two temperatures (18 degrees C, 28 degrees C). The INN (650-780 microCi) was administered intravenously 15 mins before CPB. All pigs received heparin systemically (activated coagulation time > 400 secs); CPB was instituted with a roller pump, OX (Univox 1.8 m2), AF (0.25 m2), and CR (BCR-3500, Bentley Lab, Irvine, CA). The INN distribution in the device (OX, AF, CR) and organs was imaged with a gamma camera and measured with an ion chamber and a gamma counter. The LA infusion decreased N-trapping, estimated as the percent of injected INN (mean +/- standard deviation), in OX from control (2.7 +/- 2.02)% to (0.94 +/- 0.29)%, and margination in lung from control (48 +/- 4)% to minimal levels (23 +/- 2)% (p < 0.01). In the CPB reperfusion group, a beneficial effect was observed at LA low dose and toxicity of higher N-margination at 15 mg/ kg/min. Neither CPB temperature nor Leumedin affected N-margination significantly.

Identification of a 42-kDa plant mitochondrial outer membrane protein, MOM42, involved in the import of precursor proteins into plant mitochondria.

A 42-kDa plant outer mitochondrial membrane protein, MOM42, has been identified as an essential component of the plant mitochondrial precursor protein translocation apparatus. Immunological cross-reactivity has been detected between antibodies raised against both Neurospora and yeast mitochondrial outer membrane proteins and plant mitochondrial outer membrane proteins. Immunocompetition studies showed that import of precursors to Rieske FeS protein, ATPase su9-DHFR, and the adenine nucleotide transporter was inhibited in the presence of antibody to MOM42. The inhibition of Rieske Fes and su9-DHFR import was greater than that of the adenine nucleotide transporter. The competition studies suggest that the MOM42 is involved in the translocation of bound precursor proteins. The import data and the Western blots suggest that components of the mitochondrial import system are highly conserved.

Surgical treatment for cardiac rhabdomyomas in children.

Cardiac rhabdomyomas are the most common cardiac tumor in children. These tumors may cause obstruction to blood flow, valvular insufficiency, and cardiac arrhythmias. We present two cases of cardiac rhabdomyomas in infants that were managed surgically and review the literature. Without surgical intervention, the prognosis for symptomatic cardiac rhabdomyomas is dismal, with eventual death likely due to heart failure or arrhythmias. As our two cases indicate, surgical treatment may improve this prognosis. Pediatric cardiac rhabdomyomas should be resected when the tumors cause hemodynamic compromise or cardiac arrhythmias.

Choreoathetosis after surgery for congenital heart disease.

Choreoathetosis developed in three patients after cardiopulmonary bypass with hypothermia. None had significant hypotension or hypoxemia; all had hypocapnia and respiratory alkalosis during the rewarming period. We postulate that hypocapnia-induced cerebral vasoconstriction may have contributed to ischemic damage in focal central nervous system areas.

Long-term surgical results in sudden death syndrome associated with cardiac dysfunction after myocardial infarction.

To evaluate the surgical results in patients with inducible ventricular tachyarrhythmias due to coronary disease and left ventricular dysfunction, the authors reviewed their experience in 170 patients who had survived one or more cardiac arrests after myocardial infarction and were unresponsive to drug therapy based on electrophysiologic studies (EPS). There were nine operative deaths (5%). Based on intraoperative EPS, surgical remodeling of left ventricular dysfunction (aneurysm resection, infarct debulking, and septal reinforcement) with map-guided cryoablation and coronary artery bypass graft was performed in 34 patients (group A), and left ventricular remodeling and coronary artery bypass graft without guided endocardial resection was performed in 25 patients (group B). Forty-three patients (group C) had coronary artery bypass graft with implantation of an automatic implantable cardioverter defibrillator (AICD). Group D (68 patients) received AICD only. After operation, based on EPS results, four patients in group A (12%) and three patients in Group B (15%) required AICD implantation. Overall survival at 6 years was 65%, 48%, 85%, and 58% in patient groups A, B, C, and D, respectively (p = not significant). During follow-up in group A patients, none died suddenly and none needed AICD. In group B, two patients required AICD 3 and 5 years later, and five patients died suddenly. The incidence of sudden death was 2.3%/patient/year and 3.5%/patient/year after AICD implantation (groups C and D). At 6 years, cardiac-event-free survival was 80% and 70% for groups A and B and 38% and 24% for groups C and D, respectively (p less than 0.001). Patients receiving map-guided ablative procedures had significantly improved cardiac-event-free survival rates.

Aneurysm of the right ventricular outflow tract: a complication of aorta-main pulmonary (central) shunt.

The ascending aorta-main pulmonary artery (central) polytetrafluoroethylene (PTFE) Gore-Tex shunt was introduced in 1975 by Gazzaniga and coworker. It is a widely used palliative procedure. We present a case study with an unusual late complication. An aneurysm was discovered at autopsy in a patient who was diagnosed at birth with hypoplastic right ventricle, pulmonary valve atresia, small main and branched pulmonary arteries. At 4 days of age, the patient underwent an aorta to main pulmonary artery (PTFE) Gore-Tex shunt. Subsequent echocardiogram showed dilatation of the right ventricular outflow tract. To our knowledge, this is the first reported case of right ventricular outflow tract (RVOT) aneurysm following central aortopulmonary shunt.

Bull-worker syncope: congenital subclavian steal syndrome following isometric exercise.

A patient with congenital great artery abnormality facilitating subclavian steal is presented. Sustained isometric upper body exercise, using a "Bull-Worker," resulted in vertebrobasilar steal symptoms (subclavian steal syndrome) shortly after exercise. A mechanism for the timing of symptoms following isometric exercise is suggested.