A sporadic third layer in the ionosphere of Mars.

The daytime martian ionosphere has been observed as a two-layer structure with electron densities that peak at altitudes between about 110 and 130 kilometers. The Mars Express Orbiter Radio Science Experiment on the European Mars Express spacecraft observed, in 10 out of 120 electron density profiles, a third ionospheric layer at altitude ranges of 65 to 110 kilometers, where electron densities, on average, peaked at 0.8 x 10(10) per cubic meter. Such a layer has been predicted to be permanent and continuous. Its origin has been attributed to ablation of meteors and charge exchange of magnesium and iron. Our observations imply that this layer is present sporadically and locally.

Performance standards: piece of cake or pie in the sky?

BACKGROUND: Centrally mandated levels of performance are now common in the Veterans Health Administration. Performance standards for ambulatory procedures were developed based on HCFA data. The 11 procedures to be measured were arthroscopy, breast biopsy, eyelid procedures, lens/cataracts, bronchoscopy, endoscopy, colonoscopy, hernia repair, cystoscopy, laparoscopy, and cardiac catheterization. Were the performance standards for ambulatory procedures reasonable and achievable in a tertiary care VA? METHODS: Ambulatory procedure performance standards for the 11 selected procedures were evaluated for Fiscal Year 1998 at one tertiary care VA and at each of the 22 Veteran's Integrated Service Networks (VISNs). Further review was undertaken for those procedures in which performance was below the fully successful level. This included chart reviews at the tertiary care VA and analysis of caseloads by VISN. Descriptive statistics were used as well as Student's t test to analyze the difference in means. RESULTS: The tertiary care VA performed at the fully successful level for 6 procedures and at the exceptional level for 3 procedures. Performance levels for bronchoscopy and laparoscopy were below the preset goals. At the VISN level, 8 VISNs performed at the fully successful/exceptional level for all 11 procedures. The remaining 14 were deficient in 1 to 4 procedures. Eight of the VISNs were deficient in 2 or 3 procedures. Six VISNs were deficient in laparoscopy. CONCLUSIONS: The majority of centrally mandated performance standards appear to be reasonable and achievable. One notable exception is laparoscopy. Surgeons should understand how performance standards are calculated at their institution and review the data carefully for any systematic errors. Underperformance can be used as an opportunity to improve both data collection and outcomes.

Using the Veterans Administration National Surgical Quality Improvement Program to improve patient outcomes.

BACKGROUND: The primary goal of collecting quality assurance data is to ultimately improve patient care. The VA National Surgical Quality Improvement Program (NSQIP) provides each station with risk-adjusted morbidity and mortality data on a regular basis. This report of one medical center's use of the risk-adjusted data shows how it can be used to improve patient care. MATERIALS AND METHODS: Risk-adjusted surgical outcome data for Fiscal Year 1996 (FY96) was received from the NSQIP coordinating center. The Salt Lake City VA medical center was identified as a high outlier for morbidity in general surgery. Patient charts were reviewed and data analyzed to determine practice patterns and to determine if there were any provider issues. Data analysis revealed a large number of wound complications and uncovered a practice pattern of closure of contaminated wounds. Using these data and data from the literature, wound infection and disruption prevention protocols were instituted in the fall of 1997. Wound complications from January to December 1996 (preprotocol) and January to December 1998 (postprotocol) were compared using Student's t test. RESULTS: The total number of operations in 1998 was 719 compared with 634 in 1996. Superficial wound infections dropped from 3.6 to 1.7%, while overall wound complications dropped from 5.5 to 2.9%. None of these changes were statistically significant. CONCLUSIONS: Although introduction of wound infection and disruption prevention protocols did not result in a statistically significant decrease in wound complication, it did result in a clinically significant improvement in patient care.

Identification of a mutation cluster in mevalonate kinase deficiency, including a new mutation in a patient of Mennonite ancestry.

Mevalonate kinase (MKase) deficiency (MKD) is a rare autosomal recessive disorder in the pathway of cholesterol and nonsterol isoprenoid biosynthesis. Thus far, two disease-causing missense alleles have been identified, N301T and A334T. We report four additional mutations associated with MKD: L264F, T243I, L265P, and I268T, the last found in a patient of Mennonite ancestry. Electrophoretic analysis of bacterially expressed wild-type and mutant MKase indicated that I268T and T243I mutants produced normal or somewhat reduced amounts of MKase protein; conversely, L264F and L265P mutations resulted in considerably decreased, or absent, MKase protein. Immunoblot analysis of MKase from all patients suggested that the MKase polypeptide was grossly intact and produced in amounts comparable to control levels. Three mutations resulted in significantly diminished MKase enzyme activity (<2%), whereas the I268T allele yielded approximately 20% residual enzyme activity. Our results should allow more-accurate identification of carriers and indicate a mutation "cluster" within amino acids 240-270 of the mature MKase polypeptide.

Hematological abnormalities and cholestatic liver disease in two patients with mevalonate kinase deficiency.

We describe two patients with mevalonate kinase deficiency and prominent hematologic abnormalities and cholestatic liver disease. Patient R.B. was not anemic at birth, but developed petechiae and cutaneous extramedullary hematopoiesis, hepatosplenomegaly, leukocytosis, and recurrent febrile events without positive bacterial or viral cultures. Patient N.M. manifested minor anomalies, hepatosplenomegaly, anemia, thrombocytopenia, recurrent febrile crises, and facial rashes. Mevalonic aciduria was found by urinary organic acid analysis, and mevalonate kinase deficiency was documented in both. The clinical spectrum of normocytic hypoplastic anemia, leukocytosis, thrombocytopenia, and abnormal blood cell forms led to diagnoses of congenital infection, myelodysplastic syndromes, or chronic leukemia in these patients before recognition of mevalonate kinase deficiency. Mevalonate kinase deficiency represents a single-gene abnormality that may be associated with significant hematologic findings. Recognition of the variability of this disorder with some patients manifesting only mild neurologic findings, yet significant hepatosplenomegaly, normocytic anemia, thrombocytopenia, and leukocytosis is important for all specialists who need to be aware of this organic aciduria.

Two exon-skipping mutations as the molecular basis of succinic semialdehyde dehydrogenase deficiency (4-hydroxybutyric aciduria).

Succinic semialdehyde dehydrogenase (SSADH) deficiency, a rare metabolic disorder of 4-aminobutyric acid degradation, has been identified in approximately 150 patients. Affected individuals accumulate large quantities of 4-hydroxybutyric acid, a compound with a wide range of neuropharmacological activities, in physiological fluids. As a first step in beginning an investigation of the molecular genetics of SSADH deficiency, we have utilized SSADH cDNA and genomic sequences to identify two point mutations in the SSADH genes derived from four patients. These mutations, identified by standard methods of reverse transcription, PCR, dideoxy-chain termination, and cycle sequencing, alter highly conserved sequences at intron/exon boundaries and prevent the RNA-splicing apparatus from properly recognizing the normal splice junction. Each family segregated a mutation in a different splice site, resulting in exon skipping and, in one case, a frameshift and premature termination and, in the other case, an in-frame deletion in the resulting protein. Family members, including parents and siblings of these patients, were shown to be heterozygotes for the splicing abnormality, providing additional evidence for autosomal recessive inheritance. Our results provide the first evidence that 4-hydroxybutyric aciduria, resulting from SSADH deficiency, is the result of genetic defects in the human SSADH gene.

Inhaled nitric oxide versus conventional therapy: effect on oxygenation in ARDS.

A randomized, controlled clinical trial was performed with patients with acute respiratory distress syndrome (ARDS) to compare the effect of conventional therapy or inhaled nitric oxide (iNO) on oxygenation. Patients were randomized to either conventional therapy or conventional therapy plus iNO for 72 h. We tested the following hypotheses: (1) that iNO would improve oxygenation during the 72 h after randomization, as compared with conventional therapy; and (2) that iNO would increase the likelihood that patients would improve to the extent that the FI(O2) could be decreased by > or = 0.15 within 72 h after randomization. There were two major findings. First, That iNO as compared with conventional therapy increased Pa(O2)/FI(O2) at 1 h, 12 h, and possibly 24 h. Beyond 24 h, the two groups had an equivalent improvement in Pa(O2)/FI(O2). Second, that patients treated with iNO therapy were no more likely to improve so that they could be managed with a persistent decrease in FI(O2) > or = 0.15 during the 72 h following randomization (11 of 20 patients with iNO versus 9 of 20 patients with conventional therapy, p = 0.55). In patients with severe ARDS, our results indicate that iNO does not lead to a sustained improvement in oxygenation as compared with conventional therapy.

Post-translational regulation of mevalonate kinase by intermediates of the cholesterol and nonsterol isoprene biosynthetic pathways.

To assess the potential for feedback inhibition by isoprene intermediates in the cholesterol and nonsterol isoprene biosynthetic pathway, we expressed human cDNAs encoding mevalonate kinase (MKase), phosphomevalonate kinase (PMKase), and mevalonate diphosphate decarboxylase (MDDase) as fusion proteins in Escherichia coli DH5alpha, and purified these proteins by affinity chromatography. Several phosphorylated and non-phosphorylated isoprenes were analyzed as inhibitors of the enzymes using a standard spectrophotometric assay. Of the three proteins, only MKase was inhibited through competitive interaction at the ATP-binding site. The intermediates studied (and their relative inhibitory capacity) were: geranylgeranyl-diphosphate (GGPP, C20) > farnesyl-diphosphate (FPP, C15) > geranyl-diphosphate (GPP, C10) > isopentenyl-diphosphate (IPP, C5) > or = 3,3-dimethylallyl-diphosphate (DMAPP, C5) > farnesol (C15) > dolichol-phosphate (DP, C(80-100)). Mevalonate-diphosphate, geraniol, and dolichol were not inhibitors. Our data further define the spectrum of physiologic inhibitors of MKase, and provide the first evidence for feedback inhibition of MKase by a nonsterol isoprene produced by the branched pathway, dolichol-phosphate. These results provide additional evidence that MKase may occupy a central regulatory role in the control of cholesterol and nonsterol isoprene biosynthesis.

Identification of an active site alanine in mevalonate kinase through characterization of a novel mutation in mevalonate kinase deficiency.

Sequencing of polymerase chain reaction-amplified cDNAs from cultured cells of three patients with mevalonate kinase deficiency revealed a G --> A transversion at nucleotide 1000 of the coding region, converting alanine to threonine at position 334 (A334T). To characterize this defect, we expressed wild-type and mutant cDNAs in Escherichia coli as the glutathione S-transferase fusion proteins, with purification by affinity chromatography. SDS-polyacrylamide gel electrophoresis analysis for wild-type and mutant fusion proteins indicated an expected molecular mass of 42-43 kDa. Kinetic characterization of the wild-type fusion protein yielded Km values of 150 +/- 23 and 440 +/- 190 microM (mean +/- S.E.) for substrates (RS)-mevalonate and ATP, respectively. Expressed wild-type mevalonate kinase (MKase) had a maximum velocity of 13.6 +/- 1.4 units/mg of protein (n = 22, +/-S.E.), whereas the A334T mutation yielded an enzyme with average Vmax of 0.26 +/- 0.02 unit/mg of protein (n = 6, +/-S.E.), representing a decrease to 1.4% of control Vmax. Restriction digestion with HhaI, in conjunction with direct sequencing of cDNAs, revealed that two patients were homozygous and one heterozygous for the A334T allele, establishing autosomal recessive inheritance within families. Although the A334T enzyme had a normal Km for ATP of 680 +/- 226 microM (n = 3, +/-S.E.), the Michaelis constant for (RS)-mevalonate was increased >30-fold to 4623 +/- 1167 microM (n = 4, +/-S.E.) under standard assay conditions. Comparable kinetic results were obtained using extracts of lymphoblasts, which were homozygous for the A334T allele. Alanine 334 is invariant in MKase from bacteria to man and located in a glycine-rich region postulated to have homology with ATP-binding sequences. Our results indicate that the bacterial expression system for human MKase will provide a useful model system in which to analyze inherited mutations and identify the first active site residue in MKase associated with stabilization of mevalonate binding.

The ionosphere of Europa from Galileo radio occultations.

The Galileo spacecraft performed six radio occultation observations of Jupiter's Galilean satellite Europa during its tour of the jovian system. In five of the six instances, these occultations revealed the presence of a tenuous ionosphere on Europa, with an average maximum electron density of nearly 10(4) per cubic centimeter near the surface and a plasma scale height of about 240 +/- 40 kilometers from the surface to 300 kilometers and of 440 +/- 60 kilometers above 300 kilometers. Such an ionosphere could be produced by solar photoionization and jovian magnetospheric particle impact in an atmosphere having a surface density of about 10(8) electrons per cubic centimeter. If this atmosphere is composed primarily of O2, then the principal ion is O2+ and the neutral atmosphere temperature implied by the 240-kilometer scale height is about 600 kelvin. If it is composed of H2O, the principal ion is H3O+ and the neutral temperature is about 340 kelvin. In either case, these temperatures are much higher than those observed on Europa's surface, and an external heating source from the jovian magnetosphere is required.

Melatonin and a 21-aminosteroid attenuate shock after hemorrhage but differentially affect serum cytokines.

UNLABELLED: Melatonin and 21-aminosteroids (lazaroids) are potent antioxidants and may attenuate the increased membrane permeability associated with profound shock. Our purpose was to test the effect of melatonin and a lazaroid (U74389-G) on cytokine production and fluid requirements after shock. METHODS: Male C3H/HeN mice, 20-25 g, were hemorrhaged via a femoral artery catheter to a mean arterial pressure of 35 +/- 5 mm Hg, which was maintained for 1 hr, and then resuscitated with shed blood and crystalloid (2x vol of shed blood). Experimental mice received melatonin at 10 or 50 mg/kg, U74389-G at 3 mg/kg, or vehicle i.v. upon resuscitation, and blood was returned at 0.1 cc/min and crystalloid at 0.05 cc/min. The percentage of total crystalloid required to reach stabilization (mean arterial pressure remaining within 2 mm Hg for 5 min) was recorded. Animals were sacrificed at 1 hr postshock. Serum and anti-CD3-stimulated splenocyte culture supernatants were assayed for interleukin-6 (IL-6) and gamma-IFN by ELISA. RESULTS: Mice receiving lazaroid or melatonin (50 mg/kg) required significantly less fluid to reach stabilization, with lazaroid-treated animals requiring 24 +/- 1% and melatonin-treated animals requiring 28 +/- 2% of total crystalloid compared to 40 +/- 3% for untreated animals. Melatonin-treated mice (50 mg/kg) had lower serum IL-6 levels (368 +/- 154 vs 1078 +/- 146 pg/ml) and lazaroid-treated mice had lower gamma-IFN levels (7 +/- 6 vs 52 +/- 15 pg/ml) compared to those of the untreated group (P < 0.05). There were no differences in splenocyte cytokine production. CONCLUSIONS: Treatment with lazaroid and melatonin both reduced postshock fluid requirements. Melatonin reduced serum IL-6 levels, while lazaroid reduced serum gamma-IFN levels, suggesting different mechanisms of action.

Molecular cloning of the mature NAD(+)-dependent succinic semialdehyde dehydrogenase from rat and human. cDNA isolation, evolutionary homology, and tissue expression.

Three rat brain cDNA clones approximately 3500, 1465, and 1135 base pairs in length encoding succinic semialdehyde dehydrogenase (SSADH; EC 1.2.1.24) were isolated from two cDNA libraries using a polymerase chain reaction derived probe. Restriction mapping and DNA sequencing revealed that the 3.5-kilobase clone contained an 84-base pair (28 amino acid) insert in the coding region. Composite clones encoding mature SSADH predicted proteins with 488 amino acids (M(r) = 52,188) when including the insert and 460 amino acids (M(r) = 48,854) without the insert. The cDNA clones were confirmed by expression of enzyme activity in bacteria and protein sequence data obtained from sequencing purified rat brain SSADH. Two human liver SSADH cDNA clones of 1091 and 899 base pairs were also isolated. Human and rat SSADH share 83 and 91% identity in nucleotide and protein sequence, respectively. Northern blot analysis revealed two differentially expressed SSADH transcripts of approximately 2.0 and 6.0 kilobases in both rat and human tissues. Human genomic Southern blots indicate that the two SSADH transcripts are encoded by a greater than 20-kilobase single copy gene. Mammalian SSADH contains significant homology to bacterial NADP(+)-succinic semialdehyde dehydrogenase (EC 1.2.1.16) and conserved regions of general aldehyde dehydrogenases (EC 1.2.1.3), suggesting it is a member of the aldehyde dehydrogenase superfamily of proteins.

Overview and outcomes.

A great deal of progress has been made regarding improved prehospital transport, the quality of trauma care, and injury prevention research. The analysis of the four determinants of outcome in the trauma victim allowed for the discovery of subgroups who may benefit from a change in triage, resuscitation, or management. Our recent investigation into the effect of host factors on mortality resulted in the discovery that pre-existing illness predicts outcome independent of other determinants, including age and ISS. This article serves as an introduction to the effect of PED on trauma victims, including prevalence of specific PED, as well as disease-specific treatment considerations. The bottom line in care of any trauma victim is that all deviations from normal must be noted, but they should be evaluated properly with respect to the acute injuries. It is the authors' hope that this overview will guide the intensivist in focusing on the treatment of acute injuries without losing sight of the importance of both recognizing and managing chronic illnesses so their detrimental effect on patient outcome can be minimalized. A large multicenter investigation is needed to see whether these recommendations will, in fact, positively impact on trauma victim outcome.

Sonography in blunt abdominal trauma: a preliminary progress report.

Evaluation of blunt abdominal trauma is clinically challenging. Diagnostic peritoneal lavage (DPL) and computed tomographic (CT) scanning have become primary diagnostic modalities. We examined the efficacy and role of ultrasonographic (US) studies in the initial abdominal evaluation of blunt trauma patients. Over an 8-month period, patients whose abdominal work-up indicated the need for DPL or CT were evaluated sonographically within the first hour after admission by trauma fellows (PGY-6) with at least 1 hour of theoretical training and 1 hour of practical training. Sonograms considered positive were those showing free peritoneal fluid or organ disruption. Hard copies of the sonograms were evaluated by a staff radiologist without knowledge of the fellows' interpretations or of DPL or CT results. Based on the fellows' interpretation of the real-time sonograms, among the first 163 patients studied were 11 true-positive, 146 true-negative, one false-positive, and five false-negative results. Sixteen patients had intra-abdominal injury documented by DPL, CT, or laparotomy. Ultrasonography was 91% sensitive in detecting the presence of hemoperitoneum. Overall, ultrasonography was 69% sensitive, 99% specific, and 96% accurate in diagnosing abdominal injury. We conclude that emergency sonography on admission can serve as a valuable adjunct to the physical diagnosis of clinically significant hemoperitoneum. It is noninvasive, portable, and accurate in determining the need for further diagnostic/surgical intervention.

Voyager radio science observations of neptune and triton.

The Voyager 2 encounter with the Neptune system included radio science investigations of the masses and densities of Neptune and Triton, the low-order gravitational harmonics of Neptune, the vertical structures of the atmospheres and ionospheres of Neptune and Triton, the composition of the atmosphere of Neptune, and characteristics of ring material. Demanding experimental requirements were met successfully, and study of the large store of collected data has begun. The initial search of the data revealed no detectable effects of ring material with optical depth tau [unknown] 0.01. Preliminary representative results include the following: 1.0243 x 10(26) and 2.141 x 10(22) kilograms for the masses of Neptune and Triton; 1640 and 2054 kilograms per cubic meter for their respective densities; 1355 +/- 7 kilometers, provisionally, for the radius of Triton; and J(2) = 3411 +/- 10(x 10(-6)) and J(4) = -26(+12)(-20)(x10(-6)) for Neptune's gravity field (J>(2) and J(4) are harmonic coefficients of the gravity field). The equatorial and polar radii of Neptune are 24,764 +/- 20 and 24,340 +/- 30 kllometers, respectively, at the 10(5)-pascal (1 bar) pressure level. Neptune's atmosphere was probed to a pressure level of about 5 x 10(5) pascals, and effects of a methane cloud region and probable ammonia absorption below the cloud are evident in the data. Results for the mixing ratios of helium and ammonia are still being investigated; the methane abundance below the clouds is at least 1 percent by volume. Derived temperature-pressure profiles to 1.2 x 10(5) pascals and 78 kelvins (K) show a lapse rate corresponding to "frozen" equilibrium of the para- and ortho-hydrogen states. Neptune's ionosphere exhibits an extended topside at a temperature of 950 +/- 160 K if H(+) is the dominant ion, and narrow ionization layers of the type previously seen at the other three giant planets. Triton has a dense ionosphere with a peak electron concentration of 46 x 10(9) per cubic meter at an altitude of 340 kilometers measured during occultation egress. Its topside plasma temperature is about 80 +/- 16 K if N(2)(+) is the principal ion. The tenuous neutral atmosphere of Triton produced distinct signatures in the occultation data; however, the accuracy of the measurements is limited by uncertainties in the frequency of the spacecraft reference oscillator. Preliminary values for the surface pressure of 1.6 +/- 0.3 pascals and an equivalent isothermal temperature of 48 +/- 5 K are suggested, on the assumption that molecular nitrogen dominates the atmosphere. The radio data may be showing the effects of a thermal inversion near the surface; this and other evidence imply that the Triton atmosphere is controlled by vapor-pressure equilibrium with surface ices, at a temperature of 38 K and a methane mixing ratio of about 10(-4).