beta-Hydroxyaspartic acid and beta-hydroxyasparagine residues in recombinant human protein S are not required for anticoagulant cofactor activity or for binding to C4b-binding protein

Among the vitamin K-dependent plasma proteins, only protein S contains the post-translationally modified amino acid erythro-beta-hydroxyasparagine (Hyn). Protein S also contains erythro-beta-hydroxyaspartic acid (Hya). The function of these unusual amino acids, located in the epidermal growth factor-like domains, is unknown. To determine if these post-translational modifications contribute to the functional integrity of human protein S (HPS), recombinant human protein S lacking Hya and Hyn (rHPSdesHya/Hyn) was purified from the medium of human kidney 293 cells that were transfected with HPS cDNA and grown in the presence of the hydroxylase inhibitor 2,2'-dipyridyl. Solution-phase equilibrium binding studies revealed that rHPSdesHya/Hyn binds C4b-binding protein (C4BP) in a manner indistinguishable from recombinant HPS and plasma-derived HPS, exhibiting a Kd in the presence of 2 mM CaCl2 of approximately 0.7 nM and a Kd in the presence of 4 mM EDTA approximately 10-fold higher. In a purified component system, rHPSdesHya/Hyn displayed normal anticoagulant cofactor activity in the activated protein C-catalyzed inactivation of coagulation factor Va bound in the prothrombinase complex. In addition, digestion of rHPSdesHya/Hyn with thrombin in the presence of EDTA appeared normal, and 2 mM CaCl2 prevented the cleavage. Together these results suggest that the post-translational modifications of Asn and Asp residues are not necessary for the macromolecular or Ca2+ interactions associated with the anticoagulant and C4BP binding characteristics of HPS.

Plasma beta-endorphin in neonates: effect of prematurity, gender, and respiratory status

A consecutive cohort of 87 infants (46 infants less than 37 weeks gestational age and 41 term infants greater than or equal to 37 weeks gestation) admitted to the Neonatal Intensive Care Unit (NICU) and a convenience cohort of 27 term well babies at the University of Nebraska Medical Center (Omaha, NE) were evaluated for plasma beta-endorphin (beta E) levels during the first 4 h after birth. Demographic data, maternal history, and respiratory status at the time of sampling as well as development of documented apneic episodes during the initial hospitalization were analyzed for all infants. All NICU infants had higher plasma beta E levels than the control infants. Premature infants had significantly higher neonatal plasma beta E levels than term infants in either the control or NICU groups, but the response was gender specific; premature males had higher plasma beta E than premature females (P = 0.008). Perinatal stress, including respiratory problems, was associated with the increase in plasma beta E, but prematurity and being male were significantly predictors of an elevated plasma beta E level. Immaturity in respiratory control, as evaluated by the development of documented apneic episodes during the infant's initial hospitalization, did not correlate with an elevated perinatal plasma beta E level.

Fetal habituation to vibroacoustic stimulation in uncomplicated term pregnancies

The use of transabdominal vibroacoustic stimulation has been shown to improve the efficiency of antepartum fetal surveillance. The ability of the fetus to habituate to such a stimulus has also been suggested as a means of assessing the function of the central nervous system. The purpose of this blinded prospective investigation was to evaluate fetal habituation in a group of low-risk pregnancies anticipated to deliver within 1 week. One hundred sixteen uncomplicated pregnancies underwent repetitive vibroacoustic stimulation using a Corometrics Model 146 fetal acoustic stimulator. Fetal habituation was defined as a sustained elevation of the heart rate baseline for more than 15 minutes or a failure to produce an adequate acceleration of the fetal heart rate after an initial response. Habituation was present in 106 (91.4%) cases, whereas 10 (8.6%) failed to habituate to the stimulus. All infants failing to habituate in utero ultimately did well after delivery. Their birthweights, Apgar scores, umbilical artery blood gas determinations, and courses in the newborn nursery were similar to those of infants who responded to in utero sound stimulation. However, cesarean delivery for fetal distress and gross placental abnormalities (such as infarction and abruption) occurred more commonly in those fetuses failing to habituate. Additional investigations of fetal habituation to a vibroacoustic stimulus may be helpful in the intrapartum risk assessment of uncomplicated term pregnancies.

An electrodynographic study of foot function in shoes of varying heel heights

Forty-three female test subjects had electrodynographic gait analysis performed in barefoot, low-heel shoe, and high-heel shoe conditions. Comparisons of segmental foot function, actual pressures, and pressure durations were determined. The findings suggest that an increased duration of forefoot loading, rather than an increased actual pressure, is responsible for pedal pathology secondary to wearing high-heel shoes. Contrary to previous reports in the literature, evidence of abnormal pronation in high heels was not found in this study.

Clinical tests applicable to the study of chronic low-back disability

This symposium has evaluated the possible directions to be taken in designing reliable and valid questionnaires, screening examinations, and paraclinical tests applicable to studies in LBP. The detailed design of such test instruments, field testing, measures of reliability, and validity represent the next step if the current barriers to collaborative clinical research in LBP are to be overcome.

In utero arterial embolism from renal vein thrombosis with successful postnatal thrombolytic therapy

Thromboembolic events in the pediatric age group occur most commonly in neonates, and newborns of diabetic mothers are particularly at risk. We report a newborn with right renal vein and inferior vena cava thrombosis who apparently embolized across the foramen ovale antenatally with resultant right brachial artery occlusion. The baby was delivered by cesarean section from an insulin-dependent diabetic mother. At the time of birth, there was severe right arm ischemia with absent brachial and radial pulses. There was clinical evidence of distal embolization with a "trash" lesion of the distal right middle finger as well as a midforearm area of full-thickness skin loss. Ultrasound demonstrated a right renal vein thrombosis and a 95% occlusion of the inferior vena cava. Regional urokinase therapy was instituted through a lower extremity vein with a 5,000 U/kg bolus and then 5,000 U/kg/h continuous infusion. Twelve hours of infusion of urokinase led to clinical resolution of the right arm ischemia, with return of pulses. Follow-up ultrasound showed the right renal vein thrombosis and inferior vena cava clot to be completely resolved. The right middle finger and forearm lesions subsequently have healed primarily. We report this as a case of in utero arterial embolization with successful postnatal therapy using regional urokinase infusion.

Solution-phase equilibrium binding interaction of human protein S with C4b-binding protein

Solution-phase equilibrium binding studies of human protein S (HPS) and C4b-binding protein (C4BP) were undertaken using purified components. Free C4BP was measured in solutions at equilibrium by using HPS immobilized on a solid phase, coupled with an antibody detection system. Disruption of the solution-phase equilibrium was minimized by using a brief (15 min) exposure to the solid-phase HPS. These studies yielded an equilibrium dissociation constant (Kd) approximately 6 x 10(-10) M and a stoichiometry of approximately 1.7 molecules of HPS bound to each molecule of C4BP. This Kd is between 27-fold and 930-fold lower than previously published values obtained by using solid-phase and nonequilibrium methods. Equilibrium was achieved in solutions containing low nanomolar concentrations of both HPS and C4BP in less than or equal to 1 h at 37 degrees C, suggesting a rapid association rate constant for the interaction. Thrombin cleavage of HPS had no effect on the observed binding parameters. The binding interaction between HPS and C4BP appears to be partly calcium dependent, since in the presence of EDTA the Kd was increased to about 6 x 10(-9) M, with no change in the stoichiometry. This high-affinity binding interaction between HPS and C4BP, whose Kd is more than 500-fold lower than the proteins' plasma concentrations, heightens the apparent physiologic importance of complex formation.

A 5.3-kb deletion including exon XIII of the protein S alpha gene occurs in two protein S-deficient families

Genomic DNA samples from 12 protein S-deficient families with hereditary thrombophilia were analyzed by Southern hybridization using protein S cDNA probes. Protein S-deficient members of families A and B possessed identical restriction fragment length polymorphisms, which suggest the absence of 5.3 kb from one of their protein S alpha alleles. The abnormal alleles from individuals A7 and B1 were amplified by the polymerase chain reaction using a forward primer in intron K and a reverse primer in exon XIV. The amplified DNA was cloned and sequenced. Sequence comparison with the normal protein S alpha gene showed that most of intron L (roughly 4.7 kb), the entire exon XIII (151 bp), and about a quarter of intron M (407 bp) were missing from both the A7 and B1 clones. Exon XIII contains all three potential N-glycosylation sites in human protein S. This deletion may result in RNA transcripts in which exon XII is spliced to exon XIV. Such an arrangement would generate a stop codon at position 463 and consequently produce a nonglycosylated protein S molecule truncated by 173 amino acids.

A comparison of motor unit behaviour in young and aged subjects

We evaluated motor unit behaviour in young and aged subjects during ramped tension development and release to 10% maximum voluntary contraction requiring 10 seconds to complete. Six young and six elderly adults performed isometric abductor digiti minimi muscle contractions while motor units were recorded with implanted fine wire electrodes. Computer interactive programs yielded interspike interval (ISI) data for 16 units from the young and for 15 units from the aged subjects. Mean ISIs for young were 88.4 ms for shortening and 96.5 ms for lengthening contractions. Units from the aged had ISIs of 110.5 ms and 117.1 ms for shortening and lengthening contractions. Some evidence for between-group differences in firing pattern during ascending and descending ramps was also found.

Prostaglandin F1 alpha levels during and after neonatal extracorporeal membrane oxygenation

Infants receiving extracorporeal membrane oxygenation therapy undergo long-term cardiopulmonary bypass, are systemically heparinized, and frequently receive platelet transfusions. Prostacyclin is a powerful inhibitor of platelet aggregation as well as a potent vasodilator. The levels of its stable metabolite prostaglandin F1 alpha increase significantly in children undergoing cardiopulmonary bypass during heart operations but decrease to preoperative levels after bypass. To determine the effect of long-term bypass on prostacyclin levels, multiple plasma samples were analyzed in 10 human neonates both during extracorporeal membrane oxygenation therapy and within 24 hours after extracorporeal membrane oxygenation. Prostaglandin F1 alpha, the stable metabolite of prostacyclin, was quantitated by radioimmunoassay in picograms per milliliter. Prostaglandin F1 alpha levels were elevated while the patients received extracorporeal membrane oxygenation therapy but decreased with duration of extracorporeal membrane oxygenation. In most infants, prostaglandin F1 alpha levels rose again during weaning from extracorporeal membrane oxygenation and remained elevated for 24 hours after extracorporeal membrane oxygenation. Extracorporeal membrane oxygenation course influenced circulating prostaglandin F1 alpha levels. Fluctuating prostaglandin F1 alpha levels are of clinical significance in the management of vasomotor tone and platelet function, common problems in the care and the prevention of hemorrhage in these critically ill infants.

Temperature and Thermal Emissivity of the Surface of Neptune's Satellite Triton

Analysis of the preliminary results from the Voyager mission to the Neptune system has provided the scientific community with several methods by which the temperature of Neptune's satellite Triton may be determined. If the 37.5 K surface temperature reported by several Voyager investigations is correct, then the photometry reported by the imaging experiment on Voyager requires that Triton's surface have a remarkably low emissivity. Such a low emissivity is not required in order to explain the photometry from the photopolarimeter experiment on Voyager. A low emissivity would be inconsistent with Triton having a rough surface at the approximately 100-microm scale as might be expected given the active renewal processes which appear to dominate Triton's surface.

Purification and characterization of human kidney cytosolic cysteine conjugate beta-lyase activity

The central role of cysteine conjugate beta-lyase (beta-lyase) in the bioactivation of nephrotoxic halogenated hydrocarbons and the possibility of human exposure to these chemicals has focused interest on the beta-lyase from human kidney. Human kidney tissue was collected as surgical waste material, and subcellular fractions were isolated by differential centrifugation. Human beta-lyase activity, determined with S-(2-benzothiazolyl)-L-cysteine (BTC) as the substrate, was present in the cytosolic, mitochondrial, and microsomal fractions, but was highest in the cytosolic fraction. Activity in human kidney cytosol was about 10% of that present in rat kidney cytosol. Human kidney cytosolic beta-lyase activity, with BTC as the substrate, was not stimulated by pyridoxal phosphate or by exogenous 2-keto acids. Cytosolic beta-lyase activity was purified 280-fold with a yield of 12% from human kidneys unsuitable for transplantation. The beta-lyase activity copurified with cytosolic glutamine transaminase K and exhibited a molecular mass of 85 kDa on a Sephacryl 5300 column and a subunit molecular mass of 45 kDa by gel electrophoresis. Both BTC and its homocysteine analogue S-(2-benzothiazolyl)-L-homocysteine were excellent substrates, exhibiting Km and kcat values of 0.97 mM and 2.78 mM and 9.35 min-1 and 6.90 min-1, respectively. beta-Lyase activity was inhibited by aminooxyacetic acid, indicating that the human cytosolic enzyme contains pyridoxal phosphate, and by the nephrotoxins S-(1,2-dichlorovinyl)-L-cysteine and S-(1,2-dichlorovinyl)-L-homocysteine, which serve as alternative substrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Photometry from Voyager 2: Initial Results from the Neptunian Atmosphere, Satellites, and Rings

The Voyager photopolarimeter successfully accomplished its objectives for the Neptune encounter, performing measurements on the planet, several of its satellites, and its ring system. A photometric map of Neptune at 0.26 micrometer (microm) shows the planet to be bland, with no obvious contrast features. No polar haze was observed. At 0.75 microm, contrast features are observed, with the Great Dark Spot appearing as a low-albedo region and the bright companion as being substantially brighter than its surroundings, implying it to be at a higher altitude than the Great Dark Spot. Triton's linear phase coefficients of 0.011 magnitudes per degree at 0.26 microm and 0.013 magnitudes per degree at 0.75 microm are consistent with a solid-surface object possessing high reflectivity. Preliminary geometric albedos for Triton, Nereid, and 1989N2 were obtained at 0.26 and 0.75 microm. Triton's rotational phase curve shows evidence of two major compositional units on its surface. A single stellar occultation of the Neptune ring system elucidated an internal structure in 1989N1R, in the approximately 50-kilometer region of modest optical depth. 1989N2R may have been detected. The deficiency of material in the Neptune ring system, when compared to Uranus', may imply the lack of a "recent" moon-shattering event.

Antithrombin inactivation by neutrophil elastase requires heparin

In certain thrombotic states, large declines in the levels of functional circulating antithrombin occur, which may reflect the highly active nature of the endothelial surface in suppressing excessive amounts of activated coagulation enzymes. Alternatively, we have recently observed an unexpected and paradoxical in vitro functioning of heparin that could result in the inactivation of antithrombin in pathologic conditions. Specifically, antithrombin was rendered nonfunctional as an inhibitor of clotting enzymes as a result of a limited, heparin-dependent cleavage by neutrophil elastase. This inactivation occurred only in the presence of the active anticoagulant heparin fraction, which suggested that the heparin-antithrombin complex was the substrate for elastase attack. Interestingly, neutrophil elastase was found to bind tightly to heparin and heparin-like materials. Neutrophil elastase has been previously linked to nonspecific proteinolysis occurring in inflammatory thrombotic reactions. This affinity of both antithrombin and elastase for heparin suggests a novel mechanism of potential specificity. An important component of this hypothesis is the localization of the elastase/antithrombin reaction away from the high circulating levels of elastase inhibitors. The proposed inactivation of antithrombin on the vascular surface would likely occur only in pathologic states associated with neutrophil sequestration and activation. Nevertheless, this mechanism could lead to a localized reversal of the nonthrombogenic nature of the endothelium and potentially lead to significant reductions of functional antithrombin in certain disease states.

Ventilatory changes in convalescent infants positioned in car seats

Because premature infants have been shown to be at risk for hypoxia and bradycardia when positioned in standard car seats, this study was done to confirm this finding in a larger sample, to investigate convalescent term infants in the neonatal intensive care unit for respiratory compromise in car seats, and to determine the physiologic mechanism or mechanisms responsible. Extensive multichannel polygraph recordings were obtained and pulmonary function tests were performed on 50 convalescent infants from the neonatal intensive care unit before, during, and after placement in a Cosco-Peterson First Ride car seat. Mean total dynamic compliance, total pulmonary resistance, and work of breathing improved in the car seat. Thirty percent of premature infants experienced hypoxia, bradycardia, or both in a car seat; in this group, tidal volume was lower (p = 0.02). In 11 of 16 infants with abnormal findings, oxygen desaturation was temporally related to episodes of short and mixed apnea. No term convalescent infant experienced respiratory difficulty in a car seat regardless of primary diagnosis. We conclude that premature infants may have respiratory compromise of a multifactorial nature when in car seats. Further development of car seats is necessary if such respiratory problems are to be avoided.

Vasoconstriction in telencephalic microvessels: a response to one model for intraventricular hemorrhage in beagle pups

Telencephalic microvessels were morphologically and morphometrically evaluated in beagle pups at 24, 48, and 72 hours of age following an experimental insult consisting of exposure to acute hypovolemic hypotension followed by rapid corrective blood reinfusion. Animals were anesthetized throughout the procedure and maintained for 75 minutes prior to sacrifice. Microvessels from the germinal matrix, where intraventricular hemorrhage (IVH) most commonly occurs, were compared to those of the adjacent cerebral cortex and choroid plexus. Perfusion, fixation and processing of the tissue followed our previously published protocol (Leuschen et al.: Anatomical Record 208:435-443, 1984). Both germinal matrix and cortical microvessels had collapsed lumens and normal endothelial cell morphology; mitochondria contained distinct cristae, junctional complexes were present and a basement lamina completely surrounded most vessels. Morphometric data on matrical and cortical microvessels supported vasoconstriction. Microvessels from choroid plexus were not vasoconstricted; tight junctions were infrequently seen and microvesicular elements were present. An increased cerebral blood flow to the germinal matrix and the adjacent cerebral cortex has been reported during and immediately following hypovolemic hypotensive insult. By 75 minutes following insult, our ultrastructural studies support a rebound phenomena including vasoconstriction of microvessels. The resulting vasoconstriction and associated cerebral ischemia may play an important role in subsequent tissue damage to the matrical area and ultimately to the etiology of IVH.

A general method of site-specific mutagenesis using a modification of the Thermus aquaticus polymerase chain reaction

A specific mutagenic change in the cDNA of human protein S was introduced by a modification of the polymerase chain reaction that permits the introduction of a mutation at any position in a double-stranded DNA molecule. The method employed four synthetic oligonucleotide primers. One oligonucleotide contained a single-base mismatch to direct the mutagenesis; the other three oligonucleotides were designed to allow selective amplification of the mutated sequence with Thermus aquaticus polymerase. The mutagenized cDNA was cloned into a plasmid vector and transformed into Escherichia coli RR1 cells for characterization. The desired cytosine to guanine change in the target cDNA was confirmed by the predicted appearance of an AluI restriction site and by dideoxynucleotide sequencing. No other sequence changes were detected within the amplified region. This method of site-specific mutagenesis can be applied to any linear double-stranded DNA large enough for primer annealing and obviates specialized cloning vectors, DNA constructs, and selection techniques. It has the advantage over a recently published PCR technique (R. Higuchi, B. Krummel, and R. Saki (1988) Nucleic Acids Res. 16, 7351-7367) in requiring no diafiltration to remove primers between steps and in requiring only a single mutagenic oligonucleotide to be synthesized for each mutant construct made after the initial one.

Inactivation of human antithrombin by neutrophil elastase. Kinetics of the heparin-dependent reaction

Human neutrophil elastase catalyzes the inactivation of antithrombin by a specific and limited proteinolytic cleavage. This inactivation reaction is greatly accelerated by an active anticoagulant heparin subfraction with high binding affinity for antithrombin. A potentially complex reaction mechanism is suggested by the binding of both neutrophil elastase and antithrombin to heparin. The in vitro kinetic behavior of this system was examined under two different conditions: 1) at a constant antithrombin concentration in which the active anticoagulant heparin was varied from catalytic to saturating levels; and 2) at a fixed, saturating heparin concentration and variable antithrombin levels. Under conditions of excess heparin, the inactivation could be continuously monitored by a decrease in the ultraviolet fluorescence emission of the inhibitor. A Km of approximately 1 microM for the heparin-antithrombin complex and a turnover number of approximately 200/min was estimated from these analyses. Maximum acceleratory effects of heparin on the inactivation of antithrombin occur at heparin concentrations significantly lower than those required to saturate antithrombin. The divergence in acceleratory effect and antithrombin binding contrasts with the anticoagulant functioning of heparin in promoting the formation of covalent antithrombin-enzyme complexes and is likely to derive from the fact that neutrophil elastase is not consumed in the inactivation reaction. A size dependence was observed for the heparin effect since an anticoagulantly active octasaccharide fragment of heparin, with avid antithrombin binding activity, was without effect on the inactivation of antithrombin by neutrophil elastase. Despite the completely nonfunctional nature of elastase-cleaved antithrombin and the altered physical properties of the inhibitor as indicated by fluorescence and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the inactivated inhibitor exhibited a circulating half-life in rabbits that was indistinguishable from native antithrombin. These results point to an unexpected and apparently contradictory function for heparin which may relate to the properties of the vascular endothelium in pathological situations.