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J E Thompson

Publications and source records attributed to J E Thompson.

At least 55 records · Page 3Linked to original sources
PubMed1998

Partition analysis of an enzyme acting concurrently upon two substrates in a continuous multiwavelength assay.

We describe a multiwavelength method for measuring an enzyme's discrimination of one substrate over another by continuously monitoring the reactions of the two substrates simultaneously. This method is generally applicable to ultraviolet-visible diode array or rapid-scanning spectrophotometers and the measurement requires a single incubation of enzyme with two substrates. Rates at each of the wavelengths may be fit globally by using a nonlinear least-squares fitting procedure which provides adequate statistical analysis. The specificity of trypsin for N-alpha-benzoyl-L-arginine p-nitroanilide (BRpNA) over N-t-butyloxycarbonyl-L-alanine-p-nitrophenylester (BocApNP) was 2.1 as measured by the multiwavelength partition method and 2.3 by comparing the individual kcat/K(m)'s for the two substrates. Multiwavelength analysis was applied to two enzymes in the biosynthetic pathway for fungal melanin: scytalone dehydratase and trihydroxynaphthalene reductase from Magnaporthea grisea. The specificity of trihydroxynaphthalene reductase for 2,3-dihydro-2,5-dihydroxy-4H-benzopyran-4-one compared to scytalone, a natural substrate for the enzyme, was 95. Scytalone dehydratase was eight-fold more specific for 2,3-dihydro-2,5-dihydroxy-4H-benzopyran-4-one than it was for scytalone. Multiwavelength analysis was also used to measure an equilibrium constant of 0.040 for the reaction ¿dihydroorotate + oxonic acid<-->orotate + dihydrooxonic acid¿ catalyzed by dihydroorotate dehydrogenase. Advantages, limitations, and further applications of this steady-state method, which directly measures relative substrate specificities, are delineated. All studies described in this paper were at pH 7.0 and 25 degrees C.

Ascomycota↗
PubMed1998

Association of an intracranial arteriovenous malformation and a meningioma.

A case of a simultaneously discovered arteriovenous malformation (AVM) and a meningioma is presented. A review of the literature revealed only four similar cases, but there have been 30 reports of other intracranial tumors in association with AVM. The possible mechanisms of this rare association are discussed.

Cerebral Arteries↗
PubMed1998

Single-breath CO2 analysis as a predictor of lung volume in a healthy animal model during controlled ventilation.

OBJECTIVE: To examine the utility of single-breath CO2 analysis as a measure of lung volume. DESIGN: A prospective, animal cohort study comparing 21 parameters derived from single-breath CO2 analysis with lung volume measurements determined by nitrogen washout in animals during controlled ventilation. SETTING: An animal laboratory in a university-affiliated medical center. SUBJECTS: Seven healthy lambs. INTERVENTIONS: The single-breath CO2 analysis station consists of a mainstream capnometer, a variable orifice pneumotachometer, a signal processor and computer software with capability for both on- and off-line data analysis. Twenty-one derived components of the CO2 expirogram were evaluated as predictors of lung volume. Lung volume was manipulated by 3 cm H2O incremental increases in positive end-expiratory pressure from 0 to 21 cm H2O, and ranged between 147 and 942 mL. MEASUREMENTS AND MAIN RESULTS: Fifty-five measurements of lung volume were available for comparison with derived variables from the CO2 expirogam. Stepwise linear regression identified four variables that were most predictive of lung volume: a) dynamic lung compliance; b) the slope of phase 3; c) the slope of phase 2 divided by the mixed expired CO2 tension; and d) airway deadspace. The multivariate equation was highly statistically significant and explained 94% of the variance (adjusted r2 =.94, p < .0001). The bias and precision of the calculated lung volume was .00 and 51, respectively. The mean percent difference for the lung volume estimate derived from the single-breath CO2 analysis station was 0.79%. CONCLUSIONS: Our data indicate that analysis of the CO2 expirogram can yield accurate information about lung volume. Specifically, four variables derived from a plot of expired CO2 concentration vs. expired volume predict changes in lung volume in healthy lambs with an adjusted coefficient of determination of .94. Prospective application of this technology in the setting of lung injury and rapidly changing physiology is essential in determining the clinical usefulness of the technique.

Animals↗
PubMed1998

Molecular characterization of an Arabidopsis gene encoding hydroperoxide lyase, a cytochrome P-450 that is wound inducible.

Hydroperoxide lyase (HPL) cleaves lipid hydroperoxides to produce volatile flavor molecules and also potential signal molecules. We have characterized a gene from Arabidopsis that is homologous to a recently cloned HPL from green pepper (Capsicum annuum). The deduced protein sequence indicates that this gene encodes a cytochrome P-450 with a structure similar to that of allene oxide synthase. The gene was cloned into an expression vector and expressed in Escherichia coli to demonstrate HPL activity. Significant HPL activity was evident when 13S-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid was used as the substrate, whereas activity with 13S-hydroperoxy-9(Z),11(E)-octadecadienoic acid was approximately 10-fold lower. Analysis of headspace volatiles by gas chromatography-mass spectrometry, after addition of the substrate to E. coli extracts expressing the protein, confirmed enzyme-activity data, since cis-3-hexenal was produced by the enzymatic activity of the encoded protein, whereas hexanal production was limited. Molecular characterization of this gene indicates that it is expressed at high levels in floral tissue and is wound inducible but, unlike allene oxide synthase, it is not induced by treatment with methyl jasmonate.

Aldehyde-Lyases↗
PubMed1998

Pulmonary blood flow distribution during partial liquid ventilation.

Regional pulmonary blood flow was investigated with radiolabeled microspheres in four supine lambs during the transition from conventional mechanical ventilation (CMV) to partial liquid ventilation (PLV) and with incremental dosing of perfluorocarbon liquid to a cumulative dose of 30 ml/kg. Four lambs supported with CMV served as controls. Formalin-fixed, air-dried lungs were sectioned according to a grid; activity was quantitated with a multichannel scintillation counter, corrected for weight, and normalized to mean flow. During CMV, flow in apical and hilar regions favored dependent lung (P < 0.001), with no gradient across transverse planes from apex to diaphragm. During PLV the gradient within transverse planes found during CMV reversed, most notably in the hilar region, favoring nondependent lung (P = 0.03). Also during PLV, flow was profoundly reduced near the diaphragm (P < 0.001), and across transverse planes from apex to diaphragm a dose-augmented flow gradient developed favoring apical lung (P < 0.01). We conclude that regional flow patterns during PLV partially reverse those noted during CMV and vary dramatically within the lung from apex to diaphragm.

Animals↗
PubMed1998

Usefulness of proton MR spectroscopy in the evaluation of temporal lobe epilepsy.

OBJECTIVE: The purpose of our study was to compare the ability of MR spectroscopy with that of standard presurgical methods to accurately lateralize the abnormal hippocampus in a group of patients with complex partial seizures. SUBJECTS AND METHODS: Ten healthy volunteers (five male, five female) without a history of seizures, significant head trauma, or other neurologic abnormalities were chosen to participate in the study. Twelve consecutive patients (three male, nine female) having intractable temporal lobe epilepsy and undergoing presurgical evaluation for temporal lobectomy were chosen to participate in the study. The condition of all patients was refractory to medications. All patients underwent presurgical examination with interictal and video ictal electroencephalography, ictal single-photon emission computed tomography, interictal positron emission tomography, MR imaging, and neuropsychologic testing. When noninvasive data were inconclusive, depth or grid recordings were performed. The results of MR spectroscopy were also compared with postsurgical seizure control as defined by the Engel classification. RESULTS: Nine (90%) of 10 control subjects showed no significant difference in N-acetyl aspartate. One control subject showed 16% asymmetry in N-acetyl aspartate between sides. The control group showed no statistically significant differences in ratios of N-acetyl aspartate:creatine, N-acetyl aspartate:choline, or creatine:choline when comparing sides (p < .05). All 12 patients showed clearly lateralizing values identified by the index of asymmetry in N-acetyl aspartate (range, 24-93%), with a mean difference of 51% (SD, 22) (p = .01). Additionally, as a group, statistically significant indexes of asymmetry (p = .01) were seen in ratios of N-acetyl aspartate:choline (mean, 42; SD, 22%), N-acetyl aspartate:creatine (mean, 41; SD, 27), and N-acetyl aspartate:creatine + choline (mean, 42; SD, 22). Using an N-acetyl aspartate index of asymmetry of greater than 15%, which represents the mean index of asymmetry of the control subjects +/- two SDs, as our cutoff level for lateralization, the correct side was identified in all patients. When comparing both hippocampi using an asymmetry index of 15% for N-acetyl aspartate:choline + creatine, 11 (92%) of 12 were correctly lateralized. When comparing the unaffected temporal lobes between patients and control subjects, no statistically significant differences were detected in any metabolites or ratios. CONCLUSION: Our study agrees with others in showing decreased N-acetyl aspartate in the hippocampus of seizure patients when compared with control subjects. Using N-acetyl aspartate, N-acetyl aspartate:creatine, N-acetyl aspartate:choline, and N-acetyl aspartate:creatine + choline as our parameters, patients with mesial temporal lobe epilepsy were correctly lateralized with MR spectroscopy when compared with clinical consensus criteria. We consider MR spectroscopy to be complementary to MR imaging. Both studies can be performed as a single integrated examination.

Adult↗
PubMed1998

Faculty preparation: a new solution to an old problem.

Concern regarding adequate faculty preparation has been an issue in nursing for many years. Because of the small number of nurses with educational preparation, expert clinicians rather than educators increasingly have filled faculty positions. Although the clinical expertise of this faculty is extremely valuable, they lack critical educational skills. This creates a dilemma for administrators, senior faculty, and the clinicians themselves. This article presents a new solution to this continuing problem. The development, purpose, and outcomes of the Teacher Education Center at the University of Pennsylvania are described. This center has met with success in preparing a specific group of expert clinicians, nurse practitioners, and nurse midwives for their faculty roles.

Curriculum↗
PubMed1998

MR spectroscopy in the evaluation of epilepsy.

MR spectroscopy may be a helpful, reliable, noninvasive test with which to lateralize the seizure focus in patients with partial complex seizures. MR spectroscopy is complementary to other studies, especially MR imaging, and both may be performed in a single integrated examination and result in improved surgical management and outcome.

Brain↗
PubMed1998

White blood cell count is a poor predictor of severity of disease in the diagnosis of appendicitis.

The white blood cell (WBC) count is considered to be a useful test in the diagnosis of appendicitis. The purpose of this study was to examine the clinical features of patients with normal WBC appendicitis and also to determine whether a higher WBC count correlates with a more advanced stage of appendicitis. Patients with pathologically confirmed appendicitis from January 1989 to December 1994 were included in the study (n = 1919). The age, gender, temperature, length of hospital stay, and severity of disease (1 = acute appendicitis; 2 = gangrenous appendicitis; 3 = perforated appendicitis with abscess formation; 4 = appendicitis with diffuse peritonitis) were compared for patients with a normal WBC count (range, 3.8-10.9) versus those who had an elevated WBC count. A normal WBC count was seen in 11 per cent of patients (n = 209). There was no difference in age, temperature, gender, or severity of disease in the patients with a normal WBC count compared with those with an elevated WBC count (P > 0.05). The severity of disease of patients with a normal WBC count were: 1 = 58 per cent; 2 = 13 per cent; 3 = 7 per cent; and 4 = 22 per cent. For patients with an elevated WBC count the scores were: 1 = 57 per cent; 2 = 17 per cent; 3 = 13 per cent; and 4 = 14 per cent. The proportion of gangrenous and perforated appendicitis in the patients with a normal WBC count is the same as in the patients with an elevated WBC count.

Abscess↗
PubMed1997

Xyloglucan undergoes interpolymeric transglycosylation during binding to the plant cell wall in vivo: evidence from 13C/3H dual labelling and isopycnic centrifugation in caesium trifluoroacetate.

Xyloglucan from the walls of Rosa cells that had been cultured on [12C]- or [13C]-glucose formed bands in caesium trifluoroacetate with mean buoyant densities of 1.575 or 1.616 g/ml respectively. Incubation of a mixture of [13C,3H]xyloglucan and [12C,1H]xyloglucan in the presence of xyloglucan endotransglycosylase (XET) activity caused the mean buoyant density of the radioactive material to decrease, indicating that interpolymeric transglycosylation could be detected in vitro. We used two 13C/3H-dual-labelling protocols to look for interpolymeric transglycosylation in vivo. In protocol A, [13C]glucose-grown Rosa cells were transferred into [12C]glucose medium 6 h after a approximately 2 h pulse of l-[1-3H]arabinose (which radiolabels the xylose residues of xyloglucan). The mean buoyant density of the wall-bound [3H]xyloglucan decreased during the following 7 days in culture. This indicates that, during or after the wall-binding of newly synthesized [12C,1H]xyloglucan, it became covalently attached to previously wall-bound [13C, 3H]xyloglucan. In protocol B, [12C]glycerol- or [12C]glucose-grown Rosa cells were transferred into [13C]glucose medium, 20 or 60 min before a approximately 2 h pulse of [3H]arabinose. The buoyant density of the earliest wall-bound [3H]xyloglucan showed that it had a 12C/13C ratio of approximately 1:1. This indicates that, during (or, implausibly, before) wall-binding, the newly synthesized [13C, 3H]xyloglucan became covalently attached to previously synthesized [12C]xyloglucan. During the following 7 days in culture, the mean buoyant density of the [3H]xyloglucan increased, showing that later-synthesized [13C,1H]xyloglucan can be covalently attached to previously wall-bound [12C,13C,3H]xyloglucan. The only known mechanism by which segments of xyloglucans could become covalently attached to each other in the cell wall is by interpolymeric transglycosylation catalysed by XET. We conclude that XET-catalysed interpolymeric transglycosylation accompanies, and probably causes, the integration of newly secreted xyloglucan into the cell-wall architecture.

Carbon Isotopes↗
PubMed1997

Cancer incidence among an HIV-infected cohort. Pulmonary Complications of HIV Infection Study Group.

Malignancies, particularly Kaposi's sarcoma and non-Hodgkin's lymphoma (NHL), are associated with human immunodeficiency virus (HIV) infection. Cancer incidence among 1,073 asymptomatic HIV-infected individuals from the Pulmonary Complications of HIV Infection Study cohort, persons from six states followed from 1988 to 1994, was examined. Total cancer incidence was 3.99/100 person-years; for Kaposi's sarcoma, incidence was 2.64 cases/100 person-years, and for NHL, it was 1.18 cases/100 person-years. Total cancer (n = 156 cases) was higher among nonblacks than among blacks (rate ratio = 2.8, 95% confidence interval 1.3-6.1), with similar results for Kaposi's sarcoma and NHL. The rate of lung cancer (n = 5) among white, homosexual/bisexual males was 0.18 per 100 person-years, suggesting a high risk of lung cancer.

Adult↗
PubMed1997

Trihydroxynaphthalene reductase from Magnaporthe grisea: realization of an active center inhibitor and elucidation of the kinetic mechanism.

Active trihydroxynaphthalene reductase (3HNR) is essential for the biosynthesis of fungal melanin by Magnaporthe grisea and is a focus of inhibitor design studies directed toward control of blast disease in rice. Tricyclazole, a preventative fungicide against rice blast, has been previously characterized as inhibiting 3HNR noncompetitively [Viviani, F., Vors, J. P., Gaudry, M., & Marquet, A. (1993) Bull. Soc. Chem. Fr. 136, 395-404] with respect to its naphthol substrate. Our steady-state kinetic and fluorescence titration studies show that instead the inhibitor binds competitively with respect to the naphthol substrate and that it binds to 3HNR forms with the preferences 3HNR.NADPH > 3HNR.NADP+ > 3HNR (unliganded): Kt = 15 nM, 0.56 microM, and Kd = 8.5 microM, respectively. Analysis of the frontier molecular orbitals of tricyclazole and NADP(H) provides a basis for the affinity differences of tricyclazole for 3HNR.NADP(H) enzyme forms. Fluorescence titrations show that NADPH and naphthol substrates form binary complexes with 3HNR [Kd(NADP+) = 38 microM and Kd(U7278, an alternate naphthol-like substrate) = 220 microM]. However, the overwhelmingly preferred order of productive binding is NADPH followed by naphthol substrate, as shown by the uncompetitive inhibition of 3HNR by tricyclazole with respect to NADPH. Consistent with this mechanism, the K(m)'s for the naphthol substrates U7278 and scytalone (5 and 6 microM, respectively) are much lower than the Kd's of the binary complexes. The partition ratio of U7278 and a physiological substrate (scytalone) was 95:1 and unchanged on varying 3HNR.NADP+/3HNR(unliganded), which is also consistent with the ordered mechanism. The pH dependence of the hydride transfer rate from U7278 to NADP+ was measured, as was the pH dependence of Kcat/K(m)(NADP+). Hydride transfer had a pH dependence which suggests a single deprotonated residue (pKa = 6.0) is required for catalysis. Khyd, the rate constant for hydride transfer, was 9-fold larger than Kcat with U7278 as a substrate. A burst in the pre-steady-state suggests that release of one or both of the products is rate limiting to Kcat at pH 7.0. The pH dependence of Kcat/K(m)(NADP+) indicates a requirement for a single deprotonated group and this ionization is assigned to the 2' phosphate of NADP+. 3HNR was found to be 800-fold more specific for NADP+ relative to NAD+. Analysis of sequence and structure [Anderson, A., Jordan, D. B., Schneider. G., & Lindqvist. Y. (1996) Structure 4, 1161-1170] reveals that 3HNR is a member of the short-chain dehydrogenase superfamily of enzymes.

Antifungal Agents↗
PubMed1997

Preemptive analgesia in patients undergoing appendectomy.

OBJECTIVE: To evaluate the use of preemptive analgesia in patients who were undergoing an operation for acute appendicitis. DESIGN: Double-blind, randomized control trial. SETTING: Public hospital. PATIENTS: Patients who presented with presumed appendicitis. INTERVENTION: Patients received 1 of the following treatments: group 1, preemptive analgesia with a combination of lidocaine hydrochloride and bupivacaine hydrochloride; group 2, preemptive analgesia with saline solution; or group 3, nothing. MAIN OUTCOME MEASURES: The Wong-Baker FACES Pain Rating Scale, analgesic requirements, number of analgesic doses required, and length of hospital stay. RESULTS: No differences were noted in postoperative pain, the total number of analgesic doses per day, the quantity of narcotic medication administered, and the length of hospital stay. CONCLUSIONS: Compared with healthy control subjects, preemptive analgesia did not reduce postoperative pain, reduce analgesic requirements, or shorten the length of hospital stay in patients who underwent an appendectomy. Premptive analgesia may be applicable only for patients without preoperative pain.

Acute Disease↗
PubMed1997

High-frequency intratracheal pulmonary ventilation: improved gas exchange at lower airway pressures.

PURPOSE: Conventional ventilation in the neonatal intensive care unit causes iatrogenic injury to fragile newborn lungs, especially those with preexisting pathology or prematurity. Intratracheal pulmonary ventilation (ITPV), developed by Dr Theodor Kolobow and associates at the National Institutes of Health (NIH), incorporates a continuous flow of humidified gas through a reverse thrust catheter positioned at the distal end of the endotracheal tube. In animal studies ITPV was shown to facilitate gas exchange at low peak pressures by reducing physiological dead space, facilitating exhalation, and enhancing CO2 elimination. The specific aims of this project were (1) to invent a new ITPV-specific ventilator; (2) to optimize gas exchange in a newborn animal model at low airway pressures using higher frequency ITPV; and (3) to demonstrate efficacy and improved ventilation at lower airway pressures in a prematurity model. METHODS: (1) A new ventilator had to be constructed. The first prototype is microprocessor driven, incorporating controls for flow, pressures, and concentrations of gases. The ventilator has the capability to vary Fio2, respiratory rate (0 to 15 Hz), and inspiratory-expiratory I:E ratio. (2) Prototype testing was performed. Newborn lambs (n = 3, 6 to 7 kg) underwent tracheotomy and placement of arterial and venous lines. Lambs were initially supported on conventional mechanical ventilation (CMV). Animals were allowed to achieve steady state with measurements of baseline vital signs, arterial blood gases, and ventilatory settings. ITPV was instituted at a rate of 100 breaths per minute and flow adjusted to achieve lower peak carinal pressures than obtainable on conventional ventilation. In a stepwise fashion, respiratory rate, I:E ratio, and ITPV flows were varied while initially maintaining Paco2 constant, and then allowing improvement. (3) These experiments were repeated in preterm lambs (n = 6, 1.8 to 3.6 kg). RESULTS: At the time of transition from CMV to ITPV (rate, 100, I:E, 1:3), gas exchange was maintained despite a documented drop in average peak carinal pressure for the newborn lambs from 28.3 cm H2O on CMV to 10.3 cm H2O on ITPV (P = .028). The average peak carinal pressure fell even further at higher ITPV rates with adjustments in I:E ratio. For the premature lambs, peak carinal pressures also fell significantly on ITPV (44 to 32 cm H2O, P = .002) with corresponding significant improvement in ventilation (Paco2 from 52.2 to 31.9 mm Hg, P = .029). CONCLUSIONS: (1) Our new ITPV ventilator operates at rates and I:E ratios previously unobtainable. (2) In newborn and premature lambs ITPV functions most effectively at higher rates with higher gas flow rates and with longer exhalation, providing significantly improved gas exchange at significantly lower peak carinal pressures. (3) ITPV may prove beneficial in achieving gas exchange in newborns while avoiding barotrauma. Based on these data, we have initiated human clinical studies of ITPV in newborns with congenital diaphragmatic hernia or prematurity to improve gas exchange and reduce barotrauma in the neonatal intensive care unit.

Animals↗
PubMed1997

Effect of inhaled nitric oxide on endothelin-1 and cyclic guanosine 5'-monophosphate plasma concentrations in newborn infants with persistent pulmonary hypertension.

OBJECTIVE: To examine the role of endogenous nitric oxide (NO) and endothelin-1 (ET-1) in the pathogenesis of persistent pulmonary hypertension of the newborn (PPHN) and to determine whether inhaled NO, currently under investigation as a new therapy for PPHN, affects plasma concentrations of these vasoactive mediators. METHODS: Circulating ET-1 and cyclic guanosine monophosphate (cGMP) concentrations were measured by radioimmunoassay in 15 healthy term newborn infants and 46 newborn infants with PPHN enrolled in a randomized, controlled trial of inhaled NO. These concentrations were followed up longitudinally and compared between the NO and the conventionally treated group. RESULTS: Concentrations of ET-1 were significantly higher and cGMP concentrations significantly lower in infants with PPHN compared with healthy newborn infants (median ET-1, 28 vs 11 pmol/L; p = 0.0001; median cGMP, 35 vs 61 pmol/ml; p = 0.0001, respectively). ET-1 concentrations showed an upward trend at 1 and 24 hours of treatment and a subsequent decline at recovery in both subgroups of patients, with the most pronounced decrease in the NO group. cGMP concentrations increased significantly only in the NO group, with a peak at 1 hour of treatment (median, 61 pmol/ml). As the dose of NO decreased, cGMP concentrations declined. In contrast, conventionally treated infants manifested no change in cGMP concentrations from baseline until recovery, when a significant decrease was noted (median decrease of 13 pmol/ml; p = 0.002). We did not find a significant difference between ET-1 and cGMP concentrations in infants who required extracorporeal membrane oxygenation compared with those who did not. CONCLUSIONS: PPHN is associated with increased ET-1 and decreased cGMP plasma concentrations, which may contribute to the pathogenesis of the disease. Inhaled NO appears to modulate these mediators during the disease process, suggesting an interaction between ET-1 and NO in vivo.

Administration, Inhalation↗