julilili42/papers huggingface dataset:
Naltrexone Does Not Relieve Uremic Pruritus
2000-03-01

Abstract. Improvement of uremic pruritus was reported under short-term administration of the μ-receptor antagonists naltrexone and naloxone. The aim of the present study was to confirm the efficacy and safety of the oral μ-receptor antagonist naltrexone during a 4-wk treatment period in patients on hemodialysis and peritoneal dialysis. A placebo-controlled, double-blind crossover study of uremic patients with persistent, treatment-resistant pruritus was performed. Of 422 patients screened between December 1997 and June 1998, 93 suffered from pruritus and 23 were eligible for the study. Patients were started either with a 4-wk naltrexone sequence (50 mg/d) or matched placebo. This was followed by a 7-d washout, and patients continued with a 4-wk sequence of the alternate medication. Pruritus intensity was scored daily by a visual analogue scale (VAS) and weekly by a detailed score assessing scratching activity, distribution of pruritus, and frequency of pruritus-related sleep disturbance. Sixteen of 23 patients completed the study. During the naltrexone period, pruritus decreased by 29.2% (95% confidence interval [CI], 18.7 to 39.6) on the VAS and by 17.6% (95% CI, 4.2 to 31.1) on the detailed score. In comparison, pruritus decreased by 16.9% (95% CI, 6.8 to 26.9) on the VAS and by 22.3% (95% CI, 9.3 to 35.2) on the detailed score during the placebo period. The difference between the naltrexone and the placebo treatment period was not statistically significant. Nine of 23 patients complained of gastrointestinal disturbances during the naltrexone period compared with only one of 23 patients during the placebo period ( P &lt; 0.05). These results show that treatment of uremic pruritus with naltrexone is ineffective. In addition, a high incidence of adverse effects was observed during treatment with naltrexone.
Direct Quantitative Transcript Analysis of the agr Regulon of Staphylococcus aureus during Human Infection in Comparison to the Expression Profile In Vitro
2000-03-01

ABSTRACT Bacteria possess a repertoire of distinct regulatory systems promoting survival in disparate environments. Under in vitro conditions it was demonstrated for the human pathogen Staphylococcus aureus that the expression of most virulence factors is coordinated by the global regulator agr . To monitor bacterial gene regulation in the host, we developed a method for direct transcript analysis from clinical specimens. Quantification of specific transcripts was performed by competitive reverse transcription-PCR, and results were normalized against the constitutively expressed gene for gyrase ( gyr ). Using sputum from cystic fibrosis (CF) patients infected with S. aureus we examined the transcription of the effector molecule RNAIII of agr , of spa (protein A), generally repressed by agr , and of hla (alpha-toxin), generally activated by agr . In the CF lung RNAIII was expressed poorly, indicating an inactive agr in vivo. Despite the low level of RNAIII expression, spa was detectable only in minute amounts and an irregular transcription of hla was observed in all sputum samples. After subculturing of patient strains agr -deficient isolates and isolates with unusual expression profiles, i.e., not consistent with those obtained from prototypic strains, were observed. In conclusion, the agr activity seems to be nonessential in CF, and from the described expression pattern of spa and hla , other regulatory circuits aside from agr are postulated in vivo.
Stochastic volatility models: conditional normality versus heavy-tailed distributions
2000-03-01

Most of the empirical applications of the stochastic volatility (SV) model are based on the assumption that the conditional distribution of returns, given the latent volatility process, is normal. In this paper, the SV model based on a conditional normal distribution is compared with SV specifications using conditional heavy-tailed distributions, especially Student's t-distribution and the generalized error distribution. To estimate the SV specifications, a simulated maximum likelihood approach is applied. The results based on daily data on exchange rates and stock returns reveal that the SV model with a conditional normal distribution does not adequately account for the two following empirical facts simultaneously: the leptokurtic distribution of the returns and the low but slowly decaying autocorrelation functions of the squared returns. It is shown that these empirical facts are more adequately captured by an SV model with a conditional heavy-tailed distribution. It also turns out that the choice of the conditional distribution has systematic effects on the parameter estimates of the volatility process. Copyright © 2000 John Wiley & Sons, Ltd.
L/M cone ratios in human trichromats assessed by psychophysics, electroretinography, and retinal densitometry
2000-03-01

Estimates of the relative numbers of long-wavelength-sensitive (L) and middle-wavelength-sensitive (M) cones vary considerably among normal trichromats and depend significantly on the nature of the experimental method employed. Here we estimate L/M cone ratios in a population of normal observers, using three psychophysical tasks-detection thresholds for cone-isolating stimuli at different temporal frequencies, heterochromatic flicker photometry, and cone contrast ratios at minimal flicker perception--as well as flicker electroretinography and retinal densitometry. The psychophysical tasks involving high temporal frequencies, specifically designed to tap into the luminance channel, provide average L/M cone ratios that significantly differ from unity with large interindividual variation. In contrast, the psychophysical tasks involving low temporal frequencies, chosen to tap into the red-green chromatic channel, provide L/M cone ratios that are always close to unity. L/M cone ratios determined from electroretinographic recordings or from retinal densitometry correlate with those determined from the high-temporal-frequency tasks. These findings suggest that the sensitivity of the luminance channel is directly related to the relative densities of the L and the M cones and that the red-green chromatic channel introduces a gain adjustment to compensate for differences in L and M cone signal strength.
A Conserved Domain of the Arabidopsis GNOM Protein Mediates Subunit Interaction and Cyclophilin 5 Binding
2000-03-01

The Arabidopsis GNOM protein, a guanine nucleotide exchange factor (GEF) that acts on ADP ribosylation factor (ARF)-type G proteins, is required for coordination of cell polarity along the apical-basal embryo axis. Interallelic complementation of gnom mutants suggested that dimerization is involved in GNOM function. Here, direct interaction between GNOM molecules is demonstrated in vitro and by using a yeast two-hybrid system. Interaction was confined to an N-terminal domain conserved within a subgroup of large ARF GEFs. The same domain mediated in vitro binding to cyclophilin 5 (Cyp5), which was identified as a GNOM interactor in two-hybrid screening. Cyp5 displayed peptidylprolyl cis/trans-isomerase and protein refolding activities that were sensitive to cyclosporin A. Cyp5 protein accumulated in several plant organs and, like GNOM, was partitioned between cytosolic and membrane fractions. Cyp5 protein was also expressed in the developing embryo. Our results suggest that Cyp5 may regulate the ARF GEF function of the GNOM protein during embryogenesis.
Construction and Characterization of an agr Deletion Mutant of Staphylococcus epidermidis
2000-03-01

ABSTRACT The physiological significance of the accessory gene regulator ( agr ) system of Staphylococcus epidermidis was investigated by construction of an agr deletion mutant via allelic replacement with a spectinomycin resistance cassette. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the protein pattern was strongly altered in the mutant; the amounts of most surface proteins were higher, whereas the amounts of most exoproteins were lower. The agr system of S. epidermidis thus appears to have an important impact on growth phase-dependent protein synthesis as has been shown for Staphylococcus aureus . The activity of the exoenzymes lipase and protease, assumed to be involved in staphylococcal pathogenicity, was investigated by agar diffusion assays and SDS-PAGE activity staining. A general reduction of these enzyme activities in the agr mutant was found. The difference in overall lipase activity was small, but zymographic analysis suggested a clear defect in lipase processing in the agr mutant.
Role of Na+/H+exchanger NHE3 in nephron function: micropuncture studies with S3226, an inhibitor of NHE3
2000-03-01

Na + /H + exchanger NHE3 is expressed in the luminal membrane of proximal tubule and thin and thick ascending limb of Henle's loop. To further define its role, the novel NHE3 inhibitor S3226 was employed in micropuncture experiments in nephrons with superficial glomeruli of anesthetized rats. Microperfusion of proximal convoluted tubule with S3226 revealed a dose-dependent inhibition of reabsorption (IC 50 of 4–5 μM) with a maximum inhibition of 30% for fluid and Na + . During microperfusion of Henle's loop (last superficial proximal to first superficial distal tubular loop), no effect of S3226 (10 or 30 μM) on the reabsorption of fluid or Na + was observed. Finally, S3226 (30 μM) left the tubuloglomerular feedback response unaltered as determined by the fall in proximal tubular stop-flow pressure in response to increasing loop of Henle perfusion rate. These studies indicate that NHE3 significantly contributes to fluid and Na + reabsorption in proximal convoluted tubule. NHE3 appears not to significantly contribute to fluid or Na + reabsorption in the loop of Henle (including the S3 segment of proximal tubule) or macula densa control of nephron filtration.
Mycorrhiza formation and elevated CO2 both increase the capacity for sucrose synthesis in source leaves of spruce and aspen
2000-03-01

The effects of mycorrhiza formation in combination with elevated CO 2 concentrations on carbon metabolism of Norway spruce ( Picea abies ) seedlings and aspen ( Populus tremula × Populus tremuloides ) plantlets were analysed. Plants were inoculated for 6 wk with the ectomycorrhizal fungi Amanita muscaria and Paxillus involutus (aspen only) in an axenic Petri‐dish culture at 350 and 700 μl l −1 CO 2 partial pressure. After mycorrhiza formation, a stimulation of net assimilation rate was accompanied by decreased activities of sucrose synthase, an increased activation state of sucrose‐phosphate synthase, decreased fructose‐2,6‐bisphosphate and starch, and slightly elevated glucose‐6‐phosphate contents in source leaves of both host species, independent of CO 2 concentration. Exposure to elevated CO 2 generally resulted in higher net assimilation rates, increased starch as well as decreased fructose‐2,6‐bisphosphate (aspen only) content in source leaves of both mycorrhizal and nonmycorrhizal plants. Our data indicate only slightly improved carbon utilization by mycorrhizal plants at elevated CO 2 . They demonstrate however, that both factors which modulate the sink‐source properties of plants increase the capacity for sucrose synthesis in source leaves mainly by allosteric enzyme regulation.
Implicit and explicit dialogue structuring in virtual learning groups
2000-03-01

Background. The promotion of virtual learning groups by instructional means is gaining importance with the spread of telematic learning. In virtual learning groups, students discuss certain learning materials or cooperate in problem solving by means of computer‐mediated communication. Due to the specific features of electronic communication, supportive means appear to be necessary for such learning situations. Aims. The investigation focuses on testing two different forms of dialogue structuring in virtual learning groups, in which students discuss a given subject matter together and clarify problems in understanding by means of synchronous computer‐mediated communication. Sample. Forty‐five students from various disciplines at the University of Tubingen, except students of physics, participated in the investigation. Method. An experiment was conducted involving three‐person groups in a telematic setting with two different kinds of dialogue structuring: implicit structuring induced group discussion on the subject matter by working on key questions in a preceding learning phase, whilst explicit structuring provided additional rules for discussion. These rules prompted group members to argue and aimed at directing them to equal participation. Results. Compared to a control group, both implicit and explicit structuring showed greater orientation on the subject matter and showed less off‐task talk. Moreover, explicit structuring led to more coherence in subject matter discussion with regard to the completion of topics. However, post‐test performance showed no significant difference in knowledge over that of the control group. Conclusion. The results of the investigation show that dialogue structuring can be an adequate pedagogical approach for virtual learning groups.
Concentration-Dependent Potentiating and Inhibitory Effects of Boswellia Extracts on 5-Lipoxygenase Product Formation inStimulated PMNL
2000-03-01

Preparations from the gum of Boswellia spec. have been used in the traditional medicine for the treatment of inflammatory diseases. Extracts from B. serrata gum were shown to inhibit leukotriene biosynthesis by impairing the 5-lipoxygenase (5-LO) activity. In order to identify the minimal effective concentrations of extracts in vitro we studied the effects of ethanolic extracts from commercially available resins from two regions (B. serrata gum from India and Olibanum in granis from Arabia) on the 5-LO product formation from endogenous substrate in calcium and ionophore stimulated neutrophils in a defined concentration range. Both extracts inhibited 5-LO product formation in vitro in concentrations greater than 10 to 15 micrograms/ml as reported previously for an ethanolic B. serrata extract. In contrast, lower concentrations of extracts (1 to 10 micrograms/ml) even potentiated 5-LO product formation, especially the biosynthesis of 5(S)-HETE. The in vitro data underline the major importance of drug standardization when Boswellia resin containing preparations are used for the treatment of diseases.
Blood flow velocity waveforms of the fetal pulmonary artery and the ductus arteriosus: reference ranges from 13 weeks to term
2000-03-01

Objective To establish reference ranges for blood flow velocity waveforms of the fetal main pulmonary artery and the ductus arteriosus during the second and third trimesters of pregnancy. Methods A prospective cross‐sectional echocardiographic study was performed in 222 normal fetuses from 13 to 41 weeks of gestation using high resolution/color Doppler ultrasound equipment. Results Gestational age‐specific reference ranges are given for peak velocity across the pulmonary valve, velocities in the ductus arteriosus, peak systolic velocity in the ductus arteriosus‐to‐peak velocity across the pulmonary valve ratio, ductal systolic velocity‐to‐diastolic velocity ratio, ductal resistance index and ductal pulsatility index. In the ductus arteriosus, increasing fetal heart rate was significantly associated with increasing end‐diastolic velocity and decreasing systolic‐to‐diastolic ratio, decreasing resistance index, and decreasing pulsatility index. Conclusions Based on a prospective study in more than 200 normal fetuses, the data provide gestational age specific reference ranges for blood flow velocity waveforms of the fetal pulmonary artery and the ductus arteriosus. The reference ranges may be helpful in prenatal diagnosis of cardiac malformations and ductal obstruction from 13 to 41 weeks of gestation.
Hormone Autotrophic Growth and Differentiation Identifies Mutant Lines of Arabidopsis with Altered Cytokinin and Auxin Content or Signaling
2000-03-01

Abstract We describe mutant tissue lines of Arabidopsis that are able to grow in vitro as callus on hormone-free medium. The 14 lines presented here show different hormone autotrophic differentiation behaviors that can be classified into three categories: (a) forming roots (rooty callus), (b) forming shoots or shoot-like structures (shooty callus), or (c) growing without organ formation (callus). Three fast-growing lines showed altered steady-state mRNA levels of the Cdc2 andCycD3 cell cycle genes. Three of the six rooty callus lines contained about 20- to 30-fold higher levels of auxins than wild-type callus. These and two other lines with normal auxin content showed an increased steady-state level ofIAA1 and IAA2 transcripts in the absence of exogenous auxin. Five of the six shooty callus lines had increased steady-state mRNA levels of the CKI1 gene and/or of the homeobox genes KNAT1 andSTM, suggesting that the phenotype is linked to altered cytokinin signaling. Also, one cytokinin-overproducing line with only 5% of wild-type cytokinin oxidase activity was identified. These results indicate that screening for hormone-autonomous growth identifies mutants with altered hormone content or signaling.
Molecular Epidemiology of Community‐AcquiredStaphylococcus aureusin Families with and without Cystic Fibrosis Patients
2000-03-01

The molecular epidemiology of Staphylococcus aureus nasal commensal strains and community-acquired infecting strains was assessed by comparison of prevalence, persistence, transmission rate, and clonal distribution of S. aureus in families with and without cystic fibrosis (CF) patients. Isolates were typed by pulsed-field gel electrophoresis. CF patients without antibiotic treatment had a significantly higher nasal prevalence (66%) of S. aureus than did treated patients (29%; P<.001) or healthy controls (32%; P<.001), suggesting that persons with CF have a higher susceptibility to this organism. Strain transmission was frequent within both CF (55%) and non-CF (62%) families. After 3 and 19 months, 57% and 21%, respectively, of all persons still harbored the same S. aureus strain. Most of the isolates (78%) belonged to 8 of 38 genome types common in CF patients and in healthy persons. The predominant occurrence of a limited number of S. aureus clones within the community suggests evolutionary mechanisms for the selection of certain strains without an obvious association with disease.
Physical Exercise-Induced Expression of Inducible Nitric Oxide Synthase and Heme Oxygenase-1 in Human Leukocytes: Effects ofrrr-α-Tocopherol Supplementation
2000-03-01

This study evaluated the effects of RRR-alpha-tocopherol (500 IU/day, 8 days) on in vivo cytokine response and cytoplasmic expression of inducible nitric oxide synthase (iNOS) and the antioxidant stress protein heme oxygenase-1 (HO-1) in human leukocytes after exhaustive exercise. Thirteen men were investigated in a double-blind, placebo-controlled, cross-over study with a wash-out period of 28 days. The exercise procedure consisted of an incremental treadmill test followed by a continuous run until exhaustion at 110% of the individual anaerobic threshold (total duration 28.5 +/- 0.8 min). HO-1 and iNOS protein were assessed in mono- (M), lympho-, and granulocytes (G) using flow cytometry. Plasma interleukin-6 (IL-6) and IL-8 were measured by ELISA. IL-6 rose significantly whereas IL-8 did not exhibit significant changes after exercise. Changes of IL-6 were not affected by RRR-alpha-tocopherol. Exercise induced an increase of iNOS protein primarily in M and G. A small, but significant, increase of HO-1 protein was measured in M and G. RRR-alpha-Tocopherol did not show any significant effects on cytoplasmic expression of iNOS and HO-1 at rest and after exercise. In conclusion, exhaustive exercise induces expression of iNOS and HO-1 in human leukocytes by a mechanism that is not sensitive to RRR-alpha-tocopherol supplementation.
Reference ranges for two‐dimensional echocardiographic examination of the fetal ductus arteriosus
2000-03-01

Objectives To establish reference ranges for 2D‐echocardiographic examination of the fetal ductus arteriosus and its relationship to the main pulmonary artery and the aorta. Methods A prospective cross‐sectional echocardiographic study was performed in 222 normal fetuses from 13 to 41 weeks of gestation using high resolution/color Doppler ultrasound equipment. Results Gestational age‐specific reference ranges are given for the diameter of the pulmonary valve anulus, diameter of the ductus arteriosus at its beginning, middle, and end, ductal length, ductal diameter‐to‐pulmonary valve anulus diameter ratio, and the spatial relationship of the ductus arteriosus to the main pulmonary artery and to the aorta. Conclusions The presented data derived from a study group of 222 normal fetuses provide in‐vivo insights into the morphology of the ductus arteriosus and its relationship to the adjacent vessels. The reference ranges may be helpful in prenatal diagnosis of cardiac malformations and abnormalities of the ductus arteriosus, such as obstruction or aneurysm from 13 to 41 weeks of gestation.
Computer note. POPDIST, version 1.1.1: a program to calculate population genetic distance and identity measures
2000-03-01

In this note we announce the release of POPDIST version 1.1.1. This is a program to calculate genetic distance and identity measures, including the measure of Tomiuk and Loeschcke, which also allows calculation of genetic similarity measures for comparisons involving polyploid and parthenogenetic populations. The program is available for free from the Internet as C source code, or compiled for the Macintosh, MS Windows 95, and various brands of UNIX.
17α-Hydroxylase/17,20-Lyase Deficiency as a Model to Study Enzymatic Activity Regulation: Role of Phosphorylation*
2000-03-01

Cytochrome P450 17alpha-hydroxylase (CYP17) is a single gene-encoded protein with two activities: 17alpha-hydroxylase and 17,20-lyase. The two catalytic activities are differentially regulated in health and disease. We took advantage of naturally occurring human mutations to understand the molecular bases of this differential regulation. We identified eight novel mutations in the CYP17 gene, different in nature and spread throughout the gene. As posttranslational modifications appear to be important for activity control, we investigated the phosphorylation state of wild-type and mutant CYP17 proteins. Although phospholabeled protein was seen when the wild-type and most mutant proteins were expressed, no phosphorylation was detected for the F417C mutant. F417C is the only 17,20-lyase deficiency case confirmed at the molecular level and represents the first phosphorylation CYP17-deficient mutant. In search of the physiological agents involved in this process, the effect of cAMP was tested on activity and phosphorylation state of our mutant CYP17 proteins. cAMP stimulates activity and phosphorylation in all cases, except in the F417C and R35L mutants. The lack of response to the physiological second messenger might explain the different phenotypes. The F417C mutant protein, which is already shown to be associated with the lack of electron transfer, provides for the first time a link between the electron transfer system and the phosphorylation state of the CYP17 enzyme in the control of 17,20-lyase activity.