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Biomedical subjects

J Weiss

Publications and source records attributed to J Weiss.

At least 37 records · Page 2Linked to original sources
PubMed2003

Enhanced inhibition of Escherichia coli O157:H7 by lysozyme and chelators.

This study examined the effects of three chelating agents (EDTA, disodium pyrophosphate [DSPP], and pentasodium tripolyphosphate [PSTPP]) on the inhibition of the growth of Escherichia coli O157:H7 by lysozyme. The objective of this study was to identify replacement chelators that exhibit synergistic properties similar to those of EDTA. The inhibitory effects of EDTA at 300 to 1,500 microg/ml and of DSPP and PSTPP at 3,000 to 15,000 microg/ml in combination with lysozyme at 200 to 600 microg/ml for up to 48 h at pHs of 6.0, 7.0, and 8.0 on four strains of E. coli O157:H7 was studied with the use of a microbroth dilution assay. The addition of EDTA enhanced lysozyme's inhibitory effect on strains of E. coli O157:H7. EDTA at > or = 300 microg/ml combined with lysozyme at 200 to 600 microg/ml was sufficient to inhibit the growth of the strains at pHs of 6.0 and 8.0. At pH 7.0, lysozyme at 200 to 600 microg/ml and EDTA concentrations of > or = 1,000 microg/ml were effective in inhibiting three of the four strains. DSPP at pH 6.0 was inhibitory at > or = 10,000 microg/ml when combined with lysozyme at 200 to 300 microg/ml. In contrast, PSTPP increased the inhibitory activity of lysozyme more effectively at pH 8.0. Lysozyme at 200 to 600 microg/ml was effective against two strains of E. coli O157:H7 when used in conjunction with PSTPP at > or = 5,000 microg/ml. The remaining strains were inhibited by PSTPP at > or = 10,000 microg/ml. Our results indicate that inhibition occurred with each lysozyme-chelator combination, but the concentrations of phosphates required to increase the antimicrobial spectrum of lysozyme against E. coli O157:H7 were higher than the EDTA concentrations required to achieve the same effect.

Anti-Infective Agents↗
PubMed2002

Modern stationary phases for ion chromatography.

Due to the better understanding of the processes taking place at the surface of the stationary phases, the number of ion-exchange materials for ion chromatography (IC) has increased tremendously over recent years. As a result, the multitude of commercially available columns today with their different selectivities for anion and cation chromatography is almost confusing. Hence, the aim of this article is to describe the different principles determining selectivity and ion-exchange capacity and to classify the various ion-exchange materials accordingly. To ensure a fair comparison of these columns, the selectivity differences are illustrated by showing separations of standards rather than individual samples.

Journal Article↗
PubMed2002

Seizure-associated brain injury in term newborns with perinatal asphyxia.

BACKGROUND: There is controversy over whether seizures, the most common manifestation of neonatal brain injury, may themselves damage the developing brain. OBJECTIVE: To determine if neonatal seizures are independently associated with brain injury in newborns with perinatal asphyxia. METHODS: Ninety term neonates were studied with MRI and single-voxel (1)H-MRS on median day of life 6 (range 1 to 13 days). The severity of MR abnormality in the (1)H-MRS regions of interest was scored using a validated scale. Seizure severity was scored based on seizure frequency and duration, EEG findings, and anticonvulsant administration. Multivariable linear regression tested the independent association of seizure severity with impaired cerebral metabolism measured by lactate/choline and compromised neuronal integrity measured by N-acetylaspartate/choline in both regions. RESULTS: Clinical seizures occurred in 33 of 90 infants (37%). Seizure severity was associated with increased lactate/choline in both the intervascular boundary zone (p < 0.001) and the basal nuclei (p = 0.011) when controlling for potential confounders of MRI abnormalities and amount of resuscitation at birth. Each increase in seizure score was independently associated with a 21% increase in lactate/choline in the intervascular boundary zone (95% CI, 5.1-38.2%) and a 15% increase in the basal nuclei (95% CI, 0.1-31.7%). Seizure severity was independently associated with diminished N-acetylaspartate/choline in the intervascular boundary zone (p = 0.034). CONCLUSION: The severity of seizures in human newborns with perinatal asphyxia is independently associated with brain injury and is not limited to structural damage detectable by MRI.

Asphyxia Neonatorum↗
PubMed2002

Selective block of urethral sphincter contraction using a modified Brindley electrode in sacral anterior root stimulation of the dog.

AIMS: Patients with spinal cord injury often present with dysfunction of urinary bladder and urethral sphincter. One treatment option is sacral rhizotomy and sacral anterior root stimulation with the Finetech Brindley stimulator. However, a major disadvantage is the lack of selective stimulation, resulting in simultaneous contraction of sphincter and bladder followed by unphysiological micturition. This study investigated the possibility of selective bladder stimulation by using a Brindley electrode. METHODS: In 11 male anaesthetized foxhounds, a complete posterior rhizotomy was perormed. The anterior S2 roots were stimulated with different quasi-trapezoidal (QT) pulses (pulse length range, 600-1,400 microsec; stimulation current, 0.1-2.0 mA; frequency, 20 Hz) by using a tripolar Brindley electrode. Sphincter and bladder pressures were measured urodynamically. RESULTS: All 11 animals showed a maximal reduction of the highest sphincter pressure over 80%, and in 6 of 11 trials, the sphincter pressure was inhibited completely (100%). With stimulations at maximal sphincter blockade, the average achievable bladder pressure was 33.48 cm H(2)O higher than the average sphincter pressure, and in three cases, a strong micturition was observed. Selective blockade of the sphincter was possible by applying QT pulses. The bladders remained uninfluenced by this blockade and kept their excitability at any time. CONCLUSIONS: This study shows that selective bladder stimulation with little or no coactivation of the sphincter is possible. A physiological micturition can be achieved by using a tripolar Brindley electrode. Introduction of this stimulation technique into clinical practice should not face major difficulties, considering that the device is an established electrode.

Animals↗
PubMed2002

Efficacy of desmopressin in the treatment of nocturia: a double-blind placebo-controlled study in men.

OBJECTIVE: To investigate the efficacy and safety of oral desmopressin in the treatment of nocturia in men. PATIENTS AND METHODS: Men aged >/=18 years with verified nocturia (>or=two voids/night) and nocturnal urine production greater than their maximum functional bladder capacity were recruited. A 3-week dose-titration phase established the optimum desmopressin dose (0.1, 0.2 or 0.4 mg). After a 1-week 'washout' period, patients who responded in the dose-titration period were randomized to receive the optimal dose of desmopressin or placebo in a double-blind design for 3 weeks. RESULTS: In all, 151 patients entered the double-blind period (86 treated with desmopressin, 65 with placebo). In the desmopressin group 28 (34%) patients and in the placebo group two (3%) patients (P<0.001) had fewer than half the number of nocturnal voids relative to baseline; the mean number of nocturnal voids decreased from 3.0 to 1.7 and from 3.2 to 2.7, respectively, reflecting a mean decrease of 43% and 12% (P<0.001). The mean duration of the first sleep period increased by 59% (from 2.7 to 4.5 h) in the desmopressin group, compared with an increase of 21% (from 2.5 to 2.9 h) in the placebo group (P<0.001). The mean nocturnal diuresis decreased by 36% (from 1.5 to 0.9 mL/min) in the desmopressin group and by 6% (from 1.7 to 1.5 mL/min) in the placebo group (P<0.001). The mean ratio of night/24-h urine volume decreased by 23% and 1% (P<0.001), and the mean ratio of night/day urine volume decreased by 27% and increased by 3% (P<0.001) for the desmopressin and placebo groups, respectively. In the double-blind treatment period, similar numbers of patients had adverse events; 15 (17%) patients in the desmopressin and 16 (25%) patients in the placebo group. Most adverse events were mild. Serum sodium levels were <130 mmol/L in 10 (4%) patients and this occurred during dose-titration. CONCLUSIONS: Orally administered desmopressin is an effective and well-tolerated treatment for nocturia in men.

Administration, Oral↗
PubMed2001

Test of low-energy theorems for 1H(--> gamma, pi(0))(H)in the threshold hegion.

The photon asymmetry in the reaction 1H(--> gamma,pi(0))(1)H close to threshold has been measured for the first time with the photon spectrometer TAPS using linearly polarized photons from the tagged-photon facility at the Mainz Microtron MAMI. The total and differential cross sections were also measured simultaneously with the photon asymmetry. This allowed determination of the S-wave and all three P-wave amplitudes. The values obtained at threshold are E(0+) = [-1.33+/-0.08(stat)+/-0.03(syst)] x 10(-3)/m(pi(+)), P(1) = [9.47 +/- 0.08(stat) +/- 0.29(syst)] x 10(-3)q/m(2)(pi(+)), P(2) = [-9.46 +/- 0.1(stat) +/- 0.29(syst)] x 10(-3)q/m(2)(pi(+)), and P(3) = [11.48 +/- 0.06(stat) +/- 0.35(syst)] x 10(-3)q/m(2)(pi(+)).

Journal Article↗
PubMed2001

Direct observation of a rho decay of the D13(1520) baryon resonance.

The reaction gammap-->pi(+)pi(0)n has been measured at MAMI for photon energies up to 820 MeV. Invariant mass spectra of the particles in the final state (pi(+)n), (pi(0)n), (pi(+)pi(0)) have been determined for several bins of incident photon energy. Differences in pi(+)pi(0) and simultaneously measured pi(0)pi(0) invariant mass distributions are assigned to a rho branch of the D13(1520) nucleon resonance.

Journal Article↗
PubMed2001

Inherited disorders of the gonadotropin hormones.

Pulsatile GnRH acts at the GnRH receptor on gonadotropes to stimulate gonadotropin gene expression, hormone synthesis and secretion. The pituitary gonadotropins, LH and FSH, stimulate steroid production and gametogenesis in males and in females. Gonadotropin production thus requires the normal development and function of hypothalamic GnRH-producing neurons and pituitary gonadotrope cells. Genes involved in gonadotrope development and/or gene expression include SF1, DAX1, KAL, GNRHR, PC1, HESX1, LHX3, PROP1, LH beta, and FSH beta. Given the complex control of gonadotropin biosynthesis and secretion, it is not surprising that genetic abnormalities have been identified at several of these steps. Some of the mutations that will be reviewed include: (1) SF1 and DAX1-orphan nuclear receptors that are expressed at multiple levels throughout the reproductive axis; (2) KAL-X-linked Kallmann syndrome, where there is abnormal development of hypothalamic GnRH-producing neurons; (3) PC1-causing abnormal processing of GnRH and GNRHR mutations that impair action at the GnRH receptor; (4) HESX1, LHX3, PROP1-abnormal development/function of the gonadotrope cell lineage; (5) LH beta and FSH beta-mutations in the gonadotropin genes that cause structural abnormalities in the hormones. Although all of these gene defects lead to gonadotropin deficiency, each disorder is associated with unique phenotypic or hormonal features. Characterization of the molecular basis of gonadotropin deficiency is useful for directing therapy and for genetic counseling. Identification of these mutations also provides insight into the pathways that govern reproduction.

Animals↗
PubMed2001

Intermittent dislocation flow in viscoplastic deformation.

The viscoplastic deformation (creep) of crystalline materials under constant stress involves the motion of a large number of interacting dislocations. Analytical methods and sophisticated 'dislocation dynamics' simulations have proved very effective in the study of dislocation patterning, and have led to macroscopic constitutive laws of plastic deformation. Yet, a statistical analysis of the dynamics of an assembly of interacting dislocations has not hitherto been performed. Here we report acoustic emission measurements on stressed ice single crystals, the results of which indicate that dislocations move in a scale-free intermittent fashion. This result is confirmed by numerical simulations of a model of interacting dislocations that successfully reproduces the main features of the experiment. We find that dislocations generate a slowly evolving configuration landscape which coexists with rapid collective rearrangements. These rearrangements involve a comparatively small fraction of the dislocations and lead to an intermittent behaviour of the net plastic response. This basic dynamical picture appears to be a generic feature in the deformation of many other materials. Moreover, it should provide a framework for discussing fundamental aspects of plasticity that goes beyond standard mean-field approaches that see plastic deformation as a smooth laminar flow.

Journal Article↗
PubMed2001

Latex sensitization in health care workers and in the US general population.

Sensitization to natural rubber latex is a prerequisite to type I immediate hypersensitivity reactions (urticaria, angioedema, anaphylaxis, and allergic rhinitis) that result from subsequent latex exposure. This study examines occupations in which latex glove use is common to determine whether it is associated with increased prevalence odds of latex sensitization (measured by latex-specific immunoglobulin E antibodies) by using data from 5,512 adults aged 17--60 years from the Third National Health and Nutrition Examination Survey (1988--1991). After other factors associated with latex sensitization were controlled for, there was a nonsignificant association between longest-held jobs in health care and latex sensitization (odds ratio (OR) = 1.49, 95 percent confidence interval (CI): 0.92, 2.40). For current occupations, latex sensitization was not associated with health care work in which gloves were used (OR = 1.17, 95 percent CI: 0.51, 2.65) or with other occupations in which latex glove use is common (OR = 1.01, 95 percent CI: 0.49, 2.07) compared with other occupations. Current health care workers who reported not using gloves were at increased risk of latex sensitization, both among those without a history of childhood atopy (OR = 2.30, 95 percent CI: 1.04, 5.13) and those with such a history (OR = 28.04, 95 percent CI: 3.64, 215.97). This odds ratio heterogeneity suggests that subjects with childhood atopy may be at high risk of latex sensitization.

Adolescent↗
PubMed2001

Estrogen receptor binding to DNA is not required for its activity through the nonclassical AP1 pathway.

In the classical signaling pathway, the estrogen receptor (ER) binds directly to estrogen response elements (EREs) to regulate gene transcription. To test the hypothesis that the nonclassical pathway involves ER interactions with other proteins rather than direct binding to DNA, mutations were introduced into the DNA binding domain (DBD) of the mouse ERalpha. The effects of these DBD mutations were examined in DNA binding assays using reporter constructs containing either EREs (classical) or AP1 (nonclassical) response elements. Using the AP1 reporter, there was a reversal of ER action relative to that seen with the ERE reporter. Estradiol induced suppression, and the antiestrogen ICI 182,780 stimulated transcription of the AP1 reporter. DBD mutations in the proximal (P-box) of the first zinc finger of the ER (E207A/G208A and E207G/G208S) eliminated ERE binding. These mutants were inactive using the ERE reporter but retained partial or full activity with the AP1 reporter. The DBD mutant ERs interacted with Jun when tested in mammalian cell two-hybrid assays. Two mutations (K366D and I362R) in the ER ligand binding domain known to alter coactivator interactions impaired transcriptional responses using either the ERE or AP1 reporters. We concluded that ER action through the AP1 response element involves interactions with other promoter-bound proteins instead of, or in addition to, direct binding to DNA. Interactions with coactivators were required for both pathways. These data supported a model in which ER-mediated transcriptional activation or repression is dependent on the ligand and the nature of the response element in the target gene.

Amino Acid Sequence↗
PubMed2001

Monitoring of the infrared radiation emitted from skin layers during CO2 laser resurfacing: a possible basis for a depth navigation device.

CO2 laser resurfacing is very accurate, but it is not free of complications such as scarring. The objectives of the present study were to evaluate the pattern of the infrared (IR) radiation emitted from skin layers and to use this pattern to distinguish between these layers during resurfacing. A CO2-resurfacing laser (Sharplan SilkTouch) was used for the de-epithelialisation of skin. A silver halide optical fibre delivered the radiation emitted from the skin during resurfacing to an IR photonic detector. Time-dependent curves of the signals emitted from the skin layers were statistically evaluated and showed significant differences between the epidermis and the dermal layers. Similar results were obtained during in-vivo and ex-vivo measurements. The difference between the skin layers emission may be used for depth navigation during laser resurfacing.

Analysis of Variance↗
PubMed2001

Identification of microcystins in cyanobacteria from the Bleiloch former drinking-water reservoir (Thuringia, Germany).

The presence of microcystins in cyanobacterial samples collected from the Bleiloch reservoir, formerly an important drinking-water supply in Thuringia, Germany, was proven by application of a combination of recently developed analytical methods. The raw extracts were cleaned by size-exclusion chromatography (SEC) or solid-phase extraction (SPE). The determination of microcystins was achieved by different HPLC separation followed by the application of alternative detection methods (UV, diode array detection (DAD), and mass spectrometry (MS), respectively). Furthermore, the different results of clean-up by SPE and SEC are demonstrated. The identity of microcystins was verified by MS/MS measurements. In the cyanobacterial sample from 1998, microcystin-RR, -LR and -YR were found, whereas in 1999 only microcystin-LR and -YR were detectable. In addition to detection of cell-bound microcystins, in 1999 traces of dissolved microcystins in water from the Bleiloch reservoir were detected. It can be assumed that not only the Bleiloch reservoir is contaminated with hepatotoxins but also many similar lakes still used for drinking water supply.

Chromatography, High Pressure Liquid↗
PubMed2001

Color changes in hydrocarbon oil-in-water emulsions caused by Ostwald ripening.

The influence of Ostwald ripening on the optical properties of hydrocarbon oil-in-water emulsions stabilized by sodium dodecyl sulfate was investigated. The droplet size, spectral reflectance, and tristimulus color coordinates (L, a, and b) of a series of n-hexadecane and n-octadecane oil-in-water emulsions were measured in the presence and absence of a water-soluble red dye (FD&C Red No. 40). The droplets grew more rapidly in the emulsion containing n-hexadecane than in the emulsion containing n-octadecane because of the higher solubility of n-hexadecane molecules in the aqueous phase. Ostwald ripening caused appreciable changes in n-hexadecane emulsion spectral reflectance and color L, a, and b values due to the growth of emulsion droplets. L, a, and b color values and spectral reflectances of n-octadecane emulsions did not significantly change during the course of the experiment. The results were explained in terms of Ostwald ripening theory and a previously described light scattering theory. The model enables emulsion manufacturers to predict color changes in oil-in-water emulsions that exhibit transcondensational ripening.

Color↗