Biomedical subjects

J Kucera

Publications and source records attributed to J Kucera.

At least 37 records · Page 2Linked to original sources

PubMed2001

Preparation and characterization of a set of IAEA reference air filters for quality control in air-pollution studies.

Several sets of reference air filters were prepared as part of an IAEA evaluation of the performance of laboratories involved in air-pollution studies. Each set comprised three polycarbonate membrane filters, two of which were loaded with urban air particulate matter (APM) obtained in Vienna or Prague, and one unloaded filter. The filters were loaded by filtration of a suspension of the APM materials in water. The homogeneity both of bulk APM materials and of the loaded filters was evaluated and found suitable by determining several elements by instrumental neutron-activation analysis (INAA), proton-induced X-ray emission (PIXE), and micro-X-ray energy-dispersive fluorescence analysis (micro-EDXRF). After evaluation of the homogeneity, INAA, PIXE, EDXRF, atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), and ICP mass spectrometry (ICP-MS) were used to characterize the filter materials and establish "target values" and their associated standard deviations for 15 elements. Problems encountered during the preparation of these unique, simulated air filters and the criteria for setting both the target values and standard deviations are presented.

Air Pollutants↗

PubMed2001

The validation of Kayzero-assisted NAA in Budapest, Rez, and Ljubljana via the analysis of three BCR certified reference materials.

After installation and calibration of k0-assisted NAA in three Central European research institutes (AEKI-Budapest, NPI-Rez, and IJS, Ljubljana), its validation was established via the analysis of three BCR certified reference materials. The matrices of choice were: CRM 277 estuarine sediment, CRM 038 coal fly ash from pulverized coal, and CRM 101 spruce needles. For some elements, e.g. Zn, Cd, and Hg, the analyses were not only performed instrumentally (INAA), but also in the radiochemical mode (RNAA). The work was performed in the framework of a European Copernicus Project.

Carbon↗

PubMed2001

Installation and calibration of Kayzero-assisted NAA in three Central European countries via a Copernicus project.

An account is given of the installation and calibration of k0-based NAA--assisted by the DSM Kayzero/Solcoi software package--at the KFKI-AEKI, Budapest, the NPI, Rez and the IJS, Ljubljana. Not only the calibration of the Ge-detectors and the irradiation facilities are discussed, but also other important topics such as gamma-spectrometric hard- and software, QC/QA of the IRMM-530 Al-Au flux monitor and the upgrade of the Kayzero/Solcoi code. The work was performed in the framework of a European Copernicus JRP, coordinated by the Laboratory of Analytical Chemistry, Gent, with DSM Research, Geleen, as the industrial partner.

Journal Article↗

PubMed2001

Neurotrophin-3 modulates noradrenergic neuron function and opiate withdrawal.

Somatic symptoms and aversion of opiate withdrawal, regulated by noradrenergic signaling, were attenuated in mice with a CNS-wide conditional ablation of neurotrophin-3. This occurred in conjunction with altered cAMP-mediated excitation and reduced upregulation of tyrosine hydroxylase in A6 (locus coeruleus) without loss of neurons. Transgene-derived NT-3 expressed by noradrenergic neurons of conditional mutants restored opiate withdrawal symptoms. Endogenous NT-3 expression, strikingly absent in noradrenergic neurons of postnatal and adult brain, is present in afferent sources of the dorsal medulla and is upregulated after chronic morphine exposure in noradrenergic projection areas of the ventral forebrain. NT-3 expressed by non-catecholaminergic neurons may modulate opiate withdrawal and noradrenergic signalling.

Aging↗

PubMed2001

Dissection of NT3 functions in vivo by gene replacement strategy.

The development of the peripheral nervous system is governed in part by a family of neurotrophic factors that signal through Trk tyrosine kinase receptors. Neurotrophin 3 (NT3) ablation in mice causes a more severe neuronal phenotype than deletion of its receptor TrkC, suggesting that NT3 acts also through other non-preferred Trk receptors. To study the role of low-affinity ligand receptor interactions in vivo, we have replaced the Nt3 gene with the gene for brain-derived neurotrophic factor (BDNF), a TrkB ligand. As in NT3 and TrkC null mice, the proprioception system of these mutants failed to assemble. However, sensory fiber projections in the embryonic spinal cord suggest chemotropic effects of BDNF in vivo. In the dorsal root ganglia, the developmental dynamic of neuron numbers demonstrates that NT3 is required for activation of TrkB during neurogenesis and that TrkA is required during target tissue innervation. In the inner ear, the ectopic BDNF rescued the severe neuronal deficits caused by NT3 absence, indicating that TrkB and TrkC activate equivalent pathways to promote survival of cochlear neurons. However, specific increased innervation densities suggest unique functions for BDNF and NT3 beyond promoting neuronal survival. This mouse model has allowed the dissection of specific spatiotemporal Trk receptor activation by NT3. Our analysis provides examples of how development can be orchestrated by complex high- and low-affinity interactions between ligand and receptor families.

Animals↗

PubMed2001

Possibilities of low-level determination of silicon in biological materials by activation analysis.

The capabilities of neutron and photon activation analysis (NAA and PAA, respectively) for low-level determination of silicon in biological materials have been examined. Sensitivities of a variety of modes of NAA and PAA with radiochemical separation have been evaluated. Results are presented for silicon in reference materials CSRM 12-2-03 Lucerne, Bowen's Kale, NIST SRM-1571 Orchard Leaves, and NIST SRM-1515 Apple Leaves. The results were obtained by employing the 29Si(n,p)29Al reaction with fast reactor neutrons and the radiochemical procedure developed for aluminium separation. Possibilities of further improvement of the silicon determination limit down to the microg g(-1) level by employing NAA and PAA with radiochemical separation are outlined.

Activation Analysis↗

PubMed2001

Monitoring of occupational exposure in manufacturing of stainless steel constructions. Part I: Chromium, iron, manganese, molybdenum, nickel and vanadium in the workplace air of stainless steel welders.

Exposure to workplace airborne pollutants was examined in a group of 20 workers dealing mainly with welding, polishing, drilling and assembling of stainless steel constructions. Airborne particulate matter (APM) collected using both personal and stationary samplers was analyzed by instrumental neutron activation analysis (INAA). Quality assurance procedures of both sampling and analytical stages are described. Of the elements determined, results are presented for chromium, iron, manganese, molybdenum, nickel and vanadium. The median values of element concentrations exceeded the maximum admissible limits for workplace pollutants only for chromium, while for nickel the limit was exceeded in several individual cases. Sampling of hair, nails, blood, urine and saliva to be used for biological monitoring of the exposed and control groups is also described.

Adult↗

PubMed2000

Inactivation of one copy of the mouse neurotrophin-3 gene induces cardiac sympathetic deficits.

Whether two copies of the neurotrophin-3 (NT3) gene are necessary for proper development of cardiac sympathetic innervation was investigated in mice carrying a targeted inactivation of the NT3 gene. Heterozygous (+/-) and null (-/-) mutant mice had fewer stellate ganglion neurons than did wild-type (+/+) mice at postnatal day 0 (P0 or birth), and this deficit was maintained between adult (P60) +/- and +/+ mice. The sympathetic innervation of the heart matured postnatally in +/+ and +/- mice. Tyrosine hydroxylase (TH)-positive axons were restricted largely to the epicardium at P0, were concentrated around large blood vessels in the myocardium at P21, and were present among cardiac myocytes at P60. Cardiac norepinephrine (NE) concentrations paralleled the growth of the sympathetic axons into the heart. NE concentrations were equivalent among +/+, +/-, and -/- mice at birth, but differences between +/- and +/+ mice increased with age. Adult +/- mice also exhibited lower resting heart rates and sympathetic tonus than +/+ mice. Thus deletion of one copy of the NT3 gene translates into anatomical, biochemical, and functional deficits in cardiac sympathetic innervation of postnatal mice, thereby indicating a gene-dosage effect for the NT3 gene.

Aging↗

PubMed2000

Formation of a full complement of cranial proprioceptors requires multiple neurotrophins.

Inactivation of neurotrophin-3 (NT3) completely blocks the development of limb proprioceptive neurons and their end organs, the muscle spindles. We examined whether cranial proprioceptive neurons of the trigeminal mesencephalic nucleus (TMN) require NT3, brain-derived neurotrophic factor (BDNF) or neurotrophin-4 (NT4) for their development. Complements of TMN neurons and masticatory muscle spindles were decreased by 62% in NT3 null mutants, 33% in BDNF null mutants, and 10% in NT4 null mutant mice at birth. The extent of proprioceptive deficiencies differed among different masticatory muscles, particularly in NT3 null mice. Masticatory muscles of embryonic mice heterozygous for the NT3(lacZneo) or BDNF(lacZ) reporter genes expressed both NT3 and BDNF, consistent with target-derived neurotrophin support of TMN neurons. Although more than 90% of TMN neurons expressed TrkB as well as TrkC receptor proteins by immunocytochemistry in wild-type newborns, TrkC or TrkB null mice exhibited only partial proprioceptive deficiencies similar to those present in NT3 or BDNF;NT4 null mice. Thus, in terms of the survival outcome, two main subpopulations of TMN neurons may exist during embryogenesis, one dependent on TrkC/NT3 functioning and the other utilizing TrkB/BDNF signaling. The differential dependence of TMN neurons on neurotrophins may reflect differential accessibility of the neurons to limiting amounts of NT3, BDNF, or NT4 in target tissues, especially if the tissue distribution or levels of BDNF, NT3, and NT4 were dynamically regulated both spatially and temporally.

Animals↗

PubMed2000

Comparison of the TOX A/B test to a cell culture cytotoxicity assay for the detection of Clostridium difficile in stools.

The TOX A/B Test (Techlab, Blacksburg, VA, USA) was compared to cell culture cytotoxicity assay on 1109 consecutive diarrheal stool samples collected from patients with the presumptive diagnosis of Clostridium difficile disease. The TOX A/B Test is an enzyme immunoassay in a microtiter format that detects both toxins A and B. The procedure used for this study takes approximately 1.5 h to perform. Cell culture cytotoxicity was performed by using a fibroblast cell line in a microtiter format read at 4 h, 24 h, and 48 h. One hundred ninety-four of the 1109 samples were positive by the "gold standard" cytotoxicity assay, whereas 189 were positive by EIA. There was a 98.5% agreement between the two assays. When compared to the cytotoxicity assay, the EIA had an initial sensitivity of 94.3% and a specificity of 99.3%. However, after resolution of six discrepants using another ELISA for toxin A detection the sensitivity, specificity, positive and negative predictive values for the TOX A/B test are as follows: 94.5%; 100%; 100%; 98.8%. The corresponding values for the cytotoxicity assay are: 97%; 100%; 100%; and 99.3%. This test seems to have excellent sensitivity and specificity as compared to an in-house cell culture cytotoxicity assay. It is sensitive enough to use as a stand-alone test for the detection of C. difficile toxin in laboratories that do not have cell culture cytotoxicity testing capability.

Cell Culture Techniques↗

PubMed2000

Development of sensory neurons in the absence of NGF/TrkA signaling in vivo.

The neurotrophin survival dependence of peripheral neurons in vitro is regulated by the proapoptotic BCL-2 homolog BAX. To study peripheral neuron development in the absence of neurotrophin signaling, we have generated mice that are double null for BAX and nerve growth factor (NGF), and BAX and the NGF receptor TrkA. All dorsal root ganglion (DRG) neurons that normally die in the absence of NGF/TrkA signaling survive if BAX is also eliminated. These neurons extend axons through the dorsal roots and collateral branches into the dorsal horn. In contrast, superficial cutaneous innervation is absent. Furthermore, rescued sensory neurons fail to express biochemical markers characteristic of the nociceptive phenotype. These findings establish that NGF/TrkA signaling regulates peripheral target field innervation and is required for the full phenotypic differentiation of sensory neurons.

Animals↗

PubMed1999

Alterations in nigrostriatal dopaminergic function within BDNF mutant mice.

The influence of brain-derived neurotrophic factor (BDNF) upon the nigrostriatal dopaminergic system was evaluated in weanling and adult mice carrying a targeted inactivated BDNF gene. Regional specificity of this BDNF mutation was assessed by assaying catecholamine concentrations within the corpus striatum, hypothalamus, and olfactory bulbs. In weanling mice dopamine, but not norepinephrine, concentrations within the corpus striatum of homozygous mutant (-/-) mice were significantly reduced with levels being 54% that of the wild-type controls (+/+) and 49% that of the heterozygous mutant (+/-) mice. While no differences were obtained among the three genotypes for hypothalamic dopamine, norepinephrine concentrations of -/- mice were significantly lower, being 62% of +/+ mice and 49% of +/- mice. The dopamine concentrations of -/- mice within the olfactory bulb were significantly reduced (69%) compared to the +/-, but not +/+ mice. Olfactory bulb norepinephrine concentrations showed a statistically significant difference among each of the three conditions with minimal levels in -/- mice (62% of +/+ and 45% of +/-). In the adults, catecholamine concentrations were measured only in +/+ and +/- mice since -/- mice do not typically survive past 21 days. Dopamine, but not norepinephrine, concentrations within the corpus striatum were significantly increased (116%) in +/- compared to +/+ mice. No other statistically significant differences were obtained in catecholamine concentrations within the hypothalamus or olfactory bulb in these adult mice. These results show that homozygous BDNF mutations produce severe depletions within the nigrostriatal dopaminergic system and substantial reductions of norepinephrine within the hypothalamus and olfactory bulb. Interestingly, maximal catecholamine concentrations for all areas sampled at both ages were observed in the +/- mice. These latter findings may indicate some subtle changes in catecholamine functions resulting from a heterozygous BDNF mutation.

Animals↗

PubMed1999

INAA and PIXE of atmospheric and combustion aerosols.

Using instrumental neutron activation analyses and photon-induced x-ray emission techniques for analysis of size-fractionated atmospheric and combustion aerosols and other emission samples arising from fluidized-bed combustion of North Bohemian lignites up to 42 elements were determined in all samples types. This allowed the evaluation of element enrichment, time trends, and inter-element correlations and the performance of factor analysis of various fractions of atmospheric aerosols. The data obtained on mass and element size distributions of aerosols and emission samples obtained upon lignite combustion in an experimental scale atmospheric fluidized-bed combustor without and with added hydrated lime and limestone were used to elucidate the mechanism of abatement of toxic trace and matrix elements from flue gas.

Aerosols↗

PubMed1999

Matrix effects in PIXE analysis of aerosols and ashes.

A comparison of instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE) results for size-fractionated atmospheric aerosols ("coarse" and "fine" fractions with an equivalent aerodynamic diameter of 2-10 microns and < 2 microns, respectively, or the PM10 fraction) showed that PIXE yielded significantly lower results for the PM10 and coarse fractions, especially for elements with a low Z resulting from a particle size effect. Somewhat lower PIXE results were also obtained for the fine fraction of atmospheric aerosols. A correction is also needed for irregularly shaped deposits of combustion aerosols collected by a cascade impactor in 11 size fractions ranging from 0.016 to 14.3 microns, as well as for thick samples of fly and bottom ashes. An equivalent layer thickness (ELT) model is proposed to correct the matrix effects in PIXE. The approaches for the calculation of ELT using a comparison of PIXE and INAA results or by comparing PIXE results obtained using two different incident proton beam energies (1.31 and 2.35 MeV) are described. The correction for the ash pellets and irregular deposits are also discussed.

Aerosols↗

PubMed1999

Why adult mammalian intrafusal and extrafusal fibers contain different myosin heavy-chain isoforms.

Multiple isoforms of the contractile protein myosin are present in mammalian skeletal muscles. The diversity of the heavy-chain subunits of myosin (MyHCs) in intrafusal fibers is thought to reflect a pathway of differentiation that is unique to muscle spindles. In fact, intrafusal MyHCs are developmental isoforms expressed by the prenatal precursors of both intrafusal and extrafusal fibers. In adult limbs, developmental MyHCs persist in intrafusal, but not extrafusal fibers principally due to the afferent neurons that arrest their maturational replacement by MyHCs associated with faster shortening velocities. The slow shortening velocities that are characteristic of developmental MyHCs might be adaptive for precise calibration of muscle spindles as sense organs.

Afferent Pathways↗

PubMed1999

Corrigendum.

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Journal Article↗

PubMed1999

A role for p75 receptor in neurotrophin-3 functioning during the development of limb proprioception.

Neurotrophin-3 is indispensable for the development of limb proprioceptive neurons and their end organs, muscle spindles. To determine whether the low-affinity p75 receptor potentiates the actions of neurotrophin-3, we examined the development of the proprioceptive system in p75 null mutant mice that had either normal or decreased tissue levels of neurotrophin-3. Postnatal mice lacking both copies of the p75 gene had fewer sensory neurons in dorsal root ganglia, but normal complements of muscle spindles in fast hindlimb muscles, although the slow soleus muscle showed a 50% loss of spindles. However, compound mutants lacking both copies of the p75 gene as well as one copy of the neurotrophin-3 gene displayed a dystonic/ataxic phenotype similar to that observed previously in neurotrophin-3 null mutants devoid of proprioception. The compound mutants also exhibited a commensurate loss of parvalbumin-expressing (proprioceptive) neurons in dorsal root ganglia. The degree of deficiency of spindles (and presumably proprioceptive neurons) in the compound mutants exceeded the sum of deficits in single mutants lacking either both copies of p75 genes or one copy of neurotrophin-3 gene, suggesting a synergistic interaction between the p75 receptor and neurotrophin-3. Neuronal deficits in the compound mutants were present prior to embryonic day 14, indicating an early role for the p75 receptor in sensory neuronogenesis. Collectively, these data indicate that the p75 receptor is not essential for the survival and differentiation of most limb proprioceptive neurons when neurotrophin-3 is expressed at normal levels. However, the p75 receptor may act in synergy with neurotrophin-3 to enhance the survival of proprioceptive neurons when tissue levels of neurotrophin-3 are a limiting factor.

Animals↗

PubMed1999

Our standard method of reconstruction of the penis and urethra in female to male transsexuals.

The authors used as a standard a one-stage method of microsurgical reconstruction of the penis, urethra and glans in 38 transsexual patients, a combination of Biemer's method, Trengove-Jones and Horton's suture of the glans. The reconstruction method is described in detail. Although reconstruction of the penis and urethra involved a group of 49 patients and accounted for less than 10% of all microsurgical tissue transfers in traumatology, oncological surgery and congenital defects, they are an important activity in systematic surgery.

Anastomosis, Surgical↗