bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the dehydroepiandrosterone (DHEA) metabolism via oxysterol 7α‐hydroxylase and 17‐ketosteroid reductase activity in the human brain
Authors: Steckelbroeck Stephan , Watzka Matthias , Lütjohann Dieter , Makiola Paul , Nassen Alexander , Hans Volkmar H. J. , Clusmann Hans , Reissinger Annette , Ludwig Michael , Siekmann Lothar , Klingmüller Dietrich 
Published: March 2003

AbstractDehydroepiandrosterone and its sulphate are important factors for vitality, development and functions of the CNS. They were found to be subjects to a series of enzyme‐mediated conversions within the rodent CNS. In the present study, we were able to demonstrate for the first time that membrane‐associated dehydroepiandrosterone 7α‐hydroxylase activity occurs within the human brain. The cytochrome P450 enzyme demonstrated a sharp pH optimum between 7.5 and 8.0 and a mean KM value of 5.4 µm, corresponding with the presence of the oxysterol 7α‐hydroxylase CYP7B1. Real‐time RT–PCR analysis verified high levels of CYP7B1 mRNA expression in the human CNS. The additionally observed conversion of dehydroepiandrosterone via cytosolic 17β‐hydroxysteroid dehydrogenase activity could be ascribed to the activity of an enzyme with a broad pH optimum and an undetectably high KM value. Subsequent experiments with cerebral neocortex and subcortical white matter specimens revealed that 7α‐hydroxylase activity is significantly higher in the cerebral neocortex than in the subcortical white matter (p < 0.0005), whereas in the subcortical white matter, 17β‐hydroxysteroid dehydrogenase activity is significantly higher than in the cerebral neocortex (p < 0.0005). No sex differences were observed. In conclusion, the high levels of CYP7B1 mRNA in brain tissue as well as in a variety of other tissues in combination with the ubiquitous presence of 7α‐hydroxylase activity in the human temporal lobe led us to assume a neuroprotective function of the enzyme such as regulation of the immune response or counteracting the deleterious effects of neurotoxic glucocorticoids, rather than a distinct brain specific function such as neurostimulation or neuromodulation.
In depolarized and glucose‐deprived neurons, Na+ influx reverses plasmalemmal K+‐dependent and K+‐independent Na+/Ca2+ exchangers and contributes to NMDA excitotoxicity
Authors: Czyż Aneta , Kiedrowski Lech 
Published: March 2003

AbstractCerebellar granule cells (CGCs) express K+‐dependent (NCKX) and K+‐independent (NCX) plasmalemmal Na+/Ca2+ exchangers which, under plasma membrane‐depolarizing conditions and high cytosolic [Na+], may reverse and mediate potentially toxic Ca2+ influx. To examine this possibility, we inhibited NCX or NCKX with KB‐R7943 or K+‐free medium, respectively, and studied how gramicidin affects cytosolic [Ca2+] and 45Ca2+ accumulation. Gramicidin forms pores permeable to alkali cations but not Ca2+. Therefore, gramicidin‐induced Ca2+ influx is indirect; it results from fluxes of monovalent cations. In the presence of Na+, but not Li+ or Cs+, gramicidin induced Ca2+ influx that was inhibited by simultaneous application of KB‐R7943 and K+‐free medium. The data indicate that gramicidin‐induced Na+ influx reverses NCX and NCKX. To test the role of NCX and/or NCKX in excitotoxicity, we studied how NMDA affects the viability of glucose‐deprived and depolarized CGCs. To assure depolarization of the plasma membrane, we inhibited Na+,K+‐ATPase with ouabain. Although inhibition of NCX or NCKX reversal failed to significantly limit 45Ca2+ accumulation and excitotoxicity, simultaneously inhibiting NCX and NCKX reversal was neuroprotective and significantly decreased NMDA‐induced 45Ca2+ accumulation. Our data suggest that NMDA‐induced Na+ influx reverses NCX and NCKX and leads to the death of depolarized and glucose‐deprived neurons.
Constitutively and autonomously active protein kinase C associated with 14‐3‐3 ζ in the rodent brain
Authors: Dai Jian‐Guo , Murakami Kentaro 
Published: March 2003

AbstractPersistent activation of protein kinase C (PKC) is required for the expression of synaptic plasticity in the brain. There are several mechanisms proposed that can lead to the prolonged activation of PKC. These include long lasting production of lipid activators (diacylglycerol and fatty acid) through mitogen‐activated protein (MAP) kinase pathway, and a modification of PKC by reactive oxygen species. In nerve growth factor (NGF)‐differentiated PC12 cells, we found that constitutive and autonomous Ca2+‐independent PKC activity is associated with 14‐3‐3 ζ. Because PKC and 14‐3‐3 ζ are both involved in synaptic plasticity and learning and memory, we examined whether PKC interacts with 14‐3‐3 ζ in the brain and whether the PKC/14‐3‐3 ζ complex has autonomous activity. Here we show that three subclasses of PKC, Ca2+‐dependent classical PKC, Ca2+‐independent novel PKC, and Ca2+‐independent and diacylglycerol‐insensitive atypical PKC, all interact with 14‐3‐3 ζ in the rodent brain. The pool size of 14‐3‐3 ζ bound form of PKC is small (1–4% of each PKC isoform), but they show constitutive and autonomous activity. Our study indicates that the binding of PKC with 14‐3‐3 ζ is at least in part independent of phosphorylation of PKC and that the C1 domain of PKC is involved in the binding. As both molecules are enriched in synaptic locus, the constitutive PKC activity and its interaction with 14‐3‐3 ζ could be a mechanism for the persistent PKC activation in the brain.
The synaptophysin/synaptobrevin interaction critically depends on the cholesterol content
Authors: Mitter Diana , Reisinger Clemens , Hinz Britta , Hollmann Susanne , Yelamanchili Sowmya V. , Treiber‐Held Stephanie , Ohm Thomas G. , Herrmann Andreas , Ahnert‐Hilger Gudrun 
Published: March 2003

AbstractSynaptophysin interacts with synaptobrevin in membranes of adult small synaptic vesicles. The synaptophysin/synaptobrevin complex promotes synaptobrevin to built up functional SNARE complexes thereby modulating synaptic efficiency. Synaptophysin in addition is a cholesterol‐binding protein. Depleting the membranous cholesterol content by filipin or β‐methylcyclodextrin (β‐MCD) decreased the solubility of synaptophysin in Triton X‐100 with less effects on synaptobrevin. In small synaptic vesicles from rat brain the synaptophysin/synaptobrevin complex was diminished upon β‐MCD treatment as revealed by chemical cross‐linking. Mice with a genetic mutation in the Niemann–Pick C1 gene developing a defect in cholesterol sorting showed significantly reduced amounts of the synaptophysin/synaptobrevin complex compared to their homo‐ or heterozygous littermates. Finally when using primary cultures of mouse hippocampus the synaptophysin/synaptobrevin complex was down‐regulated after depleting the endogenous cholesterol content by the HMG‐CoA‐reductase inhibitor lovastatin. Alternatively, treatment with cholesterol up‐regulated the synaptophysin/synaptobrevin interaction in these cultures. These data indicate that the synaptophysin/synaptobrevin interaction critically depends on a high cholesterol content in the membrane of synaptic vesicles. Variations in the availability of cholesterol may promote or impair synaptic efficiency by interfering with this complex.
Transient ischemia enhances tyrosine phosphorylation and binding of the NMDA receptor to the Src homology 2 domain of phosphatidylinositol 3‐kinase in the rat hippocampus
Authors: Takagi Norio , Sasakawa Kyoko , Besshoh Shintaro , Miyake‐Takagi Keiko , Takeo Satoshi 
Published: March 2003

AbstractTyrosine phosphorylation of the NMDA receptor has been implicated in the regulation of the receptor channel. We investigated the effects of transient (15 min) global ischemia on tyrosine phosphorylation of NMDA receptor subunits NR2A and NR2B, and the interaction of NR2 subunits with the SH2 domain of phosphatidylinositol 3‐kinase (PI3‐kinase) in vulnerable CA1 and resistant CA3/dentate gyrus of the hippocampus. Transient ischemia induced a marked increase in the tyrosine phosphorylation of NR2A in both regions. The tyrosine phosphorylation of NR2B in CA3/dentate gyrus after transient ischemia was sustained and greater than that in CA1. PI3‐kinase p85 was co‐precipitated with NR2B after transient global ischemia. The SH2 domain of the p85 subunit of PI3‐kinase bound to NR2B, but not to NR2A. Binding to NR2B was increased following ischemia and the increase in binding in CA3/dentate gyrus (4.5‐fold relative to sham) was greater than in CA1 (1.7‐fold relative to sham) at 10 min of reperfusion. Prior incubation of proteins with an exogenous protein tyrosine phosphatase or with a phosphorylated peptide (pYAHM) prevented binding. The results suggest that sustained increases in tyrosine phosphorylation and increased interaction of NR2B with the SH2 domain of PI3‐kinase may contribute to altered signal transduction in the CA3/dentate gyrus after transient ischemia.
Altered levels and distribution of microtubule‐associated proteins before disease onset in a mouse model of amyotrophic lateral sclerosis
Authors: Farah C. Abi , Nguyen M. D. , Julien J. P. , Leclerc N. 
Published: March 2003

AbstractAlterations of the axonal transport and microtubule network are potential causes of motor neurodegeneration in mice expressing a mutant form of the superoxide dismutase 1 (SOD1G37R) linked to amyotrophic lateral sclerosis (ALS). In the present study, we investigated the biology of microtubule‐associated proteins (MAPs), responsible for the formation and stabilization of microtubules, in SOD1G37R mice. Our results show that the protein levels of MAP2, MAP1A, tau 100 kDa and tau 68 kDa species decrease significantly as early as 5 months before onset of symptoms in the spinal cord of SOD1G37R mice, whereas decrease in levels of tau 52–55 kDa species is most often noted with the manifestation of the clinical symptoms. Interestingly, there was no change in the protein levels of MAPs in the brain of SOD1G37R mice, a CNS organ spared by the mutant SOD1 toxicity. Remarkably, as early as 5 months before disease onset, the binding affinities of MAP1A, MAP2 and tau isoforms to the cytoskeleton decreased in spinal cord of SOD1G37R mice. This change correlated with a hyperphosphorylation of the soluble tau 52–55 kDa species at epitopes recognized by the antibodies AT8 and PHF‐1. Finally, a shift in the distribution of MAP2 from the cytosol to the membrane is detected in SOD1G37R mice at the same stage. Thus, alterations in the integrity of microtubules are early events of the neurodegenerative processes in SOD1G37R mice.
Martentoxin, a novel K+‐channel‐blocking peptide: purification, cDNA and genomic cloning, and electrophysiological and pharmacological characterization
Authors: Ji Yong‐Hua , Wang Wei‐Xi , Ye Jian‐Guo , He Lin‐Lin , Li Ya‐Jun , Yan Yan‐Ping , Zhou Zhuan 
Published: March 2003

AbstractMartentoxin, a novel K+‐channel‐specific peptide has been purified and characterized from the venom of the East‐Asian scorpion (Buthus martensi Karsch). The whole cDNA precursor sequence suggested that martentoxin was composed of 37 residues with a unique sequence compared with other scorpion neurotoxins. The genomic DNA of martentoxin showed an additional intron situated unexpectedly in the 5′ UTR region, besides one located close to the C‐terminal of the signal peptide. The patch‐clamp recording found that martentoxin at the applied dose of 100 nm could strongly block large‐conductance Ca2+‐activated K+ (BKCa) currents in adrenal medulla chromaffin cells, and BKCa currents blocked by martentoxin could be fully recovered within 30 seconds after washing, which is at least 10 times faster than recovery after charybdotoxin. Meanwhile, a biosensor binding assay showed a fast association rate and a slow dissociation rate of martentoxin binding on rat brain synaptosomes. The binding of martentoxin on rat brain synaptosomes could be inhibited regularly by charybdotoxin, and gradually by toosendanin in a concentration‐dependent manner, but not by either apamin or P03 from Buthus martensi. The results thus indicate that martentoxin is a new member in the family of K+‐channel‐blocking ligands.
Co‐expression of vesicular glutamate transporters (VGLUT1 and VGLUT2) and their association with synaptic‐like microvesicles in rat pinealocytes
Authors: Morimoto Riyo , Hayashi Mitsuko , Yatsushiro Shouki , Otsuka Masato , Yamamoto Akitsugu , Moriyama Yoshinori 
Published: March 2003

AbstractA vesicular glutamate transporter (VGLUT) is responsible for the accumulation of l‐glutamate in synaptic vesicles in glutamatergic neurons. Two isoforms, VGLUT1 and VGLUT2, have been identified, which are complementarily expressed in these neurons. Mammalian pinealocytes, endocrine cells for melatonin, are also glutamatergic in nature, accumulate l‐glutamate in synaptic‐like microvesicles (SLMVs), and secrete it through exocytosis. Although the storage of l‐glutamate in SLMVs is mediated through a VGLUT, the molecular nature of the transporter is less understood. We recently observed that VGLUT2 is expressed in pinealocytes. In the present study, we show that pinealocytes also express VGLUT1. RT–PCR and northern blot analyses indicated expression of the VGLUT1 gene in pineal gland. Western blotting with specific antibodies against VGLUT1 indicated the presence of VGLUT1 in pineal gland. Indirect immunofluorescence microscopy with a section of pineal gland and cultured cells indicated that VGLUT1 and VGLUT2 are co‐localized with process terminal regions of pinealocytes. Furthermore, immunoelectronmicroscopy as well as subcellular fractionation studies revealed that both VGLUT1 and VGLUT2 are specifically associated with SLMVs. These results indicate that both VGLUTs are responsible for storage of l‐glutamate in SLMVs in pinealocytes. Pinealocytes are the first exception as to complementary expression of VGLUT1 and VGLUT2.
GABA‐induced neurite outgrowth of cerebellar granule cells is mediated by GABAA receptor activation, calcium influx and CaMKII and erk1/2 pathways
Authors: Borodinsky Laura N. , O'Leary Deirdre , Neale Joseph H. , Vicini Stefano , Coso Omar A. , Fiszman Mónica L. 
Published: March 2003

AbstractDuring neuronal development, GABAA‐mediated responses are depolarizing and induce an increase in the intracellular calcium concentration. Since calcium oscillations can modulate neurite outgrowth, we explored the capability of GABA to induce changes in cerebellar granule cell morphology. We find that treatment with GABA (1–1000 µm) induces an increase in the intracellular calcium concentration through the activation of GABAA receptors and voltage‐gated calcium channels of the L‐subtype. Perforated patch‐clamp recordings reveal that this depolarizing response is due to a chloride reversal potential close to − 35 mV. When cells are grown in depolarizing potassium chloride concentrations, a shift in reversal potential (Erev) for GABA is observed, and only 20% of the cells are depolarized by the neurotransmitter at day 5 in vitro. On the contrary, cells grown under resting conditions are depolarized after GABA application even at day 8. GABA increases the complexity of the dendritic arbors of cerebellar granule neurons via a calcium‐dependent mechanism triggered by voltage‐gated calcium channel activation. Specific blockers of calcium‐calmodulin kinase II and mitogen‐activated protein kinase kinase (KN93 and PD098059) implicate these kinases in the intracellular pathways involved in the neuritogenic effect of GABA. These data demonstrate that GABA exerts a stimulatory role on cerebellar granule cell neuritogenesis through calcium influx and activation of calcium‐dependent kinases.
Organization, work and work reactions: a study of the relationship between organizational aspects of nursing and nurses' work characteristics and work reactions
Authors: Tummers Gladys E.R. , Landeweerd Jan A. , Van Merode Godefridus G. 
Published: March 2003

Organization, work and work reactions: a study of the relationship between organizational aspects of nursing and nurses' work characteristics and work reactions This article describes a quantitative, correlational study of the relationship between organizational aspects (such as the predictability of the care), work characteristics (autonomy and workload) and work reactions (work satisfaction and health complaints) in nursing work. The variables have been measured by questionnaires. Subjects were 155 nurses from nine units in two general hospitals in the Netherlands. Several organizational aspects seem to be correlated with work characteristics and work reactions. Organizational aspects particularly influence work characteristics and play, therefore, a mediating role in the relationship between organizational aspects and work reactions. Job satisfaction is not only correlated with the autonomy, but also with workload. Health complaints appeared to be mainly correlated with the workload. It is concluded that for an improvement of job satisfaction and reduction of health complaints, it is not only necessary to improve autonomy and reduce workload, but also to pay attention to organizational aspects because these may influence the work characteristics.
Dental phobic patients' view of dental anxiety and experiences in dental care: a qualitative study
Authors: Abrahamsson Kajsa H. , Berggren Ulf , Hallberg Lillemor , Carlsson Sven G. 
Published: March 2003

Dental phobic patients' view of dental anxiety and experiences in dental care: a qualitative study The aim of this study was to explore and describe dental phobic patients' perceptions of their dental fear and experiences in dental care. The study sample consisted of 18 participants (12 women), with a mean age of 39.4 years, selected consecutively from patients applying for treatment at a specialized dental fear clinic in Göteborg, Sweden. Dental fear, assessed by the Dental Anxiety Scale, showed score levels well over established levels for severe dental fear. The method for sampling and analysis was inspired by the constant comparative method for Grounded Theory (GT). The thematized in‐depth interviews took place outside the clinic and lasted for 1–1.5 h. All the interviews were conducted by the first author (KHA), audiotaped and transcribed verbatim. Three higher‐order categories were developed and labelled existential threat, vulnerability and unsupportive dentist. Existential threat was identified as the core category, describing the central meaning of the subjects' experiences in dental care. The core category included two dimensions, labelled threat of violation and threat of loss of autonomy and independence. The core category and the descriptive categories are integrated in a model framing the process of dental fear, as described by the informants. In conclusion, the onset of dental fear was commonly related to individual vulnerability and to traumatic dental care experiences, where perceived negative dentist behaviour played a significant role. The patient was caught in a `vicious circle' that was difficult to break, and where fear and anxiety were maintained by negative expectations about treatment and about patient's own ability to cope in dental care situations.
Characterization of new microsatellite loci from Vitis vinifera and their conservation in some Vitis species and hybrids
Authors: Lefort F. , Kyvelos CH. J. , Zervou M. , Edwards K. J. , Roubelakis‐Angelakis K. A. 
Published: March 2003

AbstractWe present here characterization data for seven new microsatellite markers designed from new microsatellite loci isolated from a microsatellite‐enriched DNA library from Vitis vinifera. The observed heterozygosity varied from 0.73 up to 0.93 and the number of alleles per locus ranged from 12 to 26. This high polymorphism makes these new markers interesting for use in genotyping studies and completing the set of microsatellite markers already available for V. vinifera. Additionally these seven new markers appear to be conserved in four other Vitis species and 15 Vitis hybrids used as rootstocks for V. vinifera cultivation.
Isolation and characterization of microsatellite loci in the Galápagos Opuntia weevil Gerstaeckeria galapagoensis (Coleoptera, Curculionidae)
Authors: Dhuyvetter Hilde , Verdyck Peter , Gaublomme Eva , Desender Konjev , Mondor‐Genson Guenaelle , Rasplus Jean‐Yves 
Published: March 2003

AbstractFive microsatellite loci were isolated from the Galápagos weevil Gerstaeckeria galapagoensis. Polymorphism ranged from two to seven alleles, and observed and expected heterozygosities ranged from 0.286 to 0.917 and 0.254 to 0.683, respectively.
Eleven new microsatellites for hop (Humulus lupulus L.)
Authors: Jakše J. , Bandelj D. , Javornik B. 
Published: March 2003

AbstractWe present a new set of 11 polymorphic microsatellite primer sequences for use with Humulus lupulus. Microsatellite‐enriched libraries for GAn and GTn types of repeats were produced. Sequencing of 72 clones revealed 42 unique inserts containing microsatellites, out of which 19 primer pairs were designed and microsatellite amplification was tested on 39 wild hops and cultivars. Eleven primer pairs showed single locus amplification with 2–13 alleles, average 7.2, of which 17 unique alleles were discovered. One primer pair amplified too strong stutter bands, one locus was monomorphic and multilocus amplification was obtained with the remaining six primer pairs.
Changes in self‐esteem during a 3 year pre‐registration diploma in higher education (nursing) programme
Authors: Randle Jacqueline 
Published: March 2003

AbstractThis paper reports the findings of a longitudinal study that evaluated changes in the self‐esteem of pre‐registration student nurses taking a 3 year diploma in nursing programme. Quantitative data were collected at the start (n = 68) and the end (n = 61) of the programme. Self‐esteem was measured using the Tennessee Self‐concept Scale (Roid & Fitts 1988). Students also participated in unstructured, qualitative interviews at the start (n = 56) and end (n = 39) of the course. Results showed that global self‐esteem decreased dramatically between the start and end of the programme. Categories grounded in the qualitative data suggest that self‐esteem becomes fragmented and students become powerless to be the type of nurse they wish to be. The implications for nursing practice and education are discussed.
Does supplementary calcium reduce the cost of reproduction in the Pied Flycatcher Ficedula hypoleuca?
Authors: Mänd Raivo , Tilgar Vallo 
Published: March 2003

Studies in acidified as well as in naturally base‐poor areas have recently revealed that availability of extra calcium‐rich food items is an important component of habitat quality affecting breeding performance in several bird species. However, these mostly short‐term studies have provided equivocal results concerning the exact consequences of calcium shortage on different species in different regions. We studied the effect of calcium availability on reproduction of the Pied Flycatcher Ficedula hypoleuca breeding in pine forests in Estonia, NE Europe, over a period of 4 years. Experimental pairs were provided with supplementary calcium‐rich material when breeding, while control pairs were left unsupplemented. Experimental females laid larger eggs and their nestlings had longer tarsi than those of controls. Moreover, the mass and condition of females tending larger than average clutches were increased by calcium‐supplementation. Our results provide the first experimental evidence that calcium availability may affect the overall cost of reproduction in free‐living passerines. We compared these results with similar data for the Great Tit Parus major, collected from the same area during the same study period. Great Tits responded to low calcium availability mainly by restrained reproductive behaviour and reduced breeding success, while Pied Flycatchers invested significantly more in current reproductive effort despite the increased cost of reproduction. Thus, the effects of calcium deficiency on birds seem to be species‐specific or population‐specific. This partly explains discrepancies between the results of earlier studies.