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Biomedical subjects

P Mestres

Publications and source records attributed to P Mestres.

At least 19 recordsLinked to original sources
PubMed2004

[Platelet retention test Homburg (RTH) and drug monitoring of platelet adhesive properties of von Willebrand factor].

Platelet plug formation is initiated by the process of platelet adhesion, mainly mediated by the von Wille-brand factor (VWF). Therefore, apart from established criteria the platelet adhesion property is a further criterion to determine VWF e. g. in diagnosis and treatment of von Willebrand disease (VWD). The new platelet retention test Homburg (RTH) is designed to close this gap. It is characterized by its non-thrombogenic filter with interconnecting pores, which retains platelets from blood when pressed through this filter due to the resulting shear stress. The RTH, in particular, proved to be highly sensitive in detecting the platelet adhesive property of VWF after its release from endogenous storage sites by desmopressin or infusion in VWD patients or its supplementation in vitro.

Drug Monitoring↗
PubMed2001

Resveratrol induces colon tumor cell apoptosis independently of p53 and precede by epithelial differentiation, mitochondrial proliferation and membrane potential collapse.

Resveratrol, a polyphenol present in wine and grapes, can inhibit tumor cell growth in vitro and tumorigenesis in vivo. Some of its effects have been linked to activation of the p53 tumor suppressor; however, p53 is frequently mutated in tumors, particularly in the common and often therapy-resistant colon cancers. Using the human wild-type p53-expressing HCT116 colon carcinoma cell line and HCT116 cells with both p53 alleles inactivated by homologous recombination, we show in the current study that resveratrol at concentrations comparable to those found in some foods can induce apoptosis independently of p53. The cell death is primarily mitochondria-mediated and not receptor-mediated. No cells survived in cultures continuously exposed to 100 microM resveratrol for 120 hr. When compared with 5-FU, resveratrol stimulated p53 accumulation and activity only weakly and with delayed kinetics and neither the increased levels nor the activity affected apoptosis detectably. The apoptosis agonist Bax was overproduced in response to resveratrol regardless of p53 status, yet the kinetics of Bax expression were influenced by p53. Remarkably, apoptosis was preceded by mitochondrial proliferation and signs of epithelial differentiation. Thus, resveratrol triggers a p53-independent apoptotic pathway in HCT116 cells that may be linked to differentiation.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Endogenous brain-derived neurotrophic factor and neurotrophin-3 antagonistically regulate survival of axotomized corticospinal neurons in vivo.

Neuronal growth factors regulate the survival of neurons by their survival and death-promoting activity on distinct populations of neurons. The neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) promote neuronal survival via tyrosine kinase (Trk) receptors, whereas NGF and BDNF can also induce apoptosis in developing neurons through p75(NTR) receptors in the absence of their respective Trk receptors. Using mutant mice and inactivation of neurotrophins and their receptors with antibodies in rats, we show that endogenous NT-3 induces death of adult BDNF-dependent, axotomized corticospinal neurons (CSNs). When NT-3 is neutralized, the neurons survive even without BDNF, suggesting complete antagonism. Whereas virtually all unlesioned and axotomized CSNs express both trkB and trkC mRNA, p75 is barely detectable in unlesioned CSNs but strongly upregulated in axotomized CSNs by day 3 after lesion, the time point when cell death occurs. Blocking either cortical TrkC or p75(NTR) receptors alone prevents death, indicating that the opposing actions of NT-3 and BDNF require their respective Trk receptors, but induction of death depends on p75(NTR) cosignaling. The results show that neuronal survival can be regulated antagonistically by neurotrophins and that neurotrophins can induce neuronal death in the adult mammalian CNS. We further present evidence that signaling of tyrosine kinase receptors of the trk family can be crucially involved in the promotion of neuronal death in vivo.

Animals↗
PubMed2000

Motor neuron cell death in a mouse model of FALS is not mediated by the p53 cell survival regulator.

Mutant Cu/Zn superoxide dismutase (SOD1) associated with familial amyotrophic lateral sclerosis (FALS) causes selective motor neuron loss through unknown mechanisms of cell damage. Damaged neurons frequently undergo apoptosis mediated by the p53 cell survival regulator. We therefore studied whether motor neuron disease (MND) in mice expressing the human SOD1 mutant G93A is dependent on p53 by crossing G93A mice with p53-knockout mice. Since p53-/- mice's life expectance is usually shorter (160+/-49 days, n=11) than the time at which the G93A mice die from MND (212+/-50 days, n=7), only a few of the G93A/p53-/- double transgenics were expected to live to experience MND. Nevertheless, four of the 22 G93A/p53-/- mice succumbed to MND after 160+/-28 days, as expected under these conditions of competing death risks if the absence of p53 fails to protect from MND. Thus, MND in mice expressing G93A does not require p53. This conclusion is supported by histology: pre-symptomatic G93A mice display disease-associated vacuoles within the dendrites of motor neurons regardless of p53 status.

Aging↗
PubMed2000

The endogenous survival promotion of axotomized rat corticospinal neurons by brain-derived neurotrophic factor is mediated via paracrine, rather than autocrine mechanisms.

The previously reported rescue of corticospinal neurons (CSN) from axotomy-induced death by intracortical glial cell line-derived neurotrophic factor (GDNF)- and neurotrophin-3 (NT-3)-infusions depends on endogenous cortical brain-derived neurotrophic factor (BDNF). The present study examines whether BDNF, GDNF, or NT-3 can stimulate an autocrine or paracrine BDNF-support of lesioned CSN. BDNF-infusions increase BDNF mRNA-expression throughout cortical layers 2-5 and NT-3-treatment results in upregulation of BDNF-transcripts in the upper cortical layers. In contrast, GDNF-treatment had no effect. While virtually all CSN express the BDNF-receptor trkB, less than half of them express BDNF, and these expression patterns are unchanged after axotomy and the different neurotrophic factor treatments. The findings suggest that axotomized CSN are supported via a paracrine BDNF-mechanism which can be stimulated by BDNF- and NT-3-, but not by GDNF.

Animals↗
PubMed2000

An axotomy model for the induction of death of rat and mouse corticospinal neurons in vivo.

To study trophic dependencies of rat and mouse corticospinal neurons (CSN), we established a lesion model for the induction of death of analogous populations of CSN in these rodent species. Before lesion, CSN were retrogradely labeled with Fast Blue (FB). A stereotaxic cut lesion through the entire internal capsule (ICL) was used to axotomize CSN. The extent of axotomy was determined by application of a control tracer. In both species, FB-labeled CSN were localized in three major areas: (1) the sensory motor cortex; (2) the supplementary motor and medial prefrontal cortex; and (3) the somatosensory cortex. ICL does not lead to complete axotomy of CSN of the rat and mouse somatosensory cortex. In rats, ICL results in complete axotomy of CSN of the sensory motor cortex and incomplete axotomy of the caudal portion of the supplementary motor and medial prefrontal cortex. In mice, the area of axotomized CSN extends significantly further frontally. In both species, axotomy-induced death of CSN is observed in the center of the sensory motor cortex. This lesion model is useful for investigations on the response of CSN of the sensory motor cortex to lesion and therapeutic drugs.

Animals↗
PubMed2000

IgG-mediated cytotoxicity to myenteric plexus cultures in patients with paraneoplastic neurological syndromes.

Autoantibodies against neuronal and tumour proteins have been described in many paraneoplastic neurological syndromes (PNS), but it is not clear whether these antibodies are pathogenic or simply a useful diagnostic tool. We took seven sera that were positive on routine screening for antineuronal antibodies and the IgG fractions. As controls we used sera from health blood-donors, other neurological autoimmune diseases and patients with SCLC without PNS. We tested them on dissociated rat myenteric plexus cultures for cytotoxic effects. After incubation for 24 h, cytotoxicity was determined by a double fluorescence test (calcein green for living cells and ethidium homodimer-1 for dead cells). We found an increased cell death rate in cultures incubated with the PNS sera, compared with all controls (P< 0.05). Isolated IgG fractions were also cytotoxic whereas the IgG-free serum fraction did not show any significant increase in cytotoxicity. After incubation with PNS IgG, FACS analysis revealed an increased cytotoxicity rate only of the neurones, but not the glial cells. Our results indicate that in PNS a complement-independent, antibody-mediated cytotoxicity against neurones may contribute to the pathogenesis of these syndromes.

Animals↗
PubMed2000

Reaggregation of rat dissociated myenteric plexus in extracellular matrix gels.

The aim of this study was to investigate the growth behavior of freshly dissociated myenteric plexus in a three-dimensional extracellular matrix (ECM) environment with and without stimulation of glial cell line-derived neurotrophic factor (GDNF). Therefore, cell suspensions of the dissected myenteric plexus of newborn rats were cultured in freshly prepared gels of commercially available mixtures of collagen, laminin, and hepatoglycans as a first step towards mimicking the natural environment of the myenteric plexus. The cultures were kept either in chemically defined serum-free medium alone or supplemented with GDNF. Cultures on polylysinc-coated glass cover slips served as controls. Dissociated myenteric plexus grown on polylysine formed dense clusters of neurons with radially outgrowing nerve fibers, while the neurons cultured in the gel reaggregated to much smaller clusters. These contained, depending on the culture conditions, 2-10 neurons. The morphology of the network that was seen in the gels after a few days in vitro resembled very closely the in situ situation of the submucous plexus and the myenteric plexus in hypoganglionic children. Electron microscope investigations showed a high degree of organization with fiber bundles and vesicle-containing varicosities and growth cones. Independent of the method of culturing, GDNF obviously influenced the growth behavior of the dissociated plexus. The size of the ganglia was larger, and the secondary network denser when GDNF was supplemented. Moreover, the enteric neurons in the gel cultures tended to be larger in size when treated with GDNF. Three-dimensional cultures of dissociated myenteric plexus in an ECM gel might be a valuable tool towards the understanding of the formation of the enteric nervous system during development, especially considering pathological conditions such as Hirschsprung's disease or other dysganglionic diseases.

Animals↗
PubMed2000

Surface treated catheters with ion beam based process for blood access.

Infection, thrombosis, and stenosis are among the most frequent complications associated with blood contacting catheters. Because these problems are usually related to surface properties of the base catheter material, surface treatment processes such as ion implantation and ion beam assisted deposition (IBAD) (silver based coatings) can be used to mitigate such complications. Because these ion beam based processes affect only the near-surface region (approximately the outer 1 microm), there is little effect on bulk material properties. This study evaluated silver coated large bore catheters used for extracorporeal detoxification. In a 135 patient prospective study, 170 large bore catheters were inserted into the internal jugular or subclavian veins. Seventy-eight surface treated catheters (Spi-Argent, Spire Corporation, Bedford, MA, U.S.A.; n = 32 acute catheters, n = 46 long-term catheters) were inserted in 55 patients. Ninety-two untreated catheters placed in 80 patients served as controls (n = 40 acute catheters, n = 52 long-term catheters). After removal, the catheters were cultured for bacterial colonization using standard microbiologic assays. They also were examined using a scanning electron microscope (SEM). Bacterial colonization was observed in 7% of the treated catheters compared with 35.3% of untreated catheters. The SEM investigations showed all treated catheters to possess low thrombogenicity. Results of the study indicate that ion beam based processes can be used to improve thrombus and infection resistance of blood contacting catheters.

Adult↗
PubMed2000

Undergraduate medical education: tendencies and requirements in a rapidly developing Europe.

This study pinpoints the necessity to constantly monitor local approaches in undergraduate medical education on an inter-European scale. Traditional undergraduate medical curricula need restructuring to account for the increasing amount of medical knowledge and rapid changes and developments in societies, nosology, therapy and IT. European undergraduate medical curricula should be harmonized not egalized, with a focus on inter-European sharing of resources, mobility, credit (allocation, accumulation and transfer), definition of European and trans-European mission statements, identification of quality metrics, advice on dealing with conflicting aims such as specialization and generalization, on communicating core knowledge instead of providing overabundance of information, and on introducing multifaceted teaching and learning methods, as well as providing strategies for life long learning. Sound medical education can no longer and nowhere be considered under the autonomous auspices of individual Medical Schools or national philosophies. It has to be perceived and structured as a competitive and flexible approach which promotes life long learning of teachers, students, physicians and other related staff with international awareness. It is stressed that student and staff mobility, as well as virtual mobility in the form of worldwide available teaching modules and expertise have to be incorporated into national medical curricula. This is to guarantee up-to-date education in support of patient demands, future professionality and competitiveness of students, physicians and Public Health System institutions. The formal approaches of traditional subject related curricula as well as problem based learning must be linked with quality approved state of the art ODL, evaluated international CME strategies and training in the utilization of IT in preparation of lifelong learning. Strategies for the use of IT need updating on a regular basis to diminish the gap between undergraduate and postgraduate medical education. General European perspectives of medical education are discussed in relation to ECTS, ODL, compulsory credited and evaluated CME and relicensing of physicians. Prime features of ETM--the most reputed and well-known European medical CME initiative fostering quality assured international awareness are described and recommended for local and nationwide implementation. Specific links of the Bonn undergraduate medical curriculum with credited and evaluated CME and imminent European strategies are detailed. The authors conclude that European universities not adapting at least some of the outlined curricular necessities will rapidly lose their competitiveness compared to other national and international Medical Schools. Harmonized European ethical mission statements and consequent utilization of IT deserve special considerations in this context.

Computer-Assisted Instruction↗
PubMed1999

Morphological changes of the myenteric plexus during early postnatal development of the rat.

The enteric nervous system needs to adapt itself constantly to the postnatal changes of the developing gut. The aim of this study was to examine the morphological changes between the distal and proximal segments of the gastrointestinal (GI) tract during the first two postnatal weeks. Myenteric plexus from the duodenum, proximal and distal colon of 1-, 7- and 14-day-old rat pups was dissected and examined under the scanning electron microscope. Wholemounts from the same regions and postnatal stages were stained with cuprolinic blue. Neuronal numbers per ganglionic area were counted and neuronal sizes were measured. Furthermore, segments of the above-mentioned areas were embedded in resin and semithin sections were cut. The thickness of the circular and longitudinal muscle layers was measured. The morphology of the myenteric plexus depends on localization as well as on the age of the animal. While in younger animals the myenteric plexus is usually densely packed, the network expands with increasing age. Similarly, the thickness of the circular and the longitudinal muscle layers increases. Nerve cell numbers per ganglionic area increase from duodenum to distal colon and decrease from the 1-day (P1) to the 14-day-old (P14) animal. The longest diameters and the area of the nerve cells decrease from duodenum to distal colon and increase with age of the animal. The intensity of the cuprolinic blue staining varies also according to age and segment of the gut. During the first two postnatal weeks the three-dimensional architecture of the myenteric plexus as well as the size and densities of the enteric neurons change according to the increasing gut length and the thickness of the muscle layer. The differences between duodenum and colon might reflect the different physiological properties of the proximal and distal gut as well as a varying grade of maturity, which is also supported by a variation in the cuprolinic blue staining intensity.

Animals↗
PubMed1999

BDNF, but not NT-3, promotes long-term survival of axotomized adult rat corticospinal neurons in vivo.

Axotomy-induced death of corticospinal neurons (CSN) is prevented by intracotrical infusions of BDNF or NT-3 within the first week after axotomy. The present study examined whether this represents merely a delay of CSN death or whether BDNF and NT-3 can promote long-term survival of these neurons in vivo. The neurotrophins were infused for an initial period of 14 days to lesioned CSN which was followed by 28 days without treatment. BDNF was able to promote CSN survival for at least 42 days while NT-3 had no significant effect. These results suggest that initial BDNF treatment induces an endogamous mechanism that promotes survival of axotomized CSN without further exogenous neurotrophic factor supply. These findings may be important for the design of therapeutic strategies for motoneuron disease.

Animals↗
PubMed1999

The GDNF-induced neurite outgrowth and neuronal survival in dissociated myenteric plexus cultures of the rat small intestine decreases postnatally.

Glial cell-line-derived neurotrophic factor (GDNF), a member of the transforming growth-factor-(TGF-) beta-family, is an essential factor for the development of the enteric nervous system (ENS) during embryogenesis. In the present study, the effects of GDNF on postnatal ENS development were investigated using cultures of myenteric plexus from the small intestine of newborn albino rats of different developmental phases (P1, P7, P14). Myenteric plexus was dissociated and cultivated as mixed cultures of enteric neurons and glial cells. After seeding, the cultures were kept for 24 h or 7 days in serum-free medium containing various doses (1, 10, 100 ng/ml) of GDNF. The effect of the neurotrophic factor was evaluated using parameters such as cell size, neuronal survival, or neurite elongation. While neither glial-cell nor neuronal size was influenced by GDNF, there was an observable effect upon neuronal survival and neurite elongation. The cultures treated with GDNF displayed increased neurite outgrowth. The promoting effect was dose- and age-dependent, decreasing clearly during the early postnatal period. Already after 24 h, neuronal survival was increased in P1 and P7, but not in P14 cultures. In long-term cultures, a marked tendency to form cell aggregates and dense fiber networks was observed when treated with GDNF. These observations suggest that GDNF plays an important role not only in pre-, but also in postnatal development of the enteric nervous system.

Animals↗
PubMed1999

Identification of somatosensory pathways by focal-cooling-induced changes of somatosensory evoked potentials and EEG-activity--an experimental study.

OBJECT: Function-preserving neurosurgery requires methods to identify functionally important CNS-areas intraoperatively. We investigated whether a combination of focal cerebro-cortical cooling and monitoring of somatosensory evoked potentials (SEP) is suited for this task, i.e. whether it is able to outline structures belonging to the somatosensory pathway. METHODS: In 17 Wistar rats the somatosensory cortex was focally cooled by 20 degrees C below the initial tissue temperature for periods of five minutes. A cryoprobe with a tip diameter of 3 mm was used and tissue temperatures were measured below and at different distances to the cryoprobe. Tibial nerve evoked SEPs and EEG-spectra were recorded continuously. RESULTS: During cortical cooling the SEP-responses showed a marked delay and amplitude increase of the cortically generated components P13 and N18 and a small latency increase of the subcortically generated wave III. EEG-spectra were depressed mainly in the low frequency range. All cooling effects were reversible and in light- as well as electron-microscopic examinations no tissue damage was found. CONCLUSIONS: Focal cooling of the cortex induces easily recognizable and reversible changes of the bio-electrical activity without causing any histological damage. Therefore the method seems suitable for identifying eloquent areas. It can be expected that clinical application of the cooling technique in combination with intraoperative electrophysiological monitoring will be helpful to further lower the risk of neurosurgical operations. We propose that cooling mainly interferes with the synaptic transmission within the somatosensory cortex, because the observed amplitude increase can be explained by cold-induced depression of inhibitory cortical activity (disinhibition).

Animals↗
PubMed1999

The IL-6/sIL-6R fusion protein hyper-IL-6 promotes neurite outgrowth and neuron survival in cultured enteric neurons.

The undisturbed development of the enteric nervous system depends on the supply of various neurotrophic factors during ontogenesis. Besides glial cell line-derived neurotrophic factor (GDNF), leukemia inhibitory factor (LIF) and ciliary neurotrophic factor (CNTF) take part in its development. CNTF and LIF belong to the interleukin-6 (IL-6) family of cytokines. The combination of IL-6 and the soluble IL-6 receptor accelerates peripheral nerve regeneration. In this study, we examined the effect of the fusion protein Hyper-IL-6, which consists of IL-6 and the soluble receptor sIL-6R, on neurite outgrowth and neuronal survival in vitro. Myenteric plexus of newborn rats was dissected and dissociated. Cells were grown in either serum-free chemically defined medium alone or medium supplemented with sIL-6R, IL-6, sIL-6+IL-6, Hyper-IL-6, CNTF, LIF, or GDNF. Average neurite outgrowth per neuron was highest in GDNF-treated and Hyper-IL-6-treated cultures. The number of neurite-bearing neurons was reduced in GDNF cultures compared with Hyper-IL-6-treated cells, so that the total neurite outgrowth was maximal after Hyper-IL-6 stimulation. Hyper-IL-6 furthermore stimulated neuronal survival and morphologic differentiation of the enteric glia.

Animals↗
PubMed1998

The survival-promoting effect of glial cell line-derived neurotrophic factor on axotomized corticospinal neurons in vivo is mediated by an endogenous brain-derived neurotrophic factor mechanism.

Autocrine trophic functions of brain-derived neurotrophic factor (BDNF) have been proposed for many central neurons because this neurotrophin displays striking colocalization with its receptor trkB within the CNS. In the cortex, the distribution patterns of BDNF and trkB expression are almost identical. Corticospinal neurons (CSNs) are a major cortical long-distance projecting system. They are localized in layer V of the somatosensory cortex, and their axons project into the spinal cord where they contribute to the innervation of spinal motoneurons. We have shown recently that adult CSNs express trkB mRNA and are rescued from axotomy-induced death by BDNF treatment. Half of the axotomized CSNs survived without BDNF infusions. These findings raise the possibility that endogenous cortical BDNF is involved in the trophic support of this neuronal population. To test the hypothesis that endogenous cortical BDNF promotes survival of adult CSNs, we infused the BDNF-neutralizing affinity-purified antibody RAB to axotomized and unlesioned CSNs for 7 d. This treatment resulted in increased death of axotomized CSNs. Survival of unlesioned CSNs was not affected by RAB treatment. In situ hybridizations for BDNF and trkB mRNA revealed that virtually all CSNs express trkB, whereas only half of them express BDNF. Thus, autocrine/paracrine mechanisms are likely to contribute to the endogenous BDNF protection of axotomized CSNs. We have demonstrated previously that, in addition to BDNF, glial cell line-derived neurotrophic factor (GDNF) and neurotrophin 3 (NT-3) also rescue CSNs from axotomy-induced death. We now show that the rescuing by GDNF requires the presence of endogenous cortical BDNF, implicating a central role of this neurotrophin in the trophic support of axotomized CSNs and a trophic cross-talk between BDNF and GDNF regarding the maintenance of lesioned CSNs. In contrast, NT-3 promotes survival of axotomized CSNs even when endogenous cortical BDNF is neutralized by RAB, indicating a potential of compensatory mechanisms for the trophic support of CSNs.

Animals↗
PubMed1998

Infusion of GDNF into the cerebral spinal fluid through two different routes: effects on body weight and corticospinal neuron survival.

Survival of axotomized adult rat corticospinal neurons (CSN) is supported by glial cell line-derived neurotrophic factor (GDNF). We have evaluated the trophic effects of intrathecally applied GDNF on CSN survival and rat body weight. Body weight reduction is the major side effect of intracerebral neurotrophic factor treatment. GDNF was tested at total doses of 30, 100 and 300 microg over 7 days after axotomy via different application routes: intracerebroventricularly (i.c.v.) and cisternally (cis). Animals injected i.c.v. displayed severe body weight reduction at all doses tested but CSN rescue only at the highest dose. In contrast, cis-infusion of GDNF promoted CSN survival at all doses and only the highest dose reduced the body weight. These results show that intracisternal, but not i.c.v., GDNF infusion at low doses can promote CSN survival without negatively affecting rat body weight. This finding may have implications for the clinic use of GDNF.

Animals↗