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M Meyer

Publications and source records attributed to M Meyer.

At least 127 records · Page 7Linked to original sources
PubMed2000

Glial cell line-derived neurotrophic factor stimulates the morphological differentiation of cultured ventral mesencephalic calbindin- and calretinin-expressing neurons.

Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor for mesencephalic dopaminergic neurons. Subpopulations of these neurons express the calcium-binding proteins calbindin (CB) and calretinin (CR). Understanding the specific effects of GDNF on these neurons is important for the development of an optimal cell replacement therapy for Parkinson's disease. To investigate the effects of GDNF on the morphological complexity of mesencephalic tyrosine hydroxylase (TH)-immunoreactive (-ir), CB-ir, and CR-ir neurons, dissociated cultures of embryonic (E14) rat ventral mesencephalon were prepared. Chronic administration of GDNF (10 ng/ml) for 7 days promoted the survival of TH-ir and CB-ir neurons but did not alter the density of CR-ir neurons. Total fiber length/neuron and number of branching points/neuron of CB-ir and CR-ir cells were significantly increased after GDNF treatment (2x for CB-ir cells and 1.4x and 1.7x, respectively, for CR-ir cells), which resulted in a significantly larger size of neurite field/neuron (2.9x and 1.5x for CB-ir and CR-ir neurons, respectively). The number of primary neurites/neuron of CB-ir neurons was found to be 1.5x larger, while no difference could be detected for CR-ir cells. Assessment of the effects of GDNF on TH-ir neurons unveiled a similar outcome with an increased total fiber length/neuron (1.5x), an increased number of primary neurites/neuron (1.6x), and a twofold larger size of neurite field/neuron. In conclusion, our findings recognize GDNF as a neurotrophic factor that stimulates the morphological differentiation of ventral mesencephalic CB-ir and CR-ir neurons.

Animals↗
PubMed2000

Improved survival of embryonic porcine dopaminergic neurons in coculture with a conditionally immortalized GDNF-producing hippocampal cell line.

Transplantation of embryonic nigral tissue is used as an experimental therapy for patients with Parkinson's disease but is hampered by a limited survival rate of dopaminergic neurons. Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for nigrostriatal dopaminergic neurons, and the present in vitro study aimed at improving the survival of dopaminergic neurons in porcine mesencephalic brain slice cultures by adding transfected, immortalized, temperature-sensitive GDNF-releasing HiB5 cells (HiB5-GDNF). Embryonic (E27/28) porcine ventral mesencephalic brain slices were placed on membrane inserts in six-well plates with serum-containing medium, and HiB5-GDNF, nontransfected HiB5 cells (HiB5-control), or green fluorescent protein-producing HiB5 cells (HiB5-GFP) were seeded onto each tissue slice. The concentration of GDNF in the coculture medium was 0.49 +/- 0.13 ng/ml at day 9 and 0. 22 +/- 0.05 ng/ml at day 19 (mean +/- SEM) as measured by GDNF ELISA. The decrease in release of GDNF over time was paralleled by a gradual reduction in the number of HiB5-GFP cells expressing the reporter gene (EGFP). At day 12, HPLC analysis revealed that medium from HiB5-GDNF cocultures contained 2.0 times more dopamine than medium from HiB5-control cocultures. At day 21 there was 1.6 times more dopamine. Similar results were obtained for the dopamine metabolite 3,4-dihydroxyphenylacetic acid. At day 21, cell counts showed that HiB5-GDNF cocultures contained 1.5 times more tyrosine hydroxylase immunoreactive neurons than HiB5-control cocultures, which must be compared with a 1.8 fold increase after chronic treatment with rhGDNF (10 ng/ml). In conclusion, the better survival of HiB5-GDNF cocultures is promising for the generation of effective cell lines for local delivery of neurotrophic factors to intracerebral nigral grafts.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

p27(kip1) expression in rectal cancer correlates with disease-free survival.

BACKGROUND: The cell-cycle inhibitor p27(kip1) is a potential tumor suppressor and might serve as a prognostic marker in rectal cancer, in particular with regard to patient selection for adjuvant therapy. MATERIALS AND METHODS: Immunohistochemical analysis was performed, using an anti-p27(kip1) monoclonal antibody, on paraffin sections of two matched [age, gender, UICC stage, year of operation (1982-1991)] groups of patients (n = 2 x 82) with rectal carcinoma curatively treated by surgery alone. The groups differed only in subsequent metachronous distant metastatic spread. All patients had to meet the selection criterion "free of local disease," in order to exclude surgical influence. Follow-up was prospective (median of 74 months). The intensity of staining (-, +, ++, ) and rate of positive cells (as a percentage of total tumor volume) were judged separately for cytoplasms and nuclei. RESULTS: On multivariate analysis, cytoplasmic staining intensity proved to be the best prognostic factor of disease-free survival and approached statistical significance (P = 0.0552, Cox regression). On univariate analysis, considering cytoplasmic staining alone, intensely stained ( ) tumors showed significantly poorer disease-free survival (vs ++, +, -; Kaplan-Meier, logrank, P = 0.0185). CONCLUSIONS: The demonstrated correlation between cytoplasmic compartmentalization of p27(kip1) and increased metastatic spread as well as disease-free survival underscores the role of p27(kip1) in rectal cancer. However, since other reports emphasize the importance of nuclear p27(kip1) expression, the mechanisms of steady-state and subcellular distribution of p27(kip1) remain unclear, and further investigation is needed.

Adenocarcinoma↗
PubMed2000

In vivo protection of nigral dopamine neurons by lentiviral gene transfer of the novel GDNF-family member neublastin/artemin.

The glial cell line-derived neurotrophic factor (GDNF)-family of neurotrophic factors consisted until recently of three members, GDNF, neurturin, and persephin. We describe here the cloning of a new GDNF-family member, neublastin (NBN), identical to artemin (ART), recently published (Baloh et al., 1998). Addition of NBN/ART to cultures of fetal mesencephalic dopamine (DA) neurons increased the number of surviving tyrosine hydroxylase (TH)-immunoreactive neurons by approximately 70%, similar to the maximal effect obtained with GDNF. To investigate the neuroprotective effects in vivo, lentiviral vectors carrying the cDNA for NBN/ART or GDNF were injected into the striatum and ventral midbrain. Three weeks after an intrastriatal 6-hydroxydopamine lesion only about 20% of the nigral DA neurons were left in the control group, while 80-90% of the DA neurons remained in the NBN/ART and GDNF treatment groups, and the striatal TH-immunoreactive innervation was partly spared. We conclude that NBN/ART, similarly to GDNF, is a potent neuroprotective factor for the nigrostriatal DA neurons in vivo.

Amino Acid Sequence↗
PubMed2000

[In vivo administration of purified supernatant of fetal and postnatal osteoblast cultures: initial results].

With increasing age of an organism, the osseous regenerative potential is reduced. In osteoblast-like cell cultures, cells of older donors that would not proliferate under standard conditions start to proliferate and express a differentiated phenotype when supplemented with the supernatant of fetal osteoblast-like cultures. The aim of this study was an evaluation of the fetal supernatant actions in vivo. Rat calvaria-derived osteoblasts of fetal and 21-day-old donors were isolated enzymatically and cultured. Their osteoblastic phenotype was confirmed by the expression of typical osteoblast synthesis products. The supernatant of the cultures of each age group was collected and pooled. The supernatant was purified by HPLC and concentrated approximately ten times. Additionally, several age-dependent differences within the purified protein fractions were documented by MALDI. After resuspension, the purified supernatant proteins were transferred on a collagen carrier and implanted into critical size defects of the calvaria of adult Wistar rats. In a control group, the collagen carriers were implanted containing isotonic salt solution. After 2, 4, and 8 weeks, a radiographic and histologic analysis of the regeneration process was performed which revealed differences in the progress of mineralization. The methods used in this study might help to identify age-dependent differences regarding the osteoblastic synthesis of osteoanabolic peptides and their impact on the regeneration of osseous defects.

Age Factors↗
PubMed2000

[Can continence function after rectal resection be prognostically estimated?].

AIM: To determine clinical and physiologic parameters enabling the prognosis of continence after protective ileostomy closure secondary to rectal resection for rectal cancer. METHODS: Patients who had undergone rectal resection (n = 65, of whom 24 had had radiochemotherapy) were evaluated by clinical examination, anorectal manometry and orthograde contrast enema before ileostomy closure. Continence was evaluated by clinical findings 91 +/- 52 weeks after stoma closure with the help of standardized questionnaires and classified according to the Wexner continence score. The relationship between findings before stoma closure and continence score was calculated with Pearson's correlation coefficient. RESULTS: Correlations were found to be significant between the continence score and the level of anastomosis (r = -0.58, p < 0.001), median resting pressure (r = -0.52, p < 0.001), rectal compliance (r = -0.43, p < 0.001). Additionally, radiochemotherapy impairs continence (p = 0.0001). Correlations were not significant between continence and functional sphincter length, squeeze pressure, threshold for perception, urge and maximal tolerable volume, and continence for semiliquid contrast medium. CONCLUSION: Incontinence after rectum resection is multifactorial: the level of anastomosis, resting pressure, rectal compliance and radiochemotherapy all play a dominant role. Based on these findings, the continence score can be calculated before closure of a diverting ileostomy by applying multivariate analysis with the help of the following formula: Continence score = 18.23 - 0.94 x level of anastomosis - 0.18 x resting pressure + 3.72 x radiochemotherapy.

Adult↗
PubMed2000

The HIV-1 protease inhibitor indinavir impairs insulin signalling in HepG2 hepatoma cells.

AIMS/HYPOTHESIS: Patients treated with human immunodeficiency virus-1 protease inhibitors often develop impaired glucose tolerance or diabetes, most likely due to an induction of insulin resistance. We therefore investigated whether the protease inhibitor indinavir alters insulin signalling. METHODS: We incubated HepG2 cells for 48 h without or with indinavir (100 micromol/l). Subsequently 125I-insulin binding to the cells and the effects of insulin stimulation on insulin-receptor substrate-1-phosphorylation, association of phosphatidylinositol 3-kinase with insulin-receptor substrate-1 and Akt-Thr308-phosphorylation were measured. RESULTS: In cells not exposed to indinavir, insulin (100 nmol/l) led to rapid increases of insulin-receptor substrate-1-phosphorylation, association of phosphatidylinositol 3-kinase with insulin-receptor substrate-1 and Akt-phosphorylation during the first 75 s, followed by subsequent decreases. In indinavir-treated cells, these insulin-stimulated increases during the first 75 s were reduced by 30-60% and this was not associated with alterations in cell number or viability, insulin binding to the cells or cellular insulin-receptor substrate-1-content. CONCLUSION/INTERPRETATION: Effects of indinavir on initial insulin signalling could cause, or contribute to, the metabolic effects of human immunodeficiency virus-1 protease inhibitors.

Carcinoma, Hepatocellular↗
PubMed2000

Expression and cell-specific localization of the cholecystokinin B/gastrin receptor in the human stomach.

Gastrin stimulates gastric acid secretion by acting on the cholecystokinin B/gastrin receptor (CCK-BR). The localization of this receptor at the cellular level showed conflicting results in animal studies and has not been described in man by immunohistochemistry. The aim of the present study is to characterize the precise cellular location of the CCK-BR in the human stomach. Polyclonal antisera were raised against different epitopes of the CCK-BR molecule and used for immunohistochemical investigations. CCK-BR mRNA was detected in paraffin tissue sections by the highly sensitive method of in situ reverse transcriptase-polymerase chain reaction (RT-PCR). Using immunohistochemistry, CCK-BR could successfully be localized in gastric parietal cells. In the majority of parietal cells, CCK-BR immunoreactivity was present a he basolateral cell membrane domain. In some parietal cells, a granular pattern of immunoreactivity was exclusively confined to the cytoplasm of the cells. CCK-BR mRNA was found in parietal cells and in enterochromaffin-like (ECL) cells by means of in situ RT-PCR. No expression of CCK-BR was found in the gastric antral mucosa. Our data support the concept that gastrin stimulates gastric acid secretion directly via CCK-B receptors on parietal cells and indirectly by inducing histamine release from histamine-containing ECL cells, which contributes to acid secretion by parietal cells.

Amino Acid Sequence↗
PubMed2000

D3 lymph node dissection in gastric cancer: evaluation of postoperative mortality and complications.

Since November 1995 we have been performing a D3 lymph node dissection in patients undergoing an operation for gastric cancer with a curative intent. The aim of the present study was to evaluate whether this procedure results in an increased postoperative mortality or complication rate in a Western population. Between November 1995 and August 1997 the postoperative courses of 76 patients were retrospectively assessed (45.3 lymph nodes per patient, lymph node ratio: 0.16). The patient outcome was compared with data from a historic control group of patients (n = 383) in whom the newly established D2 dissection was studied in our department. Regarding the demographic, clinical, and tumor-pathologic data, and the choice of resection and reconstructive procedures, the two groups differed only slightly. The postoperative mortality of 1% was lower (vs 6.8%) while the overall complication rate of 34% (vs 32.1%) was identical. In particular, no anastomotic leakage (vs 9.4%) and fewer nonsurgical complications (17.1% vs 27.9%) occurred. The reoperation rate was 1% vs 9.7%. However, in 6% of the patients drainage tubes had to be inserted under computed tomographic guidance. The average hospital stay remained unchanged (21.9 vs 20.7 days). A D3 dissection was shown to be feasible while demonstrating no disadvantages in the patients when compared with the D2 procedure.

Adenocarcinoma↗
PubMed2000

Indicanines B and C, two isoflavonoid derivatives from the root bark of Erythrina indica.

In addition to two known compounds, 5,4'-di-O-methylalpinumisoflavone and cajanin, a new 3-phenylcoumarin metabolite, named indicanine B, and a new isoflavone derivative, named indicanine C, were isolated from the root bark of Erythrina indica. By means of spectroscopic analysis, the structures of the new compounds were characterized as 4-hydroxy-3-(4'-hydroxyphenyl)-5-methoxy-2",2"-dimethylpyrano [5",6":6,7] coumarin and 4'-hydroxy-5-methoxy-2",2"-dimethylpyrano [5",6":6,7] isoflavone, respectively. The 13C-NMR data of cajanin and the in vitro antimicrobial spectrum and potencies of the isolated compounds are also reported.

Anti-Bacterial Agents↗
PubMed2000

Nicotine effects on proliferation and the bombesin-like peptide autocrine system in human small cell lung carcinoma SHP77 cells in culture.

OBJECTIVES: To determine whether nicotine affects the proliferation and expression of the bombesin-like peptide autocrine system in human small cell lung carcinoma (SCLC) SHP77 cells compared with nonmalignant human bronchial epithelial BEAS 2B cells as non-neuroendocrine controls. METHODS: Human lung cells were cultured in defined serum-free medium with various concentrations of nicotine added for various times. Proliferation was measured by cell counts and colorimetric assay, bombesin-like peptide receptor expression was assayed by specific binding assays and quantitative competitive PCR, and bombesin-like peptides determined by ELISA. RESULTS: Nicotine significantly stimulated the growth of human SCLC SHP77 and NCI-H865 cells, but not BEAS 2B cells. Bombesin-like peptide receptor specific binding and mRNA expression were not affected by nicotine exposure in SHP77 cells or BEAS 2B cells. An increase in SHP77 cellular bombesin-like peptide content was observed. CONCLUSIONS: Human SCLC SHP77 cells express the components of the bombesin-like peptide autocrine system. Increased proliferation in the presence of nicotine may be due in part to increased levels of bombesin-like peptides in SHP77 cultured in nicotine. Nicotine effects on nonmalignant pulmonary neuroendocrine cells may provide additional insight into how nicotine itself may promote lung carcinogenesis.

Binding, Competitive↗
PubMed2000

Neurocognition of auditory sentence comprehension: event related fMRI reveals sensitivity to syntactic violations and task demands.

The present study investigates the sensitivity of distinct brain regions to the syntactic processing of running speech. Experimental conditions varied the grammaticality of sentence types (correct vs. incorrect). Moreover, two different groups of subjects listened to the same sentence material, but followed two different task instructions. All participants were asked to listen to the auditory stimuli and to perform in a grammaticality judgment-task, whereas only half of the subjects were instructed to additionally repair incorrect sentences covertly. Significantly increased brain responses occurred in several left temporal areas as a function of sentences' grammaticality, particularly, in the 'pure' judgment-group. Spatial extent as well as the strength of focal brain activation changed as a function of grammaticality and task demand. A generally enhanced pattern of local blood supply to the right peri-sylvian cortex could be observed when individuals additionally realized the repair-task. In particular, the right inferior frontal gyrus (pars opercularis and pars triangularis) and the right temporal transverse gyrus (Heschl's gyrus) were more strongly affected by the repair-task demand. In contrast, an anterior portion of the superior temporal gyrus (planum polare) displayed increased activation bilaterally. Although left hemisphere activation varied clearly as a function of a sentence's grammaticality, the present findings demonstrate an involvement of the right peri-sylvian cortex, in particular, when task demands explicitly require an on-line repair. The results as a whole suggest a reconsideration of the notion that auditory language comprehension is restricted to the left hemisphere. The underlying mechanisms and the respective roles of both the left and the right hemisphere during speech processing are discussed.

Acoustic Stimulation↗
PubMed2000

[Nosocomial intestinal infections in an infant ward. The importance of phone inquiries of the families].

UNLABELLED: Intestinal nosocomial infections remain a major concern in pediatric wards where they occur synchronously with syncytial respiratory virus infections. MATERIAL AND METHODS: During the 1997-1998 winter, we systematically listed the intestinal nosocomial infections that emerged in the pediatric wards of the Clermont-Ferrand hospital. After their discharge, the families of the children who were not hospitalized for acute diarrhea were contacted by telephone. RESULTS: Among 817 hospitalized children, 27% were admitted to the hospital for acute epidemic gastroenteritis. One hundred forty-four children were listed as having nosocomial gastroenteritis, 96 (66.6%) during the hospital stay and 48 (33%) after discharge, which represents 5.8% of all the admissions. Intestinal nosocomial infections increased with the number of admissions per day and per month, and occurred in 28.1% of the cases of syncytial respiratory virus bronchiolitis that concern children of the same age. Rotavirus was found in 28% of nosocomial infections, yet it was responsible for 85.5% of the hospital readmissions for nosocomial infections. CONCLUSION: Further studies should try to find solutions to decrease the frequency of those concomitant diseases.

Acute Disease↗
PubMed2000

Indicanine A, a new 3-phenylcoumarin from root bark of Erythrina indica.

A new 3-phenylcoumarin, indicanine A (1), has been isolated from the root bark of the African medicinal plant Erythrina indica, together with three known compounds, robustic acid (2), daidzein, and 8-prenyldaidzein. The structure of the new compound was characterized, as 4-hydroxy-5-methoxy-3-(4'-methoxyphenyl)-2" -(1-methylethenyl)dihydrofurano[4",5":6,7]coumarin by means of extensive spectroscopic analyses. The compounds were found to be devoid of in vitro antibacterial activity.

Coumarins↗
PubMed2000

Identification of mutations in 15 Hungarian families with hereditary protein C deficiency.

Hereditary protein C deficiency represents about 2-9% of inherited thrombophilias. Our aim was to elucidate the molecular basis of protein C deficiency in 25 members of 15 Hungarian families with venous thromboembolic diseases and to identify hitherto undescribed genetical defects in the protein C (PROC) gene. The exons of the PROC gene were screened for mutations with the combination of polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE), and/or PCR and single-strand conformation polymorphism (SSCP) analysis. The amplified DNA fragments with aberrant migration during DGGE and SSCP were sequenced. Mutations were determined in the PROC gene in all of the examined families: one nonsense mutation, one rare frameshift deletion and nine different missense mutations, of which three were novel (1493 A-->G, 35Asp-->Gly; 6231 G-->A, 173Gly-->Glu; 8476 C-->T, 254Thr-->Ile). The combination of hereditary protein C deficiency with other hereditary thrombophilias was rather common. DGGE and SSCP were proved to be efficient and cost-effective screening methods in the genetic analysis of hereditary protein C deficiency.

Adult↗
PubMed2000

Alterations in Purkinje cell spines of calbindin D-28 k and parvalbumin knock-out mice.

The second messenger Ca2+ is known to act in a broad spectrum of fundamental cell processes, including modifications of cell shape and motility, through the intermediary of intracellular calcium-binding proteins. The possible impact of the lack of the intracellular soluble Ca2+-binding proteins parvalbumin (PV) and calbindin D-28 k (CB) was tested on spine morphology and topology in Purkinje cell dendrites of genetically modified mice. Three different genotypes were studied, i.e. PV or CB single knock-out (PV-/-, CB-/-) and PV and CB double knock-out mice (PV-/-CB-/-). Purkinje cells were microinjected with Lucifer Yellow and terminal dendrites scanned at high resolution with a confocal laser microscope followed by three-dimensional (3-D) reconstruction. The absence of PV had no significant effect on spine morphology, whereas the absence of CB resulted in a slight increase of various spine parameters, most notably spine length. In double knock-out mice, the absence of both PV and CB entailed a doubling of spine length, an increase in spine volume and spine surface, a higher spine density along the dendrites, as well as a more clustered spine distribution. In all three genotypes, a reduction in the number of stubby spines was observed compared with wild-type animals. These results suggest a morphological compensation for the lack of the soluble calcium buffers in the cytoplasm of Purkinje cell dendritic spines. The increase in various spine parameters, particularly volume, may counteract the lack of the calcium buffers, such as to adjust Ca2+-transients at the transitional zone between spines and dendrites.

Animals↗
PubMed2000

Estrogen augments the vasodilatory effects of vascular endothelial growth factor in the uterine circulation of the rat.

OBJECTIVE: Pregnancy augments uterine artery vasodilatation in response to vascular endothelial growth factor, although the underlying mechanism is not known. The aim of this study was to test the hypothesis that estrogen and progesterone, the primary sex steroids of pregnancy, are responsible for this effect through increased endothelial secretion of nitric oxide. STUDY DESIGN: Adult female Sprague-Dawley rats underwent oophorectomy at 9 weeks of age with concomitant placement of 21-day timed-release pellets containing either 17beta-estradiol (n = 6) or progesterone (n = 6), or a combination of these (n = 6). Control rats also underwent oophorectomy but did not receive hormone replacement (n = 6). Two to 3 weeks after oophorectomy the rats were killed and the main uterine artery was dissected free, cannulated in an arteriograph, and pressurized to 50 mm Hg. After constriction with phenylephrine, concentration-response curves to vascular endothelial growth factor (0.1-20 nmol/L) were performed to compare arterial sensitivity to and maximal effects of vascular endothelial growth factor among the 4 treatment groups. Vessels were then treated with N omega-nitro-L -arginine (0.24 mmol/L), an inhibitor of nitric oxide synthase, and the maximally effective concentration of vascular endothelial growth factor was reapplied to evaluate the relative contribution of nitric oxide to the overall effect. RESULTS: Comparisons of the effective concentration of vascular endothelial growth factor that elicited 50% of the maximal dilatation revealed the vessels of the estrogen group to be approximately 10 times more sensitive than the control group (0.4 +/- 0.11 nmol/L vs 4.2 +/- 1.13 nmol/L, respectively; P <. 05). Responses of vessels from the progesterone and combined groups were intermediate (progesterone, 2.3 +/- 0.66 nmol/L; combined, 1.1 +/- 0.28 nmol/L). Maximal vasodilatory responses were greatest in the groups with treatment including estrogen (estrogen, 61% +/- 3. 1%; combined, 54% +/- 3.4%; progesterone, 42% +/- 5.8%, control, 40% +/- 3.5%; P <.05). Addition of N omega-nitro-L -arginine inhibited maximal vascular endothelial growth factor-induced dilatation by approximately 40% irrespective of treatment group. CONCLUSION: The presence of estrogen rather than progesterone leads to an enhancement of vascular endothelial growth factor-induced arterial dilatation during pregnancy. This effect results from a proportional increase in endothelial nitric oxide secretion, along with that of another, as yet unidentified vasodilatory substance.

Animals↗