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Biomedical subjects

M Schmitt

Publications and source records attributed to M Schmitt.

At least 73 records · Page 4Linked to original sources
PubMed2001

Dehydroepiandrosterone stimulates proliferation and gene expression in MCF-7 cells after conversion to estradiol.

Dehydroepiandrosterone (DHEA) is a mitogen for estrogen-dependent MCF-7 breast cancer cells. Our aims were to determine whether DHEA required conversion to estrogens in order to stimulate cell proliferation and estrogen-dependent gene expression. After incubation of cells with 100 nM DHEA for 4 days, estradiol was present in the medium at a concentration of approximately 200 pM. Other compounds identified were testosterone ( approximately 300 pM) and estrone. Significant stimulation of cell proliferation by 1 nM estradiol and 100 nM DHEA was observed after 38 h and 4 days of incubation, respectively, indicating the necessity of DHEA conversion. DHEA doses > or = 10 nM induced estrogen-dependent reporter gene expression in MCF-7 cells transfected with a luciferase reporter gene under the control of the estrogen response element. DHEA-dependent stimulation of proliferation and luciferase induction could be inhibited by the anti-estrogens ICI182,780 and tamoxifen, respectively, and by the aromatase inhibitor 4-hydroxyandrostenedione. An androgenic effect of DHEA on proliferation and gene expression of MCF-7 cells was not observed. We conclude that conversion of DHEA to estrogens, particularly estradiol, is required to exert a mitogenic response.

Androstenedione↗
PubMed2001

Cell hydration controls autophagosome formation in rat liver in a microtubule-dependent way downstream from p38MAPK activation.

Autophagic proteolysis in rat liver is under the control of the cellular hydration state. Because the morphological site of swelling-dependent proteolysis regulation has not yet been identified, the formation of autophagosomes was investigated with transmission electron microscopy in slices from perfused livers. In livers from fed rats, hypo-osmotic exposure (185 mosmol/l) led within 30 min to a decrease in fractional cytoplasmic autophagosome volume that was sensitive to colchicine and p38(MAPK) inhibition. Similarly, the decrease in autophagosome volume, but not the increase in cell volume caused by insulin or glutamine/glycine, was strongly inhibited by colchicine and SB 203580, an inhibition of p38(MAPK) activation. Immune complex assays from perfused liver showed that hypo-osmotic activation of p38(MAPK) was not inhibited by colchicine. Further, experiments using confocal laser microscopy in cultivated hepatocytes incubated with mouse-derived anti-(alpha-tubulin) showed that microtubular structures were not influenced by the inhibition of p38(MAPK) by SB 203580. It is concluded that the sequestration of autophagic vacuoles is a major site of proteolysis regulation by cell hydration. Swelling-induced activation of p38(MAPK) is required for this process and occurs upstream of the putative microtubule regulation site.

Animals↗
PubMed2001

Hydroxamate-type matrix metalloproteinase inhibitor batimastat promotes liver metastasis.

Overexpression of matrix metalloproteinases (MMPs) facilitates tumor cell invasion. Synthetic MMP inhibitors such as batimastat have been designed to treat cancer. We report that because of batimastat treatment, human breast carcinoma cells metastasized to the liver in nude mice and that an increase of liver metastases of murine T-cell lymphoma cells was observed in syngeneic mice. Batimastat treatment also caused liver-specific overexpression of MMPs-2, -9, and mRNA up-regulation of angiogenesis factors and caspase-1, even in tumor-free animals. Induction of organ-specific side effects need to be taken into account regarding further development and clinical use of synthetic MMP inhibitors.

Angiogenesis Inducing Agents↗
PubMed2001

Mutations in the X-linked RSK2 gene (RPS6KA3) in patients with Coffin-Lowry syndrome.

RSK2 is a growth factor-regulated serine-threonine protein kinase, acting in the Ras-Mitogen-Activated Protein Kinase (MAPK) signaling pathway. Mutations in the RSK2 gene (RPS6KA3) on chromosome Xp22.2, have been found to cause Coffin-Lowry syndrome (CLS), an X-linked disorder characterized by psychomotor retardation, characteristic facial and digital abnormalities, and progressive skeletal deformations. By screening of 250 patients with clinical features suggestive of Coffin-Lowry syndrome, 71 distinct disease-associated RSK2 mutations have been identified in 86 unrelated families. Thirty-eight percent of mutations are missense mutations, 20% are nonsense mutations, 18% are splicing errors, and 21% are short deletion or insertion events. About 57% of mutations result in premature translation termination, and the vast majority are predicted to cause loss of function of the mutant allele. These changes are distributed throughout the RSK2 gene and show no obvious clustering or phenotypic association. However, some missense mutations are associated with milder phenotypes. In one family, one such mutation was associated solely with mild mental retardation. It is noteworthy that nine mutations were found in female probands, with no affected male relatives, ascertained through learning disability and mild but suggestive facial and digital dysmorphisms.

Abnormalities, Multiple↗
PubMed2001

Quality of life measurement in children and adolescents: issues, instruments, and applications.

There is increasing interest in measuring quality of life (QL) in children and adolescents, but this interest has developed without careful attention given numerous important issues. Consequently, there is much diversity and confusion in this measurement area. We discuss at a conceptual level herein how to construe and define QL, approach its measurement, and the implications of for whom this is done. Methodological issues pertaining to validation, proxy report, and child development are also discussed. Guidelines for selecting QL measures are provided and a set of generic QL measures is recommended for further consideration. Finally, applications of the QL concept in the policy, service and care, and science areas are delineated.

Adolescent↗
PubMed2001

Expression of latent matrix metalloproteinase 9 (MMP-9) predicts survival in advanced ovarian cancer.

OBJECTIVE: Matrix metalloproteinases (MMPs) are frequently expressed in malignant tumors and play an important role in tumor invasion and metastasis. MMP-2 and MMP-9 expression has been correlated with poor survival in some tumors, but data for ovarian cancer are lacking, despite clinical trials with MMP inhibitors. The aim of this study was to assess activity of MMP-2 and MMP-9 and correlate it to prognosis in ovarian cancer. METHODS: MMP-2 and MMP-9 gelatinolytic activity was analyzed in 84 patients with advanced ovarian cancer FIGO stage III and 19 benign ovarian tumors by gelatin zymography. MMP-9 immunoreactivity was detected by immunohistochemistry and gelatinolytic activity was localized in ovarian cancer tissue by in situ zymography. RESULTS: were correlated with patient survival, with a median follow-up period of 55 months. Results. Median pro-MMP-9 activity was at 0.00 U/microg protein in benign ovarian tissues and 4.82 U/microg protein in ovarian cancer (P = 0.001); activated MMP-9 was not detected. Pro-MMP-2 expression in benign ovarian tissue did not differ from that of malignant ovarian tissue, whereas active MMP-2 was present in 52% of ovarian cancers, but absent in benign ovarian tissues. Analyzing all patients high pro-MMP-9 activity was associated with short overall survival (P = 0.019) while pro-MMP-2 and activated MMP-2 did not predict overall survival. When analyzing the subgroups of patients with and without residual tumor mass at the time of surgery, pro-MMP-9 was of prognostic value only in the subgroup of patients with no residual tumor mass. In univariate analysis pro-MMP-9 activity, residual tumor mass, age, ascites volume, and grading were of prognostic significance for overall survival. However, in multivariate analyses, including all biological and clinicopathologic variables, only pro-MMP-9 and residual disease remained statistically independent prognostic factors. In situ zymography localized gelatinolytic activity predominantly to the tumor cell nests displaying MMP-9 immunoreactivity. CONCLUSIONS: Pro-MMP-9 gelatinolytic activity, but not active MMP-2 or MMP-9, serves as a useful statistically independent prognostic factor in ovarian cancer FIGO stage III, thus helping to identify ovarian cancer patients with an aggressive form of the disease.

Adult↗
PubMed2001

Nitric oxide synthase-I containing cortical interneurons co-express antioxidative enzymes and anti-apoptotic Bcl-2 following focal ischemia: evidence for direct and indirect mechanisms towards their resistance to neuropathology.

Neuronal nitric oxide-I is constitutively expressed in approximately 2% of cortical interneurons and is co-localized with gamma-amino butric acid, somatostatin or neuropeptide Y. These interneurons additionally express high amounts of glutamate receptors which mediate the glutamate-induced hyperexcitation following cerebral injury, under these conditions nitric oxide production increases contributing to a potentiation of oxidative stress. However, perilesional nitric oxide synthase-I containing neurons are known to be resistant to ischemic and excitotoxic injury. In vitro studies show that nitrosonium and nitroxyl ions inactivate N-methyl-D-aspartate receptors, resulting in neuroprotection. The question remains of how these cells are protected against their own high intracellular nitric oxide production after activation. In this study, we investigated immunocytochemically nitric oxide synthase-I containing cortical neurons in rats after unilateral, cortical photothrombosis. In this model of focal ischemia, perilesional, constitutively nitric oxide synthase-I containing neurons survived and co-expressed antioxidative enzymes, such as manganese- and copper-zinc-dependent superoxide dismutases, heme oxygenase-2 and cytosolic glutathione peroxidase. This enhanced antioxidant expression was accompanied by a strong perinuclear presence of the antiapoptotic Bcl-2 protein. No colocalization was detectable with upregulated heme oxygenase-1 in glia and the superoxide and prostaglandin G(2)-producing cyclooxygenase-2 in neurons. These results suggest that nitric oxide synthase-I containing interneurons are protected against intracellular oxidative damage and apoptosis by Bcl-2 and several potent antioxidative enzymes. Since nitric oxide synthase-I positive neurons do not express superoxide-producing enzymes such as cyclooxygenase-1, xanthine oxidase and cyclooxygenase-2 in response to injury, this may additionally contribute to their resistance by reducing their internal peroxynitrite, H(2)O(2)-formation and caspase activation.

Animals↗
PubMed2001

Expression of the peripheral-type benzodiazepine receptor and apoptosis induction in hepatic stellate cells.

BACKGROUND AND AIMS: Hepatic stellate cell (HSC) transformation and proliferation play an important role in liver fibrogenesis, and HSC apoptosis may be involved in the termination of this response. METHODS: Expression of the peripheral benzodiazepine receptor (PBR) and PBR-ligand-induced apoptosis were studied in cultured rat liver HSC. RESULTS: Transformation of HSC led to a transient expression of PBR at the messenger RNA and protein level, which was maximal after about 3 and 7 days of culture, respectively, and declined thereafter. Immunoreactive PBR showed a punctate staining and colocalized with mitochondrial manganese-dependent superoxide dismutase and adenine nucleotide translocator 1. The selective PBR ligands 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK11195) and 4' chlorodiazepam (Ro5-4864), but not the centrally acting benzodiazepine ligand clonazepam, induced dose-dependent apoptosis in HSC. The apoptotic potency of PK11195 paralleled the level of PBR expression. PK11195 induced dephosphorylation of protein kinase B/Akt and Bad and a downregulation of Bcl-2. Collapse of the mitochondrial membrane potential preceeded PBR-ligand-induced apoptosis. No apoptosis was induced by PK11195 in parenchymal cells, despite the presence of PBR, and PK11195 had no effect in these cells on Bad phosphorylation and Bcl-2 expression. CONCLUSIONS: Transformation of HSC leads to a transient expression of PBR and renders the cells sensitive to PBR-ligand-induced apoptosis, involving protein kinase B/Akt and Bad-dependent mechanisms.

Animals↗
PubMed2001

Tauroursodesoxycholate-induced choleresis involves p38(MAPK) activation and translocation of the bile salt export pump in rats.

BACKGROUND & AIMS: Canalicular secretion of bile acids is stimulated by tauroursodesoxycholate (TUDC). This study investigates the underlying mechanisms. METHODS: TUDC effects on mitogen-activated protein (MAP) kinases, taurocholate (TC) excretion, proteolysis, and the localization of the bile salt export pump (Bsep) were studied in rat hepatocytes and perfused liver. RESULTS: TUDC induced a transient and concentration-dependent activation of p38(MAPK) and of extracellular signal-regulated kinase 2 (Erk-2), but not of c-Jun-N-terminal kinase (JNK). In perfused liver, TUDC concentrations of 20 micromol/L was sufficient to elicit the MAP kinase responses and TC choleresis. SB 202190, a specific inhibitor of p38(MAPK), had no effect on TUDC- induced Erk activation but abolished the stimulatory effect of TUDC on TC excretion in perfused liver, indicating the requirement of p38(MAPK) in addition to the reported Erk dependence for the choleretic response. TUDC-induced stimulation of TC excretion was accompanied by a p38(MAPK)-dependent insertion of subcanalicular immunoreactive Bsep into the canalicular membrane. In addition TUDC induced a p38(MAPK)-sensitive inhibition of proteolysis. CONCLUSIONS: TUDC-induced stimulation of canalicular TC excretion involves a MAP kinase-dependent translocation of subcanalicular Bsep to the canalicular membrane. Dual activation of Erks and p38(MAPK) is required for the choleretic effect of both TUDC and hypo-osmotic cell swelling.

Animals↗
PubMed2001

Regulation of the dynamic localization of the rat Bsep gene-encoded bile salt export pump by anisoosmolarity.

Canalicular transport via the bile salt export pump (Bsep) represents the rate-controlling step in taurocholate excretion, whose capacity is under osmotic control. The short-term effects of anisoosmolarity and Ca(2+)-withdrawal on the localization of Bsep and the tight junction proteins Zo-1 and occludin were studied in perfused rat liver by immunohistochemistry, confocal microscopy, and densitometry. Under normoosmotic conditions, Bsep was found in the canalicular membrane and showed a punctate intracellular localization. Hypoosmolarity resulted in the translocation of intracellular Bsep to the canalicular membrane, whereas hyperosmolarity induced a retrieval of Bsep. Following hyperosmolar retrieval of Bsep and multidrug resistance protein 2 (Mrp2) from the canalicular membrane, in the putative intracellular vesicles Bsep and Mrp2 colocalized in 15% of these vesicles, whereas 85% stained either positive for Bsep (61%) or Mrp2 (24%). Anisotonicity had no effect on the linear staining patterns of occludin and Zo-1, indicating no increase in paracellular permeability. Omission of calcium produced cholestasis characterized by a disruption of occludin, whereas the localization of Zo-1, Bsep, and Mrp2 remained unaffected. It is concluded (1) that hyperosmolarity induces retrieval of Bsep from the canalicular membrane, which correlates to cholestasis. Hypoosmolarity leads to choleresis accompanied by a rapid recruitment of intracellular Bsep to the canalicular membrane. (2) Bsep- and Mrp2-specific vesicles participate in the short-term osmoregulation of canalicular secretion, however, a cause-effect relationship between bile salt excretion and transporter localization remains to be established. (3) Ca(2+)-depletion induces cholestasis by disruption of occludin-determined tight junctional permeability, whereas internalization of canalicular transporters play a minor role.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Protein kinase C-dependent distribution of the multidrug resistance protein 2 from the canalicular to the basolateral membrane in human HepG2 cells.

The subcellular localization of hepatobiliary transport proteins directly affects the rate of bile formation, e.g., the conjugate export pump multidrug resistance protein 2 (MRP2) is regulated on a short-term scale by retrieval from and insertion into the canalicular membrane in the liver. This study reports on the effects of protein kinase C on MRP2 localization and activity in human hepatoblastoma HepG2 cells. MRP2 was detected in HepG2 cells by immunocytochemistry and Western blot analysis. Functional activity was assessed by confocal laser scanning microscopy using fluorescent MRP2 substrates. In untreated HepG2 cells MRP2 was almost exclusively localized at the apical membrane. Treatment of HepG2 cells with phorbol-12-myristate-13-acetate (PMA) resulted in a rapid decrease of apically localized MRP2 and a loss of more than 90% of pseudocanaliculi within 4 hours. This was accompanied by a reduced pseudocanalicular secretion of the MRP2 substrate glutathione-methylfluorescein. Interestingly, PMA treatment (1-100 nmol/L) led to the appearance of immunoreactive MRP2 at the basolateral membrane within 30 minutes. This was shown by its colocalization with MRP1, human dipeptidylpeptidase IV (DPPIV), and transfected rat Ntcp. The effects of PMA on MRP2 localization were sensitive to the protein kinase C (PKC) inhibitor Gö6850 but insensitive to inhibition of MEK by PD098059. Basolateral MRP2-appearance was not inhibited by cycloheximide or by disruption of microtubules or microfilaments. In rat livers cholestasis was induced by PMA (100 nmol) and MRP2 was detected at the basolateral membrane in some areas, colocalizing with Ntcp. The data suggest that retargeting of canalicular MRP2 to the basolateral membrane due to PKC activation may represent a novel mechanism that may contribute to cholestasis.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2001

[Perfusion MR imaging of the heart with TrueFISP].

OBJECTIVE: Development and test of a saturation-recovery TrueFISP (SR-Trufi) pulse sequence for myocardial perfusion MR imaging (MRI) using improved gradient hardware. MATERIAL AND METHODS: Measurements were performed on a 1.5 T scanner with prototype gradients (50 mT/m, minimum rise time 300 microseconds). T1-weighted first-pass MRI of Gd-DTPA (0.025 mumol/kg) kinetics in the myocardium was performed using an SR-Trufi pulse sequence (TR/TE/alpha = 2.6 ms/1.4 ms/55 degrees) with a saturation preparation of TD = 30 ms before the TrueFISP readout. Measurements were performed in volunteers (n = 4) and in a pig model of chronic ischemia (n = 1). RESULTS: In phantoms, the signal intensity was linear with contrast concentration up to 0.9 mmol/kg Gd-DTPA. MR images obtained with SR-Trufi had a good image quality and high spatial resolution of 2.1 mm x 2.1 mm. Differences of the contrast agent's kinetics between a subendocardial perfusion deficit and neighboring myocardium were well visible on both MR images and signal-time curves derived from the region-of-interest analysis. CONCLUSION: SR-Trufi appears to be an interesting new technique for the assessment of myocardial microcirculation using dedicated cardiovascular MR systems.

Adult↗
PubMed2001

Antenatal diagnosis of Multicystic Renal Dysplasia.

Multicystic Renal Dysplasia (MRD) was discovered during antenatal ultrasound examination in 138 fetuses between 1980 and 1995. Associated malformations were present in 66 % (42 % urological) and 22 % of the fetuses did not survive the pregnancy or the peri-natal period.Anatomical analysis showed a wider variety of MRD than in classical descriptions. Obstruction of the urinary tract was almost invariable. Like the hypothesis published by Beck in 1971, our view is that, with a very early obstruction of the urinary tract (during the first trimester), there is a dysplastic evolution of renal tissue, while later in pregnancy the same obstruction can induce a hydronephrosis with corticomedullary dysplasia.We advise complete neonatal urological investigation, and surgical removal of multicystic kidneys, to avoid multiple and inadequate evaluations of those children with a single functioning renal unit.

Female↗
PubMed2001

Bowel management with antegrade colonic enema using a Malone or a Monti conduit--clinical results.

During this last decade, major surgical improvements have been proposed for the treatment of patients suffering from faecal incontinence or intractable constipation. Between 1996 and 1999, 12 patients mainly presenting with spina bifida were operated for antegrade colonic enema (ACE). In seven cases, a Malone procedure was performed. In 5 cases we used a Monti plasty to create a continent catheterisable conduit. In 4 cases the neoconduit was placed between the transverse colon and the umbilicus. The mean follow-up was 15 months. Bowel control and continence were obtained in 11 cases, postoperatively. One early complete stenosis of the cutaneous stoma occurred, after which the patient did not wish to carry on. Another patient stopped using his ACE stoma after several months because he was able to manage his bowel evacuation voluntarily without requiring an enema. The other ten patients have greatly improved their quality of life. Complications included principally stomal stenosis which can be regularly dilated by the patient himself using the Hegar dilator. Patients with umbilical stoma have a result comparable to patients with Malone procedure. Our series shows that ACE can be performed without an appendix using a Monti plasty. Implantation of the continent conduit in the caecum or in the transverse colon does not modify the overall results of ACE.

Adolescent↗
PubMed2001

The structure of subjective well-being in middle adulthood.

Subjective well-being (SWB) is at the centre of much ageing research due to its relationship to such important outcomes as health, morbidity and successful ageing. This paper discusses essential problems associated with its definition, measurement and dimensionality. Exploratory and confirmatory factor analyses were computed for data from the Interdisciplinary Longitudinal Study of Adult Development in order to assess whether SWB is a unidimensional or a multidimensional construct. The results suggest that SWB is unidimensional.

Activities of Daily Living↗