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Biomedical subjects

M Kirsch

Publications and source records attributed to M Kirsch.

At least 109 records · Page 6Linked to original sources
PubMed1997

Use of cell ELISA for the screening of neurotrophic activities on minor cell populations in retinal monolayer cultures.

In this study we describe a large-scale screening cell ELISA protocol which is suitable for the characterization of exogenic factor effects in mixed central nervous system (CNS) culture. The main novelty of the assay is that it permits the measurement of cellular responses in populations comprising as little as 2-4% of the total cell number. For standardization of the assay, we employed antibodies against opsin and microtubule-associated protein (MAP2) which label distinct retinal cell classes. Embryonic chick retinal neurons were grown in microtiter plates and directly processed for detection of antibody binding on the same plate. Binding of the antibodies was saturable and the ELISA signal was proportional to the number of immunoreactive cells comprising 2-4% and 16% of the total cell number with opsin and MAP2 antibodies, respectively. A minimum of 2000 opsin-positive cells could be reliably determined. Using our cell ELISA protocol, we demonstrate a developmental increase of both cell markers which reflected an increase in the number of opsin-positive cells but an enhanced expression per cell in the case of MAP2. We also show that growth-promoting activity-the presumed chick ciliary neurotrophic factor (CNTF)-stimulated the expression of opsin in retinal cultures (EC50; 2.3 pM) and that a corresponding activity is specifically expressed in the developing retina. Our results show that the cell ELISA protocol allows the rapid screening for distinct, low-percentage cell populations responding to exogenous factors in mixed CNS cultures.

Animals↗
PubMed1997

Rapid decrease in cellular sodium and chloride content during cold incubation of cultured liver endothelial cells and hepatocytes.

Hypothermia, as used for organ preservation in transplantation medicine, is generally supposed to lead to an intracellular accumulation of sodium, and subsequently of chloride, via inhibition of the Na+/K+-ATPase. However, on studying the cellular sodium concentration of cultured liver endothelial cells using fluorescence microscopy, we found a 55% decrease in the cellular sodium concentration after 30 min of cold incubation in University of Wisconsin (UW) solution. To confirm this surprising result, we set up a capillary electrophoresis method that allowed us to determine the cellular contents of inorganic cations and of inorganic anions. Using this method we measured a decrease in the cellular sodium content from 104+/-11 to 55+/-4 nmol/mg of protein, accompanied by a decrease in the chloride content from 71+/-9 to 25+/-5 nmol/mg of protein, after 30 min of cold incubation in UW solution. When the endothelial cells were incubated in cold Krebs-Henseleit buffer or in cold cell culture medium instead of UW solution, similar early decreases in cellular sodium and chloride contents were observed, thus excluding the possibility of the decreases being dependent on the preservation solution used. Furthermore, experiments with cultured rat hepatocytes yielded a similar decrease in sodium content during initiation of cold incubation in UW solution, so the decrease does not appear to be cell-specific either. These results suggest that, contrary to current opinion, sodium efflux predominates over sodium influx during the early phase of cold incubation of cells.

Adenosine↗
PubMed1997

Differential regulation of ciliary neurotrophic factor (CNTF) and CNTF receptor alpha expression in astrocytes and neurons of the fascia dentata after entorhinal cortex lesion.

Neurotrophic factors have been implicated in reactive processes occurring in response to CNS lesions. Ciliary neurotrophic factor (CNTF), in particular, has been shown to ameliorate axotomy-induced degeneration of CNS neurons and to be upregulated at wound sites in the brain. To investigate a potential role of CNTF in lesion-induced degeneration and reorganization, we have analyzed the expression of CNTF protein and CNTF receptor alpha (CNTFR alpha) mRNA in the rat dentate gyrus after unilateral entorhinal cortex lesions (ECLs), using immunocytochemistry and nonradioactive in situ hybridization, respectively. In sham-operated as in normal animals, CNTF protein was not detectable by immunocytochemistry. Starting at 3 d after ECL, upregulation of CNTF expression was observed in the ipsilateral outer molecular layer (OML). Expression was maximal at around day 7, and at this stage immunoreactivity could be specifically localized to astrocytes in the ipsilateral OML. By day 14 postlesion, CNTF immunoreactivity had returned to control levels. CNTFR alpha mRNA was restricted to neurons of the granule cell layer in controls. Three days postlesion, prominent CNTFR alpha expression was observed in the deafferented OML. A similar but less prominent response was noticed in the contralateral OML. After 10 d, CNTFR alpha expression had returned to control levels. Double labeling for CNTFR alpha mRNA and glial fibrillary acidic protein (GFAP) showed that upregulation of CNTFR alpha occurred in reactive, GFAP-immunopositive astrocytes of the OML. A substantial reduction of CNTFR alpha expression in the deafferented granule cells was transiently observed at 7 and 10 d postlesion. Our results suggest a paracrine or autocrine function of CNTF in the regulation of astrocytic and neuronal responses after brain injury.

Animals↗
PubMed1997

Molecular aspects of neuro-oncology.

Detailed understanding of molecular events responsible for brain tumor growth is a prerequisite for the development of effective therapeutic modalities leading to improved prognosis and cure. Advances in molecular biology in the past decades have revolutionized our understanding of cancer, including brain tumors. We have learned that abnormal proliferation, inability of the cells to die and their potential to modify their tissue environment result from accumulation of genetic aberrations. This article reviews genetic mechanisms implicated in the pathogenesis of nervous system tumors, such as unactivation of tumor suppressor and replication error genes, generation of abnormal growth factor loops, alterations of apoptotic pathways and angiogenesis.

Apoptosis↗
PubMed1997

Expression of ciliary neurotrophic factor receptor-alpha messenger RNA in neonatal and adult rat brain: an in situ hybridization study.

Ciliary neurotrophic factor is a pleiotropic molecule thought to have multiple functions in the developing and adult nervous system. To investigate the role of ciliary neurotrophic factor in the developing and mature brain by defining putative target cells the expression of the ligand-binding alpha-subunit of the ciliary neurotrophic factor receptor was studied in neonatal and adult rat brains using a digoxygenin-labelled probe for in situ hybridization. Neuronal populations expressing ciliary neurotrophic factor receptor-alpha messenger RNA were found in many functionally diverse brain areas including the olfactory bulb (mitral cells and other neurons) neocortex (layer V) and other cortical areas (pyramidal cell layers in the piriform cortex and hippocampus, granule cell layer of the dentate gyrus) and distinct nuclei in the thalamus, hypothalamus and brainstem. In the latter, reticular nuclei and both cranial motor and sensory nerve nuclei showed intense hybridization signals in the neonatal brain. The nucleus ruber, substantia nigra pars reticularis, deep cerebellar nuclei and a subpopulation of cells in the internal granular layer of the cerebellum were also labelled. In many areas (e.g. in thalamic, midbrain and pontine nuclei) ciliary neurotrophic factor receptor-alpha expression became undetectable with maturation; however, there were other areas (e.g., olfactory bulb, cerebral cortex and hypothalamus) where expression was higher in the adult. The neuroepithelium of the neonatal rat displayed a highly selective expression of ciliary neurotrophic factor receptor-alpha in areas which are known to exhibit high rates of postnatal cell proliferation in the germinal zones. Generally, neurons which have been reported to respond to exogenous ciliary neurotrophic factor were labelled by the ciliary neurotrophic factor receptor-alpha probe. This was not the case, however, for striatal and septal neurons. The results of this study suggest that ciliary neurotrophic factor receptor-alpha ligands have even broader functions than previously thought, acting on different neuronal populations in the developing and mature brain, respectively.

Age Factors↗
PubMed1997

Platelet-derived growth factor in human brain tumors.

This paper initially reviews ligand and receptor systems for the PDGF family and the signalling systems they use as well as their role in neural developments. It then describes the putative role of this family in astrocytoma, meningioma, and pituitary adenoma pathogenesis. Potential therapies with receptor antagonists or dominant negative mutants are discussed in the final sections.

Animals↗
PubMed1997

Evidence for multiple, local functions of ciliary neurotrophic factor (CNTF) in retinal development: expression of CNTF and its receptors and in vitro effects on target cells.

There is increasing, although largely indirect, evidence that neurotrophic factors not only function as target-derived survival factors for projection neurons, but also act locally to regulate developmental processes. We studied the expression of ciliary neurotrophic factor (CNTF) and the CNTF-specific ligand-binding alpha-subunit of the CNTF receptor complex (CNTFR alpha) in the rat retina, a well-defined CNS model system, and CNTF effects on cultured retinal neurons. Both CNTF and CNTFR alpha (mRNA and protein) are expressed during phases of retinal neurogenesis and differentiation. Retina-specific Müller glia are immunocytochemically identified as the site of CNTF production and CNTFR alpha-expressing, distinct neuronal cell types as potential CNTF targets. Biological effects on corresponding neurons in culture further support the conclusion that locally supplied CNTF plays a regulatory role in the development of various retinal cell types including ganglion cells and interneurons.

Animals↗
PubMed1997

Pill-induced esophageal obstruction: discovery of a peptic stricture.

The patient described in this report had complete esophageal obstruction shortly after a new medication had been prescribed. When the obstructing pill was removed endoscopically, a peptic stricture was discovered. Curiously, the patient had had only rare transient dysphagia before this episode.

Aged↗
PubMed1997

Transient up-regulation of ciliary neurotrophic factor receptor-alpha mRNA in axotomized rat septal neurons.

Using non-radioactive in situ hybridization we investigated the effect of fimbria-fornix transection on the expression of ciliary neurotrophic factor receptor alpha (CNTFR alpha) mRNA in axotomized septohippocampal neurons of the rat septal complex. Whereas CNTFR alpha expression was undetectable in the medial septal nucleus/diagonal band complex (MSDB) of control animals, specific up-regulation was observed in MSDB neurons after fimbria-fornix transection. CNTFR alpha expression was maximal 7-10 days after the lesion and had returned to control levels after 3 weeks. Following unilateral fimbria-fornix transection, CNTFR alpha up-regulation was restricted to the MSDB ipsilateral to the lesion. When cholinergic septal neurons were selectively eliminated by immunolesioning with 192 IgG-saporin prior to fimbria-fornix transection, the lesion-induced expression of CNTFR alpha was still observed in many medial septal nucleus neurons. These results demonstrate that after fimbria-fornix transection CNTFR alpha expression is transiently induced in axotomized, non-cholinergic neurons of the medial septal nucleus, suggesting a postlesion function of locally supplied CNTF.

Animals↗
PubMed1997

Ductuloendocrine cell proliferation in the pancreas of two young dogs with diabetes mellitus.

Two cases of diabetes mellitus in juvenile dogs (a 3-4 month-old Golden Retriever and a 2-month-old Labrador Retriever) are described here in terms of their clinical, histologic, and immunohistologic findings. Only very few insulin-positive cells were demonstrated immunohistochemically in one dog. In the second dog, the alterations of the pancreas consisted of hydropic vacuolar degeneration of B cells in the islets of Langerhans. In both cases, hyperplasia of the vacuolated cells was prominent. These cells formed tubular structures and were immunohistochemically positive for cytokeratin and proliferating cell antigen (MIB-1). Furthermore, within these vacuolated areas, some cells were positive to varying degrees for insulin, glucagon, somatostatin, and pancreatic polypeptide. Apoptotic cells could be seen in the exocrine pancreas, in vacuolated areas, and occasionally in the islets of both dogs. We interpret these alterations as ductuloendocrine cell proliferation, probably as an idiopathic compensatory response.

Age Factors↗
PubMed1997

Expression and activation of epidermal growth factor receptors in meningiomas.

Previous studies have demonstrated expression of epidermal growth factor receptors (EGFRs) in human cerebral meningiomas. However, the activation status of the EGFRs and whether they activate cytoplasmic mitogenic signaling pathways are not known. In this study, using Northern blot analysis and the polymerase chain reaction, the authors report expression of epidermal growth factor, transforming growth factor-alpha, and EGFR messenger RNA in 27 meningioma specimens. Using Western blot and immunohistochemical analyses of the meningioma samples, the authors demonstrate that the EGFRs expressed by these meningiomas are activated. These activated EGFRs interact with and phosphorylate Shc, an SH2 domain-containing adapter protein that is important in transducing mitogenic signals from EGFRs to the nucleus via activation of the Ras signaling pathway. These results support the concept that activation of EGFRs in human meningiomas by autocrine/paracrine stimulation may contribute to their proliferation.

ErbB Receptors↗
PubMed1997

Analysis of the BRCA1 and BRCA2 genes in sporadic meningiomas.

Several lines of evidence suggest a relationship between the occurrence of meningiomas and that of breast carcinomas: Both occur more frequently in women than in men, and a higher incidence of meningiomas has been observed in patients with a history of breast carcinoma. Both tumor types also express receptors that are associated with a proliferative response to progesterone, estrogen, and androgen hormones. Despite this clinical evidence, no genetic links between the two tumor types have been found. The breast carcinoma genes BRCA1 and BRCA2 have been linked to familial and sporadic forms of breast cancer and ovarian cancer, providing an opportunity to test this clinical observation. We conducted studies to detect alterations of the BRCA genes in meningiomas. Evaluation of 60 sporadic meningiomas with a panel of eight microsatellite and two restriction fragment length polymorphism markers at the locations of BRCA1 and BRCA2 demonstrated no loss of heterozygosity. Microsatellite instability was detected for one meningioma at two markers close to the BRCA2 locus. Northern blot analysis did not reveal any differences in mRNA expression of meningiomas compared to control tissues. These results suggest that alterations of the BRCA1 and BRCA2 genes are not common pathogenetic events in the development of sporadic meningiomas.

BRCA2 Protein↗
PubMed1996

Down-regulation of plant V-type H+ -ATPase genes after light-induced inhibition of growth.

Cell extension growth in the mesocotyl tip of dark-grown Zea mays L. seedlings is dependent on vacuole enlargement and massive flux of ER and Golgi vesicles. Water flow into the expanding vacuole is driven by ion accumulation, which in turn is energized by the vacuolar H+-ATPase (V-ATPase). The V-ATPase energizes the secondary ion transport into the expanding vacuole. As light exposure leads to a strong inhibition of extension growth, the effect of light on transcript levels for subunits A and c of the V-ATPase was analyzed. Partial homologous cDNAs for subunit A and two isoforms of subunit c were cloned by RT-PCR. In dark-grown seedlings transcript levels for both subunits were much higher in the growing mesocotyl tip than in the fully differentiated mesocotyl tissue. Only in the tip region did light exposure lead to a strong and coordinate down-regulation of both mRNAs whereas in the differentiated mesocotyl only a slight decrease was observed. The results indicate that expression of the 'housekeeping' V-type H+-ATPase is strongly regulated in response to growth rate.

Adenosine Triphosphatases↗
PubMed1996

CNTF exerts opposite effects on in vitro development of rat and chick photoreceptors.

Effects of ciliary neurotrophic factor (CNTF) on photoreceptor development in dissociated cultures of embryonic chick and newborn rat retina were studied using opsin immunoreactivity to characterize photoreceptor differentiation. In the presence of CNTF, the number of photoreceptors was increased by up to 200% in chick cultures, but was reduced by 82-99% in rat cultures. The EC50 determined for CNTF effects in chick and rat cultures were 0.06 ng ml-1 and 0.02 ng ml-1, respectively. By studying the time course of in vitro development we showed that CNTF transiently stimulated the generation of photoreceptors from opsinnegative precursor cells of chick retina, but completely prevented the same process in rat cultures. These results suggest that CNTF is involved in the regulation of photoreceptor development, but that it can have different actions in the two species, at least in vitro.

Animals↗
PubMed1996

Salt stress induces an increased expression of V-type H(+)-ATPase in mature sugar beet leaves.

In the halotolerant sugar beet co-expression of V-ATPase and a vacuolar Na+/H(+)-antiporter provides a mechanism for vacuolar salt sequestration. To analyze salt-induced changes in the expression of the vacuolar H(+)-ATPase (V-ATPase) a partial cDNA of the proton-channel forming subunit c was cloned by RT-PCR. Southern blot analysis indicated a small gene family. In control plants transcript levels were high in roots and young growing leaves but low in fully expanded leaves. In mature leaves salt exposure (400 mM, 48 h) induced a strong increase in subunit c-mRNA. Transcripts for the catalytic subunit A followed a similar developmental and stress-modulated pattern, indicating a coordinate regulation of transcripts for both V-ATPase subunits. Concomittant with the mRNA increases the amount of V-ATPase protein increased as well.

Amino Acid Sequence↗