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K Schilling

Publications and source records attributed to K Schilling.

At least 55 records · Page 3Linked to original sources
PubMed1996

Differential mRNA transport and the regulation of protein synthesis: selective sensitivity of Purkinje cell dendritic mRNAs to translational inhibition.

Although the majority of mRNAs expressed in neurons are confined to the perikaryon, a growing number appear to be transported into dendrites. It is likely that this allows for the local regulation of protein synthesis within discrete subcellular compartments. Here, three different subcellular distribution patterns are demonstrated for four mRNAs that encode proteins highly expressed in Purkinje cells and their dendrites; mRNAs are found in the perikaryon only, perikaryon and proximal dendrite, or perikaryon and proximal plus distal dendrites. Further, it is shown that transport of an mRNA into the dendrites increases its sensitivity to translational inhibition by diphtheria toxin. These data suggest a simple model whereby the transport machinery can regulate the translation of selected mRNAs. Thus, environmental signals that generally affect translational efficiency in concert with the selectivity provided by the transport machinery could provide a means to locally regulate the synthesis of a restricted pool of proteins.

Animals↗
PubMed1996

Growth factor-induced c-fos expression defines distinct subsets of midbrain dopaminergic neurons.

Growth factors are considered pivotal for the development, maintenance, and function of mesencephalic dopaminergic neurons. Recent studies have identified a plethora of growth factors which support the survival and differentiation of embryonic dopaminergic neurons. However, the exact cellular targets of these growth factors, and, thus, their precise mechanisms of action, remain largely unknown. To identify these cellular targets, we analysed, at the single cell level, growth factor-induced c-fos expression in dissociated mesencephalic cell cultures derived from a fos-lac Z transgenic mouse line. Pharmacological interference with cell-cell communication was utilized to control for direct growth factor effects. beta-Galactosidase-expressing cells were phenotypically characterized by immunocytochemistry to specific neural cell markers. Glia cell line-derived neurotrophic factor, basic fibroblast growth factor, brain-derived neurotrophic factor, and neurotrophin-3 directly induced Fos expression in differently sized, yet overlapping, populations of tyrosine hydroxylase-immunoreactive dopaminergic neurons. In an additional subpopulation of dopaminergic neurons, neurotrophin-3 induced fos-lac Z expression indirectly through a glutamate-mediated activation of N-methyl-D-aspartate receptors. Consistent with their proposed glial-mediated mode of action, transforming growth factor alpha and platelet-derived growth factor induced Fos expression predominantly in glia but only in a very small number of dopaminergic neurons. These findings demonstrate that individual dopaminergic neurons represent the direct targets of different sets of extracellular growth factors. Our findings further establish that growth factors affect dopaminergic neurons by indirect mechanisms which require specific cell-cell communication. These data also suggest a potential role for growth factors in the establishment of the morphological and functional diversity of midbrain dopaminergic neurons.

Animals↗
PubMed1996

Activation of dopaminergic D1 receptors promotes morphogenesis of developing striatal neurons.

The early dopaminergic input from the midbrain may play an important role in the development of the basal ganglia. We therefore investigated whether and how dopamine affects the morphogenesis of striatal target neurons. Dissociated cell cultures of embryonic day 17 rat striatum were raised for seven days. Cells were then incubated with dopamine or various receptor-specific ligands for 1 h. At various times after termination of the treatment, cells were immunostained for growth-associated protein-43. Morphological parameters including numbers of growth cones, length of neurites, number of bifurcations, and neuronal soma size were assessed by means of a computer-based morphometric device. Treatment with dopamine in low concentrations as well as with the D1-like receptor agonist SKF 38393 increased the numbers of growth cones and neurite length and arborization. The morphogenetic effect took several hours to evolve and remained stable for at least 24 h. It could be blocked by the D1-like receptor antagonist SCH 23390 or by cycloheximide but not by pretreatment of the cultures with tetrodotoxin. The D2-like receptor agonist quinpirole had no effect on the morphological parameters and did not contribute to that of SKF 38393. Dopamine and SKF 38393 but not quinpirole also induced an increase in the number of neurons immunoreactive for Fos-like proteins. However, this effect was restricted to growth-associated protein-43-negative neurons. This is the first observation of a positive regulatory effect of D1-like receptors on neuronal morphogenesis. We conclude that the changes reflect true differentiation rather than short-term modulation of cellular properties and that c-fos induction is not an obligatory step in the transduction pathway coupling D1-like receptors to neurite outgrowth. Our results suggest that the differentiation of embryonic striatal neurons is promoted by the dopaminergic nigrostriatal projection through D1-like receptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1995

Glycosylphosphatidylinositol-alkaline phosphatase from calf intestine as substrate for glycosylphosphatidylinositol-specific phospholipases--microassay using hydrophobic chromatography in pipet tips.

An electrophoretically homogeneous glycosylphosphatidylinositol- alkaline phosphatase fraction from calf intestine, obtained by hydrophobic chromatography, was used as "enzyme-labeled" substrate for testing phospholipase activity. The reaction products were separated by (i) hydrophobic chromatography in pipet tips and (ii) Triton X-114 phase partitioning. The chromatographic method presented permits high test frequencies, does not need temperature-controlled sample handling, and is only slightly disturbed by detergents, organic solvents, and proteins. The method was used to characterize phosphatidylinositol- specific phospholipase C from Bacillus cereus and phospholipase D from calf serum. Measurement of substrate hydrolysis by phospholipases is apparently linear to enzyme concentration and time. Relative activity of both enzymes is maximum at pH 6.5, corresponding to the optimal pH range found with other glycosylphosphatidylinositol substrates and phosphatidylinositol-specific phospholipases of other sources. Maximum activity of phospholipase C was found at 0.03% Triton X-100, 0.01% Brij 35, and 0.2% n-octylglucoside. The activity is not affected by Ca(2+), NaHCO(3), o-phenanthroline, or EDTA, increasingly inhibited by MgCl(2), MnCl(2), and ZnCl(2), and slightly activated by Na+ and K+. Calf serum phospholipase D shows maximum activity at 0.05% Triton X-100, 0.02% Brij 35, and 0.4% n-octylglucoside. The apparent Km values for phospholipase C (12.25 micron) and phospholipase D (4.94 micron) found with glycosylphosphatidylinositol-alkaline phosphatase are compared with values published for other glycosylphosphatidylinositol substrates.

Alkaline Phosphatase↗
PubMed1995

Induction and variants of neuronal nitric oxide synthase type I during synaptogenesis.

In the adult central nervous system, nitric oxide (NO) is formed from L-arginine by the so-called constitutive or type I NO synthase (NOS-I155). However, expression of NOS-I155 immunoreactivity and activity was low or not detectable in developing mouse and rat brain. NOS-I155 was sharply induced coincident with the onset of synaptogenesis in specific brain regions. This was followed by a second phase in which total NOS-I155 expression decreased both in specific cell populations and in the total synaptosomal subcellular fraction.Furthermore, two putative variants of NOS-I were transiently observed: an NOS-I-immunoreactive protein with increased electrophoretic mobility (NOS-I144) and a transient hypersensitivity of NOS-I155 to the competitive substrate inhibitor N omega-nitro-L-arginine. It is concluded that NOS-I expression is not constitutive but locally induced. In the central nervous system, this regionally specific, biphasic pattern of postnatal NOS-I induction is consistent with a role for NO in synaptogenesis and synaptic plasticity.

Amino Acid Oxidoreductases↗
PubMed1995

Screening and diagnostic breast imaging procedures. A look at lesions through a radiologist's eyes.

Breast cancer is the most common cancer among American women, and primary care physicians can be instrumental in ensuring a timely diagnosis. Women should be taught breast self-examination by the time they are in their late teens. Patients of all ages should be encouraged to have regular physician-conducted breast examinations and mammographic screening at a high-quality center. The consistent care and individualized follow-up provided in a primary care office are vital components of the total effort toward good breast health.

Biopsy↗
PubMed1995

Integration of information-seeking skills and activities into a problem-based curriculum.

Recent trends in medical education include a shift from the traditional, didactic, lecture-oriented approach to a more student-driven, problem-based approach to learning. This trend provides librarians with an opportunity to develop programs to teach information-gathering skills that support and are integrated into problem-based learning (PBL). In 1992, the University of Pittsburgh School of Medicine implemented the initial phase of a curriculum revision that emphasizes PBL. Since that time, Falk Library of the Health Sciences has provided a large-scale, intensive program integrating information-seeking skills and activities into the first-year Patient-Doctor Relationship course, a sequence that initiates medical school. A multimodal approach to information seeking and sources is emphasized, utilizing print and audiovisual materials, computerized resources, and subject experts. The Falk Library program emphasizes the gathering and use of information as central to both PBL and student skills development. An informal, post-course evaluation was conducted to gauge which information resources were used and valued most by students. This article presents evaluation results, including data on the use of information sources and services, and student perceptions of the librarian's role in the PBL sessions.

Curriculum↗
PubMed1994

Nitric oxide synthase expression reveals compartments of cerebellar granule cells and suggests a role for mossy fibers in their development.

The developmental expression and cellular distribution of nitric oxide synthase was investigated in the murine cerebellum and in cerebellar neurons developing under controlled in vitro conditions. Cerebellar granule cells expressed nitric oxide synthase only after migration to the internal granule cell layer. Initially, the nascent internal granule cell layer throughout the cerebellum stained uniformly for nitric oxide synthase, but during the second postnatal week, a pattern emerged consisting of clusters of heavily stained granule cells separated by areas of unstained granule cells. This pattern persisted into adulthood. There was a close temporal correlation between innervation of the granule cell layer by mossy fibers and the emergence of granule cell compartments as defined by levels of nitric oxide synthase expression. Granule cells in dissociated cultures derived from cerebellar anlagen prior to mossy fiber innervation also express nitric oxide synthase. The time-course of nitric oxide expression was independent of electrical activity of the neuronal network forming in vitro. However, suppression of spontaneous electrical activity resulted in enhanced nitric oxide synthase expression. These findings indicate that granule cell precursors are endowed with an intrinsic program which regulates nitric oxide synthase induction and which is executed independently of correct positional cues. The data also suggest that electrical activity of ingrowing mossy fibers down regulates nitric oxide synthase expression and plays an important role in the generation of granule cell compartments. These compartments may contribute to the functional organization of the cerebellar cortex.

Afferent Pathways↗
PubMed1993

Continuous c-fos expression precedes programmed cell death in vivo.

The development of a multicellular organism involves a delicate balance among the processes of proliferation, differentiation and death. Naturally occurring cell death aids tissue remodelling, eliminates supernumerary cell populations and provides structural elements such as hair and skin. In the nervous system, selective cell death contributes to the formation and organization of the spinal cord and sympathetic ganglia, retina and corpus callosum. But cell death also occurs in several neuropathological conditions, such as amyelotrophic lateral sclerosis and Alzheimer's disease. Therefore an elucidation of the mechanisms responsible for cell death is critical for an appreciation of both normal development and neuropathological disorders. Using a fos-lacZ transgenic mouse, we provide evidence showing that the continuous expression of Fos, beginning hours or days before the morphological demise of the cell, appears to be a hallmark of terminal differentiation and a harbinger of death.

3T3 Cells↗
PubMed1993

Control of segment-like patterns of gene expression in the mouse cerebellum.

A Purkinje cell-specific transgene, L7-lacZ, is expressed in a series of parasagitally oriented stripes in the mouse cerebellum. This banding pattern can be perturbed by promoter mutation, showing that a combination of positive and negative control elements contributes to the temporal and spatial map of L7 gene expression. In addition to the parasagittal stripes, certain mutations reveal Purkinje cells organized into compartments oriented in the transverse plane of the cerebellum. Transcription factors of the POU or homeobox families appear to be involved in controlling L7 expression in the transverse orientation. Strikingly, some of the domains of gene expression revealed by the mutations appear to correspond to functional compartments of Purkinje cells, thereby suggesting an underlying genetic principle used to orchestrate functional organization in the nervous system.

Animals↗
PubMed1993

A fos-lac Z transgenic mouse that can be used for neuroanatomic mapping.

Cellular immediate-early genes are rapidly induced by a diverse range of agents and conditions. Since many cIE genes encode known or potential transcription factors, they are believed to couple extracellular stimuli to long-lasting alterations in cellular phenotype through the regulation of gene transcription. In addition, the localization of the products of cIE genes has been used as a method for determining the cellular sites of action of particular agents in the nervous system. However, the methods of analysis are tedious, and the results may be ambiguous because of cross-reaction of reagents with related proteins. To further the utility of this approach, a bacterial gene encoding beta-galactosidase (lac Z) has been fused, in frame, into the fourth exon of c-fos, and this fos-lac Z fusion gene has been introduced into the germ line of mice. We have analyzed the expression of beta-galactosidase (under the control of the c-fos promoter) in the developing and adult nervous systems of these transgenic mice. As far as can be determined, the constitutive and stimulated expression of the transgene accurately reflects the expression of cognate c-fos in both cultured cells and the intact animal. This study has also revealed novel sites of constitutive and induced expression of c-fos that were overlooked using conventional analysis. In particular, constitutive expression of c-fos is associated with cells that are entering terminal differentiation and are destined to die. In addition, induced expression of the transgene in adult brain mirrors the pattern of neurotoxicity elicited by kainic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗