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K H Schäfer

Publications and source records attributed to K H Schäfer.

At least 19 recordsLinked to original sources
PubMed2004

Three-dimensional co-culture model of enterocytes and primary enteric neuronal tissue.

AIM: The aim of this study was to establish a three-dimensional model of the innervated mucosal barrier using a co-culture of an enterocyte cell line and enteric glial and nerve cells. Such a model might form the basis for further studies of interactions between the single compartments of the bowel wall, as well as of extrinsic influences on intestinal development and plasticity. METHODS: Isolated and dissociated myenteric plexus was resuspended in either collagen or extracellular matrix (ECM) solutions. After incubation at 37 degrees C the solution gelled and formed stable plugs where neurons and glial cells reaggregated to form secondary neuronal networks. HT-29-enterocytes were seeded on top of the gels either immediately (collagen, ECM), or after adding a thin layer of collagen II (ECM). RESULTS: While the neuronal tissue formed complex networks within the gel, the enterocytes on top of the gels grew differently depending on the substrate and innervation. So enterocytes on ECM gels did not grow to confluence, while on collagen gels or on ECM plus collagen larger patches and increasing confluence could be observed. In general HT-29 grew better on innervated gels than on gels with no neuronal tissue. CONCLUSIONS: With the presented model of different compartments of the bowel wall, various parameters of intercellular dependencies and influences can be observed in vitro. Moreover, the first results are also steps towards developing an innervated gut wall in vitro which might be able to restore functional capacity in infants with short bowel syndrome or other disorders that severely impair bowel function.

Animals↗
PubMed2003

Activation of apical K+ conductances by muscarinic receptor stimulation in rat distal colon: fast and slow components.

In the epithelium of rat distal colon the acetylcholine analogue carbachol induces a transient increase of short-circuit current (Isc) via stimulation of cellular K+ conductances. Inhibition of the turnover of inositol-1,4,5-trisphosphate (IP3) by LiCl significantly reduced both the amplitude and the duration of this response. When the apical membrane was permeabilized with nystatin, LiCl nearly abolished the carbachol-induced activation of basolateral K+ conductances. In contrast, in epithelia, in which the basolateral membrane was bypassed by a basolateral depolarization, carbachol induced a biphasic increase in the K+ current across the apical membrane consisting of an early component carried by charybdotoxin- and tetraethylammonium-sensitive K+ channels followed by a sustained plateau carried by channels insensitive against these blockers. Only the latter was sensitive against LiCl or inhibition of protein kinases. In contrast, the stimulation of the early apical K+ conductance by carbachol proved to be resistant against inhibition of phospholipase C or protein kinases. However, apical dichlorobenzamil, an inhibitor of Na+/Ca2+ exchangers, or a Ca2+-free mucosal buffer solution significantly reduced the early component of the carbachol-induced apical K+ current. The presence of an apically localized Na+/Ca2+-exchanger was proven immunohistochemically. Taken together these experiments reveal divergent regulatory mechanisms for the stimulation of apical Ca2+-dependent K+ channels in this secretory epithelium, part of them being activated by an inflow of Ca2+ across the apical membrane.

Amiloride↗
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

Spontaneous contractions of intestinal smooth muscle re-aggregates from the new-born rat triggered by thromboxane A2.

Isolated smooth muscle cells from the small intestine of new-born rats were prepared by enzymatic digestion. These cells re-aggregate after 1 day in culture to clusters. The re-aggregates show spontaneous rhythmical contractions at 37 degrees C with a frequency (13.1 +/- 0.8 min-1, n = 49), which is similar to that of the intact smooth muscle layer. The cholinergic agonist carbachol (5 x 10(-5) mol l-1) caused an increase in the frequency of the spontaneous contractions often ending in a permanent contraction. A similar effect was achieved with the thromboxane A2 (TXA2) agonist, U-46619 (10(-5) mol l-1). In contrast, both the TXA2 receptor blocker, Bay u3405 (5 x 10(-4) mol l-1), as well as the Ca2+ channel blocker, verapamil (5 x 10(-5) mol l-1), suppressed the spontaneous contractions. The observed contractility was insensitive against the neuronal blocker tetrodotoxin (10(-6) mol l-1). These analyses of video images were supported by the measurement of relative changes in the intracellular Ca2+ concentration with the Ca(2+)-sensitive dye, fura-2. Spontaneous contractions were paralleled by spikes in the intracellular Ca2+ concentration, which were abolished by Bay u3405, but stimulated by U-46619 or carbachol. In summary, these results obtained at re-aggregates of intestinal smooth muscle cells support the hypothesis of a role of TXA2 in the generation of spontaneous intestinal smooth muscle contractions in vitro.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
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

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

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↗
PubMed1999

Intracellular localization and in vivo trafficking of p24A and p23.

Recently, p24A and p23 (also termed Tmp21), two members of the p24 protein family, have been proposed to function as integral receptors for the COPI-vesicle coat. This study describes the intracellular localization and trafficking of p24A in comparison to p23. For immunolocalization of p24A and p23, strong reduction and denaturation conditions were necessary to allow antibody interaction. Both p24A and p23 cycle continuously between intermediate compartment (IC) elements and the cis-Golgi network. In vivo trafficking of p24A and p23 tagged to green fluorescent protein (GFP) revealed that both proteins travel by large (up to 1 micrometer in length) microtubule-dependent pre-Golgi carriers with a maximum speed of up to 1.6 micrometer s-1 from the IC to the Golgi cisternae. Aluminum fluoride, a general activator of heterotrimeric G-proteins, blocked peripheral pre-Golgi movements of GFP-p24A/p23 and inhibited fluorescence recovery after photobleaching in the perinuclear Golgi area. p24A and p23 are predominantly colocalized. Overexpression of GFP-p24A, to an extent which did not destroy the Golgi complex, induced delocalization of part of the proteins into ER elements. This study therefore gives new insights into the localization and trafficking behavior of the two COPI-binding proteins p24A and p23.

Aluminum Compounds↗
PubMed1998

Protein extracts from the gut wall influence the postnatal development of rat myenteric neurons in vitro.

Neurons migrating from the neural crest into the presumptive gut wall need an appropriate microenvironment to survive and differentiate during ontogenesis. The rat enteric nervous system (ENS) keeps developing beyond birth. The aim of this study was to investigate the neurotrophic effects of the postnatal microenvironment. Myenteric plexus was isolated from the smooth muscle layer of newborn rats at different ages (postnatal day (p)1, p7, p14) and grown as dissociated cell cultures. The culture medium (hormone-supplemented, serum-free) was supplemented either with glial-cell-line-derived-neurotrophic factor (GDNF) or with protein extracts from homogenized smooth muscle layer of p7 rats. Cultures kept in defined medium alone were used as controls. After 18 h in vitro both GDNF and protein extract had a neuritogenic effect upon p1 and p7 neurons, while p14 neurons were only stimulated by the protein extracts. The GDNF effect upon these neurons did not differ significantly from the effects in defined medium alone. The average neurite outgrowth in extract-supplemented cultures was always longer than that seen in those treated with GDNF. Although GDNF influences the postnatal development of myentric neurons in vitro it could not be detected immunohistochemically either in Western blots of the protein extracts or in cryostat sections of the gut.

Abdominal Muscles↗
PubMed1998

Improved osmication, dehydration and flat embedding of vibratome sections and delicate whole mount preparations.

A simple method for flat embedding vibratome sections or delicate whole mount preparations in epoxy resin is described that allows thin layers of interest within the specimen to be cut and studied as a whole in one plane. The fatal curling that occurs during dehydration was avoided or at least minimized by dehydrating the specimens in a layer of filter paper and a plastic meshwork under permanent slight pressure. The flatness of the structures was maintained through a graded series of ethanols followed by acetone. The specimens were transferred to the resin and polymerized between two coated glass slides making it possible to view and select the material without direct handling of the thin resin layer.

Epoxy Resins↗
PubMed1997

A new method for the isolation of myenteric plexus from the newborn rat gastrointestinal tract.

The myenteric plexus is not only essential for gastrointestinal functions, but it is also a very interesting model for the study of neuronal circuits and neuron-glial interrelationships and may be a valuable source of donor tissue, for grafting into different regions of the central nervous system. For both grafting and culture procedures it is a great advantage to obtain the maximum amount of tissue. To date, most studies have isolated the myenteric plexus by manual microdissection after collagenase digestion. Using this method, it has only been possible to obtain relatively small amounts of the myenteric plexus, mostly from the cecum and proximal colon of the guinea-pig or rat. We present here a new method, which enables much greater quantities of the plexus from the small intestine and colon to be obtained. The myenteric plexus of the entire small intestine can be isolated by a combination of enzymatic digestion and mechanical agitation. The method works from birth up to 3 week old pups, and with some modifications tissue from older or even adult animals can also be processed. Another advantage over the microdissection method is that the myenteric plexuses of the different parts of the intestine can be cultured and studied separately.

Animals↗
PubMed1997

Human newborn and adult myenteric plexus grows in different patterns.

Whilst embedded within the gut wall the inaccessibility of the enteric nervous system (ENS) is a major drawback for the establishment of an in vitro model for the human ENS. Using a method which combines collagenase digestion, mechanical agitation and manual dissection it was possible to dissect myenteric plexus from human colon of patients at all ages, from newborn to old-age. While complex networks of ganglia and their interconnecting strands could be isolated from newborn gut, the adult tissue allowed only single or small groups of ganglia to be dissected coherently. Pieces of plexus were cultivated on glass coverslips or on plastic sheets respectively. Explants from newborn or older patients displayed different growth patterns. The cytological behaviour of the newborn explants is characterized by an intensive neurite outgrowth. After 1 to 2 days in culture, glial cells start to leave the explant while proliferating and forming a dense cellular carpet. The axons appear partly arranged in bundles, expanding above the glial carpet. Single neurites can leave the carpet and attach directly on the substrate. Semithin sections and EM studies reveal the existence of numerous neurons within the ganglia. The characteristic dense arrangement of neurons, glial cells and neuropil of the myenteric ganglia in vivo was only partly conserved in newborns while in cultured adult ganglia the cells were sparsely scattered throughout the explant with large clefts between the single cells. The ganglia of the adults do not show any considerable neurite outgrowth, which correlates with the low amount of neurons within the ganglia. The migratory behaviour of the adult glial cells is rather moderate, also the proliferation rate compared to the newborn cultures. In general single cells leave the explant without forming an glial carpet as seen in the newborn cultures. The described method delivers an in vitro paradigm for the study of human myenteric plexus. It underlines the differences in growth pattern, neurite outgrowth and glial proliferation from newborn and older children, as well as from adult patients, thus establishing a base line for future studies.

Adolescent↗
PubMed1995

Trophic actions of 2-chloroadenosine and bFGF on cultured myenteric neurones.

The effects of the stable adenosine analogue, 2-chloroadenosine (2-CA) and basic fibroblast growth factor (bFGF) on myenteric neurones in dissociated cell culture were examined. 2-CA had no effect on neuronal numbers, but increased neurite length, in a dose-dependent manner. bFGF increased both the number of myenteric neurones and neurite length. When 2-CA was applied together with bFGF, an enhanced increase in neurite outgrowth, but no additional increase in neuronal numbers was observed. 2-CA-induced effects were blocked by the adenosine antagonist 8-(p-sulphophenyl)theophylline. These results show, for the first time, that both purines and bFGF may have trophic actions on myenteric neurones and also indicate that purines enhance some effects of bFGF, in a synergistic manner.

2-Chloroadenosine↗
PubMed1989

Chronic electroconvulsive shock treatment elicits up-regulation of CRF and AVP mRNA in select populations of neuroendocrine neurons.

The effects of repeated electroconvulsive seizures (ECS) on expression of mRNAs coding for corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) in neuroendocrine neurons of the hypothalamo-pituitary-adrenocortical (HPA) axis and hypothalamo-neurohypophysial system (HNS) were assessed via semi-quantitative in situ hybridization histochemical analysis. Measures of mRNA content were accompanied by measurement of peptide- and hormone-expression in the relevant neuroendocrine systems. Following 7 daily ECS treatments, CRF mRNA was significantly increased in the medial parvocellular paraventricular nucleus (PVN) of treated rats relative to controls. CRF peptide content of whole PVN homogenates was decreased to 50% of control levels. Changes in CRF message and peptide levels were accompanied by increases in pituitary ACTH content and by elevated plasma corticosterone, suggesting ECS elicits long-term up-regulation of the HPA axis. AVP mRNA in the medial parvocellular PVN, which is known to up-regulate in response to HPA challenge by adrenalectomy, was not increased by ECS. Chronic ECS causes a clear up-regulation of HNS neurons of the supraoptic nucleus, characterized by increased AVP mRNA content, decreased AVP peptide content, and depletion of neurohypophysial AVP. However, no changes were observed in magnocellular vasopressinergic neurons of the PVN, indicating that magnocellular SON and PVN neurons respond differentially to stimulation by ECS. The data indicate that ECS is a potent stimulus for activation of select components of both the HPA axis and the HNS. As such, ECS provides a useful tool for examining mechanisms underlying neuroendocrine processes.

Animals↗
PubMed1987

Infantile hypertrophic pyloric stenosis after prenatal exposure to thalidomide.

In a retrospective study of 832 cases of thalidomide embryopathy (ThE) between October 1, 1959 and July 31, 1962, a highly significant accumulation of cases with infantile hypertrophic pyloric stenosis (IHPS) was registrated. Clinical course, X-ray and surgical findings and the sex ratio (male preponderance) were identical to IHPS occurring spontaneously. In the order of frequency of defects in ThE, IHPS is on position 11; among inner organ abnormalities, IHPS is on position 3 after heart and kidney defects. Thus, IHPS is the predominant gastrointestinal abnormality in ThE. For the first time, a substance (thalidomide) could be identified which obviously is able to influence manifestation of IHPS. There is a remarkable coincidence of IHPS and malformations such as hiatus hernia and tracheo-oesophageal fistula with or without oesophagus atresia. From the male preponderance, which is also observed in the ThE type of IHPS, it is concluded that thalidomide is not a primary cause in this process, but that disease manifestation is decisively influenced by thalidomide on the base of a genetic or familiar predisposition. Cause and development of IHPS are multifactorial; the mode of inheritance is polygenic. Probably, other substances may replace thalidomide.

Female↗
PubMed1984

[Lymphocyte function in children with iron deficiency].

In 23 children with mild iron-deficiency anemia, 22 children with latent iron-deficiency, and in 46 healthy controls the 3H-thymidine incorporation in blood lymphocytes after stimulation with phytohemagglutinin, concanavalin A, pokeweed mitogen, and serum against thymocyte cells was measured. In 11 of the children with iron-deficiency anemia, in 13 of the children with latent iron-deficiency, and in 20 controls the lymphotoxin secretion after phytohemagglutinin stimulation was also performed. All patients studied were without intercurrent infections and were well nourished. No alteration of the lymphocyte function in the patients was found. The concentrations of immunoglobulins and the components C3 and C4 of complement system were also found to be normal. It is suggested that lymphocyte functions are eventually only altered in more severe states of iron-deficiency anemia.

Anemia, Hypochromic↗