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K Braun

Publications and source records attributed to K Braun.

At least 91 records · Page 5Linked to original sources
PubMed1996

Slice cultures of the imprinting-relevant forebrain area medio-rostral neostriatum/hyperstriatum ventrale of the domestic chick: immunocytochemical characterization of neurons containing Ca(2+)-binding proteins.

The forebrain area medio-rostral neostriatum/hyperstriatum ventrale, a presumed analogue to the mammalian prefrontal cortex, displays a variety of synaptic changes during auditory filial imprinting. In order to study the underlying basic mechanisms of this synaptic plasticity we developed slice cultures of the medio-rostral neostriatum/hyperstriatum ventrale from newly hatched chicks. As a prerequisite for these investigations and in order to test the suitability of this system for future studies, we performed a thorough characterization of the in vitro tissue, of its cellular components and some of their biochemical features in comparison with in situ tissue. Since in situ the medio-rostral neostriatum/hyperstriatum ventrale has been previously shown to contain three distinct neuron populations characterized by the activity-regulated Ca(2+)-binding proteins parvalbumin, calbindin D28K and calretinin, we used these proteins as neuronal markers to study the survival and preservation of the morphological features of medio-rostral neostriatum/hyperstriatum ventrale neurons in vitro. In agreement with in vivo studies the three Ca(2+)-binding proteins are confined to neuronal cells and they are not colocalized, i.e. they appear to characterize three different neuron populations. The immunoreactive neurons in medio-rostral neostriatum/hyperstriatum ventrale cultures to a certain extent appear to form synaptic contacts with each other, shown by the double immuncytochemical experiments. One difference between cells in vivo and in vitro is their soma size, which is much larger in vitro than in vivo. This and our previous study on neuronal morphology demonstrates that morphologically and biochemically intact neurons can be maintained in medio-rostral neostriatum/hyperstriatum ventrale slice cultures, which may thus provide a suitable in vitro system for further studies of neuronal and synaptic plasticity in vitro.

Animals↗
PubMed1996

Stimulus-evoked increase of glutamate in the mediorostral neostriatum/hyperstriatum ventrale of domestic chick after auditory filial imprinting: an in vivo microdialysis study.

Imprinting in chicks is a form of juvenile learning that has been used to study the basic cellular mechanisms of learning and memory. The forebrain area mediorostral neostriatum/hyperstriatum ventrale (MNH) is a center for acoustic imprinting. Electrophysiological and pharmacological behavioral studies in the MNH have demonstrated that the glutamatergic system and the associated receptors are critically involved in auditory filial imprinting. Accordingly, we investigated the hypothesis that stimulus-evoked glutamate release may be altered after this learning process. Using an in vivo microdialysis technique, we observed a significantly higher increase of extracellular glutamate level in tone-imprinted chicks during exposure to the previously imprinted tone than in socially imprinted control chicks. In a further series of experiments, where we exposed animals from both experimental groups to handling distress, glutamate levels in MNH showed only a slight increase, whereas we observed a pronounced increase of extracellular glutamate in the lobus parolfactorius (LPO), the avian analogue of the basal ganglia. No difference of distress-evoked glutamate release was found in MNH and LPO between tone-imprinted and socially imprinted chicks. The tone-evoked enhanced glutamate response in tone-imprinted chicks suggests that during auditory imprinting glutamatergic synapses develop the potential to increase transmitter release in response to the imprinting stimulus.

Acoustic Stimulation↗
PubMed1996

[Synaptic reorganization in early childhood experience and learning processes: relevance for the development of psychological diseases].

This article presents a neurobiological hypothesis of experience- and learning dependent synaptic reorganization processes in the juvenile brain and their influence on the normal development of intellectual, emotional and social abilities. Based on experimental data we offer the theory that during early learning events (also termed as imprinting) the initially relatively unspecifically organized synaptic network in the higher associative brain areas undergoes an experience- and learning-dependent reorganization. This process involves synaptic sprouting as well as synaptic pruning of redundant synaptic connections and results in a more specific and efficient neuronal network, which provide the basis for learning processes during later life. Sensory or social deprivation during early childhood impairs this synaptic reorganization of the brain and thereby prevents the normal development of intellectual, emotional and social abilities. Under adverse environmental and familial circumstances these deficits may eventually lead to mental disorders such as neuroses. Since early learning and the underlying synaptic reorganization processes are restricted to specific sensitive phases during brain development the resulting mental and social deficits are remarkably stable, which may be one explanation of the resistance of certain mental disorders to psychotherapy. The intention of this provocative hypothesis is to stimulate future research initiatives using an interactive neurobiological and neuropsychological approach to gain more insight into these cellular mechanisms and to develop innovative therapeutical strategies.

Adolescent↗
PubMed1995

Slice cultures of the imprinting-relevant forebrain area MNH of the domestic chick: quantitative characterization of neuronal morphology.

The persistence of morphological features of neurons in slice cultures of the imprinting-relevant forebrain area MNH (mediorostral neostriatum and hyperstriatum ventrale) of the domestic chick was analysed at 7, 14, 21 and 28 days in vitro. After having been explanted and kept in culture the neurons in vitro have larger soma areas, longer and more extensively branched dendritic trees and lower spine frequencies compared to the neurons in vivo. During the analyzed culturing period, the parameters soma area, total and mean dendritic length, number of dendrites, number of dendritic nodes per dendrite and per neuron as well as the spine densities in different dendritic segments showed no significant differences between early and late periods. Highly correlated in every age group were the total dendritic length and the number of dendritic nodes per neuron, indicating regular ramification during dendritic growth. Since these morphological parameters remain stable during the first 4 weeks in vitro, this culture system may provide a suitable model to investigate experimentally induced morphological changes.

Animals↗
PubMed1995

Doxazosin in the treatment of benign prostatic hyperplasia in normotensive patients: a multicenter study.

A 16-week, double-blind, placebo controlled, dose titration study was done on 100 normotensive patients age 45 years or older to determine the efficacy and safety of doxazosin, a selective alpha 1-adrenoceptor antagonist, in the treatment of benign prostatic hyperplasia (BPH). Of the 41 efficacy evaluable patients 88% underwent dose titration to a maximum of 8 mg. doxazosin once daily. Maximum and average urinary flow rates increased significantly above baseline with doxazosin (2.9 ml. per second and 1.4 ml. per second, respectively) compared with placebo (0.7 ml. per second and 0.3 ml. per second, respectively). A significant effect on maximum flow rate was noted as early as week 2 of double-blind treatment at the initial efficacy evaluation. Doxazosin was superior to placebo in patient and investigator assessments of total, obstructive and irritative BPH symptoms. The onset of efficacy for total patient-assessed symptoms was significant for doxazosin compared to placebo 4 weeks after the start of the treatment regimen. Statistically significant decreases in mean blood pressure of 4 to 6 mm. Hg were noted with doxazosin compared with placebo. Adverse events, primarily mild to moderate in severity, were reported in 44% of patients given doxazosin and 30% of those given placebo. Our results strongly demonstrate that doxazosin is significantly superior to placebo in the treatment of BPH in normotensive patients, with the patient experiencing significant relief early after initiation of therapy.

Aged↗
PubMed1995

Ovarian angiogenesis. Phenotypic characterization of endothelial cells in a physiological model of blood vessel growth and regression.

Angiogenesis occurs during embryogenesis and is a down-regulated process in the healthy adult that is almost exclusively linked to pathological conditions such as tumor growth, wound healing, and inflammation. Physiological angiogenic processes in the adult are restricted to the female reproductive system where they occur cyclically during the ovarian and uterine cycle as well as during pregnancy. By systematically analyzing the phenotypic changes of endothelial cells during bovine corpus luteum (CL) formation and regression, we have established a physiological model of blood vessel growth and regression. Quantitation of vessel density, percentage of vessels with lumen, and ratio of Bandeiraea simplicifolia-I to von Willebrand Factor-positive endothelial cells were established as parameters of angiogenesis. Sprouting endothelial cells invade the growing CL and continue to grow throughout the first third of the ovarian cycle. Thereafter the mature CL is characterized by a dense network of vessels with gradually decreasing vessel density. During luteolysis and for several weeks thereafter (regressing and residual CL) all newly formed vessels regress, which is accompanied by gradual foreshortening and rounding of endothelial cells and subsequent detachment. Based on histochemical detection of nucleosomal fragmentation products physiological blood vessel regression in the cyclic CL does not appear to involve endothelial cell apoptosis. Lectin histochemical analysis revealed a distinct alteration of endothelial cell glycoconjugate expression during ovarian angiogenesis comparable with the distinct pattern of hyperglycosylation of cultured migrating endothelial cells (up-regulation of binding sites for Lycopersicon esculentum lectin, wheat germ agglutinin, neuraminidase-treated peanut agglutinin, and Ricinus communis agglutinin-I on sprouting ECs). Northern blot analysis of glycosyltransferases during the different stages of angiogenesis revealed an up-regulation of beta-galactoside alpha 2,6-sialyltransferase and alpha 1,3-galactosyltransferase mRNA expression during the angiogenic stages of CL formation. These data establish the ovarian angiogenesis model as a suitable experimental system to study the functional and phenotypic properties of endothelial cells in sprouting and regressing blood vessels and provide additional evidence for the importance of endothelial cell surface glycoconjugates during angiogenesis.

Animals↗
PubMed1994

Characterization of proteoglycans synthesized by murine embryonal carcinoma cells (P19) reveals increased expression of perlecan (heparan sulfate proteoglycan) during neuronal differentiation.

Proteoglycans (PGs) incorporated into cell layer and secreted into media were characterized during retinoic acid-induced neuronal differentiation of cultured P19 murine embryonal carcinoma cells. Heparan sulfate significantly increased (P < 0.01) in cell layer following neuronal differentiation of P19 cells by 3.9-fold. CL-4B gel chromatography revealed the major PGs present in cell layer of stem cells eluted as a broad peak with a Kav = 0.65, and was susceptible to chondroitin ABC lyase. The chondroitin ABC lyase resistant material eluted as a broad peak between Kav = 0.40 and Kav = 0.60, and was only partially digested with heparitinase/heparinase (with resistant material eluting at Kav = 0.70). Therefore, the cell layer of stem cells contained primarily chondroitin sulfate/dermatan sulfate (CS/DS) PGs, with lesser amounts of heparan sulfate proteoglycans (HSPGs). This was confirmed by SDS-PAGE. The CS/DS PGs in the cell layer of stem cells had an apparent M(r) of approximately > 200 kDa, and the HSPGs had an apparent M(r) of approximately 140-230 kDa. In contrast, the major PGs in the cell layer of neurons consisted primarily of HSPGs, with only a minor proportion of CS/DS PGs. Furthermore, both gel filtration chromatography and SDS-PAGE analysis revealed a larger HSPG in the cell layer of neurons (Kav = 0.3-0.6 on CL-4B following chondroitin ABC lyase digestion; M(r) 170 kDa- > 400 kDa on SDS-PAGE) in comparison to stem cells (Kav = 0.4-0.6 on CL-4B following chondroitin ABC lyase digestion; M(r) 140-230 kDa on SDS-PAGE). Likewise, the major PGs secreted into media of stem cells consisted almost exclusively of CS/DS PGs, with lesser amounts of HSPGs, whereas an increase in HSPGs in the media of neurons was apparent. Western, Northern, and immunocytochemical analysis demonstrated that mRNA transcript and protein levels for a specific HSPG (i.e., perlecan) markedly increased in cell layer following P19 neuronal differentiation. Perlecan core protein was identified by Western blot analysis using specific monoclonal and polyclonal antibodies, as a large HSPG with a core protein of apparent M(r) approximately 370-400 kDa, and was observed primarily in extracts from neurons. Northern blot analysis with a cDNA to perlecan revealed a significant (P < 0.01) 12.7-fold increase in expression of perlecan in neurons (day 9) in comparison to stem cells. The increase in perlecan message during P19 neuronal differentiation was concomitant with a significant (P < 0.01) 26.3-fold increase in message for beta-amyloid precursor protein (beta PP).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Parvalbumin, calbindin D-28k, and calretinin immunoreactivity in the ascending auditory pathway of horseshoe bats.

In the subcortical auditory system of Rhinolophus rouxi, antibodies directed against the calcium-binding proteins parvalbumin, calbindin D-28k, and calretinin yield partly overlapping and partly complementary labeling patterns which are described in detail for each nucleus. The most general features of the labeling patterns are that: 1) Parvalbumin is a potent marker for large and heterogeneous populations of cells and puncta (presumed axon terminals) throughout the auditory pathway. 2) Immunostaining with the monoclonal calbindin-antiserum was typically absent or sparse in most auditory brainstem centers, but prominent in auditory nerve fibers and in cells of the medial geniculate body (MGB). 3) Calretinin label is abundant but more restricted to subsets of auditory nuclei or subpopulations of cells than parvalbumin. 4) Calcium-binding proteins are useful markers to define particular subregions or cell types in auditory nuclei: for example, i) different labeling patterns are obtained within the nuclei of the lateral lemniscus and adjacent tegmental zones; ii) in the inferior colliculus both calbindin- and calretinin-antisera yield similar regional specific staining patterns, but label different cell types; iii) subregions of the medial geniculate body have characteristic profiles of calcium-binding proteins; and iv) analyses of different nuclei showed that there is no simple common denominator for cells characterized by the expression of particular calcium-binding proteins, nor does labeling correspond in a straightforward way with specific functional systems. 5) there are profound differences between the calbindin labeling patterns seen in Rhinolophus and those in other mammals.

Animals↗
PubMed1993

[Equestrian accidents in children].

In a retrospective study we reviewed 262 horse riding related injuries in children younger than 16 which were treated between 1975 and 1989 at the Section of Traumatology in the Department of Surgery, University Hospital Homburg/Saar. In 155 of these accidents, detailed information was gained via a questionnaire. The typical patient profile was that of young female equestrians with little experience and little weekly riding practice, without practicing falling-exercises and warming up often using different horses. At the time of the accident only 59% were wearing a head protection. Most accidents happened in the summer months in the afternoon during leisure riding on a large familiar horse in the riding hall. Apart from the typical accidents like falling of the horse (64.9%) and falling with the horse (5.7%) accidents in handling the horse were of special significance: Kick by horse's hoof (11.8%), being stepped by horse (3.8%), horsebite (7.3%) and injuries of horse's bridle had their own pattern of injuries. Injuries of the distal parts of the upper extremity are preeminent in falling of the horse, whilst in falling with the horse head injuries and shoulder injuries are preeminent. Remarkably often injuries of kick by horse's hoof were causing sometimes even dangerous head injuries (41.6%). Overall in horse riding related injuries in childhood superficial soft tissue injuries (48.6%) and fractures (30.6%) were predominant. Fractures of the clavicle which are well known as a riding injury proved to be typical for a fall with the horse, whilst a fractured vertebra was only seen once amongst the 262 children treated. The severity of the injuries was lower than expected: In 85.1% of all the injuries only one body region was injured, 90.1% could be assigned to an injury severity score (ISS) of 1-3. Ponyriders had less severe injuries than riders of large horses. One fatal accident happened in handling a horse, in these situations preventive measures are often disregard. Active (better education, warming up, falling practice) an passive (head protection!) safety measurements are recommended for prevention of injuries in young riders in particular.

Adolescent↗
PubMed1992

Changes in Ca(2+)-binding proteins in human neurodegenerative disorders.

The cellular distribution of Ca(2+)-binding proteins has been extensively studied during the past decade. These proteins have proved to be useful neuronal markers for a variety of functional brain systems and their circuitries. Their major roles are assumed to be Ca2+ buffering and transport, and regulation of various enzyme systems. Since cellular degeneration is accompanied by impaired Ca2+ homeostasis, a protective role for Ca(2+)-binding proteins in certain neuron populations has been postulated. As massive neuronal degeneration takes place in several brain diseases of humans, such as Alzheimer's disease, Parkinson's disease and epilepsy, changes in the expression of Ca(2+)-binding proteins have therefore been studied during the course of these diseases. Although the data from these studies are inconsistent, the detection and quantification of Ca(2+)-binding proteins and the neuron populations in which they occur may nevertheless be useful to estimate, for example, the location and extent of brain damage in the various neurological disorders. If future studies advance our knowledge about the physiological functions of these proteins, the neuronal systems in which they are expressed may become important therapeutical targets for preventing neuronal death in an array of neurodegenerative diseases.

Alzheimer Disease↗
PubMed1991

Parvalbumin-, calretinin- and calbindin-D28k-immunoreactivity and GABA in a forebrain region involved in auditory filial imprinting.

The distribution and morphology of neurons containing the Ca-binding proteins parvalbumin (PV), calbindin-D28k (CaBP) and calretinin (CaR) are described in a rostral forebrain region (MNH) of the chick, known to be involved in auditory filial imprinting. PV immunoreactivity is chiefly a marker for numerous large to medium-sized neurons in the neostriatal part of MNH. They show patchy staining of their dendrites, but PV-positive spines are not visible. CaBP is represented in a different neuron population with on the average slightly smaller-sized somata, which carry long, spiny, CaBP-positive dendrites. In contrast to PV and CaBP, CaR immunoreactivity is a marker chiefly for neuropil in MNH but only for few stained neurons. They may be spiny and show the largest size variations. The density of CaR-immunoreactive neuropil is highest in the hyperstriatal part of MNH. Double immunostaining for PV and CaBP reveals that these proteins are expressed mostly in different neuron populations, with only few neurons containing both proteins. These neuron populations appear to form an interconnected network within MNH. A possible relationship between the expression of either Ca-binding protein and the presence of the inhibitory transmitter GABA is also examined. The GABA-antibody labels scattered, very small to medium-sized neurons and dense punctate neuropil. The comparison of the area histograms of somata reveals an overlap with all 3 Ca-binding protein containing cell populations, except for a large proportion of small GABA-positive neurons. The characteristics of immunostained neuron populations are compared to the previously described 3 Golgi-types of neurons in MNH, and possibilities of a functional implication of the proteins in MNH plasticity are examined.

Acoustic Stimulation↗
PubMed1991

Parvalbumin and calbindin-D28K immunoreactivity as developmental markers of auditory and vocal motor nuclei of the zebra finch.

The posthatch developmental profiles of parvalbumin and calbindin-D28K immunoreactivity were compared for the auditory nucleus mesencephalicus lateralis pars caudalis in the midbrain, n. ovoidalis in the thalamus, and telencephalic field L, as well as for the telencephalic vocal motor nuclei hyperstriatum ventrale pars caudalis and n. robustus archistriatalis. The two calcium-binding proteins showed specific temporal patterns of expression in each nucleus, without following an ascending or descending sequence. Calbindin-D28K immunoreactivity usually preceded parvalbumin immunoreactivity. Onset of expression, especially of parvalbumin-immunostaining, was earlier in auditory nuclei than in vocal motor nuclei. The developmental order of appearance of immunoreactivity in somata, dendrites and axons was different in various brain regions. In some structures parvalbumin or calbindin-D28K immunoreactivity occurred only transiently. The two antibodies bound to separate but spatially complementary groups of cells in the nucleus mesencephalicus lateralis pars dorsalis and n. ovoidalis, as has previously been described in visual nuclei. This pattern was maintained into adulthood. These hitherto unknown subcompartments may reflect internal functional organization in these nuclei. A transitory neostriatal zone containing parvalbumin-positive neurons and fibres was observed between the immature field L and the emerging hyperstriatum ventrale pars caudalis. Some comparative aspects are discussed as to the way in which neurons distinguished by the two Ca-binding proteins may differ in energy metabolism, activity pattern and other functional mechanisms.

Animals↗