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Biomedical subjects

H Wenk

Publications and source records attributed to H Wenk.

At least 55 records · Page 3Linked to original sources
PubMed1989

The nucleus basalis magnocellularis Meynert (NbmM) complex--a central integrator of coded "limbic signals" linked to neocortical modular operation? A proposed (heuristic) model of function.

Since the discovery of the NbmM as an afferent cholinergic projection system supplying the entire cortical mantle, its morphological organization has been extensively investigated. Applying the principle of convergence and divergence--an important principle of the integrative function of the CNS discerned by Sherrington a long time ago--the topistic organization of this projection could enable the system to exert a high degree of integrative influence on cortical neuronal activity. Candidates for putative regulatory afferents to the NbmM in the main seem to originate within structures linked to the limbic system. With the main centres of this system--ventral tegmental area, mediodorsal thalamus, basolateral amygdala, limbic compartment of striatum, hippocampal formation, paralimbic cortex--the NbmM seems to be interconnected bidirectionally by feedforward and feedback connections. With this central position within the limbic circuitries the NbmM complex--regarded as a morpho-functional entity--could play a key role, in both (i) the filtering and selection of "limbic signals" carrying coded information from the CNS-external (objective-surrounding) and CNS-internal (cognitive-emotional) world, and in (ii) the processing and transmission of these informations together with sequential integration into circuitries of neocortical processing. On the basis of the modular operation of the neocortex a speculative model of action of the NbmM complex is proposed which explains its possible role as an important central integrator in cognitive brain function.

Animals↗
PubMed1989

[Postnatal ontogenesis of cholinergic fibers in the rat cerebral cortex].

Approximately 80% of the activities of cortical cholinergic marker enzymes are restricted to afferent fibres and terminals of the magnocellular basal nucleus of Meynert (NbmM) (Wenk et al. 1980). In the evolution this nucleus strongly follows a phylogenetic gradation (Brockhaus 1942) which is positively correlated to the cerebralization, i.e. the neocortical development which an animal species has reached (Gorry 1963). Moreover, in contrast to the brain stem, in vertebrate brains of different phylogenetic levels only the telencephalon showed a clear progressive representation of cholinergic markers (Wächtler 1980, 1981). However, the increased cholinergic activity of the telencephalon in higher forms can not be ascribed to a special hemispheric component (Wächtler 1982). Using the quantitative-histochemical evaluation of the cholinergic marker enzyme acetylcholinesterase (AChE) in the epithalamus (nucleus medialis habenulae) and in different cortical areas of rats during postnatal ontogenesis it is shown that (i) the cholinergic differentation in the thalamic structure seems to be already finished immediately after birth and (ii) the cholinergic synaptogenesis in the cerebral cortex does not start until birth, but takes place postnatally in phylogenetic graduated cortices in temporal echeloned steps (paleo- greater than archi- greater than neocortex). These ontegenetic results correspond to the phylogenetic trends and reflect - in accordance with the biogenetic basic rule - the phylogenetic gradation in the development of the cholinergic basal nucleus of Meynert and its cortical projections shortened in ontogenesis.

Acetylcholinesterase↗
PubMed1989

[Changes in biliary lithogenicity caused by 4 weeks' weight reduction].

In 2 of 12 patients (16.6%) cholesterol monohydrate crystals occurred in duodenal bile samples after a 4 weeks fasting period (452 kcal/day). Cholesterol monohydrate crystals could be observed until recently mainly in patients with cholesterol gallstones. Therefore, this finding indicates increased biliary lithogenicity despite a non statistical decrease in CSI from 1.35 +/- 0.35 to 1.19 +/- 0.64. Presumably the increased lithogenicity may be caused by an increased glycoprotein concentration and an improvement in gallbladder contractility. Short time fasting obviously will be a risk factor for the development of gallstones, if weight and metabolic normalisation cannot be achieved.

Adult↗
PubMed1988

[Laser-induced shockwave lithotripsy--in vitro trial and animal experiment studies].

Laser induced shock wave lithotripsy is a new procedure to destroy gallstones. Stones of up to 500 mg are destroyed within 5 min. Severe reactions of the soft tissue cannot be observed in animal studies. No perforations, stenoses or thermic lesions after wound healing were observed. The development of an optomechanical transducer replacing the optical lens system at the end of the transmission guide allows its handling in flexible endoscopes. Clinical use is therefore possible from the technical aspect.

Animals↗
PubMed1987

[Intraoperative, endoscopic lithotripsy of pancreatic duct calculi. A contribution to the surgical treatment of chronic calcifying pancreatitis].

The problem of chronical calcifying pancreatitis is demonstrated in two female patients. Resection of the pancreas is necessary, if prepapillar concrements cannot be extracted. By two new techniques, ultrasound-lithotripsy and laser-induced shock-wave-lithotripsy, it is possible to destroy concrements and to remove them. These new techniques are now used primarily in surgery.

Adult↗
PubMed1986

[Imipenem/cilastatin in surgical intensive medicine].

26 patients from the surgical intensive care unit, University Hospital Lübeck, received imipenem/cilastatin for severe abdominal, respiratory or urogenital infections. 500 mg imipenem/cilastatin were infused i.v. over 30 min q. i. d. The treatment was successful in 84,6% of the patients suffering from severe infections. Two cases were considered to be failures. 36 of the 43 isolated pathogens (83.7%) were eliminated. Transitory elevations of liver enzymes were the most frequent side-reactions observed; an increase in serum creatinine, diarrhoea or fungal colonization were less common.

Abdomen↗
PubMed1982

[Behavioral investigations following cholinergic deafferentiation of the hippocampus by septal lesions in rats (author's transl)].

Acquisition and retention of a visual discrimination task as well as changes in the exploratory activity and emotional state of the animals were investigated in rats with different lesions in the telencephalic septal area. The cholinergic deafferentiation of the hippocampal formation due to the lesion was determined by quantitative histochemical estimations of the loss in acetylcholine esterase activity in the various subfields of the hippocampus and the results were correlated to the behavioral experiments. Total bilateral septal lesion resulted mainly in an impairment of the acquisition processes of the discrimination task combined with an enhancement of the retention index. Slight tendencies for attenuated activity in the exploratory and emotional behavior were also present in this group. Assymmetric septal lesions leaving one lateral septal nucleus undamaged caused higher activities in the exploratory and emotional behavior. Some enhancement of the retention index was found, too. The degree of cholinergic innervation of the hippocampus was partially involved in the behavioral effects.

Acetylcholinesterase↗
PubMed1981

[Acetylcholinesterase containing neurons in the rat brain after DFP-pretreatment (author's transl)].

The AChE activity was demonstrated in some brain regions of adult rats after intoxication with DFP ( (di-isopropyl-fluorophosphate). Within these nuclear areas (Caudate-Putamen-Complex, Globus pallidus, Nucleus accumbens septi, Substantia nigra, Locus coeruleus) various proportions of the neuron population could be shown to be AChE positive. There is a characteristic morphology of the AChE containing neurons. Comparing them with staining and silver impregnation, cytological attributability appears feasible.

Acetylcholinesterase↗
PubMed1981

[Cholinergic mechanisms in the retina of rats].

In rats with extra- or intracranial dissection of the visual pathway the activities of acetylcholinesterase (AChE) and choline acetyltransferase (ChAc) were determined in retina, optic nerve and optic tract quantitatively by bio- and histochemical methods after one or five weeks of survival time. One week after intracranial (chiasma-near) dissection of the optic nerve an initial ipsilateral enhancement in the enzyme activity of AChE was found histochemically in retina layers and optic nerve. Five weeks following the dissection significant losses in AChE activity could be determined in the optic nerve, less pronounced in the retina. However, the activity of ChAc in the retina never was changed, neither after short nor after long survival times. Therefore, the high activity of both enzymes connected with cholinergic transmission normally present in different retinal layers must belong to local neurons, probably amacrine cells. To elucidate the question of the existence of a centrifugal cholinergic innervation of the retina one eye was enucleated. One week after operation a significant increase in the activity of AChE and ChAc was found in central parts of the dissected optic nerve and in the opposite optic tract indicating the existence of centrifugal cholinergic fibers in the optic nerve, but no evidence for the origin of these fibres could be obtained. The possible role of a central cholinergic control of the visual information processing already in retinal level is discussed in analogy to similar results obtained in the olfactory bulb.

Acetylcholinesterase↗
PubMed1980

Cholinergic projections from magnocellular nuclei of the basal forebrain to cortical areas in rats.

Acetylcholinesterase (AChE) and choline acetyltransferase (CHAc) activities were studied by quantitative histochemical (AChE) as well as biochemical methods (AChE, ChAc) in certain cortical brain areas in rats after stereotaxic lesions had been placed in several structures of the basal forebrain. After lesioning the magnocellular nuclei of the substantia innominata (nuc. basalis Meynert, NBM) the activities of AChE and ChAc decreased to moderate or low residual values in the ipsilateral cortical areas. This indicated that cholinergic pathways were directly linked to frontal, sensory-motor, auditory and visual cortex. After lesions of the globus pallidus the decrease in cortical AChE activity was less pronounced. Lesions of the caudate, accumbens or entopeduncular nucleus did not influence the cortical AChE activities. The results are discussed with respect to the similarity of the organization of the cholinergic projection to the cortex arising from NBM cells and the monoaminergic system which innervates the cortex. It is suggested that both neurotransmitter systems by their interaction might modulate and control cortical information processing and behavior in a manner analogous to the control of peripheral activity by the sympathetic and parasympathetic system.

Acetylcholinesterase↗
PubMed1977

[Enzyme histochemical investigations of the nucleus nervi oculomotorii of Salmo irideus (Gibbons 1855) during biomorphosis. I. Transmitter enzymes].

1. The activities of the transmitter enzymes acetylcholine esterase (AChE), monoamine oxidase (MAO) and gamma-aminobutyrate transaminase (GABA-TR) were investigated in the nucleus nervi oculomotorii of Salmo irideus (Teleostei) during biomorphosis. 2. AChE as well as MAO-activity could be demonstrated already before the time of hatching, whereas GABA-TR occured from the 10th day post hatching. 3. In earliest stages the AChE activity was found in the neuronal pericarya of the nucleus n. III, but later on a strong increase occured in vestibular presynaptic terminals establishing synaptic contacts with the lateral surface of the large pericarya, especially in the medial part of the dorsal subnucleus and the ventral subnucleus. In adults the enzyme activity was localized in vestibular nerve fiber terminals exclusively due to the loss of enzyme activity in the pericarya. 4. The activity of MAO was found surrounding the neurons of the nucleus nervi oculomotorii with stronger deposits of reaction product at the medial surface that is not occupied by cholinergic terminals. 5. Besides non reacting neurons in all parts of the nucleus some cells in the transition zone between the medial and lateral area of the dorsal subnucleus, exhibited high cytoplasmatic GABA-TR activity. 6. The different ways of chemical transmission between nerve terminals and the neurons of the nucleus nervi oculomotorii are discussed.

4-Aminobutyrate Transaminase↗
PubMed1975

[Histochemistry of cholinergic systems in the CNS. I. Topochemical and quantitative changes in acetylcholinesterase activity in the limbic cortex after septal lesions in the rat (author's transl)].

In brains of female albino rats the influence of septal and paraseptal lesions on the activity of acetylcholinesterase in the limbic cortex (hippocampal formation, regio limbica anterior et posterior, regio retrosplenialis) was investigated topochemically and also by a quantitative histophotometrical method. On the 4th day after bilateral lesion of the nuclei septi mediales the AChE-activity was diminished to residual values of 10 to 20% in comparison with sham-operated animals in all regions and layers of hippocampus and area dentata. Unilateral lesions of ncl. septi medialis cause stronger decreases in activity only ipsilaterally. Lesions surrounding the medial septal nuclei (ncl. septi lateralis, rostral septum, lateral hypothalamus, area preoptica especially) did not influence the enzyme activity in the hippocampal formation. After lesions in the rostral part of septum with intact medial nuclei, a reduced activity was found ipsilaterally in the layers of cingular cortex with residual values of 25 to 75% of the unaffected contralateral side. After destruction of the gyrus cinguli itself significantly lesser residual activities could be detected in this region caudal to the lesion. Quantitative estimations showed that 80 to 90% of the AChE-activity which was established by histochemical means in the hippocampal formation is immediately related to septal neurones. From these results it is evident that the hippocampal formation receives nearly all its cholinergic innervation from the medial septum exclusively. However, the cingular cortex seems to be an integrating field of other cholinergic afferences.

4-Aminobutyrate Transaminase↗