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Biomedical subjects

U Meyer

Publications and source records attributed to U Meyer.

At least 163 records · Page 9Linked to original sources
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

[Morphology of coronaviruses-- electron microscopic demonstration by negative contrast technic of the transmissible gastroenteritis virus of swine].

This contribution to the morphology of corona virus is based on the use of electron microscopy in a negative contrast investigation of the virus of transmissible gastroenteritis of swine. Viruses of transmissible gastro-enteritis are spherical or, in rare cases, pleomorphous particles of typical corona virus structure. The viruses investigated by the authors were 132 nm in diameter. The surface projections, consisting of a flattened knob and conical shaft, are 18 nm in length. Internal bodies, 50 +/- 2 nm in diameter, occur as "filled" or "empty" particles. The thickness of all internal bodies and virus membranes is 8 +/- 1 nm. Differences were found to exist between virus of transmissible gastro-enteritis and particles similar to corona virus and isolated from faecal samples. A first comparison had been made for that purpose. Those differences were relating to shape and size of individual particles and to morphological setup of surface projections.

Animals↗
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↗
PubMed1978

[Transmissible gastroenteritis of swine as a model for infectious diarrhea].

Transmissible gastro-enteritis is a virus-caused diarrhoeal disease of swine which may result in up to a total loss among newborn animals. Changes are, primarily, of pathologicoanatomic nature and take place in the small intestine. The epithelium of the intestinal villi is completely destroyed, and diarrhoea is the result. Deformation in blood composition is a secondary sequel. The diarrhoea proper causes dehydration and acidosis which, in conjunction with abnormal heart function due to hyperkalaemia, cause death of the piglets affected. Reference is made to the intrinsic immunological conditions in swine, and possibilities are discussed for immunoprophylactic control of transmissible gastro-enteritis by induction of effective lactogenic immunity. The approaches taken to vaccine application should largely correspond to the natural route of infection.

Animals↗
PubMed1978

[Coagulation inhibition caused by selective thrombin blockade with hirudin].

Hirudin causes a rapid inhibition of blood coagulation as shown by in vitro and in vivo experiments in the dog. The substance appears to be a rather specific antithrombin. Its inhibitory action is linearly dose related and therefore easy to control and reproduce. Side effects can be expected to be abolished after further purification of the substance.

Animals↗
PubMed1977

Influence of fetal sex on the concentration of amniotic fluid testosterone: antenatal sex determination?

Amniotic fluid testosterone was measured by radioimmunoassay in 226 samples taken between the 12th week of pregnancy and birth. The effect of fetal sex on the level of this androgen was determined and the usefulness of the parameter for predicting fetal sex assessed. Testosterone was measured using an antibody raised in rabbits against testosterone-3-carboxymethyloxime-BSA. The antiserum cross-reacted strongly with 5alpha-dihydrotestosterone so that the values reported were refered to as measuring "immunoreactive testosterone" levels. Male fetal values were highest between the 12th and 15th week of pregnancy reaching a maximum mean of 501 +/- 185 pg/ml gradually falling during the remainder of pregnancy to 281 +/- 74 pg/ml, the difference in values between the first half and the end of pregnancy being highly significant (p less than 0.0005). Female fetal values did not vary significantly during the course of gestation, the minimum mean value being 179 +/- 50 and maximum 253 +/- 98 pg/ml. The fetal amniotic fluid sex difference was highly significant during the first half of pregnancy (p less than 0.0005) and at 12-15 weeks a successful prediction of fetal sex was possible, using testosterone, in 39 out of 41 cases. At birth on the other hand there was no difference between male and female fetal fluid levels. The method can also be used to detect disturbances of intrauterine sexual development as exemplified by the case of a Klinefelter syndrome where female testosterone values were found at the time of sexual differentiation. Thus the measurement of unconjugated testosterone in amniotic fluid would seem to offer not only an addition to chromosomal analysis for prediction of fetal gender but also be a valuable tool for detection of disturbances of intrauterine sexual development i.e. when genetic sex and sex-specific hormone production are discrepant.

Amniotic Fluid↗
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

[Studies on the degree of hypoxic and pharmacological coronary dilation (author's transl)].

On 11 isolated dog hearts, perfused with arterial blood of a donor dog, the degree of hypoxic dilatation and the maximum coronary blood flow achieved by adenosine were compared. The maximum coronary blood flow under adenosine infusion amounted to 455ml/minx100g, that means an increase of about 600% of the normal flow. If coronary venous pO2 was below 5mm Hg coronary blood flow was increased to 420ml/minx100g, which is 93% of the pharmacologically achieved maximum increase of the coronary blood flow. The difference between the maximum hypoxic and the maximum pharmacological dilatation is due to the method; it is caused by an increase of the extravascular component of coronary resistance under the influence of catecholamines in the case of hypoxic dilatation. It is pointed out that in order to achieve a maximum hypoxic dilatation oxygen pressure has to be below the critical value. It can be concluded that the intravascular component of coronary resistance is as low under hypoxic as under pharmacological dilatation.

Adenosine↗
PubMed1975

[Experimental studies on the circulation of the vascular area of the subdiaphragm using a newly developed pulse-wave pump].

A new developed partial artificial heart system is presented, which allows pulsatile perfusion of vital organs. The results presented reveal the possibility to duplicate pressure curves and peak systolic pressure in the perfused area-similar to physiological preoperative measurements. The kidney function remains intact. Angiographically there is no damage of the kidney vessels evident. The results are compared with datas of other investigators. Especially there opinion about the disturbance of renal flow and function under nonpulsatile conditions are critically evaluated. A possible connnection between the postoperative renal failure after cardio-pulmonary bypass and non-pulsatile perfusion and other pathophysiological mechanisms are discussed.

Abdomen↗
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↗