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Biomedical subjects

M Vogt

Publications and source records attributed to M Vogt.

At least 235 records · Page 13Linked to original sources
PubMed1977

Histamine H2-receptors in the brain and sleep produced by clonidine.

Sleep was induced in chicks aged 4-7 days by intravenous injection of clonidine hydrochloride 0.04 mumol/kg. Sleep was not prevented or altered by a preceding intramuscular injection of blockers of histamine H2-receptors which were used in doses (as mumol/kg) of up to 800 (metiamide) and 2400 (cimetidine). Clonidine, therefore, does not cause sleep by stimulating H2-receptors in the brain. The highest dose of cimetidine used had a hypnotic action of its own.

Animals↗
PubMed1976

Increase by visual stimuli in turnover of 5-hydroxytryptamine in the superior colliculi of the rabbit.

1. Irregular light falshes were played on to one eye of dark adapted rabbits for periods of 20-80 min. The concentration of 5-hydroxyindol-3-ylacetic acid (5-HIAA) and of 5-hydroxytryptamine (5-HT) were estimated in left and right superior colliculi, thalami and hippocampi. 2. In rabbits exposed to such visual stimuli for 30-60 min, there was an increase in the 5-HIAA content of the colliculus contralateral to the stimulated retina which aberaged 17% (P = 0-02), but no rise was seen if the exposure was shortened to 20 or prolonged to 80 min. At no time was there a difference in 5-HIAA content between right and left thalamus or right and left hippocampus. 3. Stationary or strictly repetitive visual stimuli produced no difference between the 5-HIAA content of left and right superior colliculus. 4. No difference in 5-HT concentration between the two colliculi was found after any form of visual stimulation, nor did any changes occur in the other parts of the brain which were examined. 5. Irregular, prolonged visual stimualtion thus appears to activate tryptaminergic neurones terminating in the colliculi. The possibility is discussed that the 5-HT released at this site might act as a brake to neuronal activity under conditions when habituation to the stimuli is not yet complete.

Animals↗
PubMed1976

Proposed structure of two defective viral DNA oligomers produced in 3T3 cells transformed by the ts-a mutant of polyoma virus.

The various oligomeric viral DNA species produced at 32 C by two related syblines of ts-a-transformed mouse 3T3 cells were characterized. Results from the analysis of the cleavage products observed after digestion with restriction endonucleases from Haemophilus parainfluenzae, Escherichia coli RI, and Haemophilus suis are consistent with the assumption that in both sublines, the major oligomeric component is a dimer from which a segment of different length is deleted. The major oligomeric (27S) component in subline 1 was estimated to be 1.77 times the size of the viral monomer, and the major (25.5S) component in subline 15 was estimated to be 1.54 times the size of the viral monomer. These size estimates were confirmed by electron micrograph measurements. The larger oligomers produced by both sublines were found to be multiples of the major oligomeric component of each subline.

Animals↗
PubMed1975

In vitro polyoma DNA synthesis: self-annealing properties of short DNA chains.

Short DNA chains, isolated from in vitro pulse-labeled replicating polyoma DNA, exhibit some degree of self-complementarity (28% resistance to S1 nuclease after self-annealing to plateau levels). This level of self-annealing is not increased if short DNA chains present as free single-stranded DNA after extraction are included in the hybridization, excluding a selective loss of chains from one side of the growing fork and supporting a semi-discontinuous mode of chain growth. This mode also applies to restricted synthesis conditions under which a relative excess of short chains is made, since no increase in the self-annealing of such short chains is observed. The self-annealing that can be measured is higher for the faster sedimenting portion (46%) of the short DNA chains than for the slower sedimenting portion (18.5%), indicating that it is most likely due to contaminating continuously growing strands from the other side of the fork. High self-annealing values (up to 60%) are obtained if virus stocks generating defective DNA are used for infection. Restriction endonuclease (Hpall) characterization of such DNA shows evidence for the presence of multiple origins of replication. One of several possible mechanisms is discussed by which replicating defective DNA can generate self-complementary short chains despite a semi-discontinuous mode of replication.

Animals↗
PubMed1974

The effect of lowering the 5-hydroxytryptamine content of the rat spinal cord on analgesia produced by morphine.

1. Injection of 5,6-dihydroxytryptamine (5,6-DHT, 50 mug) into a lateral cerebral ventricle of male rats lowered the 5-hydroxytryptamine (5-HT) content of the lumbar cord to 12.8% and reduced the analgesic effect of low doses of morphine (0.64-1.63 mg/kg), tested by exerting pressure on the foot; after doses of morphine of 1.33-1.63 mg/kg, the analgesic response was reduced or abolished in 33% of the rats, and after 0.64 mg/kg, 58% of the animals failed to respond normally.2. Two days after an I.P. injection of p-chlorophenylalanine (pCPA, 320 mg/kg), the loss of analgesic potency of morphine was more pronounced than after intraventricular 5,6-HDT. The 5-HT content was lowered to about 8% in the lumbar cord, and to 20% or less in pons and medulla.3. The experiments show that interference with the descending tryptaminergic axons innervating the cord is by itself sufficient to reduce analgesia due to morphine, but they do not exclude the possibility that other tryptaminergic neurones take part in the effect of pCPA. The contribution to the analgesic effect of morphine made by the interaction of tryptaminergic axons with the interneurones ;gating' the afferent impulses in the posterior columns is discussed.

Journal Article↗
PubMed1973

Release of transmitters into the perfused third cerebral ventrical of the cat.

1. The third cerebral ventricle of cats treated with nialamide and anaesthetized with chloralose was perfused, and the effluent was tested for 5-hydroxytryptamine (5-HT) and also for acetylcholine (ACh) when the perfusion fluid contained neostigmine.2. Under ;resting' conditions a 25 min sample of effluent contained from < 1 to 6 ng 5-HT; the release remained steady during many hours of perfusion. It was necessary to watch out for traces of blood which might contribute to the 5-HT content and which were only visible after centrifugation.3. A number of regions in the ventral mid-brain and hind-brain were stimulated, including the two most anterior nuclei of the raphe, nucleus linearis rostralis and intermedius. Release of 5-HT (rarely more than 2 ng) was only obtained on stimulation of these two nuclei, whereas ACh was released by stimulating many points, such as the reticular formation or the decussation of the superior cerebellar peduncles, but not the two raphe nuclei.4. Low frequencies of stimulation were more effective at releasing 5-HT, and high frequencies at releasing ACh.5. Since the amount of 5-HT released on stimulation was rarely more than 2 ng, a powerful re-uptake process was suspected and confirmed by the use of chlorimipramine. Intravenous, intraperitoneal and intraventricular use of this drug temporarily increased the basal release to values ranging from 20 to 50 ng in 25 min samples, and about trebled the release on stimulation of either of the linear nuclei.6. Intravenous administration of chlorimipramine (10 mg/kg) caused the disappearance of electrical responses evoked in the brain stem by afferent sensory stimuli.

Acetylcholine↗