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P Zangger

Publications and source records attributed to P Zangger.

27 records · Page 2Linked to original sources
PubMed1978

Effect of repetitive activation on the afterhyperpolarization in dorsal spinocerebellar tract neurones.

1. The changes in the afterhyperpolarization (a.h.p.) with repetitive activation have been studied in dorsal spinocerebellar tract cells of the cat using intracellular recording techniques. 2. The a.h.p. following a single spike was conditioned at different interspike intervals by a single preceding spike. In the majority of neurones the a.h.p. following a spike added approximately linearly with that generated by a preceding spike. 3. In other cells the a.h.p. following a spike was instead depressed by a preceding spike. THis depression was approximately constant at interspike intervals less than the a.h.p. duration (50-100 msec). Thereafter the a.h.p. slowly recovered during the next 100-300 msec. There was no associated decrease in the initial brief hyperpolarizing undershoot. 4. With shortlasting repetitive activation at high frequency (greater than 100 impulses/sec) the a.h.p, peak amplitude increased progressively with successive spikes (5-15 spikes). No change in the time constant of decay was observed. A good correspondence was found between the observed increase in peak amplitude of the a.h.p.s and that given by a theoretical linear superposition of the successive a.h.p.s. 5. Changes in the brief hyperpolarizing undershoot with repetitive activation is also described.

Action Potentials↗
PubMed1978

Firing behaviour of dorsal spinocerebellar tract neurones.

1. The repetitive discharge evoked by constant current injection from an intracellular micropipette has been studied in dorsal spinocerebellar tract cells of the cat. 2. The discharge frequency decreased with time, the decrease being more pronounced at high current intensities. Most of the frequency change occurred during the first ten intervals but the decrease continued slowly for several seconds. In some cells the frequency rose initially, the first interspike interval being larger than immediately succeeding ones. 3. The frequency-current (f/I) curves for the first interspike intervals were S-shaped, as found in spinal motoneurones. With successive intervals the lower leg of the f/I curve extended to higher frequencies, giving a progressive linearization of the f/I curves. In almost all cells this linearization was completed at 200 msec after current onset. 4. The experimental f/I curves were compared with the f/I curves obtained with a simple neurone model based on the properties of the postspike afterhyperpolarization. For the first interspike interval there was a good agreement between the experimental and calculated f/I curves of individual neurones up to frequencies of several hundred impulses per second. In the high frequency range, it was necessary to compensate for changes in initial postspike voltage trajectories caused by the injected current. Other aspects of the firing of real neurones, such as the progressive linearization of the f/I curves, the negative adaptation and the changes in the interspike voltage trajectories with increasing current were also reproduced by the neurone model. 5. It is concluded that the conductance process underlying the postspike afterhyperpolarization is a major factor in the regulation of repetitive firing in dorsal spinocerebellar tract neurones.

Action Potentials↗
PubMed1976

Central generation of locomotion in the spinal dogfish.

After a transection of the spinal cord a dogfish performs continuous swimming movements with a phase lag between adjacent segments. It is shown that the intersegmental coordination remains after an extensive dorsal root transection as well as after curarization. In the former case the motor activity was recorded electromyographically in several segments along the body, in the latter case the intersegmental coordination was evaluated by recording the efferent activity in different ventral roots along the body. It was concluded that a spinal central network can account for the phase lag observed between successive segments during swimming. It was also shown that the efferent activity from parts of the spinal cord with no dorsal roots intact could be influenced by peripheral stimuli such as pressure on the pelvic fins; this result suggests that some afferent fibres reach the spinal cord via the ventral roots.

Animals↗
PubMed1976

Muscle spindle control during locomotor movements generated by the deafferented spinal cord.

In acute spinalized (Th 12) cats, treated with DOPA, curarized or with all lumbosacral dorsal roots transected, stepping patterns were elicited in the hindlimbs by continuous electrical stimulation of the dorsal roots. Single primary endings in dorsal root filaments or single gamma and alpha efferents in muscle nerve filaments from flexors and extensors were recorded together with the efferent nerve activity to various hindlimb muscles. The experiments showed a clear coactivation of the intra- and extrafusal system to the same muscle. The alpha efferent discharges typically started with a very short first interspike interval. It is concluded that there exists a central spinal alpha-gamma-linkage for locomotion in the hindlimbs.

Animals↗
PubMedDate not supplied

MRI findings in Caroli's disease and intrahepatic pigmented calculi.

This paper reports a case of Caroli's disease confined to the left lobe of the liver that mimicked left portal vein thrombosis on MRI studies because of the very high signal intensity on T1-weighted images of intrahepatic pigmented calculi. The preoperative diagnosis was a cholangiocarcinoma infiltrating the left hepatic bile duct and portal branch. The final macroscopic and histological diagnosis was Caroli's disease of the left liver lobe with wide enlarged left bile duct containing multiple pigmented calculi.

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