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Biomedical subjects

U Proske

Publications and source records attributed to U Proske.

161 records · Page 9Linked to original sources
PubMed1969

An electrophysiological analysis of responses from lizard muscle spindles.

1. Stretch receptor discharges were recorded in the lizard Tiliqua nigrolutea. Responses were identified as coming from muscle spindles by their ;in parallel' behaviour during a twitch.2. Recordings from spindles in the iliofibularis muscle which contains many single innervated fibres revealed spindles which discharged on the rising phase of the muscle contraction. This ;in series' response increased in frequency and duration at high resting tensions on the muscle and was attributed to a specific intrafusal contraction.3. The ;in series' discharge could be induced by stimulation of only one small filament of the muscle nerve. This suggested a focal intrafusal motor innervation.4. Responses from spindles in the semitendinosus muscle, which contains many multiple innervated fibres provided examples of an ;in series' response which could be produced by stimulation of several muscle nerve filaments. This was interpreted as being an example of multiple intrafusal motor innervation.5. Spindles with short or elongated sensory regions were subjected to ;ramp' stretches. The presence of distinct phasic and tonic responses from the two types was confirmed and related to the behaviour of mammalian spindles.

Animals↗
PubMed1968

Infrared receptors in the facial pits of the Australian python Morelia spilotes.

There is a series of pits in the scales of the rostrum and posterior portion of the lower lips in some pythons and boas. In the Australian python Morelia spilotes, these pits are innervated by the maxillary and mandibular branches of the trigeminal nerve. Structural and neurophysiological evidence indicate that in the pits there are receptors that function as detectors of radiant heat flux.

Action Potentials↗
PubMed1968

Histological and electrophysiological investigation of lizard skeletal muscle.

1. The patterns of innervation and electrical properties of muscle fibres in a skeletal muscle of the blue tongue lizard Tiliqua nigrolutea have been investigated.2. Gold impregnation of nerve terminals and staining of muscle fibre junctional areas for cholinesterase showed that there are two histological types of muscle fibre in scalenus muscles of the lizard: (a) those usually receiving single en plaque innervation, and (b) those that receive multiple en grappe terminations.3. In normal solution and in solutions to which small doses of curare were added, two types of subthreshold post-junctional response were recorded following nerve stimulation, (a) potentials with rapid rates of rise and a half-decay time of less than 10 msec and (b) responses with fast rise times and long half-decay times (50 msec or more).4. Fast time course subthreshold responses often gave rise to propagated action potentials. In curarized preparations ((+)-tubocurarine 0.4-1.0 mug/ml.) action potentials failed, giving way to junction potentials of decreasing amplitude, when stimulation was maintained at rates of 5/sec or more. The decay phases of fast time course potentials were closely approximated by error functions.5. Slow time course responses summated during repetitive stimulation, but action potentials were never produced. The decays of slow junction potentials were well fitted by exponentials. It is suggested that fibres in which they were recorded received distributed, en grappe innervation.6. Fibres in which fast time course junction potentials were recorded were excited by direct stimulation via an intracellular micro-electrode. They had apparent membrane resistance and capacity of about 4000 Omega. cm(2) and 7 muF/cm(2).7. Fibres exhibiting slow junction potentials could not be excited directly, even when depolarizing pulses were preceded by hyperpolarizations of 50 mV or more for more than 20 msec. Such fibres had an apparent membrane resistance of 31 x 10(3) Omega.cm(2) (mean) and a capacity of less than 3 muF/cm(2) (eight fibres).8. Curarized muscles developed tension in response to nerve stimulation at frequencies of 5/sec or more. The tension profile was smooth at even the lowest frequencies at which a response was elicited. Normal fusion frequency was around 50/sec.9. It is suggested that fibres exhibiting slow junction potentials were functionally similar to amphibian tonic fibres.10. Some fibres were found in which action potentials could be elicited by stimulation of one or more axons. Their subthreshold responses and passive properties were not determined and it remains uncertain to which of the two structural types they belong.

Action Potentials↗
PubMedDate not supplied

Electroreceptors in the platypus.

It has been known since the last century that the bill of the platypus contains densely packed arrays of specialized receptor organs and their afferent nerves. Until recently these were thought to be largely mechanoreceptive in function. However Scheich et al. provide both behavioural and electrophysiological evidence that there are electroreceptors in the bill of the platypus. These authors were able to record evoked potentials from the somatosensory cortex of the brain in response to weak voltage pulses applied across the bill. Behavioural observations showed that a platypus could detect weak electric dipoles and it was suggested the animal was able to locate moving prey by the electrical activity associated with muscle contractions. From these observations, and in view of the fact that it was known that the bill contained gland receptors which in several respects resembled the ampullary electroreceptors in fresh-water fish, Scheich et al. concluded that the receptor array of the platypus bill included electroreceptors. In this report we present direct electrophysiological evidence for the existence of such receptors.

Animals↗
PubMedDate not supplied

Damage to the human quadriceps muscle from eccentric exercise and the training effect.

Nine participants performed two bouts of a step exercise, during which the quadriceps muscle of one leg acted eccentrically. Before and after the exercise, isokinetic torque was measured over a range of knee angles to determine the optimum angle for torque. Immediately after the first bout of exercise, the quadriceps showed a significant (P < 0.05) shift of 15.6 +/- 1.4 degrees (mean +/-sx) of its optimum angle in the direction of longer lengths, suggesting the presence of damage. A drop in peak torque, together with delayed soreness and swelling, confirmed that damage to muscle fibres had occurred. After the second bout of exercise, 8 days later, the shift in optimum angle was 10.4 +/- 1.0 degrees, which was significantly less than after the first bout (P < 0.05). Other indicators of damage were also reduced. In addition, the muscle exhibited a sustained shift in optimum angle (3.4 +/- 0.9 degrees), suggesting that some adaptation had taken place after the first bout of exercise. We conclude that muscles like the quadriceps can show evidence of damage after a specific programme of eccentric exercise, followed by an adaptation response. This is despite the fact that the quadriceps routinely undergoes eccentric contractions in everyday activities.

Adult↗