Factors determining sweating competence of cattle skin

Significant differences in sweating rate between micro-areas of cattle skin have been demonstrated and the differences in morphology between these contrasting areas investigated.

Spontaneous and evoked activity of neurones in the somatosensory thalamus of the waking cat

1. Adult cats were prepared for chronic micro-electrode recording in the nucleus ventralis posterolateralis (VPL) of the ventrobasal complex (VB) of the thalamus. Spontaneous and evoked activity of single neurones was recorded extracellularly while the animal stood in a hammock. The behavioural state of the animal and the electroencephalogram (e.e.g.) were observed and recorded.2. Three hundred and twenty-five single neurones sensitive to movement of hairs, depression of skin or movement of claws were isolated and studied. Peripheral receptive fields were on the contralateral surface of the body. They remained constant in size and location over long periods of time and despite changes in the behavioural state of the animal. Most of the receptive fields covered a cutaneous area at least as large as an entire paw and many covered an entire limb and extended on to the trunk. These fields are larger than those described by other investigators using natural stimulation in anaesthetized or paralysed animals.3. Moving hairs or touching skin in the peripheral receptive field elicited a burst of spikes at frequencies between 100 and 150/sec. Repeated stimulation did not result in obvious alteration or habituation of the response. There was no apparent change in responsiveness of neurones to peripheral stimulation when the animal was asleep.4. Except for claw-sensitive units, all neurones were active in the absence of intentional stimulation of the receptive field. When the animals were awake, VPL neurones fired more regularly than during sleeping. In slow sleep, with e.e.g. slow waves and spindles, firing patterns were characterized by the presence of more high-frequency bursts of spikes and more long interspike intervals than in waking. Claw-sensitive units, silent during waking, fired in bursts during sleep. When small doses of barbiturate were injected intravenously while recording the activity of neurones, the firing pattern changed to one in which all of the activity occurred in the form of high-frequency bursts. Interburst intervals were variable.5. The level of spontaneous activity in VB in conscious cats is greater than in sensory and sensorimotor cortex to which it projects. The pronounced effect of behavioural state on spontaneous activity of these neurones suggests that the background activity in somatosensory systems may play some role in the processing of afferent input.

Changes in body temperature of the unanaesthetized monkey produced by sodium and calcium ions perfused through the cerebral ventricles

1. In the unanaesthetized Rhesus monkey, solutions containing sodium, calcium, potassium or magnesium in excess of the normal concentration of extracellular fluid were perfused from a lateral to the fourth ventricle through chronically implanted cannulae.2. Sodium (11.0-88.0 mM in excess of the physiological concentration) perfused through the ventricles, caused an immediate rise in body temperature which was accompanied by vasoconstriction, piloerection and shivering. The latency of the hyperthermia was related directly to the rate of perfusion and the concentration of sodium, whereas the magnitude of the response depended upon the concentration only. When the perfusion was terminated, shivering ceased and the temperature of the monkey returned to the base line level.3. When calcium ions were perfused in concentrations 2.5-47.9 mM in excess of that of extracellular fluid, a fall in the temperature of the animal occurred. The magnitude of the decreases depended upon the concentration of calcium in the perfusion fluid. Vasodilatation, sedation and a reduction in withdrawal reflexes accompanied the calcium-induced hypothermia. After the perfusion ended, the temperature continued to fall until the monkey began to shiver and vasoconstriction was observed in many skin areas.4. The perfusion through the cerebral ventricles with modified Krebs solution alone or with the Krebs solution which contained potassium or magnesium ions in concentrations five to ten times normal had virtually no effect on the temperature of the monkey.5. Since the temperature of the monkey was unchanged as long as the physiological ratio of sodium to calcium in the perfusion fluid remained constant, we conclude that the balance between these two essential cations within the brain stem could determine the neural mechanism whereby the set-point for body temperature of the primate is established.

Hair transplantation in male-pattern alopecia

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The overall pattern of hair follicle arrangement in the rat and mouse

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