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Biomedical subjects

D C Taylor

Publications and source records attributed to D C Taylor.

At least 163 records · Page 9Linked to original sources
PubMed1983

The use of fluorescent tracers in the peripheral sensory nervous system.

We have developed an injection technique which simplifies the use of fluorescent tracers in investigating the projections of peripheral nerves both in rats and pigeons, and avoids the difficulties experienced with the cut nerve technique. The tracers are injected into the peripheral nerve and transported to cell bodies in the dorsal root ganglia (DRG). By a careful choice of tracer it is possible to investigate the projections of two or more nerves in the same preparation. We have used two combinations of tracer which can be viewed simultaneously in the cell at the same excitation wavelength (405 nm): (1) propidium iodide (PI) and bisbenzimide (Bb) which produce an orange cytoplasmic fluorescence and blue nuclear fluorescence respectively; and (2) Fast blue (FB) and Nuclear yellow (NY) which label the cytoplasm blue and the nucleus yellow. This distribution of tracers is similar to that reported in central neurones but differs from that reported in the efferent peripheral nervous system. Using these tracers we have observed double-labelled neurones in the DRG of both rats and pigeons, which is an indication for the dichotomizing of peripheral fibres. The existence of two tracers in double-labelled cells has been confirmed microspectrophotometrically.

Animals↗
PubMed1982

Double fluorescence labelling supports electrophysiological evidence for dichotomizing peripheral sensory nerve fibres in rats.

The technique of double labelling with fluorescent tracers has been used to demonstrate that some sensory neurones in the sixth lumbar dorsal root ganglion (L6) of the rat possess peripheral processes which dichotomize into both the pudendal and sciatic nerves. Bisbenzimide (Bb) was injected into the pudendal nerve and propidium iodide (PI) into the sciatic. Double labelled neurones were observed which fluoresced with a blue nucleus and orange cytoplasm (PI) at 405 nm excitation. The double fluorescence was confirmed by microspectrophotometric measurements. Injection of Nuclear Yellow into the sciatic nerve and Fast Blue into the pudendal nerve also produced double labelled neurones in L6.

Animals↗
PubMed1982

Electrophysiological evidence for a somatotopic sensory projection to the striatum of the rat.

The somatosensory projection to the striatum of the rat was investigated by electrophysiological mapping. Fifty-five units were encountered that responded to specific forms of stimulation delivered to particular parts of the body. Units that responded to stimuli delivered to the hindlimb, scrotum and tail were found in the most caudal regions of the striatum while those that responded to stimulation of the forelimb, head and neck were found in the anterior regions of the striatum. The results strongly suggest that there is, in the striatum of the rat, a sensory map of the body that is organized on topographical principles.

Animals↗
PubMed1982

Counselling the parents of handicapped children.

The parents of handicapped children have to adjust to a wide variety of emotional and psychological problems when first confronted with the failure of their reproductive expectations. Counselling is a formal procedure or transaction in which both counsellor and parents aim to find a mutually acceptable plan of adjustment. Parents may need support to cope with their own personal inadequacies as well as with their own personal inadequacies as well as with the needs of the child. Counselling should be a continuous process, in which the parents can learn to accept the child as a different rather than a lesser person.

Counseling↗
PubMed1982

Distribution of sensory neurons of the pudendal nerve in the dorsal root ganglia and their projection to the spinal cord. Horseradish-peroxidase studies in the rat.

The morphology and distribution of the sensory neurons of the pudendal nerve within the spinal ganglia of rats were investigated by use of horseradish peroxidase (HRP). The labelling was visualized in diaminobenzidine (DAB) or tetramethyl-benzidine (TMB)-stained sections. Injection of HRP directly into the pudendal nerve labelled perikarya predominantly in the sixth lumbar DRG (L6). Following injection of HRP into the scrotal skin, however, additional cells were labelled in L5 and S1. Labelling was invariably unilateral. Approximately equal numbers of small (less than 30 micrometers) and large neurones (greater than 40 micrometers) were labelled following subcutaneous injections although injections into the nerve marked twice as many small cells as large cells. This suggests that, in the rat, most of the small-diameter fibers within the pudendal nerve ascend through L6. Although a cluster of neurones was observed in one experiment, the remaining 25 experiments did not reveal any somatotopic arrangement since the labelled perikarya were distributed evenly throughout the ganglion. Similar numbers of retrogradely labelled neurones (somatopetal transport of the tracer) were observed in both DAB- and TMB-stained sections, although TMB allowed the demonstration of anterograde (somatofungal) HRP transport by terminal labelling in the superficial laminae of the lumbar spinal cord, extending into laminae II--IV.

3,3'-Diaminobenzidine↗
PubMed1982

The effects of nucleus raphe magnus lesions on an ascending thermal pathway in the rat.

1. In the thalamus and hypothalamus of rats, anaesthetized with Urethane, single unit recordings have been made from cells which respond to small innocuous changes in scrotal skin temperature applied with a water-perfused brass thermode. 2. Once a scrotal temperature-sensitive neurone had been isolated the brain stem was electrolytically lesioned through implanted tungsten electrodes to determine whether the input from the scrotal skin temperature sensors ascends through the brain stem lemniscal pathways or the mid-line raphe nuclei. All recordings sites and lesions were identified histologically. 3. Thirty-six neurones have been studied of which half were located in the ventrobasal thalamus, six were located in the anterior thalamic nuclei and the remainder were in the medial hypothalamus. 4. The nucleus raphe magnus was lesioned on eighteen separate occasions; in each case the temperature-responsive activity of the thalamic or hypothalamic neurone was abolished. 5. Extensive brain-stem lesions which spared only the mid-line nucleus raphe magnus had no discernible effect on the responses of the thalamic or hypothalamic neurones to scrotal skin temperature. 6. The ascending pathway from the thermal sensors of the rat scrotal skin must pass through, or relay in, the nucleus raphe magnus.

Action Potentials↗
PubMed1982

An analysis of a thermal afferent pathway in the rat.

1. Single unit activity has been recorded in the thalamic, hypothalamic and raphe magnus nuclei of rats anaesthetized with Urethane.2. Neurones were sought which responded to changes in scrotal skin temperature applied with a water-perfused brass thermode. All sixty-nine neurones in the thalamus and hypothalamus responded with abrupt changes in activity as the scrotum was warmed (;switching response'). The majority responded with an increase in activity from minimal to maximal firing rate as the scrotum was warmed over a range of less than 0.5 degrees C; in about 20% of the neurones the converse was observed.3. To determine whether the switching response of the thalamic and hypothalamic neurones depended upon a cortico-thalamic feed-back loop, the cortical surface was cooled to 18-20 degrees C to reversibly abolish cortical post-synaptic activity.4. Cortical cooling abolished the positive switching response of nearly all (15/19) ventrobasal thalamic neurones to scrotal warming. All eight ventrobasal thalamic neurones with negative switching responses, and all twenty-two scrotal temperature-responsive neurones in other thalamic and hypothalamic nuclei were unaffected.5. Twenty recordings were also made from scrotal temperature-responsive neurones in the nucleus raphe magnus. All possessed switching responses similar to those observed in the thalamus and hypothalamus.6. None of the scrotal temperature-responsive neurones in the nucleus raphe magnus was affected by cortical cooling. Six neurones were observed in decerebrate rats with properties apparently identical to those in intact rats.7. We conclude that the switching response of thalamic and hypothalamic scrotal temperature-responsive neurones is probably generated in the nucleus raphe magnus and passed in parallel to the thalamus and hypothalamus. In addition, thalamic neurones depend on an intact link with the cerebral cortex for the generation of their switching responses.

Afferent Pathways↗
PubMed1981

Chronic dog intestinal loop model for studying drug absorption as exemplified by beta-adrenoreceptor blocking agents, atenolol and propranolol.

Chronic in situ loops of dog small intestine (jejunum or ileum) were used to investigate the absorption of the beta-adrenoreceptor blocking agents atenolol and propranolol. Absorption measurements were made in conscious dogs by monitoring drug disappearance from solution in the loop, with correction for intestinal water absorption. The jejunum had a mean resting pH of 7.3 and a slight net secretion of water into the lumen; the ileum had a resting pH of 7.9 and a strong net absorption of water. Propranolol absorption was rapid and first order in both regions, with the ileum showing faster absorption than the jejunum due to its higher resting pH. In contrast, atenolol absorption was negligible in the jejunum and only moderate in the ileum. The data were quantitatively consistent with the pH-partition mechanism for the absorption of propranolol but not for atenolol. The model was validated for atenolol by showing that, following drug administration into jejunal and ileal loops, drug disappearance rates were similar to absorption rates calculated from systemic blood levels. This technique is useful, realistic, and relatively simple for studying intestinal drug absorption without seriously perturbing normal GI conditions.

Animals↗
PubMed1981

Lipid composition of metacestodes of Taenia taeniaeformis and lipid changes during growth.

A lipid analysis was performed on developing metacestodes of Taenia taeniaeformis removed from the livers of rats at times varying from 3 to 35 weeks post infection. Lipid accounted for 7-21% of the dry weight of the parasites. The highest proportions were found at the earlier stages. The distribution was as follows; neutral lipid 27-45%; glycolipid 5-11%; and phospholipid 50-61%. The major neutral lipid was cholesterol, and minor neutral lipids were sterol esters, triglycerides, diglycerides and monoglycerides. Hydrocarbons were present throughout development, but in the highest amounts at the earlier stages. Five different glycolipids were found, all of which were identified as glycosphingolipids. An increase in the proportion of more complex glycolipids was noted as parasites grew older. Ten different phospholipids were identified, with the major components being phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. Other phospholipids were: lysophosphatides, phosphatidylinositol, phosphatidic acid, diphosphatidylglycerol, sphingomyelin, and an unknown phospholipid component. Changes in the relative amounts of the two major phospholipids were found when the early and late stages were compared. Two lipids found throughout development were identified as glycosylated dolichol phosphates, and they comprised between 1 and 3% of the total phospholipid fraction. Nineteen fatty acids were detected, and the fatty acid distribution for each lipid class at each stage was determined. Seven major fatty acids were common to each. These were: hexadecanoic, octadecanoic, oleic, linoleic, arachidonic, docosanoic, and docosahexaenoic.

Animals↗
PubMed1981

Precurrent self-prompting operants in children: "Remembering".

IN EXPERIMENT I, ONE OF THREE FORMS OF COLLATERAL BEHAVIOR WAS TRAINED: Differential collateral behavior specific in form to one of two discriminative stimuli; Common collateral behavior of a single form regardless of the stimulus; or Nondifferential collateral behavior of either form regardless of the stimulus. Children were next given a short-delay matching-to-sample task in which the discriminative stimuli served as samples, and the children's previously trained collateral behavior terminated the delay and presented the comparison stimuli. Subjects engaging in sample-specific collateral behavior immediately acquired matching. Subjects engaging in sample-nonspecific collateral behavior failed to acquire matching or did so gradually. In Experiment II the minimal delay in the matching task was varied in a mixed sequence, first with collateral behavior required, and then with collateral behavior prohibited. When emitting collateral behavior Common and Nondifferential subjects showed delay-related decrements in matching while Differential subjects did not. When not emitting collateral behavior all subjects showed delay-related decrements in matching. Common and Nondifferential subjects matched more accurately when prohibited from emitting collateral behavior. Differential subjects matched more accurately when emitting collateral behavior. The results accord with Skinner's (1953, 1968) analysis of precurrent operants.

Journal Article↗
PubMed1980

Hughlings Jackson's Dr Z: the paradigm of temporal lobe epilepsy revealed.

On 10 January 1894, a distinguished physician died in London of an overdose of chloral hydrate. The event was of vital interest to Hughlings Jackson who attended the post-mortem examination with a bevy of witnesses. He begged his colleague Walter Colman "to search the taste region of Ferrier on each half of the brain very carefully." They were rewarded by finding " a very small focus of softening in that region (in the uncinate gyrus) of the left half of the brain." Jackson had thus discovered the most discrete and circumscribed lesion of the temporal lobe yet described to assoicate with the most detailed and elegant self report of psychomotor epilepsy yet published. For the physician, whom Jackson and Colman called "Dr Z" in their report in Brain(2) had been Jackson's patient since 1877 and his own account of his epileptic experience had occupied six pages of Jackson's 1888 article "On a particular variety of epilepsy...."(7) Jackson had himself witnessed several of Dr Z's attacks. The case enabled Jackson to argue that the complex symptomatology of the seizure was due to "reflex" effects of epileptic discharges in that area of brain. It is the paradigm of temporal lobe epilepsy.

Adult↗
PubMed1979

Facial thermal input to the trigeminal spinal nucleus of rabbits and rats.

In rabbits and rats under urethane anesthesia, a systematic survey was made of the caudal trigeminal nucleus, using glass coated tungsten microelectrodes. This revealed many neurons in the marginal layer sensitive either to warming or cooling the facial skin. The majority of these neurons were specifically temperature sensitive. In rats, a somatotopic arrangement of cold receptive fields was evident within the marginal layer of the trigeminal nucleus, with the ophthalmic division of the trigeminal nerve represented most laterally, the mandibular most medially and the maxillary division represented over most of the recording region. This arrangement is similar to the mediolateral distribution seen in cats. In rabbits, the distribution was less rigorous but the ophthalmic division tended to be represented caudally and the mandibular division rostrally. The maxillary division was represented over most of the recording region. All receptive fields were ipsilateral and showed spatial convergence of input. Both rabbits and rats possessed a concentration of thermal receptive-fields around the nose, whisker pad and mouth. At steady skin temperatures, marginal units gave bell-shaped intensity functions which were very similar to those reported for the cold and warm receptors. With rapid changes of temperature, neurons responded with a dynamic outburst which corresponded to the equivalent receptor response.

Animals↗