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Biomedical subjects

J E Gregory

Publications and source records attributed to J E Gregory.

At least 91 records · Page 5Linked to original sources
PubMed1979

The responses of Golgi tendon organs to stimulation of different combinations of motor units.

1. Afferent discharges were recorded from stretch receptors identified as Golgi tendon organs, in the medial gastrocnemius and soleus muscles of the cat. 2. The response of a tendon organ was recorded during stimulation of one or more motor units selected for the intensity of discharge elicited from the receptor during twitch and tetanic contractions. 3. Repetitive stimulation of a single motor unit could evoke in a tendon organ a firing rate of up to 174 impulses/sec. The mean rate for a total of 90 motor units was 65 (+/- 32 S.D.) impulses/sec. No significant difference in effectiveness could be detected between motor units covering a wide range of contraction speeds, tetanic tensions and susceptibility to fatigue. 4. The response of a tendon organ to contraction of several motor units in combination was greater than from stimulating any one motor unit alone but less than predicted from the algebraic sum of individual responses. 5. The relation between firing rate and tension was plotted for combined stimulation of up to ten motor units. The relation was found to be a straight line provided the size of the response elicited by each motor unit in the stimulated bundle was similar or when responses were ranked according to their intensity. When one motor unit evoked a much more powerful response than others it tended to dominate the discharge and disturb the linearity. 6. Evidence is provided that the sites of stimulus transduction for motor units which exert their effect directly on the receptor can be relatively independent of one another. It is argued that on such occasions summation of responses may be attributed to mechanisms operating at the level of impulse generation.

Action Potentials↗
PubMed1979

Urethritis attributable to Neisseria meningitidis, group X: a case report.

Neisseria meningitidis, Group X, was recovered from the anterior urethra of a 27-year-old male patient with urethritis. This isolate represents the first reported recovery of this organism from this anatomic site in association with this disease. He was treated with probenicid by mouth, followed by 4.8 million units of aqueous procaine penicillin G injected intramuscularly and became asymptomatic in three days. His recovery strongly indicates that the meningococcus was the etiologic agent of the urethritis since the condition promptly cleared with penicillin therapy.

Adult↗
PubMed1978

The stiffness of amphibian slow and twitch muscle during high speed stretches.

Experiments were carried out to compare the stiffness of cross-bridges in amphibian slow and twitch muscle. An isolated iliofibularis muscle was subjected to rapid, small stretches during contraction of either slow or twitch fibres at a number of different isometric tensions. The method of analysis allowed the compliance of the cross-bridges to be distinguished from other sources of compliance. Provided that the muscle was stretched sufficinetly rapidly to obtain limiting values of stiffness, little difference was found between the mechanical properties of the cross-bridges in slow and twitch muscle. It is concluded that the difference in observed stiffness of the two muscle types is due to a lower turnover rate of cross-bridges and a smaller number of sarcomeres in slow fibres.

Animals↗
PubMed1978

Mycoplasma salivarium in the blood of a child with leukemia.

Mycoplasma salivarium was recovered from the blood of a five-year-old girl who had leukemia and subsequently developed pneumonitis. The patient's pneumonitis failed to respond to nafcillin, a cell-wall-active antibiotic, but eventually she recovered from the pneumonia after a regimen of erythromycin. Sputum, oropharyngeal, and nasopharyngeal cultures revealed normal bacterial flora; a blood culture was negative for bacteria. Throat and sputum cultures were negative for mycoplasma; however, M salivarium was recovered from the patient's blood. The patient had a cold hemagglutinin titer of 1:250.

Child, Preschool↗
PubMed1977

A 'late supernormal period' in the recovery of excitability following an action potential in muscle spindle and tendon organ receptors.

1. Discharge patterns have been recorded from five types of stretch receptor; frog muscle spindles, lizard tendon organs, cat soleus tendon organs and primary and secondary endings of cat soleus muscle spindles.2. The fully adapted discharge of each type of receptor is irregular, especially for frog spindles and primary endings of cat spindles as compared with the other three types (the ;regularly firing' receptors). Frog spindles and some cat spindle primary endings would maintain a discharge at very low mean rates (1/sec or less) while the remaining receptors would stop suddenly, as soon as their rate of discharge fell below a critical value characteristic for each individual ending.3. This pattern of discharge suggests that there is a peak in the excitability of ;regularly firing' receptors at a time following a preceding impulse, which corresponds to the intervals between impulses at each particular receptor's slowest rate of maintained firing, and that the excitability subsequently falls again. Primary endings of cat muscle spindles also showed some evidence of such a ;late supernormal period', but frog spindles did not.4. Direct evidence for the ;late supernormal period' was obtained from experiments in which a maintained discharge was restarted by an antidromic action potential in a receptor which had stopped firing, and to which had been applied a stretch just too small to restart the discharge.5. It is shown in an Appendix that a model receptor in which the recovery of excitability following an impulse has a hyperbolic time course, and in which Gaussian distributed noise is superimposed on the generator potential, can have a discharge pattern very closely resembling that of a frog spindle (cf. Buller, 1965).6. After addition of a late supernormal period to the model, its discharge pattern could mimic closely that of a lizard or cat tendon organ, or of a secondary ending of a cat spindle.

Action Potentials↗
PubMed1975

Responses of tendon organs in a lizard.

1. In the lizard Tiliqua the tendons of the caudo-femoralis muscle are supplied by a nerve which runs separately from the muscle nerve. 2. Recordings of afferent discharges in the tendon nerve revealed the presence in the tendon of stretch-sensitive mechanoreceptors which responded to both passive changes in limb position and to muscle contraction. 3. A preparation of the tendon and its nerve were dissected free of surrounding tissue and studied in isolation while recording the activity of single functional units. The minimum tension in the tendon necessary for a maintained response from a receptor lay in the range 5-35 g (mean 16 g) and the firing rates at these tensions were in the range 5-14 impulses/sec (mean 9 impulses/sec). 4. Receptors showed a steep increase in firing rate with increase in tension up to about 120 g. The firing rate 30 sec after the onset of a tension change did not exceed 40 impulses/sec. 5. During the tension change the receptor responded with a burst of impulses whose frequency depended on the velocity of stretch. With large, rapidly rising tension steps peak firing rates of up to 300 impulses/sec were observed. 6. Tension and length changes recorded during rapid tendon-stretches were very similar, with little sag in tension at the new length. The response of all units however continued to fall throughout the stretch. Some of the possible causes of this adaptation have been discussed.

Action Potentials↗
PubMed1973

An electrophysiological investigation of the receptor apparatus of the duck's bill.

1. The properties of receptors in the duck's bill have been studied by recording from units isolated by dissecting fine filaments from the maxillary and ophthalmic nerves.2. The units studied were divisible into three groups, phasic mechanoreceptors responsive to vibration, thermoreceptive units, and high threshold mechanoreceptors.3. Vibration-sensitive mechanoreceptors (113 units) had small receptive fields, showed a rapidly adapting discharge to mechanical stimulation of the bill, were sensitive to vibratory but not to thermal stimuli and showed no background discharge.4. Temperature receptors (twenty-one units) were insensitive to mechanical stimulation and showed a temperature-dependent background discharge. Sudden cooling produced a transient increase in discharge frequency.5. High threshold mechanosensitive units (eight units) gave a slowly adapting discharge to strong mechanical stimulation and were insensitive to vibratory and thermal stimulation.6. It is concluded that the low-threshold, vibration-sensitive responses come from Herbst corpuscles. No specific function can yet be assigned to the Grandry corpuscles.

Action Potentials↗
PubMed1970

Mycoplasma recovery from the male genitourinary tract: voided urine versus the urethral swab.

A study of Mycoplasma recovery from the genitourinary tract was made on a group of 50 males attending a venereal disease clinic. The purpose of the investigation was to compare recovery rates of mycoplasma from two types of clinical specimens-the urethral swab and voided urine. The total number of positive cultures did not differ significantly when either the swab or urine was used; Mycoplasma hominis type 1 was the only taxonomic species isolated, either alone or mixed with T-strain mycoplasma. Recovery rates of the two types from both the swab and the urine did not differ significantly. Age did not relate to the presence of mycoplasma in the group studied.

Adolescent↗