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Biomedical subjects

A Montgomery

Publications and source records attributed to A Montgomery.

At least 91 records · Page 5Linked to original sources
PubMed1985

Postural EMG activity in the soleus muscle of adult rats following thyroidectomy.

An electrode array was implanted for chronic recording of EMG activity in both soleus muscles (SOL) in adult albino rats (Wistar strain) of 250 g mean body weight. After 12-13 days, surgical thyroidectomy was performed and the postural EMG activity in both SOL muscles up to 16 weeks after the operation was quantitatively compared (spikes per minute) with the EMG activity before the operation. The results showed that the EMG activity in the SOL is significantly decreased after thyroidectomy.

Action Potentials↗
PubMed1984

The health planning process: are consumers really in control?

This study of the governing board of a Health Systems Agency tends to support those who argue that a numerical majority of consumers does not guarantee consumer control of the decision-making process. Empirical support stems from the fact that consumers, relative to providers, appeared to be at a decided disadvantage in three areas: 1. Consumers see themselves as experiencing greater communication problems. 2. Consumers are more likely to perceive their knowledge as being inadequate. 3. Consumers are more likely to feel intimidated by other governing board members. The consumers' disadvantages in these three areas likely diminish the amount of influence they hold. Indeed, both provider and consumer board members felt consumers held less than one-fourth of the influence on the governing board. Although consumers wanted more influence they did not desire majority control. Staff was seen as exerting most of the influence within the HSA.

Community Participation↗
PubMed1981

Subchronic treatment with the tricyclic antidepressant DMI increases isolation-induced fighting in rats.

Male rats treated with desmethylimipramine (DMI) (20 mg/kg for 7 days) were more likely than controls to attack an intruder rat placed in their home cage; they were also more likely to submit when attacked by the intruder. These behavioural changes were not seen at lower doses of DMI. Similar results were obtained in experiments in which is drugged animal and a control were placed together in a "neutral" cage; in this paradigm it was also found that lower doses of DMI were effective, provided that either the period of drug treatment was increased, or a delay of 3-4 days after withdrawal of DMI preceded behavioural testing. A dose dependent resistance to handling developed during drug treatment; drugged animals also showed weight loss and decreased open-field activity. In previous studies, acute treatment with tricyclic antidepressants has not been found to increase fighting; the present results underline the importance of chronic drug studies.

Aggression↗
PubMed1978

Further observations on myelinated axon numbers in normal and dystrophic mice.

Counts of the number of myelinated axons in the nerves to slow-twitch soleus and fast-twitch plantaris muscles of 129 ReJ dy/dy dystrophic mice at 4, 15 and 24 weeks of age have shown statistically significant reductions when compared to normal values. In addition muscle fibre losses had occurred in both muscles at the earliest age point studied. There was no suggestion of a progressive loss of myelinated axons. There was a greater percentage reduction in the soleus than in the plantaris nerves. The number of myelinated axons in the nerves to the plantaris and soleus muscles of the 129 ReJ +/+ normal animals was approximately the same, in contrast to the C57BL/6J strain where the soleus nerve always contained a greater number. Statistically significant reductions in the number of myelinated axons in the nerves to the medial gastrocnemius muscles of C57BL/6J dy2J/dy2J dystrophic mice have been observed at both 15 and 72 weeks of age. Muscle fibre losses have also been recorded in 72 weeks dystrophic medial gastrocnemius muscles.

Age Factors↗
PubMed1977

Dystrophic mice show age related muscle fibre and myelinated axon losses.

Although many differences between age matched normal and dystrophic animals have been found, there have been few demonstrations of a time related quantitative change from normal to a characteristically dystrophic situation within the dystrophic strain itself. Here we report such a change-normal numbers of muscle fibres present in young dystrophic mice were rapidly lost, such that older animals showed the reduced number of muscle fibres characteristic of murine dystrophy. Although these losses began after a demonstrable loss of myelinated axons had occurred, it is not possible to say if the loss of muscle fibres was a result of the loss of nerve fibres.

Aging↗
PubMed1977

The effect of prolonged inactivity upon the contraction characteristics of fast and slow mammalian twitch muscle.

1. Prolonged inactivity of soleus (slow twitch) and medial head of flexor digitorum longus (fast twitch: previously commonly known as flexor hallucis longus and hereafter referred to as FDL) muscles of the cat was produced by sodium pentobarbitone anaesthesia or spinal isolation. Isometric contraction characteristics were examined after 4-22 days and 8-49 days respectively.2. Sleep of up to 3 weeks' duration was associated with progressive changes in the weight, maximum tetanic tension, speed of contraction and absolute refractory period of fast twitch muscle. The slow muscle showed corresponding changes which were not so pronounced. Cord isolation resulted in similar changes which tended to be reversed after longer periods of disuse.3. Fast muscle frequently exhibited an after-contraction with corresponding electromyographic activity following two weeks or more of disuse.4. The time to peak of FDL was prolonged, becoming approximately one and a half times normal. In contrast to other reports of disuse, that of soleus was normal or slightly prolonged.5. The ratio of twitch to tetanic tension of FDL increased to twice the normal value or greater and remained high. The soleus muscle showed a smaller increase with evidence of a return towards normal after longer periods of inactivity.6. Absolute refractory period of FDL was considerably prolonged (more than 50%) following barbiturate sleep and this also occurred, but to a lesser degree, with soleus after 4-7 weeks of cord isolation.7. The observation that inactivity produced slowing rather than an increased speed of switch contraction indicates that aggregate activity is not the controlling factor. Changes seen in the contraction characteristics of FDL are noted to show a general similarity to those occurring following denervation.

Anesthesia, General↗
PubMed1976

Parabiotic reinnervation in normal and myopathic (BIO 14.6) hamsters.

Parabiotic reinnervation is a technique whereby the muscles of one animal can be reinnervated by peripheral nerves of another animal. This technique has been used to test the hypothesis that the myopathy in the BIO 14.6 strain of hamster may result from a derangement of the trophic function that a nerve exerts upon the muscle which it innervates. The percentage of internal nuclei in muscle fibres has been used as a criterion to define the myopathic state. The percentage of internal nuclei was high in myopathic hamster muscles but very low in normal or "self-reinnervated" normal muscles. There was no indication that the percentage of internal nuclei in myopathic muscles fell after parabiotic reinnervation with normal nerves. Similarly, there was no evidence that the percentage increased in normal muscles that had been parabiotically reinnervated with dystrophic nerves. On the basis of these results, it was concluded that there was no positive evidence in favour of a neural aetiology for the myopathy in the BIO 14.6 strain of hamsters.

Animals↗
PubMed1975

Children's articulatory and auditory awareness of differences between vowel sounds.

Thirty-four normal 4th grade children were asked to nonverbally describe tongue positions for American vowels in terms of tongue height and tongue advancement. The same children then rated all pairs of vowels in terms of perceptual-similarity. Results indicate that children are unable to provide an articulatory description of vowels in terms of conventional phonetic descriptors, but they perform in an adult-like fashion when they perceptually sort out differences in vowel quality perceived auditorily between paired vowels.

Age Factors↗
PubMed1975

Parabiotic reinnervation in normal and dystrophic mice. Part 1. Muscle weight and physiological studies.

A technique called parabiotic reinnervation has been developed. This technique consisted of suturing the sectioned peripheral end of the common peroneal nerve of a normal mouse, strain 129 ReJ +/+ to that of the distal stump remaining after sectioning that same nerve in a dystrophic mouse, strain 129 ReJ dy/dy. The animals were then parabiosed and allowed to recover and thus it was possible to innervate a dystrophic muscle with a normal nerve and vice-versa. This made it possible to test the hypothesis that a derangement of the trophic function normally exerted by a nerve on a muscle might be an element in the pathogenesis of muscular dystrophy in the adult mouse. Studies on the weights and isometric twitch characteristics of such parabiotically reinnervated muscles led to the conclusion that a derangement of the trophic function exerted by a nerve on a muscle is not an element in the pathogenesis of muscular dystrophy in the adult 129 ReJ dy/dy strain of mouse.

Animals↗
PubMed1975

Parabiotic reinnervation in normal and dystrophic mice. Part 2. Morphological studies.

The technique of parabiotic reinnervation has been used to test directly the neurogenic theory of the aetiology of muscular dystrophy in mice. Dystrophic muscles contain significantly fewer muscle fibres than their normal controls; they also have a much broader spectrum of fibre size because of a much higher proportion of very small fibres and are poorly differentiated into histochemical fibre types. These criteria were used to assess whether there was any amelioration of the dystrophic process in response to the introduction of a normal nerve supply, or whether dystrophic changes were induced in normal muscle reinnervated with a dystrophic nerve. Self-reinnervated normal and dystrophic TA and EDL muscles contained the same numbers of fibres as unoperated controls. The process of parabiosis alone resulted in no changes in normal or dystrophic muscles. In the process of parabiotic reinnervation, the efficiency of the reinnervation process was not affected by the parabiotic state. The parabiotic reinnervation of dystrophic muscle by normal nerve resulted in no significant increase in fibre numbers and the spectrum of fibre sizes was essentially the same as in unoperated dystrophic muscle. The parabiotic reinnervation of normal muscle by dystrophic nerve resulted in a reduction of fibre numbers in only some of the muscles examined. However, the spectrum of fibre diameters remained essentially normal, and the differentiation of the fibres into histochemical fibre types was characteristic of reinnervated normal muscle. There was a marked absence of necrosis or of other histological signs of dystrophy in these muscles. Since there was no positive evidence to show that conversion of normal to dystrophic, or dystrophic to normal muscle occurred under the influence of parabiotic nerve transposition, two alternative conclusions were admissible. Firstly, the influence of dystrophic nerve upon muscle may be operative in fetal or neonatal life and may be irreversible by means of the subsequent introduction of a normal nerve supply. Secondly, the dystrophic state in muscle may be determined by genetic factors independent of nerve supply.

Adenosine Triphosphatases↗