Search PubMed⌕ Search

Biomedical subjects

J Quinlan

Publications and source records attributed to J Quinlan.

11 recordsLinked to original sources
PubMed1993

From the families...

Explore the source record for details and available documents.

Adaptation, Psychological↗
PubMed1985

System for automatic activation of skinned muscle fibers.

A system is described for automatically changing the solutions surrounding skinned muscle fibers at a controlled temperature. The system consists of a complex muscle chamber and solenoid valve-controlled vacuum-driven syringe pumps. The chamber has a muscle trough, a conduit for circulating coolant, and channels for precooling solutions. After traveling through the cooling channels, the solutions are injected into one end of the muscle trough and removed by suction at the other. The volume of the trough (approximately 40 microliter) is kept as low as possible to minimize the amount of solution required for complete solution exchange (approximately 400 microliter). Solution changes are complete within 400 ms. The timing of the sequence of solution changes is precisely controlled by digital timers that activate the solenoid valves of the pumps. By exposing the fibers briefly to a high concentration of free calcium and then changing to a buffered calcium solution, it is possible to achieve steady tension levels in 1-2 s, even when partially activating the fibers. Such rapid partial activation is possible because the exposure to free calcium can be precisely timed. The timers also allow the solution changes to be synchronized with other perturbations.

Animals↗
PubMed1984

Lack of effect of exercise on platelet activation and platelet reactivity.

The effects of brief maximal exertion on platelet activation and reactivity have been studied in normal subjects. Although initial studies in seven subjects showed apparent exercise-induced platelet activation and enhanced platelet reactivity, these findings could not be confirmed in 13 subjects studied subsequently. There was no change in the platelet aggregate ratio, platelet fluorescent granule number or the plasma platelet factor 4 (PF4) or beta-thromboglobulin, although transient and significant increases in the platelet count and plasma heparin neutralizing activity (HNA) occurred. These results were reproducible in subjects studied more than once. It is postulated that in vitro platelet activation, most likely associated with blood collection, explained the initial results. It is concluded from the subsequent studies that in normal subjects brief maximal exercise causes neither platelet activation nor altered platelet reactivity but does cause a transient increase in the platelet count. The increase in HNA with exertion, without any accompanying increase in the PF4, demonstrates that these assays measure different substances and that the increase in HNA following exertion is most unlikely to be derived from platelets.

Adult↗
PubMed1983

Twitch potentiation after voluntary contraction.

Twitch potentiation was studied in human tibialis anterior (TA) and plantarflexor (PF) muscles after maximal voluntary contractions (MVCs). Potentiation was greater in TA and other dorsiflexor (DF) muscles than in PF and was dependent on the intensity of the voluntary effect. It was also observed that potentiation was maximal after MVCs of approximately 10-s duration; after longer voluntary contractions, the potentiation was partially suppressed by fatigue, especially in the TA. Potentiation was significantly larger when muscles were tested in a shortened position regardless of the position at which the preceding MVCs had been performed.

Adult↗
PubMed1983

A method for detecting functional weakness.

A simple electrophysiological method is described for detecting weaknes of psychiatric origin. The method involves the interpolation of a single indirect stimulus to a muscle during the course of a supposedly maximal voluntary contraction. Incomplete motor activation is revealed by the presence of a twitch superimposed on the recording of voluntary torque.

Ankle↗
PubMed1982

Influence of joint position on ankle plantarflexion in humans.

The contractile properties of the triceps surae (medial and lateral gastrocnemii and soleus) have been studied in humans. In comparison with most other human muscles, the triceps complex had a slow twitch (mean contraction and half-relaxation times 112.4 +/- 11.1 and 99.6 +/- 14.4 ms, respectively) and a low tetanus fusion frequency (60 Hz). Stretching the muscle caused both the contraction and half-relaxation times to become longer. With the knee bent, the optimum length for torque development corresponded to almost full dorsiflexion of the ankle. Similar results were obtained with the knee extended. The optimum position of the ankle differed considerably from the position of the joint when the leg was at rest. Although the position of the ankle joint affected electromyographic (EMG) activity recorded during maximal voluntary contraction, there was little change in the EMG-to-M wave ratio.

Adult↗
PubMed1981

Influence of joint position on ankle dorsiflexion in humans.

A method is described for investigating the contractile properties of the dorsiflexor muscles of the ankle. With the joint in the midposition the tibialis anterior was found to contribute less than half of the maximum voluntary torque, the remainder presumably being provided by the long extensors of the toes. The mean contraction and half-relaxation times of tibialis anterior muscles in healthy young men were 81.2 +/- 7.4 (SD) ms and 83.6 +/- 17.2 ms, respectively. When the tibialis anterior was stretched, the twitch became slower and more complete fusion of the contractions occurred during tetanic stimulation at low frequencies. Stimulation of tibialis anterior at 30 and 40 Hz disclosed that the optimum length of the muscle corresponded to about 10 degrees of plantarflexion. Maximum voluntary torque was also developed at 10 degrees of plantarflexion and decreased sharply as the ankle was dorsiflex beyond 5 degrees. The position assumed by the ankle joint at rest depended on whether the subject was sitting, standing, or lying, but was always greater, in the plantarflexed direction, than the "optimum" position for torque development. At low rates of stimulation the torque continued to increase throughout the full range of plantarflexion, probably because of the elasticity of the tendon. During maximum effort motoneuronal excitability did not appear to be influenced significantly by changes in joint angle.

Adult↗
PubMedDate not supplied

Psychiatric home care: an introduction.

Healthcare has undergone many changes in the past 5 years. Hospitalization has become extremely expensive to the consumer and the payor. Alternative healthcare services are being considered and used, with the emphasis on cost containment and cost and clinical effectiveness. Psychiatric home care is clinically effective and less costly.

Aged↗