Recovery profile of single motoneurons after electrical stimuli in man

The H-reflex of 120 soleus motoneurons was recorded using fibre EMG. The recovery profile of these motoneurons was studied during monitoring surface H-reflex records in 28 adult subjects. The spectrum of motoneurons tested was homogeneous with two extremes of neurons having different characteristics. A motoneuron population (forming about 69% of our sample) had a high threshold level for electrical stimuli, short recovery time, and short recovery fringe time (called type A). A second population of motoneurons (forming about 20-30% of our sample) had a low threshold level for electrical stimuli, long recovery fringe time (called type B). During an isometric muscle contraction every motoneuron showed an early shift in recovery time (i.e. each had a shorter recovery time) with shortened recovery fringe time. These changes were larger for motoneurons type B than motoneurons type A. With paired identical electrical stimuli of varying interstimulus intervals a motoneuron may fire in response to the conditioning and test stimuli giving an H2, but not in response to both stimuli. This occurred for interstimulus intervals of 4-11 ms. A strong inhibition period was recorded with interstimulus intervals of 12-80 ms in which all motoneurons did not show any recovery. Most motoneurons recovered in orderly fashion between 80 and 300 ms of interstimulus interval, and this recovery coincided with the fast recovery recorded in surface H-reflex. All motoneurons were recovered by 3000 ms of interstimulus intervals. These findings emphasize the importance of eliciting the H-reflex every 3-5 s in H-reflex methodology in order to be assured that all excited motoneurons have been recovered.     

Rhinovirus infections in Tecumseh, Michigan: frequency of illness and number of serotypes

We studied rhinovirus-associated illnesses from 1976 to 1981 among residents of the community of Tecumseh, Michigan, in a continuation of similar studies done in 1966-1971. Rhinoviruses were the most frequently isolated respiratory pathogen in all age groups, including young children. The pattern of age-specific isolation rates was similar to that for total respiratory illness. Rhinovirus-associated illnesses were generally mild but of relatively long duration; restriction of daily activity was frequent, especially in certain age groups. Typing of all isolates has been completed; with high-quality antisera nearly all isolates could be typed. Thus, new serotypes are probably not evolving, and most have already been identified. Differences in frequency of occurrences of different serotypes were evident, but ranking in order of importance was difficult based on existing data.     

Relation between temperature and processes of spontaneous quantum and non-quantum mediator release from motor nerve endings of the mouse

The spontaneous quantal and nonquantal acetylcholine release was investigated at the temperature range from 10 to 35 degrees C in white mouse semidiaphragm. The quantal release was evaluated by calculation of miniature end-plate potentials frequency, while the nonquantal one--from the H-effect value. The spontaneous quantal release increased exponentially with the temperature growth. The temperature dependence of the nonquantal release showed two relative maxima: at 20 degrees and 35 degrees C. At 10 degrees C the nonquantal release was absent. The value of calculated effective energy of activation of the quantal release was 57.0 kJ/mol in the investigated temperature range. The effective energy of activation for the nonquantal release process in intervals 15-20 degrees C and 25-35 degrees C was 45.5 and 38.2 kJ/mol, relatively. It is suggested that the nonquantal release is rather due to active transport processes than to simple diffusion of acetylcholine molecules.     

Factors relating to the sensory acuity of limbs with peripheral vascular insufficiency

We examined several possible causes for the high incidence of poor sensory acuity in the limbs of 176 patients with moderate to severe peripheral vascular insufficiency. We investigated the relationships of diabetes, alcoholism, and smoking, as well as the severity of peripheral vascular disease, to the integrity of basic sensory modalities such as two-point discrimination and perception of light touch. The presence or absence of diabetes exerted the strongest effect on peripheral sensation. In patients who did not have diabetes, sensation in the limbs was most strongly affected by whether the patient was an alcoholic. Smoking did not have a significant effect on limb sensation. Among nondiabetic, nonalcoholic patients, there was a weak residual effect related to the severity of the peripheral vascular insufficiency. Even among these patients, however, systemic factors predominated in determining the loss of sensation. We also examined the extent to which loss of sensation might be related to the development of ulcers. Among patients who were not diabetic, there was a highly significant relationship between loss of sensation and the presence of limb ulceration. Surprisingly, however, there was no discernable relationship between the presence of ulcers in diabetic patients and the degree of loss of peripheral sensation. This result suggests that a large percentage of ulcers seen in diabetic patients are not of neurogenic origin.     

Using sobriety tests to increase awareness of alcohol impairment

There is a need to investigate methods by which drinkers canbe made aware of their level of alcohol impairment prior todriving. In the current research, 195 students at various bloodalcohol concentration (BAC) levels participated in an evaluationof three simple sobriety tests: a ruler drop/reaction time task,a balance test and a verbal task. Although self-reported measuresof impairment were the best predictors of BAC, both the rulerdrop and body balance tests accounted for significant portionsof BAC variance. These tasks were also perceived by the studentsas reflecting substantial driving ability. Unfortunately, asBAC increased, poor test performance was less likely to resultin a decision not to drive. These results are discussed in termsof the need to continue studying ways to educate drinkers abouttheir level of alcohol impairment so that they can make informeddrinking/driving decisions.