Stereotactically guided thalamotomy for treatment of parkinsonian tremor isolated to the lower extremity. Case report.

The authors present a case of tremor isolated to the lower extremity that was treated with stereotactically guided thalamotomy in a patient with Parkinson's disease. The technology that makes this procedure effective for this particular manifestation of parkinsonism is discussed.

A novel carbon fiber bundle microelectrode and modified brain slice chamber for recording long-term multiunit activity from brain slices.

The fabrication and characteristics of a novel multiunit recording electrode and modified brain slice chamber suitable for long-term recording from brain slices are described. The electrode consisted of an electrolyte-filled glass micropipette with a 20-50 microns thick wax-coated bundle of 5-micron diameter carbon fibers extending 2.5 cm from the tapered end and an AgCl-coated silver wire inserted into the open end and connected to a preamplifier. Both ends of the electrode were sealed with wax to prevent evaporation of the electrolyte. The brain slice was maintained over this extended period in an interface-type brain slice chamber modified to completely surround the slice with medium. Using this electrode, regular 24-h oscillations of spontaneous multiunit activity were recorded for 3 days from a single location in a 500 microns thick rat suprachiasmatic nucleus brain slice. Preliminary data suggest that this novel carbon fiber bundle electrode will be a favorable alternative to traditional metal electrodes for long-term recording of multiunit activity from brain slices.

Intrinsic neuronal rhythms in the suprachiasmatic nuclei and their adjustment.

The central role of the suprachiasmatic nuclei in regulating mammalian circadian rhythms is well established. We study the temporal organization of neuronal properties in the suprachiasmatic nucleus (SCN) using a rat hypothalamic brain slice preparation. Electrical properties of single neurons are monitored by extra-cellular and whole-cell patch recording techniques. The ensemble of neurons in the SCN undergoes circadian changes in spontaneous activity, membrane properties and sensitivity to phase adjustment. At any point in this cycle, diversity is observed in individual neurons' electrical properties, including firing rate, firing pattern and response to injected current. Nevertheless, the SCN generate stable, near 24 h oscillations in ensemble neuronal firing rate for at least three days in vitro. The rhythm is sinusoidal, with peak activity, a marker of phase, appearing near midday. In addition to these electrophysiological changes, the SCN undergoes sequential changes in vitro in sensitivities to adjustment. During subjective day, the SCN progresses through periods of sensitivity to cyclic AMP, serotonin, neuropeptide Y, and then to melatonin at dusk. During the subjective night, sensitivities to glutamate, cyclic GMP and then neuropeptide Y are followed by a second period of sensitivity to melatonin at dawn. Because the SCN, when maintained in vitro, is under constant conditions and isolated from afferents, these changes must be generated within the clock in the SCN. The changing sensitivities reflect underlying temporal domains that are characterized by specific sets of biochemical and molecular relationships which occur in an ordered sequence over the circadian cycle.

Do the suprachiasmatic nuclei oscillate in old rats as they do in young ones?

The basis of the decline in circadian rhythms with aging was addressed by comparing the patterns of three behavioral rhythms in young and old rats with the in vitro rhythm of neuronal activity in the suprachiasmatic nuclei (SCN), the primary circadian pacemaker. In some old rats, rhythms of body temperature, drinking, and activity retained significant 24-h periodicities in entraining light-dark cycles; in others, one or two of the rhythms became aperiodic. When these rats were 23-27.5 mo old they were killed, and single-unit firing rates in SCN brain slices were recorded continuously for 30 h. There was significant damping of mean peak neuronal firing rates in old rats compared with young. SCN neuronal activities were analyzed with reference to previous entrained behavioral rhythm patterns of individual rats as well. Neuronal activity from rats with prior aperiodic behavioral rhythms was erratic, as expected. Neuronal activity from rats that were still maintaining significant 24-h behavioral rhythmicity at the time they were killed was erratic in most cases but normally rhythmic in others. Thus there was no more congruence between the behavioral rhythms and the brain slice rhythms than there was among the behavioral rhythms alone. These results, the first to demonstrate aberrant SCN firing patterns and a decrease in amplitude in old rats, imply that aging could either disrupt coupling between SCN pacemaker cells or their output, or cause deterioration of the pacemaking properties of SCN cells.

The organization of the suprachiasmatic circadian pacemaker of the rat and its regulation by neurotransmitters and modulators.

The long-term goal of our research is to understand how cells of the suprachiasmatic nucleus (SCN) are organized to form a 24-hr biological clock, and what roles specific neurotransmitters and modulators play in timekeeping and resetting processes. We have been addressing these questions by assessing the pattern of spontaneous neuronal activity, using extracellular and whole-cell patch recording techniques in long-lived SCN brain slices from rats. We have observed that a robust pacemaker persists in the ventrolateral region of microdissected SCN, and have begun to define the electrophysiological properties of neurons in this region. Furthermore, we are investigating changing sensitivities of the SCN to resetting by exogenous neurotransmitters, such as glutamate, serotonin, and neuropeptide Y, across the circadian cycle. Our findings emphasize the complexity of organization and control of mammalian circadian timing.

Midwest wrestling study: prediction of minimal weight for high school wrestlers.

This study determined the validity of previously published or newly derived equations to predict fat-free body mass (FFB) in high school wrestlers from the midwestern United States. Five laboratories participated in the data-pooling study (total sample of 860 subjects). Measures included body composition by underwater weighing and anthropometric measurements of body mass, stature, and selected circumferences, diameters, and skinfolds. Cross-validation of selected equations to predict FFB revealed the lowest levels of error from the equations of Lohman, Thorland et al., Katch and McArdle, and Behnke and Wilmore. Modification of the constants in these equations or generation of new equations did not substantially reduce prediction error. Overall, total error for these top equations ranged from 2.44 to 2.59 kg. However, based on observed trends, this error was of lower magnitude with the younger and lighter subjects and of higher magnitude with the older and heavier subjects. We conclude that these equations could be used singularly or collectively to determine FFB, and a minimal weight could then be derived and assigned to a scholastic wrestler.

Physical activity and hypophysectomy on the aerobic capacity of ligaments and tendons.

Traditionally, ligaments and tendons (L and T) have been regarded as metabolically inert structures. However, sufficient biochemical evidence on the metabolism of collagen has indicated that such a concept is no longer tenable. To determine whether L and T respond to increased or decreased levels of chronic exercise, studies were undertaken to measure their aerobic capacities. For comparative purposes, similar measurements were obtained from liver and skeletal muscles secured from normal and hypophysectomized male rats. Oxygen consumption and cytochrome oxidase (CO) activity was recorded from cell suspensions that had been prepared with the inclusion of collagenase and with elastase added to the medium. The O2 results showed that L and T had values that were approximately 10 times lower than liver tissue and 7.5 times less than the means from skeletal muscles. Hypophysectomy caused marked reductions in O2 uptake of liver and muscle tissues; but had no impact on L and T. When CO activity of these connective tissues were evaluated, immobilization and hypophysectomy caused significant reductions that ranged from -36% to -59% respectively. Training, on the other hand, resulted in increases of less than 10% in the activity of this enzyme within L and T while being elevated in muscle tissue by 58%. It was concluded that the metabolic activity of L and T was lowered with decreased levels of physical activity but it was unclear why chronic exercise did not produce the opposite effect.

Response of immunosympathectomized rats to training.

The influence of chronic exercise was investigated with male rats assigned to normal (N) and sympathectomized (IS) groups. Animals in the latter group were injected daily for 5 days with the antiserum to the nerve growth factor beginning 24 h after birth. Training was introduced when the animals were 35--45 days old and lasted for 12 wk. The exercise program used by both groups was progressive in nature and modified in accordance with the performance capability of the IS animals. When IS and N rats performed a standardized treadmill test, the IS rats had significantly higher rectal temperatures than normal animals. Significant training differences were observed in resting heart rate and in mean blood pressures, but only in the N animals. However, both trained groups exhibited significantly less vasoconstricting ability to conditions of lower body negative pressure than their nontrained controls. Varied doses of epinephrine and norepinephrine were injected into both groups and training per se had no significant influence on the responses recorded. However, both IS group had changes which indicated that a supersensitivity to catecholamines had occurred. Although selective training adaptations can occur without sympathetic nerves, it was concluded that an intact nervous system was essential for maximal training effects to occur.

Iowa wrestling study: weight classification systems.

Many wrestlers lose a large amount of weight in a relatively short period of time to become certified for interscholastic competition. In most states, there are twelve certified weight classes with intervals ranging from 6 to 18 pounds. Using anthropometric data obtained from 834 "average" wrestlers that were measured 5-8 weeks before competition, we predicted their "minimal" body weights and assigned them into arbitrarily designated weight classes of 6, 8 and 10 pound intervals. In addition, the 1973-74 and the 1974-75 certifying records for Iowa wrestlers were examined with regard to frequency distribution patterns. The results indicated that the majority of students were certifying for a weight classes. In fast, forty percent of the more than 8900 students were certified for the 119-138 classes and 57% of the population were located within the 112-145 weight classes. Inspection of the frequency distribution patterns of wrestlers assigned to the arbitrary classes also showed a marked concentration of wrestlers who weighed between 120 and 140 pounds and this relationship became more apparent when ten pound intervals were considered. From these findings we recommended that state high school associations consider: 1) allowing more than one wrestler per team to compete in a single weight class; 2) porviding more weight classes than the current twelve; and 3) promoting body composition assessments during the pre-season period in order to minimize the problems created by the "making of weight."

Iowa wrestling study: changes in the urinary profiles of wrestlers prior to and after competition.

During the 1973 and 1974 state high school wrestling championships, urine samples were obtained from wrestlers prior to the weigh-in, immediately before they wrestled, and immediately after the subjects had completed their match. Specific gravity, osmolarity, pH, sodium and potassium determinations, as well as qualitative tests for protein and ketones, indicated that the wrestlers were in a dehydrated state at the time of weigh-in. After the five hour interim between the weigh-in and the first match, all but the pH measure remained essentially unchanged. This absence of significant changes in the urinary profile suggests that the wrestlers were unable to rehydrate during the five hour time period between the weigh-in and the first match and that they were competing in a dehydrated state. Urine samples collected after competition were significantly lower in specific gravity, osmolarity and potassium concentration than samples obtained before the match. The urinary potassium levels were of interest because at the three conditions (weigh-in, before the first match, after competition) they were 73-182% higher than values reported for high school students who were nonwrestlers.