Functional properties of rat and human neocortical voltage-sensitive sodium currents

1. The functional properties of sodium currents in acutely dissociated adult human, neonatal rat [postnatal day (P) 3 and P10], and mature rat (P21-23) neocortical pyramidal neurons were studied using whole-cell patch-clamp techniques. 2. The voltage dependence of activation and steady-state inactivation of neonatal rat sodium currents was shifted in the positive direction when compared with mature rat sodium currents. In contrast, no difference was detected between the voltage dependence of activation and steady-state inactivation of mature rat and adult human sodium currents. 3. The fast inactivation of rat (neonatal and mature) and human neocortical sodium currents were best fit with three components; a fast decay component, a slow decay component, and a persistent component. The magnitude of the persistent current in neocortical neurons averaged 1-3% of the peak current. Inactivation was faster for sodium currents in neonatal rat neocortical neurons than in mature neurons. No difference was detected in the kinetics of inactivation between mature rat and adult human sodium currents. 4. Saxitoxin (STX) inhibited neuronal sodium currents at nanomolar concentrations in neonatal and mature rat and adult human neocortical neurons. STX-insensitive channels were not detected. 5. STX affinity was also assayed using 3H-STX. A single high-affinity binding site was found in neonatal rat, mature rat, and adult human neocortical tissue. A developmental increase in STX binding site density in the rat neocortex was tightly correlated with the increase in the sodium current density (normalized to cell capacitance). Human neocortical tissue and mature rat neocortical tissue did not differ in STX binding site density or sodium current density. 6. From these electrophysiological and autoradiographic studies we conclude that 1) the increase in the normalized sodium current density and STX binding density with age postnatally reflects an increase in binding sites of sodium channels functionally expressed on neuronal membranes, 2) the functional differences in channel behavior with maturation can explain the higher threshold for excitation in neonatal neocortical neurons and the increase in accommodation or adaptation in firing in the mature neuron, and 3) mature rat neocortical neurons represent a valid model for the study of adult human pyramidal neocortical neurons in terms of Na+ channel expression and function.     

Surgical management of osteochondritis dissecans of the capitellum

Ten cases of osteochondritis dissecans of the humeral capitellum which were treated surgically are reviewed. All 10 cases were males and involved the dominant side. The ages at surgery ranged from 13 to 17 years. Follow-up ranged from 1 to 7 years. All of the youths had competed in organized athletics, either baseball or football. By position there were three pitchers, two catchers, two infielders, and one outfielder; in addition there were one quarterback and one linebacker. Only one patient presented with locking of the elbow, whereas the others presented with pain and limitation of extension. The locked elbow was explored immediately and the others were explored after immobilization failed to relieve their symptoms. In seven of the joints a loose fragment of the capitellum was found lying either in the joint or in a defect in the capitellum. The fragment had multiple small holes. In three cases there was no loose fragment. In this situation a corticol window was cut above the capitellum. The capitellum was then drilled and bone was grafted from above. Over all, there were one excellent, six good, one fair, and two poor results. There seemed to be little difference between curretting alone or curetting and drilling. The cases with the cartilage intact and bone grafted from above did worse, with one fair and one poor result of three cases. The two poor results required further surgery, which consisted of partial excision of the capitellum. All cases lacked elbow extension before and after surgery, but nine of 10 gained some motion after surgery. Pre- and postoperative x-rays are shown in this report and a brief review of the literature concerning osteochondritis dissecans is presented.     

The Yugoslavia cardiovascular disease study. II. Factors in the incidence of coronary heart disease

In a 7-year follow-up of 11,121 Yugoslav men first examined in 1964-1965 when they were 35-62 years old, it was found that the incidence of coronary heart disease (CHD) was one-fourth that of a comparable Framingham (USA) group. Incidence in rural men was only 59% of urban men. In both urban and rural groups, men with higher blood pressures had greater CHD incidence, and cigarette smoking was also associated with greater incidence. In the urban but not the rural groups serum cholesterol and weight/height were also CHD risk factors. Levels of serum cholesterol and weight were lower in urban Yugoslavia than Framingham and lowest in rural Yugoslavia. At the same levels of these characteristics Framingham incidence was 3 times that in Yugoslavia. At the very low rural levels of weight and blood pressure CHD incidence was the same in urban as rural Yugoslav groups.