Phospholipase C-induced "Na-channels" in the crystalline lens.

When present on the posterior side of the lens (in vitro in a divided Ussing-type chamber) phospholipase C increased translenticular p.d. and short-circuit current (SCC) while on the anterior it decreased these parameters. The electrical resistance, $\text{Δ}\text{p.d.}\text{Δ}\text{SCC}$, was unchanged. These effects were absent or reduced when the side of the lens exposed to the enzyme was bathed with Na-free, choline Ringer. On the posterior, the enzyme increased Na flux from the posterior to anterior bathing solutions but the Na flux in the opposite direction was unchanged. On the anterior it had the converse effect. Fluxes of K and Cl were unaffected. The enzyme increased the intracellular accumulation of Na when present on either side. Lithium could partly substitute for Na as the effects on p.d. and SCC were still seen. The results are of interest both with respect to the mechanism of Na movement across the lens and the possible nature of “Na-channels” in membranes.     

A comparative study of low doses of heparin and a heparin analogue in the prevention of postoperative deep vein thrombosis

The efficacy of heparin and a semi-synthetic heparin analogue as compared for the prevention of postoperative deep vein thrombosis (DVT) in a prospective, randomized trial involving 200 patients. 12 (12.5%) out of 95 patients in the heparin group developed DVT compared to 6 (6.3%) out of 94 patients who received the analogue. Serious bleeding did not occur in any of the patients in either group and the difference in the operative and postoperative bleeding was not statistically significant. In this entire series of 190 patients, wound haematoma developed in 3, and all were in the heparin group. In 50 patients (25 in each group) plasma heparin levels, kaolincephalin clotting time (KCCT) and antithrombin III (At IIII) activity were measured in the samples withdrawn before, during and immediately after surgery and also on the first postoperative day. Significantly higher mean plasma heparin levels were obtained in the pat-ients receiving the analogue than those receiving heparin. Yet there was no difference in the prolongation of the KCCT observed in the two groups when measured by the clotting assay; the analogue had greater potentiating effect on At III activity as compared to heparin; the difference being statistically significant (p < 0.005). These findings provide further evidence for our preliminary observations that the heparin analogue selectively potentiates antithrombin III activity $\text{in vivo}$ while having little effect on overall clotting. The results presented indicate that it is as effective as heparin in preventing postoperative DVT.     

The choroidal artery to the fourth ventricle and its radiological significance

The choroidal artery to the fourth ventricle has been studied in 25 brain specimens and 100 normal posterior fossa angiograms, including 25 angiotomograms. Its variable origin, course and radiological significance have been stressed.     

Residents' hours and supervision

One year of graduate medical education, the internship, had become the norm for graduates of most U.S. medical schools by 1920, and subsequently was adopted by most states as a criterion for licensure. The original concept of a "resident physician" carried with it responsibility for patients 24 hours per day, seven days per week. Recent public and media attention to the issues of residents' supervision and working hours has led to governmental efforts to restrict their hours and set minimum requirements for supervision. New York is the first state to impose specific requirements. The New York recommendations have implications for the concept of graded responsibility for residents, for learning the natural course of illness, and for the need to provide service in hospitals. Further, the recommendations raise four objections: they do not recognize differences by type of specialty or year of training; they might affect the length of time needed to acquire aggregate clinical skills; they affect different types of hospitals differently; and they would have a major effect on physician manpower. Hospitals and residency programs will face several difficult choices in responding to the regulations. To provide its members with guidelines for action, the Executive Council of the Association of American Medical Colleges has issued recommendations for residency hours and supervision, including the use of an 80-hour work-week averaged over four weeks, the continued use of graded supervision of residents in emergency rooms and in inpatient and ambulatory settings, and control of housestaff moonlighting.