δ9-Tetrahydrocannabinol: Effects of route of administration on onset and duration of activity and tolerance development

Pigeons trained to key-peck for food reinforcement on a VI 3, were injected either orally, intramuscularly, or intravenously with ⁹-tetrahydrocannabinol and the onset and duration of this drug were determined. Onset of action was much faster for the intravenous route than the other two routes. Speed of and duration of effect were also affected by drag dosage. Using the same methods, the development of tolerance to the behavioral effects were investigated. Tolerance occurred with all three routes at about the same rate.     

Staging in tubular oxygenators — Experimental results

The oxygenation rate of blood flowing through permeable tubes can be increased by mixing or turbulence of the blood. Staging of the tubes has been suggested as one means of enhancing the oxygenation rate. A series of experiments has been performed to investigate the feasibility of staging and the results show a definite advantage in oxygen transfer compared with regular straight tubes.     

Immunity Studies for Gonorrhea

This is an abbreviated review of the results of studies carried out at the Laboratory Centre for Disease Control, towards the development of a gonococcus vaccine. This work has already been presented, in part, in four separate papers^{1, 2, 3, 4} which contain the supporting data for the views expressed in this article.     

The Recognition and Incidence of Splenic Artery Aneurysms

Calcified splenic artery aneurysms will be frequently detected if there is an awareness of their radiographic appearances. These calcified aneurysms occur most frequently in elderly females over the age of 50 years and in patients with liver disease. They may appear as large, multiple, overlapping curvilinear ring and ovoid shadows in the left upper quadrant of the abdomen at the level of D.12/L.1, or as single ring shadows anywhere along the line of the splenic artery. These shadows frequently represent completely calcified, thrombosed splenic artery aneurysms. They may also appear as smaller (0.5 cm) round shadows more heavily calcified within. These occur near the hilum of the spleen. It is estimated that these appearances will be found in approximately 2.5% of females over the age of 50 years. Calcified aneurysms are also found in patients with liver disease over the age of 50 years. These calcified aneurysms are almost always asymptomatic and benign and require no further treatment or investigation unless left upper quadrant pain is present.     

Architectural alterations of rat hind-limb skeletal muscles immobilized at different lengths

Modifications in architectural profiles of the rat soleus (Sol), medial gastrocnemius (MG), and tibialis anterior (TA) muscles were studied after hind-limb immobilization with an external brace. The muscles were chronically lengthened, shortened, or maintained at approximately resting length (neutral) for 4 weeks, when muscle weight and length, and cross-sectional areas of fibers (F-XSA) and whole muscle were measured. Compared with control muscles, the Sol and MG immobilized in a lengthened position were able to maintain muscle weight better than when immobilized neutrally (approximately 85 versus 55% of control weight) due, in part, to elongation of muscle fibers of the Sol and MG (123 and 111% of control length, respectively). In addition, the F-XSAs of lengthened Sol and MG muscles were 72 and 20% greater, respectively, compared with neutrally fixed muscle fibers. Immobilization in a shortened position resulted in the most extreme muscle atrophy due to significantly shorter fibers (86% of control Sol; 74% of control MG) and reduced F-XSA (42% of control Sol; 42% of control MG). In contrast to the Sol and MG, muscle weight, fiber length, and F-XSA of the TA immobilized with the ankle in extreme plantarflexion were not significantly different from neurtrally fixed muscle. That the TA was unaffected in this position is due presumably to a difference in the anatomic attachment of the distal tendon of this muscle, compared with that of the Sol and MG. These results suggest that for muscle affected by immobilization at extreme joint angles, chronic lengthening is a potent stimulus for elongation of muscle fibers and more normally maintained F-XSA. In contrast, the removal of this stimulus leads to extreme muscle atrophy which is manifested by reductions in both muscle fiber length and F-XSA.     

Skinfold measurement techniques for estimating percentage body fat

Skinfold thickness measurements have been advocated as an important supplementary criterion of change in behavior therapy of the obese. This paper describes technical procedures for obtaining reliable data from four body sites and provides a summary of validated and extrapolated norms for converting skinfold data to percentage body fat in males and females.