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Biomedical subjects

J Alberts

Publications and source records attributed to J Alberts.

6 recordsLinked to original sources
PubMed1998

Reach-to-grasp movements during obstacle avoidance.

The transport and grip components are two controlled components of a prehensile movement. These components are coordinated so that objects of varying size and shape resting in diverse locations can be grasped easily. It has been suggested that the timing between these two components is a specified parameter, although the origin of such timing is unknown. The present study examines the interdependency of the reach and grasp components when the transport component is modified by placing an obstacle of varying height (9 cm and 11 cm) in the hand path between the starting position and the target object location. Subjects were asked to reach over a Plexiglas barrier and grasp a 2-cm dowel. To reach the object, the subject had to elevate the hand. At issue in this experiment is whether changes in hand path trajectory caused by obstacle avoidance produce corresponding changes in the kinematics of grip aperture. The findings showed that reaching in the presence of an obstacle resulted in the prolongation of most transport component time parameters except peak acceleration and a few amplitude parameters. Changes in the transport component also produced systematic prolongation in all time parameters of grip kinematics, including grip closure time. Temporal prolongation was also reflected in a significant decrease in grip opening and closing velocity; only relative time-to-peak closing velocity was maintained. Closure distance and maximum grip aperture were smaller for the obstacle conditions. Together with the observed smaller variability for the distance to peak aperture, these findings suggest that spatial localization of the hand aperture is an important prehensile movement control feature. Parameterization processes for the grip component are closely linked to those of the transport component, and their organization appears to be interdependent.

Adult↗
PubMed1992

"Primatization" of recombinant antibodies for immunotherapy of human diseases: a macaque/human chimeric antibody against human CD4.

Immunoglobulin variable region genes from non-human primates, cynomolgus macaques, were shown to have 85%-98% homology with human immunoglobulin sequences and yet macaques are phylogenetically distant enough to respond against conserved human antigens. Immunoglobulin genes were isolated from monkeys immunized with human CD4 antigen and a human/monkey chimeric anti-CD4 antibody with 91-92% homology to human immunoglobulin framework regions was cloned and expressed. The antibody has an apparent affinity of 3.2 x 10(-11) M and exhibits potent immunosuppressive properties in vitro.

Animals↗
PubMed1990

Hemodynamic events in a prospective randomized trial of propranolol versus placebo in the prevention of a first variceal hemorrhage.

In a double-blind randomized trial, the hemodynamic events following the administration of propranolol (n = 51) or a placebo (n = 51) were prospectively studied in cirrhotic patients with esophageal varices. The hepatic venous pressure gradient, heart rate, and variceal size were determined at the baseline and 3, 12, and 24 months after the beginning of therapy. Baseline values were similar in both groups. At 3 months, the hepatic venous pressure gradient decreased significantly in propranolol-treated patients (from 18.1 +/- 4.2 to 15.7 +/- 3.4 mm Hg; P less than 0.05) but not in patients receiving the placebo (19.6 +/- 6.8 to 17.5 +/- 5.3 mm Hg; NS). At subsequent time intervals this gradient decreased significantly from the baseline value in both groups. Heart rate decreased significantly in the propranolol-treated group at all times (P less than 0.001). Variceal hemorrhage occurred in 13 patients (11 placebo-, 2 propranolol-treated; P less than 0.01), all of whom had a hepatic venous pressure gradient greater than 12 mm Hg. In 21 patients (14 propranolol-, 7 placebo-treated) the hepatic venous pressure gradient decreased to less than or equal to 12 mm Hg; none of them bled from esophageal varices, and their mortality rate also decreased. Because most of the bleeding events occurred during the first year (10 placebo-, 1 propranolol-treated; P less than 0.01), propranolol seems to have its protective effect during the period associated with the largest reduction in the hepatic venous pressure gradient. Because a reduction in the hepatic venous pressure gradient to less than 12 mm Hg protects from variceal bleeding and increases the rate of survival, this should be the aim of the pharmacological therapy of portal hypertension.

Adult↗
PubMed1985

Synthetic pheromones that promote inter-male aggression in mice.

Two volatile constituents of male mouse urine, dehydro-exo-brevicomin and 2-(sec-butyl)-dihydrothiazole, have been found active in bioassays of inter-male aggressive behavior. The two synthetic compounds act synergistically when added to castrated male urine but not when added to water, and they provoke fighting that is quantitatively and qualitatively comparable to that elicited by intact male urine.

Aggression↗