Sensorimotor cortical representation in the rat and the role of the cortex in the production of sensory myoclonic jerks.

1. After administration of 1,2-dihydroxybenzene (catechol) to anaesthetized rats, rabbits and cats, a reflex jerk consisting of three distinct components was evoked in the limb muscles by peripheral stimulation. The second component of the jerk in the forelimb muscles of all three animals was specifically abolished by lesions confined to the contralateral forelimb sensorimotor cortex.

Inhibition of hormone-stimulated lipolysis by clofibrate. A possible mechanism for its hypolipidemic action.

The present study was undertaken to investigate the mechanism of the antilipolytic action of clofibrate (p-chlorophenoxyisobutyrate). Clofibrate, in the dose range of 10-80 mg/199 ml, inhibited the initial rate of norepinephrine-stimulated lipolysis 17-44 percent in isolated rat fat cells. At a dose corresponding to therapeutic levels in vivo (10 mg/100 ml) clofibrate also inhibited hormone-stimulated lipolysis by 20-30 percent in fragments of human subcutaneous fat.

Regulation of cholesterol storage in adipose tissue.

Adipose tissue is a major site of cholesterol storage. In an attempt to define mechanisms controlling this process, a variety of nutritional and metabolic alterations were employed and their effects on adipose tissue cholesterol levels were determined by direct chemical analysis. When rats were raised on Purina chow, a linear increase in the cholesterol/DNA ratio in relation to animal weight (from 120 g [5-6 wk] to 700 g [2 yr]) occurred.

Bimodal effect of insulin on hormone-stimulated lipolysis: relation to intracellular 3',5'-cyclic adenylic acid and free fatty acid levels.

The present study was undertaken to determine the relationship between the antilipolytic and lipolytic effects of insulin on hormone-stimulated lipolysis and the mechanisms of these reactions. The dose-response curve of norepinephrine-stimulated lipolysis in rat adipocytes was not sigmoidal but biphasic in nature. Intracellular free fatty acid levels were linearly related to lipolytic rate and also described a biphasic profile in response to increments in norepinephrine concentration.

Studies on the compartmentation of lipid in adipose cells. II. Cholesterol accumulation and distribution in adipose tissue components.

Adipose tissue was shown to contain 0.6-1.6 mg of cholesterol per gram wet weight.

Reduction in adipocyte ATP by lipolytic agents: relation to intracellular free fatty acid accumulation.

Epinephrine, norepinephrine, ACTH, and dibutyryl 3',5'-cyclic AMP reduced adipocyte ATP levels during 60 min incubation; glucose displayed a protective effect. The reduction in adipocyte ATP levels could not be attributed solely to: a direct hormone effect, deficiency in metabolic substrate, activation of adenyl cyclase with ATP consumption, loss of adenine nucleotide from the cell or loss of cells during incubation, lipolytic rate per se, or extracellular accumulation of FFA or glycerol. To determine whether intracellular FFA accumulation was a causative factor, intracellular FFA levels were measured during hormone-stimulated lipolysis.

Intracellular accumulation of free fatty acids in isolated white adipose cells.

A simple, rapid, and accurate method was developed for measuring intracellular FFA levels in isolated white adipose cells using sucrose-(14)C or inulin carboxyl-(14)C as nontransportable, nonutilizable markers of the extracellular space. Following incubation, medium and cells were separated by centrifugation and the infranatant medium was removed by aspiration. The volume of medium trapped between cells was determined by measuring the amount of sucrose-(14)C or inulin carboxyl-(14)C retained in the floating packed adipose cells.

Studies on the compartmentation of lipid in adipose cells. I. Subcellular distribution, composition, and transport of newly synthesized lipid: liposomes.

The subcellular distribution and composition of endogenously synthesized lipid in isolated white adipose cells were studied to determine the nature and extent of lipid compartmentation. After brief incubation of cells with labeled glucose, acetate, or palmitic acid, over 90% of newly synthesized triglyceride was localized in the bulk-lipid phase, indicating rapid intracellular transport and storage. From 13 to 20% of the newly formed lipid was diglyceride, and over 95% of it was localized in the central lipid-storage vacuole rather than in organelle systems concerned with esterification, thus indicating intracellular segregation of newly synthesized partial glycerides.