L.J. Brown

Catecholamine-induced lipolysis in swine

1. 1. Catecholamines stimulate lipolysis in in vitro preparations from swine. The order of effectiveness of the adrenergic agonists was isoproterenol > norepinephrine > epinephrine, and the relative potency was ca. 1 : 15 : 35. 2. 2. The use of adrenergic blocking agents indicated that the epinephrine agonistic response was inhibited by low concentrations of propanolol and alprenolol and by higher concentrations of sotalol. 3. 3. The inhibition by these β-adrenergic antagonists plus the greater response to isoproterenol indicates that the receptors were primarily of the β-type. 4. 4. The epinephrine agonistic response could be blocked by phentolamine, an α-adrenergic blocker but only at extremely great concentrations.

Ontogenic development of swine (Sus domesticus) adipose tissue lipases.

1. The in vitro activities of lipoprotein lipase (LPL) and hormone sensitive lipase (HSL) were examined in adipose tissue preparations from pigs 0-150 days of age. 2. The activities of both LPL and HSL increased 3- to 4-fold between birth and day 2 postpartum, remained at relatively high levels through weaning, and fell sharply in the oldest animals (150 days). 3. The decline in enzyme activities at older ages could partially be attributed to an increase in adipocyte size.

Ontogeny of Adenylate Cyclase and Phosphodiesterase Activities in Swine Tissues

The ontogenic patterns of the basal- and fluoride-stimulated adenylate cyclase and the cAMP phosphodiesterase activites as well as the tissue levels of cAMP were assessed in swine adipose tissue, heart, skeletal muscle, and liver. The developmental patterns were complex. However, there was a general tendency in all tissues toward lower enzyme activities in the oldest animals (150 days) for both enzymes. In adipose tissue, the decreased enzyme levels could partially be attributed to an increase in adipocyte size.

In vitro activity of sorghum-selective fluorophenyl urea herbicides

Abstract The use of N -cyclopropyl- N′ -(2-fluorophenyl) urea as a selective herbicide in grain sorghum has recently been disclosed (U.S.P. 4,344,916). Evaluation of analogs of this compound has included two assays on isolated pea chloroplasts—photosynthetic electron transport and competition for atrazine binding sites. Of all the analogs studied in at least one of these assays, the most active in vitro were the N -cyclopropyl-, N-n -butyl-, and N-n -pentyl-derivatives of 2,5-difluorophenyl urea. The two in vitro assays correlated well with each other, and binding activity demonstrated a strong correlation with whole-plant phytotoxicity following postemergence application. Several postulated sorghum metabolites of N -cyclopropyl- N′ -(2-fluorophenyl) urea showed weak or no activity in vitro , as would be expected from the compouds selectivity properties.

Substrates and inhibitors of ATP: Citrate lyase from adipose tissue

Abstract 1. 1. The ATP:citrate lyase from swine adipose tissue can be assayed using conditions to produce either linear or biphasic double-reciprocal plots of citrate saturation curves; the former had lesser velocity than the latter. 2. 2. The ionic forms of the substrate were probably Mg·ATP 2− and either Mg·citrate − or citrate 3− . There was little effect of ATP 4− and inhibition by high Mg 2+ concentrations. 3. 3. The enzyme was inhibited by hydroxycitrate and by ADP, both probably as the magnesium complexes. 4. 4. The ionic form of the inhibitor, tricarballylate, was uncertain.