Acute effects of beta-adrenergic agonists on porcine adipocyte metabolism in vitro

Backfat was obtained at slaughter from market weight hogs to study the acute effects of clenbuterol (CB), ractopamine (RAC) or epinephrine (EPI), in the presence and absence of theophylline (THEO) or adenosine deaminase (ADA), on rates of lipolysis and fatty acid synthesis in vitro. Only EPI increased lipolytic rate in the absence of THEO or ADA. In the presence of THEO or ADA, RAC and CB were lipolytic, although CB had a lower maximal response. With THEO present, RAC and EPI increased lipolysis with a similar potency and responsiveness. Lipolytic responses from all agonists were prevented by propranolol. Insulin stimulated glucose incorporation into fatty acids 50 to 100%; stimulated rates were not influenced by any agonist, either alone or in the presence of ADA. When THEO was present, EPI and RAC inhibited fatty acid synthesis approximately 50%. Clenbuterol was not inhibitory under any conditions. Results indicate that, under appropriate conditions, beta-adrenergic agents increase lipolysis and decrease lipogenesis in porcine adipocytes. Combined evidence suggests that lipolysis is more sensitive to beta-adrenergic stimulation than is insulin-stimulated lipogenesis. Finally, RAC and CB possess only partial agonist activity relative to EPI, CB being least active.     

Determination of the affinity of ractopamine and clenbuterol for the beta-adrenoceptor of the porcine adipocyte

Dissociation constants (Kd) of ractopamine and clenbuterol for the swine adipocyte beta-adrenergic receptor were estimated from competition studies with epinephrine for the stimulation of lipolysis. Both compounds competitively inhibited epinephrine-stimulated lipolysis in the absence of adenosine deaminase. Three methods for estimating Kd values were used and similar estimates were obtained with each method. Ractopamine and clenbuterol showed greater affinity for the beta-receptor than did epinephrine and had similar Kd values of 1 to 2 x 10(-7) M. The low capacity of ractopamine and clenbuterol to stimulate lipolysis in vitro does not result from poor coupling to the beta-receptor. Ractopamine and clenbuterol may be considered partial agonists, possessing high affinity for the beta-adrenoceptor but exhibiting a relative ineffectiveness for adenylate cyclase activation.     

Hubble Space Telescope Imaging of Neptune's Cloud Structure in 1994

Images of Neptune taken at six wavelengths with the Hubble Space Telescope in October and November 1994 revealed several atmospheric features not present at the time of the Voyager spacecraft encounter in 1989. Furthermore, the largest feature seen in 1989, the Great Dark Spot, was gone. A dark spot of comparable size had appeared in the northern hemisphere, accompanied by discrete bright features at methane-band wavelengths. At visible wavelengths, Neptune's banded structure appeared similar to that seen in 1989.     

Regulation of porcine adipocyte metabolism by insulin and adenosine

The acute effects of insulin and adenosine on rates of lipolysis and lipogenesis in pig adipocytes were investigated to determine what limits the expression of the insulin response in vitro. Adenosine and insulin independently inhibited isoproterenol-stimulated lipolysis. Adenosine, acting through the pertussis toxin-sensitive G-protein Gi, was more effective than insulin and could completely inhibit lipolysis. Fatty acid synthesis from glucose was increased by both adenosine and insulin. Neutralization of endogenous adenosine with adenosine deaminase decreased basal rates of lipogenesis and increased the insulin response from 30 to 60% above basal. Neutralization of Gi with pertussis toxin further decreased the basal rate and increased the insulin response to 160% above basal. These data indicate that Gi, and the ligands that signal through Gi, stimulate glucose incorporation into fatty acids and can attenuate the insulin response. It seems likely that an exaggerated rate of glucose metabolism in the absence of insulin contributes to the inconsistent insulin responses exhibited in pig adipose tissue in vitro. These data also demonstrate that insulin and adenosine have major roles in regulating pig adipose tissue metabolism.     

Prediction of kiwifruit orchard characteristics from satellite images

Precision Agriculture - The dry matter content of New Zealand kiwifruit is currently measured using destructive testing of a 90-fruit sample. Dry matter content varies from 14 to 20% with a...     

Designing fecal pellet surveys for snowshoe hares

Index methods can be valuable for monitoring forest-dwelling vertebrates over broad spatial or temporal scales. Fecal pellet counts are often used as an index of density or habitat use of snowshoe hares, Lepus americanus, but previous surveys have used different plot types and sample sizes, leading to problems comparing results from different studies and questions about the inferential power of each study. In this paper, we use field data and simulations to examine how the precision, bias, and efficiency of four commonly used plot types vary with plot type, pellet density, and sample size. Although no one plot type was consistently superior, we recommend thin rectangles (5.08 cm × 305 cm (2 in. × 10 ft), 0.155 m²) or 1 m² circles over 0.155 m² circles or 10 cm × 10 m (1 m²) rectangles. We recommend that researchers explicitly address the power of their survey design to detect different pellet densities, because much larger sample sizes are needed at low pellet densities than at high pellet densities to obtain similar precision. Small sample sizes are also much more likely to be biased, which could lead to incorrect inferences about management of snowshoe hare populations. Both uncleared and cleared plots performed well and will have value in different research contexts.     

Development of intraosseous infusion of the distal phalanx to access the foot lamellar circulation in the standing,conscious horse

Intraosseous (IO) infusion of the distal phalanx (IOIDP) as a delivery route targeting hoof lamellar tissue of standing, conscious horses was evaluated. Following sedation and regional nerve blockade in six Standardbred horses, a microdialysis (MD) probe was implanted into the hoof lamellar tissue of one forelimb. A purpose designed cannulated bone screw was introduced into the body of the distal phalanx, approximately 6 cm from the MD probe. Gentamicin solution (25 mg/mL) was infused at 20 μL/min through the bone screw for 2 h without the application of a tourniquet. MD and blood samples were collected at regular intervals and analysed for gentamicin concentrations.Gentamicin was present in lamellar tissue at much higher concentrations than peripheral serum. The mean concentration of gentamicin was 24.4, 20.5 and 4.4 μg/mL in extracellular fluid (ECF) and 0.28, 0.5 and 0.32 μg/mL in serum samples collected 60, 120 and 150 min after IOIDP was started, respectively. A clinically safe and efficacious IO drug delivery to the hoof lamellar tissue of standing, conscious horse was developed.