Teresa DeGolier

Neurotensin elevates hepatic bile acid secretion in chickens by a mechanism requiring an intact enterohepatic circulation

Neurotensin (NT), given intravenously at 10-50 pmol/kg per min to anesthetized female chickens equipped with a bile duct fistula, dose-dependently elevated hepatic bile flow and bile acid output but only when the enterohepatic circulation was maintained by returning the bile to the intestinal lumen. Infusion of NT at 10 and 50 pmol/kg per min increased the average hepatic bile acid output over a 30-min period to 138 +/- 11 and 188 +/- 13% of control, respectively. During infusion of NT, plasma levels of immunoreactive NT (iNT) increased in time from the basal level (14 +/- 1.3 pM) to reach steady state at 30 min. There was a near linear relationship between the dose of NT infused and the increment in plasma iNT. In addition, infusion of NT at 40 pmol/kg min gave a plasma level of iNT (approximately/= 88 pM) which was within the range of those observed during duodenal perfusion with lipid (54-300 pM) and near to that measured in hepatic portal blood from fed animals (52 +/- 5 pM). Perfusion of duodenum with lipid released endogenous NT and increased the rate of hepatic bile flow. When NT antagonist SR48692 was given, bile flow rate decreased to the basal level. These results suggest that intestinal NT, released by lipid, may participate in the regulation of hepatic bile acid output by a mechanism requiring an intact enterohepatic circulation.

Neurotensin modulates the composition of pancreatic exocrine secretions in chickens

The effects of neurotensin on pancreatic exocrine secretion were examined in fasted, conscious White Leghorn hens. A cannula was surgically implanted in the central duct serving the ventral lobe of the pancreas in order to collect pure pancreatic juice. Following recovery, neurotensin was infused intravenously at 3.6 or 10.8 pmol/kg*min. The volume and pH of the pancreatic secretions were recorded and total pancreatic protein concentration, amylase, lipase, trypsin, and chymotrypsin activity were measured every 30 min for 2 hr and compared to secretions following the infusion of 0.9% saline. Our results demonstrated that neurotensin did not affect the pH nor the pancreatic juice protein concentration, but did increase secretion rate following neurotensin infusion at 3.6 pmol/kg*min. Amylase activity was significantly depressed during neurotensin infusions, while lipase (both pancreatic and carboxylester lipase) activity was significantly elevated. The ratio of amylase to lipase activity was especially depressed by neurotensin infusion at 10.8 pmol/kg*min. Insufficient secretory activity prevented a balanced statistical analysis of chymotrypsin activity, but from a pooled analysis, neurotensin had no effect on protease activity in the pancreatic juice. These results support our current research indicating that neurotensin may be a hormonal regulator of postprandial lipid digestion in chickens.

Effect of galanin on isolated strips of smooth muscle from the gastrointestinal tract of chickens

The contractile effects of galanin on isolated longitudinal smooth muscle strips of pre-crop esophagus, proventriculus, duodenum, colon, and cecum of chickens were investigated. Application of galanin (5.0-100.0 nM) evoked strong contractions from the colon and cecum (hindgut), but evoked minimal responses from the pre-crop esophagus, proventriculus, and duodenum (foregut). Previous studies have demonstrated that the central administration of galanin stimulates food consumption in rats. Since galanin-like immunoreactivity is present in the chicken brain, we speculate that the central release of galanin may increase food intake and possibly be involved in a hypothalamic-colonic reflex modulating hindgut motility and generating a defecation. Thus, the results of this study demonstrate the presence of galanin receptors in the chicken gut and suggest a possible link with their functional presence in the hindgut to the chicken central nervous system.

Small Mammal Habitat Preferences in a Patchwork of Adjacent Reconstructed Grasslands Subject to Semiannual Burns

This study used small mammal capture-recapture methods within a mosaic of side-by-side prairie reconstructions to evaluate the relationship between floristic diversity, the effect of prescribed burns, and habitat use. This unique 10.4 ha study of opportunity consisted of multiple plots of three habitat types: low floristic diversity exotic cool-season grasses (CSG), low floristic diversity grass plantings dominated by native warm-season grasses (WSG), and floristically diverse, mixed prairie (MP) plantings with > 45 species of forbs. Data for calculating small mammal abundances (new captures/trap effort) were determined by trapping in August following spring burns in 2002 and 2004, and unburned years in 2003 and 2005. Fire-positive species (meadow jumping mice, Peromyscus spp.) preferred fields with a more open understory (MP plantings), and a reduced thatch thickness and leaf litter layer (burned fields). Fire-negative species (meadow voles, northern short-tailed shrews) populated all restorations (CSG, WSG, MP plantings) but only during the unburned years when the fields provided a high density of vegetative cover. Even though the distinct floristic diversity found within the three reconstruction types influenced small mammal foraging preferences, the effect of semiannual burns on floristic structures had a noteworthy impact on their distributions. The results of this study demonstrate an important take home message for restoration practitioners: techniques that promote differences in structural characteristics are just as important as creating plantings with high floristic diversity.

Release of avian neurotensin in response to intraluminal contents in the duodenum of chickens

Peripheral and hepatic-portal plasma levels of neurotensin (NT) in fed and fasted chickens were determined using RIA. Portal levels of NT(1-13) (fed = 61.3 ± 3.9 fmol/mL; fasted = 44.5 ± 3.9 fmol/mL) were significantly higher than peripheral levels (fed = 8.2 ± 3.3 fmol/mL; fasted = 7.8 ± 3.0 fmol/mL) collected from the wing vein, indicating that some NT is metabolized in the liver. Portal plasma levels of NT collected from fed birds were also significantly higher than portal plasma levels of NT collected from fasted birds. Neurotensin, as identified by HPLC, exhibited a 2-fold increase in plasma extracts following perfusion of the proximal ileum with a 10-mg sample of oleic acid, as compared with control samples of plasma collected before oleic acid perfusion. In whole-animal studies, the injection of a micellar solution of oleic acid into isolated segments of the duodenum resulted in elevated plasma immunoreactive NT in blood collected from the pancreaticoduodenal vein. Injection of a 1,000 mOsm sodium chloride solution had a slightly lesser and delayed effect compared with oleic acid, but a greater effect than 0.1 N hydrochloric acid in isotonic saline solution. Injection of an amino acid solution (10% Travasol), 300 mOsm glucose solution, or pure corn oil had no effect. These results demonstrate that intraduodenal oleic acid is a potent stimulus for the release of NT from the duodenum into the hepatic-portal circulation of chickens.

Neurotensin and cholecystokinin contract gallbladder circular muscle in chickens

The contractile effects of neurotensin (NT) and cholecystokinin octapeptide (CCK-8) on isolated circular smooth muscle strips of chicken gallbladder were investigated. The NT (0.25-300 nM) produced concentration-dependent contractions on smooth muscle with an EC50 of 8.5 nM (95% confidence limits = 5.3-13.6 nM). In comparison, CCK-8 produced concentration-dependent contractions with an EC50 of 13 nM (95% confidence limits of 9-20 nM). There were no statistical differences in contractile responses when comparing NT and CCK-8 at equimolar concentrations. The NT appears to act directly on smooth muscle tissue in the chicken; the contractile responses were not blocked by 10 µM atropine or tetrodotoxin. A portion of the activity is mediated by extracellular calcium as 100 nM nifedipine inhibited 30% of peptide-induced muscle tension. The NT receptor (NTR) type 1 antagonist SR 48692 (0.1 µM) did not significantly reduce NT potency. The contractile effects of CCK-8 remained unaltered in tissues pretreated with atropine, TTX, or nifedipine. The CCK-A antagonist lorglumide, at a concentration of 1 µM, reduced the contractile potency of CCK-8 by one-half. Avian receptors for NT and CCK may differ pharmacologically from their mammalian counterparts, but their contractile actions on the gallbladder resulting in increased biliary output by flow are further evidence of their role in the postprandial regulation of lipid digestion in chickens.

Using Critical-Thinking Skills to Substantiate or Challenge Controversial Claims Endorsing a Myriad of Weight-Loss Products

ABSTRACT This exercise engages students in critically evaluating weight-loss products and programs. Specific objectives are to investigate, analyze, and substantiate claims made by the weight-loss industry and interpret how these claims may be fraudulent, misleading, or perhaps even truthful.

Neurotensin and cholecystokinin depress motility in isolated Lumbricus terrestris crop-gizzard preparations.

The effects of neurotensin (NT) and cholecystokinin (CCK) were studied on isolated crop-gizzard preparations of Lumbricus terrestris suspended in a smooth muscle organ bath. Changes in the amplitude and frequency of contractions associated with spontaneous motility were observed in response to neurotransmitters known to have an excitatory effect (acetylcholine) and an inhibitory effect (serotonin); and to the hormones NT and CCK, which in vertebrate models have both been shown to inhibit gastric motility. The overall contractile amplitude and frequency of crop-gizzard contractions were decreased in response to increasing concentrations of NT and CCK. In general, both hormone-induced responses were similar when compared at equal molar concentrations. Cholecystokinin, however, did exhibit a greater reduction in contractile frequency than NT. It is speculated that possible desensitization of earthworm NT-receptors to higher hormone concentrations resulted in a depressed maximal response in the concentration-response curve. Despite that possibility, the overall hormonal inhibition was statistically significant. These results infer that NT- and CCK-induced inhibition of crop-gizzard motility may have a modulatory role in the transport of nutrients and overall efficiency of worm metabolism.

Research Article: Pharmacological effects of the aqueous extract of Caulophyllum thalictroides (blue cohosh) on isolated Mus musculus uteri

Abstract The roots and rhizomes of Caulophyllum thalictroides (blue cohosh), traditionally used as an aid for childbirth, contain several active alkaloids and saponins, which act directly on uterine smooth muscle resulting in an oxytocic response. The historical use of this herbal supplement has been well documented, but there are few clinical studies addressing its efficacy and potential side effects. This research investigated the physiological and pharmacological responses of blue cohosh on isolated strips of murine uterine tissue. Uterine horns from mice were suspended in a smooth muscle bath and exposed to the aqueous extract of blue cohosh (doses ranging from 0.037–23.8 mg). All tissues showed an increase in the strength of contractile force, the frequency of the contraction, and basal tonus. Contractile forces were significantly greater with higher doses (P = 0.0027). The stages of estrous were determined by vaginal smears and dose-dependency was consistent in all stages of estrous observed (diestrus, estrus, metestrus). Blocking experiments with d-tubocuranine, a nicotinic receptor antagonist, were inconclusive as decreases in contractile responses were not statistically different from the observed fatigue following control cumulative dosing.

Using a Guided-Inquiry Approach for Investigating Metabolic Rate in Mice

thorough understanding about how the content of science comes to be understood. In other words, students should “learn science the way that reflects how science actually works” (National Science Education Standards 1996). An effective strategy to facilitate this process is to let students discover the knowledge for themselves by engaging them in inquiry-based activities, which by design, enables students to take more active ownership in teaching themselves how to learn by thinking as a scientist thinks (National Science Education Standards 1996).