Effects of nicotine on the digestive performance of nectar-feeding birds reflect their relative tolerance to this alkaloid.

The paradox of secondary metabolites, toxic defence compounds produced by plants, in nectar and fruits is well known. Deterrence of feeding by nectarivorous and frugivorous birds is better understood than the effect of these chemicals on the digestive performance of birds. Digestive parameters such as transit time and sugar assimilation are important in assessing nutrient utilization and deterrence may be related to post-ingestive effects involving these parameters. Nectar and many fruits contain mainly sugars and water, and avian consumers compensate for low sugar content in their diet by increasing food intake: this may also increase their intake of secondary metabolites. We investigated how the alkaloid nicotine, naturally present in nectar of Nicotiana species, influences compensatory feeding and digestive performance of nectar-feeding birds. High nicotine concentration negatively affected compensatory feeding and apparent assimilation efficiency of white-bellied sunbirds Cinnyris talatala and Cape white-eyes Zosterops virens; but nicotine slowed gut transit time only in the latter species. In contrast, food intake and digestive performance of dark-capped bulbuls Pycnonotus tricolor was unaffected by nicotine up to a concentration of 50µM. Bulbuls are primarily frugivorous; hence, they are more exposed to secondary metabolites than sunbirds and possibly white-eyes. Because their diet is richer in toxins, frugivorous birds may have evolved more efficient detoxification strategies than those of specialist nectar-feeding birds.

Effects of agave nectar versus sucrose on weight gain, adiposity, blood glucose, insulin, and lipid responses in mice.

Agave nectar is a fructose-rich liquid sweetener derived from a plant, and is often promoted as a low glycemic alternative to refined sugar. However, little scientific research has been conducted in animals or humans to determine its metabolic and/or health effects. The aim of this study was to explore the influence of agave nectar versus sucrose on weight gain, adiposity, fasting plasma blood glucose, insulin, and lipid levels. Eighteen (n=18) male ICR mice (33.8±1.6 g) were divided into two groups (n=6 for agave nectar and n=12 for sucrose) and provided free access to one of two diets of equal energy densities differing only in a portion of the carbohydrate provided. Diets contained 20% carbohydrate (by weight of total diet) from either raw agave nectar or sucrose. Epididymal fat pads were excised, and blood was collected after 34 days. Weight gain (4.3±2.2 vs. 8.4±3.4 g), fat pad weights (0.95±0.54 vs. 1.75±0.66 g), plasma glucose (77.8±12.2 vs. 111.0±27.9 mg/dL), and insulin (0.61±0.29 vs. 1.46±0.81 ng/mL) were significantly lower (P≤.05) for agave nectar-fed mice compared to sucrose-fed mice respectively. No statistically significant differences in total cholesterol or triglycerides were detected. These results suggest that in comparison to sucrose, agave nectar may have a positive influence on weight gain and glucose control. However, more research with a larger sample of animals and/or with human subjects is warranted.

Insecticide residues in pollen and nectar of a cucurbit crop and their potential exposure to pollinators.

Neonicotinoids are systemic insecticides widely used on many pollinated agricultural crops, and increasing evidence indicates that they move to some extent into pollen and nectar. This study measured levels of neonicotinoid residues in pollen and nectar from a pumpkin crop treated with formulated products containing imidacloprid, dinotefuran, and thiamethoxam using different timings and application methods. Environmental conditions have a significant effect on overall residue levels; nectar residues were 73.5-88.8% less than pollen residues, and metabolites accounted for 15.5-27.2% of the total residue amounts. Foliar-applied treatments and chemigated insecticides applied through drip irrigation during flowering resulted in the highest residues of parent insecticide and metabolites, which may reach average levels up to 122 ng/g in pollen and 17.6 ng/g in nectar. The lowest levels of residues were detected in treatment regimens involving applications of insecticides at planting, as either seed dressing, bedding tray drench, or transplant water treatment.

Comparison of standardized bariums with varying rheological parameters on swallowing kinematics in males.

This study measured dose-response of a range of commercially available liquid barium materials designed for use in videofluoroscopic oropharyngeal swallowing assessments, particularly as they relate to the necessity of adding a thickening agent for swallow safety. A group of 25 adult males representing various medical diagnoses consented to participate, with 16 qualifying to complete a videofluoroscopic swallowing assessment with liquid barium materials of three viscosities (nectar: 300 cP, thin honey: 1,500 cP, thick honey: 3,000 cP). Outcome measures included airway invasion (Penetration-Aspiration score), postswallow residue, and patient preference. Penetration-Aspiration and residue scores did not significantly differ between thin honey and thick honey bariums. Significantly more severe airway invasion was observed with nectar boluses than with two levels of honey boluses (p < 0.001). Significantly more residue was observed in the oral cavity (p < 0.002) and valleculae (p < 0.001) with thin and thick honey bariums than with nectar barium. Thin honey was rated as "easy" or "average" to drink by 67% of subjects, compared with 54% for thick honey. This study supports the use of thin honey barium over thick honey barium during videofluoroscopic swallowing assessments because the two honey bariums were comparable in terms of airway protection and postswallow residue in the oropharynx and the thin honey was preferred by patients.