Biomedical subjects

Sue Brandon

Publications and source records attributed to Sue Brandon.

4 recordsLinked to original sources

PubMed2005

Rapid absorption of dietary 1,8-cineole results in critical blood concentration of cineole and immediate cessation of eating in the common brushtail possum (Trichosurus vulpecula).

The blood concentration of 1,8-cineole and its metabolites was measured in six male brushtail possums while they voluntarily fed on diets laced with varying concentrations of cineole for 3 d. On the third day, blood samples were collected during and after each bout of feeding for 3 hr. Blood cineole was measured by using headspace solid-phase microextraction (SPME), while cineole metabolites were measured by liquid-liquid extraction followed by gas chromatography-mass spectroscopy. Feeding patterns were measured by continual recording of residual food weight and time. Cineole absorption was rapid, resulting in a peak blood concentration at the end of each feeding bout. The blood concentration of cineole did not exceed a critical value (51.8 +/- 14.1 micromol/l) regardless of the concentration in the diet. Food and, therefore, cineole intake was regulated. The amount of food ingested in the first feeding bout decreased from 236 +/- 52 g on the control diet to 36 +/- 20 g on the 4% cineole diet. The amount of cineole ingested in the first bout (1.18 +/- 1.10 g) was the same regardless of the dietary concentration and was controlled by the size of the meal. Total food eaten during the 7-hr feeding session decreased by 64% from 368 +/- 94 g (control diet) to 131 +/- 52 g (4% diet). Total cineole intake increased from 2.47 +/- 0.60 g (1% diet) to 5.05 +/- 2.41 g (4% diet). Cineole metabolites accumulated throughout the sampling period and were generally still rising at the end of blood sampling period. Blood levels of metabolites were at least 10-fold higher than cineole levels. The immediate control of feeding seems to be regulated by blood levels of cineole, whereas metabolites are likely to be more important in regulating the chronic ingestion of cineole.

Analysis of Variance↗

PubMed2004

Jensenone: biological reactivity of a marsupial antifeedant from Eucalyptus.

The resistance of Eucalyptus to browsing mammals has been related to the level and type of formylated phloroglucinol compounds (FPCs) present in the leaf. The antifeedant activity of FPCs appears to depend on their aldehyde groups, but little else is known of their mode of action. We have sought to elucidate this further by examining the biological reactivity and disposition of jensenone, a model FPC. Neither jensenone nor any metabolites were detected in urine or feces of marsupial brushtail or ringtail possums that had ingested up to 725 mg x kg(-0.75). When jensenone was incubated in rat gastrointestinal segments in vitro, it rapidly disappeared. Jensenone also reacted rapidly with glutathione, cysteine, glycine, ethanolamine, and trypsin, and more slowly with acetylcysteine and albumin. Sideroxylonal, a more complex FPC, exhibited the same reactivity. Torquatone, a related compound that lacks both aldehyde groups and antifeedant activity, was unreactive. Mass spectroscopic analysis indicated that the adducts were Schiff bases formed between the aldehyde groups of FPCs and amine groups of the conjugating molecules. Successive adducts were formed with the two aldehyde groups of jensenone, and the four groups of sideroxylonal. The jensenone bis-glutathione adduct appeared to cyclize to the disulfide form. These findings suggest that the antifeedant effects of FPCs are due to their facile binding to amine groups on critical molecules in the gastrointestinal tract, leading to a loss of metabolic function. The consequent toxic reaction, probably involving chemical mediators such as 5-hydroxytryptamine (5HT), may cause colic, nausea, and a general malaise, resulting in anorexia.

Adaptation, Physiological↗

PubMed2003

Glucuronuria in the koala.

Glucuronuria is normal in marsupial folivores such as the koala (Phascolarrctos cinereus), which excretes 2-3 g glucuronic acid daily. Although this has long been attributed to the metabolites of Eucalyptus terpenes, we have found that these are mostly excreted in the unconjugated form. We now report on the aglycones that account for most of the glucuronic acid in koala urine. Urine (24 hr) was collected from six male koalas (8.8 +/- 0.4 kg, mean +/- SE) that were maintained on E. cephalocarpa foliage. Urine samples were analyzed by liquid and gas chromatography (LC and GC) coupled with mass spectrometry (MS). Glucuronides were readily identified by LC-MS/MS, which generated characteristic product ions at m/z 113 and 175. From the corresponding parent glucuronide ions, the masses of the aglycones were calculated. Confirmation of identity was by GC-MS after hydrolysis with beta-glucuronidase and comparison with standard compounds. Quantitation was by GC. The major non-terpene aglycones were 4-methylcatechol, resorcinol, salicyl alcohol, and two unidentified C7H8O2 phenols. Smaller amounts of benzoic acid, benzyl alcohol, orcinol, p-cresol, phenol, and phloroglucinol were detected. We have previously reported that terpene metabolites account for about 10% urinary glucuronides in the same koalas fed E. cephalocarpa. The present study found that an additional 60% urinary glucuronic acid is conjugated with non-terpene, mainly phenolic, aglycones. It seems likely that these phenolic compounds are present in leaves as glycosides and are chiefly responsible for the glucuronuria in koalas.

Animals↗

PubMed2002

Application of solid-phase microextraction to the quantitative analysis of 1,8-cineole in blood and expired air in a Eucalyptus herbivore, the brushtail possum (Trichosurus vulpecula).

We have developed two solid-phase microextraction (SPME) methods, coupled with gas chromatography, for quantitatively analysing the major Eucalyptus leaf terpene, 1,8-cineole, in both expired air and blood from the common brushtail possum (Trichosurus vulpecula). In-line SPME sampling (5 min at 20 degrees C room temperature) of excurrent air from an expiratory chamber containing a possum dosed orally with 1,8-cineole (50 mg/kg) allowed real-time semi-quantitative measurements reflecting 1,8-cineole blood concentrations. Headspace SPME using 50 microl whole blood collected from possums dosed orally with 1,8-cineole (30 mg/kg) resulted in excellent sensitivity (quantitation limit 1 ng/ml) and reproducibility. Blood concentrations ranged between 1 and 1380 ng/ml. Calibration curves were prepared for two concentration ranges (0.05-10 and 10-400 ng/50 microl) for the analysis of blood concentrations. Both calibration curves were linear (r(2)=0.999 and 0.994, respectively) and the equations for the two concentration ranges were consistent.

Air↗