Application of synchronous fluorescence spectroscopy with multivariate data analysis for determination of butter adulteration

The potential of fluorescence spectroscopy for detection of butter adulteration with palm and coconut oils was investigated. Synchronous fluorescence spectra were collected in the range of 240–700 nm with wavelength intervals (?λ) of 10, 30, 60 and 80 nm. The applied technique was used to detect the addition of palm and coconut oils to butter, and the lowest limit of detection for adulteration (LOD – 5.5%) was observed after applying the wavelength interval of 60 nm. The multiple linear regression (MLR) models were used to calculate the level of adulteration with the lowest root mean square error of calibration (RMSEC) and root mean square error of validation (RMSEV) of 3.8 and 3.9%, respectively, for the measurements acquired at the wavelength interval of 60 nm.     

Intestinal bile acid absorption. Na(+)-dependent bile acid transport activity in rabbit small intestine correlates with the coexpression of an integral 93-kDa and a peripheral 14-kDa bile acid-binding membrane protein along the duodenum-ileum axis

The anatomical localization of the Na+/bile acid cotransport system from rabbit small intestine was determined using brush border membrane vesicles prepared from eight different segments of the small intestine. Na(+)-dependent transport activity for bile acids, both for [3H]taurocholate and [3H]cholate, was found in the distal segment 8 only representing the terminal 12% of the small intestine. In contrast, the Na(+)-dependent D-glucose transporter and the H(+)-dependent oligopeptide transporter were found over the whole length of rabbit small intestine in all segments. Photoaffinity labeling with 7,7-azo- and 3,3-azo-derivatives of taurocholate with subsequent fluorographic detection of labeled polypeptides after one- and two-dimensional gel electrophoresis showed that an integral membrane polypeptide of M(r) 87,000 is present in the entire small intestine, whereas an integral membrane protein of M(r) 93,000 together with a peripheral membrane protein of M(r) 14,000 are exclusively expressed in the distal small intestine correlating with Na(+)-dependent bile acid transport activity. Photoaffinity labeling with the cationic bile acid derivative 1-(7,7-azo-3 alpha,12 alpha-dihydroxy-5 beta[3 beta-3H]cholan-24-oyl)-1,2- diaminoethane hydrochloride and 7,7-azo-3 alpha,12 beta-dihydroxy-5 beta[12 alpha-3H]cholan-24-oic acid did not result in a specific labeling of the above mentioned proteins, demonstrating their specificity for physiological bile acids. Photoaffinity labeling of the 93- and 14-kDa bile acid-binding proteins was strongly Na(+)-dependent. Significant labeling of the 93- and 14-kDa proteins occurred only in the presence of Na+ ions with maximal labeling above 100 mM [Na+] showing a parallel [Na+] dependence to transport activity. Inactivation of Na(+)-dependent [3H]taurocholate uptake by treatment of ileal brush border membrane vesicles with 4-nitrobenzo-2-oxa-1,3-diazol chloride led to a parallel decrease in the extent of photoaffinity labeling of both the 93- and 14-kDa protein. Sequence analysis of the membrane-bound 14-kDa bile acid-binding protein surprisingly revealed its identity with gastrotropin, a hydrophobic ligand-binding protein exclusively found in the cytosol from ileocytes and thought to be involved in the intracellular transport of bile acids from the brush border membrane to the basolateral pole of the ileocyte. In conclusion, the present studies suggest that both an integral 93- and a peripheral 14-kDa membrane protein, identified as gastrotropin, and both exclusively expressed in the terminal ileum, are essential components of the Na+/bile acid cotransport system in rabbit terminal ileum.     

Effect of bombesin, a natural tetradecapeptide, on myoelectrical and mechanical activity of isolated, ex vivo perfused, canine stomach

Electrical and mechanical activity were recorded from the canine stomach, isolated and ex vivo perfused with homologous blood. The action of Bombesin, a natural tetradecapeptide, was compared with the action of pentagastrin, methacholine and electrical stimulation on the electrical and mechanical activity of this isolated preparation. All drugs used and vagal stimulation resulted in premature control potentials, uncoupling of the normal phase locked pattern of electrical control activity, appearance of response activity and appearance of mechanical reaction. These responses were blocked or decreased by atropine, tetrodotoxin and hexamethonium. It appears that the neural release of acetylcholine is implicated in the mechanism of action of Bombesin gastrointestinal motility.     

Characterization of errors in the use of integrating-sphere systems in the calibration of scanning radiometers

Laboratory measurements were performed to characterize the geometrical effects in the calibration of the NASA's cloud absorption radiometer (CAR). The measurements involved three integrating sphere sources (ISSs) operated at different light levels and experimental setups to determine radiance variability. The radiance gradients across the three ISS apertures were 0.2%-2.6% for different visible, near-infrared, and shortwave infrared illumination levels but <15% in the UV. Change in radiance with distance was determined to be 2%-20%, being highest in the UV. Radiance variability due to the edge effects was found to be significant; as much as 70% due to the sphere aperture and <10% due to the CAR telescope's secondary mirror.     

"Hairy" single-walled carbon nanotubes prepared by atom transfer radical polymerization

"Hairy nano-objects" are hybrid nanostructures comprising a core surrounded by a "hairlike" corona of flexible polymer chains, the role of which is typically to improve the solubility of the core material or to improve its dispersability and adhesion in other polymer matrices. Both aspects could be particularly useful with carbon nanotubes, especially in their applications as reinforcing agents. The controlled synthesis of hairy carbon nanotubes is accomplished by chemical modification with 2-bromopropionate followed by extension with poly(n-butyl acrylate) through atom transfer radical polymerization. The obtained hairy nanotubes are visualized at nearly molecular resolution with tapping-mode atomic force microscopy, providing insight into the uniformity of grafted chain lengths and grafting density. The grafting densities vary from approximately 1.0-10.0 chains nm(-1) along the nanotubes. Such a wide range of grafting density may indicate some chemical heterogeneity along and between the nanotubes; it may be also an indication of the challenges associated with carrying out chemical modification of nano-objects having high tendency to aggregate.     

Effect of age and sex on histamine-induced gastric secretion in laboratory rats

Rats pretreated by daily depot injections of pentagastric for 24 days, responded with a significant increase of gastric secretion volume, and HC1 concentration and output, when infused intravenously with bethanechol chloride. In these rats, the total weight of the stomach and the height of the fundic mucosa were also increased. Pretreatment with histamine had no effect on rat gastric tissue or gastric secretion, under identical conditions of stimulation.