Structure and proteoglycan composition of specialized regions of the elastic tendon of the chicken wing

The elastic tendon of the avian wing has been described by others as a unique structure with elastic properties due to the predominance of elastic fibers in the midsubstance. Further analyses of the tendon have shown it to possess five anatomically distinct regions. Besides the major elastic region, a distally located fibrocartilage and three tendinous regions are present. The tendinous regions connect: (1) the muscle to the elastic region, (2) the elastic region to the fibrocartilage and (3) the latter to the insertion site. The elastic region possesses thick and abundant elastic fibers and very thin, interconnecting collagen fibers. The collagen fibers in the sesamoid fibrocartilage are thick and interwoven, defining spaces occupied by fibrochondrocytes embedded in a non-fibrillar and highly metachromatic matrix. Biochemical analyses have shown that the fibrocartilage has about tenfold the amount of glycosaminoglycans (GAGs) found in the other regions. The main GAG in this region was chondroitin sulfate (CS) (plus keratan sulfate as detected immunocytochemically), while the other regions showed variable amounts of CS, dermatan sulfate (DS) and heparan sulfate. Further analyses have shown that a large CS-bearing proteoglycan is found in the fibrocartilage. The elastic region possesses two main proteoglycans, a large CS-bearing proteoglycan (which reacted with an antibody against keratan sulfate after chondroitinase ABC treatment) and a predominant DS-bearing proteoglycan, which showed immunoreactivity when assayed with an anti-biglycan antibody. The results demonstrate that the elastic tendon is a complex structure with complex regional structural and compositional adaptations, suited to different biomechanical roles.     

Determination of zearalenone and its metabolites in urine and tissue samples of cow and pig by LC-MS/MS

For the sensitive and selective determination of zeranol, taleranol, α-zearalenol, β-zearalenol and zearalenone in animal urine and tissue a LC-MS/MS method has been developed. Sample preparation included extraction of meat samples and enzymatic digest of urine samples followed by solid-phase extraction with RP-18 columns for sample clean-up. Mass spectrometric determination was carried out with an atmospheric pressure chemical ionisation interface (APCI) in the multi-reaction monitoring mode (MRM). Using the negative ion mode detection limits between 0.1 and 0.5 ppb and determination limits between 0.5 and 1 ppb could be achieved. With zearalanone as internal standard, a linear range between 0.5 (1.0) and 100 ppb in urine samples (cow; pig) and between 1 and 100 ppb in meat samples (cow, calf, pig) could be established. Depending on the biological matrix and analyte standard deviations were below 8.2 %, with recovery rates between 86 and 102 % in spiked samples. The applicability of the method was demonstrated via several contaminated cow and pig urine samples.     

Investigations on metabolism of zearalenone in broilers

Two experiments were carried out with male broilers to examine excretion kinetics of zearalenone (ZEA) and its metabolites (Exp. 1) and their occurrence in blood plasma and bile fluid (Exp.2) after a single oral dose of ZEA (approximately 6 µg/kg body weight) from naturally contaminated wheat. In addition, this ZEA bolus was administered either in absence or presence of a detoxifying agent (Mycofix® Plus, Biomin GmbH, Herzogenburg, Austria). Specimens were sampled at different times after ZEA bolus of up to 48 h. Excretion of ZEA and alpha-zearalenol as the only detectable metabolite of ZEA peaked at approximately 6.5 h after administration of the bolus. Cumulative excretion of both substances amounted approximately 58 % of ZEA intake after 48 h. Peak concentrations of ZEA and alpha-zearalenol in bile were detected in the time period of approximately 2 to 6 h after bolus whereas detection in plasma was not possible for each measurement point. Mycofix® Plus supplementation seemed to have only minor or no effects on the parameters examined.     

Toxikologische Bewertung von Ochratoxin A: Offene Fragen und Forschungsbedarf

Ochratoxin A (OTA) is an important food and feed contaminant with potential adverse effects in humans and animals. In view of present discussions on limit values for OTA in foods, essential elements of a toxicological risk assessment are outlined. The exposure situation in Europe is now well documented. The data base, with respect to a characterization of hazard and dose-response relationships, allowed to calculate a provisional tolerable daily intake for OTA suited to protect the consumer against undesirable toxic effects. Nonetheless, further research on OTA is indicated in view of unresolved issues regarding the following points:

1. 1.
   mechanisms of action (mode of genotoxicity, role of bioactivation/metabolism, identification of DNA-adducts and dose-dependency);
    
2. 2.
   combinations of OTA and other mycotoxins (studies of relevant mixtures/conditions);
    
3. 3.
   individual susceptibility and/or situation-based vulnerability.
    

Better information on mechanistic aspects of mycotoxin-induced toxicities will further improve our knowledge on the “margin of safety” between a given exposure and a potential impairment of human health.     

Dynamical complexity and temporal plasticity in pancreatic gβb-cells

We discuss some of the biological and mathematical issues involved in understanding and modelling the bursting electrical activity in pancreatic beta-cells. These issues include single-cell versus islet behaviour, parameter heterogeneity, channel noise, the effects of hormones, neurotransmitters, and ions, and multiple slow biophysical processes. Some of the key experimental and modelling studies are described, and some of the major open questions are discussed.     

Behavioral response ofGraminella nigrifrons (Homoptera: Cicadellidae) to experimentally manipulated vibrational signals

Mate recognition for the leafhopper Graminella nigrifrons(Forbes) occurs when a male spontaneously emits a multisectional vibrational calling song to which females respond by emitting simple pulses. Significant differences were found among males in the duration, number of chirps, and chirp rate within sections of the song and the total song. Repeatability (proportion of total variation due to differences among males) of call features ranged from very low (0.04 for total chirps in song) to high (0.67 for section 3 chirp rate). However, song modification and playback experiments revealed that the variation in the measured song features was not important in determining whether a female will respond. Rather, female response depended only on the presence of two of the three types of pulses which comprise a chirp. These essential pulses were found within chirps of all call sections that contain chirps. Manipulation of chirp rates from 0.58 to 2.70 times the normal rate did not affect female response, nor did changing the period of silence between the essential pulse types from 0.25 to 1.75 times the normal period. These results suggest that components of the male calling song function in mate recognition but are not used by females to discriminate among conspecific males.     

Lipolytic and peroxidative enzyme expressions in cultured potato tuber cells

Potato cells (cv. Norchip) were cultured from tuber parenchymal tissue and subcultured to dissociate and habituate the despecialized cells. After several subculturings on a minimal nutrient media, this line of cells demonstrated repeatable physical growth profiles for dry weight (DW), fresh weight (FW) and protein. Two enzymes of plant lipid metabolism were investigated, lipolytic acyl hydrolase (LAH) and lipoxygenase (LOX), which respectively liberate and peroxidize fatty acids from lipid in cellular membranes. LAH, measured as p-nitrophenyl palmitate hydrolase, was present in this line of cells in easily detectable amounts (317 units g^-1 DW) albeit much lower than that found in mother tuber (9878 units g^-1 DW). The presence of LAH in this line is significant because LAH isozymes are often described as storage proteins, yet activity per gram fresh weight in these unorganized cells is reasonably constant until culture growth exits the linear phase. However, LOX, the most active free fatty acid metabolizing enzyme in potato tubers (89,800 units g^-1 DW), was not detectable in this line of callus or suspension cultured cells. The absence of LOX activity in this line of cells was verified by a number of assay approaches and was confirmed by activity staining of extracted enzymes separated in polyacrylamide gels. The absence of LOX in these cultured cells is especially important in determining the functions of this lipid peroxidation system and how it may be genetically regulated.Mention of company or trade name does not imply endorsement by the United States Department of Agriculture over others not named.A laboratory cooperatively operated by the Midwest Area, Agricultural Research Service, U.S. Department of Agriculture, The Minnesota Agricultural Experiment Station, the North Dakota Agrcultural Experiment Station, and the Red River Valley Potato Grower's Association.     

Evidence for a phospholipid requirement of chitin synthase inSchizophyllum commune

Evidence for a lipid dependence of membrane-associated chitin synthase inSchizophyllum commune is based on the following observations: Arrhenius plots of the temperature dependence of this enzyme showed deflections from linearity that are characteristic for lipid-affected membrane-bound enzymes. The activity of chitin synthase dissociated by digitonin decreased at increasing digitonin/protein ratios and could be restored by addition of egg lecithin. After further delipification by sucrose gradient centrifugation, enzyme activity progressively decreased, banded at higher densities, and was less effectively restored by lecithin. The activity of dissociated chitin synthase was also restored by soybean phosphatidylcholine and low concentrations of phosphatidylinositol and phosphatidylserine. At higher concentrations, phosphatidylinositol and phosphatidylserine were inhibitory. Lysophosphatidylcholine and phosphatidylethanolamine were slightly stimulatory, whereas no effect resulting from ergosterol was observed.