Determination of aflatoxin levels in peanut butter using HPLC and ELISA procedures: Inter-laboratory comparison

Mycotoxin Research - Six laboratories analyzed portions of the same aqueous acetonitrile extracts of three peanut butters for aflatoxin concentrations by an HPLC procedure (using immunoaffinity...     

Synthesis and degradation of fructose 2,6-bisphosphate in endosperm of castor bean seedlings

The aim of this work was to examine the possibility that fructose 2,6-bisphosphate (Fru-2,6-P₂) plays a role in the regulation of gluconeogenesis from fat. Fru-2,6-P₂ is known to inhibit cytoplasmic fructose 1,6-bisphosphatase and stimulate pyrophosphate:fructose 6-phosphate phosphotransferase from the endosperm of seedlings of castor bean (Ricinus communis). Fru-2,6-P₂ was present throughout the seven-day period in amounts from 30 to 200 picomoles per endosperm. Inhibition of gluconeogenesis by anoxia or treatment with 3-mercaptopicolinic acid doubled the amount of Fru-2,6-P₂ in detached endosperm. The maximum activities of fructose 6-phosphate,2-kinase and fructose 2,6-bisphosphatase (enzymes that synthesize and degrade Fru-2,6-P₂, respectively) were sufficient to account for the highest observed rates of Fru-2,6-P₂ metabolism. Fructose 6-phosphate,2-kinase exhibited sigmoid kinetics with respect to fructose 6-phosphate. These kinetics became hyperbolic in the presence of inorganic phosphate, which also relieved a strong inhibition of the enzyme by 3-phosphoglycerate. Fructose 2,6-bisphosphatase was inhibited by both phosphate and fructose 6-phosphate, the products of the reaction. The properties of the two enzymes suggest that in vivo the amounts of fructose-6-phosphate, 3-phosphoglycerate, and phosphate could each contribute to the control of Fru-2,6-P₂ level. Variation in the level of Fru-2,6-P₂ in response to changes in the levels of these metabolites is considered to be important in regulating flux between fructose 1,6-bisphosphate and fructose 6-phosphate during germination.     

A biochemical analysis of the effects of arachidonic acid on sarcoplasmic reticulum function

Discontinuous sucrose gradients were used to determine the degree of association between arachidonic acid and sarcoplasmic reticulum vesicle membranes. Fraction analyses showed that arachidonic acid migrated to a different region of the sucrose gradient in the presence of sarcoplasmic reticulum membranes. This could suggest that arachidonic acid was complexed into the membranes. Arrhenius curves representing the temperature dependency of Ca2+-Mg2+-ATPase activity and calcium uptake in the presence and absence of arachidonic acid were constructed. The activation energy for ATPase did not change significantly due to the presence of arachidonic acid. The curve representing control calcium uptake did not show a discontinuity. However, the curve representing calcium uptake in the presence of arachidonic acid showed discontinuities at 18 degrees C and 21 degrees C. Activation energy increased sharply between these temperatures. The results suggest that arachidonic acid reached the critical micellar concentration between these temperatures. Enthalpy decreased in the presence of arachidonic acid. This observation could suggest a transition of the protein-phospholipid complex to a less rigid state since decreased order in the membrane would decrease the energy barrier for activation of ATPase.     

Eimeria saudiensis N. Sp. (Apicomplexa: Eimeriidae) from the Arabian Oryx (Oryx leucoryx) in Saudi Arabia

Oocysts of Eimeria saudiensis n. sp. (Apicomplexa: Eimeriidae) are described from the feces of the Arabian oryx, Oryx leucoryx , from the Riyadh Zoo, Saudi Arabia. The oocysts were ellipsoidal or slightly ovoid, 31.2 times 24.5 (24.3–36.5 times 20.0–27.6) μm with a bilayered wall about 1.7 μm thick. The micropyle was covered by a dome-shaped cap. The oocyst residuum was absent, but tiny polar granules were present. The sporocysts were elongate ovoid, 14.3 times 7.2 (11.5–18.5 times 6.0–9.0) μm, had a Stieda body, but lacked a substiedal body. The sporocyst residuum was present, composed of numerous small granules. The sporozoites were elongate club-shaped, and contained two prominent refractile bodies.     

Feeding patterns of elephants at the Atherstone Collaborative Nature Reserve

The African savannah elephant (Loxodonta africana Blumenbach) is a generalist herbivore that relies on widely distributed resources. Vegetation decline, aggravated by these elephants, can compromise local conservation efforts. Thus it imperative to understand the factors that drive them to consume specific plant species and plant parts. The objective of our study was to investigate the feeding patterns of African savannah elephants in the enclosed bushveld savannah at the Atherstone Collaborative Nature Reserve in South Africa. For 1 year, we examined elephant selection of woody versus herbaceous vegetation, and identified which plant species and parts were preferentially consumed. We accomplished this by directly observing feeding elephants, and by utilizing data collected on elephant footprints, dung piles, stripped bark and broken branches. We further conducted vegetation surveys to determine selection frequency relative to species abundance. Elephants showed a preference for different plant parts consumption in the feeding plots. In total, leaves, branches and bark contributed mostly to their diet. Seasonal selection patterns showed an increasing proportion of bark and branch consumption during the dry season.     

EARLY STARVATION1 specifically affects the phosphorylation action of starch‐related dikinases

Starch phosphorylation by starch‐related dikinases glucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD) is a key step in starch degradation. Little information is known about the precise structure of the glucan substrate utilized by the dikinases and about the mechanisms by which these structures may be influenced. A 50‐kDa starch‐binding protein named EARLY STARVATION1 (ESV1) was analyzed regarding its impact on starch phosphorylation. In various in vitro assays, the influences of the recombinant protein ESV1 on the actions of GWD and PWD on the surfaces of native starch granules were analyzed. In addition, we included starches from various sources as well as truncated forms of GWD. ESV1 preferentially binds to highly ordered, α‐glucans, such as starch and crystalline maltodextrins. Furthermore, ESV1 specifically influences the action of GWD and PWD at the starch granule surface. Starch phosphorylation by GWD is decreased in the presence of ESV1, whereas the action of PWD increases in the presence of ESV1. The unique alterations observed in starch phosphorylation by the two dikinases are discussed in regard to altered glucan structures at the starch granule surface.