Trace element metabolism in the chemically diabetic rat

It is well-established that the metabolism of essential trace metals is homeostatically controlled. However, the factors responsible for coordinating processes of absorption, excretion, and flux among and within tissues remain unknown. Using the streptozotocin-diabetic rat as a model, we have obtained information in support of the hypothesis that the relative amounts of insulin and glucagon in plasma have a marked influence on the metabolism of the micronutrients Zn, Cu, Mn, and Fe. We have also found that alterations in trace metal metabolism during periods of acute stress (increased plasma glucagon to insulin ratio) are necessary for biochemical adaptation to the physiological state. Finally, we suggest that changes in the tissue distribution of these trace metals during periods of chronic endocrine imbalance may contribute to the onset of secondary complications.     

Cadmium accumulation and metabolism by rat liver parenchymal cells in primary monolayer culture

Primary cultures of adult rat liver parenchylmal cells, isolated by the collagenase perfusion technique and maintained as a monolayer,l were used to investigate the characteristics of hepatic cadmium accumulation and metabolism. Cadmium accumulation was found to be temperature- and concentration-dependent process that required sulfhydryl groups and was significantly stimulated by the addition of dexamethasome to the medium. Once taken up, cadmium was less available for exit-exchange processes than its biologically required congener, zinc. Moreover, cadmium influx enhanced zinc efflux. While most of the intracellular cadmium was located in the cytosol, its distribution within this fraction was altered with time. Initially the metal was bound to both high molecular weight species (>50 000) and metallothionein. As the incubation period increased, the cytosol concentration of cdmium and the percentage of this metal associated with metallothionein was likewise increased. [³H]Amino acid incorporation studies indicated that the accumulation of cadmium resulted in de novo synthesis of the 1 and 2 forms of metallothionein.     

Bacterial and fungal growth in total parenteral nutrition solutions,.

The most serious complication of prolonged intravenous infusion of hypertonic dextrose and amino acids is infection. Frequently, the etiology is fungal rather than bacterial. Previous authors have suggested that bacterial survival and growth in the solutions is suppressed by (a) high dextrose concentration, (b) high osmolality, or (c) low pH. This paper presents evidence that proposals (a) and (b) are untenable and (c) is only partly responsible. We call attention to the presence of a factor that is antibacterial but not antifungal; namely, a high concentration of glycine.     

Climate change in Europe and effects on thermal resources for crops

Atmospheric variables play a fundamental role in driving man-managed ecosystems and more specifically in agro-ecosystems, determining the quantity and quality of crop production. On the other hand, climate variability can be seen as the superimposition of gradual and abrupt changes. This paper is focused on European surface air temperature in the period 1951–2010. Analysis of this dataset identified breakpoints that define two homogeneous sub-periods: 1951–1987 and 1988–2010. Thermal resources for crops were analyzed adopting a “normal heat hours” approach. Computation highlighted a general increase in thermal resources in the European continent for crop groups II and III (C3 and C4 plants adapted to high or moderate temperatures), while a decline of thermal resources for crop group I (cold adapted C3) was highlighted in the Mediterranean area. The climate variability justifies a change in the potential latitudinal limits of different groups of crops, representing a fundamental step for crop adaptation to climate change.     

Effects of the hunting method on meat quality from fallow deer and wild boar and preliminary studies for predicting lipid oxidation using visible reflectance spectra

This study examines the influence of hunting methods on the colour and lipid oxidation state of meat from wild boar (Sus scrofa) and fallow deer (Dama dama). In addition, the feasibility of using visible reflectance spectra (360 to 740 nm) to predict the lipid oxidation of meat was evaluated. A total of 25 wild boars and 14 fallow deer were hunted with two different methods, dog-driven hunting (DH) and harvest culling (HC), that imply different animal stresses before shooting. Lipid oxidation increased in the meat from both species, which had been frozen for 3 months. The increase was higher in the DH group than the HC group (P?<?0.05). Our results confirm the importance of hunting stress on meat quality and lipid stability. The multivariate regression analysis showed a high correlation (R ²?=?0.968) between the predicted and measured thiobarbituric acid-reactive substances (TBARS) values, suggesting that visible spectroscopy should prove useful for predicting meat oxidation.     

Cyclic accumulation of zinc by Candida utilis during growth in batch culture

Intracellular accumulation of zinc by Candida utilis NRRL-Y-7634 was mediated by an energy-and temperature-dependent, highly specific process exhibiting saturation kinetics. In zinc-supplemented medium, uptake occured only during the lad and late-exponential phases; this type of transport did not occur with zinc in bacteria nor with iron in either yeast or bacteria. Cells of C. utilis did not possess a zinc-efflux system; they could reduce their level of intracellular zinc only by dilution of the metal into daughter cells. Zinc-deficient organisms accumulated 12 times more zinc than did cells of the same culture age grown in zinc-supplemented medium. The varied, but experimentally reproducible levels of intracellular zinc that occured in response to the physiological and environmental parameters had no detectable effects on respiration, rate of growth, total cell yield, or cell viability. Neither the mechanism underlying the cyclic accumulation of sinc nor the function of such behaviour are understood.     

Zinc uptake by isolated rat liver parenchymal cells

Primary cultures of rat liver parenchymal cells maintained as a monolayer in serum-free culture medium were used to investigate the characteristics of zinc accumulation in vitro. Liver parenchymal cells accumulated zinc by a temperature-dependent, saturable process that was inhibited by cyanide, azide, oligomycin, N-ethylmaleimide and iodoacetamide. Cadmium reversibly inhibited zinc accumulation in both serum-free and serum-containing media. Gel filtration chromatographic studies showed that recently accumulated intracellular zinc was present as a low molecular weight complex smaller than metallothionein, the zinc storage protein, but larger than individual amino acids.The quantity of zinc accumulated was affected by preincubation of the cells with various hormones. Dexamethasone, prednisone and prednisolone each increased zinc uptake by 40–50% when either insulin or glucagon was also present. Hydrocortisone, cortisone and sex steroids did not influence zinc accumulation. Removal of the polypeptide hormones from the medium abolished the stimulatory effect of the synthetic glucocorticoid steroid hormones on zinc accumulation.