Intestinal glucose absorption but not endogenous glucose production differs between colostrum- and formula-fed neonatal calves

Glucose supply markedly changes during the transition to extrauterine life. In this study, we investigated diet effects on glucose metabolism in neonatal calves. Calves were fed colostrum (C; n = 7) or milk-based formula (F; n = 7) with similar nutrient content up to d 4 of life. Blood plasma samples were taken daily before feeding and 2 h after feeding on d 4 to measure glucose, lactate, nonesterified fatty acids, protein, urea, insulin, glucagon, and cortisol concentrations. On d 2, additional blood samples were taken to measure glucose first-pass uptake (FPU) and turnover by oral [U-(13)C]-glucose and i.v. [6,6-(2)H(2)]-glucose infusion. On d 3, endogenous glucose production and gluconeogenesis were determined by i.v. [U-(13)C]-glucose and oral deuterated water administration after overnight feed deprivation. Liver tissue was obtained 2 h after feeding on d 4 and glycogen concentration and activities and mRNA abundance of gluconeogenic enzymes were measured. Plasma glucose and protein concentrations and hepatic glycogen concentration were higher (P < 0.05), whereas plasma urea, glucagon, and cortisol (d 2) concentrations as well as hepatic pyruvate carboxylase mRNA level and activity were lower (P < 0.05) in group C than in group F. Orally administered [U-(13)C]-glucose in blood was higher (P < 0.05) but FPU tended to be lower (P < 0.1) in group C than in group F. The improved glucose status in group C resulted from enhanced oral glucose absorption. Metabolic and endocrine changes pointed to elevated amino acid degradation in group F, presumably to provide substrates to meet energy requirements and to compensate for impaired oral glucose uptake.

Secretion and degradation of glucagon by HIT cells

HIT cells have been widely used to study synthesis and secretion of insulin. It has been assumed that this cell line secretes no other islet hormones. To ascertain whether HIT cells synthesize, secrete, and degrade glucagon, we examined cell extracts for this peptide and compared secretion and degradation of glucagon and insulin during stimulation of the cells by arginine. Glucagon levels in acid extracts of HIT cells were found to be 0.72 +/- 0.15 pmol/mg protein. Both glucagon and insulin were maximally stimulated in a glucagon/insulin molar ratio of 0.029 by arginine concentrations of 25-50 nM, and the concentration of arginine that provided half-maximum responses for both hormones was approximately 3 mM. Diminution of arginine-induced glucagon secretion was caused by somatostatin, a physiological inhibitor of pancreatic islet alpha-cell function. HPLC was used to authenticate the glucagon levels stimulated by arginine for 60 min and measured by RIA. Thirty-six percent of immunoreactive glucagon was found in the fractions representing authentic glucagon, whereas the remaining 64% eluted earlier. Experiments examining the fate of radiolabeled glucagon exposed to HIT cells revealed time-dependent degradation of the radioisotope to earlier eluting forms, which accounted for approximately 50% of the radioactivity by 60 min and was complete by 18 h, indicating that the early peak detected by RIA represented a metabolite of glucagon. Radioisotopic insulin was degraded more slowly with an apparent half-life of approximately 36 h. We conclude that HIT cells are not only able to synthesize, secrete, and degrade insulin, but also much smaller amounts of glucagon.

The influence of physical state on shikimic acid ozonolysis: a case for in situ microspectroscopy

Atmospheric soluble organic aerosol material can become solid or semi-solid. Due to increasing viscosity and decreasing diffusivity, this can impact important processes such as gas uptake and reactivity within aerosols containing such substances. This work explores the dependence of shikimic acid ozonolysis on humidity and thereby viscosity. Shikimic acid, a proxy for oxygenated reactive organic material, reacts with O3 in a Criegee-type reaction. We used an environmental microreactor embedded in a scanning transmission X-ray microscope (STXM) to probe this oxidation process. This technique facilitates in situ measurements with single micron-sized particles and allows to obtain near-edge X-ray absorption fine structure (NEXAFS) spectra with high spatial resolution. Thus, the chemical evolution of the interior of the particles can be followed under reaction conditions. The experiments show that the overall degradation rate of shikimic acid is depending on the relative humidity in a way that is controlled by the decreasing diffusivity of ozone with decreasing humidity. This decreasing diffusivity is most likely linked to the increasing viscosity of the shikimic acid–water mixture. The degradation rate was also depending on particle size, most congruent with a reacto-diffusion limited kinetic case where the reaction progresses only in a shallow layer within the bulk. No gradient in the shikimic acid concentration was observed within the bulk material at any humidity indicating that the diffusivity of shikimic acid is still high enough to allow its equilibration throughout the particles on the timescale of hours at higher humidity and that the thickness of the oxidized layer under dry conditions, where the particles are solid, is beyond the resolution of STXM.

Characterization and performance of carbonaceous materials obtained from exhausted sludges for the anaerobic biodecolorization of the azo dye Acid Orange II.

This work presents the preliminary study of new carbonaceous materials (CMs) obtained from exhausted sludge, their use in the heterogeneous anaerobic process of biodecolorization of azo dyes and the comparison of their performance with one commercial active carbon. The preparation of carbonaceous materials was conducted through chemical activation and carbonization. Chemical activation was carried out through impregnation of sludge-exhausted materials with ZnCl2 and the activation by means of carbonization at different temperatures (400, 600 and 800°C). Their physicochemical and surface characteristics were also investigated. Sludge based carbonaceous (SBC) materials SBC400, SBC600 and SBC800 present values of 13.0, 111.3 and 202.0m(2)/g of surface area. Biodecolorization levels of 76% were achieved for SBC600 and 86% for SBC800 at space time (τ) of 1.0min, similar to that obtained with commercial activated carbons in the continuous anaerobic up-flow packed bed reactor (UPBR). The experimental data fit well to the first order kinetic model and equilibrium data are well represented by the Langmuir isotherm model. Carbonaceous materials show high level of biodecolorization even at very short space times. Results indicate that carbonaceous materials prepared from sludge-exhausted materials have outstanding textural properties and significant degradation capacity for treating textile effluents.

Induction of autophagy is a key component of all-trans-retinoic acid-induced differentiation in leukemia cells and a potential target for pharmacologic modulation

Acute myeloid leukemia (AML) is characterized by the accumulation of immature blood cell precursors in the bone marrow. Pharmacologically overcoming the differentiation block in this condition is an attractive therapeutic avenue, which has achieved success only in a subtype of AML, acute promyelocytic leukemia (APL). Attempts to emulate this success in other AML subtypes have thus far been unsuccessful. Autophagy is a conserved protein degradation pathway with important roles in mammalian cell differentiation, particularly within the hematopoietic system. In the study described here, we investigated the functional importance of autophagy in APL cell differentiation. We found that autophagy is increased during all-trans-retinoic acid (ATRA)-induced granulocytic differentiation of the APL cell line NB4 and that this is associated with increased expression of LC3II and GATE-16 proteins involved in autophagosome formation. Autophagy inhibition, using either drugs (chloroquine/3-methyladenine) or short-hairpin RNA targeting the essential autophagy gene ATG7, attenuates myeloid differentiation. Importantly, we found that enhancing autophagy promotes ATRA-induced granulocytic differentiation of an ATRA-resistant derivative of the non-APL AML HL60 cell line (HL60-Diff-R). These data support the development of strategies to stimulate autophagy as a novel approach to promote differentiation in AML.

Light-independent degradation of stromal proteins in intact chloroplasts isolated from Pisum sativum L. leaves: requirement for divalent cations

Intact chloroplasts were isolated from mature pea (Pisum sativum L.) leaves in order to study the degradation of several stromal proteins in organello. Changes in the abundances of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), phosphoribulokinase (EC 2.7.1.19), glutamine synthetase (EC 6.3.1.2) and ferredoxin-dependent glutamine:α-ketoglutarate aminotransferase (glutamate synthase; EC 1.4.7.1) were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by Coomassie-staining of the gels or immunoblotting using specific antibodies for the different enzymes. Degradation of several stromal proteins was strongly stimulated when intact chloroplasts were incubated in the light in the presence of dithiothreitol. Since free radicals may artificially accumulate in the chloroplast under such conditions and interfere with the stability of stromal proteins, the general relevance of these processes remains questionable. In the absence of light, proteolysis proceeded slowly in isolated chloroplasts and was not stimulated by dithiothreitol. Inhibition by ethylenediaminetetraacetic acid (EDTA), 1,10-phenanthroline or excess zinc ions as well as the requirement for divalent cations suggested that a zinc-containing metalloprotease participated in this process. Furthermore, light-independent degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase and phosphoribulokinase was enhanced in chloroplasts isolated from leaves in which senescence was accelerated by nitrogen starvation. Our results indicate that light-independent stromal protein degradation in intact chloroplasts may be analogous to proteolysis that occurs in intact leaves during senescence.