Light- and electronmicroscopic and some histochemical investigations on the major excretory ducts of pancreas and liver was carried out on 24 adult chicken. The epithelium of both ducts was shown to ...include: cells with apical secretory granules, non-differenciated duct cells, ciliated cells and migrating cells. In addition the epithelium of the pancreatic ducts included goblet cells. The distal plasmalemm and the microvilli are covered with surfacecoat, which like the secretory granules produces precipitate with PA-silver. This area of the cell also shows a strong reaction to M++ and Ca++ activated ATPase.
Light-and electron-microscopic and some histochemical investigations on the epithelium or the ductus pancreaticus major were carried out in sheep. At least six different cell types are recognizable: ...(1) nondifferentiated duct cells; (2) cells containing apical secretory granules; (3) goblet cells; the mucosubstances of type 2 and 3 are PAS- and Alcian-blue-positive, also reacting wih methenamine silver; (4) ciliated cells, containing a single cilium with the microtubular pattern 9+2; (5) tuft cells with extremely long and wide microvilli and a pear-shaped cell body; (6) migrating cells, mainly lymphocytes and some assumed eosinophils, showing reaction to Mg++-activated ATPase.
Elevated mitochondrial hydrogen peroxide (H
O
) emission and an oxidative shift in cytosolic redox environment have been linked to high-fat-diet-induced insulin resistance in skeletal muscle. To test ...specifically whether increased flux through mitochondrial fatty acid oxidation, in the absence of elevated energy demand, directly alters mitochondrial function and redox state in muscle, two genetic models characterized by increased muscle β-oxidation flux were studied. In mice overexpressing peroxisome proliferator-activated receptor-α in muscle (MCK-PPARα), lipid-supported mitochondrial respiration, membrane potential (ΔΨ
), and H
O
production rate (
H
O
) were increased, which coincided with a more oxidized cytosolic redox environment, reduced muscle glucose uptake, and whole body glucose intolerance despite an increased rate of energy expenditure. Similar results were observed in lipin-1-deficient, fatty-liver dystrophic mice, another model characterized by increased β-oxidation flux and glucose intolerance. Crossing MCAT (mitochondria-targeted catalase) with MCK-PPARα mice normalized
H
O
production, redox environment, and glucose tolerance, but surprisingly, both basal and absolute insulin-stimulated rates of glucose uptake in muscle remained depressed. Also surprising, when placed on a high-fat diet, MCK-PPARα mice were characterized by much lower whole body, fat, and lean mass as well as improved glucose tolerance relative to wild-type mice, providing additional evidence that overexpression of PPARα in muscle imposes more extensive metabolic stress than experienced by wild-type mice on a high-fat diet. Overall, the findings suggest that driving an increase in skeletal muscle fatty acid oxidation in the absence of metabolic demand imposes mitochondrial reductive stress and elicits multiple counterbalance metabolic responses in an attempt to restore bioenergetic homeostasis.
Prior work has suggested that mitochondrial dysfunction is an underlying cause of insulin resistance in muscle because it limits fatty acid oxidation and therefore leads to the accumulation of cytotoxic lipid intermediates. The implication has been that therapeutic strategies to accelerate β-oxidation will be protective. The current study provides evidence that genetically increasing flux through β-oxidation in muscle imposes reductive stress that is not beneficial but rather detrimental to metabolic regulation.
Estrogen receptor-α (ERα) is a nuclear receptor family member thought to substantially contribute to the metabolic regulation of skeletal muscle. However, previous mouse models utilized to assess the ...necessity of ERα signaling in skeletal muscle were confounded by altered developmental programming and/or influenced by secondary effects, making it difficult to assign a causal role for ERα. The objective of this study was to determine the role of skeletal muscle ERα in regulating metabolism in the absence of confounding factors of development.
A novel mouse model was developed allowing for induced deletion of ERα in adult female skeletal muscle (ERαKOism). ERαshRNA was also used to knockdown ERα (ERαKD) in human myotubes cultured from primary human skeletal muscle cells isolated from muscle biopsies from healthy and obese insulin-resistant women.
Twelve weeks of HFD exposure had no differential effects on body composition, VO2, VCO2, RER, energy expenditure, and activity counts across genotypes. Although ERαKOism mice exhibited greater glucose intolerance than wild-type (WT) mice after chronic HFD, ex vivo skeletal muscle glucose uptake was not impaired in the ERαKOism mice. Expression of pro-inflammatory genes was altered in the skeletal muscle of the ERαKOism, but the concentrations of these inflammatory markers in the systemic circulation were either lower or remained similar to the WT mice. Finally, skeletal muscle mitochondrial respiratory capacity, oxidative phosphorylation efficiency, and H2O2 emission potential was not affected in the ERαKOism mice. ERαKD in human skeletal muscle cells neither altered differentiation capacity nor caused severe deficits in mitochondrial respiratory capacity.
Collectively, these results suggest that ERα function is superfluous in protecting against HFD-induced skeletal muscle metabolic derangements after postnatal development is complete.
•Induced skeletal muscle specific ERαKO (ERαKOism) examines the role of ERα without confounding factors of development.•Skeletal muscle glucose uptake is not impaired in ERαKOism.•Skeletal muscle mitochondrial function is not impaired in ERαKOism.•ERαKD in human myotubes does not severely affect mitochondrial respiratory capacity.
Light- and electron microscopic investigations were conducted on the epithelium of the area glandulae gastricae propriae of the abomasum, using material of 12 East African game ruminants of nine ...species. The members of the main feeding categories (Hofmann, Stewart 1972): concentrate selector, roughage eater and intermediate feeder did not differ much in the ultrastructure of the fundic stomach epithelium but showed greater differences with respect to the height and shape of the glandular tubules and the arrangement of the epithelial cell types. Specifically the following cell types were observed: mucoid cells, chief cells, parietal cells, seven different endocrine cells, tuft cells and two types of migrating cells. In some epithelial celltypes of the concentrate selector dikdik, cristalloid cytoplasmic inclusions were found.
The mucous membrane of the Cloaca was investigated light and electronmicroscopically in 20 hens. Some histochemical investigations and a reabsorption test were carried out. The surface of the ...Coprodaeum is being formed by villi and deep crypts. The former disappears gradually within the Urodaeum. The latter crypts can be found down to the Proctodaeum. The epithelium of the Coprodaeum and Urodaeum consists of goblet cells and highprismatic cells containing secretory granules. The Proctodaeum can be subdivided into three parts. A cranial, containing the same epithelium as the Coprodaeum, a middle with a two layered highprismatic epithelium and a caudal part with a multilayered squamours epithelium. The columnar cells of all parts of the cloaca show a strong reaction to acid phosphatase and ATPase, whereas alkaline phosphatase is almost negative.
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