Enzyme cytochemical observations on the tissue stages of the life cycle of Eimeria acervulina and Eimeria necatrix

Cytochemical studies concerning the presence and distribution of various enzymes in the tissue stages of the life cycle of Eimeria acervulina and E. necatrix have been undertaken.Acid and alkaline phosphatases as well as ATPase (pH 7·2) were found to be present in all the stages of the life cycles examined, the latter enzyme being very strong in the plastic granules of the macrogametocytes and in the inner membrane of the oocyst wall. The reaction for all three enzymes was observed in the cytoplasm but not the nucleus. Non-specific esterase and glucose-6-phosphatase were also found in all stages examined, the latter occurring in greater amounts in stages where deposition of glycogen (amylopectin) was pronounced. Succinic dehydrogenase occurred only in the second generation schizonts and merozoites of E. necatrix and in the formed oocysts of both species. No reaction for β-glucuronidase or leucine naphthylamidase was apparent in any stage, although a slight reaction for leucine naphthlyamidase was seen in the second generation merozoites of E. necatrix lying free in the intestinal lumen.The presence and distribution of these enzymes and their possible function were discussed.     

Characterization of a Novel Intestinal Glycerol-3-phosphate Acyltransferase Pathway and Its Role in Lipid Homeostasis

Dietary triglycerides (TG) are absorbed by the enterocytes of the small intestine after luminal hydrolysis into monacylglycerol and fatty acids. Before secretion on chylomicrons, these lipids are reesterified into TG, primarily through the monoacylglycerol pathway. However, targeted deletion of the primary murine monoacylglycerol acyltransferase does not quantitatively affect lipid absorption, suggesting the existence of alternative pathways. Therefore, we investigated the role of the glycerol 3-phosphate pathway in dietary lipid absorption. The expression of glycerol-3-phosphate acyltransferase (GPAT3) was examined throughout the small intestine. To evaluate the role for GPAT3 in lipid absorption, mice harboring a disrupted GPAT3 gene (Gpat3^−/−) were subjected to an oral lipid challenge and fed a Western-type diet to characterize the role in lipid and cholesterol homeostasis. Additional mechanistic studies were performed in primary enterocytes. GPAT3 was abundantly expressed in the apical surface of enterocytes in the small intestine. After an oral lipid bolus, Gpat3^−/− mice exhibited attenuated plasma TG excursion and accumulated lipid in the enterocytes. Electron microscopy studies revealed a lack of lipids in the lamina propria and intercellular space in Gpat3^−/− mice. Gpat3^−/− enterocytes displayed a compensatory increase in the synthesis of phospholipid and cholesteryl ester. When fed a Western-type diet, hepatic TG and cholesteryl ester accumulation was significantly higher in Gpat3^−/− mice compared with the wild-type mice accompanied by elevated levels of alanine aminotransferase, a marker of liver injury. Dysregulation of bile acid metabolism was also evident in Gpat3-null mice. These studies identify GPAT3 as a novel enzyme involved in intestinal lipid metabolism.     

Intestinal absorption of copper from drinking water containing fulvic acids and an infant formula mixture studied in a suckling rat model

The purpose of this study was to investigate if the intestinal absorption of copper in drinking water is altered in the presence of complexing agents from a fulvic acid mixture and an infant formula powder. Ten to twelve day old rat pups were given a single oral dose of radio-labeled Cu in deionized water (0.93 mg Cu/l), in water containing fulvic acids (10 mg/l), in infant formula mixed with deionized water, or in infant formula mixed with water containing fulvic acids. Six hours after dosage, radioactive Cu was analyzed in the mucosa of the small intestine, the liver and the remaining carcass (excluding the liver and gastrointestinal tract) by gamma counting. Dialysis and centrifugation experiments showed that Cu was complexed by components in the fulvic acid and formula mixtures, although the presence of fulvic acids in the water did not alter the Cu fractionation in the formula. The fractional Cu uptake (% of dose) from the intestinal lumen to the mucosa was not markedly changed by the presence of the chelating agents. However, the retention of Cu in the intestinal mucosa was increased by both fulvic acids and formula. Concomitantly, the absorption rate of Cd to the circulatory system was decreased. No interactive effect between fulvic acids and formula was found on the Cu absorption. These findings indicate that the water quality may be an important determinant of the rate of intestinal Cu absorption from drinking water. Moreover, in the future risk assessment of copper in drinking water, the possibility of alterations in absorption of drinking-water Cu has to be considered when the drinking water is used for cooking.     

Maintenance of Functional Stem Cells in Isolated and Cultured Adult Intestinal Epithelium

We have previously described a method for the primary culture of adult large intestinal epithelium, suggesting that stem cells had survived both the isolation and the culture procedures. However, as no markers for such cells exist, confirmation of stem cell survival is difficult-only the functional properties can be used to define them. Unfortunately, many of these (e.g., differentiation, crypt regeneration) do not occur in culture, probably due to suboptimal conditions. To address this problem both freshly isolated and cultured small and large intestinal crypts were grown subcutaneously in an immunocompromized mouse. All initially formed cysts lined by a simple epithelium which gradually became multicellular and formed invaginations containing many mitoses and apoptoses. Epithelial differentiation, as assayed by Goblet cell mucin production, was also apparent. Mucin maturation was also typical of the normal intestine. The lumen was frequently filled with mucin and apoptotic bodies. Interestingly, in grafts displaying pronounced crypt-like morphology the regions of proliferation were situated toward the base of the structure and the Goblet cells toward the lumen, i.e., a typical crypt-like morphology. Hence, functional adult stem cells appear to survive isolation and tissue culture, permitting organotypic regeneration, possibly involving homeobox gene expression. This may now allow direct stem cell characterization and experimental manipulation, such as transfection, and may ultimately permit transplantation and therapeutic gene therapy.     

In vivo, villin is required for Ca(2+)-dependent F-actin disruption in intestinal brush borders.

Villin is an actin-binding protein localized in intestinal and kidney brush borders. In vitro, villin has been demonstrated to bundle and sever F-actin in a Ca(2+)-dependent manner. We generated knockout mice to study the role of villin in vivo. In villin-null mice, no noticeable changes were observed in the ultrastructure of the microvilli or in the localization and expression of the actin-binding and membrane proteins of the intestine. Interestingly, the response to elevated intracellular Ca(2+) differed significantly between mutant and normal mice. In wild-type animals, isolated brush borders were disrupted by the addition of Ca(2+), whereas Ca(2+) had no effect in villin-null isolates. Moreover, increase in intracellular Ca(2+) by serosal carbachol or mucosal Ca(2+) ionophore A23187 application abolished the F-actin labeling only in the brush border of wild-type animals. This F-actin disruption was also observed in physiological fasting/refeeding experiments. Oral administration of dextran sulfate sodium, an agent that causes colonic epithelial injury, induced large mucosal lesions resulting in a higher death probability in mice lacking villin, 36 +/- 9.6%, compared with wild-type mice, 70 +/- 8.8%, at day 13. These results suggest that in vivo, villin is not necessary for the bundling of F-actin microfilaments, whereas it is necessary for the reorganization elicited by various signals. We postulate that this property might be involved in cellular plasticity related to cell injury.     

大洋性头足类胃和肠道中的微塑料——以秘鲁外海茎柔鱼为例

海洋动物摄入微塑料已得到广泛证实,但对于大洋性头足类动物仍存在较大空白.茎柔鱼是头足类商业捕捞中产量最高的物种,在东太平洋生态系统占主导地位.本研究以秘鲁外海茎柔鱼成体为对象,定量分析胃和肠道内微塑料的丰度与组成,并探究微塑料在组织和性别间的潜在差异.结果 表明:茎柔鱼雌、雄个体相同组织内存在相似的微塑料丰度与组成.组...     

Casein kinase 1‐epsilon or 1‐delta required for Wnt‐mediated intestinal stem cell maintenance

The intestinal epithelium holds an immense regenerative capacity mobilized by intestinal stem cells (ISCs), much of it supported by Wnt pathway activation. Several unique regulatory mechanisms ensuring optimal levels of Wnt signaling have been recognized in ISCs. Here, we identify another Wnt signaling amplifier, CKIε, which is specifically upregulated in ISCs and is essential for ISC maintenance, especially in the absence of its close isoform CKIδ. Co‐ablation of CKIδ/ε in the mouse gut epithelium results in rapid ISC elimination, with subsequent growth arrest, crypt–villous shrinking, and rapid mouse death. Unexpectedly, Wnt activation is preserved in all CKIδ/ε‐deficient enterocyte populations, with the exception of Lgr5⁺ ISCs, which exhibit Dvl2‐dependent Wnt signaling attenuation. CKIδ/ε‐depleted gut organoids cease proliferating and die rapidly, yet survive and resume self‐renewal upon reconstitution of Dvl2 expression. Our study underscores a unique regulation mode of the Wnt pathway in ISCs, possibly providing new means of stem cell enrichment for regenerative medicine.     

猪源乳酸菌产乳酸及其抑菌特性研究

研究了5株(L1、12、L3、L5和L7)分离自仔猪肠道的乳酸菌的产乳酸能力及抑菌特性。结果表明：L5菌株产乳酸的速度最快,培养液中乳酸含量最高,L5菌株培养液pH值的下降速度最快,终末pH值最低,而L1菌株产乳酸的速度最慢,培养液乳酸含量最低。5株乳酸菌对大肠杆菌K88、K99、987P、O141和大肠杆菌E1及金黄色葡萄球菌均有不同程度的抑制作用;排除酸的影响后仍有22％～53％抑菌效果;经热处理后保持有92％以上的抑菌效果;蛋白酶处理后保持85％以上的抑菌效果。     

Ultrastructure of Enteromyxum leei (Diamant, Lom, & Dyková, 1994) (Myxozoa), an Enteric Parasite Infecting Gilthead Sea Bream (Sparus aurata) and Sharpsnout Sea Bream (Diplodus puntazzo)

ABSTRACT. The ultrastructure of the developmental stages of the myxozoan Enteromyxum leei parasitizing gilthead seabream ( Sparus aurata ) intestine and sharpsnout sea bream ( Diplodus puntazzo ) intestine and gallbladder are described. The earliest stage observed was a small dense trophozoite located among enterocytes. Proliferative stages, observed intercellularly in the epithelium of the intestine and gallbladder as well as in the lumen, possessed the typical cell-in-cell configuration throughout their development. Secondary cells were seen undergoing division within a common vacuolar membrane that also encompassed pairs of tertiary cells. Cytochemical studies showed that primary cells stored mainly lipids whereas secondary cells stored abundant β-glycogen granules. Sporogonic development resembled that described for other disporous myxozoans. Within sporogonic stages, nonsporogonic secondary cells were observed accompanying two developing spores. Mature spores had a binucleated sporoplasm in which glycogen stores were abundant and no sporoplasmosomes were found. Our observations are discussed in relation to our knowledge on other myxozoans of the genus Enteromyxum .