Interaction of microorganisms with enterocytes after oral administration of pesticides

Intragastral administration of the pesticides Sumi-alpha and Omait to rats significantly increases the number of parietal microorganisms in the jejunum, ileum, and particularly in the cecum. Electron microscopy shows that parietal microorganisms invade goblet cells during secretion and then enter prismatic cells via the lateral plasma membrane. The number of parietal microorganisms entering enterocytes after Sumi-alpha is higher than after less toxic Omait, reaching the maximum 5 h after administration. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 123, No. 4, pp. 467–470, April, 1997     

Chylomicron Retention Disease: The Role of Ultrastructural Examination in Differential Diagnosis

Three children with malabsorption presumably caused by celiac disease had undergone jejunal biopsy. While a histological examination revealed microvacuolization of enterocytes in the absence of celiac lesions, an ultrastructural investigation disclosed numerous chylomicrons and larger lipid vacuoles inside the cytoplasm of enterocytes, mostly in the supranuclear region. No chylomicrons were evident in the interstitium between adjacent enterocytes, as observed in normal subjects. These ultrastructural findings allowed for the diagnosis of "Chylomicron retention disease" (CRD). CRD was described for the first time by Anderson in 1961, and it is included in the group of disorders of biosynthesis and secretion of B apolipoproteins (apoB). This disease, in particular, appears to result from a specific defect involving the secretion of lipoproteins containing apoB-48 from the gut, with the complete absence of post prandial chylomicrons in the sera. CRD needs to be recognized early because of its adverse effects on growth and its potential for neurological and ocular complications, and the ultrastructural identification of chylomicron-size lipid droplets clustered in the enterocytes, with the absence of fat outside the cells, represents the gold standard to identify CRD. together with clinical aspects and laboratory measurements. In this study, we describe the histological and ultrastructural aspects observed in three pediatric cases of CRD.     

Insulin induced hypoglycaemia and sugar transport across the brush border and basolateral membranes of rat jejunal enterocytes

Abstract. Acute hypoglycaemia enhances intestinal sugar uptake but the mechanisms involved are unknown. Results from the present study show increased galactose movement across the brush border and basolateral membranes of isolated upper, but not mid-villus, jejunal enterocytes 45 min after intravenous administration of insulin to rats at a level which reduced by half plasma glucose concentration. Incubation of upper villus cells from uninjected animals with insulin (100 mU ml^-1) for 40 min was without effect on brush border or basolateral sugar transport. Insulin treatment of rats did not affect glucose uptake by brush border vesicles prepared from upper villus cells when the process was driven by an inwardly directed 100 mM sodium thiocyanate gradient. In contrast, glucose uptake using a 100 mM inwardly directed sodium chloride gradient was reduced by 49% following hypoglycaemia. It is concluded that the enhanced sugar uptake following insulin hypoglycaemia involves both brush border and basolateral membranes of only the most mature villus cells at the villus tip. Upregulation of Na⁺-sugar cotransport at the brush border is best explained by an increased electrochemical driving force for Na ⁺-sugar cotransport rather than increased numbers of transporters. The transport response is not due to a direct effect of insulin on the enterocyte and the possible systemic factors involved are discussed.     

Translocation of protein kinase-C with IP3-induced calcium mobilization by heat-stable enterotoxin of Vibrio cholerae non-O1 in isolated rat enterocytes

The activity of the calcium- and phospholipid-dependent enzyme protein kinase C (PKC) in response to heat-stable enterotoxin (NAG-ST) of Vibrio cholerae non-O1 was examined in isolated rat enterocytes. Optimal stimulation of the membrane-bound PKC activity (about 4.3-fold) was observed after 1 min of incubation of cells with 10 ng/ml toxin; and the effects were dose dependent. Following NAG-ST treatment an increase in PKC activity in the membrane fraction was found with a concomitant decrease in the cytosolic fraction suggesting the redistribution of the enzyme. The pronounced enzyme activity in presence of a classical pseudosubstrate and its complete inhibition by G? 6976 suggested the involvement of a calcium-dependent isoform of PKC (PKC-alpha). A time course study employing an immunoblot assay provided evidence that NAG-ST led to almost complete translocation of PKC-alpha to the membrane. A 65% inhibition of enzyme activity in the membrane fraction and inhibition of its translocation to some extent by dantrolene treatment further suggested that the enzyme was translocated with the rise of intracellular calcium ([Ca2+]i). The phosphorylation of three membrane proteins by toxin-induced PKC in vitro and abolition of this phosphorylation by G? 6976 demonstrated that phosphorylation of these membrane proteins was PKC-alpha mediated and might be involved in the alteration of membrane functions.     

Erythropoietin acts as a trophic factor in neonatal rat intestine

BACKGROUND: Erythropoietin (Epo) receptors are present on enterocytes of fetal and neonatal small bowel but the role of Epo in the bowel is not known. AIMS: We tested the following hypotheses: (1) enterally dosed Epo is absorbed from the intestines of neonatal rats, (2) Epo acts as a trophic factor in developing small bowel, and (3) the trophic effects of Epo are dependent on the route of administration. METHODS: The dose dependent effects of enterally dosed recombinant human erythropoietin (rEpo 0--1000 U/kg/day) were studied in artificially raised rat pups and compared with dam raised controls and dam raised pups given rEpo in rat milk. After one week, reticulocyte counts, haematocrits, and plasma Epo concentrations were measured, and calibrated morphometric measurements of villi were performed. The effects of route of rEpo administration (enteral v parenteral) on erythropoiesis, bowel growth, and disaccharidase activity were studied in nursing pups treated for one and two weeks. RESULTS: Serum Epo concentrations ranged from undetectable (<0.6 mU/ml) to 8.4 mU/ml in control and enterally dosed pups (median 1.8 mU/ml), and from 4.9 to 82.3 mU/ml (median 20.4 mU/ml) in parenterally dosed animals. No increase in haematocrit or reticulocyte count was noted in enterally treated pups compared with controls after up to two weeks of treatment. Small bowel length was greater in rEpo treated pups, and a dose dependent increase in villus surface area which was independent of the route of dosing and associated with increased BrdU uptake was found. CONCLUSIONS: rEpo is not enterally absorbed in an intact and functional form from the intestines of neonatal rat pups. Thus enterally dosed rEpo has no erythropoietic effects. However, rEpo acts as a trophic factor in developing rat small bowel whether given enterally or parenterally.     

参环毛蚓不同部位细胞原代培养及鉴定

目的：筛选出参环毛蚓体内细胞培养的最佳部位,为建立参环毛蚓细胞原代培养方法提供实验基础。方法：分别提取参环毛蚓的皮、肠道、嗉囊、前列腺细胞进行培养,观察其细胞生长。结果：参环毛蚓的表皮和肠道细胞经培养后,细胞均有生长,并发现肠道细胞生长良好,5~6天后基本达到融合,细胞呈多边鹅卵石样,透明度及折光性强。另发现参环毛蚓的嗉囊、前列腺等部位的细胞没有增长迹象。结合形态学鉴定,原代培养及传代的细胞98%以上为肠上皮细胞。结论：参环毛蚓的肠道是建立细胞系的首选材料,采用此方法分离培养的肠上皮细胞数量多,均一性生长佳,可重复性强。     

Characteristics of the chicken proximal cecum hexose transport system

The properties of the sugar transport system present in chicken proximal cecum have been studied and compared to the jejunal transport system. Experiments were carried out in isolated enterocytes from 5- to 7-weak-old birds. Results show that: (1) Cecal cells are capable of high sugar transport rates by a phloridzin-sensitive mechanism. After 60 min incubation, the accumulation ratio (control/phloridzin-incubated cells) for 0.1 mmol/l -methyl-d-glucoside (-MG) was 43 and that of 3-oxy-methyl-d-glucose (3-OMG) was 25. In jejunal cells, ratios were 37 for -MG and 13 for 3-OMG. The differences found in cumulative capacity of 3-OMG between cecal and jejunal cells suggest that the sodium-independent pathway offers a very small contribution to sugar efflux in the steady-state in the former cells. (2) Lowering external Na⁺ concentration reduces the steady-state -MG accumulation in cecal cells (as in jejunal cells), indicating that the transport system is Na⁺-dependent. (3) The process depends on the electrochemical Na⁺ gradient across the cell membrane since both 2,4-dinitrophenol (0.2 mmol/l) and ouabain (0.25 mmol/l) abolish sugar accumulation. (4) Addition of 10 mmol/l 3-OMG to the incubation medium markedly reduces the uptake of -MG (concentration: 0.1 mmol/l), indicating that the cecal transport system can be inhibited by analogues of the transported substrate. (5) The specific sugar transport process is a saturable function of -MG concentration, the apparentK _m being 1.02 mmol/l andV _m 10.7 nmol/mg cell protein · min. Kinetic constants in jejunal enterocytes were 1.58 mmol/l (K _m) and 24.7 nmol/mg cell protein · min (V _m), respectively. In brief, the proximal cecal epithelium has a sugar transport system with properties similar to those of the jejunum which suggests a role of this epithelium in the absorption of hexoses of either ileal or cecal origin.     

Proteomic profiling of halloysite clay nanotube exposure in intestinal cell co‐culture

Halloysite is aluminosilicate clay with a hollow tubular structure with nanoscale internal and external diameters. Assessment of halloysite biocompatibility has gained importance in view of its potential application in oral drug delivery. To investigate the effect of halloysite nanotubes on an in vitro model of the large intestine, Caco‐2/HT29‐MTX cells in monolayer co‐culture were exposed to nanotubes for toxicity tests and proteomic analysis. Results indicate that halloysite exhibits a high degree of biocompatibility characterized by an absence of cytotoxicity, in spite of elevated pro‐inflammatory cytokine release. Exposure‐specific changes in expression were observed among 4081 proteins analyzed. Bioinformatic analysis of differentially expressed protein profiles suggest that halloysite stimulates processes related to cell growth and proliferation, subtle responses to cell infection, irritation and injury, enhanced antioxidant capability, and an overall adaptive response to exposure. These potentially relevant functional effects warrant further investigation in in vivo models and suggest that chronic or bolus occupational exposure to halloysite nanotubes may have unintended outcomes. Copyright © 2013 John Wiley & Sons, Ltd.