Msh2 status modulates both apoptosis and mutation frequency in the murine small intestine.
(25/6741)
Deficiency in genes involved in DNA mismatch repair increases susceptibility to cancer, particularly of the colorectal epithelium. Using Msh2 null mice, we demonstrate that this genetic defect renders normal intestinal epithelial cells susceptible to mutation in vivo at the Dlb-1 locus. Compared with wild-type mice, Msh2-deficient animals had higher basal levels of mutation and were more sensitive to the mutagenic effects of temozolomide. Experiments using Msh2-deficient cells in vitro suggest that an element of this effect is attributable to increased clonogenicity. Indeed, we show that Msh2 plays a role in the in vivo initiation of apoptosis after treatment with temozolomide, N-methyl-N'-nitro-N-nitrosoguanidine, and cisplatin. This was not influenced by the in vivo depletion of O6-alkylguanine-DNA-alkyltransferase after administration of O6-benzylguanine. By analyzing mice mutant for both Msh2 and p53, we found that the Msh2-dependent apoptotic response was primarily mediated through a p53-dependent pathway. Msh2 also was required to signal delayed p53-independent death. Taken together, these studies characterize an in vivo Msh2-dependent apoptotic response to methylating agents and raise the possibility that Msh2 deficiency may predispose to malignancy not only through failed repair of mismatch DNA lesions but also through the failure to engage apoptosis. (+info)
Mucosal events in the pathogenesis of human immunodeficiency virus type 1 infection.
(26/6741)
The interaction between human immunodeficiency virus type 1 (HIV-1) and primary mucosal cells isolated from normal human small intestine was investigated. Purified primary intestinal epithelial cells could transport cell-free HIV-1 to mononuclear cells, although the epithelial cells did not support viral replication. An unexpected finding was that primary intestinal macrophages were markedly less permissive to HIV-1 than were blood monocytes. The reduced permissiveness appeared to be due to the near absence of surface CCR5 on resident intestinal macrophages. Surface CCR5 could be up-regulated on the monocytes but not the intestinal macrophages by HIV-1 and gp120. Impaired permissiveness of intestinal macrophages to HIV-1 may play an important role in the low prevalence of HIV-1 mRNA-expressing macrophages in the lamina propria during HIV-1 infection in vivo. Characterization of the biologic properties of HIV-1 transport and infection in primary mucosal cells will be key to elucidating the pivotal role of mucosal surfaces in HIV-1 disease. (+info)
Western blot analysis of bile or intestinal fluid from patients with septic shock or systemic inflammatory response syndrome, using antibodies to TNF-alpha, IL-1 alpha and IL-1 beta.
(27/6741)
Septic shock or systemic inflammatory response syndrome (SIRS) often develops in patients following burns, traumatic injury, surgery or biliary obstruction. Although the inflammatory cytokines TNF-alpha and IL-1 have been strongly implicated in the development of these syndromes, treatment of patients by the systemic administration of inhibitors of TNF-alpha or IL-1 has shown limited effectiveness. Recent reports suggest that septic shock may be perpetuated by inflammatory cytokines secreted by the liver in response to bacterial translocation resulting from cytokine-induced gastrointestinal damage. The present study sought to demonstrate the presence of high levels of inflammatory cytokines in the bile or small intestine of patients suffering from septic shock or SIRS, with a view to the development of strategies for the reduction of gastrointestinal damage through intraduodenal administration of cytokine inhibitors. Western blot analysis of human bile or intestinal fluid using anti-TNF-alpha antibodies resulted in the detection of a number of bands in samples from patients with septic shock or SIRS. However, these proteins differed antigenically from human recombinant TNF-alpha (rTNF-alpha) and showed no activity in a biological assay for TNF-alpha. Antibodies to IL-1 alpha and IL-1 beta detected several strong bands, some of which appeared to be identical to recombinant IL-1 alpha and IL-1 beta. It is concluded that proteins resembling several known inflammatory cytokines are present in the bile and intestine of septic shock patients, but it is suggested that further work is required to determine the nature and function of these molecules. (+info)
Effect of intraluminal oxygen on experimental ischaemia of the intestine.
(28/6741)
The small bowel of 44 rats has been made ischaemic for 120 minutes by occluding the superior mesenteric artery. Gaseous oxygen was introduced into the small bowel lumen of 18 of the rats, and gaseous nitrogen into the bowel lumen of a further eight, 30 minutes after the start of the ischaemia. The mortality rate of the control group of 18 rats was 89%, significantly higher than the 39% mortality of the oxygen-treated rats (p less than 0-005). None of the eight rats treated with intraluminal nitrogen survived. Histological changes caused by ischaemia were much reduced in the intestine of the oxygen treated rats. It is suggested that intraluminal oxygen might be useful additional form of therapy for the treatment of the partially ischaemic bowel that may be retained after the resection of definitely non-viable ischaemic bowel at initial laparotomy. (+info)
Sugars and sugar derivatives which inhibit the short-circuit current of the everted small intestine of the rat.
(29/6741)
1. The short-circuit current of everted rat intestine supported on a perforated cannula proved to be stable for up to 3 hr and has been used to study competition between transportable and non-transportable sugars. 2. 4,6-O-Ethylidene-alpha-D-glucopyranose (ethylidene glucose) and 4,6-O-benzylidene-e alpha-D-glucopyranos (benzylinene glucose), two nontransportable inhibitors of the hexose transfer system in human erythrocytes, were found to reduce the short-circuit current generated by transportable sugars such as galactose or 3-O-methyl glucose. 3. These compounds were also found to reduce the basal short-circuit current established by the everted intestine in a sugar-free Krebs solution. Both types of inhibition approached saturation at the higher concentrations used. 4. Similar inhibitory properties were shown by mannose, a non-actively accumulated monosaccharide, and by the beta-disaccharides lactose and cellobiose. 5. It is suggested that this common pattern of behaviour is due to the ability of these compounds to react with the sites for active hexose transfer but without translocation by the system. The significance of the inhibition of the basal short-circuit current is briefly discussed in this context. (+info)
Effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae.
(30/6741)
The effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae (L3) to rats were investigated. A significantly higher body length was observed in L3 from filter paper culture (597.3 +/- 32.2 microns) than those in fecal (509.9 +/- 35.0 microns) and nutrient broth culture (503.3 +/- 31.0 microns) (P < 0.05). Larval infectivity was assessed by exposing rats to 1,000 L3 from each culture and worms were recovered from the lungs and small intestines. Recovery rate of these worms did not show any significant difference. A significantly greater body length of adults was recorded in those corresponding to the L3 harvested from filter paper (2,777.5 +/- 204.4 microns) and nutrient broth culture (2,732.5 +/- 169.8 microns) than those corresponding to the L3 obtained from fecal culture (2,600.5 +/- 172.4 microns) (P < 0.05). Although worm fecundity and EPG counts differed among culture methods but worm burdens and course of infection did not. These findings suggest that the methods of cultures have a significant effect on the morphological development of the larvae to the L3 stage, but do not influence the infectivity to rats. (+info)
Cyclooxygenase 2 is up-regulated and localized to macrophages in the intestine of Min mice.
(31/6741)
Expression of cyclooxygenase 2 (COX-2) is believed to play an important role in adenoma formation in murine polyposis models, and inhibition of COX-2 activity may, at least, partly explain the chemopreventative activity of non-steroidal anti-inflammatory drugs against colorectal cancer in humans. However, the mechanism by which COX-2 acts in intestinal tumorigenesis remains unresolved because of conflicting data on the cellular localization of COX-2 in intestinal mucosa. Using immunohistochemistry with specific COX-2 antiserum, we have shown that COX-2 protein is localized to interstitial cells at the base of and within adenomas of the small and large intestine of multiple intestinal neoplasia (Min) mice. No COX-2 staining was observed in dysplastic epithelial cells within adenomas or in histologically normal epithelium. Moreover, COX-2 staining was observed in lamina propria cells of histologically normal intestine of Min mice. No staining was demonstrated in wild-type littermates. The rat monoclonal antibody F4/80 was used to show that COX-2-positive cells represented a subset of the macrophage population present in the intestine of Min mice. Localization of COX-2 to macrophages implies a paracrine effect of COX-2 function on epithelial cells in adenomas and also on histologically normal epithelium. Up-regulation of COX-2 expression in lamina propria macrophages may precede loss of the second functional Apc allele in epithelial cells before adenoma formation in the Min mouse model of intestinal tumorigenesis. (+info)
Assessment of the effects of endothelin-1 and magnesium sulphate on regional blood flows in conscious rats, by the coloured microsphere reference technique.
(32/6741)
There is evidence to suggest that magnesium (Mg2+) is beneficial in the treatment of a number of conditions, including pre-eclampsia and acute myocardial infarction. The mode of action of Mg2+ in these conditions is not clear, although the vasodilator properties of Mg2+ are well documented both in vitro and in vivo. Previously, we demonstrated that i.v. infusion of magnesium sulphate (MgSO4) alone, or in the presence of vasoconstrictors, caused increases in flow and conductance in the common carotid, internal carotid and hindquarters vascular beds, in conscious rats. Therefore, the objective of the present study was to investigate the regional and subregional changes in haemodynamics in response to the vasoconstrictor peptide endothelin-1 (ET-1) and MgSO4 in more detail, using the coloured microsphere reference technique. Infusion of ET-1 and MgSO4 had similar effects on heart rate and mean arterial pressure as in our previous study. Infusion of ET-1 caused a rise in mean arterial pressure and a fall in heart rate, and infusion of MgSO4 returned mean arterial pressure to control levels with no effect on heart rate. The responses to MgSO4 in the presence of ET-1 showed considerable regional heterogeneity with blood flow increasing (e.g. skeletal muscle), decreasing (e.g. stomach) or not changing (e.g. kidney). Of particular interest was the finding that MgSO4 caused increases in flow in the cerebral and coronary vascular beds. This, and our previous studies, have shown that MgSO4 can reverse vasoconstriction in a number of vascular beds, and indicate that this compound may have therapeutic benefit in conditions associated with vasospasm. (+info)