The structures of the colonic mucosa-associated and luminal microbial communities are distinct and differentially affected by a prolonged murine stressor

The commensal microbiota of the human gastrointestinal tract live in a largely stable community structure, assisting in host physiological and immunological functions. Changes to this structure can be injurious to the health of the host, a concept termed dysbiosis. Psychological stress is a factor that has been implicated in causing dysbiosis, and studies performed by our lab have shown that restraint stress can indeed shift the cecal microbiota structure as well as increase the severity of a colonic infection caused by Citrobacter rodentium. However, this study, like many others, have focused on fecal contents when examining the effect of dysbiosis-causing stimuli (e.g. psychological stress) upon the microbiota. Since the mucosa-associated microbiota have unique properties and functions that can act upon the host, it is important to understand how stressor exposure might affect this niche of bacteria. To begin to understand whether chronic restraint stress changes the mucosa-associated and/or luminal microbiota mice underwent 7 16-hour cycles of restraint stress, and the microbiota of both colonic tissue and fecal contents were analyzed by sequencing using next-gen bacterial tag-encoded FLX amplicon technology (bTEFAP) pyrosequencing. Both control and stress groups had significantly different mucosa-associated and luminal microbiota communities, highlighting the importance of focusing gastrointestinal community structure analysis by microbial niche. Furthermore, restraint stress was able to disrupt both the mucosa-associated and luminally-associated colonic microbiota by shifting the relative abundances of multiple groups of bacteria. Among these changes, there was a significant reduction in the immunomodulatory commensal genus Lactobacillus associated with colonic mucosa. The relative abundance of Lactobacillus spp. was not affected in the lumen. These results indicate that stressor-exposure can have distinct effects upon the colonic microbiota situated at the mucosal epithelium in comparison to the luminal-associated microbiota.     

High throughput sequencing reveals distinct microbial populations within the mucosal and luminal niches in healthy individuals

Background: The intestinal microbiota is associated with human health and diseases. The luminal microbiota (LM) and the mucosal-associated microbiota (MAM) are 2 distinct ecosystems with different metabolic and immunological functions. Aim: To characterize the intestinal LM and MAM in humans using high throughput sequencing of the 16S rRNA gene. Methods: Fresh fecal samples and distal colonic mucosal biopsies collected from 24 healthy subjects before (fecal) and during (mucosa) a flexible sigmoidoscopy of an un-prepared bowel. High throughput sequencing of the 16S rRNA gene was used to characterize bacterial communities. Sequences were processed using the QIIME pipeline. Results: LM and MAM populations were significantly different (ANOSIM: R = 0.49, P = 0.001). The LM displayed tighter clustering compared to the MAM (average weighted UniFrac distances 0.27 ± 0.05 vs. 0.43 ± 0.09, P < 0.001, respectively), and showed higher diversity (Shannon diversity index: 4.96 ± 0.37 vs 4.14 ± 0.56, respectively, P < 0.001). The dominant phyla in the LM and MAM were significantly different: Firmicutes (41.4% vs. 29.1%, FDR < 0.0001, respectively), Bacteroidetes (20.2% vs. 26.3%, FDR < 0.05, respectively), Actinobacteria (22% vs. 12.6%, FDR < 0.0001, respectively) and Proteobacteria (9.3% vs. 19.3%, FDR < 0.0001, respectively). The abundance of 56 genera differed significantly (FDR < 0.1) between the 2 niches. All of the genera in the fecal microbiota were present in the MAM while 10 genera were found to be unique to the MAM. Conclusion: The LM and MAM are distinct microbial ecosystems that differ significantly from each other in microbial diversity and composition. These two microbial niches should be investigated independently to better understand the role of the intestinal microbiota in health and disease.     

High throughput sequencing reveals distinct microbial populations within the mucosal and luminal niches in healthy individuals

Background: The intestinal microbiota is associated with human health and diseases. The luminal microbiota (LM) and the mucosal-associated microbiota (MAM) are 2 distinct ecosystems with different metabolic and immunological functions. Aim: To characterize the intestinal LM and MAM in humans using high throughput sequencing of the 16S rRNA gene. Methods: Fresh fecal samples and distal colonic mucosal biopsies collected from 24 healthy subjects before (fecal) and during (mucosa) a flexible sigmoidoscopy of an un-prepared bowel. High throughput sequencing of the 16S rRNA gene was used to characterize bacterial communities. Sequences were processed using the QIIME pipeline. Results: LM and MAM populations were significantly different (ANOSIM: R = 0.49, P = 0.001). The LM displayed tighter clustering compared to the MAM (average weighted UniFrac distances 0.27 ± 0.05 vs. 0.43 ± 0.09, P < 0.001, respectively), and showed higher diversity (Shannon diversity index: 4.96 ± 0.37 vs 4.14 ± 0.56, respectively, P < 0.001). The dominant phyla in the LM and MAM were significantly different: Firmicutes (41.4% vs. 29.1%, FDR < 0.0001, respectively), Bacteroidetes (20.2% vs. 26.3%, FDR < 0.05, respectively), Actinobacteria (22% vs. 12.6%, FDR < 0.0001, respectively) and Proteobacteria (9.3% vs. 19.3%, FDR < 0.0001, respectively). The abundance of 56 genera differed significantly (FDR < 0.1) between the 2 niches. All of the genera in the fecal microbiota were present in the MAM while 10 genera were found to be unique to the MAM. Conclusion: The LM and MAM are distinct microbial ecosystems that differ significantly from each other in microbial diversity and composition. These two microbial niches should be investigated independently to better understand the role of the intestinal microbiota in health and disease.     

Dynamic changes of the luminal and mucosa-associated gut microbiota during and after antibiotic therapy with paromomycin

Gut microbiota play a key role in the host''s health system. Broad antibiotic therapy is known to disrupt the microbial balance affecting pathogenic as well as host-associated microbes. The aim of the present study was to investigate the influence of antibiotic paromomycin on the luminal and mucosa-associated microbiota at the DNA (abundance) and RNA (potential activity) level as well as to identify possible differences. The influence of antibiotic treatment on intestinal microbiota was investigated in 5 healthy individuals (age range: 20–22 years). All participants received the antibiotic paromomycin for 3 d. Fecal samples as well as sigmoidal biopsies were collected before and immediately after cessation of antibiotic treatment as well as after a recovery phase of 42 d. Compartment- and treatment status-specific indicator operational taxonomic units (OTUs) as well as abundance- and activity-specific patterns were identified by 16S rRNA and 16S rRNA gene amplicon libraries and high-throughput pyrosequencing. Microbial composition of lumen and mucosa were significantly different at the DNA compared to the RNA level. Antibiotic treatment resulted in changes of the microbiota, affecting the luminal and mucosal bacteria in a similar way. Several OTUs were identified as compartment- and/or treatment status-specific. Abundance and activity patterns of some indicator OTUs differed considerably. The study shows fundamental changes in composition of gut microbiota under antibiotic therapy at both the potential activity and the abundance level at different treatment status. It may help to understand the complex processes of gut microbiota changes involved in resilience mechanisms and on development of antibiotic-associated clinical diseases.     

Dynamic changes of the luminal and mucosa-associated gut microbiota during and after antibiotic therapy with paromomycin

Gut microbiota play a key role in the host's health system. Broad antibiotic therapy is known to disrupt the microbial balance affecting pathogenic as well as host-associated microbes. The aim of the present study was to investigate the influence of antibiotic paromomycin on the luminal and mucosa-associated microbiota at the DNA (abundance) and RNA (potential activity) level as well as to identify possible differences. The influence of antibiotic treatment on intestinal microbiota was investigated in 5 healthy individuals (age range: 20–22 years). All participants received the antibiotic paromomycin for 3 d. Fecal samples as well as sigmoidal biopsies were collected before and immediately after cessation of antibiotic treatment as well as after a recovery phase of 42 d. Compartment- and treatment status-specific indicator operational taxonomic units (OTUs) as well as abundance- and activity-specific patterns were identified by 16S rRNA and 16S rRNA gene amplicon libraries and high-throughput pyrosequencing. Microbial composition of lumen and mucosa were significantly different at the DNA compared to the RNA level. Antibiotic treatment resulted in changes of the microbiota, affecting the luminal and mucosal bacteria in a similar way. Several OTUs were identified as compartment- and/or treatment status-specific. Abundance and activity patterns of some indicator OTUs differed considerably. The study shows fundamental changes in composition of gut microbiota under antibiotic therapy at both the potential activity and the abundance level at different treatment status. It may help to understand the complex processes of gut microbiota changes involved in resilience mechanisms and on development of antibiotic-associated clinical diseases.     

The metabolic effects of endotoxin are differentially affected by the pattern of GH administration in the rat

GH treatment can increase the mortality and morbidity of critically ill patients. The mechanisms of these harmful effects of GH are unknown but have been, in part, ascribed to interactions between GH and the immune system. Because GH has pattern-dependent actions we have now compared the dose-related effects of continuous and intermittent GH treatment given with or without an endotoxin (lipopolysaccharide; LPS) challenge. Male Wistar rats (n=6 per group) were treated for 5 days with recombinant human GH (0, 10, 100 or 1000 microg/kg per day) using either continuous s.c. infusion by osmotic minipump or intermittent twice daily s.c. injections. On day 4, endotoxin (5 mg/kg, i.p.) was injected and the animals monitored for a further 16 h. LPS administration alone led to neutrophilia and lymphopoenia, with increased plasma concentrations of urea, cholesterol, triglyceride, insulin and leptin, and decreased levels of IGF-I. High dose GH infusion (1000 microg/kg per day) followed by LPS caused greater increases in plasma urea, cholesterol, triglyceride, sodium and magnesium, but lower plasma glucose and insulin levels, than treatment with LPS alone. In contrast, twice daily injections of GH did not enhance these effects of endotoxin. In conclusion, the effects of endotoxin on plasma electrolytes, lipids, urea, glucose and insulin are differentially affected by the pattern of GH administration in the rat.     

Dietary destabilisation of the balance between the microbiota and the colonic mucus barrier

It has long been acknowledged that dietary fibres are important to maintain a healthy gut. Over the past decade, several studies have shown that loss of complex polysaccharides from the Western diet has resulted in alterations to our colonic microbiota. The concurrent increase in the incidence of inflammatory bowel disease in the Western world has driven us to explore the potential mechanistic link between diet, the microbiota and the host defence systems that normally prevent inflammation. Using mice fed a low fibre Western-style diet and robust live tissue analytical methods we have now provided evidence that this diet impairs the colonic inner mucus layer that normally separates bacteria from host cells. Western societies urgently need to develop their understanding of the molecular mechanisms of the diet-microbiota-mucus axis and its implications for inflammatory diseases.     

Freeze-dried fecal samples are biologically active after long-lasting storage and suited to fecal microbiota transplantation in a preclinical murine model of Clostridioides difficile infection

ABSTRACT

Fecal microbiota transplantation is now recommended for treating recurrent forms of Clostridioides difficile infection. Recent studies have reported protocols using capsules of either frozen or freeze-dried stool allowing oral administration in in- and out-patient settings. However, a central question remains the viability, engraftment, and efficacy of the microbiome over time during storage life. This study shows that both the freeze-drying and freezing procedures for fecal samples allowed preserving viability, short-chain fatty acids concentration, and anti-Clostridioides difficile properties of microbiota without significant alteration after storage for 12 months. Fecal transplantation with freeze-dried microbiota allowed engraftment of microbiota leading to clearance of Clostridioides difficile infection in a preclinical murine model with a survival rate of 70% versus 53-60% in mice treated with frozen inocula, and 20% in the untreated group. Moreover, the freeze-dried powder can be used to fill oral hard capsules using a very low amount (0.5%) of glidant excipient, allowing oral formulation. Altogether, this study showed that freeze-dried inocula can be used for the treatment of Clostridioides difficile infection with long-lasting stability of the fecal microbiota. This formulation facilitates biobanking and allows the use of hard capsules, an essential step to simplify patient access to treatment.     

Distinct forms of Gq-receptor-dependent plasticity of excitatory transmission in the BNST are differentially affected by stress

Long-term depression (LTD) is an important synaptic mechanism for limiting excitatory influence over circuits subserving cognitive and emotional behavior. A major means of LTD induction is through the recruitment of signaling via G_q-linked receptors activated by norepinephrine (NE), acetylcholine, and glutamate. Receptors from these transmitter families have been proposed to converge on a common postsynaptic LTD maintenance mechanism, such that hetero- and homosynaptic induction produce similar alterations in glutamate synapse efficacy. We report that in the dorsolateral and ventrolateral bed nucleus of the stria terminalis (BNST), recruitment of G_q-linked receptors by glutamate or NE initiates mechanistically distinct forms of postsynaptically maintained LTD and these LTDs are differentially regulated by stress exposure. In particular, we show that although both mGluR5- and α₁-adrenergic receptor (AR)-dependent LTDs involve postsynaptic endocytosis, the α₁-AR-initiated LTD exclusively involves modulation of signaling through calcium-permeable AMPA receptors. Further, α₁-AR- but not mGluR5- dependent LTD is disrupted by restraint stress. α₁-AR LTD is also impaired in mice chronically exposed to ethanol. These data thus suggest that in the BNST, NE- and glutamate-activated G_q-linked signaling pathways differentially tune glutamate synapse efficacy in response to stress.     

The impact of in utero HIV exposure on gut microbiota,inflammation, and microbial translocation

ABSTRACT

HIV-exposed but uninfected (HEU) children represent a growing population and show a significantly higher number of infectious diseases, several immune alterations, compromised growth, and increased mortality rates when compared to HIV-unexposed children. Considering the impact that the gut microbiota has on general host homeostasis and immune system development and modulation, we hypothesized that HEU children present altered gut microbiota that is linked to the increased morbidity and the immune system disorders faced by them. Our experiments revealed no differences in beta and alpha diversity of the gut microbiota between HEU and unexposed children or between HIV-infected and uninfected mothers. However, there were differences in the abundance of several taxa from the gut microbiota between HEU and unexposed children and between HIV-infected and uninfected mothers. Functional prediction based on 16S rRNA sequences also indicated differences between HEU and unexposed children and between infected and uninfected mothers. In addition, we detected no differences between HEU and unexposed children in relation to weight, weight-for-age z scores, albumin serum levels, or microbial translocation and inflammation markers. In summary, HIV-infected mothers and their HIV-exposed children present alterations in the abundance of several taxa in the gut microbiome and the predicted functional metagenome when compared to uninfected mothers and unexposed children. Knowledge about the gut microbiome of HEU children in different settings is essential in order to determine better treatments for this susceptible population.     

Gut microbial diversity is reduced and is associated with colonic inflammation in a piglet model of short bowel syndrome

Background and objectives

Following small bowel resection (SBR), the luminal environment is altered, which contributes to clinical manifestations of short bowel syndrome (SBS) including malabsorption, mucosal inflammation and bacterial overgrowth. However, the impact of SBR on the colon has not been well-defined. The aims of this study were to characterize the colonic microbiota following SBR and to assess the impact of SBR on mucosal inflammation in the colon.

Results

Analysis of the colonic microbiota demonstrated that there was a significant level of dysbiosis both two and six weeks post-SBR, particularly in the phylum Firmicutes, coupled with a decrease in overall bacterial diversity in the colon. This decrease in diversity was associated with an increase in colonic inflammation six weeks post-surgery.

Methods

Female (4-week old) piglets (5−6/group) received a 75% SBR, a transection (sham) or no surgery. Compositional analysis of the colonic microbiota was performed by high-throughput sequencing, two- and six-weeks post-surgery. The gene expression of the pro-inflammatory cytokines interleukin (IL)-1β, IL-6, IL-8, IL-18 and tumor necrosis factor (TNF)-α in the colonic mucosa was assessed by qRT-PCR and the number of macrophages and percentage inducible nitric oxide synthase (iNOS) staining in the colonic epithelium were quantified by immunohistochemistry.

Conclusions

SBR significantly decreased the diversity of the colonic microbiota and this was associated with an increase in colonic mucosal inflammation. This study supports the hypothesis that SBR has a significant impact on the colon and that this may play an important role in defining clinical outcome.     

The effects of dairy and dairy derivatives on the gut microbiota: a systematic literature review

ABSTRACT

The effects of dairy and dairy-derived products on the human gut microbiota remains understudied. A systematic literature search was conducted using Medline, CINAHL, Embase, Scopus, and PubMed databases with the aim of collating evidence on the intakes of all types of dairy and their effects on the gut microbiota in adults. Risk of bias was assessed using the Cochrane risk-of-bias tool.The search resulted in 6,592 studies, of which eight randomized controlled trials (RCTs) met pre-determined eligibility criteria for inclusion, consisting of a total of 468 participants. Seven studies assessed the effect of type of dairy (milk, yogurt, and kefir) and dairy derivatives (whey and casein) on the gut microbiota, and one study assessed the effect of the quantity of dairy (high dairy vs low dairy). Three studies showed that dairy types consumed (milk, yogurt, and kefir) increased the abundance of beneficial genera Lactobacillus and Bifidobacterium. One study showed that yogurt reduced the abundance of Bacteroides fragilis, a pathogenic strain. Whey and casein isolates and the quantity of dairy consumed did not prompt changes to the gut microbiota composition. All but one study reported no changes to bacterial diversity in response to dairy interventions and one study reported reduction in bacterial diversity in response to milk intake.In conclusion, the results of this review suggest that dairy products such as milk, yogurt, and kefir may modulate the gut microbiota composition in favor to the host. However, the broader health implications of these findings remain unclear and warrant further studies.     

Inhibition of corticosteroid-binding globulin caused by a severe stressor is apparently mediated by the adrenal but not by glucocorticoid receptors

The effect of stress on serum corticosteroid-binding globulin (CBG) was studied in adult male Sprague-Dawley rats. CBG was measured either by a homologous radioimmunoassay (RIA) or by a binding assay (BA) using 3H-corticosterone. Exposure of adult male rats to a severe stressor such as immobilization (IMO) for 1 h did not alter serum CBG levels, but a significant decrease was found after 6 and especially 24 h IMO. This decrease was not observed after 24 h exposure to a milder treatment such as food and water deprivation. The effect of different periods of exposure to two stressors, IMO or restraint, was also studied. The following results were obtained: serum CBG levels were reduced by IMO, but not by restraint; IMO-induced reduction of CBG levels was always observed 24 h after starting exposure to IMO, independently of the actual period of exposure to the stressor; and IMO-induced inhibition of CBG was proportional to the hours of exposure to the stressor. Although IMO-induced inhibition of CBG was prevented by adrenalectomy, a role for glucocorticoid acting through their classical type II receptors is unclear as far as treatment of rats with the glucocorticoid receptor antagonist RU486 (100 mg/kg) did not prevent the inhibition caused by IMO. The present data clearly indicate that acute exposure to a stressor is able to decrease CBG levels provided that duration of exposure to the stressor and its intensity are high and that the effect is tested at least 6 h after the onset of stress. The effect appears to be mediated by some adrenal factor(s) other than glucocorticoids.     

Endothelin-like immunoreactivity in lactotrophs, gonadotrophs, and somatotrophs of rat anterior pituitary gland are affected differentially by ovarian steroid hormones

It has been previously found that all hormone-producing phenotypes of the anterior lobe of the pituitary gland are capable of producing endothelin (ET)-like substances. The aim of this study was to determine whether the expression of ET-1-like peptides in lactotrophs, gonadotrophs, and somatotrophs is influenced by different in vivo ovarian hormonal conditions. Anterior lobes of the pituitary gland were harvested from ovariectomized and ovarian steroid-replaced adult female rats 10–12 d after surgery. Quantitative immunocytochemistry was performed on enzymatically dispersed pituitary cells. The presence of ET-1-like immunoreactivity in prolactin-, luteinizing hormone-, or growth hormone-producing cells was demonstrated by double-label immunocytochemistry. The incidence of ET-1 immunopositive pituitary cells was unaffected by progesterone treatment alone. Estradiol replacement caused a modest decrease in the number of lactotrophs and somatotrophs expressing ET-1 but increased the incidence of ET-1 immunopositive cells among gonadotrophs. Combined treatment with estradiol and progesterone robustly increased the incidence of ET-1 immunopositive lactotrophs and gonadotrophs but had no effect on somatotrophs. These data reveal that the synthesis of ET-1-like peptides in lactotrophs and gonadotrophs (and, to a lesser extent, in somatotrophs) is sensitive to ovarian steroids. Furthermore, these findings predict that ovarian steroids modulate ET-1 biosynthesis during the estrous cycle, suggesting a possible mechanism by which the ovarian steroid milieu may regulate the responsiveness of lactotrophs and gonadotrophs to their hypothalamic secretagogues.     

Bacterial adaptation to the gut environment favors successful colonization: microbial and metabonomic characterization of a simplified microbiota mouse model

Rodent models harboring a simple yet functional human intestinal microbiota provide a valuable tool to study the relationships between mammals and their bacterial inhabitants. In this study, we aimed to develop a simplified gnotobiotic mouse model containing 10 easy-to-grow bacteria, readily available from culture repositories, and of known genome sequence, that overall reflect the dominant commensal bacterial makeup found in adult human feces. We observed that merely inoculating a mix of fresh bacterial cultures into ex-germ free mice did not guarantee a successful intestinal colonization of the entire bacterial set, as mice inoculated simultaneously with all strains only harbored 3 after 21 d. Therefore, several inoculation procedures were tested and levels of individual strains were quantified using molecular tools. Best results were obtained by inoculating single bacterial strains into individual animals followed by an interval of two weeks before allowing the animals to socialize to exchange their commensal microbes. Through this procedure, animals were colonized with almost the complete bacterial set (9/10). Differences in the intestinal composition were also reflected in the urine and plasma metabolic profiles, where changes in lipids, SCFA, and amino acids were observed. We conclude that adaptation of bacterial strains to the host's gut environment (mono-colonization) may predict a successful establishment of a more complex microbiota in rodents.     

The interplay between the gut microbiota and NLRP3 activation affects the severity of acute pancreatitis in mice

ABSTRACT

Early dysbiosis of the gut microbiota is associated with the severity of acute pancreatitis (AP), although the underlying mechanism is unclear. Here, we investigated the role of crosstalk between NLRP3 and the gut microbiota in the development of AP utilizing gut microbiota deficient mice, as well as NLRP3 knockout (KO) mouse models. Pancreatic damage and systemic inflammation were improved in antibiotic-treated (Abx) and germ-free (GF) mice, accompanied by weakened activity of the intestinal NLRP3 inflammasome. Interestingly, fecal microbiota transplantation (FMT) reactivated the intestinal NLRP3 inflammasome and exacerbated the disease in Abx and GF mice. Although the gut barrier in GF and Abx mice was disrupted, gut microbiota deficiency ameliorated the severity of AP, probably due to the reduction in bacterial translocation from the gut to the pancreas. The composition of the gut microbiota was significantly different between NLRP3 KO mice and wild-type (WT) mice at baseline, and there were alterations in response to the induction of AP. While a dramatic shift in the gut microbiota with overgrowth of Escherichia-Shigella was observed in WT mice suffering from AP, there was no significant change in NLRP3 KO mice with or without AP, suggesting that NLRP3 deficiency counteracts AP-induced microbial disturbance. With a strengthened gut barrier and decreased systemic inflammation, NLRP3 KO mice showed less severe AP, as revealed by reduced pancreatic neutrophilic infiltration and necrosis. Taken together, these results identified the bidirectional modulation between the gut microbiota and NLRP3 in the progression of AP, which suggests the interplay of the host and microbiome during AP.     

The effect of sildenafil, a phosphodiesterase-5 inhibitor, on acetic acid-induced colonic inflammation in the rat

Background and Aim:  Sildenafil, a selective and potent inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase (PDE)5, has a relaxant effect on the smooth muscle cells of the arterioles supplying the human corpus cavernosum acting via nitric oxide (NO)-dependent mechanism. This study aimed to investigate the possible protective effect of sildenafil citrate on the extent of tissue integrity, oxidant-antioxidant status and neutrophil infiltration to the inflamed organ in a rat model of acetic acid-induced colitis.
Methods:  Colitis was induced by intrarectal administration of 1 mL of 5% acetic acid to Sprague-Dawley rats (200–250 g; n  = 7–8/group). Control rats received an equal volume of saline intrarectally. In treatment groups, the rats were treated with either sildenafil citrate (5 mg/kg/day; subcutaneously) or saline for 3 days. After decapitation, distal colon was weighed and scored macroscopically and microscopically. Tissue samples were used for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity, and oxidant production. Trunk blood was collected for the assessment of serum tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels.
Results:  In the colitis group, the colonic tissue was characterized by lesions, increased lipid peroxidation with a concomitant reduction in GSH content, increased MPO activity and oxidant production. Serum TNF-α and IL-1β levels were higher in the colitis group compared to control values. Sildenafil reversed these inflammatory parameters nearly back to control values.
Conclusions:  Sildenafil citrate administration to rats with acetic acid-induced colitis seems to be beneficial via prevention of lipid peroxidation, oxidant generation, cytokine production and neutrophil accumulation.     

AKR murine thymic leukemias are from a distinct thymic cell lineage and do not express the beta chain of the T-cell antigen receptor.

Characterization of tumors that arise spontaneously in the AKR mouse indicates that they are derived from cells of a distinct T-cell lineage. Cells in this subclass bear surface antigens, designated Tpre, Tthy, Tind, and Tsu, which are encoded by genes in the Tsu linkage group on murine chromosome 12. We have examined the rearrangement and expression of genes encoding the T-cell alpha, beta, and gamma chains in these tumors. Although these cells contain alpha-chain mRNA, they do not produce a normal-sized beta-chain mRNA. Most of them also lack gamma-chain mRNA. Each thymic leukemia was derived from a cell arrested at a different stage of development as defined by their expression of terminal deoxynucleotidyl transferase and Thy-1 mRNA. The data presented here are consistent with a model in which thymocytes expressing Tpre, Tthy, Tind, or Tsu undergo somatic development parallel to the development of other T cells. However, these thymocytes do not appear to differentiate into cells bearing alpha-beta heterodimers of the T-cell antigen receptor.