Low calcium diet and 1,25-dihydroxyvitamin D(3) infusion modulate immune responses during Mycobacterium paratuberculosis infection in beige mice

A 12-month study was conducted to evaluate the effects of feeding a low calcium (Ca) diet or 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3) infusion on the persistence of Mycobacterium paratuberculosis infection using a mouse model. Male beige mice 6-8 weeks of age were assigned to one of the following treatments: (1) non-infected, (2) infected,(3) non-infected/1,25(OH)(2)D(3), (4) infected/1,25(OH)(2)D(3), and (5) infected/low Ca (0.15 percent) diet. Infected mice were inoculated intravenously with live M. paratuberculosis. At 1, 6 and 12 months postinfection, mice in Treatments 3 and 4 were implanted subcutaneously with mini-osmotic pumps to deliver 1,25(OH)(2)D(3). Infusion with 1,25(OH)(2)D(3) exacerbated M. paratuberculosis infection in most tissues at all time points. Mice infused with 1,25(OH)(2)D(3) had higher bacterial counts in spleen, liver, and ileum compared with control infected mice after 1 month of infection. In contrast, feeding a low Ca diet reduced the number of viable organisms cultured from the liver and ileum of infected mice. Plasma Ca and 1,25(OH)(2)D(3) were increased in mice infused with 1,25(OH)(2)D(3) at all time points but values for low Ca mice were not different than for non-infused mice. Splenocyte production of TNF, IL-1 and IL-6 was higher for mice fed the low Ca diet compared with control infected mice after 1 month of infection. Inducible IL-6 activity remained higher for this treatment at 6 months postinfection. These results suggest that feeding a low Ca diet to mice chronically infected with M. paratuberculosis appears to enhance their ability to clear the infection in a manner distinct from any effect of 1,25(OH)2D3.     

Influence of vitamin D3 infusion and dietary calcium on secretion of interleukin 1, interleukin 6, and tumor necrosis factor in mice infected with Mycobacterium paratuberculosis

OBJECTIVE: To study the effects of 1,25(OH)2D3 and calcium (Ca) on splenocyte cytokine secretion during Mycobacterium paratuberculosis infection. DESIGN: Mice were assigned to the following treatments: 1-noninfected, 2-infected, 3-noninfected/1,25(OH)2D3, 4-infected/1,25(OH)2D3, and 5-infected/low-Ca diet (0.15%). ANIMALS--Male beige mice averaging 6 weeks of age and 20 g in body weight. PROCEDURE: After acclimation to their diets, mice in treatments 2, 4, and 5 were inoculated IV with 10(8) colony-forming units of M paratuberculosis. At 1, 6, and 12 months after infection, mice in treatment groups 3 and 4 had miniosmotic pumps implanted subcutaneously that delivered 13 ng of 1,25(OH)2D3/day for 14 days. Treatment 5 was included as a control for comparison with treatment 4 because low dietary Ca should increase endogenous 1,25(OH)2D3 values. Splenocytes were isolated from mice at 1, 6, and 12 months and stimulated in vitro with medium alone (nonstimulated), lipopolysaccharide (LPS), concanavalin A, and M paratuberculosis whole-cell sonicate (MpS). RESULTS: Production of interleukin 6 after stimulation with LPS, concanavalin A, or MpS was higher (P < 0.05) for splenocytes isolated from mice fed the low-Ca diet, compared with control infected mice 1 and 6 months after infection. Interleukin 1 and tumor necrosis factor activities were increased (P < 0.05) in splenocytes cultured with LPS and MpS after isolation from mice of the low-Ca group. Mice infused with 1,25(OH)2D3 had higher (P < 0.05) interleukin 1 secretion after stimulation of splenocytes with LPS and higher (P < 0.05) tumor necrosis factor production after incubation with MpS. CONCLUSION: 1,25(OH)2D3 and low dietary Ca increase cytokine secretion in mice infected with M paratuberculosis.     

Arginine-supplemented diets inhibit endotoxin-induced bacterial translocation in mice

We studied the effects of supplemental dietary arginine (ARG) on endotoxin-induced bacterial translocation. Mice were fed a 20%-casein diet (control) or a 20%-casein diet supplemented with 2% or 4% ARG and then injected with lipopolysaccharide (1 mg/500 microliters). The incidence of bacterial translocation was noted by the recovery of viable organisms from the mesenteric lymph node (MLN) and spleen. The mortality rates of the mice were 40%, 10%, and 20% in the control group and 2%- and 4%-ARG groups, respectively. Of the surviving mice, bacterial translocation occurred in 100% of the control group, in 56% (MLN) and 56% (spleen) in the 2%-ARG group, and in 36% (MLN) and 25% (spleen) in the 4%-ARG group. Quantitative colony counts and median numbers of viable bacteria were lower (p < 0.05) in the 2%-ARG group and slightly lower in the 4%-ARG group compared with the control group. MLN and spleen weights expressed as a percentage of body weight were heavier (p < 0.05) only in the 2%-ARG group. These results support the concept that bacteria may translocate from the gut to other organs and be a potential source of lethal infection after injury, and that supplementation with 2% or 4% ARG could improve outcome.     

Differences in the kinetics of T cell accumulations in C3H/HeN (Bcg-resistant) and C57BL/6 (Bcg-susceptible) mice infected with Mycobacterium paratuberculosis

The accumulation of various T cell subsets in Bcg-susceptible (C57BL/6) and- resistant (C3H/HeN) strains of mice were compared following an intraperitoneal infection with Mycobacterium paratuberculosis. Groups of mice from both strains were killed at 3, 5, 10, 15, 30, and 150 days after infection and lymphocytes were harvested from the peritoneal exudate cells (PEC), spleen, intestinal epithelial lymphocytes (IEL), lamina propria lymphocytes (LPL), Peyer's patches, and mesenteric lymph node (MLN) and labelled with monoclonal antibodies to CD3, CD4, CD8, gamma delta TCR, CD25, and CD44 for flow cytometric analysis. Uninfected C3H/HeN mice had higher proportions of CD4+ cells in the spleen, MLN, LPL, IEL, and Peyer's patches, while uninfected C57BL/6 mice had higher proportions of CD8+ and/or gamma delta T cells. Significant increases in accumulation of CD8+ and gamma delta T cells were detected in the peritoneum and other tissues in both strains of mice after infection. Higher CD4/CD8 ratios were observed in most lymphoid tissues of C3H/HeN mice, while increased proportions of CD8+ and/or gamma delta T cells were present in C57BL/6 mice. These results indicate that significant differences in T cell profiles exist between these two strains of mice, both inherently and in response to infection with M. paratuberculosis. Innately lower levels of CD4+ cells and/or higher percentages of CD8+ and gamma delta T cells may play a role in the increased suspectibility of C57BL/6 mice to infection with M. paratuberculosis.     

Ischemia-induced transplant arteriosclerosis in the rat. Induction of peptide growth factor expression

A 3-wk feeding trial with 240 sexed, day-old broiler chickens was conducted to determine the efficacy of microbial phytase at different levels of dietary Ca on performance and utilization of minerals in broiler chickens fed a low-P corn-soybean diet. The experimental design was a 3 x 2 factorial arrangement of treatments; Ca at 0.6, 1.0, and 1.25% and phytase at 0 and 600 phytase U/kg diet. Phytase supplementation, regardless of Ca level, increased (P < or = 0.005) feed intake, (P < or = 0.0001) body weight, and (P < or = 0.025) feed efficiency at 21 d; the optimum levels of body weight, feed intake, and feed efficiency were obtained with low (0.6%) dietary Ca plus phytase. Retentions of P, Ca, and N were increased (P < or = 0.05) by phytase supplementation. Although maximum retentions of P and N were obtained at the 1.0 and 1.25% Ca levels, respectively, they were not significantly different from the values obtained at 0.6% Ca. The increasing level of dietary Ca decreased plasma P ( P < or = 0.05) and Cu (P < or = 0.06). Phytase supplementation had the opposite effect; i.e., increased plasma P (P < or = 0.03) and Cu (P < or = 0.02). The maximum level of plasma P was obtained with phytase at the 1.0% Ca level, but this value was not significantly different from the value obtained with phytase at the 0.6% Ca level. Phytase supplementation increased (P < 0.04) the ash content of both tibia head and shaft but had no effect on mineral contents in the ash. The optimum level of ash content was observed with the 0.06% Ca diet plus phytase. The results show that microbial phytase supplementation to a low P diet improved growth performance and mineral utilization in broiler chickens. Dietary Ca levels had a significant effect on the response to phytase; the optimum growth performance and mineral utilization were achieved at the low (0.6%) level of dietary Ca supplemented with phytase.     

A data-reduction process for long-term EEGs. Feature extraction through digital processing in a multiresolution framework

The ability of Mycobacterium avium subsp. paratuberculosis to survive in bovine monocytes was studied using radiometric (BACTEC) culture, standard plate counting and microscopic counting of acid-fast stained monocyte monolayers. Results of microscopic counts sharply contrasted with results of viable counts determined both by plate counting and radiometric counting. We observed an early phase (the first 6 d after in vitro infection) of intracellular bacillary growth, followed by a later phase of mycobacteriostasis or killing (up to 12 d after in vitro infection) in monocytes from non-infected cows. The data suggest that multiplication and death of M. avium subsp. paratuberculosis occur simultaneously in bovine monocytes infected in vitro. Using the BACTEC method, we compared the ability of bovine monocytes from normal cows and cows infected with M. avium subsp. paratuberculosis and showing evidence of a strong Thl-like cellular immune response to ingest and inhibit the intracellular growth of M. avium subsp. paratuberculosis. There was a trend toward greater phagocytosis and faster killing of Mycobacterium avium subsp. paratuberculosis by monocytes from the infected, immune responder cows. However, the observed numbers of viable M. avium subsp. paratuberculosis at each time after monocyte infection were not significantly different between normal and infected cows.     

Immunity to Cryptosporidium muris infection in mice is expressed through gut CD4+ intraepithelial lymphocytes

The role of gut intraepithelial lymphocytes (IEL) in immunity to cryptosporidial infection was investigated with a murine infection model involving Cryptosporidium muris. Oocyst shedding was monitored in severe combined immunodeficiency (SCID) mice infected with C. muris following intravenous injection of mesenteric lymph node (MLN) cells or intestinal IEL from BALB/c donor mice which were naive or previously infected with C. muris. SCID mice receiving no lymphoid cells developed chronic infections and excreted large numbers of oocysts until the end of the experiment. SCID mice injected with IEL from immune animals, however, were able to overcome the infection, and furthermore, these animals produced fewer oocysts and recovered sooner than ones which received IEL or MLN cells from naive BALB/c donors. Similar levels of protection were obtained in SCID mice injected with either 2 X 10(6) IEL or MLN cells from immune donor mice. Depletion of CD4+ cells from immune IEL, however, abrogated the ability to transfer immunity to SCID mice, while depletion of CD8+ cells only marginally reduced the protective capacity of immune IEL. Finally, control SCID mice which received no lymphocytes had < or = 1% CD4+ cells in the IEL from the small intestine, whereas the IEL from SCID mice recovered from infection, as a result of injection with immune IEL, contained 15% CD4+ cells. Thus, the ability to control C. muris infection correlated with the presence of the protective CD4+ cells in the gut epithelium.     

B-cell activation in the mesenteric lymph nodes of resistant BALB/c mice infected with the murine nematode parasite Trichuris muris

Immune responses in resistant BALB/c mice infected with the murine nematode parasite Trichuris muris were examined. Following the establishment of infection, worm burdens of T. muris were expelled by BALB/c mice by day 21 postinfection (p.i.). Specific immunoglobulin G1 (IgG1) antibodies to T. muris excretory/secretory (E/S) antigens were detected in sera from infected mice, though specific IgG2a antibodies were not observed during infection. Ig-producing cells increased in the mesenteric lymph nodes (MLN) of infected mice on days 7, 14, and 21 p.i., with the greatest increase in numbers of IgG- and IgA-producing cells occurring on day 14. Marked increases in the relative percentages of B220+ and surface Ig+ (sIg+) cells were observed in the MLN of infected mice on days 14 and 21 p.i. Furthermore, cellular expansion of the MLN in infected mice resulted in an increase in the absolute numbers of B220+ and sIg+ cells. The levels of interleukin 2 (IL-2), IL-4, and interferon-gamma (IFN-gamma) detected in the supernatants from concanavalin A-stimulated MLN cells of infected mice were higher than those found in normal mice. Consequently, the expulsion of T. muris in resistant BALB/c mice was concomitant with cytokine production and B-cell activation in the MLN of infected mice. These results suggest the involvement of B-cell responses in protective immunity to T. muris infection.     

Comparison of the resistance of C57BL/6 and C3H/He mice to infection with Mycobacterium paratuberculosis

Susceptibility of C57BL/6 (Bcgs) and C3H/HeN (Bcgr) mice to an intraperitoneal infection with Mycobacterium paratuberculosis strain 19698 was compared (by histopathology and the number of mycobacteria isolated from the spleen). Mycobacterial counts from the spleen of Bcgr mice progressively decreased over the course of infection but remained unchanged in Bcgs mice. Granulomatous lesions and acid-fast bacteria were consistently present in the liver and lymph nodes of Bcgs mice, whereas lesions were transient or absent in Bcgr mice. These results indicate that Bcgr mice are inherently resistant to M. paratuberculosis, whereas Bcgs mice are inherently susceptible. These differences may prove useful in elucidating the mechanisms of resistance and susceptibility to paratuberculosis and other mycobacterial infections.     

Mesenteric lymph node T cells but not splenic T cells maintain their proliferative response to concanavalin-A following peroral infection with Toxoplasma gondii

The suppression of T cell responsiveness which occurs after infection with Toxoplasma gondii in mice has been widely studied using spleen cells. Because the natural route of infection with T. gondii is the peroral route, we examined the proliferative responses of mesenteric lymph node (MLN) cells, in addition to spleen cells, to Concanavalin-A (Con-A) in mice perorally infected with T. gondii. Proliferative responses of spleen cells were significantly suppressed seven and ten days after infection when compared with spleen cells from uninfected mice (62% and 91% reduction, respectively). In contrast, proliferative responses of MLN cells from these infected mice did not differ from those of normal MLN cells. Since IFN-gamma-induced reactive nitrogen intermediate (RNI) production has been reported to play a major role in suppression of proliferative responses in spleen cells of infected mice, we compared production of IFN-gamma and RNI by spleen and MLN cells following infection. MLN cells produced as much IFN-gamma as did spleen cells, but produced 70% less nitrite (as a measure of RNI) after Con-A stimulation. Proliferative responses of MLN cells were suppressed when co-cultured with spleen cells from infected mice, and addition of an inhibitor of RNI to these co-culture inhibited this suppression, suggesting that reduced RNI production by MLN cells contributes to their maintenance of higher proliferative responses. These results demonstrated a clear difference in activity of T cells in the MLN and spleen during the acute stage of the infection.     

Mycobacterium paratuberculosis: a potential food-borne pathogen?

Mycobacterium paratuberculosis commonly infects dairy cattle, leading to Johne's disease, which is also known as paratuberculosis. The infection is chronic progressive, and incurable. As the infection progresses, excretion of M. paratuberculosis in feces and milk occurs, and the bacterium spreads through the blood to multiple internal organs. Consequently, raw products originating from cattle may harbor M. paratuberculosis. Thermal treatments, such as pasteurization, are commonly relied on to kill food-borne bacterial pathogens that can infect humans. The small number of studies conducted to determine the thermal resistance of M. paratuberculosis suggest that it is less susceptible to destruction by heat killing than are milkborne zoonotic bacterial pathogens such as Listeria spp. or Mycobacterium bovis. Published reports concerning the thermal resistance of M. paratuberculosis in milk are reviewed herein, and key issues concerning the efficacy of pasteurization for elimination of M. paratuberculosis from milk are summarized.     

Cellular dynamics and cytokine responses in BALB/c mice infected with Eimeria papillata during primary and secondary infections

BALB/c mice were infected with the intestinal intracellular parasite Eimeria papillata to characterize lymphocyte responses and cytokine profiles throughout primary and secondary infections. Lymphocytes from the mesenteric lymph node (MLN) and the gastrointestinal tract (GIT) of infected mice were phenotypically analyzed using flow cytometry and immunofluorescence microscopy, respectively. Lymphocytes isolated from the MLN during primary infections of BALB/c mice with E. papillata do not proliferate, compared to day 0 uninfected controls, when stimulated in vitro with conconavalin A and express TH2-type cytokines (interleukin [IL]-4 and IL-10) on day 3 PI followed by the release of TH1-type cytokines (IL-2 and interferon-gamma) during patency. In the small intestine, significantly more T cells and their subsets were observed during primary infection. During secondary infections, IL-2 was the only 1 of the 4 cytokines that was expressed earlier and at higher levels in the MLN when compared to primary infections. In the small intestine, significantly more alphabeta+ and CD8+ T lymphocytes were observed in mice during secondary infection. Oocyst antigens did not induce cellular proliferation at any time point during primary or secondary infections. We conclude that primary oral infection of BALB/c mice with E. papillata is associated with localized immunosuppression that may be mediated, in part, by early TH2-type cytokines. Immunity to secondary infection may be mediated by intestinal alphabeta+ CD8+ T lymphocytes through an IL-2-dependent mechanism.     

Duodenal and ileal adaptation to dietary calcium restriction: in vivo studies in the rat

Intestinal adaptation by the growing rat to a low-calcium diet was studied by in situ perfusion of duodenum and ileum in vivo. Rats were fed diets containing either 1.2 or 0.02% Ca for 17-24 days. To study plasma-to-lumen flux and net calcium absorption, rats were loaded parenterally with 45Ca and perfused intraluminally with 3.4 mM calcium. Calcium restriction caused net absorption in ileum to increase fourfold, in duodenum almost twofold. With calcium restriction, plasma-to-lumen flux decreased in duodenum but not in ileum and was small relative to absorption. However, net calcium secretion, when measured in a separate set of animals by intraluminal perfusion of NaCl, decreased in ileum but not in duodenum in response to calcium restriction. The magnitude of adaptation is greater in ileum than duodenum and is largely the result of increased lumen-to-plasma flux. The distal small intestine is probably crucial for calcium homeostasis in dietary calcium deficiency.     

Disposition and metabolism of rifapentine, a rifamycin antibiotic, in mice, rats, and monkeys

Mycobacterium avium is an intracellular pathogen that is associated with disseminated infection in acquired immunodeficiency syndrome (AIDS). Patients with AIDS appear to acquire M. avium mainly through the gastrointestinal tract. Previous studies have shown that healthy mice given M. avium orally develop disseminated infection after 2-4 weeks. The chief site of M. avium invasion of the intestinal mucosa is the terminal ileum. To learn more about the pathophysiology of M. avium infection of the intestinal mucosa, C57BL/6 bg+ bg+ mice were infected orally with M. avium strain 101 and groups of six mice were killed each week for 8 weeks. The terminal ileum was then prepared for histopathological studies and electron microscopy. A delayed inflammatory response was observed and influx of neutrophils in the Peyer's patches was the only abnormality seen at 1 week. A severe inflammatory response was seen from week 2 to week 5 and necrosis of intestinal villi was observed 6 weeks after infection. These results indicate that invasion and infection of the normal intestine by M. avium results in a severe inflammatory response with segmental necrosis of the intestinal mucosa.     

Ionotropic and metabotropic glutamate receptor agonist-induced [Ca2+]i increase in isolated rat supraoptic neurons

Although a number of studies have shown that various free fatty acids (FFAs) and monoacylglycerides (MGs) have bactericidal properties in vitro, the role of these compounds in vivo has not been determined. This study evaluated the antibacterial properties of medium-chain MGs and FFAs for different bacterial enteropathogens with an in-vitro bacterial killing assay and an in-vivo model of intestinal colonisation. Incubation of test bacteria with medium-chain MGs for 4 h led to 100-10,000-fold reductions in numbers of viable cells of Vibrio cholerae, Salmonella typhi, Shigella sonnei and enterotoxigenic Escherichia coli (ETEC). Lauric acid was the only medium-chain FFA to show comparable in-vitro bactericidal activity. The ability of dietary MGs to reduce or eliminate bacterial colonisation of the intestinal tract was evaluated in mice that were predisposed to bacterial colonisation by treatment with streptomycin (STR+). Mice were treated with streptomycin, challenged intragastrically with V. cholerae or ETEC, and given monocaprin (C10:0 MG) either concurrently or as part of the daily diet. Control mice given STR+ without MGs and challenged with V. cholerae or ETEC showed high numbers of challenged bacteria in gastrointestinal contents by 1 h after administration. Concurrent administration of V. cholerae and C10:0 MG (2.5 mg/ml) caused > 1000-fold reduction in numbers of V. cholerae recovered from the gastrointestinal tracts of STR+ mice. Concurrent administration of C10:0 MG with ETEC did not cause a reduction in the number of viable ETEC present in the intestinal tract of STR+ mice. Administration of C10:0 MG in the diet had no effect on the number of viable V. cholerae or ETEC associated with caecal or ileal tissue of STR+ mice when C10:0 MG in the diet was started 1 day before, the same day, or 2 days after bacterial challenge. Collectively, these results suggested that dietary MGs may prevent intestinal colonisation by bacterial enteropathogens if administered at the time of exposure, but have little effect on established intestinal infections.     

Bacterial translocation is inhibited in inducible nitric oxide synthase knockout mice after endotoxin challenge but not in a model of bacterial overgrowth

BACKGROUND: Studies have shown that nitric oxide (NO) and NO synthase (NOS) inhibitors injure and protect organs after endotoxin (lipopolysaccharide [LPS]) challenge. OBJECTIVE: To test the hypothesis that LPS-induced gut injury and bacterial translocation (BT) are mediated through activation of inducible NOS (iNOS). DESIGN: A randomized, controlled study using genetically altered, iNOS gene knockout mice. SETTING: University research laboratory. METHODS: Forty-five wild-type (iNOS+/+) or homozygous mutant (iNOS-/-) mice weighing 25 to 35 g were challenged with Escherichia coli LPS or saline (10 mg/ kg) intraperitoneally (n = 8/group). In a second set of experiments, a bacterial overgrowth model of BT (E coli monoassociation) was tested (n = 6-7/group). The mesenteric lymph nodes and cecums were cultured, and liver, ileal, and blood nitrite and nitrate levels measured 24 hours after LPS or E coli monoassociation. RESULTS: After LPS challenge, 87.5% of the iNOS+/+ mice but 0% of the iNOS-/- mice had BT to their mesenteric lymph nodes (P < .01; chi 2 analysis). Nitrite and nitrate levels of the liver, ileum, and blood were higher in the iNOS+/+ mice (P < .05). In the E coli overgrowth model, BT to mesenteric lymph nodes occurred in 100% of iNOS-/- and iNOS+/+ mice. CONCLUSIONS: In this limited study, LPS-induced BT did not occur in iNOS-deficient mice, suggesting that LPS induction of increased iNOS activity is necessary for LPS-induced BT to occur. In contrast, iNOS activation does not seem to be necessary in a bacterial overgrowth model of BT.     

Translocation of Escherichia coli from the gastrointestinal tract to the mesenteric lymph nodes in gnotobiotic mice receiving Escherichia coli vaccines before colonization

Germfree mice were immunized orally or intraperitoneally for 6 weeks with heat-killed vaccines of indigenous Escherichia coli or nonindigenous E. coli O 127: B8 before colonization with these strains. The mice exhibited increases in specific serum antibodies and intestinal immunoglobulin A reacting with the E coli antigens. Prior immunization did not reduce the gastrointestinal population levels of the E. coli strains attained 3 and 7 days after colonization. Neither oral nor intraperitoneal immunization with the E. coli strains before colonization decreased the incidence of bacterial translocation to the mesenteric lymph nodes or reduced the number of viable E. coli cells per mesenteric lymph node. There also was no relation in individual mice between serum antibody titers and the numbers of viable E. coli cells translocating to the mesenteric lymph nodes. Thus, prior vaccination with E. coli in this study did not decrease the incidence or reduce the numbers of viable E. coli translocating to the mesenteric lymph nodes in gnotobiotic mice monoassociated with E. coli.     

Biliary cholesterol excretion: a novel mechanism that regulates dietary cholesterol absorption

The regulation of dietary cholesterol absorption was examined in C57BL/6 and transgenic mice with liver overexpression of the scavenger receptor BI (SR-BI Tg). In C57BL/6 animals, feeding 0.02 to 1% (wt/wt) dietary cholesterol resulted in a dose-dependent decrease in the percentage of dietary cholesterol absorbed. A plot of total daily mass of dietary cholesterol absorbed versus the percentage by weight of cholesterol in the diet yielded a curve suggesting a saturable process with a Km of 0.4% (wt/wt) and a Vmax of 0.65 mg cholesterol/g body weight per day. Dietary cholesterol suppressed hepatic 3-hydroxy-3-methylglutaryl CoA reductase activity, stimulated cholesterol 7alpha-hydroxylase activity, and enhanced fecal excretion of bile acids, but none of these changes correlated with the percentage of dietary cholesterol absorption. Dietary cholesterol also caused an increase in biliary cholesterol concentration, and in this case the concentration of biliary cholesterol was strongly and inversely correlated with the percentage dietary cholesterol absorption (r = -0.63, P < 0.0001). Biliary cholesterol concentration was also directly correlated with daily cholesterol intake, dietary cholesterol mass absorption, and liver cholesterol ester content. Transgene-induced overexpression of SR-BI resulted in a stimulation of excretion of cholesterol into the bile and suppressed percentage dietary cholesterol absorption. Furthermore, biliary cholesterol levels in SR-BI Tg mice were strongly and inversely correlated with the percentage of dietary cholesterol absorbed (r = -0.99, P < 0.0008). In summary, these results suggest that the excretion of cholesterol into the bile plays an important role in regulating the percentage absorption of dietary cholesterol.     

Trimucytin: a collagen-like aggregating inducer isolated from Trimeresurus mucrosquamatus snake venom

OBJECTIVE: This study tested the hypothesis that gut stasis induced by parenteral morphine sulfate (MS) leads to enhanced bacterial translocation in rats on total parenteral nutrition (TPN). SUMMARY BACKGROUND DATA: TPN and MS are common adjuncts in the care of critically ill patients. TPN is known to provoke a variable degree of translocation. MS induces gut stasis with an accompanying bacterial overgrowth. The effect of these two treatments in combination on translocation is not known. METHODS: Rats were provided with central and subcutaneous lines for the continuous infusion of nutrients and drugs, respectively. Intestinal transit was assessed by the caudal movement of a fluorescent marker intubated into the proximal duodenum. Quantitative bacteriology was carried out from various segments of the gut and from ileocecal mesenteric lymph nodes (MLN), spleen, liver, and systemic blood obtained by cardia puncture on sacrifice at 96 hours. RESULTS: Transit was unchanged by TPN alone but prolonged when given in combination with MS. Bacterial overgrowth was also enhanced by MS and increased the bacterial translocation to MLN from 50% of animals with TPN, to 100% in those receiving both TPN and MS; the colony-forming units per MLN increased from 33 +/- 14 with TPN alone to 2079 +/- 811 (STD) with TPN plus MS. Furthermore, no bacteria were found at systemic sites with TPN alone, but in 93.3% of animals receiving TPN and MS. In a subgroup of rates provided with glutamine in TPN, the TPN plus MS effects on translocation were not reversed. CONCLUSIONS: These observations demonstrate the important role that morphine plays in promoting translocation, presumably by disrupting fasting motility and enhancing bacterial overgrowth.