Biomedical subjects

D G Gall

Publications and source records attributed to D G Gall.

At least 19 recordsLinked to original sources

PubMed2004

Aquaporin expression is downregulated in a murine model of colitis and in patients with ulcerative colitis, Crohn's disease and infectious colitis.

Colitis is associated with alterations in electrolyte and water transport. These changes give rise to some of the symptoms experienced by patients with colitis. Alterations in fluid flux may also contribute to increased susceptibility to mucosal injury. Recently, endogenous water channel proteins (aquaporins; AQPs), have been identified in colonic tissue. The expression of AQP4, AQP7 and AQP8 was examined, via reverse transcription/polymerase chain reaction, Western blotting and immunohistochemistry, in a murine model of colitis and in patients with inflammatory bowel disease or infectious colitis. Colitis was induced in C57BL/6 mice by the addition of 2.5% dextran sodium sulphate (DSS) to their drinking water. AQP expression in these mice was assessed following 12 h to 7 days of DSS exposure and during the recovery phase from 1 to 15 days following cessation of DSS exposure. Colonic water transport was measured after 1 and 3 days of DSS and following 7 days of recovery. The expression of AQP4 and AQP8 mRNA was significantly decreased after 12-24 h of DSS exposure and remained depressed throughout the treatment period. Expression of AQP7 was more variable. Protein expression followed a similar pattern to that observed for AQP mRNA. Significant alteration in colonic fluid secretion was correlated with reduced expression of AQP isoforms. Significantly, patients with active ulcerative colonic, Crohn's colitis or infectious colitis had similar dramatic reductions in AQP expression that appeared to be correlated with disease activity. Thus, colonic injury in both mouse and man is associated with a downregulation in AQP expression.

Animals↗

PubMed2002

The effect of epidermal growth factor on the distribution of SGLT-1 in rabbit jejunum.

The effect of epidermal growth factor (EGF) on the cellular and villous distribution of the sugar transporter SGLT-1 was examined. New Zealand White rabbits (1 kg) were anesthetized, and two jejunal blind loops were isolated and exposed to either 0.9% saline or EGF (60 ng/mL saline), for 1 h. In separate experiments, tissue was harvested for brush border membrane vesicles (BBMV), microsomal membranes, or fixed for immunohistochemistry. SGLT-1 was measured in membrane fractions by Western immunoblot or localized along the villus-crypt axis by immunofluorescent microscopy. EGF increased BBMV SGLT-1 content compared with paired controls. EGF stimulation also induced a corresponding decrease in microsomal SGLT-1 levels and induced the expression of additional SGLT-1 immunoreactivity further down the villus axis. The findings suggest that EGF upregulates intestinal glucose transport by stimulating the translocation of SGLT-1 from an internal microsomal pool into the brush border, thereby recruiting more villus enterocytes into the glucose transporting population.

Animals↗

PubMed2002

Mucosal inflammation in a genetic model of spontaneous type I diabetes mellitus.

The BioBreeding (BB) rat provides a model of spontaneous type I diabetes mellitus that closely resembles the human disease. Diabetes-prone BB rats demonstrate increased intestinal permeability prior to the development of insulinitis. Studies suggest that alterations in intestinal permeability can lead to increased intestinal inflammatory activity. Diabetes-prone (BBdp) and diabetes-resistant (BBdr) BB rats were examined at 45 days and at >70 days of age following the development of clinical disease (BBd). In separate experiments, tissue was assayed for myeloperoxidase (MPO) or fixed for histological assessment and immunohistochemistry. Blood was obtained for leukocyte MPO measurements and morphological assessment of circulating leukocytes. MPO activity was significantly elevated in the distal small intestine of 45-day-old BBdp rats. In contrast, at >70 days of age, MPO activity was significantly increased throughout the small intestine of BBd and non-diabetic BBdp rats. Subsequently, all measurements were performed in >70-day-old rats. An increase in inflammatory infiltrate was noted in the distal small intestine of BBd rats by light microscopy. Infiltrating cells were identified as bands (a maturing cell type of the neutrophil lineage) and mature neutrophils. The findings suggest diabetes susceptibility is associated with an increase in intestinal inflammatory activity.

Animals↗

PubMed2000

Effect of proinflammatory interleukins on jejunal nutrient transport.

AIM: We examined the effect of proinflammatory and anti-inflammatory interleukins on jejunal nutrient transport and expression of the sodium-glucose linked cotransporter (SGLT-1). METHODS: 3-O-methyl glucose and L-proline transport rates were examined in New Zealand White rabbit stripped, short circuited jejunal tissue. The effects of the proinflammatory cytokines interleukin (IL)-1alpha, IL-6, and IL-8, IL-1alpha plus the specific IL-1 antagonist, IL-1ra, and the anti-inflammatory cytokine IL-10 were investigated. In separate experiments, passive tissue permeability was assessed and brush border SGLT-1 expression was measured by western blot in tissues exposed to proinflammatory interleukins. RESULTS: The proinflammatory interleukins IL-6, IL-1alpha, and IL-8 significantly increased glucose absorption compared with control levels. This increase in glucose absorption was due to an increase in mucosal to serosal flux. IL-1alpha and IL-8 also significantly increased L-proline absorption due to an increase in absorptive flux. The anti-inflammatory IL-10 had no effect on glucose transport. The receptor antagonist IL-1ra blocked the ability of IL-1alpha to stimulate glucose transport. IL-8 had no effect on passive tissue permeability. SGLT-1 content did not differ in brush border membrane vesicles (BBMV) from control or interleukin treated tissue. CONCLUSIONS: These findings suggest that intestinal inflammation and release of inflammatory mediators such as interleukins increase nutrient absorption in the gut. The increase in glucose transport does not appear to be due to changes in BBMV SGLT-1 content.

3-O-Methylglucose↗

PubMed2000

Bacterial colonization and healing of gastric ulcers: the effects of epidermal growth factor.

Experimental gastric ulcers are rapidly colonized by various bacteria, resulting in significantly impaired healing. Epidermal growth factor (EGF) is capable of preventing bacterial colonization of the healthy intestinal mucosa. In this study, we examined the possibility that EGF accelerates gastric ulcer healing by reducing bacterial colonization of the ulcer. Gastric ulcers were induced by serosal application of acetic acid. The effect of daily administration of EGF on ulcer healing and bacterial colonization was assessed and compared with the effect of daily treatment with broad-spectrum antibiotics. EGF administration reduced colonization levels and accelerated ulcer healing as effectively as the antibiotic treatment. EGF was without effect on acid secretion or neutrophil infiltration into the ulcer. Bacterial growth was not inhibited in the presence of EGF in vitro. These results demonstrate that EGF reduces bacterial colonization during an established infection of a compromised mucosal surface. This effect may contribute to the ability of EGF to accelerate gastric ulcer healing. This effect is acid independent and not due to an anti-inflammatory effect or to direct bactericidal actions.

Administration, Oral↗

PubMed1999

The role of the epidermal growth factor receptor in microbial infections of the gastrointestinal tract.

The epidermal growth factor receptor (EGFr) is a transmembrane glycoprotein with an intrinsic tyrosine kinase. Ligand-binding to the EGFr activates cell signaling, phosphorylates protein kinases, and rearranges cytoskeletal proteins - responses that resemble those induced by microbial attachment to cell surfaces, a process known to be mediated by host cell receptors in a number of cases. This article critically reviews the possible role played by the EGFr in microbial colonization, and discusses how modulation of the EGF-EGFr axis may affect infection of the gastrointestinal tract.

Animals↗

PubMed1999

Effect of a dietary nonionic surfactant on small intestinal nutrient transport.

Nonionic surfactants are commonly present in many prepared foods and drug formulations as stabilizing agents. The aim of the current study was to examine the effect of the common nonionic surfactant Tween-80 on jejunal glucose transport. New Zealand White rabbits (800-1200 g) were fasted for 24 hr. Jejunal tissue was stripped and mounted in short-circuited Ussing chambers. Unidirectional 3-O-methyl glucose fluxes were determined during a 15-min basal transport period and a subsequent 15-min experimental period after the mucosal addition of Tween-80 at final concentrations of 0.001%, 0.01%, 0.05%, and 0.1%. Tween-80 at final concentrations of 0.1% and 0.05% significantly increased net 3-O-methyl glucose transport over basal levels. The increase in Jnet was due to a significant increase in the absorptive Jm-s flux. Tween-80 at 0.01% and 0.001% did not significantly alter net glucose transport although Jm-s was significantly increased in the presence of 0.01% Tween-80. Tween-80, in concentrations commonly found in prepared foods, enhances the intestinal absorption of glucose.

3-O-Methylglucose↗

PubMed1999

Intestinal permeability and postheparin plasma diamine oxidase activity in the prediction of Crohn's disease relapse.

A method of detecting presymptomatic relapse of Crohn's disease could allow for the selective use of maintenance or intensified medical therapy in those with an increased risk of relapse. The aim of this study was to evaluate three potential laboratory markers of relapse: intestinal and gastroduodenal permeability and plasma diamine oxidase activity. Intestinal permeability (lactulose/mannitol test), gastroduodenal permeability (urinary sucrose excretion), and postheparin plasma diamine oxidase activity were serially measured in 61 adults with Crohn's disease in remission (CDAI <150) for at least 30 days. Subjects were followed periodically for clinical relapse (CDAI >150 and increased by at least 100 points or the need for steroids or surgery). Fourteen patients (23%) relapsed. A cut-off of 0.030 for the lactulose/mannitol ratio was defined. Those with ratios above the cutoff had a 7.0 times greater risk of relapse (p<0.001). Three subjects who went from a normal ratio to an abnormal ratio relapsed, whereas none of 32 subjects with a repeatedly normal ratio relapsed. Sucrose excretion and plasma diamine oxidase activity did not predict relapse. Serial testing of intestinal permeability, but not of gastroduodenal permeability or plasma diamine oxidase activity, was useful in predicting relapse in asymptomatic patients.

Adult↗

PubMed1999

The effect of epidermal growth factor on brush border surface area and function in the distal remnant following resection in the rabbit.

BACKGROUND: Epidermal growth factor (EGF) has been shown to increase intestinal absorptive surface area and transport function in normal animals. AIMS: To examine the effect of EGF on absorptive surface area and brush border membrane function in a model of massive small bowel resection. METHODS: New Zealand white rabbits were randomised into two groups: a resected group (60% proximal small bowel resection); and an unmanipulated control group. Distal remnant tissue was examined 10 and 21 days postsurgery. In separate experiments oral EGF (40 g/kg/day) was administered to resected animals from days 3 to 8 and animals were studied on day 10. RESULTS: Ten days postsurgery brush border surface area and total absorptive surface area were significantly increased in remnant tissue while brush border membrane vesicle (BBMV) glucose uptake was significantly decreased compared with controls. By 21 days brush border surface area returned to control levels though BBMV glucose uptake remained depressed. EGF treatment induced a further increase in brush border surface area in remnant intestine but did not alter BBMV glucose uptake. CONCLUSIONS: Surgical resection results in significant elevations in absorptive surface area coupled with a decrease in brush border membrane transport function distal to the site of anastomosis. EGF enhances glucose uptake in remnant intestine via recruitment of additional microvillus membrane into the brush border.

Animals↗

PubMed1999

Macromolecular transport across the rabbit proximal and distal colon.

BACKGROUND: Although many studies have investigated macromolecular uptake in the stomach and small intestine, little is known about macromolecular uptake in the colon. AIMS: To investigate the mechanisms involved in the transport of large antigenically intact macromolecules across the proximal and distal colonic epithelium in the rabbit. METHODS: The mucosal to serosal movement of bovine serum albumin (BSA) was examined in modified Ussing chambers under short circuited conditions. The mucosal surface was exposed to varying concentrations of BSA, and after a 50 minute equilibration period, the mucosal to serosal flux of immunologically intact BSA was determined by ELISA. Total BSA flux was determined by the transport of radiolabelled 125I-BSA. RESULTS: Intact BSA transport in proximal and distal colonic tissue showed saturable kinetics. Intact BSA transport in the proximal and distal segment was 7% and 2% of the total 125I-BSA flux respectively. Immunologically intact BSA transport in the distal segment was significantly less than that in the proximal segment. Intact BSA transport in the proximal colon was significantly reduced following treatment with sodium fluoride, colchicine, and tetrodotoxin. Cholinergic blockade had no effect on the uptake of intact BSA. CONCLUSION: The findings indicate that the transport of intact macromolecules across the proximal and distal large intestine is a saturable process. Further, intact BSA transport in the proximal colon is an energy dependent process that utilises microtubules and is regulated by the enteric nervous system.

Animals↗

PubMed1999

Role of actin in EGF-induced alterations in enterocyte SGLT1 expression.

Na+-glucose cotransporter (SGLT1) expression and the role of actin in epidermal growth factor (EGF)-induced alterations in glucose transport and brush-border surface area were examined in New Zealand White rabbit jejunal loops. In separate experiments, EGF or EGF concurrent with cytochalasin D, an inhibitor of actin polymerization, was administered to the experimental loop and compared with its vehicle control. SGLT1 expression was measured by Western blot in brush-border membrane vesicles (BBMV) after 5-min and 1-h exposure. Glucose kinetics were determined by a rapid filtration technique, and brush-border surface area was examined by electron microscopy after 1-h exposure. The effect of cytochalasin D alone on BBMV glucose kinetics and brush-border surface area was also assessed. EGF resulted in a significant increase in BBMV SGLT1 expression (P < 0.05), glucose maximal uptake (Vmax; P < 0.001), and absorptive brush-border surface area (P < 0.001). These effects were abolished with concurrent cytochalasin D treatment. Cytochalasin D alone had no effect on glucose transport or brush-border surface area. The findings suggest that EGF acutely upregulates jejunal brush-border surface area and the Vmax for jejunal glucose uptake via the recruitment and insertion of SGLT1 from an internal pool into the brush border by a mechanism that is dependent on actin polymerization.

Actins↗

PubMed1999

Increased gastrointestinal permeability is an early lesion in the spontaneously diabetic BB rat.

The BB rat spontaneously develops autoimmune diabetes. Feeding these animals a hydrolyzed casein diet significantly reduces the incidence of this disease, suggesting that a dietary antigen is involved in the pathogenesis of this disease. In other syndromes associated with luminal antigens, including celiac and Crohn's disease, increased intestinal permeability has been suggested to play an etiological role. Therefore, the objective of this study was to evaluate whether increased permeability was also present in BB rats before disease development. By measuring gastrointestinal permeability, in animals on a regular or hydrolyzed casein diet, we were able to demonstrate that increased gastric and small intestinal permeability appeared before the development of both insulitis and clinical diabetes. Although hydrolysis of dietary protein significantly reduced the incidence of diabetes, it did not alter the small intestinal permeability abnormality, suggesting that this is an early event. Increased permeability appears to have an early role in the genesis of several immunological diseases and may represent a common event in these diseases.

Aging↗

PubMed1998

Atrial natriuretic peptide-induced secretory responses in rabbit vs rat ileum.

The aim of this study was to characterize and compare the effect of atrial natriuretic peptide (ANP) on ileal transport function in two common laboratory animals, the Hooded-Lister rat and the New Zealand White rabbit. ANP 1 microM produced a maximal increase in short circuit current (Isc) that was Cl- dependent in both rat and rabbit. The maximal response in rat tissue was twice the magnitude of that seen in the rabbit. Furthermore, the rabbit Isc response was rapid and transient compared with that of the rat. In both rats and rabbits, the ANP response was dependent on extracellular Ca++. Neural blockade had no effect on the rat ANP response but significantly inhibited the ANP response in rabbits. In the rat, the effect of ANP is mediated by seratonin (5-HT) acting through 5-HT2 receptors. In contrast, no role for 5-HT could be seen in the rabbit ileal ANP response. In intact tissue in both rat and rabbit, ANP stimulated a significant rise in cGMP levels. ANP had no effect on cAMP levels in either species. The findings suggest a separate and distinct mechanism for ANP-mediated intestinal Cl- secretion in the rat ileum compared with the rabbit.

Animals↗

PubMed1998

Effects of orally administered epidermal growth factor on enteropathogenic Escherichia coli infection in rabbits.

The increased intestinal absorption induced by epidermal growth factor (EGF) is associated with diffuse lengthening of brush border microvilli. The aim of this study was to examine the in vivo effects of oral administration of EGF during infection with enteropathogenic Escherichia coli. New Zealand White rabbits (4 weeks old) received orogastric EGF daily starting 3 days prior to infection with enteropathogenic E. coli RDEC-1 and were compared with sham-treated infected animals and uninfected controls. Weight gain, food intake, fecal E. coli, and stool consistency were assessed daily. On day 10, segments of jejunum, ileum, proximal, and distal colon were assessed for gram-negative bacterial colonization, disaccharidase activities, and epithelial ultrastructure. Effects of EGF on E. coli RDEC-1 proliferation were studied in vitro. E. coli RDEC-1 caused diarrhea and reduced weight gain. Seven days postinfection, the small and large intestines were colonized with numerous bacteria, brush border microvilli were disrupted, and maltase and sucrase activities were significantly reduced in the jejunum. Daily treatment with EGF prevented the occurrence of diarrhea and reduction of weight gain. These effects were associated with significant inhibition of E. coli colonization in the small and large intestine, improved jejunal maltase and sucrase activities and reduced microvillous injury. EGF did not affect the proliferation of E. coli in vitro. The findings suggest that EGF protects the gastrointestinal tract against colonization by enteropathogenic E. coli.

Administration, Oral↗

PubMed1997

Transport of albumin into the intestinal lumen of the rat.

The intestine is considered a major site for the breakdown and clearance of serum proteins. The mechanism of transport of macromolecules from the serosa into the lumen is unclear. The present study was designed to characterize the serosal to mucosal movement of albumin. Transport of bovine serum albumin (BSA) was assessed in short-circuited Ussing chambers, using stripped rat jejunum devoid of Peyer's patches. To define the kinetics of serosal to mucosal albumin transport the serosal surface was exposed to BSA at varying concentrations (0.5-5 mg.mL-1). Fluids from the mucosal compartment were sampled over time and assayed for immunologically intact BSA by ELISA. All subsequent experiments utilized a concentration of cold BSA (2 mg.mL-1) that produced maximal levels of intact BSA transport. To assess total BSA transport (intact BSA plus degraded BSA), 10 microCi (1 Ci = 37 GBq) 125I-labelled BSA was added to the serosal surface in addition to 2 mg.mL-1 cold BSA. To further characterize BSA transport tissues were treated with sodium fluoride (NaF) (metabolic inhibitor) or colchicine (an inhibitor of microtubule polymerization) or with the nerve blocker tetrodotoxin (TTX). All experiments using inhibitors were performed in paired tissues obtained from the same animal. Transport of intact BSA into the intestinal lumen was a saturable process, with a Vmax of 251 +/- 13 ng.cm-2.h-1 and a Km of 0.72 +/- 0.1 mg.mL-1, and represented 7% of the total BSA flux into the intestinal lumen. In the presence of NaF (2 x 10(-3) M), transport of both intact and total BSA was significantly inhibited (intact: control 374 +/- 80 vs. NaF 46 +/- 11, 88% inhibition; total: control 3288 +/- 296 vs. NaF 2550 +/- 235 ng.cm-2.h-1, 22% inhibition; p < 0.05). In addition, colchicine significantly inhibited intact BSA transport (control 339 +/- 15 vs. colchicine 206 +/- 13 ng.cm-2.h-1, 39% inhibition; p < 0.05). TTX had no effect on intact BSA flux. The findings suggest that transport of intact BSA from the serosa into the intestinal lumen is a saturable, energy-dependent process, which involves microtubules but is not under neural regulation.

Animals↗

PubMed1997

Mast cell hyperplasia and increased macromolecular uptake in an animal model of giardiasis.

Giardiasis has been associated with an increase in allergic disease following infection suggesting an alteration in mucosal immune function. Jejunal in vivo and in vitro macromolecular transport, epithelial permeability, and mucosal and connective tissue mast cell counts were examined in Mongolian gerbils (35-45 g) orogastrically inoculated (I) with a pathogenic strain of Giardia lamblia and compared to age- and weight-matched, sham-treated controls (C) 6 and 21 days postinoculation. Macromolecular uptake was significantly increased in infected tissue at 6 days both in vivo (I 134 +/- 19 vs. C 74 +/- 17 ng/hr; n = 8; P < 0.05) and in vitro (I 125 +/- 17 vs. C 67 +/- 8 ng/hr/cm; n = 12; P < 0.05). Macromolecular uptake did not differ between groups at 21 days. Infection had no effect on mucosal permeability of [51Cr]EDTA. Mucosal mast cell counts did not differ at 6 days but were significantly elevated in infected tissue at 21 days (I 33.3 +/- 6.8 vs. C 2.7 +/- 0.4 per high magnification field; n = 5; P < 0.01) as were connective tissue mast cell counts (I 1.7 +/- 0.2 vs. C 1.0 +/- 0.1 per high magnification field; n = 13; P < 0.005). The findings indicate that during the peak phase of giardiasis, jejunal active antigen uptake is increased leading to a delayed recruitment of mucosal and connective tissue mast cells. These changes may play a role in the increased incidence of hypersensitivity reactions associated with Giardia infection.

Animals↗

PubMed1996

The role of nitric oxide in the regulation of macromolecular transport in rat jejunum.

1. Nitric oxide is known to affect epithelial and microvascular permeability and is a major non-adrenergic non-cholinergic neurotransmitter in the intestine. We have previously demonstrated neuronal regulation of macromolecular transport in the intestine. To define this regulation further the role of nitric oxide was investigated. 2. Stripped rat jejunum was mounted in Ussing chambers exposing the mucosal surface to bovine serum albumin (BSA; 2 mg ml-1), or BSA (2 mg ml-1) plus [125I]BSA (10 microCi). Following a 50 min equilibration, serosal fluids were sampled for four 10 min periods, and fluxes determined for intact BSA by enzyme-linked immunosorbent assay (ELISA) and total BSA by [125I]BSA under basal conditions, and after treatment with NG-nitro-L-arginine-methyl ester (L-NAME) alone or in conjunction with L-arginine or decarboxylated molsidomine (SIN 1). 3. L-NAME significantly increased intact BSA uptake. Total (intact + degraded) BSA flux was not altered. The L-NAME effect was reversed by L-arginine and SIN 1. Additional experiments were performed by adding the nitric oxide donors sodium nitroprusside and SIN 1 directly to control tissue. Nitric oxide donors did not further decrease intact BSA flux below levels obtained from control tissue. The L-NAME enantiomer D-NAME had no effect. Sodium-free bathing solutions also had no effect on intact BSA uptake. Non-specific permeability, as assessed by the serosal to mucosal movement of [51Cr]ethylene-diamine-tetraacetate ([51Cr]EDTA), was decreased with L-NAME. 4. The findings indicate that nitric oxide downregulates intact macromolecular flux in the small intestine.

Albumins↗

PubMed1996

Role of ornithine decarboxylase in enterocyte mitochondrial function and integrity.

We examined the role of ornithine decarboxylase (ODC) and polyamine biosynthesis in regulating mitochondrial function and integrity along the crypt-villus axis in male Sprague-Dawley rats. Isolated villus tip enterocytes from control rats demonstrated a greater cellular capacity for glucose oxidation than crypt enterocytes. Mitochondrial enzyme activities were similar along the crypt-villus axis. The role of ODC was assessed by treating experimental rats with the irreversible ODC inhibitor alpha-difluoromethylornithine (DFMO) for 24 h. Animals receiving DFMO demonstrated a decreased CO2 production from [2-(14)C]pyruvate along the entire crypt-villus axis coupled with an increase in lactate production in the upper cell populations. CO2 production from [14C]glucose and total ATP levels were not affected by DFMO treatment. Ultrastructural examination revealed localized mitochondrial swelling and bursting only in enterocytes corresponding to the population of cells newly emerged from the crypt during DFMO treatment. In DFMO-treated animals, 2 microM spermine completely prevented the structural mitochondrial injury and restored the metabolic crypt-villus gradient. These results suggest that as enterocytes migrate from the crypt up the villus, mitochondrial function increases to handle the increased metabolic demands placed on the cell by nutrient absorption. ODC activity and polyamines are necessary for this increased mitochondrial function and have a role in the maintenance of mitochondrial integrity in maturing enterocytes migrating from the crypt onto the villus.

Animals↗