Biomedical subjects

M H Perdue

Publications and source records attributed to M H Perdue.

At least 19 recordsLinked to original sources

PubMed1992

Mucosal damage during intestinal anaphylaxis in the rat. Effect of betamethasone and disodium cromoglycate.

In this study, two antiallergic compounds, betamethasone and disodium cromoglycate were tested in an animal model of intestinal anaphylaxis. Rats, immunized with Nippostrongylus brasiliensis, were challenged intravenously with whole worm antigen or saline. Antigen challenge resulted in significant abnormalities: epithelial damage with shorter villi, decreased activity of digestive enzymes, decreased levels of mucosal histamine, a mast cell mediator, and increased blood uptake of [51Cr]EDTA from the lumen. Low-dose betamethasone, 24 and 48 hr before antigen, was not effective in preventing the effects: villus damage and increased [51Cr]EDTA uptake were seen, although mucosal mast cell numbers were significantly reduced by the drug. High-dose betamethasone completely prevented intestinal anaphylaxis: villus height, digestive function, and [51Cr]EDTA recovery in antigen-challenged animals were not significantly different from controls. Mucosal histamine levels and mast cells were significantly reduced in the high dose betamethasone group. Oral disodium cromoglycate did not prevent the abnormalities but provided a slight beneficial effect.

Analysis of Variance↗

PubMed1992

Role of T lymphocytes in intestinal mucosal injury. Inflammatory changes in athymic nude rats.

To determine the role of T cells versus mast cells in mucosal injury, we documented structural and functional changes in the intestine of congenitally athymic nude rats during infection with the enteric parasite, Nippostrongylus brasiliensis. Studies were conducted at days 4, 7, 10, and 21 postinfection; controls were uninfected. Villus damage was indicated by morphological abnormalities at days 7, 10, and 21 and reduced activities of disaccharidase enzymes at days 10 and 21. The activity of the proliferative enzyme, thymidine kinase, was increased only at day 21, at which time the crypts were elongated. Epithelial permeability increased significantly: 5-hr recovery (in urine and blood) of the probe molecule, [51Cr]EDTA, following injection into ligated jejunal segments, was elevated at days 7 and 10. Uptake of a protein antigen, ovalbumin, from lumen to blood followed a similar pattern. No evidence of functional T cells was demonstrated. However, mucosal mast-cell activation was indicated by elevated serum levels of rat mast-cell protease II at days 7 and 10. We conclude that the absence of thymus-derived T cells does not preclude mucosal damage involving impaired barrier and digestive function. Mucosal mast cells may be involved in causing the injury in this model.

Animals↗

PubMed1992

Gastrointestinal food hypersensitivity: basic mechanisms of pathophysiology.

Gastrointestinal symptoms occur in a large number of patients with food allergies. Immediate hypersensitivity mechanisms may give rise to the nausea, vomiting, abdominal pain, and diarrhea experienced by these patients. However, there are limited human data about the pathophysiological basis for these symptoms. Most of the available information comes from a variety of animal models. This article reviews the literature using models of intestinal food hypersensitivity, as well as human studies, that have contributed to our understanding of the pathophysiological mechanisms in gastrointestinal food hypersensitivity.

Animals↗

PubMed1992

Antigen-mediated effects on epithelial function.

In summary, immediate hypersensitivity reactions to luminal antigens occur in the intestine and result in pathophysiology including increased permeability and ion secretion. The mechanism involves activation of mast cells with neural amplification (FIG. 5). Released mediators/neurotransmitters may act independently or synergistically on the epithelium to elicit Cl ion secretion. In addition, a cyclooxygenase product of arachidonic acid metabolism, possibly of mesenchymal cell origin, may be a common mediator. However, additional effector cell(s) besides mast cells are undoubtedly involved. This system demonstrates undeniably the concept of neuro-immuno-physiology of gut mucosa.

Animals↗

PubMed1991

Macrophage engulfment of mucosal mast cells in rats treated with dexamethasone.

The effects of corticosteroid treatment on mucosal mast cells in rat jejunal mucosa were examined. Rats previously infected with Nippostrongylus brasiliensis received a single IP injection of 1 mg dexamethasone. Three hours later, one third of mucosal mast cells demonstrated minor granular changes (fusion or peripheral clear zones) by electron microscopy. At 7 hours, by light microscopy, the majority of mucosal mast cells appeared abnormal with clustering of granules. By electron microscopy, 151 of 233 (65%) mucosal mast cells had been engulfed by enlarged macrophages and were in various stages of degeneration inside large phagosomes. By 24 hours, the number of mucosal mast cells had decreased to less than 10% of the initial number with parallel decreases in tissue rat mast cell protease II and histamine levels. Serum levels of rat mast cell protease II did not increase, and intestinal morphology was invariably normal with no evidence of inflammatory changes up to and including 24 hours. Observations were similar in uninfected animals. In contrast, in rats undergoing antigen-induced anaphylaxis, a significant elevation of serum rat mast cell protease II level was evident at 3 and 7 hours, and macrophage engulfment of mucosal mast cells was never seen, although tissue edema, enterocyte loss, and hemorrhage were observed. It is concluded that dexamethasone treatment results in macrophage engulfment and destruction of mucosal mast cells that occurs without granular mediator release and local inflammatory effects.

Animals↗

PubMed1991

Mast cell/nerve interactions in vitro and in vivo.

In this report, we review the evidence for mast cell/nerve interactions. We believe that the morphologic and functional evidence now strongly support a purposeful and biologically significant interaction between these two cell types. This interaction has physiologic consequences and appears to be able to regulate such local events as chloride ion secretion by epithelial cells of the intestinal and respiratory tracts in experimental models. In this way, the mast cell and nerve may be considered as a functional homeostatic regulatory unit. The extent to which this unit may be involved in maintenance of normal integrity of mucous membranes or other structures, in health and in disease, is not clear at the present and will require considerably more investigation and elucidation. However, the concept of such an interaction is an interesting one and may bring new approaches of a therapeutic and diagnostic nature to bear on some old problems. The observations reviewed in this report that psychologic conditioning may itself cause mucosal mast cell degranulation and mediator release in the rat is significant. We consider that this evidence of central nervous system control of mast cell degranulation is an extension of the idea that mast cells and nerves communicate.

Animals↗

PubMed1991

Role of mast cells in ion transport abnormalities associated with intestinal anaphylaxis. Correction of the diminished secretory response in genetically mast cell-deficient W/Wv mice by bone marrow transplantation.

To investigate the role of mast cells in transport abnormalities during intestinal anaphylaxis, we examined responses to antigen in isolated intestinal preparations from ovalbumin-sensitized genetically mast cell-deficient WBB6F1-W/Wv (W/Wv) mice and congenic normal WBBGF1(-)+/+ (+/+) mice. Changes in ion transport (primarily secretion of chloride ions) were indicated by increases in short-circuit current (Isc). In tissues from +/+ mice, antigen caused increases in Isc which were significantly inhibited by antagonists to histamine (diphenhydramine) and serotonin (ketanserin), by a cyclooxygenase inhibitor (piroxicam) and by a neurotoxin (tetrodotoxin). In preparations from W/Wv mice, antigen-stimulated responses were approximately 30% of that in +/+ mice and were inhibited only by piroxicam. Responses to electrical transmural stimulation of nerves were approximately 50% in W/Wv versus +/+ mice, and were inhibited by antagonists of mast cell mediators in +/+ but not W/Wv mice. Reconstitution of mast cells in W/Wv mice by intravenous injection of +/+ bone marrow cells restored the normal responses to both antigen and nerve stimulation. Our results indicate that mast cell-dependent mechanisms are primarily responsible for the ion secretion associated with intestinal anaphylaxis, but that other cells are also involved. In addition, our data provide evidence for the functional importance of bidirectional communication between nerves and mast cells in the regulation of ion transport in the gastrointestinal tract.

Anaphylaxis↗

PubMed1991

The dynamics of intestinal eosinophil depletion in rats treated with dexamethasone.

We examined the effects of corticosteroid treatment on eosinophils in the jejunal mucosa of rats previously infected with Nippostrongylus brasiliensis. Rats received a single intraperitoneal injection of 1 mg of dexamethasone. At a light microscopic level, the number of eosinophils with typical nuclei and granules was significantly decreased as early as 3 hours after injection, and had diminished to 17% of starting values at 24 hours. Pyknotic cells containing eosinophilic granules or fragments were observed scattered in the subepithelial interstitial space 3 and 7 hours after injection. By electron microscopy, more than 20% of eosinophils demonstrated nuclear abnormalities. Degenerating eosinophils without granular changes (27 of 127, 14.1%) or with or with granular changes (9 of 127, 7.1%) increased at 3 hours compared with untreated rats (8 of 233, 3.4%; 4 of 233, 1.7%). At 7 hours, 47 of 96 (49.0%) eosinophils were located inside phagocytic vacuoles of macrophages. Single macrophages occasionally engulfed two or more eosinophils. Only a few degeneration eosinophils (7 of 96) were observed outside macrophages. At 13 hours, the percentage of degenerating eosinophils and eosinophils inside macrophages was decreased; at 24 hours, few eosinophils were seen and eosinophil structures could not be identified inside macrophages. The epithelium and lamina propria did not show structural damage typical of an inflammatory reaction at any time. Eosinophil numbers in mesenteric lymph nodes, spleens, and peripheral blood were also reduced by dexamethasone. Similar observations were made in the jejunal mucosa of noninfected rats. We observed the slow restoration of eosinophil numbers in the intestinal wall, finally reaching preinjection numbers after 14 days. We conclude that dexamethasone has important effects on eosinophils causing (a) nuclear degeneration and (b) changes in the granular matrix. Subsequently, these damaged eosinophils are engulfed by macrophages and swiftly disappear from the intestinal mucosa. These effects appear to be due to the induction of apoptosis. Our findings offer an explanation for one of the significant antiinflammatory effects observed with the use of corticosteroids.

Animals↗

PubMed1990

Ion transport abnormalities in inflamed rat jejunum. Involvement of mast cells and nerves.

Basal and stimulated changes in ion transport in vitro were examined in jejunal mucosa from rats during inflammation produced after infection with the nematode Nippostrongylus brasiliensis. The gut was acutely inflamed at days 7 and 10 when net secretion of Na+ and Cl- ions was evident. Serum levels of rat mast cell protease II were elevated, providing evidence for mast cell activation. In addition, the magnitude of the short-circuit current responses to electrical transmural stimulation of enteric nerves (but not to histamine in the presence of neural blockade) were significantly reduced (p less than 0.01) to 17%-33% of control values, suggesting abnormalities of mucosal nerves. Following worm expulsion, serum levels of rat mast cell protease II and ion transport returned to normal. However, mastocytosis was apparent in gut mucosa and parasite antigen stimulated net secretion. In the absence of antigen, short-circuit current responses to nerve stimulation were increased (to 122% of controls; p less than 0.05). These findings suggest that changes in mast cells and enteric nerves occur during inflammation in this model and implicate neural and mast cell interactions with the epithelium in producing the ion-transport abnormalities.

Animals↗

PubMed1990

Allergic reactions of rat jejunal mucosa. Ion transport responses to luminal antigen and inflammatory mediators.

This study examined the electrophysiological responses to antigen and to various stimuli in jejunal mucosa from rats sensitized to egg albumin with alum and pertussis adjuvants. Luminal antigen caused an immediate increase in short-circuit current, a measure of net ion transport, which was one of three different patterns. All were inhibited by the chloride channel blocker diphenyl-2-carboxylate, by chloride-free buffer, and by doxantrazole, a mast cell stabilizer. Depending on the pattern, the histamine-1 antagonist diphenhydramine, the 5-hydroxytryptamine-2 antagonist ketanserin, and the cyclooxygenase inhibitor piroxicam also reduced the responses. A neural component was indicated by inhibition of the responses to luminal antigen by the neurotoxin tetrodotoxin and by neonatal capsaicin treatment, which depletes substance P-containing nerves. In the absence of antigen, histamine and substance P caused increases in short-circuit current; the magnitude of these changes was significantly greater in tissues from sensitized animals than in controls. These data suggest that sensitization itself may result in hypersecretory responses to some inflammatory mediator and neurotransmitter substances.

Animals↗

PubMed1990

Changes in distribution of Ia antigen on epithelium of the jejunum and ileum in rats infected with Nippostrongylus brasiliensis.

This study compared the tissue distribution and cellular expression of Ia antigen in jejunal and ileal epithelium at various stages of intestinal inflammation produced by infecting rats with the nematode parasite Nippostrongylus brasiliensis. Tissues were examined at Day 0 (control), Day 4 (early), Day 10 (acute), and Day 16 (recovering). Frozen sections were stained with the MRC OX-4 anti-Ia monoclonal antibody using an immunoperoxidase technique. Control jejunal sections demonstrated positive epithelial Ia expression mainly in the mid-regions of the villi. The stain appeared to be mostly intracellular in the supranuclear area; the basolateral membrane stained faintly. At Day 4, a greater percentage of the epithelial cells expressed Ia, including those at the tips of the villi. The Day 10 sections demonstrated no staining at all of villus enterocytes, but the crypt epithelium was Ia positive. At Day 16, the pattern of Ia expression was similar to that seen in the early infection. In the ileum, stain was present in enterocytes over most of the villus and crypt regions except in the villus-crypt junction and did not change significantly during infection. We conclude that the changes in the expression of Ia antigen by intestinal epithelium are local to the site of infection and probably occur as a consequence of the host's inflammatory response.

Animals↗

PubMed1990

Antigen-induced mucosal damage and restitution in the small intestine of the immunized rat.

Intestinal mucosal damage and restitution were examined following antigen-induced systemic anaphylaxis in Nippostrongylus brasiliensis immunized rats. The rats were injected intravenously with N. brasiliensis antigen or saline. At 60 min, morphological and biochemical parameters were determined in jejunum and ileum, and the epithelial permeability was assessed by measuring recovery of 51Cr-ethylenediaminetetraacetic acid in the blood after injecting it into a ligated segment. Antigen challenge resulted in significant abnormalities: (1) villus damage with sloughing of enterocytes; (2) decreased activities of brush border enzymes; (3) decreased levels of mucosal histamine and rat mast cell protease II (mast cell mediators), and (4) increased uptake of 51Cr-ethylenediaminetetraacetic acid. Progression of the injury was examined by taking consecutive biopsies at 15-min intervals for 60 min and then at 5 h. At 15 min, an abnormality was present in all sections which ranged from minor oedema and enterocyte detachment at villus tips to virtual complete destruction of the apical region. Restitution occurred by villus contraction with migration of the epithelium over the damaged regions. At 5 h, the epithelium had resealed, but the villi were significantly reduced in height.

Anaphylaxis↗

PubMed1990

Ion transport in rat tracheal epithelium in vitro. Role of capsaicin-sensitive nerves in allergic reactions.

Tracheas from control rats or rats sensitized to egg albumin (EA) were studied in vitro in Ussing chambers, and changes in short-circuit current (Isc) induced by the addition of antigen or agonists on the mucosal (luminal) side were recorded. Addition of EA (100 micrograms/ml) to tracheas from sensitized but not from control rats caused a slow increase of Isc beginning after 15 to 30 s and maximal at 3 to 4 min. This response was inhibited in the presence of doxantrazole, a mucosal mast-cell-stabilizing agent, but not by sodium cromoglycate. A separate group of rats was treated neonatally with capsaicin to deplete peptide neurotransmitters. Responses to EA were significantly lower in capsaicin-treated, sensitized rats than in untreated, sensitized control littermates. No difference was seen in the level of serum EA-specific IgE in these two groups. In tracheas from untreated rats, addition of substance P, capsaicin, platelet-activating factor, and acetylcholine caused an immediate and marked increase in Isc. Responses to substance P and acetylcholine were unaffected by capsaicin treatment. However, responses to capsaicin itself and also to PAF were reduced. These data indicate that changes of net ion transport across the airway epithelium are early phenomena of local hypersensitivity reactions, and that neurotransmitters such as substance P may play an important role in the control of these phenomena.

Animals↗

PubMed1989

Intestinal mucosal injury is associated with mast cell activation and leukotriene generation during Nippostrongylus-induced inflammation in the rat.

We examined mucosal injury in the jejunum of the rat during infection with the nematode parasite, Nippostrongylus brasiliensis (Nb). Injury was documented morphologically (increase in crypt length with or without villus atrophy) and biochemically (activities of digestive or proliferative enzymes) and related to mast cell activation and leukotriene generation. At day 4 crypt length and thymidine kinase activity were increased; no changes in villus parameters were recorded. No evidence of mast cell activation was found and leukotriene levels in the mucosa were normal. At day 7, the gut was acutely inflamed and edema was present at the tips of the villi. This progressed to enterocyte detachment, resulting in villus atrophy with decreased activities of brush border enzymes. At this stage mucosal histamine was decreased and rat mast cell protease II (RMCP II) was increased in serum, indicating mast cell activation. In addition, mucosal leukotrienes (LTB4, LTC4, LTE4) were present in significant quantities. Following worm expulsion, the villus abnormalities resolved and serum RMCP II returned to normal. However, the crypt hyperplasia persisted. Our results suggest that during Nb infection at least two components of injury can be identified. One component, epithelial injury at the villus tips, may be related to activation of mucosal mast cells.

Animals↗

PubMed1989

Novel cellular interactions and networks involving the intestinal immune system and its microenvironment.

The interactions we have described enable the intestine to respond appropriately to antigenic challenge in an effective and coordinated way. This is of vital importance when one considers the dual role of the intestine as a first line of defence against harmful microorganisms and as the route by which the animal obtains nutrition. Under normal circumstances, these interactions select for an appropriate cell phenotype by providing a network of interactions that contribute to intestinal homeostasis. If there is dysfunction of any component, then other cells will be affected. For example, if down-regulation of the mucosal immune response is not effective, damage to the epithelium, nerves and muscle may occur during an inflammatory response. Similarly, if the integrity of the epithelium is disrupted, damage to the elements of the mucosal immune system may occur. This model would suggest that these interactions must be considered if one wishes to adequately explain diseases such as IBD and design innovative therapeutic regimens. Future interdisciplinary research will shed light on the web of interactions occurring in the intestinal environment and provide a novel view of the respective contributions of the immune system and its local environment to cell differentiation, function and regulation.

Animals↗

PubMed1989

Effects of platelet-activating factor on ion transport in isolated rat jejunum.

In isolated normal rat jejunum, platelet-activating factor (PAF) induced a dose-dependent increase in short-circuit current (Isc) that was reduced in chloride-free buffer and inhibited by the Cl- channel blocker, diphenylamine-2-carboxylate. An immediate rise in Isc (early phase) occurred that fell to a new elevated base line by 15 min (late phase). These responses to PAF occurred only when experiments were conducted at or before approximately 9 A.M. Early phase responses were blocked by the specific PAF antagonists, BN52021 and WEB2086, and were inhibited by the neurotoxin, tetrodotoxin. Early and late phases were also reduced by cyclooxygenase inhibitors and by doxantrazole, a mast cell stabilizing drug. However, histamine and serotonin antagonists were ineffective. We conclude that PAF causes changes in ion transport that include Cl- secretion and acts on the epithelium possibly via an intermediate cell and enteric nerves. In addition, known PAF receptors are involved in one component of the response that appears to follow a circadian rhythm.

Animals↗

PubMed1988

Role of nonspecific cytotoxic cells in intestinal epithelial cell injury in Nippostrongylus brasiliensis infection.

We have employed a cultured crypt-like intestinal epithelial rat cell line (IEC-18) to assess whether killing by nonspecific cytotoxic cells contributes to epithelial cell destruction in Nippostrongylus brasiliensis (N.b.) infection. Spleen cells from N.b.-infected Sprague-Dawley rats, 11-13 days postinfection when villus atrophy and crypt hyperplasia were evident, killed IEC-18 in a 4-hr 51Cr-release assay. In contrast, intraepithelial leukocytes (IEL) from N.b.-infected rats showed decreased killing of IEC-18 compared to controls in a 16-hr assay. Spleen NK activity was increased in N.b.-infected rats whereas IEL NK activity was decreased. We conclude that direct cytotoxicity of crypt-like intestinal epithelial cells by nonspecific cytotoxic cells appears to play no significant role in intestinal injury in N.b. infection.

Animals↗

PubMed1988

Changes in intestinal permeability and epithelial differentiation during inflammation in the rat.

We examined changes in gut permeability in a controlled model of inflammation produced in rats after infection with the nematode parasite, Nippostrongylus brasiliensis. The probe, 51Cr-EDTA, was injected into ligated loops of jejunum in vivo and recovery of radioactivity was measured in urine, kidney, and intact loop at five hours. Urinary recovery was significantly increased during the early (day 7) and acute (day 10) stages of the infection compared with values in control rats but subsequently returned to normal. Urinary clearance of the probe after iv injection was unaltered during infection. Villus atrophy occurred only at the stage, whereas crypt hyperplasia was evident at both the early and acute stages. The terminal ileum appeared normal and showed normal permeability when compared with controls. We conclude that permeability changes are local to the site of inflammation, are reversible after healing and may be related to an increase in the proportion of relatively undifferentiated epithelium.

Animals↗