Biomedical subjects

C Singaram

Publications and source records attributed to C Singaram.

15 recordsLinked to original sources

PubMed1995

Development of TCR-gamma delta CD4-CD8+ alpha alpha but not TCR-alpha beta CD4-CD8+ alpha alpha i-IEL is resistant to cyclosporin A.

Present evidence suggests that cyclosporin A (CSA) inhibits the development of both alpha beta and gamma delta T cells in the thymus. However, whether CSA can inhibit the development of murine intestinal intraepithelial lymphocytes (i-IEL) is unknown as most i-IEL are clearly derived from a different lineage than the conventional thymus-derived T cells found in the periphery. Using the adult thymectomized, lethally irradiated bone-marrow reconstituted chimera (ATXBM mice) as a model for the development of extrathymically derived i-IEL and the fetal thymus-grafted (FTG) nude mice as a model for the development of thymically derived i-IEL, we demonstrate that CSA nearly completely inhibited the development of extrathymically, and possibly thymically, derived TCR-alpha beta i-IEL. Most of the TCR-alpha beta i-IEL whose development was inhibited by CSA belonged to the CD4-CD8+ alpha alpha subset. In contrast, the development of extrathymically and thymically derived TCR-gamma delta i-IEL was completely resistant to CSA. The phenotype of CSA-resistant TCR-gamma delta i-IEL in these models was not different from those in control mice, and the TCR-gamma delta i-IEL in CSA-treated mice appear to be mature and activated as most were large, granular, and CD69+. Lastly, we demonstrate that CSA does not affect the extrathymic positive selection of V delta 4 i-IEL in C3H hosts. These results suggest that despite their similarity, the intracellular activation cascade involved after TCR stimulation between TCR-alpha beta CD4-CD8+ alpha alpha and TCR-gamma delta CD4-CD8+ alpha alpha i-IEL are markedly different.

Animals↗

PubMed1995

Dopaminergic defect of enteric nervous system in Parkinson's disease patients with chronic constipation.

Clinical studies suggest that gut disorders are common in Parkinson's disease, but the morphological basis is unknown. Depletion of dopamine-containing neurons in the central nervous system is a basic defect in Parkinson's disease. We compared colonic tissue from 11 patients with advanced Parkinson's disease, 17 with adenocarcinoma (normal tissue was studied), and five who underwent colectomy for severe constipation. Immunohistochemistry was used to stain myenteric and submucosal neurons for dopamine, tyrosine hydroxylase, and vasoactive intestinal polypeptide (VIP). Each class of neurons was quantified as a percentage of the total neuronal population stained for the marker protein gene product 9.5. Nine of the 11 Parkinson's disease patients had substantially fewer dopaminergic myenteric neurons than the other subjects (mean 0.4 [SE 0.2] vs 6.9 [2.3] in controls and 5.7 [2.0] in constipated subjects). There was very little difference between the groups in numbers of tyrosine-hydroxylase and VIP neurons. Two Parkinson's disease patients had similar distributions of all types of neurons, including dopaminergic myenteric neurons, to the controls. High-performance liquid chromatography showed lower levels of dopamine in the muscularis externa (but not mucosa) in four Parkinson's disease patients than in four controls (7.3 [5.1] vs 24.2 [4.6] nmol per g protein), but levels of dopamine metabolites were similar in the two groups. The identification of this defect of dopaminergic neurons in the enteric nervous system in Parkinson's disease may lead to better treatment of colorectal dysfunction in this disease.

Adenocarcinoma↗

PubMed1995

Peptidergic and nitrinergic denervation in congenital esophageal stenosis.

Congenital esophageal stenosis (CES) is a rare disorder with narrowed esophageal lumen that presents as dysphagia from childhood and that is often associated with tracheobronchial remnants or webs. The pathogenesis of CES is unknown. The aim of this study was to examine the histological and immunohistochemical features of CES. Esophagi from 2 young adults with CES and 3 controls with no motility disorders underwent routine H&E staining, trichrome staining for collagen, and detailed immunocytochemical studies for general neuronal markers (protein gene product 9.5, neuron-specific enolase, and S-100) and neurotransmitters (vasoactive intestinal polypeptide, substance P, and galanin) and nitric oxide synthase by beta-nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase and a specific NO synthase antibody. Quantitative experiments compared the numbers of myenteric neurons and amounts of fibers at the circular muscle. CES esophagi showed infiltration of neutrophils in the myenteric plane, without any increase in collagen. NADPH-diaphorase histochemistry showed a significant reduction of myenteric nitrinergic neurons (7 +/- 3.4 vs. 2.7 +/- 1.8 neurons per high-power field) and fibers at the circular muscle. Other peptidergic neurons studied were not significantly reduced in CES. The specific total lack of NO inhibitory innervation may be an important mechanism in the pathogenesis of stenosis and aperistalsis of the esophagus in this disorder.

Adult↗

PubMed1995

Electrophysiological and pharmacological responses of chronically denervated lower esophageal sphincter of the opossum.

BACKGROUND & AIMS: Achalasia is characterized by loss of myenteric neurons and incomplete relaxation of the lower esophageal sphincter (LES). The aim of this study was to develop an achalasia model in the opossum using the surfactant benzyldimethyltetradecylammonium chloride (BAC). This study further characterizes the achalasia model. METHODS: BAC or saline was injected circumferentially into the LES of 14 adult opossums. Eight months after injection, manometry, isolated muscle bath studies, electrical field stimulation, and histochemical analysis were performed. RESULTS: Manometrically, the LES of BAC-treated opossums showed higher pressures (38.7 +/- 12 mm Hg vs. 17 +/- 3.0 mm Hg) and reduced esophageal body contraction amplitudes (4.2 +/- 3 mm Hg vs. 27.4 +/- 12 mm Hg). Isolated muscle strips challenged with carbachol and sodium nitroprusside contracted and relaxed similarly to controls. Electrical field stimulation failed to induce relaxation in BAC-treated tissue but did induce contraction. Contractile responses were markedly reduced by tetrodotoxin and atropine in BAC-treated animals and controls. An altered nitric oxide system was shown by the lack of response to L-arginine and N omega-nitro-L-arginine. Histology showed loss of myenteric neurons and increased cholinergic nerve bundles. CONCLUSIONS: Loss of NO inhibitory myenteric neurons markedly reduces the relaxation of the LES, and histology and pharmacological responses suggest a proliferation of cholinergic nerves into the LES contributing to the static elevated pressures of the amyenteric LES.

Analysis of Variance↗

PubMed1995

Nitrinergic and peptidergic innervations and their inter-relationships in human colon.

The distribution and colocalization of nitrinergic and peptidergic nerves were examined in six human colons. The tissues were fixed, cryosectioned, and standard immunohistochemistry was performed for several known neuropeptides. The same sections were stained for NADPH-diaphorase to denote nitric oxide synthase. NADPH-diaphorase-positive myenteric neurons were counted and colocalization noted for each peptide, as well as for peptide terminations. Galanin was the only neuropeptide that colocalized to a significant extent (23.0 +/- 7.21%) with NADPH-diaphorase-positive myenteric neurons. Many neuropeptide-containing nerve fibers had extensive terminations onto NADPH-diaphorase-positive neurons. Vasoactive intestinal peptide was the only neuropeptide that colocalized with NADPH-diaphorase to any extent in nerve fibers within circular muscle (59.5 +/- 9.3%). Fiber distribution in the longitudinal muscles showed a similar, but less dense pattern. These observations provide morphological evidence for the presence of nitric oxide, a candidate nonadrenergic noncholinergic neurotransmitter in the human colon.

Aged↗

PubMed1995

A severe case of diversion colitis with large ulcerations.

Diversion colitis is an inflammatory condition that develops in the excluded segment of colon after surgical diversion. Inflammatory changes include aphthous-type ulcerations, crypt abscesses, and mucosal friability. These features may be seen in other inflammatory diseases of the colon, making diagnosis difficult. Even though symptoms such as cramping pain, bleeding, and mucous discharge have been described with diversion colitis, most cases are asymptomatic. In this article we report a patient who presented with sepsis secondary to severe diversion colitis with several large (2-4 cm in diameter), deep ulcerations and air in the colonic wall, requiring colectomy.

Colectomy↗

PubMed1995

Delayed postpolypectomy bleeding.

Complications of colonoscopic polypectomy include perforation, infection, and bleeding. The incidence of bleeding after polypectomy is reported to range from one to seven per 1000 polypectomies. This complication usually occurs within a few days after the standard procedure using bipolar electrocautery. The longest time interval between polypectomy and significant bleeding thus far reported is 14 days. Most cases of postpolypectomy bleeding are easily recognizable and can be effectively treated by colonoscopic electrocauterization. We report here a patient who underwent colonoscopic removal of a flat adenomatous polyp at the cecum and presented 29 days postprocedure with acute onset of severe bleeding from the polypectomy site. A repeat colonoscopy identified this lesion, and cauterization successfully stopped this bleeding.

Adenomatous Polyposis Coli↗

PubMed1994

Cholestatic hepatitis after ingestion of chaparral leaf: confirmation by endoscopic retrograde cholangiopancreatography and liver biopsy.

The use of herbal and other "natural" health products by healthy and ill people is more common than is appreciated by many health care providers. Since most of these substances are not categorized as medicines, they are exempt from U.S. Government approval processes, and are essentially uncontrolled. In this article we describe a patient who developed painless jaundice, fatigue, and pruritus after taking chaparral tablets, 160 mg/day, for approximately 2 months. Serial liver biopsies and serum chemistries documented severe cholestasis and hepatocellular injury, i.e., a severe cholangiolitic hepatitis. Serum enzyme levels were markedly elevated: alk. phos. to four-fold, alanine aminotransferase and aspartate aminotransferase to 25-fold, total bilirubin to 30-fold, and gamma-glutamyl transpeptidase to 35-fold. Endoscopic retrograde cholangiopancreatography showed smooth, but severely narrowed biliary ducts without sclerosing cholangitis, distal obstruction, tumor, or stenosis. The diagnosis remained in doubt until the publication of two cases of chaparral hepatotoxicity. Because of the similarity of our patient's illness to those cases we concluded that chaparral was almost certainly the cause. Chaparral, also known as creosote or greasewood, is used by some practitioners to treat a diverse group of ailments including ethanol withdrawal. This report should heighten the awareness by primary care physicians and gastroenterologists that any chaparral herbal preparation is a potential hepatotoxin that can lead to serious illness.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcoholism↗

PubMed1994

Nitrinergic and peptidergic innervation of the human oesophagus.

The distribution, colocalisation, and interconnections of nitrinergic and peptidergic neurons and nerves in the human oesophagus were examined. Cryosections of surgically resected tissues from eight subjects were studied with indirect immunofluorescence for the presence of 11 neuropeptides and neuron specific enolase. After immunohistochemistry, nitric oxide synthase was shown on the same sections with the beta nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemical reaction. The histochemical findings were verified immunohistochemically on other sections with an antiserum against nitric oxide synthase. Most myenteric neurons (55%) were nitrinergic. Most (96%) received terminations positive for vasoactive intestinal polypeptide (VIP), calcitonin gene related peptide (CGRP) (80%), and galanin (59%). The neuronal somata of 14% also contained VIP, while 10% had galanin. Of the NADPH-diaphorase containing fibers seen in the muscle layers, many had closely associated VIP and galanin, but only rarely CGRP and substance P. Thus, despite abundant representation of both peptidergic and nitrinergic systems in oesophageal smooth muscle, only VIP and galanin colocalised to any significant extent with the nitrinergic elements. These findings provide morphological support for the role of nitric oxide as the non-adrenergic non-cholinergic inhibitory mediator in the human oesophagus and for its possible interactive role with the peptidergic system.

Adult↗

PubMed1994

Innervation of an esophageal ectatic submucosal blood vessel in achalasia and a comparison with normals.

Achalasia is a disease of the esophagus characterized by incomplete relaxation of the lower esophageal sphincter, resulting in obstruction. Aperistalsis and dilation of the esophageal body occurs later, contributing to the esophageal dysfunction. Gastrointestinal bleeding in achalasia is an infrequent complication usually caused by stasis ulcer, esophageal varices, carcinoma, or pneumatic dilation of the sphincter. We describe here a patient with longstanding achalasia who bled vigorously from a proximal esophageal site that can be identified as arterial bleeding by endoscopy. Subsequent esophageal resection allowed detailed histological and immunohistochemical examination, which revealed a vascular ectasia. This lesion was associated with an unusually rich network of nerve fibers containing calcitonin gene-related peptide. Neuropeptide Y- and substance P-containing fibers were found to be decreased in this lesion as compared with controls. On the other hand vasoactive intestinal peptide- and nitric oxide synthase-containing fibers appeared quantitatively similar to those of controls. Calcitonin gene-related peptide is known to be involved in angiogenesis and may have played a causative role in the development of this lesion. Vascular ectasia may represent a hitherto unreported complication of achalasia.

Blood Vessels↗

PubMed1992

Tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6 expression in inflammatory bowel disease.

The etiology of ulcerative colitis (UC) and Crohn's disease (CD) remains enigmatic. Infiltrating intestinal macrophages are capable of producing the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and interleukin-6 (IL-6). We investigated the presence of IL-6, TNF-alpha and IL-1 beta mRNA transcripts in inflammatory bowel disease (IBD), normal, and other inflammatory intestinal specimens utilizing the polymerase chain reaction (PCR). TNF-alpha mRNA levels did not very between inflammatory bowel disease and control specimens. IL-1 beta mRNA levels were highest in active UC and noninflammatory bowel disease inflammatory specimens while IL-6 mRNA levels were highest in active IBD specimens. Infiltrating T cells, macrophages, and B cells were identified as sources of IL-6 protein in inflammatory bowel disease specimens by immunofluorescent staining. IL-6 transcripts were elevated only in active inflammatory bowel disease specimens, suggesting that IL-6-mediated immune processes are ongoing in the inflammatory mucosal environment of CD and UC.

B-Lymphocytes↗

PubMed1992

Reinnervation of villi of rat jejunum following severe mucosal damage.

We studied the time course of the regeneration of the jejunal mucosa of the rat after it was damaged by exposure to the surfactant, benzalkonium chloride. We placed particular emphasis on assessing the morphology of the nerve fibers within the villi during and after regeneration. The application of benzalkonium chloride resulted in virtually complete loss of villi within the treated segment; however, the crypts were only partially damaged. The mucosa began to regenerate within 6 hr of the insult. The villus lengths and crypt depths returned to pretreatment values within two to four days. The mucosal innervation was assessed through immunohistochemistry for vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and neuron-specific enolase (NSE). At all stages of regeneration, VIP, NPY, and NSE immunopositive fibers within the lamina propria extended to the tips of the villi. The density of the immunopositive fibers in the lamina propria at four days after mucosal insult was similar to that in control tissues regardless of the neuronal marker visualized. We conclude that the nerve fibers innervating the small intestinal mucosa grow at a rate of approximately 100 microns/day and that the entire length of each villus contains nerve fibers throughout the regeneration process. The innervation of the regenerated mucosa appears identical to that of control mucosa.

Animals↗

PubMed1991

Peptidergic innervation of the human esophageal smooth muscle.

Studies were performed to define the peptidergic nature of intramural nerves in the human esophagus. Cryosections of uninvolved surgically resected tissues from 14 individuals were studied by immunofluorescence for the localization of 10 neuropeptides. Myenteric neurons showed bombesin-, calcitonin gene-related peptide-, galanin-, substance P-, vasoactive intestinal polypeptide-, leucine-enkephalin-, methionine-enkephalin-, neuropeptide Y-, and somatostatin-like immunoreactivity. Submucous neurons had all the above except neuropeptide Y, methionine-enkephalin, leucine-enkephalin, and bombesin. Both groups of neurons received nerve terminations positive for calcitonin gene-related peptide, galanin, neuropeptide Y, substance P, and vasoactive intestinal polypeptide. Myenteric neurons additionally received terminations positive for neuropeptide Y, methionine-enkephalin, and somatostatin. All muscle layers had varicose fibers that reacted for calcitonin gene-related peptide, galanin, neuropeptide Y, and substance P. Longitudinal and circular muscle received few nerves reactive for leucine-enkephalin, whereas methionine-enkephalin was localized in a few nerve endings in the circular muscle. Somatostatin- and bombesin-reactive nerves occurred in longitudinal muscle. No cholecystokinin-reactive nerves were found. This study extends the results of previous studies and shows the previously undescribed presence of calcitonin gene-related peptide- and galanin-reactive nerves in the human esophagus and identifies neuropeptides that may serve as motor, sensory, and modulatory neurotransmitters of esophageal nerves.

Adult↗

PubMed1991

Localization of calcitonin gene-related peptide in human esophageal Langerhans cells.

Previously undescribed calcitonin gene-related peptide-immunoreactive intraepithelial cells were seen in specimens of esophageal mucosa obtained by biopsy or surgical resection from 14 individuals. These calcitonin gene-related peptide-immunoreactive cells were sparsely seen in normal mucosa but increased markedly in esophagitis. They were inaccessible to routine histological stains, but osmication showed them as dendritic forms resembling Langerhans cells of the skin. Their cytological identity was determined with immunocytochemical tests for human antigenic markers such as Ia, HLA-DR, and OKT6 for Langerhans cells, Leu-M5 and Leu-M3 for intraepithelial macrophages, CD3 and TCR-1 for T-lymphocytes, Leu-14 for B-lymphocytes, S-100 for Merkel cells, and chromogranin for amine precursor uptake and decarboxylation cells. Double localization showed that calcitonin gene-related peptide immunoreactivity colocalized with Ia, HLA-DR, and OKT6 but not with the other markers. These studies show that intraepithelial Langerhans cells in the esophageal mucosa contain calcitonin gene-related peptide, which may serve as an immunomodulator.

Calcitonin Gene-Related Peptide↗

PubMed1990

Mucosal peptidergic innervation of the opossum esophagus and anal canal: a comparison with snout skin.

Nerves within and under the esophageal epithelium of the opossum esophagus were investigated morphologically with osmication and immunohistochemically for ten neuropeptides. The structurally similar but functionally diverse epithelia of the anal canal and snout skin, on which no immunohistochemical information exists, were similarly investigated for comparison. Total innervation was estimated from osmication, which revealed intraepithelial nerves in all three tissues in the following order of density: snout skin greater than anal canal greater than esophagus. Calcitonin gene-related peptide and substance P occurred in all three organs. The snout skin had intraepithelial galanin nerves but not vasoactive intestinal polypeptide, while conversely the esophagus and anal canal had vasoactive intestinal polypeptide but not galanin. All peptides found intraepithelially also occurred subepithelially. Calcitonin gene-related peptide, galanin, neuropeptide Y, substance P and vasoactive intestinal polypeptide subepithelial nerves occurred in all the tissues, while gastrin releasing peptide nerves occurred infrequently in the subepithelial regions of the esophagus and anal canal, but not the snout skin. As these epithelia neither secrete nor absorb, their nerves are presumably sensory. The peptides investigated could not account for all intraepithelial nerves demonstrated by osmium. Differences in the innervation of these epithelia may result from their differing sensory requirements.

Anal Canal↗