A novel partial 5HT3 agonist DDP733 after a standard refluxogenic meal reduces reflux events: a randomized, double-blind, placebo-controlled pharmacodynamic study.

BACKGROUND: DDP733, a selective partial 5HT(3) receptor agonist, increases lower oesophageal sphincter pressure in experimental animal models. However, its effect on gastro-oesophageal reflux or lower oesophageal sphincter pressure in humans remains unknown. AIM: To evaluate the effect of DDP733 on reflux episodes in healthy volunteers receiving a refluxogenic meal. METHODS: A randomized, double-blind, placebo-controlled cross-over study evaluated the pharmacodynamic effects of DDP733 (0.5, 0.8 and 1.4 mg). Healthy subjects underwent oesophageal manometry and intra-oesophageal multichannel intraluminal impedance and pH after a refluxogenic meal. RESULTS: DDP733 0.5 mg significantly (P = 0.013) reduced the rate of reflux episodes after a refluxogenic meal from 10 (+/-2.2) on placebo to 6 (+/-1.2) on drug over a 2-h period. DDP733 0.8 and 1.4 mg had no significant effect on reducing the number of reflux episodes. Significant differences in resting lower oesophageal sphincter pressure and the proportion of time pH was <4 (placebo minus drug) after a refluxogenic meal were not observed. No serious adverse events were reported. CONCLUSION: In healthy subjects, the partial 5HT(3) agonist DDP733 at a dose of 0.5 mg significantly reduces the rate of reflux events, but did not result in a significant change in lower oesophageal sphincter pressure at 1 h postdosing.

Over-utilization of the J delta 3 gene-segment in Crohn's disease.

A majority of normal human intestinal intraepithelial lymphocytes (iIEL) are CD8+, express the alpha beta-T cell receptor (TCR) and are oligoclonal. The remainder of normal iIELs, which are also oligoclonal, express the gamma delta-TCR and preferentially utilize variable regions (V delta 1 and V delta 3) which are different from adult peripheral blood lymphocytes (V delta 2). The junctional region usage of gamma delta-TCRs in intestinal diseases is largely unknown. The aim of this study was to examine gamma delta-T cell clonality and junctional region usage of V delta 1 and V delta 3 transcripts in Crohn's Disease (CD) in comparison to several other chronic inflammatory diseases of the colon by polymerase chain reaction amplification, cloning and sequencing. As previously observed in normal subjects, all inflammatory cases examined, including CD (n = 3), ulcerative colitis (n = 1), diverticulitis (n = 1) and lymphocytic colitis (n = 1), the V delta 1 and V delta 3 transcripts contained reiterated sequences consistent with the expansion of gamma delta-T cells expressing these receptors. In 2/3 CD cases, but none of the non-CD inflammatory cases, transcripts containing J delta 3, a rarely used J delta, was observed among the V delta 1 and/or V delta 3 transcripts. Thus, in a subset of CD, gamma delta-T cells expressing J delta 3 may be expanded implicating a role for unique ligands that drive the expansion of T cells expressing these receptors.

V gamma (I) expression in human intestinal lymphocytes is restricted.

The majority of human intestinal intraepithelial lymphocytes (HIELS) express CD8+, and the T cell Receptor (TCR) alpha beta. A minority of HIELS utilize TCR gamma delta chains. V delta 1 is established as the TCR-delta expressed by most TCR gamma delta HIELS. Since V delta 1 is the dominant intestinal TCR and V gamma (I) family is preferentially used in forming a heterodimer, this study was conducted to characterize individual V gamma (I) utilization in HIELS. Intestinal lymphocytes were isolated from four samples of colonic epithelium obtained from patients undergoing colon resection or endoscopy. RNA was isolated and cDNA synthesized. PCR amplification was performed with consensus J gamma and V gamma primers in these regions. PCR products were cloned and sequenced. All samples had V gamma 4 transcripts, a majority V gamma 3 whereas V gamma 2 and V gamma 8 were less frequent. No V gamma 2 transcripts had any predicted TCR protein products. Similarly, very few potentially productive V gamma 3 transcripts were found. In contrast, almost all V gamma 4 transcripts were found to be in-frame and the only V gamma 8 transcript was in-frame. The CDR3 region of the gamma transcripts were small compared to published intestinal TCR delta recombinations. All CDR3 regions contained at least one charged amino acid. The limited number of functional transcripts adds evidence to the oligoclonality of intestinal TCRs expressing the TCR V gamma (I) family. The short CDR3 regions support the concept of limited antigen recognition by this lymphocyte population.

Tissue distribution of the non-polymorphic major histocompatibility complex class I-like molecule, CD1d.

The CD1 gene family is composed of five distinct molecules: CD1a, b, c, d and e. CD1a, b and c are primarily expressed thymically with limited extrathymic expression. Preliminary studies have shown that CD1d is primarily expressed extrathymically in gastrointestinal epithelial cells, renal tubular epithelial cells and B cells. This report characterizes the expression of CD1d in a variety of human tissues by immunohistochemistry using two anti-human CD1d monoclonal antibodies (mAb). CD1d was found in a wide range of tissues including the intestine, liver, pancreas, skin, kidney, uterus, conjunctiva, epididymis, thymus and tonsil. Within those tissues CD1d was mainly present in epithelial cells, vascular smooth muscle cells and parenchymal cells. Therefore, the tissue distribution of CD1d is distinct from CD1a-c and classical major histocompatibility complex (MHC) proteins implicating a unique role for CD1d in the immune system.

Glucose-dependent insulinotropic peptide: structure of the precursor and tissue-specific expression in rat.

Glucose-dependent insulinotropic peptide (GIP) is a 42-amino acid gastrointestinal regulatory peptide that stimulates insulin secretion from pancreatic beta cells in the presence of glucose. Approximately 7.8 x 10(5) recombinant clones of a neonatal rat intestinal cDNA library were screened by using plaque hybridization, and three clones were identified and sequenced with the dideoxynucleotide chain-termination method. The translated amino acid sequence deduced from the nucleotide sequence of the cDNA indicated that rat GIP was derived by proteolytic processing of a 144-amino acid precursor polypeptide. The mature peptide is flanked by a 43-amino acid NH2-terminal peptide that contains a 21-amino acid signal peptide and by a 59-amino acid COOH-terminal peptide. Analysis of the nucleotide and amino acid sequence of rat GIP revealed only two substitutions from the known human GIP peptide. The use of high-stringency RNA blot-hybridization analysis of total RNA extracted from various organs demonstrated expression of the GIP gene in the duodenum and jejunum and, to a lesser extent, in the ileum. In addition, expression of the GIP gene was observed in the submandibular salivary gland both by RNA analysis and RIA. In response to duodenal perfusion of a 20% Lipomul meal for 60 min, duodenal mucosal GIP mRNA concentrations increased by 42.8% and 48.2% at 30 and 60 min, respectively.

Expression of a nonpolymorphic MHC class I-like molecule, CD1D, by human intestinal epithelial cells.

The human CD1 locus encodes three nonpolymorphic MHC class I-like cell surface glycoproteins, CD1a-c, which are expressed primarily by immature thymocytes. A mAb and antipeptide antiserum were utilized to determine the tissue distribution of a fourth CD1 molecule, CD1d. Within the lymphoid lineage, CD1d was expressed on B cells but not on thymocytes. Immunoperoxidase staining of fresh frozen intestinal tissues demonstrated that the majority of intestinal epithelial cells, with the exception of cells at the base of some crypts, expressed CD1d. The CD1d staining was observed in the cytoplasm and along the basolateral membranes of the epithelial cells. The intestinal epithelial cell expression of CD1d was confirmed by immunoblotting with a CD1d antipeptide antiserum. Further immunoperoxidase studies indicated that CD1d, unlike murine CD1, was also expressed by nonlymphoid tissues outside of the gastrointestinal tract. The expression of CD1d outside the lymphoid and myeloid lineages clearly distinguishes this molecule from CD1a-c and suggests that it may serve a distinct function. The prominent expression of CD1d by intestinal epithelial cells suggests that this molecule may be an important ligand for T lymphocytes within the gut-associated lymphoid tissue.

Oligoclonal expansion and CD1 recognition by human intestinal intraepithelial lymphocytes.

A human intestinal intraepithelial lymphocyte (IEL) T cell line was established from jejunum to characterize the structure and function of the alpha beta T cell antigen receptors (TCRs) expressed by this population. Single-sided polymerase chain reaction (PCR) amplification cloning and quantitative PCR amplification of the TCR chains from the cell line and from fresh IELs demonstrated that IELs were oligoclonal. The IEL T cell line exhibited CD1-specific cytotoxicity and a dominant IEL T cell clone was CD1c-specific. Thus, human jejunal intraepithelial lymphocytes are oligoclonal and recognize members of the CD1 gene family.

A method for quantitating the contributions of the pathways of acetoacetate formation and its application to diabetic ketosis in vivo.

A method has been developed for estimating in the intact cell the contribution of deacylation of acetoacetyl-CoA to the formation of acetoacetate relative to acetoacetate's formation via hydroxymethylglutaryl (HMG)-CoA. Estimates depend upon the fraction of the terminal four carbons of an even carbon-containing fatty acid that are converted to acetoacetate without prior conversion to acetyl-CoA, since in the formation of acetoacetate via HMG-CoA the omega-2 and omega-3 carbons of the fatty acid are converted to acetyl-CoA. Incorporation of 14C from [16-14C]palmitic acid into carbon 2 relative to carbon 4 of acetoacetate is used as the measure of the formation of the acetoacetate from the omega and omega-1 carbons of the fatty acid without acetyl-CoA as an intermediate. Incorporation of 14C from [13-14C]palmitic acid into carbon 1 relative to carbon 3 of acetoacetate is the measure of the formation of acetoacetate from the omega-2 and omega-3 carbons without acetyl-CoA as an intermediate. Comparison of these incorporations is made with incorporation into the carbons of acetoacetate of 14C from palmitic acid labeled with 14C in any of its first 12 carbons since such incorporation must proceed via acetyl-CoA as an intermediate. In an application of this approach, the specifically 14C-labeled palmitic acids were injected into rats in diabetic ketosis. Hydroxybutyric acid that each rat excreted was isolated and degraded. From the ratios of incorporation into the carbons of the hydroxybutyrates, as a minimum, 11% of the total quantity of hydroxybutyrate excreted by the rats was formed from acetoacetyl-CoA without HMG-CoA as an intermediate.