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W O Dobbins

Publications and source records attributed to W O Dobbins.

At least 19 recordsLinked to original sources
PubMed1993

Cultured adult rat jejunal explants as a model for studying regulation of CYP3A.

Enzymes within the CYP3A subfamily are major Phase I drug-metabolizing enzymes present in hepatocytes and small bowel enterocytes. These enzymes are highly inducible in the liver by many structurally diverse compounds, including a number of commonly used medications. Studies indicate that CYP3A enzymes present in small bowel enterocytes are also inducible. However, the regulation of CYP3A enzymes in this tissue has not been well characterized, in part because in vivo studies are difficult, especially in humans. Our goals was to develop an in vitro model to study the regulation of CYP3A in enterocytes. To this end, we defined culture conditions under which adult rat jejunal explants maintained viable appearing villi for 21 hr. When dexamethasone, the prototypical inducer of CYP3A1 in rat hepatocytes, was added to the culture medium, there was a time-dependent induction of CYP3A1 mRNA and CYP3A protein in explant enterocytes which was essentially indistinguishable from the time course of induction of CYP3A1 mRNA and protein in enterocytes in vivo. This effect of dexamethasone appeared to be specific since dexamethasone had no consistent effect on the explant concentration of another enterocyte specific mRNA, intestinal fatty acid binding protein. Using this explant culture model, we found that CYP3A1 mRNA was also inducible by clotrimazole but we were unable to detect induction by rifampicin or troleandomycin. Our observations suggest that jejunal explants may provide an appropriate model for the study of the regulation of CYP3A and other drug-metabolizing enzymes.

Animals↗
PubMed1992

Familial visceral neuropathy with neuronal intranuclear inclusions: diagnosis by rectal biopsy.

A family with a visceral neuropathy manifested as chronic idiopathic intestinal pseudo-obstruction is reported. Diagnoses were made histologically by simple rectal biopsy. Discrete eosinophilic intranuclear inclusions, diagnostic of a disease known as neuronal intranuclear inclusion disease, were found in the submucosal ganglion cells. Abnormalities of the autonomic nervous system were identified by pupillary examination and electroretinography. In this family, three of four siblings were affected by the disease, which is apparently transmitted from the paternal side. This pedigree was unique for several reasons: (a) diagnosis in multiple members of two generations indicates that this familial visceral neuropathy was expressed in an autosomal dominant manner, (b) central autonomic nervous system abnormalities were detected by eye examination, and (c) the definitive pathological diagnosis was established antemortem by rectal biopsy in all cases.

Adult↗
PubMed1992

Heterogeneity of cytochrome P450IIIA expression in rat gut epithelia.

The P450IIIA (CYP3A) cytochromes are a major family of enzymes that play an important role in the metabolism of many medications, including cyclosporine A, as well as some dietary xenobiotics, including aflatoxin B1. The purpose of the studies was to detect, localize, and characterize P450IIIA enzymes present throughout the digestive tract. To this end, P450IIIA-specific antibodies were used to examine gut epithelial microsomes and histological tissue sections obtained from the digestive tract of both male and female rats. P450IIIA-related proteins were detected in epithelia throughout the gut; however, the specific proteins expressed appeared to differ among digestive organs and between male and female rats. RNA obtained from the gut epithelia was also analyzed using P450IIIA-specific synthetic oligonucleotides as probes on Northern blots and as primers for the polymerase chain reaction. P450IIIA1, which is a dexamethasone inducible enzyme in liver, was also found to be induced by dexamethasone treatment in epithelia from stomach and jejunum, but not from colon or esophagus. It was concluded that P450IIIA enzymes are present in mature epithelia throughout the gastrointestinal tract. However, expression of the P450IIIA enzymes is influenced by anatomic location and gender.

Animals↗
PubMed1990

Long-term maintenance of the adult pattern of liver-specific expression for P-450b, P-450e, albumin and alpha-fetoprotein genes in intrasplenically transplanted hepatocytes.

Hepatocytes isolated from livers of Fischer 344 rats and transplanted into the spleens of rats from the same strain survived for at least 15 mo in the absence of immunosuppressive drugs. Hepatocytes attached themselves only in the red pulp of the spleen, most commonly in clumps without a discernible structure. Throughout the 15-mo period, intrasplenically transplanted hepatocytes expressed cytochrome P-450b, P-450e and albumin messenger RNAs, whereas alpha-fetoprotein messenger RNA was not expressed. In addition, the relative expression of albumin and P-450 genes was similar to that in liver. For example, albumin messenger RNA was expressed to higher levels than P-450b or e messenger RNAs. Northern blots hybridized with oligonucleotides specific for P-450b or P-450e showed that, as in liver, both P-450b and P-450e genes were induced in response to phenobarbital. Quantitative slot-blot hybridizations performed at 15 days and 1, 6, and 15 mo after hepatocyte transplantation revealed that cytochrome P-450b and P-450e messenger RNAs were induced about 20- to 30-fold by a single dose of phenobarbital. This level of induction was also similar to that observed in liver. Hence, intrasplenically transplanted hepatocytes represent a unique system in which hepatocytes, cultured in an extrahepatic in vivo environment, maintain for at least 15 mo a pattern of expression for these four liver genes similar to that in the adult liver. Moreover, these studies suggest that neither the organization of liver into acini nor a specific zonal sinusoidal microenvironment is necessary for adult hepatocytes to respond to phenobarbital with induction of P-450b and P-450e genes.

Albumins↗
PubMed1990

Characterization of mucous cell synthetic functions in a new primary canine gastric mucous cell culture system.

Mucin is a critical component of the protective layer secreted by gastrointestinal mucous cells. A detailed understanding of the molecular processing of gastric mucin and the physiology of its secretion has been limited by the lack of an adequate model for their study. We have developed a primary culture system of canine gastric mucous cells that has permitted us to study their synthetic and secretory functions. It was found that [3H]glucosamine used for metabolic labeling studies was incorporated into both mucin and lipid components of gastric mucus. To measure mucin with this model, a new immunoassay was developed to quantitate canine gastric mucin. Mucin was purified from the canine stomach, a polyclonal antibody was generated, and an enzyme-linked immunosorbent assay for gastric mucin was established. Mast cells were frequent contaminants of the gastric mucous cell preparation, and two methods were developed to limit their contamination. A new culture system has been developed for the study of gastric mucous cells. These cells synthesize and secrete both mucin and phospholipids. This system will permit us to study the molecular processing of mucin and the physiology of its production and release.

Animals↗
PubMed1988

Whipple's disease.

Explore the source record for details and available documents.

Anti-Bacterial Agents↗
PubMed1988

Studies of the rectal mucosa in coeliac sprue: the intraepithelial lymphocyte.

The dynamics of the rectal surface epithelial lymphocyte and leucocyte response to wheat, gluten, and gliadin enema challenges in control individuals and in patients with coeliac sprue in remission is shown. There is a clear increase in intraepithelial lymphocytes and polymorphonuclear (PMN) leucocytes in response to these enemas in coeliac sprue, but not in controls. The peak response was at eight hours and cleared within 24 hours. There was no change in the crypt epithelium. These data add further support to the role of wheat, gluten, and gliadin in the pathogenesis of coeliac sprue, at least in the rectal mucosa.

Celiac Disease↗
PubMed1987

HLA antigens in Whipple's disease.

The prevalence of HLA-A and B antigen loci in patients with Whipple's disease was determined from data obtained in a review of the literature and from personal communications. Data on the HLA-A and B locus typing of 30 patients were available (with the exception that 1 of the patients was not typed for the HLA-B locus), and for an additional 18 patients, HLA-B27 data were available. Of the 47 patients typed for B27, 13 (28%) were B27 positive. Twelve of the 48 patients had sacroiliitis, and 2 (17%) of them were B27 positive. These data suggest that Whipple's disease may be associated with HLA-B27, even in the absence of concomitant sacroiliitis.

Arthritis↗
PubMed1987

Neuronal dysplasia and chronic intestinal pseudoobstruction: rectal biopsy as a possible aid to diagnosis.

We report a patient with an unusual cause of chronic intestinal pseudoobstruction, i.e., neuronal intestinal dysplasia. This disorder is characterized by hyperplasia of the nerve plexuses of the intestine or colon, or both. Detailed morphologic and manometric studies are provided. The discussion emphasizes the various motor abnormalities that may be found in chronic intestinal pseudoobstruction. We propose that rectal biopsy may be of value in the diagnosis of this unusual form of pseudoobstruction.

Aged↗
PubMed1987

Glycine-extended progastrin processing intermediates: accumulation and cosecretion with gastrin.

Glycine-extended intermediates of peptide processing serve as substrates for carboxyl-terminal amidation, hence activation, of many brain-gut peptides. To explore the dynamics of accumulation and secretion of these important intermediates we utilized primary cultures of canine antral mucosal G-cells as a model system. Glycine-extended progastrin processing intermediates (G-Gly) accumulated rapidly in G-cells cultured in ascorbate-deficient media, exhibiting a fourfold increase over a 51-h culture period, while gastrin content fell to less than half of the initial level. In contrast, G-cells cultured in ascorbate-supplemented media accumulated G-Gly at a relatively low rate, while gastrin was preserved at a higher level. Under either condition, G-Gly and gastrin were progressively released into the culture media. The release of both immunoreactivities could be stimulated by bombesin and inhibited by somatostatin in similar fashion. By electron microscopy, the cultured G-cells exhibited no ultrastructural alterations. These data suggest that 1) the cellular homeostasis of G-Gly is regulated by the activity of an ascorbate-dependent amidation enzyme similar to one previously described in pituitary tissues, 2) carboxyl-terminal amidation is not an obligatory step for secretion of gastrin, and 3) the proportions of gastrin and G-Gly cosecreted from G-cells reflect their proportional accumulation within G-cell secretory granules. The physiological relevance of the released G-Gly has yet to be determined.

Animals↗
PubMed1986

Immunoelectron microscopic localization of HLA-DR antigen in control small intestine and colon and in inflammatory bowel disease.

We have elucidated the distribution of I2 (HLA-DR) antigen in control and inflammatory bowel disease specimens, using immunoelectron microscopic methods. Control small intestinal epithelium and inflammatory bowel disease epithelium expressed 12 antigen, while control colonic epithelium did not. I2 expression by enterocytes was more frequent on the lateral and basal surface than on the microvillus surface. Two of three M cells in control ileum expressed I2 antigen. I2-positive intraepithelial lymphocytes were rarely detected in both control and disease specimens. I2-positive lamina propria lymphocytes were significantly increased in inflammatory bowel disease, while I2-positive lamina propria lymphocytes were virtually absent in control specimens. I2-positive mononuclear cells in the intestinal lamina propria were largely macrophages and monocytes in both control and inflammatory bowel disease specimens. I2-positive mononuclear cells resembling dendritic cells were not detected in control or disease specimens. Furthermore, there were no significant morphological differences in I2-positive or -negative macrophages and monocytes in control and disease specimens. The expression of I2 antigen on Schwann cells was detected more frequently in disease specimens than in control specimens. Capillary endothelia of both control and disease specimens expressed I2 antigen. We demonstrate that I2 expression is present on surface membranes of both immune and nonimmune cells of the intestine and colon and show that this expression is more prominent in inflammatory bowel disease than in control intestine and colon. Further studies are required to determine whether this finding is meaningful in terms of antigen presentation and whether this apparent "immune activation" is involved in the pathogenesis of inflammatory bowel disease.

Antibodies, Monoclonal↗
PubMed1986

Gastric xanthomatosis and cholestasis. A causal relationship.

We report two cases of gastric xanthomatosis which developed in patients with marked cholestasis. In both cases, one with acute and one with chronic cholestasis, the gastric xanthomas disappeared with resolution of the cholestasis. A review of the literature is also provided.

Adult↗
PubMed1986

Immunohistological characterization of intraepithelial and lamina propria lymphocytes in control ileum and colon and in inflammatory bowel disease.

Using monoclonal antibodies to T and B lymphocytes, to natural killer cells, and to HLA-DR antigen, we characterized the lymphocyte population within the epithelial and lamina propria regions in control intestine and colon, and in grossly involved and in grossly uninvolved intestine and colon of patients with active inflammatory bowel disease. There were significantly more intraepithelial T cells in control ileum than in control colon. In comparison to control, there was a heterogeneity of alterations in intraepithelial and lamina propria T lymphocyte subsets (T11+, T8+, T4+) in inflammatory bowel disease. B lymphocytes were not detected within the lamina propria, except when found in and adjacent to lymphoid aggregates. Leu 7+ cells were uncommon in the lamina propria of control ileum and colon and in diseased tissues. The majority of intraepithelial lymphocytes did not express HLA-DR. Epithelial cells of control colon did not express HLA-DR while epithelial cells of control ileal tissues and of diseased colonic and ileal specimens expressed HLA-DR antigen. Only small numbers of lamina propria T cells expressed HLA-DR in both control and disease tissues. There was intense expression of HLA-DR by monocytes and modest expression of HLA-DR by capillary and lymphatic endothelial cells. The induction of HLA-DR expression by diseased colonic epithelium and the observation that lymphatic endothelium expresses HLA-DR are new observations, and we established that Leu 7+ cells are present in very small numbers in both normal and diseased intestine and colon.

Antibodies, Monoclonal↗