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D Hollander

Publications and source records attributed to D Hollander.

At least 73 records · Page 4Linked to original sources
PubMed1992

Molecular cloning of the mouse integrin beta 7 subunit.

The complete analysis of a cDNA clone encoding the mouse integrin beta 7 subunit that was isolated from a lambda gt10 cDNA library prepared from interleukin-4-activated mouse spleen B cells is reported. The 805-amino acid sequence deduced from the cDNA revealed a signal peptide, a 704-amino acid extracellular domain with eight N-glycosylation sites, a transmembrane domain, and a 61-amino acid intracellular domain. Several structural features were conserved with other integrin beta chains including the four cysteine-rich epidermal growth factor-like repeat sequences in the extracellular domain. Comparative analysis of the mouse and human beta 7 subunits revealed 87% sequence identity with conservation of three potential intracellular tyrosine phosphorylation sites. The cDNA hybridized to two mRNA transcripts of 3 and 2 kilobases (kb) in size. The 3-kb transcript, which is considered the productive form, was found in T and B leukemic cell lines, a macrophage line, and a mastocytoma cell line. Suprisingly, the smaller 2-kb transcript, which seems unlikely to encode a complete beta 7 protein, was found expressed in epithelial cells cultured from mouse skin. The integrin beta 7 subunit displays sequence identity with the beta subunit of the M290 antigen found expressed almost exclusively on intraepithelial lymphocytes in the small intestine suggesting that beta 7 may play an adhesive role in intraepithelial lymphocytes immunosurveillance of the gut mucosa. The cellular distribution of beta 7 transcripts is more extensive than the T-lineage-restricted distribution of the M290 antigen, indicating that beta 7 may be the common beta subunit for more than one receptor or that translation of beta 7 transcripts varies in different cell types.

Amino Acid Sequence↗
PubMed1992

Immunologic and structural relatedness of the integrin beta 7 complex and the human intraepithelial lymphocyte antigen HML-1.

We recently cloned the newest human integrin beta subunit, termed beta 7, from a cDNA library constructed from SEA-activated T lymphocytes. In this communication, we report on the structure of the human integrin beta 7 protein complex determined using a rabbit anti-beta 7 peptide antibody raised to an N-terminal 22 amino acid residue sequence deduced from the human beta 7 subunit cDNA. The beta 7 subunit (Mr 116,000) expressed on PHA lymphoblasts associates with a single major alpha subunit (alpha H) that is distinct from the prominent T cell marker, integrin alpha 4. The alpha H subunit (Mr 180,000 nonreduced) displays a distinctive shift in size on reduction to an apparent Mr of 150,000. We show that these structural properties of the integrin beta 7 complex are shared with the cell surface antigen HML-1 found highly expressed on T cells which populate the intestinal epithelium and are proposed to be involved in mucosal immunity. Sequential immunoprecipitation and Western blotting demonstrate identity or close homology between the alpha H beta 7 and HML-1 proteins.

Amino Acid Sequence↗
PubMed1992

Practical pharmacology and cost-effective management of peptic ulcer disease.

The clinical approach to the therapy of peptic ulcer disease has changed over the years as our understanding of its pathogenesis has grown. No longer is excess acid production seen as the single cause of ulcer disease; rather, its pathogenesis is viewed as the disturbance of a complex balance of ulcerogenic and protective factors. Today, the clinician's aim is to restore the balance between protective and aggressive factors. Simultaneously, the development of new classes of medications has provided the clinician with the tools to decrease intragastric acidity, neutralize or suppress acid production, and enhance the protective and restorative properties of the mucosa.

Anti-Ulcer Agents↗
PubMed1992

Effect of aging and caloric restriction on intestinal permeability.

Intestinal permeability is increased in several disorders such as Crohn's disease or rheumatoid arthritis. Since aging leads to alteration of many biological functions, the effect of aging on intestinal permeability was studied by measuring the intestinal permeability in aging rats gavaged with different size permeability probes--mannitol, polyethylene glycol (PEG) 400, and inulin. In rats fed with control diet, there was a significant increase in intestinal permeability to medium size probes PEG 400 (14.8 +/- 0.4 and 21.0 +/- 1.1% at 3 and 28 months respectively, p less than .01) and mannitol (3.41 +/- 0.4 and 5.3 +/- 0.5% at 3 and 28 months, respectively, p less than .01). Intestinal permeability of the large macromolecule inulin did not change (0.42 +/- 0.03 and 0.38 +/- 0.02% at 3 and 28 months, respectively) with aging. There was no correlation between weight of the rats and their intestinal permeability. Because dietary caloric restriction has been found to prolong the life span, retard deterioration of several biological functions, and affect intestinal absorptive functions, we examined the effect of lifelong calorie restriction on intestinal permeability changes. Lifelong calorie-restricted diet did not affect age-related change in intestinal permeability. We conclude that intestinal permeability of medium size probes increases with aging and that lifelong caloric restriction does not prevent this change. We speculate that age-associated deterioration in intestinal barrier functions could permit increased systemic absorption of lumenal antigens and could perhaps contribute to the genesis of antigen-related age-associated diseases.

Aging↗
PubMed1992

Prostaglandin but not cimetidine reduces spontaneous degeneration of isolated gastric gland cells.

We studied the effect of either placebo, 16,16-dimethyl-prostaglandin E2 (16,16-dimethyl-PGE2), or cimetidine on spontaneous degeneration of isolated rat gastric glands maintained in vitro in a basic oxygenated medium for 24 h. We assessed the viability of gland cells with fast green exclusion, measured release of lactate dehydrogenase (LDH) into the medium, and assessed the cell ultrastructure using a scanning electron microscope. Gastric glands incubated in medium for 6, 12, and 24 h underwent spontaneous degeneration reflected by a decrease in cell viability, increase in LDH release into the medium, and ultrastructural cell damage. 16,16-Dimethyl-PGE2 either at 0.1, 1, or 10 micrograms/ml significantly reduced the decrease in cell viability, increasing cell survival; reduced LDH release into the medium; and ultrastructural damage. Incubation with cimetidine at 1 or 10 micrograms/ml did not affect cell viability at 6, 12, or 24 h, whereas 100 micrograms/ml reduced cell viability (vs. placebo) at 12 and 24 h. LDH release and ultrastructural damage were not affected (not reduced) by cimetidine. Our study indicates that 16,16-dimethyl-PGE2, but not cimetidine, directly protects isolated gastric gland cells against degeneration in vitro, under conditions independent of systemic, neural, and hormonal factors.

Animals↗
PubMed1992

Immunoglobulin A (IgA) and IgG serum antibodies to mycobacterial antigens in Crohn's disease patients and their relatives.

Sera from patients with Crohn's disease, their relatives, their spouses, and unrelated healthy controls were assayed by enzyme-linked immunosorbent assay for immunoglobulin G (IgG) and IgA antibodies to Mycobacterium tuberculosis, M. avium, and M. gordonae. The patients had significantly higher IgA responses to mycobacterial antigens than did either their relatives or the controls. On the other hand, both the patients and their relatives had significantly higher IgG responses against these antigens than did the controls. The elevated IgA response was more pronounced against isopentanol-extracted whole bacterial cells than it was against soluble protein extracts, and it appeared to be directed against fixed surface antigens that lie under the loosely bound peptidoglycolipid or glycolipid antigens of mycobacteria.

Adult↗
PubMed1992

Endothelin-induced calcium responses in human vascular smooth muscle cells.

The effects of endothelin-1 (ET) on the cytosolic free Ca (Cai) and cytosolic pH (pHi) were examined in primary cultures of human umbilical artery (HUA) vascular smooth muscle cells (VSMCs), respectively, loaded with fura-2 and 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. In 1 mM Ca, ET produced a dose-dependent, biphasic increase in the signal with a maximal effect at 400 nM ET. At this concentration, ET produced a Cai transient (mean +/- SE; a rise from basal Cai of 86 +/- 16 to 216 +/- 33 nM) that lasted for approximately 50-60 s. The Cai transient was followed by a slow but sustained increase in Cai. Both ET-induced Cai transient and posttransient Cai were attenuated in Ca deficient medium or by verapamil and nicardipine. In contrast to ET, thrombin elicited only a monophasic Cai response in HUA VSMCs. This response was also partially sensitive to Ca removal or verapamil. KCl (45 mM) depolarization did not elicit a Cai response. However, the presence of voltage sensitive Ca channels in HUA VSMCs was demonstrated by enhanced Mn uptake in cells depolarized with KCl. Both ET and thrombin treatment did not alter pHi. HUA VSMCs demonstrated a single class of ET receptors (approximately 13,000 sites/cell) with an equilibrium dissociation constant of 0.34 nM. Nicardipine did not alter ET binding. These observations suggest a dual effect of ET on the Cai profile in HUA VSMCs that is mediated by Ca mobilization and Ca entry through Ca channels. The Ca entry could include influx through receptor-operated Ca channels, voltage-sensitive Ca channels, or both, but without a direct interaction between ET and these channels.

Calcium↗
PubMed1992

Intrathecal thyrotropin-releasing hormone does not alter the progressive course of ALS: experience with an intrathecal drug delivery system.

Evidence that thyrotropin-releasing hormone (TRH) has prominent trophic effects on the motor system led to several negative therapeutic trials in amyotrophic lateral sclerosis, a disease of the motor system. Since TRH crosses the blood-brain barrier poorly, if at all, we postulated that the negative parenteral clinical trials could be a result of insufficient drug-receptor interaction. We thus carried out a blinded, placebo-controlled, crossover study of intrathecal TRH in 36 patients by delivery through an implanted, constant infusion pump achieving a steady-state CSF level comparable with that shown to be effective in tissue culture experiments. Utilizing a quantitative measurement technique to assess motor unit loss, we did not observe any alteration of the progressive course during 6 months on TRH and 6 months on saline placebo. However, the implanted pump delivery system proved to be safe, reliable, and well tolerated.

Adult↗
PubMed1992

IEC-18, a nontransformed small intestinal cell line for studying epithelial permeability.

Small intestinal epithelium is leaky and allows permeation of hydrophilic molecules of various sizes. Passively absorbed hydrophilic permeability probes have been shown to permeate across intestinal epithelium mainly through the paracellular pathways. In this study we introduce microporous filter-grown IEC-18 epithelial cells, a nontransformed small intestinal cell line, as a in vitro model of intestinal epithelium for the study of epithelial permeability. IEC-18 cells, originally derived from native rat ileal crypts, form confluent epithelium when grown on hydrated collagen-coated Millicell-CM permeable inserts (Millipore Corp., Bedford, Mass.). With scanning and transmission electron microscopy, the presence of tight junctions and desmosomes between cells and the development of microvilli at the apical surface were confirmed. Immunofluorescent labeling of ZO-1 proteins and desmoplakins verified the presence of tight-junctional proteins (ZO-1) and desmosomes in the intercellular junctions of confluent IEC-18 epithelium. The net electrical resistance of IEC-18 epithelium (28 omega-cm2) was similar to resistance values obtained from small intestinal tissue with (50 to 100 omega-cm2) or without (20 to 45 omega-cm2) muscularis and serosal layers. Assessment of mannitol and dextran permeation revealed early "maturation" of paracellular pathway, with increasing restriction of permeation to both probes through day 4. Resistance across IEC-18 epithelium also reached plateau levels between 4 and 7 days. Permeability studies with various probes indicate that cross-sectional diameter rather than molecular weight of the probe is the important determinant of permeation rate. IEC-18 epithelium selectively restricted the permeation of probes proportional to probe size; permeation of larger probes such as albumin was negligible. We conclude that cultured IEC-18 epithelial cells, because of their native crypt origin, similarity in resistance to small intestinal epithelia, retention of ability to differentiate into villus-like enterocytes, and permeability characteristics, are a useful model of intestinal epithelium for the study of permeability and paracellular transport.

Animals↗
PubMed1991

An endogenous carrier-mediated uptake system for folate in oocytes of Xenopus laevis.

We investigated the existence of an endogenous uptake system for folate in Xenopus laevis oocytes. This was done by performing uptake measurements using [3H]folic acid. Uptake of folic acid was linear with time for 4 h of incubation, and was similar in collagenase-treated and non-treated oocytes. The uptake process was carrier-mediated, as suggested by the saturation of folic acid uptake with concentration, and by the ability of unlabelled folic acid and its related compounds to significantly inhibit the uptake of [3H]folic acid. The apparent Km and Vmax of the uptake process were 42 +/- 7 nM and 10.56 +/- 0.46 fmol per oocyte per 2 h, respectively. The uptake of folic acid was independent of the presence of Na+ in the incubation medium, but was highly pH dependent with severe inhibition occurring at pH lower than 6.5. Folic acid uptake was energy- and temperature-dependent, and was significantly inhibited by the anion transport inhibitors DIDS and SITS. These results demonstrate the existence of an endogenous carrier-mediated system for folic acid uptake in Xenopus oocytes. Further characterization of the molecular mechanism of folic acid uptake and its regulation in this non mammalian in vitro unicellular system may prove useful in furthering our understanding of folate movement across biological membranes.

Animals↗
PubMed1991

Identity between the novel integrin beta 7 subunit and an antigen found highly expressed on intraepithelial lymphocytes in the small intestine.

A cDNA clone encoding the N-terminal sequence of the murine integrin beta 7 subunit, a novel member of the leukocyte cell adhesion molecule subset (Leu-CAM), has been isolated. An N-terminal region of 13 contiguous amino acids deduced from the cDNA shows complete identity with the N-terminus of the 120 kDa subunit of the M290 antigen, a surface molecule found highly expressed on mouse intestinal intraepithelial lymphocytes (IEL). This unexpected result focuses two previously unconnected areas of research and suggests that integrins may have a special role to play in the defence of the gut mucosa.

Amino Acid Sequence↗
PubMed1991

Oxygen free radical injury of IEC-18 small intestinal epithelial cell monolayers.

Oxygen radicals can cause endothelial and epithelial permeability changes and mucosal injury of the small intestine. There is no clear consensus concerning the relative injurious potential of individual oxygen radicals. In this study, the small intestinal cell line IEC-18 was used as an in vitro model to study the relative injurious effects of reactive oxygen metabolites. By introducing different combinations of oxygen metabolite-producing enzymes, xanthine oxidase, superoxide dismutase, and catalase, and an iron chelator, deferoxamine, to the fully confluent monolayers and to proliferating IEC-18 cells, the differential injurious effects of the oxygen metabolites O2-, H2O2, and OH. could be evaluated. The extent of cellular injury was assessed using [3H]thymidine uptake, 51Cr release, and morphological evaluations. Our results suggest that OH. produced as a by-product of O2- and H2O2 via the Haber-Weiss reaction was the most injurious oxygen species involved in cellular injury of IEC-18 monolayers induced by xanthine oxidase. O2- produced by xanthine oxidase appeared to be only minimally injurious, and H2O2 produced by xanthine oxidase and as a result of conversion of O2- by superoxide dismutase was moderately injurious. Superoxide dismutase and deferoxamine at appropriate concentrations were protective against xanthine/xanthine oxidase-induced monolayer injury. H2O2 added directly or produced indirectly by glucose oxidase was very injurious to the intestinal monolayers, and this injury was mitigated by catalase.

Animals↗
PubMed1991

An Na(+)-dependent and an Na(+)-independent system for glutamine transport in rat liver basolateral membrane vesicles.

In the present study the transport of glutamine across rat liver basolateral membrane was examined with special emphasis on the existence of an Na(+)-independent system and on the characteristics of the Na(+)-dependent system with respect to stoichiometry of glutamine to Na+. Well-validated and purified liver basolateral membrane vesicles were used in the study. Results of studies on the effect of incubation medium osmolarity and incubation temperature indicated that glutamine uptake by liver basolateral membrane vesicles is largely the result of transport of the substrate into the intravesicular compartment with little binding to basolateral membrane vesicles. Transport of glutamine with time was Na+ gradient dependent (out greater than in) with a distinct "overshoot" phenomenon. Replacing Na+ with an equivalent concentration of K+, NH4+, choline, or mannitol caused significant inhibition of the initial rate of glutamine transport; on the other hand, Li+ could partially substitute for Na+. The initial rate of transport of glutamine as a function of concentration (0.05-12 mmol/L) was saturable both in the presence and in the absence of an inwardly directed Na+ gradient. Apparent Km values of 2.95 and 3.35 mmol/L and Vmax values of 11,565 and 6663 pmol.mg protein-1.10s-1 were calculated in the presence and absence of a Na+ gradient, respectively. Both in the presence and absence of an Na+ gradient (out greater than in), transport of [3H]glutamine was significantly inhibited by the addition to the incubation medium of unlabeled glutamine as well as histidine, asparagine, and serine. Transport of glutamine by the Na(+)-dependent process was significantly inhibited or stimulated, respectively, by inducing a relatively positive or negative intravesicular space. On the other hand, glutamine transport by the Na(+)-independent process was not affected by changes in transmembrane electrical potential. Using the "activation method," the stoichiometry of glutamine Na+ transport was found to be 1:1. These results show that glutamine transport in rat liver basolateral membrane vesicles is carrier mediated both in the presence and absence of an Na+ gradient. Furthermore, the Na(+)-dependent process is electrogenic in nature (net positive) and cotransports one glutamine molecule with one Na+. Transport of glutamine by the Na(+)-independent system, on the other hand, is electroneutral in nature.

Animals↗
PubMed1991

Intestinal absorption of linoleic acid in experimental renal failure.

Linoleic acid (LA) transport in rats with experimental short-term and long-term renal failure (RF) was compared with that of sham-operated normal animals on liberal food intake and pair-fed animals. The perfusions in vivo and incubations in vitro were conducted using a micellar solution containing a wide range of LA concentrations. Both absorption in vivo and uptake in vitro of LA were significantly reduced in animals with short-term RF. Lipid extraction and separation by thin-layer chromatography revealed a marked LA trapping as trilinolein (TL) in the perfused intestinal tissue in the short-term RF group. The esterification process, as defined by the rate of LA incorporation into TL, was moderately reduced in short-term RF animals. The thickness of the unstirred water layer showed no significant difference among the groups studied. In contrast, animals with long-term RF exhibited normal absorption of LA in vivo at all concentrations tested. In conclusion, LA absorption is reduced in short-term RF and restored in long-term RF. Several steps including LA transport into and TL transport out of the enterocyte and the esterification process were impaired in short-term RF. These changes are not due to alteration in the unstirred water layer, anorexia, weight loss or a rapid effect of uraemic chemical environment or circulatory factors.

Animals↗
PubMed1991

Is there a role for dietary essential fatty acids in gastroduodenal mucosal protection?

A great deal is known about methods to diminish intragastric acid concentration, but far less is known about the ability of the gastroduodenal mucosa to resist injury or accelerate its healing. One group of compounds that plays a key role in the endogenous ability of the mucosa to protect itself against injury and perhaps to accelerate healing is the prostaglandins (PGs). The gastroduodenal mucosa synthesizes PGs from fatty acids precursors--predominantly linoleic and arachidonic. PGE1 or PGE2 have been shown to possess cytoprotective activity in the stomach and duodenum. In laboratory animals, linoleic acid feeding increased PG synthesis and diminished injury. When presented in a detergent solubilized form, arachidonic acid can also provide acute protection against injury by alcohol, bile acids, and aspirin. Arachidonic acid can also promote angiogenic response and thereby, perhaps, accelerate the healing process. Epidemiological evidence points toward a parallel between the decrease in peptic ulcer disease virulence and incidence and the total ingestion of linoleic acid by the population in the U.S. and the United Kingdom. Therefore, dietary essential fatty acids may play a key role in mucosal defense and restitution, and perhaps in the diminished incidence and virulence of peptic ulcer disease in the Western world.

Animals↗