Biomedical subjects

J B Matthews

Publications and source records attributed to J B Matthews.

At least 127 records · Page 7Linked to original sources

PubMed1995

Activation of Cl secretion during chemical hypoxia by endogenous release of adenosine in intestinal epithelial monolayers.

Intestinal ischemia is characterized by rapid early inhibition of absorptive function and the appearance of net secretion, although why active secretion persists in the setting of a mucosal energy deficit is unknown. The cryptlike epithelial line T84, a well-characterized model of intestinal Cl- secretion, develops a prominent increase in short-circuit current (Isc, indicative of active Cl- transport) in response to "hypoxia" induced by metabolic inhibitors. The increased Isc is associated with the initial decrease in monolayer ATP content. The Isc is transient and disappears with progressive energy depletion, although graded degrees of ATP depletion induce a more sustained Isc response. Chromatographic analysis and secretory bioassays show that the Isc response to metabolic inhibitors is related to the endogenous release of adenosine into the extracellular space in quantities sufficient to interact locally with stimulatory adenosine receptors. Unlike its classical role as a metabolic feedback inhibitor, adenosine appears to function as an autocrine "feed-forward" activator of active intestinal Cl- secretion. These studies suggest a novel role for adenosine in the conversion of the gut from an absorptive to a secretory organ during ischemic stress, thus contributing to the initial diarrheal manifestation of intestinal ischemia.

Adenosine↗

PubMed1995

Ammonia inhibits cAMP-regulated intestinal Cl- transport. Asymmetric effects of apical and basolateral exposure and implications for epithelial barrier function.

The colon, unlike most organs, is normally exposed to high concentrations of ammonia, a weak base which exerts profound and diverse biological effects on mammalian cells. The impact of ammonia on intestinal cell function is largely unknown despite its concentration of 4-70 mM in the colonic lumen. The human intestinal epithelial cell line T84 was used to model electrogenic Cl- secretion, the transport event which hydrates mucosal surfaces and accounts for secretory diarrhea. Transepithelial transport and isotopic flux analysis indicated that physiologically-relevant concentrations of ammonia (as NH4Cl) markedly inhibit cyclic nucleotide-regulated Cl- secretion but not the response to the Ca2+ agonist carbachol. Inhibition by ammonia was 25-fold more potent with basolateral compared to apical exposure. Ion substitution indicated that the effect of NH4Cl was not due to altered cation composition or membrane potential. The site of action of ammonia is distal to cAMP generation and is not due simply to cytoplasmic alkalization. The results support a novel role for ammonia as an inhibitory modulator of intestinal epithelial Cl- secretion. Secretory responsiveness may be dampened in pathological conditions associated with increased mucosal permeability due to enhanced access of lumenal ammonia to the basolateral epithelial compartment.

Ammonia↗

PubMed1995

Isoperistaltic jejunal interposition for intractable postgastrectomy alkaline reflux gastritis.

BACKGROUND: The Roux-en-Y gastrojejunostomy is a popular method in the operative treatment of alkaline reflux gastritis and other postgastrectomy sequelae, but is associated with a high incidence of the so-called "Roux stasis syndrome." The Henley jejunal interposition has been used occasionally, albeit not widely, as an alternative to the Roux-en-Y reconstruction. STUDY DESIGN: Six patients underwent Henley gastrojejunoduodenostomy to treat severe (Visick grade IV) symptoms following Billroth I and II procedures for peptic ulcer disease. All interposed jejunal segments were 40 cm in length and isoperistaltic in orientation. All patients had follow-up examination and telephone interview (mean 4.3 years, range 2.2 to 7.8 years). RESULTS: All patients noted dramatic improvement after remedial surgery in the first year of follow-up. After the first postoperative year, all patients remained virtually symptom-free (Visick grade I and II) with no complaints of gastrojejunal stasis or bile acid reflux. CONCLUSIONS: This experience suggests that the Henley jejunal interposition is our effective method of treating reflux gastritis and is not associated with the poor emptying frequently associated with the Roux-en-Y reconstruction.

Adult↗

PubMed1995

Mast cells in laser and surgical wounds.

Precooling of tissues was investigated as a possible means of reducing thermal damage during CO2 laser surgery of the oral mucosa. The changes in mast cells in scalpel, and in non-cooled and precooled (tissue temperature lowered to approximately 10 degrees C) CO2 laser wounds were studied. Standard wounds five mm in length were created with the CO2 laser or scalpel on the dorsum of the tongues of 32 Sprague-Dawley rats under general anesthesia with fentanyl/fluanisone and midazolam. Animals were killed with excess anesthetic immediately or six hours after surgery, their tongues were removed, trimmed, fixed in neutral formalin and processed to paraffin wax. Acid (pH 1.4) toluidine blue stained sections were used to count normal and degranulated mast cells in five fields (0.1 mm2) located at defined positions immediately adjacent to the wound site. At both 0 and 6 hours normal mast cell numbers were significantly different between treatment groups (P<0.045; ANOVA) with mean numbers highest in scalpel wounds and lowest in uncooled laser wounds. Similarly, at 0 time, there were significant differences in degranulated mast cells between treatment groups (P=0.004; ANOVA) but highest numbers were detected in uncooled laser wounds and lowest in scalpel wounds. There were no significant differences in degranulated mast cell counts at six hours although there was a similar distribution in numbers between groups. Total numbers of mast cells (normal + degranulated) did not differ between treatment groups. These results demonstrated that i) laser wounds are associated with greater levels of mast cell degranulation than scalpel wounds and ii) precooling of tissues prior to laser treatment decreases the level of mast cell degranulation. It is concluded that tissue damage in CO2 laser surgery may be reduced by precooling of tissue.

Analysis of Variance↗

PubMed1994

Na-K-2Cl cotransport in intestinal epithelial cells. Influence of chloride efflux and F-actin on regulation of cotransporter activity and bumetanide binding.

Although cAMP-dependent epithelial chloride secretion is largely regulated via apical membrane chloride channels, cAMP also remodels basolateral F-actin and activates basolateral Na-K-2Cl cotransport. Whether activation of cotransport is a primary event or secondary to activation of chloride efflux is not established, and the basis for the cytoskeletal dependence is unknown. We studied cotransport in the intestinal line HT29 (which lacks cAMP-regulated chloride efflux) and in its subclone Cl.19A (in which this pathway is present). Cotransporter activity was enhanced by forskolin in both lines but to a considerably greater extent in subclone Cl.19A, in which the number of bumetanide binding sites was also observed to increase. The F-actin stabilizer phalloidin markedly attenuated cAMP-stimulated cotransport in Cl.19A monolayers, but the increase in bumetanide binding was preserved. These studies identify two mechanisms for activation of Na-K-2Cl cotransport by cAMP: components independent and dependent of cAMP-elicited chloride efflux. Additional Na-K-2Cl cotransporters become accessible to the cell surface coincident with the salt efflux-dependent activation of cotransport. While F-actin rearrangements influence salt efflux-dependent up-regulation of the cotransporter, this influence occurs independently of increases in bumetanide-accessible cotransporters.

Actins↗

PubMed1994

TGF-beta receptor regulation mediates the response to exogenous ligand but is independent of the degree of cellular differentiation in human oral keratinocytes.

This study examined the expression of TGF-beta cell-surface receptors, the response to exogenous TGF-beta 1 and the autocrine production of TGF-beta in normal and squamous cell carcinoma-derived human oral keratinocytes with variable degrees of cellular differentiation. TGF-beta receptor expression, the response to exogenous ligand and the autocrine production of TGF-beta appeared unrelated to cellular differentiation. Cells expressed variable proportions of type-I, -II and -III TGF-beta receptors. The expression of type-III receptors correlated inversely with the expression of type-I receptors, but there was no relationship between type-II and either type-I or type-III TGF-beta receptors. Normal cells and the majority (7 of 8) of tumour-derived keratinocytes were inhibited by exogenous TGF-beta 1 and the degree of inhibition correlated with the expression of type-I, but not type-II or type-III, TGF-beta receptors. One tumour-derived cell line was refractory to exogenous TGF-beta 1 although it expressed all 3 receptor types. Endogenous TGF-beta was produced by both normal and tumour-derived keratinocytes and correlated inversely to the expression of type-I, but not type-II, TGF-beta receptors. Further, cells that produced more autocrine TGF-beta had a diminished response to exogenous TGF-beta 1. The data indicate a complex interaction between the expression of TGF-beta cell-surface receptors, endogenous ligand production and the cellular response to exogenous TGF-beta 1.

3T3 Cells↗

PubMed1994

Parastomal hernia. Is stoma relocation superior to fascial repair?

OBJECTIVE: To evaluate methods of parastomal hernia repair. DESIGN: Retrospective analysis. SETTING: Two tertiary care institutions. PATIENTS: Eighty patients undergoing 94 parastomal hernia repairs between 1983 and 1991. INTERVENTIONS: Three methods of repair were examined: fascial repair, stoma relocation, and fascial repair with prosthetic material. MAIN OUTCOME MEASURE: Parastomal hernia recurrence and short- and long-term complications. RESULTS: Fifty-five (93%) of 59 living patients were available and examined at a median of 31.5 months following repair, providing 68 repairs for consideration. Fascial repair was used in 36 cases, stoma relocation in 25 cases, and fascial repair with prosthetic material in seven cases. Overall, 63% of patients developed a recurrent parastomal hernia and 63% had at least one postoperative complication. Following first-time repair, parastomal hernia recurrence developed in 22 (76%) of 29 patients who had fascial repair but in only six (33%) of 18 patients who had stoma relocation (P < .01). When repair was undertaken for recurrent parastomal hernia, fascial repair failed in all seven cases, stoma relocation failed in five (71%) of seven cases, and fascial repair with prosthetic material failed in one (33%) of three cases. The only factor that significantly affected the recurrence rate was the technique of repair. Complications were more common following stoma relocation (88%) than following fascial repair (50%) (P < .05). In particular, incisional hernias developed in 52% of patients following stoma relocation but in only 3% of patients following fascial repair. When postoperative occurrence of all abdominal-wall hernias was compared, there was no significant difference between the fascial repair group (29 [81%] of 36 repairs) and the stoma relocation group (17 [68%] of 25 repairs). Furthermore, the reoperation rate for hernia repair was nearly identical (31% vs 28%) between these two groups. CONCLUSIONS: Parastomal hernia repair is often unsuccessful and rarely without complication. For first-time parastomal hernia repairs, stoma relocation is superior to fascial repair. For recurrent parastomal hernias, repair with prosthetic material is the most promising of a group of poor alternatives.

Adult↗

PubMed1994

F-actin differentially alters epithelial transport and barrier function.

Vectorial ion transport and barrier function are two fundamental and defining properties of all epithelial cells. To define the role of F-actin in these dual properties, we studied the effects of two probes of cytoskeletal function on the well-differentiated human intestinal epithelial cell line T84: cytochalasin D, a fungal metabolite widely used to disrupt microfilament function by an uncertain mechanism, and phalloidin, a more specific agent which binds and stabilizes F-actin with high affinity, thus preventing actin depolymerization. T84 cells grown on collagen-coated permeable supports were studied by dual voltage-current clamping; transepithelial resistance to passive ion flow (R, an indirect measure of junctional integrity) and short-circuit current (a measure of net electrogenic ion transport response to the adenylate cyclase activator forskolin was preserved. In contrast, stabilization of F-actin by incubation with phalloidin for up to 24 hr produced no change in R but caused a profound inhibition of cAMP-stimulated short-circuit current. Thus, cytochalasin D was found to perturb barrier but not transport function of T84 monolayers; conversely, stabilization of F-actin by phalloidin was found not to affect barrier function but markedly attenuated electrogenic ion transport. The results suggest that the dual properties of barrier function and ion transport in intestinal epithelia may be differentially influenced by dynamic alterations in F-actin.

Actins↗

PubMed1994

Dynamic role of microfilaments in intestinal chloride secretion.

The importance of microfilaments in the regulation of chloride (Cl-) secretion by the human intestinal cell line T84 was investigated using the cytoskeletal probe phalloidin to bind and stabilize F-actin. Phalloidin was found to inhibit secretion mediated by cyclic adenosine monophosphate (cAMP) and the sustained secretory response to the calcium (Ca+2) ionophore ionomycin but not to affect the transient Ca+2-mediated response to carbachol and histamine. Fluorescent microscopic examination of F-actin revealed regionally restricted microfilament remodeling in cAMP- and ionomycin-treated cells. Normal regulation of apical Cl- and basolateral potassium (K+) channel functions was evident in phalloidin-loaded cells. It is concluded that prevention of cytoskeletal remodeling by actin stabilization inhibits the generation of a sustained Cl- secretory response by a mechanism that does not involve Cl- or K+ channels. Depolymerization of F-actin plays an integral role in the regulation of intestinal Cl- secretion.

Actin Cytoskeleton↗

PubMed1994

Epidermal growth factor and transforming growth factor alpha characteristics of human oral carcinoma cell lines.

This study examined the expression of epidermal growth factor (EGF) cell-surface receptors, the response to exogenous ligand and the autocrine production of transforming growth factor alpha (TGF-alpha) in normal and carcinoma-derived human oral keratinocytes. One of eight malignant cell lines overexpressed EGF receptors, while the remainder expressed receptor numbers similar to normal cells. Exogenous EGF stimulated incorporation of tritiated thymidine in a dose-dependent manner. In keratinocytes expressing normal numbers of EGF receptors, the cellular response to exogenous EGF correlated positively with total EGF receptor number. SCC-derived keratinocytes produced more TGF-alpha than normal cells. There was no statistical correlation between the autocrine production of TGF-alpha, EGF cell-surface receptor expression and cellular response to exogenous EGF. While the growth-stimulatory effects of exogenous TGF-alpha were inhibited by the addition of a neutralising antibody, the presence of this antibody in conditioned medium failed to produce a similar decrease in growth. The results indicate that overexpression of EGF receptors is not an invariable characteristic of human oral squamous carcinoma-derived cell lines. Further, the contribution of TGF-alpha to the growth of normal and carcinoma-derived human oral keratinocytes in vitro may be less significant than previously documented.

Adult↗

PubMed1994

Site-specific alkaline phosphatase levels in gingival crevicular fluid in health and gingivitis: cross-sectional studies.

Using a recently developed chemiluminescent assay enabling alkaline phosphatase (ALP) quantification in nanolitre volumes of gingival crevicular fluid (GCF), we have investigated GCF ALP levels in health and in the presence of gingivitis. In gingival health, there was a site-specific pattern of ALP concentration with higher enzyme concentrations around the upper and lower anterior teeth. Furthermore, clinically normal sites that had been subjected to different levels of plaque control produced significantly different ALP levels, (p < 0.03). This indicates that biochemical components of GCF may be used to measure subclinical inflammatory status. The ratio of GCF to serum ALP varied from 6:1 to 11:1, suggesting that a major source of the enzyme is through local production. The main cross-sectional study of 30 patients with gingivitis (276 sites) demonstrated that total GCF ALP levels, collected over a 30-s sampling time were higher for a gingival index of 1 than of 0 (p < 0.014). There was no significant relationship between total GCF ALP and plaque levels of the enzyme, and analysis of plaque within the study group demonstrated very low levels of ALP, indicating that the enzyme is likely to be largely derived from the periodontal tissues. The ratio of GCF ALP levels to those of saliva within individuals was 530:1, thereby eliminating saliva contamination as a risk, when total GCF ALP is being measured.

Adult↗

PubMed1994

Quantification of PCNA+ cells within odontogenic jaw cyst epithelium.

The aim of this study was to investigate the reactivity of the epithelial linings of the three major types of odontogenic cyst with a monoclonal antibody to proliferating cell nuclear antigen (PCNA; clone PC10). PCNA expression was studied in odontogenic cysts (n = 31) and normal oral epithelium (n = 10) using a biotin-streptavidin method on routinely processed paraffin sections. PCNA+ cells were counted manually and related to the length of basement membrane (mm) and the epithelial area (mm2) as determined by TV image analysis. The epithelial linings of odontogenic keratocysts (OKC; n = 11) contained the highest number of PCNA+ cells, most of which were located in the suprabasal layers. The mean value of PCNA+ cells in OKC linings (94.4 +/- 22.7 cells/mm) was similar to that of oral epithelia (80.8 +/- 20.6 cells/mm), but both were significantly higher than that of dentigerous (n = 10, 5.1 +/- 3.0 cells/mm) and radicular (n = 10, 11.0 +/- 4.1 cells/mm) cyst linings (P < 0.005). The epithelial distribution of PCNA+ cells differed between groups with the basal/suprabasal PCNA+ cell ratio in OKC linings (0.05 +/- 0.02) being significantly lower than that of normal oral epithelium (0.5 +/- 0.14), dentigerous (1.6 +/- 1.23) and radicular (1.9 +/- 1.09) cyst linings respectively (P < 0.005). These results demonstrate differences in PCNA expression between the epithelial linings of the major odontogenic cyst types, indicating differences in proliferative and differentiation processes within these lesions.

Antigens, Neoplasm↗

PubMed1994

Interferon-gamma induces a cell surface phenotype switch on T84 intestinal epithelial cells.

Intestinal epithelia are in intimate contact with submucosal and intraepithelial lymphocytes. The concentration of intraepithelial lymphocytes increases during inflammatory processes, and, when stimulated, these cells generate cytokines such as interferon-gamma (IFN-gamma). In this study, we examined the effect of recombinant human IFN-gamma on ion transport events in T84 cells, a crypt epithelial cell line widely used to study electrogenic Cl- secretion, the transport event responsible for mucosal hydration. Epithelial exposure to IFN-gamma brought about a marked attenuation in stimulated Cl- secretion, as measured by generation of short-circuit current (ISC). This IFN-gamma-elicited decrease in the Cl- secretory response was present for a variety of specific agonists, appeared largely due to IFN-gamma interactions with the basolateral surface, and did not result from a defect in second messenger generation. Efflux and uptake studies were utilized to functionally define the individual cell surface transport proteins that participate in Cl- secretion and revealed that, in response to epithelial exposure to IFN-gamma, apical Cl- channels and basolateral Na(+)-K(+)-2Cl- cotransporters, K+ channels, and Na-K-adenosinetriphosphatase were all functionally downregulated. [3H]bumetanide binding assays suggested that surface expression of the cotransporter was diminished by > 70% after IFN-gamma preexposure. Concurrently, surface immunofluorescence studies revealed that epithelial exposure to IFN-gamma brought about the induction of major histocompatibility complex (MHC) class II molecule expression on T84 epithelial monolayers and markedly increased MHC class I surface expression. Finally, neutrophil-epithelial adhesion studies revealed that preexposure of epithelial monolayers to IFN-gamma elicited a beta 2-integrin-dependent induction of neutrophil adhesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Carrier Proteins↗

PubMed1994

Effects of fixation method on image cytometric measurement of DNA content and distribution in cells stained for fluorescence with propidium iodide.

We performed image cytometric measurements of DNA content and distribution on cycling human HCT-8 cells stained for fluorescence with propidium iodide (PI). Seven different fixation protocols were evaluated for stoichiometry of PI staining and for their ability to preserve in vivo chromatin structure. Bimodal integrated optical intensity (IOI) histograms were obtained with all fixation protocols. Increased accessibility of DNA to the dye was evident in increased values of the IOI at the GI peak. The fixatives studied, in order of increasing accessibility to DNA, were Regaud's Boehm-Sprenger, Carnoy's, air-drying, methanol, ethanol, and acetone/methanol. In general, the coefficient of variation of the IOI within the G1 peak was higher for fixatives where DNA is less accessible. Features describing the spatial distribution of stain exhibited dramatic changes for Boehm-Sprenger fixation, which were consistent with the observation that in vivo conformation of chromatin is best preserved with this method.

Adenocarcinoma↗

PubMed1994

Chemical hypoxia increases junctional permeability and activates electrogenic ion transport in human intestinal epithelial monolayers.

BACKGROUND: The intestinal epithelial tight junction restricts the paracellular permeation of ions and nonelectrolytes. We hypothesized that this function could be altered or disrupted during cellular adenosine triphosphate (ATP) depletion (chemical hypoxia). METHODS: T84 monolayers grown on permeable supports were studied by electrophysiologic and flux techniques. Mitochondrial and glycolytic inhibitors were used to deplete cellular ATP. RESULTS: Transepithelial resistance to passive ion flow (R) rapidly decreased to 36% of control values with chemical hypoxia, an effect that was reversible if control conditions were restored within 1 hour. As ATP levels declined, a transient Cl- secretory current developed but disappeared as ATP levels reached 5% of control values. Both the secretory current and fall in R were abolished when ambient Cl- was replaced with gluconate but not with Br- or NO3-, or when N-methylglucamine replaced Na+. Transepithelial flux of mannitol but not inulin was increased during ATP depletion. Dual Na(+)-mannitol flux analysis confirmed that the decrease in R was due to an increase in paracellular, not transcellular, permeability. Dilution potentials indicated altered charge selectivity of the junctional pathway. CONCLUSIONS: Chemical hypoxia in intestinal epithelial monolayers alters but does not disrupt the permselectivity properties of the junctional complex.

Adenosine Triphosphate↗

PubMed1994

A preliminary investigation into the extent of increased radioresistance or hyper-radiosensitivity in cells of hamster cell lines known to be deficient in DNA repair.

The response to low doses of X rays was assessed in cells of three hamster cell lines which are defective in DNA repair and was compared with their parental lines. Cells of the V79-derived double-strand break repair-deficient line XR-V15B showed no radioresistance in the 0.5-Gy range compared with the V79B wild type, but instead showed an exponential response. Cells of the single-strand break repair-deficient line EM9 showed hyper-radiosensitivity and exhibited increased radioresistance. Most interestingly, cells of the UV-20 cell line appeared to respond exponentially, as a continuation of the hyper-radiosensitive portion of the curve, with no evidence of increased radioresistance. This line is defective in an incision step of excision repair and is sensitive to crosslinking agents. Further studies are warranted to address the possible role of single- and double-strand break repair and excision repair in hyper-radiosensitivity and increased radioresistance.

Animals↗

PubMed1994

Distribution of pyruvate dehydrogenase dihydrolipoamide acetyltransferase (PDC-E2) and another mitochondrial marker in salivary gland and biliary epithelium from patients with primary biliary cirrhosis.

Previous studies in which quantitative immunofluorescence was used have shown that certain biliary epithelial cells in liver with primary biliary cirrhosis show increased levels of pyruvate dehydrogenase dihydrolipoamide acetyltransferase compared with controls. This study was designed to determine whether the increase in intensity of pyruvate dehydrogenase dihydrolipoamide acetyltransferase in biliary epithelial cells is accounted for by an increase in the number of mitochondria in the same cells. A double-antibody staining technique was used with antibodies specific for pyruvate dehydrogenase dihydrolipoamide acetyltransferase and another mitochondrial inner membrane marker, recognized by the mouse monoclonal antibody MCA151A. Distribution of the antigens was studied in sections of liver and salivary gland, an additional site that is frequently involved in primary biliary cirrhosis. Confocal microscopy was used to quantify the intensity of fluorescence resulting from binding of fluorochrome-labeled antibody. In both liver and salivary glands MCA151A binding was similar in normal and sections with primary biliary cirrhosis and corresponded to the predicted distribution of mitochondria in these tissues. In the liver staining was less intense in biliary epithelial cells than in hepatocytes. In salivary gland binding of both antibodies was predominantly localized to duct cells, with those forming striated ducts, known to be rich in mitochondria, being most intensely stained. There was high coincidence of the two antigens in salivary glands (p < 0.01) and in biliary epithelial cells from normal liver (p = 0.01). However, in liver with primary biliary cirrhosis, despite high coincidence between the antigens on hepatocytes, biliary epithelial cells showed high intensity of pyruvate dehydrogenase dihydrolipoamide acetyltransferase but not MCA151A.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗

PubMed1993

Recurrent cholangitis with and without anastomotic stricture after biliary-enteric bypass.

We recently surgically treated 24 patients incapacitated by recurrent cholangitis after biliary-enteric anastomosis performed for benign disease. Contrary to commonly held dogma, as many as one third of the patients had no evidence of anastomotic stricture indicated by radiologic and operative findings. We identified several other primary and coexistent pathogenetic factors including intrahepatic stricture in 42% of the patients, intrahepatic calculi in 25%, improperly constructed enteric conduits in 13%, and conditions that predispose to bacterial overgrowth in the biliary tree in 17%. Seventy-one percent of the patients had multiple etiologic factors, and of those patients without demonstrable anastomotic stricture, intrahepatic stricture was particularly common. Seventy-one percent remained symptom-free in their first year after operation. The most difficult situation to manage, and the factor responsible for most recurrences after our reoperation, involved intrahepatic stricture. A combined surgical and interventional radiologic approach to complex cases may be useful in selected patients.

Adult↗