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Biomedical subjects

T J Layden

Publications and source records attributed to T J Layden.

At least 19 recordsLinked to original sources
PubMed1997

Effect of obesity on pharmacokinetics and biologic effect of interferon-alpha in hepatitis C.

To examine potential adverse effects of obesity in reducing the response to interferon-alpha (IFN-alpha) in chronic hepatitis C (HCV), IFN-alpha and HCV RNA levels in serum and the 2',5'-oligoadenylate synthetase (2-5 OAS) levels in peripheral blood mononuclear cells (PBMC) were compared between six obese and five nonobese patients before and after a single, 10 mIU dose of IFN-alpha2b. There were no differences in the mean histologic activity index between the two groups. The maximal IFN concentration and the area under the serum IFN concentration-time curve were higher in nonobese patients. These two parameters were inversely correlated with body weight and body surface area. No differences were found in the mean reduction in HCV RNA levels between the two groups following IFN-alpha. The maximal 2-5 OAS level after treatment divided by the pretreatment 2-5 OAS level (2-5 OAS response ratio) was greater in the nonobese patients, suggesting stronger biologic response upon exposure to exogenous IFN-alpha in nonobese patients.

2',5'-Oligoadenylate Synthetase↗
PubMed1996

Calcium regulated chloride permeabilities in primary cultures of rabbit colonocytes.

To determine if calcium-dependent secretagogues directly act on epithelial cells to elicit Cl- secretion, their effects on Cl- transport and intracellular Ca(2+) concentrations ([Ca2+]i) were determined in primary cultures of rabbit distal colonic crypt cells. The Cl- sensitive fluorescent probe, 6-methoxyquinolyl acetoethyl ester, MQAE and the Ca(2+)-sensitive fluorescent probe, fura-2AM were used to assess Cl- transport and [Ca2+]i, respectively. Basal Cl- transport (0.274 +/- 0.09 mM/sec) was inhibited significantly by the Cl- channel blocker diphenylamine-2-carboxylate (DPC, 50 microM, 0.068 +/- 0.02 mM/sec; P < 0.001) and the Na+/K+/ 2Cl- cotransport inhibitor furosemide (1 microM, 0.137 +/- 0.04 mM/sec; P < 0.01). Ion substitution studies using different halides revealed the basal influx to be l- > F- > or = Cl- > Br-. DPC inhibited l- influx by approximately 50%, F- influx by 80%, Cl-influx by 85%, and Br- influx by 90%. Furosemide significantly inhibited influx of Br- (84%) and Cl- (81%) but not of F- and l-. The effects of agents known to alter biological response by increasing [Ca2+]i in other epithelial systems were used to stimulate Cl- transport. Cl- influx in mM/second was stimulated by 1 microM histamine (0.58 +/- 0.05), 10 microM neurotensin (2.07 +/- 0.32), 1 microM serotonin (1.63 +/- 0.28), and 0.1 microM of the Ca2+ ionophore A23187 (2.05 +/- 0.40). The Cl- permeability stimulated by neurotensin, serotonin, and A23187 was partially blocked by DPC or furosemide added alone or in combination. Histamine-induced Cl- influx was significantly inhibited by only furosemide. Indomethacin blocked histamine-stimulated Cl- permeability but had no effect on the actions of the other agents. These studies, focusing on isolated colonocytes without the contribution of submucosal elements, reveal that (1) histamine stimulates Cl- transport by activating the Na+/K+/2Cl- cotransporter via a cyclooxygenase-dependent pathway; (2) neurotensin, serotonin, and A23187 activate both Cl- channels and the cotransporter, and their actions are cyclooxygenase-independent.

Animals↗
PubMed1996

Intestinal distribution of human Na+/H+ exchanger isoforms NHE-1, NHE-2, and NHE-3 mRNA.

The identity of Na+/H+ exchanger (NHE) isoforms in the human small intestine and colon and their role in vectorial Na+ absorption are not known. The present studies were undertaken to examine the regional and vertical axis distribution of NHE-1, NHE-2, and NHE-3 mRNA in the human intestine. Ribonuclease protection assays were used to quantitate the levels of mRNA of these isoforms in various regions of the human intestine. In situ hybridization technique was used to localize NHE-2 and NHE-3 mRNA in the colon. The NHE-1 isoform message was present uniformly throughout the length of the human intestine. In contrast, mRNA levels for human NHE-2 and NHE-3 isoforms demonstrated significant regional differences. The NHE-3 abundance was found in decreasing order: ileum > jejunum > proximal colon = distal colon. The NHE-2 message level in the distal colon was significantly higher than in the proximal colon but was evenly distributed in the small intestine. In addition, NHE-2 mRNA was present in surface epithelial cells as well as in cells of the crypt region, suggesting the presence of NHE-2 message throughout the vertical axis of the colonic crypts. In contrast, NHE-3 mRNA was localized to surface colonocytes in the proximal colon. On the basis of this tissue-specific localization of NHE-2 and NHE-3 mRNA, it can be speculated that the relative contribution of NHE-2 and NHE-3 isoforms in Na+ absorption in the human intestine may be region specific, and these putative apical isoforms may be differentially regulated.

Amino Acid Sequence↗
PubMed1995

NHE-1 isoform of the Na+/H+ antiport is expressed in the rat and rabbit esophagus.

BACKGROUND & AIMS: Rabbit esophageal cells show an amiloride-sensitive Na+/H+ antiporter activity. Several distinct molecular isoforms of the Na+/H+ exchanger family (NHE) are reported to be present in the gastrointestinal tract of rats and rabbits. The aim of this study was to examine which isoforms are present in rabbit and rat esophageal cells and whether this isoform could be up-regulated by serum factors. METHODS: Specific primers designed from the rat NHE-1-4 and the rabbit NHE-1-3 isoform sequences were used for reverse-transcription polymerase chain reaction analysis with RNA from rabbit and rat esophageal cells. Ribonuclease protection assay was used to determine the serum-induced up-regulation of NHE-1. Antibodies raised against the NHE-1 C-terminal fragment were used for Western blotting with rabbit esophageal membranes. RESULTS: In both the rat and rabbit esophagus, only the NHE-1 isoform messenger RNA could be detected. The NHE-1 messenger RNA, detected in rabbit esophageal cells grown from tissue explants, was up-regulated by serum factors. The antibody detected a 95-kilodalton protein in esophageal cell membranes. CONCLUSIONS: The rabbit and rat esophagus exclusively express the NHE-1 isoform, hypothesized to be involved in cytoplasmic pH regulation. Therefore, the results of this study suggest a role for NHE-1 in protecting cells against gastric acid that is refluxed into the esophagus.

Animals↗
PubMed1995

Diagnosis and management of fulminant hepatic failure.

Fulminant hepatic failure is defined as the development of hepatic encephalopathy within 8 weeks of the onset of illness. While there are many causes of FHF, viral hepatitis, particularly hepatitis B, remains the most common etiology. Several drugs and toxins can also lead to FHF, most notably acetaminophen. Even with improvements in ICU care, mortality remains very high for these patients. Conservative management focuses on invasive monitoring and the prevention and treatment of complications like cerebral edema, infection, renal failure, and coagulopathy. Only orthotopic liver transplantation has reduced mortality from 80% to 30% to 50%. Therefore, the goals of management and treatment now include determining which patients are appropriate for liver transplant and finding a donor in a timely fashion.

Acetylcysteine↗
PubMed1994

Hepatitis C infection in potential recipients with normal liver biochemistry does not preclude renal transplantation.

The hepatitis C virus (HCV) may be an important cause of chronic liver disease in renal transplant recipients. We investigated retrospectively the incidence and outcome of HCV infection in long-term renal transplant recipients and patients on hemodialysis. Stored, pretransplant sera of transplant recipients with normal liver biochemistry at surgery were tested for hepatitis C by a second-generation enzyme immunoassay. Hemodialysis patients were tested by a first-generation enzyme-linked immunosorbent assay (ELISA) against c100-3. We studied 252 renal transplant recipients and 58 hemodialysis patients followed for 65 +/- 10 months and 26 +/- 6 months, respectively. Fifteen percent (38/252) of the transplant recipients were HCV positive as were 3/58 (5%) of the hemodialysis patients. Overt liver disease occurred in 22/252 (8.7%) transplant recipients and none in the hemodialysis group. Thirty-six percent (8/22) of transplant recipients with overt liver disease were HCV positive. No HCV-positive patients died of liver failure. Of six biopsies in the HCV-positive transplant group, two had histological evidence of CAH. CAH was seen in six of eight biopsies in the HCV-negative transplants and two of these latter patients progressed to cirrhosis. No hemodialysis patients had clinical or histological evidence of chronic liver disease. Two HCV-negative transplant patients died of liver failure, while no deaths related to liver disease occurred in hemodialysis patients regardless of HCV status. We conclude that hepatitis C may cause chronic hepatitis in renal transplant patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Clinical and histologic predictors of response to interferon-alpha in patients with chronic hepatitis C viral infection.

To evaluate if any pretreatment characteristics of patients with chronic hepatitis C (HCV) can be used to predict response to the current recommended dose (3 million units three times a week) and higher doses of interferon-alpha (IFN), we retrospectively assessed the response of 37 patients with HCV who were treated with IFN. Sixteen patients (43%) responded to the standard dose of IFN with normalization of ALT. Weight and liver histology were found to be significant factors for response. The responders weighed significantly less than nonresponders (161.8 +/- 35.5 lb versus 200.3 +/- 45.4 lb, P = 0.008). Seventy-five percent of patients with chronic lobular or persistent hepatitis were responders, whereas only 28% of patients with more advanced hepatitis responded (P = 0.01). There was no correlation between the degree of bile duct damage or steatosis and response rate. This study suggests that obesity and severe histologic injury are negative predictive factors of response to the current recommended dose of IFN. The adequacy of the current recommended dose of IFN in overweight patients needs to be investigated.

Alanine Transaminase↗
PubMed1994

Diagnosis of acute hepatitis E infection utilizing enzyme immunoassay.

Acute hepatitis E infection was diagnosed in a Pakistani immigrant admitted to the University of Illinois Hospital. Utilizing enzyme immunoassay (EIA) tests, specific IgG and IgM class antibodies to three different epitopes of hepatitis E virus (HEV) were detected 12 weeks after the onset of illness and in the early convalescent stage. Sixteen months after the onset of hepatitis, IgM anti-HEV was no longer detectable. Low levels of IgG class anti-HEV antibodies continued to be detected. We demonstrate the utility of the EIA HEV assay to diagnose prospectively acute HEV infection.

Acute Disease↗
PubMed1994

Escherichia coli heat-stable enterotoxin-mediated colonic Cl- secretion is absent in cystic fibrosis.

BACKGROUND/AIMS: Calcium- and adenosine 3',5'-cyclic monophosphate (cAMP)-mediated Cl- secretions in the human colon are abnormal in cystic fibrosis, but the effect of guanosine 3',5'-cyclic monophosphate (cGMP) is unknown. This study examined the effects of the cGMP activator Escherichia coli heat-stable enterotoxin (STa) on rectal ion transport of controls and subjects with cystic fibrosis. METHODS: In vivo rectal potential difference (PD) was measured in response to 10(-7) mol/L STa in adult cystic fibrosis (n = 6) and control subjects (n = 7). Cl- transport was also evaluated in 24-hour primary cultures of human colonocytes using 6-methoxy-quinolyl-acetoethyl ester in response to STa (1 mumol/L) and 8-bromo-cGMP (100 mumol/L) with or without Cl- transport inhibitors. RESULTS: Whereas STa increased rectal potential difference in controls, there was no effect in cystic fibrosis subjects. STa stimulated the cGMP concentration in rectal biopsy specimens from both control and cystic fibrosis subjects approximately twofold. In vitro Cl- transport in non-cystic fibrosis colonocytes increased threefold and fivefold with STa and 8-bromo-cGMP, respectively. These transport increases were inhibited by furosemide and the Cl- channel blocker diphenylamine-2-carboxylate. CONCLUSIONS: Human colonocytes secrete Cl- in response to STa and cGMP in normal subjects, but this response is absent in cystic fibrosis.

Adult↗
PubMed1994

Cyclic AMP- and phorbol ester-regulated Cl- permeabilities in primary cultures of human and rabbit colonocytes.

Chloride transport in 24-h primary cultures of human and rabbit distal colonic crypt cells (90 +/- 5% viable) were characterized using the Cl(-)-sensitive fluorescent probe 6-methoxyquinolyl acetoethyl ester. To calculate the Cl- influx in millimolar per second, the Stern-Volmer quenching constant was determined to be 24.3 M-1 for human and 24.6 M-1 for rabbit colonocytes. Cl- influx was dependent on extracellular Cl- concentration ([Cl-]0), with maximal influx at [Cl-]0 > or = 20 mM. The adenosine 3',5'-cyclic monophosphate (cAMP)-dependent secretagogues forskolin (1 microM), prostaglandin E1 (1 microM), and 8-bromoadenosine 3',5'-cyclic monophosphate (100 microM) increased Cl- influx in human colonocytes from 0.35 +/- 0.08 to 2.14 +/- 0.65, 1.85 +/- 0.51, and 0.84 +/- 0.04 mM/s (n = 4), respectively, and in rabbit colonocytes from 0.22 +/- 0.03 to 1.04 +/- 0.11, 1.24 +/- 0.12, and 1.08 +/- 0.07 mM/s (n = 5), respectively. Depending on the secretagogue, this influx was inhibited 50-90% by the Cl- channel blocker diphenylamine-2-carboxylate (DPC; 50 microM) and > or = 65% by the Na-K-2Cl cotransport inhibitor furosemide (10 microM). Phorbol 12,13-dibutyrate, an activator of protein kinase C, increased Cl- permeability 3.8-fold in human and 2.4-fold in rabbit colonocytes. The phorbol 12,13-dibutyrate-stimulated Cl- permeabilities were sensitive to DPC and furosemide but not to indomethacin. These studies demonstrate DPC and furosemide-sensitive Cl- permeabilities in isolated cultured human and rabbit colonocytes, which can be activated by cAMP and protein kinase C stimulators.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1994

The esophageal mucosal resistance: structure and function of an unique gastrointestinal epithelial barrier.

The purpose of this review is to delineate the factors that contribute to the innate epithelial resistance of the esophageal mucosa when challenged with potentially damaging intraluminal aggressive factors that are present as a result of gastroesophageal reflux. The ability of this mucosa to act as an effective barrier is dependent on the structural complexity of its 20 to 30 cell layer-thick stratified squamous epithelia, its convoluted intercellular spaces (paracellular resistance), and the cellular ion transport mechanisms that maintain intracellular homoestasis (cellular resistance). Because H+ ion is the most important damaging agent in the gastroesophageal refluxate, we have primarily focused on mechanisms that impede or prevent H+ ion entry into the mucosa ("pre-epithelial" and "mucosal factors"), cellular mechanisms that allow cells to maintain their intracellular pH in the presence of an external acid environment ("cellular factors"), mechanisms that limit continued mucosal and cellular injury ("submucosal factors") and reparative processes that come into play after damage has occurred.

Animals↗
PubMed1993

Rabbit esophageal cells show regulatory volume decrease: ionic basis and effect of pH.

BACKGROUND: Regulatory volume decrease (RVD) after osmotic cellular swelling has been shown in several gastrointestinal epithelia but not in esophageal cells. In acid reflux disease, esophageal injury may be related in part to loss of RVD. METHODS: Isolated basal esophageal cells were exposed to an external hyposmolar solution, and changes in relative cell size were assessed using a Coulter counter (Hilaleah, FL) in the presence of K+ and Cl- transport inhibitors and at varying extracellular pH (pHo). RESULTS: At pHo 7.4, a 30% hyposmotic dilution of the external solution caused an initial peak cell swelling (1.15 +/- 0.05-fold) followed by a return to starting cell size by 5 minutes (RVD). RVD was inhibited by Ba2+ (4 mmol/L), quinine (1 mmol/L), or increasing the [K+]o > or = 10 mmol/L. RVD was also inhibited by depleting [Cl-]i or in the presence of 0.5 mmol/L 4,4'-diisothiocyanastostilbene-2,2'-disulfonic acid disodium salt (DIDS) or 50 mumol/L diphenylamine-2-carboxylate, a Cl- conductance inhibitor. To test the effect of pH on RVD, cells in solutions at pHo 7.4, 7.0, or 6.8 were subjected to hyposmotic stress; RVD was significantly inhibited at pHo 6.8. This pH-dependent inhibition of RVD was reversed in the presence of valinomycin, a K+ ionophore. CONCLUSIONS: These studies show that isolated esophageal cells possess RVD mechanisms that are mediated by Cl(-)- and pH-dependent K+ effluxes. RVD appears to be inhibited by a decrease in pHo, suggesting the possibility that acid-induced esophageal injury results from inhibition of normal volume regulatory mechanisms.

Animals↗
PubMed1993

Rabbit esophageal cells possess K+ channels: effect of hyposmotic stress on channel activity.

BACKGROUND: In many cell types, basolateral K+ channels are important in maintaining transepithelial Na+ absorption and regulatory volume decrease (RVD) after hyposmolar stress. However, in the esophagus the effect of K+ transport in maintaining baseline short-circuit current (SCC) (Na+ absorption) and RVD is unknown. METHODS: Ussing chambers were used to evaluate changes in SCC of rabbit esophageal mucosa in response to serosal Ba2+ (4 mmol/L), quinine (1 mmol/L), and increasing serosal [K+]. To determine whether K+ channel(s) are activated in RVD, changes in SCC in response to serosal hyposmolarity (156 mOsm) were assessed in the presence or absence of serosal quinine. RESULTS: Serosal Ba2+, quinine, or increased serosal [K+] caused a decline in baseline SCC. Serosal hyposmolarity caused an increase in SCC that was not blocked by mucosal application of amiloride (10(-4) mmol/L). In contrast, serosal quinine completely blocked the hyposmolar-induced increase in SCC. CONCLUSIONS: These studies suggest that rabbit esophageal cells possess Ba(2+)- and quinine-sensitive basolateral K+ channel(s) that are active under baseline conditions. Potassium conductance(s) also appear to be activated by external serosal hyposmolarity and may be involved in the process of RVD.

Amiloride↗
PubMed1993

Gallstones: choosing the right therapy despite vague clinical clues.

Therapeutic decisions are quite clear-cut for asymptomatic gallstone disease and acute cholecystitis. However, the appropriate therapeutic course for older patients with chronic cholecystitis may be less obvious. Watchful waiting may be reasonable for patients with mild and infrequent symptoms. For healthy patients, cholecystectomy is recommended if symptoms are becoming more frequent and severe. Laparoscopy may reduce the complication rate and be safely performed even in those with underlying medical illness. Oral dissolution therapy can be attempted for qualifying symptomatic patients who are at poor surgical risk or who refuse surgery. Shock wave lithotripsy and contact dissolution therapy show some promise but are currently experimental.

Acute Disease↗
PubMed1992

Rabbit esophageal cell cytoplasmic pH regulation: role of-antiport and-dependenttransport systems.

Regulation of cytoplasmic pH (pHi) of esophageal cells assumes importance as these cells can be exposed to mucosally absorbed acid during gastroesophageal reflux episodes. In this study, we examined whether esophageal cells possess pHi transport systems. Esophageal cells were harvested utilizing a gentle trypsin technique that yieldedcells per esophagus. Cells were attached to a glass cover slip that had been pretreated with rat-tail collagen, and pHi was measured continuously in a spectrofluorometer utilizing 2',7'-bis(2-carboxyethyl)-5(-6)- carboxyfluoroscein acetoxymethyl ester as a pH-sensitive fluorescent probe.The basal pHi of cells exposed to a-containing solution averaged 7.52 ± 0.20 (n = 6). The pHi declined slightly but not significantly to 7.46 ± 0.12 with the addition of 5%and 28 mMWhen H2 4,4'-diisothiocyanatostilbene- 2,2'-disulfonic acid (DIDS; 0.5 mM) was added, pHi was unchanged. However, addition ofM amiloride caused pHi to decrease to 7.29 ± 0.18 (P less than 0.01). When cells were acidified (pHi 6.3-7.0) using a(20 mM) pulse technique, pHi was rapidly restored toward neutrality in the presence of a-free externalconcentration ([]o)-containing solution (pH units/min = 0.26 ± 0.12; n = 8). Alkalinization was completely blocked withM amiloride. In the presence ofM amiloride, 28 mM, and 5%, acidified cells also alkalinized, although at a slower rate (0.11 ± 0.04 pH units/min; n = 16).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Epidemiology considerations in peptic ulcer disease.

Peptic ulcer disease is a common clinical problem. The lifetime risk of peptic ulcer disease is at least 10%. Millions of Americans are affected each year, imposing a major economic burden on the health care system. The overall hospitalization and mortality rates for peptic ulcer disease seem to have decreased substantially over the past few decades. There is much to suggest, however, that these changes were occurring even before effective medical therapy became available. In addition, other influences, such as increasing age of the population at risk, changes in smoking prevalence, and increasing use of nonsteroidal anti-inflammatory drugs, have impacted on the changing epidemiology of peptic ulcer disease. Hospitalization rates for patients with complications of peptic ulcer disease have remained relatively stable or, especially in the case of elderly women with gastric ulcers, increased significantly in recent years. Understanding the epidemiology of peptic ulcer disease will allow improved assessment of the effects of medical and surgical therapy and, hopefully, provide better clues to the etiology of this diverse group of diseases.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1991

Isolation, characterization, and attachment of rabbit distal colon epithelial cells.

The authors investigated various enzymatic digestion procedures for isolating epithelial cells from the distal colon of New Zealand White male rabbits. Rabbit mucosa was washed, diced, and digested for 90 minutes in one of five different solutions, including a new combination consisting of 0.03% collagenase IV and 0.1% pronase (solution V). Solution I (0.3% dispase) yielded 14.2 +/- 8.2 x 10(6) colonocytes/g mucosa, solution II (0.15% dispase and 0.03% collagenase) yielded 7.7 +/- 2.8 x 10(6) colonocytes/g mucosa, and solution III (0.03% collagenase IV) yielded 15.4 +/- 10(6) cells/g mucosa. Solutions I-III have previously been described for the isolation of colonocytes. Solution IV (0.1% pronase and 325 U/mL DNAase) was originally described for the isolation of nasal epithelial cells but yielded only 2.5 +/- 1.2 x 10(6) cells/g mucosa when applied to the isolation of colonocytes. The new combination of pronase and collagenase, solution V, yielded significantly more colonocytes, 34.5 +/- 3.0 x 10(6) cells/g mucosa, than previously described methods (P less than 0.01). Inclusion of 5 mmol/L ethylenediaminetetraacetic acid in any of the solutions enhanced neither viability nor yield. The digestion product of solution V could be enriched for crypts by serial low-speed centrifugations. The epithelial origin of the colonocytes was confirmed by immunofluorescent staining for cytokeratins. Functional viability was tested by determining the presence of a Na+/H+ exchanger, using the pH fluorescent dye bis(carboxymethyl)-5(6)-carboxyfluorescein acetoxymethyl ester to measure intracellular pH. The authors document that sodium-dependent restoration of intracellular pH in colonocytes acid-loaded to a pH of 6.30 occurred at a rate of 0.19 +/- 0.02 pH U/min. Amiloride at concentrations of 1 mmol/L completely inhibited operation of the exchanger, as did sodium substitution with choline or tetramethylammonium. Lineweaver-Burke analysis at this intracellular pH showed a Michaelis constant of 10.71 mmol/L Na+ and a maximum velocity of 0.12 pH U/min. Exposing the colonocytes to 100 nmol/L phorbol 12,13-dibutyrate increased antiporter activity by 62.0%. Finally, the authors describe the synthesis of a new biomatrix composed of the basement membrane of 3T3 NIH fibroblasts that permits significantly improved colonocyte attachment than to glass, plastic, collagen types I or IV, or matrigel.

Animals↗