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T J Layden

Publications and source records attributed to T J Layden.

At least 37 records · Page 2Linked to original sources
PubMed1998

The inaccuracy of duplex ultrasonography in predicting patency of transjugular intrahepatic portosystemic shunts.

BACKGROUND & AIMS: A prospective double-blinded study with preset sonographic criteria has not been performed to assess the accuracy of duplex ultrasonography in determining the patency of transjugular intrahepatic portosystemic shunts (TIPS). The purpose of this study was to determine the sensitivity and specificity of duplex ultrasonography in predicting shunt malfunction using accepted preset sonographic criteria. METHODS: Sixty ultrasonographic and venographic follow-up comparisons were made on 38 cirrhotic patients who had undergone TIPS placement for variceal bleeding (n = 28) or intractable ascites (n = 10). Ultrasonographic results were analyzed by one of two board-certified ultrasonographers without knowledge of venographic findings. RESULTS: Of the 31 occluded (n = 8) and stenotic (n = 23) shunts, ultrasonography accurately predicted a shunt malfunction (occlusion or stenosis) in only 11 studies and incorrectly predicted patency in 20. Compared with venography, ultrasonography had a sensitivity of 35% and a specificity of 83% in predicting TIPS stenosis or occlusion. CONCLUSIONS: These results suggest that duplex sonography is not a sensitive test in predicting the presence of a hemodynamically significant stenosis and that shunt status should be assessed by venography and direct portal pressure measurements until a more reliable and proven noninvasive ultrasonographic criterion is devised.

Adult↗
PubMed1998

Acute acid exposure increases rabbit esophageal cell proliferation.

In the present study we examined whether an acute infusion of HCl into the esophagus of rabbits would cause an increase in esophageal cellular proliferation independent of morphologic evidence of cell injury. To examine this question, the distal two thirds of the rabbit esophagus was infused for 1 hour with either 40 mmol/L HCl or NSS (control), and cellular proliferation was studied 24 and 48 hours later by using bromodeoxyuridine (BrDu) to label the nuclei of dividing cells and ornithine decarboxylase (ODC) enzyme activity as a biochemical index of cell division. Although there was no gross or microscopic evidence of cell necrosis or mucosal inflammation 24 hours after H+ infusion, BrDu labeling of basal cell nuclei was significantly greater 24 hours after H+ infusion (31%+/-6%) as compared with that in control animals infused with NSS (15%+/-4%). This increase in labeling index was paralleled by a threefold greater ODC enzyme activity at 24 hours with H+ infusion. Rete pegs were infrequent in control tissues (4+/-4 rete pegs per 100 microm of esophageal length) or in animals examined 24 hours after acid exposure (4+/-2 rete pegs per 100 microm). However, rete pegs were very prominent 48 hours after acid infusion (22+/-6 rete pegs per 100 microm). A short exposure to acid can cause a significant increase in mucosal proliferation independent of injury, suggesting that esophageal cell acidification either directly or indirectly acts as a tissue mitogen.

Animals↗
PubMed1998

Early HCV RNA values after interferon predict response.

The aim of this study is to determine in patients infected with hepatitis C virus (HCV) whether early HCV RNA measurements at 48 hr following standard doses of interferon-alpha (IFN-alpha) (3 million IU) would predict response during six months of therapy. Twenty-three patients with HCV were treated with IFN-alpha 3 million IU three times a week and HCV RNA levels were quantified by branched-chain (b-)DNA analysis at baseline and 24 and 48 hr following IFN-alpha and at one, three, and six months. Mean baseline HCV RNA levels significantly declined from 6.0 +/- 1.6 Meq/ml at baseline to 2.4 +/- 0.7 Meq/ml 24 hr after IFN-alpha. However, HCV RNA values increased to 4.3 +/- 1.1 Meq/ml by 48 hr. Mean HCV RNA values at one and six months were not significantly lower than 48-hr values. In six patients in whom HCV RNA was negative by bDNA at 48 hr, three were negative by polymerase chain reaction at six months. Of the 17 patients who were positive by bDNA at 48 hr, all were positive at one and three months; and in the nine of nine who continued therapy for six months, there was no further decrease in HCV RNA levels. In patients receiving standard doses of IFN-alpha (3 million IU), serum RNA values 48 hr after the first injection predict long-term response.

Female↗
PubMed1998

Cl- transport in an immortalized human epithelial cell line (NCM460) derived from the normal transverse colon.

Cells of a newly described, immortalized, epithelial, human transverse colonic cell line, NCM460, reach approximately 90% confluence on plastic and develop transepithelial resistances of 120-250 Omega . cm2 on porous substrates. Its utility as a model for the transverse human colon was validated by comparing second messenger-mediated Cl- transport, using the fluorescent probe 6-methoxy-quinolyl acetoethyl ester, in NCM460 cells and colonocytes isolated from human transverse crypts. Basal Cl- influx was increased (P < 0.01) by PGE1 (1 microM), forskolin (1 microM), 8-bromoadenosine 3'5'-cyclic monophosphate (100 microM), heat-stable Escherichia coli enterotoxin (STa; 1 microM), 8-bromoguanosine 3'5'-cyclic monophosphate (100 microM), histamine (1 microM), and phorbol 12,13-dibutyrate (1 microM) in both cell types. The Cl- channel blocker diphenylamine 2-carboxylic acid (50 microM) and the Na+-K+-2Cl- cotransport inhibitor furosemide (1 microM), but not the K+ channel blocker Ba2+ (3 mM), inhibited these Cl- permeabilities. These cells possess transcripts for cystic fibrosis transmembrane conductance regulator, Na+-K+-2Cl- cotransporter, STa receptor, and intestine-specific cGMP-dependent protein kinase II. Thus cAMP-, cGMP-, and Ca2+-dependent secretagogues act on NCM460 and primary colonocytes to stimulate Cl- transport. This validates the utility of NCM460 as a model for transverse colonic crypts and is the first demonstration of a colonic cell line whose origin is known.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1997

Dose-dependent acute clearance of hepatitis C genotype 1 virus with interferon alfa.

To determine if the clearance of hepatitis C genotype 1 virus (HCV) is dependent on the dose of interferon alfa-2b (IFN-alpha2b), the acute clearance of HCV after a single dose of either 3, 5, or 10 mIU of IFN-alpha was compared in patients with chronic hepatitis C. HCV-RNA levels following IFN-alpha administration were measured. At 24 hours, mean percentage serum viral reduction was 41.4%, 63.7%, and 85.5% for 3, 5, and 10 mIU, respectively (P < .001). At 48 hours, the mean viral reduction was consistently less than the reduction at 24 hours, averaging 22.9%, 61.9%, and 74.3%, respectively (P < .001), indicating that the drug effect diminishes before 48 hours. Regression analysis showed a positive correlation between dose and percent reduction of HCV-RNA levels (r = .6; P < .001). A mathematical model showed that such dose dependence is expected if IFN-alpha partially blocks viral production. Minimum clearance and production rates of HCV were estimated from measurements of HCV-RNA levels after the 10-mIU dose. HCV decay followed an exponential decline with a minimum estimate of the viral clearance rate constant of 2.8 per day, corresponding to a virion half-life of 0.3 days or less. A minimal estimate of the daily HCV production and clearance is 3.7 x 10(11) virions per day, indicating a high rate of replication and turnover. These results indicate that there is a dose-dependent effect of IFN-alpha in clearance of HCV genotype 1. Because the virion production rate is very rapid and because the current recommended dose of IFN-alpha (3 mIU) is often ineffective, larger doses should be considered to treat genotype 1-infected patients.

Adult↗
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↗