The involvement of ammonia with the mechanisms that enhance GABA-ergic neurotransmission in hepatic failure.
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Ammonia↗
Biomedical subjects
E A Jones
Publications and source records attributed to E A Jones.
Direct enhancement of GABA-ergic neurotransmission by ammonia.
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Ammonia↗
Sequences in the proximal 5' flanking region of the rat neuron-specific enolase (NSE) gene are sufficient for cell type-specific reporter gene expression.
We investigated the regulation of the rat neuron-specific enolase gene using a transient transfection approach. Recent transgenic mouse studies have shown that a 1.8-kb segment of the rat NSE gene 5' flanking region, including the first (noncoding) exon but not the first intron, is able to drive expression of a reporter gene in parallel with endogenous NSE. These data suggest that cis-acting elements responsible for the spatial and temporal pattern of NSE gene expression are located within the proximal 1.8 kb of the 5' flanking sequence. To further investigate this region, we joined the 1.8-kb regulatory cassette to the cat reporter gene and generated a number of constructs in which the flanking sequence was progressively deleted from the 5' end. These constructs were tested by transient transfection into neuronal and nonneuronal cells, followed by an assay for CAT activity. We found that as little as 255 bp of 5' flanking sequence was able to confer cell type-specificity on the reporter gene. Further truncation to 120 bp of 5' sequence resulted in a sharp downregulation of reporter activity in PC12 cells but a significant rise in both Neuro-2A neuroblastoma cells and nonneuronal Ltk- cells, indicating that cis-acting elements controlling the regulation of NSE in Ltk-, Neuro-2A, and PC12 cells may lie within the 135 bp region covered by this deletion. This region contains an AP-2 site and an element similar in sequence and position to a motif identified in the proximal promoter region of the neuron-specific peripherin gene. Reduction to 95 bp of 5' sequence resulted in a slight downregulation of CAT activity in all cell lines tested, and further truncation to 65 bp of 5' sequence caused a universal reduction to background levels of CAT activity, concomitant with the disruption of the basal NSE promoter. Our results show that the 5' flanking region of the NSE gene is capable of conferring cell type-specificity on a heterologous gene in transfected cells and that elements responsible for this are located within the proximal 255 bp.
Animals↗
Lack of complications following short-term stent therapy for extrahepatic bile duct strictures in primary sclerosing cholangitis.
BACKGROUND: In 10% to 20% of patients with primary sclerosing cholangitis, a dominant stricture of an extrahepatic bile duct is responsible for symptoms and an exacerbation of cholestasis. The complications of a dominant stricture can usually be relieved by endoscopic placement of a stent through the stricture. The conventional policy of leaving stents in situ for 2 to 3 months is associated with a high incidence (e.g., 50%) of clinical deterioration due to stent occlusion. We have attempted to overcome this problem by substantially reducing the duration of stent placement. METHODS: Sixteen patients with symptomatic primary sclerosing cholangitis and dominant extrahepatic bile duct strictures were treated by stent placement for a median interval of only 9 days. RESULTS: In all patients endoscopic stent therapy was technically successful with a 7% incidence of transient procedure-related complications. During median follow-up of 19 months (range 7 to 27 months) serum biochemical evidence of cholestasis decreased substantially and 13 (81%) of the 16 patients became asymptomatic. No patient had a recurrence or exacerbation of either symptoms or biochemical evidence of cholestasis that could be attributed to stent occlusion. CONCLUSIONS: Short-term endoscopic stent therapy is a safe and effective treatment for symptomatic dominant extrahepatic bile duct strictures in patients with primary sclerosing cholangitis.
Adolescent↗
Precipitation of overt encephalopathy in the portacaval shunted rat: towards the development of an adequate model of chronic portal systemic encephalopathy.
OBJECTIVE: To assess the feasibility of developing a model of overt portal-systemic encephalopathy (PSE) in rats with a surgically constructed portacaval anastomosis (PCA). DESIGN: The ability of increasing the load of nitrogenous substances in the gastrointestinal tract and/or further decreasing hepatocellular function to induce overt encephalopathy in rats with a PCA was determined. METHODS: The load of nitrogenous substances in the gastrointestinal tract was increased by feeding a pure horse-meat diet or by gavaging with blood. Partial hepatectomy and the induction of cirrhosis were used to decrease hepatocellular function further. The severity of encephalopathy was assessed using a neurobehavioural scale. RESULTS: Overt encephalopathy was not induced in rats by a PCA alone, by a PCA plus a horse-meat diet, by a PCA plus induction of cirrhosis, or by a PCA plus a 50% hepatectomy. Predominantly mild, but overt, encephalopathy was induced in rats with a PCA alone by gavaging with blood and a higher incidence of more severe overt encephalopathy was induced in rats with a PCA combined with either cirrhosis or partial hepatectomy by gavaging with blood. Although these models of PSE were associated in some instances with plasma ammonia concentrations about 25 times higher than normal, no seizures were observed. CONCLUSION: A syndrome that resembles overt PSE in humans can be induced in the rat with a PCA by further reducing hepatocellular function and also gavaging with blood. Although the rat with a PCA has been. extensively used as a model in studies relating to the pathogenesis of PSE, a syndrome resembling overt PSE in humans cannot readily be induced in rats with a PCA.
Ammonia↗
Concurrent hormone resistance (pseudohypoparathyroidism type Ia) and hormone independence (testotoxicosis) caused by a unique mutation in the G alpha s gene.
Defects in the G (guanine nucleotide-binding)-protein subunit (G alpha s) which stimulates adenylyl cyclase may result in either loss or gain of endocrine function. Reduced G alpha s activity is found in the hormone resistance syndrome, pseudohypoparathyroidism type Ia (PHP-Ia), while constitutive activation of G alpha s is associated with endocrine organ overactivity, including the gonadotropin-independent sexual precocity seen in patients with McCune-Albright syndrome. We identified two unrelated boys presenting with concurrent PHP-Ia and gonadotropin-independent sexual precocity (testotoxicosis). Mutational screening by denaturing gradient gel electrophoresis and sequencing of PCR-amplified exons of the G alpha s gene revealed a point mutation which generates an alanine-to-serine substitution in codon 366 of one G alpha s allele (A366S), an alanine present at the homologous position in all G-proteins. We have previously shown in transfected testis cells that the A366S mutation activates G alpha s by decreasing affinity for GDP, thereby increasing the rate of nucleotide exchange in a receptor-independent fashion. In contrast to differential stability of the activated mutant G alpha s protein in Leydig cells, with stability at 32 degrees C but not at 37 degrees C, skin fibroblasts with the mutation had the same reduced G alpha s levels at both temperatures. Our findings explain the limitation of clinical manifestations of G alpha s overactivity to testis, without involvement of other body appendages which are generally at lower than core body temperature. This unique mutation at a critically conserved residue of G alpha s is the first mutant G-protein which affects guanine nucleotide affinity and is associated with human disease, producing widely divergent and tissue-specific effects.
Blotting, Northern↗
Recommendations for the registration of agents used in the prevention and treatment of glucocorticoid-induced osteoporosis.
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Animals↗
Flosequinan in chronic heart failure: how is exercise capacity improved?
OBJECTIVE: Diuretics, angiotensin converting enzyme inhibitors and digoxin have become "standard" triple therapy for many patients with chronic cardiac failure. Flosequinan increases exercise duration and improves symptoms when added to standard triple therapy. Despite intensive study, the clinical pharmacology of flosequinan remains uncertain. SETTING: The University Hospital of Wales, a Regional Cardiac Centre. PATIENTS: Twenty four patients with chronic heart failure who remained symptomatic despite standard therapy including ACE inhibitors. METHODS: A double-blind placebo-controlled parallel group study of 100 mg daily of flosequinan. We measured changes in exercise duration using cardiorespiratory exercise testing and changes in large artery distensibility using Doppler ultrasound. RESULTS: Exercise duration after 8 weeks flosequinan treatment was significantly greater than following placebo treatment. The flosequinan-related increase in exercise duration (+14%) was associated with a significant reduction in VE/VCO2 slope (-16%). Brachial-radial pulse wave velocities were unaltered by flosequinan treatment. CONCLUSIONS: Our results confirm that flosequinan improves exercise duration in patients with chronic heart failure. They suggest that this observed beneficial effect is independent of any change in large artery distensibility and that in the presence of ACE inhibitors, this improvement may be independent of any vasodilating action of flosequinan. Although this study confirms the beneficial symptomatic effects of flosequinan in chronic cardiac failure, clinical trials have subsequently demonstrated an overall increase in mortality in patients treated with 100 mg flosequinan daily. This has resulted in the withdrawal of flosequinan from routine clinical use.
Adult↗
Endoscopic stent therapy for dominant extrahepatic bile duct strictures in primary sclerosing cholangitis.
BACKGROUND: In 15% to 20% of patients with primary sclerosing cholangitis, a dominant stricture of the extrahepatic bile ducts may be responsible for declining results of serum biochemical liver tests and may contribute to symptoms such as jaundice, cholangitis, pruritus, and right upper quadrant pain. METHODS: Retrospectively, over the period 1985 to 1994, we evaluated 25 patients who had been treated by endoscopic stent therapy after declining results of serum biochemical liver tests and symptoms attributable to dominant extrahepatic bile duct strictures. Serum biochemical liver test results and symptoms were compared before and after treatment. RESULTS: Endoscopic therapy was technically successful in 21 patients (84%). In these 21 patients results of all serum biochemical liver tests improved significantly (p < 0.001) within 6 months of stent therapy. During median follow-up of 29 (2 to 120) months after stent removal, 12 patients (57%) remained asymptomatic with stable serum biochemical liver tests and 4 (19%) had clinical and biochemical relapse of disease that responded favourably to additional endoscopic therapy. Early procedure-related complications occurred in 14% of therapeutic endoscopic biliary procedures. CONCLUSIONS: Endoscopic stent therapy is a safe and effective treatment modality for an acute exacerbation of disease caused by dominant extrahepatic bile duct strictures in patients with primary sclerosing cholangitis.
Adult↗
Cytokine mRNA expression in the liver of patients with primary biliary cirrhosis (PBC) and chronic hepatitis B (CHB).
The expression of cytokine mRNA species was determined in liver biopsies from six normal subjects, 18 patients with PBC and 14 patients with hepatitis B e antigen (HBeAg)-positive CHB using a reverse transcriptase-polymerase chain reaction (RT-PCR) technique. cDNA, obtained by reverse transcription using oligo d(T) primers, was amplified by PCR using primers specific for the coding region of seven different cytokines (IL-1, IL-2, IL-4, IL-5, IL-6, interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha)). The abundance of some cytokines (IL-2, IL-4, IL-5 and IFN-gamma) was also estimated by semiquantitative RT-PCR, using as standards dilutions of synthetic cytokine mRNA transcripts, that could be distinguished electrophoretically from respective native cytokine mRNAs. Hepatic inflammation was assessed by a semiquantitative histologic score and by amplification of mRNA for T cell receptor (TCR)-alpha. mRNAs for IL-1 and IL-6 were detected in only one control liver. In CHB, mRNAs for IL-1, IL-2, IL-4, IL-5 and IFN-gamma were detected in 43%, 60%, 80%, 20%, and 54% of biopsies, respectively. mRNA for IFN-gamma and IL-4, but not IL-1, tended to be associated with severe inflammation. In five biopsies semiquantitative analyses revealed increased levels of mRNA for TCR-alpha and, when transcripts were detectable, high levels of mRNA for IFN-gamma and IL-4. In PBC, mRNA for IFN-gamma was detected in 60% of biopsies, but no mRNAs for IL-1, IL-2, IL-4, IL-5, or IL-6, or for TNF-alpha, were detected. Semiquantitative analyses revealed that absolute levels of mRNA for IFN-gamma tended to correlate with the severity of hepatic inflammation. The results suggest that: (i) there may be fundamental differences in the roles that cytokines play in the hepatic inflammatory processes of PBC and CHB; and (ii) while hepatic IFN-gamma mRNA expression is not specific for PBC, IFN-gamma may play a prominent role in the immunopathogenesis of PBC.
Adult↗
Natural benzodiazepines and hepatic encephalopathy.
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Animals↗
An aflatoxin-associated mutational hotspot at codon 249 in the p53 tumor suppressor gene occurs in hepatocellular carcinomas from Mexico.
The p53 tumor suppressor gene is commonly mutated in human hepatocellular carcinoma (HCC). The most frequent mutation in HCC in populations exposed to a high dietary intake of aflatoxin B1 (AFB1) is an AGGarg-->AGTser missense mutation in codon 249 of the p53 gene. We analyzed HCCs from Monterrey, Mexico, for the codon 249ser hotspot mutation. We also analyzed the serum AFB1-albumin adduct levels of the donors and family members to measure the current AFB1 exposure in this population. Moreover, the presence of hepatitis B and/or C viral infection (HBV or HCV) was analyzed serologically in the patients. Tumor cells were microdissected from tissue sections and exon 7 p53 sequences were amplified by polymerase chain reaction from genomic DNA and sequenced directly. The serological tests for anti-p53 antibodies, HBV or HCV were done by ELISA. Immunohistochemical analysis of p53 protein was done using a polyclonal rabbit antiserum (CM-1). Eight of 21 cases were positive by p53 immunohistochemistry. Of the 16 cases sequenced for exon 7 of p53 three codon 249 AGGarg-->AGTser mutations were found. Serum antibodies recognizing p53 protein were found in one of 18 patients. Positive serology for HBV and/or HCV was found in 12 of 20 cases. The serum AFB1-albumin adduct levels in this population ranged from 0.54 to 4.64 pmol aflatoxin/mg albumin. These results indicate that dietary AFB1 and hepatitis viruses are etiological agents in the molecular pathogenesis of HCC in this geographic region of Mexico.
Adult↗
Hepatic concentrations of proenkephalin-derived opioids are increased in a rat model of cholestasis.
The liver of adult rats with cholestasis secondary to bile duct resection has been shown to express the proenkephalin gene and, by immunohistochemical stains, to contain met-enkephalin. To further study hepatic opioids in cholestasis, concentrations of proenkephalin-derived endogenous opioids were measured in a rat model of cholestasis by the use of radioimmunoassays. The specificity of the immunoreactivity detected by the assays was confirmed by high performance liquid chromatography (HPLC). In adult male rats with cholestasis due to BDR, the concentrations of three proenkephalin-derived opioid peptides were increased. Specifically, the mean hepatic concentrations of met-enkephalin, Met-Enk-Arg6-Phe7 and leu-enkephalin were 2.5 (p < 0.005), 2.1 (p < 0.005) and 2.5 (p < 0.01) fold higher than the corresponding mean for controls. These findings provide further independent evidence that opioid peptides accumulate in the liver in a model of cholestasis and are consistent with de novo synthesis of opioid peptides occurring in the cholestatic liver. This phenomenon may have relevance to the altered function of the opioid system in cholestasis and to the role of the liver as a neuroendocrine organ.
Animals↗
Why do cholestatic patients itch?
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Cholestasis↗
Mesoderm and endoderm differentiation in animal cap explants: identification of the HNF4-binding site as an activin A responsive element in the Xenopus HNF1alpha promoter.
The gene encoding the tissue-specific transcription factor HNF1alpha (LFB1) is transcriptionally activated shortly after mid-blastula transition in Xenopus embryos. We have now shown that the HNF1alpha protein is localized in the nuclei of the liver, gall bladder, gut and pronephros of the developing larvae. In animal cap explants treated with activin A together with retinoic acid, we induced HNF1alpha in pronephric tubules and epithelial gut cells, i.e. in mesodermal as well as in endodermal tissues. HNF1alpha can also be induced by activin A, but not by retinoic acid alone. To define the promoter element responding to the activin A signal, we injected various HNF1alpha promoter luciferase constructs into fertilized eggs and cultured the isolated animal caps in the presence of activin A. From the activity profiles of the promoter mutants used, we identified the HNF4-binding site as an activin-A-responsive element. As HNF4 is a maternal protein in Xenopus and localized in an animal-to-vegetal gradient in the cleaving embryo, we speculate that the activin A signal emanating from the vegetal pole cooperates with the maternal transcription factor HNF4 to define the embryonic regions expressing HNF1alpha.
Activins↗
Recognizing the allergic child.
The delivery of health care is currently in a state of transition with managed care emerging as a frequently used method for health care delivery. A major tenet of many managed care systems is that specialized care is costly and thus is to be delayed or avoided when possible. The end result of this philosophy is that primary care physicians will find themselves providing patient care which, in the past, had been provided by the specialist. In the field of allergy, as in any other specialty, providing adequate and appropriate care to the patient is incumbent on recognizing that the patient's symptoms are allergic in etiology. This is especially true when presenting symptoms are different from the classical signs and symptoms of allergy. This paper presents: (1) specific comments and suggestions which will enable the primary care physician to recognize the allergic child, (2) data from over 800 children referred for allergy evaluation to support the foregoing comments and suggestions and, (3) recommendations as to how primary care physicians might effectively manage most children with certain types of allergic disease without referral to an allergist.
Adolescent↗
Effects of retinoic acid on Xenopus embryos.
Retinoic acid (RA) has powerful dose-dependent dysmorphogenic effects on Xenopus embryos. The defects produced are dependent upon the stage and duration of treatment. Characteristic dysmorphogenic effects occur in the visceral (branchial) arch region and the tail. These regions correspond to the domains of expression of the retinoid receptors RAR gamma and RXR beta. By expressing domain-swapped and dominant negative derivatives of RAR gamma in embryos, we have shown that the effects of RA are mediated transcriptionally. Furthermore, the expression of dominant negative receptors in the absence of exogenous ligand has no apparent harmful effect upon early development. Finally, we have identified a novel MAP kinase phosphatase whose expression pattern is localized to regions similar to RAR gamma, and which is upregulated by RA.
Animals↗