Folic acid in the prevention of neural tube defects.
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Clinical Trials as Topic↗
Biomedical subjects
D G Weir
Publications and source records attributed to D G Weir.
Correlation of the ratio of S-adenosyl-L-methionine to S-adenosyl-L-homocysteine in the brain and cerebrospinal fluid of the pig: implications for the determination of this methylation ratio in human brain.
1. Pigs were maintained in air or in an atmosphere of nitrous oxide which dramatically changes the S-adenosyl-L-methionine to S-adenosyl-L-homocysteine ratio in neural tissues. Samples of cerebrospinal fluid, cortex, cerebellum and spinal cord were then extracted and analysed for S-adenosyl-L-methionine and S-adenosyl-L-homocysteine. Regression analyses were carried out on values obtained in cerebrospinal fluid and in neural tissues. 2. Highly significant correlations were obtained between levels of S-adenosyl-L-homocysteine (r2 = 0.42-0.69; P less than 0.001) and S-adenosyl-L-methionine/S-adenosyl-L-homocysteine ratios (r2 = 0.56-0.65; P less than 0.001) in cerebrospinal fluid and levels and ratios in cortex, cerebellum and spinal cord. The levels of S-adenosyl-L-methionine did not show a significant correlation. 3. We conclude that the ratio of these metabolites in the cerebrospinal fluid may reflect the ratio in the central nervous system and we suggest that this may also be true in human tissues. This finding will permit the determination of the probable methylation ratio in the central nervous system in human conditions, such as vitamin B12 deficiency and acquired immune deficiency syndrome, where a similar myelopathy occurs to that seen in the nitrous oxide-treated pig. All three myelopathies may arise from an inhibition of methyltransferases involved in the synthesis of myelin that would occur when the methylation ratio is reduced.
Animals↗
Cobalt-vitamin B-12 deficiency decreases methionine synthase activity and phospholipid methylation in sheep.
Two groups of lambs were fed either a Co-deficient or a Co-sufficient whole barley-based diet for 28 wk to induce a severe Co-vitamin B-12 deficiency. Holo and apo methionine synthase activities were significantly lower in the liver, kidney and spinal cord of Co-deficient animals compared with controls. Neither form of this enzyme in the brain was affected by Co deficiency. The ratio of the tissue concentrations of S-adenosyl methionine to S-adenosyl homocysteine was significantly lower only in the liver of Co-deficient animals, suggesting that the activity of hepatic SAM-dependent methyltransferase enzymes would be impaired. Measurements of tissue concentrations of phosphatidyl choline and phosphatidyl ethanolamine revealed lower concentrations of phosphatidyl choline and a lower phosphatidyl choline:phosphatidyl ethanolamine ratio in both liver and brain of the Co-deficient animals. The latter finding occurred in the absence of changes in either methionine synthase activity or the methylation ratio and may result from impaired availability of hepatic phosphatidyl choline for transport into the brain.
5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
Non-invasive diagnosis of portal vein occlusion by radionuclide angiography.
The accuracy of non-invasive radionuclide angiography in detecting portal vein occlusion was assessed in 61 patients--10 with portal vein occlusion confirmed by conventional portography, 25 with chronic liver disease and a patent portal vein (mild = 12, severe = 13), and 26 with normal liver function, who served as controls. The median percentage portal venous flow for the portal vein occlusion group was 8% (range 1-30) (consistent with negligible flow) compared with 78% (52-87) for control subjects (p < 0.005) and 68% (61-80) and 49% (23-59) respectively for patients with mild and severe liver disease (p < 0.001 and p < 0.005). At a portal venous inflow of < 20%, the procedure had a specificity of 100% and sensitivity of 90% in diagnosing portal vein occlusion. Non-invasive radionuclide angiography provides a safe and accurate screening method for evaluating portal vein patency or occlusion in the investigation of portal hypertension or before liver transplantation.
Adult↗
Evidence of brain methyltransferase inhibition and early brain involvement in HIV-positive patients.
The myelopathy associated with human immunodeficiency virus (HIV) infection closely resembles that in subacute combined degeneration, a disorder of vitamin B12 metabolism. To investigate whether the disorders share a pathogenetic mechanism, S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) were measured in the cerebrospinal fluid (CSF) of 20 HIV-seropositive patients and 30 HIV-negative patients who were undergoing lumbar puncture for other medical reasons. The HIV-seropositive patients had significantly lower CSF concentrations of SAM (mean 77 [SD 25] vs 131 [35] nmol/l; p less than 0.001) and significantly higher concentrations of SAH (30.5 [6.8] vs 19.0 [7.1] nmol/l; p less than 0.001) than the controls. There was therefore a significant difference between the groups in the SAM/SAH (methylation) ratio (HIV 2.7 [1.0] vs control 7.6 [3.4]; p less than 0.001). There were no correlations between SAM or SAH concentrations or methylation ratio and age or sex in both groups, or serum B12 and folate concentrations, CSF folate, serum or CSF methylmalonic acid, risk factors, body mass index, specific drug treatment received, or disease stage in the HIV group. This finding suggests that HIV affects the brain from a very early stage of the infection. We suggest that, as in the pig, the CSF methylation ratio closely reflects that in the brain. In HIV-infected patients a reduced brain methylation ratio would inhibit methyltransferase enzymes, which would lead to hypomethylation in the central nervous system and ultimately to neurological lesions. In a pig model of subacute combined degeneration and in vitamin-B12-deficient human beings, the primary cause of the low methylation ratio is impaired recycling of SAH back to SAM, a process which requires vitamin-B12-dependent methionine synthase. The HIV patients in this study were vitamin B12 and folate replete, which suggests a different cause for the low methylation ratio.
Adult↗
Mucosal and systemic IgA anti-gliadin antibody in celiac disease. Contrasting patterns of response in serum, saliva, and intestinal secretions.
Serum IgA anti-gliadin antibody estimation is a recognized screening method for celiac disease. However, celiac disease is primarily a small intestinal mucosal disorder, and so we have examined the possibility that secreted, mucosal IgA anti-gliadin antibody might provide a more relevant measure of gluten sensitivity than that obtained from serum tests. Serum IgA anti-gliadin antibody and serum, salivary, and small intestinal aspirate IgA anti-gliadin antibody were measured by enzyme-linked immunosorbent assay. Serum IgA and IgG anti-gliadin antibody were markedly increased in untreated celiacs (N = 31) as compared to normals (N = 20) or disease controls (N = 39) (P less than 0.0001). Levels were lower in treated (N = 30) than untreated celiacs (P less than 0.001). In intestinal aspirates both untreated and treated patients had similar levels of IgA anti-gliadin antibody (P = 0.48), but both were significantly higher than in controls (P less than 0.01). Salivary IgA anti-gliadin antibody, by contrast, was not increased in celiac patients as compared to controls. Serum IgA anti-gliadin antibody was the most sensitive (84%) and specific (95%) test for detecting untreated celiac disease. It was also the most useful in patient follow-up where it provides an early objective indicator of adherence to a gluten-free diet. Mucosal IgA responses to gliadin in celiac disease appear to be compartmentalized, with different portions of the gastrointestinal tract functioning as separate immunological organs. Our results also demonstrate that serum and secretory IgA production are under independent control.
Adult↗
Betaine-homocysteine methyltransferase: organ distribution in man, pig and rat and subcellular distribution in the rat.
1. Conflicting reports exist as to the organ distribution of betaine-homocysteine methyltransferase (EC 2.1.1.5). It is important to establish its presence or absence in brain, since its substrate, betaine, has recently become established in the treatment of certain diseases involving this organ. 2. It remains unclear whether the reported success of this treatment results from the use of betaine to methylate homocysteine and produce methionine in situ in neural tissue, or whether the effect is secondary to these same reductions happening in other organs, such as the liver. The former would require the presence of betaine-homocysteine methyltransferase in neural tissue. 3. This study demonstrates the complete absence of any activity for this enzyme in the brain of the three species examined. The enzyme was found to be present in both the liver and kidney of man and pig, but only in the liver of the rat. 4. The only source of betaine in cells is via the oxidation of choline. Since the enzymes involved in this conversion have never been shown to exist anywhere other than the mitochondria, it has been assumed that the methyltransferase is also mitochondrial. In this study, it is demonstrated that the enzyme exists only in the cytoplasm of rat liver cells.
Animals↗
Gliadin antibodies identify gluten-sensitive oral ulceration in the absence of villous atrophy.
This study demonstrates gluten-sensitive recurrent oral ulceration (ROU) in the absence of gastrointestinal abnormalities which is associated with a humoral response to wheat protein. Ten patients with severe ROU were investigated; all had normal small intestinal biopsies. Four patients had raised levels of antibodies to alpha gliadin, a wheat protein fraction; in three of these four, the ulceration remitted on treatment with a gluten-free diet (G.F.D.) and relapsed on gluten challenge. None of the remaining six patients had raised alpha gliadin antibody (AGA) levels and none responded to G.F.D. Thus raised AGA levels can be used to identify patients with ROU who are likely to respond to a GFD.
Adult↗
Dissolution of cholesterol gall stones using methyltertbutyl ether: a safe effective treatment.
Methyltertbutyl ether (MTBE) administered by percutaneous transhepatic catheter rapidly dissolves radiolucent cholesterol gall bladder stones. However, complete dissolution and clearance of non-cholesterol debris is essential to prevent recurrence. In this study we analysed 25 consecutive patients with reference to efficacy and recurrence based on the presence or absence of non-cholesterol stone fragments after dissolution. Placement of the catheter was successful in 24 patients, one patient requiring cholecystectomy for bile peritonitis. MTBE was infused and aspirated continuously, four to six cycles per minute, resulting in rapid stone dissolution (median six hours; range 4-23 hours for solitary stones and median seven hours, range 4-30 hours for multiple stones). In 18 patients who had complete dissolution, four (22%) had recurrent stones within six to 18 months. Five patients had residual debris which failed to clear completely despite bile acid treatment. One patient with an incomplete rim of calcium in a large stone did not respond to MTBE treatment. A further patient required cholecystectomy for symptomatic recurrence. There were no serious side effects observed. MTBE treatment is a rapid, safe, and effective treatment for patients who refuse surgery or who for medical reasons cannot undergo cholecystectomy. The results of this study confirm that complete dissolution of all fragments is essential and may prevent recurrence.
Adult↗
A new high performance liquid chromatographic method for the simultaneous measurement of S-adenosylmethionine and S-adenosylhomocysteine. Concentrations in pig tissues after inactivation of methionine synthase by nitrous oxide.
A rapid gradient method has been established to measure simultaneously the tissue levels of S-adenosylmethionine (AdoMet) and S-adenosylhomocysteine (AdoHcy). The method involves application of a 15%-25% linear gradient of methanol over a period of 10 min to an initial mobile phase of 15% methanol with 25 mM sodium phosphate, 10 mM 1-heptanesulfonic acid solution at pH 3.2 and a flow rate of 1 mL/min. AdoHcy elutes at 9.5 min and AdoMet at 12.6 min. The assay has a detection limit of 10 pmol and is linear in the concentration range 30-800 pmol. The method was used to assess changes in AdoMet and AdoHcy concentrations of pig tissues after seven days exposure to the anaesthetic gas nitrous oxide which irreversibly inactivates methionine synthase and induces an inability to recycle homocysteine, particularly in neural tissues. The treatment caused significant alterations in cellular AdoMet:AdoHcy ratios which were principally due to a dramatic rise in AdoHcy concentrations.
5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
The auditory P300 event-related potential: an objective marker of the encephalopathy of chronic liver disease.
Recently many variants of electroencephalogram-evoked responses have been studied as potential diagnostic aids in the detection and evaluation of hepatic encephalopathy. This study assesses the value of the auditory P300 event-related potential--a slow component of the auditory evoked response--as a tool in this field. Twenty-one nonencephalopathic and 12 encephalopathic (grade 1/2) cirrhotic patients and 26 controls were assessed clinically and psychometrically. Electroencephalogram spectral analysis and visual evoked response recordings were also conducted. An auditory P300 wave was elicited using the standard two-tone discrimination paradigm. The latency and amplitude of this wave were measured. The latency of the P300 was found to be significantly increased in the encephalopathic patients compared with both nonencephalopathic cirrhotic and control groups (p less than 0.05). Amplitude of the wave was decreased in both nonencephalopathic and encephalopathic patients, but this was not statistically significant. This study suggests that the latency of the P300 is a good marker of grades 1 and 2 clinical hepatic encephalopathy. The delays in the P300 latency may indicate that encephalopathic patients have a deterioration of their stimulus evaluation abilities.
Chronic Disease↗
Effects of an enteric anaerobic bacterial culture supernatant and deoxycholate on intestinal calcium absorption and disaccharidase activity.
Fifty two strains of anaerobic bacteria isolated from the upper gut of patients with small intestinal bacterial overgrowth were screened for phospholipase activity. Bacteroides melaninogenicus spp intermedius had the greatest activity. The effects of culture supernatants of this organism and deoxycholate on intestinal calcium absorption and disaccharidase activity were studied using a rat closed loop model. The supernatant decreased the in vitro uptake of calcium by 15% (p less than 0.001). Deoxycholate reduced calcium uptake by 16% (p less than 0.001). Combined culture supernatant and deoxycholate reduced calcium uptake by 39% (p less than 0.001) suggesting a potentiation of supernatant activity by deoxycholate. Culture supernatant and deoxycholate, both alone and combined, significantly reduced lactase, sucrase, and maltase activity. Electron microscopic evidence showed degeneration of microvilli, disruption of mitochondrial structure, and swelling of the endoplasmic reticulum after exposure of the intestinal loops to the supernatant or deoxycholate.
Animals↗
The role of nutrition in neural tube defects.
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Animals↗
Chemiluminescence by polymorphonuclear leucocyte subpopulations in chronic inflammatory bowel disease. Influence of the cell separation procedure.
Chemiluminescence (CL) is a simple quantitative assay of polymorphonuclear leucocyte (PMNL) oxidative metabolism. PMNL CL was found to be significantly higher in patients with chronic inflammatory bowel disease than in normal controls (167 +/- 60 vs. 139 +/- 50 mV/10(5) cells, p less than 0.05). There were no significant differences between patients with ulcerative colitis and Crohn's disease. Disease controls with rheumatoid arthritis and with bronchiectasis also demonstrated elevated CL. These results were obtained using a two-step gelatin/Ficoll-Hypaque procedure for PMNL separation. However when PMNLs were prepared using a one-step Ficoll-Hypaque procedure PMNL CL was found to be depressed in chronic inflammatory bowel disease (CIBD). It was demonstrated that this disparity was caused by the elimination of low-density neutrophils with high CL production by the one-step procedure. These data indicate that reports of abnormal in vitro neutrophil function in CIBD should be interpreted with caution since separation techniques which are satisfactory in normal individuals may significantly influence results in patients with inflammatory diseases. Furthermore these data indicate the presence of a subpopulation of activated low-density PMNL in patients with CIBD.
Cell Separation↗
Diagnosis and treatment of gluten-sensitive enteropathy.
Celiac disease is defined as a GSE. The small intestinal histological appearance of villous atrophy with crypt hyperplasia, inflammatory cell infiltrate of the lamina propria, and epithelial cell abnormalities is characteristic but not pathognomonic of the disorder. Confirmation of the diagnosis depends on histological improvement when gluten is removed from the diet and deterioration following gluten reintroduction. The pathogenesis of celiac disease appears to require interaction between a number of factors both intrinsic (genetic susceptibility, activation of the immune system) and extrinsic (gluten susceptibility, activation of the immune system) and extrinsic (gluten and possibly other environmental factors). The diagnosis of GSE may be delayed or missed unless the clinician is aware of the broad clinical spectrum of disease presentation. Although celiac disease is widely perceived as a malabsorption syndrome of childhood, the diagnosis is increasingly being made for the first time in adult life. A significant number of patients have no GI symptoms whatsoever. Small intestinal biopsy through the endoscope is the initial and definitive investigation. Most patients show excellent clinical and histological response to a gluten-free diet. The commonest reason for poor response is continuing intentional or inadvertent gluten intake. A minority of patients develop complications, in particular intestinal malignancy, including enteropathy-associated T-cell lymphoma.
Celiac Disease↗
The evolving spectrum of viral hepatitis.
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Hepatitis, Viral, Human↗
Necrolytic migratory erythema with elevated plasma enteroglucagon in celiac disease.
Necrolytic migratory erythema is the distinctive skin rash of the glucagonoma syndrome. Its presence is virtually pathognomonic of a glucagon-producing pancreatic islet cell neoplasm. Results of a study of a patient with hyperglucagonemia and necrolytic migratory erythema complicating untreated celiac disease are reported. Whereas pancreatic glucagon was only mildly elevated, there was marked elevation of enteroglucagon. Immunofluorescence staining demonstrated numerous (19.6 cells per square millimeter of mucosa) enteroglucagon-positive small intestinal crypt cells. Treatment with gluten-free diet not only resulted in resolution of malabsorption and improvement in small intestinal histology but was paralleled by disappearance of necrolytic migratory erythema, normalization of plasma glucagon levels, and marked reduction in the number of enteroglucagon-producing crypt cells (0.2/mm2 mucosa). The findings demonstrate that necrolytic migratory erythema is not an exclusively paraneoplastic phenomenon and that it can occur in association with excess production of enteroglucagon by the intestinal mucosa.
Celiac Disease↗
Prolonged IgM antibodies and histopathological evidence of chronicity in hepatitis A.
The case of a young man with hepatitis A and a chronic course is presented. The patient received a short course of steroid therapy for recurrence of symptoms following acute hepatitis A. Thereafter, liver enzymes have remained marginally elevated for 4 years and annual liver biopsies have shown evidence of chronicity. HAV IgM Ab persisted for 1034 days with subsequent development of HAV IgG Ab. The possibility of other viruses in the aetiology and the role of steroids in the development of chronicity are discussed.
Adult↗