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PubMed1967

Tyrosinase inhibition: its role in suntanning and in albinism.

Tyrosinase inhibitor (molecular weight less than 5000; extracted from various melanomas) fully inhibits soluble tyrosinase but only partially inhibits tyrosinase "aggregated" into melanosomes; the inhibitor can be inactivated by ultraviolet light. S91 Albinotyrosinase Type B apparently cannot "aggregate" into melanosomes because its protein carrier is genetically altered. Therefore, albinotyrosinase remains vulnerable to its inhibitor and cannot produce melanin, even though the enzyme has a functioning active center.

Albinism↗
PubMed2002

The Karlsburg type 1 diabetes risk study of a normal schoolchild population: association of beta-cell autoantibodies and human leukocyte antigen-DQB1 alleles in antibody-positive individuals.

The intent of this study was to analyze the prevalence of diabetes-associated autoantibodies (AAbs) at or above the 99(th) percentile as well as their association with human leukocyte antigen (HLA)-DQB1 alleles in a normal population of 6,337 schoolchildren. AAbs against glutamic acid decarboxylase (GADA), tyrosine phosphatase IA-2 (IA-2A), and/or insulin (IAA) were detected by (125)I-antigen binding and islet cell antibodies (ICA) immunohistochemically in 181 (2.86%) schoolchildren. HLA-DQB1 alleles were analyzed in 178/181 children and subsequently compared with 119 controls. 2.37% (150/6,337) possessed only one AAb, whereas 0.49% (31/6,337) had multiple AAbs but at increased levels (P < 0.001). Subjects with GADA, IA-2A, or IAA revealed an increased frequency of the diabetes-associated HLA-DQB1 alleles *0302 and/or *02 (P = 0.001-0.006) as well as a decreased frequency in the protective allele *0602 (P < 0.001-0.022). DQB1*0602 was completely absent within children with multiple AAbs or with GADA, IA2-A, or IAA at or above the 99.9(th) percentile. In comparison to children with single AAbs, the frequency of associated/protective alleles of children with multiple AAbs was enhanced/diminished (P = 0.004-0.009). The study shows that also in the general population the multiple AAbs or high level single AAbs predict rather certainly a HLA-DQB1-mediated diabetes susceptibility as shown for first degree relatives of type 1 diabetic patients.

Adult↗
PubMedDate not supplied

Involvement of reactive oxygen species in the induction of (S)-N-p-coumaroyloctopamine accumulation by beta-1,3-glucooligosaccharide elicitors in potato tuber tissues.

Treatment of potato tuber tissues with beta-1,3-glucooligosaccharide induces accumulation of (S)-N-p-coumaroyloctopamine (p-CO). We examined the role of reactive oxygen species (ROS) and nitric oxide (NO) in the signal transduction leading to p-CO accumulation. Induction was suppressed by an NADPH-oxidase inhibitor, diphenyleneiodonium chloride, and oxygen radical scavengers. H2O2 was generated in the tuber tissue within a few minutes of treatment with beta-1,3-glucooligosaccharide. On the other hand, treatment with NO specific scavenger, nitric oxide synthase inhibitor, and serine protease inhibitor did not inhibit p-CO induction. Our findings suggest that ROS generated by the action of NADPH-oxidase play an important role in this system, while NO and serine protease are unlikely to be involved in this process.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗
PubMed2001

Macroamylasemia attributable to gluten-related amylase autoantibodies: a case report.

BACKGROUND: Macroamylasemia (MA) is a benign condition caused by circulating macroamylase complexes of pancreatic or salivary amylase bound to plasma proteins, which cannot be cleared by the renal glomeruli. In most cases, the macromolecular amylase represents a complex of normal amylase and either immunoglobulin A or G and may be a specific antigen-antibody complex. Celiac disease (CD) is a permanent intolerance to ingested gluten that results in immunologically mediated inflammatory damage of the small intestinal mucosa. Several recent population-based serologic surveys have shown CD to be a common disorder, possibly affecting 1 in 200 to 250 individuals in most countries studied, including the United States, where overt CD is rare, indicating a high proportion of subclinical disease. The diagnosis of CD currently rests on the histological demonstration of the characteristic lesion in the small intestine and the subsequent clinical response to the introduction of a gluten-free diet. MA associated with CD has been described in adult patients, and in a few cases, MA decreased or resolved after a strict gluten-free diet. A few single cases of MA have been described in childhood, but no association with CD has been reported so far. We report a girl with CD, autoimmune thyroiditis, and MA, in whom CD-related antibodies to amylase and to exocrine pancreas tissue resolved with a gluten-free diet. CASE REPORT: An 11-year-old girl was referred for chronic abdominal pain and growth retardation associated with persistent hyperamylasemia and suspected chronic pancreatitis. We confirmed elevated serum amylase, normal serum lipase, and very low 24-hour urine amylase and amylase clearance/creatinine clearance ratio, consistent with MA. Serologic tests for CD were positive, and the diagnosis was confirmed by small bowel biopsy showing subtotal villous atrophy. Thyroid function tests showed a pronounced hypothyroidism, associated with high titers of thyroid microsomal and thyroglobulin antibodies. Screening for other autoantibodies-including antinuclear, islet cell, glutamic acid decarboxylase, protein tyrosine phosphatase islet antigen 512, adrenal gland, and cytoplasmic neutrophil granulocyte antibodies-was negative. A diagnosis of CD, MA, and hypothyroidism attributable to autoimmune thyroiditis was made. A gluten-free diet and oral replacement with L-thyroxine was started with clinical improvement. Serum amylase and amylase clearance/creatinine clearance ratio normalized, consistent with resolution of MA. STUDY DESIGN AND METHODS: The patient's serum samples were obtained at the time of CD diagnosis and at 3 and 12 months after instituting a gluten-free diet. Serum samples from 10 consecutive untreated celiac children were disease controls, and 39 participants with no gastrointestinal symptoms and no family history of CD served as healthy controls. The origin of MA as determined by complexes of amylase with circulating immunoglobulins was tested by the measurement of amylase on supernatants after precipitation of immune complexes with either protein A Sepharose or polyethylene glycol. The precipitation of >60% of amylase activity was consistent with the presence of MA. Immunoglobulin G (IgG) and immunoglobulin A (IgA) circulating autoantibodies to amylase were measured using recently developed enzyme-linked immunosorbent assay (ELISA), using porcine amylase as antigen. Results were expressed as arbitrary units (AUs). Statistical analysis was performed by Student's t test for unpaired data. IgA and IgG antibodies to exocrine pancreas tissue were detected by indirect immunofluorescence on human pancreas cryosections. RESULTS: Serum immunoprecipitation with either protein A Sepharose or polyethylene glycol reduced amylase activity from 1698 to 89 U/L (94.8%) and to 75 U/L (95.6%), with only marginal reduction in control serum samples. The ELISA for autoantibodies to amylase detected high values, both IgA (3531 AU) and IgG (1855 AU), in the serum sample from the patient at CD diagnosis. IgA autoantibodies (mean +/- standard deviation) were 3.4 +/- 2.5 AU in healthy controls, and 2.1 +/- 1.2 AU in celiac controls; IgG autoantibodies were 10 +/- 4.8 AU in healthy controls and 8.5 +/- 3.2 AU, respectively. Autoantibodies to exocrine pancreas tissue were documented in patient sera at the time of CD diagnosis, both IgA and IgG, but not in control groups. Preincubation of patient's serum with excess of alpha-amylase specifically inhibited antibody binding to coated amylase in the ELISA, and partially inhibited immunoreactivity to exocrine pancreas. Autoantibodies to alpha-amylase and to exocrine pancreas declined in CD patients after institution of a gluten-free diet. CONCLUSIONS: Few cases of MA have been described in children, and in all amylase determination was part of the clinical investigation for abdominal pain or trauma. (ABSTRACT TRUNCATED)

Amylases↗
PubMed1999

[Augmentation of the immune response to islet cell antigens with development of diabetes mellitus caused by interferon-alpha therapy in chronic hepatitis C].

We report on a 36-year-old patient suffering from chronic hepatitis C. Because of elevated liver enzymes and histology showing chronic inflammation and periportal fibrosis, interferon-alpha (IFN) therapy was started with a dosage of 5 Mio units three times a week. Four months later the patient hat to be hospitalized due to the typical clinical features of a recent onset type 1 diabetes (BG > 300 mg/dl, HbA1c 9.6%, ketonuria). In serum samples prior to and following interferon therapy, we analyzed titers of diabetes-related autoantibodies responding to GAD65 (glutamic acid decarboxylase), IA2c (tyrosine phosphatase) and ICA (islet cell autoantibodies). While ICA were negative before starting therapy, IA2c-antibodies were highly elevated. In contrast. GAD65-antibodies were elevated only slightly over the cut-off of the assay before therapy (controlled by a second different RIA assay) and increased 100 fold during IFN-alpha treatment. Additionally thyroid antibodies appeared. After the end of the IFN therapy, GAD65- and IA2c antibodies remained on high levels and also ICA could now be found. The patient was positive for HLA-DR4. This case supports the hypothesis that IFN-alpha therapy may lead to an augmented autoimmune reaction against islet cell antigens resulting in the development of diabetes mellitus type 1, especially if there are other predisposing factors before IFN treatment. We further discuss the possible involvement of interferon-alpha in the pathogenesis of autoimmune diabetes with reference to recent studies.

Adult↗
PubMed1976

Enzymatic microassay of pyridoxal-5'-phosphate using L-tyrosine apodecarboxylase and L-(1-14C) tyrosine.

A microassay for pyridoxal-5'-phosphate (PLP) is described, which incorporates both the enzymatic and radioisotopic techniques. The method is based upon the stoichiometric decarboxylation of L-(1-14C) tyrosine by L-tyrosine apodecarboxylase and PLP. This method is an extensive modification of the ones reported by us previously, the main features of this present method being the ease of preparation of the enzyme extract and the substrate, elimination of the preincubation period and shortening of the 14CO2-trapping step. The assay as described here is rapid, highly sensitive and specific.

Apoenzymes↗
PubMed1999

[Autoantibodies in the pathogenesis and diagnosis of insulin-dependent diabetes mellitus].

Insulin-dependent diabetes mellitus is considered an autoimmune disease. The immune response is targeted on autoantigens of B-cells of the islets of Langerhans. The most important autoantigens are glutamic acid decarboxylase, protein tyrosine phosphatase and insulin. Despite the fact that their role in the pathogenesis of insulin-dependent diabetes mellitus is not clear, they are used in diagnosis and can identify subjects at high risk for the development of the disease.

Autoantibodies↗
PubMed2001

[Latent autoimmune diabetes in adults(LADA): part of the clinical spectrum of type-1 diabetes mellitus of autoimmune origin].

According to the most recent classification of diabetes mellitus the latent autoimmune diabetes in adults belongs to the group of type 1 autoimmune diabetes mellitus, as a slowly progressive form. It is not clear whether LADA is a distinct clinical entity or it is a part of the clinical spectrum of type 1 diabetes mellitus. The authors compare the antropologic (body mass index, waist to hip ratio), immunologic (occurrence of islet cell cytoplasmic autoantibodies and autoantibodies against glutamic acid decarboxylase and tyrosin phosphatase), genetic (HLA DR and DQ alleles known to be associated to type 1 diabetes mellitus) characteristics and occurrence of the features of the metabolic syndrome in the groups of type 1 and type 2 diabetes and LADA. 81 type 1 and 190 type 2 diabetics and 38 LADA patients were involved into the study. Freshly diagnosed type 1 diabetics served for controls of the autoantibody study: 48 patients manifested < or = 16 years of age and 89 type 1 diabetics manifested above 16 years of age. The three main diabetic groups differed in age: the average age in the type 1, type 2 and LADA groups were 37, 63 and 58 years respectively. There was no difference among the three groups in gender. The duration of the disease differed significantly between the type 2 and LADA groups (4.0 and 8.0 years respectively). In spite of the shorter duration of the disease in the LADA group, compared to the type 2 diabetics the frequency of insulin dependency was significantly higher in the LADA (81.6%) than in the type 2 group (46.7%). The BMI and WHR were comparable between the type 1 and LADA patients (average values were 23 and 0.83 in type 1 patients and 23.25 and 0.89 in LADA). The type 2 group differed significantly from type 1 and LADA (average values were 29.1 and 0.5). The concentration of glycated hemoglobin was comparable in the three groups. But there was a significant difference in HbA1c concentration between the freshly diagnosed subgroups of type 1 and LADA patients: 10.85% and 8% respectively. The fasting C-peptid levels were significantly higher in the sera of type 2 diabetics (0.75 pmol/l) compared to type 1 (0.2 pmol/l) and LADA patients (0.29 pmol/l). There was a significant difference in C-peptid concentrations between the type 1 and LADA groups, too. The insulin deficiency in LADA seemed to be not as severe as in type 1 diabetes. The serum total cholesterol and triglyceride levels were significantly higher and the HDL cholesterol concentration significantly lower in type 2 diabetics comparing to type 1 and LADA patients and there was no significant difference in this respect between the type 1 and LADA groups. The frequency of occurrence of hypertension differed no significantly between type 2 and LADA, but that of in type 1 diabetes was significantly lower than both type 2 and LADA. The occurrence of multiple autoantibodies (ICA + GADA + anti-IA2) was much more frequent in type 1 diabetes compared to LADA. In the sera of LADA patients the occurrence of ICA and GADA alone or ICA + GADA was characteristic (31.5% - 21.1% - 15.8% respectively). There was no difference between type 1 diabetes and LADA in the occurrence of the alleles of the MHC kown to be associated with type 1 diabetes. The occurrence of the haplotypes HLA DQ2/DR3 and/or DQ8/DR4 was observed in two thirds of type 1 diabetic and LADA patients. Chronic diabetic complications were observed in all of the groups and there was only a secondary connection of the complications with the type of the diabetes. Based on the results the authors suggest that LADA is a part of the clinical spectrum of type 1 diabetes of autoimmune origin.

Adolescent↗
PubMed1986

[The effects of protein and amino acids on DNA synthesis in regenerating liver].

In order to estimate the effects of protein and amino acids on regenerating liver, the induction of enzymes involved in synthesis of DNA was studied in rats fed protein free diet. In the regenerating livers of rats of the protein free diet, increase of liver weight and DNA content were stopped 48 hours after hepatectomy, and induction of DNA synthesizing enzymes such as dCMP deaminase, ribonucleotide reductase, and thymidine kinase were depressed and shortened. On the other hand, induction of protein or RNA synthesizing enzymes such as polyamine, ornithine decarboxylase, and tyrosine aminotransferase were not depressed by protein deprivation. The results indicate that protein deprivation inhibits the DNA synthesizing enzymes specifically, and regenerating liver cells can not enter S phase of cell cycle. When rats were maintained solely by total parenteral nutrition after hepatectomy, amino acids were essential for induction of DNA synthesizing enzymes. In particular, induction of these enzymes were regulated by 7 amino acids include Val, Leu, Ile, Met, Trp, Phe, and Thr, and most of these plasma amino acid levels were depressed after hepatectomy. By administration of amino acids for 12 hours just after hepatectomy, the DNA synthesizing enzymes were almost normally induced. This suggests that amino acids administration just after hepatectomy is effective to induce the DNA synthesizing enzymes for hepatic regeneration.

Amino Acids↗