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Biomedical subjects

H F Merk

Publications and source records attributed to H F Merk.

At least 73 records · Page 4Linked to original sources
PubMed1999

Erythropoietic protoporphyria: identification of novel mutations in the ferrochelatase gene and comparison of biochemical markers versus molecular analysis as diagnostic strategies.

BACKGROUND: Erythropoietic protoporphyria (EPP) results from an inherited deficiency of the last enzyme of the heme biosynthetic pathway, ferrochelatase (FC). EPP is usually inherited in an autosomal dominant fashion, and the mutations in the FC gene on chromosome 18q21.3 detected in EPP patients are heterogeneous. METHODS: In this study, we screened the FC gene for mutations in 12 patients from 10 unrelated families with EPP and their family members using heteroduplex analysis, automated sequencing, and restriction enzyme digestion. RESULTS: We detected 8 different mutations in these patients, including 1 missense mutation, 5 frameshift mutations, and 2 splice site mutations, 6 of which are previously undescribed. CONCLUSIONS: We have established the molecular basis of EPP in 10 unrelated families, thereby providing further evidence for the heterogeneity in this disorder. Importantly, molecular diagnosis allowed revisions in the status of several clinically unaffected silent mutation carriers within the families. We compare the value of genetic research strategies with the combination of biochemical data and clinical phenotype as diagnostic tools to confirm a putative diagnosis in EPP.

Biomarkers↗
PubMed1999

Allergy, skin and environment.

The skin is very often the target organ of allergic reactions. This may be explained by many immunological competent cells in this organ such as the Langerhans cell, mast cells, lymphocytes, neutrophils and eosinophils. This is especially true for the antigen-presenting Langerhans cell. Therefore in many cases, the skin is a signalling organ for allergic reactions. Examples include food allergy which precipitates with signs and symptoms of skin diseases in about 45% and drug allergy to beta-lactam-antibiotics in about 90%. Also the skin serves as a test organ in allergic diseases of other organs such as rhinitis allergica or asthma. Examples include Reibtest, prick-, intracutaneous-, scratch- and patch test. Therefore it is no surprise, that allergic diseases of the skin are the most often diagnosed skin diseases such as urticaria, angioedema, vasculitis, contact dermatitis and atopic dermatitis. At these diseases, their diagnose and therapy and especially the promising progress in research with regard to these diseases which has been obtained during the last years will be focussed in this review.

Dermatitis↗
PubMed1999

Interdisciplinary clinical assessment of patients with illness attributed to environmental factors.

Patients with health problems attributed to environmental factors such as chemical pollutants and electromagnetic fields often do not present evidence of an environmental aetiology of their symptoms. It has been postulated, that their problems are due to disorders diagnosed by other medical disciplines, especially allergology and psychiatry. Our study was designed to subject these patients to a comprehensive diagnostic program involving several medical disciplines in order to achieve diagnoses appropriate to explain the patients' symptoms. Fifty patients consecutively referred to the department of environmental medicine in the university hospital of Aachen, Germany, were submitted to the following examinations: (i) environmental medicine (history, clinical examination, biological and/or ambient monitoring for environmental agents); (ii) allergological examination (history, clinical examination, skin tests); (iii) psychiatric examination (psychopathological examination, psychometric and neuropsychological testing). In addition, the patients were examined in other hospital departments according to the symptoms presented. The findings were discussed in case conferences attended by the physicians involved in order to achieve individual diagnoses. The numbers of patients to whom diagnoses were given by different medical disciplines are as follows: psychiatry (32 patients), dermatology (4), allergology (2), neurology (2), rheumatology (2), gynaecology (1), haematology (1). The most frequent mental disorders diagnosed by the psychiatrists were somatoform disorders (19), followed by schizophreniform and delusion disorders (7). In spite of extensive diagnostic efforts, patients with health problems attributed to the environment usually do not present sufficient evidence of an environmental aetiology of their symptoms. On the other hand the symptoms often meet the diagnostic criteria of other diseases, especially of mental disorders.

Adult↗
PubMed1998

Identification and characterization of autoreactive T cell responses to bullous pemphigoid antigen 2 in patients and healthy controls.

Antibodies against the extracellular domain of bullous pemphigoid antigen 2 (BPAG2) are thought to play a key role in the pathogenesis of bullous pemphigoid (BP), the most frequent autoimmune bullous disease of the skin. Autoreactive T cell responses to BPAG2 were investigated in 16 BP patients and 24 healthy controls by coculture of PBMC with two recombinant BPAG2 proteins (extracellular domain of BPAG2). Primary in vitro T cell responses to BPAG2 were observed in 10/12 BP patients expressing the BP-associated HLA-DQB1*0301 allele and 8/10 DQB1*0301 positive healthy individuals. DQB1*0301 also restricted three autoreactive T cell lines from two BP patients and a healthy donor. In contrast, PBMC from 14 normal patients carrying HLA class II alleles other than DQB1*0301 were not stimulated by BPAG2. Autoreactive BPAG2-specific CD4(+) T cell lines and clones from five BP patients produced both Th1 and Th2 cytokines, whereas three autoreactive T cell lines from three DQB1*0301 positive normal patients produced exclusively IFN-gamma. The absence of BPAG2-specific Th2 cells in healthy individuals strongly suggests that autoreactive Th2 responses to BPAG2 are restricted to BP patients and may thus be critical in the pathogenesis of BP.

Adult↗
PubMed1998

Cytochrome P450 1B1: a major P450 isoenzyme in human blood monocytes and macrophage subsets.

In this study, cytochrome P450 (CYP; EC 1.14.14.1)-dependent activities and P450 isoenzyme patterns were determined in human monocytes and macrophages, which play a major role in antigen processing including small molecular weight compounds which cause contact dermatitis or drug-allergic reactions. Using reverse transcriptase-polymerase chain reaction (RT-PCR) we determined the mRNA expression of eight CYPs (1A1, 1A2, 1B1, 2B6/7, 2E1, 3A3/4, 3A7 and 4B1) in human blood monocytes and macrophage subsets 27E10 and RM3/1. To study the influence of known P450 inducers, monocytes were incubated in vitro with ethanol, dexamethasone, cyclosporin A (CSA), benzanthracene (BA), phenobarbital (PB), lipopolysaccharide (LPS) and 12-O-tetradecanoyl-phorbol-13-acetat (TPA) for 24 hr. Percoll density gradient isolated monocytes as well as the pro-inflammatory macrophage subtype 27E10 expressed 1B1, 2E1 and 2B6/7. On the other hand, in the anti-inflammatory macrophage subtype RM3/1, predominantly 1B1 and to some extent 2B6/7 were found. Treatment with cyclosporin A, phenobarbital, benzanthracene or ethanol resulted in induction of the expression of 3A3/4. CYP1B1 was the predominant isoenzyme in all monocytes and macrophages. In monocytes purified by adherence or induced by benzanthracene, lipopolysaccharide or 12-O-tetradecanoyl-phorbol-13-acetat, 1A1 was also expressed. Northern blot analysis confirmed the presence of CYP1B1 in monocytes and macrophages, a presence which was also demonstrated on the protein level by immunoblot and by immunohistochemical staining of the cells. The expression of several CYPs in monocytes/macrophages suggests that these cells may be important in the metabolism of small molecular weight compounds, which play a role in allergic contact dermatitis and drug reactions. Of particular interest is the remarkably strong expression of the recently identified dioxin inducible CYP1B1, known to be present in a wide range of malignant tumors.

Aryl Hydrocarbon Hydroxylases↗
PubMed1998

Recurrent missense mutation in the protoporphyrinogen oxidase gene underlies variegate porphyria.

The porphyrias represent a heterogeneous group of disorders of porphyrin or porphyrin-precursor metabolism, resulting from the inherited or acquired dysregulation of one of the eight enzymes in the porphyrin-heme biosynthetic pathway. Variegate porphyria, one of the acute hepatic porphyrias, is characterized by a partial reduction in the activity of the penultimate enzyme in the heme biosynthetic pathway, protoporphyrinogen oxidase (PPO). Recently, VP has been linked to the PPO gene on chromosome 1q22-23, and several disease-causing mutations have been described. In this study, we identified the underlying genetic lesion in two unrelated patients with VP and investigated all available family members by polymerase chain reaction, heteroduplex analysis, automated sequencing, and restriction enzyme digestion. Mutation analyses in both families revealed a G-to-A transition in exon 6 of the PPO gene resulting in the substitution of arginine by histidine at position 168 of the protein (R168H). This arginine residue is evolutionarily conserved in human, mouse, and Bacillus subtilis, indicating the importance of this residue in PPO function. Our study establishes a recurrent missense mutation as the underlying genetic defect in two unrelated patients with VP and explains the occurrence of the phenotype in their families.

Adult↗
PubMed1998

Detection of IgG autoantibodies in the sera of patients with bullous and gestational pemphigoid: ELISA studies utilizing a baculovirus-encoded form of bullous pemphigoid antigen 2.

Autoantibodies against the extracellular domain of bullous pemphigoid antigen 2 (BPAG2) are thought to play a key role in the pathogenesis of bullous pemphigoid and their detection may thus be of diagnostic and prognostic value. The aim of this study was to develop a standardized enzyme-linked immunosorbent assay utilizing the baculovirus-derived protein BV13 (extracellular domain of BPAG2 devoid of 68 amino acids at the C terminus linked to glutathione-S-transferase and 6x His tag) to detect BPAG2-specific autoantibodies. For the enzyme-linked immunosorbent assay, nickel agarose affinity-purified BV13 protein was incubated with sera from patients with bullous pemphigoid (n = 39), gestational pemphigoid (n = 10), and pemphigus vulgaris/pemphigus foliaceus (PV/PF; n = 15), or normal human sera (NHS; n = 18). Nickel affinity-purified proteins from wild-type baculovirus-infected insect cells served as a control. A positive enzyme-linked immunosorbent assay value was defined as reactivity (OD(BV13) - OD(WT)) > mean reactivity + 1 SD of the negative control sera (PV/PF; NHS). Thirty-five of 39 bullous pemphigoid sera and 10 of 10 gestational pemphigoid sera were reactive to BPAG2 compared with none of 15 PV/PF sera and one of 18 NHS (sensitivity, 91.8%; specificity, 97%). Of 16 BPAG2-reactive sera in the enzyme-linked immunosorbent assay, only six were BPAG2-reactive in the western blot, whereas 14 sera immunoprecipitated BPAG2 from extracts of epidermal keratinocytes. The enzyme-linked immunosorbent assay utilizing an eukaryotic BPAG2 protein thus seems to be highly sensitive and specific in the detection of BPAG2-specific antibodies and, hence, may be useful in the diagnosis of bullous autoimmune diseases, such as bullous pemphigoid and gestational pemphigoid.

Adult↗
PubMed1998

C73R is a hotspot mutation in the uroporphyrinogen III synthase gene in congenital erythropoietic porphyria.

Congenital erythropoietic porphyria (CEP) results from profoundly deficient activity of the fourth enzyme of the haeme biosynthetic pathway, uroporphyrinogen III synthase (UROIIIS). CEP is a rare, recessively inherited disorder, and mutations in the UROIIIS gene detected in CEP patients are heterogeneous. The notable exception to this rule is a single missense mutation, designated C73R, which represents over 40% of all mutant UROIIIS alleles. In this study, we investigated three separate families with CEP from different ethnic backgrounds. We performed haplotype analysis using two microsatellite markers that closely flank the UROIIIS gene on chromosome 10q24, spanning a region of 4 cM on the GB4 linkage panel. Haplotype analysis revealed the occurrence of C73R on different haplotypes in four out of four disease chromosomes studied. The results are consistent with the hypothesis that C73R is a hotspot mutation for CEP, and does not represent wide dispersion of a single ancestral mutant C73R allele.

Base Sequence↗
PubMed1998

Variegate porphyria: identification of a nonsense mutation in the protoporphyrinogen oxidase gene.

The porphyrias are disorders of porphyrin metabolism that result from inherited or acquired aberrations in the control of the heme biosynthetic pathway. Variegate porphyria is characterized by a partial reduction in the activity of protoporphyrinogen oxidase. In this study, we identified the first nonsense mutation in a family with variegate porphyria. The mutation consisted of a previously unreported G-to-T transversion in exon 5 of the protoporphyrinogen oxidase gene, resulting in the substitution of glutamic acid by a nonsense codon, designated E133X. Our investigation establishes that a nonsense mutation in the protoporphyrinogen oxidase gene is the underlying mutation in this family with variegate porphyria.

Adult↗
PubMed1998

Genotype and phenotype of N-acetyltransferase 2 (NAT2) polymorphism in patients with contact allergy.

We investigated whether patients with contact allergy differed from non-contact-allergic, non-atopic controls with regard to genotype and phenotype of the polymorphic enzyme N-acetyltransferase 2 (NAT2). 55 contact-allergic patients recruited from the Information Network of Departments of Dermatology (IVDK) were compared to 85 controls from among local health care personnel. NAT2 activity was calculated from HPLC analysis of the ratio of the caffeine metabolites 5-acetylamino-6-formylamino-3-methyluracil (AFMU) and 1-methylxanthine (1MX) in the urine. NAT2 genotype was determined by polymerase chain reaction (PCR). A statistically significantly increased proportion of rapid acetylators was found in contact-allergic patients. This may have 2 possible implications: acetylation may enhance contact sensitization; or NAT2 status may be a genetic marker for contact sensitizability.

Acetylation↗
PubMed1997

Short-term immunotherapy: a prospective, randomized, double-blind, placebo-controlled multicenter study of molecular standardized grass and rye allergens in patients with grass pollen-induced allergic rhinitis.

BACKGROUND: Short-term immunotherapy (STI) can be beneficial for patients who are noncompliant with long-term specific immunotherapy. OBJECTIVE: The efficacy and tolerance of STI with seven preseasonal injections of molecular standardized allergens from grass and rye pollen has been investigated in a double-blind, placebo-controlled multicenter study with 87 patients at 12 German University hospitals. METHODS: Symptoms of the eyes, nose, and bronchi and use of symptomatic drugs were documented daily in diaries by patients with allergic rhinitis to grass and/or rye pollen and without bronchial asthma. Patients were monitored by skin prick test titration and measurement of levels of specific IgE and IgG4. RESULTS: The median nasal score for the 10 weeks with the strongest symptoms during the grass pollen season was significantly lower (p = 0.014) with 35.0 for STI (n = 41) versus 69.0 for placebo (n = 40); the overall symptom score was 54.0 for STI versus 97.5 for placebo (p = 0.020). Only STI-treated patients exposed to less than 40 pollen grains per cubic meter per week showed a significantly lower nasal symptom score of 39.0 versus 75.0 for placebo (p = 0.006); these patients also had fewer nasal symptoms and less use of topical nasal drugs (p < 0.001). The threshold dose in skin prick tests was significantly higher, being 9.06 histamine equivalent for skin prick test (HEP) for STI-treated patients who received the maximum dose (n = 22) versus 4.33 HEP for placebo (p = 0.005). Specific IgE levels were significantly higher, being 55.9 SU/ml for STI versus 39.2 SU/ml for placebo after seven injections (p = 0.006) and level of specific IgG4 was 5.36% for STI versus 1.28% for placebo (p < 0.001). No severe systemic reactions were observed. CONCLUSION: STI with seven preseasonal injections with molecular standardized allergens is effective and well tolerated.

Adolescent↗
PubMed1997

[The skin and allergy].

The skin is very often the target organ of allergic reactions. This may be explained by many immunological competent cells in this organ such as the Langerhans cell, mast cells, lymphocytes, neutrophils and eosinophils. This is especially true for the antigen-presenting Langerhans cell. Therefore in many cases, the skin is a signalling organ for allergic reactions. Examples include food allergy which precipitates with sign and symptoms of skin diseases in about 45% and drug allergy to beta-lactam-antibiotics in about 90%. Also the skin serves as test organ in allergic diseases of other organs such as rhinitis allergica or asthma. Examples include Reibtest, prick-, intracutaneous-, scratch- and patch test. Therefore it is no surprise, that allergic diseases of the skin are the most often diagnosed skin diseases such as urticaria, angioedema, vasculitis, contact dermatitis and atopic dermatitis. At these diseases, their diagnose and therapy and especially the promising progress in research with regard to these diseases which has been obtained during the last years will be focussed in this review.

Dermatitis, Allergic Contact↗