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Biomedical subjects

I Meier

Publications and source records attributed to I Meier.

At least 37 records · Page 2Linked to original sources
PubMed1991

DNA methylation in the digestive tract of F344 rats during chronic exposure to N-methyl-N-nitrosourea.

The formation of O6-methyldeoxyguanosine (O6-MedGuo) was determined by an immuno-slot-blot assay in DNA of various tissues of F344 rats exposed to N-methyl-N-nitrosourea (MNU) in the drinking water at 400 ppm for 2 weeks. Although the pyloric region of the glandular stomach is a target organ under these experimental conditions, the extent of DNA methylation was highest in the forestomach (185 mumol O6-MedGuo/mol guanine). Fundus (91 mumol/mol guanine) and pylorus (105 mumol/mol guanine) of the glandular stomach, oesophagus (124 mumol/mol guanine) and duodenum (109 mumol/mol guanine) showed lower levels of O6-MedGuo but differed little between each other. Thus, no correlation was observed between target organ specificity and the extent of DNA methylation. This is in contrast to the gastric carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), which preferentially alkylates DNA of the pylorus, the main site of induction of gastric carcinomas by this chemical. In contrast to MNU, the non-enzymic decomposition of MNNG is accelerated by thiol compounds (reduced glutathione, L-cysteine), which are present at much higher concentrations in the glandular stomach than in the forestomach and oesophagus. During chronic exposure to MNNG (80 ppm), mucosal cells immunoreactive to O6-MedGuo are limited to the luminal surface [Kobori et al. (1988) Carcinogenesis 9:2271-2274]. Although MNU (400 ppm) produced similar levels of O6-MedGuo in the pylorus, no cells containing methylpurines were detectable by immunohistochemistry, suggesting a more uniform methylation of mucosal cells by MNU than by MNNG. After a single oral dose of MNU (90 mg/kg) cells containing methyl-purines were unequivocally identified using antibodies to O6-MedGuo and the imidazole-ring-opened product of 7-methyldeoxyguanosine. In the gastric fundus, their distribution was similar to those methylated by exposure to MNNG, whereas the pyloric region contained immunoreactive cells also in the deeper mucosal layers. After a 2-week MNU treatment, the rate of cell proliferation, as determined by bromodeoxyuridine immunoreactivity, was only slightly enhanced in the oesophagus and in the fundus, but markedly in the forestomach and the pyloric region of the glandular stomach. It is concluded that the overall extent of DNA methylation, the distribution of alkylated cells within the mucosa and the proliferative response all contribute to the organ-specific carcinogenicity of MNU.

Administration, Oral↗
PubMed1991

Elicitor-inducible and constitutive in vivo DNA footprints indicate novel cis-acting elements in the promoter of a parsley gene encoding pathogenesis-related protein 1.

The presence of three genes encoding pathogenesis-related protein 1 (PR1) in cultured parsley cells and the activation of all three genes by fungal elicitor are demonstrated. In vivo dimethyl sulfate footprinting was used to identify two putative sites of protein-DNA interaction in the promoter of one PR1 gene, located around positions -240 and -130 relative to the transcription start site. The TATA-distal footprint was elicitor dependent and appeared within 30 minutes of elicitor treatment, concomitant with the onset of PR1 transcription. The second footprint was observed irrespective of whether elicitor was present or absent. The two footprinted regions contain, in opposite orientation, nearly identical 11-base pair motifs that are unrelated to any known cis-acting element in elicitor-activated or pathogen-activated plant genes. The results demonstrate the usefulness of in vivo footprinting for the identification of cis-acting elements within promoters not accessible to other types of analysis.

Base Sequence↗
PubMed1991

Alkylating potency of nitrosated amino acids and peptides.

The alkylating potency of unstable N-nitrosamino acids and N-nitrosopeptides was investigated in vitro using 4-(para-nitrobenzyl)pyridine (NBP) as nucleophile. Of the amino acids, Met and those with an aromatic side chain were the most potent. The relative overall alkylating potency was 23:10:5:4:2:1: for Trp, Met, His, Tyr, Phe and Gly, respectively. The homo-dipeptides were much more potent than the amino acids, with relative potencies of 400:110:100:8:3:1, for Trp-Trp, Tyr-Tyr, Met-Met, Asp-Asp, Phe-Phe and Gly, respectively. In the one-phase reaction system (in which NBP is already present during the nitrosation reaction at acidic pH), all amino acids tested showed a second-order reaction for nitrite. In the two-phase system (in which NBP is added only after bringing the nitrosation reaction mixture to neutrality), all amino acids tested except one again showed a second-order reaction for nitrite (Phe, His, Asp and the dipeptide artificial sweetener aspartame); only Met under these conditions had a reaction order of one for nitrite. This could mean that nitrosation of the side chain of Met produces a second N-nitroso product which is relatively stable in acid but reacts with NBP under neutral conditions. In the human stomach, this side-chain nitrosation might become more important than the reactions at the primary amino group, firstly because of the greater stability of the product(s) in acid and secondly because of the first-order reaction rate for nitrite.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkylation↗
PubMed1990

A 125 bp promoter fragment is sufficient for strong elicitor-mediated gene activation in parsley.

We describe the nucleotide sequence and some structural characteristics of a single copy gene encoding pathogenesis-related protein 2 (PR2) in parsley (Petroselinum crispum). Transcriptional activation of this gene in cultured parsley cells treated with fungal elicitor leads to a rapid, large and transient accumulation of PR2 mRNA. The deduced PR2 protein belongs to a novel class of evolutionarily conserved polypeptides which are closely related to disease resistance in plants. Functional analysis of a series of truncated PR2 promoter fusions with the beta-glucuronidase reporter gene, using parsley protoplasts for transient expression studies, identified a 5' upstream element between positions -168 and -52 necessary for strong elicitor responsiveness. This small promoter fragment is active in conjunction with its own TATA box region as well as with the corresponding region from a heterologous promoter. The PR2 regulatory region exhibits no sequence similarity to any other elicitor-responsive promoter known to date.

Amino Acid Sequence↗
PubMed1990

Nitrosation of aspartic acid, aspartame, and glycine ethylester. Alkylation of 4-(p-nitrobenzyl)pyridine (NBP) in vitro and binding to DNA in the rat.

In a colorimetric assay using 4-(p-nitrobenzyl)pyridine (NBP) as a nucleophilic scavenger of alkylating agents, the nitrosation and alkylation reactions were investigated for a number of amino acids and derivatives. The alkylating activity increased with the square of the nitrite concentration. The nitrosation rate constants for aspartic acid, aspartame, and glycine ethylester (= precursors C) were 0.08, 1.4 and less than or equal to 0.2, respectively, expressed in terms of the pH-dependent k2 rate constant of the equation dNOC/dt = k2.[C].[nitrite]2. The rates correlated inversely with the basicity of the amino group. The stability of the alkylating activity was astonishingly high, both in acid and at neutral pH. Half-lives of 500, 200, and 30 min were determined for aspartic acid (pH 3.5), aspartame (pH 2.5), and glycine ethylester (pH 2.5). Values of 60, 15, and 2 min, respectively, were found at pH 7. It is concluded that rearrangement of the primary N-nitroso product to the ultimate alkylating agent could be rate-limiting. The potential of nitrosated alpha-amino acids to bind to DNA in vivo was investigated by oral gavage of radiolabelled glycine ethylester to rats, followed immediately by sodium nitrite. DNA was isolated from stomach and liver and analysed for radioactivity and modified nucleotides. No indication of DNA adduct formation was obtained. Based on an estimation of the dose fraction converted from glycine ethylester to the nitroso product under the given experimental conditions, the maximum possible DNA-binding potency of nitroso glycine ethylester is about one order of magnitude below the methylating potency of N-nitrosomethylurea in rat stomach. The apparent discrepancy to the in vitro data could be due to efficient detoxification processes in mammalian cells.

Alkylation↗
PubMed1989

[Follow-up study of affect, anxiety and aggression in inpatient treatment of anorexia nervosa].

Under the assumption of affect-defense (alexithymia) n = 20 anorexia nervosa patients being treated in the University Hospital of Hamburg-Eppendorf from 1980 to 1982 were examined with respect to their affects of anxiety and aggressivity by employing speach samples (three times a week)--according to Gottschalk-Gleser--and questionnaires (ANIS) during hospitalization and compared to n = 10 control patients from somatic clinics (orthopedics, surgery, gynecology). Particularly examined were emotional responses toward events during the in-patient period. As the most important result we found distinct affectivity in the anorexia patients that was partly stronger than that of the somatic control patients, so that (judged from our sample of anorexia nervosa) the hypothesis of alexithymia has to be rejected.

Adult↗
PubMed1988

Saturation mutagenesis of the Tn10-encoded tet operator O1. Identification of base-pairs involved in Tet repressor recognition.

Saturation mutagenesis of Tn10-encoded tet operator O1 was performed by chemical synthesis of 30 sequence variants yielding all possible point mutations of an operator half side. Their effect on Tet repressor binding was scored by an in-vivo repressor titration system. Tet repressor affinities of selected operator mutants were further characterized in vitro by dissociation rate measurements. The O1 sequence spans 19 base-pairs. Out of these, all 18 palindromic base-pairs are involved in Tet repressor recognition. The central base-pair does not contribute to sequence-specific binding of Tet repressor. At position 1 a pyrimidine residue is sufficient for maximal affinity to the repressor. At positions 2, 3 and 4, each mutation reduces repressor binding at least tenfold. Mutations at positions 5, 6, 7, 8 and 9 result in less drastic reductions of Tet repressor binding. Differential effects of mutations at a given position are used to deduce the chemical functions contacted by Tet repressor. The T.A to A.T transversion at position 9 increases Tet repressor affinity slightly, while all other mutations decrease repressor binding. The increased affinity of the wild-type tet operator O2 compared to wild-type O1 results from the addition of two favorable transversions at positions +/- 9 and an unfavorable T.A to C.G transition at position -7. Deletion or palindromic doubling of the central base-pair of the O1 palindrome reveals that the wild-type spacing of both operator half sides is crucial for efficient Tet repressor binding.

Base Sequence↗
PubMed1988

Differential regulation of the Tn10-encoded tetracycline resistance genes tetA and tetR by the tandem tet operators O1 and O2.

The Tn10-encoded tet transcriptional control sequence consists of bidirectional, overlapping promoters which are superimposed by a tandem operator arrangement. Three mutations have been constructed by oligonucleotide-directed mutagenesis which reduce binding of Tet repressor to either one or both of the tandem tet operators 1000-fold as determined by DNAseI footprinting in vitro. The affinity of Tet repressor for mutant tet operators is not affected by the presence of an already occupied neighbouring wild-type operator, indicating little or no cooperativity. The regulation of the divergently oriented tet promoters PA and PR by the tet operators O1 and O2 and Tet repressor provided in trans is determined using transcriptional fusions of the promoters to lacZ and galK indicator genes located with different polarity on the same plasmid. The results demonstrate that expression of the resistance gene tetA is regulated by Tet repressor bound to either O1 or O2. Expression of the repressor gene tetR is only marginally reduced when Tet repressor is bound to O2. This result is discussed with respect to the double promoter structure found for PR. Occupation of O1 with Tet repressor turns off transcription from PR completely. The implications of these findings on the establishment of tetracycline resistance upon induction are discussed.

Base Sequence↗
PubMed1988

Dimensions of the 'endangered self' in anorexia nervosa. Empirical study based on comparison with normal controls.

In addition to the diagnosis of symptoms we recently proposed the empirical analysis of psychodynamic levels; this paper aims at an empirical study of a third, and most essential, problem area: disturbances and/or regulatory processes of the self-system. Based on Deneke's newly developed questionnaire, 30 anorexia nervosa patients were examined, and then compared with 64 normal controls (female university students). A self-profile comprising 18 scales is used to graphically illustrate the disturbances. The primary deficits were found in the subscales of the 'endangered self' and the 'hypochondriac self', while the subscales of the 'classic narcissistic self' and the 'idealistic self' were found to be irrelevant. The significant self-system scales were then related to the symptomatology. The conclusion of the paper contains some therapy considerations.

Adolescent↗
PubMed1988

Clinical process studies on anxiety and aggressiveness affects in the inpatient therapy of anorexia nervosa.

Under the assumption of affect defense (alexithymia), 20 anorexia nervosa patients being treated in the University Hospital of Hamburg-Eppendorf were examined with respect to their affects of anxiety and aggressivity by employing speech samples (three times a week)--according to Gottschalk-Gleser--and questionnaires (ANIS) during hospitalization and compared to 10 control patients from somatic clinics (orthopedics, surgery, gynecology). Particular attention was given to emotional responses toward events during the inpatient period. The most important result found was the distinct affectivity in the anorexia patients, which was partly stronger than that of the somatic control patients, so that judging from our anorexia nervosa sample the hypothesis of alexithymia will have to be renewed and requires a more differentiated discussion.

Adult↗
PubMed1986

Tn10 tet operator mutations affecting Tet repressor recognition.

The effect of single base pair alterations of the Tn10 encoded tet operator on recognition of Tet repressor was studied in vivo using a repressor titration system and in vitro by dissociation rate determinations of the respective complexes. Both methods reveal that the two operators, O1 and O2, which are in a tandem arrangement in the wild type, are recognized with a two-fold different affinity when separated. Studies on synthetic operator sequences indicate that the Tet repressor binds with higher affinity to the non-palindromic O2 wildtype than to the respective palindromic sequences. The in vivo repressor titration system links the expression of lacZ to the affinity of tet operator to Tet repressor. It was used to isolate tet operator mutations with reduced affinity to the repressor. The in vivo and in vitro obtained results with these mutants agree quantitatively and indicate, that the GC base pairs at positions 2, 6, and 8 are involved in interaction with the Tet repressor. Their importance for recognition decreases in that order. Transitions at position 7 of the tet operator show smaller effects on recognition than transversions.

Drug Resistance, Microbial↗
PubMed1983

Control of expression of the Tn10-encoded tetracycline resistance genes. Equilibrium and kinetic investigation of the regulatory reactions.

The transposon Tn10-encoded TET repressor controls the expression of tetracycline resistance as well as its own synthesis. The antibiotic tetracycline functions as an inducer for both genes, which are transcribed in divergent directions from a common start area. The interaction of the TET repressor with the regulatory sequence of the tetracycline resistance operon is investigated by equilibrium and kinetic methods. The wild-type control sequence contains two nearly identical operators separated by only ten base-pairs. A deletion mutant lacking one of the operators is constructed by controlled digestion with exonuclease Bal31. It serves to prove that the two TET operators are each occupied by a TET repressor dimer in the wild-type tet operon regulatory sequence. The association constants are approximately identical for both operators between 10(12) and 10(13) M-1 as derived from kinetic data. The half-life of the TET repressor--tet operator complex is 12 minutes when competed with tet operator DNA and two minutes when competed with the inducer tetracycline. The dissociation of the repressor--operator complex has no apparent activation enthalpy but has an activation entropy of -320 J/mol K, indicating the involvement of solvent or counterion condensation. The dissociation rate constant of the tetracycline--TET repressor complex depends strongly on temperature. The activation enthalpy is 160 kJ/mol, indicating extremely strong binding of the drug. This result is discussed with respect to the necessary sensitivity of a regulated resistance gene. The native structure of the TET repressor is a dimer, as demonstrated by molecular exclusion chromatography. The elution behavior of the TET repressor--tetracycline complex indicates clearly that the repressor--inducer complex remains a dimer. The results are discussed with respect to the regulatory functions of the components.

Base Sequence↗
PubMed1976

[Evaluation of orthodontic cases by means of key-punch cards. 3. Data from follow-up examinations].

484 orthodontic patients were subjected to follow-up examination. The kind of treatment, the evaluation and the factors that are of importance to continuing successes and recurrences, respectively, are described. It is pointed out that the present communication and the two previous ones aim at illustrating that the orthodontic practitioner is able to document and evaluate his cases easily with the aid of key-word cards.

Activator Appliances↗
PubMed1976

[Relationship between frequency components of phonocardiography, vectorcardiography parameters and anatomic data].

Regarding heart volume, fundamental frequency of the first and second part of first heart sound (SI), vectorcardiographic parameters and constitutional data, the formerly found strong correlation between fundamental frequency of the first part of SI and heart volume was re-established. Heart volume guess got even better utilizing certain VCG-parameters, whereas constitutional measurement data gave no further approach. Correlations between VCG-data and fundamental frequencies of both parts of SI are referred to.

Adolescent↗
PubMed1975

[Interpretation of orthodontically treated by means of punched cards. 2. Data at the completion of treatment].

The authors analysed the key-word cards of 3245 terminated orthodontic cases. Statistical data were obtained about treatment results, therapeutical aids, duration of treatment and co-operation of the patients. These data give a survey on the achievements of the orthodontic practitioner, the choice of his methods and the utilization of his therapeutical aids. The authors could draw certain conclusions as to their own work in practice. Furthermore, they realized that the use of key-word cards permits to evaluate critically their achievements and to perform collective scientific studies.

Dental Records↗