Biomedical subjects

M Werner

Publications and source records attributed to M Werner.

At least 235 records · Page 13Linked to original sources

PubMed1995

Sex differences in hexachlorobutadiene biotransformation and nephrotoxicity.

Hexachlorobutadiene is nephrotoxic in rats, causing damage to the proximale tubules. Renal toxicity is presumed to be due to bioactivation by glutathione S-conjugate formation. Hexachlorobutadiene is conjugated with glutathione to S-(1,2,3,4,4-pentachlorobutadienyl)glutathione and further transformed to S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine (PCBC), which is N-acetylated in the liver to form N-acetyl-S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine (N-ac-PCBC). N-ac-PCBC is accumulated in the kidney. Renal acylases cleave N-ac-PCBC to PCBC, which is a substrate for renal cysteine conjugate beta-lyase and transformed to a reactive thioketene. Binding of this intermediate to renal macromolecules is most likely responsible for the nephrotoxicity of hexachlorobutadiene. In this study, we administered [14C]HCBD (200 mg/kg, per gavage) to male and female Wistar rats and compared the distribution and biotransformation. No significant differences in the disposition and rates of excretion of [14C]hexachlorobutadiene-derived radioactivity were observed between male and female rats. A portion of the dose (15.6 +/- 4.2) was excreted in the feces and 3.1% ( +/- 0.7) in the urine of male rats, and 11.1% ( +/- 3.8) of the dose was excreted in the feces and 4.5% ( +/- 1.5) in the urine of female rats. The major metabolite excreted by female rats was N-ac-PCBC, while small amounts of PCBC were also detected. In the urine of male rats, in addition to small amounts of PCBC and N-ac-PCBC, N-acetyl-S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine sulfoxide and [14C]hexachlorobutadiene were identified. Formation of the electrophile N-ac-PCBC sulfoxide must be considered as an alternative, beta-lyase-independent, bioactivation pathway for hexachlorobutadiene-derived S-conjugates. In isolated rat renal tubular cells, N-ac-PCBC sulfoxide induced a significantly more marked loss in cell viability than N-ac-PCBC. After identical doses of hexachlorobutadiene, the extent of necrosis to the pars recta of the proximal tubules was increased in male rats compared to the necrotic changes in female rats. While female animals showed a normal liver histology, male rats revealed slight toxic centrilobular liver changes in addition to the renal necroses. In vitro, only liver microsomes from male rats catalyzed the formation of N-ac-PCBC sulfoxide from N-ac-PCBC. Our results describe a new pathway of hexachlorobutadiene biotransformation in male rats, the formation of a mercapturic acid sulfoxide. The formation of this Michael acceptor may contribute to sex differences in hexachlorobutadiene nephrotoxicity.

Animals↗

PubMed1995

Calcifying solitary bone cyst: morphological aspects and differential diagnosis of sclerotic bone tumours.

Fourteen solitary bone cysts (SBC) with large areas of calcification (7 in the femur, 4 in the humerus, and 1 each in the pelvis, the tibia and the scapula) and 402 SBC from the Hamburg Bone Tumour Registry were reviewed in a retrospective study. The analysis was done with emphasis on the clinical, radiological and histological appearances. SBC are well known lesions, but calcifying SBC (CSBC) or extensive extragnathic cement-like bone productions are rare. The clinical and radiological differential diagnosis includes fibrous dysplasia, chondroma, low-grade chondrosarcoma and osteosarcoma. Bits of this cement-like matrix are detectable within the wall of approximately 70% (278 of 402) of SBC from the registry. CSBC are changed SBC. The intraoperative confirmation of the diagnosis on a frozen section by the bone pathologist leads to curettage which is currently the most common therapy in this benign lesion.

Adolescent↗

PubMed1995

The bcl-2/JH gene rearrangement is undetectable in Hodgkin's lymphomas: results from the German Hodgkin trial.

Ninety-one Hodgkin's lymphomas (HD), 52 non-Hodgkin lymphomas (NHL) and 33 specimens of non-neoplastic lymphatic tissues were investigated by polymerase chain reaction (PCR) for the presence of the bcl-2/JH gene rearrangement. The majority of the HD cases were drawn from the files of the German Hodgkin trial where diagnoses are established by a panel of four independent histopathologists. Using the very sensitive PCR method which detected 1 positive among 10000 negative cells, the bcl-2/JH gene rearrangement was found in 7/52 NHL and 3/16 tonsils with follicular hyperplasia, but in none of the 91 HD. The bcl-2 protein, however, was expressed by malignant cells of B and T cell lymphomas and by the giant tumour cells in 2/13 HD lymphocyte predominant, 11/28 HD nodular sclerosing I, 14/17 HD nodular sclerosing II, 10/27 HD mixed cellularity and 3/3 HD lymphocyte depleted. The bcl-2/JH rearrangement is thus independent of protein over-expression, the latter being found in all types of lymphomas. Our results do not confirm the findings of others who have detected the bcl-2/JH rearrangement in HD. These discrepancies may be explained by differences in choice of material, the gene rearrangement actually occurring in bystander cells but not in Reed-Sternberg or Hodgkin cells, or by contamination.

Chromosomes, Human, Pair 18↗

PubMed1995

Trisomy 1 and 8 occur frequently in hepatocellular carcinoma but not in liver cell adenoma and focal nodular hyperplasia. A fluorescence in situ hybridization study.

Conventional cytogenetic studies revealed gains and structural aberrations of chromosome 1 to be the most consistent chromosomal aberrations in hepatocellular carcinoma (HCC). We investigated touch preparations of eight HCC, five cholangiocellular carcinomas (CCC), five liver cell adenomas (LCA), four focal nodular hyperplasias (FNH) as well as nine specimens of normal liver tissue using fluorescence in situ hybridization (FISH) with centromere specific probes for chromosomes 1 and 8. Polysomies of chromosome 1, especially trisomy 1, were found in five of eight HCC and four of five CCC but in no normal liver tissue or benign tumour. Only three of seven cases of HCC revealed trisomy 8 whereas the five benign liver tumours and all normal liver tissues examined had disomy 8. Our results confirm conventional cytogenetic findings in terms of chromosome 1 aberrations in HCC although they are not specific for these types of malignant liver tumours. Since alpha-satellite probes were used in our study, only gains or losses including the centromeric regions of the chromosomes 1 and 8 could be detected. Nevertheless, our findings suggest that FISH may help in the differential diagnosis of malignant versus benign neoplasms of the liver.

Adenoma, Liver Cell↗

PubMed1995

[The new Hannover method of synthetic embedding of bone marrow. Cold polymerization of methylmethacrylate].

A patented low-temperature polymerization method for methylmethacrylate (MMA) infiltrated bone marrow biopsies is described: it has been developed from our previous MMA technique and is a patented procedure. Differences from the previous method are (1) removal of stabilizer from the MMA monomer before its application, (2) the use of a different starter, (3) avoidance of O2 influence during polymerization by means of vacuum exchange with N2, and (4) polymerisation in a water bath to draw off residual heat. After this procedure, all immunohistochemical reactions are possible provided that the previous fixation is adequate. The effects of different fixatives are reviewed briefly without detailed analysis. Technically, this plastic embedding can be performed at least as rapidly as the classic paraffin embedding after decalcification. The advantages over the latter method are: (1) the cells can be better differentiated because semi-thin sections can be made; (2) the immunoreactions can also be performed on the basis of semithin sections, which means they can be interpreted more easily; (3) morphometric analyses yield more reliable results because of the constant thickness of sections; (4) osteological examination of bone trabeculae, especially the search for mineralisation deficiencies, is possible; (5) the plastic embedding procedure is less dependent on individual instabilities in the quality of performance of the staff members involved. Furthermore, it is worth mentioning that the costs for additional equipment necessary remain below DM 100,000 including an excellent microtome.

Biomarkers, Tumor↗

PubMed1995

[Cytogenetics and molecular studies confirm the histopathologic diagnosis of chronic myeloproliferative diseases].

The histopathological classification of chronic myeloproliferative disorders can be supported by applying cytogenetics and molecular genetics to the analysis of bone marrow or blood cells, as demonstrated in 253 cases evaluated. The Philadelphia translocation (9;22) is the most important genetic parameter, being specific for chronic myeloid leukemia. Conventional methods for the detection of the t(9;22) are karyotyping and Southern blot analysis of the bcr gene. The newly established technique of fluorescence in situ hybridization (FISH) allows visualization of bcr-abl fusion even in non dividing cells. Molecular cytogenetics for t(9;22) yield results that are rapid and reliable as well as easily quantifiable.

Biopsy↗

PubMed1995

Reversed BCR/ABL rearrangement detected by FISH in Philadelphia negative chronic myelocytic leukemia.

We investigated leukemic cells from a patient with chronic myelocytic leukemia (CML) and a normal 46,XX karyotype. Molecular studies revealed rearrangement of the M-bcr region and formation of BCR/ABL fusion mRNA with b3a2 configuration. Fluorescence in situ hybridization (FISH) using the abl probe showed signal on both chromosomes 9 band q34, while the bcr probe hybridized to one chromosome 22 and to one chromosome 9. In this case, as in three other cases recently described (Hagemeijer et al. and Nachava et al.), the bcr/abl rearrangement is shown to be on 9q34, instead of the usual location on 22q11.

Chromosomes, Human, Pair 9↗

PubMed1995

Demonstration of the Philadelphia translocation by fluorescence in situ hybridization (FISH) in paraffin sections and identification of aberrant cells by a combined FISH/immunophenotyping approach.

The Philadelphia translocation was demonstrated by two-colour fluorescence in situ hybridization (FISH) in decalcified paraffin sections of bone marrow from patients with chronic myelogenous leukaemia. FISH was combined with immunocytochemical detection of different membrane-bound or cytoplasmic antigens. With this new technique, the cells bearing the 9:22 translocation can be identified morphologically, as well as immunocytochemically, in tissue sections.

Antigens, CD↗

PubMed1995

Simultaneous formation of inv dup(15) and dup(15q) in a girl with developmental delay: origin of the abnormal chromosomes.

Two de novo abnormal derivatives of chromosome 15, inv dup(15) and dup(15q) were found in a girl with developmental delay and mild dysmorphological signs. Fluorescence in situ hybridization, using DNA probes of the Prader-Willi/Angelman syndromes (PWS/AS) critical region and chromosome-15-specific alpha-satellite, combined with molecular analysis using dinucleotide repeat polymorphisms within the PWS/AS region and the parent-of-origin specific methylation sites at the locus D15S63, shed light on how the abnormal karyotype was formed. We suggest that a translocation between the two homologues of maternal chromosomes 15 resulted in the formation of dup(15q) and two reciprocal products: an acentric fragment of 15q that was lost and a centric fragment that underwent U-type reunion to form inv dup(15).

Angelman Syndrome↗

PubMed1995

Cardiorespiratory responses to acute hypoxia and hyperoxia in adult and neonatal spontaneously hypertensive and normotensive rats.

The aim of this study was to investigate whether there are differences between particular characteristics of breathing regulation in primary hypertensive and normotensive states which might indicate significant differences in arterial chemoreceptor reflex function. Under air-breathing conditions, minute ventilation was similar in adult spontaneously hypertensive rats (SHR) (50 +/- 2ml/min x 100 g) and in Wistar-Kyoto rats (WKY) (54 +/- 3 ml/min x 100 g) but significantly lower in randomly bred normotensive Wistar rats (NWR) (39 +/- 1 ml/min x 100 g). In seven-day-old rats minute ventilation was 10.5 +/- 1.2ml/min x 10 g in SHR and 10.2 +/- 1.4 ml/min x 10 g in WKY. Our data indicate that there is no elevation of the ventilatory drive under air-breathing conditions which can be unequivocally associated with primary hypertension in adult and neonatal animals. Acute inhibition of ventilation caused by hyperoxia indicated that oxygen dependent peripheral chemoreceptor activity during air-breathing was similar in SHR and normotensive controls both in the unanesthetized neonatal state and in anesthetized adult animals. No well defined association between the characteristics of the hypoxic ventilatory response and primary hypertension could be demonstrated although responses in adult anesthetized SHR tended to be faster and of higher amplitude than in normotensive controls.

Acute Disease↗

PubMed1995

The role of cytochrome P4503A1/2 in the sex-specific sulfoxidation of the hexachlorobutadiene metabolite, N-acetyl-S-(pentachlorobutadienyl)-L-cysteine in rats.

Hexachlorobuta-1,3-diene (HCBD) is a selective nephrotoxin and a potent nephrocarcinogen in rodents. Its toxicity and carcinogenicity is based on a multistep bioactivation pathway. Glutathione conjugation seems to be the only bioactivation pathway for HCBD leading to reactive intermediates, which are thought to be responsible for the observed nephrotoxic effects. Recent in vivo studies revealed a novel urinary metabolite in male, but not female, rats after administration of [14C]HCBD. This metabolite was identified as (E)-N-acetyl-S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine-sulfoxide (N-Ac-PCBC-SO). The objective of this study was to elucidate the enzyme(s) involved in this particular oxidation and to find an explanation for the sex differences in the formation of N-Ac-PCBC-SO. Both cytochrome P450 and flavin-containing monooxygenases (FMO) may catalyze the oxidation of N-Ac-PCBC-SO. The use of various competitive and allosteric inhibitors of cytochrome P450 and FMO (i.e. metyrapone, N-benzylimidazole, thiobenzamide, CO, n-octylamine, and heat inactivation studies) showed that the sulfoxidation of (E)-N-acetyl-S-(1,2,3,4,4-pentachlorobutadienyl)- L-cysteine is catalyzed by cytochrome P450 enzymes. In microsomes from male rats pretreated with pyridine, phenobarbital, and dexamethasone, an increase in the rates of sulfoxide formation was only seen in microsomes from dexamethasone- and phenobarbital-induced animals. Moreover, troleandomycin, a selective chemical inhibitor for enzymes of the cytochrome P4503A family, inhibited sulfoxide formation by > 80%. Correlation of sulfoxide formation with testosterone 6 beta-hydroxylation, a marker of cytochrome P4503A1/2 in the rat, underlined the finding that cytochrome P4503A is the predominant cytochrome P450 responsible for this particular oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcysteine↗

PubMed1995

A model for medical decision making and problem solving.

Clinicians confront the classical problem of decision making under uncertainty, but a universal procedure by which they deal with this situation, both in diagnosis and therapy, can be defined. This consists in the choice of a specific course of action from available alternatives so as to reduce uncertainty. Formal analysis evidences that the expected value of this process depends on the a priori probabilities confronted, the discriminatory power of the action chosen, and the values and costs associated with possible outcomes. Clinical problem-solving represents the construction of a systematic strategy from multiple decisional building blocks. Depending on the level of uncertainty the physicians attach to their working hypothesis, they can choose among at least four prototype strategies: pattern recognition, the hypothetico-deductive process, arborization, and exhaustion. However, the resolution of real-life problems can involve a combination of these game plans. Formal analysis of each strategy permits definition of its appropriate a priori probabilities, action characteristics, and cost implications.

Artificial Intelligence↗

PubMed1995

Karyotype findings and molecular analysis of the bcr gene rearrangement supplementing the histologic classification of chronic myeloproliferative disorders.

BACKGROUND: Histologic examination of bone marrow is important in establishing diagnoses among chronic myeloproliferative disorders (CMPD). Only a few studies, however, have compared cytogenetic or molecular genetic findings to histopathology in CMPD. Diverging results on the presence of the Ph1-translocation in patients with myelofibrosis have been reported. EXPERIMENTAL DESIGN: Cytogenetic studies and molecular analysis of the bcr gene were performed in bone marrow cells of patients with CMPD simultaneously with histopathologic examination of plastic-embedded bone marrow biopsies. RESULTS: The Ph1-chromosome was found in 120/128 (93%) cases with histopathologic diagnosis of chronic myeloid leukemia (CML), including a notable proportion of cases with an increase of megakaryocytes and/or myelofibrosis; the latter was associated with a significant increase of chromosome aberrations, in addition to Ph1. Among those additional changes in myelofibrosis of Ph1-positive CML were del (13q) and t(1;11) in one case each. A bcr gene rearrangement was detected in 92% (24/26) of the CML cases examined. All other groups of CMPD, comprising cases of myelofibrosis and unclassifiable cases, were Ph1-negative by both cytogenetics (n = 102) and molecular analysis (n = 18). Karyotype changes associated with myelofibrosis in various CMPD concerned mainly balanced translocations involving 1p36 and 11q11, deletions of 5q13-34, 3p, 11q23, 13(q12,q22), and 20q12 as well as gain of 1q and trisomy 3, 8, 19, or 21. In histologically unclassifiable CMPD, karyotyping provided additional information for the differential diagnosis. CONCLUSIONS: The correlation of cytogenetic findings and histopathologic features is helpful in confirming or supporting histopathologic diagnoses and in characterizing new marker chromosomes in CMPD.

Aged↗

PubMed1994

Directing transcription of an RNA polymerase III gene via GAL4 sites.

A yeast chimeric RNA polymerase III transcription system was constructed to explore the ordered, multistep process of gene activation in vivo. A promoter-deficient U6 RNA gene harboring GAL4-binding sites could be reactivated by fusing the GAL4 DNA-binding domain to components of the general transcription factor TFIIIC (tau) or TFIIIB. Expression of chimeric tau 138 or tau 131 (but not tau 95) subunits activated transcription from GAL4-binding sites located at various positions, including upstream of or within the gene. The function(s) of the B block binding domain of TFIIIC was provided by the fused GAL4-(1-147) domain. The GAL4-(1-147)-TFIIIB70 fusion protein acted at a distance like an activator of transcription. In contrast, none of the 10 different GAL4-(1-147)-polymerase subunit fusions was able to induce transcription, suggesting that RNA polymerase recruitment is not sufficient to initiate transcription.

Base Sequence↗

PubMed1994

Effects of antigen retrieval by microwave heating in formalin-fixed tissue sections on a broad panel of antibodies.

Formaldehyde fixation of biopsy specimens for routine purposes has often been held responsible for the poor reproducibility of immunohistochemical studies. Recently, antigen retrieval (AGR) using microwave irradiation was described as a potential tool to enhance immunostaining. A comparison of conventional staining and staining after microwave heating was performed for 52 markers, using tissues fixed in formaldehyde for 24 h, 1 to 6 weeks and 3 years respectively, as well as consultant case material. After adequate duration of fixation (24 h), only a few markers (17%) showed better results after AGR, but this percentage was increased to 50% when tissues were fixed for longer periods. Maximal enhancement was obtained in the group of consultant cases (58% of tested markers demonstrated better staining results), in which the period of fixation and tissue processing was unknown. To achieve reliable enhancement with AGR, continuous heating (100 degrees C) should not be shorter than 20 min. In conclusion, AGR may become the most important tool to simplify and equalize immunohistochemical techniques, if critically evaluated.

Antibodies, Monoclonal↗

PubMed1994

[Cytogenetics in addition to histopathology exemplified by myelodysplastic syndrome].

The value of cytogenetics performed simultaneously with histopathology was evaluated in patients with myelodysplastic syndrome (MDS). Clonal karyotype changes of the bone marrow cells supporting the histological diagnosis were found in 38/69 cases (55%). The chromosome aberrations, especially complex changes, were significantly correlated to distinct histopathological findings such as atypias of the haematopoietic cell lines and myelosclerosis. Complex karyotype changes were further associated with short survival of the MDS patients. Our results demonstrate that cytogenetic analyses are helpful in supplementing the histopathological diagnoses. Recent developments in molecular cytogenetics even allow the detection of chromosomal aberrations in non-dividing cells from cytological preparations or tissue sections which may become available for routine diagnosis.

Aged↗

PubMed1994

[Micro-callus formation of spongiosa. An up to now underestimated repair mechanism of the skeletal system].

Microcallus formations are demonstrable in nearly all cancellous bones by means of suitable preparation techniques. Histologically, these structures are immature fibrous bone formed in local overloaded parts of the trabeculae. Using a preparation technique that allows combined two- and three-dimensional analysis, 26 normal human spines and 11 osteoporotic spines were investigated for microcallus. Microcallus formations occur frequently in people over 45 years of age. They are mainly localized in the lower thoracic and lumbar spine and occur significantly more frequent in females than in males. The number of microcallus formations depends more on the microarchitecture of the cancellous bone than on individual trabecular parameters. In about 33% of cases microfractures are demonstrable in the centre of the microcallus formation. In non-invasive studies the bone mass could be misinterpreted due to microcallus. Although it indicates instability of the bone structure, microcallus formation is not a purely negative mechanism. It stabilizes and regenerates the bone tissue. Furthermore, complete new trabeculae can be formed due to bridges of microcallus between residual trabeculae. Osteoporosis is not the result of an inability to form microcallus.

Adolescent↗

PubMed1994

[Osteosarcoma--apoptosis and proliferation. Study of bcl-2 expression].

The relationship between the growth of tumors and the expression of the protooncogene Bcl-2 could be shown in epithelial tumors. A bcl-2 expression leads to a prolonged cell survival due to an inhibition of apoptosis. The potential meaning of bcl-2 expression in mesenchymal tumors remains still unknown. The fact, that the heterogenous group of osteosarcoma is not sufficiently characterized at present, suggested to investigate the bcl-2 expression in osteosarcoma. Thus, immunohistochemistry was used to analyze 47 specimens of different osteosarcomas of 36 patients. Sixteen cases (46%) showed a strong expression of bcl-2 and 13 cases (35%) were moderately positive for bcl-2. Seven cases (19%) were negative for bcl-2. The heterogenous, negative up to strong expression of bcl-2 yield clues, that the Bcl-2 controlled regulation of programmed cell death could be an important factor of cellular kinetics. Additionally the cellular proliferation rate was determined with the monoclonal antibody MIB 1, directed against the Ki-67 epitope. The data of bcl-2 expression and cellular proliferation rate lead to a classification correlating with the histological classification. To verify the importance of apoptosis in the genesis of mesenchymal tumors and whether Bcl-2 may play an important role as a predictive factor for the prognosis of osteosarcoma, further investigations will be needed.

Adolescent↗