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K Becker

Publications and source records attributed to K Becker.

At least 181 records · Page 10Linked to original sources
PubMed1999

Gq/11-coupled receptors and protein synthesis in rat cardiomyocytes: role of Gi-proteins and protein kinase C-isozymes.

Our recent findings indicate that, in rat neonatal ventricular cardiomyocytes, endothelin-1 (ET-1) induces increases in the rate of protein synthesis in a partly pertussis toxin (PTX)-sensitive manner, and that angiotensin II-evoked increases in the rate of protein synthesis are brought about via local secretion of ET-1. The aim of this study was to find out: (1) whether noradrenaline (NA) and the thromboxane A2 (TXA2)-mimetic U 46619-induced increases in the rate of protein synthesis may be also partly PTX-sensitive and/or mediated by ET-1, and (2) whether the growth-promoting effects of NA and U 46619 as well as ET-1 might involve activation of the same set of protein kinase C (PKC) isozymes. For this purpose we first studied the effects of NA and U 46619 on inositol phosphate (IP)-formation (assessed as accumulation of total [3H]IPs in myo-[3H]inositol prelabelled cells) and on the rate of protein synthesis (assessed as [3H]phenylalanine incorporation) (1) in the presence and absence of the ET(A)-receptor antagonist BQ-123, and (2) in nontreated and PTX-pretreated cells. Second, we assessed the effects of the PKC-inhibitors bisindolylmaleimide I and Gö 6976 and of phorbol-12-myristate-13-acetate (PMA; 1 microM overnight)-pretreatment on U 46619-, NA- and ET-1-induced increases in the rate of protein synthesis. NA (0.01-10 microM) concentration-dependently increased IP-formation (maximum increase: 115-/+23% above basal, n=4) and [3H]phenylalanine incorporation (maximum increase: 40+/-3% above basal, n=20). Both responses were antagonized by the alpha1-adrenoceptor antagonist prazosin (1 microM), but were not significantly affected by BQ-123 (1 microM). U 46619 (0.01-100 microM) concentration-dependently increased IP-formation (maximum increase: 89+/-12% above basal, n=8) and [3H]phenylalanine incorporation (maximum increase: 33+/-4% above basal, n=16). Both responses were slightly but significantly antagonized by the TP-receptor antagonist SQ 29548 (1 microM), but were not affected by BQ-123 (1 microM). Pretreatment of the cardiomyocytes with 250 ng ml(-1) PTX overnight did not significantly affect NA- and U 46619-evoked increases in IP-formation and [3H]phenylalanine incorporation. The PKC-inhibitor bisindolylmaleimide I (5 microM) as well as pretreatment of the cells with PMA (1 microM) significantly reduced the effects of NA, U 46619 and ET- I on the rate of protein synthesis; in contrast, the PKC-inhibitor Gö 6976 (5 microM) was without any effects. We conclude that, in rat neonatal ventricular cardiomyocytes, stimulation of Gq/11-coupled receptors increases the rate of protein synthesis; this involves activation of the same PKC-isozymes (very likely PKC-delta and/or -epsilon). NA and U 46619 cause their growth-promoting effects in a PTX-insensitive manner; ET-1 is not involved in their effects.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1999

Nutritional studies on rats and fish (carp Cyprinus carpio) fed diets containing unheated and heated Jatropha curcas meal of a non-toxic provenance.

Unheated and heated (121 degrees C, 66% moisture; 15, 30 and 45 min) Jatropha meals of non-toxic provenance from Veracruz state in Mexico were evaluated using rats and fish. With rats, the weight gain was highest for the casein diet followed by heated (30 min; only this treatment was studied using rats) and unheated Jatropha meal containing diets. The protein efficiency ratio (PER) for unheated and heated Jatropha meal containing diets was 37 and 86%, respectively, of the casein diet. On the other hand, the body weight gain, PER and feed conversion ratio of fish were statistically similar for unheated and heated (15, 30 and 45 min) Jatropha meal containing diets fed for a period of 35 days. Although these parameters were statistically similar for the unheated and heated Jatropha meal containing diets, the body weight gain, PER and protein productive value were highest and the feed conversion ratio lowest with 15 min heated Jatropha meal, suggesting that the heat treatment for 15 min is optimal for the meal. Trypsin inhibitor and lectin activities decreased drastically (>83 and 99%, respectively) after 30 and 45 min of heat treatment and after 15 min, the residual lectin activity was negligible and the residual trypsin inhibitor activity was 34%. These results, together with the nutritional parameters investigated, imply that Jatropha trypsin inhibitors and lectins do not have any adverse effects on carp at least up to 35 days of feeding. The nutritional value of Jatropha meal of the non-toxic provenance is high, and potential exists for its incorporation into the diets of monogastrics, fish and possibly humans.

Animal Nutritional Physiological Phenomena↗
PubMed1999

Use of polymerase chain reaction for postmortem diagnosis of malaria.

Delay or failure in diagnostic or therapeutic management of Plasmodiumfalciparum malaria may result in avoidable deaths, often incurring medicolegal procedures. Advanced postmortem autolytic processes and putrefication may thwart malaria diagnosis by traditional microscopic and histologic examinations. The authors describe the usefulness of polymerase chain reaction to confirm postmortem diagnosis of malaria.

Adolescent↗
PubMed1999

Antigen trafficking and accessory cell function in respiratory epithelial cells.

We investigated accessory cell function, antigen (Ag) trafficking, and uptake of immune complexes in isolated nasal epithelial cells (NEC) and airway epithelial cells (AEC), as well as in the two respiratory epithelial cell lines A549 and BEAS-2B. The NEC and AEC were capable of supporting Ag-specific as well as phytohemagglutinin-induced and anti-CD3 antibody-induced T-cell proliferation. We colocalized fluorescein isothiocyanate (FITC)-labeled Ags with human leukocyte antigen (HLA)-DR in A549 and BEAS-2B, utilizing laser confocal microscopy. Respiratory epithelial cells stimulated and unstimulated with interferon (IFN)-gamma were pulsed with FITC-labeled Ags for varying periods and evaluated for their ability to internalize Ag. In the unstimulated cells, intracellular punctate staining was evident at 60 min and persisted up to 120 min. In the IFN-gamma-stimulated cells (100 U/ml for 48 h), uptake occurred at 30 min, was maximal at 60 min, and diminished at 120 min. We conducted kinetic studies in the A549 and BEAS-2B cells, utilizing electron microscopy with colloidal gold-conjugated Ags (Au-OVA). At 15 min, Au-OVA was evident in the early compartments resembling the compartment of uncoupling of receptor and ligand. At 30 min, multivesicular bodies were labeled with Au-OVA, and by 60 min Au-OVA was present in the primary and secondary lysosomes. The FITC-labeled Ags colocalized with an early endosomal marker (anti-cathepsin D), a late endosomal marker (M6PR), a lysosomal marker (CD63), and with 3-(2, 4-dinitroanilino)-3'-aminomethyldipropylamine, a marker of acidic vesicles. The BEAS-2B and A549 cells, and NEC and AEC, expressed surface Fcgamma receptor and internalized IgG immune complexes. The NEC and AEC also expressed the costimulatory molecules CD80 and CD86 as determined with flow cytometry, the reverse transcription-polymerase chain reaction for RNA, and immunohistochemistry, and T-cell proliferation could be blocked by treating NEC and AEC with anti-CD80 and anti-CD86 antibodies. Our findings suggest that respiratory epithelial cells may have a role in local Ag presentation.

Antigen-Antibody Complex↗
PubMed1999

Gender and risk of autoimmune diseases: possible role of estrogenic compounds.

A striking common feature of many autoimmune diseases in humans and experimental animals, despite differences in pathology, is that females are highly susceptible to autoimmune conditions compared to males. In several animal models, estrogens promote, whereas androgens abrogate, B-cell-mediated autoimmune diseases. To understand mechanisms by which estrogens regulate autoimmunity, it is first necessary to decipher estrogen effects on the normal immune system. Estrogen treatment of nonautoimmune mice diminished lymphocyte numbers in both developmental and mature lymphoid organs. Estrogen dysregulated T- and B-cell balance by inducing selective T-cell hypoactivity and B-cell hyperactivity. Even though estrogen did not alter the relative percentages of splenic T-cell subsets, splenic lymphocytes had a reduced proliferative response to T-cell stimulants and were refractory to rescue from activation-induced apoptosis compared to cells from placebo-treated mice. In contrast, estrogen induced B-cell hyperactivity (promoted autoantibodies to double-stranded DNA and phospholipids, increased numbers of plasma cells, and increased autoantibody yield per B cell). Note that treatment of normal mice with estrogen can alter T- and B-cell regulation and overcome B-cell tolerance to result in autoimmunity in normal individuals. Could environmental estrogens promote some human autoimmune disorders? Is there a link between environmental estrogens and autoimmune disorders, especially since these disorders are reported possibly more frequently? These provocative questions warrant investigation. Our findings on immunomodulatory effects may serve as a benchmark to examine whether endocrine-disrupting chemicals will have similar immunologic effects.

Animals↗
PubMed1999

Cardiotoxicity of the antiproliferative compound fluorouracil.

The antimetabolite fluorouracil (5-FU) is frequently administered for chemotherapy of various malignant neoplasms. The drug is well known for its adverse effects involving bone marrow, skin, mucous membranes, intestinal tract and central nervous system, whereas its cardiotoxicity is less familiar to clinicians. The pathophysiology of fluorouracil-associated cardiac adverse events is controversial and conclusions are based on clinical studies and case reports more than on solid experimental evidence. While clinical and electrocardiographic features suggest myocardial ischaemia as a main aetiological factor, possibly induced by coronary vasospasm, histomorphological and biochemical studies indicate a more direct drug-mediated cytotoxic action. Estimates of the overall incidence of fluorouracil cardiotoxicity have varied widely from 1.2 to 18% of patients. Patients may present with angina-like chest pain, cardiac arrhythmias or myocardial infarction. There is no unequivocally effective prophylaxis or treatment in this syndrome. Once fluorouracil administration is discontinued symptoms are usually reversible, although fatal events have been described. The overall mortality rate has been estimated to be between 2.2 and 13.3%. There is a high risk of relapse when patients are re-exposed to this drug following previous cardiac incidents. From the present data it is concluded that cardiotoxicity is a relevant but underestimated problem in fluorouracil treatment. Since the mechanisms of fluorouracil-associated cardiotoxicity are not yet fully understood, all patients undergoing this chemotherapy have to be carefully evaluated and monitored for cardiac risk factors and complaints. After cardiotoxic events, fluorouracil should definitely be withdrawn and replaced by an alternative antiproliferative regimen.

Antimetabolites, Antineoplastic↗
PubMed1999

[Cavernous hemangioma of the rectum--a rare differential per anal hemorrhage diagnosis].

A 19-year-old woman suffered from recurrent peranal hemorrhage. Over a period of five years she was treated under the suspicion of ulcerative colitis. After a sigmoid resection with a colostomy, proctectomy with an end colostomy followed due to recurrent intractable peranal hemorrhage. Histology of the specimen showed surprisingly a hemangioma of the rectum. Thereafter reconstruction was performed by colopouchanal anastomosis. Afterwards the patient was free of disease and had a good stool-continence. Stool-frequency was twice daily. The second case consisted in a 27-year-old woman who underwent emergency sigmoidectomy due to massive peranal hemorrhage. Here as well diagnosis was a hemangioma of the sigmoid. One year after the first operation the patient had a recurrence of peranal bleeding again due to rectal hemangioma. Since endoscopy and endosonography confirmed a rectal hemangioma a rectal exstirpation with a colopouchanal reconstruction was performed successfully. The reviewed literature shows including the two presented cases a total of 81 cases with rectal hemangiomas. Because of the good results concerning function and morbidity the therapy of choice is rectal exstirpation with colopouchanal reconstruction.

Adult↗
PubMed1999

Purine quantification in digesta from ruminants by spectrophotometric and HPLC methods.

The method of Zinn & Owens (1986; Canadian Journal of Animal Science 66, 157-166), based on release of purine bases by HClO4 followed by their precipitation with AgNO3, was used to study recovery of purines from lyophilized rumen microbial or Escherichia coli preparations added to matrices such as cellulose, starch and neutral-detergent fibre. The recovery of purines was poor (approximately 50%). Under the hydrolysis conditions (12 M-HClO4, 90-95 degrees for 1 h) used in the method of Zinn & Owens (1986), the recovery of purines from the rumen microbial preparations added to matrices measured using an HPLC method was 95-102%, suggesting that the lower recovery of purines in the method of Zinn & Owens (1986) was not due to incomplete hydrolysis of nucleic acids. Using the HPLC method, adenine and allopurinol (an internal standard) were found to be heat-labile as substantial destruction was observed on heating at 121 degrees. On the other hand, another commonly used internal standard, caffeine, was stable at 121 degrees. A complete hydrolysis of nucleic acids from the rumen microbial preparation was observed with 2.5 ml 0.6 M-HClO4 in a total volume of 3 ml (0.5 M-HClO4 during hydrolysis) at 90-95 degrees for 1 h, and under these conditions adenine, guanine, allopurinol and caffeine were stable. Moreover, under these milder hydrolysis conditions, the recovery of purine bases from the rumen microbial or E. coli preparations added to matrices ranged from 92 to 108% using the method of Zinn & Owens (1986). Based on the results, changes in hydrolysis conditions have been proposed for accurate determination of purine bases using spectrophotometric or HPLC methods.

Adenine↗
PubMed1999

Fecal excretion of alpha 2-macroglobulin: a novel marker for disease activity in patients with inflammatory bowel disease.

BACKGROUND: Quantification of fecal alpha 1-antitrypsin (AAT) excretion is established for estimation of enteric protein loss and assessment of disease activity in inflammatory bowel disease (IBD). In contrast, little is known about prevalence, course, and clinical significance of intestinal leakage of larger-size serum antiproteinases in these disorders. SUBJECTS AND METHODS: Firstly, 23 IBD patients (Crohn's disease, CD, n = 17, and ulcerative colitis, UC, n = 6) were examined at 34 independent episodes (relapse, n = 16, remission, n = 18) for parallel serum and fecal alpha 2-macroglobulin (AMG) and AAT concentrations by standard immunonephelometry, and compared to 40 healthy controls. From these IBD patients, secondly, a random cohort of twelve individuals (9 CD, 3 UC) was prospectively followed for those parameters at about monthly intervals for 7-14 (median 10.5) months. RESULTS: The threshold of detection for fecal AMG concentration was about 0.06 mg per gram dry weight stool (mg/g dws) under the present analytical conditions. While in healthy subjects fecal AMG was demonstrated at very low levels only (< or = 0.07 mg/g dws), it was found in CD and UC patients at elevated concentrations of < 0.06-3.18 (median 0.17) and < 0.06-1.91 (median 0.40) mg/g dws, respectively. Fecal AMG contents were more increased in active IBD compared to quiescent disease (p = 0.03), and they correlated to Crohn's Disease Activity Index in CD patients (p = 0.05), while not to Clinical Activity Index in UC individuals (p = 0.46). Post hoc evaluation of follow-up data suggested two distinct groups of IBD patients either with or without consistently detectable fecal AMG excretion, with the first ones exhibiting a more active clinical course than the latter ones (p < or = 0.02). CONCLUSIONS: AMG is excreted in feces of healthy subjects in traces only, while its stool concentration is largely increased in IBD patients where it reflects clinical disease activity. This novel stool parameter may be of potential value in the diagnostic and prognostic management of these individuals.

Adolescent↗
PubMed1999

[1998 environment survey--initial results].

In close connection with the German National Health Interview and Examination Survey 1998, a third round of the German Environmental Survey (GerES III) was carried out using a random subsample of about 4,500 subjects, which are representative for the German population aged 18 to 69 years. The GerES was carried out by the Federal Environmental Agency on behalf of the Federal Ministry for Environment, Nature Conservation and Reactor Safety. The participants had to undergo an examination in human-biomonitoring. An environmental questionnaire was used to get exposure-related information. Preliminary results indicate a reduction of the body burden with metals in 1998 compared with 1990/92. However, some individuals showed elevated values. For those people health effects are possible or cannot be excluded with sufficient certainty. Using the results of GerES III it will be possible for the first time to establish reference values for organochlorine compounds on a representative data basis. The examination of the tap water used in the subjects households shows that the limit and guideline values of the German Drinking Water Ordinance have not always been met in 1998. This holds especially for lead, copper, and zinc which are being used as pipe-material for domestic plumbing.

Adolescent↗
PubMed1998

[Skin diseases associated with chronic hepatitis C].

The authors are discussing hepatic and extrahepatic pathologic processes caused by hepatitis C virus (HCV) infection and they focus their interest to the skin disorders appearing in the presence of chronic, active HCV infections. The trigger of the immunologic processes leading to dermatologic manifestations are the activated T cells (CD8 + cytotoxic T lymphocytes), cytokins, and also the expansion of certain B cells. Pathologic immunologic phenomena may initiate various dermatologic manifestations. Immunoglobulins, immuncomplexes generated by the disease itself are manifested as various forms of cutan vasculitis. In the present series of patients (pts), HCV related skin disorders known from the literature were diagnosed in eleven cases and they were representing 7 different disease entities. These were palpable purpura (3 pts), urticaria, prurigo and alopecia areata (2-2 pts), lichen ruber planus, pruritus and vitiligo (1-1 patient respectively). The case reports of 2 pts, one with palpable purpura (vasculitis purpurica), one with prurigo and vitiligo are presented in details.

Adult↗
PubMed1998

Transgenic systems in studies on genotoxicity of alkylating agents: critical lesions, thresholds and defense mechanisms.

Transgenic systems, both cell lines and mice with gain or loss of function, are being used in order to modulate the expression of DNA repair proteins, thus allowing to assess their contribution to the defense against genotoxic mutagens and carcinogens. In this review, questions have been addressed concerning the use of transgenic systems in elucidating critical primary DNA lesions, their conversion into genotoxic endpoints, low-dose effects, and the relative contribution of individual cellular functions in defense. It has been shown that the repair protein alkyltransferase (MGMT) is decisive for protection against methylating and chloroethylating compounds. Protection pertains also to tumor formation, as revealed by the response of MGMT transgenic and knockout mice. Overexpression of genes involved in base excision repair (N-methylpurine-DNA glycosylase, apurinic endonuclease, DNA polymerase beta) is in most cases not beneficial in increasing the protection level, whereas their down-modulation or inactivation increases cellular sensitivity. This indicates that non-repaired base N-alkylation lesions and/or repair intermediates possess genotoxic potential. Modulation of mismatch repair and poly(ADP)ribosyl transferase has also been shown to affect the cellular response to alkylating agents. Furthermore, the role of Fos, Jun and p53 in cellular defense against alkylating mutagens is discussed.

Alkylating Agents↗
PubMed1998

Human placenta thioredoxin reductase. Isolation of the selenoenzyme, steady state kinetics, and inhibition by therapeutic gold compounds.

Human thioredoxin reductase is a pyridine nucleotide-disulfide oxidoreductase closely related to glutathione reductase but differing from the latter in having a Cys-SeCys (selenocysteine) sequence as an additional redox center. Because selenoproteins cannot be expressed yet in heterologous systems, we optimized the purification of the protein from placenta with respect to final yield (1-2 mg from one placenta), specific activity (42 units/mg), and selenium content (0.94 +/- 0.03 mol/mol subunit). The steady state kinetics showed that the enzyme operates by a ping-pong mechanism; the value of kcat was 3330 +/- 882 min-1, and the Km values were 18 microM for NADPH and 25 microM for Escherichia coli thioredoxin. The activation energy of the reaction was found to be 53.2 kJ/mol, which allows comparisons of the steady state data with previous pre-steady state measurements. In its physiological, NADPH-reduced form, the enzyme is strongly inhibited by organic gold compounds that are widely used in the treatment of rheumatoid arthritis; for auranofin, the Ki was 4 nM when measured in the presence of 50 microM thioredoxin. At 1000-fold higher concentrations, that is at micromolar levels, the drugs also inhibited human glutathione reductase and the selenoenzyme glutathione peroxidase.

Antirheumatic Agents↗