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D Becker

Publications and source records attributed to D Becker.

At least 127 records · Page 7Linked to original sources
PubMed1996

Morphological and biochemical changes in neurons: apoptosis versus mitosis.

Apoptosis and mitosis are often thought to share certain morphological similarities and therefore to be regulated by similar sets of enzymes. In this study, the Golgi apparatus and nuclear lamina were examined in PC12 cells and rat superior cervical ganglion neurons undergoing apoptosis in response to withdrawal of nerve growth factor or addition of staurosporine. We found that the Golgi apparatus disperses during apoptosis, without obvious degradation, in a manner similar to that occurring in mitosis. In contrast, the nuclear lamina did not become completely solubilized during apoptosis, as occurs in mitosis, but remained as a distinct structure around the nucleus, although some degradation of nuclear lamins was seen. To assess the integrity of the nuclear envelope, fluorescent probes were introduced into the cytoplasm of live and dying cells. High molecular weight tracers were still excluded from the nuclei of apoptotic cells, demonstrating the continued existence of a functional nuclear barrier. These data suggest, therefore, that cell death is unlikely to occur simply as a result of inappropriate activation of cell cycle enzymes.

Animals↗
PubMed1996

An approach to predictive testing of contact sensitizers in vitro by monitoring their influence on endocytotic mechanisms.

Endocytotic activation of epidermal Langerhans cells (LC) by immunogenic haptens is an early event during development of allergic contact dermatitis. In this work a fast and objective flow-cytometric assay for predictive in vitro testing of contact sensitizers by monitoring their influence on endocytotic mechanisms in murine LC was developed. Epidermal cell suspensions were labelled with a monoclonal antibody directed to MHC class II molecules and pH-sensitive fluorochrome-coupled second-step reagents. For untreated LC a significant quenching of fluorescence intensity by internalization of the MHC-antibody complexes into acidic compartments was noticed. Similar results were obtained in the presence of irritants, the lectin concanavalin A and the phorbol ester phorbol 12-myristate 13-acetate. In contrast stimulation with several well-defined sensitizing compounds resulted in partial conservation of the fluorescence intensity due to the internalization of the labelled complexes into less acidic compartments. Monitoring this modulation of endocytosis is an effective in vitro method to test for properties typical for moderate and strong contact sensitizers. It will help to assess the risk of unknown chemicals to act as haptens and should be useful for restriction of animal experimentation in this field.

Animals↗
PubMed1996

Further insights into transsexualism.

Transsexualism is a challenging entity posing diagnostical, etiological, ethical and moral questions with no general consensus of opinion and a controversial management policy. The present article tries to deal with these questions by drawing a parallel with another psychiatric syndrome in which there is also a disturbance in body image, namely anorexia nervosa. The parallel is at the level of clinical presentation, psychodynamic etiology and their common socioepidemic dimension.

Anorexia Nervosa↗
PubMed1996

Yields of OH in gamma-irradiated DNA as a function of DNA hydration: hole transfer in competition with OH formation.

In this work, we report the yields of hydroxyl radicals, as G values and "destruction constants," in the DNA hydration shell as a function of the level of hydration. Electron spin resonance spectroscopy of gamma-irradiated DNA at low temperatures is employed for detection of the hydroxyl radical. Due to the glassy nature of the DNA hydration layer at low temperature, the hydroxyl radical gives a broad ESR resonance which is easily distinguished from the hydroxyl radical in a polycrystalline ice phase; thus .OH in both glassy and ice regions is quantified. Three regimes of radiological behavior for waters of hydration in DNA are found. For the first approximately 9 waters/nucleotide (which are glassy), no significant amounts of .OH are found, suggesting hole transfer to DNA. The second regime of hydration waters comprises up to about 12 additional glassy waters/nucleotide (gamma = 21). In this regime, substantial amounts of glassy .OH are found, suggesting that only a few holes which escape recombination in spurs charge-transfer to the DNA. In these two glassy regimes no trapped electrons are found, which is in accord with previous work that has reported that all electrons which do not undergo recombination in spurs transfer to DNA. The third regime of hydration water is comprised of bulk (or bulk-like) polycrystalline ice which forms when levels of hydration over 21 waters/nucleotide are reached. These waters form a separate phase from the DNA/glassy-water system, and neither hole nor substantial electron transfer to the DNA occurs; .OH in this ice phase is observed with G values that vary slightly with the amount of water in the ice phase, but which are close to the values found for pure ice.

Animals↗
PubMed1996

Radiation-induced DNA damage as a function of hydration. II. Base damage from electron-loss centers.

The induction of base damage products in gamma-irradiated DNA, hydrated between 2.5 and 32.8 moles of water per mole of nucleotide (tau), was investigated using the gas chromatography/mass spectrometry-selected ion monitoring technique. In general, the yields of the measured base damage products were found to be dependent on the extent of the hydration when the DNA was irradiated under nitrogen. At low hydrations (tau < or = 13), the highest yields of the measured products were found for 7,8-dihydro-8-oxo-guanine, 5,6-dihydrothymine and, to a lesser extent, 2,6-diamino-4-oxo-5-formamidopyrimidine, products which are consistent with the base radicals found in low-temperature ESR studies. At higher hydrations (tau < or = 13), changes in DNA conformation and an increase in the attack of bulk water radicals on DNA play a significant role in the formation of radiation-induced DNA base damage products. Additional findings in our study include: (1) the sum of the yields of the products formed from electron-loss centers is greater than the sum of the yields of the products formed from electron-gain centers, indicating that there might be other electron-gain products which have not been identified; (2) the combined yield for the base damage products and the release of unaltered bases at tau < or = 13 is constant, implying that radiation damage in the tightly bound water molecules of the primary hydration layer causes DNA damage (quasi-direct effect) that is similar to the damage caused by direct ionization of the DNA (direct effect); and (3) the yields of the individual base damage products that were formed from electron-loss centers can be modeled on the basis of both the known reactions that lead to the formation of the initial charged base radicals in irradiated DNA, and the known reactions that involve the conversion of these initial DNA radicals into their respective nonradical end products.

Adenine↗
PubMed1996

Electron spin resonance of DNA irradiated with a heavy-ion beam ([16]O[8+]): evidence for damage to the deoxyribose phosphate backbone.

The free radicals produced from the irradiation of hydrated DNA with a heavy-ion beam have been investigated by ESR spectroscopy. The dominant free radical species formed after 60 MeV/nucleon (16)O(8+) ion-beam irradiations at low temperatures (77 K) are the same as those previously identified from studies using low-LET radiation, pyrimidine electron-gain radicals and purine electron-loss radicals; however, greater relative amounts of neutral carbon-centered radicals are found with the higher-LET radiation, and a new phosphorus-centered radical is identified. The fraction of neutral carbon radicals is also found to increase along the ion-beam track with the highest amounts found in the Bragg peak. The neutral carbon-centered radicals likely arise in part from the sugar moiety. The G values found for total trapped radicals at 77 K are significantly smaller for the (16)O(8+) ion beam than those found for low-LET radiation. The new phosphorus-centered radical species is identified by its large 31P parallel hyperfine coupling of about 780 G as a phosphoryl radical. This species is produced linearly with dose and is not found in significant amounts in DNA irradiated with low-LET radiation. The phosphoryl radical must be produced by the fragmentation of a P-O bond and suggests the possibility of a direct strand break. The yield of phosphoryl species is small (about 0.1% of all radicals); however, it clearly indicates that new mechanisms of damage which are not significant for low-LET radiation must be considered for high-LET radiation.

Animals↗
PubMed1996

Molecular analysis of melanoma precursor lesions.

Atypical (dysplastic) nevi are melanocytic lesions, which are precursors of melanoma as well as markers of increased melanoma risk. Although these lesions exhibit distinct clinical and histological features, their molecular features are largely unknown. To determine whether atypical, compared to benign nevi, from patients with a clinical history of malignant melanoma reveal molecular changes, we analyzed these lesions for the expression of two growth factors (basic fibroblast growth factor and transforming growth factor alpha), their receptors (fibroblast growth factor receptor-1 and epidermal growth factor receptor), and two cell adhesion molecules (MUC18 and alpha v beta 3 integrin), all of which are expressed in primary and metastatic melanomas. The results demonstrated a statistically significant correlation (P = 0.02) between increasing degrees of histological atypia and expression of epidermal growth factor receptor in the epidermal keratinocytes of atypical melanocytic lesions. Furthermore, both atypical and benign nevi revealed considerably high levels of overall gene activity in their dermal melanocytic and epidermal keratinocytic compartments. In contrast, the epidermal-dermal junction wherein melanoma evolves showed little gene activity, suggesting that molecular events occurring adjacent to this junction may be important for melanocytic transformation.

Antigens, CD↗
PubMed1996

[Intraoperative monitoring of gastric intramucosal pH].

BACKGROUND: Gastric mucosal pH may be a good indicator of splanchnic tissue oxygenation. AIM: To study the effects of abdominal surgical procedures on gastric mucosal pH. PATIENTS AND METHODS: Eighteen patients subjected to abdominal surgery were studied. All patients received general anesthesia and hemodynamic parameters were maintained within 20% of basal values. A tonometer was placed in the stomach after induction of anesthesia. Arterial blood gases and samples from the tonometer were obtained 30 minutes after induction and at 2 hours of surgery. Intramucosal pH was calculated using Henderson-Haselbach equations. RESULTS: Basal gastric mucosal pH was 7.4 +/- 0.1 and did not change during surgery. Two patients had a pH persistently below 7.35 without hemodynamic alterations or systemic acidosis. CONCLUSIONS: Gastric mucosal pH is not modified by abdominal surgery and some patients have low values despite the absence of hemodynamic derangement.

Abdomen↗
PubMed1995

Cloning and electrophysiological analysis of KST1, an inward rectifying K+ channel expressed in potato guard cells.

Potassium uptake by guard cells represents part of the osmotic motor which drives stomatal opening. Patch-clamp measurements have identified inward rectifying K+ channels capable of mediating K+ uptake in guard cells and various other plant cell types. Here we report the molecular cloning and characterization of a voltage-dependent K+ channel (KST1) from potato (Solanum tuberosum L.) guard cells. In situ hybridization shows expression of kst1 in guard cells. Two-electrode voltage-clamp and patch-clamp studies of the gene product after cRNA injection into Xenopus oocytes identified KST1 as a slowly activating, voltage-dependent, inward rectifying K+ channel. The single channel current voltage curve was linear in the range -160 to +20 mV, with a deduced single channel conductance of 7 pS in symmetrical 100 mM K+. This channel type, modulated by pH changes within the physiological range, required ATP for activation. In line with the properties of a K(+)-selective channel, KST1 was permeable to K+, Rb+ and NH4+ and excluded Na+ and Li+. Cs+ at submillimolar concentrations blocked the channel in a voltage-dependent manner. Related studies on potato guard cell protoplasts confirmed the biophysical characteristics of the kst1 gene product (KST1) in the heterologous expression system. Therefore, KST1 represents a major K+ uptake channel in potato guard cells.

Amino Acid Sequence↗
PubMed1995

A new method for phenotyping proliferating cell nuclear antigen positive cells using flow cytometry: implications for analysis of the immune response in vivo.

The incorporation of radioactive nucleotides into newly synthesized DNA has been established as a standard method for the detection of proliferation in eucaryotic cells. Unfortunately the use of this method makes it harder to obtain information on the phenotype of proliferating cells in mixed cell populations. For this reason we established a flow-cytometric approach employing a monoclonal antibody specific for murine as well as human proliferating cell nuclear antigen (PCNA) and a double labeling technique for detection of cell membrane-expressed phenotypic markers. The efficiency of this immunostaining procedure was confirmed by simultaneous and highly specific detection of PCNA in nuclear structures as well as cell membrane-expressed antigens using cytological techniques. In vitro experiments with mitogen- and alloantigen-stimulated murine lymph node cells (LNC) and human peripheral blood mononuclear leukocytes (PBML) revealed a good correlation of total [3H]thymidine incorporation into DNA and expression of PCNA. For the analysis of proliferating cells activated in vivo the method was employed to evaluate the local lymph node assay which assesses the allergenicity of small chemicals. LNC prepared from the cervical lymph nodes of mice treated on 4 consecutive days with sensitizing concentrations of the contact allergens oxazolone, TNCB and DNFB as well as the irritants benzoic acid and SLS in comparison to the solvent control showed a dramatic increase in the total amount of proliferating cells for contact allergen-treated animals in comparison to the solvent control and irritant-treated mice. In addition a detailed phenotyping of the proliferating cell populations was possible. This approach offers an easy to perform, non-radioactive method for the assessment of proliferation of murine as well as human leukocytes in vitro and especially in vivo and will be of great advantage for situations where the phenotype of proliferating cellular subsets in heterogeneous populations is of interest.

Allergens↗
PubMed1995

The promoter of coconut foliar decay-associated circular single-stranded DNA directs phloem-specific reporter gene expression in transgenic tobacco.

A full-length double-stranded DNA copy of the single-stranded circular DNA associated with coconut foliar decay virus (CFDV) was constructed. Full-length CFDV DNA and smaller fragments were transcriptionally fused to the beta-glucuronidase reporter gene and examined for promoter activity in vivo. In stably transformed tobacco plants, the CFDV DNA promoter confered a tissue-specific expression pattern in that the reporter gene was specifically expressed in the phloem tissue of the vascular system in stem, leaves and flower. These results are in agreement with the previously reported association of CFDV DNA with the phloem of its coconut host plant.

Base Sequence↗
PubMed1995

Inward rectifier potassium channels in plants differ from their animal counterparts in response to voltage and channel modulators.

We have investigated the electrophysiological basis of potassium inward rectification of the KAT1 gene product from Arabidopsis thaliana expressed in Xenopus oocytes and of functionally related K+ channels in the plasma membrane of guard and root cells from Vicia faba and Zea mays. The whole-cell currents passed by these channels activate, following steps to membrane potentials more negative than -100 mV, with half activation times of tens of milliseconds. This voltage dependence was unaffected by the removal of cytoplasmic magnesium. Consequently, unlike inward rectifier channels of animals, inward rectification of plant potassium channels is an intrinsic property of the channel protein itself. We also found that the activation kinetics of KAT1 were modulated by external pH. Decreasing the pH in the range 8.5 to 4.5 hastened activation and shifted the steady state activation curve by 19 mV per pH unit. This indicates that the activity of these K+ channels and the activity of the plasma membrane H(+)-ATPase may not only be coordinated by membrane potential but also by pH. The instantaneous current-voltage relationship, on the other hand, did not depend on pH, indicating that H+ do not block the channel. In addition to sensitivity towards protons, the channels showed a high affinity voltage dependent block in the presence of cesium, but were less sensitive to barium. Recordings from membrane patches of KAT1 injected oocytes in symmetric, Mg(2+)-free, 100 mM-K+, solutions allowed measurements of the current-voltage relation of single open KAT1 channels with a unitary conductance of 5 pS. We conclude that the inward rectification of the currents mediated by the KAT1 gene product, or the related endogenous channels of plant cells, results from voltage-modulated structural changes within the channel proteins. The voltage-sensing or the gating-structures appear to interact with a titratable acidic residue exposed to the extracellular medium.

Animals↗
PubMed1995

Degradation of 4-chloro-2-methylphenol by an activated sludge isolate and its taxonomic description.

The Gram-negative strain S1, isolated from activated sludge, metabolized 4-chloro-2-methylphenol by an inducible pathway via a modified ortho-cleavage route as indicated by a transiently secreted intermediate, identified as 2-methyl-4-carboxymethylenebut-2-en-4-olide by gas chromatography/mass spectrometry. Beside 4-chloro-2-methylphenol only 2,4-dichlorophenol and 4-chlorophenol were totally degraded, without an accumulation of intermediates. The chlorinated phenols tested induced activities of 2,4-dichlorophenol hydroxylase and catechol 1,2-dioxygenase type II. Phenol itself appeared to be degraded more efficiently via a separate, inducible ortho-cleavage pathway. The strain was characterized with respect to its physiological and chemotaxonomic properties. The fatty acid profile, the presence of spermidine as main polyamine, and of ubiquinone Q-10 allowed the allocation of the strain into the alpha-2 subclass of the Proteobacteria. Ochrobactrum anthropi was indicated by fatty acid analysis as the most similar organism, however, differences in a number of physiological features (e.g. absence of nitrate reduction) and pattern of soluble proteins distinguished strain S1 from this species.

Biodegradation, Environmental↗
PubMed1995

[Granuloma anulare disseminatum as a rare side effect of allopurinol].

During long-term therapy of hyperuricaemia with allopurinol (300 mg/d) two patients developed generalized granuloma annulare. The diagnoses were confirmed by histology; concomitant diseases, especially diabetes mellitus, were not detectable. Following discontinuation of allopurinol therapy, cutaneous granulomas healed without relapse. Hyperuricaemia could be controlled by low-purine diet and medication avoiding allopurinol. The clinical history of our two patients suggested a causal connection between allopurinol therapy and generalized granuloma annulare. For this reason we rate the development of this disease in both cases as a rare but significant side effect of allopurinol. This should give rise to critical assessment of concomitant drug therapy during development of generalized granuloma annulare.

Aged↗
PubMed1995

High mortality from unidentified CVD in IDDM: time to start screening?

Mortality in insulin-dependent diabetes is markedly increased compared to the general population. Although strong associations have been found between renal disease and the risk of cardiovascular disease (CVD) the interaction between these two factors is not well understood. This study, which addresses risk factors for mortality in IDDM with a particular focus on the renal-CVD link, is based on the prospective Epidemiology of Diabetes Complications study. Thirty-seven (mean age 36 years, mean duration of IDDM 28 years at baseline) of the 658 IDDM individuals (mean age 28 years, mean duration of IDDM 20 years at baseline) have died in the first 4 years of follow up. A nested case-control study was performed, matching on sex and duration of diabetes. Twenty-two (59%) of the deaths were attributed to coronary heart disease, with an additional 16% attributed to diabetic coma. Only nine (41%) of the 22 individuals who died from cardiovascular disease had clinical evidence of coronary heart disease when seen for their last biennial exam. However, 54% of those who died of CVD without prior evidence did have evidence of lower extremity arterial disease. A strong link with renal disease was confirmed, with 81% of those with a coronary artery disease death having renal disease. Multivariate analyses suggest that smoking history, triglycerides and total platelet count are independent predictors of mortality, while LDL cholesterol best predicted CVD mortality. These results suggest a need for more intensive screening for cardiovascular disease, and correction of cardiovascular risk factors, in order to reduce the increased rate of mortality in this population. Efforts to prevent or delay the onset of renal disease may also be of benefit.

Adult↗