Biomedical subjects

M Kastner

Publications and source records attributed to M Kastner.

At least 19 recordsLinked to original sources

PubMed2002

Isotope fractionation of toluene: a perspective to characterise microbial in situ degradation.

A concept to assess in situ biodegradation of organic contaminants in aquifers is presented. The alteration of the carbon isotope composition of contaminants along the groundwater flow path indicates microbial degradation processes and can be used as an indicator for in situ biodegradation. The Rayleigh equation was applied to calculate the percentage of the in situ biodegradation (B[%]) using the change in the isotopic composition of contaminants (Rt/R0) along the ground water flow path and a kinetic carbon isotope fractionation factor (alphaC) derived from defined biodegradation experiments in the laboratory. When the groundwater hydrology is known and a representative source concentration (C0) for a groundwater flow path can be determined, the extent of in situ biodegradation can be quantified.

Carbon Isotopes↗

PubMed2001

Concomitant manifestation of achalasia and sphincter of Oddi dysfunction.

We report the case of a 44-year-old woman who suffered from biliary-type pain after cholecystectomy, dysphagia, and weight loss. Examinations revealed sphincter of Oddi dysfunction (SOD) and achalasia. Complete relief of symptoms was achieved by endoscopic sphincterotomy and pneumatic dilation of the distal esophagus. This case report demonstrates for the first time the concomitant manifestation of two motility disorders of the upper gastrointestinal tract, i.e. achalasia and SOD. At present, any causal relationship seems speculative; however, both diseases were successfully treated using endoscopic procedures.

Adult↗

PubMed2000

Direct observation of subcritical fluctuations during the formation of strained semiconductor islands

We have directly imaged subcritical fluctuations during the nucleation phase of three-dimensional islands in strained layer epitaxy. The fluctuations are defect mediated and are found to be large even at low growth temperatures. We attribute the existence of large fluctuations to the time dependence of the supersaturation. This indicates classical nucleation concepts are relevant, even at low growth temperatures.

Journal Article↗

PubMed2000

Modeling tanning salon behavioral tendencies using appearance motivation, self-monitoring and the theory of planned behavior.

The constructs of appearance motivation and self-monitoring were added to the Theory of Planned Behavior in the prediction of tanning salon use in young people. The variables of the Theory of Planned Behavior proved effective at predicting tanning salon behavioral intentions and tendencies. Intentions and perceived behavioral control predicted tanning salon behavioral tendencies, while attitudes, subjective norms and perceived behavioral control predicted tanning salon behavioral intentions. Appearance motivation did not show any direct or interaction effects in the prediction of tanning salon behavioral intentions. It did, however, prove superior to health orientation in the prediction of tanning salon attitudes. Self-monitoring interacted with subjective norms in the prediction of tanning salon intentions, with high self-monitors showing stronger subjective norm-intention relationships than low self-monitors. These results imply that appearance-related interventions could prove efficacious in reducing young people's tanning salon behavioral tendencies. Furthermore, it may be important to consider individual's self-monitoring status when targeting skin cancer prevention information to young people.

Adolescent↗

PubMed2000

Broad histogram method: extension and efficiency test

Compared to standard histogram techniques, the broad histogram method allows us to increase the efficiency of Monte Carlo simulations by a tremendous amount. This gain of efficiency is achieved by measuring simulation averages of particular system observables (different from those used in standard histogram techniques), while the algorithm of the simulation can be left unchanged. In this paper, the broad histogram method is reformulated in a more mathematical and precise way. Furthermore, the method is extended to estimate the density of states as a function of more than one parameter. A quantitative investigation of the gain of efficiency of Monte Carlo simulations is performed. For the broad histogram method, we find a gain of efficiency which amounts to orders of magnitude in comparison to the standard histogram method.

Journal Article↗

PubMed1999

A phylogenetic analysis of microbial communities associated with methane hydrate containing marine fluids and sediments in the Cascadia margin (ODP site 892B).

Methane hydrates represent an enormous carbon and energy source in many low temperature deep marine sediments. However, little information is available concerning the nature of the microbial communities associated with these structures. Here, we describe a phylogenetic analysis based on ribosomal DNA (rDNA) sequences obtained from sediment and fluid samples present in a region of gas hydrate formation in shallow sediments within the Cascadia margin in and around Ocean Drilling Program (ODP) Site 892B. Our studies detected diverse sulfur-utilizing microbes, methanogens, methanotrophs, and non-thermophilic members of the kingdom Crenarchaeota. This is the first culture-independent phylogenetic analysis of a gas hydrate habitat.

Archaea↗

PubMed1999

Oceanic minerals: their origin, nature of their environment, and significance.

The chemical and isotopic compositions of oceanic biogenic and authigenic minerals contain invaluable information on the evolution of seawater, hence on the history of interaction between tectonics, climate, ocean circulation, and the evolution of life. Important advances and greater understanding of (a) key minor and trace element cycles with various residence times, (b) isotopic sources and sinks and fractionation behaviors, and (c) potential diagenetic problems, as well as developments in high-precision instrumentation, recently have been achieved. These advances provided new compelling evidence that neither gradualism nor uniformitarianism can explain many of the new important discoveries obtained from the chemistry and isotopic compositions of oceanic minerals. Presently, the best-developed geochemical proxies in biogenic carbonates are 18O/16O and Sr/Ca ratios (possibly Mg/Ca) for temperature; 87Sr/86Sr for input sources, Cd/Ca and Ba/Ca ratios for phosphate and alkalinity concentrations, respectively, thus also for ocean circulation; 13C/12C for ocean productivity; B isotopes for seawater pH;, U, Th isotopes, and 14C for dating; and Sr and Mn concentrations for diagenesis. The oceanic authigenic minerals most widely used for chemical paleoceanography are barite, evaporite sulfates, and hydrogenous ferromanganese nodules. Marine barite is an effective alternative monitor of seawater 87Sr/86Sr, especially where carbonates are diagenetically altered or absent. It also provides a high-resolution record of seawater sulfate S isotopes, (evaporite sulfates only carry an episodic record), with new insights on factors affecting the S and C cycles and atmospheric oxygen. High-resolution studies of Sr, Nd, and Pb isotopes of well-dated ferromanganese nodules contain invaluable records on climate driven changes in oceanic circulation.

Journal Article↗

PubMed1998

Sulfur isotopic composition of cenozoic seawater sulfate

A continuous seawater sulfate sulfur isotope curve for the Cenozoic with a resolution of approximately 1 million years was generated using marine barite. The sulfur isotopic composition decreased from 19 to 17 per mil between 65 and 55 million years ago, increased abruptly from 17 to 22 per mil between 55 and 45 million years ago, remained nearly constant from 35 to approximately 2 million years ago, and has decreased by 0.8 per mil during the past 2 million years. A comparison between seawater sulfate and marine carbonate carbon isotope records reveals no clear systematic coupling between the sulfur and carbon cycles over one to several millions of years, indicating that changes in the burial rate of pyrite sulfur and organic carbon did not singularly control the atmospheric oxygen content over short time intervals in the Cenozoic. This finding has implications for the modeling of controls on atmospheric oxygen concentration.

Journal Article↗

PubMed1998

Identification of mouse crystallins in 2D protein patterns by sequencing and mass spectrometry. Application to cataract mutants.

The eye lens proteins of the mouse were separated into 1940 polypeptide spots by two-dimensional electrophoresis in large gels. All 16 crystallins ubiquitous in mammals were identified by protein sequencing and mass spectrometry except for (gamma)-F, which shows an almost identical sequence with (gamma)-E. Two crystallins, (beta)-A2 and (gamma)-S, were shown for the first time to occur in the mouse lens. An investigation of the murine cataract mutant Cat2(nop)((gamma)-B gene) demonstrated that a monogenic mutation might affect a broad spectrum of proteins.

Amino Acid Sequence↗

PubMed1996

Glacial to Interglacial Fluctuations in Productivity in the Equatorial Pacific as Indicated by Marine Barite

An empirical correlation between marine barite (BaSO4) accumulation rate in core-top sediment samples from two equatorial Pacific transects (at 140°W and 110°W) and the estimated primary productivity of the overlying water column were used to evaluate glacial to interglacial changes in productivity. Fluctuations in barite accumulation rates down-core indicate that during glacial periods of the past 450,000 years, the productivity in the central and eastern equatorial Pacific was about two times that during intervening interglacial periods. This result is consistent with other evidence that productivity was high in the eastern and central equatorial Pacific during the last glacial.

Journal Article↗

PubMed1994

Characterization of cytochromes P-450 purified from untreated and 14C-2,3,7,8-tetrachlorodibenzo-p-dioxin--treated marmoset monkeys: identification of the major form as a possible orthologue of P-450 1A2.

Three purified cytochrome P-450 (P-450) forms obtained from liver microsomes of marmoset monkeys induced with 14C-2,3,7,8-tetrachlorodibenzo-p-dioxin (14C-TCDD) were characterized. Comparison of electrophoretic and spectral properties and reconstituted methoxy-and ethoxyresorufin O-dealkylase (MROD and EROD) activities with those of forms isolated from untreated marmosets indicated that one of these (form F) is likely constitutive. Another form (D) had MROD and EROD activities which were 100 and 15 times those observed for form F. A form having biophysical properties similar to those of form D was also found in untreated animals. A third form (C) had an appreciable capacity to bind its inducing agent and showed a TCDD-to-P-450 molar ratio for detergent-free solutions of 0.66 +/- 0.13 to 1. In immunoblot analyses of these forms with antibodies raised against specific peptide sequences derived from rat P-450 1A1 and 1A2, the only positive reactions seen were those for untreated and inducible forms D with anti-rat 1A2. This provides evidence that the main or sole P-450 1A form in marmoset liver microsomes is 1A2, as in humans, and that this is inducible by TCDD.

Animals↗

PubMed1992

Purification of cytochromes P-450 derived from liver microsomes of untreated and 2,3,7,8-tetrachlorodibenzo-p-dioxin-treated marmoset monkeys.

The purification of multiple forms of cytochrome P-450 (P450) from 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-treated marmosets using fast protein liquid chromatography (FPLC) is described. The main aim was to achieve a better separation of certain closely related P450 sub-forms from each other than that previously obtained using conventional chromatography. An 8-aminooctyl-Sepharose fraction of cholate-solubilized microsomes was obtained first and, after fast desalting on Sephadex G-25, loaded on to a preparative Mono Q column. Five of the six gradient peaks contained P450 and were each rechromatographed on an analytical Mono Q column. The pass-through peak was fractionated further using a Mono S column. Other HPLC-quality anion- and cation-exchange gels were compared. For removal of excess of non-ionic detergent, five types of hydroxyapatite gels were compared. Seven purified forms of P450 and cytochrome b5 and P420 were isolated and characterized according to PHAST sodium dodecylsulphate-polyacrylamide gel electrophoretic apparent molecular masses, catalytic, spectral and magnetic properties and also TCDD-binding capacity (molar ratio of [14C]TCDD to P450). There are at least two sub-forms which appear to be TCDD inducible, one showing a substantial ethoxyresorufin-O-deethylase activity and the other having a high TCDD-binding molar ratio. Two other forms appear to be constitutive, as deduced from comparisons with forms purified from untreated animals.

Animals↗

PubMed1992

Ca2+/calmodulin-dependent cytochrome c reductase activity of brain nitric oxide synthase.

Nitric oxide acts as a widespread signal molecule and represents the endogenous activator of soluble guanylyl cyclase. In endothelial cells and brain tissue, NO is enzymatically formed from L-arginine by Ca2+/calmodulin-regulated NO synthases which require NADPH, tetrahydrobiopterin, and molecular oxygen as cofactors. Here we show that purified brain NO synthase binds to cytochrome c-agarose and exhibits superoxide dismutase-insensitive cytochrome c reductase activity with a Vmax of 10.2 mumol x mg-1 x min-1 and a Km of 34.1 microM. Cytochrome c reduction was largely dependent on Ca2+/calmodulin and cochromatographed with L-citrulline formation during gel filtration. When reconstituted with cytochrome P450, NO synthase induced a moderate Ca(2+)-independent hydroxylation of N-ethylmorphine. NO synthase also reduced the artificial electron acceptors nitro blue tetrazolium and 2,6-dichlorophenolindophenol. Cytochrome c, 2,6-dichlorophenolindophenol, and nitro blue tetrazolium inhibited NO synthase activity determined as formation of L-citrulline from 0.1 mM L-arginine in a concentration-dependent manner with half-maximal effects at 166, 41, and 7.3 microM, respectively. These results suggest that NO synthase may participate in cellular electron transfer processes and that a variety of electron-acceptors may interfere with NO formation due to the broad substrate specificity of the reductase domain of NO synthase.

2,6-Dichloroindophenol↗

PubMed1992

Analysis of chronic lymphoid leukaemias according to FAB.

We have studied the immunophenotypic features in patients with chronic lymphoid leukaemia and investigated the suitability of classification according to guidelines of the French-American-British (FAB) group. Immunophenotyping was carried out on cytocentrifuge preparations of mononuclear blood leukocytes using the alkaline phosphatase-antialkaline phosphatase (APAAP) method. The 114 leukaemias, including 58 cases of B-chronic lymphocytic leukaemia (B-CLL), 3 Waldenström's macroglobulinaemia, 6 prolymphocytic leukaemia (B-PL), 13 B-CLL/PL, 4 B-CLL of mixed cell type, 8 splenic lymphoma with villous lymphocytes (SLVL), 8 hairy cell leukaemia (HCL), two HCL variant, three leukaemic phase of follicular lymphoma, two leukaemic phase of intermediate lymphoma, two plasma cell leukaemia and two chronic T-cell leukaemia, were investigated. The 111 of 112 B-chronic lymphoid leukaemias (B-CLL + B-PL + B-CLL/PL + SLVL + HCL etc.) showed monotypic light chains. The antibody HML1 was highly specific for HCL. The antibodies CD11c and CD25 were positive in all HCL cases, but were not specific for this disease. CD5 positivity and CD22s negativity were found in most patients with B-CLL, B-CLL/PL and B-CLL of mixed type. This marker type has a limited value for differentiation from the other chronic lymphoid leukaemias. We also studied three patients with chronic lymphoid leukaemia which were not described by the FAB classification. We conclude that a study of the morphology of the leukaemic cells was the most useful basis for the diagnosis of these leukaemias, whereas immunotyping was apparently valuable only in individual cases.

Antigens, CD↗

PubMed1992

Proximal impact deposits at the Cretaceous-Tertiary boundary in the Gulf of Mexico: a restudy of DSDP Leg 77 Sites 536 and 540.

Restudy of Deep Sea Drilling Project Sites 536 and 540 in the southeast Gulf of Mexico gives evidence for a giant wave at Cretaceous-Tertiary boundary time. Five units are recognized: (1) Cenomanian limestone underlies a hiatus in which the five highest Cretaceous stages are missing, possibly because of catastrophic K-T erosion. (2) Pebbly mudstone, 45 m thick, represents a submarine landslide possibly of K-T age. (3) Current-bedded sandstone, more than 2.5 m thick, contains anomalous iridium, tektite glass, and shocked quartz; it is interpreted as ejecta from a nearby impact crater, reworked on the deep-sea floor by the resulting tsunami. (4) A 50-cm interval of calcareous mudstone containing small Cretaceous planktic foraminifera and the Ir peak is interpreted as the silt-size fraction of the Cretaceous material suspended by the impact-generated wave. (5) Calcareous mudstone with basal Tertiary forams and the uppermost tail of the Ir anomaly overlies the disturbed interval, dating the impact and wave event as K-T boundary age. Like Beloc in Haiti and Mimbral in Mexico, Sites 536 and 540 are consistent with a large K-T age impact at the nearby Chicxulub crater.

Animals↗

PubMed1991

High-performance metal chelate affinity chromatography of cytochromes P-450 using Chelating Superose.

High-performance metal chelate affinity chromatography [immobilized metal ion affinity chromatography (IMAC)] using Chelating Superose (iminodiacetic acid adsorbent) was investigated for its suitability in purifying phenobarbital-induced rat liver microsomal cytochrome P-450 isozymes (P450) and optimized for preparative purposes. Starting with an 8-aminooctyl-Sepharose fraction of partially purified P450, it was found that only Ni(2+)- and Cu(2+)-charged columns could bind P450. No binding was ever observed when Zn2+, Co2+, Mn2+, Cd2+, Fe3+, Fe2+ or Tl3+ ions were employed. Of eight commonly used elution buffers, imidazole and tryptamine were found to cause some denaturation of P450. For desorption of proteins bound to Ni(2+)-charged columns, the following order of decreasing elution buffer strength was determined: cysteine approximately histidine greater than glycine greater than histamine greater than tryptophan greater than ammonium chloride. During protein desorption with some of these buffers, metal ions were found to bleed from the gel, resulting in P450 denaturation. This could be eliminated by prebleeding the charged columns prior to sample application and had an effect on product recovery and homogeneity. Ni2+ and glycine were chosen as a standard for further optimization involving sample adsorption conditions as influenced by equilibration buffer, detergent, load capacity and flow, gradient and temperature conditions. In this way, potassium phosphate (pH 7.75) and 0.4% Emulgen 911 were used to equilibrate a 1.6-ml column and purify 20-50 nmol of P450 (5-15 mg of protein) within 15 min. One gradient fraction consisted of a single sodium dodecyl sulphate-polyacrylamide gel electrophoresis band as judged by silver staining and represented about 25% of the total P450 applied to the column; total recoveries were usually more than 80%. Comparison with the molecular weights and spectral, catalytic and immunological properties of P450 forms isolated according to established procedures indicated that the form isolated here using Chelating Superose comprises mainly P450 2B1 (PB-B). A method is described for fully automated, programmable column regeneration and sample runs.

Animals↗

PubMed1991

Isolation of cytochrome P-450 components from marmoset liver microsomes by high-performance liquid chromatography.

A fast protein liquid chromatographic (FPLC) system with pre-packed and laboratory-packed columns was used for the analytical and preparative isolation of marmoset monkey cytochrome P-450 (P450) and NADPH-P450-reductase. Chromatographic separations also allowed the recovery of cytochrome b5, NADH-b5-reductase and epoxide hydratase. Cholate-solubilized liver microsomes from phenobarbital-induced marmosets were crudely purified on 8-aminooctyl-Sepharose or 6-aminohexyl-Sepharose and then fractionated into several isoenzyme groups using hydroxyapatite. Further purification on Mono S or CM-Sepharose and finally on phenyl-Superose, phenyl-Sepharose or octyl-Sepharose yielded a P450 fraction which was apparently homogeneous as judged by sodium dodecyl sulphate-polyacrylamide gel electrophoresis in the automated Phast system using silver staining. Removal of excess of non-ionic detergent was effected by hydroxyapatite columns, and this was compared with other methods. For the isolation of P450 isoenzymes from untreated marmosets, Mono Q columns were employed and yielded at least two highly purified forms. NADPH-P450-reductase was recovered from the 8-aminooctyl-Sepharose column or crudely fractionated on DEAE-Sepharose Fast Flow. Subsequent purification via 2',5'-ADP-Sepharose and Superose 12 chromatography resulted in a homogeneous preparation.

Animals↗

PubMed1991

Ontogeny of monooxygenase activities in the marmoset monkey (Callithrix jacchus).

The pre- and postnatal development of monooxygenases in the liver and adrenal gland of marmoset monkeys (Callithrix jacchus) was investigated. Cytochrome P450 was detected in the fetal adrenal gland, but aldrin epoxidase, ethoxycoumarin O-deethylase, and ethoxyresorufin O-deethylase activities were below detection limits. Although fetal hepatic cytochrome P450 was not detected, low activities of aldrin epoxidase and ethoxycoumarin O-deethylase, but no ethoxyresorufin O-deethylase, could be detected in fetal liver. These enzymes attained adult marmosets activities when the offspring were approximately 2 months of age.

7-Alkoxycoumarin O-Dealkylase↗