Biomedical subjects

U Meierhenrich

Publications and source records attributed to U Meierhenrich.

5 recordsLinked to original sources

PubMed2001

Analysis of oxidative degradation products of 2,4,6-trichlorophenol treated with air ions.

The analysis of oxidative degradation products of 2,4,6-trichlorophenol (TCP) treated with air ions, which are generated by electric discharge, is reported. Due to the complex nature of the degradation products, a combination of different detection techniques was employed to characterize them. The oxidative degradation of TCP is usually dependent on the treating approaches, and in this system, a stepwise degradation, beginning with the formation of a major product 2,6-dichloro-1,4-benzenediol as well as other minor ones (e.g., 3,5-dichlorocatechol) via substitution, is first proposed through a detailed analysis of GC/MS, etc., though some chromogenic quinones can transiently be present. Furthermore, high dechlorination (53%) was observed for TCP after a 60-min treatment, indicating that air ions can serve as an efficient dechlorination means.

Air↗

PubMed1999

Molecular parity violation via comets?

Recent theoretical and experimental investigations referring to the origin of homochirality are reviewed and integrated into the hitherto known state of the art. Attention is directed to an extraterrestrial scenario, which describes the interaction of circularly polarized synchrotron radiation with interstellar organic matter. Following this Bonner-Rubenstein hypothesis, optically active molecules could be transferred to Earth via comets. We plan to identify any enantiomeric enhancement in organic molecules of the cometary matter in situ. The present preliminary experimental study intends to optimize gas-chromatographic conditions for the separation of racemates into their enantiomer constituents on the surface of the comet 46P/Wirtanen. Underivatized racemic pairs of alcohols, diols, and phenyl-substituted amines have been separated with the help of a stationary trifluoroacetyl-cyclodextrin phase. We are still developing a technique that will enable us to detect any enantiomeric enhancement of specific simple organic molecules both in cometary or Martian matter in situ and in meteorites found on Earth.

Alcohols↗

PubMed1998

[Dichlorvos insect strips indoors: pollution and risk assessment].

Exposure to Danger and Assessing the Hazards: Application of the highly potent pest control agent dichlorvos (DDVP) involves the hazard of effects on the central nervous system and a risk of human cancer. Consumers use dichlorvos in pest strips to protect their rooms from insects. This undifferentiated pest control can lead to chronic exposure. Over several weeks we found an indoor air concentration of dichlorvos between 60 and 1300 micrograms/m3 in 34 m3-experimental-room (chamber). Textiles and foodstuffs in this room were also contaminated. Beside the inhalative intake the oral and dermal intake can also lead to an additional loading of the residents. The ADI-resp. DTA-value of 4 micrograms/kg body-weight and day is exceeded about 10-15 times on the average by inhalative exposure only.

Adolescent↗

PubMed1986

Dose response relationships of anticoagulant activities after subcutaneous administration of two low molecular weight heparins in healthy individuals.

This study was performed to estimate appropriate dosages of two low molecular weight heparins (LMWH) for clinical trials on subcutaneous perioperative thrombosis prophylaxis. Anticoagulatory activities and platelet function were investigated after single doses of two LMWH and of unfractionated sodium heparin (UFH) in 24 healthy individuals. Twelve subjects received subcutaneous injections of 1000, 1500, and 2500 i.u. (aPTT) of LMHW 1, and the other 12 received LMWH 2 at same dosages. The following parameters were determined before 30 min, 1 h, 90 min, 2 h, 3 h, 4 h, 6 h, 8 h, and 10 h after either LMWH or 5000 i.u. (aPTT) UFH: aPTT, thrombin time, anti-Xa activity (S 2222, Coatest heparin), and anti-IIa activity (Chromozym TH). Bleeding time, platelet count, and adrenalin-, collagen-, and ADP-induced platelet aggregation were assessed before and 3 h after administration. After application of 1500 i.u. LMWH 1 and LMWH 2, the anti-Xa and anti-IIa levels were already significantly higher than after 5000 i.u. UFH. 2500 i.u. LMWH 1 and LMWH 2 evoked significantly greater prolongations of aPTT and thrombin time values than did 5000 i.u. UFH. This was not the case after 1000 and 1500 i.u. LMWH. The half-lives of anticoagulatory effects after LMWH were markedly longer than after UFH. Platelet function was not altered by any of the heparins tested. Our results indicate that LMWH cause anticoagulatory effects in vivo that cannot be predicted by in vitro studies and that the appropriate single dosages of LMWH in subcutaneous perioperative thrombosis prophylaxis have to be estimated by dosage determinations in healthy subjects.

Adult↗

PubMedDate not supplied

ESA mission ROSETTA will probe for chirality of cometary amino acids.

New crucial theoretical investigations on the origin of biomolecular chirality are reviewed briefly. With the goal to investigate these theories our team is going to perform the 'chirality-experiment' in the near future with cometary matter. In 2012 the robotical lander RoLand will detach from the orbiter of the ROSETTA spacecraft and set down on the surface of comet 46P/Wirtanen in order to separate and identify cometary organic compounds via GC-MS in situ. Chiral organics will be separated into their enantiomers by application of 3 capillary columns coated with different kinds of stationary phases. Non-volatile compounds like amino acids will be derivatized in especially developed gas phase alkylation steps avoiding reactions in the liquid phase. The results of these preliminary gas phase reactions are presented in this article.

Amino Acids↗