Helical polyacetylene-a conductive material for self-contained molecular electronic device use.

We describe mono-substituted helical poly(phenyl)acetylene, a structural variation of polyacetylene that may overcome its problem: the lack of chemical stability. Helical polyacetylene shows an intrinsic stiff rod structure, which can be enhanced by the choice of suitable side groups. The structure looks like a narrow spiral with a conjugated electron system, covered by attached side groups spiralling in the opposite sense. We consider this unique material as a prototype for molecular electronic device use. It provides the electronic function, mechanical packaging and electrical insulation through a variety of side groups and exhibits useful self-assembly properties. We provide evidence that such materials, in many variations, show the expected overall structure, can be synthesized through living polymerization (which is necessary for the fabrication of monomers by monomer controlled structures), do show enhanced chemical stability, are amenable to self-assembly, may be deposited in an oriented fashion and do show electrical conductivity.

Effect of a reduced vitamin K supplementation on prothrombin time in prematures and high-risk neonates.

Recommendations for vitamin K supplementation were recently changed to 3 x 1 mg orally in healthy term neonates and 0.2 mg parenterally in prematures and high-risk neonates. Prothrombin times (PT) at reduced vitamin K doses (120 patients, 170 samples) during the first 6 weeks of life were below 40% in 6 patients only; all low PTs were unrelated to vitamin K. In the remaining patients, median PT was 100%; 79% of patients had values above 70%. PT was related to birthweight, gestational age and age. There was no decrease over the observation period. Following reduced oral and parenteral vitamin K regimens PTs were well within published reference values for neonates given larger amounts of vitamin K.

Macromolecular adducts caused by environmental chemicals.

We describe three biomonitoring studies in which hemoglobin (Hb) adducts were used as biochemical markers to assess indirectly the target dose of genotoxic chemicals. We monitored the exposure to 1,3-butadiene in occupationally exposed workers and in two control groups by analyzing the adducts formed by the reaction of the first activation product, butadiene monoepoxide, with the terminal valine of Hb; we also measured hydrolyzable adducts formed by the reaction of metabolically formed nitroso derivatives with Hb from five selected nitropolycyclic aromatic hydrocarbons (1-nitropyrene; 2-nitrofluorene, 3-nitrofluoranthrene, 6-nitrochrysene, and 9-nitrophenanthrene) in coke oven workers of different job categories and control workers of the same geographical area. We detected hydrolyzable adducts from monocyclic nitroarenes in blood from individuals living in a contaminated area where explosives had been produced and from controls. The contaminants considered were 2,4,6-trinitrotoluene; 2,4- and 2,6-dinitrotoluene; and 1,3-dinitrobenzene. Differences between groups were significant, but interindividual variation was great and back-ground exposures must be considered.

Induction of micronuclei in peripheral blood and bone marrow erythrocytes of rats and mice exposed to 1,3-butadiene by inhalation.

Female CB6F1 mice and male Wistar rats were exposed to different concentrations of 1,3-butadiene (1,3-BD) by inhalation. Micronucleus tests using both peripheral blood erythrocytes and femoral marrow cells of these animals were performed. Cells were stained either using conventional acridine orange (AO) staining or supravitally using AO-coated slides. Dose-dependent increases in the frequency of micronuclei (MN) were observed both in blood and in bone marrow cells in mice. 1,3-BD did not, however, increase the frequency of MN in either blood or bone marrow cells of rats at any of the tested concentrations.

Biological monitoring of 1,3-butadiene: species differences in haemoglobin binding in rat and mouse.

The adduct formed by the reaction of 1,3-butadiene monoxide, a major metabolite of the mutagen and carcinogen 1,3-butadiene, with the N-terminal valine of haemoglobin was used as a dosimeter for the bioavailability of reactive metabolites. The dose-dependence of adduct formation was studied in female CB6F1 mice and female Wistar rats exposed to 0, 50, 200, 500 or 1300 ppm butadiene in an open inhalation chamber for 6 h per day for five consecutive days. Globin was isolated 18 h after the last exposure, and N-terminal valine was obtained by a modified Edman degradation procedure. Adduct levels were five times higher in mice than in rats (17 and 3.5 nmol/g globin, respectively, at 500 ppm), which may partially explain the greater susceptibility of mice to tumour formation. Adduct levels increased linearly with dose in rats, whereas in mice this slope of the curve became flatter at 500 ppm and increased with higher doses. Similar results were obtained in male and female C3H x 101/EL mice.

Mixtures of lecithin with polymerizable derivatives of cholesterol. A monolayer film balance study.

One of the best investigated binary lipid mixtures is the lecithin-cholesterol system. We show here that it is possible to modify the cholesterol in such a way that it can be polymerized without changing its behaviour in mixtures with lecithin. The polymerizable derivatives exhibit a very similar phase diagram in the mixture with dipalmitoylphosphatidylcholine as the cholesterol itself. This is demonstrated by filmbalance measurements.

Stable biomembrane surfaces formed by phospholipid polymers.

Phospholipids (phosphatidylcholines) with diacetylene in each acyl chain have been deposited in Langmuir-Blodgett multilayers on a variety of substrates. Upon irradiation the diacetylene groups polymerise and link the phospholipid molecules together with a conjugated chain made up of alternating single, double and triple bonds. Advantage has been taken of this polymerisation process to increase the stability of these lipids layers and to produce stable biomembrane hydrophilic surface. These surfaces may be useful for studies of blood coagulation and protein adsorption. In addition they could also have medical application.

[Results of incidence analyses in external hemorrhoids]. / Häufigkeitsanalytische Ergebnisse über Marisken.

The perianal region of 294 healthy persons (151 male, 143 female) of different age was examined and the size, the localization and the number of the skin tags were registered. The frequency increases in women especially at the beginning of the second decade and in men especially at the fourth decade of life. 80% of all women and 60% of all men have skin tags. The size of the skin tag increases while the person becomes older. In the average women have bigger skin tags than men. Most of the skin tags are located in the region of 12 and 6 h lithotomy position.