Biomedical subjects
Publications and source records attributed to M Bolte.
The structure of hexaamminenickel(II) dichloride determined previously by Essmann et al. [Essmann, Kreiner, Niemann, Rechenbach, Schmieding, Sichla, Zachwieja & Jacobs (1996). Z. Anorg. Allg. Chem. 622, 1161-1166] was redetermined at 173 K. There are no significant differences between these two structures.
The photoinduced degradation of an alcohol ethoxylate (AE) (Brij 30) by Fe(III) in aqueous solution has been investigated. The study was carried out with the major fraction of ethoxymers having an alkyl chain length of 12 carbon atoms and n ethoxy units E (C12En). The Fe(III) sensitised degradation of this fraction occurs efficiently at 365 nm. The rate of degradation depends on the concentration of Fe(OH)2+, the most photoreactive species in terms of .OH radical formation. Formate ethoxylates were identified as photoproducts and shortening of the ethoxylated chain all along the degradation process was observed. The mechanism of Brij 30 degradation implies a major .OH radicals attack on the polyethoxylated chain. For prolonged irradiations, the total degradation of Brij 30 and of the photoproducts is obtained. Consequently, the degradation photoinduced by iron (III) could be an efficient method of AEs removal in water.
The Fe(III)-photoinduced degradation of 4-dodecylbenzenesulphonate (DBS) in aqueous solution was investigated. The mixing of DBS (1 mm) and Fe(III) (1 mm) solutions immediately led to the formation of a precipitate that contained DBS and monomeric Fe(OH)2+, the predominant Fe(III) species. Both species were also present in the supernatant. Irradiation of the supernatant solution resulted in a photoredox process that yielded Fe(II) and *OH radicals. The disappearance of DBS was shown to involve only attack by *OH radicals; the quantum yield of DBS disappearance is similar to the quantum yield of *OH radical formation. A wavelength effect was also observed; the rate of DBS disappearance was higher for shorter wavelength irradiation. Five photoproducts, all containing the benzene sulphonate group, were identified. *OH radicals preferentially abstract hydrogen from the carbon in the alpha position of the aromatic ring. The results show that the Fe(III)-photoinduced degradation of DBS could be used as an alternative method for polluted water treatment.
The resorption of teeth in Ambystoma mexicanum during postembryonal ontogenesis and induced metamorphosis occurs by means of light-microscopic detectable giant-cells. These have morphological and functional characters similar to those of odontoclasts of other vertebrates. The multinucleated odontoclasts resorb not only the pedicel (base), but the stalk of the tooth, too. When active, the cells form a ruffled border and a sealing zone. In this way they are able to demineralize the hard tissues of teeth (dentin and mineral of the pedicel) and to dissolve the extracellular matrix. Resorption of enamel has not been observed. Marks of resorption resemble the Howship's lacunae of other tetrapods. TRAP as a typical enzyme of odontoclasts could not be detected histochemically. Dependence of PTH, which is supposed to be necessary for the formation and activation of odontoclasts as well as of thyroxine can be excluded, although the resorbing cells are functionally and cytologically identical with those of other vertebrates. This demands some other mechanism for the formation and regulation of the odontoclasts in A. mexicanum.
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The product of the addition reaction of 1,1,1,4,4,4-hexachloro-1, 4-disilabutane with N-methylimidazole is &mgr;-ethylene-C(1):C(2)-bis[dichlorotris(1-methylimidazole-N(3))sili con(IV)] dichloride, C(26)H(40)Cl(4)N(12)Si(2)(2+).2Cl(-). Two of the six Cl atoms are replaced by aromatic nitrogen bases and the coordination sphere of silicon is extended from four to six. The molecule is located on a crystallographic centre of inversion. The environment around the Si atom can be described as a slightly distorted octahedron with the Cl atoms occupying axial positions and the three N-methylimidazole ligands and the ethylene bridge in the equatorial plane.
The reaction of 2,6-dimethylpyridine with TiBr(4) affords the title compound, [TiBr(4)(C(7)H(9)N)], which is the first example of a neutral TiBr(4)L complex (L is a singly bonded ligand). The environment around the Ti atom can be described as a somewhat distorted trigonal bipyramid, with the nitrogen base occupying an equatorial position. The crystal was a non-merohedral twin.
We have determined the crystal structures of bicyclo[2.2. 1]hept-2-ene-endo-cis-5,6-dicarboxylic anhydride, C(9)H(8)O(3), (I), 1,2,3,4,7,7-hexachlorobicyclo[2.2.1]hept-2-ene-endo-cis-5, 6-dicarboxylic anhydride diethyl ether solvate, C(9)H(2)Cl(6)O(3).0. 16C(4)H(10)O, (II), bicyclo[2.2.1]hept-2-ene-endo-cis-5, 6-dicarboxylic acid, C(9)H(10)O(4), (III), 1,2,3,4,7, 7-hexachlorobicyclo[2.2.1]hept-2-ene-endo-cis-5,6-dicarboxylic acid, C(9)H(4)Cl(6)O(4), (IVa) and (IVb), and ethyl 1,2,3,4,7, 7-hexachloro-6-carboxybicyclo[2.2. 1]hept-2-ene-endo-cis-5-carboxylate monohydrate, C(11)H(8)Cl(6)O(4). H(2)O, (V). Compounds (I) and (II) were prepared by a standard Diels-Alder reaction from maleic anhydride and cyclopentadiene or hexachlorocyclopentadiene, respectively. The crystal-growing processes of these compounds led to surprising results: rapid recrystallization of (I) from diethyl ether and (II) from petroleum ether gave crystals of these compounds, however, crystallization by slow evaporation techniques using common solvents yielded new compounds in which the five-membered heterocycle has been cleaved.
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Unexpected stability is observed for the palladacycloheptane rac-2, which is obtained as major product and single diastereomer from the cyclization of 1 and Pd(0). Up to a temperature of 50 degrees C 2 shows neither reductive elimination nor intramolecular insertion of another olefin.
The maxim governing the accomplishment of medical tasks by the Medical Service of the Bundeswehr stipulates that the soldiers will, in case of illness, accident or injury, receive medical treatment to the standard they can expect in the Federal Republic of Germany. In this context the introduction of telemedical applications into the Medical Service will improve the quality of the medical care through better and faster access for the medical officer assigned to a unit or a ship for requesting support to expert knowledge from military facilities or the civilian sector. The telemedical system is based on a high-class commercial PC. This workstation can be extended as needed with medical devices (x-ray film digitizer, dermatoscope, otoscope) and allows linkage to other imaging methods (e.g., videocamera, ultrasound). Currently this system is under evaluation in a multi centre trial. The participants of this telemedical network communicate via EURO ISDN lines with sufficient bandwidth. If terrestrial lines are not available the communication will be based on satellite capacity. The application of internet-technology additionally provides access to medical data bases respectively allows civil-military co-operation and the interoperability between medical services of allied armed forces. This future-orientated telemedical approach with its modular upwards-compatibility will provide, especially in its mobile version and by using communication standards, the possibility to support necessary civil-military co-operation in the area of disaster relief and missions outside of Germany in the future.
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A procedure is presented for exact, detailed comparison of light and electron microscopic analyses of tissues with complex architecture. Earlier techniques require one to make drawings of tissue pieces to be analyzed by electron microscopy to permit rough localization of the origin of the tissue pieces. Specifically, exact analysis of fetal cartilage and bone is hampered by the complicated arrangement of both tissue components, severely limiting the assessment of electron microscopic analyses. The advantage of the technique described here is that it allows precise localization of the tissue sample in the original tissue area. Punches 1 min in diameter were obtained from femora and coxae with a syringe and embedded for light and electron microscopy. The remaining tissue with its exactly defined punctures is prepared for standard histology. Human fetal cartilage and bone tissue were used to demonstrate this technique, but this procedure may be used for other kinds of tissues.
The wall of the pulp cavity, fracture faces and the demineralized surfaces of teeth from larvae and adults of Ambystoma mexicanum were investigated by scanning electron microscopy (SEM). Calcium and phosphate contents were determined by microanalysis. The apical part of the tooth (crown, tooth apex) contains dentin canals. In the larva, these do not reach the enamel-dentin border but end below this border in front of a denser hard substance, possibly enameloid. The pedicel in the adult and the basal portion of the tooth in the larva (base) are without dentin canals. These parts of the teeth are characterized by longitudinally arranged collagen fibres as visualized on the demineralized surfaces. These observations indicate a congruency in early-larval and adult teeth between base and pedicel as well as apex and crown. This partition is also confirmed by the calcium and phosphate values which were identical in larvae and adults. Highest values are found in enamel and lowest values in the tooth-bearing bone. Calcium and phosphate content show a clear difference between dentin and the basal part of the tooth (pedicel and base). The ring-like dividing zone in the adult tooth is less well mineralized.
OBJECTIVE: Blockade of the stellate ganglion is an established and highly effective diagnostic and therapeutic procedure for management of certain acute and chronic pain syndromes or other disorders. The paratracheal injection of a local anaesthetic is the simplest and most frequently used approach for blocking the cervicothoracic sympathetic nerves (ganglion stellate). However, since serious complications can occur during or following the anterior paratracheal technique including accidental intravenous or intraarterial injection, non-invasive methods for blockade of the stellate ganglion have been suggested. In 1980 Jenkner (15) reported the successful interruption of the sympathetic outflow from the stellate ganglion together with the relief of pain by transcutaneous electrical nerve stimulation (TENS), followed by the development of an "optimal wave form" in 1981 (14). Since we were unable to reproduce Jenkner's results of sympathetic blockade in our patients, this study was designed to investigate the effects of TENS on the sympathetic activity of the stellate ganglion in healthy volunteers. METHODS: 50 healthy volunteers were randomised into two groups (n = 25). In group I the left stellate ganglion was stimulated for 20 min by the mode described by Jenkner (monophasic pulse, small anode, large cathode, frequency 20 Hz), while group II was stimulated by conventional TENS (biphasic pulse, electrodes of identical size, frequency 100 Hz). The method of stimulation was blinded to both the investigator and the subjects investigated. Measurements included cutaneous blood flow of the volar forearm (laser Doppler), skin temperature on two sites of the cheeks (thermistor), pupil diameter and size of the palpebral fissures, sweat production (ninhydrine test) and global sensitivity and pain perception thresholds on both sides (electrical stimulation). Measurements were performed before TENS of the stellate ganglion, after 5, 10, 15 and 20 min of stimulation and 10 min after termination of TENS. Statistical analysis of the obtained data was performed by Friedman-Test and by Mann-Whitney-U-Test. p < 0.05 was assigned statistical significance. MAIN RESULTS: Skin temperature increased in both groups and on both sides by 1.2 degrees C, while skin perfusion rate, pupil size, size of the palpebral fissure and sweat production remained unchanged. Global sensitivity and pain perception thresholds of forehead decreased in both groups and on both sides, while there was no change of both parameters on the hands. CONCLUSION: No signs and symptoms of sympathetic blockade could be demonstrated in any of the groups, neither by TENS of the stellate ganglion as described by Jenkner nor by unspecific TENS. Thus, pain relief by TENS of the stellate ganglion as reported in the literature must involve other mechanisms than sympathetic blockade. In addition, TENS may not replace traditional blockade of the stellate ganglion by local anesthetics, if sympathetic blockade is required for diagnostic and therapeutic purposes.
We tested the hypothesis that the perceived availability of safety resources plays an influential role in fear prediction bias. Claustrophobic Ss (N = 37) completed a claustrophobic challenge under conditions of either low or high proximity to safety. Proximity to safety was operationalized as distance from the exit. We examined the effects of proximity to safety on Ss' predicted fear, actual fear, and discrepancy between predicted and actual fear (prediction bias). Consistent with prediction, the availability of safety resources had a more pronounced effect on Ss' actual fear than Ss' predicted fear. Moreover, subjects displayed a significant underprediction bias when proximity to safety was low and a slight (albeit nonsignificantly) overprediction bias when proximity to safety was high. Our results lend further support for the hypothesis that anxious Ss underutilize safety information when confronting perceived threats. Possible mechanisms underlying this tendency are discussed.