Biomedical subjects
Publications and source records attributed to G Fleischer.
Upon heating, concentrated solutions of star polymers and block copolymer micelles in a good solvent, representing soft spheres, undergo a reversible gelation. This phenomenon is attributed to the formation of clusters causing a partial dynamic arrest of the swollen interpenetrating spheres at high temperatures. A phase diagram analogous to that of sterically stabilized colloids is proposed.
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Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) was used to investigate the self-diffusion behavior of water molecules in cartilage, polymeric cartilage components, and different model polymers. The short-time self-diffusion coefficients (diffusion time delta approximately/= 13 msec) are found to decrease steadily with decreasing water content. This holds equally well for cartilage and cartilage components. The short-time diffusion coefficients are subjected to a rather nonspecific obstruction effect and mainly depend on the water content of the sample. The long-time diffusion coefficients in cartilage (delta approximately/= 500 msec), however, reflect structural properties of this tissue. Measurements with varying observation times as well as experiments involving enzymatic treatment of articular cartilage suggest that the collagenous network in cartilage is likely to be responsible for the observed restricted diffusion.
The study presents an analysis of 20 cases of acute acoustic trauma caused by toy pistols. The problem generally involves boys within the age range from 6 to 11 years. Half of the incidents involved attacks with toy pistols used as weapons. Auditory damage appeared in two types, each of which had a notch in the audiogram at the frequency range between 10 and 14 kHz. In children, a shot close to one ear can damage both ears. Great differences in the severity of tinnitus were apparent. The most severe cases of tinnitus were observed in the children with no or minor permanent auditory damage. Children experiencing long periods of uninterrupted tinnitus suffer significantly. This is not only detrimental to family life, but also to the performance of the children at school. The total expenses of treatment for these 20 cases were estimated to be approximately 80,000 DM (40,000 Euro).
In order to understand the repeated occurrences of auditory impairments caused by toy pistols, an analysis of the circumstances involved was performed at Justus-Liebig University of Giessen. The acoustic impact of toy pistols on the ear was determined with a special measuring system for impulse noise. Results were compared with the acoustic impacts of the G3 common rifle of the German military on the ear of the soldier. It was apparent that all of the five randomly selected types of toy pistols were much louder than the military rifle, if fired close to the ear. The current standard of the European Union related to the safety of toys (EN 71-1) tolerates peaks of impulse noise from toy pistols that are actually illegal for workplaces without auditory protection. Measurements showed that the toy pistols tested were even louder than that tolerated by the EU standard. Problems related to acute acoustic trauma caused by these toys are discussed using recent examples. In order to prevent such injuries, we suggest limiting the loudness of the "worst case" instead of using unrealistic measurements.
We report on self-diffusion measurements of all the components in distinct phases of the ternary system water/n -heptane/Igepal CA-520 with pulsed field gradient NMR. The phases are also investigated with electron microscopy. The observed self-diffusion coefficients are discussed in comparison with the structural data obtained from the micrographs. They intimately reflect the effect of the phase state and phase boundaries on the molecular transport in this system.
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Transverse nuclear magnetic relaxation and self-diffusion of water were measured in hydrated collagen II. Self-diffusion measurements were conducted by pulsed field gradient NMR (PFG NMR) and weighting of the different species in the signal by variable T2 relaxation in the experiment. Two fractions of water protons were detected, one with a short T2 value but high diffusivity and one with a long T2 value and low, completely restricted diffusion. The distance of the diffusion barriers was determined to be 2.3 microns. Possible reasons for the restriction in the movement of the water molecules in comparison with structural models of collagen II are discussed.
Quasistatic loading of the isolated pelvis and of the pelvis in situ is reported; dynamic loading with an impactor and on 90 degrees car/car side impact are then considered. The isolated pelvis was loaded laterally at the ala of the ilium and the pelvis in situ in the anterior-posterior direction in the area of the symphysis with universal dynamometer; the loading profile was a rigid disk 150 mm in diameter. Some dynamic tests were performed with an impactor with rigid disk 80 mm in diameter as impact surface; the impact was applied against the trochanter major area at a velocity of 30-35 km/h. Otherwise, the pelvic area was stressed by impact through the intrusion of the car side or by impaction of the pelvis against a rigid wall. In the tests conducted with isolated pelves, forces of 850-4850 N were measured; pelvic fractures were observed, specifically fractures of the acetabular margin, pubic bone, and ischium, and comminuted fractures of the symphysis and the iliosacral. In the impactor tests, forces of 6.5-11 kN were enough to cause, pelvic fracture except in one case, and fractures of the femoral neck were found in some cases in addition. With quasistatic anterior-posterior loading of the pelvis in situ, forces of 4,700-10,000 N were measured in cases in which fractures were found.
The sorption and desorption of water in rape seeds was measured. From the sorption isotherm it follows that for water content greater than about 6% the water molecules tend to form clusters. The mutual diffusion coefficient of water into and out of the seeds was determined from the time dependence of sorption and desorption. There is a pronounced hysteresis in the sorption-desorption process, desorption proceeds faster than sorption. The self-diffusion of water (at maximum humidity of the seeds) and oil within the seeds was investigated by the pulsed field gradient NMR. The measurement of oil self-diffusion shows restricted diffusion of the oil within droplets and allows the determination of the droplet radii and their distribution width.
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The sensitivity of three different enzyme-linked immunosorbent assays (ELISAs: Enzygnost-Rubella/Behring Co., Rubazyme (M)/Abbott Co., Rubelisa M/M.A.B.) was examined for detection of rubella-specific IgM and IgG antibodies. The screening of the sera of 20 s.c. vaccinated persons (rubella strain Cendehill) using these diagnostic systems revealed that the ELISAs are capable to detect the rubella IgG antibodies reliably. Additional haemagglutination inhibition (HI), and single radial haemolysis (SRH) tests confirmed this fact. Antibody kinetics seen in Enzygnost-Rubella are similar to those determined by HI. In contrast, it was found that the Rubazyme test is able to detect largely late IgG antibodies in agreement with the data obtained by SRH, which may be helpful to exclude a rubella reinfection. A result negative in Rubazyme, but positive in HI should indicate a positive rubella IgM test. For the determination of subclass-specific IgG antibodies the sandwich assay was extended to a 4-phases-test, using specific antibodies to IgG1-IgG4. After acute rubella infection or vaccination the antibodies of the IgG3 subclass appear before the other. The rubella antibodies in the IgG3 exceed its quantitative distribution in the total IgG (about 7.5%). The determination of IgM-specific rubella antibodies with the Enzygnost-Rubella and Rubazyme M systems proved also to be rather sensitive and reliable. No interference was seen from rheumatoid factor activity, IgG competition and heterologous IgM. In contrast, the Rubelisa M system should be improved in evaluation procedures. However, since all systems showed also differences to HI using IgM fractions, it seems to be advisable to apply an additional rubella IgM test beside ELISA in critical cases.
Dolphins have the most highly developed acoustical system in nature. They are not only able to hear far into the realm of ultrasound, but they have also developed a magnificent echolocation system. Baleen whales, on the other hand, are specialists for extremely low frequencies, without echolocation. In order to overcome technical problems it was necessary to drastically alter the construction of the hearing organ, of the entire skull, and even the skin. A short review of the current knowledge is presented, along with a discussion of the biotechnology involved.
A case of brachial artery rupture following compound dislocation of the elbow is reported. Arterial injury is a well-known complication of a supracondylar fracture of the humerus, but is very rare in association with elbow dislocation. A reversed saphenous vein graft was used for treatment of the arterial injury and is the recommended method of management.
One hundred and twenty consecutive liver injuries treated at the Royal Prince Alfred Hospital have been studied prospectively. The overall mortality of 17.5% and the mortality for blunt injury of 23% compare quite favourably with figures in other reported series of similar injuries. The surgeon who treats liver injury must have a repertoire of procedures appropriate for different circumstances and must remain flexible in his approach. Simple suture haemostasis and the provision of adequate drainage will cope with most injuries. Debriding resections are safe, allow adequate haemostasis to be achieved, and give reasonably good access to the retrohepatic vena cava and hepatic veins. Formal lobectomy is very rarely indicated. Drainage of the common bile duct is to be avoided, but cholecystostomy has some marginal advantages and appears safe. The problems of retrohepatic vena caval injury and major hepatic vein tears have not all been solved.
Membrane microenvironmental changes associated with thrombin-induced platelet activation were followed by fluorescence intensity and polarization studies of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labeled human platelets. The labeling of washed platelets with DPH did not alter platelet intactness and morphology. In response to thrombin, DPH-labeled platelets exhibited reduced serotonin release, yet aggregation was barely inhibited. Shape change induced by thrombin or ADP was indistinguishable in control and in DPH-labeled platelets. During platelet aggregation induced by thrombin, fluorescence intensity increased by about 14%, which may indicate a more hydrophobic exposure of the probe. However, no change in fluorescence was detected during platelet shape change, induced either by thrombin in presence of EDTA or by ADP. Thrombin-activated platelets exhibited an increase in values of fluorescence polarization (P) during the stages of shape change and secretion, which further increased during aggregation. A similar pattern of increase in P values characterized platelet shape changes, caused either by thrombin in the presence of EDTA or by ADP. Changes in individual platelets are discernible from the alterations of the aggregating cells. These results may indicate that platelet activation is accompanied by an increase in rigidity of the membrane lipids. Functionally, the elevated "microviscosity" may reflect a primary role of membrane lipids in modulating the process of platelet activation or secondary transitions in lipids due to membrane events mediated by proteins.
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Foam-Test by Clements is a valuable method for determining the foetus maturity of lungs. We introduce this test along with other parameters for the maturity-diagnosis since one year. In 15% result, the Foam-Test was not applicable because of blood, or meconic amniotic fluid, other wise wrong negative and in 0% wrong positive results. By unmatured child, there was doubtable results with Foam-Test. Since it is important to determine the early delivery of unmatured children, particularly the case of foetus maturity of lungs must be exact, we therefore decided to use the Lecithin/Sphingomyelinquotients in some cases. The results of Lecithin/Sphingomyelinquotient in unmatured children are almost with the approximated date under two. From this, one must deduce from these children, that the intrauterine unmatured lungs lately took place.