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Biomedical subjects

G Meyer

Publications and source records attributed to G Meyer.

At least 325 records · Page 18Linked to original sources
PubMed1989

[Root canal preparation with Canal-Finder system. Scanning electron microscopy and clinical studies].

Root canal preparation was performed with the new Canal-Finder-System in extracted teeth and in simulated root canals in resin blocks. The results of SEM- and stereomicroscopic investigation showed severe alterations of root canal morphology in the apical part of the canal in many cases. Excellently cleaned and shaped canal walls were found as well as parts, which were not instrumented at all or covered with smear layer and debris. The Canal-Finder-System was found to be a good and suitable device for the initial instrumentation of narrow and severely curved canals, but cannot replace hand instrumentation as the standard method of root canal preparation.

Dental Pulp Cavity↗
PubMed1989

[Factors influencing the corrosion of amalgams].

In a comparative corrosion test specimen were produced from eleven different amalgams using two different plugging pressures and were exposed to two different corrosive solutions. As was to be expected containing amalgams corroded the most. A more accurate differentiation between the individual non gamma 2 amalgams and the two different plugging pressures was only possible with the stronger corrosive solution. Therefore this solution seemed to be better suited for a standardized corrosion test according to DIN 13904, part 2. The greater plugging pressure inhibits corrosion especially in badly corroding amalgams. This seems to be due to the limited diffusion which is the result of a smaller pore size.

Corrosion↗
PubMed1989

[Temperature determination of root surfaces in manual and mechanical preparation of root canals].

In in vitro studies it was determined which temperatures develop on the root surface using different root canal preparation techniques. 62 teeth were filed manually, by conventional mechanic technique and by ultrasonic driven instruments. Practicing manual and mechanic filing critical temperatures for the cell structures of the desmodont did not develop. Ultrasonic and ultrasonic--like instruments, however, develop high temperatures on the root surface so that the cooling effect of the irrigation liquid after each instrumentation is not sufficient and a continuous irrigation during filing is indicated.

Hot Temperature↗
PubMed1989

Direct projections from the medulla oblongata to selective cortical areas in the rat.

Injections of horseradish peroxidase into different cortical areas reveal that neurons located in the rostroventral medulla oblongata innervate restricted cortical areas: the anterior and posterior cingulate cortex and the insular cortex. Other cortical areas do not receive medullary projections. Neurons projecting to both the anterior and the posterior cingulate cortex lie scattered throughout a wide territory of the ventrorostral medulla, whereas neurons projecting to the insular cortex are restricted to more medial regions.

Animals↗
PubMed1988

Early postnatal development of cholecystokinin-immunoreactive structures in the visual cortex of the cat.

The early postnatal development of cholecystokinin-immunoreactive (CCK-ir) neurons was analyzed in visual areas 17 and 18 of cats aged from postnatal day 0 to adulthood. Neurons were classified mainly by axonal criteria. According to their chronology of appearance neurons are grouped into three neuronal populations. The first population consists of five cell types which appear perinatally in areas 17 and 18. Four of them have axons terminating in layer VI. Neurons with columnar dendritic fields of layers IV and V display a conspicuous dendritic arborization with the long dendrites always arranged parallel to each other. This way they form a vertically oriented dendritic column. The neurons differentiate at around P 2 and are present until the end of the second postnatal week. They disappear possibly by degeneration and cell death. Multipolar neurons of layer VI have long dendrites and axonal domains of up to 800 micron in diameter. Three percent of these neurons send out two axons instead of only one. Neurons differentiate at P 0 and the cell type persists into adulthood. Bitufted to multipolar neurons of layer V constitute a frequent type; 10% of these cells issue two axons. They differentiate at P 2 and the type survives into adulthood. Bitufted to multipolar neurons of layers II/III appear at P 2 and send their axons into layer VI. So, early postnatally an axonal connection from superficial cortical layers to layer VI is established. The cell type persists into adulthood. The fifth cell type of the first population is constituted by the neurons of layer I with intralaminar axons which differentiate at P 2. Although they derive from the early marginal zone, the cell type survives into adulthood. The second population consists of two cell types which appear around the end of the second and during the third postnatal week in areas 17 and 18. Multipolar neurons of layer II have horizontally or obliquely arranged basket axons which, during the second postnatal month, form patches of high fiber and terminal density along the layer I/II border. Neurons with descending main axons issuing horizontal and oblique collaterals of layers II-IV form broad axonal fields. The third population in area 17 is constituted by three cell types: Bitufted neurons with axons descending in form of loose bundles of layers II/III differentiate during the fifth postnatal week. Small basket cells of layers II/III with locally restricted axonal plexuses and somewhat larger basket cells of layer IV appear during the sixth and seventh week.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1988

Uncoupling of Na+H+ from Cl-HCO3- exchange under some steady state conditions in rabbit gallbladder.

The transapical Cl- influx and transepithelial Na+ transport were measured in rabbit gallbladder. Only 11.7% of the transported Na+ was found to be accompanied by HCO3-. 10(-4) M SITS eliminated the HCO3- dependent fraction of Cl- influx (50%) but did not significantly alter intracellular Na+ activity and Na+ transport. Exposure to HCO3-free salines or to 10(-4) M acetazolamide about halved Cl- influx and Na+ transport. 25 mM SCN- reduced Cl- influx to zero, decreased intracellular Na+ activity, but only halved Na+ transport which under these conditions was abolished only in the absence of HCO3-. Exposure to a Cl- -free saline produced effects similar to those caused by SCN-. These results suggest that when Cl-/HCO3- exchange is inhibited at the apical membrane, Na+/H+ exchange and transepithelial Na+ transfer are unmodified if HCO3- is available for transport. The permanent uncoupling of the exchangers and the elevated transepithelial transport of Na+ are not due to an increased activity of the parallel Na+-Cl- cotransport but to a redirection of HCO3- flux toward the basolateral side.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1988

Individual reconstruction of palatal concavities.

The biomechanical function of the incisor teeth and their relationship to the skeletal bases and the TMJ suggest certain criteria for the reconstruction of palatal surfaces of the maxillary incisors. The finding that occlusal morphology has the same protrusive curve and can be described by one constant confirms the possibility of reconstructing the palatal concavities individually. An instrument is described to facilitate formulation of these strategic surfaces.

Biomechanical Phenomena↗
PubMed1988

Environmental fate and distribution of sodium [14C] pentachlorophenate in a section of urban wasteland ecosystem.

An urban terrestrial microecosystem has been used under outdoor conditions to study the transfer of chemical residues within the system components. The microecosystem consisted of soil monoliths obtained from a site with an established vegetation cover dominated by goldenrod, Solidago gigantea. The microecosystem contained integrated food chain elements composed of primary producers, herbivores and carnivores. The system was stocked with indicator insect species, snails (Cepaea nemoralis) and earthworms (Allolobophora caliginosa), captured from the original site. Evaluation of the system was made using radiolabelled sodium pentachlorophenate (PCP-Na) which was applied as a single application at an equivalent rate of 5 kg ha-1. The mass balance revealed that, after 131 days, in the autumn, and after 222 days, in the winter, that 43 and 39% radiocarbon, respectively, was recoverable from the microecosystem. The unaccounted radiocarbon was very probably removed through volatilization and photomineralization of the compound. PCP residues on foliage decreased rapidly, 50% of which were metabolised within 15 days. Most of the radiocarbon remaining in the system after 131 days was in the top soil and plant litter, transmitted mainly through washing off by rain and leaf litter fall. There was a variation in the uptake of PCP-Na residues in the food chain organisms, where the total radiocarbon concentrations during the first 19 days of exposure ranged, e.g. in snails, from 3 to 0.6 micrograms g-1, in springtails from 5 to 105; in beetles (Amara fusca) from 3 to 1, in spiders from 13 to 11, and in harvestman from 31 to 77 micrograms g-1. The ecological magnification indices (EM) of all the organisms with respect to their main food source, i.e. plant litter, demonstrated no bioconcentration effects. This is attributed to the metabolism of PCP-Na by the organisms and its rapid excretion. The urban wasteland ecosystem contained in outdoor lysimeters employed as a model gives valuable information and has considerable value in predicting the ecological fate of industrial chemicals.

Animals↗
PubMed1988

Gliomatosis peritonei with endometriosis externa.

A case of gliomatosis peritonei developed 9 years after the removal of an immature ovarian teratoma is reported. An unique association of gliomatosis with endometriosis externa was found without the usual symptoms of endometriosis. The prognosis of gliomatosis is generally excellent and depends on the histological grade of the primary tumor and on the presence of organ metastasis or immature tumor elements in the implants. Pathogenetical aspects of both lesions are discussed briefly.

Child↗
PubMed1988

[Intermediate term results of treatment with the Francobal endoprosthesis in osteoarthritis].

Results one to eight years with a mean of five years after implantation of sixty Francobal-endoprostheses for total trapeziometacarpal joint replacement in fifty patients with osteoarthritis are presented. 91% of the patients achieved clinically good or very good results using a new standardized evaluation score. A worrying problem is the radiologic finding of asymptomatic lucencies in 43%, mainly around the stem component. Loosening, predominantly of the cup, has occurred in 18% and has been followed by two revision operations so far. Heavy manual work increases the risk of loosening, and such patients have to be excluded from this method.

Aged↗