Das piezoelektrische Verhalten der menschlichen Zahnhartgewebe

Zusammenfassung Bei menschlichen Zähnen wurde piezoelektrisches Verhalten festgestellt; dieses ist gebunden an den Kollagenfaseranteil des Dentins und des Zahnzementes. Schmelz ist nicht piezoelektrisch; entmineralisierte Zähne zeigen ein verstärktes piezoelektrisches Verhalten.Es besteht eine piezoelektrische Achse in der physiologischen Zahnlängsrichtung, deren Richtungssinn bei allen Zähnen des Ober- und Unterkiefers gleich ist und offenbar der morphogenetischen Entwicklungsrichtung des Zahnes entspricht. Außerdem besteht rund um die piezoelektrische Längsachse herum in allen radialen Richtungen zwischen Pulpahöhle und Zahnaußenseite piezoelektrisches Verhalten, das möglicherweise in Beziehung zur Struktur der Dentinlamellen und damit zur morphogenetischen Zahnentwicklung in radialer Richtung steht.Die piezoelektrischen Effekte zeigen von Zahn zu Zahn eine erhebliche biologische Streubreite. Bei unserem Untersuchungsmaterial lagen die Effekte zwischen 3,5·10^–10 und 1,9·10^–9 est E Ldg./dyn. Diese Werte entsprechen etwa 0,5 bis 2,8% des piezoelektrischen Koeffizienten d₁₁ von -Quarz.

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Summary Human teeth are piezoelectric. This is due to the collagen-fibril content of the dentine and tooth cement. Enamel is not piezoelectric; decalcified teeth show increased piezoelectric behaviour.There is a piezoelectrical axis corresponding to the physiological longitudinal tooth axis, which is in the same direction in all teeth of both upper and lower jaws, and which seems to correspond to the morphogenetical development axis of teeth. Piezoelectric behaviour also exists between the pulp cavity and outer surface of the tooth in all directions radial to the piezoelectric longitudinal axis. The latter is possibly due to the dentine lamellae, and therefore may be connected with the radial direction of morphogenetical tooth development.The piezoelectric effects show large biological variations in different teeth. The effects from our research materials vary between 3.5·10^–10 and 1.9·10^–9 e.s.u./dynes. These results correspond to about 0.5 to 2.8% of the piezoelectrical coefficient d₁₁ of -quartz.

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Unterstützt durch Sachbeihilfen der Deutschen Forschungsgemeinschaft.

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cand. med. dent. und derzeit Doktorand an der Klinik und Poliklinik für Zahn-, Mund- und Kieferkrankheiten, Universität Kiel.     

Bellevalia ciliata (Cyr.) Nees (Hyacinthaceae) neu für Bulgarien

(Bellevalia ciliata was recorded in north-east Bulgaria south of the Dobrudsha, within field and steppe vegetation. Vegetation records and a distribution map are presented. Based on taxonomic studies it is proposed to combineB. ciliata, B. sarmatica (Pall.) Wor. andB. speciosa Wor. under the oldest nameB. ciliata (Cyr.) Nees.     

Multiple proteins bind to the P2 promoter region of the zein gene pMS1 of maize

Summary A 216 by promoter fragment of the 19 kDa protein zein gene pMS1, containing the CCAAT and TATA boxes, was analysed by a variety of techniques for in vitro interactions with nuclear proteins from endosperm tissue. HMG proteins were found to form stable complexes with these A/T-rich promoter sequences and several specific DNA-binding proteins appear to be involved in the formation of DNA-protein complexes with this fragment. A 29 bp region spanning the two CCAAT boxes was protected from DNase I digestion in footprinting experiments.     

Nickel accumulation and storage in Bradyrhizobium japonicum

Hydrogenase-derepressed (chemolithotrophic growth conditions) and heterotrophically grown cultures of Bradyrhizobium japonicum accumulated nickel about equally over a 3-h period. Both types of cultures accumulated nickel primarily in a form that was not exchangeable with NiCl2, and they accumulated much more Ni than would be needed for the Ni-containing hydrogenase. The nickel accumulated by heterotrophically incubated cultures could later be mobilized to allow active hydrogenase synthesis during derepression in the absence of nickel, while cells both grown and derepressed without nickel had low hydrogenase activities. The level of activity in cells grown with Ni and then derepressed without nickel was about the same as that in cultures derepressed in the presence of nickel. The Ni accumulated by heterotrophically grown cultures was associated principally with soluble proteins rather than particulate material, and this Ni was not lost upon dialyzing an extract containing the soluble proteins against either Ni-containing or EDTA-containing buffer. However, this Ni was lost upon pronase or low pH treatments. The soluble Ni-binding proteins were partially purified by gel filtration and DEAE chromatography. They were not antigenically related to hydrogenase peptides. Much of the 63Ni eluted as a single peak of 48 kilodaltons. Experiments involving immunoprecipitation of 63Ni-containing hydrogenase suggested that the stored source of Ni in heterotrophic cultures that could later be mobilized into hydrogenase resided in the nonexchangeable Ni-containing fraction rather than in loosely bound or ionic forms.     

A microdeletion of less than 250 kb, including the proximal part of the FMR-1 gene and the fragile-X site, in a male with the clinical phenotype of fragile-X syndrome

A gene designated "FMR-1" has been isolated at the fragile-X locus. One exon of this gene is carried on a 5.1-kb EcoRI fragment that exhibits length variation in fragile-X patients because of amplification of or insertion into a CGG-repeat sequence. This repeat probably represents the fragile site. The EcoRI fragment also includes an HTF island that is hypermethylated in fragile-X patients showing absence of FMR-1 mRNA. In this paper, we present further evidence that the FMR-1 gene is involved in the clinical manifestation of the fragile-X syndrome and also in the expression of the cellular phenotype. A deletion including the HTF island and exons of the FMR-1 gene was detected in a fragile X-negative mentally retarded male who presented the clinical phenotype of the fragile-X syndrome. The deletion involves less than 250 kb of genomic DNA, including DXS548 and at least five exons of the FMR-1 gene. These data support the hypothesis that loss of function of the FMR-1 gene leads to the clinical phenotype of the fragile-X syndrome. In the fragile-X syndrome, there are pathogenetic mechanisms other than amplification of the CGG repeat that do have the same phenotypic consequences.     

Prey selection of the shallow water fishPomatoschistus minutus (Gobiidae,Teleostei) in the SW Baltic

The aim of this investigation is to demonstrate the reasons of an opportunist feeder to select some components of the available food supply and to avoid others. Object of this test is the eurytopic and euryhaline sand goby,Pomatoschistus minutus (Pallas), from the Luebeck Bight. It inhabits both sand habitats as well as bottoms mixed with pebbles or continuous hard substrates. Therefore, it is often in close contact withMytilus-belts which present a very rich food supply of small crustaceans. The selectivity behaviour of sand gobies from a sand/clay ecotone was compared with that of populations from a stony pier and a sand bottom during the reproduction period. Regarding the numbers of prey organisms, crustaceans of the periphyton were generally preferred at the pier but avoided in the ecotone. The same is valid for prey organisms of the psammal which were preferred by gobies of the sand bottom but mostly avoided by populations of mixed bottoms. Analyses of size selections revealed that the preferred gammarids orJaera isopods were between 2 and 5 mm length. A balanced relation of goby biomass and utilizable food supply (predatory impact index) seems to effect positive selectivity of gammarids in theMytilus-belts or of harpacticoids in the sand bottom.     

Approximate digestibility of fibre for a graminivorous caterpillar

Final instar Persectania ewingii (Westwood) (Lepidoptera: Noctuidae) were fed seedling Triticum aestivum L. for 2 days to determine the approximate digestibility of the cell wall and cell content fractions. Cell wall content was estimated using a micro-analytical neutral detergent fibre technique. Approximate digestibilites of neutral detergent fibre, neutral detergent solubles and dry matter were calculated for individuals and pooled samples. P. ewingii larvae digested a small but significant proportion of the fibre ingested (13–21%), higher than that previously reported for herbivorous insects. The micro-analytical and previously used macro-analytical techniques produced similar estimates of digestibility although both techniques have inherent shortcomings, the latter requiring the pooling of samplex and the former limiting the number of replicates during chemical analysis. Differences in the amount of larval frass collected during the feeding trial (corrected for consumption) explained much of the variation in digestibility values, while there were no effects of larval mass, overall consumption and total frass produced on digestibility estimates. These results confirm that plant cell contents are the major source of nutrients to larval Lepidoptera although there is some chemical disruption of the plant cell wall.