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Biomedical subjects

M Beier

Publications and source records attributed to M Beier.

At least 19 recordsLinked to original sources
PubMed2004

Endolymphatic calcium supply for fish otolith growth takes place via the proximal portion of the otocyst.

The presence of calcium within the utricle of larval cichlid fish Oreochromis mossambicus was analysed by means of energy-filtering transmission electron microscopy. Electron-spectroscopic imaging and electron energy loss spectra revealed discrete calcium precipitations that were more numerous in the proximal endolymph than in the distal endolymph, clearly indicating a decreasing proximo-distal gradient. This decreasing proximo-distal gradient was also present within the proximal endolymph between the sensory epithelium and the otolith. Further calcium particles covered the peripheral proteinaceous layer of the otolith. They were especially pronounced at the proximal surface of the otolith indicating that otolithic calcium incorporation takes place here. Other calcium precipitates accumulated at the macular junctions clearly supporting an earlier assumption according to which the endolymph is supplied with calcium via a paracellular pathway. The present results clearly show that the apical region of the macular epithelium is involved in the release of calcium and that the calcium supply of the otoliths takes place via the proximal endolymph.

Animals↗
PubMed2004

Effect of hypergravity on carboanhydrase reactivity in inner ear ionocytes of developing cichlid fish.

It has been shown earlier that hypergravity slows down inner ear otolith growth in developing fish. Otolith growth in terms of mineralization mainly depends on the enzyme carboanhydrase (CA), which is responsible for the provision of the pH-value necessary for calcium carbonate deposition. Larval siblings of cichlid fish (Oreochromis mossambicus) were subjected to hypergravity (3 g, hg; 6 h) during development and separated into normally and kinetotically swimming individuals following the transfer to 1 g (i.e., stopping the centrifuge; kinetotically behaving fish performed spinning movements). Subsequently, CA was histochemically demonstrated in inner ear ionocytes (cells involved in the endolymphatic ion exchange) and enzyme reactivity was determined densitometrically. It was found that both the total macular CA-reactivity as well as the difference in reactivities between the left and the right maculae (asymmetry) were significantly lower (1) in experimental animals as compared to the 1 g controls and (2) in normally swimming hg-animals as compared to the kinetotically behaving hg-fish. The results are in complete agreement with earlier studies, according to which hypergravity induces a decrease of otolith growth and the otolithic calcium incorporation (visualized using the calcium-tracer alizarin complexone) of kinetotically swimming hg-fish was higher as compared to normally behaving hyper-g animals. The present study thus strongly supports the concept that a regulatory mechanism, which adjusts otolith size and asymmetry as well as otolithic calcium carbonate incorporation towards the gravity vector, acts via activation/deactivation of macular CA.

Animals↗
PubMed2004

Calcium-tracers disclose the site of biomineralization in inner ear otoliths of fish.

Since changing gravity (concerning direction and amplitude) strongly affects inner ear otolith growth and otolithic calcium incorporation in developing fish, it was the aim of the present study to locate the site of mineralization in order to gain cues and insights into the provenance of the otoliths inorganic compounds. Therefore, larval cichlid fish (Oreochromis mossambicus) were incubated in the calcium-tracer alizarin complexone (AC; red fluorescence). After maintenance in aquarium water for various periods (1, 2, 3, 6, 9 and 12 h; 1, 2, 3, 5, 6, 7, 15, 29, 36 and 87 d), the animals were incubated in the calcium-tracer calcein (CAL; green fluorescence). AC thus labeled calcium being incorporated at the beginning of the experiment and would subsequently accompany calcium in the course of a possible dislocation, whereas CAL visualized calcium being deposited right at the end of the test. Subsequently, the otoliths were analyzed using a laser scanning microscope and it was shown that the initial site of calcium incorporation was located directly adjacent to the sensory epithelium and the otolithic membrane. Later, calcium deposits were also found on further regions of the otoliths' surface area, where they had been shifted to in the course of dislocation. This finding strongly indicates that the sensory epithelium plays a prominent role in otolithic biomineralization, which is in full agreement with an own electron microscopical study [ELGRA News 23 (2003) 63].

Animals↗
PubMed2002

Influence of hypergravity on fish inner ear otoliths: II. Incorporation of calcium and kinetotic behaviour.

Larval siblings of cichlid fish (Oreochromis mossambicus) were subjected to hypergravity (hg; 3 g, 14 days) during development. Following the transfer to 1 g (i.e., stopping the centrifuge) they were separated into normally and kinetotically swimming individuals (the latter performed spinning movements). During hg, the animals were maintained in aquarium water containing alizarin-complexone (AC), a fluorescent calcium tracer. Densitometric measurements of AC uptake into inner ear otoliths (optical density of AC/micrometers2) revealed that the kinetotic individuals had incorporated significantly more AC/calcium than the normally behaving fish. Since the amount of otolithic calcium can be taken as an approximation for otolith weight, the present results indicate that the otoliths of kinetotically swimming samples were heavier than those of the normally behaving larvae, thus exhibiting a higher absolute weight asymmetry of the otoliths between the right vs. the left side of the body. This supports an earlier concept according to which otolith (or statolith) asymmetry is the cause for kinetoses such as human static space sickness.

Animals↗
PubMed2002

Influence of hypergravity on fish inner ear otoliths: I. Developmental growth profile.

Inner ear stones (otoliths) of larval cichlid fish Oreochromis mossambicus were marked with the calcium-tracer alizarin-complexone (AC) at 1 g earth gravity before and after a 3, 7, 14 or 21 days stay of the animals at hypergravity conditions (hg; 3 g, centrifuge). After the experiment, the otoliths' area between the two AC-labellings was measured with regard to size and asymmetry (size difference between the left and the right stones). Both utricular and saccular otoliths (lapilli and sagittae, respectively) continued growing in a linear way at hg, but growth was significantly slowed down as compared to parallely raised 1 g-control specimens. In case of bilateral asymmetry between the corresponding otoliths its formation in hg-animals became reduced as compared to the 1 g controls. The reduction of asymmetry was much more pronounced in the sagittae than in the lapilli. The latter result supports an earlier hypothesis, according to which especially a low sagittal asymmetry has a functional advantage. In general, the results strongly suggest that otolith growth is continuously regulated in dependence of the environmental gravity vector.

Animals↗
PubMed2002

Complexities in ETS-domain transcription factor function and regulation: lessons from the TCF (ternary complex factor) subfamily. The Colworth Medal Lecture.

The ETS-domain transcription factor family can be divided into a series of subfamilies. Elk-1 represents the founding member of the ternary complex factor (TCF) subfamily. By focusing on the TCF subfamily, we can demonstrate the complexities that exist in the function and regulation of ETS-domain transcription factors. This article focuses on Elk-1 in detail and summarizes the functions of other TCFs. The key themes covered include the domain structure of the TCFs, the mechanisms of complex formation with serum response factor, regulation of TCFs by mitogen-activated protein kinase cascades, and transcriptional regulatory properties of the TCFs. Finally, the emerging role of the TCFs in vivo is discussed. A picture is developing indicating that, while these proteins exhibit significant sequence and functional conservation, key differences in their structure and regulation are being identified which may relate to unique functions of these proteins in vivo.

Amino Acid Sequence↗
PubMed2002

Neuronal regulation of otolith growth and kinetotic behaviour.

Inner ear stones (otoliths) of larval cichlid fish were labelled with the calcium-tracer alizarin-complexone (AC) before animals were subjected to hypergravity (hg; 3 g). After the experiment, the otoliths' area between the two AC-labellings was measured. Growth of hg-otoliths was significantly slowed down as compared to 1 g-control specimens. In the course of a second experiment, the vestibular nerve was unilaterally transacted in neonate swordtail fish which were subsequently incubated in AC. Incorporation of AC was considerably lower in the otoliths of the transacted side. The results strongly suggest that otolith growth is continuously regulated in dependence of the environmental gravity vector. Since the otolithic calcium incorporation ceased on the transected head sides, it is concluded that the regulation of otolith growth is based on the central nervous efferent vestibular system.

Research Support, Non-U.S. Gov't↗
PubMed2001

Manufacturing DNA microarrays of high spot homogeneity and reduced background signal.

Analyses on DNA microarrays depend considerably on spot quality and a low background signal of the glass support. By using betaine as an additive to a spotting solution made of saline sodium citrate, both the binding efficiency of spotted PCR products and the homogeneity of the DNA spots is improved significantly on aminated surfaces such as glass slides coated with the widely used poly-L-lysine or aminosilane. In addition, non-specific background signal is markedly diminished. Concomitantly, during the arraying procedure, the betaine reduces evaporation from the microtitre dish wells, which hold the PCR products. Subsequent blocking of the chip surface with succinic anhydride was improved considerably in the presence of the non-polar, non-aqueous solvent 1,2-dichloroethane and the acylating catalyst N:-methylimidazole. This procedure prevents the overall background signal that occurs with the frequently applied aqueous solvent 1-methyl-2-pyrrolidone in borate buffer because of DNA that re-dissolves from spots during the blocking process, only to bind again across the entire glass surface.

DNA Probes↗
PubMed2001

A 2-step non-surgical procedure and systemic antibiotics in the treatment of rapidly progressive periodontitis.

BACKGROUND: In the last few years knowledge about periodontal infections has increased enormously, nevertheless practitioners are still seeking guidelines for suitable treatment concepts. METHODS: The aim of this study was to examine the effect of doxycycline, metronidazole, and clindamycin used adjunctively in a 2-step nonsurgical procedure in patients with rapidly progressive periodontitis (RPP). The first step included scaling, root planing, and polishing (SRP) in each quadrant using 4 to 5 visits. The second step included full-mouth enhanced root planing (RP) and wound dressing in 1 or 2 visits after SRP and the beginning of antibiotic therapy. Forty-eight patients (mean age 32.4 years) with generalized RPP, with an average of 16 sites with probing depths (PD) deeper than 8 mm, and high counts of Porphyromonas gingivalis were randomly assigned to 4 different groups: group 1 (doxycycline) n = 12, group 2 (metronidazole) n = 15, group 3 (clindamycin) n = 11, and group 4 (control group; no antibiotic treatment) n = 10. Clinical evaluations, including plaque index (PI), sulcus bleeding index (SBI), probing depth (PD), clinical attachment level (CAL), and bacteriological and crevicular cell sampling, were done at baseline (BL), 3 weeks after SRP, and 6 and 24 months after RP. RESULTS: After the first step (SRP), we observed an improvement of PI and SBI in all 4 groups, but did not see any statistically significant PD reduction 3 weeks after SRP compared to baseline. However, 6 and 24 months after the second step (RP) we observed a significantly greater reduction of PD in groups 2 and 3 and a significantly greater CAL gain in comparison to groups 1 and 4. After 24 months, the attachment level gain in group 1 and group 4 was less than 1.5 mm, and less than 1.0 mm in PD site categories 6 to 9 mm and >9 mm. PI showed no significant difference between the groups throughout the period after SRP until 24 months, compared to 3 weeks after SRP. SBI decreased most in the metronidazole and clindamycin groups. P. gingivalis and Actinobacillus actinomycetemcomitans were almost completely eradicated in these 2 groups 24 months after RP. In addition, the phagocytotic capacity of crevicular polymorphonuclear neutrophils was increased in groups 2 and 3 after the second step. CONCLUSIONS: The present results show that metronidazole and clindamycin are effective antibiotics when used adjunctively in a 2-step nonsurgical procedure of scaling and root planing in RPP patients.

Adult↗
PubMed2000

Construction and immunogenicity in mice of attenuated Salmonella typhi expressing Plasmodium falciparum merozoite surface protein 1 (MSP-1) fused to tetanus toxin fragment C.

One strategy to develop a multi-antigen malaria vaccine is to employ live vectors to carry putative protective Plasmodium falciparum antigens to the immune system. The 19 kDa carboxyl terminus of P. falciparum merozoite surface protein 1 (MSP-1), which is essential for erythrocyte invasion and is a leading antigen for inclusion in a multivalent malaria vaccine, was genetically fused to fragment C of tetanus toxin and expressed within attenuated Salmonella typhi CVD 908. Under conditions in the bacterial cytoplasm, the fragment C-MSP-1 fusion did not form the epidermal growth factor (EGF)-like domains of MSP-1; monoclonal antibodies failed to recognize these conformational domains in immunoblots of non-denatured protein extracted from live vector sonicates. The MSP-1 was nevertheless immunogenic. One month following intranasal immunization of BALB/c mice with the live vector construct, four out of five mice exhibited > or =four-fold rises in anti-MSP-1 by ELISA (GMT=211); a single intranasal booster raised titers further (GMT=1280). Post-immunization sera recognized native MSP-1 on merozoites as determined by indirect immunofluorescence. These data encourage efforts to optimize MSP-1 expression in S. typhi (e.g. as a secreted protein), so that the EGF-like epitopes, presumably necessary for stimulating protective antibodies, can form.

Animals↗
PubMed2000

Production by quantitative photolithographic synthesis of individually quality checked DNA microarrays.

For DNA chip analyses, oligonucleotide quality has immense consequences for accuracy, sensitivity and dynamic range. The quality of chips produced by photolithographic in situ synthesis depends critically on the efficiency of photo-deprotection. By means of base-assisted enhancement of this process using 5'-¿2-(2-nitrophenyl)-propyloxycarbonyl-2'-deoxynucleoside phosphoramidites, synthesis yields improved by at least 12% per condensation compared to current chemistries. Thus, the eventual total yield of full-length oligonucleotide is increased more than 10-fold in the case of 20mers. Furthermore, the quality of every individual array position was checked quantitatively after synthesis. Subsequently, the quality tested chips were used in successive hybridisation experiments.

DNA↗
PubMed1999

Versatile derivatisation of solid support media for covalent bonding on DNA-microchips.

A chemistry was developed that permits on DNA-arrays both the covalent immobilisation of pre-fabricated nucleic acids-such as oligonucleotides, PCR-products or peptide nucleic acid oligomers-and the in situ synthesis of such compounds on either glass or polypropylene surfaces. Bonding was found to be stable even after some 30 cycles of stripping. Due to a dendrimeric structure of the linker molecule, the loading can be modified in a controlled manner and increased beyond the capacity of glass without negative effects on hybridisation efficiency. Also, the chemistry warrants the modulation of other surface properties such as charge or hydrophobicity. Preferentially, attachment of nucleic acids takes place only via the terminal amino-group of amino-modified oligonucleotides or the terminal hydroxyl-group of unmodified molecules so that the entire molecule is accessible to probe hybridisation. This derivatisation represents a support chemistry versatile enough to serve nearly all current forms of DNA-arrays or microchips.

Base Sequence↗
PubMed1999

Chemical etiology of nucleic acid structure: comparing pentopyranosyl-(2'-->4') oligonucleotides with RNA.

All four members of the family of pentopyranosyl-(2'-->4') oligonucleotide systems that contain beta-ribo-, beta-xylo-, alpha-lyxo-, or alpha-arabinopyranosyl units as repeating sugar building blocks are found to be much stronger Watson-Crick base-pairing systems than RNA. The alpha-arabinopyranosyl system is the strongest of all and in fact belongs to the strongest oligonucleotide base-pairing systems known. Whatever the chemical determinants by which nature selected RNA as a genetic system, maximization of base-pairing strengths within the domain of pentose-derived oligonucleotide systems was not the critical selection criterion.

Arabinose↗
PubMed1994

Expression of human immunodeficiency virus antigens in an attenuated Salmonella typhi vector vaccine.

Human immunodeficiency virus is known to enter the host at parenteral and mucosal sites and consequently an effective vaccine should stimulate immunity at both routes of entry. One approach toward stimulating HIV-specific mucosal and systemic immunity is the use of candidate live oral Salmonella typhi vector vaccine, strain CVD 908, which has been shown to stimulate mucosal and systemic immunity in volunteers. Using recombinant DNA techniques we constructed an expression cassette which comprises the lpp promoter (Plpp) and sequences encoding recombinant gp120 (rgp120). When the Plpp-rgp120 expression cassette is integrated into the chromosome of CVD 908 in the delta aroC allele, high levels of recombinant gp120 expression are observed. It is likely that effective immunity against HIV in humans will require immunization with multiple HIV antigens. Hence, a second expression cassette encoding two additional HIV antigens with vaccine potential, p24 (a HIV-1 gag gene product) and Nef (a putative regulator of HIV-1 gene expression) has been constructed. We plan to integrate the p24-Nef-encoding expression cassette into the aroD locus in the chromosome of CVD 908 delta aroC::rgp120 in a stable manner to produce a CVD 908-HIV vector vaccine that expresses multiple HIV antigens.

AIDS Vaccines↗
PubMed1993

Long-term persistence of sterile immunity in a volunteer immunized with X-irradiated Plasmodium falciparum sporozoites.

Three volunteers were immunized by repeated exposure to the bites of Plasmodium falciparum-infected, X-irradiated mosquitoes to characterize immunologic responses and duration of protective immunity. A primary series of immunizations had been shown previously to induce sterile immunity in these volunteers against sporozoite-induced P. falciparum malaria. In the current study, antibodies to sporozoites circulated at high levels for at least 9-12 months after the volunteers were administered booster bites from X-irradiated infective mosquitoes. One volunteer challenged a second time with P. falciparum 9 months after his last immunization was again shown to be protected, whereas all 5 control subjects developed patent infections. These results set a new standard for persistence of sterile immunity against experimental P. falciparum infection.

Adult↗
PubMed1993

Confirmation that Plasmodium falciparum has aperiodic infectivity to Anopheles gambiae.

In preparation for field studies of transmission-blocking malaria vaccines, a study was carried out to determine whether P. falciparum infections obtained in An. gambiae blood-fed at 16.00 hours were quantitatively similar to infections obtained at 23.00 hours. Using a group of children aged 5-12 years from villages at Ahero, near Kisumu in Kenya, 71/74 (96%) of whom were found to be positive for P.falciparum parasitaemia, one batch of fifty colony-bred An.gambiae females were fed on volunteers at 16.00 hours and another batch at 23.00 hours. No statistically significant differences were found in the proportions of mosquitoes becoming infected, the numbers of children infecting mosquitoes or the mean numbers of malaria oocysts developing in mosquitoes blood-fed at the different times. Because mosquito infections obtained by day (16.00 hours) are equivalent in quantity to those obtained at night (23.00 hours), experimental infections can be carried out in the afternoon, when it is most convenient, rather than during the night.

Animals↗
PubMed1991

Successful immunization of humans with irradiated malaria sporozoites: humoral and cellular responses of the protected individuals.

Two groups of volunteers were vaccinated by repeated exposure to the bites of Plasmodium falciparum-infected, x-irradiated mosquitoes in order to characterize the humoral and cellular immune responses of sporozoite-immunized, protected individuals. One of the two volunteers in the first immunization trial, when challenged by the bite of P. falciparum-infected mosquitoes, developed an infection only after a prolonged prepatent period. A second group of three volunteers who were exposed more frequently to larger numbers of infected mosquitoes irradiated with a lower x-ray dose was completely protected against sporozoite challenge. These individuals and the volunteer with delayed infection had high levels of antibodies to sporozoites and to the repeat region of the circumsporozoite (CS) protein. The CS-specific cellular immune responses of these volunteers were also stimulated by sporozoite immunization, as determined by proliferation of peripheral blood mononuclear cells (PBMC) and mitogen or antigen-expanded PBMC, in response to in vitro challenge with a recombinant P. falciparum CS protein. Based upon the assays used in this study, it is not possible to reach conclusions regarding specific immunologic responses and protection from sporozoite challenge.

Adult↗