PubMed Health⌕ Search

Biomedical subjects

O Stamm

Publications and source records attributed to O Stamm.

At least 19 recordsLinked to original sources
PubMed2005

Comparative study of six rotary nickel-titanium systems and hand instrumentation for root canal preparation.

AIM: To compare ex vivo various parameters of root canal preparation using a manual technique and six different rotary nickel-titanium (Ni-Ti) instruments (FlexMaster, System GT, HERO 642, K3, ProTaper, and RaCe). METHODOLOGY: A total of 147 extracted mandibular molars were divided into seven groups (n = 21) with equal mean mesio-buccal root canal curvatures (up to 70 degrees), and embedded in a muffle system. All root canals were prepared to size 30 using a crown-down preparation technique for the rotary nickel-titanium instruments and a standardized preparation (using reamers and Hedströem files) for the manual technique. Length modifications and straightening were determined by standardized radiography and a computer-aided difference measurement for every instrument system. Post-operative cross-sections were evaluated by light-microscopic investigation and photographic documentation. Procedural errors, working time and time for instrumentation were recorded. The data were analysed statistically using the Kruskal-Wallis test and the Mann-Whitney U-test. RESULTS: No significant differences were detected between the rotary Ni-Ti instruments for alteration of working length. All Ni-Ti systems maintained the original curvature well, with minor mean degrees of straightening ranging from 0.45 degrees (System GT) to 1.17 degrees (ProTaper). ProTaper had the lowest numbers of irregular post-operative root canal diameters; the results were comparable between the other systems. Instrument fractures occurred with ProTaper in three root canals, whilst preparation with System GT, HERO 642, K3 and the manual technique resulted in one fracture each. Ni-Ti instruments prepared canals more rapidly than the manual technique. The shortest time for instrumentation was achieved with System GT (11.7 s). CONCLUSIONS: Under the conditions of this ex vivo study all Ni-Ti systems maintained the canal curvature, were associated with few instrument fractures and were more rapid than a standardized manual technique. ProTaper instruments created more regular canal diameters.

Dental Alloys↗
PubMed1999

Spleen-specific expression of the malaria-inducible intronless mouse gene imap38.

We characterize the mouse gene imap38 and its inducibility by Plasmodium chabaudi malaria among different lymphoid tissues and mouse strains of different H-2 complex and non-H-2 background. Imap38 is a single copy gene assigned to chromosome 6B. It consists of only one exon of 1900 base pairs encoding a highly basic 25.8-kDa protein. Confocal laser scanning microscopy localizes differently tagged IMAP38 proteins in nuclei of transfected cells. Reporter gene assays reveal that the 1730-base pair 5'-flanking region, containing an RSINE1 repeat immediately adjacent to initiation site +1, exhibits promoter activity in nonmurine cells, while it is largely repressed in diverse mouse cell lines, which corresponds to the situation in mouse tissues. P. chabaudi malaria induces imap38 expression almost exclusively in the spleen but not in other lymphoid organs. Parasite lysates are able to induce imap38 in the spleen, but not in spleen cells ex vivo. Activation of spleen cells by LPS and other stimuli is not sufficient to induce imap38. Inducibility of imap38 requires signals from both parasites and the intact spleen, and it is controlled by genes of that non-H-2 background, which also controls development of protective immunity against P. chabaudi malaria.

5' Untranslated Regions↗
PubMed1999

Testosterone signaling through internalizable surface receptors in androgen receptor-free macrophages.

Testosterone acts on cells through intracellular transcription-regulating androgen receptors (ARs). Here, we show that mouse IC-21 macrophages lack the classical AR yet exhibit specific nongenomic responses to testosterone. These manifest themselves as testosterone-induced rapid increase in intracellular free [Ca(2+)], which is due to release of Ca(2+) from intracellular Ca(2+) stores. This Ca(2+) mobilization is also inducible by plasma membrane-impermeable testosterone-BSA. It is not affected by the AR blockers cyproterone and flutamide, whereas it is completely inhibited by the phospholipase C inhibitor U-73122 and pertussis toxin. Binding sites for testosterone are detectable on the surface of intact IC-21 cells, which become selectively internalized independent on caveolae and clathrin-coated vesicles upon agonist stimulation. Internalization is dependent on temperature, ATP, cytoskeletal elements, phospholipase C, and G-proteins. Collectively, our data provide evidence for the existence of G-protein-coupled, agonist-sequestrable receptors for testosterone in plasma membranes, which initiate a transcription-independent signaling pathway of testosterone.

Androgen Antagonists↗
PubMed1999

Functional testosterone receptors in plasma membranes of T cells.

T cells are considered to be unresponsive to testosterone due to the absence of androgen receptors (AR). Here, we demonstrate the testosterone responsiveness of murine splenic T cells in vitro as well as the presence of unconventional cell surface receptors for testosterone and classical intracellular AR. Binding sites for testosterone on the surface of both CD4(+) and CD8(+) subsets of T cells are directly revealed with the impeded ligand testosterone-BSA-FITC by confocal laser scanning microscopy (CLSM) and flow cytometry, respectively. Binding of the plasma membrane impermeable testosterone-BSA conjugate induces a rapid rise (<5 s) in [Ca2+]i of Fura-2-loaded T cells. This rise reflects influx of extracellular Ca2+ through non-voltage-gated and Ni2+-blockable Ca2+ channels of the plasma membrane. The testosterone-BSA-induced Ca2+ import is not affected by cyproterone, a blocker of the AR. In addition, AR are not detectable on the surface of intact T cells when using anti-AR antibodies directed against the amino and carboxy terminus of the AR, although T cells contain AR, as revealed by reverse transcription-polymerase chain reactions and Western blotting. AR can be visualized with the anti-AR antibodies in the cytoplasm of permeabilized T cells by using CLSM, though AR are not detectable in cytosol fractions when using the charcoal binding assay with 3H-R1881 as ligand. Cytoplasmic AR do not translocate to the nucleus of T cells in the presence of testosterone, in contrast to cytoplasmic AR in human cancer LNCaP cells. These findings suggest that the classical AR present in splenic T cells are not active in the genomic pathway. By contrast, the cell surface receptors for testosterone are in a functionally active state, enabling T cells a nongenomic response to testosterone.

Animals↗
PubMed1998

Catabolite inactivation of the high-affinity hexose transporters Hxt6 and Hxt7 of Saccharomyces cerevisiae occurs in the vacuole after internalization by endocytosis.

After addition of high concentrations of glucose, rates of high-affinity glucose uptake in Saccharomyces cerevisiae decrease rapidly. We found that the high-affinity hexose transporters Hxt6 and Hxt7 are subject to glucose-induced proteolytic degradation (catabolite inactivation). Degradation occurs in the vacuole, as Hxt6/7 were stabilized in proteinase A-deficient mutant cells. Degradation was independent of the proteasome. The half-life of Hxt6 and Hxt7 strongly increased in end4, ren1 and act1 mutant strains, indicating that the proteins are delivered to the vacuole by endocytosis. Moreover, both proteins were also stabilized in mutants defective in ubiquitination. However, the initial signal that triggers catabolite inactivation is not relayed via the glucose sensors Snf3 and Rgt2.

Base Sequence↗
PubMed1976

[The frequency and causes of spontaneous abortion following artifitial insemination (author's transl)].

This paper is concerned with the causes of spontaneous abortion in a sample of 200 pregnancies induced by artificial insemination. In particular it examines the importance of the following factors: existing disorders in the woman's menstrual cycle, the influence of hormone treatment during the conception cycle, the age of the woman treated, and the type of semen used. Of the 200 pregnancies in our treatment sample 27 terminated in abortions (13.5%). Clinical examination before treatment established the presence of menstrual disorders in 69 of 180 women to be treated: 23.9% exhibited corpus luteum deficiency, 12% anovular cycles, and 2% oligomenorrhea. On the basis of this preliminary examination the principal cause of abortion proved to be an existing corpus luteum deficiency, since 15 of the 27 abortions occurred in women with this type of menstrual disorder. Our observations show that it is important when performing artificial insemination to correct the patient's existing menstrual disorders by means of hormone treatment. This emerges from the following figures: In 26 cases without hormone treatment the incidence of abortion was 35%. In 174 cases that received hormone treatment during the successful cycle only 18 abortions occurred (an incidence of 10.3%). Breaking down hormone treatment into 6 basic types, we get incidences of abortion ranging from 0 to 25% in the different groups. Dividing the treatment sample into age groups reveals an 11 to 14% incidence of abortion in the 30 to 34 age group; in the 35 to 40 group age group the incidence doubles to 26%. Whereas existing menstrual disorders and adequate hormone treatment significantly influence the incidence of abortion, there is no close relationship between incidence of abortion and the type of semen used. The innocuousness of using deep-frozen semen with an admixture of glycerine has been shown by various authors reporting on laboratory and clinical investigations. For 117 pregnancies induced purely with deep-frozen semen we had an incidence of abortion of 13.7%. This figure is of the same order as the incidence of abortion in pregnancies induced by insemination with fresh semen. The results obtained permit one to conclude that incidence of abortion is not significantly dependent on the type of semen used. Our work demonstrates the importance of assessing the patient's genital constitution from both the functional and the organic points of view, not merely in order to achieve conception but also for the purposes of preventing abortion by means of the appropriate hormone treatment. If satisfactory therapeutic results are to be achieved candidates for artificial insemination must therefore be given a thorough diagnostic examination beforehand and, if necessary, adequate hormone treatment during the insemination cycle.

Abortion, Spontaneous↗
PubMed1975

[Continuous subcutaneous pH monitoring in newborns with abnormal metabolism (author's transl)].

In newborns with postpartum acidosis the subcutaneous interstitiel space pH was monitored continuously with the special electrode of Stamm and Moeller. This was compared with intermittent determinations of the pH in the capillary blood from the heel of the infant. The severity of the metabolic disturbance can be recognized in all test cases with both methods. The correction of the acidosis develops in a concordant manner, in a concordant magnitude and at a largely synchronous rate. The observations show that it is possible to monitor the postpartum adaptation phase by continuous pH monitoring in the interstitial space of the subcutaneous tissue and to observe the efficiency of the treatment of acidosis, administration of oxygen, or a buffer infusion.

Acidosis↗