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Biomedical subjects

T Schmidt

Publications and source records attributed to T Schmidt.

At least 199 records · Page 11Linked to original sources
PubMed1996

MoMuLV proviral integrations identified by Sup-F selection in tumors from infected myc/pim bitransgenic mice correlate with activation of the gfi-1 gene.

Infecting mice with a mutant Moloney murine leukemia virus which contains the bacterial suppressor tRNA supF in its LTR allows rapid cloning of proviral integration sites from genomic tumour DNA. In a previous study Emu pim-1/Emu L-myc bitransgenic mice had been inoculated neonatally with MoMuLV supF virus. The retroviral infection led to acceleration of lymphomagenesis indicating the proviral activation of further oncogenes cooperating with myc and pim-1 in tumour development. Using a functional supF screen for analysis of genomic mouse tumour DNA libraries which had been constructed in the phage vector EMBL3A, a common proviral integration site on mouse chromosome 5 was cloned and found to be identical to the proviral integration site evi-5 which has recently been identified in an AKXD T-cell lymphoma and which is located 18 kb upstream of the gfi-1 gene. Tumours bearing evi-5 integrations showed an enhanced gfi-1 expression level suggesting that gfi-1 is the target gene for insertions at the evi-5 locus. Together with three other previously described Moloney integration clusters all responsible for enhanced gfi-1 expression the number of tumours from infected double transgenic Emu L-myc/Emu pim-1 transgenic mice with retrovirally activated gfi-1 added up to 53% underscoring the role of GFI-1 as an effective collaborator for MYC and PIM-1 in the process of lymphomagenesis.

Animals↗
PubMed1996

Zinc finger protein GFI-1 cooperates with myc and pim-1 in T-cell lymphomagenesis by reducing the requirements for IL-2.

The clonality of lymphomas that originate in myc/pim-1 bitransgenic mice due to synergistic action of both oncogenes indicates the requirement of additional events for progression to full malignancy. To isolate genes that cooperate with both myc and pim-1, we have used provirus tagging with E mu L-myc/pim-1 double transgenic mice. We find accelerated tumour formation in infected animals and show that the gfi-1 gene and neighbouring loci on mouse chromosome 5 are occupied by proviruses in about 53% of the tumours leading in all cases to high level gfi-1 expression. In agreement with data from Gilks et al. (1993) we find that forced expression of the gfi-1 encoded zinc finger protein in IL-2 dependent T-cells provokes increased survival upon IL-2 depletion and we present evidence that this occurs at least in part through stimulation of proliferation. Our data suggest that gfi-1 is a proto-oncogene cooperation with both myc and pim-1 genes in T-cell lymphomagenesis.

Amino Acid Sequence↗
PubMed1996

The genomic and physical organization of Ty1-copia-like sequences as a component of large genomes in Pinus elliottii var. elliottii and other gymnosperms.

A DNA sequence, TPE1, representing the internal domain of a Ty1-copia retroelement, was isolated from genomic DNA of Pinus elliottii Engelm. var. elliottii (slash pine). Genomic Southern analysis showed that this sequence, carrying partial reverse transcriptase and integrase gene sequences, is highly amplified within the genome of slash pine and part of a dispersed element >4.8 kbp. Fluorescent in situ hybridization to metaphase chromosomes shows that the element is relatively uniformly dispersed over all 12 chromosome pairs and is highly abundant in the genome. It is largely excluded from centromeric regions and intercalary chromosomal sites representing the 18S-5.8S-25S rRNA genes. Southern hybridization with specific DNA probes for the reverse transcriptase gene shows that TPE1 represents a large subgroup of heterogeneous Ty1-copia retrotransposons in Pinus species. Because no TPE1 transcription could be detected, it is most likely an inactive element--at least in needle tissue. Further evidence for inactivity was found in recombinant reverse transcriptase and integrase sequences. The distribution of TPE1 within different gymnosperms that contain Ty1-copia group retrotransposons, as shown by a PCR assay, was investigated by Southern hybridization. The TPE1 family is highly amplified and conserved in all Pinus species analyzed, showing a similar genomic organization in the three- and five-needle pine species investigated. It is also present in spruce, bald cypress (swamp cypress), and in gingko but in fewer copies and a different genomic organization.

Amino Acid Sequence↗
PubMed1996

Imaging of single molecule diffusion.

In recent years observations at the level of individual atoms and molecules became possible by microscopy and spectroscopy. Imaging of single fluorescence molecules has been achieved but has so far been restricted to molecules in the immobile state. Here we provide methodology for visualization of the motion of individual fluorescent molecules. It is applied to imaging of the diffusional path of single molecules in a phospholipid membrane by using phospholipids carrying one rhodamine dye molecule. For this methodology, fluorescence microscopy was carried to a sensitivity so that single fluorescent molecules illuminated for only 5 ms were resolvable at a signal/noise ratio of 28. Repeated illuminations permitted direct observation of the diffusional motion of individual molecules with a positional accuracy of 30 nm. Such capability has fascinating potentials in bioscience--for example, to correlate biological functions of cell membranes with movements, spatial organization, and stoichiometries of individual components.

Fluorescent Dyes↗
PubMed1996

High-resolution mapping of repetitive DNA by in situ hybridization: molecular and chromosomal features of prominent dispersed and discretely localized DNA families from the wild beet species Beta procumbens.

Members of three prominent DNA families of Beta procumbens have been isolated as Sau3A repeats. Two families consisting of repeats of about 158 bp and 312 bp are organized as satellite DNAs (Sau3A satellites I and II), whereas the third family with a repeat length of 202 bp is interspersed throughout the genome. Multi-colour flourescence in situ hybridization was used for physical mapping of the DNA families, and has shown that these tandemly organized families occur in large heterochromatic and DAPI positive blocks. The Sau3A satellite I hybridized exclusively around or near the centromeres of 10, 11 or 12 chromosomes. The Sau3A satellite family I showed high intraspecific variability and high-resolution physical mapping was performed on pachytene chromosomes using differentially labelled repeats. The physical order of satellite subfamily arrays along a chromosome was visualized and provided evidence that large arrays of plant satellite repeats are not contiguous and consist of distinct subfamily domains. Re-hybridization of a heterologous rRNA probe to mitotic metaphase chromosomes revealed that the 18S-5.8S-25S rRNA genes are located at subterminal position on one chromosome pair missing repeat clusters of the Sau3A satellite family I. It is known that arrays of Sau3A satellite I repeats are tightly linked to a nematode (Heterodera schachtii) resistance gene and our results show that the gene might be located close to the centromere. Large arrays of the Sau3A satellite II were found in centromeric regions of 16 chromosomes and, in addition, a considerable interspersion of repeats over all chromosomes was observed. The family of interspersed 202 bp repeats is uniformly distributed over all chromosomes and largely excluded from the rRNA gene cluster but shows local amplification in some regions. Southern hybridization has shown that all three families are specific for genomes of the section Procumbentes of the genus Beta.

Base Sequence↗
PubMed1996

Expression of the Arxula adeninivorans glucoamylase gene in Kluyveromyces lactis.

The glucoamylase gene of the yeast Arxula adeninivorans was expressed in Kluyveromyces lactis by using the GAP promoter from Saccharomyces cerevisiae and a multicopy plasmid vector. The transformants secreted 90.1% of the synthesized glucoamylase into the culture medium. The secreted glucoamylase activities are about 20 times higher in comparison to those of Saccharomyces cerevisiae transformants using the same promoter. Secreted glucoamylase possesses identical N-terminal amino acid sequences to those secreted by A. adeninivorans showing that cleavage of the N-terminal signal peptide takes place at the same site. Biochemical characteristics of glucoamylase expressed by K. lactis and A. adeninivorans are very similar.

Amino Acid Sequence↗
PubMed1996

[Methodology of surgical management of orbital floor fractures: a comparison from ophthalmologic viewpoint between implant and antral balloon].

BACKGROUND: Several methods are available for treatment of orbital floor fractures: antral balloon catheters, orbital implants, combinations of both methods, or no treatment at all. This study compares the outcome of the different surgical approaches. PATIENTS AND METHODS: In a retrospective study 153 patients with unilateral orbital floor fractures were analysed with particular emphasis on the extend of the fracture regarding to Motility, enophthalmos, globe position and loss of sensitivity as analytical parameters. RESULTS: After treatment with antral balloon catheters development of motility in the upper field of gaze was significantly better (p < 0.03) than using combinations of antral balloon catheters and implants. In addition least enophthalmos and bulbus deviation resulted from antral balloon catheters when treating small and medium size fractures. A significant difference was found in enophthalmos (p < 0.02) and vertical globe position (p < 0.01) between implantation and no treatment at all. While exophthalmos and lifting of the bulbus are more often associated with implantation, enophthalmos and vertical depression of the bulbus may result when no treatment is given. Implantation results in least loss of sensitivity of N. V/2 (49%). In contrast the combination of implantation and antral balloon catheter shows the worst outcome (65%). CONCLUSIONS: In small and medium fractures best results are achieved when using the antral balloon catheter. However high filling-pressures should be avoided and preferably anatomically shaped catheters used. Implantations are only indicated when treating major fractures. In the presence of possible prion transmission alloplastic or autologous materials should be used. The combination of antral balloon catheters and implants are only indicated in exceptional circumstances, furthermore even in small orbital floor fractures surgical treatment is always indicated.

Adult↗
PubMed1996

Effect of intestinal resection on human small bowel motility.

BACKGROUND: Few data are available on adaptive changes of human small bowel motility after intestinal resection. AIM: To characterise jejunal motility after extensive and limited distal intestinal resection. METHODS: Seven patients with a short bowel syndrome after total ileal and partial jejunal resection (residual jejunal segments between 60 and 100 cm) and six patients with limited distal ileal resection (resected segment between 30 and 70 cm) underwent ambulatory 24 hour jejunal manometry 15 (6-24) months after the operation. Normal values were obtained from 50 healthy subjects. Fasting motility and the motor response to a 600 kcal solid meal were analysed visually and by a computer program. RESULTS: Limited ileal resection did not result in changed jejunal motility. After extensive distal resection, patients had a significantly shorter migrating motor complex (MMC) cycle and a significantly shorter duration of the postprandial motor response compared with controls (p < 0.005). Intestinal resection had no influence on jejunal contraction frequency and amplitude and did not lead to any abnormal motor pattern. CONCLUSION: Extensive distal resection of the small intestine produces distinct abnormalities of fasting and postprandial motility in the intestinal remnant. The shortening of digestive motility and the increased frequency of MMC cycling could contribute to malabsorption and diarrhoea in the short bowel syndrome.

Adult↗
PubMed1996

The molecular structure, chromosomal organization, and interspecies distribution of a family of tandemly repeated DNA sequences of Antirrhinum majus L.

Monomers of a major family of tandemly repeated DNA sequences of Antirrhinum majus have been cloned and characterized. The repeats are 163-167 bp long, contain on average 60% A+T residues, and are organized in head-to-tail orientation. According to site-specific methylation differences two subsets of repeating units can be distinguished. Fluorescent in situ hybridization revealed that the repeats are localized at centromeric regions of six of the eight chromosome pairs of A. majus with substantial differences in array size. The monomeric unit shows no homologies to other plant satellite DNAs. The repeat exists in a similar copy number and conserved size in the genomes of six European species of the genus Antirrhinum. Tandemly repeated DNA sequences with homology to the cloned monomer were also found in the North American section Saerorhinum, indicating that this satellite DNA might be of ancient origin and was probably already present in the ancestral genome of both sections.

Base Sequence↗
PubMed1996

Chromosomal and genomic organization of Ty1-copia-like retrotransposon sequences in the genus Avena.

A cloned repetitive sequence, pAvKB30, obtained from an Avena vaviloviana (AB genome) genomic library, along with two polymerase chain reaction products derived from the conserved region of the reverse transcriptase (RT) gene of retrotransposons, were characterized molecularly and cytologically. The cloned DNA fragment was a dispersed repeat present in all Avena species used in this study (A. strigosa, A. clauda, A. vaviloviana, A. magna, and A. sativa). The fragment was sequenced (210 bp) and found to be 69.5% homologous to part of WIS-2-1A, and 60.5% homologous to the leader sequence of BARE-1; both of these elements have been characterized as Ty1-copia-like retrotransposons in wheat and barley, respectively. In situ hybridization of pAvKB30 to diploid, tetraploid, and hexaploid oat species revealed that the probe is present on both arms of all chromosomes (A, B, C, and D genomes) but is excluded from their centromeric and nucleolar organizer regions. By using double in situ hybridization in hexaploid A. sativa (ACD genome), pAvKB30 was found to be present in lower copy numbers in C-genome chromosomes compared with A- and D-genome chromosomes. Furthermore, under low stringency conditions, pAvKB30 hybridized on Southern blots containing barley, wheat, rye, and Arrhenatherum DNA. However, under high stringency conditions, it hybridized only on Arrhenatherum DNA, which is considered to be the genus most closely related to Avena. All Avena species included in this study yielded a PCR product when the primers from the RT domain of retrotransposons were used. Two products, rtA, obtained by using A. strigosa (A(s) genome) as template, and rtC, obtained by using A. clauda (Cp genome) as template, gave Southern and in situ hybridization results similar to pAvKB30, but each was more abundant in its genome of origin.

Avena↗
PubMed1996

Ambulatory 24-hour jejunal motility in diarrhea-predominant irritable bowel syndrome.

BACKGROUND: Whether small-bowel motility is abnormal in the irritable bowel syndrome (IBS) is a controversy at present. The aim of our study was to compare ambulatory long-term jejunal motility in 35 IBS patients with predominant diarrhea to normal values obtained in 50 healthy controls. METHODS: Twenty-four-hour motility was recorded in the proximal jejunum with a portable datalogger and tube-mounted miniature pressure sensors. Fasting motility in the waking (W) and sleeping (S) state and the motor response to a standardized evening meal of 600 kcal underwent visual and computer-aided analysis. RESULTS: Fasting motility in patients showed migrating motor complex (MMC) cycles of normal length and composition. Uninterrupted runs of discrete clustered contractions during phase II (W) occurred in 57% of patients and 52% of controls but had a significantly longer duration in patients (33 +/- 5 versus 19 +/- 7 min; p < 0.005). During phase II (W) IBS patients had an increase in aborally propagated contractions (41 +/- 2% versus 35 +/- 2%; p < 0.01) and higher contraction amplitudes (26.3 +/- 0.8 versus 23.0 +/- 0.5 mm Hg; p < 0.01). Similar differences were obtained during postprandial motility (47 +/- 3% versus 39 +/- 3%; p < 0.01, and 25.9 +/- 0.9 versus 23.8 +/- 0.05 mm Hg; p < 0.02). In three patients (8.6%) disturbed aboral migration of phase III and irregular burst activity, manometric features of chronic idiopathic intestinal pseudo-obstruction, were identified. Whereas 57% of patients had an entirely normal 24-h manometry, 43% had at least one finding not present in any healthy control. CONCLUSION: Small-intestinal motility is frequently but not universally abnormal in diarrhea-predominant IBS. The abnormal manometric findings are heterogeneous and range from subtle quantitative changes to severe qualitative abnormalities resembling chronic idiopathic intestinal pseudo-obstruction in a small subset of patients.

Adult↗
PubMed1996

[Scanning electron microscopy studies of morphologic changes in ultra-high molecular weight polyethylene materials after various processing steps].

UNLABELLED: Scanning electron microscopic (SEM) studies were carried out on various orthopaedic implants made of ultra-high molecular weight polyethylene (UHMWPE). Both non-sterilized and gamma-sterilized machined (milled) implants were used. Milled implants showed significant surface irregularities, and cross-sections also revealed irregularities in deeper layers of the polyethylene. In gamma-sterilized implants, cracks measuring 10-30 microns in length were found at a depth of 1.5 to 2.5 mm. Crater-like defects were also occasionally seen. CLINICAL RELEVANCE: On the basis of these findings, direct compression moulding and a sterilization process in which oxygen is eliminated can be recommended as ways of improving the quality of UHMWPE used for orthopaedic implants.

Humans↗
PubMed1996

[Is Hylamer a suitable substance for use in endoprosthetics?].

UNLABELLED: In the present study, original UHMWPF implants obtained from different manufacturers were evaluated using Differential Scanning Calorimetry (DSC), Infrared Spectroscopy and Wide Angle X-ray Scattering (WAXS). DSC measurements revealed clear differences in the crystallinity of the implants with figures varying between 58.2% and 73.2%. The highest level of crystallinity (73.2%) was found in the Hylamer material. The results of IR spectroscopy confirmed these findings WAXS investigations showed that Hylamer has both a orthorrhomboid and a monoclinic phase. Remelting was followed by a disappearance of the ortherhomboid phase. CLINICAL RELEVANCE: The use of Hylamer that has been processed by secondary companies is not recommended. The product Hylamer makes clear how the original crystal structure of UHMWPE can be altered. The clearly increased crystallinity in Hylamer also increases the risk of implant failure due to brittleness.

Crystallization↗