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Biomedical subjects

J Schmidt

Publications and source records attributed to J Schmidt.

At least 415 records · Page 23Linked to original sources
PubMed1994

Protein substitution in chloroplast ribosome evolution. A eukaryotic cytosolic protein has replaced its organelle homologue (L23) in spinach.

The chloroplast translational system differs from the eubacterial ones in containing several ribosomal proteins (RPs) that have no apparent homologues in eubacteria, and in having their RP genes distributed in two cellular genome compartments. The genes maintained in the organelle genome encode mainly ribosome assembly proteins. The discovery in spinach and related plants (Caryophyllidae) of a disrupted chloroplast gene encoding the ribosome assembly protein L23 raised speculations about the transfer of the functional rpl23 gene to the nucleus or the evolutionary loss of L23 protein requirement. To solve this problem, we overexpressed in E. coli the intact rpl23 gene from corn (Zea mays), purified the protein and raised antibodies. Based on immunoanalysis, we show that a prokaryotic-type L23 protein is absent in spinach. Concomittantly we have isolated a new protein from spinach chloroplast 50 S ribosomal subunits and determined its amino acid sequence. The data revealed an unexpectedly high sequence identity to the eukaryotic family of cytosolic L23 proteins (reported from yeast, trypanosome and rat), with conservation of a peptide motif responsible for the specific interaction of these proteins with domain III of 26 S and 23 S rRNA. We propose that the prokaryotic-type L23 protein in the chloroplast ribosomes of Caryophyllidae has been replaced by a homologue of the eukaryotic cytosolic L23 family. These results represent the first case of a protein (gene) substitution in chloroplast ribosome evolution, and open a new view on how the nuclear genome could progressively exert stronger control over the chloroplast translational system. We also describe experiments on the incorporation of chloroplast L23 into E. coli ribosomes, its effect on cell growth, and an unexpected immuno cross-reaction between two chloroplast RP families.

Amino Acid Sequence↗
PubMed1994

Disruption of the murine p53 gene by insertion of an endogenous retrovirus-like element (ETn) in a cell line from radiation-induced osteosarcoma.

The mammalian genome harbors a large number of endogenous retroviruses and retrovirus-like elements. Increasing evidence is found that such elements can be activated and act as insertional mutagens. The activation of endogenous retroviral elements can be induced by a variety of environmental factors including irradiation. We have observed the insertion of a murine endogenous retrovirus-like ETn element into intro 4 of the p53 gene in an osteosarcoma cell line derived from a radiation-induced osteosarcoma. The insertion resulted in a p53-ETn-p53 fusion mRNA, a novel form of p53 mutation. This is the first report on insertion of an endogenous retroviral element into the p53 tumor suppressor gene. The data suggest that activated endogenous retroviruses and retrovirus-like elements might pose an enhanced risk for individuals exposed to noxae, which activate endogenous retroviral elements.

Animals↗
PubMed1994

Biosynthesis of lipooligosaccharide nodulation factors: Rhizobium NodA protein is involved in N-acylation of the chitooligosaccharide backbone.

Rhizobium meliloti interacts symbiotically with alfalfa by forming root nodules in which the bacteria fix nitrogen. The Rhizobium nodulation genes nodABC are involved in the synthesis of lipooligosaccharide symbiotic signal molecules, which are mono-N-acylated chitooligosaccharides. These bacterial signals elicit nodule organogenesis in roots of legumes. To elucidate the role of the NodA protein in lipooligosaccharide biosynthesis, we prepared a radiolabeled tetrasaccharide precursor carrying an amino group as a potential attachment site for N-acylation at the nonreducing glucosamine residue. Various criteria demonstrate that NodA is involved in the attachment of a fatty acyl chain to this tetrasaccharide precursor, yielding a biologically active nodulation factor.

Acyltransferases↗
PubMed1994

Calcium influx blocks the skeletal muscle acetylcholine receptor alpha-subunit gene in vivo.

The transcriptional activity of the acetylcholine receptor alpha-subunit gene was measured in denervated chick skeletal muscle in response to calcium-active drugs, using a ribonuclease protection version of the conventional run-off assay. The L-channel agonist (-)Bay-K6844 and the calcium ionophore A23187 mimicked, and the intracellular chelator BAPTA and the calcium channel blockers D600 and nifedipine blocked, the effect of electrostimulation. These results suggest that influx of extracellular calcium is an integral component of the membrane depolarization-receptor gene inactivation cascade.

Animals↗
PubMed1994

Rapid inhibition of myogenin-driven acetylcholine receptor subunit gene transcription.

In investigating the coupling of depolarization and transcription in skeletal muscle we have focused on how protein kinase C suppresses acetylcholine receptor subunit genes. The activity of acetylcholine receptor subunit promoters in non-muscle cells co-transfected with myogenic factors and E proteins was measured, and their response to protein kinase C activation analyzed. To simplify interpretation of results, gene activities rather than levels of reporter enzymes were assayed, transcriptional effects of phorbol esters were determined, with drug exposures brief enough to preclude kinase depletion, and analysis was carried out with HeLa cells, which are not liable to myogenic conversion. Myogenin, which had been postulated previously to play a role in denervation supersensitivity (Neville et al., Mol. Cell. Neurobiol., 12, 511-527, 1992), was found to be the only myogenic factor whose inactivation kinetics can account for the plasma membrane-protein kinase C-receptor gene cascade observed in intact muscle (Huang et al., Neuron, 9, 671-678, 1992).

Gene Expression Regulation↗
PubMed1994

Clinical use of the simple 3D-calculation in scoliosis.

In this paper we show the clinical application of a simple method for calculating three-dimensional shape in scoliosis by the use of two tables based on normal standard X-rays in the anteroposterior and lateral projections. The three-dimensional alignment should be considered in both conservative and operative correction. In 57 patients with 87 scoliotic curves we measured the well-known Cobb angle (alpha) and determined the vertebral rotation according to the method of Nash and Moe. We compared this information with the results of the calculated three-dimensional angles of scoliosis (angle beta between the curvature plane and the sagittal plane, angle sigma as the true angle of scoliosis in this curvature plane). In 76 curves (87%) our method was practicable. The true angle sigma is always higher than the projected angle alpha, especially in the clinically relevant range of 20 degrees-40 degrees. Poor correlation is shown between the projected angle alpha and the true angle sigma (r = 0.41 for thoracic curves and r = 0.57 for lumbar curves) and almost no correlation between vertebral rotation and the true angle sigma (r = 0.10 for thoracic curves and r = 0.44 for lumbar curves) and the curvature plane (beta) (r = 0). The three-dimensional shape of scoliosis cannot be estimated by the well-established projected angles and indices and we recommend the use of our simple method for the radiological investigation of scoliotic patients.

Humans↗
PubMed1994

Videofluoroscopic evidence of aspiration predicts pneumonia and death but not dehydration following stroke.

In order to assess the risk of pneumonia, dehydration, and death associated with videofluoroscopic evidence of aspiration following stroke, the clinical records of 26 patients with aspiration and 33 randomly selected, case-matched, dysphagic controls without videofluoroscopic evidence of aspiration were reviewed. The videofluoroscopic modified barium swallow technique included 5 ml-thin and thick liquid barium, 5 ml barium pudding, and 1/4 cookie coated with barium, plus additional 20 and 30 ml of thin liquid barium. Patients were assessed a mean of 2 +/- 1 SD months poststroke and were followed for a mean of 16 +/- 8 SD months poststroke. The odds ratio for developing pneumonia was 7.6 times greater for those who aspirated any amount of barium irrespective of its consistency (p = 0.05). The odds ratio for developing pneumonia was 5.6 times greater for those who aspirated thickened liquids or more solid consistencies compared with those who did not aspirate, or who aspirated thin liquids only (p = 0.06). Dehydration was unrelated to the presence or absence of aspiration. The odds ratio for death was 9.2 times greater for those aspirating thickened liquids or more solid consistencies compared with those who did not aspirate or who aspirated thin liquids only (p = 0.01). Aspiration documented by modified videofluoroscopic barium swallow technique is associated with a significant increase in risk of pneumonia and death but not dehydration following stroke.

Aged↗
PubMed1994

The Cenos hollow stem in total hip arthroplasty: first experiences in a prospective study.

Due to its hollow construction, which gives it elasticity, the Cenos hollow stem (Artos) reduces stress shielding in the intertrochanteric region and reduces bone remodelling at the distal tip after implantation of a cementless stem in the femoral canal. This should contribute to a longer implant survival time and reduce the number of revision procedures required for implant loosening. Its anatomical shape means that it fits well in the femoral canal and additionally improves load distribution. We prospectively studied patients in whom the Cenos hollow stem was implanted in our clinic. The clinical results after 1 year and 40 implantations are very satisfactory. No thigh pain has been reported so far, which is probably due to the effectiveness of the increased elasticity and the better fit of the stem. Preoperative planning with a special template is very accurate, and in combination with the anatomical shape of the stem makes the surgical procedure easy. The relatively high number of ectopic ossifications found in our series is obviously not related to the stem itself. In our opinion it is a result of the lateral approach. However, no clinical disadvantage resulted from these ossifications.

Adult↗
PubMed1994

Osteosarcomagenic doses of radium (224Ra) and infectious endogenous retroviruses enhance proliferation and osteogenic differentiation of skeletal tissue differentiating in vitro.

Cartilage tissue from embryonic mice which undergoes osteogenic differentiation during in vitro cultivation was used to study the effect of osteosarcomagenic doses of alpha-irradiation and bone-tumor-inducing retroviruses on proliferation and phenotypic differentiation of skeletal cells in a defined tissue culture model. Irradiated mandibular condyles showed dose-dependent enhancement of cell proliferation at day 7 of the culture and increased osteogenic differentiation at day 14. Maximal effects were found with 7.4 Bq/ml of 224Ra-labeled medium. Doses of 740 and 7400 Bq/ml of 224Ra-labeled medium induced increasing cell death. Retrovirus infection enhanced osteogenic differentiation and extended the viability of irradiated cells. After transplantation none of the treated tissues developed tumors in syngeneic mice.

Animals↗
PubMed1994

Histamine increases anti-CD3 induced IL-5 production of TH2-type T cells via histamine H2-receptors.

Besides its proinflammatory functions histamine released from basophils and mast cells during immediate-type hypersensitivity reactions is known to inhibit several lymphocyte functions like IL-2 and gamma-IFN production. Recently, it has been shown that T helper cells of type 2 phenotype (TH2) represent the T cell fraction which may play a pivotal role in the promotion of the allergic inflammatory eosinophilic late-phase reaction by secretion of cytokines, especially IL-4 and IL-5. We have investigated the effect of histamine on anti-CD3 induced IL-4 and IL-5 production by TH2 cells. Histamine in concentrations between 10(-7) and 10(-5) mol/l concentration-dependently increased anti-CD3 induced IL-5 production up to 120%, whereas IL-4 production was not affected. The activity of histamine in increasing IL-5 production was mimicked by the H2-receptor agonist dimaprit. Histamine induced increase in IL-5 production was inhibited by histamine H2-receptor antagonists, but remained unaffected by H1- or H3-receptor antagonists. Administration of forskolin which directly stimulates the production of cAMP, the second messenger of the H2-receptor, also resulted in an increase in anti-CD3 induced IL-5 production. These results indicate that the histamine-mediated increase in anti-CD3 induced IL-5 production is mediated via H2-receptors. Consequently, histamine released from mast cells and basophils during the early-phase allergic reaction may act as an important stimulatory signal for the initiation of the allergic inflammatory late-phase reaction by increasing local IL-5 production of allergen triggered TH2 cells.

Animals↗
PubMed1994

Effects of flezelastine and its enantiomers on LPS-induced IL-1 beta generation in vitro and LPS-induced pyrexia in vivo.

The effects of the novel antiasthmatic/antiallergic compound flezelastine on LPS-induced actions were investigated in vitro and in vivo. In monocytes, IL-1 beta generation stimulated by LPS was inhibited dose dependently. In vivo, LPS-induced fever in rats, which is at least partly driven by the release of IL-1 beta, was also inhibited by flezelastine. These findings suggest that flezelastine inhibits IL-1 synthesis and/or release in vitro and in vivo.

Animals↗
PubMed1994

[A dental arch index related to tooth size and facial breadth].

Taking as its starting point the often postulated criticism of Pont's Index, the intent of the study was to develop a diagnostic procedure which took into consideration the objection that the Pont Index doesn't take the shape of the patient's skull into consideration. On the basis of the data obtained from the models and anthropological measurements of 50 adult subjects with fairly eugnathic dentition, the first step was to follow Pont and study which skull size exhibited the highest correlation to the posterior dental arch. Of all the relevant sizes the zygomatic arch width exhibited the highest correlation. Reference values for the posterior dental arch width, which were obtained with the help of regression analysis, which took into consideration both the total upper incisor width and zygomatic arch width as variables, were then established. These reference values were conclusively shown to have the best prognostic value. From this it can be concluded that a comprehensive orthodontic diagnosis should include an improved assessment of dental arch width.

Adult↗
PubMed1994

The primary stability of intertrochanteric osteotomies. An experimental comparison of techniques.

We have compared the quality of intertrochanteric functional pre-bending with other techniques for varus and flexion intertrochanteric osteotomies by measuring interfragmentary compression, the tension in the angled blade-plates used and the stability of the different procedures. Intertrochanteric osteotomies with any kind of plate pre-bending gave the best results in our experimental studies. Impacting techniques gave poor primary stability and the Schneider method produced only moderate stability in flexion osteotomies. Using intertrochanteric functional prebending, varus and flexion osteotomies produced the best primary stability and the most equitable interfragmentary compression. This could be achieved with the highest precision by using a sawing gauge system at operation.

Biomechanical Phenomena↗
PubMed1994

Removal of bone cement from the femoral canal using an acoustic emission-controlled milling device.

The removal of bone cement from the femoral canal in the case of hip prosthesis loosening takes a considerable amount of time and carries the additional risk of complications, thus risking bone damage and perhaps even endangering the successful reimplantation of a new prosthesis. We have demonstrated experimentally that the milling of bone and bone cement produces acoustic emission waves of different intensity. These waves can be measured by a commercial acoustic emission transducer. This method enables us to control a milling device during the removal of bone cement from deep in the femoral canal, avoiding the serious damage to the bone and thus enabling a new prosthesis to be reimplanted.

Acoustics↗
PubMed1994

Frequent alterations of the tumor suppressor genes p53 and DCC in human pancreatic carcinoma.

BACKGROUND/AIMS: The pathogenesis of pancreatic cancer is poorly understood. The multigenetic nature of carcinogenesis has been best documented in colon cancer. The relevance of this model was suggested for other epithelial tumors. Only advanced stages of pancreatic cancer are usually detected because of late diagnosis. Analysis of accumulated, diverse genetic changes could allow further understanding of putative mechanisms involved in tumor development. Activated c-Ki-ras oncogene has been shown to be a frequent event. However, additional alterations of tumor suppressor genes are expected. Therefore, concomitant genetic changes of p53 and deleted in colon carcinoma (DCC) in pancreatic carcinoma cell lines and primary tumors were analyzed. METHODS: p53 protein and transcript expression were revealed by immunocytochemistry and immunohistochemistry, immunoassay, and Northern blot analysis. p53 mutations were identified by sequence analysis. DCC expression was investigated by reverse-transcription polymerase chain reaction. RESULTS: p53 overexpression was observed in 9 of 12 cell lines. p53 point mutations were confirmed in seven cell lines overexpressing p53. The majority of cell lines showed concomitant p53 and DCC alterations. Four of 6 primary tumors overexpressing p53 also showed loss of DCC expression. CONCLUSIONS: p53 and DCC genetic changes are associated with pancreatic cancer and the frequently activated c-Ki-ras oncogene. Therefore, the multihit model of carcinogenesis could prove relevant for pancreatic cancer.

Base Sequence↗
PubMed1994

Primary sequence determination of the most basic myonecrotic phospholipase A2 from the venom of Vipera russelli.

The most basic phospholipase A2 (PLA2), VRV-PL-VIIIa, was purified from (Sri Lankan) Vipera russelli venom. It is a major component of the venom, contributing over 40% to the whole venom PLA2 activity. The purity of VRV-PL-VIIIa was ascertained by electrophoresis and by reverse phase high-pressure liquid-chromatography (RP-HPLC). VRV-PL-VIIIa had an apparent mol. wt of 13,000 and was a single polypeptide. The protein was reduced, pyridylethylated and subjected to sequence analysis. The N-terminal amino acid sequence was established up to the 39th residue. Pyridylethylated VRV-PL-VIIIa was digested with endoprotease Glu-C, and several peptides were purified by RP-HPLC; six purified peptides were sequenced. The sequence of the C-terminal was established by sequencing a CNBr-produced peptide purified by RP-HPLC. Several peptides were also generated by digestion with endoprotease Asp-N. Two peptides were sequenced to obtain overlapping regions. The complete structure was deduced from sequences of overlapping peptides and through homology with other group II PLA2 sequences. Sequence homology was greatest with ammodytoxin A: 99 amino acid residues out of 121 occurred in identical positions. Myotoxin III of Bothrops asper showed 73% homology, 89 out of 121 residues. In agreement with the sequence data, polyclonal antiserum against VRV-PL-VIIIa cross-reacted in ELISA with ammodytoxin A and, to a lesser extent, with caudoxin.

Amino Acid Sequence↗
PubMed1994

Depolarization-transcription signals in skeletal muscle use calcium flux through L channels, but bypass the sarcoplasmic reticulum.

Membrane depolarization inactivates acetylcholine receptor (AChR) genes in skeletal muscle. We have studied this process in C2C12 cells, focusing on the role of calcium. Cytoplasmic calcium was monitored with fluo-3, and the activity of receptor genes was measured with a sensitive transcript elongation assay. Removal of extracellular calcium or blockage of L-type calcium channels disrupts signaling, even when release of calcium from the sarcoplasmic reticulum (SR) is not impeded, whereas L channel agonists induce signaling without membrane depolarization or release of calcium from intracellular stores. Activators of calcium release from the SR do not inhibit AChR genes, either in C2C12 or in chicken skeletal muscle in vivo. It appears that calcium ions do not act as messengers between sarcolemma and nucleus but target a sensor near their port of entry where they initiate a signal that bypasses the SR.

Action Potentials↗