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Biomedical subjects

J Schmidt

Publications and source records attributed to J Schmidt.

At least 361 records · Page 20Linked to original sources
PubMed1995

The depolarization response element in acetylcholine receptor genes is a dual-function E box.

All acetylcholine receptor subunit genes contain E boxes and are blocked by membrane depolarization. We have used transfected C2C12 myogenic cells to investigate the response, to electrical stimulation and KCl, of wildtype and mutant regulatory regions of the chick acetylcholine receptor alpha, gamma and delta subunit, and the mouse MLC genes. Point mutations revealed that E boxes function as activating elements targeted by the depolarization signal. These experiments suggest, and insertion of a depolarization response element into an unrelated promoter confirms, that plasma membrane depolarization switches the depolarization response element from an activating to a repressive mode.

Action Potentials↗
PubMed1995

The role of the CANNTG promoter element (E box) and the myocyte-enhancer-binding-factor-2 (MEF-2) site in the transcriptional regulation of the chick myogenin gene.

We have carried out an analysis of 833 bp of the chick myogenin gene 5' flanking sequence. A 131-bp segment of this upstream region, which contains a CANNTG promoter element (E box) and a myocyte-enhancer-binding-factor-2 (MEF-2) site, acts as a full promoter. It resembles the human and the mouse myogenin promoters in the structure and disposition of regulatory elements, including a TATA box and the transcription start site. Examination of eight myogenic factor/E protein combinations cotransfected with several myogenin promoter constructs into HeLa cells, reveals that the chick myogenin/E2-5 combination maximally activates the myogenin promoter. This activation is mediated through the E box motif; the MEF-2 site limits the factor combinations that can activate the myogenin promoter and enhances activation by myogenin/E2-5. We have found previously that activation of protein kinase C inactivates the transcription of the chick myogenin gene [Huang, C.-F., Neville, C. M. & Schmidt, J. (1993) Control of myogenic factor genes by the membrane depolarization/protein kinase C cascade in chick skeletal muscle, FEBS Lett. 319, 21-25]. In this study, we show that the activation of protein kinase C inhibits the factor bound to the E box, which thereupon negatively regulates the activity of the MEF-2 binding protein.

Animals↗
PubMed1995

In vitro sulfotransferase activity of Rhizobium meliloti NodH protein: lipochitooligosaccharide nodulation signals are sulfated after synthesis of the core structure.

The Rhizobium common nod gene products NodABC are involved in the synthesis of the core lipochitooligosaccharide (Nod factor) structure, whereas the products of the host-specific nod genes are necessary for diverse structural modifications, which vary in different Rhizobium species. The sulfate group attached to the Rhizobium meliloti Nod signal is necessary for activity on the host plant alfalfa, while its absence renders the Nod factor active on the non-host plant vetch. This substituent is therefore a major determinant of host specificity. The exact biosynthetic pathway of Nod factors has not been fully elucidated. In particular, it is not known why some chemical modifications are introduced with high fidelity whereas others are inaccurate, giving rise to a family of different Nod factor structures produced by a single Rhizobium strain. Using protein extracts and partially purified recombinant NodH protein obtained from Escherichia coli expressing the R. meliloti nodH gene, we demonstrate here NodH-dependent in vitro sulfotransferase activity. Kinetic analyses with Nod factors, chitooligosaccharides, and their deacetylated derivatives revealed that Nod factors are the preferred substrate for the sulfate transfer. Moreover, the tetrameric Nod factor, NodRm-IV, was a better substrate than the trimer, NodRm-III, or the pentamer, NodRm-V. These data suggest that the core lipochitooligosaccharide structure must be synthesized prior to its host-specific modification with a sulfate group. Since in R. meliloti tetrameric Nod factors are the most abundant and the most active ones, high affinity of NodH for the appropriate tetrameric substrate guarantees its modification and thus contributes to the fidelity of host-specific behavior.

Bacterial Proteins↗
PubMed1995

[Nosocomial Legionella pneumophila infection in a nephrology department].

During the autumn and winter of 1993-94 four cases of legionellosis were diagnosed in a Department of Nephrology. Three of the patients were kidney transplanted patients. Two of the patients died. The diagnosis was based on positive culture in two patients and by positive urinary antigen test in the other two patients. Serology was negative for all four patients. Legionella pneumophila was initially found in the cold and hot shower water, in ice-water from the ice machine, from the hot water tank and in the cold water inlet to the building. The isolate from patient no. one and isolates of serogroup 5 from the ice machine and the shower water had identical REA profiles, different from the profiles of the isolate from patient no. four. We concluded that at least one of the four patients was likely to have been infected from the water in the department, either by inhalation of contaminated aerosols from the shower or by aspiration of contaminated ice-water. Precautions were taken to reduce the number of Legionella in the shower- and ice-water. In addition, restrictions in the use of showers and ice-water from the ice machine were introduced.

Aged↗
PubMed1995

Akv murine leukemia virus enhances bone tumorigenesis in hMT-c-fos-LTR transgenic mice.

hMt-c-fos-LTR transgenic mice (U. Rüther, D. Komitowski, F. R. Schubert, and E. F. Wagner. Oncogene 4, 861-865, 1989) developed bone sarcomas in 20% (3/15) of females at 448 +/- 25 days and in 8% (1/12) of males at 523 days. After infection of newborns with Akv, an infectious retrovirus derived from the ecotropic provirus of the AKR mouse, 69% (20/28) of female animals and 83% (24/29) of males developed malignant fibrous-osseous tumors. The tumors in infected transgenics developed with higher frequency and a 200-days shorter mean tumor latency period. The hMt-c-fos-LTR transgene was expressed in all the fibrous-osseous tumors. They also showed newly integrated Akv proviruses, but in most tumors Akv was detected and expressed in only a small number of the tumor cells. Wild-type C3H mice infected with Akv developed benign osteomas with an incidence of 33% and a latency period of 474 days. The data indicate that Akv exerts distinct pathogenic effects on the skeleton. In hMt-c-fos-LTR transgenic mice, predisposed to bone sarcomagenesis, Akv acts synergistically with the fos transgene, resulting in the development of fibrous-osseous tumors.

AKR murine leukemia virus↗
PubMed1995

Akv murine leukemia virus enhances lymphomagenesis in myc-kappa transgenic and in wild-type mice.

The contribution of endogenous retroviruses to the multistep process of lymphomagenesis was investigated in wild-type mice and in two different myc-kappa transgenic mouse lines by infection with Akv. This retrovirus is derived from the endogenous ecotropic provirus of the AKR mouse and was previously considered to be nonlymphomagenic. The mice of the two myc-k transgenic lines are predisposed to B-cell lymphomagenesis and were therefore considered to be more susceptible to Akv. For comparison, the same mouse strains were also infected with the exogenous Moloney murine leukemia virus (MoMuLV). Both MoMuLV and Akv increased the tumor incidence and shortened the tumor latency period in wild-type mice and in the transgenic mouse lines. The differences in pathogenicity, number of provirus integrations, and level of virus expression between MoMuLV and Akv indicate different mechanisms of lymphomagenesis: while MoMuLV induced tumors apparently by insertional mutagenesis involving common integration sites similar to previous reports, the enhancement of lymphomagenesis by Akv seems to be directed by other mechanisms.

AKR murine leukemia virus↗
PubMed1995

Changes in retinal arbors in compressed projections to half tecta in goldfish.

In adult goldfish, electrophysiological studies have shown that the retinotectal projection reorganizes, following removal of half of the tectum, to form a complete but compressed projection over the remaining half tectum. As a result, each fiber terminates more rostrally than normal. Electron microscopic studies suggest a competition between retinal fibers for a fixed number of synaptic sites. The current study examines whether retinal arbors in the compressed projection are smaller than normal in extent or branching and whether the fiber paths in the tectum show the rostral movements and the search strategy that the retinal fibers use. The caudal half tectum was removed without cutting retinal fibers except those at the cut edge. At 3 to 19 months afterward, retinal fibers were labeled with horseradish peroxidase. In whole-mounted tecta, fibers and terminals were drawn under camera lucida and compared with normal arbors. The axonal paths were also traced across the tectum to their termination sites. At 3 to 6 months (early stages of compression), the arbors were rather normal in appearance, although they were actually significantly larger (23%) than normal in linear extent, arborized somewhat deeper and had fewer branches (18%). The fibers normally terminating in the rostral tectum followed normal stereotyped paths, whereas those cut at the edge had grown back and forth loops (apparent searching behavior) with little branching. By 10 months when compression is complete, arbors were significantly smaller than normal (19%), were arborizing significantly deeper, and had significantly fewer branches (19%). The differences were more pronounced in arbors of coarse and medium caliber than in fine caliber axons. The axons still ran in stereotyped fascicles, but included an extrafascicular portion that, unlike any axons in normals, turned back in a rostral direction before branching. This striking effect, present even in far rostral tectum, indicated that arbors had been forced to move rostrally to accomodate those from the ablated half. The small effect on arbor extent suggests that this is influenced by factors other than the magnification factor of the map, perhaps postsynaptic dendritic extent. The increased depth of termination is consistent with the increased thickness of the retinal terminal layer. The decreased number of branches is consistent with the conclusion that the remaining fixed number of synaptic sites shared among the full complement of retinal fibers should result in fewer synapses per retinal fiber.

Animals↗
PubMed1995

Measurement of blood flow in pancreatic exchange capillaries with FITC-labeled erythrocytes.

Characterization of pancreatic capillary blood flow by in vivo microscopy has been limited by technical shortcomings associated with the use of plasma tracers and the lack of quantitative data. Therefore, fluorescent-labeled erythrocytes were evaluated for quantitation of pancreatic capillary blood flow in rats in physiological state and under defined conditions of increased and impaired pancreatic blood flow. Physiological blood flow was 1.21 +/- 0.06 nl/min per capillary with stable capillary perfusion pattern. Reduction of pancreatic blood flow by decreasing systemic arterial pressure to 60 mmHg through controlled hemorrhage produced a profound decrease of volumetric flow to 0.21 +/- 0.05 nl/min (P < 0.05). The number of perfused capillaries was reduced to 52 +/- 8% of baseline (P < 0.001) and the intermittent perfusion pattern was altered in 26 +/- 5% (P < 0.001) of observed capillaries. Stimulation of pancreatic perfusion with intravenous secretin (5 CU/kg/hr) induced a transient decline to 0.94 nl/min (P < 0.05) followed by a continuous increase to 2.39 nl/min (P < 0.001). The intermittent flow pattern was modified in 15 +/- 3% of capillaries (P < 0.05). Fluorescent-labeled erythrocytes provide unique and reliable qualitative and quantitative data about pancreatic microcirculatory changes. Confinement of the fluorescent tracer to erythrocytes prevents extravasation and minimizes phototoxicity, thereby improving intravital analysis of blood flow in pancreatic exchange capillaries.

Animals↗
PubMed1995

Prevention of deep venous thrombosis in ambulatory or discharged orthopaedic patients. Actual management.

In recent years the problem of deep venous thrombosis (DVT) in outpatients and discharged patients has grown into a medical and juridical problem. In traumatology certain recommendations and statistical material exist: similar recommendations were made by the Berufsverband der Arzte für Orthopädie, Germany, pointing out the lack of sufficient statistical material. With the present study we tried to evaluate the actual management of DVT in discharged patients or outpatients in leading orthopaedic hospitals. The results from December 1993 reveal an inhomogeneous procedure which does not precisely follow the above recommendations. However, most orthopaedic surgeons agree that either general or individual means to prevent DVT should be available for ambulatory and discharged patients with plaster immobilisation of the leg according to presently accepted standards, i.e. low-dose heparin or low-molecular-weight heparins. Reduced weight-bearing, in contrast, is considered not to require preventive heparinisation to any great extent.

Ambulatory Care↗
PubMed1995

Diversity of nosocomial Xanthomonas maltophilia (Stenotrophomonas maltophilia) as determined by ribotyping.

Seventy-seven clinical isolates of Xanthomonas maltophilia (Stenotrophomonas maltophilia) were consecutively collected from the Rigshospitalet, Copenhagen, ribotyped and compared with the ribotypes of 25 other clinical and reference strains of Xanthomonas maltophilia. Using restriction enzyme EcoRI, 20 different ribotypes were observed, with 78 isolates displaying the five most common types. Using another enzyme, BamHI, these 78 isolates were further subdivided into 16 different ribotypes. Three patients harboured two strains with different ribotypes. No type was found related to only one department and no single-strain outbreak was detected. The origin of this wealth of different strains in hospital patients needs to be established.

Bacterial Typing Techniques↗
PubMed1995

Effect of microcirculatory perfusion on distribution of trypsinogen activation peptides in acute experimental pancreatitis.

Extraintestinal trypsinogen activation peptides (TAP) have been shown to correlate with severity of acute pancreatitis in humans as well as in various animal models. Ischemia superimposed on experimental pancreatitis, however, increases acinar cell injury without increasing TAP in plasma. We speculated that TAP generated in the pancreas might not reach the circulation in necrotizing pancreatitis due to decreased pancreatic perfusion. To test the hypothesis that generation of TAP in plasma is related to pancreatic perfusion and that plasma TAP may therefore underestimate acinar cell injury in necrotizing disease, we correlated TAP in pancreatic tissue and body fluids with capillary pancreatic blood flow in necrotizing and edematous pancreatitis. The ratio between necrosis and TAP in tissue was similar in both models; the ratio between TAP in plasma and tissue, however, was significantly lower in necrotizing pancreatitis, indicating that a certain amount of TAP generated in the pancreas did not reach the circulation. Decreased pancreatic perfusion found in necrotizing pancreatitis was consistent with this finding. Our data suggest that TAP in tissue is most reliable to indicate severity of acute pancreatitis, whereas plasma TAP may underestimate pancreatic injury in necrotizing disease due to decreased pancreatic perfusion.

Acute Disease↗
PubMed1995

Anions and the anomalous gel filtration behavior of notexin and scutoxin.

Based on their mol. wts, notexin and scutoxin elute later than expected from gel filtration columns in multiple peaks [Francis et al. (1991) Toxicon 29, 85-96]. Notexins present in these peaks have identical amino acid sequences and unmodified amino acid side-chains. Scutoxin is an isoform of notexin which contains arginine at position 16 and glutamate at position 82. Like notexin, it also elutes in different fractions on a gel filtration column, yet the fractions show identical amino acid sequence. This perplexing chromatographic behavior appears to be caused by the association of these proteins with different anions, since dissolving notexin in buffers containing different anions produces up to a 30% change in elution volume. Certain anions promote an apparent reduction in the interaction of notexin with gel filtration matrix, hence earlier elution. These anions include citrate, 3-phosphoglycerate and 2-phosphoglycerate, which also inhibit the PLA2 activity of notexin. However, even under conditions which minimize protein-matrix interaction the toxins elute later than expected based on their mol. wt.

Amino Acid Sequence↗
PubMed1995

Effect of phosphodiesterase inhibition on IL-4 and IL-5 production of the murine TH2-type T cell clone D10.G4.1.

The effect of various phosphodiesterase (PDE) inhibitors on anti-CD3 induced interleukin-(IL)-4 and IL-5 production of the murine T helper cell clone of type 2 phenotype D10.G4.1 (D10) has been investigated in vitro. D10 cells were incubated in the presence of drugs and anti-CD3 mAb for 16 h before measurement of cytokines in the cell supernatants by ELISA. Whereas all PDE inhibitors tested exerted minimal effects on anti-CD3 induced IL-4 production, a marked increase in IL-5 production by the non-selective PDE inhibitors IBMX, theophylline and enprofylline was observed. The action of these non-selective PDE inhibitors was mimicked by the PDE IV-selective inhibitor rolipram and in part by the PDE III-selective inhibitors motapizone and milrinone, whereas the PDE V-selective inhibitor zaprinast was inactive. Rolipram and motapizone enhanced IL-5 production in a synergistic fashion. In support of the functional importance of PDE III and IV for IL-5 synthesis in intact murine D10 cells, we have found PDE III and IV to be the predominant isoenzyme activities in corresponding cell lysates. The stimulatory effect of rolipram on IL-5 production was almost totally reversed by the protein kinase A inhibitor KT-5720. In addition, the membrane-permeable cAMP analogue 8-bromo-cAMP mimicked the stimulatory effect of PDE inhibitors on IL-5 production while leaving IL-4 levels unaffected. Both results support the view that the action of the PDE inhibitors on murine D10 cells is mediated via an elevation of intracellular cAMP.

8-Bromo Cyclic Adenosine Monophosphate↗