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Biomedical subjects

J Seiler

Publications and source records attributed to J Seiler.

13 recordsLinked to original sources
PubMed2002

Influence of seedling roots, environmental factors and soil characteristics on soil CO2 efflux rates in a 2-year-old loblolly pine (Pinus taeda L.) plantation in the Virginia Piedmont.

To understand the role of managed forests in carbon sequestration an understanding of factors controlling soil CO2 efflux will be necessary. This study examined the influence of seedling roots, environmental factors, nutrient availability, and soil characteristics on soil CO2 efflux patterns in a 2-year-old pine plantation in the Virginia Piedmont. Efflux rates were measured both near the base of seedlings and midway between rows in plots that had received fertilization and mulch treatments in a factorial combination. Soil CO2 efflux rates were consistently higher near the base of seedlings, fertilization increased seedling growth with no significant effect on rates. and mulching increased winter efflux rates. In a regression analysis of seasonal soil CO2 efflux, soil temperature explained 42.2% of the variance followed by the interaction of soil temperature and moisture and of soil temperature and plot position, which together explained an additional 9.8% of the observed variance in seasonal rates. During March 2000 measurements, the spatial pattern of soil CO2 efflux between plots was most influenced by differences in soil nitrogen and pine root biomass. Furthermore, spatial differences observed in mean annual efflux rates were found to be highly influenced by the amount of soil coarse fragments in the upper soil profile.

Biomass↗
PubMed2000

The influence of elevated carbon dioxide and water availability on herbaceous weed development and growth of transplanted loblolly pine (Pinus taeda).

Loblolly pine (Pinus taeda L.) seedlings were grown in competition with native weeds using soil and seed bank collected from recently chopped and burned areas near Appomattox, Virginia. One-year-old seedlings were planted and weeds allowed to germinate from the native seed bank while being exposed to CO(2) (ambient and elevated - approximately 700 ppm) and water (water stressed and well watered) treatments for approximately one growing season in a greenhouse. Elevated CO(2) did not influence total weed biomass; however, C(3) weed community development was favored over C(4) weed community development in elevated CO(2) regardless of water availability. This suggests that weed community composition may shift toward C(3) plants in a future elevated CO(2) atmosphere. Pine growth was significantly greater in the well watered and elevated CO(2) treatments compared to the water stressed and ambient treatments, respectively, even though they were competing with native herbaceous weeds for resources. There was a significant water and CO(2) interaction for pine root:shoot ratio. Under elevated CO(2), root:shoot ratio was significantly greater in the water stressed treatment than the well watered treatment. In contrast, there was no significant difference in the root:shoot ratio under the ambient CO(2) treatment for either water treatment. These results suggest that loblolly pine seedlings will respond favorably in an elevated CO(2) atmosphere, even under dry conditions and competing with herbaceous weeds.

Journal Article↗
PubMed2000

Activation of STAT5 during EPO-directed suppression of apoptosis.

The ligand-dependent activation of the JAK/STAT (Januskinase/Signal Transducer and Activator of Transcription) pathway has been implicated in the explanation of cytokine-specific regulation of gene expression. Previous studies have reported conflicting results on the role of the transcription factor STAT5 in erythropoietin (EPO)-induced cellular responses. In this study we focused on the functional importance of STAT5 docking sites in the intracellular EPO receptor (EPOR) domain for the mediation of antiapoptotic activities. We demonstrate that EPO-dependent survival of erythroleukemic cell lines is accompanied by sustained STAT5 DNA-binding activity. The role of single tyrosine residues was dissected by the analysis of myeloid FDCP-1 cells stably expressing mutant EPOR proteins. The data show that receptors having a high potential to mediate antiapoptotic signals also effectively activate STAT5, whereas receptors lacking STAT5 docking sites are diminished in both activities. We conclude that the transcription factor STAT5 is functionally implicated in the EPO-dependent survival of cells.

Animals↗
PubMed2000

Induction of erythroid proliferation and differentiation by a trophoblast-specific cytokine involves activation of the JAK/STAT pathway.

Pregnancy is characterized by increased erythropoiesis within maternal and fetal compartments. The placenta has been shown to produce factors that stimulate erythropoiesis but convincing evidence for placental production of erythropoietin (EPO) is still lacking. Prolactin-like protein E (PLP-E) was recently found to stimulate expression of the adult beta major globin gene in mouse erythroleukemia cells. Here we demonstrate that PLP-E transiently expressed in COS-7 cells stimulates proliferation and erythroid differentiation of murine and human erythroid progenitor cell lines. Electrophoretic mobility shift assays were used to show the activation of STAT5 by PLP-E in the human erythroid cell line TF1. Furthermore, we compared the effects of PLP-E on murine myeloid FDCP1 cells which do not express EPO receptors (EPORs) with effects on cells genetically engineered to express functional EPORs. We provide evidence that PLP-E-dependent proliferation and STAT5 activation is independent of the expression of the EPOR. Taken together, these data suggest that PLP-E acts on specific receptors of erythroid-committed murine and human cells by the activation of intracellular signaling pathways promoting cell growth and differentiation.

Animals↗
PubMed1999

SHP1 protein tyrosine phosphatase negatively modulates erythroid differentiation and suppression of apoptosis in J2E erythroleukemic cells.

The SH2 domain-containing tyrosine phosphatase SHP1 is known to play a crucial role in the regulation of hematopoiesis. It has been shown previously that SHP1 associates with the activated erythropoietin receptor (EPOR) and negatively regulates mitogenic signaling. To further elucidate the role of SHP1 in erythropoietin (EPO)-induced cellular responses we employed J2E erythroleukemic cells as a model for erythroid maturation and cytokine-triggered suppression of apoptosis. Our data indicate that overexpressed SHP1 inhibits both EPO-induced differentiation as well as prevention of apoptosis. The specific signaling pathways responsible are not unraveled so far. Therefore, we analyzed the involvement of SHP1 in two established EPO-stimulated pathways, the JAK/STAT and the MAP kinase cascades, by transient coexpression of reporter constructs containing binding sites for transcription factors targeted by these pathways and a SHP1 cDNA. Both pathways are inhibited by SHP1 as indicated by the lower induction of reporter gene activity. In conclusion, SHP1 regulates the transcriptional activity stimulated by the EPO-induced JAK/STAT and MAPK pathways and is involved in the signaling machinery responsible for erythroid differentiation and suppression of apoptosis.

Animals↗
PubMed1995

Two independent targeting signals in the cytoplasmic domain determine trans-Golgi network localization and endosomal trafficking of the proprotein convertase furin.

Furin, a subtilisin-like eukaryotic endoprotease, is responsible for proteolytic cleavage of cellular and viral proteins transported via the constitutive secretory pathway. Cleavage occurs at the C-terminus of basic amino acid sequences, such as R-X-K/R-R and R-X-X-R. Furin was found predominantly in the trans-Golgi network (TGN), but also in clathrin-coated vesicles dispatched from the TGN, on the plasma membrane as an integral membrane protein and in the medium as an anchorless enzyme. When furin was vectorially expressed in normal rat kidney (NRK) cells it accumulated in the TGN similarly to the endogenous glycoprotein TGN38, often used as a TGN marker protein. The signals determining TGN targeting of furin were investigated by mutational analysis of the cytoplasmic tail of furin and by using the hemagglutinin (HA) of fowl plague virus, a protein with cell surface destination, as a reporter molecule, in which membrane anchor and cytoplasmic tail were replaced by the respective domains of furin. The membrane-spanning domain of furin grafted to HA does not localize the chimeric molecule to the TGN, whereas the cytoplasmic domain does. Results obtained on furin mutants with substitutions and deletions of amino acids in the cytoplasmic tail indicate that wild-type furin is concentrated in the TGN by a mechanism involving two independent targeting signals, which consist of the acidic peptide CPSDSEEDEG783 and the tetrapeptide YKGL765. The acidic signal in the cytoplasmic domain of a HA-furin chimera is necessary and sufficient to localize the reporter molecule to the TGN, whereas YKGL is a determinant for targeting to the endosomes. The data support the concept that the acidic signal, which is the dominant one, retains furin in the TGN, whereas the YKGL motif acts as a retrieval signal for furin that has escaped to the cell surface.

Amino Acid Sequence↗
PubMed1991

[Is Etolip suitable for treatment of various types of hyperlipoproteinemias?].

Etolip is the first Czechoslovak hypolipidaemic preparation produced in the Pharmaceutical Research Institute in Modra. As to the chemical structure it is ethophylline clofibrate. It was administered to 39 manual workers with hyperlipoproteinaemia type IIa, IIb, III, IV and V-500 mg/day, i.e. 2-0-2 capsules. The mean age of the patients varied round 43 +/- 6.1 years. They were subdivided into study possible, comparing Lipanthyl and Etolip. Despite the fact that the subjects did not adhere to a strict diet and occasionally consumed 50-100 g alcohol, Etolip (E) reduced the triacylglycerol concentration (TG) in serum for a period of one month after administration on average by 28% (p less than 0.01) in workers with hyperlipoproteinaemia (HL) type IIb, III, IV and V. In group A it is reduced from 2.8 +/- 1.0 mmol/l to 1.7 +/- 0.5 mmol/l and in group B from 2.4 +/- 1.0 mmol/l to 2.0 +/- 1.0 mmol/l. The total cholesterol concentration (CH) in serum declines after E on average in both groups by 11.4% (p less than 0.01) in the mentioned types of HL, whereby in subjects with HL type IIa and III it is practically unchanged. The apolipoprotein B concentration declines in serum of groups A and B from 185.6 +/- 37.8 to 137.5 +/- 44.2 mg/dl and from 144.9 +/- 27.9 to 113.3 +/- 23.6 mg/dl. After one month treatment with this drug the blood sugar level, and serum creatinine concentration does not rise, the haemogram and the uric acid concentration do not change. E raises the AST and ALT concentration to double the initial value which is still at the borderline of normal values.

Adult↗
PubMed1986

The muscular dystrophies.

Duchenne muscular dystrophy, the most common childhood-onset muscular dystrophy, is X-linked and is associated with cardiac and mental abnormalities. Becker's muscular dystrophy is similar to but milder than Duchenne muscular dystrophy. The rare facioscapulohumeral muscular dystrophy has an autosomal dominant mode of transmission. Myotonic muscular dystrophy is the most common of the adult-onset muscular dystrophies. Treatable diseases that must be excluded include polymyositis, potassium disorders and endocrine abnormalities.

Child↗