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Biomedical subjects

W Jelkmann

Publications and source records attributed to W Jelkmann.

At least 73 records · Page 4Linked to original sources
PubMed1997

Infectious cDNA clone used to identify strawberry mild yellow edge-associated potexvirus as causal agent of the disease.

A full-length in vivo infectious cDNA clone of strawberry mild yellow edge-associated potexvirus (SMYEaV) was constructed and used to inoculate Fragaria vesca 'Alpine' seedlings and Rubus rosifollus. Both host plants could be infected using particle bombardment or agroinoculation, but not by mechanical inoculation. A method that used potted strawberry plants for particle bombardment resulted in high survival and infection rates. The plants developed systemic infection and virus particles were detected by ELISA and immunoelectron microscopy. Mechanical inoculation of Chenopodium quinoa and C. foetidum with the 35S construct resulted in localized infections. F. vesca 'Alpine' indicator plants produced symptoms that were indistinguishable from control plants inoculated with a naturally occurring isolate of strawberry mild yellow edge by graft or aphid transmission. These results suggest that SMYE potexvirus is the causal agent of strawberry mild yellow edge disease. As this virus is capable of causing the disease, we propose the name strawberry mild yellow edge potexvirus, with the acronym SMYEPV, to replace the name strawberry mild yellow edge-associated potexvirus.

Animals↗
PubMed1997

Perioperative use of recombinant human erythropoietin in patients refusing blood transfusions. Pathophysiological considerations based on 5 cases.

The efficacy of the administration of recombinant human erythropoietin (rHuEPO) in the treatment of anaemia in critically ill surgical patients refusing red cell transfusions requires further documentation. Herein, we report the outcome of 5 consecutive severely anaemic Jehovah's Witness patients (lowest haemoglobin concentration 27 g/1), who were discharged from the hospital in good condition after treatment. RHuEPO (50-280 U/kg body weight) was daily administered to 4 of the patients, who either exhibited preoperative anaemia or developed postoperative anaemia refractory to endogenous EPO probably due to inflammation. RHuEPO treatment was followed by a steep rise in reticulocytes and haemoglobin concentration. The fifth patient, who exhibited no signs of systemic inflammation following emergency hemicolectomy, was also treated with intravenous iron, but not with rHuEPO. His blood haemoglobin concentration rose from 27 g/l to 92 g/l in 3 wk. These observations indicate that the administration of rHuEPO is justified in the management of life-threatening anaemia, although only on a humanitarian basis, because there is no predictor for the possible spontaneous recovery.

Adult↗
PubMed1997

Serum thrombopoietin and interleukin 6 concentrations in tumour patients and response to chemotherapy-induced thrombocytopenia.

The relation between the number of platelets in blood and the concentrations of immunoreactive thrombopoietin (TPO), interleukin 6 and interleukin 11 (IL-6, IL-11) was studied in the sera of 32 normal subjects, of 29 untreated tumour patients and of 6 tumour patients following chemotherapy with ifosfamide, carboplatin and etoposide (ICE). Platelet counts, TPO and IL-6 concentrations were higher than normal in blood of tumour patients before chemotherapy. However, no statistical relation existed between these variables. Following chemotherapy, the number of circulating platelets decreased reaching a nadir at d 10-13, while the serum concentration of TPO increased concomitantly. Circulating IL-6 did not increase during chemotherapy-induced thrombocytopenia. IL-11 was not detectable in any serum. Thus, the reactive thrombocytosis in tumour patients could be related to elevated TPO and IL-6 levels. In contrast to circulating TPO, however, neither serum IL-6 nor IL-11 levels increase significantly in thrombocytopenia following myelosuppressive. chemotherapy.

Adult↗
PubMed1997

Decreased erythropoietin response in Plasmodium falciparum malaria-associated anaemia.

One of the most serious manifestations of Plasmodium falciparum malaria is anaemia. Its established causes are increased red cell destruction and ineffective erythropoiesis. Since proinflammatory cytokines have been shown to suppress the in vitro synthesis of erythropoietin (Epo), we measured serum immunoreactive Epo in 90 Sudanese patients suffering from malaria. Even in severe cases of anaemia (blood haemoglobin < 80 g/l), serum Epo levels rarely exceeded 300 U/l. For comparison, serum Epo was increased up to 12,000 U/l in a reference group of Caucasian patients with anaemia not associated with infection. Moreover, the slope of the log Epo/haemoglobin regression line was less steep in malarial anaemia. Thus, as documented for other chronic inflammatory disorders, there is a relative lack of Epo in malaria-associated anaemia. Treatment with the antimalarial drug chloroquine may aggravate the defect in Epo production, because chloroquine inhibited Epo synthesis when tested in cell culture.

Adolescent↗
PubMed1997

Erythropoietin gene expression is suppressed after lipopolysaccharide or interleukin-1 beta injections in rats.

Proinflammatory cytokines play an important role in the pathogenesis of anemia in inflammatory diseases. Interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) have been reported to inhibit the synthesis of erythropoietin (EPO) in vitro. To evaluate the in vivo significance of this observation, we have investigated effects of the administration of bacterial lipopolysaccharide (LPS) and IL-1 beta on renal EPO production in rats. Measurements by competitive reverse-transcription polymerase chain reaction showed that EPO mRNA levels were significantly reduced in the kidneys of normoxic rats 6 h after the injection of LPS (0.1 or 1 mg/kg). In addition, LPS and IL-1 beta (1 microgram/kg) inhibited the increase in EPO mRNA and plasma EPO levels when administered to rats before hypoxia exposure (8% O2 in the inspiratory gas). Evidence for an inflammatory reaction in the kidneys of LPS-treated rats was provided by measurements of greatly elevated renal TNF-alpha mRNA levels. Furthermore, kidneys isolated from LPS-created rats produced less immunoreactive EPO when perfused hypoxically in vitro for 2 h. Thus mediators of the immune response inhibit renal EPO gene expression in vivo, which is relevant with respect to the impaired synthesis of EPO in inflammatory diseases in humans.

Animals↗
PubMed1996

Genome analysis of the 3'-terminal part of the little cherry disease associated dsRNA reveals a monopartite clostero-like virus.

The high molecular weight dsRNA associated with little cherry disease (LCD) was extracted from infected plant tissue and cloned as cDNA. The sequence of the 3' 8337 nucleotides was determined. Computer assisted translation of the sequence portion identified six open reading frames potentially encoding proteins (from 5' to 3') with molecular masses of 70 kDa, 61 kDa, 46 kDa, 76 kDa, 21 kDa and 27 kDa respectively. A 3'-terminal non-translated region of 210 nucleotides was present. The 70 kDa protein represents a homolog of the cellular HSP70 heat shock proteins, and the 61 kDa protein showed homology to the similarly encoded products of beet yellows (BYV), citrus tristeza (CTV) and lettuce infectious yellows (LIYV) closteroviruses. The putative coat protein (CP) was found to be of 46 kDa and its diverged copy of 76 kDa. The potential coding capacity of these notably large closterovirus proteins was confirmed by their expression in vitro and immunoblotting. No proteins with significant similarity to the two C-terminal proteins were identified, but they are related in molecular mass and location to BYV. The gene arrangement as well as the alignments of the closteroviruses CPs and their diverged copies suggest that the mealybug transmissible virus associated with LCD takes an intermediate evolutionary position between the aphid- and whitefly transmissible closteroviruses.

Amino Acid Sequence↗
PubMed1996

Interleukin 1 beta and phorbol ester induce tumour necrosis factor alpha production in a hepatic cell line (HepG2).

Tumour necrosis factor "alpha" (TNF "alpha") is a pleiotropic cytokine that is produced mainly by monocytes and macrophages. TNF "alpha" appears to be responsible for many of the inflammatory and necrotic changes seen in malignant or infectious liver diseases. In addition, blood levels of TNF "alpha" have been reported to be elevated in those with hepatic diseases. Although TNF "alpha" is synthesized mainly by monocytes and macrophages, its production has recently been found in nonhaemopoietic cells as well. Therefore we have used the human liver cell line HepG2 to test for the inducible production of TNF "alpha" in hepatic parenchymal cells. No constitutive TNF "alpha" gene expression was detected by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). However, treatment with the proinflammatory cytokine interleukin 1 "beta" (IL-1 "beta") or phorbol 12-myristate-acetate (PMA) led to a marked increase in TNF "alpha" mRNA levels. Maximal TNF "alpha" mRNA levels were observed after 3-h incubation periods, decreased thereafter and became undetectable after 12 h. The culture supernatant from cells treated with IL-1 "beta" or PMA contained significant amounts of TNF "alpha" protein which was immunologically detectable and biologically active. We believe that our report of inducible TNF "alpha" production in this widely available hepatic cell line adds a valuable tool for understanding TNF "alpha" gene expression in nonhaematopoietic cells.

Cell Line↗
PubMed1996

Erythropoietin in the control of red cell production.

The understanding of the endocrine regulation of red cell production has been extended greatly since the erythropoietin gene was cloned and recombinant human erythropoietin has become available for experimental and clinical applications. Human erythropoietin is a 30 kDa glycoprotein. It is composed of 165 amino acids and 4 carbohydrate side chains. Studies in rodents have shown that blood-borne erythropoietin originates from peritubular cells, possibly fibroblasts, in the renal cortex and from parenchymal cells in the liver. In addition, erythropoietin mRNA has been demonstrated in spleen, lung and brain. Tissue hypoxia is the main stimulus for erythropoietin synthesis. Erythropoietin gene expression is controlled by DNA-binding proteins, primarily by hypoxia-inducible factor 1. Erythropoietin maintains red cell production by inhibiting apoptosis of erythrocytic progenitors, and by stimulating their proliferation and differentiation into normoblasts. The functional human erythropoietin receptor, a 484-amino acid glycoprotein, is member of the class I cytokine receptor superfamily. Lack of erythropoietin results in anaemia. Recombinant human erythropoietin is efficient for treatment of the anaemia of chronic renal failure. In addition, the drug is increasingly administrated to persons suffering from anaemia of chronic diseases and to surgical patients, thus abolishing the need for homologous red cell transfusion.

Animals↗
PubMed1996

Serum erythropoietin levels in patients with sepsis and septic shock.

The role of the immune system in the control of the production of erythropoietin is still poorly understood. Herein, the levels of circulating immunoreactive erythropoietin, tumour necrosis factor alpha, interleukin-1 beta and interleukin-6 were determined in 10 septic patients for up to 4 d following the admission to an internal intensive care unit. The data show that the production of erythropoietin was not suppressed despite an increase in the levels of proinflammatory cytokines. Circulating erythropoietin and interleukin-6 greatly increased in the 6 nonsurviving patients. The pattern of the serum erythropoietin level in the nonsurvivors resembled that of acute phase proteins and was independent of the blood haemoglobin concentration. Similar to interleukin 6, abnormally high serum erythropoietin levels appear to be a negative prognostic indicator in patients suffering from septic shock.

Adult↗
PubMed1996

Erythropoietin induces Ca2+ mobilization and contraction in rat mesangial and aortic smooth muscle cultures.

Reportedly, recombinant human erythropoietin (rhEpo) can induce constriction of isolated resistance vessels. We have studied whether rhEpo affects cytosolic calcium concentration, [Ca2+]i, and contraction of cultured smooth-muscle cells grown from rat renal corpuscles and aortae. rhEpo at high dose (> or = 20 U/mL) induced a transient increase in [Ca2+]i as detected by fura-2 fluorescence analysis. The number of cells responding with an increase in [Ca2+]i was dose-dependent. No significant changes of [Ca2+]i occurred when lower doses of rhEpo (< 20 U/mL) were applied. The effect of Epo on contraction was studied by phase-contrast microscopy. The number of cells responding with contraction was dose-dependent, too (76% mesangial cells contracting at 200 U rhEpo per mL). The receptor mechanism of this unusual action of Epo still needs to be clarified.

Animals↗
PubMed1996

[Use of recombinant erythropoietin in surgery--are the costs justified?].

The combination of autologous blood donation and rHuEPO therapy is rarely justified for medical and economic reasons. Adequate alternative indications for the use of rHuEPO perioperatively have yet to be studied. Therefore, in addition to the increasing costs of safe homologous blood products and the decreasing costs of recombinant proteins, a reevaluation of the cost-effectivity relationship will be mandatory for rHuEPO in surgery.

Blood Transfusion, Autologous↗
PubMed1995

Pericellular PO2 and O2 consumption in monolayer cell cultures.

The current study was based on the uncertainty as to how well monolayer cell cultures growing in customary polystyrene dishes are supplied with O2. For dishes maintained in an air-5% CO2 atmosphere at 37 degrees C, microelectrode measurements revealed that the pericellular steady-state PO2 was 78 mm Hg in confluent bovine endothelial, 110 mm Hg in rat renal mesangial, and 0 (< 0.2) mm Hg in renal (LLC-PK1 and LLC-MK2) or hepatic (HepG2, Hep3B) epithelial cell cultures. These measured PO2 values were in good agreement with those calculated from Fick's law of gas diffusion, applied for the present culture conditions (one-dimensional O2 diffusion, 0.52 cm medium height), the individual cell layer density and the tissue-specific rate of O2 utilization. Our results provide reasons to speculate that conventional monolayer cultures are often hypoxic when incubated in an air-5% CO2 atmosphere. Diffusion-limitations of cellular O2 availability are to be taken into consideration when tissue cultures are used to study PO2-dependent processes.

Animals↗
PubMed1995

Cherry virus A: cDNA cloning of dsRNA, nucleotide sequence analysis and serology reveal a new plant capillovirus in sweet cherry.

The nucleotide sequence (7383 nucleotides) of a newly identified member of the genus Capillovirus, cherry virus A (CVA), was obtained from cDNA clones. The cDNA was generated from dsRNA extracted from plant tissue infected with little cherry virus (LCV). Small amounts of LCV dsRNA served as template nucleic acid and enabled the construction of a library of which, unexpectedly, 7.5% of the recombinant plasmids were specific for CVA. The genome organization of CVA resembles that of apple stem grooving virus (ASGV), the type member of the genus Capillovirus and is composed of a 266 kDa polyprotein (ORF1), a 52 kDa ORF2 located within ORF1 and a poly(A) tail. The 266 kDa ORF1 contains all the elements of a replication-related protein and has high identity with 'Sindbis-like' viruses. The ORF encodes the coat protein (CP) in the C-terminal region. The 52 kDa ORF2 has high identities with the putative viral cell-to-cell movement proteins of capillo- and trichoviruses. The CP was identified in immunoblot analysis and estimated to have a molecular mass of 24 kDa. Antiserum was obtained by expression of antigens as fusion proteins in Escherichia coli. There is significant sequence identity between CVA CP and the corresponding proteins of other capillo- and trichoviruses. However, no serological cross-reaction was obtained in immunoblot analysis with ASGV, apple chlorotic leafspot trichovirus (ACLSV), apple stem pitting virus (ASPV) and cherry mottle leaf virus (CMLV) antisera. Flexuous filamentous CVA virions were identified in extracts of sweet cherry by immunosorbent electron microscopy (ISEM) and decorated with the antiserum to the fusion protein. CVA was identified in three cherry sources of different disease status by ISEM, immunoblot analysis and hybridization to dsRNA. CVA is not closely related to any of the currently described diseases in cherry but it has all the properties of a capillovirus. It is suggested that CVA should be classified as a new member of the genus capillovirus.

Amino Acid Sequence↗
PubMed1994

Distinct signaling pathways mediate phorbol-ester-induced and cytokine-induced inhibition of erythropoietin gene expression.

Hypoxia-induced erythropoietin (Epo) production in vitro is suppressed by interleukin 1 beta (IL-1 beta), tumor necrosis factor alpha (TNF) and phorbol esters. Herein, the Epo-synthesizing human hepatoma cell line HepG2 was used to investigate whether protein kinase C (PKC) is involved in the inhibitory action of the cytokines. Within 1 h after the onset of hypoxia, Epo mRNA levels were markedly increased in untreated HepG2 cells as quantitated by competitive reverse transcription PCR. The cytokines IL-1 beta and TNF prevented this hypoxia-induced increase in Epo mRNA levels. In phorbol-ester-treated cells first inhibitory effects on Epo mRNA levels were observed only after 3 h. Western blot analyses revealed the presence of four isoenzymes of PKC in HepG2 cells. None of these isoenzymes was translocated in response to TNF or IL-1 beta, suggesting that the cytokines do not activate PKC in HepG2 cells. In contrast, phorbol esters translocated and, upon prolonged exposure, down-regulated PKC isoenzymes alpha and epsilon. Activation of protein kinase A by dibutyryl-cAMP partially antagonized the cytokine-dependent inhibition of Epo production but did not influence the inhibitory effect of phorbol esters. Endogenous cAMP levels in HepG2 cells were unchanged by cytokine treatment. Obviously, at least two signaling pathways exist that can confer inhibition of Epo production in HepG2 cells. One of these may be mediated by down-regulation of the PKC alpha or epsilon isoenzyme. The other pathway, however, which is triggered by IL-1 beta and TNF, is independent of PKC.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Role of hydrogen peroxide in hypoxia-induced erythropoietin production.

The addition of exogenous H2O2 inhibited hypoxia-induced erythropoietin (Epo) production in the human hepatoma cell line HepG2. Likewise, elevation of endogenous H2O2 levels by the addition of menadione or the catalase inhibitor, aminotriazole, dose-dependently lowered Epo production. The inhibitory effect of exogenous H2O2 on Epo formation could be completely overcome by co-incubation with catalase. When GSH levels in HepG2 cells were lowered, Epo production was more susceptible to H2O2-induced inhibition, indicating that H2O2 might affect thiol groups in regulatory proteins. Endogenous production of H2O2 in HepG2 cells was dependent on the pericellular O2 tension, being lowest under conditions of hypoxia. Our results support the hypothesis that an H2O2-generating haem protein might be part of the O2 sensor that controls Epo production. High H2O2 levels under conditions of normoxia suppress, whereas lower levels in hypoxic cells allow epo gene expression.

Amitrole↗