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Biomedical subjects

W Jelkmann

Publications and source records attributed to W Jelkmann.

At least 19 recordsLinked to original sources
PubMed2006

High plasma VEGF relates to low carbohydrate intake in patients with type 2 diabetes.

OBJECTIVE: Vascular endothelial growth factor (VEGF) has been suggested to enhance glucose transport across the blood-brain barrier, thereby increasing brain glucose supply. Increased brain glucose concentration is known to suppress food intake and to decrease body mass via action on hypothalamic regulation centers. Based on the crucial role of VEGF on brain glucose supply, we hypothesized that higher VEGF concentrations are associated with lower food intake and body mass in humans. METHODS: Intending to investigate subjects with high variance of blood glucose, we examined patients with type 2 diabetes mellitus. Our hypothesis was tested in a population-based cohort of 190 subjects with type 2 diabetes. Plasma VEGF levels in conjunction with other parameters known to modulate food intake were measured and subsequently correlated with food intake patterns at a breakfast buffet as well as with body mass. RESULTS: We found that subjects with higher concentrations of plasma VEGF had 17% less carbohydrate intake (P=0.003) and 4.8% lower body mass (P=0.017) than those with lower VEGF concentrations. Intake of protein and fat did not correlate with VEGF concentrations. These associations of plasma VEGF were confirmed in multiple linear regression analyses controlling for several parameters interacting with food intake. CONCLUSION: We conclude that high plasma VEGF concentrations are associated with less carbohydrate intake and lower body mass in type 2 diabetes. The role VEGF plays in facilitating glucose access to the brain represents a new aspect of food intake regulation and energy homeostasis, with relevance for diseases with body mass disturbances.

Analysis of Variance↗
PubMed2005

Effects of erythropoietin on brain function.

This article is a selective extension of a review on recombinant human erythropoietin (rHu-EPO) as an anti-anaemic drug, published in this journal in 2000. It summarises the recent advances in understanding the molecular mechanisms by which the hypoxia-inducible transcription factor 1 (HIF-1) regulates O(2)-dependent genes, including the EPO gene in brain. With respect to brain integrity, EPO exerts positive effects in two different ways. First, rHu-EPO raises the blood haemoglobin concentration and, hence, the O(2) capacity of the blood in anaemic patients. The restored O(2) supply ameliorates attention difficulties and psychomotor slowing, improves memory capacities and normalises neuroendocrine functions. Second, EPO can act as a neurotrophic and neuroprotective factor directly in brain. EPO and its receptor are expressed in the cerebral cortex, cerebellum, hippocampus, pituitary gland and spinal cord. In vitro EPO protects against glutamate-induced cell death in a dose-dependent way. In animal models it reduces volumes of brain ischaemia, protects the cortex from hypoxic damage and leads to survival of neurons and synapses. One can expect that in the near future rHu-EPO will be used therapeutically in cerebral ischaemia, brain trauma, inflammatory diseases, and neural degenerative disorders. A first clinical trial has shown the neuroprotective effectiveness of the drug in cerebral ischaemia.

Animals↗
PubMed2004

Little cherry virus-2: sequence and genomic organization of an unusual member of the Closteroviridae.

The complete genomic sequence of variant USA6b of Little cherry virus-2 (LChV-2), has been determined and is 15045 nucleotides in length, coding for 11 open reading frames (ORFs). The sequence shares 77.2% identity with a previously published, ca. 6 kb partial replicase sequence of LChV-2 (variant USA6a). Both LChV-2/USA6a and LChV-2/USA6b were obtained from the same tree infected with little cherry disease, and would suggest a mixed infection. LChV-2/USA6b is more closely related to the partially determined genomic sequence of a Canadian isolate of LChV-2, strain LC5 (92.9% identity). LChV-2/USA6b has an unusual genomic organization compared to other members of the Closteroviridae. The LChV-2/USA6b genome is potentially ambi-sense, with a negative sense ORF0 at the 5' terminus, from which an 18.1 kDa protein of unknown function can be expressed in vitro. The N-terminal region of the LChV-2/USA6 ORF1a translation product does not code for a papain-like protease motif. ORF1 codes for a novel motif, of unknown function, also present in isolates of the Grapevine leafroll associated virus-3, (genus Ampelovirus) as well as viruses of the family Flexiviridae. ORF3 lacks an AUG start codon, but could potentially be expressed via read-through of the ORF2 stop codon. At the 3' end, there is a re-organization of encoded genes compared with other members of the Closteroviridae including separation of the coat protein and coat protein duplicate genes by 4 other genes as found for LChV-2/LC5.

Amino Acid Sequence↗
PubMed2004

Strain diversity and conserved genome elements in Strawberry mild yellow edge virus.

The complete nucleotide sequence of Strawberry mild yellow edge virus isolate D74, and the sequences of a 878 nt region of the coat protein and flanking regions of twenty three isolates of SMYEV were obtained and analysed. The full sequence of the aphid transmissible strain D74 was deduced and found to have an 86% sequence identity to the non-transmissible Agrobacterium infectious MY18 strain. In contrast to isolate MY18 the 5' terminal nucleotides (GAAAAC) of D74 are typical of those from other potexviruses. However, both MY18 and D74 have a non-AUG initiation codon for ORF2 encoding the triple gene block protein 1 (TGB1), and an overlapping TGB3 and coat protein (CP), features unique in the Potexvirus genus. Other conserved features of the genome, including stem-loop structures in the untranslated regions, and motifs common to related viruses are described. The previously postulated ORF6 of MY18 is absent in twenty of the isolates sequenced, including D74. Phylogenetic analysis places all isolates in one of three distinct groups/strains named here I (type-D74), II (type-9Redland), and III (type-MY18), with the majority of isolates, including all European isolates tested, belonging to strain I (type-D74).

Amino Acid Motifs↗
PubMed2003

Erythropoietin.

This article summarizes recent advances in understanding the production and action of the hormone erythropoietin (Epo) with respect to high altitude physiology and sports medicine. Hypoxia is the main stimulus for Epo gene expression. An O2-labile protein (hypoxia-inducible factor 1, HIF-1) has been identified that is hydroxylated and degraded under normoxic conditions but active in hypoxia, where it enhances Epo gene transcription resulting in elevated hemoglobin levels and O2 capacity of the blood. The stimulation of Epo production at lowered arterial O2 tension can be maladaptive, if erythrocytosis develops such as seen in high altitude habitants. Within physiological limits the aerobic power increases in parallel with blood O2 capacity. Therefore, some elite athletes have misused recombinant human Epo (rhEpo), which is a beneficial anti-anemic drug in clinical practice. Indirect and direct methods to detect rhEpo doping have been recently developed.

Altitude↗
PubMed2003

Multiplex RT-PCR detection of four aphid-borne strawberry viruses in Fragaria spp. in combination with a plant mRNA specific internal control.

The principal aphid-borne viruses infecting Strawberry (Fragaria spp.) Strawberry crinkle virus (SCV), Strawberry mild yellow edge virus (SMYEV), Strawberry mottle virus (SMoV) and Strawberry vein banding virus (SVBV) can cause serious crop losses. In this paper, a multiplex reverse transcriptase polymerase chain reaction (RT-PCR) method is described for the simultaneous detection of all four viruses in combination with a plant mRNA specific internal control which can be used as an indicator of the effectiveness of the extraction and RT-PCR. In total, 18 strawberry isolates infected naturally were analysed by this method. Every combination of RNA virus was able to be detected and a full complement of all four viruses were found together in three isolates, all taken from wild strawberry (Fragaria chiloensis (L.) Duch.) in Chile. The upper detection limit for the four viruses was at an extract dilution of 1/200. The broad applicability of the RNA specific internal control primers-which produced a PCR fragment of the expected size in 25 of 27 plant species tested-combined with improvements, made in extraction methods described provides potentially a standard method for comparable RT-PCR analyses in a wide variety of plant species.

Animals↗
PubMed2002

Detection of four apple viruses by multiplex RT-PCR assays with coamplification of plant mRNA as internal control.

Two multiplex RT-PCR assays with specific coamplification of plant mRNA as an internal control from total nucleic acids are described for the parallel detection of Apple chlorotic leaf spot virus, Apple stem pitting virus, Apple mosaic virus and Apple stem grooving virus. All are important economically and common pathogens in commercial apple and pear cultivars, except for Apple mosaic virus. Four virus specific primer pairs and one primer pair which allows the specific amplification of mRNA of the mitochondrial nad5 gene are described. Specificity of all primer pairs was confirmed by sequencing the RT-PCR products. A range of different virus isolates from various geographic origins could be detected by these multiplex RT-PCR assays all year round. Viruses were detected reliably in composite extracts at a ratio of one part total nucleic acid extract from an infected sample mixed with 39 parts of extract from healthy samples. The use of the internal control minimizes the risk of obtaining false negative RT-PCR results, which is desirable for routine testing, and avoids the need to eliminate contaminating DNA in extracts. To our knowledge, this is the first report on the use of a specific internal RNA control from total nucleic acids. The multiplex RT-PCR assays described are reliable, rapid and sensitive methods for the detection of these viruses, and may replace techniques need commonly like indexing by woody indicators or ELISA.

Malus↗
PubMed2002

Characterization and complete nucleotide sequence of Strawberry mottle virus: a tentative member of a new family of bipartite plant picorna-like viruses.

An isolate of Strawberry mottle virus (SMoV) was transferred from Fragaria vesca to Nicotiana occidentalis and Chenopodium quinoa by mechanical inoculation. Electron micrographs of infected tissues showed the presence of isometric particles of approximately 28 nm in diameter. SMoV-associated tubular structures were also conspicuous, particularly in the plasmodesmata of C. quinoa. DsRNA extraction of SMoV-infected N. occidentalis yielded two bands of 6.3 and 7.8 kbp which were cloned and sequenced. Gaps in the sequence, including the 5' and 3' ends, were filled using RT-PCR and RACE. The genome of SMoV was found to consist of RNA1 and RNA2 of 7036 and 5619 nt, respectively, excluding a poly(A) tail. Each RNA encodes one polyprotein and has a 3' non-coding region of approximately 1150 nt. The polyprotein of RNA1 contains regions with identities to helicase, viral genome-linked protein, protease and polymerase (RdRp), and shares its closest similarity with RNA1 of the tentative nepovirus Satsuma dwarf virus (SDV). The polyprotein of RNA2 displayed some similarity to the large coat protein domain of SDV and related viruses. Phylogenetic analysis of the RdRp region showed that SMoV falls into a separate group containing SDV, Apple latent spherical virus, Naval orange infectious mottling virus and Rice tungro spherical virus. Given the size of RNA2 and the presence of a long 3' non-coding region, SMoV is more typical of a nepovirus, although atypically for a nepovirus it is aphid transmissible. We propose that SMoV is a tentative member of an SDV-like lineage of picorna-like viruses.

3' Untranslated Regions↗
PubMed2001

Chronic inborn erythrocytosis leads to cardiac dysfunction and premature death in mice overexpressing erythropoietin.

The most common cause of an increase of the hematocrit is secondary to elevated erythropoietin levels. Erythrocytosis is assumed to cause higher blood viscosity that could put the cardiovascular system at hemodynamic and rheological risks. Secondary erythrocytosis results from tissue hypoxia, and one can hardly define what cardiovascular consequences are caused by chronic erythrocytosis or hypoxia. Herein, a novel transgenic (tg) mouse line is characterized that is erythrocytotic because of chronic overexpression of the human erythropoietin gene. These mice grow up well, reaching a hematocrit of about 0.80 in adulthood. Blood volume of adult tg mice was markedly increased by 75%. Unexpectedly, blood pressure was not elevated and cardiac output was not decreased. Still, the adult tg mice showed features of cardiac dysfunction with increased heart weight. In vivo, high-frequency echocardiography revealed marked ventricular dilatation that was confirmed by histologic examination. Furthermore, by transmission electron microscopy, a prominent intracellular edema of the cardiomyocytes was seen. Exercise performance of the tg mice was dramatically reduced, unmasking the severity of their compromised cardiovascular function. In addition, life expectancy of the tg mice was significantly reduced to 7.4 months. Our findings suggest that severe erythrocytosis per se results in cardiac dysfunction and markedly reduced life span.

Age Factors↗
PubMed2001

Biology of erythropoietin.

Hypoxia induces tissue-specific gene products such as erythropoietin (EPO) and vascular endothelial growth factor (VEGF), which improve the peripheral O2 supply, and glucose transporters and glycolytic enzymes, which adapt cells to reduced O2 availability. EPO has been the fountainhead in research on pO2-dependent synthesis of proteins. The EPO gene enhancer (like the flanking DNA-elements of several other pO2-controlled genes) contains a consensus sequence (CGTG) that binds the trans-acting dimeric hypoxia-inducible factor 1 (HIF-1alpha/beta). The alpha-subunit of HIF-1 is rapidly degraded by the proteasome under normoxic conditions, but it is stabilized on occurrence of hypoxia. HIF-1 DNA-binding is also increased by insulin, and by interleukin-1 and tumor necrosis factor. Thus, in some aspects there is synergy in the cellular responses to hypoxia, glucose deficiency and inflammation. In viewing clinical medicine recombinant human EPO (rHu-EPO) has become the mainstay of treatment for renal anemia. Endogenous EPO and rHu-EPO are similar except for minor differences in the pattern of their 4 carbohydrate chains. RHu-EPO is also administered to patients suffering from non-renal anemias, such as in autoimmune diseases or malignancies. The correction of anemia in patients with solid tumors is not merely considered a palliative intervention. Hypoxia promotes tumor growth. However, the benefits of the administration of rHu-EPO to tumor patients with respect to its positive effects on tumor oxygenation, tumor growth inhibition and support of chemo- and radiotherapy is still debatable ground.

Anemia↗
PubMed2001

Complete nucleotide sequence of cherry necrotic rusty mottle virus.

A virus closely related to cherry green ring mottle virus (CGRMV) was isolated from a tree displaying typical symptoms of cherry necrotic rusty mottle disease. We have named this virus cherry necrotic rusty mottle virus (CNRMV) and report here its complete genomic sequence as determined from overlapping cloned cDNAs. CNRMV has a genome of 8,432 nucleotides excluding the 3' poly(A) sequence and codes for 7 significant open reading frames (ORFs). Five of these ORFs are conserved among all fovea-, allexi-, potex- and carlaviruses and code for a methyltransferase/helicase/polymerase polypeptide, the triple gene block movement proteins and the coat protein. Two further ORFs, ORFs 2a and 5a, are nested completely within ORFs 2 and 5, respectively. The putative translation products from these ORFs display sequence similarity with putative translation products from two similarly nested ORFs present in the CGRMV genome. The function of these two ORFs is unknown, nor are they conserved among other related viruses.

Amino Acid Sequence↗
PubMed2001

Vascular endothelial growth factor gene expression in the human breast cancer cell line MX-1 is controlled by O2 availability in vitro and in vivo.

The vascular endothelial growth factor (VEGF) plays an important role in angiogenesis. Mediated by the hypoxia-inducible transcription factor HIF-1alpha/beta, a reduction in O2 tension (pO2) leads to increased VEGF gene expression in nonmalignant tissues. In tumor cells VEGF mRNA levels are often constitutively elevated. We examined pO2-dependent VEGF mRNA expression and VEGF protein formation in the human breast cancer cell line MX-1 in vitro and in vivo. For in vitro study MX-1 cultures were grown on dishes with a gas-permeable bottom to expose the cells to defined O2 concentrations (from 95% to 0%) for 4 h. Northern blot analysis showed significant VEGF mRNA in MX-1 cultures under normoxic conditions which was further increased by hypoxia. The amount of secreted VEGF was also elevated in hypoxic cultures. Western blot analysis revealed a correlation between the severity of hypoxia and HIF-1alpha protein amounts in the nucleus. Furthermore, DNA-binding activity of HIF-1 could be demonstrated by gel-shift assays. For in vivo study immunodeficient nude mice bearing MX-1 tumor transplants were exposed to inspiratory hypoxia (10% O2). Northern blot and immunohistochemical analyses of MX-1 tumor transplants showed that VEGF mRNA and VEGF protein levels were increased in mice 17 h after the induction of inspiratory hypoxia. Thus, pO2-dependence of VEGF gene expression can be maintained in cancer cells, even in vivo, which may be relevant in regard to therapeutic attempts to inhibit tumor angiogenesis by increasing tumor oxygenation.

Adult↗
PubMed2001

Subcellular localization of thrombopoietin in human blood platelets and its release upon thrombin stimulation.

Thrombopoietin (TPO) is a major regulator of platelet production. The concentration of circulating TPO seems to be determined by its binding and internalization by megakaryocytes and platelets. To elucidate the platelet compartments involved in TPO metabolism, we investigated intraplatelet TPO by post-embedding immunoelectron microscopy, incubated platelets with recombinant human (rh)TPO coupled to colloidal gold and visualized the TPO uptake using electron microscopy. TPO concentrations were measured in 12 platelet concentrates (PC) before and after stimulation with thrombin and after disruption of platelets by freezing-thawing. In resting platelets, immunogold labelling revealed a prevailing cytoplasmic localization of TPO antigen and minor labelling within the surface-connected canalicular system (SCCS); storage granules were devoid of labelling. In tracer experiments, TPO-gold was observed on the plasma and SCCS membranes and within the cytoplasm. Upon thrombin stimulation, endogenous TPO was still detected within the cytoplasm by immunolabelling, and tracer experiments revealed TPO-gold within the cytoplasm and on fibrin fibres. After thrombin stimulation of PC, the plasma TPO levels increased to an average of 535%, and after platelet lysis to an average of 1625% compared with plasma values in unstimulated PC. We conclude that platelets contain releasable immunoreactive TPO within the SCCS and within their cytoplasm, but not within granular compartments. Stored immunoreactive TPO is released upon thrombin stimulation, but only to a minor degree.

Blood Platelets↗
PubMed2001

Blunted erythropoietic response to anemia in multiply traumatized patients.

OBJECTIVES: To assess the relations between anemia, serum erythropoietin (EPO), iron status, and inflammatory mediators in multiply traumatized patients. DESIGN: Prospective observational study. SETTING: Intensive care unit. PATIENTS: Twenty-three patients suffering from severe trauma (injury severity score > or =30). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Blood samples were collected within 12 hrs after the accident (day 1) and in the morning on days 2, 4, 6, and 9 to determine blood cell status, serum EPO, tumor necrosis factor-alpha (TNF-alpha), soluble tumor necrosis factor-receptor I (sTNF-rI), interleukin-1 receptor antagonist (IL1-ra), interleukin-6 (IL-6), neopterin, and iron status, respectively. Hemoglobin concentration was low at admission (mean, 10.0 g/dL; range, 6.8-12.9 g/dL) and did not increase during the observation time. Serum EPO concentration was 49.8 U/L (mean value) on day 1 and did not show significant increases thereafter. No correlation was found between EPO and hemoglobin concentrations. TNF-alpha remained within the normal range. sTNF-rI was high at admission and increased further. IL1-ra was above the normal range. IL-6 was very high at admission and did not decrease thereafter. The initial neopterin concentration was normal, but increased until day 9. Serum iron was significantly decreased on day 2 posttrauma and remained low during the study. Serum ferritin increased steadily from day 2, reaching its maximum on day 9. In contrast, concentrations of transferrin were low from admission onward. CONCLUSIONS: Multiply traumatized patients exhibit an inadequate EPO response to low hemoglobin concentrations. Thus, anemia in severe trauma is the result of a complex network of bleeding, blunted EPO response to low hemoglobin concentrations, inflammatory mediators, and a hypoferremic state.

Adult↗
PubMed2001

The role of the liver in the production of thrombopoietin compared with erythropoietin.

The liver plays an important role in the production of haemopoietic hormones. It acts as the primary site of synthesis of erythropoietin (EPO) in the fetal stage, and it is the predominant thrombopoietin (TPO)-producing organ for life. In contrast to that of EPO and other liver proteins, the hepatic synthesis of TPO is influenced little by external signals. Hepatocytes express the TPO gene in a constitutive way, i.e. irrespective of the level of platelets in blood. Megakaryocytes and platelets remove the hormone from blood by means of their high-affinity TPO receptors. Normally, the plasma level of TPO is relatively low ( approximately 10(-12) mol/l). However, in thrombocytopenic states due to marrow failure or bleeding, the concentration of circulating TPO may increase greatly. The simple feedback regulation by TPO and its target cells is efficient in maintaining constant platelet numbers in healthy people. Persisting thrombocytopenia develops only in severe liver or marrow failure. On the other hand, an increase in circulating TPO and interleukin 6 (IL-6) may cause reactive thrombocytosis in inflammatory diseases, including cancer. The indications for recombinant human thrombopoietin (rHuTPO) therapy and its impact on transfusion medicine are still under investigation.

Animals↗
PubMed2001

Cytosolic Ca(2+) levels and DNA synthesis of human umbilical vein endothelial cell cultures are unresponsive to thrombopoietin treatment.

The hormone thrombopoietin (TPO) induces proliferation of megakaryocytic progenitors and augments agonist-induced mobilization of Ca(2+) in platelets. Because the action of TPO is not restricted to the megakaryocytic lineage, we studied the occurrence of TPO receptor mRNA and protein, and effects of TPO on cytosolic Ca(2+) levels and DNA synthesis in human umbilical vein endothelial cell cultures (HUVECs). Polymerase chain reaction following reverse transcription (RT-PCR) of total mRNA revealed that TPO receptor (MPL) mRNA was expressed only at low level in our samples. TPO receptor protein was not detectable in HUVEC lysates investigated by immunoprecipitation and immunoblotting. In contrast to vascular endothelial growth factor (VEGF), TPO did neither alter fura2 fluorescence as a measure of cytosolic Ca(2+) levels nor increase 5-bromo-2'-deoxyuridine incorporation into DNA of HUVECs. In conclusion, our data demonstrate that HUVECs are neither structurally nor functionally responsive to TPO.

Calcium↗
PubMed2001

Pitfalls in the measurement of circulating vascular endothelial growth factor.

BACKGROUND: Vascular endothelial growth factor (VEGF) is a protein with antiapoptotic, mitogenic, and permeability-increasing activities specific for vascular endothelium. VEGF mRNA, which has five isoforms, is produced by nonmalignant cells in response to hypoxia and inflammation and by tumor cells in constitutively high concentrations. Because VEGF plays a crucial role in physiological and pathophysiological angiogenesis, measurements of circulating VEGF are of diagnostic and prognostic value, e.g., in cardiovascular failures, inflammatory diseases, and malignancies. However, there are major quantitative differences in the published results. This review attempts to identify reasons for these disparities. APPROACH: The literature was reviewed through a Medline search covering 1995 to 2000. A selection of exemplary references had to be made for this perspective overview. CONTENT: Data are included from studies on healthy humans, gynecological patients, and persons suffering from inflammatory or malignant diseases. The results indicate that competitive immunoassays detect the total amount of circulating VEGF, which enables observations regarding the increase in VEGF in pregnancy and preeclampsia to be made. In these cases, capture immunoassays utilizing neutralizing antibodies are insufficient because of an accompanying increase in VEGF-binding soluble receptors (sFlt-1). Measurements of circulating free VEGF are useful for study of malignant diseases, which are associated with both genetically and hypoxia-induced overproduction of VEGF. The VEGF isoform specificity of the antibodies is also critical because both VEGF(121) and VEGF(165) are secreted. It is important to consider that platelets and leukocytes release VEGF during blood clotting. CONCLUSIONS: Future efforts should concentrate on the balance between free VEGF, total VEGF, and sFlt-1. Plasma, rather than serum, should be used for analysis.

Endothelial Growth Factors↗