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Biomedical subjects

N Blom

Publications and source records attributed to N Blom.

At least 19 recordsLinked to original sources
PubMed2003

99mTc-MIBI myocardial perfusion imaging in myocarditis.

Myocardial perfusion imaging with technetium-99m-labelled methoxyisobutyl isonitrile single photon emission computed tomography (99mTc-MIBI SPECT) has proven to be an important clinical procedure in assessing the severity of myocardial ischaemia. The uptake and clearance of 99mTc-MIBI by the myocardium is affected by cell viability and membrane integrity. Consequently, infectious diseases, such as myocarditis, may also affect myocardial perfusion by inducing local inflammation and necrosis. We compared 99mTc-MIBI myocardial perfusion imaging with other heart monitoring methods in order to assess its value in the diagnosis of children with Coxsackie viral myocarditis. We examined 46 patients (age, 3-12 years) with Coxsackie viral myocarditis using 99mTc-MIBI myocardial perfusion imaging and compared the perfusion data with myocardial enzymes, electrocardiographic findings and echocardiography. Regions of hypoperfusion were found in all 46 patients. Seventeen patients (37%) showed two or more areas of diminished perfusion. Myocardial hypoperfusion was mild-to-moderate (<30%) in 33 (72%) patients and severe (>30%) in 13 (28%) patients. Characteristic creatine-kinase isoenzyme (CK-MB) increases, ST-T segment changes and diminished heart function were significantly correlated with reduced myocardial perfusion (all comparisons P<0.05). The results of this study suggest that the presence of myocardial uptake of 99mTc-MIBI may be a marker of myocardial inflammation and necrosis. All 46 patients with Coxsackie viral myocarditis showed a certain degree of reduced perfusion. When the perfusion findings were compared with other parameters, it was shown that myocardial enzyme levels, ST-T segment changes and left ventricular function correlated well with the 99mTc-MIBI-established perfusion defect severity. 99mTc-MIBI SPECT imaging is therefore helpful in providing additional diagnostic information in patients with Coxsackie viral myocarditis.

Child↗
PubMed2002

Prediction of human protein function from post-translational modifications and localization features.

We have developed an entirely sequence-based method that identifies and integrates relevant features that can be used to assign proteins of unknown function to functional classes, and enzyme categories for enzymes. We show that strategies for the elucidation of protein function may benefit from a number of functional attributes that are more directly related to the linear sequence of amino acids, and hence easier to predict, than protein structure. These attributes include features associated with post-translational modifications and protein sorting, but also much simpler aspects such as the length, isoelectric point and composition of the polypeptide chain.

Computational Biology↗
PubMed2001

Ultrastructural morphology and localisation of cisplatin-induced platinum-DNA adducts in a cisplatin-sensitive and -resistant human small cell lung cancer cell line using electron microscopy.

Ultrastructural morphology (transmission electron microscopy) and localisation of cisplatin-induced platinum (Pt)-DNA adducts (immunoelectron microscopy) were analysed in the human small cell lung cancer cell line GLC(4) and its 40-fold in vitro acquired cisplatin-resistant subline GLC(4)-CDDP, which is characterised by, among other things, a decreased DNA platination. Immunolabelling of Pt-DNA adducts was performed with the polyclonal antibody GPt, known to detect the main Pt-containing intrastrand and interstrand DNA adducts. Morphological analysis of GLC(4) and GLC(4)-CDDP at the ultrastructural level showed cells with a high nucleus/cytoplasm ratio with the majority of nuclei containing one or more nucleoli. GLC(4)-CDDP showed, in contrast to GLC(4), an extensive Golgi apparatus and an increased number of mitochondria. DNA platination was detectable in both GLC(4) and GLC(4)-CDDP. Immunoelectron microscopy showed Pt-DNA adducts primarily in the nucleus, preferentially at loci with high-density chromatin (e.g. heterochromatin, pars granulosa around nucleoli, condensed DNA in proliferating and apoptotic cells), and in mitochondria. The level of detectable Pt-DNA adducts was cell cycle status-dependent. In both cell lines, Pt-DNA adduct levels increased from non-dividing interphase cells to dividing cells and were highest in cells undergoing apoptosis. Overall localisation of Pt-DNA adducts was comparable in GLC(4) and GLC(4)-CDDP cells.

Antibodies↗
PubMed2001

Uptake of pp65 in in vitro generated pp65-positive polymorphonuclear cells mediated by phagocytosis and cell fusion?

OBJECTIVE: The cytomegalovirus (CMV) antigenemia consists of the detection of CMV pp65 in the nucleus of polymorphonuclear granulocytes (PMN), but it is unclear where and how PMN pick up virus particles or proteins. In an in vitro model for CMV antigenemia we investigated the mechanism of pp65 uptake by PMN that results in its expression in the nucleus. METHODS: A series of inhibitors of different mechanisms was used to study the uptake of pp65 by PMN during coculture with CMV-infected endothelial cells and we performed a morphological analysis by light and transmission electron microscopy. RESULTS: Nocodazole and cytochalasin B inhibited uptake of pp65 by PMN with 59.4 +/- 14.1 and 73.3 +/- 12.7%, respectively. The presence of anti-CMV hyperimmune globulin or lactoferrin during coculture reduced the number of pp65-positive PMN with 45.8 +/- 7.0 or 40.6 +/- 3.2%. Furthermore, a small number of the pp65-positive PMN obtained after coculture had fused to large cells with multilobed nuclei. PMN were observed that enclosed viral particles as well as free viral particles containing PMN in the cytoplasm. CONCLUSION: Fusion of viral particles with PMN and phagocytosis are both involved in the uptake of pp65.

Antibodies, Viral↗
PubMed2000

In vivo protection of nigral dopamine neurons by lentiviral gene transfer of the novel GDNF-family member neublastin/artemin.

The glial cell line-derived neurotrophic factor (GDNF)-family of neurotrophic factors consisted until recently of three members, GDNF, neurturin, and persephin. We describe here the cloning of a new GDNF-family member, neublastin (NBN), identical to artemin (ART), recently published (Baloh et al., 1998). Addition of NBN/ART to cultures of fetal mesencephalic dopamine (DA) neurons increased the number of surviving tyrosine hydroxylase (TH)-immunoreactive neurons by approximately 70%, similar to the maximal effect obtained with GDNF. To investigate the neuroprotective effects in vivo, lentiviral vectors carrying the cDNA for NBN/ART or GDNF were injected into the striatum and ventral midbrain. Three weeks after an intrastriatal 6-hydroxydopamine lesion only about 20% of the nigral DA neurons were left in the control group, while 80-90% of the DA neurons remained in the NBN/ART and GDNF treatment groups, and the striatal TH-immunoreactive innervation was partly spared. We conclude that NBN/ART, similarly to GDNF, is a potent neuroprotective factor for the nigrostriatal DA neurons in vivo.

Amino Acid Sequence↗
PubMed1999

Sequence and structure-based prediction of eukaryotic protein phosphorylation sites.

Protein phosphorylation at serine, threonine or tyrosine residues affects a multitude of cellular signaling processes. How is specificity in substrate recognition and phosphorylation by protein kinases achieved? Here, we present an artificial neural network method that predicts phosphorylation sites in independent sequences with a sensitivity in the range from 69 % to 96 %. As an example, we predict novel phosphorylation sites in the p300/CBP protein that may regulate interaction with transcription factors and histone acetyltransferase activity. In addition, serine and threonine residues in p300/CBP that can be modified by O-linked glycosylation with N-acetylglucosamine are identified. Glycosylation may prevent phosphorylation at these sites, a mechanism named yin-yang regulation. The prediction server is available on the Internet at http://www.cbs.dtu.dk/services/NetPhos/or via e-mail to NetPhos@cbs. dtu.dk.

Amino Acid Motifs↗
PubMed1999

PhosphoBase, a database of phosphorylation sites: release 2.0.

PhosphoBase contains information about phosphorylated residues in proteins and data about peptide phosphorylation by a variety of protein kinases. The data are collected from literature and compiled into a common format. The current release of PhosphoBase (October 1998, version 2.0) comprises 414 phosphoprotein entries covering 1052 phosphorylatable serine, threonine and tyrosine residues. The kinetic data from peptide phosphorylation assays for approximately 330 oligopeptides is also included. The database entries are cross-referenced to the corresponding records in the Swiss-Prot protein database and literature references are linked to MedLine records. PhosphoBase is available via the WWW at http://www.cbs.dtu. dk/databases/PhosphoBase/

Animals↗
PubMed1998

Statistical analysis of protein kinase specificity determinants.

The site and sequence specificity of protein kinases, as well as the role of the secondary structure and surface accessibility of the phosphorylation sites on substrate proteins, was statistically analyzed. The experimental data were collected from the literature and are available on the World Wide Web at http://www.cbs.dtu.dk/databases/PhosphoBase/. The set of data involved 1008 phosphorylatable sites in 406 proteins, which were phosphorylated by 58 protein kinases. It was found that there exists almost absolute Ser/Thr or Tyr specificity, with rare exceptions. The sequence specificity determinants were less strict and were located between positions -4 and +4 relative to the phosphorylation site. Secondary structure and surface accessibility predictions revealed that most of the phosphorylation sites were located on the surface of the target proteins.

Amino Acids↗
PubMed1998

Enhanced electron-density envelopes by extended solvent definition.

Extended delineation of water molecules, monitored using Rfree values, afforded considerable improvement in quality of electron-density maps for structure determination of mammalian class I and E. coli class II aldolases. Augmented solvent definition results in an additional decrease in Rfree values of 3-4% and is reflected in significantly enhanced electron-density envelopes enabling tracing of amino-acid sequences through regions of otherwise discontinuous or weak electron density.

Electrons↗
PubMed1998

PhosphoBase: a database of phosphorylation sites.

PhosphoBase is a database of experimentally verified phosphorylation sites. Version 1.0 contains 156 entries and 398 experimentally determined phosphorylation sites. Entries are compiled and revised from the literature and from major protein sequence databases such as SwissProt and PIR. The entries provide information about the phosphoprotein and the exact position of its phosphorylation sites. Furthermore, part of the entries contain information about kinetic data obtained from enzyme assays on specific peptides. To illustrate the use of data extracted from PhosphoBase we present a sequence logo displaying the overall conservation of positions around serines phosphorylated by protein kinase A (PKA). PhosphoBase is available on the WWW at http://www.cbs.dtu.dk/databases/PhosphoBase/

Amino Acid Sequence↗
PubMed1996

Cleavage site analysis in picornaviral polyproteins: discovering cellular targets by neural networks.

Picornaviral proteinases are responsible for maturation cleavages of the viral polyprotein, but also catalyze the degradation of cellular targets. Using graphical visualization techniques and neural network algorithms, we have investigated the sequence specificity of the two proteinases 2Apro and 3Cpro. The cleavage of VP0 (giving rise to VP2 and VP4), which is carried out by a so-far unknown proteinase, was also examined. In combination with a novel surface exposure prediction algorithm, our neural network approach successfully distinguishes known cleavage sites from noncleavage sites and yields a more consistent definition of features common to these sites. The method is able to predict experimentally determined cleavage sites in cellular proteins. We present a list of mammalian and other proteins that are predicted to be possible targets for the viral proteinases. Whether these proteins are indeed cleaved awaits experimental verification. Additionally, we report several errors detected in the protein databases. A computer server for prediction of cleavage sites by picornaviral proteinases is publicly available at the e-mail address NetPicoRNA@cbs.dtu.dk or via WWW at http:@www.cbs.dtu.dk/services/NetPicoRNA/.

Amino Acid Sequence↗
PubMed1993

Ultrastructural analysis of circulating cytomegalic cells in patients with active cytomegalovirus infection: evidence for virus production and endothelial origin.

The presence of cytomegalic inclusion cells in the peripheral blood of patients with an active cytomegalovirus infection has recently been demonstrated. Immunologic staining showed that these cells were of endothelial origin. Study of circulating cytomegalic cells by transmission electron microscopy showed the cells to be productively infected with cytomegalovirus. Viral capsids were present in the nucleus and virus particles and dense bodies were found in the cytoplasm. The results indicate that these circulating cytomegalic cells could disseminate cytomegalovirus throughout the body. In addition, the finding of a cluster of cytomegalic cells in the peripheral blood linked together by zonula adherens type cell junctions is further evidence that these cells are of endothelial origin and suggests that the endothelial damage may be extensive.

Cell Nucleus↗
PubMed1993

Clonal chronic lymphocytic leukaemia-like B lymphocytes in the blood of patients with cutaneous T-cell disorders.

A population of B cells with characteristics of chronic lymphocytic leukaemia was found in the peripheral blood of four patients who presented with cutaneous infiltration of atypical CD4+ T cells with cerebriform nuclei. The B cells had a low density of immunoglobulin on their surface membrane, expressed CD5-positivity, and showed monoclonality based on the restriction to either kappa or lambda light chains. In one patient with tumourous pleiomorphic CD4+CD30- T-cell lymphoma of the skin, it was the first manifestation of a concomitant B-cell non-Hodgkin's lymphoma of low-grade malignancy. In three other patients with reactive atypical T-cell erythroderma, there was no evidence for the coexistence of a B-cell malignancy. The number of CD5+ B cells decreased in two erythroderma patients with clinical remission of the cutaneous lesions. It is speculated that the presence of a monoclonal B cell population in patients with T-cell disorders of the skin is due either to a reactive process possibly conferring some protective effect, or a response to an unknown stimulus produced by the T cells.

Aged↗
PubMed1992

[Alzheimer's dementia and amyloid precursor-protein].

Alzheimer's dementia is a severe form of dementia characterised by three neuropathological changes: amyloid plaques, neurofibrillary tangles and neurodegeneration. Several laboratories are involved in studies of the molecular mechanisms underlying development of Alzheimer's disease. As a result of recent research, the main component of amyloid plaques, the beta A4-peptide, is focused upon in hypotheses of the pathogenesis of the disease. The beta A4-peptide is produced by cleavage of the larger amyloid precursor protein (APP). During normal processing of APP, production of beta A4 is hindered and the peptide is therefore presumably a result of alternative cleavage mechanisms. Several factors may increase alternative processing of APP. One possibility is that conformational changes in APP, e.g. induced by mutations in the APP gene, may facilitate alternative cleavage of APP and thereby production of beta A4. This seems to be the case in certain families with familial Alzheimer's disease. Another possibility for increased beta A4 production is excessive expression of APP. This seems to be the case in persons with trisomy 21 who all have neuropathological signs of Alzheimer's disease after the age of 40 years. The gene for APP is localised to the human chromosome 21 and these persons have 1.5 times the normal expression of APP. Furthermore, excessive APP-expression may be induced by an acute phase response in the brain. In vitro studies and neuropathological examinations indicate that alpha 2-macroglobulin in neurons may be induced by cytokines. The protease inhibitor activity of this protein may prevent normal cleavage of APP, thereby resulting in increased alternative cleavage and deposition of beta A4.(ABSTRACT TRUNCATED AT 250 WORDS)

Alzheimer Disease↗
PubMed1992

Evaluation of elutriated single donor platelets collected and stored in a closed system.

Single donor platelets (SDPC) were collected by the elutriation technique in a closed-system integrated with large storage containers. Seven runs of SDPC were stored in a 1.5 liter polyvinyl-chloride trimellitate (PVC-TOTM) storage container, making the ratio of platelet concentrate volume to container volume 1:4.5. An equal volume of pooled multiple donor platelet concentrates (MDPC) was stored in parallel under the same conditions. All haematological data were comparable for both products, except for the degree of leukocyte contamination (5-fold increase in the pool). Under these conditions, the functional, morphological, and metabolic characteristics of elutriated platelets throughout 7-day storage were superior to those of pooled platelets. Although the platelet count was not significantly different in both types of concentrates, the mean pH of pooled MDPC fell to 6.0 on day 5 of storage. Leukocytes were shown to contribute to this pH fall. The extent of cell damage, however, as evidenced by LDH leakage (42.7 LDH units/10(11) platelets/day by differential centrifugation, compared to 5.3 units by elutriation) could not be explained solely on the basis of the leukocyte effect. This indicated that the processing method itself influences the platelet quality. By increasing the surface/volume ratio of SDPC, the initial pH of 7.1 was well maintained throughout storage, platelet metabolic rate was slowed, and the function and ultrastructure improved significantly.

Blood Donors↗
PubMed1992

Stabilization of standard platelet concentrates and minimization of the platelet storage lesion by a prostacyclin analogue.

Platelet concentrates were pretreated with a stable synthetic prostacyclin analogue (Iloprost) at two different concentrations before the second centrifugation step (pelleting step) of preparation. This resulted in loss of platelet sensitivity to aggregating agents. To mimic the situation after transfusion and to assess the reversibility of platelet inhibition, platelets were washed during and after storage and resuspended in fresh-frozen autologous plasma. The Iloprost-treated and washed platelets exhibited an increased sensitivity to the aggregating agents, compared with the control platelets (p less than 0.01). Post-storage recovery of the synergistic aggregation was more than 80% of prestorage aggregation. Beta-thromboglobulin (beta TG) release and thromboxane B2 (TXB2) formation were significantly inhibited in Iloprost-treated platelets (p less than 0.01). After the second centrifugation step, beta TG release was 0.7% +/- 0.3%, compared with 2.7% +/- 0.9% for the controls. TXB2 was 99 +/- 91 pg/ml, compared with 495 +/- 356 pg/ml for the controls. Platelet morphology and ultrastructure were well preserved during 5-day storage. In addition, Iloprost exerted a cytoprotective effect, as evidenced by the significant reduction in lactate dehydrogenase leakage. Post-storage LDH was 378 +/- 159 and 415 +/- 239 U/l respectively by the two Iloprost concentrations, compared with 1180 +/- 937 U/l for the control platelets. The inhibitory and cytoprotective effects of Iloprost were sustained throughout storage, in contrast to the effect of PGE1 (Prostin) which was limited to the early phase of storage.

Alprostadil↗