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Biomedical subjects

A Holm

Publications and source records attributed to A Holm.

At least 19 recordsLinked to original sources
PubMed2006

Leishmania donovani requires functional Cdc42 and Rac1 to prevent phagosomal maturation.

Leishmania donovani promastigotes survive inside macrophage phagosomes by inhibiting phagosomal maturation. The main surface glycoconjugate on promastigotes, lipophosphoglycan (LPG), is crucial for survival and mediates the formation of a protective shell of F-actin around the phagosome. Previous studies have demonstrated that this effect involves inhibition of protein kinase C alpha. The present study shows that functional Cdc42 and Rac1 are required for the formation of F-actin around L. donovani phagosomes. Moreover, we present data showing that phagosomes containing LPG-defective L. donovani, which is unable to induce F-actin accumulation, display both elevated levels of periphagosomal F-actin and impaired phagosomal maturation in macrophages with permanently active forms of Cdc42 and Rac1. We conclude that L. donovani engages Cdc42 and Rac1 to build up a protective coat of F-actin around its phagosome to prevent phagosomal maturation.

Actins↗
PubMed2005

Charged meson rapidity distributions in central Au+Au collisions at square root(sNN) = 200 GeV.

We have measured rapidity densities dN/dy of pi+/- and K+/- over a broad rapidity range (-0.1 < y < 3.5) for central Au + Au collisions at square root(sNN) = 200 GeV. These data have significant implications for the chemistry and dynamics of the dense system that is initially created in the collisions. The full phase-space yields are 1660 +/- 15 +/- 133 (pi+), 1683 +/- 16 +/- 135 (pi-), 286 +/- 5 +/- 23 (K+), and 242 +/- 4 +/- 19 (K-). The systematics of the strange to nonstrange meson ratios are found to track the variation of the baryochemical potential with rapidity and energy. Landau-Carruthers hydrodynamics is found to describe the bulk transport of the pions in the longitudinal direction.

Journal Article↗
PubMed2004

Nuclear stopping in Au+Au collisions at square root of S(NN)=200 GeV.

Transverse momentum spectra and rapidity densities, dN/dy, of protons, antiprotons, and net protons (p-p) from central (0%-5%) Au+Au collisions at square root of S(NN)=200 GeV were measured with the BRAHMS experiment within the rapidity range 0</=y</=3. The proton and antiproton dN/dy decrease from midrapidity to y=3. The net-proton yield is roughly constant for y<1 at dN/dy approximately 7, and increases to dN/dy approximately 12 at y approximately 3. The data show that collisions at this energy exhibit a high degree of transparency and that the linear scaling of rapidity loss with rapidity observed at lower energies is broken. The energy loss per participant nucleon is estimated to be 73+/-6 GeV.

Journal Article↗
PubMed2004

Results and costs of intensive care in a tertiary university hospital from 1996-2000.

BACKGROUND: Costs of intensive care may be 20% of all hospital costs. Population aging likely increases the demand for intensive care services, while health care has financial limitations. Therefore data about outcome and costs of intensive care are needed. We studied changes in patient characteristics, outcome, intensity of care and costs of intensive care in a tertiary university hospital in Finland. METHODS: We analyzed retrospectively data of patients admitted to the ICU between 1 January 1996 and 31 December 2000 using the patient data management system. Postoperative and ICU patients were analyzed separately. Data included age, Apache II score, cause of intensive care admission, length and intensity of ICU care. ICU, hospital and 6-month mortality were analyzed. Intensity of care was assessed by TISS points and the annual costs of intensive care were evaluated. RESULTS: The number of ICU admissions from 1996-2000 was 11,323. The proportions of ICU and postoperative patients were 39% and 61%, respectively. The mean age of the patients did not change. The mean Apache II score increased over time both in the ICU and postoperative patients. There was no change in crude hospital mortality. Total ICU costs decreased from 8,660,000 euros (in 1997) to 7,480,000 euros (in 2000). In the ICU patients, the costs of hospital survival decreased towards the end of the study period. CONCLUSIONS: We treated more severely ill patients with unchanged outcome but at lower costs towards the end of the study period. Costs of intensive care are not necessarily increasing.

APACHE↗
PubMed2003

Transverse-momentum spectra in Au+Au and d+Au collisions at sqrt[s(NN)]=200 GeV and the pseudorapidity dependence of high-p(T) suppression.

We present spectra of charged hadrons from Au+Au and d+Au collisions at sqrt[s(NN)]=200 GeV measured with the BRAHMS experiment at RHIC. The spectra for different collision centralities are compared to spectra from p+(-)p collisions at the same energy scaled by the number of binary collisions. The resulting ratios (nuclear modification factors) for central Au+Au collisions at eta=0 and eta=2.2 evidence a strong suppression in the high p(T) region (>2 GeV/c). In contrast, the d+Au nuclear modification factor (at eta=0) exhibits an enhancement of the high p(T) yields. These measurements indicate a high energy loss of the high p(T) particles in the medium created in the central Au+Au collisions. The lack of suppression in d+Au collisions makes it unlikely that initial state effects can explain the suppression in the central Au+Au collisions.

Journal Article↗
PubMed2003

Role of protein kinase C alpha for uptake of unopsonized prey and phagosomal maturation in macrophages.

Protein kinase C alpha (PKC alpha) participates in F-actin remodeling during phagocytosis and phagosomal maturation in macrophages. Leishmania donovani promastigotes, which inhibit phagosomal maturation, cause accumulation of periphagosomal F-actin instead of the disassembly observed around other prey [Cell. Microbiol. 7 (2001) 439]. This accumulation is induced by promastigote lipophosphoglycan (LPG), which has several effects on macrophages including inhibition of PKC alpha. To investigate a possible connection between PKC alpha and LPG's effects on actin dynamics, we utilized RAW264.7 macrophages overexpressing dominant-negative PCK alpha (DN PKC alpha). We found increased cortical F-actin and decreased phagocytic capacity, as well as defective periphagosomal F-actin breakdown and inhibited phagosomal maturation in the DN PKC alpha-overexpressing cells, effects similar to those seen in controls subjected to LPG-coated prey. The results indicate that PKC alpha is involved in F-actin turnover in macrophages and that PKC alpha-dependent breakdown of periphagosomal F-actin is required for phagosomal maturation, and endorse the hypothesis that intracellular survival of L. donovani involves inhibition of PKC alpha by LPG.

Actins↗
PubMed2003

Rapidity dependence of charged antihadron to hadron ratios in Au+Au collisions at sqrt[s(NN)]=200 GeV.

We present ratios of the numbers of charged antihadrons to hadrons (pions, kaons, and protons) in Au+Au collisions at sqrt[s(NN)]=200 GeV as a function of rapidity in the range y=0-3. While the ratios at midrapidity are approaching unity, the K(-)/K(+) and p;/p ratios decrease significantly at forward rapidities. An interpretation of the results within the statistical model indicates a reduction of the baryon chemical potential from mu(B) approximately 130 MeV at y=3 to mu(B) approximately 25 MeV at y=0.

Journal Article↗
PubMed2003

Determination of rotenone in river water utilizing packed capillary column switching liquid chromatography with UV and time-of-flight mass spectrometric detection.

Fast and sensitive packed capillary column switching liquid chromatography methodology has been developed for the determination of the pesticide rotenone in river water. Sample volumes of up to 1 ml are loaded onto a 23 x 0.25 mm, 5 microm Kromasil C18 packed capillary precolumn using a noneluting solvent composition of water-acetonitrile (99:1, v/v) at flow-rates up to 100 microl/min prior to solute backflushing onto a 200 x 0.32 mm, 3.5 microm Kromasil C18 packed capillary analytical column using a mobile phase of water-acetonitrile (30:70, v/v) at a flow-rate of 5 microl/min. The method was evaluated using river water samples spiked with rotenone in the concentration range 0.5-50 ng/ml using UV detection. The within-assay precision was between 5.0 and 7.7% relative standard deviation (RSD, n = 6) and the between assay precision was between 7.5 and 8.9% RSD (n = 6). The method was linear within the investigated mass range displaying a calibration curve correlation factor of 0.997. The mass limit of detection was 10 pg corresponding to a concentration limit of detection of 10 pg/ml, using time-of-flight mass spectrometry.

Chromatography, Liquid↗
PubMed2003

Sensitive quantitative predictions of peptide-MHC binding by a 'Query by Committee' artificial neural network approach.

We have generated Artificial Neural Networks (ANN) capable of performing sensitive, quantitative predictions of peptide binding to the MHC class I molecule, HLA-A*0204. We have shown that such quantitative ANN are superior to conventional classification ANN, that have been trained to predict binding vs non-binding peptides. Furthermore, quantitative ANN allowed a straightforward application of a 'Query by Committee' (QBC) principle whereby particularly information-rich peptides could be identified and subsequently tested experimentally. Iterative training based on QBC-selected peptides considerably increased the sensitivity without compromising the efficiency of the prediction. This suggests a general, rational and unbiased approach to the development of high quality predictions of epitopes restricted to this and other HLA molecules. Due to their quantitative nature, such predictions will cover a wide range of MHC-binding affinities of immunological interest, and they can be readily integrated with predictions of other events involved in generating immunogenic epitopes. These predictions have the capacity to perform rapid proteome-wide searches for epitopes. Finally, it is an example of an iterative feedback loop whereby advanced, computational bioinformatics optimize experimental strategy, and vice versa.

HLA-A Antigens↗
PubMed2003

Brain biopsy prior to treatment of Alzheimer's disease.

A cortical biopsy was analyzed using immunohistochemical methodology in a total of 213 patients with suspected normal pressure hydrocephalus (NPH). Normal intracranial pressure (ICP) was registered in 121 (43 %) of patients with suspected NPH. The incidence of Alzheimer's disease (AD) related lesions was quite high, since 38 % of all subjects displayed beta-amyloid (betaA4) aggregates and in 8 % of subjects paired helical filament-tau (PHF-tau) pathology was noted. The AD associated pathologies were more common in subjects with normal than elevated ICP. Of the 121 subjects with NPH, 16 (13 %) had subclinical, histopathologically verified AD and a further 40 subjects (33 %) could be considered to be at high risk to develop AD. Pharmacological treatment trials of AD should be carried out on subjects with evident brain pathology (betaA4 aggregates or PHF-tau pathology) especially during the early stage of the disease, i.e., the subclinical stage. For this purpose a simple cortical biopsy with a low risk of complication would represent a diagnostic "method" of choice.

Aged↗
PubMed2002

Neuronal involvement in the effect of an antisecretory factor-derived peptide on induced secretion in the porcine small intestine.

The antisecretory factor is a protein inhibiting enterotoxin-induced intestinal inflammation and hypersecretion. We studied the signaling pathway of three antisecretory factor-derived peptides (A1, A3 and A4) in the proximal and distal porcine small intestine. In vivo (ligated loops), only A3 significantly reduced the cholera toxin-induced fluid accumulation and only in proximal loops. A3 and A4 reduced Escherichia coli heat-labile enterotoxin-induced fluid accumulation in the proximal segment, whereas A1 and A3 reduced the Escherichia coli heat-labile enterotoxin-induced fluid accumulation in the distal segment. The secretory response to intraluminally added 5-hydroxytryptamine was not significantly inhibited by the peptides. The amount of intraluminal 5-hydroxytryptamine accumulated in cholera toxin-stimulated loops from the proximal segment was significantly reduced by A3. In vitro,the effect of A3 on secretagogue-induced increases in short-circuit current was recorded from proximal small intestine by the Ussing chamber technique. A3 decreased the tetrodotoxin sensitive effect of substance P. The in vivo results suggest that the antisecretory effect may involve inhibition of the local release of 5-hydroxytryptamine induced by cholera toxin, but not inhibition of secretory reflexes induced by 5-hydroxytryptamine. The in vitro results suggest that the effect of A3 lies beyond the surface epithelium, and involves mucosal neuronal structures.

Animals↗
PubMed2002

Pseudorapidity distributions of charged particles from Au + Au collisions at the maximum RHIC energy, square root[s(NN)] = 200 GeV.

We present charged-particle multiplicities as a function of pseudorapidity and collision centrality for the 197Au+197Au reaction at square root[s(NN)] = 200 GeV. For the 5% most central events we obtain dN(ch)/deta/(eta = 0) = 625+/-55 and N(ch)/(-4.7< or =eta < or =4.7) = 4630 +/- 370, i.e., 14% and 21% increases, respectively, relative to square root[s(NN)] = 130 GeV collisions. Charged-particle production per pair of participant nucleons is found to increase from peripheral to central collisions around midrapidity. These results constrain current models of particle production at the highest RHIC energy.

Journal Article↗
PubMed2001

Peptide-derived antagonists of the urokinase receptor. affinity maturation by combinatorial chemistry, identification of functional epitopes, and inhibitory effect on cancer cell intravasation.

The high-affinity interaction between urokinase-type plasminogen activator (uPA) and its glycolipid-anchored receptor (uPAR) plays an important role in pericellular plasminogen activation. Since proteolytic degradation of the extracellular matrix has an established role in tumor invasion and metastasis, the uPA-uPAR interaction represents a potential target for therapeutic intervention. By affinity maturation using combinatorial chemistry we have now developed and characterized a 9-mer, linear peptide antagonist of the uPA-uPAR interaction demonstrating specific, high-affinity binding to human uPAR (K(d) approximately 0.4 nM). Studies by surface plasmon resonance reveal that the off-rate for this receptor-peptide complex is comparable to that measured for the natural protein ligand, uPA. The functional epitope on human uPAR for this antagonist has been delineated by site-directed mutagenesis, and its assignment to loop 3 of uPAR domain III (Met(246), His(249), His(251), and Phe(256)) corroborates data previously obtained by photoaffinity labeling and provides a molecular explanation for the extreme selectivity observed for the antagonist toward human compared to mouse, monkey, and hamster uPAR. When human HEp-3 cancer cells were inoculated in the presence of this peptide antagonist, a specific inhibition of cancer cell intravasation was observed in a chicken chorioallantoic membrane assay. These data imply that design of small organic molecules mimicking the binding determinants of this 9-mer peptide antagonist may have a potential application in combination therapy for certain types of cancer.

Animals↗
PubMed2001

Urokinase-catalysed cleavage of the urokinase receptor requires an intact glycolipid anchor.

Urokinase (uPA) has the striking ability to cleave its receptor, uPAR, thereby inactivating the binding potential of this molecule. Here we demonstrate that the glycosylphosphatidylinositol (GPI) anchor of uPAR, which is attached to the third domain, is an important determinant in governing this reaction, even though the actual cleavage occurs between the first and second domains. Purified full-length GPI-anchored uPAR (GPI-uPAR) proved much more susceptible to uPA-mediated cleavage than recombinant truncated soluble uPAR (suPAR), which lacks the glycolipid anchor. This was not a general difference in proteolytic susceptibility since GPI-uPAR and suPAR were cleaved with equal efficiency by plasmin. Since the amino acid sequences of GPI-uPAR and suPAR are identical except for the C-terminal truncation, the different cleavage patterns suggest that the two uPAR variants differ in the conformation or the flexibility of the linker region between domains 1 and 2. This was supported by the fact that an antibody to the peptide AVTYSRSRYLE, amino acids 84-94 in the linker region, recognizes GPI-uPAR but not suPAR. This difference in the linker region is thus caused by a difference in a remote hydrophobic region. In accordance with this model, when the hydrophobic lipid moiety was removed from the glycolipid anchor by phospholipase C, low concentrations of uPA could no longer cleave the modified GPI-uPAR and the reactivity to the peptide antibody was greatly decreased. Naturally occurring suPAR, purified from plasma, was found to have a similar resistance to uPA cleavage as phospholipase C-treated GPI-uPAR and recombinant suPAR.

Animals↗
PubMed2001

Rapidity dependence of antiproton-to-proton ratios in Au+Au collisions at square root of (sNN) = 130 GeV.

Measurements, with the BRAHMS detector, of the antiproton-to-proton ratio at midrapidities and forward rapidities, are presented for Au+Au reactions at square root of [s(NN)] = 130 GeV, and for three different collision centralities. For collisions in the 0%-40% centrality range, we find N(&pmacr;)/N(p) = 0.64+/-0.04((stat))+/-0.06((syst)) at y approximately 0, 0.66+/-0.03+/-0.06 at y approximately 0.7, and 0.41+/-0.04+/-0.06 at y approximately 2. The ratios are found to be nearly independent of collision centrality and transverse momentum. The antiproton and proton rapidity densities vary differently with rapidity, and indicate a significant degree of collision transparency, although a net-baryon free midrapidity plateau (Bjorken limit) is not yet reached.

Journal Article↗
PubMed2001

Time-dependent expression and processing of a hypothetical protein of possible importance for regulation of the Chlamydia pneumoniae developmental cycle.

Chlamydia pneumoniae is an obligate intracellular human pathogen infecting epithelial cells of the upper respiratory tract. It is a Gram-negative bacteria and has a unique biphasic developmental cycle. In this study, we use two-dimensional gel electrophoresis in combination with radioactive labeling to investigate time-dependent expression and processing of C. pneumoniae proteins. We report on (i) the identification of a hypothetical protein which is expressed late in the developmental cycle and subsequently processed; we speculate that this protein may be of importance for the developmental cycle of Chlamydia; (ii) the identification of the major outer membrane protein in three different variants, which may all be present in vivo.

Bacterial Proteins↗
PubMed2001

Quantitative predictions of peptide binding to MHC class I molecules using specificity matrices and anchor-stratified calibrations.

Peptides are key immune targets. They are generated by fragmentation of antigenic proteins, selected by major histocompatibility complex (MHC) molecules and subsequently presented to T cells. One of the most selective requirements is that of peptide binding to MHC. Accurate descriptions and predictions of peptide-MHC interactions are therefore important. Quantitative matrices representing MHC class I specificity can be used to search any query protein for the presence of MHC binding peptides. Assuming that each peptide residue contributes to binding in an additive and sequence independent manner, such "crude" matrix-driven predictions can be expressed as a quantitative estimates of binding strength. Crude matrix-driven predictions are reasonably uniform (i.e. precise), however, there is a general tendency towards overestimating binding (i.e. being inaccurate). To evaluate and possibly improve predictions, we have measured the MHC class I binding of a large number of peptides. In an attempt to further improve predictions and to include sequence dependency, we subdivided the panel of peptides according to whether the peptides had zero, one or two primary anchor residues. This allowed us to define unique anchor-stratified calibrations, which led to predictions of improved precision and accuracy.

Animals↗