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Biomedical subjects

P Sims

Publications and source records attributed to P Sims.

At least 19 recordsLinked to original sources
PubMed2001

Generation of a humanized, high affinity anti-tissue factor antibody for use as a novel antithrombotic therapeutic.

Blocking the cofactor function of human tissue factor may be beneficial in various coagulation-mediated diseases. The murine antibody D3 binds to the membrane proximal substrate interaction region of human tissue factor and blocks tissue factor function even in the presence of bound factor VIIa. The cloned murine D3 antibody was humanized and affinity matured by exchanging amino acids in the complementarity determining regions as well as in the antibody framework. The humanized antibody, D3H44, bound to tissue factor with a 100-fold increased affinity (KD 0.1 nM) as compared to the original murine and chimeric versions. Depending on the particular disease, different pharmacokinetic properties of the antibody may be required and, therefore, several antibody variants-- F(ab), F(ab')2, IgG2, IgG4 and IgG4b-were generated. In vitro, the humanized D3 antibodies displayed potent inhibition of plasma clotting and tissue factor: factor VIIa-mediated activation of factors IX and X (e.g. D3H44-F(ab')2, IC50(F.X) 47 pM). In addition, D3H44-F(ab')2 completely prevented fibrin deposition in a human ex vivo thrombosis model under venous blood flow conditions (IC50 37 nM). The humanized D3 antibodies may be utilized for treatment of cardiovascular diseases which involve tissue factor activity, e.g. acute coronary syndrome and venous thrombosis.

Amino Acid Sequence↗
PubMed2000

Confocal, scanning and transmission electron microscopic study of cerebellar mossy fiber glomeruli.

A correlative microscopic study of vertebrate cerebellar mossy fiber glomeruli has been carried out to obtain a three-dimensional view of the multisynaptic contacts formed by afferent mossy fibers with the granule and Golgi cell dendrites and by the monosynaptic relationship of Golgi cell axonal ramifications with granule cell dendrites. Samples of mice, hamsters, teleost fishes and human species were studied by means of one of the following procedures: confocal laser scanning microscopy (CLSM), ethanol-cryofracturing technique and conventional scanning electron microscopy (CSEM) and transmission electron microscopy (TEM) by ultrathin sections and freeze-etching replicas. CLSM, by means of montages of z-series of the cerebellar granular layer, provided a new approach to explore mossy fiber trajectory and branching bifurcation pattern and the quantitative relationship between mossy fibers and granule cell dendrites. CSEM and freeze-fracture method for SEM offered a more detailed in-depth, higher resolution image of outer and inner surface organization of mossy fiber glomeruli. TEM, either by ultrathin sections or freeze-etching replicas, was used as complementary technique for proper orientation, comparative purposes and rational identification of pre- and postsynaptic structures. Freeze-etching replicas showed in addition the real extent of glial cell cytoplasm encapsulating the synaptic glomeruli. The integrated microscopy approach offers a new and more comprehensive view of three-dimensional morphology, organization and quantitative aspects of mossy fiber glomeruli.

Animals↗
PubMed1999

Thrombopoietin (Tpo) in the fetus and neonate: Tpo concentrations in preterm and term neonates, and organ distribution of Tpo and its receptor (c-mpl) during human fetal development.

Little is known about thrombopoietin (Tpo) production in human fetuses and neonates. As a step toward determining whether Tpo is relevant to platelet production in the fetus and neonate, we hypothesized that: (1) like other cytokines, Tpo is present in the cord blood in higher concentrations than in adult plasma; (2) Tpo and its receptor (c-mpl) are expressed in fetuses at, and following, 5-6 weeks post-conception (when platelet production begins); and (3) the sites of Tpo and c-mpl production in the fetus are similar to those of adults. We quantified Tpo, by ELISA, in the plasma of 50 adults, as well as in the umbilical cord plasma of 50 preterm and term infants. We also characterized, by RT-PCR, the organ distribution of Tpo and c-mpl during fetal development (at 8 and 16 weeks). Tpo concentrations were measurable (> or =41 pg/ml) in only two of the 50 adult samples (44 and 46 pg/ml), but in 24 of the 50 cord plasma samples (of the 24 samples, the median was 62 pg/ml; mean+/-SD, 80+/-39 pg/ml). Tpo levels did not correlate with either gestational age or platelet count at birth. Similarly to adults, in the fetal tissues, Tpo transcripts were found in all organs tested, but the most dense bands were from liver. C-mpl transcripts were also predominantly from liver. We conclude that: (1) Tpo is present in higher concentrations in cord plasma than in venous plasma of adults; (2) Tpo and c-mpl transcripts are detected in human fetuses as early as the onset of platelet appearance; and(3) Tpo and c-mpl have a similar organ distribution in fetuses and adults.

Adult↗
PubMed1999

Thrombopoietic cytokines and reversal of thrombocytopenia after liver transplantation.

OBJECTIVES: Thrombopoietin (TPO), the key regulator of platelet production, is mainly produced by the liver and reduced expression of TPO could cause thrombocytopenia in liver cirrhosis. Reversal of thrombocytopenia by orthotopic liver transplantation seems to be mediated through an increase in TPO plasma levels after transplantation, but other cytokines with thrombopoietic activity could augment the actions of TPO on post transplant platelet recovery. DESIGN: Measurement of thrombopoietic cytokines before and for 14 days post liver transplantation in a cohort of thrombocytopenic liver transplant patients. METHODS: TPO, interleukin-3 (IL-3), IL-6, and IL-11 plasma levels as well as peripheral platelet count were analysed in thrombocytopenic patients with liver disease undergoing orthotopic liver transplantation (17 patients) and followed for 14 days after the intervention. RESULTS: Before liver transplantation, TPO plasma levels were undetectable and IL-3, IL-6, and IL-11 levels were normal. Sixteen out of 17 patients showed a significant rise of TPO levels within 2 days after transplantation, with a peak between days 4 and 6, while IL-3 and IL-6 levels did not show a significant rise. IL-11 levels remained normal. Platelet counts were significantly higher than pretransplantation levels by day 14 post transplantation. CONCLUSION: Restitution of normal TPO production by liver replacement seems to be of key importance for reversal of thrombocytopenia in liver disease. The early acting thrombopoietic factor IL-3 and the late acting factors IL-6 and IL-11 do not play a major role for recovery of peripheral platelet count after orthotopic liver transplantation.

Analysis of Variance↗
PubMed1999

Cytoarchitectonic arrangement and intracortical circuits of hamster cerebellum. A study by means of confocal scanning laser microscopy.

The FM4-64, a member of the family of fluorescent dyes, has been applied to the cerebellar cortex to study its cytoarchitectonic arrangement and intracortical course of mossy and climbing fibers. Slabs of hamster cerebellum, 1-2 mm thick, were incubated in 10, 30 and 100 microM solutions of FM4-64 in 0.1 M sodium phosphate buffer and observed in a slow scan confocal laser scanning microscope. Cellular tomography of cerebellar cortex allowed us to follow the course of mossy and climbing fibers in the cerebellar white and gray substance. They exhibited high fluorescence signal at the level of myelin sheath. Mossy fibers were identified only in the granular layer by their typical rosette formations and dichotomous bifurcation pattern. Climbing fiber bundles were observed crossing the granular layer and giving off collateral branches in the granular and molecular layers in a crossing-over pattern. They ascend to the Purkinje cell layer in their way to the molecular layer. Cerebellar macroneurons (Golgi and Purkinje cells) and microneurons (granule, basket and stellate cells) showed optimal intracellular staining of cell soma, axonal and proximal dendritic processes. The montage of z-series of stacked optodigital sections allowed us to explore in depth the cytoarchitectonic arrangement, nerve and glial cell morphology, and the topographic relationship of intrinsic cerebellar neurons with the afferent mossy and climbing fibers.

Animals↗
PubMed1998

Blunted thrombopoietin response to interferon alfa-induced thrombocytopenia during treatment for hepatitis C.

Thrombocytopenia is common in advanced-stage liver disease and is partly caused by inadequate thrombopoietin (TPO) production in the failing liver. Treatment of chronic hepatitis C with interferon alfa (IFN-) often induces thrombocytopenia, sometimes even leading to discontinuation of treatment. TPO regulation in response to IFN--induced thrombocytopenia was studied in patients with chronic hepatitis C with and without cirrhosis (Child A). An in vitro culture system with HepG2 cells was used to demonstrate any direct effects of IFN- on TPO mRNA expression, TPO synthesis, or TPO secretion from liver cells. Thrombocyte count was lower (U test: P < .05) in patients with hepatitis C cirrhosis compared with patients with chronic hepatitis C without cirrhosis before IFN therapy, and decreased in both patient groups (Wilcoxon matched-pairs test: P < . 05) on IFN therapy, the median decrease in both groups being comparable (noncirrhotic patients, 35%; cirrhotic patients, 32%; U test: P = .57). TPO levels rose in noncirrhotic patients (Wilcoxon matched-pairs test: P < .05), but not in patients with cirrhosis (noncirrhotic patients' median increase: 43% vs. cirrhotic patients' median decrease: 5%; U test: P < .001). Even in patients without cirrhosis, the increase in TPO levels was relatively small for the decrease in platelet count. No effect of IFN- could be demonstrated on TPO mRNA expression in vitro, but TPO secretion from liver cells was significantly reduced. Lower platelet counts but similar TPO levels in patients with chronic hepatitis C and cirrhosis compared with noncirrhotic patients and a moderate increase in TPO levels in noncirrhotic patients with a missing increase in cirrhotic patients during IFN--induced thrombocytopenia provide further evidence for an impairment of TPO production in patients with cirrhosis and during IFN therapy. Recombinant human TPO could be of value in patients developing severe thrombocytopenia under IFN- therapy.

Adult↗
PubMed1996

A prolonged outbreak of streptococcal infection among workers at a meat plant.

We describe an outbreak of skin sepsis due to an erythromycin-resistant strain of Streptococcus pyogenes in workers at a meat plant. The outbreak began among butchers in the boning room but subsequently spread to other groups of workers in the plant. Despite the introduction of additional control measures, the outbreak persisted for 7 months and affected 46/194 staff with 'hands on' occupations. Spread of infection from the plant to a retail butcher was documented.

Disease Outbreaks↗
PubMed1994

Phanerochaete chrysosporium and its natural substrate.

We seek to define more fully how Phanerochaete chrysosporium degrades its natural substrate, lignocellulose. This contribution concerns several relevant topics. Mineralisation of [14C]DHP, as a model for lignin degradation, showed that a set of genetically defined meiotically derived products of strain ME446 differed in their degradative ability and also that, under optimum conditions for mineralisation, extracellular lignin peroxidase activity was absent. Xylanolytic and xylosidase/beta(1-->3) glucanase activities are also described. The complexity of the CBHI gene family is described and differential splicing of a CBHI gene transcript is proposed. In contrast to the multiplicity of CHBI genes there is a single CBHII gene. PCR methods were developed to analyse differential gene expression on different substrates. We have also developed a transformation system involving a reporter construct for the analysis of CBHI promoter function.

Basidiomycota↗
PubMed1993

Isozyme specific polymerase chain reaction analysis of differential gene expression: a general method applied to lignin peroxidase genes of Phanerochaete chrysosporium.

Analysis of differential expression of closely related genes is a general problem. The lignin peroxidase genes of Phanerochaete chrysosporium represent a typical case. They are differentially expressed according to the conditions encountered during growth. We show that the expression of two such genes, LIG1 and LIG5, can be differentiated at the mRNA level using a highly specific form of the polymerase chain reaction. This generally applicable method allows rapid and accurate analysis of complex and closely related mRNA populations.

Base Sequence↗