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Biomedical subjects

P Harrison

Publications and source records attributed to P Harrison.

At least 145 records · Page 8Linked to original sources
PubMed1994

Actin mRNA levels and myofibrillar growth in leg muscles of the European lobster (Homarus gammarus) in response to passive stretch.

An actin cDNA clone from the European lobster, Homarus gamarus, has been generated by RT-PCR and used as a probe to quantify the relative abundance of actin mRNA in lobster leg muscles following imposition of passive stretch by leg flexion. The sarcomere lengths of a population of fibers in the same muscles were measured to provide an indirect marker of myofibrillar growth. Stretch resulted in a 70% increase in actin mRNA levels compared with unstretched controls animals between weeks 1 and 2 after flexion of the legs. Sarcomere lengths increased by 23% immediately after imposition of the stretch. During the same period of observed increase in actin mRNA, the sarcomere lengths returned to their initial values, indicating that longitudinal growth of the myofibrils had occurred. Results are discussed in relation to the role of stretch in crustacean muscle growth during the moult.

Actins↗
PubMed1993

Effect of type IIB von Willebrand disease mutation Arg(545)Cys on platelet glycoprotein Ib binding--studies with recombinant von Willebrand factor.

Type IIB von Willebrand disease (vWD) is characterized by a selective loss of high molecular weight von Willebrand factor (vWF) multimers in plasma due to their abnormally enhanced reactivity with platelets. Several missense mutations in the platelet glycoprotein Ib (GPIb) binding domain of vWF were recently characterized that cause type IIB vWD. The effect of type IIB mutation Arg(545)Cys on vWF binding to platelet GPIb was studied using recombinant wild type (rvWFWT) and mutant rvWFR545C expressed in COS-7 cells. In the absence of ristocetin, 50% of rvWFR545C bound spontaneously to platelet GPIb and the binding increased to 70% in the presence of 0.2 mg/ml ristocetin; rvWFWT did not bind significantly under either condition. Botrocetin-induced binding of rvWFR545C was only slightly increased compared to rvWFWT. These data demonstrate that the Arg(545)Cys mutation increases the affinity of vWF for GPIb, resulting in the characteristics gain-of-function type IIB vWD phenotype.

Arginine↗
PubMed1993

Translocation (8;13) and T-cell lymphoma. A case report.

A patient with a myeloproliferative disorder is described with an eosinophilia together with T-cell lymphoma. A unique translocation t(8;13)(p11.2;q12) was present in all bone marrow cells examined at presentation. No evidence of this translocation was found in a peripheral blood lymphocyte culture. Chromosome analysis after 9 months revealed this same translocation as well as an extra chromosome 21 in all cells; 4.5% of cells also had an additional chromosome 9. The morphologic diagnosis at this stage was chronic myelomonocytic leukemia. Immunophenotyping 3 months later was consistent with a stem-cell leukemia.

Bone Marrow↗
PubMed1993

Quantitative and qualitative assessment of plasma von Willebrand factor in classic Kaposi's sarcoma.

BACKGROUND: von Willebrand factor (vWF) is synthesized almost exclusively by endothelial cells and is stored there as ultra-high-molecular-weight multimers. The vWF multimers that are detected in the plasma are smaller than those stored within the endothelium. In two previous studies, comprising small series of cases with classic Kaposi's sarcoma (KS), an endothelium-derived tumor, increased levels of plasma von Willebrand factor antigen (VWF:Ag, the antigenic structure) were reported, suggesting that vWF:Ag may be a marker of endothelium proliferation. OBJECTIVE: Our purpose was to investigate the quantitative as well as qualitative alterations of plasma vWF in a large series of patients with classic KS at various stages of the disease. METHODS: Levels of plasma vWF:Ag were studied in 38 patients with classic KS confined to the skin at various stages of the disease and compared with a control group. Thirty-three patients had active KS (i.e., with skin lesions) and five were in remission. In five patients with active KS multimeric analysis of plasma vWF was also performed. RESULTS: The levels of vWF:Ag were significantly higher among KS patients than in the control group (n = 29, p < 0.01). Levels of vWF:Ag were also significantly higher in patients with active disease as compared with those in remission (p < 0.05). No correlation was found between vWF:Ag levels and the extent of KS. Analysis of the multimeric pattern of plasma vWF showed enhanced staining of all bands, particularly the intermediate and high molecular weight forms, which resemble the endothelial forms as opposed to normal circulating vWF multimers. CONCLUSION: Quantitative as well as qualitative alterations in plasma vWF were found in patients with KS, which may reflect the destruction or activation of endothelial cells within the lesions. vWF:Ag may serve as a marker of disease activity in classic KS; however, it is not a good marker for the extent of the disease.

Aged↗
PubMed1993

Platelet alpha-granules.

Platelets contain a vast number of biologically active molecules within cytoplasmic granules which are classified according to their respective distinct ultrastructures, densities and content. The alpha-granule is a unique secretory organelle in that it exhibits further compartmentalization and acquires its protein content via two distinct mechanisms: (1) biosynthesis predominantly at the megakaryocyte (MK) level (with some vestigial platelet synthesis) (e.g. platelet factor 4) and (2) endocytosis and pinocytosis at both the MK and circulating platelet levels (e.g. fibrinogen (Fg) and IgG). The currently known list of alpha-granular proteins continues to enlarge and includes many adhesive proteins (e.g. Fg, von Willebrand factor (vWf) and thrombospodin (TSP)), plasma proteins (e.g. IgG and albumin), cellular mitogens (e.g. platelet derived growth factor and TGF beta), coagulation factors (e.g. factor V) and protease inhibitors (e.g. alpha 2-macroglobulin and alpha 2-antiplasmin). More recently the inner lining of the alpha-granule unit membrane has been demonstrated to contain a number of physiologically important receptors including glycoprotein IIb/IIIa (alpha IIb beta 3) and P-selectin. The alpha-granules originate from small precursor granules which can be observed budding from the trans-Golgi network within the platelet precursor cell the MK. During MK maturation the alpha-granules become very prominent and are ultimately packaged into platelets during thrombopoiesis. The alpha-granular contents are destined for release during platelet activation at sites of vessel wall injury and thus play an important role in haemostasis, inflammation, ultimate wound repair and in the pathogenesis of atherosclerosis.

Animals↗
PubMed1993

Different patterns of regulation of the genes encoding the closely related 56 kDa selenium- and acetaminophen-binding proteins in normal tissues and during carcinogenesis.

A full-length cDNA encoding a 56 kDa liver protein recently implicated in the detoxification of acetaminophen (AP56) has been cloned by virtue of its similarity to the 56 kDa selenium-binding protein (SP56): in fact, the deduced AP56 amino acid sequence differs at only 14 residues from SP56. Isolation of genomic DNA recombinants from a Balb/c mouse cosmid genomic DNA library shows that SP56 and AP56 are encoded by two different genes. Using reverse transcription/PCR with oligonucleotide primers that distinguish the AP56 and SP56 mRNAs shows that the SP56 mRNA is highly expressed in liver, kidney and, to a lesser extent, lung; whereas the AP56 mRNA is mainly expressed in liver. Both mRNAs tend to be down-regulated in liver cell lines but remain high in DEN-induced liver tumours in vivo. The relevance of these findings is evaluated in terms of the postulated functions of the two proteins in mediating the anti-carcinogenic effects of selenium and detoxification mechanisms.

Acetaminophen↗
PubMed1993

Porcine platelets contain an increased quantity of ultra-high molecular weight von Willebrand factor and numerous alpha-granular tubular structures.

Immunoelectronmicroscopy of human platelet alpha-granules reveals that von Willebrand factor (vWf:Ag) colocalizes with a small number of discrete tubular structures which appear identical to those observed within the Weibel-Palade bodies of endothelial cells. Although it is likely that tubules are composed of vWf:Ag as they are absent in severe vWD porcine platelets, their exact structural and functional nature is still unclear. In this study quantitative/qualitative analysis of vWf:Ag was undertaken in a series of platelet preparations obtained from normal pigs, normal humans and various vWD patients. Electron microscopy confirmed that normal pig platelet alpha-granules contain numerous, regularly spaced tubular structures eccentrically located and coincident with immunogold staining of vWf:Ag. In contrast, normal human platelet alpha-granules contain significantly fewer tubules (usually four to six) which are absent or reduced in number within various vWD platelet sections. Furthermore, the pig platelet lysates not only contained a full complement of multimers but also demonstrated significant intense staining of ultra-high MW material, irrespective of the presence or absence of proteolytic inhibitors. This ultra-high MW vWf appears similar to that observed within lysates prepared from endothelial cells and is susceptible to degradation to lower MW multimers. This study suggests that the tubular structures within alpha-granules and Weibel-Palade bodies may be composed of, or structurally related to, the ultra-high MW intracellular form of vWf:Ag.

Animals↗
PubMed1993

Examination of alumina ceramic components from total hip arthroplasties.

Materials analysis has been conducted on retrieved Mittelmeier-Autophor ceramic components from total hip arthroplasties, correlating articulating surface wear morphology with clinical reasons for failure. Plastically deformed, agglomerated wear debris (30-60 microns) has been identified on femoral head articulation wear surfaces, displaying exaggerated wear, especially during the initiation stage. Such surfaces were associated with clinical failures involving displacement of the acetabular cup and perforation of the cortex by the femoral stem. It is thought that this wear debris may play an important role in the promotion of the 'avalanche' wear mechanism, as it is adherent and thus difficult to remove from the wear interface.

Acetabulum↗