Recombinant human megakaryocyte growth and development factor stimulates thrombocytopoiesis in normal nonhuman primates

Megakaryocyte growth and development factor (MGDF) is a novel cytokine that binds to the c-mpl receptor and stimulates megakaryocyte development in vitro and in vivo. This report describes the ability of recombinant human (r-Hu) MGDF to affect megakaryocytopoiesis in normal nonhuman primates. r-HuMGDF was administered subcutaneously to normal, male rhesus monkeys once per day for 10 consecutive days at dosages of 2.5, 25, or 250 micrograms/kg of body weight. Bone marrow and peripheral blood were assayed for clonogenic activity and peripheral blood counts were monitored. Circulating platelet counts increased significantly (P < .05) for all doses within 6 days of r-HuMGDF administration and reached maximal levels between day 12 and day 14 postcytokine administration. The 2.5, 25.0, and 250.0 micrograms/kg/d doses elicited peak mean platelet counts that were 592%, 670%, and 449% of baseline, respectively. Bone marrow-derived clonogenic data showed significant increases in the concentration of megakaryocyte (MEG)- colony-forming unit (CFU) and granulocyte-erythroid-macrophage- megakaryocyte (GEMM)-CFU, whereas that of granulocyte-macrophage (GM)- CFU and burst-forming unit-erythroid (BFU-e) remained unchanged during the administration of r-HuMGDF. These data show that r-HuMGDF is a potent stimulator of thrombocytopoiesis in the normal nonhuman primate.     

Identification of Bakb, a new platelet-specific antigen associated with posttransfusion purpura

Baka is a platelet alloantigen whose putative allele, Bakb, has not been identified previously. By using a serum, "Har," obtained from a patient with posttransfusion purpura, we describe the platelet alloantigen Bakb. The Har serum reacted with an NP-40-extractable platelet membrane protein of 142 kd with mobility similar to platelet glycoprotein IIb alpha. We found that the antigen recognized by the Har serum is inherited in an autosomal dominant mode with an apparent gene frequency of .39. Chi-square analysis of observed and expected phenotype frequencies indicated that serum Har recognizes Bakb, the anticipated allele of Baka. Our findings provide new evidence for polymorphism of glycoprotein IIb and for the association of posttransfusion purpura with alloimmunization to determinants on this glycoprotein.     

Human platelet fibrinogen: purification and hemostatic properties

Conditions were developed in which 80% to 90% of platelet fibrinogen could be routinely purified in nondegraded form from the fluid phase of platelet suspensions stimulated with the calcium ionophore, A23187, in the presence of calcium, leupeptin, and prostaglandin E1. Fibrinogen was separated from other released proteins by chromatography on diethylaminoethanol (DEAE)-cellulose using a continuous pH and ionic strength gradient. Purified platelet fibrinogen, greater than 98% homogeneous by immunoelectrophoresis and sodium-dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE), consisted of intact A alpha, B beta and gamma A chains, but not gamma' chains, and was 95% to 96% clottable. Platelet fibrinogen was shown to compete for the binding of radiolabeled plasma fibrinogen to ADP-activated platelets in a manner identical to that of unlabeled plasma fibrinogen itself. Also, at equivalent protein concentrations, platelet and plasma fibrinogens supported platelet aggregation to an equivalent extent. Based upon these results, we conclude that there is no significant difference between platelet and plasma fibrinogen with respect to their size, their clottability, their affinity for the activated platelet fibrinogen receptor, or their capacity to support subsequent platelet aggregation.     

Molecular cloning, chromosomal location, and tissue-specific expression of the murine cathepsin G gene

We previously have characterized a cluster of genes encoding cathepsin G (CG) and two other CG-like hematopoietic serine proteases, CGL-1 and CGL-2, on human chromosome 14. In this report, we clone and characterize a novel, related murine hematopoietic serine protease gene using human CG (hCG) cDNA as the probe. This murine gene spans approximately 2.5 kb of genomic DNA, is organized into five exons and four introns, and bears a high degree of homology to hCG at both nucleic acid (73%) and deduced amino acid (66%) levels. The predicted cDNA contains an open reading frame of 783 nucleotides that encodes a nascent protein of 261 amino acids. Processing of a putative signal (pre) peptide of 18 residues and an activation (pro) dipeptide would generate a mature enzyme of approximately 27 Kd that has an estimated pI of 12.0. Conserved residues at His44, Asp88, and Ser181 form the characteristic catalytic triad of the serine protease superfamily. The gene is tightly linked to the CTLA-1 locus on murine chromosome 14, where the serine protease genes mCCP1-4 are clustered. Expression of this gene is detected only in the bone marrow and is restricted to a small population of early myeloid cells. These findings are consistent with the identification of the gene encoding murine CG.     

Opposite effects of enalapril and nitrendipine on natriuretic response to atrial natriuretic factor. Renal function evaluated with clearance studies in humans

In clearance studies, we analyzed the effect of Ca2+ entry blockade with nitrendipine treatment (20 mg b.i.d. for 4 days) and of converting enzyme inhibition with enalapril treatment (20 mg b.i.d. for 4 days) on renal response to atrial natriuretic factor (ANF) (25 micrograms bolus followed by an infusion of 0.03 microgram/kg/min for 90 minutes) in six healthy volunteers who were taking 300 mmol sodium daily. In a control study ANF was administered without Ca2+ entry blockade or converting enzyme inhibition. Natriuresis rose from 239 +/- 38 to 605 +/- 137 mumol/min in the control study (p less than 0.05), from 330 +/- 53 to 943 +/- 152 mumol/min with Ca2+ entry blockade (p less than 0.05), and from 236 +/- 22 to 344 +/- 39 mumol/min with converting enzyme inhibition (NS). ANF induced a rise in maximal free water clearance, inulin clearance, and in the excretion of multiple electrolytes except potassium. Fractional lithium reabsorption fell. In general, these effects were stronger during Ca2+ entry blockade and blunted during converting enzyme inhibition. p-Aminohippurate clearance tended to decrease during the control study (NS), remained constant during Ca2+ entry blockade, and decreased significantly when ANF was infused during converting enzyme inhibition (p less than 0.05 vs. control and vs. Ca2+ entry blockade study). Blood pressure was lowered by Ca2+ entry blockade and, to a somewhat greater extent, by converting enzyme inhibition, but ANF administration induced no additional fall except for a short-term drop during Ca2+ entry blockade.(ABSTRACT TRUNCATED AT 250 WORDS)     

Therapeutic efficacy of recombinant human leukemia inhibitory factor in a primate model of radiation-induced marrow aplasia

The therapeutic efficacy of recombinant human leukemia inhibitory factor (LIF) was examined in a nonhuman primate model of radiation- induced marrow aplasia. Rhesus monkeys received 450 cGy of total-body, 1:1 mixed neutron:gamma radiation. For 23 days thereafter, each monkey received a daily subcutaneous injection of LIF or human serum albumin (HSA) at a dose of 15 micrograms/kg body weight. Complete blood counts and white blood cell differentials were monitored for 60 days postirradiation. Administration of LIF significantly decreased (P < or = .05) the duration of thrombocytopenia (platelet count < 30,000 or 20,000/microL), ie, 9.3 days or 6.3 days, respectively, versus the HSA- treated control monkeys, 12.2 days or 10.2 days, respectively. Treatment with LIF did not alter the duration of neutropenia (absolute neutrophil count < 1,000/microL) as compared with the HSA-treated control monkeys. Cytokine administration did not exacerbate the radiation-induced anemia observed in the HSA-treated control monkeys.     

Variability of flow mediated dilation: consequences for clinical application

BACKGROUND: Flow mediated vasodilatation (FMD), a non-invasive tool to assess endothelial function, has been shown to have prognostic value for the development of cardiovascular disease. Conventional B-mode ultrasonography has been criticised for its 'limited' resolution in vivo, which complicates reliable detection of the minute diameter changes during reactive hyperaemia. In the present study we evaluated the physical resolution, reproducibility and the capability to detect FMD impairment of a wall tracking system (WTS). METHODS: The resolution of WTS was compared with that of intravascular ultrasound (IVUS) in pig femoral arteries in vivo. Subsequently, intra- and interobserver variability of FMD testing with WTS was evaluated in 75 healthy volunteers. Finally, the effect of smoking as single risk factor for atherosclerosis on FMD in vivo was assessed. RESULTS: WTS and IVUS readings were not different (difference in arterial cross sectional area 1.97 mm(2), r=0.87). Intrasession coefficient of variation in baseline diameter was 1.1% (extremes 0.06--2.0%). Inter-session baseline diameter variation was 3.6 and 3.8% for each observer and 4.1% between observers. Intra-individual variability in FMD between sessions was considerable with coefficients of variation of 13.9% for FMD and 9.3% for NTG. Smokers had impaired FMD responses compared with matched non-smokers (4.7+/-2.4 vs. 9.6+/-4.4%, P<0.001), whereas NTG induced vasodilatation did not differ (13.4+/-6.2 vs. 15.4+/-5.1%; p=ns). CONCLUSION: WTS is a suitable technique for reproducibly assessing the brachial artery diameter in vivo with a accuracy comparable to that of IVUS. Using this sensitive technique the reproducibility of FMD in vivo proves to be poor mainly due to physiological factors. Whereas this seriously limits the use of FMD as follow-up parameter for individual subjects, FMD is demonstrated to be a useful research tool at group level.     

Is endothelial progenitor cell dysfunction involved in altered angiogenic processes in patients with hypertension?

Hypertension represents one of the most frequent modifiable risk factors for cardiovascular disease (CVD). Despite the arrival of novel antihypertensive drugs and progress in primary prevention and screening, the improvement of blood pressure control does not similarly reduce the incidence of end-organ damage associated with hypertension. Recently, the concept of reduced angiogenesis as a new CVD risk factor has gained the interest of an increasing number of investigators in the field. Indeed, pharmacologic and stem cell-based strategies aimed to induce angiogenesis seem to improve the course of ischemic vascular disease. However, few to no reports have studied the possible therapeutic potential of angiogenesis in essential hypertension. In this review, we discuss the potential involvement of endothelial progenitor cells in modulating angiogenesis and their putative therapeutic role in improving capillary rarefaction and arterial stiffness in essential hypertensive patients.     

Activation of leukocytes by postprandial lipemia in healthy volunteers

Activation of leukocytes is obligatory for inflammation and atherogenesis by adhering to the endothelium via specific ligands. Although in vitro studies have shown that triglycerides (TG) can activate leukocytes, it is unknown whether this occurs in vivo. Using flowcytometry, we studied the expression of leukocyte activation markers CD11A, CD11B, CD62L (all involved in endothelium adhesion) and CD66B (a neutrophil degranulation marker) during a 6 h fat challenge (50 g/m2) and a water test in 10 healthy males (52 +/- 3 years). After fat, neutrophil counts were increased between t=1 and t =6 h, with a maximum at t=3 h (+32% versus t=0, P <0.05), while they remained unchanged after water. Both tests showed gradual lymphocyte count increments. The expression of activation markers on lymphocytes was low and showed comparable responses after both tests. After fat, a significant increase up to a maximum at t=6 h was seen for CD11B on monocytes and on neutrophils for CD11B, CD62L and CD66B. Postprandial activation of monocytes and neutrophils was higher after fat than after water. The maximal postprandial TG increment was significantly related to the increase of CD11B on monocytes (Pearson's R=0.64, P <0.05). In conclusion, postprandially there is a TG-specific increase of neutrophil counts and increased activation of monocytes and neutrophils. These results are suggestive of a pro-inflammatory situation that may correspond with increased adhesive capacity of these cells contributing to the inflammatory component of atherosclerosis.     

The formation of Ca++-dependent complexes of platelet membrane glycoproteins IIb and IIIa in solution as determined by crossed immunoelectrophoresis

Triton X-100 soluble proteins from 125I-labeled human platelets were studied by crossed immunoelectrophoresis employing a multispecific rabbit antibody raised against whole normal platelets. Emphasis was placed upon an analysis of immunoprecipitates containing 125I-labeled major membrane glycoproteins, and in particular, a prominent immunoprecipitate containing a glycoprotein antigen (s) previously designated as protein 16. SDS-polyacrylamide gel electrophoresis of protein 16 precipitated by a monospecific alloantibody. IgG L . . . , confirmed the presence of both glycoproteins IIb and IIIa. 125I-IgG L . . . , at concentration below that capable of precipitating protein 16 by itself, bound specifically to the precipitate containing protein 16 produced by the multispecific rabbit antibody. No other precipitates formed by the rabbit antibody contained either glycoprotein IIb or IIIa. When platelet proteins, incubated with optimum concentrations of ethylenediamine tetraacetic acid (EDTA) or ethyleneglycol bis (B- aminoethylether) NN1-tetraacetic acid (EGTA), were electrophoresed against the rabbit antibody, previously unobserved immunoprecipitates that contained either free glycoprotein IIb or free glycoprotein IIIa were detected. Upon readdition of excess Ca++, but not Mg++, to the same protein samples, a single immunoprecipitate containing both glycoproteins was once again observed. It is thus demonstrated that glycoproteins IIb and IIIa can form Ca++-dependent complexes (protein 16) in Triton X-100 extracts of normal platelets. The potential significance of the reversible association of these glycoproteins to normal platelet function is discussed.