Munchmeyer's disease-a rare case report and review of literature.

Munchmeyer's disease is a rare variety of myositis ossificans. It is a significant clinical entity, diagnosing and understanding its pathophysiology can save a patient from spurious medical workups and anxiety of a suspected neoplasm. The number of authentic cases of this disease in the literature is small. The purpose of this article is to present a case of Munchmeyer's disease and review the literature for the same to date. The rare incidence, obscure aetiology, unknown definitive treatment plan and poor prognosis make this condition an enigma.

Differential regulation of human platelet responses by cGMP inhibited and stimulated cAMP phosphodiesterases.

Platelets contain two cAMP phosphodiesterases (PDEs) which regulate intracellular cAMP levels, cGMP-inhibited cAMP PDE (PDE3A) and cGMP-stimulated PDE (PDE2A). Using the PDE3 inhibitor, milrinone and the PDE2 inhibitor, erythro-9-(2-hydroxyl-3-nonyl)adenine (EHNA), we have explored the contribution of each PDE to the regulation of platelet function. Inhibition of PDE2 resulted in higher levels of intracellular cAMP than inhibition of PDE3A suggesting this PDE may be the more important regulator of cAMP in human platelets. However, a concentration-dependent inhibition of agonist-induced aggregation was observed with milrinone while little effect was seen with EHNA. In addition, we observed a concentration-dependent inhibition in the increase of intracellular Ca2+ with PDE3 inhibition and significantly less with PDE2 inhibition. PDE3 inhibition also resulted in a concentration-dependent increase in cAMP-mediated phosphorylation of the vasodilator-stimulated phospho-protein (VASP) whereas there was no significant increase with PDE2 inhibition. In each of these experiments, synergism was noted with the combination of milrinone and EHNA. These results suggest that cAMP pools may be localized and the various PDEs regulate specific pools. These data also suggest that inhibitors of PDE3A may be more effective antiplatelet agents.

Interpreting the International Normalized Ratio (INR) in individuals receiving argatroban and warfarin.

The effects of argatroban, a direct thrombin inhibitor, on the International Normalized Ratio (INR), activated partial thromboplastin time (aPTT) and functional factor X during warfarin co-administration were established to provide means to interpret INRs during argatroban/warfarin co-therapy. Twenty-four subjects receiving warfarin (7.5 mg, day 1; 3-6 mg/day, days 2-10) and argatroban (1-4 microg/kg/min over 5 h, days 1-11) were assessed daily for these coagulation parameters prior to argatroban infusion (warfarin "monotherapy") and at its conclusion ("co-therapy"). Argatroban increased aPTTs dose-dependently. Co-therapy INR increased linearly with monotherapy INR, with slope sensitive to argatroban dose and thromboplastin used. Prediction errors for monotherapy INRs were < or =+/- 0.4 for argatroban 1-2 microg/kg/min but > or = +/-1.0 for higher doses. Despite co-therapy INRs >7, no major bleeding occurred. Factor X remained > or =37% of normal. Therefore, the predictable effect of argatroban (< or =2 microg/kg/min only) [corrected] on INRs during warfarin co-therapy allows for reliable prediction of the level of oral anticoagulation.

Assessment of the potential pharmacokinetic and pharmacodynamic interactions between erythromycin and argatroban.

Argatroban, a direct thrombin inhibitor, is metabolized in vitro by CYP3A4/5 and therefore may be susceptible to clinically relevant CYP3A drug interactions. The effect of erythromycin, a potent CYP3A4/5 inhibitor, on the pharmacokinetics and pharmacodynamics of argatroban was evaluated in 14 healthy male volunteers in an open-label, crossover study with a 5-day washout between regimens. Argatroban 1 microgram/kg/min was infused alone for 5 hours (regimen A) and again on day 6 of a 7-day oral regimen of 500 mg erythromycin four times daily (regimen B). Serial blood samples for the determination of activated partial thromboplastin time (aPTT) and argatroban concentrations were collected for up to 48 hours following infusion. Mean values for argatroban area under the concentration-time curves (AUC0-inf), maximum concentration (Cmax), and half-life (t1/2) were similar between regimens. Mean aPTT values were not affected significantly by the concomitant administration of argatroban and erythromycin compared to argatroban alone. No serious adverse events or bleeding episodes occurred during the study. These results suggest that oxidative metabolism by CYP3A4/5 is unlikely to be an important in vivo elimination pathway for argatroban. Therefore, coadministration of CYP3A4/5 inhibitors should not require a modification in the dosage of argatroban.

Distribution of prostaglandin IP and EP receptor subtypes and isoforms in platelets and human umbilical artery smooth muscle cells.

Prostaglandins act through specific receptors to stimulate cyclic AMP formation which inhibits platelet activation and relaxes vascular smooth muscle. We have used RT-PCR combined with Southern blot analysis to determine the subtypes of prostaglandin receptor on platelets. Platelets expressed the EP4 rather than the EP2 prostaglandin EP receptor subtype, whereas vascular smooth muscle cells predominantly expressed the EP2 receptor. The IP receptor, which binds prostacyclin and couples to stimulation of adenylyl cyclase, and three isoforms of the inhibitory EP3 receptor were equally expressed in platelets, HEL cells and umbilical artery smooth muscle cells. The EP3-II isoform showed variation in level of expression among the three cell types. As a positive control for the presence of platelet RNA, PCR was performed using primers specific for the alpha chain of the platelet membrane glycoprotein Ib. As a negative control for the absence of T and B cell contamination in the platelet RNA, PCR was performed using primers specific for the cell specific cluster determinants CD2 (a T-cell marker) and CD20 (a B-cell marker). The finding that platelets express both stimulatory and inhibitory prostaglandin receptors provides confirmation of a homeostatic model of regulation of platelet adenylyl cyclase previously proposed.

Isolation and regulation of the cGMP-inhibited cAMP phosphodiesterase in human erythroleukemia cells.

The predominant cAMP phosphodiesterase in human platelets is the low K(m) cGMP-inhibited phosphodiesterase (PDE 3A). We have isolated native PDE3A from platelets and human erythroleukemia (HEL) cells and studied its kinetics. The platelet and HEL cell enzymes hydrolyze cAMP with a K(m) = 0.5 microM. Incubation of cell supernatant with cAMP dependent protein kinase resulted in a rapid increase in activity within minutes, which resulted from a 2-fold decrease in K(m) with no increase in Vmax. HEL cells grown for 24 h in the presence of 50 microM forskolin, an adenylate cyclase activator, demonstrate further increase in PDE3A of 274% of control (p = 0.03). Cells incubated with forskolin and cycloheximide or actinomycin D demonstrated no increase suggesting that cAMP stimulates PDE3A synthesis by transcriptional regulation. The results indicate that cAMP affects both the short and long-term regulation of PDE3A. The latter effect may play a role in the developing hematopoietic cell and the cardiovascular system to regulate cAMP levels.

Cyclic AMP phosphodiesterases in human lymphocytes.

The function of lymphocytes, like platelets, has been shown to be inhibited by agents which increase intracellular cyclic AMP. Two high-affinity cAMP phosphodiesterases (PDEs), the cyclic GMP-inhibited cAMP phosphodiesterase, PDE3, and the cAMP-specific phosphodiesterase PDE4, are known to regulate cAMP concentration in haemopoietic cells by degrading cAMP to AMP. We characterized the relative contribution of the two PDEs to total lymphocyte PDE activity. We then determined which of the different gene products, PDE3A, typical of myocardium and platelets, or PDE3B, typical of adipocytes, were present in lymphocytes. The PDE3-specific inhibitor, milrinone, and the PDE4 inhibitor, rolipram, suppressed hydrolysis by 70% and 30% respectively, which indicated that both PDE4 and PDE3 were present, and that PDE3 was predominant. RT-PCR yields the expected size fragment for the primer pair PDE3B and not for PDE3A. The DNA sequence obtained had >95% identity with PDE3B. PDE3B appears to be the major cAMP PDE in lymphocytes. In contrast to human platelets, human lymphocytes appear to contain the PDE3B subtype. Since PDE3B in adipocytes is subject to hormonal regulation, lymphocytes may be similarly modulated. Understanding the role of cAMP regulation and the involvement of cAMP in lymphocyte function may have important implications in drug development.

Characterization of P2 purinergic receptors on human erythro leukemia cells.

We have investigated the nature of the nucleotide receptors on human erythro leukemia (HEL) cells, a cell line with some megakaryocytic properties, using a combination of pharmacological, photoaffinity labeling, and molecular biological techniques. Fura-2 loaded HEL cells responded to 2-methylthio ATP, ATP, 2-methylthio ADP, ADP and UTP with an increase in intracellular calcium. 2 Methylthio ADP was the most potent agonist. When external calcium was chelated with EDTA, calcium responses were observed indicating the mobilization of intracellular stores. These responses showed evidence of both homologous and heterologous receptor desensitization. In photoaffinity labeling experiments, beta-[32P]-AzPET-ADP was incorporated into three protein species with mobilities corresponding to M(r) approximately 55 kDa (doublet) and approximately 43 kDa. Labeling of approximately 55 kDa proteins was specifically inhibited by ADP, while that of the approximately 43 kDa was inhibited specifically by UTP. Nucleotide sequence analysis of the positive clones obtained by screening the HEL cell cDNA library with mouse P2U cDNA revealed that the P2U receptor from HEL cells is identical to the previously cloned human P2U receptor. These experiments suggest that the HEL cells contain a P2Y purinoceptor responding to ADP, in addition to a P2U receptor and possibly also a third P2 purinoceptor with a unique agonist profile.

Platelet cAMP and cGMP Phosphodiesterases.

Platelets respond to a wide variety of exogenous agonists that bind to distinct receptors on the platelet surface resulting in the intracellular generation of second messengers or the opening of ion channels, setting off a cascade of events leading to both physical and functional changes in the platelet. The cyclic nucleotides, cyclic adenosine 3'5'-monophosphate (CAMP) and cyclic guanosine 3'5'-monophosphate (cGMP) initiate a sequence of intracellular events that modulate many of these reactions in the platelet.

Protein S and C alterations in acutely ill patients.

Protein C, a potent vitamin K-dependent protein activated by an endothelial cell cofactor, thrombomodulin, has anticoagulant and profibrinolytic activity. Free protein S, a cofactor for protein C, potentiates protein C activity at the endothelial cell surface. Pulmonary thromboemboli are a consistent finding in adult respiratory distress syndrome (ARDS). To determine if protein S or protein C were affected by widespread endothelial cell damage in ARDS, we measured bound and free protein S levels and protein C antigenic and functional levels in 18 patients with acute lung injury, 6 critically ill patients without lung history, and 22 normal subjects. Free (PS:F) and bound (PS:Ag) protein S and protein C antigen (PC:Ag) levels were measured using an enzyme-linked immunoassay and protein C function (PC:Fn) by measuring its anticoagulant activity. We found a significant decrease in bound and free protein S levels of both patient groups in comparison to normal and a shift toward the inactive, bound protein S form. In addition, a significant decrease in free protein S compared to bound protein S in both patient groups was observed. While both PC:Ag and PC:Fn were significantly reduced compared to normal, the PC:Fn was significantly and severely decreased out of proportion to the PC:Ag in both patient groups. There was no difference between those with and without lung injury for both protein S and protein C. Analyzed according to etiology of lung injury, there was no difference in the bound and free protein S, nor in PC:Ag and PC:Fn levels between patients with sepsis and trauma. However, there were significant decreases in both protein S and protein C levels compared with normal subjects. Levels of both PS and PC levels in patients who survived did not differ from those who died. In summary, our data show that both protein S and C are markedly deranged in acutely ill patients who suffered from either sepsis or trauma, and these changes are independent of lung injury. The marked reductions in functional activity of PS and PC may be contributing factors to the thromboembolic complications often observed in these patients.