Bidisomide (SC-40230), a new antiarrhythmic agent: initial study of tolerability and pharmacokinetics.

Forty-nine healthy male volunteers received the test article for bidisomide (SC-40230) in a double-blind, placebo-controlled, dose-ranging study. Intravenous doses ranged from 0.03 to 2.5 mg/kg. There was a close relationship between the dose and the peak plasma concentration. The PR, QRS, QT, RR, and QTc intervals each demonstrated a statistically significant response to the dose administered. The PR and QRS intervals lengthened and the other intervals shortened (although to a lesser degree). The compound was well tolerated, with mild symptoms only at higher doses. Bioavailability was studied in 12 male volunteers, with each receiving 2.0 mg/kg of bidisomide, both orally and intravenously, in an open-label crossover trial. After a 10-minute zero-order intravenous infusion, bidisomide plasma levels could best be described in terms of a three-compartment pharmacokinetic model with the mean half-life values of alpha, beta, and gamma phases of 0.12, 1.77, and 12.3 hours, respectively. The mean absolute oral bioavailability was 43%.

An increase or a decrease in myosin II phosphorylation inhibits macrophage motility.

Myosin II purified from mammalian non-muscle cells is phosphorylated on the 20-kD light chain subunit (MLC20) by the Ca2+/calmodulin-dependent enzyme myosin light chain kinase (MLCK). The importance of MLC20 phosphorylation in regulating cell motility was investigated by introducing either antibodies to MLCK (MK-Ab) or a Ca2+/calmodulin-independent, constitutively active form of MLCK (MK-) into macrophages. The effects of these proteins on cell motility were then determined using a quantitative chemotaxis assay. Chemotaxis is significantly diminished in macrophages containing MK-Ab compared to macrophages containing control antibodies. Moreover, there is an inverse relationship between the number of cells that migrate and the amount of MK-Ab introduced into cells. Interestingly, there is also an inverse relationship between the number of cells that migrate and the amount of MK- introduced into cells. Other experiments demonstrated that MK-Ab decreased intracellular MLC20 phosphorylation while MK- increased MLC20 phosphorylation. MK- also increased the amount of myosin associated with the cytoskeleton. These data demonstrate that the regulation of MLCK is an important aspect of cell motility and suggest that MLC20 phosphorylation must be maintained within narrow limits during translational motility by mammalian cells.

Pericardial actinomycosis with cardiac tamponade from a contiguous thoracic lesion.

A case of acute pericardial tamponade due to actinomycotic infection is reported, in which computed tomography showed a mass adjacent to the heart and a pericardial effusion. The patient had aggressive medical treatment with penicillin and survived.

Silver staining of Pneumocystis carinii in the rat's lung.

The backscattered electron imaging mode of the scanning electron microscope was used to study the ontogenetic acquisition of argyrophilia in Pneumocystis carinii in rats. Silver staining continually increased from the late trophozoite to the mature cyst stage. The silver uptake began with a fine outline at the surface of the bodies of the late trophozoites; their cellular extensions, however, did not stain. The oblate precyst forms acquired the silver in heterogeneous patches. On spherical cysts the silver staining became more uniform and intense with at least one dense spot. The spherical and collapsed cysts also had short silver staining projections that may represent microvilli. Collapsed forms were paler than spherical ones and appear to be cysts that have undergone partial or complete release of sporozoites. These cell surface observations confirm and amplify previous transmission electron microscopical and histochemical studies indicating that silver staining correlates with the acquisition of the cell pellicle.

Mucoepidermoid carcinoma of the lung with intracranial metastases.

Discussed is the first roentgenographic and post-mortem description of a patient with mucoepidermoid carcinoma of the lung who presented with intracranial metastases. The patient's primary tumor eluded physical diagnosis and bronchoscopic delineation. The autopsy confirmed minimal tumor involvement of the bronchial wall despite bulky regional and distant metastases.

Augmentation of rat alveolar macrophage migration by surfactant protein.

Since the alveolar macrophage (AM) resides in an environment made unique by the presence of pulmonary surfactant, we studied the effect of constituents of pulmonary surfactant on the migration of these cells in vitro. Whole pulmonary surfactant, surfactant phospholipids, and a delipidated preparation of surfactant consisting mainly of protein were tested for their effect on AM migration. Migration was measured in multiwell chemotaxis chambers with endotoxin-activated rat serum (EARS) as the stimulus. The delipidated surfactant material (DSM) markedly augmented the migration of rat AM. Enhancement was seen only when migration was stimulated with EARS. Augmentation of stimulated migration occurred over a wide range of protein concentrations in DSM (3.5 to 56 micrograms/ml) in a dose-dependent fashion. Rat AM that were preincubated with DSM and then tested in the chemotaxis assay without DSM showed increased migration towards EARS when compared with AM preincubated in buffer alone. The enhancing effect of DSM on AM migration was significantly diminished by heating the DSM and by enzymatic digestion with trypsin, suggesting that the active constituent in DSM was protein. Thus, it appears that proteins isolated from pulmonary surfactant augment the stimulated migration of AM via an interaction between the protein and the macrophage. Although the identity of these proteins remains to be elucidated, it is unlikely they include albumin since purified rat serum albumin in concentrations comparable to that of protein in DSM did not enhance the stimulated migration of AM. These results represent further confirmation that constituents of surfactant modulate the clearance function of AM in vitro. Thus, it is likely that surfactant plays a role in lung defense mediated by AM.

An ethanol/ether soluble apoprotein from rat lung surfactant augments liposome uptake by isolated granular pneumocytes.

Ethanol/ether soluble apoproteins, comprising 17% of the total recovered surfactant-associated proteins, were isolated from rat lung surfactant and purified by silicic acid chromatography. The protein that eluted in 4:1 chloroform/methanol accounted for greater than 85% of protein in the ethanol/ether soluble fraction and was termed surfactant apoprotein Et (Apo Et). By sodium dodecyl sulfate polyacrylamide gel electrophoresis, this protein had an apparent molecular weight of approximately 10,500. Apo Et was evaluated for its effect on uptake of synthetic phospholipids in liposomal form by isolated granular pneumocytes (Type II alveolar epithelial cells) in primary culture. Liposomes were prepared to approximate the phospholipid composition of the alveolar surfactant, and uptake was measured by the accumulation of the radioactively labeled dipalmitoyl phosphatidyl choline fraction. The uptake of liposomal phosphatidylcholine by cells incubated for 2 h with Apo Et was increased by 61% over control. Most of the cell-associated phospholipid uptake was resistant to treatment with trypsin, suggesting an increased internalization of liposomal material in the presence of Apo Et. The effect of Apo Et on uptake was concentration and time dependent and was not associated with cell damage, phospholipase activity, or detergent properties of the protein. Apo Et had no significant effect on phosphatidylcholine uptake by granular pneumocytes maintained for 7 d in primary culture. Apo Et augmented the uptake of phospholipids by alveolar macrophages although total uptake by these cells was less than that observed with granular pneumocytes. Because Apo Et increases the rate of uptake of surfactant phospholipids by alveolar cells (granular pneumocytes and alveolar macrophages), this protein may represent a physiologically important regulator for clearance of lung surfactant phospholipids.

"Hydrophobic" surfactant apoproteins and augmentation of phospholipid recycling.

A 10,000-11,000 molecular weight apoprotein was isolated from an ethanol-ether extract of rat lung surfactant and purified by silicic acid chromatography. The protein (Apo Et) significantly augmented the uptake of phospholipids in liposomal form by cultured rat granular pneumocytes by a time-dependent process that varied with protein concentration and liposome composition. The protein had no effect on cell viability and showed no phospholipase activity. The mechanism for this augmented phospholipid uptake is not known but could be due to an alteration of physical form of the phospholipids by the protein or to a receptor-mediated uptake of phospholipids. This protein may prove to be a physiologically important regulator of the recycling of lung surfactant phospholipids.

Uptake of liposomal phosphatidylcholine by granular pneumocytes in primary culture.

Reuptake of pulmonary surfactant phospholipids was investigated with rat granular pneumocytes in primary culture and L-alpha-[2-palmitoyl-9,10-3H]dipalmitoyl phosphatidylcholine:egg phosphatidylcholine:phosphatidylglycerol:cholesterol (10:5:2:3, mol/mol) liposomes. Uptake of liposomal phosphatidylcholine by granular pneumocytes increased with time and concentration of phosphatidylcholine in the medium. With 150 microM phosphatidylcholine, uptake was about 5 nmol/mg cell protein in 2 h. Phosphatidylcholine uptake was in large part due to net transfer of vesicles as indicated by uptake of [14C]sucrose encapsulated in the aqueous compartment of liposomes. Using dipalmitoyl phosphatidylcholine:cholesterol (1:1) liposomes, uptake was inhibited significantly at 26 degrees C and completely at 4 degrees C. Inhibitors and uncouplers of oxidative phosphorylation had no effect on uptake although uptake was somewhat inhibited in the presence of either 5.6 mM 2-deoxy-D-glucose or 10 mM sodium fluoride. Cell-associated lipid radioactivity decreased after treatment with 0.25% trypsin. The percent radioactivity that was trypsin releasable decreased with increasing time and phosphatidylcholine concentration. The results suggest that uptake of phospholipids by these cells is by surface binding followed by internalization. After 2 h of incubation, 65.3 +/- 3.1% of the cell-associated radioactivity was present in phosphatidylcholine, a small fraction in phosphatidylglycerol, and the remainder in lysophosphatidylcholine, free fatty acids, and other neutral lipids, suggesting metabolic degradation of internalized lipids. This process of phospholipid uptake and degradation may have a physiological role in metabolism of surfactant phospholipids in the lung.

Crotalocytin: recognition and purification of a timber rattlesnake platelet aggregating protein.

After being envenomated by the timber rattlesnake, a patient was found to have a platelet count of 5000 per microliter, prothrombin time and activated partial thromboplastin time both greater than 150 sec, plasma fibrinogen 0 mg/dl, and fibrinogen split products 2560 microgram/ml. However, this patient did not appear to have acute disseminated intravascular coagulation since coagulation factors II-XII were normal. We postulated that this venom contained, in addition to a fibrinogen clotting enzyme, a platelet activating protein, Crotalocytin. Crotalocytin was purified from crude timber rattlesnake venom by Sephadex G-100 gel-filtration, low ionic strength precipitation, and DEAE-A50 Sephadex chromatography. By sodium dodecyl sulfate gel electrophoresis and gel-filtration Crotalocytin was a single chain polypeptide, molecular weight 55,000. Thrombocytopenia after timber rattlesnake bite appeared to be due to a protein that directly activated platelets. Timber rattlesnake bite mimicked the clinical presentation of disseminated intravascular coagulation.