Myelination inhibition factor: dissociation from induction of experimental allergic encephalomyelitis

Sensitization of guinea pigs with purified myelin basic protein induces experimental allergic encephalomyelitis (EAE) but does not induce a serum factor which inhibits myelin formation in vitro. This factor, induced by some unidentified constituent of whole central nervous system tissue, should not be characterized as a component of "EAE serum."     

Propolypeptide of von Willebrand factor circulates in blood and is identical to von Willebrand antigen II

The generally mild bleeding disorder of von Willebrand disease is associated with abnormalities of two distinct plasma proteins, the large multimeric von Willebrand factor (vWF), which mediates platelet adhesion, and von Willebrand antigen II (vW AgII), which is of unknown function. The two proteins were found to have a common biosynthetic origin in endothelial cells and megakaryocytes, which explains their simultaneous absence in the severe form of this hereditary disease. Shared amino acid sequences from a 100-kilodalton plasma glycoprotein and from vW AgII are identical to amino acid sequences predicted from a complementary DNA clone encoding the 5' end of vWF. In addition, these proteins have identical molecular weights and immunologic cross reactivities. Monoclonal antibodies prepared against both proteins recognize epitopes on the pro-vWF subunit and on a 100-kilodalton protein that are not present on the mature vWF subunit in endothelial cell lysates. In contrast, polyclonal antibodies against vWF recognize both pro-vWF and vWF subunits. Thus, the 100-kilodalton plasma glycoprotein and vW AgII are identical proteins and represent an extremely large propolypeptide that is first cleaved from pro-vWF during intracellular processing and then released into plasma.     

Hycanthone analogs: dissociation of mutagenic effects from antischistosomal effects

N-Oxidation at the diethylamino group of hycanthone, of lucanthone, and of two chlorobenzothiopyranoindazoles resulted in a marked reduction in mutagenic activity, while antischistosomal activity was retained or even enhanced. Introduction of chlorine into the 8-position of benzothiopyranoindazoles reduced acute toxicity but had no effect on chemnotherapeutic potency. These dissociations of biological activities indicate that safer antischistosomal compounds of this class can be developed.     

Vasoconstriction: a new activity for platelet-derived growth factor

Platelet-derived growth factor (PDGF) is a potent mitogen for vascular smooth muscle cells that has been implicated in the pathogenesis of atherosclerosis. The potential role of PDGF in the altered vasoreactivity of atherosclerotic vessels has been studied through an examination of its effects on contractility in the rat aorta. PDGF caused a concentration-dependent contraction of aortic strips and was significantly more potent on a molar basis than the classic vasoconstrictor peptide angiotensin II. Furthermore, PDGF increased the cytosolic free calcium concentration in cultured rat aortic smooth muscle cells. These observations suggest a new biological activity for PDGF that may contribute to the enhanced vasoreactivity of certain atherosclerotic vessels.     

Structures of glycoprotein Ibalpha and its complex with von Willebrand factor A1 domain

Transient interactions of platelet-receptor glycoprotein Ibalpha (GpIbalpha) and the plasma protein von Willebrand factor (VWF) reduce platelet velocity at sites of vascular damage and play a role in haemostasis and thrombosis. Here we present structures of the GpIbalpha amino-terminal domain and its complex with the VWF domain A1. In the complex, GpIbalpha wraps around one side of A1, providing two contact areas bridged by an area of solvated charge interaction. The structures explain the effects of gain-of-function mutations related to bleeding disorders and provide a model for shear-induced activation. These detailed insights into the initial interactions in platelet adhesion are relevant to the development of antithrombotic drugs.     

Human von Willebrand factor (vWF): isolation of complementary DNA (cDNA) clones and chromosomal localization

Human factor VIII--von Willebrand factor (vWF) is a large, multimeric glycoprotein that plays a central role in the blood coagulation system, serving both as a carrier for factor VIIIC (antihemophilic factor) and as a major mediator of platelet-vessel wall interaction. Diminished or abnormal vWF activity results in von Willebrand's disease (vWD), a common and complex hereditary bleeding disorder. Overlapping vWF cDNA clones that span 8.2 kilobases of the vWF messenger RNA have been obtained. vWF accounts for approximately 0.3 percent of endothelial cell messenger RNA and was undetectable in several other tissues examined. A large single copy gene for vWF is located on the short arm of chromosome 12 (12p12----12pter). No gross gene rearrangement or deletion was detected in the DNA of two patients with severe vWD.     

Molluscan cells: dissociation and reaggregation

Dissociation of the ovotestes of Helix pomatia requires the presence of carbohydrates as well as trypsin, but is independent of cation content. Dispersed cells obtained from the ovotestes reaggregate rapidly into histotypically organized tissue. The role of cellular adhesiveness is facilitated by centrifugation, but pseudopodial activity of the cells is suggested as another factor in reaggregation.     

Hypotensive activity of fibroblast growth factor

Acidic and basic fibroblast growth factors (FGFs) are members of a family of proteins that are broad-spectrum mitogens, have diverse hormone-like activities, and function in tumorigenesis. FGF's ability to raise the concentration of intracellular calcium ion suggests that FGF could induce the synthesis of endothelium-derived relaxing factor (EDRF) and consequently vasodilation. Systemic administration of FGF decreased arterial blood pressure. This effect was mediated by EDRF and by adenosine triphosphate-sensitive potassium ion channels. The hypotensive effect of FGF was segregated from its mitogenic activity by protein engineering. These results extend the range of FGF autocrine activities and potential therapeutic applications, emphasize the role of endothelium as an arterial blood pressure--regulating organ, and provide insight on the structural basis of FGF functions.     

Inhibition of factor VIIa-tissue factor coagulation activity by a hybrid protein

Lipoprotein-associated coagulation inhibitor (LACI) appears to inhibit tissue factor (TF)-induced blood coagulation by forming a quaternary inhibitory complex containing factor Xa, LACI, factor VIIa, and TF. A genetically engineered hybrid protein consisting of the light chain of factor Xa and the first Kunitz-type inhibitor domain of LACI is shown to directly inhibit the activity of the factor VIIa-TF catalytic complex. Unlike inhibition of factor VIIa-TF activity by native LACI, inhibition by the hybrid protein is not dependent on factor Xa. In an assay of TF-induced coagulation, 50% TF inhibition occurs with hybrid protein at 35 nanograms per milliliter, whereas LACI at 2.5 micrograms per milliliter is required for an equivalent effect. gamma-Carboxylation of glutamic acid residues in the factor Xa light chain portion of the hybrid protein is required for inhibitory activity, indicating that the first Kunitz-type domain of LACI alone is not sufficient for inhibition of factor VIIa-TF.     

Adipsin and complement factor D activity: an immune-related defect in obesity

Adipsin is a serine protease that is secreted by adipocytes into the bloodstream; it is deficient in several animal models of obesity, representing a striking example of defective gene expression in this disorder. Recombinant mouse adipsin was purified and its biochemical and enzymatic properties were studied in order to elucidate the function of this protein. Activated adipsin has little or no proteolytic activity toward most substrates but has the same activity as human complement factor D, cleaving complement factor B when it is complexed with activated complement component C3. Like authentic factor D, adipsin can activate the alternative pathway of complement, resulting in red blood cell lysis. Decreased (58 to 80 percent) complement factor D activity, relative to lean controls, was observed as a common feature of several experimental models of obesity, including the ob/ob, db/db, and monosodium glutamate (MSG)-injected mouse and the fa/fa rat. These results suggest that adipsin and the alternative pathway of complement may play an unexpected but important role in the regulation of systemic energy balance in vivo.     

Unit activity: motiviation-dependent responses from midbrain neurons

Single neurons in the midbrain tegmentum of rats showed clear discriminatory responses to three tones announcing either food or water or no reinforcement. Subjects were required to press a single lever and remain motionless for 2 seconds during which time unit activity from several brain sites was recorded. One of the tones, randomly designated, was sounded halfway through this period. Manipulation of drive states revealed that the highest activity was associated with tones announcing the reinforcement for which the animal was most strongly motivated. Thus, from a hungry animal sustained or increased firing rates were elicited by a " food" tone and differentially lowered rates by the other tones.     

Metabolic dissociation of short-lived barium-137m from its cesium-137 parent

At 4 to 7 days after Cs(137) administration, Ba(137m) was found to exceed Cs(137)-Ba(137m) equilibrium proportions in bone and plasma by factors of 3 and 14, respectively, in the living animal. This demonstrated the in vivo escape of Ba(137m) from sites of Cs(137) accumulation. Liver tissue was slightly deficient in Ba(137m), whereas tissues such as bone marrow and spleen showed little or no deviation from equilibrium.     

Hybridization experiments: evidence of dissociation equilibrium in hemerythrin

Partial succinylation of hemerythrin alters its electrophoretic mobility even though it remains an octameric macromolecule. Mixtures of this modified protein and unmodified hemerythrin generate species of intermediate electrophoretic mobility. Such behavior provides strong evidence that the octameric macromolecule is in mobile equilibrium with monomeric subunits.     

Particulate bioluininescence in dinoflagellates: dissociation and partial reconstitution

With the same extraction conditions used for Gonyaulax polyedra, soluble and particulate bioluminescence can be isolated from two additional species, Pyrodinium bahamense and Pyrocystis lunula. We have been able, for all three species, to dissociate soluble luciferin and luciferase from the particulate system. Luciferin can be incorporated into both reacted and unreacted particulate systems.     

Lactate dehydrogenase isozymes: dissociation and denaturation by dilution

The tetrameric enzyme lactate dehydrogenase dissociates into its constituent monomeric subunits in a high ion to protein concentration ratio, in certain ionic environments when frozen, and at extreme dilution. Dissociation by dilution involves changes in tertiary conformation which inactivate the enzyme. The dissociation is strongly inhibited by homologous native proteins, but only slightly by denatured or unrelated proteins.     

Induction of macrophage tumoricidal activity by granulocyte-macrophage colony-stimulating factor

Monocytes are a subpopulation of peripheral blood leukocytes, which when appropriately activated by the regulatory hormones of the immune system, are capable of becoming macrophages--potent effector cells for immune response to tumors and parasites. A complementary DNA for the T lymphocyte-derived lymphokine, granulocyte-macrophage colony-stimulating factor (GM-CSF), has been cloned, and recombinant GM-CSF protein has been expressed in yeast and purified to homogeneity. This purified human recombinant GM-CSF stimulated peripheral blood monocytes in vitro to become cytotoxic for the malignant melanoma cell line A375. Another T cell-derived lymphokine, gamma-interferon (IFN-gamma), also stimulated peripheral blood monocytes to become tumoricidal against this malignant cell line. When IFN-gamma activates monocytes to become tumoricidal, additional stimulation by exogenously added lipopolysaccharide is required. No such exogenous signals were required for the activation of monocytes by GM-CSF.