ABSTRACT
The eukaryotic cell is compartmentalized by a series of vesicular organelles which constitute the endocytic and exocytic transport pathways. Each vesicular compartment has distinct sets of membrane proteins, structures and functions. Despite continuous vesicular transport, each vesicular compartment maintains its structure and function by use of retention and retrieval signal for its own resident proteins. Proteins in transit along the endocytic and exocytic pathway are transported without admixing with cytoplasmic constituents by successive steps of budding from the donor vesicles, formation of intermediate transport vesicles, transport, targeting to and fusion with acceptor vesicles. Specificity and fidelity of the vesicular transport are conferred by vesicular membrane proteins and small molecular weight GTP-binding proteins of the Rab subfamily. Proteins for export are packaged into specific vesicles for their final destinations. Insertion into and retrieval from the plasma membrane of transport proteins in response to cellular stimulus are a new paradigm of cellular regulatory mechanism. Secretion of neurotransmitters, hormones and enzymes by exocytosis involves a complex set of cytosolic proteins, G-proteins, proteins on the secretory granule membrane and plasma membrane. Much progress has been recently made in identifying proteins and factors involved in the exocytosis. But the molecular interactions among identified proteins and regulatory factors are unknown and remain to be elucidated. Finally our chemiosmotic hypothesis which involves the H+ electrochemical gradient across the secretory granule membrane generated by an ATP-dependent electrogenic H(+)-ATPase as the potential driving force for fusion and release of granule contents will be discussed.
Subject(s)
Humans , Biological Transport , Exocytosis , Organelles/metabolismABSTRACT
The blood eanticoagulant factor (G. E.) in garlic was isolated. This substance was precipitated at a neutral pH as the calcium salt in water, and then the calcium salt was dissolved at a pH of 3.0. Calcium was removed by adding sodium oxalate. Then G. E. was precipitated by adding two volumes of 95% ethanol. The effect of G. E. on blood coagulation was studied; prothrombin time, blood clotting time, antithrombin, anti-Ac-globulin and fibrinolysis. A half mg of G. E. completely inhibited one ml of blood from coagulating. The blood specimen containing G.E. showed a prolongation of the prothrombin time. As the calcium ion concentration increased, the prothrombin time of the plasma containing G. E. was reduced, but not to that of the control(oxalated plasma). This indicated that G. E. inhibited the prothrombin time by precipitating calcium ions, and, in addition to this calcium precipitation, another means of G. E. inhibition may be present. G. E. showed fibrinolytic effects and, in the prothrombin time tests, the plasma containing G. E. always showed less fibrin formation than was shown with oxalated plasma. G. E. showed inhibition of fibrin formation in experiments on its antithrombic effect. But this action may not be due to the antithrombin effect of G. E. but to the fibrinolytic effect of G. E. In in-vivo experiments G. E. did not show any anticoagulant effect. From these facts, it may be said that G. E. has an anticoagulant effect in at least two ways in vitro; first by precipitating calcium ions and secondly by causing fibrinolysis.
Subject(s)
Anticoagulants/pharmacology , Chemistry , Garlic , In Vitro Techniques , Plants, MedicinalABSTRACT
Effect of varying hematocrit ratio on the gastric acid production was studied in the heart-stomach preparation of the frog. When the hematocrit ratio was raised by injecting packed red blood cells obtained from the same species of frog, the acid production was increased significantly as compared to the low hematocrit group in which hematocrit ratio was lowered by injecting frog's normal saline. When a small amount of histamine was added to the medium of 25degree C, the acid production was increased in all cases, but the difference in the acid production between the high and the low hematocrit groups was abolished. However, when the temperature of the medium was lowered to 15degree C, the differences in the acid production between the two groups became significant. When a large amount of acetazolamide was added to the medium at 25degree C, the acid production was decreased significantly in both groups without showing a significant difference between the two groups. The reason(s) responsible for the increased acid production in the high hematocrit group was discussed.