Protective effects of soluble CR1 in complement- and neutrophil-mediated tissue injury.

Complement activation is an important step for triggering of acute inflammatory reactions. Soluble human recombinant complement receptor type 1 (sCR1) blocks complement activation by both classical and alternative pathways. In addition to glycogen-induced peritonitis, three models of complement-dependent acute inflammatory injury have been used to assess the protective effects of sCR1: lung and dermal injury after intraalveolar or intradermal deposition of IgG immune complexes; acute lung injury resulting from intravascular activation of complement after the i.v. injection of cobra venom factor; and acute skin and lung injury (at 4 h) after thermal trauma involving 25 to 30% total body surface area. Vascular injury was quantified by increases in vascular permeability, hemorrhage, neutrophil infiltration, and, as indicated, tissue water content. Intravenous infusion of sCR1 reduced lung and dermal vascular injury in all models studied. In glycogen-induced peritoneal exudates sCR1-reduced neutrophil accumulation by 79%. In animals undergoing IgG immune complex-induced alveolitis, sCR1 treatment reduced vascular permeability and hemorrhage by 72 and 71%, respectively, and tissue accumulation of neutrophils was reduced by 68%. After cobra venom factor injection, sCR1 reduced increases in lung vascular permeability by 67%, hemorrhage by 73%, and lung myeloperoxidase content by 55%. Four hours after thermal injury of skin, sCR1-treated animals demonstrated significant protection against lung injury; increases in vascular permeability and hemorrhage were reduced by 45 and 46%, respectively, and myeloperoxidase content was lowered by 39%. In thermal injury of the skin, sCR1 injection reduced dermal vascular permeability by 25% at 1 h (p = NS) and 44% at 4 h. Water content in skin biopsies was also decreased. There was a dose-response relationship between the amount of sCR1 infused and the extent of protection in each of the injury models. These data demonstrate that sCR1 offers significant protection against complement-dependent tissue injury in the animal models studied and that the protective effects are related to reduced neutrophil content.     

Selection of T cell receptor expression mutants through the functionally linked Ly-6A

Ly-6A is a glycosyl-phosphatidylinositol (GPI)-anchored molecule that participates in murine T cell activation. Activation of T cell hybridomas with anti-Ly-6A monoclonal antibody (mAb) leads to production of interleukin-2 (IL-2), but also to a paradoxical growth inhibition, which was used to select for signaling mutants. Fifteen subclones derived from two independent mutageneses and anti-Ly-6A selection were characterized. Thirteen subclones responded poorly or not at all to soluble anti-Ly-6A mAb. Although the selective pressure was exerted through Ly-6A, only one mutant did not express the Ly-6A antigen. Interestingly, 10 of the 15 subclones expressed either nondetectable or a very low level of T cell receptor/CD3 complex (TCR/CD3). Preferential expansion of TCR/CD3 expression mutants following anti-Ly-6A selection further established functional linkage between Ly-6A and TCR/CD3 complex. The mechanism of the functional coupling was investigated by analyzing the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), one of the early events in T cell activation. We showed that PIP2 was not hydrolyzed in response to anti-Ly-6A in TCR/CD3-negative mutants. Aluminum fluoride, which activates G protein directly, did induce PIP2 hydrolysis in these cells. These data suggest that activation signals originated from Ly-6A must be transmitted first to TCR/CD3 complex, which then couples to the G protein/phospholipase C system. A similar requirement also applies to the Thy-1 protein and lectin receptors. Thus, the TCR/CD3 complex plays a central role in the integration and transmission of activation signals that originated from several T cell surface molecules.     

Transfer of 1-pyrroline-5-carboxylate as oxidizing potential from hepatocytes to erythrocytes.

The interconversions of proline and 1-pyrroline-5-carboxylate form an intercellular cycle that is the basis of a metabolic interaction between hepatocytes and erythrocytes. The cycle transfers oxidizing potential from hepatocytes to erythrocytes, which stimulates pentose phosphate pathway in erythrocytes. This interaction depends on the differential metabolism of proline and 1-pyrroline-5-carboxylate in erythrocytes and hepatocytes and consists of the following: in hepatocytes proline oxidase converts proline into 1-pyrroline-5-carboxylate, which is released into the medium and taken up by erythrocytes; erythrocyte 1-pyrroline-5-carboxylate reductase converts 1-pyrroline-5-carboxylate into proline and concomitantly generates NADP+; the generated oxidizing potential drives glucose metabolism through the pentose phosphate pathway in erythrocytes; finally, erythrocytes release proline into the medium, enabling it to re-enter hepatocytes and repeat the cycle. The increased activity of the pentose phosphate pathway in erythrocytes may enhance the production of 5-phosphoribosyl pyrophosphate, a necessary moiety for the processing of purines.     

Linkage of the HMP pathway to ATP generation by the proline cycle

The reactions catalyzed by proline oxidase and pyrroline-5-carboxylate reductase form a catalytic cycle linking the hexose-monophosphate pentose (HMP) pathway to mitochondrial ATP generation. The cycling of proline and pyrroline-5-carboxylate couples glucose oxidation to ATP generation by a mechanism independent of the Embden-Meyerhof pathway and the tricarboxylic acid cycle.     

Dynamic light scattering characterization of the detergent-free,delipidated (Ca2+ + Mg2+)-ATPase from sarcoplasmic reticulum

Dynamic light scattering studies have been conducted on the delipidated and detergent-removed (Ca²⁺ + Mg²⁺)-ATPase protein assemblies. Specific characterization of the state of aggregation and the extent of conformation change upon delipidation and detergent removal has been made. The results show that the prominent species are dimers and tetramers of very globular nature, with axial ratios of less than 2 : 1. The hydrodynamic radii of the dimers and the tetramers are, respectively, 57.5 Å and 74.5 Å.The globular nature of these observed entities differ from the delipidated ATPase proteins recently obtained (LeMaire, M., Jorgensen, K.E., Roigaard-Petersen, H. and Moller, J.V. (1976) Biochemistry 15, 5805–5812). Present results suggest that upon the removal of detergents from the lipid-free ATPase protein assembly, only a rather limited degree of aggregation takes place. Such a condition is consistent with models of the membrane protein system which has limited regions of hydrophobic contact. Oligomeric assemblies with aqueous channels is a possible active Ca²⁺ transport model consistent with results of the present data, as well as the data from several other recent studies.     

Interactions of aminopyridines with potassium channels of squid axon membranes.

The effects of aminopyridines on ionic conductances of the squid giant axon membrane were examined using voltage clamp and internal perfusion techniques. 4-Aminopyridine (4-AP) reduced potassium currents, but had no effect upon transient sodium currents. The block of potassium channels by 4-AP was substantially less with (a) strong depolarization to positive membrane potentials, (b) increasing the duration of a given depolarizing step, and (c) increasing the frequency of step depolarizations. Experiments with high external potassium concentrations revealed that the effect of 4-AP was independent of the direction of potassium ion movement. Both 3- and 2-aminopyridine were indistinguishable from 4-AP except in potency. It is concluded that aminopyrimidines may be used as tools to block the potassium conductance in excitable membranes, but only within certain specific voltage and frequency limits.     

Studies of trachoma in families on Taiwan.

This study was undertaken to clarify the natural history and pathogenesis of trachoma. A group of families who live in a formerly trachoma hyperendemic area of Southern Taiwan were placed under continuous surveillance. The development in recent years of the micro immunofluorescence test for trachoma antibody, along with improved cell culture isolation methods, have allowed this surveillance to include repeated effective laboratory studies in addition to clinical observations. After four years' study of one group of families and three years of another, a number of interesting findings have been obtained. Evidence is presented supporting our hypothesis that trachoma is a disease of immumopathology and results from repeated reinfections with the trachoma organisms. The clinical findings of papillae, especially those of an acute nature, has been the clinical finding most closely associated with the isolation of the organism and the demonstration of antibody. Evidence is presented that transmission of the organism is usually within the family group. Although only trachoma immunotypes B and C previously had been associated with trachoma infection on Taiwan, data is presented from one family in which type D infections occurred. While a series of new and reinfections with trachoma organisms were demonstrated in some of the families under observation, the majority of the families not only showed no new infections but showed spontaneous healing or disappearance of clinical and laboratory evidence of trachoma infection. This tendency of active trachoma infection to disappear from a family in the absence of transmission of the organism parallels the rapid fall and prevalence of active trachoma on Taiwan during the past decade.