Shigeru Arai

Inhibition of Corynebacterium parvum-primed and lipopolysaccharide-induced hepatic necrosis in rats by selective depletion of neutrophils using a monoclonal antibody.

To examine whether neutrophils are involved in the pathogenesis of experimental liver dysfunction, we observed the effect of selective in vivo neutrophil depletion by a monoclonal antibody (RP‐3) on the pathogenesis of acute experimental hepatic necrosis in rats induced by a preparative injection of heat‐killed Corynebacterium parvum and a challenging dose of lipopolysaccharide (LPS) (positive control group). The serum transaminase titer 8 h after LPS injection was reduced by selective depletion of peripheral blood neutrophils as a result of RP‐3 treatment (RP‐3 group). A kinetic study showed that the serum transaminase titer of the RP‐3 group was significantly lower than that of the positive control group from 4 to 24 h after LPS injection. The transaminase level was significantly lower in the group with less than 400/mm3 peripheral blood neutrophils than in the group with a greater number. The effect of RP‐3 on the transaminase level was due neither to the injection of cancer ascites nor to RP‐3 injection with the accompanying decrease in complement titer. These results suggest that neutrophils play an important role in the induction of liver dysfunction in this system.

Inhibition of mouse natural killer cytotoxicity by heparin

The effect of heparin on mouse natural killer (NK) cytotoxicity was investigated. Heparin greatly inhibited NK activity at a concentration of more than 10 units/ml. Inhibition of NK cytotoxicity was observed only when heparin was present in the reaction mixture of the cytotoxicity assay. The results of kinetic study of NK inhibition and target-effector binding assay proposed the possibility that heparin inhibits NK cytotoxicity after the binding of effector cells to target cells. Dextran sulfate, the heparin analog, which has potent negative charge also had an inhibitory effect on NK activity. Fractionation of heparin on Sephadex A-25 column revealed the parallelism of the negative charge and the inhibitory effect of heparin on NK cytotoxicity. These results demonstrated that polyanion could modulate NK cytotoxicity.

Effector phenotypes and mechanisms of antitumor immune reactivity of tumor-immunized and tumor-bearing mice in two syngeneic tumors

By using two different syngeneic tumors, Meth A sarcoma and RL male 1 lymphoma of BALB/c origin, the present study was designed to investigate the subset(s) of T cells mediating in vivo antitumor immune responses and some of the effector mechanisms of in vivo protective immunity in BALB/c mice immunized against tumor or bearing tumor. Spleen cells from the mice immunized against Meth A tumor or bearing Meth A tumor inhibited the growth of Meth A tumor in the Winn assay. In the Meth A-immunized mice, L3T4+ (CD4+) cells played a major role in mediating the inhibitory activity against Meth A tumor growth, whereas in the Meth A-bearing mice, the antitumor protective immunity was mediated by both L3T4+ and Lyt-2+ (CD8+) cells. Spleen cells from the Meth A-immunized or Meth A-bearing mice were not able to generate cytotoxic T lymphocytes (CTL) directed against Meth A tumor after the in vitro restimulation of spleen cells with mitomycin C (MMC)-treated Meth A cells, while fresh spleen cells from the Meth A-immunized or Meth A-bearing mice were able to induce the strong delayed-type hypersensitivity (DTH) responses to Meth A tumor. The DTH response to Meth A tumor was mediated by L3T4+ cells in the Meth A-immunized mice and by both L3T4+ and Lyt-2+ cells in the Meth A-bearing mice. In the similar experiments performed in the RL male 1 lymphoma, the antitumor activity in spleen cells from the RL male 1-immunized or RL male 1-bearing mice depended on Lyt-2+ but not L3T4+ cells in the Winn assay. When spleen cells from the RL male 1-immunized or RL male 1-bearing mice were cultured with MMC-treated RL male 1 cells for 5 days, an appreciable CTL response to RL male 1 tumor was induced. These results suggest that the nature of tumor and/or tumor antigens determines which T cell subset is required to exhibit the protective immunity against tumor and thus the different effector mechanisms could be induced in the different tumor models. Furthermore, these data support the conclusion that antitumor T cell responses are affected by the immune state of host to tumor.

The Mechanisms of Cytotoxicity to Tumor Cells by Polymorphonuclear Leukocytes Stimulated with Cytokines

The mechanisms of tumor cytotoxicity of rat polymorphonuclear leukocytes (PMN) activated with cytokine(s) were studied with the use of supernatants from a rat myelomonocytic leukemia cell line, WRT‐7, incubated in the presence of bacterial lipopolysaccharide (LPS) (LPS WRT‐7 sup) as a source of cytokine. Rat peritoneal PMN treated with LPS WRT‐7 sup showed cytostasis from 3 hr after the start of incubation, while significant cytolysis was first observed after 24 hr. When target tumor cells were separated from PMN at 6 or 12 hr after the start of the assay, 3H‐UdR release from the separated target cells comparable to that from the group incubated with PMN for the whole assay time of 40 hr was observed during the following incubation, which indicates that priming for subsequent lysis occurs at a relatively early stage of the assay. None of various scavengers of active oxygens, inhibitors of heme enzymes, and inhibitors of neutral proteinases inhibited cytolysis mediated by PMN stimulated with LPS WRT‐7 sup. Heparin inhibited PMN cytolysis only when it was added within 1 hr after the start of the assay. Fractionation of heparin by ion exchange chromatography showed a parallelism between the negative charge and the inhibitory effect of heparin on PMN cytotoxicity.

T cell mitogenicity of a novel β-d-galactoside-specific lectin from the beetle, Allomyrina dichotoma (allo A)

We examined the lymphocyte mitogenicity of a novel beta-D-galactoside-specific lectin from the beetle Allomyrina dichotoma, named allo A. Allo A was mitogenic to spleen cells of various strains of mice and rats and to human peripheral blood lymphocytes. When the selectivity of mitogenicity to T or B lymphocytes was examined with mouse spleen cells, allo A was selectively mitogenic to T-enriched spleen cells, which indicates that allo A is a T cell mitogen. Thymocytes from non-treated mice hardly responded to allo A, while those from cortisone-treated mice did to a great extent, indicating that allo A is mitogenic to mature thymocytes. The lymphocyte activation with allo A was inhibited by lactose, but not by melibiose, N-acetyl-D-glucosamine, or methyl-alpha-D-mannoside, which suggests that cell surface molecules containing beta-D-galactosyl residues are of importance in the structure of allo A receptors on the cell surface.

Stress-strain relation of cardiac muscle determined from ventricular pressure-time relationships during isovolumic contractions

Abstract The stress-strain relation of systolic muscle fibers which constitute the left ventricular wall of a canine heart was derived only from pressure-time relationships at different ventricular volumes of isovolumic beat by using a largely deformable thick spherical shell model as a first approximation. The strain energy function being independent of the magnitude of forces generated by contraction was found to be uniquely determined by assuming those forces as forces caused by an eigen stress. The result based on this assumption was verified by several pressure-volume relationships obtained experimentally.

Hypertension and Plasma Renin Activity in Experimentally Induced Chronic Pyelonephritis

The present authors conducted a series of experiments with mongrel dogs, in which unilateral chronic pyelonephritis was induced and postoperative changes in blood pressure and plasma renin activity were observed over a period of 3 months. The pyelonephritis infection was brought about by a method involving vesicoureteral reflux and ureteral dysfunction, as described in a previous paper. Pre- and postoperative levels of systolic pressure were compared, but no definite trends were found for the first 3 weeks after operation. At 30, 60 and 90 days the pressures were found to have risen by 21.2 +/- 14.6 and 17.1 +/- 16.7 mm Hg, respectively. No appreciable change in the plasma renin activity was found, however, at any stage. From these results it was concluded that experimentally induced chronic pyelonephritis in dogs caused a rise in blood pressure. No connection between the pyelonephritis and the renin angiotensin system was found.

Residual Stress in the Left Ventricle

The left ventricle is a highly deformable, thick-walled structure that is subjected to intraventricular pressure and myocardial contractile force. Stress in the left-ventricular wall may not be zero even if the intraventricular pressure is not present; such a stress is called the residual stress. The values of stresses must be obtained from the appropriate mathematial model, which should be as simple as possible. In the mathematical models proposed so far, the residual stress has not been considered. If the effect of residual stress is ignored, the extreme concentration of the stress occurs near the endocardium, so that there exists a contradiction between the oxygen consumption and the local mechanical work because of stress and strain along the wall thickness. First, a mathematical model was proposed that was valid for isovolumic and isobaric contractions in which the ventricle was subjected to both intraventricular pressure and myocardial contractile force. Expressions for the stress components were derived without assuming the functional form of the stress-strain relation, thus differing from those; assumed previously by many researchers. The residual strain was obtained from experimental work using canine ventricles. Then, the residual stress was introduced to improve the model to avoid the contradiction just mentioned. As a result, the extreme concentration of stress at the endocardium was largely reduced in the improved ventricular model.

An Immunohistochemical Study on Isotypes of the Immune Complexes Trapped by Follicular Dendritic Cells (FDC) in Various Human Lymphoid Tissues

Follicular dendritic cells (FDC) are well known to trap and retain immune complexes (IC) containing various isotypes of immunoglobulins1,2,3. In addition, it has been reported that FDC retained IC with peculiar isotypes of immunoglobulins in certain diseases (IgAl in IgA nephropathy4,5, IgE in Kimura’s disease6 etc). These observations imply the particular relationships between isotype of the immunoglobulin constituting IC retained by FDC and immune responses or pathogenesis of certain immunopathological conditions. In the present study, distribution of each isotype of immunoglobulins was systemically examined in human various lymphoid tissues using immunohistochemical techniques with special reference to the reactivity within germinal centers (GC).