Kouzo Hirai

Role of β3-adrenergic receptors in the action of a tumour lipid mobilizing factor

Induction of lipolysis in murine white adipocytes, and stimulation of adenylate cyclase in adipocyte plasma membranes, by a tumour-produced lipid mobilizing factor, was attenuated by low concentrations (10−7–10−5 M) of the specific β3-adrenoceptor antagonist SR59230A. Lipid mobilizing factor (250 nM) produced comparable increases in intracellular cyclic AMP in CHOK1 cells transfected with the human β3-adrenoceptor to that obtained with isoprenaline (1 nM). In both cases cyclic AMP production was attenuated by SR59230A confirming that the effect is mediated through a β3-adrenoceptor. A non-linear regression analysis of binding of lipid mobilizing factor to the β3-adrenoceptor showed a high affinity binding site with a Kd value 78±45 nM and a Bmax value (282±1 fmole mg protein−1) comparable with that of other β3-adrenoceptor agonists. These results suggest that lipid mobilizing factor induces lipolysis through binding to a β3-adrenoceptor.

A high-frequency polymorphism in exon 6 of the CD45 tyrosine phosphatase gene (PTPRC) resulting in altered isoform expression

CD45 (leukocyte common) antigen is a hemopoietic cell-specific tyrosine phosphatase essential for antigen receptor-mediated signaling in lymphocytes. The molecule undergoes complex alternative splicing in the extracellular domain, and different patterns of CD45 splicing are associated with distinct functions. Lack of CD45 leads to severe combined immunodeficiency, and alterations of CD45 splicing, because of a polymorphism in exon 4, have been associated with altered immune function. Here we describe a polymorphism in exon 6 (A138G) of the gene encoding CD45 that interferes with alternative splicing. The polymorphism results in an amino acid substitution of Thr-47 to Ala in exon 6, a potential O- and N-linked glycosylation site. This exon 6 A138G variant is present at a frequency of 23.7% in the Japanese population but is absent in Caucasoids. Peripheral blood T cells from individuals carrying the A138G variant show a significant decrease in the proportion of cells expressing the A, B, and C CD45 isoforms and a high frequency of CD45R0+ cells. These phenotypic alterations in the A138G carriers may lead to changes in ligand binding, homodimerization of CD45, and altered immune responses, suggesting the involvement of natural selection in controlling the A138G carrier frequency.

Microwave endometrial ablation for menorrhagia caused by large submucous myomas

Aim: To examine the feasibility of microwave endometrial ablation (MEA), using a curved microwave applicator, in patients with menorrhagia caused by a submucous myoma greater than 3 cm in diameter, which is among the contraindications for conventional endometrial ablation.

Lipolytic activity of anemia-inducing substance from tumor-bearing rabbits.

Anemia-inducing substance (AIS) is a protein of approximately 50,000 molecular weight secreted by malignant tumor tissue that depresses erythrocyte and immuno-competent cell functions; in this study, its biological effects on adipocytes were examined. Changes in body weight, total body fat, and food intake were investigated in rabbits after VX2 carcinoma transplantation, and the results showed reductions of 11%, 24%, and 30%, respectively, at 40 days after transplantation compared with baseline values (before transplantation). The values were even more markedly reduced 70 days after transplantation. When cyclic plasma perfusion (2 times/wk) was started at 40 days after transplantation, the values at 70 days after transplantation (30 days after beginning plasma perfusion) recovered to 91%, 84%, and 87%, respectively, of the baseline values. AIS fractions were isolated from rabbit plasma by using a phenyl-Sepharose column before transplantation, 40 and 70 days after transplantation, and 30 days after start of plasma perfusion, and AIS activity and lipolytic activity were measured. The results showed enhancement of AIS activity and lipolytic activity as the tumors grew. Lipolytic activity also returned to baseline value as AIS was removed by adsorption by plasma perfusion, and there was a high correlation between lipolytic activity and AIS kinetics. These results strongly suggest that AIS might be one of the substances involved in the enhanced lipolytic activity in advanced tumor-bearing subjects.

Microwave power and duration without extrauterine thermal damage in microwave endomyometrial ablation at 2.45 GHz

Aim: We investigated microwave power and duration of use, which does not affect extrauterine organs, in order to treat organic menorrhagia caused by myomas or adenomyosis.

Metabolic and Morphologic Characteristics of Adipose Tissue Associated with the Growth of Malignant Tumors

Changes in total body fat and the metabolic and morphologic characteristics of adipose tissue were sequentially investigated in individual rabbits implanted with VX2 tumors to elucidate the pathology of the fat reduction in animals with malignant tumors as compared with that of diet‐restricted rabbits. Lipogenesis in normal, VX2–implanted, and diet‐restricted rabbit groups on day 40 after the start of the experiments was 19.1±2.9, 13.3±3.5, and 41.7±6.0×l05 cpm/g/h, respectively, and glycerol liberation by their adipose tissue was 199±21, 528±94, and 301±45 nmol/g/h, respectively. In addition, apoptotic cells were noted in the adipose tissue of VX2–implanted rabbits on days 20–30 after implantation, but not in diet‐restricted rabbits. The results showed clear differences between the total body fat reduction profiles of VX2–implanted rabbits and diet‐restricted rabbits, suggesting a characteristic lipid metabolism with enhanced lipolysis and diminished lipogenesis in VX2–implanted rabbits. The results strongly suggest that adipocyte apoptosis might be involved in these phenomena.

Neutropenia Accompanying Parvovirus B19 Infection after Gynecologic Surgery

The hematologic data and symptoms of 7 patients seropositive for parvovirus B19 IgM antibody after gynecologic surgery were analysed. Parvovirus may have been transmitted by fibrin glue prepared from heat-treated human plasma and used for hemostasis during surgery. The peripheral blood neutrophil count decreased to below 1 × 109/l between postoperative day (POD) 10 and 18, but recovered spontaneously to within the normal range. G-CSF injection was effective in preventing neutropenia or obtaining a prompt recovery. The reticulocyte count fell below 10 × 109/l between POD 13 and 19, and also recovered spontaneously. A slapped-cheek rash was not observed in any of the 7 patients.

Geographical distribution and disease associations of the CD45 exon 6 138G variant

CD45 is crucial for normal lymphocyte signalling, and altered CD45 expression has major effects on immune function. Both mice and humans lacking CD45 expression are severely immunodeficient, and single-nucleotide polymorphisms in the CD45 gene that cause altered splicing have been associated with autoimmune and infectious diseases. Recently, we identified an exon 6 A138G polymorphism resulting in an increased proportion of activated CD45RO T cells and altered immune function. Here we report a significantly reduced frequency of the 138G allele in hepatitis C Japanese patients and a possibly reduced frequency in type I diabetes. The allele is widely distributed in the Far East and India, indicating that it may have a significant effect on disease burden in a large part of the human population.

Apoptosis of muscle cells causes weight loss prior to impairment of DNA synthesis in tumor-bearing rabbits

The mechanism of weight loss induced by the growth of malignant tumors is still unknown. We investigated it by focusing on apoptosis of skeletal muscle. VX2‐tumor was implanted into rabbits and the apoptotic index (AI) of skeletal muscle was measured by in situ end‐labeling assay. Plasma of the tumor‐bearing rabbits was perfused repeatedly through non‐coated charcoal resin. The AI reached 54.6% early after tumor implantation, when weight loss amounted to an 18% decrease in lean body mass (LBM) without change in muscle DNA synthesis or urinary 3‐methylhistidine/ creatinine ratio (3‐MH/Cr). When the decrease of LBM reached 30%, DNA synthesis was decreased by 48% and 3‐MH/Cr was increased by 104%, whereas AI was only 4.7%. The plasma perfusion did not prevent apoptosis in muscle, but unproved LBM, DNA synthesis, and 3‐MH/Cr. There may be two mechanisms of muscle depletion during the tumor growth: apoptosis in the early stage and metabolic abnormalities in muscle in the late stage.

Expression of apoptosis regulatory proteins in the skeletal muscle of tumor-bearing rabbits.

We reported finding that apoptosis occurred in skeletal muscle in the early stage after implantation. In the present study, we investigated expression of the apoptosis‐related proteins Bax and Bcl‐2 to determine the mechanism of the apoptosis. In the early stage of tumor bearing, 20 days after implantation, lean body mass (LBM) was reduced by 5.06±1.10% in the tumor‐bearing group, compared with an increase of 4.96±1.26% in the control group. The apoptotic index (AI) of the skeletal muscle in the tumor‐bearing group increased to 40.5±3.20% but was 0% in the control group, and Bax expression was strongly positive in 5 of the 10 rabbits in the tumor‐bearing group, and significantly stronger than in the control group (P=0.0002). In the late stage of tumor bearing, 40 days after implantation, the AI had declined to 0.93±0.96% in the tumor‐bearing group, but was still 0% in the control group. Bax expression was rarely detected in either the tumor‐bearing group or the control group, and there was no significant difference between the two groups (P=0.706). No significant changes in Bcl‐2 were observed in either group. The above results showed that apoptosis via Bax played a role in muscle wasting associated with progression of the malignant tumor. However, the apoptosis and expression of Bax were seen only in the early stage, within 20 days after implantation, not in the late stage. This suggested that the muscle wasting in the early stage might be caused by a different mechanism from that in the late stage.