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Biomedical subjects

M Imai

Publications and source records attributed to M Imai.

At least 541 records · Page 30Linked to original sources
PubMed1982

Control of renal function in freshwater and marine teleosts.

The glomerular filtration rate (GFR) of teleost fishes is highly variable and is influenced by glomerular intermittency, environmental salinity, renal perfusion pressure, and some hormones. In freshwater (FW) teleosts, the primary function of the kidney is to excrete excess water while retaining most of the filtered solutes, and GFR is a major determinant of urine flow. Low permeability to water prevails in the distal nephron of FW teleosts, and the majority of the filtered Na and Cl is reabsorbed without osmotic accompaniment of water. Prolactin appears to regulate osmotic permeability to water. Isolated and perfused distal tubules from FW teleosts revealed a transepithelial voltage (Vt) that was positive in the lumen. Both Na and Cl participate in generating lumen-positive Vt. Marine teleosts, which are exposed to Na loading and dehydration, ingest seawater to compensate for their osmotic water loss, and secrete divalent ions, mainly Mg and SO4, from the kidney. The urine flow of marine teleosts is primarily determined by fluid secretion accompanied by divalent ions and subsequent isosmotic reabsorption with NaCl. Interdependence of Na and Cl transport has been noted in the urinary bladder of marine teleosts. There is presently no known humoral substance that regulates NaCl and divalent ion transport in the teleost kidney.

Animals↗
PubMed1981

Purification of human lymphoblastoid interferon by a simple procedure with high yields.

Human Namalwa cell interferon, induced by Sendai virus and composed of a single species with molecular weight of 17,000, was purified to 4.5 X 10(8) international reference units/mg of protein by a combination of salt precipitation, ion exchange chromatography, metal chelate chromatography, hydrophobic chromatography, and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. By immunization of a rabbit with this purified interferon and by extensive absorption with Namalwa cells and an impurity column, highly specific antibody was obtained. Namalwa cells, treated with 5-bromo-2'-deoxyuridine, produced 10-fold more interferon upon induction by Sendai virus. Interferon in this case consisted of heterogeneous species with molecular weight ranging from 15,000 to 24,000. These heterogeneous interferon molecules were purified to 7.6 X 10(8) international reference units/mg of protein by successive chromatography using immobilized highly specific rabbit anti-interferon antibody, Blue Sepharose, and immobilized goat anti-rabbit IgG antibody. The overall recovery of interferon activity was 72%, and the purity of the final preparation was ascertained by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate.

Cell Line↗
PubMed1981

Tubular forms of hepatitis B surface antigen bind with the nucleus of 22-nm spherical HBsAg particles.

Spherical hepatitis B surface antigen particles (HbsAg) of 22-nm diameter were treated with sodium dodecylsulphate in the absence of reducing agents, and their nuclei were exposed. Factors that interact with the nucleus of HbsAg were detected in the serum of HBsAg carriers who were seropositive for hepatitis B e antigen and identified as tubular forms of HBsAg. The other categories of hepatitis B antigen, Dane particles, and 22-nm spherical HBsAg did not bind with the nucleus of HBsAg. When tubular forms of HBsAg had been treated with a proteolytic enzyme, they lost the reactivity to bind with the nucleus of HBsAg. On the basis of the results obtained, tubular forms of HBsAg bear the receptor of protein nature for the nucleus of 22-nm spherical HBsAg. The receptor allows rapid determination of tubular forms by a haemagglutination method for the evaluation of their clinical and epidemiological implications.

Carrier State↗
PubMed1981

Effects of parathyroid hormone and N6,O2'-dibutyryl cyclic AMP on Ca2+ transport across the rabbit distal nephron segments perfused in vitro.

Effects on Ca2+ transport of parathyroid hormone (PTH) and N6,O2'-dibutyryl adenosine 3',5'-cyclic monophosphate (DB-cAMP) were examined in the rabbit distal nephron segments including the cortical thick ascending limb of Henle's loop (CAL), the connecting tubule (CNT) and the cortical collecting tubule (CCT) by the in vitro perfusion technique. When PTH (10(-8) mol . l-1) was added to the bath, efflux of Ca2+ (pmol . mm-1 . min-1) was increased from 6.29 +/- 1.46 to 7.96 +/- 1.66 (P less than 0.02) in the CAL, and from 8.55 +/- 1.30 to 13.73 +/- 1.24 (P less than 0.001) in the CNT, respectively, without changes in influx of Ca2+. The effect of PTH on Ca2+ transport in the CAL, however, was abolished when phosphate concentration in the medium was reduced from 3.0 to 1.0 mmol . l-1. When DB-cAMP (10(-3) mol . l-1) was added to the bath, efflux of Ca2+ was also increased from 7.01 +/- 0.83 to 9.40 +/- 0.82 (P less than 0.05) in the CAL, and from 13.11 +/- 0.89 to 19.74 +/- 0.52 (P less than 0.005) in the CNT, respectively. By contrast, neither PTH nor DB-cAMP affected efflux of Ca2+ in the CCT. PTH did not affected the transepithelial voltage either in the CAL or in the CNT. But in the CNT, DB-cAMP decreased the voltage from -14.1 to -9.4 mV. The response of adenylate cyclase activity to PTH in the collagenase treated isolated nephron segments was also examined. Significant increases in adenylase cyclase activity were observed in the CAL as well as in the CNT with 10(-6) mol . l-1 PTH. These data indicate that PTH stimulates Ca2+ transport across the CNT probably via activation of the adenylate cyclase-cyclic AMP system. The hormone may also stimulate Ca2+ transport across the CAL in a special condition where plasma phosphate concentration is elevated.

Adenylyl Cyclases↗
PubMed1981

Demonstration of the immunogenicity of hepatitis B core antigen in a hepatitis B e antigen polypeptide (P19).

The core of Dane particles, the presently accepted hepatitis B virus nucleocapsid, contains two polypeptides (P19 and P45) with the antigenicity of hepatitis B e antigen (HBeAg). The antigenicity of hepatitis B core antigen (HBcAg) was not detectable in either of them by the conventional in vitro assay methods, despite the fact that both of these polypeptides were derived from the core of Dane particles. When a rabbit had been immunized with the purified preparation of P19 emulsified in complete Freund's adjuvant, however, humoral antibody against HBcAg was produced in addition to the antibody against HBeAg. Amino acid analysis of P19 disclosed a high content of arginine (12.9%), leucine (11.9%), serine (10.3%) and proline (10.2%). The amino acid composition of P19 was found to be strikingly similar to the composition of the 183 amino acid sequence deduced from the sequence of hepatitis B virus DNA which has been presumed to be encoding HBcAg. We conclude that both HBeAg and HBcAg are antigenic determinants borne by the major polypeptide (P19) constituting the core of Dane particles.

Amino Acids↗
PubMed1981

Bacteriophage phi X174-specific mRNA synthesis in cells deficient in termination factor rho activity.

A previous report (Hayashi et al., Proc. Natl. Acad. Sci. U.S.A. 73:3519-3523, 1976) indicated that in vivo bacteriophage phi X174 mRNA's terminate after genes J, F, G, and H. However, termination at these sites is not stringent. To determine whether termination of phi X174 transcription depends on rho factor activity, we introduced a temperature-sensitive rho mutation (nitA) into a phi X174-sensitive host cell line and determined termination sites in wild-type and nitA cells. We found that (i) normal phi X174 terminators were recognized in phi X174-infected nitA cells, (ii) the rho mutation relieved polar effects caused by nonsense mutations in the phage genome or by chloramphenicol treatment of the host cells, and (iii) polarity was not caused by premature termination of transcription at the site of the polar mutation. RNA synthesis continued beyond the site to the first rho-sensitive site.

Bacteriophage phi X 174↗
PubMed1981

Potentiation of natural killer activity of human lymphocytes by Staphylococcus aureus bacteria and its protein A.

Cytotoxic activity of human lymphocytes against the myeloid cell line K-562 was augmented greatly by 24-h incubation with Staphylococcus aureus Cowan I bacteria (SpA CoI) and its protein A. This effect was not observed when these stimulants were added after preincubation, suggesting that this activity was different from so-called lectin-induced cellular cytotoxicity. Potentiation required at least 12 to 18 h incubation of lymphocytes with these stimulants. Macrophage depletion did not affect the potentiation by protein A or SpA coI, although the potentiation by poly I:C or OK-432, an immunopotentiator of Streptococcus pyogenes was completely reduced. Further cell separation procedures revealed that neither T cells nor FcR- cells, which showed little natural killer (NK) activity, were enhanced by protein A or SpA coI. On the other hand, (a) null cells which were obtained from nylon column (NC)-passed fraction by depleting T cells and surface membrane Ig-positive cells, and (b) FcR+ E- cells which were obtained from NC-passed fraction by depleting FcR- cells and T cells, showed marked NK activity by themselves and were further augmented by these stimulants. FcR+ E+ cells failed to show NK activity even if they were stimulated by these stimulants. Thus, it was found that protein A and SpA CoI, as well as human interferon, could stimulate NC-non-adherent, FcR+, E- NK cells and potentiate markedly their NK activity.

Adjuvants, Immunologic↗
PubMed1981

Use of the immune adherence hemagglutination test for titration of breast cancer patients' sea cross-reacting with purified mouse mammary tumor virus.

Ninety-two sera from patients with breast cancer, 42 sera from patients with neoplastic diseases other than breast cancer and 59 sera from apparently healthy women were examined by means of the immune adherence hemagglutination (IAHA) test using purified mouse mammary tumor virus (MMTV) fron RII mouse milk. It was found that 36.4% (34/96) of the sera from breast cancer patients, 7.1% (3/42) of the sera from patients with other neoplastic diseases and 5.1% (3/59) of the sera from apparently healthy women showed a positive reaction. Among the IAHA positive sera from breast cancer patients, 82.9% (29/35) showed a titer of more than 1:16. On the other hand, none of the positive sera from patients with cancers other than breast cancer showed a titer of more than 1:16. The sera from 4 breast cancer patients, which showed a positive reaction with RII MMTV in the IAHA test, were tested to examine the specificity of the reaction by using milk samples from sources other than RII mice, including C57BL mice, dogs, cattle and humans. None of the 4 sera showed a positive reaction with milk samples from sources other than the RIII mouse.

Adult↗
PubMed1981

Immunological reaction between sera from neutron-irradiated W/FU rats and mouse mammary tumor virus.

Sera from W/Fu rats from the presence of anti mouse mammary tumor virus (MMTV) antibodies were examined by the use of an immunofluorescence (IF) test and an immune adherence hemagglutination (IAHA) test. Sera from W/Fu rats subjected to neutron irradiation or neutron irradiation followed by grafting of pituitary tumor (MtT) as a source of prolactin gave a positive IF reaction with mouse mammary tumor cells (MMT) producing type-A and type-B virus particles. Nine out of 20 (45.0%) sera from rats given irradiation alone, 17 out of 25 (68.0%) sera from rats subjected to irradiation followed by grafting of MtT and 8 out of 10 (80%) sera from rats given only grafting of MtT gave a positive reaction with the cells, whereas 5 out of 19 (26.3%) sera from normal rats showed a positive reaction with the cells. The specificity of the reaction was confirmed by the distribution pattern of specific fluorescence in MMT cells and by absorption experiments with suitable materials. The results of the IAHA test also showed that some sera from W/Fu rats reacted specifically with purified MMTV, although the incidence of appearance of antibodies in rat sera as detected by IAhA test was low as compared with that detected by IF tests. The IAHA titers of positive rat sera ranged from 1:8 to 1:128. Furthermore, the above results suggest that MtT grafting into W/Fu rats, whether or not they are subjected to neutron irradiation, results in an increase in the frequency of rats carrying antibodies against MMTV.

Animals↗