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Biomedical subjects

A Ito

Publications and source records attributed to A Ito.

At least 883 records · Page 49Linked to original sources
PubMed1984

Spinal cord tumors induced by N-ethyl-N-nitrosourea in rats: presence of spinal subpial target cells.

The correlation between induction of spinal cord tumor by N-ethyl-N-nitrosourea (ENU) (CAS: 759-73-9; 1-ethyl-1-nitrosourea) and postnatal cellular differentiation of the spinal cord was examined in 6 different strains of rats [noninbred Wistar and inbred F344, WF, LE, WF (female) X LE (male), and LE (female) X WF (male)]. By perinatal injection of 40 mg ENU/kg, 258 spinal cord tumors were induced in 175 of 372 ENU-treated rats. The spinal cords of rats at ages ranging from day 1 to day 8 after birth were particularly susceptible to the oncogenic effect of ENU. All spinal cord tumors developed in the white matter without any segmental predilection site. Moreover, most (93%) were found in the subpial region of the spinal cord and were classified as oligodendrogliomas. Morphologic and autoradiographic examinations revealed accumulation of spinal subpial immature glial cells from day 1 to day 8 after birth when the spinal cord had a high susceptibility and most of the cells were destined to differentiate into oligodendrocytes. These data show the existence of target cells in the spinal cords of rats after ENU carcinogenesis.

Aging↗
PubMed1984

Prolactin and aging: X-irradiated and estrogen-induced rat mammary tumorigenesis.

Both sexes of inbred WF rats at either 8 or 28-60 weeks of age were exposed to 200 rad whole-body radiation, 2.5 or 5.0 mg 17 beta-estradiol (E2), or both agents The female rats treated with E2 alone or with both X-rays and E2 at 8 weeks of age showed a high incidence of mammary carcinomas (MCA), a large increase in pituitary weight, and a rise in serum prolactin (PRL) levels. However, the same treatments to males did not induce MCA despite a moderate increase in both pituitary weight and serum PRL. Ovariectomy prior to E2 treatment failed to modify the occurrence of MCA or pituitary tumors. When X-rays and E2 were given to female rats at 28-60 weeks of age, pituitary weight, serum PRL levels, and the incidence of MCA were unaffected. When the E2 pellet was kept for the first 24 weeks and withdrawn during the last 12 weeks, the incidence of MCA, pituitary weight, and serum PRL was low. It was concluded that: 1) the pituitary glands of young female rats were susceptible to E2 treatment but were insensitive in older females, and 2) the occurrence of MCA in female rats appeared to be promoted by elevated PRL levels secreted by E2-induced pituitary tumors. Mammary tissue of male rats was less sensitive to PRL levels in the development of MCA.

Aging↗
PubMed1984

Synchrotron system for monochromatic uv irradiation (greater than 140 nm) of biological material.

An irradiation system of monochromatic uv radiation down to the wavelength of 140 nm was constructed for biological irradiation experiments in the vacuum-uv range using synchrotron radiation (SR) from the electron storage ring. The system consists of premirror chamber, vacuum-uv monochromator, irradiation chamber, and vacuum systems. Along with the detailed description of all components of the system, the installation at the storage ring and the performance characteristics are presented.

Particle Accelerators↗
PubMed1984

Correlation between induction of duodenal tumor by hydrogen peroxide and catalase activity in mice.

Incidences of duodenal tumor induced by oral administration of hydrogen peroxide (HPO) and catalase activities in the duodenal mucosa, blood and liver were correlated in C3H/HeN, C57BL/6N, (C57BL X C3H)F1 (B6C3F1) and hypocatalasemic C3H/Cbs mice. A solution of 0.4% HPO was given to the mice as drinking water for about 6 months. Incidences of duodenal tumor were 11.1% in C3H, 31.8% in B6C3F1, 100% in C57BL and 91.7% in C3H/Cbs mice. Catalase activities (10(-4) k/mg protein) in the duodenal mucosa, blood and liver were 5.3, 7.8 and 75.3 in C3H, 1.7, 7.7 and 62.8 in B6C3F1, 0.7, 5.1 and 40.7 in C57BL, and 0.4, 0.4 and 33.3 in C3H/Cbs mice, respectively. The coefficients of correlation (r) of catalase activities with the incidences of duodenal tumor in C3H, B6C3F1 and C57BL mice are -0.83 in duodenal mucosa, -0.98 in blood and -0.99 in liver. The results indicate that the incidence of duodenal tumor induction by HPO is dependent on the individual mouse strain and may be determined by the genes controlling the catalase activities.

Animals↗
PubMed1984

Action spectra for inactivation of dry phage T1 after monochromatic (150-254 nm) synchrotron irradiation in the presence and absence of photoreactivation and dark repair.

Dry phage T1 was irradiated with monochromatic uv radiation (150-254 nm) in vacuo. The inactivation sensitivity was highest at 150 nm. On Escherichia coli Bs-1, the phage inactivation sensitivity was two and four times higher at 150 nm than at 254 and 230 nm, respectively. Action spectra for phage inactivation on both E. coli B and Bs-1 fit the absorption spectrum of phage DNA, except around 190 nm. The host-cell- reactivable fraction for vacuum-uv radiation (below 190 nm) was smaller than that with far-uv radiation. There was almost no photoreactivation at 150 nm, in contrast to a photoreactivation sector of about 0.3 at 254 nm.

DNA Repair↗
PubMed1983

Two homologous cytochromes b5 in a single cell.

The amino acid sequence of the heme-binding domains of rat liver cytochromes b5 from outer mitochondrial membranes and from microsomes has been determined by a combination of automatic and manual degradation of fragments generated by trypsin digestion and by cleavage at tryptophan. Tryptic peptides were separated by high-pressure liquid chromatography. The sequence of microsomal cytochrome b5 is identical with the one published by Ozols and Heinemann after completion of this study [Biochim. Biophys. Acta (1982) 704, 163-173]. The sequence of outer membrane cytochrome b5 differs from the microsomal one at 38 positions out of 91. There are 40 positions invariant between this sequence and the eight microsomal sequences published thus far. The non-conservative substitutions are located at the surface of the known three-dimensional structure of calf microsomal cytochrome b5 except for the substitution of histidine-15 by arginine. This paper brings the final proof that two iso-cytochromes b5 exist in the same cell. Their high degree of similarity as well as their differential cellular localization raise some questions which are briefly discussed.

Amino Acid Sequence↗
PubMed1983

Comparative evaluation of depressed automaticity in sick sinus syndrome by Holter monitoring and overdrive suppression test.

To ascertain whether the long cardiac pauses on the Holter ECGs of patients with the sick sinus syndrome were related to the spontaneously occurring overdrive suppression, the heart rates for the 12 seconds preceding the cardiac pauses longer than 5 seconds were compared with that averaged for 24 hours. Even in six out of seven patients with bradycardia-tachycardia syndrome the former rate was not significantly greater than the latter, indicating that episodes of such long cardiac pauses may not result from spontaneously occurring overdrive suppression. This observation was also consistent with the result that no statistically significant correlation was obtained between the maximum pauses measured from Holter ECGs of sick sinus syndrome and those obtained by the overdrive suppression test. In conclusion, many episodes of long life-threatening cardiac pauses observed in sick sinus syndrome may be attributed to accidental depression of the sinus nodal and subsidiary pacemaker activity rather than to spontaneously occurring overdrive suppression; therefore, Holter monitoring may be useful as an additional tool for diagnosis of sick sinus syndrome.

Adolescent↗
PubMed1983

Hymenolepis nana: maturation in an immunosuppressed unnatural rat host.

When eggs of the dwarf tapeworm Hymenolepis nana, cycled exclusively and directly through mice for more than 10 years, were inoculated into previously uninfected inbred Fischer (F344) strain rats, they failed to mature in the rat intestinal lumen. Eggs of H. nana inoculated into the rat developed normally into cysticercoids (cysts) in the intestinal tissue, but thereafter failed to mature in the lumen except when the host was treated with cortisone acetate from the day of cyst maturation. The Fischer rat initially given eggs of H. nana became completely immune to egg challenge within 2 days of egg inoculation; no cysts derived from challenge eggs were found in the immunized rat. Immunosuppression, assessed by the success of cyst recovery in the tissue 4 days after egg challenge, had no promotive effect on the recovery of adult worms derived from eggs initially inoculated. Rats initially given eggs and immunosuppressed by cyclophosphamide or antithymocyte serum did not harbor any adult worms. Cortisone acetate treatment which was sufficient for eggs inoculated to mature (a total of 75 or even 200 mg, from Day 5 of egg inoculation) had no effects of immunosuppression, whereas cortisone acetate treatment which was sufficient for immunosuppression (a total of 150 mg from Day -2, two days prior to the initial egg inoculation) induced some adult formation as well. In addition, when mouse-derived cysts were inoculated into the rat instead of eggs, they also failed completely to mature even when the rat was treated with cyclophosphamide or antithymocyte serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Partial purification and characterization of gelatinase and metal dependent peptidase from rabbit uterus and their synergistic action on gelatin in vitro.

Two metal dependent proteases were investigated in rabbit uterus using a synthetic substrate, 2,4-dinitrophenyl-Pro-Gln-Gly-Ile-Ala-Gly-Gin-D-Arg (Dnp-peptide). One was extracted by homogenization in 50 mM Tris-HCl/0.25% Triton X-100/100 mM CaCl2, pH 7.4, from rabbit uterus, and the other from the insoluble fraction by heating at 60 degrees C for 4 min in 50 mM Tris-HCl/100 mM CaCl2, pH 7.4. Both enzymes were partially purified by gel filtration, ion-exchange chromatography and chromatofocusing, and further characterized. The soluble enzyme was a metal dependent peptidase, and hydrolysed 4-phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-D-Arg as well as Dnp-peptide. Its molecular weight was about 7.0 X 10(4), and the cleavage sites for Dnp-peptide were Gln-Gly and possibly Gly-Ile in the ratio of 3:1. On the other hand, the enzyme extracted from the insoluble fraction was present as a latent form, and was found to be activated by 4-aminophenylmercuric acetate but not by trypsin. The activated enzyme hydrolysed gelatin, in addition to Dnp-peptide, indicating that the enzyme is a gelatinase. The molecular weight was about 7.4 X 10(4) for the active form, and the cleavage site for Dnp-peptide was only the Gly-Ile bond. The rabbit uterine metal dependent peptidase obtained here had negligible activity on gelatin, but once it had been cleaved by the above gelatinase, the presence of metal dependent peptidase accelerated the action of gelatinase. Thus, the actions of both enzymes on gelatin were found to be synergistic.

Amino Acid Sequence↗
PubMed1983

Atrophic gastritis induced by injection of xenogeneic stomach antigen in mice.

Wistar/Furth rat stomach antigen emulsified with an equal volume of Freund's complete adjuvant was subcutaneously injected into several strains of mice. Atrophy of the glandular stomach was produced in A/HeJ mice, but not in CF1, C57BL/6J or ICR/JCL mice. Atrophy of the glandular stomach was found to become most severe in 4-month-old animals. In 6-month-old mice and 12-month-old mice, atrophy was not observed. The increase in atrophy corresponds with the dose of antigen.

Age Factors↗