Search PubMed⌕ Search

Biomedical subjects

K Higashi

Publications and source records attributed to K Higashi.

At least 361 records · Page 20Linked to original sources
PubMed1983

Screening for carcinogens by DNA-synthesis inhibition test using mouse L-cells.

Bacterial test systems for potential carcinogens sometimes give false negative results. To overcome this problem, several short term test systems have been described. One of them is the DNA-synthesis inhibition test described by Painter (1977). Our DNA-synthesis inhibition test system using mouse L-cells gave positive results when monocrothaline, phenacetin and thioacetamide, which were negative in the Ames test, were tested.

Animals↗
PubMed1983

Altered distribution of constitutive forms of microsomal cytochrome P-450 in tumor-bearing mouse liver.

Changes of microsomal cytochrome P-450 species in the livers of mice were examined after the inoculation of Ehrlich ascites tumor cells i.p. into male ddY mice. The total content of hepatic cytochrome P-450 was observed to decrease around 6 days after the tumor-inoculation and reached the level of 40 to 50% of those of control mice (27.8 nmol P-450/g of control liver) after 10 days, while the liver weights of tumor-bearing mice slightly increased even at the end of the 2nd week. Microsomal proteins of tumor-bearing mice remained at the level of around 80% of control livers at the end of the 2nd week. The activity of 7-ethoxycoumarin deethylation decreased roughly in proportion to the content of microsomal cytochrome P-450. On the contrary, the specific activity of benzphetamine N-demethylase per nmol of P-450 in the tumor-bearing mouse liver increased to more than 2 fold of the value of normal liver (25 nmol HCHO/nmol P-450/min for control liver) during the last stage of the second week. These results suggest that the reduction of individual forms of cytochrome P-450 in the tumor-bearing mouse liver was not random and a new steady state of distribution of these hemeproteins was established under the pathological conditions.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1983

A spin-label and hydrogen-deuterium exchange reaction kinetics study of protein-lipid interactions in lipid-replaced Ca2+-ATPase of rabbit skeletal muscle sarcoplasmic reticulum.

The Ca2+-ATPase of sarcoplasmic reticulum from rabbit skeletal muscle was incorporated into vesicles made from dimyristoylphosphatidylcholine or dipalmitoylphosphatidylcholine. The Ca2+-ATPase activity of these reconstituted membranes became appreciable above 20 degrees C and 30 degrees C, respectively, in accord with the results of previous investigators. Measurement by the spin-labeling technique of the fluidity of the bulk lipid revealed the gel-to-liquid crystalline phase transition at 29 degrees C and 39 degrees C, respectively, while the fluidity of the boundary lipid in both samples was found to be low throughout the temperature range studied. The rotational mobility of the Ca2+-ATPase protein in both samples, measured by saturation transfer electron spin resonance, was also very low throughout the temperature range studied and its temperature-dependence did not show any break or jump corresponding to the phase transition of the bulk lipid. On the other hand, the structural fluctuation of the Ca2+-ATPase protein in dimyristoylphosphatidylcholine-recombinant, measured in terms of hydrogen-deuterium exchange reaction kinetics, showed a jump at about 27 degrees C, apparently in accordance with the phase transition of the bulk lipid. Results obtained in this study suggested that the Ca2+-ATPase protein molecules are in an aggregated state in these reconstituted membranes and that the Ca2+-ATPase activity is neither directly correlated to the fluidity of the boundary lipid nor to the rotational mobility of the Ca2+-ATPase, contrary to the suggestions of previous investigators (Hesketh et al. (1976) Biochemistry 15, 4145-4151; Hidalgo et al. (1978) J. Biol. Chem. 253, 6879-6887).

Animals↗
PubMed1983

Regulation by estrogen and progesterone of protein kinases in rabbit myometrium.

We report on hormonal regulation of protein kinases in the rabbit myometrium. The injection of estrogen or progesterone produced 5.2 +/- 0.7- or 4.7 +/- 0.4-fold increases, respectively, of the total activity when histone was used as the substrate in the cytosol fraction of the tissue. The analysis of the activity by DEAE-cellulose column chromatography revealed that estrogen had no effect on increases in the levels in both types I and II cAMP-dependent protein kinases, on the basis of mg protein, while progesterone produced a 50% decrease in type I cAMP-dependent protein kinase and a 50% increase in type II cAMP-dependent protein kinase. Thus, the activity ratio of types II to type I did not change by treatment with estrogen and increased from 2.8 to 7.9 with progesterone administration. As the activity patterns by treatment with human chorionic gonadotropin closely resembled those seen with progesterone, our findings in case of the latter hormone are probably valid. The results indicate that the levels of protein kinases in the myometrium are altered in response to estrogen and progesterone and may possibly be involved in the physiological functions of the tissue.

Animals↗
PubMed1983

Hormone treatments and pregnancy alter myosin light chain kinase and calmodulin levels in rabbit myometrium.

Myosin light chain kinase activity and the amount of calmodulin were measured in rabbit myometrium after the rabbits had been treated with oestrogen, progesterone and human chorionic gonadotrophin, and also during pregnancy. Injections of oestrogen and progesterone produced significant increases of of 2.8- and 2.1-fold in the enzyme activity/mg protein and of 1.4- and 1.2-fold in the calmodulin content/mg protein respectively. The increases seen with oestrogen treatment were inhibited by cycloheximide administration, suggesting that protein synthesis is involved in the process. Calmodulin increased about twofold in the particulate fraction under conditions of oestrogen and progesterone treatments and the raised level of calmodulin detected in the cytosol fraction was not due to translocation from the particulate fraction. During pregnancy the specific enzyme activity significantly increased in comparison with the values seen in samples from the non-treated rabbits. These findings suggest that myosin light chain kinase and calmodulin in the myometrium are under hormonal regulation and may play a role in expulsion of the fetus at the latter phase of pregnancy.

Animals↗
PubMed1983

Malignant degeneration of benign cystic teratoma of the bilateral ovaries: adenosquamous carcinoma in the right tumor and squamous carcinoma in the left tumor.

An extremely rare case of malignant degeneration arising separately in benign cystic teratoma of the bilateral ovaries is reported in a 51-year-old woman. The solid part of the right tumour consisted basically of squamous cell carcinoma, but had a small area of adenocarcinoma, whereas the solid part of the left tumour consisted of squamous cell carcinoma. It was found that in both the cystic teratomas, squamous cell carcinoma had developed separately from the columnar epithelium by a process of squamous metaplasia and malignant change in situ. It is suggested that these malignant degenerations of benign cystic teratoma of the bilateral ovaries had occurred independently due to local carcinogenic agents in the constituents of each cyst content.

Adenocarcinoma↗
PubMed1982

Purification and characterization of a Ca2+- and calmodulin-dependent protein kinase from rat brain.

A Ca2+- and calmodulin-dependent protein kinase was purified from rat brain cytosol fraction to apparent homogeneity at approximately 800-fold and with a 5% yield. The purified enzyme had a molecular weight of 640,000 as determined by gel filtration analysis on Sephacryl S-300 and a sedimentation coefficient of 15.3 S by sucrose density gradient centrifugation, and resulted in a single protein band of MW 49,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results suggest that the native enzyme has a large molecular weight and consists of 11 to 14 identical subunits. The purified enzyme exhibited Km values of 109 and 30 microM for ATP and chicken gizzard myosin light chain, respectively, and Ka values of 12 nM and 1.9 microM for brain calmodulin and Ca2+, respectively. In addition to myosin light chain, myelin basic protein, casein, arginine-rich histone, microtubule protein, and synaptosomal proteins were phosphorylated by the enzyme in a CA2+- and calmodulin-dependent manner. The purified enzyme was phosphorylated without the addition of the catalytic subunits of cyclic AMP-dependent protein kinase. Our findings indicate that there is a multifunctional Ca2+- and calmodulin-dependent protein kinase in the brain and that this enzyme may regulate the reactions of various endogenous proteins.

Animals↗
PubMed1982

Dissociation of alterations in levels of myosin light chain kinase and cyclic AMP-dependent protein kinase in rabbit myometrium during pregnancy.

The alteration in levels of myosin light chain kinase and cyclic AMP-dependent protein kinase was studied in rabbit myometrium during pregnancy. The specific activity of myosin light chain kinase was 160.9 +/- 2.7, 128.1 +/- 3.5, and 126.5 +/- 4.4% at the 10th, 20th and 28th days after pregnancy, respectively, in comparison with the value seen in samples from non-pregnant rabbits. On the other hand, the specific activity of cyclic AMP-dependent protein kinase gradually decreased to 75.9 +/- 1.7, 58.7 +/- 3.5 and 36.9 +/- 1.9% of that of the control at each time with the increase in the time of gestation. The protein kinase inhibitor was not involved in the decrease in cyclic AMP-dependent protein kinase. These results suggest that the dissociation of the dynamic states of the two enzymes may make it possible for the myometrium to efficiently respond to contraction in the last stage of pregnancy.

Animals↗