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Biomedical subjects

S Horiuchi

Publications and source records attributed to S Horiuchi.

At least 361 records · Page 20Linked to original sources
PubMed1981

Degradation kinetics and mechanism of aminocephalosporins in aqueous solution: cefadroxil.

The degradation kinetics and mechanism of a new, orally effective cephalosporin derivative, cefadroxil, in aqueous solution were investigated at pH 2.51-11.5 at 35 degrees and ionic strength 0.5. The degradation rates were determined by high=pressure liquid chromatography. At constant pH and temperature, the degradation followed first-order kinetics and a log k-pH profile was presented. The shape of the rate-pH profile resembled that for cephalexin or cephradine under the same conditions. Citrate and phosphate buffers enhanced general acid and base catalysis of the degradation. In aqueous solution, cefadroxil was shown to degrade by three parallel reactions: (a) intramolecular aminolysis by the C-7 side-chain amino group on the beta-lactam moiety, (b) water-catalyzed or spontaneous hydrolysis, and (c) beta-lactam cleavage by the nucleophilic attack of hydroxide ion. In neutral and weak alkaline solutions, the main degradation products were two piperazine-2, 5-diones and 3-hydroxy-4-methyl-2(5H)-thiophenone, the former being formed from Reaction a, while the latter arose via the degradation pathways of Reaction b and/or c.

Buffers↗
PubMed1980

The molecular forms of gamma-glutamyl transferase in bile and serum of icteric rats.

Alterations in the molecular form of gamma-glutamyl transferase (5-glutamyl)-peptide:amino-acid 5-glutamyltransferase, EC 2.3.2.2.) were studied in the bile and serum of rats under surgical ligation of the bile duct. Polyacrylamide gel electrophoresis of the bile, followed by the enzyme stain, revealed a major, slowly migrating broad band and a minor, faster migrating band. The former was converted to the latter upon limited proteolysis of the bile with a very small amount of papain. This conversion was accompanied by a decrease in molecular size of the enzyme. Both enzyme forms were specifically adsorbed to a concanavalin A-Sepharose column. Most of the papain-treated enzyme preparation could be eluted from the column by alpha-methyl-D-glucoside, a haptenic sugar of this lectin. On the other hand, the predominant form of the enzyme in the untreated bile was eluted only in the presence both of the sugar and Triton X-100. Based on the chromatographic behavior of the two enzyme forms (detergent-solubilized and protease-solubilized form) purified from rat renal brush border membrane on concanavalin A-Sepharose column, it was concluded that the predominant form of the enzyme in the bile was the detergent-solubilized form and that the minor component represents the protease-solubilized enzyme. The serum from icteric rats was also found to contain both types of the enzyme. However, the relative amount of the protease-solubilized form to the detergent-solubilized form in the serum was much greater than that in the bile. These findings suggested that gamma-glutamyl transferase in the hepatobiliary membrane systems was solubilized into the bile mainly as the detergent-solubilized form, and that, during the process of translocation into the blood circulation, the enzyme was partly converted to the protease-solubilized form by some protease-like action.

Animals↗
PubMed1980

Circular dichroism of cattle rhodopsin and bathorhodopsin at liquid nitrogen temperatures.

The photoevent in vision has been considered to be the conversion of rhodopsin to bathorhodopsin, which is caused by photoisomerization of the chromphoric retinal. Recently some objections were raised to this hypothesis. The reliability of the hypothesis was verified by measurement of circular dichroism of bathorhodopsin. The measurement of circular dichroism of rhodopsin extract (containing 66% or 75% of glycerol) at liquid nitrogen temperatures (-195 degrees C) by a conventional spectropolarimeter induced an extraordinary large signal, owing to linear dichroism originated from conversion of rhodopsin to bathorhodopsin by the measuring light. The similar linear dichrolism can be induced by irradiation of rhodopsin extract at -195 degrees C with polarized light or natural light. At photosteady state the linear dichroism disappeared. Circular dichroism spectrum of cattle rhodopsin displayed two positive peaks ([theta]max = 80 800 degrees at 335 nm, and [theta]max = 42 600 degrees at 500 nm) at -195 degrees C, whereas, bathorhodopsin displayed a positive peak ([theta]max = 43 100 degrees at 334 nm) and a negative peak ([theta]max = 163 000 degrees at 540 nm). The change of the positive sign to negative one at alpha-band of circular dichroism spectrum supports the hypothesis that the conversion of rhodopsin is due to rotation of the chromophoric retinal about C-11--12 double bond ('photoisomerization model').

Animals↗
PubMed1979

Effects of a systematic application of human chorionic gonadotropin, gonadotropin-releasing hormone analog and bovine anterior pituitary gonadotropin in cows with cystic ovarian disease.

Fourty-one cows with ovarian follicular cysts (cysts) diagnosed by rectal palpation and observation of estrus behavior were injected intramuscularly (i.m.) with 20,000 IU of human chorionic gonadotropin (HCG). Ten days after this treatment all the cows were examined per rectum for changes in the ovaries with special regard to luteinization of cysts. Cows not responding to HCG were administered 500(10)mug of an analog of gonadotropin-releasing hormone (Gn-RH), Des-Gly-LH-RH-ethylamide, i.m.. If the cysts remained unchanged 10 days subsequent to the second treatment, a third treatment, 400 KE of bovine anterior pituitary gonadotropin (APG), was given i.m. HCG was clinically effective in only 8 cows (20 %). All of the 8 cows conceived. Of 33 cows not responding to HCG, 18 cows (55 %) responded to Gn-RH analog and 12 cows (36 %) conceived. Eleven (73 %) of 15 cows failing to respond to Gn-RH analog were successfully treated with APG and 6 cows (40 %) conceived. In 37 cases, treatment effects were also evaluated by determining serum levels of progesterone prior to and 10 days subsequent to each treatment. When effects of treatment were judged by 1.0 ng/ml or more increase of serum progesterone levels 10 days after treatment, HCG was effective in 13 of 37 cows (35 %), retreatment with Gn-RH analog was successful in 8 of 16 cows (50 %) and APG was ineffective in 3 cows not responding to both HCG and Gn-RH analog. It may be concluded that the therapeutic effect of HCG is disappointing and about half of the cases not responding to HCG were successfully treated with Gn-RH analog. If the cows did not respond to both HCG and Gn-RH analog, they may not respond to APG either.

Journal Article↗
PubMed1979

Myosin from abdominal flexor muscle in a crayfish, Procambarus clarki Girard.

1. Crayfish (Procambarus clarki) myosin was obtained from abdominal flexor muscle. The Ca2+-ATPase activity of crayfish myosin was much lower than that of rabbit skeletal myosin. However, F-actin-activated Mg2+-ATPase of crayfish and its superprecipitation closely resembled those of rabbit skeletal myosin. This fact suggests that the ability of crayfish myosin to combine with F-actin is essentially the same as that of skeletal myosin, although the chemical structures of both the myosin molecules when involved in their Ca2+-ATPast activity must be different from each other. 2. Crayfish and rabbit skeletal myosins were subjected to SDS-polyacrylamide gel electrophoresis. Crayfish myosin was found to have one heavy chain and two distinct light chain components (CF-gl and CF-g2), which have molecular weights of 18,000 and 16,000, respectively. These light chains correspond in molecular weight to the light chains (SK-g2 and SK-g3) in rabbit skeletal myosin. 3. CF-g1 could be liberated from the crayfish myosin molecule reacting with 5,5'-dithio-bis (2-nitrobenzoic acid), (Nbs2), without recovery of ATPase activity by the addition of DTT. These properties are equivalent to those of SK-g2 in rabbit skeletal myosin, although Nbs2-treated crayfish myosin did not recover its ATPase activity at all.

Adenosine Triphosphatases↗