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Biomedical subjects

K Horiuchi

Publications and source records attributed to K Horiuchi.

At least 271 records · Page 15Linked to original sources
PubMed1980

Mode of action of furosemide on the chloride-dependent short-circuit current across the ciliary body epithelium of toad eyes.

The effects of furosemide on the chloride-dependent short-circuit current across the toad ciliary epithelium were examined. Under control conditions, the short-circuit current obeyed Michaelis-Menten kinetics against medium chloride concentration, the Michaelis constant (Km) for chloride being 90 mM and the maximal short-circuit current (Vmax) 128 mu A/cm2. Furosemide added to the aqueous side of the epithelium rapidly reduced the short-circuit current; the effect was reversible. The effect of furosemide addition to the stromal side was much smaller and slower than that from the aqueous side. The dose-dependent range of furosemide action was from 0.1 micro M to 1 mM with 50% inhibition occurring at about 3 micro M. Lineweaver-Burk plot of the short-circuit current against the chloride concentration showed that furosemide decreased the value of Vmax and increased the Km; the inhibition being of mixed type. A Hill plot of the dose-response curve yielding a slope of unity suggested one furosemide molecule combines with one chloride transport site. Probenecid, a competitive inhibitor of organic acid transport reduced the effects of furosemide significantly when added simultaneously. The involvement of organic acid transport system in the mechanism of furosemide action on chloride transport was suggested.

Animals↗
PubMed1980

Origin of DNA replication of bacteriophage f1 as the signal for termination.

Restriction fragments that contain the origin of DNA replication of bacteriophage f1 were inserted in vitro into circular f1 DNA molecules to form genomes that contain two origins. This DNA was used to transfect Escherichia coli. Analyses of the DNA of the progeny phage indicated that one origin and the DNA segment located between the two origins in the infecting DNA molecules had been eliminated. This result is interpreted to mean that the nucleotide sequence of the origin for plus (viral)-strand synthesis also serves as the signal for the termination of DNA synthesis.

Base Sequence↗
PubMed1979

Photochemical reaction of 9-cis-retro-gamma-rhodopsin at low temperatures.

9-cis-Retro-gamma-rhodopsin (lambda max = 420 nm) was prepared from 9-cis-retro-gamma-retinal and cattle opsin. After cooling to liquid nitrogen temperature (77 K), the pigment was irradiated with light at 380 nm. The spectrum shifted to the longer wavelengths, owing to formation of a batho product. This fact indicates that the conjugated double bond system from C-5 to C-8 of the chromophoric retinal in rhodopsin was not necessary for formation of bathorhodopsin. Reirradiation of the batho product with light at wavelengths longer than 520 nm yielded a mixture composed of presumably 9- or 11-cis forms of retro-gamma-rhodopsin. These three isomers are interconvertible by light at liquid nitrogen temperature. Thus the retro-gamma-rhodopsin system is similar in photochemical reaction at 77 K to cattle rhodopsin system. Each system has its own batho product. Based on these results, it was infered that the formation of batho-rhodopsin is due to photoisomerization of the chromophoric retinal of rhodopsin and is not due to translocation of a proton on the ring or on the side chain from C-6 to C-8 of the chromophoric retinal to the Schiff-base nitrogen.

Animals↗