Biomedical subjects

A Yasutake

Publications and source records attributed to A Yasutake.

At least 55 records · Page 3Linked to original sources

PubMed1986

Strain difference in mercury excretion in methylmercury-treated mice.

The strain differences in mercury excretion and organ distribution after administration of methylmercuric chloride (5 mg/kg) were studied in male mice of four strains, C57BL/6N, BALB/cA, C3H/HeN and AKR. The urinary excretion rate of mercury for 5 days following administration was 3.9-4.7 times higher in the C57BL strain than in the other three strains, whereas the mercury level in feces was highest in the AKR strain. Although the blood mercury concentration in the C57BL strain was almost half that in the others up to the 5th day, the plasma levels did not vary so widely. C57BL showed the highest ratio of plasma to whole blood mercury level, which was thought to originate from the lower affinity of methylmercury for hemoglobin. The variation of the plasma/whole blood ratios was rather small throughout the experimental period in each strain examined. In the C57BL strain, the mercury levels in brain, liver, kidney and blood were significantly lower on and after the 5th day than in the other three strains, probably because of the rapid elimination of body mercury into urine, but the mercury uptake by the brain and kidney 5 min after administration was at a rather higher rate than in the other strains. On the other hand, the highest tissue levels were shown by the C3H strain in the brain and liver, and by the BALB/c strain in the kidney. It was suggested that in the C57BL strain, the higher mercury distribution in plasma and rapid uptake by the kidney might result in higher urinary excretion.

Animals↗

PubMed1986

Sex and age differences in mercury distribution and excretion in methylmercury-administered mice.

Sex differences in mercury distribution and excretion after single administration of methylmercury chloride (MMC, 5 mg/kg) were studied in mice. A sex difference in urinary mercury excretion was found in sexually mature mice (age of 7 wk) of C57BL/6N and BALB/cA strains. Males showed higher mercury levels in urine than females, though no significant difference was found in fecal mercury levels 24 h post exposure to MMC. The higher urinary excretion rates in males accounted for significant lowering of mercury levels in the brain, liver, and blood, but not in the kidney, which showed higher values. At 5 min, however, these sex difference was found only in the kidney, showing higher levels in males. Changes in mercury distribution with time were studied in C57BL/6N mice. The brain mercury increased in both sexes up to 3 d, and decreased only in males on d 5. Liver and blood mercury decreased with time in both sexes, and these were constantly higher in females than in males. Renal mercury in males decreased to similar levels to females on d 3. The sex differences at various ages were studied with C57BL/6N mice 24 h after dosing. Two-week-old mice, the youngest in this study, did not show significant sex difference in the mercury distribution and excretion, and their urinary mercury levels were much lower as compared to the older mice. Then, urinary mercury excretion in both sexes increased at 4 wk of age and then decreased at 45 wk of age. At 4, 7, 10, and 45 wk of age, males showed higher urinary mercury levels than females. These studies demonstrated sex and age differences in the mercury distribution and urinary excretion after methylmercury administration in mice. From these findings, it has been suggested that urinary mercury excretion may be related to sex hormones, especially androgens.

Aging↗

PubMed1982

Cyclic peptides. XIV. Syntheses of [4-l-leucine]-, [4-D-leucine]-, and [3-L-proline, 4-D-leucine]-Cyl-2.

Cyl-2 is a phytotoxic cyclic tetrapeptide with the sequence of cyclo(D-Tyr(Me)-L-Ile-L-Pip-Aoe-): Aoe, 2-amino-8-oxo-9,10-epoxydecanoic acid. The configuration of Aoe is unknown. Three analogs, cyclo(-D-Try(Me)-L-Ile-L-Pip-L(and D)-Leu-) (1 and 2) and cyclo(-D-Tyr(Me)-L-Ile-L-Pro-D-Leu-) (3), were synthesized and spectroscopic features of these analogs were compared. 1H-N.m.r. spectra of cyclo(D-Tyr(Me)-L-Ile-L-Pip-L-Leu) (1), cyclo(-D-Tyr(Me)-L-Ile-L-Pro-L-Leu-) (4), and Cyl-2 showed a similar pattern. On the other hand, the spectra of analogs 2 and 3 showed a different pattern, the Ile-Pro bond in 3 being in cis conformation.

Indicators and Reagents↗

PubMed1981

Reactivity of human leukocyte elastase and porcine pancreatic elastase toward peptide 4-nitroanilides containing model desmosine residues. Evidence that human leukocyte elastase is selective for cross-linked regions of elastin.

Elastin contains a number of cross-linking amino acid residues such as desmosine and isodesmosine which are primarily hydrophobic in character, but have a positively charged pyridinium ring. These cross-linking residues are formed by the action of lysyl oxidase upon Lys residues in tropoelastin, a precursor of elastin. A series of tetrapeptide 4-nitroanilides which contain Lys and a series of modified lysine residues were synthesized. The modified lysine residues [epsilon-carbobenzyloxy (Z), epsilon-benzoyl (Bz), epsilon-benzimidoyl (Bim), and epsilon-2-picolinoyl (Pic)] have various characteristics of desmosine and isodesmosine residues, such as a positive charge, a hydrophobic aromatic ring, or a pyridine ring. The reactivity of the tetrapeptide 4-nitroanilides containing the model desmosine residues at P4, P3, or P2 with human leukocyte (HL) and porcine pancreatic (PP) elastase was measured at pH 7.5 and 25 degrees C. HL elastase exhibited high reactivity toward the substrates with P4 or P3 hydrophobic groups (Z, Bz, or Pic), and MeO-Suc-Lys(Pic)-Ala-Pro-Val-NA is 7 times more reactive than the previous best HL elastase substrate, MeO-Suc-Ala-Ala-Pro-Val-NA. The major change occurred in KM values. The substrates containing Lys residues were either nonreactive or poor. Except for two substrates with P2 hydrophobic residues (Bz and Pic), PP elastase was less reactive toward the substrates containing model desmosine residues than toward MeO-Suc-Ala-Ala-Pro-Val-NA. The data support the hypothesis that HL elastase cleaves elastin selectively ner cross-linking residues. The results also indicate that HL elastase binds tightly to these regions and would be poorly effective toward regions of elastin or tropoelastin which contain Lys residues.

Amino Acids↗

PubMed1981

Cyclic peptides. X. Bitter taste and chymotryptic hydrolysis of cyclic depsidipeptides containing a tryptophan residue.

Four stereoisomers (I-LL, I-LD, I-DL and I-DD) of a cyclic depsidipeptide (I) containing a tryptophan and a 2-hydroxy-4-methylpentanoic acid residue were synthesized, and their taste and chymotryptic susceptibility were examined. Compound I-LL is a depsipeptide analog of a bitter principle BP-II, cyclo(-L-Trp-L-Leu-), obtained from casein hydrolyzate. All of the four stereoisomers of I are strongly bitter to taste. Another depsipeptide analog, L-aspartyl-L-2-hydroxy-3-phenylpropanoic acid methyl ester, of the sweet H-L-Asp-L-Phe-OMe showed bitter taste instead of sweet. Chymotrypsin hydrolyzed I-LL and I-LD in moderate rates, and I-DL and I-DD very slowly.

Chymotrypsin↗

PubMed1980

Cyclic peptides. VIII. Synthesis and tryptic hydrolysis of cyclic depsidipeptides containing a lysine residue.

Four stereoisomers of a cyclic depsidipeptide containing a lysine and a 2-hydroxy-3-phenylpropanoic acid (Hpp) residue have been synthesized and their susceptibility toward trypsin examined. Trypsin hydrolyzed cyclo(-L-Lys-L-Hpp-) (I-LL) and cyclo(-L-Lys-D-Hpp-) (I-LD) rapidly and cyclo(-D-Lys-L-Hpp-) (I-DL) and cyclo(-D-Lys-D-Hpp-) (I-DD) very slowly. Proteolytic coefficients of these substrates and a reference compound are shown as follows: I-LL, 112; I-LD, 34; I-DL, 0.34; I-DD, 0.11, and Ac-L-Lys-OEt, 44. Possible mode of actin of trypsin on these substrates was discussed.

Amino Acid Sequence↗

PubMed1980

Cyclic peptides. VII. Synthesis and conformation of diastereomeric analogs of cyl-2 containing L-proline and L-leucine.

Two diastereomeric cyclic tetrapeptides with a sequence of cyclo (-D (and L)-Tyr (me)-L-Ile-L-Pro-L-Leu-) (ID and IL) have been synthesized, which are simplified analogs of a phytotoxic peptide Cyl-2, and contain an L-proline and an L-leucine residue in place of an L-pipecolic acid and a 2-amino-8-oxo-9,10-epoxydecanoic acid residue, respectively, in Cyl-2. The cyclization of the H-D-Tyr(Me)-L-Ile-L-Pro-L-Leu-ONSu proceeded smoothly to give ID in excellent yield (50%), but the cyclization of H-L-Tyr(Me)-L-Ile-L-Pro-L-Leu-ONSu gave IL in much lower yield (10%). Based on the results of 1H- and 13C-n.m.r. studies, differential N-methylation and model buildings of ID, the backbone structure of ID has been proposed to be a unique trans-trans-cis-trans conformation, the L-Ile-L-Pro bond being cis.

Amino Acid Sequence↗

PubMed1979