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Biomedical subjects

M Irie

Publications and source records attributed to M Irie.

At least 325 records · Page 18Linked to original sources
PubMed1977

Photooxidation and carbethoxylation of a minor ribonuclease from Aspergillus saitoi.

In order to investigate the nature of amino acid residues involved in the active in the active site of a ribonuclease from Aspergillus saitoi, the pH dependence of the rates of inactivation of RNase Ms by photooxidation and modification with diethylpyrocarbonate were studied. (1) RNase Ms was inactivated by illumination in the presence of methylene blue at various pH's. The pH dependence of the rate of photooxidative inactivation of RNase Ms indicated that at least one functional group having pKa 7.2 was involved in the active site. (2) Amino acid analyses of photooxidized RNase Ms at various stages of photooxidative inactivation at pH's 4.0 and 6.0 indicated that one histidine residue was related to the activity of RNase Ms, but that no tryptophan residue was involved in the active site. (3) 2',(3')-AMP prevented the photooxidative inactivation of RNase Ms. The results also indicated the presence of a histidine residue in the active site. (4) Modification of RNase Ms with diethylpyrocarbonate was studied at various pH's. The results indicated that a functional group having pKa 7.1 was involved in the active site of RNase Ms.

Aspergillus↗
PubMed1977

Thyroid function in molar pregnancy.

Various aspects of thyroid hormone economy were examined in 15 patients with molar pregnancy and in 5 patients with choriocarcinoma. None of the patients with molar pregnancy was clinically thyrotoxic, though serum thyroxine (T4) was increased in 13 and free T4 concentrations were above normal in four of ten in whom measurements were made. In 2 patients with elevated serum T4 levels and in one patient with normal serum T4 levels, the daily rate of T4 disposal was increase, and most of 131I derived from 131I-T4 was excreted into urine in two patients in whom estimation of urinary excretion was made. Serum total triiodothyronine (T3) concentrations closely paralleled those of serum T4, but T3/T4 ratios were lower than those previously found in patients with toxic diffuse goiter of Graves' disease. Unresponsiveness to exogenous thyrotropin-releasing hormone (TRH) was observed in 5 patients with molar pregnancy whose serum total T4 and T3 levels were increased. Human chorionic gonadotropin (hCG) concentrations in serum ranged from 0.5 to 2830 IU/ml and were less than 200 IU/ml in 36% of the patients, possibly because molar pregnancy was diagnosed by ultrasonography, rather than high titers of urinary or serum hCG. Serum thyroid stimulating activity measured by the McKenzie bioassay closely paralleled values for hCG (r:+0.94). All thyroid abnormalities disappeared quickly after removal of the mole. In choriocarcinoma, no abnormality of thyroid function was found. These results suggest that: 1) some patients with molar pregnancy display a marked elevation of serum T4, T3, and free T4 concentrations, probably as a result of the action of a thyroid stimulator which is closely related to serum hCG or may be hCG itself; 2) T4 production rates are increased in these patients, and the pituitary responds to TRH in a manner similar to that found in thyrotoxicosis. Despite this, frank clinical thyrotoxicosis is usually absent, possibly because of relatively low serum T3/T4 ratios, possibly because of the limited duration of thyroid hyperfunction, and possibly because of other factors that for the present remain unknown.

Adult↗
PubMed1976

[Microdetermination of TSH in dried blood spot--its use in the mass-screening for congenital or juvenile primary hypothyroidism (author's transl)].

Blood TSH (Thyroid Stimulating Hormone) was successfully measured by radioimmunoassay in a dried blood spot on filter paper which is obtained in newborn screening for metabolic disorders. By this method, the minimal detectable level of blood TSH was about 10 muU/ml, which is the approximate upper limit of normal values of blood TSH. Good correlation was found between the TSH values obtained from this specimen and from liquid serum samples from the same subjects. The duplication of assay of a single sample was not necessary. A screening program using the method described here was initiated and a 4 year old infant was found to have primary hypothyroidism, later verified by other testing methods. Since the technique is simple and adequately sensitive for the detection of hypothyroidism, it could be a valuable method for use in mass-screening of newborns for congenital hypothyroidism.

Child, Preschool↗
PubMed1976

Further studies on the specificity of the minor ribonuclease from Aspergillus saitoi.

In order to investigate the base specificity of the minor RNase [EC 3.1.4.23] from Aspergillus saitoi, the kinetic constant of the enzyme was measured with 16 dinucleoside phosphates (XpY's) as substrates at pH 5.5 and 25 degrees. The maximum rates of transesterification of GpY's were in the range of 10,000 to 2,800 and were markedly larger than those of other XpY's, including XpG's. The average Km values of UpY, CpY, ApY, and GpY increased in the order A, C, U, and G. This order coincides with that of the rates of release of 4 common nucleotides from RNA by RNase Ms (the rates decreased in the order 3'-GMP, 3'-AMP, 3'-CMP, and 3'-UMP), except for the case of GpY. Therefore the rates of release of nucleotides seem to be dependent on the affinity constant of the X base in XpY, except in the case of GpY. The high rate of release of guanylic acid from RNA was explained by the findings that higher rates of hydrolysis of GpY's compensate for their lower affinity to the enzyme. These results suggested that the base specificity was rather dependent upon the X nucleotide in XpY. The Ki values of various nucleotides and nucleosides towards RNase Ms were measured. These compounds inhibited the RNase competitively. Although the inhibitory effect depends on the bases, sugars and location of phosphate, when the location of phosphate on the sugar was the same, the Ki values of ribonucleotides decreased in the order U, G, C, and A and those of deoxyribonucleotides decreased in the order T, G, C, and A. The dependence of the inhibitory effect of ribonucleosides on the bases was similar to that of ribonucleotides, but that of deoxyribonucleosides was in the order dT, dA, dG, and dC.

Aspergillus↗