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Biomedical subjects

K Yabe

Publications and source records attributed to K Yabe.

At least 73 records · Page 4Linked to original sources
PubMed1991

Enzymatic conversion of norsolorinic acid to averufin in aflatoxin biosynthesis.

5'-Hydroxyaverantin (HAVN) was isolated from a mold, Emericella heterothallica IFO 30842. Aspergillus parasiticus NIAH-26, a UV-irradiated mutant of A. parasiticus SYS-4, produced neither aflatoxins nor precursors in yeast extract-sucrose (YES) medium. When the postmicrosome (cytosol) fraction of NIAH-26, which had been prepared from the culture in YES medium, was incubated with norsolorinic acid (NA) in the presence of NADH or NADPH, averantin (AVN) was produced. The reverse reaction from AVN to NA was promoted by the addition of NAD or NADP (dehydrogenase reaction). When the microsome fraction of NIAH-26 was incubated with AVN, HAVN was produced in the presence of NADPH (monooxygenase reaction). HAVN was, furthermore, oxidized to averufin (AVR) by the cytosol fraction of NIAH-26 in the presence of NAD or NADP (dehydrogenase reaction). In the feeding experiments with A. parasiticus NIAH-26, aflatoxins were produced from AVN, HAVN, NA, and AVR but not from averufanin or averythrin. These results indicate that the reaction sequence NA in equilibrium AVN----HAVN----AVR is involved in the biosynthetic pathway of aflatoxins. The enzyme activities described here were dependent on the culture medium, and no enzyme activities were observed in the nonaflatoxigenic strain A. oryzae SYS-2 (IFO 4251).

Aflatoxins↗
PubMed1991

[Estimation of age from soft X-ray findings of lumbar vertebrae using image processing].

The age changes that occur in human trabecular bone were examined by calculating the bone density in the soft X-ray films taken from the 3rd lumbar vertebra with an image processing system. The samples were obtained from 177 adult corpses (98 males and 69 females). Loss of the trabecular bone density was found in and after the age group of 30s in both sexes, especially in the age group of 50s in female the decrease in bone density was remarkable. The bone density scattered widely in all age groups, even in the young group. The wide dispersion of bone density in the same age group may produce some unreliable results for estimating the age, so this estimation method should cautiously be applied to actual identification cases.

Adult↗
PubMed1991

Atlas of the rat brain: quantitative distribution of the choline acetyltransferase.

We have developed a fluorescence microphotometry system for microanalysis of the quantitative distribution of neurotransmitters and their related chemical substances in the brain slice. In the present study, the extensive distributions of cholinergic systems were analyzed quantitatively and in detail throughout the rat whole brains by this novel method through immunohistochemical staining of choline acetyltransferase (CAT). The rat whole brain was slice coronally and continuously, and 50 slices were chosen at approximately 500 microns intervals and stained immunohistochemically for CAT. Immunohistochemical fluorescence intensities were measured through a 6 microns phi (on the slice) pinhole of a microscope, the brain slice was moved along the X- or Y-axes stepwise at 40 microns intervals under the objective lens of the microscope, and the distributions of fluorescence intensities were analyzed over the entire surface of the slice. The brain was divided into approximately 5,000,000 areas, and immunohistochemical fluorescence intensities of those areas were quantitatively measured. The obtained fluorescence intensities of CAT were classified into 8 ranks and were indicated by color coding and by three-dimensional graphics. Also, the actual fluorescence intensity values in large brain regions were presented. This type of brain atlas of the neurotransmitter or its related chemical substances provides very important information on their dynamics in the brain under experimental as well as pathological conditions. Also, this quantitative and detailed analysis is useful for combining morphological data with those from neurochemical and behavioral analyses of brain function.

Anatomy, Artistic↗
PubMed1990

[Rhabdomyolysis due to paraphenylenediamine (hair dye)--report of an autopsy case].

An autopsy case of rhabdomyolysis following homicidal intoxication of paraphenylenediamine was reported and the toxicological mechanism of PPD against skeletal muscles was discussed. The case was a 44 years old, previously healthy male, drinking a beverage containing PPD, prepared for a homicidal use. Total intake of PPD was about 3 g (63 mg/kg). Principal clinical manifestation of the patient was muscle rigor with tenderness, initially developed in the lower extremities and subsequently extending to all over the skeletal muscles. Laboratory examinations disclosed high CPK (137,600), LDH (3895), GOT (3400) and GPT (545), and leukocytosis (26600), indicating massive skeletal muscle necrosis. ECG revealed mild depression of ST junction in the II and aVF leads. Urine showed dark brownish discoloration and diminished in volume subsequently. Scattered necrosis of muscular fibers was observed in a biopsy of the femoral muscles. The consciousness was rather clear during the course. The patient collapsed suddenly and soon died in the course of about 30 hours. Clinically, the cause of death was thought to be acute renal failure due to rhabdomyolysis. Afterwards PPD was detected in the urine obtained in the hospital. Autopsy confirmed the clinical diagnosis: Renal collecting ductules and distal tubules were occluded by dark brownish myoglobin casts and its epithelium massively necrotized; Skeletal muscles showed scatteredly coagulation necrosis and were partially associated with inflammatory cell infiltration.

Adult↗
PubMed1989

Effects of pre-motion electromyographic silent period on dynamic force exertion during a rapid ballistic movement in man.

The effects of pre-motion silent period (PSP) on dynamic force exertion were studied in ten healthy subjects performing ballistic elbow extensions. The experiments were designed to evaluate the significance of mean differences between the averaged dynamic force curves of two groups: PSP-presence groups and PSP-absence groups. The presence of PSP was judged quantitatively and automatically by means of a newly developed method using statistical analysis. The results indicated that there were two effects of PSP on dynamic force exertion: one was a reducing effect, observed prior to the movement; the other was a reinforcing effect, observed in the first part of the ballistic movement. The duration of the reinforcement was significantly correlated with the duration of the reducing effect of PSP. The findings suggested that the reinforcement of dynamic force may be produced by the pre-stretch of agonistic muscles caused by prior force reduction due to PSP occurrence. The fact that PSP plays an important role in dynamic force exertion suggests that PSP may be incorporated in the central motor control system designed to interrupt the background activity, to stretch the agonist and to reinforce the dynamic force.

Adult↗
PubMed1989

Two distinct O-methyltransferases in aflatoxin biosynthesis.

The substances belonging to the sterigmatocystin group bear a close structural relationship to aflatoxins. When demethylsterigmatocystin (DMST) was fed to Aspergillus parasiticus NIAH-26, which endogenously produces neither aflatoxins nor precursors in YES medium, aflatoxins B1 and G1 were produced. When dihydrodemethylsterigmatocystin (DHDMST) was fed to this mutant, aflatoxins B2 and G2 were produced. Results of the cell-free experiment with S-adenosyl-[methyl-3H]methionine showed that first the C-6-OH groups of DMST and DHDMST are methylated to produce sterigmatocystin and dihydrosterigmatocystin (O-methyltransferase I) and then the C-7-OH groups are methylated to produce O-methylsterigmatocystin (OMST) and dihydro-O-methylsterigmatocystin (DHOMST) (O-methyltransferase II). However, no methyltransferase activity was observed when either OMST, DHOMST, 5,6-dimethoxysterigmatocystin, 5-methoxysterigmatocystin, or sterigmatin was incubated with the cell extract. Treatment of the cell extract with N-ethylmaleimide inhibited O-methyltransferase I activity but not that of O-methyltransferase II. Furthermore, these O-methyltransferases were different in their protein molecules and were involved in both the reactions from DMST to OMST and DHDMST to DHOMST. The reactions described in this paper were not observed when the same mold had been cultured in YEP medium.

Aflatoxins↗
PubMed1988

Hydrolysis of histones by proteinases.

Hydrolysis of histones by proteinases from rat liver, skin and other sources was studied by using a rat thymus histone preparation as the substrate and polyacrylamide-gel electrophoresis and densitometric analysis as the methods to detect histone subtypes and their hydrolysis. The rat mast-cell proteinase I effectively hydrolysed histones except type H4. Thrombin hydrolysed effectively histones H1 and H2A, whereas plasmin hydrolysed all types of histones. Cathepsin D hydrolysed especially histone H2A. Cathepsins B and L hydrolysed all histones more slowly, and cathepsin H hydrolysed them extremely slowly. Epidermal aminoendopeptidase did not hydrolyse histones. Trypsin and chymotrypsin were used as reference enzymes, which hydrolysed all types of histones in very low concentrations. This study suggests that a variety of proteinases could play a role in histone hydrolysis. Hydrolysis of a specific subtype of histones, such as histone H2A at pH 6 by cathepsin D, may be directly involved in regulation of epidermal-cell differentiation.

Aminopeptidases↗
PubMed1988

Isolation and characterization of Aspergillus parasiticus mutants with impaired aflatoxin production by a novel tip culture method.

A convenient procedure consisting of UV photography (K. Yabe, Y. Ando, M. Ito, and N. Terakado, Appl. Environ. Microbiol. 53:230-234, 1987) and a tip culture method has been devised for the isolation and characterization of Aspergillus parasiticus mutants relating to aflatoxin production. With the latter procedure, the production of aflatoxins excreted into the culture medium and precursors in the mycelium were easily measured quantitatively or semiquantitatively. A total of 38 mutants in which the aflatoxigenicity was decreased or lost were obtained by UV radiation; 3 were found to be blocked mutants, which accumulated the aflatoxin precursors versicolorin A or averantin.

Aflatoxins↗
PubMed1988

Biosynthetic relationship among aflatoxins B1, B2, G1, and G2.

Aspergillus parasiticus NIAH-26, a UV-irradiated mutant of A. parasiticus SYS-4 (NRRL 2999), produces neither aflatoxins nor precursors. When sterigmatocystin (ST) or O-methylsterigmatocystin was fed to this mutant in YES medium, aflatoxins B1 (AFB1) and G1 (AFG1) were produced. When dihydrosterigmatocystin (DHST) or dihydro-O-methylsterigmatocystin was fed to this mold, aflatoxins B2 (AFB2) and G2 (AFG2) were produced. The reactions from ST to AFB1 and DHST to AFB2 were also observed in the cell-free system and were catalyzed stepwise by the methyltransferase and oxidoreductase enzymes. In the feeding experiments of strain NIAH-26, the convertibility from ST to AFB1-AFG1 was found to be remarkably suppressed by the coexistence of DHST in the medium, and the convertibility from DHST to AFB2-AFG2 was also suppressed by the presence of ST. When some other mutants which endogenously produce a small amount of aflatoxins (mainly AFB1 and AFG1) were cultured with DHST, the amounts of AFB1 and AFG1 produced were significantly decreased, whereas AFB2 and AFG2 were newly produced. In similar feeding experiments in which 27 kinds of mutants including these mutants were used, most of the mutants which were able to convert exogenous ST to AFB1-AFG1 were also found to convert exogenous DHST to AFB2-AFG2. These results suggest that the same enzymes may be involved in the both biosynthetic pathways from ST to AFB1-AFG1 and DHST to AFB2-AFG2. The reactions described herein were not observed when the molds had been cultured in the YEP medium.

Aflatoxin B1↗
PubMed1988

[Markers of bone pain in hemodialysis patients with renal insufficiency].

The patients receiving maintenance hemodialysis were divided into two groups in the absence and the presence of bone pain and investigated the markers of bone pain in these patients. These results suggested that the duration of receiving hemodialysis, serum concentrations of alkaline phosphatase, osteocalcin and parathyroid hormone became to be the markers of bone pain.

Adolescent↗
PubMed1987

Separation and identification of cathepsins in newborn rat epidermis.

Cathepsins B, D, H, and L were identified in the extract of 2-day-old rat epidermis and separated by gel filtration from aminoendopeptidase with a Mr of 400,000 and from the low-molecular-weight cysteine proteinase inhibitor. They were further purified by ion exchange column chromatography. The final separation for cathepsins B and H was performed by gel filtration, while cathepsin D was purified by pepstatin affinity chromatography and cathepsin L by fast protein liquid chromatography (FPLC). Substrate specificity, inhibitor susceptibility, and apparent molecular weights of the separated proteinases were determined and values compared to rat liver enzymes. Apparent molecular weights for epidermal cathepsins B, H, and L were higher than those for comparable liver enzymes of adult rats. The cysteine proteinase inhibitor in epidermis was found to inhibit cathepsins B, H, and L but not cathepsin D and aminoendopeptidase of rat epidermis. This study demonstrates the presence of cathepsin L in the epidermis and describes simultaneous separation and comparison of epidermal catheptic proteinases.

Animals↗
PubMed1987

Simple method for screening aflatoxin-producing molds by UV photography.

UV absorption by aflatoxins was monitored in GY agar medium by UV photography. In the UV photographs, aflatoxin-producing molds were identified as gray or black colonies, whereas aflatoxin-nonproducing molds appeared as white colonies. By cellophane transplantation experiments and silica gel thin-layer chromatography, the products absorbing UV light substantially were found to be mainly aflatoxins B1 and G1 excreted from the mold mycelium into the agar medium. UV absorption did not occur when the agar medium contained aflatoxin-noninducible carbon sources instead of glucose. Various inhibitors of aflatoxin production, such as dichlorovos and dimethyl sulfoxide, also decreased the intensity of UV absorption. These results indicate that this technique can be used as a simple, safe, and rapid method of screening aflatoxin-producing molds.

Aflatoxins↗
PubMed1985

Immunological detection of a cysteine protease in the skin and other tissues.

Monospecific antibody directed to cysteine protease of 2-day-old rat epidermis recently characterized as being different from the proteases previously reported was produced in rabbits. By immunofluorescence microscopy and immunoperoxidase staining with an avidin-biotin-peroxidase method the protease was found to be present in the epidermis of rodents of different ages as well as that of humans, but not in the dermis. The staining in germinative cells was more intense than in cells in the superficial layers. It appeared as irregular patches in the nuclei and stained more diffusely in the cytoplasm where small granular components, strongly stained, were identified. The staining patterns in granular cells showed accumulation of the antigen in a granular form. The morphology and distribution of granules resembled those of keratohyalin-like granules in the nucleus and dense homogeneous deposits in the cytoplasm. In cornified cells the reaction product was localized by the plasma membrane where concentration of the dense homogeneous deposits occurred, suggesting that the cysteine protease is one component of the unique and characteristic structure of differentiated keratinocytes. In addition, the cysteine protease antigen having the same molecular weight as the epidermal enzyme was detected in liver, kidney and lung indicating a wider tissue distribution of the protease. The significance of the protease in regulation of cellular functions remains to be investigated.

Animals↗
PubMed1985

Postural adjustments for jumping reaction movement in mentally retarded children: findings from EMG patterns.

EMG patterns during a jumping reaction task were studied in 53 mentally retarded children. EMGs were recorded from the knee extensors (VM and RF) and the knee flexors (hamstrings). Lack of synchronization between onset of phasic discharge in the VM and the RF and between onset in the hamstrings and the knee extensors was characteristic of retarded children. Deviation from the EMG pattern of normal adults decreased with increasing MA. The premotor time tended to be prolonged with increasing time differences between the VM and the RF responses. Shorter RT between the VM and the RF was consistent across EMG patterns. These were more apparent in subjects with MAs above 7 than in those with MAs below 6. It is suggested that the asynchronized EMG pattern reflects postural requirements due to poor formation of preparatory set.

Adolescent↗
PubMed1985

Developmental trends of jumping reaction time by means of EMG in mentally retarded children.

Developmental trends of jumping reaction time (RT) in mentally retarded children were studied cross-sectionally. Fifty-three boys, ranging in CA from 7 to 18 years, took part in the jumping RT task. RT measurements were obtained from EMG of an agonist muscle (rectus femoris). There was a significant decrease in RT with increasing CA. Correlation between RT and MA was highly significant, but discontinuity in the distribution was found between MA of 6 and 7 years. The subjects with a MA below 6 were characterized by large variability as well as slowness in RT. RT was not correlated with CA holding MA constant among the subjects with a MA below 6. The subjects with a MA above 7 showed relatively small variability within and between subjects. RT in subjects with a MA above 7 decreased with CA holding MA constant but RIV showed no change. RT in children with a very low MA is prolonged by inefficiency which reflects difficulty in maintaining attention or arousal level. The efficiency in information processing may change between the MAs of 6 and 7 years.

Adolescent↗