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Biomedical subjects

K Mabuchi

Publications and source records attributed to K Mabuchi.

At least 109 records · Page 6Linked to original sources
PubMed1991

A long helix from the central region of smooth muscle caldesmon.

The central region of smooth muscle caldesmon is predicted to form alpha-helices on the basis of its primary structure. We have isolated a fragment (CT54) that contains this region. The hydrodynamic properties and the electron microscopic images suggest that CT54 is an elongated (35 nm), monomeric molecule. The circular dichroic spectrum yields an overall alpha-helical content of 55-58%. These results are consistent with the model that the middle portion of CT54 forms a long stretch of single-stranded alpha-helix. Such a structure, if it in fact exists, is thought to be stabilized by numerous salt bridges between charged residues at positions i and i + 4. The structural characteristics of this fragment not only represent an unusual protein configuration but also provide information about the functional role of caldesmon in smooth muscle contraction.

Amino Acid Sequence↗
PubMed1991

Regulation of myosin and overall protein degradation in mouse C2 skeletal myotubes.

We compared the breakdown of total cellular protein with that of the contractile protein, myosin, in cultured C2 mouse skeletal myotubes. The degradation of long-lived cellular proteins (which comprise the vast majority of myotube proteins) was inhibited by serum, insulin, and rat insulin-like growth factor-2. A physiological concentration of insulin was effective, but most of the effect of insulin occurred at concentrations well above the physiological range. IGF-2 inhibited protein breakdown at concentrations well within the range of total IGF-2 known to be present in the serum of fetal and neonatal rats. The breakdown of short-lived proteins was not altered by insulin or serum. We measured myosin degradation using a monoclonal antibody directed against myosin heavy chain. The half-life of myosin was 27 hours, and myosin breakdown was not altered by serum withdrawal applies to certain proteins, but not to others.

Animals↗
PubMed1991

Electron microscopic studies of chicken gizzard caldesmon and its complex with calmodulin.

Caldesmon samples mounted on a stage rotating about a horizontal axis were shadowed keeping the shadow angle at about 3 degrees. This technique minimizes background metal deposits compared with the conventional method. The identity of caldesmon was confirmed by comparing the images of caldesmon alone with those of the caldesmon-calmodulin complex. In these samples the caldesmon molecules appeared to be elongated; most were between 30 and 80 nm in length. The maximum length was in good agreement with the earlier estimate of 74 nm based on hydrodynamic studies. Our observations also suggested the presence of a rather rigid 30-40 nm stretch in the middle of the caldesmon molecule, which was always visible under rotary shadowing, and a flexible structure of about 20 nm in length at each end of the molecule, which may or may not be visible depending on their orientation on the mica surface. In the samples of caldesmon crosslinked with calmodulin, we noticed the existence of complexes containing two calmodulin molecules per caldesmon molecule, separated by a distance of 60 nm, consistent with the suggestion that each end of caldesmon can interact with calmodulin.

Animals↗
PubMed1991

Heavy-meromyosin-decorated actin filaments: a simple method to preserve actin filaments for rotary shadowing.

It has become accepted that deep-freeze-drying at or below -90 degrees C is necessary to preserve the structure of supramolecular assemblies such as actin filaments (AFs) for metal shadowing. This has kept the metal shadowing technique from widespread use in the study of proteins complexed with AFs because of the limited availability of the apparatus for deep-freeze-drying. I report here that adsorption to freshly cleaved mica, treatment with buffered uranyl acetate in glycerol solution, rinsing, and removal of liquid eliminate the need of freeze-drying to preserve the structure of AFs. This technique, in combination with metal shadowing, was applied to the study of AFs decorated with heavy meromyosin (HMM). It was observed that (1) when HMM molecules are associated with single AFs in the majority of cases only one head of each HMM molecule makes contact at the point furthest from the neck region; (2) binding of HMM causes bundling of AFs, probably by the two heads of each molecule binding different filaments; and (3) the binding of HMM to the bundled AFs appears to be more stable than that to a single AF. This method of specimen preparation requires no freeze-drying and is therefore easily applicable to other large protein complexes.

Actins↗
PubMed1991

Antitumor activity of fluoropyrimidines and thymidylate synthetase inhibition.

Experimental chemotherapy with 5-fluorouracil (5-FU; 60 mg/kg), 1-hexylcarbamoyl-5-fluorouracil (HCFU; 70 mg/kg), 3-(3-(6-benzoyloxy-3-cyano-2-pyridyloxycarbonyl)benzoyl)-1-ethoxym ethyl-5- fluorouracil (BOF-A2; 30 mg/kg) and UFT (20 mg/kg as tegafur with uracil at a molar ratio of 1:4) was performed using human gastric (H-111) and colon (Co-4) carcinoma strains in nude mice. 5-FU was administered ip with a q4d x 3 schedule and the other agents were given po daily for three weeks. Concentrations of 5-FU in the serum and the tumor were assessed by gas chromatography-mass fragmentography, two hours or 12 days (5-FU) after the last treatment, and thymidylate synthetase (TS) was assayed according to the method of Spears et al. using the same schedule. The antitumor activity of the agents was assessed in terms of the actual tumor weight at the end of the experiment. HCFU was effective against both strains and 5-FU was effective against Co-4, although the other agents were ineffective against either strain. Statistically significant correlations were found between the serum and tumor concentrations of 5-FU and antitumor activity. Statistically significant correlations were also observed between the antitumor activity and TS inhibition rate (TSIR) and the activity of free thymidylate synthetase (TSfree), with higher TSIR and lower TSfree resulting in higher antitumor activity. Therefore, TSIR and TSfree were thought to be promising indicators for predicting the antitumor activity of fluoropyrimidines.

Adenocarcinoma↗
PubMed1991

Parathyroid tumors in atomic bomb survivors in Hiroshima: epidemiological study from registered cases at Hiroshima Prefecture Tumor Tissue Registry, 1974-1987.

An examination of registered cases of parathyroid tumor in Hiroshima Prefecture between 1974 and 1987 revealed 23 cases. An epidemiological study showed that the incidence of parathyroid tumors in Hiroshima Prefecture was significantly higher in the total exposed, especially among the proximally exposed (within 2,000 m from the hypocenter), than in the control nonexposed group (P less than 0.001). A similar trend was seen for parathyroid tumor associated with primary hyperparathyroidism.

Humans↗
PubMed1991

Stiffness of canine stifle joint ligaments at relatively high rates of elongation.

A falling-weight impact tester was developed specifically to evaluate the tensile characteristics of animal joints at high elongation rates. The tensile force and elongation in the ligaments of the canine stifle joint were measured using a force transducer, a linear variable displacement transducer, and a digital storage oscilloscope. Stiffness and elongation rates were determined at 1 mm and at 2 mm elongation. The stiffness was calculated as the slope of the force-elongation curve, and the elongation rate was calculated as the slope of the elongation-time curve. Results demonstrated that stiffness in the canine stifle joints was not affected by the rate of elongation in the 0.1 to 1.0 m/s range.

Animals↗
PubMed1991

Direct correlation of parvalbumin levels with myosin isoforms and succinate dehydrogenase activity on frozen sections of rodent muscle.

Parvalbumin (PV) is a soluble Ca++ binding protein which is particularly concentrated in fast muscles of rodents. We have developed a new protocol to fix frozen sections of muscle by formaldehyde vapor, which enabled us to immunochemically stain serial frozen sections for PV. Fiber types were defined on the basis of myosin ATPase stability, and of isomyosins identified by a variety of antibodies because ATPase stability alone yielded ambiguous results in the mouse. Slow Type I fibers in mouse and rat were devoid of PV and had intermediate to high SDH levels. Fast fiber subtypes IIA, IIB, and IIX-like were defined in the mouse on the basis of the similarity of their myosin heavy chain immunoreactivity to these types in the rat. The soleus muscle was usually PV negative, but a small population of strongly PV-positive IIX-like fibers was present in the mouse. In mouse fast muscle, small diameter IIA fibers were PV negative with high SDH activity. In both mouse and rat, PV reactivities of IIB and IIX fibers were higher than those of IIA and I, whereas SDH levels of IIA, IIX, and I fibers were higher than those of IIB. Thus, PV content correlated with the type of myosin ATPase but not with SDH levels. The method described for immunocytochemistry of PV may be applicable to other highly soluble proteins.

Animals↗
PubMed1991

Cytogenetic and molecular changes in leukemia among atomic bomb survivors.

Seventy five radiation-related leukemia patients in Hiroshima including 16 patients exposed to more than one Gray were cytogenetically examined. Statistical analysis of data on the frequencies of chromosomal aberrations in the survivor groups according to bone marrow doses by DS86 estimation revealed that the heavily exposed group tended to have significantly higher aberration rates compared to the non-exposed group. Furthermore, the chromosomal aberrations in the survivors were observed to be of a more complex nature and had the characteristic findings of secondary leukemia. These observations therefore suggest that patients with a history of heavy exposure to atomic bomb radiation had leukemic cells originating from a stem cell which had been damaged by irradiation at the time of the bombing as well as cells involved in complex chromosome abnormalities. Molecular biologic studies on ras genes in acute and chronic leukemias and the bcr gene in chronic myelocytic leukemia were performed in exposed and non-exposed groups. So far, no distinctive differences have been observed in the frequency and sites of point mutations in N- and K-ras genes or in the rearrangement of the bcr gene. Further, retrospective analysis using DNA from leukemia patients who developed this disease in the early period from atomic bomb radiation exposure would be useful for the elucidation of the mechanisms of radiation-induced leukemia.

Aged↗
PubMed1991

Parathyroid tumors in atomic bomb survivors in Hiroshima: a review.

Parathyroid tumors in A-bomb survivors in Hiroshima have been studied. Thirteen cases of parathyroid tumor were confirmed from 4,136 autopsy cases between 1961 to 1977, and an elevated incidence of tumor with increase of dose (T65D) was demonstrated (P less than 0.01). A high proportion of 42.9%, 6 out of 14 parathyroid tumors extirpated at Hiroshima University Hospital between 1956 and 1988, were atomic bomb survivors exposed within 4.1 km from the hypocenter. From an epidemiological study using 23 parathyroid tumor cases detected in Hiroshima Prefecture between 1974 and 1987, an elevated incidence of parathyroid tumors with increase of dose (proximally exposed, other exposed and control nonexposed) was demonstrated (P less than 0.001).

Humans↗
PubMed1991

A review of forty-five years study of Hiroshima and Nagasaki atomic bomb survivors. Tumor registries and cancer incidence studies.

A tumor registry is essential in the systematic collection and analysis of tumor data in a defined population. Population-based tumor registries have been in operation for more than 30 years in Hiroshima and Nagasaki. While the tumor registry data have previously been used for many site-specific cancer studies in atomic bomb survivors, overall analysis of tumor registry based cancer incidence data among the atomic bomb survivors has not been undertaken for some time. However, a recent improvement in the tumor registries has made it possible to analyze most recent cancer incidence data among the Life Span Study population. Preliminary analysis under way indicates a potential power of the data. There are a few methodological problems associated with the use of the incidence data, especially relating to consistency of data and migration. Several measures taken to resolve such problems are discussed.

Female↗
PubMed1991

Mortality and cancer risk among the offspring (F1) of atomic bomb survivors.

The Atomic Bomb Casualty Commission (ABCC) and its successor Radiation Effect Research Foundation (RERF) has over the years conducted many studies to determine possible genetic effects of atomic bomb radiation among the offspring of atomic bomb survivors. Findings concerning mortality and cancer incidence of the offspring are summarized in this chapter.

Child↗
PubMed1990

Melting of myosin and tropomyosin: electron microscopic observations.

A method was devised to maintain a very low angle (2-3 degrees) during the metal casting of specimens for electron microscopy. With this modified rotary shadowing procedure the melting of myosin and tropomyosin (TM) was investigated. When protein solutions were sprayed on mica sheets and then heated to melt alpha-helices, myosin molecules did not show any sign of chain separation but appeared to have collapsed into loose clumps. A few molecules showed separation of the two chains at the light meromyosin-heavy meromyosin hinge region. Heating myosin in bulk solution at 65 degrees C before spraying caused extensive fusing of the myosin heads. In contrast, in the case of TM, separation of the chains appeared to occur at temperatures at which the unfolding of alpha-helices had been shown by circular dichroism. Dissolution of TM and myosin in 0.5% SDS followed by 150-fold dilution led to single chain species. This method capable of detecting single chain peptides of melting TM whose thickness is of the order of 1 nm may be applicable to the study of the structure of proteins previously not considered possible.

Animals↗
PubMed1990

Percutaneous fiberoptic spinal laser endoscopy.

For percutaneous observation of lesions near the spinal cord and percutaneous spinal laser surgery under the visual field, we studied a method and approach to the spinal cord and intraspinal surgical procedures with laser using a newly developed, small-diameter laser endoscope. The subarachnoid and epidural spaces of a goat were punctured using a 17-gauge epidural needle, and the endoscope (diameter 0.7 mm) was inserted through the needle. The spinal cord and surrounding tissue were observed. Next, an endoscope (diameter 1.5 mm) was inserted into the subarachnoid space, and the quality of the picture and manageability of the endoscope were examined. The Xe:Cl excimer laser was irradiated to a nerve root through a 0.4 mm optical fiber for laser transmission through this endoscope. The spinal cord, nerve roots, and arachnoid were clearly observed through this endoscope. The pulsation of the artery accompanying a root was seen clearly, and the quality of the picture of the endoscope was thought to be sufficient for diagnosis. The nerve root was cut within 30 seconds by excimer laser, and the possibility of laser surgery was demonstrated. Although it was shown that this endoscope could be a useful diagnostic and therapeutic tool, improvement in the manageability of the tip of the endoscope was considered to be important for a clinically usable endoscope.

Animals↗