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Biomedical subjects

K Mabuchi

Publications and source records attributed to K Mabuchi.

At least 55 records · Page 3Linked to original sources
PubMed1998

RNA from decades-old archival tissue blocks for retrospective studies.

The validity of molecular studies using DNA and RNA extracted from decades-old formalin-fixed and paraffin-embedded tissue blocks has been demonstrated. The quality and usability of DNA and RNA from archival tissues are modified by various factors, such as the fixative, the fixation time, and the postmortem time. However, in contrast to DNA, there are no comprehensive studies quantitatively addressing the feasibility of RNA from old (more than 10 years) archival samples. This study examined the integrity of RNA extracted from 738 autopsy liver and 63 autopsy thyroid cancer tissue blocks procured during a span of nearly four decades, beginning in 1952 and ending in 1989, from the atomic bomb survivors. The integrity of RNA was assessed by amplification of c-BCR messenger RNA (mRNA) between two sequential exons with an intervening intron by reverse-transcription polymerase chain reaction (RT-PCR). The integrity of RNA was influenced by the age of the samples and the postmortem time, but not by the formalin-fixation period. It was possible to amplify more than 60% of the samples. Using these RNAs, the HCV genome in liver cancers and the H4-RET gene in thyroid cancers were detectable. This study illustrates the possibility of molecular studies using RNA from routinely prepared paraffin blocks stored for long periods and provides the statistics and critical factors to consider in assessing the feasibility of such contemplated studies.

Drosophila Proteins↗
PubMed1998

Physiological control of a total artificial heart: conductance- and arterial pressure-based control.

To obtain a physiological response by a total artificial heart (TAH), while eliminating the hemodynamic abnormalities commonly observed with its use, we proposed the use of a conductance- and arterial pressure-based method (1/R control) to determine TAH cardiac output. In this study, we endeavored to make use of a variable more closely tied to central nervous system (CNS) efferents, systemic conductance, to provide the CNS with more direct control over the output of the TAH. The control equation that calculates the target cardiac output of the TAH was constructed on the basis of measurement of blood pressures and TAH flow. The 1/R control method was tested in TAH-recipient goats with an automatic method by using a microcomputer. In 1/R control animals, the typical TAH pathologies, such as mild arterial hypertension and substantial systemic venous hypertension, did not occur. Cardiac output varied according to daily activity level and exercise in a manner similar to that observed in natural heart goats. These results indicate that we have determined a control method for the TAH that avoids hemodynamic abnormalities exhibited by other TAH control systems and that exhibits physiological responses to exercise and daily activities under the conditions tested. The stability of the control and the complete lack of inappropriate excursions in cardiac output is suggestive of CNS involvement in stabilizing the system.

Animals↗
PubMed1997

Expression in insect cells and characterization of the 110 kDa anchoring subunit of myosin light chain phosphatase.

The major myosin light chain phosphatase is composed of three subunits with apparent molecular masses of 130, 38 and 20 kDa, corresponding to the myosin-binding, catalytic and a regulatory subunit of unknown function, respectively. In this work, we have amplified the cDNA coding for each of the three subunits by the polymerase chain reaction, and expressed the 130 kDa subunit in insect cells using the baculovirus expression system. Limited chymotrypsin digestion show that the folding of the expressed protein is similar to that in the native holoenzyme. N-Terminal sequencing reveals that our recombinant protein is authentic. Mass spectrometry shows that the expressed protein is full length. The recombinant protein is capable of binding myosin based on the ELISA assay and myosin affinity chromatography. Finally, rotary shadowing electron microscopy reveals an elongated structure with three globular domains connected by flexible strands. These results pave the way for future biochemical, structural and site-directed mutagenesis studies on the myosin light chain phosphatase. We also found that the cDNA of the 20 kDa subunit may code for a smaller protein with a molecular mass of 18.5 kDa.

Animals↗
PubMed1997

Association of calponin with desmin intermediate filaments.

Our previous immunoelectron microscopy studies of chicken gizzard smooth muscle cells showed that in certain areas the distribution of anti-calponin exhibits a high degree of overlap with beta-actin, filamin, and in particular, desmin, suggesting that in situ a fraction of calponin may be associated with intermediate filaments of the cytoskeleton. In this work we further explore this idea by studying the interaction between calponin and desmin. We found that at physiological salt concentrations, calponin bound only weakly to synthetic desmin intermediate filaments. On the other hand, calponin bound strongly to nonfilamentous desmin tetramers and was incorporated into intermediate filaments when the two proteins were mixed in a buffer containing 6 M urea and dialyzed into a buffer containing 0.15 M NaCl. Anti-calponin was found to label a portion of intermediate filaments and dense bodies isolated from gizzard tissues. Our findings suggest that in chicken gizzard smooth muscle cells, calponin may be an integral component of desmin intermediate filaments in the vicinity of dense bodies. Since calponin is also known to bind actin, we hypothesize that one of the functions of calponin might be to bridge intermediate filaments with actin in dense bodies.

Animals↗
PubMed1997

Salivary gland tumors among atomic bomb survivors, 1950-1987.

BACKGROUND: Malignant and benign tumors of the salivary glands have been associated with exposure to ionizing radiation from various sources, including the atomic bombings in Hiroshima and Nagasaki. However, questions remain unanswered regarding the nature and size of the risk and specific types of tumors involved. METHODS: The incidence and pathology of malignant and benign tumors of the salivary glands was studied in the Life Span Study cohort of atomic bomb survivors followed by the Radiation Effects Research Foundation (RERF) in Hiroshima and Nagasaki, Japan. Incident cases diagnosed during the period 1950-1987 were ascertained from the tumor and tissue registries of Hiroshima and Nagasaki and supplemented by additional case findings from autopsy, biopsy, and surgical specimens maintained at RERF and other institutions. Pathology slides and medical documents were reviewed by a panel of four pathologists who classified tumors using the World Health Organization classification scheme. Analyses were performed of histologic features associated with radiation exposure. RESULTS: Of 145 tumors of the salivary glands identified (119 of the major and 26 of the minor salivary glands), 120 (83%) were histologically confirmed by the current investigators. Among 41 malignant tumors, the frequency of mucoepidermoid tumor was disproportionately high at high radiation doses (P = 0.04); among 94 benign tumors, the frequency of Warthin's tumor increased with increasing radiation dose (P = 0.06). The nature of the tumor was undetermined for the remaining ten cases. Mortality from malignant tumors of the salivary gland was inversely related to radiation dose, reflecting the predominance of mucoepidermoid carcinoma at high dose levels in this series. In one case with high radiation exposure, mucoepidermoid carcinoma of the parotid gland was accompanied by a preexisting or coexisting Warthin's tumor. CONCLUSIONS: These findings, supported by population-based analyses in a companion study reported elsewhere, suggest a causal role for ionizing radiation in salivary gland tumorigenesis, particularly for mucoepidermoid carcinoma, and in the induction of one type of benign tumor (Warthin's tumor).

Adult↗
PubMed1997

The motor domain and the regulatory domain of myosin solely dictate enzymatic activity and phosphorylation-dependent regulation, respectively.

While the structures of skeletal and smooth muscle myosins are homologous, they differ functionally from each other in several respects, i.e., motor activities and regulation. To investigate the molecular basis for these differences, we have produced a skeletal/smooth chimeric myosin molecule and analyzed the motor activities and regulation of this myosin. The produced chimeric myosin is composed of the globular motor domain of skeletal muscle myosin (Met1-Gly773) and the C-terminal long alpha-helix domain of myosin subfragment 1 as well as myosin subfragment 2 (Gly773-Ser1104) and light chains of smooth muscle myosin. Both the actin-activated ATPase activity and the actin-translocating activity of the chimeric myosin were completely regulated by light chain phosphorylation. On the other hand, the maximum actin-activated ATPase activity of the chimeric myosin was the same as skeletal myosin and thus much higher than smooth myosin. These results show that the C-terminal light chain-associated domain of myosin head solely confers regulation by light chain phosphorylation, whereas the motor domain determines the rate of ATP hydrolysis. This is the first report, to our knowledge, that directly determines the function of the two structurally separated domains in myosin head.

Actins↗
PubMed1997

Phosphatidylserine liposomes can be tethered by caldesmon to actin filaments.

Rotary shadowing electron microscopy revealed that attachment of caldesmon to phosphatidylserine (PS) liposomes was mainly through its C-terminal end. To determine the PS-binding sites of caldesmon, we have made use of synthetic peptides covering the two C-terminal calmodulin binding sites and a recombinant fragment corresponding to the N-terminal end of the C-terminal domain that contains an amphipathic helix. Interactions of these peptides with the PS liposomes were studied by nondenaturing gel electrophoresis and fluorescence spectroscopy. The results showed that both calmodulin-binding sites of caldesmon were able to interact with PS. The affinity (Kd) of PS for these sites was in the range of 1.8-14.3 x 10(-5) M, compared to 0.69 x 10(-5) M for the whole caldesmon molecule. Fragments located outside of calmodulin-binding sites bound PS weakly (3.85 x 10(-4) M) and thus may contain a second class of lipid-binding sites. Binding of PS induced conformational changes in regions other than the C-terminal PS-binding sites, as evidenced by the changes in the susceptibility to proteolytic cleavages. Most significantly, the presence of caldesmon greatly increased binding of PS to F-actin, suggesting that caldesmon may tether PS liposomes to actin filaments. These results raise the possibility that caldesmon-lipid interactions could play a functionally important role in the assembly of contractile filaments near the membranes.

Actins↗
PubMed1997

Increased friction of animal joints by experimental degeneration and recovery by addition of hyaluronic acid.

OBJECTIVE: To investigate the lubricating ability in osteoarthritic (OA) stifle joints. DESIGN: An experimental study in rabbit stifles in vitro. BACKGROUND: The lubricating ability in OA joints, and the effects of the application of hyaluronic acid (HA), a drug for OA, to the osteoarthritic joints have not yet been reported. METHODS: The friction in OA stifles induced by two different methods, the intra-articular injection of papain, and transection of the anterior cruciate ligament (ACL) was measured using a robotic arm under force control. RESULTS: The frictional coefficient in the papain-injected model, that caused slight degeneration in the articular cartilage, was 1.3 to 1.8 times as large as that in the contralateral uninjected stifles. The elevated values decreased significantly by addition of HA to the articular surface (P < 0.05). In another group (n = 4), the frictional coefficient in the stifle at 9 months after ACL transection that caused severe degeneration in the articular cartilage was 1.6 to 7.8 times as large as that in the contralateral unoperated stifle. The addition of HA decreased the elevated values in three of the four ACL-transected joints. CONCLUSION: Friction was higher in the OA joints than in the healthy joints. The addition of HA was effective in the early stage of OA represented by papain injected case, while its effect seems not to be evident for advanced OA produced ACL transection which accompanies macroscopic shape changes. RELEVANCE: The present findings are relevant to the current research investigating the case of human osteoarthritis. We measured the frictional coefficients of experimentally degenerated rabbit stifles. The frictional coefficients can be used as an index of joint degeneration. We also assessed the recovery of the lubricating ability by addition of hyaluronic acid, a drug used for human osteoarthritis.

Journal Article↗
PubMed1997

Development of the undulation pump total artificial heart.

The undulation pump is a small size continuous flow displacement type blood pump that has been developed for an artificial heart. Using undulation pumps, 2 types of implantable total artificial hearts (TAHs), the undulation pump TAH (UPTAH) type 1 (UPTAH 1) and UPTAH type 2 (UPTAH 2) were developed. Both UPTAHs were designed to be small enough to implant into the chest of a goat, the experimental animal. UPTAH 1 could be reduced in size to 75 mm in diameter and 78 mm in length. The weight was 520 g. UPTAH 2 could be reduced in size to 75 mm in diameter and 80 mm in length. The weight was 650 g. UPTAH 2 could be tested in an animal experiment using an adult female goat weighing 52.3 kg. The UPTAH 2 could be implanted successfully into the goat's chest with a good fit. The goat stood after the surgery and extubation and survived for 3 h and 40 min; thus, the potential of the UPTAH for a practical implantable TAH was demonstrated.

Animals↗
PubMed1997

Cancer mortality among atomic bomb survivors exposed in utero or as young children, October 1950-May 1992.

Cancer mortality for the period from October 1950 through May 1992 was analyzed in atomic bomb survivors exposed in utero. Risk estimates for this group were also compared to those for survivors who were less than 6 years old at the time of exposure. The cohorts studied include 807 in utero survivors and 5,545 persons exposed during childhood with all members of both groups having estimated doses of at least 0.01 Sv. The comparison group includes 10,453 persons with little (<0.01 Sv) or no exposure. Analyses were limited mainly to cancer deaths occurring between the ages of 17 and 46. Only 10 cancer deaths were observed among persons exposed in utero. However, there is a significant dose response with an estimate of excess relative risk per sievert (ERR/Sv) of 2.1 (90% confidence interval of 0.2 to 6.0). This estimate does not differ significantly from that for survivors exposed during the first 5 years of life. The cancer deaths among those exposed in utero involved leukemia (2), female-specific organs (3) and digestive organs (5). Nine deaths occurred in females, where the excess risk for all solid cancers has a 90% confidence interval on the ERR/Sv of 1.6 to 17. Significant risks were found for cancers of the digestive system [90% confidence interval (CI) on the ERR/Sv of 0.7 to 20] and for female-specific cancers (90% CI on the ERR/Sv of 0.7 to 42). These risks do not differ significantly from those seen in females exposed as children. There were no deaths from solid cancer in men exposed in utero. The ERR/Sv has an upper 95% confidence bound of 2.5 which does not differ from that for exposed children, where the upper 95% confidence bound is 1.5. The sexes differ even when female-specific cancers are excluded from the comparison. Although there were only two leukemia deaths among those exposed in utero, the leukemia death rate for this group is higher than that in the comparison group (P = 0.054) with an exposure effect that is about half the magnitude and not significantly different from that seen after childhood exposure (P = 0.103). However, there is no evidence of a dose response among those exposed in utero because no high-dose leukemia deaths were observed, a result that differs considerably from that for those exposed as children. There is a need for caution in the interpretation of these data. First, the number of cancer deaths is small; second, there is unexplained significant difference in the mortality from solid cancer between the sexes; and third, the excess of leukemia in those exposed in utero is not reflected in an increasing dose response.

Adult↗
PubMed1997

Use of a catecholamine sensor in the control of an artificial heart system.

An electrochemical sensor system to allow real-time measurement and feedback of catecholamine concentrations was developed for use in the control of artificial hearts. Electrochemical analyses were carried out using a carbon fiber working electrode, an Ag-AgCl reference electrode, and a potentiostat. The operating parameters of the pneumatically-driven artificial heart system were altered in accordance with the algorithm for changes in the catecholamine concentration. The minimum detectable concentrations of both adrenaline and noradrenaline in a mock circulatory system using a phosphate-buffered solution were approximately 1-2 ng/ml (10(-8) mol/L). An artificial heart control system utilizing this set-up performed satisfactorily without delay, although sensor sensitivity decreased when placed in goat plasma instead of a phosphate-buffered solution, due to the adsorption of various substances such as plasma proteins onto the electrodes. This study demonstrated the future feasibility of a feedback control system for artificial hearts using catecholamine concentrations.

Adsorption↗
PubMed1997

Issues in the comparison of risk estimates for the population in the Techa River region and atomic bomb survivors.

Plutonium production in the former Soviet Union began in 1949 at the Mayak Production Association located between the cities of Chelyabinsk and Ekaterinbourg in the southern Ural mountains about 1200 km east to Moscow. During the first few years of Mayak's operation, almost 30,000 people living on the banks of the Techa River received significant internal and external exposures as a consequence of the release of large quantities of radioactive materials from Mayak. Studies of levels of radioactive contamination and health effects in this population began in the early 1950s. A systematic follow-up of a fixed cohort that includes all people who were living in Techa River villages in 1949 was begun about 30 years ago. In this paper we describe the Techa River cohort, outline the nature of the exposures and discuss the status of follow-up for the period from 1950 through 1989. While noting the limitations of the current epidemiological follow-up data, we also compare the demographic and mortality structure of the Techa River cohort with the Life Span Study cohort of Japanese atomic bomb survivors. It is seen that, despite a number of limitations, the current data suggest that the risks of mortality from leukemia and other cancers increase with increasing radiation dose in the Techa River cohort. This finding suggests that, with continued improvements in the quality of the follow-up and dosimetry, the Techa River cohort has the potential to provide quantitative estimates of the risks of chronic low-dose-rate radiation exposures for an unselected general population that will be an important complement to the estimates based on the Life Span Study that are used as the primary basis for numerical assessments of radiation risk.

Environmental Exposure↗
PubMed1996

Heat treatment could affect the biochemical properties of caldesmon.

Smooth muscle caldesmon (CaD) exhibits apparent heat stability. A widely used purification procedure of CaD involves extensive heat treatment (Bretscher, A. (1984) J. Biol. Chem. 259, 12873-12880). CaD thus purified co-sediments with actin, inhibits actomyosin ATPase activity, and interacts with Ca2+/calmodulin, similarly to the unheated protein. On the other hand, heat-treated CaD binds to actin filaments in a tether-like fashion, whereas lengthwise binding dominates in vivo (Mabuchi, K., Lin, J. J.-C., and Wang, C.-L. A. (1993) J. Muscle Res. Cell Motil. 14, 54-64), suggesting that differences do exist between heat-purified CaD and the native protein. We have isolated, without heat treatment, full-length recombinant chicken gizzard CaD overexpressed in insect cells (High-FiveTM) using a baculovirus expression system. We found that such unheated CaD interacts with calmodulin 10 times stronger than does the heated CaD; its inhibitory action on actomyosin ATPase is reversed by a much lesser amount of calmodulin. Moreover, electron microscopic examination indicated that actin binding at the N-terminal region is more frequent in the unheated CaD, resulting in more lengthwise binding. These findings point to the fact that CaD is not entirely heat-stable; the C-terminal CaM-binding regions and the N-terminal actin-binding region are possibly affected by heat treatment.

Actins↗
PubMed1996

Immunocytochemical localization of caldesmon and calponin in chicken gizzard smooth muscle.

The distribution of caldesmon and calponin in chicken gizzard smooth muscle was investigated with immunofluorescence and immunogold electron microscopy. Immunofluorescence microscopy showed that in verapamil treated (relaxed) muscles the distributions of caldesmon and myosin appeared to be uniform throughout the cytoplasm, but clearly more textured than that of actin filaments as revealed by the distribution of tropomyosin. In shortened muscles both caldesmon and myosin became segregated, in contrast to the distribution of actin, which remained uniform. The distribution of calponin was even more textured, with no similarity to those of caldesmon or myosin. Instead, considerable overlap was observed between calponin and the cytoskeletal protein desmin and, to a lesser extent, beta-actin. By immunogold electron microscopy caldesmon appeared mostly near and around myosin filaments in both relaxed and shortened muscle. Calponin, on the other hand, was found primarily at the periphery of cytoskeletal structures in the same general region as desmin, and very often adjacent to beta-actin, which is mainly in the core. These observations indicated that caldesmon and calponin are associated with different subsets of actin filaments, caldesmon with contractile actin, while calponin with cytoskeletal actin. Thus the in situ localization of caldesmon is consistent with its proposed regulatory function. Calponin, on the other hand, is unlikely to directly regulate actomyosin interactions in these cells; instead, it may function as a bridging protein between the actin and the intermediate filament networks.

Animals↗
PubMed1996

Use of robotics technology to measure friction in animal joints.

A new system to measure friction in animal joints has been designed. The system utilizes a robotic arm. Force control of the robotic arm was used to survey the geometry of a sliding surface before the friction of the joint is measured. This enables the precise measurement of friction in joints of complex shape. To test the reliability of the new system we took friction measurements from 10 rabbit stifles. The experimental conditions were: (i) intact joints, (ii) joints after the surfaces were washed. The mean values of the frictional coefficients were 0.008 in the intact joints and 0.015 in the washed joints. These mean values were similar to some previous results obtained from canine hip joints under the same experimental conditions. Furthermore, the standard deviations in this study were smaller than in the previous study. These facts suggest that the new system is reliable. RELEVANCE:--The pathology of osteoarthritis is related to the lubrication mechanisms of joints. In any study of the lubrication mechanisms, an accurate friction measurement is important. In this study we used robotics technology to measure friction in joints.

Journal Article↗
PubMed1996

A percutaneously accessible pulsatile left ventricular assist device: modified assist device type 5.

To provide percutaneous access, a new circulatory assist system was developed. We call this newly developed system the modified assist device (MAD). The system is composed of a sac-type blood pump and cannula. Inflow and outflow valves are mounted in the apex and at the side wall 10 cm from the apex of the cannula, respectively. During systole, the blood is sucked from the left ventricle through the inflow valve of the cannula connected to the blood pump, and during diastole, the blood is ejected to the root of the aorta through the outflow valve. In vitro and in vivo evaluations of the pump performance were performed. The maximum flow rate of 1.9 L/min was obtained in the mock circulatory system. In our animal experiment, effective systolic unloading and diastolic augmentation were observed by activation of this system during regular sinus rhythm. In conclusion, the MAD-5 is thought to be percutaneously accessible and increases systemic and coronary flow.

Animals↗
PubMed1996

A long-term cohort study of the atomic-bomb survivors.

The Atomic Bomb Casualty Commission (ABCC), the predecessor of the Radiation Effects Research Foundation (RERF), was established in 1947 to conduct long-term, comprehensive epidemiological and genetic studies of the atomic-bomb (A-bomb) survivors. Today this study still depends upon the voluntary cooperation of several tens of thousands of survivors of the bombings of Hiroshima and Nagasaki. An in-depth follow-up study of mortality in the study population of 120,000 persons, including A-bomb survivors and controls, has continued since 1950. The study of tumor incidence was initiated through record linkage with a tumor registry system in Hiroshima and Nagasaki in 1958. In the same year, biennial medical examinations of 20,000 individuals began. Follow-up studies also have been conducted on in-utero-exposed persons and first-generation offspring of the survivors. On the basis of these studies spanning nearly half a century, we know that the occurrence of leukemia and cancers associated with A-bomb radiation is higher than among the non-exposed. Among the A-bomb survivors, radiation cataracts, hyperparathyroidism, delayed growth and development, and chromosomal aberrations also occur more often. However, to date no evidence exists of genetic effects in the children of A-bomb survivors. It should be kept in mind that such study results could never be obtained without the cooperation of A-bomb survivors.

Aged↗