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Biomedical subjects

H Asai

Publications and source records attributed to H Asai.

At least 145 records · Page 8Linked to original sources
PubMed1982

Heterogeneity in enzymatic sites of heavy meromyosin shown by measuring F-actin-inactivated hydrolysis of beta-naphthyl triphosphate.

Enzymatic characteristics of heavy meromyosin (HMM) were investigated by measuring beta-naphthyl triphosphate (beta-NapP3) hydrolysis in the presence and absence of F-actin. beta-NapP3 hydrolysis by HMM was inactivated by F-actin in the presence of Mg ions; in the presence of sufficient F-actin, the activity was about one-half of that in the absence of F-actin. In the presence of Ca ions the activity disappeared almost completely on addition of sufficient F-actin. Two different values of the Michaelis constant (Km) were obtained from the data for beta-NapP3 hydrolysis by HMM in the presence of Mg ions; one of them vanished in the presence of sufficient F-actin, and only one Km value was obtained in the presence of Ca ions. These results suggest the existence of two distinct enzymatic sites in HMM, one inactivated by F-actin in the presence of Mg or Ca ions, the other inactive in the presence of Ca ions but active in the presence of Mg ions and not influenced by F-actin. Use of subfragment-1(A1) (S-1(A1)) and S-1(A2) instead of HMM confirmed that these enzymatic characteristics are not due to a difference in the alkali light chains on myosin heads.

Actins↗
PubMed1982

Comparison between AP and SP parameters in trans- and extratympanic electrocochleography.

Results of the comparison of action potential (AP) and summating potential (SP) parameters in trans- (TT) and extratympanic (ET) methods in 2 normal-hearing ears and 20 hearing-impaired ears with various etiologies and audiogram shapes are reported. In normal and impaired ears the TT/ET ratio of N1 amplitude was intensity dependent and was greater at higher intensities than at lower intensities. N1 latency was identical in both methods. The AP waveform was almost identical in both methods in ears except in a noise-induced hearing loss: N1/N2 ratio was greater in the TT method than in the ET method. In the TT method +SP at high frequency tone bursts and -SP at low frequency tone burst were recorded in Menière's disease and progressive sensorineural hearing loss, while in the ET method only -SP was recorded at a tone burst of each frequency. Origins of N1 and N2 and a clinical value of -SP and +SP are discussed.

Acoustic Stimulation↗
PubMed1981

The average number of distinct sites visited by a one-dimensional random walker and its application to isotope exchange in polypeptides.

The average number of distinct sites visited by a random walker moving with arbitrary transition probability on a one-dimensional lattice is calculated. Asymptotic forms of this quantity for both asymmetric and symmetric random walks are determined, and an exact solution for the latter case is also given for any number of steps. The average number of sites visited is then analyzed for intermediate numbers of steps by introducing an exponent. This approach is applied to explain the results of isotope exchange experiments in polypeptides, and applications of asymmetric random walks to other biological problems are briefly discussed.

Journal Article↗
PubMed1981

Amphoteric charge distribution at the enzymatic site of 1,N6-ethenoadenosine triphosphate-binding heavy meromyosin determined by dynamic fluorescence quenching.

The features of the charge distribution in the vicinity of the ATP-binding site of heavy meromyosin (HMM) were investigated by the technique of dynamic fluorescence quenching. Instead of ATP, 1,N6-ethenoadenosine triphosphate (epsilon-ATP), a fluorescent derivative of ATP, was attached to the ATP-binding site in the presence of an ATP-regenerating system. The I- ion and acrylamide were used as negative- and zero-charged quenchers. In addition to these quenchers, we used the TI+ ion, which has recently been found to be a highly efficient quencher with positive charge, and to be generally applicable to fluorescence-labeled proteins. The Stern-Volmer quenching constants of TI+ and I- for epsilon-ATP bound to HMM both decreased with increasing ionic strength of the solvent. This result means that there is an electrostatic attractive force between the fluorophore ad both TI+ and I-. On the other hand, the Stern-Volmer quenching constant of acrylamide was not significantly affected by a change in ionic strength. This result confirms that no significant change in protein conformation in the vicinity of the epsilon-ATP-binding site of HMM occurs with change in ionic strength. In order to interpret these results, we propose a model in which a positive charge is located on one side of the epsilon-adenine ring and a negative charge is located on the opposite side. The negative charge is attributed to the phosphate group in epsilon-ATP and positive one is probably attributable to a lysyl residue in the polypeptide chain of HMM.

Adenosine Triphosphate↗
PubMed1981

Inhibition of palmitoyl CoA of EDTA- and Mg2+-ATPase of heavy meromyosin from rabbit skeletal muscle.

Palmitoyl CoA inhibited EDTA-ATPase of heavy meromyosin (HMM) prepared from rabbit skeletal muscle. The concentration for half maximum inhibition of EDTA-ATPase was about 18 microM. Myristoyl CoA, the other long chain fatty acyl CoA, also inhibited EDTA-HMM ATPase, but CoA and short chain CoA thioesters, such as butyryl CoA, acetoacetyl CoA and acetyl CoA, at 40 microM hardly inhibited EDTA-ATPase. Less than 20% inhibition of EDTA-HMM ATPase was obtained with Na-palmitate and Na-myristate at 40 microM, whereas about 90% inhibition of the enzyme occurred in the presence of 40 microM palmitoyl CoA and myristoyl CoA. Palmitoyl carnitine, as well as carnitine, failed to inhibit EDTA-HMM-ATPase. The inhibition of palmitoyl CoA of EDTA-ATPase was reversed by bovine serum albumin and spermine. Mg2+-HMM ATPase activity was enhanced by palmitoyl CoA at 2, 5, and 10 microM. About a 25% increase in Mg2+-HMM ATPase activity was obtained at 5 and 10 microM. At higher concentrations than 20 microM, the enzyme was inhibited by palmitoyl CoA and the degree of inhibition was related to the concentration of the CoA thioester. At 80 microM, the activity was about 15% of the maximum value. The efficacy of myristoyl CoA on Mg2+-ATPase was almost the same as that of palmitoyl CoA. Mg2+-ATPase activity was not enhanced by CoA, butyryl CoA, acetoacetyl CoA, Na-myristate, Na-palmitate, palmitoyl carnitine, or carnitine at 10 microM, and was hardly reduced by these substances at 40 microM. Serum albumin and spermine also canceled, to some extent, these effects of palmitoyl CoA on Mg2+-ATPase.

Acyl Coenzyme A↗
PubMed1981

Intertest reliability in non-invasive electrocochleography.

Intertest reliability of action potential (AP) and summating potential (SP) parameters in non-invasive electrocochleography (ECochG) was studied in 4 normal ears and 7 hearing-impaired ears with stable audiograms. The interval between test and retest was 10 days to 2 years and 5 months. Intertest differences in AP response threshold and -SP detection threshold were within 10 dB. N1 amplitude, N1 latency, -SP amplitude, and -SP/AP ratio had excellent correlations between test and retest. N1 latency had a better intertest reliability than N1 amplitude. Waveform had almost the same shape in retest as in test. The intertest differences in AP and SP parameters were examined. On the basis of these data values for the criteria of significant change in test and retest in non-invasive ECochG are presented. The non-invasive ECochG is particularly suitable for monitoring both progressive and fluctuant hearing loss.

Adolescent↗
PubMed1980

Diffusion of H-meromyosin in F-actin plus ATP solution at a very low electrolyte concentration.

The translational diffusion coefficient (D) of H-meromyosin in actin (F-actin) and ATP solution was measured under conditions wherein the actin-activated ATPase activity is close to its maximal value at a very low electrolyte concentration. The results were compared with similar data obtained with 0.1 M KCl, where H-meromyosin and actin were almost completely dissociated. With 0.1 M KCl, it was found that there was no dependence of the D of H-meromyosin on actin concentration. On the other hand, at a very low electrolyte concentration, it was found that the D of H-meromyosin did depend on actin concentration; at a rather high actin concentration (and activation of ATPase), it was slightly larger than at low or zero actin concentrations. This behavior of D at a low electrolyte concentration is interpreted on the assumption that even in solution, H-meromyosin molecules can actively slide on actin filaments due to the ATPase activity.

Actins↗
PubMed1980

Hepatitis B virus and alcoholic liver damage in the Airin district. (Osaka's skid row area).

Healthy adults and non-liver disease patients in the Airin district gave a positivity rate for HBs antigen of approximately 2%, which is not so much different from the average of the entire Japanese population. In this district, the positive rate of HBs antigen 5% (11 out of 244) in chronic liver disease is much lower than that (31%) of control group patients at Osaka City University Hospital (O.C.U.H.). However the positive rate of anti-HBs antibody in this district is 46% which is extremely high compared with that (23.4%) in the rest of Japan. The positive for anti-HB antibodies (including of anti-HBs and anti-HBc antibody) accounted for 67% of non-liver disease patients and 68% of chronic liver disease patients in the Airin district. Corresponding values for patients at O.C.U.H. were 44% and 43% respectively. There were no significant differences in the histological picture between HBs antigen-negative patients with and those without demonstrable anti-HBs antibodies. Changes in the liver exhibited by heavy drinkers inhabitating the Airin district were primarily those of alcoholic liver damage.

Antibodies, Viral↗
PubMed1980

Clinical application of non-invasive electrocochleography.

Non-invasive extratympanic electrocochleography (ECochG) was performed in normal-hearing subjects and patients with sensorineural deafness. Action potential (AP) threshold, N1 input-output function, waveform, summating potential (SP) are presented. AP thresholds were within 15 dB in normal-hearing ears and within 30 dB in hearing-impaired ears above subjective thresholds for the click. Correlational analysis showed that click-evoked AP thresholds are best correlated to pure tone thresholds at 2 to 4 kHz. Four types of N1 input-output functions were classified. Normal functions appeared in moderate high tone loss only at 8 kHz and low tone loss with almost normal threshold above at 4 kHz. Many ears with a flat loss had recruiting responses, while many ears with a high tone loss had either dissociated responses or responses with prolonged latency. Several types of waveforms were distinguished. Enhanced--SP was observed in Meniére's disease and late congenital syphilis to which endolymphatic hydrops is common. The clinical value of the non-invasive ECochG is discussed.

Adolescent↗
PubMed1980

Fluorometric method for estimating the kinetic parameters of beta-naphthyl triphosphate and ATP hydrolysis by acto-heavy meromyosin.

We have established a method to estimate the values of various kinetic parameters of acto-heavy meromyosin (acto-HMM) ATPase, using a fluorescent ATP analog, beta-naphthyl triphosphate (beta-NapP3); from the fluorescence intensity change accompanying beta-NapP3 hydrolysis, the various kinetic parameters of beta-NapP3 hydrolysis, including its product inhibition, were obtained. beta-NapPd3 hydrolysis is inhibited competitively by ATP, resulting in different time courses of fluorescence intensity change in the presence and absence of ATP. From this difference, the values of kinetic parameters of ATP hydrolysis, including its product inhibition, can be estimated. By extending this method to the acto-HMM system, seventeen parameters in a reaction scheme for the concurrent hydrolysis of ATP and beta-NapP3, including association constants between F-actin and substrate-free or substrate-bound HMM, were obtained. The kinetic-parameters estimated for ATP hjydrolsis were in good agreement with those in the literature.

Adenosine Triphosphatases↗
PubMed1980

Electric potential at regions near the two specific thiols of heavy meromyosin determined by the fluorescence quenching technique. I. Effect of ATP.

Electric potentials at regions near the two specific thiol groups, SH1 and SH2, of the heavy meromyosin (HMM) molecule were studied by the fluorescence quenching technique. The effects of binding of ATP to HMM upon the electric potentials were also studied. N-(p(2-Benzimidazolyl)phenyl)maleimide (BIPM) was used as a thiol-directed fluorescent reagent. Prior to the labeling of SH2 with BIPM, the SH1 group was blocked with N-ethylmaleimide (NEM). Iodide ions (I-), thallium ions (Tl+), and acrylamide were used as quenchers of fluorescence. The sign of the electric potential was collectively determined from the dependence of the Stern-Volmer constants upon the ionic strength of solutions. 1. The region near SH1 was at a negative electric potential, whereas the electric potential at the region near SH2 was almost zero. 2. On the addition of ATP, the fluorescence intensity of BIPM bound to SH1 was unchanged, whereas that of BIPM bound to SH2 was greatly decreased to about 50% of the original level. The fluorescence intensity recovered as the added ATP was split into ADP and orthophosphate, and became saturated. The saturated level of the fluorescence intensity was, however, smaller than the original one, due to binding of the produced ADP to HMM. 3. On the addition of ATP, the negative electric potential at the region near SH1 was unchanged, whereas a negative electric potential with large gradient was newly introduced at the region near SH2. The value of the newly introduced electric potential was calculated on the basis of various assumptions. These results are discussed in connection with the functions of myosin.

Acrylamides↗
PubMed1980

Charge effects on the dynamic quenching of fluorescence of 1,N6-ethenoadenosine oligophosphates by iodide, thallium (I) and acrylamide.

Systematic studies were carried out to determine how the dynamic quenching of fluorescence was affected by electrostatic interaction between charges carried by the fluorophore and the quencher. 1,N6-Ethenoadenosine oligophosphates (epsilon-ATP, epsilon-ADP, epsilon-AMP, and epsilon-Ad) were used as fluorophores; these compounds have the same luminous group (epsilon-adenine ring) with variously charged phosphate groups. Acrylamide and the iodide (I-), well known to be effective quenchers carrying zero and one negative charge, respectively, were used as quenchers. The thallium (I) (Tl+) was also found to be an effective quencher as a result of studies of the quenching activity of various positively charged ions. Results which agreed qualitatively with those expected were obtained for the charge effects on the dynamic quenching and the effects of ionic strength on it. That is, the repulsive force exerted between I- and phosphate groups decreased the quenching rate, and increasing ionic strength of solutions mitigated these charge effects. The results obtained, however, were not quantitatively consistent with theoretical expectations for ionic reaction rates in solutions. One reason for the quantitative disagreement is that the negatively charged phosphate groups are located at a distance from the luminous group. By theoretical analysis of the quenching data, the distance was calculated to be 9.6 A + delta r, where delta r changes according to the number of phosphate groups. Furthermore, through a theoretical analysis of the disagreement, we found a new factor, the "size effect" of a luminous group, which modifies the charge effects on dynamic quenching. The size effect provides information on the gradient of the electric potential generated by the phosphate groups. These studies provide a basis for the study of electric potential at local regions of proteins.

Acrylamides↗