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Biomedical subjects

H Iwamoto

Publications and source records attributed to H Iwamoto.

At least 163 records · Page 9Linked to original sources
PubMed1993

Crossbridge rotation in EDC-crosslinked striated muscle fibers.

The rotatability of the strong- and weak-binding myosin heads was tested by stretching glycerinated rabbit psoas fibers after crosslinking the heads to actin by using a carbodiimide EDC. The equatorial 1,1 reflection intensity (I1,1) decreased by approximately 10% upon 1% stretch in the presence of various ligands (ATP, ATP-gamma-S, pyrophosphate and AMPPNP). As the action of ligands to dissociate actomyosin increased, the relaxation of tension response to stretch and the I1,1 decrease were accelerated. This result is best explained if the ligand converts the crosslinked head to a weak-binding state, in which the head is rotatable because of its acquired elasticity. Conversely, the weak-to-strong transition was induced in the crosslinked system by removing a ligand (ATP-gamma-S) from myosin. Force was produced upon weak-to-strong transition and was accounted for by the increased stiffness of each crosslinked myosin head. However, the comparison of stress-strain curves for the weak- and strong-binding myosin showed that the equilibrium angle of myosin attachment was unchanged, making it unlikely that the weak-to-strong transition is the sole mechanism for active contraction. The calcium-activated force of the same crosslinked fibers showed several features in marked contrast to the force produced by the weak-to-strong transition. This leads to a possibility that the active force is supported by a third class of intermediate which is distinct not only from the weak-binding but also from the strong-binding intermediates in a classical sense.

Actins↗
PubMed1993

Measurement of transverse stiffness change during contraction in frog skeletal muscle by scanning laser acoustic microscope.

The scanning laser acoustic microscope (SLAM) was utilized to measure the change in the propagation velocity in the transverse direction during contraction in living skeletal muscles of the frog. The SLAM was operated at 100 MHz and interferograms were produced on a CRT in real time. The images of the interferogram were processed by image-analyzer and the propagation velocity was calculated from the shift of the interference line at rest and during contraction. In all the measurements (n = 15), the velocities during contraction were clearly slower (-7.6 m/s) than at rest and this means that the transverse stiffness decreased during contraction (-2.4 x 10(7) N/m2). The decrease in the propagation velocity preceded the increase in force by 30-40 ms after stimulation, suggesting that the decrease in the transverse stiffness reflects the basic molecular change in muscle contraction.

Animals↗
PubMed1993

The surgeon's technical skill in suturing: an analysis of the actual suture tracks.

Ideal suturing was defined as advancing a needle along its curvature (needle circle) to minimize tissue trauma, while placing the suture with its intended span and tissue bite in the expected place. Actual suture tracks were analyzed to find the keys to produce such suturing. Correspondence of those tracks to the ideal track was then determined by the span, the initial needle angle (IA) into the tissue, and the center of the needle circle. Eight surgeons with 4-7 years of experience produced 22 ideal sutures in two types of tissue simulants: The entrance and exit points of the needle were level in flat suturing, while the entrance point was slanted 45 degrees for slant saturing. The correspondence was better with slant suturing than flat suturing (P < 0.01). The IA in flat suturing was 49.0 +/- 2.0 (mean +/- SE) degrees versus 33.0 for ideal suturing (P < 0.01), while that in slant suturing was 35.5 +/- 1.9 (P: ns). In conclusion, the IA was the key to good results, and was optimized in slant suturing, which was instinctively utilized in practice by using forceps. The forceps avoided a derangement of suturing stemming from the configuration of the needle employed and from the range of motion of the surgeon's arm (human engineering), while satisfying the surgeons inclination to take a large IA.

Clinical Competence↗
PubMed1993

Prevalence of type 2 (non-insulin-dependent) diabetes mellitus and impaired glucose tolerance in the Japanese general population: the Hisayama Study.

We determined the population-based prevalence of diabetes mellitus in members of the Japanese community, Hisayama aged 40-79 years old by a 75-g oral glucose tolerance test. The basic population used to calculate diabetic prevalence was 1,077 men (72.8% of the whole population in the same age range) and 1,413 women (80.8%) including ten diabetic patients on insulin therapy. In addition, we compared the prevalence of history of diabetes which was acquired by interview or questionnaire, between participants and non-participants in the 75-g oral glucose tolerance test, but they were not statistically different. The age-adjusted prevalence of diabetes to world population was 12.7% for men and 8.4% for women, and that of impaired glucose tolerance was 19.6% for men and 18.4% for women. These figures were much higher than those previously reported from several Japanese communities. The results obtained from the present study could reveal true prevalence of diabetes among the Japanese population. In addition, the reasons for the increasing prevalence of diabetes among the recent Japanese population are also discussed.

Adult↗
PubMed1993

Screening of the mis-sense mutation producing the 717Val-->Ile substitution in the amyloid precursor protein in Japanese familial and sporadic Alzheimer's disease.

We investigated a C to T transition at base pair 2149 in the amyloid precursor protein gene in 41 Japanese cases of early-onset familial Alzheimer's disease (FAD), late-onset FAD and sporadic Alzheimer's disease (AD) by polymerase chain reaction and restriction enzyme polymorphism with BclI. Among 9 early-onset FAD patients derived from independent families, only one patient had the mis-sense mutation. Neither 5 patients with late-onset FAD nor 27 patients with sporadic AD had the mutation. Our result and the previous reports from Japan indicate that this type of mis-sense mutation is present in several cases of Japanese early-onset FAD. On the other hand, our data suggest that this mutation is not a common cause of Japanese early-onset FAD. Moreover, this mutation could be absent in late-onset FAD and sporadic AD in Japan. Because the mutation has been reported to be rare in Caucasian early-onset FAD and to be absent in Caucasian late-onset FAD and sporadic AD, the situation of this mutation in Alzheimer's disease may be common beyond the ethnic background.

Adult↗
PubMed1993

Breed differences in the histochemical properties of the M. pubo-ischio-femoralis pars medialis myofibre of domestic cocks.

1. Histochemical properties of M. pubo-ischio-femoralis pars medialis (PIF muscle) were compared in 7 breeds of cocks. This muscle was largely composed of Type I fibres and their transitional form (Type I tr). Type IIA fibres were observed in the cranial part. 2. The weight and cross-sectional area of the PIF muscle increased with increasing body weight. However, the relative muscle development to body weight differed among the 7 breeds. 3. A quarter of Type I fibres were of the transitional variety in bantam fowls. Conversely, few, if any, Type I tr fibres were observed in the large breeds where the muscle was poorly developed. 4. As the histochemical properties of Type I fibres made an effective response to the different body weights and the relative PIF muscle development among breeds, it was concluded that PIF muscle performed an important function in supporting the body weight and maintaining posture.

Adenosine Triphosphatases↗
PubMed1993

Different growth rates of male chicken skeletal muscles related to their histochemical properties.

1. Early, M. pubo-ischio-femoralis pars medialis (PIF muscle) and late, M. iliotibialis lateralis pars postacetabularis (ITL muscle), maturing muscles were studied. These two muscles contained different populations of histochemical fibre types. 2. The profile measurements of the muscles showed diphasic allometric growth relative to the weights. In the early stage of growth (up to 15 weeks after hatching), the muscle length, width and depth all increased, while in the later stage (from 15 to 35 weeks) muscle growth resulted mainly from the marked increase in the depth and to a lesser degree, from an increase in the width. 3. Type I fibres, observed predominantly in PIF muscle matured earlier than the Type II fibres of ITL muscle. 4. From these results, the detailed process of skeletal muscle growth in the chicken was discussed.

Animals↗
PubMed1993

Interaction between pullulanase from Klebsiella pneumoniae and cyclodextrins.

The interaction between pullulanase from Klebsiella pneumoniae and alpha-, beta-, and gamma-cyclodextrins and 6-O-alpha-glucosyl-alpha-cyclodextrin and 6-O-alpha-glucosyl-beta-cyclodextrin was examined by means of inhibition studies of the enzyme activity, UV difference spectroscopy, and flow calorimetry. All the above cyclodextrins were found to be competitive inhibitors, but beta-cyclodextrin and 6-O-alpha-glucosyl-beta-cyclodextrin showed strong inhibition, the inhibitor constants being two orders of magnitude less than those of alpha- and gamma-cyclodextrins. The difference spectra of beta-cyclodextrin were slightly but significantly different from those of the other cyclodextrins, showing blue shift of a few nanometers. Moreover, only beta-cyclodextrin has a positive entropy change upon binding with the enzyme; all the other cyclodextrins have negative values. These results show that the binding mode of beta-cyclodextrin is subtly different from those of alpha- and gamma-cyclodextrins.

Calorimetry↗
PubMed1993

Comparative study of the stability of the folding intermediates of the calcium-binding lysozymes.

Unfolding profiles of two calcium-binding lysozymes, equine milk lysozyme and pigeon egg-white lysozyme, were obtained by circular dichroism and proton NMR measurements. Equine lysozyme unfolds through a stable molten globule intermediate. The molten globule of equine lysozyme was characterized as more ordered than that of bovine alpha-lactalbumin. On the other hand, pigeon lysozyme unfolds by a two-state mechanism and the intermediate could not be observed in guanidine or thermal unfolding, the same as with conventional non-calcium-binding lysozymes. Thus, from the point of view of the unfolding profile, equine lysozyme belongs to the group of alpha-lactalbumin, but pigeon lysozyme belongs to the conventional lysozyme group.

Animals↗
PubMed1993

Splenic hemangiosarcoma with sinus endothelial differentiation.

A case of primary splenic hemangiosarcoma where the tumors entirely replaced the spleen is reported. Histologically, the splenic tumors consisted of two major components: (i) solid and nodular areas, in which spindle cells (SC) were arranged in interlacing fascicles; and (ii) vasoformative areas, in which vascular lining cells (VC) closely resembled normal splenic sinus endothelial cells (SSEC) in shape. Both SC and VC were immunoreactive with the markers of vascular endothelial cells (EC) including SSEC, JC70, von Willebrand factor, OKM5, vimentin MAb and Ulex europaeus-1 lectin. The tumor cells were positive for OKM5 MAb as well as normal SSEC and sheathed arterial EC, but other vascular EC in normal spleen were negative. Enzyme-histochemically, the tumor cells and normal SSEC revealed naphthol AS-D acetate esterase activity but no reaction for ALPase, whereas normal vascular EC other than SSEC in the spleen were positive for the latter but negative for the former. These studies revealed that the tumor cells expressed the same phenotype as normal SSEC. To the present author's knowledge this is the first report demonstrating sinus endothelial differentiation of splenic hemangiosarcoma, enzyme- and immuno-histochemically.

Aged↗
PubMed1993

Purification and characterization of alpha-glucosidase from Torulaspora pretoriensis YK-1.

alpha-Glucosidase was partially purified 103-fold from a cell-free extract of Torulaspora pretoriensis YK-1 by column chromatography on Toyopearl HW55F, DEAE-Toyopearl 650M, hydroxylapatite and phenyl-Toyopearl 650M. Further purification by preparative polyacrylamide gel electrophoresis (PAGE) gave the homogenous protein, but the specific activity was reduced. The molecular weight of the enzyme was estimated to be 69,000 by SDS-PAGE and 60,000 by gel filtration. Optimum pH and temperature were 6.8 and 35 degrees C, respectively. The enzyme was inhibited strongly by AgNO3, HgCl2, sodium dodecyl sulfate, and N-ethylmaleimide. The Km (mM) for p-nitrophenyl alpha-D-glucopyranoside, maltose, maltotriose, isomaltose, methyl alpha-glucoside, and sucrose were 0.15, 150, 45, 17, 18, and 29, and Vmax (mumol/min/mg protein) for those substrates were 87, 0.23, 2.4, 9.0, 12, and 7.4, respectively. The N-terminal amino acid sequence of the enzyme was PEVKNHPETQPKWWKEATVY. The properties of alpha-glucosidase from T. pretoriensis YK-1 were similar to those from Saccharomyces cerevisiae.

Amino Acid Sequence↗
PubMed1993

Measurement of glomerular filtration rate by free vitamin B12 clearance.

We determined the vitamin B12 clearance using an ultrafiltration technique and assessed whether the clearance of this vitamin B12 could be used to estimate the glomerular filtration rate (GFR). Fourteen subjects (5 had renal disease, 7 had diabetes mellitus, one had liver cirrhosis and one had cholelithiasis) divided into two groups were studied (group 1, 5 patients without vitamin B12 preloading; group 2, 9 patients with vitamin B12 preloading). Vitamin B12 clearance was significantly correlated with inulin clearance (r = 0.81, p < 0.001) in group 1; group 2 showed an even better correlation (r = 0.94, p < 0.001) with the presaturated vitamin B12 binding protein. In group 2, the mean inulin and vitamin B12 clearance values do not differ significantly (40.3 +/- 13.6 vs 48.2 +/- 17.2 ml/min), but there was a significant difference between mean inulin and creatinine clearance (40.3 +/- 13.6 vs 64.9 +/- 19.9 ml/min, p < 0.05). In conclusion, vitamin B12 clearance appears to be a more reliable method of estimating GFR than creatinine clearance.

Adult↗
PubMed1993

Measurement of transverse stiffness during contraction in frog skeletal muscle using scanning laser acoustic microscope.

The change in the transverse propagation velocity was measured by the scanning laser acoustic microscope (SLAM) during contraction in living frog skeletal muscles. The images of the interferogram were processed by image-analyzer and the propagation velocity was calculated from the shift of the interference lines at rest and during contraction. In all the measurements, the velocities during contraction were clearly slower than at rest and this fact indicates that the transverse stiffness decreased during contraction. After stimulation, the beginning of the decrease in the propagation velocity preceded that of the increase in force by 30-40 ms, suggesting that the decrease in the transverse stiffness reflects the molecular mechanism of force development in muscular contraction.

Acoustics↗
PubMed1993

[Hyperinsulinemia and hypertension in an elderly Japanese population--the Hisayama Study].

Hyperinsulinemia has been closely associated with hypertension in several epidemiological studies, but little is known about this condition in the elderly. The authors studied the relationship between serum insulin and blood pressure levels, and the prevalence of hypertension according to insulin levels in the elderly in a Japanese rural community, Hisayama. In 1988, 75 g oral glucose tolerance test was performed on 426 male and 567 female Hisayama residents aged 60 to 79 years. Fasting and 2 hr serum insulin values were measured by radioimmunoassay. In the subjects, excluding those receiving antihypertensive drugs, the sum of fasting and 2 hr postload insulin (sigma IRI) significantly correlated with systolic (r = 0.15 and 0.25 for males and females, respectively) and diastolic blood pressure (r = 0.20, 0.16). In multiple regression analyses, the correlation with systolic blood pressure remained significant in females after controlling for age, body mass index, alcohol intake, smoking habits, serum total cholesterol, HDL-cholesterol, triglycerides, and fasting plasma glucose. In contrast, sigma IRI did not remain as an independent variable relevant to blood pressure among males. The age-adjusted prevalence rates of hypertension (> or = 160/95 mmHg or receiving drug treatment) significantly increased with increasing quartiles of sigma IRI in females. The prevalence of hypertension which was not treated with drugs also increased significantly with increasing sigma IRI in females. However, no significant association was observed in males. In conclusion, the present study suggests that hyperinsulinemia can be related to hypertension in the female elderly in the general population of Japan.

Aged↗
PubMed1993

The relationship between muscle growth and the growth of different fiber types in the chicken.

A relationship of muscle growth to fiber growth was investigated histochemically and allometrically in the chicken from 1 to 35 wk of age. Muscle fibers were classified into three types (I, IIA, and IIB) based on the reactivities for myosin adenosine triphosphatase and reduced nicotinamide adenine dinucleotide dehydrogenase. Fiber type composition widely varied in the four muscles examined in this study. Longus colli dorsalis contained all three types. The Pectoralis was composed only of IIB fibers. The caudal portion of Femorotibialis medius was made up of Type I and IIA fibers. The caudal Iliotibialis lateralis and the cranial portion of Femorotibialis medius were composed of two types, IIA and IIB. These latter two muscles showed a progressive increase of Type IIA fibers and decrease of Type IIB fibers with advancing age. Two processes controlling muscle growth were elongation and enlargement of muscle fibers. The elongation of muscle fibers stops by 15 wk of age, coincident with the cessation of bone growth. However, the enlargement of muscle fibers, the increase in diameter of muscle fibers, continued until 35 wk of age. The rate of enlargement of muscle fibers varied by muscle and fiber type. In general, greatest growth occurred in Type IIB fibers of hindlimb muscles.

Aging↗
PubMed1993

Mitral valve suturing technique. Needle grips of choice determined from a geometric basis.

Placing sutures in the mitral annulus is often difficult due to its awkward anatomical location. The needle grips of choice were therefore determined by geometric analysis. The operating space model was restrictively designed so as to provide only narrow visualization of the uppermost portion of the annulus. The needle used was half-circled and 20 mm in length. The general rule of needle grips for addressing the needle on the annulus was as follows: those for the lower half of the annulus were grips holding the needle obliquely 30 degrees (oblique grip) at its midpoint, with ordinary suturing (advancing the needle by supination) for the cephalad half of the annulus and with the reversed grip (pronation) for the caudal half. For the lowermost portion, the choice was the reversed grip, obliqued 60 degrees and held near the swage. For the upper half, the choice was the grip holding the needle at its midpoint after rotation (rotated grip). However, the extent of rotation was 60 degrees for the uppermost portion, but 30 degrees for all others. This rule is useful as a general guide not only in the mitral annulus, but also in other operating fields where sutures can be placed in vertical tissues only through a narrow pass.

Humans↗