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Biomedical subjects

O Yamaguchi

Publications and source records attributed to O Yamaguchi.

At least 109 records · Page 6Linked to original sources
PubMed1984

Relationship between maximum active stress and contractile protein contents in the chronically obstructed ureter.

Maximum active stress and contractile protein contents of the dilated ureter were determined using the chronically obstructed rabbit ureter. Active length-tension curve was demonstrated for tissue strips obtained from normal and dilated ureters. In the normal ureter, maximum active stress of the strips was 10.4 +/- 2.04 X 10(4) dyne/cm.2 while the myosin and actin contents in the tissue were 6.05 +/- 0.44 and 15.46 +/- 1.96 mg./gm. tissue, respectively. Maximum active stress of the obstructed ureter varied from 5.1 X 10(4) to 19.0 X 10(4) dyne/cm.2 The amount of contractile protein in the obstructed ureter varied from 0.57 to 8.07 mg./gm. tissue for myosin and from 8.16 to 22.9 mg./gm. tissue for actin. For various degrees of ureteral dilatation, the active stress and contractile protein content showed similar changes. A significant correlation was demonstrated between maximum active stress and contractile protein content. The myosin amount was more closely correlated with maximum active stress, indicating that the content of myosin is a means of predicting contractility of the obstructed, dilated ureter.

Actins↗
PubMed1983

Urodynamic studies on hemiplegic patients after cerebrovascular accident.

Thirty-nine hemiplegic patients were evaluated by complete urodynamic study after cerebrovascular accidents. Computerized tomography was performed to identify localization of the brain lesion. The common urinary symptoms were frequency and urgency incontinence (26/39), while 13 patients complained of dysuria or urinary retention. Ten of the 11 patients who had frontal and internal capsular lesions showed hyperactive bladder, and 6 showed uninhibited sphincter relaxation. Nine of the 10 patients who had putaminal lesions showed hyperactive bladder. Normal sphincter activity was demonstrated in 7 of these 10 patients. In the remaining patients with the other types of lesions, no correlation was found between urodynamic dysfunction and type of brain injury.

Aged↗
PubMed1983

Animal model of megaureter.

A rabbit model with a megaureter was produced by the partial obstruction of the ureter. The resultant dilatation obtained after the chronic obstruction (more than 100 days) was approximately 4 times greater than the normal ureteral diameter.

Animals↗
PubMed1981

Multiple-coupled pacemaker system in renal pelvis of the unicalyceal kidney.

The characteristics of spontaneous contractility in the renal pelvis were examined in the unicalyceal kidney of the rabbit. In vitro isometric studies were done on whole as well as renal pelvic segments dissected longitudinally and radially. The results show that the contractile frequency of isolated segments was highest in the proximal region (4.188 +/- 0.162 min-1) and decreased distally to (2.178 +/- 0.330 min-1). There was no significant frequency gradient in the circumferential direction. A modulation of wave form (waxing and waning phenomena) was observed in both the proximal and middle regions of the pelvis. Based on these results, a simulation of the renal pelvic activity was made by using a chain of coupled linear oscillators. At high values of coupling a pacemaker contraction of the renal pelvis was reproduced by the coupled oscillator model. The modulation of wave form was observed when the coupling of the circumferential direction was weak. These results are discussed in the context of the hierarchically organized multiple-coupled pacemaker system, which characterizes an integrative activity of the unicalyceal renal pelvis.

Animals↗
PubMed1980

Linkage disequilibrium in isolated populations of Drosophila melanogaster.

In order to test the interaction effect of overdominance and random genetic drift on the formation of linkage disequilibria under the condition of multiplicative gene action, linkage disequilibria between isozyme genes, inter se, and between polymorphic inversions and isozyme genes were tested for the second chromosomes of Drosophila melanogaster sampled from two isolated Pacific islands and one locality of the northern district of the mainlands of Japan. The effective sizes of these populations were known to be approximately 3,000 to 6,000 on the basis of the allelism rate of lethal chromosomes and their frequencies. The following results were obtained: (1) No linkage disequilibrium considered to be induced by epistasis, including the interaction between overdominance and random genetic drift, was detected. (2) Nonrandom association between polymorphic inversions and isozyme genes that are included in the inversions or located in the adjacent region outside the inversions was detected. (3) On the basis of the comparison of chi (2) values, indicating the magnitudes of linkage disequilibrium, between the present isolated populations and the Raleigh, N.C., population (Mukai et al. 1974, 1977), the characteristics of the isolated populations and the nature of these linkage disequilibria are discussed.

Animals↗
PubMed1979

Dynamics of upper urinary tract during pacemaker blockade induced by pentobarbital.

The transport efficiency of the dog's pelviureteral system was examined during pacemaker blockade induced by pentobarbital. For an analog representation of transport efficiency, changes in balance level between the input and the output were registered and recorded on a polygraph together with perfusion rate, renal pelvic pressure, ureteral electromyogram and bolus volume. Pentobarbital dramatically blocked the pacemaker activity of the renal pelvis, and the ureter simultaneously became aperistaltic. During the period of pacemaker rest, the balance level was maintained at a high level in all dogs studied, indicating that a part of the perfusion fluid was accumulated in the pelviureteral system. Furthermore, the accumulated fluid overflowed through the aperistaltic ureter as a free flow. These results are discussed in relation to the transport efficiency of normal peristaltic transport.

Animals↗
PubMed1978

The simultaneous recording of the rhythmic contraction and electrical activity of the renal previs--a new in vitro method.

A new in vitro method which enables the simultaneous recording of the electromyogram from various regions of the renal pelvis and the pressure changes associated with those electrical activities is described in an experiment on canine kidney. At the proximal end of the renal pelvis, the interval of the electromyogram was constant and pelvic pressure changes showed rhythmic activity, while the discharge interval of the proximal end was the same as the pressure interval. However, the discharge intervals of both the pelvic center and the pelviureteric junction were found to be multiples of that of the proximal end of the pelvis.

Animals↗
PubMed1978

Transport efficiency of ureteral peristalsis correlated to pacemaker activity of renal pelvis.

The transport efficiency of ureteral peristalsis under the control of the pacemaker was examined during renal pelvic perfusion in dogs. Simultaneous recordings of the perfusion rate, renal pelvic pressure, ureteral electromyogram, and bolus volume were made during each period of perfusion at a constant rate. For a graphic representation of transport efficiency of each peristaltic contraction, changes in balance level between the perfusion rate and the bolus volume were registered by a presettable binary counter. A quantitative evaluation of transport efficiency was also made of each group of peristaltic contractions that was classified by its characteristic distribution of the interperistaltic internal. The pacemaker activity of the renal pelvis and its control of ureteral peristalsis were identified in this preparation. Most of the peristaltic contractions excreted the same volume of fluid that had entered the pelviureteral system during the preceding period of nonperistalsis within the range of studied perfusion rates. The transport efficiency defined as interperistaltic interval x perfusion rate/bolus volume showed a small variation around the value 1 for peristaltic contractions in each group.

Animals↗
PubMed1977

A constant electrical activity of the renal pelvis correlated to ureteral peristalsis.

Using a bipolar macroelectrode, simultaneous recordings of both pelvic and ureteral electromyograms (EMG) were carried out in dogs. The recordings were performed at 3 stages of urine flow; oliguric, increasing and diuretic stages. The results showed that the interval of the pelvic discharge was constant while its speed of propagation was slower than that of the ureter (1.32 cm/sec and 2.12 cm/sec, respectively). At oliguric stage the interperstaltic interval in the ureter constituted a multiple of the pelvic discharge interval. Ureteral peristaltic rate reached that of the renal pelvis with increasing urine flow. These results are discussed in relation to a hypothesis of a renal pacemaker.

Animals↗