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Biomedical subjects

K Imanaka

Publications and source records attributed to K Imanaka.

At least 55 records · Page 3Linked to original sources
PubMed1996

Evident difference in the excitability of the motoneuron pool between normal subjects and patients with spasticity assessed by a new method using H-reflex and M-response.

The excitability of the motoneuron (MN) pool in the resting state was compared between normal control subjects and patients with spasticity resulting from HTLV-I-associated myelopathy, using a new parameter, Hslp/Mslp, and the conventional parameters Hmax/Mmax and Hth/Mth. Differences in the excitability of the MN pool between these two groups reached a high degree of statistical significance only when assessed with the new parameter. This suggests the methodological advantage of the Hslp/Mslp over both Hmax/Mmax and Hth/Mth for evaluation of the excitability of the MN pool in the resting state.

Action Potentials↗
PubMed1996

Truncation at the C-terminus of the DAX-1 protein impairs its biological actions in patients with X-linked adrenal hypoplasia congenita.

The DAX-1 [DSS (dosage-sensitive sex)-AHC critical region in the X, gene 1] gene has been reported to be responsible for X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism. However, the function and structure of the DAX-1 protein have not been characterized. In this study, molecular analysis of the DAX-1 gene from 6 patients with AHC, including 2 siblings, identified 5 novel mutations with 3 nonsense mutations and 2 frameshift mutations. Case 1 had a nonsense mutation at position 395 (Q395X). Cases 2 and 3, who were siblings, had a nonsense mutation at position 91 (Y91X). Case 4 had a 2-base deletion (AT) at nucleotides 1610 and 1611 and a 1-base insertion (G) resulting in a premature stop codon at position 462 (1610-1611 del AT ins G). Case 5 had a nonsense mutation at position 271 (Y271X). Case 6 had a 1-base deletion (C) at nucleotide 1169, which induced a frame shift and a premature stop codon at position 371 (1169 del C). All mutated DAX-1 proteins had truncated C-terminal domains. In addition, reverse transcription-PCR and direct sequencing characterized the mutant messenger ribonucleic acid in testis from case 1. Our results suggest that these 5 novel mutations are responsible for X-linked AHC and that the C-terminus of the DAX-1 protein, especially the terminal 11 amino acids, is necessary for normal adrenal cortical embryogenesis.

Adolescent↗
PubMed1996

Inhibition of the soleus H-reflex during dorsiflexion is dependent on individual differences in maximal soleus H-reflex as a test reflex.

The quantitative differences among individuals in the natural reciprocal inhibition of the soleus H-reflex during dorsiflexion were examined, in conjunction with the maximal H-reflex as the test reflex size in each individual. Maximal H-reflex was expressed relative to the maximal M-response (H(max)) when compared among individuals. Analysis showed that with increases in H(max) at rest in each individual, the inhibitory effect was first enhanced, then reached a peak, and was finally alleviated. This pattern was similar to the intraindividual pattern of the inhibitory effect induced by specific conditioning stimulus as a function of the test reflex size.

Adolescent↗
PubMed1996

[Successful redo-AVR with cryopreserved allograft for prosthetic valve endocarditis : report of a case].

A 20-year-old male undergoing mechanical aortic valve replacement suffered from prosthetic valve endocarditis by Coagulase negative Staphylococci 3 months postoperatively. Echocardiography revealed left ventricular distention, severe paravalvular leakage, valve detachment and large periannular abscess adjacent to the left main coronary artery. Redo-AVR was successfully performed with a cryopreserved aortic allograft by cylinder technique. The orifice of abscess was covered with the aortic wall of the graft. Postoperative echocardiography showed trivial central regurgitation and the abscess cavity went on vanishing. He discharged from hospital 2 months later without any symptom.

Abscess↗
PubMed1996

[Echocardiographic evaluation of hemodynamic function of CarboMedics heart valve in the aortic position in patients with small aortic annuli].

Hemodynamic parameter of CarboMedics heart valve in the aortic position was evaluated using Doppler echocardiography in 46 patients with small aortic annuli. The size of prosthetic valve were 19 mm in 6 cases, 21 mm in 15 and 23 mm in 25. In patients with 19 mm valve, trans-valvular peak pressure gradient was 42.2 +/- 11.8 mmHg, mean pressure gradient was 17.3 +/- 9.3 mmHg, and left ventricular systolic pressure was 174 +/- 12 mmHg. These values were significantly larger than those of the other two groups. Effective orifice area index, discharge coefficient, doppler velocity index and stroke volume showed no significant difference among each group. After aortic valve replacement for aortic stenosis, left ventricular mass decreased to around 70% of preoperative value in all groups, but significant left ventricular hypertrophy remained at two years postoperatively. We conclude that hemodynamic performance of CarboMedics heart valve in the aortic position was satisfactory, although 19 mm valve seemed to be fairly small for adult patients and deliberate patient selection is necessary.

Adult↗
PubMed1995

Hemispace asymmetries and laterality effects in arm positioning.

Hemispace asymmetries and laterality effects were examined on an arm positioning reproduction task. Sixteen male subjects were asked to reproduce both abductive and adductive positioning movements with the left or right arm within either the left or the right hemispace. Hemispace was manipulated using a 90 degrees head-rotation paradigm. A left hemispace advantage in positioning accuracy was predicted for both left and right arm movements on the grounds that the perceptual-motor control of positioning movements made in left hemispace is primarily mediated by the right hemisphere which is known to be advantageous for tasks which are spatial in nature (Heilman, Bowers, & Watson, 1984). No arm laterality effects were predicted to occur because the proximal musculature involved in the control of arm movements is innervated from both contralateral and ipsilateral cerebral hemispheres (Brinkman & Kuypers, 1973). Results showed that the predicted left hemispace advantage was evident for the right arm on the positioning variability measure alone, whereas it was absent for all other possible conditions on all error measures. Laterality (arm) effects were absent as predicted. The experiment also demonstrated a greater degradation of reproduction performance under the "crossed" arm-hemispace conditions than under the "uncrossed" conditions. A plausible explanation for the uncrossed advantage for the task is that under normal conditions, a single hemisphere is primarily responsible for both controlling the contralateral arm and directing attention to the contralateral hemispace, and consequently potential interhemispheric interference is minimized. A clear response bias effect in movement reproduction was also evident as a function of the direction of concurrent arm movement and head rotation. Arm movements made in the same direction as head rotation were systematically undershot in reproduction to a much greater degree than arm movements made in the opposite direction to head rotation.

Adolescent↗
PubMed1995

Frontal N30 potential following a sustained voluntary movement.

With 6 male subjects we investigated whether the decreased amplitude in the frontal N30 potential of Somatosensory Evoked Potentials is related to a sustained voluntary movement or not. We concluded that the diminution of frontal N30 was also closely related to the sustained voluntary movement.

Evoked Potentials, Somatosensory↗
PubMed1994

Threshold of the soleus muscle H-reflex is less sensitive to the change in excitability of the motoneuron pool during plantarflexion or dorsiflexion in humans.

In the present study, we investigated whether weak (10% of maximal voluntary contraction) tonic dorsiflexion (DF) and plantarflexion (PF) affects the two conventional parameters used for evaluating the excitability of the soleus motoneuron (MN) pool, i.e. the ratio of the threshold of H-reflex to that of M-response (Hth:Mth) and the ratio of the maximal amplitude of H-reflex to that of M-response (Hmax:Mmax) in human subjects. The results showed that the Hmax:Mmax decreased during DF and increased during PF compared with that during rest, whereas no clear alteration was observed in Hth:Mth. These results are consistent with the scheme proposed by earlier workers, who have argued that neither inhibitory nor facilitatory effects of the conditioning stimulus apply to specific spinal reflex circuits occurring around the threshold of the test H-reflex. It is suggested, therefore, that the conventional use of the Hth:Mth ratio as a parameter reflecting the excitability of the MN pool should be reconsidered.

Adult↗
PubMed1994

Reconsidering the 90 degrees head-rotation paradigm used in neuropsychological research: are there reflexive rather than hemispatial effects?

The 90 degrees head-rotation paradigm has often been used in neuropsychological studies to manipulate external hemispace (circumcorporeal space) relative to the head. Under the 90 degrees head-rotation paradigm, the performance of limb and hand movements carried out within the left or right hemispace as defined by head positions relative to the body is likely to be affected by the reflexive effect due to the neck and vestibular afferent inputs elicited by the head rotations, as well as by the hemispatial effect. Using the H-reflex technique, the present study examined whether the reflexive effect on the spinal motoneuron excitability occurred with head rotations under the 90 degrees head-rotation paradigm. The results showed that the amplitudes of H-reflexes evoked on both the thumb flexor and soleus muscles were not affected by head rotations, indicating no reflexive change in the spinal motoneuron excitability for both the thumb and soleus muscles. This finding suggests that the reflexive effect due to neck and vestibular afferent inputs can be ruled out from possible causal factors influencing the motor performance of limb and hand movements performed within the left or right hemispace as manipulated by the 90 degrees head-rotation paradigm.

Adolescent↗
PubMed1994

[Conservative surgery for renal cell carcinoma].

During the nine years period from April 1984 through March 1993, we performed conservative surgery on 26 kidneys in 25 patients with renal cell carcinoma. Of these 25 patients the indication was imperative in 8 patients (the imperative group) and elective in 17 patients (the elective group). Eight patients of imperative group consisted of 5 patients with bilateral renal cell carcinoma (3 synchronous and 2 asynchronous), 1 patient who had renal cell carcinoma on one side and renal pelvic carcinoma on the other side, and 2 patients with renal cell carcinoma in a solitary kidney. In these 8 patients of the imperative group, conservative surgery was performed on 9 kidneys since 1 of 3 patients with synchronous bilateral renal cell carcinoma underwent the conservative surgery for both kidneys. In the elective group, all 17 patients had a small renal cell carcinoma, with the contralateral kidney normal in all. Enucleation was conducted on 4 kidneys out of 9 kidneys in 8 patients of the imperative group. On a total of 22 kidneys consisting of the remaining 5 kidneys and 17 kidneys of the elective group partial nephrectomy was done. The tumor size ranged from 0.9 to 7.0 cm (mean: 3.5 cm) for the imperative group and from 0.8 to 3.0 cm (mean: 2.3 cm) for the elective group. Thus, the tumor size was less than 3.0 cm in all of these 17 cases. As to the histologic atypia, 12 patients were classified as grade 1 and 14 patients as grade 2. None of the patients were classified as grade 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Surgical treatment of acute Stanford Type-A aortic dissection].

Twelve cases of Stanford Type-A aortic dissection were operated in an acute phase. The male vs female ratio was 3:9, and their ages ranged from 47 to 79 (mean 61.3) years old. Most of them complained of chest and/or back pain, and four of them complained of syncope. Eight patients had the history of hypertension. As to the complications of aortic dissection, cardiac tamponade was seen in two cases, myocardial infarction in one, and transient hemiplegia and paraplegia in one case each. In five cases, moderate to severe aortic regurgitation was also noted. All but one case were operated within twenty-four hours after admission. The replacement of the ascending aorta with a tube graft was performed in all cases including the two cases whose entries were located in the aortic arch. CABG was done concomitantly in three cases, and aortic valve replacement and CABG in one case. The open distal anastomosis was carried out under the systemic circulatory arrest combined with the retrograde cerebral perfusion. The systemic perfusion was reinstituted after the distal anastomosis was completed. In cases whose dissecting pseudo-lumen of the distal aorta was not thrombosed, the arterial cannulation site was shifted from the femoral artery to the tube graft. All but two cases were discharged from the hospital in good condition. One case, who had been transferred to the operating room under cardiac massage due to myocardial infarction, was lost by severe LOS three weeks postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1994

Excitability of the soleus motoneuron pool revealed by the developmental slope of the H-reflex as reflex gain.

The excitability of a motoneuron (MN) pool was evaluated by the developmental slope of H-reflexes (Hslp) evoked at a range of a stimulus intensity less than the threshold of an M-response. The Hslp has been regarded as the "reflex gain", which is the changing rate in MN excitability as a function of the increase of Ia input to an MN pool. In a comparison of two parameters used in the H-reflex technique, such as the ratio of the maximal H-reflex to the maximal M-response and the ratio of the threshold of an H-reflex to that of an M-response, the Hslp was predicted to be a reasonable parameter to evaluate motoneuronal excitability, because the Hslp is free from the effect of any collision between the H-reflex discharge and the antidromic volley drived from the occurrence of an M-response within the alpha-efferents, and the Hslp can estimate the recruitment properties of a whole MN pool. The Hslp was alleviated during dorsi-flexion and steepened during plantar-flexion, according to the inhibitory or facilitatory synaptic modifications onto soleus MNs. The developmental slope of an M-response (Mslp), which shows the recruitment property of axons of soleus MNs, was alleviated especially in plantar-flexion. In order to exclude the peripheral neuromuscular factors in evaluating substantial MN excitability, the Hslp/Mslp is proposed as a more effective parameter than the Hslp.

Adolescent↗
PubMed1993

Information-processing mediating the location-distance interference in motor short-term memory.

We reviewed the literature on basic psychological correlates of the well-known phenomenon of the location-distance interference in motor short-term memory (Kerr, 1978; Walsh, Russell, Imanaka, & James, 1979). The location-distance interference in motor short-term memory has frequently been demonstrated as an unavoidable interference phenomenon observed in the reproduction of movement location and distance in arm positioning. The most important aspect of this phenomenon is that even when a subject concentrates on a specific cue (i.e., either end-location or distance) the other cue is also coded unintentionally and, as a result, the reproduction movement guided on the basis of the specific cue is unavoidably influenced by the other nonspecific cue. In this review article, we first reviewed the literature on the basic theories and nature of short-term memory, particularly on the limited processing capacity. We then referred to the unlimited, automatic processing in visual-verbal domains, referring to the Stroop phenomenon. Finally, in conjunction with the notion of automatic processing, we examined the possible aspects of information processing which may be responsible for mediating the location-distance interference in motor short-term memory.

Cues↗
PubMed1993

[Computed tomography in the diagnosis of transitional cell carcinoma of the renal pelvis].

CT scans were carried out on 25 patients with transitional cell carcinoma of the renal pelvis. Of the 25 patients, tumors were identified in 24 patients (96%) and not in one patient on CT scan. Of the 24 patients the tumor was delineated as a solid mass in the renal pelvis and/or calyx in 15 and as an infiltrating mass in the renal parenchyma in 8 on CT scan. The depth of invasion was correctly estimated by CT in 18 of the 25 patients (72%). Whereas the tunica muscularis of the renal pelvis or the renal parenchyma was found involved in 3 of 10 patients (30%) in whom the diagnosis was made that the tumor was limited to the renal pelvic mucosa, the correct diagnosis was possible in 22 of 25 patients (88%) in whom the tumor was confined to the renal pelvic wall (pTa-pT2) or more invasive (pT3-pT4). In 6 of 7 patients with lymph nodes matastases enlarged lymph nodes were seen on the CT scan. In all 7 cases the primary tumor was classified as a pT3 or pT4 invasive disease. Based on the results presented above, it may be concluded that CT scan is valuable in making the diagnosis of transitional cell carcinoma of the renal pelvis and also in determining whether the tumor has invaded beyond the renal pelvic wall, thereby providing guidelines for the adequate treatment.

Adult↗
PubMed1993

[Partial colpocleisis for vesicovaginal fistulas].

Four patients with a vesicovaginal fistula were operated upon transvaginally using the Latzko technique of partial colpocleisis. In 3 of the 4 patients, the fistulas had been formed after total hysterectomy for myoma uteri or endometriosis. The periods from fistulization-to-surgery intervals in these 3 patients were 4 months, 12 months, and 4 years and 4 months, respectively. The fistulas in the remaining one patient had been formed after forceps delivery. The patient underwent surgery 8 days after delivery. An indwelling catheter was retained for 3 to 14 days after surgery. The 4 patients were all cured of vesicovaginal fistulas after a single operation. This paper describes our partial colpocleisis technique and discusses its clinical utility. The partial colpocleisis has the advantages of dispensing with such procedures as fistula excision, fistula opening suture, and suturation of the bladder musculature, and of closing the fistulas using a demucosated vaginal wall. Having minimal surgical invasiveness and being easy to perform and reliable, the technique appears to be excellent for coping with vesicovaginal fistulas.

Adult↗
PubMed1992

[Application of CT simulation system to stereotactic radiosurgery--experimental study in phantoms].

Stereotactic radiosurgery with linear accelerator requires accurate localization of target and accurate spatial delivery of radiation. In phantom study, geometric accuracy of radiosurgery was assessed in combination of CT simulation system (CTSS), which had been developed in our institute, and linear accelerator with supplemental collimator. After determination of target and its isocenter with CTSS, phantom was placed on treatment table so that isocenter meet at the intersection of mechanical axes (gantry, turn table). Displacement of the isocenter from the center of the radiation field was 1 mm in average. It was concluded that this combination could be applied to radiosurgery.

Computer Simulation↗
PubMed1992

Interference Between Location and Distance Information in Motor Short-Term Memory: The Respective Roles of Direct Kinesthetic Signals and Abstract Codes.

Interference between location and distance information in motor short-term memory has been hypothesized on the basis of the systematic pattern of undershooting and overshooting in movement reproduction that occurs when the starting position for reproduction movements is shifted. To determine the possible contribution of limb-specific kinesthetic information to this systematic undershooting-overshooting pattern, we compared the reproduction of linear arm positioning movements performed under either same-limb or switched-limb conditions. Ten subjects were assigned to either a location or distance cue condition, and each subject completed a total of 40 trials, 20 under same-limb and 20 under switched-limb conditions. Each trial consisted of criterion and reproduction movements, separated by a 10-s retention interval. The starting position for the reproduction movement was shifted by 0, 2, or 4 cm in either direction from that of the criterion movement. The systematic undershooting-overshooting pattern, which occurs when either the movement location or distance is reproduced, arose under both the same-limb and switched-limb conditions, suggesting that the primary cause of the location-distance interference is not limb-specific kinesthetic information. Rather, more abstract information in the form of a conceptual memory code appears to be the probable cause of the location distance interference phenomenon.

Journal Article↗