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Biomedical subjects

Kenji Shimada

Publications and source records attributed to Kenji Shimada.

At least 19 recordsLinked to original sources
PubMed2007

The origin recognition complex functions in sister-chromatid cohesion in Saccharomyces cerevisiae.

High-fidelity chromosomal segregation requires the properly timed establishment of sister-chromatid cohesion mediated by the Cohesin complex, and its resolution at the metaphase-to-anaphase transition. We have examined cell-cycle progression in a yeast strain from which the origin recognition complex protein Orc2 was depleted after the assembly of prereplication complexes. We find that Orc2 depletion causes a delay in progression through mitosis, reflecting activation of both the DNA-damage and Mad2-spindle checkpoints. Surprisingly, sister-chromatid cohesion is impaired in Orc2-depleted cells, although Cohesin subunits are properly associated with chromatin. Reexpression of Orc2 in late G2/M phase restores chromatid cohesion. Finally, the targeting of Orc2 to a specific chromosomal locus suppresses premature sister-chromatid separation locally in a temperature-sensitive cohesin mutant. We conclude that ORC mediates sister-chromatid interaction on a pathway that is additive with Cohesin-mediated pairing.

Acetyltransferases↗
PubMed2006

An efficient numerical technique for bioheat simulations and its application to computerized cryosurgery planning.

As a part of ongoing efforts to develop computerized planning tools for cryosurgery, the current study focuses on developing an efficient numerical technique for bioheat transfer simulations. Our long-term goal is to develop a planning tool for cryosurgery that takes a 3D reconstruction of a target region, and suggests the best cryoprobe layout. Toward that goal, a planning algorithm, termed "force-field analogy," has been recently presented, based on a sequence of bioheat transfer simulations, which are by far the most computationally expensive part of the planning method. The objective in the current study is to develop a finite difference numerical scheme for bioheat transfer simulations, which reduces the overall run time of computerized planning, thereby making it clinically relevant. While the general concept of variable grid size and time intervals is not new, its application to the phase change problem of cryosurgery is the unique contribution of the current study.

Computer Simulation↗
PubMed2006

Botryoid Wilms' tumor of the renal pelvis extending into the bladder.

We report a case of botryoid Wilms' tumor that occupied the renal pelvis and extended into the bladder. A 3-year-old boy was referred to us with a chief complaint of gross hematuria and micturition pain. Computed tomography showed tumor occupying the right renal pelvis and ureter and extending into the bladder. Right radical nephroureterectomy was performed. The resected specimen showed a botryoid sarcoma-like appearance, occupied the right renal pelvis and ureter, and protruded into the bladder. Histologic findings showed typical triphasic Wilms' tumor. Botryoid Wilms' tumor has been reported in only 16 cases in the literature and in only 3 cases extended into the bladder.

Child, Preschool↗
PubMed2006

Staged treatment of hypoplastic bladder: a case with single ectopic ureter in a solitary kidney.

We report on a successful treatment of hypoplastic bladder in a 5-month-old girl with single ectopic ureter in a solitary kidney. Side-to-side anastomosis was performed first between the urethral ectopic ureter and side wall of the bladder. Nine months later when the bladder capacity increased to 70 ml, ureterocystoneostomy was done through psoas hitch procedure. She retains urine of about 270 ml and evacuate completely at 14 years of age.

Abnormalities, Multiple↗
PubMed2006

Two-phase computerized planning of cryosurgery using bubble-packing and force-field analogy.

BACKGROUND: Cryosurgery is the destruction of undesired tissues by freezing, as in prostate cryosurgery, for example. Minimally invasive cryosurgery is currently performed by means of an array of cryoprobes, each in the shape of a long hypodermic needle. The optimal arrangement of the cryoprobes, which is known to have a dramatic effect on the quality of the cryoprocedure, remains an art held by the cryosurgeon, based on the cryosurgeon's experience and "rules of thumb." An automated computerized technique for cryosurgery planning is the subject matter of the current paper, in an effort to improve the quality of cryosurgery. METHOD OF APPROACH: A two-phase optimization method is proposed for this purpose, based on two previous and independent developments by this research team. Phase I is based on a bubble-packing method, previously used as an efficient method for finite element meshing. Phase II is based on a force-field analogy method, which has proven to be robust at the expense of a typically long runtime. RESULTS: As a proof-of-concept, results are demonstrated on a two-dimensional case of a prostate cross section. The major contribution of this study is to affirm that in many instances cryosurgery planning can be performed without extremely expensive simulations of bioheat transfer, achieved in Phase I. CONCLUSIONS: This new method of planning has proven to reduce planning runtime from hours to minutes, making automated planning practical in a clinical time frame.

Computer Simulation↗
PubMed2006

Method for screening and quantitative determination of serum levels of salicylic Acid, acetaminophen, theophylline, phenobarbital, bromvalerylurea, pentobarbital, and amobarbital using liquid chromatography/electrospray mass spectrometry.

We investigated a method for the simultaneous screening, identification, and quantitative determination of salicylic acid, acetaminophen, theophylline, barbiturates, and bromvalerylurea, drugs that frequently cause acute poisoning in Japan and therefore require rapid analysis for effective treatment in the clinical setting. The method employs liquid chromatography/electrospray mass spectrometry (LC/MS) of solid-phase extracted serum samples. For LC/MS ionization, the electrospray-ionization method was used, with acetaminophen in the positive-ion mode, and salicylic acid, theophylline, phenobarbital, bromvalerylurea, pentobarbital, amobarbital, and o-acetamidophenol (internal standard) in the negative-ion mode, the base ions were used in each case for quantitative analysis. Quantitation was possible for the following sample concentration ranges: salicylic acid and acetaminophen, 100 to 5 microg/ml; theophylline, 100 to 0.5 microg/ml; and phenobarbital, bromvalerylurea, pentobarbital, and amobarbital, 100 to 1 microg/ml. Using full-scan mass spectrometry, the lower detection limits of 1 microg/ml for salicylic acid and acetaminophen, 0.1 microg/ml for theophylline, and 0.5 microg/ml for phenobarbital, bromvalerylurea, pentobarbital, and amobarbital were adequate for identifying acute poisoning. When each compound was added to serum to a final concentration of 5 microg/ml and solid-phase extraction was performed using Oasis HLB 1-cc (30-mg), the mean recovery rate of each compound was 89.2 to 96.1% (n=5), and the coefficients of variation of the intraday and interday assays were 3.55 to 6.05% (n=5) and 3.68 to 6.38% (n=5), respectively, which are acceptable. When this method of analysis was applied in testing the sera of a female patient who had consumed a large amount of an unknown commercial drug, salicylic acid and bromvalerylurea were identified, and the treatment strategy could be determined in accordance with the serum concentration of those drugs.

Acetaminophen↗
PubMed2006

Computer-aided navigation for arthroscopic hip surgery using encoder linkages for position tracking.

While arthroscopic surgery has many advantages over traditional surgery, this minimally invasive surgical technique is not often applied to the hip joint. There are two main reasons for this: the difficulties of navigating within the joint and of correctly placing portal incisions without damaging critical neurovascular structures. This paper proposes a computer-aided navigation system to address the challenges of arthroscopic hip surgery. Unlike conventional arthroscopic methods, this system uses encoder linkages to track surgical instruments, thus eliminating the problems associated with standard tracking systems. The encoder position information is used to generate a computer display of patient anatomy to supplement the restricted view from a typical arthroscopic camera.

Arthroscopy↗
PubMed2006

Bubble packing application in computerized planning of cryosurgery.

Among many factors, the effectiveness of the cryoprocedure is determined by the quality of the cryoprobes layout. A computerized planning tool for optimizing this layout has the potential of improving the outcome of cryosurgery, reducing post-operative complications, and reducing the cost of the clinical operation. As part of an ongoing effort to develop planning tools for cryosurgery, the current study takes a novel approach, based on bubble-packing method. This study shows that the application of bubble-packing shortens runtime by an order of magnitude. In this study, the bubble-packing method is integrated with bioheat transfer simulations to demonstrate the quality of planning.

Algorithms↗
PubMed2005

Pancreatic pseudocyst arising from ectopic pancreas and isolated intestinal duplication in mesocolon caused hydronephrosis in a girl with horseshoe kidney.

Ectopic pancreas is a relatively common congenital anomaly and is usually asymptomatic. Pancreatitis in the ectopic site and pseudocyst formation is extremely rare. To date, only 2 cases have been reported. We present a case of a 3-year-old girl with recurrent pancreatitis and unilateral hydronephrosis of the horseshoe kidney, which was produced by pancreatic pseudocyst arising from ectopic pancreas and isolated intestinal duplication in mesocolon. This is the first case of pancreatic pseudocyst that expanded to the retroperitoneal space and caused urinary tract obstruction.

Child, Preschool↗
PubMed2005

Urinary control after the definitive reconstruction of cloacal anomaly.

PURPOSE: Urinary control after definitive repair of a cloacal anomaly is difficult to achieve. The present report aims to describe the clinical course of urinary control, and the need for the management of bladder dysfunction after reconstruction. METHODS: The present consecutive series consisted of 11 girls who underwent definitive repair of cloacal anomalies over a period of 11 years. Eight patients were associated with hydrocolpos. Radiological examination included a plain X-ray radiograph of the lumbosacral spine and a voiding cystourethrography with or without a urodynamic study. RESULTS: Reconstruction of the cloaca was performed on patients aged between 1 and 3 years using a posterior sagittal approach. Vaginal reconstruction was carried out 13 times in 11 patients using tubularized vaginal flap, distal rectal segment, perineal skin flap, or total urogenital sinus mobilization. Cystostomy or vesicostomy was carried out in four newborns/infants. Another seven patients could void spontaneously but incompletely with residual urine. Occult spinal dysraphism was found in five patients and hemisacrum in two patients. After definitive reconstruction, most patients acquired an adequate to normal bladder volume for 1-year-olds. Normal detrusor-sphincter function was seen in three patients. Detrusor areflexia was seen in two patients who underwent in utero vesico-amniotic shunt. Detrusor underactivity was observed in six patients. Bladder compliance was good in all patients except for one. No patients in the present series showed persistent urinary incontinence from the bladder neck or urethral dysfunction. CONCLUSION: It is postulated that wetting after definitive repair may be the result of overflow incontinence and poor bladder contractility rather than sphincter injury. The main clinical characteristic of bladder dysfunction was a failure to empty. We could not define the exact etiology, but iatrogenic injury from extensive dissection can lead to the higher risks of peripheral nerve damage. Accomplishment of definitive repair involves not only anatomical reconstruction, but also postoperative urinary control, including the initiation of clean intermittent catheterizations under repeated urodynamic evaluations.

Child, Preschool↗
PubMed2005

Malignant retroperitoneal tumor arising in a multicystic dysplastic kidney of a girl with Schinzel-Giedion syndrome.

We report the first case of malignant retroperitoneal tumor arising in a multicystic dysplastic kidney of an 8-year-old girl with Schinzel-Giedion syndrome. Although conservative treatment has been regarded as the standard management for asymptomatic multicystic dysplastic kidney, prophylactic surgical removal should be considered for selected children with potential risk of malignancy.

Abnormalities, Multiple↗
PubMed2005

Analysis of the blood level of micafungin involving patients with hematological diseases: new findings regarding combination therapy with tacrolimus.

In 29 patients (40 samples) with hematological diseases who had been treated with a candin antifungal agent, micafungin (MCFG), we measured the blood level of MCFG by high-performance liquid chromatography (HPLC). There was a correlation between the dose and the blood level of MCFG (r = 0.729, p < 0.001). In addition, there was a correlation between the total bilirubin level and the C/D value (r = 0.458, p < 0.01), which was calculated by dividing the blood level of MCFG by the dose, although there was no correlation between creatinine clearance and the C/D value. These findings suggest that the dose of MCFG must be regulated in patients with biliary stasis-type liver hypofunction. In addition, there was no significant difference in the blood level of MCFG between the group in which tacrolimus (FK506) was combined with MCFG and the group in which MCFG alone was administered. These results suggest that there are no changes in the blood level of MCFG even when MCFG is combined with FK506.

Adult↗
PubMed2005

[Augmentation ureterocystoplasty in children: 7-years follow-up].

OBJECTIVES: We retrospectively reviewed our experience of augmentation ureterocystoplasty in children to evaluate its long-term results. MATERIALS AND METHODS: From February 1996 to March 1999 four children (2 boys and 2 girls) with neurogenic bladder had augmentation cystoplasty using dilated ureter in our institute. After trans-uretero-ureterostomy the lower two thirds of the unilateral ureter was used to perform the augmentation cystoplasty. Follow-up varied between 59 and 96 months (mean 85). RESULTS: In early post-operative period bladder volume and compliance increased from 96 (64-150) to 113 (40-220) ml and from 2.7 (1.3-5.8) to 4.5 (2.0-11.0) ml/H2O respectively. Incontinence was improved in all children and two had dry interval of 3-hour catheterization. Although bladder volume and compliance kept increasing gradually (239 (237-241) ml, 11.5 (5.7-18.5) ml/H2O respectively) over 5 years postoperatively, 2 elder patients had repeat augmentation cystoplasty using gastrointestinal tract because of hydronephrosis and deterioration of renal function. CONCLUSION: Our long-term result of ureterocystoplasty was no good. Ureter is not an ideal material to provide adequate bladder capacity and compliance for elder children unless their bladder becomes as large as that of adults early post-operatively.

Anastomosis, Surgical↗
PubMed2005

[A case of intracranial infectious granuloma extending into subcutaneous and subdural space].

A case of intracranial infectious granuloma extending into subcutaneous and subdural space mimicking malignant bone tumor was reported. A 49-year-old male was admitted to our service with complaint of left frontal subcutaneous and bone tumor. Neurological examination demonstrated mild disorientation only except for pre-existeng Schizophrenia. CT scan and Gadolinium-enhanced MRI revealed left frontal intraosseous and subdural mass accompanied with remarkable edema. Left frontal bone was destructed by this mass. However, inflammatory sign nor malignant tumor could be observed and left frontal craniotomy and removal of the tumor was performed. The tumor was solid, elastic hard and existing from intra-osseous, epidural and subdural space compressing the cortex. No abscesss cavity could be found. Histological examination revealed infectious granuloma accompanied by remarkable neutrophil infiltration only. The patient showed good post-operative course, and returned to previous condition, pre-existeng Schizophrenia only. Intracranial infectious granuloma extending into subcutaneous and subdural space destructing the bone was rare condition. From literature, similar cases could be found in granuloma arising from osteomyelitis. In this case, destructed bone beneath the epi- and subdural tumor support this route of infection.

Brain Diseases↗
PubMed2004

Simultaneous determination of ingredients in a cold medicine by cyclodextrin-modified microemulsion electrokinetic chromatography.

Cyclodextrin-modified microemulsion electrokinetic chromatography (CD-MEEKC) was used to simultaneously determine 14 active ingredients (thiamine nitrate, anhydrous caffeine, acetaminophen, riboflavin, guaifenesin, pseudoephedrine hydrochloride, ascorbic acid, ethenzamide, DL-methylephedrine hydrochloride, dihydrocodeine phosphate, ibuprofen, noscapine, carbinoxamine maleate, and bromhexine hydrochloride) in a cold medicine. Separation of the ingredients was optimized by changing the SDS concentration and oil type and the addition of 2-propanol and cyclodextrin (CD) to the separation solution. The separation selectivity was improved dramatically by changing CD type. All of the active ingredients and formulation excipients were successfully separated with the use of a separation solution consisting of 0.81% (w/w) pentane, 6.61% (w/w) 1-butanol, 2% (w/w) 2-propanol, 4.47% (w/w) SDS, and 86.11% (w/w) 10 mM sodium tetraborate solution with 3 mM 2,6-di-O-methyl-beta-CD. The established method was then validated and demonstrated to be applicable to the determination of the active ingredients in a model cold medicine. No interference from the formulation excipients was observed. Good linearities were obtained with correlation coefficients above 0.999. Recovery and precision ranged from 99.1 to 100.7% and from 0.5 to 2.8% R.S.D., respectively. The detection limit for ingredients ranged from 0.6 to 4.2 microg ml(-1). Good agreement was obtained between the established method and the traditional HPLC method. These results suggest that CD-MEEKC can be used for the determination of multiple ingredients in cold medicine.

Chromatography, High Pressure Liquid↗
PubMed2004

Development of a novel analytical method for determination of chondroitin sulfate using an in-capillary enzyme reaction.

A novel analytical method for determination of total amount of chondroitin sulfate (CS) based on its conversion to desulfated chondro-disaccharide via an enzyme-catalyzed reaction, was developed. Using the in-capillary enzyme reaction, the method was also applied to the successful construction of an on-line analytical system. Within this system, electrophoretic migration was used to mix zones containing the enzyme mixture (chondroitinase ABC, chondro-4-sulfatase, chondro-6-sulfatase and 2-o-sulfatase) and the substrate (CS). The reaction was then allowed to proceed in the presence of a weak electric field and, finally, the product (desulfated chondro-disaccharide) of enzyme reaction migrated to the detector under the influence of an applied electric field. A polyvinyl alcohol-coated capillary was used to reduce protein adsorption. Desulfated chondro-disaccharide was successfully migrated toward the anode in 10 mM Tris-acetate buffer (pH 7.0) under reversed polarity and detected at 232 nm. The established method was validated and demonstrated to be applicable in the determination of total amount of CS in a commercial ophthalmic solution. No interference from the formulation excipients was observed. Good linearity was obtained, with correlation coefficients above 0.999. Recoveries and precisions ranged from 100.0 to 100.5%, and from 0.2 to 0.6% of the relative standard deviation, respectively. Good agreement was obtained between the established method and traditional photometric method based on carbazole reaction. In this study, application of the method to disaccharide compositional analysis was also performed.

Chondroitin Sulfates↗
PubMed2004

Redundancy, insult-specific sensors and thresholds: unlocking the S-phase checkpoint response.

DNA damage that is not properly repaired during genomic replication is a major source of gross chromosomal rearrangements and sequence loss during cell proliferation. In higher eukaryotes such mutations increase the risk of cancer. Eukaryotic cells have multiple checkpoint responses activated by DNA damage and stalled replication forks. We focus here on fork-associated events that activate and respond to S-phase checkpoint kinases.

Animals↗