Biomedical subjects

T Yasunaga

Publications and source records attributed to T Yasunaga.

At least 19 recordsLinked to original sources

PubMed2005

Laparoscopic cholecystectomy using a newly developed laparoscope manipulator for 10 patients with cholelithiasis.

BACKGROUND: Laparoscopic surgery has continued to gain popularity in almost all fields of abdominal surgery, and robotic systems have been introduced in general surgery. Naviot is a new remote-controlled laparoscope manipulator system controlled by the operator's hand. This study assessed its introduction into clinical practice. METHODS: A group of 10 consecutive patients with cholelithiasis underwent laparoscopic cholecystectomy assisted by the Naviot system (Naviot group). Another group of 41 patients who underwent laparoscopic cholecystectomy with a conventional human camera holder (human camera group) were selected for a comparison of their operative results with those of the Naviot group. RESULTS: The operative time of 89.3 +/- 27.1 min for the Naviot group was significantly longer than that of 74.8 +/- 28.1 min for the human camera group (p < 0.05). However, when the setup time for the Naviot system was excluded, the operative time was not significantly different from that for the human camera group. Other operative results showed no significant difference between the two groups. CONCLUSIONS: The authors believe that the new Naviot system is feasible for clinical use, and that it enables surgeons to perform solo gastrointestinal surgery.

Aged↗

PubMed2004

Magnetic resonance evaluation of the presence of an extensive intraductal component in breast cancer.

PURPOSE: To determine whether the presence of extensive intraductal components (EIC) in breast carcinomas can be accurately evaluated on magnetic resonance (MR) images. MATERIAL AND METHODS: Ninety-three women with breast cancer, aged between 32 and 79 years (mean 54 years), underwent three-dimensional dynamic MR imaging (dyMRI) with fat suppression and magnetization transfer contrast before breast-conserving surgery. The tumors were classified on dyMRI as circumscribed, microlobulated, and/or speculated, and their size was measured. Spotty or linear continuous enhancement (SLE) from the main tumor to the nipple and segmental enhancement surrounding the main tumor (SE) were considered indicative of intraductal tumor spread. The correlation between preoperative MRI and macroscopic and microscopic findings was examined. RESULTS: On MR images, the tumor sizes ranged from 0.8 to 3.4 cm. These measurements coincided with histologic measurements in circumscribed tumors. However, in tumors with microlobulated or spiculated borders, tumor size tended to be underestimated on MR images. Of 93 patients, 59 (63.4%) had histologically confirmed EIC; 42 of the 59 cancers (71.2%) manifested SLE or SE on MR images. The sensitivity, specificity, and accuracy of MR imaging in detecting EIC were 71%, 85%, and 76%, respectively. CONCLUSION: MR imaging facilitates the detection of EIC in breast masses. This information is valuable for the planning of breast-conserving surgery.

Adult↗

PubMed2004

Evaluation of tumor angiogenesis using dynamic enhanced magnetic resonance imaging: comparison of plasma vascular endothelial growth factor, hemodynamic, and pharmacokinetic parameters.

PURPOSE: To assess whether tumor angiogenesis of breast cancers can be predicted on the basis of dynamic magnetic resonance imaging (MRI). MATERIAL AND METHODS: Seventy-one patients with 71 breast cancers underwent Gd-DTPA enhanced dynamic MRI. Two regions of interest measurements were obtained in the periphery and in the center of the breast cancers. Hemodynamic parameters obtained by dynamic MRI included peak time, contrast enhancement ratio (CE ratio), and washout ratio. The triexponential concentration curve of Gd-DTPA was fitted to a theoretical model based on compartmental analysis. The transfer constant (or permeability surface product per unit volume of compartment "k") was obtained using this method. Tumor angiogenesis was assessed by plasma vascular endothelial growth factor (P-VEGF). RESULTS: The P-VEGF was positive in 28 of 71 tumors (39%). The CE ratio, washout ratio, and k in the periphery in P-VEGF positive breast cancers (mean 178%, 18%, and 1.5 x 10(-2) (s(-1)) were significantly greater (P<0.01, P<0.05, and P<0.03)) than those for P-VEGF negative breast cancers (mean: 151%, 14%, and 1.1 x 10(-2) (s(-1)). The peak time in the periphery in P-VEGF positive breast cancers was more marked than for P-VEGF negative breast cancers, but this difference was not significant. CONCLUSION: The hemodynamic and pharmacokinetic analysis of MRI provides valuable information about angiogenesis of breast cancers.

Adenocarcinoma↗

PubMed2001

Ca(2+)-induced switching of troponin and tropomyosin on actin filaments as revealed by electron cryo-microscopy.

Muscle contraction is regulated by the intracellular Ca(2+ )concentration. In vertebrate striated muscle, troponin and tropomyosin on actin filaments comprise a Ca(2+)-sensitive switch that controls contraction. Ca(2+ )binds to troponin and triggers a series of changes in actin-containing filaments that lead to cyclic interactions with myosin that generate contraction. However, the precise location of troponin relative to actin and tropomyosin and how its structure changes with Ca(2+ )have been not determined. To understand the regulatory mechanism, we visualized the location of troponin by determining the three-dimensional structure of thin filaments from electron cryo-micrographs without imposing helical symmetry to approximately 35 A resolution. With Ca(2+), the globular domain of troponin was gourd-shaped and was located over the inner domain of actin. Without Ca(2+), the main body of troponin was shifted by approximately 30 A towards the outer domain and bifurcated, with a horizontal branch (troponin arm) covering the N and C-terminal regions of actin. The C-terminal one-third of tropomyosin shifted towards the outer domain of actin by approximately 35 A supporting the steric blocking model, however it is surprising that the N-terminal half of tropomyosin shifted less than approximately 12 A. Therefore tropomyosin shifted differentially without Ca(2+). With Ca(2+), tropomyosin was located entirely over the inner domain thereby allowing greater access of myosin for force generation. The interpretation of three-dimensional maps was facilitated by determining the three-dimensional positions of fluorophores labelled on specific sites of troponin or tropomyosin by applying probabilistic distance geometry to data from fluorescence resonance energy transfer measurements.

Actins↗

PubMed2001

Nested genomic structure of haploid germ cell specific haspin gene.

The haspin gene specifically expressed in haploid germ cells encodes a unique Ser/Thr protein kinase. We have cloned a mouse haspin genomic clone using cDNA as a probe. Sequencing data showed that the haspin gene was not interrupted by introns and was bordered by appropriate direct repeat. The transcription start site of the gene was not preceded by a TATA box. The whole transcription unit was located at an intron of integrin alphaM290 gene, and transcription direction of these two genes was different. Southern blotting analysis under stringent condition showed that haspin was a single gene. Phylogenetic analysis suggested that the diversion of haspin gene from other kinase family might be very ancient: the early stage of plant-fungus-animal split.

Animals↗

PubMed2001

Complete genome sequence of enterohemorrhagic Escherichia coli O157:H7 and genomic comparison with a laboratory strain K-12.

Escherichia coli O157:H7 is a major food-borne infectious pathogen that causes diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. Here we report the complete chromosome sequence of an O157:H7 strain isolated from the Sakai outbreak, and the results of genomic comparison with a benign laboratory strain, K-12 MG1655. The chromosome is 5.5 Mb in size, 859 Kb larger than that of K-12. We identified a 4.1-Mb sequence highly conserved between the two strains, which may represent the fundamental backbone of the E. coli chromosome. The remaining 1.4-Mb sequence comprises of O157:H7-specific sequences, most of which are horizontally transferred foreign DNAs. The predominant roles of bacteriophages in the emergence of O157:H7 is evident by the presence of 24 prophages and prophage-like elements that occupy more than half of the O157:H7-specific sequences. The O157:H7 chromosome encodes 1632 proteins and 20 tRNAs that are not present in K-12. Among these, at least 131 proteins are assumed to have virulence-related functions. Genome-wide codon usage analysis suggested that the O157:H7-specific tRNAs are involved in the efficient expression of the strain-specific genes. A complete set of the genes specific to O157:H7 presented here sheds new insight into the pathogenicity and the physiology of O157:H7, and will open a way to fully understand the molecular mechanisms underlying the O157:H7 infection.

Bacterial Proteins↗

PubMed2001

Neonatal periventricular-intraventricular hemorrhage. Subacute and chronic MR findings.

PURPOSE: To evaluate MR findings at subacute and chronic stages after neonatal periventricular-intraventricular hemorrhage (PIVH), and to determine the clinical significance of follow-up MR. MATERIAL AND METHODS: Twenty-six children (estimated gestational age, 23-39 weeks; mean 29 weeks) with a history of previous PIVH underwent MR examination during their subacute and chronic clinical courses. PIVHs were initially detected with ultrasound examination in all cases. PIVH was divided into three grades (mild, moderate, and severe) according to the findings at the initial US studies, which were correlated to the MR findings. RESULTS: Abnormal signal intensities related to hemorrhage were demonstrated in 10 of 21 patients (47.6%) on initial MR studies; the very low signal intensities on T2-weighted images found on the periventricular wall with a linear or a spotty shape had disappeared at one year after the initial US. The children with ventriculomegaly and periventricular leukomalacia (PVL) were increased in number on the follow-up studies. CONCLUSION: MR imaging provided valuable information about the consequences of neonatal PIVH such as developments of ventriculomegaly or PVL. It is noteworthy that hemorrhagic lesions could not be detected in half of the cases at the subacute or chronic stage of PIVH.

Brain↗

PubMed2001

Relocation of Cys374 of actin induced by labeling with fluorescent dyes.

Cys374 is an important landmark of actin, because its sulfhydryl group is reactive and can be labeled with various reagents. The atomic coordinates of actin Cys374 have been determined by X-ray crystallography of co-crystals of actin with either profilin or gelsolin. However, the positions of Cys374 in the crystals determined were not consistent with the data obtained through fluorescence resonance energy transfer. Here, we examined its position by means of probabilistic distance geometry using published fluorescence resonance transfer data and found that Cys374 of actin was relocated when Cys374 was labeled with fluorescent dyes that caused steric hindrance. The atomic coordinates of Cys374 after heavy atom labeling have been found to be different from those for the native crystal. This is consistent with our results. Therefore, the position of Cys374 is sensitive to chemical modification that introduces a bulky reagent. This also suggests that the conformation of the C-terminal region of actin could also be sensitive to the environment.

Actins↗

PubMed2001

Preoperative small-dose ketamine prevented tourniquet-induced arterial pressure increase in orthopedic patients under general anesthesia.

UNLABELLED: The mechanism of tourniquet-induced arterial pressure increase is not known. We investigated the effect of preoperative ketamine on tourniquet-induced arterial pressure and heart rate changes in 85 patients undergoing knee surgery with a tourniquet under general anesthesia. Patients were randomly assigned into three groups; Large Ketamine (n = 28; ketamine 1.0 mg/kg), Small Ketamine (n = 28; ketamine 0.25 mg/kg), and Control (n = 29; normal saline) groups. Anesthesia was maintained with 1.5%-2.5% sevoflurane and 66% N(2)O in oxygen with endotracheal intubation. Ketamine or normal saline was given in a double-blinded fashion before skin incision and tourniquet inflation. Arterial pressure and heart rate were recorded every 10 min until 60 min after the start of tourniquet inflation and again after deflation. Arterial pressure and heart rate were compared among the three groups by using repeated-measures analysis of variance. In the Large and Small Ketamine groups, arterial pressure was not significantly changed, but in the Control group arterial pressure was significantly increased 40, 50, and 60 min after the start of tourniquet inflation (P < 0.05). Development of more than a 30% increase in systolic arterial pressure during tourniquet inflation was more frequent in the Control group than the other groups. The results show that preoperative IV ketamine, 0.25 mg/kg or more, significantly prevented tourniquet-induced systemic arterial pressure increase in patients under general anesthesia. IMPLICATIONS: Preoperative small-dose ketamine, IV, significantly prevented a systemic arterial pressure increase during prolonged tourniquet inflation in patients under general anesthesia.

Adolescent↗

PubMed2001

Histologic change of the meniscus and cartilage tissue after meniscal suture.

The influence of suturing on cell infiltration into the meniscus and surrounding tissue is not well known. Histologic changes in the meniscus after suturing and prediction of histologic changes using magnetic resonance imaging were studied. Forty knees in 20 mongrel dogs were studied using four types of 4-0 suture material: nonabsorbable monofilament, nonabsorbable braided, absorbable monofilament, and absorbable braided. Each type of suture material was used for meniscal suture on eight knees each. The other eight knees were not subjected to meniscal suture. Specimens obtained at 1 and 3 months were studied by magnetic resonance imaging and light microscopic analysis. The maximum width of change of meniscal tissue was measured. Changes from the nonabsorbable suture group were smaller than that of the absorbable suture group in magnetic resonance imaging. Histologic changes as seen by light microscope were larger in the absorbable group than in the nonabsorbable group at 1 and 3 months after surgery. Injury was found in the articular cartilage of the femoral condyle in the nonabsorbable braided suture group. Histologic changes were significantly greater when changes in magnetic resonance imaging signal intensity were larger. The current study showed that non-absorbable monofilament suture material results in the least damage to the meniscus and surrounding tissue.

Alcian Blue↗

PubMed2001

Association of the urease gene with enterohemorrhagic Escherichia coli strains irrespective of their serogroups.

Among various diarrheagenic Escherichia coli strains from clinical sources, we found that the urease gene was specifically associated with enterohemorrhagic E. coli (EHEC) strains irrespective of their serogroups. The results suggest that the urease gene can be a useful genetic marker for the detection of EHEC strains and for the diagnosis of infections caused by EHEC strains in the clinical situation.

Diarrhea↗

PubMed2001

[Evaluation of patients who received treatment (procedures) that involved minor surgical techniques at home].

We retrospectively examined the clinical records of 24 patients who underwent minor surgery under local anesthesia among 207 who were taken care of at home by our staff, from December 1986 to March 2001. There were 17 men and 7 women. Their mean age was 74 years and the range was 50 to 92 years old. The treatment consisted of central vein catheterization in 14 patients, skin suture in 6, subcutaneous implantation of port establishment and epidural catheterization in 3 patients each, treatment of anus, thorax centesis, skin tumor resection, and treatment of bed sores 2 patients each, wash of thorax, ovarian cyst centesis, and transcutaneous trachocentesis 1 patient each. A relationship of trust with the patient and the family and informed consent were thought as the most important aspects regarding treatment involving minor surgery provided at home.

Aged↗

PubMed2000

Complete nucleotide sequence of the prophage VT1-Sakai carrying the Shiga toxin 1 genes of the enterohemorrhagic Escherichia coli O157:H7 strain derived from the Sakai outbreak.

Shiga toxins 1 and 2 (Stx1 and Stx2) are encoded by prophages lysogenized in enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains. Lytic growth of the phage particles carrying the stx1 genes (stx1A and stx1B) of the EHEC O157:H7 strain RIMD 0509952, which was derived from the Sakai outbreak in 1996 in Japan, was induced after treatment with mitomycin C, but the plaque formation of the phage was not detected. We have determined the complete nucleotide sequence of the prophage VT1-Sakai. The integration site of the prophage was identified within the yehV gene at 47.7 min on the chromosome. The stx1 genes were downstream of the Q gene in the prophage genome, suggesting that their expression was regulated by the Q protein, the regulator of the late gene expression of the phage, which is similar to that of the stx1 or stx2 genes carried by the lambdoid phages reported previously. The sequences of the N gene and its recognition sites, nutL and nutR, were not homologous to those of the phages carrying the stx genes thus far reported, but they were very similar to those of bacteriophage phi21. The sequences of the repressor proteins, CI and Cro, that regulate expression of the early genes had low similarities with those of the known repressors of other phages, and their operator sequences were different from any sequence reported. These data suggest that multiple genetic recombination among bacteriophages with different immunities took place to generate the prophage VT1-Sakai. Comparison between the sequences of VT1-Sakai and lambda suggests that the ancestor of VT1-Sakai was produced by illegitimate excision, like lambda gal and bio phages.

Amino Acid Sequence↗

PubMed2000

Role of residues 230 and 236 of actin in myosin-ATPase activation by actin-tropomyosin.

The Dictyostelium/Tetrahymena-chimeric actin (Q228K/T229A/A230Y) showed higher Ca(2+)-activation of myosin S1 ATPase in the presence of tropomyosin-troponin. The crystal structure of the chimeric actin is almost the same as that of wild-type except the conformation of the side chain of Leu236. Here, we introduced an additional mutation (L236A), in which the side chain of Leu236 was truncated, into the chimeric actin (Q228K/T229A/A230Y/L236A). Without regulatory proteins, the new mutant actin showed normal myosin S1 activation and normal sliding velocity. However, in the presence of tropomyosin, the new mutant actin activated myosin S1 ATPase higher than the wild-type actin and showed higher velocities in in vitro motility assay at low HMM concentrations. These results suggest that the mutations of A230Y and L236A in the actin subdomain-4 facilitate the transition of thin filaments from a "closed" state to an "open" state.

Actins↗

PubMed2000

Histomorphometric study on high-strength hydroxyapatite/poly(L-lactide) composite rods for internal fixation of bone fractures.

The purpose of this study was to investigate the bone-implant interface of high-strength hydroxyapatite (HA)/poly(L-lactide) (PLLA) composite rods. As reinforcing particles, two types of HA particles-calcined HA (c-HA) and uncalcined HA (u-HA)-were applied to allow comparison of their suitability as bioactive fillers. Four types of composites (c-HA30, c-HA40, u-HA30, and u-HA40), which contained 30 or 40% by weight of each HA particle, were used. Unfilled PLLA rods were used as controls. A hole was drilled in the distal femora of 50 rabbits, and a composite or unfilled PLLA rod was implanted in a press-fit manner. Two, 4, 8, and 25 weeks after implantation, the samples were examined histologically by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). An image analyzer was used for histomorphometric analysis of the bone-implant interface. An affinity index was calculated for each material; this was the length of bone directly apposed to the rods expressed as a percentage of the total length of the rod surface. In all the composites, histologic examination showed new bone formation at 2 weeks after implantation. The bone gradually grew along the composite surface. SEM showed direct bone contact with the composites without intervening fibrous tissue. During follow-up, the affinity indices of all the composite rods were significantly higher than those of the unfilled PLLA rods (p < 0.01; two-way ANOVA). The maximum affinity index (41%) was attained at 4 weeks in c-HA40 rods. In contrast, little bone contact was seen in unfilled PLLA rods. The only significant difference in affinity indices among the composites was that c-HA40 had a higher affinity index than u-HA40 (p < 0.05 at 4 weeks). No disintegration of rods or polymer debris, which could elicit inflammatory tissue reactions, was observed even at 25 weeks. Our results indicate that osteoconductive bone formation on composites could enhance the stability between bone and implant in fracture repair.

Absorbable Implants↗

PubMed2000

V-Type H+-ATPase/synthase from a thermophilic eubacterium, Thermus thermophilus. Subunit structure and operon.

V-type ATPase (V(o)V(1)) capable of ATP-driven H(+) pumping and of H(+) gradient driven ATP synthesis was isolated from a thermophilic eubacterium, Thermus thermophilus. When the enzyme was analyzed by gel electrophoresis in the presence of sodium dodecyl sulfate, it showed eight polypeptide bands of which four were subunits of V(1). We also isolated the V(o)V(1) operon, containing nine genes in the order of atpG-I-L-E-X-F-A-B-D, which encoded proteins with molecular sizes of 13, 43, 10, 20, 35, 11, 64, 53, and 25 kDa, respectively. The last four genes were identified as those for V(1) subunits; atpA, B, D, and F encoded the A, B, gamma, and delta subunits, respectively. The first five genes, atpG-atpX, were identified as genes for the V(o) subunits. The product of atpL, the proteolipid subunit, lacked a 19-amino acid presequence and, unlike V-type ATPases, contained two membrane-spanning domains rather than four. The hydrophobic 43-kDa product of atpI is the smallest member so far found of the eukaryotic 100-kDa subunit family. Its electrophoretic band overlapped with the band of the A subunit. Therefore, all the gene products were found in our purified V(o)V(1). We isolated the A(3)B(3) subcomplex reconstituted from the isolated subunits and the A(3)B(3)gamma subcomplex from subunit-expressing Escherichia coli. Electron microscopic observation of these subcomplexes revealed that the gamma subunit of V(1) filled the central cavity of A(3)B(3) and might be central subunit, similar to the gamma subunit of F(1)-ATPase.

Amino Acid Sequence↗

PubMed2000

Structural basis for the higher Ca(2+)-activation of the regulated actin-activated myosin ATPase observed with Dictyostelium/Tetrahymena actin chimeras.

Replacement of residues 228-230 or 228-232 of subdomain 4 in Dictyostelium actin with the corresponding Tetrahymena sequence (QTA to KAY replacement: half chimera-1; QTAAS to KAYKE replacement: full chimera) leads to a higher Ca(2+)-activation of the regulated acto-myosin subfragment-1 ATPase activity. The ratio of ATPase activation in the presence of tropomyosin-troponin and Ca(2+) to that without tropomyosin-troponin becomes about four times as large as the ratio for the wild-type actin. To understand the structural basis of this higher Ca(2+)-activation, we have determined the crystal structures of the 1:1 complex of Dictyostelium mutant actins (half chimera-1 and full chimera) with gelsolin segment-1 to 2.0 A and 2.4 A resolution, respectively, together with the structure of wild-type actin as a control. Although there were local changes on the surface of the subdomain 4 and the phenolic side-chain of Tyr230 displaced the side-chain of Leu236 from a non-polar pocket to a more solvent-accessible position, the structures of the actin chimeras showed that the mutations in the 228-232 region did not introduce large changes in the overall actin structure. This suggests that residues near position 230 formed part of the tropomyosin binding site on actin in actively contracting muscle. The higher Ca(2+)-activation observed with A230Y-containing mutants can be understood in terms of a three-state model for thin filament regulation in which, in the presence of both Ca(2+) and myosin heads, the local changes of actin generated by the mutation (especially its phenolic side-chain) facilitate the transition of thin filaments from a "closed" state to an "open" state. Between 394 and 469 water molecules were identified in the different structures and it was found that actin recognizes hydrated forms of the adenine base and the Ca ion in the nucleotide binding site.

Actins↗

PubMed2000

Acetylation at the N-terminus of actin strengthens weak interaction between actin and myosin.

The N-terminus of all actins so far studied is acetylated. Although the pathways of acetylation have been well studied, its functional importance has been unclear. A negative charge cluster in the actin N-terminal region is shown to be important for the function of actomyosin. Acetylation at the N-terminus removes a positive charge and increases the amount of net negative charges in the N-terminal region. This may augment the role of the negative charge cluster. To examine this possibility, actin with a nonacetylated N-terminus (nonacetylated actin) was produced. The nonacetylated actin polymerized and depolymerized normally. In actin-activated heavy meromyosin ATPase assays, the nonacetylated actin showed higher K(app) without significantly changing V(max), compared with those of wild-type actin. This is in contrast to the effect of the N-terminal negative charge cluster, which increases V(max) without changing K(app). These results indicate that the acetylation at the N-terminus of actin strengthens weak actomyosin interaction.

Acetylation↗