Clinical outcomes of sentinel node navigation surgery in patients with preoperatively estimated stage IA endometrial cancer and evaluation of validity for continuing sentinel node navigation surgery based on dispersion of recurrence probability.

BACKGROUND: To evaluate the feasibility of the use and continuation of sentinel lymph node navigation surgery (SNNS) as an alternative to pelvic lymph node dissection (PLND) for patients with preoperatively estimated stage IA endometrial cancer. METHODS: This retrospective study selected the electronic medical records of all patients who had received CT scans and MRI imaging before surgery from April 1, 2009 to March 31, 2021. Sentinel lymph nodes (SLNs) were detected by administrating 99mTc-phytate and/or indocyanine green into the cervix, and the clinical outcomes of the patients who underwent SNNS or PLND were evaluated. Furthermore, in case of nodal recurrence, a new procedure to determine whether the facility should continue with SNNS or not was developed that compares the maximum likelihood hypothesis and an alternative one based on recurrence rates. RESULTS: Among 137 patients, SLN biopsies with ultrastaging were performed on 91 patients. The SLN detection rate was 95.6%. Over a 59-month median observation period, no statistically significant differences were shown in overall survival, disease-specific survival and disease-free survival between the SNNS and PLND groups when introducing the propensity score method (p-values: 0.06, 0.153, and 0.625, respectively). Our procedure demonstrated that, in our department without recurrence up to the 65th attempt, it was possible to continue SNNS if a recurrence occurs at the 66th attempt. CONCLUSION: This study suggests the validity of SNNS as an alternative to PLND. Even in the absence of evidence from randomized controlled trials, we can confirm the validity of continuing SNNS using our procedure.

Questionnaire survey regarding current status of minimally invasive surgery for endometrial cancer in Japan: A cross-sectional survey for JSGOE members.

AIM: Minimally invasive surgery (MIS) has been introduced as an alternative to more radical surgical procedures. The Japan Society of Gynecologic and Obstetric Endoscopy and Minimally Invasive Therapy conducted a cross-sectional questionnaire survey to ascertain the status of MIS for endometrial cancer. METHODS: The survey was conducted between May 10 and June 30, 2022. The questionnaire included information on personal attributes, academic affiliations, qualifications, hysterectomies, and intraoperative procedures performed. RESULTS: The total number of questionnaire respondents was 436 (9.2% of the membership). The hysterectomy methods and percentage performed were as follows: simple total hysterectomy (equivalent to benign surgery), 3%; simple total hysterectomy with care to avoid shaving the cervix, 31%; extended total hysterectomy, 48%; and modified radical hysterectomy, 15%. An analysis of hysterectomies performed using MIS for endometrial cancer by qualified gynecologists of endoscopy or board-certified gynecologic oncologists showed a tendency not to choose simple total hysterectomy compared to the gynecologists who did not hold certification (p = 0.019, p = 0.045, and p = 0.010, respectively). Additionally, 67% of respondents did not use uterine manipulators, and 59% of the respondents did not perform lymph node dissection following the guidelines for treating endometrial cancer in Japan. CONCLUSION: This study provided the current status of MIS for endometrial cancer in Japan. The hysterectomy method, use of uterine manipulators, and criteria for omitting lymph node dissection were generally in agreement with the guidelines. Currently, an extra-fascial simple hysterectomy, including at least not shaving the cervix, was a major method for early invasive endometrial cancer using MIS.

Surgical skill and oncological outcome of laparoscopic radical hysterectomy: JGOG1081s-A1, an ancillary analysis of the Japanese Gynecologic Oncology Group Study JGOG1081.

OBJECTIVES: We investigated whether surgical skill and procedure were related to oncological outcomes in cervical cancer patients who underwent Laparoscopic Radical Hysterectomy (LRH). METHODS: We previously assessed data of LRH from 251 patients with FIGO stage (2009) IA2, IB1and IIA1 cervical cancer collected for JGOG 1081s study. 1) The JGOG 1081s cohort study was re-examined to refine the surgical details and extend the follow-up period as chart review. 2) Unedited videos for recurrent cases and matched non-recurrent control cases were newly compared by experts for various surgical skills and surgical procedures using the modified Objective Structured Assessment of Technical Skills (OSATS) tool, without awareness of the recurrence status as video review. RESULTS: After a median follow-up of 46 months, tumors had recurred in 31 of the 251 patients. The five-year Recurrence-Free Survival rate was 86.9% (81.8-90.6) and five-year Overall Survival rate was 93.7% (87.5-96.8). Multivariate analysis from chart reviews found that an experience with LRH of less than 20 cases per institution was an independent prognostic factor for recurrence (Hazard Ratio (HR) 2.49, 95%CI 1.12-5.53, p = 0.025). For the surgical video review, we compared 23 videos of recurrent cases with 23 background-matched non-recurrent controls. Lower modified OSATS scores from the video review were consistently trended to have a higher risk of recurrence. CONCLUSIONS: Our new study has found that LRH surgical experience and skill trended to have better oncological outcomes.

Survey of the clinical practice pattern of using sentinel lymph node biopsy in patients with gynecological cancers in Japan: the Japan Society of Gynecologic Oncology study.

BACKGROUND: Sentinel lymph node (SN) biopsy is essential for evaluating survival and minimal treatment-related morbidity associated with cervical, endometrial, and vulvar cancer in Japan. As such, our aim in this study was to evaluate the current practice pattern of using SN biopsy for cervical, endometrial, and vulvar cancer in Japan. METHODS: We deployed a 47-question survey on the use of SN biopsy for gynecological cancers to 216 gynecological oncology training facilities. The survey included information on the use of SN biopsy for uterine (cervical and endometrial) and vulvar cancers; details on the type, timing, and concentration of tracers used; surgical approach used for SN biopsy; method of biopsy and pathological examination; and facilities' experience with clinical research on SN biopsy. RESULTS: The response rate was 84% (181/216), with 40 facilities (22%) having experience in SN biopsy for gynecological cancers, 34 (85%) for uterine cancers, and 15 (37%) for vulvar cancers. Radioisotope, indocyanine green (ICG), and blue dyes were available for the detection of uterine cancers in 21 (52%), 25 (62%), and 19 (48%) facilities and for vulvar cancers in 9 (22%), 3 (7%), and 11 (27%) facilities, respectively. Thirty-four facilities (85%) used intraoperative frozen section procedure for diagnosis when possible, with 24 (71%) of these facilities using 2-mm specimen cuts. Diagnosis included pathological examination (85%), immunostaining (57%), and one-step nucleic acid amplification (5%). CONCLUSION: Increasing research evidence, providing insurance coverage for radioisotope tracers, and increasing the availability of training are expected to increase the use of SN biopsy in Japan.

[The current situation and agendas in the prevention and control of non-communicable diseases in Vietnam].

Objectives　In Vietnam, the number of patients with non-communicable diseases (NCDs) has been increasing in recent years in association with the country's remarkable economic growth and corresponding changes in its population's lifestyle. The purposes of this research were to identify the challenges in the prevention and control of NCDs in Vietnam and to discuss countermeasures for NCDs in Vietnam and Japan.Methods　As a 2015 Regional Public Health Overall Promotion Project, an investigation team consisting of 11 public health physicians visited Hanoi, the capital of Vietnam, and its vicinities from January 11, 2016 to January 15, 2016. In Hanoi and its vicinities, we visited local healthcare institutions, such as the World Health Organization(WHO) Representative Office in Vietnam and Ministry of Health of Vietnam, and discussed the prevention and control of NCDs in Vietnam and Japan.Results　According to a survey in 2014, 73% of people of all age groups in Vietnam died from NCDs and the number of people suffering from NCDs has been sharply increasing in recent years. Major behavioral risk factors are dietary risks, tobacco smoke, alcohol use, and physical inactivity. There are four main problems with prevention and control of NCDs: 1) low awareness among the people of NCDs, 2) regional disparity of medical services, 3) shortage of healthcare staff members with professional knowledge, and 4) poor NCD surveillance.　In Vietnam, an NCD program with screening methods and medical guidelines for respective diseases was developed in 2002. However, it only covered tertiary prevention and did not fully describe the primary and secondary prevention measures. Currently, with the technical assistance of the WHO, the implementation of countermeasures emphasizing prevention and control to reduce NCD risk factors has only just begun.Conclusion　It was considered that educating each person in Vietnam on NCD prevention measures would be necessary and that a national policy, like Healthy Japan 21 of Japan, and a nationwide screening project, such as specific medical checkups, could serve as a useful reference. We found that public health activities in Japan to penetrate a region mainly involving public health nurses had played important roles for Japanese people's health. Furthermore, Japan shares with Vietnam the challenges including the shortage of human resources, and therefore, the securement of healthcare staff members who confront health challenges and the enhancement of their abilities is required.

Use of microscale heterogeneity in samples for spectral factorization-A strategy to build robust prediction models for nondestructive analyses.

Nondestructive spectroscopic analysis is widely used to evaluate food composition. However, distinguishing analytes of interest from other compounds remains challenging. Since most foods are heterogeneous when viewed under a microscope, we hypothesized that spectra measured at microscopic points would be "purer" than spectra acquired from a larger area. By coupling this data with nonnegative matrix factorization (NMF), the analytes of interest can be separated. This preliminary study discusses the quantification of glucose in mixtures of different sugars. Samples were made by mixing glucose with other powders in different ratios and Raman spectra were measured at 200 micro-points for each sample. NMF was applied to factorize the mixed spectra into spectra of pure compounds and their concentrations, leading to the accurate quantification of glucose, while eliminating the effects of other compounds. While this study targets simple powders, separation of analytes using microscale heterogeneity is applicable for measuring more complex foods.

Tumor-Infiltrating CD8-Positive T-Cells Associated with MMR and p53 Protein Expression Can Stratify Endometrial Carcinoma for Prognosis.

BACKGROUND: Inspired by the molecular classification of endometrial carcinoma (EC) proposed by The Cancer Genome Atlas Research Network (TCGA), we investigated tumor-infiltrating CD8-positive T-cell as well as DNA mismatch repair (MMR) protein and p53 protein expression, and we developed a new classification system for ECs to predict patients' prognosis using immunohistochemical methods. METHODS: The study included 128 patients with ECs who underwent surgery. Paraffin-embedded tissue sections of the tumor were stained using antibodies against MMR protein, p53, and CD8. Cases were stratified into four classes by a sequential algorithm. An immunohistochemical classification system for ECs (ICEC) was created, including HCD8, MMR-D, LCD8, and p53 LCD8. RESULTS: In ICEC, 16 cases (12.5%), 27 cases (21.09%), 67 cases (52.34%), and 18 cases (14.06%) belonged to HCD8, MMR-D, LCD8, and p53 LCD8, respectively. ICEC did not show any correlation with clinical stage, lymphovascular space invasion, or lymph node metastasis. However, the p53 LCD8 class contained a significantly higher proportion of G3 ECs and serous carcinoma (p < 0.0001). ICEC showed prognostic significance in overall survival (OS) (p < 0.0001) and disease-free survival (DFS) (p < 0.0001). The class of p53 LCD8 showed the worst prognosis among the classes. CONCLUSIONS: ICEC classification is useful in predicting the prognosis of ECs.

A case of tricuspid valvular nonbacterial thrombotic endocarditis associated with advanced ovarian cancer.

Nonbacterial thrombotic endocarditis (NBTE) is characterized by the deposition of thrombi on the heart valves without bacteremia and predominantly affects patients with hypercoagulable state. Since the lesion of NBTE often exists in the left-sided valves, involvement of the tricuspid valve (TV) is rare. We herein report a 34-year-old woman with advanced ovarian cancer and pulmonary embolization showing NBTE on the TV. Plasma D-dimer level was markedly elevated and echocardiography showed highly mobile masses on the TV with moderate to severe regurgitation. After the initiation of heparin therapy, reduction of plasma D-dimer levels along with shrinkage of the TV vegetations was observed. However, she was forced to discontinue the heparin because its supply was interrupted in association with coronavirus disease 2019. Coupled with systemic metastasis of ovarian cancer, elevated plasma D-dimer level and exacerbation of NBTE were observed. Thereafter, she resumed subcutaneous injection of heparin, resulting in re-improvement. Learning objective: Involvement of tricuspid valve (TV) by nonbacterial thrombotic endocarditis (NBTE) is rare, especially when they are associated with advanced cancer. Our case underlines the importance of listing the NBTE as a differential diagnosis in cancer patients showing valve vegetations even in the TV.

A Case of Endometrial Carcinosarcoma Containing Sertoliform Endometrioid Carcinoma Component.

Carcinosarcomas (CSs) of the endometrium have admixture of malignant epithelial and mesenchymal components. The carcinomatous component exhibit endometrioid, serous, or clear cell differentiation, or are undifferentiated. CSs are considered homologous or heterologous according to the type of sarcomatous component. Sertoliform endometrioid carcinomas (SECs) of the endometrium which comprise a rare subtype of endometrial cancer, typically occur in the ovary. SECs as a carcinomatous component of CS of the endometrium have not been reported. Here, we report an endometrial carcinosarcoma that contains an SEC component. An 88-year-old female presented to a clinic with atypical genital bleeding. She was referred to our hospital and underwent total hysterectomy, bilateral adnexectomy and partial omentectomy due to endometrial carcinoma. Gross examination revealed a polypoid mass in the uterine cavity with massive myometrial invasion. Histologically, the tumor was a high-grade endometrioid carcinoma. In addition to an ordinary conventional endometrioid carcinoma, approximately 30% of the area exhibited sex cord-like pattern and contained small hollow tubules, anastomosing cords and trabeculae, and tightly packed nests. Immunohistochemically, the SEC component showed diffuse p53 staining. Sex cord-like area, especially the solid area, showed positive staining for EMA, vimentin, α-inhibin, CD99, calretinin, p53, CD56, synaptophysin, and chromogranin A, which is a staining pattern similar to that previously reported SEC of the endometrium. Diminished membranous and positive cytoplasmic staining for ß-catenin was observed. This is the first case report of an endometrial carcinosarcoma containing an SEC component. SECs of the endometrium might exhibit sex cord-like differentiation in contrast to SECs of the ovary, which do not exhibit sex cord differentiation.

TP53 codon 72 polymorphism and cervical cancer: a pooled analysis of individual data from 49 studies.

BACKGROUND: Cervical cancer is caused primarily by human papillomaviruses (HPV). The polymorphism rs1042522 at codon 72 of the TP53 tumour-suppressor gene has been investigated as a genetic cofactor. More than 80 studies were done between 1998 and 2006, after it was initially reported that women who are homozygous for the arginine allele had a risk for cervical cancer seven times higher than women who were heterozygous for the allele. However, results have been inconsistent. Here we analyse pooled data from 49 studies to determine whether there is an association between TP53 codon 72 polymorphism and cervical cancer. METHODS: Individual data on 7946 cases and 7888 controls from 49 different studies worldwide were reanalysed. Odds ratios (OR) were estimated using logistic regression, stratifying by study and ethnic origin. Subgroup analyses were done for infection with HPV, ethnic origin, Hardy-Weinberg equilibrium, study quality, and the material used to determine TP53 genotype. FINDINGS: The pooled estimates (OR) for invasive cervical cancer were 1.22 (95% CI 1.08-1.39) for arginine homozygotes compared with heterozygotes, and 1.13 (0.94-1.35) for arginine homozygotes versus proline homozygotes. Subgroup analyses showed significant excess risks only in studies where controls were not in Hardy-Weinberg equilibrium (1.71 [1.21-2.42] for arginine homozygotes compared with heterozygotes), in non-epidemiological studies (1.35 [1.15-1.58] for arginine homozygotes compared with heterozygotes), and in studies where TP53 genotype was determined from tumour tissue (1.39 [1.13-1.73] for arginine homozygotes compared with heterozygotes). Null results were noted in studies with sound epidemiological design and conduct (1.06 [0.87-1.29] for arginine homozygotes compared with heterozygotes), and studies in which TP53 genotype was determined from white blood cells (1.06 [0.87-1.29] for arginine homozygotes compared with heterozygotes). INTERPRETATION: Subgroup analyses indicated that excess risks were most likely not due to clinical or biological factors, but to errors in study methods. No association was found between cervical cancer and TP53 codon 72 polymorphism when the analysis was restricted to methodologically sound studies. FUNDING: German Research Foundation (DFG).

Management of pelvic lymph nodes by sentinel node navigation surgery in the treatment of invasive cervical cancer.

OBJECTIVE: Diagnosis of lymph node metastasis is a critical issue in the treatment of cervical cancer. Many studies describing sentinel node navigation surgery (SNNS) for examination of node status have been reported in the past decade. In this study, the feasibility of node status diagnosis by SNNS, including intraoperative frozen section diagnosis, in patients with early and advanced cervical cancer was evaluated. PATIENTS AND METHODS: Fifty-eight cervical cancer patients with early and advanced stage disease were enrolled. All patients were treated with backup pelvic lymphadenectomy after SNNS. To detect sentinel lymph nodes (SLNs), radioactive material and/or blue dye were used as tracers. Lymph nodes confirmed as SLNs were immediately sent to pathologists and diagnosed by frozen section intraoperatively. RESULTS: A total of 118 and 16 SLNs were pathologically investigated in early and advanced stage cervical cancer, respectively. The detection rate of SLNs in the early and advanced stages was 94.7% and 66.7%, respectively, whereas the detection rate using 1 or 2 tracers was 62.5% and 90%, respectively. The false-negative rate and negative predictive value was 0% and 100% for all stages. Pathological diagnosis by frozen section was completed within 30 minutes in all cases. CONCLUSIONS: Our data demonstrate that SNNS in cervical cancer is a promising procedure for patients with early stage (up to Ib1) disease, especially patients with small tumor diameter (<2.0 cm). However, SNNS raises several points for discussion before it can be established as a practical clinical procedure or as part of a subsequent radical hysterectomy.

Suppression of invasive characteristics by antisense introduction of overexpressed HOX genes in ovarian cancer cells.

HOX genes encode transcription factors that function to establish basic body pattern during embryogenesis and maintain the function of specific organs in the adult. Recent studies have demonstrated that HOX genes are also involved in oncogenesis in a range of malignancies. To elucidate whether HOX genes contribute to ovarian carcinogenesis, we created an expression profile of HOX genes using ovarian derived materials from surgical samples and epithelial ovarian cancer cells derived from five different cell lines. Real-time quantitative RT-PCR assay indicated overexpression of 14 HOX genes in clusters A and B but only 2 genes in clusters C and D. Of the 16 HOX genes, overexpression of paralogs of HOX3, HOX4 and HOX7 is seen in cluster A and B, and of HOX13 in all paralogs. In addition, HOXB7, HOXA13 and HOXB13 showed high levels of overexpression in cancer cells and tissues whereas no or little expression was observed in normal controls. To examine whether overexpressed HOX genes regulate invasion of ovarian cancer cells directly, we introduced an antisense DNA fragment of overexpressed HOXB7 and HOXB13, and HOXC5 that did not show overexpression into SKOV3 cells by electroporation. Antisense introduction followed by chemoinvasion assay using matrigel chamber demonstrated that SKOV3 cells introduced an antisense of each HOXB7 and HOXB13 showed 85% and 50% reduction of invasion ability compared to the parental SKOV3 cells, respectively. In contrast, antisense of HOXC5 introduced cells showed no significant difference of the invasion ability. These results suggest an important role of overexpressed HOX genes, especially for invasive characteristics of ovarian cancer cells.

Regulation of tumor invasion by HOXB13 gene overexpressed in human endometrial cancer.

During the last two decades, a group of homeobox-containing genes, the HOX gene family, has been studied both in the context of embryonic development and neoplasia. In particular, there is accumulating evidence of the involvement of HOX abnormalities in a variety of malignancies, including breast cancer. However, little is known about the association of HOX genes with endometrial cancer, which is the most common malignancy of the female genital tract and is thought to be dependent on estrogen, like breast cancer. In this study, we detected overexpression of the HOXB13 gene in endometrial cancer cells and tissues from patients by quantitative real-time RT-PCR. To investigate whether overexpression of HOXB13 is involved in invasion or metastasis of endometrial cancer, we transfected antisense HOXB13/pcDNA3.1+ plasmid vector into endometrial cancer AN3CA cells by electroporation and performed in vitro chemoinvasion assay. We revealed that the invasive ability of antisense-transfectants showed a 90% reduction compared with parental cells and control transfectants (p<0.01). In addition, administration of 17beta-estradiol induced time- and dose-dependent responses of the HOXB13 expression in endometrial cancer AN3CA cells. These results suggest that overexpression of HOXB13 in endometrial cancer may be associated with the invasive ability of cancer cells with regulation by estrogen.

Trends in fatal coronary heart disease among people aged 25-74 years in Oita City, Japan, from 1987-1998.

Serum cholesterol has been increasing in recent years in Japan. There is concern that risk of coronary heart disease (CHD) may be increasing too, but there is little information on validated fatal CHD trends in the Japanese population. We identified 1,056 deaths from heart disease and other deaths possibly hiding CHD from death certificates of residents aged 25-74 years in Oita City, Japan in 1987-1988, 1992-1993, and 1997-1998 (mean population, 273,000 in 1997-1998). We validated 994 of them by medical record review and physician interviews, classifying them into definite fatal acute myocardial infarction (AMI) and possible fatal AMI or CHD death based on Monitoring Trends and Determinants in Cardiovascular Disease project's criteria. Sudden death was defined to estimate the number of CHD sudden deaths. In men, age-adjusted mortality rates due to validated fatal CHD remained quite stable over 10 years (25.3 per 100,000 [95% CI, 15.0-35.5] in 1987-1988 to 24.2 per 100,000 [95% CI, 16.1-32.3] in 1997-1998). When 50% or all sudden deaths were included as fatal CHD, the rates for men tended to decline. This was due to decreasing out-of-hospital deaths in connection with a declining CHD death rate among men aged 65-74 years, whereas in-hospital CHD deaths were level. In women, the rate of validated fatal CHD was highest in 1992-1993, but the 1997-1998 rate was similar to the 1987-1988 rate. We did not find that fatal CHD rates increased in Oita men and women from 1987-1998. Rather, out-of-hospital fatal CHD tended to decline in Oita men.

Cefpirome sulphate for gynaecological infections and prophylaxis of non-laparotomy surgery in patients with benign disease.

We organized a study group to conduct a clinical trial in patients with various gynaecological infections, and we also assessed the efficacy of a single dose of cefpirome sulphate as prophylaxis after vaginal hysterectomy. Cefpirome sulphate (CROM) was administered to 100 patients with gynaecological infections and the clinical and antibacterial efficacy was evaluated in 88 patients. The improvement rate was 77.0% (67/87) and the bacterial eradication rate 67.8% (40/59). Nineteen of the 210 patients enrolled in the comparison of CROM with cefmetazole sodium (CMET) prophylaxis developed postoperative infections. The incidence of infection showed no significant difference between the CROM group (n=11, 10.6%) and the CMET group (n=8, 7.5%) (P=0.56). Although these results suggest that CROM may be effective for the treatment of gynaecological infections and has a good safety profile, it was not superior to CMET as prophylaxis in women undergoing non-laparotomy procedures at our hospital.

Relationship between expression of matrix metalloproteinase-2 and matrix metalloproteinase-9 and invasion ability of cervical cancer cells.

Constitutive overexpression of matrix metalloproteinases (MMPs) is frequently observed in malignant tumors. MMPs are a family of zinc endopeptidases consisting of at least 20 different members. In particular, MMP-2 and MMP-9 are reported to be closely associated with invasion and metastasis in several cancers. We investigated whether expression of MMP-2 and MMP-9 is associated with invasion ability of seven cervical cancer cells by administration of o-phenanthroline as MMP inhibitor. In two cell lines, Siha and Caski, MMP-2 mRNA and protein were expressed at high levels. After treatment with o-phenanthroline, the rate of invasion in these two cell lines was significantly decreased. In contrast, in the other two cell lines, HT-3 and Caski, high levels of MMP-9 mRNA and protein were expressed but there was no decrease in the rate of invasion in these cells after treatment with o-phenanthroline. The data suggest that expression level of MMP-2 mRNA may regulate with invasion ability of cervical cancer.

A stability-based mechanism for hysteresis in the walk-trot transition in quadruped locomotion.

Quadrupeds vary their gaits in accordance with their locomotion speed. Such gait transitions exhibit hysteresis. However, the underlying mechanism for this hysteresis remains largely unclear. It has been suggested that gaits correspond to attractors in their dynamics and that gait transitions are non-equilibrium phase transitions that are accompanied by a loss in stability. In the present study, we used a robotic platform to investigate the dynamic stability of gaits and to clarify the hysteresis mechanism in the walk-trot transition of quadrupeds. Specifically, we used a quadruped robot as the body mechanical model and an oscillator network for the nervous system model to emulate dynamic locomotion of a quadruped. Experiments using this robot revealed that dynamic interactions among the robot mechanical system, the oscillator network, and the environment generate walk and trot gaits depending on the locomotion speed. In addition, a walk-trot transition that exhibited hysteresis was observed when the locomotion speed was changed. We evaluated the gait changes of the robot by measuring the locomotion of dogs. Furthermore, we investigated the stability structure during the gait transition of the robot by constructing a potential function from the return map of the relative phase of the legs and clarified the physical characteristics inherent to the gait transition in terms of the dynamics.

Hysteresis in the gait transition of a quadruped investigated using simple body mechanical and oscillator network models.

We investigated the dynamics of quadrupedal locomotion by constructing a simple quadruped model that consists of a body mechanical model and an oscillator network model. The quadruped model has front and rear bodies connected by a waist joint with a torsional spring and damper system and four limbs controlled by command signals from the oscillator network model. The simulation results reveal that the quadruped model produces various gait patterns through dynamic interactions among the body mechanical system, the oscillator network system, and the environment. They also show that it undergoes a gait transition induced by changes in the waist joint stiffness and the walking speed. In addition, the gait pattern transition exhibits a hysteresis similar to that observed in human and animal locomotion. We examined the hysteresis mechanism from a dynamic viewpoint.

[Influence of physical workload patterns and breaks on heart rate recovery].

It is necessary to try to achieve quick recovery from work strain by setting adequate breaks and shortening continuous working hours to prevent the accumulation of fatigue. However, there has been no research investigating the influence of the timing and lengths of breaks on individual aerobic capacities in recovery from work strain. In this study, we set three load patterns based on the length and timing of breaks: "no breaks", "one break" and "regular small breaks". We examined the differences of the heart rate variation in the recovery time after working considering the individual aerobic capacities (VO(2)max) of ten male subjects (mean age 22.3 +/- 1.7 yr) in the case of 50 W or 100 W workloads on a bicycle ergometer. When individual aerobic capacity was not considered, the "regular small breaks" condition led to the quickest recovery to the level of the resting heart rate at 50 W workload. Not all conditions showed heart rate recovery within 30 min at 100 W workload. On the other hand, when individual aerobic capacity was considered, the "regular small breaks" condition showed the quickest recovery to the level of the resting heart rate at 50 W workload in the low aerobic capacity group (VO(2)max mean 42.2 +/- 3.7 ml/kg/min). However, in the high aerobic capacity group (VO(2)max mean 54.5 +/- 4.1 ml/kg/min), the "regular small breaks" condition resulted in the quickest recovery of the level to the resting heart rate at 100W workload. Two-way repeated measures ANOVA was performed for the recovery time with respect to the rate of increase from resting heart rate to examine the influence on heart rate recovery of physical activity loads, workload patterns and individual fitness. Physical activity loads were strongly related to the increase from resting heart rate in recovery time, and workload patterns showed that the regular small breaks condition was related to the heart rate recovery in the high fitness subjects in the case of the exercise intensity of 100 W. The effect of work strain decreased by workload patterns was defined by the relationship between physical activity load and individual fitness. In future occupational health activities, it will be important to manage work in order to aim for quick recovery from work strain by using ergonomics. The evaluation of the level of the physical activity load and distribution of proper break times during working in addition to individual aerobic capacities are important in considerations of quick recovery from work strain.