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Biomedical subjects

K Akazawa

Publications and source records attributed to K Akazawa.

At least 37 records · Page 2Linked to original sources

An easily customized, random allocation system using the minimization method for multi-institutional clinical trials.

In a randomized clinical trial, random allocation of patients to treatment groups should be done to balance in the distribution of prognostic factors. Random allocation in a multi-institutional randomized clinical trial is conducted by a coordinating center, independent of the medical institution the attending doctor uses for his/her practice. This study provides a sophisticated system for doing an exact random allocation of patients to treatment groups. The minimization method proposed by Pocock was applied to this system to balance the distribution of prognostic factors between two treatment groups, even when the number of registered patients is relatively small (S.J. Pocock, Allocation of patients to treatment in clinical trial, Biometrics 35 (1979) 183-197). Furthermore, Zelen's method is used to balance the number of patients allocated to the two groups within each institution (M. Zelen, The randomization and stratification of patients to clinical trials, J. Chron. Dis. 27 (1974) 365-375.). This system was created by the 'PERL’ language for writing common gateway interface (CGI) script, and can therefore, be easily extended to include data entry function by attending doctors as well as the random allocation function. This system is being used effectively in thirteen multi-institutional randomized clinical trials for stomach, colon-rectum and breast cancers in Japan.

Clinical Trials as Topic↗

Laparoscopic adrenalectomy: lateral transabdominal approach vs posterior retroperitoneal approach.

Laparoscopic adrenalectomy has been used to remove a wide variety of adrenal neoplasms. Although several laparoscopic approaches to the adrenal gland have been described, the lateral transabdominal approach has several advantages when compared with other approaches for laparoscopic adrenalectomy. From October 1995 to July 1999, we performed laparoscopic adrenalectomies on 16 patients, including eight posterior retroperitoneal approaches and eight lateral transabdominal approaches. Sixteen patients, ranging in age from 23 to 69 years, were treated for the following conditions: non-functioning adenoma, four patients; aldosteronoma, seven patients; pheochromocytoma, three patients; Cushing's adenoma, two patients. The average tumor size was 2.5 +/- 0.5 cm (1.8-3.0 cm, median 2.4 cm) in the lateral transabdominal approach, 1.2 +/- 0.8 cm (0.8-3.2 cm, median 1.75 cm) in the posterior retroperitoneal approach. Average operative time of lateral transabdominal approach was significantly shorter than that of the posterior retroperitoneal approaches (mean 129 min vs 269 min, P = 0.0005). Conversion to laparotomy was required in one patient in the posterior approach. Postoperative complication occurred in one pneumothorax in the lateral transabdominal approach and two subcutaneous emphysemas in the posterior retroperitoneal approach. There was no statistical difference in blood loss during the operation in the two groups. There was no mortality in either group. The lateral transabdominal approach is a safe and efficient technique for the removal of the adrenal neoplasms. Compared with other approaches, this technique has a wider working space and also good exposure for removing the adrenal gland.

Abdomen↗

Accessing endoscopic images for remote conference and diagnosis using WWW server with a secure socket layer.

Out of 137 hospitals in Niigata prefecture, 13 are connected to the Internet. The number of private clinics using the Internet has also increased. It is thought that an endoscopic information exchange over the Internet connection is useful for the cooperation between hospitals, clinics and organizations in related fields. A conventional World Wide Web (WWW) server of endoscopic images has been built around a compressed JPEG (Joint Panel Expert Group) format, for remote conferences and diagnoses. It has been made secure using a proxy server, a firewall server and a Secure Socket Layer (SSL). It is easy to access the server and view these endoscopic images using the usual homepage browsing method. Ordinarily, gastroenterologists would diagnose lesions with endoscopy in most cases. It is suggested that this conventional WWW server will be effective for remote conferences in some cases, even consultation will be possible.

Endoscopy, Gastrointestinal↗

Thymus-independent expansion of T lymphocytes in children after allogeneic bone marrow transplantation.

The contribution of the thymus-dependent pathway and thymus-independent pathways for T cell regeneration after BMT in children is still unclear. We analyzed the kinetics of T cell regenerative pathways after allogeneic BMT. The number of CD4+CD45RA+ T cells, a thymus-dependent population, was very low until 3 months after BMT. The numbers of CD28- T cells and CD8+ T cells expressing CD8alpha/alpha homodimer (CD8alpha/alpha+ T cells), a thymus-independent population, increased shortly after BMT, beyond the levels of healthy children in some patients. The numbers of Vgamma9+Vdelta2+ and Valpha24+ T cells, which represent populations of extrathymic development, were less than 200/microl during the 6 months after BMT. There was a significant inverse correlation between the percentages of CD4+CD45RA+ and CD28-T cells at 1 month, and a positive correlation between the percentages of CD28- and CD8alpha/alpha+ T cells at 2 and 3 months after BMT. The mean age at BMT was higher in patients with a high level of CD8alpha/alpha+ T cells than in those without an increase in these cells, suggesting the influence of thymic function on the regenerative pathways. These results suggest that the thymus-independent pathway is the dominant source of T cells even in children shortly after allogeneic BMT.

Acute Disease↗

Prospective evaluation of preoperative chemotherapy in resectable squamous cell carcinoma of the thoracic esophagus.

A prospective study was performed to clarify the surgical outcome of patients with esophageal carcinoma who would benefit from induction chemotherapy followed by surgery. Of 55 eligible patients, 42 (76.3%) agreed to randomization with either chemotherapy followed by surgery (n = 21) or surgery alone (n = 21). The other 13 refused. The chemotherapy consisted of cisplatin, 5-fluorouracil and leucovorin. All 55 patients underwent esophagectomy with two- or three-field resection, including two (3.6%) hospital mortalities. Of the 21 patients receiving chemotherapy, the response rate was 33.3% after the first course and 60% after the second course. A complete response was not obtained. Responders to the first course showed a prolonged survival, however time to treatment failure did not differ between patients treated with chemotherapy followed by surgery or surgery alone. This chemotherapy offered a worse surgical outcome for patients with pretreatment diagnosis of T3. Multivariate analysis identified a partial response to the first course of chemotherapy to be a favorable prognostic indicator. Preoperative chemotherapy does not give a survival benefit over surgery alone for patients with advanced tumor (T3). Initial response to the first dose of chemotherapy is deemed to be a prognostic factor for patients with less advanced tumor (T1/T2).

Aged↗

Time trends of surgical treatment and the prognosis for Japanese patients with gastric cancer.

The incidence of gastric cancer is much higher in Japan than in other countries even though diagnostics and treatments of such patients have improved. The objective of this study was to present an overview of the past, present and future of surgical treatment for our patients with gastric cancer. We analysed data on 2152 Japanese men and women with gastric cancer who underwent surgical resection from 1965 to 1995 at Kyushu University in Fukuoka, Japan, based on a univariate and the multivariate analysis. We focused on time trends of surgical treatment and the postoperative outcome. Over the years, there have been favourable changes in the numbers of patients with early gastric cancer. In all cases of gastric cancer, the rate of 18% in the first six year period (group 1) was 57% in the last 5 year period (group 6). Size of the tumour was smaller, well-differentiated tumour tissue was more common, and lymphatic involvement was less frequent. Lymph node metastasis, liver metastasis and peritoneal dissemination all decreased. Extensive lymph node dissection was more frequently done and the rate of curative resection (curability A and B) increased. With increases in identifying the early stage of cancer and better perioperative care, mortality rates 30 days after the surgery greatly decreased. Multivariate analysis revealed that the 10 factors of depth of invasion, lymph node metastasis, lymph node dissection, tumour size, liver metastasis, peritoneal dissemination, lymphatic invasion, vascular invasion, lesion in the whole stomach and lesion in the middle stomach were independent factors for determining the prognosis. Detection of the tumour in an early stage, standardized surgical treatment, including routine lymph node dissection, close follow-up schedules and better perioperative management are expected to increase survival time for patients with this malignancy.

Female↗

Evaluation of a new amplified enzyme immunoassay (EIA) for the detection of Chlamydia trachomatis in male urine, female endocervical swab, and patient obtained vaginal swab specimens.

AIMS: To compare the performance of a new generation dual amplified enzyme immunoassay (EIA) with a molecular method for the diagnosis of Chlamydia trachomatis, using a range of urogenital samples, and to assess the reliability of testing self collected vaginal specimens compared with clinician collected vaginal specimens. METHODS: Two population groups were tested. For the first population group, first void urine samples were collected from 193 male patients with urethritis, and endocervical swabs were collected from 187 high risk commercial sex workers. All urine and endocervical specimens were tested by a conventional assay (IDEIA chlamydia), a new generation amplified immunoassay (IDEIA PCE chlamydia), and the Amplicor polymerase chain reaction (PCR). Discrepant results obtained among the three sample types were confirmed using a nested PCR test with a different plasmid target region. For the second population group, four swab specimens, including one patient obtained vaginal swab, two clinician obtained endocervical swabs, and one clinician obtained vaginal swab, were collected from 91 high risk sex workers. Self collected and clinician collected vaginal swabs were tested by IDEIA PCE chlamydia. Clinician obtained endocervical swabs were assayed by IDEIA PCE chlamydia and Amplicor PCR. RESULTS: The performance of the IDEIA PCE chlamydia test was comparable to that of the Amplicor PCR test when male urine and female endocervical swab specimens were analysed. The relative sensitivities of IDEIA, IDEIA PCE, and Amplicor PCR on male first void urine specimens were 79.3%, 91.4%, and 100%, respectively. The relative sensitivities of the three tests on female endocervical specimens were 85.0%, 95.0%, and 100%, respectively. The positivity rates for patient collected vaginal specimens and clinician collected vaginal specimens by IDEIA PCE were 25.2% and 23.1%, respectively, whereas those for clinician collected endocervical swabs by PCR and IDEIA PCE were both 27.5%. CONCLUSIONS: IDEIA PCE chlamydia is a lower cost but sensitive alternative test to PCR for testing male urine samples and female endocervical swabs. In addition, self collected or clinician collected vaginal specimens tested by IDEIA PCE chlamydia are a reliable alternative to analysing endocervical specimens.

Chlamydia Infections↗

The effect of tranilast on experimental proliferative vitreoretinopathy.

BACKGROUND: Tranilast has been clinically used for various allergic diseases. Recently, it has also been found to inhibit excessive scarring in wound healing processes. In this study, we examined the effects of tranilast on the treatment for experimental proliferative vitreoretinopathy (PVR). METHODS: Cultured rabbit conjunctival fibroblasts were injected intravitreously (50000 cells/eye) into the rabbit vitreous to induce experimental PVR. Immediately after that, tranilast (0.5-5 mg/ml, 0.1 ml/eye) was injected into the vitreous. Injection of vehicle solution was used as a negative control. PVR was clinically evaluated by masked observers using ophthalmoscopy and graded into six stages: 0 (no PVR) to 5 (severe PVR). The amount of transforming growth factor beta1 (TGF-beta1) in the vitreous was measured by ELISA method. Functional and morphological changes induced by 5 mg/ml tranilast were sought by electroretinography, light microscopy, and electron microscopy on day 28. RESULTS: The average stage of PVR in the eyes treated with tranilast (1 or 5 mg/ml) was significantly lower than that in the control group on days 14 and 28. There was no difference between the eyes treated with low-dose tranilast (0.5 mg/ml) and the control group. The amount of TGF-beta1 in the vitreous of tranilast-treated eyes was significantly lower than in the control group. The morphological and functional studies did not show any deleterious effect of tranilast on the retinal function and morphology. CONCLUSION: Tranilast effectively inhibits the progression of PVR without showing apparent toxicity of the eye. This agent has therapeutic value for PVR.

Animals↗

Rhythmic changes in the stomach movement of the human fetus with congenital duodenal obstruction during the third trimester of pregnancy.

In order to reveal whether or not rhythmic changes exist in fetal stomach movement (FSM), in utero FSM was assessed in three fetuses between 27 and 33 weeks' gestation with congenital duodenal obstruction. A total of four observations, one each at 27, 29, 31 and 33 weeks' gestation, was obtained. The longitudinal transection of each fetal stomach was continuously observed for 60 min using real-time ultrasound. The configuration and the area of the stomach were analyzed for each 15-s epoch. The complexity of the stomach configuration was quantified and defined as stomach complexity. For each case, the chronological changes of the stomach complexity were analyzed using the least median square of regression. The correlation between changes of the stomach complexity and the area of the stomach was analyzed using the cross-correlation method. (1) For gestational ages of 27, 29, 31 and 33 weeks, the 240 sequential measurements of the stomach complexity were significantly stratified into outlying and non-outlying points. The outlying points were 13.3% (32/240), 30.8% (74/240), 32.9% (79/240) and 36.3% (87/240) of the total observation points, respectively. (2) The percentages in which outlying points lasted 3 min (12 points) or more were 0% (0/240), 5.0% (12/240), 28.3% (68/240) and 30.4% (73/240) of the total observation points, respectively. (3) For each gestational age, no significant time series correlation was found between the stomach complexity and the area of the stomach. These findings suggest that: (1) two different conditions emerge in the FSM, at the latest at 27 weeks' gestation, and begin manifesting from 29 weeks' gestation onwards. (2) These chronological changes cluster into 'active' and 'quiet' phases from 31 weeks' gestation onwards. (3) FSMs are not related to the changes in the stomach area throughout the observation periods. The underlying mechanism of this rhythmicity may represent the development of ultradian rhythm of the stomach movement, generated by the central nervous system.

Duodenal Obstruction↗

Postoperative chemo-endocrine treatment with mitomycin C, tamoxifen, and UFT is effective for patients with premenopausal estrogen receptor-positive stage II breast cancer. Nishinihon Cooperative Study Group of Adjuvant Therapy for Breast Cancer.

The effectiveness of combining mitomycin C (MMC), tamoxifen (TAM), and 1-(2-tetrahydrofuryl)-5-fluorouracil (tegafur) was evident in patients with estrogen receptor-positive (ER+) breast cancers. UFT, an oral preparation of tegafur and uracil at a molar ratio of 1:4, was reported to have higher antitumor effects than tegafur alone for patients with breast cancer. Therefore, the combined chemotherapy of MMC, TAM and UFT may possibly be effective for breast cancer. From 1988 to 1991. we studied the effects of postoperative adjuvant therapy for Japanese women with stage 11 breast cancer, all seen at 71 institutions in western areas of Japan. Five hundred and ninety four patients with stage II primary breast cancer who had undergone curative surgery, including total mastectomy and axillary lymph node dissection, were enrolled. On the day of surgery, each patient was given 13 mg/m2 of MMC intravenously. Patients with ER+ tumors were then assigned to group A or group B. Group A received 30 mg/day of TAM given orally from postoperative 2 weeks, for 2 years. Group B was additionally given an oral dose of 300 mg/day of UFT for 2 years, given concomitantly with 30 mg/day of TAM. Patients with ER- tumors were assigned to group C or group D. Group C were prescribed 300 mg/day of UFT, orally, from postoperative 2 weeks for 2 years, and group D were additionally given an oral dose of 30 mg/day of TAM together with 300 mg/day of UFT. There were no differences among the groups regarding prognostic factors or doses of MMC and TAM in ER+ patients and MMC and UFT in ER- patients. Toxicity rates for leukopenia, anorexia, and nausea/vomiting were higher in group B than in group A patients. There were no statistical differences in the overall survival and disease-free survival times between groups A and B, or groups C and D, for all eligible cases. In a retrospective subgroup analysis using Bonferroni's adjustments, the additional effect of UFT on the combined treatment of MMC and TAM lengthened the disease-free survival time for patients with premenopausal ER+ cancers (corrected P value by Bonferroni's adjustments <0.05). Multivariate analysis showed that effects of the combined treatment of MMC, TAM, and UFT was significantly related to the menopausal status (P<0.01). Our findings show that postoperative ingestion of MMC, TAM, and UFT was effective for patients with premenopausal ER+ stage II breast cancer.

Adult↗

An analysis of risk factors for upper urinary tract deterioration in patients with myelodysplasia.

OBJECTIVE: To identify the risk factors for upper urinary tract deterioration in a retrospective study of patients with myelodysplasia. PATIENTS AND METHODS: The medical history, radiographic studies and urodynamic results from 39 children with myelodysplasia who were treated at our hospital were reviewed retrospectively to obtain more accurate data in the prognosis of such patients. The upper urinary tracts were assessed by cysto-urethrography and excretory urography to determine the incidence of vesico-ureteric reflux (VUR) and hydronephrosis. The relationships between the urodynamic variables, including vesical compliance, detrusor hyper-reflexia, detrusor-sphincter dyssynergia (DSD) and the maximum urethral closing pressure (MUCP) to such upper tract deterioration were evaluated using both univariate and multiple logistic regression analysis. RESULTS: The univariate analysis showed low vesical compliance, a high level of MUCP and the presence of DSD to be significant factors for the incidence of VUR. Low vesical compliance and a high level of MUCP also correlated with the incidence of hydronephrosis. The multivariate analysis showed a significant relationship between urodynamic values and upper urinary tract deterioration. The incidence of VUR was strongly correlated with a high MUCP and the presence of DSD. A high MUCP was also a significant factor in the incidence of hydronephrosis. CONCLUSION: Urodynamic results associated directly with the abnormal function of urethral control are significantly correlated with the cause of upper tract deterioration in patients with myelodysplasia.

Adolescent↗

Properties of rat cone-mediated electroretinograms during light adaptation.

PURPOSE: Our aim was to better understand how to isolate the cone-mediated response in rats. Therefore, we studied the difference of ERGs in the course of light adaptation between 2 and 20 Hz stimulus frequencies. METHODS: A total of 90 rats divided into 18 different groups were used following overnight dark adaptation. ERGs were recorded against 3 different adapting field luminances (1.15, 1. 50 or 1.75 log cd/m(2)) with a combination of 3 stimulus flash intensities (0.86, 1.30 or 2.03 log cd sec/m( 2)). The responses were obtained at 2 minute intervals for 25 minutes of light adaptation. RESULTS: The response of the rat cone ERG was large despite the small number of cones. The mean amplitude increased systematically from the dark-adapted value requiring more than 15 minutes to reach an asymptote at 2 Hz stimulation, but only 10 minutes at 20 Hz stimulation. The 2 Hz adaptation curves had biphasic pattern compared to the monophasic 20 Hz curve. This second increase in the amplitude at 2 Hz appeared at around 7-8 minutes as a function of adaptation time. This tendency was most evident when using a low adapting field luminance with a high flash intensity. CONCLUSIONS: Our results suggest that the rods intrude much more during light adaptation at 2 Hz stimulation in rodents than in humans. Therefore, 20 Hz flicker stimulation can better isolate more the cone-mediated function than 2 Hz stimulation during the course of light adaptation in rats. Furthermore, the functional characteristics of the cone in rats may be different from that in humans.

Adaptation, Ocular↗

Factors affecting maternal anxiety about child rearing in Japanese mothers.

In order to determine the factors causing anxiety in raising young children, data were collected from questionnaires completed by 1164 mothers of 3-y-old children at a standardized baby check-up. Factors concerning demographic characteristics, delivery and child rearing practice were used in multivariate logistic regression analysis. Stepwise logistic regression analysis showed that mothers rearing first children and toddlers who were susceptible to common illnesses were likely to worry. Improvements in the child rearing environment are needed.

Anxiety↗

Quality of life after laparoscopy-assisted Billroth I gastrectomy.

OBJECTIVE: To evaluate the quality of life of patients who had undergone laparoscopy-assisted Billroth I gastrectomy (LAG) for cure of cancer. SUMMARY BACKGROUND DATA: In 1994, the authors reported the first case of LAG for early gastric cancer, and this approach quickly has been adopted by Japanese surgeons. However, little is known about the subjective clinical results of this less invasive surgery. METHODS: Quality of life was estimated using the 24-item questionnaire with a scoring system of 1, 2, and 3 and was compared between 41 consecutive patients with LAG and 35 with conventional open gastrectomy. All patients underwent Billroth I gastrectomy for early gastric cancer from January 1993 to July 1997 and were alive without recurrence. RESULTS: Patients who had undergone LAG were taking a normal diet (100%) with >66% of volume at each meal (90%), showed no decreased performance status (90%), and were satisfied with their surgical results (88%). Patients with LAG, when compared with open gastrectomy, showed significantly better results with regard to weight loss, difficulty in swallowing, heartburn and belch, early dumping syndrome, and total score. LAG was better accepted by the patients. CONCLUSIONS: Quality of life after Billroth I gastrectomy was significantly better in patients in whom a laparoscopic technique was used than in those who underwent a conventional method. LAG is less invasive and better accepted by patients and is the procedure of choice for the treatment of early gastric cancer.

Aged↗

The available period and kind of exercise for increasing osteo sono assessment index in women.

PURPOSE: The purpose of this study is to determine the optimum period and kind of exercise which are more effective for increasing the calcaneus osteo sono assessment index (OSI) in adolescent women. METHODS: The subjects consisted of 600 female students aged from 19 to 21 studying at the Department of Food and Nutrition at Nakamura Gakuen University. The calcaneus OSI was measured by ultrasonic bone absorptiometry. The factors associated with an increased OSI were determined using piecewise linear regression analyses. RESULTS: Experience in performing impact-loading exercise either in junior high school or high school was found to be a significant predictive factor for increased calcaneus OSI after adjusting for age and weight. Regarding other exercise-related factors such as subjective intensity, frequency, hours at a time, and total duration of exercise, a piecewise liner regression analysis showed that a total duration of over 7 yr and a high subjective intensity of the impact-loading exercise during high school and junior high school periods caused a significant increase in the calcaneus OSI. However, the OSI decreased when the subjective intensity of the impact-loading exercise during the high school period was reported to be "very strenuous." CONCLUSIONS: Impact-loading exercise in junior high school and high school is important for increasing calcaneus OSI; however, impact-loading exercise in high school with a "very strenuous" subjective intensity was also found to possibly decrease the calcaneus OSI.

Adult↗

Role of transforming growth factor-beta 1 in invasion and metastasis in gastric carcinoma.

PURPOSE: Transforming growth factor-beta1 (TGF-beta1) is a major modulator of cellular proliferation and extracellular matrix formation. We determined the role of TGF-beta1 in invasion and metastasis in gastric cancer. MATERIALS AND METHODS: We detected TGF-beta1 expression in primary and lymph node metastatic lesions of gastric cancer, using an antibody and in situ hybridization. The plasma TGF-beta1 levels in the peripheral vein and in the tumor drainage vein were assayed. RESULTS: In the cytoplasm of cancer cells, TGF- beta1 was immunostained in 35.9% (78 of 217) of primary gastric carcinomas, and this expression was confirmed by in situ hybridization. Of 59 gastric carcinomas with a TGF-beta1-negative primary tumor, metastatic lymph nodes were positive for TGF-beta1 staining in 32 cases (54.2%). Positive staining of TGF-beta1 in gastric cancer tissues was closely related to serosal invasion, infiltrative growth, and lymph node metastasis. Multivariate analysis showed that the expression of TGF-beta1 was an independent risk factor for serosal invasion and infiltrative growth of the tumor. The plasma level of TGF-beta1 did not differ between TGF-beta1-negative and -positive groups. There were also no differences in plasma TGF-beta1 levels among each tumor stage, between the peripheral and the tumor drainage veins, and between preoperative and postoperative testings. CONCLUSION: Transforming growth factor-beta1 is closely related to the invasion and metastasis of gastric cancer, and production of TGF-beta1 in the tumor does not contribute to the total amount of TGF-beta1 in the blood circulation. We interpret our observations to mean that in a tumor microenvironment, TGF-beta1 alters the biologic behavior of the tumor.

Aged↗

Prognostic significance of polo-like kinase expression in esophageal carcinoma.

PLK (polo-like kinase), which belongs to a family of serine/threonine kinases and represents the human counterpart of structurally related protein kinases, polo of Drosophila melanogaster and CDC5 of Saccharomyces cerevisiae, may be implicated in spindle formation and chromosome segregation during mitosis. There are, however, few reports on the significance of PLK gene expression in human carcinomas. In order to evaluate its clinical significance, we examined the expression of the PLK mRNA in 49 esophageal and 75 gastric carcinomas, using reverse transcription-polymerase chain reaction analysis. In esophageal carcinomas, PLK overexpression was detected in 47 carcinomas (97%) when compared to the corresponding normal tissues. It is noteworthy that the patients with high-grade PLK overexpression represented a significantly poorer prognosis group than those with low-grade PLK overexpression (3-year survival rate: 54.9% vs 24.8%, p<0.05). A multivariate analysis demonstrated that the PLK mRNA expression status was an independent prognostic factor for patients with esophageal carcinoma. On the other hand, 55 gastric carcinomas (73%) were revealed to overexpress PLK mRNA, but the expression status showed no correlation with prognosis. This study demonstrated that the PLK overexpression was frequently observed in esophageal and gastric carcinomas, and appeared to be an independent prognostic factor for patients with esophageal carcinoma.

Adenocarcinoma↗

Relation between intrinsic viscoelasticity and activation level of the human finger muscle during voluntary isometric contraction.

The purpose of the present study was to isolate the length perturbation-evoked force attributed to intrinsic muscle viscoelasticity, and to investigate the relation between muscle viscoelasticity and the level of muscle activation during isometric contraction in five healthy male subjects. A small length perturbation (stretching or contraction) was applied to the flexor pollicis longus muscle while the subject maintained constant isometric force; the time courses of the length perturbation was found to be almost identical in all the experiments. The force (Fv) induced by the muscle viscoelasticity was calculated using the equation Fv = F - Fc - Fp over an interval of 35 ms after the onset of perturbation, where F is the measured force, Fc is the tonic isometric force before the onset of perturbation and Fp is the force at rest obtained from the same length perturbation. The force response attributed to the stretch reflex is not included during this interval. These experiments were repeated at varying levels of isometric force. An almost linear relationship was obtained between the muscle viscoelasticity-induced force and the tonic isometric force during both the stretching and contraction of the muscle, i.e. the intrinsic muscle viscoelasticity varied almost linearly with the level of isometric contraction.

Adult↗