Biomedical subjects

H Tohyama

Publications and source records attributed to H Tohyama.

At least 19 recordsLinked to original sources

PubMed2006

Expression of vascular endothelial growth factor and angiogenesis in patellar tendon grafts in the early phase after anterior cruciate ligament reconstruction.

The aim of this study was to clarify vascular endothelial growth factor (VEGF) expression and angiogenesis in the patellar tendon (PT) autograft in the early phase after anterior cruciate ligament (ACL) reconstruction using a rabbit model. The right knees of 30 Japanese white rabbits underwent ACL reconstruction using the medial third of the PT complex. We evaluated the grafted tendon at 1, 2, 3, 4, and 8 weeks after ACL reconstruction by immunohistology for proliferating cell nuclear antigen, VEGF, and CD31, which is a marker for vascular endothelial cells. At week 1 , few cells were observed at the midsubstance of the grafted tendon. A number of proliferating cells were observed at the surface area of the PT graft 2 weeks after graft transplantation, while no vessel formation was observed in the graft at the same time. VEGF was highly expressed 2-3 weeks postoperatively. Vessel formation in the PT graft increased with time from 3 to 8 weeks after ACL reconstruction. The rates of proliferating cells and VEGF-expressing cells decreased with time from 3 to 8 weeks. This study has suggested that VEGF is involved in the graft remodeling process particularly at the early phase after ACL reconstruction.

Animals↗

PubMed2005

Growth kinetics and integrin expression of fibroblasts infiltrating devitalised patellar tendons are different from those of intrinsic fibroblasts.

We compared the biological characteristics of extrinsic fibroblasts infiltrating the patellar tendon with those of normal, intrinsic fibroblasts in the normal tendon in vitro. Infiltrative fibroblasts were isolated from the patellar tendons of rabbits six weeks after an in situ freeze-thaw treatment which killed the intrinsic fibroblasts. These intrinsic cells were also isolated from the patellar tendons of rabbits which had not been so treated. Proliferation and invasive migration into the patellar tendon was significantly slower for infiltrative fibroblasts than for normal tendon fibroblasts. Flow-cytometric analysis indicated that expression of alpha5beta1 integrin at the cell surface was significantly lower in infiltrative fibroblasts than in normal tendon fibroblasts. The findings suggest that cellular proliferation and invasive migration of fibroblasts into the patellar tendon after necrosis are inferior to those of the normal fibroblasts. The inferior intrinsic properties of infiltrative fibroblasts may contribute to a slow remodelling process in the grafted tendon after ligament reconstruction.

Animals↗

PubMed2002

The effect of increased stress on the patellar tendon.

We performed a biomechanical and histological study to clarify the effect of stress enhancement on the in situ frozen-thawed patellar tendon of the rabbit as a tendon autograft model. We used 48 Japanese White rabbits divided into three groups. In group 1, the patellar tendon underwent in situ freeze-thaw treatment with liquid nitrogen to kill intrinsic fibroblasts. In group 2, after similar treatment, the medial and lateral portions were resected so that the cross-sectional area was reduced by a third. In group 3, after treatment, the cross-sectional area was reduced by a half. In groups 2 and 3, the stress in the tendon was calculated theoretically to be 150% and 200% of the physiological stress during locomotion. Eight rabbits in each group were killed at three and six weeks, respectively. At three weeks, the mean values for the tensile strength of groups 2 and 3 were 113.7% and 75.7% of that of group 1, and at six weeks 101.2% and 57.4%, respectively. The tensile strength in group 3 was significantly lower than that in groups 1 and 2. The histological findings in group 2 were similar to those in group 1, although an acellular area appeared to be wider in the core portion compared with group 1 at each period. In group 3, the collagen bundles of the tendon were less organised than those of groups 1 and 2. Our findings showed that stress enhancement affects the remodelling of the frozen-thawed patellar tendon and that excessively high stress reduces the mechanical properties of the tendon. This indicates that high stress on the patellar tendon autograft should be avoided during ligament reconstruction.

Animals↗

PubMed2001

Comparisons of intraosseous graft healing between the doubled flexor tendon graft and the bone-patellar tendon-bone graft in anterior cruciate ligament reconstruction.

PURPOSE: The purpose of this study was to compare intraosseous graft healing between the doubled flexor tendon (FT) graft and the bone-patellar tendon-bone (BPTB) graft in anterior cruciate ligament (ACL) reconstruction. TYPE OF STUDY: Randomized trial. METHODS: A biomechanical and histologic study was conducted with 24 adult beagle dogs. Bilateral ACL reconstructions were performed in each animal. Autogenous doubled FT and BPTB grafts were used for the left and right knees, respectively. Each end of the 2 grafts was tethered with a polyester suture to a screw post with a washer. The animals were then allowed unrestricted activities in their cages. Eight animals were killed at 3, 6, and 12 weeks, respectively. RESULTS: Histologically, the FT graft was anchored to the tunnel wall with newly formed collagen fibers resembling Sharpey's fibers by 12 weeks. These fibers were more abundant in the anterior (ventral) gap than in the posterior (dorsal) gap. In the BPTB graft, the bone plug was anchored with newly formed bone at 3 weeks, although osteocytes in the plug trabeculae were necrotic for 12 weeks. Degeneration of the tendon-bone junction in the plug progressed at 6 weeks. Tensile testing showed that the weakest site was different not only between the 2 grafts but also between the observation periods. In the FT graft, the weakest site was the graft-wall interface at 3 weeks and the intraosseously grafted tendon at 6 weeks. In the BPTB graft, the weakest site was the graft-wall interface at 3 weeks and the proximal site in the bone plug at 6 weeks. The ultimate failure load of the FT graft was significantly inferior (45.8%) to that of the BPTB graft at 3 weeks (P =.021). At 6 weeks, the load of the FT graft was 85% that of the BPTB graft without a significant difference (P =.395). CONCLUSIONS: As to the clinical relevance, the fixation device chosen for soft-tissue fixation appears to be more important than comparing it to the BPTB graft, although this has yet to be conclusively proven.

Animals↗

PubMed2000

The effects of stress enhancement on the extracellular matrix and fibroblasts in the patellar tendon.

The purpose of the present study is to determine the effect of the stress enhancement and intrinsic fibroblasts on the extracellular matrix of the patellar tendon. Thirty-two female Japanese White rabbits were divided into four groups. In Group 1, the patellar tendon underwent the in situ freeze-thaw treatment to kill intrinsic fibroblasts of the patellar tendon and the patellar tendon underwent the wrapping treatment with nylon membrane filters to inhibit extrinsic cell infiltration. In Group 2, the medial and the lateral portions of the frozen-thawed patellar tendon were resected to enhance the stress, and then the central two-thirds of the patellar tendon underwent the wrapping treatment. In Group 3, the patellar tendon without the freeze/thaw treatment underwent the wrapping treatment. In Group 4, the patellar tendon was narrowed and wrapped in the same manner. All rabbits were killed 6 weeks after surgery. While the elastic modulus and the tensile strength of the patellar tendon in Group 2 were significantly less than those in Group 1, we could not find any significant differences in these parameters between Groups 3 and 4. Histologically, while no fibroblasts were observed in Groups 1 and 2, fibroblasts were found in Groups 3 and 4. This study revealed that stress enhancement decreases the elastic modulus and the tensile strength of the extracellular matrix of the patellar tendon and that intrinsic fibroblasts prevent the detrimental effect of stress enhancement on mechanical properties of the patellar tendon.

Analysis of Variance↗

PubMed2000

Interference screw fixation of doubled flexor tendon graft in anterior cruciate ligament reconstruction - biomechanical evaluation with cyclic elongation.

OBJECTIVE: To biomechanically evaluate interference screw fixation of the doubled flexor tendon graft in anterior cruciate ligament reconstruction using cyclic elongation. DESIGN: Biomechanical properties of the interference screw fixation of the flexor tendons were compared with those of three standard fixation techniques which had been commonly performed in anterior cruciate ligament reconstruction. BACKGROUND: The interference screw fixation of the flexor tendon graft has attracted notice because of various possible advantages. METHODS: Forty fresh frozen porcine hind limbs were divided into four groups of ten knees each. Anterior cruciate ligament reconstruction was carried out in each group using one of four different procedures. For each group, five femur-graft-tibia complexes underwent submaximal cyclic elongation of 5000 cycles after initial tension of 80 N was applied. Then, tensile testing was performed in the same manner for the complex with a tensile tester. The remaining five complexes were examined in the same tensile test without applying any cyclic elongation. RESULTS: The initial tension was more rapidly relaxed by cyclic elongation in the flexor tendon graft fixed with interference screws than in the bone-patellar tendon-bone graft fixed with two standard techniques. After cyclic elongation, while the ultimate failure load of the former was significantly lower than the latter, the linear stiffness of the former was significantly higher than the flexor tendon graft fixed with sutures. CONCLUSION: The present study has clarified that the advantage of the interference fixation for the doubled flexor tendon graft is the high linear stiffness of the FGT complex, and the disadvantage of this screw is the low ultimate failure load of the FGT complex. RELEVANCE: The present study has suggested that vigorous activities should not be permitted for the patients in the early period after anterior cruciate ligament reconstruction using this fixation technique, because of its low ultimate failure load.

Animals↗

PubMed2000

Extrinsic cell infiltration and revascularization accelerate mechanical deterioration of the patellar tendon after fibroblast necrosis.

This study was performed to determine the contribution of extrinsic cell infiltration and revascularization into the patellar tendon in alteration of the mechanical properties of the patellar tendon after intrinsic fibroblast necrosis using 77 rabbits. In Group I, after the patellar tendon underwent the in situ freeze-thaw treatment, a wrapping treatment was performed to inhibit any extrinsic cell infiltration into the tendon. In Group II, the patellar tendon underwent the freeze-thaw treatment without any of the wrapping treatment. In Group III, the patellar tendon underwent the same wrapping treatment but without any freeze-thaw treatment. The cell culture study demonstrated that the in situ freeze-thaw treatment killed from 97 to 100 percent of the cells in the patellar tendon. Histologically, no cells were found in the midsubstance of the patellar tendon in Group I at 1, 3, and 6 weeks. In Group II, a number of cells and some vessels were found scattered in the tendon at 3 and 6 weeks. Mechanically, the elastic modulus and the tensile strength of the patellar tendon of Group II were significantly lower than those of Groups I and III at 3 and 6 weeks. These facts suggest that extrinsic cell infiltration and revascularization from the surrounding tissues accelerate the deterioration of the mechanical properties of the patellar tendon matrix after intrinsic fibroblast necrosis.

Animals↗

PubMed2000

[Clinical training and home therapy in our clinic].

Since 1986, we have practiced clinical training. In this training, the physician trainee acts as the head of our clinic, managing programs including the medical teams for outpatient clinics and home therapy. Our home therapy started in 1975 and successive resident trainees have held conferences, cooperation between hospitals and clinics between clinics, and also held home patient and family parties. In our clinical training, therefore, the resident can effectively gain generalized clinical abilities.

Aged↗

PubMed1999

Application of an artificial neural network and genetic algorithm for determination of process orbits in the koji making process.

In order to estimate alpha-amylase, glucoamylase, acid proteinase, and acid carboxypeptidase activities in koji from the process variables and initial conditions of the koji making process, artificial neural network (ANN) models (ANN-10, -11, -15, and -21) were constructed with 10, 11, 15, and 21 input variables, respectively. These models could estimate the enzyme activities with high accuracy. Temperature and humidity orbits were then acquired by a genetic algorithm searching in the reverse direction using ANN-10, -11, -15, and -21 (GA-10, -11, -15, and -21). The orbits acquired by GA-15 and -11 were almost identical to the actual orbits, but those acquired by GA-21 and -10 were different. Enzyme activities acquired by GA-15 had 1.3% errors compared with the target values, while those acquired by GA-11 had 9.7% errors. GA-15 was, therefore, selected as the most suitable algorithm and was used to determine temperature and humidity orbits for target enzyme activities. Test koji making was then carried out according to the orbits acquired. As a result, the enzyme activities of the koji produced were almost the same as the target values.

Journal Article↗

PubMed1998

Significance of graft tension in anterior cruciate ligament reconstruction. Basic background and clinical outcome.

The purpose of this paper is to review scientific evidence that graft tension affects remodelling of the autograft in ligament reconstruction. The in situ freezing model of the patellar tendon, an ideal patellar tendon autograft model, demonstrated that subsequent cellular proliferation following fibroblast necrosis reduces the mechanical properties of the autograft. Stress shielding enhances reduction of the strength in the once-frozen patellar tendon. The strength of the patellar tendon also changes depending on the degree of stress shielding. Transmission electron micrographs revealed that the number of small-diameter fibrils decreases in the stress-shielded tendons compared with non-stress-shielded tendons after in situ freezing. Restressing essentially restores the mechanical properties of patellar tendon autografts even if the strength has been much reduced by complete stress shielding. The effects of restressing may depend on the period of stress shielding applied before restressing. Unphysiologically high tension significantly reduces the mechanical properties of the in situ frozen anterior cruciate ligament (ACL). Therefore, not only stress-deprivation but also stress-enhancement significantly affect the mechanical properties of tendon autografts. Results of in vivo and in vitro studies suggest that cyclic tensile loading may inhibit the deterioration in mechanical strength of the transplanted tendon. Clinically, our prospective randomized study demonstrated that a relatively high initial tension reduces the postoperative anterior laxity of the knee joint after ACL reconstruction using the doubled autogenous hamstring tendons connected in series with polyester tapes, when the tension applied is less than 80 N. Our experimental and clinical results indicate that the initial tension is one of the significant factors that affect the results of ACL reconstruction, although the optimal initial tension for the other graft materials still remains unknown.

Animals↗

PubMed1998

Swelling and curling behaviors of articular cartilage.

A new experimental method was developed to quantify parameters of swelling-induced shape change in articular cartilage. Full-thickness strips of cartilage were studied in free-swelling tests and the swelling-induced stretch, curvature, and areal change were measured. In general, swelling-induced stretch and curvature were found to increase in cartilage with decreasing ion concentration, reflecting an increasing tendency to swell and "curl" at higher swelling pressures. An exception was observed at the articular surface, which was inextensible for all ionic conditions. The swelling-induced residual strain at physiological ionic conditions was estimated from the swelling-induced stretch and found to be tensile and from 3-15 percent. Parameters of swelling were found to vary with sample orientation, reflecting a role for matrix anisotropy in controlling the swelling-induced residual strains. In addition, the surface zone was found to be a structurally important element, which greatly limits swelling of the entire cartilage layer. The findings of this study provide the first quantitative measures of swelling-induced residual strain in cartilage ex situ, and may be readily adapted to studies of cartilage swelling in situ.

Animals↗

PubMed1998

[Blood products use and related factors in Japan].

PURPOSES: To examine the use of blood products in Japan by prefectures and to determine the factors associated with the amount of blood products used. METHODS: The amounts of blood products used in November 1995 were surveyed in 8,723 hospitals throughout Japan. The survey also included whether the blood products in hospitals were stored and managed based on the guidelines for appropriate use of blood products. RESULTS: 1. 4,675(90.9%) of the 5,141 respondents used blood products in 1995. 2. The amount of use of each blood product was considerably different among the prefectures. Larger amounts of red blood products and plasma products were used in urban areas. 3. The amounts of use of red blood cell products, plasma products and platelet concentrates showed similar geographical distributions at a significant correlation (r > or = 0.6) each other. The amount of use of albumin products correlated significantly (r = 0.69) with that of immunoglobulin products. 4. Among the various blood products surveyed in this study, the amount of use of only red blood cell products was comparatively larger in the prefectures where blood products were appropriately stored and managed. 5. The number of surgical operations performed under general anesthetization correlated positively with the amount of use of red blood cell products, plasma products and platelet concentrates; a similar correlation was observed between the number of operations for malignant neoplasm and cardiac diseases. CONCLUSION: The amounts of use of blood products used were significantly different among the prefectures in Japan. The amount of use of red blood cell products possibly reflects demand and consumption of blood products as a whole.

Anesthesia, General↗

PubMed1997

Laxity and flexibility of the ankle following reconstruction with the Chrisman-Snook procedure.

The effect of reconstruction of the anterior talofibular ligament with the Chrisman-Snook procedure on neutral zone laxity (anterior-posterior displacement at low loads) and flexibility (a measure of the nonlinear load-displacement response) of the ankle was investigated in vitro during the anterior drawer test. Neutral zone laxity was defined as the magnitude of anterior-posterior displacement of the ankle joint at +/- 2.5 N of applied load. The flexibility parameter was defined as the slope of a line between the natural logarithm of the anterior load applied to the ankle and the resulting displacement. After reconstruction with the Chrisman-Snook procedure, the values for neutral zone laxity of the ankle were significantly less than normal at 0 degree of plantar flexion, whereas the flexibility values were significantly greater than normal. This study revealed that, after the Chrisman-Snook procedure, values for ankle flexibility are not restored to normal even if those for neutral zone laxity are reduced to less than normal. The findings suggest that this nonanatomical reconstruction procedure does not reproduce normal kinematics of the ankle joint. This may help explain some of the adverse clinical reports associated with the Chrisman-Snook reconstruction procedure.

Adolescent↗

PubMed1997

Mode of antifungal action of benanomicin A in Saccharomyces cerevisiae.

The mechanism of fungitoxic action of an antifungal antibiotic benanomicin A was studied with intact cells and protoplasts of Saccharomyces cerevisiae as well as with its enzymic preparations. The results obtained are summarized as follows: (1) benanomicin A at relatively high concentrations (almost equal to MIC) was fungicidal and disrupted the cell permeability barrier, inducing leakage of intracellular K+ and ATP in growing cells, while the antibiotic had none of these effects in non-growing cells; (2) no biosynthesis of any of several major cellular constituents in yeast cells was inhibited markedly or selectively enough to explain its fungitoxic activity; (3) whereas benanomicin A induced lysis of metabolically active yeast protoplasts incubated in the presence of glucose, inactive yeast protoplasts incubated without glucose were refractory to the lytic action of the antibiotic; (4) osmotically shocked yeast cells became feasible to the cidal action of benanomicin A; (5) benanomicin A substantially inhibited uptake of 6-deoxy-glucose by yeast cells; (6) liposomes composed of phospholipids and cholesterol were not susceptible to benanomicin A; and (7) benanomicin A inhibited in vitro activity of H(+)-ATPase from yeast cell membranes to a greater extent than that for H(+)-ATPase from yeast mitochondria or H(+)-ATPase from yeast vacuolar membranes. Based on these and our previous data that benanomicin A preferentially binds to mannan or mannoproteins constituting the cell wall and cell membrane of yeasts, such binding of the antibiotic is suggested to deteriorate the normal structure and function of those cell membranes of yeasts which are in a growing or metabolically active state, ultimately leading to cell death.

Adenosine Triphosphatases↗

PubMed1996

Binding of benanomicin A to fungal cells in reference to its fungicidal action.

An antifungal antibiotic, benanomicin A, binds in the presence of Ca2+ to susceptible fungi and some bacteria, but not to antibiotic-resistant bacteria and mammalian cells. With the susceptible yeast Saccharomyces cerevisiae, benanomicin A binds similarly to whole cells and to protoplasts. Studies using benanomicin A and three structurally related derivatives suggested that a carboxylic acid in the D-alanine moiety and a sugar moiety in the benanomicin A molecule are essential for both binding and antifungal activities against growing S. cerevisiae. An amino substituent on the sugar moiety can be replaced with a hydroxyl group without the loss of activities. Benanomicin A binds to various yeast mannans which differ in glycosidic linkages. These results indicate that binding of benanomicin A to the mannan portion of fungal cells is essential for exertion of the antifungal activity.

Anthracyclines↗

PubMed1996

[Outcome of the cases of chronic liver disease type C who exhibited long term response to interferon therapy; comparison of the cases with or without serum HCV-RNA].

We evaluated the outcome of 71 Japanese patients with chronic hepatitis C who exhibited a sustained normal level of serum ALT for one to five years after the cessation of interferon (IFN) therapy. Patients were classified into two groups: 9 (13%) cases with a sustained positive for serum HCV-RNA (incomplete responders: ICR) and 62 (87%) cases with a sustained negative for serum HCV-RNA (complete responders: CR). The anti-C100-3 titer was similarly decreased in both groups especially up to one year after cessation of IFN becoming negative in 50% of each group over a 4-year period. The anti-C-22 titer was also decreased in the CR group and stabilized at about 100U (RIA). The titer of anti-C-22 was either increased or maintained at pretreatment levels in most cases of ICR. Monitoring of anti-C-22 may be useful in distinguishing the presence of HCV viremia from a previous HCV infection. According to the backgrounds between both groups, ICR cases were significantly older and more often of genotype 1b (67%) than CR cases (1b; 32%), however there were no significant differences in sex, liver histology or pretreatment levels of HCV-RNA. Serum levels of HCV-RNA in ICR cases after IFN therapy either increase or remained similar to pretreatment levels however most patients with ICR showed an improvement in liver histology. Thus if the serum ALT level remained normal in case of ICR the objective of administering IFN to treat chronic hepatitis C was considered to have been achieved despite the persistence of HCV viremia.

Female↗

PubMed1995

Biomechanical analysis of the ankle anterior drawer test for anterior talofibular ligament injuries.

The effect of sectioning the anterior talofibular ligament on the load-displacement behavior of the ankle was evaluated in vitro during the anterior drawer test using the flexibility approach. Controlled forces were applied across the ankle joint in the anterior-posterior direction, and the resulting displacements were measured at four flexion angles (10 degrees of dorsiflexion, neutral, and 10 degrees and 20 degrees of plantar flexion). The anterior talofibular ligament then was sectioned, and the anterior-posterior loadings were repeated at the four flexion angles. Two parameters were developed to describe the nonlinear load-displacement response of the ankle joint: neutral zone laxity (joint displacement between +/- 2.5 N) and flexibility (a measure of the nonlinear load-displacement response of the ankle between 10 and 50 N of anterior drawer loading). After sectioning the anterior talofibular ligament, significant increases in neutral zone laxity were observed at all angles of ankle flexion. The largest increases in neutral zone laxity were found with the ankle in 10 degrees of plantar flexion (76.3% increase) and 20 degrees of plantar flexion (89.7% increase). After sectioning the ligament, a significant increase (19.3%) in flexibility of the ankle was observed at 10 degrees of dorsiflexion, but no change in flexibility was observed with the ankle in the neutral and plantar flexed positions. These findings indicate that anterior drawer testing of the anterior talofibular ligament-deficient ankle between 10 degrees and 20 degrees of plantar flexion results in the largest increase in neutral zone laxity compared with the normal ankle with intact ligaments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Determination of a zero strain reference for the anteromedial band of the anterior cruciate ligament.

The objective of this study was to verify a method previously used to determine a reference length for calculations of anterior cruciate ligament strain. In nine knee specimens, an arthroscopic force probe and a Hall effect transducer were placed in the anteromedial band of the ligament. Anteroposterior-directed shear loads then were applied to the knee joint with the knee flexed to 30 degrees. From the sigmoidal curve for shear load versus displacement of the anterior cruciate ligament midsubstance, the length of the transducer at the inflection point was determined graphically by two independent examiners. Previous studies suggested that the inflection point corresponds to the slack-taut transition of the anteromedial band. The force probe was used to determine the actual length of the transducer when the anteromedial band became load bearing. No significant differences were found between the reference lengths determined by the inflection point method and the force probe. The force probe demonstrated that the anterior cruciate ligament became load bearing when an anterior shear load of 8.8 N was applied to the tibia with the knee at 30 degrees of flexion. Furthermore, multiple cycles of anteroposterior shear loading did not influence these values. The force probe verified that the inflection method provides a reasonable estimate of the absolute strain reference (within 0.7% strain).

Adult↗