Effects of the Frequency and Duration of Cyclic Stress on the Mechanical Properties of Cultured Collagen Fascicles From the Rabbit Patellar Tendon

2005 ◽  
Vol 127 (7) ◽  
pp. 1168-1175 ◽  
Author(s):  
Ei Yamamoto ◽  
Daisuke Kogawa ◽  
Susumu Tokura ◽  
Kozaburo Hayashi
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Patellar Tendon ◽  
Load Condition ◽  
Peak Stress ◽  
Cyclic Stress ◽  
Control Group ◽  
Significant Difference

The effects of frequency or duration of cyclic stress on the mechanical properties of collagen fascicles were studied by means of in vitro tissue culture experiments. Collagen fascicles of approximately 300μm in diameter were obtained from rabbit patellar tendons. During culture, cyclic stress having the peak stress of approximately 2MPa was applied to the fascicles at 1Hz for 1hour∕day (1Hz-1h group), at 1Hz for 4hours∕day (1Hz-4h group), or at 4Hz for 1hour∕day (4Hz-1h group). The frequency of 4Hz and the duration of 1hour∕day are considered to be similar to those of the in vivo stress applied to fascicles in the intact rabbit patellar tendon. After culture for 1 or 2weeks, the mechanical properties of the fascicles were determined using a micro-tensile tester, and were compared to the properties of non-cultured, fresh fascicles (control group) and the fascicles cultured under no load condition (non-loaded group). The tangent modulus and tensile strength of fascicles in the 4Hz-1h group were similar to those in the control group; however, the fascicles of the 1Hz-1h and 1Hz-4h groups had significantly lower values than those of the control group. There was no significant difference in the tensile strength between the 1Hz-1h and non-loaded groups, although the strength in the 1Hz-4h group was significantly higher than that of the non-loaded group. It was concluded that the frequency and duration of cyclic stress significantly affect the mechanical properties of cultured collagen fascicles. If we apply cyclic stress having the frequency and duration which are experienced in vivo, the biomechanical properties are maintained at control, normal level. Lower frequencies or less cycles of applied force induce adverse effects.

Effects of Cyclic Stress on the Mechanical Properties of Cultured Collagen Fascicles from the Rabbit Patellar Tendon

2003 ◽  
Vol 125 (6) ◽  
pp. 893-901 ◽  
Author(s):  
Ei Yamamoto ◽  
Susumu Tokura ◽  
Kozaburo Hayashi
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Patellar Tendon ◽  
Control Level ◽  
Quadratic Function ◽  
Peak Stress ◽  
Cyclic Stress ◽  
Original Strength

Effects of cyclic stress on the mechanical properties of collagen fascicles were studied by in vitro tissue culture experiments. Collagen fascicles (approximately 300 μm in diameter) obtained from the rabbit patellar tendon were applied cyclic load at 4 Hz for one hour per day during culture period for one or two weeks, and then their mechanical properties were determined using a micro-tensile tester. There was a statistically significant correlation between tensile strength and applied peak stress in the range of 0 to 5 MPa, and the relation was expressed by a quadratic function. The maximum strength (19.4 MPa) was obtained at the applied peak stress of 1.8 MPa. The tensile strength of fascicles were within a range of control values, if they were cultured under peak stresses between 1.1 and 2.6 MPa. Similar results were also observed in the tangent modulus, which was maintained at control level under applied peak stresses between 0.9 and 2.8 MPa. The stress of 0.9 to 1.1 MPa is equivalent to approximately 40% of the in vivo peak stress which is developed in the intact rabbit patellar tendon by running, whereas that of 2.6 to 2.8 MPa corresponds to approximately 120% of the in vivo peak stress. Therefore, the fascicles cultured under applied peak stresses of lower than 40% and higher than 120% of the in vivo peak stress do not keep the original strength and modulus. These results indicate that the mechanical properties of cultured collagen fascicles strongly depend upon the magnitude of the stress applied during culture, which are similar to our previous results observed in stress-shielded and overstressed patellar tendons in vivo.

Effects of Static Stress on the Mechanical Properties of Cultured Collagen Fascicles From the Rabbit Patellar Tendon

2001 ◽  
Vol 124 (1) ◽  
pp. 85-93 ◽  
Author(s):  
Ei Yamamoto ◽  
Wataru Iwanaga ◽  
Hiroshi Miyazaki ◽  
Kozaburo Hayashi
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Applied Stress ◽  
Patellar Tendon ◽  
Control Level ◽  
Peak Stress ◽  
Static Stress ◽  
Tangent Modulus

In-vitro tissue culture experiments were performed to study the effects of static stress on the mechanical properties of collagen fascicles obtained from the rabbit patellar tendon. After collagen fascicles having the diameter of approximately 300 μm were cultured for 1 and 2 wk under static stress between 0 and 3 MPa, their mechanical properties and crimp morphology were determined using a micro-tensile tester and a light microscope, respectively. The tensile strength and tangent modulus of the fascicles were significantly decreased by culture under no load compared to control fascicles. A statistically significant correlation, which was described by a quadratic curve, was observed between applied stress and tensile strength. The maximum tensile strength (16.7 MPa) was obtained at the applied stress of 1.2 MPa; the strength was within a range of control values. There was a similar correlation between applied stress and tangent modulus, and the modulus was maintained at control level under 1.3 MPa stress. The stress of 1.2 to 1.3 MPa is equivalent to approximately 50 percent of the peak stress developed in the intact rabbit patellar tendon by running. Strain at failure of cultured collagen fascicles was negatively correlated with applied stress, and that at 1.2 to 1.3 MPa stress was almost the same as the control value. Crimp morphology in the fascicles cultured under about 1.2 MPa stress was similar to that in control fascicles. These results indicate that cultured collagen fascicles change the mechanical properties and structure in response to static tensile stress. In addition, their mechanical properties and structure are maintained at control level if the static stress of 50 percent of in-vivo peak stress is applied.

scholarly journals Design Optimization and In Vitro-In Vivo Evaluation of Orally Dissolving Strips of Clobazam

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
Rajni Bala ◽  
Sushil Khanna ◽  
Pravin Pawar
Keyword(s):  
Tensile Strength ◽  
Drug Release ◽  
Content Uniformity ◽  
In Vivo Evaluation ◽  
Disintegration Time ◽  
Significant Difference ◽  
Film Formulation ◽  
Test Film

Clobazam orally dissolving strips were prepared by solvent casting method. A full 32 factorial design was applied for optimization using different concentration of film forming polymer and disintegrating agent as independent variable and disintegration time, % cumulative drug release, and tensile strength as dependent variable. In addition the prepared films were also evaluated for surface pH, folding endurance, and content uniformity. The optimized film formulation showing the maximum in vitro drug release, satisfactory in vitro disintegration time, and tensile strength was selected for bioavailability study and compared with a reference marketed product (frisium5 tablets) in rabbits. Formulation (F6) was selected by the Design-expert software which exhibited DT (24 sec), TS (2.85 N/cm2), and in vitro drug release (96.6%). Statistical evaluation revealed no significant difference between the bioavailability parameters of the test film (F6) and the reference product. The mean ratio values (test/reference) of Cmax (95.87%), tmax (71.42%), AUC0−t (98.125%), and AUC0−∞ (99.213%) indicated that the two formulae exhibited comparable plasma level-time profiles.

scholarly journals Effect of Titanium Implants Coated with Radiation-Crosslinked Collagen on Stability and Osseointegration in Rat Tibia

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2520 ◽  
Author(s):  
Eun-Bin Bae ◽  
Ji-Hyun Yoo ◽  
Sung-In Jeong ◽  
Min-Su Kim ◽  
Youn-Mook Lim ◽  
...  
Keyword(s):  
Gamma Radiation ◽  
Human Mesenchymal Stem Cells ◽  
Region Of Interest ◽  
Bone Volume ◽  
Titanium Implants ◽  
Control Group ◽  
Gene Expressions ◽  
Significant Difference

This study aimed to evaluate the titanium (Ti) implants coated with collagen type Ⅰ crosslinked using gamma-irrigation or glutaraldehyde (GA). The in vitro surface observations, quantification assay, and cell studies using human mesenchymal stem cells (hMSCs) were conducted. For in vivo experiments, the implants were divided into three groups and inserted into the rat tibias: control group (non-treated Ti implant), GA group (Ti implants coated with GA-crosslinked collagen) and 25 kGy group (Ti implants coated with gamma-radiation-crosslinked collagen at dose of 25 kGy). The animals were sacrificed at 4 weeks after implantation and the tissue sections were obtained. New bone volume (mm3) and bone-to-implant contact (BIC, %) within the region of interest (ROI) was measured. The in vitro results showed the highest osteogenic differentiation and levels of osteogenesis-related gene expressions in the 25 kGy group without cytotoxicity. The new bone volume of GA group was significantly higher than the control (p < 0.05). In the result of the BIC, the 25 kGy group was significantly higher than the control (p < 0.05). However, there was no significant difference between the experimental groups. Within the limitations of this study, Ti implant coated with gamma-radiation-crosslinked collagen has potential utility without side effects from chemical agents.

scholarly journals Effect of 5% Calcium Hypochlorite on Mechanical Properties of Root Dentin: An in vitro Study

2016 ◽  
Vol 1 (2) ◽  
pp. 56-59
Author(s):  
Natanasabapathy Velmurugan ◽  
Poornima Reddy ◽  
Suma Balla ◽  
Sandhya S Raghu ◽  
Garlapati T Gupta ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Modulus Of Elasticity ◽  
In Vitro Study ◽  
Chlorine Concentration ◽  
Control Group ◽  
Calcium Hypochlorite ◽  
Significant Difference ◽  
Root Dentin

ABSTRACT Introduction The aim of this study was to compare in vitro the effect of 5% calcium hypochlorite [Ca(OCl)2] and 5% sodium hypochlorite (NaOCl) on flexural strength and modulus of elasticity of root dentin. Materials and methods The available chlorine concentration of each solution was determined using iodometric titration. Standardized planoparallel dentin bars (n= 20) were divided into two test groups and one control group. The control, group 1, consisted of dentin bars stored in normal saline. The dentin bars in the two test groups were treated by exposure to following solutions: Group 2 to 5% Ca(OCl)2; and group 3 to 5% NaOCl. All the three test solutions were changed once in 15 minutes for 30 minutes. The dentin bars were then loaded to failure using three-point bend test. Results Available chlorine concentration was 64% in both the test solutions. There was a significant reduction in the flexural strength of 5% NaOCl group compared to 5% Ca(OCl)2-treated ones. A significant difference in modulus of elasticity was observed between the test groups and the control groups and also between the 5% Ca(OCl)2 and 5% NaOCl groups. Conclusion Within the limitations of this study, 5% NaOCl reduced the flexural strength and modulus of elasticity of root dentin bars more when compared to 5% Ca(OCl)2. How to cite this article Reddy P, Balla S, Raghu SS, Velmurugan N, Gupta GT, Sahoo HS. Effect of 5% Calcium Hypochlorite on Mechanical Properties of Root Dentin: An in vitro Study. J Oper Dent Endod 2016;1(2):56-59.

scholarly journals Effect of hydroxychloroquine on SARS-CoV-2 viral load in patients with COVID-19

2020 ◽  
Author(s):  
Klinger Soares Faíco-Filho ◽  
Danielle Dias Conte ◽  
Luciano Kleber de Souza Luna ◽  
Joseane Mayara Almeida Carvalho ◽  
Ana Helena Sitta Perosa ◽  
...  
Keyword(s):  
Viral Load ◽  
Prospective Study ◽  
Nasal Swab ◽  
Effective Drug ◽  
Medical Decision ◽  
Control Group ◽  
Sample Collection ◽  
Significant Difference

ABSTRACTBackgroundSome studies have shown that hydroxychloroquine (HCQ) is an effective drug in reducing the in vitro replication of SARS-CoV-2. However, the in vivo effect of HCQ still unclear. This study aims to evaluate viral load clearance in patients with COVID-19 who underwent HCQ treatment in comparison with a control group that did not receive the drug.MethodsThis prospective study comprised consecutive viral load measurements in patients with COVID-19 hospitalized with a moderate illness. Patients received 400 mg of HCQ every 12 hours for 10 days according to the medical decision. Nasal swab samples were collected at the 1st, 7th, and 14th days of the admission.Results155 samples were collected from 66 patients with COVID-19 (60% female), with a median age of 58 years. The viral load between studied groups, assumed as a semiquantitative measure of cycle threshold (Ct) values, presented no significant difference within the three consecutive measures (ΔCt) (p>0.05). We also analyzed the ΔCt viral load at different intervals of sample collection (Δt <7; 7-12 and >12 days) without significant differences at any ΔCt (p>0.05).ConclusionIn this study, we did not observe any change in viral load in vivo with the use of HCQ.SummaryWe evaluate viral load clearance in patients with COVID-19 who took hydroxychloroquine (HCQ) for treatment and those who not. Prospective viral load measurements have shown any change in viral load in vivo with the use of HCQ.

47 CRYOPRESERVATION OF BOVINE GERM CELL USING ANTIFREEZE POLYAMINO-ACID (CARBOXYLATED POLY-L-LYSINE)

2017 ◽  
Vol 29 (1) ◽  
pp. 131
Author(s):  
T. Fujikawa ◽  
C. Kubota ◽  
T. Ando ◽  
S. Imamura ◽  
M. Tokumaru ◽  
...  
Keyword(s):  
Survival Rate ◽  
Germ Cell ◽  
Embryo Transfer ◽  
Conception Rate ◽  
Control Group ◽  
Vitro Fertilization ◽  
Polyamino Acid ◽  
Significant Difference

Carboxylated poly-l-lysine (CPLL) is an ampholytic polymer compound, and it is obtained by converting 65% amino groups to carboxyl groups after synthesising ε-poly-l-lysine aqueous solution and succinic anhydride. CPLL has cryoprotective property similar to antifreeze protein, and addition of CPLL into cryopreservation medium improves the post-thaw survival rate of cells and embryos. In this research, we examined the effectiveness of CPLL as a bovine germ cell cryoprotective material. In experiment 1 (in sperm), the conventional cryopreservation medium used for control group was consisted of 6.5% (vol/vol) glycerin, and the cryopreservation medium used for CPLL group was consisted of 3.25% (vol/vol) glycerin and 0.5% CPLL (wt/vol). The post-thaw survival and motility were assessed by using Sperm Motility Analysis System (DITECT Corp., Tokyo, Japan). There was no significant difference for post-thaw survival rate and motility (control v. CPLL; 98.8% v. 96.6% and 69.7% v. 62.2%, respectively). Artificial insemination was carried out in 65 cows (control v. CPLL; 34 v. 31), and the conception rate of the CPLL group was higher than that of the control group (80.6% v. 67.6%; P = 0.23). In experiment 2 (embryos), the conventional cryopreservation medium used for control group was consisted of 5% (vol/vol) ethylene glycol and 6% (vol/vol) propylene glycol in PBS. In the CPLL group, 7% (wt/vol) CPLL was added to the conventional medium. In vitro fertilization embryos were cryopreserved at Day 7 and Day 8. There was no significant difference in survival rate at 0, 24, and 48 h and hatched rate until 72 h after thawing (control v. CPLL: 93.6% v. 93.2%, 69.0% v. 64.7%, 56.1% v. 56.3%, 12.9% v. 10.2%, respectively). Embryos obtained by superovulation treatment and in vivo fertilization at Day 7 were cryopreserved using above 2 media, and transferred non-surgically into synchronized recipient cows (1 embryo per animal). Embryo transfer (ET) was carried out in 81 cows (control v. CPLL: 31 v. 50), and recipients were diagnosed for pregnancy ultrasonically 50 days after embryo transfer. Conception rate of CPLL group was higher than control group (50.0% v. 29.0%; P = 0.063). In both experiments, the significant differences between control group and CPLL group were determined by chi-squared test. The effectiveness of CPLL in cells and embryos has been reported; however, there is no report using CPLL in bovine germ cells. In this research, CPLL improved the conception rate of AI and ET, probably due to its low toxicity and protection of the cell membrane. These results suggest that CPLL is available as a new cryoprotective material for bovine sperm and embryo in slow freezing methods.

Functions of Glycosylation Cooled Rabbit Platelets In Vivo and In Vitro.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3902-3902
Author(s):  
Bao-An Chen ◽  
Cheng-Yin Huang ◽  
Xiao-Ping Pei ◽  
Chong Gao ◽  
Jia-Hua Ding ◽  
...  
Keyword(s):  
Survival Time ◽  
Bleeding Time ◽  
Rabbit Platelet ◽  
Control Group ◽  
Platelet Counts ◽  
Rabbit Ear ◽  
Significant Difference ◽  
Rabbit Platelets

Abstract This study was aimed to investigate functions of glycosylation cooled rabbit platelets in vivo and in vitro and the method to store cold platelets with UDP-gal. We collected rabbit heart blood, prepared concentrated platelet suspensions in a normal way to which we added UDP-Gal, and then stored them for ten days in 4° refrigerator. Thereafter platelet counts, mean platelet volume, platelet distributing width, platelet aggregation function, the activity to urge coagulation including PF3aT and APCT and apoptosis were determine- d. Meanwhile, survival time in vivo was tested after cold-stored rabbit platelets labeled with Cr51 were transfused into rabbits. Rabbit ear bleeding time and percentage plate recovery(PPR) were determined 1 hour and 24 hour after they were transfused into rabbit thrombocytopenia model. Results show that there was not significant difference in PLT counts, MPV, PDW, PF3aT and APCT between UDP-Gal cold-stored platelet group and fresh platelet group(p>0.05). On the contrary, platelet counts decreased significantly, MPV, PDW jumped and PF3aT and APCT went down in cold control group compared to fresh platelet group(p<0.01). Apoptosis increase in UDP-Gal cold-stored platelet group compared with fresh platelet group(p<0.05), but was significantly lower than that in cold control group(p<0.01). Although PagT(inducing reagent: C-PG) decreased, it could still be above 50% of fresh platelets. Survival time in rabbit vivo was close between UDP-Gal cold-stored platelet group and fresh platelet group(p<0.05). Survival rate seventy-two hours after transfusion in fresh platelet group, UDP-Gal cold-stored platelet group and cold control group was 57.5%±7.2%,50.3%±6.3% and 0.1%±0.1% respectively. Rabbit ear bleeding time was significantly shortened after transfusion of galactosylation cooled rabbit platelet (p<0.01), In contrast, it had less change in cold control group(p>0.05). PPR was 66.1%±0.5%,47.8%±0.6%;60.9%±0.3%,41.6%±0.4%;47.7%±0.5%,9.4%±0.5% respectively in fresh platelet group, UDP-Gal cold-stored platelet group and cold control group. PPR after transfusion of galactosylation cooled rabbit platelet had no statistical difference compared with that of fresh platelet group(p>0.05), and they in both groups were much higher than that in cold control group(p<0.01). Conclusion: Galactosylation can improve functions of cooled rabbit platelets in vivo and in vitro. and prolong the storage time of them.

scholarly journals Aesculus hippocastanum L. Extract Does Not Induce Fibroblast to Myofibroblast Conversion but Increases Extracellular Matrix Production In Vitro Leading to Increased Wound Tensile Strength in Rats

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1917
Author(s):  
Ivan Kováč ◽  
Nikola Melegová ◽  
Matúš Čoma ◽  
Peter Takáč ◽  
Katarína Kováčová ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Tensile Strength ◽  
Smooth Muscle Actin ◽  
In Vitro Study ◽  
Dermal Fibroblasts ◽  
Control Group ◽  
Horse Chestnut ◽  
Sprague Dawley

The ability of horse chestnut extract (HCE) to induce contraction force in fibroblasts, a process with remarkable significance in skin repair, motivated us to evaluate its wound healing potential in a series of experiments. In the in vitro study of the ability of human dermal fibroblasts to form myofibroblast-like cells was evaluated at the protein level (Western blot and immunofluorescence). The in vivo study was conducted on male Sprague-Dawley rats with inflicted wounds (one open circular and one sutured incision) on their backs. Rats were topically treated with two tested HCE concentrations (0.1% and 1%) or sterile water. The control group remained untreated. The incisions were processed for wound tensile strength (TS) measurement whereas the open wounds were subjected to histological examination. On the in vitro level the HCE extract induced fibronectin-rich extracellular matrix formation, but did not induced α-smooth muscle actin (SMA) expression in dermal fibroblasts. The animal study revealed that HCE increased wound TS and improved collagen organization. In conclusion, the direct comparison of both basic wound models demonstrated that the healing was significantly increased following HCE, thus this extract may be found useful to improve healing of acute wounds. Nevertheless, the use of an experimental rat model warrants a direct extrapolation to the human clinical situation.

scholarly journals Expression of miR-302 in human embryo derived from in-vitro matured oocyte

2019 ◽  
Author(s):  
Parvin Dorfeshan ◽  
Marefat Ghaffari Novin ◽  
Mohammad Salehi ◽  
Fatane Farifteh
Keyword(s):  
Human Embryo ◽  
Embryo Quality ◽  
Molecular Study ◽  
Quality Score ◽  
Control Group ◽  
Polar Bodies ◽  
Significant Difference ◽  
Negative Effect

Background: The expression of miR-302 over the period of early embryogenesis could possibly regulate the maternal transcript clearance. Zygotic transcription activation is mostly related to maternal messages degradation. Objective: In this study, the effects of in-vitro maturation technique (IVM) on the expression of miR-302 in human embryo produced from immature and mature human oocytes (matured in vitro and in vivo, before sperm exposure) obtained from females under gonadotrophin therapy were evaluated for assisted reproduction. Materials and Methods: Immature oocytes were cultured in vitro. The injection of oocytes-producing polar bodies was given using fresh sperm. Then, the embryo quality score was assessed in the IVM group compared with the control group. In both the groups, embryos with normal morphology were included in the molecular study. Only one blastomere was removed from three-day embryos and then the embryos were frozen. The expression of miR-302 in embryos was measured through quantitative realtime polymerase chain reaction. Results: Our data showed a significant reduction of miR-302 expression in the IVM group vs. the control group (p = 0.02). The embryo quality score showed a significant difference between the two groups (p = 0.01). Conclusion: The present study demonstrated that the IVM process had a negative effect on the expression level of miR-302 in human pre-implantation embryos. Considering the major role of expression miR-302, a reduced potential in miR-302 expression could be related to a decrease in the early embryonic development.

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