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21.
Kathy K H Svoboda Petra Moessner Tamara Field Jesus Acevedo 《Developmental dynamics》2004,229(3):579-590
The embryonic chicken corneal epithelium is a unique tissue that has been used as an in vitro epithelial sheet organ culture model for over 30 years (Hay and Revel [1969] Fine structure of the developing Avian cornea. Basel, Switzerland: S. Karger A.G.). This tissue was used to establish that epithelial cells could produce extracellular matrix (ECM) proteins such as collagen and proteoglycans (Dodson and Hay [1971] Exp Cell Res 65:215-220; Meier and Hay [1973] Dev Biol 35:318-331; Linsenmayer et al. [1977] Proc Natl Acad Sci U S A 74:39-43; Hendrix et al. [1982] Invest Ophthalmol Vis Sci 22:359-375). This historic model was also used to establish that ECM proteins could stimulate actin reorganization and increase collagen synthesis (Sugrue and Hay [1981] J Cell Biol 91:45-54; Sugrue and Hay [1982] Dev Biol 92:97-106; Sugrue and Hay [1986] J Cell Biol 102:1907-1916). Our laboratory has used the model to establish the signal transduction pathways involved in ECM-stimulated actin reorganization (Svoboda et al. [1999] Anat Rec 254:348-359; Chu et al. [2000] Invest Ophthalmol Vis Sci 41:3374-3382; Reenstra et al. [2002] Invest Ophthalmol Vis Sci 43:3181-3189). The goal of the current study was to investigate the role of ECM in epithelial cell survival and the role of Rho-associated kinase (p160 ROCK, ROCK-1, ROCK-2, referred to as ROCK), in ECM and lysophosphatidic acid (LPA) -mediated actin reorganization. Whole sheets of avian embryonic corneal epithelium were cultured in the presence of the ROCK inhibitor, Y27632 at 0, 0.03, 0.3, 3, or 10 microM before stimulating the cells with either collagen (COL) or LPA. Apoptosis was assessed by Caspase-3 activity assays and visualized with annexin V binding. The ROCK inhibitor blocked actin cortical mat reformation and disrupted the basal cell lateral membranes in a dose-dependent manner and increased the apoptosis marker annexin V. In addition, an in vitro caspase-3 activity assay was used to determine that caspase-3 activity was higher in epithelia treated with 10 microM Y-27632 than in those isolated without the basal lamina or epithelia stimulated with fibronectin, COL, or LPA. In conclusion, ECM molecules decreased apoptosis markers and inhibiting the ROCK pathway blocked ECM stimulated actin cortical mat reformation and increased apoptosis in embryonic corneal epithelial cells. 相似文献
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We tested the hypothesis that overestimations of performance by children with learning disabilities (LD) are self-protective and will dissipate following positive feedback. Twenty-three boys and 17 girls with LD (ages 10.6 to 13.5 years) and a control group of non-LD matched children (22 boys and 17 girls) provided a prediction of their performance on a spelling test prior to completing the test. Subsequently, they were randomly assigned to either a positive feedback or a no-feedback condition. Finally, they provided a second prediction of performance on an equivalent spelling test. In children with LD, there was a positive bias in their predictions of performance, and, following positive feedback, their predictions became accurate. In children without LD, there was no positive bias and no effect of feedback. The results provide further support for the presence of a positive illusory bias and for the self-protective hypothesis in children with LD. 相似文献
24.
A new method for evaluating hand preshaping during reaching-to-grasp movement is proposed. The method makes use of all five fingers in estimation of prehension. The investigation was performed on six healthy subjects grasping three different objects at various positions and orientations. The objects were presented to the subjects by means of a robot, which also induced perturbations in both object position and orientation. Positions of markers attached to the finger-tips and dorsum of the hand were recorded by means of a 3D optical tracking system. In the data analysis, the adjacent fingertips were interconnected, thus obtaining a planar pentagon whose various characteristics were investigated and discussed. New parameters for the evaluation of finger preshaping, such as pentagon surface area, angle between the pentagon and hand normal vectors, and the angle between the pentagon and object normal vectors were introduced. The proposed pentagon approach is expected to be useful in future work when examining grasping abilities of subjects with neuromuscular disorders. 相似文献
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26.
Chondroitin sulfate A released from platelets blocks RANTES presentation on cell surfaces and RANTES-dependent firm adhesion of leukocytes 总被引:3,自引:0,他引:3
Mack M Pfirstinger J Weber C Weber KS Nelson PJ Rupp T Maletz K Brühl H Schlöndorff D 《European journal of immunology》2002,32(4):1012-1020
The sequestration of chemokines on the surface of microvascular endothelium is an early event in the selective recruitment of leukocytes. The sequestration and presentation of chemokines must be tightly controlled to confine the extravasation of leukocytes and to prevent uncontrolled inflammation. We investigated whether soluble molecules released under physiological conditions could control chemokine immobilization on cell surfaces and function as regulatory chemokine binding molecules. We determined that human serum contains a molecule that suppresses RANTES (CCL5) binding to endothelial cells, PBMC and CHO cells. Using platelet-rich and platelet-free plasma, serum from patients with thrombocytopenia, and purified platelets, we identified platelets as the source of the chemokine-binding molecule and further identified it as chondroitin sulfate A. In contrast to platelet-derived fully-sulfated chondroitin sulfate A, low-sulfated chondroitin sulfate A present in plasma was almost inactive. Under physiological flow conditions chondroitin sulfate A was found to block RANTES-mediated firm adhesion of monocytes to endothelial cells. It also prevented RANTES-mediated influx of calcium in CCR5-transfected CHO cells while internalization of CCR5 was only marginally reduced. Taken together, chondroitin sulfate A released from platelets appears to act as an important regulatory molecule for cellular responses to chemokines. 相似文献
27.
C57BL/6J (B6) and DBA/2J (D2) mice differ in maternal behavior and nest building, but previous observations on nest building appear to be contradictory. Lactating B6 females spent more time nest building than lactating D2 females [Physiol. Behav. 67 (1999) 599.]; however, pregnant D2 females have been reported to build better nests than pregnant B6 females [Physiol. Behav. 29 (1982) 153.]. To resolve this apparent discrepancy, virgin B6 and D2 females were mated, and the nest quality of nulligravid, primigravid and lactating primiparous females was compared between groups and with that of virgin females. There were no strain differences in the nest ratings of virgin or mated nulligravid females, nor did these groups differ within strains. Pregnant and lactating females of both strains built better nests than nonpregnant females. There was an increase in nest ratings in both strains on the day of parturition. The nest ratings of pregnant and lactating females were higher in B6 than D2 females. The largest strain differences were observed between pregnant B6 and D2 females. One hypothesis to account for these results is that females of these two strains differ in their levels of or sensitivity to hormones during pregnancy and parturition. 相似文献
28.
Ramaz Katsarava Tamara Kartvelishvili Tamara Khosruashvili Vakhtang Beridze 《Macromolecular chemistry and physics.》1995,196(9):3061-3074
A new synthesis pathway to polyurethanes (PURs) by polycondensation of active carbonates of diols with hexamethylenediamine was investigated in detail including model studies. It has been shown that high-molecular-weight PURs (ηred ≤ 3,8 dL/g) can be obtained under optimum reaction conditions. Salts of the diamine and its N,N′-trimethyl-silylated derivative were also used for the synthesis of film- and fiber-forming PURs. 相似文献
29.
OBJECTIVE: To investigate the retraction time, forces, and torques applied to the football helmet during removal of the face mask with different face-mask removal tools. DESIGN AND SETTING: Subjects retracted the face mask of a football helmet mounted to a force platform in a laboratory setting. They removed a standard face mask by cutting or removing (or both) the lateral plastic loop straps using 4 different tools: the Trainer's Angel (TA), FM Extractor (FM), power screwdriver (SD), and Quick Release System (QR) in a counterbalanced fashion. SUBJECTS: Eighteen certified athletic trainers participated in this study. MEASUREMENTS: We started measuring time when the subject picked up the tool and ended when the face mask was in a fully retracted position. Maximum forces and torques were measured from the force platform during the retraction process. RESULTS: The SD and QR retracted the face mask significantly faster than the TA and FM. Forces producing superior-inferior translation were least with the SD. The SD and QR produced less lateral translation and rotation and lateral flexion moment than the TA and FM. The FM produced less torque in the lateral flexion moment than the TA. CONCLUSIONS: Tools that removed the loop straps (SD, QR) were faster and produced less force and torque on the helmet than the tools that cut through the loop straps (TA, FM). 相似文献
30.
Chiu-Tsao ST Duckworth TL Hsiung CY Li Z Williamson J Patel NS Harrison LB 《Medical physics》2003,30(7):1732-1735
Many new models of 125I seeds are being introduced, mainly due to the increase in prostate seed implants. We have evaluated the SourceTech Medical (STM), model STM1251, 125I seed using thermoluminescent dosimeters (TLDs) in a solid water phantom. TLD cubes, LiF TLD-100, with dimension 1 mm on each edge, were irradiated at various distances, 1, 2, 3, and 5 cm, at angles ranging from 0 degrees to 90 degrees in 10 degrees increments. Sensitivity calibration of the TLDs was achieved by irradiation to 10 cGy with 6 MV x rays from a clinical linear accelerator, Clinac 600C. Concurrent with the 125I seed exposures, several TLDs were also exposed to 10 cGy with the 600C as a control set. Dose rates per unit air kerma strength were determined based on the 1999 NIST traceable standard for the STM1251 seed. They are presented as a function of distance r and angle theta. The TG-43 parameters, including the dose rate constant, lambda, anisotropy function, F(r,theta), radial dose function, g(r), anisotropy factor, phian(r), and anisotropy constant, phi, were obtained for use in radiation treatment planning software. The value of lambda was determined as 1.07 +/- 5.5% cGy U(-1) h(-1), which is comparable to model 6702 and to the value determined using the point extrapolation method by Kirov and Williamson. We also find agreement between our TLD data and their Monte Carlo results for g(r), F(r,theta), phian(r), and phi. Additionally, agreement is found with the TLD data of Li and Williamson for lambda and g(r). 相似文献