Key Engineering Materials Vols. 277-279

Abstract: Estrogen-related receptors (ERRs), orphan nuclear receptors, share a significant amino acid sequence homology with estrogen receptors (ERs), yet their ligands do not respond in the same manner. In fact, some of the ligands that are known as agonists of ERs show antagonistic effect in ERRs. Accordingly, the current study investigated the structures of the ligand-binding domains using homology model building and docking studies. The results showed clear differences between the ligand-binding pockets of ERRs and ERs, thereby providing structural insights into the activities related to the ligands.

Abstract: Ag-doped hydroxyapatite films were deposited on a ZrO2 substrate using r.f. magnetron sputtering to improve the bioaffinity and mechanical properties of the hydroxyapatite. The resulting hydroxyapatite films exhibited a variation in their microstructure and mechanical properties relative to the Ag content. The variation in the (Ca, Ag)/P ratios suggested that some of the Ca2+ ions in the hydroxyapatite were replaced with Ag+ ions. After annealing at 800oC, the hydroxyapatite films showed a microstructure with crystalline nano-grains, whereas the Ag-doped hydroxyapatite films revealed the formation of crystallites embedded in the amorphous matrix. The hydroxyapatite films showed an average roughness of about 3~4nm, very smooth surface, and dense microstructure. The hardness and modulus of the films decreased with an increasing Ag content.

Abstract: The development of a human papillomavirus vaccine has received a lot of recent attentiondue to the connection between HPV infections and cervical cancer. One promising vaccine to prevent HPV infections is an HPV virus-like particle, and various studies have already shown that HPV VLP immunization elicits a humoral immune response. However, cell mediated immunity is important for the prevention of HPV infections and cancer therapy. Therefore, to check the elicitation of a CTL response by yeast-derived virus- like particles consisting of the HPV16 capsid protein L1, HPV16 L1 VLPs were produced and purified, then C57BL/6 mice immunized with the HPV16 L1 VLPs by subcutaneous injection. Thereafter, the splenocytes from the immunized mice were isolated and a chromium release assay performed using recombinant B16/HPV16 L1cells constantly expressing the HPV16 L1 protein. As a result, the data demonstrated that the T cells from the HPV16 L1 VLP immunized mice exhibited a significantly higher cytotoxic T lymphocyte activity against the recombinant B16/HPV16 L1 cells than the T cells from the PBS immunized control mice.

Abstract: Current anatomical theory does not recognize the existence of an extended floating threadlike structure inside the blood vessels. Nonetheless, this study developed a new method for observing such an intravascular threadlike structure. The key technique involves injecting acridineorange into the femoral vein to circulate along the blood vessels and stain the nuclei of the intravascular threads inside the blood vessels. In-situ observations were then made under a fluorescence stereomicroscope after saline-perfusion. Confocal microscope images revealed a distinctive characteristic pattern of nucleus distribution that was clearly distinguishable from fibrin, capillaries, small venules, arterioles, or lymph vessels. Accordingly, it is suggested that the identified intravascular threads are part of the Bonghan's circulatory network that is distributed throughout the body, including inside the blood vessels.

Abstract: The Penna model for biological aging was modified. The reproducibility of each individual was determined according to the number of mutations relevant at that time. The results of Monte-Carlo calculations using the modified model show that the ranges of the reproducible age are broadened as time goes by, thus showing self-organization in biological aging to the direction of maximum self-conservation. In addition, the population, survival rate, and average life span were calculated and analyzed by changing the number of new mutations at birth. It is observed that the more the number of new mutations at birth is considered, the shorter the average life span that is obtained.

Abstract: Caprolactam-attached C3-monoacetylated diglyceride (MADG) was successfully synthesized starting from 16-bromohexadecanoic acid.

Abstract: We examined how the central nervous system adjusts postural responses to an increased postural challenge due to an initial lean. Postural feedback responses scale to accommodate biomechanical constraints, such as an allowable ankle joint torque. Initial forward leaning, which is observed among the elderly who are inactive or afraid of falling, brings subjects near to the limit of stability and makes the biomechanical constraints more difficult to obey. We hypothesized that the central nervous system is aware of body dynamics and restrains postural responses when subjects initially lean forward. To test this hypothesis, fast backwards perturbations of various magnitudes were applied to 12 healthy young subjects (3 male, 9 female) aged 20 to 32 years. The subjects were instructed to stand quietly on a hydraulic servo-controlled force platform with their arms crossed over their chests, then to recover from a perturbation by returning to their upright position, without stepping or lifting their heels off the ground, if possible. Initially, the subjects were either standing upright or leaning forward. The force platform was movable in the translational direction and programmed to move backward with various ramp displacements ranging from 1.2 to 15 cm, all with the duration of 275 msec. For each trial, the kinematics and ground reaction force data were recorded, then used to compute the net joint torques, employing a least squares inverse dynamics method. Optimization methods were used to identify a set of equivalent feedback control gains for each trial so that the biomechanical model incorporating this feedback control would reproduce the empirical response. The results showed that the kinematics, joint torque, and feedback gains gradually scaled as a function of the perturbation magnitude before they reached the biomechanical constraint, and the scaling became more severe with an initial forward lean. For example, the model suggested that the magnitude of the ankle joint angle feedback to ankle torque was smaller in the leaning trials than in the initially upright trials, as if the subjects experienced a larger postural perturbation in the leaning trials. These results imply that the central nervous system restrained the postural responses to accommodate the additional biomechanical constraint imposed by the forward posture, thereby suggesting that the central nervous system is aware of body dynamics and biomechanical constraints. The scaling of the postural feedback gains with the perturbation magnitude and initial lean indicates that the postural control can be interpreted as a feedback scheme with scalable gains.

Abstract: We hypothesized that multi-sensory processing at the central nervous system (CNS) in human postural control can be described using an optimal estimator model. The estimates on body dynamics from multi-sensory signals contain sensory noise, transmission delays, and process disturbances. The state estimates approximate actual body movement. Erroneous estimates degrade the performance of feedback control and could cause a loss of balance if distorted severely. To test the hypothesis, we examined the frequency response of a visually-induced postural sway with stimulus frequency ranging from 0.075 to 1Hz and established an optimal estimator model. Two healthy young (33yrs ± 1) subjects stood on a force platform located 1.25m behind a projection screen with their arms crossed over their chests. They were asked to maintain an upright posture against the sinusoidal visual field stimuli. Each sinusoidal visual stimulus was generated by a projector for 200secs in pitch direction with a maximum pitch angle of 20o. Kinematics data was recorded to calculate the frequency response function of the center of mass (COM). There were three components in the modeling procedure: a biomechanical model of body and sensor dynamics, a linear feedback control model to stabilize the biomechanical model, and a state estimator to estimate body dynamic states based on multi-sensory outputs. We modeled the sensor dynamics of the semicircular canal, otolth, vision, and muscle spindles at the ankle and hip joint. We used the Kalman filter and linear quadratic regulator to determine feedback gains. Results showed that the frequency response function of a visually-induced postural sway decreased as stimulus frequency increased, and this low-pass filtering characteristic with an approximate cutoff frequency of 0.2Hz was also simulated by the postural feedback control model with optimal estimator. Low-pass filtering characteristics of the frequency response are mainly due to body and sensor dynamics, which show reduced responses for high frequency stimulus. The Kalman filter represents that the CNS utilizes redundant sensory information in a way that minimizes discrepancies between actual body dynamics and estimated body dynamics based on sensory output and an internal model. The results suggest that the CNS may make use of an internal representation of body dynamics, and can integrate sensory information in an optimal way to best estimate human postural responses.

Abstract: To find a novel exopolysaccharide, marine bacterial strains were isolated from coastal regions of Korea. Strain 00SS11568 was then selected as it produced a mucous exopolysaccharide during the stationary phase in a batch culture. The isolate was identified as Alteromonas sp. based on its 16S rDNA sequence, morphological, and biochemical properties. The exopolysaccharide, designated as p-11568, exhibited an emulsifying ability. The Emulsification Index (E24) of 0.1% p- 11568 was 77.4% with an emulsified kerosene content, and was higher than those of commercial polysaccharides, such as xanthan gum (26.1%), gellan gum (1.3%), and sodium alginate (2.0%). p- 11568 was found to be composed of glucose and galactose as the main natural sugars in a molar ratio of 1.3:1, along with uronic acid (18.9%, w/w) and sulfate groups (1.2% w/w). The average molecular mass was 4.4 x 105 daltons by gel filtration chromatography. The effects of pH, temperature, inorganic compounds, and C and N sources were tested to obtain the optimal medium composition for the production of p-11568. Under optimal growth conditions with the M-11568 medium, 14.9 g of crude p-11568 per liter was obtained.

Abstract: Extracellular signal-regulated kinases (ERKs) are phosphorylated on threonine and tyrosine residues at 183 and 185, respectively, and then translocated from cytosol to nucleus. ERK2 is retained in the nucleus for several hours by nerve growth factor (NGF), and this sustained retention of ERK2 in the nucleus has effect on the fate of biological response toward differentiation by neurite outgrowth in PC12 cells. The overexpression of Green Fluorescent Protein (GFP)-ERK2 and mutated GFP-ERK2 constructs without anchoring protein MEK1 were distributed throughout the resting and the activated cells. When GFP-ERK2 coexpressed along with MEK1, cytosolic localization of GFP-ERK2 is retained by MEK1 in the resting PC12 cells. This cytosolic retention was due to the binding of ERK2 to the MEK1. Upon stimulation by growth factors, the association between GFP-ERK2 and MEK1 was detached from each other, and then GFP-ERK2 was translocated into the nucleus. However, inactive form of the MKP-3 cytosolic phosphatase forced ERK cytosolic retention in PC12 cells were either left untreated or stimulated by NGF. When the transfected PC12 cells were treated for 72hrs with NGF, GFP-ERK2 was distributed the cytosol. Regarding its subcellular localization, the roles of residues 179-185 located in the activation loop of ERK2 were examined. The substitution of residues in the activation loop to alanine showed different localization on the nuclear translocation of ERK2 in PC12 cells.