Localization of cells using magnetized patterned thin films.

In this study, the nasopharyngeal carcinoma cell line was cultured in a superparamagnetic iron oxide nanoparticle aqueous solution with a concentration of 1 µg/mL by using magnetic labeling technology. The cells took up superparamagnetic nanoparticles through the endocytosis process, which caused the cells to become magnetic and manipulable by a magnetic field gradient. Each cell contained 5.266 × 106 superparamagnetic nanoparticles, as determined using the magnetophoresis method. A specific domain configuration and its related distribution of magnetic poles in a patterned thin film were obtained after applying a magnetic field in a specific direction. Here, patterned magnetic thin films were designed to form square grid and square ring structures. When the magnetic field of 3000 G was applied along the diagonal of the square (45° direction) and then released, magnetic cells were trapped at the intersection of the square grid and the 45° diagonal corner of the square ring structure. From micromagnetic simulation results, it was determined that head-to-head and tail-to-tail domain walls with a high magnetic pole density formed at the corners of the square ring structure in the 45° diagonal direction, and the attractive force between a head-to-head/tail-to-tail domain wall and a cell at a height of 1 µm above the corner was approximately 2.055 × 10-10 N. In the square grid case, the attractive force between the domain wall at the intersection and a cell at a height of 1 µm above the intersection was approximately 2.245 × 10-10 N. The results of this study demonstrated that cells can simultaneously be arranged at designated locations physically by using patterned magnetic thin films in a noninvasive manner without chemical modification of the substrate.

Selective synchronization of Tetrahymena pyriformis cell populations and cell growth kinetics during the cell cycle.

A selection synchronization technique based on ingestion of tantalum particles has been applied to obtain synchronized cultures of the filter feeding ciliate Tetrahymena pyriformis. Cell concentrations and cell volume distributions of synchronized cell populations have been monitored for more than four average generation times. A simple curve-fitting method has been used to decompose the cell volume distributions of a synchronous population into two populations representing cells before and after cell division. In this way, the time course of the growth of an initially synchronous culture is decomposed into the growth of successive generations. The data indicate that at any given time only two generations of cells are present in significant numbers. The measured cell volume distributions show that T. pyriformis has a complicated growth pattern during the cell cycle. Newborn T. pyriformis cells do not grow significantly at the beginning of the cell cycle. After the nongrowing stage, cells start growing in a possibly exponential rate before cells enter into a second nongrowing stage. The second nongrowing stage lasts until cell division. The presented data demonstrate that growing cell populations can be viewed as the composite of cells belonging to different generations. This concept has important implications for solving corpuscular models of cell growth.

Electromyographic analysis of habituation processes of treadmill walking to floor walking.

Electromyography (EMG) is an essential tool for assessing muscle performance in human locomotion. The aim of this research is to utilize EMG for assessing the habituation processes of normal adults during treadmill walking compared to floor walking. In this research, EMG activity is presented in linear envelope (LE) form to meet physiological meanings and parameter estimation. The EMG LE is generated from the raw EMG signal through band-pass filtering, rectifying, integration, and normalization procedures. The ensemble averaging of EMG LEs is used to demonstrate the pooled data of six normal subjects. The variance ratio (VR) of the EMG LE is applied to analyze the repeatability of EMG activity and thus to quantify the habituation process of normal adults walking on a treadmill. The habituation results indicated that no pretibial group reached a steady state during 12 minutes of treadmill walking. However the majority of calf groups habituated after 2 minutes of treadmill walking. In addition, changes in EMG phasic activities could be observed for both pretibial and calf groups during treadmill walking.

[Cloning and sequencing of hemolysin gene from clinical Aeromonas hydrophila].

Aerolysin is one of the important virulence factors for Aeromonas hydrophila infection. To understand the characteristics of the aerolysin gene in clinical A. hydrophila, a genomic library was constructed by using pUC19 as cloning vector. The positive clone containing the aerolysin gene was selected by the colony hybridization method, using the aerolysin probe (an 48 mer oligonucleotide) of aquatic A. hydrophila. Four positive out of 1,200 transformants were obtained from the primarily screened genomic library, and were further identified for specific binding capability by the dot blot hybridization method. One of three positive clones, designated as pAH-1, was further analyzed by the restriction mapping technique. For further sequencing the aerolysin gene nucleotides, the 3.0 kb fragment of A. hydrophila isolated from pAH-1 was cloned into pBluescriptII, pKS+, resulting in plasmid pKAH-1. Subclones of pKAH-1 were constructed and determined for the presence of 48 mer aerolysin gene sequence by dot blot hybridization method. These (subclones pKS+SS and pSK+SS) were selected for nucleotide sequencing by single-stranded dideoxy sequencing method. The nucleotide sequence similarity coefficient between clinical and aquatic strains of A. hydrophila was 76%; whereas between clinical strains of A. hydrophila and A. sobria was 71%. Since the length of the A. hydrophila DNA fragment cloned into pAH-1 is 3.0 kb, a larger size than the aerolysin gene of aquatic A. hydrophila (1.45 kb) and, also, includes 3' region of aerolysin gene in aquatic A. hydrophila, the indication is that the clone, pKAH-1, contains an entire aerolysin gene of A. hydrophila. The similarity between a small region (containing 8 amino acids) of the aerolysin in the clinical A. hydrophila and the alpha toxin of Staphylococcus aureus suggests that there is functional significance in this region.

Intrauterine single fetal demise in a twin gestation. A case report.

Intrauterine demise of one fetus in a twin gestation as a rare occurrence not only entails the higher premature and neonatal death rates, fetal distress or abnormal presentation on the surviving twin, but also threatens the mother with toxemia. The consumptive coagulopathy imposes a potential risk of health on both mother and the surviving fetus or neonate. We herein report a 29-year-old nullipara in such case who finally delivered a stillborn and a living one. High risk management and careful pediatric follow-up are recommended.