Effects of electric pulses on liver cancer cells: apoptosis induction and decrease of mitochondrial transmembrane potential / 生物医学工程学杂志

In order to investigate the effects of electric pulses on cancer cells, we carried out the experiments with exposing HepG2 and L02 to electric pulses (1 kV/cm, l00 micros, 1 Hz) for different lengths of time (8 s, 15 s, 30 s, 60 s). Annexin V-FITC Kit and Flow cytometry were used to study the apoptosis of treated cells. The results showed that the electric pulses of 1 kV/cm, l00 micros, 1 Hz for 8 s could not induce tumor cells apoptosis. Apoptosis was observed when tumor cells were stimulated for 15 s and longer, and the apoptosis percentage increased with the increase of stimulation time. Furthermore, tumor cells were more sensitive than normal cells in response to electrical pulses. Rhodamine 123 and Laser Scanning Confocal Microscope (LSCM) were used to make a real-time study of mitochondrial transmembrane potential (Deltapsim) when the tumor cells were exposed to electric pulses for 60 s. No significant change of Deltapsim was observed within 30 s stimulation. After that, the Deltapsim increased sharply and declined later, suggesting that the mitochondrial pathway may be one of the apoptosis mechanism induced by electric pulses.

A new progress of cancer therapy: irreversible electrical breakdown of pulse therapy / 生物医学工程学杂志

Depending on the specified electric field parameters such as electrical field strength and duration, electrical pulses have generally been applied in biomedical fields. Conventional electroporation is commonly used for cell fusion, transfection, electrochemotherapy and so on. Recently, pulse electric fields with high strength (MV/cm) and duration of several tens of nanoseconds can affect intracellular signal transduction and intracellular structures with plasma intact, owing to the application of intracellular manipulation. Most researches indicate that parameters between those two ranges could be used to result in an inreversible apoptosis of cancer cells. The procedure between electroporation and intracellular manipulation is irreversible electrical breakdown (IREB). IREB selectively kills tumor cells by inducing cell apoptosis; thus it might provide a new method for cancer therapy.

Expression of mechano-growth factor in osteoblasts under mechanical stretch / 中华创伤杂志

Objective To analyze the protein expression and subcellular distribution of mechanogrowth factor (MGF) in ostcoblasts under stretch stimulation. Methods Cyclic stretching was applied to osteohlasts by a mechanical stretching device. The whole-cell proteins were extracted from controlled and stretched osteoblasts for detecting the protcin expression level of MGF by Western blot and observing the intracellular distribution of MGF by fluorescent immunocytological method. Results Western blot showed significant increase of expression of MGF in osteoblasts under stimulation of cyclic stretching. The level of protein was increased by four folds after 12-hour stretching of osteohlasts, and then declined sharply. Immunofluorescence analysis showed that MGF was mainly distributed in the nuclei of osteoblasts. ConcinsionsUnder the cyclic stimulation, the expression of MGF reaches a short period of peak in osteoblasts, which may be related to the injury of osteoblasts caused by stretching. MGF is mainly distributed in the nuclei of osteoblasts, indicating that MGF may contain nuclear localization signal and modulate the expression of relative genes.

The study of apoptosis and mechanism of cells exposed to steep pulse / 生物医学工程学杂志

This experiment was designed to study the apoptosis and related mechanism of adherent liver tumor cells (SMMC-7721) and adherent normal liver cells (HL-7702) when they were exposed to the steep pulse generated by the steep pulse apparatus for tumor treatment. The results showed that the steep pulse of 200 V could induce tumor cells apoptosis. The tumor cells presented with their apoptosis when they were exposed to the steep pulse from 200 V to 250 V. Laser scanning confocal microscopy was used to make a real time study of calcium burst when the adherent tumor cells were exposed to the steep pulse. The results showed:On the condition of no extracellular Ca2+, the concentration of Ca2+ in tumor cells exposed to the steep pulse of 150 V did not change; the concentration of Ca2+ in tumor cells exposed to the steep pulse of 200 V decreased; the concentration of Ca2+ in tumor cells exposed to the steep pulse of 250 V decreased more evidently. On the condition of existing extracellular Ca2+, the concentration of Ca2+ in tumor cells exposed to the steep pulse of 150 V did not change; the concentration of Ca2+ in tumor cells exposed to the steep pulse of 200 V decreased little; the concentration of Ca2+ in tumor cells exposed to the steep pulse of 250 V reduced little, too. Maybe the change of calcium burst in the tumor cells is the mechanism of apoptosis when cells are exposed to the steep pulse.

The physiological response of osteoblasts to pulsatile fluid flow shear stress in vitro / 生物医学工程学杂志

This is an experimental study in the realm of physiology inquiring about the effect of pulsatile fluid flow shear stress on the proliferation, differentiation and functions of osteoblasts;the objective is to validate the important effect of fluid flow shear stress on the mechanics adaptability of bone tissue. The osteoblasts derived from Wistar rat's calvaria were exposed to fluid shear stress 5, 10, 20 and 30 mN/cm2 for 3, 6, 9, 12, 24, 36h respectively in the flow chamber. The ability of proliferation, alkaline phosphatase (ALP) activity and extracellular calcium secretion of osteoblasts were assessed. The results showed that fluid flow shear stress at 5, and 10 mN/cm2 increased the proliferation, but at 20 and 30 N/cm2, the shear stress inhibited the proliferation. The shear stress at 5, 10, 20 mN/cm2 increased the ALP activity and extracellular calcium secretion of osteoblasts, and advanced the time of the peak value of ALP activity during the experiment period, but the shear stress at 30 mN/cm2 decreased ALP activity. So osteoblasts responded rapidly to shear stress; the proliferation, differentiation and mineralization of cells were regulated in the presence of some shear stress; and such regulation exhibited a pattern of dependence on the mN/cm2 level of shear stress.

Expression of mechano-growth factor in Escherichia coli and activity analysis / 生物工程学报

Mechano-growth factor (MGF) is one of IGF-1 isoforms. MGF is mechanosensitive and has important functions in muscle hypertrophy, regeneration and nerve injury recovery. In this study, MGF cDNA (330 bp) was cloned from stretched osteoblasts by RT-PCR. In order to avoid prolin residue inhibiting enterokinase cleavage, 9bp of MGF cDNA 5' end sequence was truncated by primer, then the obtained truncated MGF (des(1-3)MGF) cDNA (321 bp) was subcloned in pET32a(+) vector to construct a prokaryotic recombination expression plasmid. Trx/des(1-3)MGF fusion protein, existing in forms of solution, was expressed in transformed Escherichia coli strain BL21(DE3) by IPTG induction at 30 degres C. The supernatant of cell lysates was subjected to ion exchange chromatography and Ni2+ metal affinity chromatography, and the fusion protein was obtained with the purity over 95%. After the fusion protein was cleaved by enterokinase, Trx and des(1-3)MGF was isolated by reverse-phase HPLC. Through these procedures, des(1-3) MGF was obtained with the purity of 98%. The protein molecular mass was conformity to the theoretical value by SDS-PAGE and mass spectrometry analysis. The purified des(1-3)MGF was incubated with MC3T3-E1 for cell proliferation and migration assays. The results show that des(1-3)MGF exhibited more facilitative effects on proliferation and migration of MC3T3-E1 than that of des(1-3)IGF-1.

Effects of mechanical strain on the proliferation and expression of IGF-1 mRNA in rat osteoblasts / 生物医学工程学杂志

With the use of a cyclic strain unit, the proliferation and gene expression of IGF-1 in the rat osteoblasts that underwent mechanical strain were studied. The cells were subjected to 15% elongation at frequency 20 cycles/min for different loading time. Under the action of different loading time, the relative proliferation index of the rat osteoblasts was the biggest of all when loading time was 12h; during the course, the expression of IGF-1 mRNA increased significantly, and then gradually tended toward 1 with the increase of the loading time. These results demonstrate that osteoblasts respond to the mechanical forces which may regulate the activities of osteoblasts indirectly by promoting the autocrine effect of IGF-1. Loaded osteoblasts can adjust and adapt themselves to new mechanical stimulation, and hence maintain a new state of equilibrium.

Effect of overload environment on IGF-1 expression of osteoblasts / 生物医学工程学杂志

In the study of the relationship between cells overloading and the formation, regeneration and growth of bone, the text discussed osteoblasts express IGF-1 variation under overloading environment. The research of overloading on cellular level may elucidate the mechanical effect on the formation, regeneration and growth of bone and the mechanism of cell response in bone.

The mechanotransduction mechanism of how osteoblasts respond to mechanical stimulation / 生物医学工程学杂志

The stress environment regulates the factors of growth, resorption and remolding in bone tissue. Mechanical stimulation at cell physical level affects the physiological activity of osteoblasts, including proliferation, ALP activity and osteocalcin production. Mechanotransduction is a procedure which transduces the biophysical force into biochemical responses. It is also the basis of many physiological functions. The early response genes (c-fos, c-jun), the second message systems (Ca2+, NO, cAMP) and the mechano-sensitive cation channel are involved in the mechanotransduction course when osteoblasts respond to the mechanical stimulation.

Tensegrity of Cell Structure / 生物化学与生物物理进展

Tensegrity structure is comprised of compression-resis tant elements and a set of continuous tensile elements that are interconnected w ith each other. The stability of such system depends on maintenance of tensional integrity inside the structure, or what has come to be termed “tensegrity”. A ccording to studies on biology, cell structures are assembled on the basis of te nsegrity mechanism. Tensegrity of cytoskeleton can affect cell shape and functio n. Furthermore, some basic rules of mechanochemical transduction in cells can be well explained using tensegrity theory.