Biomineralization of a calcifying ureolytic bacterium Microbacterium sp. GM-1

Background: Biomineralization is a significant process performed by living organisms in which minerals are produced through the hardening of biological tissues. Herein, we focus on calcium carbonate precipitation, as part of biomineralization, to be used in applications for environmental protection, material technology, and other fields. A strain GM-1, Microbacterium sp. GM-1, isolated from active sludge, was investigated for its ability to produce urease and induce calcium carbonate precipitation in a metabolic process. Results: It was discovered that Microbacterium sp. GM-1 resisted high concentrations of urea up to 60 g/L. In order to optimize the calcification process of Microbacterium sp. GM-1, the concentrations of Ni2+ and urea, pH value, and culture time were analyzed through orthogonal tests. The favored calcite precipitation culture conditions were as follows: the concentration of Ni2+ and urea were 50 µM and 60 g/L, respectively, pH of 10, and culture time of 96 h. Using X-ray diffraction analysis, the calcium carbonate polymorphs produced by Microbacterium sp. GM-1 were proven to be mainly calcite. Conclusions: The results of this research provide evidence that Microbacterium sp. GM-1 can biologically induce calcification and suggest that strain GM-1 may play a potential role in the synthesis of new biominerals and in bioremediation or biorecovery.

Detection of acute cerebral hemorrhage in rabbits by magnetic induction

Acute cerebral hemorrhage (ACH) is an important clinical problem that is often monitored and studied with expensive devices such as computed tomography, magnetic resonance imaging, and positron emission tomography. These devices are not readily available in economically underdeveloped regions of the world, emergency departments, and emergency zones. We have developed a less expensive tool for non-contact monitoring of ACH. The system measures the magnetic induction phase shift (MIPS) between the electromagnetic signals on two coils. ACH was induced in 6 experimental rabbits and edema was induced in 4 control rabbits by stereotactic methods, and their intracranial pressure and heart rate were monitored for 1 h. Signals were continuously monitored for up to 1 h at an exciting frequency of 10.7 MHz. Autologous blood was administered to the experimental group, and saline to the control group (1 to 3 mL) by injection of 1-mL every 5 min. The results showed a significant increase in MIPS as a function of the injection volume, but the heart rate was stable. In the experimental (ACH) group, there was a statistically significant positive correlation of the intracranial pressure and MIPS. The change of MIPS was greater in the ACH group than in the control group. This high-sensitivity system could detect a 1-mL change in blood volume. The MIPS was significantly related to the intracranial pressure. This observation suggests that the method could be valuable for detecting early warning signs in emergency medicine and critical care units.

Mechanical analysis on laparoscopic instruments when contacting with biological tissues / 医用生物力学

Objective To establish the contact deformation model of biological tissues contacting with endoscopic instruments, and to make mechanical analysis on contact stress and strain. Methods Based on Kelvin-Voigt model and Hertz contact theory, the contact deformation model of instruments (with both wedge-shaped teeth and cylinder-shaped teeth) contacting with biological tissues was established, and the variation of contact stress and strain changing with time in different endoscopic instruments were obtained through finite element analysis method and bio-impedance measurement. Results Endoscopic instruments with different structures of the teeth could cause different strain and stress on tissues during laparoscopic grasping. The stress of the instrument with wedge-shaped teeth on tissues was largest, while that with cylinder-shaped teeth was smallest, and that of instrument with hybrid structure of wedge-shaped and cylinder-shaped teeth was in between. Conclusions The hybrid structure of wedge-shaped and cylinder-shaped teeth can effectively reduce the peak pressure during laparoscopic grasping, thus prevent less tissue damage caused by wedge-shaped teeth, and enhance the grasping ability with cylinder-shaped teeth. This study provides an important reference for the safety use and better design of laparoscopic instruments in clinic.

Interfacial reaction of microwave radiating field upon lamellar materials / 第三军医大学学报

Objective To explore the rule of energy distribution on the interfaces between lamellar materials,especially the dependence upon the radiating directions for a microwave(MW) radiation and to get some experimental evidences for further research of the shielding and protective mechanism of biological effects of MW.Methods Some MW shielding lamellar materials elaborately chosen,including fiber & metal wires intertexture,MW exposure suit materials by chemical treatment,nano-carbon coated metal sheets and fresh pigskin treated as biological tissue material,were exposed to the defined frequency(9.3 GHz) MW field and the characteristics of MW interfacial reactions upon the materials were detected by a micro-spectrometer.Results The fiber & insulated metal wires intertexture did not possess obvious MW-shielding function.The MW exposure suit materials by chemical treatment were strong reflecting type MW-shielding materials.The nano-carbon coated metal sheets had a "transparent window" for a rather wide range of MW incidence angles and so were used as MW secret materials.As biological tissue material,the fresh pigskin treated was identified as a kind of complex MW absorbing and reflecting material.Otherwise,the interaction between MW and biological material interfaces might vary regularly as the change in water-content occurred by the MW heating effect.Conclusion Although all the kinds of experimental samples exhibited the coherence with the reflection law to MW sheaf,there was plenty of significant diversity in detail nearby the MW reflecting region.The experimental evidence might be of characteristic classification for interaction between MW directional radiation and different material interfaces.Otherwise,as skin tissues absorb microwave rather sharply in little incident angles,this part of radiations should be considered more in the protective mechanism of MW.

Detection of aconitine in biological samples by GC/MS / 中国法医学杂志

Objective To establish a method used for qualitative determination of aconitine in biological samples by GC/MS. Methods using MSTFA as derivative reagent and pyridine as solvent leaving in 60℃ for 30min then detected by GC/MS-SIM. Results The limit of detection of aconitine was 20ng (S/N≥100). Conclusion This method is sensitive, fast, and accurate. It is useful for forensic medical practice.