Pharmacokinetics and tissue distribution of pefloxacin mesylate in chickens

A specific, sensitive and stable high‐performance liquid chromatography (HPLC)‐based analytical method was established to determine the level of pefloxacin mesylate (PM) in the plasma and various tissues of chickens. Chickens were randomly assigned to 12 equal experiment groups, including 11 treatment groups and one control group. The chickens in the treatment groups received oral administration of PM and were sacrificed at different pre‐determined time points, with their blood and various organs harvested, extracted and analyzed by HPLC to quantify the level of the residual antibiotic. Method validation studies indicated that the HPLC measurement showed excellent precision, reproducibility, stability and robustness. The obtained pharmacokinetic parameters suggested that PM reached peak levels in various tissues within 1–2 h after its oral administration, and was mainly concentrated in liver and kidney. The antibiotic was also found to be cleared from chicken crureus, brain, testes, ovaries and pancreas at higher rates compared with other organs. Overall, the rapid accumulation of PM could at least be partially attributed to its relatively slow organ clearance. These results could serve as a useful guidance for the rational use of PM and other quinolone‐derived antimicrobials in the treatment of infectious diseases in chickens and other animals.     

Minimally Invasive & Long‐lasting Neural Probes from a Materials Perspective

Neurological disorders in aging society have created the need to understand how the brain works. At present, there are limited engineered “non‐invasive” tools to study and characterize the brain activity. Advancement in neuroscience research is highly focused on the fabrication of implantable neural probes that can effectively integrate with the neural tissue. Challenges associated with the commercially available probes has driven the development of mechanically compliant and non‐invasive neural implants. Engineering the mechanical and electrical performance of these probes is necessary to obtain tremendous sensitivity and selectivity along with chronic functionality. Selection of proper materials and understanding their fundamentals plays an essential role in achieving the desired neural interface. In this review, we have highlighted the recent progress in the utilization of new materials to attain a neural probe with improved flexibility, biocompatibility and signal quality.     

Analytical Solution of Compression,Free Swelling and Electrical Loading of Saturated Charged Porous Media

Analytical solutions are derived for one-dimensional consolidation, free swelling and electrical loading of a saturated charged porous medium. The governing equations describe infinitesimal deformations of linear elastic isotropic charged porous media saturated with a mono-valent ionic solution. From the governing equations a coupled diffusion equation in state space notation is derived for the electro-chemical potentials, which is decoupled introducing a set of normal parameters, being a linear combination of the eigenvectors of the diffusivity matrix. The magnitude of the eigenvalues of the diffusivity matrix correspond to the time scales for Darcy flow, diffusion of ionic constituents and diffusion of electrical potential.     

Multivariate Image Analysis of Magnetic Resonance Images with the Direct Exponential Curve Resolution Algorithm (DECRA): Part 2: Application to Human Brain Images

Owing to the heterogeneity of living tissues, it is challenging to quantify tissue properties using magnetic resonance imaging. Within a single voxel, contributions to the signal may result from several types of¹H nuclei with varied chemical (e.g., −CH₂−, −OH) and physical environments (e.g., tissue density, compartmentalization). Therefore, mixtures of¹H environments are prevalent. Furthermore, each unique type of¹H environment may possess a unique and characteristic spin–lattice relaxation time (T₁) and spin–spin relaxation time (T₂). A method for resolving these unique exponentials is introduced in a separate paper (Part 1. Algorithm and Model System) and uses the direct exponential curve resolution algorithm (DECRA). We present results from an analysis of images of the human head comprising brain tissues.     

An object-oriented designed finite-difference time-domain simulator for electromagnetic analysis and design in MRI--applications to high field analyses

This paper presents a finite-difference time-domain (FDTD) simulator for electromagnetic analysis and design applications in MRI. It is intended to be a complete FDTD model of an MRI system including all RF and low-frequency field generating units and electrical models of the patient. The program has been constructed in an object-oriented framework. The design procedure is detailed and the numerical solver has been verified against analytical solutions for simple cases and also applied to various field calculation problems. In particular, the simulator is demonstrated for inverse RF coil design, optimized source profile generation, and parallel imaging in high-frequency situations. The examples show new developments enabled by the simulator and demonstrate that the proposed FDTD framework can be used to analyze large-scale computational electromagnetic problems in modern MRI engineering.     

适用于医学诊断的超高速成象技术的研究

本文介绍了超高速成象技术在医学诊断上的最新进展,并提出了一种新的超高速成象技术——利用瞬变受激喇曼散射进行图象信号放大的超快时间门技术。     

HPLC测定自制胃粘附制剂在大鼠胃内的组织残留量

采用Diamonsil-C18色谱柱（200×4.6mm,5μm）,甲醇-水（20：80）为流动相,甲硝唑为内标,紫外检测波长317nm,流速1.0mL/min,柱温30℃,高效液相色谱法（HPLC）测定自制替硝唑胃粘附制剂在SD大鼠胃内的组织残留量。结果表明,替硝唑浓度在0.5-50mg·L^-1范围内与替硝唑峰面积和甲硝唑峰面积之比线性关系良好（r=0.9998）,检出限为0.15mg·L^-1,相对标准偏差小于6.7%,平均回收率为94.0%—102.6%。方法简便,准确可靠,适用于生物组织样品中替硝唑的测定。     

细胞外溶液的近红外光热响应取决于其吸收特性

光热效应是激光与生物组织相互作用中的一个主要因素, 但其产生、传输和作用机理尚不十分清晰. 本文采用双波长近红外激光辐照和膜片钳技术相结合的方法, 选择980 nm和845 nm两个波长的近红外激光, 因其在水中的吸收系数分别为0.502 cm^-1和0.0378 cm^-1, 接近十倍差异. 若溶液是产生光热响应的主要介导物质, 则期望这两个波长的激光辐照所产生的溶液温升也将呈现相应的十倍比例关系. 研究中把溶液光热响应过程分为温升的建立和耗散两个阶段. 在温升建立阶段,理论模型的建立采用长时程 (激光作用时程长于介质的热弛豫时间)作用理论的研究结果, 实验是使用膜片钳系统来测量细胞外溶液中, 已进行温度标定的、充灌溶液的玻璃微电极电导变化, 根据这个电导变化来定量研究溶液光热响应与其吸收特性的关联性; 在耗散阶段, 使用膜片钳系统监测神经细胞的电生理功能变化. 理论和实验两方面的结果都表明, 溶液对低强度近红外激光的吸收特性决定了其光热响应. 这一结果, 可以直接用于生物组织光热响应特性相关的机理研究. 关键词： 光热响应 双波长的方法 近红外激光和生物组织相互作用 空电极方法     

In vivo NMR T2 relaxation of experimental brain tumors in the cat: A multiparameter tissue characterization

Experimental gliomas (F98) were inoculated in cat brain for the systematic study of their in vivo T₂ relaxation time behavior. With a CPMG multi-echo imaging sequence, a train of 16 echoes was evaluated to obtain the transverse relaxation time and the magnetization M(0) at time t = 0. The magnetization decay curves were analyzed for biexponentiality. All tissues showed monoexponential T₂, only that of the ventricular fluid and part of the vital tumor tissue were biexponential. Based on these NMR relaxation parameters the tissues were characterized, their correct assignment being assured by comparison with histological slices. T₂ of normal grey and white matter was 74 ± 6 and 72 ± 6 msec, respectively. These two tissue types were distinguished through M(0) which for white matter was only 0.88 of the intensity of grey matter in full agreement with water content, determined from tissue specimens. At the time of maximal tumor growth and edema spread a tissue differentiation was possible in NMR relaxation parameter images. Separation of the three tissue groups of normal tissue, tumor and edema was based on T₂ with T_2(normal) < T_2(tumor) < T_2(edema). Using M(0) as a second parameter the differentiation was supported, in particular between white matter and tumor or edema. Animals were studied at 1–4 wk after tumor implantation to study tumor development. The magnetization M(0) of both tumor and peritumoral edema went through a maximum between the second and third week of tumor growth. T₂ of edema was maximal at the same time with 133 ± 4 msec, while the relaxation time of tumor continued to increase during the whole growth period, reaching values of 114 ± 12 msec at the fourth week. Thus, a complete characterization of pathological tissues with NMR relaxometry must include a detailed study of the developmental changes of these tissues to assure correct experimental conditions for the goal of optimal contrast between normal and pathological regions in the NMR images.     

Magnetic Resonance Imaging (MRI) of hormone-induced breast changes in young premenopausal women

Objectives

We conducted a pilot study to identify whether MRI parameters are sensitive to hormone-induced changes in the breast during the natural menstrual cycle and whether changes could also be observed during an oral contraceptive (OC) cycle.

Materials and Methods

The New York University Langone Medical Center Institutional Review Board approved this HIPAA-compliant prospective study. All participants provided written informed consent. Participants were aged 24-31 years.We measured several non-contrast breast MRI parameters during each week of a single menstrual cycle (among 9 women) and OC cycle (among 8 women). Hormones were measured to confirm ovulation and classify menstrual cycle phase among naturally cycling women and to monitor OC compliance among OC users. We investigated how the non-contrast MRI parameters of breast fibroglandular tissue (FGT), apparent diffusion coefficient (ADC), magnetization transfer ratio (MTR), and transverse relaxation time (T2) varied over the natural and the OC cycles.

Results

We observed significant increases in MRI FGT% and ADC in FGT, and longer T2 in FGT in the luteal vs. follicular phase of the menstrual cycle. We did not observe any consistent pattern of change for any of the MRI parameters among women using OCs.

Conclusions

MRI is sensitive to hormone-induced breast tissue changes during the menstrual cycle. Larger studies are needed to assess whether MRI is also sensitive to the effects of exogenous hormones, such as various OC formulations, on the breast tissue of young premenopausal women.