孕妇外周血中无细胞胎儿DNA的研究进展及应用

孕妇外周血中无细胞胎儿DNA(cffDNA)是无创性产前诊断中重要的胎儿物质的检测来源.由于孕妇血中大部分是母体DNA,而游离胎儿DNA的量非常少,仅占3％～6％.因此从孕妇血中成功分离cffDNA,对后续的无创性产前诊断有着十分重要的意义.本文分别从孕妇外周血中cffDNA的发现来源,cffDNA的结构与稳定性,分离孕妇外周血中的cffDNA的实验方法,及在无创性产前诊断中的应用等方面进行介绍,并着重对该技术近年来的研究进展作一综述.旨在探寻较高效率分离孕妇外周血中cffDNA的实验方法,为无创性产前诊断提供较高浓度的检测物质,提高其准确率及成功率.     

Repetitive tissue pO2 measurements by electron paramagnetic resonance oximetry: current status and future potential for experimental and clinical studies

Tissue oxygen plays a crucial role in maintaining tissue viability and in various diseases, including responses to therapy. Useful knowledge has been gained by methods that can give limited snapshots of tissue oxygen (e.g., oxygen electrodes) or evidence of a history of tissue hypoxia (e.g., EF5) or even indirect evidence by monitoring oxygen availability in the circulatory system (e.g., NMR methods). Each of these methods has advantages and significant limitations. EPR oximetry is a technique for direct measurement of tissue pO2, which has several advantages over the other existing methods for applications in which the parameter of interest is the pO2 of tissues, and information is needed over a time course of minutes to hours, and/or for repetitive measurements over days or weeks or years. The aim of this article is to provide an overview of EPR oximetry using particulates to readers who are not familiar with this technique and its potential in vivo and clinical applications. The data presented here are from the experiments currently being carried out in our laboratory. We are confident that in vivo EPR oximetry will play a crucial role in the understanding and clinical management of various pathologies in the years to come.     

The potential of electron beam radiation for simultaneous surface modification and bioresorption control of PLLA

Bioresorbable polymers have been widely investigated as materials exhibiting significant potential for successful application in the fields of tissue engineering and drug delivery. Further to the ability to control degradation, surface engineering of polymers has been highlighted as a key method central to their development. Previous work has demonstrated the ability of electron beam (e-beam) technology to control the degradation profiles and bioresorption of a number of commercially relevant bioresorbable polymers (poly-l-lactic acid (PLLA), L-lactide/DL-lactide co-polymer (PLDL) and poly(lactic-co-glycolic acid (PLGA)). This work investigates the further potential of e-beam technology to impart added biofunctionality through the manipulation of polymer (PLLA) surface properties. PLLA samples were subjected to e-beam treatments in air, with varying beam energies and doses. Surface characterization was then performed using contact angle analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy. Results demonstrated a significant increase in surface wettability post e-beam treatment. In correlation with this, XPS data showed the introduction of oxygen-containing functional groups to the surface of PLLA. Raman spectroscopy indicated chain scission in the near surface region of PLLA (as predicted). However, e-beam effects on surface properties were not shown to be dependent on beam energy or dose. E-beam irradiation did not seem to affect the surface roughness of PLLA as a direct consequence of the treatment.     

Bone tissue in osteogenesis imperfecta: light and electron microscopic studies

Osteogenesis imperfecta was studied by light and electron microscopic techniques in 36 cases, of them there were 10 postmortem and 26 bone biopsies. The persons' age was from 0 to 38 years. There were 25 males and 11 females. The microscopic studies indicated a decrease in the basic substance and an increase in the number of osteocytes. The electron microscopic studies revealed a reduction in the granular endoplasmic reticulum, as well as matrix swelling in the mitochondria, their crista degeneration, and the presence of mitochondrial hydroxyappatite; non-uniform mineralization of collagenous structures, their disintegration, a change in the diameter of collagenous fibril, and a decrease in their transversal lines.     

一种新的种子细胞——滑膜间充质干细胞

滑膜间充质干细胞作为一种新的间充质干细胞在组织工程中有着广阔的应用前景。滑膜间充质干细胞能够分化为软骨、骨、脂肪、骨骼肌，具有取材方便，供区并发症少等优点。因此，滑膜间充质干细胞是软骨、骨、脂肪及骨骼肌的种子细胞的理想来源。介绍了滑膜间充质干细胞的分离、获取以及其生物学特性，并对其在组织工程中应用的研究进展做一回顾。     

Degradation of electrospun nanofiber scaffold by short wave length ultraviolet radiation treatment and its potential applications in tissue engineering

Development in the field of tissue engineering has brought much attention in the fabrication and preparation of scaffold with biodegradable synthetic polymer nanofibers. Electrospun biodegradable polymeric nanofibers are increasingly being used to fabricate scaffolds for tissue engineering applications as they provide high surface area-to-volume ratio and possess high porosity. One common way to sterilize polymeric nanofiber scaffolds is 254-nm ultraviolet (UV) irradiation. In this study, we aim to evaluate the effects of UV radiation on the degradation in polymeric nanofibers, and then capitalize on UV-induced degradation and UV photolithography in polymeric nanofiber scaffolds for tissue engineering applications. Poly(D,L-lactic-co-glycolic) acid (PLGA, 75:25) and poly(L-lactide-co-epsilon-caprolactone) [P(LLA-CL), 70:30] nanofibrous meshes were produced by electrospinning. The nanofibers were irradiated by commercial germicide UV (lambda=254 nm) lamp for different intervals. We found that UV sterilization induced significant degradation of nanofiber. At 1 h UV irradiation, the average molecular weight of PLGA and P(LLA-CL) nanofibers were reduced by 46% and 35%, respectively, with corresponding reduction in the tensile strength of 26% for PLGA and 28% for P(LLA-CL). Hence, precautions may have to be taken into consideration when sterilizing polymeric nanofibers by UV treatment. UV-induced degradation on nanofibers was applied to fabrication of a three-dimensional (3D) tissue engineering scaffold by UV photolithography. Masked exposure to UV could generate patterned holes (d=100 microm) on the nanofibrous mesh. Cell culture study showed that smooth muscle cells were able to migrate into the holes. This method can be used to fabricate a 3D nanofibrous scaffold with micropores.     

Cytogenetic studies on cultured fibroblast-like cells derived from basal cell carcinoma tissue

Chromosomal investigations were performed on fibroblast cultures established from tumour tissue of six patients with multiple basal cell carcinoma, and from one patient with a solitary basal cell carcinoma. In four instances, fibroblast cultures from specimens of unaffected skin areas Were examined simultaneously. Metaphases of peripheral blood lymphocytes were analysed in all patients. Three individuals showed increased rates of chromosomal breakage and rearrangement; the possibility of a relationship between these findings and the Occurrence of multiple basal cell carcinoma is discussed:

• 1). 

  The chromosomal aberrations noted in one patient with multiple arsenic-induced basal cell carcinoma probably reflect the long-term effect of exposure to arsenic.
• 2). 

  In the second case, the aberrations found in cultures from unaffected skin and blood lymphocytes may be due to repeated X-ray therapy of multiple nevoid basal cell carcinoma
• 3). 

  In the third patient, likewise affected by multiple nevoid basal cell carcinoma, the etiology of the increased frequency of chromosomally altered cells remains obscure. Taken together with two other observations (Happle et al. 1971, Happle & Kupferschmid 1972), the aberrations could indicate that in some patients with nevoid basal cell carcinoma syndrome the incidence of spontaneous chromosomal breakage tends to increase.

     

新的组织工程种子细胞--内皮祖细胞

内皮祖细胞作为一种在血管领域的干细胞在组织工程中有着广阔的应用前景.内皮祖细胞取材方便,参与新生血管的形成,具有成熟内皮细胞相似的特性.因此,内皮祖细胞可能是组织工程血管、血管植入物再内皮化以及构建组织工程器官血管网络的种子细胞的理想来源.简单介绍了内皮祖细胞的来源、特性以及体外扩增技术,并对其在组织工程中应用的研究进展做一回顾.     

新的组织工程种子细胞——内皮祖细胞

内皮祖细胞作为一种在血管领域的干细胞在组织工程中有着广阔的应用前景。内皮祖细胞取材方便，参与新生血管的形成，具有成熟内皮细胞相似的特性。因此，内皮祖细胞可能是组织工程血管、血管植入物再内皮化以及构建组织工程器官血管网络的种子细胞的理想来源。简单介绍了内皮祖细胞的来源、特性以及体外扩增技术，并对其在组织工程中应用的研究进展做一回顾。     

Scattered radiation from applicators in clinical electron beams

In radiotherapy with high-energy (4-25 MeV) electron beams, scattered radiation from the electron applicator influences the dose distribution in the patient. In most currently available treatment planning systems for radiotherapy this component is not explicitly included and handled only by a slight change of the intensity of the primary beam. The scattered radiation from an applicator changes with the field size and distance from the applicator. The amount of scattered radiation is dependent on the applicator design and on the formation of the electron beam in the treatment head. Electron applicators currently applied in most treatment machines are essentially a set of diaphragms, but still do produce scattered radiation. This paper investigates the present level of scattered dose from electron applicators, and as such provides an extensive set of measured data. The data provided could for instance serve as example input data or benchmark data for advanced treatment planning algorithms which employ a parametrized initial phase space to characterize the clinical electron beam. Central axis depth dose curves of the electron beams have been measured with and without applicators in place, for various applicator sizes and energies, for a Siemens Primus, a Varian 2300 C/D and an Elekta SLi accelerator. Scattered radiation generated by the applicator has been found by subtraction of the central axis depth dose curves, obtained with and without applicator. Scattered radiation from Siemens, Varian and Elekta electron applicators is still significant and cannot be neglected in advanced treatment planning. Scattered radiation at the surface of a water phantom can be as high as 12%. Scattered radiation decreases almost linearly with depth. Scattered radiation from Varian applicators shows clear dependence on beam energy. The Elekta applicators produce less scattered radiation than those of Varian and Siemens, but feature a higher effective angular variance. The scattered radiation decreases somewhat with increasing field size and is spread uniformly over the aperture. Experimental results comply with the results of simulations of the treatment head and electron applicator, using the BEAM Monte Carlo code, and Siemens, but feature a higher effective angular variance. The scattered radiation decreases somewhat with increasing field size and is spread uniformly over the aperture. Experimental results comply with the results of simulations of the treatment head and electron applicator, using the BEAM Monte Carlo code.     

Histopathological and tissue culture studies of a melanizing cell line derived from a retinoblastoma

Histological examination of the enucleated eye of a 7-mth-old child revealed a retinoblastoma with areas of rosette formation as well as focal areas of melanin pigmentation. Biopsy derived cells readily established a continuous cell line in liquid culture. The cells which have now been cultured continuously for over 3 yr, were shown to be malignant by being non-contact inhibitable, by readily forming colonies in semi-solid nutrient agar medium and by producing tumours in nude mice. When grown to the point of overcrowding in liquid culture the cells became heavily melanized. Electron microscopy of the melanized cultured cells showed the melanin to be contained in melanosomes. These findings suggest that retinoblastomas may be derived from bipotential primitive retinal cells which retain the capacity for both nuclear cell and pigment cell differentiation. Alternatively, separate malignant transformations may have occurred in each of 2 different progenitor cell types committed to a separate differentiation pathway. The clinical behaviour of this tumour has not differed from that expected of non-pigmented retinoblastomas.     

A biodegradable nanofiber scaffold by electrospinning and its potential for bone tissue engineering

Microporous, non-woven poly( epsilon -caprolactone) (PCL) scaffolds were made by electrostatic fiber spinning. In this process, polymer fibers with diameters down to the nanometer range, or nanofibers, are formed by subjecting a fluid jet to a high electric field. Mesenchymal stem cells (MSCs) derived from the bone marrow of neonatal rats were cultured, expanded and seeded on electrospun PCL scaffolds. The cell-polymer constructs were cultured with osteogenic supplements under dynamic culture conditions for up to 4 weeks. The cell-polymer constructs maintained the size and shape of the original scaffolds. Scanning electron microscopy (SEM), histological and immunohistochemical examinations were performed. Penetration of cells and abundant extracellular matrix were observed in the cell-polymer constructs after 1 week. SEM showed that the surfaces of the cell-polymer constructs were covered with cell multilayers at 4 weeks. In addition, mineralization and type I collagen were observed at 4 weeks. This suggests that electrospun PCL is a potential candidate scaffold for bone tissue engineering.     

Microspectroscopy and imaging in the THz range using coherent CW radiation

A novel THz near-field spectrometer is presented which allows the performance of biological and medical studies with high spectral resolution combined with a spatial resolution down to lambda/100. In the setup an aperture much smaller than the used wavelength is placed in the beam very close to the sample. The sample is probed by the evanescent wave behind the aperture. The distance is measured extremely accurately by a confocal microscope. We use monochromatic sources which provide powerful coherent cw radiation tuneable from 50 GHz up to 1.5 THz. Transmission and reflection experiments can be performed which enable us to study solids and molecules in aqueous solution. Examples for spectroscopic investigations on biological tissues are presented.     

Time-resolved,light scattering measurements of cartilage and cornea denaturation due to free electron laser radiation

Light scattering is used to monitor the dynamics and energy thresholds of laser-induced structural alterations in biopolymers due to irradiation by a free electron laser (FEL) in the infrared (IR) wavelength range 2.2 to 8.5 microm. Attenuated total reflectance (ATR) Fourier-transform IR (FTIR) spectroscopy is used to examine infrared tissue absorption spectra before and after irradiation. Light scattering by bovine and porcine cartilage and cornea samples is measured in real time during FEL irradiation using a 650-nm diode laser and a diode photoarray with time resolution of 10 ms. The data on the time dependence of light scattering in the tissue are modeled to estimate the approximate values of kinetic parameters for denaturation as functions of laser wavelength and radiant exposure. We found that the denaturation threshold is slightly lower for cornea than for cartilage, and both depend on laser wavelength. An inverse correlation between denaturation thresholds and the absorption spectrum of the tissue is observed for many wavelengths; however, for wavelengths near 3 and 6 microm, the denaturation threshold does not exhibit the inverse correlation, instead being governed by heating kinetics of tissue. It is shown that light scattering is useful for measuring the denaturation thresholds and dynamics for different biotissues, except where the initial absorptivity is very high.     

Generating intestinal tissue from stem cells: potential for research and therapy

Intestinal resection and malformations in adult and pediatric patients result in devastating consequences. Unfortunately, allogeneic transplantation of intestinal tissue into patients has not been met with the same measure of success as the transplantation of other organs. Attempts to engineer intestinal tissue in vitro include disaggregation of adult rat intestine into subunits called organoids, harvesting native adult stem cells from mouse intestine and spontaneous generation of intestinal tissue from embryoid bodies. Recently, by utilizing principles gained from the study of developmental biology, human pluripotent stem cells have been demonstrated to be capable of directed differentiation into intestinal tissue in vitro. Pluripotent stem cells offer a unique and promising means to generate intestinal tissue for the purposes of modeling intestinal disease, understanding embryonic development and providing a source of material for therapeutic transplantation.     

Patient radiation doses for electron beam CT

A Monte Carlo based computer model has been developed for electron beam computed tomography (EBCT) to calculate organ and effective doses in a humanoid hermaphrodite phantom. The program has been validated by comparison with experimental measurements of the CT dose index in standard head and body CT dose phantoms; agreement to better than 8% has been found. The robustness of the model has been established by varying the input parameters. The amount of energy deposited at the 12:00 position of the standard body CT dose phantom is most susceptible to rotation angle, whereas that in the central region is strongly influenced by the beam quality. The program has been used to investigate the changes in organ absorbed doses arising from partial and full rotation about supine and prone subjects. Superficial organs experience the largest changes in absorbed dose with a change in subject orientation and for partial rotation. Effective doses for typical clinical scan protocols have been calculated and compared with values obtained using existing dosimetry techniques based on full rotation. Calculations which make use of Monte Carlo conversion factors for the scanner that best matches the EBCT dosimetric characteristics consistently overestimate the effective dose in supine subjects by typically 20%, and underestimate the effective dose in prone subjects by typically 13%. These factors can therefore be used to correct values obtained in this way. Empirical dosimetric techniques based on the dose-length product yield errors as great as 77%. This is due to the sensitivity of the dose length product to individual scan lengths. The magnitude of these errors is reduced if empirical dosimetric techniques based on the average absorbed dose in the irradiated volume (CTDIvol) are used. Therefore conversion factors specific to EBCT have been calculated to convert the CTDIvol to an effective dose.