Gas transport during high-frequency ventilation: Theoretical model and experimental validation

We present a theoretical model of gas transport through the dead space during high-frequency ventilation (HFV) with volumes less than dead space volume. The analysis is based on the axial distribution of transit times of gas moving through the dead space. The model predicts that for tidal volumes (V) much less than dead space (V_d), gas exchange will be proportional to the product of frequency (f) and V². If gas transport is analyzed in terms of Fick's law, then the effective diffusion coefficient (D_eff) can be shown to be equal to fV² times a constant, whose value equals the square of the coefficient of dispersion of axial transit times through the dead space . Experimental results in straight tubes fit the predictions of this model quite well. A through the entire dead space of about 30% is more than sufficient to account for gas exchange during HFV in physical models or in intact animals. An axial dispersion of this magnitude can be measured directly from a typical Fowler dead space determination in healthy subjects.     

Effect of a Water‐Soluble Polymer on Polymer Interdiffusion in P(MMA‐co‐BA) Latex Films

We describe non‐radiative energy‐transfer experiments to measure the rates of polymer interdiffusion in P(MMA‐co‐BA) latex films formed in the presence of poly(vinyl alcohol) (PVOH). PVOH had relatively little effect on the initial efficiency of energy transfer, even when the amount of PVOH was large enough to form the continuous phase. Since Φ_ET(0) is a measure of the interfacial area between D‐ and A‐labeled cells in the film, we conclude that under these circumstances the dispersed P(MMA‐co‐BA) copolymer is in the form of clusters with many contacts between particles containing D and A labels. These large amounts of PVOH also reduce the amount of polymer diffusion that takes place when the films are annealed. When smaller amounts of PVOH are present, the effects are measurable but much smaller. In the presence of 2 to 17 wt.‐% PVOH, the polymer diffusion rate is retarded. The magnitude of the effect increases with the amount of PVOH present, and the effect is larger at 45 °C than at 63 °C. We show that the PVOH has its largest influence at the very early stages of polymer diffusion.

Schematic representation of an energy transfer experiment, which monitors polymer interdiffusion in a latex film.     

兔眼前房压强在体连续测量方法的研究

为了解眼睛房水压强变化规律,进一步建立闭角型青光眼模型和对疾病的治疗及视功能康复提供参考,探讨一种在体连续测量正常兔眼前房压强的方法。将正常成年新西兰白兔麻醉后,先用静脉留置针(20G)自角膜缘外行前房穿刺术,然后通过套管将Millar导管植入兔眼的前房,兔眼的前房压强信号经过Powerlab系统进行滤波、放大和模数转换后,通过Chart软件进行实时显示。结果表明:用该方法测得的正常兔眼24 h前房压强的变化范围为(1.31±0.21—2.74±0.83)KPa。前房压强的分布凌晨较低(0~5点),然后逐渐升高(5~10点),到中午或下午(11—17点)时达到最高峰,晚上又逐渐下降(18~23点)。结果证明本实验在体连续测量兔眼前房压强的方法是可行的。     

Rapid steady-state analysis of blood-brain glucose transfer in rat

A new kinetic analysis of blood-brain glucose transport is described, based on a steady-state model that takes account of cerebral blood flow, mean capillary glucose concentration, and cerebral metabolic rate. The maximal rate (T_max) and half-saturation constant (K_m) of glucose transport from blood to brain were determined in rats by measuring the rate of blood-to-brain glucose transfer at different blood glucose concentrations. Each determination lasted 20 seconds. For whole-brain, T_max and K_m averaged 258±33 (S.E.) μmol (100 g)^-1 min^-1 and 5.9±1.6 (S.E.) mmol 1^-1, respectively. The regional variations were insignificant. The new approach permits kinetic parameters to be measured locally in brain in rapidly changing functional states.     

The hippocampus and neurotransplantation

The present article is a review of our own results from histological and electron microscopic studies of hippocampal neurotransplants with different levels of integration with recipient brains. A model providing complete isolation from the brain was obtained using transplants developing in the anterior chamber of the eye. The growth, development, and cytological composition of transplanted tissue was found to depend on factors such as the age of the donor embryo tissue, the genetic compatibility between the donor and recipient, and the level of integration with the brain. Ultrastructural analysis of intraocular and intracortical transplants showed that overall, nerve and glial cells have the characteristics of highly differentiated, mature elements; the numerical density and structures of synaptic contacts were similar to those in normal conditions. However, transplanted tissues contained morphological features providing evidence of continuing growth of several nerve processes and increases in non-synaptic and transport-metabolic intercellular interactions. The ultrastructural deviations observed here are regarded as the manifestations of compensatory-adaptive changes during the development of tissues in conditions deficient in natural afferent synaptic influences. It is also demonstrated that the axons of transplanted neurons lacking adequate cellular targets can establish functional synaptic contacts with neuronal elements in the recipient brain which are not their normal targets.Translated from Zhurnal Vysshei Nervnoi Deyatelnosti, Vol. 54, No. 2, pp. 149–162, March–April, 2004.     

Biodegradation studies on periodate oxidized cellulose

Sodium periodate oxidized cellulose was found to degrade into small molecules when implanted subcutaneously in rats. Thus the potentiality of using oxidized cellulose as a biodegradable drug carrier is envisaged.     

Antimicrobial Activity of Various Extracts of Ocimum Basilicum L. and Observation of the Inhibition Effect on Bacterial Cells by Use of Scanning Electron Microscopy

The antimicrobial activities of chloroform, acetone and two different concentrations of methanol extracts of Ocimum basilicum L. were studied. These extracts were tested in vitro against 10 bacteria and 4 yeasts strains by the disc diffusion method. The results indicated that the methanol extracts of O. basilucum exhibited the antimicrobial activity against tested microorganisms. While the chloroform and acetone extracts had no effect, the methanol extracts showed inhibition zones against strains of Pseudomonas aeruginosa, Shigella sp., Listeria monocytogenes, Staphylococcus aureus and two different strains of Escherichia coli. The cells of microorganisms, which were treated and untreated with plant extracts, were observed by using the scanning electron microscope. It was observed that the treated cells were damaged.     

Transwell侵袭小室技术的改良及其在人骨髓间充质干细胞诱导分化中的应用

目的：分离、培养和鉴定人骨髓间充质干细胞（Mesenchymal stem cells，MSCs），应用改良的Transwell侵袭小室技术，探讨血管内皮生长因子（VEGF）及内皮细胞条件诱导液对其体外诱导分化中的作用。方法：采用Percoll（1．073g／ml）分离液分离骨髓单个核细胞，体外培养MSCs，流式细胞术分析鉴定MSCs的纯度，Transwell侵袭小室技术结合LSCM，实时监测MSCs在Matrigel与VEGF／内皮细胞条件诱导液构成的内皮细胞生长微环境中的运动迁移情况。结果：经Percoll分离、体外培养扩增的MSCs，细胞纯度可达95％左右；VEGF组迁移的深度虽高于对照组（P〈0．05），但迁移至聚碳酸脂膜下的细胞与对照组相比，并无统计学意义（P〉0．05）。内皮细胞条件诱导液促进MSCs的迁移，在Matrigel内迁移的深度及迁移至聚碳酸脂膜下的细胞均明显多于对照组（P〈0．05）。结论：共聚焦激光扫描显微术与Transwell侵袭小室技术的结合，能够从时间和空间上对后者进行观察，使该实验得到改良；利用内皮细胞条件诱导液与Matrigel模拟体外内皮细胞生长的微环境，并从空间上观测了MSCs穿越人工基底膜的情况，为MSCs向内皮细胞体外诱导开辟了新的思路。     

A method for simultaneous recording of electrical activities and spectrophotometric signals from brain slice preparations in vitro

Organ spectrophotometry has been applied to analyze cytochrome redox changes in brain slice preparations. An interface-chamber method for maintaining metabolism of brain slice tissues was devised to reduce noise on recording traces of spectrophotometric signals, and then used for continuous monitoring and simultaneous recording of electrical and optical signals from brain slices. With this method, the noise level during the recording of redox states of cytochromes was decreased to 0.0004 A unit.     

一种平板流动腔重力灌流系统的力学分析

本文分析了一种采用重力灌流的平板流动腔灌流系统，并根据实验结果确定出相应的阻力系数，获得平板流动腔剪应力、雷诺数以及入口长度与流体重力灌流高度的关系。