Changes in rabbit and cow lens shape and volume upon imposition of anisotonic conditions

In vivo, mammalian lenses have the capacity to effect fully reversible changes in shape, and possibly volume, during the accommodation process. Isolated lenses also change shape by readily swelling or shrinking when placed in anisotonic media. However, the manner by which the lens changes its shape when its volume is changed osmotically is not firmly established. Putatively, the lens could swell or shrink evenly in all directions, or manifest distinctive swelling and/or shrinking patterns when exposed to anisotonic media. The present study measured physical changes in lenses consistent with the latter alternative using methods we developed for determining rapid changes in lens shape and volume. It was found in isolated rabbit and cow lenses that the length of the axis between the anterior and posterior poles (A-P length) primarily increases under hypotonic conditions (−40 to −100 mOsM), with smaller, or no changes, in equatorial diameter (ED). Hypertonic conditions (+50 to +100 mOsM) on rabbit lenses elicited a predominant reduction in ED, while the A-P length was only marginally reduced. Hypertonic solutions of +150 mOsM were required to obtain similar changes in cow lens shape. The ratio of the A-P length to the ED was taken as a measure of “circularity”. This ratio increased gradually in rabbit and cow lenses bathed in hypotonic solutions because of the increase in the A-P length. The calculated lens volume increased in tandem with the increase in “circularity”. Lens circularity also increased under hypertonic conditions due to the decrease in ED, but this increase in circularity during shrinkage was not as pronounced as that which occurred during swelling. As such, the lens has a tendency upon swelling to change its shape by approaching the structure of a globular spheroid (as occurs during accommodation for near focusing), but lens shrinkage does not result in a flatter lens with a reduced A-P length as occurs during dis-accommodation for distance focusing. Moreover, osmotically evoked shape changes appear irreversible, in contrast to the mechanically elicited shape changes of accommodation.     

Use of a vapor pressure osmometer to measure brain osmolality

A method is described for determining brain osmolality with a vapor pressure osmometer. This instrument measures dew point temperature depression of a solution in vapor equilibrium in a closed chamber. The principles of vapor pressure osmolality measurement suggest that it may have some advantages over freezing point depression methodology for analysis of tissue samples. Standard solutions (sodium chloride, 290 mOsm/kg water) of 10–20 μl and at temperatures considerably lower than ambient temperature may be delivered to the osmometer and measured without effects on recorded osmolality. Quick-frozen tissue specimens that were dissected while frozen into the shape of a thin slice (0.5–1.0 mm in thickness, 4–5 mm in diameter) and delivered to the machine while still in the frozen state resulted in osmolality values with high reproducibility. With this method, the osmolality of the cerebral hemispheres of pentobarbital anesthetized rats is 305.86 ± 0.74 mOsm/kg water, a value that is significantly higher than plasma values from the same animals (297.6 ± 0.72 mOsm/kg water).The findings of this study suggest that with the use of a vapor pressure osmometer, small samples of brain tissue can be measured for osmolality with speed and high reproducibility and without the need for dilutions, weighings, calculations, and external determinations of tissue water content.     

基于眼部特点的麝丹即型凝胶的制备与评价

该实验采用中心组合设计-效应面法制备并优化了温敏型麝丹眼用即型凝胶,其处方最佳基质为18%的泊洛沙姆407(P407)和5%的泊洛沙姆188(P188);应用安东帕MCR302 流变仪对其进行了流变学考察,振幅扫描结果显示应控制其应变(γ)<0.5%,在高频区其弹性模量(G')大于黏性模量(G"),表现为凝胶特征,有较好的稳定性,通过温度扫描G',G"及相角(δ)的变化来确定了其相变温度(T_SG)为33.25 ℃,触变性实验显示其结构恢复时间短于5 s;分别采用表面张力仪、露点渗透压仪分别测定了其表面张力和渗透压,结果分别为36.43 mN·m^-1,320.6 mOsm·kg^-1;荧光标记示踪法观察了其在眼角膜的滞留时间为180 min;其溶出实验表现为零级释放动力学特征,麝香酮和丹酚酸B的释放与药物溶蚀线性相关;眼部刺激性实验显示其无刺激性。麝丹即型凝胶有望为临床视网膜静脉阻塞治疗提供一种新型外用长效制剂。     

评价VAPRO 5520渗透压分析仪性能

目的对VAPRO 5520渗透压分析仪性能进行评价，判断其分析性能是否满足临床要求。方法按照国家实验室认可及CAP认可要求，依照NCCLS EP5-A文件，分析VAPRO 5520日内和日间精密度；用能力对比（PT）评价分析方法的准确度；按照NCCLS EP6-P文件评价分析方法的线性范围；评价分析方法的最低检测限；并对说明书的参考范围进行验证。结果VAPRO 5520日内精密度高、低值分别为0．78％和0．54％，日间精密度高、低值分别为1．23％和1，25％。分析方法的能力比对结果合格；分析方法的线性范围为50．0～1000．0mmol/kg，符合临床要求；分析方法提供的参考范围符合实验室需要；其它指标符合性能评价要求。结论VAPRO 5520渗透压分析仪性能符合实验室性能标准。     

冰点下降法测定流感病毒裂解疫苗的渗透压摩尔浓度

目的:考察国内流感病毒裂解疫苗的渗透压摩尔浓度,为提高该品种的国家标准提供依据。方法:按照中国药典2010年版三部附录,采用冰点下降法测定市售6家企业生产的54批流感病毒裂解疫苗的渗透压摩尔浓度。结果:所考察产品的渗透压摩尔浓度范围在261～308 mOsmol.kg-1之间。结论:所考察产品的渗透压摩尔浓度值存在一定差异,因渗透压摩尔浓度是考察流感病毒裂解疫苗安全性的一项重要指标,在流感病毒裂解疫苗成品质量标准中增加渗透压摩尔浓度检查项是必要的。