Estimation of instantaneous flow from the indicator-dilution curve after bolus injection of indicator

The indicator-dilution technique is commonly used to determine mean flow estimates. The estimation of instantaneous flow from the shape of an indicator-dilution curve is the objective of this study. Based on a mixing chamber approach to the flow system, a mathematical relationship is derived to reconstruct momentary flow from an indicator-dilution curve. This relationship is verified in a model setup both with only constant flow and with a sinusoidal flow variation superimposed. This method proved to give good flow estimates for limited values of flow parameters. Also, some preliminary experiments were performed in a pulsating flow system simulating heart action. The results were promising although the method proved to be very sensitive to baseline offset.     

Mixing is required for uniform reconstitution of filter-dried protein antigens in a single-injection vaccine formulation

Ambient temperature filter dried vaccine formulations have been proposed to simultaneously achieve thermostability and offer a ready-to-use immunisation device that combines reconstitution and injection. Vaccine concentration should be uniform at the point of injection, but the uniformity following direct reconstitution of filter-dried vaccines has not been reported. We present here a study of vaccine mixing and release following dissolution of filter-dried model protein and toxoid antigens within a single syringe, filter and needle unit. Release was better for filters made from glass than cellulose. Without additional mixing, uniformity was poor and only 41% of input protein was released from protein filter-dried onto glass fiber. In contrast, adding a simple glass bead and mixing by inversion, 100% release antigen solution was achieved, with uniform concentration at exit from the needle throughout a simulated injection. Adsorption onto alum adjuvant had no detectable effect on vaccine dissolution and mixing. The uniformity and yield of low doses of diphtheria and tetanus toxoid was also improved by mixing, albeit with a lower yield of 60–68%. We conclude that uniformity and mixing should be studied to ensure safety and efficacy of directly reconstituted filter-dried vaccine formulations.     

Association between food mixing ability and mandibular movements during chewing of a wax cube

The purpose of this study was to clarify whether masticatory movements during chewing of a wax cube associate with food mixing ability. Twenty-six dentate subjects (mean age 25.3 years) were directed to chew a two-coloured paraffin wax cube for 10 strokes on preferred chewing side. Mixing Ability Index (MAI) was determined from the colour mixture and shape of the chewed wax cube. MAI was employed as an estimate of food mixing ability. Mandibular movements during chewing of the wax cube were recorded using a six-degrees-of freedom jaw movements recording system, and motion of a lower incisal point of the mandible was computed. Twelve parameters of masticatory movements in relation to mandibular excursion, angle, velocity, cycle duration, duration of each phase were measured for each masticatory cycle. In addition, unilateral maximum biting was performed, and the maximum force during biting was measured using a force-transducer. A multiple regression analysis identified vertical amplitude, closing duration, closing angle and maximum bite force as significant predictors accounting for 63% of inter-subject variation (adjusted R(2)) in the MAI (P < 0.05). Only some parameters of masticatory movements seem to have an influence on the MAI in dentate subjects.     

苦碟子注射液与5种大输液配伍的稳定性考察

目的:考察苦碟子注射液与临床5种常用大输液配伍的稳定性。方法:模拟临床用药浓度,分别在复方氨基酸3AA、复方氨基酸18AA、复方氨基酸18AA-V、甘油果糖注射液、20%甘露醇注射液中按1∶50的比例加入苦碟子注射液,振摇均匀后倒置,于1、15、30、60min进行外观观察,并测定pH、微粒数、紫外吸收度。结果:苦碟子注射液与复方氨基酸3AA、18AA、18AA-V混合后pH无显著变化;与甘油果糖混合后pH升高;与20%甘露醇混合后pH略有下降。除与20%甘露醇混合后出现白色结晶、微粒数大大超标外,与其它4种大输液混合后微粒数变化均符合《中国药典》规定。相同浓度混合溶液的紫外吸收度较蒸馏水直接稀释的苦碟子紫外吸收度增大,但随时间延长吸收度有一定下降。结论:苦碟子注射液不能与20%甘露醇注射液配伍;可以选择复方氨基酸3AA、18AA、18AA-V注射液与其进行配伍,配药时应注意临用现配、尽早用完;其与甘油果糖注射液配伍比较安全。     

丙硫氧嘧啶缓释微丸的制备及释放度研究

目的:制备丙硫氧嘧啶缓释微丸,并研究其体外释放规律。方法:采用挤出滚圆法制备丙硫氧嘧啶缓释微丸,以实际释放速率与理想释放速率相似因子(f2)为主要指标,采用混料均匀设计法优化处方。考察转速(50、75、100r·min-1)、释放介质(pH1.0盐酸溶液、pH4.0磷酸缓冲液、pH6.8磷酸缓冲液、水)对药物释放的影响,并进行释药模型拟合。结果:乙基纤维素、微晶纤维素及丙硫氧嘧啶的最优配比为0.1:0.25:0.65,优化处方释放速率与理想释放速率相似因子f2为71.04。3种转速对药物释放无影响,f2均>65,但50r·min-1释放速率较慢,能更好地模拟体内环境;4种释放介质对药物释放无影响,f2均>70。单指数模型及Higuchi方程拟合较好,药物释放以扩散为主。结论:丙硫氧嘧啶缓释微丸累积释放度达到了设计要求,体外释药符合Fick扩散机制。     

注射用甲磺酸帕珠沙星与3种止血药在氯化钠注射液中配伍的稳定性考察

目的:考察注射用甲磺酸帕珠沙星与3种止血药在氯化钠注射液中配伍的稳定性。方法:分别在25℃、自然光环境下,模拟临床常用的浓度,考察注射用甲磺酸帕珠沙星与酚磺乙胺注射液、维生素K1注射液、氨甲苯酸注射液配伍8h内混合液的外观、pH值、不溶性微粒和甲磺酸帕珠沙星含量的变化。结果:注射用甲磺酸帕珠沙星与氨甲苯酸注射液及酚磺乙胺注射液混合,8h内混合液外观、pH值、不溶性微粒、含量均无明显改变;与维生素K1注射液混合时,2h内混合液外观、pH值、含量均无明显改变,但1h后不溶性微粒检查不合格,4h后出现白色沉淀,甲磺酸帕珠沙星含量也有所下降。结论:注射用甲磺酸帕珠沙星与氨甲苯酸及酚磺乙胺注射液配伍,室温下8h内性质稳定;注射用甲磺酸帕珠沙星与维生素K1注射液配伍则应慎重。     

银汞充填对口腔科医生健康影响的调查

目的　研究使用银汞合金充填牙齿对口腔科医生健康的影响。方法　将 10 0位口腔科医生按用汞量分为两组 ,观察组 5 1名 ,为每月用汞量 80克以上的医生 ,对照组 4 9名 ,为每月用汞量 2 0克以下的医生 ,详细记载两组的工作环境、操作方法、防护和体检情况。结果　观察组医生出现牙龈炎、头晕、失眠、腰痛、记忆力减退、性格变急躁易怒 ,手指颤、唾液分泌增多、尿汞高等症状和体征与对照组间差异有显著性意义 (P <0 0 5 )。结论　长期大量使用手工调制的银汞合金 ,如不注意防护 ,口腔科医生易患慢性汞中毒。     

Generation of monodisperse alginate microbeads and <Emphasis Type="Italic">in situ</Emphasis> encapsulation of cell in microfluidic device

A microfluidic method for the in situ production of monodispersed alginate hydrogels using chaotic mixing is described. Aqueous droplets comprising of alginate and calcium as a cross-linking agent were formed as an immiscible continuous phase, and then the alginate and calcium in the droplet came into contact and were rapidly mixed. Gelation of the hydrogel was achieved in situ by the chaotic mixing of the droplets in the microfluidic device. Important operating parameters included: the capillary number (Ca) and the flow rate of the continuous phase, which mainly influenced the formation of three distinctive flow regimes, such as fluctuation, stable droplets, and laminar flow. Under the stable formation of droplets regime, monodispersed alginate microbeads having a narrow size distribution (below 3% of CV) were produced in the microfluidic device and the size of the microbeads, ranging from 60 to 95 μm, could be easily modulated by varying the flow rate, viscosity, and interfacial tension. In addition, this approach can be applied to the encapsulation of yeast cells in alginate hydrogels with a high monodispersity. This simple microfluidic technique for the production of monodispersed hydrogels and encapsulation of biomolecules shows strong potential for use in biosensors, cell sensors, drug delivery systems, and cell transplantation applications.     

The optimised CO-rebreathing method: a new tool to determine total haemoglobin mass routinely

A routine method to determine total haemoglobin mass (tHb) in clinical practice and sports medicine is non-existent. Radioactive tracers or other dilution procedures like the common CO-rebreathing method (Proc_com) are impractical, the latter in particular because of the relatively long time of respiration. According to the multicompartment model of Bruce and Bruce (J Appl Physiol 95:1235–1247, 2003) the respiration time can be considerably reduced by inhaling a CO-bolus instead of the commonly used gas mixture. The aim of this study was to evaluate this theoretical concept in practice. The kinetics of the HbCO formation were compared in arterialised blood sampled from an hyperaemic earlobe after inhaling a CO-bolus (Proc_new) for 2 min and a CO–O₂ mixture (Proc_com) for ∼10 min. The reliability of Proc_new was checked in three consecutive tests, and phlebotomy was used to determine the validity. VO_2max was determined with and without previous application of Proc_new and the half-time of HbCO was registered also in arterialised blood after resting quietly and after the VO_2max test. Proc_new yielded virtual identical tHb values compared to Proc_com when HbCO determined 5 min after starting CO-rebreathing was used for calculation. The typical error of Proc_new was 1.7%, corresponding to a limit of agreement (95%) of 3.3%. The loss of 95 g (19) haemoglobin was detected with an accuracy of 9 g (12). After application of Proc_new VO_2max was reduced by 3.0% (3.7) (P=0.022) and half-time was lowered from 132 min (77) to 89 min (23) after the VO_2max test. Inhaling a CO-bolus markedly simplifies the CO-rebreathing method without reducing validity and reliability and can be used for routine determination of tHb for various indications.     

Effects of aging and job demands on cognitive flexibility assessed by task switching

In a cross-sectional, electrophysiological study 91 workers of a big car factory performed a series of switch tasks to assess their cognitive control functions. Four groups of workers participated in the study: 23 young and 23 middle aged assembly line employees and 22 young and 23 middle aged employees with flexible job demands like service and maintenance. Participants performed three digit categorisation tasks. In addition to single task blocks, a cue-based (externally guided) and a memory-based (internally guided) task switch block was administered. Compared to young participants, older ones showed the typical RT-decline. No differences between younger and older participants regarding the local switch costs could be detected despite the source of the current task information. In contrast, whereas the groups did not differ in mixing costs in the cued condition, clear performance decrements in the memory-based mixing block were observed in the group of older employees with repetitive work demands. These findings were corroborated by a number of electrophysiological results showing a reduced CNV suggesting an impairment of task specific preparation, an attenuated P3b suggesting reduced working memory capacity and a decreased Ne suggesting deficits in error monitoring in older participants with repetitive job demands. The results are compatible with the assumption that long lasting, unchallenging job demands may induce several neurocognitive impairments which are already evident in the early fifties. Longitudinal studies are needed to confirm this assumption.