云南特有螺类光肋螺蛳主要生物学特征研究

光肋螺蛳（Margarya mansugi）是仅分布于云南省的特有螺类。受过度捕捞、栖息环境破坏等人为因素影响,光肋螺蛳自然种群急剧萎缩,目前已被世界自然保护联盟列为极危物种。由于光肋螺蛳的研究资料匮乏,其生物学特征尚未被完全掌握,制约了光肋螺蛳保护对策的制定。为此,通过室内人工驯养观察,记述了光肋螺蛳的形态、活动习性、食性、生长和繁殖等主要生物学特征。光肋螺蛳壳质厚且坚硬,呈长圆锥形,褐色,角质厣,螺壳一般有5~6个螺层,体螺层有4条环肋,雌螺体型一般比同龄雄螺大;喜栖息在水体底层,夜晚活动频率明显高于白天;主要以藻类为食,成螺经驯化可摄食人工配合饲料;仔螺、幼螺和成螺的生长速度顺次降低;性成熟时间需要两年以上,卵胎生,终年生产,一般在白天交配,交配时间7~10 h,分批产仔,每次产仔1~2只,观察到的一只雌螺分9批产仔,共产仔螺14只。从受精到仔螺产出需85 d以上。本研究可为光肋螺蛳基础生物学研究积累资料,同时也可为高原湖泊特有螺类的人工驯养繁育提供参考。     

A gait index may underestimate changes of gait: a comparison of the Movement Deviation Profile and the Gait Deviation Index

The ability of the Movement Deviation Profile (MDP) and Gait Deviation Index (GDI) to detect gait changes was compared in a child with cerebral palsy who underwent game training. Conventional gait analysis showed that sagittal plane angles became mirrored about normality after training. Despite considerable gait changes, the GDI showed minimal change, while the MDP detected a difference equal to a shift between 10-9 on the Functional Assessment Questionnaire scale. Responses of the GDI and MDP were examined during a synthetic transition of the patient's curves from before intervention to a state mirrored about normality. The GDI showed a symmetric response on the two opposite sides of normality but the neural network based MDP gave an asymmetric response reflecting faithfully the unequal biomechanical consequences of joint angle changes. In conclusion, the MDP can detect altered gait even if the changes are missed by the GDI.     

Finite element analysis of Stryker Xia pedicle screw in artificial bone samples with and without supplemental cement augmentation

A validated, using in vitro biomechanical testing, finite element model was used to evaluate the affects of (1) cement augmentation and (2) an intact posterior cortex in osteoporotic bone. The presence of augmentation and/or a posterior cortical cortex increased the stabilization of the pedicle screw 2–5 fold. Placement of cement influenced failure load and toggle; with distal placement having the largest increase in failure load and decrease in cephalad–caudad toggle. The presence of posterior cortex caused a decrease in the amount of toggle, a proximal shift of the center of rotation and an increase in the maximum failure force.     

Toward the Development of Metal‐Free Synthetic Nucleases: Cleavage of a Model Substrates by 1,4‐Diazabicyclo[2.2.2]Octane Derivatives

Artificial ribonucleases of A_nBCL series were synthesized by solid‐phase method. They consist of a hydrophobic alkyl radical A (n = 3–12 carbon atoms), an “RNA‐binding domain” B (bisquaternary salt of 1,4‐diazabicyclo[2.2.2]octane), a “catalytic domain” C (histidine residue) and a “linker” L that joins the domains B and C. The effect of the alkyl radical on the catalytic properties of the chemical catalyst was studied using three activated phosphate ester substrates: p‐nitrophenyl phosphate, bis‐p‐nitrophenyl phosphate, and thymidine‐3′‐p‐nitrophenyl phosphate.     

A nanofibrous PHBV tube with Schwann cell as artificial nerve graft contributing to Rat sciatic nerve regeneration across a 30-mm defect bridge

Abstract

A nanofibrous PHBV nerve conduit has been used to evaluate its efficiency based on the promotion of nerve regeneration in rats. The designed conduits were investigated by physical, mechanical and microscopic analyses. The conduits were implanted into a 30-mm gap in the sciatic nerves of the rats. Four months after surgery, the regenerated nerves were evaluated by macroscopic assessments and histology. This polymeric conduit had sufficiently high mechanical properties to serve as a nerve guide. The results demonstrated that in the nanofibrous graft with cells, the sciatic nerve trunk had been reconstructed with restoration of nerve continuity and formatted nerve fibers with myelination. For the grafts especially the nanofibrous conduits with cells, muscle cells of gastrocnemius on the operated side were uniform in their size and structures. This study proves the feasibility of artificial conduit with Schwann cells for nerve regeneration by bridging a longer defect in a rat model.     

Process intensification in fed-batch production bioreactors using non-perfusion seed cultures

ABSTRACT

Although process intensification by continuous operation has been successfully applied in the chemical industry, the biopharmaceutical industry primarily uses fed-batch, rather than continuous or perfusion methods, to produce stable monoclonal antibodies (mAbs) from Chinese hamster ovary (CHO) cells. Conventional fed-batch bioreactors may start with an inoculation viable cell density (VCD) of ~0.5 × 10⁶ cells/mL. Increasing the inoculation VCD in the fed-batch production bioreactor (referred to as N stage bioreactor) to 2–10 × 10⁶ cells/mL by introducing perfusion operation or process intensification at the seed step (N-1 step) prior to the production bioreactor has recently been used because it increases manufacturing output by shortening cell culture production duration. In this study, we report that increasing the inoculation VCD significantly improved the final titer in fed-batch production within the same 14-day duration for 3 mAbs produced by 3 CHO GS cell lines. We also report that other non-perfusion methods at the N-1 step using either fed batch or batch mode with enriched culture medium can similarly achieve high N-1 final VCD of 22–34 × 10⁶ cells/mL. These non-perfusion N-1 seeds supported inoculation of subsequent production fed-batch production bioreactors at increased inoculation VCD of 3–6 × 10⁶ cells/mL, where these achieved titer and product quality attributes comparable to those inoculated using the perfusion N-1 seeds demonstrated in both 5-L bioreactors, as well as scaled up to 500-L and 1000-L N-stage bioreactors. To operate the N-1 step using batch mode, enrichment of the basal medium was critical at both the N-1 and subsequent intensified fed-batch production steps. The non-perfusion N-1 methodologies reported here are much simpler alternatives in operation for process development, process characterization, and large-scale commercial manufacturing compared to perfusion N-1 seeds that require perfusion equipment, as well as preparation and storage vessels to accommodate large volumes of perfusion media. Although only 3 stable mAbs produced by CHO cell cultures are used in this study, the basic principles of the non-perfusion N-1 seed strategies for shortening seed train and production culture duration or improving titer should be applicable to other protein production by different mammalian cells and other hosts at any scale biologics facilities.