Effect of shear stress on expression of a recombinant protein by Chinese hamster ovary cells

A flow chamber was used to impart a steady laminar shear stress on a recombinant Chinese hamster ovary (CHO) cell line expressing human growth hormone (hGH). The cells were subjected to shear stress ranging from 0.005 to 0.80 N m(-2). The effect of shear stress on the cell specific glucose uptake, cell specific hGH, and lactate productivity rates were calculated. No morphological changes to the cells were observed over the range of shear stresses examined. When the cells were subjected to 0.10 N m(-2) shear in protein-free media without Pluronic F-68, recombinant protein production ceased with no change in cell morphology, whereas control cultures were expressing hGH at 0.35 mug/10(6) cells/h. Upon addition of the shear protectants, Pluronic F-68 (0.2% [w/v]) or fetal bovine serum (1.0% [v/v] FBS), the productivity of the cells was restored. The effect of increasing shear stress on the cells in protein-free medium containing Pluronic F-68 was also investigated. Cell specific metabolic rates were calculated for cells under shear stress and for no-shear control cultures performed in parallel, with shear stress rates expressed as a percentage of those obtained for control cultures. Upon increasing shear from 0.005 to 0.80 N m(-2), the cell specific hGH productivity decreased from 100% at 0.005 N m(-2) to 49% at 0.80 N m(-2) relative to the no-shear control. A concurrent increase in the glucose uptake rate from 115% at 0.01 N m(-2) to 142% at 0.80 N m(-2), and decreased lactate productivity from 92% to 50%, revealed a change in the yield of products from glucose compared with the static control. It was shown that shear stress, at sublytic levels in medium containing Pluronic F-68, could decrease hGH specific productivity. (C) 2002 Wiley Periodicals, Inc.

Identification of cellular changes associated with increased production of human growth hormone in a recombinant Chinese hamster ovary cell line

A proteomics approach was used to identify the proteins potentially implicated in the cellular response concomitant with elevated production levels of human growth hormone in a recombinant Chinese hamster ovary (CHO) cell line following exposure to 0.5 mM butyrate and 80 muM zinc sulphate in the production media. This involved incorporation of two-dimensional (2-D) gel electrophoresis and protein identification by a combination of N-terminal sequencing, matrix-assisted laser desorption/ionisation-time of flight mass spectrometry, amino acid analysis and cross species database matching. From these identifications a CHO 2-D reference,map and annotated database have been established. Metabolic labelling and subsequent autoradiography showed the induction of a number of cellular proteins in response to the media additives butyrate and zinc sulphate. These were identified as GRP75, enolase and thioredoxin. The chaperone proteins GRP78, HSP90, GRP94 and HSP70 were not up-regulated under these conditions.

Rapport-building through call in teaching Chinese as a foreign language: An exploratory study

Technological advances have brought about the ever-increasing utilisation of computer-assisted language learning ( CALL) media in the learning of a second language (L2). Computer-mediated communication, for example, provides a practical means for extending the learning of spoken language, a challenging process in tonal languages such as Chinese, beyond the realms of the classroom. In order to effectively improve spoken language competency, however, CALL applications must also reproduce the social interaction that lies at the heart of language learning and language use. This study draws on data obtained from the utilisation of CALL in the learning of L2 Chinese to explore whether this medium can be used to extend opportunities for rapport-building in language teaching beyond the face-to-face interaction of the classroom. Rapport's importance lies in its potential to enhance learning, motivate learners, and reduce learner anxiety. To date, CALL's potential in relation to this facet of social interaction remains a neglected area of research. The results of this exploratory study suggest that CALL may help foster learner-teacher rapport and that scaffolding, such as strategically composing rapport-fostering questions in sound-files, is conducive to this outcome. The study provides an instruction model for this application of CALL.

Tympanometric norms for Chinese schoolchildren

Current tympanometric norms have acknowledged the relevance of age as,in influencing factor. However, little attention has been afforded to other potentialities such its the non-pathological effects of gender, ear asymmetry, and racial heritage. This study aimed to examine normative tympanometric findings in a large sample of Chinese schoolchildren. Using a Madsen 901 Middle Ear Analyzer, data was collected from 269 children (538 ears), ranging in age from 6.2-12.7 years (mean = 9.4 years, SD = 1.7), in Jiangsu province. Descriptive statistics were calculated for the parameters of equivalent car canal volume (chi = 1.03, SD = 0.25, 90% = 0.68-1.46), peak compensated static acoustic admittance (chi = 0.58, SD = 0.34, 90% = 0.26-1.13), tympanometric width (chi = 112, SD=36, 90% = 62-156), and peak pressure (chi = -25, SD = 30, 90% = -85-+10). Statistically significant car asymmetry and grade/age effects were estabished, although differences found were minor. In comparison with past studies in Caucasian paediatric populations, the Chinese normative data displayed minimal disparities.

An examination of the effects of print media exposure and contact on subjective social reality and acculturation attitudes

This study draws upon cultivation theory, acculturation theory, and works on intergroup relations to examine the effects of print media exposure and contact on subjective social reality and acculturation attitudes of Chinese immigrants in Australia. Data was gathered via a survey administered to 265 respondents with Chinese origin. Results indicate that exposure to mainstream newspapers is only positively related to one indicator of subjective reality, namely, outgroup perception whereas exposure to ethnic newspapers was not significantly related to any of the indicators of subjective reality. Acculturation attitudes, on the other hand, are more closely related to group perception and contact but not closely associated with exposure to print media. These findings have again challenged the direct effect assumption of cultivation theory, paved the ground for combining mediated communication variables with interpersonal communication variables in acculturation research and suggested policy implications for interethnic coexistence. (c) 2005 Elsevier Ltd. All rights reserved.

An examination of the relationship between social locations of Chinese immigrants and their ethnic newspaper dependency

This study drew upon media system dependency theory (MSD) and social identity theory to examine the relationship between social locations of Chinese immigrants and their dependency on Chinese ethnic newspapers. Data was obtained from a survey participated by 265 respondents with Chinese origin but currently residing in Australia. Results indicated that among the three indicators of social location, age appeared to be a strong positive predictor of the dependency on ethnic newspapers for information. Respondents who stayed longer in the host country tended to be more frequent readers of ethnic newspapers as well. Education did not appear as a significant predictor of ethnic newspaper dependency. These findings suggested the need for us to further investigate the impact of ethnic print media on ethnic minorities in the age of various information sources offered by new technologies.

Linking Agentive Objects in Mandarin Chinese

This paper is concerned with the problem of argument-function mismatch observed in the apparent subject-object inversion in Chinese consumption verbs, e.g., chi 'eat' and he 'drink', and accommodation verbs, e.g., zhu 'live' and shui 'sleep'. These verbs seem to allow the linking of [agent-SUBJ theme-OBJ] as well as [agent-OBJ theme-SUBJ], but only when the agent is also the semantic role denoting the measure or extent of the action. The account offered is formulated within LFG's lexical mapping theory. Under the simplest and also the strictest interpretation of the one-to-one argument-function mapping principle (or the theta-criterion), a composite role such as ag-ext receives syntactic assignment via one composing role only. One-to-one linking thus entails the suppression of the other composing role. Apparent subject-object inversion occurs when the more prominent agent role is suppressed and thus allows the less prominent extent role to dictate the linking of the entire ag-ext composite role. This LMT account also potentially facilitates a natural explanation of markedness among the competing syntactic structures.

Refractive index tomography of turbid media by bifocal optical coherence refractometry

We demonstrate tomographic imaging of the refractive index of turbid media using bifocal optical coherence refractometry (BOCR). The technique, which is a variant of optical coherence tomography, is based on the measurement of the optical pathlength difference between two foci simultaneously present in a medium of interest. We describe a new method to axially shift the bifocal optical pathlength that avoids the need to physically relocate the objective lens or the sample during an axial scan, and present an experimental realization based on an adaptive liquid-crystal lens. We present experimental results, including video clips, which demonstrate refractive index tomography of a range of turbid liquid phantoms, as well as of human skin in vivo.