Daniel I.C. Wang: a tribute to an inspirational leader and colleague

Daniel I.C. Wang has been an influential leader of the biotechnology industry over the past four decades through his inspirational research activities, the legions of students and other researchers that have studied under him, his development of many research and educational initiatives, both nationally and internationally, and the advice he has given worldwide to companies, research institutions, universities, and governments. He has played an important role in the mentoring and nurturing of junior faculty members, and has been a supportive collaborator in research and teaching. This two-part article provides a brief overview of Danny Wang's many contributions to furthering the global development of biotechnology, with particular emphasis on his recent activities in Asia, and concludes with an account of his research collaborations with the author over the past two decades.     

Calcium metabolism and cardiovascular function after spaceflight.

To determine the influence of dietary calcium on spaceflight-induced alterations in calcium metabolism and blood pressure (BP), 9-wk-old spontaneously hypertensive rats, fed either high- (2%) or low-calcium (0.02%) diets, were flown on an 18-day shuttle flight. On landing, flight animals had increased ionized calcium (P < 0.001), elevated parathyroid hormone levels (P < 0.001), reduced calcitonin levels (P < 0.05), unchanged 1,25(OH)(2)D(3) levels, and elevated skull (P < 0.01) and reduced femur bone mineral density. Basal and thrombin-stimulated platelet free calcium (intracellular calcium concentration) were also reduced (P < 0.05). There was a tendency for indirect systolic BP to be reduced in conscious flight animals (P = 0.057). However, mean arterial pressure was elevated (P < 0.001) after anesthesia. Dietary calcium altered all aspects of calcium metabolism (P < 0.001), as well as BP (P < 0.001), but the only interaction with flight was a relatively greater increase in ionized calcium in flight animals fed low- compared with high-calcium diets (P < 0.05). The results indicate that 1) flight-induced disruptions of calcium metabolism are relatively impervious to dietary calcium in the short term, 2) increased ionized calcium did not normalize low-calcium-induced elevations of BP, and 3) parathyroid hormone was paradoxically increased in the high-calcium-fed flight animals after landing.     

Orthogonal arrays are absent from the membranes of human glioblastomatous tissues

Human astrocytic gliomas were studied with the freeze fracture technique. Orthogonal arrays of particles were noted in the plasma membranes of low-grade astrocytoma tissues. However, no such arrays were found in the plasma membranes of anaplastic glioma or glioblastoma tissues. Gap junctions were rarely seen in the membranes of these higher-grade gliomas; when seen, they consisted of relatively few particles in poorly organized plaques. These plasma membranes were dominated by randomly distributed single particles. These findings constitute aspects of the loss of differentiation in these malignant tumors.     

Use of an adaptable cell culture kit for performing lymphocyte and monocyte cell cultures in microgravity

The results of experiments performed in recent years on board facilities such as the Space Shuttle/Spacelab have demonstrated that many cell systems, ranging from simple bacteria to mammalian cells, are sensitive to the microgravity environment, suggesting gravity affects fundamental cellular processes. However, performing well-controlled experiments aboard spacecraft offers unique challenges to the cell biologist. Although systems such as the European ‘Biorack’ provide generic experiment facilities including an incubator, on-board 1-g reference centrifuge, and contained area for manipulations, the experimenter must still establish a system for performing cell culture experiments that is compatible with the constraints of spaceflight. Two different cell culture kits developed by the French Space Agency, CNES, were recently used to perform a series of experiments during four flights of the ‘Biorack’ facility aboard the Space Shuttle. The first unit, Generic Cell Activation Kit 1 (GCAK-1), contains six separate culture units per cassette, each consisting of a culture chamber, activator chamber, filtration system (permitting separation of cells from supernatent in-flight), injection port, and supernatent collection chamber. The second unit (GCAK-2) also contains six separate culture units, including a culture, activator, and fixation chambers. Both hardware units permit relatively complex cell culture manipulations without extensive use of spacecraft resources (crew time, volume, mass, power), or the need for excessive safety measures. Possible operations include stimulation of cultures with activators, separation of cells from supernatent, fixation/lysis, manipulation of radiolabelled reagents, and medium exchange. Investigations performed aboard the Space Shuttle in six different experiments used Jurkat, purified T-cells or U937 cells, the results of which are reported separately. We report here the behaviour of Jurkat and U937 cells in the GCAK hardware in ground- based investigations simulating the conditions expected in the flight experiment. Several parameters including cell concentration, time between cell loading and activation, and storage temperature on cell survival were examined to characterise cell response and optimise the experiments to be flown aboard the Space Shuttle. Results indicate that the objectives of the experiments could be met with delays up to 5 days between cell loading into the hardware and initial in flight experiment activation, without the need for medium exchange. Experiment hardware of this kind, which is adaptable to a wide range of cell types and can be easily interfaced to different spacecraft facilities, offers the possibility for a wide range of experimenters successfully and easily to utilise future flight opportunities. J. Cell. Biochem. 70:252–267, 1998. © 1998 Wiley-Liss, Inc.     

Cell death from bursting bubbles: Role of cell attachment to rising bubbles in sparged reactors

Bursting bubbles are thought to be the dominant cause of cell death in sparged animal or insect cell cultures. Cells that die during the bubble burst can come from three sources: cells suspended near the bubble; cells trapped in the bubble lamella; and cells that attached to the rising bubble. This article examines cell attachment to rising bubbles using a model in which cell attachment depends on cell radius, bubble radius, and cell–bubble attachment time. For bubble columns over 1 m in height and without protective additives, the model predicts significant attachment for 0.5‐ to 3‐mm radius bubbles, but no significant attachment in the presence of protective additives. For bubble columns over 10 cm in height, and without protective additives, the model predicts significant attachment for 50‐ to 100‐μm radius bubbles, but not all protective additives prevent attachment for these bubbles. The model is consistent with three sets of published data and with our experimental results. Using hybridoma cells, serum‐free medium with antifoam, and 1.60 ± 0.05 mm (standard error) radius bubbles, we measured death rates consistent with cell attachment to rising bubbles, as predicted by the model. With 1.40 ± 0.05 mm (SE) radius bubbles and either 0.1% w/v Pluronic‐F68 or 0.1% w/v methylcellulose added to the medium, we measured death rates consistent with no significant cell attachment to rising bubbles, as predicted by the model. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 468–478, 1999.