Simple spinner bottle with rotating basket packed with carriers for hybridoma cell culture

r-69B is a mouse-mouse hybridoma cell line, producing monoclonal antibody IgG against human r-IFN. It was cultured for 21 days in the 1.0-L spinner bottle which was assembled with a rotating basket packed with the 8.0-g Fibra-Cel carriers. The agitation was 100 r/min. The results showed that 53.5% of the cells can be trapped within the carriers in the basket and the cell concentration and MAb was about double those in the suspension culture. The spinner bottle could be assembled simply and used in general laboratories. It also could be used for different kinds of cells, including anchorage-dependent and independent cells.

Accelerated development of genital Chlamydia trachomatis serovar E in McCoy cells grown on microcarrier beads

Chlamydia trachomatis serovar E is a major cause of bacterially-acquired sexually transmitted infections. Stock cultures of these obligate intracellular bacteria are often propogated in McCoy cells. We recently reported that greater infectious titers of chlamydiae could be obtained if the McCoy cells were cultured on collagen-coated microcarrier beads versus plastic flasks, although the reason for the difference in efficiency was not clear. This study analyzed the development of C. trachomatis grown in McCoy cells by the two methods. Transmission electron microscopy analysis revealed an accelerated chlamydial development, with maturation of reticulate bodies into elementary bodies sooner in McCoy cells grown on the porous substratum. Comparison of particle counts versus infectivity titers indicated the production of fewer numbers of elementary bodies but which were highly infectious sooner from the infected McCoy cell-microcarrier bead cultures than from duplicate infected McCoy cell cultures grown in plastic tissue culture flasks.

Versatile fluid-mixing device for cell and tissue microgravity research applications

Microgravity life-science research requires hardware that can be easily adapted to a variety of experimental designs and working environments. The Biomodule is a patented, computer-controlled fluid-mixing device that can accommodate these diverse requirements. A typical shuttle payload contains eight Biomodules with a total of 64 samples, a sealed containment vessel, and a NASA refrigeration-incubation module. Each Biomodule contains eight gas-permeable Silastic T tubes that are partitioned into three fluid-filled compartments. The fluids can be mixed at any user-specified time. Multiple investigators and complex experimental designs can be easily accommodated with the hardware. During flight, the Biomodules are sealed in a vessel that provides two levels of containment (liquids and gas) and a stable, investigator-controlled experimental environment that includes regulated temperature, internal pressure, humidity, and gas composition. A cell microencapsulation methodology has also been developed to streamline launch-site sample manipulation and accelerate postflight analysis through the use of fluorescent-activated cell sorting. The Biomodule flight hardware and analytical cell encapsulation methodology are ideally suited for temporal, qualitative, or quantitative life-science investigations.

Large volume ex vivo expansion of CD34-positive hematopoietic progenitor cells for transplantation

A large volume culture system was developed for the ex vivo expansion of CD34 positive (+) hematopoietic progenitors, using cell donated by 15 patients receiving high-dose chemotherapy with autologous hematopoietic progenitor cell support (AHPCS). Substantial expansion of myeloid (181-fold) and megakaryocyte (41-fold) progenitors cells was demonstrated, using the conditions that we determined to be optimal: CD34+ progenitors cultured unperturbed for 7 (marrow) or 10 (blood) days in Teflon-coated bags with X-Vivo-10 medium containing 10% autologous plasma, 100 ng/ml, respectively, of recombinant stem cell factor (SCF), interleukin 3 (IL-3), interleukin 6 (IL-6), and granulocyte colony-stimulating factor (G-CSF). The studies demonstrated that (a) CD34 selection was necessary to obtain large, clinically relevant numbers of hematopoietic progenitors, (b) the addition of G-CSF to the baseline regimen of SCF/IL-3/IL-6 significantly enhanced the expansion of myeloid progenitors, (c) the addition of IL-1 to SCF/IL-3/IL-6 did not significantly enhance myeloid progenitor cell expansion, (d) CD34+ G-CSF-mobilized peripheral blood progenitor cells (PBPC) produced higher numbers of myeloid progenitors in culture than CD34+ marrow cells, and (e) long-term tissue culture (LTC) assays demonstrate the preservation of long-term initiating cells in ex vivo culture. The short-term and long-term reconstituting capability of CD34+ PBPC cultured in this system remains to be determined and will be evaluated in a clinical trial where they will be used as the sole source of AHPCS following high-dose therapy.

A system for culture of endothelial cells in 20-50-microns branching tubes

OBJECTIVE

To construct an in vitro endothelial cell culture system which would mimic the geometry and hemodynamic conditions of the arteriolar microcirculation.

METHODS

Using a photolithography technique, semicircular channels (20-50 microns in diameter) were etched in mirror-image patterns on pairs of borosilicate microscope slide glass. One-half of each plate pair was predrilled with perfusion port holes at funnel-shaped fluid entrance regions. The perfusion system was constructed of micropipette glass and Teflon tubing, and imbedded in Sylgard. Two types of endothelial cells were grown to confluence within the half-channels: rabbit lung microvascular endothelial cells (a gift of Dr. M.E. Gerritsen, Miles Inc.) and human umbilical vein endothelial cells. After the cells were confluent, the two mirror images were aligned and clamped together to form a complete branching system of tubes lined with endothelial cells.

RESULTS

This cell culture system can be perfused at physiological flow rates corresponding to wall shear stress values in the range 0.03-48 dyn/cm2. The fluid velocity profiles can be measured in this system by tracking the velocity and flow paths of 0.5-micron fluorescently labeled microspheres. Endothelial cells which grow within the channel exhibit F-actin alignment along the long axis of the channel by 3 days after seeding. Scanning electron micrographs indicate that 4 hr after seeding, endothelial cells commonly form cellular projections extending across the half-channel; by 5 days after seeding, the projections appear to have flattened out along the bottom of the channel.

CONCLUSIONS

An in vitro endothelial cell culture system was constructed which mimics the geometry and hemodynamics conditions of resistance arterioles. This system can be used to examine endothelial cell responses to flow and flow gradients under defined and controllable conditions which mimic the arteriolar microcirculation.

Transmission of the effect of an antifungal agent within a single hypha

A micro-compartment culture method was devised in which a single hypha of Rhizopus stolonifer growing on an agar section traversed an antifungal non-diffusible barrier to another agar section; thus the local environment of the distal or proximal part of the hypha could be controlled independently. The responses in terms of hyphal extension of the test fungus to local application of amphotericin B in this culture system were estimated by using an automatic analysing system. After hyphae had traversed the barrier, distal application of amphotericin B caused no appreciable effect on the proximal hyphae. In contrast, proximal application of amphotericin B caused inhibition of the extension of distal hyphae. The reversal of polarized cytoplasmic streaming also occurred during the inhibition of distal hyphal extension. The extents of inhibition of the distal hyphal extension and the cytoplasmic streaming were dependent upon the hyphal distance between the amphotericin B application site and the hyphal tip. These results show that the effect of an antifungal agent on a hypha depends on the region of the hypha exposed. Cytoplasmic streaming may play key role in the transmission of antifungal effects within a single hypha.

Effects of the hydrodynamic environment and shear protectants on survival of erythrocytes in suspension

Survival of media-suspended porcine erythrocytes exposed to various hydrodynamic environments was investigated with and without such shear protectant additives as bovine serum albumin, dextran and the non-ionic surfactant Pluronic F68. Erythrocytes provided a model cell population with cells of a uniform size, metabolic state and shear tolerance. Because the cells were non-growing, any shear adaptation effects were avoided. Cell lysis was followed by microscopic counts or release of haemoglobin. The cells were susceptible to agitation damage in unaerated shake flasks agitated at 100 rpm or greater. Relative to additives-free operation, the presence of 0.1% (w/v) dextran or albumin prolonged cell survival, but Pluronic F68 actually enhanced cell lysis in flasks agitated at 100 rpm. The protective effect of the additives depended on the hydrodynamic conditions. The protective effect of albumin was demonstrated also in aerated conditions in a split-cylinder airlift bioreactor (aspect ratio of 8.8; riser-to-downcomer cross-sectional area ratio of 1.0; specific power input of 0.34 W m-3). Comparison of the cell lysis characteristics in the airlift device and the best case performance of the shake flask showed longer survival in the flask (100 rpm); however, the length of survival in the reactor (approx. 70 h) was sufficient for practical purposes. In all cases, the cell lysis pattern conformed initially to zero-order dependence in cell concentration, becoming first-order after varying degrees of exposure to hydrodynamic forces. Fatigue failure of cells was inferred.

Retroviral-mediated gene transfer in human bone marrow cells growth in continuous perfusion culture vessels

Hematopoietic stem cell gene therapy holds the promise of being able to treat a variety of inherited and acquired diseases of the hematopoietic stem cell. However, to date, genetic modification of the human hematopoietic stem cell has been relatively inefficient. Here, we report the results of using a bioreactor system to expand hematopoietic cells after a brief retrovirus infection using a high titer, replication defective virus encoding for murine CD18. The retrovirus transduced culture continued to produce genetically modified hematopoietic progenitors for up to 6 weeks, the duration of the culture period. Up to one-third of the long-term culture initiating cell (LTC-IC) are genetically modified by the culture conditions. Murine CD18 can be expressed on the cell surface of up to 20% of the mature cells generated by the culture system, suggesting that clinically significant levels of gene transfer may be occurring. These results demonstrate the feasibility of using continuous perfusion bioreactors as a method of efficiently modifying human hematopoietic stem cells.

Oxygenation of intensive cell-culture system

The abilities of various methods of oxygenation to meet the demands of high-cell-density culture were investigated using a spin filter perfusion system in a bench-top bioreactor. Oxygen demand at high cell density could not be met by sparging with air inside a spin filter (oxygen transfer values in this condition were comparable with those for surface aeration). Sparging with air outside a spin filter gave adequate oxygen transfer for the support of cell concentrations above 10(7) ml-1 in fully aerobic conditions but the addition of antifoam to control foaming caused blockage of the spinfilter mesh. Bubble-free aeration through immersed silicone tubing with pure oxygen gave similar oxygen transfer rates to that of sparging with air but without the problems of bubble damage and fouling of the spin filter. A supra-optimal level of dissolved oxygen (478% air saturation) inhibited cell growth. However, cells could recover from this stress and reach high density after reduction of the dissolved oxygen level to 50% air saturation.

Advantages of using microfabricated extracellular electrodes for in vitro neuronal recording

We describe fabrication methods and the characterisation and use of extracellular microelectrode arrays for the detection of action potentials from neurons in culture. The 100 microns2 platinised gold microelectrodes in the 64 electrode array detect the external current which flows during an action potential with S:N ratios of up to 500:1, giving a maximum recorded signal of several millivolts. The performance of these electrodes is enhanced if good sealing of the cells over the electrodes is obtained and further enhanced if the electrodes and the cells lie in a deep groove in the substratum. The electrodes can be used for both recording and stimulation of activity in cultured neurons and for recording from multiple sites on a single cell. The use of such electrodes to obtain recordings from invertebrate neurons is described. The particular advantages of these electrodes, their long term stability, non-invasive nature, high packing density, and utility in stimulation, are demonstrated.

Performance of a membrane-dialysis bioreactor with a radial-flow fixed bed for the cultivation of a hybridoma cell line

A bioreactor system for the continuous cultivation of animal cells with a high potential for scale-up is presented. This reactor system consists of radial-flow fixed-bed units coupled with a dialysis module The dialysis membrane enables the supply of low-molecular-weight nutrients and removal of toxic metabolites, while high-molecular-weight nutrients and products (e.g., monoclonal antibodies) are retained and accumulated. This concept was investigated on the laboratory scale in a bioreactor with an integrated dialysis membrane. The efficiency of the reactor system and the reproducibility of the cell activity (hybridoma cells) under certain process conditions could be demonstrated in fermentations up to 77 days. Based on model calculations, an optimized fermentation strategy was formulated and experimentally confirmed. Compared to chemostat cultures with suspended cells, a ten-times higher mAb concentration (383 mg1(-1)) could be obtained. The highest volumetric specific mAb production rate determined was 6.1 mg mAb (1 fixed bed)-1h-1.

Culture of human adult endothelial cells on endarterectomy surfaces

OBJECTIVES

Endothelial cell seeding of prosthetic grafts has not been as successful as initially hoped and the application of seeding technology to alternative reconstructive procedures such as endarterectomy and angioplasty has been increasingly considered. The success of such seeding depends on the ability of the seeded cells to attach to, and form a monolayer on the endarterectomised vessel wall which was the aim of this study.

METHODS

Using a seeding chamber model, heterologous human adult endothelial cells were seeded onto fresh human endarterectomy specimens and cultured. Studies of endothelial call adherence to endarterectomy specimens were performed using 111-Indium oxine labelled cells using methodology analogous to graft seeding.

RESULTS

Mean endothelial cell adherence of 70% (S.D. 10%) after 1 h incubation was achieved and the successful development of a monolayer of human adult venous endothelial cells on endarterectomised arteries was demonstrated in vitro.

CONCLUSIONS

These results indicate that closed endarterectomy appears to offer a surface with cell attachment that is superior to prosthetic grafts. Where femoral endarterectomy is appropriate, endothelial seeding potentially offers a method of reducing thrombogenicity and intimal hyperplasia, improving patency and avoiding a prosthetic graft whilst preserving collateral circulation and autologous vein.

An experimental rabies vaccine produced with a new BHK-21 suspension cell culture process: use of serum-free medium and perfusion-reactor system

An experimental rabies vaccine was prepared from the BHK-21 cell line adapted to culture in suspension using bioreactors. A new serum-free medium (MDSS2) (Merten et al., Cytotechnology, 1994, 14, 47) developed for the culture of various cell lines and for the production of several biologicals, was used for cell culture and virus production. The PV-Paris/BHK-21 rabies virus strain (adapted to the BHK-21 grown in monolayer) was adapted to BHK-21 cells cultivated in suspension and in the serum-free medium. High titres of rabies virus were obtained with bioreactors equipped with a perfusion system using BHK-21 cells grown in suspension in MDSS2. Experimental vaccines were prepared and had satisfactory protective activity when tested in mice. This new and low cost technology for rabies vaccine production could be suitable for developing countries where rabies is an important health problem.

Growth of B cell colonies independent of T cells: a new perspective

Growth of human peripheral blood B cells in a B cell colony assay system is a useful technique to study the function of B cell biology. In the initial reports, T and B cells were admixed in the culture system, prior to which the T cells were treated with mitomycin or irradiation to prevent their proliferation. There were reports that optimal growth of B cell colonies required T cells to be in contact with the B cells. However, we were able to grow B cell colonies physically separated from T cells which were placed on a filter. We speculated then that T cells contacted B cells via pseudopods through the pores of the filter. We now report the growth of B cell colonies independent of T cells and conclude that B cell colony growth depends upon a critical number of B cells plated rather than on T cell help.

Clinorotation inhibits chondrogenesis in micromass cultures of embryonic mouse limb cells

Studies of the response of mammalian chondrocytes to gravitational changes in vivo, in organ culture, and in cell culture show that chondrogenesis is reduced in microgravity or by unloading, and increased by low levels of excess g. To investigate the cellular responses to microgravity using a ground based model, micromass cultures were exposed to simulated weightlessness on two clinostats. For rotation on the large clinostat, cultures were set up in Rose chambers, and cells were videotaped and photographed at several time periods after rotation began. For the smaller clinostat, cultures were set up in T-flasks, and two axes of rotation for clinostated cultures were used. Stationary controls [+1 g, -1 g (upside-down), and sideways] as well as rotation controls were employed. Rotation rate was 30 rpm for both clinostatted cultures and rotation controls. Chondrocyte differentiation was assessed by cartilage specific alcian blue staining. Significantly fewer alcian blue stained nodules were present in clinostatted cultures than in stationary controls or rotation controls. Nodules that did not stain with alcian blue, probably due to unsulfated matrix were present in all cultures. The number of nodules in sideways controls was greater than in any other culture (108% of +1 g controls), probably due to ongoing stimulus of the cell via cytoskeletal components. The results show that chondrocytes in culture respond to changes in the gravity vector in a predictable manner, and that carefully controlled clinostat studies can be useful adjuncts to and predictors for spaceflight experiments.

Bioreactor expansion of human bone marrow: comparison of unprocessed, density-separated, and CD34-enriched cells

Scale-up of human hematopoietic cultures was previously described in continuously perfused systems with bone marrow mononuclear cells (BMMNC), yielding expansion of both progenitors and long-term culture-initiating cells (LTC-IC). We report here on the use of these systems for expansion of unprocessed whole BM cells (WBMC) and CD34-enriched cells. Density separation recovered 84% of CFU-GM and 65% of LTC-IC from WBMC. Subsequent CD34 selection recovered 17% of CFU-GM and 48% of LTC-IC from the MNC fraction. The unabsorbed (CD34-depleted) fraction contained 37% of CFU-GM and 38% of LTC-IC, accounting for most of the lost cells. WBMC, BMMNC, and CD34-depleted cells were each placed directly in bioreactors, whereas CD34-enriched cells were placed in bioreactors containing preformed irradiated stroma. After 14 days, an average of 3.82 x 10(7) (12.7-fold expansion), 3.54 x 10(7) (11.8-fold), 2.85 x 10(7) (9.5-fold), and 3.65 x 10(7) (1298-fold) total cells were obtained from bioreactors inoculated with WBMC, BMMNC, CD34-depleted, and CD34-enriched cells on stroma, respectively. These cultures yielded 1.64 x 10(5) (27.9-fold expansion), 1.69 x 10(5) (14.3-fold), 8.36 x 10(4) (13.0-fold), and 1.91 x 10(5) (41.4-fold) CFU-GM each, respectively. Cell recovery and expansion data were combined to determine the number of expanded CFU-GM obtained per ml of BM aspirate, allowing direct comparison of performance between the four culture inocula. WBMC generated 3.76 x 10(6) CFU-GM per ml BM aspirate, whereas MNC resulted in 1.42 x 10(6) CFU-GM. CD34-enriched cells (on irradiated stroma) gave 7.00 x 10(5) CFU-GM per ml BM aspirate, whereas CD34-depleted cells generated 4.97 x 10(5) CFU-GM. The high productivity from WBMC cultures was studied further and was found to be reproducible at different inoculum densities. WBMC cultures had elevated levels of endogenous EGF and PDGF production, which may have been responsible for the more extensive stromal development observed. Flow cytometric analysis showed that the final culture composition, with respect to T and B lymphocytes, monocytes, granulocytes, and erythrocytes, was not significantly affected by the inoculum composition and in all cases was comprised of multiple lineages. Therefore, each step in cell purification resulted in the loss of primitive and accessory cells, which in turn resulted in a net decrease in the number of expanded cells obtained per ml BM aspirate.

A new model for rapid stretch-induced injury of cells in culture: characterization of the model using astrocytes

The purpose of this study was to develop a simple, reproducible model for examining the morphologic, physiologic, and biochemical consequences of stretch-induced injury on tissue-cultured cells of brain origin. Rat cortical astrocytes from 1- to 2-day-old rats were cultured to confluency in commercially available 25-mm-diameter tissue culture wells with a 2-mm-thick flexible silastic bottom. A cell injury controller was used to produce a closed system and exert a rapid positive pressure of known amplitude (psi) and duration (msec). The deformation of the membrane, and thus the stretch of the cells growing on the membrane, was proportional to the amplitude and duration of the air pressure pulse. Extent of cell injury was qualitatively assessed by light and electron microscopy and quantitatively assessed by nuclear uptake of the fluorescent dye propidium iodide, which is excluded from cells with intact membranes. Lactate dehydrogenase (LDH) enzyme release was measured spectrophotometrically. Cell injury was found to be proportional to the extent of the silastic membrane deformation. Increasing cell stretch caused mitochondrial swelling and vacuolization as well as disruption of glial filaments. Stretching also caused increased dye uptake, with maximum dye uptake occurring with a 50 msec pressure pulse duration, whereas deformations produced over longer periods of time (seconds) caused little dye uptake. With increasing postinjury survival fewer cells took up dye, implying cell repair. LDH release was also proportional to the amplitude of cell stretch, with maximum release occurring within 2 h of injury. In summary we have developed a simple, reproducible model to produce graded, strain-related injuries in cultured cells. Our continuing experiments suggest that this model can be used to study the biochemistry and physiology of injury as well as serve as a tool to examine the efficacy of therapeutic agents.

Microfabricated surface designs for cell culture and diagnosis

Grooved and holed surfaces with a well fabricated design may serve as microsubstrates for cell culture and microreactors for diagnosis. In this study, the authors prepared chemically treated, micrometer scale grooved and holed glass surfaces by combined surface modification and ultraviolet (UV) excimer laser ablation techniques, as follows. 1) Microcell-culture substrate: Amino group attached glass surfaces, prepared by the treatment with an aminopropylsilane, were condensed with a carboxylated radical initiator. Subsequently, polyacrylamide was grafted by surface initiated radical polymerization to create a very hydrophilic surface layer. Ultraviolet excimer laser beams (KrF: 248 nm) were irradiated through a microscope onto surfaces to create grooves or holes that were 10 and 50 microns in width or diameter, respectively. The depth, depending on the irradiation light strength, ranged from a few to several tenths of a micrometer. On endothelial cell (EC) seeding, ECs adhered and grew on the bottoms of the grooved or holed surface where glass was exposed on ablation. Little cell adhesion was observed on non ablated, grafted surfaces. Endothelial cells aligned along the groove, resulting in very narrow tube like tissue formation, whereas ECs tended to form a multilayered spherical aggregate in a hole. A single cell resided in a 10 microns square hole. 2) Microreactor for diagnosis: The glass surface, treated with a fluorinated silane, was ablated to create round holes. On addition of a few microliters of water, water could be quantitatively transferred into a hole because of the water repellent characteristics of non ablated, fluorinated glass. As a model of a microreactor, enzyme reactions to affect different levels of glucose were carried out in tiny holed surfaces.

Cultivation of hamster kidney cells in a dynamic cell culture system in space (Spacelab IML-1 Mission)

Cell proliferation, tissue plasminogen activator (t-PA) production and metabolic changes of Hamster Kidney cells (HaK) grown on microcarriers in an automatic Dynamic Cell Culture System (DCCS) were determined on the first International Microgravity Mission (IML-1) Spacelab (22-30 January 1992). The DCCS was designed for two cell culture chambers (volume: 200 microliters each), one operating as a hatch system, the other as a perfusion system. Medium exchange was achieved with an osmotic pump (flow rate 1 microliter h-1). Two major items were investigated: the biological performance of the DCCS in space and the effect of microgravity on HaK cells. The results obtained demonstrated that (1) the DCCS can be used for biological experiments on long term Spacelab missions. In fact, higher cell densities and higher concentration of glucose but lower concentration of lactate in the perfusion chambers than in the batch chambers were measured. The concentration of t-PA, glutamine and ammonia was similar in all chambers. (2) Microgravity had no effect on cell growth and metabolism of HaK cells.

The predicted and observed decline in onchocerciasis infection during 14 years of successful control of Simulium spp. in west Africa

In 55 villages from the well-protected central area of the Onchocerciasis Control Programme in West Africa (OCP), skin snip surveys have been carried out at regular intervals since the programme started, and the latest round of surveys was undertaken after 12-14 years of successful vector control. The observed trends in the prevalence and intensity of onchocerciasis infection in cohorts of adults were compared with the trends predicted using a host-parasite model. After 12-14 years of control the community microfilarial load (CMFL) was close to zero in all villages. During the last few years of control, the prevalence of infection declined at an accelerated rate, and this was predicted by the model. There was generally good agreement between observed and predicted trends. The predictions were based on an estimated average duration of infection of 10.4 years, which corresponds to a mean reproductive lifespan for Onchocerca volvulus of 9-9.5 years, and an upper limit of 15 years for 95% of the infections. Differences between the observed and predicted data included the trend in CMFL between the first and second surveys, which in 18 villages did not show the predicted decline. Furthermore, the observed final decline in prevalence was faster than predicted in the north-eastern part of the central OCP area. After 14 years of vector control, the level of onchocerciasis has fallen to such a low level that consideration is being given to ending larviciding.

Problems in the differential diagnosis of choroidal nevi and malignant melanomas. The XXXIII Edward Jackson Memorial Lecture

This article describes a novel method for preparing several spherical multicellular aggregates (spheroids) that have almost the same diameter on a microfabricated chip. The chip, fabricated by a simple method that uses a micromilling system, consisted of several thousand cavities, 100-500 microm in diameter, in a triangular arrangement on a polystyrene plate. Although no spheroid was formed on any chip when cultured under stationary conditions, hepatocytes formed spheroids in the cavities when turning force was applied with a rotary shaker. Especially on the chip with cavities 300 microm in diameter, one spheroid formed in each cavity; an orderly array of spheroids (1100 spheroids/cm(2)) of almost the same diameter was constructed. Ammonia removal and albumin secretion by the spheroids on the chip continued to occur at initial levels for at least 14 days of culture. Enzyme P-450 activity of the spheroids was also maintained and detected on this transparent chip by fluorescence of resorufin converted from ethoxyresorufin. The spheroid microarray chip seems to be a promising cellular platform for various biomedical applications such as in cell-based biosensors for toxicological and pharmacological examinations, and in bioartificial livers.

The circumfusion system for multipurpose culture chambers. I. Introduction to the mechanics, techniques, and basic results of a 12-chamber (in vitro) closed circulatory system

A self-contained mechanical system for circulating nutrient fluid through 12 tissue culture chambers is described in detail. This system utilizes nonperforated cellophane membranes in the chambers which separate the circulating nutrient from the tissue culture environments. The nutrient, therefore, is dialyzed through the cellophane of each chamber; some cell products are retained in the microenvironment between the closely apposed cellophane and cover slip, whereas the other cell products move from chamber to chamber in the circulating nutrient. The resultant environmental conditions directed by the circumfusion systems are highly favorable for maintaining the differentiation of chick embryo tissues over protracted periods; a number of micrographs are shown.