Microfluidic synthesis of microfibers for magnetic-responsive controlled drug release and cell culture

This study demonstrated the fabrication of alginate microfibers using a modular microfluidic system for magnetic-responsive controlled drug release and cell culture. A novel two-dimensional fluid-focusing technique with multi-inlets and junctions was used to spatiotemporally control the continuous laminar flow of alginate solutions. The diameter of the manufactured microfibers, which ranged from 211 μm to 364 μm, could be well controlled by changing the flow rate of the continuous phase. While the model drug, diclofenac, was encapsulated into microfibers, the drug release profile exhibited the characteristic of a proper and steady release. Furthermore, the diclofenac release kinetics from the magnetic iron oxide-loaded microfibers could be controlled externally, allowing for a rapid drug release by applying a magnetic force. In addition, the successful culture of glioblastoma multiforme cells in the microfibers demonstrated a good structural integrity and environment to grow cells that could be applied in drug screening for targeting cancer cells. The proposed microfluidic system has the advantages of ease of fabrication, simplicity, and a fast and low-cost process that is capable of generating functional microfibers with the potential for biomedical applications, such as drug controlled release and cell culture.     

Immunochemical detection of cell cycle synchronization in a human erythroleukemia cell line, K562

Cells of the human erythroleukemic line K562 can be induced by manipulation of culture conditions to arrest within the G1 phase of the cell cycle, and subsequently to enter S phase synchronously after release from G1. Cell cultures subjected to serum deprivation and hydroxyurea (HU) treatment demonstrated less than 5% of the cells to be in S phase. Four hours after release from HU, 63% of the cells were in S phase, as detected by immunofluorescent staining. This protocol offers a method for synchronization of K562 cells at the G1/S border and a technique for detection of S-phase cells without the use of radioisotopes or flow cytometry instrumentation.     

Ovarian plasminogen activator: relationship to ovulation and hormonal regulation.

A technique is described for detecting fibrinolytic activity of single cells in culture. This method was applied to the analysis of rat ovarian granulosa cells. Cells obtained from follicules shortly before ovulation show high levels of fibrinolytic activity. This activity is plasminogen-dependent, indicating that it is due to plasminogen activator. The appearance of this activity is correlated with ovulation by temporal and functional criteria, and can be demonstrated both in immature animals primed with hormones and in mature cycling animals. Granulosa cell cultures can be stimulated to release plasminogen activator by exposure in vitro either to luteinizing hormone or to dibutyryl cyclic AMP.     

Variations in the response of enzyme-dissociated rat pituitary cells to thyrotropin releasing hormone.

While exploring the interaction between thyrotropin releasing hormone (TRH) and normal rat anterior pituitary cells in monolayer culture we observed that cells dissociated with the use of trypsin did not respond to TRH with an increase in either TSH or prolactin (PRL) release. The dissociated cells were cultured for 3 days, then washed to remove serum proteins and exposed to 10^?6M TRH for 3 hours. TSH and PRL secretion from stimulated and unstimulated cultures was determined by radio-immunoassay and normalized using cell protein. When such trypsin-dissociated cells were exposed to 0.5 mM dibutyryl cyclic AMP the release of both TSH and PRL doubled indicating that the intracellular secretory machinery was functional and that the block to TRH was proximal to the formation of cyclic AMP and presumably at the level of a TRH surface receptor. Previous studies have shown that such trypsin-dissociated cells respond to LHRH and a crude hypothalamic extract with a dose dependent increase in LH, FSH and ACTH release. This rules out a non-specific effect of trypsin. When pituitary cells were dissociated with a non-trypsin technique, the unstimulated release of both TSH and PRL was comparable to that found with the trypsin-dissociated cultures. However, these cultures did respond to TRH with an increase in TSH release although again no effect was seen with PRL. The susceptibility of the cells to trypsin suggests the possibility that a protein moiety may be closely associated with the function of the receptor.     

In vitro prostaglandin release from and platelet-activating factor accumulation in isolated endometrial cells from pregnant and pseudopregnant rabbits.

Prostaglandin (PG) release from and platelet-activating factor (PAF) accumulation by enzymatically isolated endometrial epithelial and stromal cells from Day 6 pregnant and Day 6 pseudopregnant rabbits were studied in vitro, using RIA for PG measurement and a platelet aggregation assay for PAF measurement. On the first day of culture in serum-free media, PGF release into the medium was significantly higher from epithelial cells from Day 6 of pregnancy than from stromal cells from Day 6 of pregnancy or pseudopregnancy. PGE release did not differ significantly among these cell types. The addition of indomethacin (10(-5) M) to similar cultures inhibited release of both PGs from both cell types, but to a much greater extent from stromal than from epithelial cells. Significant stimulation of PG release by A23187 was achieved under all conditions on the fifth day of culture; PGE release was significantly greater than PGF release from stromal cells from Day 6 of pregnancy and pseudopregnancy, and release of both PGs from stromal cells was significantly greater from Day 6 of pregnancy than from Day 6 of pseudopregnancy. PG release from similar cells, cultured in medium containing 10% calf serum, was highest on the first or second day of culture and then, especially for PGF, declined with continued culture. PGE release was significantly higher than PGF release from stromal cells on the third and fourth days of culture. The ratios of PGF/PGE release from epithelial cells were significantly higher than those from stromal cells over the 5-day culture period for both reproductive stages. These ratios indicate the differential release of PGE and PGF from rabbit endometrial cell subpopulations and indicate a preferential release of PGE from stromal and of PGF from epithelial cells. Under basal conditions, PAF was not detected in epithelial or stromal cells cultured for 2 or 4 days, or in the associated culture media. If PAF had been released into the medium, it would have rapidly metabolized. Short exposure to calcium ionophore A23187 (10(-5) M) was able to stimulate PAF accumulation in epithelial and stroma cells in serum-free media, probably via the remodeling pathway. PAF was not detected in the medium. Intracellular PAF accumulation after exposure to A23187 (10(-5) M) for 5 min was significantly greater on the second day of culture than on the fourth day in epithelial and stromal cells from Day 6 of pregnancy.(ABSTRACT TRUNCATED AT 400 WORDS)     

Release of cytoplasmic enzymes into culture fluid

The release of enzymatic activities from cells grown in protein-and lipid-free synthetic media into culture fluids was investigated. Cell strains employed were the derivatives from mouse fibroblasts, rat liver parenchymal cells, rat ascites hepatoma cells and HeLa cells. Activities of acid DNase, acid RNase and alkaline phosphatase (ALP)-I were detected in culture fluids as early as one day after renewal of medium, whereas those of β-glucuronidase and acid phosphatase were not found. This release of enzymes was unlikely to be caused by cell disruption during cultivation. The release of Dnase was inhibited by the addition of cycloheximide or actinbomycin D, whereas that of ALP-I was not inhibited.     

Culture of human pituitary prolactin and growth hormone cells

Summary Fragments of pituitary tissue obtained from a total of 37 patients with either breast cancer, diabetic retinopathy, galactorrhea, or acromegaly were dissociated into single cell suspensions prior to cell culture. Release of human growth hormone (hGH) and human prolactin (hPRL) into the culture medium was measured by radioimmunoassay. During a 3-week culture period, prolactin cells released 9–13 times the intracellular levels of hPRL at the time of seeding, whereas hGH release from growth hormone cells was only 1–2 times that of their initial intracellular level during this same time. Both growth hormone and prolactin cells retained distinctive ultrastructural features during culture. The prolactin cells responded to TRH stimulation by elevated release of PRL into the medium. No evidence for mitotic division of prolactin cells in vitro was found.This work was supported by NCI Contract NO 1-CB-23863     

Microcarriers: A new approach to pancreatic islet cell culture

Summary Free islet cell suspensions were prepared from isolated fetal rat islets using a modified enzyme dispersion technique. The islet cells were dispensed into a culture flask containing microcarriers (Cytodex) suspended in culture medium RPMI 1640 by a slowly rotating bar magnet. Microscopical examination of the beads showed that the islet cells attached and then progressively proliferated on the surface of the beads as a monolayer. A highly sustained release of insulin from the beads to the medium was observed during the 7 d culture period. The functional viability of the cultured islet cells was further demonstrated by the ability of batches of the cell-coated beads to synthesize insulin and to increase the insulin release in response to an acute challenge (16.7 mmol/l glucose plus 5 mmol/l theophylline). The results suggest that bead microcarriers may provide a new approach to monolayer islet cell culture providing functional monolayers, which can easily be transferred to different test systems and further manipulated. Financial support for the study was received from the University of Uppsala, the Swedish Diabetes Association, Stiftelsen Expressens Prenatalforskningsfond, Nordisk Insulinfond, Stiftelsen Claes Groschinskys Minnesfond, the Swedish Society of Medical Sciences and the Swedish Medical Research Council (Grants No. 12X-109 and 12X-2297). This work was presented in part at the 15th Annual Meeting of the Scandinavian Society for the Study of Diabetes (June 5–7, 1980; Oslo, Norway) and the 16th Annual Meeting of the European Association for the Study of Diabetes (September 24–27th, 1980; Athens, Greece).     

Hyaluronan digestion and synthesis in an experimental model of metastatic tumour

To approach the question of hyaluronan catabolism in tumours, we have selected the cancer cell line H460M, a highly metastatic cell line in the nude mouse. H460M cells release hyaluronidase in culture media at a high rate of 57 pU/cell/h, without producing hyaluronan. Hyaluronidase was measured in the H460M cell culture medium at the optimum pH 3.8, and was not found above pH 4.5, with the enzyme-linked sorbent assay technique and zymography. Tritiated hyaluronan was digested at pH 3.8 by cells or cell membranes as shown by gel permeation chromatography, but no activity was recorded at pH 7 with this technique. Hyaluronan was digested in culture medium by tumour slices, prepared from tumours developed in nude mice grafted with H460M cells, showing that hyaluronan could be digested in complex tissue at physiological pH. Culture of tumour slices with tritiated acetate resulted in the accumulation within 2 days of radioactive macromolecules in the culture medium. The radioactive macromolecular material was mostly digested by Streptomyces hyaluronidase, showing that hyaluronan was its main component and that hyaluronan synthesis occurred together with its digestion. These results demonstrate that the membrane-associated hyaluronidase of H460M cells can act in vivo, and that hyaluronan, which is synthesised by the tumour stroma, can be made soluble and reduced to a smaller size by tumour cells before being internalised and further digested.     

A convenient, high-throughput method for enzyme-luminescence detection of dopamine released from PC12 cells

This protocol represents a novel enzyme-luminescence method to detect dopamine sensitively and rapidly with high temporal resolution. In principle, dopamine is first oxidized with tyramine oxidase to produce H(2)O(2), and then the produced H(2)O(2) reacts with luminol to generate chemiluminescence in the presence of horseradish peroxidase (POD). We applied this method successfully to perform real-time monitoring of dopamine release from PC12 cells using a luminescence plate reader upon stimulation with several drugs (e.g., acetylcholine, bradykinin). The results indicated that the dopamine release from PC12 cells was modulated by these drugs in a way similar to that found by using several conventional analytical techniques, such as HPLC-electrochemical detector (ECD). Unlike other assays, this assay technique is simple, rapid, highly sensitive and thus useful for assessment of effects of drugs on the nervous system. The dopamine release assay takes only < or =1 h once reagent setup and culture plates' preparation are finished.     

A simple qualitative method for the detection of nucleases

A method has been developed for growing cultured cells in 200-μl capillary pipets in order to measure the uptake and release of materials by the cells. Feeding is accomplished by means of continuous superfusion of culture medium over the cells. The technique virtually eliminates problems caused by cultured cells detaching from the substratum during experiments and has been used to study the depolarization-dependent processes of [³H]-acetylcholine release and ²²Na⁺ uptake by NG108-15 neuroblastoma × glioma hybrid cells.     

Direct opioid regulation of pituitary release of bovine luteinizing hormone

Although endogenous opioid peptides (EOP) are thought to alter pituitary release of luteinizing hormone (LH) by modifying the release of gonadotropin-releasing hormone (GnRH) from the brain, EOP may also directly affect the release of LH from pituitary cells. This hypothesis was tested using dispersed cells from the bovine anterior pituitary gland. Pituitaries were enzymatically dissociated, preincubated for 18 h and then cultured for either 2 or 24 h with GnRH, naloxone, methionine-enkephalin (Met-enk) or their combinations. Basal release of LH into media was 18.2 and 38.4 ng/100,000 cells after culture for 2 or 24 h, respectively. When cultured for 2 or 24 h with 10 nM GnRH, LH release was 296% and 131% of the basal release for each culture period. Cellular viability (75% vs 68%) and total (cells + medium) LH (128 vs 134 ng/100,000 cells) did not differ (P greater than .05) between cells cultured for 2 or 24 h. Naloxone (1 microM) increased (P less than .01) basal release of LH by 57% after 2 h of culture but not after 24 h of culture. Naloxone did not augment the amount of LH released in response to 10 nM GnRH. Addition of Met-enk (1 nM to 1 microM) suppressed (P less than .05) basal release of LH (23% to 62%) after 2 h of culture. Similar suppressive effects (8% to 49%) occurred in a dose-dependent manner (0.1 nM to 1 microM) after 24 h of culture. Met-enk (1 and 100 nM) antagonized (P less than .05) the stimulatory effect of naloxone and reduced (P less than .05) the amount of LH released in response to GnRH after 2 h of culture. In summary, the stimulatory effect of naloxone on the basal release of LH suggests that EOP may directly regulate pituitary cell function; the inhibitory effect of physiological concentrations of Met-enk on the basal in vitro release of LH suggests that EOP may directly affect the release of LH in vivo; the antagonism between the stimulatory effect of naloxone and the inhibitory effect of Met-enk is consistent with effects exerted through opioid receptors; and the stimulatory effect of GnRH may be partially reduced by Met-enk. These results are consistent with the hypothesis that opioids may directly modulate the release of LH at the pituitary level.     

Endogenous Amino Acid Release from Cultured Cerebellar Neuronal Cells: Effect of Tetanus Toxin on Glutamate Release

Endogenous amino acid release was measured in developing cerebellar neuronal cells in primary culture. In the presence of 25 mM K+ added to the culture medium, cerebellar cells survived more than 3 weeks and showed a high level of differentiation. These cultures are highly enriched in neurons, and electron-microscopic observation of these cells after 12 days in vitro (DIV) confirmed the presence of a very large proportion of cells with the morphological characteristics of granule cells, making synapses containing many synaptic vesicles. Synaptogenesis was also confirmed by immunostaining the cells with antisera against synapsin I and synaptophysin, two proteins associated with synaptic vesicles. From these cultures, endogenous glutamate release stimulated by 56 mM K+ was already detected after only a few days in culture, the maximal release value (1,579% increase over basal release) being reached after 10 DIV. In addition to that of glutamate, the release of aspartate, asparagine, alanine, and, particularly, gamma-aminobutyric acid (GABA) was stimulated by 56 mM K+ after 14 DIV, but to a lesser extent. No increase in serine, glutamine, taurine, or tyrosine release was observed during K+ depolarization. The effect of K+ on amino acid release was strictly Ca2+-dependent. Stimulation of the cells with veratridine resulted in a qualitatively similar effect on endogenous amino acid release. In the absence of Ca2+, 30% of the veratridine effect persisted. The Ca2+-dependent release was quantitatively similar after stimulation by veratridine and K+. Treatment of cerebellar cells with tetanus toxin (5 micrograms/ml) for 24 h resulted in a total inhibition of the Ca2+-dependent component of the glutamate release evoked by K+ or veratridine. It is concluded that glutamate is the main amino acid neurotransmitter of cerebellar cells developed in primary culture under the present conditions and that glutamate is probably mainly released through the exocytosis of synaptic vesicles.     

Release of peptide leukotrienes from rat Kupffer cells

Kupffer cells isolated from the normal rat liver were incubated with calcium ionophore A23187, and the levels of peptide leukotrienes (LTC4, LTD4, and LTE4) contained in the culture supernatant were determined by the combined technique of reverse-phase high-performance liquid chromatography and radioimmunoassay. In response to A23187, Kupffer cells released LTC4, LTD4, and LTE4. After 10 min-preincubation of Kupffer cells with AA861, a 5-lipoxygenase inhibitor, the generation of LTC4, LTD4, and LTE4 from A23187-stimulated Kupffer cells was significantly suppressed. Platelet activating factor (PAF), a phospholipid mediator, significantly enhanced the release of LTC4, LTD4, and LTE4 from Kupffer cells stimulated with A23187. These results suggested that Kupffer cells may participate in inflammatory and immunologic events in the liver tissue by the release of peptide leukotrienes.     

Method for monitoring of mitochondrial cytochrome c release during cell death: Immunodetection of cytochrome c by flow cytometry after selective permeabilization of the plasma membrane.

BACKGROUND: Cytochrome c release from mitochondria to cytosol is a hallmark of apoptosis and is used to characterize the mitochondria-dependent pathway of this type of cell death. Techniques currently used to measure cytochrome c release, Western blot and fluorescence microscopy of immunolabeled cells, are time-consuming and inaccurate, and the latter is still limited by sample size. METHODS: We developed a rapid and reliable technique to detect cytochrome c release during drug-induced apoptosis, using flow cytometry. Plasma membrane of apoptotic HL-60 cells and thymocytes, treated with staurosporine and dexamethasone, respectively, were selectively permeabilized by digitonin at a low concentration. The released cytochrome c was quickly washed out from cells and that which remained in the mitochondria was immunolabeled after fixing the cells. RESULTS: The fraction of cells that retained their mitochondrial cytochrome c, or the highly fluorescent cells, gradually decreased so that after 4-8 h of drug treatment almost all the cells lost their cytochrome c and emerged as a population of low fluorescent cells. This was confirmed by parallel fluorescence microscopy of cells immunolabeled for cytochrome c. CONCLUSIONS: This technique allows the analysis of cytochrome c release from mitochondria of a large number of apoptotic cells in a short period of time and is proposed as an alternative to the methods currently used for this same purpose.     

Catecholamine stimulation of androgen production by rat Leydig cells. Interactions with luteinizing hormone and luteinizing hormone-releasing hormone

The mechanism(s) of the development of response to catecholamines (CA) by Leydig cells in culture was investigated with the use of primary culture of purified Leydig cells of adult rats. The interactions of a CA agonist, isoproterenol (ISOP), with luteinizing hormone (LH) and a luteinizing hormone-releasing hormone agonist analog (LHRHa) on production of androgen by the Leydig cells were also studied. Cells incubated with ISOP for 3 h increased release of cyclic adenosine 3',5'-monophosphate (cAMP) to similar extents at 0, 3, and 24 h of culture. The beta-agonist did not increase androgen release at 0 h but had a concentration-dependent effect at 3, 24, and 48 h of culture, with maximal effects at 24 h. LH stimulated high increases in production of cAMP and androgen by the cells at 0-24 h of culture. Leydig cell beta-receptors decreased with culture time. Low concentrations but not high levels of LH had additive effects with ISOP on androgen release. ISOP showed a complex interaction with LHRHa on androgen release. Chronic exposure of Leydig cells to LHRHa reduced basal androgen release as well as release of androgen stimulated by ISOP, forskolin, and LH. These studies suggest that the development of response to CA by rat Leydig cells is a postreceptor, postcAMP event and showed that CA can interact with LH or LHRH to regulate Leydig cell function.     

Cultured juxtaglomerular cells: production and localization of renin

Trypsin- or collagenase-dispersed renal cortical cells from newborn mice were filtered and cultured. The cultures comprised 25% juxtaglomerular cells as identified by immunocytochemistry. Renin was measured by radioimmunoassay in the culture medium and in the cells at various time intervals. This in vitro system was responsive to isoproterenol, which stimulated renin release in a dose-dependent manner.     

Cytoplasmic protein phosphorylation related to multihormonal regulation of prolactin in pituitary cells

The specialized functions of mammotropic cells from the anterior pituitary and of the pituitary tumor derived GH cell lines can be regulated by a large number of neurohormones and other substances. Although the biological responses to many of these regulatory signals are well documented, much less is known about the intracellular mechanisms involved in their action. Various “second messengers” are generated, which in turn regulate other intracellular activities like protein phosphorylation reactions. Thyrotropin-releasing hormone stimulates both prolactin synthesis and release by mammotrophs of the anterior pituitary, or by GH₄C₁ cells in culture. Thyrotropin-releasing hormone simultaneously enhances the phosphorylation of a small number of cytoplasmic proteins in GH₄C₁ cells, as revealed by two-dimensional polyacrylamide gel electrophoresis after ³²PO₄³⁻ labelling. On a pharmacological basis, two distinct subsets were identified among the seven phosphoproteins affected by thyrotropin-releasing hormone: set I, proteins 1–6, whose phosphorylation could be related to the regulation of prolactin synthesis; set II, proteins 7 and 8, whose phosphorylation was related to the modulation of prolactin release (Sobel A. and Tashjian A. H. Jr. (1983) J. Biol. Chem. 258, 10312–10324). Phosphorylation of all these proteins but protein 1 was alkali-resistant, indicating that it might take place on tyrosine residues. Protein 1, which could be visualized by silver-staining and whose phosphorylation resulted in a shift of its position on two-dimensional gels, was present also in normal rat pituitary cells in primary culture. Moreover, thyrotropin-releasing hormone induced its phosphorylation as in GH₄C₁ cells, thus indicating that this reaction is a normal regulatory process, not related to the tumoral origin of GH₄C₁ cells. This observation allowed us to study some physiologically important regulatory mechanisms which were lost in GH cells as, for example, the inhibition of prolactin synthesis and release by dopamine: in normal anterior pituitary cells in culture, dopamine also prevented the thyrotropin-releasing hormone induced phosphorylation of protein 1. This result is in good agreement with those obtained with GH₄C₁ cells, and extends them. The same technique allowed us to detect a protein with two-dimensional gel migration properties identical to those of protein 1 in certain tissues, like the adrenal medulla, but not in others, like the adrenal cortex. This tissue specificity might be related to the specific regulatory function of protein 1 in the cell.     

A novel mechanism of autolysis in Helicobacter pylori: possible involvement of peptidergic substances

BACKGROUND: Helicobacter pylori survival in a hostile acidic environment is known to be caused by its production of urease, which is not released by known secretion pathways. It has been proposed that H. pylori cells undergo spontaneous autolysis during cultivation and that urease becomes surface-associated only concomitant with bacterial autolysis. The aim of this study was to elucidate mechanisms by which H. pylori cells undergo autolysis during cultivation. MATERIALS AND METHODS: Autolysis of H. pylori KZ109 cells was estimated by measuring the turbidity of the culture, by detection of cytoplasmic protein release into the culture supernatant and by scanning electron microscopic observation of H. pylori cells during cultivation. An autolysis-inducing factor (AIF) was partially purified from the culture supernatant by a partition method using ethyl acetate. RESULTS: Bacterial turbidity of KZ109 cells was drastically decreased after late-log phase accompanying release of urease and HspB into the extracellular space. Concomitantly, cell lytic activity was detected in the culture supernatant. Scanning electron microscopic observation suggested that partially purified AIF induced cell lysis. It was also shown that the AIF is different from other autolytic enzymes or substances so far reported. CONCLUSIONS: This study demonstrated the presence of the peptidergic autolytic substances in the culture supernatant of H. pylori KZ109 cells. The results of this study should be useful for further studies aimed at elucidation of the strategy of survival of H. pylori in the gastric environment and elucidation of the mechanisms of pathogenesis induced by H. pylori.     

Lectin receptor sites at the cell surface employed for affinity separation of tissue culture cells : Basic requirements as realized by lens culinaris lectin (LCL) immobilized on 2B-Sepharose

Lens culinaris lectin (LCL) immobilized on large 2B-Sepharose beads has been used to investigate the lectin-binding capacity of cell surfaces for the separation of cells by affinity chromatography. Immobilized LCL induced the tissue culture cells studied (HeLa, SV3T3) to bind to the agarose beads. This binding could be prevented by the addition of hapten sugars such as methyl-α -mannopyranoside (MαMP) and methyl-α -glucopyranoside (MαGP) according to the affinity of these sugars to LCL in a concentration-dependent manner. The cell-bead linkages were sufficiently strong to resist any appreciable mechanical breakage. The binding of the cells occurred so fast that any release could be started before the cells interacted unspecifically with the beads. Immobilized LCL released most of the cells upon addition of the competing sugar MαMP in a concentration-dependent manner under physiological conditions. The cells retained viability during the separation procedure as demonstrated by subsequent growth in culture. The difficulties so far observed with procedures involving columns have been overcome by a batch technique for controlled cell binding and release. For rapid separation of free from bound cells a gauze of defined pore size is introduced. Methodological problems such as agarose concentration, cell stickiness, lectin amount, and mechanical stability of the bead-cell complex are discussed.