Immunonanoshells for targeted photothermal ablation of tumor cells

Consisting of a silica core surrounded by a thin gold shell, nanoshells possess an optical tunability that spans the visible to the near infrared (NIR) region, a region where light penetrates tissues deeply. Conjugated with tumor-specific antibodies, NIR-absorbing immunonanoshells can preferentially bind to tumor cells. NIR light then heats the bound nanoshells, thus destroying the targeted cells. Antibodies can be consistently bound to the nanoshells via a bifunctional polyethylene glycol (PEG) linker at a density of approximately 150 antibodies per nanoshell. In vitro studies have confirmed the ability to selectively induce cell death with the photothermal interaction of immunonanoshells and NIR light. Prior to incubation with anti-human epidermal growth factor receptor (HER2) immunonanoshells, HER2-expressing SK-BR-3 breast carcinoma cells were seeded alone or adjacent to human dermal fibroblasts (HDFs). Anti-HER2 immunonanoshells bound to HER2-expressing cells resulted in the death of SK-BR-3 cells after NIR exposure only within the irradiated area, while HDFs remained viable after similar treatment since the immunonanoshells did not bind to these cells at high levels. Control nanoshells, conjugated with nonspecific anti-IgG or PEG, did not bind to either cell type, and cells continued to be viable after treatment with these control nanoshells and NIR irradiation.     

Insights on cryoprotectant toxicity from gene expression profiling of endothelial cells exposed to ethylene glycol

Cryopreservation consists of preserving living cells or tissues generally at −80 °C or below and has many current applications in cell and tissue banking, and future potential for organ banking. Cryoprotective agents such as ethylene glycol (EG) are required for successful cryopreservation of most living systems, but have toxic side effects whose mechanisms remain largely unknown. In this work, we investigated the mechanisms of toxicity of ethylene glycol in human umbilical vein endothelial cells (HUVECs) as a model of the vascular endothelium in perfused organs. Exposing cells to 60% v/v EG for 2 h at 4 °C resulted in only a slight decrease in subsequent cell growth, suggesting only modest toxicity of EG for this cell type. Gene expression analysis with whole genome microarrays revealed signatures indicative of a generalized stress response at 24 h after EG exposure and a trend toward partial recovery at 72 h. The observed changes involved signalling pathways, glycoproteins, and genes involved in extracellular and transmembrane functions, the latter suggesting potential effects of ethylene glycol on membranes. These results continue to develop a new paradigm for understanding cryoprotectant toxicity and reveal molecular signatures helpful for future experiments in more completely elucidating the toxic effects of ethylene glycol in vascular endothelial cells and other cell types.     

Fluorescent metal nanoshell and CK19 detection on single cell image

In this article, we report the synthesis strategy and optical properties of a novel type of fluorescence metal nanoshell when it was used as imaging agent for fluorescence cell imaging. The metal nanoshells were made with 40 nm silica cores and 10 nm silver shells. Unlike typical fluorescence metal nanoshells which contain the organic dyes in the cores, novel metal nanoshells were composed of Cy5-labelled monoclonal anti-CK19 antibodies (mAbs) on the external surfaces of shells. Optical measurements to the single nanoparticles showed that in comparison with the metal free labelled mAbs, the mAb-Ag complexes displayed significantly enhanced emission intensity and dramatically shortened lifetime due to near-field interactions of fluorophores with metal. These metal nanoshells were found to be able to immunoreact with target cytokeratin 19 (CK19) molecules on the surfaces of LNCAP and HeLa cells. Fluorescence cell images were recorded on a time-resolved confocal microscope. The emissions from the metal nanoprobes could be clearly isolated from the cellular autofluorescence backgrounds on the cell images as either individuals or small clusters due to their stronger emission intensities and shorter lifetimes. These emission signals could also be precisely counted on single cell images. The count number may provide an approach for quantifying the target molecules in the cells.     

Cytotoxic effects of cladribine and tezacitabine toward HL-60

The aim of the study was to determine the relation between the cytotoxic and cytostatic effects of tezacitabine and cladribine on a HL-60 cell line and the time of exposure of cells to these drugs. Cell viability and induction of apoptosis were assessed using flow cytometry methods. Apoptosis was confirmed by direct microscopic observation. Growth inhibition was examined by cell counting. After 24 h incubation tezacitabine was equally or less toxic compared to cladribine. However, toxicity of tezacitabine strongly rose after 48 h incubation leading to massive cell death at doses much lower than those of cladribine. Assessment of the effect of increased exposure time on the clinical efficacy of tezacitabine is indicated.     

On-line monitoring of adhesion and proliferation of cultured hepatoma cells using optical waveguide lightmode spectroscopy (OWLS)

Monitoring of cell adhesion, cell spreading, and cell proliferation opens attractive perspectives in the on-line control of monolayer cell cultures in toxicity tests, in bioreactors as used for the serial production of skin grafts, or in extracorporeal liver devices. In this study the hepatoma Hep G2 cell adhesion and proliferation was monitored using an integrated optical method, optical waveguide lightmode spectroscopy (OWLS). This method is based upon refractive index measurements within a 100-nm thin layer above a Si(Ti)O(2) surface on which the cells were cultured and exposed to cytotoxic and cytostatic agents. The OWLS signal was proportional to cell density during the spreading period (4 h), and in long-term experiments (46 h) the OWLS signal correlated on a logarithmic scale with cell density. After administration of the protein synthesis inhibitor cycloheximide (4 microg/mL) to fully spread hepatoma cells, cell growth was arrested and change of the OWLS signal became noticeable within 6 h after drug administration. For exposure to increasing concentrations of the anticancer drug cyclophosphamide (2.5-20 mM) a concentration-dependent reduction of the OWLS signal was found. For cycloheximide and cyclophospamide the OWLS signal was also confirmed by cell viability measurements using the neutral red assay, the thiazolylblue tetrazoliumbromide assay, total protein measurements, and cell morphology. It was demonstrated that the OWLS signal detects minor changes in cell adhesion, which serve as indicators of metabolic state and growth behavior. OWLS is thus a quantitative tool to characterize impaired cell growth mediated by culture medium, by extracellular matrix, or after exposure to a toxin.     

Plasmonic Heating-Assisted Transformation of SiO2/Au Core/Shell Nanospheres (Au Nanoshells): Caveats and Opportunities for SERS and Direct Laser Writing

The selective modification of silica/gold nanospheres (gold nanoshells) driven by plasmonic heating is demonstrated. Direct laser writing and reshaping of nanoshell assemblies can be easily controlled and exploited for nanofabrication purposes. The modified nanoshells exhibit improved surface enhanced Raman scattering, allowing to settle most of the issues related to nanoshell stability under working conditions.

Neuroprotective effects of erythropoietin on 6-hydroxydopamine-treated ventral mesencephalic dopamine-rich cultures

Parkinson's disease (PD) is a neurodegenerative disorder with motor symptoms caused by the loss of dopaminergic (DA) cells and consequently dopamine release in the nigrostriatal system. In vivo and in vitro 6-hydroxydopamine (6-OHDA) PD models are widely used to study the effect of striatal dopamine depletion as well as novel neuroprotective or restorative therapeutic strategies for PD. In the present study, we investigated in vitro the toxicity of 6-OHDA on DA neurons derived from E14 rat ventral mesencephalon (VM) and the neuroprotective efficiency of erythropoietin (Epo) on VM-derived cell cultures against 6-OHDA toxicity. Using E14 VM-derived DA-rich primary cultures, we could demonstrate that 6-OHDA toxicity works in a time-and concentration-dependent way, and leads to cell death not only in DA cells but also in non-DA cells in direct relation to concentration and incubation times. In addition, we found that 6-OHDA toxicity induces caspase-3 activation and an increment of intracellular reactive oxygen species (ROS) in VM-derived cultures. When 6-OHDA-treated VMs were cultured in the presence of the anti-apoptotic protein erythropoietin (Epo), the total neuronal population, including the DA neurons, was protected. However, untreated VM cultures exposed to Epo showed an increase in the total neuronal population, but not an additional increase in DA neuron cell number.These findings suggest that 6-OHDA toxicity is time and concentration-dependent and does not exclusively affect DA neurons. In high concentration and long incubation times, 6-OHDA influences the survival of other neuronal and non-neuronal cell populations derived from the VM cultures. 6-OHDA toxicity induces caspase-3 activation, indicating cell death via the apoptotic pathway which could be restricted or even prevented by pre-exposure to Epo, known to interact via the apoptotic pathway. Our results support and expand on previous findings showing that Epo is an interesting candidate molecule to mediate neuroprotective effects on DA neurons in PD. Furthermore, it could be used in promoting the survival of DA neurons after transplantation in clinical trials.     

Near- and Far-Field Plasmonic Properties of Different Types of Eccentric Core-Shell Nanodimers

Finite element method (FEM) simulations have been carried out on free-standing and finite dielectric substrate-supported eccentric (i) silica core-gold nanoshell dimers and (ii) gold core-silica nanoshell dimers for understanding their near- and far-field plasmonic properties. In the case of eccentric silica core-gold nanoshell dimers, multiple peaks are observed in the near- and far-field spectra due to the plasmon hybridization. The number of peaks is found to be sensitive to the core offset parameters of the nanoshells forming nanodimer. The wavelength locations of the peaks due to the constructive coupling of the lower order modes found relatively more sensitive to the dielectric substrate. The number of peaks in the near- and far-field spectra found the same presence and absence of the dielectric substrate. The values of full width at half maximum (FWHM) of the peaks observed in the near-field spectra are found larger as compared to those observed in the far-field spectra. In contrast, in the case of eccentric gold core-silica nanoshell dimers, multiple peaks have not been observed. The FWHM of the observed peak is found sensitive to the core offset parameters of the nanoshells, and the number of peaks in the near field- and far-field spectra found not same in the presence and absence of the dielectric substrate. Moreover, the differences in near- and far-field spectra of plasmonically coupled (i) concentric nanoshells, (ii) eccentric nanoshells, and (iii) concentric and eccentric nanoshells also investigated numerically.

     

Specific antitumor targetable beta-cyclodextrin-poly(ethylene glycol)-folic acid drug delivery bioconjugate

The tumor targeting properties of a new drug carrier synthesized by bioconjugation of folic acid (FA) to beta-cyclodextrins through a poly(ethylene glycol) (PEG) spacer (CD-PEG-FA) were investigated. Surface plasmon resonance demonstrated that CD-PEG-FA specifically interacts with immobilized folate binding protein (FBP) while the naked beta-cyclodextrins do not display any specific interaction. In vitro studies demonstrated that CD-PEG-FA was devoid of cell toxicity. [(3)H]-folic acid/CD-PEG-FA competition binding investigations performed with folate receptor overexpressing human epidermal carcinoma KB cells showed that CD-PEG-FA had about 14 times lower tumor cell binding capacity than free folic acid. The carrier cell trafficking properties were investigated using rhodamine-B as fluorescent probe, which possesses 3000 and 4580 M(-)(1) inclusion constants for CD-PEG-FA and beta-cyclodextrins, respectively. Cell-associated fluorescence measurements showed that CD-PEG-FA does not promote the rhodamine-B uptake into non-folate receptor expressing human lung carcinoma MCF7 cells while 19% higher accumulation in KB cells was found with respect to rhodamine-B loaded beta-cyclodextrins. Confocal laser scanning microscopy indicated the presence of cytosolic red fluorescent spots after 2 h of incubation of KB cells with rhodamine-B included CD-PEG-FA. The fluorescent dye resided primarily in small spots, namely, endosomes and multivesicular bodies. At 1 h after pulsed incubation, wider red fluorescent cellular structures appeared as a fusion of previous structures.     

Cytostatic activity of in vitro generated macrophages: evidence for a prostaglandin-independent reversible cytostatic mechanism

Culture of spleen cells for 5 days has previously been shown to result in the generation of strongly adherent cells from nonadherent precursors. In the current report it is shown that the majority (85-95%) of adherent cells are Mac-1+, FcR+, Thy 1.2- macrophages. Expression of effector activity by these macrophages requires exposure to activating signals. Coculture of the macrophages with Con A-stimulated spleen cells results in the expression of cytostatic activity against lymphocytic and monocytic tumor cell lines. Significant cytostatic activity is apparent within 6 hr after addition of the activating cells. Culture supernates of Con A-stimulated spleen cells (CAS-CM) are not effective in inducing cytostatic activity in the adherent macrophage population either alone or in the presence of additional Con A. However, stimulation of the culture generated macrophages with LPS in the presence of CAS-CM does induce cytostatic activity. The effector cell must be metabolically active in order to effect cytostasis insofar as heat fixation of the culture generated macrophage population eliminates effector activity. Proliferation of the tumor cells is significantly reduced after a 4-hr incubation period with the activated macrophages and is reduced two- to threefold after an 8- to 12-hr incubation period. The cytostatic effect is rapidly reversible. Proliferative activity of the tumor cells returned to control level within 12-24 hr after removal from activated macrophages. Cell cycle analysis indicated that the target cells were not arrested in a single stage of cell cycle, although an increase in frequency of cells in G1-phase was observed. Fluorescence analysis of bromodeoxyuridine (BrdU) incorporation rate demonstrated that the rate of DNA synthesis was reduced in all of the cells in the target population and that the mean rate of BrdU incorporation of the inhibited cells was three- to fivefold lower than control cells. RNA and protein synthesis were not affected to the same degree as DNA synthesis. The cytostatic effect was not mediated by prostaglandins or thymidine insofar as addition of indomethacin and 2-deoxycytidine did not prevent the cytostatic activity of the macrophages. The supernates of activated macrophages contained little inhibitory activity especially when indomethacin was included in the culture medium (19% inhibition of tumor cell proliferation by 1:1 dilution of supernate). The activity that was present could be eliminated by dialysis against fresh culture medium using Spectropor membranes with a 1000-Da molecular cutoff.(ABSTRACT TRUNCATED AT 400 WORDS)     

The induction of oxidative stress and cellular death by the drinking water disinfection by-products,dichloroacetate and trichloroacetate in J774.A1 cells

The in vitro toxicity of the drinking water disinfection by products dichloroacetate (DCA) and trichloroacetate (TCA) were studied using the J774A.1 macrophage cell line. DCA and TCA were added to cell cultures at concentrations ranging between 8-32 mM and incubated for 24, 36 and 60 h. DCA and TCA effects on cellular viability, lactate dehydrogenase (LDH) release and superoxide anion (SA) production by the cells, as well as superoxide dismutase (SOD) activities of the cells were determined. DCA and TCA caused time- and concentration-dependent increases in cellular death, in LDH release and production of SA by the cells. The compounds also caused modulations in SOD activities of the cells, with increases observed at the lower concentrations and/or shorter periods of incubations and suppression with the higher concentrations and/or longer periods of incubation. The results of the study indicate that DCA and TCA induce macrophage activation and that the activation is associated with cellular toxicity. Also, DCA and TCA are found to be equitoxic to J774.A1 cells.     

Diclofenac toxicity in Gyps vulture is associated with decreased uric acid excretion and not renal portal vasoconstriction

Diclofenac (DF), a non-steroidal anti-inflammatory drug (NSAID), is largely regarded as one of the most devastating environmental toxicant in recent times, after accidental exposure via their food-chain lead to massive mortalities in three vulture species on the Asian subcontinent. Although the use of diclofenac was recently banned on the Indian subcontinent, following the favourable safety profile of meloxicam, its mechanism of toxicity remains unknown. In an attempt to establish this mechanism, we test three hypotheses using models established from either the domestic chicken (Gallus domesticus) or the African White-backed vulture (Gyps africanus). We demonstrate that both DF and meloxicam are toxic to renal tubular epithelial (RTE) cells following 12 h of exposure, due to an increase in production of reactive oxygen species (ROS), which could be temporarily ameliorated by pre-incubation with uric acid (UA). When cultures were incubated with either drug for only 2 h, meloxicam showed no toxicity in contrast to diclofenac. In both cases no increase in ROS production was evident. In addition, diclofenac decreased the transport of uric acid, by interfering with the p-amino-hippuric acid (PAH) channel. We conclude that vulture susceptibility to diclofenac results from a combination of an increased ROS, interference with UA transport and the duration of exposure.     

Proanthocyanidins suppress NLRP3 inflammasome and M1 macrophage polarization to alleviate severe acute pancreatitis in mice

The role of reactive oxygen species (ROS) is crucial for the pathogenesis of acute pancreatitis (AP). Proanthocyanidins (PAs) have been confirmed to exert antioxidant activity. Our study aimed to determine whether PAs alleviated SAP via reducing ROS, suppressing NLRP3 inflammasome, and inhibiting M1 macrophage polarization. Our study investigated the protective effects of PAs on pancreatic histopathological injury using SAP mice. The effects of PAs on macrophages were investigated in inflammatory RAW 264.7 cells or mouse bone marrow-derived macrophages (BMDMs) induced by lipopolysaccharide (LPS). Immunofluorescence staining and/or western blot assay were employed to evaluate NLRP3 inflammasome in macrophages and pancreatic tissue. Cell counting kit-8 (CCK-8) was used to access effects of PAs on cell viability and cytometry flow was used to determine the effects of the PAs on the ROS levels of the RAW 264.7 cells. Then, we evaluated M1 macrophage polarization using flow cytometry or real-time quantitative polymerase chain reaction (RT-qPCR). PAs administration alleviated pancreatic inflammation in SAP mice. The PAs depressed NLRP3 inflammasome and inhibited M1 macrophage polarization in pancreatic tissue. We also found that the PAs showed no cellular toxicity but decreased ROS levels in RAW 264.7 cells, downregulated the NLRP3 inflammasome in the macrophages, and inhibited cell M1 macrophage polarization. Our study indicates the anti-inflammatory properties of the PAs on SAP mice by decreasing ROS levels, suppressing NLRP3 inflammasome, and M1 macrophage polarization.     

Kolaviron and selenium reduce hydrogen peroxide-induced alterations of the inflammatory response

The abilities of kolaviron and selenium (either separately or in combination) to prevent hydrogen peroxide-induced alterations in cell viability and activation were investigated. The cell line U937 was incubated with the antioxidants (i.e. kolaviron or selenium) for 24?h before exposure to hydrogen peroxide and cell viability was assessed via trypan blue dye exclusion assay. The U937 cells were also transformed to the macrophage form, incubated with the antioxidants before exposure to hydrogen peroxide. Subsequently, production of nitric oxide and pro-inflammatory cytokines were assessed as indices of macrophage activation. The myoblast cell line H9c2 was also incubated with Se and kolaviron for 24?h before exposure to hydrogen peroxide. Cell viability and generation of reactive oxygen species (ROS) were assessed via MTT and DCHF assays. The results revealed that hydrogen peroxide significantly reduced (p?<?0.05) the viability of U937 cells which was ameliorated by kolaviron and selenium. Kolaviron and selenium also reduced hydrogen peroxide-induced secretion of nitric oxide, TNF-α, IL-1 and IL-6 by transformed U937 cells. Hydrogen peroxide also significantly reduced (p?<?0.05) the viability of H9c2 cells which was significantly restored by kolaviron. Though selenium had no effect on the proliferation of H9c2 cells, co-treatment with kolaviron significantly reduced hydrogen peroxide-induced alterations. Both kolaviron and selenium also reduced hydrogen peroxide-mediated ROS production by H9c2 cells. In all cases, the combined action of kolaviron and selenium offered greater amelioration of the hydrogen peroxide-induced alterations than their separate effects (p?<?0.05) but may not be synergistic or additive.     

Intracellular degradation of microspheres based on cross-linked dextran hydrogels or amphiphilic block copolymers: a comparative raman microscopy study

Micro- and nanospheres composed of biodegradable polymers show promise as versatile devices for the controlled delivery of biopharmaceuticals. Whereas important properties such as drug release profiles, biocompatibility, and (bio)degradability have been determined for many types of biodegradable particles, information about particle degradation inside phagocytic cells is usually lacking. Here, we report the use of confocal Raman microscopy to obtain chemical information about cross-linked dextran hydrogel microspheres and amphiphilic poly(ethylene glycol)-terephthalate/poly(butylene terephthalate) (PEGT/PBT) microspheres inside RAW 264.7 macrophage phagosomes. Using quantitative Raman microspectroscopy, we show that the dextran concentration inside phagocytosed dextran microspheres decreases with cell incubation time. In contrast to dextran microspheres, we did not observe PEGT/PBT microsphere degradation after 1 week of internalization by macrophages, confirming previous studies showing that dextran microsphere degradation proceeds faster than PEGT/PBT degradation. Raman microscopy further showed the conversion of macrophages to lipid-laden foam cells upon prolonged incubation with both types of microspheres, suggesting that a cellular inflammatory response is induced by these biomaterials in cell culture. Our results exemplify the power of Raman microscopy to characterize microsphere degradation in cells and offer exciting prospects for this technique as a noninvasive, label-free optical tool in biomaterials histology and tissue engineering.     

The phagocytosis and toxicity of amorphous silica

Background

Inhalation of crystalline silica is known to cause an inflammatory reaction and chronic exposure leads to lung fibrosis and can progress into the disease, silicosis. Cultured macrophages bind crystalline silica particles, phagocytose them, and rapidly undergo apoptotic and necrotic death. The mechanism by which particles are bound and internalized and the reason particles are toxic is unclear. Amorphous silica has been considered to be a less toxic form, but this view is controversial. We compared the uptake and toxicity of amorphous silica to crystalline silica.

Methodology/Principal Findings

Amorphous silica particles are phagocytosed by macrophage cells and a single internalized particle is capable of killing a cell. Fluorescent dextran is released from endo-lysosomes within two hours after silica treatment and Caspase-3 activation occurs within 4 hours. Interestingly, toxicity is specific to macrophage cell lines. Other cell types are resistant to silica particle toxicity even though they internalize the particles.The large and uniform size of the spherical, amorphous silica particles allowed us to monitor them during the uptake process. In mCherry-actin transfected macrophages, actin rings began to form 1-3 minutes after silica binding and the actin coat disassembled rapidly following particle internalization. Pre-loading cells with fluorescent dextran allowed us to visualize the fusion of phagosomes with endosomes during internalization. These markers provided two new ways to visualize and quantify particle internalization. At 37°C the rate of amorphous silica internalization was very rapid regardless of particle coating. However, at room temperature, opsonized silica is internalized much faster than non-opsonized silica.

Conclusions/Significance

Our results indicate that amorphous and crystalline silica are both phagocytosed and both toxic to mouse alveolar macrophage (MH-S) cells. The pathway leading to apoptosis appears to be similar in both cases. However, the result suggests a mechanistic difference between FcγRIIA receptor-mediated and non-opsonized silica particle phagocytosis.     

Evaluation of oxidative status in acetaminophen treated rat hepatocytes in culture

The present study describes the estimation of acetaminophen (AAP) toxicity in cultured rat hepatocytes. We used different concentrations of AAP - 1, 2.5, 5, 10 and 20 mM, to test influence of AAP on cellular viability, functional capacity and oxidative status at given time intervals. WST 1 test showed decrease of dehydrogenase activity in 5, 10 and 20 mM AAP to 75 % of control values after 1 hour of incubation. At 12 h of treatment, all AAP concentrations decreased WST-1 signal; no enzyme activity was found since 18 h in cells treated with 20 mM AAP according to LDH leakage test performed at 24 h of incubation. Functional capacity was tested by albumin assay where the decrease was strictly related to AAP dose. Intracellular oxidative status was assessed by analysis of GSH/GSSG levels and time course of ROS production and glutathione reductase (GR) activity. Increased ROS production was found already after 3 h of incubation in 2.5, 5, 10 and 20 mM AAP, respectively. The highest ROS production was measured after 12 h treatment. GR activity was decreased already after 3 h of incubation and remained also decreased in cells treated with 2.5, 5, 10 and 20 mM AAP during further incubation.     

Autoradiographic method for detection of lactate dehydrogenase-elevating virus-infected cells in primary mouse macrophage cultures.

Peritoneal cells from starch-injected Swiss mice were propagated in plastic petri dishes and on cover slips in a mouse L-cell-conditioned medium for 12 to 24 h and then infected with various multiplicities of lactate dehydrogenase-elevating virus (LDV). Over 95% of the cells in these cultures phagocytosed latex particles and were, therefore, considered macrophages. Infected and mock infected macrophage cultures were supplemented with [3H]uridine at various times after infection and with actinomycin D 30 min before addition of the [3H]uridine. After 1 or 2 h of further incubation, plate cultures were analyzed for LDV-specific RNA, and cover slip cultures were investigated by autoradiography. Other cultures were labeled in the absence of actinomycin D, and the culture fluid was analyzed for labeled LDV. There was a good correlation between the production of LDV-specific RNA and LDV and the number of heavily labeled cells in these cultures. The labeled cells in these cultures. The labeled cells, therefore, were equated with productively infected cells. Only a maximum of about 20% of the macrophages, however, became heavily labeled regardless of the multiplicity of infection or the time, after infection, at which the cells were exposed to [3H]uridine. Only background labeling was observed in the remainder of the cells and in mock-infected cells treated with actinomycin D. The highest proportion of labeled cells was observed when the cells were infected with a multiplicity of infection of about 2,000 mouse infectious units per cell and labeled from 6 to 8 h after infection. Thereafter, the proportion of productively infected cells decreased progressively, concomitant with a decrease in the amounts of viral specific RNA and of LDV produced by the cultures. The results indicate that the majority of the macrophages in primary macrophage cultures do not support LDV replication. Their nonpermissiveness may depend on the physiological state of the cells or reflect the presence of subpopulations of macrophages, but no morphological differences between productively infected an uninfected cells were detectable.     

Cytofluorometric studies on the action of podophyllotoxin and epipodophyllotoxins (VM-26, VP-16-213) on the cell cycle traverse of human lymphoblasts

Flow microfluorometric analysis of human lymphoid cells exposed in vitro to cytostatic concentrations of podophyllotoxin (0.01-5 mug/ml for 24 h) shows that a major part of this population (40-60%) has the DNA content of cells in the G2-M part of the cell cycle, and that approximately 60% of these cells are arrested in mitosis. Although a similar pattern of DNA distribution is seen in cultures exposed to cytostatic concentrations of VM-26(0.01 mug/ml) and VP--16-213(0.1 mug/ml), no mitotic cells are seen in these cultures. Exposure to higher concentrations: of VM-26 (0.1 mug/ml) and VP-16-213 (1.0 mug/ml) inhibits cell cycle traverse, and after 24 hr of exposure a major part of the population is arrested with the DNA content of cell in the S part of the cell cycle. Exposure to higher drug concentrations leads to a reduction in the number of cells with the late S-G2DNA content. Whereas the cell cycle block induced by cytostatic concentrations of podophyllotoxin (0.01 mug/ml) is readily reversible by reincubation of cells in drug-free medium, cells blocked by VM-26 and VP-16-213 are unable to resume cell-cycle traverse under similar conditions.     

In vitro effects of human recombinant alpha-2b interferon on Ph1+ chronic myelogenous leukemia cells maintained in long term marrow cultures: a functional and morphological analysis

In this study in vitro results obtained with hu rec IFN-alpha 2b on Ph1+ stem cells from patients with chronic myelogenous leukemia in chronic phase (CML in CP) will be discussed: cells were incubated with different IFN concentrations (100, 1000, 10000 IU/ml) for different times (24, 96 hrs, 8, 15, days) and maintained in long term marrow cultures (LTMC); CFU-GM assay, cytochemistry and cytogenetic analyses were performed weekly. A high sensitivity of CML cells to the in vitro treatment with IFN was observed. Cell count in LTMC showed a progressive reduction inversely proportional to time of incubation and concentration of IFN; a marked decrease in colony growth was observed at the end of incubations and during the course of LTMC. Low concentrations of IFN permitted a morphological maturation and the expression of alkaline phosphatase. Cytogenetic analyses showed a marked reduction of mytoses in cultures treated with high concentrations of IFN as result of a combined cytostatic and cytolitic effect; the persistance of 100% Ph1+ cells in LTMC and in CFU-GM colonies might be related, as opposed to in vivo results, to different IFN exposure conditions or might be influenced by other factors.