Effect of treatment of shell vial cell cultures with dimethyl sulfoxide and dexamethasone and age of MRC-5 monolayers for detection of cytomegalovirus

Pretreatment of MRC-5 cell monolayers in commercially prepared shell vials with 1% dimethyl sulfoxide (DMSO) and 10(-5) mol/L dexamethasone (DEX) was evaluated. Preliminary experiments indicated enhanced infectivity of AD-169 for pretreated MRC-5 cells in shell vials of ages 9 and 16 days. Compared with untreated shell vials, DMSO-DEX increased positivity (day 9, 19 vs. 26 shell vials, p less than 0.03; day 16, 13 vs. 29 shell vials, p less than 0.001) and increased the mean number of fluorescent foci (days 9 and 16, p less than 0.001). Pretreatment of 8-15-day-old monolayers was evaluated clinically using 146 urine specimens. Fifty specimens were positive for cytomegalovirus (CMV) in both treated and untreated shell vials with ten positive in untreated only and three positive in treated only (p = NS). The median number of fluorescent foci was not significantly higher in treated shell vials. Increased toxicity of MRC-5 cells was observed in treated monolayers (p less than 0.0001). Pretreatment with DMSO-DEX did not enhance CMV isolation from clinical specimens and can be toxic to MRC-5 monolayers.

Lineage directed HL-60 cell sublines as a model system for the study of early events in lineage determination of myeloid cells

Current experimental models are poorly suited to study the early biochemical and molecular events of the lineage determination process in myeloid progenitor cells. Viable lineage-committed precursors cannot be identified until after they have expressed their mature phenotype and these precursors cannot be grown to large number while lineage is committed but still immature. Recently, we have identified stable sublines of the HL-60 human leukemia cell line which differ from each other in that they selectively differentiate to either neutrophils (UR-1-4), monocyte/macrophages (MRI), eosinophils (clones 2 and 15), or mixtures of two (clones 7 and 8) or of all three lineages (UR-1-2) when stimulated to mature with butyric acid under identical conditions. Characterization of these sublines provided evidence that the expression of lineage in HL-60 cells is a multistep process and that the lineage tendencies (lineage direction) the clones exhibited when cultured with butyric acid represent a step in that process earlier than irreversible lineage commitment but later than the multipotential wild type HL-60 cells. First, treatment of these sublines with compounds that induce differentiation of HL-60 cells to specific lineages (dimethylsulfoxide, neutrophil; 1,25-(OH)2 vitamin D3, monocyte), generally induced differentiation to the lineage associated with that inducer rather than the butyrate-associated lineage. Second, culture of neutrophil or monocyte-directed sublines in medium of elevated pH for two months leads to the development of eosinophils. Culturing the sublines first in butyric acid for variable lengths of time and switching to either DMSO or VD3 indicated that irreversible lineage commitment develops on a time course similar to the development of the commitment to mature. Markers of monocytic and eosinophilic differentiation could not be simultaneously demonstrated in single mature cells, consistent with the phenomenon of lineage fidelity. In addition, several assays were validated that could reliably classify mature HL-60 cells to their lineage. The collection of these sublines appears to constitute a model system with well-defined behavior with respect to the early events of lineage determination that can be grown to quantities sufficient for biochemical and molecular analysis. Exploring the differences between these clones may provide a new way to examine the early events of the lineage development process in myeloid cells.

Modifications of microfilaments and microtubules induced by two hepatic tumor promoters, phenobarbital and biliverdin in non-transformed and transformed hepatic cell lines

Microfilaments and microtubules are components of the cytoskeleton which could be implicated in neoplastic transformation. We studied the effect of two hepatic tumor promoters, phenobarbital (PB) and biliverdin (BV), on microfilaments and microtubules of non-transformed (Cl3) and transformed (FV) hepatic epithelial cells. Cl3 non-transformed cells cultured in the presence of 1 X 10(-6) M BV for 48 h showed a loss of F-actin, fragmentation of actin and the appearance of star-like structures in the cytoplasm, as well as loosening of the peripheral bundle of actin, and some ruffling of cell membranes. In Cl3 cells exposed to 0.2 X 10(-3) M PB a similar disappearance of F-actin staining and a very prominent ruffling of cell membrane were observed. BV and PB also produced in these cells modifications of microtubules characterized by a disappearance of centrosome staining in numerous cells, a condensed ring of tubulin around the nucleus and a depolymerized aspect of the microtubular network. All these modifications of microfilaments and microtubules closely resembled those observed in FV transformed cells in the absence of any treatment (Solvent DMSO only). We did not observe an effect of BV and PB on FV cells. The present data demonstrate that the cytoskeleton of non-transformed epithelial liver cells is sensitive to the action of liver tumor promoters suggesting that it might play a role as to yet be defined in the promotion mechanism.

Butyrate induces expression of transfected human fetal and endogenous mouse embryonic globin genes in GM 979 erythroleukemia cells

We have analyzed the expression of endogenous murine genes and of transfected human fetal A gamma globin gene in GM 979, a mouse erythroleukemia line which produces adult as well as embryonic globins. Optimal induction of the endogenous murine adult globin genes was obtained with DMSO or HMBA while the epsilon y and beta h1 embryonic genes were preferentially induced by butyrate. Similarly, the transferred human A gamma-globin gene was preferentially induced by butyrate. These results as well as previous observations in vivo or in erythroid cell cultures suggest that butyrate preferentially induces the expression of fetal globin genes.

Specific effects of retinoic acid on the skeletal morphogenesis of the 11-day mouse embryo forelimb bud in vitro

Using our improved method for culturing 11-day mouse forelimb buds in vitro, we have investigated the effects of a local application of all-trans-retinoic acid (RA) on growth, cartilaginous differentiation and skeletal patterning in the mammalian limb bud. Carrier implants of catgut impregnated with DMSO or various doses of RA in DMSO were inserted at the apex of the buds in the proximo-distal axis just beneath the apical ectodermal ridge. After 6 days of culture, cartilaginous skeletons were stained and explants were processed for morphological analysis and quantitative study using computerized optical image analysis. Buds treated with low doses of RA exhibited stimulated growth and chondrogenesis. Moreover, hypertrophied and fused metacarpals were seen within explants treated with the lowest dose. High doses strongly inhibited growth and skeletal morphogenesis. An intermediate dose sustained cartilaginous differentiation at the same level as low doses, but concomitantly disturbed the skeletal pattern. These results are discussed considering reported RA effects on other experimental systems including avian limb bud as an in vivo model or cell cultures as an in vitro simplified model.

Dimethyl sulfoxide elevates intracellular Ca2+ and mimics effects of increased light intensity in a photoreceptor

A 1% (v/v) solution of dimethyl sulfoxide (DMSO) added to the saline bath of isolated Balanus eburneus photoreceptors increased receptor potential amplitude by 40-50% and shortened time to peak amplitude and latency by 20-25%. The light-sensitive membrane current of voltage-clamped cells was increased systematically as DMSO concentration was increased from 1% to 10%. The null potential of the light sensitive current was unaffected by DMSO with short pulses of light, indicating that DMSO has no direct effect on ion selectivity of the light-sensitive channel. Absorbance changes of cell injected with the calcium indicator arsenazo III show that DMSO elevates intracellular Ca2+ (Cai). Current-voltage relations in darkness reveal that DMSO induces a small sustained inward current (approximately 5 nA) which has a null potential similar to the light-induced current. DMSO may activate the light-sensitive conductance via the increase in Cai. However, the altered kinetics and increased amplitude of the receptor current are opposite to the desensitizing effects normally observed with increased Cai.

Enhancement of the in vitro skin permeability of azidothymidine (AZT) via iontophoresis and chemical enhancer

Azidothymidine (AZT) was used as a model drug to study the effect of iontophoresis on the skin permeation of a neutral compound. The rate of in vitro permeation across hairless rat skin was low and highly variable. With iontophoresis treatment the permeation rate was two- to threefold greater than by passive diffusion. The addition of varying amounts of sodium chloride to the donor enhanced the iontophoretic permeation rate an additional two- to threefold possibly due to convective forces. The addition of N-decylmethyl sulfoxide (C10MSO) to the donor increased the permeation rate by several hundred-fold over passive diffusion for hairless rat skin and approximately 75-fold for human skin. No additional enhancement was observed with the combination of C10MSO and iontophoresis treatment at constant current or constant voltage. It may be that the presence of C10MSO lowers the zeta potential of the skin, thus enhancement due to convective flow is minimized.

Hydroxyl radical generation by postischemic rat kidney slices in vitro

To quantitate the formation of hydroxyl radicals (HO.) in ischemia and reoxygenation, dimethyl sulfoxide (DMSO) was added to "trap" evolving HO. in normal, in ischemic, and in ischemic and reoxygenated rat kidney slices, incubated in short-term organ culture in vitro. Hydroxyl radical generation was measured as the accumulation of the specific product of DMSO oxidation by HO., methane sulfinic acid (MSA) in the kidney tissue and surrounding medium using a new colorimetric assay. A mean difference of 7 nmol cumulative HO./gram tissue was detected in rat kidney slices subjected to ischemia and reoxygenation. This amount of HO. generation was not significantly greater than that found in nonischemic or in ischemic but not reoxygenated control tissues, and does not appear to represent the highly toxic burst of HO. radicals implied in current theoretical discussions of reperfusion injury. However, the addition of EDTA chelated iron (1:1) to the incubation medium led to marked postischemic HO. generation. We conclude that clearly toxic numbers of HO. radicals are not formed during reoxygenation in rat kidney slices, either because there is insufficient iron, because only a small fraction of cells in the kidney tissue make oxygen radicals, or because cellular defenses against HO. formation are more powerful than currently appreciated.

Inhibition of cytotoxicity by intracellular superoxide dismutase supplementation

The role of intracellular oxyradicals in H2O2 and neutrophil-induced cytotoxicity is suggested by previous studies showing protection by inhibitors such as deferroxamine, dimethylthiourea, and dimethyl sulfoxide. In the current studies, the role of intracellular O2- is specifically examined by evaluating the effects of intracellular superoxide dismutase (SOD) supplementation on cytotoxicity of rat pulmonary artery endothelial cells induced by H2O2 and activated neutrophils. To minimize in vitro manipulation, supplementation was accomplished by incubating endothelial cells in the presence of SOD (1-20 mg/mL). Increases up to greater than 17-fold the baseline SOD activity were achievable using this approach, with uptake being maximal after 6 h of incubation. This increase was resistant to trypsin digestion, suggesting the intracellular location of SOD. Compared to controls, SOD-supplemented cells showed significantly increased resistance to killing by H2O2 and activated neutrophils. Inactive SOD failed to provide protection. The degree of protection was dependent on the dose of cytotoxic agent and the extent of SOD supplementation. The results provide new evidence that intracellular O2- participates in the killing process induced by these two stimuli. The intracellular source of O2- remains to be determined, although previous studies suggest xanthine oxidase as a likely candidate.

Effects of oxygen radical scavengers on the inactivation of SS phi X174 DNA by the semi-quinone free radical of the antitumor agent etoposide

We have studied the effects of oxygen radical scavengers on the inactivation of ss phi X174 DNA by the semi-quinone free radical of the antitumor agent etoposide (VP 16-213), which was generated from the ortho-quinone of etoposide at pH greater than or equal to 7.4. A semi-quinone free radical of etoposide is thought to play a role in the inactivation of ss phi X174 DNA by its precursors 3',4'-ortho-quinone and 3',4'-ortho-dihydroxy-derivative. The possible role of oxygen radicals formed secondary to semi-quinone formation in the inactivation of DNA by the semi-quinone free radical was investigated using the hydroxyl radical scavengers t-butanol and DMSO, the spin trap DMPO, the enzymes catalase and superoxide dismutase, the iron chelator EDTA and potassium superoxide. Hydroxyl radicals seem not important in the process of inactivation of DNA by the semi-quinone free radical, since t-butanol, DMSO, catalase and EDTA had no inhibitory effect on DNA inactivation. The spin trapping agent DMPO strongly inhibited DNA inactivation and semi-quinone formation from the ortho-quinone of etoposide at pH greater than or equal to 7.4 with the concomitant formation of a DMPO-OH adduct. This adduct probably did not arise from OH. trapping but from trapping of O2-(.). DMSO increased both the semi-quinone formation from and the DNA inactivation by the ortho-quinone of etoposide at pH greater than or equal to 7.4. Potassium superoxide also stimulated phi X174 DNA inactivation by the ortho-quinone at pH less than or equal to 7. From the present study, it is also concluded that superoxide anion radicals probably play an important role in the formation of the semi-quinone free radical from the ortho-quinone of etoposide, thus indirectly influencing DNA inactivation.

Fluorescence anisotropy of viruses treated with formaldehyde and dimethyl-sulfoxide

The fluorescence anisotropy changes observed in A-1 (H1N1) influenza and Sendai parainfluenza viruses in aqueous suspensions when formaldehyde (0.1 to 1.0 p.c.) and dimethyl-sulfoxide (0.3 to 5.0 p.c.) were added, using both intrinsic fluorescence of viral proteins and that of the membrane fluorescent probe--DPH, showed significant differences with regard to the virus and the history of the suspensions used, allowing under rigorous standardized conditions the use of fluorescence anisotropy measurements for viral antigen and vaccine control.

Effects of the monoamine oxidase inhibitor, tranylcypromine, on induction of HL60 cell differentiation by hexamethylene bisacetamide and N-acetyl-1,6-diaminohexane

Hexamethylene bisacetamide (HMBA) is converted by successive deacetylation and oxidation reactions to four major metabolites; in vitro, the initial deacetylated metabolite, N-acetyl-1,6-diaminohexane (NAD-AH), is more potent than HMBA (Synder, S.W.; Egorin, M.J.; Geelhaar, L.A.; Hamburger, A.W.; Callery, P.S. Cancer Res. 48:3613-3616; 1988). We propose that monoamine oxidase (MAO) catalyzed metabolism of NADAH to 6-acetamidohexanoic acid (AcHA) is an inactivation pathway and, therefore, investigated whether blocking such metabolism with the MAO inhibitor, tranylcypromine, would potentiate induction of cell differentiation by HMBA and NADAH. Tranylcypromine, at concentrations up to 30 micrograms/mL, did not inhibit HL60 cell growth and did not induce differentiation of HL60 cells. Tranylcypromine did, however, produce concentration-dependent enhancement of HMBA- and NADAH-induced differentiation. In contrast, 30 micrograms/mL of tranylcypromine did not effect the ability of dimethylsulfoxide, at concentrations between 0.25% and 1.25%, to induce differentiation of HL60 cells. Tranylcypromine, at 30 micrograms/mL, did not change cellular concentrations of HMBA or NADAH but did reduce intracellular concentrations of AcHA, consistent with inhibition of MAO catalyzed conversion of NADAH to AcHA. These results support the hypothesis that MAO catalyzed metabolism of NADH to AcHA is an inactivation pathway and may provide the basis for a clinical trail in which HMBA metabolism is modulated with concurrent tranylcypromine therapy.

Detection of hydroxyl radical in the mitochondria of ischemic-reperfused myocardium by trapping with salicylate

Although the presence of free radicals has been indicated in ischemic-reperfused heart, the exact nature and source of these free radicals are not known. The present study utilized a chemical trap, salicylic acid, to trap hydroxyl radical which could be detected as hydroxylated benzoic acid using high pressure liquid chromatography. Since the hydroxylated product is extremely stable, heart was subjected to subcellular fractionation after ischemia and reperfusion, and each fraction was separately examined for the presence of hydroxyl radical. The results indicated for the first time the presence of hydroxyl radical in the mitochondrial fraction during early reperfusion, which decreased in intensity as the reperfusion progressed.

Augmented production of platelet-activating factor in human polymorphonuclear leukocytes by ketone bodies

The production of platelet-activating factor (PAF) in A23187-stimulated human polymorphonuclear leukocytes was markedly increased in the presence of 5 mM acetoacetate and beta-hydroxybutyrate. Such an augmentation was observed even at 500 microM but not at 50 microM. The augmented production of PAF by acetoacetate was also observed in the presence of autologous serum and was most prominent in the case of opsonized zymosan-stimulation rather than A23187-stimulation. These observations suggest that increased levels of acetoacetate and beta-hydroxybutyrate in blood may lead to the augmented production of PAF, which would amplify the various PAF-mediated biological reactions.

Hypoxia increases plasma glutathione disulfide in rats

We tested the hypothesis that hypoxia causes cellular oxidative stress by measuring plasma concentrations of glutathione disulfide (GSSG) in rats exposed to acute and subacute hypoxia. In awake, unanesthetized, catheter-implanted rats, exposure to 8% O2 for 10 min caused pulmonary vasoconstriction and increased plasma GSSG. This increase in plasma GSSG was reversible upon re-exposure to room air. In another group of rats exposed to 48 hours of hypobaric hypoxia (Pb 450 mmHg, equivalent to about 14,500 feet altitude), plasma GSSG, but not total glutathione, was significantly increased over control values (2.83 +/- 0.24 vs 1.84 +/- 0.14 nmol/ml, p less than 0.05). While lung tissue GSSG in high altitude-exposed rats were somewhat higher than in controls (17.4 +/- 7.0 vs 11.9 +/- 3.6 nmol/g wet lung wt.), the difference was not statistically significant. Treatment of the rats with a radical scavenger, DMSO, before altitude exposure, blocked the increase in plasma GSSG (1.86 +/- 0.16 nmol/ml). We conclude that both acute and subacute hypoxia increase plasma GSSG in rats and speculate that hypoxia induces cellular oxidative stress in vivo.

Multiple sequential periods of DNA synthesis and quiescence in primary hepatocyte cultures maintained on the DMSO-EGF on/off protocol

Repeated periods of DNA synthesis activity (each period consisting of two to three cycles) separated by intervals of quiescence in primary rat hepatocytes can be stimulated by sequential addition and removal of 2% dimethyl sulfoxide (DMSO) in the presence of epidermal growth factor (EGF). Hepatocytes can be kept in nonproliferating cultures for 7 days in media supplemented with 2% DMSO and EGF. If DMSO is removed while EGF is maintained, rat and human hepatocytes enter a 3 to 4 day period of DNA synthesis that declines rapidly by days 4 and 5. If DMSO is reintroduced into cultures at that point, kept on for 3 more days and removed again, hepatocytes reenter into proliferation with another self-limited response of 3 to 4 days. Similar phenomena can seen with hepatocytes maintained in the presence of 3 mM phenobarbital. These protocols demonstrate that loss of responsiveness to mitogens in primary hepatocyte cultures is not an irreversible process. They also raise the possibility that signals for termination of DNA synthesis in hepatocytes emanate from hepatocytes themselves. These studies also suggest for the first time the possibility of designing in vitro systems that will allow clonal expansion of differential hepatocytes.

Adrenergic regulation of c-fos expression in cultured BC3H1 muscle cells

Administration of adrenergic agonists induced c-fos mRNA in the salivary glands of the mouse and in the heart of the mouse, rat, and hamster (Barka et al., 1986, Mol. Cell Biol. 6, 2984-2989; 1987; Oncogene 1, 439-443). To further analyze transcriptional and post-transcriptional control of c-fos expression by adrenergic receptors and the putative role of fos in replication and differentiation pathways, we have examined c-fos expression in BC3H1 cells, a tumor-derived nonfusing muscle cell line. BC3H1 cells possess alpha 1- and beta 2-adrenergic receptors as well as receptors for histamine and acetylcholine. Furthermore, rapidly proliferating BC3H1 cells undergo differentiation toward muscle phenotype when exposed to low serum-containing culture media. Both alpha- and beta-adrenergic agonists and the tumor promoter 12-O-tetradecanoylphorbol-13-acetate caused a rapid, transient increase in the steady-state level of c-fos mRNA. This induction was essentially independent of whether the cells were in the proliferative, relatively quiescent, or differentiated state. Protein synthesis inhibitors cycloheximide and anisomycin also increased markedly the concentration of c-fos mRNA, and in the presence of anisomycin c-fos mRNA was superinduced by the alpha-adrenergic agonist norepinephrine. Run-on transcription assays indicated that the c-fos gene is expressed in both proliferating and differentiated cells, although the steady-state levels of c-fos mRNA were low, or even undetectable, in such cells. The adrenergic agonists and the tumor promoter stimulated the transcription of the c-fos gene in both proliferating and differentiated cells. This stimulation, however, was modest, two- to three-fold compared to controls, in contrast to the marked elevation of the level of c-fos mRNA they caused. Neither the proliferation nor the expression of muscle type creatine kinase activity was influenced by adrenergic agonists. It is suggested that activation of the c-fos gene is a consequence of adrenoreceptor stimulation in diverse cell types, and thus it is involved in pleiotropic cellular responses to adrenergic agonists. Catecholamines may be one of the physiologic regulators of the c-fos gene.

Expression of vimentin and nuclear lamins during the in vitro differentiation of human promyelocytic leukemia cells HL-60

We have reported previously that the human promyelocytic leukemia cell line HL-60, in its undifferentiated state, is devoid of cytoplasmic intermediate filament proteins and nuclear lamins A and C, but does express lamin B. Using immunofluorescence and immunoblotting techniques, we have further investigated the expression of vimentin and lamins A and C during differentiation of these tumor cells along the macrophage or granulocytic pathway in response to the inducing effects of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) or dimethyl sulfoxide. Our results show that, while the expression of lamin B remains largely unchanged, the synthesis of vimentin and lamins A and C is dramatically enhanced during the maturation of HL-60 cells along both hemopoietic pathways. Northern blot analysis of cellular RNAs isolated from untreated and TPA-treated HL-60 cell populations as well as from control HeLa cells was performed using two oligonucleotides, one complementary to the 5' region common to human lamin A/C mRNAs and the other to the 5' region of hamster vimentin mRNA. Very low but still detectable amounts of vimentin and lamin A/C mRNAs were found in untreated HL-60 cell population, in accordance with the detection of small quantities of vimentin and lamins A and C in these populations. This is probably due to the presence of a small number of spontaneously differentiating cells. On the other hand, strong signals comparable to those obtained with RNA from control HeLa cells were detected for the three mRNA species from TPA-treated cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of unscheduled DNA synthesis by a whole cell counting method

A procedure was developed for the quantification of the autoradiographic assay for unscheduled DNA synthesis. Relative to commonly used practices for grain counting, this procedure provides a more accurate net nuclear grain count by eliminating the subjectivity currently associated with selection of the areas to be counted for the cytoplasmic background count. Briefly, the object area and aperture area modes of an ARTEK 880 colony counter are used to collect values for the total number of silver grains over a particular cell (nuclear and cytoplasmic counts), as well as for the nuclear and cytoplasmic areas. These values are then employed in a short algorithm to determine the net nuclear grain count. This new method provides greater sensitivity for defining weak UDS responses and the data collected readily lends itself to statistical analysis.

Captopril and ramiprilat protect against free radical injury in isolated working rat hearts

The protection of angiotensin converting enzyme (ACE) inhibitors, captopril and ramiprilat, against free radical-mediated myocardial injury were studied in isolated working rat hearts. Free radicals were generated by electrolysis of Krebs-Henseleit solution with 10 mA direct current for 1 min. Both captopril (360 mumol/l) and ramiprilat (12.5 mumol/l) significantly reduced the decrease of left ventricle dP/dt'max, coronary flow (CF), myocardial superoxide dismutase (SOD) and creatine kinase (CK) activities and the elevation of S-T segment of epicardial ECG as well as the rise of myocardial malondialdehyde (MDA) content caused by electrolysed perfusate. Captopril afforded a dose-dependent protection on cardiac functions with various concentrations of 45, 90, 180 and 360 mumol/l. Iloprost (30 nmol/l), a stable mimetic of prostacyclin, could also alleviate free radical-mediated myocardial injuries. All the beneficial effects of ramiprilat (12.5 mumol/l) were abolished by the administration of indomethacin (5 mumol). In contrast, captopril (90 mumol/l) still exhibited significant protective effects after indomethacin (9 mumol) was administered, though these protective effects were insignificantly weakened. In order to assess the role of sulfhydryl (-SH) group in the effects of captopril, a SH-containing drug S8 and a disulfide DG4, both are deficient in ACE inhibitory properties in vitro, were examined. Data showed that S8 (180 mumol/l) provided a significant protection while DG4 showed no protective effect. It is concluded that ACE inhibitors can protect against free radical-induced myocardial damage. Ramiprilat, a non-SH-containing ACE inhibitor, inhibits free radical-induced damages mainly by stimulation of prostacyclin synthesis and/or release. In addition to this effect, captopril, a SH-containing ACE inhibitor, may exert additional anti-free radical effects by a mechanism which is probably related to the sulfhydryl group.

[A comparative study of the cryoprotective properties of dimethylacetamide and dimethyl sulfoxide in preserving thrombocytes at moderately low temperatures]

Comparative characteristics of cryoprotective properties of dimethylacetamide and dimethyl sulfoxide (DMAC and DMSO, respectively), used for freezing and storage of platelets at -80 degrees C, have been presented. It is shown that with the studied final concentrations of the cryoprotectors (5% of DMSO, 2.5% of DMAC), solutions containing DMSO display higher cryoprotective properties. Positive effect of autoplasma in the mixture with the platelet-protecting solution has been manifest in the maintaining of the functional properties of platelets after defrosting.

Activation of protein kinase C assists insulin producing cells in recovery from raised cytoplasmic Ca2+ by stimulating Ca2+ efflux

The effects of protein kinase C (PKC) activation on the cytoplasmic free Ca2+ concentration ([Ca2+]i) were studied in clonal insulin-producing RINm5F cells, using the fluorescent Ca2+ indicators quin-2 and fura-2. Both under basal and stimulatory conditions PKC activation lowered [Ca2+]i in these cells by promoting an active extrusion of Ca2+ to the extracellular space. PKC activation therefore assists insulin-producing cells in recovery from raised [Ca2+]i. Such an effect might be part of the signal regulating the insulin secretory process.

The inducible trimethylamine N-oxide reductase of Escherichia coli K12: its localization and inducers

We used an anti-trimethylamine-N-oxide reductase (EC 1.6.6.9) serum and different immunological techniques (Ouchterlony, rocket immunoelectrophoresis, immunoblotting) to show that dimethylsulphoxide (DMSO), tetrahydrothiophene 1-oxide (THTO) and pyridine N-oxide (PNO) were effective inducers of the inducible form of trimethylamine N-oxide reductase. We confirmed this genetically and biochemically using a strain in which phage MudII 1734 carrying lacZ was inserted into torA, the structural gene for inducible trimethylamine-N-oxide reductase. By subcellular fractionation and quantitation with rocket immunoelectrophoresis, we showed that the enzyme was principally localized in the periplasmic fraction. Constitutive trimethylamine-N-oxide reductase was localized in the membrane fraction and, like the inducible enzyme showed a broad specificity with respect to various compounds such as DMSO, THTO and PNO. Apart from their immunological properties, the two enzymes could be clearly differentiated by their temperature stability.