Blue-emitting InP quantum dots participate in an efficient resonance energy transfer process in water

Development of stable blue-emitting materials has always been a challenging task because of the necessity of high crystal quality and good optical properties. We have developed a highly efficient blue-emitter, based on environmentally friendly indium phosphide/zinc sulphide quantum dots (InP/ZnS QDs) in water, by controlling the growth kinetics of the core as well as the shell. A rational combination of less-reactive metal-halides, phosphorus, and sulphur precursors is the key for achieving the uniform growth of the InP core and ZnS shell. The InP/ZnS QDs showed long-term stable photoluminescence (PL) in the pure-blue region (∼462 nm), with an absolute PL quantum yield of ∼50% and a colour purity of ∼80% in water. Cytotoxicity studies revealed that the cells can withstand up to ∼2 micromolar concentration of pure-blue emitting InP/ZnS QDs (∼120 μg mL^-1). Multicolour imaging studies show that the PL of InP/ZnS QDs was well-retained inside the cells as well, without interfering with the fluorescence signal of commercially available biomarkers. Moreover, the ability of InP based pure-blue emitters to participate in an efficient Förster resonance energy transfer (FRET) process is demonstrated. Installing a favorable electrostatic interaction turned out to be crucial in achieving an efficient FRET process (E ∼75%) from blue-emitting InP/ZnS QDs to rhodamine B dye (Rh B) in water. The quenching dynamics fits well with the Perrin formalism and the distance-dependent quenching (DDQ) model, which confirms an electrostatically driven multi-layer assembly of Rh B acceptor molecules around the InP/ZnS QD donor. Furthermore, the process of FRET was successfully translated into the solid state, proving their suitability for device-level studies as well. In short, our study expands the spectrum of aqueous QDs based on InP towards the blue region for future biological and light harvesting studies.

Self-Reporting Polysaccharide Polymersome for Doxorubicin and Cisplatin Delivery to Live Cancer Cells

We report self-reporting fluorescent polysaccharide polymersome nanoassemblies for enzyme-responsive intracellular delivery of two clinical anticancer drugs doxorubicin (DOX) and cisplatin to study the real-time drug-releasing aspects by fluorescent resonance energy transfer (FRET) bioimaging in live cancer cells. Fluorescent polymersomes were tailor-made by tagging an aggregation-induced emission (AIE) optical chromophore, tetraphenylethylene (TPE), and a plant-based vesicular directing hydrophobic unit through enzyme-biodegradable aliphatic ester chemical linkages in the polysaccharide dextran. The blue-luminescent polymersome self-assembled in water and exhibited excellent encapsulation capability for the red-luminescent anticancer drug DOX. FRET between the AIE polymersome host and DOX guest molecules resulted in a completely turn-off probe. At the intracellular level, the lysosomal enzymatic disassembly of the polymersome restored the dual fluorescent signals from DOX and TPE at the nucleus and the lysosomes, respectively. Live-cell confocal microscopy coupled with selective photoexcitation was employed to study the real-time polymersome disassembly by monitoring the turn-on fluorescent signals in human breast cancer cell lines. Alternatively, carboxylic acid-functionalized AIE polymersomes were also tailor-made for cisplatin stitching to directly monitor Pt drug delivery. The polymersome nanoassemblies exhibited excellent structural tolerance for the chemical conjugation of the Pt drugs, and the fluorescence signals were unaltered. An in vitro drug release study confirmed that the cisplatin-stitched fluorescent polymersomes were very stable under physiological conditions and underwent lysosomal enzymatic degradation to inhibit the cancer cell growth. A lysosomal colocalization experiment using confocal microscopy substantiates the enzyme-responsive degradation of these polymersomes to release both the encapsulated and conjugated drugs at the intracellular level. The present design provides a unique opportunity to deliver more than one anticancer drug from a single polymersome platform in cancer research.

An AIE-driven fluorescent polysaccharide polymersome as an enzyme-responsive FRET nanoprobe to study the real-time delivery aspects in live cells

An enzyme-responsive FRET nanoprobe was designed and developed based on AIE-driven fluorescent polysaccharide polymersomes to study the real-time delivery aspects in the intracellular compartments in live cancer cells.

Sequence of a cDNA encoding bovine apolipoprotein H

The nucleotide sequence of the ApoH cDNA encoding the bovine apolipoprotein H (ApoH) has been determined. The deduced protein, which contains a 19-amino-acid (aa) signal peptide and the 326-aa mature ApoH, shows 89% and 86% homology with human and rat ApoH, respectively.

Selective regulation of beta 2-adrenergic receptor gene expression by interleukin-1 in cultured human lung tumor cells

The regulation of beta 1- and beta 2-adrenergic receptors (beta 1AR and beta 2AR) and receptor gene expression by interleukin-1 alpha (IL-1 alpha) was studied in cultured A549 human lung adenocarcinoma cells. The density and affinity of beta 1 AR and beta 2 AR were analyzed by computerized curve fitting of 125I-pindolol binding and its displacement by subtype selective antagonists. Steady state levels of receptor mRNAs were quantified by DNA excess solution hybridization assays. A549 cells in preconfluent cultures had fewer beta 1AR than beta 2AR (beta 1: 1.9 +/- 0.3 vs beta 2: 4.0 +/- 0.5 fmol/mg protein, means +/- SE), but lost most of their beta 2 AR upon reaching confluency (beta 1: 2.7 +/- 0.4, beta 2: 0.8 +/- 0.3 fmol/mg). Incubation of preconfluent cells for 24 hr with 20 pM of human recombinant IL-1 alpha did not modify the density of either of the beta AR subtypes. Similar incubations of confluent cells increased the density of beta 2 AR from 0.8 +/- 0.3 to 4.2 +/- 0.9 fmol/mg, while the density of beta 1 AR and the antagonist affinities of both receptors remained unaltered. The IL-1 alpha-induced increase in beta 2 AR density in confluent cells was antagonized in a concentration-dependent manner by a recombinant protein antagonist of type I IL-1 receptors (IC50: 0.2 nM). The IL-1 alpha-induced increase in beta 2AR density was preceded by an increase in the steady state level of beta 2AR mRNA, while levels of beta 1AR mRNA remained unchanged. IL-1 alpha increased the stability as well as the rate of transcription of beta 2AR mRNA. These findings demonstrate for the first time that activation of type I IL-1 receptors in A549 cells leads to a cell density-dependent, selective upregulation of beta 2AR, and that the mechanism of this effect involves increased formation and stability of the beta 2AR message.

Biphasic protein kinase C translocation in PC12 cells in response to short-term and long-term ethanol exposure

Short-term and long-term effects of ethanol on protein kinase C (PKC) activity and PKC translocation from cytosol to membrane were examined in PC12 cells, a clonal cell line of neural crest origin. Treatment of PC12 cells with ethanol (30-100 mM) for 2 hr had no effect on PKC activity and PKC translocation. When PC12 cells were treated with 100 mM ethanol for 18, 44 and 74 hr, there was a biphasic effect on PKC translocation. At 18 and 44 hr ethanol treatment, PKC translocation was significantly (P < 0.001) increased, at 74 hr ethanol treatment, there was a significant decrease (P < 0.05). Less than 100 mM of ethanol had no effect on PKC activity and PKC translocation. Cyclic AMP and cyclic GMP-dependent protein kinase had no effect on PKC translocation. These findings indicate that biphasic PKC translocation from cytosol to membrane forms the basis of acute and chronic effects of ethanol on neurotransmission.

Effects of IL-1 and cortisol on beta-adrenergic receptors, cell proliferation, and differentiation in cultured human A549 lung tumor cells

The effects of IL-1 and cortisol, and their interactions on the density of beta-adrenergic receptors (beta AR), cell proliferation, and the adherence of cells to plastic were studied in cultured human A549 lung tumor cells. The density of beta AR, assayed by 125I-pindolol binding, was increased two- to threefold by a 24-h incubation of the cells with IL-1 alpha, IL-1 beta, and TNF-alpha (EC50: 2.7, 8.2, and 24 pM, respectively), although a series of other cytokines and growth factors did not have this effect. Cortisol also increased beta AR density (EC50: 30 nM) and markedly potentiated the effects of IL-1 alpha, IL-1 beta, and TNF-alpha. Neither IL-1 nor cortisol influenced the proportion of cell surface vs internalized beta AR. The IL-1-induced increase in beta AR density was half-maximal after 6 h, was reversible at a similar rate, and was blocked by 1 microM of cycloheximide. The effect of IL-1 on beta AR was specific, as the density of glucocorticoid receptors, measured by 3H-dexamethasone binding, was reduced by IL-1. Both cortisol and IL-1 potentiated the isoproterenol-induced increase in cAMP accumulation. IL-1 inhibited cell proliferation and thymidine uptake, and increased the adherence of A549 cells to the plastic culture flask, as quantified by a cell detachment assay. The effect of IL-1 on cell adherence was not inhibited by cycloheximide. Cortisol decreased cell adherence and prevented the IL-1-induced increase in adherence. The results indicate that multiple effects of IL-1 in a cultured tumor cell line involve different mechanisms, suggesting heterogeneity of IL-1R and/or coupling of IL-1R to distinct, nuclear, and nonnuclear, effector pathways.

Effects of IL-1 and cortisol on beta-adrenergic receptors, cell proliferation, and differentiation in cultured human A549 lung tumor cells

The effects of IL-1 and cortisol, and their interactions on the density of beta-adrenergic receptors (beta AR), cell proliferation, and the adherence of cells to plastic were studied in cultured human A549 lung tumor cells. The density of beta AR, assayed by 125I-pindolol binding, was increased two- to threefold by a 24-h incubation of the cells with IL-1 alpha, IL-1 beta, and TNF-alpha (EC50: 2.7, 8.2, and 24 pM, respectively), although a series of other cytokines and growth factors did not have this effect. Cortisol also increased beta AR density (EC50: 30 nM) and markedly potentiated the effects of IL-1 alpha, IL-1 beta, and TNF-alpha. Neither IL-1 nor cortisol influenced the proportion of cell surface vs internalized beta AR. The IL-1-induced increase in beta AR density was half-maximal after 6 h, was reversible at a similar rate, and was blocked by 1 microM of cycloheximide. The effect of IL-1 on beta AR was specific, as the density of glucocorticoid receptors, measured by 3H-dexamethasone binding, was reduced by IL-1. Both cortisol and IL-1 potentiated the isoproterenol-induced increase in cAMP accumulation. IL-1 inhibited cell proliferation and thymidine uptake, and increased the adherence of A549 cells to the plastic culture flask, as quantified by a cell detachment assay. The effect of IL-1 on cell adherence was not inhibited by cycloheximide. Cortisol decreased cell adherence and prevented the IL-1-induced increase in adherence. The results indicate that multiple effects of IL-1 in a cultured tumor cell line involve different mechanisms, suggesting heterogeneity of IL-1R and/or coupling of IL-1R to distinct, nuclear, and nonnuclear, effector pathways.

Alteration in calcium-binding activity in synaptosomal membranes from rat brains in association with physical dependence upon ethanol

The effects of ethanol treatment on calcium-binding activity in synaptosomal membrane fraction from rat brains were studied. The synaptosomal membrane fraction from the hippocampus, the cortex and the cerebellum from control, single dose (6 g/kg), dependent intoxicated (prodromal) and dependent withdrawing (ethanol withdrawal syndrome) rats were used. Two different methods were used for determining the calcium activity in these membrane preparations: the calcium chelator fluorescence probe, chlortetracycline (CTC), was used to measure Ca2+ binding sites in the membranes, and radioactive calcium (45Ca) was used to measure the calcium binding to the synaptosomal membranes. Both methods provided similar conclusions; the calcium activity was higher during the dependent intoxicated phase of the ethanol withdrawal period. The synaptosomal membranes from the hippocampus showed more drastic changes in calcium-binding activity than the cortex and the cerebellum. These results suggest that ethanol dependence is associated with changes in calcium-binding activity in certain areas of the rat brain.

Cerebral alteration in calmodulin levels associated with the induction of physical dependence upon ethanol in rats

Calmodulin levels were measured in different areas of brain in rats rendered physically dependent and after single doses (6 g/kg) of ethanol. After single doses of ethanol no changes in the calmodulin levels were found in the cortex, but those in the hippocampus and caudate nuclei were increased while those in the cerebellum were reduced. In the dependent intoxicated (prodromal) rats, calmodulin levels were elevated in all these regions except the cerebellum. In rats undergoing ethanol withdrawal syndrome, the calmodulin levels decreased in all regions of the brain except caudate nuclei.

Release of aspartate and glutamate caused by chloride reduction in synaptosomal incubation media

Release of the amino acid neurotransmitter candidates aspartate and glutamate from synaptosomes can be stimulated by reduction of [Cl-] in the incubation medium by replacement with the impermeant anions propionate and isethionate. Replacement by the permeant anion Br- is without effect on amino acid release. This release offers a biochemical method of studying the Cl-ion channel in CNS membrane.

Calcium-induced proteolysis of spectrin and band 3 protein in rat erythrocyte membranes

Calcium-dependent protease activity capable of degrading a number of endogenous proteins was found in rat red blood cell membranes. This protease activity, like that found in human red blood cells, was activated by low concentrations of calcium, but in the rat red blood cells, unlike the human red blood cells, calcium-activated protease activity was membrane-bound. A number of endogenous membrane-bound proteins were degraded after the addition of calcium to the membranes. These included spectrin bands 1 and 2 as well as bands 3, 2.1, and 2.2. No calcium-induced aggregation (transglutaminase activity) was noted in the rat red blood cell membranes.

Enrichment of cell populations containing terminal deoxynucleotidyl transferase activity by free flow electrophoresis

Terminal deoxynucleotidyl transferase (TdT) is an enzyme that has been utilized as a biochemical marker for following certain leukemia patients during treatment and remission. The potential usefulness of this enzyme in predicting the onset of relapse before any morphological indications has been demonstrated in chronic myelogenous leukemia patients in blast phase of the disease. In order to be able to detect low levels of TdT activity, especially during remission phase, we have used the technique of free flow electrophoresis to enrich cell populations containing TdT. With this technique we have achieved up to 20-fold enrichment of TdT-positive cell populations from normal human bone marrow, cells from patients with acute lymphoblastic leukemia and chronic myelogenous leukemia in blast phase of the disease. TdT positive cells were not detected in patients with acute myelogenous leukemia and B cell lines. This technique should prove to be useful in early detection of relapse in patients in remission and for enrichment of cell populations containing other biochemical markers.

Changes in erythrocyte ghost protein phosphorylation associated with physical dependence upon ethanol

The effects of ethanol on phosphorylation in the erythrocyte ghost membranes was studied. Four groups of rats were used: controls; prodromal phase; overt withdrawal syndrome; and treated with a single dose (6g/kg) of ethanol. Spectrin (Band 2) phosphorylation was enhanced during prodromal phase (200 +/- 12%) and during overt ethanol withdrawal syndrome (150 +/- 18%), while a single dose of ethanol produced no significant change. Addition of micromolar calcium chloride solution to the phosphorylating medium produced pronounced decrease in spectrin phosphorylation in the ghost membranes isolated from controls and those treated with a single dose of ethanol, while this effect of calcium was less pronounced in the ghost membranes isolated from rats in the prodromal phase and in the withdrawal syndrome. This suggests that due to prolonged ethanol treatment membrane phosphorylating properties were less sensitive to the change in calcium concentration. The membrane polypeptide composition was unaffected upon ethanol treatment.

Enrichment of terminal deoxynucleotidyl transferase activity by cell separation

Terminal deoxynucleotidyl transferase is a unique DNA polymerase that can carry out DNA synthesis on an initiator molecule in the absence of a template. The usefulness of this enzyme as a biological marker for following patients during treatment and remission has been suggested. The potential usefulness of this enzyme in predicting the onset of relapse before any morphological indications has been demonstrated in chronic myelogenous leukemia patients in blast phase of the disease. In order to be able to detect low levels of TdT activity especially during remission phase, we have used cell separation techniques which can enrich cell populations containing TdT activity. A number of cell separation techniques have been developed to separate different cell types. We have used the techniques of unit gravity sedimentation and free flow electrophoresis to achieve enrichment of TdT positive cell populations. Our results show that up to 20 fold enrichment of TdT activity in normal human bone marrow can be accomplished by using cell separation techniques. With the use of free flow electrophoresis, we have achieved enrichment of TdT positive cell populations from normal human bone marrow, cells from patients with acute lymphoblastic leukemia and chronic myelogenous leukemia in blast phase of the disease. No TdT positive cells were detected in patients with acute myelogenous leukemia. These cell separation techniques should prove to be useful in early detection of relapse in patients in remission.

Terminal transferase in acute lymphoblastic leukemia in gibbons

Terminal deoxynucleotidyl transferase, an enzyme which catalyzes the polymerization of deoxyribonucleoside triphosphates on a 3'-OH end of an initiator molecule in the absence of a template, has been suggested as a biological marker for human acute lymphoblastic leukemia. Examination of a cell line, 6G1, recently established from the peripheral blood of a gibbon ape with acute lymphoblastic leukemia showed the presence of terminal deoxynucleotidyl transferase. This enzyme after purification by successive column chromatography on DEAE-cellulose, phosphocellulose and hydroxyapatite, was found to have biochemical properties similar to those reported for terminal transferase from calf thymus and human leukemic cells. These studies suggest that terminal transferase can be used as a useful biological marker for acute lymphoblastic leukemia in both humans and subhuman primates.