Fluorescent liposome flow markers for microscale particle-image velocimetry

Unilamellar liposomes carrying both encapsulated and surface-immobilized fluorophores have been synthesized as novel fluorescent markers to image flow profiles in microfabricated structures. The unilamellar liposomes were made with phospholipids and cholesterol by extrusion through a polycarbonate membrane. They contained carboxyfluorescein in the aqueous core and fluorescein-labeled lipids in the bilayer to render them both a surface and volume fluorescer, maximizing their fluorescence intensity. The lipid composition was chosen to impart a net negative charge to liposomes to minimize self-aggregation as well as interaction with negatively charged glass surfaces of the channels. These liposomes were monodisperse (mean diameter 283 nm), neutrally buoyant, and hydrophilic and exhibited no adsorption on glass surfaces. Unlike polystyrene spheres, they were readily broken up by surfactants, thereby allowing for easy and complete removal from microfluidic channels. The fluorescent liposomes were used to investigate pressure-driven flow in an offset cross intersection in a microfluidic chip and provided images with excellent signal-to-noise ratio. A novel computational scheme that is particularly suitable for analyzing particle-image velocimeby data in micrometer-scale flow channels was employed to anabze the images. These liposomes are easily synthesized and can be custom-made for various applications to offer a broad range of surface and volume characteristics such as charge, size, and surface chemistry.

Relaxin decreases renal interstitial fibrosis and slows progression of renal disease

BACKGROUND

Relaxin, a hormone of the insulin-growth factor family, promotes collagen remodeling. In rodent models of pulmonary and dermal fibrosis, relaxin reduced interstitial fibrosis. To study relaxin's effect in renal disease, we used the experimental bromoethylamine (BEA) model that leads to severe renal interstitial fibrosis, a decrease in glomerular filtration rate, and albuminuria at one month.

METHODS

Rats were injected with BEA one week prior to implantation of an osmotic pump delivering relaxin (2 microg/hour) or vehicle continuously for 28 days.

RESULTS

BEA caused a significant decrease in creatinine clearance, which was partially prevented by relaxin. In the relaxin-treated BEA rats, serum creatinine was normal, and albumin excretion was slightly decreased. By morphometric measurement, relaxin administration was associated with a significant decrease in interstitial fibrosis at the corticomedullary junction. This was accompanied by a decrease in the number of ED-1 positive cells (an index of macrophage infiltration) and in the intensity of immunohistochemical staining for transforming growth factor-beta. This antifibrotic effect of relaxin did not appear to be mediated by systemic hemodynamic changes since the mean arterial pressure was not significantly different among the groups.

CONCLUSIONS

Relaxin may have a useful application in decreasing interstitial fibrosis and thereby slowing the progression of renal disease.

Tissue-specific variations in the induction of Hsp70 and Hsp64 by heat shock in insects

The patterns of heat-induced synthesis (37 degrees C to 45 degrees C) of heat shock proteins (Hsps) in different tissues of grasshoppers and cockroaches from natural populations and in laboratory-reared gram-pest (Heliothis armigera) were examined by 35S-methionine labeling and sodium dodecyl sulfate-polyacrylamide gel electrophoresis fluorography. Whereas 45 degrees C was lethal in most cases, optimal induction of Hsp synthesis was seen between 37 degrees C and 42 degrees C. The ongoing protein synthesis was not much affected at these temperatures, except in the tissues of adult H. armigera exposed to 42 degrees C. The profiles of the Hsps induced in the tissues of the insects, however, were different. From the relative abundance of the synthesis of 70-kDa (Hsp70) and 64-kDa (Hsp64) polypeptides, three categories of heat shock response were identified: (1) induction of abundant Hsp70 but little Hsp64 (malpighian tubules, male accessory glands, and ovaries of adult grasshoppers), (2) abundant Hsp64 but little Hsp70 (testes of adult grasshoppers, testes and malpighian tubules of adult cockroaches, and testes, malpighian tubules, and fat bodies of H. armigera larvae), and (3) induction of both Hsp70 and Hsp64 in more or less equal abundance (ovaries of adult cockroaches, salivary glands of H. armigera larvae, and malpighian tubules, male accessory glands, testes, and ovaries of adult H. armigera). Cockroaches collected from storerooms showed detectable synthesis of Hsp64 and/or Hsp70 only after heat shock, but those collected from drains showed detectable synthesis of both Hsp70 and Hsp64 in different tissues without heat stress. Western blotting showed that the 64-kDa polypeptide in these insects is a member of the Hsp60 family. Grasshopper testes, which synthesized negligible Hsp70 but abundant Hsp64 after heat shock, developed thermotolerance. Thus, heat shock response is modulated by developmental and environmental factors in different tissues of insects.

Glioblastoma multiformis, rapidity of growth--importance of repeat CT scan

A case of glioblastoma multiformis (GBM) where lesion appeared within a month of normal CT scan is reported. It emphasises the importance of early CT scan after neurological deterioration particularly in older patients because of rapid growth of glioblastoma.

Benzimidazolone activators of chloride secretion: potential therapeutics for cystic fibrosis and chronic obstructive pulmonary disease

The diseases of cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) are characterized by mucus-congested airways. Agents that stimulate the secretion of Cl- are anticipated to facilitate mucociliary clearance and thus be of benefit in the treatment of CF and COPD. Recently 1-EBIO (1-ethyl-2-benzimidazolinone or 1-ethyl-1,3-dihydro-2H-benzimidazol-2-one) was shown to stimulate chloride secretion albeit at relatively high concentrations (0.6-1 mM). The studies reported here were undertaken to develop a more potent benzimidazolone. Structure activity studies with 30 benzimidazolone derivatives revealed that ethyl and hydrogen groups at the 1 and 3 nitrogen positions, respectively, were critical for the activation of hIK1 K+ channels and that other alkyl groups were not tolerated at these positions without some loss in potency. Substitutions at the 5 and 6 positions improved the potency of 1-EBIO. Compared with 1-EBIO, the most potent of these derivatives, DCEBIO (5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one) was severalfold better in a 86Rb+ uptake assay, 20-fold better in short circuit current measurements on T84 monolayers, and 100-fold better in patch-clamp assays of hIK1 activity. Short circuit current studies revealed DCEBIO stimulates Cl- secretion via the activation of hIK1 K+ channels and the activation of an apical membrane Cl- conductance. The improved potency of DCEBIO strengthens the possibility that compounds in this class may be of therapeutic benefit in the treatment of CF and COPD.

QSAR for acetylcholinesterase inhibition and toxicity of two classes of phosphoramidothioates

Methamidophos (Met) is a weak inhibitor of housefly head AChE but at the same time it is highly toxic to the common housefly. The lethality of Met is believed to be due to AChE inhibition. An extensive QSAR study may help in determining the mode of action of Met in vivo and in vitro and provide a rational for its high insecticidal toxicity. Acephate (Ace), like Met, is a poor inhibitor of AChE in vitro and has a comparable to Met insect toxicity in vivo. Contrary to Met, though, Ace has much lower mammalian toxicity. Understanding the structural properties which make insecticides toxic to insects but not to mammals is of great importance, since mammals (including humans) are inadvertently exposed to these compounds. Our results were consistent with the model in which both the in vitro and in vivo toxicity of Met depends on the inhibition of the active center of AChE by the unchanged Met. An optimal susceptibility to hydrolysis is needed for Met and its analogs to have high insecticidal activity since in order to phosphorylate AChE they need to be hydrolyzed and at the same time their stability is of great importance in vivo for accumulating at the site of action. The insecticidal activity of Ace analogs may be due to direct interaction with the active center of the AChE. The mammalian toxicity of Ace analogs may be due to interaction with an 'allosteric' reaction center in the AChE.

Pasteurella (Mannheimia) haemolytica leukotoxin-induced cytolysis of bovine leukocytes: role of arachidonic acid and its regulation

Pasteurella (Mannheimia) haemolytica leukotoxin (Lkt) is the major factor that contributes to lung injury in bovine pneumonic pasteurellosis. Lkt is a pore-forming exotoxin that has the unique property of inducing cytolysis only in ruminant leukocytes and platelets. Cytolysis of many cell types is mediated by arachidonic acid (AA) and its generation by phospholipases is regulated by G-protein-coupled receptors. However, the contribution of Lkt-induced AA generation to cytolysis and the signalling cascade underlying AA generation in bovine leukocytes have not been determined. We have determined whether AA mediates Lkt-induced cytolysis and delineated the signalling mechanisms underlying AA generation in bovine leukocytes. Bovine lymphoma cells were used as an experimental system to investigate the Lkt-induced [(3)H] AA release, an index of AA generation and lactate dehydrogenase release, an index of cytolysis. The results indicate that Lkt induces AA release and cytolysis in a concentration- and time-dependent fashion. The AA analog, 5,8,11,14-eicosatetraynoic acid inhibited Lkt-induced cytolysis, but not AA release. Lkt-induced AA release and cytolysis were inhibited by pertussis toxin, inhibitors of cytosolic phospholipase A(2)(cPLA(2)), phospholipase C and protein kinase C (PKC), and by chelation of intracellular calcium. Furthermore, Western blot analysis revealed the presence of G(i), G(s)and G(q)type G-proteins. These results demonstrate that AA metabolites from cPLA(2)activation contribute to Lkt-induced cytolysis and G(i)type G-proteins, Ca(2+)and PKC, regulate the cPLA(2)activity.

Bovine eye 1-Cys peroxiredoxin: expression in E. coli and antioxidant properties

Peroxiredoxins constitute a molecular family of novel antioxidant proteins and are distributed broadly in non-mammalian and mammalian tissues, including the eye. In this study, a recombinant bovine eye 1-Cys peroxiredoxin (BRPrx) was expressed in Escherichia coli (E. coli). The recombinant protein protected glutamine synthetase from oxidative damage caused by a metal ion-catalyzed oxidation system (ascorbate/Fe3+/O2) in the presence of dithiothreitol as an electron donor. The protector activity of BRPrx is attributed to its peroxidase activity exhibited in the presence of dithiothreitol. Both hydrogen peroxide and short chain hydroperoxides are substrates for the protein. Glutathione could not support antioxidant properties of the recombinant protein. The antioxidant activity of BRPrx in the glutamine synthetase protection assay was as high as the activity of catalase and about one order of magnitude lower than that of selenium glutathione peroxidase. These results support the premise that Prx is an important component of the antioxidant defense system in eye tissues.

Liposomes labeled with biotin and horseradish peroxidase: a probe for the enhanced amplification of antigen--antibody or oligonucleotide--DNA sensing processes by the precipitation of an insoluble product on electrodes

Liposomes labeled with biotin and the enzyme horseradish peroxidase (HRP) are used as a probe to amplify the sensing of antigen-antibody interactions or oligonucleotide-DNA binding. The HRP-biocatalyzed oxidation of 4-chloro-1-naphthol (1) in the presence of H2O2, and the precipitation of the insoluble product 2 on electrode supports, are used as an amplification route for the sensing processes. The anti-dinitrophenyl antibody (DNP-Ab) is sensed by a dinitrophenyl-L-cysteine antigen monolayer associated with an Au electrode. A biotinylated anti-IgG-antibody (Fc-specific) is linked to the antigen-DNP-Ab complex, and the biotin-labeled HRP-liposomes associate with the assembly through an avidin bridge. The biocatalyzed precipitation of 2 on the electrode increases the electron-transfer resistances at the electrode-solution interface or the electrode resistance itself. The binding events of the different proteins on the electrode and the biocatalyzed precipitation of 2 on the conductive support are followed by Faradaic impedance spectroscopy or constant-current chronopotentiometry. DNP-Ab concentrations as low as 1 x 10(-11) g x mL(-1) can be detected by this method. The labeled liposomes were also used for the amplified detection of DNA 3. The oligonucleotide 4, complementary to a part of the target DNA 3 that is a model nucleic acid sequence for the Tay-Sachs genetic disorder, is assembled on an Au electrode. Hybridization of the analyte 3 followed by the association of the biotin-tagged oligonucleotide 5 yields a three-component double-stranded assembly. Sensing of the analyte 3 is amplified by the association of avidin, the labeled liposomes, and the subsequent biocatalyzed precipitation of 2 on the electrodes. The DNA 3 is detected with a sensitivity that corresponds to 6.5 x 10(-13) M. Faradaic impedance spectroscopy and chronopotentiometry were employed to follow the stepwise assembly of the systems and the electronic transduction of the detection of the analyte DNA 3.

QSAR for the organophosphate-induced inhibition and 'aging' of the enzyme neuropathy target esterase (NTE)

QSAR was devised for the neuropathy potency of various organophosphate (OP) compounds. The neuropathy-target-esterase (NTE) inhibition data were either obtained from the literature for a number of OP compounds or were determined experimentally for methamidophos, acephate, coumaphos and EPN. Aging Index that determined whether or not an OP would age NTE, correlated with molecular depth (MD) and the index density* dipole-moment (density* omega) (Eq. (1)). The t1/2 values that represented the time (min) during which 50% of the OP-inhibited brain NTE undergoes 'aging', correlated with the topological indices Dif3 and 1/Dif4 (Eq. (2)). Log10I50 for AChE that determined the OP concentration causing 50% inhibition in AChE activity, correlated with EBOND and Charge-1 (Eq. (3)). Log10I50 for NTE correlated with 1/HS2 and H-Bonding (Eq. (4)). The (Log10I50NTE)/(Log10I50AChE) ratio that determined an OPs neuropathy potential relative to its cholinergic toxicity potential, correlated with log P and Log10Polarity (Eq. (6)). Equation (3) accurately predicted AChE inhibition by methamidophos, coumaphos and EPN, but not by acephate. Equations (1), (2), (4)-(6), accurately predicted their respective biological indices. Therefore, it is proposed that the QSAR models developed in this study may accurately predict the neuropathy potential of OP compounds. The only exception is Eq. (3) that did not accurately predict the acephate-induced inhibition of AChE, possibly because acephate and other OPs inhibit the enzyme by distinct mechanisms.

Gangliosides as receptors for biological toxins: development of sensitive fluoroimmunoassays using ganglioside-bearing liposomes

Gangliosides, glycosphingolipids present in the membranes of neuronal and other cells, are natural receptors for a number of bacterial toxins and viruses whose sensitive detection is of interest in clinical medicine as well as in biological warfare or terrorism incidents. Liposomes containing gangliosides mimic cells that are invaded by bacterial toxins and can be used as sensitive probes for detecting these toxins. We discuss detection of three bacterial toxins-tetanus, botulinum, and cholera toxins using ganglioside-bearing liposomes. Tetanus and botulinum toxins selectively bind gangliosides of the G1b series, namely, GT1b, GD1b, and GQ1b; and cholera toxin binds GM1 very specifically. Unilamellar liposomes containing GT1b or GM1 as one of the constituent lipids were prepared by extrusion through polycarbonate membranes. To impart signal generation capability to these liposomes, fluorophore-labeled lipids were incorporated in the bilayer of liposomes. The fluorescent liposomes, containing both a marker (rhodamine) and a receptor (GT1b or GM1) in the bilayer, were used in sandwich fluoroimmunoassays for tetanus, botulinum, and cholera toxins and as low as 1 nM of each toxin could be detected. The apparent dissociation constants of liposome-toxin complexes were in 10(-8) M range, indicating strong binding. This is the first report on detection of tetanus and botulinum toxins based on specific recognition by gangliosides. The fluorescent liposomes are attractive as immunoreagents for another reason as well--they provide enormous signal amplification for each binding event as each liposome contains up to 22,000 rhodamine molecules. The present approach using receptors incorporated in bilayers of liposomes offers a unique solution to employ water-insoluble receptors, such as glycolipids and membrane proteins, for sensitive detection of toxins and other clinically important biomolecules.

Inducible nitric oxide synthase in the central nervous system of patients with X-adrenoleukodystrophy

X-Adrenoleukodystrophy (X-ALD) is an inherited peroxisomal disorder of deficient catabolism of very long-chain (VLC) fatty acids with resulting neuroinflammatory demyelinating disease. Our recent documentation of nitric oxide (NO)-mediated increase in VLC fatty acid levels in glial cells and demonstration of greater increase of VLC fatty acids levels in the inflammatory region (plaque) of X-ALD brain as compared to the normal-looking region away from the plaque prompted us to investigate the possible involvement of NO in the pathophysiology of X-ALD. Herein we provide evidence of the expression of inducible nitric oxide synthase (iNOS) in the CNS of X-ALD patients. In situ hybridization demonstrated that iNOS mRNA was present in brain tissues from X-ALD patients but not in normal controls. Double-labeling immunofluorescence studies using cell-specific markers confirmed that iNOS-expressing cells in the CNS of X-ALD were astrocytes and microglia/macrophages. Finally, antibodies against nitrotyrosine strongly immunoreacted with tissues from the center of the plaque region of X-ALD brains suggesting the presence of the NO reaction product nitrotyrosine in the CNS of X-ALD. Taken together, these results demonstrate that iNOS is expressed in the brains of patients with X-ALD and may contribute to the pathogenesis of the disease.

Thiosalicylic acid-immobilized Amberlite XAD-2: metal sorption behaviour and applications in estimation of metal ions by flame atomic absorption spectrometry

Thiosalicylic acid (TSA)-modified Amberlite XAD-2 (AXAD-2) was synthesized by coupling TSA with the support matrix AXAD-2 through an azo spacer. The resulting chelating resin was characterized by elemental analyses, thermogravimetric analysis (TGA) and infrared spectra. The newly designed resin quantitatively sorbs CdII, CoII, CuII, FeIII, NiII and ZnII at pH 3.5-7.0 when the flow rate is maintained between 2 and 4 ml min-1. The HCl or HNO3 (2 mol l-1) instantaneously elutes all the metal ions. The sorption capacity is 197.5, 106.9, 214.0, 66.2, 309.9 and 47.4 mumol g-1 of the resin for cadmium, cobalt, copper, iron, nickel and zinc, respectively, whereas their preconcentration factor is between 180-400. The breakthrough volume of HCl or HNO3 for elution of these metal ions was found to be 4-8 ml. The limit of detection (LOD) for CdII, CoII, CuII, FeIII, NiII and ZnII was 0.48, 0.20, 4.05, 0.98, 1.28 and 3.94 micrograms l-1, respectively, and the limit of quantification (LOQ) was found to be 0.51, 0.29, 4.49, 1.43, 1.58 and 4.46 micrograms l-1, respectively. The loading half time, t1/2, for the cations was found to be less than 2.0 min, except for nickel for which the value was 13.1 min. The determination of each of these six cations is possible in the presence of other five, if their concentration is up to 4 times. All six metals were determined in river water (RSD approximately 0.7-7.7%) and tap water samples (RSD approximately 0.3-5.7%). The estimation of Co was made in the samples of multivitamin tablets (RSD < 2.3%). The results agree with those quoted by manufacturers.

A polystyrene based membrane electrode for cadmium(II) ions

A polystyrene based membrane of 3,4:12,13-dibenzo-2,5,11,14-tetraoxo- 1,6,10,15-tetraazacyclooctade-cane shows a Nernstian response to Cd(II) ions over a wide concentration range (3.16 x 10(-6) - 1.00 x 10(-1) mol L(-1) with a Nernstian slope of 29.8 mV/decade of concentration, between pH 2.0 and 6.0. This electrode has been found to be chemically inert and of adequate stability with a response time of 20s. The electrode gives reproducible results with a lifetime of 130 days. The membrane works satisfactorily in a partially non-aqueous medium up to a maximum 35% (v/v) content of methanol and ethanol. The practical utility of the proposed chemical sensor has been observed by using it as end-point indicator in the titration of Cd(II) ions with EDTA. The potentiometric selectivity coefficient values indicate that the membrane sensor is highly selective for Cd(II) ions over a number of cations. Small amounts of surfactants do not disturb the functioning of the sensor. This electrode has also been used to estimate cadmium ions in real samples.

Inhibition of enterotoxin-induced porcine colonic secretion by diarylsulfonylureas in vitro

Muscle-stripped piglet colon was used to evaluate changes in short-circuit current (I(sc)) as an indicator of anion secretion. Mucosal exposure to Escherichia coli heat-stable (STa) or heat-labile enterotoxins (LT) stimulated I(sc) by 32 +/- 5 and 42 +/- 7 microA/cm(2), respectively. Enterotoxin-stimulated I(sc) was not significantly affected by either 4,4'-diaminostilbene-2, 2'-disulfonic acid or CdCl(2), inhibitors of Ca(2+)-activated Cl(-) channels and ClC-2 channels, respectively. Alternatively, N-(4-methylphenylsulfonyl)-N'-(4-trifluoromethylphenyl)urea (DASU-02), a compound that inhibits cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl(-) secretion, reduced I(sc) by 29 +/- 7 and 34 +/- 11 microA/cm(2), respectively. Two additional diarylsulfonylurea (DASU)-based compounds were evaluated for their effects on enterotoxin-stimulated secretion. The rank order of potency for inhibition by these three closely related DASU structures was identical to that observed for human CFTR. The degree of inhibition by each of these compounds was similar for both STa and LT. The structure- and concentration-dependent inhibition shown indicates that CFTR mediates both STa- and LT-stimulated colonic secretion. Similar structure-dependent inhibitory effects were observed in forskolin-stimulated rat colonic epithelium. Thus DASUs compose a family of inhibitors that may be of therapeutic value for the symptomatic treatment of diarrhea resulting from a broad spectrum of causative agents across species.