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.

Treatment of the alcohol intoxications: ethylene glycol, methanol and isopropanol

Intoxications with ethylene glycol, methanol, and isopropanol are among the most common ingestions, in the treatment of which a nephrologist plays an important role. These three substances have the ideal characteristics for intervention by hemodialysis, and the three parent compounds and their metabolites are readily dialyzable. Two of the three substances, ethylene glycol and methanol, are metabolized to more toxic substances, so that an early treatment strategy that removes the parent compound or blocks its metabolism can prevent the development of many of the adverse events that are often seen in these ingestions. Fomepizole, an inhibitor of alcohol dehydrogenase, slows the metabolism of these substances and is now approved by the US Food and Drug Administration for use in ethylene glycol intoxication. The present review addresses recent advances in the diagnosis and treatment of intoxication with ethylene glycol, methanol and isopropanol.

Estrogen inhibition of cystic fibrosis transmembrane conductance regulator-mediated chloride secretion

Cystic fibrosis (CF) is an autosomal genetic disease associated with impaired epithelial ion transport. Mutations in the CF gene alter the primary sequence of the CF transmembrane conductance regulator (CFTR). Several therapeutic modalities have been proposed for CF patients, including the phytoestrogen genistein. Experiments were completed in cellular and subcellular systems to evaluate the impact of naturally occurring and synthetic estrogens on epithelial ion transport, and specifically on the CF protein CFTR. 17beta-Estradiol, a naturally occurring estrogen, caused a rapid and reversible inhibition of forskolin-stimulated chloride secretion across T84 epithelial cell monolayers with a K(i) of 8 microM. In addition, 17alpha-estradiol, a stereoisomer that fails to bind and activate nuclear estrogen receptors was equipotent with 17beta-estradiol, arguing against a genomic-mediated mechanism of action. Synthetic estrogens, including diethylstilbesterol and the antiestrogen tamoxifen likewise inhibited forskolin-stimulated ion transport. Aldosterone, dexamethasone, and cholesterol were without effect at the highest concentrations tested (>/=1 mM). Studies indicated that diethylstilbesterol and other synthetic estrogens that inhibited anion secretion in intact monolayers likewise inhibited CFTR chloride channel activity with similar concentration dependencies in excised membrane patches. Experiments with radioactive photoactivatable estrogen derivatives demonstrated that these compounds bind directly to CFTR expressed in insect cells. Taken together, the data suggest that estrogens can interact directly with CFTR to alter anion transport.

Episomal and stable expression of the luciferase reporter gene for quantifying Leishmania spp. infections in macrophages and in animal models

We have expressed the reporter firefly luciferase gene (LUC) in Leishmania donovani and Leishmania major either as part of episomal vectors or integrated into the parasite genome under the control of their respective ribosomal promoter regions. An excellent linear correlation between parasite number and luciferase activity was observed with all the transfectants. LUC-expressing recombinant parasites were useful to monitor Leishmania spp. infections in macrophages or in animal models. For prolonged growth in absence of drug selection, such as within animal models, quantitation of parasites is more reliable when the reporter gene LUC is stably integrated in the parasite genome. These recombinant strains should be useful tools to monitor Leishmania growth under a number of conditions.

Role of angiotensin II in diabetic nephropathy

Considerable evidence suggests that the intrarenal renin-angiotensin system plays an important role in diabetic nephropathy. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II (Ang II) receptor blockers (ARBs) can attenuate progressive glomerulosclerosis in disease models and can slow disease progression in humans. Because agents that interfere with Ang II action may decrease glomerular injury without altering glomerular pressures, it has been suggested that Ang II has direct effects on glomerular cells to induce sclerosis independent of its hemodynamic actions. To study nonhemodynamic effects of Ang II on matrix metabolism, many investigators have used cell culture systems. Glucose and Ang II have been shown to produce similar effects on renal cells in culture. For instance, incubation of mesangial cells in high-glucose media or in the presence of Ang II stimulates matrix protein synthesis and inhibits degradative enzyme (e.g., collagenase, plasmin) activity. Glucose and Ang II also can inhibit proximal tubule proteinases. Glucose increases expression of the angiotensinogen gene in proximal tubule cells and Ang II production in primary mesangial cell culture, which indicates that high glucose itself can activate the renin-angiotensin system. The effects of glucose and Ang II on mesangial matrix metabolism may be mediated by transforming growth factor-beta (TGF-beta). Exposure of mesangial cells to glucose or Ang II increases TGF-beta expression and secretion. Their effects on matrix metabolism can be blocked by anti-TGF-beta antibody or ARBs such as losartan, which also prevents the glucose-induced increment in TGF-beta secretion. Taken together, these findings support the hypothesis that the high-glucose milieu of diabetes increases Ang II production by renal, and especially, mesangial cells, which results in stimulation of TGF-beta secretion, leading to increased synthesis and decreased degradation of matrix proteins, thus producing matrix accumulation. This may be an important mechanism linking hyperglycemia and Ang II in the pathogenesis of diabetic nephropathy.

A simple method to detect an albumin permeability factor in the idiopathic nephrotic syndrome

BACKGROUND

Several investigators have detected an albumin permeability factor in the serum of patients with the idiopathic nephrotic syndrome (INS), that is, minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS), but the methods used have been complex.

METHODS

We describe here a simpler method using cultured rat glomerular epithelial cell monolayers grown to confluence on Millicell filters, which allow sampling of apical and basolateral media. 125I-labeled human serum albumin (125I-HSA) was added to the basolateral compartment, and its leakage across the epithelial cell monolayer into the apical compartment was measured.

RESULTS

In untreated cells (negative control), the albumin leakage reached 5.3% at 18 hours. Cell monolayers fixed with 95% ethanol (positive control) showed 62% leakage. Sera from three out of four patients with MCD and three out of four with FSGS resulted in considerable albumin leakage, whereas sera from nine patients with other types of nephrotic renal disease and five normal subjects caused no leakage.

CONCLUSION

This study shows that the Millicell system provides a simple and useful method to screen for permeability factors in the INS.

Outcome of patients with rectal adenocarcinoma and localized pelvic non-nodal metastatic foci

PURPOSE

The aim of this study was to evaluate the outcome of patients with primary rectal adenocarcinoma and soft tissue metastatic foci restricted to the pelvis and to determine whether this entity, which is considered N1 disease in the American Joint Committee on Cancer staging system, behaves like completely replaced nodal disease or the first sign of M1 disease. The clinical course for patients with this finding is not well-described in the literature.

METHODS

The authors retrospectively reviewed the medical records of 395 patients with rectal adenocarcinoma who received radiation treatment. Eighteen patients had pelvic soft tissue metastatic foci. Exclusions from this study included 1) cases without metastatic pelvic foci; 2) cases of recurrent cancer; 3) cases with known distant metastatic disease as defined by American Joint Committee on Cancer criteria; and 4) cases with extrapelvic metastatic foci. All patients received adjuvant radiotherapy. Thirteen cases received preoperative radiotherapy. Four cases received postoperative radiotherapy. One case received both preoperative and postoperative radiotherapy. Eight cases received chemotherapy.

RESULTS

All eighteen patients had T3 or T4 lesions. Thirteen patients had lymph nodes that contained metastatic disease and would therefore have been scored N1 or N2 even without the pelvic tumor implants. Sixteen of 18 (89 percent) patients died of disease after a survival time of 12 to 37 (mean, 25) months. Only 1 of 18 (6 percent) patients was disease free at five years. The other remaining survivor was undergoing palliative therapy for metastatic disease to the lung. This is significantly worse than our institution's experience with T3,4N+ disease after preoperative radiation (5-year survival, 11 vs. 56 percent; P = 0.0002, Generalized Wilcoxon of Breslow). There was a high incidence of local (9/18) and distant (14/18) failure. No other factor, including radiation dose, margin status, chemotherapy, T stage, and number of involved nodes or soft tissue implants, correlated independently with outcome.

CONCLUSIONS

Pelvic metastatic foci confer a significantly worse prognosis than other T3,4N+ disease. Such cases should be excluded from prospective trials for localized disease. Although this entity probably represents M1 disease for most patients, survival can be long, and aggressive locoregional and systemic treatment is warranted.

Evaluation of (99m)Tc-labeled photosan-3, a hematoporphyrin derivative, as a potential radiopharmaceutical for tumor scintigraphy

A quick and reproducible method for radiolabeling of Photosan-3(R), a photosensitizer used worldwide for photodynamic therapy (PDT) of cancer, with radioisotope of technetium ((99m)Tc) was developed. The radiotracer was evaluated for radiochemical purity, stability, and finally tissue distribution in a murine tumor model. The (99m)Tc-Photosan-3 prepared by using (99m)Tc-pertechnetate in place of reduced (99m)Tc demonstrated better labeling efficiency (>90%) and reproducibility. The procedure also minimized the radiation exposure to the radiochemist as handling time was considerably reduced. Due to the commercial availability of Photosan-3, the risk of batch-to-batch variation in the in situ synthesis of hematoporphyrin derivative, which is a complex mixture of at least five compounds, was also significantly reduced. The biodistribution studies and tumor scintigraphy confirmed that (99m)Tc-labeled Photosan-3 was preferentially taken up by the neoplastic tissue in a manner similar to the parent compound. In addition to applications in tumor imaging, (99m)Tc-Photosan-3 could also be used for estimating tumor uptake of Photosan-3 as may be required for individualization of clinical protocols of PDT.

Design, synthesis and antitumor cytotoxicity of novel bis-benzimidazoles

A series of novel bis-benzimidazoles, IIa-e, IIIa-e and IVa-g, was designed, synthesized and evaluated for anticancer properties. Certain additional analogs were also designed by introducing the p-quinone moiety, a characteristic feature found in mitomycin C, indolequinones and other examples of bioreductively activated alkylating agents. Structural changes of the bis-benzimidazole nucleus with various leaving groups were investigated for their effects on their pharmacological properties. These compounds were evaluated for their cytotoxicity against human cancer cell lines. The results of the studies indicate that the compounds IIa, IIc, IVa, IVc, IVd and IVg possess significant cytotoxic activities against 22 cell lines in seven cancer panels with GI50 values between <0.01 and 99.5 microM especially in the cases of renal cancer, CNS cancer, colon cancer, melanoma and breast cancer.

Growing skull fracture of ethmoid: a report of two cases

We describe a rare sequel of ethmoid fracture--a growing skull fracture associated with cerebrospinal fluid rhinorrhoea following trauma sustained in adult life. The natural history of its development, diagnosis, and the results of surgery are discussed. The literature is reviewed with regard to aetiology, incidence, imaging characteristics and management of this rare post-traumatic complication.

Amberlite XAD-7 impregnated with Xylenol Orange: a chelating collector for preconcentration of Cd(II), Co(II), Cu(II), Ni(II), Zn(II) and Fe(III) ions prior to their determination by flame AAS

A new chelating resin, Xylenol Orange coated Amberlite XAD-7, was prepared and used for preconcentration of Cd(II), Co(II), Cu(II), Fe(III), Ni(II) and Zn(II) prior to their determination by flame atomic absorption spectrophotometry. The optimum pH values for quantitative sorption of Cd(II), Co(II), Cu(II), Fe(III), Ni(II) and Zn(II) are 4.5-5.0, 4.5, 4.0-5.0, 4.0, 5.0 and 5.0-7.0, respectively, and their desorptions by 2 mol L(-1) HCl are instantaneous. The sorption capacity of the resin has been found to be 2.0, 2.6, 1.6, 1.6, 2.6 and 1.8 mg g(-1) of resin for Cd, Co, Cu, Fe, Ni and Zn, respectively. The tolerance limits of electrolytes, NaCl, NaF, NaI, NaNO3, Na2SO4 and of cations, Mg2+ and Ca2+ in the sorption of the six metal ions are reported. The preconcentration factor was between 50 and 200. The t1/2 values for sorption are found to be 5.3, 2.9, 3.2, 3.3, 2.5 and 2.6 min for the six metals, respectively. The recoveries are between 96.0 and 100.0% for the different metals at preconcentration limits between 10 to 40 ng mL(-1). The preconcentration method has been applied to determine the six metal ions in river water samples after destroying the organic matter (if present in very large amount) with concentrated nitric acid (RSD < or = 8%, except for Cd for which it is upto 12.6%) and cobalt content of vitamin tablets with RSD of approximately 3.0%.