Disappearing cystic cerebellar medulloblastoma: the ghost tumour

A case of medulloblastoma, which disappeared following steroid administration and a single sitting of radiotherapy (8Gy) is presented. At surgical exploration tumour was not found, multiple biopsies were negative. Post operative CT scan too did not show the tumour. Five months later, tumour reappeared in left cerebellar lobe in cystic and solid form. Patient was reoperated and tumour was decompressed. The biopsy showed medulloblastoma. To our knowledge, medulloblastomas are not known to be completely responsive to either of these modalities.

Development of quantitative structure-activity relationship (QSAR) models for predicting risk of exposure from carcinogens in animals

Quantitative structure-activity relationship (QSAR) models capable of predicting acute toxicity and carcinogen potency of polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated hydrocarbons, and chlorinated insecticides have been formulated. Median lethal dose (LD50) for PCDD-exposed mice correlated negatively with polarity and positively with (H acceptor x 2 chi), whereas LD50 for PCDD-exposed guinea pigs correlated with (H acceptor x density). Both (H acceptor x 2 chi) and (H acceptor x density) exhibited parabolic relationship with log P (partition coefficient). Carcinogenic potency, determined from order of magnitude (OM) values, correlated negatively with log P and positively with (length x width). Thus, a hydrophobic mechanism plays a key role in the lethal effects of PCDD in mice, whereas both hydrophobic and electronic mechanisms are involved in the lethal effects of PCDD in guinea pigs. However, the molecule's lipophilicity, length, and width may play important roles in the carcinogenic effects of chlorinated compounds.

Reversed-phase electrochromatography of amino acids and peptides using porous polymer monoliths

Efficient and rapid separation of minute levels of amino acids and bioactive peptides is of significant importance in the emerging field of proteomics as well as in the clinical and pharmaceutical arena. We have developed novel UV-initiated acrylate-based porous polymer monoliths as stationary phases for capillary- and chip-electrochromatography of cationic, anionic, and neutral amino acids and peptides, followed by absorbance or laser-induced fluorescence detection. The rigid monoliths are cast-to-shape and are tunable for charge and hydrophobicity. For separations at low pH, monoliths containing quaternary amine moieties were used to achieve high electroosmotic flow, and for high pH separations monoliths with acidic sulfonic acid groups were employed. Efficient and reproducible separations of phenylthiohydantoin-labeled amino acids, native peptides, and amino acids and peptides labeled with naphthalene-2,3-dicarboxaldehyde (NDA) were achieved using both negatively- and positively-charged polymer monoliths in capillaries. Separation efficiencies in the range of 65,000-371,000 plates/m were obtained with capillary electrochromatography. Buffer composition and the degree of column hydrophobicity were studied systematically to optimize separations. The monoliths were also cast in the microchannels of glass chips and electrochromatographic separation followed by laser-induced fluorescence detection of three NDA-labeled bioactive peptides was obtained.

Differences between men and women in reporting of symptoms during an asthma exacerbation

STUDY OBJECTIVE

Compared with men, women presenting to the emergency department with acute asthma are more likely to be admitted and to have a longer hospital stay. This study compares peak expiratory flow rate (PEFR) with reported symptom severity between men and women with acute asthma. The null hypothesis was that men and women report similar severity symptoms for similar levels of airway obstruction.

METHODS

This study combined data from 4 prospective cohort studies performed from 1996 to 1998 as part of the Multicenter Airway Research Collaboration. Using a standardized protocol, investigators at 64 EDs in 21 US states and 4 Canadian provinces provided 24-hour per day coverage for a median of 2 weeks.

RESULTS

Of the 1,291 patients with moderate to severe exacerbations (initial percentage of predicted PEFR <80%), 62% were women. Women were more likely than men to report "severe" complaints in terms of symptom frequency, symptom intensity, and resulting activity limitations (all P <.05). Women with moderate exacerbations were especially likely to describe their exacerbation as causing "severe" activity limitations (sex-PEFR interaction, P =.05).

CONCLUSION

Men are less likely than women to report severe asthma symptoms and activity limitations in the presence of airway obstruction. This finding supports use of objective measures of airway obstruction when managing patients with asthma so that those whose symptoms do not reflect the severity of their obstruction can be recognized and properly treated. It also reconfirms the need for increased research on differences between men and women in acute asthma.

Environmental issue of exotic catfish culture in Uttar Pradesh

A survey was conducted in Uttar Pradesh to enlist the available exotic fish species in culture. The culture and feeding details of unofficially introduced Clarias gariepinus was collected from 419 ponds existing in rural areas of 23 districts of Uttar Pradesh. The data indicated that 32% ponds were culturing exotic fishes of which 79% cases are of monoculture of exotic African catfish. Feeding analysis of these exotic African catfish revealed that 7% cases subsist on natural pond feed while 29% cases are fed on slaughter house waste. In 32% cases of the exotic magur monoculture, chicken waste was given whereas 11% cases were recorded with fish waste feeding. The possible threats and environmental risks of such unauthorised and indiscreminate culture of exotic magur has been discussed in this paper.

Peroxiredoxin in bovine ocular tissues: immunohistochemical localization and in situ hybridization

Peroxiredoxins are widely distributed in nature and constitute a molecular family of antioxidant enzymes which decompose hydrogen peroxide and alkyl hydroperoxides. We have previously characterized a peroxiredoxin from bovine ciliary body and deduced its amino acid sequence from analysis of cDNA clones encoding the protein. In this work, we investigated the immunolocalization of this novel antioxidant enzyme and its mRNA expression in bovine eye tissues. High levels of immunoreactivity and mRNA for the enzyme were detected in corneal epithelium. Distinct immunoreactivity and mRNA expression for peroxiredoxin were also detected in uveal tissues, some of the retinal cell layers and ocular vasculature.

Study of radon concentrations in oil refinery premises and city dwellings

Radon and its progeny concentrations were measured in several dwellings at an oil refinery premises and these concentrations were compared with those found in dwellings in Mathura and Agra cities. Radon progeny concentrations were measured using LR-115 type II nuclear track etch detectors. The radon concentrations were estimated by using a value of 0.42 for the equilibrium factor. The geometric means (GM) of radon concentrations in the refinery dwellings, Mathura city and Agra city dwellings were 97, 91 and 75 Bq m(-3) with geometric standard deviations of 1.7, 1.8 and 1.8 respectively. The average lifetime risk of lung cancer for an adjusted annual average chronic radon exposure of 69 Bq m(-3) (7.8 mWL; WL = working level) with an occupancy factor of 0.7 comes out to be 5.4 x 10(-3).

An oligo astrocytoma with widespread calcification along axonal fibres

A rare case of a young man with a diffusely calcified oligo astrocytoma in right parieto occipital region, which spread along the axonal fibres into right temporal lobe and to the left parietal lobe is presented. Computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated the extent of the lesion. The mass was partially resected.

Quinalizarin anchored on Amberlite XAD-2. A new matrix for solid-phase extraction of metal ions for flame atomic absorption spectrometric determination

Amberlite XAD-2 has been functionalized by coupling it to quinalizarin [1,2,5,8-tetrahydroxyanthraquinone] by means of an -N = N- spacer. Elemental analysis, thermogravimetric analysis, and infrared spectra were used to characterize the resulting new polymer matrix. The matrix has been used to preconcentrate Cu(II), Cd(II), Co(II), Pb(II), Zn(II), and Mn(II) before their determination by flame atomic absorption spectrometry (FAAS). UO2(II) has been preconcentrated for fluorimetric determination. The optimum pH values for maximum adsorption of the metals are between 5.0 and 7.0. All these metal ions are desorbed (recovery 91-99%) with 4 mol L(-1) HNO3. The adsorptive capacity of the resin was found to be in the range 0.94-5.28 mg metal g(-1) resin and loading half-life (t1/2) between 5.3 and 15.0 min. The effects of NaF, NaCl, NaNO3, Na2SO4, Na3PO4, Ca(II), and Mg(II) on the adsorption of these metal ions (0.2 microg mL(-1)) are reported. The lower limits of detection for these metal ions are between 1 and 15.0 microg L(-1). After enrichment on this matrix flame AAS has been used to determine these metal ions (except the uranyl ion) in river water samples (RSD < or = 6.5%); fluorimetry was used to determine uranyl ion in well water samples (RSD < or = 6.3%). Cobalt from pharmaceutical vitamin tablets was preconcentrated by use of this chelating resin and estimated by FAAS (RSD approximately 4%).

Development of QSAR models to predict estrogenic, carcinogenic, and cancer protective effects of phytoestrogens

An integrated QSAR model has been formulated to predict estrogenic, carcinogenic, and cancer protective effects of phytoestrogens (PE). Relative binding of PEs to estrogen receptors ER alpha and ER beta exhibited a parabolic relationship with dipole moment (mu). The high-affinity binding of PEs to ER alpha correlated with Dif0 (0 chi-0 chi v difference index encoding nonsigma electronic charge), while the low-affinity binding of PEs to ER alpha correlated with H bonding (positive coefficient) and % hydrophilic surface (negative coefficient). The high-affinity binding of PEs to ER beta correlated with molecular with (MWd) and Dif0, while the low-affinity binding of PEs to ER beta correlated with H bonding (positive coefficient) and hydrophilic-lipophilic balance (negative coefficient). Thus an increase in electronic or ionic charge, formation of H bonds, or a decrease in hydrophilic property of PEs may increase their binding to ER. The relative transcription activity (RTA) of ER alpha correlated with Dif0-Dif1, while RTA of ER beta correlated with H bonding and polarity. The PE-induced stimulation of DNA synthesis in estrogen-sensitive breast cancer (BC) cells correlated positively with (MD*4 chi v) where MD is molecular depth and 4 chi v is the valence of a 4th order fragment. IC50 for PE-induced inhibition of DNA synthesis in estrogen-sensitive BC cells correlated with (MD*Log P) and Dif3 (3 chi-3 chi v difference index encoding nonsigma electronic charge of fragments consisting of four atoms and three bonds) and Dif3(2). IC50 for PE-induced inhibition of DNA synthesis in estrogen-independent cancer cell lines correlated with (MD*Log P) and 1/water solubility. Thus molecular shape and molecular connectivity of PEs play a key role in modulating estrogen-induced transactivation activity and DNA synthesis in BC cells.

Immunopathogenesis of the antiphospholipid antibody syndrome: an update

The primary antiphospholipid antibody syndrome is characterized clinically by the presence of venous and arterial thrombosis, recurrent fetal loss, and thrombocytopenia. The presence of antiphospholipid antibodies is a central serologic finding in primary antiphospholipid antibody syndrome, and plays a critical role in diagnosis. Contrary to initial reports, it is now widely accepted that these autoantibodies are directed predominantly against two antigens: phospholipid-binding plasma protein beta2-glycoprotein I and prothrombin. The mechanism by which antiphospholipid antibodies cause disease is under vigorous investigation. It is hypothesized that antiphospholipid antibodies induce a procoagulant state by binding to antigens on endothelial cells and trophoblast cell surfaces. Indeed, beta2-glycoprotein I appears to function as a cofactor that facilitates this interaction. The resulting endothelial cell activation is associated with cell-surface expression of adhesion molecules that lead to monocyte adhesion - the first steps in thrombosis. Although the precise mechanism that mediates endothelial cell-platelet interaction have not been fully elucidated, platelet binding to the endothelium appears to be the next phase in thrombosis. Thus, the antiphospholipid antibody may be a triggering or activating factor in placental spiral artery thrombosis and subsequent placental infarction. More recently, a role for annexin V has emerged. Studies suggest that thrombosis in the antiphospholipid syndrome may be due to disruption of the annexin shield by antiphospholipid (and cofactor) antibodies, which results in the increased exposure of trophoblasts and endothelial cells to thrombogenic phospholipids.

Inhibitory effect of silibinin on ligand binding to erbB1 and associated mitogenic signaling, growth, and DNA synthesis in advanced human prostate carcinoma cells

We recently showed the inhibitory effect of a flavonoid antioxidant, silymarin, on erbB1-Shc activation in prostate cancer (PCA) DU145 cells. In the present study, we performed more detailed mechanistic and molecular modeling studies with pure silibinin to assess and define its effect on membrane signaling related to erbB1 activation in human PCA LNCaP and DU145 cells. Studies also were performed to establish the biologic responses toward extracellular signal-regulated protein kinase 1/2 (ERK1/2) activation, cell growth, and DNA synthesis. Treatment of serum-starved cells with various doses of silibinin for 2 h followed by (125)I-epidermal growth factor (EGF) showed 30-75% inhibition in ligand binding and 55-95% inhibition in its internalization in LNCaP cells and 20-64% and 12-27% inhibition in these two events in DU145 cells. Time-response studies showed similar effects. In further studies, treatment of serum-starved cultures with silibinin followed by EGF showed strong inhibitory effects on membrane and cytoplasmic signaling molecules. In the case of erbB1 activation, silibinin showed a 58-75% decrease in LNCaP and a 40-100% decrease in DU145 cells at 50, 75, and 100-microg/mL doses. Inhibitory effects of silibinin also were evident on ERK1/2 activation (20-80% inhibition) in both cell lines. Treatment of serum-starved cultures with silibinin resulted in 20-40% and 30-55% inhibition of LNCaP and DU145 cell growth, respectively, at similar doses after 1-3 d of treatment, and 10-50% cell death in both cell lines. Under 10% serum conditions, identical silibinin treatments resulted in 20-65% inhibition of cell growth in LNCaP and DU145 cells but did not cause any cell death. Similar doses of silibinin treatments for 24 h also resulted in 25-60%, 35-40%, and 36-50% inhibition of DNA synthesis when cells were cultured in 10% serum, totally serum starved, and serum starved plus stimulated with EGF, respectively. Molecular modeling of silibinin showed that it is a highly lipophilic compound, suggesting that it interacts with lipid-rich plasma membrane, including binding with erbB1, thereby competing with the EGF-erbB1 interaction. Because the ligand-erbB1 autocrine-loop is causally involved in advanced and androgen-independent PCA, the observed effects of silibinin and its strong lipophilic nature could be useful in developing this agent for the prevention and therapy of PCA.

A beta-blocker, not magnesium, is effective prophylaxis for atrial tachyarrhythmias after coronary artery bypass graft surgery

OBJECTIVE

To evaluate magnesium as a sole or adjuvant agent with currently used prophylactic drugs in suppressing postoperative atrial tachyarrhythmias (POAT) after coronary artery bypass graft (CABG) surgery.

DESIGN

Single-center prospective, randomized clinical trial.

SETTING

University hospital.

PARTICIPANTS

Patients (n = 400) undergoing CABG surgery.

INTERVENTIONS

Patients were randomized among 6 prophylaxis regimens: (1) control (no antiarrhythmics), (2) magnesium only, (3) digoxin only, (4) magnesium and digoxin, (5) propranolol only, and (6) magnesium and propranolol. Patients randomized to a regimen including magnesium received 12 g given during 96 hours postoperatively. Patients in a digoxin regimen received 1 mg after cardiopulmonary bypass and 0.25 mg daily. Patients in a propranolol regimen received 1 mg intravenously every 6 hours until able to take 10 mg orally 4 times a day. Prophylaxis regimens were discontinued after 4 days postoperatively.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was a sustained POAT or discharge from the hospital. Control patients had an incidence of POAT (38%) not significantly different from patients in magnesium-only (38%), digoxin-only (31%), and magnesium with digoxin (37%) regimens. Patients treated with propranolol had a significant reduction in POAT. Nearly identical POAT rates in the propranolol-only (18%) and propranolol with magnesium (19%) groups support the lack of efficacy of magnesium in this trial. Study design allowed analysis of and showed a beta-blocker withdrawal effect in addition to suppressive benefit of postoperative beta-blockers.

CONCLUSION

beta-Blocker prophylaxis is indicated to reduce the incidence of POAT in CABG surgery patients and to prevent a beta-blocker withdrawal effect in patients receiving these medications preoperatively. Digoxin and magnesium as sole or adjuvant agents do not offer suppressive or ventricular rate reduction benefits in POAT.

Pattern of ear, nose, pharynx, larynx and oesophagus(enplo) cancers in a rural based hospital

A total of 1527 cases of total body cancer (TBC) presented at M G I M S between 1(st) Jan. 1992 to 30(th) April 1999. ENPLO cancers comprised 656 (42.9%)casees. Ca cervix was the commonest cancer amongst TBC comprising 15.3% cases. Ca oral cavity was the commoncest among ENPLO cancers comprising 24.3% cases followed by Ca oesophagus comprising 19.1% Ca oropharynx comprising 16.9%, Ca hypopharynx comprising 13.4%, Ca larynx comprising 11.3% and Ca Nose and PNS comprising 5.7% cases. ENPLI cancers constiuted the major burden of TBC in our hospital.

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.