Photocatalytic degradation of fluoroquinolone antibiotics using chitosan biopolymer functionalized copper oxide nanoparticles prepared by facile sonochemical method

Photocatalytic degradation is an excellent method for removing pharmaceutical residues due to their simplicity, ecological benignity, high efficiency, and exceptional stability. Herein, we demonstrate the sonochemically synthesised chitosan biopolymer functionalized copper oxide nanoparticles as an efficient photocatalyst for the degradation of fluoroquinolone-based antibiotics. The X-ray diffraction Rietveld refinement revealed the formation of single-phase copper oxide (CuO) with a monoclinic structure. The presence of biopolymer functionalization was corroborated by Fourier Transform Infrared spectroscopy by observing the -NH2 and -OH functional groups. The high-resolution transmission electron microscopic images inferred that Chitosan functionalized copper oxide (C-CuO) particles are nano-sized with a smooth texture and aggregation-free particles. The strong absorbance and the broad photoluminescence emission in the ultraviolet-visible region confirm the suitability of CuO and C-CuO nanoparticles for photocatalytic applications. The catalytic activity was studied against fluoroquinolone-based antibiotics such as ciprofloxacin and norfloxacin under direct sunlight illumination. Interestingly, the C-CuO catalyst demonstrated 71.07 % (@140 min.) and 71.9 % (@60 min.) of degradation for ciprofloxacin and norfloxacin, respectively. The obtained photocatalytic activity of the prepared CuO and C-CuO catalysts was superior to the CuO particles prepared by the coprecipitation method (CC-CuO).

Factors predicting prolonged hospitalization after abdominal wall hernia repair - a prospective observational study

Objective: The aim of this study was to identify the factors predicting prolonged hospitalization following abdominal wall hernia repair.

Material and Methods: This was a prospective observational study which included patients operated for elective and emergency abdominal wall hernias. Details of the patients including demographic profile, hernia characteristics, and perioperative factors were collected. Patients were followed up till discharge from the hospital to record the postoperative local and systemic complications. Patients who stayed for more than three days were considered as longer hospital stay. Analysis was performed to identify factors associated with the longer hospital stay.

Results: A total of 200 consecutive patients of abdominal wall hernia were included over a period of two years. Female sex (p< 0.05), obesity (p= 0.022), and smoking and alcohol consumption (0.002) led to a prolonged hospital stay. Patients with incisional hernias (p< 0.05), American Society of Anesthesiologists (ASA) class of two or more (p= 0.002), complicated hernia (p= 0.007), emergency surgeries (p= 0.002), general anesthesia (p= 0.001), longer duration of surgery (>60 minutes, p< 0.05), usage of drain (p< 0.05), and surgical site infection (SSI, p= 0.001) were significantly associated with increased length of hospital stay. Whereas, age distribution, socio-economic status, co-morbidities, recurrent surgery, type of hernia repair and the level of surgeon did not affect the length of hospital stay.

Conclusion: The risk factors associated with prolonged hospital stay in patients undergoing abdominal wall hernia repair were female sex, obesity, smoking and alcoholism, incisional hernia, complicated hernias, higher ASA class, and prolonged duration of surgeries.

Buffer Layer Assisted Chemistry over Amorphous Solid Water: Oxide Thin Film or Metallic Nanoparticles Formation

Novel procedures to grow pure thin metal oxide films are always welcome in view of their wide range of applications including photocatalysis, solar cells, sensors, and more. In this paper we present a unique way to grow pure nanofilms of metal oxides in vacuo at the temperature range 110-170 K. The reactive layer assisted deposition (RLAD) procedure for thin oxide films growth is based on the evaporation of a reactive metal element on top of a condensed layer of amorphous solid water (D₂O-ASW). When applied to metals that do not react with the water layer, the process yields metal nanoclusters on the substrate. We observed that metal oxide films are formed if the redox potential is of -1.0 V or less, leading to deuterium molecules ejection to the gas phase (e.g., Ti and Al) while metals such as Zn, Fe, and Ag, with redox potentials more than -1.0 V, transform into nanoclusters, as revealed by SEM studies. We conclude that the redox potential ia a parameter that enables one to predict the nature and outcome of the ASW buffer layer assisted chemistry.

Comparison of haematological and biochemical changes between non-anaemic and anaemic primigravid women in a north Indian population to establish normative values

Pregnancy is accompanied by several haemodynamic, biochemical and haematological changes, which may lead to severe problems, if they are not suitably addressed. The current study highlights the haematological and biochemical differences observed in anaemic (AP) and non-anaemic primigravida (NAP), in the 2nd trimester, in a north Indian population. There were significant differences (p < 0.05) in the body weight and body temperature of NAP compared with AP. A significant decrease (p < 0.001) in haematological parameters including haemoglobin, haematocrit, erythrocyte count, MCH and MCHC, was observed in AP; however, MCV was found to be significantly higher (p = 0.038). Many biochemical parameters viz. potassium, albumin, total protein and calcium levels were significantly reduced (p < 0.01) in AP, except alkaline phosphatase whose level was found significantly increased (p < 0.01). The findings of the study suggest that haematological and biochemical changes take place in anaemia during pregnancy. Further, the results obtained should be used for establishing normative values for similar populations.

Stress produces aversion and potentiates cocaine reward by releasing endogenous dynorphins in the ventral striatum to locally stimulate serotonin reuptake

Activation of the dynorphin/κ-opioid receptor (KOR) system by repeated stress exposure or agonist treatment produces place aversion, social avoidance, and reinstatement of extinguished cocaine place preference behaviors by stimulation of p38α MAPK, which subsequently causes the translocation of the serotonin transporter (SERT, SLC6A4) to the synaptic terminals of serotonergic neurons. In the present study we extend those findings by showing that stress-induced potentiation of cocaine conditioned place preference occurred by a similar mechanism. In addition, SERT knock-out mice did not show KOR-mediated aversion, and selective reexpression of SERT by lentiviral injection into the dorsal raphe restored the prodepressive effects of KOR activation. Kinetic analysis of several neurotransporters demonstrated that repeated swim stress exposure selectively increased the V(max) but not K(m) of SERT without affecting dopamine transport or the high-capacity, low-affinity transporters. Although the serotonergic neurons in the dorsal raphe project throughout the forebrain, a significant stress-induced increase in cell-surface SERT expression was only evident in the ventral striatum, and not in the dorsal striatum, hippocampus, prefrontal cortex, amygdala, or dorsal raphe. Stereotaxic microinjections of the long-lasting KOR antagonist norbinaltorphimine demonstrated that local KOR activation in the nucleus accumbens, but not dorsal raphe, mediated this stress-induced increase in ventral striatal surface SERT expression. Together, these results support the hypothesis that stress-induced activation of the dynorphin/KOR system produces a transient increase in serotonin transport locally in the ventral striatum that may underlie some of the adverse consequences of stress exposure, including the potentiation of the rewarding effects of cocaine.

Ligand directed signaling differences between rodent and human κ-opioid receptors

KOR activation of Gβγ dependent signaling results in analgesia, whereas the dysphoric effects of KOR agonists are mediated by a different pathway involving G protein receptor kinase and non-visual arrestin. Based on this distinction, a partial KOR agonist that does not efficiently activate arrestin-dependent biased signaling may produce analgesia without dysphoria. No KOR-selective partial agonists are currently available, and preclinical assessment is complicated by sequence differences between rodent (r) and human (h) KOR. In this study, we compared the signaling initiated by the available partial agonists. Pentazocine was significantly more potent at activating p38 MAPK in hKOR than rKOR expressed in HEK293 cells but equally potent at arrestin-independent activation of ERK1/2 in hKOR and rKOR. Similarly, butorphanol increased phospho-p38-ir in hKOR-expressing cells but did not activate p38 in rKOR-HEK293. Like pentazocine, butorphanol was equally efficacious at activating ERK1/2 in rKOR and hKOR. In contrast, levorphanol, nalorphine, and U50,488 did not distinguish between hKOR and rKOR in p38 MAPK activation. Consistent with its low potency at p38 activation, pentazocine did not produce conditioned place aversion in mice. hKOR lacks the Ser-369 phosphorylation site in rKOR required for G protein receptor kinase/arrestin-dependent p38 activation, but mutation of the Ser-358 to asparagine in hKOR blocked p38 activation without affecting the acute arrestin-independent activation of ERK1/2. This study shows that hKOR activates p38 MAPK through a phosphorylation and arrestin-dependent mechanism; however, activation differs between hKOR and rKOR for some ligands. These functional selectivity differences have important implications for preclinical screening of partial KOR agonists.

G Protein-coupled receptor kinase 5 is localized to centrosomes and regulates cell cycle progression

G protein-coupled receptor kinases (GRKs) are important regulators of G protein-coupled receptor function and mediate receptor desensitization, internalization, and signaling. While GRKs also interact with and/or phosphorylate many other proteins and modify their function, relatively little is known about the cellular localization of endogenous GRKs. Here we report that GRK5 co-localizes with γ-tubulin, centrin, and pericentrin in centrosomes. The centrosomal localization of GRK5 is observed predominantly at interphase and although its localization is not dependent on microtubules, it can mediate microtubule nucleation of centrosomes. Knockdown of GRK5 expression leads to G2/M arrest, characterized by a prolonged G2 phase, which can be rescued by expression of wild type but not catalytically inactive GRK5. This G2/M arrest appears to be due to increased expression of p53, reduced activity of aurora A kinase and a subsequent delay in the activation of polo-like kinase 1. Overall, these studies demonstrate that GRK5 is localized in the centrosome and regulates microtubule nucleation and normal cell cycle progression.

Selective p38α MAPK deletion in serotonergic neurons produces stress resilience in models of depression and addiction

Maladaptive responses to stress adversely affect human behavior, yet the signaling mechanisms underlying stress-responsive behaviors remain poorly understood. Using a conditional gene knockout approach, the α isoform of p38 mitogen-activated protein kinase (MAPK) was selectively inactivated by AAV1-Cre-recombinase infection in specific brain regions or by promoter-driven excision of p38α MAPK in serotonergic neurons (by Slc6a4-Cre or ePet1-Cre) or astrocytes (by Gfap-CreERT2). Social defeat stress produced social avoidance (a model of depression-like behaviors) and reinstatement of cocaine preference (a measure of addiction risk) in wild-type mice, but not in mice having p38α MAPK selectively deleted in serotonin-producing neurons of the dorsal raphe nucleus. Stress-induced activation of p38α MAPK translocated the serotonin transporter to the plasma membrane and increased the rate of transmitter uptake at serotonergic nerve terminals. These findings suggest that stress initiates a cascade of molecular and cellular events in which p38α MAPK induces a hyposerotonergic state underlying depression-like and drug-seeking behaviors.

Non-visual arrestins are constitutively associated with the centrosome and regulate centrosome function

In addition to regulating receptor activity, non-visual arrestins function as scaffolds for numerous intracellular signaling cascades and as regulators of gene transcription. Here we report that the two non-visual arrestins, arrestin2 and arrestin3, localize to the centrosome, a key organelle involved in microtubule nucleation and bipolar mitotic spindle assembly. Both arrestins co-localized with the centrosomal marker gamma-tubulin during interphase and mitosis and were found in purified centrosome preparations. In vitro binding assays demonstrated that both arrestins directly interact with gamma-tubulin. Knockdown of either arrestin by RNA interference resulted in multinucleation, centrosome amplification, and mitotic defects, although only the loss of arrestin2 triggered aberrant microtubule nucleation. Importantly, overexpression of wild type arrestin rescued the multinucleation phenotype and restored normal centrosome number in arrestin siRNA-transfected cells. Moreover, overexpression of arrestin2 or -3 rescued the multinucleation defect observed in MDA-MB-231 breast cancer cells. Taken together, our data reveal that non-visual arrestins are novel centrosomal components and regulate normal centrosome function.

Studies on sorption properties of pathogens on natural materials

Presence of pathogens in high numbers in waste water is a cause of concern. Techno economic feasibility has restricted the conventional and non conventional treatment approaches for pathogen removal. Despite prolific use, carbon adsorption technology remains an expensive treatment process. The present study investigates the use of rice husk (RH), saw dust (SD), groundnut shells (GS) as natural agro-residues and partially weathered deccan trap basalt (PWDTB) for their sorption capacities and desorption pattern for two indicator organisms viz. Escherichia coli K12 and Staphylococcus aureus. Sorption experiments were carried out at flow-rate of 1.5 bed volumes per hour (bv hr(-1)) forcell suspension volume of 4, 8, 16 and 32 bed volumes. PWDTB have shown high sorption coefficient and log removal for E. coli K12 whereas GS have shown high sorption coefficient and log removal for S. aureus. PWDTB have shown maximum desorption constant and log retention for E. coli K12 whereas GS have shown maximum desorption constant and log retention for S. aureus during desorption experiment. Retention pattern suggest that adsorption is partially irreversible for almost all the materials used. It suggest that PWDTB in combination with RH and / GS could help in removal of pathogens from waste water.

Hematopoietic lineage cell-specific protein-1 (HS1) regulates PAR-mediated ERK activation and thromboxane generation in platelets

Thrombin-induced platelet activation leads to tyrosine phosphorylation of hematopoietic lineage cell-specific protein-1 (HS1), a 75 kDa adapter protein expressed exclusively in cells of hematopoietic lineage. We have shown HS1 to be a functionally important signaling molecule downstream of PAR-4 and GPVI collagen receptor. We have thus begun to elucidate PAR signaling pathway of HS1 phosphorylation, and its functional implications. PAR-1 and PAR-4 activating peptides (SFLLRN and AYPGKF, respectively) induced HS1 phosphorylation in a Gq-dependent manner as shown by incubation with the Gq inhibitor, YM254890. Consistently, HS1 phosphorylation was abolished in platelets from Gq deficient mice upon AYPGKF stimulation. Treatment with ADP receptor antagonists did not affect HS1 phosphorylation. Pretreatment of platelets with Src kinase inhibitors abolished HS1 phosphorylation. Further Syk activation, as measured by tyrosine phosphorylation of Syk (residues 525/526), in response to PAR activation was abolished in the presence of Src inhibitors. HS1 null mice show inhibition of PAR-mediated thromboxane A2 generation compared to wild type littermates. Phosphorylation of Erk, a key signaling molecule in thromboxane generation, was also diminished in HS1 null mice platelets. Based on these findings, we conclude that tyrosine phosphorylation of HS1 occurs downstream of both PAR-1 and PAR-4. HS1 phosphorylation is a Gq mediated response regulated by Src kinases. Thus, HS1 may mediate PAR-induced thromboxane generation through regulation of Erk phosphorylation.

Synthesis, characterization and photocatalytic activity of nanotitania loaded W-MCM-41

Nanocrystalline titanium oxide (TiO(2)) is a promising material as a photocatalyst for photodecomposition of hazardous organic pollutants under illumination, because it is cheap, safe, environmentally benign, and chemically stable. However, the control of particle size and monodispersity of TiO(2) is a challenging task. The use of MCM-41, an inorganic template of uniform pore size (2-10 nm), can overcome this difficulty and produce stable nanoparticles of uniform size and shape. In an attempt to extend light absorption of the TiO(2)-based photocatalyst towards the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction, a new photocatalyst (25%TiO(2)-loaded W-MCM-41) powder was prepared. W-MCM-41, with different ratios of Si to W (Si/W = 25, 50, 75), was synthesized by a hydrothermal method and loaded with 25 wt% TiO(2) utilizing a sol-gel method. In order to compare the photocatalytic activity of our sample, titania-loaded plain MCM-41 was also prepared. These materials were characterized by various physiochemical techniques such as UV-visible absorption spectroscopy, x-ray diffraction, nitrogen adsorption-desorption isotherm measurement, Fourier transform infrared (FT-IR) spectroscopy, and transmission electron microscopy. The photocatalytic activity of the prepared samples was evaluated using methyl orange as a model organic compound. It was found that the photodegradation ability of 25% TiO(2)-loaded W-MCM-41 was highly related to the amount of W atoms present in the sample; the optimum atomic ratio of Si to W was 25. It has been confirmed that the recombination rate of electrons/holes in 25%TiO(2)/W-MCM-41 declined due to the existence of W atoms in the sample.

Municipal wastewater treatment using novel constructed soil filter system

The study gives a new approach for contaminant removal from municipal wastewater using constructed soil filter (CSF) and presents performance of two CSF units located in Mumbai, India. In this system, natural weathered rock is formulated which combines sedimentation, infiltration and biochemical processes to remove suspended solids and oxidisable organics and inorganics of the wastewater. Results show elevated dissolved oxygen (DO) levels, removal of COD (136-205 to 38-40 mg l(-1)) and BOD (80-125 to less than 12 mg l(-1)) suspended solids from 135-203 to 13-18 mg l(-1) and turbidity from 84-124 to 8-11 NTU, bacterial removal of 2.4-3.1 log order for Total coliform and Fecal coliform from site I which is almost 8 years old facility, and site II which is 3 years old. Estimated hydraulic retention time of 0.5-1.0 h, hydraulic loading of 0.036-0.047 m(3)m(-2)h(-1), no pretreatment, high DO levels in the effluent, no bio-sludge production, no mechanical aeration, low energy requirement (0.04 kW h m(-3)) and green aesthetic ambience are its unique features.

Regulation and functional consequences of ADP receptor-mediated ERK2 activation in platelets

We have previously shown that ADP-induced thromboxane generation in platelets requires signalling events from the G(q)-coupled P2Y1 receptor (platelet ADP receptor coupled to stimulation of phospholipase C) and the G(i)-coupled P2Y12 receptor (platelet ADP receptor coupled to inhibition of adenylate cyclase) in addition to outside-in signalling. While it is also known that extracellular calcium negatively regulates ADP-induced thromboxane A2 generation, the underlying mechanism remains unclear. In the present study we sought to elucidate the signalling mechanisms and regulation by extracellular calcium of ADP-induced thromboxane A2 generation in platelets. ERK (extracllular-signal-regulated kinase) 2 activation occurred when outside-in signalling was blocked, indicating that it is a downstream event from the P2Y receptors. However, blockade of either P2Y1 or the P2Y12 receptors with corresponding antagonists completely abolished ERK phosphorylation, indicating that both P2Y receptors are required for ADP-induced ERK activation. Inhibitors of Src family kinases or the ERK upstream kinase MEK [MAPK (mitogen-activated protein kinase)/ERK kinase] abrogated ADP-induced ERK phosphorylation and thromboxane A2 generation. Finally ADP- or G(i)+G(z)-induced ERK phosphorylation was blocked in the presence of extracellular calcium. The present studies show that ERK2 is activated downstream of P2Y receptors through a complex mechanism involving Src kinases and this plays an important role in ADP-induced thromboxane A2 generation. We also conclude that extracellular calcium blocks ADP-induced thromboxane A2 generation through the inhibition of ERK activation.

Nucleotide receptor signaling in platelets

Upon injury to a vessel wall the exposure of subendothelial collagen results in the activation of platelets. Platelet activation culminates in shape change, aggregation, release of granule contents and generation of lipid mediators. These secreted and generated mediators trigger a positive feedback mechanism potentiating the platelet activation induced by physiological agonists such as collagen and thrombin. Adenine nucleotides, adenosine diphosphate (ADP) and adenosine triphosphate (ATP), released from damaged cells and that are secreted from platelet-dense granules, contribute to the positive feedback mechanism by acting through nucleotide receptors on the platelet surface. ADP acts through two G protein-coupled receptors, the Gq-coupled P2Y1 receptor, and the Gi-coupled P2Y12 receptor. ATP, on the other hand, acts through the ligand-gated channel P2X1. Stimulation of platelets by ADP leads to shape change, aggregation and thromboxane A2 generation. ADP-induced dense granule release depends on generated thromboxane A2. Furthermore, costimulation of both P2Y1 and P2Y12 receptors is required for ADP-induced platelet aggregation. ATP stimulation of P2X1 is involved in platelet shape change and helps to amplify platelet responses mediated by agonists such as collagen. Activation of each of these nucleotide receptors results in unique signal transduction pathways that are important in the regulation of thrombosis and hemostasis.

G-protein Dependent Platelet Signaling - Perspectives for Therapy

Platelet activation and aggregation is an integral component of the pathophysiology that leads to thrombotic and ischemic diseases such as cerebral stroke, peripheral vascular disease and myocardial infarction. Anti-platelet agents (such as aspirin, ADP receptor antagonists, and GPIIb/IIIa antagonists), phosphodiesterase inhibitors and anti-coagulants are major part of the current treatment towards treating ischemic diseases. However, their limited efficacy in the setting of arterial thrombosis, unfavorable side effect profile and cost-to-benefit issues substantiate the need for the development of newer and more efficacious antithrombotic drugs. Various platelet agonists like adenosine diphosphate (ADP), thrombin and thromboxane A2 (TXA2) activate platelets by acting via their respective surface receptors, which couple to one or more distinct G-proteins belonging to either the G(i), G(q), G(12/13) or G(s) families. Upon activation, each of these G-proteins trigger a series of intracellular signaling cascades, causing the platelets to undergo shape change, secrete their granular contents, generate positive feedback mediators and form stable platelet aggregates. In addition, various G-protein-mediated signaling cascades act in synergy with one another to amplify the magnitude of the platelet responses. The significance of G-proteins as key mediators of the platelet function and normal hemostasis is further corroborated by extensive gene knockout studies. In this review we will limit our discussion to understanding the role of G-proteins in the process of platelet activation and discuss some of the anti-thrombotic drugs that mediate their beneficial effects by interfering with or preventing the initiation of the G-protein signaling pathway.

G-protein-gated inwardly rectifying potassium channels regulate ADP-induced cPLA2 activity in platelets through Src family kinases

ADP-induced TXA2 generation requires the costimulation of P2Y1, P2Y12, and the GPIIb/IIIa receptors. Signaling events downstream of the P2Y receptors that contribute to ADP-induced TXA2 generation have not been clearly delineated. In this study, we have investigated the role of G-protein-gated inwardly rectifying potassium channels (GIRKs), a recently identified functional effector for the P2Y12 receptor, in the regulation of ADP-induced TXA2 generation. At 10-microM concentrations, the 2 structurally distinct GIRK channel blockers, SCH23390 and U50488H, caused complete inhibition of ADP-induced cPLA2 phosphorylation and TXA2 generation, without affecting the conversion of AA to TXA2 or ADP-induced primary platelet aggregation in aspirin-treated platelets. In addition, Src family kinase selective inhibitors abolished 2MeSADP-mediated cPLA2 phosphorylation and TXA2 generation. Furthermore, these GIRK channel blockers completely blocked Gi-mediated Src kinase activation, suggesting that GIRK channels are upstream of Src family tyrosine kinase activation. In weaver mouse platelets, which have dysfunctional GIRK2 subunits, ADP-induced TXA2 generation was impaired. However, we did not observe any defect in 2MeSADP-induced platelet functional responses in GIRK2-null mouse platelets, suggesting that functional channels composed of other GIRK subunits contribute to ADP-induced TXA2 generation, via the regulation of the Src and cPLA2 activity.

P2Y12 receptor-mediated potentiation of thrombin-induced thromboxane A2 generation in platelets occurs through regulation of Erk1/2 activation

BACKGROUND

Thromboxane A2 (TXA2) is a positive feedback lipid mediator that is generated upon stimulation of platelets with various agonists. Aspirin works as an antithrombotic drug by blocking the generation of TXA2. The aim of this study was to evaluate the role of the purinergic P2Y receptors in thrombin-induced TXA2 generation.

RESULTS

PAR1-activating peptide (SFLLRN), PAR4-activating peptide (AYPGKF), and thrombin, induced the activation of cytosolic phospholipase A2 (cPLA2), release of arachidonic acid (AA) from membrane-bound phospholipids, and subsequent TXA2 generation in human platelets. The actions of these agonists were significantly inhibited in the presence of the P2Y12 receptor antagonist, AR-C69931MX, but not the P2Y1 receptor antagonist, MRS2179. In addition, AYPGKF- and thrombin-induced TXA2 generation was significantly reduced in platelets from mice dosed with clopidogrel, confirming the results obtained with the human platelets. Also, Pearl mouse platelets that lack releasable nucleotides generated significantly less TXA2 when compared with the wild-type littermates in response to PAR stimulation. Inhibition of extracellular signal-regulated protein kinase 1/2 (Erk 1/2) activation using U0126, an inhibitor of MAP kinase kinase (MEK), suppressed PAR-mediated cPLA2 phosphorylation and TXA2 generation. Further, platelets that were pretreated with AR-C69931MX, as well as Pearl mouse platelets, displayed the reduced levels of Erk1/2 phosphorylation upon stimulation with the PAR agonists.

CONCLUSIONS

Based on these findings, we conclude that thrombin-induced Erk1/2 activation is essential for PAR-mediated TXA2 generation, which is potentiated by the P2Y12 receptor-mediated signaling pathway but not the P2Y1 receptor-mediated signaling pathway. Finally, using selective inhibitors of Src kinases, we show that PAR-mediated Src activation precedes Erk1/2 activation.

Molecular mechanism and functional implications of thrombin-mediated tyrosine phosphorylation of PKCdelta in platelets

Thrombin has been known to cause tyrosine phosphorylation of protein kinase C delta (PKCdelta) in platelets, but the molecular mechanisms and function of this tyrosine phosphorylation is not known. In this study, we investigated the signaling pathways used by protease-activated receptors (PARs) to cause tyrosine phosphorylation of PKCdelta and the role of this event in platelet function. PKCdelta was tyrosine phosphorylated by either PAR1 or PAR4 in a concentration- and time-dependent manner in human platelets. In particular, the tyrosine 311 residue was phosphorylated downstream of PAR receptors. Also the tyrosine phosphorylation of PKCdelta did not occur in Galpha(q)-deficient mouse platelets and was inhibited in the presence of a phospholipase C (PLC) inhibitor U73122 and calcium chelator BAPTA (5,5'-dimethyl-bis(o-aminophenoxy)ethane-N, N, N ', N '-tetraacetic acid), suggesting a role for Galpha(q) pathways and calcium in this event. Both PAR1 and PAR4 caused a time-dependent activation of Src (pp60c-src) tyrosine kinase and Src tyrosine kinase inhibitors completely blocked the tyrosine phosphorylation of PKCdelta. Inhibition of tyrosine phosphorylation or the kinase activity of PKCdelta dramatically blocked PAR-mediated thromboxane A2 generation. We conclude that thrombin causes tyrosine phosphorylation of PKCdelta in a calcium- and Src-family kinase-dependent manner in platelets, with functional implications in thromboxane A2 generation.

Platelet receptors for adenine nucleotides and thromboxane A2

Adenosine diphosphate (ADP) and thromboxane A (2) (TXA (2)) are important physiological activators of platelets and exert their effects by acting on cell surface receptors. Platelet nucleotide receptors can be distinguished as three separate subtypes of the P2 receptor family. The P2X (1) receptor is a ligand-gated adenosine triphosphate (ATP) receptor that was originally mistaken for an ADP receptor. This calcium-influx-causing receptor mediates platelet shape change and plays an important role in thrombus formation in small arterioles. The P2Y (1) receptor, through activation of G (q) and phospholipase C, is required for ADP-induced platelet shape change, fibrinogen receptor activation, and TXA (2) generation. The G (i)-coupled P2Y (12) receptor plays an important role in platelet aggregation, potentiation of dense granule release, and TXA (2) generation. Both the P2Y receptors are crucial for in vivo thrombus formation. TXA (2) stimulates two subtypes of G protein-coupled TP receptor, TPalpha and TPbeta, but its effects in platelets are mediated predominantly through the alpha isoform. Although interference with the activation of G protein-coupled ADP or TP receptors results in increased bleeding times and protection from thromboembolism, TP receptor antagonists did not translate into effective antiplatelet drugs. Blockade of ADP receptor is a mode of newer classes of antithrombotic drugs in the coming era. This review focuses on the contribution of different nucleotide receptors and TP receptors to platelet function and their potential as antithrombotic agents.

Differential requirements for calcium and Src family kinases in platelet GPIIb/IIIa activation and thromboxane generation downstream of different G-protein pathways

G(12/13) or G(q) signaling pathways activate platelet GPIIb/IIIa when combined with G(i) signaling. We tested whether combined G(i) and G(z) pathways also cause GPIIb/IIIa activation and compared the signaling requirements of these events. Platelet aggregation occurred by combined stimulation of G(i) and G(z) pathways in human platelets and in P2Y1-deficient and G alpha(q)-deficient mouse platelets, confirming that the combination of G(i) and G(z) signaling causes platelet aggregation. When G(i) stimulation was combined with G(z) stimulation, there was a small mobilization of intracellular calcium. Chelation of intracellular calcium decreased the extent of this platelet aggregation, whereas it abolished the G(q) plus G(i)-mediated platelet aggregation. Costimulation of G(i) plus G(z) pathways also caused thromboxane generation that was dependent on outside-in signaling and was inhibited by PP2, a Src family tyrosine kinase inhibitor. Src family tyrosine kinase inhibitors also inhibited platelet aggregation and decreased the PAC-1 binding caused by costimulation of G(i) and G(z) signaling pathways in aspirin-treated platelets. However, Src family kinase inhibitors did not affect G(q) plus G(i)-mediated platelet aggregation. We conclude that the combination of G(i) plus G(z) pathways have different requirements than G(q) plus G(i) pathways for calcium and Src family kinases in GPIIb/IIIa activation and thromboxane production.

Role of G protein-gated inwardly rectifying potassium channels in P2Y12 receptor-mediated platelet functional responses

The role of the G(i)-coupled platelet P2Y(12) receptor in platelet function has been well established. However, the functional effector or effectors contributing directly to alphaIIbbeta3 activation in human platelets has not been delineated. As the P2Y(12) receptor has been shown to activate G protein-gated, inwardly rectifying potassium (GIRK) channels, we investigated whether GIRK channels mediate any of the functional responses of the platelet P2Y(12) receptor. Western blot analysis revealed that platelets express GIRK1, GIRK2, and GIRK4. In aspirin-treated and washed human platelets, 2 structurally distinct GIRK inhibitors, SCH23390 (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride) and U50488H (trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(pyrrolidinyl)cyclohexyl] benzeneacetamide methanesulfonate), inhibited adenosine diphosphate (ADP)-, 2-methylthioADP (2-MeSADP)-, U46619-, and low-dose thrombin-mediated platelet aggregation. However, the GIRK channel inhibitors did not affect platelet aggregation induced by high concentrations of thrombin, AYPGKF, or convulxin. Furthermore, the GIRK channel inhibitors reversed SFLLRN-induced platelet aggregation, inhibited the P2Y(12)-mediated potentiation of dense granule secretion and Akt phosphorylation, and did not affect the agonist-induced G(q)-mediated platelet shape change and intracellular calcium mobilization. Unlike AR-C 69931MX, a P2Y(12) receptor-selective antagonist, the GIRK channel blockers did not affect the ADP-induced adenlylyl cyclase inhibition, indicating that they do not directly antagonize the P2Y(12) receptor. We conclude that GIRK channels are important functional effectors of the P2Y(12) receptor in human platelets.

Differential Role of Protein Kinase Cδ Isoform in Agonist-induced Dense Granule Secretion in Human Platelets

Several platelet agonists, including thrombin, collagen, and thromboxane A(2), cause dense granule release independently of thromboxane generation. Because protein kinase C (PKC) isoforms are implicated in platelet secretion, we investigated the role of individual PKC isoforms in platelet dense granule release. PKCdelta was phosphorylated in a time-dependent manner that coincided with dense granule release in response to protease-activated receptor-activating peptides SFLLRN and AYPGKF in human platelets. Only agonists that caused platelet dense granule secretion activated PKCdelta. SFLLRN- or AYPGKF-induced dense granule release and PKCdelta phosphorylation occurred at the same respective agonist concentration. Furthermore, AYPGKF and SFLLRN-induced dense granule release was blocked by rottlerin, a PKCdelta selective inhibitor. In contrast, convulxin-induced dense granule secretion was potentiated by rottlerin but was abolished by Go6976, a classical PKC isoform inhibitor. However, SFLLRN-induced dense granule release was unaffected in the presence of Go6976. Finally, rottlerin did not affect SFLLRN-induced platelet aggregation, even in the presence of dimethyl-BAPTA, indicating that PKCdelta has no role in platelet fibrinogen receptor activation. We conclude that PKCdelta and the classical PKC isoforms play a differential role in platelet dense granule release mediated by protease-activated receptors and glycoprotein VI. Furthermore, PKCdelta plays a positive role in protease-activated receptor-mediated dense granule secretion, whereas it functions as a negative regulator downstream of glycoprotein VI signaling.

PEG-bovine hemoglobin: safety in a canine dehydrated hypovolemic-hemorrhagic shock model

An initial evaluation of PEG-bHb was performed using a modified hypovolemic shock model. PEG-bHb had a substantially longer intravascular half-life than native Hb and no measurable hemoglobinuria was observed in the canine. PEG-bHb allowed successful resuscitation with an oxygen carrying capacity of 14-22% over that of lactated Ringer's solution.

Effect of soluble and immobilized plasmin on fibrinogen and platelets

Plasmin was immobilized on collageno-elastic tubes (CET) using carbodiimide as the cross-linking agent. The effects of plasmin-CET grafts and corresponding soluble plasmin on fibrinogen, thrombin-mediated fibrinogen activation, and platelet activity, were investigated. There was a significant increase in fibrinogen deposition on plasmin-CETs over non-plasmin (i.e. control) CETs. Furthermore, exposure of fibrinogen to plasmin CETs enhances its deposition to control grafts situated downstream. Plasmin-bound CETs retained higher platelet deposition when preliminarily coated with fibrinogen. Finally, plasmin exerted a positive effect on thrombin-mediated fibrinogen activation at low plasmin concentrations. A mechanistic hypothesis aimed at interpreting this finding is proposed.

In vitro and in vivo studies of heparinized-collageno-elastic tubes

Heparin was covalently coupled to collageno-elastic grafts (CET) derived from lamb carotid arteries, by using the crosslinking agent 1-ethyl-3 (3-dimethyl-aminopropyl) carbodiimide (EDC). The collagenous grafts were pretreated with various aminating agents in order to enhance the number of available binding sites on the collagen surface. By varying the EDC/heparin weight ratio, the pH of the immobilization media, and the pretreatment agent, a global search pattern maximized heparin loading at 3.90 +/- 0.36 USP heparin/cm2 collagenous graft surface when the EDC/heparin ratio was 2:1 at a pH of 1.5 with 1 M hydroxylamine sulfate as the pretreatment agent. Heparinized CETs were superior to nonheparinized CETs by exhibiting both enhanced antiplatelet activity in using an in vitro differential recirculation reactor with chromium-51 tagged platelets and enhanced patency when interposed in canine carotid arteries. Both antiplatelet activity and patency duration for heparinized CETs were independent of heparin loading.

Co-immobilization and interaction of heparin and plasmin on collageno-elastic tubes

Heparin and plasmin were co-immobilized on collageno-elastic tubes (CETs) in order to develop a thromboresistant and fibrinolytic vascular prosthesis. The mutual interaction between heparin and plasmin both in the soluble and in the immobilized state was studied. The immobilization condition rendering maximum co-immobilized heparin and plasmin activity was identified to require heparin immobilization followed by plasmin immobilization. Soluble heparin exerts a positive synergistic effect on soluble plasmin. Immobilized heparin enhances plasmin loading on the CET as compared to the heparin-free graft. Heparin, in both the soluble or immobilized state, significantly decreases the Michaelis-Menten (M-M) parameter Km for immobilized plasmin over heparin-free immobilized plasmin. Furthermore, the M-M parameter Vmax for the immobilized plasmin in the presence of heparin decreases over heparin-free immobilized plasmin. These results suggest a decrease in the kinetic constant k3 for heparin-modified immobilized plasmin over the heparin-free form. Co-immobilized heparin-plasmin collagenous grafts represent a unique advance in the development of fibrinolytically active prostheses.

Detection of goat pox antigen and antibody by the counter immunoelectrophoresis test

The counterimmunoelectrophoresis (CIE) test was standardised for the detection of goat pox antigen and antibody using inactivated antigens. The chloroform inactivated and live antigens were equally sensitive for detection of goat pox precipitins. The precipitinogens of goat pox virus (GPV) were found to be soluble in nature. The CIE test was quick as well as more sensitive than the agar gel precipitation test for detection of GPV antibody/antigen. The CIE employing inactivated antigen has been used for the first time in the detection of GPV antibodies/antigens.

Application of ELISA in the detection of goat pox antigen and antibodies

Enzyme linked immunosorbent assay (ELISA) was standardized for detection of goat pox virus (GPV) antibodies and antigen using live and inactivated antigens and hyperimmune serum (HIS), convalescent, post-vaccinal, as also post-challenge sera. The ELISA was most sensitive in detection of antibody when compared with agar gel precipitation (AGP) and counterimmunoelectrophoresis (CIE) tests. There was no complete correlation between the antibody status of vaccinated goats and protective immunity as animals having detectable seroconversion were also solidly immune to virulent challenge. The application of ELISA in pox infections of goats has been discussed.

Enhanced in vitro fibrinolytic activity of immobilized plasmin on collagen beads

Plasmin was immobilized on collagenous substrates using carbodiimide as a linking agent. The kinetics of soluble and immobilized plasmin were monitored by reacting them with the chromogenic substrate S-2251 (H-D-Val-Leu-Lys-pNA) in the presence and absence of a2-antiplasmin (a2-PI). The ability of immobilized plasmin to lyse synthetic clots formed from fibrinogen and thrombin was determined by detecting the formation of fibrin degradation products (FDP). The activity of immobilized plasmin was 0.02 casein units (CU)/mg of collagen. The kinetic analysis of soluble and immobilized plasmin in the presence and absence of a2-PI shows that while soluble plasmin activity was inhibited by the presence of a2-PI, the plasmin inhibitor did not interfere with the ability of immobilized plasmin to attack fibrin. In the absence of a2-PI, the ability of the immobilized plasmin to lyse synthetic clots was the same as that of soluble plasmin. In the presence of a2-PI, immobilized plasmin produced twice the amount of FDP as did soluble plasmin. The immobilized plasmin activity was stable for a period of at least 3 months.

Studies on heparin immobilization to collagen

After activation of carboxyl groups with carbodiimide, heparin binds to collagen by a stable covalent linkage. Covalent binding of heparin to collagen results in enhanced stability of the preparation. Also, heparin bound collagen retains its anticoagulative activity.

Metabolic effects of theophylline in preterm infants

A loading dose of theophylline produces significant metabolic changes, including increase of plasma glucose concentration and an early rise in serum insulin in some infants. The chronic effects of theophylline on plasma glucose, serum insulin, and glucagon are not known at this time. The potential for development of metabolic derangements must be kept in mind when theophylline is used for protracted periods in premature infants.