Gerald Soslau - Academia.edu (original) (raw)

Papers by Gerald Soslau

Annals of the New York Academy of Sciences, Dec 1, 1990

Platelet serotonin and ATP may participate significantly in the maintenance of vascular tone and ... more Platelet serotonin and ATP may participate significantly in the maintenance of vascular tone and hemostatic processes under normal and pathological conditions. We have previously shown that extracellular ATP may modulate platelet function by phosphorylation of surface proteins and increasing cAMP levels.' Bleeding times were found to correlate with platelet release of ATP and serotonin content in renal failure patients2 To further explore the function of serotonin and ATP within the circulatory system, we analyzed their effect on platelet aggregation and arterial contraction. ATP and its nonhydrolyzable analogues, a$-methylene adenosine 5'-triphosphate (a&-ATP) and P,y-methylene adenosine 5'-triphosphate (P,y-ATP), were employed in these studies. ATP and its analogues (36-200 p M) inhibit collagen-induced platelet aggregations at similar levels in both whole blood and platelet-rich plasma (PRP) (TABLE I), indicating that ATP and not a metabolite is active. Small sample size within many experimental groups accounts for several nonsignificant p values. A clear trend, however, is established. Similar results were observed with ADP-induced aggregations; however, the ATP analogues were not as effective as ATP and were virtually inactive with P R P (TABLE l), indicating that a whole blood factor may be involved. ATP (180 p M) added to maximally ADP-or collagen-induced aggregated platelets partially reversed aggregation. Both a,P-ATP and P,y-ATP reversed collagen-induced platelet aggregates to levels similar to those attained with ATP, but neither analogue was as effective as ATP with ADP-induced aggregates (data not shown). ATP and its analogues may act, in part, via signal transduction to increase platelet cAMP

Nucleic Acids Research, 1986

These studies employed the synthetic linear DNA, poly dGdC. in the B and cobalt hexanmine chlorid... more These studies employed the synthetic linear DNA, poly dGdC. in the B and cobalt hexanmine chloride (Co (-Induced Z fora to detemine the effect of conformation on protein-DNA Interactions. The rate of the reaction of the restriction endonucleasea, Hha 1 and Cfo I, are reduced with Z DNA as coapared to B DNA. The ability of both restriction endonucleases to react with an aggregate forn of Z DNA (Z* DNA) is found to depend upon how the V DNA Is formed. When Z* DNA is induced by low concentrations of Co (50 uM) , the endonucleases renain active. In the presence of 100 uM Co, which causes increased aggregation, the endonucleases are Inactive. The Hha I DNA Bethyltransferase reacts at equal rates with the B, Z and low cobalt Z* foras and at a greatly reduced rate with the high cobalt Z* forn. These results are significantly different than those observed with Z forn dGdC tracts inserted into circular DNA aolecules.

Biochemical and Biophysical Research Communications, Mar 1, 1984

Science, Oct 23, 1998

The Allegheny University of the Health Sciences (AUHS) and eight of its hospitals in Philadelphia... more The Allegheny University of the Health Sciences (AUHS) and eight of its hospitals in Philadelphia, all affiliates of the Allegheny Health Education and Research Foundation (AHERF) in Pittsburgh, are in the process of reorganization in the U.S. Bankruptcy Court in Pittsburgh (Random Samples, 9 Oct.,

Journal of Experimental Zoology Part A: Ecological and Integrative Physiology, Oct 18, 2021

The serotonergic system, serotonin (5HT), serotonin transporter (SERT), and serotonin receptors (... more The serotonergic system, serotonin (5HT), serotonin transporter (SERT), and serotonin receptors (5HT‐x), is an evolutionarily ancient system that has clear physiological advantages to all life forms from bacteria to humans. This review focuses on the role of platelet/plasma serotonin and the cardiovascular system with minor references to its significant neurotransmitter function. Platelets transport and store virtually all plasma serotonin in dense granules. Stored serotonin is released from activated platelets and can bind to serotonin receptors on platelets and cellular components of the vascular wall to augment aggregation and induce vasoconstriction or vasodilation. The vascular endothelium is critical to the maintenance of cardiovascular homeostasis. While there are numerous ligands, neurological components, and baroreceptors that effect vascular tone it is proposed that serotonin and nitric oxide (an endothelium relaxing factor) are major players in the regulation of systemic blood pressure. Signals not fully defined, to date, that direct serotonin binding to one of the 15 identified 5HT receptors versus the transporter, and the role platelet/plasma serotonin plays in regulating hypertension within the cardiovascular system remain important issues to better understand many diseases and to develop new drugs. Also, expanded research of these pathways in lower life‐forms may serve as important model systems to further our understanding of the evolution and mechanisms of action of serotonin.

Journal of Theoretical Biology, Jun 1, 2018

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights  the formation of membrane pores for transport in a primordial cell composed of ribonucleopeptides;  tRNA non-coding and coding peptide synthesis built upon prior papers and the addition of new potential pathways for non-coding peptide synthesis and maturation of tRNAs;  role of circular RNAs in the RNA world, their role in gene regulation in the primordial cell and their role in the transition to the DNA world.

Biochemical and Biophysical Research Communications, Dec 1, 1982

Biochimica Et Biophysica Acta - Proteins And Proteomics, May 1, 1991

An anucleated cell system has been used for the first time to study mitochondrial topoisomerase a... more An anucleated cell system has been used for the first time to study mitochondrial topoisomerase activity. Mitochondrial extracts from human blood platelets contained type I topoisomerase. The type I classification was based on ATP-independent activity, inhibition by ATP or camptothecin, and the lack of inhibition by novobiocin. Platelet mitochondrial topoisomerase I relaxation activity was inhibited linearly by increasing concentrations of EGTA. Topoisomerase activity greater than 90% inhibited by 175 microM EGTA was partially restored to 16 and 50% of the initial level of activity by the subsequent addition of 50 and 100 microM Ca2+, respectively. Additionally, results from studies of partially purified platelet mitochondrial topoisomerase I were consistent with the crude extract data. This work supports the hypothesis that platelet mitochondria contain a type I topoisomerase that is biochemically distinct from that previously isolated and characterized from cell nuclei.

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2001

Thrombin plays a central role in normal and abnormal hemostatic processes. It is assumed that ␣-t... more Thrombin plays a central role in normal and abnormal hemostatic processes. It is assumed that ␣-thrombin activates platelets by hydrolyzing the protease-activated receptor (PAR)-1, thereby exposing a new N-terminal sequence, a tethered ligand, which initiates a cascade of molecular reactions leading to thrombus formation. This process involves cross-linking of adjacent platelets mediated by the interaction of activated glycoprotein (GP) IIb/IIIa with distinct amino acid sequences, LG-GAKQAGDV and/or RGD, at each end of dimeric fibrinogen molecules. We demonstrate here the existence of a second ␣-thrombin-induced platelet-activating pathway, dependent on GP Ib, which does not require hydrolysis of a substrate receptor, utilizes polymerizing fibrin instead of fibrinogen, and can be inhibited by the Fab fragment of the monoclonal antibody LJIb-10 bound to the GP Ib thrombin-binding site or by the cobra venom metalloproteinase, mocarhagin, that hydrolyzes the extracellular portion of GP Ib. This alternative ␣-thrombin pathway is observed when PAR-1 or GP IIb/ IIIa is inhibited. The recognition sites involved in the cross-linking of polymerizing fibrin and surface integrins via the GP Ib pathway are different from those associated with fibrinogen. This pathway is insensitive to RGDS and anti-GP IIb/IIIa antibodies but reactive with a mutant fibrinogen, ␥407, with a deletion of the ␥-chain sequence, AGDV. The reaction is not due to simple trapping of platelets by the fibrin clot, since ligand binding, signal transduction, and second messenger formation are required. The GP Ib pathway is accompanied by mobilization of internal calcium and the platelet release reaction. This latter aspect is not observed with ristocetin-induced GP Ib-von Willebrand factor agglutination nor with GP Ib-von Willebrand factor-polymerizing fibrin trapping of platelets. Human platelets also respond to ␥-thrombin, an autoproteolytic product of ␣-thrombin, through PAR-4. Co-activation of the GP Ib, PAR-1, and PAR-4 pathways elicit synergistic responses. The presence of the GP Ib pathway may explain why anti-␣-thrombin/anti-platelet regimens fail to completely abrogate thrombosis/restenosis in the cardiac patient.

Emerging therapeutic targets, 1997

Current funding and associated licensing restrictions Relevant patent information Inhibition of a... more Current funding and associated licensing restrictions Relevant patent information Inhibition of a thrombin-glycoprotein Ib(GPlb)-GPllb/llla pathway We have recently demonstrated that thrombin can induce platelet or megakaryocyte aggregation via an RGDS-independent, non-proteolytic thrombin-GPlb-IlMlla pathway. Chronic thrombotic events such as may occur in atherosclerosis and restenosis Small moleculdpeptide that binds to either the GPlb thrombin binding site or to the non-RGDS CPllbAlla-fibrin binding site($

Thrombosis Research, Jun 1, 1982

The loss of sialic acid was determined in human platelets stored during a seven day period in the... more The loss of sialic acid was determined in human platelets stored during a seven day period in their homologous plasma. Approximately 30% of the sialic acid was lost during the first three days of incubation at room temperature and a total of 73% was lost after seven days. The rapid in vitro loss of sialic acid may mimic a slower in vivo loss. It was found that platelets with a greater density had a higher sialic acid content than the less dense platelets. The loss of sialic acid from stored platelets could be completely inhibited by the addition of silyl compounds to the incubation plasma. The trisaccharide, N-acetylneuramin-lactose, gave a greater degree of protection than fetuin at comparable concentrations.

Tissue & Cell, Aug 1, 2009

Blood cells from three different sea turtle species were cultured for approximately 3 weeks in nu... more Blood cells from three different sea turtle species were cultured for approximately 3 weeks in nutrient medium supplemented with recombinant human cytokines known to induce terminal maturation of human hematological stem cells. Cultured turtle erythrocytes were translucent, approximately 10× larger than human erythrocytes, contained a single fluorescent inclusion body, contained nuclear epsilon (embryonic) globin proteins, and, absent of organelles while fresh cells contained few, but well defined mitochondria. Cells with basophilic cytoplasm and in all stages of proliferation were observed in cytokine-supplemented cultures and appeared to possess active protein synthesis. Cultured thrombocytes aggregated in response to agonists for at least 8 days, post-collection, contained P-selectin in the nucleus of 6 day cultured cells which appeared to be released after activation with collagen, and after 6 days had no organelles or open canalicular-like system (OCS) while freshly isolated cells demonstrated few, if any organelles but had a well developed OCS. The response of turtle cells to apparently homologous but unnatural human cytokines and the sustained biological properties of thrombocytes identify this suspension culture system as a powerful tool to explore the evolution of cell types and molecular components of hematopoiesis and hemostasis.

Biochimica et biophysica acta. Molecular cell research, Jul 1, 1995

Our previous studies have demonstrated that platelets possess ATP purinergic receptors in additio... more Our previous studies have demonstrated that platelets possess ATP purinergic receptors in addition to the ADP, P2T, receptor. Occupancy of the P2 receptor by ATP inhibited agonist-induced platelet aggregation. This study demonstrated that the mechanism of inhibition may involve ATP inhibition of agonist-induced mobilization of internal calcium. Within the cardiovascular system, the ATP inhibition of calcium mobilization is unique to platelets. All other cell types in the cardiovascular system, where calcium mobilization is affected by extracellular ATP, responded with an increased mobilization as opposed to inhibition. The platelet inhibitory response to ATP was enhanced by the addition of an ATP generating system, creatine phosphate/phosphocreatine kinase. ATP and ATP analogues were found to inhibit calcium mobilization with a rank order of aft-methylene ATP, f/y-methylene ATP = ATP > benzoyl ATP> 2 methylthio ATP which is a characteristic of P2x-like receptors. The inhibitory effect of ATP could be abrogated by prolonged treatment of platelets with the P2x desensitizing agent, aft-methylene ATP. Also, UTP and CTP were approximately as effective inhibitors as ATP while GTP was not. ATP competition with ADP for the P2T receptor was excluded in studies with platelets derived from an aspirin-treated individual which were essentially insensitive to ADP. The agonist-induced calcium mobilization and inhibition by ATP occurred with the thromboxane A 2 mimetic, U46619, collagen and thrombin; however, the kinetics of mobilization varied somewhat with the different agonists. The responses to extracellular ATP were independent of extracellular Ca 2+, where 1 mM calcium or 0.3 mM EGTA was added to the reaction mixture. The inhibition of calcium mobilization coupled to inhibition of platelet aggregation by extracellular ATP may serve an important physiologic role. ATP, released from activated platelets at localized sites of vascular injury, may help to limit the size of the platelet plug-clot that, if left unregulated, could occlude the injured blood vessel.

Archives of Biochemistry and Biophysics, Oct 1, 1983

Platelets, incubated with radiolabeled thymidine and purified free of contaminating nucleated cel... more Platelets, incubated with radiolabeled thymidine and purified free of contaminating nucleated cells, were analyzed for their ability to synthesize DNA. The only DNA species isolated from these purified platelets was mitochondrial DNA. The CsCl gradientpurified platelet DNA was treated with the restriction endonucleases EcoRI, Hind111 and HpuI yielding the expected pattern for human mitochondrial DNA. Nitrocellulose blots of the electrophoresed, restriction endonuclease-treated DNA were fluorographed. All of the DNA fragments generated by the restriction enzymes were labeled, indicating de nmo synthesis. This was further substantiated by inhibition of DNA synthesis by ethidium bromide and 2',3'-dideoxythymidine. Platelet DNA appeared to become greatly fragmented after 4 to 7 days storage while all of the thymidine incorporated was observed in intact mitochondrial DNA. These results indicate a continuous degradation of platelet mitochondrial DNA with no apparent repair mechanism. The ability of platelets to synthesize DNA may be associated with the protein synthetic capacity of platelets previously described.

Biochimica et biophysica acta. Molecular cell research, Jun 1, 1993

This report demonstrates that plateletes possess P2 purinoceptors with unique properties that dis... more This report demonstrates that plateletes possess P2 purinoceptors with unique properties that distinguish them from the ADP (P2T) receptor. Extracellular ATP, and its poorly hydrolyzable analogues, inhibit collagen-and U46619 (a thromboxane mimetic)-induced platelet aggregations. Adenosine deaminase was without effect on ATP action while reversing the inhibitory effect of adenosine. A unique aspect of the P2 receptor is the sensitivity to UTP and CTP and insensitivity to GTP. The rank order of inhibition by fly-methylene ATP, aft-methylene ATP > ATP indicates that a P2~-like receptor is present on the platelet membrane. This conclusion is further supported by the nearly complete desensitization to ATP by pre-exposure of platelets to afl-methylene-ATP. However, unlike previously described P2~ purinoceptors, the inhibition of platelet aggregation by extracellular ATP appears to result, at least in part, from the ATP-induced increase of intracellular cyclic AMP levels apparently coupled through a G s protein. The combined addition of iloprost (0.14 to 1.39 nM) and ATP (18 /zM) or ATP (20-40 /~M) and the phosphodiesterase inhibitor theophylline (0.5 to 1 mM) synergistically inhibited platelet aggregation implying a common interactive site with adenylate cyclase. This is further substantiated by the ability of the adenylate cyclase inhibitor, 2',5'-dideoxyadenosine, to abrogate the inhibitory effects of ATP. The protein kinase A (PKA) inhibitor H1004 blocks ATP inhibition of platelet aggregation while the protein kinase C inhibitor H7 did not. This implies that the generation of cyclic AMP, with the subsequent activation of PKA and phosphorylation of selected proteins is required, in part, for the action of ATP.

Experimental Biology and Medicine, Mar 1, 1997

Serotonin (5HT) and ATP are simultaneously released from activated platelets at the site of vascu... more Serotonin (5HT) and ATP are simultaneously released from activated platelets at the site of vascular injury and are hypothesized to play a significant role in hemostasis. Our laboratory investigated the modulation of vascular contraction of arterial ring segments by 5HT plus ATP as a model of the potential regulation of localized vascular tone by platelet releasates in regions of arterial damage. This study expands our focus on how these two vasoactive components, released from platelet dense granules, regulate vascular tone. 5HT- and 5HT analog-induced vasoconstrictions were measured in the presence or absence of ATP and ATP analogs with intact or deendothelialized rat pulmonary arterial ring segments suspended in organ baths. The possible presence of 5HT2 and 5HT1A receptor types in the rat pulmonary artery was demonstrated by vasoconstrictions induced by 5HT and (+)-8-hydroxy-2-(di-N-propylamino) tetralin hydrobromide (DPAT). The DPAT response was only 30%-50% of that induced by comparable concentrations of 5HT. The 5HT-induced contraction was inhibited by the 5HT2 antagonist, ketanserin. ATP equally relaxed 5HT and DPAT contracted tissue while the P2X agonist, alphabeta-methylene ATP, increased the contracted state of DPAT-treated arteries to a significantly greater extent than observed with 5HT. The P2y agonist, 3'-O-(4-benzoyl)benzoyl ATP (BzATP), the P2X agonist betagamma-methylene ATP, and ATP all relaxed 5HT-induced contractions to similar levels under a number of physiological conditions. The final level of 5HT-induced tissue contraction was the same whether ATP was added prior to, after, or simultaneously with 5HT. ATP and the phosphodiesterase inhibitor, theophylline, inhibited 5HT-induced vasoconstriction in an additive fashion. The ATP effects were endothelium dependent, while the inhibition by theophylline was not. The distribution of 5HT and ATP receptor types, as indicated by these and numerous other studies, appears to vary within different regions of the cardiovascular system. Extracellular ATP can synergistically enhance or inhibit 5HT-contracted blood vessels differentially at localized regions, which would significantly impact on localized vascular tone, and this in turn may modulate hemostasis and thrombosis.

Journal of Cellular Physiology, Aug 1, 1980

Cell lines resistant to ethidium bromide have been developed from cultured mammalian BHK21/C13 ce... more Cell lines resistant to ethidium bromide have been developed from cultured mammalian BHK21/C13 cells and these same cells transformed by Rous sarcoma virus (C13/B4). Cells resistant to 2 μg ethidium bromide per milliliter have been cloned. One clone of the control and one of the virus‐transformed cell lines has been employed for characterization. The resistant cells, in the presence of 2 μg ethidium bromide/ml, grow at approximately the same rate as the untreated parental cells. The control cells possess a “normal” karyotype (44 chromosomes), while the corresponding ethidium bromide mutant has a reduced chromsome number of 41 and a number of translocations. The mitochondria displayed morphological alterations compared to the parental lines during the transition phase prior to the isolation of the ethidium bromide‐resistant cells. The mitochondria of the ethidium bromide‐resistant mutants appear somewhat enlarged with a normal morphology.The effect of ethidium bromide on selected respiratory enzymes in normal and virus‐transformed ethidium bromide‐resistant baby hamster kidney cells was determined. Ethidium bromide‐resistant cells exhibited a depressed level of cytochrome aa3. This depression could not be reversed by growth in ethidium bromide‐free media. Ethidium bromide‐resistant cells possessed the same cytochrome b, c, and c1 levels per cell as their corresponding parental lines.Purified mitochondria isolated from virus‐transformed ethidium bromide‐resistant cells exhibited a depression in cytochrome oxidase‐specific activity, while the ethidium bromide‐resistant control cells did not. All cell lines studied showed a depression in NADH‐ferricyanide and NADH‐cytochrome c reductase‐specific activities relative to parental BHK21/C13 cells. An increase in succinate dehydrogenase and succinate cytochrome c reductase‐specific activities was observed in ethidium bromide‐resistant control cells relative to their parental BHK21/C13 cells. No increase was observed in virus‐transformed ethidium bromide‐resistant cells.Ethidium bromide‐resistant control cells exhibited a two‐fold increase in oligomycin‐insensitive adenosine triphosphatase activity relative to their parental cells. All of the cell lines studied possessed equivalent oligomycin‐sensitive adenosine triphosphatase‐specific activity except for the virus‐transformed, dyeresistant mutant, whose activity was increased.

Thrombosis Research, Oct 1, 1993

This study compared the responses of canine and human platelets to various aggregating agonists i... more This study compared the responses of canine and human platelets to various aggregating agonists in the presence or absence of extracellular ATP and ATP analogues. Canine and human platelets were approximately equally reactive with ADP or collagen while the canine platelets were about 10 fold more sensitive to thrombin. Canine platelets were insensitive to the thromboxane mimetic U46619 but were synergistically aggregated by a mixture of ADP and U46619. Human platelets were very sensitive to U46619. Aggregations of human platelets with all of the above agonists were inhibited by extracellular ATP; p,y methylene ATP (PyATP) and benzoyl ATP (BzATP) with a rank order suggestive of an interaction with P,-like purinoceptors which support our previous findings. The comparable aggregations of canine platelets were likewise inhibited by ATP and its analogues but with a rank order suggestive of an interaction with P,-like purinoceptors. ATP inhibited U46619-and ADP-induced aggregation of human platelets and ADPinduced aggregation of canine platelets, presumably, in part, due to competition for the ADP Prr receptor. However, when U46619 was added to either ATP or ATP analogue-inhibited ADP-treated canine platelets, the inhibition was nullified. Furthermore, we demonstrated, for the first time, that the canine thromboxane receptor becomes reactive to U46619 alone after incubation at room temperature for 3.5-5 hrs while human platelets become inactive under similar conditions. The implication of these studies is that there are significant differences in the canine and human platelet thromboxane and purine receptors. The future characterization of these differences and the mechanism by which they function should further our understanding of the impact of extracellular ATP on hemostasis and thrombosis.

Archives of Biochemistry and Biophysics, May 1, 1982

Aspects of the cytochrome levels and function in stored human platelets were investigated. Platel... more Aspects of the cytochrome levels and function in stored human platelets were investigated. Platelets stored in a synthetic medium lose cytochrome c very rapidly with virtually all of the cytochrome c being lost by 3 days. Platelets aged in their homologous plasma, however, lose cytochrome c more slowly with a half-life of 7.3 days which is assumed to be more closely related to the in viva situation. Cytochrome oxidase activity does not change in platelets stored up to 8 days in plasma. Oxygen consumption by platelets maintained in vitro drops slowing during the first 4 days of storage, however, by the fifth and sixth day the oxygen consumption drops dramatically and is accompanied by a reduction in coupling. The observed changes in the cytochrome levels and respiration are discussed with regard to platelet function and survival.