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Biomedical subjects

R J Gould

Publications and source records attributed to R J Gould.

At least 19 recordsLinked to original sources
PubMed1992

Immunocytochemical localization of platelets in baboon hepatic sinusoids using monoclonal mouse anti-human platelet glycoprotein IIIa following induction of thrombocytopenia.

A commercially available mouse monoclonal antibody to human platelet glycoprotein IIIa was used to demonstrate sequestration of platelets in hepatic biopsies obtained from baboons following intravenous infusion of echistatin, a novel fibrinogen receptor antagonist derived from the venom of the snake Echis carinatus. Biopsies of liver and spleen were taken prior to administration of echistatin. The hepatic biopsies were either snap-frozen in Freon-22/liquid nitrogen or fixed in 10% neutral buffered formalin. Biopsies of spleen were snap-frozen. During infusion of echistatin (2.3 micrograms/kg/min), circulating platelet counts decreased from 331,000/mm3 to 167,000/mm3. Selective sequestration within the liver was confirmed using whole body gamma camera imaging to demonstrate 111Indium-oxine labeled platelet accumulation within the liver during the thrombocytopenic episode. Hepatic biopsies were again taken and either snap-frozen in Freon-22/liquid nitrogen or fixed in 10% neutral buffered formalin. Biopsies of spleen and inguinal lymph node were also snap-frozen. Platelet rich plasma smears, included as positive controls, dewaxed paraffin sections, and cryosections of liver, spleen, and lymph node were stained with monoclonal mouse anti-human platelet glycoprotein IIIa using an avidin biotinylated peroxidase complex (ABC) technique. Prior to infusion of echistatin, platelet staining within the liver was minimal. After echistatin infusion, hepatic cryosections showed prominent platelet staining within hepatic sinusoids. No localization was shown in lymph node, however, the spleen showed prominent platelet staining both before and after echistatin infusion. Platelet rich plasma smears were intensely positive. No prominent platelet staining was observed in formalin-fixed, paraffin-embedded material. Thus, this immunocytochemical technique may help localize platelets in cryosections of tissues from baboons and other primate species.

Animals↗
PubMed1992

Methionine in the treatment of nitrous-oxide-induced neuropathy and myeloneuropathy.

Two cases of severe myeloneuropathy and macrocytic anemia associated with a low serum level of vitamin B12 after prolonged exposure to nitrous oxide are reported. In both cases, the neurological manifestations worsened initially despite B12 supplementation, although in one case the use of methionine seemed to arrest the progression of the disease and accelerate recovery. This offers further support for the biochemical hypothesis of methionine synthetase inhibition by nitrous oxide and reproduces in man previously reported animal studies with methionine. Methionine may be an important first-line therapy in the initial treatment of neuropathy and myeloneuropathy induced by nitrous oxide, and has a hypothetical role in the treatment of subacute combined degeneration of the cord.

Adult↗
PubMed1992

Fanconi anemia: a model for genetic causes of abnormal brain development.

Fanconi anemia is an autosomal recessive disease resulting in bone-marrow failure, phenotypical abnormalities and predisposition to malignancy. The authors reviewed 257 clinical and neuropathology results from the International Fanconi Anemia Registry at The Rockefeller University. Two patients had hydrocephalus and ventriculoperitoneal shunts. Of 15 neuropathology reports, 10 found CNS abnormalities, with the most common--ventriculomegaly--seen in six, two of whom required shunts. Aqueductal stenosis, agenesis of the corpus callosum and septum pellucidum, and holoprosencephaly were found. The authors conclude that neurological derangements are probably more common in Fanconi anemia than previously recognised. Fanconi anemia cells in culture are highly sensitive to oxidative stress and alkylating agents; Fanconi anemia may provide a model for a genetic disorder potentially predisposing to environmental insults.

Abnormalities, Multiple↗
PubMed1991

Steroid-responsive chorea in moyamoya disease.

We report the case of a 13-year-old boy with disabling chorea due to moyamoya disease. His chorea seemed to improve with steroid therapy. We conclude that steroid therapy may ameliorate moyamoya-associated chorea, and perioperative steroids can confound neurosurgical outcome. We are unable to assess the effect of cerebrovascular bypass procedures on the outcome of chorea in this patient.

Adolescent↗
PubMed1991

Hypothalamic-midbrain dysregulation syndrome: hypertension, hyperthermia, hyperventilation, and decerebration.

Certain decerebrate lesions of brain stem or hypothalamus induce pharmacologically reversible hypertension and hyperthermia in animals. We observed three young patients with episodic decerebration, hyperthermia, hypertension, and hyperventilation during recovery from comas of different etiologies. The shared pathology on neurologic examinations and computed tomographic scans was hypothalamic-mesencephalic dysfunction, suggesting a diencephalic-brain-stem disconnection syndrome or brain-stem release mechanism. Propranolol was the most effective drug tested, but only two patients responded, one dramatically. This novel clinical syndrome may have localizing and therapeutic significance in pediatric coma that needs to be further defined in future studies.

Adolescent↗
PubMed1991

Stroke in children.

Childhood stroke, although similar to adult stroke, is characterized by congenital and genetic causes. The evaluation and treatment of the child with stroke requires special considerations. Currently, drug therapy is untested and as a result, therapeutic interventions are problematic. Platelet antagonists are rational prophylactically; warfarin probably has a role in preventing cardiogenic embolus in the older child. However, chronic anticoagulation in the toddler is dangerous due to frequent trauma and is therefore relatively contraindicated. Vascular malformations are surgically repaired but alternative therapies, including radiation and embolization, may be used for inoperable lesions. Aneurysms are primarily surgical lesions. Newer imaging modalities will clarify the pathophysiologic picture and improve treatment.

Brain↗
PubMed1990

Proaggregatory effect of epinephrine on rabbit platelets inhibited by ticlopidine.

Ticlopidine is a potent inhibitor of ADP-induced aggregation of rabbit platelets ex vivo. In vivo, however, multiple agonists play a role in platelet activation. In this study, we examined the effect of epinephrine on the antiplatelet action of ticlopidine in rabbit platelets. Epinephrine reversed the inhibitory effect of drug on ADP-induced platelet aggregation. The potentiating effect of epinephrine was mediated through alpha 2-adrenergic receptors, was reversed by pretreatment with the Na+/H+ exchange inhibitor dimethylamiloride, and was mimicked by agents that increased intracellular sodium or pH. Ticlopidine had no effect on resting intracellular pH, an indication that the effect of epinephrine was not compensating for a drug-induced intracellular acidification. While this potentiation was also found to be inhibited by aspirin, it did not involve enhanced release of thromboxane A2. Our results demonstrate that epinephrine can overcome the inhibitory effect of ticlopidine on ADP-induced aggregation through a mechanism involving activation of Na+/H+ exchange and through an as yet unidentified mechanism sensitive to aspirin.

Adenosine Diphosphate↗
PubMed1990

Echistatin is a potent inhibitor of bone resorption in culture.

The venom protein, s-echistatin, originally derived from the saw-scaled viper Echis carinatus, was found to be a potent inhibitor of bone resorption by isolated osteoclasts. This Arg24-Gly25-Asp26-(RGD)-containing protein inhibited the excavation of bone slices by rat osteoclasts (IC50 = 0.1 nM). It also inhibited the release of [3H]proline from labeled bone particles by chicken osteoclasts (IC50 = 100 nM). By comparison, the tetrapeptide Arg-Gly-Asp-Ser (RGDS) inhibited resorption by rat or chicken osteoclasts with an IC50 of 0.1 mM while ala24-echistatin was inactive. Video microscopy showed that rat osteoclast attachment to substrate was more sensitive to s-echistatin than was the attachment of mononuclear cells or chicken osteoclasts. The difference in sensitivity of rat and chicken osteoclasts to s-echistatin may be due to differences between receptors on rat and chicken osteoclasts for s-echistatin. Antibody localization of echistatin on these cells showed much greater echistatin binding to rat osteoclasts than to chicken osteoclasts. Laser scanning confocal microscopy after immunohistochemical staining showed that s-echistatin binds to osteoclasts, that s-echistatin receptors are most abundant at the osteoclast/glass interface, and that s-echistatin colocalizes with vinculin. Confocal interference reflection microscopy of osteoclasts incubated with s-echistatin, demonstrated colocalization of s-echistatin with the outer edges of clusters of grey contacts at the tips of some lamellipodia. Identification of the echistatin receptor as an integrin was confirmed by colocalization of echistatin fluorescence with staining for an alpha-like subunit. Attachment of bone particles labeled with [3H]proline to chicken osteoclasts confirmed that the mechanism of action of echistatin was to inhibit osteoclast binding to bone presumably by disrupting adhesion structures. These data demonstrate that osteoclasts bind to bone via an RGD-sequence as an obligatory step in bone resorption, that this RGD-binding integrin is at adhesion structures, and that it colocalizes with vinculin and has an alpha-like subunit.

Amino Acid Sequence↗
PubMed1990

Disintegrins: a family of integrin inhibitory proteins from viper venoms.

Disintegrins represent a new class of low molecular weight, RGD-containing, cysteine-rich peptides isolated from the venom of various snakes. They interact with the beta 1 and beta 3 families of integrins and their potency is at least 500-2000 times higher than short RGDX peptides. Analysis of the amino acid sequences of 14 different disintegrins suggests that the RGD sequence, in the spatial configuration determined by the appropriate pairing of the cysteine residues, functions as a cell recognition site. However, certain nonconserved amino acids appear to modify the activity of disintegrins, their specificity for various receptors, and their ability to compete specifically with various ligands.

Amino Acid Sequence↗
PubMed1990

A model of gastric emptying in cats shows solid emptying is promoted by MK-329: a CCK antagonist.

The effect of MK-329, a potent, orally active, nonpeptidal cholecystokinin (CCK) antagonist, was measured on the gastric emptying rate of a solid meal in cats. External scintigraphy of cats that had been fed a meal of technetium-99m-(99mTc) labeled rabbit liver and light cream allowed the measurement of the emptying rates of either the liquid or solid portion of a meal under physiologic conditions. In cats, liquids emptied 2.6 times faster than solids [163 +/- 11 min vs. 62 +/- 3 min (mean +/- s.e.)]. At 3 or 10 mg/kg p.o., MK-329 gastric emptying was significantly accelerated, with the mean half-time of emptying being decreased by 34 +/- 11% (mean +/- s.e.) of the control half-times (p less than 0.02). Using only responders (five of six animals), mean half-time was decreased by 55 +/- 4% of the control half-times. CCK is important in regulating the emptying of solid food from the stomach because the CCK antagonist MK-329 accelerates that emptying.

Animals↗
PubMed1989

Expression and secretion of biologically active echistatin in Saccharomyces cerevisiae.

A synthetic gene coding for a platelet aggregation inhibitor, echistatin (ECS), was inserted into a Saccharomyces cerevisiae expression vector utilizing the alpha-mating factor pre-pro leader sequence and galactose-inducible promoter, GAL10. Cleavage of the pre-pro leader sequence in vivo results in the secretion of a properly processed recombinant ECS with the native N-terminal glutamic acid residue. Recombinant ECS was recovered from yeast supernatants and purified by reverse phase high performance liquid chromatography. Recombinant ECS expressed and purified from yeast was identical to native ECS in its ability to inhibit platelet aggregation.

Amino Acid Sequence↗
PubMed1989

High-level expression in Escherichia coli of a chemically synthesized gene for [Leu-28]echistatin.

A gene (Ecs) encoding a platelet aggregation inhibitor, echistatin (Ecs), has been chemically synthesized. Met at position 28 of the native protein was replaced by Leu in the recombinant Ecs. To express this synthetic gene in Escherichia coli, an expression vector, pJC264, was constructed by inserting portions of the E. coli cheB and cheY gene complex into the plasmid pUC13. High-level expression of the synthetic [Leu-28]Ecs was achieved by its fusion with the E. coli cheY gene in the expression vector. Recombinant [Leu-28]Ecs was liberated from the fusion protein by CNBr cleavage at the Met inserted between the CheY protein and [Leu-28]Ecs. The recombinant [Leu-28]Ecs was purified to homogeneity by reverse-phase high-performance liquid chromatography. The refolded [Leu-28]Ecs was identical to native Ecs in inhibiting platelet aggregation, suggesting that Met at position 28 is not essential for the biological activity of this platelet aggregation inhibitor.

Amino Acid Sequence↗
PubMed1989

A monoclonal antibody against the platelet fibrinogen receptor contains a sequence that mimics a receptor recognition domain in fibrinogen.

The binding of fibrinogen to its platelet receptor, the glycoprotein IIb-IIIa complex, is mediated, in part, by an Arg-Gly-Asp (RGD) sequence within the fibrinogen A alpha chain. PAC1 is an IgM-kappa murine monoclonal antibody that binds to the platelet fibrinogen receptor, and its binding is inhibited by both fibrinogen and RGD-containing peptides. To identify the regions of PAC1 that interact with the fibrinogen receptor, we determined the mRNA sequences of PAC1 immunoglobulin heavy and light chain variable regions. Five out of the six complementarity-determining regions (CDRs) of PAC1 had entirely germline sequences with no regions of similarity to fibrinogen. However, CDR3 of the PAC1 heavy chain (H-CDR3) was very large and unique due to the insertion of a novel D region segment. H-CDR3 contained a sequence, Arg-Tyr-Asp (RYD), that, if present in the proper conformation, might behave like the RGD sequence in fibrinogen. A 21-residue synthetic peptide encompassing the H-CDR3 region inhibited fibrinogen-dependent platelet aggregation as well as the binding of PAC1 (Ki = 10 microM) and fibrinogen (Ki = 5 microM) to activated platelets. The RYD region of H-CDR3 appeared to be central to its function, because substitution of the tyrosine with glycine increased the inhibitory potency of the peptide by 10-fold, while replacing the tyrosine with D-alanine or inverting the RYD sequence sharply reduced the inhibitory potency. Thus, the linear sequence, RYD, within H-CDR3 of PAC1 appears to mimic the RGD receptor recognition sequence in fibrinogen. This type of immunologic approach could be useful in studying the structural basis of other receptor-ligand interactions.

Amino Acid Sequence↗
PubMed1989

Chemical synthesis of echistatin, a potent inhibitor of platelet aggregation from Echis carinatus: synthesis and biological activity of selected analogs.

Echistatin, a polypeptide from the venom of the saw-scaled viper, Echis carinatus, containing 49 amino acids and 4 cystine bridges was synthesized by solid-phase methodology in 4% yield. In the final step, air oxidation of the octahydroderivative was found to be optimal at pH 8. The synthetic product was shown to be physically and biologically indistinguishable from native material. It inhibits fibrinogen-dependent platelet aggregation stimulated by ADP with IC50 = 3.3 x 10(-8) M and also prevents aggregation initiated by thrombin, epinephrine, collagen, or platelet-activating factor. Reduction of purified synthetic echistatin to octahydroechistatin with dithiothreitol followed by air oxidation regenerated homogeneous echistatin in quantitative yield. This highly specific refolding strongly suggests that the linear sequence of octahydroechistatin contains all of the information that is required for the proper folding of the peptide. The sequence Arg24-Gly-Asp of echistatin occurs also in adhesive glycoproteins that bind to the platelet fibrinogen receptor--a heterodimeric complex composed of glycoproteins IIb and IIIa. In an effort to evaluate the role of this putative binding site we have synthesized analogs of echistatin with substitution of Arg-24. Replacement with ornithine-24 (Orn-24) resulted in an analog having a platelet aggregation inhibitory activity with IC50 = 1.05 x 10(-7) M. Substitution with Ala-24 gave IC50 = 6.1 x 10(-7) M. The inhibitory activity of the corresponding short sequence analogs Arg-Gly-Asp-Phe (IC50 = 6 x 10(-6) M), Orn-Gly-Asp-Phe (IC50 = 1.3 x 10(-4) M), and Ala-Gly-Asp-Phe (IC50 = 5.0 x 10(-4) M) was also determined. These results suggest that arginine plays a more important role in the binding of the tetrapeptide than in that of echistatin.

Amino Acid Sequence↗
PubMed1989

Exaggeration of the cholecystokinin-induced motor response in the cat gastrointestinal tract.

A stimulation of distal colonic motor activity was produced in anesthetized cats following intravenous administration of cholecystokinin. The contractile response elicited by cholecystokinin was not reduced following pretreatment with atropine. However, when animals were treated with agents which increased the net cholinergic input to the colon, a marked exaggeration of the subsequent cholecystokinin-induced response occurred. This cholinergically mediated exaggeration was produced following administration of the cholinergic agonist bethanechol, or after removal of tonic inhibitory systems mediated by prostaglandin or alpha-adrenergic input, whose blockade results in atropine-sensitive colonic stimulation. Cholecystokinin was also found to produce stimulation of motor activity in the pylorus, jejunum, proximal colon and gallbladder. Cholinergically mediated exaggeration of the cholecystokinin response was also present in the pylorus and proximal colon, but not gallbladder or jejunum. An inhibition of spontaneous motor activity was produced in the ileum or duodenum following cholecystokinin administration.

Animals↗
PubMed1989

Differential interaction of guanabenz with receptor binding sites in rat brain and kidney.

The alpha 2-adrenoceptor selective agonist, [3H]guanabenz ([ 3H]GBZ), labels a unique population of binding sites in whole kidney which are not labeled by [3H]p-aminoclonidine ([3H]PAC). These binding sites are saturable and of high affinity (Kd = 10-12 nM). [3H]GBZ was not displaced from these sites by other alpha 1- or alpha 2-ligands, suggesting that they are non-adrenergic. This hypothesis is further supported by the insensitivity of renal guanabenz binding to regulation by guanyl nucleotides or to destruction by trypsin. Also, there appears to be no effect of guanabenz on the potency of isoproterenol in competing for beta-adrenoceptors in the kidney, which has been previously reported to be sensitive to clonidine. The absence of any effect of guanabenz on isoproterenol displacement of [3H]dihydroalprenolol in kidney suggests there are subtle differences in activation of alpha-receptors by clonidine and guanabenz in the kidney. In the brain, [3H]GBZ labels two binding sites. Part of the binding of [3H]GBZ in the brain is to sites essentially identical to the alpha 2-adrenoceptors labeled by [3H]PAC. The remainder of the binding resembles the non-adrenergic binding in kidney. The relationship of this unique binding site to the pharmacologic actions of guanabenz is currently not known.

Animals↗
PubMed1988

Echistatin. A potent platelet aggregation inhibitor from the venom of the viper, Echis carinatus.

A 49-residue protein, echistatin, which inhibits platelet aggregation, was purified from the venom of the saw-scaled viper Echis carinatus. The purification procedure included gel filtration on Sephadex G-50, cation-exchange chromatography on Mono S, and C18 reverse-phase high pressure liquid chromatography. The purified protein was homogeneous as judged by polyacrylamide gel electrophoresis, isoelectric focusing, reverse-phase high pressure liquid chromatography, and NH2-terminal sequence analysis. Echistatin is a single-chain polypeptide with a molecular weight of 5400 and a native isoelectric point of 8.3. The most abundant amino acid, cysteine, accounts for 8 of the 49 residues in the protein. A 10-residue segment of echistatin shows 90% identity to a portion of the sequence of trigramin, a platelet aggregation inhibitor from the green tree viper Trimereserus gramineus (Huang, T.-F., Holt, J. C., Lukasiewicz, H., and Niewiarowski, S. (1987) J. Biol. Chem. 262, 16157-16163). Echistatin contains the sequence arginine-glycine-aspartic acid, which is common to proteins which bind to the glycoprotein IIb/IIIa complex. It also contains the sequence proline-arginine-asparagine-proline, which is found in the A alpha chain of human fibrinogen at position 267-270. The purified protein inhibits fibrinogen-dependent platelet aggregation initiated by ADP with an IC50 of 3 x 10(-8) M and also prevents aggregation initiated by thrombin, epinephrine, collagen, or platelet-activating factor. Reduction of echistatin abolished its inhibitory activity.

Amino Acid Sequence↗