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Biomedical subjects

P Goldsmith

Publications and source records attributed to P Goldsmith.

At least 37 records · Page 2Linked to original sources
PubMed1995

Rationalized polytherapy for epilepsy.

In the past, epilepsy was usually treated with polytherapy, but with little knowledge as to the interactions and side-effects of the combinations of the anti-epileptic drugs used. Adverse events and sparse clinical knowledge led to monotherapy becoming the treatment regime of choice. A new generation of drugs, which are well-tolerated and have few or predictable interactions, have enabled the reassessment of polytherapy for the treatment of epilepsy. Extensive clinical trials of these drugs are allowing the emergence of a new, rationalized approach to polytherapy. In our study, 19 patients with refractory partial epilepsy, and who were 'socially active and integrated into society', received vigabatrin as add-on therapy. Patients were taking a mean of 1.5 drugs, and five patients were taking small doses of drugs which lead to tolerance, such as barbiturates and benzodiazepines. With vigabatrin as add-on therapy, 14 patients (73%) had a greater than 50% reduction in seizure frequency, and 10 (52%) had a greater than 70% reduction in seizure frequency. In one patient, seizure frequency increased, and two patients developed myoclonic jerks. Vigabatrin was not shown to have any harmful effects in extensive laboratory, EEG and cognitive function tests. In fact, a minor improvement occurred in visual memory, which was probably related to the reduction in seizures. Addition of vigabatrin may, therefore, be of benefit to patients with partial epilepsy refractory to monotherapy with standard anti-epilepsy drugs.

Anticonvulsants↗
PubMed1994

Coupling of endothelin B receptors to the calcium pump and phospholipase C via Gs and Gq in rat liver.

We have demonstrated in liver from male rats that both endothelin A (ETA) and ETB receptors coexist in equal proportion and that ETA receptors mediate a calcium-dependent activation of glycogenolysis. We describe here a sex difference in endothelin action in hepatocytes because, in female rats, 80% of the ET receptors are of ETB type and, accordingly, activation of glycogenolysis is an ETB-mediated process (EC50 = 0.03 pM). ET-1 stimulation of glycogenolysis in female rats was consecutive to activation of phosphatidylinositol 4,5-bisphosphate hydrolysis (EC50 = 0.03 pM) and to inhibition of the calcium extrusion pump (IC50 = 0.03 pM) in plasma membranes, with ET-1 approximately sarafotoxin S6C approximately ET-3. Endothelin regulation of each effector was potentiated by GTP gamma S. ET-1 did not stimulate adenylyl cyclase activity. To identify the nature of the guanine nucleotide regulatory proteins (G protein(s)) coupling ETB receptors to each effector, we used antibodies against the COOH terminus of different G protein alpha subunits. Antibodies reactive with Gs alpha (RM) blocked ET-1 inhibition of the calcium pump, while they did not affect ET-1 stimulation of phospholipase C. Antibodies reactive with Gq alpha (QL) dose-dependently antagonized stimulation of phospholipase C by ET-1 and vasopressin, without affecting ET-1 inhibition of the calcium pump. Antibodies reactive with Gi1 alpha/Gi2 alpha (AS) had no effect on either system. We conclude that the calcium signal provoked by endothelins in hepatocyte is not only consecutive to activation of phospholipase C but also to inhibition of the plasma membrane calcium pump, each effector being coupled to ETB receptors by different G proteins, Gq, and Gs.

Amino Acid Sequence↗
PubMed1993

Pheromone action regulates G-protein alpha-subunit myristoylation in the yeast Saccharomyces cerevisiae.

Myristic acid (C14:0) is added to the N-terminal glycine residue of the alpha subunits of certain receptor-coupled guanine nucleotide-binding regulatory proteins (G proteins). The G alpha subunit (GPA1 gene product) coupled to yeast pheromone receptors exists as a pool of both myristoylated and unmyristolyated species. After treatment of MATa cells with alpha factor, the myristoylated form of Gpa1p increases dramatically, and the unmyristoylated form decreases concomitantly. This pheromone-stimulated shift depends on the function of STE2 (alpha-factor receptor), STE11 (a protein kinase in the response pathway), and NMT1 (myristoyl-CoA:protein N-myristoyltransferase) genes and uses the existing pool of fatty acids (is not blocked by cerulenin). Myristoylated Gpa1p persists long after pheromone is removed. Because myristoylation is essential for proper G alpha-G beta gamma association and receptor coupling, pheromone-dependent stimulation of Gpa1p myristoylation may be an important contributing factor in adaptation after signal transmission.

Amino Acid Sequence↗
PubMed1993

Polypeptide variants of beta-arrestin and arrestin3.

Retinal arrestin (S-antigen) inactivates the phototransduction cascade by binding to light-activated phosphorylated rhodopsin and thereby "arresting" coupling to the G protein transducin. beta-Arrestin (beta arr), a ubiquitous arrestin homolog, acts analogously to desensitize the beta 2-adrenergic receptor by disrupting Gs receptor interaction. In an attempt to identify additional "arrestins" which might regulate the multitude of G protein-coupled receptors, we have isolated two bovine brain cDNAs which encode polypeptide variants of an arrestin homolog which we have designated arrestin3 (arr3). The open reading frames of these two cDNAs are identical except that the long form, arr3L, contains an 11-amino-acid insert between residues 361 and 362. Arr3 is more closely related to bovine beta arr (78% identity) than to bovine visual arrestin (56% identity). Polymerase chain reaction amplification of RNA and immunoblotting of lysates with an arr3-specific antibody suggest that the short form, arr3S, is the major form of arr3 in all bovine tissues and that it is most abundant in the spleen. Furthermore, polymerase chain reaction amplification of beta arr mRNA indicates that in several tissues (lung, liver, spleen, and pituitary), the major form of beta arr lacks 8 amino acids which are present in brain beta arr. Immunoblotting with an antibody which recognizes beta arr and arr3 with equal sensitivity demonstrates that beta arr (either the long or the short polypeptide) is the major arrestin in all (non-photoreceptor bearing) tissues examined. These observations suggest that in some tissues, as many as four arrestin homolog variants may play a role in the regulation of G protein-coupled receptors.

Amino Acid Sequence↗
PubMed1993

Gs mediates hormonal inhibition of the calcium pump in liver plasma membranes.

We have reported that the calcium pump in liver plasma membranes is coupled to Gs or a Gs-like protein. However, we show here that isoproterenol, which activated adenylyl cyclase via Gs, had no effect on the calcium pump, while human calcitonin, human parathyroid hormone, and mini-glucagon, which inhibited this system, did not affect adenylyl cyclase activity. In order to determine the nature of the G protein coupled to the calcium pump, we used the RM antibody, raised against the carboxyl-terminal decapeptide of Gs alpha, which antagonized adenylyl cyclase activation by isoproterenol or glucagon. The RM antibody specifically blocked calcium pump inhibition by mini-glucagon, calcitonin, or parathyroid hormone, while it did not affect guanosine 5'-O-(thiotriphosphate) inhibition. Its effect was mimicked by the corresponding decapeptide RMHLRQYELL. The AS/7 antibody, reactive with Gt alpha, Gi 1 alpha, and Gi2 alpha, was ineffective. Complementation of liver plasma membranes with in vitro translated Gs alpha-2, the large form of Gs alpha, led to a 40% decrease in calcium pump activity, with a parallel 2-fold increase in adenylyl cyclase activity. In vitro translated Gi1 alpha did not affect the calcium pump activity, while it evoked a 40% inhibition of adenylyl cyclase activity. We conclude that a same Gs alpha may be coupled either to the calcium pump or to adenylyl cyclase. However, Gs is functionally specialized, since it does not ensure cross-talk between the two receptor-effector systems. These results point out the possible compartmentalization of Gs.

Adenylyl Cyclases↗
PubMed1993

Endothelin inhibits the calcium pump and stimulates phosphoinositide phospholipase C in liver plasma membranes via two different G proteins, Gs and Gq.

We have shown previously that in liver, endothelin (ET) binding to plasma membranes causes a rise in cytosolic calcium and activation of glycogenolysis. Here we show that the calcium extrusion pump in liver plasma membranes is inhibited by ET peptides, with ET-1 > or = ET-3 = sarafotoxin S6C-inhibition of the system being potentiated by GTP gamma S. Also, ET-1 stimulates PIP2 hydrolysis in liver plasma membranes in a guanine nucleotide-dependent manner, with ET-1 > or = ET-3 = sarafotoxin S6C. In order to determine the nature of G protein(s) coupling of the ETB receptor to both effectors, antibodies against the C-terminus of different G-protein alpha-subunits were used. Antibodies reactive with Gs alpha blocked ET-1 inhibition of the calcium pump, but they had no effect on ET-1 stimulation of PIP2 hydrolysis. Antibodies reactive with Gq alpha dose-dependently antagonized stimulation of PIP2 breakdown by ET-1 without affecting ET-1 inhibition of the calcium pump. Antibodies reactive with Gi1 alpha/Gi2 alpha had no effect on both systems. We conclude that the calcium signal induced by endothelins in hepatocytes may be consequent to both an activation of phospholipase C and inhibition of the calcium pump, both effectors being coupled to the ETB receptor by different G proteins, Gq and Gs, respectively.

Amino Acid Sequence↗
PubMed1993

Task dependence of responses in first dorsal interosseous muscle to magnetic brain stimulation in man.

1. The response of the first dorsal interosseous (1DI) muscle to non-invasive magnetic and scalp electrical stimulation of the brain have been investigated during performance of different manual tasks. 2. The six tasks tested required activation of the 1DI muscle, either in isolation (during abduction of the index finger) or as part of a more complex pattern of muscle synergies (e.g. during power grip). The level of 1DI EMG activity across tasks was kept constant by providing subjects with visual feedback of their muscle activity. 3. In every subject (n = 14) magnetic stimulation produced larger responses during performance of complex tasks than during the simple index abduction task. The pooled results from all subjects showed that four of the five complex tasks were associated with significantly larger 1DI responses (paired t test, P < 0.05). 4. These results were confirmed at the single motor unit level for nine motor units recorded from six subjects. Subjects were requested to produce a steady discharge of the same motor unit during performance of different tasks. The probability of motor unit discharge in response to magnetic stimulation was significantly greater during complex tasks (rotation or pincer grips) than during abduction. 5. Scalp electrical stimulation was performed in three subjects with the cathode at the vertex and the anode over the contralateral motor cortex. The pattern of response amplitudes in the different tasks tended to parallel that obtained for magnetic stimulation, but the task-related differences were smaller. 6. These results suggest that during performance of the different tasks, the corticospinal volleys evoked by magnetic stimulation may vary in amplitude. The task-related cortical mechanisms that may contribute to this variability are discussed.

Adult↗
PubMed1993

The new H1 antihistamines. Treatment of urticaria and other clinical problems.

The new H1 antihistamines are a major therapeutic advancement in the treatment of allergic disorders such as urticaria and allergic rhinitis. Their efficacy combined with greatly reduced sedating and anticholinergic side effects makes the new class of H1 antihistamines the first-line treatment in the management of urticaria and mild angioedema. The choice of a particular low-sedating H1 antihistamine depends on pharmacokinetic considerations, the severity of the problem (systemic steroids and epinephrine are the first-line treatment for severe angioedema), and the requirement for limiting the frequency of administration. The efficacy of the new H1 antihistamines in the treatment of itch due to atopic eczema and systemic disease remains uncertain, and further controlled clinical trials are needed to elucidate their possible role in these conditions.

Astemizole↗
PubMed1992

The development of corticospinal projections to tail and hindlimb motoneurons studied in infant macaques using magnetic brain stimulation.

The EMG responses evoked in tail, leg and foot muscles by magnetic stimulation (MS) of the brain were investigated in two male macaque monkeys under ketamine sedation. The animals were studied longitudinally over a period of 7 months (from 2.75 to 9.75 months old). MS was generally ineffective in eliciting responses when the animals were 2.75-4.5 months old, even at maximum stimulator output (1.5 Tesla). After this time the threshold for evoking EMG responses decreased considerably, and there was an increase in the probability of occurrence of the responses. These age-related changes plateaued at about 7.5 months, after which they remained fairly constant at adult levels. In both animals the maturation of these responses in tail and hindlimb muscles occurred later than in forelimb muscles.

Afferent Pathways↗
PubMed1992

Gonadotropin-releasing hormone neuronal cell lines.

Gonadotropin-releasing hormone (GnRH) cell lines were developed by genetically targeted tumorigenesis in transgenic mice. The cell lines designated GT1 cells have a neuronal phenotype, express neuronal but not glial markers and express the GnRH gene at high levels. The GnRH prohormone is processed in the cells to multiple molecular forms including biologically active GnRH and GnRH-associated peptide. Basal secretion of GnRH from the cells is regulated in part by fast Na+ channels necessary for propagated action potentials. In many instances, basal GnRH release is pulsatile with an interpulse frequency similar to that seen in castrated rodents, suggesting that GnRH neurons are the pulse generator and are capable of synchronizing their secretion in vitro. The secretion of GnRH is stimulated by depolarization and by the neurotransmitter norepinephrine. In related studies we have demonstrated that expression of Simian virus 40 T antigen in GnRH neurons of transgenic mice leads to hypothalamic hypogonadism due to the inability of GnRH nerve terminals to organize in the median eminence. These findings support the use of genetically-directed tumorigenesis to establish highly differentiated GnRH neuronal cell lines that are a valuable model to study the cell biology and regulation of the neurons.

Animals↗
PubMed1991

The G protein coupled to the thromboxane A2 receptor in human platelets is a member of the novel Gq family.

The thromboxane A2 (TXA2) receptor in human platelets is coupled to a pertussis toxin-insensitive G protein whose identity has remained unknown. Candidates for this role include the atypical G protein known as Gz and members of a recently discovered G protein family known as Gq. Because of the proven utility of antibodies directed against the C terminus of G protein alpha subunits as functional probes, we prepared an antibody against a synthetic decapeptide corresponding to the C-terminal sequence shared by alpha 11 and alpha q, two members of the new family. This antibody (QL) does not recognize known alpha subunits but selectively binds to a 42-kDa protein in a variety of tissues, including human platelet membranes. QL and two other C-terminal antibodies, QN and AS, known to recognize alpha z and alpha i2, respectively, were tested for their ability to block agonist-stimulated GTPase activity in human platelet membranes. Pretreatment of platelet membranes with AS has previously been shown to interfere with alpha 2 adrenergic receptor-mediated inhibition of adenylylcyclase. As expected, only AS antibody produced inhibition of alpha 2 receptor-stimulated GTPase. Pretreatment of membranes with QL, but not QN or AS, caused marked inhibition of TXA2 receptor-stimulated GTPase. This identifies the G protein coupled to human platelet TXA2 receptors as a member of the novel Gq family.

Amino Acid Sequence↗
PubMed1990

Corticosteroid treatment reduces mast cell numbers in inflammatory bowel disease.

Mast cell degranulation in the gut causes mucus secretion, mucosal edema, and increased gut permeability and may be responsible for some of the symptoms and signs of inflammatory bowel disease. We have used a novel monoclonal antibody (AAI) against tryptase expressed exclusively in the granules of mast cells to enumerate mast cells in rectal biopsies in order to study the effect of inflammatory bowel disease and drug treatment upon rectal mast cell numbers. Rectal mast cell numbers are significantly reduced in inflammatory bowel disease patients taking corticosteroids (mean 4.95 cells/mm2) when compared with control patients (10.1, P less than 0.001) and inflammatory bowel disease patients not taking corticosteroids (9.7, P less than 0.001 Wilcoxon rank sum test). The reduction in mast cell counts was independent of the degree of inflammation or architectural distortion. There was a negative correlation between the dose of corticosteroids and mast cell count (r = 0.53, P less than 0.05 Spearman rank correlation), and the mast cell count was reduced within a few days of treatment and remained low throughout steroid therapy. Mucosal mast cell depletion may be an important mechanism of action of corticosteroids in inflammatory bowel disease.

Adrenal Cortex Hormones↗
PubMed1990

The status of expectancy-arousal theory: comparative credibility of systematic desensitization and rational-emotive therapy in the treatment of anxiety about study.

96 university students were asked to imagine that they were suffering from study anxiety to the point of wishing to receive help with the problem. They were then asked to read a booklet detailing either (a) the rationale for systematic desensitization or Rational-Emotive Therapy and (b) told that counselling lasted for 5 or 15 weeks. They then assessed the credibility of the therapy using Borkovec's credibility rating method. Meta-analysis has shown that systematic desensitization has superior outcomes when compared to other treatments, but this could be attributed to the different expectations of benefit that the therapies arouse. This notion has been called the expectancy-arousal hypothesis. Results from the present experiment did not support Shapiro's 1981 findings that systematic desensitization was more credible than Rational-Emotive Therapy, which disconfirms the expectancy-arousal hypothesis, but the basis for this remains unclear.

Adult↗
PubMed1990

Immunolocalization of G protein alpha-subunits in the Drosophila CNS.

In order to uncover the role of G proteins in the integrative functioning and development of the nervous system, we have begun a multidisciplinary study of the G proteins present in the fruit fly, Drosophila melanogaster. In this report, we describe the distribution of 3 different G protein alpha-subunits in the adult Drosophila CNS as determined by immunocytochemical localization using affinity-purified antibodies generated to synthetic oligopeptide sequences unique to each alpha-subunit. Western blot analysis of membranes prepared from Drosophila heads indicates that antibodies specific for the Drosophila Go alpha and Gs alpha homologs recognize the appropriate protein species predicted by molecular cloning (Quan et al., 1989; Thambi et al., 1989). The Gi alpha homolog could not be detected in head membranes by Western blotting, consistent with the negligible levels of expression observed for Gi alpha on Northern blots of head mRNA (Provost et al., 1988). However, a Drosophila Gi alpha fusion protein could be detected by these antibodies following expression in E. coli. Immunolocalization studies revealed that the Go alpha and Gs alpha homologs are expressed at highest levels in neuropils and at intermediate levels in the cortex of all brain and thoracic ganglion areas. Only the lamina contained low levels of these alpha-subunits in the CNS. Additionally, Gs alpha appears to be associated with the cell membranes of neuronal cell bodies, while Go alpha has a more diffuse distribution, suggesting its presence in the cytoplasm as well as cell membranes. In contrast to the wide distribution of Go alpha and Gs alpha, Gi alpha has a surprisingly restricted distribution in the CNS. It is present at high levels only in photoreceptor cell terminations, glomerulae of the antennal lobes, and the ocellar retina. Little or no Gi alpha was detected in other brain regions or in the thoracic ganglion. Gi alpha, then, appears to be uniquely associated with some primary sensory afferents and their terminations, suggesting the presence of specific receptor and/or effector systems which mediate the transmission of primary sensory information in Drosophila.

Animals↗
PubMed1988

Purification of heterotrimeric GTP-binding proteins from brain: identification of a novel form of Go.

Using high-resolution Mono-Q anion-exchange chromatography, we purified four distinct GTP-binding proteins from bovine brain. Each consists of alpha and associated beta/gamma subunits, and each is a substrate for pertussis toxin catalyzed ADP-ribosylation. We defined the relationship between the alpha subunits of the purified proteins and cloned cDNAs encoding putative alpha subunits (1) by performing immunoblots with peptide antisera with defined specificity and (2) by comparing the migration on two-dimensional gel electrophoresis of the purified proteins, and of the in vitro translated products of cDNAs encoding alpha subunits. Purified G proteins with alpha subunits of 39, 41, and 40 kDa (G39, G41, and G40 in order of abundance) correspond to the products of Go, Gi1, and Gi2 cDNAs. We purified a novel G protein with an alpha subunit slightly above 39 kDa (G39*). G39* is less abundant than G39, elutes earlier than G39 on Mono-Q chromatography, and has a more basic pI (6.0 vs 5.6) than G39. G39 and G39*, however, are indistinguishable on immunoblots with a large number of specific antisera. The data suggest that G39* may represent a novel form of Go, differing in posttranslational modification rather than primary sequence.

Animals↗
PubMed1988

An antibody directed against the carboxyl-terminal decapeptide of the alpha subunit of the retinal GTP-binding protein, transducin. Effects on transducin function.

An antibody (AS/7) prepared against the carboxyl-terminal decapeptide of the alpha subunit of transducin (alpha T) has been used in various reconstitution studies aimed at characterizing the role of the carboxyl-terminal domain in the different functional activities of transducin. The peptide-specific antibody is a potent inhibitor of the rhodopsin-stimulated GTPase activity in phospholipid vesicle systems containing pure rhodopsin and pure holo-transducin, or rhodopsin and the purified alpha T and beta/gamma (beta gamma T) subunit components, with the highest levels of inhibition (80-95%) occurring under conditions where the molar ratio of holo-transducin (or alpha T) to AS/7 approximately equal to 1. The inhibition of the receptor-stimulated GTPase does not represent an interference in the interactions between the alpha T subunit and the beta gamma T complex, since essentially identical levels of inhibition are observed when AS/7 is preincubated with either free alpha T, holo-transducin, or alpha T in the presence of excess beta gamma T, prior to assay. The AS/7-induced inhibition also does not appear to reflect an alteration in the ability of alpha T to bind or hydrolyze GTP and, in fact, the incubation of alpha T with AS/7 results in a stimulation of the intrinsic GTPase activity for alpha T alone (i.e. in the absence of rhodopsin). Thus, we conclude that the inhibition of the rhodopsin-stimulated GTPase activity by AS/7 is due to the direct blocking (by the antibody) of rhodopsin-alpha T interactions. While AS/7 is capable of uncoupling rhodopsin-transducin interactions, it appears to promote the stimulation of the cyclic GMP phosphodiesterase (PDE) by an activated alpha T subunit. Specifically, when the pure alpha T-guanosine 5-O-(3-thiotriphosphate) (alpha TGTP gamma S) species is preincubated with AS/7 prior to its addition to an assay solution containing PDE, there is at least a 4-fold increase in the resultant cyclic GMP hydrolysis relative to the activities measured with alpha TGTP gamma S, alone, or with alpha TGTP gamma S preincubated with nonimmune (control) rabbit IgG. The AS/7-induced promotion is specific for the active form of alpha T; the inactive alpha TGDP species does not stimulate PDE activity either in the presence or absence of the antibody. The different effects by AS/7 on the various activities of the alpha T subunit highlight the existence of distinct functional domains on alpha T.(ABSTRACT TRUNCATED AT 400 WORDS)

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1988

Identification of the GTP-binding protein encoded by Gi3 complementary DNA.

Three closely related, but distinct, GTP-binding proteins (G-proteins) are encoded by cDNAs arbitrarily designated Gi1, Gi2, and Gi3. The in vitro translated products of mRNAs prepared from Gi1, Gi2, and Gi3 cDNAs migrate as 41-, 40-, and 41-kDa proteins, respectively, on sodium dodecyl sulfate-polyacrylamide gels. Antisera were raised against synthetic decapeptides corresponding to a divergent sequence (residues 159-168 for Gi1 and Gi3; 160-169 for Gi2) of the three cDNAs and tested on immunoblots for reactivity with three purified G-proteins, G41 and G40 from brain and G41 from HL-60 cells. LD antisera (Gi1 peptide) react only with brain G41. LE antisera (Gi2 peptide) react only with brain G40, and SQ antisera (Gi3 peptide) react exclusively with HL-60 G41. The results indicate that the 41-kDa G-protein purified from HL-60 cells differs from the purified brain 41-kDa protein and suggest that the HL-60 cell protein corresponds to that encoded by Gi3 cDNA.

Amino Acid Sequence↗