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M Rubinstein

Publications and source records attributed to M Rubinstein.

At least 55 records · Page 3Linked to original sources
PubMed2000

Quantitative analysis of the dopamine D4 receptor in the mouse brain.

The D4 receptor (D4R), a member of the dopamine D2-like receptor family, has been implicated in the pathophysiology of several diseases and has been the target of various investigations regarding its distribution and quantification. The brain distribution of the D4R has been well described in various species, but the quantification is still an issue of controversy, because no specific ligand is commercially available. To circumvent this difficulty we have performed a biochemical and autoradiographical study in brain samples obtained from mice lacking D4Rs and their wild-type siblings; comparison of their binding parameters allows a more accurate quantification of the members of the D2-like receptor family (D2, D3, and D4 receptors). We found that the distribution of D2-like receptors in mouse brain is similar to that of rat brain, i.e., caudate putamen, nucleus accumbens, olfactory tubercle, and hippocampus. The contribution of the D4R to the overall population of D2-like receptors is 17% in nucleus accumbens, 21% in caudate putamen and olfactory tubercle, and 40% in hippocampus. Based on our study we conclude that nemonapride probably binds to nondopaminergic sites that if not properly blocked may lead to overestimations of D4R levels. We observed that the experimental condition that better estimates the density of D4 receptors is the displacement of D2 and D3 [3H]nemonapride binding sites with cold raclopride.

Animals↗
PubMed2000

Production of a biologically active human interleukin 18 requires its prior synthesis as PRO-IL-18.

Interleukin (IL-)18 is an activator of NK cells and a co-inducer of Th(1)cytokines, sharing structural features with the IL-1 family of proteins. Unlike most other cytokines, IL-18 and IL-1beta lack a signal peptide, have an all beta-pleated sheet structure and are synthesized as biologically inactive precursors (pro-IL-18 and pro-IL-1beta). These precursors are cleaved by caspase-1 (IL-1beta-converting enzyme, ICE) to form the biologically active mature cytokines. Direct expression of mature recombinant human IL-18 in E. coli resulted in a partially active cytokine. We tested the possibility that correct folding of huIL-18 requires its prior synthesis as pro-IL-18. Because caspase-1 is not readily available, we constructed an expression vector encoding human pro-IL-18 in which the caspase-1 cleavage site was mutated into a factor Xa site. To facilitate purification, the mutated pro-IL-18 cDNA was fused in frame to a glutathione-S-transferase (GST) coding sequence. The GST-pro-IL-18 fusion protein was expressed in E. coli, captured on glutathione agarose and mature human IL-18, exhibiting high biological activity was released upon cleavage with factor Xa. This result indicates that correct folding of huIL-18 occurs at the level of pro-IL-18 and provides a practical way to produce biologically active huIL-18.

Amino Acid Sequence↗
PubMed2000

Lack of operant ethanol self-administration in dopamine D2 receptor knockout mice.

RATIONALE: Dopamine D2 receptors are postulated to play an important role in modulating the reinforcing effects of abused drugs including ethanol. OBJECTIVES: This experiment examined operant ethanol self-administration in dopamine D2 receptor knockout (KO) mice and wild-type (WT) mice using a continuous access procedure. METHODS: Adult male KO and WT mice were trained in 30-min sessions to perform a lever press response for access to 10% v/v ethanol. After training, the mice were placed in test chambers on a continuous (23 h/day) basis with access to food (one lever press, i.e., FR1), 10% v/v ethanol (four lever presses, i.e., FR4), and water from a sipper tube (phase 1). After 30 consecutive sessions, response patterns were determined for 0, 5, 10, 20 and 30% v/v ethanol (phase 2). Saccharin (0.2% w/v) was subsequently added to the ethanol mixture and responding was examined for 0, 5, 10 and 20% ethanol (phase 3). RESULTS: During phase 1, WT mice displayed higher ethanol-lever responding compared to KO mice. Food lever responding and water intake was the same in both genotypes. During phase 2, WT mice displayed concentration-dependent ethanol lever responding, whereas KO mice responded at low rates regardless of ethanol concentration. WT mice also responded more for food compared to KO mice. Each genotype showed similar water intakes except at the 20% ethanol concentration, where WT mice had lower intakes. During phase 3, WT mice continued to show higher responding for all concentrations including saccharin alone. WT mice also continued to respond more for food compared to KO mice, but drank less water. In each phase, WT mice displayed episodic (bout) responding on the ethanol lever. KO mice did not respond for ethanol in bouts. CONCLUSIONS: Reduced responding in the KO mice for several reinforcers including ethanol indicates a more general role for dopamine D2 receptors in motivated responding rather than a specific role in ethanol reinforcement.

Animals↗
PubMed2000

Ethanol-conditioned place preference is reduced in dopamine D2 receptor-deficient mice.

Pharmacological blockade studies have supported a role of the dopamine system in ethanol reward for many years, but receptor subtype specificity has been difficult to establish. Recently, genetically engineered mice lacking functional dopamine D2 receptors have been shown to drink less ethanol in a two-bottle choice task. To determine whether reduced ethanol intake reflects a reduction in ethanol reward, D2 receptor-deficient [knockout (KO)] mice were compared to heterozygous (HET) and wild-type (WT; C57BL/6xDBA/2 F2 hybrid) mice in a place conditioning task. Under conditions that produced reliable place preference in both WT and HET mice, KO mice showed no evidence of place conditioning, suggesting that D2 receptor gene inactivation reduced ethanol reward or the ability to learn about ethanol reward. Consistent with previous findings, this mutation also produced a gene dose-related reduction in basal activity levels. Moreover, KO and HET mice showed enhancement of ethanol-stimulated activity relative to WT mice. However, differences in basal and ethanol-stimulated activity did not explain the differences in place conditioning. Overall, this study strongly supports the conclusion that dopamine D2 receptors normally influence ethanol reward in mice.

Animals↗
PubMed2000

The indirect basal ganglia pathway in dopamine D(2) receptor-deficient mice.

Recent pathophysiological models of basal ganglia function in Parkinson's disease predict that specific neurochemical changes in the indirect pathway would follow the lack of stimulation of D(2) dopamine receptors. Post mortem studies of the basal ganglia in genetically modified mice lacking functional copies of the D(2) dopamine receptor gene allowed us to test these predictions. When compared with their congenic N(5) wild-type siblings, mice lacking D(2) receptors show an increased expression of enkephalin messenger RNA in the striatum, and an increased activity and expression of cytochrome oxidase I in the subthalamic nucleus, as expected. In addition, D(2) receptor-deficient mice display a reduced expression of glutamate decarboxylase-67 messenger RNA in the globus pallidus, as the basal ganglia model predicts. This reduction contrasts with the lack of change or increase in glutamate decarboxylase-67 messenger RNA expression found in animals depleted of dopamine after lesions of the mesostriatal dopaminergic system. Furthermore, D(2) receptor-deficient mice show a significant decrease in substance P messenger RNA expression in the striatonigral neurons which form the direct pathway. Finally, glutamate decarboxylase-67 messenger RNA expression in the basal ganglia output nuclei was not affected by mutations in the D(2) receptor gene, a fact that could probably be related to the absence of a parkinsonian locomotor phenotype in D(2) receptor-deficient mice. In summary, these findings provide compelling evidence demonstrating that the lack of endogenous stimulation of D(2) receptors is sufficient to produce subthalamic nucleus hyperactivity, as assessed by cytochrome oxidase I histochemistry and messenger RNA expression, and strongly suggest the existence of interactions between the basal ganglia direct and indirect pathways.

Animals↗
PubMed2000

Disparate spinal and supraspinal opioid antinociceptive responses in beta-endorphin-deficient mutant mice.

The role of endogenous opioid systems in the analgesic response to exogenous opiates remains controversial. We previously reported that mice lacking the peptide neurotransmitter beta-endorphin, although unable to produce opioid-mediated stress-induced antinociception, nevertheless displayed intact antinociception after systemic administration of the exogenous opiate morphine. Morphine administered by a peripheral route can activate opioid receptors in both the spinal cord and brain. However, beta-endorphin neuronal projections are confined predominantly to supraspinal nociceptive nuclei. Therefore, we questioned whether the absence of beta-endorphin would differentially affect antinociceptive responses depending on the route of opiate administration. Time- and dose-response curves were obtained in beta-endorphin-deficient and matched wild-type C57BL/6 congenic control mice using the tail-immersion/withdrawal assay. Null mutant mice were found to be more sensitive to supraspinal (i.c.v.) injection of the micro-opioid receptor-selective agonists, morphine and D-Ala(2)-MePhe(4)-Gly-ol(5) enkephalin. In contrast, the mutant mice were less sensitive to spinal (i.t.) injection of these same drugs. Quantitative receptor autoradiography revealed no differences between genotypes in the density of mu, delta, or kappa opioid receptor binding sites in either the spinal cord or pain-relevant supraspinal areas. Thus we report that the absence of a putative endogenous ligand for the mu-opioid receptor results in opposite changes in morphine sensitivity between discrete areas of the nervous system, which are not simply caused by changes in opioid receptor expression.

Analgesics, Opioid↗
PubMed2000

The neutralization of type I IFN biologic actions by anti-IFNAR-2 monoclonal antibodies is not entirely due to inhibition of Jak-Stat tyrosine phosphorylation.

A panel of monoclonal antibodies (mAb) derived against human interferon-alpha/beta receptor-2 (IFNAR-2) was evaluated for their ability to antagonize the biologic effects of type 1 interferons (IFN-alpha1, IFN-alpha2a, and IFN-beta). Anti-IFNAR-2 mAb 117.7, 35.9, 53.2, and 51.44 neutralized type I IFN-mediated antiviral, antiproliferative, and major histocompatibility complex (MHC) class I upregulation functions. However, only mAb 51.44 neutralized IFN-alpha2a and IFN-beta-mediated natural killer (NK) cell cytotoxicity. In BIAcore and cell binding studies, only mAb 51.44 and 234.28 inhibited IFN-alpha2a and IFN-beta binding to its receptor. The receptor blockade by mAb 51.44 and 234.28 resulted in the inhibition of IFN-alpha2a and IFN-beta-induced tyrosine phosphorylation of Jak1, Tyk2, Stat1/2/3, and IFNAR-1/2 and inhibition of IFN-stimulated gene factor 3 (ISGF3) formation. mAb 117.7, 35.9, and 53.2, although antagonists of IFN's biologic activities, did not block the binding of IFN-alpha/beta to its receptor. The 117.7 mAb, representative of this class of receptor nonblocking mAb, induced hyper-tyrosine phosphorylation of IFNAR-2 in the presence of IFN-alpha/beta but did not inhibit IFN-alpha/beta-induced Jak-Stat tyrosine phosphorylation and ISGF3 complex formation. These results show that the neutralization of type I IFN biologic actions by anti-IFNAR-2 mAb cannot be entirely explained by inhibition of Jak-Stat tyrosine phosphorylation.

Antibodies, Monoclonal↗
PubMed2000

Harvesting the human genome: the Israeli perspective.

The post-genome era is at our door, and soon the complete human genome sequence will be available for the next set of goals. Israel is well equipped and skilled to join the worldwide harvest of the human genome, but additional massive government investment is required. This will affect various domains of activity, including the fields of diagnostics and therapeutics. The technologies and know-how described above constitute the basis for future human genome applications in Israel.

Computational Biology↗
PubMed1999

D3 receptor knockdown through antisense oligonucleotide administration supports its inhibitory role in locomotion.

To study the specific contribution of the D3 dopamine receptor in the generation of locomotor activity, total or partially dopamine-depleted rats were pretreated with an antisense oligodeoxynucleotide for the D3 receptor (D3R-as) and locomotor activity induced by apomorphine was measured. A 35.7% increase in locomotor activity was seen in the totally dopamine-depleted rats pretreated with the D3R-as, whereas the same antisense, caused a significantly greater increase in the locomotor response (95%) in the partially dopamine-depleted rats compared with control groups (pretreated with a control oligodeoxynucleotide or vehicle). In situ autoradiography for D3 receptors showed a 27% fall in the density of D3 receptors in the islands of Calleja compared with control animals. Our results seem to confirm that D3 receptors exert an inhibitory effect on locomotor activity, through the stimulation of both pre- and postsynaptic components.

Adrenergic Uptake Inhibitors↗
PubMed1999

Ethanol oral self-administration is increased in mutant mice with decreased beta-endorphin expression.

The relationship between ethanol (EtOH) administration and the endogenous opioid system has been studied for many years and a considerable body of evidence supports the contention that EtOH modulates the production and/or release of endogenous opioid peptides. However, substantially less is known about the converse influence: the effect that opioids have on EtOH sensitivity. In this study, we used the beta-endorphin deficient mutant mouse line C57BL/6-Pomc1(tm1Low) to investigate the possible role of a specific opioid peptide on EtOH consumption. Homozygous knockout mice (entirely lacking beta-endorphin), heterozygous mice (50% beta-endorphin expression) and sibling wildtype mice from the same strain were evaluated in a two-bottle free choice paradigm for oral self-administration of EtOH. Across varying EtOH concentrations only the heterozygous mice were found to consistently drink more than wildtype mice. These data support the hypothesis that beta-endorphin modulates the response to EtOH.

Alcohol Drinking↗
PubMed1999

K+ channel modulation in rodent neurohypophysial nerve terminals by sigma receptors and not by dopamine receptors.

1. Sigma receptors bind a diverse group of chemically unrelated ligands, including pentazocine, apomorphine (a dopamine receptor agonist) and haloperidol (a dopamine receptor antagonist). Although sigma binding sites are widely distributed, their physiological roles are poorly understood. Here, the whole-terminal patch-clamp technique was used to demonstrate that sigma receptors modulate K+ channels in rodent neurohypophysis. 2. Previous work suggested that dopamine type 4 (D4) receptors modulate neurohypophysial K+ current, so this study initially tested the role of dopamine receptors. Experiments using transgenic mice lacking D2, D3 or D4 receptors indicated that the reduction of K+ current by PPHT and U101958 (ligands thought to be selective for dopamine receptors) is not mediated by dopamine receptors. The sensitivity of the response to U101958 (a drug that binds to D4 receptors) was the same in both wild-type and D4 receptor-deficient mice. 3. Experiments with other ligands revealed a pharmacological signature inconsistent with any known dopamine receptor. Furthermore, dopamine itself (at 100 microM) had no effect. Thus, despite the activity of a number of putative dopamine receptor ligands, dopamine receptors play no role in the modulation of neurohypophysial K+ channels. 4. Because of the negative results regarding dopamine receptors, and because some of the dopamine receptors ligands used here are known to bind also to sigma receptors, experiments were conducted to test for the involvement of sigma receptors. In rat neurohypophysis the sigma receptor ligands SKF10047, pentazocine, and ditolylguanidine all reversibly inhibited K+ current in a concentration-dependent fashion, as did haloperidol and apomorphine (ligands that bind to both dopamine and sigma receptors). The activity of these and other ligands tested here matches the reported binding specificity for sigma receptors. 5. Fifteen candidate endogenous sigma receptor ligands, including biogenic amines (e.g dopamine and serotonin), steroids (e.g. progesterone), and peptides (e.g. neuropeptide Y), were screened for activity at the sigma receptor. All were without effect. 6. Haloperidol reduced K+ current proportionally at all voltages without shifting the voltage dependence of activation and inactivation. Sigma receptor ligands inhibited current through two distinct K+ channels, the A-channel and the Ca2+-dependent K+ channel. In rat, all drugs reduced current through both channels proportionally, suggesting that both channels are modulated by a single population of sigma receptors. In contrast, mouse peptidergic nerve terminals either have two receptors which are sensitive to these drugs, or a single receptor that is differentially coupled to ion channel function. 7. The inhibition of voltage-activated K+ current by sigma receptors would be expected to enhance the secretion of oxytocin and vasopressin from the neurohypophysis.

Animals↗
PubMed1999

The dopamine D2, but not D3 or D4, receptor subtype is essential for the disruption of prepulse inhibition produced by amphetamine in mice.

Brain dopamine (DA) systems are involved in the modulation of the sensorimotor gating phenomenon known as prepulse inhibition (PPI). The class of D2-like receptors, including the D2, D3, and D4 receptor subtypes, have all been implicated in the control of PPI via studies of DA agonists and antagonists in rats. Nevertheless, the functional relevance of each receptor subtype remains unclear because these ligands are not specific. To determine the relevance of each receptor subtype, we used genetically altered strains of "knock-out" mice lacking the DA D2, D3, or D4 receptors. We tested the effects of each knock-out on both the phenotypic expression of PPI and the disruption of PPI produced by the indirect DA agonist d-amphetamine (AMPH). No phenotypic differences in PPI were observed at baseline. AMPH significantly disrupted PPI in the D2 (+/+) mice but had no effect in the D2 (-/-) mice. After AMPH treatment, both DA D3 and D4 receptor (+/+) and (-/-) mice had significant disruptions in PPI. These findings indicate that the AMPH-induced disruption of PPI is mediated via the DA D2 receptor and not the D3 or D4 receptor subtypes. Uncovering the neural mechanisms involved in PPI will further our understanding of the substrates of sensorimotor gating and could lead to better therapeutics to treat gating disorders, such as schizophrenia.

Acoustic Stimulation↗
PubMed1999

Low-dose aspirin treatment improves ovarian responsiveness, uterine and ovarian blood flow velocity, implantation, and pregnancy rates in patients undergoing in vitro fertilization: a prospective, randomized, double-blind placebo-controlled assay.

OBJECTIVE: To determine the effects of low-dose aspirin on ovarian response, uterine and ovarian blood flow velocity, and implantation and pregnancy rates in patients undergoing IVF. DESIGN: Prospective, randomized, double-blind placebo-controlled assay. SETTING: Department of Reproductive Medicine, CER Medical Institute, Buenos Aires, Argentina. PATIENT(S): Two hundred ninety-eight infertile patients (mean [+/- SDI age, 35.6+/-4.09 years) undergoing IVF cycles. INTERVENTION(S): In the treatment group, 149 patients underwent controlled ovarian hyperstimulation and received a daily dose of 100 mg of aspirin. In the control group, 149 patients underwent controlled ovarian hyperstimulation in association with placebo. MAIN OUTCOME MEASURE(S): Number of follicles, number of oocytes retrieved, serum E2 levels, uterine and ovarian pulsatility index, cancellation rate, number of embryos transferred, and implantation and pregnancy rates. RESULT(S): There were statistically significant differences between the treatment group and the control group, respectively, in the number of follicles (19.8+/-7.2 versus 10.2+/-5.3), number of oocytes retrieved (16.2+/-6.7 versus 8.6+/-4.6), serum E2 levels (2,923.8+/-1,023.4 versus 1,614.3+/-791.7 pg/mL), uterine pulsatility index (1.22+/-0.34 versus 1.96+/-0.58), ovarian pulsatility index (1.18+/-0.31 versus 1.99+/-0.56), pregnancy rate (45% versus 28%), and implantation rate (17.8% versus 9.2%). CONCLUSION(S): Low-dose aspirin treatment significantly improves ovarian responsiveness, uterine and ovarian blood flow velocity, and implantation and pregnancy rates in IVF patients.

Adult↗
PubMed1999

Interleukin-18 binding protein: a novel modulator of the Th1 cytokine response.

An interleukin-18 binding protein (IL-18BP) was purified from urine by chromatography on IL-18 beads, sequenced, cloned, and expressed in COS7 cells. IL-18BP abolished IL-18 induction of interferon-gamma (IFNgamma), IL-8, and activation of NF-kappaB in vitro. Administration of IL-18BP to mice abrogated circulating IFNgamma following LPS. Thus, IL-18BP functions as an inhibitor of the early Th1 cytokine response. IL-18BP is constitutively expressed in the spleen, belongs to the immunoglobulin superfamily, and has limited homology to the IL-1 type II receptor. Its gene was localized on human chromosome 11q13, and no exon coding for a transmembrane domain was found in an 8.3 kb genomic sequence. Several Poxviruses encode putative proteins highly homologous to IL-18BP, suggesting that viral products may attenuate IL-18 and interfere with the cytotoxic T cell response.

Amino Acid Sequence↗
PubMed1999

Dopamine D2 receptor-deficient mice exhibit decreased dopamine transporter function but no changes in dopamine release in dorsal striatum.

Presynaptic D2 dopamine (DA) autoreceptors, which are well known to modulate DA release, have recently been shown to regulate DA transporter (DAT) activity. To examine the effects of D2 DA receptor deficiency on DA release and DAT activity in dorsal striatum, we used mice genetically engineered to have two (D2+/+), one (D2+/-), or no (D2-/-) functional copies of the gene coding for the D2 DA receptor. In vivo microdialysis studies demonstrated that basal and K+-evoked extracellular DA concentrations were similar in all three genotypes. However, using in vivo electrochemistry, the D2-/- mice were found to have decreased DAT function, i.e., clearance of locally applied DA was decreased by 50% relative to that in D2+/+ mice. In D2+/+ mice, but not D2-/- mice, local application of the D2-like receptor antagonist raclopride increased DA signal amplitude, indicating decreased DA clearance. Binding assays with the cocaine analogue [3H]WIN 35,428 showed no genotypic differences in either density or affinity of DAT binding sites in striatum or substantia nigra, indicating that the differences seen in DAT activity were not a result of decreased DAT expression. These results further strengthen the idea that the D2 DA receptor subtype modulates activity of the striatal DAT.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1999

Leptin modulates the glucocorticoid-induced ovarian steroidogenesis.

Leptin regulates food intake and other activities through its hypothalamic receptor. Leptin receptors are also found in other organs, including the ovary. Direct effects of leptin in ovarian steroid production were studied in primary rat granulosa cells and in rat and human granulosa cell lines. Leptin (0.6-18 nM) suppressed ovarian steroid synthesis costimulated by FSH and dexamethasone. Production of pregnenolone, progesterone, and 20alpha-hydroxy-4-pregnen-3-one was inhibited by leptin. This inhibition was due at least in part to reduced expression of adrenodoxin, a component of the P450scc system enzyme. Costimulation of progesterone production by forskolin and dexamethasone was also inhibited by leptin, whereas the forskolin-induced cAMP production was not affected. We find that leptin induces c-Jun expression and attenuates the transcriptional activity of the glucocorticoid receptor (GR) in granulosa cells. Elevation of c-Jun expression by other means, e.g. 12-O tetradecanoyl-phorbol-13-acetate or transfecting with a c-Jun expression vector, abolished the transcriptional activity of the GR. A leptin-induced elevation of c-Jun modulates the transcriptional activity of the GR, possibly leading to the observed attenuation of steroidogenesis. It was recently shown that glucocorticoids stimulate leptin expression in vivo, which in turn, inhibits cortisol synthesis. A direct action of leptin on the ovary is an additional element of a regulatory network that maintains the homeostasis of steroid production.

20-alpha-Dihydroprogesterone↗