Gene expression analysis by massively parallel signature sequencing (MPSS) on microbead arrays

We describe a novel sequencing approach that combines non-gel-based signature sequencing with in vitro cloning of millions of templates on separate 5 microm diameter microbeads. After constructing a microbead library of DNA templates by in vitro cloning, we assembled a planar array of a million template-containing microbeads in a flow cell at a density greater than 3x10(6) microbeads/cm2. Sequences of the free ends of the cloned templates on each microbead were then simultaneously analyzed using a fluorescence-based signature sequencing method that does not require DNA fragment separation. Signature sequences of 16-20 bases were obtained by repeated cycles of enzymatic cleavage with a type IIs restriction endonuclease, adaptor ligation, and sequence interrogation by encoded hybridization probes. The approach was validated by sequencing over 269,000 signatures from two cDNA libraries constructed from a fully sequenced strain of Saccharomyces cerevisiae, and by measuring gene expression levels in the human cell line THP-1. The approach provides an unprecedented depth of analysis permitting application of powerful statistical techniques for discovery of functional relationships among genes, whether known or unknown beforehand, or whether expressed at high or very low levels.

Low-density lipoprotein receptor-related protein-5 binds to Axin and regulates the canonical Wnt signaling pathway

To understand how the Wnt coreceptor LRP-5 is involved in transducing the canonical Wnt signals, we identified Axin as a protein that interacts with the intracellular domain of LRP-5. LRP-5, when expressed in fibroblast cells, showed no effect on the canonical Wnt signaling pathway by itself, but acted synergistically with Wnt. In contrast, LRP-5 mutants lacking the extracellular domain functioned as constitutively active forms that bind Axin and that induce LEF-1 activation by destabilizing Axin and stabilizing beta-catenin. Addition of Wnt caused the translocation of Axin to the membrane and enhanced the interaction between Axin and LRP-5. In addition, the LRP-5 sequences involved in interactions with Axin are required for LEF-1 activation. Thus, we conclude that the binding of Axin to LRP-5 is an important part of the Wnt signal transduction pathway.

Limitations in bonding to dentin and experimental strategies to prevent bond degradation

The limited durability of resin-dentin bonds severely compromises the lifetime of tooth-colored restorations. Bond degradation occurs via hydrolysis of suboptimally polymerized hydrophilic resin components and degradation of water-rich, resin-sparse collagen matrices by matrix metalloproteinases (MMPs) and cysteine cathepsins. This review examined data generated over the past three years on five experimental strategies developed by different research groups for extending the longevity of resin-dentin bonds. They include: (1) increasing the degree of conversion and esterase resistance of hydrophilic adhesives; (2) the use of broad-spectrum inhibitors of collagenolytic enzymes, including novel inhibitor functional groups grafted to methacrylate resins monomers to produce anti-MMP adhesives; (3) the use of cross-linking agents for silencing the activities of MMP and cathepsins that irreversibly alter the 3-D structures of their catalytic/allosteric domains; (4) ethanol wet-bonding with hydrophobic resins to completely replace water from the extrafibrillar and intrafibrillar collagen compartments and immobilize the collagenolytic enzymes; and (5) biomimetic remineralization of the water-filled collagen matrix using analogs of matrix proteins to progressively replace water with intrafibrillar and extrafibrillar apatites to exclude exogenous collagenolytic enzymes and fossilize endogenous collagenolytic enzymes. A combination of several of these strategies should result in overcoming the critical barriers to progress currently encountered in dentin bonding.

Cellular mechanisms of neuropathic pain, morphine tolerance, and their interactions

Compelling evidence has accumulated over the last several years from our laboratory, as well as others, indicating that central hyperactive states resulting from neuronal plastic changes within the spinal cord play a critical role in hyperalgesia associated with nerve injury and inflammation. In our laboratory, chronic constriction injury of the common sciatic nerve, a rat model of neuropathic pain, has been shown to result in activation of central nervous system excitatory amino acid receptors and subsequent intracellular cascades including protein kinase C translocation and activation, nitric oxide production, and nitric oxide-activated poly(ADP ribose) synthetase activation. Similar cellular mechanisms also have been implicated in the development of tolerance to the analgesic effects of morphine. A recently observed phenomenon, the development of "dark neurons," is associated with both chronic constriction injury and morphine tolerance. A site of action involved in both hyperalgesia and morphine tolerance is in the superficial laminae of the spinal cord dorsal horn. These observations suggest that hyperalgesia and morphine tolerance may be interrelated at the level of the superficial laminae of the dorsal horn by common neural substrates that interact at the level of excitatory amino acid receptor activation and subsequent intracellular events. The demonstration of interrelationships between neural mechanisms underlying hyperalgesia and morphine tolerance may lead to a better understanding of the neurobiology of these two phenomena in particular and pain in general. This knowledge may also provide a scientific basis for improved pain management with opiate analgesics.

Axin and Frat1 interact with dvl and GSK, bridging Dvl to GSK in Wnt-mediated regulation of LEF-1

Wnt proteins transduce their signals through dishevelled (Dvl) proteins to inhibit glycogen synthase kinase 3beta (GSK), leading to the accumulation of cytosolic beta-catenin and activation of TCF/LEF-1 transcription factors. To understand the mechanism by which Dvl acts through GSK to regulate LEF-1, we investigated the roles of Axin and Frat1 in Wnt-mediated activation of LEF-1 in mammalian cells. We found that Dvl interacts with Axin and with Frat1, both of which interact with GSK. Similarly, the Frat1 homolog GBP binds Xenopus Dishevelled in an interaction that requires GSK. We also found that Dvl, Axin and GSK can form a ternary complex bridged by Axin, and that Frat1 can be recruited into this complex probably by Dvl. The observation that the Dvl-binding domain of either Frat1 or Axin was able to inhibit Wnt-1-induced LEF-1 activation suggests that the interactions between Dvl and Axin and between Dvl and Frat may be important for this signaling pathway. Furthermore, Wnt-1 appeared to promote the disintegration of the Frat1-Dvl-GSK-Axin complex, resulting in the dissociation of GSK from Axin. Thus, formation of the quaternary complex may be an important step in Wnt signaling, by which Dvl recruits Frat1, leading to Frat1-mediated dissociation of GSK from Axin.

Intrathecal MK-801 and local nerve anesthesia synergistically reduce nociceptive behaviors in rats with experimental peripheral mononeuropathy

The hyperalgesia and spontaneous pain that occur following peripheral nerve injury may be related to abnormal peripheral input or altered central activity, or both. The present experiments investigated these possibilities by examining the effects of MK-801 (a non-competitive N-methyl-D-aspartate, NMDA, receptor antagonist) and bupivacaine (a local anesthetic agent) on thermal hyperalgesia and spontaneous nociceptive behaviors in rats with painful peripheral mononeuropathy. Peripheral mononeuropathy was produced by loosely ligating the rat's common sciatic nerve, a procedure which causes chronic constrictive injury (CCI) of the ligated nerve. The resulting hyperalgesia to radiant heat and spontaneous nociceptive behaviors was assessed by using a foot-withdrawal test and a spontaneous pain behavior rating method, respectively. CCI rats receiving 4 daily intraperitoneal (i.p.) MK-801 injections (0.03, 0.1, 0.3 mg/kg) beginning 15 min prior to nerve ligation exhibited less hyperalgesia (i.e., longer foot-withdrawal latencies) on days 3, 5, 7, 10, and 15 after nerve ligation as compared to those receiving saline injections. Thermal hyperalgesia also was reduced when a single MK-801 injection was given intrathecally (i.t.) onto the spinal cord lumbar segments on Day 3 after nerve ligation. This effect of postinjury MK-801 treatment was dose-dependent (2.5-20 nmol) and lasted for at least 48 h after injection. Moreover, i.t. injection of MK-801 (10 nmol) reliably lowered spontaneous pain behavior rating scores in CCI rats compared to those in the saline group. The spinal site of MK-801 action is situated within the caudal (probably lumbar) spinal cord, since i.t. injection of MK-801 (10 nmol) onto the spinal cord thoracic segments did not affect thermal hyperalgesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Dishevelled proteins lead to two signaling pathways. Regulation of LEF-1 and c-Jun N-terminal kinase in mammalian cells

Dishevelled (Dsh/Dvl) proteins are known to mediate Wnt signaling by up-regulating beta-catenin levels and stimulating T cell factor (TCF)/LEF-1-dependent transcription. We have identified a new Dvl-mediated signaling pathway in that mouse Dvl proteins, when expressed in COS-7 cells, stimulate c-Jun-dependent transcription activity and the kinase activity of the c-Jun N-terminal kinase (JNK). The DEP domain of Dvl1 is essential for JNK activation. By contrast, all three conserved domains of Dvl, including DIX, PDZ, and DEP, are required for up-regulation of beta-catenin and for stimulation of LEF-1-mediated transcription in mammalian cells. Thus, Dvl can lead to two different signaling pathways. Furthermore, the small G proteins of Cdc42 or Rac1, which are involved in JNK activation by many stimuli, do not appear to play a major role in Dvl-mediated JNK activation, because the dominant negative mutants of Cdc42 and Rac1 could not inhibit Dvl-induced JNK activation. This suggests that Dvl may activate JNK via novel pathways.

The t(10;11)(p13;q14) in the U937 cell line results in the fusion of the AF10 gene and CALM, encoding a new member of the AP-3 clathrin assembly protein family

The translocation t(10;11)(p13;q14) is a recurring chromosomal abnormality that has been observed in patients with acute lymphoblastic leukemia as well as acute myeloid leukemia. We have recently reported that the monocytic cell line U937 has a t(10;11)(p13;q14) translocation. Using a combination of positional cloning and candidate gene approach, we cloned the breakpoint and were able to show that AF10 is fused to a novel gene that we named CALM (Clathrin Assembly Lymphoid Myeloid leukemia gene) located at 11q14. AF10, a putative transcription factor, had recently been cloned as one of the fusion partners of MLL. CALM has a very high homology in its N-terminal third to the murine ap-3 gene which is one of the clathrin assembly proteins. The N-terminal region of ap-3 has been shown to bind to clathrin and to have a high-affinity binding site for phosphoinositols. The identification of the CALM/AF10 fusion gene in the widely used U937 cell line will contribute to our understanding of the malignant phenotype of this line.

Molecular characterization, sequence analysis, and taxonomic position of newly isolated fish iridoviruses

Within the past decade, iridoviruses have been identified as the causative agents of systemic disease in a variety of commercially and recreationally important fish. Here we examine nine iridoviruses from fish, reptiles, and amphibians and demonstrate that all isolates were more similar to frog virus 3, the type species of the genus Ranavirus, than to lymphocystis disease virus, the type species of the genus Lymphocystivirus. Comparison of viral protein synthesis profiles, restriction endonuclease digestion patterns, and the amino acid sequence of the major capsid protein indicated that iridoviruses isolated from the same geographic region were similar, if not identical, whereas viruses from different areas were distinct. Moreover, using primers complementary to the conserved major capsid protein, we found that both PCR and RT-PCR successfully amplified virus-specific nucleic acid from all nine isolates. These studies demonstrate that the piscine iridoviruses examined here were members of the genus Ranavirus, and suggest that surveys of pathogenic "fish viruses" may need to include neighboring amphibian and reptilian populations. In addition, the results indicate that PCR readily identified vertebrate iridoviruses and suggest that PCR will be useful in the diagnosis of fish disease.

Roles of Wnt/β-catenin signaling in the gastric cancer stem cells proliferation and salinomycin treatment

The Wnt1 protein, a secreted ligand that activates Wnt signaling pathways, contributes to the self-renewal of cancer stem cells (CSCs) and thus may be a major determinant of tumor progression and chemoresistance. In a series of gastric cancer specimens, we found strong correlations among Wnt1 expression, CD44 expression, and the grade of gastric cancer. Stable overexpression of Wnt1 increased AGS gastric cancer cells' proliferation rate and spheroids formation, which expressed CSC surface markers Oct4 and CD44. Subcutaneous injection of nude mice with Wnt1-overexpressing AGS cells resulted in larger tumors than injection of control AGS cells. Salinomycin, an antitumor agent, significantly reduced the volume of tumor caused by Wnt1-overexpressing AGS cells in vivo. This is achieved by inhibiting the proliferation of CD44+Oct4+ CSC subpopulation, at least partly through the suppression of Wnt1 and β-catenin expression. Taken together, activation of Wnt1 signaling accelerates the proliferation of gastric CSCs, whereas salinomycin acts to inhibit gastric tumor growth by suppressing Wnt signaling in CSCs. These results suggest that Wnt signaling might have a critical role in the self-renewal of gastric CSCs, and salinomycin targeting Wnt signaling may have important clinical applications in gastric cancer therapy.

A chiral rhodium complex for rapid asymmetric transfer hydrogenation of imines with high enantioselectivity

[formula: see text] A chiral rhodium complex, (R)-Cp*RhCl[(1S,2S)-p-TsNCH(C6H5)CH(C6H5)NH2] (1a, (S,S)-Cp*RhClTsDPEN), generated from [Cp*RhCl2]2 and (1S,2S)-N-p-toluenesulfonyl-1,2-diphenylethylenediamine [(S,S)-TsDPEN], and its enantiomer 1b were found to provide superior catalysts for the rapid, high-yielding, asymmetric transfer hydrogenation of some heterocyclic imines, using an HCO2H-Et3N azeotrope as the hydrogen source.

Intrathecal treatment with dextrorphan or ketamine potently reduces pain-related behaviors in a rat model of peripheral mononeuropathy

The therapeutic effects of dextrorphan and ketamine, two non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists, on neuropathic pain-related behaviors were examined in rats with peripheral mononeuropathy induced by loose ligation of the common sciatic nerve (chronic constrictive injury, CCI). Four daily intrathecal treatments (beginning 1 h after nerve ligation) with dextrorphan or ketamine (12.5-100 nmol) reliably attenuated hyperalgesia to radiant heat and spontaneous pain-related behaviors in CCI rats. Thermal hyperalgesia also was reduced in CCI rats receiving a single intrathecal treatment with either dextrorphan or ketamine (50 and 100 nmol for each compound) on day 3 after nerve ligation when thermal hyperalgesia was well developed. Since both dextrorphan and ketamine are currently utilized in other clinical applications, the results suggest a new therapeutic utility of these 'old' compounds in treatment of neuropathic pain syndromes resulting from peripheral nerve injury.

NMDA and opioid receptors: their interactions in antinociception, tolerance and neuroplasticity

Over the last several years, significant progress has been made in our understanding of interactions between the N-methyl-D-aspartate (NMDA) and opioid receptors. Such interactions have been demonstrated at two distinct sites: (1) modulation of NMDA receptor-mediated electrophysiological events by opioids; and (2) intracellular events involving interactions between NMDA and opioid receptors. Furthermore, a considerable number of studies have shown the involvement of such interactions in neural mechanisms of nociceptive transmission, antinociception in acute and chronic pain states, opioid tolerance/dependence, and neuroplasticity. Importantly, emerging evidence indicates that activation of NMDA receptors may differentially modulate functions mediated by distinct opioid receptor subtypes, namely mu, delta, and kappa receptors. These studies have greatly enriched our knowledge regarding both NMDA and opioid receptor systems and have shed light on neurobiology of both acute and chronic pain. The advancement of such knowledge also promotes new strategies for better clinical management of pain patients.

Anomalous cerebral structure in dyslexia revealed with magnetic resonance imaging

OBJECTIVE

To develop quantitative methods for identifying cerebral anomalies on magnetic resonance images of subjects with language disorders and other learning disabilities.

DESIGN

Partially blinded comparison of subjects with dyslexia, unaffected relatives, and a control group balanced for age and socioeconomic status. Criterion standard: clinical diagnosis of dyslexia by physician or learning disabilities specialist on the basis of clinical assessment and family history.

SETTINGS

Hospital pediatric neurology clinic and private reading clinic.

PATIENTS AND OTHER PARTICIPANTS

VOLUNTEERS

individuals with dyslexia (seven male and two female, aged 15 to 65 years) from professional families; unaffected first- and second-degree relatives (four male and six female, aged 6 to 63 years) available in the geographical area; and controls (five male and seven female, aged 14 to 52 years).

INTERVENTIONS

Gradient echo three-dimensional scan in Seimens 1-Tesla Magnetom; 128 1.25-mm consecutive sagittal images.

MAIN OUTCOME MEASURES

(1) Average length of the temporal (T) and parietal (P) banks of the planum temporale; (2) interhemispheric coefficients of asymmetry for T and P banks: Left-Right interhemispheric coefficients of asymmetry = (L-R)/[(L+R)/2]; (3) intrahemispheric coefficients of asymmetry = (T-P)/[(T+P)/2]; and (4) qualitative assessment of gyral variants in the parietotemporal operculum.

RESULTS

All groups had left-sided asymmetry for the temporal bank and right-sided asymmetry for the parietal bank. The group with dyslexia had exaggerated asymmetries, owing to a significant shift of right planar tissue from the temporal to parietal bank. They also had a higher incidence of cerebral anomalies bilaterally (subjects with dyslexia, six of nine; relatives, two of 10; and controls, zero of 12).

CONCLUSIONS

Quantitative assessment of high-resolution magnetic resonance images can reveal functionally relevant variations and anomalies in cerebral structure. Further refinement of these measurement techniques should improve the diagnosis, classification, and treatment of language disorders and other learning disabilities.

Differential roles of NMDA and non-NMDA receptor activation in induction and maintenance of thermal hyperalgesia in rats with painful peripheral mononeuropathy

Central activation of excitatory amino acid receptors has been implicated in neuropathic pain following nerve injury. In a rat model of painful peripheral mononeuropathy, we compared the effects of non-competitive NMDA receptor antagonists (MK 801 and HA966) and a non-NMDA receptor antagonist (CNQX) on induction and maintenance of thermal hyperalgesia induced by chronic constrictive injury (CCI) of the rat common sciatic nerve. Thermal hyperalgesia to radiant heat was assessed by using a foot-withdrawal test and NMDA/non-NMDA receptor antagonists were administered intrathecally onto the lumbar spinal cord before and after nerve injury. Four daily single treatments with 20 nmol HA966 or CNQX beginning 15 min prior to nerve ligation (pre-injury treatment), reliably reduced thermal hyperalgesia in CCI rats on days 3, 5, 7 and 10 after nerve ligation. Thermal hyperalgesia was also reduced in CCI rats receiving a single post-injury treatment with HA966 (20 or 80 nmol) or MK 801 (5 or 20 nmol) on day 3 after nerve ligation when thermal hyperalgesia was well developed. In contrast, a single post-injury CNQX (20 or 80 nmol) treatment failed to reduce thermal hyperalgesia or to potentiate effects of HA966 or MK 801 (5 or 20 nmol) on thermal hyperalgesia in CCI rats. Moreover, multiple post-injury CNQX treatments utilizing the same dose regime as employed for the pre-injury treatment attenuated thermal hyperalgesia but only when the treatment began 1 or 24 h (but not 72 h) after nerve ligation.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific involvement of G proteins in regulation of serum response factor-mediated gene transcription by different receptors

Regulation of serum response factor (SRF)-mediated gene transcription by G protein subunits and G protein-coupled receptors was investigated in transfected NIH3T3 cells and in a cell line that was derived from mice lacking Galphaq and Galpha11. We found that the constitutively active forms of the alpha subunits of the Gq and G12 class of G proteins, including Galphaq, Galpha11, Galpha14, Galpha16, Galpha12, and Galpha13, can activate SRF in NIH3T3 cells. We also found that the type 1 muscarinic receptor (m1R) and alpha1-adrenergic receptor (AR)-mediated SRF activation is exclusively dependent on Galphaq/11, while the receptors for thrombin, lysophosphatidic acid (LPA), thromboxane A2, and endothelin can activate SRF in the absence of Galphaq/11. Moreover, RGS12 but not RGS2, RGS4, or Axin was able to inhibit Galpha12 and Galpha13-mediated SRF activation. And RGS12, but not other RGS proteins, blocked thrombin- and LPA-mediated SRF activation in the Galphaq/11-deficient cells. Therefore, the thrombin, LPA, thromboxane A2, and endothelin receptors may be able to couple to Galpha12/13. On the contrary, receptors including beta2- and alpha2-ARs, m2R, the dopamine receptors type 1 and 2, angiotensin receptors types 1 and 2, and interleukin-8 receptor could not activate SRF in the presence or absence of Galphaq/11, suggesting that these receptors cannot couple to endogenous G proteins of the G12 or Gq classes.

A common region of 10p deleted in DiGeorge and velocardiofacial syndromes

DiGeorge (DGS, MIM 188400) and velocardiofacial (VCFS, MIM 192430) syndromes may present many clinical problems including cardiac defects, hypoparathyroidism, T-cell immunodeficiency and facial dysmorphism. They are frequently associated with deletions within 22q11.2, but a number of cases have no detectable molecular defect of this region. A number of single case reports with deletions of 10p suggest genetic heterogeneity of DGS. Here we compare the regions of hemizygosity in four patients with terminal deletions of 10p (one patient diagnosed as having hypoparathyroidism and three as DGS) and one patient with a large interstitial deletion (diagnosed as VCFS). Fluorescence in situ hybridization (FISH) analysis demonstrates that these patients have overlapping deletions at the 10p13/10p14 boundary. A YAC contig spanning the shortest region of deletion overlap (SRO) has been assembled, and allows the size of SRO to be approximated to 2 Mb. As with deletions of 22q11, phenotypes vary considerably between affected patients. These results strongly support the hypothesis that haploinsufficiency of a gene or genes within 10p (the DGSII locus) can cause the DGS/VCFS spectrum of malformation.

Pain-related increases in spinal cord membrane-bound protein kinase C following peripheral nerve injury

Neuropathic pain following nerve injury is thought to involve central nervous system Ca(2+)-mediated neuronal plastic changes. This study provides evidence that induction and/or maintenance of post-injury neuropathic pain behaviors in the rat is associated with increases in membrane-bound protein kinase C (PKC), a Ca(2+)-dependent process known to mediate central nervous system neuronal plasticity. In addition, spinal cord administration of GM1 ganglioside, an intracellular inhibitor of PKC translocation/activation, reverses both increased levels of membrane-bound PKC and pain-related behaviors. Thus, persistent post-injury neuropathic pain may be mediated by the initiation of excitatory neuropathological processes resulting from an increase in membrane-bound PKC.

Structural basis of the recognition of the dishevelled DEP domain in the Wnt signaling pathway

The DEP domain of Dishevelled (Dvl) proteins transduces signals to effector proteins downstream of Dvl in the Wnt pathway. Here we report that DEP-containing mutants inhibit Wnt-induced, but not Dvl-induced, activation of the transcription factor Lef-1. This inhibitory effect is weakened by a K434M mutation. Nuclear magnetic resonance spectroscopy revealed that the DEP domain of mouse Dvl1 comprises a three-helix bundle, a beta-hairpin 'arm' and two short beta-strands at the C-terminal region. Lys 434 is located at the tip of the beta-hairpin 'arm'. Based on our findings, we conclude that DEP interacts with regulators upstream of Dvl via a strong electric dipole on the molecule's surface created by Lys 434, Asp 445 and Asp 448; the electric dipole and the putative membrane binding site are at two different locations.

Increases in protein kinase C gamma immunoreactivity in the spinal cord of rats associated with tolerance to the analgesic effects of morphine

Our previous studies have indicated a critical role of protein kinase C (PKC) in intracellular mechanisms of tolerance to morphine analgesia. In the present experiments, we examined (1) the cellular distribution of a PKC isoform (PKC gamma) in the spinal cord dorsal horn of rats associated with morphine tolerance by utilizing an immunocytochemical method and (2) the effects of the N-methyl-D-aspartate receptor antagonist MK-801 on tolerance-associated PKC gamma changes. In association with the development of tolerance to morphine analgesia induced by once daily intrathecal administration of 10 micrograms morphine for eight days, PKC gamma immunoreactivity was clearly increased in the spinal cord dorsal horn of these same rats. Within the spinal cord dorsal horn of morphine tolerant rats, there were significantly more PKC gamma immunostained neurons in laminae I-II than in laminae III-IV and V-VI. Such PKC gamma immunostaining was observed primarily in neuronal somata indicating a postsynaptic site of PKC gamma increases. Moreover, both the development of morphine tolerance and the increase in PKC gamma immunoreactivity were prevented by co-administration of morphine with 10 nmol MK-801 between Day 2 and Day 7 of the eight day treatment schedule. In contrast, PKC gamma immunoreactivity was not increased in rats receiving a single i.t. administration of 10 micrograms morphine on Day 8, nor did repeated treatment with 10 nmol MK-801 alone change baseline levels of PKC gamma immunoreactivity. These results provide further evidence for the involvement of PKC in NMDA receptor-mediated mechanisms of morphine tolerance.

Guanine nucleotide exchange factor GEF115 specifically mediates activation of Rho and serum response factor by the G protein alpha subunit Galpha13

Signal transduction pathways that mediate activation of serum response factor (SRF) by heterotrimeric G protein alpha subunits were characterized in transfection systems. Galphaq, Galpha12, and Galpha13, but not Galphai, activate SRF through RhoA. When Galphaq, alpha12, or alpha13 were coexpressed with a Rho-specific guanine nucleotide exchange factor GEF115, Galpha13, but not Galphaq or Galpha12, showed synergistic activation of SRF with GEF115. The synergy between Galpha13 and GEF115 depends on the N-terminal part of GEF115, and there was no synergistic effect between Galpha13 and another Rho-specific exchange factor Lbc. In addition, the Dbl-homology (DH)-domain-deletion mutant of GEF115 inhibited Galpha13- and Galpha12-induced, but not GEF115 itself- or Galphaq-induced, SRF activation. The DH-domain-deletion mutant also suppressed thrombin- and lysophosphatidic acid-induced SRF activation in NIH 3T3 cells, probably by inhibition of Galpha12/13. The N-terminal part of GEF115 contains a sequence motif that is homologous to the regulator of G protein signaling (RGS) domain of RGS12. RGS12 can inhibit both Galpha12 and Galpha13. Thus, the inhibition of Galpha12/13 by the DH-deletion mutant may be due to the RGS activity of the mutant. The synergism between Galpha13 and GEF115 indicates that GEF115 mediates Galpha13-induced activation of Rho and SRF.

Oral administration of dextromethorphan prevents the development of morphine tolerance and dependence in rats

Combined oral administration of morphine sulfate (MS) and the over-the-counter antitussive drug and N-methyl-D-aspartate receptor antagonist dextromethorphan (DM) prevented the development of tolerance to the antinociceptive effects of MS (15, 24, or 32 mg/kg) in rats. This combined oral treatment regimen also attenuated signs of naloxone-precipitated physical dependence on morphine in the same rats. A wide range of ratios of MS to DM (2:1, 1:1, and 1:2) were effective for preventing the development of morphine tolerance and dependence. In addition, we provide evidence that under certain circumstances DM increases the acute antinociceptive effects of MS. All of these results indicate that oral treatment that combines DM with opiate analgesics may be a powerful approach for simultaneously preventing opiate tolerance and dependence and enhancing analgesia in humans.

Muscle atrophy and procedures for training after spinal cord injury

Functional electrical stimulation (FES) of paralyzed muscles holds promise as a strategy to assist patients in executing functional movements after spinal cord injuries. Muscle atrophy is one of the major problems that must be addressed for this approach to be successful. Loss of muscle mass may occur as a result of lesions to motoneurons in either the spinal cord or the central command pathway, or a combination of the two. For injuries to spinal motoneurons, muscle fibers undergo denervation atrophy. Damage to the central command pathway, on the other hand, results in disuse atrophy. In association with atrophy, the low contractile forces and inability of the muscles to sustain contractions are of direct therapeutic concern. In this review, methods aimed at recovery of function of paralyzed limbs by reducing susceptibility to fatigue and atrophy of paralyzed muscles are discussed. One is related to promoting nerve sprouting in partially denervated muscles to reinnervate muscle fibers and reverse denervation atrophy. The other regards training of paralyzed muscles to increase strength (muscle force) and endurance (fatigue resistance) by means of FES. Most training regimens with low-frequency FES increase muscle endurance. Efforts to design optimal regimens for increasing both muscle strength and endurance must involve consideration of several factors that are still controversial. These factors, which include muscle properties (such as fiber type composition and physiological type) and conditions imposed on the muscle (such as loading) during contractions elicited by FES, are discussed in detail.