Effects of Monoamine Reuptake Inhibitors in Assays of Acute Pain-Stimulated and Pain-Depressed Behavior in Rats

Pain is associated with stimulation of some behaviors (eg, withdrawal reflexes) but depression of many other behaviors (eg, feeding, locomotion, positively reinforced operant behavior). Drugs that block reuptake of serotonin, norepinephrine, and/or dopamine are widely used to treat depression, and they have also emerged as useful drugs for treatment of pain. This study compared effects of selective and mixed-action inhibitors of serotonin, norepinephrine, and/or dopamine reuptake in assays of acute pain-stimulated and pain-depressed behavior. Intraperitoneal injection of dilute acid served as a noxious stimulus to stimulate a writhing response or depress intracranial self-stimulation (ICSS) in Sprague Dawley rats. Selective reuptake inhibitors of serotonin (citalopram, clomipramine) and norepinephrine (nisoxetine, nortriptyline) and a mixed-action reuptake inhibitor of serotonin and norepinephrine (milnacipran) blocked acid-stimulated writhing but failed to block acid-induced depression of ICSS. Selective dopamine reuptake inhibitors (RTI-113 [3ß-(4-chlorophenyl)tropane-2ß-carboxylic acid phenyl ester hydrochloride], bupropion) and a triple reuptake inhibitor of dopamine, serotonin, and norepinephrine (RTI-112 [3ß-(3-methyl-4-chlorophenyl)tropane-2ß-carboxylic acid methyl ester hydrochloride]) blocked both acid-stimulated writhing and acid-induced depression of ICSS, although these drugs also produced an abuse-related facilitation of ICSS in the absence of the noxious stimulus. These results support further consideration of dopamine reuptake inhibitors as candidate analgesics, although abuse liability remains a concern.PerspectiveMonoamine reuptake inhibitors are used to treat depression and some forms of pain. This study examined effects of monoamine reuptake inhibitors in a preclinical assay of pain-related behavioral depression. The results support further consideration of dopamine reuptake inhibitors as candidate analgesics under selected circumstances, although abuse liability remains a concern.     

Assembly factors for the membrane arm of human complex I

Mitochondrial respiratory complex I is a product of both the nuclear and mitochondrial genomes. The integration of seven subunits encoded in mitochondrial DNA into the inner membrane, their association with 14 nuclear-encoded membrane subunits, the construction of the extrinsic arm from 23 additional nuclear-encoded proteins, iron–sulfur clusters, and flavin mononucleotide cofactor require the participation of assembly factors. Some are intrinsic to the complex, whereas others participate transiently. The suppression of the expression of the NDUFA11 subunit of complex I disrupted the assembly of the complex, and subcomplexes with masses of 550 and 815 kDa accumulated. Eight of the known extrinsic assembly factors plus a hydrophobic protein, C3orf1, were associated with the subcomplexes. The characteristics of C3orf1, of another assembly factor, TMEM126B, and of NDUFA11 suggest that they all participate in constructing the membrane arm of complex I.In mammalian mitochondria, complex I (NADH:ubiquinone oxidoreductase) provides the entry point for electrons from NADH into the electron transport chain. For each two electrons transferred from NADH to ubiquinone, four protons are ejected from the mitochondrial matrix, thereby contributing to the proton motive force across the inner membrane (1). The mammalian enzyme has 44 subunits, with a combined molecular mass of about 1 MDa, assembled into an L-shaped complex, with one arm embedded in the inner membrane and the other protruding into the matrix of the organelle (2–4). Seven hydrophobic subunits (ND1–ND6 and ND4L) of the membrane arm of NADH dehydrogenase (complex I) are encoded in mitochondrial DNA, and synthesized on mitochondrial ribosomes (5). The remainder are nuclear gene products, made in the cytoplasm and imported into mitochondria (6). The seven proteins encoded in mitochondrial DNA and seven nuclear-encoded subunits conserved in prokaryotic complexes I, constitute the catalytic cores of the membrane and peripheral arms, respectively (1). The latter contains binding sites for NADH, the primary electron acceptor FMN, and seven iron–sulfur clusters that link FMN and the terminal electron acceptor, ubiquinone, bound at the juncture between the peripheral and membrane arms (1, 7). The membrane arm has four antiporter-like domains that probably provide pathways for translocating protons (1). The remaining 30 so-called supernumerary subunits of mammalian complex I have no direct role in catalysis (2). Their functions are mostly unknown, but they may be involved in assembly, stability, or regulation of the complex (2, 8).There is no atomic structure for any eukaryotic complex I, but the arrangement and folds of the 14 core subunits in the mammalian enzyme are likely to be closely similar to those of bacterial orthologs, with the supernumerary subunits attached peripherally around the core (2, 9). The distribution of supernumerary subunits in bovine complex I is known from the subunit compositions of subcomplexes (3, 10, 11). Subcomplex Iλ is the peripheral arm, subcomplex Iα is a combination of Iλ and the adjacent region of the membrane arm, subcomplex Iβ is the distal region of the membrane arm, and subcomplex Iγ is another fragment from the membrane arm. The supernumerary subunits in a fungal enzyme from Yarrowia lipolytica seem to be distributed similarly (12, 13).The assembly of mitochondrial complex I involves building the 44 subunits emanating from two genomes into the two domains of the complex. The enzyme is put together from preassembled subcomplexes, and their subunit compositions have been characterized partially (14, 15). Extrinsic assembly factors of unknown function become associated with subcomplexes that accumulate when assembly and the activity of complex I are impaired by pathogenic mutations. Some assembly factor mutations also impair its activity (16). Other pathogenic mutations are found in all of the core subunits, and in 10 supernumerary subunits (NDUFA1, NDUFA2, NDUFA9, NDUFA10, NDUFA11, NDUFA12, NDUFB3, NDUFB9, NDUFS4, and NDUFS6) (17–26). Those in supernumerary subunits NDUFA2, NDUFA10, NDUFS4, and NDUFS6 are associated with a reduced level of intact complex and accumulation of subcomplexes, indicating a defect in assembly or stability of the complex, or both.As described here, suppression of the expression of the supernumerary membrane subunit NDUFA11 impairs assembly of complex I, leading to the accumulation of subcomplexes with estimated molecular masses of 550 and 815 kDa associated with eight known assembly factors, plus three other proteins, especially C3orf1. NDUFA11 has the characteristics of an intrinsic assembly factor for complex I and together with C3orf1 and another extrinsic assembly factor TMEM126B (27), they probably help to assemble the membrane arm of the complex.     

Detection of Human Monkeypox in the Republic of the Congo Following Intensive Community Education

Monkeypox is an acute viral infection with a clinical course resembling smallpox. It is endemic in northern and central Democratic Republic of the Congo (DRC), but it is reported only sporadically in neighboring Republic of the Congo (ROC). In October 2009, interethnic violence in northwestern DRC precipitated the movement of refugees across the Ubangi River into ROC. The influx of refugees into ROC heightened concerns about monkeypox in the area, because of the possibility that the virus could be imported, or that incidence could increase caused by food insecurity and over reliance on bush meat. As part of a broad-based campaign to improve health standards in refugee settlement areas, the United Nations International Children''s Emergency Fund (UNICEF) sponsored a program of intensive community education that included modules on monkeypox recognition and prevention. In the 6 months immediately following the outreach, 10 suspected cases of monkeypox were reported to health authorities. Laboratory testing confirmed monkeypox virus infection in two individuals, one of whom was part of a cluster of four suspected cases identified retrospectively. Anecdotes collected at the time of case reporting suggest that the outreach campaign contributed to detection of suspected cases of monkeypox.     

Synthesis, ligand binding, QSAR, and CoMFA study of 3 beta-(p-substituted phenyl)tropane-2 beta-carboxylic acid methyl esters

A series of 3 beta-(p-substituted phenyl)tropane-2 beta-carboxylic acid methyl esters (2) were synthesized and found to possess high affinity for the cocaine binding site in rat striatum. The p-chloro (2c) and p-iodo (2n) compounds, which were the most potent analogues prepared, were found to be 85 and 78 times more potent than (-)-cocaine. The p-bromo (2m) and p-methyl (2d) were also 56 and 60 times more potent than cocaine. QSAR and CoMFA studies were conducted to correlate binding affinity of the cocaine analogues with their structural features. Whereas the QSAR study gave relatively low correlations, the CoMFA study gave a correlation with high predictive value.     

Event-free survival following nonemergency myocardial revascularization during hypothermic fibrillatory arrest

To better assess the late results of hypothermic fibrillatory arrest during myocardial revascularization, 1,000 consecutive patients having nonemergency coronary artery grafting during hypothermic fibrillatory arrest from August, 1979, through November, 1984, were studied to determine event-free survival. Hospital mortality was 0.4% and the rate of perioperative myocardial infarction, 1.8%. At follow-up (mean, 30.5 months), 11 patients had sustained an interval nonfatal myocardial infarction, 3 had had percutaneous angioplasty, and 2 had undergone reoperative revascularization. Actuarial survival at five years was 91.6 +/- 2.0%. Actuarial event-free rates at five years were 97.7 +/- 0.8% for myocardial infarction, 99.4 +/- 0.4% for percutaneous transluminal coronary angioplasty, 99.5 +/- 0.4% for reoperative revascularization, and 88.6 +/- 2.2% for all combined morbidity and mortality. Among the 122 patients meeting randomizable admission criteria of the Coronary Artery Surgery Study, there were no operative deaths and no perioperative infarctions, and the actuarial survival was 97.5% at five years. Hypothermic fibrillatory arrest is effective for myocardial preservation during coronary revascularization and when combined with complete revascularization, yields excellent event-free survival.     

Parathyroid imaging with thallium-201 subtraction scintigraphy: a report of 33 cases

Thallium-201 subtraction scintigraphy has been used in Wellington Hospital for preoperative localisation of parathyroid adenomas since 1984. The technique wa audited by comparing the scan reports with the outcome at operation in 33 patients, 30 of whom underwent a primary exploration. In our unselected patients we found the technique to have poor sensitivity (45.4%) with a high false positive rate (21%). There was no difference in the mean size of the glands correctly identified compared to those that were missed. Our experience has led us to believe that thallium-201 subtraction scintigraphy has not lived up to its early promise and is not a useful technique for routine preoperative localisation of parathyroid adenomas.