Phosphatidic acid-mediated mitogenic activation of mTOR signaling

The mammalian target of rapamycin (mTOR) governs cell growth and proliferation by mediating the mitogen- and nutrient-dependent signal transduction that regulates messenger RNA translation. We identified phosphatidic acid (PA) as a critical component of mTOR signaling. In our study, mitogenic stimulation of mammalian cells led to a phospholipase D-dependent accumulation of cellular PA, which was required for activation of mTOR downstream effectors. PA directly interacted with the domain in mTOR that is targeted by rapamycin, and this interaction was positively correlated with mTOR's ability to activate downstream effectors. The involvement of PA in mTOR signaling reveals an important function of this lipid in signal transduction and protein synthesis, as well as a direct link between mTOR and mitogens. Furthermore, these studies suggest a potential mechanism for the in vivo actions of the immunosuppressant rapamycin.

Generation of destabilized green fluorescent protein as a transcription reporter

The green fluorescent protein (GFP) is a widely used reporter in gene expression and protein localization studies. GFP is a stable protein; this property allows its accumulation and easy detection in cells. However, this stability also limits its application in studies that require rapid reporter turnover. We created a destabilized GFP for use in such studies by fusing amino acids 422-461 of the degradation domain of mouse ornithine decarboxylase (MODC) to the C-terminal end of an enhanced variant of GFP (EGFP). The fusion protein, unlike EGFP, was unstable in the presence of cycloheximide and had a fluorescence half-life of 2 h. Western blot analysis indicated that the fluorescence decay of EGFP-MODC-(422-461) was correlated with degradation of the fusion protein. We mutated key amino acids in the PEST sequence of EGFP-MODC-(422-461) and identified several mutants with variable half-lives. The suitability of destabilized EGFP as a transcription reporter was tested by linking it to NFkappaB binding sequences and monitoring tumor necrosis factor alpha-mediated NFkappaB activation. We obtained time course induction and dose response kinetics similar to secreted alkaline phosphatase obtained in transfected cells. This result did not occur when unmodified EGFP was used as the reporter. Because of its autofluorescence, destabilized EGFP can be used to directly correlate gene induction with biochemical change, such as NFkappaB translocation to the nucleus.

Mice lacking dopamine D4 receptors are supersensitive to ethanol, cocaine, and methamphetamine

The human dopamine D4 receptor (D4R) has received considerable attention because of its high affinity for the atypical antipsychotic clozapine and the unusually polymorphic nature of its gene. To clarify the in vivo role of the D4R, we produced and analyzed mutant mice (D4R-/-) lacking this protein. Although less active in open field tests, D4R-/- mice outperformed wild-type mice on the rotarod and displayed locomotor supersensitivity to ethanol, cocaine, and methamphetamine. Biochemical analyses revealed that dopamine synthesis and its conversion to DOPAC were elevated in the dorsal striatum from D4R-/- mice. Based on these findings, we propose that the D4R modulates normal, coordinated and drug-stimulated motor behaviors as well as the activity of nigrostriatal dopamine neurons.

Adipokines and cytokines in non-alcoholic fatty liver disease

BACKGROUND

Several adipocytokines have been implicated in the pathogenesis non-alcoholic fatty liver disease (NAFLD).

AIM

To assess adipocytokines in NAFLD patients and controls.

METHODS

A total of 95 patients (26 non-alcoholic steatohepatitis (NASH), 19 simple steatosis (SS), 38 obese controls and 12 non-obese controls) were included. Fasting serum insulin, glucose, visfatin, resistin, adiponectin, tumour necrosis factor-alpha (TNF-alpha), interleukin-8 (IL-8) and IL-6 were determined. Univariate and multivariate analyses were used to compare groups and determine associations.

RESULTS

Serum TNF-alpha and IL-8 were higher in NAFLD patients when compared with both obese and non-obese controls. Analysis involving all patients revealed a significant correlation between serum TNF-alpha and IL-8 (P < 6.319e-08), and between IL-6 and IL-8 (P < 5.271e-15). Homeostatic model assessment scores negatively correlated with adiponectin in NAFLD (P < 0.0032). Serum visfatin was higher in all three obese groups than in non-obese controls (P < 0.02, P < 0.002 and P < 0.008). Visfatin in NASH patients was lower than SS and obese controls. Although TNF-alpha was associated with NAFLD (P < 0.02), it was interdependent on visfatin. In comparison to SS, four factors were independently associated with NASH: age, alanine aminotransferase, IL-8 and adiponectin (P < 0.05). Multivariate analysis indicated that TNF-alpha was the only independent predictor of fibrosis in NASH (P < 0.0004).

CONCLUSION

These findings support a complex interaction between adipocytokines and the pathogenesis of NAFLD.

A 10-kDa structural protein of porcine reproductive and respiratory syndrome virus encoded by ORF2b

The major structural proteins of porcine reproductive and respiratory syndrome virus (PRRSV) are derived from ORFs 5, 6, and 7. Western blots of sucrose gradient-purified virions and PRRSV-infected MARC-145 cells, probed with immune pig serum, showed the presence of an additional 10-kDa protein. Nucleotide sequence analysis of North American PRRSV isolate SDSU-23983 revealed a small ORF within ORF2, named ORF2b, which, when translated, produced a 73-amino-acid nonglycosylated protein. Recombinant 2b protein expressed by a baculovirus clone, AcVR2, comigrated with the 10-kDa virus-associated protein. The loss of 10-kDa protein immunoreactivity after absorption of immune sera with lysates from AcVR2-infected insect cells demonstrated that the 2b and 10-kDa proteins are immunologically similar. Immunoblots were also used for the detection of anti-2b activity in serum samples from experimentally infected adult pigs. Antibodies against PRRSV were apparent by 14 days postinfection, followed by anti-2b activity and serum neutralizing activity. The putative ORF2b start codon is only 6 nucleotides downstream of the adenine of the ORF2a start codon. The expression of ORF2a and 2b as enhanced green fluorescent fusion proteins showed that both proteins were translated; however, the ORF2b was preferentially expressed. These results suggest that the 2b protein is virion associated and the principal product of ORF2.

Activated Notch2 signaling inhibits differentiation of cerebellar granule neuron precursors by maintaining proliferation

In the developing cerebellar cortex, granule neuron precursors (GNPs) proliferate and commence differentiation in a superficial zone, the external granule layer (EGL). The molecular basis of the transition from proliferating precursors to immature differentiating neurons remains unknown. Notch signaling is an evolutionarily conserved pathway regulating the differentiation of precursor cells of many lineages. Notch2 is specifically expressed in proliferating GNPs in the EGL. Treatment of GNPs with soluble Notch ligand Jagged1, or overexpression of activated Notch2 or its downstream target HES1, maintains precursor proliferation. The addition of GNP mitogens Jagged1 or Sonic Hedgehog (Shh) upregulates the expression of HES1, suggesting a role for HES1 in maintaining precursor proliferation.

Association between a GABRB3 polymorphism and autism

Autistic disorder (OMIM 209850) is a disease with a significant genetic component of a complex nature.(1) Cytogenetic abnormalities in the Prader-Willi/Angelman syndrome critical region (15q11-13) have been described in several individuals with autism.(1) For this reason, markers across this region have been screened for evidence of linkage and association, and a marker (155CA-2) in the gamma-aminobutyric acid type-A receptor beta3 subunit gene (GABRB3) has been associated in one study(2) but not others.(3-5) We completed an association analysis with 155CA-2 using the transmission disequilibrium test (TDT) in a set of 80 autism families (59 multiplex and 21 trios). We also used four additional markers (69CA, 155CA-1, 85CA, and A55CA-1) localized within 150 kb of 155CA-2. The use of multi-allelic TDT (MTDT) (P < 0.002), as well as the TDT (P < 0.004), demonstrated an association between autistic disorder and 155CA-2 in these families. Meiotic segregation distortion could be excluded as a possible cause for these results since no disequilibrium was observed in unaffected siblings. These findings support a role for genetic variants within the GABA receptor gene complex in 15q11-13 in autistic disorder.

Natural animal coloration can Be determined by a nonfluorescent green fluorescent protein homolog

It is generally accepted that the colors displayed by living organisms are determined by low molecular weight pigments or chromoproteins that require a prosthetic group. The exception to this rule is green fluorescent protein (GFP) from Aequorea victoria that forms a fluorophore by self-catalyzed protein backbone modification. Here we found a naturally nonfluorescent homolog of GFP to determine strong purple coloration of tentacles in the sea anemone Anemonia sulcata. Under certain conditions, this novel chromoprotein produces a trace amount of red fluorescence (emission lambda(max) = 595 nm). The fluorescence demonstrates unique behavior: its intensity increases in the presence of green light but is inhibited by blue light. The quantum yield of fluorescence can be enhanced dramatically by single amino acid replacement, which probably restores the ancestral fluorescent state of the protein. Other fluorescent variants of the novel protein have emission peaks that are red-shifted up to 610 nm. They demonstrate that long wavelength fluorescence is attainable in GFP-like fluorescent proteins.

ATR/ATM-mediated phosphorylation of human Rad17 is required for genotoxic stress responses

Genotoxic stress triggers the activation of checkpoints that delay cell-cycle progression to allow for DNA repair. Studies in fission yeast implicate members of the Rad family of checkpoint proteins, which includes Rad17, Rad1, Rad9 and Hus1, as key early-response elements during the activation of both the DNA damage and replication checkpoints. Here we demonstrate a direct regulatory linkage between the human Rad17 homologue (hRad17) and the checkpoint kinases, ATM and ATR. Treatment of human cells with genotoxic agents induced ATM/ATR-dependent phosphorylation of hRad17 at Ser 635 and Ser 645. Overexpression of a hRad17 mutant (hRad17AA) bearing Ala substitutions at both phosphorylation sites abrogated the DNA-damage-induced G2 checkpoint, and sensitized human fibroblasts to genotoxic stress. In contrast to wild-type hRad17, the hRad17AA mutant showed no ionizing-radiation-inducible association with hRad1, a component of the hRad1-hRad9-hHus1 checkpoint complex. These findings demonstrate that ATR/ATM-dependent phosphorylation of hRad17 is a critical early event during checkpoint signalling in DNA-damaged cells.

Bidirectional modulatory effect of orphanin FQ on morphine-induced analgesia: antagonism in brain and potentiation in spinal cord of the rat

1. The present study was designed to investigate further the effects of the newly discovered orphanin FQ (OFQ)-the endogenous ligand for the orphan opioid receptor (called, e.g., ORL, and LC132)-on pain modulation in the rat. We used the tail-flick assay as a nociceptive index. 2. When injected into a cerebral ventricle, OFQ (4 fmol-10 nmol) has no effect on basal tail-flick latency by itself at any dose, but dose-dependently antagonizes systemic morphine analgesia (400 fmol 50 nmol). 3. Injected intrathecally, OFQ (3 and 10 nmol) displayed an analgesic effect without producing motor dysfunction, and potentiated morphine analgesia (1 and 10 nmol). 4. The anti-opioid effect of OFQ in rat brain and the high level of expression of LC132/ORL, receptor in the locus coeruleus indicated a possible role of OFQ in the precipitation of opiate withdrawal symptoms. However, no such precipitation was observed by OFQ in morphine-dependent rats.

Expression of synaptobrevin II, cellubrevin and syntaxin but not SNAP-25 in cultured astrocytes

Astrocytes, a sub-type of glial cell in the central nervous system, can release the excitatory transmitters glutamate and aspartate in response to elevated levels of internal calcium. To investigate potential release mechanisms that may be present in these cells we have determined whether protein components of the neuronal secretory apparatus are expressed in astrocytes. Western blots, immunocytochemistry and RT PCR demonstrate that astrocytes express cellubrevin, synaptobrevin II and syntaxin, proteins known to form a macromolecular fusion complex. However, SNAP-25 which is another neuronal protein of the fusion complex, was not detected. Astrocyte cellubrevin and synaptobrevin II were also shown to be sensitive to the proteolytic activity of tetanus toxin. Together these data indicate that astrocytes express some proteins that are known to form a fusion complex indicating that regulated exocytosis might mediate calcium-regulated transmitter release from these cells.

Hsp90 regulates androgen receptor hormone binding affinity in vivo

The regulation of human androgen receptor (AR) by the molecular chaperone Hsp90 was investigated using the yeast Saccharomyces cerevisiae as a model system. These studies were performed in strains expressing a conditional temperature-sensitive mutant allele of the hsp82 gene, which encodes Hsp90 protein. At the restrictive temperature in the mutant, there is a decrease in hormone-dependent transactivation by the AR, although steady state levels of AR protein are unchanged. Quantitative hormone binding studies at the permissive temperature revealed the presence of both high affinity and low affinity hormone binding states. At the restrictive temperature in the hsp82 mutant, the high affinity state was abolished, and only the low affinity state was observed. The change in hormone binding affinity was further investigated by a competition assay with the anti-androgen hydroxyflutamide. Under permissive conditions, hydroxyflutamide competes poorly for the synthetic androgen R1881, but under restrictive conditions in the hsp82 mutant strain, hydroxyflutamide was shown to be a potent competitive inhibitor. Our findings indicate that Hsp90 participates in the activation process by maintaining apoAR in a high affinity ligand binding conformation which is important for efficient response to hormone.

Expression of early nodulin genes in alfalfa mycorrhizae indicates that signal transduction pathways used in forming arbuscular mycorrhizae and Rhizobium-induced nodules may be conserved

Transcripts for two genes expressed early in alfalfa nodule development (MsENOD40 and MsENOD2) are found in mycorrhizal roots, but not in noncolonized roots or in roots infected with the fungal pathogen Rhizoctonia solani. These same two early nodulin genes are expressed in uninoculated roots upon application of the cytokinin 6-benzylaminopurine. Correlated with the expression of the two early nodulin genes, we found that mycorrhizal roots contain higher levels of trans-zeatin riboside than nonmycorrhizal roots. These data suggest that there may be conservation of signal transduction pathways between the two symbioses-nitrogen-fixing nodules and phosphate-acquiring mycorrhizae.

Hierarchy in the expression of the locus of enterocyte effacement genes of enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) elicit changes in host cell morphology and cause actin rearrangement, a phenotype that has commonly been referred to as attaching/effacing (AE) lesions. The ability of EPEC to induce AE lesions is dependent upon a type III protein secretion/translocation system that is encoded by genes clustered in a 35.6 kb DNA segment, named the locus of enterocyte effacement (LEE). We used transcriptional fusions between the green fluorescent protein (gfp) reporter gene and LEE genes rorf2, orf3, orf5, escJ, escV and eae, together with immunoblot analysis with antibodies against Tir, intimin, EspB and EspF, to analyse the genetic regulation of the LEE. The expression of all these LEE genes was strictly dependent upon the presence of a functional integration host factor (IHF). IHF binds specifically upstream from the ler (orf1) promoter and appears to activate expression of ler, orf3, orf5 and rorf2 directly. The ler-encoded Ler protein was involved in activating the expression of escJ, escV, tir, eae, espB and espF. Expression of both IHF and Ler was needed to elicit actin rearrangement associated with AE lesions. In conclusion, IHF directly activates the expression of the ler and rorf2 transcriptional units, and Ler in turn mediates the expression of the other LEE genes.

Conformation of beta-Lactoglobulin Studied by FTIR: Effect of pH, Temperature, and Adsorption to the Oil-Water Interface

The structure of mixed A and B genetic variants of beta-lactoglobulin (beta-lg) in its native and denatured states has been studied by FTIR. The denaturation was achieved through either heating at various temperatures at pH 6 and 7 or by adsorption to the surfaces of oil droplets in oil-in-water emulsions. The time dependence of the structural changes of the adsorbed protein was also studied. It was found that beta-lg was more resistant to heat denaturation at pH 6 than at pH 7. Conversely, the adsorbed protein appeared to be more deformable at pH 6 than at pH 7. Although heating at lower temperatures (70 and 80 degreesC) for a longer time causes extensive denaturation, as does heating at higher temperature (90 degreesC) for a short time, the structure of the denatured protein was different in the two cases. When denatured at lower temperatures, more beta-structure remained as indicated by the presence of bands around 1632 cm-1 in the IR spectrum, whereas evidence for extensive intermolecular beta-structure was found on the sample heated at higher temperature, indicated by the strong adsorption band at 1684 cm-1. This explains that although gelation of the protein can be achieved in both cases, the gel structure may be different. Denaturation of beta-lg during heat treatment and upon adsorption appears to occur via similar intermediate structures, which begin with the loss of beta-sheet structure, but whereas heat denaturation generates more intermolecular beta-sheet and a small amount of unordered structure, adsorption of the protein to the oil-water interface induces a larger amount of unordered structure and a small amount of intermolecular beta-sheet. The denaturation of beta-lg on the interface is a much slower process compared to heat denaturation; even though some changes are detectable shortly after the adsorption of the protein, more extensive denaturation occurs during storage of the emulsions for 72 h. Copyright 1997 Academic Press.

SBA1 encodes a yeast hsp90 cochaperone that is homologous to vertebrate p23 proteins

The Saccharomyces cerevisiae SBA1 gene was cloned by PCR amplification from yeast genomic DNA following its identification as encoding an ortholog of human p23, an Hsp90 cochaperone. The SBA1 gene product is constitutively expressed and nonessential, although a disruption mutant grew more slowly than the wild type at both 18 and 37 degreesC. A double deletion of SBA1 and STI1, encoding an Hsp90 cochaperone, displayed synthetic growth defects. Affinity isolation of histidine-tagged Sba1p (Sba1(His6)) after expression in yeast led to coisolation of Hsp90 and the cyclophilin homolog Cpr6. Using an in vitro assembly assay, purified Sba1(His6) bound to Hsp90 only in the presence of adenosine 5'-O-(3-thiotriphosphate) or adenyl-imidodiphosphate. Furthermore, interaction between purified Sba1(His6) and Hsp90 in yeast extracts was inhibited by the benzoquinoid ansamycins geldanamycin and macbecin. The in vitro assay was also used to identify residues in Hsp90 that are important for complex formation with Sba1(His6), and residues in both the N-terminal nucleotide binding domain and C-terminal half were characterized. In vivo analysis of known Hsp90 substrate proteins revealed that Sba1 loss of function had only a mild effect on the activity of the tyrosine kinase v-Src and steroid hormone receptors.

Avian host and mosquito (Diptera: Culicidae) vector competence determine the efficiency of West Nile and St. Louis encephalitis virus transmission

The ability of the invading NY99 strain of West Nile virus (WNV) to elicit an elevated viremia response in California passerine birds was critical for the effective infection of Culex mosquitoes. Of the bird species tested, Western scrub jays, Aphelocoma coerulescens, produced the highest viremia response, followed by house finches, Carpodacus mexicanus, and house sparrows, Passer domesticus. Most likely, few mourning, Zenaidura macroura, or common ground, Columbina passerine, doves and no California quail, Callipepla californica, or chickens would infect blood-feeding Culex mosquitoes. All Western scrub jays and most house finches succumbed to infection. All avian hosts produced a lower viremia response and survived after infection with an endemic strain of St. Louis encephalitis virus. Culex species varied in their susceptibility to infection with both viruses, with Culex stigmatosoma Dyar generally most susceptible, followed by Culex tarsalis Coquillett, and then Culex p. quinquefasciatus Say. Populations within Culex species varied markedly in their susceptibility, perhaps contributing to the focality of WNV amplification. Transmitting female Cx. tarsalis expectorated from six to 3,777 plaque-forming units (PFU) of WNV during transmission trials, thereby exposing avian hosts to a wide range of infectious doses. Highly susceptible house finches and moderately susceptible mourning doves were infected by subcutaneous inoculation with decreasing concentrations of WNV ranging from 15,800 to <0.3 PFU. All birds became infected and produced comparable peak viremias on days 2-3 postinoculation; however, the rise in viremia titer and onset of the acute phase of infection occurred earliest in birds inoculated with the highest doses. WNV virulence in birds seemed critical in establishing elevated viremias necessary to efficiently infect blood feeding Culex mosquitoes.

Predicting DNA-binding proteins: approached from Chou's pseudo amino acid composition and other specific sequence features

DNA-binding proteins play a pivotal role in gene regulation. It is vitally important to develop an automated and efficient method for timely identification of novel DNA-binding proteins. In this study, we proposed a method based on alone the primary sequences of proteins to predict the DNA-binding proteins. DNA-binding proteins were encoded by autocross-covariance transform, pseudo-amino acid composition, dipeptide composition, respectively and also the different combinations of the three encoded methods; further, these feature matrices were applied to support vector machine classifiers to predict the DNA-binding proteins. All modules were trained and validated by the jackknife cross-validation test. Through comparing the performance of these substituted modules, the best result was obtained from pseudo-amino acid composition with the overall accuracy of 96.6% and the sensitivity of 90.7%. The results suggest that it can efficiently predict the novel DNA-binding proteins only using the primary sequences.

The FKBP12-rapamycin-binding domain is required for FKBP12-rapamycin-associated protein kinase activity and G1 progression

The immunosuppressant rapamycin, in complex with its cellular receptor FKBP12, targets the cellular protein FKBP12-rapamycin-associated protein/mammalian target of rapamycin/rapamycin and FKBP12 target 1 (FRAP/mTOR/RAFT1) and inhibits/delays G1 cell cycle progression in mammalian cells. As a member of the novel phosphatidylinositol kinase-related kinase family, FRAP's kinase activity is essential for its signaling function. The FKBP12-rapamycin binding (FRB) domain in FRAP is also speculated to play an important role in FRAP function and signaling. However, the biochemical and physiological functions of FRB, as well as the mechanism for rapamycin inhibition, have been unclear. The present study focuses on investigation of FRB's role and the functional relationship between FRB domain and kinase domain in FRAP. Microinjection of purified FRB protein into human osteosarcoma MG63 cells results in a drastic blockage of the G1 to S cell cycle progression; such a dominant negative effect is reversed by a point mutation (Trp2027 --> Phe). The same mutation also abolishes kinase activity of FRAP without affecting ATP binding, and truncation studies suggest that upstream sequences including FRB are required for kinase activity in vitro. Given these data, we propose a model for FRAP function, in which the FRB domain is required for activation of the kinase domain, possibly through the interaction with an upstream activator. In addition, our observations provide direct evidence linking FRAP function to G1 cell cycle progression.

Human alveolar macrophages present antigen ineffectively due to defective expression of B7 costimulatory cell surface molecules

Alveolar macrophages, resident phagocytic cells in the lung that derive from peripheral blood monocytes, are paradoxically ineffective in presenting antigen to T cells. We found that antigen presentation by alveolar macrophages could be restored by the addition of anti-CD28 mAb to cultures of T cells and macrophages, indicating that costimulation by alveolar macrophages via the CD28 pathway was defective. In addition, we found that alveolar macrophages activated with IFN-gamma failed to express B7-1 or B7-2 antigens, which normally ligate CD28 on T cells and provide a costimulatory signal required for the activation of T cells. These observations are the first to demonstrate the inability of a "professional" antigen-presenting cell type to effectively express the costimulatory molecules B7-1 and B7-2. Inasmuch as immune reactions within the lung are inevitably associated with inflammatory injury to pulmonary tissue, these observations suggest that reduced expression of B7-1 and B7-2 by alveolar macrophages may be advantageous, as a critical mechanism involved in the induction of peripheral tolerance to the abundance of antigens to which mucosal tissues are continuously exposed.

Detection of U.S., Lelystad, and European-like porcine reproductive and respiratory syndrome viruses and relative quantitation in boar semen and serum samples by real-time PCR

Transmission of porcine reproductive and respiratory syndrome virus (PRRSV) via boar semen has been documented. Since semen is widely disseminated for artificial insemination and the virus can cause significant health and economic consequences, it is essential to have well-validated, rapid diagnostic techniques to detect and quantitate the virus for diagnostic and research purposes. Previously, boar semen was tested by a nested PCR (nPCR) assay which was compared to the "gold standard" swine bioassay. A correlation of 94% was observed, indicating that, most of the time, PCR detected infectious virus. Subsequently, a real-time PCR targeting the 3' untranslated region of the PRRSV genome was compared with nPCR by testing 413 serum and semen samples from PRRSV-inoculated and control boars. There was 95% agreement between the results of the two tests, with the majority of samples with discordant results containing virus at the lower range of detection by the assays. The virus in all samples was quantitated by using a standard curve obtained by serial dilution of an in vitro transcript. By using the in vitro transcript, the lower limit of sensitivity was observed to be approximately 33 copies/ml. Reactivity with a panel of more than 100 PRRSV isolates from various geographical regions in the United States was also documented. No reactivity with nine nonrelated swine viruses was noted. A real-time PCR was also developed for the detection of the European Lelystad virus and the European-like PRRSV now found in the United States. In six of six PRRSV-inoculated boars, peak levels of viremia occurred at 5 days postinoculation (DPI) and were most consistently detectable throughout 22 DPI. In five of six boars, PRRSV was shed in semen for 0 to 2 days during the first 10 DPI; however, one of six boars shed the virus in semen through 32 DPI. Therefore, in general, the concentration and duration of PRRSV shedding in semen did not correlate with the quantity or duration of virus in serum. These differences warrant further studies into the factors that prevent viral replication in the reproductive tract.

Greater movement-related cortical potential during human eccentric versus concentric muscle contractions

Despite abundant evidence that different nervous system control strategies may exist for human concentric and eccentric muscle contractions, no data are available to indicate that the brain signal differs for eccentric versus concentric muscle actions. The purpose of this study was to evaluate electroencephalography (EEG)-derived movement-related cortical potential (MRCP) and to determine whether the level of MRCP-measured cortical activation differs between the two types of muscle activities. Eight healthy subjects performed 50 voluntary eccentric and 50 voluntary concentric elbow flexor contractions against a load equal to 10% body weight. Surface EEG signals from four scalp locations overlying sensorimotor-related cortical areas in the frontal and parietal lobes were measured along with kinetic and kinematic information from the muscle and joint. MRCP was derived from the EEG signals of the eccentric and concentric muscle contractions. Although the elbow flexor muscle activation (EMG) was lower during eccentric than concentric actions, the amplitude of two major MRCP components-one related to movement planning and execution and the other associated with feedback signals from the peripheral systems-was significantly greater for eccentric than for concentric actions. The MRCP onset time for the eccentric task occurred earlier than that for the concentric task. The greater cortical signal for eccentric muscle actions suggests that the brain probably plans and programs eccentric movements differently from concentric muscle tasks.

Meta-analysis of randomized clinical trials on safety and efficacy of biliary drainage before surgery for obstructive jaundice

BACKGROUND

This meta-analysis aimed to investigate whether preoperative biliary drainage (PBD) is beneficial to patients with obstructive jaundice.

METHODS

Data from randomized clinical trials related to safety and effectiveness of PBD versus no PBD were extracted by two independent reviewers. Risk ratios, rate ratios or mean differences were calculated with 95 per cent confidence intervals (c.i.), based on intention-to-treat analysis, whenever possible.

RESULTS

Six trials (four using percutaneous transhepatic biliary drainage and two using endoscopic sphincterotomy) including 520 patients with malignant or benign obstructive jaundice comparing PBD (265 patients) with no PBD (255) were included in this review. All trials had a high risk of bias. There was no significant difference in mortality (risk ratio 1.12, 95 per cent c.i. 0.73 to 1.71; P = 0.60) between the two groups. Overall serious morbidity (grade III or IV, Clavien-Dindo classification) was higher in the PBD group (599 complications per 1000 patients) than in the direct surgery group (361 complications per 1000 patients) (rate ratio 1.66, 95 per cent c.i. 1.28 to 2.16; P < 0.001). Quality of life was not reported in any of the trials. There was no significant difference in length of hospital stay between the two groups: mean difference 4.87 (95 per cent c.i. -1.28 to 11.02) days (P = 0.12).

CONCLUSION

PBD in patients undergoing surgery for obstructive jaundice is associated with similar mortality but increased serious morbidity compared with no PBD. Therefore, PBD should not be used routinely.