The sequence of the human genome

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.

Observation of Gravitational Waves from a Binary Black Hole Merger

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

Folate deficiency causes uracil misincorporation into human DNA and chromosome breakage: implications for cancer and neuronal damage

Folate deficiency causes massive incorporation of uracil into human DNA (4 million per cell) and chromosome breaks. The likely mechanism is the deficient methylation of dUMP to dTMP and subsequent incorporation of uracil into DNA by DNA polymerase. During repair of uracil in DNA, transient nicks are formed; two opposing nicks could lead to chromosome breaks. Both high DNA uracil levels and elevated micronucleus frequency (a measure of chromosome breaks) are reversed by folate administration. A significant proportion of the U.S. population has low folate levels, in the range associated with elevated uracil misincorporation and chromosome breaks. Such breaks could contribute to the increased risk of cancer and cognitive defects associated with folate deficiency in humans.

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0×10^{4}  years. We infer the component masses of the binary to be between 0.86 and 2.26  M_{⊙}, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17-1.60  M_{⊙}, with the total mass of the system 2.74_{-0.01}^{+0.04}M_{⊙}. The source was localized within a sky region of 28  deg^{2} (90% probability) and had a luminosity distance of 40_{-14}^{+8}  Mpc, the closest and most precisely localized gravitational-wave signal yet. The association with the γ-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ-ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.

Role of poly(ADP-ribose) polymerase (PARP) cleavage in apoptosis. Caspase 3-resistant PARP mutant increases rates of apoptosis in transfected cells

An early transient burst of poly(ADP-ribosyl)ation of nuclear proteins was recently shown to be required for apoptosis to proceed in various cell lines (Simbulan-Rosenthal, C., Rosenthal, D., Iyer, S., Boulares, H., and Smulson, M. (1998) J. Biol. Chem. 273, 13703-13712) followed by cleavage of poly(ADP-ribose) polymerase (PARP), catalyzed by caspase-3. This inactivation of PARP has been proposed to prevent depletion of NAD (a PARP substrate) and ATP, which are thought to be required for later events in apoptosis. The role of PARP cleavage in apoptosis has now been investigated in human osteosarcoma cells and PARP -/- fibroblasts stably transfected with a vector encoding a caspase-3-resistant PARP mutant. Expression of this mutant PARP increased the rate of staurosporine and tumor necrosis factor-alpha-induced apoptosis, at least in part by reducing the time interval required for the onset of caspase-3 activation and internucleosomal DNA fragmentation, as well as the generation of 50-kilobase pair DNA breaks, thought to be associated with early chromatin unfolding. Overexpression of wild-type PARP in osteosarcoma cells also accelerated the apoptotic process, although not to the same extent as that apparent in cells expressing the mutant PARP. These effects of the mutant and wild-type enzymes might be due to the early and transient poly(ADP-ribose) synthesis in response to DNA breaks, and the accompanying depletion of NAD apparent in the transfected cells. The accelerated NAD depletion did not seem to interfere with the later stages of apoptosis. These results indicate that PARP activation and subsequent cleavage have active and complex roles in apoptosis.

NMDA antagonist neurotoxicity: mechanism and prevention

Antagonists of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor, including phencyclidine (PCP) and ketamine, protect against brain damage in neurological disorders such as stroke. However, these agents have psychotomimetic properties in humans and morphologically damage neurons in the cerebral cortex of rats. It is now shown that the morphological damage can be prevented by certain anticholinergic drugs or by diazepam and barbiturates, which act at the gamma-aminobutyric acid (GABA) receptor-channel complex and are known to suppress the psychotomimetic symptoms caused by ketamine. Thus, it may be possible to prevent the unwanted side effects of NMDA antagonists, thereby enhancing their utility as neuroprotective drugs.

Identification of a natural soluble form of the vascular endothelial growth factor receptor, FLT-1, and its heterodimerization with KDR

A soluble form of the vascular endothelial growth factor (VEGF) receptor FLT-1 was identified in conditioned culture medium of human umbilical vein endothelial cells. The endogenous soluble FLT-1 (sFLT-1) receptor is chromatographically and immunologically similar to recombinant human sFLT-1 and binds [125I]VEGF with a comparable high affinity. Human sFLT-1 is shown to form a VEGF-stabilized complex with the extracellular domain of KDR in vitro, suggesting that not only full-length receptors are capable of forming ligand-induced heterodimeric complexes but also sFLT-1 can form a dominant negative complex with the mitogenically competent full-length KDR receptor.

Structures of the native and swollen forms of cowpea chlorotic mottle virus determined by X-ray crystallography and cryo-electron microscopy

BACKGROUND

RNA-protein interactions stabilize many viruses and also the nucleoprotein cores of enveloped animal viruses (e.g. retroviruses). The nucleoprotein particles are frequently pleomorphic and generally unstable due to the lack of strong protein-protein interactions in their capsids. Principles governing their structures are unknown because crystals of such nucleoprotein particles that diffract to high resolution have not previously been produced. Cowpea chlorotic mottle virions (CCMV) are typical of particles stabilized by RNA-protein interactions and it has been found that crystals that diffract beyond 4.5 A resolution are difficult to grow. However, we report here the purification of CCMV with an exceptionally mild procedure and the growth of crystals that diffract X-rays to 3.2 A resolution.

RESULTS

The 3.2 A X-ray structure of native CCMV, an icosahedral (T = 3) RNA plant virus, shows novel quaternary structure interactions based on interwoven carboxyterminal polypeptides that extend from canonical capsid beta-barrel subunits. Additional particle stability is provided by intercapsomere contacts between metal ion mediated carboxyl cages and by protein interactions with regions of ordered RNA. The structure of a metal-free, swollen form of the virus was determined by cryo-electron microscopy and image reconstruction. Modeling of this structure with the X-ray coordinates of the native subunits shows that the 29 A radial expansion is due to electrostatic repulsion at the carboxyl cages and is stopped short of complete disassembly by preservation of interwoven carboxyl termini and protein-RNA contacts.

CONCLUSIONS

The CCMV capsid displays quaternary structural interactions that are unique compared with previously determined RNA virus structures. The loosely coupled hexamer and pentamer morphological units readily explain their versatile reassembly properties and the pH and metal ion dependent polymorphism observed in the virions. Association of capsomeres through inter-penetrating carboxy-terminal portions of the subunit polypeptides has been previously described only for the DNA tumor viruses, SV40 and polyoma.

Highly pathogenic H5N1 influenza virus infection in migratory birds

H5N1 avian influenza virus (AIV) has emerged as a pathogenic entity for a variety of species, including humans, in recent years. Here we report an outbreak among migratory birds on Lake Qinghaihu, China, in May and June 2005, in which more than a thousand birds were affected. Pancreatic necrosis and abnormal neurological symptoms were the major clinical features. Sequencing of the complete genomes of four H5N1 AIV strains revealed them to be reassortants related to a peregrine falcon isolate from Hong Kong and to have known highly pathogenic characteristics. Experimental animal infections reproduced typical highly pathogenic AIV infection symptoms and pathology.

Large-Scale Synthesis of Aligned Carbon Nanotubes

Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica. Scanning electron microscope images show that the nanotubes are approximately perpendicular to the surface of the silica and form an aligned array of isolated tubes with spacings between the tubes of about 100 nanometers. The tubes are up to about 50 micrometers long and well graphitized. The growth direction of the nanotubes may be controlled by the pores from which the nanotubes grow.

Multiplex PCR for detection of genes for Staphylococcus aureus enterotoxins, exfoliative toxins, toxic shock syndrome toxin 1, and methicillin resistance

A multiplex PCR assay for detection of genes for staphylococcal enterotoxins A to E (entA, entB, entC, entD, and entE), toxic shock syndrome toxin 1 (tst), exfoliative toxins A and B (etaA and etaB), and intrinsic methicillin resistance (mecA) was developed. Detection of femA was used as an internal positive control. The multiplex PCR assay combined the primers for sea to see and femA in one set and those for eta, etb, tst, mecA, and femA in the other set. Validation of the assay was performed using 176 human isolates of Staphylococcus aureus. This assay offers a very specific, quick, reliable, and inexpensive alternative to conventional PCR assays used in clinical laboratories to identify various staphylococcal toxin genes.

Structure of an E6AP-UbcH7 complex: insights into ubiquitination by the E2-E3 enzyme cascade

The E6AP ubiquitin-protein ligase (E3) mediates the human papillomavirus-induced degradation of the p53 tumor suppressor in cervical cancer and is mutated in Angelman syndrome, a neurological disorder. The crystal structure of the catalytic hect domain of E6AP reveals a bilobal structure with a broad catalytic cleft at the junction of the two lobes. The cleft consists of conserved residues whose mutation interferes with ubiquitin-thioester bond formation and is the site of Angelman syndrome mutations. The crystal structure of the E6AP hect domain bound to the UbcH7 ubiquitin-conjugating enzyme (E2) reveals the determinants of E2-E3 specificity and provides insights into the transfer of ubiquitin from the E2 to the E3.

Risk factors for disease severity, unimprovement, and mortality in COVID-19 patients in Wuhan, China

OBJECTIVE

In December 2019, coronavirus disease (COVID-19) emerged in Wuhan. However, the characteristics and risk factors associated with disease severity, unimprovement and mortality are unclear and our objective is to throw some light on these.

METHODS

All consecutive patients diagnosed with COVID-19 admitted to the Renmin Hospital of Wuhan University from January 11 to February 6, 2020, were enrolled in this retrospective cohort study.

RESULTS

A total of 663 COVID-19 patients were included in this study. Among these, 247 (37.3%) had at least one kind of chronic disease; 0.5% of the patients (n = 3) were diagnosed with mild COVID-19, while 37.8% (251/663), 47.5% (315/663), and 14.2% (94/663) were in moderate, severe, and critical conditions, respectively. In our hospital, during follow-up 251 of 663 patients (37.9%) improved and 25 patients died, a mortality rate of 3.77%. Older patients (>60 years old) and those with chronic diseases were prone to have a severe to critical COVID-19 condition, to show unimprovement, and to die (p <0.001, <0.001). Multivariate logistic regression analysis identified being male (OR = 0.486, 95%CI 0.311-0.758; p 0.001), having a severe COVID-19 condition (OR = 0.129, 95%CI 0.082-0.201; p <0.001), expectoration (OR = 1.796, 95%CI 1.062-3.036; p 0.029), muscle ache (OR = 0.309, 95%CI 0.153-0.626; p 0.001), and decreased albumin (OR = 1.929, 95%CI 1.199-3.104; p 0.007) as being associated with unimprovement in COVID-19 patients.

CONCLUSION

Male sex, a severe COVID-19 condition, expectoration, muscle ache, and decreased albumin were independent risk factors which influence the improvement of COVID-19 patients.

GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence

We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5σ. The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of 3.4_{-0.9}^{+0.7}×10^{-22}. The inferred source-frame initial black hole masses are 14.2_{-3.7}^{+8.3}M_{⊙} and 7.5_{-2.3}^{+2.3}M_{⊙}, and the final black hole mass is 20.8_{-1.7}^{+6.1}M_{⊙}. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of 440_{-190}^{+180}  Mpc corresponding to a redshift of 0.09_{-0.04}^{+0.03}. All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.

A PPxY motif within the VP40 protein of Ebola virus interacts physically and functionally with a ubiquitin ligase: implications for filovirus budding

VP40, the putative matrix protein of both Ebola and Marburg viruses, possesses a conserved proline-rich motif (PY motif) at its N terminus. We demonstrate that the VP40 protein can mediate its own release from mammalian cells, and that the PY motif is important for this self-exocytosis (budding) function. In addition, we used Western-ligand blotting to demonstrate that the PY motif of VP40 can mediate interactions with specific cellular proteins that have type I WW-domains, including the mammalian ubiquitin ligase, Nedd4. Single point mutations that disrupted the PY motif of VP40 abolished the PY/WW-domain interactions. Significantly, the full-length VP40 protein was shown to interact both physically and functionally with full-length Rsp5, a ubiquitin ligase of yeast and homolog of Nedd4. The VP40 protein was multiubiquitinated by Rsp5 in a PY-dependent manner in an in vitro ubiquitination assay. These data demonstrate that the VP40 protein of Ebola virus possesses a PY motif that is functionally similar to those described previously for Gag and M proteins of specific retroviruses and rhabdoviruses, respectively. Last, these studies imply that VP40 likely plays an important role in filovirus budding, and that budding of retroviruses, rhabdoviruses, and filoviruses may proceed via analogous mechanisms.

Lipopolysaccharide induces Rac1-dependent reactive oxygen species formation and coordinates tumor necrosis factor-alpha secretion through IKK regulation of NF-kappa B

Reactive oxygen species (ROS) are important second messengers generated in response to many types of environmental stress. In this setting, changes in intracellular ROS can activate signal transduction pathways that influence how cells react to their environment. In sepsis, a dynamic proinflammatory cellular response to bacterial toxins (e.g. lipopolysaccharide or LPS) leads to widespread organ damage and death. The present study demonstrates for the first time that the activation of Rac1 (a GTP-binding protein), and the subsequent production of ROS, constitutes a major pathway involved in NFkappaB-mediated tumor necrosis factor-alpha (TNFalpha) secretion following LPS challenge in macrophages. Expression of a dominant negative mutant of Rac1 (N17Rac1) reduced Rac1 activation, ROS formation, NFkappaB activation, and TNFalpha secretion following LPS stimulation. In contrast, expression of a dominant active form of Rac1 (V12Rac1) mimicked these effects in the absence of LPS stimulation. IKKalpha and IKKbeta were both required downstream modulators of LPS-activated Rac1, since the expression of either of the IKK dominant mutants (IKKalphaKM or IKKbetaKA) drastically reduced NFkappaB-dependent TNFalpha secretion. Moreover, studies using CD14 blocking antibodies suggest that Rac1 induces TNFalpha secretion through a pathway independent of CD14. However, a maximum therapeutic inhibition of LPS-induced TNFalpha secretion occurred when both CD14 and Rac1 pathways were inhibited. Our results suggest that targeting both Rac1- and CD14-dependent pathways could be a useful therapeutic strategy for attenuating the proinflammatory cytokine response during the course of sepsis.

AKT1/PKBalpha kinase is frequently elevated in human cancers and its constitutive activation is required for oncogenic transformation in NIH3T3 cells

Extensive studies have demonstrated that the Akt/AKT1 pathway is essential for cell survival and inhibition of apoptosis; however, alterations of Akt/AKT1 in human primary tumors have not been well documented. In this report, significantly increased AKT1 kinase activity was detected in primary carcinomas of prostate (16 of 30), breast (19 of 50), and ovary (11 of 28). The results were confirmed by Western blot and immunohistochemical staining analyses with phospho-Ser473 Akt antibody. The majority of AKT1-activated tumors are high grade and stage III/lV (13 of 16 prostate, 15 of 19 breast, and 8 of 11 ovarian carcinomas). Previous studies showed that wild-type AKT1 was unable to transform NIH3T3 cells. To demonstrate the biological significance of AKT1 activation in human cancer, constitutively activated AKT1 (Myr-Akt) was introduced into NIH3T3 cells. Overexpression of Myr-Akt in the stably transfected cells resulted in malignant phenotype, as determined by growth in soft agar and tumor formation in nude mice. These data indicate that AKT1 kinase, which is frequently activated in human cancer, is a determinant in oncogenesis and a potential target for cancer intervention.

Selective peptide antagonist of the class E calcium channel from the venom of the tarantula Hysterocrates gigas

We describe the first potent and selective blocker of the class E Ca2+channel. SNX-482, a novel 41 amino acid peptide present in the venom of the African tarantula, Hysterocrates gigas, was identified through its ability to inhibit human class E Ca2+ channels stably expressed in a mammalian cell line. An IC50 of 15-30 nM was obtained for block of the class E Ca2+ channel, using either patch clamp electrophysiology or K+-evoked Ca2+ flux. At low nanomolar concentrations, SNX-482 also blocked a native resistant or R-type Ca2+ current in rat neurohypophyseal nerve terminals, but concentrations of 200-500 nM had no effect on R-type Ca2+ currents in several types of rat central neurons. The peptide has the sequence GVDKAGCRYMFGGCSVNDDCCPRLGCHSLFSYCAWDLTFSD-OH and is homologous to the spider peptides grammatoxin S1A and hanatoxin, both peptides with very different ion channel blocking selectivities. No effect of SNX-482 was observed on the following ion channel activities: Na+ or K+ currents in several cultured cell types (up to 500 nM); K+ current through cloned potassium channels Kv1.1 and Kv1. 4 expressed in Xenopus oocytes (up to 140 nM); Ca2+ flux through L- and T-type Ca2+ channels in an anterior pituitary cell line (GH3, up to 500 nM); and Ba2+ current through class A Ca2+ channels expressed in Xenopus oocytes (up to 280 nM). A weak effect was noted on Ca2+ current through cloned and stably expressed class B Ca2+ channels (IC50 > 500 nM). The unique selectivity of SNX-482 suggests its usefulness in studying the diversity, function, and pharmacology of class E and/or R-type Ca2+ channels.

Fate of enterohemorrhagic Escherichia coli O157:H7 in bovine feces

Dairy cattle have been identified as a principal reservoir of Escherichia coli O157:H7. The fate of this pathogen in bovine feces at 5, 22, and 37 degrees C was determined. Two levels of inocula (10(3) and 10(5) CFU/g) of a mixture of five nalidixic acid-resistant E. coli O157:H7 strains were used. E. coli O157:H7 survived at 37 degrees C for 42 and 49 days with low and high inocula, respectively, and at 22 degrees C for 49 and 56 days with low and high inocula, respectively. Fecal samples at both temperatures had low moisture contents (about 10%) and water activities ( < 0.5) near the end of the study. E. coli O157:H7 at 5 degrees C survived for 63 to 70 days, with the moisture content (74%) of feces remaining high through the study. Chromosomal DNA fingerprinting of E. coli O157:H7 isolates surviving near the completion of the study revealed that the human isolate strain 932 was the only surviving strain at 22 or 37 degrees C. All five strains were isolated near the end of incubation from feces held at 5 degrees C. Isolates at each temperature were still capable of producing both verotoxin 1 and verotoxin 2. Results indicate that E. coli O157:H7 can survive in feces for a long period of time and retain its ability to produce verotoxins. Hence, bovine feces are a potential vehicle for transmitting E. coli O157:H7 to cattle, food, and the environment. Appropriate handling of bovine feces is important to control the spread of this pathogen.

GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2

We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10∶11:58.6 UTC by the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70 000 years. The inferred component black hole masses are 31.2_{-6.0}^{+8.4}M_{⊙} and 19.4_{-5.9}^{+5.3}M_{⊙} (at the 90% credible level). The black hole spins are best constrained through measurement of the effective inspiral spin parameter, a mass-weighted combination of the spin components perpendicular to the orbital plane, χ_{eff}=-0.12_{-0.30}^{+0.21}. This result implies that spin configurations with both component spins positively aligned with the orbital angular momentum are disfavored. The source luminosity distance is 880_{-390}^{+450}  Mpc corresponding to a redshift of z=0.18_{-0.07}^{+0.08}. We constrain the magnitude of modifications to the gravitational-wave dispersion relation and perform null tests of general relativity. Assuming that gravitons are dispersed in vacuum like massive particles, we bound the graviton mass to m_{g}≤7.7×10^{-23}  eV/c^{2}. In all cases, we find that GW170104 is consistent with general relativity.

Frequent activation of AKT2 and induction of apoptosis by inhibition of phosphoinositide-3-OH kinase/Akt pathway in human ovarian cancer

We previously demonstrated that AKT2, a member of protein kinase B family, is activated by a number of growth factors via Ras and PI 3-kinase signaling pathways. Here, we report the frequent activation of AKT2 in human primary ovarian cancer and induction of apoptosis by inhibition of phosphoinositide-3-OH kinase (PI 3-kinase)/Akt pathway. In vitro AKT2 kinase assay analyses in 91 ovarian cancer specimens revealed elevated levels of AKT2 activity (>3-fold) in 33 cases (36.3%). The majority of tumors displaying activated AKT2 were high grade and stages III and IV. Immunostaining and Western blot analyses using a phospho-ser-473 Akt antibody that detects the activated form of AKT2 (AKT2 phosphorylated at serine-474) confirmed the frequent activation of AKT2 in ovarian cancer specimens. Phosphorylated AKT2 in tumor specimens localized to the cell membrane and cytoplasm but not the nucleus. To address the mechanism of AKT2 activation, we measured in vitro PI 3-kinase activity in 43 ovarian cancer specimens, including the 33 cases displaying elevated AKT2 activation. High levels of PI 3-kinase activity were observed in 20 cases, 15 of which also exhibited AKT2 activation. The remaining five cases displayed elevated AKT1 activation. Among the cases with elevated AKT2, but not PI 3-kinase activity (18 cases), three showed down-regulation of PTEN protein expression. Inhibition of PI 3-kinase/AKT2 by wortmannin or LY294002 induces apoptosis in ovarian cancer cells exhibiting activation of the PI 3-kinase/AKT2 pathway. These findings demonstrate for the first time that activation of AKT2 is a common occurrence in human ovarian cancer and that PI 3-kinase/Akt pathway may be an important target for ovarian cancer intervention.

Molecular typing of Borrelia burgdorferi sensu lato: taxonomic, epidemiological, and clinical implications

Borrelia burgdorferi sensu lato, the spirochete that causes human Lyme borreliosis (LB), is a genetically and phenotypically divergent species. In the past several years, various molecular approaches have been developed and used to determine the phenotypic and genetic heterogeneity within the LB-related spirochetes and their potential association with distinct clinical syndromes. These methods include serotyping, multilocus enzyme electrophoresis, DNA-DNA reassociation analysis, rRNA gene restriction analysis (ribotyping), pulsed-field gel electrophoresis, plasmid fingerprinting, randomly amplified polymorphic DNA fingerprinting analysis, species-specific PCR and PCR-based restriction fragment length polymorphism (RFLP) analysis, and sequence analysis of 16S rRNA and other conserved genes. On the basis of DNA-DNA reassociation analysis, 10 different Borrelia species have been described within the B. burgdorferi sensu lato complex: B. burgdorferi sensu stricto, Borrelia garinii, Borrelia afzelii, Borrelia japonica, Borrelia andersonii, Borrelia valaisiana, Borrelia lusitaniae, Borrelia tanukii, Borrelia turdi, and Borrelia bissettii sp. nov. To date, only B. burgdorferi sensu stricto, B. garinii, and B. afzelii are well known to be responsible for causing human disease. Different Borrelia species have been associated with distinct clinical manifestations of LB. In addition, Borrelia species are differentially distributed worldwide and may be maintained through different transmission cycles in nature. In this paper, the molecular methods used for typing of B. burgdorferi sensu lato are reviewed. The current taxonomic status of B. burgdorferi sensu lato and its epidemiological and clinical implications, especiallly correlation between the variable clinical presentations and the infecting Borrelia species, are discussed in detail.

Early steps in reovirus infection are associated with dramatic changes in supramolecular structure and protein conformation: analysis of virions and subviral particles by cryoelectron microscopy and image reconstruction

Three structural forms of type 1 Lang reovirus (virions, intermediate subviral particles [ISVPs], and cores) have been examined by cryoelectron microscopy (cryoEM) and image reconstruction at 27 to 32-A resolution. Analysis of the three-dimensional maps and known biochemical composition allows determination of capsid protein location, globular shape, stoichiometry, quaternary organization, and interactions with adjacent capsid proteins. Comparisons of the virion, ISVP and core structures and examination of difference maps reveal dramatic changes in supra-molecular structure and protein conformation that are related to the early steps of reovirus infection. The intact virion (approximately 850-A diam) is designed for environmental stability in which the dsRNA genome is protected not only by tight sigma 3-mu 1, lambda 2-sigma 3, and lambda 2-mu 1 interactions in the outer capsid but also by a densely packed core shell formed primarily by lambda 1 and sigma 2. The segmented genome appears to be packed in a liquid crystalline fashion at radii < 240 A. Depending on viral growth conditions, virions undergo cleavage by enteric or endosomal/lysosomal proteases, to generate the activated ISVP (approximately 800-A diam). This transition involves the release of an outer capsid layer spanning radii from 360 to 427 A that is formed by 60 tetrameric and 60 hexameric clusters of ellipsoidal subunits of sigma 3. The vertex-associated cell attachment protein, sigma 1, also undergoes a striking change from a poorly visualized, more compact form, to an extended, flexible fiber. This conformational change may maximize interactions of sigma 1 with cell surface receptors. Transcription of viral mRNAs is mediated by the core particle (approximately 600-A diam), generated from the ISVP after penetration and uncoating. The transition from ISVP to core involves release of the 12 sigma 1 fibers and the remaining outer capsid layer formed by 200 trimers of rod-shaped mu 1 subunits that span radii from 306 to 395 A. In the virion and ISVP, flower-shaped pentamers of the lambda 2 protein are centered at the vertices. In the ISVP-to-core transition, domains of the lambda 2 subunits rotate and swing upward and outward to form a turret-like structure extending from radii 305 to 400 A, with a diameter of 184 A, and a central channel 84 A wide. This novel conformational change allows the potential diffusion of substrates for transcription and exit of newly synthesized mRNA segments.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of shape-discrimination training on the selectivity of inferotemporal cells in adult monkeys

Through extensive training, humans can become "visual experts, " able to visually distinguish subtle differences among similar objects with greater ease than those who are untrained. To understand the neural mechanisms behind this acquired discrimination ability, adult monkeys were fully trained to discriminate 28 moderately complex shapes. The training effects on the stimulus selectivity of cells in area TE of the inferotemporal cortex were then examined in anesthetized preparations. Area TE represents a later stage of the ventral visual cortical pathway that is known to mediate visual object discrimination and recognition. The recordings from the trained monkeys and untrained controls showed that the proportion of TE cells responsive to some member of the 28 stimuli was significantly greater in the trained monkeys than that in the control monkeys. Cell responses recorded from the trained monkeys were not sharply tuned to single training stimuli, but rather broadly covered several training stimuli. The distances among the training stimuli in the response space spanned by responses of the recorded TE cells were significantly greater in the trained monkeys than those in the control monkeys. The subset of training stimuli to which individual cells responded differed from cell to cell with only partial overlaps, suggesting that the cells responded to features common to several stimuli. These results are consistent with a model in which visual expertise is acquired through the development of differential responses by inferotemporal cells to the images of relevant objects.

Mechanical properties and microstructures of glass-ionomer cements

OBJECTIVE

The objective of this study was to determine the flexural strength (FS), compressive strength (CS), diametral tensile strength (DTS), Knoop hardness (KHN) and wear resistance of ten commercial glass-ionomer cements (GICs). The fracture surfaces of these cements were examined using scanning electron microscopic (SEM) techniques to ascertain relationships between the mechanical properties and microstructures of these cements.

METHODS

Specimens were fabricated according to the instructions from each manufacturer. The FS, CS, DTS, KHN and wear rate were measured after conditioning the specimens for 7 d in distilled water at 37 degrees C. One-way analysis of variance with the post hoc Tukey-Kramer multiple range test was used to determine which specimen groups were significantly different for each test. The fracture surface of one representative specimen of each GIC from the FS tests was examined using a scanning electron microscope.

RESULTS

The resin-modified GICs (RM GICs) exhibited much higher FS and DTS, not generally higher CS, often lower Knoop hardness and generally lower wear resistance, compared to the conventional GICs (C GICs). Vitremer (3M) had the highest values of FS and DTS; Fuji II LC (GC International) and Ketac-Molar (ESPE) had the highest CS; Ketac-Fil (ESPE) had the highest KHN. Ketac-Bond (ESPE) had the lowest FS; alpha-Silver (DMG-Hamburg) had the lowest CS. Four GICs (alpha-Fil (DMG-Hamburg), alpha-Silver, Ketac-Bond and Fuji II) had the lowest values of DTS, which were not significantly different from each other; alpha-Silver and Ketac-Silver had the lowest values of KHN. The highest wear resistance was exhibited by alpha-Silver and Ketac-Fil; F2LC had the lowest wear resistance. The C GICs exhibited brittle behavior, whereas the RM GICs underwent substantial plastic deformation in compression. The more integrated the microstructure, the higher were the FS and DTS. Higher CS was correlated with smaller glass particles, and higher KHN was found where there was a combination of smaller glass particles and lower porosity. Larger glass particle sizes and a more integrated microstructure contributed to a higher wear resistance.

SIGNIFICANCE

The mechanical properties of GICs were closely related to their microstructures. Factors such as the integrity of the interface between the glass particles and the polymer matrix, the particle size, and the number and size of voids have important roles in determining the mechanical properties.