Search

KM2A is one of the main sub-arrays of LHAASO, working on gamma ray astronomy and cosmic ray physics at energies above 10 TeV. Detector simulation is the important foundation for estimating detector performance and data analysis. It is a big challenge to simulate the KM2A detector in the framework of Geant4 due to the need to track numerous photons from a large number of detector units (>6000) with large altitude difference (30 m) and huge coverage (1.3 km2). In this paper, the design of the KM2A simulation code G4KM2A based on Geant4 is introduced. The process of G4KM2A is optimized mainly in memory consumption to avoid memory overflow. Some simplifications are used to significantly speed up the execution of G4KM2A. The running time is reduced by at least 30 times compared to full detector simulation. The particle distributions and the core/angle resolution comparison between simulation and experimental data of the full KM2A array are also presented, which show good agreement.

Introduction: One of main scientific goals of the Large High Altitude Air Shower Observatory (LHAASO) is to accurately measure the energy spectra of different cosmic ray compositions around the ‘knee’ region. The Wide Field-of-View (FoV) Cherenkov Telescope Array (WFCTA), which is one of the main detectors of LHAASO and has 18 telescopes, is built to achieve this goal. Multiple telescopes are put together and point to connected directions for a larger FoV. Method: Telescopes are deployed spatially as close as possible, but due to their own size, the distance between two adjacent telescopes is about 10 m. Therefore, the Cherenkov lateral distribution and the parallax between the two telescopes should be considered in the event building process for images crossing over the boundaries of FoVs of the telescopes. An event building method for Cherenkov images measured by multiple telescopes of WFCTA is developed. The performance of the shower measurements using the combined images is evaluated by comparing with showers that are fully contained by a virtual telescope in simulation. Results and conclusion: It is proved that the developed event building process can help to increase the FoV of WFCTA by 30% while maintaining the same reconstruction quality, compared to the separate telescope reconstruction method.

Purpose: Observation of high energy and very high emission from Gamma Ray Bursts (GRBs) is crucial to study the gigantic explosion and the underline processes. With a large field-of-view and almost full duty cycle, the Water Cherenkov Detector Array (WCDA), a sub-array of the Large High Altitude Air Shower Observatory (LHAASO), is appropriate to monitor the very high energy emission from unpredictable transients such as GRBs. Method: Nevertheless, the main issue for an extensive air shower array is the high energy threshold which limits the horizon of the detector. To address this issue a new trigger method is developed in this article to lower the energy threshold of  WCDA for GRB observation. Result: The proposed method significantly improves the detection efficiency of WCDA for gamma-rays around the GRB direction at 10-300 GeV. The sensitivity of the WCDA for GRB detection with the new trigger method is estimated. The achieved sensitivity of the quarter WCDA array above 10 GeV is comparable with that of Fermi-LAT. The data analysis process and corresponding fluence upper limit for GRB 190719C is presented as an example.

The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 1015electronvolts) indicates the existence of the so-called PeVatrons—cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays1. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref. 2). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane3–6, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.

Purpose: The main scientific goal of LHAASO-WCDA is to survey gamma-ray sources with energy from 100 GeV to 30 TeV. To observe high-energy shower events, especially to measure the energy spectrum of cosmic rays from 100 TeV to 10 PeV, a dynamic range extension system (WCDA++) is designed to use a 1.5-inch PMT with a dynamic range of four orders of magnitude for each cell in WCDA-1. Method: The dynamic range is extended by using these PMTs to measure the effective charge density in the core region of air shower events, which is an important parameter for identifying the composition of primary particles. Result and Conclusion: The system has been running for more than one year. In this paper, the details of the design and performance of WCDA++ are presented.

The aim of this study was to investigate the inhibition effects of cordycepin and its derivatives on endometrial cancer cell growth. Cytotoxicity MTT assays, clonogenic assays, and flow cytometry were used to observe the effects on apoptosis and regulation of the cell cycle of Ishikawa cells under various concentrations of cordycepin, cisplatin, and combinations of the two. Validated in silico docking simulations were performed on 31 cordycepin derivatives against adenosine deaminase (ADA) to predict their binding affinities and hence their potential tendency to be metabolized by ADA. Cordycepin has a significant dose-dependent inhibitory effect on cell proliferation. The combination of cordycepin and cisplatin produced greater inhibition effects than did cordycepin alone. Apoptosis investigations confirmed the ability of cordycepin to induce the apoptosis of Ishikawa cells. The in silico results indicate that compound MRS5698 is least metabolized by ADA and has acceptable drug likeness and safety profiles. This is the first study to confirm the cytotoxic effects of cordycepin on endometrial cancer cells. This study also identified cordycepin derivatives with promising pharmacological and pharmacokinetic properties for further investigation in the development of new treatments for endometrial cancer.

The article presents a study about the performance of VAPPRO 844, a polymolecular volatile corrosion inhibitor (VCI), on steel via colloid formation through its reaction with seawater ions. The physical and chemical properties of seawater were examined. In addition, the corrosion and degradation of materials are also explored.

The article offers information related to protection of military vehicles and equipment against corrosion. Topics discussed include the development of the Office of Corrosion Policy and Oversight (CPO) by the U.S. Department of Defense (DoD) to control corrosion in military services and the U.S. Army, the growing popularity of corrosion inhibitors in military and electronic equipment and cooling water systems, and three groups of corrosion inhibitors including anodic, cathodic, and adsorption.

The main contribution of this article is the proposal of a path-following method for fixed-wing unmanned aerial vehicles. This path-following method employs the multi-loop framework that consists of an outer guidance loop and an inner control loop. The guidance loop relies on the idea of tracking a virtual target. The virtual target is assumed to travel along the defined path and its speed is explicitly specified. This guidance law guarantees the asymptotic convergence to the desired path and can anticipate the transition of the flight path in advance, which reduces the command for the inner control loop. In the inner control loop, the flight control law based on dynamic surface control is derived to overcome the ‘explosion of complexity’ problem in the backstepping design. The numerical simulation result illustrates the effectiveness of the proposed method.

The role of B cells in transplant tolerance remains unclear. Although B‐cell depletion often prolongs graft survival, sometimes it results in more rapid rejection, suggesting that B cells may have regulatory activity. We previously demonstrated that tolerance induction by anti‐CD45RB antibody requires recipient B cells. Here, we show that anti‐CD45RB in combination with anti‐TIM‐1 antibody has a synergistic effect, inducing tolerance in all recipients in a mouse islet allograft model. This effect depends on the presence of recipient B cells, requires B‐cell IL‐10 activity, and is antigen‐specific. These data suggest the existence of a regulatory B‐cell population that promotes tolerance via an IL‐10‐dependent pathway.

A layer of nickel–phosphorus alloy was electroless plated on the surface of microarc oxidised AZ31 magnesium alloy first, and then sealing treatment was performed on the electroless nickel plated coating using bis-(triethoxysilylpropyl)tetrasulphide silane. Fourier transform infrared spectroscopy, scanning electron microscope (SEM), energy dispersed X-ray spectroscope analyses, electrochemical techniques and immersion test were used for the analyses of surface morphology and structure and corrosion resistance of electroless nickel plated samples before and after sealing treatment. The results showed that the silane film by sealing treatment improves its corrosion resistance significantly.

A theorem is established to show that nanoscale energy deposition in water by X-rays can be greatly enhanced via the geometry of nanostructures. The calculated results show that enhancement over background water can reach over 60 times for a single nanoshell made of gold. Other geometries and nanostructures are investigated, and it is found that a shell of gold nanoparticles can generate similar enhancement. The concepts of composition, matrix, and satellite effects are established and studied, all of which can further increase the enhancement of the effect of X-rays.

Although the combination of lamivudine (LAM) and high-dose intravenous (IV) hepatitis B immunoglobulin (HBIG) is very effective in preventing hepatitis B virus (HBV) recurrence after liver transplantation (LT), the major limitation of this regimen is its high cost. A more cost-effective, convenient and widely accepted regimen is urgently needed. We evaluated the safety and efficacy of another strategy using LAM and individualized low-dose intramuscular (IM) HBIG. Between May 2002 and December 2009, a total of 254 adult patients undergoing LT for HBV-related benign end-stage liver diseases received this regimen in our center. The mean follow-up of these patients was 41.2 ± 22.7 months. Their 1-, 3- and 5-year survival rates were 85.3, 77.4 and 76.4, respectively, and 1-, 3- and 5-year HBV recurrence rates were 2.3, 6.2 and 8.2. Fourteen patients experienced posttransplant HBV recurrence. Pretransplant high viral load and posttransplant prednisone withdrawal time were observed to be associated with recurrence. In conclusion, combination therapy with LAM and individualized low-dose IM HBIG provides a safe and effective prophylaxis against HBV recurrence after LT at about 5 of the cost of conventional high-dose IV HBIG regimens.

The bottleneck of alkaline hydrogen evolution reaction lies in the kinetically sluggish brought from multistep reaction processes involving water adsorption and dissociation, as well as hydrogen adsorption. In this work, we successfully synthesized o-CoSe2/c-CoSe2heterostructures anchored on MoSe2nanosheets to powerfully promote reaction processes. As an electrocatalyst, it exhibits a low overpotential of 112 mV at 10 mA/cm2and a Tafel slope of 96.9 mV/dec for an alkaline hydrogen evolution reaction. Moreover, the as-prepared catalyst can behave as both cathode and anode for overall water splitting, which only requires 1.61 V cell voltage at 10 mA/cm2. Significantly, the cell voltage can be further reduced to 1.53 V at 10 mA/cm2for water electrolysis under the simulated solar irradiation owing to such a semiconductor-based heterostructure that facilitates the separation of photogenerated charges. Here, the improving overall performance of this ternary electrocatalyst is attributed to the multifunctionality and synergistic interaction of different components in this heterogeneous material. The work provides a novel strategy to design active catalysts simultaneously using electric energy and solar energy for effective water splitting.

Transforming growth factor-β (TGF-β) is the prototype of a large family of signaling molecules. TGF-β signaling profoundly influences tumor development as demonstrated in several engineered mouse models. The present study was designed to identify differences by cDNA microarray and MALDI-TOF MS analyses in mammary carcinomas with and without TGF-β signaling. The results demonstrate a significant potential for combination of profiling technologies to further understand the molecular mechanisms of breast cancer. Keywords: microarray • MALDI-TOF mass spectrometry • mammary tumor • transgenic mouse

A carboxyl-terminated N-isopropylacrylamide/vinyl laurate (VL) copolymer was prepared and coupled with chitosan (molecular weight = 2000) to produce a chitosan−NIPAAm/VL copolymer (PNVLCS) vector. The aqueous solution of PNVLCS displayed an obvious thermoresponsive behavior with a lower critical solution temperature (LCST) about 26 °C. The transmission electron microscopy (TEM) showed that the size of PNVLCS/DNA complexes varied with charge ratios (+/−), and the smaller nanoparticles were formed at higher charge ratios. DLS revealed that the size of complex particles was dependent on temperature. The results of temperature-variable circular dichroism (CD), UV, and electrophoresis retardation indicated that at lower charge ratios, DNA in the complexes assume a B conformation, whereas increasing charge ratios caused B → C type conformation transformation; the dissociation−formation of PNVLCS/DNA complexes could be tuned by varying temperature:  at 37 °C, the collapse of PNIPAAm in PNVLCS was favorable for the formation of compact complexes, shielding more DNA from exposure; at 20 °C, the hydrated and extended PNIPAAm chains facilitated the unpacking of DNA from PNVLCS, increasing the exposure of DNA. PNVLCS was used to transfer plasmid-encoding β-galactosidase into C2C12 cells. The level of gene expression could be controlled by varying incubation temperature. The transfection efficiency of PNVLCS was well improved by temporarily reducing culture temperature to 20 °C, whereas naked DNA and Lipofectamine 2000 did not demonstrate the characteristics of thermoresponsive gene transfection.

The liquid crystalline alignment medium based on a quasi-ternary surfactant system comprising cetylpyridinium bromide (CPBr)/hexanol/sodium bromide [6.5% CPBr/hexanol (1/1.33, w/w), 30 mM NaBr in 10 mM glycine/HBr buffer, pH 3.0] was characterized. We assessed the morphology of the amphiphilic aggregates by electron microscopy. The images show a network of elongated wormlike structures that are 5.5 nm wide ranging up to 1 μm in length. In the bulk medium, they are closely packed with an average center-to-center spacing of ~5 nm as measured by negative staining and ~10 nm as determined directly by cryo-electron microscopy. Solid-state ²H and ³¹P NMR spectroscopies were used to determine the orientational order parameters of the aromatic ring and the aliphatic chain of the surfactant as well as the alcohol. Order parameter analysis revealed that the pyridinium ring is tilted with respect to the CPBr molecular symmetry axis. The cetyl chain has the typical order profile of hydrocarbon chains in liquid-crystalline phases:  an order plateau for methylene segments near the pyridinium ring and rapidly decreasing order for the second half of the chain toward the terminal methyl group. Hexanol shows a similar order profile. However, its order is much lower than the order of the CPBr chains. To demonstrate the efficacy of this alignment medium for structure determination by NMR, we measured a large set of residual dipolar couplings for the potent HIV-1 inactivating protein, cyanovirin-N, determined the orientation of the alignment tensor, and verified the fold of this molecule at low pH.

Ca(2+) levels in plants, fungi, and bacteria are controlled in part by H(+)/Ca(2+) exchangers; however, the relationship between primary sequence and biological activity of these transporters has not been reported. The Arabidopsis H(+)/cation exchangers, CAX1 and CAX2, were identified by their ability to suppress yeast mutants defective in vacuolar Ca(2+) transport. CAX1 has a much higher capacity for Ca(2+) transport than CAX2. An Arabidopsis thaliana homolog of CAX1, CAX3, is 77% identical (93% similar) and, when expressed in yeast, localized to the vacuole but did not suppress yeast mutants defective in vacuolar Ca(2+) transport. Chimeric constructs and site-directed mutagenesis showed that CAX3 could suppress yeast vacuolar Ca(2+) transport mutants if a nine-amino acid region of CAX1 was inserted into CAX3 (CAX3-9). Biochemical analysis in yeast showed CAX3-9 had 36% of the H(+)/Ca(2+) exchange activity as compared with CAX1; however, CAX3-9 and CAX1 appear to differ in their transport of other ions. Exchanging the nine-amino acid region of CAX1 into CAX2 doubled yeast vacuolar Ca(2+) transport but did not appear to alter the transport of other ions. This nine-amino acid region is highly variable among the plant CAX-like transporters. These findings suggest that this region is involved in CAX-mediated Ca(2+) specificity.

Tumor necrosis factor-alpha (TNF-alpha) is a multifunctional cytokine that induces a broad spectrum of responses including angiogenesis. Angiogenesis promoted by TNF-alpha is mediated, at least in part, by ephrin A1, a member of the ligand family for Eph receptor tyrosine kinases. Although TNF-alpha induces ephrin A1 expression in endothelial cells, the signaling pathways mediating ephrin A1 induction remain unknown. In this study, we investigated the signaling mechanisms of TNF-alpha-dependent induction of ephrin A1 in endothelial cells. Both TNFR1 and TNFR2 appear to be involved in regulating ephrin A1 expression in endothelial cells, because neutralizing antibodies to either TNFR1 or TNFR2 inhibited TNF-alpha-induced ephrin A1 expression. Inhibition of nuclear factor-kappaB (NF-kappaB) activation by a trans-dominant inhibitory isoform of mutant IkappaBalpha did not affect ephrin A1 induction, suggesting that NF-kappaB proteins are not major regulators of ephrin A1 expression. In contrast, ephrin A1 induction was blocked by inhibition of p38 mitogen-activated protein kinase (MAPK) or SAPK/JNK, but not p42/44 MAPK, using either selective chemical inhibitors or dominant-negative forms of p38 MAPK or TNF receptor-associated factor 2. These findings indicate that TNF-alpha-induced ephrin A1 expression is mediated through JNK and p38 MAPK signaling pathways. Taken together, the results of our study demonstrated that induction of ephrin A1 in endothelial cells by TNF-alpha is mediated through both p38 MAPK and SAPK/JNK, but not p42/44 MAPK or NF-kappaB, pathways.

This study compares the identifying characteristics between the impressions made with original Chinese seals and photopolymer replicate seals, and between the impressions made with two photopolymer replicate seals that originate from one single negative. Various seal materials common to the Chinese community such as cow's horns and ivory are employed. Other than the common factors such as different incident angle upon imprinting or different degree of inking that constitute the natural variation in impressions, the physical changes of the seal materials with temperature will be considered. This study concludes that photopolymer replicate seal impressions can be differentiated from the originals in respect to print density and stroke morphology, but it is very difficult to differentiate between two photopolymer replicate seal impressions with the same origin. This study also proposes a simple method for the examination of forged Chinese seal impressions.

Heavy metal clusters derivatized to bind to designated chemical groups on proteins have great potential as density labels for cryo-electron microscopy. Smaller clusters offer higher resolution and penetrate more easily into sterically restricted sites, but are more difficult to detect. In this context, we have explored the potential of tetrairidium (Ir4) as a density label by attaching it via maleimide linkage to the C-terminus of the hepatitis B virus (HBV) capsid protein. Although the clusters are not visible in unprocessed cryo-electron micrographs, they are distinctly visible in three-dimensional density maps calculated from them, even at only partial occupancy. The Ir4label was clearly visualized in our maps at 11–14 Å resolution of both size variants of the HBV capsid, thus confirming our previous localization of this site with undecagold (Zlotnick, A., Cheng, N., Stahl, S. J., Conway, J. F., Steven, A. C., and Wingfield, P. T., Proc. Natl. Acad. Sci. USA94, 9556–9561, 1997). Ir4penetrated to the interior of intact capsids to label this site on their inner surface, unlike undecagold for which labelling was achieved only with dissociated dimers that were then reassembled into capsids. The Ir4cluster remained visible as the resolution of the maps was lowered progressively to ∼25 Å.

We previously characterized PP1bp134 and PP1bp175, two neuronal proteins that bind the protein phosphatase 1 catalytic subunit (PP1). Here we purify from rat brain actin-cytoskeletal extracts PP1(A) holoenzymes selectively enriched in PP1gamma(1) over PP1beta isoforms and also containing PP1bp134 and PP1bp175. PP1bp134 and PP1bp175 were identified as the synapse-localized F-actin-binding proteins spinophilin (Allen, P. B., Ouimet, C. C., and Greengard, P. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 9956-9561; Satoh, A., Nakanishi, H., Obaishi, H., Wada, M., Takahashi, K., Satoh, K., Hirao, K., Nishioka, H., Hata, Y., Mizoguchi, A., and Takai, Y. (1998) J. Biol. Chem. 273, 3470-3475) and neurabin (Nakanishi, H., Obaishi, H., Satoh, A., Wada, M., Mandai, K., Satoh, K., Nishioka, H. , Matsuura, Y., Mizoguchi, A., and Takai, Y. (1997) J. Cell Biol. 139, 951-961), respectively. Recombinant spinophilin and neurabin interacted with endogenous PP1 and also with each other when co-expressed in HEK293 cells. Spinophilin residues 427-470, or homologous neurabin residues 436-479, were sufficient to bind PP1 in gel overlay assays, and selectively bound PP1gamma(1) from a mixture of brain protein phosphatase catalytic subunits; additional N- and C-terminal sequences were required for potent inhibition of PP1. Immunoprecipitation of spinophilin or neurabin from crude brain extracts selectively coprecipitated PP1gamma(1) over PP1beta. Moreover, immunoprecipitation of PP1gamma(1) from brain extracts efficiently coprecipitated spinophilin and neurabin, whereas PP1beta immunoprecipitation did not. Thus, PP1(A) holoenzymes containing spinophilin and/or neurabin target specific neuronal PP1 isoforms, facilitating efficient regulation of synaptic phosphoproteins.

Chimeric oligonucleotides consisting of RNA and DNA residues have been shown to catalyze site-directed genetic alteration in mammalian cells both in vitro and in vivo. Since the frequency of these events appears to be logs higher than the rates of gene targeting, a process involving homologous recombination, we developed a system to study the mechanisms of chimera-directed gene conversion. Using a mammalian cell-free extract and a genetic readout in Escherichia coli, we find that point mutations and single base deletions can be corrected at frequencies of approximately 0.1% and 0.005%, respectively. The reaction depends on an accurately designed chimera and the presence of functional hMSH2 protein. The results of genetic and biochemical studies reported herein suggest that the process of mismatch repair functions in site-directed gene correction.

The polycomb group (Pc‐G) genes are responsible for maintaining the repressed state of homeotic genes during development. It has been suggested that the Pc‐G exerts its transcriptional control by regulating higher order chromatin structure. In particular, the finding of genetic and molecular similarities to components involved in heterochromatin formation, led to the proposal that homeotic genes are permanently repressed by mechanisms similar to those responsible for heterochromatin compaction. Because of synergistic effects, Pc‐G gene products are thought to act in a multimeric complex. Using immunoprecipitation we show that two members of the Pc‐G, Polycomb and polyhomeotic, are constituents of a soluble multimeric protein complex. Size fractionation indicates that a large portion of the two proteins are found in a distinct complex of molecular weight 2–5 × 10(6) Da. During embryogenesis the two proteins show the same spatial distribution. In addition, by double‐immunofluorescence labelling we can demonstrate that Polycomb and polyhomeotic have exactly the same binding patterns on polytene chromosomes of larval salivary glands. We propose that some Pc‐G proteins act in multimeric complexes to compact the chromatin of stably repressed genes like the homeotic regulators.

A comparison of efficacies, costs, and effects on vaginal microflora of one preoperative and three postoperative 1-g doses of cefazolin versus those of one preoperative 1-g dose of ceftriaxone was done with 65 and 73 women, respectively, undergoing elective vaginal hysterectomy. Patient infection rates were not statistically different between the cefazolin group (six events in 6 of 73 patients [8.2%]) and the ceftriaxone group (11 events in 9 of 65 patients [13.8%]). Side effects, including diarrhea, were minimal and similar between the two groups. Significant shifts in the cervicovaginal microflora of the patients occurred postoperatively, with a marked increase in enterococci and a drop in nonenterococcal streptococci. No shifts among aerobic, facultative gram-negative rods and staphylococci were observed. Among the anaerobes, a significant decrease in the number of patients harboring nonsporulating, gram-positive rods and a less striking concomitant increase in Bacteriodes species and members of the family Peptococcaceae were noted. No qualitative differences were noted between the two groups that received prophylactic therapy. Aside from enterococci, cefazolin or ceftriaxone resistance among vaginal isolates (greater than or equal to 10(3)/ml) was minimal. Selection of resistant isolates was not different between the treatment groups. We could not detect a difference between a single 1-g dose of ceftriaxone and multidose cefazolin for infection prophylaxis in patients undergoing a vaginal hysterectomy. However, the total acquisition, preparation, and administration costs were greater for the ceftriaxone regimen than they were for the cefazolin regimen. Cefazolin should therefore remain the drug of choice for infection prophylaxis in uncomplicated vaginal hysterectomies.

A total of 598 clinical isolates of anaerobic bacteria were tested against ciprofloxacin by the agar dilution technique with 10(5) CFU on Wilkins-Chalgren medium. Selected strains representative of the six major genera of anaerobes relatively resistant to the quinolones were tested for interactions with ciprofloxacin in combination with clindamycin, metronidazole, cefoxitin, cefotaxime, or mezlocillin by using a checkerboard agar dilution technique. Cefotaxime-ciprofloxacin and clindamycin-ciprofloxacin were the most effective combinations, with 16% of all isolates and 44% of the Bacteroides fragilis group isolates responding synergistically to the former combination and 9% of all isolates and 37% of Peptostreptococcus isolates responding synergistically to the latter. Occasional synergy was seen with all other antibiotic combinations except for metronidazole-ciprofloxacin. Likewise, synergism was seen with all groups of anaerobes except for Fusobacterium species. Antagonistic interactions were observed only with a Peptostreptococcus intermedius strain tested against clindamycin-ciprofloxacin. These data suggest that combinations of ciprofloxacin with these agents may be useful for certain resistant anaerobic infections.

Midrange petroleum products such as charcoal lighters and paint thinners represent a potential source of evidence in arson fires which have been little studied. The objective of this study is to characterize a series of 22 such products using capillary gas chromatography (GC) and three-dimensional (3-D) fluorescence spectroscopy.It was found that 3-D fluorescence is well able to differentiate among products whose characteristics, including GC, are quite similar. It can also determine if two samples could be the same brand or not. When samples are evaporated or combusted, it is still possible to obtain 3-D fluoresence spectra and GCs. The GCs are even more nondescript, whereas evaporated 3-D spectra are reproducible and characteristic although they do not correlate well with those of neat samples. 3-D fluorescence spectra of combusted samples do not reproduce well because of the inability to properly control the conditions of combustion.

Bacteriophage capsid assembly pathways provide excellent model systems to study large-scale conformational changes and other mechanisms that regulate the formation of macromolecular complexes. These capsids are formed from proheads: relatively fragile precursor particles which mature by undergoing extensive remodeling. Phage HK97 employs novel features in its strategy for building capsids, including assembly without a scaffolding protein, and the formation of a network of covalent cross-links between neighboring subunits in the mature virion. In addition, proteolytic cleavage of the capsid protein from 42 kDa to 31 kDa is essential for maturation. To investigate the structural bases for proteolysis and cross-linking, we have used cryo-electron micrographs to reconstruct the three-dimensional structures of purified particles from four discrete stages in the assembly pathway: Prohead I, Prohead II, Head I and Head II. Prohead I has icosahedralT= 7 packing of blister-shaped pentamers and hexamers. The pentamers are 5-fold symmetric, but the hexamers exhibit an unusual departure from 6-fold symmetry, as if two trimers had undergone a shear dislocation of about 25 Å. Proteolytic conversion to Prohead II leaves the outer surface largely unchanged, but a major loss of density from the inner surface is observed, which we infer to represent the excision of the aminoterminal domains of the capsid protein. Upon expansion to the Head I state, the capsid becomes markedly larger, thinner walled, and more polyhedral: moreover, the capsomer shapes change radically; especially notable is the disappearance of the large hexon dislocation. No differences between Head I and the covalently cross-linked Head II could be observed at the current resolution of about 25 Å, from which we infer that it is the conformational rearrangements effected by expansion that create the micro-environments needed for the autocatalytic formation of the iso-dipeptide bonds found in the mature virions (“pseudo-active sites”).

Recently, recombinant baculoviruses have been used to show that expression of six herpes simplex virus type 1 genes results in the formation of capsid-like particles. We have applied cryoelectron microscopy and three-dimensional image reconstruction to establish their structural authenticity to a resolution of approximately 2.7 nm. By comparing capsids assembled with and without the expression of gene UL35, we have confirmed the presence of six copies of its product, VP26 (12 kDa), around each hexon tip. However, VP26 is not present on pentons, indicating that the conformational differences between the hexon and penton states of the major capsid protein, VP5, extend to the VP26 binding site.

Infection by certain human papillomavirus types is regarded as the major risk factor in the development of cervical cancer, one of the most common cancers of women worldwide. Analysis of the immunogenic and structural features of papillomavirus virions has been hampered by the inability to efficiently propagate the viruses in cultured cells. For instance, it has not been established whether the major capsid protein L1 alone is sufficient for virus particle assembly. In addition, it is not known whether L1, L2 (the minor capsid protein), or both present the immunodominant epitopes required for induction of high-titer neutralizing antibodies. We have expressed the L1 major capsid proteins of bovine papillomavirus type 1 and human papillomavirus type 16 in insect cells via a baculovirus vector and analyzed their conformation and immunogenicity. The L1 proteins were expressed at high levels and assembled into structures that closely resembled papillomavirus virions. The self-assembled bovine papillomavirus L1, in contrast to L1 extracted from recombinant bacteria or denatured virions, also mimicked intact bovine papillomavirus virions in being able to induce high-titer neutralizing rabbit antisera. These results indicate that L1 protein has the intrinsic capacity to assemble into empty capsid-like structures whose immunogenicity is similar to infectious virions. This type of L1 preparation might be considered as a candidate for a serological test to measure antibodies to conformational virion epitopes and for a vaccine to prevent papillomavirus infection.

We hypothesized that withdrawal of nasal continuous positive airway pressure (CPAP) in patients with sleep apnea would produce a measurable stress response. To test this hypothesis, we ceased CPAP in eight patients regularly using nasal CPAP long term and measured the effect on sleep apnea as well as plasma and urinary levels of the stress hormones, noradrenaline, cortisol and adrenocorticotropic hormone (ACTH). CPAP withdrawal led to an immediate recurrence of sleep apnea with increases in apnea index, arousal index and oxygen desaturation (all p < .0001) but no change in levels of noradrenaline, cortisol or ACTH. We conclude that acute withdrawal of CPAP in patients with sleep apnea does not lead to a classic stress response.

Uridine kinase has been purified to homogeneity from Ehrlich ascites tumor cells. For the phosphate acceptor site, the enzyme shows substrate specificity only for ribopyrimidine nucleosides and is active with various analogs that have limited structural alterations; both endocyclic and exocyclic substituents can be acceptable. Of nucleosides that have been used in the chemotherapy of cancer, 5-fluorouridine, 6-azauridine, and 3-deazauridine are good substrates, whereas arabinosylcytosine is a poor substrate. No analogs are better substrates than the physiological substrates uridine and cytidine. 5', 5''' -P1, P4-Bisnucleoside oligophosphate bisubstrate analogs (e.g., Ap4U, Ap5U) were synthesized and tested as inhibitors. The most effective compound was Ap4U; with a Ki of 197 microM, it bound more tightly than ATP but no better than uridine. Ap3A, Ap4A, and Ap5A were also tested, with the result that both Ap4A and Ap4U were most effective, suggesting that this size of bisubstrate analog most closely approaches the spacing of the catalytic site.

Nine cases in the literature and seven patients in our series with hipache due to avascular necrosis of the femoral head have been reviewed. The onset of symptoms is related to pregnancy.

Substrate inhibition was observed with the heterodimeric (p66/p51) and the homodimeric (p66/p66, p51/p51) forms of human immunodeficiency virus type 1 reverse transcriptase (RNA-dependent DNA polymerase, EC 2.7.7.49). An apparent Ki value of 195 +/- 37 microM was determined for dTTP using the bacterial cloned and expressed heterodimer. Similar values were obtained with the homodimeric and the virus-encoded enzymes. When poly-(rC).p(dG)10 was used as template-primer, dGTP exhibited substrate inhibition with an apparent Ki value of 189 +/- 32 microM. Substrate inhibition was not observed with dTTP when DNA.DNA template-primers were used. Hill coefficients for substrate binding determined in the presence of saturating concentrations of template-primer were equal to 1.0, suggesting that substrate inhibition of the heterodimer is not the result of an allosteric mechanism involving the p51 subunit. Furthermore, UV crosslinking experiments with [gamma-32P]dTTP showed crosslinking only to the p66 subunit. Substrate inhibition was not as pronounced with other retroviral reverse transcriptases as it was with human immunodeficiency type 1 reverse transcriptase.