Molecular distinction of phosphatidylcholine synthesis between the CDP-choline pathway and phosphatidylethanolamine methylation pathway

In addition to the CDP-choline pathway for phosphatidylcholine (PC) synthesis, the liver has a unique phosphatidylethanolamine (PE) methyltransferase activity for PC synthesis via three methylations of the ethanolamine moiety of PE. Previous studies indicate that the two pathways are functionally different and not interchangeable even though PC is the common product of both pathways. This study was designed to test the hypothesis that these two pathways produce different profiles of PC species. The PC species from these two pathways were labeled with specific stable isotope precursors, D9-choline and D4-ethanolamine, and analyzed by electrospray tandem mass spectrometry. Our studies revealed a profound distinction in PC profiles between the CDP-choline pathway and the PE methylation pathway. PC molecules produced from the CDP-choline pathway were mainly comprised of medium chain, saturated (e.g. 16:0/18:0) species. On the other hand, PC molecules from the PE methylation pathway were much more diverse and were comprised of significantly more long chain, polyunsaturated (e.g. 18:0/20:4) species. PC species from the methylation pathway contained a higher percentage of arachidonate and were more diverse than those from the CDP-choline pathway. This profound distinction of PC profiles may contribute to the different functions of these two pathways in the liver.

Phosphatidylethanolamine N-methyltransferase from liver

Phosphatidylethanolamine N-methyltransferase (PEMT) converts phosphatidylethanolamine to phosphatidylcholine. Most PEMT activity (PEMT1) is associated with endoplasmic reticulum. A second form of the enzyme (PEMT2) has been localized to the mitochondria-associated membrane. PEMT2 is a 22.5-kDa protein that has been purified from rat liver. The rat liver PEMT2 cDNA and the murine PEMT gene have been cloned and characterized. The PEMT gene encodes both forms of the enzyme. Deletion of the PEMT gene eliminates all activity in liver that converts phosphatidylethanolamine to phosphatidylcholine. The activity of PEMT is regulated by supply of the substrates, phosphatidylethanolamine and S-adenosylmethionine, and by the product S-adenosylhomocysteine. The expression of the gene is regulated during development and by the supply of choline in the diet. There is reciprocal regulation of the Kennedy pathway for phosphatidylcholine biosynthesis (via CDP-choline) and phosphatidylethanolamine N-methyltransferase. Several experimental approaches suggest that this enzyme might play a role in regulation of hepatocyte growth and cell division.

Genome-wide gene expression profiles of the developing mouse hippocampus

We have analyzed the developmental molecular programs of the mouse hippocampus, a cortical structure critical for learning and memory, by means of large-scale DNA microarray techniques. Of 11,000 genes and expressed sequence tags examined, 1,926 showed dynamic changes during hippocampal development from embryonic day 16 to postnatal day 30. Gene-cluster analysis was used to group these genes into 16 distinct clusters with striking patterns that appear to correlate with major developmental hallmarks and cellular events. These include genes involved in neuronal proliferation, differentiation, and synapse formation. A complete list of the transcriptional changes has been compiled into a comprehensive gene profile database (http://BrainGenomics.Princeton.edu), which should prove valuable in advancing our understanding of the molecular and genetic programs underlying both the development and the functions of the mammalian brain.

Chitosan-based nanoparticles for topical genetic immunization

Numerous studies have reported the prophylactic and therapeutic use of genetic vaccines for combating a variety of infectious diseases in animal models. Recent human clinical studies with the gene gun have validated the concept of direct targeting of dendritic cells (Langerhan's cells) in the viable epidermis of the skin. However, it is unclear whether the gene gun technology or other needle-free devices will become commercially viable. The objective of our studies was to investigate the topical application of chitosan-based nanoparticles containing plasmid DNA (pDNA) as a potential approach to genetic immunization. Two types of nanoparticles were investigated: (i) pDNA-condensed chitosan nanoparticles, and (ii) pDNA-coated on pre-formed cationic chitosan/carboxymethylcellulose (CMC) nanoparticles. These studies showed that both chitosan and a chitosan oligomer can complex CMC to form stable cationic nanoparticles for subsequent pDNA coating. Selected pDNA-coated nanoparticles (with pDNA up to 400 microg/ml) were stable to challenge with serum. Several different chitosan-based nanoparticles containing pDNA resulted in both detectable and quantifiable levels of luciferase expression in mouse skin 24 h after topical application, and significant antigen-specific IgG titer to expressed beta-galactosidase at 28 days.

A genetic defect in phosphatidylcholine biosynthesis triggers apoptosis in Chinese hamster ovary cells

We have investigated the cell death of a Chinese hamster ovary mutant (MT-58) with a thermo-sensitive CTP:phosphocholine cytidylyltransferase, the rate-limiting enzyme of the CDP-choline pathway for phosphatidylcholine biosynthesis (Esko, J. D., Wermuth, M. M., and Raetz, C. R. H. (1981) J. Biol. Chem. 256, 7388-7393). After MT-58 cells were shifted to the restrictive temperature of 40 degrees C, the cytidylyltransferase was inactivated immediately leading to a decrease in phosphatidylcholine biosynthesis and cell death. DNA content and number of cells in the S phase decreased significantly in the dying MT-58 cells according to flow cytometrical analyses. The fragmentation of genomic DNA was detected by DNA ladders in agarose gel and release of the prelabeled genomic DNA into cytosolic fractions 14 h after the temperature shift. The dying cells underwent a dramatic reduction of cellular volume while maintaining the membrane containment of cellular contents. These events indicated that the inactivation of cytidylyltransferase triggered apoptosis in Chinese hamster ovary cells. This is the first report that apoptosis was induced in cultured cells, not by an added agent, but by a mutation in phospholipid biosynthesis.

Bradyrhizobium liaoningense sp. nov., isolated from the root nodules of soybeans

Seventeen strains of extra-slowly growing (ESG) soybean rhizobia isolated from root nodules of Glycine soja and Glycine max growing in five provinces (Liaoning, Heilongjiang, Shanxi, Hubei, and Anhui) in the People's Republic of China were compared with 48 reference strains belonging to the genera Bradyrhizobium, Rhizobium, and Agrobacterium by performing a numerical analysis of 191 phenotypic features. Our results showed that all of the ESG strains examined clustered closely in the genus Bradyrhizobium but were separated from Bradyrhizobium japonicum at the species level and that they could be differentiated from Rhizobium and Agrobacterium species at the genus level. On the basis of the results of our numerical taxonomy analysis, a genomic DNA G & C content analysis, DNA-DNA hybridization experiments, a partial 16S rRNA sequence analysis, a serological analysis, an N and C content analysis, and an N/C ratio analysis of members of the three groups of soybean rhizobia, we propose the name Bradyrhizobium liaoningense sp. nov. for the ESG strains; the type strain of this species is strain 2281.

Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.

Peroral endoscopic remyotomy for failed Heller myotomy: a prospective single-center study

BACKGROUND AND STUDY AIMS

Recurrence/persistence of symptoms occurs in approximately 20 % of patients after Heller myotomy for achalasia. Controversy exists regarding the therapy for patients in whom Heller myotomy has failed. The aim of the current study was to evaluate the efficacy and feasibility of peroral endoscopic myotomy (POEM), a new endoscopic myotomy technique, for patients with failed Heller myotomy.

PATIENTS AND METHODS

A total of 12 patients with recurrence/persistence of symptoms after Heller myotomy, as diagnosed by established methods and an Eckardt score of ≥ 4, were prospectively included. The primary outcome was symptom relief during follow-up, defined as an Eckardt score of ≤ 3. Secondary outcomes were procedure-related adverse events, lower esophageal sphincter (LES) pressure on manometry, reflux symptoms, and medication use before and after POEM.

RESULTS

All 12 patients underwent successful POEM after a mean of 11.9 years (range 2 - 38 years) from the time of the primary Heller myotomy. No serious complications related to POEM were encountered. During a mean follow-up period of 10.4 months (range 5 - 14 months), treatment success was achieved in 11/12 patients (91.7 %; mean score pre- vs. post-treatment 9.2 vs. 1.3; P < 0.001). Mean LES pressure was 29.4 mmHg pre-treatment and 13.5 mmHg post-treatment (P < 0.001). One patient developed mild reflux symptoms and required intermittent medication with proton pump inhibitors.

CONCLUSIONS

POEM seems to be a promising new treatment for failed Heller myotomy resulting in short-term symptom relief in > 90 % of cases. Previous Heller myotomy may make subsequent endoscopic remyotomy more challenging, but does not prevent successful POEM.

First result from the Alpha Magnetic Spectrometer on the International Space Station: precision measurement of the positron fraction in primary cosmic rays of 0.5-350 GeV

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250  GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

Construction of a stable microbial community with high cellulose-degradation ability

We bred a microbial community capable of degrading rice straw with high efficiency. The microbial community degraded more than 60% of rice straw within 4 days at 50 degrees C. The high stability of the community's degradation ability was demonstrated by its tolerance of being subcultured several times in medium with/without cellulosic material, being heated to 95 degrees C, and freezing at -80 degrees C. The community degraded both nonsterilized and sterilized substrate; and its degradation ability was not affected by pH changes in the medium (initial pH 5-9). PCR-denaturing gradient gel electrophoresis (DGGE) analyses based on 16S rDNA fragments showed that the community structure remained constant after multiple subcultures extending over 2 years. DNA sequence analyses of DGGE bands indicated the coexistence of both aerobic and anaerobic bacteria in the community.

The multidrug resistance-associated protein (MRP) subfamily (Yrs1/Yor1) of Saccharomyces cerevisiae is important for the tolerance to a broad range of organic anions

We have cloned and characterized a Saccharomyces cerevisiae gene YRS1 that complements the phenotype of the mutant sensitive to the anionic drug reveromycin A. The YRS1 gene, which is identical to the recently identified YOR1 gene, encodes a protein with extensive homology to the human multidrug resistance-associated protein (MRP) and the yeast cadmium factor (Ycf1). A chromosomal deletion of YRS1 lead to viable Deltayrs1 cells, which exhibited hypersensitivity to reveromycin A. Elevation of the YRS1 gene dosage in wild type cells conferred increased resistance to reveromycin A. By analyzing the effect of YRS1 disruption and overexpression it was demonstrated that Yrs1 is involved in the detoxification of a wide range of the organic anions that contain carboxyl group(s) but none of the other type of toxic compounds examined. Fluorescence-activated cell sorter analysis indicated the increased accumulation of the anionic fluorescent compound rhodamine B in Deltayrs1 cells. The expression of YRS1 was induced strikingly by reveromycin A. These results suggest that Yrs1 is a multispecific organic anion transporter important for tolerance against toxic environmental organic anions. Yrs1 had an overlapping specificity with Ycf1 in the resistance to cadmium.

Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station

Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.

Electron and positron fluxes in primary cosmic rays measured with the alpha magnetic spectrometer on the international space station

Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ∼30  GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

High statistics measurement of the positron fraction in primary cosmic rays of 0.5-500 GeV with the alpha magnetic spectrometer on the international space station

A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above ∼200  GeV the positron fraction no longer exhibits an increase with energy.

Double pancake bonds: pushing the limits of strong π-π stacking interactions

The concept of a double-bonded pancake bonding mechanism is introduced to explain the extremely short π-π stacking contacts in dimers of dithiatriazines. While ordinary single pancake bonds occur between radicals and already display significantly shorter interatomic distances in comparison to van der Waals (vdW) contacts, the double-bonded pancake dimer is based on diradicaloid or antiaromatic molecules and exhibits even shorter and stronger intermolecular bonds that breach into the range of extremely stretched single bonds in terms of bond distances and binding energies. These properties give rise to promising possibilities in the design of new materials with high electrical conductivity and for the field of spintronics. The analysis of the double pancake bond is based on cutting edge electron correlation theory combining multireference (nondynamical) effects and dispersion (dynamical) contributions in a balanced way providing accurate interaction energies and distributions of unpaired spins. It is also shown that the present examples do not stand isolated but that similar mechanisms operate in several analogous nonradical molecular systems to form double-bonded π-stacking pancake dimers. We report on the amazing properties of a new type of stacking interaction mechanism between π conjugated molecules in the form of a "double pancake bond" which breaks the record for short intermolecular distances and provides formidable strength for some π-π stacking interactions.

Antirotation proximal femoral nail versus dynamic hip screw for intertrochanteric fractures: a meta-analysis of randomized controlled studies

BACKGROUND

Previous studies comparing proximal femoral nail antirotation (PFNA) with dynamic hip screw (DHS) for peritrochanteric fractures reported conflicting findings. The objective of this meta-analysis was to compare the efficacy and safety of PFNA and DHS for pertrochanteric fractures.

HYPOTHESIS

PFNA achieves better efficacy for peritrochanteric fractures compared with DHS.

MATERIALS AND METHODS

Relevant randomized controlled trials comparing PFNA with DHS for pertrochanteric fractures were assessed for eligibility and included into this meta-analysis. Data were extracted independently and methodological quality was further assessed. The inclusion criteria of this meta-analysis were: randomized controlled trials comparing PFNA with DHS for pertrochanteric fractures and reporting at least one of these main outcomes, including operating time, blood loss, all causes mortality, and complications.

RESULTS

Five randomized controlled trials were finally included into this meta-analysis. Pooled results showed there were less blood loss (weighted mean difference Blood loss=-249.75ml, 95%CI -303.83 to -195.67, P<0.0001) and fewer complications (Odds ratio=0.40, 95%CI 0.23 to 0.70, P=0.001) in the PFNA group compared with the DHS group. However, there was no difference in term of mortality between those two groups (Odds ratio mortality=1.13, 95%CI 0.47 to 2.69, P=0.79). Sensitivity analysis by sequential omission of individual studies showed that the significance of pooled odds ratios was robust, which suggested this outcome was credible.

DISCUSSION

PFNA can benefit peritrochanteric fractures patients with less blood loss and fewer complications compared with DHS. The significant heterogeneity among the included trials for intraoperative blood loss, and operation time may be attributable to variation in the skills of the surgeons and the different types of perirochanteric fractures. In addition, more powered randomized studies are needed to identify the findings from this meta-analysis, and the effects of long-term follow-up also need further study, especially the impact on the mortality.

LEVEL OF EVIDENCE

Level II, meta-analysis of low powered randomized study.

Lysozyme separation by hollow-fibre ultrafiltration

This paper discusses the purification of lysozyme from chicken egg white using hollow-fibre ultrafiltration (30kDa MWCO, polysulphone membrane). Lysozyme is preferentially transmitted through the membrane while the membrane largely retains other egg white proteins. Improvement in system hydrodynamics resulted in an increase in permeate flux while lysozyme transmission remained unaffected, leading to higher productivity. The percentage purity of lysozyme obtained was generally insensitive to system hydrodynamics. The permeate flux and productivity increased with increase in transmembrane pressure (TMP) before levelling off around 0.7bar. However, the TMP did not have any pronounced effect on the transmission and the purity of lysozyme. Experiments carried out in the diafiltration mode showed that moderately pure lysozyme (80-90%) could be obtained in an extended operation.

Expression of phosphatidylethanolamine N-methyltransferase-2 is markedly enhanced in long term choline-deficient rats

When rats are fed a choline-deficient (CD) diet, acute fatty liver develops along with other biochemical changes. However, when choline deficiency is prolonged, the growth rate of CD rats is similar to that of control rats fed a choline-supplemented diet. Furthermore, CD rats maintain their levels of choline-containing lipids, such as phosphatidylcholine, lysophosphatidylcholine, and sphingomyelin. The mechanism for this compensation in CD rats was investigated. We screened the major tissues for the activities of two important enzymes involved in the biosynthesis of phosphatidylcholine, CTP:phosphocholine cytidylyltransferase (CT) and phosphatidylethanolamine N-methyltransferase (PEMT). Only the livers of CD rats had higher specific enzyme activities of PEMT and CT than control animals. The amount of PEMT2, one of two PEMTs in liver, increased 5-fold in CD rats after 6 weeks on the CD diet. A similar increase in the level of PEMT2 mRNA suggested that this activation was due to enhanced expression of the PEMT2 gene in CD livers. The labeling of phosphatidylcholine in isolated hepatocytes from CD rats was consistent with the conversion of PE to PC being increased as a result of a higher expression of liver PEMT. We conclude that activation of PE methylation at the level of gene expression may be the mechanism by which CD rats compensate for the lack of dietary choline.

Antiproton Flux, Antiproton-to-Proton Flux Ratio, and Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on 3.49×10^{5} antiproton events and 2.42×10^{9} proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range ∼60 to ∼500  GV, the antiproton p[over ¯], proton p, and positron e^{+} fluxes are found to have nearly identical rigidity dependence and the electron e^{-} flux exhibits a different rigidity dependence. Below 60 GV, the (p[over ¯]/p), (p[over ¯]/e^{+}), and (p/e^{+}) flux ratios each reaches a maximum. From ∼60 to ∼500  GV, the (p[over ¯]/p), (p[over ¯]/e^{+}), and (p/e^{+}) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

Yeast gene YRR1, which is required for resistance to 4-nitroquinoline N-oxide, mediates transcriptional activation of the multidrug resistance transporter gene SNQ2

We have cloned and characterized a Saccharomyces cerevisiae gene YRR1 that is important for resistance to the mutagen 4-nitroquinoline N-oxide (4-NQO). The wild-type YRR1 gene encodes a protein that contains a Zn(II)2Cys6-type zinc-finger motif. Disruption of the YRR1 gene leads to hypersensitivity to 4-NQO. A dominant mutation (YRR1-1) that confers strong resistance to 4-NQO has been identified. Epistasis analysis demonstrated that 4-NQO resistances mediated by the YRR1 and YRR1-1 alleles require the presence of the SNQ2 gene that encodes a multidrug resistance ATP binding cassette superfamily protein responsible for 4-NQO export. Northern blot analysis of SNQ2 mRNA levels indicated that Yrr1p is involved in basal and drug-induced transcriptional activation of SNQ2, whereas Pdr1p/Pdr3p transcription factors are mainly involved in basal SNQ2 expression. In the YRR1-1 mutant, the level of SNQ2 mRNA is constitutively elevated. These results establish that Yrr1p is important for 4-NQO resistance by mediating transcriptional activation of the SNQ2 gene in response to the stress imposed by 4-NQO. The gain-of-function mutation of Yrr1-1p was attributable to the duplication of a 12-amino-acid sequence generated near the carboxy terminus.

A comparative genetic map of rat, mouse and human genomes

The increasing availability of molecular markers and the development of highly efficient gene mapping strategies for the mouse, rat and human genomes have generated vast quantities of information allowing for the progressive refinement of comparative maps. In this publication we report on an updated version of our rat/mouse/human comparative genetic map, based on the mouse map. Databases for mouse, rat and human gene mapping were used for the collection of homologs mapped in the species. The comparative map was constructed with a total of 1,235 mouse loci having known homologs in the rat and/or human: 16 having homologs only in the rat, 884 having only in the human and 335 both in the rat and human. The combined length of the segments conserved between the rat and mouse spans 758 cM on the mouse map. This indicates that about 47% of the mouse genome is now covered by known rat homologous regions. Five novel regions homologous for the rat and mouse were identified. This comparative genetic map should be useful for researchers working on genetic studies in the rat, mouse and human.