Cis peptide bonds in proteins: residues involved, their conformations, interactions and locations

An analysis of a non-redundant set of protein structures from the Brookhaven Protein Data Bank has been carried out to find out the residue preference, local conformation, hydrogen bonding and other stabilizing interactions involving cis peptide bonds. This has led to a reclassification of turns mediated by cis peptides, and their average geometrical parameters have been evaluated. The interdependence of the side and main-chain torsion angles of proline rings provided an explanation why such rings in cis peptides are found to have the DOWN puckering. A comparison of cis peptides containing proline and non-proline residues show differences in conformation, location in the secondary structure and in relation to the centre of the molecule, and relative accessibilities of residues. Relevance of the results in mutation studies and the cis-trans isomerization during protein folding is discussed.

More hydrogen bonds for the (structural) biologist

Why does a given protein structure form and why is this structure stable? These fundamental biochemical questions remain fascinating and challenging problems because the physical bases of the forces that govern protein structure, stability and folding are still not well understood. Now, a general concept of hydrogen bonding in proteins is emerging. This concept involves not only N-H and O-H donor groups, but also C-H, and not only N and O as acceptor groups, but also pi-systems. We postulate that the incorporation of the entirety of these interactions leads to a more complete description of the problem, and that this could provide new perspectives and possibly new answers.

The interrelationships of side-chain and main-chain conformations in proteins

The accurate determination of a large number of protein structures by X-ray crystallography makes it possible to conduct a reliable statistical analysis of the distribution of the main-chain and side-chain conformational angles, how these are dependent on residue type, adjacent residue in the sequence, secondary structure, residue-residue interactions and location at the polypeptide chain termini. The interrelationship between the main-chain (phi, psi) and side-chain (chi 1) torsion angles leads to a classification of amino acid residues that simplify the folding alphabet considerably and can be a guide to the design of new proteins or mutational studies. Analyses of residues occurring with disallowed main-chain conformation or with multiple conformations shed some light on why some residues are less favoured in thermophiles.

Non-hydrogen bond interactions involving the methionine sulfur atom

Of all the nonbonded interactions, hydrogen bond, because of its geometry involving polar atoms, is the most easily recognizable. Here we characterize two interactions involving the divalent sulfur of methionine (Met) residues that do not need any participation of proton. In one an oxygen atom of the main-chain carbonyl group or a carboxylate side chain is used. In another an aromatic atom interacting along the face of the ring is utilized. In these, the divalent sulfur behaves as an electrophile and the other electron-rich atom, a nucleophile. The stereochemistry of the interaction is such that the nucleophile tends to approach approximately along the extension of one of the covalent bonds to S. The nitrogen atom of histidine side chain is extensively used in these nonbonded contacts. There is no particular geometric pattern in the interaction of S with the edge of an aromatic ring, except when an N-H group in involved, which is found within 40 degrees from the perpendicular to the sulfide plane, thus defining the geometry of hydrogen bond interaction involving the sulfur atom. As most of the Met residues which partake in such stereospecific interactions are buried, these would be important for the stability of the protein core, and their incorporation in the binding site would be useful for molecular recognition and optimization of the site's affinity for partners (especially containing aromatic and heteroaromatic groups). Mutational studies aimed at replacing Met by other residues would benefit from the delineation of these interactions.

Packing of aromatic rings against tryptophan residues in proteins

The geometry of the interaction of the aromatic side chains of phenylalanine (Phe), tyrosine (Tyr), tryptophan (Trp) and histidine (His) with the indole ring of Trp has been analyzed using the structures in the Protein Data Bank in order to understand the dependence of the packing behaviour on the size and chemical nature of the aromatic rings. The Phe ring prefers to interact either perpendicularly, with its edge pointing towards the Trp face, or in an offset-stacked arrangement. The edge-to-face motif is typical of a Trp-Trp pair. While parallel stacking is the dominant feature of Trp-His interaction, Tyr packs in a more uniform manner around Trp with a higher than expected occurrence at the edge and a few cases of possible OH-pi interaction.

Type II odontoid fractures in the elderly: an evidence-based narrative review of management

Considerable controversy exists regarding the optimal management of elderly patients with type II odontoid fractures. There is uncertainty regarding the consequences of non-union. The best treatment remains unclear because of the morbidity associated with prolonged cervical immobilisation versus the risks of surgical intervention. The objective of the study was to evaluate the published literature and determine the current evidence for the management of type II odontoid fractures in elderly. A search of the English language literature from January 1970 to date was performed using Medline and the following keywords: odontoid, fractures, cervical spine and elderly. The search was supplemented by cross-referencing between articles. Case reports and review articles were excluded although some were referred to in the discussion. Studies in patients aged 65 years with a minimum follow-up of 12 months were selected. One-hundred twenty-six articles were reviewed. No class I study was identified. There were two class II studies and the remaining were class III. Significant variability was found in the literature regarding mortality and morbidity rates in patients treated with and without halo vest immobilisation. In recent years several authors have claimed satisfactory results with anterior odontoid screw fixation while others have argued that this may lead to increased complications in this age group. Lately, the posterior cervical (Goel-Harms) construct has also gained popularity amongst surgeons. There is insufficient evidence to establish a standard or guideline for odontoid fracture management in elderly. While most authors agree that cervical immobilisation yields satisfactory results for type I and III fractures in the elderly, the optimal management for type II fractures remain unsolved. A prospective randomised controlled trial is recommended.

Different types of interactions involving cysteine sulfhydryl group in proteins

Various types of interactions involving the sulfhydryl group of free cysteine residues have been analyzed using known protein structures. In a hydrogen bond the -SH group is more amenable to donating its proton to a carbonyl group, rather than acting as a proton acceptor. It rarely interacts with a carboxylate group, and is a poor ligand to bind an anionic substrate. It is quite prone to make contacts that are definitely non-hydrogen bond type. In the S...C=O interaction the S atom is placed on the face of an amide group (mostly from the main-chain, but there are cases from the side-chain also) close to the C atom. Cases of S...N interaction, where the S atom is on top of the N atom of another residue (both main-, as well as side-chains, including the guanidinium group) are also observed. A considerable number of Cys residues have aromatic residues as neighbors, and here too, the preferred mode of interaction is along the face. The intra-residue S...C=O interaction constrains the main-chain and side-chain torsion angles (psi and chi1), whereas the inter-residue interactions are non-local and stabilize the tertiary structure. The S...C=O interaction may have a role in lowering the pKa values of the Cys residues in enzyme active sites.

Noninvasive, transthoracic, low-frequency ultrasound augments thrombolysis in a canine model of acute myocardial infarction

BACKGROUND

Limitations of coronary thrombolysis include the time to reperfusion, patency rate, and bleeding. We evaluated the use of noninvasive transcutaneous ultrasound to augment coronary thrombolysis.

METHODS AND RESULTS

In 24 dogs, a thrombotic occlusion of the left anterior descending coronary artery was induced and documented by 12-lead ECG and coronary angiography. After >/=60 minutes of occlusion, tissue-type plasminogen activator (t-PA; 1.42 mg/kg) was given intravenously over 90 minutes. A total of 12 of the 24 dogs had concomitant transcutaneous application of low-frequency ultrasound (27 kHz) over the chest. At 90 minutes, the mean TIMI grade flow in the t-PA alone group was 0.92+/-1.4 compared with 2. 42+/-1.9 in the t-PA plus ultrasound group (P=0.006). TIMI 2 to 3 flow was present in 4 of 12 cases receiving t-PA alone compared with 10 of 12 cases receiving t-PA plus ultrasound (P=0.003). At 180 minutes, mean TIMI grade flow was 0.75+/-1.4 in the t-PA alone group versus 2.58+/-0.9 in the t-PA plus ultrasound group (P=0.001). Pathological examination confirmed the angiographic patency rate and did not reveal injury secondary to ultrasound in the skin, soft tissues, heart, or lungs.

CONCLUSIONS

In vivo, the noninvasive transthoracic application of low-frequency ultrasound (1) greatly augments the efficacy of t-PA-mediated thrombolysis, (2) seems safe, and (3) has substantial potential as a noninvasive adjunct to improve coronary patency without increasing the risk of bleeding.

Electroencephalographic coherence and cortical acetylcholine during ketamine-induced unconsciousness

BACKGROUND

There is limited understanding of cortical neurochemistry and cortical connectivity during ketamine anaesthesia. We conducted a systematic study to investigate the effects of ketamine on cortical acetylcholine (ACh) and electroencephalographic coherence.

METHODS

Male Sprague-Dawley rats (n=11) were implanted with electrodes to record electroencephalogram (EEG) from frontal, parietal, and occipital cortices, and with a microdialysis guide cannula for simultaneous measurement of ACh concentrations in prefrontal cortex before, during, and after ketamine anaesthesia. Coherence and power spectral density computed from the EEG, and ACh concentrations, were compared between conscious and unconscious states. Loss of righting reflex was used as a surrogate for unconsciousness.

RESULTS

Ketamine-induced unconsciousness was associated with a global reduction of power (P=0.02) in higher gamma bandwidths (>65 Hz), a global reduction of coherence (P≤0.01) across a broad frequency range (0.5-250 Hz), and a significant increase in ACh concentrations (P=0.01) in the prefrontal cortex. Compared with the unconscious state, recovery of righting reflex was marked by a further increase in ACh concentrations (P=0.0007), global increases in power in theta (4-10 Hz; P=0.03) and low gamma frequencies (25-55 Hz; P=0.0001), and increase in power (P≤0.01) and coherence (P≤0.002) in higher gamma frequencies (65-250 Hz). Acetylcholine concentrations, coherence, and spectral properties returned to baseline levels after a prolonged recovery period.

CONCLUSIONS

Ketamine-induced unconsciousness is characterized by suppression of high-frequency gamma activity and a breakdown of cortical coherence, despite increased cholinergic tone in the cortex.

In vivo proton MR spectroscopy evaluation of pyogenic brain abscesses: a report of 194 cases

BACKGROUND AND PURPOSE

The combination of nonspecific clinical findings and similarities in morphologic appearances on imaging often makes it difficult to distinguish abscesses from other brain lesions. We present a retrospective analysis of in vivo (1)H-MR spectroscopy data for characterization of the etiology of the brain abscess based on the established criteria and demonstrate the sensitivity and specificity of metabolite markers assigned to specific bacterial groups defined by the microbial culture in 194 patients.

MATERIALS AND METHODS

Conventional MR imaging and in vivo (1)H-MR spectroscopy data were evaluated from patients with pyogenic brain abscesses, with ages ranging from 3 to 60 years. Imaging and (1)H-MR spectroscopy were performed on a 1.5T scanner. After MR imaging was performed and analyzed, pus aspirates were obtained in all patients. The causative organisms were confirmed by pus cultures.

RESULTS

Resonance of AAs with or without other metabolites on in vivo (1)H-MR spectroscopy was observed in 80% of abscesses, with a sensitivity and specificity of 0.72 and 0.30, respectively. Most obligate anaerobes and some facultative anaerobes showed the presence of Lac/Lip, AAs, and Ac with or without Suc. Mostly obligate aerobes or facultative anaerobes showed the presence of Lac and AAs, with or without lipids.

CONCLUSIONS

The presence of AAs on in vivo (1)H-MR spectroscopy is a sensitive marker of pyogenic abscess, but its absence does not rule out a pyogenic etiology. The presence of Ac with or without Suc favors an anaerobic bacterial origin of the abscess; however, this may also be seen in some of the abscesses secondary to facultative anaerobes.

Suppressed pi(0) production at large transverse momentum in central Au+Au collisions at sqrt[s(NN)]=200 GeV

Transverse momentum spectra of neutral pions in the range 1<p(T)<10 GeV/c have been measured at midrapidity by the PHENIX experiment at BNL RHIC in Au+Au collisions at sqrt[s(NN)]=200 GeV. The pi(0) multiplicity in central reactions is significantly below the yields measured at the same sqrt[s(NN)] in peripheral Au+Au and p+p reactions scaled by the number of nucleon-nucleon collisions. For the most central bin, the suppression factor is approximately 2.5 at p(T)=2 GeV/c and increases to approximately 4-5 at p(T) approximately 4 GeV/c. At larger p(T), the suppression remains constant within errors. The deficit is already apparent in semiperipheral reactions and increases smoothly with centrality.

Transport of acyclovir ester prodrugs through rabbit cornea and SIRC-rabbit corneal epithelial cell line

The purpose of this study is to assess the permeability of acyclovir (ACV) prodrugs through the rabbit corneal cell line (SIRC) as well as the cornea, and characterize the SIRC cell line for transport and metabolism studies of ester prodrugs. Prodrug derivatization of an acycloguanosine antiviral agent, acyclovir, was employed to improve its permeability across the cornea. New Zealand albino rabbits were used as an animal model for corneal studies. The SIRC cell line grown on polyester membranes was used for transport of these prodrugs. SIRC cells grown on the membrane support for 10 days developed four to six layers of epithelial cells, and this is comparable to the normal rabbit corneal epithelial layer. Transport experiments were conducted across the rabbit cornea and confluent SIRC cells using side-by-side diffusion-cell apparatus. Enzymatic hydrolysis of these compounds was evaluated in SIRC cell lysates. Appropriate reversed phase HPLC method(s) were employed for quantitation of both the prodrug and ACV simultaneously. Corneal permeabilities of some of these prodrugs (Malonyl ACV and Acetyl ACV) were higher relative to ACV. The SIRC cell line permeability values of all the prodrugs were higher compared to that of the intact cornea. The total amount of ACV-prodrugs transported, i.e., unhydrolyzed prodrugs and regenerated ACV, across the SIRC cell line was more relative to ACV. Hydrolytic studies in the SIRC cell line homogenate demonstrated the bioreversion potential of the prodrugs and the presence of enzymes, particularly the cholinesterase in the SIRC cell line. It may be concluded that the SIRC cell line is leakier compared to the cornea. Keeping in mind the limitations, the SIRC cell line after further characterization may be used for transport and metabolism studies of ester prodrugs.

Estrogen modulates paracellular permeability of human endothelial cells by eNOS- and iNOS-related mechanisms

Estradiol had a biphasic effect on permeability across cultures of human umbilical vein endothelial cells (HUVEC): at nanomolar concentrations it decreased the HUVEC culture permeability, but at micromolar concentrations it increased the permeability. The objective of the present study was to test the hypothesis that the changes in permeability were mediated by nitric oxide (NO)-related mechanisms. The results revealed dual modulation of endothelial paracellular permeability by estrogen. 1) An endothelial NO synthase (eNOS)-, NO-, and cGMP-related, Ca2+-dependent decrease in permeability was activated by nanomolar concentrations of estradiol, resulting in enhanced Cl- influx, increased cell size, and increases in the resistance of the lateral intercellular space (RLIS) and in the resistance of the tight junctions (RTJ); these effects appeared to be limited by the ability of cells to generate cGMP in response to NO. 2) An inducible NO synthase (iNOS)- and NO-related, Ca2+-independent increase in permeability was activated by micromolar concentrations of estradiol, resulting in enhanced Cl- efflux, decreased cell size, and decreased RLIS and RTJ. We conclude that the net effect on transendothelial permeability across HUVEC depends on the relative contributions of each of these two systems to the total paracellular resistance.

Modulation of cellular adhesion in bovine brain microvessel endothelial cells by a decapeptide

The importance of cell adhesion molecules in maintaining the cellular integrity of the endothelial layer is well recognized, yet their exact participation in regulating the blood-brain barrier (BBB) is poorly understood. Both Ca(2+)-dependent and Ca(2+)-independent cell adhesion molecules are found in endothelial cells. In this study, we used immunofluorescence, ELISA, Western blot and cell adhesion assay to identify a Ca(2+)-dependent cell adhesion molecule, E-cadherin, in bovine brain microvessel endothelial cells (BBMECs). Monoclonal anti-E-cadherin antibody specifically interacted with cultured BBMECs and decorated the cellular junctions with a series of punctate fluorescence spots as seen by indirect immunofluorescence using a confocal microscope. The intensity of these fluorescence spots increased after brief treatment with hIFN-gamma or CPT-cAMP. In the cellular extract of BBMECs, a 120 kDa protein was immunoprecipitated with anti-E-cadherin antibody. BBMECs did not react with anti-N-cadherin antibody, but recognized the FITC-labeled LRAHAVDVNG-NH2, a decapeptide generated from the EC-1 domain of N-cadherin, which decorated the lateral margins of the cells with fluorescence spots. A concentration-dependent binding of this decapeptide was also observed in the flow cytometry assay. BBMECs dissociated with trypsin plus Ca2+ were able to reaggregate only in the presence of Ca2+. However, such cell-cell aggregations of BBMECs were prevented by the presence of either anti-E-cadherin antibody or the decapeptide in the assay medium. These results confirm that BBMECs possess a distinct Ca(2+)-dependent cell adhesion mechanism that can be modulated by the decapeptide. This modulation of cell-cell adhesion in BBMECs by the decapeptide is thought-provoking for creating channels for paracellular drug delivery across the BBB.

Retinoids regulate tight junctional resistance of cultured human cervical cells

The objective of the study was to determine the effect of retinoids on paracellular resistance across the cervical epithelium and the mechanisms involved. The experimental model was cultures of human CaSki cells on filters, which retain phenotypic characteristics of the endocervical epithelium. End points for paracellular resistance were measurements of transepithelial electrical resistance and fluxes of pyranine (a trisulfonic acid that traverses the epithelium via the intercellular space). Paracellular resistance was significantly increased in cells grown in retinoid-free medium; the effect could be blocked and reversed with all-trans-retinoic acid (tRA) and with agonists of RAR and RXR receptors but only partially with retinol. The effect of tRA was dose dependent and saturable, with a 50% effective concentration of 0.8 nM. The increases in paracellular resistance induced by vitamin A deficiency required longer incubation in retinoid-free medium than decreases in resistance induced by retinoic acid. tRA had only a minimal effect on paracellular resistance in cells maintained in regular medium. Retinoid-free medium increased and tRA decreased the relative cation mobility across CaSki cultures. Also the effects of tRA were nonadditive to those of cytochalasin D (which decreases tight junctional resistance) and additive to those of ionomycin (which decreases the resistance of the lateral intercellular space), suggesting that tRA modulates tight junctional resistance. It is concluded that vitamin A determines the degree of paracellular resistance across cervical cells by a mechanism that involves modulation of tight junctional resistance.

Long-term in vitro maintenance of clonal abundance and leukaemia-initiating potential in acute lymphoblastic leukaemia

Lack of suitable in vitro culture conditions for primary acute lymphoblastic leukaemia (ALL) cells severely impairs their experimental accessibility and the testing of new drugs on cell material reflecting clonal heterogeneity in patients. We show that Nestin-positive human mesenchymal stem cells (MSCs) support expansion of a range of biologically and clinically distinct patient-derived ALL samples. Adherent ALL cells showed an increased accumulation in the S phase of the cell cycle and diminished apoptosis when compared with cells in the suspension fraction. Moreover, surface expression of adhesion molecules CD34, CDH2 and CD10 increased several fold. Approximately 20% of the ALL cells were in G0 phase of the cell cycle, suggesting that MSCs may support quiescent ALL cells. Cellular barcoding demonstrated long-term preservation of clonal abundance. Expansion of ALL cells for >3 months compromised neither feeder dependence nor cancer initiating ability as judged by their engraftment potential in immunocompromised mice. Finally, we demonstrate the suitability of this co-culture approach for the investigation of drug combinations with luciferase-expressing primograft ALL cells. Taken together, we have developed a preclinical platform with patient-derived material that will facilitate the development of clinically effective combination therapies for ALL.

Main-chain conformational features at different conformations of the side-chains in proteins

An analysis of the known protein structures has shown that the main-chain torsion angles, phi and psi of a residue can be affected by the side-chain torsion angle, chi1. The (chi1, psi) plot of all residues (except Gly, Ala and Pro) show six distinct regions where points are concentrated-although some of these regions are nearly absent in specific cases. The mean of these clusters can show a shift along the psi axis by as much as 30 degrees as chi1 is changed from around 180 to -60 to 60 degrees. Because of the lesser steric constraint points are more diffused along the psi axis when chi1 is approximately -60 degrees. Although points are more spread out along the phi axis in the (chi1, phi) plot, the dependence of phi on chi1 shows up in a shortened phi range (by about 30 degrees) when chi1 is around -60 degrees, and a distinct tendency of clustering of points into two regions when chi1 is approximately equal to 60 degrees, especially for the aromatic residues. Based on the dependence of the backbone conformation on its side-chain the 17 amino acids can be grouped into five classes: (i) aliphatic residues branched at the Cbeta position (although Thr is atypical), (ii) Leu (branched at the Cgamma position), (iii) aromatic residues (Trp can show some deviations), (iv) short polar residues (Asp and Asn), and (v) the remaining linear-chain residues, mainly polar. Ser and Thr have the highest inclination to occur with two different orientations of the side-chain that can be located through crystallography. Such residues exhibiting two chi1 angles have their phi and psi angles in a region that is common to the Ramachandran plots at the two different chi1 angles. The dependence of phi and psi angles on chi1 can be used to understand the helical propensities of some residues. Moreover, the average phi, psi values in the alpha-helices vary with the side-chain conformation.

Long COVID following Omicron wave in Eastern India-A retrospective cohort study

Long coronavirus disease (COVID) or postacute sequelae of coronavirus disease of 2019 (COVID-19) is widely reported but the data of long COVID after infection with the Omicron variant is limited. This study was conducted to estimate the incidence, characteristics of symptoms, and predictors of long COVID among COVID-19 patients diagnosed during the Omicron wave in Eastern India. The cohort of COVID-19 patients included were adults (≥18 years) diagnosed as severe acute respiratory syndrome coronavirus 2 positive with Reverse Transcription Polymerase Chain Reaction. After 28 days of diagnosis; participants were followed up with a telephonic interview to capture data on sociodemographic, clinical history, anthropometry, substance use, COVID-19 vaccination status, acute COVID-19 symptoms, and long COVID symptoms. The long COVID symptoms were self-reported by the participants. Logistic regression was used to determine the predictors of long COVID. The median follow-up of participants was 73 days (Interquartile range; 67-83). The final analysis had 524 participants' data; among them 8.2% (95% Confidence Interval [CI]: 6%-10.9%) self-reported long COVID symptoms. Fatigue (34.9%) was the most common reported symptom followed by cough (27.9%). In multivariable logistic regression only two predictors were statistically significant-number of acute COVID-19 symptoms ≥ five (Adjusted odds ratio (aOR) = 2.95, 95% CI: 1.30-6.71) and past history of COVID-19 (aOR = 2.66, 95% CI: 1.14-6.22). The proportion of self-reported long COVID is considerably low among COVID-19 patients diagnosed during the Omicron wave in Eastern India when compared with estimates during Delta wave in the same setting.

Protein folding in Escherichia coli: role of 23S ribosomal RNA

Post-translational control of Escherichia coli ribosome on newly synthesised polypeptide leading to its active conformation (protein folding) has been shown in the case of the enzyme beta-galactosidase. As expected, antibiotics chloramphenicol and lincomycin, which bind to 23S rRNA/50S subunit and kasugamycin and streptomycin which interact with the 30S subunit instantaneously inhibited protein synthesis when they were added to the growing cells. The increase in beta-galactosidase activity, though stopped immediately after the addition of chloramphenicol and lincomycin, went on considerably in the presence of streptomycin and kasugamycin even after the stoppage of protein synthesis.

Noninvasive transcutaneous low frequency ultrasound enhances thrombolysis in peripheral and coronary arteries

Previous studies have shown that external ultrasound with low frequencies and high intensities can enhance thrombolytic drug-induced clot dissolution during in vitro experiments. In this series of studies, we evaluated the efficacy of peripheral and coronary thrombolysis in vivo in animals by using noninvasive transcutaneous ultrasound combined with thrombolytic drugs (streptokinase and tPA) and/or microbubbles agents (dodecafluoropentane [DDFP] and perfluorocarbon-exposed sonicated dextrose albumin [PESDA]). Thrombotic occlusions were induced in 74 rabbit iliofemoral arteries and 24 canine left anterior descending (LAD) coronary arteries in this in vivo study. By using the combination of transcutaneous ultrasound and streptokinase, the angiographic patency rate in rabbit iliofemoral arteries was higher (56%-100%) than with ultrasound (6%; P < or = 0.0036) and streptokinase alone (6%; P < or = 0.0012). Also, with transcutaneous ultrasound and microbubbles, the angiographic patency rates were 76%-100% as compared with ultrasound alone (0%, P < or = 0.0003) or microbubbles alone (9%, P < or = 0.0001). In the canine study of acute myocardial infarction, thrombolysis in myocardial infarction (TIMI) grade flow at 90 minutes in the tPA alone group was 0.92 +/- 1.4 as compared with 2.42 +/- 1.9 in the tPA plus transthoracic ultrasound group (P = 0.006). There was much improved reperfusion with tPA plus ultrasound as compared with tPA alone. In vivo animal studies demonstrate that noninvasive transcutaneous ultrasound can greatly enhance the effect of clot dissolution with thrombolytic drugs and/or microbubbles, and has the potential for clinical application as an adjunctive method to improve arterial thrombolysis.

GABA in pedunculopontine tegmentum increases rapid eye movement sleep in freely moving rats: possible role of GABA-ergic inputs from substantia nigra pars reticulata

Pedunculopontine tegmentum (PPT) has GABA-ergic neurons and receives GABA-ergic projections from substantia nigra pars reticulata (SNrpr). Based on the recent studies from our and other laboratories, it was hypothesized that GABA in PPT promotes rapid eye movement (REM) sleep. In order to further study the role of GABA in PPT in REM sleep regulation, we microinjected GABA-A agonist, muscimol (200 nL, 3.5 mM), into the PPT. Muscimol in PPT significantly enhanced the amount of REM sleep by increasing the mean number of REM sleep bouts. Besides the local interneurons, GABA-ergic afferents from SNrpr are another source of GABA in PPT. In order to understand the contribution of GABA-ergic inputs from SNrpr into PPT for REM sleep regulation, SNrpr was electrically stimulated either alone or simultaneously along with the infusion of GABA-A antagonist, picrotoxin (200 nL, 0.86 mM), into the PPT. The experiment was designed with the premise that stimulation of SNrpr should increase GABA levels in PPT which should increase REM sleep comparable to that after muscimol microinjection in PPT. Further, the effect of stimulation of SNrpr on REM sleep should be antagonized by simultaneous infusion of picrotoxin into PPT. The electrical stimulation of SNrpr did not produce any significant change in sleep-wake states although it was sufficient to counter the effect of picrotoxin injection into the PPT. To overcome the limitations and confounds of electrical stimulation, SNrpr was pharmacologically stimulated by glutamate microinjection (200 nL, 5.34 mM). Infusion of glutamate into SNrpr enhanced REM sleep by increasing the mean number of REM sleep bouts, which was similar and comparable to the effect of muscimol injection into the PPT. The results confirm that GABA in PPT either from local neurons or from SNrpr promotes REM sleep.

Elliptic flow of identified hadrons in Au+Au collisions at sqrt sNN =200 GeV

The anisotropy parameter (v(2)), the second harmonic of the azimuthal particle distribution, has been measured with the PHENIX detector in Au+Au collisions at sqrt[s(NN)]=200 GeV for identified and inclusive charged particle production at central rapidities (|eta|<0.35) with respect to the reaction plane defined at high rapidities (|eta|=3-4 ). We observe that the v(2) of mesons falls below that of (anti)baryons for p(T)>2 GeV/c, in marked contrast to the predictions of a hydrodynamical model. A quark-coalescence model is also investigated.

Enhanced production of direct photons in Au + Au collisions at square root(S(NN)) = 200 GeV and implications for the initial temperature

The production of e+ e- pairs for m(e+ e-)<0.3 GeV/c2 and 1<p(T)<5 GeV/c is measured in p+p and Au+Au collisions at square root(S(NN))=200 GeV. An enhanced yield above hadronic sources is observed. Treating the excess as photon internal conversions, the invariant yield of direct photons is deduced. In central Au+Au collisions, the excess of the direct photon yield over p+p is exponential in transverse momentum, with an inverse slope T=221+/-19(stat)+/-19(syst) MeV. Hydrodynamical models with initial temperatures ranging from T(init) approximately 300-600 MeV at times of approximately 0.6-0.15 fm/c after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at approximately 170 MeV.