Multicentre study of hospitalised patients with sports- and recreational cycling-related traumatic brain injury in Hong Kong.

INTRODUCTION: Cycling is associated with a greater risk of traumatic brain injury (TBI) than other recreational activities. This study aimed to investigate the epidemiology of sports-related TBI in Hong Kong and to examine predictors for recreational cycling-induced intracranial haemorrhage. METHODS: This retrospective multicentre study included patients diagnosed with sports-related TBI in public hospitals in Hong Kong from 2015 to 2019. Computed tomography scans were reviewed by an independent assessor. The primary endpoint was traumatic intracranial haemorrhage. The secondary endpoint was an unfavourable Glasgow Outcome Scale (GOS) score at discharge from hospital. RESULTS: In total, 720 patients were hospitalised with sports-related TBI. The most common sport was cycling (59.2%). The crude incidence of cycling-related TBI was 1.1 per 100 000 population. Cyclists were more likely to exhibit intracranial haemorrhage and an unfavourable GOS score, compared with patients who had TBI because of other sports. Although 47% of cyclists had intracranial haemorrhage, only 15% wore a helmet. In multivariate analysis, significant predictors for intracranial haemorrhage were age ≥60 years, antiplatelet medication, moderate or severe TBI, and skull fracture. Among 426 cyclists, 375 (88%) had mild TBI, and helmet wearing was protective against intracranial haemorrhage, regardless of age, antiplatelet medication intake, and mechanism of injury. Of 426 cyclists, 31 (7.3%) had unfavourable outcomes on discharge from hospital. CONCLUSIONS: The incidence of sports-related TBI is low in Hong Kong. Although cycling-related head injuries carried greater risks of intracranial haemorrhage and unfavourable outcomes compared with other sports, most cyclists experienced good recovery. Helmet wearing among recreational cyclists with mild TBI was protective against intracranial haemorrhage and skull fracture.

Idiopathic Internal Thoracic Artery (ITA) Pseudoaneurysm treated with Endovascular Embolization.

A 44-year-old female was diagnosed with an ITA pseudoaneurysm in the right supraclavicular fossa. She was successfully treated with endovascular embolization. The challenges of diagnosis and treatment are discussed.

Ions and RNAs: Free Energies of Counterion-Mediated RNA Fold Stabilities.

We present an implicit ion model fo the calculation of the electrostatic free energies of RNA conformations in the presence of divalent counterions such as Mg(2+). The model was applied to the native and several non-native structures of the hammerhead ribozyme and the group I intron in Tetrahymena to study the stability of candidate unfolding intermediates. Based on a rigorous statistical mechanical treatment of the counterions that are closely associated with the RNA while handling the rest of the ions in the solution via a mean field theory in the Grand Canonical ensemble, the implicit ion model accurately reproduces the ordering of their free energies, correctly identifying the native fold as the most stable structure out of the other alternatives. For RNA concentrations in the range below 0.1 µM, divalent concentrations of ∼0.5 mM or above, and over a wide range of solvent dielectric constants, the equilibrium number of divalent ions associated with the RNA remains close to what is needed to exactly neutralize the phosphate negative charges, but the stability of compact RNA folds can be reversed when the divalent ion concentration is lower than ∼0.1 mM, causing the number of associated ions to underneutralize the RNA. In addition to calculating counterion-mediated free energies, the model is also able to identify potential high-affinity electronegative ion binding pockets on the RNA. The model can be easily integrated into an all-atom Monte Carlo RNA simulation as an implicit counterion model.

RNA Conformational Sampling: II. Arbitrary Length Multinucleotide Loop Closure.

In this paper, we describe how the inverse kinematic solution to the loop closure problem may be generalized to reclose a RNA segment of arbitrary length containing any number of nucleotides without disturbing the atomic positions of the rest of the molecule. This generalization is made possible by representing the boundary conditions of the closure in terms of a set of virtual coordinates called RETO, allowing the inverse kinematics to be reduced from the original six-variable/six-constraint problem to a four-variable/four-constraint problem. Based on this generalized closure solution, a new Monte Carlo algorithm has been formulated and implemented in a fully atomistic RNA simulation capable of moving loops of arbitrary lengths using torsion angle updates exclusively. Combined with other conventional Monte Carlo moves, this new algorithm is able to sample large-scale RNA chain conformations much more efficiently. The utility of this new class of Monte Carlo moves in generating large-loop conformational rearrangements is demonstrated in the simulated unfolding of the full-length hammerhead ribozyme with a bound substrate.

The sign problem in real-time path integral simulations: using the cumulant action to implement multilevel blocking.

A practical method to tackle the sign problem in real-time path integral simulations is proposed based on the multilevel blocking idea. The formulation is made possible by using a cumulant expansion of the action, which in addition to addressing the sign problem, provides an unbiased estimator for the action from a statistically noisy sample of real-time paths. The cumulant formulation also allows the analytical gradients of the action to be computed with little extra computational effort, and it can easily be implemented in a massively parallel environment.

Path integral studies of the rotations of methane and its heavier isotopomers in 4He nanoclusters.

Path integral Monte Carlo simulations have been carried out to study the rotations of a methane molecule and its heavier isotopomers inside a small cluster of 4He atoms at 0.3 K in order to determine how the renormalization in the methane's rotational constant is related to the quantum statistics and superfluidity of the helium shell. By changing the mass of the hydrogens and systematically varying the moment of inertia of the methane, we were able to study the effects of its rotations on the quantum statistics of the helium atoms and their countereffects on the methane's effective rotational constant. The renormalized rotational constant depends strongly on the intrinsic moment of inertia of the methane. A heavy probe favors strong templating of the helium density as well as a large renormalization in the probe's rotational constant, but a light probe shows almost no effect on the shell density or the effective rotational constant. These results suggest that in order to fully understand the superfluidity of the helium shell, the probe must be treated as an integral part of the system. We rationalize the findings in terms of a rotational smearing effect and suggest that there is no clearly quantifiable relationship between the superfluid fraction of the shell and the renormalized rotational constant of the probe for cases where the probe molecule is either light or has weak anisotropic interactions with the helium atoms.

RNA conformational sampling. I. Single-nucleotide loop closure.

We consider the loop-closure problem for nucleic acids and describe an efficient numerical algorithm for closing single-nucleotide loops in nucleic acids. Using six new internal coordinates to represent the nucleotide conformation, which we call the R-representation, the original closure problem with six free torsion angles in each nucleotide can be reduced to one with only four degrees of freedom. Simple numerical techniques have been used to solve the resulting loop-closure equations, and a test of the closure algorithm on a set of RNAs consisting of more than 7000 nucleotides was able to regenerate the native torsion angles in every nucleotide in the test set without exception. We show how the conformational probability density transforms when the original torsion angle representation is mapped onto the new R-representation. We also present statistical evidence showing that the delta and nu(2) torsion angles are coupled, and how this coupling affects the conformation probability density in the R-representation. In addition to the backbone, the same loop-closure algorithm can also be applied to close the ribose ring. The algorithm is freely available at http://tyrosine.use.edu/closure.

Cloning and differential expression of manganese superoxide dismutase (Mn-SOD) of Trichinella pseudospiralis.

The complete coding sequence of manganese superoxide dismutase (Mn-SOD) of Trichinella pseudospiralis (Tp) was obtained and characterized for the first time by degenerative reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of complementary DNA ends (RACE) reactions. The open reading frame of Tp Mn-SOD contained 663 nucleotides, encoding 220 amino acid residues. This included the conserved histidine and aspartate residues for metal binding, cysteine residues for disulfide bond formation, and arginine residue for directing the superoxide ion to the protein. The presence of mitochondrial transit peptides and maturation cleavage site suggest that the cloned Tp Mn-SOD gene is a mitochondrial enzyme. It is a single copy gene containing three introns. Northern blotting suggested that the expression level of Mn-SOD is lower than Cu/Zn SOD in infective stage larvae. Semi-quantitative RT-PCR demonstrated that a single dominant transcript of Tp Mn-SOD was highly expressed in the infective-stage larvae but not in adult worms. The information provides a better understanding of the highly compartmentalized superoxide dismutases of adenophorean nematodes.

Reverse monte carlo method and its implications for generalized cluster algorithms.

We describe a novel switching algorithm based on a "reverse" Monte Carlo method, in which the potential is stochastically modified before the system configuration is moved. This new algorithm facilitates a generalized formulation of cluster-type Monte Carlo methods, and the generalization makes it possible to derive cluster algorithms for systems with both discrete and continuous degrees of freedom. The roughening transition in the sine-Gordon model has been studied with this method, and high-accuracy simulations for system sizes up to 1024(2) were carried out to examine the logarithmic divergence of the surface roughness above the transition temperature, revealing clear evidence for universal scaling of the Kosterlitz-Thouless type.

Heat-inducible translationally controlled tumor protein of Trichinella pseudospiralis: cloning and regulation of gene expression.

To elucidate the mechanism of inducing translationally controlled tumor protein (TCTP) in stress adaptation of adenophorean nematodes, the complete coding sequence of TCTP of the infective-stage larvae of Trichinella pseudospiralis was characterized. Two cDNA clones with different 3' untranslated region were identified. Tp-TCTP contained an open reading frame of 534 bp encoding 177 residues. The gene with five introns was expressed as histidine-tagged fusion protein having a molecular mass of 17.5 kDa. Quantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis showed that TCTP RNA was not accumulated when the infective-stage larvae were heat-shocked for 1 h at 45 or 60 degrees C. Using enzyme-linked immunosorbent assay and antiserum against the fusion protein, the expression of TCTP was found to be up-regulated at the translational level. The data suggest that translational regulation of TCTP may play an important role in the early heat-stress adaptation of the trichinellid. Cluster analysis demonstrated that the TCTP sequence of T. pseudospiralis is closely related to that of T. spiralis, but is diverged from the secernentean species.

Large-scale simulations of the two-dimensional melting of hard disks.

Large-scale computer simulations with more than four million particles have been performed to study the melting transition in a two-dimensional hard disk fluid. The van der Waals loop previously observed in the pressure-density relationship of smaller simulations is shown to disappear systematically with increase in sample size, but even with these large system sizes, the freezing transition still exhibits what appears to be weakly first-order behavior, though the scaling of the bond orientation order is consistent with the Halperin-Nelson-Young picture. Above this freezing transition region, scaling analysis of the translational order yields a lower bound for the melting density that is much higher than previously thought and provides compelling evidence that the solid phase first melts into a hexatic phase via a continuous transition, before it goes into the isotropic phase.

Cloning and characterization of the Cu/Zn superoxide dismutase of Trichinella pseudospiralis.

Copper/zinc (Cu/Zn) superoxide dismutase (SOD) activity was identified for the first time in both crude somatic extracts (CE) and excretory/secretory (E/S) products of Trichinella pseudospiralis. It was the dominant SOD in infective-stage larvae. Native polyacrylamide gel electrophoresis of CE and E/S products yielded a prominent band, which was cyanide-sensitive and was partly inhibited by hydrogen peroxide in SOD assay. Cytosolic Cu/Zn SOD was cloned. The 471-bp full-length cDNA sequence contained an open reading frame of 157 amino acids. The gene contained three introns. Quantitative reverse transcription-polymerase chain reaction indicated that the expression of cytosolic Cu/Zn SOD was substantially higher in infective-stage larvae than in adult worms. Cluster analysis showed that the sequence of the Cu/Zn SOD of T. pseudospiralis, an adenophorean nematode, is related to those of Brugia pahangi, Acanthocheilonema viteae, Onchocerca volvulus, and Haemonchus contortus (all belonging to the sercenentean group).

Stochastic potential switching algorithm for Monte Carlo simulations of complex systems.

This paper describes a new Monte Carlo method based on a novel stochastic potential switching algorithm. This algorithm enables the equilibrium properties of a system with potential V to be computed using a Monte Carlo simulation for a system with a possibly less complex stochastically altered potential V. By proper choices of the stochastic switching and transition probabilities, it is shown that detailed balance can be strictly maintained with respect to the original potential V. The validity of the method is illustrated with a simple one-dimensional example. The method is then generalized to multidimensional systems with any additive potential, providing a framework for the design of more efficient algorithms to simulate complex systems. A near-critical Lennard-Jones fluid with more than 20,000 particles is used to illustrate the method. The new algorithm produced a much smaller dynamic scaling exponent compared to the Metropolis method and improved sampling efficiency by over an order of magnitude.

Superfluidity in CH4-doped H2 nanoclusters.

We report a theoretical study of superfluidity in CH(4)-doped para-H(2) nanoclusters. Path integral simulations for clusters of 12-16 H(2) around a single CH(4) molecule were carried out at temperatures between 0.5 and 2 K to study the superfluid response of the cluster. The results indicate that a rapid increase in the superfluid response is expected to occur around 1 K. We analyzed the structures and statistics of these clusters and found that the larger permutation cycles which dominate the superfluid component tend to adopt ringlike structures on the surface of the CH(4) molecule.

Cloning and characterization of the mitochondrial heat-shock protein 60 gene of Trichinella spiralis.

The full-length cDNA of mitochondrial heat-shock protein (hsp) 60 of the infective-stage larva of Trichinella spiralis was cloned by degenerative PCR and rapid amplification of cDNA end reactions. The 1,945 bp full-length cDNA sequence contained an open reading frame of 576 amino acids. A mitochondrial signal peptide was located at the N-terminal and a GGM motif at the C-terminal. The gene contained ten exons and nine introns. RT-PCR analysis indicated that thermal, cold, acidic and oxidative treatment did not elicit significant changes in the expression of mitochondrial hsp 60 in the larvae. Cluster analysis showed that the sequence of the hsp 60 gene of T. spiralis is closely related to that of Drosophila melanogaster.

Characterization and cloning of metallo-proteinase in the excretory/secretory products of the infective-stage larva of Trichinella spiralis.

Inhibitor sensitivity assays using azocaesin and FTC-caesin as substrates showed that the excretory/secretory (E/S) products of the infective-stage larvae of Trichinella spiralis contained serine, metallo-, cysteine and aspartic proteinases. The activity of the metallo-proteinase was zinc ion dependent (within a range of ZnSO(4) concentrations). Gelatin-substrate gel electrophoresis revealed two bands of molecular mass 48 and 58 kDa which were sensitive to the metallo-proteinase inhibitor EDTA. The former peptide was probably a cleavage product of the latter. The authenticity of the 58 kDa metallo-proteinase as an E/S product was confirmed by immunoprecipitation. Using PCR and RACE reactions, a complete nucleotide sequence of the metallo-proteinase gene was obtained. It comprised 2,223 bp with an open reading frame encoding 604 amino acid residues. The 3' untranslated region consisted of 352 bp, including a polyadenylation signal AATAA. A consensus catalytic zinc-binding motif was present. The conserved domains suggest that the cloned metallo-proteinase belongs to the astacin family and occurs as a single copy gene with 11 introns and 10 exons. Cluster analysis showed that the sequence of the metallo-proteinase gene of T. spiralis resembles those of Caenorhabdites elegans and Strongyloides stercoralis.

Identification of some heat-induced genes of Trichinella spiralis.

Three heat-induced genes of the infective-stage larvae of Trichinella spiralis were successfully identified by the suppression subtractive hybridization (SSH) technique. As indicated by reverse Northern blotting, 19 of 25 clones were scored as differentially transcribed in the heat-shocked infective-stage larvae. The sequencing data showed the presence of 12 different genes. Three were homologous to histone H3, histone H2B and translationally controlled tumour protein (TCTP). A 0.6 kb cDNA of histone H3 was generated by the RACE method and sequenced. It contained an open reading frame of 136 amino acids that demonstrated 94% identity with genes from Drosophila hydei. Semi-quantitative RT-PCR indicated that after heat-shock treatment, the expression levels of histone H3, histone H2B and TCTP increased 4.8, 27 and 5.7-fold, respectively. Northern analysis confirmed the upregulation of histone H3, histone H2B and TCTP transcripts. The upregulation of these genes during stress conditions has not been reported in parasitic organisms. The stress proteins may play an active role to sustain the parasite after exposure to hostile host factors.

DNA-binding activity in the excretory-secretory products of Trichinella pseudospiralis (Nematoda: Trichinelloidea).

A novel DNA-binding peptide of Mr approximately 30 kDa was documented for the first time in the excretory-secretory (E-S) products of the infective-stage larvae of Trichinella pseudospiralis. Larvae recovered from muscles of infected mice were maintained for 48 h in DMEM medium. E-S products of worms extracted from the medium were analysed for DNA-binding activity by the electrophoretic mobility shift assay (EMSA). Multiple DNA-protein complexes were detected. A comparison of the Mr of proteins in the complexes indicated that they could bind to the target DNA as a dimer, tetramer or multiples of tetramers. Site selection and competition analysis showed that the binding has a low specificity. A (G/C-rich)-gap-(G/T-rich)-DNA sequence pattern was extracted from a pool of degenerate PCR fragments binding to the E-S products. Results of immunoprecipitation and electrophoretic mobility supershift assay confirmed the authenticity of the DNA-binding protein as an E-S product.

Single-stranded endonuclease activity in the excretory--secretory products of Trichinella spiralis and Trichinella pseudospiralis.

A novel acidic extracellular single-stranded endonuclease was demonstrated for the first time in the excretory-secretory (E-S) products of 2 species of Trichinella. Unlike the double-stranded endonuclease reported earlier, the single-stranded molecule is divalent cation independent and is detected in both T. spiralis and T. pseudospiralis E-S products. It hydrolysed single-stranded DNA and RNA at comparable rates. The single-stranded endonuclease was sensitive to inhibition by Zn2+ and to high concentrations of NaCl. Zymographic analysis indicated that it was encoded by at least 3 peptides of Mr approximately 50-60 kDa. The rate of hydrolysis of single-stranded targets by the E-S products was substantially higher than that of the double-stranded molecule. Due to the differences in peptide profile, divalent cation dependence, and species-specific expression, the single and double-stranded endonucleases are likely to be encoded by different proteins and may have different functions.

Characterization of endonuclease activity from excretory/secretory products of a parasitic nematode, Trichinella spiralis.

Double-stranded endonuclease activity was demonstrated for the first time in the excretory/secretory (ES) products of a parasitic nematode, Trichinella spiralis, which can reorganize host muscle cells. The endonuclease introduced double-stranded breaks to the native DNA. The ES double-stranded endonuclease(s) was sequence nonspecific, with a pH optimum below 6, and required divalent cations as a cofactor. Its activity was inhibited by the Zn2+ ion. It was detected mainly in the ES products of the infective-stage larvae of T. spiralis collected at 37 degrees C and was present in much smaller amounts in samples collected at 43 degrees C and in the products of T. pseudospiralis, a nonencapsulated species. The activity of endonuclease was blocked by antibodies against ES products. Zymographic analysis showed that the endonuclease activity was associated with at least three molecular forms, designated approximately 25, 30 and 58 kDa, respectively.