Chromosome-level Dinobdella ferox genome provided a molecular model for its specific parasitism

BACKGROUND

Dinobdella ferox is the most frequently reported leech species parasitizing the mammalian nasal cavity. However, the molecular mechanism of this special parasitic behavior has remained largely unknown.

METHODS

PacBio long-read sequencing, next-generation sequencing (NGS), and Hi-C sequencing were employed in this study to generate a novel genome of D. ferox, which was annotated with strong certainty using bioinformatics methods. The phylogenetic and genomic alterations of D. ferox were then studied extensively alongside the genomes of other closely related species. The obligatory parasitism mechanism of D. ferox was investigated using RNA-seq and proteomics data.

RESULTS

PacBio long-read sequencing and NGS yielded an assembly of 228 Mb and contig N50 of 2.16 Mb. Along Hi-C sequencing, 96% of the sequences were anchored to nine linkage groups and a high-quality chromosome-level genome was generated. The completed genome included 19,242 protein-coding genes. For elucidating the molecular mechanism of nasal parasitism, transcriptome data were acquired from the digestive tract and front/rear ends of D. ferox. Examining secretory proteins in D. ferox saliva helped to identify intimate connections between these proteins and membrane proteins in nasal epithelial cells. These interacting proteins played important roles in extracellular matrix (ECM)-receptor interaction, tight junction, focal adhesion, and adherens junction. The interaction between D. ferox and mammalian nasal epithelial cells included three major steps of pattern recognition, mucin connection and breakdown, and repair of ECM. The remodeling of ECM between epithelial cells of the nasal mucosa and epithelial cells of D. ferox may produce a stable adhesion environment for parasitism.

CONCLUSIONS

Our study represents the first-ever attempt to propose a molecular model for specific parasitism. This molecular model may serve as a practical reference for parasitism models of other species and a theoretical foundation for a molecular process of parasitism.

A new species of medicinal leech in the genus Hirudo Linnaeus, 1758 (Hirudiniformes, Hirudinidae) from Tianjin City, China

Medicinal leeches in the genus Hirudo have been utilized for therapeutic procedures for thousands of years. To date, six known species of Hirudo are widely distributed in different regions of the Eurasian continent. In this study, a new medicinal leech species Hirudotianjinensis Liu, sp. nov. is described based upon specimens collected from Tianjin City, China. The new species can be distinguished from its congeners by a combination of characters: blackish green dorsum with five continuous yellow longitudinal stripes; six sensillae on dorsal annulus a2 of segments VIII–XXV; greyish green ventrum with irregular bilateral dark brown spots; dorsum and abdomen separated by a pair of pale yellow stripes; front half atrium wrapped by white prostate; apparent albumen gland; epididymis massive in relation to ejaculatory bulb. The phylogenetic tree based upon COI implies a sister relationship to H.nipponia Whitman, 1886. A key to the known species is provided.

Pauli Shielding and Breakdown of Spin Statistics in Multielectron Multi-Open-Shell Dynamical Atomic Systems

We report on C^{3+}(1s2ℓ2ℓ^{'} ^{2S+1}L)-resolved cross sections of electron capture in collisions of swift C^{4+}(1s2s ^{3}S) ions with helium and hydrogen. The study focuses on the formation of doubly excited triply open-shell C^{3+}(1s2s2p) ^{4}P and ^{2}P_{±} states with emphasis on the ratio R of their cross sections as a measure of spin statistics. Using zero-degree Auger projectile spectroscopy and a three-electron close-coupling semiclassical approach, we resolve a long-standing puzzle and controversy on the value of R and on the effect of cascades, to clarify the underlying physics. The present results invalidate the frozen core approximation generally used in the past when considering electron capture in multielectron multi-open-shell quantum systems. A distinctive screening effect due to the Pauli exclusion principle (Pauli shielding) is proposed to account for the value of R, consistent with our findings.

Evaluation and Countermeasures of the Implementation of Forensic Clinical Identification Standards Based on the Perspective of Accreditation

Abstract

The new Standardization Law, implemented in 2018, has added a standard post-implementation evaluation system, aiming to continuously improve the quality of standards through post-implementation evaluation. Standards in the forensic science field are closely related to accreditation activities. Forensic science standards are not only the criteria on which accreditation activities are carried out, but also one of the key contents of the inspection of forensic science institutions in accreditation activities. Since 2018, the certification and accreditation policies in the forensic science field have also been changed, which has brought impacts on the construction of a standard system based on accreditation.This paper analyzes the standard data from China National Accreditation Center from Conformity Assessment on forensic clinical identification accreditation assessment. It points out that the current coverage of laboratory accreditation activities is limited, the development in different provinces is unbalanced, and there is overlap and crossover in the standards in use. It is emphasized that the construction of the national forensic science standardization technical committee, the improvement of the forensic science standard system, the establishment of the standard implementation evaluation index system, and promotion of the coordination of standards, and the certifications and accreditations should be accelerated, in order to continue to promote the standardization and accreditation activities in the field of forensic science.

Double Electron Capture in H^{+}+H^{-} Collisions

We have investigated the double electron capture process in the H^{+}+H^{-} collision system for energies from 60 eV to 20 keV. Despite the apparent simplicity of this highly correlated system, all previous calculations fail to reproduce the experimental total cross sections. Moreover, the latter exhibit oscillations that have been previously attributed to quantum interferences between the gerade and ungerade ionic states of the transient molecule formed during the collision. For this process, we present the absolute cross sections obtained from a fully correlated two-active-electron semiclassical atomic-orbital close-coupling approach. Our results reproduce well the experimental data in both magnitude and shape. Furthermore, we demonstrate that the oscillations stem from coherence effects between double electron capture and other two-electron inelastic channels, namely the transfer-excitation processes. This alternative interpretation is supported by a Rosenthal-like model based on a molecular treatment of the collision. Our results shed new light on this old but challenging problem.

Serum matrix metalloproteinases-3 levels in patients with ankylosing spondylitis

Cumulated evidence indicates that matrix metalloproteinase-3 (MMP-3) is significantly involved in cancer progression. Recent studies yielded conflicting results regarding the association between serum MMP-3 and ankylosing spondylitis (AS). To clarify this correlation, we performed a meta-analysis. Potential relevant studies were identified by searching the following databases: PubMed, Embase, CINAHL, Science Citation Index database, the Cochrane Library, Current Contents Index, Chinese Biomedical, the Chinese Journal Full-Text, and the Weipu Journal. Data from eligible studies were extracted and included into the meta-analysis using a random-effect model. Standardized mean differences (SMDs) and 95% confidence intervals (CIs) were used to assess the association between serum MMP-3 levels and AS. Thirteen case-control studies, including 707 AS cases and 442 healthy controls, were selected for the meta-analysis. The results indicate a significantly higher serum MMP-3 level in patients with AS than that in the controls (cases vs controls: SMD = 1.31, 95%CI = 0.84-1.78, P < 0.001). Ethnicity-subgroup analysis indicated a higher MMP-3 level in Asian and Caucasian patients with AS (all P < 0.05). This meta-analysis indicates that increased serum MMP-3 level correlates with the development of AS, suggesting that MMP-3 may present a clinical value in reflecting the progression of AS. Further larger sample size studies are warranted.

Room temperature electrical and thermal switching CNT/hexadecane composites

A large contrast in the electrical and thermal conductivities via a first order phase transition in surface-functionalized carbon nanotube(CNT)/hexadecane composites is reported. Surface modification of the CNTs improves the electrical conductivity contrast and the stability of the composites. We demonstrate that, with these composites, the electrical conductivity changes above 10(5) times and the thermal conductivity varies up to 3 times at 18 °C.

Experimental investigation of heat conduction mechanisms in nanofluids. Clue on clustering

Heat conduction mechanisms in nanofluids, fluids seeded with nanoparticles, have been extensively scrutinized in the past decades to explain some experimental observations of their enhanced thermal conductivity beyond the effective medium theory. Although many mechanisms such as Brownian motion, clustering, ballistic transport, and internanoparticle potential are speculated, experimental proof of any of the mechanisms has been difficult. Here, we investigate the mechanisms experimentally by thermal conductivity measurements and structural analysis for the same materials in both liquid and solid states. These studies strongly suggest that clustering holds the key to the thermal conductivity enhancement of nanofluids.

Enhanced recovery of a secreted mammalian protein from suspension culture of genetically modified tobacco cells

Increasing the level of recovery of mammalian proteins secreted by a genetically modified Nicotiana tabacum was explored in suspension culture. As a model protein system, a mouse monoclonal antibody heavy chain gamma (MAb HC) with an antigen specificity for p-azophenylarsonate was used. Consistent with findings for other plant cell suspension culture systems expressing proteins with mammalian leader sequences, the synthesized mouse MAb HC was secreted through the plasma membrane. In addition, the majority of the MAb HC was also secreted through the cell wall into the growth medium. However, efficient recovery of the protein was only possible when the protein stabilizing agent, polyvinylpyrrolidone (PVP) was present in the plant cell growth medium. The presence of PVP increased the recovered concentration of secreted protein 35-fold from 0.010 to 0.36 micrograms protein/ml culture medium. Biological activity of the approximately 50-kDa MAb HC polypeptide was demonstrated by arsonate affinity matrix binding as determined by Western blot analysis. In addition to antigen binding activity, the secreted protein also exhibited reactivity to protein G, a protein which specifically binds mouse IgG. These findings are important because they demonstrate that culture conditions can significantly influence the concentration of a biologically active foreign protein secreted from plant cells into the media of suspension cultures. The ability to increase the efficiency of mammalian protein production in plant suspension culture systems should provide significant advantage over protein production in intact transgenic plants which require cultivation, harvesting, and expensive extraction procedures to obtain nonsecreted foreign proteins.