Global Trends in Highly Cited Studies in COVID-19 Research.

Importance: Since the onset of the COVID-19 outbreak, an extremely high number of studies have been published worldwide, with variable quality. Research trends of highly cited papers may enable identification of influential research, providing insights for new research ideas; it is therefore important to investigate trends and focus on more influential publications in COVID-19-related studies. Objective: To examine research trends of highly cited studies by conducting a bibliometric analysis of highly cited studies in the previous 2 months about COVID-19. Design, Setting, and Participants: In this cross-sectional study, Essential Science Indicators (ESI) and Web of Science (WOS) Core Collection were used to find studies with a focus on COVID-19 that were identified as highly cited studies from Clarivate Analytics. Highly cited studies were extracted from the ESI database bimonthly between January 2020 and December 2022. Bibliographic details were extracted from WOS and combined with ESI data using unique accession numbers. The number of highly cited studies was counted based on the fractional counting method. Data were analyzed from January through July 2023. Main Outcomes and Measures: The number of publications by research field, country, and institutional affiliation. Results: The number of published COVID-19-related highly cited studies was 14 studies in January to February 2020, peaked at 1292 studies in November to December 2021, and showed a downward trend thereafter, reaching 649 studies in November to December 2022. China had the highest number of highly cited studies per 2-month period until July to August 2020 (138.3 studies vs 103.7 studies for the US, the second highest country), and the US had the greatest number of highly cited studies afterward (159.9 studies vs 157.6 studies for China in September to October 2020). Subsequently, the number of highly cited studies per 2-month period published by China declined (decreasing from 179.7 studies in November to December 2020 to 40.7 studies in September to October 2022), and the UK produced the second largest number of such studies in May to June 2021 (171.3 studies). Similarly, the top 5 institutional affiliations in May to June 2020 by highly cited studies per 2-month period were from China (Huazhong University: 14.7 studies; University of Hong Kong: 6.8 studies; Wuhan University: 4.8 studies; Zhejiang University: 4.5 studies; Fudan University: 4.5 studies), while in November to December 2022, the top 5 institutions were in the US and UK (Harvard University: 15.0 studies; University College London: 11.0 studies; University of Oxford: 10.2 studies; University of London: 9.9 studies; Imperial College London: 5.8 studies). Conclusions and Relevance: This study found that the total number of highly cited studies related to COVID-19 peaked at the end of 2021 and showed a downward trend until the end of 2022, while the origin of these studies shifted from China to the US and UK.

CD81 inhibition with the cytoplasmic RNA vector producing anti-CD81 antibodies suppresses arthritis in a rat CIA model.

OBJECTIVE: Cluster of differentiation 81 (CD81) is a tetraspanin membrane protein consisting of 4 transmembrane domains and 2 outer membrane loops. CD81 inhibition is a potential treatment for rheumatoid arthritis (RA). Here, we investigated the therapeutic effects of the cytoplasmic RNA vector expressing anti-CD81 antibodies (the anti-CD81 vector) on the ankle joint synovium in collagen-induced arthritis (CIA) rats. METHODS: Body weight, paw volume, and clinical scores were measured on days 0, 7, and 10 and daily thereafter. On day 28, the ankle joints of the rats were removed and stained with haematoxylin, eosin, and Safranin O. Arthritic changes such as inflammatory cell infiltration, synovial proliferation, articular cartilage destruction, and bone erosion were evaluated by histological scoring. RESULTS: Symptom onset was delayed in the right lower limbs of the rats administered the cytoplasmic RNA vector (CIA + anti-CD81) compared with that in the control group (CIA + control). The CIA + anti-CD81 rats were heavier than the CIA + control rats. The paw volume and clinical scores were significantly lower in the CIA + anti-CD81 than in the CIA + control. The histological scores indicated significantly milder manifestations of RA in the CIA + anti-CD81 than in the CIA + control. CONCLUSIONS: Administration of the cytoplasmic RNA vector expressing anti-CD81 antibodies suppressed arthritis and joint destruction in CIA rats. Our findings suggest that the cytoplasmic RNA vector can be used to treat RA.

Source- and polymer-specific size distributions of fine microplastics in surface water in an urban river.

There is increasing concern about the environmental behaviors of microplastics (MPs), in particular fine MPs (FMPs), such as their concentrations, sources, size distributions, and fragmentation by weathering in waters. However, there is little information about size distributions of MP polymer types and their relationships to their sources. Here, we analyzed concentrations, compositions, and size distributions of 18 polymer types of MPs of >20 µm by micro-Fourier transform infrared spectroscopy with a novel pretreatment method in surface waters at five sites from the headwaters to the mouth of a Japanese river, and in influent and effluent from a sewage treatment plant (STP). The microplastic concentrations ranged from 300 to 1240 particles/m3 in surface waters. Cluster analysis identified two primary sources of MPs: residential wastewater at the headwater site and non-point sources from urban areas at downstream sites; concentrations of chemical contaminants from STPs were much higher at the downstream sites. The median particle sizes (D50) of MPs increased in urban areas at the downstream sites and were larger than those in influent and effluent. These results imply the release of larger MPs from non-point sources in urban areas. The size distributions of each polymer and all MPs could be fitted significantly to the Weibull distribution function. Values of D50, shape parameters, and scale parameters estimated from the functions were useful indicators for evaluating size distributions in detail. A significant positive correlation of D50 with the tensile strengths of virgin polymers among 13 dominant polymers detected in the surface water suggests that the fragmentation properties of each polymer are influenced by its physical strength. Multidimensional analysis with concentrations, polymeric compositions, and size distributions of MPs, including FMPs, could provide useful information about their sources and their environmental behaviors.