Formulation of chitosan microsphere-based oral vaccine against the scuticociliate parasite Miamiensis avidus: Evaluation of its protective immune potency in olive flounder (Paralichthys olivaceus).

Miamiensis avidus is a parasitic pathogen that causes scuticociliatosis, a severe and often lethal marine infection that affects marine fishes worldwide, including olive flounder (Paralichthys olivaceus) in Korea. This parasite infects all size groups of flounder year-round, causing recurring mortalities and huge economic losses to the Korean flounder industry each year. However, few efforts have been made to implement effective remedial measures to control this parasite. Therefore, our study sought to develop a chitosan microsphere (MS)-encapsulated inactivated vaccine (IMa + chitosan) for oral delivery (adsorbed in feed) to flounder fingerlings and assess its protective efficacy at different modalities via three in vivo experimental trials. Immunisation trial-1 was conducted to determine the effective concentration of chitosan. Our findings indicated that an IMa + chitosan 0.05 % vaccine formulation was safe and effective in providing moderate protection [46.67%-53.3 % relative percent survival (RPS)] against M. avidus intraperitoneal (IP) injection challenge at two weeks post-vaccination (wpv) compared to the IMa + chitosan 0.01 % and IMa + chitosan 0.005 % vaccines (0%-13.3 % RPS) irrespective of the antigen doses. In trial-2, the IMa + chitosan 0.05 % vaccine elicited similar protective immunity (30.8%-57.1 % RPS) in olive flounder against M. avidus at varying antigen doses (high: 2.38 × 106 cells/fish; low: 1.5 × 105 cells/fish), immunisation periods (2 and 5 wpv), and challenge modes (IP injection and immersion). Furthermore, experimental trial-3 validated the use of chitosan MS as an IMa antigen carrier to improve survivability (41.7 % RPS) in the host by significantly (p < 0.05) upregulating specific anti-M. avidus antibody titres in the fish sera and mucus of the group immunised with IMa-containing chitosan MS. In contrast, non-specific immunomodulatory effects (16.7 % RPS and enhanced mucosal antibody titres) were observed in the group treated with chitosan MS without IMa. Therefore, our findings suggested that oral administration of chitosan MS (0.05 %)-encapsulated IMa vaccine is a promising immunisation strategy against M. avidus that can protect the IMa antigen from digestive degradation, facilitates its targeted delivery to the host immune organs, and helps in orchestrating protective immune induction in olive flounder, thus controlling parasite infection.

Gonadal Abnormality and Intersexuality of Oplegnathus fasciatus (Teleostei: Oplegnathidae) Collected from the Southern Coast of Korea: A Case Report.

We report on the gonadal structure abnormality and intersexuality found from a survey regarding the reproductive potential of the rock bream, Oplegnathus fasciatus, along the southern coast of Korea. In total, 448 samples were collected for histological analysis (total length 27.5±6.8 cm; total weight 522.9±385.6 g). The sex ratio (F:M) was 1:0.46 (n=307:141), with 68.5% being females. The frequency of oocyte atresia and ovarian neoplasm in the females was 85.3% and 21.5%, respectively, and the frequency of testicular lobule and cyst deformation and testicular neoplasm in the males was 73.1% and 37.6%, respectively. The scale formation in the ovary and testis was approximately 2.0% for both sexes. The intersexuality was 42.2%, with the intersexuality among females being 49.5%, which was significantly higher than that of males (26.2%). Such findings indicate a negative impact on the reproductive output of the rock bream along the southern coast of Korea; however, a more detailed study is required to ascertain accurate causes.

Transparent, Ultrahigh-Refractive Index Polymer Film (n ∼1.97) with Minimal Birefringence (Δn <0.0010).

High refractive index (RI) thin films are of critical importance for advanced optical devices, and the high refractive index polymers (HRIPs) constitute an interesting class of materials for high RI thin films due to low cost, good processability, light weight, and high flexibility. However, HRIPs have yet to realize their full potential in high RI thin film applications due to their relatively low RI, strong absorption in the blue light region, and limited film formation methods such as rapid vitrification. Herein, we report a development of a new HRIP thin film generated through a one-step vapor-phase process, termed sulfur chemical vapor deposition (sCVD), using elemental sulfur and divinyl benzene. The developed poly(sulfur-co-divinyl benzene) (pSDVB-sCVD) film exhibited RI (measured at 632.8 nm) exceeding 1.97, one of the highest RIs among polymers without metallic elements reported to date. Because the sCVD utilized vaporized sulfur with a unique sulfur-cracking step, formation of long polysulfide chains was suppressed efficiently, while high sulfur content as high as 85 wt % could be achieved with no apparent phase separation. Unlike most of inorganic high RI materials, pSDVB-sCVD was highly transparent in the entire visible range and showed extremely low birefringence of 10 × 10-4. The HRIP thin film with unprecedentedly high RI, together with outstanding transparency and low birefringence, will serve as a key component in a wide range of high-end optical device applications.

One-step vapor-phase synthesis of transparent high refractive index sulfur-containing polymers.

High refractive index polymers (HRIPs) have recently emerged as an important class of materials for use in a variety of optoelectronic devices including image sensors, lithography, and light-emitting diodes. However, achieving polymers having refractive index exceeding 1.8 while maintaining full transparency in the visible range still remains formidably challenging. Here, we present a unique one-step vapor-phase process, termed sulfur chemical vapor deposition, to generate highly stable, ultrahigh refractive index (n > 1.9) polymers directly from elemental sulfur. The deposition process involved vapor-phase radical polymerization between elemental sulfur and vinyl monomers to provide polymer films with controlled thickness and sulfur content, along with the refractive index as high as 1.91. Notably, the HRIP thin film showed unprecedented optical transparency throughout the visible range, attributed to the absence of long polysulfide segments within the polymer, which will serve as a key component in a wide range of optical devices.

Indirect Evidence on Sex Reversal of Sinonovacula constricta (Bivalvia: Euheterodonta) and Gomphina veneriformis (Bivalvia: Veneridae).

This study attempts to propose the possibility of the sex reversal in Sinonovacula constricta and Gomphina veneriformis by confirming the changes in the sex ratio with the shell length in the same population level. For analysis of sex ratio, 100 individuals of S. constricta (SL 26.5-95.0 mm) and 2385 individuals of G. veneriformis (SL 15.1-60.1 mm) were used. Sex was analyzed histologically. Both species displayed the tendency of increase in the female proportion with increase in shell length. In this study, changes in the sex ratio in accordance with the growth of S. constricta and G. veneriformis are determined to be indirect evidence that signifies their sex reversal.