Makoto Haritani

Ag, Cu, Zn, Ti, and Au nanoparticles show enhanced photocatalytic properties. Efficient indoor disinfection strategies are imperative to manage the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Virucidal agents, such as ethanol, sodium hypochlorite, 222-nm UV light, and electrolyzed water inactivate SARS-CoV-2 in indoor environments. Tungsten trioxide (WO₃₎ photocatalyst and visible light disinfect abiotic surfaces against SARS-CoV-2. The titanium dioxide (TiO₂)/UV system inactivates SARS-CoV-2 in aerosols and on deliberately contaminated TiO₂-coated glass slide surfaces in photocatalytic chambers, wherein 405-nm UV light treatment for 20 min sterilizes the environment and generates reactive oxygen species (ROS) that inactivate the virus by targeting S and envelope proteins and viral RNA. Mesoscopic calcium bicarbonate solution (CAC-717) inactivates pathogens, such as prions, influenza virus, SARS-CoV-2, and noroviruses, in fluids; it presumably acts similarly on human and animal skin. The molecular complexity of cementitious materials promotes the photocatalysis of microorganisms. In combination, the two methods can reduce the pathogen load in the environment. As photocatalysts and CAC-717 are potent disinfectants for prions, disinfectants against prionoids could be developed by combining photocatalysis, gas plasma methodology, and CAC-717 treatment, especially for surgical devices and instruments.

Here, the virucidal effect of calcium bicarbonate with a mesoscopic structure (CAC-717) on severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was determined. Assays showed that CAC-717 had a strong virucidal effect on all examined SARS-CoV-2 isolates, including variant strains. The viral infectivity decreased within 15 s, and the virucidal activity of CAC-717 at a 1:49 ratio was similar to that of ethanol disinfectant. CAC-717 neutralization eliminated this virucidal effect, indicating that the alkaline condition of CAC-717 is important for virus inactivation and is an indicator of its mesoscopic structure and virucidal activity. The virucidal effect was observed in the presence of organic matter (bovine serum albumin). CAC-717 is a non-invasive and non-flammable substance with a low environmental burden, and its usefulness as a novel disinfectant has been confirmed.

Xanthomonas campestris pv. campestris (Xcc) is an important seed-borne bacterial pathogen that causes black rot in brassica. Current seed disinfection methods for Xcc have disadvantages; chemical treatment has associated environmental risks, hot water immersion reduces germination, and dry heat treatment is protracted. Here, we treated Xcc-contaminated seeds with CAC-717, a recently developed disinfectant produced by applying an electric field and water flow to distilled water containing calcium hydrogen carbonate to produce mesoscopic crystals. The decimal reduction time (D-value) of Xcc suspension (8.22 log₁₀ colony forming units (CFU)/mL) by CAC-717 treatment was 0.319 min. Treatment of Xcc-contaminated cabbage seeds at 25 °C for 30 min with CAC-717 significantly reduced bacterial cell numbers recovered from the seeds (0.36 log₁₀ CFU/mL (SEM (standard error of the mean) = 0.23 log₁₀ CFU/mL)) compared with distilled water treatment (3.52 log₁₀ CFU/mL (SEM = 0.12 log₁₀ CFU/mL)). Moreover, there was a lower incidence of black rot after treatment with CAC-717 (26.67% ± 3.33%) versus distilled water (56.67% ± 8.82%). For non-contaminated seeds, there was no significant difference in germination rate and plant stem length between distilled water and CAC-717 treatment after 5 days of cultivation. In conclusion, CAC-717 is a promising seed disinfectant without deleterious effects on germination or plant growth.

A 4-month-old female mixed-breed cat showed gait disturbance and eventual dysstasia with intention tremor and died at 14 months of age. Postmortem histological analysis revealed degeneration of neuronal cells, alveolar epithelial cells, hepatocytes, and renal tubular epithelial cells. Infiltration of macrophages was observed in the nervous system and visceral organs. The cytoplasm of neuronal cells was filled with Luxol fast blue (LFB)-negative and periodic acid-Schiff (PAS)-negative granules, and the cytoplasm of macrophages was LFB-positive and PAS-negative. Ultrastructurally, concentric deposits were observed in the brain and visceral organs. Genetic and biochemical analysis revealed a nonsense mutation (c.1017G>A) in the SMPD1 gene, a decrease of SMPD1 mRNA expression, and reduced acid sphingomyelinase immunoreactivity. Therefore, this cat was diagnosed as having Niemann-Pick disease with a mutation in the SMPD1 gene, a syndrome analogous to human Niemann-Pick disease type A.

In the 1960s, Opitz discovered the formation of complex oxide protective layers (Belag) on worn surfaces of tools when cutting Ca deoxidized steel. Belag formation is used in a free-cutting technique for steel and cast iron because it significantly reduces diffusional wear by preventing direct contact between the tool and work material; hence, tool life can be dramatically prolonged. For Belag to form, one condition is that the tool material should contain TiC. It has been reported that Belag adheres to tool surfaces because TiC in the tool oxidizes and reacts with Belag. Our study aims to clarify the formation and adhesion mechanisms of Belag. In this study, Ca deoxidized steel was machined with noncoated carbide P10 tools, and the state of the interface between the tool and Belag layer was investigated by transmission electron microscopy (TEM) and elemental analyses. As a result, we found that Belag directly adhered to Ti carbide (Ti–W–C) particles on tool surfaces. In contrast, Belag did not directly adhere to WC or Co on tool surfaces. Unlike previous studies, we could not confirm the formation of the TiC oxide or its oxide layer near the interface to which Belag adhered. In addition, when we machined a Ca deoxidized steel containing MnS, a CaS layer formed in Belag at the interface between the tool and Belag layer.

Pathological and pathogenic examinations were carried out on three heifers suffering severe respiratory disease on a dairy farm. Extensive fibrinonecrotic inflammation was evident in the respiratory mucosa from the nasal cavity to the lung, nonsuppurative inflammation was found in the trigeminal ganglia, pons and medulla oblongata, and the presence of eosinophilic intranuclear inclusion bodies was detected in the laryngeal glands. Bovine herpesvirus type 1 (BHV-1) antigens and herpesvirus particles were detected in these lesions, and BHV-1 was isolated from the nasal swabs. The lesions in the brain stem were confined to the nuclei associated with the trigeminal nerve tract. The results indicate that the virus produced both lesions in the respiratory mucosa and central nervous system, and suggest that the virus might have reached the brain stem along the trigeminal nerve tract as the predominant route.