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Multi‐walled carbon nanotube‐7 (MWCNT‐7) fibers are biopersistent and have a structure similar to asbestos. MWCNT‐7 has been shown to induce malignant mesothelioma when administered by intrascrotal or intraperitoneal injection in rats and mice, and an inhalation study demonstrated that rats exposed to respirable MWCNT‐7 developed lung tumors. MWCNT‐N, which is similar to MWCNT‐7, was shown to induce both lung tumors and malignant mesothelioma in rats when administered by trans‐tracheal intrapulmonary spraying (TIPS). The present study was performed to investigate the carcinogenicity of MWCNT‐7 when administered by the TIPS method. Ten‐week‐old male F344/Crj rats were divided into 3 groups and administered 0.5 mL vehicle, 0.250 μg/mL MWCNT‐7 or 0.250 μg/mL crocidolite once a week for 12 weeks (total doses of 1.5 mg/rat) and then observed for up to 104 weeks. Rats in the MWCNT‐7 group began to die from pathologies associated with the development of malignant mesothelioma 35 weeks after the final TIPS administration. Overall, the incidence of malignant mesothelioma in the MWCNT‐7 group was significantly higher than in the vehicle or crocidolite groups.

Background Biological effects of tailor-made multi-walled carbon nanotubes (MWCNTs) without functionalization were investigated in vivo in a two-year carcinogenicity study. In the past, intraperitoneal carcinogenicity studies in rats using biopersistent granular dusts had always been negative, whereas a number of such studies with different asbestos fibers had shown tumor induction. The aim of this study was to identify possible carcinogenic effects of MWCNTs. We compared induced tumors with asbestos-induced mesotheliomas and evaluated their relevance for humans by immunohistochemical methods. Methods A total of 500 male Wistar rats (50 per group) were treated once by intraperitoneal injection with 10 9 or 5 × 10 9 WHO carbon nanotubes of one of four different MWCNTs suspended in artificial lung medium, which was also used as negative control. Amosite asbestos (10 8 WHO fibers) served as positive control. Morbid rats were sacrificed and necropsy comprising all organs was performed. Histopathological classification of tumors and, additionally, immunohistochemistry were conducted for podoplanin, pan-cytokeratin, and vimentin to compare induced tumors with malignant mesotheliomas occurring in humans. Results Treatments induced tumors in all dose groups, but incidences and times to tumor differed between groups. Most tumors were histologically and immunohistochemically classified as malignant mesotheliomas, revealing a predominantly superficial spread on the serosal surface of the abdominal cavity. Furthermore, most tumors showed invasion of peritoneal organs, especially the diaphragm. All tested MWCNT types caused mesotheliomas. We observed highest frequencies and earliest appearances after treatment with the rather straight MWCNT types A and B. In the MWCNT C groups, first appearances of morbid mesothelioma-bearing rats were only slightly later. Later during the two-year study, we found mesotheliomas also in rats treated with MWCNT D – the most curved type of nanotubes. Malignant mesotheliomas induced by intraperitoneal injection of different MWCNTs and of asbestos were histopathologically and immunohistochemically similar, also compared with mesotheliomas in man, suggesting similar pathogenesis. Conclusion We showed a carcinogenic effect for all tested MWCNTs. Besides aspect ratio, curvature seems to be an important parameter influencing the carcinogenicity of MWCNTs.

Background The Canadian Council on Animal Care and American Veterinary Medical Association classify intraperitoneal (IP) pentobarbital as an acceptable euthanasia method in rats. However, national guidelines do not exist for a recommended dose or volume and IP euthanasia has been described as unreliable, with misinjections leading to variable success in ensuring a timely death. The aims of this study were to assess and improve efficacy and consistency of IP euthanasia. In a randomized, blinded study, 51 adult female Sprague-Dawley rats (170–495 g) received one of four treatments: low-dose low-volume (LL) IP pentobarbital ( n = 13, 200 mg/kg pentobarbital), low-dose high-volume (LH) IP pentobarbital ( n = 14, 200 mg/kg diluted 1:3 with phosphate buffered saline), high-dose high-volume (HH, n = 14, 800 mg/kg pentobarbital), or saline. Times to loss of righting reflex (LORR) and cessation of heartbeat (CHB) were recorded. To identify misinjections, necropsy examinations were performed on all rats. Video recordings of LL and HH groups were analyzed for pain-associated behaviors. Between-group comparisons were performed with 1-way ANOVA and Games-Howell post hoc tests. Variability in CHB was assessed by calculating the coefficient of variation (CV). Results The fastest euthanasia method (CHB) was HH (283.7 ± 38.0 s), compared with LL (485.8 ± 140.7 s, p = 0.002) and LH (347.7 ± 72.0 s, p = 0.039). Values for CV were: HH, 13.4%; LH, 20.7%; LL, 29.0%. LORR time was longest in LL (139.5 ± 29.6 s), compared with HH (111.6 ± 19.7 s, p = 0.046) and LH (104.2 ± 19.3 s, p = 0.01). Misinjections occurred in 17.0% (7/41) of euthanasia attempts. Pain-associated behavior incidence ranged from 36% (4/11, LL) to 46% (5/11, HH). Conclusions These data illustrate refinement of the IP pentobarbital euthanasia technique. Both dose and volume contribute to speed of death, with a dose of 800 mg/kg (HH) being the most effective method. An increase in volume alone does not significantly reduce variability. The proportion of misinjections was similar to that of previous studies.

The therapeutic potential of bacteriophages (phages) in a mouse model of acute Burkholderia cenocepacia pulmonary infection was assessed. Phage treatment was administered by either intranasal inhalation or intraperitoneal injection. Bacterial density, macrophage inflammatory protein 2 (MIP-2), and tumor necrosis factor α (TNF-α) levels were significantly reduced in lungs of mice treated with intraperitoneal phages (P < .05). No significant differences in lung bacterial density or MIP-2 levels were found between untreated mice and mice treated with intranasal phages, intraperitoneal ultraviolet-inactivated phages, or intraperitoneal λ phage control mice. Mock-infected mice treated with phage showed no significant increase in lung MIP-2 or TNF-α levels compared with mock-infected/mock-treated mice. We have demonstrated the efficacy of phage therapy in an acute B. cenocepacia lung infection model. Systemic phage administration was more effective than inhalational administration, suggesting that circulating phages have better access to bacteria in lungs than do topical phages.

Therapeutic vaccines capable of eliciting CD8 T cell responses are a promising approach in cancer, but the magnitude of immune responses to peptide-based vaccine technologies has so far been modest in humans. The cationic liposome adjuvant CAF®09b has recently shown promising results in clinical trials, where it is administered intraperitoneally (i.p.), as preclinical studies demonstrated superior CD8 T cell responses when using this route compared to subcutaneous delivery. Exploring the mechanism of CAF09b in mice we investigated biodistribution of the adjuvant and associated antigen in murine studies. We further examined local innate cell recruitment and CD8 T cell responses in the peritoneal cavity. We observed that i.p. injected CAF09b associated with visceral fatty tissues and created a vaccine depot in the peritoneal cavity. This led to recruitment of BATF3-dependent conventional type I dendritic cells (cDC1) displaying a migratory cDC1 phenotype (CD11c+XCR1+CD103+). Gene ontology analysis further revealed similarities with visceral adipose tissue DCs. CAF09b injection i.p. led to early priming of CD8 T cells localized to the peritoneal cavity and this response was resistant to FTY720 treatment. This study demonstrates that adjuvants can facilitate recruitment of cDC1s to the peritoneal cavity, a feature that may contribute to the effectiveness of i.p. administration on elicitation of CD8 T cell responses. Furthermore, we demonstrate that CAF09b-induced CD8 T cell responses require BATF3-dependent cDC1 cells. Understanding cDC1 and CD8 T cell dynamics via different immunization routes may aid in the design of more effective vaccine strategies. This work was primarily supported by the Danish Research Council (FTP fund no. 9041-00131b). •Adjuvants administered i.p. effectively recruits migratory cDC1 cells to the peritoneal cavity.•Intraperitoneal injection of CAF09b induces bone marrow mobilization of cDC1 progenitors.•CAF09b injection i.p. led to early priming of CD8 T cells localized to the peritoneal cavity.•Priming of CD8 T cell responses by CAF09b requires cDC1 cells.

Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC) is a promising approach with a high optimization potential for the treatment of peritoneal carcinomatosis. To study the efficacy of PIPAC and drugs, first rodent cancer models were developed. But inefficient drug aerosol supply and knowledge gaps concerning spatial drug distribution can limit the results based on such models. To study drug aerosol supply/deposition, computed tomography scans of a rat capnoperitoneum were used to deduce a virtual and a physical phantom of the rat capnoperitoneum (RCP). RCP qualification was performed for a specific PIPAC method, where the capnoperitoneum is continuously purged by the drug aerosol. In this context, also in-silico analyses by computational fluid dynamic modelling were conducted on the virtual RCP. The physical RCP was used for ex-vivo granulometric analyses concerning drug deposition. Results of RCP qualification show that aerosol deposition in a continuous purged rat capnoperitoneum depends strongly on the position of the inlet and outlet port. Moreover, it could be shown that the droplet size and charge condition of the drug aerosol define the deposition efficiency. In summary, the developed virtual and physical RCP enables detailed in-silico and ex-vivo analyses on drug supply/deposition in rodents.

BackgroundIn the last 20 years, intraperitoneal chemotherapy (IPC) has been explored as a modality for the management of peritoneal metastases of gynecologic, gastrointestinal, and primary peritoneal tumors. Direct delivery of chemotherapeutic agents to the peritoneal cavity space has proved superior to systemic chemotherapy when evaluating characteristics such as drug concentration reached in the peritoneal space, penetration into peritoneal metastases, and chemotherapy-related toxicity. Traditionally, IPC is delivered by peritoneal lavage with a liquid solution. This form of delivery has limitations, including inhomogeneous intraperitoneal distribution and limited ability to penetrate tissues and metastatic nodules. An alternative mode of delivery is so-called pressurized intraperitoneal aerosol chemotherapy (PIPAC). Within this context, the present study sought to identify the pattern of spatial distribution of therapeutic solutions aerosolized into the peritoneal space using a single-port PIPAC device and ascertain whether the aerosolized method is superior to the traditional (liquid) mode of IPC delivery.MethodsAnalysis of the rate of intra-abdominal staining with aerosolized 2% silver nitrate in five porcine models.ResultsAssessment of differences in stain impregnation between the upper, middle, and lower abdomen did not reveal significant differences (p = 0.42). The median sum scores were 1 for the upper abdomen and 3 for the middle and lower abdomen.ConclusionsAerosolization does not reach all regions of the abdomen homogeneously. However, adequate exposure of the upper abdomen, mid-abdomen, and lower abdomen to chemotherapeutic agents can be achieved with PIPAC.

The main objective of this experiment was to study the metabolism of arginine in juvenile largemouth bass ( Micropterus salmoides ). A total of 300 healthy fish (average weight of 25 ± 0.5 g) were randomly assigned to ten groups. Experimental fish were orally administered or intraperitoneally injected with 0.9% sodium chloride, arginine, arginine-aspartate, citrulline, and glutamate solutions, respectively. They were euthanized at 10, 30, 60, 120, and 240 min after oral administration or intraperitoneal injection, and various tissue samples were subsequently collected for analysis. The results revealed that serum ornithine and citrulline concentrations of largemouth bass were significantly increased by oral administration of arginine or arginine-aspartate ( P  < 0.05). Intraperitoneal injection of arginine or arginine-aspartate solution significantly elevated the concentrations of ornithine and citrulline in the serum, liver, kidney, and muscles ( P  < 0.05). The concentrations of citrulline, ornithine, and arginine in serum and muscle increased significantly at 4 h after intraperitoneal injection of glutamate ( P  < 0.05). Intraperitoneal injection of citrulline significantly increased the concentrations of ornithine and arginine in the serum and muscles ( P  < 0.05). The research findings demonstrate that both free and small peptide forms of arginine were rapidly degraded to ornithine due to the high arginase activity in various tissues of largemouth bass. Additionally, the pathway of synthesizing citrulline from glutamate and then arginine from citrulline may exist in largemouth bass, but the exact location of this synthesis process may differ from that found in mammals.

Colorectal cancer is one of the major causes of cancer-related death in Taiwan and worldwide. Patients with peritoneal metastasis from colorectal cancer have reduced overall survival and poor prognosis. Hybrid protein-inorganic nanoparticle systems have displayed multifunctional applications in solid cancer theranostics. In this study, a gold nanocore-encapsulated human serum albumin nanoparticle (Au@HSANP), which is a hybrid protein-inorganic nanoparticle, and its radioactive surrogate 111In-labeled Au@HSANP (111In-Au@HSANP), were developed and their biological behaviors were investigated in a tumor/ascites mouse model. 111In-Au@HSANP was injected either intravenously (iv) or intraperitoneally (ip) in CT-26 tumor/ascites-bearing mice. After ip injection, a remarkable and sustained radioactivity retention in the abdomen was noticed, based on microSPECT images. After iv injection, however, most of the radioactivity was accumulated in the mononuclear phagocyte system. The results of biodistribution indicated that ip administration was significantly more effective in increasing intraperitoneal concentration and tumor accumulation than iv administration. The ratios of area under the curve (AUC) of the ascites and tumors in the ip-injected group to those in the iv-injected group was 93 and 20, respectively. This study demonstrated that the ip injection route would be a better approach than iv injections for applying gold-albumin nanoparticle in peritoneal metastasis treatment.

Short-chain fatty acids (SCFAs) are microbial metabolites, mainly generated by the action of gut microbiota on dietary fibers. Acetate, propionate, and butyrate are the three main SCFAs produced typically in a 60:20:20 molar ratio in the colon. Acetate, propionate, and butyrate, when given individually as supplements, have shown a protective role in obesity and hyperglycemia; however, the sex-specific effects of a mixture of SCFAs, when given in 60:20:20 ratio, on the regulation of lipid metabolism and lipid profile are not known. Male and female Long–Evans rats were given a mixture of SCFAs (acetate, propionate, and butyrate; molar ratio 60:20:20) each day for seven days intraperitoneally; plasma and hepatic lipids, gene expression, and lipidomics profile were analyzed. SCFAs significantly decreased plasma and hepatic triglycerides and cholesterol in males, whereas the fatty acyl composition of cholesteryl esters, triglycerides, and phospholipids was modulated in females. SCFAs decreased the mRNA expression of hepatic acetyl-CoA carboxylase-1 in both males and females. Our findings demonstrate for the first time that SCFAs (60:20:20) improved plasma and hepatic lipid levels and fatty acyl composition in a manner that may provide cardio-protective and anti-inflammatory effects in both sexes, via independent mechanisms.