scholarly journals Carcinogenesis Models Using Small Fish

2021 ◽  
Vol 69 (10) ◽  
pp. 962-969
Author(s):  
Takashi Kawasaki ◽  
Yuki Shimizu
Author(s):  
William E. Hawkins ◽  
Robin M. Overstreet ◽  
William W. Walker

Small fish species are potentially good environmental carcinogenesis models because they are sensitive to several types of carcinogens, develop tumors rapidly, and are economical to breed and maintain. To gain a better understanding of the origin and progression of neoplastic lesions, we exposed 6-10-day-old specimens of seven small fish species to the direct-acting carcinogen methylazoxymethanol acetate (MAM-Ac) and all seven developed hepatic neoplasms. We examined livers of two species, Japanese medaka (Oryzias latipes) and king cobra guppy (Poecilia reticulata), by electron microscopy at various intervals after MAM-Ac exposure. Livers were processed by routine procedures. Tissues were minced, fixed by immersion in 3% phosphate-buffered glutaraldehyde, rinsed in buffer, postfixed in 1% phosphate-buffered osmium tetroxide, and processed into Embed 812.


2003 ◽  
Vol 31 (1_suppl) ◽  
pp. 88-91 ◽  
Author(s):  
William E. Hawkins ◽  
William W. Walker ◽  
John W. Fournie ◽  
C. Steve Manning ◽  
Rena M. Krol

A need exists for whole animal toxicity, mutagenesis, and carcinogenesis models that are alternative to the traditional rodent test models and that are economical, sensitive, and scientifically acceptable. Among small fish models, the Japanese medaka (Oryzias latipes) is preeminent for investigating effects of carcinogenic and/or toxic waterborne hazards to humans. The guppy (Poecilia reticulata ), although less widely used, is valuable as a comparison species. Both species are easy to maintain and handle in the laboratory and there is a large body of background information on their responsiveness to a range of classes of carcinogens. There are considerable data on the occurrence of background diseases and on spontaneous neoplastic lesions, both of which occur relatively rarely. With few modifications, the medaka and guppy are amenable to carcinogenicity testing under the rigid standards established by the National Toxicology Program (NTP) for rodent tests. The advantages of the small fish in carcinogenesis studies are best realized in long-term studies that involve environmentally realistic exposures. Studies to identify chronic effects can be conducted in about 12 months, near the life span of medaka in our laboratory. Practically, 9-month studies are optimal but shorter study cycles and a variety of exposure/growout and initiation/promotion scenarios are available. Studies on 3 compounds tested in medaka under NTP protocols are under review and preliminary analysis indicates that chronic carcinogenicity bioassays with medaka, guppy, and potentially with other small fish species are feasible and scientifically valid.


2013 ◽  
Vol 133 (8) ◽  
pp. 1616-1624
Author(s):  
Zu Soh ◽  
Kentaro Miyamoto ◽  
Akira Hirano ◽  
Toshio Tsuji

Author(s):  
P. Bala Bhaskaran

The case is structured around the takeover of Mindtree Ltd (ML) by Larsen & Toubro Ltd (L&T) in June 2019. ML was founded and nurtured by a group of software professionals. In two decades, it had blossomed into an enterprise with global presence, US$ 1 billion turnover and a unique organizational culture. In a strange sequence of events, more than 20% of ML’s shares landed in L&T’s lap. L&T grabbed this opportunity and ran a systematic campaign to acquire the company. In about 100 days, L&T achieved its objective and got into the driver’s seat. The case traces the evolution of ML from a start-up to a publicly held company with global standing. It examines the circumstances and events leading to L&T getting the initial stake in the company; it examines the acquisition campaign of L&T and the response of the top management of ML. Research Questions Was there a strategic fit between ML and L&T? Were the capital market processes just and fair to all the stakeholders involved in the acquisition? Was L&T fair, prudent and sensitive in the acquisition process? Was Siddhartha loyal and fair to the founders of ML? Link to Theory The theoretical concepts that would enable a better comprehension of the case are: Analysis of strategic fit in M&A situations Capital market: Theory and practice Strategy for corporate control of an enterprise Significance of culture and ecosystem in knowledge organizations Phenomenon Studied Leadership styles relevant at different stages of evolution of an enterprise are different. A leader, at a given point of time, is successful when he is able to match his aspirations with the leadership needs of the enterprise at that point of time. The case can be used to demonstrate this phenomenon. Case Context Context of the case is that of an emerging infotech enterprise, coming under corporate raid and the unfolding capital market processes. The case highlights the shortcomings of the co-founders, leading to their unseating as also the sensitivity of the incoming management in handling the transition. Findings The case demonstrates the ability of the capital market to be fair to all stakeholders ensuring reward for competence and punishment for sloppiness. The case emphasizes the need for co-founders to have an effective strategy for corporate control; only then they could hope to achieve the long-term objectives. The case also illustrates the significance of sensitivity in handling softer issues like people and ecosystem in ensuring long-term success. Discussions At the outset, the case may appear to be that of a big fish swallowing a small fish. But a closer scrutiny would reveal the multiple dimensions of the case. Consider the role of Siddhartha. He seeded the idea of the company; he was a financier to it; he remained an investor in the company longer than most of the founders; when he pulled out, the co-founders could not hold the company together. Neither Siddhartha nor the co-founders had the far-sightedness to consolidate their shareholdings for effective control of the company into the future. This would trigger discussions on the differing roles of technocrats, managers, leaders and founders. Another point worthy of discussion would be: How were the co-founders choosing their leaders? Was it by rotation among themselves, or did they engage a set of criteria to identify an incumbent capable of leading a global company?


Hydrobiologia ◽  
2021 ◽  
Author(s):  
Holly A. Wellard Kelly ◽  
Katya E. Kovalenko ◽  
Tyler D. Ahrenstorff ◽  
Bethany J. Bethke ◽  
Valerie J. Brady ◽  
...  
Keyword(s):  

2015 ◽  
Vol 72 (8) ◽  
pp. 2398-2408 ◽  
Author(s):  
Lotfi Rabaoui ◽  
Yu-Jia Lin ◽  
Mohammad A. Qurban ◽  
Rommel H. Maneja ◽  
Javier Franco ◽  
...  

Abstract Because of the increasing oil industry development in the Arabian Gulf, hundreds of oil and gas facilities have been installed in both offshore and inshore areas during the last few decades. However, no studies have been conducted till now on the influence of these platforms on the structure and composition of marine faunal assemblages. The present work addresses this issue to propose environmental management measures connected to the utilization of fishery resources. Offshore and inshore surveys were carried out along the Saudi Gulf waters using trawl and beach-seine nets, respectively. Data relative to only fish (offshore) and fish and invertebrates (inshore) were collected concurrently with several factors: density of oil and gas facilities (offshore), distance to the nearest coastal platform (inshore), oceanographic variables, and habitat characteristics. Results of offshore surveys indicated higher fish density—both total and of fishery resources—in locations with a higher number of oil and gas facilities within a 5 km radius, whereas biomass density was not significantly different. Hence, oil and gas facilities seem to serve as nursery areas for small fish. For inshore communities, more species and diversity were found in stations closer to coastal oil and gas facilities. In addition, among the five coastal embayments sampled, those with more oil and gas facilities had more species. The findings of the present work support the hypothesis of a positive net ecological role of oil and gas platforms of the Saudi Arabian Gulf, with the implication that this effect could be extended to improve the sustainability of important fishery resources.


MethodsX ◽  
2021 ◽  
pp. 101510
Author(s):  
Matthias Pitsch ◽  
Wilko Heimann ◽  
Gersom Burghardt ◽  
Martina Heynen
Keyword(s):  

Author(s):  
Kendra A. Byrd ◽  
Lauren Pincus ◽  
Monica M. Pasqualino ◽  
Farayi Muzofa ◽  
Steven M. Cole
Keyword(s):  

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