V. van Ginneken

“Infectobesity: viral infections (especially with human adenovirus-36: Ad-36) may be a cause of obesity

In recent years viral infections have been recognized as possible cause of obesity, alongside the traditionally recognized causes (genetic inheritance, and behaviour/environmental causes such as diet exercise, cultural practices and stress). Although four viruses have been reported to induce obesity (infectoobesity) in animal models (chickens, mice, sheep, goat, dogs, rats and hamsters), until recently the viral etiology of human obesity has not received sufficient attention, possibly because the four viruses are not able to infect humans. In a series of papers over the last ten years, however, the group of Prof. Dhurandhar (Pennington Biomedical Research Center, LA, USA) demonstrated that a human adenovirus, adenovirus-36 (Ad-36), is capable of inducing adiposity in experimentally infected chickens, mice and non-human primates (marmosets). Ad-36 is known to increase the replication, differentiation, lipid accumulation and insulin sensitivity in fat cells and reduces those cells leptin secretion and expression. It also affects human primary preadipocytes. In rats increased adiposity was observed due to Ad-36 infection. Recent studies have shown that, in the USA, antibodies to Ad-36 were more prevalent in obese subjects (30%) than in non-obese subjects (11%). We postulate that Ad-36 may be a contributing factor to the worldwide rising problem of obesity. We suggest the extension of comparative virological studies between North America and Europe, and studies between discordant twins (both dizygous and monozygous).

Effects of Swimming on Silvering and Maturation of the European Eel, Anguilla anguilla L.

Abbreviations 11-KT: 11-ketotestosteron; ACTH: adrenocorticotropic hormone; Ca: calcium; DHP: dihydroxy progesterone (17, 20β-dihydroxy-4-pregnen-3one); E2: 17β-estradiol; EI: eye index; ERα: estradiol receptor α; FSH: follicle stimulating hormone; FSH-β: FSH specific subunit β; FW: fresh water; GnRH: gonadotropin releasing hormone; GPα: gonadotropin common α subunit; GSI: gonadosomatic index (relative gonad mass); LH: luteinising hormone; LH-β: LH specific subunit β; NEFA: non-esterified fatty acids; q-rtPCR: quantitative real time polymerase chain reaction; StAR: steroidogenic acute regulatory protein; SW: salt water; T: testosteron; VTG: vitellogenin; αMSH: melanophore-stimulating hormone α

Impact of Eel Viruses on Recruitment of European Eel

Eels have an uncommon catadromic life cycle with exceptional migratory patterns to their spawning grounds several thousand kilometres away: the European eel (Anguilla anguilla) travels over 5,500 km to the Sargasso Sea (Schmidt 1923; McCleave and Kleckner 1987; Tesch 1982; Tesch and Wegner 1990); the American eel (A. rostrata) migrates over 4,000 km also to the Sargasso Sea (Castonguay and McCleave 1987; McCleave and Kleckner 1987; Tesch and Wegner 1990); the Australian eel (A. aus-tralis) travels over 5,000 km into the Pacific Ocean to spawn (Jellyman 1987); and the Japanese eel (A. japonica) travels over 4,000 km to an area near the Marianna Islands in the Philippines to spawn (Tsukamoto 1992). Evidently such long distance swimming will place those fishes under extra stress caused by the long starvation period, the high energy cost of the journey, and the many changes in the environment such as salt water, darkness, high pressure, and low temperatures, among other stress factors. Stress is often a basis for disease in eel, especially in intensive eel culture (Haenen and Engelsma, 2005 unpublished finding). Nowadays, global transport of live fishes for aquaculture has facilitated the global spread of pathogens from diseased to healthy stocks. Within the last few decades, aquaculture has become an important production branch in our society. Its global production has more than doubled between 1986 and 1996 in tonnage and value, and over one quarter of human fish consumption at world scale is now produced in aquaculture (Naylor et al. 2000). The Netherlands is one of the leading eel producing & trading countries (Heinsbroek and Kamstra 1995). Blanc (1997) showed that nearly 100 pathogens have been introduced into European water bodies since the introduction of aquaculture. Worldwide many diseases are known in both wild and cultured eel. Parasites, for example trematodes, Anguillicola crassus(nematode), and Myxidium giardi (myxosporean)occur naturally in wild eel populations, mostly in low numbers, without causing mortality (Koie 1988; Van Banning and Haenen 1990; Borgsteede et al. 1999). However, under culture conditions, with eels kept in high densities, they may be harmful. Eel pathogenic bacteria like Vibrio vulnificus, Vibrio anguillarum, Pseudomonas anguillisepticaand Edwardsiella tardamay also cause disease, especially when a stress factor is involved or when the eel is injured (Veenstra et al. 1993; Austin and Austin 1999; Haenen and Davidse 2001). As far as we know, the clinical signs are often more severe under culture conditions compared to in the wild.

The Effect of PCBs on the Spawning Migration of European Silver Eel (Anguilla anguilla L.)

Organochlorine compounds were widely used after the Second World War because they were cheap to produce and useful for many purposes, such as in agriculture for insecticides, in public health to control disease insect vectors and in industry (Pelletier et al. 2002). It is estimated that 16–30% of the 1 million tons of PCBs produced are still present in aquatic and terrestrial ecosystems (Borlakoglu and Haegele 1991). In spite of discharge restrictions, the concentrations of PCBs and chemically similar compounds in natural environments will likely remain elevated because of atmospheric transport and the internal cycling of contaminants already present in ecosystems. So, when not retrieved or destroyed, the rest of the PCBs will be released into the environment and eventually reach the oceans (Klamer et al. 1991). PCBs encompass a class of chlorinated compounds that includes up to 209 variations, or congeners, with different physical and chemical characteristics. They are ubiquitous environmental contaminants with specific modes of action (Safe 1984, 1990) and exposure to each of the congeners is associated with different levels of risk for harmful effects. Technical mixtures of PCBs, referred to by the trade names such as Aroclor, Phenoclor and Kanechlor, have been widely used for a variety of industrial purposes: hydraulic fluids in mining activities, plasticisers, fluid-filled capacitors and transformers, heat transfer fluids and paints. There are no known natural sources of PCBs. Most PCBs are oily liquids whose colour darkens and viscosity increases with rising chlorine content. PCBs with fewer chlorine atoms are more soluble, more amenable to chemical and biological degradation, and less persistent in the environment than those PCBs with more chlorine atoms bound to the biphenyl core (Safe 1984) (Fig. 15.1). Chapter 15 The Effect of PCBs on the Spawning Migration of European Silver Eel (Anguilla anguilla L.)