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The Origins of Aging
Published in Shamim I. Ahmad, Aging: Exploring a Complex Phenomenon, 2017
The universality of the predator–prey biomass scaling relationship in diverse ecosystems underscores the essential role this relationship plays in trophic cascades within ecosystems. Ripple et al. (2014) reviewed the ecological effects of large mammalian carnivore species. These apex predators, despite their low population densities, regulate both directly and indirectly such ecosystem properties as population density of prey species and smaller predators, abundance and diversity of plant species, and river/stream morphology, as well as nutrient recycling. An earlier article by Ripple and Beschta (2005) summarized the multiple trophic cascades that were regulated by wolves in ecosystems within the western hemisphere. These regulatory functions performed by wolves were amply demonstrated in ecosystems in which wolves had been eliminated by purposeful human actions. As noted in a previous section, Hatton et al. (2015) documented that the relationship between predator and prey biomass across numerous ecosystems, both terrestrial and aquatic, follows the same scaling rule. Such a universal feature points to a level of ecosystem structure/function regulation that would necessitate species-specific aging and death programs (Singer 2016). In fact, optimal multifunctionality of an ecosystem requires regulated interactions across the multiple trophic groups comprising that ecosystem (Soliveres et al. 2016).
Effects of temperature on feeding and digestive processes in fish
Published in Temperature, 2020
Helene Volkoff, Ivar Rønnestad
Digestion consists of a series of complex series of processes with the overall aim to maximize absorption of dietary nutrients (Figure 5). After ingestion, food is mainly degraded by digestive enzymes and to some extent mechanically by muscular movements of the GIT. Among fish species, different feeding habits (e.g. herbivore, omnivore, carnivore) result in different GIT morphologies. Carnivores usually have short and straight intestines, most often with the presence of a true stomach and pyloric ceca (finger-like appendages in the proximal intestine, which increase the overall intestinal absorptive surface area) whereas herbivores tend to have longer intestines without ceca and sometimes no true stomach [83]. Agastric fish may possess an intestinal bulb or an enlargement in the anterior intestine that might somewhat increase retention time [84]. A number of gastrointestinal factors (hormones, neurotransmitters) act locally to regulate digestive processes [85]. Temperature affects the secretory activity of digestive juices (by its effect on food ingestion), GIT motility, the activity of digestive enzymes, and digestion and absorption rates [86].
High intake of dietary fructose in overweight/obese teenagers associated with depletion of Eubacterium and Streptococcus in gut microbiome
Published in Gut Microbes, 2019
Roshonda B Jones, Tanya L Alderete, Jeniffer S Kim, Joshua Millstein, Frank D Gilliland, Michael I Goran
Studies in animal models have demonstrated that the composition of gut microbiota is related to macronutrient intake.14–16 One study found that kittens who consumed a high protein low carbohydrate diet had a lower abundance of Bifidobacterium compared to those consuming a moderate protein and carbohydrate diet, which is a genus of bacteria has been linked to decreased intestinal health.14 In a murine model, a high fat diet resulted in a microbiota that had a low percentage of Bacteroidetes and higher percentages of Firmicutes and Proteobacteria.15 Lastly, a recent study by our group found that rats with ad libitum access to a sugar solution had a higher abundance of pathogenic bacteria, including the phylum Proteobacteria, compared to rats given a water control.16 Generally among mammals, not only has it been shown that carnivores and herbivores have distinct gut microbial communities but there is also a distinction between carnivores and omnivores, suggesting that the digestion of complex plant-based carbohydrates helps to shape the composition of the gut microbiota.8 Despite this, few studies have examined the associations between specific dietary macronutrients and the composition of the gut microbiota in adolescents.
Facts and ideas from anywhere
Published in Baylor University Medical Center Proceedings, 2018
Atherosclerosis (“blockages,” “hardening of the arteries”) is caused by cholesterol, and the higher the blood cholesterol level, the greater the chance of having an atherosclerotic event. At least four factors support the cholesterol cause of atherosclerosis. 1) Atherosclerosis is easy to produce experimentally. If a high-cholesterol diet is given to herbivores (rabbits, monkeys), atherosclerotic plaques develop rapidly in the animals’ arteries. (It is not possible to produce atherosclerosis experimentally in carnivores [dogs, cats, tigers, lions] unless the animal is previously made hypothyroid.) 2) Cholesterol is present in the arterial plaques. 3) Societies with high blood cholesterol levels have far more atherosclerotic events than societies with low blood cholesterol levels. 4) Lowering the blood cholesterol level, and specifically the low-density lipoprotein (LDL) cholesterol level, lowers the frequency of atherosclerotic events.