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Comparative Immunology
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
The dinosaurs, although related to the reptile Archosaurs, were sufficiently different from true reptiles to be placed in a class of their own, the Dinosaura. Although the great majority of dinosaurs disappeared 65 million years ago at the end of the cretaceous period, their modern descendants are probably the birds, the members of the class Aves. Unlike the reptiles, birds are, and dinosaurs probably were, endothermic (warm blooded). As a result of this, birds share with mammals all the benefits that come from greatly increased physiological and biochemical efficiency The thymus in birds and in primitive mammals is essentially similar to that seen in most mammals. Germinal centers cannot be found in fish, amphibian, and reptile spleens. In contrast, the germinal centers of birds are large and well defined.
Changing Circumstances and Diets
Published in Christopher Cumo, Ancestral Diets and Nutrition, 2020
Viewed from an evolutionary vantage point, primates are latecomers to the biota. Life originated roughly 3.8 billion years ago, but primates are no older than 65 million years, when the dinosaurs’ demise at the end of the Cretaceous Period (145–165 million years ago) opened niches for mammals and promoted speciation. Even this date may be too early because the first species with primate characteristics may not have been primates and are probably best thought precursors rather than true to type.10 Fossils suggest that these animals resembled squirrels (Sciurus species) and tree shrews (Tupaia species). Small, the proto primates radiated heat because of a large surface to volume ratio. But being warm-blooded like all mammals, these creatures had to sustain a high metabolism to offset heat loss and so needed many nutrients and calories.
Temperature and Chemicals
Published in Sue Binkley, Biological Clocks, 2020
Warm-blooded animals (the birds and mammals, homeotherms) maintain body temperatures around 37°C. There are circadian fluctuations in body temperature (about 1°C in a human, as much as 5°C in a house sparrow). Birds have higher body temperatures than mammals. Some homeotherms are able to drop their body temperatures on a nightly (daily torpor) or a seasonally (hibernation).85
Human thermal perception and time of day: A review
Published in Temperature, 2021
Marika Vellei, Giorgia Chinazzo, Kirsi-Marja Zitting, Jeffrey Hubbard
Humans, like nearly all mammals and avian species, are homeotherms (warm-blooded), meaning that their internal body temperature remains stable irrespective of environmental influence [26]. This is in contrast to poikilotherms (cold-blooded), such as fish, reptiles, and amphibians, whose internal temperature fluctuates widely depending on different factors, and can both influence metabolic rate and radically alter cellular processes (i.e. protein denaturing at high temperature) [27]. In the past, thermoregulation was thought to be exclusively under the control of the preoptic hypothalamus, a brain region located posterior to the optic nerve, and ventral to cortical structures [28]. Generally speaking, the hypothalamus is responsible for the regulation of a wide array of autonomic functions, including appetite and sleep initiation, and forms a critical part of the hypothalamic-pituitary-adrenal axis, which controls among others, stress reactions. In recent years, however, its role in regards to being the sole controller of thermoregulation in the brain has been redefined [29]. For example, thermoreceptors have been found in other areas, including the brain stem, and indeed in other central nervous system structures such as the spinal cord [30], underscoring the fact that the thermoregulatory system is diffuse [31].
Tick transmission of toxoplasmosis
Published in Expert Review of Anti-infective Therapy, 2019
Toxoplasmosis is thought to be acquired by the transmission of T. gondii from the definitive to intermediate hosts, from intermediate to definitive hosts, as well as between similar definitive and between similar intermediate hosts. Intermediate hosts are all warm-blooded animals (mammals and birds), including humans. Definitive hosts are members of the family Felidae, for example, domestic cats [2]. Humans most commonly acquire toxoplasmosis by ingestion of T. gondii cysts in infected meat or by the ingestion of sporulated oocysts from water, soil or food contaminated indirectly from feline feces, or less frequently, directly from feline feces [2,9]. In the US, T. gondii is second only to Salmonella as a domestically acquired foodborne illness resulting in death [10]. Transmission by blood transfusion [11] and organ transplantation [12] has also been reported. Little is known about the relative importance of horizontal transmission of T. gondii between different host species or the epidemiologic impact of the different sources causing infection or disease.
Current status of human rabies prevention: remaining barriers to global biologics accessibility and disease elimination
Published in Expert Review of Vaccines, 2019
Charles E. Rupprecht, Naseem Salahuddin
As a basic operational definition, rabies is an acute, progressive encephalitis caused by a lyssavirus [1]. Lyssaviruses are bullet-shaped, genetically mono-phyletic, single-stranded, negative-sense RNA viruses, taxonomically residing in the Order Mononegavirales, Family Rhabdoviridae [2]. With advances in pathogen detection methods, more than 17 lyssavirus species have been described since the 1950s [3–11]. Lyssaviruses are highly neurotropic, deposited into a wound from the saliva after an animal bite. Virions undergo retrograde transmission within the neuronal axoplasm, before replication in the CNS and subsequent passage to the salivary glands [12]. Rabies is distributed on all continents, except for Antarctica [13]. All warm-blooded vertebrates are susceptible, with significant representatives among mammalian carnivores and bats [14]. Rabies virus is the most important member of the Lyssavirus Genus. Although polyhostality is a significant feature in support of perpetuation, the domestic dog remains the major global reservoir and source of most human cases [15]. As with many neglected tropical diseases (NTDs), the actual burden of human fatalities is poorly known. This is due in part to inadequate reporting, with suggestions of tens of millions of human exposures, resulting in tens of thousands of deaths annually, typically with a substantial representation among a cohort less than 18 years of age, particularly among the Lesser Developed Countries (LDCs) in Africa and Asia [16].