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A Biophysical View on the Function and Activity of Endotoxins
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Ulrich Seydel, Andre Wiese, Andra B. Schromm, Klaus Brandenburg
Ramos-Sanchez et al. (155) and Rodrigues-Torres et al. (156) investigated the phase behavior of endotoxin preparations of Brucella and other gram-negative bacteria. They describe endotherms in biologically irrelevant temperature regions. Thus, endotherms between 108 and 200°C were assigned to transitions in the polysaccharide moiety due to depolymerization and an endotherm between—13 and—36°C (“cooling phase transition”) was attributed to transitions between structural forms differing in hydrogen bonding within the polysaccharide moiety of LPS. These authors did not report on the β ↔ α transition probably because they investigated dry LPS samples (see above).
The environment
Published in Francesco E. Marino, Human Fatigue, 2019
Previous chapters outlined the significance and advantages of bipedal locomotion, a characteristic unique to humans and apparently intimately tied to our thermoregulatory strategy (see Chapter 1). This is a key concept since thermoregulation is not just a physiological response to a given environmental challenge but an interactive survival strategy as evidenced by the varying ways in which animals are able to produce and offload heat (Angilletta et al. 2010) – for example, heterothermy, the ability of some animals to switch from having to depend on the environment to adjust their body temperature (poikilothermic) to being able to produce their own body heat (endothermic). Mammals and birds are normally described as having the capacity to maintain a constant temperature (homeotherms). This is undoubtedly an impressive capability which is dependent on the exchange of heat between the body and the environment as given by the equation: Where S is heat storage, M is metabolic rate of the body, W is the mechanical work produced, E is rate of total evaporative loss due to evaporation of sweat and Q is total rate of heat loss from the skin. Although homeotherms are able to maintain a relatively constant body temperature, it is now apparent that they are also able to vary their body temperature over the lifespan, with this variation likely to be relative to the latitude of their habitat (Angilletta et al. 2010)
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
Both endotherms and ectotherms use a variety of mechanisms to affect body temperature. (1) Altered heat exchange with the environment: increasing BLOOD flow (VASODILATION) of vessels near the body surface (in the SKIN) produces heat loss; VASOCONSTRICTION helps retain heat. A mechanism known as counter-current heat exchange is used by many endotherms—warmer blood in arteries travelling from the body core heats cooler blood in veins returning. In addition many animals have fur or feathers which insulate them: PILOERECTION (adjustment of the position of individual hairs) aids heat loss. (2) Evaporation: water is lost during BREATHING (either normal breathing or panting; dogs for example lose heat in this way) and by perspiration— SWEAT GLANDS in the skin allow evaporation of water which produces heat loss. (3) Behavioural responses: moving to warmer or cooler environments helps regulate temperature. SOCIAL BEHAVIOUR (for example huddling together to share and conserve heat) is also important. The construction of clothing or specialized dwellings (burrows, nests and so on) is also a behavioural adaptation to aid thermoregulation. MIGRATION, HIBERNATION and AESTIVATION are all behavioural adaptations to enable animals to deal with changed environmental temperatures. All of these processes can be used by endotherms and ectotherms. (4) In addition, endotherms have another mechanism: endogenous heat production. Muscle activity is important in this, as is SHIVERING (which is caused by neural impulses causing muscles to contract desynchronously) a response triggered by the brain's detection of lowered body temperature. NON-SHIVERING THERMOGENESIS is the production of heat by other endogenous means, principally through the action of BROWN ADIPOSE TISSUE (popularly known as BROWN FAT) and in the LIVER—some 20% of the body's heat is generated here.
Preoptic bombesin-like receptor-3 neurons heat it up
Published in Temperature, 2022
Ramón A. Piñol, Marc L. Reitman
A defining characteristic of endotherms, including mammals, is a warm, highly regulated, and stable core body temperature (Tb). Identifying the network of neurons controlling Tb is essential for understanding this fundamental physiology. The preoptic area (POA) is a brain region that receives afferent and local Tb sensory information and harbors efferent neurons of autonomic and behavioral thermoregulatory pathways [1]. These pathways contribute to thermoregulatory behavior, shivering and non-shivering thermogenesis, cutaneous vasomotion and cardiovascular responses. Researchers have identified POA neuronal populations in mice that reduce Tb when activated, regulating heat defense, torpor, and thermoregulation during sleep. A dozen such populations are marked by the expression of genes encoding enzymes, neuropeptides, and/or receptors and are predominantly glutamatergic. Future studies will need to better characterize these heterogenous neuronal populations, uncovering overlaps and defining subpopulations with more precise roles. A POA population that increases Tb when activated has been proposed and likely uses glutamatergic projections to the dorsomedial hypothalamus (DMH) [2]. We have now identified POA neurons expressing bombesin-like receptor-3 (POABRS3) as the first defined, specific population whose activation increases Tb [3]. This is driven by non-shivering thermogenesis through brown adipose tissue (BAT) activation, with concomitant increases in heart rate and blood pressure.
In vitro metabolism of imidacloprid and acetamiprid in rainbow trout and rat
Published in Xenobiotica, 2020
Richard C. Kolanczyk, Mark A. Tapper, Barbara R. Sheedy, Jose A. Serrano
Kinetic data was determined for the microsomal conversion of IMI to IMI-1 in both the RBT and rat. Comparison of IMI-1 kinetics showed a lower Km for the fish (79.2 µM) versus rat (158.7 µM) and hence a greater enzymatic affinity for IMI substrate for this reaction. A much higher rate of formation (Vmax) for this reaction was observed in the rat (38.4 pmole/min/mg) versus the fish (0.75 pmole/min/mg). A calculation ignoring species differences for Q10 resulted in a value of 4.5 which is outside of the typical range of Q10 =2 to 3. There is an inherent problem with comparing rates across species with vastly different physiological temperatures at different levels of evolution as well as comparison of an ectotherm with an endotherm.
Panax ginseng root, not leaf, can enhance thermogenic capacity and mitochondrial function in mice
Published in Pharmaceutical Biology, 2020
Su-hui Wu, Han-bing Li, Gen-Lin Li, Yue-juan Qi, Juan Zhang, Bai-yan Wang
The thermoregulation capacity of endotherms is easy influenced by the environment temperature. Thermoneutral zones (TNZ) are regarded as the range of ambient air temperatures, over which the BMR or resting metabolic rate (RMR) is maintained constant at the basal level (i.e., BMR as the lowest level for an endotherm to stay conscious; Cannon and Nedergaard 2011; Gordon 2012). It has been shown that BMR/RMR, which is more commonly measured, could contribute approximately 50% of daily energy expenditure (DEE; McNab 2002). Values for BMR and RMR usually differ by less than 10% and sometimes are used interchangeably.