A clinical and hemogasometric survey of neonatal lambs

In order to provide adequate medical assistance to neonates, the extent of vitality impairment has to be investigated through complementary exams, as well as clinical assessment. This investigation aimed to identify the physiological changes that occur during neonatal adaptation and to develop a clinical approach that can be performed during the first hour of life in neonatal lambs born through vaginal eutocic labor. The neonatal vitality of 14 Santa Ines lambs was verified using the Apgar system and rectal temperature at birth and after 5 and 60 min after birth. From the total number of neonates, 7 lambs were randomly selected for blood gas analysis and glucose immediately at birth and 1 h after birth. The lambs had hypoglycemia immediately after birth, as well as acidosis due to metabolic and respiratory causes. Given their hypoxemia at birth, lambs immediately exhibit tachycardia and tachypnea. However, neonatal lambs reached Apgar score superior than 7 after 5 min of birth. Ovine neonates are relatively mature at birth, with adequate thermoregulation and active mechanisms to compensate for physiological acid-base imbalances. In conclusion, a systematic clinical examination of newborn sheep should include the implementation of the Apgar score coupled with the confirmation of any acid-base imbalances. Further research should evaluate neonatal adaptation to this critical period over a longer period of time. (C) 2012 Elsevier B.V. All rights reserved.

A heat transfer model of the human upper limbs

A steady state multi-segmented heat transfer model of the human upper limbs was developed. The main purpose was to evaluate the impact of blood flow through superficial veins and subcutaneous vascular structures in the palm of the hands over the heat transfer between the limbs and the environment. The distinguishing feature of the model is the inclusion of a detailed circulatory network composed of vessels with diameter larger than 1 mm. The model was validated by comparing its results from exposures to a hot, a neutral, and a cold environment to experimental data presented in the literature. (C) 2011 Elsevier Ltd. All rights reserved.

Evolution of Body Elongation in Gymnophthalmid Lizards: Relationships with Climate

The evolution of elongated body shapes in vertebrates has intrigued biologists for decades and is particularly recurrent among squamates. Several aspects might explain how the environment influences the evolution of body elongation, but climate needs to be incorporated in this scenario to evaluate how it contributes to morphological evolution. Climatic parameters include temperature and precipitation, two variables that likely influence environmental characteristics, including soil texture and substrate coverage, which may define the selective pressures acting during the evolution of morphology. Due to development of geographic information system (GIS) techniques, these variables can now be included in evolutionary biology studies and were used in the present study to test for associations between variation in body shape and climate in the tropical lizard family Gymnophthalmidae. We first investigated how the morphological traits that define body shape are correlated in these lizards and then tested for associations between a descriptor of body elongation and climate. Our analyses revealed that the evolution of body elongation in Gymnophthalmidae involved concomitant changes in different morphological traits: trunk elongation was coupled with limb shortening and a reduction in body diameter, and the gradual variation along this axis was illustrated by less-elongated morphologies exhibiting shorter trunks and longer limbs. The variation identified in Gymnophthalmidae body shape was associated with climate, with the species from more arid environments usually being more elongated. Aridity is associated with high temperatures and low precipitation, which affect additional environmental features, including the habitat structure. This feature may influence the evolution of body shape because contrasting environments likely impose distinct demands for organismal performance in several activities, such as locomotion and thermoregulation. The present study establishes a connection between morphology and a broader natural component, climate, and introduces new questions about the spatial distribution of morphological variation among squamates.

Acute hypoxia induces hypertriglyceridemia by decreasing plasma triglyceride clearance in mice

Jun JC, Shin MK, Yao Q, Bevans-Fonti S, Poole J, Drager LF, Polotsky VY. Acute hypoxia induces hypertriglyceridemia by decreasing plasma triglyceride clearance in mice. Am J Physiol Endocrinol Metab 303: E377-E388, 2012. First published May 22, 2012; doi:10.1152/ajpendo.00641.2011.-Obstructive sleep apnea (OSA) induces intermittent hypoxia (IH) during sleep and is associated with elevated triglycerides (TG). We previously demonstrated that mice exposed to chronic IH develop elevated TG. We now hypothesize that a single exposure to acute hypoxia also increases TG due to the stimulation of free fatty acid (FFA) mobilization from white adipose tissue (WAT), resulting in increased hepatic TG synthesis and secretion. Male C57BL6/J mice were exposed to FiO(2) = 0.21, 0.17, 0.14, 0.10, or 0.07 for 6 h followed by assessment of plasma and liver TG, glucose, FFA, ketones, glycerol, and catecholamines. Hypoxia dose-dependently increased plasma TG, with levels peaking at FiO(2) = 0.07. Hepatic TG levels also increased with hypoxia, peaking at FiO(2) = 0.10. Plasma catecholamines also increased inversely with FiO(2). Plasma ketones, glycerol, and FFA levels were more variable, with different degrees of hypoxia inducing WAT lipolysis and ketosis. FiO(2) = 0.10 exposure stimulated WAT lipolysis but decreased the rate of hepatic TG secretion. This degree of hypoxia rapidly and reversibly delayed TG clearance while decreasing [H-3]triolein-labeled Intralipid uptake in brown adipose tissue and WAT. Hypoxia decreased adipose tissue lipoprotein lipase (LPL) activity in brown adipose tissue and WAT. In addition, hypoxia decreased the transcription of LPL, peroxisome proliferator-activated receptor-gamma, and fatty acid transporter CD36. We conclude that acute hypoxia increases plasma TG due to decreased tissue uptake, not increased hepatic TG secretion.

INTERACTION BETWEEN THE CARBON MONOXIDE AND NITRIC OXIDE PATHWAYS IN THE LOCUS COERULEUS DURING FEVER

FAPESP [2010/50882-1]

Intrauterine food restriction alters the expression of uncoupling proteins in brown adipose tissue of rat newborns

A previous study from our laboratory showed that maternal food restriction (MFR) delays thermoregulation in newborn rats. In neonates brown adipose tissue (BAT) is essential for thermogenesis due to the presence of uncoupling proteins (UCPs). The aim of this study was to evaluate the influence of MFR on the UCPs mRNA and protein expression in BAT and skeletal muscle (SM) of the newborn rat. Female Wistar EPM-1 control rats (CON) received chow ad libitum during pregnancy, whereas food-restricted dams (RES) received 50% of the amount ingested by CON. Fifteen hours after birth, the litters were weighed and sacrificed. Blood was collected for hormonal analysis. BAT and SM were used for determination of UCPs mRNA and protein expression, and Ca2+-ATPase sarcoplasmic reticulum (SERCA1). RES pups showed a significant reduction in body weight and fat content at birth. MFR caused a significant increase in the expression of UCP1 and UCP2 in BAT, without changes in UCP3 and SERCA1 expression in BAT and SM. No differences between groups were found for leptin, T4 and glucose levels. RES pups showed increased insulin and decreased T3 levels. The delay in development of thermoregulation previously described in RES animals appears not to result from impairment in thermogenesis, but from an increase in heat loss, since MFR caused low birth weight in pups, leading to greater surface/volume ratio. The higher expression of UCP1 and UCP2 in BAT suggests a compensatory mechanism to increased thermogenesis. (C) 2011 Elsevier Ltd. All rights reserved.

Dual function of egg-covering in the Kentish plover Charadrius alexandrinus

Many bird species take recesses during incubation, and while the nests are unattended, the eggs may both be vulnerable to predation and reach suboptimal temperatures for embryo development. Perhaps to avoid these negative possibilities, some birds cover their eggs with materials when they depart from nests. We examined experimentally, using the ground-nesting Kentish plover as model species, whether egg-covering allows egg temperatures to remain within optimal limits for embryogenesis in unattended nests, thus reducing the requirements of contact incubation, and simultaneously maintain the eggs' camouflage. There was a negative relationship between nest attendance and ambient temperature, but only during mid-morning, the period of the day when egg-covering was most frequent. Indeed, during mid-morning egg-covering not only served to better camouflage the eggs, but also to maintain egg temperatures within optimal thermal thresholds for embryogenesis while the nests remained unattended. During other periods of the day, covered eggs in unattended nests overheated (e.g., afternoon) or did not reach the optimal temperature for embryogenesis (e.g., early morning). During periods in which eggs may be uncovered to alleviate overheating, unattended nests may be easier to locate by predators, because the eggs are less well camouflaged. Therefore, camouflage and appropriate thermal environment are inseparable functions of egg-covering in the ground-nesting Kentish plover.

Human thermal comfort: an irreversibility-based approach emulating empirical clothed-body correlations and the conceptual energy balance equation

Exergetic analysis can provide useful information as it enables the identification of irreversible phenomena bringing about entropy generation and, therefore, exergy losses (also referred to as irreversibilities). As far as human thermal comfort is concerned, irreversibilities can be evaluated based on parameters related to both the occupant and his surroundings. As an attempt to suggest more insights for the exergetic analysis of thermal comfort, this paper calculates irreversibility rates for a sitting person wearing fairly light clothes and subjected to combinations of ambient air and mean radiant temperatures. The thermodynamic model framework relies on the so-called conceptual energy balance equation together with empirical correlations for invoked thermoregulatory heat transfer rates adapted for a clothed body. Results suggested that a minimum irreversibility rate may exist for particular combinations of the aforesaid surrounding temperatures. By separately considering the contribution of each thermoregulatory mechanism, the total irreversibility rate rendered itself more responsive to either convective or radiative clothing-influenced heat transfers, with exergy losses becoming lower if the body is able to transfer more heat (to the ambient) via convection.