Case study of skin temperature and thermal perception in a hot outdoor environment

Focusing on the understanding and the estimation of the biometeorological conditions during summer in outdoor places, a field study was conducted in July 2010 in Athens, Greece over 6 days at three different sites: Syntagma Square, Ermou Street and Flisvos coast. Thermo-physiological measurements of five subjects were carried out from morning to evening for each site, simultaneously with meteorological measurements and subjective assessments of thermal sensation reported by questionnaires. The thermo-physiological variables measured were skin temperature, heat flux and metabolic heat production, while meteorological measurements included air temperature, relative humidity, wind speed, globe temperature, ground surface temperature and global radiation. The possible relation of skin temperature with the meteorological parameters was examined. Theoretical values of mean skin temperature and mean radiant temperature were estimated applying the MENEX model and were compared with the measured values. Two biometeorological indices, thermal sensation (TS) and heat load (HL)—were calculated in order to compare the predicted thermal sensation with the actual thermal vote. The theoretically estimated values of skin temperature were underestimated in relation to the measured values, while the theoretical model of mean radiant temperature was more sensitive to variations of solar radiation compared to the experimental values. TS index underestimated the thermal sensation of the five subjects when their thermal vote was ‘hot’ or ‘very hot’ and overestimated thermal sensation in the case of ‘neutral’. The HL index predicted with greater accuracy thermal sensation tending to overestimate the thermal sensation of the subjects.     

Androgynic phenotypes in obese women

A sample of 521 Caucasian women from an outpatient obesity clinic were classified by androgynic design. Photographs and outline sketches were obtained and eventually characteristic body outline patterns were developed. The distinct patterns of androgynic phenotypes were useful in recording the amount, distribution and texture of fat tissue. The phenotypic patterns remained relatively constant despite weight fluctuations. In the group studied the magnitude of obesity and the age at which it first occurred were related to androgynic patterns. Early menarche and early onset of obesity were associated. Constitutional differences, as shown by the body outline drawings, are clinically useful in evaluating the kind and degree of obesity.     

Ambient temperature perception in plants

Since plants are sessile they must be able to sense and rapidly respond to changes in ambient temperature. Key aspects of plant development, including the transition to flowering and the circadian clock, have important inputs from ambient temperature. In the model system Arabidopsis thaliana, molecular candidates for mediating these roles have recently been uncovered, which will be critical for obtaining an understanding of the mechanisms involved.     

Visual perception from the perspective of a representational,non-reductionistic,level-dependent account of perception and conscious awareness

This article proposes a new model to interpret seemingly conflicting evidence concerning the correlation of consciousness and neural processes. Based on an analysis of research of blindsight and subliminal perception, the reorganization of elementary functions and consciousness framework suggests that mental representations consist of functions at several different levels of analysis, including truly localized perceptual elementary functions and perceptual algorithmic modules, which are interconnections of the elementary functions. We suggest that conscious content relates to the ‘top level’ of analysis in a ‘situational algorithmic strategy’ that reflects the general state of an individual. We argue that conscious experience is intrinsically related to representations that are available to guide behaviour. From this perspective, we find that blindsight and subliminal perception can be explained partly by too coarse-grained methodology, and partly by top-down enhancing of representations that normally would not be relevant to action.     

Body surface area prediction in normal-weight and obese patients

None of the equations frequently used to predict body surface area (BSA) has been validated for obese patients. We applied the principles of body size scaling to derive an improved equation predicting BSA solely from a patient's weight. Forty-five patients weighing from 51.3 to 248.6 kg had their height and weight measured on a calibrated scale and their BSA calculated by a geometric method. Data were combined with a large series of published BSA estimates. BSA prediction with the commonly used Du Bois equation underestimated BSA in obese patients by as much as 20%. The equation we derived to relate BSA to body weight was a power function: BSA (m(2)) = 0.1173 x Wt (kg)(0.6466). Below 10 kg, this equation deviated significantly from the BSA vs. body weight curve, necessitating a different set of coefficients: BSA (m(2)) = 0.1037 x Wt (kg)(0.6724). Covariance of height and weight for patients weighing <80 kg reduced the Du Bois BSA-predicting equation to a power function, explaining why it provides good BSA predictions for normal-size patients but fails with obesity.     

The functional impact of mental imagery on conscious perception

Mental imagery has been proposed to contribute to a variety of high-level cognitive functions, including memory encoding and retrieval, navigation, spatial planning, and even social communication and language comprehension. However, it is debated whether mental imagery relies on the same sensory representations as perception, and if so, what functional consequences such an overlap might have on perception itself. We report novel evidence that single instances of imagery can have a pronounced facilitatory influence on subsequent conscious perception. Either seeing or imagining a specific pattern could strongly bias which of two competing stimuli reach awareness during binocular rivalry. Effects of imagery and perception were location and orientation specific, accumulated in strength over time, and survived an intervening visual task lasting several seconds prior to presentation of the rivalry display. Interestingly, effects of imagery differed from those of feature-based attention. The results demonstrate that imagery, in the absence of any incoming visual signals, leads to the formation of a short-term sensory trace that can bias future perception, suggesting a means by which high-level processes that support imagination and memory retrieval may shape low-level sensory representations.     

Erythrocyte ouabain binding and intracellular Na+ in normotensive obese women and obese women receiving medication for hypertension

People with "primary obesity" may be hypertensive because they have lost their ability to compensate for the effect of low Na+-K+-ATPase levels on blood pressure. In obese patients receiving hypertensive medication (n = 13), but not in normotensive nonmedicated patients (n = 42), diastolic blood pressure was inversely correlated with erythrocyte ouabain binding (P less than 0.02) and directly correlated with intracellular Na+ concentration (P less than 0.01). Moreover, there was a stronger inverse relationship between ouabain binding and intracellular Na+ in patients receiving medication for hypertension (P less than 0.01) than in normotensive patients (P less than 0.05). These data suggest that patients receiving hypertensive medication may be less able to compensate than normotensive patients, (a) for the potential effect of Na+-K+-ATPase levels on intracellular Na+ and (b) for the potential effect of intracellular Na+ concentration on diastolic blood pressure. We propose that obese people with low levels of ouabain binding (primary obesity) may have an increased risk of developing hypertension if their compensatory mechanisms fail.     

Perception of foot temperature in young women with cold constitution: analysis of skin temperature and warm and cold sensation thresholds

To examine the disease state of cold constitution, physiological measurements of the foot were conducted by investigating thermal sensations under an environmental condition of 25 degrees C-26 degrees C (neutral temperature) in 29 young women with and without cold constitution. The subjects were classified into 3 groups according to their experiences with cold constitution: cold constitution, intermediate, and normal groups. Foot skin temperature was measured by thermography. Thermal sensations were measured on the dorsum of the left foot using a thermal stimulator. Cold and warm spots on the dorsum of the right foot were ascertained. Thermal stimulation was delivered by a copper probe. No significant differences in foot skin temperature among these 3 groups were identified as measured in a laboratory under neutral temperature conditions. However, the mean warm sensation threshold was +6.3+/-1.09 degrees C (mean+/-SEM) for the cold constitution group (n=14), +3.4+/-2.10 degrees C (mean+/-SEM) for the intermediate group (n=7), and -0.25+/-1.96 degrees C (mean+/-SEM) for the normal group (n=6). The difference was significant between the cold constitution and normal groups. No significant differences among the 3 groups were found in the cold sensation threshold. This may be attributable to the distribution of thermal receptors and to chronically reduced blood flow in subcutaneous tissues, where the skin temperature receptors responsible for temperature sensation are located.     

Obestatin and ghrelin in obese and in pregnant women

We identified, through qPCR, receptor mRNA for a number of gut peptides in female human omental fat: the incretins, GIP and GLP-1, the orexigenic peptides PYY-Y1 and -Y2 and ghrelin, and the anorexigenic peptide obestatin. Four cohorts of women were examined: lean controls (BMI<23), obese (BMI>41), obese diabetic and term pregnant women. Human fat expressed receptor mRNAs for all six peptides. Pregnant women expressed roughly three times as much orphan GPR-39 receptor, a proposed obestatin receptor, than other women and less than half as much of the ghrelin receptor (GHSR-1a). An immunoblot probed with a GPR-39 selective antibody yielded a single band corresponding to the correct molecular weight (52 kDa) for the proposed obestatin receptor. Fluorescent immunohistochemistry of human fat employing the same antibody indicated the receptor protein was localized to the adipocyte cell membrane. The concentration of obestatin circulating in blood was measured in the same cohort of women and was significantly lower in obese and obese diabetic women compared to control.     

Differences in daily rhythms of wrist temperature between obese and normal-weight women: associations with metabolic syndrome features

The circadian rhythm of core body temperature is associated with widespread physiological effects. However, studies with other more practical temperature measures, such as wrist (WT) and proximal temperatures, are still scarce. The aim of this study was to investigate whether obesity is associated with differences in mean WT values or in its daily rhythmicity patterns. Daily patterns of cortisol, melatonin, and different metabolic syndrome (MetS) features were also analyzed in an attempt to clarify the potential association between chronodisruption and MetS. The study was conducted on 20 normal-weight women (age: 38 ± 11 yrs and BMI: 22 ± 2.6 kg/m(2)) and 50 obese women (age: 42 ± 10 yrs and BMI: 33.5 ± 3.2 kg/m(2)) (mean ± SEM). Skin temperature was measured over a 3-day period every 10 min with the "Thermochron iButton." Rhythmic parameters were obtained using an integrated package for time-series analysis, "Circadianware." Obese women displayed significantly lower mean WT (34.1°C ± 0.3°C) with a more flattened 24-h pattern, a lower-quality rhythm, and a higher intraday variability (IV). Particularly interesting were the marked differences between obese and normal-weight women in the secondary WT peak in the postprandial period (second-harmonic power [P2]), considered as a marker of chronodisruption and of metabolic alterations. WT rhythmicity characteristics were related to MetS features, obesity-related proteins, and circadian markers, such as melatonin. In summary, obese women displayed a lower-quality WT daily rhythm with a more flattened pattern (particularly in the postprandial period) and increased IV, which suggests a greater fragmentation of the rest/activity rhythm compared to normal-weight women. These 24-h changes were associated with higher MetS risk.     

Body temperature and skin blood flow during a 14-day bed-rest in a head-down tilt position in humans

Exposure to microgravity or simulated microgravity is known to affect regulatory function in autonomic nervous system. With regard to thermoregulation, simulated microgravity impairs sweating and induces lower skin and higher internal temperatures during physical work. During supine rest after HDT bed rest, the internal temperatures were reported to be higher than those of pre-HDT bed rest in some studies but not in others. There is no report about the dynamic changes of skin blood flow during 14-day HDT bed rest. The process of HDT bed-rest deconditioning on the function of the thermoregulatory system is virtually unknown. The HDT induces an immediate cephalad fluid shift which would inhibit the sympathetic outflow through the arterial and cardiopulmonary baroreflexes, which may increase the skin blood flow. On the other hand, prolonged HDT bed rest induces dehydration, which will increase sympathetic outflow through cardiopulmonary baroreceptor modulation. Both sympathetic activation and dehydration itself will decrease skin blood flow. It seems probable that the general effect on skin blood flow may reverse along the HDT bed rest. However, the dynamic characters of skin blood flow and body temperature during the HDT bed rest have not been studied thoroughly. Therefore, the purpose of present study was to investigate the changes of skin blood flow and body temperature during 14 days HDT bed rest.