Fur Thickness Research Articles

Targeting senescence induced by age or chemotherapy with a polyphenol-rich natural extract improves longevity and healthspan in mice

Accumulating senescent cells within tissues contribute to the progression of aging and age-related diseases. Botanical extracts, rich in phytoconstituents, present a useful resource for discovering therapies that could target senescence and thus improve healthspan. Here, we show that daily oral administration of a standardized extract of Salvia haenkei (Haenkenium (HK)) extended lifespan and healthspan of naturally aged mice. HK treatment inhibited age-induced inflammation, fibrosis and senescence markers across several tissues, as well as increased muscle strength and fur thickness compared with age-matched controls. We also found that HK treatment reduced acutely induced senescence by the chemotherapeutic agent doxorubicin, using p16LUC reporter mice. We profiled the constituent components of HK by mass spectrometry, and identified luteolin—the most concentrated flavonoid in HK—as a senomorphic compound. Mechanistically, by performing surface plasmon resonance and in situ proximity ligation assay, we found that luteolin disrupted the p16–CDK6 interaction. This work demonstrates that administration of HK promotes longevity in mice, possibly by modulating cellular senescence and by disrupting the p16–CDK6 interaction.

Exploring the pivotal variables of tongue diagnosis between patients with acute ischemic stroke and health participants

Background and aimStroke is a major cause of disability worldwide, and ischemic stroke is the most common type of stroke. The prevention and treatment of ischemic stroke remain a challenge worldwide. Traditional Chinese medicine (TCM) is often sought to provide an alternative therapy for the prevention and rehabilitation intervention of ischemic stroke in Taiwan. Therefore, this study explored the pivotal variables of tongue diagnosis among acute ischemic stroke and healthy participants in middle and older age. Experimental procedureThis was a cross-sectional and case-controlled study. Data were collected from 99 patients with acute ischemic stroke and 286 healthy participants who received tongue diagnoses at Changhua Christian Hospital (CCH) from September 1, 2014, to December 31, 2016. Tongue features were extracted using the automatic tongue diagnosis system. Nine tongue features, including tongue shape, tongue color, fur thickness, fur color, saliva, tongue fissures, ecchymoses, teeth marks, and red spots were analyzed. Results and conclusionObjective image analysis techniques were used to identify significant differences in the many tongue features between patients with acute ischemic stroke and individuals without stroke. According to the logistic regression analysis, pale tongue color (OR:5.501, p = 0.001), bluish tongue color (OR:4.249, p = 0.014), ecchymoses (OR:1.058, p < 0.001), and tongue deviation angle (OR:1.218, p < 0.001) were associated with significantly increased odds ratios for acute ischemic stroke. The research revealed that tongue feature abnormalities were significantly related to the occurrence of ischemic stroke.

An Efficient and Portable LED Multispectral Imaging System and Its Application to Human Tongue Detection

LED illumination-based multispectral imaging has a fast switching ability, high cost-effectiveness, and a simple structure. It has been used in some applications, especially color recognition. In this paper, we introduce an efficient and portable LED multispectral imaging system for human tongue detection. The spatial pixels are categorized based on cosine similarity to reduce the optimization calculation times. Further, segment linear calibration is used to improve the recovery quality. Simulation results show that this method greatly improves the reconstruction speed and that recovered images maintain a high spatial and spectral quality. This LED multispectral imaging system captures images quickly and obtains multispectral images in a timely fashion. We also built a small prototype for human tongue detection in traditional Chinese medicine. The recovered spectra were used to calculate the tongue body color and fur color. By combining these with the spatial information, the fur distribution and fur thickness were analyzed. The results of this study verified the effectiveness of this LED multispectral imaging system. Further experiments will be undertaken for the quantitative analysis of tongue features. The study was approved by the Institutional Review Board (or Ethics Committee) of Shenzhen Institute of Advanced Technology Chinese Academy of Sciences.

Tongue diagnosis index of chronic kidney disease

BackgroundTo apply non-invasive Automatic Tongue Diagnosis System (ATDS) in analyzing tongue features in patients with chronic kidney disease (CKD). MethodsThis was a cross-sectional, case-controlled observational study. Patients with CKD who met the inclusion and exclusion criteria were enrolled and divided into the following groups according to renal function and dialysis status: non-dialysis CKD group; end-stage renal disease (ESRD) group; and control group. Tongue images were captured and eight tongue features—shape, color, fur thickness, saliva, fissure, ecchymosis, teeth marks, and red dots—were imaged and analyzed by ATDS. Results117 participants (57 men, 60 women) were enrolled in the study, which included 16 in control group, 38 in non-dialysis CKD group, and 63 in ESRD group. We demonstrated significant differences in the fur thickness (p = 0.045), color (p = 0.005), amounts of ecchymosis (p = 0.010), teeth marks (p = 0.016), and red dot (p < 0.001) among three groups. The areas under receiver operating characteristic curve for the amount of ecchymosis was 0.757 ± 0.055 (95% confidence interval, 0.648–0866; p < 0.001). Additionally, with increase in ecchymosis by one point, the risk of CKD dialysis rose by 1.523 times (95% confidence interval, 1.198–1.936; p = 0.001). After hemodialysis, the amount of saliva (p = 0.038), the area of saliva (p = 0.048) and the number of red dots (p = 0.040) were decreased significantly among patients with ESRD. On the contrary, the percentage of coating (p = 0.002) and area of coating (p = 0.026) were increased significantly after hemodialysis. ConclusionBlood deficiency and stasis with qi deficiency or blood heat syndrome (Zheng pattern) is common in patients with CKD. The risk of CKD dialysis increases with increasing ecchymosis. Hemodialysis can affect saliva, tongue coating, and relieve heat syndrome among ESRD patients.

A Perspective on Tongue Diagnosis in Patients with Breast Cancer.

Introduction Breast cancer (BC) is the most common cancer in women and patients with BC often undergo complex treatment. In Taiwan, nearly 80% of patients with BC seek traditional Chinese medicine (TCM) during adjuvant chemotherapy to relieve discomfort and side effects. This study investigated tongue features and pattern differentiation through noninvasive TCM tongue diagnosis in patients with BC. Materials and Methods This cross-sectional, case-controlled, retrospective observational study collected patient data through a chart review. The tongue features were extracted using the automatic tongue diagnosis system (ATDS). Nine tongue features, including tongue shape, tongue color, fur thickness, fur color, saliva, tongue fissures, ecchymoses, teeth marks, and red dots, were analyzed. Results and Discussion. Objective image analysis techniques were used to identify significant differences in the many tongue features between BC patients and non-BC individuals. A significantly larger proportion of patients with BC had a small tongue (p < 0.001), pale tongue (p < 0.001), thick fur (p < 0.001), yellow fur (p < 0.001), wet saliva (p < 0.001), thick tongue fur (p < 0.001), fissures (p=0.040), and ecchymoses in the heart-lung area (p=0.013). According to logistic regression, small tongue shape, pale tongue color, yellow fur color, wet saliva, and the amounts of fissures were associated with a significantly increased odds ratio for BC. Conclusions This study showed significant differences in tongue features, such as small tongue shape, pale tongue color, thick fur, yellow fur color, wet saliva, fissure, and ecchymoses in the heart-lung area in patients with BC. These tongue features would imply yin deficiency, deficiencies of blood, stagnation of heat, and phlegm/blood stasis in TCM theory. There is a need to investigate effective and safe treatment to enhance the role of TCM in integrated medical care for patients with BC.

A Nonlinear Association between Tongue Fur Thickness and Tumor Marker Abnormality: A Cross-Sectional Study.

Background Many associations between tongue fur and different physiological and biochemical indexes have been revealed. However, the relationship between tongue fur and tumor markers remains unexplored. Methods We collected the medical examination reports of 1625 participants. Participants were residents of Chengdu, China, undergoing routine health checkups at the health management center of the Affiliated Hospital of Chengdu University of Traditional Chinese Medicine between December 2018 and September 2020. The participants' tongue fur thickness was measured using the DAOSH four-diagnostic instrument. Tumor marker levels, including t-PSA, AFP, CEA, CA125, and CA199, were measured in the clinical laboratory. Curve-fitting and multivariable logistic regression were used to analyze the association between tongue fur thickness and tumor marker abnormality. Results Curve-fitting showed that the relationship between tongue fur thickness and abnormal tumor marker rate was nonlinear, similar to a U shape. As the tongue fur thickness value increased, the abnormal tumor marker probability initially decreased and then increased. Logistic regression showed that, in the crude model, compared with the thin tongue fur group, the odds ratios (ORs) and 95% confidence intervals (CIs) of the less or peeling tongue fur group and thick tongue fur group for tumor marker abnormality were 1.79 (1.02–3.17) and 1.70 (1.13–2.54), respectively. After adjusting gender, age, body mass index (BMI), smoking history, drinking history, tongue color, the form of the tongue, and fur color, the ORs and 95% CIs of the less or peeling tongue fur group and thick tongue fur group were 1.93 (1.04–3.57) and 1.82 (1.17–2.81), respectively. Conclusions Excessive or very little tongue fur is associated with tumor marker abnormality. Further cross-sectional studies are needed to evaluate the clinical value of tongue fur for cancer diagnosis and screening.

The tongue features associated with chronic kidney disease.

Background:Traditional Chinese medicine (TCM) tongue diagnosis plays an important role in differentiation of symptoms because the tongue reflects the physiological and pathological condition of the body. The automatic tongue diagnosis system (ATDS), which noninvasively captures tongue images, can provide objective and reliable diagnostic information. Chronic kidney disease (CKD) currently is an important global public health problem and contributor to morbidity and mortality from non-communicable diseases. Thus, it is interesting to analyze and probe the relationship between tongue examination and CKD.Methods:This protocol is a cross-sectional, case-controlled observational study investigating the usefulness of the ATDS in clinical practice by examining its efficacy as a diagnostic tool for CKD. Volunteers over 20 years old with and without CKD will be enrolled. Tongue images will be captured and the patients divided into 2 groups: CKD group and healthy group. Nine primary tongue features will be extracted and analyzed, including tongue shape, tongue color, tooth mark, tongue fissure, fur color, fur thickness, saliva, ecchymosis, and red dots.Result:The results of this study will systematically evaluate tongue manifestations of patients and examine its efficacy as an early detection and diagnosis of CKD.Discussion:The aim of this protocol is to investigate discriminating tongue features to distinguish between CKD and normal people, and establish differentiating index to facilitate the noninvasive detection of CKD.Trial registries:ClinicalTrials.gov; Identifier: NCT04708743.

Gender- and age-dependent tongue features in a community-based population.

This study, an important groundwork for clinical tongue diagnosis and future traditional Chinese medicine (TCM) research, tested the hypothesis that some tongue features vary significantly between different gender and age groups by utilizing an automatic tongue diagnosis system (ATDS).A cross-sectional study of 1487 participants from a community-based population was performed. Study subjects with ages ranging from 20 to 92 were categorized into 3 groups: <40, 40 to 64, and ≥65 years old, and the subjects were also stratified according to gender. Tongue images were collected at the end of each normal health examination routine to further derive the relevant tongue features of every participant by using the ATDS developed by our team. There were a total of nine tongue features that were identified: tongue shape, tongue color, fur thickness, fur color, saliva, tongue fissure, ecchymosis, teeth mark, and red dot. The corresponding tongue features, demography, and physical/laboratory examination data were compared between different gender and age groups.Our study showed that, compared to females, males had enlarged tongue shape, thicker fur, more fissures and fewer teeth marks (all P < .001), and also had more red tongue color (P = .019), normal saliva (P = .001), more red dots (P = .005) and yellower fur (P = .014). In females, increasing age was associated with more enlarged tongue shape, thicker fur, yellower fur, more saliva, fissures and fewer teeth marks (all P < .001), more ecchymoses (P = .009), and more red tongue color (P = .023). These associations of age with more fissures, fewer teeth marks, fewer red dots (P < .001), median tongue shape (P = .029), and wet saliva (P = .014) were also evident in males, but other relationships were not clearly evident.Even though most of the common tongue features derived from a community-based population are consistent with TCM theory, yet some significantly gender- and age-dependent tongue characteristics were identified. These disparities in tongue features associated with gender or age shall be prudently taken into consideration in clinical tongue diagnosis and future TCM research.

The tongue features associated with type 2 diabetes mellitus.

Diabetes mellitus (DM) is a public problem closely associated with numerous oral complications, such as coated tongue, xerostomia, salivary dysfunction, etc. Tongue diagnosis plays an important role in clinical prognosis and treatment of diabetes in the traditional Chinese medicine (TCM). This study investigated discriminating tongue features to distinguish between type 2 DM and non-DM individuals through non-invasive TCM tongue diagnosis.The tongue features for 199 patients with type 2 DM, and 372 non-DM individuals, serving as control, are extracted by the automatic tongue diagnosis system (ATDS). A total of 9 tongue features, namely, tongue shape, tongue color, fur thickness, fur color, saliva, tongue fissure, ecchymosis, teeth mark, and red dot. The demography, laboratory, physical examination, and tongue manifestation data between 2 groups were compared.Patients with type 2 DM possessed significantly larger covering area of yellow fur (58.5% vs 22.5%, P < .001), thick fur (50.8% vs 29.2%, P < .001), and bluish tongue (P < .001) than those of the control group. Also, a significantly higher portion (72.7% vs 55.2%, P < .05) of patients with long-term diabetics having yellow fur color than the short-term counterparts was observed.The high prevalence of thick fur, yellow fur color, and bluish tongue in patient with type 2 DM revealed that TCM tongue diagnosis can serve as a preliminary screening procedure in the early detection of type 2 DM in light of its simple and non-invasive nature, followed by other more accurate testing process. To the best of our knowledge, this is the first attempt in applying non-invasive TCM tongue diagnosis to the discrimination of type 2 DM patients and non-DM individuals.

Diabetes with pyogenic liver abscess—A perspective on tongue assessment in traditional Chinese medicine

This novel study provides a time series analysis of tongue features extracted from a diabetic patient with pyogenic liver abscess (PLA), treated with the integration of western medicine and traditional Chinese medicine (TCM). The features, namely, tongue color, tongue fur thickness and fur color, identified from a series of tongue images taken every two days, exhibit significant transitions matching closely with the progression of disease. These tongue features could serve as effective, non-intrusive indices for different progression stages of diabetes with PLA. A 76-year-old male diabetic patient was admitted for hyperglycemic hyperosmolar state. Intermittent fever and abdominal discomfort were noted. After performing abdominal computed tomography and laboratory studies, the results indicated pyeogenic liver abscess, Klebsiella pneumoniae ssp. pneumoniae related. As PLA progressed, the patient suffered spiking fever and right upper abdominal pain. Tongue examination revealed features with red tongue, white-yellow and thick fur. After receiving pigtail catheter drainage, the fever subsided and the pus-like fluid was drained smoothly. During the course of this process, gradually dwindled tongue fur witnessed through periodic tongue examination coincides consistently with laboratory data, namely, body temperature, fasting plasma glucose and plasma glucose level gathered. This is the first time series analysis of applying tongue examination to the progression of a specific disease. Through a series of tongue images taken periodically, tongue color, tongue fur thickness and fur color are identified to closely linked to the progression of diabetes with PLA, as indicated by data gathered through means of plasma glucose and abdominal sonographic follow-ups. Based on this promising finding, our future study will further extend the application of tongue assessment to evaluate the tongue characteristics of diabetic patients.

Thermal adaptation in endotherms: climate and phylogeny interact to determine population‐level responses in a wild rat

Summary1. The ecology of endotherms is driven by their great energetic need for thermoregulation, which renders mammals and birds particularly vulnerable to environmental temperature and resource fluctuations. Important outstanding questions are whether populations are specialized to their particular climate, and to what extent gene × environment interactions determine thermal responses.2. Here, we show that phylogenetic relatedness and climate interact to determine metabolic capacities, body temperature and morphology in a wild rat (Rattus fuscipes).3. Mitochondrial metabolic capacities are greater in warm climate populations, indicating that these responses are not the result of cold adaptation. However, glycolytic capacities, fur thickness and capacity for nonshivering thermogenesis are greater in cool climate populations. In populations from cooler climates, body temperatures are lower, but more variable. Together, these changes lead to substantial energy savings in cool climate populations, although all traits are constrained by phylogenetic relatedness.4. We demonstrate for the first time that gene × environment interactions determine thermal responses in wild mammal populations, and we suggest that physiological variability among populations may render the species more resilient to climate change because it increases whole‐species performance breadth. Climate envelope modelling is therefore insufficient to predict the future impact of climate change.

Plasticity in body temperature and metabolic capacity sustains winter activity in a small endotherm ( Rattus fuscipes)

Small mammals that remain active throughout the year at a constant body temperature have a much greater energy and food requirement in winter. Lower body temperatures in winter may offset the increased energetic cost of remaining active in the cold, if cellular metabolism is not constrained by a negative thermodynamic effect. We aimed to determine whether variable body temperatures can be advantageous for small endotherms by testing the hypothesis that body temperature fluctuates seasonally in a wild rat ( Rattus fuscipes); conferring an energy saving and reducing food requirements during resource restricted winter. Additionally we tested whether changes in body temperature affected tissue specific metabolic capacity. Winter acclimatized rats had significantly lower body temperatures and thicker fur than summer acclimatized rats. Mitochondrial oxygen consumption and the activity of enzymes that control oxidative (citrate synthase, cytochrome c-oxidase) and anaerobic (lactate dehydrogenase) metabolism were elevated in winter and were not negatively affected by the lower body temperature. Energy transfer modeling showed that lower body temperatures in winter combined with increased fur thickness to confer a 25 kJ day − 1 energy saving, with up to 50% owing to reduced body temperature alone. We show that phenotypic plasticity at multiple levels of organization is an important component of the response of a small endotherm to winter. Mitochondrial function compensates for lower winter body temperatures, buffering metabolic heat production capacity.

Seasonal variations in basal metabolic rate, lower critical temperature and responses to temporary starvation in the arctic fox (Alopex lagopus) from Svalbard

Metabolic rates of four resting, post-absorptive male adult summer- and winter-adapted captive arctic foxes (Alopex lagopus) were recorded. Basal metabolic rates (BMR) varied seasonally with a 36% increase from winter to summer, while body mass was reduced by 17% in the same period. The lower critical temperature (T 1c) of the winter-adapted arctic fox was estimated to −7°C, whereas T lc during summer was 5°C. The similarity of these values, which are much higher than hitherto assumed (e.g. Scholander et al. 1950b), is mainly due to a significantly (P<0.05) lower BMR in winter than in summer. Body core (stomach) temperature was stable, even at ambient temperatures as low as −45°C, but showed a significant (P<0.05) seasonal variation, being lower in winter (39.3±0.33°C) than in summer (39.8±0.16°C). The thermal conductivity of arctic fox fur was the same during both seasons, whereas the thermal conductance in winter was lower than in summer. This was reflected in an increase in fur thickness of 140% from summer to winter, and in a reduced metabolic response to ambient temperatures below T lc in winter. Another four arctic foxes were exposed to three periods of forced starvation, each lasting 8 days during winter, when body mass is in decline. No significant reduction in mass specific BMR was observed during the exposure to starvation, and respiratory quotient was unchanged at 0.73±0.02 during the first 5 days, but dropped significantly (P<0.05) to 0.69±0.03 at day 7. Locomotor activity and body core (intraperitoneal) temperature was unaltered throughout the starvation period, but body mass was reduced by 18.5±2.1% during these periods. Upon re-feeding, locomotor activity was significantly (P<0.05) reduced for about 6 days. Energy intake was almost doubled, but stabilised at normal levels after 11 days. Body mass increased, but not to the level before the starvation episodes. Instead, body mass increased until it reached the reduced body mass of ad libitum fed control animals. This indicates that body mass in the arctic fox is regulated according to a seasonally changing set point.

Simulation of sensible and latent heat losses from wet-skin surface and fur layer

A simulation model that simultaneously calculates heat and mass transfer from a wetted skin surface and fur layer of a cow is presented. The model predicts evaporative, convective and radiant heat losses for different levels of skin and fur wetness, air velocity, air temperature and relative humidity. In the model, fur layer (hair coat) properties such as fur thickness and hair density assumed are that of summer conditions. Evaporative cooling from wet-skin surface and hair coat is the dominant mode of heat mitigation mechanism in stressful hot environments and is further enhanced by increased air velocity. Evaporative cooling is, however, depressed by increased relative humidity because of deficit of water-vapor concentration between the skin surface and ambient air.

Seasonal Adaptation vs Physiological constraint: Photoperiod, Thermoregulation and Flight in Colias Butterflies

1. Photoperiod is already a known cue for the seasonal (spring and autumn) wing underside darkening, a polyphenism which is adaptive by increasing solar absorptivity, of the North American butterfly, Colias eurytheme. We now report that photoperiod is also a cue for seasonal (spring and autumn) deepening of thoracic «fur» (actually modified scales), which increases the insects'insulation against convective cooling, and thus is likewise adaptive to flight in these cooler seasons. Conversely, the less absorptive and less insulated summer forms are more adaptive in warm conditions because of lesser susceptibility to dangerous overheating. 2. Changes in absorptivity and fur thickness cued by photoperiod are in an uncorrelated fashion

Effects of Body Size and Fur on Heat Loss of Collared Lemmings, Dicrostonyx groenlandicus

Collared lemmings ( Dicrostonyx groenlandicus ) differ from many arvicoline rodents by increasing in size and developing white pelage in response to short photoperiod. I examined the relative contributions of body size and fur changes to heat loss in photoperiod-induced morphs. Heat loss as a function of ambient temperature was calculated from metabolic data and a heat-transfer model, and measured directly on pelts. Winter-morph lemmings were significantly longer and heavier than summer morphs; they were significantly rounder than both summer morphs and colony lemmings. The white winter pelage was significantly longer, thicker, and more dense than that of summer morphs. Calculated heat losses did not differ between morphs; however, heat loss through winter pelts was significantly lower than for summer pelts. Simulations predicted that heat loss of lemmings was more sensitive to changes in fur thickness and density than body mass; however, optimal body size increased by 10 g for lemmings at low temperatures. These results suggest that changes in size and shape may be of significance; nevertheless, fur insulation has the greatest influence on the energy budget of collared lemmings. The energetics of environmentally induced changes in body size of small mammals should be re-evaluated in the context of pelage response. I conclude with an evaluation of the thermal-conductance index as a measure of fur insulation, with recommendations for its replacement by more biologically relevant measures.

Thermoregulation and Flight in Colias Butterflies: Elevational Patterns and Mechanistic Limitations

This study identifies the physical determinants of thermoregulation in Colias, develops and tests models that predict the patterns of body temperature and flight activity along an elevational gradient (1.7-3.9 km), and explores the relationship of the thermoregulatory characteristics to these patterns among Colias populations. The limitations on adaptation provided by environmental vari- ability and the adaptive mechanisms involved are emphasized. Colias behaviorally thermoregulate by body orientation to solar radiation to achieve the body temperatures (30'-40'C) needed for flight. There are differences among Colias populations in solar absorptivity of the ventral hind wing and fur thickness on the ventral thorax which correlate with elevation. Energy balance and behavioral models based on meteorological inputs and the thermoreg- ulatory characteristics of the butterfly are developed and tested. These accurately predict body tem- peratures and flight activity of the population throughout the day at each site. High levels of flight activity occur whenever body temperatures are 30'-40', particularly at higher elevations. Short-term meteorological variation, such as intermittent cloudy periods, can rapidly reduce body temperature excess and flight activity to zero. The time available for flight activity per day is greater in low- elevation than in higher-elevation populations, even when differences in cloudiness are taken into account. Climate space analysis reveals that the overlap in flight space for populations at low and high elevations is -80% for sunny conditions. The minimum possible overlap in flight space between Colias butterflies is -40%, due to limitations imposed by the mechanisms of thermoregulation and wing color determination. These limitations are inadequate to explain the observed differences in flight activity with elevation. The microevolution of thermoregulation in Colias is discussed in terms of mechanistic limitations to adaptation, population tracking of the thermal environment, and the role of environmental variability.

ACCLIMATIZATION TO COLD: OBSERVATIONS ON THE MECHANISM OF THE REDUCED IMMEDIATE ADRENAL RESPONSE

The incorporation of inorganic phosphorus labelled with P32 into the inorganic phosphorus of the adrenal gland was measured in rats acclimatized to cold for 4 weeks. Previously it was reported that the immediate pituitary–adrenal response to brief cold exposure (2 hours at −5 °C), as judged by the increased P32 incorporation is considerably decreased in rats that have been acclimatized. Some observations are now reported on the mechanism of this reduced immediate response.The administration of ACTH, pitressin, or adrenaline caused similar increases in the adrenal phosphorus metabolism in acclimatized and non-acclimatized control rats. Acclimatization could still be demonstrated in rats after the fur had been removed by clipping.From these results it is concluded that the decreased immediate pituitary–adrenal response to an exposure to more severe cold, observed in acclimatized rats, is not the result of an increased fur thickness, nor is it the result of a decreased sensitivity of the adrenal tissue to ACTH, or to a decreased sensitivity of the pituitary or hypothalamus to a given stimulus. It is suggested that the reduction in the immediate pituitary–adrenal response to a more severe cold stress in acclimatized rats might be due to an alteration in the sensitivity of the peripheral nerve receptors, or in the mechanism, nervous or otherwise, whereby the pituitary is stimulated.

ACCLIMATIZATION TO COLD: OBSERVATIONS ON THE MECHANISM OF THE REDUCED IMMEDIATE ADRENAL RESPONSE

The incorporation of inorganic phosphorus labelled with P32 into the inorganic phosphorus of the adrenal gland was measured in rats acclimatized to cold for 4 weeks. Previously it was reported that the immediate pituitary–adrenal response to brief cold exposure (2 hours at −5 °C), as judged by the increased P32 incorporation is considerably decreased in rats that have been acclimatized. Some observations are now reported on the mechanism of this reduced immediate response.The administration of ACTH, pitressin, or adrenaline caused similar increases in the adrenal phosphorus metabolism in acclimatized and non-acclimatized control rats. Acclimatization could still be demonstrated in rats after the fur had been removed by clipping.From these results it is concluded that the decreased immediate pituitary–adrenal response to an exposure to more severe cold, observed in acclimatized rats, is not the result of an increased fur thickness, nor is it the result of a decreased sensitivity of the adrenal tissue to ACTH, or to a decreased sensitivity of the pituitary or hypothalamus to a given stimulus. It is suggested that the reduction in the immediate pituitary–adrenal response to a more severe cold stress in acclimatized rats might be due to an alteration in the sensitivity of the peripheral nerve receptors, or in the mechanism, nervous or otherwise, whereby the pituitary is stimulated.

Heat production and heat loss in the dog at 8-36 degrees C environmental temperature.

Metabolic and thermal responses of three dogs were made in a rapid responding calorimeter at temperatures ranging from 8°C to 36°C. These dogs were acclimatized to a kennel temperature of 27°C and had critical temperatures between 23°C and 25°C. The only physiological responses to low environmental temperatures were a moderate decrease in total heat content and an increase in heat production. The tissue conductance and the cooling constant of the fur did not effectively decrease below the levels obtaining throughout the neutral zone. In a hot environment heat loss from the respiratory tract was greatly increased. Although there was a great increase in the tissue conductance in the hot environment, conductance of heat through the tissue became decreasingly important as the air temperature approached body temperature so that panting became increasingly important for maintaining thermal balance. It is concluded that the vasomotor response of the peripheral vascular system is primarily a mechanism for dissipating excess heat produced during exercise; it is practically unimportant as a heat conserving mechanism. Effective changes in the total insulation of the fur can only be achieved by changing the surface area of the body, particularly those areas which are thinly furred, and not by any important change in the fur thickness through pilomotor activity.