Water nanodroplets make a greater contribution to facial skin moisture levels in air-conditioned rooms during winter than in summer.

BACKGROUND/PURPOSE: By performing experiments in air-conditioned chamber, we previously demonstrated that the presence of water nanodroplets (mist) improved facial skin moisture levels without reducing water loss from the facial skin surface or inducing excessive humidity. Some previous studies have demonstrated that the epidermis is a less effective barrier to water in winter because the corneocytes that comprise facial skin become smaller in winter as skin turnover increases in cold environments. We hypothesized that it would be easier for mist to penetrate into the facial stratum corneum (SC) in winter than in summer. In the present study, we investigated the ability of mist to improve facial skin moisture levels in winter and summer. METHODS: We examined transepidermal water loss (TEWL) as an index of barrier function and skin conductance as an index of SC hydration at the forehead, lateral canthus, and cheeks in eight healthy Japanese females (mean ± SD: 45.5 ± 3.2 years) in the presence or absence of mist in February-March and July. RESULTS: In the absence of mist, skin conductance at the forehead and lateral canthus was significantly higher in summer than in winter, but these seasonal differences were diminished in the presence of mist. In the presence of mist, skin conductance was increased in winter and decreased in summer at the lateral canthus; however, these changes were not significant. Thus, our findings suggest that mist penetrates into the SC and improves skin moisture levels in winter. CONCLUSION: We demonstrated that it is easier for mist to penetrate into the SC at the lateral canthus during winter than in summer. Thus, mist is expected to improve facial moisture levels in winter by penetrating into and remaining in the SC. Hence, mist could be used to help prevent facial skin from becoming dry in air-conditioned rooms during winter.

The effects of facial fanning on thermal comfort sensation during hyperthermia.

We studied how facial fanning during hyperthermia improves the thermal comfort sensation. Experiments were carried out on ten male subjects. They were immersed in hot water at 40 degrees C for 45 min. At 20 min and 35 min, fanning (1 m x s(-1)) was applied to their faces for 5 min. Core temperature (Tc) measured as esophageal temperature (Tes) and tympanic temperature (Tty) continued to rise during the immersion, but temporarily decreased during fanning with a delay of 2 or 3 min. Skin temperatures (Ts) on the forehead and cheek continued to increase slightly during immersion, but decreased immediately after the start of fanning. During immersion before face fanning, the time trend of thermal sensation towards the warm level was similar to that of skin temperature on the face, whereas the time trend of thermal comfort ratings towards the uncomfortable level was similar to that of Tc. The scores of both thermal sensation and thermal comfort were reduced significantly immediately after the start of fanning, and their time courses were different to those of Ts and Tty. These results support previous reports that thermal sensation depends on skin temperature, and that thermal comfort depends on both the skin and core temperatures. Moreover, they indicate that both thermal sensation and comfort ratings are affected by the dynamic responses of the cutaneous thermoreceptors when fanning is applied to the face during hyperthermia.

Irregular activation of individual sweat glands in human sole observed by a videomicroscopy.

Sweat secretion from individual sweat glands on the human sole was observed in four male subjects by using a videomicroscope and correlated with sudomotor neural activity recorded from the tibial nerve by means of microneurography. Individual sweat glands could be distinguished as active, less active and inactive according to the incidence of sweat secretion during spontaneous sweating. The threshold amplitude of the sudomotor burst necessary for sweat secretion varied from gland to gland. The number of sweat secretion was significantly related to the threshold amplitude. Sweat glands often failed to produce sweat secretion even when a suprathreshold burst occurred: only 46.1+/-3.8% (mean +/- S.E.M.) of the suprathreshold bursts elicited sweat secretion. Failure of the sweat secretion tended to appear after several bursts occurred consecutively with short intervals. In spite of the variability in sweat gland activity, the number of sweat glands recruited was linearly related to the amplitude of the sudomotor burst (P < 0.001). Thus, although sweat secretion from each sweat gland depends primarily on the intensity of sudomotor neural activity. the activity of each sweat gland may fluctuate temporally as the result of irregular activation of sudomotor fibers and possibly some intrinsic factors of the gland.

Vasodilator component in sympathetic nerve activity destined for the skin of the dorsal foot of mildly heated humans.

1. Skin sympathetic nerve activity (SSNA) was recorded in seven male subjects from the peroneal nerve by microneurography, and the temporal correspondence of spontaneously occurring SSNA bursts with vasodilatation and sweating responses on the dorsal foot was studied during a mild body heating at rest. 2. Some SSNA bursts were followed by a sweat expulsion with a latency of 2.4 +/- 0.4 s, and some bursts by a transient vasodilatation with a latency of 2.2 +/- 0.4 s (means +/- S.D.). SSNA bursts followed both by a sweat expulsion and by a vasodilatation response (Type 1), those followed only by a sweat expulsion (Type 2) and those followed only by a vasodilatation, response (Type 3) were 70%, 10% and 1% of the total bursts examined, respectively. 3. For Type 1 bursts, there was a significant, but weak linear relationship among the burst amplitude, the amplitude of the corresponding vasodilatation and the amplitude of the corresponding sweat expulsion. 4. It was concluded that SSNA contains vasodilatory activity which is synchronous with sudomotor nerve activity. The results suggest that such vasodilatory activity contributes to sustaining the sweat gland function by supplying sufficient blood.

Altered response in cutaneous sympathetic outflow to mental and thermal stimuli in primary palmoplantar hyperhidrosis.

Skin sympathetic nerve activities (SSNAs) were recorded simultaneously from the tibial and peroneal nerves by microneurography at an ambient temperature of 25 degrees C in five subjects with primary palmoplantar hyperhidrosis. The resting of the tibial SSNA innervating the sole (glabrous skin) increased moderately (36.5 +/- 1.5 bursts/min), while mental arithmetic provoked marked responses (1,003.3 +/- 457.4% compared with the resting level) in the hyperhidrosis group compared with the control normohidrosis group (n = 5, 25.3 +/ 4.2 bursts/min and 142.2 +/- 58.4%, respectively). Differentiation of the tibial SSNA into sudomotor (innervating sweat glands) and vasoconstrictor (innervating presphincter of skin vessels) revealed that this SSNA enhancement was attributable to not only sudomotor but also vasoconstrictor components during mental arithmetic. In contrast, the responses in the peroneal SSNA (innervating the dorsum pedis, hairy skin) of the hyperhidrosis group were only slightly changed, exhibiting no significant difference from those in the normohidrosis group. Reflex bursts elicited by sound and electric stimulation were normal in amplitude and latency. When the ambient temperature was elevated to 30 degrees C, the tibial SSNAs became more enhanced than did the peroneal SSNAs. The tibial SSNA was markedly enhanced in the hyperhidrosis group (290.0 +/- 78.5%) compared with the normohidrosis group (78.3 +/- 25.4%). We conclude that the excessive responses in SSNA to the plantar glabrous skin to both mental and thermal stimuli may be responsible for the profuse sweating in subjects with primary palmoplantar hyperhidrosis.

Impairment of calcitonin gene-related peptide-induced potentiation of cholinergic sweat secretion in patients with multiple system atrophy.

Loss of sweating is a characteristic feature of multiple system atrophy (MSA) with autonomic failure, and widespread anhidrosis may lead to hyperthermia and collapse in a hot environment. Calcitonin gene-related peptide (CGRP) is present in the periglandular nerves around sweat glands and is a strong stimulant of methacholine (MCH)-mediated cholinergic sweating. The present study evaluated CGRP-related regulation of cholinergic sweating in patients with MSA. CGRP-induced potentiation of MCH-mediated cholinergic sweating was significantly reduced in MSA patients as compared with normal age-matched controls. These results suggest that regulation of sweating is extensively affected in MSA as a consequence of peptidergic dysfunction.

Cutaneous vasodilatation responses synchronize with sweat expulsions.

To examine whether cutaneous active vasodilatation is mediated by sudomotor nerve fibres we recorded cutaneous blood flow and sweat rates continuously with laser-Doppler flowmetry and capacitance hygrometry, respectively, from the dorsal and plantar aspects of the foot in 11 male subjects at varying ambient temperatures (Ta) between 22 and 40 degrees C (relative humidity 40%). In a warmer environment (Ta 29-40 degrees C), predominant responses of the blood flow curve from the sole of the foot were transient depressions (negative blood flow responses, NBR), whereas those from the dorsal foot were transient increases (positive blood flow responses, PBR). The PBR on the dorsal foot occurred spontaneously or in response to mental or sensory stimuli, and when PBR did not fuse with each other the rate of PBR was linearly related to tympanic temperature. When dorsal foot sweating was continuous, PBR on the dorsal foot almost entirely synchronized with sweat expulsion. When dorsal foot sweating was intermittent PBR sometimes occurred on the dorsal foot without corresponding sweat expulsions, but these PBR showed a complete correspondence with subthreshold sweat expulsion seen on a methacholine-treated area. The amplitude and the duration of PBR showed a significant linear relationship with the amplitude and the duration of the corresponding sweat expulsion. In a thermoneutral or cooler environment (Ta 22-29 degrees C), PBR occurred on the sole of the foot when mental or sensory stimuli elicited sweating in that area. Thus, PBR occurred when and where sweating appeared. Atropine failed to abolish PBR on the dorsal foot. Blockade of the peroneal nerve eliminated both PBR and NBR on the dorsal foot.(ABSTRACT TRUNCATED AT 250 WORDS)

Sudomotor dysfunction in amyotrophic lateral sclerosis.

We performed a quantitative sudomotor function test on 11 patients with classic amyotrophic lateral sclerosis (ALS) and 11 age-matched control subjects. Thermal warming increased the sweat rate in the forearm of ALS patients and in the forearm and thigh of control subjects. The sweat rate in the thigh of ALS patients was lower than that of controls. Thyrotropin releasing hormone increased the sweat rate in the forearm and thigh and decreased oral temperature in both ALS and controls but the lower extremity response was reduced in ALS. Results of the sudomotor axon reflex test on the thigh indicate that in ALS, there is mild postganglionic sudomotor dysfunction. We conclude that patients with ALS have mild thermoregulatory sweat dysfunction due to postganglionic lesions in the lower extremities.

Different thermal dependency of cutaneous sympathetic outflow to glabrous and hairy skin in humans.

We investigated the effects of ambient temperature on the sudomotor and vasoconstrictor components of skin sympathetic nerve activity (SSNA). The sympathetic traffic was measured by simultaneous microneurographic recording from post-ganglionic nerve fibres in the tibial and the peroneal nerves. When the ambient temperature was raised from 25 degrees C to 34 degrees C, both sudomotor and vasoconstrictor components of SSNA were enhanced in the peroneal nerve but were suppressed in the tibial nerve. The sudomotor and vasoconstrictor sympathetic outflows were elevated in both nerves when the temperature was lowered from 34 degrees C to 18 degrees C. Our results suggested that the sudomotor and the vasoconstrictor components of SSNA are differently modulated by ambient temperature. The difference in sudomotor and vasoconstrictor components of SSNA in the tibial and the peroneal nerves at different ambient temperature may have been responsible for the differences observed in sweating and vasoconstriction in glabrous and hairy skin.

Human cardiovascular responses to a 60-min bath at 40 degrees C.

This study was designed to determine human cardiovascular responses to a 60-min bath at 40 degrees C compared with a thermoneutral bath at 34.5 degrees C. We measured mean blood pressure (MBP), heart rate (HR), skin blood flow (SBF) and core temperature in 8 healthy young males bathing at two different temperatures, 34.5 degrees C and 40 degrees C. During the thermoneutral bath (34.5 degrees C), heart rate tended to decrease, but all other variables showed no significant change. Ten min after entering the 40 degrees C bath, MBP decreased while HR and SBF increased. At the same time core temperature increased. We conclude that bathing at 40 degrees C may induce remarkable changes in the cardiovascular system by increasing core temperature when immersion in a hot bath for more than 10 min.

Effects of body and head positions on bilateral difference in tympanic temperatures.

We have examined the nonparallel changes in tympanic membrane temperatures (Tty) from the two ears in response to various changes in body and head positions. Upon assuming a lateral recumbent position, the Tty on the lower side increased while that on the upper side decreased. Pressure application over a wide area of the lateral chest only caused inconsistent and obscure asymmetric changes in Tty. A lateral flexion of the head with the subject sitting upright and a rotation of the head to the side in a supine position induced an increase in the Tty on the lower side compared to that on the upper side. The temperature and blood flow of the forehead often decreased on the lower side and increased on the upper side, although such responses were not always concomitant with the asymmetric changes in Tty. A dorsal flexion of the head with the subject in a reclining position caused a slight increase in the Tty, whereas raising the head upright induced a slight decrease in them. Two additional experiments were carried out with single photon emission computed tomography using 99mTc-hexamethylpropyleneamine oxime as tracer, and a slight, relative decrease in counts was noted in the right hemisphere during rotation of the head to the right. These results would strongly suggest that unilateral increases and decreases in Tty could have been caused by one-sided decreases and increases, respectively, in blood flow to the brain and/or the tympanic membrane, induced by a vasomotor reflex involving vestibular stimulation.

[Laser-Doppler flowmetry].

Laser-Doppler flowmetry (LDF) is a non-invasive technique for measuring the tissue blood flow. It has been shown in the skin that LDF discloses blood flow fluctuations due to vasomotor nerve activity. LDF can give measurements of blood flow at various sites of different tissue. Furthermore, LDF may enable selective measurement of blood flow at different depths within the tissue, when the device and the probe are appropriately chosen. Thus, LDF is available for examining vasomotor responses at various tissue sites. For clinical application, a method for calibrating the LDF signal in absolute units should be established.

Preferred ambient temperature for old and young men in summer and winter.

To investigate the effects of age on thermal sensitivity, preferred ambient temperature (Tpref) was compared between old (71-76 years) and young (21-30 years) groups, each consisting of six male subjects in summer and winter. The air temperature (Ta) was set at either 20 degrees C or 40 degrees C at commencement. The subject was directed to adjust the Ta for 45 min by manipulating a remote control switch to the level at which he felt most comfortable. In the older group, the Tpref was significantly lower in trails starting at 20 degrees C than that starting at 40 degrees C in summer. The fluctuation of Tpref (temperature difference between maximum and minimum Ta during the last 10 min) was significantly wider in the older group in both summer and winter. Repetition of the same experiment on each subject showed a poorer reproducibility of Tpref in the older group than in the younger group in summer. Tympanic and esophageal temperatures of the older group kept falling throughout the trial starting at 20 degrees C in summer. These results suggest that thermal sensitivity is decreased with advancing age and that thermal perception in the elderly, especially to cold, is less sensitive in summer.

The assessment of sudomotor dysfunction in multiple system atrophy.

We studied sudomotor function in 21 patients with multiple system atrophy and in 11 age-matched controls. The extent and severity of the sudomotor deficit was assessed using the quantitative thermoregulatory sweat test. Central sudomotor function was studied by measuring sweating in response to raising body heat and administering thyrotropin-releasing hormone. Postganglionic sudomotor function was studied using the sudomotor axon reflex test evoked by nicotine. We conclude that in multiple system atrophy, thermoregulatory sudomotor dysfunction was more severe in the lower extremities. Heat stimulation increased the frequency of sweat expulsion and sweat rate on the forearm in moderate multiple system atrophy to a similar degree as controls but failed to do so on the thigh. Thyrotropin-releasing hormone enhanced sweating in moderate multiple system atrophy and controls. Results of the sudomotor axon reflex test indicate that in multiple system atrophy there is postganglionic sudomotor dysfunction which may be due to transsynaptic changes. These results suggest that the main lesion responsible for sudomotor dysfunction in multiple system atrophy is within the intermediolateral column cells of the spinal cord.

Dynamic sweating response of man to infrared irradiation in various spectral regions.

In an attempt to detect differences in the thermal effect of infrared irradiation of different wave-lengths, transient sweating response to infrared irradiation in various spectral regions was examined. In Series 1, the ventral or dorsal surface of the nude subject was irradiated repetitively for a period of 4 min (2 min on, 2 min off) by each of three kinds of infrared heaters with main emissivity in 'near-infrared' (NIR; 0.7-2.8 microns), 'intermediate-infrared' (MIR; 1.5-5.8 microns), and 'far-infrared' (FIR; 2.8-25 microns) regions. The sweating response on a non-irradiated area tended to be the greatest with MIR, while the magnitude of the sweating response on the irradiated area showed no consistent differences among various wavelengths. The results infer that MIR stimulated cutaneous thomoreceptors most effectively, while its direct effect on local sweat gland activity was minimal. In Series 2, the effects of 9-12 min irradiations in more restricted ranges of wavelength were compared by the combination of the three kinds of heaters with filters (translucent to wavelength ranges of 1.3-2.7, 2.7-3.5, 3.6-8.0 microns, respectively). The sweating response on a remote area was predominantly greater with the range of 2.7-3.5 microns than with the other wavelength ranges, while the local effect on sweating was minimal with this range. The results of Series 2 reinforce those of Series 1, indicating that the degree of stimulation of cutaneous thermoreceptors and of direct thermal effect on sweat gland activity differ with spectral regions incident on the skin, thus affecting local and remote effects on the sweating response.

Identification of sudomotor activity in cutaneous sympathetic nerves using sweat expulsion as the effector response.

In a warm environment at ambient temperatures between 25 degrees and 38 degrees C (relative humidity 50%-60%) the relationship between sympathetic activity in cutaneous nerves (SSA) and pulses of sweat expulsion was investigated in five young male subjects. The SSA was recorded from the peroneal nerve using a micro-electrode. Sweat expulsion was identified on the sweat rate records obtained from skin areas on the dorsal side of the foot, for spontaneous sweating and drug-induced sweating, using capacitance hygrometry. Sweat expulsion was always preceded by bursts of SSA with latencies of 2.4-3.0 s. This temporal relationship between bursts of SSA and sweat expulsion was noted not only in various degrees of thermal sweating but also in the sweating evoked by arousal stimuli, or by painful electric stimulation. The amplitude of the sudomotor burst was linearly related to the maximal rate of increase of the corresponding sweat expulsion, the amplitude of the expulsion and the integrated amount of sweat produced for the duration of the expulsion. The results provide direct evidence that sweat expulsion reflects directly centrally-derived sudomotor activity.