Fibroblast-mediated contraction in actinically exposed and actinically protected aging skin

The changes in skin morphology over time are a consequence of both chronologic aging and the accumulation of environmental exposure. Through observation, we know that actinic radiation intensifies the apparent aging of skin. We have investigated the effects of aging and actinic radiation on the ability of fibroblasts to contract collagen-fibroblast lattices. Preauricular and postauricular skin samples were obtained from eight patients aged 49 to 74 undergoing rhytidectomy. The samples were kept separate, and the fibroblasts were grown in culture. Lattices constructed with preauricular fibroblasts consistently contracted more than lattices containing postauricular fibroblasts. The difference in amount of contraction in 7 days between sites was greatest for the younger patients and decreased linearly as donor age increased (r = -0.96). This difference may be due to preauricular fibroblasts losing their ability to contract a lattice as aging skin is exposed to more actinic radiation.     

The long-term results of ruby laser depilation in a consecutive series of 346 patients

The goal of this study was to prospectively assess the long-term results of ruby laser depilation in 346 consecutive patients who underwent hair removal at 402 anatomical sites. The patients were treated using a ruby laser, with mean power ranging from 8.6 J to 15.7 J according to skin type. Results were assessed using two outcome measures-the percentage reduction in hair density and the hair-free interval. The median reduction in hair density was 55 percent (range, 0 to 100 percent) at a median time of 1 year after the last treatment session. The median hair-free interval was 8 weeks. Patients underwent a median number of four treatment sessions. Forty-three of the 346 patients were treated at more than one anatomical site. Of the sites treated, 75 percent reduction in hair density was achieved in 22 percent, 90 percent reduction was achieved in 2.2 percent, and complete depilation was achieved in only 0.7 percent. Darker colored hair was more effectively treated. Treatment efficacy was not affected by anatomical site, with the exception of the faces of male patients, which were found to be particularly resistant to treatment. There was a significant correlation between the number of treatments given and the outcome. The overall complication rate was 9.0 percent (36 of 402 sites) with respect to pigmentary changes and blistering, but varied according to Fitzpatrick skin type. The complication rate was highest in skin types V and VI (24.7 percent), with no complications in skin type I. Although a greater than 50 percent reduction in hair density was achieved in half of the 346 patients treated, complete depilation was achieved in only an extremely limited number of patients.     

LATERAL CYSTS AND FISTULAS OF THE NECK

The embryonic origin of lateral cysts and fistulas remains controversial. They are, however, located in the general anatomic pattern of the embryonic thymic duct, which starts in the lateral pharyngeal wall and passes under the sternomastoid muscle to enter the mediastinum. The cyst is a unilocular, semiattached, non-translucent mass which has a tendency to become infected in 30 per cent of cases.The preauricular sinus occurs in front of the ear and is due either to a branchial cleft or an inclusion of one of the six primitive buds which form the external ear.Cystic hygroma is due to sequestrated lymphatic channels. These are always multilocular and rather invasive and may extend into mediastinum and arms.Diagnosis and treatment are considered in this presentation.     

Effect of soil mechanical impedance on root growth of two rice varieties under field drought stress

Two upland rice varieties, Azucena and Bala, were screened for root growth under droughted and irrigated treatments in two field sites at the West Africa Rice Development Association (WARDA) experimental farm, Côte d’Ivoire, during the dry season of 1999/2000. The sites were chosen to represent contrasting soil profile penetration resistance (PR) characteristics on upland sites, although both were relatively impeding. The number of nodal root axes per unit area passing through horizontal transects (root density) was counted at 35, 56, 77 and 98 days after sowing (DAS) at 10 cm depth intervals. Azucena consistently maintained a greater root density than Bala and a greater proportion of Azucena roots grew to 30 cm depth (22.7% vs. 8.4% at 77 DAS). There was little detectable effect of water regime on root distribution but evidence of lower root numbers at depths below 20 cm in the higher PR site was revealed. A site by variety by soil depth interaction suggests that Azucena roots are more strongly affected by very high PR than those of Bala. PR between 0–30 cm depth increased greatly with decreasing soil water content during the drought as the soil dried. This increase is likely to have prevented or greatly impaired further nodal root growth within this layer. At 40 cm depth, PR was high (3–4 MPa) but did not increase during the drought. At this depth root growth rate was likely to be greatly reduced despite the availability of water. These results demonstrate that varietal differences in root morphology characterised in the laboratory can be also detected in impeding field soils as differences in the density of roots at depth. Relatively poor root growth in these fields in the absence of drought was probably due to the high mechanical impedance and/or the physiological stress of the plants in the dry season. Our results indicate that high mechanical impedance was a more fundamental constraint on root growth than soil water availability during the drought. Thus, varietal differences in root penetration ability might be very important for drought avoidance in soils of this type.     

Relevance of the lesser occipital nerve in facial rejuvenation surgery

Nerve injuries are possible during facial rejuvenation surgery. The great auricular nerve has been studied; however, little is known about the lesser occipital nerve and its relevance in facial rejuvenation surgery. To understand the importance of the lesser occipital nerve in a face lift procedure, the specific anatomy of the nerve was studied in the laboratory in 19 hemifaces, with additional nerve observations in the operating room. The course of the lesser occipital nerve, its branches, and the relationship with the surrounding structures were evaluated and recorded. The great auricular nerve was also dissected to compare the two nerve territories. In the majority of the dissections, the lesser occipital nerve supplied the superior ear and the mastoid area, whereas the great auricular nerve innervated the inferior ear and a portion of the preauricular area. The nerves, however, were variable in size and distribution. Five lesser occipital nerves provided the dominant supply to the ear, compensating for a small great auricular nerve contribution. Therefore, injury to the lesser occipital nerve can result in a major sensory deficit of the ear. We also found the lesser occipital nerve to have a subcutaneous course at a proximal and variable level. These nerve branches can be superficial, and therefore postauricular flap dissection can injure the nerve if the flap is dissected at the fascial level. We therefore suggest that the dissection be at a more superficial level to avoid nerve injury. And finally, if SMAS/platysma suspension sutures are placed, we suggest these be done in a vertical-oblique direction along the course of the lesser occipital nerve, because this should minimize the possibility of trapping terminal branches.     

Millimeter wave dosimetry of human skin

To identify the mechanisms of biological effects of mm waves it is important to develop accurate methods for evaluating absorption and penetration depth of mm waves in the epidermis and dermis. The main characteristics of mm wave skin dosimetry were calculated using a homogeneous unilayer model and two multilayer models of skin. These characteristics included reflection, power density (PD), penetration depth (delta), and specific absorption rate (SAR). The parameters of the models were found from fitting the models to the experimental data obtained from measurements of mm wave reflection from human skin. The forearm and palm data were used to model the skin with thin and thick stratum corneum (SC), respectively. The thin SC produced little influence on the interaction of mm waves with skin. On the contrary, the thick SC in the palm played the role of a matching layer and significantly reduced reflection. In addition, the palmar skin manifested a broad peak in reflection within the 83-277 GHz range. The viable epidermis plus dermis, containing a large amount of free water, greatly attenuated mm wave energy. Therefore, the deeper fat layer had little effect on the PD and SAR profiles. We observed the appearance of a moderate SAR peak in the therapeutic frequency range (42-62 GHz) within the skin at a depth of 0.3-0.4 mm. Millimeter waves penetrate into the human skin deep enough (delta = 0.65 mm at 42 GHz) to affect most skin structures located in the epidermis and dermis.     

Prediction of human sperm penetrating ability using computerized motion parameters

The sperm penetration assay (SPA) is used to assess male fertilizing potential but it is tedious and costly. Computer analysis could replace the need for the SPA in some cases, if computerized sperm motility parameters are highly predictive of SPA performance. The objective of this study was to determine whether computerized motility parameters from fresh semen samples could be used to predict SPA performance. Computer automated semen analysis (CASA; CellSoft, Cryo Resources) was used to quantitate sperm concentration (CONC), percent motility (MOT), curvilinear velocity (VEL), linearity of swimming trajectory (LIN), mean amplitude of lateral head displacement (ALH), and beat/cross frequency (B/CF). The SPA was performed using either Biggers, Whitten, and Whittingham's medium (BWW) or TEST-yolk buffer (TYB). Patients were divided into three groups depending on SPA performance: group 1, BWW-treated, 0% versus greater than 0% penetration; group 2, TYB-treated, 0% versus greater than 0% penetration; and group 3, TYB-treated, less than 20% versus less than or equal to 20% penetration. SPA performance was highly correlated with CONC, MOT, VEL, and B/CF. CONC, MOT, VEL, and B/CF were significantly higher for patients who penetrated in the SPA than for those who failed to penetrate. Discriminant function analysis (DFA) successfully classified 76% of all patients treated with TYB (group 2) who penetrated and 86% of nonpenetrators based on their computerized motility parameters. For group 2 DFA predicted that 93 men would penetrate in the SPA with TYB. Of these, 90 (97%) successfully penetrated at least one egg.(ABSTRACT TRUNCATED AT 250 WORDS)     

Personal experiences and algorithm of endoscopically assisted subperiosteal face lift in orientals for 5 years.

Orientals are anatomically distinct from Caucasians and are characterized by a thick dermis, a Mongoloid slant of the palpebral fissure, a relatively prominent zygoma and mandible angle, and a relatively flat nose. Given these characteristics, it was believed that the subperiosteal face lift was not suitable for Orientals. However, at our institution, endoscopically assisted subperiosteal face lifts were performed from May of 1994 to October of 1998 on 236 patients; variable pitfalls, as well as satisfying results, were reported. Patient ages ranged from 29 to 66 years (mean age, 55.2 years), and follow-up ranged from 6 to 44 months (mean follow-up, 23 months). All forehead and brow lifts were performed using an endoscopic guide, and routine corrugator resections and procerus myotomies were performed. Three slanted cortical tunnels were made at the corresponding locations on the outer table of the calvarium, and 1-0 nylon or screw suspension and fixation were performed after a 1-cm to 2-cm lift. Midface lifts were performed through lower blepharoplasty incisions and vertical temporal incisions instead of through conventional preauricular and postauricular incisions. Dissections were made subperiosteally and over the deep layers of deep temporal fascia. Malar fat pads were suspended with 1-0 nylon and affixed to deep temporal fascia.Most patients have been satisfied with their postoperative results, but unfavorable results and complications have been reported. Complications were classified as early or late complications or unfavorable results on the basis of the 3-week postoperative evaluation. There were 28 early complications (11.9 percent), consisting of ecchymosis with edema (persisting for up to 4 weeks), paresthesia, lagophthalmos, accentuated Mongoloid slant, small dimpling on the scalp, and scalp fold formation on the fixation site. There were 13 late complications/unfavorable results (5.5 percent), consisting of insufficient lift, exaggeration of sunken upper eyelids, intermittent headaches, itching sensations, and paresthesia on the scalp. The unfavorable results occurred in the patients who had previously undergone blepharoplasty and in those who had a history of foreign body injections into the face, fatty and thick faces, sunken upper eyelids, Mongoloid slants, and asymmetric facial expressions. Through understanding the anatomic characteristics of the Oriental face (i.e., thick dermis, Mongoloid slant of palpebral fissure, prominent zygoma and mandible angle, and flat nose), satisfying results were achieved by appropriate application of the modified procedures.     

Ballistic impact of single particles into gelatin: experiments and modeling with application to transdermal pharmaceutical delivery

The impact and penetration of high speed particles with the human skin is of interest for targeted drug delivery by transdermal powder injection. However, it is often difficult to perform penetration experiments on dermal tissue using micron scale particles. To address this, a finite element model of the impact and penetration of a 2 μm gold particle into the human dermis was developed and calibrated using experiments found in the literature. Using dimensional analysis, the model was linked to a larger scale steel ball-gelatin system in order to extract key material parameters for both systems and perform impact studies. In this manner, an elastic modulus of 2.25 MPa was found for skin, in good agreement with reported values from the literature. Further gelatin experiments were performed with steel, polymethyl methacrylate, titanium, and tungsten carbide balls in order to determine the effects of particle size and density on penetration depth. Both the finite element model and the steel-gelatin experiments were able to predict the penetration behavior that was found by other investigators in the study of the impact of typical particles used for vaccine delivery into the human dermis. It can therefore be concluded that scaled up systems utilizing ballistic gelatins can be used to investigate the performance of transdermal powder injection technology.     

Theoretical evidence that root penetration ability interacts with soil compaction regimes to affect nitrate capture

Background and AimsAlthough root penetration of strong soils has been intensively studied at the scale of individual root axes, interactions between soil physical properties and soil foraging by whole plants are less clear. Here we investigate how variation in the penetration ability of distinct root classes and bulk density profiles common to real-world soils interact to affect soil foraging strategies.MethodsWe utilize the functional–structural plant model ‘OpenSimRoot’ to simulate the growth of maize (Zea mays) root systems with variable penetration ability of axial and lateral roots in soils with (1) uniform bulk density, (2) plow pans and (3) increasing bulk density with depth. We also modify the availability and leaching of nitrate to uncover reciprocal interactions between these factors and the capture of mobile resources.Key ResultsSoils with plow pans and bulk density gradients affected overall size, distribution and carbon costs of the root system. Soils with high bulk density at depth impeded rooting depth and reduced leaching of nitrate, thereby improving the coincidence of nitrogen and root length. While increasing penetration ability of either axial or lateral root classes produced root systems of comparable net length, improved penetration of axial roots increased allocation of root length in deeper soil, thereby amplifying N acquisition and shoot biomass. Although enhanced penetration ability of both root classes was associated with greater root system carbon costs, the benefit to plant fitness from improved soil exploration and resource capture offset these.ConclusionsWhile lateral roots comprise the bulk of root length, axial roots function as a scaffold determining the distribution of these laterals. In soils with high soil strength and leaching, root systems with enhanced penetration ability of axial roots have greater distribution of root length at depth, thereby improving capture of mobile resources.     

Retinoic acid and CO2 laser resurfacing

The purpose of this study was to analyze the effect of retinoic acid on wound healing and depth of injury in an animal skin model resurfaced with a CO2 laser. The dorsal skin of 21 Hartley guinea pigs was divided into halves. One-half received a daily application of 0.05% retinoic acid for 28 days, whereas the other half served as the control. The animals were divided into three treatment groups of seven animals. Group A was laser resurfaced with one pass of the Coherent UltraPulse CO2 laser (300 mJ, 60 W, density 40 percent). Group B received two passes, and group C received three passes. Histologic studies were obtained before laser resurfacing and days 1, 4, and 7 after resurfacing. Depth of injury, thickness, number of squamous cell and granular cell layers, and epithelialization rates were measured. We found that the depth of injury was statistically less in animals pretreated with retinoic acid. Granular cells were thicker and more numerous at day 4 in pretreated animals but similar to controls by day 7. Animals pre-treated with retinoic acid overall seemed to heal wounds earlier. In conclusion, pretreatment with retinoic acid may reduce the depth of injury in laser resurfacing and speed healing rates.     

Habitat use by Nonnative Rainbow Trout, Oncorhynchus mykiss, and Native Little Colorado spinedace, Lepidomeda vittata

We evaluated overlap in microhabitat use between nonnative rainbow trout, Oncorhynchus mykiss, and native Little Colorado spinedace, Lepidomeda vittata, a federally threatened cyprinid, in natural and experimental settings. In natural settings, we also examined occurrence and microhabitat use of two other native fishes, speckled dace, Rhinichthys osculus, and bluehead sucker, Catostomus discobolus. Native species co-occurred, as did rainbow trout and bluehead sucker. However, occurrences of Little Colorado spinedace and speckled dace were not significantly correlated with occurrence of rainbow trout. Total lengths of all three native species were significantly smaller at allopatric sites than at sites sympatric with rainbow trout. Microhabitat characteristics at sites with rainbow trout did not differ from those where the other three species were found, but did differ among the native species. In laboratory experiments with Little Colorado spinedace and rainbow trout, rainbow trout used the lower depth zone most, and spinedace increased use of the lower depth zone upon addition of rainbow trout. In addition, species tended to co-occur in zones, but used cover independently of one-another, suggesting a low level of agonistic interactions. However, after addition of a high density of rainbow trout, spinedace tended to use cover less than before. We suggest that the species can coexist at low rainbow trout densities. Potential negative effects of rainbow trout on Little Colorado spinedace likely increase with increasing densities of rainbow trout, and rainbow trout likely affect smaller size classes of Little Colorado spinedace more than larger ones.     

Computerized tomography of the otic capsule and otoliths in the oyster toadfish,Opsanus tau

The neurocranium of the toadfish (Opsanus tau) exhibits a distinct translucent region in the otic capsule (OC) that may have functional significance for the auditory pathway. This study used ultrahigh resolution computerized tomography (100 µm voxels) to compare the relative density of three sites along the OC (dorsolateral, midlateral, and ventromedial) and two reference sites (dorsal: supraoccipital crest; ventral: parasphenoid bone) in the neurocranium. Higher attenuation occurs where structural density is greater; thus, we compared the X‐ray attenuations measured, which provided a measure of relative density. The maximum attenuation value was recorded for each of the five sites (x and y) on consecutive sections throughout the OC and for each of the three calcareous otoliths associated with the sensory maculae (lagena, saccule, and utricle) in the OC. All three otoliths had higher attenuations than any sites in the neurocranium. Both dorsal and ventral reference sites (supraoccipital crest and parasphenoid bone, respectively) had attenuation levels consistent with calcified bone and had relatively small, irregular variations along the length of the OC in all individuals. The lowest relative attenuations (lowest densities) occurred consistently at the three sites along the OC. In addition, the lowest attenuations measured along the OC occurred at the ventromedial site around the saccular otolith for all seven fish. The decrease in bone density along the OC is consistent with the hypothesis that there is a low‐density channel in the skull to facilitate transmission of acoustic stimuli to the auditory endorgans of the ear. J. Morphol. 276:228–240, 2015. © 2014 Wiley Periodicals, Inc.     

Observations of external ear—An Indian study

Somatoscopy of the external ear provides a general idea of the shape of an ear, form of the helix, presence (or absence) of Darwin's tubercle and of the attachment of an ear lobe to a cheek, etc. It is of great importance not only to physical anthropologists but also to plastic surgeons, physicians and forensic scientists. There is no detailed somatoscopic study of the ear morphology concerning the entire Indian subcontinent. Hence, in the present study an attempt has been made to report the frequency of various somatoscopic features of various parts of the auricle of adult males and females who live in the central region of India.In both sexes oval-shaped ears and normally rolled helix were most common. The preauricular region was found to be clear with very few cases of the occurrence of pits and sinuses. Free lobules were more frequent among females than males but it was vice versa for Darwin's tubercle. The position of the ear's upper edge was most commonly located at the eyebrow tail while its lower edge was located at an upper lip level in both sexes. Hypoplastic lobules were noted in one-fifth of males but were very rare among females. Very few cases of lop ear, preauricular appendage and preauricular pit were observed.Some of these somatoscopic features act as soft biometric traits that improve the performance of the primary biometric system of personal identification. Somatoscopy of external ear acts as an aid to surgeons while reconstructing deformed ears and also helps physicians in detecting anomalies, for example, Edward's, cleft lip/cleft palate syndromes.     

Are mountain passes higher in the tropics? Janzen's hypothesis revisited

Synopsis In 1967 Daniel Janzen published an influential paper titled "Why Mountain Passes Are Higher in the Tropics." Janzen derived a simple climatic-physiological model predicting that tropical mountain passes would be more effective barriers to organismal dispersal than would temperate-zone passes of equivalent altitude. This prediction derived from a recognition that the annual variation in ambient temperature at any site is relatively low in the tropics. Such low variation within sites not only reduces the seasonal overlap in thermal regimes between low- and high-altitude sites, but should also select for organisms with narrow physiological tolerances to temperature. As a result, Janzen predicted that tropical lowland organisms are more likely to encounter a mountain pass as a physiological barrier to dispersal (hence "higher"), which should in turn favor smaller distributions and an increase in species turnover along altitudinal gradients. This synthetic hypothesis has long been at the center of discussions of latitudinal patterns of physiological adaptation and of species diversity. Here we review some of the key assumptions and predictions of Janzen's hypothesis. We find general support for many assumptions and predictions, but call attention to several issues that somewhat ameliorate the generality of Janzen's classic hypothesis.     

Combined rhytidectomy and full-face laser resurfacing

A series of patients undergoing a combined face lifting procedure with simultaneous laser resurfacing is described. Although resurfacing is accepted as safe for deep-plane face lifts and forehead lifts, there are reports of preauricular skin loss with a standard face lift. In this series, 26 consecutive cases are described. A superficial musculoaponeurotic system (SMAS) face lift technique was used. A skin flap was developed no more than 3.0 cm from the preauricular area, and most of that was excised. Full-face laser resurfacing was done with the SilkTouch laser. An 8-mm square pattern was used at 16 to 18 W. Three to four passes were done. Care was taken, however, to do very superficial lasering of the periphery, especially over the small amount of undermined skin that remained. There was no preauricular skin loss. This series demonstrates the safety of combining laser resurfacing with the SMAS technique face lift in regard to preauricular skin loss.     

Regional differences in capillary density of the normal human dermis

Quantitative study of the capillary density of normal dermis of 113 biopsy specimens taken from 20 body sites from 6 cadavers was carried out. Histologic quantification of dermal capillaries using the alkaline phosphatase method to delineate vascular endothelium and automated image analysis demonstrates statistically significantly greater capillary density in the head-face/neck region both in the papillary and reticular dermis than in the lower parts of the body. The smallest numbers of the dermal capillary density were noted in the calf and shin areas. These data support the hypothesis that random-pattern skin flaps can be safely raised longer in the face and neck than in other parts of the body.     

Frequency and site-dependent variations in vibration detection thresholds on the face

An adaptive psychophysical procedure was used to estimate the vibration detection threshold at seven spatially matched sites on the two sides of the face and at one scalp site. Repeated measurements over six testing sessions were made for stimuli vibrating at 1, 10 and 100 Hz for each of 21 neurologically healthy, young adult females. Approximately 14 stimulus trials were required to obtain each estimate of the threshold amplitude. Thresholds varied as a function of frequency ( p < 0.0001), side ( p < 0.001) and site ( p < 0.0001). Compared to stimulation at 100 Hz at which the estimates were lowest, thresholds were 3.1 times greater at 10 Hz and 5.4 times greater at 1 Hz. Thresholds were lowest on the vermilion and highest on the cheek and chin. The preauricular skin and scalp exhibited an intermediate level of sensitivity. Whereas thresholds were comparable on the two sides of the face for stimulation at 1 Hz, they averaged 1.33 times greater on the right side for stimulation at 10 and 100 Hz. Moreover, thresholds obtained during the last two sessions were 16% higher than those obtained during the first two sessions ( p < 0.02), suggesting that subjects on average became more conservative in reporting the presence of the stimulus. The sensitivity in discriminating differences in tactile function favors use of the rapidly administered testing procedure in a clinical setting.     

REPRODUCTIVE OUTPUT AND BIOMASS ALLOCATION IN SESBANIA EMERUS IN A TROPICAL SWAMP

This study examined the correlation of moisture, reproductive phenology, density of mature plants, and herbivory of apical meristems with the morphology and reproductive output of Sesbania emerus, an annual legume growing along a moisture gradient in a swamp in Guanacaste Province, Costa Rica. It also determined how biomass allocation varied and how it was related to reproductive output of plants growing along the moisture gradient within the swamp. Morphological changes included production of more stems and branches in response to herbivory, more and higher prop roots and more aerenchyma as water depth increased, and greater stem diameter in lower densities. Plant height varied greatly within a site, but not among habitats. Plants began to produce flowers and fruits later in wet sites than in dry sites. Reproductive output was generally more sensitive to environmental variables than was plant size. Fruit number and plant height were positively correlated for almost every treatment. Greater fruit and seed production were correlated with drier sites, earlier phenology, and lower density, but not with herbivory. Total biomass accumulation did not vary among moisture sites, but root production appeared to occur at the expense of reproductive output in the wetter sites. Plants in the wetter sites had both a greater percent and a greater absolute amount of biomass in roots, and a lower percent and a lower absolute amount of biomass in fruits and seeds than plants in drier sites. The root: shoot ratio was nearly five times higher in the wet than the dry site. Seed number per plant ranged from a mean of 6,800 at the wet site to a mean of 16,878 at the dry site. If this striking phenotypic variation in reproductive output and biomass accumulation has a genetic basis, the possibility of ecotypic differentiation exists in S. emerus.     

Frequency and site-dependent variations in vibration detection thresholds on the face

An adaptive psychophysical procedure was used to estimate the vibration detection threshold at seven spatially matched sites on the two sides of the face and at one scalp site. Repeated measurements over six testing sessions were made for stimuli vibrating at 1, 10 and 100 Hz for each of 21 neurologically healthy, young adult females. Approximately 14 stimulus trials were required to obtain each estimate of the threshold amplitude. Thresholds varied as a function of frequency (p < 0.0001), side (p < 0.001) and site (p < 0.0001). Compared to stimulation at 100 Hz at which the estimates were lowest, thresholds were 3.1 times greater at 10 Hz and 5.4 times greater at 1 Hz. Thresholds were lowest on the vermilion and highest on the cheek and chin. The preauricular skin and scalp exhibited an intermediate level of sensitivity. Whereas thresholds were comparable on the two sides of the face for stimulation at 1 Hz, they averaged 1.33 times greater on the right side for stimulation at 10 and 100Hz. Moreover, thresholds obtained during the last two sessions were 16% higher than those obtained during the first two sessions (p < 0.02), suggesting that subjects on average became more conservative in reporting the presence of the stimulus. The sensitivity in discriminating differences in tactile function favors use of the rapidly administered testing procedure in a clinical setting.