Adjacent Hairs Research Articles

Combining Deep Learning With Optical Coherence Tomography Imaging to Determine Scalp Hair and Follicle Counts.

One of the challenges in developing effective hair loss therapies is the lack of reliable methods to monitor treatment response or alopecia progression. In this study, we propose the use of optical coherence tomography (OCT) and automated deep learning to non-invasively evaluate hair and follicle counts that may be used to monitor the success of hair growth therapy more accurately and efficiently. We collected 70 OCT scans from 14 patients with alopecia and trained a convolutional neural network (CNN) to automatically count all follicles present in the scans. The model is based on a dual approach of both detecting hair follicles and estimating the local hair density in order to give accurate counts even for cases where two or more adjacent hairs are in close proximity to each other. We evaluate our system on 70 OCT manually labeled scans taken at different scalp locations from 14 patients, with 20 of those redundantly labeled by two human expert OCT operators. When comparing the individual human predictions and considering the exact locations of hair and follicle predictions, we find that the two human raters disagree with each other on approximately 22% of hairs and follicles. Overall, the deep learning (DL) system predicts the number of follicles with an error rate of 11.8% and the number of hairs with an error rate of 18.7% on average on the 70 scans. The OCT system can capture one scalp location in three seconds, and the DL model can make all predictions in less than a second after processing the scan, which takes half a minute using an unoptimized implementation. This approach is well-positioned to become the standard for non-invasive evaluation of hair growth treatment progress in patients, saving significant amounts of time and effort compared with manual evaluation. Lasers Surg. Med. © 2020 Wiley Periodicals, Inc.

A multi-scale model for simulating liquid-hair interactions

The diverse interactions between hair and liquid are complex and span multiple length scales, yet are central to the appearance of humans and animals in many situations. We therefore propose a novel multi-component simulation framework that treats many of the key physical mechanisms governing the dynamics of wet hair. The foundations of our approach are a discrete rod model for hair and a particle-in-cell model for fluids. To treat the thin layer of liquid that clings to the hair, we augment each hair strand with a height field representation. Our contribution is to develop the necessary physical and numerical models to evolve this new system and the interactions among its components. We develop a new reduced-dimensional liquid model to solve the motion of the liquid along the length of each hair, while accounting for its moving reference frame and influence on the hair dynamics. We derive a faithful model for surface tension-induced cohesion effects between adjacent hairs, based on the geometry of the liquid bridges that connect them. We adopt an empirically-validated drag model to treat the effects of coarse-scale interactions between hair and surrounding fluid, and propose new volume-conserving dripping and absorption strategies to transfer liquid between the reduced and particle-in-cell liquid representations. The synthesis of these techniques yields an effective wet hair simulator, which we use to animate hair flipping, an animal shaking itself dry, a spinning car wash roller brush dunked in liquid, and intricate hair coalescence effects, among several additional scenarios.

A Note on the Specific Cuticle Structure of Wool Hairs in Otters (Lutrinae)

The cuticle structure of the wool hairs (secondary hairs) of six otter species was examined by scanning electron microscopy to clarify the specific function of this hair type in the Lutrinae. The species studied were chosen according to the different genera, climatic regions, and degrees of association to water of the Lutrinae. Independent of their preferred habitats, the cuticle of every wool hair examined exhibited in all animals a rather similar shape and arrangement of the scales. This specific adaptive feature allows a flexible interlocking of adjacent wool hairs, which also helps to form thin wool hair bundles that surround small oval shaped spaces. Thus, the trapping of an effective insulating air layer is facilitated and heat loss from the body is reduced.

CaEGTA uncompetitively inhibits calcium activation of whorl morphogenesis inAcetabularia

The spacing between adjacent hairs in vegetative whorls ofAcetabularia acetabulum (formerlyA. mediterranea) was earlier reported as being quantitatively responsive to calcium ion concentration in the culture medium. We here report a quantitative response to the concentration of the calcium-chelator EGTA, in the opposite sense to the effect of calcium. (Increasing [Ca2+] diminishes the spacing; increasing [EGTA] increases it.) The earlier work was interpreted in terms of control of the spacing by a putative reaction-diffusion mechanism in the cell membrane, in which a receptor R was activated by calcium-binding to initiate the process. We extend this interpretation by treating CaEGTA as an uncompetitive inhibitor of the effect of calcium on R. This leads to thermodynamic constants for CaEGTA binding to the CaR complex: ΔH 298 0 =−250 ± 60 kJ/mol; ΔS 298 0 =−820 ± 200 J/mol · K. Consistency of the concentration and temperature dependences reported here with the postulated dynamic mechanism increases the probability that this mechanism is correct.

Reliability and effectiveness of transmission from exteroceptive sensory neurons to spiking local interneurons in the locust

Mechanosensory information from exteroceptive hairs on the legs of a locust is first processed in a segmental ganglion by a midline population of spiking local interneurons for use in adjustments of posture and locomotion. Each interneuron receives excitatory inputs from a characteristic array of these receptors so that the surface of a leg is mapped onto the whole population of interneurons as a series of overlapping receptive fields. The properties of this first synaptic connection, and the contributions of individual afferents forming the receptive fields of the interneurons are examined. The gain of the excitatory synaptic connection between the hair afferents and the interneurons is often high, so that a single afferent spike can lead directly to a spike in the interneuron. Repetitive spikes in a hair afferent evoke EPSPs in an interneuron that decline in amplitude but that may summate. The first EPSP in any sequence is always the largest. The high frequencies of afferent spikes that are evoked by a normal deflection of a hair saturate the synaptic connection so that the amplitude of depolarization is no greater than to a single spike. The EPSPs from two hairs in a receptive field can summate but lead to no heterosynaptic facilitation. High-frequency bursts of spikes in one afferent can reduce the postsynaptic effect of another afferent. The amplitude of the EPSPs and the gain of the synaptic connections differ markedly between the hairs that comprise the receptive field of an interneuron. There are gradients of effectiveness, generally according to the axes of the leg, with one group of adjacent hairs producing the largest-amplitude EPSPs and having the highest gains. Individual hairs may contribute to the receptive field of more than one interneuron, and the gain of these connections may differ. The complexity of a receptive field is further accentuated by the specificity of connections made by the different physiological types of hair receptors. High-threshold hairs may make synaptic connections with an interneuron, but adjacent low-threshold hairs may not. This organization of the receptive fields means that the interneurons are sensitive to certain inputs and can reliably pass on a signal from one hair. It also implies that greater weighting is given to inputs from certain regions.

The effect of the nutrient intensity and buffering power of a soil, and the absorbing power, size and root hairs of a root, on nutrient absorption by diffusion

A portion of a single plant root is treated as an absorbing cylindrical sink to which nutrients move by diffusion. Assuming that the rate of uptake of nutrient is proportional to its concentration at the root surface, and that the nutrient, though reacting with the solid, moves only through the soil solution, standard diffusion equations are used to calculate the effect of soil and plant characteristics on the rate of uptake. The treatment is applicable to phosphorus and potassium. Among soil properties uptake should increase directly with the soil solution concentration. It should also increase, but only slowly, with increasing buffering power. It increases with increasing soil moisture. Among plant characteristics, uptake should increase with the root absorbing power until diffusion through the soil becomes limiting. Absorption by unit surface area of root increases as the root radius decreases. A root hair is shown to interfere quickly with the uptake of adjacent hairs. The hairs increase absorption by the root because they can exploit rapidly the soil between the hairs, and they have the effect of extending the effective root surface to their tips.

New specific sensory structures in hairy skin

1. Cutaneous “touch spots” in hairy skin, with mechanical thresholds as low as 2 mg. weight, were identified by recording electrically from single myelinated cutaneous afferent nerve fibres in anaesthetised cats. 2. The discharge elicited by mechanical stimulation of a “touch spot” was slowly-adapting. Movements of the adjacent hairs were ineffective stimuli unless the hairs were pressed down on to the “touch spot”. A brief low frequency afferent discharge could be elicited by lowering the temperature of the skin. 3. The “touch spots” could be seen on the surface of the skin in the living animal as hemispherical domes, 100 to 250 μ diameter. Histological examination of a “spot” showed a specialised epithelium, containing flat terminal nerve discs, 10 μ diameter, innervated by branches of a single thick myelinated axon. 4. It is suggested that the results provide strong support for the concept of a specialisation of function and structure in some cutaneous afferent nerves.

PIGMENTATION AND HAIR GROWTH IN BLACK RATS, AS MODIFIED BY THE CHRONIC ADMINISTRATION OF THIOUREA, PHENYL THIOUREA AND ALPHA-NAPHTHYL THIOUREA1

OBSEKVATIONS have often been made of the fact that hair growth is intermittent, so that at any particular time some hairs are growing actively while other neighboring ones are not lengthening at all. In measuring the growth of marked human hairs Trotter (1924) found that the underlying cause of this apparent irregularity is a rhythmic alternation between activity and quiescence in individual hair follicles. In man the distribution of active and inactive follicles would seem to be random, so that of two adjacent hairs one can be growing while the other has reached its maximum length and protrudes from a temporarily inactive follicle. In many laboratory animals, however, there is a certain regional coordination in activity, with the result that at any given time hair is being produced from most if not all follicles in some areas while no growth occurs from those elsewhere. This fact was known, for instance, to Forster (1929) who used cats rather than mice, rats or rabbits to study hair growth stimulants, be...