Compound Hair Follicles Research Articles

Comparative histological analysis of the skin for forensic investigation of some animal species.

Macroscopical and histological analysis of the skin is fundamental in both human and veterinary forensic investigations. However, databases of differential skin histology of various animal species are rare. The aim of the present study is to identify species-specific differential histological features of the skin that could be used in forensic investigations including animal identification. For this purpose, skin specimens were collected from the neck region of various farm animals including buffalo, cow, camel, sheep, goat, dog, and donkey, and were processed for histological analysis. Our comparative analysis revealed specific histological features in the skin that could differentiate between the studied animal species. The epidermis layer of the skin was very thick in buffalo, intermediate in cow, sheep, goat, dog, and donkey, but very thin in camel. The papillomatous epidermis was very frequent in buffalo, but very rare in cow. In the dermis layer of the skin, four structures were located which showed differential features between the studied animal species: the papillary layer, which was thick in buffalo, camel, sheep, dog, and donkey but thin in cow and goat. The sweat glands, which were few in buffalo, cow, goat, and dog, but numerous and deeply located in the dermis of sheep; they were individually located in all studied animals except in camel and donkey they were arranged in clusters. The hair follicles were characteristic for the skin of sheep as they were present at two different levels in the dermis with simple and compound hair follicles. The sebaceous glands were large and multi-lobular in buffalo, but small and uni-lobular in cow and camel. The hypodermis layer of the skin was very thick in sheep and goat in contrast to all other analyzed animals. In conclusion, the present study provides comprehensive information on the differential histological features of the skin of seven different domestic animal species that could be used as a key in forensic investigations.

Histology of Hair Follicles in Different Breeds of Rabbits

Background: Rabbit farming provides a valuable additional source of income in the rural areas of the county. Skin is the largest organ in the body and the hair coat forms the first line of defense against the invading pathogenic organisms as well as the physical environment. So far, no detailed comparative study has been conducted on the skin of various breeds of rabbits. Hence, the present work was undertaken to compare the structure and distribution of hair follicles in different breeds of rabbits commonly reared in Kerala.Methods: The study was conducted on the skin of six breeds of rabbits namely, Soviet Chinchilla, New Zealand White, Grey Giant, White Giant, Angora and crossbred. In total, 36 animals were used for the study. From each animal, skin samples were collected from eight representative areas of the body viz., dorsal nasal region, pinna, dorsal neck, dorsal thorax, dorsal abdomen, ventral abdomen, perineal and carpal regions. Standard procedures were adopted for histological studies.Result: All the six breeds of rabbits showed compound hair follicles with primary and secondary follicles with associated sebaceous glands. Arrangement of hair follicles showed differences among the breeds. There was no difference in the histology of hair/hair follicle among the breeds. This work will form a basis for further breed specific research in the area of fur and leather industry and skin penetration studies.

Histomorphological differentiation of the skin of leopard (Panthera pardus), leopard cat (Prionailurus bengalensis), Bengal tiger (Panthera tigris), and golden jackal (Canis aureus).

Background and Aim:Leopard (Panthera pardus), leopard cat (Prionailurus bengalensis) Bengal tiger (Panthera tigris), and golden jackal (Canis aureus) are carnivores. Leopard and Bengal tiger are listed in the red list as vulnerable species by the International Union for Conservation of Nature and Natural resources. Leopard cat and golden jackal are grouped under animals of least concern. A wide variation exists in the structure of the skin and pattern of hair follicles among domestic and wild mammals. Thus, the study aims to create a baseline data on the skin of leopard, leopard cat, Bengal tiger, and golden jackal and the data so obtained may form an indispensable tool in wildlife forensics.Materials and Methods:Skin samples of leopard (n=3), leopard cat (n=4), Bengal tiger (n=3), and golden jackal (n=4) were collected from the Department of Pathology, College of Veterinary and Animal Sciences, Pookode. The samples were processed for paraffin embedding. Horizontal and vertical sections of 5 µm thickness were used for histological staining techniques. Observations on the layers and features of epidermis, hair follicle pattern and glands, namely, sweat and sebaceous were recorded.Results:Skin comprised an outer epidermis and an inner dermis. Keratinized stratified squamous epithelium made up the epidermis. Stratum basale, stratum spinosum, stratum granulosum, and stratum corneum were discernible in leopard, Bengal tiger, and golden jackal. In leopard cat, stratum basale, stratum spinosum, and stratum corneum were present. Compound hair follicles were a characteristic feature of all species. However, the pattern varied. In leopard, leopard cat and Bengal tiger, a single large primary guard hair was encircled by compound follicles. The number of surrounding compound follicles ranged between five to seven in leopard, two to five in leopard cat, and three to seven in Bengal tiger. Each compound follicle, in turn contained, one to two coarse primary hair follicles and several fine secondary hair follicles. Compound follicles arranged as clusters of three were a salient attribute in jackal. The central follicle was comparatively larger than the lateral ones. Each compound follicle comprised a single long, primary hair, and six to eight smaller secondary hairs.Conclusion:Histological variation in the skin of the leopard, leopard cat, Bengal tiger, and golden jackal was established. The data form a valuable basis for comparative histology of wild carnivores. Further, the data may be of value in the identification of the unknown skin samples of wild carnivores.

The Morphological Basis of vicuña wool: Skin and gland structure in Vicugna vicugna (Molina 1782)

The vicuña (Vicugna vicugna) is the smallest member of the Camelidae with one of the most valuable fibers in the world. However, little is known of the structural basis for this fiber or of the skin glands used in chemical communication in this species. The objective of this study was to examine the histological structure of the skin and hair follicles and the cutaneous glands. Skin samples from the fleece, belly and legs and glandular areas – metatarsal, caudal, anal and interdigital areas – were obtained from animals accidentally killed in captive captures at a government camelid ranch in Jujuy, Argentina. These samples were studied with histological techniques for light and electron microscopy to examine follicular structure and density in fleece compared to belly and leg areas. Glandular areas were similarly studied to determine type and density of skin glands. Compound hair follicles were found with an extremely high density of secondary hairs in relation to primary hairs (S:P ratio) in fleece (42±2, mean±standard error) and a significantly lesser density (p<0.001) in belly and legs (12.0±0.7). Follicle and hair diameters from the two areas were also significantly different with the fleece areas having smaller diameters. Secondary hair diameters in fleece were similar to previously published values (13.2±0.3μm). With respect to the glandular areas, the metatarsal glands had a striking appearance with an epithelium resembling a hollow honeycomb and a dermis showing a great deal of glandular tissue (simple tubular glands) with excretory ducts. Large sebaceous glands were found in the ventral region of the tail and eccrine sudoriferous glands in the interdigital region. The possible importance of these glands in chemical communication is discussed.

Spatial Distribution of Stem Cell-Like Keratinocytes in Dissected Compound Hair Follicles of the Dog.

Hair cycle disturbances are common in dogs and comparable to some alopecic disorders in humans. A normal hair cycle is maintained by follicular stem cells which are predominately found in an area known as the bulge. Due to similar morphological characteristics of the bulge area in humans and dogs, the shared particularity of compound hair follicles as well as similarities in follicular biomarker expression, the dog is a promising model to study human hair cycle and stem cell disorders. To gain insight into the spatial distribution of follicular keratinocytes with stem cell potential in canine compound follicles, we microdissected hair follicles in anagen and telogen from skin samples of freshly euthanized dogs. The keratinocytes isolated from different locations were investigated for their colony forming efficiency, growth and differentiation potential as well as clonal growth. Our results indicate that i) compound and single hair follicles exhibit a comparable spatial distribution pattern with respect to cells with high growth potential and stem cell-like characteristics, ii) the lower isthmus (comprising the bulge) harbors most cells with high growth potential in both, the anagen and the telogen hair cycle stage, iii) unlike in other species, colonies with highest growth potential are rather small with an irregular perimeter and iv) the keratinocytes derived from the bulbar region exhibit characteristics of actively dividing transit amplifying cells. Our results now provide the basis to conduct comparative studies of normal dogs and those with hair cycle disorders with the possibility to extend relevant findings to human patients.

An experimental investigation of chemical communication in the polar bear

AbstractThe polar bear (Ursus maritimus), with its wide‐ranging movements, solitary existence and seasonal reproduction, is expected to favor chemosignaling over other communication modalities. However, the topography of its Arctic sea ice habitat is generally lacking in stationary vertical substrates routinely used for targeted scent marking in other bears. These environmental constraints may have shaped a marking strategy, unique to polar bears, for widely dispersed continuous dissemination of scent via foot pads. To investigate the role of chemical communication, pedal scents were collected from free‐ranging polar bears of different sex and reproductive classes captured on spring sea ice in the Beaufort and Chukchi seas, and presented in a controlled fashion to 26 bears in zoos. Results from behavioral bioassays indicated that bears, especially females, were more likely to approach conspecific scent during the spring than the fall. Male flehmen behavior, indicative of chemosignal delivery to the vomeronasal organ, differentiated scent donor by sex and reproductive condition. Histologic examination of pedal skin collected from two females indicated prominent and profuse apocrine glands in association with large compound hair follicles, suggesting that they may produce scents that function as chemosignals. These results suggest that pedal scent, regardless of origin, conveys information to conspecifics that may facilitate social and reproductive behavior, and that chemical communication in this species has been adaptively shaped by environmental constraints of its habitat. However, continuously distributed scent signals necessary for breeding behavior may prove less effective if current and future environmental conditions cause disruption of scent trails due to increased fracturing of sea ice.

Histological characteristics of hair follicle pattern in Indian bison (Bos gaurus), black buck (Antelope cervicapra) and nilgai (Boselaphus tragocamelus)

Background and Aim: Indian bison, Black buck and Nilgai are in danger of extinction because people are hunting them for their meat and horns for sports, trophies etc. These animals are also protected under International Union for Conservation of Nature and Natural Resources (IUCN) and Conservation on International trade in Endangered Species of Wild Fauna and Flora (CITES). Taking note of the vulnerability of these animals to extinction, we characterized the hair follicle pattern of these animals for future reference. This study included a total of 30 skin samples comprised of 8 samples of bison, 10 samples of black buck and 12 samples of nilgai. Materials and Methods: Skin samples were obtained from Sri Jayachamarajendra Zoological Park, Mysore, Karnataka, India and Bannerghatta Biological Park, Bangalore, Karnataka, India and also from confiscated skins from forest and police officials of Karnataka. The skin samples were processed and horizontal section of 6-7 µm thickness was used for the routine histological technique using different special staining techniques. Observation such as hair follicle pattern, sebaceous glands and sweat glands distribution, blood vessels, nerve fibre, collagen and elastic fibres were noted. Results: In the bison, compound hair follicles were uniformly distributed and were rectangular in shape comprising of a primary hair follicle associated with 3-4 secondary hair follicles in addition to their sebaceous glands. Uniformly distributed coiled tubular sweat glands were also noticed which were lined by simple cuboidal epithelium. In the black buck, the compound hair follicles were densely distributed and were arranged linearly in the dermis of skin. Within the compound follicle, linear arrangements of primary and secondary follicles were observed. Each primary hair follicle was supported by 24 secondary hair follicles and the primary hair follicle was always present at the centre when it was present with 2 secondary hair follicles. In nilgai, the compound hair follicles were densely distributed in the dermis of skin. The primary hair follicles were bilaterally surrounded by 2-3 secondary hair follicles. Each primary and secondary hair follicle was associated with sebaceous glands. Conclusion: The histological pattern of the hair follicle data was established and the hair follicle pattern will be of use in the identification of the wild ruminant skins which are commonly poached by the poachers. It will also be useful to compare the histological characteristics amongst the wild ruminants.

Transverse sectioning for histological assessment of sebaceous glands in healthy dogs and canine sebaceous adenitis

To evaluate transverse sectioning for histological assessment of canine sebaceous glands in health and disease. Skin specimens were obtained from the cadavers of six healthy beagle dogs and from an archive of tissue sections of 24 dogs with a histological diagnosis of sebaceous adenitis. In healthy beagle dogs, both the mean numbers of compound hair follicles and sebaceous lobes observed in transverse sections were approximately threefold higher (P < 0. 001) than those seen in vertical sections. A similar relationship was noted in examples of sebaceous adenitis. In cases of sebaceous adenitis, there was a complete absence of sebaceous glands in paired transverse and vertical sections in 14 cases, whereas in 3 dogs glands were observed in transverse sections where none were seen in vertical sections. The percentages of hair follicles with associated sebaceous glands in affected dogs did not vary between transverse (12. 3%) and vertical (13 . 3%) sections, whereas 89% (vertical) and 96% (transverse) of follicles had associated glands in the healthy beagle dogs. Transverse sectioning of canine skin specimens to allow visualization of the follicular isthmus or deep portion of the common infundibulum enhances the histological assessment of sebaceous glands in both health and disease.

Effect of age and sex on fiber and follicle characteristics of an Iranian native sheep

The mammalian hair fibers represent an interesting biological material which also is used in the textile industry. Histological structures of the fibers and follicles differ not only among different species but also among different areas and ages in an animal species. Skin samples were collected from neonatal (1-2 months), young (3-9 months), young adult (1-2 years) and old adult age groups (3 years and more). In each age group, six animals (3 each sex) were utilized. Immediately after slaughtering the animals, tissues were collected from eight regions namely belly, neck, leg, rump, flank, forearm, shoulder and hip and were fixed in 10 percent neutral buffered formalin. Histologic sections were stained with hematoxylin-eosin and special stains. It was found that the general histological features of all Bakhtiari sheep fibers used in this study were similar to many other breeds sited in literature, however there were also some differences. All hairs of the various skin regions had a medulla. All the hair follicles were surrounded by associated structures such as the sweat and sebaceous glands and arrector pili muscles and located only in papillary layer of the dermis. The most common number of the secondary hair follicles in compound hair follicles was 4. The histology of all fibers and follicles in various skin regions showed no significant differences by sex in all the age groups studied. By age increase, all the fibers and their follicles were larger and well organized in all different skin regions.

Histology of ferret skin: preweaning to adulthood

Ferrets are important companion animals that incur a multitude of cutaneous diseases requiring diagnostic dermatohistopathology. This study provides a description of the histology of normal ferret skin, emphasizing changes in the interval from preweaning to adulthood, an essential basis for identification of pathological situations. Skin samples obtained post-mortem from 29 topographical sites on 41 ferrets, revealed in the haired, general body surface skin an epidermis consisting of strata basale, spinosum, granulosum, and corneum and a dermis consisting of strata papillare and reticulare. Adult skin contained compound hair follicles composed of one primary hair and a collection of secondary hairs with a primary to secondary ratio of 1/5-1/15. All hairs emerged through the same follicle outlet of the skin surface. There was associated with each primary follicle, an arrector pili muscle, a multilobular sebaceous gland, and a coiled tubular sweat gland, but secondary hairs lacked these features. Compound follicles, grouped mainly as triads across the body surface, were already fully formed in the youngest group studied (3 to 6 weeks). The secondary hairs all developed from one specific region of the primary follicles and smaller ones were formed with increasing age. The differences found in specialized body regions are described. Demodex sp. mites were found in follicles and sebaceous glands in nine of 25 individuals in the perianal, vulvar, preputial, facial, and caudal abdominal skin.

The histology of normal llama skin.

Skin biopsy specimens of normal llama skin were examined histologically. Adnexal structures similar to those of most other domestic mammals included epitrichial sweat glands, sebaceous glands and arrector pili muscles. Unique features of normal llama skin included a very thick dermis with marked differences between superficial and deep dermis, prominent cutaneous vascular plexuses, unidentified cells with eosinophilic granules within the adventitia of the vascular plexuses, both simple and compound hair follicles, 'metatarsal glands', 'interdigital glands', footpad glands and the absence of eyelid tarsal glands.

TRICHOSTASIS SPINULOSA

ABSTRACT: Fifty‐one patients with trichostasis spinulosa were studied. Lesions were confined to the nose, where a maximum of 86 hairs were found in a single hair follicle. Histologically, compound hair follicles with numerous vellous hairs and keratin filled sebaceous glands were observed. Compound hair follicles influenced by endocrines and probably actinic rays may be responsible for this condition.

Hair Growth and Replacement in the Cat

SUMMARY Observations were made on the histology of the skin from 66 cats of different ages. The extreme thinness of the epidermis of this species is noteworthy. Development of the pelage resembles that of the dog, hair germs being produced at intervals along the epidermis, and these then grow down into the dermis. Sebaceous glands and apocrine glands are produced from the hair germs. Primary hairs are produced first, subsequently the first secondary hairs develop on either side of the primary hairs and these soon produce hair germs from which develop more .secondary hairs to compete the compound follicle. In both housed and unconfined cats the primary and secondary hair bulbs decreased in activity after December, with total inactivity in January. This was maintained during February and March, activity recommencing in April. There followed a period of maximum activity of two to four months duration in unconfined cats. Subsidiary cycles of activity followed until December. It is considered that increasing photoperiod is the stimulus for hair loss and replacement in Spring. Neutered cats showed a comparable cycle to entire animals. Hair replacement did not progress over the body in waves as in rodents, but mosaically as in man. Variable stages of activity of the hair roots were observed in compound hair follicles. Rates of hair growth of adult cats are comparable to those of man, approximating to 300 microns daily. The rate of primary hair growth was greater than that of secondary hairs. In three housed cats the maximum rate of hair growth occurred in late April with minimal hair growth in February.

Giant compound hair follicles in the skin of the rabbit.

THE hair of the rabbit grows from a compound follicle1 which contains one large outercoat hair, a few smaller outercoat hairs of intermediate morphology and numerous fine undercoat hairs. The true compound nature of the follicle is best seen during the growth-phase, when the follicles extend into the dermis forming distinctive groups at their deepest level (Fig. 1). As the hair shafts reach the surface the compound follicle is subdivided by fibrous septa into smaller groups which surround the large outer-coat hair. Each of these smaller groups of undercoat hairs penetrate the skin through a common follicle opening, whereas the outercoat hair has a separate opening.