The structure and formation of pigment granules in human hair

Birbeck, M. S. C.; Mercer, E. H.; Barnicot, N. A.

doi:10.1016/0014-4827(56)90022-2

Cited by 118 publications

(31 citation statements)

References 11 publications

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“…An account of some of this work (9)(10)(11), particularly where it relates to pigment formation, has already appeared. The present account will be divided for convenience into three Parts.…”

Section: Introductionmentioning

confidence: 99%

The Electron Microscopy of the Human Hair Follicle

Birbeck

Mercer

1957

The Journal of Cell Biology

247

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1. The presumptive cortical cells of hair in the undifferentiated matrix of the bulb contain mitochondria, agranular vesicles, and many small dense R.N.P. particles, but no keratin, pigment granules, or endoplasmic reticulum. 2. In the mid-bulb region intercellular adhesion is limited to small localised areas. Intercellular gaps are common and the cell surfaces are irregularly convoluted. The melanocyte processes penetrate the cell gaps. The relation between their pigment-bearing tips and the involutions of the cell membranes suggests an active phagocytosis of the tips. 3. Fibrous keratin first appears in loose parallel strands of fine filaments (ca. 60 A diameter) in the mid-bulb. The filaments, the long mitochondria, and elongated nucleus are all parallel to the long axis of the cell and the axis of the follicle. 4. At the level of the constriction of the bulb and above, a dense amorphous substance appears between the fine filaments and apparently acts as adhesive cement. The bundles of filaments now form well defined fibrils. The packing of the filaments within the fibrils is in places hexagonal and elsewhere in the form of "whorls." 5. At higher levels further filaments and interfilamentous cement are added together and the whole cytoplasmic space becomes packed with fibrils which finally condense to massive blocks of keratin. The residual cellular material occupies the interstices. 6. The addition of the interfilamentous substance is regarded as an essential factor in keratinisation. Keratin is considered to be a complex made of fine filaments (α-filaments) embedded in an amorphous substance (γ-keratin) which has the higher cystine content. 7. The wide-angle fibre-type x-ray pattern is thought to be due to scattering by the fine α-filaments and some low angle lateral spacings to the filament-plus-cement structure.

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Section: Introductionmentioning

confidence: 99%

The Electron Microscopy of the Human Hair Follicle

Birbeck

Mercer

1957

The Journal of Cell Biology

247

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“…They are dissimilar therefore to the melanin granules of human epidermis and hair follicles, which appear to be made up of lamellae or some related organised lattice (Birbeck, Mercer, and Barnicot, 1956;Charles and Ingram, 1959;Drochmans, 1960).…”

Section: Cell Membranes and Melanin Granulesmentioning

confidence: 99%

An Electron Microscope Study of the Fine Structure of Feather Keratin

Filshie

Rogers

1962

The Journal of Cell Biology

147

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Thin sections of thc rachis of rcgcncrating follicles of pigmented fowl feathers and of maturc non-pigmcntcd seagull fcathcr rachis, cmbcddcd in mcthacrylatc and Aralditc rcspcctivcly, wcrc studicd in thc electron microscopc. Thc late stagcs of development of keratin fibrils wcrc cxamincd in OsO4-fixcd follicle matcrial, and aftcr poststaining with icad hydroxide the kcratin aggrcgatcs wcrc found to bc composed of finc microfibrils approximatcly 3 ° A in diamctcr apparently cmbcddcd in a matrix matcrial which had absorbed thc Icad stain. The centre-to-centre scparation of thc microfibrils was of the ordcr of 35 A. Aftcr bulk trcatmcnt by reduction with thioglycollic acid, OsO~ staining, and poststaining with Icad hydroxide, a similar microfibrillar finc structurc was obscrvcd in mature rachis. Only aftcr Icad staining could the microfibrils bc dclincatcd, and their diameter and separation wcrc similar to that found in thc keratin of thc follicle. It is suggcstcd that fcathcr keratin rcscmblcs c~-kcratins in consisting of microfibrils cmbcddcd in an amorphous protein matrix. However, in comparison with cz-kcratins, the microfibrils are much smaller in diamctcr, their arrangcment is less orderly, and on the basis of the rcactions towards the clcctron staining proccdures, the cystinc content of the matrix appears to bc not greatly differcnt from that of the microfibrils. Thc significance of a microfibrillar constitution of feather keratin is discussed in relation to currcnt structural modcls for this fibrous protein dcduccd from x-ray diffraction studies. The boundaries bctwccn thc component cells of fcathcr rachis arc dcsmosomal in character and similar to thosc of related kcratinous structures and a numbcr of different typcs of cells; the melanin granulcs arc dissimilar to thosc of mammalian epidermis in thcir apparcnt lack of mclanin-protein lamcllac.

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“…Melanin is produced within specialized cells called melanocytes in the form of granules, which are then transferred to adjacent cells via the dendritic projections of the melanocytes (Birbeck et al 1956). Deposition of melanin within the skin aids in protecting the underlying tissues from the damaging effects of ultraviolet light (UVL) (Pathak 1967).…”

Section: Introductionmentioning

confidence: 99%

Pigmented Spots in the WoolBearing Skin of White Merino Sheep Induced by Ultraviolet Light

Forrest¹,

Fleet²

1986

Aust. Jnl. Of Bio. Sci.

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Black-grey pigmented skin spots, some of which contained pigmented wool fibres, were observed in a flock of 8· 5-year-old white Merino ewes. The spots were concentrated along the backline and increased in number following shearing, suggesting exposure to sunlight to be of importance in the development of these non-congenital pigmented skin spots in genetically white Merino sheep. To test the effect of ultraviolet light, white Merino sheep, ranging in age from 3 to 8 years, had a closely clipped mid side area of wool-bearing skin irradiated on each of 28 consecutive days. Pigmented skin spots developed in 6 of the 16 white Merino sheep irradiated. Spots first appeared after 10 days of irradiation, the number subsequently increasing with time, and two skin spots were found to contain sparse numbers of blackgrey pigmented wool fibres. Histological examination showed both the naturally occurring and irradiationinduced pigmented skin spots resulted from an increase in both number and activity of melanocytes localized along the epidermal-dermal border of the epidermis. With time, the melanocytes were observed to have entered, to varying depths, the outer-root sheath of follicles still producing white wool fibres. These ultraviolet-light-induced changes to epidermal melanocytes in white Merino sheep presumably occur due to alterations within the local tissue environment in which the melanocytes lie.

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The structure and formation of pigment granules in human hair

Cited by 118 publications

References 11 publications

The Electron Microscopy of the Human Hair Follicle

The Electron Microscopy of the Human Hair Follicle

An Electron Microscope Study of the Fine Structure of Feather Keratin

Pigmented Spots in the WoolBearing Skin of White Merino Sheep Induced by Ultraviolet Light

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