The ridgeback anomaly. A new follicular pattern of the scalp

Samlaska, Curt P.; Benson, Paul M.; James, William D.

doi:10.1001/archderm.125.1.98

Cited by 4 publications

(2 citation statements)

References 15 publications

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“…It therefore seems more suitable to consider HSs, like the follicle, as possessing rather a single, left‐right (L‐R) axis of symmetry (Dry, ; Findlay & Harris, ; Samlaska, Benson & James, ; Devenport & Fuchs, ). Common descriptions of elliptic hair cross sections would thereby represent dialectic over‐abstractions (or scientific simplifications).…”

Section: Hair Curvature: Mechanical and Morphological Considerationsmentioning

confidence: 99%

Hair curvature: a natural dialectic and review

Nissimov¹,

Chaudhuri

2014

Biological Reviews

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Although hair forms (straight, curly, wavy, etc.) are present in apparently infinite variations, each fibre can be reduced to a finite sequence of tandem segments of just three types: straight, bent/curly, or twisted. Hair forms can thus be regarded as resulting from genetic pathways that induce, reverse or modulate these basic curvature modes. However, physical interconversions between twists and curls demonstrate that strict one-to-one correspondences between them and their genetic causes do not exist. Current hair-curvature theories do not distinguish between bending and twisting mechanisms. We here introduce a multiple papillary centres (MPC) model which is particularly suitable to explain twisting. The model combines previously known features of hair cross-sectional morphology with partially/completely separated dermal papillae within single follicles, and requires such papillae to induce differential growth rates of hair cortical material in their immediate neighbourhoods. The MPC model can further help to explain other, poorly understood, aspects of hair growth and morphology. Separate bending and twisting mechanisms would be preferentially affected at the major or minor ellipsoidal sides of fibres, respectively, and together they exhaust the possibilities for influencing hair-form phenotypes. As such they suggest dialectic for hair-curvature development. We define a natural-dialectic (ND) which could take advantage of speculative aspects of dialectic, but would verify its input data and results by experimental methods. We use this as a top-down approach to first define routes by which hair bending or twisting may be brought about and then review evidence in support of such routes. In particular we consider the wingless (Wnt) and mammalian target of rapamycin (mTOR) pathways as paradigm pathways for molecular hair bending and twisting mechanisms, respectively. In addition to the Wnt canonical pathway, the Wnt/Ca(2+) and planar cell polarity (PCP) pathways, and others, can explain many alternatives and specific variations of hair bending phenotypes. Mechanisms for hair papilla budding or its division by bisection or fission can explain MPC formation. Epithelial-to-mesenchymal (EMT) and mesenchymal-to-epithelial (MET) transitions, acting in collaboration with epithelial-mesenchymal communications are also considered as mechanisms affecting hair growth and its bending and twisting. These may be treated as sub-mechanisms of an overall development from neural-crest stem cell (NCSC) lineages to differentiated hair follicle (HF) cell types, thus providing a unified framework for hair growth and development.

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Section: Hair Curvature: Mechanical and Morphological Considerationsmentioning

confidence: 99%

Hair curvature: a natural dialectic and review

Nissimov¹,

Chaudhuri

2014

Biological Reviews

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“…Among the many hypotheses done on their origin, most speculated the association between the hair whorls and central nervous system abnormalities. [ 2 3 4 ] Familiar clusters have been reported in the literature, and a possible genetic linkage has been postulated. [ 5 ]…”

Section: Introductionmentioning

confidence: 99%

Scalp hair whorl patterns in patients affected by Neurofibromatosis Type 1: A case-control study

et al. 2020

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Background: The hair whorl denotes the spiral disposition of hairs around an axis, which is determined by the follicle growing direction. Atypical variants of scalp hair patterns, identified by abnormally placed or multiple whorls, have been associated with early brain developmental disorders and several dysmorphic syndromes. Materials and Methods: A 6-month case–control, prospective monocentric study included an overall number of 557 children. A logistic regression analysis was performed to evaluate the relationship between localization, the number of scalp hair whorls, and their association with neurofibromatosis type 1 (NF1). Results: NF1 positively correlates with a frontal localization, whereas a negative association was found with a parietal whorl pattern ( P < 0.001). Conclusion: Evaluation of scalp whorls gains importance in the neonatal settings and may contribute to suspect the early diagnosis of NF1, as the related National Institutes of Health diagnostic criteria cannot be usually observed at an early age.

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