Hair follicle group and skin follicle population of Australian Merino sheep

Hb, Carter; Clarke, WH

doi:10.1071/ar9570091

Cited by 96 publications

(46 citation statements)

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“…Other histological and histochemical techniques used were those described by Lyne and Hollis (1968). Counts of the follicle popUlation density (made on six fields of 1 mm2 in area) were corrected for skin shrinkage as described by Carter and Clarke (1957). Measurements of the interfollicular epidermal thickness were obtained from sections (811-thick) cut at right angles to the skin surface and stained with haematoxylin, eosin, and picric acid (HEP).…”

Section: Methodsmentioning

confidence: 99%

Effects of Freezing the Skin and Plucking the Fibres in Sheep, With Special Reference to Pigmentation

Lyne¹,

Hollis²

1968

Aust. Jnl. Of Bio. Sci.

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SummaryMacroscopic and microscopic changes in the skin of seven adult Suffolk and Merino sheep were studied for periods of up to 513 days following the application of solid carbon dioxide to hair-and wool-growing areas after clipping or plucking of the fibres. Observations were also made on the effect of plucking alone.A colour change from black to whit,e occurred in the coat subsequent to freezing skin which previously grew black hair in Suffolks and black hair or black wool in Merinos. In contrast, follicles which grew white wool in Suffolks and in an isolated white area on an otherwise "black" Merino sheep were induced to grow black or partially coloured fibres for periods ranging from a few days to several months when damaged by freezing the skin or plucking the fibres. The outer root sheaths of the follicles in the regions which normally grew white wool in these animals were the only source of the melanocytes which appeared near the dermal papillae of regenerating follicles and passed pigment into the new fibres. When the skin was frozen after the fibres had been plucked, the melanocytes in the follicle outer root sheaths were usually destroyed and the new fibres were non-pigmented.Other changes which frequently resulted from freezing the skin were an increase in the thickness of the epidermis, destruction of the sweat glands, a reduction in the number of follicles per unit area of skin, and a reduction in the innervation of the skin. No follicle neogenesis was seen. An increase in the length of the fibres, due either to an increased growth rate or to an increase in the duration of the growth cycle, sometimes occurred.

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Section: Methodsmentioning

confidence: 99%

Effects of Freezing the Skin and Plucking the Fibres in Sheep, With Special Reference to Pigmentation

Lyne¹,

Hollis²

1968

Aust. Jnl. Of Bio. Sci.

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“…Most of the counts were made on at least six fields of 1 mm2, on HEP·stained sections. The follicle density counts were corrected for skin shrinkage as described by Carter and Clarke (1957a).…”

Section: Dorsal Nose(l)mentioning

confidence: 99%

The Skin of the Sheep: a Comparision of Body Regions

Lyne¹,

Hollis²

1968

Aust. Jnl. Of Bio. Sci.

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SummaryLight-microscope studies reveal distinctive features in the hair-and woolgrowing skin of adult sheep. The epidermis is variable in thickness-usually thin on wool-growing regions and thicker on haired regions. The follicles are mostly in groups containing one, two, or three primary (P) follicles and a number of secondary (S) follicles. The SIP follicle ratios vary from zero to about 30, depending on the breed and body region. The capillaries, myoepithelium of sweat glands, and dermal papillae of the follicles are often reactive for alkaline phosphatase. This enzyme is also asymmetrically distributed in some follicle bulbs and here it might be related in some way to the segmentation of the fibre cortex and perhaps to the formation of crimped wool. The dermal and follicle nerve networks contain cholinesterases. The latter may also contain alkaline phosphatase. Encapsulated end-organs and tactile disks are occasionally present in both hair-and wool-growing skin. Melanocytes, most common near the dermo-epidermal junction, may also be present in the outer root sheaths of the follicles, sebaceous glands, sweat glands, and dermis. Acetylcholinesterase-positive branched cells are invariably present in the epidermis in all regions where there are follicles. Sebaceous glands are associated with all follicles and apocrine sweat glands with the P follicles only. The P follicles also possess erector muscles that react for cholinesterases. Both the subaceous glands and sweat glands are usually larger in haired regions than in wool-growing regions. Large "eccrine" glands open on the naked part of the muzzle.

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“…Fleece characteristics are influenced during these periods of foetal development. Although traits such as wool follicle densities are highly heritable (Carter and Clarke, 1957;Jackson et al, 1975;Hancock et al, 1979), the foetal and maternal environments can also contribute to fleece characteristics (Short, 1955;Gregory, 1982).…”

Section: Introductionmentioning

confidence: 99%

The effects of short-term manipulation of thyroid hormone status coinciding with primary wool follicle development on fleece characteristics in Merino sheep

McDowall

Edwards

Hynd

2011

Animal

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Thyroidectomy surgery performed late in gestation results in perturbations in wool follicle development in foetal sheep, showing the importance of thyroid hormones for wool follicle development. The aim of this study was to determine the influence of transient manipulation of thyroid hormone status at a time corresponding with foetal primary wool follicle initiation. Pregnant Merino ewes (n 5 12 per treatment) were treated daily between gestational days 55 and 64 with control (vehicle), exogenous thyroxine (T4) or propylthiouracil (PTU), an inhibitor of T4 synthesis, and conversion to the active form of the thyroid hormone (triiodothyronine). There were no significant differences in birth weight, gestational lengths and birth coat scores of the resultant lambs. The total primary and secondary follicle densities were significantly lower in lambs exposed to exogenous T4 compared with other treatments (P , 0.05). However, the T4 group displayed a higher proportion of mature secondary follicles (reflected by increased mature secondary follicle densities and mature secondary/primary follicle ratios) than the other treatment groups (P , 0.05). The skin morphology of the lambs differed 12 months later, with the T4 group having significantly higher total follicle densities compared with the PTU group, largely attributed to increased mature and total secondary follicle densities. However, this increase in wool follicle densities did not translate to differences in the fleece yields and weight, fibre diameter, staple lengths or any other fibre parameters. This study showed that transient manipulation of thyroid hormone status during foetal primary follicle initiation does have long-term consequences on the morphology of wool follicles, in particular the maturity of secondary wool follicles.

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Hair follicle group and skin follicle population of Australian Merino sheep

Cited by 96 publications

References 0 publications

Effects of Freezing the Skin and Plucking the Fibres in Sheep, With Special Reference to Pigmentation

Effects of Freezing the Skin and Plucking the Fibres in Sheep, With Special Reference to Pigmentation

The Skin of the Sheep: a Comparision of Body Regions

The effects of short-term manipulation of thyroid hormone status coinciding with primary wool follicle development on fleece characteristics in Merino sheep

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