Curli Fibers Research Articles

Massive somatodendritic sprouting of cortical neurons in Alzheimer's disease

In addition to neurofibrillary tangles and senile plaques, antibodies to human tau revealed extensive tau-immunoreactive meshworks in layers III and V of the neocortex affected with Alzheimer's disease. The meshworks consisted of innumerable abnormally curly fibers, which were coming from somata and dendrites of pyramidal cells. Their morphological appearance suggests that those curlt fibers represent somatodendritic sprouting.

The secretion of the eggshell of Schistocerca gregaria: ultrastructure of the follicle cells during the termination of vitellogenesis and eggshell secretion.

The secretion of the eggshell by the follicle cells in the desert locust, Schistocerca gregaria, was studied using the electron microscope. The 3 layers of the eggshell, the vitelline membrane, the endochorion, and the exochorion, are produced in sequence over a short period of about 30-36 h. The follicle cells contain little rough endoplasmic reticulum (RER) and small inconspicuous Golgi bodies during vitellogenesis. As eggshell secretion approaches there is an increase in the amount of RER and Golgi cisternae contain electron-dense product. At each stage of the 3-phase secretion cycle the follicle cells contain Golgi bodies and secretion vesicles with distinct morphology. The follicle cells increase in breadth and decrease in height between the beginning and end of eggshell secretion. The endochorion ridges arise at the junction between follicle cells and appear to be moulded by the microvilli formed at this position. In the ovary prior to ovulation, the eggshell consists of a thin (0.5 micrometer) electron-dense vitelline and an outer fibrillar exochorion layer, 20-30 micrometer thick. Further changes take place in the vitelline membrane and the endochorion after oviposition, and a layer of curly fibres, the extrachorion, is secreted in the oviduct.

Birthcoat–adult fleece relationship: a study of kemp succession in a coarse wool breed of sheep

SummaryThe birthcoat of coarse wool Barki lambs was investigated at the age of 1–1·5 months. Lambs were covered when they were 2 months old to study kemp succession, and some other adult fleece traits, at the age of 16 months in relation to the birthcoat fibre type arrays. Samples were taken from three dorsal and three lateral positions. The average halo hair grade was 5·45% and the coarse fibre type array, plateau, contributed 64·7% of the birthcoat arrays, the rest were of the less coarse, saddle, type. Halo hair grade and fibre type arrays showed an antero-posterior gradient, increasing in score and coarseness posteriorly.All halo hairs, 41·9% of super sickles and 22·6% of hairy tip curly tip fibres were shed as first generation kemp (G1 Curly tip and histerotrich fibres shed the least and they contributed the majority of the total persistent fibres. When pre-curly tip fibres increased in the birthcoat samples, that was followed by more kemp in the adult fleece.The average G1% kemp was 4·43. Kemp decreased in subsequent generations, values were 34·50 and 8·37 for G2/G1% and G1/%, respectively. G1%, and G2/G1% kemp showed a general trend of an increase towards posterior positions; the shoulder position was an exception to that.Coarse birthcoat fibre type arrays, plateau, were followed by more kemp in G1% and in successive generations than were the less coarse, saddle, arrays. High values of G2/G1% kemp were followed by significantly high G3/G1% kemp. Within animals, there was a significant correlation (P < 0·01) between halo hair grade and G1% kemp.Staple length showed a tendency to increase towards posterior positions and females showed slightly longer staples than those of males. A slight trend of decrease in staple length was observed following the less coarse array, saddle, as compared with that which followed the coarse array, plateau.For selection against kemp at an early stage, though birthcoat halo hair grade was positively correlated with G1% kemp, a high halo hair grade is essential for the lamb's early survival, hence fibre type arrays should be considered in selection. Less coarse birthcoat arrays, saddle in the present material, and a high, within array, curly tip: pre-curly tip ratio would be preferrable.

The development of the fleece and follicle population in Herdwick sheep

1. The development of the fleece and follicle population was studied in six Herdwick and two Herdwick × Swaledale sheep on their native farm in Cumberland. Six of these sheep survived the first 14 months of the experiment, and four were kept under observation for a further 12 months. Growth in body weight, body surface area, and area of tattooed squares was recorded and discussed.2. Fibre type arrays (at the mid-side positions) were ‘Plateau’ in all but one of the pure Herdwick lambs, and ‘Saddle’ in the remaining three animals.3. The earliest fibres of the array (halos and coarse super-sickles) were mostly ribbon-shaped in their pre-natal and early post-natal portions, below which they became cylindrical. These fibres were ‘birth coat kemps’ and were shed about 10 weeks after birth. At this time later-developed fibres (sickles and curly-tips) showed ‘crisis thinning’ but did not shed, whilst late curly tips and histerotrichs were not affected. These three groups gave rise to three corresponding groups of fibres in the adult fleece, namely kemps, hairs and fine fibres.4. Two generations of kemp fibres were grown each year, ‘spring kemps’ commencing growth about April and shedding by July; and ‘autumn kemps’ commencing growth in July and forming ‘brush-roots’ in the autumn and early winter, although the majority remain in their follicles until the following spring.5. The majority of the curly tip fibres of the birth coat grow into long hair fibres, which are of hetero-typical shape. In summer they are more or less coarse, and medullated, whilst in winter they become fine and lose their medulla; many cease growth during the middle of the winter period after producing a short length of fine fibre, and commence growth again in the spring. The late curly tip and histerotrichs fibres continue to grow as the fine undercoat fibres of the fleece, without any medullation.6. A large proportion of both primary and secondary follicles shed their fibres during the winter months. When this proportion is sufficiently high this leads to a severe ‘winter break’ in the wool staple. The visible ‘break’ is the result of the combined effect of the winter fining of heterotype hairs and the shedding of some of all types. Fibres traversing the break were found to be either long heterotypes or long fine fibres.7. The adult colour of any individual Herdwick sheep is the result of the interaction of several factors of which the main ones are: (1) later fibre types tend to be less pigmented than early types; (2) less vigorous growth of an individual fibre tends to reduce its pigmentation; (3) a more or less extensive acromelanic pigmentation; (4) the white areas may be affected by various degrees of speckling or roaning; (5) the kemp-like hairs of the face and legs are black at birth, and these are eventually shed and replaced by similar but unpigmented fibres.8. Numerical data on the fibre and follicle population are presented. The mean proportion of the three main fibre types (all sheep, all seasons) was: coarse 18%, medium 25%, fine 59%. The mean adult follicle density was 1012 per sq.cm. and the mean adult S/P ratio was 3·37:1.

XIII.—The Appearance in Cross-section of the Hairs of some Carnivores and Rodents

Examination of mammalian pelts reveals the presence of two types of hair—long, glossy fibres known as “guard”- or “top-hair,” and shorter, softer, more curly fibres termed ”ground”- or “under-wool.” Guard-hairs are of two kinds: primary fibres classified by Toldt (1910) as “Leithaare,” and shorter, less robust secondary fibres which Toldt described as “Grannenhaare.” The under-wool is analogous to Toldt's “Wohlhaare.” More recently Toldt (1935) has described the appearance of the various fibre types occurring in hair from a wide range of mammals, and gives an extensive bibliography on hair from many orders of mammalia, including the two at present under consideration. Glaister (1931) made a photomicrographic survey of whole mounts and transverse sections of fibres from a large number of mammals. This work, however, suffers from the disadvantage that the photomicrographs were taken at low magnifications. When photographed at magnifications of the order × 500, transverse sections of fibres readily demonstrate the distribution and structure of cuticle, cortex and medulla. Such information is valuable as a means of studying structural variations in hair from different types of mammals, and often possesses considerable taxonomic significance and practical value—Dearborn (1939) reports the use of cross-sections of mammalian guard-hairs as a help to identifying small hairs found in the stomachs and excreta of predators, while the importance of fibre histology in forensic science has been reviewed by Smith and Glaister (1939). Furthermore, microchemical tests carried out on wool fibres (Bekker and King, 1931) and on transverse sections of kolinsky and hare fibres (Stoves, 1943a) have shown that cuticle, cortex, and medulla exhibit different chemical properties, so that morphological differentiation is accompanied by variation in chemical reactivity.