Restoration of hair growth by surgical implantation of follicular dermal sheath.

The capacity of lower follicle dermal sheath to restore hair growth was tested by removing the lower halves of follicles, and then immediately implanting material containing dermal sheath cells from these bases, into the remaining upper epidermal follicle cavity. Over 60% of recipient follicles produced stout emergent vibrissa fibres and some operations resulted in multiple hair production from a single follicle. Histological examination revealed new dermal papillae within large bulb structures which were sited below the level of amputation--a feature that indicated that the new dermal papilla was derived from implanted material. For many follicles, the failure to produce emergent fibres could be accounted for after histological examination. These results provide clear evidence that lower follicle dermal sheath cells are capable of replacing those of the dermal papilla and it shows that they can do so in the context of the upper follicle. However, because elements of lower follicle epidermis were present in the implant material, the interactive sequence of events cannot be established. Dermal sheath cells have immense potential for papilla cell replacement: questions remain as to whether the distinction between sheath and papilla cells is one of context, or whether the transition requires specific external influences.     

A re-evaluation of Cercidiphyllum-like plant fossils from the British early Tertiary

The occurrence of Cercidiphyllum -like leaves, infructescences, fruits and seeds in the British early Tertiary is reviewed. Material previously described from the London Clay Formation, Lower Headon Beds (upper Barton Formation), Oldhaven Formation, and Woolwich and Reading Formation, are evaluated along with specimens from a new late Palaeocene locality in the Reading Beds. The leaves are assigned to Trochodendroides prestwichii; and infructescences, fruits and seeds, previously assigned to Carpolithus gardneri and Jenkinsella apocynoides , are united as a single species Nyssidium arcticum. The evidence that Trochodendroides and Nyssidium are parts of a single kind of fossil plant is supported, and the reconstructed ' Nyssidium plant' is compared with extant taxa, particularly extant Cercidiphyllum. The fossil plant shows a combination of characters not seen in any living genus, and the structure of the infructescence, as well as other features, precludes placing it within Cercidiphyllum. 'Nyssidium' and Cercidiphyllum are closely related. The morphological and sedimentological evidence indicates that 'Nyssidium' was an important colonizer of a variety of open flood-plain environments during the early Tertiary.     

Seasonal hair follicle activity and fibre growth in some New Zealand Cashmere-bearing goats (Caprus hircus)

Hair follicle activity and fibre growth were studied using histological sections from the skin of five adult feral does sampled every four weeks for 18 months. The main period of guard hair growth in primary follicles was from November to April. Secondary follicles grew fine, long, nonmedullated fibres (cashmere) from December to June. Shedding of these fibres from secondary follicles had commenced by July and cashmere was absent from the fleece by November. From September to December a subsidiary hair cycle occurred in many secondary follicles which produced minute (vellus) fibres, less than 2.4 mm in length. Some secondary follicles probably shed their cashmere fibres and remain quiescent over spring. Annual pelage changes were therefore achieved with one main growth period, although many secondary follicles underwent another brief hair cycle in spring.     

Induction of follicle formation and hair growth by vibrissa dermal papillae implanted into rat ear wounds: vibrissa-type fibres are specified.

Adult vibrissa follicle dermal papillae have the capacity to induce hair growth and follicle formation when associated with epidermis from various sources. However, the range of conditions under which hair follicle induction will take place has not been established. The question of whether or not the adult papilla carries information to impose fibre-type specificity has also not been fully answered. This study describes how the implantation of isolated papillae into small incisional cuts on the rat ear pinna resulted in the subsequent emergence of abnormally large hair fibres from the wound sites. Many of these hairs were found to display vibrissa-type characteristics. Histological observations indicated that the papillae had interacted with the edges of the wound epidermis to produce new, and particularly large follicles, while immunohistochemical staining revealed that early follicle construction was accompanied by a profusion of the basement membrane constituents laminin and type IV collagen in the subjacent dermis. These findings show that adult rat papillae retain the capacity, as displayed by embryonic dermis, to determine vibrissa specificity in induced follicles.     

766. CERCIDIPHYLLUM MAGNIFICUM – Systematic placement and fossil history of Cercidiphyllum Siebold & Zuccarini

Cercidiphyllum Sieb. & Zucc. comprises two very similar living species, Cercidiphyllum japonicum Sieb. & Zucc. and Cercidiphyllum magnificum (Nakai) Nakai, both commonly referred to as the katsura tree. The systematic placement and fossil history of Cercidiphyllum are described, and aspects of its cultivation and conservation are discussed. Cercidiphyllum magnificum is illustrated.     

Late Cretaceous follicular fruits from southern Sweden with systematic affinities to early diverging eudicots

Eight new species in seven new genera of follicular fruits are described from the Late Cretaceous of southern Sweden. They are Agapitocarpus emisxus , Chontrocarpus pachytoichus , Maiandrocarpus moirasmenus , Malliocarpus batrachoides , Mitocarpus elegans , Xylocarpus rhitidoides , Zeugarocarpus adroagathus and Z. leptoagathus . The fossil follicles are borne along infructescence axes or more commonly occur as isolated, dispersed fruits. Three genera, Maiandrocarpus , Mitocarpus and Zeugarocarpus , have follicles in distinct pairs borne spirally on an infructescence axis. Each follicle of a pair faces the axis with its ventral slit, which strongly indicates that the paired follicles were derived from two separate, monocarpellate flowers rather than from a single, bicarpellate flower. One genus ( Malliocarpus ) has follicles borne individually in the infructescence and three others ( Agapitocarpus , Chontrocarpus and Xylocarpus ) are known only as dispersed follicles. The paired follicles share many features with most of the dispersed follicles, including a sessile stigmatic area, a three-layered simple follicle wall, a simple vascular system composed of one dorsal and two lateral bundles, as well as a marginal-linear placentation bearing several anatropous ovules. Accordingly they are thought to belong to the same complex of taxa. The general structure of the fossils and comparison with modern angiosperms suggest that the fossils might represent an extinct lineage within or close to basal eudicots and many characters are shared with members of extant Proteaceae.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 377–407.     

High follicle density does not decrease sweat gland density in Huacaya alpacas

When exposed to high ambient temperatures, mammals lose heat evaporatively by either sweating from glands in the skin or by respiratory panting. Like other camelids, alpacas are thought to evaporate more water by sweating than panting, despite a thick fleece, unlike sheep which mostly pant in response to heat stress. Alpacas were brought to Australia to develop an alternative fibre industry to sheep wool. In Australia, alpacas can be exposed to ambient temperatures higher than in their native South America. As a young industry there is a great deal of variation in the quality and quantity of the fleece produced in the national flock. There is selection pressure towards animals with finer and denser fleeces. Because the fibre from secondary follicles is finer than that from primary follicles, selecting for finer fibres might alter the ratio of primary and secondary follicles. In turn the selection might alter sweat gland density because the sweat glands are associated with the primary follicle. Skin biopsy and fibre samples were obtained from the mid-section of 33 Huacaya alpacas and the skin sections were processed into horizontal sections at the sebaceous gland level. Total, primary, and secondary follicles and the number of sweat gland ducts were quantified. Fibre samples from each alpaca were further analysed for mean fibre diameter. The finer-fibred animals had a higher total follicle density (P<0.001) and more sweat glands (P<0.001) than the thicker-fibred animals. The fibre diameter and total follicle density were negatively correlated (R²=0.56, P<0.001). Given that the finer-fibred animals had higher follicle density and more sweat glands than animals with thicker fibres, we conclude that alpacas with high follicle density should not be limited for potential sweating ability.     

Multiple roles for elastic fibers in the skin.

Dermal elastic fibers are believed to have a primary role in providing elastic stretch and recoil to the skin. Here we compare the structural arrangement of dermal elastic fibers of chick skin and different animal species. Most elastic fibers in chick skin are derived from cells that line the feather follicle and/or smooth muscle that connects the pterial and apterial muscle bundles to feather follicles. Elastic fibers in the dermis of animals with single, primary hair follicles are derived from cells lining the hair follicle or from the ends of the pili muscle, which anchors the muscle to the matrix or to the hair follicle. Each follicle is interconnected with elastic fibers. Follicles of animals with primary and secondary (wool) hair follicles are also interconnected by elastic fibers, yet only the elastic fibers derived from the primary follicle are connected to each primary follicle. Only the primary hair follicles are connected to the pili muscle. Human skin, but not the skin of other primates, is significantly different from other animals with respect to elastic fiber organization and probably cell of origin. The data suggest that the primary role for elastic fibers in animals, with the possible exception of humans, is movement and/or placement of feathers or hair.     

Effects of intradermally injected and topically applied mouse epidermal growth factor on wool growth, skin and wool follicles of merino sheep

Twice daily intradermal (ID) injections of mouse epidermal growth factor (mEGF) in sterile saline for 1-4 days into delineated areas of skin of Merino sheep produced dose-dependent changes in wool follicles and fibres, ranging from slight reduction in follicle bulb size and transient disturbance of cuticle formation on some fibres to the induction of catagen of follicles and shedding of fibres with distorted, tapered ends. Regeneration of follicles commenced by day 7. By contrast, ID injections of saline did not affect follicle activity. The epidermis became thicker and more parakeratotic after multiple injections of mEGF than after injection of saline, but was almost normal again by day 14. Persistent small increases in sebaceous gland size, additional to those induced by ID injections of saline, and delayed small increases in sweat gland size also occurred after multiple injections of mEGF. Daily topical applications of mEGF in 50% (v/v) aqueous propylene glycol 5 days each week for 4 weeks did not affect wool growth or the follicles and other skin components. The only effect observed, due to application of the aqueous propylene glycol, was an increase in the number of layers of cornified cells in the stratum corneum of the epidermis, with the cells arranged in clearly discernible stacks. The effects produced by ID injections of mEGF indicate that mEGF acts directly on the pilosebaceous and epidermal components of skin.     

A theory of follicle selection: I. Hypotheses and examples

A theory of follicle selection is developed in which all follicles, ovulatory and atretic, inherit the same developmental plan for responding to circulating concentrations of estradiol and gonadotropins. In the model, this plan is represented by a maturation surface that determines the rate of follicle growth as a function of follicle maturity and circulating hormone concentration. Examples of maturation surfaces are constructed for single and multiple spontaneous ovulators. When model follicles are activated from the reserve pool at random times, spontaneous and coordinated cycles of maturation develop in which the number of ovulatory follicles is controlled within a small and predictable range. For a given maturation surface, this range is nearly independent of the number of follicles in the interacting population, their activation times, and their initial maturities. The theory is therefore consistent with Lipschütz's Law of Follicular Constancy. The theory can account for certain statistical effects that occur with age on the timing of ovulation and the control of ovulation number. Maturation surfaces are also constructed that exhibit spontaneous transitions from cyclic to steady anovulatory behavior. The theory predicts an important regulatory role for atretic follicles in controlling both the timing of maturation and the number of follicles that reach ovulatory maturity.     

The patchwork mouse phenotype: implication for melanocyte replacement in the hair follicle.

Mice homozygous for the recessive patchwork (pwk) mutation are characterized by a variegated pigment pattern with a mixture of unpigmented and normally pigmented hairs. The pigmented hair bulbs contain functional melanocytes. By contrast, the unpigmented hair bulbs contain no melanocytes. This lack results from the death of melanoblasts in the hair follicle at the end of embryogenesis. Here, we report that melanoblasts and melanocytes are found in the epidermis of pwk/pwk mice. Furthermore, these epidermal pigment cells are able to colonize new hair follicles after skin wounding. Despite the presence of epidermal pigment cells with a colonization potential, a follicle that had produced an unpigmented hair produces a new unpigmented hair during the successive hair growth cycles. This hair color continuity is also true for the pigmented hair follicles. Thus, in normal conditions, the hair acts as an independent functional unit as regards its pigment cells population.     

Morphological changes in the skin and wool fibres of Merino sheep infused with mouse epidermal growth factor

Intravenous infusion of 4.5-4.7 mg of mouse epidermal growth factor (mEGF) into nine castrated male Merino sheep for 26 h resulted in complete casting of the fleeces 6-8 days later. The morphological changes which occurred in the skin were studied in skin samples taken before infusion and at intervals between 1 h and 42 days after the infusion had begun. Wool fibres from the shed fleeces were examined with the scanning electron microscope. Increased cell proliferation occurred in the epidermis and sebaceous glands, whereas the wool follicles regressed. Transient dermal haemorrhages occurred during the first 3 h of infusion. The fibre and inner root sheath in the keratogenous zone of 30-40% of the follicles were partially disrupted within the first 6 h of mEGF infusion; catagen began in all follicle bulbs within 24 h. Fibre and inner root sheath production, although markedly reduced, continued in about 60% of follicles which had partially regressed, but production ceased in the remainder in which tapered ends formed on the fibres prior to shedding. Follicles began to regenerate asynchronously 4-8 days after the beginning of infusion and completed their development during the next 3 weeks. The follicle regression and fleece casting induced by mEGF infusion, and subsequent follicle regeneration were completed more rapidly than observed previously with other depilatory agents, and, except for prolonged epidermal thickening, there was no lasting cutaneous abnormality.     

First record of Cercidiphylloxylon(Cercidiphyllaceae)from the Palaeocene of Fushun,NE China

Cercidiphylloxylon spenceri(Brett)Pearson is described from the Lizigou Formation,Palaeocene in China.The growth rings are distinct; pores are diffuse,solitary,with somewhat angular outlines in cross section;vessel elements long with long scalariform perforation plates; intervessel pitting is opposite to scalariform; fibertracheids are present; axial parenchyma is scarce; rays are mostly biseriate and heterogeneous.All wood characters of the fossil specimen fall into the range of those of extant Cercidiphyllum(Cercidiphyllaceae).The finding is one of the earliest fossil wood records of Cercidiphyllaceae.     

Evolution of the diameters of the largest healthy and atretic follicles during the human menstrual cycle

Analysis of ovaries from 31 women with normal ovarian function permitted study of the diameter of the largest healthy and atretic follicles during the menstrual cycle. The follicle destined to ovulate is selected during the early follicular phase (Days 1-5). Throughout the cycle the diameter of the largest healthy follicles, with the exception of the dominant follicle, did not exceed, on average, 6 mm during the follicular phase and 4 mm during the luteal phase. Consequently, excluding the dominant follicle during the second half of the follicular phase, the largest follicles present in the human ovary are atretic. From these data, it was concluded that a new ovulation could not occur very soon after a spontaneous or experimentally induced premature disappearance of the dominant follicle or the corpus luteum of the cycle.     

How do the ovaries count?

A model is studied that regulates follicle development through hormonal feedback. The model takes the form of a many body problem where each body (follicle) is assumed to inherit the same maturation function and interact through a common summed variable (estradiol). Numerical solutions are obtained to a system of ordinary differential equations in which the number of equations changes in time as new follicles randomly enter into the interacting population from a dormant immature pool. Spontaneous cycles of follicle development emerge in which the number of follicles that reach full maturity is well controlled and insensitive to the rate of activation. The system of N interacting follicles is transformed to a gradient system on the unit sphere. Its stability properties are analyzed and compared with numerical and experimental results. Features of both spontaneous and induced ovulators are simulated. For certain parameter values solutions are obtained that correspond to known pathology. The model also suggests that the large number of follicles that are activated but atrophy before reaching full maturity help to regulate the cycle.     

Overexpression of Sonic Hedgehog suppresses embryonic hair follicle morphogenesis

The Sonic Hedgehog (Shh) signalling pathway plays a central role in the development of the skin and hair follicle and is a major determinant of skin tumorigenesis, most notably of basal cell carcinoma (BCC). Various mouse models involving either ablation or overexpression of key members of the Shh signalling pathway display a range of skin tumours. To further examine the role of Shh in skin development, we have overexpressed Shh in a subset of interfollicular basal cells from 12.5 dpc under the control of the human keratin 1 (HK1) promoter. The HK1-Shh transgenic mice display a range of skin anomalies, including highly pigmented inguinal lesions and regions of alopecia. The most striking hair follicle phenotype is a suppression in embryonic follicle development between 14.0 and 19.0 dpc, resulting in a complete absence of guard, awl, and auchene hair fibres. These data indicate that alternative signals are responsible for the development of different hair follicles and point to a major role of Shh signalling in the morphogenesis of guard, awl, and auchene hair fibres. Through a comparison with other mouse models, the characteristics of the HK1-Shh transgenic mice suggest that the precise timing and site of Shh expression are key in dictating the resultant skin and tumour phenotype.     

Gap junction amplification in rat ovarian granulosa cells: I. A direct response to follicle-stimulating hormone

The ability of follicle-stimulating hormone (FSH), the estrogens, estradiol-17β and diethylstilbestrol, and the estrogen antagonists, clomiphene and enclomiphene citrate to affect the growth and internalization of hypophysectomized rat granulosa cell gap junction membranes was compared in ovarian follicles assigned to one of four follicle size classes (60–149, 150–249, 250–319, and 320–450 μm diameter). In the absence of exogenous hormone stimulation, atresia prevents follicle growth beyond 320 μm in diameter but surface gap junction membrane increases throughout this early follicle growth. Internalization of gap junction membrane is first detected at the 150- to 249-μm follicle stage and also increases with follicle size. Therefore, growth and turnover of gap junction membrane occur at a basal rate in the absence of gonadotropin or steroid hormone stimulation. Estrogen and estrogen antagonist injections result in no significant differences in the amount of surface or internalized junction membrane in the three smallest follicle size classes when compared to the untreated hypophysectomized animals. However, estrogen but not estrogen antagonists rescues growing follicles from atresia and permits their further growth into the 320- to 450-μm follicle size class. As a result of the additional follicle growth, both surface and internalized junction membrane increase beyond that seen in the largest follicles from hypophysectomized animals. In contrast to other treatments, FSH stimulation promotes amplification of gap junction membrane in all size classes and, like estrogen, rescues follicles from atresia and promotes their entry into the 320- to 450-μm follicle size class. Surface gap junction membrane is amplified two- to fourfold over other treatments in the first three follicle size classes, but reaches maximal levels in the 250- to 319-μm follicles. The internalized junction membrane which first appears in the 150- to 249-μm size class is dramatically increased over other treatments in the 250- to 319- and 320- to 450-μm size classes. These studies indicate that exogenous estrogen stimulation promotes gap junction growth indirectly by sustaining the basal rate of junction synthesis in follicles rescued from atresia. In contrast, exogenous FSH stimulation directly amplifies the developmental sequence of gap junction growth and turnover. During early follicle growth, FSH stimulation preferentially promotes increases in surface gap junctions while internalization of surface junctions is increased during later follicle growth.     

Wool fibre crimp is determined by mitotic asymmetry and position of final keratinisation and not ortho- and para-cortical cell segmentation

Crimp, a distinguishing feature of sheep fibres, significantly affects wool value, processing and final fabric attributes. Several explanations for fibre bending have been proposed. Most concentrate on relative differences in the physicochemical properties of the cortical cells, which comprise the bulk of the fibre. However, the associations between cortical properties and fibre crimp are not consistent and may not reflect the underlying causation of fibre curvature (FC). We have formulated a mechanistic model in which fibre shape is dictated primarily by the degree of asymmetry in cell supply from the follicle bulb, and the point at which keratinisation is completed within the follicle. If this hypothesis is correct, one would anticipate that most variations in fibre crimp would be accounted for by quantitative differences in both the degree of mitotic asymmetry in follicle bulbs and the distance from the bulb to the point at which keratinisation is completed. To test this hypothesis, we took skin biopsies from Merino sheep from sites producing wool differing widely in fibre crimp frequency and FC. Mitotic asymmetry in follicle bulbs was measured using a DNA-labelling technique and the site of final keratinisation was defined by picric acid staining of the fibre. The proportion of para- to ortho-cortical cell area was determined in the cross-sections of fibres within biopsy samples. Mitotic asymmetry in the follicle bulb accounted for 0.64 (P < 0.0001) of the total variance in objectively measured FC, while the point of final keratinisation of the fibre accounted for an additional 0.05 (P < 0.05) of the variance. There was no association between ortho- to para-cortical cell ratio and FC. FC was positively associated with a subjective follicle curvature score (P < 0.01). We conclude that fibre crimp is caused predominantly by asymmetric cell division in follicles that are highly curved. Differential pressures exerted by the subsequent asymmetric cell supply and cell hardening in the lower follicle cause fibre bending. The extent of bending is then modulated by the point at which keratinisation is completed; later hardening means the fibre remains pliable for longer, thereby reducing the pressure differential and reducing fibre bending. This means that even highly asymmetric follicles may produce a straight fibre if keratinisation is sufficiently delayed, as is the case in deficiencies of zinc and copper, or when keratinisation is perturbed by transgenesis. The model presented here can account for the many variations in fibre shape found in mammals.     

Ovary genes and molecular pathology

In the ovary, primordial follicles have to pass different stages in order to become preovulatory follicles. In the past few years, new genes and therefore new proteins have been recognized as major players in folliculogenesis. Atm, kit ligand and its receptor c-kit are necessary for the maintenance of ovarian follicle pool. GDF-9, BMP15, originating from the oocyte play a major role in early folliculogenesis. Pro and antiapoptotic proteins such as Bax and Bcl2 complete in granulosa cells, in order to maintain or not the follicle alive. FSH receptor is necessary for final follicular maturation, from the preantral stage and beyond. LH receptor is necessary for follicle ovulation. However, new genes and their regulation need to be identified as many ovarian diseases such as premature ovarian failure are not yet clarified.     

Regulation of mouse follicle development by follicle-stimulating hormone in a three-dimensional in vitro culture system is dependent on follicle stage and dose

The developmental requirements of ovarian follicles are dependent on the maturation stage of the follicle; in particular, elegant studies with genetic models have indicated that FSH is required for antral, but not preantral, follicle growth and maturation. To elucidate further the role of FSH and other regulatory molecules in preantral follicle development, in vitro culture systems are needed. We employed a biomaterials-based approach to follicle culture, in which follicles were encapsulated within matrices that were tailored to the specific developmental needs of the follicle. This three-dimensional system was used to examine the impact of increasing doses of FSH on follicle development for two-layered secondary (100-130 microm; two layers of granulosa cells surrounding the oocyte) and multilayered secondary (150-180 microm, several layers of granulosa cells surrounding the oocyte) follicles isolated from mice. Two-layered secondary follicles were FSH responsive when cultured in alginate-collagen I matrices, exhibiting FSH dose-dependent increases in follicle growth, lactate production, and steroid secretion. Multilayered secondary follicles were FSH dependent, with follicle survival, growth, steroid secretion, metabolism, and oocyte maturation all regulated by FSH. However, doses greater than 25 mIU/ml of FSH negatively impacted multilayered secondary follicle development (reduced follicle survival). The present results indicate that the hormonal and environmental needs of the follicular complex change during the maturation process. The culture system can be adapted to each stage of development, which will be especially critical for translation to human follicles that have a longer developmental period.