Simulation of marked root hair curling in Rhizobium-legume symbiosis

The soil bacterium Rhizobium infects its leguminous host plants in temperate regions of the world mostly by way of the growing root hairs. Root hair curling is a prerequisite for root hair infection, although sidelong root hair infections occasionally have been observed. The processes underlying Rhizobium -induced root hair curling are unknown.
Computer simulation of root hair growth indicates that one-sided tip growth inhibition by Rhizobium can result in root hair curling when three conditions are simultaneously fulfilled: 1) rhizobial growth inhibition is strong enough to prevent removal out of the tip growth range: 2) root hair surface growth between the attached Rhizobium and the root hair top is inhibited; 3) rhizobial growth inhibition is limited to one side of the root hair.
The results predict that root hair curling by stimulation of tip growth is improbable. This study accentuates the need for information about the growth processes contributing to tip growth in leguminous root hairs.     

Change in Hair Cycle and Hair Length in Nude Mice by Administration of Deuterium Oxide

D₂O increased hair length in Balb/c nu/nu (nude) mice in our previous study although it has an antimitotic effect in cells. To investigate the mechanism of the effect on the hair length, we examined the change by the administration of D₂O in the duration of the hair cycle and the proliferating activity of the hair matrix in relation with hair length in nude mice. The results showed that 20 or 30% D₂O administration did not change the gross structure of the hairs, the proliferative activity and keratinization of the hair matrix cells, but elongated the hair cycle. The duration of the hair cycle increased by the administration of D₂O in a dose-dependent manner over the examined range and these effects were reversible by discontinuation of D₂O. The change in the hair length correlated with the change in the hair-existing phase particularly. We also showed that the mast cell density in the skin, which is related to the hair cycle, increased in the deuterated mice at anagen VI stage which nearly corresponds to the hair-existing phase. The increase in the mast cell density may be related to the increase in the hair cycle duration. These findings indicate that the increase in hair length may be due to the increase in the duration of the hair cycle, in particular, an increase in the hair-existing phase. This study thus suggests that D₂O slows not only short-term cycles such as circadian clock or ultradian clock, but also the hair cycle which is a long-term cycle.     

Essential roles of BMPR-IA signaling in differentiation and growth of hair follicles and in skin tumorigenesis

Hair differentiation and growth are controlled by complex reciprocal signaling between epithelial and mesenchymal cells. To better understand the requirement and molecular mechanism of BMP signaling in hair follicle development, we performed genetic analyses of bone morphogenetic protein receptor 1A (BMPR-IA) function during hair follicle development by using a conditional knockout approach. The conditional mutation of Bmpr1a in ventral limb ectoderm and its derivatives (epidermis and hair follicles) resulted in a lack of hair outgrowth from the affected skin regions. Mutant hair follicles exhibited abnormal morphology and lacked hair formation and pigment deposition during anagen. The timing of the hair cycle and the proliferation of hair matrix cells were also affected in the mutant follicles. We demonstrate that signaling via epithelial BMPR-IA is required for differentiation of both hair shaft and inner root sheath from hair matrix precursor cells in anagen hair follicles but is dispensable for embryonic hair follicle induction. Surprisingly, aberrant de novo hair follicle morphogenesis together with hair matrix cell hyperplasia was observed in the absence of BMPR-IA signaling within the affected skin of adult mutants. They developed hair follicle tumors from 3 months of age, indicating that inactivation of epidermal BMPR-IA signaling can lead to hair tumor formation. Taken together, our data provide genetic evidence that BMPR-IA signaling plays critical and multiple roles in controlling cell fate decisions or maintenance, proliferation, and differentiation during hair morphogenesis and growth, and implicate Bmpr1a as a tumor suppressor in skin tumorigenesis.     

Mesenchymal–epithelial interactions during hair follicle morphogenesis and cycling

Embryonic hair follicle induction and formation are regulated by mesenchymal–epithelial interactions between specialized dermal cells and epidermal stem cells that switch to a hair fate. Similarly, during postnatal hair growth, communication between mesenchymal dermal papilla cells and surrounding epithelial matrix cells coordinates hair shaft production. Adult hair follicle regeneration in the hair cycle again is thought to be controlled by activating signals originating from the mesenchymal compartment and acting on hair follicle stem cells. Although many signaling pathways are implicated in hair follicle formation and growth, the precise nature, timing, and intersection of these inductive and regulatory signals remains elusive. The goal of this review is to summarize our current understanding and to discuss recent new insights into mesenchymal–epithelial interactions during hair follicle morphogenesis and cycling.     

构树钟乳体毛的发育及钟乳体成分研究

构树(Broussonetis Papyrifea)幼茎、芽、叶的表面具钟乳体毛。它是一长圆锥状单细胞毛,基部有无管漏斗状基座包裹,腔内有呈轮纹状沉积的钟乳体。钟乳体毛发生很早,自芽的第3幼叶(自叶原基数起)开始发生。原表皮细胞进行不均等的垂周分裂,其小的发育成表皮细胞,大的发育成钟乳体毛。基座由原表皮细胞垂周及横分裂而形成。其内钟乳体发育较迟,要等叶长至6cm,宽4—5cm时,才从毛尖或毛尖之下侧壁处开始沉积。构树钟乳体成分中含硫酸钙,这可能正是构树积累硫的速度快,净化大气中有害的SO2气体和可能抗SO2污染很强的原因。对筛选和培育抗SO2毒气更强的植物提供了参考。     

Estrogen leads to reversible hair cycle retardation through inducing premature catagen and maintaining telogen

Estrogen dysregulation causes hair disorder. Clinical observations have demonstrated that estrogen raises the telogen/anagen ratio and inhibits hair shaft elongation of female scalp hair follicles. In spite of these clinical insights, the properties of estrogen on hair follicles are poorly dissected. In the present study, we show that estrogen induced apoptosis of precortex cells and caused premature catagen by up-regulation of TGF β2. Immediately after the premature catagen, the expression of anagen chalone BMP4 increased. The up-regulation of BMP4 may further function to prevent anagen transition and maintain telogen. Interestingly, the hair follicle stem cell niche was not destructed during these drastic structural changes caused by estrogen. Additionally, dermal papilla cells, the estrogen target cells in hair follicles, kept their signature gene expressions as well as their hair inductive potential after estrogen treatment. Retention of the characteristics of both hair follicle stem cells and dermal papilla cells determined the reversibility of the hair cycle suppression. These results indicated that estrogen causes reversible hair cycle retardation by inducing premature catagen and maintaining telogen.     

Further serial transmission electron microscopy studies of auditory hair cell innervation in lizards and in a snake

Auditory hair cells of three lizard and one snake species were studied by serial transmission electron microscopy (TEM) sections of two unidirectional hair cells (UHC) and two bidirectional hair cells (BHC) and by nonserial section montages of each entire papilla cut at 2-microns intervals across the papillar width. The unidirectional hair cell region of the agamid lizard, Acanthosaura crucigera, lacked efferent innervation. Another agamid lizard, Agama agama, studied by nonserial section only, also lacked efferent innervation to the UHC. Afferent innervation to both the UHC and BHC of Acanthosaura was primarily exclusive (each nerve fiber innervates only one hair cell), although an occasional nerve fiber innervated two hair cells. Both the UHC and the BHC of the anguid, Celestus costatus, were exclusively innervated. Both hair cell types of the varanid, Varanus exanthematicus, were nonexclusively innervated (all afferent nerve fibers innervate two or more hair cells). The auditory papilla of the colubrid snake, Elaphe obsoleta, has only one type of hair cell and each is nonexclusively innervated. The numbers of afferent and efferent nerve fibers and of afferent synapses are presented in tabular form.     

Segmental Igfbp5 expression is specifically associated with the bent structure of zigzag hairs

The murine hair coat consists of four different hair types that are characterised by hair length, the number of medulla columns, and the presence and number of bends. The molecular mechanisms underlying the establishment and maintenance of distinct hair follicle fates are unknown. We identify Igfbp5 as the first molecular marker that distinguishes among different hair follicle types. High-resolution expression analysis revealed that its expression in the medulla of hair shafts is associated with the bend-forming zones of zigzag hairs. To directly examine the functional importance of segmental gene expression in the hair follicle, we have generated transgenic mice expressing Igfbp5 in differentiating keratinocytes of the medulla and inner root sheath. Ectopic expression of Igfbp5 resulted in the appearance of remarkable curvatures and thinning of hair shafts, two hallmarks of hair bends. Both effects and the natural bending process are under negative control of IGF signalling. Thus, our data identify Igfbp5 as a central regulator of hair shaft differentiation and hair type determination.     

Notch1 is essential for postnatal hair follicle development and homeostasis

Notch genes encode evolutionarily conserved large, single transmembrane receptors, which regulate many cell fate decisions and differentiation processes during fetal and postnatal life. Multiple Notch receptors and ligands are expressed in both developing and adult epidermis and hair follicles. Proliferation and differentiation of these two ectodermal-derived structures have been proposed to be controlled in part by the Notch pathway. Whether Notch signaling is involved in postnatal hair homeostasis is currently unknown. Here, we investigate and compare the role of the Notch1 receptor during embryonic hair follicle development and postnatal hair homeostasis using Cre-loxP based tissue specific and inducible loss-of-function approaches. During embryonic development, tissue-specific ablation of Notch1 does not perturb formation and patterning of hair follicle placodes. However, Notch1 deficient hair follicles invaginate prematurely into the dermis. Embryonic as well as postnatal inactivation of Notch1 shortly after birth or in adult mice results in almost complete hair loss followed by cyst formation. The first hair cycle of Notch1 deficient mice is characterized by shortened anagen and a premature entry into catagen. These data show that Notch1 is essential for late stages of hair follicle development during embryogenesis as well as for post-natal hair follicle development and hair homeostasis.     

The structure of a hair mechanoreceptor in the antennule of crayfish (Crustacea)

Summary In this study we examine the fine structure of mechanosensory hairs in the antennule of crayfish. The sensory hair is a stiff shaft with feather-like filaments. The hair's base is a large expansion of membrane which allows the hair shaft to deflect. The sensory transducing elements are located far from the hair, but are coupled mechanically with the hair shaft by a fine extracellular chorda. The sensory element is a type of scolopidium which consists of a scolopale cell and three sensory cells with a 9 + 0 type ciliary process.This type of scolopidium is characteristic of the chordotonal organ that has no cuticular structure on the surface of the exoskeleton. In this crustacean hair receptor, the deflection of the cuticular hair is transmitted through the chorda to the scolopidium which is a tension-sensitive transducer. The present study reveals that the mechanosensory hair of decapod crustaceans is a chordotonal organ accompanied by a cuticular hair structure. We also discuss comparative aspects of cuticular and subcuticular chordotonal organs in arthropods.     

Histochemical study on the external ear of Suncus murinus (Indian musk shrew)

The histochemical study of the Ear of female Suncus murinus (Indian musk shrew) was studied by the use of the cholinesterase technique. Good and sharp results were obtained while studing the AChE activity in the hair, hair follicle, hair papillae, muscle spindle, and nerve endings. The investigations were performed under constant pH, temperatures 37 degrees C to 40 degrees C, and incubation times, from 16 hours to 18 hours. The hair follicle and hair shafts showed strong positive reaction; hair papillae also showed strong positive reaction of AChE activity, while hair showed the banded appearance and the muscle spindles showed mild reaction of the AChE activity.     

Hoxc13在毛囊发育中的作用

Hoxc13属于Hox(Homobox)基因家族Abd-B类成员之一, 与毛囊形成和毛发生长密切相关。毛发结构蛋白KP(角蛋白)和KAP(角蛋白关联蛋白)的表达都受Hoxc13的严格调控, Hoxc13表达水平会直接影响毛发的特性, 对维持毛囊的正常形态也至关重要。文章就Hoxc13的表达水平对毛囊发育和毛发生长的影响及Hoxc13与相关基因的调控进行了综述。     

Hair analysis for abused and therapeutic drugs

This review focuses on basic aspects and recent studies of hair analysis for abused and therapeutic drugs and is discussed with 164 references. Firstly, biology of hair and sampling of hair specimens have been commented for the sake of correct interpretation of the results from hair analysis. Then the usual washing methods of hair samples and the extraction methods for drugs in hair have been shown and commented on. Analytical methods for each drug have been discussed by the grouping of three analytical methods, namely immunoassay, HPLC–CE and GC–MS. The outcomes of hair analysis studies have been reviewed by dividing into six groups; morphine and related, cocaine and related, amphetamines, cannabinoids, the other abused drugs and therapeutic drugs. In addition, reports on stability of drugs in the living hair and studies on drug incorporation into hair and dose–hair concentration relationships have been reviewed. Applications of hair analysis to the estimation of drug history, discrimination between OTC drug use and illegal drug use, drug testing for acute poisoning, gestational drug exposure and drug compliance have also been reviewed. Finally, the promising prospects of hair analysis have been described.     

Pigment synthesis in the Himalayan mouse

The effect of temperature on pigment synthesis in adult and juvenile Himalayan mice was investigated. Since pigment synthesis only occurs in actively growing hair, adult mice were plucked to induce hair growth. The extent of darkening of the hair was recorded by photography against a reference scale. The presence of pigment granules in hair follicles was investigated histologically. Housing adult and juvenile mice at 15 degrees C results in the synthesis of pigment in growing hair follicles whereas housing at 30 degrees C results in the absence of pigment granules in the growing hair follicles.     

Change in Hair Cycle and Hair Length in Nude Mice by Administration of Deuterium Oxide

D₂O increased hair length in Balb/c nu/nu (nude) mice in our previous study although it has an antimitotic effect in cells. To investigate the mechanism of the effect on the hair length, we examined the change by the administration of D₂O in the duration of the hair cycle and the proliferating activity of the hair matrix in relation with hair length in nude mice. The results showed that 20 or 30% D₂O administration did not change the gross structure of the hairs, the proliferative activity and keratinization of the hair matrix cells, but elongated the hair cycle. The duration of the hair cycle increased by the administration of D₂O in a dose-dependent manner over the examined range and these effects were reversible by discontinuation of D₂O. The change in the hair length correlated with the change in the hair-existing phase particularly. We also showed that the mast cell density in the skin, which is related to the hair cycle, increased in the deuterated mice at anagen VI stage which nearly corresponds to the hair-existing phase. The increase in the mast cell density may be related to the increase in the hair cycle duration. These findings indicate that the increase in hair length may be due to the increase in the duration of the hair cycle, in particular, an increase in the hair-existing phase. This study thus suggests that D₂O slows not only short-term cycles such as circadian clock or ultradian clock, but also the hair cycle which is a long-term cycle.     

Properties of the trochanteral hair plate and its function in the control of walking in the cockroach.

1. The physiological properties of the group of long hair sensilla of the trochanteral hair plate in the cockroach metathoracic leg were studied. The sensilla were divided into type I and type II according to their responses to imposed displacements. 2. Type I hair sensilla responded to dynamic displacements whereas type II hair sensilla responded to both dynamic and static displacements. The hair sensilla are normally excited by phasic flexion movements of the femur near the end of leg protraction. 3. Activity in the trochanteral hair plate afferents had a short latency excitatory effect on the motoneurone producing slow extension movements of the femur and an inhibitory effect on the femur flexor motoneurones. 4. Removal of the trochanteral hair plate in one leg caused overstepping of that leg in a walking animal due to exaggerated flexion of the femur. This change in leg movement can be explained by the removal of the inhibitory influence from the hair plate afferents to the femur flexor motoneurones. 5. We conclude that one function of the trochanteral hair plate is to limit femur flexion during a step cycle.     

Adsorption and elution of metals on hair

The adsorption of zinc and lead on hair was dependent on the acidity of the hair and/or the medium in which the hair sample was immersed, suggesting that hair is an ion exchanger. The pKa was estimated to be between 4.5 and 5.0. The coexistence of mercuric ion or PCMB reduced zinc adsorption by only a few percent, whereas zinc inhibited mercuric ion adsorption to a greater extent. These facts suggest that the binding sites in hair for metals are located on functional groups like carboxyl groups rather than sulfhydryl groups. The removal and/or elution of metals from hair were observed for 18 elements by various washing procedures. By treating hair with a water solution of detergent, alkaline metals were eluted to a great extent, whereas alkaline earth metals were eluted to some extent. The other metals did not vary with any procedures tested.     

Sex hormone levels and body hair growth in !Kung San and Kavango men from Namibia

The relation between hair growth and levels of sex hormones in serum and saliva was investigated in 256 !Kung San and Kavango men (ages 18 to 39 years) from Namibia/Southern Africa. Serum concentrations of total testosterone (Tser), 5α-dihydrotestosterone (DHT), and estradiol (E2) as well as the level of bioavailable non-SHBG-bound testosterone in the saliva (Tsal) were determined by radioimmunoassay. The distribution and density of scalp and facial hair as well as the development of terminal hair on the chest, abdomen, pubic area, arms, fingers, and legs were categorized using objective criteria. Covariance analyses revealed marked differences in the distribution of body hair in the San and the Negro sample. This is partly explained by a significant influence of androgen and estrogen levels on the growth of terminal hair. DHT and the ratio DHT/Tser are significantly positively related to midphalangeal hair growth and negatively to pubic hair development. Tsal, the bioavailable fraction of total testosterone, exerts a weak positive influence on the degree of arm and leg hair growth; the most significant positive effect on the growth of abdominal, arm, and leg hair in our samples is caused by E2. The ratio Tser/E2 correlates significantly negatively with the arm and leg hair development and the ratio DHT/E2 with the degree of abdominal, pubic, arm, and leg hair, whereas lower DHT concentrations occur in men with stronger hair development. © 1993 Wiley-Liss, Inc.     

A Qualitative and Quantitative Study of a Sensory Epithelium in the Inner Ear of a Fish (Colisa labiosa; Anabantidae)

The macula lagenae of the anabantide fish Colisa labiosa was studied with light and transmission electron microscopy. (1) The sensory area is naturally divided in a central area (A) surrounded by a peripheral part (B). (2) Generally the central hair cells are separated by supporting cells, while the peripheral hair cells are found in groups. The cells of a group are not separated by supporting cells. (3) Tubuli-like structures, hexagonal in cross section, are found in all cells. In peripheral hair cells the longitudinally oriented tubuli-like structures are aggregated in thick bundles. (4) Variation in shape, electron density, stereocilia arrangement and size of mitochondria was found in different hair cells. (5) The central hair cells contain large accumulations of presynaptic bodies (10–44). Contrarily, the peripheral hair cells contain only a few pre-synaptic bodies (1–3). (6) The central hair cells are innervated by thick afferent (6–15 μm) and fine presumed efferent (less than 1 μm nerve fibres, while the peripheral hair cells are innervated by thin (1–6 μm) afferent nerve fibres only.