Dorsal skin responses to subchronic ultraviolet B (UVB)-irradiation in Wistar-derived hypotrichotic WBN/ILA-Ht rats

Dorsal skin responses to a subchronic UVB-irradiation (10kJ/m2/rat /day), were examined in Wistar-derived hypotrichotic WBN/ILA-Ht rats for up to 3 months. Hyperplasia of epidermal cells and hair follicle epithelial cells as well as parakeratosis developed at 1 month and progressed thereafter, resulting in a prominent epidermis thickening and formation of epidermal ingrowths projecting into the dermis. At the same time, the percentage of proliferating cell nuclear antigen (PCNA)-positive epidermal cells significantly increased after I month. In some portions of the hyperplastic epidermis, especially of the epidermal ingrowths, keratinocytes were somewhat pleomorphic and migrated into the dermis. In the upper dermis, edema with capillary congestion, mast cell infiltration and fibroblast proliferation developed at I month, and the intensity of edema and the number of dermal mast cells was most prominent at 3 months. Edema spread to the epidermis, resulting in intercellular edema and subsequent dissociation of epidermal cells. Degeneration of collagen fibers was also detected in the upper dermis, especially beneath the epidermis. In addition, although not significant because of a large individual difference, the serum IgE concentration, showed a tendency to increase after 2 months. The present study clarified the characteristics of the dorsal skin responses to a subchronic UVB-irradiation in rats.     

Role of tissue interaction between pineal primordium and neighboring tissues in avian pineal morphogenesis studied by intraocular transplantation

Tissue interactions play an essential role in organogenesis during embryonic development. However, virtually no attempts have been made to study the role of tissue interaction in pineal development. In the present study we examined the inductive role of the epidermis and mesenchyme in the morphogenesis of quail pineal glands. The pineal rudiment is first observed at embryonic day 2 (E2: 2 days of incubation) at the dorsal midline of the diencephalon as a short semi-spherical protrusion. Electron microscopic observations revealed that no mesenchymal cells are found between the epidermis and the distal end of the E2 pineal primordium but that a thin layer of mesenchymal cells separate the epidermis from the pineal primordium at E3. Small pieces containing pineal rudiment were cut off from E2 or E3 embryos. They were treated with enzymes to eliminate the epidermis and/or mesenchyme, grafted into E5 chicken eyes, and cultured there for 1 week. When E3 pineal rudiment was treated with Dispase to remove the epidermis, the pineal gland developed normally. When the rudiment was further treated with collagenase to remove the surrounding mesenchymal cells, a multi-follicular structure was still formed, but to a lesser extent than when rudiments were treated with Dispase alone. When E2 quail pineal rudiment with the epidermis was grafted without any treatment, a multi-follicular structure developed which morphologically resembled embryonic pineal organs. When the epidermis was removed from E2 rudiments by Dispase, a single large vesicular structure was formed. These results suggest that the overlying epidermis and/or mesenchymal cells play some inductive role in the initial pineal development, while the mesenchymal tissue plays an important role in pineal follicular formation later during development. Since only a few experimental studies have been done to examine pineal morphogenesis, the present study provides fundamental insights into avian pineal development.     

Development of interfollicular epidermis on the surface of collagen framework of the dermis in experimental animals]

The fate of interfollicular epidermis keratinocytes which filled the hair follicles bursas of collagen dermis framework was investigated in the autotransplantation experiment. Collagen dermis framework was prepared from the skin flap. Interfollicular epidermis was detached with the help of suction method and transferred to the collagen dermis framework surface which was placed previously on the full thickness skin defect surface. It was established that in this environment keratinocytes not only developed, but some of them migrated into the hair follicle bursas cavities. It resulted in the follicular-like structures formation, cell elements of which differentiated in the manner characteristic of interfollicular epidermis. However, in spite of the fact that the epidermal cells partially retained their proliferating ability, ingrowing would completely disappear by the 15th to 20th day after the transplantation.     

桃树叶片的角质蒸腾实验

折枝处理降低了叶片下表皮蒸腾速率，提高了上表皮角质蒸腾占叶总蒸腾的比值，使角质蒸腾的上下振幅增大。２ ｍ 高度叶片低于１ ｍ 高度叶片的上表皮角质蒸腾。位于黑纸套内及阴处的叶片上表皮角质蒸腾占叶总蒸腾的比值均增大，而全日上表皮角质蒸腾的振幅却减少。     

Experimental studies on the effect of Gyrodactylus colemanensis and G. salmonis (Monogenea) on density of mucous cells in the epidermis of fry of Oncorhynchus mykiss

Fry of Oncorliynclius mykiss were experimentally infected with the ectoparasites Gyroducrylus rolenirmensis and Gyroducrylus salnionis (Monogenea) and changes in mucous cell density in the epidermis covering the caudal fin were monitored during an ensuing 42 day epidemic. At 10° C, infections of G. colemanensis rose to a recorded peak of 90 to 1 15 worms on day 27 post-infection and then declined toward extinction. Intensity of G. salmonis remained low throughout the experiment. Infection produced no clinical signs of disease and did not influence fry growth or survival. However, infected fish did have a 50% reduction in the number of mucous cells in the epidermis of the fin. The changes were first detected on day 24 post-infection and became increasingly pronounced during the subsequent 1 day period when parasite numbers declined drastically. The study hypothesizes that parasite activity on the surface indirectly leads to reduction in mucous cells through disruption of cell dynamics within the epidermis.     

Development of ATPase-positive,immature Langerhans cells in the fetal mouse epidermis and their maturation during the early postnatal period

Summary The development and maturation of Langerhans cells during the differentiation of skin was studied in mice from fetal day 13 to adult using 3 indices: (1) ATPase activity; (2) ultrastructure; and (3) quantitative evaluation of the cell population.ATPase-positive Langerhans cells appeared in the epidermis at first at fetal day 16, and they increased in number in the differentiating epidermis during the late fetal period. The earliest appearance of Birbeck granules was at postnatal day 4. Cored tubules were also formed in the Langerhans cells in the dermis at around the same age. The cells containing Birbeck granules or cored tubules are considered to be mature Langerhans cells. In the Langerhans-cell lineage, those cells in the epidermis at stages earlier than postnatal day 4 and not yet containing specific organelles are considered to be immature Langerhans cells. These immature Langerhans cells can be identified ultrastructurally in the epidermis at fetal day 16, coinciding with the appearance of ATPase-positive cells. The increase in the number of immature Langerhans cells during the perinatal period was shown by quantitative analysis of nuclear density and relative Langerhans-cell area on the electron micrographs.It is concluded that ATPase is a marker of the Langerhans-cell lineage from the early development stages, while Birbeck granules and cored tubules are markers that identify mature Langerhans cells in electron micrographs.     

Purification,properties, and titer of a hemolymph trophic factor in larvae and pupae of Manduca sexta

Purification of a hemolymph protein (hemolymph trophic factor, or HTF) from last instar larvae of Manduca sexta was achieved using Sephadex G15-120 gel filtration and DEAE anion exchange chromatography. Homogeneity was visualized using SDS gel electrophoresis and ampholytic chromatofocusing. HTF was estimated to be a tetrameric protein with a molecular weight of 286 K and a Stokes' radius of 55.3 × 10⁻⁸ cm by agarose bead gel filtration; chromatofocusing suggests an isoionic point > 10. Polyclonal antibodies to HTF were prepared in rabbits and an ELISA was developed. The ELISA was used to titer HTF during the last larval instar and day 1 and 14 of the pupal stage and estimates a maximum of 1.5 mg/ml larval hemolymph on day 6 with a smaller larval peak of 0.75 mg/ml at day 3 and titers of 0.70 and 0.35 mg/ml on the 2 pupal days, respectively. ELISA of aqueous extracts of larval fat body, epidermis, and cuticle demonstrate that HTF comprises nearly a third of the soluble fat body protein and is a lesser component of epidermis and cuticle. The physiological role of HTF has not yet been determined.     

Differential expression of the epidermal K1 and K10 keratin genes during mouse embryo development.

Induction of genes coding for the K1 and K10 keratins during mouse development was studied by measuring the accumulation of their respective mRNAs in day 10 to 17 embryos using an RNase protection assay. Although these two keratins are coexpressed in the suprabasal layers of the epidermis, it was found that while K1 mRNA was detectable as soon as day 10, K10 mRNA was not detectable before day 12. The expression of these genes at this stage of development was not expected since they are specifically associated with keratinization, a process that does not begin before day 17 of gestation. Histological examination of the epidermis of day 10 to 17 embryos suggests that both genes are induced in cells committed to epidermal differentiation, after stratification has started but before the onset of keratinization. It was also found that the two mRNAs increased in abundance steadily and significantly until day 16 and that, in spite of the expectation that filaments should contain equivalent amounts of each subunit, K1 mRNA remained more abundant than K10 mRNA at all times including in adult epidermis. These observations indicate that the two genes are regulated independently during development.     

Der Tryptophanstoffwechsel und die Ommochromsynthese während der Embryonalentwicklung der Stabheuschrecke Carausius morosus

The synthesis of ommochromes, ommin, and xanthommatin, was studied during the embryonic development of Carausius morosus. Ommochrome synthesis begins in the epidermis of the embryo at the 46th day after egg laying. The ommochrome accumulation is directly related to the continuous increase of pigment spots on the epidermis of the pharate larva.The concentration of free tryptophan increases progressively from the germ band formation (15th day), until the final position of the embryo in the egg, with the head immediately beneath the operculum (44th day). Subsequent decrease in concentration of tryptophan coincides with the appearance of ommochrome in the epidermis of the embryo. The tryptophan levels decrease considerably from 44th day till the 60th day. During the stage of the pharate first instar larva tryptophan levels remain low until hatching. The concentrations of the intermediates, kynurenine and 3-HO-kynurenine, show no accumulation and remain low during the whole of ommochrome synthesis.     

A histoquantitative study of the effect of maternal hypervitaminosis A on the differentiation of the foetal mouse skin.

The skin of albino mouse foetuses aged 13, 15, 17, 19 and 21 days was studied histologically and quantitatively. The skin of foetuses aged 21 days after maternal hypervitaminosis A, was compared with that of 21 days controls. On the 13th day, the epidermis consisted of one layer of cuboidal cells. The stratum intermedium appeared on the 15th day, the stratum granulosum on the 19th day and the stratum corneum on the 21st day of intrauterine life. The quantitative study showed that although the epidermis increased more rapidly in thickness in the interval between the 13th and 17th day than in the subsequent 4 days, yet in the latter period differentiation of the stratum granulosum and corneum took place. On the other hand, the rate of proliferation of the epithelial cells concerned in the follicle formation was more rapid in the last two days of intrauterine life than in any previous prenatal stage. After maternal hypervitaminosis A, the whole thickness of the epidermis was reduced by 50% and the dermis showed an oedematous appearance. The hair follicle primordia showed a decreased volume.     

Muc5ac Mucin Expression During Rat Skin Development

Some mucin genes have been detected during human embryonic and fetal organ development; however, little is known about mucin expression in epidermal development, neither in humans nor in other species. The present research was developed to explore Muc5ac skin expression during pre- and post-natal rat development. Immunohistochemistry (IHC), Western blotting (WB) and RT-PCR were employed. By IHC, Muc5ac protein was found early in embryonic epidermis from day 13 of gestation until seven days after birth when the surface epidermis became negative and the reaction was restricted to secreting sebum cells. In coincidence with IHC findings, WB analysis showed a band at approximately 200KDa at the same periods of development. Results were also confirmed by RT-PCR.Muc5ac expression in rat embryonic epidermis suggests that Muc5ac may play a protective role in embryonic skin previous to birth which may be replaced by pile covering. To our knowledge, this is the first report that confirmed Muc5ac expression during skin development.Key words: Muc5ac, skin, rat, development     

小鼠皮肤及其毛囊早期发育的组织学观察

目的探讨小鼠皮肤及其毛囊的早期发育规律。方法采用常规石蜡切片和H-E染色技术,观察昆明系小鼠出生前后皮肤及其毛囊的形态发育。结果(1)孕龄16 d胎鼠的皮肤表面形成凹凸不平的深褶皱,但在生后3 d~5 d不仅皱褶的数量减少,而且凹陷变浅;(2)胎鼠孕龄16 d至19 d,其皮肤的表皮、真皮及皮肤总厚度呈现平稳增厚。但是,出生后,其表皮、真皮和皮肤总厚度急剧降低;在生后第1天至第9天,表皮呈现平稳增厚,而真皮则在生后快速厚度,第7天达到最高值(1861.50μm);(3)孕龄16 d的胎鼠皮肤中可观察到初级毛囊,至生后第7天其密度呈现平稳增长;与其相比,次级毛囊从18 d胎鼠开始出现,其密度增长非常迅速,出生后第7天达到1257.14/mm;毛囊的总密度与次级毛囊呈现相似的变化趋势。出生第7天后,由于毛囊的数量急剧增加,无法观察初级毛囊和次级毛囊的变化规律;(4)初级毛囊和次级毛囊的长度与深度变化在出生前后的相对缓慢,与其相比在第3天以后至第7天呈现迅速变化趋势。结论小鼠皮肤及其毛囊的生长性发育发生在胎儿晚期和生后的早期,而其周期性变化可能从出生后的第9天以后开始出现;在孕期16 d至生后第7天可能是检测毛囊特异性基因表达的最佳期。     

Electron microscopy of wound healing in the skin of Gasterosteus aculeatus

The process of healing of a small surgical incision in the skin of Gasterosteus aculeatus has been studied by electron microscopy. The wounds were made in the mid-ventral line where no muscle intervenes between the skin and the peritoneum. The epidermis moved in through the incision and spread outwards beneath the dermis; the migrating epithelial cells were shown to be phagocytic. The wound was closed when cells at the surface of the epidermis met across the gap, forming a plug of epidermal tissue which was then invaded by dermal tissue from either side. Formation of new basement membrane apparently depended on the interaction of epidermal and dermal components. Leucocyte types were identified by electron microscopy; acid phosphatase tests were positive in macrophages and in neutrophil granulocytes, negative in lymphocytes and in eosinophil granulocytes. These four types of leucocyte are present in normal skin; after wounding, more migrated into the epidermis from the blood. The number of neutrophils in the epidermis reached a peak 24 h after wounding and declined during the second day. The number of macrophages rose to a peak by the third day and returned to normal by day 8. The numbers of eosinophil granulocytes and of lymphocytes showed little change. Neutrophil granulocytes were shown to be phagocytic, although not to the same extent as the macrophages.     

Senescence in the nongreening region of the rice (Oryza sativa) coleoptile

Summary The coleoptile of rice (Oryza sativa L. cv. Nippon-bare) emerges from the imbibed seed on day 2 after sowing and ceases its growth on day 3. In cross section, the cells near the outer epidermis turn into green between days 2 and 3, while those near the inner epidermis remain colorless. In this study, the complete process of the development in the nongreening cells in the coleoptile was examined by fluorescence and electron microscopy. Embryonic morphology on day 0 was rapidly converted into the differentiated greening or nongreening cells between days 1 and 2. Senescence in the inner, nongreening region first appeared on day 4 in the third or fourth cell layer from the inner epidermis and then spread towards both the inner and the outer epidermis, and the inner cells collapsed completely before the outer cells senesced. Cells adjacent to the inner epidermis, which senesced slowly, followed a sequence of events during development: (1) degradation of plastid DNA; (2) dispersal of nuclear chromatin, differentiation of plastids into amyloplasts, degradation of mitochondrial DNA; (3) degradation of the starch in amyloplasts; (4) disorganization of plastids; (5) condensation of the nucleus, shrinkage of mitochondria; (6) complete loss of cellular components, distortion of cell walls. In the interior cells, the early events including degeneration of plastid DNA and mitochondrial DNA occurred in parallel with those in the cells adjacent to the inner epidermis, yet rapid collapse of all the cellular components proceeded between days 3 and 5, and nuclear condensation could not be detected.Abbreviations cpDNA chloroplast DNA - DAPI 4,6-diamidino-2-phenylindole - DiOC₇ 3,3-dihexyloxacarbocyanine - IE inner epidermis - mtDNA mitochondrial DNA - mt-nucleoid mitochondrial nucleoid - OE outer epidermis - ptDNA plastid DNA - pt-nucleoid plastid nucleoid     

Contribution to ontogenesis of Merkel cells

Merkel cells appear in the epidermis of planum nasale of the rat fetuses from the 16th day of i. u. development, namely in the 2nd-3rd layer of epidermal cells. Nerve fibres appear in the subepidermal connective tissue from the 20th day of i.u. development. Long cytoplasmic processes filled in with specific dense core vesicles grow from Merkel cells against them. Intraepidermally, nerve fibres appear in postnatal period (from 3rd day after birth). Granular vesicles of Merkel cells probably have the leading role in the formation and maintenance of contacts between Merkel cell and the nerve ending. The results of studying ontogenetic development of Merkel cells in the rat are favour of hypothesis about the differentiation of Merkel cells in the epidermis, however, the possibility of secondary equipment of epidermis with Merkel cells independently on the development of nerve fibres is not eliminated.     

Correlations between epidermal cell structure and endogenous hormone titers during the fifth larval instar of the tobacco hornworm, Manduca sexta

Epidermal cell morphology and cuticle production in Manduca sexta are directly influenced by both ecdysterone and juvenile hormone. Up to day 6 of the last larval instar, post-molt endocuticle is continuously deposited even though cells undergo a partial and temporary separation from the overlying cuticle at the time when a small ecdysteroid peak is detected (approximately day 3.5). At about days 6--7 when another, larger ecdysteroid peak is present, apolysis occurs accompanied by the appearance of edcysial droplets. Following apolysis, layers of pupal cuticle are deposited. Increased quantities of rough endoplasmic reticulum characterize the epidermis at times of peak endocuticle deposition (day 3, larval cuticle; day 9, pupal cuticle). Dense pigment inclusions are found in epidermis from the day of ecdysis to the last larval instar until they are eliminated 5 days later. These dense bodies migrate from cell apex to base in the absence of juvenile hormone (or in the presence of a negligible amount of juvenile hormone) and probably contain insecticyanin.     

The two duplicated insecticyanin genes, ins-a and ins-b are differentially expressed in the tobacco hornworm, Manduca sexta.

Two gene-specific probes were generated from the unique sequences in the 3' non-coding regions of the two insecticyanin genes, ins-a and ins-b to study the developmental expression of these genes in Manduca sexta. Both genes were initially transcribed in the freshly hatched first instar larvae and then expressed in the epidermis and to a lesser degree in the fat body during every larval feeding stage. In the epidermis of the 4th and 5th instar larvae, both mRNAs appeared shortly before ecdysis and accumulated to maximal levels within a day. As the larval epidermis became pupally committed on day 3 of the 5th (final) instar, INS-a mRNA quickly decreased, whereas INS-b mRNA showed a second peak of accumulation. In the fat body, both genes showed a similar expression pattern within the 4th instar to that of the epidermis except that levels were lower and ins-b mRNA dominated. In the final instar, only ins-b mRNA was present in significant amount. These findings not only reveal that the two duplicated insecticyanin genes have diverged in their expression pattern but also demonstrate, for the first time, that fat body also expresses insecticyanin genes.     

Differentiation of pure chick embryo epidermis grown in primary serum-free culture

The differentiation of precocious embryonic epidermis in serum-free primary culture was analyzed by light and electron microscopic methods. Explants of 7-day chick embryo epidermis were grown on collagen or poly-L-lysine substrates in the absence of dermal mesenchyme. The serum substitute consisted of a mixture of insulin, transferrin, putrescine and seleneous acid together with (or without) Nerve Growth Factor. These culture conditions were shown to support proliferation, growth and development (evaluated using morphological criteria) of the epidermal explants up to 4-5 days; during this period, the epidermis underwent stratification; well-developed desmosomes as well as tonofilaments were formed and the epidermis achieved a morphology close to that of 10-11 day epidermis in ovo. However long-term survival of the explants was not obtained as cellular death, starting on day 5, progressively led to the necrosis of most parts of the explant. This morphological study demonstrates that the early phases of epidermal growth and maturation can occur to some extent in the virtual absence of dermal elements and serum factors. Chick embryo epidermal cells may thus possess the intrinsic ability to go through, at least for short periods in vitro, their differentiation programme. Then, at the onset of epidermal keratinization (12 days in ovo), they require specific exogenous factors to fully differentiate in vitro.