Biomedical subjects

G Imokawa

Publications and source records attributed to G Imokawa.

At least 73 records · Page 4Linked to original sources

PubMed1993

Skin organ culture model for examining epidermal melanization.

To clarify the regulatory mechanism of skin pigmentation through epidermal proliferation and differentiation, organ cultures of pigmented guinea pig skins have been studied for their melanogenic responses to exogenous stimuli. Melanogenic activity was measured by both tyrosinase activity assessed by observing release of 3H2O from tissue after incubation with 3H-tyrosine and melanin synthesis, indicated by the incorporation of 14C-2-thiouracil into tissue. Those skin explants that were maintained in serum-free media under air conditions equilibrated with 5% CO2, 50% O2, and 45% N2 formed new, chemically analyzable pigment in the tissue within 4 d of culture. This melanization was accompanied by an increased number of melanocytes as well as by enhanced tyrosinase activity and elevated melanin synthesis. This organ culture system responded well to known tyrosinase inhibitors such as phenylthiourea, which decreased melanogenic activity. Of the arachidonic acid metabolites tested, PGE2, LTC4, LTB4, and 5-HETE were found to significantly stimulate melanogenic activity as indicated by tyrosinase activity, whereas PGF2-alpha, 12-HETE, and 15-HETE did not. Among several known growth factors, only bFGF significantly stimulated melanogenesis in the organ cultured melanocytes. TGF-alpha, which increased DNA synthesis, had a slightly stimulating effect on melanogenesis, whereas TGF beta, which inhibited DNA synthesis, did not stimulate melanogenesis, but rather slightly decreased it. 8-methoxypsoralen+ultraviolet A-treated skin that underwent a marked pigmentation within 14 d in vivo demonstrated enhanced melanogenesis in the organ culture system in proportion to its in vivo pigmentation. Our organ culture system might provide an opportunity to examine the mechanism of action of epidermal melanization.

Animals↗

PubMed1993

Metastatic behavior and tumorigenicity of a human melanoma cell line (MM-RU) after injection into nude mice.

The ability of the human amelanotic melanoma cell line MM-RU to produce experimental metastases and to grow tumors at subcutaneous inoculation sites in 4-week-old nude mice was examined. After i.v. inoculation of 10(6) cells, all injected mice (n = 21) developed consistent numbers of metastatic pulmonary colonies within 32 days. The coefficients of variation for the number of colonies were between 17%-23% in three independent experiments. Survival time after i.v. inoculation was 63 +/- 7 days (mean +/- SD) (n = 20). Within 20 days, subcutaneous inoculation of 5 x 10(6) cells resulted in tumor growths of 13 +/- 3 mm (mean +/- SD) at the inoculation sites in all nude mice (n = 12). The MM-RU cell line seems to be a simple, fast vehicle for testing the effect of melanoma growth modulators on experimental pulmonary metastases as well as on subcutaneously growing melanoma.

Animals↗

PubMed1993

Quantitative analysis of stratum corneum lipids in xerosis and asteatotic eczema.

Sphingolipids, a major constituent of intercellular lipids, are an important determinant for both water-holding and permeability barrier function in the stratum corneum. To assess the pathogenic role of sphingolipids in the stratum corneum of dry skin disorders such as xerosis and asteatotic eczema in leg skin, ceramides were quantified by thin layer chromatography after n-hexane/ethanol extraction of resin-stripped stratum corneum and evaluated as micrograms/mg stratum corneum. In healthy leg skin (n = 49), there was age-related decline in the total ceramide, whereas xerosis (n = 25) and asteatotic eczema (n = 16) suffering significantly reduced water-holding properties, exhibited no definite decrease, rather slight increase in ceramide quantity with the same composition of each individual ceramide as compared to healthy age-matched controls. These data indicate that the seemingly elevated level of ceramide is an artificial effect due to inflammatory processes which result from susceptibility to dryness. Analysis of sebum-derived lipids present in the stratum corneum revealed that there was a significant decline in free fatty acids in xerosis and asteatotic eczema as compared to age-matched healthy controls, and a similar decline in triglycerides in the above three groups when compared to younger controls. Although the observed decrease in the stratum corneum lipids may well explain the high incidence of winter dry skin in older people, the progression toward asteatotic eczema can not be accompanied solely by a decrease in ceramide quantity, suggesting that the evolution of xerotic skin is associated with other moisturizing factors and/or environmental stimuli.

Adult↗

PubMed1993

New inhibitors of melanogenesis, OH-3984 K1 and K2. I. Taxonomy, fermentation, isolation and biological characteristics.

Melanogenesis inhibitors, OH-3984 K1 and K2 were isolated from fermentation broth of Streptomyces sp. OH-3984. OH-3984 K1 and K2 inhibited the melanogenesis of B16 melanoma cells at concentrations of 7.5 and 3.8 micrograms/ml, respectively, whereas inhibition of tyrosinase activity has not been observed. The microbial metabolites showed no antimicrobiological activities against Gram-positive and Gram-negative bacteria, fungi or yeast at a concentration of 1,000 micrograms/ml.

Anti-Bacterial Agents↗

PubMed1993

New inhibitors of melanogenesis, OH-3984 K1 and K2. II. Physico-chemical properties and structural elucidation.

New melanin synthesis inhibitors, OH-3984 K1 and K2, were isolated from the fermentation broth of Streptomyces sp. OH-3984, and their structures were elucidated by spectroscopic methods and by chemical transformations. OH-3984 K1 (M.W.: 306; C18H26O4) and K2 (M.W.: 308; C18H28O4) have unique gamma-lactone rings, both of which correspond to oxidative products derived from C1-O14 cleavage of the 14-membered lactone group.

Anti-Bacterial Agents↗

PubMed1992

Endothelins secreted from human keratinocytes are intrinsic mitogens for human melanocytes.

We recently demonstrated that human melanocyte proliferation and differentiation could be stimulated by endothelin (ET) derivatives via a receptor-mediated signal transduction pathway (Yada, Y., Higuchi, K., and Imokawa, G. (1991) J. Biol. Chem. 266, 18352-18357). We show here that the growth factors for human melanocytes are produced and secreted by the surrounding cells, namely human keratinocytes for ET-1 and Big-ET-1. Northern blots have revealed the presence of ET-1 gene transcripts in proliferating human keratinocytes. The ET-1 production by human keratinocytes increased after irradiation with ultraviolet B (UVB) in a dose-dependent manner, accompanied by the significant secretion of interleukin 1 alpha (IL-1 alpha). Among the cytokines related to UVB-induced cellular reactions and keratinocyte growth, only IL-1 alpha and -1 beta stimulated the secretion of ET-1 and Big-ET-1 but not of ET-3 and Big-ET-3 in a time-dependent manner. Northern blots for IL-1 alpha-stimulated or UVB-exposed human keratinocytes revealed that production of ET-1 gene transcripts markedly increased (by about 300 or 1,200%) with constant levels of beta-actin gene transcripts. In a parallel study, the medium conditioned by UVB-exposed human keratinocytes elicited a significant anti-ET-1 antibody-suppressible increase in DNA synthesis by cultured human melanocytes in a UV dose-dependent manner, which was associated with a marked and rapid (80 s) increase in the intracellular calcium level upon incubation with human melanocytes. These studies suggest that ETs produced and secreted by keratinocytes play an essential role in the maintenance of melanocyte proliferation and UV hyperpigmentation in the epidermis.

Actins↗

PubMed1992

A rapid and simple assay method for UDP-glucose:ceramide glucosyltransferase.

We have developed a simple rapid method for measuring UDP-glucose:ceramide glucosyltransferase; the method utilizes ceramide immobilized on the surface of silica gel and [14C]UDP-glucose as substrate. The reaction product, [14C]glucosylceramide, formed on the surface of the silica gel was easily separated from free [14C]UDP-glucose, either by centrifugation or by filtration. The reliability of this solid phase method was evaluated by using rat brain membrane fraction as an enzyme source. This enzyme had an optimal pH of 6.4-6.5 and required Mn2+, Mg2+ in the presence of 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). Apparent Km values of 8.7 microM for UDP-glucose and 292 microM for ceramide were determined using the new method. Under the optimal conditions, the solid phase method yielded 2-5-times more product than did the method using micellar system. Moreover, the reaction was highly quantitative in its enzyme dose-activity relationship.

Animals↗

PubMed1992

Role of asparagine-linked carbohydrates in pulmonary metastasis of B16-F10 murine melanoma cells: implication through glycosylation inhibition by nojirimycin.

N-linked oligosaccharide moieties of cell surface glycoconjugates may be involved in the metastatic potential of tumour cells. Many studies have examined the anti-metastatic properties of inhibitors of carbohydrate synthesis or processing in vitro. However, there has so far been little evidence of such inhibitory factors on metastasis in vivo because of the general high toxicity of the inhibitors. In this study, we found nojirimycin (NM) to be a substantially non-toxic carbohydrate synthesis inhibitor that inhibited the experimental metastasis of B16-F10 melanoma cells not only in vitro but also in vivo. When NM was administered intraperitoneally to syngeneic C57BL/6 mice, the inhibition was dose-dependent, with 40-75% suppression of pulmonary colonization observed after 5 days exposure to NM (at 0.4 or 4 mg/day). An in vitro lectin sensitivity assay showed that NM-treated B16-F10 cells were less susceptible to the lectin concanavalin-A, suggesting alteration or decrease of high mannose-type carbohydrate moieties on the cell surface. Further in vitro analysis of adhesiveness between B16-F10 cells and endothelial cells demonstrated that NM treatment causes reduced binding of B16-F10 cells to endothelial cells. We have also studied the effect of NM on natural killer (NK) cells in mice. NM treatment elicited no substantial increase in the cytotoxic activity of splenic NK cells against YAC-1 target cells. These results indicate that NM acts on the process of adhesion and that specific structures of the cell surface carbohydrate moieties may be involved in the colonization phase of metastasis in vivo.

1-Deoxynojirimycin↗

PubMed1992

Allergic contact dermatitis releases soluble factors that stimulate melanogenesis through activation of protein kinase C-related signal-transduction pathway.

Phenylazo-naphthol (PAN) allergy induces visibly well-defined and late-appearing hyperpigmentation of brownish yellow guinea pig skin in clear contrast to dinitrochlorobenzene (DNCB) allergy, which has very low incidence of hyperpigmentation. Skin extract from PAN allergy at 20-29 d post-challenge exhibited marked melanogenic stimulatory effects (3H2O release and 14C-thiouracil incorporation) when added to cultured guinea pig melanocytes. The time course in the appearance of melanogenic factor was definitely consistent with the induction pattern of visible pigmentation. By contrast, the addition of DNCB-challenged skin extract demonstrated no significant stimulating effect on melanogenesis in either assay system on any of the post-challenge days tested. Assay of intracellular inositol 1,4,5-trisphosphate formed through incubation with the melanocytes demonstrated that the PAN-allergy skin extract at day 28, which contains definite melanogenic factors, stimulated the formation of inositol 1,4,5-trisphosphate that occurs around 50 seconds in contrast to no or little increase with extracts obtained at days 0 and 1 post-challenge. Gel chromatographic analysis revealed that the PAN-allergy skin extract at day 28 contained a newly generated melanogenic fraction with a molecular weight of approximately 9000 Da which was also capable of stimulating DNA synthesis and activating the signal-transduction process (inositol trisphosphate formation) when added to guinea pig melanocytes. Both stimulations of melanogenesis and DNA synthesis by the 9000 Da fraction were completely abolished by the prior and simultaneous addition of protein kinase C (PKC) inhibitor (H-7) or its down-regulatory agent, phorbol 12,13-dibutyrate (PdBu). Taken together, these results suggest that PAN allergy provides a new mechanism of hypermelanization in which endogenous factors synthesized within skin induce the activation of signal-transduction pathways such as phosphoinositide turnover through ligands-receptor binding, resulting in the stimulation of melanocytes possibly through the activation of PKC.

Animals↗

PubMed1992

beta-Glucocerebrosidase activity in murine epidermis: characterization and localization in relation to differentiation.

The intercellular lipids of the stratum corneum, which are highly enriched in ceramides, are critical for the mammalian epidermal permeability barrier. During the terminal stages of epidermal differentiation, the glucosylceramide content is dramatically reduced, while the content of free ceramides increases. To investigate whether beta-glucocerebrosidase (beta-GlcCer'ase) could be responsible for this change in lipid content, we characterized its activity in murine epidermis, compared enzyme activity to other murine tissues, and localized beta-GlcCer'ase activity within the epidermis. Epidermal extracts demonstrated linear 4-methylumbelliferyl-beta-D-glucose hydrolysis (to 3 h) with protein concentrations between 1 and 250 micrograms/ml. Whole epidermis contained comparable beta-glucosidase activity (9.1 +/- 0.4 nmol/min per mg DNA) to murine brain and liver, and 5-fold higher activity than spleen. Epidermal beta-glucosidase activity was stimulated greater than 15-fold by sodium taurocholate at pH 5.6, and inhibited at acidic pH (3.5-4.0). Bromoconduritol B epoxide (greater than or equal to 1.0 microM), inhibited epidermal enzyme activity by greater than 75%, while activity in brain, liver, and spleen was only inhibited by 6, 17, and 14%, respectively. Moreover, beta-GlcCer'ase mRNA expression in murine epidermis exceeded levels in liver, brain, and spleen. Finally, beta-GlcCer'ase activity was highest in the outer, more differentiated epidermal cell layers including the stratum corneum. In summary, mammalian epidermis contains an usually high percentage (approximately 75%) of beta-glucocerebrosidase activity, and the concentration of activity in the more differentiated cell layers may account for the replacement of glucosylceramide by ceramides in the outer epidermis.

Animals↗

PubMed1991

Effects of endothelins on signal transduction and proliferation in human melanocytes.

We demonstrate here that human melanocytes could be regulated by endothelin (ET) derivatives, potent vasoconstrictive peptides synthesized by endothelial cells, to stimulate their proliferation and melanization via a receptor-mediated signal transduction pathway. Receptor-binding assay using [125I]ET indicated that unlabeled ET-1 or ET-2 competitively inhibited each binding of labeled ETs to melanocytes with a concentration for half-maximal inhibition (IC50) of 0.7 or 0.9 nM, respectively. The dissociation constant (Kd) and the number of sites of the specific bindings of ET-1 and those of ET-2 were almost the same (Kd: 1.81 nM, binding sites: 7.0-8.0 x 10(4) per cell). Upon incubation with cultured cells, the mass contents of inositol 1,4,5-trisphosphate and intracellular calcium level were substantially increased by 10 nM ET-1, ET-2, and ET-3, but not by big-ET with maximal response at 80-130-s postincubation. The addition of ET-1 and ET-2 at 1-50 nM concentrations caused human melanocytes to significantly stimulate DNA [( 3H]thymidine incorporation) and melanin synthesis (3H2O release and [14C] thiouracil incorporation). Furthermore, ETs exhibited an additive stimulatory effect on basic fibroblast growth factor-stimulated DNA synthesis. In a long-term serum-free culture system, the strongest stimulation of growth by 10 nM ET-1 or ET-2 was observed in the presence of 10 nM cholera toxin and 0.2% bovine pituitary extract, resulting in a 4.5-fold increase in cell number for 12 culture days. These findings strongly suggest involvement of ET in the mechanism regulating proliferation and melanization of human melanocytes.

Binding, Competitive↗

PubMed1991

Decreased level of ceramides in stratum corneum of atopic dermatitis: an etiologic factor in atopic dry skin?

Stratum corneum lipids are an important determinant for both water-retention function and permeability-barrier function in the stratum corneum. However, their major constituent, ceramides, have not been analyzed in detail in skin diseases such as atopic dermatitis that show defective water-retention and permeability-barrier function. In an attempt to assess the quantity of ceramides per unit mass of the stratum corneum in atopic dermatitis, stratum corneum sheet was removed from the forearm skin by stripping with cyanoacrylate resin and placed in hexane/ethanol extraction to yield stratum corneum lipids. The stratum corneum was dispersed by solubilization of cyanoacrylate resin with dimethylformamide, and after membrane filtration, the weight of the stratum corneum mass was measured. The ceramides were quantified by thin-layer chromatography and evaluated as microgram/mg stratum corneum. In the forearm skin of healthy individuals (n = 65), the total ceramide content significantly declined with increasing age. In atopic dermatitis (n = 32-35), there was a marked reduction in the amount of ceramides in the lesional forearm skin compared with those of healthy individuals of the same age. Interestingly, the non-lesional skin also exhibited a similar and significant decrease of ceramides. Among six ceramide fractions, ceramide 1 was most significantly reduced in both lesional and non-lesional skin. These findings suggest that an insufficiency of ceramides in the stratum corneum is an etiologic factor in atopic dry skin.

Adolescent↗

PubMed1991

Stratum corneum lipids serve as a bound-water modulator.

Stratum corneum lipids have been found to be an important determinant involved in the water-holding function of the stratum corneum. In order to further elucidate the significance of stratum corneum lipids in the water-holding properties, the hydration behavior of the stratum corneum following depletion and replenishment of the lipids has been studied, using an isolated human forearm stratum corneum sheet, by differential scanning calorimetry parallel to ultrastructural changes of intercellular lipids in the stratum corneum. Extraction of the stratum corneum sheet with acetone/ether (1/1) decreased the bound-water content from 33.3% to 19.7%, where the melting temperature of ice remained constant. Further extraction with water, which released a large amount of water-soluble materials such as amino acids, did not change the bound-water content, but definitely raised the melting temperature of ice. The application of the stratum corneum lipids, which were solubilized in squalane containing 1% alpha-monomethyl heptadecyl glyceryl ether to the lipid-depleted stratum corneum sheet, caused a significant recovery of bound-water content to the previous, almost normal level. In accordance with the hydration behavior, electron microscopic analysis of the acetone/ether-treated stratum corneum sheet revealed selective depletion of lipids from the intercellular spaces, accompanied by a marked disruption of multiple lamellar structures. In contrast, the application of stratum corneum lipids into the lipid-depleted stratum corneum sheet resulted in the restoration of the lamellar structure between the stratum corneum cells. These findings strongly suggest that stratum corneum lipids serve a water-holding function through the formation of lamellar structures within the stratum corneum.

Adult↗

PubMed1990

Analysis of carbohydrate properties essential for melanogenesis in tyrosinases of cultured malignant melanoma cells by differential carbohydrate processing inhibition.

In order to clarify the biologic significance of carbohydrate processing in tyrosinases for melanogenesis, we have studied the effect of differential carbohydrate processing inhibitors on the recovery process of interrupted melanization which occurs after exposure of cultured B-16 melanoma cells to the inhibitor of core carbohydrate synthesis, glucosamine (Glc). Treatment of this glycosylation-dependent repigmentation process with the early-stage carbohydrate processing inhibitors deoxynojirimycin (dNM), castanospermine (CS), and monensin (MS) at 0.8 mM, 40 micrograms/ml, and 30 nM, respectively, in the presence of 2 mM theophylline (Tp) almost completely inhibits the reappearance of the pigment 48-72 h after removal of Glc. In contrast, treatment with the later stage carbohydrate processing inhibitor swaisonine (SW) at 40-80 micrograms/ml does not interrupt the repigmentation process. Electrophoretic analysis of tyrosinases in the soluble fractions of these melanoma cells demonstrates that the alteration of soluble tyrosinase isozymes by all the processing inhibitors is associated with a dose-dependent loss of sialic acid-rich T1 tyrosinase and the concomitant appearance or increase of sialic acid-poor tyrosinases. In the large granule fraction, a recovery of membrane-bound tyrosinase (T3) is seen following both MS and SW treatments, whereas dNM treatment results in the substantial loss of T3 tyrosinase. At the electron microscopic level, a translocation of tyrosinase from GERL and coated vesicles to many unmelanized vacuolar premelanosomes occurs in MS-treated cells in contrast to its predominant distribution in the GERL-coated vesicle system of dNM-treated cells, which contain many unmelanized premelanosomes. The present evidence for differential effects on intracellular tyrosinase transfer and melanization by different stages of carbohydrate processing inhibition suggests that asparagine-linked oligosaccharides, relating to the first mannose-trimming stages, determine the function of tyrosinase transfer as well as melanization through a specific intracellular recognition process in pigment cells.

Animals↗

PubMed1989

Importance of intercellular lipids in water-retention properties of the stratum corneum: induction and recovery study of surfactant dry skin.

In order to further clarify the role of intercellular lipids in the water-retention properties of the stratum corneum, forearm skin of six healthy male volunteers was treated with 5% sodium dodecyl sulfate (SDS) for 1, 10, and 30 min. All treatment periods induced chapping and scaling of the stratum corneum without any inflammatory reaction, accompanied by a significant decrease in its water-retention function. Electron-microscopic analysis of SDS-treated stratum corneum revealed selective depletion of the lipids from the intercellular spaces, accompanied by marked disruption of multiple lamellae structures. Lipid analysis also showed a considerable and selective loss of intercellular lipids such as cholesterol, cholesterol ester, free fatty acid, and sphingolipids. To evaluate the recovery potential for intercellular lipids, lipids which were separated as sebaceous-rich lipids (SLs) and stratum corneum lipids (SCLs) were applied daily on SDS-treated forearm skin. Two daily applications of the SCLs which were emulsified at 10% concentration in W/O (water in oil) cream caused a significant increase in conductance, accompanied by a definite improvement in the level of scaling over no application or W/O emulsion base only, whereas SLs in the W/O emulsion base led to no significant recovery in either conductance value or scaling. When two daily topical applications of four chromatographically separated lipid fractions (cholesterol ester, free fatty acid, cholesterol, and sphingolipid) from the SCL were carried out at 1% concentration in the same system, the cholesterol ester and sphingolipid fractions were found to induce a significant increase in the conductance value over no application.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

A possible role of prostaglandins in PUVA-induced inflammation: implication by organ cultured skin.

The role of arachidonate metabolites in UV-induced inflammation was analyzed by measuring the amounts of prostaglandins or leukotrienes released into a culture medium in the organ culture of biopsied guinea pig skin following UV exposure. Increased concentrations of prostaglandin E2, F2 alpha, and 6-oxo-F1 alpha were found in the medium subjected to UVB radiation followed by 24 h incubation in the organ culture, compared to medium from non-exposed skin, whereas LTC4 was at an undetectable level in both. This release occurred in UVB dose-dependent fashion and was completely inhibited by the addition of indomethacin to the medium. Exposure to monochromatic UV light of 250, 300, and 350 nm released prostaglandin E2, F2 alpha, and 6-oxo-F1 alpha, in increasing order of 250, 300, and 350 nm, but not LTC4. This order of amount released almost paralleled the intensity of inflammation that occurred with each wavelength. Exposure of skin to UVA following intraperitoneal injection of 8-methoxypsoralen (PUVA) was also found to stimulate the synthesis of prostaglandin E2 in UVA dose-dependent fashion, and the stimulation through an increasing dose of UVA occurred more significantly than UVB exposure. The time course of prostaglandin release following UVB and PUVA exposures was found to have a pattern similar to their dynamics in association with erythema and edema, conditions which could be significantly diminished by the topical application of indomethacin. The present studies demonstrate that prostaglandins play an important role in the production of inflammation by UVB as well as UVA and PUVA.

Animals↗

PubMed1989

Analysis of initial melanogenesis including tyrosinase transfer and melanosome differentiation through interrupted melanization by glutathione.

Because glycosylation-dependent melanization inhibition induced in cultured B-16 melanoma cells by glucosamine is reversible, producing synchronized initiation of melanogenesis after its removal, we have analyzed the possible dynamics of initial melanogenesis through their interruption by glutathione. The addition of glutathione at 0.2% concentration to the theophylline-stimulated recovery process completely interrupts the initiation of melanization for at least 72 h. At the electron microscopic level, theophylline-treated cells have many vacuolar melanosomes with distinct pigmentation which contain some vesicles (64% of total premelanosomes) or amorphous, filamentous, or granular materials within the interior which are suggestive of pheomelanotic melanosomes. The addition of glutathione induces a complete absence of melanization in the premelanosomes, within which a filamentous interior with periodicity is generally re-formed with almost complete disappearance of internal vesicles, providing dramatic changes to the size and shape characteristic of eumelanotic melanosome. Electron microscopic dopa reaction of glutathione-treated cells shows a predominant localization of tyrosinase activity in the Golgi-associated endoplasmic reticulum-lysosome and coated vesicles, but not in premelanosomes, in contrast to their dispersed distribution in all melanogenic organelles in the theophylline-treated control, suggesting a lack of tyrosinase translocation. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of tyrosinase in the large granule fraction shows that in analogy with electron microscopic observations, glutathione blocks the reappearance of membrane-bound T3 tyrosinase which occurs in the theophylline-treated control during the recovery process, whereas the dynamics of T1 tyrosinase is almost the same as that of the control. These findings suggest that glutathione provides a new situation of interrupted melanogenesis in which melanization cannot proceed despite complete formation of melanosome matrix structure and a lack of inhibition of cellular metabolisms including protein glycosylation.

Animals↗

PubMed1989

[Physiological analysis of the facial skin by corneocyte morphology and stratum corneum turnover].

In order to clarify the properties of facial skin, we measured corneocyte size and stratum corneum turnover rate on the face of healthy female volunteers in relation to age and compared the data with those from the flexor surface of the forearm. The corneocyte size on the face was found to be significantly smaller and the percentage of nucleated corneocytes was distinctly higher than those on the forearm. Stratum corneum turnover rate on the face was also approximately two times faster than on the forearm. The corneocyte size increased with aging on the forearm, but not on the face. Additionally, turnover rate decreased with aging on the forearm, but not on the face. These findings suggest that the facial skin is apparently influenced by some exogenous or endogenous factors which seem to overcome the influence of intrinsic aging effects.

Adolescent↗