The effect of vitamin D status on cutaneous sterologenesis in vivo and in vitro

Recent studies have shown that cutaneous sterologenesis is autonomous from the influence of circulating sterols, and that the epidermis is an important site of sterologenesis which is regulated by permeability barrier requirements. In addition to barrier function, an additional, important function of the epidermis is to synthesize sterol precursors of vitamin D3. The present study was designed, first, to determine whether vitamin D status and/or circulating levels of 1,25-dihydroxyvitamin D3 might play a role in regulating cutaneous sterol synthesis in vivo and, second, whether 1,25-dihydroxyvitamin D3 modulates sterologenesis in cultured human keratinocytes. Hairless mice were maintained on a vitamin D-deficient diet in the dark and supplemented with various doses of vitamin D3/day. Despite demonstrating serum 25-hydroxyvitamin D3 levels ranging from less than 10 to 343 ng/ml, the incorporation of tritiated water into cholesterol and total nonsaponifiable lipids in both the epidermis and dermis was similar in the four groups of animals. Likewise, administration of various doses of 1,25-dihydroxyvitamin D3 to vitamin D-deficient mice resulted in serum levels of 1,25-dihydroxyvitamin D3 ranging from less than 10 to 85 pg/ml; yet, cholesterol and total nonsaponifiable lipid synthesis was similar in both the dermis and epidermis in all groups of animals. Moreover, administration of 0.6 micrograms/kg per day of 1,25-dihydroxyvitamin D3 to 'normal' vitamin D-replete mice also had no effect on cutaneous sterol synthesis. Furthermore, conversion of 7-dehydrocholesterol to cholesterol in vitamin D-deficient vs. supplemented animals did not differ. Finally, addition of 1,25-dihydroxyvitamin D3 to cultured keratinocytes over a concentration range of 10(-12)-10(-7) M did not affect sterologenesis, except at supraphysiologic doses (10(-7) M). Together, these results suggest that vitamin D status does not influence sterol synthesis in the skin.     

1,25-Dihydroxyvitamin D3 modulates bone marrow macrophage precursor proliferation and differentiation. Up-regulation of the mannose receptor

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3), the biologically active form of vitamin D3, has been shown to inhibit proliferation and promote monocytic differentiation of leukemic cell lines. In the present communication, we extend these observations to normal bone marrow macrophage precursors, and 1) identify the stage of monocytic maturation wherein the steroid exerts its antiproliferative effect, and 2) demonstrate that 1,25-(OH)2D3 promotes bone marrow macrophage differentiation as manifest by specific up-regulation of the lineage-specific membrane protein, the mannose-fucose receptor. In these experiments, the 1,25-(OH)2D3-mediated inhibitory effect on colony formation was shown to be independent of attendant levels of colony stimulating factor-1 and targeted through the adherent bone marrow macrophage precursor. Examination of this steroid-sensitive adherent precursor population demonstrates that its specific binding of 125I-mannose bovine serum albumin spontaneously and progressively increases with time in culture. Whereas adherent bone marrow macrophages cultured for 2 days express 3 X 10(4) mannose receptors/cell, the number of binding sites increases to 7 X 10(4)/cell by day 4. When bone marrow macrophage precursors are exposed to 1,25-(OH)2D3, an additional stepwise enhancement of 125I-mannose bovine serum albumin obtains with time. Four days of culture with the steroid results in 1.6 X 10(5) mannose receptors/cell, a 100% increase as compared to control cells. Neither duration of culture nor exposure to 1,25-(OH)2D3 alters the KD of 125I-mannose bovine serum albumin which approximates 3-5 X 10(-9) ml-1. Finally, the "specificity" of vitamin D-mediated up-regulation of the mannose receptor was established by demonstrating that the steroid does not alter binding of 125I-alpha-thrombin by bone marrow-derived macrophage precursors.     

Degradation of oxidative stress-induced denatured albumin in rat liver endothelial cells

We previously identified conformationally denatured albumin (D2 and D3 albumin) in rats with endotoxicosis (Bito R, Shikano T, and Kawabata H. Biochim Biophys Acta 1646: 100–111, 2003). In the present study, we attempted first to confirm whether the denatured albumins generally increase in conditions of oxidative stress and second to characterize the degradative process of the denatured albumin using primary cultured rat liver endothelial cells. We used five models of oxidative stress, including endotoxicosis, ischemic heart disease, diabetes, acute inflammation, and aging, and found that serum concentrations of D3 albumin correlate with the serum levels of thiobarbituric acid-reactive substance (R = 0.87), whereas the concentrations of D2 albumin are 0.52. Ligand blot analysis showed that the D3 albumin binds to gp18 and gp30, which are known endothelial scavenger receptors for chemically denatured albumin. Primary cultured rat liver endothelial cells degraded the FITC-D3 albumin, and the degradation rate decreased to 60% of control levels in response to anti-gp18 and anti-gp30 antibodies, respectively. An equimolar mixture of these antibodies produced an additive inhibitory effect on both uptake and degradation, resulting in levels 20% those of the control. Furthermore, filipin and digitonin, inhibitors of the caveolae-related endocytic pathway, reduced the FITC-D3 albumin uptake and degradation to <20%. Laser-scanning confocal microscopic observation supported these data regarding the uptake and degradation of D3 albumin. These results indicate that conformationally denatured D3 albumin occurs generally under oxidative stress and is degraded primarily via gp18- and gp30-mediated and caveolae-related endocytosis in liver endothelial cells. serum albumin; denaturation; scavenger receptor; caveolae     

Restricted Transport of Vitamin D and A Derivatives Through the Rat Blood-Brain Barrier

The present studies measure the transport of retinol, retinoic acid, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], and 25-hydroxyvitamin D3 [25-(OH)D3] through the rat brain capillary endothelial wall, i.e., the blood-brain barrier (BBB). The vitamin A and D derivatives bind both to albumin and to specific high-affinity binding proteins in plasma. In the presence of physiologic concentrations of plasma proteins, the extraction by brain of all four compounds was 5% or less.     

Photosynthesis of vitamin D in the skin: effect of environmental and life-style variables

Exposure to sunlight continues to play a major role in providing adequate vitamin D nutrition for most of the population of the world, including those who live in countries that practice fortification of dairy, margarine, and cereal products with vitamin D. During exposure to sunlight, the high-energy UV photons (290-315 nm) penetrate the epidermis and photolyze 7-dehydrocholesterol (provitamin D3) to previtamin D3. Once formed, previtamin D3 undergoes a thermally induced isomerization to vitamin D3 that takes 2-3 days to reach completion. Melanin effectively competes with provitamin D3 for the UV radiation that enters the epidermis and limits its photolysis to previtamin D3. However, this is not the major factor that prevents excess production of vitamin D in the skin of people who are constantly exposed to sunlight. During the initial exposure to sunlight, provitamin D3 is efficiently converted to previtamin D3. However, because previtamin D3 is photolabile, continued exposure to sunlight causes the isomerization of previtamin D3, principally to lumisterol. Thus, no more than 10-20% of the initial provitamin D3 concentrations ultimately end up as previtamin D3. Aging, sunscreens, seasonal changes, time of day, and latitude also significantly affect the cutaneous production of this vitamin-hormone.     

Combined effect of cyclin D3 expression and abrogation of cyclin D1 prevent mouse skin tumor development

We have previously demonstrated that ras-mediated skin tumorigenesis depends on signaling pathways that act preferentially through cyclin D1 and D2. Interestingly, the expression of cyclin D3 inhibits skin tumor development, an observation that conflicts with the oncogenic role of D-type cyclins in the mouse epidermis. Here, we show that simultaneous up and downregulation of particular members of the D-type cyclin family is a valuable approach to reduce skin tumorigenesis. We developed the K5D3/cyclin D1^-/- compound mouse, which overexpresses cyclin D3 but lacks expression of cyclin D1 in the skin. Similar to K5D3 transgenic mice, keratinocytes from K5D3/cyclin D1^-/- compound mice show a significant reduction of cyclin D2 levels. Therefore, this model allows us to determine the effect of cyclin D3 expression when combined with reduced or absent expression of the remaining two members of the D-type cyclin family in mouse epidermis. Our data show that induced expression of cyclin D3 compensates for the reduced level of cyclin D1 and D2, resulting in normal keratinocyte proliferation. However, simultaneous ablation of cyclin D1 and downregulation of cyclin D2 via cyclin D3 expression resulted in a robust reduction in ras-mediated skin tumorigenesis. We conclude that modulation of the levels of particular members of the D-type cyclin family could be useful to inhibit tumor development and, in particular, ras-mediated tumorigenesis.     

Stimulatory effect of 1,25-dihydroxyvitamin D3 on transferrin synthesis in primary cultures of adult rat hepatocytes

The effect of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] on protein synthesis was studied in primary cultures of adult rat hepatocytes, in comparison with those of dexamethasone (DEX). The transferrin (TF) level in the culture medium assayed by a radioimmunoassay (RIA), after incubation for 24 hr was increased in the presence of 1,25-(OH)2D3, significantly at concentrations of more than 10(-12) M and maximally to about 140% of that in control cultures at 10(-8) M, without change in the albumin concentrations, assayed by an EIA. Other vitamin D3 metabolites had similar but weaker effects in increasing transferrin synthesis. On the other hand, incubation with 10(-6) M Dex for 24 hr enhanced the syntheses of both transferrin and albumin. Addition of 10(-7) M actinomycin D did not significantly block the effect of 1,25-(OH)2D3, but did suppress that of dexamethasone. These results indicate that 1,25-(OH)2D3 stimulates TF synthesis of cultured rat hepatocytes with different mechanism(s) of action from that of dexamethasone.     

Albumin binding as a general strategy for improving the pharmacokinetics of proteins

Plasma protein binding can be an effective means of improving the pharmacokinetic properties of otherwise short lived molecules. Using peptide phage display, we identified a series of peptides having the core sequence DICLPRWGCLW that specifically bind serum albumin from multiple species with high affinity. These peptides bind to albumin with 1:1 stoichiometry at a site distinct from known small molecule binding sites. Using surface plasmon resonance, the dissociation equilibrium constant of peptide SA21 (Ac-RLIEDICLPRWGCLWEDD-NH(2)) was determined to be 266 +/- 8, 320 +/- 22, and 467 +/- 47 nm for rat, rabbit, and human albumin, respectively. SA21 has an unusually long half-life of 2.3 h when injected by intravenous bolus into rabbits. A related sequence, fused to the anti-tissue factor Fab of D3H44 (Presta, L., Sims, P., Meng, Y. G., Moran, P., Bullens, S., Bunting, S., Schoenfeld, J., Lowe, D., Lai, J., Rancatore, P., Iverson, M., Lim, A., Chisholm, V., Kelley, R. F., Riederer, M., and Kirchhofer, D. (2001) Thromb. Haemost. 85, 379-389), enabled the Fab to bind albumin with similar affinity to that of SA21 while retaining the ability of the Fab to bind tissue factor. This interaction with albumin resulted in reduced in vivo clearance of 25- and 58-fold in mice and rabbits, respectively, when compared with the wild-type D3H44 Fab. The half-life was extended 37-fold to 32.4 h in rabbits and 26-fold to 10.4 h in mice, achieving 25-43% of the albumin half-life in these animals. These half-lives exceed those of a Fab'(2) and are comparable with those seen for polyethylene glycol-conjugated Fab molecules, immunoadhesins, and albumin fusions, suggesting a novel and generic method for improving the pharmacokinetic properties of rapidly cleared proteins.     

Keratinization in the epidermis of amphibians and the lungfish: comparison with amniote keratinization

Keratinization in the epidermis of amphibians and the lungfish has been studied by electron microscopy, autoradiography and immunocytochemistry to determine whether histidine-rich proteins, filaggrin and loricrin are present. In the lungfish and amphibian tadpoles, anti-keratin antibodies (AE1 and AE3) stain the whole epidermis but not the AE2 antibody, a marker for keratinization. In adult epidermis, the AE2 antibody mainly stains keratinized layers, AE1 mainly stained basal cells, less suprabasal cells and no pre-keratinized and keratinized layers, and AE3 stains all epidermal layers. This staining pattern resembles that of amniote epidermis. Little tritiated histidine is taken up in toad epidermis at 4-6 h post-injection but 24 h after injection the radioactivity is most concentrated in the replacement layer beneath the corneus. This indicates that protein synthesis takes place in the epidermis but, due to the metabolic conversion that takes place in 24 h, it is unlikely that histidine-rich proteins are formed. Neither filaggrin-like nor loricrine-like immunoreactivities are present in amphibian and lungfish epidermis. This indicates absence of histidine-rich matrix proteins and corneous cell envelope proteins and only mucus is present among keratin filaments. Filaggrine-like and loricrin-like proteins are characteristic of amniotes epidermis and might have originated in basic amniotes (cotylosaurs).     

Successful Application of Video-Projected Human Images for Signalling to Dogs

Dogs were tested (1) in a two‐way choice experiment, where the experimenter indicated a baited bowl by pointing; and (2) in a task where the owner was asked to command the dog to execute simple obedience tasks. In expt 1 dogs (n = 10) were tested at first in the presence of the experimenter (three dimensional condition, 3D), that was followed by a series of pointing trials when the life‐sized image of the experimenter was projected onto the wall by the means of a video‐projector (two dimensional condition, 2D). Dogs performed correctly more often than expected by chance in both 3D and 2D conditions. In expt 2 the commanding owner was either present in the room (3D), or her/his image was projected on the screen (2D), or only her/his voice was audible for the dog through a speaker (0D). The performance of the dogs (n = 10) decreased to great extent comparing the 3D and 0D condition, as the number of different actions the dogs obeyed was significantly less in the 0D condition. However, there was no difference in the number of different actions obeyed in the 3D and 2D conditions. Our results show that dogs readily obey life‐sized, interactive moving image in various communicative situtations. We suppose that the difference between 2D and 3D conditions can be attributed partially to the lack of some additional communicative signals as sounds (verbal cues) and odours (from the human), and to some changes in the context.     

Interactions of Recombinant Mouse Erythrocyte Transglutaminase with Membrane Skeletal Proteins

In this study, we chose a differentiation-competent rat epidermal keratinocyte (REK) cell line to examine the role of Cx26 and disease-linked Cx26 mutants in organotypic epidermal differentiation. First, we generated stable REK cell lines expressing three skin disease-linked mutants (G59A, D66H and R75W). Second, we used an RNAi approach to knock down the expression of Cx26 in REKs. Interestingly, the three-dimensional (3D) architecture of the organotypic epidermis altered the intracellular spatial distribution of the mutants in comparison to 2D cultured REKs, highlighting the importance of using organotypic cultures. Unexpectedly, the presence of disease-linked mutants or the overexpression of wild-type Cx26 had little effect on the differentiation of the organotypic epidermis as determined by the architecture of the epidermis, expression of molecular markers indicative of epidermis differentiation (keratin 10, keratin 14, involucrin, loricrin) and stratification/cornification of the epidermis. Likewise, organotypic epidermis continued to differentiate normally upon Cx26 knockdown. While Cx26 has been reported to be upregulated during wound healing, no reduction in wound closure was observed in 2D REK cultures that expressed loss-of-function, dominant Cx26 mutants. In conclusion, we demonstrate that gain or loss of Cx26 function does not disrupt organotypic epidermal differentiation and offer insights into why patients harboring Cx26 mutations do not frequently present with more severe disease that encompasses thin skin. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

An Arabidopsis ACT2 dominant-negative mutation, which disturbs F-actin polymerization, reveals its distinctive function in root development

Eight functional actin genes are present in ARABIDOPSIS: The functional characterization of these genes in loss-of-function mutants is difficult, because highly conserved isovariants are generally expressed in the same tissue. We isolated a novel semi-dominant mutant allele (act2-2D) of an actin gene, ACT2, with a missense mutation which causes an amino acid substitution at the surface of the ACT2 protein. ACT2 promoter::ACT2-2D transgenic plants showed the same phenotype as act2-2D, indicating that act2-2D is a dominant-negative mutant. act2-2D exhibited defects in the initiation and elongation of root hairs, the elongation of root epidermal cells, and growth in aerial portions. Specifically, radial cell expansion was reduced and occasional cell death occurred in trichoblasts but not in atrichoblasts of the root epidermis. In contrast, cell division patterns in the root meristem were not affected. act2-3, a loss-of-function ACT2 mutant, did not develop most of these morphological abnormalities. Actin filament (F-actin) bundles in root epidermal cells of act2-2D were shorter than in the wild type and in the loss-of-function mutant. We conclude that defective F-actin polymerization caused the aberrant cell morphology in a dominant-negative manner, and that ACT2 functions in cell elongation and root hair formation.     

超声评价糖尿病肾病的临床价值

分析超声检查技术在糖尿病肾病（diabetic nephropathy,DN）中的应用,并探讨二维灰阶超声（two—dimensionalgray—scale ultrasonographyic,2D—US）、超声背向散射积分（integral backscatter signal, IBS ）、彩色多普勒血流成像（color doppler flow imaging,CDFI）、彩色多普勒能量图（color doppler energy,CDE）、三维超声（three—dimensional ultrasonographyie,3D—US）、超声造影（Contrast—enhanced ultrasound,CEUS）等超声检查技术对糖尿病肾病的临床价值。     

Keratinization of the epidermis of the Australian lungfish Neoceratodus forsteri (dipnoi)

The differentiation of the epidermis in sarcopterigian fish may reveal some trend of keratinization followed by amphibian ancestors to adapt their epidermis to land. Therefore, the process of keratinization of the epidermis of the Australian lungfish Neoceratodus forsteri was studied by histochemistry, electron microscopy, and keratin immunocytochemistry. The epidermis is tri-stratified in a 2-3-month-old tadpole but becomes 6-8 stratified in young adults. Keratin filaments increase from basal to external cells where loose tonofilament bundles are present. This is shown also by the comparison of positivity to sulfhydryl groups and increasing immunoreactivity to alpha-keratins in more external layers of the epidermis. Two broad-spectrum anti alpha-keratin monoclonal antibodies (AE1 and AE3) stain all epidermal layers as they do in actinopterigian fish. In the adult epidermis, but not in that of the larva, the AE2 antibody (a marker of keratinization in mammalian epidermis) often immunolabels more heavily the external keratinized layers where sulfhydryl groups are more abundant. Mucous granules are numerous and concentrate on the external surface of the epidermis to be discharged and contribute to cuticle formation. Keratin is therefore embedded in a mucus matrix, but neither compact keratin masses nor cell corneous envelope were seen in external cells. It is not known whether specific matrix proteins are associated with mucus. There was no immunolocalization of the keratin-associated proteins, filaggrin and loricrin, which suggests that the epidermis of this species lacks the matrix and cell corneus envelope proteins characteristic of that of amniotes. In conclusion, while specific keratins (AE2 positive) are probably produced in the uppermost layers as in amphibian epidermis, no interkeratin, matrix proteins seem to be present in external keratinocytes of the lungfish other than mucus.     

The Three-Dimensional Human Skin Reconstruct Model: a Tool to Study Normal Skin and Melanoma Progression

Most in vitro studies in experimental skin biology have been done in 2-dimensional (2D) monocultures, while accumulating evidence suggests that cells behave differently when they are grown within a 3D extra-cellular matrix and also interact with other cells (1-5). Mouse models have been broadly utilized to study tissue morphogenesis in vivo. However mouse and human skin have significant differences in cellular architecture and physiology, which makes it difficult to extrapolate mouse studies to humans. Since melanocytes in mouse skin are mostly localized in hair follicles, they have distinct biological properties from those of humans, which locate primarily at the basal layer of the epidermis. The recent development of 3D human skin reconstruct models has enabled the field to investigate cell-matrix and cell-cell interactions between different cell types. The reconstructs consist of a "dermis" with fibroblasts embedded in a collagen I matrix, an "epidermis", which is comprised of stratified, differentiated keratinocytes and a functional basement membrane, which separates epidermis from dermis. Collagen provides scaffolding, nutrient delivery, and potential for cell-to-cell interaction. The 3D skin models incorporating melanocytic cells recapitulate natural features of melanocyte homeostasis and melanoma progression in human skin. As in vivo, melanocytes in reconstructed skin are localized at the basement membrane interspersed with basal layer keratinocytes. Melanoma cells exhibit the same characteristics reflecting the original tumor stage (RGP, VGP and metastatic melanoma cells) in vivo. Recently, dermal stem cells have been identified in the human dermis (6). These multi-potent stem cells can migrate to the epidermis and differentiate to melanocytes.     

Synthesis and Structure of a New Copper(II) Coordination Polymer Alternately Bridged by Oxamido and Carboxylate Groups: Evaluation of DNA/BSA Binding and Cytotoxic Activities

A new one‐dimensional (1D) copper(II) coordination polymer {[Cu₂(dmaepox)(dabt)](NO₃)·0.5 H₂O}_n, where H₃dmaepox and dabt denote N‐benzoato‐N′‐(3‐methylaminopropyl)oxamide and 2,2′‐diamino‐4,4′‐bithiazole, respectively, was synthesized and characterized by single‐crystal X‐ray diffraction and other methods. The crystal structure analysis revealed that the two copper(II) ions are bridged alternately by cis‐oxamido and carboxylato groups to form a 1‐D coordination polymer with the corresponding Cu···Cu separations of 5.1946(19) and 5.038(2) Å. There is a three‐dimensional supramolecular structure constructed by hydrogen bonding and π–π stacking interactions in the crystal. The reactivity towards herring sperm DNA (HS‐DNA) and bovine serum albumin (BSA) indicated that the copper(II) polymer can interact with the DNA in the mode of intercalation, and bind to BSA responsible for quenching of tryptophan fluorescence by the static quenching mechanism. The in vitro cytotoxicity suggested that the copper(II) polymer exhibits cytotoxic effects against the selected tumor cell lines.     

Synthetic 3D multicellular systems for drug development

Since the 1970s, the limitations of two dimensional (2D) cell culture and the relevance of appropriate three dimensional (3D) cell systems have become increasingly evident. Extensive effort has thus been made to move cells from a flat world to a 3D environment. While 3D cell culture technologies are meanwhile widely used in academia, 2D culture technologies are still entrenched in the (pharmaceutical) industry for most kind of cell-based efficacy and toxicology tests. However, 3D cell culture technologies will certainly become more applicable if biological relevance, reproducibility and high throughput can be assured at acceptable costs. Most recent innovations and developments clearly indicate that the transition from 2D to 3D cell culture for industrial purposes, for example, drug development is simply a question of time.     

1,25-Dihydroxyvitamin D production and receptor binding in human keratinocytes varies with differentiation

Human foreskin keratinocytes in culture produce 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) and 24,25-dihydroxycholecalciferol (24,25-(OH)2D3) from 25-hydroxycholecalciferol (25-(OH)D3). The production of 1,25-(OH)2D3 by these cells correlated with the early events of differentiation such as expression of transglutaminase activity and the levels of a precursor protein for the cornified envelopes, involucrin. In contrast, the increased production of 24,25-(OH)2D3, as 1,25-(OH)2D3 production declined, correlated with the terminal differentiation marker, cornified envelope formation. Exogenous 1,25-(OH)2D3 (10(-11)-10(-9) M) inhibited the 1-alpha-hydroxylase at all stages of growth of these cells. Keratinocytes in culture expressed receptors for 1,25-(OH)2D3 which had similar sedimentation behavior in sucrose density gradients as chick intestinal cytosol receptors. Cells in early stages of growth (preconfluent and confluent) contained higher numbers of receptors (26-27 fmol/mg protein) than post-confluent cells. The dissociation constant (237-278 pM) of these receptors for 1,25-(OH)2D3 was not consistently altered by differentiation. Since 1,25-(OH)2D3 is a potent stimulator of cell differentiation in a variety of systems including the epidermis, our results suggest the possibility that endogenous 1,25-(OH)2D3 production may participate in the differentiation of keratinocytes in culture and, perhaps, in vivo.     

Functionalization of a poly(D,L)lactic acid surface with galactose to improve human keratinocyte behavior for artificial epidermis

The production of artificial epidermis using reabsorbable polymeric matrices is one of possible goals; one of most used strategies in this field is the polymer substrate functionalitation using specific growth factors, in order to accelerate and improve keratinocyte adhesion and proliferation. In this study films of poly(D,L)lactide (P(D,L)LA), have been functionalized with various concentrations of galactose (GAL, 1-5-10%, w/v) conjugated with poly-L-lysine (PLL) using 1-etil-3-(3-diaminopropil) carbodiimide (EDC) as a coupling agent. GAL is a disaccharide present in the extracellular matrix (ECM) and it is bind by Galectines, a family of cell receptors whose activation regulate the cell-matrix interaction and cell growth and apoptosis. One of these receptors, Galectin-7 (Gal-7), is selectively expressed by human keratinocytes. Spontaneously immortalized human keratinocytes (HaCaT) that express high level of Gal-7 were allowed to adhere for 4 h in serum free condition on control P(D,L)LA (PLA), and on PLA-GAL and cell proliferation; the production of matrix metalloproteinases (MMP-2, MMP-9, and MMP-28), involved in cellular migration and tissue homeostasis have been analyzed after 24 h. The presence of GAL onto the polymer surface increased both cell adhesion, spreading and proliferation along with MMP-9 and MMP-28 production, suggesting that polymer functionalization using GAL could be an useful tool for the production of an artificial epidermis.     

Effect of a short term fast on the distribution of cytoplasmic albumin messenger ribonucleic acid in rat liver. Evidence for formation of free albumin messenger ribonucleoprotein particles

Recently, using molecular hybridization techniques with albumin [3H]cDNA, we have determined that in normally fed rats 98% of total liver polyribosomal albumin mRNA sequences are found in membrane-bound polyribosomes (Yap, S. H., Strair, R. K., and Shafritz, D. A. (1977) Proc. Natl. Acad. Sci. U. S. A. 74, 5397-5401). We now observe that a 24- to 30-h withdrawal of food leads to major changes in the amount and subcellular distribution of albumin mRNA molecules. The total amount of cytoplasmic albumin mRNA per liver and concentration of albumin mRNA per unit of membrane-bound polyribosomal RNA are decreased. However, the proportion of albumin mRNA present in the postribosomal supernatant fraction increases dramatically in a short term fast, so that it now represent 60% of total cytoplasmic albumin mRNA sequences. Most of the albumin mRNA sequences in the postribosomal supernatant fraction sediment between 30 S and 50 S. These findings suggest that albumin mRNA is probably stored in the messenger ribonucleoprotein fraction during the fasting state.