Displaying publications 1 - 20 of 80 in total

  1. Faridah MN, Shahrom AW
    Malays J Pathol, 2001 Dec;23(2):111-4.
    PMID: 12166591
    This paper describes a modified method of quantitative determination of histamine in human skin wounds using fluorescence spectrophotometer. In this study, histamine was used as an indicator to differentiate antemortem from postmortem wounds. Skin samples were obtained from 20 corpses which were brought to Hospital Kuala Lumpur and Universiti Kebangsaan Malaysia for medicolegal autopsy. Sections of human skin were processed biochemically for histamine determination using fluorescence spectrophotometer. Results revealed no significant difference in the histamine content of the antemortem wounds in comparison to postmortem wounds. Based on these results, detection of histamine is not suitable to differentiate antemortem from postmortem wounds.
    Matched MeSH terms: Skin/metabolism*
  2. Pandey M, Choudhury H, Gunasegaran TAP, Nathan SS, Md S, Gorain B, et al.
    Drug Deliv Transl Res, 2019 04;9(2):520-533.
    PMID: 29488170 DOI: 10.1007/s13346-018-0480-1
    Atopic dermatitis (AD) is a chronically relapsing eczematous skin disease characterised by frequent episodes of rashes, severe flares, and inflammation. Till date, there is no absolute therapy for the treatment of AD; however, topical corticosteroids (TCs) are the majorly prescribed class of drugs for the management of AD in both adults and children. Though, topical route is most preferable; however, limited penetration of therapeutics across the startum cornum (SC) is one of the major challenges for scientists. Therefore, the present study was attempted to fabricate a moderate-potency TC, betamethasone valerate (BMV), in the form of chitosan nanoparticles (CS-NPs) for optimum dermal targeting and improved penetration across the SC. To further improve the targeting efficiency of BMV and to potentiate its therapeutic efficacy, the fabricated BMV-CS-NPs were coated with hyaluronic acid (HA). The prepared NPs were characterised for particle size, zeta potential, polydispersity index (PDI), entrapment efficiency, loading capacity, crystallinity, thermal behaviour, morphology, in vitro release kinetics, drug permeation across the SC, and percentage of drug retained into various skin layers. Results showed that optimised HA-BMV-CS-NPs exhibited optimum physicochemical characteristics including finest particle size (skin surface (pH 5.5). Drug permeation efficiency of BMV was comparatively higher in case of BMV-CS-NPs; however, the amount of drug retained into the epidermis and the dermis was comparatively higher in case of HA-BMV-CS-NPs, compared to BMV-CS-NPs. Conclusively, we anticipate that HA-BMV-CS-NPs could be a promising nanodelivery system for efficient dermal targeting of BMV and improved anti-AD efficacy.
    Matched MeSH terms: Skin/metabolism
  3. Nawaz A, Wong TW
    J Microsc, 2016 07;263(1):34-42.
    PMID: 26695532 DOI: 10.1111/jmi.12371
    The chitosan has been used as the primary excipient in transdermal particulate dosage form design. Its distribution pattern across the epidermis and dermis is not easily accessible through chemical assay and limited to radiolabelled molecules via quantitative autoradiography. This study explored Fourier-transform infrared spectroscopy imaging technique with built-in microscope as the means to examine chitosan molecular distribution over epidermis and dermis with the aid of histology operation. Fourier-transform infrared spectroscopy skin imaging was conducted using chitosan of varying molecular weights, deacetylation degrees, particle sizes and zeta potentials, obtained via microwave ligation of polymer chains at solution state. Both skin permeation and retention characteristics of chitosan increased with the use of smaller chitosan molecules with reduced acetyl content and size, and increased positive charge density. The ratio of epidermal to dermal chitosan content decreased with the use of these chitosan molecules as their accumulation in dermis (3.90% to 18.22%) was raised to a greater extent than epidermis (0.62% to 1.92%). A larger dermal chitosan accumulation nonetheless did not promote the transdermal polymer passage more than the epidermal chitosan. A small increase in epidermal chitosan content apparently could fluidize the stratum corneum and was more essential to dictate molecular permeation into dermis and systemic circulation. The histology technique aided Fourier-transform infrared spectroscopy imaging approach introduces a new dimension to the mechanistic aspect of chitosan in transdermal delivery.
    Matched MeSH terms: Skin/metabolism
  4. Chua LS, Lee SY, Abdullah N, Sarmidi MR
    Fitoterapia, 2012 Dec;83(8):1322-35.
    PMID: 22521793 DOI: 10.1016/j.fitote.2012.04.002
    Labisia pumila is a traditional herb widely used as post-partum medication for centuries. Recently, extensive researches have been carried out on the phytochemical identification, biological and toxicological studies for the herb. Phytochemicals found in the herbal extract showed high antioxidant properties, which were essential for various pharmacological activities. The significant findings are anti-estrogenic deficiency and -immunodeficiency diseases. Another finding that has considerable impact on natural product research is the contribution of L. pumila in promoting skin collagen synthesis. The performance of the herb as anti-aging agent due to natural aging process and accelerated by UV radiation was reviewed critically.
    Matched MeSH terms: Skin/metabolism*
  5. Ng SF, Rouse JJ, Sanderson FD, Meidan V, Eccleston GM
    AAPS PharmSciTech, 2010 Sep;11(3):1432-41.
    PMID: 20842539 DOI: 10.1208/s12249-010-9522-9
    Over the years, in vitro Franz diffusion experiments have evolved into one of the most important methods for researching transdermal drug administration. Unfortunately, this type of testing often yields permeation data that suffer from poor reproducibility. Moreover, this feature frequently occurs when synthetic membranes are used as barriers, in which case biological tissue-associated variability has been removed as an artefact of total variation. The objective of the current study was to evaluate the influence of a full-validation protocol on the performance of a tailor-made array of Franz diffusion cells (GlaxoSmithKline, Harlow, UK) available in our laboratory. To this end, ibuprofen was used as a model hydrophobic drug while synthetic membranes were used as barriers. The parameters investigated included Franz cell dimensions, stirring conditions, membrane type, membrane treatment, temperature regulation and sampling frequency. It was determined that validation dramatically reduced derived data variability as the coefficient of variation for steady-state ibuprofen permeation from a gel formulation was reduced from 25.7% to 5.3% (n = 6). Thus, validation and refinement of the protocol combined with improved operator training can greatly enhance reproducibility in Franz cell experimentation.
    Matched MeSH terms: Skin/metabolism*
  6. Karami A, Karbalaei S, Zad Bagher F, Ismail A, Simpson SL, Courtenay SC
    Environ Pollut, 2016 Aug;215:170-177.
    PMID: 27182978 DOI: 10.1016/j.envpol.2016.05.014
    Skin is a major by-product of the fisheries and aquaculture industries and is a valuable source of gelatin. This study examined the effect of triploidization on gelatin yield and proximate composition of the skin of African catfish (Clarias gariepinus). We further investigated the effects of two commonly used pesticides, chlorpyrifos (CPF) and butachlor (BUC), on the skin gelatin yield and amino acid composition in juvenile full-sibling diploid and triploid African catfish. In two separate experiments, diploid and triploid C. gariepinus were exposed for 21 days to graded CPF [mean measured: 10, 16, or 31 μg/L] or BUC concentrations [Mean measured: 22, 44, or 60 μg/L]. No differences in skin gelatin yield, amino acid or proximate compositions were observed between diploid and triploid control groups. None of the pesticide treatments affected the measured parameters in diploid fish. In triploids, however, gelatin yield was affected by CPF treatments while amino acid composition remained unchanged. Butachlor treatments did not alter any of the measured variables in triploid fish. To our knowledge, this study is the first to investigate changes in the skin gelatin yield and amino acid composition in any animal as a response to polyploidization and/or contaminant exposure.
    Matched MeSH terms: Skin/metabolism*
  7. Khan NR, Wong TW
    Expert Opin Drug Deliv, 2016 09;13(9):1209-19.
    PMID: 27212391 DOI: 10.1080/17425247.2016.1193152
    OBJECTIVES: Skin drug retention is required in local treatment of skin cancer. This study investigated the interplay effects of ethosomes and microwave in transdermal drug delivery. Skin pre-treatment by microwave and applied with liquified medicine is deemed to 'cement' the skin thereby raising skin drug deposition.

    METHODS: 5-fluorouracil-loaded ethosomes were prepared and subjected to size, zeta potential, morphology, drug content, drug release and skin permeation tests. The molecular characteristics of untreated, microwave and/or ethosome-treated skins were examined by Fourier transform infrared and raman spectroscopy, thermal and electron microscopy techniques.

    RESULTS: The skin drug retention was promoted using larger ethosomes with negative zeta potentials that repelled anionic lipids of skin and hindered vesicle permeation into deep layers. These ethosomes had low ethanol content. They were less able to fluidize the lipid and defluidize the protein domains at epidermis to enlarge aqueous pores for drug permeation. Pre-treatment of skin by 2450 MHz microwave for 2.5 min further increased skin drug penetration and retention of low ethanol ethosomes and provided lower drug permeation than cases treated for 1.15 min and 5 min. A 2.5 min treatment might be accompanied by specific dermal protein fluidization via C=O moiety which translated to macromolecular swelling, narrowing of intercellular spaces at lower skin layers, increased drug retention and reduced drug permeation.

    CONCLUSION: Ethosomes and microwave synergized to promote skin drug retention.

    Matched MeSH terms: Skin/metabolism*
  8. Imrigha NAA, Bidin N, Lau PS, Musa N, Zakaria N, Krishnan G
    J Biophotonics, 2017 Oct;10(10):1287-1291.
    PMID: 28464516 DOI: 10.1002/jbio.201600295
    Q-switched Nd: YAG laser is the most effective laser for tattoo removal. Photobiomodulation (PBM) therapy is an alternative method applied to accelerate the wound healing. This paper investigated the effects of PBM therapy using 808 nm diode laser on tattooed skin after laser tattoo removal. Forty-five rats were selected and tattooed with black ink on their dorsal, and then distributed into three groups. G0 was received non-laser irradiation. G1 was treated by laser tattoo removal using 1064 nm with energy density of 3.4 J/cm2 without PBM therapy, while G2 was treated daily with PBM therapy using 808 nm diode laser of 5 J/cm2 after a single session of laser tattoo removal. The effects of tattoo removal and healing progress of the wound were analyzed using histological studies. Findings showed 808 nm laser promotes the healing process through enhancing epithelialization and collagen deposition. Moreover, PBM therapy stimulated immune cells to improve phagocytosis process for removing the tattoo ink fragments effectively. The PBM therapy treated group was capable of improving the healing process and increasing the quality of skin following the laser tattoo removal. It was also found that stimulation of cellular function by PBM therapy increased tattoo clearance efficiency.
    Matched MeSH terms: Skin/metabolism
  9. Abdulbaqi IM, Darwis Y, Assi RA, Khan NAK
    Drug Des Devel Ther, 2018;12:795-813.
    PMID: 29670336 DOI: 10.2147/DDDT.S158018
    Introduction: Colchicine is used for the treatment of gout, pseudo-gout, familial Mediterranean fever, and many other illnesses. Its oral administration is associated with poor bioavailability and severe gastrointestinal side effects. The drug is also known to have a low therapeutic index. Thus to overcome these drawbacks, the transdermal delivery of colchicine was investigated using transethosomal gels as potential carriers.

    Methods: Colchicine-loaded transethosomes (TEs) were prepared by the cold method and statistically optimized using three sets of 24 factorial design experiments. The optimized formulations were incorporated into Carbopol 940® gel base. The prepared colchicine-loaded transethosomal gels were further characterized for vesicular size, dispersity, zeta potential, drug content, pH, viscosity, yield, rheological behavior, and ex vivo skin permeation through Sprague Dawley rats' back skin.

    Results: The results showed that the colchicine-loaded TEs had aspherical irregular shape, nanometric size range, and high entrapment efficiency. All the formulated gels exhibited non-Newtonian plastic flow without thixotropy. Colchicine-loaded transethosomal gels were able to significantly enhance the skin permeation parameters of the drug in comparison to the non-ethosomal gel.

    Conclusion: These findings suggested that the transethosomal gels are promising carriers for the transdermal delivery of colchicine, providing an alternative route for drug administration.

    Matched MeSH terms: Skin/metabolism*
  10. Wang R, Hu X, Lü A, Liu R, Sun J, Sung YY, et al.
    Fish Shellfish Immunol, 2019 Nov;94:510-516.
    PMID: 31541778 DOI: 10.1016/j.fsi.2019.09.039
    Skin plays an important role in the innate immune responses of fish, particularly towards bacterial infection. To understand the molecular mechanism of mucosal immunity of fish during bacterial challenge, a de novo transcriptome assembly of crucian carp Carassius auratus skin upon Aeromonas hydrophila infection was performed, the latter with Illumina Hiseq 2000 platform. A total of 118111 unigenes were generated and of these, 9693 and 8580 genes were differentially expressed at 6 and 12 h post-infection, respectively. The validity of the transcriptome results of eleven representative genes was verified by quantitative real-time PCR (qRT-PCR) analysis. A comparison with the transcriptome profiling of zebrafish skin to A. hydrophila with regards to the mucosal immune responses revealed similarities in the complement system, chemokines, heat shock proteins and the acute-phase response. GO and KEGG enrichment pathway analyses displayed the significant immune responses included TLR, MAPK, JAK-STAT, phagosome and three infection-related pathways (ie., Salmonella, Vibrio cholerae and pathogenic Escherichia coli) in skin. To our knowledge, this study is the first to describe the transcriptome analysis of C. auratus skin during A. hydrophila infection. The outcome of this study contributed to the understanding of the mucosal defense mechanisms in cyprinid species.
    Matched MeSH terms: Skin/metabolism*
  11. Loh EYX, Fauzi MB, Ng MH, Ng PY, Ng SF, Mohd Amin MCI
    Int J Biol Macromol, 2020 Sep 15;159:497-509.
    PMID: 32387606 DOI: 10.1016/j.ijbiomac.2020.05.011
    In skin tissue engineering, a biodegradable scaffold is usually used where cells grow, produce its own cytokines, growth factors, and extracellular matrix, until the regenerated tissue gradually replaces the scaffold upon its degradation. However, the role of non-biodegradable scaffold remains unexplored. This study investigates the potential of a non-biodegradable bacterial nanocellulose/acrylic acid (BNC/AA) hydrogel to transfer human dermal fibroblasts (HDF) to the wound and the resulting healing effects of transferred HDF in athymic mice. Results demonstrated that the fabricated hydrogel successfully transferred >50% of HDF onto the wound site within 24 h, with evidence of HDF detected on day 7. The gene and protein study unveiled faster wound healing in the hydrogel with HDF group and characterized more mature newly formed skin microstructure on day 7, despite no visible differences. These findings give a new perspective regarding the role of non-biodegradable materials in skin tissue engineering, in the presence of exogenous cells, mainly at the molecular level.
    Matched MeSH terms: Skin/metabolism
  12. Ahmad Fadzil MH, Ihtatho D, Affandi AM, Hussein SH
    PMID: 19163606 DOI: 10.1109/IEMBS.2008.4650103
    Skin colour is vital information in dermatological diagnosis. It reflects pathological condition beneath the skin and commonly being used to indicate the extent of a disease. Psoriasis is a skin disease which is indicated by the appearance of red plaques. Although there is no cure for psoriasis, there are many treatment modalities to help control the disease. To evaluate treatment efficacy, PASI (Psoriasis Area and Severity Index) which is the current gold standard method is used to determine severity of psoriasis lesion. Erythema (redness) is one parameter in PASI. Commonly, the erythema is assessed visually, thus leading to subjective and inconsistent result. In this work, we proposed an objective assessment of psoriasis erythema for PASI scoring. The colour of psoriasis lesion is analyzed by DeltaL, Deltahue, and Deltachroma of CIELAB colour space. References of lesion with different scores are obtained from the selected lesions by two dermatologists. Results based on 38 lesions from 22 patients with various level of skin pigmentation show that PASI erythema score can be determined objectively and consistent with dermatology scoring.
    Matched MeSH terms: Skin/metabolism
  13. Sabri AH, Ogilvie J, Abdulhamid K, Shpadaruk V, McKenna J, Segal J, et al.
    Eur J Pharm Biopharm, 2019 Jul;140:121-140.
    PMID: 31059780 DOI: 10.1016/j.ejpb.2019.05.001
    Since the first patent for microneedles was filed in the 1970s, research on utilising microneedles as a drug delivery system has progressed significantly. In addition to the extensive research on microneedles for improving transdermal drug delivery, there is a growing interest in using these devices to manage dermatological conditions. This review aims to provide the background on microneedles, the clinical benefits, and challenges of the device along with the potential dermatological conditions that may benefit from the application of such a drug delivery system. The first part of the review provides an outline on benefits and challenges of translating microneedle-based drug delivery systems into clinical practice. The second part of the review covers the application of microneedles in treating dermatological conditions. The efficacy of microneedles along with the limitations of such a strategy to treat diseased skin shall be addressed.
    Matched MeSH terms: Skin/metabolism
  14. Mh Busra F, Rajab NF, Tabata Y, Saim AB, B H Idrus R, Chowdhury SR
    J Tissue Eng Regen Med, 2019 05;13(5):874-891.
    PMID: 30811090 DOI: 10.1002/term.2842
    The full-thickness skin wound is a common skin complication affecting millions of people worldwide. Delayed treatment of this condition causes the loss of skin function and integrity that could lead to the development of chronic wounds or even death. This study was aimed to develop a rapid wound treatment modality using ovine tendon collagen type I (OTC-I) bio-scaffold with or without noncultured skin cells. Genipin (GNP) and carbodiimide (EDC) were used to cross-link OTC-I scaffold to improve the mechanical strength of the bio-scaffold. The physicochemical, biomechanical, biodegradation, biocompatibility, and immunogenicity properties of OTC-I scaffolds were investigated. The efficacy of this treatment approach was evaluated in an in vivo skin wound model. The results demonstrated that GNP cross-linked OTC-I scaffold (OTC-I_GNP) had better physicochemical and mechanical properties compared with EDC cross-linked OTC-I scaffold (OTC-I_EDC) and noncross-link OTC-I scaffold (OTC-I_NC). OTC-I_GNP and OTC-I_NC demonstrated no toxic effect on cells as it promoted higher cell attachment and proliferation of both primary human epidermal keratinocytes and human dermal fibroblasts compared with OTC-I_EDC. Both OTC-I_GNP and OTC-I_NC exhibited spontaneous formation of bilayer structure in vitro. Immunogenic evaluation of OTC-I scaffolds, in vitro and in vivo, revealed no sign of immune response. Finally, implantation of OTC-I_NC and OTC-I_GNP scaffolds with noncultured skin cells demonstrated enhanced healing with superior skin maturity and microstructure features, resembling native skin in contrast to other treatment (without noncultured skin cells) and control group. The findings of this study, therefore, suggested that both OTC-I scaffolds with noncultured skin cells could be promising for the rapid treatment of full-thickness skin wound.
    Matched MeSH terms: Skin/metabolism*
  15. Goh CF, Boyd BJ, Craig DQM, Lane ME
    Expert Opin Drug Deliv, 2020 09;17(9):1321-1334.
    PMID: 32634033 DOI: 10.1080/17425247.2020.1792440
    BACKGROUND: Drug crystallization following application of transdermal and topical formulations may potentially compromise the delivery of drugs to the skin. This phenomenon was found to be limited to the superficial layers of the stratum corneum (~7 µm) in our recent reports and tape stripping of the skin samples was necessary. It remains a significant challenge to profile drug crystallization in situ without damaging the skin samples.

    METHODS: This work reports the application of an X-ray microbeam via synchrotron SAXS/WAXS analysis to monitor drug crystallization in the skin, especially in the deeper skin layers. Confocal Raman spectroscopy (CRS) was employed to examine drug distribution in the skin to complement the detection of drug crystallization using SAXS/WAXS analysis.

    RESULTS: Following application of saturated drug solutions (ibuprofen, diclofenac acid, and salts), CRS depth profiles confirmed that the drugs generally were delivered to a depth of ~15 - 20 µm in the skin. This was compared with the WAXS profiles that measured drug crystal diffraction at a depth of up to ~25 µm of the skin.

    CONCLUSION: This study demonstrates the potential of synchrotron SAXS/WAXS analysis for profiling of drug crystallization in situ in the deeper skin layers without pre-treatment for the skin samples. [Figure: see text].

    Matched MeSH terms: Skin/metabolism*
  16. Rehman K, Aluwi MF, Rullah K, Wai LK, Mohd Amin MC, Zulfakar MH
    Int J Pharm, 2015 Jul 25;490(1-2):131-41.
    PMID: 26003416 DOI: 10.1016/j.ijpharm.2015.05.045
    Imiquimod is a chemotherapeutic agent for many skin-associated diseases, but it has also been associated with inflammatory side effects. The aim of this study was to prevent the inflammatory effect of commercial imiquimod (Aldara(®)) by controlled release of imiquimod through a hydrogel/oleogel colloidal mixture (CA bigel) containing fish oil as an anti-inflammatory agent. Imiquimod permeability from Aldara® cream and bigel through mice skin was evaluated, and the drug content residing in the skin via the tape stripping technique was quantified. The fish oil fatty acid content in skin along with its lipophilic environment was also determined. An inflammation study was conducted using animal models, and Aldara(®) cream was found to potentially cause psoriasis-like inflammation, which could be owing to prolonged application and excessive drug permeation. Controlled release of imiquimod along with fish oil through CA bigel may have caused reduced imiquimod inflammation. NMR studies and computerized molecular modeling were also conducted to observe whether the fish oil and imiquimod formed a complex that was responsible for improving imiquimod transport and reducing its side effects. NMR spectra showed dose-dependent chemical shifts and molecular modeling revealed π-σ interaction between EPA and imiquimod, which could help reduce imiquimod inflammation.
    Matched MeSH terms: Skin/metabolism*
  17. Moshikur RM, Chowdhury MR, Wakabayashi R, Tahara Y, Moniruzzaman M, Goto M
    Int J Pharm, 2018 Jul 30;546(1-2):31-38.
    PMID: 29751143 DOI: 10.1016/j.ijpharm.2018.05.021
    The technological utility of active pharmaceutical ingredients (APIs) is greatly enhanced when they are transformed into ionic liquids (ILs). API-ILs have better solubility, thermal stability, and the efficacy in topical delivery than solid or crystalline drugs. However, toxicological issue of API-ILs is the main challenge for their application in drug delivery. To address this issue, 11 amino acid esters (AAEs) were synthesized and investigated as biocompatible counter cations for the poorly water-soluble drug salicylic acid (Sal) to form Sal-ILs. The AAEs were characterized using 1H and 13C NMR, FTIR, elemental, and thermogravimetric analyses. The cytotoxicities of the AAE cations, Sal-ILs, and free Sal were investigated using mammalian cell lines (L929 and HeLa). The toxicities of the AAE cations greatly increased with inclusion of long alkyl chains, sulfur, and aromatic rings in the side groups of the cations. Ethyl esters of alanine, aspartic acid, and proline were selected as a low cytotoxic AAE. The cytotoxicities of the Sal-ILs drastically increased compared with the AAEs on incorporation of Sal into the cations, and were comparable to that of free Sal. Interestingly, the water miscibilities of the Sal-ILs were higher than that of free Sal, and the Sal-ILs were miscible with water at any ratio. A skin permeation study showed that the Sal-ILs penetrated through skin faster than the Sal sodium salt. These results suggest that AAEs could be used in biomedical applications to eliminate the use of traditional toxic solvents for transdermal delivery of poorly water-soluble drugs.
    Matched MeSH terms: Skin/metabolism
  18. Nair RS, Billa N, Leong CO, Morris AP
    Pharm Dev Technol, 2021 Feb;26(2):243-251.
    PMID: 33274672 DOI: 10.1080/10837450.2020.1860087
    Tocotrienol (TRF) ethosomes were developed and evaluated in vitro for potential transdermal delivery against melanoma. The optimised TRF ethosomal size ranged between 64.9 ± 2.2 nm to 79.6 ± 3.9 nm and zeta potential (ZP) between -53.3 mV to -62.0 ± 2.6 mV. Characterisation of the ethosomes by ATR-FTIR indicated the successful formation of TRF-ethosomes. Scanning electron microscopy (SEM) images demonstrated the spherical shape of ethosomes, and the entrapment efficiencies of all the formulations were above 66%. In vitro permeation studies using full-thickness human skin showed that the permeation of gamma-T3 from the TRF ethosomal formulations was significantly higher (p skin (p skin permeation and high cell viability associated with this formulation suggest a promising carrier for transdermal delivery.
    Matched MeSH terms: Skin/metabolism*
  19. Ip YK, Randall DJ, Kok TK, Barzaghi C, Wright PA, Ballantyne JS, et al.
    J Exp Biol, 2004 Feb;207(Pt 5):787-801.
    PMID: 14747411
    Periophthalmodon schlosseri is an amphibious and obligatory air-breathing teleost, which is extremely tolerant to environmental ammonia. It actively excretes NH(4)(+) in ammonia loading conditions. For such a mechanism to operate efficaciously the fish must be able to prevent back flux of NH(3). P. schlosseri could lower the pH of 50 volumes (w/v) of 50% seawater in an artificial burrow from pH 8.2 to pH 7.4 in 1 day, and established an ambient ammonia concentration of 10 mmol l(-1) in 8 days. It could alter the rate of titratable acid efflux in response to ambient pH. The rate of net acid efflux (H(+) excretion) in P. schlosseri was pH-dependent, increasing in the order pH 6.0<7.0<8.0<8.5. Net acid flux in neutral or alkaline pH conditions was partially inhibited by bafilomycin, indicating the possible involvement of a V-type H(+)-ATPase. P. schlosseri could also increase the rate of H(+) excretion in response to the presence of ammonia in a neutral (pH 7.0) external medium. Increased H(+) excretion in P. schlosseri occurred in the head region where active excretion of NH(4)(+) took place. This would result in high concentrations of H(+) in the boundary water layer and prevent the dissociation of NH(4)(+), thus preventing a back flux of NH(3) through the branchial epithelia. P. schlosseri probably developed such an 'environmental ammonia detoxification' capability because of its unique behavior of burrow building in the mudflats and living therein in a limited volume of water. In addition, the skin of P. schlosseri had low permeability to NH(3). Using an Ussing-type apparatus with 10 mmol l(-1) NH(4)Cl and a 1 unit pH gradient (pH 8.0 to 7.0), the skin supported only a very small flux of NH(3) (0.0095 micromol cm(-2) min(-1)). Cholesterol content (4.5 micromol g(-1)) in the skin was high, which suggests low membrane fluidity. Phosphatidylcholine, which has a stabilizing effect on membranes, constituted almost 50% of the skin phospholipids, with phosphatidyleserine and phsophatidylethanolamine contributing only 13% and 15%, respectively. More importantly, P. schlosseri increased the cholesterol level (to 5.5 micromol g(-1)) and altered the fatty acid composition (increased total saturated fatty acid content) in its skin lipid after exposure to ammonia (30 mmol l(-1) at pH 7.0) for 6 days. These changes might lead to an even lower permeability to NH(3) in the skin, and reduced back diffusion of the actively excreted NH(4)(+) as NH(3) or the net influx of exogenous NH(3), under such conditions.
    Matched MeSH terms: Skin/metabolism
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links