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Epidermal Layer (epidermal + layer)
Selected AbstractsFrequency of Use of Suturing and Repair Techniques Preferred by Dermatologic SurgeonsDERMATOLOGIC SURGERY, Issue 5 2006BETH ADAMS MD BACKGROUND There are many closure techniques and suture types available to cutaneous surgeons. Evidence-based data are not available regarding the frequency of use of these techniques by experienced practitioners. OBJECTIVE To quantify, by anatomic site, the frequency of use of common closure techniques and suture types by cutaneous surgeons. METHOD A prospective survey of the members of the Association of Academic Dermatologic Surgeons that used length-calibrated visual-analog scales to elicit the frequency of use of specific suture techniques. RESULTS A response rate of 60% (61/101) indicated reliability of the received data. Epidermal layers were closed most often, in descending order, by simple interrupted sutures (38,50%), simple running sutures (37,42%), and vertical mattress sutures (3,8%), with subcuticular sutures used more often on the trunk and extremities (28%). The most commonly used superficial sutures were nylon (51%) and polypropylene (44%), and the most common absorbable suture was polyglactin 910 (73%). Bilayered closures, undermining, and electrocoagulation were used, on average, in 90% or more sutured repairs. The median diameters (defined as longest extent along any axis) of most final wound defects were 1.1 to 2.0 cm (56%) or 2.1 to 3.0 cm (37%). Fifty-four percent of wounds were repaired by primary closure, 20% with local flaps, and 10% with skin grafting, with the remaining 15% left to heal by second intent (10%) or referred for repair (5%). Experience-related differences were detected in defect size and closure technique: defects less than 2 cm in diameter were seen by less experienced surgeons, and defects greater than 2 cm by more experienced surgeons (Wilcoxon's rank-sum test: p=.02). But more experienced surgeons were less likely to use bilayered closures (r=,0.28, p=.036) and undermining (r=,0.28, p=.035). CONCLUSIONS There is widespread consensus among cutaneous surgeons regarding optimal suture selection and closure technique by anatomic location. More experienced surgeons tend to repair larger defects but, possibly because of their increased confidence and skill, rely on less complicated repairs. [source] The role of the cutaneous cholinergic system in guttate psoriasisEXPERIMENTAL DERMATOLOGY, Issue 7 2008W. Dyck In previous studies, high levels of acetylcholine (ACh) have been reported in psoriasis lesions. In addition, patients with guttate psoriasis respond to oral treatment with atropine. We wanted to know how the cutaneous cholinergic system could be involved in this process. Since mast cells (MC) are characteristic components of the inflammatory infiltrate of guttate psoriasis, we compared ACh receptor (AChR) composition and ACh production in both epidermis and mast cells of 10 patients with guttate psoriasis in involved and uninvolved skin on protein level using immunofluorescence and in a MC line (HMC-1) using PCR. We could confirm the presence of numerous MC in guttate psoriasis lesion. Both in vivo and in vitro, MC lacked expression of cholinacetyltransferase (ChAT), vesicular acetylcholintransorter (VAChT) and cholintransporter-1 (ChT-1) but contained high levels of acetylcholinesterase (AChE). In mast cells of both involved and uninvolved skin we found both nicotinic (,3, ,5, ,7, ,9, ,10, ,2 and ,4 subunits) and muscarinic (M1, M3, M4, M5) AChR. In HMC-1 cells all AChR subunits found in skin where present on mRNA level, except ,7 and ,2. In lesional epidermis both ACh production and AChR expression was shifted from the basal to the suprabasal layers especially the nicotinic ,3, ,5, ,9, ,2 and ,4 and the muscarinic M3 and M5 AChR subunits. Our results exclude a role of the cholinergic system in the initiation of keratinocyte proliferation in the basal epidermal layer but point towards a role of epidermal AChR in suprabasal processes, most likely terminal differentiation and barrier formation as has been shown in other systems. Most importantly, mast cells are targets of paracrine and endocrine effects mediated by ACh and choline thus modulating inflammatory processes like guttate psoriasis and explaining the clinical efficacity of anticholinergic drugs like atropine. [source] Langerhans cell microgranulomas (pseudo-pautrier abscesses): morphologic diversity, diagnostic implications and pathogenetic mechanismsJOURNAL OF CUTANEOUS PATHOLOGY, Issue 9 2002Kelly L. Burkert The term ,Langerhans cell microgranuloma' (LCM) was introduced a decade ago to draw attention to focal collections of these cells within the epidermal layer that develops during certain immune reactions. In spite of a growing awareness of this phenomenon during the past decade, few reports have focused on the development and phenotype of LCM. In this commentary, we review the historical development of the concept of LCM, demonstrate the salient immunomorphologic characteristics of LCM, and advance a hypothesis to explain their sequential evolution and formation. [source] AQP1 and AQP3, Psoriasin, and Nitric Oxide Synthases 1,3 are Inflammatory Mediators in Erythema Toxicum NeonatorumPEDIATRIC DERMATOLOGY, Issue 5 2003Giovanna Marchini M.D., Ph.D. Its etiology and physiologic significance are still unclear. The purpose of this study was to extend the search for possible inflammatory mediators of the rash. We performed immunohistochemistry on punch biopsy cryosections from lesions of four, 1-day-old infants and from four matched controls without rash, using antibodies against the water channel proteins aquaporin-1 (AQP1) and aquaporin-3 (AQP3), psoriasin, and the nitric oxide synthase (NOS) enzymes, neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS). All sections from the lesions showed a dense, nodular cellular infiltrate located near the hair follicle. The vessels in the dermis showed a high incidence of AQP1 and eNOS. Strong staining for AQP1, AQP3, and psoriasin, as well as nNOS, iNOS, and eNOS were seen in the entire epidermal layer. The infiltrate in the dermis contained numerous cells expressing AQP1, AQP3, nNOS, iNOS, and eNOS. Double immunofluorescence staining showed that AQP3 was located in CD1a-expressing Langerhans cells and other dendritic cells in the dermis, as well as in CD14-expressing macrophages, CD15-expressing neutrophils, and EG2-expressing eosinophils surrounding the hair follicle. Our findings show that AQP1 and AQP3, psoriasin, and NOSs are involved in the activation of the skin immune system at birth. [source] Distribution of P2X3 -immunoreactive fibers in hairy and glabrous skin of the ratTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 6 2009Anna M.W. Taylor Abstract The skin is innervated by two populations of unmyelinated sensory fibers, the peptidergic and nonpeptidergic, which transmit nociceptive information to the central nervous system. The peptidergic population expresses neuropeptides such as substance P (SP) and calcitonin gene-related peptide (CGRP) and has both cutaneous and visceral targets. The nonpeptidergic population expresses the purinergic receptor P2X3, binds the isolectin B4 (IB4), and innervates mainly the epidermis. To date, the peptidergic nociceptor population in cutaneous tissue of the rat has been well characterized, whereas the nonpeptidergic innervation pattern has lacked an adequate description. To this aim, we used light microscopic immunocytochemistry to investigate the pattern of P2X3 -immunoreactive (-IR) fiber innervation of both hairy and glabrous skin from male Sprague-Dawley rats. Our results show extensive P2X3 -IR fibers throughout the upper and lower dermis. Thick bundles of P2X3 -IR fibers were found to run in parallel with the dermal-epidermal junction and projected multiple thin collateral axons that penetrated the epidermal layer, creating a dense network of innervation throughout the entire epidermis. The distribution of P2X3 -IR fibers in the epidermis was far more extensive than the distribution of CGRP-IR fibers. P2X3 -IR fibers also innervate hair follicles but were rarely found in close proximity to glands and blood vessels. The present results suggest a primary role for P2X3 -IR fibers in the detection of noxious stimuli in cutaneous tissue and provide an anatomical basis for future studies examining a possible functionally distinct role of nonpeptidergic nociceptors in the transmission of nociceptive signals. J. Comp. Neurol. 514:555,566, 2009. © 2009 Wiley-Liss, Inc. [source] Ultrastructural changes induced in cutaneous collagen by ultraviolet-A1 and psoralen plus ultraviolet A therapy in systemic sclerosisTHE JOURNAL OF DERMATOLOGY, Issue 2 2008Noriyuki SAKAKIBARA ABSTRACT In the present study, we examined the ultrastructural alterations in collagen fibrils clinically softened by ultraviolet-A1 (UVA1, 340,400 nm) therapy and psoralen plus long-wave ultraviolet (PUVA) therapy and compared collagen fibril diameters in four patients with systemic sclerosis (SSc). In skin sclerosis, the dermis is compacted from the epidermal layer to the sweat glands, and the collagen bundles are thicker with decreased space between them. We obtained skin specimens before and after UVA1 or PUVA therapy, and compared cutaneous alterations in one diffuse-type patient and one limited-type patient following UVA1 therapy, and in two diffuse-type patients following PUVA treatment. Ultramicroscopic analysis revealed that UVA1 treatment decreased the diameter of the broad collagen fibrils, mainly in the upper reticular layer. PUVA induced similar alterations in the collagen fibrils, extending to the upper and middle reticular layers. PUVA therapy induced alterations in collagen fibril diameter in deeper layers than did UVA1 therapy, which might be related to the direct action of UV light and the depth of the light penetration. In three of four patients, collagen fibril diameter decreased, collagen fibril thickness equalized, and new, thin fibrils developed among the collagen fibrils, suggesting that collagen degradation and synthesis underlie the alterations induced by UVA1 and PUVA phototherapies. [source] Accumulation of apoptotic cells in the epidermis of patients with cutaneous lupus erythematosus after ultraviolet irradiationARTHRITIS & RHEUMATISM, Issue 3 2006Annegret Kuhn Objective To examine whether apoptosis contributes to the pathogenesis of skin lesions in patients with cutaneous lupus erythematosus (CLE) after ultraviolet (UV) irradiation. Methods In situ nick translation and TUNEL were performed to detect apoptosis in 85 skin biopsy specimens from patients with various subtypes of CLE. Specimens from normal healthy donors and patients with polymorphous light eruption were used as controls. In addition to assessment of primary lesions, provocative phototesting was carried out to investigate events occurring secondary to UV irradiation during a very early stage of lesion formation. Results A significant increase in apoptotic nuclei was found in the upper epidermal layer of primary and UV light,induced skin lesions of CLE patients compared with controls. In tissue sections obtained from control subjects at 24 hours after a single exposure to UV light, a slight increase in the count of epidermal apoptotic nuclei was present as compared with skin tissue from CLE patients obtained under the same conditions before lesion formation. In sections obtained from controls at 72 hours after irradiation, a significant decrease in the apoptotic nuclei count was observed, consistent with a proper clearance of apoptotic cells in the period between 24 and 72 hours after irradiation. In striking contrast, the number of apoptotic nuclei increased significantly within this period in tissue sections from patients with CLE. Conclusion These data support the hypothesis that apoptotic cells accumulate in the skin of patients with CLE after UV irradiation, as a result of impaired or delayed clearance. The nonengulfed cells may undergo secondary necrosis and release proinflammatory compounds and potential autoantigens, which may contribute to the inflammatory micromilieu that leads to formation of skin lesions in this disease. [source] Influence of blood flow and millimeter wave exposure on skin temperature in different thermal modelsBIOELECTROMAGNETICS, Issue 1 2009S.I. Alekseev Abstract Recently we showed that the Pennes bioheat transfer equation was not adequate to quantify mm wave heating of the skin at high blood flow rates. To do so, it is necessary to incorporate an "effective" thermal conductivity to obtain a hybrid bioheat equation (HBHE). The main aim of this study was to determine the relationship between non-specific tissue blood flow in a homogeneous unilayer model and dermal blood flow in multilayer models providing that the skin surface temperatures before and following mm wave exposure were the same. This knowledge could be used to develop multilayer models based on the fitting parameters obtained with the homogeneous tissue models. We tested four tissue models consisting of 1,4 layers and applied the one-dimensional steady-state HBHE. To understand the role of the epidermis in skin models we added to the one- and three-layer models an external thin epidermal layer with no blood flow. Only the combination of models containing the epidermal layer was appropriate for determination of the relationship between non-specific tissue and dermal blood flows giving the same skin surface temperatures. In this case we obtained a linear relationship between non-specific tissue and dermal blood flows. The presence of the fat layer resulted in the appearance of a significant temperature gradient between the dermis and muscle layer which increased with the fat layer thickness. Bioelectromagnetics 30:52,58, 2009. © 2008 Wiley-Liss, Inc. [source] An alginate hydrogel matrix for the localised delivery of a fibroblast/keratinocyte co-cultureBIOTECHNOLOGY JOURNAL, Issue 5 2009Nicola C. Hunt Abstract There is significant interest in the development of tissue-engineered skin analogues, which replace both the dermal and the epidermal layer, without the use of animal or human derived products such as collagen or de-epidermalised dermis. In this study, we proposed that alginate hydrogel could be used to encapsulate fibroblasts and that keratinocytes could be cultured on the surface to form a bilayered structure, which could be used to deliver the co-culture to a wound bed, initially providing wound closure and eventually expediting the healing process. Encapsulation of fibroblasts in 2 and 5% w/v alginate hydrogel effectively inhibited their proliferation, whilst maintaining cell viability allowing keratinocytes to grow uninhibited by fibroblast overgrowth to produce a stratified epidermal layer. It was shown that the alginate degradation process was not influenced by the presence of fibroblasts within the hydrogel and that lowering the alginate concentration from 5 to 2% w/v increased the rate of degradation. Fibroblasts released from the scaffold were able to secrete extracellular matrix (ECM) and thus should replace the degrading scaffold with normal ECM following application to the wound site. These findings demonstrate that alginate hydrogel may be an effective delivery vehicle and scaffold for the healing of full-thickness skin wounds. [source] Optical Coherence Tomography: A Noninvasive Method to Assess Wound ReepithelializationACADEMIC EMERGENCY MEDICINE, Issue 5 2007Adam J. Singer MD BackgroundAccurate assessment of wound healing may require invasive tissue biopsies, limiting its clinical usefulness in humans. Optical coherence tomography (OCT) is a novel, high-resolution method using light reflection to obtain noninvasive cross sectional imaging of biological tissues. ObjectivesTo evaluate the utility of OCT for assessing wound reepithelialization in a porcine model. MethodsThe authors conducted an animal study with two domestic pigs. Excisional cutaneous wounds were created over the ventral surface of the animals using an electric dermatome set at a depth of 600 ,m. The wounds were excised two or three days later and precisely marked to guide initial OCT and subsequent tissue slicing and microscopy. Comparing hematoxylin and eosin,stained histologic sections and the corresponding OCT images from each tissue sample permitted identification of the correlative micromorphology. Scatter and Bland,Altman plots were used to present the data. The primary measure of agreement was the standard deviation of the pairwise differences in percent reepithelialization between OCT and histology together with a 95% confidence interval. ResultsIn normal skin, the epidermis was characterized by a thin, bright layer indicating a high degree of light scattering on OCT. The dermis below was characterized by a thicker, darker area indicating less scattering of light. All fresh excisional wounds lacked an outer bright layer of epidermis immediately after injury. At days 2 and 3, the wounds were partially reepithelialized. A new bright layer with intense light scattering was present on OCT corresponding to the neoepidermis on hematoxylin and eosin,stained sections. The correlation between percent reepithelialization measured with OCT and histology was 0.66 (p < 0.001), and the standard deviation of the differences was 11.0% (95% confidence interval = 8.4% to 16.1%). ConclusionsOCT accurately detects the presence or absence of the epidermal layer of skin, allowing noninvasive tracking of wound reepithelialization. [source] Modulations of nerve growth factor and Bcl-2 in ultraviolet-irradiated human epidermisJOURNAL OF CUTANEOUS PATHOLOGY, Issue 6 2003Catherine M. Stefanato Background:, Ultraviolet (UV) irradiation to the skin causes apoptosis of keratinocytes. Melanocytes are more resistant to UV-induced apoptosis, due, in part, to high levels of antiapoptotic proteins such as Bcl-2. In vitro studies have shown that nerve growth factor (NGF), a neurotrophic polypeptide, is produced by keratinocytes and exerts a protective role for melanocytes by upregulating Bcl-2. The purpose of this study was to determine NGF and Bcl-2 modulations in UV-irradiated human skin. Methods:, Nine volunteers were irradiated with two minimal erythema doses using solar-simulated UV irradiation. Seventy-two hours post irradiation, skin biopsies were obtained from irradiated and sun-protected skin. The skin specimens were stained with anti-tyrosinase-related protein-1 monoclonal antibody IgG2a (Mel-5), anti-Bcl-2 (monoclonal antibody IgG-kappa), and with anti-NGF (polyclonal antibody IgG). Results:, NGF staining was identified within the cytoplasm of epidermal melanocytes, similar to the staining observed for TRP-1 and Bcl-2. While no significant difference in the number of TRP-1- and Bcl-2-positive melanocytes was observed between irradiated and non-irradiated skin within 72 h, the number of NGF-positive melanocytes decreased significantly, 72 h after UV irradiation (p < 0.024). NGF was also identified within keratinocytes, and while non-irradiated skin exhibited cytoplasmic NGF staining throughout the epidermis, NGF staining was reduced in the lower epidermal layers after UV irradiation. Conclusions:, This is the first in vivo study showing NGF to be present in melanocytes, as well as showing modulations of NGF and Bcl-2 in melanocytes, following solar-simulated UV irradiation. [source] Observations on the histochemistry and ultrastructure of regenerating caudal epidermis of the tuatara Sphenodon punctatus (Sphenodontida, Lepidosauria, Reptilia)JOURNAL OF MORPHOLOGY, Issue 2 2003Lorenzo Alibardi Abstract Study of the histology, histochemistry, and fine structure of caudal epidermal regeneration in Sphenodon punctatus through restoration of a scaled form reveals that the processes involved resemble those known in lizards. Following establishment of a wound epithelium (WE), subjacent scale neogenesis involves epidermal downgrowths into the dermis. Although the process is extremely slow, and most new scales do not overlap, their epidermal coverings reestablish epidermal generation (EG) formation. As in lizards, the flat, ,-keratogenic, WE cells contain lipids as revealed by their affinity for Sudan III. A few mucous cells that store large PAS-positive mucus-like granules also occur in WE. During differentiation of WE cells, among the bundles of 70-nm tonofilaments are many lamellar bodies (LBs) and mucous granules (MGs) that discharge their contents into the cytoplasm and extracellular spaces producing a strongly PAS-positive keratinized tissue. Richness of epidermal lipids coexistent with mucus is a primitive characteristic for amniote vertebrates, probably related to functions as a barrier to cutaneous water loss (CWL). As scale neogenesis begins, beneath the superficial WE appear 3,5 layers of irregularly shaped cells. These contain tonofilament bundles surrounded by small, round keratohyalin-like granules (KHLGs) and a keratinized matrix with ,-keratin packets and a 3,5-nm thick keratin granulation. This mixture of ,- and ,-keratogenic capacities resembles that seen in the innermost cells of a normal tuatara epidermal generation. As in the latter, but in contrast to both normal and regenerating lizard epidermis, no definable shedding complex with interdigitating clear layer and oberhautchen cells occurs (Alibardi and Maderson, 2003). The tortuous boundaries, and merging ,-keratin packets, identify subjacent keratinizing cells as precursors of the typical stratified, squamous ,-layer seen in long-term regenerated caudal skin wherein the entire vertical sequence of epidermal layers resembles that of normal scales. The sequence of events in caudal epidermal regeneration in S. punctatus resembles that documented for lizards. Observed differences between posttrauma scale neogenesis and scale embryogenesis are responses to functional problems involved in, respectively, restoring, or forming, a barrier to CWL while accommodating rapid somatic growth. J. Morphol. 256:134,145, 2003. © 2003 Wiley-Liss, Inc. [source] Melanophores: A model system for neuronal transport and exocytosis?JOURNAL OF NEUROSCIENCE RESEARCH, Issue 12 2007Sara Aspengren Abstract Black pigment cells, melanophores, from lower vertebrates are specialized in bidirectional and coordinated translocation of pigment granules, melanosomes, in the cytoplasm. Melanophores develop from the neuronal crest and are most abundant in the dermal and epidermal layers of the skin, where the intracellular distribution of the pigment significantly influences the color of the animal. The transport of pigment is dependent on an intact cytoskeleton and motor proteins associated with cytoskeletal components. The easily cultured melanophores have proved to be excellent models for organelle transport because the intracellular movements of pigment can be visualized via light microscopy, and the granules move in response to defined chemical signals. The ease of achieving a combination of morphological and functional transport studies is the advantage of the melanophore system, and studies on pigment cells have revealed new components of the transport machinery, including molecular motors, their adapters, and transfer of vesicles to other cells. Many cellular components are transported with a combination of the actin- and microtubule-based transport systems, and, since all eukaryotic organisms rely on functional intracellular transport and an intact cytoskeleton, studies on melanophores are important for many aspects of cell biology, including axonal transport. In this review, we present an overview of the research on the pigment transport system and the potential use of pigment cells as a model system. © 2006 Wiley-Liss, Inc. [source] Assessment of carcinogenic potential of repeated fish fried oil in miceMOLECULAR CARCINOGENESIS, Issue 10 2006Manoj K. Pandey Abstract Our prior studies have shown that single topical treatment of repeated fish fried oil extract (RFFE), containing various polycyclic aromatic hydrocarbons (PAHs), to the dorsal epidermis of mice caused enhancement of DNA damage along with higher expression of p53 and p21WAF1 proteins and cell-cycle arrest. In the present study carcinogenic potential of repeated fish fried oil (RFFO) and RFFE was assessed. Single topical application of RFFO (100 µL/animal) and RFFE (100,500 µg/animal) to Swiss albino female mice resulted in significant induction (1.8- to 7.4-fold) of ornithine decarboxylase activity. Twice weekly topical application of methylcholanthrene (MCA) for 24 wk or single topical application of 7,12-dimethylbenzanthracene (DMBA) or RFFO or RFFE, as initiator followed by twice weekly application of 12-O-tetradecanoyl phorbol myristate acetate (TPA) as promoter for 24 wk, resulted in development of skin papillomas after 6, 7, 18, and 9 wk, respectively. The cumulative number of tumors in MCA, DMBA/TPA, RFFE (200 µg)/TPA, and RFFE (500 µg)/TPA groups were 276, 168, 34, and 58 after 24 wk while negligible or minimal initiating activity was noticed in RFFO/TPA group. No tumors were found in animals either given twice weekly topical application of RFFO or a single initiating dose of DMBA followed by twice weekly application of RFFO. Histopathology of skin of animals treated with RFFE/TPA showed marked proliferation of epidermal layers along with abnormal mitosis and multinucleated tumor appearance. Skin of animals in groups RFFO/TPA and DMBA/RFFO showed sloughing and regeneration of epidermal layers, oedema along with proliferation of fibroblasts. Histochemical localization of ,-glutamyl transpeptidase was found to be substantially higher in skin of mice treated with RFFO/TPA and RFFE/TPA. Animals treated with RFFO/TPA, DMBA/RFFO, and RFFE/TPA resulted in significant induction of cutaneous aryl hydrocarbon hydroxylase (AHH) (421,432%), ethoxyresorufin-O-deethylase (252,316%), and glutathione S-transferase (133,245%) activities. Animals treated with RFFO/TPA, DMBA/RFFO, and RFFE/TPA led to significant reduction in glutathione content (39,44%) with a concomitant increase in lipid peroxidation (254,492%). Animals treated with RFFO/TPA and RFFE/TPA led a significant decrease in catalase (43,69%) and superoxide dismutase (20,31%) activities while glutathione reductase activity was found to be diminished (23,51%) in RFFO, RFFO/TPA, DMBA/RFFO, and RFFE/TPA treated groups. These results suggest that RFFE possess skin tumor initiating activity and that it may have weak promoting activity as well, which may involve free radicals. © 2006 Wiley-Liss, Inc. [source] Spatial coordination of aluminium uptake, production of reactive oxygen species, callose production and wall rigidification in maize rootsPLANT CELL & ENVIRONMENT, Issue 7 2006D. L. JONES ABSTRACT Aluminium (Al) toxicity associated with acid soils represents one of the biggest limitations to crop production worldwide. Although Al specifically inhibits the elongation of root cells, the exact mechanism by which this growth reduction occurs remains controversial. The aim of this study was to investigate the spatial and temporal dynamics of Al migration into roots of maize (Zea mays L.) and the production of the stress response compound callose. Using the Al-specific fluorescent probe morin, we demonstrate the gradual penetration of Al into roots. Al readily accumulates in the root's epidermal and outer cortical cell layers but does not readily penetrate into the inner cortex. After prolonged exposure times (12,24 h), Al had entered all areas of the root apex. The spatial and temporal accumulation of Al within the root is similarly matched by the production of the cell wall polymer callose, which is also highly localized to the epidermis and outer cortical region. Exposure to Al induced the rapid production of reactive oxygen species and induced a significant rigidification of the cell wall. Our results suggest that Al-induced root inhibition in maize occurs by rigidification of the epidermal layers. [source] Leaf, floret and seed infection of wheat by Pyrenophora semeniperdaPLANT PATHOLOGY, Issue 4 2003M. A. Campbell Infection processes of Pyrenophora semeniperda on seedling and adult wheat leaves and wheat ears were investigated. Almost 100% germination of conidia occurred on seedling leaves, compared with 20,30% on adult leaves. Appressoria formed over the anticlinal epidermal cell walls and haloes always accompanied infection. Sometimes papillae formed within the leaves as a resistance mechanism. Infection hyphae ramified through the intercellular spaces of the mesophyll resulting in cellular disruption. The infection processes on floral tissues were similar to those observed on leaves; however, no infection occurred on anther, stigmatic or stylar tissues. Infection of ovarian tissue occurred both with and without appressoria formation. Hyphae grew mainly in the epidermal layers and appeared unable to breach the integumental layer as no growth was observed in endosperm or embryo tissues. The optimum dew period temperature for conidial germination was 23·6°C, compared with 19·9°C for lesion development, 20·4°C for the production of infection structures on seedling leaves and 23·7°C for floret infection. Leaf disease development occurred in a logistic manner in response to dew period, with maximum infection observed after 21 h compared with > 48 h in seeds. An initial dark phase during the dew period was necessary for infection and temperature after the dew period had an effect, with significantly more numerous and larger lesions being formed at 15°C compared with 30°C. Seedling leaves were found to be more susceptible than older leaves, under both field and controlled environment conditions. Infection of wheat seeds following inoculation of ears, or after harvest burial of inoculated disease-free seeds, was demonstrated. In the latter, 3-week-old seedlings were slightly stunted, whereas older plants were unaffected. The apparent unimportance of this plant pathogen as a cause of leaf disease in relation to its poor adaptation to dew periods and dew period temperature is discussed, along with the importance of its seed borne characteristics. [source] A novel model of wound healing in the SCID mouse using a cultured human skin substituteAUSTRALASIAN JOURNAL OF DERMATOLOGY, Issue 1 2009Martin L Windsor SUMMARY Studies of skin graft behaviour in rodent excisional wound models are limited by the dominance of wound contracture and graft sloughing as primary healing responses. To slow skin contraction, polytetrafluoroethylene (Teflon) rings were inserted into dorso-lateral full-thickness wounds in SCID mice. Cultured skin substitutes (OrCel), composed of cultured human keratinocytes and fibroblasts in a bovine collagen sponge, were implanted within the rings. Examination and histology of grafts 14 days later showed graft take in four of six recipients, with 90% epithelialization and wound contraction of 31,47%. Immunohistochemical studies, using human-specific antisera to distinguish graft from host tissues, showed that regenerated tissue was predominantly human. Staining with anticytokeratin, revealed a multilayered, stratified neoepidermis. HBG were identified in keratinocytes in all epidermal layers. Langerhans cells were absent. Antihuman vimentin, used as a fibroblast marker, confirmed that cells of the neodermis were primarily of human origin. Neoepidermal keratinocytes, primarily in the basal and suprabasal layers, were also stained. Results suggest that the poly(tetrafluoroethylene) ring inhibited graft sloughing and provided a more favourable environment for the skin substitute to regenerate a substantially normal human skin. [source] | |||||||||||||