Hyaline Layer Research Articles

Assessing temporal transition between microgranular and hyaline tests of calcareous microplankton during the Late Jurassic

Calcareous microplankton increased in abundance during the latest Jurassic, coinciding with the increase in abundance of calcareous nannofossils and with the onset of deposition of pelagic calcareous oozes. However, the timing and causes of the shift from microgranular tests of the earliest microplankton (chitinoidellids) to hyaline tests of calpionellids are obscured because the ultrastructure of two-layered praecalpionellids that occur during the Tithonian is poorly documented. Here, we investigate the ultrastructure of chitinoidellids and praecalpionellids from Upper Tithonian deposits in the Western Carpathians. We show that (1) the chitinoidellid microgranular layer is formed by elongated, euhedral, densely-packed, nanometric needles rather than by fragments of calcareous nannofossils, (2) two-layered chitinoidellids (Semichitinoidella) are formed by an internal microgranular layer (identical to that of Chitinoidella) and by an external hyaline prismatic layer, and (3) two-layered Praetintinnopsella exhibits an internal hyaline layer (with densely-packed, equant microcrystals) and an external layer formed by a dark organic rim. The external layer in Praetintinnopsella thus does not have any relation to the microgranular layer in chitinoidellids and the external hyaline layer of Semichitinoidella is not equivalent in structure to the hyaline layer of Praetintinnopsella. As both single-layer and two-layered chitinoidellids appear prior to the first appearance of Praetintinnopsella but still co-occur with this genus in the lowermost Upper Tithonian deposits, the origin of two-layered Praetintinnopsella either reflects a major transformation in biomineralization towards larger and more packed crystals during their earlier divergence from the chitinoidellid lineage or an origination of two-layered tests with a hyaline layer from an independent non-chitinoidellid ancestor.

Wheat bran arabinoxylans: Chemical structure, extraction, properties, health benefits, and uses in foods.

Wheat bran (WB) is a well-known and valuable source of dietary fiber. Arabinoxylan (AX) is the primary hemicellulose in WB and can be isolated and used as a functional component in various food products. Typically, AX is extracted from the whole WB using different processes after mechanical treatments. However, WB is composed of different layers, namely, the aleurone layer, pericarp, testa, and hyaline layer. The distribution, structure, and extractability of AX vary within these layers. Modern fractionation technologies, such as debranning and electrostatic separation, can separate the different layers of WB, making it possible to extract AX from each layer separately. Therefore, AX in WB shows potential for broader applications if it can be extracted from the different layers separately. In this review, the distribution and chemical structures of AX in WB layers are first discussed followed by extraction, physicochemical properties, and health benefits of isolated AX from WB. Additionally, the utilization of AX isolated from WB in foods, including cereal foods, packaging film, and the delivery of food ingredients, is reviewed. Future perspectives on challenges and opportunities in the research field of AX isolated from WB are highlighted.

Functional and Nutritional Characteristics of Natural or Modified Wheat Bran Non-Starch Polysaccharides: A Literature Review.

Wheat bran (WB) consists mainly of different histological cell layers (pericarp, testa, hyaline layer and aleurone). WB contains large quantities of non-starch polysaccharides (NSP), including arabinoxylans (AX) and β-glucans. These dietary fibres have long been studied for their health effects on management and prevention of cardiovascular diseases, cholesterol, obesity, type-2 diabetes, and cancer. NSP benefits depend on their dose and molecular characteristics, including concentration, viscosity, molecular weight, and linked-polyphenols bioavailability. Given the positive health effects of WB, its incorporation in different food products is steadily increasing. However, the rheological, organoleptic and other problems associated with WB integration are numerous. Biological, physical, chemical and combined methods have been developed to optimise and modify NSP molecular characteristics. Most of these techniques aimed to potentially improve food processing, nutritional and health benefits. In this review, the physicochemical, molecular and functional properties of modified and unmodified WB are highlighted and explored. Up-to-date research findings from the clinical trials on mechanisms that WB have and their effects on health markers are critically reviewed. The review points out the lack of research using WB or purified WB fibre components in randomized, controlled clinical trials.

Interspecies comparison of temporomandibular joint condylar cartilage extracellular matrix from macro to microscopy

Interspecies comparisons of the extracellular matrix of temporomandibular joint (TMJ) condylar cartilage are necessary to elucidate the mechanisms underlying its superior mechanical properties, to guide the construction of animal models of TMJ-related diseases, and to establish standards for the engineering of TMJ condylar cartilage. Here we characterize and compare TMJ condylar cartilage from six different species from a materials science perspective, including structure, composition and mechanical properties from the macroscopic to the microscopic level. The gross morphology showed obvious interspecies differences in size and shape, which may be related to the different joint motion patterns. Although the condylar cartilage of all species can be divided histologically into a superficial fibrous layer and a deep hyaline layer, there are significant interspecies differences in the microstructure of the fibrils in the two layers, mainly in the diameter of the fibrils. Compositionally, there were no significant differences in collagen composition between species, but the content of glycosaminoglycans (GAGs) decreased progressively with increasing body size, with the same results obtained by Safranin O staining and biochemical analysis. Mechanically, the elastic modulus of mouse condylar cartilage was significantly higher than that of the other species and tended to decrease with increasing body size. This study shows that the TMJ condylar cartilage of different species has its own specific structure-composition-mechanics matching characteristics for their unique masticatory stress dissipation, and differences in fibril diameter and GAGs content may be the two ultimate factors influencing the differences in cartilage mechanical properties between species, while the condylar cartilage of pigs is most similar to that of humans, suggesting that pigs may be a suitable animal model for TMJ studies.

Effect of recombinant Sox9 protein on the expression of cartilage-specific genes in human dermal fibroblasts cell culture

Introduction: Damage to the hyaline layer of large joints resulting from injuries or age-related changes restricts their mobility. The repair of these disorders is an actual issue in medicine. One of the promising therapies is the usage of cell engineering constructs based on a biodegradable scaffold and a modified cell culture. A frequently used method to modify the proliferation of cell culture for tissue engineering of hyaline cartilage, which makes it possible to introduce an experimental technique into clinical practice, is the application of recombinant proteins that affect chondrogenesis and lead to increase synthesis of extracellular matrix proteins. The goal of this work was to elucidate the effect of the key transcription factor in the chondrogenesis process – Sox9 protein – on the expression of genes responsible for chondrogenesis (Tgfβ3, Sox9, Acan, Comp, Col2a1).
 Materials and methods: Human dermal fibroblasts were used as a cell culture; recombinant Sox9 was added at each change of medium; the modification was carried out for 21 days, and difference in gene expression was determined by real-time PCR and -ΔΔCt method.
 Results and discussion: To assess the effectiveness of fibroblast modification, we analyzed the changing of expression of genes responsible for chondrogenesis (Tgfß3, Sox9, Col2a1, Acan, Comp). We studied the direct effect of different concentrations of the recombinant Sox9 protein on the proliferation of dermal fibroblasts in the chondrogenic direction. We showed that the addition of the recombinant Sox9 protein in various concentration did not significantly change the expression of both the genes encoding proteins of the extracellular matrix of hyaline cartilage (Acan, Col2a1, Comp) and the genes encoding chondrogenesis inducers (Tgfß3, Sox9).
 Conclusion: As a result of the experiments, it was shown that the recombinant Sox9 protein has practically no effect on chondrogenic differentiation and does not significantly change the expression of chondrogenesis genes.

Postmortem Lung Biopsy in a Sample of COVID-19 Patients in Iraq

Background: The entire world was affected by the outbreak of novel coronavirus 2 (SARS-CoV-2), which influenced daily life worldwide and affected the medical, social, and economic prospects of all nations. This virus occurs clinically in four variants: asymptomatic; mild upper respiratory tract infection (URTI); anosmia and/ or ageusia as the only symptoms; and severe systemic disease, such as bilateral interstitial pneumonia. Approximately 20% of the population develops the severe course associated with cytokine release syndrome (CRS). Those who develop lung injury and dyspnea have higher mortality. An autopsy can reveal the pathogenesis and determine the cause of death. Objectives: To understand the pathophysiological changes in lung tissue in COVID-19-affected individuals. Patients and Methods: This is a case series of post-mortem lung histopathology examinations of deceased COVID-19-positive patients. Samples were collected from postmortem models acquired from six diseased individuals who tested positive for SARS-CoV-2 by reverse transcriptase polymerase chain (PCR) reaction and subsequently passed away in the tertiary hospital between July and September 2020 because of COVID-19. Their slides and paraffin-embedded blocks of lung biopsies, as well as their reports, were collected and sent to two pathologists for further evaluation of COVID-19-related changes in the lungs. Results: Only two of the six patients confirmed features of diffuse alveolar injury with hyaline layer and fibrin thrombi in pulmonary arteries, small vessel congestion, and pulmonary infarction. Two patients demonstrated diffuse alveolar fibrosis (organizing pneumonia), severe inflammation, and foci of squamous metaplasia, in addition to the deposition of carbon particles. One case had diffuse pulmonary fibrosis with pulmonary artery thrombosis without an inflammatory background. In another case, there were atypical large cells, ischemic necrosis, and severe inflammation with macrophages and pneumocyte hyperplasia inside the alveoli. Conclusion: the thromboembolic events suggest a role for COVID-19-induced coagulopathy. Molecular mechanisms and clinical features of COVID -19 should be studied. Atypical alterations need to be investigated to confirm their relation to COVID-19 infection.

Transmission Route Used By Parasitic Lasidium Larvae of The Freshwater Mussel Anodontites Trapesialis on Guppies Poecilia Reticulata During Short Cohabitation.

SummaryWe describe for the first time the transmission route employed by the parasitic larvae of the freshwater mussel Anodontites trapesialis (Lamarck, 1819) during cohabitation on the guppy Poecilia reticulata Peter, 1859. The freshwater mussel and fish-host were employed as a model system to investigate the infection and parasite establishment. Laboratory experiments included video recording and histopathological analysis of the infection. In vivo video observations demonstrated that lasidium larvae could be transmitted to guppies during direct contact. A series of histology samples and photography suggest that this larva attaches and colonizes possibly on-site on the outer surface of the fish, causing cellular inflammation in the epidermis layer with cellular hyperplasia in the zone of parasite attachment. An evident hyaline layer, cellular hypertrophy, and a large number of undifferentiated proliferating cells were observed. Hemorrhagic tissue and swelling were observed in the epidermis and dermic zone. The total number of larvae per male and female guppy was 525 ± 86 and 494 ± 167, respectively. No parasitic preference was detected for male versus female parasitized fish.

Hyaline Layer of Hopewell-Smith: A Morphometric and Histochemical Analysis

Hyaline Layer of Hopewell-Smith: A Morphometric and Histochemical Analysis

Specificities of Scanning Electron Microscopy and Histological Methods in Assessing Cell-Engineered Construct Effectiveness for the Recovery of Hyaline Cartilage.

Damage to the hyaline layer of the articular surface is an urgent problem for millions of people around the world. At present, a large number of experimental methods are being developed to address this problem, including the transplantation of a cell-engineered construct (CEC) composed of a biodegradable scaffold with a premixed cell culture into the damaged area of the articular surface. However, current methods for analyzing the effectiveness of such CECs have significant limitations. This study aimed to compare the SEM technique, classical histology, and cryosectioning for the analysis of CECs transplanted to hyaline cartilage.

Type V collagen regulates the structure and biomechanics of TMJ condylar cartilage: A fibrous-hyaline hybrid

This study queried the role of type V collagen in the post-natal growth of temporomandibular joint (TMJ) condylar cartilage, a hybrid tissue with a fibrocartilage layer covering a secondary hyaline cartilage layer. Integrating outcomes from histology, immunofluorescence imaging, electron microscopy and atomic force microscopy-based nanomechanical tests, we elucidated the impact of type V collagen reduction on TMJ condylar cartilage growth in the type V collagen haploinsufficiency and inducible knockout mice. Reduction of type V collagen led to significantly thickened collagen fibrils, decreased tissue modulus, reduced cell density and aberrant cell clustering in both the fibrous and hyaline layers. Post-natal growth of condylar cartilage involves the chondrogenesis of progenitor cells residing in the fibrous layer, which gives rise to the secondary hyaline layer. Loss of type V collagen resulted in reduced proliferation of these cells, suggesting a possible role of type V collagen in mediating the progenitor cell niche. When the knockout of type V collagen was induced in post-weaning mice after the start of physiologic TMJ loading, the hyaline layer exhibited pronounced thinning, supporting an interplay between type V collagen and occlusal loading in condylar cartilage growth. The phenotype in hyaline layer can thus be attributed to the impact of type V collagen on the mechanically regulated progenitor cell activities. In contrast, knee cartilage does not contain the progenitor cell population at post-natal stages, and develops normal structure and biomechanical properties with the loss of type V collagen. Therefore, in the TMJ, in addition to its established role in regulating the assembly of collagen I fibrils, type V collagen also impacts the mechanoregulation of progenitor cell activities in the fibrous layer. We expect such knowledge to establish a foundation for understanding condylar cartilage matrix development and regeneration, and to yield new insights into the TMJ symptoms in patients with classic Ehlers-Danlos syndrome, a genetic disease due to autosomal mutation of type V collagen.

A COMPARATIVE EVALUATION OF LEAF MEALS OF PAWPAW (C. Papaya), SWORDBEAN (C. gladiata), JACKBEAN (C. ensiformis) AND PIGEONPEA (C. cajan) AS FEED INGREDIENTS AND YOLK COLOURING AGENTS IN LAYERS' DIETS

Leaf meals of the above-named tropical plants at 0.2,3,4 and 5% dietary levels were investigated for their values as feed ingredients and egg yolk pigmenters in white maize based layer diets. Each diet was fed as 5 replicates of 15 hyaline layers for 14 weeks. Pawpaw leaf meal (RM) at 4% and 5% dietary levels significantly (P<0.05) depressed feed intake without affecting egg production and body weights. It, however, had no colouring affecting egg yolk. Sword Bean leaf meal (SBIM), jackbean leaf meal (JBM) and pigeon pea leaf meal (PPLM) compared favourably with the control group in terms of feed intake, egg production and body weights, SBLM exceptionally improved egg yolk colour, scoring 4, 5, 8 and 12 on the Roche egg yolk colour fan at 2,3,4 and 5% dietary levels respectively. JBLM and PPLM only gave a score of 4 and 5% dietary level. SBLM appears to be very high in biological available xanthophylls and should be considered for development as commercial egg yolk pigmenter.

Natural reinforcing effect of inorganic colloids on excavated ancient jades

The Neolithic jades excavated from southern China often exhibit a serious corrosion phenomenon called “Whitening”, where the jade mineral aggregates have lost compact textures and transform into loose white powders, which cause a substantial decline in mechanical strength and the jades cannot remain intact. Meanwhile, a glossy hyaline layer with a more compact and uniform structure can be observed on the surface of some whitened jades, exert great influence in the integral structure strength of the jades and can be considered as highly significant natural reinforcing materials. The recent excavation of a workshop for jade processing in Zhejiang Province provided us with a great opportunity to investigate the deteriorated jades and the taphonomic environmental conditions associated with it. In this study, analyses of morphology and compositions revealed that the glassy layer is a composition of geopolymers with silica-alumina gels as the major components, which can also be found between mineral grains of jade crystals closest to the surface. Notably, some jade fragments with a yellowish infusion were found to be mechanically stronger compared to other jades unearthed from the same context, which may be explained by the consolidate effect of iron ions in the soil. These results have demonstrated the remarkable protective properties of soil colloids, and thus proposed that by using soil colloids as templates, consolidants with the natural compatibility with jades synthesized by chemical precipitations of charged inorganic colloidal particles can be a promising solution for jade conservation.

Simulations of sea urchin early development delineate the role of oriented cell division in the morula-to-blastula transition

The sea urchin morula to blastula transition has long been thought to require oriented cell divisions and blastomere adherence to the enveloping hyaline layer. In a computer simulation model, cell divisions constrained by a surface plane division rule are adequate to effect morphological transition. The hyaline membrane acts as an enhancer but is not essential. The model is consistent with the orientation of micromere divisions and the open blastulae of direct developing species. The surface plane division rule precedes overt epithelization of surface cells and acts to organize the developing epithelium. It is a universal feature of early metazoan development and simulations of non-echinoid cleavage patterns support its role throughout Metazoa. The surface plane division rule requires only local cues and cells need not reference global positional information or embryonic axes.

Developmental Consequences of Temperature and Salinity Stress in the Sand Dollar Dendraster excentricus.

Animals that reside, reproduce, and develop in nearshore habitats are often exposed to strong fluctuations in abiotic conditions, including temperature and salinity. We studied the developmental response of the sand dollar Dendraster excentricus to increased temperature and reduced salinity at levels comparable to those induced by summer freshwater input into the San Juan Archipelago, Washington. We observed that embryos exposed to temperature and salinity stress exhibited polyembryony (the splitting of one embryo into multiple independent individuals), and we subsequently tested the competency of twin and normal embryos to reach metamorphosis. We found that twin embryos generated from a single egg are each capable of reaching metamorphosis. To begin investigating the mechanisms underlying polyembryony, we tested whether osmotic stress caused swelling of the fertilization envelope, thus allowing embryos the physical space to produce multiples within a single envelope. We also tested whether reduced calcium levels in low-salinity seawater reduced cell-cell adhesion and allowed cells to separate and develop as multiple embryos within a fertilization envelope. However, neither osmotic stress nor reduced calcium levels alone appear sufficient to induce polyembryony. We hypothesize that changes in the properties of the hyaline layer that lies beneath the fertilization envelope facilitate polyembryony.

High frequency of GNA14, GNAQ, and GNA11 mutations in cherry hemangioma: a histopathological and molecular study of 85 cases indicating GNA14 as the most commonly mutated gene in vascular neoplasms

Cherry hemangioma is the most common hemangioma in adult life. Neoplastic and non-neoplastic theories had both been proposed for its pathogenesis, but its nature is still poorly understood. We noted a significant subset of anastomosing hemangiomas and congenital hemangiomas harbored a population of small capillaries surrounded by a perivascular hyaline layer, reminiscent of the vessels seen in cherry hemangioma. Both anastomosing hemangioma and congenital hemangioma harbor recurrent mutations in exon 5 of GNAQ and its paralogues. In this study, we analyzed 68 cherry hemangiomas and 17 cherry hemangioma-like hemangiomas exhibiting additional non-classical features including markedly dilated, cavernous vessels, and/or a deep component extending to the deep dermis. By Sanger sequencing, GNAQ, GNA11, and GNA14 exon 5 mutations were identified in 12, 4, and 32 cherry hemangiomas, respectively, and 5, 3, and 3 cherry hemangioma-like hemangiomas, respectively. MassARRAY analysis detected mutations (including exon 2 GNAQG48V mutations) in additional 8 cherry hemangiomas and 3 cherry hemangioma-like hemangiomas. Overall, the cherry hemangiomas and cherry hemangioma-like hemangiomas had equal GNA mutation rates (82%), and GNA14 and GNAQ mutations were present in approximately half of cherry hemangiomas and cherry hemangioma-like hemangiomas, respectively. All mutations were mutually exclusive. KRASG12V mutation was also detected in one cherry hemangioma-like hemangioma without GNA mutations. In summary, our study demonstrated recurrent GNA14/GNAQ/GNA11 mutations were present in the majority of this very common hemangioma and established its neoplastic nature. Our results also expanded the morphological spectrum of GNA-mutated hemangiomas to include tumors composed of cavernous-like vessels and indicated GNA14 was the most commonly mutated gene in vascular tumors.

APPLICATION OF CO-BIOPROCESSING TECHNIQUES (ENZYMATIC HYDROLYSIS AND FERMANTATION) FOR IMPROVING THE NUTRITIONAL VALUE OF WHEAT BRAN AS FOOD FUNCTIONAL INGREDIENS

Last time the food industry pays the great attention to questions, connected with changing existing technologies for raising the efficacy of the raw materials complex processing and increasing the output of high-quality products and food ingredients with a minimal amount of waste. Cereal crops are the most reach source of functional ingredients and main component in the human food ration. The technological process of cereal crops processing at enterprises is closely connected with creating a great number of secondary raw material resources and its further utilization. For confirming the efficacy of using secondary products of grain processing as cheap raw material resources of dietary fiber and physiologically functional ingredients, there is characterized the accessibility of their biotransformation that gives a possibility to get biologically active substances of different chemical nature with a wide spectrum of physiological effects. Secondary products of cereal crops processing (bran) are multi-component substrates, formed of different histological layers of wheat grains after comminution, consisted of (external pericarp, internal pericarp, grain coat, hyaline and aleurone layer of a grain coat). Wheat bran is rich in dietary fiber, nutritive and phytochemical substances, that is why, it is most often used for feeding animals. But for today there are important proofs of using it in the food industry. The development of new innovative technologies, modern achievements in microbiology and biotechnology have an important value for secondary products of grain processing, because they allow to conduct directed technological processes at the qualitatively new level that provides using soft regimes of vegetable raw materials processing, allowing to preserve natural biologically active substances and nutrients. The modeling of the combined complex processing that includes enzymatic hydrolysis and fermentation by microorganisms improves technological, sensor and also nutritive and physiologically functional properties of wheat bran at the expanse of: bioavailability increase of phenol compounds, vitamins and minerals, assimilability of proteins and decrease of the content of anti-nutritive compounds. Enzymatic preparations allow to use vegetable raw materials rationally, to intensify technological processes, in such a way increasing the output of biologically active substances and to widen the assortment of created products. The process of wheat bran formation results in increasing the nutritional value, enriching the biopolymeric complex with probiotic microorganisms and prebiotic substances. Based on the structural peculiarities and multicomponent composition of wheat bran, presented and studied in the article, it has been established, that the use of the directed modification allows to get functional ingredients and products with set properties that influence the human health favorably. So, wheat bran must be used not only in agriculture as a cattle fodder, but also in the food industry.

PENGARUH SUHU PEMANASAN FORMALIN 10% TERHADAP PERKEMBANGAN TELUR Ascaris lumbricoides

AbstractBackground Ascaris lumbricoides eggs had very thick walls consisted of three layers, they were albuminoid layer, hyaline layer and vitelin layer. These layers were impermeable causing the Ascaris lumbricoides eggs resistant to less supportive environmental factors. Formalin 10% was a preservative that was often used to preserve faeces containing parasites such as protozoa and worm eggs. However, without heating, formalin 10% was not effective to preserve the Ascaris lumbricoides eggs because they would keep developing to become infective (containing larvae). Objective This study aims to prove whether there is an effect of adding 10% formalin which is heated at 60 C, 70 C and 80 C to the development of Ascaris lumbricoides eggs.Methods The design of this research was an experimental study with The Randomized Posttest Control Group Design. Result The Ascaris lumbricoides eggs were still growing into infective eggs in faeces although they were heated by formalin 10% at 60C, 70C and 80C. conclusion Based on the results of the study, there was no effect of heating temperature of formalin 10% on the development of Ascaris lumbricoides egg.Keywords: Formalin 10%, Ascaris lumbricoides, Heating, Soil Transmitted Helminth

EXPERIMENTAL RESULTS OF RAT HYALINE CARTILAGE SURFACE DEFECT REPLACEMENT WITH A CELL ENGINEERING STRUCTURE

Nowadays, hyaline cartilage damage therapy and repair is one of the most topical research fields in regenerative medicine. however, in spite of a large number of methods used in clinical practice, this problem has not been fully solved yet. a promising approach in dealing with this problem may be a transplantation of a cell engineering structure (CES), made up of cell culture and biodegradable scaffold (membrane). In our experiments with animal models we used a membrane made of polylactide and multipotent mesenchymal stem cells (MSC) culture, and the damage of the knee joint hyaline layer was simulated by dental boron. The cell culture was pre-modified by TGF-β-3 growth factor to promote the synthesis of extracellular matrix proteins (ECM). as a result, we observed a fourfold increase in Acan and col2a1 expression compared to the control. Damaged areas were analyzed by scanning electron microscopy (SEM) over long observation periods (up to 90 days), and the diameter of the damaged area was found to decrease after CES transplantation, while the damage area in the control group, without CES, increased more than 2.5-fold in diameter. Thus, application of cell engineering structures is a promising method of repairing the damaged layer of hyaline cartilage. however, further studies are needed to enhance the effectiveness of the cell culture modification, develop methods for combining it with biodegradable scaffold, and select the method of fixing the CES in the damaged area.

Exocuticular hyaline layer of sea scorpions and horseshoe crabs suggests cuticular fluorescence is plesiomorphic in chelicerates

AbstractThe cuticle of scorpions (Chelicerata: Arachnida) fluoresces under long‐wave ultraviolet (UV) light due to the presence of beta‐carboline and 7‐hydroxy‐4‐methylcoumarin in the hyaline layer of the exocuticle. The adaptive significance of cuticularUVfluorescence in scorpions is debated. Although several other chelicerate orders (e.g. Opiliones and Solifugae) have been reported to fluoresce on exposure toUVlight, the prevalence of cuticularUVfluorescence has not been confirmed beyond scorpions. A systematic study of living chelicerates revealed thatUVfluorescence of the unsclerotized integument is ubiquitous across Chelicerata, whereas only scorpions and horseshoe crabs (Xiphosura) exhibit cuticularUVfluorescence. Scanning electron microscopy and histological sectioning confirmed the presence of a hyaline layer in taxa exhibiting cuticular fluorescence. The hyaline layer is absent in all other chelicerates except sea scorpions (Eurypterida) in which a taphonomically altered hyaline layer, that may have fluoresced underUVlight, was observed in exceptionally preserved cuticle. CuticularUVfluorescence appears to be associated with the presence of a hyaline layer, as has long been recognized in scorpions, and may be plesiomorphic among chelicerates. The presence of a hyaline layer in horseshoe crabs and sea scorpions suggests that several putative functions for cuticularUVfluorescence in scorpions can be discounted.

Colleters in Thelypteridaceae: Unveiling mucilage secretion and its probable role in ferns

Young fronds from several fern species are covered by mucilage, but its synthesis and functional roles remain understudied. The young leaves of the tropical ferns Amauropelta cheilanthoides, Amauropelta pachyrhachis and Steiropteris decussata are covered by a hyaline layer of highly hydrophilic mucilage that is produced by glandular trichomes (GTs). In order to better understand the morphology and ultrastructure associated with mucilage secretion in these plants, we employed a combination of light and electron microscopy along with histochemical studies. The distribution and abundance of GTs varies during leaf growth. The origin and differentiation of GTs occurs early in leaf development and their secretory activity is restricted to the first stage of leaf differentiation. Glandular trichomes can be sessile or pedunculate and the secretory head commonly shows a single cell in the distal portion. In general, at the beginning of development, the distal secretory cell has a large nucleus, thin wall and dense cytoplasm with large vacuoles, endoplasmatic reticulum and active dictyosomes. In mature secretory cells the large vacuole is filled with secretion, and represents almost the entire protoplast. Observations of the early onset and duration of functional mucilaginous trichomes of Thelypteridaceae, the physicochemical nature of the secretion and the location of these trichomes indicate that the product of these structures provides protection for the apical meristem and young leaves from excessive sunlight and high levels of transpiration, thereby reducing water loss. This functional concept is the common link connecting most reports on the structure of colleters and, therefore, this work represents the first report of colleters for ferns.