Showing papers by "University of Coimbra published in 1999"
TL;DR: It is shown here that sperm mitochondria inside fertilized cow and monkey eggs are tagged by the recycling marker protein ubiquitin, which is a death sentence that is written during spermatogenesis and executed after the sperm mitochondira encounter the egg's cytoplasmic destruction machinery.
Abstract: Like other mammals, humans inherit mitochondria from the mother only, even though the sperm contributes nearly one hundred mitochondria to the fertilized egg. In support of the idea that this strictly maternal inheritance of mitochondrial DNA arises from the selective destruction of sperm mitochondria1,2, we show here that sperm mitochondria inside fertilized cow and monkey eggs are tagged by the recycling marker protein ubiquitin3. This imprint is a death sentence that is written during spermatogenesis and executed after the sperm mitochondria encounter the egg's cytoplasmic destruction machinery.
599 citations
TL;DR: The first births of rhesus monkeys produced by intracytoplasmic sperm injection at rates greater or equal to those reported by clinics are reported here.
Abstract: Intracytoplasmic sperm injection has begun an era of considerable improvements in treating male infertility. Despite its success, questions remain about the dangers of transmitting traits responsible for male infertility, sex and autosomal chromosome aberrations1 and possible mental, physical and reproductive abnormalities2,3. We report here the first births of rhesus monkeys produced by intracytoplasmic sperm injection at rates greater or equal to those reported by clinics. Essential assumptions about this process are flawed, as shown by results with the preclinical, nonhuman primate model and with clinically discarded specimens. Dynamic imaging demonstrated the variable position of the second meiotic spindle in relation to the first polar body; consequently, microinjection targeting is imprecise and potentially lethal. Intracytoplasmic sperm injection resulted in abnormal sperm decondensation, with the unusual retention of vesicle-associated membrane protein and the perinuclear theca, and the exclusion of the nuclear mitotic apparatus from the decondensing sperm nuclear apex. Male pronuclear remodeling in the injected oocytes was required before replication of either parental genome, indicating a unique G1-to-S transition checkpoint during zygotic interphase (the first cell cycle). These irregularities indicate that the intracytoplasmic sperm injection itself might lead to the observed increased chromosome anomalies4,5.
219 citations
TL;DR: In this paper, the role played by the cutting parameters, such as cutting speed, feed rate, tool geometry and tool coating, in residual stresses induced by orthogonal cutting in AISI 316L standard and resulfurized steels was investigated.
218 citations
09 May 1999
TL;DR: In this paper, a new approach, based on the average motor supply current Park's vector monitoring, was introduced for diagnosing voltage source inverter faults in variable speed AC drives.
Abstract: This paper introduces a new approach, based on the average motor supply current Park's vector monitoring, for diagnosing voltage source inverter faults in variable speed AC drives. Both simulation and laboratory tests results demonstrate the effectiveness of the proposed on-line diagnostic technique.
198 citations
TL;DR: An algebraic characterization of the feasible region in a higher-dimensional space is derived and a solution procedure akin to the interior-point approach for convex programming is proposed.
Abstract: Given a finite number of closed convex sets whose algebraic representation is known, we study the problem of finding the minimum of a convex function on the closure of the convex hull of the union of those sets. We derive an algebraic characterization of the feasible region in a higher-dimensional space and propose a solution procedure akin to the interior-point approach for convex programming.
187 citations
TL;DR: Results consistently indicate that eucalyptus oils are stronger deterrents than polyphenols, and E. globulus appears to be a key physical factor delaying fungal colonization during decomposition.
Abstract: Herein we assess the importance of leaf cuticle, polyphenolic, and essential oils contents of Eucalyptus globulus leaves to hyphomycete colonization and shredder consumption Optical and electron microscopy revealed that, at least during the first 5 weeks of conditioning, the cuticle remains virtually intact Stomata provide the main access for hyphae to internal leaf tissues and, eventually, for spore release We suggest that in E globulus leaves, fungal decomposition progresses predominantly in and from the eucalyptus leaf mesophyll to the outside Malt extract agar media supplemented with either eucalyptus essential oils or tannic acid completely inhibited (Articulospora tetracladia, Lemonniera aquatica, and Tricladium gracile) or depressed (Heliscus lugdunensis, Lunulospora curvula, and Tricladium angulatum) aquatic hyphomycetes growth The transference of both secondary compounds to alder leaves induced similar and significant reduction in Tipula lateralis larval consumption Results consistently indicate that eucalyptus oils are stronger deterrents than polyphenols The waxy cuticle of E globulus appears to be a key physical factor delaying fungal colonization during decomposition We hypothesize that the relative influence of leaf phenols and essential oils to aquatic hyphomycetes and shredders may be related to three main factors: (a) initial distribution of such compounds in the leaves; (b) possibility of their decrease through decomposition; and (c) consumption strategies of detritivores
177 citations
TL;DR: In this article, a review of the literature on mixed surfactant self-organization is presented, with a focus on micellar growth, micelle-to-vesicle transition and equilibrium vesicle formation in dilute systems.
Abstract: Mixed surfactant systems have been, for a long time, one of the favorite areas for experimental studies on interfacial and bulk properties of surfactants. Beyond the well-known synergistic properties, with relevance to technical applications, recent studies increasingly focus on the bulk aggregation behavior. As more systematic and detailed experimental data is collected (for example, by use of scattering and direct imaging techniques), increasingly refined theoretical models are developed. Most references reviewed here clearly show both the trends. Topics such as micellar growth, micelle-to-vesicle transition and equilibrium vesicle formation in dilute systems (in particular in catanionic systems) continue to expand and sometimes pose challenges to conventional notions of surfactant self-organization. As the rich polymorphism of mixed aggregates is unraveled, the possibilities of using them for broader goals also increase (e.g. mesoporous materials and polymer-aggregate gels).
177 citations
TL;DR: The results indicate that transferrin-lipoplexes deliver transgenes by endocytosis primarily via a non-receptor-mediated mechanism, and that acidification of the endosomes is partially involved in this process.
Abstract: Association of a targeting ligand such as transferrin, or an endosome disrupting peptide such as GALA, with cationic liposome-DNA complexes ('lipoplexes') results in a significant enhancement of transfection of several cell types (Simoes S et al, Gene Therapy 1998; 5: 955-964). Although these strategies can overcome some of the barriers to gene delivery by lipoplexes, the mechanisms by which they actually enhance tranfection is not known. In studies designed to establish the targeting specificity of transferrin, we found that apo-transferrin enhances transfection to the same extent as transferrin, indicating that internalization of the lipoplexes is mostly independent of transferrin receptors. These observations were reinforced by results obtained from competitive inhibition studies either by preincubating the cells with an excess of free ligand or with various 'receptor-blocking' lipoplexes. Transfection of cells in the presence of drugs that interfere with the endocytotic pathway provided additional insights into the mechanisms of gene delivery by transferrin- or GALA-lipoplexes. Our results indicate that transferrin-lipoplexes deliver transgenes by endocytosis primarily via a non-receptor-mediated mechanism, and that acidification of the endosomes is partially involved in this process.
174 citations
TL;DR: New algorithms are proposed for the uncontrained problem, which compute a super set of the K shortest paths and it is shown that ranking loopless paths does not hold in general the Optimality Principle and how the proposed algorithms for the unconstrained problem can be adapted for rankingloopless paths.
Abstract: The shortest path problem is a classical network problem that has been extensively studied. The problem of determining not only the shortest path, but also listing the K shortest paths (for a given integer K>1) is also a classical one but has not been studied so intensively, despite its obvious practical interest. Two different types of problems are usually considered: the unconstrained and the constrained K shortest paths problem. While in the former no restriction in considered in the definition of a path, in the constrained K shortest paths problem all the paths have to satisfy some condition – for example, to be loopless. In this paper new algorithms are proposed for the uncontrained problem, which compute a super set of the K shortest paths. It is also shown that ranking loopless paths does not hold in general the Optimality Principle and how the proposed algorithms for the unconstrained problem can be adapted for ranking loopless paths.
164 citations
TL;DR: Exposure of PC12 cells to A beta results in an impairment of energy metabolism, leading to a deficit in ATP levels and to the compromise of cellular viability, which seems to be a crucial event responsible for the energetic metabolic dysfunction induced by A beta.
164 citations
TL;DR: This work shows that the tetramer dissociation is apparently irreversible; and based on intrinsic tryptophan fluorescence and fluorescence quenching experiments, it is shown that the monomeric species formed upon tetramer Dissociation is non-native.
TL;DR: This study characterized new strains of the slightly thermophilic species Rubrobacter radiotolerans and the thermophobic speciesRubrobacter xylanophilus, both of which were previously represented only by the type strains isolated from Japan and the United Kingdom.
Abstract: In this study we characterized new strains of the slightly thermophilic species Rubrobacter radiotolerans and the thermophilic species Rubrobacter xylanophilus, both of which were previously represented only by the type strains isolated, respectively, from Japan and the United Kingdom. The new isolates were recovered from two hot springs in central Portugal after gamma irradiation of water and biofilm samples. We assessed biochemical characteristics, performed DNA-DNA hybridization, and carried out 16S rDNA sequence analysis to demonstrate that the new Rubrobacter isolates belong to the species R. radiotolerans and R. xylanophilus. We also show for the first time that the strains of R. xylanophilus and other strains of R. radiotolerans are extremely gamma radiation resistant.
TL;DR: In this paper, the influence of rooted macrophytes on nutrient dynamics, by comparing bare bottom sediments with eelgrass covered sediments, primary production and the development of organic detritus, was examined.
Abstract: Eutrophication of European estuaries due to massive nutrient loading from urban areas and diffuse runoff from extensively cultivated land areas is analysed. Consequences for the ecology of estuaries, namely changes in plant species composition, which also affects heterotrophic organisms, are approached based on examples showing that the result is often a fundamental structural change of the ecosystem, from a grazing and/or nutrient controlled stable systems to unstable detritus/mineralisation systems, where the turnover of oxygen and nutrients is much more dynamic and oscillations between aerobic and anaerobic states frequently occur. Several relevant aspects are examined, namely the influence of rooted macrophytes on nutrient dynamics, by comparing bare bottom sediments with eelgrass covered sediments, primary production and the development of organic detritus, and hydrodynamics and its relations to the spatial distribution of macrophytes in estuarine systems.
TL;DR: The cardioselective accumulation and persistence of 8OHdG adducts to mtDNA is consistent with the implication of mitochondrial dysfunction in the cumulative and irreversible cardiotoxicity observed clinically in patients receiving doxorubicin cancer chemotherapy.
TL;DR: In this paper, the octonions are shown to be associative up to a 3-cocycle isomorphism of a quasi-Hopf algebra associated to a group.
TL;DR: The results suggest that binding of cationic liposomes and lipoplexes to cells is governed primarily by electrostatic interactions, whereas their fusion is regulated by the lipid composition and sterically favorable interactions with cell surface molecules.
TL;DR: GSH protective effect suggests that the oxidation of protein SH-groups is involved in the inhibition of complexes II, III and V activity, whereas vitamin E and idebenone protection suggests that membrane lipid peroxidation is also involved inThe reduction of complex III activity.
TL;DR: It is suggested that salinity is an important external parameter to control the growth of E. intestinalis, the most abundant species in the Mondego estuary, which has important ecological implications for the system.
Abstract: The excessive growth of opportunistic macroalgae in estuaries and other coastal areas, characterised by enormous values of vegetal biomass in the form of dense mats, is a common and widespread picture nowadays. In such conditions, macroalgae completely dominate the nutrient dynamics in the ecosystem and function as high quality food for the microbial, meio- and macrofaunal communities. Due to their important role in the nutrient pathways of the ecosystems, it becomes essential to obtain new information on variables and processes that regulate the bloom formation of these primary producers. The Mondego estuary (west Portugal) is a eutrophic estuary, where usually macroalgae of the genera Enteromorpha seasonally bloom. Nevertheless, in years with high precipitation characterised by a significant increase of the freshwater runoff to the system, no Enteromorpha blooms are observed. Possible explanations for this are related to the reduction of light in the water column, high water speed, high sediment turbulence and low salinity values. Thus, because the decrease in salinity seemed an important feature during such periods, a set of experiments were conducted, to evaluate to what extent the growth of Enteromorpha intestinalis (the most abundant species in the Mondego estuary) is affected by fluctuations in salinity and, particularly, by low salinity values. In the laboratory, the growth rate of E. intestinalis was tested against a range of salinity, from 0 to 32 psu. E. intestinalis showed the lowest growth rates at extreme low salinity values (≤ 3 psu) and for salinity ≤ 1 psu, the algae died. Growth rates at salinity lower than 5 psu and higher than 25 psu were also low, when compared with growth between salinity of 15 and 20 psu, where E. intestinalis showed the highest growth rates. These results agree with the field observations and suggest that, in the Mondego estuary, salinity is an important external parameter to control the growth of E. intestinalis, which has important ecological implications for the system.
TL;DR: The construct representation of the cross-informant model of the Child Behavior Checklist (CBCL) and the Teacher Report Form (TRF) was evaluated using confirmatory factor analysis, and it was indicated that theCross-in Informant model fits these data poorly.
Abstract: The construct representation of the cross-informant model of the Child Behavior Checklist (CBCL) and the Teacher Report Form (TRF) was evaluated using confirmatory factor analysis. Samples were collected in seven different countries. The results are based on 13,226 parent ratings and 8893 teacher ratings. The adequacy of fit for the cross-informant model was established on the basis of three approaches: conventional rules of fit, simulation, and comparison with other models. The results indicated that the cross-informant model fits these data poorly. These results were consistent across countries, informants, and both clinical and population samples. Since inadequate empirical support for the cross-informant syndromes and their differentiation was found, the construct validity of these syndrome dimensions is questioned.
TL;DR: In this paper, the authors compared the nutrient mass balance of carbon; nitrogen and phosphorus in Spartina maritima covered areas and bare bottom sediment, with and without contribution of macrofauna, meio-fauna and microbial populations.
Abstract: Decomposition of salt marsh plants results from physical, chemical and biological processes including abiotic and biotic fragmentation, microbial decay and chemical transformation According to literature data, only a few species have the ability to feed directly on living plant material, so fungi and bacteria seem to be the principal competitors for the organic substrates Nevertheless, by consuming bacteria, protists and fungi associated to the detritus, macrofauna and meiofauna recycle the incorporated nutrients Moreover, this nutrient regeneration may be seen as an effective factor in maintaining and stimulating bacterial production In fact, it is well known that many detritus feeding species have very low assimilation efficiencies The objective of the present study was to compare the nutrient mass balance of carbon; nitrogen and phosphorus in Spartina maritima covered areas and bare bottom sediment, with and without contribution of macrofauna, meiofauna and microbial populations Nutrients mass balance was studied taking into account the initial and final nutrient concentrations in the sediment, water and plant material Faunal activity was measured as a function of remineralised carbon, nitrogen and phosphorus The experimental set-up included sixteen sub-experiments, which varied with respect to type of fauna, plant biomass and oxic status Each sub-experiment was performed in small glass containers (3 L) containing about 900 g wwt sediment and 25 L estuarine water Plant material, cut from intact plants, sediment cores and estuarine water were brought from the southern arm of the Mondego estuary (Portugal) The results showed that although the bacterial activity was responsible for the Spartina maritima degradation, the presence of meiofauna and macrofauna significantly enhanced the process Moreover, the presence of Spartina maritima positively affected the mineralisation of the sediment carbon and nitrogen, especially when the three faunal components were present, and denitrification rates were highest in the presence of the macrofauna and meiofauna The present study suggests that macrofauna and meiofauna have an important role on the ecosystem nutrient flux and that fauna might function as a sink for excess nutrients, that otherwise could be exported to the coastal waters
TL;DR: The accumulation of compatible solutes by the type strains of the slightly halophilic and thermophilic species Rhodothermus marinus and RhodotherMus obamensis at several growth temperatures and salinities was examined.
Abstract: In this study we propose revised structures for the two major compatible solutes of Rhodothermus marinus. We have also examined the accumulation of compatible solutes by the type strains of the slightly halophilic and thermophilic species Rhodothermus marinus and Rhodothermus obamensis at several growth temperatures and salinities. The major solutes of R. marinus were identified as α-mannosylglycerate (α-MG) and α-mannosylglyceramide (α-MGA), whereas R. obamensis accumulated only α-mannosylglycerate. The total osmolyte content was higher during the early exponential phase and decreased abruptly as growth continued into the stationary phase. At low growth temperatures, R. marinus responded to water stress by accumulation of α-mannosylglycerate and its amide, in addition to low levels of trehalose, glutamate, and glucose. At the highest growth temperature, α-mannosylglycerate was the major compatible solute and α-mannosylglyceramide was not detected. When both compounds were present, an increase in the salinity of the growth medium favored the accumulation of α-mannosylglyceramide over α-mannosylglycerate. The absence of α-mannosylglyceramide in R. obamensis at all growth temperatures and salinities constituted the most pronounced difference in the profiles of compatible solute accumulation by the two strains. Trehalose was also a prominent solute in this organism. Both organisms accumulated higher levels of α-mannosylglycerate as the temperature was raised. The importance of the two compounds in the mechanisms of thermoadaptation and osmoadaptation is discussed.
TL;DR: 'Homeo-proton permeability adaptation' precludes futile cycling of protons at higher growth temperatures and allows cells to sustain the proton motive force as a driving force for essential energy transducing processes.
TL;DR: A good linear correlation was found between the results from the electrochemical injection method and the conventional clinical spectrophotometric measurement after cyanidation and the blood from potentially ill donors showed deviations from the linear correlation suggesting that this may be a good method for detecting haematological problems.
TL;DR: Results suggest that H. ulvae might be suffering a change in its adaptive strategy along the eutrophication gradient, becoming closer to a typical `r' strategist in the strongly eUTrophied areas.
Abstract: Eutrophication in the Mondego estuary gave rise to qualitative changes in the benthic community, involving the replacement of eelgrass, Zostera noltii, by green algae such as Enteromorpha spp. and Ulva sp. It seems reasonable to assume that, through time, such changes may determine a selected new trophic structure. Hydrobia ulvae, a dominant species in terms of abundance and biomass, was studied with regard to life history, population dynamics and productivity in relation to changing environmental conditions along the eutrophication gradient. The purpose was to examine to what extent this species may adapt to the new emergent conditions. During the study period, H. ulvae population exhibited both temporal and spatial density variations. The settlement pattern did not change along the eutrophication gradient, and took place in March, June, July and September. However, the population was denser in the less eutrophied areas, corresponding to Z. noltii meadows, when compared to the eutrophied ones, where Enteromorpha spp. blooms are usually observed. Growth was continuous through life but growth rates were higher during spring, decreased from early summer to mid fall and practically ceased during winter, and then gradually increased again up to spring. Life span was estimated as 21 ± 3 months. Growth productivity (P) was estimated as 93.7 g AFDW . m -2 . year -1 in the Z. noltii meadows, 15.2 g AFDW . m -2 . year -1 in the eutrophied area, and 30.3 g AFDW . m -2 . year -1 in the strongly eutrophied area. Elimination productivity (E) was estimated as 30.0 g AFDW . m -2 . year -1 in the Z. noltii meadows, 51.8 g AFDW . m -2 . year -1 in the eutrophied area, and 97.5 g AFDW . m -2 . year -1 in the strongly eutrophied area. The average annual biomass ( B ) (standing stock) of the population was estimated as 70.2 g AFDW . m -2 in the Z. noltii meadows, 5.5 g AFDW . m -2 in the eutrophied area, and 7.4 g AFDW . m -2 in the strongly eutrophied area. ratios were estimated as 1.3 and 4.8 in the Z. noltii meadows, 2.8 and 9.5 in the eutrophied area, and 4.5 and 13.2 in the strongly eutrophied area, respectively. As a pattern, the standing stock decreased as a function of increasing eutrophication, while P/ B and E/ B ratios increased following the same gradient. There is evidence that H. ulvae population structure and annual production are seriously affected by eutrophication, namely by macroalgal bloom dynamics. Moreover, results suggest that H. ulvae might be suffering a change in its adaptive strategy along the eutrophication gradient, becoming closer to a typical `r' strategist in the strongly eutrophied areas.
TL;DR: An association of extensive metabolism with an increased risk for leukaemia is suggested, possibly by an increase in the metabolic activation of chemical carcinogens or linkage to another cancer-causing gene.
Abstract: Xenobiotic-metabolizing enzymes constitute an important line of defence against a variety of carcinogens. Many are polymorphic, constituting the basis for the wide inter-individual variation in metabolic capacity and possibly a source of variation in the susceptibility to chemical-induced carcinogenesis. The aim of this study was to determine the existence of any association between the main genetic polymorphisms of cytochrome P450 2D6 (CYP2D6), glutathione S-transferase M1 (GSTM1) and N-acetyltransferase 2 (NAT2) and an altered risk for haematological neoplasias. A total of 160 patients and 128 controls were genotyped by means of PCR-RFLP-based assays. Mutated alleles comprising CYP2D6*4, GSTM1*0, NAT2*5A, *5B, *5C, *6 and *7 were analysed along with the wild-type alleles. The results showed a higher frequency of CYP2D6 extensive metabolizers carrying two functional alleles in the leukaemia group, when compared with controls (76.6 versus 57.0%, P = 0.008). No differences were found in the case of Hodgkin and non-Hodgkin lymphomas. Analysis of the GSTM1 and NAT2 polymorphisms failed to show an association with any of the neoplasias, although a near significant increase in fast acetylators was also found in the leukaemia group (50.0 versus 35.9%, P = 0.06). The results suggest an association of extensive metabolism with an increased risk for leukaemia, possibly by an increase in the metabolic activation of chemical carcinogens or linkage to another cancer-causing gene. Opposite findings presented in other studies may reflect geographical differences in the type of environmental carcinogens to which different populations are exposed.
TL;DR: In this paper, fatigue studies of polypropylene/glass-fibre thermoplastic composites produced from a bi-directional woven cloth of co-mingled E-glass fibres and polyethylene fibres with a fibre volume fraction V f of 0.338 were investigated.
TL;DR: In this article, the generalized De Casteljau algorithm for cubic splines with Hermite boundary conditions and more general boundary conditions for arbitrary m. Lie groups are the most simple symmetric spaces, and for these spaces the expressions for the first and second order derivatives of curves of arbitrary order obtained from the algorithm.
Abstract: We examine the De Casteljau algorithm in the context of Riemannian symmetric spaces. This algorithm, whose classical form is used to generate interpolating polynomials in {\Bbb R}^n, was also generalized to arbitrary Riemannian manifolds by others. However, the implementation of the generalized algorithm is difficult since detailed structure, such as boundary value expressions, has not been available. Lie groups are the most simple symmetric spaces, and for these spaces we develop expressions for the first and second order derivatives of curves of arbitrary order obtained from the algorithm. As an application of this theory we consider the problem of implementing the generalized De Casteljau algorithm on an m-dimensional sphere. We are able to fully develop the algorithm for cubic splines with Hermite boundary conditions and more general boundary conditions for arbitrary m.
TL;DR: It is found that the uptake of L-arginine in retinas from control and diabetic rats occurs through a transporter resembling the Y + system, i.e. it is saturable, not affected over the pH range 6.5 to 7.4, and is independent of the extracellular Na+.
TL;DR: DNA conformational behavior in the presence of non‐stoichiometric mixtures of two oppositely charged surfactants, cetyltrimethylammonium bromide and sodium octyl sulfate, was directly visualized in an aqueous solution with the use of a fluorescence microscopy technique.
TL;DR: GluR4, which is the most rapidly desensitizing AMPA receptor subunit, may be modulated by phosphorylation, according to two-dimensional phosphopeptide analysis, which indicates that serine 842 is the major phosphorylated site on GLUR4.
Abstract: Recent studies have suggested that protein phosphorylation of glutamate receptors may play an important role in synaptic transmission Specifically, the phosphorylation of AMPA receptors has been implicated in cellular models of synaptic plasticity The phosphorylation of the glutamate receptor 1 (GluR1) subunit of AMPA receptors by protein kinase A (PKA), protein kinase C (PKC), and Ca2+/calmodulin-dependent protein kinase II (CaMKII) has been characterized extensively Phosphorylation of this subunit occurs exclusively on the intracellular C-terminal domain However, the GluR1 subunit C terminus shows low homology to the other AMPA receptor subunits In this paper we characterized the phosphorylation of AMPA receptor subunit GluR4, using site-specific mutagenesis and biochemical techniques We found that GluR4 is phosphorylated on serine 842 within the C-terminal domain in vitro and in vivo Serine 842 is phosphorylated by PKA, PKC, and CaMKII in vitro and is phosphorylated in transfected cells by PKA Two-dimensional phosphopeptide analysis indicates that serine 842 is the major phosphorylation site on GluR4 In addition, we identified threonine 830 as a potential PKC phosphorylation site These results suggest that GluR4, which is the most rapidly desensitizing AMPA receptor subunit, may be modulated by phosphorylation