Literatura académica sobre el tema "Permeable envelopes"
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Artículos de revistas sobre el tema "Permeable envelopes"
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Oterino, J., G. Sánchez Toranzo, L. Zelarayán, M. T. Ajmat, F. Bonilla y M. I. Bühler. "Behaviour of the vitelline envelope in Bufo arenarum oocytes matured in vitro in blockade to polyspermy". Zygote 14, n.º 2 (mayo de 2006): 97–106. http://dx.doi.org/10.1017/s0967199406003662.
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SummaryDuring activation of amphibian eggs, cortical granule exocytosis causes elaborate ultrastructural changes in the vitelline envelope. These changes involve modifications in the structure of the vitelline envelope and formation of a fertilization envelope (FE) that can no longer be penetrated by sperm. In Bufo arenarum, as the egg traverses the oviduct, the vitelline envelope is altered by a trypsin-like protease secreted by the oviduct, which induces an increased susceptibility of the vitelline envelope to sperm lysins. Full-grown oocytes of B. arenarum, matured in vitro by progesterone, are polyspermic, although cortical granule exocytosis seems to occur within a normal chronological sequence. These oocytes can be fertilized with or without trypsin treatment, suggesting that the vitelline envelope is totally sperm-permeable. Vitelline envelopes without trypsin treatment cannot retain either gp90 or gp96. This suggests that these glycoproteins are involved in the block to polyspermy and that trypsin treatment of matured in vitro oocytes before insemination is necessary to enable vitelline envelopes to block polyspermy. The loss of the binding capacity in vitelline envelopes isolated from B. arenarum oocytes matured in vitro with trypsin treatment and activated by electric shock suggests that previous trypsin treatment is a necessary step for sperm block to occur. When in vitro matured oocytes were incubated with the product of cortical granules obtained from in vitro matured oocytes (vCGP), vitelline envelopes with trypsin treatment were able to block sperm entry. These oocytes exhibited the characteristic signs of activation. These results support the idea that B. arenarum oocytes can be activated by external stimuli and suggest the presence of unknown oocyte surface receptors linked to the activation machinery in response to fertilization. Electrophoretic profiles obtained by SDS-PAGE of solubilized vitelline envelopes from oocytes matured in vitro revealed the conversion of gp40 (in vitro matured oocytes, without trypsin treatment) to gp38 (ascribable to trypsin activity or cortical granule product activity, CGP) and the conversion of gp70 to gp68 (ascribable to trypsin activity plus CGP activity). Taking into account that only the vitelline envelopes of in vitro matured oocytes with trypsin treatment and activated can block sperm entry, we may suggest that the conversion of gp70 to gp68 is related to the changes associated with sperm binding.
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Siebrasse, Jan Peter, Elias Coutavas y Reiner Peters. "Reconstitution of nuclear protein export in isolated nuclear envelopes". Journal of Cell Biology 158, n.º 5 (26 de agosto de 2002): 849–54. http://dx.doi.org/10.1083/jcb.200201130.
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Signal-dependent nuclear protein export was studied in perforated nuclei and isolated nuclear envelopes of Xenopus oocytes by optical single transporter recording. Manually isolated and purified oocyte nuclei were attached to isoporous filters and made permeable for macromolecules by perforation. Export of a recombinant protein (GG-NES) containing the nuclear export signal (NES) of the protein kinase A inhibitor through nuclear envelope patches spanning filter pores could be induced by the addition of GTP alone. Export continued against a concentration gradient, and was NES dependent and inhibited by leptomycin B and GTPγS, a nonhydrolyzable GTP analogue. Addition of recombinant RanBP3, a potential cofactor of CRM1-dependent export, did not promote GG-NES export at stoichiometric concentration but gradually inhibited export at higher concentrations. In isolated filter-attached nuclear envelopes, export of GG-NES was virtually abolished in the presence of GTP alone. However, a preformed export complex consisting of GG-NES, recombinant human CRM1, and RanGTP was rapidly exported. Unexpectedly, export was strongly reduced when the export complex contained RanGTPγS or RanG19V/Q69L-GTP, a GTPase-deficient Ran mutant. This paper shows that nuclear transport, previously studied in intact and permeabilized cells only, can be quantitatively analyzed in perforated nuclei and isolated nuclear envelopes.
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Cardoso, Vitor E. M., Pedro F. Pereira, Nuno M. M. Ramos y Ricardo M. S. F. Almeida. "The Impacts of Air Leakage Paths and Airtightness Levels on Air Change Rates". Buildings 10, n.º 3 (12 de marzo de 2020): 55. http://dx.doi.org/10.3390/buildings10030055.
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Southern European countries have milder climatic conditions that differ from their colder northern counterparts, which greatly influence indoor ventilation strategies. The relation between a building’s airtightness and the air change rates remains a topic to be fully tackled in these countries, since natural ventilation is very frequent. In this work, the ventilation and airtightness of a case study were analyzed in-depth to support a discussion on this topic. CO2 concentration decay and blower-door measurements were used to characterize the infiltration and ventilation conditions of the case study. The case study represents a common Portuguese situation, with highly permeable envelopes, combined with highly variable air change rates. Transient simulations were carried out for the comparison of scenarios where different configurations of possible air paths were analyzed. The simulations included both natural and mechanical ventilation scenarios. An air sweeping effect from bedroom to bathroom only occurred when the mechanical extraction ventilation (MEV) was on. Different air leakage path configurations resulted in substantial offsets, up to 63%, of the air change rate (ACH) due to natural occurring forces. The results confirmed that the relation between airtightness and air change rates should be carefully analyzed in southern European countries, as indoor air quality, comfort of occupants, and energy efficiency are highly influenced by the considered variables.
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Islam, MS, T. Akhter y M. Matsumoto. "Asterosap, an Egg Jelly Peptide, Elevate Intracellular Ca2+ and Activate the Motility of Spermatozoa". Progressive Agriculture 19, n.º 1 (18 de diciembre de 2013): 79–88. http://dx.doi.org/10.3329/pa.v19i1.17358.
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Components from the outer envelopes of the egg that influence the flagellar beating and acrosome reaction of spermatozoa are regulated by ion flux across the plasma membrane. Asterosap, a sperm-activating peptide from the starfish egg jelly layer, causes a transient increase in intracellular cyclic GMP (cGMP) through the activation of the asterosap receptor, a guanylyl cyclase (GC), and causes an increase in intracellular Ca2+. Here we describe the pathway of asterosap-induced Ca2+ elevation using different Ca2+ channel antagonists. Fluo-4 AM, a cell permeable Ca2+ sensitive dye was used to determine the channel caused by the asterosap-induced Ca2+ elevation in spermatozoa. Different L-type Ca2+ channel antagonists, a non specific Ca2+ channel antagonist (nickel chloride), and a store-operated Ca2+ channel (SOC) antagonist do not show any significant response on asterosap-induced Ca2+ elevation, whereas KB-R7943, a selective inhibitor against Na+/Ca2+ exchanger (NCX) inhibited effectively. We also analyzed the flagellar movement of spermatozoa in artificial seawater (ASW) containing the asterosap at 100 nM ml?1. We found that spermatozoa swam vigorously with more symmetrical flagellar movement in asterosap than in ASW and KB-R7943 significantly inhibited the flagellar movement.DOI: http://dx.doi.org/10.3329/pa.v19i1.17358 Progress. Agric. 19(1): 79 - 88, 2008
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Hussain, Atif y Pierre Blanchet. "Preparation of Breathable Cellulose Based Polymeric Membranes with Enhanced Water Resistance for the Building Industry". Materials 14, n.º 15 (1 de agosto de 2021): 4310. http://dx.doi.org/10.3390/ma14154310.
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This study focuses on the development of advanced water-resistant bio-based membranes with enhanced vapour permeability for use within building envelopes. Building walls are vulnerable to moisture damage and mold growth due to water penetration, built-in moisture, and interstitial condensation. In this work, breathable composite membranes were prepared using micro-fibrillated cellulose fiber (CF) and polylactic acid (PLA). The chemical composition and physical structure of CF is responsible for its hydrophilic nature, which affects its compatibility with polymers and consequently its performance in the presence of excessive moisture conditions. To enhance the dispersibility of CF in the PLA polymer, the fibers were treated with an organic phosphoric acid ester-based surfactant. The hygroscopic properties of the PLA-CF composites were improved after surfactant treatment and the membranes were resistant to water yet permeable to vapor. Morphological examination of the surface showed better interfacial adhesion and enhanced dispersion of CF in the PLA matrix. Thermal analysis revealed that the surfactant treatment of CF enhanced the glass transition temperature and thermal stability of the composite samples. These bio-based membranes have immense potential as durable, eco-friendly, weather resistant barriers for the building industry as they can adapt to varying humidity conditions, thus allowing entrapped water vapor to pass through and escape the building, eventually prolonging the building life.
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Goldberg, M. y D. Septier. "Phospholipids in Amelogenesis and Dentinogenesis". Critical Reviews in Oral Biology & Medicine 13, n.º 3 (mayo de 2002): 276–90. http://dx.doi.org/10.1177/154411130201300305.
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Phospholipids have been identified in enamel and dentin. Before demineralization, a group of phospholipids extracted by lipid solvents was associated with cell membranes and is therefore closely related to cell growth and intracellular regulations. After demineralization, a second group of phospholipids, associated with the extracellular matrix, was extracted; this group is probably linked to the mineralized phase. Using imidazole-osmium tetroxide fixation of rat incisors, we stained cellular unsaturated fatty acids, so that we could visualize the membrane domains, coated pits, and endocytic inclusions. Filipin, a probe for cholesterol, varied in density along the plasma membrane of secretory ameloblasts, and allowed us to visualize membrane remnants inside the forming enamel. With respect to phospholipids located in the extracellular matrix, the malachite-green–glutaraldehyde (MGA) method or iodoplatinate (IP) reaction retains and visualizes enamel and dentin phospholipids. In predentin, aggregates appearing as granules and filaments, or liposome-like structures, were located in the spaces between collagen fibrils. In dentin, organic envelopes coating the crystals, also named “crystal-ghost” structures, outlined groups of collagen fibrils. Histochemical data provided evidence that phospholipids are co-distributed or interact with proteoglycans. Radioautography after IP reaction established that [3H] choline was detected in dentin as early as 30 min after the intravenous injection of the labeled precursor, before any labeling was seen in odontoblasts and predentin. This suggests that blood-serum-labeled phospholipids pass between odontoblasts, cross the distal permeable junctional complex, and diffuse in dentin prior to any cellular uptake and phospholipid synthesis. Pharmacologically and genetically induced pathology also supports the suggestion that phospholipids play an important role in the formation and mineralization of dental tissues.
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EHRENMARK, ULF T. "On the normal incidence of linear waves over a plane incline partially covered by a rigid lid". Journal of Fluid Mechanics 623 (6 de marzo de 2009): 209–40. http://dx.doi.org/10.1017/s0022112008005296.
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The effect is examined on infinitesimal standing waves over a plane beach when restricted by the arbitrary placing of a finite rigid (or permeable) lid of length ℓ on the undisturbed surface. A uniformly bounded solution for the potential function is obtained by a Green's function method. The Green's function is derived and manipulated, for subsequent computational expedience, from a previously known solution for the problem of an oscillating line source placed at an arbitrary location in the sector. Applications are made to both the case of plate anchored at the origin and the case of plate anchored some distance at sea (drifted plate problem). In both cases water column potentials and equipotentials are constructed from the numerical solution of a Fredholm equation of the second kind by finite difference discretization. Solutions are further extended to include the logarithmically singular standing wave, combination with which allows the construction of progressing waves. Computation of initially incoming progressing wave envelopes demonstrates the emergence of a partially standing wave pattern shoreward of the plate. There is no difficulty, in principle, to extend the theory to any number of plates, and this is verified by computation for the case of two plates. A new shoreline radiation condition is constructed to allow formulation, in the usual way, of the reflection/transmission problem for the plate, and results are in good qualitative agreement with a similar model on a horizontal plane bed. It is argued that the Green's function constructed here could be used in a number of diverse problems, of this linear nature, where all, or part, of the submerged boundary is that of a plane incline.
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Brits, G. J. y J. C. Manning. "Seed structure and physiology in relation to recruitment ecology in Leucospermum (Proteaceae) in fynbos". Australian Journal of Botany 67, n.º 4 (2019): 290. http://dx.doi.org/10.1071/bt18199.
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Development of embryo envelopes in Leucospermum cordifolium (Salisb. ex Knight) Fourcade is presented in a detailed anatomical study, and their structure interpreted ecologically. To support interpretation results for at least six other species of Leucospermum are reviewed, confirming that L. cordifolium is representative of this shrubby group occurring in fynbos, a fire-prone Mediterranean-type vegetation subject to summer drought. The fate of the water-permeable seed coverings subsequent to dispersal is followed in seeds stored experimentally underground. The testa at maturity effectively excludes oxygen in intact soil-stored seeds, thus creating a less common type of physical dormancy which we term ‘anoxia PY’ (oxygen-impermeable physical dormancy). We postulate ‘fire-mediated desiccation-scarification’ testa breakage on a large scale in freshly dispersed (by ants) soil-stored young-seeds, dynamically regulated by drying of different testa layers through fire heat shock (but also by post-fire ambient climate heat), thus alleviating anoxia PY in, and causing undelayed germination of, a major part of the young-seed bank within the ensuing winter germination season. Concurrently a patchy disturbance pattern within a lesser portion of the young-seed cohort causes uneven underground desiccation-scarification by fire, resulting in variable degrees of oxygenation and thus temporally extended (erratic) germination of young-seeds. Both of these strategies are primary long term fitness traits in Leucospermum. By contrast the persistent older-seed cohort, stored underground during the inter-fire period, may become weathered by soil and climate factors (‘soil-mediated abrasion’), which alleviates anoxia PY in old seeds. Thermodormancy of these embryos (physiological dormancy, PD) is enforced in unburnt vegetation by two narrow habitat-dependent daily temperature requirements (~10°C × 20°C), and these have specific ecological functions. The complex Leucospermum system includes balanced adaptive responses to multiple selective pressures. We propose a coherent mechanistic profile for this fynbos genus, synthesising data partly from the literature of other fire-prone ecosystems.
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Koschinski, Andreas, Gerd Wengler, Gisela Wengler y Holger Repp. "Rare earth ions block the ion pores generated by the class II fusion proteins of alphaviruses and allow analysis of the biological functions of these pores". Journal of General Virology 86, n.º 12 (1 de diciembre de 2005): 3311–20. http://dx.doi.org/10.1099/vir.0.81096-0.
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Recently, class II fusion proteins have been identified on the surface of alpha- and flaviviruses. These proteins have two functions besides membrane fusion: they generate an isometric lattice on the viral surface and they form ion-permeable pores at low pH. An attempt was made to identify inhibitors for the ion pores generated by the fusion proteins of the alphaviruses Semliki Forest virus and Sindbis virus. These pores can be detected and analysed in three situations: (i) in the target membrane during virus entry, by performing patch-clamp measurements of membrane currents; (ii) in the virus particle, by studying the entry of propidium iodide; and (iii) in the plasma membrane of infected cells, by Fura-2 fluorescence imaging of Ca2+ entry into infected cells. It is shown here that, at a concentration of 0·1 mM, rare earth ions block the ion permeability of alphavirus ion pores in all three situations. Even at a concentration of 0·5 mM, these ions do not block formation of the viral fusion pore, as they do not inhibit entry or multiplication of alphaviruses. The data indicate that ions flow through the ion pores into the virus particle in the endosome and from the endosome into the cytoplasm after fusion of the viral envelope with the endosomal membrane. These ion flows, however, are not necessary for productive infection. The possibility that the ability of class II fusion proteins to form ion-permeable pores reflects their origin from protein toxins that form ion-permeable pores, and that entry via class II fusion proteins may resemble the entry of non-enveloped viruses, is discussed.
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Daugelavičius, Rimantas, Elena Bakiene˙ y Dennis H. Bamford. "Stages of Polymyxin B Interaction with theEscherichia coli Cell Envelope". Antimicrobial Agents and Chemotherapy 44, n.º 11 (1 de noviembre de 2000): 2969–78. http://dx.doi.org/10.1128/aac.44.11.2969-2978.2000.
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ABSTRACT The effects of polymyxin B (PMB) on the Escherichia coli outer (OM) and cytoplasmic membrane (CM) permeabilities were studied by monitoring the fluxes of tetraphenylphosphonium, phenyldicarbaundecaborane, and K+ and H+ions. At concentrations between 2 and 20 μg/ml, PMB increased the OM permeability to lipophilic compounds and induced a leakage of K+ from the cytosol and an accumulation of lipophilic anions in the cellular membranes but did not cause the depolarization of the CM. At higher concentrations, PMB depolarized the CM, forming ion-permeable pores in the cell envelope. The permeability characteristics of PMB-induced pores mimic those of bacteriophage- and/or bacteriocin-induced channels. However, the bactericidal effect of PMB took place at concentrations below 20 μg/ml, indicating that this effect is not caused by pore formation. Under conditions of increased ionic strength, PMB made the OM permeable to lipophilic compounds and decreased the K+gradient but was not able to depolarize the cells. The OM-permeabilizing effect of PMB can be diminished by increasing the concentration of Mg2+. The major new findings of this work are as follows: (i) the OM-permeabilizing action of PMB was dissected from its depolarizing effect on the CM, (ii) the PMB-induced ion-permeable pores in bacterial envelope were registered, and (iii) the pore formation and depolarization of the CM are not obligatory for the bactericidal action of PMB and dissipation of the K+gradient on the CM.
Tesis sobre el tema "Permeable envelopes"
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Giachetti, Andrea Verfasser] y Klaus [Akademischer Betreuer] [Thiele. "Wind effects on permeable building envelopes: a two-dimensional exploratory study / Andrea Giachetti ; Betreuer: Klaus Thiele". Braunschweig : Technische Universität Braunschweig, 2018. http://d-nb.info/1175387509/34.
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Giachetti, Andrea [Verfasser] y Klaus [Akademischer Betreuer] Thiele. "Wind effects on permeable building envelopes: a two-dimensional exploratory study / Andrea Giachetti ; Betreuer: Klaus Thiele". Braunschweig : Technische Universität Braunschweig, 2018. http://d-nb.info/1175387509/34.
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Giachetti, Andrea. "Wind effects on permeable building envelopes: a two-dimensional exploratory study". Doctoral thesis, 2017. http://hdl.handle.net/2158/1170715.
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The present work deals with an exploratory two-dimensional study on systems composed by an open-gap airtight screen and a rectangular section. The aerodynamic interference caused by the presence of the screen has been investigated, trying to understand the role of each potential influencing factor. The effects produced by the concurrent presence of confined (in the cavity behind the screen) and unconfined (around the whole system) flows have been analyzed, in terms of wind induced forces and pressures. Moreover, the possibility of using simplified models to evaluate the internal pressures having the external ones on a section where the cavity has not been reproduced, namely the possible external and internal pressure decoupling, has been considered.
Libros sobre el tema "Permeable envelopes"
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Minnesota. Building Codes and Standards Division., ed. Feasibility of establishing criteria for permeable envelope and/or nonmechanical ventilation for detached single one or two family residential construction: Report to the Minnesota Legislature. St. Paul, MN: Dept. of Administration, Building Codes and Standards Division, 2002.
Buscar texto completoCapítulos de libros sobre el tema "Permeable envelopes"
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Smegal, Jonathan, Graham Finch, Alejandra Nieto y Chris Schumacher. "Comparing the Enclosure Wall Performance of Low-Permeance Exterior Insulation to High-Permeance Exterior Insulation in the Pacific Northwest". En Advances in Hygrothermal Performance of Building Envelopes: Materials, Systems and Simulations, 95–121. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2017. http://dx.doi.org/10.1520/stp159920160126.
Texto completoActas de conferencias sobre el tema "Permeable envelopes"
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Bastien, Diane y Martin Winther-Gaasvig. "Permeable and Hygroscopic Building Envelopes: Hygrothermal Simulations of “Det Naturlige Hus”". En 10TH International Conference on Sustainable Energy and Environmental Protection. University of Maribor Press, 2017. http://dx.doi.org/10.18690/978-961-286-064-6.5.
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Gauvin, Florent, Vesta Tsao, Joost Vette y Henricus Jozef Hubertus Brouwers. "Physical Properties and Hygrothermal Behavior of Mycelium-Based Composites as Foam-Like Wall Insulation Material". En 4th International Conference on Bio-Based Building Materials. Switzerland: Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/www.scientific.net/cta.1.643.
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This research aims to study mycelium-based composites (MBC) by assessing their performance as foam-like wall insulation material. Various substrates have been selected to get optimized performance of the composite. Results showed that a prolonged growing period arose a denser mycelium outer layer in MBC, which rendered better water resistance due to the hydrophobicity of mycelium. Thermal conductivity and mechanical properties are highly dependent on substrate choices than other parameters of MBC, which coincided with the literature. Additionally, influences of accelerated aging test and moisture buffer capacity of MBC were first studied in this research. The results indicated that MBC not only maintained good functional performance after the accelerated aging test (i.e. drying and wetting cycles) but also constituted good moisture buffer capacity. This means that MBC has key material essences to apply as internal wall insulation material and become one of the layers in vapor-permeable building envelope systems to passively regulate indoor relative humidity and thermal comfort.
Informes sobre el tema "Permeable envelopes"
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Browdy, Craig y Esther Lubzens. Cryopreservation of Penaeid Shrimp Embryos: Development of a Germplasm Cryo-Bank for Preservation of High Health and Genetically Improved Stocks. United States Department of Agriculture, agosto de 2002. http://dx.doi.org/10.32747/2002.7695849.bard.
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The objectives of the project were to develop a successful protocol for cryopreservation of penaeid germ plasm in order to preserve a pathogen-free broodstock nucleus for commercial exploitation of marine shrimp in aquaculture. The critical parameters to be characterized in the project were: 1. Determination of chill sensitivity and chill tolerant embryonic stages, including a full description and time course study of embryonic developmental stages. 2. Development of protocols for loading and removal of cryoprotectant agents (CPAs) from embryos; determination of optimal concentrations and duration of loading. 3. Characterization of the toxicity of the selected CP As and 4. Establishing optimal cooling and thawing procedures. Studies were performed on two penaeid species: Litopenaeus vannamei (in the USA) and P. semisulcatus (in Israel). The effect of incubation temperature on embryonic development rate and hatching success was studied in L. vannamei, showing that spawns maybe maintained at temperatures ranging from 24°C to 30°C, without compromising hatchability. Embryonic development extends from 12 hr to 19 hr at 30°C and 24°C, respectively. Studies showed that advanced embryonic developmental stages were chill tolerant in the two studied species, but P. semisulcatus could better endure lower temperatures than L. vannamei. A large number of experiments were performed to determine the optimal CP As, their concentration and duration of loading. Permeating (e.g. glycerol, methanol, DMSO, 1,2- propanediol, ethylene glycol, glucose) and non-permeating CPAs (sucrose, PVP, polyethylene glycol) were tested and several combinations of permeating and non-permeating CP As, on fertilized eggs (embryos), nauplii and protozoeae. In general, nauplii tolerated higher CPA concentrations than eggs and nauplii were also more permeable to radiolabeled methanol. Chlorine treatment intended to remove the chitinous envelop from eggs, did not increase dramatically the permeation of radiolabled methanol into eggs. Cooling eggs, nauplii or protozoeae to cryogenic temperatures, by either vitrification or slow cooling protocols, did not result in full survival of thawed samples, despite exhaustive attempts testing various protocols and CP As. Results seemed more encouraging in freezing of nauplii in comparison to eggs or protozoeae. Successful preliminary results in cryopreservation of spermatozoa of P. vannamei, will facilitate preservation of genetic specific to some extent.