Excessive Water Loss Research Articles

Recurrent Transient Pseudohypoaldosteronism After Subtotal Colectomy and Ileostomy

Introduction: Pseudohypoaldosteronism(PHA) has elevated aldosterone with hyponatremia, hyperkalemia and metabolic acidosis due to inability of aldosterone to cause potassium and hydrogen secretion. There are three types of PHA, the primary inherited types I, II and secondary. Secondary PHA is mostly due to urinary tract infection or obstruction that leads to a transient resistance to aldosterone in renal tubular cells. Rarely, transient PHA occurs due to excessive salt and water loss from a high output ileostomy. We report a case of recurrent PHA after subtotal colectomy and ileostomy. Case description: A 92-year-old woman with PMH of HTN, DM, hypothyroidism and subtotal colectomy with end ileostomy due to prior diverticular bleed presented with high output from ostomy and lethargy. Physical examination revealed BP: 63/41mm Hg, HR: 72/min with poor skin turgor. She was found to have hyponatremia (130 meq/L), hyperkalemia (> 7 meq/L), metabolic acidosis (bicarbonate 13 meq/L), and Acute Kidney Injury (AKI). She had 3 prior admissions where she had similar clinical features and laboratory values which resolved after hydration. Her urine sodium(Na): 26 mmol/L (low), urine potassium(K): 77 mmol/L (< 30 is low). Stool Na: 68 mmol/L (normal ≈ 30), K: 31 mmol/L (normal ≈ 75). Cortisol, ACTH, TSH and free T4 were normal. Plasma renin activity was high at 16.97 ng/mL/hr (normal 0.5-3) and aldosterone was high at 31.4 ng/dL (normal 0-30). IV saline normalized her electrolytes, creatinine and aldosterone levels. PHA was diagnosed and family was educated about adequate fluid and salt intake. Discussion: Patients with colonic resection have significant salt and water depletion, compensated by reduced urinary Na. In high output ostomy, this adaption suffers and kidneys are unable to excrete K due to tubular Na deficiency. However, in our patient, urine K was high implicating colon's role in electrolyte disturbances. Colon is rich in mineralocorticoid receptor and after its resection, when Na and water absorption becomes critically low, aldosterone cannot maintain normal electrolytes due to an incompletely understood mechanism and leads to PHA. Hyponatremia, hyperkalemia and metabolic acidosis in adults is usually due to adrenal insufficiency or hypoaldosteronism, but rarely in patients with ileostomy, it is due to PHA. It is critical to identify PHA since the treatment is with hydration and salt supplementation and not mineralocorticoid replacement.

Potential vase life of cut roses: Seasonal variation and relationships with growth conditions, phenotypes, and gene expressions

In this work, we identified the interrelationships between gene expression levels, environmental factors, phenotypic characteristics, and vase life of cut rose ‘Lovely Lydia’ between seasons and across years. We also determined the contribution of each factor to potential vase life (PVL) of cut roses. The vase life of the cut flowers was longest in spring (12.2 d), followed by summer (11.3 d), autumn (10.0 d), and winter (9.2 d). The environmental conditions in winter were characterized by high relative humidity (RH) and low vapor pressure deficit, and cut flowers grown under these conditions had less-functional stomata and consequently excessive water loss after harvest, resulting in shortened vase life. Leaf brix was not significantly correlated with PVL, but it was strongly correlated with flower diameter, indicating that congenital sucrose may be more important for providing the substances required for flower opening than for determining the longevity of cut roses. Correlation analysis revealed that initial transcript levels of the ethylene receptor RhETR4 and the signaling component RhEIN3-2 are very important factors in determining PVL of cut roses, as are preharvest RH conditions, stomatal function, and transpiration. The transcript levels of these genes were significantly modified by growth environment, including high RH and low temperature. Importantly, we show that RH conditions during cultivation not only determine stomatal characteristics but also modify the initial transcript levels of the ethylene responsive genes, thereby modifying the PVL. Understanding the interrelationships of genetic variation with other factors in the modulation of PVL will greatly help to improve growth environments and postharvest treatments across seasons as well as to develop techniques for guaranteeing the longevity of cut flowers.

Actin filament reorganisation controlled by the SCAR/WAVE complex mediates stomatal response to darkness.

Summary Stomata respond to darkness by closing to prevent excessive water loss during the night. Although the reorganisation of actin filaments during stomatal closure is documented, the underlying mechanisms responsible for dark‐induced cytoskeletal arrangement remain largely unknown.We used genetic, physiological and cell biological approaches to show that reorganisation of the actin cytoskeleton is required for dark‐induced stomatal closure.The opal5 mutant does not close in response to darkness but exhibits wild‐type (WT) behaviour when exposed to abscisic acid (ABA) or CaCl2. The mutation was mapped to At5g18410, encoding the PIR/SRA1/KLK subunit of the Arabidopsis SCAR/WAVE complex. Stomata of an independent allele of the PIR gene (Atpir‐1) showed reduced sensitivity to darkness and F1 progenies of the cross between opal5 and Atpir‐1 displayed distorted leaf trichomes, suggesting that the two mutants are allelic. Darkness induced changes in the extent of actin filament bundling in WT. These were abolished in opal5. Disruption of filamentous actin using latrunculin B or cytochalasin D restored wild‐type stomatal sensitivity to darkness in opal5.Our findings suggest that the stomatal response to darkness is mediated by reorganisation of guard cell actin filaments, a process that is finely tuned by the conserved SCAR/WAVE–Arp2/3 actin regulatory module.

A Rapid and Reliable Method for Total Protein Extraction from Succulent Plants for Proteomic Analysis

Crassulacean acid metabolism plants have some morphological features, such as succulent and reduced leaves, thick cuticles, and sunken stomata that help them prevent excessive water loss and irradiation. As molecular constituents of these morphological adaptations to xeric environments, succulent plants produce a set of specific compounds such as complex polysaccharides, pigments, waxes, and terpenoids, to name a few, in addition to uncharacterized proteases. Since all these compounds interfere with the analysis of proteins by electrophoretic techniques, preparation of high quality samples from these sources represents a real challenge. The absence of adequate protocols for protein extraction has restrained the study of this class of plants at the molecular level. Here, we present a rapid and reliable protocol that could be accomplished in 1h and applied to a broad range of plants with reproducible results. We were able to obtain well-resolved SDS/PAGE protein patterns in extracts from different members of the subfamilies Agavoideae (Agave, Yucca, Manfreda, and Furcraea), Nolinoideae (Dasylirion and Beucarnea), and the Cactaceae family. This method is based on the differential solubility of contaminants and proteins in the presence of acetone and pH-altered solutions. We speculate about the role of saponins and high molecular weight carbohydrates to produce electrophoretic-compatible samples. A modification of the basic protocol allowed the analysis of samples by bidimensional electrophoresis (2DE) for proteomic analysis. Furostanol glycoside 26-O-β-glucosidase (an enzyme involved in steroid saponin synthesis) was successfully identified by mass spectrometry analysis and de novo sequencing of a 2DE spot from an Agave attenuata sample.

473 The stratum corneum paradox: Improving bioavailability of active molecules while reinforcing the skin barrier

Stratum corneum (SC) has to be impermeable to protect our body from external aggression and also excessive water loss. Nevertheless, to be efficient, cosmetic active ingredients must cross the SC barrier to achieve the viable cells of epidermis. A vast range of penetration enhancers has been developed following two different mechanisms: Modifying the skin polarity; Interruption of the intercellular lipid packing by delipidation leading to an increase of trans-epidermal water loss and dehydration. Knowing that consumers are increasingly seeking cosmetic products providing better results and rapid efficacy, the challenge of cosmetics industry is to improve the bioavailability of active molecules without destroying the barrier function of the SC and decreasing its hydration. In this way, we developed a phospholipid lamellar system (hydrogenated phospholipids and fatty acids) based on SC chemical and structural biomimicry using polarity modification mechanism. When applied on the skin, hydrogenated phospholipids first fuse with the skin surface forming a non-permeable and occlusive gel linked to the phospholipid organization into lamellar rigid one-dimensional network (Structural biomimicry). Furthermore, fatty acids interact with the intercorneocytar lipid cement of the SC and modify its structure leading to the creation of a water vacuoles facilitating the permeation of hydrophilic molecules through the membrane (chemical biomimicry). Different studies were performed to understand the impact of the phospholipid lamellar system on the integrity of the SC (TEWL, corneometry, electron microscopy, D-squam) and on the active ingredients permeation (bioavailability study). To conclude, the obtained results confirmed that our optimized lipid mixture meet the challenge of improving the bioavailability of active ingredients, by increasing the hydration of the SC and reinforcing its integrity.

Hair Growth Cycle Is Arrested in SCD1 Deficiency by Impaired Wnt3a-Palmitoleoylation and Retrieved by the Artificial Lipid Barrier

Stearoyl-CoA desaturase 1 (SCD1) is the dominant member of the SCD-isozyme family, regarded as a major regulator of lipid and energy metabolism in liver and adipose tissue. SCD1 deficiency impairs the desaturation of de novo-synthesized palmitoyl- and stearoyl-CoA to palmitoleoyl- and oleoyl-CoA. Scd1-/- mice develop metabolic waste syndrome and skin lesions: epidermal barrier disruption, alopecia, and degeneration of sebaceous glands. The unifying molecular link between the two divergent traits remains incompletely understood. Here we show the absence of palmitoleic acid (9Z-16:1) in the lipidome of the scd1-null mouse, which prohibits posttranslational O-palmitoleoylation of Wnt3a protein, essential for Wnt3a/ß-catenin signaling in stem cell lineage decision in development of the epidermal barrier, hair growth cycle, and sebaceous glands. Substitution of the disrupted epidermal lipid barrier by an inert hydrocarbon coat prevents excessive transepidermal water loss, normalizes thermogenesis and metabolic parameters, and surprisingly leads to the activation of hair bulge progenitor cells and reprograming of a regular hair growth cycle and development of a regular fur in scd1-/- mice. Progenitor sebocytes are not activated. Independent of age, application or removal of the artificial lipid barrier allows the reversible telogen-anagen reentry and exit of the hair growth cycle.

Phytosphingosine, sphingosine and dihydrosphingosine ceramides in model skin lipid membranes: permeability and biophysics

Ceramides based on phytosphingosine, sphingosine and dihydrosphingosine are essential constituents of the skin lipid barrier that protects the body from excessive water loss. The roles of the individual ceramide subclasses in regulating skin permeability and the reasons for C4-hydroxylation of these sphingolipids are not completely understood. We investigated the chain length-dependent effects of dihydroceramides, sphingosine ceramides (with C4-unsaturation) and phytoceramides (with C4-hydroxyl) on the permeability, lipid organization and thermotropic behavior of model stratum corneum lipid membranes composed of ceramide/lignoceric acid/cholesterol/cholesteryl sulfate. Phytoceramides with very long C24 acyl chains increased the permeability of the model lipid membranes compared to dihydroceramides or sphingosine ceramides with the same chain lengths. Either unsaturation or C4-hydroxylation of dihydroceramides induced chain length-dependent increases in membrane permeability. Infrared spectroscopy showed that C4-hydroxylation of the sphingoid base decreased the relative ratio of orthorhombic chain packing in the membrane and lowered the miscibility of C24 phytoceramide with lignoceric acid. The phase separation in phytoceramide membranes was confirmed by X-ray diffraction. In contrast, phytoceramides formed strong hydrogen bonds and highly thermostable domains. Thus, the large heterogeneity in ceramide structures and in their aggregation mechanisms may confer resistance towards the heterogeneous external stressors that are constantly faced by the skin barrier.

Isotopic constraints on water source mixing, network leakage and contamination in an urban groundwater system.

Water supply in developing countries is prone to large water losses due to leaky distribution networks and defective sewers, which may affect groundwater quality and quantity in urban areas and result in complex subsurface mixing dynamics. In this study, a multi-stable isotope approach was used to investigate spatiotemporal fluctuations of surface and sub-surface water source partitioning and mixing, and to assess nitrogen (N) contamination in the urban water cycle of As-Salt, Jordan. Water import from the King Abdullah Canal (KAC), mains waters from the network, and wastewater are characterized by distinct isotopic signatures, which allowed us to quantify city effluents into the groundwater. Temporal variations in isotopic signatures of polluted groundwater are explained by seasonally fluctuating inflow, and dilution by water that originates from Lake Tiberias and enters the urban water cycle via the KAC. Isotopic analysis (N and O) and comparison between groundwater nitrate and nitrate from mains water, water imports and wastewater confirmed that septic waste from leaky sewers is the main contributor of nitrate contamination. The nitrate of strongly contaminated groundwater was characterized by highest δ15NNO3 values (13.3±1.8‰), whereas lowest δ15NNO3 values were measured in unpolluted groundwater (6.9‰). Analogously, nitrate concentration and isotopic ratios were used for source partitioning and qualitatively confirmed δDH2O and δ18OH2O-based estimates. Dual water isotope endmember mixing calculations suggest that city effluents from leaky networks and sewers contribute 30-64% to the heavily polluted groundwater. Ternary mixing calculations including also chloride revealed that 5-18% of the polluted groundwater is wastewater. Up to two thirds of the groundwater originates from mains, indicating excessive water loss from the network, and calling for improved water supply management.

Diabetes Insipidus.

Disruption of water and electrolyte balance is frequently encountered in clinical medicine. Regulating water metabolism is critically important. Diabetes insipidus (DI) presented with excessive water loss from the kidney is a major disorder of water metabolism. To understand the molecular and cellular mechanisms and pathophysiology of DI and rationales of clinical management of DI is important for both research and clinical practice. This chapter will first review various forms of DI focusing on central diabetes insipidus (CDI) and nephrogenic diabetes insipidus (NDI ) . This is followed by a discussion of regulatory mechanisms underlying CDI and NDI , with a focus on the regulatory axis of vasopressin, vasopressin receptor 2 (V2R ) and the water channel molecule, aquaporin 2 (AQP2 ). The clinical manifestation, diagnosis and management of various forms of DI will also be discussed with highlights of some of the latest therapeutic strategies that are developed from in vitro experiments and animal studies.

Hypernatremia in extremely low birth weight infants – case presentation

Hypernatremia in extremely low birth weight (ELBW) infant is a rather frequent condition due to an imbalance between the sodium and free water loss through kidney and skin. ELBW preemies receive natrium within the parenteral nutrition solutions, as normal saline bolus for hypotension and metabolic acidosis, and sometimes with antibiotics or other drugs diluted in normal saline; all these can lead to hypernatremia, symptomatic or not. We present a case of hypernatremia causing seizures, whose etiology was an increased sodium intake and excessive free water loss, which raised questions for differential diagnosis and treatment.

Gene expression and physiological responses associated to stomatal functioning in Rosa × hybrida grown at high relative air humidity

High relative air humidity (RH≥85%) during growth disturbs stomatal functioning, resulting in excessive water loss in conditions of high evaporative demand. We investigated the expression of nine abscisic acid (ABA)-related genes (involved in ABA biosynthesis, oxidation and conjugation) and two non-ABA related genes (involved in the water stress response) aiming to better understand the mechanisms underlying contrasting stomatal functioning in plants grown at high RH. Four rose genotypes with contrasting sensitivity to high RH (one sensitive, one tolerant and two intermediate) were grown at moderate (62±3%) or high (89±4%) RH. The sensitive genotype grown at high RH showed a significantly higher stomatal conductance (gs) and water loss in response to closing stimuli as compared to the other genotypes. Moreover, high RH reduced the leaf ABA concentration and its metabolites to a greater extent in the sensitive genotype as compared to the tolerant one. The large majority of the studied genes had a relevant role on stomatal functioning (NCED1, UGT75B2, BG2, OST1, ABF3 and Rh-APX) while two others showed a minor contribution (CYP707A3 and BG1) and AAO3, CYP707A1 and DREB1B did not contribute to the tolerance trait. These results show that multiple genes form a highly complex regulatory network acting together towards the genotypic tolerance to high RH.

Abstract P636: Insulin Resistance in Obesity Results in Postprandial Salt and Water Loss

Obesity and insulin resistance contribute to the development of metabolic syndrome, a growing epidemic in our country. The obese Zucker rat is an experimental model of this disease. Previously, using Sprague Dawley rats, we have shown that the normal postprandial rise in insulin acts physiologically to prevent renal salt and water wasting after meals. This study tested whether the effects of postprandial insulin would be attenuated in insulin resistant rats and result in excess salt and water loss. Chronic artery and vein catheters were implanted in male lean and obese Zucker rats for infusion and blood sampling. Rats were housed in metabolic cages and their catheters were connected to dual-channel Instech swivels for access. Over a 24-hr period of ad libitum eating, blood glucose was not different between obese and lean rats (127±7 vs. 120±3 mg/dl) but obese rats were hyperinsulinemic (14.86 vs. 0.98 ng/ml). Obese rats had significantly greater urine volume than lean controls (22.5±1.2 vs. 14.7±0.9 ml) despite similar water intakes. Obese rats tended to excrete more Na+ than lean controls (3.46±0.15 vs. 2.97±0.35 mEq) with equal amounts of Na+ intake. To evaluate the response to a single meal while controlling for blood glucose, fasted rats were administered a glucose bolus (as 50% dextrose) that yielded peak levels of blood glucose that were not different in the two groups (589±11 vs. 596 ±3 mg/dl at t=5 min.). Plasma insulin increased from fasting in both groups to 26.35 and 9.34 ng/ml in obese and lean controls, respectively. Over the 4-hour period following the glucose administration, obese rats had significantly greater urine volume (8.6±1.3 vs. 2.2 ±0.6 ml) and Na+ excretion (0.53±0.11 vs. 0.25±0.09 mEq) than lean controls. This suggests that insulin resistance of obesity may impair the ability of postprandial insulin to participate in maintenance of Na+ and water homeostasis, but the potential role of insulin resistance specifically within the kidney requires further study.

Body Temperature Regulation in Hot Environments.

Organisms in hot environments will not be able to passively dissipate metabolically generated heat. Instead, they have to revert to evaporative cooling, a process that is energetically expensive and promotes excessive water loss. To alleviate these costs, birds in captivity let their body temperature increase, thereby entering a state of hyperthermia. Here we explore the use of hyperthermia in wild birds captured during the hot and dry season in central Nigeria. We found pronounced hyperthermia in several species with the highest body temperatures close to predicted lethal levels. Furthermore, birds let their body temperature increase in direct relation to ambient temperatures, increasing body temperature by 0.22°C for each degree of increased ambient temperature. Thus to offset the costs of thermoregulation in ambient temperatures above the upper critical temperature, birds are willing to let their body temperatures increase by up to 5°C above normal temperatures. This flexibility in body temperature may be an important mechanism for birds to adjust to predicted increasing ambient temperatures in the future.

Environmental controls of evapotranspiration in a mixed plantation in North China.

The mixed plantation plays an important role in the water cycle in the hilly area of North China. To evaluate the effect of afforestation on the water balance in this region, the temporal variation of evapotranspiration (ET) and environmental controls were investigated based on the eddy flux measurement of water vapor in a 31-year-old mixed plantation from 2006 to 2010. During 5years, annual ET ranged from 513 to 680mm, with an average of 579mm. Growing season ET accounted for 72-82% of annual ET during the 5-year period and its interannual variation was determined by the number of rainy days. In the non-growing and growing seasons, monthly ET was primarily dependent on monthly mean soil water content and monthly mean net radiation, respectively. Annual mean Priestley-Taylor coefficient (α) was 0.64, and the decoupling factor (Ω) was 0.48. High values of α and Ω implied that ET was energy limited in the growing seasons of 2006-2010. The mean annual ratio of ET to precipitation (ET/P) was 1.10. The density of the mixed plantation was around 50% higher than the optimal value determined by local water capacity, leading to a large ET/P ratio. The dense plantation needs to be thinned to prevent excessive water loss in the hilly area of North China.

Investigation of chronic diarrhoea

Abstract Chronic diarrhoea occurs, by definition, when there is an excessive intestinal loss of water and electrolytes with increased stool frequency, reduced consistency and larger volume over more than 14 days. While in developing countries often resulting from persisting infectious gastroenteritis in high incidence, in industrialized countries chronic diarrhoea is mainly related to anatomical, functional, and immunological causes. As the spectrum of aetiology is variable, flow charts for different age groups are useful in determining key features of disease severity and diagnostic criteria. The knowledge of common and rare aetiologies enables a structured approach to investigation, and facilitates critical interpretation of results in awareness of diagnostic pitfalls. Comprehensive history, physical examination, inspection and collection of stool samples of sufficient volume are pivotal to devise appropriate referral modes for diagnostic and therapeutic management, as particularly newborn and infants are susceptible to severe dehydration and metabolic disturbances.

Взаимодействие пропранолола и ингибиторов ренин-ангиотензиновой системы в эксперименте

Пропранолол (0,5 мг/кг подкожно) увеличивает у наркотизированных крыс диурез в 1,6 раза (p &lt; 0,05) с одновременным приростом выделения натрия и калия с мочой соответственно в 1,54 и 1,62 раза (p &lt; 0,05). Предварительное подавление активности ренин-ангиотензиновой системы (РАС) с помощью ингибитора АПФ эналаприла (1 мг/кг, внутрь, 7 дней) повышает чувствительность почек крыс к пропранололу, увеличивая его диуретический эффект в 2,33 раза, натрийурез — в 2,49 раза и выделения калия с мочой — в 1,8 раза (p &lt; 0,05). После предварительного введения животным антагониста АТ1-ангиотензиновых рецепторов лозартана (1 мг/кг, внутрь, 7 дней) пропранолол вызывает у крыс прирост диуреза в 1,89 раза, потери натрия с мочой — в 2,48 раза и калийуреза — в 1,71 раза (p &lt; 0,05). Предварительное введение крысам прямого ингибитора ренина алискирена (4 мг/кг, внутрь, 7 дней) сопровождается увеличением диуретического эффекта пропранолола в 2,3 раза, натрийуреза — в 2,56 раза и выделения калия с мочой — в 2,27 раза (p &lt; 0,05). Сделан вывод о том, что почечная тканевая РАС участвует в механизме действия пропранолола в почках, выполняя функцию модулятора, препятствующего избыточной потере воды и электролитов с мочой.

The effect of daytime rain on the Indian Flying Fox (Mammalia: Chiroptera: Pteropodidae Pteropus giganteus)

&lt;p&gt;Excessive water loss during the day due to heat stress in bats of the genus &lt;em&gt;Pteropus&lt;/em&gt; appears to be inevitable, because these bats are exposed to direct sunlight. Rain also affects the rest pattern of the Indian Flying Fox &lt;em&gt;Pteropus giganteus &lt;/em&gt;during the day. When rain occurred during the day, most of the bats hung in a slanting position and did not exhibit any movements. After rain, they licked both ventral and dorsal surfaces of the wing membrane and scratched their body with their thumb claws. They also licked the water droplets that remained on the leaves and branches of the tree. Even though their rest had been affected by the rain the bats utilized the water droplets to quench their thirst, cool their body and clean their fur. The construction of water reservoirs near &lt;em&gt;Pteropus &lt;/em&gt;roosts will help to assure their long-term conservation.&lt;/p&gt;&lt;div&gt; &lt;/div&gt;

Performance Evaluation of Hose-Reel Sprinkler Irrigation System

In Pakistan, surface irrigation methods are commonly used to grow crops to meet the demand of ever-increasing population. The practicing methods of agricultural water applications usually result in excessive losses of water due to non-uniformity, over irrigation etc. To combat such a situation, present-day application methods need to be replaced by efficient ones. Sprinkler is one of methods of irrigation water applications that can bring in more efficiency. However, the sprinkler too needs to be suitably designed and managed under different site-specific conditions. The performance evaluation of a system is the primary need to determine the suitability of a system under a specific crop-growing environment. In order to meet the primary requirement, a hose-reel system was selected and evaluated under this study. In addition to its technical performance parameters, the adoptability by small farmers, ease and simplicity in operation and maintenance etc. were also studied. Application and distribution uniformity were the main parameters, which were determined by adopting standard methods of evaluation. Thus, the major variable was the operating pressures under which the system was operated and results were compiled. Application efficiency and distribution uniformity of hose-reel sprinkler system were found to be varied from 71 to 76% and 66 to 74% with the respective base pressure range of 0.38–0.46MPa, respectively. This sprinkling system has higher efficiency than the traditional flood irrigation methods by saving water more than 30%. It is easy to move and operate, is cost effective, and is suitable for all soil types and small land holdings.

Stratum Corneum Lipids: Their Role for the Skin Barrier Function in Healthy Subjects and Atopic Dermatitis Patients.

Human skin acts as a primary barrier between the body and its environment. Crucial for this skin barrier function is the lipid matrix in the outermost layer of the skin, the stratum corneum (SC). Two of its functions are (1) to prevent excessive water loss through the epidermis and (2) to avoid that compounds from the environment permeate into the viable epidermal and dermal layers and thereby provoke an immune response. The composition of the SC lipid matrix is dominated by three lipid classes: cholesterol, free fatty acids and ceramides. These lipids adopt a highly ordered, 3-dimensional structure of stacked densely packed lipid layers (lipid lamellae): the lateral and lamellar lipid organization. The way in which these lipids are ordered depends on the composition of the lipids. One very common skin disease in which the SC lipid barrier is affected is atopic dermatitis (AD). This review addresses the SC lipid composition and organization in healthy skin, and elaborates on how these parameters are changed in lesional and nonlesional skin of AD patients. Concerning the lipid composition, the changes in the three main lipid classes and the importance of the carbon chain lengths of the lipids are discussed. In addition, this review addresses how these changes in lipid composition induce changes in lipid organization and subsequently correlate with an impaired skin barrier function in both lesional and nonlesional skin of these patients. Furthermore, the effect of filaggrin and mutations in the filaggrin gene on the SC lipid composition is critically discussed. Also, the breakdown products of filaggrin, the natural moisturizing factor molecules and its relation to SC-pH is described. Finally, the paper discusses some major changes in epidermal lipid biosynthesis in patients with AD and other related skin diseases, and how inflammation has a deteriorating effect on the SC lipids and SC biosynthesis. The review ends with perspectives on future studies in relation to other skin diseases.

An Endosperm-Associated Cuticle Is Required for Arabidopsis Seed Viability, Dormancy and Early Control of Germination.

Cuticular layers and seeds are prominent plant adaptations to terrestrial life that appeared early and late during plant evolution, respectively. The cuticle is a waterproof film covering plant aerial organs preventing excessive water loss and protecting against biotic and abiotic stresses. Cutin, consisting of crosslinked fatty acid monomers, is the most abundant and studied cuticular component. Seeds are dry, metabolically inert structures promoting plant dispersal by keeping the plant embryo in an arrested protected state. In Arabidopsis thaliana seeds, the embryo is surrounded by a single cell endosperm layer itself surrounded by a seed coat layer, the testa. Whole genome analyses lead us to identify cutin biosynthesis genes as regulatory targets of the phytohormones gibberellins (GA) and abscisic acid (ABA) signaling pathways that control seed germination. Cutin-containing layers are present in seed coats of numerous species, including Arabidopsis, where they regulate permeability to outer compounds. However, the role of cutin in mature seed physiology and germination remains poorly understood. Here we identify in mature seeds a thick cuticular film covering the entire outer surface of the endosperm. This seed cuticle is defective in cutin-deficient bodyguard1 seeds, which is associated with alterations in endospermic permeability. Furthermore, mutants affected in cutin biosynthesis display low seed dormancy and viability levels, which correlates with higher levels of seed lipid oxidative stress. Upon seed imbibition cutin biosynthesis genes are essential to prevent endosperm cellular expansion and testa rupture in response to low GA synthesis. Taken together, our findings suggest that in the course of land plant evolution cuticular structures were co-opted to achieve key physiological seed properties.