Too rigid to fold: Carotenoid-dependent decrease in thylakoid fluidity hampers the formation of chloroplast grana.

In chloroplasts of land plants, the thylakoid network is organized into appressed regions called grana stacks and loosely arranged parallel stroma thylakoids. Many factors determining such intricate structural arrangements have been identified so far, including various thylakoid-embedded proteins, and polar lipids that build the thylakoid matrix. Although carotenoids are important components of proteins and the lipid phase of chloroplast membranes, their role in determining the thylakoid network structure remains elusive. We studied 2D and 3D thylakoid network organization in carotenoid-deficient mutants (ccr1-1, lut5-1, szl1-1, and szl1-1npq1-2) of Arabidopsis (Arabidopsis thaliana) to reveal the structural role of carotenoids in the formation and dynamics of the internal chloroplast membrane system. The most significant structural aberrations took place in chloroplasts of the szl1-1 and szl1-1npq1-2 plants. Increased lutein/carotene ratio in these mutants impaired the formation of grana, resulting in a significant decrease in the number of thylakoids used to build a particular stack. Further, combined biochemical and biophysical analyses revealed that hampered grana folding was related to decreased thylakoid membrane fluidity and significant changes in the amount, organization, and phosphorylation status of photosystem (PS) II (PSII) supercomplexes in the szl1-1 and szl1-1npq1-2 plants. Such changes resulted from a synergistic effect of lutein overaccumulation in the lipid matrix and a decreased level of carotenes bound with PS core complexes. Moreover, more rigid membrane in the lutein overaccumulating plants led to binding of Rubisco to the thylakoid surface, additionally providing steric hindrance for the dynamic changes in the level of membrane folding.

Primary hypertrophic osteoarthropathy - a rare cause of pain and arthritis in children. Description of 5 cases.

Primary hypertrophic osteoarthropathy (PHOA) is a very rare disease. The typical triad of symptoms, i.e. digital clubbing, periosteal bone formation with bone and joint deformities and skin hypertrophy, may be accompanied by other specific conditions. In the majority of patients, the picture of the disease is incomplete. The dominant clinical symptom may be osteoarticular complaints. Moreover, the final confirmation of the diagnosis of the primary form of hypertrophic osteoarthropathy requires the analysis of much more frequent secondary causes of the disease. Diagnosing primary osteoarthropathy in children is particularly difficult. Some children report joint pain before the onset of the other symptoms of osteoarthropathy, while the physical and imaging examinations show features of arthritis. This can lead to misdiagnoses including the diagnosis of juvenile idiopathic arthritis (JIA) and the unnecessary use of immunosuppressive treatment. The present description of five patients from the Paediatric Rheumatology Department indicates diagnostic difficulties in children with PHOA. All of them were examined due to pain and features of arthritis. We observed an incomplete clinical picture of the disease. One patient required a revision of the previous diagnosis of JIA and discontinuation of ineffective treatment with disease-modifying antirheumatic drugs (DMARDs). PHOA should always be considered in the differential diagnosis of arthritis in children, due to the slow and often atypical development of symptoms, including the presence of pain and arthritis as the predominant symptom of the disease.

The Arabidopsis Accessions Selection Is Crucial: Insight from Photosynthetic Studies.

Natural genetic variation in photosynthesis is strictly associated with the remarkable adaptive plasticity observed amongst Arabidopsis thaliana accessions derived from environmentally distinct regions. Exploration of the characteristic features of the photosynthetic machinery could reveal the regulatory mechanisms underlying those traits. In this study, we performed a detailed characterisation and comparison of photosynthesis performance and spectral properties of the photosynthetic apparatus in the following selected Arabidopsis thaliana accessions commonly used in laboratories as background lines: Col-0, Col-1, Col-2, Col-8, Ler-0, and Ws-2. The main focus was to distinguish the characteristic disparities for every accession in photosynthetic efficiency that could be accountable for their remarkable plasticity to adapt. The biophysical and biochemical analysis of the thylakoid membranes in control conditions revealed differences in lipid-to-protein contribution, Chlorophyll-to-Carotenoid ratio (Chl/Car), and xanthophyll cycle pigment distribution among accessions. We presented that such changes led to disparities in the arrangement of the Chlorophyll-Protein complexes, the PSI/PSII ratio, and the lateral mobility of the thylakoid membrane, with the most significant aberrations detected in the Ler-0 and Ws-2 accessions. We concluded that selecting an accession suitable for specific research on the photosynthetic process is essential for optimising the experiment.

Bean and Pea Plastoglobules Change in Response to Chilling Stress.

Plastoglobules (PGs) might be characterised as microdomains of the thylakoid membrane that serve as a platform to recruit proteins and metabolites in their spatial proximity in order to facilitate metabolic channelling or signal transduction. This study provides new insight into changes in PGs isolated from two plant species with different responses to chilling stress, namely chilling-tolerant pea (Pisum sativum) and chilling-sensitive bean (Phaseolus coccineus). Using multiple analytical methods, such as high-performance liquid chromatography and visualisation techniques including transmission electron microscopy and atomic force microscopy, we determined changes in PGs' biochemical and biophysical characteristics as a function of chilling stress. Some of the observed alterations occurred in both studied plant species, such as increased particle size and plastoquinone-9 content, while others were more typical of a particular type of response to chilling stress. Additionally, PGs of first green leaves were examined to highlight differences at this stage of development. Observed changes appear to be a dynamic response to the demands of photosynthetic membranes under stress conditions.

Compensation Mechanism of the Photosynthetic Apparatus in Arabidopsis thaliana ch1 Mutants.

The origin of chlorophyll b deficiency is a mutation (ch1) in chlorophyllide a oxygenase (CAO), the enzyme responsible for Chl b synthesis. Regulation of Chl b synthesis is essential for understanding the mechanism of plant acclimation to various conditions. Therefore, the main aim of this study was to find the strategy in plants for compensation of low chlorophyll content by characterizing and comparing the performance and spectral properties of the photosynthetic apparatus related to the lipid and protein composition in four selected Arabidopsis ch1 mutants and two Arabidopsis ecotypes. Mutation in different loci of the CAO gene, viz., NW41, ch1.1, ch1.2 and ch1.3, manifested itself in a distinct chlorina phenotype, pigment and photosynthetic protein composition. Changes in the CAO mRNA levels and chlorophyllide a (Chlide a) content in ecotypes and ch1 mutants indicated their significant role in the adjustment mechanism of the photosynthetic apparatus to low-light conditions. Exposure of mutants with a lower chlorophyll b content to short-term (1LL) and long-term low-light stress (10LL) enabled showing a shift in the structure of the PSI and PSII complexes via spectral analysis and the thylakoid composition studies. We demonstrated that both ecotypes, Col-1 and Ler-0, reacted to high-light (HL) conditions in a way remarkably resembling the response of ch1 mutants to normal (NL) conditions. We also presented possible ways of regulating the conversion of chlorophyll a to b depending on the type of light stress conditions.

Plastoglobules - Underestimated Components of the Plant Cell / Plastoglobule ­ niedocenione skladniki komórki roslinnej.

Plastoglobules (PGs), as important components of plastids, are involved in many stages of their development: from the chloroplast biogenesis through the chloroplast-chromoplast transformations, and finally in the process of gerontoplast formation. The unique protein and lipid composition of these structures, depending on their location, suggests that PGs are both a reservoir of spare materials and a center for many metabolic reactions. Plastoglobules play an active role in the metabolism of prenylquinones, carotenoids, and jasmonic acid, and are responsible for recycling of the thylakoid disintegration products. Their direct connection with the thylakoids allows for tight relationships between these two structures and redistribution of materials, which contributes to PGs' role in response to stressful conditions. Moreover, strongly hydrophobic nature of plastoglobules, their specific proteome and a sufficiently simple isolation procedure create extraordinary possibilities of their application in plant biotechnology.

Galactolipid deficiency disturbs spatial arrangement of the thylakoid network in Arabidopsis thaliana plants.

The chloroplast thylakoid network is a dynamic structure which, through possible rearrangements, plays a crucial role in regulation of photosynthesis. Although the importance of the main components of the thylakoid membrane matrix, galactolipids, in the formation of the network of internal plastid membrane was found before, the structural role of monogalactosyldiacylglycerol (MGDG) and digalactosylidacylglycerol (DGDG) is still largely unknown. We elucidated detailed structural modifications of the thylakoid membrane system in Arabidopsis thaliana MGDG- and DGDG-deficient mutants. An altered MGDG/DGDG ratio was structurally reflected by formation of smaller grana, local changes in grana stacking repeat distance, and significant changes in the spatial organization of the thylakoid network compared with wild-type plants. The decrease of the MGDG level impaired the formation of the typical helical grana structure and resulted in a 'helical-dichotomic' arrangement. DGDG deficiency did not affect spatial grana organization but changed the shape of the thylakoid membrane network in situ from lens like into a flattened shape. Such structural disturbances were accompanied by altered composition of carotenoid and chlorophyll-protein complexes, which eventually led to the decreased photosynthetic efficiency of MGDG- and DGDG-deficient plants.

Ultrasound image of healthy skin in newborns in the first 24 hours of life.

INTRODUCTION: Ultrasound imaging is a safe, repeatable and easily available imaging procedure. Based on these qualities, it may become a useful tool for skin assessment in newborns. Aims: The aim of the study was to evaluate the usefulness of high-frequency ultrasound imaging for neonatal skin assessment. Another aim was to identify differences in ultrasound features of the skin in newborns depending on the examination site, sex, age, birth weight, and arterial blood gas results. MATERIAL AND METHOD: A total of 72 newborns in the first 24 hours of life, without any skin lesions, were included in the study. All newborns underwent ultrasound skin examinations in three body sites (forearm, abdomen and thigh) during the first 24 hours of life. DermaMed Ultrasound Scanner with a 48 MHz probe was used for imaging. A total of three structures were identified in the ultrasound images: epidermal echo, dermis, and subcutaneous tissue. The study assessed the thickness of the epidermis and dermis, and the echogenicity of the dermis and subcutaneous tissue. Data were analysed to determine possible links with sex, post-conceptional age, body weight, birth route, and results of umbilical cord blood gas analysis. RESULTS: Depending on the body site examined, the mean epidermal thickness was 0.081 to 0.083 mm, while the mean thickness of the dermis ranged between 0.679 and 0.722 mm. The newborns with higher birth weights were shown to have a thicker epidermis regardless of the examined site [R (correlation coefficient) for the forearm: 0.47 (p <0.001), abdomen: 0.53 (p <0.001), thigh: 0.48 (p <0.001)]. A positive correlation was found between epidermal and dermal thickness (R = 0.34; p = 0.004), but a comparison of the three examined sites revealed no significant differences in the thickness of the two structures. The sex of the newborn had no significant effect on the ultrasound features of the skin. None of the ultrasound parameters under study was found to correlate with the pH level in umbilical cord blood gas analysis. Subcutaneous oedema was detected in the examined sites in all the newborns studied. CONCLUSIONS: High-frequency ultrasound imaging may become a useful method for neonatal skin assessment, complementing existing diagnostic techniques for monitoring pathologically altered skin.

Dark-chilling induces substantial structural changes and modifies galactolipid and carotenoid composition during chloroplast biogenesis in cucumber (Cucumis sativus L.) cotyledons.

Plants in a temperate climate are often subject to different environmental factors, chilling stress among them, which influence the growth especially during early stages of plant development. Chloroplasts are one of the first organelles affected by the chilling stress. Therefore the proper biogenesis of chloroplasts in early stages of plant growth is crucial for undertaking the photosynthetic activity. In this paper, the analysis of the cotyledon chloroplast biogenesis at different levels of plastid organization was performed in cucumber, one of the most popular chilling sensitive crops. Influence of low temperature on the ultrastructure was manifested by partial recrystallization of the prolamellar body, the formation of elongated grana thylakoids and a change of the prolamellar body structure from the compacted "closed" type to a more loose "open" type. Structural changes are strongly correlated with galactolipid and carotenoid content. Substantial changes in the galactolipid and the carotenoid composition in dark-chilled plants, especially a decrease of the monogalactosyldiacylglycerol to digalactosyldiacylglycerol ratio (MGDG/DGDG) and an increased level of lutein, responsible for a decrease in membrane fluidity, were registered together with a slower adaptation to higher light intensity and an increased level of non-photochemical reactions. Changes in the grana thylakoid fluidity, of their structure and photosynthetic efficiency in developing chloroplasts of dark-chilled plants, without significant changes in the PSI/PSII ratio, could distort the balance of photosystem rearrangements and be one of the reasons of cucumber sensitivity to chilling.

Comparative in vitro study of calcium phosphate ceramics for their potency as scaffolds for tissue engineering.

BACKGROUND: Calcium phosphate ceramics have been widely considered as scaffolds for bone tissue engineering. Selection of the best support for cultured cells, crucial for tissue engineered systems, is still required. OBJECTIVE: We examined three types of calcium phosphate compounds: α-tricalcium phosphate - the most soluble one, carbonate hydroxyapatite - chemically the most similar to the bone mineral and biphasic calcium phosphate - with the best in vivo biocompatibility in order to select the best support for osteoblastic cells for tissue engineered systems. METHODS: Human osteoblasts were tested in direct contact with both dense samples and 3D scaffolds in either static or dynamic culture. Cell viability, cell spreading, osteogenic cell capacity, and extracellular matrix production were examined. RESULTS: The obtained data indicate that biphasic calcium phosphate is the optimal cell-supporting material. In addition, dynamic culture improved cell distribution in the scaffolds, enhanced production of the extracellular matrix and promoted cells osteogenic capacity. CONCLUSIONS: Biphasic calcium phosphate should be recommended as the most suitable matrix for osteogenic cells expansion and differentiation in tissue engineered systems.

Bone tissue engineering - a field for new medicinal products?

It was only in December 2008 that the European Union regulated the approval procedure for tissue engineered products (TEPs). Due to this regulation, TEP is classified as an advanced therapy medicinal product and as such may be recognized as a tool in pharmaceutical biotechnology. This paper gives a short review of the concept, the experimental evaluation and the clinical potency of tissue engineering (TE), with a particular focus on bone tissue engineered products. After a period of great enthusiasm about TE at the end of the 20th century a slight disappointment followed in the early 2000s. The review refers also to the continuously growing scientific interest, accompanied by the still modest representation of TEPs on the medical market. Some remarks are given on a bench-to-clinic road, including criticism concerning data originating from animal experiments. An attempt is made to foresee the still promising future of bone tissue engineered products (BTEPs) in practical use.