Key message Dehydration and cryo-stress (2196°C) caused a greater increase in the DNA methylation of embryonic axes (EAs) of beech seeds (tolerant to both stresses) than in EAs of oak (sensitive to both stresses). Simultaneously, in vitro survival of cryopreserved beech EAs was also significantly higher than in those of oak. Abstract DNA methylation plays a key role in the regulation of growth and differentiation in plants. The present study focused on global DNA methylation of embryonic axes (EAs) isolated from the seeds of pedunculate oak (Quercus robur L.) and European beech (Fagus sylvatica L.) after cryopreservation. Oak seeds can be labeled recalcitrant, i.e., sensitive to dehydration, while beech seeds fall under the suborthodox category, i.e., tolerant to dehydration. DNA methylation was determined using a specific antibody directed at the methylated cytosine in CpG dinucleotides. The analysis was carried out on DNA isolated from EA tissues and subjected to (1) dehydration (control), (2) a combination of dehydration and plant vitrification solution (PVS3) and (3) dehydration with vitrification PVS3, and rapid cooling in liquid nitrogen (LN 2 , -196°C) at a cooling rate of 32°C s -1 . Such treatments induced global DNA methylation primarily in tolerant EAs from F. sylvatica seeds. The level of global DNA methylation in this material was 30 % higher than in the control, i.e., dehydrated (not frozen) beech EAs. The same treatment in oak EAs did not evoke such changes. After 120 days of tissue growth, we observed substantially more DNA demethylation in the beech tissues after cryopreservation in LN 2 than in the controls or in tissues subjected to vitrification but not cryopreservation. Information on the global level of DNA methylation can be useful in monitoring procedures aimed at increasing the rate of recovery of EAs following cryopreservation.
Some epidemiological data and pathophysiological evidence suggest similarities and connection of two amyloidoses: diabetes mellitus type 2, (DM2) (non-insulin dependent diabetes mellitus, NIDDM) and Alzheimer's disease (AD). What they have in common is insulin resistance, neurodegeneration, development and progression of dementia, and the fact that in the course of both diseases fibrillar aggregates of specific proteins are accumulated in affected organs. What is more, experimental evidence also supports the hypothesis that small prefibrillar aggregates that emerge prior to the appearance of mature fibrils are responsible for a key step in development and cytotoxicity of both diseases. They also have similar pathogenic effects. Both peptides possess the common receptor AMY3. More and more evidence is accumulating that key cell regulation processes are similar for both diseases as well. The question is raised: can Alzheimer be a new form of diabetes disease?
Various peptides products of enzymatic cleavage of key for Alzheimer’s disease Amyloid Precursor Protein (APP) are well known, but still are matter of scientific debate. The Aβ type products are especially challenging for experimental and medical research. This paper outlines several, still poorly known, biological and medical processes such as peptides biology, i.e., formation, biodistribution, translocation, transport and finally removal from brain compartments and body fluids like Intracellular Fluid (ICF), Cerebrospinal Fluid (CSF), Interstitial Fluid (ISF), blood serum or urine. In addition, the following studies concerning AD patients might prove challenging and simultaneously promising: peptides translocation through Blood-Brain – Barrier (BBB) and Blood–Cerebrospinal Fluid Barrier (BCSFB) and their removal from the brain according to a new concept of glymphatic system; – diagnostic difficulties that stem from physico-chemical properties and the nature of proteins or fibrillating peptides itself like low concentration, short half-live and from experimental-technical problems as well like high adsorption or low solubility of Aβ, tau or amylin. The study of diagnostic parameters is very important, as it may better reflect early changes before the disease develops; one such parameter is the Aβ42/Aβ40 ratio, or the ratio with the total tau concentration combination and other new biomarkers like Aβ1-38; other factors include oxidative stress and inflammation process proteins, complement factor H, alpha-2-macroglobulin, or clusterin. The study of various forms of pathological amyloid deposits that emerge in different but specific brain regions AD patients seems to be crucial as well. The composition of the first initial pathological, pre-fibrillating monomers of fibrillating peptides and their role in AD development and disease progression have been described as well. They are even more challenging for science and simultaneously might be more promising in early diagnosis for AD patients. As always in science, research leads to endless discoveries and further inquiry. Fundamental problems in this field most probably are still far from being definitively comprehended, and multiple crucial questions await better answers. What we really need is to study more and deeper into this matter.
Various and different peptides products resulting from enzymatic protein cleavage of Amyloid Precursor Proteins (APP) are the main agents in the pathophysiology of Alzheimer's disease (AD). Although relatively well-known, they still arouse interest leading to further intense and wide-ranging research. Their biology and physico-chemical properties still are challenging for basic, experimental research and are matter of scientific debate. The APP itself and its functions are still somewhat enigmatic and therefore it is also called the All Purpose Protein. Apart from well known amyloidogenic and antiamyloidogenic (non-amyloidogenic) enzymatic cleavage pathways of APP protein this paper deals with issues connected with other, alternative pathways that seem to be interesting and important as well. They lead to other than Aβ forms of peptide products such as: N-APP, N-terminally cleavage products of APP (N-terminally truncated ) Aβ', γ- secretase-independent pathway products that involve concerted cleavages of APP by α- and β-secretase or products that emerge after caspase activity. Presence of all these peptides in CSF, ISF, blood serum and urine of the AD patients is crucial for successful diagnosis, giving rise to hope of their better detection and potentially better treatment of AD. Therefore, newly discovered products of the AβT domain cleavage (Aβ total i.e. full fibrillating domain of APP), Aβ type products and other peptides because of their biology and physico-chemical properties are very intriguing and deserve further experimental research. On the other hand after better recognition and better understanding their biology they might be enormously useful in the future for diagnosis and therapy for example Alzheimer's disease.
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