| 1. |
- Czernekova, Michaela, et al.
(author)
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A comparative ultrastructure study of storage cells in the eutardigrade Richtersius coronifer in the hydrated state and after desiccation and heating stress
- 2018
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In: PLOS ONE. - 1932-6203. ; 13:8
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Journal article (peer-reviewed)abstract
- Tardigrades represent an invertebrate phylum with no circulatory or respiratory system.Their body cavity is filled with free storage cells of the coelomocyte-type, which are responsible for important physiological functions. We report a study comparing the ultrastructure of storage cells in anhydrobiotic and hydrated specimens of the eutardigrade Richtersius coronifer. We also analysed the effect of temperature stress on storage cell structure. Firstly, we verified two types of ultrastructurally different storage cells, which differ in cellular organelle complexity, amount and content of reserve material and connection to oogenetic stage. Type I cells were found to differ ultrastructurally depending on the oogenetic stage of the animal. The main function of these cells is energy storage. Storage cells of Type I were also observed in the single male that was found among the analysed specimens. The second cell type, Type II, found only in females, represents young undifferentiated cells, possibly stem cells. The two types of cells also differ with respect to the presence of nucleolar vacuoles,which are related to oogenetic stages and to changes in nucleolic activity during oogenesis. Secondly, this study revealed that storage cells are not ultrastructurally affected by six months of desiccation or by heating following this desiccation period. However, heating of the desiccated animals (tuns) tended to reduce animal survival, indicating that longterm desiccation makes these animals more vulnerable to heat stress. We confirmed the degradative pathways during the rehydration process after desiccation and heat stress. Our study is the first to document two ultrastructurally different types of storage cells in tardigrades and reveals new perspectives for further studies of tardigrade storage cells.
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| 2. |
- Czernekova, Michaela, et al.
(author)
-
A comparative ultrastructure study of storage cells in the eutardigrade Richtersius coronifer in the hydrated state and after desiccation and heating stress
- 2018
-
In: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 13:8
-
Journal article (peer-reviewed)abstract
- Tardigrades represent an invertebrate phylum with no circulatory or respiratory system.Their body cavity is filled with free storage cells of the coelomocyte-type, which are responsible for important physiological functions. We report a study comparing the ultrastructure of storage cells in anhydrobiotic and hydrated specimens of the eutardigrade Richtersius coronifer. We also analysed the effect of temperature stress on storage cell structure. Firstly, we verified two types of ultrastructurally different storage cells, which differ in cellular organelle complexity, amount and content of reserve material and connection to oogenetic stage. Type I cells were found to differ ultrastructurally depending on the oogenetic stage of the animal. The main function of these cells is energy storage. Storage cells of Type I were also observed in the single male that was found among the analysed specimens. The second cell type, Type II, found only in females, represents young undifferentiated cells, possibly stem cells. The two types of cells also differ with respect to the presence of nucleolar vacuoles,which are related to oogenetic stages and to changes in nucleolic activity during oogenesis. Secondly, this study revealed that storage cells are not ultrastructurally affected by six months of desiccation or by heating following this desiccation period. However, heating of the desiccated animals (tuns) tended to reduce animal survival, indicating that longterm desiccation makes these animals more vulnerable to heat stress. We confirmed the degradative pathways during the rehydration process after desiccation and heat stress. Our study is the first to document two ultrastructurally different types of storage cells in tardigrades and reveals new perspectives for further studies of tardigrade storage cells.
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| 3. |
- Czernekova, Michaela, et al.
(author)
-
The structure of the desiccated Richtersius coronifer (Richters, 1903)
- 2017
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In: Protoplasma. - 0033-183X .- 1615-6102. ; 254:3, s. 1367-1377
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Journal article (peer-reviewed)abstract
- Tun formation is an essential morphological adaptation for entering the anhydrobiotic state in tardigrades, but its internal structure has rarely been investigated. We present the structure and ultrastructure of organs and cells in desiccated Richtersius coronifer by transmission and scanning electron microscopy, confocal microscopy, and histochemical methods. A 3D reconstruction of the body organization of the tun stage is also presented. The tun formation during anhydrobiosis of tardigrades is a process of anterior-posterior body contraction, which relocates some organs such as the pharyngeal bulb. The cuticle is composed of epicuticle, intracuticle and procuticle; flocculent coat; and trilaminate layer. Moulting does not seem to restrict the tun formation, as evidenced from tardigrade tuns that were in the process of moulting. The storage cells of desiccated specimens filled up the free inner space and surrounded internal organs, such as the ovary and digestive system, which were contracted. All cells (epidermal cells, storage cells, ovary cells, cells of the digestive system) underwent shrinkage, and their cytoplasm was electron dense. Lipids and polysaccharides dominated among reserve material of storage cells, while the amount of protein was small. The basic morphology of specific cell types and organelles did not differ between active and anhydrobiotic R. coronifer.
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| 4. |
- Czernekova, Michaela, et al.
(author)
-
The structure of the desiccated Richtersius coronifer (Richters, 1903)
- 2017
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In: Protoplasma. - : Springer-Verlag Wien. - 0033-183X .- 1615-6102. ; 254:3, s. 1367-1377
-
Journal article (peer-reviewed)abstract
- Tun formation is an essential morphological adaptation for entering the anhydrobiotic state in tardigrades, but its internal structure has rarely been investigated. We present the structure and ultrastructure of organs and cells in desiccated Richtersius coronifer by transmission and scanning electron microscopy, confocal microscopy, and histochemical methods. A 3D reconstruction of the body organization of the tun stage is also presented. The tun formation during anhydrobiosis of tardigrades is a process of anterior-posterior body contraction, which relocates some organs such as the pharyngeal bulb. The cuticle is composed of epicuticle, intracuticle and procuticle; flocculent coat; and trilaminate layer. Moulting does not seem to restrict the tun formation, as evidenced from tardigrade tuns that were in the process of moulting. The storage cells of desiccated specimens filled up the free inner space and surrounded internal organs, such as the ovary and digestive system, which were contracted. All cells (epidermal cells, storage cells, ovary cells, cells of the digestive system) underwent shrinkage, and their cytoplasm was electron dense. Lipids and polysaccharides dominated among reserve material of storage cells, while the amount of protein was small. The basic morphology of specific cell types and organelles did not differ between active and anhydrobiotic R. coronifer.
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| 5. |
- Czernekova, Michaela, et al.
(author)
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Ultrastructure and 3D reconstruction of the tun in Richtersius coronifer (Richters, 1903)
- 2016
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Conference paper (peer-reviewed)abstract
- Anhydrobiosis is one of the types of cryptobiosis that is caused by lack of water (desiccation). Formation of a tun seems to be the most important morphological adaptation for entering anhydrobiotic state. During this process the tardigrade body undergo anterior-posterior contraction that causes relocation of some organs such as the pharyngeal bulb. The tun wall of Richtersius coronifer (Eutardigrada, Macrobiotidae) was composed of multilayered cuticle and epidermis. The epidermis consisted of the single squamous epithelium whose cells were shrunken whereas the cuticle was composed of epi-, intra- and procuticle, flocculent coat and trilaminate layer. The storage cells of desiccated specimens filled up free inner space and surrounded the internal organs (ovary, digestive system) that were contracted. All cells of the body underwent shrinking and their metabolism was arrested. The cytoplasm of all cells was electron dense but the basic morphology of cells and organelles did not differ between active and anhydrobiotic animals. The structure and the ultrastructure of the desiccated Richtersius coronifer have been described with light and confocal microscopy as well as transmission and scanning electron microscopy. 3D reconstruction of tun based on the series of semi-thin sections was prepared with IMARIS 8.2 software (Bitplane).
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| 6. |
- Czernekova, Michaela, et al.
(author)
-
Ultrastructure and 3D reconstruction of the tun in Richtersius coronifer (Richters, 1903)
- 2016
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Conference paper (other academic/artistic)abstract
- Anhydrobiosis is one of the types of cryptobiosis that is caused by lack of water (desiccation). Formation of a tun seems to be the most important morphological adaptation for entering anhydrobiotic state. During this process the tardigrade body undergo anterior-posterior contraction that causes relocation of some organs such as the pharyngeal bulb. The tun wall of Richtersius coronifer (Eutardigrada, Macrobiotidae) was composed of multilayered cuticle and epidermis. The epidermis consisted of the single squamous epithelium whose cells were shrunken whereas the cuticle was composed of epi-, intra- and procuticle, flocculent coat and trilaminate layer. The storage cells of desiccated specimens filled up free inner space and surrounded the internal organs (ovary, digestive system) that were contracted. All cells of the body underwent shrinking and their metabolism was arrested. The cytoplasm of all cells was electron dense but the basic morphology of cells and organelles did not differ between active and anhydrobiotic animals. The structure and the ultrastructure of the desiccated Richtersius coronifer have been described with light and confocal microscopy as well as transmission and scanning electron microscopy. 3D reconstruction of tun based on the series of semi-thin sections was prepared with IMARIS 8.2 software (Bitplane).
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| 7. |
- Katsoularis, Ioannis, 1986-, et al.
(author)
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Risk of arrhythmias following COVID-19 : nationwide self-controlled case series and matched cohort study
- 2023
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In: European Heart Journal Open. - : Oxford University Press. - 2752-4191. ; 3:6
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Journal article (peer-reviewed)abstract
- Aims: COVID-19 increases the risk of cardiovascular disease, especially thrombotic complications. There is less knowledge on the risk of arrhythmias after COVID-19. In this study, we aimed to quantify the risk of arrhythmias following COVID-19.Methods and Results: This study was based on national register data on all individuals in Sweden who tested positive for SARS-CoV-2 between 1 February 2020 and 25 May 2021. The outcome was incident cardiac arrhythmias, defined as international classification of diseases (10th revision) codes in the registers as follows: atrial arrhythmias; paroxysmal supraventricular tachycardias; bradyarrhythmias; and ventricular arrhythmias. A self-controlled case series study and a matched cohort study, using conditional Poisson regression, were performed to determine the incidence rate ratio and risk ratio, respectively, for an arrhythmia event following COVID-19.A total of 1 057 174 exposed (COVID-19) individuals were included in the study as well as 4 074 844 matched unexposed individuals. The incidence rate ratio of atrial tachycardias, paroxysmal supraventricular tachycardias, and bradyarrhythmias was significantly increased up to 60, 180, and 14 days after COVID-19, respectively. In the matched cohort study, the risk ratio during Days 1–30 following COVID-19/index date was 12.28 (10.79–13.96), 5.26 (3.74–7.42), and 3.36 (2.42–4.68), respectively, for the three outcomes. The risks were generally higher in older individuals, in unvaccinated individuals, and in individuals with more severe COVID-19. The risk of ventricular arrhythmias was not increased.1 057 174 exposed (COVID-19) individuals were included in the study as well as 4 074 844 matched unexposed individuals. The incidence rate ratio of atrial tachycardias, paroxysmal supraventricular tachycardias and bradyarrhythmias was significantly increased up to 60, 180 and 14 days after COVID-19, respectively. In the matched cohort study, the risk ratio during day 1-30 following COVID-19/index date was 12.28 (10.79-13.96), 5.26 (3.74-7.42) and 3.36 (2.42-4.68), respectively for the three outcomes. The risks were generally higher in older individuals, unvaccinated individuals and in individuals with more severe COVID-19. The risk of ventricular arrhythmias was not increased.Conclusion: There is an increased risk of cardiac arrhythmias following COVID-19, and particularly increased in elderly vulnerable individuals, as well as in individuals with severe COVID-19.
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| 8. |
- Katsoularis, Ioannis, 1986-, et al.
(author)
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Risk of atrial tachycardias after covid-19 : nationwide self-controlled cases series and matched cohort study
- 2023
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In: European Heart Journal. - : Oxford University Press. - 0195-668X .- 1522-9645. ; 44:Suppl. 2
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Journal article (peer-reviewed)abstract
- Background: COVID-19 is a multiorgan disease. We previously identified COVID-19 as a risk factor for myocardial infarction, stroke (1), venous thromboembolism and bleeding (2). Less evidence exists on the risk of arrhythmias after COVID-19. Previous studies included mainly hospitalized patients with severe COVID-19, and there are no nationwide studies published.Purpose: The aim of this study was to estimate the risk of atrial tachycardias (atrial fibrillation and atrial flutter) following COVID-19, including all individuals tested positive for SARS-CoV-2 in Sweden, regardless of disease severity.Method: COVID-19 has been a notifiable disease in Sweden. All individuals in Sweden who were tested positive for SARS-CoV-2 between February 1, 2020 and May 25, 2021 were included in the study. We identified four control individuals for each COVID-19 individual matched on age, sex, and county of residence. Using Personal Identification Numbers, we cross-linked data from national registries: COVID-19 registry; Inpatient and Outpatient Registry; Cause of Death Registry; Prescribed Pharmaceutical Registry and Intensive Care Registry. Outcomes are cardiovascular events, defined using ICD-10 diagnosis codes for atrial fibrillation and atrial flutter in the registries. We performed a ‘’first-ever event’’ analysis, i.e., we excluded individuals with events before the study period. The self-controlled case series (SCCS) method was used to determine the incidence rate ratio (IRR) of a first atrial tachycardia during the risk periods 1-7, 8-14, 15-30, 31-60, 61-90, and 91-180 days after COVID-19. In the matched cohort study (MCS), Poisson regression was performed to calculate the risk ratio (RR) of a first arrhythmia event in the risk period 1-30 days following COVID-19, after adjusting for the effect of confounders, such as cardiac disease, treatment with antiarrhythmics, comorbidities and vaccination status.Results: 1 057 174 cases and 4 074 844 controls were included in the study. In the SCCS, the risk of first atrial tachycardia was significantly increased up to 60 days following COVID-19. Specifically, during days 1-7 and 8-14 post-COVID-19 the IRRs were approximately 12 and 10 respectively. Similarly, in the MCS the RR for the first atrial tachycardia during day 1-30 post-COVID-19 was approximately 11. The risks were higher in patients with more severe COVID-19; and during the first pandemic wave compared to the second and third wave.Conclusions: This study suggests that COVID-19 is a risk factor for atrial tachycardias, based on information obtained on all people who tested positive for SARS-CoV-2 in Sweden, regardless of disease severity. These results could impact recommendations on diagnostic and prophylactic strategies against atrial tachycardias after COVID-19. The importance of preventive strategies, such as risk factor control; vaccination to prevent severe COVID-19; and early review of high-risk individuals after COVID-19, is indicated.
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| 9. |
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