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SUMMARY: Among flowering plants, genome size varies remarkably, by >2200‐fold, and this variation depends on the loss and gain of noncoding DNA sequences that form distinct heterochromatin complexes during interphase. In plants with giant genomes, most chromatin remains condensed during interphase, forming a dense network of heterochromatin threads called interphase chromonemata. Using super‐resolution light and electron microscopy, we studied the ultrastructure of chromonemata during and after replication in root meristem nuclei of Nigella damascena L. During S‐phase, heterochromatin undergoes transient decondensation locally at DNA replication sites. Due to the abundance of heterochromatin, the replication leads to a robust disassembly of the chromonema meshwork and a general reorganization of the nuclear morphology visible even by conventional light microscopy. After replication, heterochromatin recondenses, restoring the chromonema structure. Thus, we show that heterochromatin replication in interphase nuclei of giant‐genome plants induces a global nuclear reorganization. Significant Statement: The replication of giant plant genomes requires a global chromatin reorganization in interphase nuclei. [ABSTRACT FROM AUTHOR]

Patients infected with human immunodeficiency virus‐1 (HIV‐1) have an increased incidence of B‐cell lymphoma, even though HIV‐1 does not infect B cells. The development of B‐cell lymphomas appears to be related to the action of the HIV‐1 transactivator protein (Tat), which is released from HIV‐infected cells and penetrates uninfected B cells, affecting host cell gene expression. Upon chronic HIV‐1 infection, Tat acts on the cells for a long time, probably allowing the cells to adapt to the presence of the viral protein. The aim of this work was to identify and study the mechanism of adaptation of cells to prolonged (chronic) exposure to HIV‐1 Tat. We performed a comparative analysis of cells expressing Tat under the action of either an inducible promoter or a constitutive promoter, allowing us to model acute and chronic Tat effects, respectively. We found that the acute action of Tat leads to the suppression of cell proliferation, probably due to the downregulation of genes associated with replication and protein synthesis. In the case of chronic action of Tat, cell proliferation was restored and the expression of genes associated with the implementation of protective (antiviral) functions of the cell was increased. Analysis using proteasome inhibitors showed that in the case of chronic action, intense Tat proteolysis occurred, which could be the main mechanism of B‐cell adaptation. Thus, B cells have a powerful mechanism to adapt to the entry of HIV‐1 Tat, the efficiency of which may determine the frequency of lymphomagenesis in HIV‐1‐infected patients. [ABSTRACT FROM AUTHOR]

Simple Summary: Our study identified specific conditions for optimal cell viability in enzymatic dissociation protocols across various endocrine tumors. For adrenal medullary tumors, the critical factor was the dissociation time, with 20 min of incubation proving most effective. In the case of adrenocortical tumors, using Collagenase IV or the MTDK enzyme kit, along with a post-dissociation procedure involving a debris removal kit, resulted in higher cell viability. No significant patterns were observed for thyroid carcinomas and pituitary neuroendocrine tumors, indicating that the effectiveness of dissociation protocols may vary significantly depending on the tissue type and its unique morphological characteristics. These findings underscore the importance of tailored dissociation protocols for different tumor types to ensure optimal outcomes in cell isolation processes. The enzymatic dissociation of human solid tissues is a critical process for disaggregating extracellular matrix and the isolation of individual cells for various applications, including the immortalizing primary cells, creating novel cell lines, and performing flow cytometry and its specialized type, FACS, as well as conducting scRNA-seq studies. Tissue dissociation procedures should yield intact, highly viable single cells that preserve morphology and cell surface markers. However, endocrine tissues, such as adrenal gland tumors, thyroid carcinomas, and pituitary neuroendocrine tumors, present unique challenges due to their complex tissue organization and morphological features. Our study conducted a morphological examination of these tissues, highlighting the intricate structures and secondary degenerative changes that complicate the dissociation process. We investigated the effects of various dissociation parameters, including the types of enzymes, incubation duration, and post-dissociation purification procedures, such as debris removal and nontarget blood cell lysis, on the viability of cells derived from different tumor types. The findings emphasize the importance of optimizing tissue digestion protocols to preserve cell viability and integrity, ensuring reliable outcomes for downstream analyses. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), the virus that causes coronavirus disease 2019 (COVID‐19), has led to an unprecedented public health emergency worldwide. While common cold symptoms are observed in mild cases, COVID‐19 is accompanied by multiorgan failure in severe patients. Organ damage in COVID‐19 patients is partially associated with the indirect effects of SARS‐CoV‐2 infection (e.g., systemic inflammation, hypoxic‐ischemic damage, coagulopathy), but early processes in COVID‐19 patients that trigger a chain of indirect effects are connected with the direct infection of cells by the virus. To understand the virus transmission routes and the reasons for the wide‐spectrum of complications and severe outcomes of COVID‐19, it is important to identify the cells targeted by SARS‐CoV‐2. This review summarizes the major steps of investigation and the most recent findings regarding SARS‐CoV‐2 cellular tropism and the possible connection between the early stages of infection and multiorgan failure in COVID‐19. The SARS‐CoV‐2 pandemic is the first epidemic in which data extracted from single‐cell RNA‐seq (scRNA‐seq) gene expression data sets have been widely used to predict cellular tropism. The analysis presented here indicates that the SARS‐CoV‐2 cellular tropism predictions are accurate enough for estimating the potential susceptibility of different cells to SARS‐CoV‐2 infection; however, it appears that not all susceptible cells may be infected in patients with COVID‐19. [ABSTRACT FROM AUTHOR]

Lung inflammation, pneumonia, is an acute respiratory disease of varying etiology that has recently drawn much attention during the COVID-19 pandemic as lungs are among the main targets for SARS-CoV-2. Multiple other etiological agents are associated with pneumonias. Here, we describe a newly-recognized pathology, namely abnormal lipid depositions in the lungs of patients who died from COVID-19 as well as from non-COVID-19 pneumonias. Our analysis of both semi-thin and Sudan III-stained lung specimens revealed extracellular and intracellular lipid depositions irrespective of the pneumonia etiology. Most notably, lipid depositions were located within vessels adjacent to inflamed regions, where they apparently interfere with the blood flow. Structurally, the lipid droplets in the inflamed lung tissue were homogeneous and lacked outer membranes as assessed by electron microscopy. Morphometric analysis of lipid droplet deposition area allowed us to distinguish the non-pneumonia control lung specimens from the macroscopically intact area of the pneumonia lung and from the inflamed area of the pneumonia lung. Our measurements revealed a gradient of lipid deposition towards the inflamed region. The pattern of lipid distribution proved universal for all pneumonias. Finally, lipid metabolism in the lung tissue was assessed by the fatty acid analysis and by expression of genes involved in lipid turnover. Chromato-mass spectrometry revealed that unsaturated fatty acid content was elevated at inflammation sites compared to that in control non-inflamed lung tissue from the same individual. The expression of genes involved in lipid metabolism was altered in pneumonia, as shown by qPCR and in silico RNA-seq analysis. Thus, pneumonias of various etiologies are associated with specific lipid abnormalities; therefore, lipid metabolism can be considered to be a target for new therapeutic strategies.