The short life of the Hoyle organ in cephalopods

Der Schlüpfvorgang aus dem Ei kann entweder durch Ausdehnung des Körpers und Kollaps der Eischalen erfolgen oder die Tiere verwenden mechanische Vorrichtungen (Eizähne oder spezielle Dornen) bzw. choriolytische Enzyme aus speziellen Schlüpfdrüsen. Bei den meisten untersuchten Cephalopoden ist eine derartige Drüse, das Hoyle Organ (HO), am hinteren Ende des Mantels zu finden. Das Organ ist als waagrechte Linie bei Oktopoden und als ankerförmige Struktur bei Dekapoden erkennbar. Es wird während der späten Embryonalentwicklung angelegt, synthetisiert Enzyme zum Auflösen der Eihüllen und wird nach dem Schlüpfen innerhalb weniger Tage abgebaut. Die intrazellulären Vorgänge während dieses Abbauprozesses sind bei Cephalopoden nur wenig untersucht, das unmittelbare Einsetzen nach dem Schlüpfen jedenfalls spricht für einen programmierten Zelltod. Diese Studie umfasst neun Arten der Ordnungen Sepiida, Sepiolida, Teuthida and Octopoda. Ziele dieser Studie sind vergleichende morphologische Untersuchungen des HO in Korrelation mit der Dicke der jeweiligen Eihülle und dem Schlüpfverhalten, die Charakterisierung der Stadien der Drüsenentwicklung und -reifung sowie die zellulären Vorgänge während des Organabbaus. Bei allen untersuchten Dekapoden konnte die Existenz eines ankerförmigen HO bestätigt werden, aber nur eine der untersuchten Oktopodenarten besitzt eine linienförmige Drüse, während bei den beiden anderen Arten keine entsprechenden Zellen nachgewiesen werden konnten. Der Abbau des HO erfolgt mittels programmiertem Zelltod (nekrotisch oder autophagisch) und ist innerhalb von ein bis zwei Tagen abgeschlossen. Die Ergebnisse bestätigen weitgehend eine Korrelation zwischen Eigröße, Schalendicke und Dimension des HO. Die rasche Rückbildung der Drüse erfolgt offensichtlich mit Hilfe von genetisch gesteuerten Zelltod-Mechanismen, obwohl eine klare Zuordnung wegen der überlappenden morphologischen Merkmale nicht immer möglich ist. Künftige molekularbiologische Analysen hinsichtlich spezifischer Zelltod-Mediator-Proteine und Genexpressionsmuster sind erforderlich, um das Verständnis für die Komplexität und Variabilität von Zelltod-Mechanismen bei Cephalopoden zu vertiefen.Animals release from their eggs by means of mechanical tools (egg teeth, hatching spine), body expansion or by chemical support of choriolytic enzymes synthesized in a hatching gland. Most observed cephalopods possess an appropriate gland on their posterior mantle pole, referred to as Hoyle organ (HO). It differs structurally between the octopods (line- shaped) and cuttlefishes and squids (anchor-shaped). The HO develops during late embryonic stages, synthesizes enzymes to weaken the egg shell and degrades after hatching within a few days. The degeneration process of the HO is far from being resolved but the rapid cellular degradation indicates a programmed cell death strategy. This study comprises nine coleoid species of the order Sepiida, Sepiolida, Teuthida and Octopoda. Main objectives are 1.) a comparison of the HO morphology in correlation with the respective egg encapsulation design and the hatching and pre-hatching behavior; 2.) to characterize and specify the HO development, maturation and degradative cell alterations after hatching. While all investigated decapodiform species have an anchor-shaped HO, only in one octopodiform species a hatching gland could be observed, whereas the other two lack this structure. The HO degradation is accomplished within 2 days by a type of necrotic cell death or autophagic cell death. The results mainly confirm a correlation between egg encapsulation and dimension of the gland. Contribution of triggered cell death mechanisms appear to be obvious for the observed species. However, a clear definition of cell death mode is difficult at this stage, since those processes are quite complex, dynamic and show overlapping characteristics. Future characterization of specific mediator proteins and gene expression pattern will help to point out the diversity of cell death strategies in cephalopods and fully understand the process of HO degradation

Inhibition of EIF2α Dephosphorylation Decreases Cell Viability and Synergizes with Standard-of-Care Chemotherapeutics in Head and Neck Squamous Cell Carcinoma

Drug resistance is a common cause of therapy failure in head and neck squamous cell carcinoma (HNSCC). One approach to tackling it is by targeting fundamental cellular processes, such as translation. The eukaryotic translation initiation factor 2α (EIF2α) is a key player in canonical translation initiation and integrates diverse stress signals; when phosphorylated, it curbs global protein synthesis. This study evaluates EIF2α expression and phosphorylation in HNSCC. A small-molecule inhibitor of EIF2α dephosphorylation, salubrinal, was tested in vitro, followed by viability assays, flow cytometry, and immunoblot analyses. Patient-derived 3D tumor spheres (PD3DS) were cultured with salubrinal and their viability assessed. Lastly, salubrinal was evaluated with standard-of-care chemotherapeutics. Our analysis of RNA and proteomics data shows elevated EIF2α expression in HNSCC. Immunohistochemical staining reveals increasing EIF2α abundance from premalignant lesions to invasive and metastatic carcinoma. In immunoblots from intraoperative samples, EIF2α expression and steady-state phosphorylation are higher in HNSCC than in neighboring normal tissue. Inhibition of EIF2α dephosphorylation decreases HNSCC cell viability and clonogenic survival and impairs the G1/S transition. Salubrinal also decreases the viability of PD3DS and acts synergistically with cisplatin, 5-fluorouracil, bleomycin, and proteasome inhibitors. Our results indicate that pharmacological inhibition of EIF2α dephosphorylation is a potential therapeutic strategy for HNSCC

No evidence for involvement of prothrombotic platelet receptor polymorphisms in acute coronary stent thrombosis

Polymorphisms of receptors involved in platelet adhesion and aggregation modulate platelet thrombogenicity and were found to predispose to premature arterial thromboses in individuals at risk. In our current study, we assessed the potential relevance of prothrombotic platelet receptor polymorphisms for the pathogenesis of acute coronary stent thrombosis. Comparing the genotype prevalences of respective polymorphisms in patients with acute coronary stent thrombosis and healthy control subjects, our data do not indicate an increased risk of carriers of prothrombotic variants of platelet receptors for this complication. Other factors such as the remodelling process and antiplatelet medication appear to be more relevant in this clinical setting. Along with our findings, screening for respective polymorphisms for risk assessment prior to coronary stenting is not indicated

Morphological characterization of the glandular system in the salamander Plethodon shermani (Caudata, Plethodontidae)

Amphibians have evolved a wide variety of mechanisms that provide a certain degree of protection against predators, including camouflage, tail autonomy, encounter behavior and noxious or toxic skin secretions. In addition to these strategies, some amphibians release a glue-like secretion onto the surface of their skin when threatened. While some information regarding the origin and production of these adhesive secretions is available for frogs such as Notaden bennetti, these aspects are only partially understood in salamanders. We contribute to an earlier study and provide additional information regarding the origin, production, and characterization of the adhesive secretion in the red-legged salamander (Plethodon shermani) at a microanatomical level. When stressed, this salamander secretes a milky, viscous liquid from its dorsal and ventral skin. This secretion is extremely adhesive and hardens within seconds upon exposure to air. This study describes two cutaneous gland types (mucous and granular) in the dorsal and ventral epithelial tissue that differ considerably in their secretory content. While the smaller mucous glands contains flocculent to granular material, mostly acidic glycoproteins, the granular glands synthesize various granules of differing size and density that consist of basic proteinaceous material. The results strongly indicate that the secretions of both gland types from the dorsal as well as the ventral side form the adhesive mucus in Plethodon shermani, consisting of basic and acidic glycoproteins, glycoconjugates with mannose and alpha-L-fucose residues as well as lipid components

Freeze Substitution Accelerated via Agitation: New Prospects for Ultrastructural Studies of Lichen Symbionts and Their Extracellular Matrix

(1) Background: Lichens, as an important part of the terrestrial ecosystem, attract the attention of various research disciplines. To elucidate their ultrastructure, transmission electron microscopy of resin-embedded samples is indispensable. Since most observations of lichen samples are generated via chemical fixation and processing at room temperature, they lack the rapid immobilization of live processes and are prone to preparation artefacts. To improve their preservation, cryoprocessing was tested in the past, but never widely implemented, not least because of an extremely lengthy protocol. (2) Methods: Here, we introduce an accelerated automated freeze substitution protocol with continuous agitation. Using the example of three lichen species, we demonstrate the preservation of the native state of algal photobionts and mycobionts in association with their extracellular matrix. (3) Results: We bring to attention the extent and the structural variability of the hyphae, the extracellular matrix and numerous crystallized metabolites. Our findings will encourage studies on transformation processes related to the compartmentation of lichen thalli. They include cryopreserved aspects of algal photobionts and observations of putative physiological relevance, such as the arrangement of numerous mitochondria within chloroplast pockets. (4) Conclusions: In summary, we present accelerated freeze substitution as a very useful tool for systematic studies of lichen ultrastructures

Freeze substitution accelerated via agitation: new prospects for ultrastructural studies of lichen symbionts and their extracellular matrix

2023 Descuento MDPI Slovak Research and Development Agency, contract No. APVV-21-0289 Slovak Grant Agency KEGA, contracts No. 008SPU-4/2023 and No. 009UPJŠ-4/2023 Field campaigns for the collection of C. gyrosa were financed by grants from the Spanish Ministry of Science and InnovationBackground: Lichens, as an important part of the terrestrial ecosystem, attract the attention of various research disciplines. To elucidate their ultrastructure, transmission electron microscopy of resin-embedded samples is indispensable. Since most observations of lichen samples are generated via chemical fixation and processing at room temperature, they lack the rapid immobilization of live processes and are prone to preparation artefacts. To improve their preservation, cryoprocessing was tested in the past, but never widely implemented, not least because of an extremely lengthy protocol. (2) Methods: Here, we introduce an accelerated automated freeze substitution protocol with continuous agitation. Using the example of three lichen species, we demonstrate the preservation of the native state of algal photobionts and mycobionts in association with their extracellular matrix. (3) Results: We bring to attention the extent and the structural variability of the hyphae, the extracellular matrix and numerous crystallized metabolites. Our findings will encourage studies on transformation processes related to the compartmentation of lichen thalli. They include cryopreserved aspects of algal photobionts and observations of putative physiological relevance, such as the arrangement of numerous mitochondria within chloroplast pockets. (4) Conclusions: In summary, we present accelerated freeze substitution as a very useful tool for systematic studies of lichen ultrastructures.Ministry of Education, Science, Research and Sports (Slovak Republic)Ministerio de Ciencia e Innovación (España)Depto. de Farmacología, Farmacognosia y BotánicaFac. de FarmaciaTRUEpubDescuento UC

Old and sticky—adhesive mechanisms in the living fossil Nautilus pompilius (Mollusca, Cephalopoda)

Nautiloidea is the oldest group within the cephalopoda, and modern Nautilus differs much in its outer morphology from all other recent species; its external shell and pinhole camera eye are the most prominent distinguishing characters. A further unique feature of Nautilus within the cephalopods is the lack of suckers or hooks on the tentacles. Instead, the animals use adhesive structures present on the digital tentacles. Earlier studies focused on the general tentacle morphology and put little attention on the adhesive gland system. Our results show that the epithelial parts on the oral adhesive ridge contain three secretory cell types (columnar, goblet, and cell type 1) that differ in shape and granule size. In the non-adhesive aboral epithelium, two glandular cell types (cell types 2 and 3) are present; these were not mentioned in any earlier study and differ from the cells in the adhesive area. The secretory material of all glandular cell types consists mainly of neutral mucopolysaccharide units, whereas one cell type in the non-adhesive epithelium also reacts positive for acidic mucopolysaccharides. The present data indicate that the glue in Nautilus consists mainly of neutral mucopolysaccharides. The glue seems to be a viscous carbohydrate gel, as known from another cephalopod species. De-attachment is apparently effectuated mechanically, i.e., by muscle contraction of the adhesive ridges and tentacle retraction

A giant virus infecting the amoeboflagellate Naegleria.

Giant viruses (Nucleocytoviricota) are significant lethality agents of various eukaryotic hosts. Although metagenomics indicates their ubiquitous distribution, available giant virus isolates are restricted to a very small number of protist and algal hosts. Here we report on the first viral isolate that replicates in the amoeboflagellate Naegleria. This genus comprises the notorious human pathogen Naegleria fowleri, the causative agent of the rare but fatal primary amoebic meningoencephalitis. We have elucidated the structure and infection cycle of this giant virus, Catovirus naegleriensis (a.k.a. Naegleriavirus, NiV), and show its unique adaptations to its Naegleria host using fluorescence in situ hybridization, electron microscopy, genomics, and proteomics. Naegleriavirus is only the fourth isolate of the highly diverse subfamily Klosneuvirinae, and like its relatives the NiV genome contains a large number of translation genes, but lacks transfer RNAs (tRNAs). NiV has acquired genes from its Naegleria host, which code for heat shock proteins and apoptosis inhibiting factors, presumably for host interactions. Notably, NiV infection was lethal to all Naegleria species tested, including the human pathogen N. fowleri. This study expands our experimental framework for investigating giant viruses and may help to better understand the basic biology of the human pathogen N. fowleri