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Results for “Planarians”

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17 recordsLinked to original sources
PubMed2026

Progress on the telomere-telomerase system in planarian neoblasts homeostasis and regeneration.

Planarians are flatworms with remarkable regenerative abilities, and their adult pluripotent stem cells, known as neoblasts, serve as the foundation for this regeneration. Neoblasts can rapidly migrate, proliferate, and undergo directed differentiation following tissue injury to complete regeneration. Telomeres are located at the ends of eukaryotic chromosomes and play a core role in maintaining chromosomal integrity. With each cell division, telomeres shorten. Telomerase is a reverse transcriptase that compensates for telomere loss during cell division by extending telomeric repeats. The telomere-telomerase system is one of the important mechanisms for maintaining stem cell homeostasis. As adult pluripotent stem cells of planarians, neoblasts are required to maintain a dynamic balance between high-frequency cell division and multilineage differentiation. The maintenance of their long-term proliferative capacity and genomic stability may depend on the precise regulation of the telomere-telomerase system. Thus, this system represents a critical entry point for understanding the remarkable regenerative ability of planarians. Integrating recent progress in regeneration, neoblast regulation, and the telomere-telomerase system, we systematically summarize the emerging evidence for telomere- telomerase involvement in neoblast homeostasis and regeneration. We aim to provide insights for research in regenerative medicine, stem cell regulation, and neural injury repair.

Animals↗
PubMed2026

Conserved innate immunity components limit transgene expression in adult planarians.

The planarian flatworm Schmidtea mediterranea has become a powerful model for studying whole-body regeneration, tissue patterning, and stem cell regulation. Yet the absence of reliable tools for transgene expression still limits the elucidation of molecular mechanisms in in this system. Here, we establish a proof-of-principle system for plasmid-based expression of NanoLuciferase (NanoLuc) in S. mediterranea, employing commercially available transfection reagents and a panel of endogenous promoter sequences. Despite successful delivery, reporter expression remained low and transient. To identify biological barriers to robust transgene expression, we investigated the role of innate immune pathways. Candidate gene searches and biochemical pull-down of cytoplasmic DNA coupled to mass spectrometry identified several planarian homologs of conserved immune regulators and putative DNA sensors. Through RNA interference screening of conserved innate immune components, we uncover roles for S. mediterranea homologs of Tank-binding kinase 1 (TBK1) and macrophage mannose receptor 1 (MRC1) as potent repressors of transgene expression. Transcriptomic and functional analyses further implicate TBK1 in regulating broad innate immune and stress-response programs, akin to its vertebrate function. Together, our findings demonstrate that innate immune signaling limits transgene expression in S. mediterranea and suggest that modulating these pathways may be key to enabling stable and efficient genetic manipulation in planarians.

Animals↗
PubMed2025

Investigating the Functions of Hox Genes Using Planarian Asexual Reproduction.

Hox genes are highly conserved developmental regulators instrumental to the formation of a wide range of diverse body plans across metazoans. While significant progress in the field of Hox gene research has been made, persistent challenges in unraveling their mechanisms of action and full repertoire of functions remain. To date, investigations of Hox gene function have been primarily conducted in research models belonging to ecdysozoa and vertebrata. Herein we summarize recent findings on Hox genes' roles in the asexual reproduction of the regenerative flatworm planaria, a member of the understudied superphylum Spiralia. We detail our optimized methods for planarian culture, gene perturbation, and induction of asexual reproduction. We aim to provide an experimentally tractable means to dissect Hox gene adult tissue functions underlying planarian asexual reproduction with broader relevance to Hox genes' established and emerging roles in regulating cellular behaviors, developmental patterning, animal behavior, and tissue regeneration.

Animals↗
PubMed1979

Analysis of the progress of hormone-receptor amplification during differentiation in regenerating planarians.

Planarians developing from isolated regenerates, when pretreated with epinephrine at different periods of their second regeneration, show a higher rate of sugar uptake than the controls, which were not treated with epinephrine. The hormone receptor development can be influenced most effectively by pretreatments performed during the 1--3 and 6--9 day periods, though some effect can be evoked at any time in the course of the second regeneration. The head regenerates developing from the anterior end of the original midpiece (and regenerating tails the second time, B1) were found to be most sensitive, while the similar regenerates developing from the hindpiece of the original planarian (C) showed the weakest reactivity. The experiments provide further evidence that the hormone receptors' activity can be amplified in the course of regenerative development, leading thus--at a later stage--to a more intense sugar uptake response of the cells.

Animals↗
PubMed1976

Use of the p-nitrophenyl phosphate method for the demonstration of acid phosphatase during starvation and cell autolysis in the planarian Polycelis tenuis Iijima.

Acid phosphatase activity is demonstrated employing p-nitrophenyl phosphate as substrate and lead acetate as coupler. The fine structural localization of the enzyme in starved planarian tissues is described. The method is used to pin-point starvation - induced acid phosphatase activity in relation to autophagy and crinophagy in the gland cells; autophagy, autolysis and cell death in parenchymal and gastrodermal cells and basement membrane lysis. Attention is also payed to the demonstration of muscle lysis. The histochemical implications of the method are discussed.

4-Nitrophenylphosphatase↗
PubMed1976

[Control of the regeneration of small pieces of the planarian Dugesia tigrina by cylic AMP and GMP nucleotides].

The effects on regeneration of cyclic nucleotides AMP and GMP were studied on small pieces of the planarian worm Dugesia tigrina. db cAMP, 8Br cGMP and substances acting on their metabolism were used in this work (aminophylline, insulin, imidazole). It seems that these second messengers play a role in a mechanism of regulation in which cGMP has a promotive action and cAMP an inhibitive one.

Animals↗
PubMed2025

Multi-omics analyses reveal DjTcf4 critical for proper timing of differentiation in planarian regeneration.

The blastema is key to forming complete tissues in regenerating Dugesia japonica (D. japonica). However, the dynamic changes in cellular compositions and transcription landscapes in blastema during regeneration are understudied. Here, through genome reannotation, 3D spatial transcriptome construction, single-cell RNA sequencing (scRNA-seq), and single-cell assay for transposase-accessible chromatin sequencing (scATAC-seq) analyses of changes in gene expression and chromatin structures, we delineate key transcription factors regulating the developmental trajectories of major cell clusters in the regenerating head. Importantly, we find that the T cell factor 4 (DjTcf4)-positive cells highly accumulate at wound areas, and its gene network is critical for the proper timing of development during regeneration in multiple progenitor cells. Depletion of DjTcf4 and its target genes leads to singular eye and/or dull tail phenotypes and delays regeneration. Taken together, we build multi-omics atlases in D. japonica and reveal the noncanonical function of the DjTcf4 network in developmental pattern formation, laying a foundation for studies of regeneration in D. japonica.

Animals↗
PubMed1975

The distribution of oxidizable mucosubstances and polysaccharides in the planarian Polycelis tenuis Iijima.

A chromic acid oxidation-silver technique was used to localize polysaccharide material in Polycelis tenuis at the electron microscope level. In the epithelium, staining was observed within apical vacuoles and on the free surfaces of the cells. A similar staining was observed in relation to the glycocalyx of the pharyngeal epithelia and that of the flame cells. Silver was deposited in the basement membrane. In the parenchyma, the major components giving a positive reaction were the cyanophil and mucous gland cells. Particularly strong silver staining (confirmed by X-ray microanalysis) was observed in the granules and Golgi apparatus of the cyanophil cells. IDPase activity was also found in relation to the Golgi apparatus and its secretory products. The overall distribution of mucopolysaccharide material was confirmed with the PAS and Alcian blue techniques. The fine structural localization of the Alcian blue was also determined using electron microscopy and X-ray microanalysis.

Animals↗
PubMed1979

Studies on the cytochemical localization of adenylate-cyclase activity in Dugesia lugubris s.I.

The localization of adenylate-cyclase activity in Dugesia lugubris s.1. has been investigated cytochemically using 5'-adenylyl-imidodiphosphate as substrate. The enzyme was localized in mucous gland cells, in rhabdite cells, in intercellular spaces and also in nerve endings of this planarian. The presence of adenylate-cyclase on the membrane suggests that it might mediate different stimulus-secretion coupling by increasing cyclic AMP synthesis in specialized areas of the planarian.

Adenylyl Cyclases↗
PubMed1979

The pigmentary system of planaria. II. Physiology and functional morphology.

The pigmentary system of the planaria, Dugesia gonocephala s.l. (Platyhelminthes, Turbellaria, Tricladida), consists of granules contained in chromatophore cells distributed in the parenchyma tissue. The administration of MSH release-inhibiting Factor (M.I.F.) leads to an easily observable general decolouration of the animal due to the migration of the pigment granules towards the deeper-lying cell nucleus. In planarians bisected transversely through the pharyngeal region, the decolouration occurs only in the cephalic segment, and the caudal segment remains dark. When, however, the decapitated caudal segment regenerates a head region, a decolouration response occurs when exposed to M.I.F. The significance of these results is discussed, and an hypothesis on the hormonal regulation of the pigmentary system is proposed.

Animals↗
PubMed1979

Measurement of the aquatic toxicity of volatile nitrosamines.

The acute toxicity of N-nitrosodimethylamine (DMN) and N-nitrosodiethylamine (DEN) was determined for three groups of aquatic organisms: algae, invertebrates, and fish. Toxicity of DMN and DEN to algae was assessed as a repression in the growth rate of either Selenastrum capricornutum or Anabaena flos-aquae in static bioassay tests. DMN and DEN concentrations of 1-10 ppm depressed algal growth in all cases. Invertebrate toxicity was determined in 96-h static bioassay tests with Dugesia dorotocephala and Gammarus limnaeus. The data indicated that these organisms are not highly susceptible to nitrosamine toxicity. The 96-h LC50s for D. dorotocephala were 1365 and 1490 ppm for DMN and DEN, respectively. Similar studies with G. limnaeus indicated LC50s of 330 and 500 ppm for DMN and DEN, respectively. Fish toxicity was also determined in 96-h statis bioassays with the fathead minnow (Pimephales promelas). Acute toxicities were calculated as LC50s of 940 and 775 ppm for DMN and DEN, respectively. Algae were calculated as LC50s of 940 and 775 ppm for DMN and DEN, respectively. Algae were quite sensitive to relative low levels of volatile nitrosamines, but higher organisms (invertebrates and fish) were relatively insensitive.

Animals↗
PubMed1975

Proposal of a new model with dopaminergic-cholinergic interactions for neuropharmacological investigations.

The motor system of Dugesia gonocephala shows a striking similarity with the extrapyramidal system of high vertebrates and of man with the evidence of correlations between dopaminergic and cholinergic neurons. The utilization of this model seems to be useful in testing drugs which presumably act on dopaminergic or cholinergic transmission. In this model, the quantification of animal behaviour seems considerably easier when compared with the difficulties met in other animal models commonly employed. Besides, it might be anticipated that this model, if correctly used, can display interesting perspectives also in neuroendocrinological investigations.

Acetylcholine↗
PubMed1979

The effect of sympathicomimetic agents on carbohydrate metabolism of planaria.

Epinephrine, ephedrine, dopamine and isoproterenol considerably influence carbohydrate utilization in planaria. Dopamine alone and in combination is the most potent, while ephedrine the least effective in this respect. The finding of increased responses to combined treatment supports the view of the existence of different receptor sites for the sympathicomimetic drugs. The results substantiate conclusions concerning the phylogenesis of hormone receptors.

Animals↗