First described by Randolph in 1897, the nature and main features of planarian neoblasts have a long rambling history. While their morphologically undifferentiated features have long been recognized, their origin and actual role during regeneration have been highly debated. Here I summarize the main stages of this rambling history: 1) undifferentiated, wandering cells of uncertain origin with a main, albeit undefined, role in regeneration (1890-1940s); 2) quiescent, undifferentiated cells whose main function is to build the blastema during regeneration, an idea which culminated in the 'neoblast theory' of the French School (1940-1960); 3) neoblasts as temporal, undifferentiated cells arising by dedifferentiation from differentiated cells (the 'cell dedifferentiation theory'; 1960-1980s); 4) a new paradigm, starting in the late 1970s-early 1980s, that brought together the role of neoblasts as the main cell for regeneration, with its more important role as somatic stem cells for the daily wear and tear of tissues and as the source of germ cells; and 5) more recent developments that culminate in the report of rescuing lethally irradiated planarians by injection of single neoblasts, which makes of neoblasts an unrivaled toti-, pluripotent somatic stem cell system in the Animal Kingdom. I finally discuss some "black boxes" regarding neoblasts which still baffle us, namely their phylogenetic and ontogenetic origins, their role in body size control, how their pool is regulated during growth and degrowth, the logic of their proliferative control, and some 'old' long-sought missing tools.

/pdf/the-planarian-neoblast-the-rambling-history-of-its-origin-eqwhve0qz0.pdf

The planarian neoblast: the rambling history of its origin and some current black boxes.

An improved method for the isolation and quantitative cultivation of embryonic cells.

Recent antarctic and subantarctic brachiopods

Publisher Summary There are structural similarities between the carcinogenic hydrocarbons and the steroids. Under certain conditions, at least in rodents, steroids might produce carcinogenic effects as dramatic as those of the hydrocarbons. The concept of a normal body constituent functioning as a carcinogen might appear paradoxical. It is under such a circumstance that the areas of contemporary thought regarding the carcinogen and carcinogenesis are challenged. The mechanism of solid state carcinogenesis is conjectural: there might be no carcinogen involved. A chemical carcinogen would have a minimal effective dose and would enhance cancer production with increasing dosage. A weak carcinogen requires the effective dose of a strong carcinogen and might not show increasing tumorigenesis with increasing dosage. A cocarcinogen does not produce cancer by itself but in conjunction with another substance, which is carcinogenic in its own right.

Carcinogenic effects of steroids.

Effects of nicotine on cultured rat heart cells

Knowledge of the chemical, physiological, and morphological relationships of living cells is now more readily attainable because of two research developments: (1) the long-focus oil-immersion phase-contrast system of microscopy; and (2) the perfusion chamber for the growth and maintenance of living cells. A number of investigators have attempted to supply tissue cultures in vitro with a constant flow of nutrient medium. Burrows' in 1912 was the first to supply tissue cultures with a constant supply of fresh medium. He used a cotton wick to carry the culture medium through the culture chamber. The fluid drained into a vessel placed lower than the culture chamber. DeHaan2 in 1928 had an apparatus which made possible the circulation of large volumes of liquid, but the apparatus was too complicated. Carrel3 in 1931 designed a pump flask for the continuous circulation of a fluid medium. This device was improved by the help of Lindbergh.4 Even though markedly better, in that attention was paid to the gas tension of the fluid, the apparatus did not allow for adequate observation of the cells. Pomerat5 uses a very simple perfusion chamber which allows observation under the best modern optical conditions, but which has the disadvantage of being temporary and requiring constant attention. His apparatus does not provide for maintenance of constant gas tensions, and it is not well adapted for prolonged observations. Christiansen, Danes, Allen and Leinfelder6 modified the Pomerat chamber and made it a permanent piece of apparatus. They standardized the dimensions and changed the medium with syringes. Their device gives control of the medium from both sides of the chamber and, if desired, allows the medium to flow through the chamber. To oxygenate the culture, the fluid is periodically replaced by air. But their apparatus is not automatic, and the equilibrium with air is not satisfactory. The conventional method for studying the effects of drugs on living cells iiz aitro has been to incorporate the drug into the medium in which the cells are explanted and grown. The disadvantages of this method are: (1) the immediate responses of the cells cannot be observed because it requires several hours before the first cells have grown out from the explant; (2) the concentration of the drug cannot be maintained; (3) the drug cannot easily be removed; (4) the effects cannot be observed on a single cell over the entire experimental period; and ( 5 ) repeated doses cannot be given to the same cell. To correct these difficulties, we have devised a general method for studying living cells under a variety of known controlled conditions. The perfusion method reported here

The effects of certain stimulants and depressants on individual fibroblasts in a perfusion chamber

Size and Shape Variation of Three Recent Brachiopods from the Strait of Magellan

Observations on planarian cells cultivated in solid and liquid media.

SummaryMice of various ages were subjected to ether anesthesia in a chamber containing a fixed quantity of ether. Old mice took longer to fall asleep than did young mice. Old and young mice took much longer to recover than did adult mice of 1-8 months, and were more variable in response to ether, both behaviorally and physiologically. Sex was a factor of minor importance in time required to fall asleep, and made no measurable difference in time to recover. Time to fall asleep was correlated with time to recover in adults, but uncorrelated in young and old mice. Recovery time was more variable than time to fall asleep. Mechanisms to explain these results are discussed.

Age and ether anesthesia in mice.

Lambert,1 Lambert and Meyer,2 and German3 believe that an ideal antiseptic is one which kills the bacteria without harming the tissue cells and they have accordingly devised methods of comparing the toxic effects of antiseptics upon bacteria and tissue cells in vitro.Lambert after exposing fragments of connective tissue for several minutes to a saline suspension of Staphylococcus aureus transferred them into various concentrations of mercuric chloride, potassium mercuric iodide, potassium cyanide, Dakin's solution, iodine, phenol, tricresol, argyrol, hydrogen peroxide, glycerol, or alcohol. After one hour the fragments were transferred to physiological salt solution where they remained from a few minutes to half an hour until explanted. Although most of the antiseptics killed the tissue cells at concentrations that did not kill the bacteria, a good growth of cells was observed after exposure for one hour to a 1:2,000 iodine solution, a strength sufficient to sterilize the tissue completely in most instanc...

Relative Toxicity of Antiseptics on Bacteria and Tissues in Cultures.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Ralph Buchsbaum

Author Tools

Chat about Author