Regeneration and pattern formation in planarians

Development ◽  
1984 ◽  
Vol 83 (1) ◽  
pp. 63-80
Author(s):  
Emili Saló ◽  
Jaume Baguñà
Keyword(s):  
Pattern Formation ◽  
Mitotic Activity ◽  
Intermediate Stage ◽  
Point Of View ◽  
Blastema Formation ◽  
Biphasic Pattern ◽  
Spatial Point ◽  
Planarian Regeneration ◽  
Undifferentiated Cells ◽  
S Period

Mitotic activity during regeneration in the planarian Dugesia (G) tigrina shows a biphasic pattern, with a first maximum at 4–12 h, a second and higher maximum at 2–4 days, and a relative minimum in between. The first peak is mainly due to pre-existing G2 cells entering mitosis shortly after cutting, whereas the second maximum is due to cells that divide after going through the S period from the onset of regeneration. From a spatial point of view, the highest mitotic values are found in stump (postblastema) regions near the wound (0–300 µm), though regions far from it also show increased mitotic values but always lower overall values. As regeneration continues the postblastema maximum shifts slightly to more proximal regions. In contrast, no mitosis has been found within the blastema, even though the number of blastema cells increases steadily during regeneration. These results suggest that blastema in planarians forms through an early accumulation of undifferentiated cells at the wound boundary, and grows by the continuous local migration of new undifferentiated cells from the stump to the base of blastema. The results obtained demonstrate that blastema formation in planarians occurs through mechanisms somewhat different to those shown to occur in the classical epimorphic models of regeneration (Annelida, Insecta, Amphibia), and suggest that planarian regeneration could represent an intermediate stage between morphallactic and epimorphic modalities of regeneration.

The respective roles of mitotic activity and of cell differentiation in Planarian regeneration

Development ◽  
1968 ◽  
Vol 20 (2) ◽  
pp. 175-188
Author(s):  
Rosine Chandebois
Keyword(s):  
Cell Differentiation ◽  
Mitotic Activity ◽  
Close Similarity ◽  
X Rays ◽  
Blastema Formation ◽  
Young Embryo ◽  
Planarian Regeneration ◽  
Undifferentiated Cells

Blastema formation, which is the first step of regeneration in adult Metazoa, is generally considered to be merely an accumulation of undifferentiated cells provided by mitotic activity, which occurs near the wound following amputation. Afterwards, these undifferentiated cells are thought to differentiate rapidly, thus affecting the organization of the regenerate. Some authors have postulated that a close similarity exists between these undifferentiated cells and the blastomeres of a young embryo, and that the influence exercised by the stump tissues in blastema differentiation is a typical inductive process. This concept would imply two successive steps in regeneration: (1) blastema formation, exclusively dependent upon mitotic activity, even after the previous accumulation of undifferentiated cells resulting from migration (Dubois, 1949), (2) the transformation of the blastema into a regenerate as differentiation occurs. Up to now, the first step seemed to be confirmed by experiment, since some authors have observed that some experimental factors which prevent regeneration (X-rays and mitoclastic poisons) inhibit mitoses.

Evidence of male germ cell redifferentiation into female germ cells in planarian regeneration

Development ◽  
1982 ◽  
Vol 70 (1) ◽  
pp. 29-36
Author(s):  
V. Gremigni ◽  
M. Nigro ◽  
I. Puccinelli
Keyword(s):  
Germ Cells ◽  
Somatic Cells ◽  
The Body ◽  
Diploid Male ◽  
Female Gonad ◽  
Anterior Portion ◽  
Male Germ Cells ◽  
Blastema Formation ◽  
Planarian Regeneration ◽  
Undifferentiated Cells

The source and fate of blastema cells are important and still unresolved problems in planarian regeneration. In the present investigation we have attempted to obtain new evidence of cell dedifferentiation-redifferentiation by using a polyploid biotype of Dugesia lugubris s.1. This biotype is provided with a natural karyological marker which allows the discrimination of triploid embryonic and somatic cells from diploid male germ cells and from hexaploid female germ cells. Thanks to this cell mosaic we previously demonstrated that male germ cells take part in blastema formation and are then capable of redifferentiating into somatic cells. In the present investigation sexually mature specimens were transected behind the ovaries and the posterior stumps containing testes were allowed to regenerate the anterior portion of the body. Along with the usual hexaploid oocytes, a small percentage (3.2%) of tetraploid oocytes were produced from regenerated specimens provided with new ovaries. By contrast only hexaploid oocytes were produced from control untransected specimens. The tetraploid oocytes are interpreted as original diploid male germ cells which following the transection take part in blastema formation and then during regeneration redifferentiate into female germ cells thus doubling their chromosome number as usual for undifferentiated cells entering the female gonad in this biotype.

Regeneration and pattern formation in planarians. II. and role of cell movements in blastema formation

Development ◽  
1989 ◽  
Vol 107 (1) ◽  
pp. 69-76 ◽  
Author(s):  
E. Salo ◽  
J. Baguna
Keyword(s):  
Pattern Formation ◽  
Cell Movement ◽  
Formation Mechanisms ◽  
Blastema Formation ◽  
Chromosomal Markers ◽  
Undifferentiated Cells ◽  
Local Cell ◽  
Number Of Cells ◽  
Wound Epithelium

In planarians, blastema cells do not divide, and growth blastema is thought to result from the steady wound epithelium, of undifferentiated cells produced in the stump. However, whether these cells come only sources or whether cells placed far from the wound can participate, after long-range migrations, in the still uncertain. To study this problem, we have parameters of the process of regeneration: cell growth; number of cells produced by mitosis in the wound (postblastema); and rates of movement undifferentiated cells using grafting procedures with chromosomal markers. The results show that: (1) cells area spread (move) at higher rates than cells placed (90–140_mday-1 versus 40–50_mday-1); (2) cells than 500_m from the wound boundary are hardly 5-day-old blastemata; and (3) the number of cells within a 200–300_m postblastema area around the wound explain, provided their rates of movement are taken increasing number of blastema cells. From this, it is blastema cells in planarians originate from local mitotic activity jointly with local cell movement postblastema area around the wound match the blastema cells during regeneration. The implications for blastema growth and pattern formation mechanisms

Cell movement in intact and regenerating planarians. Quantitation using chromosomal, nuclear and cytoplasmic markers

Development ◽  
1985 ◽  
Vol 89 (1) ◽  
pp. 57-70
Author(s):  
Emili Saló ◽  
Jaume Baguñà
Keyword(s):  
Cell Movement ◽  
Chromosomal Marker ◽  
Blastema Formation ◽  
Differentiated Cells ◽  
Planarian Regeneration ◽  
Latex Beads ◽  
Undifferentiated Cells ◽  
Speed Up ◽  
X Irradiation ◽  
Parenchymal Cells

One of the tenets of Wolff and Dubois' ‘neoblast theory’ of planarian regeneration (Wolff & Dubois, 1948) is that blastema is mainly formed by the accumulation of undifferentiated parenchymal cells (neoblasts) that can migrate, if needed, over long distances to the wound. That neoblasts migrate was claimed by these authors after partial X-irradiation, and total Xirradiation and grafting using planarian strains of different pigmentation. From this they suggested that migration of neoblasts is stimulated by the wound and directed towards it. To study the nature and extent of such ‘migration’ in intact and regenerating organisms, and in order to avoid the flaws of using pigmentation as a marker, we made grafts between sexual and asexual races of Dugesia(S)mediterranea that differ in a chromosomal marker, and between diploid and tetraploid biotypes of Dugesia(S)polychroa that differ in nuclear size. Also, fluorescent latex beads were used as cytoplasmic markers to follow ‘migration’ of differentiated cells. The hosts were irradiated or non-irradiated intact and regenerating organisms. The results show that: 1) movement of graft cells into host tissues occurs in intact organisms at a rate of ≃40µm/day, and that this increases up to ≃75µm/day in irradiated hosts; 2) movement of cells occurs evenly in all directions; 3) regeneration does not speed up rate of movement nor drives cells preferentially to the wound; 4) spreading of cells is mainly due to the movement of undifferentiated cells (neoblasts); and 5) higher rates of movement are correlated with higher mitotic indexes. From this, it is concluded that the so-called ‘migration’ of neoblasts is not a true cell migration but the result of the slow, even and progressive spreading of these cells mainly caused by random movements linked to cell proliferation. The implications of these results for blastema formation and the origin of blastema cells are discussed.

Regeneration and pattern formation in planarians. III. that neoblasts are totipotent stem cells and the cells

Development ◽  
1989 ◽  
Vol 107 (1) ◽  
pp. 77-86 ◽  
Author(s):  
J. Baguna ◽  
E. Salo ◽  
C. Auladell
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Pattern Formation ◽  
Animal Kingdom ◽  
New Approach ◽  
Blastema Formation ◽  
Quiescent Cells ◽  
Differentiated Cells ◽  
Different Types ◽  
Undifferentiated Cells

In most regenerating systems, blastema cells arise by dedifferentiation of functional tissue cells. In is still debatable whether dedifferentiated cells or a undifferentiated cells, the neoblasts, are the main cells. Moreover, it is unclear whether in the intact neoblasts are quiescent cells ‘reserved’ for serve as functional stem cells of all differentiated uncertainties partly stem from the failure to conventional labelling methods neoblasts from Here we describe a new approach to these problems regenerative and stem cell capabilities of purified differentiated cells when introduced, separately, into hosts. Introduction of neoblasts led to resumed blastema formation, and extended or complete survival differentiated cells, in contrast, never did so. neoblasts can be qualified as totipotent stem cells of blastema cells, while dedifferentiation does not either in intact or regenerating organisms. In strengthen the idea that different types of formation, linked to the tissular complexity of the present in the animal kingdom.

D’une hétérotopie à l’autre où le vagabondage au féminin (Jean Echenoz, Un an)

2014 ◽  
pp. 156-163
Author(s):  
Simona Jişa
Keyword(s):  
Point Of View ◽  
Standard Of Living ◽  
Human Being ◽  
The South ◽  
Railway Stations ◽  
Spatial Point ◽  
Strong Feeling ◽  
Continuous Decrease ◽  
One Year ◽  
Jean Echenoz

Jean Echenoz’s text presents Victoria’s story who runs away from Paris, believing that she has killed her lover. Her straying (that embraces the form of a relative deterritorialization in a Deleuzian sense) lasts one year and it is built up geographically upon a descent (more or less symbolical) to the South of France and, after that, she comes back to Paris and encloses the spatial and textual curl. From a spatial point of view, she turns into a heterotopia (Foucault) every place where she is located, fact that reflects her incapability of constituting a personal, intimate space. The railway stations, the trains, the hotels, the improvised houses of those with no fixed abode are turning, according to Marc Augé’s terminology, into a « non-lieux » that excludes human being. Her vagrancy is characterized through a continuous flight from police and people and through a continuous decrease of her standard of living and dignity. It’s not about a quest of oneself, but about a loss of oneself. Urged by a strong feeling of culpability, her vagrancy is a self-punishment that comes to an end when the concerns of her problems disappear and she finds out that her lover is alive.

On the role of germ cells in planarian regeneration

Development ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 53-63
Author(s):  
V. Gremigni ◽  
C. Miceli ◽  
I. Puccinelli
Keyword(s):  
Chromosome Number ◽  
Germ Cells ◽  
Primordial Germ Cells ◽  
Karyological Analysis ◽  
Blastema Formation ◽  
Planarian Regeneration ◽  
Somatic Tissues ◽  
Caudal Area ◽  
Complete Regeneration

Specimens from a polyploid biotype of Dugesia lugubris s.l. were used to clarify the role and fate of germ cells during planarian regeneration. These specimens provide a useful karyological marker because embryonic and somatic cells (3n = 12) can be easily distinguished from male (2n = 8) and female (6n = 24) germ cells by their chromosome number. We succeed in demonstrating how primordial germ cells participate in blastema formation and take part in rebuilding somatic tissues. This evidence was obtained by cutting each planarian specimen twice at appropriate levels. The first aimed to induce primordial germ cells to migrate to the wound. The second cut was performed after complete regeneration and aimed to obtain a blastema from a cephalic or caudal area devoid of gonads. A karyological analysis of mitotic cells present in each blastema obtained after the second cut provided evidence that cells, originally belonging to the germ lines, are still present in somatic tissues even months after complete regeneration. The role of primordial germ cells in planarian regeneration was finally discussed in relation to the phenomenon of metaplasia or transdifferentiation.

Age and Mitotic Activity in the Male Mouse, Mus Musculus L

1949 ◽  
Vol 26 (3) ◽  
pp. 261-286
Author(s):  
W. S. BULLOUGH
Keyword(s):  
Mitotic Activity ◽  
Diurnal Cycle ◽  
Male Mouse ◽  
Middle Age ◽  
Sugar Content ◽  
Rest Period ◽  
Point Of View ◽  
Bodily Activity ◽  
Vital Factor ◽  
Mitosis Rate

1. A study has been made of the mitosis rate and of the diurnal cycles of male mice during each of the first 20 months of life. The mice used belonged to the Kreyberg's white label and the Strong's CBA strains. Most of the observations were made on the ear epidermis, but some attention was also given to other tissues. 2. It was discovered that, when judged from the point of view of mitotic activity, the life of a male mouse consists of four ages. During the immature age the animals are still growing and their mitosis rate is generally high, although the ear epidermis provides an exception to this rule. During the mature age which lasts from about the 3rd to the 12th month the mitosis rate is lowered. During the middle age which follows the mitosis rate increases, but in senility it is again reduced. 3. Coincident with these changes in the mitosis rate are changes in the spontaneous bodily activity. The mice are most active during immaturity and maturity. In middle age their activity is reduced by about half, and in senility they spend almost the whole time resting. Particularly in the Strong's CBA mice there are also changes in the timing of the diurnal cycle of spontaneous bodily activity, and these are immediately mirrored by changes in the timing of the diurnal cycle of mitotic activity so that throughout life a general inverse relationship between bodily activity and mitotic activity is maintained. 4. In middle-aged Strong's CBA males the daily rest period extends almost without interruption from 06.00 to 18.00 hr. However, the most active cell division develops only at the beginning of this period, and it is evident that in prolonged sleep a lack of some vital factor develops. It is shown that subcutaneous injections of starch overcome this lack in sleeping mice and result almost immediately in the redevelopment of a high mitosis rate. Thus it would appear that sugar is the vital factor involved, and that the sugar content of the tissues is quickly used up during high mitotic activity. 5. These results are discussed particularly in relation to the problem of carcinogenesis.

scholarly journals The importance and constraints of using mathematics teaching and learning sites from the point of view of mathematics teachers in the middle stage in Riyadh: مدى أهمية ومعوقات استخدام مواقع تعليم وتعلم الرياضيات من وجهة نظر معلمات الرياضيات في المرحلة المتوسطة بمدينة الرياض

2017 ◽  
Vol 1 (8) ◽  
Author(s):  
Asma Nasser Al - Saeed - Amal Sulaiman Aldghaim - Samar Fahd
Keyword(s):  
Mathematics Teachers ◽  
Teaching And Learning ◽  
Intermediate Stage ◽  
Point Of View ◽  
Educational Standards ◽  
Middle Stage ◽  
Evaluation Form ◽  
Riyadh City ◽  
Human Sample ◽  
Descriptive Method

The aim of this research is to find out the extent to which the mathematics teachers of the intermediate stage benefit from the teaching and learning sites of mathematics, and to find the most used sites by mathematics teachers, and then study and evaluate these sites in the light of technical and educational standards for educational sites. The researchers used two tools to collect the study information, a questionnaire to identify the extent to which they benefited from the learning and learning sites of mathematics, and an evaluation form to determine the extent to which these sites are subject to technical and educational controls. The researcher applied the research using descriptive method, with the sample of the research divided into two parts: a human sample of (14) teachers of mathematics for the middle stage in Riyadh city, the second was an electronic sample of (5) mathematical sites, the research concluded the importance of these sites for the parameters , And the evaluation form showed the availability of technical and educational standards in these sites. The research recommended the establishment of a database of these educational sites on the Internet, so that teachers can benefit from them, and the need for teachers, especially mathematics teachers, to understand the importance of these sites as an activity that serves the educational content.

scholarly journals Tools for Developing a Regional Education Development Strategy

2021 ◽  
pp. 110-121
Author(s):  
Yu. N. Lapygin ◽  
S. A. Boltunov
Keyword(s):  
Development Strategy ◽  
Education System ◽  
General Scheme ◽  
Intermediate Stage ◽  
Comprehensive Analysis ◽  
Strategy Implementation ◽  
Point Of View ◽  
Instrumental Support ◽  
Wide Field ◽  
Education Development

The framework structure of the federal law on strategic planning leaves a wide field of activity for developers to use various tools in the process of building a development strategy for both the region and its sub-systems, which include the education system of the region. The methodological recommendations of the Ministry of Economic Development of the Russian Federation regarding the development of a strategy specify only the content of the main directions of the strategy, but allow the use of various methods, models and mechanisms for developing the strategy itself. Therefore, the study of the issues of instrumental support of procedures for developing strategies for regions and its subsystems is of interest from a theoretical and practical point of view.In the study of theoretical and applied problems of instrumental support of the process of developing a strategy, algorithms are built in the form of a general scheme for developing a strategy and performing a comprehensive analysis prior to development. Algorithms for developing a strategy at the initial stage were formed based on the results of a comprehensive analysis, at the stage focused on the main goal (Mission), as well as at the final stage, the goals of which are focused on the ideal state in the future — Vision. Besides. An algorithm for determining the expected results has been built. on the basis of which a scenario for the development of regional subsystems is built.The scientific novelty of the developed procedures lies in the fact that a set of tools for determining strategically significant projects and programs of the final and intermediate stages of strategy implementation is proposed; tools for agreeing strategically significant decisions were formed throughout the cycle of strategic development of the region’s education system; shows the procedure for constructing a tree of goals for the intermediate stage of the strategy implementation; a procedure for the formation of a development strategy at the intermediate stage of strategy implementation has been developed. The proposed approach to building a strategy for the development of socio-economic systems in the region is implemented in the process of adjusting the development strategy of the Vladimir region in terms of vocational education in the region.

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