The “Organization centre”

1967 ◽  
Vol 17 (4) ◽  
pp. 178-194 ◽  
Author(s):  
P. D. Nieuwkoop
Keyword(s):  
Organization Centre

scholarly journals Studies on the nature of the amphibian organization centre. I—Chemical properties of the evocator

1935 ◽  
Vol 117 (804) ◽  
pp. 289-310 ◽  
Keyword(s):  
Active Substance ◽  
Chemical Properties ◽  
Egg Laying ◽  
Embryonic Induction ◽  
Soluble Substance ◽  
Animal Kingdom ◽  
Whole Process ◽  
Adult Tissues ◽  
Regional Character ◽  
Organization Centre

During the amphibian egg-laying season of 1933, Needham, Waddington, and Needham (1933, a , b ; 1934) obtained evidence that the activity of the organization centre of the newt gastrula is partly due to the presence of an ether-soluble substance. The active ether extracts were found to be capable of evoking the formation of a neural tube from the competent presumptive epidermis of the gastrula. It seems difficult, however, to suppose that they can determine the regional character of the evoked neural plate, as normal living organizers do, and the active substance is therefore spoken of as the evocator, to emphasize the fact that its functions represent only one part of the whole process of embryonic induction. The presence of the evocator could also be demonstrated in ether extracts of adult newt tissues; and in a research carried out at the same time Holtfreter (1933) showed that the evocator is present in a large number, if not in all, adult tissues from animals belonging to nearly all the groups of the animal kingdom. Holtfreter found that evocation occurred after the implantation of adult tissues which had been killed and treated with various solvents, but he showed that a prolonged extraction with ether tended to lessen, though it did not entirely destroy, the evocating power of the tissue. This result, which so far as it went was confirmatory of Needham, Waddington, and Needham’s work, was, however, denied by Fischer and Wehmeier (1934), who, on repeating the extraction experiments, could confirm the fact that the ether extracts were active, but claimed that the evocating ability of the tissues was not much lessened by the extraction. In a more recent communication (1934, a ) Holtfreter has repeated his extractions, and finds that the activity of the extracted tissue is only slightly lowered. It is very probable, however, that there will be difficulty in extracting the whole of the active ether-soluble substances from a given mass of tissue. There is general agreement that ether extracts contain an active substance.

scholarly journals Factors Contributing to the Performance of Farmer Producer Organizations (FPOs) – a Study in Medak District of Telangana State

2021 ◽  
Vol 12 (3) ◽  
pp. 192-198
Author(s):  
Amitha, C. D. ◽  
◽  
Savitha. B. ◽  
Sudha Rani. V. ◽  
Laxminarayana, P. ◽  
...  
Keyword(s):  
Group Communication ◽  
Independent Research ◽  
Education Group ◽  
Ex Post ◽  
Ex Post Facto ◽  
Leadership Group ◽  
Overall Performance ◽  
Team Spirit ◽  
Telangana State ◽  
Organization Centre

A study was conducted on the performance of FPOs and the factors contributing to performance of FPOs in Medak district of Telangana State, India. Three FPOs were selected randomly from 3 different promoting institutes viz., Suraksha Farmers Producer Company Ltd (SFPCL) promoted by independent research organization Centre for Sustainable Agriculture (CSA), Marpalli Kisan Kranthi Producer Company Ltd (MKKPCL) promoted by Vrutti NGO and Siddipet Kisan Agro Farmers Producer Company Ltd (SKAFPCL) promoted by International Crops Research Institute for the Semi-arid Tropics (ICRISAT). The Ex-post facto research design was adopted for the study with a sample of 90 producer members, covering three FPOs in erstwhile Medak district of Telangana State. From the analysis, it was found that overall performance of FPOs in Medak district was average to poor. The factors viz., education, group leadership, group communication, adherence to rules, group participation, and team spirit had showed positive and significant relationship with performance. The results of regression analysis inferred that all the selected twelve factors put together explained the variation to the extent of 72.47% in the performance of the FPO with leadership of officials and participation of members contributing significantly to the performance of FPOs.

scholarly journals Studies on the nature of the amphibian organization centre - VI-Inductions by the evocator-glycogen complex in intact embryos and in ectoderm removed from the individuation-field

1937 ◽  
Vol 122 (828) ◽  
pp. 403-412 ◽  
Keyword(s):  
Neural Tissue ◽  
Water Bath ◽  
Boiling Water ◽  
Rabbit Liver ◽  
Chemical Stimulus ◽  
Boiling Water Bath ◽  
Amphibian Embryos ◽  
Single Chemical ◽  
Residual Tissue ◽  
Organization Centre

Several authors, including Fischer, Wehmeier and their collaborators (1933, 1935) and Waddington, Needham, Nowiński and Lemberg (1935), have obtained the induction of neural tissue in amphibian embryos by the implantation of crude glycogen or of substances extracted from it. Others (Holtfreter 1933, 1934; Woerdemann 1933) have employed it unsuccessfully. It is clear now that the activity is not due to the glycogen itself, but to some accompanying impurity, and it was suggested by Waddington, Needham and Brachet (1936) that the active evocator substance is of a sterol-like nature and forms a loose complex with glycogen and possibly with some protein as well. It therefore seemed interesting to investigate whether any difference could be detected in the evocating powers of glycogen in its two forms—the desmo-form in which it is combined with protein and the lyo-form in which it is free (Willstätter and Rohdewald 1934). Specimens of lyo- and desmo-glycogen were therefore prepared and implanted. Both showed themselves capable of evocation, and their activity was such that they seemed suited for testing the effect of a chemically homogeneous evocating mass on ectoderm isolated from the host. By implanting desmo-glycogen into isolated pieces of ectoderm, we should obtain some idea of what a single chemical stimulus is capable of evoking; does it simply induce neural tissue or is there any tendency for the isolated ectoderm to react by producing a neural organ? This question was raised at the time of the discovery of the activity of the dead organizer (Waddington 1933) and has often been mentioned subsequently (in particular Waddington 1934; Needham 1936 b ). The present results seem to answer it in favour of the first alternative. 2—Methods Preparations of desmo- and lyo-glycogen from rabbit liver were made as follows: 145 g. of liver, which had been cooled in ice as soon as it had been removed from the animal, was minced up with scissors and added in portions to 150 ml. of boiling water. When all the tissue had been added the flask was warmed for a further 20 min. on a boiling water-bath, with occasional shaking. The mixture was then filtered on a Buchner funnel (Filtrate I). The residual tissue was ground up without sand in a mortar, heated on the water-bath for 20 min. with a further 200 ml. of water, and filtered as before (Filtrate II). It was assumed that most of the lyo- glycogen would have been extracted in the first two operations, and most of the remainder was then removed from the tissue by extracting with boiling water five more times. 200 ml. of water were used for each of these extractions, which were allowed to proceed on the boiling water-bath for 1-2 hr. The extract was removed by centrifugation.

scholarly journals Studies on the nature of the amphibian organization centre III—The activation of the evocator

1936 ◽  
Vol 120 (817) ◽  
pp. 173-198 ◽  
Keyword(s):  
Normal Development ◽  
Chemical Substance ◽  
Body Cavity ◽  
Neural Plate ◽  
The Body ◽  
Gradient System ◽  
The Third ◽  
Axial Gradient ◽  
Organization Centre ◽  
Made In

The first attempts to produce a capacity for induction in tissue which is normally incapable of performing such an action were made by Spemann and Geinitz in 1927. They grafted a fragment of presumptive ectoderm into the organization centre of another embryo, and, removing it a few hours later, found that it had been “infected” with the inducing capacity of the tissues by which it had been surrounded. The experiment inevitably suggested that the inducing capacity is the property of a chemical substance which had diffused out of the organizer tissue into the grafted ectoderm fragment. A similar hypothesis could be used to explain the observation of Mangold and Spemann (1927) that in normal development the presumptive neural plate acquires inducing capacity at the same time and in proportion as it is underlain and determined by the mesodermal organizer. The first suggestion that the non-inducing parts of a Urodele gastrula themselves possess an organizing capacity, which is masked but only awaits activation or release, emerged in the work of Dürken (1926), Bautzmann (1929, a , b ), Kusche (1929), and Holtfreter (1931), and attention was first drawn to it by Huxley (1930). The German authors showed that if fragments of the gastrula are “interplanted” into the body cavity or optic vesicle of older larvae, they may develop into something other than their presumptive fate, and in particular, presumptive epidermis or neural plate may develop into various mesodermal derivatives such as notochord or muscle. Huxley pointed out the similarity between this phenomenon, which was called bedeutungsfremde Selbstdifferenzierung , and the results of isolating parts of the axial gradient system of lower organisms, which have been particularly described by Child (summaries 1928, 1929). An isolated part of an axial gradient system reconstructs a “dominant region”; and Huxley suggested that we could account for bedeutungsfremde Selbstdifferenzierung by supposing that an isolated part of a gastrula reconstructs the dominant region, i.e ., the organization centre. In the spring of 1932 one of us (C. H. W.), while on a visit to the laboratory of Dr. O. Mangold in Berlin for the purpose of learning the technique of amphibian operations, attempted to carry the matter a step further. If Huxley’s explanation were correct, one would have to suppose that a capacity for behaving like a “dominant region”, that is, for inducing, is latent in the presumptive ectoderm, and this capacity should become manifest when the ectoderm changes into a dominant region after isolation. The following experiment was therefore made to test this point. Fragments of presumptive ectoderm from a young gastrula were interplanted into the eye-cavity of Anuran tadpoles, from which the eye-ball had previously been removed. After two days the interplanted tissue was removed and grafted by the Einsteck method into the blastocoele of young newt gastrulae, to discover whether they were capable of inducing the formation of neural plate. Three sets of controls were made. In one set organizing tissues were interplanted for two days and then tested to see whether their inducing capacity had been impaired, in the second set organizing tissue was isolated for two days in Holtfreter solution, and then tested, and in the third set presumptive ectoderm was isolated for two days in Holtfreter solution and tested for inducing capacity.

scholarly journals Farmer Producer Organizations (FPOs) – Analysis of Profile of FPOs and Its Members in Medak District of Telangana

2021 ◽  
pp. 24-31
Author(s):  
C. D. Amitha ◽  
B. Savitha ◽  
V. Sudha Rani ◽  
P. Laxminarayana
Keyword(s):  
Group Composition ◽  
Middle Age ◽  
Group Cohesiveness ◽  
Independent Research ◽  
Ex Post ◽  
Ex Post Facto ◽  
Poor Group ◽  
Profile Characteristics ◽  
Organization Centre ◽  
Medium Group

This paper focused to study the profile of selected FPOs and its members. With respect to the profile of FPO members, twelve profile characteristics selected were grouped under group composition, governance and management and membership commitment. An Ex-post-facto research design was adopted for the study. Three FPOs were selected randomly from 3 different promoting institutes working in the Medak district viz., Suraksha Farmers Producer Company Ltd (SFPCL) promoted by independent research organization Centre for Sustainable Agriculture (CSA), Marpalli Kisan Kranthi Producer Company Ltd (MKKPCL) promoted by Vrutti NGO and Siddipet Kisan Agro Farmers Producer Company Ltd (SKAFPCL) promoted by International Crops Research Institute for the Semi-arid Tropics (ICRISAT). The results of the study revealed that under group composition, majority were small farmers with middle age (55.55%), primary school education (35.55%), with medium farming experience (47.77%) and with medium annual income (60.00%). Majority of respondents perceived that with respect to management and governance characteristics of FPO had poor group leadership (41.11%), fair group communication (58.88%) and medium adherence to rules(41.11%). With respect to membership commitment majority of respondents had low group participation (43.33%), medium group cohesiveness (47.77%) and low team spirit (43.33%).

The “organization centre”

1962 ◽  
Vol 16 (1-2) ◽  
pp. 57-68 ◽  
Author(s):  
P. D. Nieuwkoop
Keyword(s):  
Organization Centre

scholarly journals Studies on the nature of the amphibian organization centre - VII. Evocation by some further chemical compounds

1938 ◽  
Vol 125 (840) ◽  
pp. 365-372 ◽  
Keyword(s):  
Chemical Compounds ◽  
Acetone Solution ◽  
Water Bath ◽  
Egg Albumen ◽  
Wet Weight ◽  
Organization Centre ◽  
Made In

In a previous paper (Waddington and Needham 1935) evidence was presented that 1:9:dimethylphenanthrene, 9:10-dihydroxy-9:10-di- n -butyl-9:10-dihydro-1:2:5:6-dibenzanthracene and probably 1:2:5:6-dibenzanthracene are capable of evocating the formation of neutral tissue from the competent ectoderm of the newt gastrula. This paper records further tests with allied substances. The work was done during the spring of 1937, with eggs of Triton alpestris , specimens of which were sent from Germany. The substance to be tested was inserted into the blastocoel of the young gastrula in a finely dispersed form contained in a lump of coagulated egg albumen. The tech­nique of preparation of the coagula differed slightly from that previously employed. About 1 mg. of the substance was first dissolved in about 1 c. c. of acetone, the acetone solution added to 1 c. c. of water, and the acetone removed on a water-bath. About 1 c. c. of albumen solution, made in Holtfreter solution, was then added to the milky suspension, and the albumen coagulated on a water-bath. The dispersed substance seems to be almost completely adsorbed on the solid coagulum, giving a concentration of about 2 mg./c. c. The size of the implanted lumps was about 0·01 c. c., so that an embryo weighing roughly 5 mg. wet weight would receive about 0·02 mg. of the substance.

Studies on Regional Specificity Within the Organization Centre of Urodeles

1950 ◽  
Vol 27 (2) ◽  
pp. 126-144
Author(s):  
C. H. WADDINGTON ◽  
T. YAO
Keyword(s):  
Spina Bifida ◽  
Anterior Part ◽  
Organizer Region ◽  
Neural Plate ◽  
Normal Embryo ◽  
Median Part ◽  
Regional Specificity ◽  
Spatio Temporal ◽  
Regional Character ◽  
Organization Centre

1. In young gastrulae of Triton alpestris the median part of the organization centre immediately in front of the blastopore was excised and replaced after reversal of its anterior-posterior axis. Completely normal embryos developed in many cases, but in others there was some degree of microcephaly or spina bifida. 2. Similar normal embryos can develop after exchange of the anterior and posterior regions of the organizer, either with normal or reversed orientation. 3. The spina bifida which frequently appears is a consequence of the impediment offered by the graft to the normal gastrulation movements. 4. Microcephaly may also result if the presence of the graft prevents the proper development of the anterior part of the archenteron roof. 5. It may also be caused when the posterior organizer region is brought into the anterior region, if the host fails to convert it into anterior material. This occurs the more frequently the older the grafted posterior material is. 6. Even at the end of gastrulation (slit yolk-plug stage) the regional character of the archenteron roof is not finally determined. A fairly normal embryo (with over-thick mesoderm) may develop if an extra archenteron roof is added with reversed orientation between the normal archenteron roof and the presumptive neural plate. 7. The determination of the regional structure of the archenteron roof and the neural plate is discussed. Attention is drawn to the spatio-temporal factors involved in the production and diffusion of the evocator with the dynamic system of the gastrulating egg.

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