An introduction to Programmes for Development

Development ◽  
1984 ◽  
Vol 83 (Supplement) ◽  
pp. 1-6
Author(s):  
Herbert C. Macgregor ◽  
Alma P. Swan

The symposium of which this book is a record was first suggested in the autumn of 1982. At that time, all members of the BSDB committee were persons who were primarily concerned with studies of animal development, and the initial tendency was to think along these lines. The cytology laboratory in the University of Leicester has a long tradition in studies of the lampbrush chromosomes that are found in the growing oocytes of most animals as well as in certain stages of the life cycle of at least one simple plant, the giant unicellular alga Acetabularia mediterranea (Callan, 1982). At some stage in very early diplotene of oogenesis of an amphibian, the oocyte nucleus begins to enlarge and many regions of the nuclear chromatin begin to transcribe RNA. RNA polymerase molecules attach to hundreds of sites along the chromosomes and move progressively along the DNA strand, synthesizing long and complex molecules of RNA as they go.

Author(s):  
Letícia Do Prado

 ResumoDorothy Crowfoot Hodgkin formou-se em química pela Somerville Oxford, doutorou-se em Cambridge e liderou o grupo de pesquisa que decifrou a estrutura molecular de várias moléculas biológicas complexas como: a penicilina, a vitamina B12 e a insulina. Seu nome não foi tão ovacionado quanto o de outros ganhadores do Prêmio Nobel já que seu método de trabalho, a cristalografia de raio X para a análise de moléculas complexas era ainda pioneiro e pouco disseminado entre os laboratórios da época. Foi a busca de soluções exatas para problemas difíceis que motivaram Dorothy a superar tempos de guerra, contratempos experimentais, demandas do casamento, da maternidade e a dor física persistente, para se tornar uma das maiores cientistas do século. Neste trabalho apresentaremos brevemente a vida de Dorothy, sua infância distante dos pais e rica em experiências culturais, sua juventude, as dificuldades que precederam sua entrada na Universidade e sua vida como pesquisadora, e mais especificamente, falaremos sobre sua colaboração para a solução da estrutura molecular da penicilina no cenário da Segunda Guerra Mundial. Nosso objetivo é apresentar ao leitor o trabalho de Dorothy ancorados em suas  publicações originais e suas biografias, de maneira a contribuir com a disseminação da história das mulheres na ciência. Palavras-chave: Dorothy Crowfoot Hodgkin; Penicilina; Mulheres na Ciência.AbstractDorothy Crowfoot Hodgkin graduated in chemistry from Somerville Oxford, doctorate from Cambridge and led the research group that deciphered the molecular structure of several complex biological molecules such as penicillin, vitamin B12 and insulin. Her name was not as ovation as that of other Nobel Prize winners since their method of working, X-ray crystallography for the analysis of complex molecules was still pioneering and little disseminated among laboratories of the time. It was the search for exact solutions to difficult problems that motivated Dorothy to overcome wartime, experimental setbacks, marriage demands, maternity, and persistent physical pain to become one of the greatest scientists of the century. In this work we will briefly present the life of Dorothy, her childhood far from her parents and rich in cultural experiences, her youth and the difficulties that preceded her entrance into the University and her life as a researcher, and more specifically, we will talk about her collaboration for the solution of molecular structure of penicillin in the scene of World War II. Our goal is to present the Doroty works, anchored in her original published and her biographies in order to contribute with the dissemination of history of women in science.Keywords: Dorothy Crowfoot Hodgkin; Penicillin; Women in Science.


1965 ◽  
Vol s3-106 (75) ◽  
pp. 215-228
Author(s):  
H. C. MACGREGOR

Theories concerning the mode of origin of peripheral nucleoli in amphibian oocytes have been examined and tested. In Triturus cristatus the giant fusing loops of the 3 shortest lampbrush bivalents resemble nucleoli when viewed in phase contrast and may be considered as possible sites of production of nucleoli. Giant fusing loops, however, differ from peripheral nucleoli in certain important respects, and animals lacking giant fusing loops on their lampbrush chromosomes nevertheless have normal peripheral nucleoli. Therefore, similarity in appearance between objects attached to lampbrush chromosomes and free peripheral nucleoli may not be significant. In oocytes of T. c. carnifex, T. c. karelinii, and T. c. danubialis, peripheral nucleoli do not increase in number during the lampbrush phase of oogenesis, except by division of pre-existing nucleoli towards the end of oogenesis. There are about 1,000 nucleoli per oocyte nucleus in each of these sub-species. In T. c. cristatus there are more nucleoli in large oocytes than in small ones, and it seems likely that in this sub-species the giant fusing loops add to the existing population of nucleoli in an oocyte by successively growing and shedding new nucleoli. A similar situation probably holds in Plethodon cinereus. Hexaploid oocytes from triploid females of Ambystoma jeffersonianum have 3 times as many nucleoli as diploid oocytes from diploid females of the same species. The number of nucleoli in an amphibian oocyte nucleus is therefore related to the number of sets of chromosomes in the cell. In yolky oocytes from hypophysectomized newts most peripheral nucleoli are firmly attached to the inner surface of the nuclear membrane; whereas in similar oocytes from unoperated or gonadotrophin-treated animals none of the nucleoli is so attached. On the basis of these observations 2 mechanisms are suggested for the formation of amphibian oocyte nucleoli. The first of these mechanisms probably operates in T. c. carnifex, where all peripheral nucleoli are formed before or soon after the chromosomes assume the lampbrush form, and no part of a lampbrush chromosome is involved in a process which adds to the existing population of nucleoli. The second mechanism probably operates in T. c. cristatus, where most of the peripheral nucleoli are formed before the lampbrush phase of oogenesis but a nucleolar organizer on the lampbrush chromosomes continues to grow and detach nucleoli throughout oogenesis. Both these mechanisms are discussed in terms of what is known of the chemical composition and function of peripheral nucleoli.


1974 ◽  
Vol 15 (1) ◽  
pp. 145-161
Author(s):  
R. J. HILL ◽  
K. MAUNDRELL ◽  
H. G. CALLAN

Evidence has been obtained which indicates that disulphide bond crosslinks contribute to the morphological integrity of isolated lampbrush chromosomes (both chromomeres and lateral loops) and nucleoli. It is suggested that the progressive formation of these bonds in vitro by aerial oxidation may provide the basis for the previously recognized time-dependent hardening or ‘denaturing’ of these structures. Manually isolated germinal vesicle nuclei have been massed and fractionated by low-speed centrifugation into nucleoplasm and chromatin. Phase-contrast microscopy demonstrates the chromatin to consist of nucleoli, lampbrush chromosomes and nuclear membranes. Urea gel electrophoresis has been employed to resolve the reduced and S-carboxymethylated proteins of whole nuclei into some 12 components, negatively charged at pH 8. The nucleoplasm alone gives an essentially similar pattern, but with the distinct depletion of one component and slight depletion of another. Both of these components are much enriched in the chromatin pellet where they predominate over all other proteins. The total chromatin has been subfractionated by microdissection, taking advantage of the differential attachment of nucleoli to the nuclear membrane at different stages of oogenesis. It is concluded that the nuclear membrane per se does not contribute to the major chromatin proteins. The two major polypeptides are components of the nucleoli. Preparations of isolated lampbrush chromosomes have not, to date, provided sufficient material to give a distinctive electropherogram; only one faint band, a major component of whole nuclei, was apparent. Sodium dodecyl sulphate gel electrophoresis has resolved some 25 components in whole nuclei, and again demonstrates the enrichment of the two major species in the total chromatin fraction. The apparent molecular weights of these two species are 43 kilodaltons and 110 kilodaltons. Approximately 20 minor species are also present in the chromatin and are obviously good candidates as components of the nucleolar and chromosomal structures. Histones, at most, make only a minor contribution to the overall chromatin protein population.


1975 ◽  
Vol 17 (3) ◽  
pp. 579-588
Author(s):  
K. Maundrell

An electrophoretic analysis has been carried out on the total protein of lampbrush chromosomes, nucleoli and nuclear sap, obtained from newt oocyte nuclei. In each case, distinctive and heterogeneous banding patterns are observed. The absence of detectable quantities of histones in occyte chromatin is noted. In the case of the lampbrush chromosome preparation, it is concluded that all protein species are derived from the ribonucleoprotein matrix of the lateral loops.


Development ◽  
1987 ◽  
Vol 101 (4) ◽  
pp. 715-728
Author(s):  
C. Abbadie ◽  
D. Boucher ◽  
J. Charlemagne ◽  
J.C. Lacroix

The location of three proteins of the oocyte nucleus of Pleurodeles was studied during oogenesis and embryogenesis using monoclonal antibodies A33/22, C3/1 and C36/1. Immunoblotting of two-dimensional gel electrophoregrams of oocyte nuclear proteins showed that these antibodies recognized proteins whose relative molecular masses and isoelectric points were 80×103 and 6á4, 175×103 and 5 and 270×103 and 7, respectively. In the oocyte, all three proteins were nucleoplasmic; those revealed by antibodies A33/22 and C36/1 were detected on lampbrush chromosomes: the first one on the RNP matrix of the loops, and the second one on both the loops and the chromomeres. Protein A33/22 was observed in most nuclei during embryonic, larval and adult development, except for the young embryo, before the midblastula transition. The distribution of this protein in the oocyte and its behaviour during development suggest that it might be involved in the packaging of RNAs during transcription. Antibody C3/1 recognized an oocyte nucleoplasmic protein with biochemical and biophysical properties similar to those of protein N1-N2. After oocyte maturation, the protein moved into the cytoplasm of the animal hemisphere and, from fertilization to the midblastula stage, it shifted from the cytoplasm into the nuclei as cell division proceeded. Starting from the gastrula stage, this protein became specific to the endoderm nuclei. After hatching, it was no longer detectable. This behaviour seems to correspond to that of a nuclear protein issued from the maternal stock pile. Protein C36/1 behaved similarly during early development, but remained in most nuclei after neurulation until the adult age, with a pattern similar to that of protein A33/22. In addition, it was present on the mitotic chromosomes. Its association with mitotic as well as lampbrush chromosomes connects it with the DNP fibre proteins.


2002 ◽  
Vol 13 (10) ◽  
pp. 3466-3476 ◽  
Author(s):  
Christine Murphy ◽  
Zhengxin Wang ◽  
Robert G. Roeder ◽  
Joseph G. Gall

We used immunofluorescence to study the distribution and targeting of RNA polymerase (pol) III subunits and pol III transcription factors in the Xenopus laevis oocyte nucleus. Antibodies against several of these proteins stained Cajal bodies and ∼90 specific sites on the lampbrush chromosomes. Some of the chromosomal sites had been identified previously by in situ hybridization as the genes for 5S rRNA. The remaining sites presumably encode tRNAs and other pol III transcripts. Pol III sites were often resolvable as loops similar to the much more abundant pol II loops, but without a matrix detectable by phase contrast or differential interference contrast. This morphology is consistent with the transcription of short repeated sequences. Hemagglutinin-tagged transcripts encoding core subunits and transcription factors were injected into the oocyte cytoplasm, and the distribution of newly translated proteins inside the nucleus was monitored by immunostaining. Cajal bodies were preferentially targeted by these proteins, and in some cases the chromosomal sites were also weakly stained. The existence of pol III subunits and pol III transcription factors in Cajal bodies and their targeting to these organelles are consistent with a model of Cajal bodies as sites for preassembly of the nuclear transcription machinery.


Genome ◽  
2001 ◽  
Vol 44 (6) ◽  
pp. 1100-1103 ◽  
Author(s):  
Stefania Bucci ◽  
Letizia Giani ◽  
Giorgio Mancino ◽  
Mario Pellegrino ◽  
Matilde Ragghianti

The localization of the TATA-binding protein (TBP) associated factor II70 (TAFII70) in the germinal vesicle (GV) of newt oocytes was investigated. In spreads of GV content, anti-hTAFII70 monoclonal antibody (mAb) stained Cajal bodies (CBs) that were either attached to specific sites on the lampbrush chromosomes or free in the nucleoplasm. To confirm this localization the PwTAFII70 cDNA was cloned and myc-tagged transcripts injected into the oocyte cytoplasm. Newly translated PwTAFII70 protein was detected a few hours later in the Cajal bodies. These data support the hypothesis that Cajal bodies are the assembly sites of the transcription machinery of the oocyte nucleus. TAFII70 protein can play a role in lampbrush transcription; alternatively TAFII70 can be considered a component in the subset of TFIID complexes that do not function during oogenesis, but are accumulated in the oocyte for later use during early development.Key words: TAFII70, Cajal body, lampbrush chromosomes, RNA transcription and processing, newts, Pleurodeles.


1966 ◽  
Vol 1 (1) ◽  
pp. 85-108
Author(s):  
H. G. CALLAN

Amongst the axolotl's haploid complement of fourteen mitotic chromosomes, one of the four largest, with a greater arm asymmetry than the other three, shows a nucleolar constriction subterminally in its shorter arm. Low-temperature treatment causes further secondary constrictions to appear; these constrictions enable most of the mitotic chromosomes to be identified; the constrictions occur at similar sites in the chromosomes of tail-fin epithelial cells, hepatocytes, and brain cells. Homology between the mitotic and oocyte (lampbrush) nucleolar organizers has been established, and thus the several hundred free nucleoli in oocytes are genetically related to the two nucleoli of diploid somatic interphases. During oocyte development the free nucleoli transform from solid structures to rings and back to solid structures again without detectable increase in number. During the contraction and aggregation of the lampbrush chromosomes within the oocyte nucleus as maturity approaches, in most axolotls the free ring-shaped nucleoli become stretched between the nuclear periphery and central chromosome group, and take on a characteristic beaded appearance. These transformations of the free nucleoli are largely paralleled by forms which nucleoli attached subterminally to the shorter arm of lampbrush chromosome III concurrently assume. The question as to whether fully developed nucleoli detach from the organizer loci and add to the population of free nucleoli in oocytes remains undecided. It may well be that virtually all the DNA-generators of free nucleoli detach from the organizer loci before starting to carry out nucleolar functions, and before there is any significant accumulation of protein and RNA around them. If so, the variability in quantity of attached nucleolar material may not reflect different states in a nucleolar synthesis and detachment cycle, but rather variation in the number of nucleolar DNA Anlagen which happen to remain attached to the organizer loci after the synthesis and detachment of the great majority of the Anlagen has ceased. In occasional oocytes the only chromosomal continuity maintained across the organizer locus consists of a nucleolar ‘double bridge’; this indicates that the genetically persistent (i.e. chromosomal) organizer DNA bears the same structural relationship to neighbouring parts of a lampbrush chromosome as any other chromomere with its attendant pair of lateral loops. The lampbrush chromosomes of the axolotl have been provisionally mapped. The centromeres are represented by short portions of chromosome axis without lateral loops, and there are two spheres close to the centromeres of both chromosome VI and chromosome XIII. Other recognition characters are inconspicuous or not very reliable, and features of the lampbrush chromosomes related to the low-temperature induced secondary constrictions of mitotic chromosomes have not been identified.


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