Ultrastructure of polytene chromosomes of Drosophila isolated by microdissection

1980 ◽  
Vol 45 (1) ◽  
pp. 15-30
Author(s):  
M.R. Mott ◽  
E.J. Burnett ◽  
R.J. Hill
Keyword(s):  
Electron Microscope ◽  
Polytene Chromosomes ◽  
Ultrastructural Level ◽  
Chromosomal Proteins ◽  
Linear Arrays ◽  
Ribonucleoprotein Particles ◽  
Acid Protein

Drosophila polytene chromosomes prepared by a new micromanipulative procedure, which avoids acid squashing, have been examined at the ultrastructural level in the electron microscope. Puffs at 2B, 68C, 74EF, 75B and 85EF, have been examined in some detail, along with the chromocentre and various interbands. The ultrastructure of these chromosomes, which have never been exposed to acid protein denaturants, compares favourably with that of classical acid-fixed specimens. Ribonucleoprotein particles in puffs are seen to be organized in linear arrays and evidence is adduced for looped transcription units. Particles with characteristic sizes and morphologies are observed near the chromocentre, in puffs and in interbands. In interbands RNP particles and ‘superbead’-like chromatin particles may be distinguished. Drosophila polytene chromosomes isolated by micro-manipulation should prove useful for the localization of native chromosomal proteins at an ultrastructural level.

An Ultrastructural and Radioautographic Study of Early Oogenesis in the Toad Xenopus Laevis

1973 ◽  
Vol 12 (1) ◽  
pp. 71-93
Author(s):  
LESLEY WATSON COGGINS
Keyword(s):  
Electron Microscope ◽  
Xenopus Laevis ◽  
Thymidine Incorporation ◽  
Ultrastructural Level ◽  
Extrachromosomal Dna ◽  
Late Pachytene ◽  
Synaptonemal Complexes ◽  
Round Nucleus ◽  
A Cell ◽  
Major Period

Early oogenesis in the toad Xenopus laevis has been investigated at the ultrastructural level, with particular reference to the formation of extrachromosomal DNA. Thymidine incorporation was localized by electron microscope radioautography. In oogonia, the nucleus is irregular in outline and may contain several nucleoli. Oocytes, from premeiotic interphase to late pachytene, are found in cell nests which are estimated to consist of about 16 cells each. Adjacent oocytes within a nest are connected by intercellular bridges and develop synchronously. Each premeiotic interphase-leptotene oocyte has a round nucleus which contains one or two centrally located, spherical nucleoli. Electron-microscope radioautography showed that all nuclei in a cell nest incorporate thymidine synchronously during premeiotic S-phase. In zygotene oocytes, axial cores and synaptonemal complexes are observed in the nucleus and abut against the inner nuclear membrane in the region nearest the centre of the cell nest. The nucleolus is still more-or-less round in outline, but is asymmetrically positioned in the nucleus. It lies near the nuclear envelope on the side of the nucleus furthest away from the attachment of the chromosome ends, that is, nearest the outside of the cell nest. Each nucleolus is surrounded by a fibrillar ‘halo’ of nucleolus-associated chromatin into which a low level of thymidine incorporation occurs during zygotene. This is thought to represent the start of the major period of amplification of the ribosomal DNA. Pachytene is characterized by the presence of synaptonemal complexes in the nucleus. The nucleolus becomes very irregular in outline. The fibrillar area around it, which represents the extrachromosomal DNA, increases in size and thymidine is incorporated over the whole of this region. In late pachytene, many small fibrogranular bodies, the multiple nucleoli, are formed in it. The members of a cell nest become separated from one another at this time and begin to develop asynchronously. In diplotene, synaptonemal complexes are no longer observed in the nucleus. The most prominent structures in the nucleus are now the multiple nucleoli, which increase greatly in number in early diplotene. A large increase in cytoplasmic volume occurs and the oocyte grows in size.

scholarly journals COMPARTMENTALIZATION OF THE DEVELOPING MACRONUCLEUS FOLLOWING CONJUGATION IN STYLONYCHIA AND EUPLOTES

1970 ◽  
Vol 47 (2) ◽  
pp. 395-407 ◽  
Author(s):  
John A. Kloetzel
Keyword(s):  
Electron Microscope ◽  
Fibrous Material ◽  
Polytene Chromosomes ◽  
Genetic Constitution ◽  
Thin Sections ◽  
Macronuclear Development ◽  
Individual Bands ◽  
Second Period ◽  
Replication Bands ◽  
Material Form

The development of the macronucleus following conjugation in the hypotrichous ciliates Euplotes and Stylonychia has been examined with the electron microscope. Banded polytene chromosomes can be seen in thin sections of the macronuclear anlagen during the early periods of exconjugant development. As the chromosomes reach their maximum state of polyteny, sheets of fibrous material appear between the chromosomes and transect the chromosomes in the interband regions. Individual bands of the polytene chromosomes thus appear to be isolated in separate compartments. Subsequently, during the stage when the bulk of the polytenic DNA is degraded (1), these compartments swell, resulting in a nucleus packed with thousands of separate spherical chambers. Individual chromosomes are no longer discernible. The anlagen retain this compartmentalized condition for several hours, at the end of which time aggregates of dense material form within many of the compartments. The partitioning layers disperse shortly before replication bands appear within the elongating anlagen, initiating the second period of DNA synthesis characteristic of macronuclear development in these hypotrichs. The evidence presented here suggests that the "chromatin granules" seen in the mature vegetative macronucleus represent the material of single bands of the polytene chromosomes seen during the earlier stages of macronuclear development. The possibility is also discussed that the degradation of DNA in the polytene chromosomes may be genetically selective, which would result in a somatic macronucleus with a different genetic constitution than that of the micronucleus from which it was derived.

scholarly journals Locations of chromosomal proteins in polytene chromosomes.

1976 ◽  
Vol 73 (6) ◽  
pp. 2038-2042 ◽  
Author(s):  
C. R. Alfageme ◽  
G. T. Rudkin ◽  
L. H. Cohen
Keyword(s):  
Polytene Chromosomes ◽  
Chromosomal Proteins

scholarly journals A cytological approach to the ordering of events in gene activation using the Sgs-4 locus of Drosophila melanogaster.

1984 ◽  
Vol 99 (1) ◽  
pp. 233-238 ◽  
Author(s):  
E K Steiner ◽  
J C Eissenberg ◽  
S C Elgin
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Topoisomerase I ◽  
Gene Activation ◽  
Polytene Chromosomes ◽  
Null Alleles ◽  
Major Salivary Gland ◽  
Wild Type ◽  
Fluorescent Band ◽  
Chromosomal Proteins

The polytene chromosomes of Drosophila strains that differ in the synthesis of the major salivary gland glue protein sgs-4 were examined by indirect immunofluorescence using antisera to several nonhistone chromosomal proteins. The Oregon-R X chromosome, which produces sgs-4 messenger RNA, showed a strong fluorescent band at locus 3C11-12 when stained with anti-RNA polymerase II, whereas the null mutant Berkeley 1 failed to exhibit fluorescence at that locus. The presence of another antigen (Band 2), normally associated with developmentally active loci, was clearly evident at locus 3C11-12 of both transcriptionally competent and null strains, indicating that the association of Band 2 antigen with the chromatin is an event independent of RNA polymerase II binding. Antibodies directed against Drosophila topoisomerase I stained 3C11-12 in the Sgs-4+ (wild-type) strain brightly, but gave significantly less staining in the null strain. This indicates that the high concentrations of topoisomerase I seen at active loci are closely associated with the transcriptional event. In some of these analyses, we have made use of flies heterozygous for the wild-type and null alleles in order to make internally controlled comparisons. The results suggest that this type of analysis will enable conclusions to be drawn concerning the interdependence and order of action of chromosomal proteins involved in developmental gene activation.

An Electron Microscopical Study of Neutral Red Granules in Mouse Exocrine Pancreas

1964 ◽  
Vol s3-105 (70) ◽  
pp. 219-226
Author(s):  
JENNIFER M. BYRNE
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Golgi Apparatus ◽  
Normal Tissue ◽  
Exocrine Pancreas ◽  
Ultrastructural Level ◽  
Neutral Red ◽  
Microscopical Study ◽  
Zymogen Granules ◽  
Electron Microscopical

The neutral red granule cycle in the mouse exocrine pancreas was studied with the electron microscope in order to discover what changes appear at an ultrastructural level in cells treated with neutral red. There are no changes in the endoplasmic reticulum, the nucleus, the Golgi apparatus, the zymogen granules, or the mitochondria of stained cells when compared with normal tissue. Osmiophil inclusions are found which in their size and distribution correspond to the neutral red granules seen under the light microscope. Such inclusions are not seen in normal tissue. They resemble morphologically the lysosomes of various tissues.

scholarly journals MISE EN EVIDENCE ET ETUDE CYTOCHIMIQUE D'UNE PROTEINE BASIQUE EXTRANUCLEAIRE DANS LES SPERMATOZOIDES DES CRUSTACES DECAPODES

1967 ◽  
Vol 32 (3) ◽  
pp. 547-556 ◽  
Author(s):  
Philippe Chevaillier
Keyword(s):  
Electron Microscope ◽  
Carcinus Maenas ◽  
General Term ◽  
Relative Importance ◽  
Decapod Crustaceans ◽  
Nephrops Norvegicus ◽  
Basic Proteins ◽  
Acid Protein

Extranuclear basic proteins have been detected in the capsule of the spermatozoa of three species of decapod crustaceans (Nephrops norvegicus L., Macrura; Eupagurus bernhardus L., Anomura; Carcinus maenas Penn., Brachyura). Their properties have been studied by cytochemical methods. Their position inside the capsule of the spermatozoon has been specified with the aid of the electron microscope. Present in a constant fashion in the three species cited, their relative importance is very variable. In contrast to the refringent cone of the spermatozoon of Ascaris, which contains an acid protein, ascaradine, the capsule of the spermatozoon of the three decapod crustaceans studied contains basic proteins which we propose to designate by the general term "decapodine".

scholarly journals The use of Salvinia auriculata as a bioindicator in aquatic ecosystems: biomass and structure dependent on the cadmium concentration

2012 ◽  
Vol 72 (1) ◽  
pp. 71-77 ◽  
Author(s):  
G. Wolff ◽  
GC Pereira ◽  
EM Castro ◽  
J Louzada ◽  
FF Coelho
Keyword(s):  
Cell Wall ◽  
Electron Microscope ◽  
Aquatic Ecosystems ◽  
Cadmium Concentration ◽  
Ultrastructural Level ◽  
Multiple Level ◽  
Transmission Electron ◽  
Dry Biomass ◽  
Good Potential ◽  
Scanning Electron

This study shows, in a multiple-level approach, the responses of Salvinia auriculata to Cd pollution in aquatic ecosystems. S. auriculata ramets were cultivated in nutrient solution and subjected to five treatments with Cd for ten days. At the end of the experiment, the number of new ramets and the dry biomass were determined. For ultrastructural observations, the leaves of S. auriculata were analyzed using a scanning electron microscope and transmission electron microscope. At the end of the experiment, the plants exposed to Cd showed damage in the leaves including necrosis and chlorosis, stomate deformations and damaged trichomes. We observed a decrease in the number of new ramets and dry biomass of S. auriculata following the increase in Cd concentration in the solution. At the ultrastructural level, leaves exposed to Cd presented chloroplast deformations and deterioration in the cell wall. All the symptoms of toxicity were directly proportionate to the concentration of Cd in the solution. The results suggests that S. auriculata shows good potential for use as a bioindicator and it can be used in the biomonitoring of aquatic ecosystems contaminated by Cd.

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