The polytenic endosperm haustorium of Rhinanthus minor (Scrophulariaceae): functional ultrastructure

1992 ◽  
Vol 70 (10) ◽  
pp. 1997-2004 ◽  
Author(s):  
Walter Nagl
Keyword(s):  
Polytene Chromosomes ◽  
Ultrastructural Level ◽  
Structural Features ◽  
Synthetic Activity ◽  
Apical Region ◽  
Nuclear Surface ◽  
Chalazal Haustorium ◽  
Endosperm Haustorium ◽  
Micropylar Endosperm ◽  
Giant Nuclei

The seed of Rhinanthus undergoes an uncommon differentiation in developing both a chalazal and a micropylar endosperm haustorium. The chalazal haustorium is described at the ultrastructural level. It shows two giant nuclei with polytene chromosomes and numerous complex nucleoli. The nuclear surface is highly interdigitated with the cytoplasm and displays many pores. The cell wall of the apical region of the haustorium displays a prominent wall labyrinth. A large number of mitochondria are located in this region, while leucoplasts are mainly found in vicinity of the nuclei. The structural features of the haustorium are discussed in relation to its expected functions, i.e., synthetic activity and transfer of nutritive material from surrounding tissues to the endosperm proper. Key words: endosperm, haustorium, polyteny, Rhinanthus, transfer cell.

WHOLE MOUNT ELECTRON MICROSCOPY OF POLYTENE CHROMOSOMES FROM DROSOPHILA MELANOGASTER

1976 ◽  
Vol 18 (1) ◽  
pp. 67-77 ◽  
Author(s):  
Gary D. Burkholder
Keyword(s):  
Electron Microscopy ◽  
Drosophila Melanogaster ◽  
Polytene Chromosomes ◽  
Ultrastructural Level ◽  
Structural Features ◽  
Gene Localization ◽  
Simple Method ◽  
Longitudinal Orientation ◽  
Whole Mount ◽  
Chromosome Bands

A simple method of whole mount electron microscopy has been developed to study the fine structural organization of Drosophila melanogaster polytene chromosomes. This method preserves the structural features of these chromosomes and may be of use for rapid gene localization at the ultrastructural level. Chromosome bands were electron dense regions composed of closely packed groups of chromomeres; thin bands consisted of a single row of transverse chromomeres, while thicker bands were composed of two to several rows of chromomeres. Interband regions contained relatively straight chromatin fibres which traversed the interband zone either singly or in bundles of several fibres. The interband chromatin fibres were generally 130 Å in diameter or thicker, and appeared to be composed of two or more thinner (80-90Å) fibres. Presumptive puff regions were characterized by extended chromatin fibres having a longitudinal orientation, however some transverse rows of chromomeres were also seen in these regions, suggesting that not all of the chromomeres in a band may be involved in puff formation. The chromatin fibres in the puffs were frequently thinner than those found in the interband regions. In stretched chromosomes, the chromatin fibres were drawn out into a mass of parallel fibres without any distinction between band and interband regions, supporting the hypothesis that individual chromatids are continuous through both band and interband regions and probably extend throughout the whole chromosome. No core fibres were observed in any of the polytene chromosomes studied.

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.

scholarly journals Histological and ultrastructural changes in turkey liver under intensive rear-ing and influence of xenobiotics

2020 ◽  
Vol 22 (99) ◽  
pp. 63-68
Author(s):  
O. М. Shchebentovska ◽  
A. K. Kostyniuk
Keyword(s):  
Energy Content ◽  
Clinical Manifestations ◽  
Subsequent Development ◽  
Fatty Degeneration ◽  
Ultrastructural Level ◽  
High Energy ◽  
Ultrastructural Changes ◽  
Synthetic Activity ◽  
Standard Diet ◽  
Limited Mobility

Liver problems of various etiologies in turkeys have been reported in many countries for the last 20 years. Poultry dies having no clinical manifestations of the disease, and at pathological autopsy, diffuse haemorrhages and marked dystrophic changes of the organ are noted. To date, there are several factors that can cause such changes, these are unbalanced amino-acid feed, insufficient calcium, biotin, selenium, the very high energy content of feed; zootechnical factors – limited mobility of birds due to cage density violations, high temperature; genetic factors – the influence of estrogens; infectious factors – E. coli, Clostridium, and viruses of Picornaviridae family. The article describes the histopathological and ultrastructural changes in the turkey liver under the influence of various factors. The material for the research was obtained from a farm where turkeys of the “Hybrid Converter” cross are grown, same age, fed with a standard diet that changed according to the technological map of cultivation. On the 50th day of life, a pathological autopsy of the dead poultry was performed, pieces of liver were selected for histological and ultrastructural examination. The visual assessment revealed significantly enlarged liver, the colour from dark red to light brown, flabby consistency. In some cases, diffuse fatty infiltrations of hepatocytes were histologically revealed, in other cases, focal necrosis with the growth of the connective tissue and the formation of massive perivascular couplings were registered. Large vacuolar fatty degeneration of hepatocytes with subsequent development of fibrosis indicates chronic intoxication, probably caused by slow breakdown of fatty acids in cells due to insufficient oxidative phosphorylation, as well as reduced levels of lipotropic factors: choline, methionine and the vitamins. At the ultrastructural level, a large number of lipid inclusions of various sizes, dystrophic changes in mitochondria were observed, which indicates a decrease in the synthetic activity of cells.

Observations on the structure of the small intestine on foetal, neo-natal and sucklings pigs

1971 ◽  
Vol 259 (834) ◽  
pp. 517-531 ◽  
Keyword(s):  
Small Intestine ◽  
Structural Features ◽  
Surface Pattern ◽  
Apical Region ◽  
Intercellular Spaces ◽  
Large Numbers ◽  
Newborn Pigs ◽  
Dilated Intercellular Spaces ◽  
Vacuolated Cells ◽  
Newborn Animals

Light and electronmicroscopic observations of changes throughout the small intestine of foetal, and both suckled and unsuckled newborn pigs are reported. Foetal animals between 73 days gestation and term showed vacuolation in the terminal ileum. This was most extensive between 90 and 100 days when the terminal 30% of the small intestine contained vacuolated cells. The apical region of such cells contained a system of smooth tubes and vesicles, some of which showed evidence of a characteristic surface pattern. The vacuoles contained material of variable electron density and were sometimes seen apparently discharging their contents into the dilated intercellular spaces. Unsuckled newborn animals showed most of the features described above, but, in addition, the vacuolated cells contained large numbers of electron dense inclusions. In suckled animals from birth to 70 h of age there were considerable variations in cellular structure, which could be related to the position in the small intestine, the position on the villus and the age of the animal. The structural features described are discussed in relation to the transfer of colostrum immunoglobulins into the circulation. Keywords: swine, foetus, newborn, small intestine, structure.

scholarly journals ULTRASTRUCTURE AND CYTOCHEMISTRY OF METABOLIC DNA IN TIPULA

1966 ◽  
Vol 30 (1) ◽  
pp. 177-192 ◽  
Author(s):  
A. Lima-de-Faria ◽  
M. J. Moses
Keyword(s):  
Electron Microscope ◽  
Close Contact ◽  
Tritiated Thymidine ◽  
Polytene Chromosomes ◽  
The Body ◽  
Outer Shell ◽  
Synthetic Activity ◽  
Fast Green ◽  
Azure B ◽  
Basic Features

A DNA body is present in the females of the fly Tipula oleracea and is formed in contact with the sex chromosomes in the oogonial interphases. At each oogonial mitosis, the DNA body follows the chromosomes to one anaphase group and is included in one of the telophase nuclei. The body increases appreciably in size during the interphase of meiosis. All oocytes have the body, but only a few nurse cells possess it. The DNA body synthesizes its DNA at a different time than the chromosomes, as is shown by incorporation of tritiated thymidine, and contains 59% of the DNA of the nucleus, as is disclosed by spectrophotometric measurements. At late diplotene the DNA body disintegrates, releasing its DNA into either the nucleus or the cytoplasm. When studied in the electron microscope, the DNA body appears composed of a tight mass of intertwined fibrils. Demonstration that the main mass of the body is composed of DNA is obtained from cytochemical tests which reveal that the DNA body is Feulgen positive, stains green with azure B, incorporates H3-thymidine, and after digestion with DNase is Feulgen negative. The DNA of the body is complexed with histone, like the DNA of the chromosomes, as is revealed by an intense alkaline fast green staining. Electron microscope examination of oocytes reveals that one side of the DNA body is in close contact with the nuclear envelope and that the other side possesses an outer shell composed mainly of particles 150 to 250 A in diameter. Between the outer shell and the chromosomes there is a band of low electron opacity, 4000 to 7000 A thick. In the light microscope, this light band together with the outer shell is Feulgen negative and stains violet with azure B; this is confirmation of the presence of RNA. In the oocytes the nucleoli are found inside the DNA body. These nucleoli have a nucleolonema composed mainly of particles 150 to 250 A. The nucleoli are Feulgen negative, alkaline fast green negative, stain violet with azure B, and do not stain with azure B after RNase digestion, thus confirming their RNA content. The presence of the nucleoli inside the DNA body and of a band of RNA between the body and the chromosomes is indicative of a high RNA synthetic activity. Since the DNA of the body is complexed with histone, as in the chromosomes, and the nucleoli are located inside the body, the simplest interpretation of the DNA body is that it represents hundreds of copies of the operons of the nucleolar organizing region or neighboring regions. The situation found in Tipula has several basic features in common with the polytene chromosomes of other Diptera and with the hundreds of nucleoli present in Triturus oocytes. In all three cases, genes seem to be copied hundreds of times but are kept in different types of packages. A DNA body like the one in Tipula oleracea is found in other species of Diptera and in the Coleoptera. There is no indication, from the present investigation, that the DNA body is in any way associated with a virus.

scholarly journals Anti-Idiotype scFv Localizes an Autoepitope in the Globular Domain of C1q

2021 ◽  
Vol 22 (15) ◽  
pp. 8288
Author(s):  
Nadezhda Todorova ◽  
Miroslav Rangelov ◽  
Vanya Bogoeva ◽  
Vishnya Stoyanova ◽  
Anna Yordanova ◽  
...  
Keyword(s):  
3D Model ◽  
Potent Inhibitor ◽  
3D Structure ◽  
Recombinant Antibodies ◽  
Structural Features ◽  
Phage Library ◽  
Apical Region ◽  
Globular Domain ◽  
Potential Inhibitors ◽  
First Time

We addressed the issue of C1q autoantigenicity by studying the structural features of the autoepitopes recognized by the polyclonal anti-C1q antibodies present in Lupus Nephritis (LN) sera. We used six fractions of anti-C1q as antigens and selected anti-idiotypic scFv antibodies from the phage library “Griffin.1”. The monoclonal scFv A1 was the most potent inhibitor of the recognition of C1q and its fragments ghA, ghB and ghC, comprising the globular domain gC1q, by the lupus autoantibodies. It was sequenced and in silico folded by molecular dynamics into a 3D structure. The generated 3D model of A1 elucidated CDR similarity to the apical region of gC1q, thus mapping indirectly for the first time a globular autoepitope of C1q. The VH CDR2 of A1 mimicked the ghA sequence GSEAD suggested as a cross-epitope between anti-DNA and anti-C1q antibodies. Other potential inhibitors of the recognition of C1q by the LN autoantibodies among the selected recombinant antibodies were the monoclonal scFv F6, F9 and A12.

The Uptake of Tritiated Uridine and Phenylalanine by the Ovaries of Rats and Monkeys

1969 ◽  
Vol 4 (3) ◽  
pp. 655-675
Author(s):  
T. G. BAKER ◽  
HEATHER M. BEAUMONT ◽  
L. L. FRANCHI
Keyword(s):  
Electron Microscope ◽  
Ovarian Tissue ◽  
Ultrastructural Level ◽  
Neonatal Rat ◽  
General Distribution ◽  
Synthetic Activity ◽  
Primordial Follicles ◽  
Ovarian Stroma ◽  
Morphological Identity ◽  
Silver Grains

Rats and monkeys (Macaca mulatta, M. irus) were injected with tritiated uridine or phenylalanine and ovarian tissue was recovered at intervals from 15 min to 24 h later. Autoradiographs were prepared and studied by light microscopy; in addition some specimens which received uridine were examined using the electron microscope. The two isotopes are taken up by the ovaries of both species. The trace obtained with phenylalanine shows a very general distribution, whereas uridine seems to be more selectively incorporated by the various components of the ovary. The nuclei of primordial and growing oocytes are labelled with uridine, and so are the granulosa cells in follicles at all stages of development. The theca surrounding multilayered and vesicular follicles also shows a trace which appears heavier than that over the ovarian stroma. In the neonatal rat, the nuclei of oocytes at the pachytene and diplotene stages take up uridine. Autoradiographs prepared from ovaries fixed from 30 min to 4 h after injection and examined under the electron microscope show silver grains associated with the nucleoli and electron-dense chromosomal cores which are characteristic of these stages in meiotic prophase. Oocytes in primordial follicles, in immature and mature rats, are also labelled, showing that nuclear uptake continues as oocytes enter the ‘resting’ or dictyate stage. Since the chromosomes lose their morphological identity at this time, however, silver grains appear to be randomly distributed over the nuclear matrix. Primordial oocytes in the monkey also have a heavy nuclear label, seen under the light microscope to be associated with chromosomes and nucleoli. At the ultrastructural level, most of the extra-nucleolar silver grains are associated with condensed fibrillar material thought to represent part of the lateral component of chromosomes which are of the ‘lampbrush’ type. The synthetic activity of germinal and somatic elements in the ovary is discussed, and possible differences in the structure and metabolic activity of oocyte chromosomes are considered in relation to intra- and inter-specific variations in radiosensitivity.

DNA amplification, chromatin variations, and polytene chromosomes in differentiating cells of common bread wheat in vitro and roots of regenerated plants in vivo

Genome ◽  
1991 ◽  
Vol 34 (5) ◽  
pp. 799-809 ◽  
Author(s):  
Xiao Min Shang ◽  
Wen Chung Wang
Keyword(s):  
Triticum Aestivum ◽  
Cell Differentiation ◽  
Polytene Chromosomes ◽  
Dna Amplification ◽  
Root Tips ◽  
Embryogenic Calli ◽  
Double Minutes ◽  
Regenerated Plants ◽  
Giant Nuclei

Polytene chromosomes and giant nuclei were observed in differentiating cells of embryogenic calli and root tips of wheat plants (Triticum aestivum cv. Mustang) regenerated from long-term cell suspension cultures and selected cell lines after high-temperature stress. Many giant nuclei almost completely occupied the cellular space of the large parenchyma cells. The amount of DNA from the giant nuclei was as high as 174 C, equivalent to 3.03 × 104 pg of DNA, as revealed by Feulgen cytophotometry. Following cell differentiation, the giant nuclei that were endoaneupolyploid and polytene developed from interphase nuclei (aneuploid) and micronuclei. Polytene chromosomes from the B genome were tentatively identified by their banding patterns, as shown by the HCl–KOH–Giemsa banding method. Variations of polytene chromosomes were cable-like, dispersed, heterochromatinizated, or granulated at the different developmental stages. The number of granular chromatin particles in the cells was 85 to more than 300 when disintegration of the giant nuclei occurred. Some were exclusively heterochromatic, and many others consisted of both euchromatin and heterochromatin. The amount of DNA for these granular chromatin particles was estimated from 0.17 to 5.54 pg. Many minutes and double minutes existed in various stages of dividing and differentiating cells and accompanied the generation and disintegration of the giant nuclei. The DNA sizes of these minutes were estimated as 2.56 × 105 – 1.05 × 107 bp. These results suggested that DNA amplification, polytene chromosomes, minutes, and double minutes were induced in polyploid species with large chromosomes and maintained in embryogenic calli in vitro and apical segments of root tips of regenerated plants in vivo.Key words: giant nucleus, endoaneupolyploidy, polyteny, minutes and double minutes, cell differentiation, Triticum aestivum.

scholarly journals Structure of the PCBP2/stem–loop IV complex underlying translation initiation mediated by the poliovirus type I IRES

2020 ◽  
Vol 48 (14) ◽  
pp. 8006-8021
Author(s):  
Simone A Beckham ◽  
Mehdi Y Matak ◽  
Matthew J Belousoff ◽  
Hariprasad Venugopal ◽  
Neelam Shah ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Limited Proteolysis ◽  
Structural Features ◽  
Full Length ◽  
Apical Region ◽  
Type I ◽  
Stem Loop ◽  
Poliovirus Type ◽  
Linker Region ◽  
Radical Cleavage

Abstract The poliovirus type I IRES is able to recruit ribosomal machinery only in the presence of host factor PCBP2 that binds to stem–loop IV of the IRES. When PCBP2 is cleaved in its linker region by viral proteinase 3CD, translation initiation ceases allowing the next stage of replication to commence. Here, we investigate the interaction of PCBP2 with the apical region of stem–loop IV (SLIVm) of poliovirus RNA in its full-length and truncated form. CryoEM structure reconstruction of the full-length PCBP2 in complex with SLIVm solved to 6.1 Å resolution reveals a compact globular complex of PCBP2 interacting with the cruciform RNA via KH domains and featuring a prominent GNRA tetraloop. SEC-SAXS, SHAPE and hydroxyl-radical cleavage establish that PCBP2 stabilizes the SLIVm structure, but upon cleavage in the linker domain the complex becomes more flexible and base accessible. Limited proteolysis and REMSA demonstrate the accessibility of the linker region in the PCBP2/SLIVm complex and consequent loss of affinity of PCBP2 for the SLIVm upon cleavage. Together this study sheds light on the structural features of the PCBP2/SLIV complex vital for ribosomal docking, and the way in which this key functional interaction is regulated following translation of the poliovirus genome.

Structural features of 3C6/C7 interband chromatin organization in Drosophila melanogaster polytene chromosomes

2013 ◽  
Vol 7 (4) ◽  
pp. 347-351 ◽  
Author(s):  
O. V. Andreenkov ◽  
E. I. Volkova ◽  
V. F. Semeshin ◽  
I. F. Zhimulev ◽  
S. A. Demakov
Keyword(s):  
Drosophila Melanogaster ◽  
Polytene Chromosomes ◽  
Structural Features ◽  
Chromatin Organization
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