Loop size in newt lampbrush chromosomes

Chromosoma ◽  
1990 ◽  
Vol 99 (1) ◽  
pp. 83-86 ◽  
Author(s):  
Pedro León ◽  
James Kezer
Keyword(s):  
Lampbrush Chromosomes ◽  
Loop Size

Oligodeoxynucleotide folding in solution: loop size and stability of B-hairpins

Biochemistry ◽  
1988 ◽  
Vol 27 (17) ◽  
pp. 6321-6326 ◽  
Author(s):  
Luigi Emilio Xodo ◽  
Giorgio Manzini ◽  
Franco Quadrifoglio ◽  
Gijs A. Van der Marel ◽  
Jacques H. Van Boom
Keyword(s):  
Loop Size

scholarly journals Histone H4 acetylation and transcription in amphibian chromatin.

1993 ◽  
Vol 120 (2) ◽  
pp. 277-290 ◽  
Author(s):  
J Sommerville ◽  
J Baird ◽  
B M Turner
Keyword(s):  
Transcriptional Activation ◽  
Histone Deacetylation ◽  
Dense Matrix ◽  
Lampbrush Chromosomes ◽  
Loop Formation ◽  
Triturus Cristatus ◽  
Immature Oocytes ◽  
Intense Fluorescence ◽  
Histone H4 Acetylation ◽  
Lysine Residues

Lampbrush chromosomes from oocytes of the amphibian Triturus cristatus have been used to examine the role of histone acetylation in transcription by indirect immunofluorescence with antisera to H4 acetylated at specific lysine residues. Electrophoresis on acid-urea-Triton gels and Western blotting have confirmed the specificity of these antisera and defined the order in which particular lysine residues are acetylated in amphibian cells. As in mammals, lysine 16 is acetylated first, followed by 8 and/or 12 and then 5. With lampbrush chromosomes from immature (previtellogenic) oocytes, antisera to H4 acetylated at lysines 8, 12, and 16 labeled fluorescent foci at the bases of transcription loops. Antisera to H4 acetylated at lysine 5 labeled weakly (i.e., the tri- and tetraacetylated isoforms must be rare). Loops showed weak labeling of the chromatin axis but intense fluorescence at particular points, which probably represent incompletely decondensed chromatin. The RNP matrix of loops, including the RNP-rich sphere bodies and the dense matrix of "marker" loops, was not labeled. Treatment of immature oocytes with butyrate for 12 h to inhibit histone deacetylation did not affect immunolabeling, suggesting that turnover of H4 acetates is slow. In contrast, in chromosomes from mature oocytes, in which loops have retracted and transcription is low, butyrate caused an increase in labeling with all antisera, followed by the appearance of vestigial loops, weakly labeled, but with regions of intense fluorescence. These loops contain RNP and are presumably transcriptionally active. We conclude that H4 acetates turn over more rapidly in mature than immature oocytes and that histone hyperacetylation precedes, and possibly induces, loop formation and transcriptional activation.

In situ hybridization to lampbrush chromosomes: a potential source of error exposed

1980 ◽  
Vol 41 (1) ◽  
pp. 115-123
Author(s):  
H.G. Callan ◽  
R.W. Old
Keyword(s):  
Lampbrush Chromosome ◽  
Single Pair ◽  
Lampbrush Chromosomes ◽  
Triturus Cristatus ◽  
Rna Transcripts ◽  
Potential Source ◽  
Source Of Error ◽  
Simple Sequence ◽  
Do So

Denatured 3H-labelled DNAs containing Xenopus or human globin sequences hybridize to RNA transcripts on a single pair of lateral loops on lampbrush chromosome IX of Triturus cristatus carnifex, and to no other loops on this chromosome or the rest of the complement. However they do so, not because of the globin sequences in the probes, but rather because the plasmids from which the probes were prepared were constructed with G.C homopolymer tails. Simple sequence poly d(C/G)n probes also hybridize with RNA transcripts on this same pair of loops, and with no others.

scholarly journals Structure of landmark loop ribonucleoprotein matrices in Pleurodeles waltlii lampbrush chromosomes visualized by scanning electron microscopy

1986 ◽  
Vol 81 (1) ◽  
pp. 29-42
Author(s):  
M.L. Bonnanfant-Jais ◽  
E. N'Da ◽  
M. Penrad-Mobayed ◽  
N. Angelier
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Basic Structure ◽  
Spatial Arrangement ◽  
Lampbrush Chromosomes ◽  
Specific Morphology ◽  
Pleurodeles Waltlii ◽  
Scanning Electron

Landmark loop ribonucleoprotein (RNP) matrices of Pleurodeles waltlii lampbrush chromosomes were systematically examined by scanning electron microscopy (SEM). The results, which corroborated similar studies by electron microscopy (EM), showed that RNP transcripts in normal loops, and RNP matrices in granular, globular and dense loops, are composed of one basic structure: an RNP particle with a diameter of 30 nm. SEM observations also clarified the spatial arrangement of this particle in the RNP matrices of all the loop types examined. The specific morphology of normal, granular, globular and dense loop RNP matrices depended on the degree of compaction of the transcription products; this compaction resulted both from the packaging of RNP transcripts and the progressive coiling of the loop axis.

Effects of cordycepin on morphology and RNA synthesis of amphibian lampbrush chromosomes

1972 ◽  
Vol 75 (1) ◽  
pp. 11-14 ◽  
Author(s):  
L. Fiume ◽  
I. Nardi ◽  
S. Bucci ◽  
G. Mancino
Keyword(s):  
Rna Synthesis ◽  
Lampbrush Chromosomes

scholarly journals Modifications of lampbrush chromosome structure of the European domestic goose <i>Anser anser</i>

2012 ◽  
Vol 55 (1) ◽  
pp. 84-96
Author(s):  
K. Andraszek ◽  
E. Smalec
Keyword(s):  
Transcriptional Activity ◽  
Morphological Structure ◽  
Reproductive Period ◽  
Lampbrush Chromosomes ◽  
Anser Anser ◽  
Transcription Activity ◽  
Physiological Processes ◽  
Before And After ◽  
Regulation Changes ◽  
Model Structures

Abstract. Lampbrush chromosomes (LBCs) represent a new model in avian cytogenetics and are increasingly more often used in poultry chromosome analyses. Additionally, lampbrush chromosomes are considered as model structures in the study of transcription regulation. Changes in transcription activity are reflected as modifications of LBC morphological structure and associated with physiological processes in the organism. The aim of the present study was to compare transcriptional activity of the first five lampbrush macrochromosomes and ZW sex lampbrush bivalents sampled from the oocytes of geese prior to and after the reproductive period. The respective bivalents sampled before and after reproduction have similar sizes but differ in morphological structure. Side loops of lampbrush chromosomes are sites of transcription activity. The activity varies according to the loop size. As the loops become more prominent, the activity grows and vice versa. Lampbrush chromosomes sampled after reproduction have smaller side loops. On the other hand, inactive chromomeres become prominent in the chromosomes. Marker loops are the last structures to be degraded after the end of reproduction. Consequently, they are used for identifying particular bivalents at different stages of cellular transcriptional activity.

The Actions of Enzymes on Lampbrush Chromosomes

1962 ◽  
Vol s3-103 (62) ◽  
pp. 173-203
Author(s):  
H. C. MACGREGOR ◽  
H. G. CALLAN
Keyword(s):  
Proteolytic Enzymes ◽  
Lampbrush Chromosomes ◽  
Triturus Cristatus ◽  
Trichloracetic Acid ◽  
Protease Digestion ◽  
Lateral Loop ◽  
Peptic Digestion ◽  
Rnase Digestion ◽  
Break Chromosome ◽  
Loop Matrix

The chromomeres of lampbrush chromosomes of Triturus cristatus are Feulgen-positive; they therefore contain DNA. After removal of their DNA in boiling trichloracetic acid, the chromomeres stain with fast green at alkaline pH; they therefore contain basic protein. The lateral loops are Feulgen-negative; they stain with toluidine blue at acid pH, but much less intensely following RNase digestion; they therefore contain RNA. The spheres of chromosomes V and VIII do not contain RNA. Unfixed lampbrush chromosomes retain a life-like appearance in 0.07 M K/NaCl at pH 6.2; in this medium the nuclear sap disperses. As pH is raised to 8.5 the matrices of lateral loops dissolve but chromosome axes remain unbroken. Above pH 8.5 lampbrush chromosomes dissolve. As pH is lowered from 6.2, at between 5.8 and 5.4 coagulation occurs. If pH is rapidly reduced still further, a persistent relaxed condition sets in between 2.5 and 2. In concentrations of K/NaCl above 0.5 M lampbrush chromosomes dissolve. Lateral loop matrices dissolve in 0.25 M K/NaCl but chromosome axes remain unbroken. In concentrations of K/NaCl below 0.05 M lateral loop matrices dissolve, but even in distilled water chromosome axes remain unbroken. Trypsin at pH 6.2 and at pH 7.8 strips the matrices from lateral loops and occasionally breaks matrix fusions. It causes chromomeres to swell and coalesce, but fails to break chromosome axes. The action of ‘pan-protease’ resembles that of trypsin in all respects. Pepsin at pH 6.2 strips the matrices from lateral loops, but does not destroy chromomeres. At low pH peptic digestion is slow: the enzyme is attacking coagulated chromosomes; but if peptic digestion precedes a lowering of pH the overall outcome is a rapid solution of loop matrix, and under these conditions matrix and sphere fusions are broken. If trypsin or ‘pan-protease’ digestion precedes a lowering of pH there is a similarly rapid solution of loop matrix; thus the action is not specifically referable to pepsin. Under no conditions does pepsin break the axes of lampbrush chromosomes. RNase at pH 6.2 strips the matrices from lateral loops; this action is detectable at extreme dilution. RNase does not destroy chromomeres, nor does it break chromosome axes. If tryptic digestion follows RNase digestion this too fails to break chromosome axes. Unlike the proteolytic enzymes and RNase, DNase at pH 6.2 breaks the fibril between adjacent chromomeres, and it also breaks the axes of lateral loops. Contrary to Mazia's experience with salivary gland chromosomes, versene does not break the axes of lampbrush chromosomes even when applied in media of low electrolyte concentration. These results indicate that uninterrupted fibres of DNA run throughout the lengths of lampbrush chromosomes.

The Form of Bivalent Chromosomes in Newt Oocytes at First Metaphase of Meiosis

1963 ◽  
Vol s3-104 (66) ◽  
pp. 281-295
Author(s):  
I. D. WATSON ◽  
H. G. CALLAN
Keyword(s):  
Genetic Recombination ◽  
Great Majority ◽  
Meiotic Metaphase ◽  
Gene Products ◽  
Lampbrush Chromosomes ◽  
Female Sex ◽  
Chiasma Localization

Lampbrush chromosomes in the ovarian oocytes of newts are associated as bivalents. Some connexions between lampbrush chromosomes are chiasmata; others are known to be fusions of gene products; yet others, namely reflected, centromere, and telomere fusions, do not appear to be due simply to the fusion of gene products. Whether chiasmata are involved in reflected, centromere, and telomere fusions cannot be decided from examination of the chromosomes at the lampbrush stage. Bivalents from oocytes at first meiotic metaphase were therefore studied. The oocytes of newts reach first meiotic metaphase after ovulation, whilst they are free in the coelome. Reflected, centromere, and the great majority of telomere fusions do not persist to first meiotic metaphase: thus chiasmata are not involved in them. In oocyte bivalents of Triturus helveticus chiasmata are not restricted in their distribution, whereas in spermatocyte bivalents of this species chiasmata are proterminally localized. In oocyte bivalents of 3 subspecies of T. cristatus chiasmata are procentrically localized, whereas in spermatocyte bivalents of these subspecies chiasmata are not restricted in their distribution. Thus in T. helveticus meiosis in the female sex is mainly responsible for genetic recombination, whereas in T. cristatus the situation is reversed. We conclude that to base genetical and evolutionary inferences on information drawn from the meiosis of one sex only is unjustified, and we doubt the validity of the claim that chiasma localization has arisen so as to restrict genetic recombination.

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