Structure of the secondary constriction region of the satellited chromosomes in triticinae

1963 ◽  
Vol 50 (10) ◽  
pp. 381-381 ◽  
Author(s):  
M. D. Upadhya ◽  
A. T. Natarajan
Keyword(s):  
Secondary Constriction ◽  
Constriction Region

CONSTITUTIVE HETEROCHROMATIN OF INDIAN MUNTJAC CHROMOSOMES REVEALED BY DNASE TREATMENT AND A C-BANDING TECHNIQUE

1974 ◽  
Vol 16 (2) ◽  
pp. 273-280 ◽  
Author(s):  
H. Kato ◽  
K. Tsuchiya ◽  
T. H. Yosida
Keyword(s):  
Secondary Constriction ◽  
Constitutive Heterochromatin ◽  
Banding Technique ◽  
Size Difference ◽  
Indian Muntjac ◽  
C Banding ◽  
Dnase Treatment ◽  
Muntiacus Muntjak ◽  
Secondary Constrictions ◽  
Constriction Region

A karyotype of a female Indian muntjac, Muntiacus muntjak vaginalis, was described. The karyotype was unique in that No. 1 and No. 3 homologous pairs were heteromorphic with respect to the size of their secondary constrictions. In these pairs, one of the homologs always had a longer secondary constriction than that on the corresponding homolog. Heterochromatin in the secondary constriction region was visualized with difficulty by a C-banding technique, but was demonstrated clearly by a DNase treatment followed by Giemsa staining, which also revealed the size difference of the secondary constriction. Centromeric constitutive heterochromatin of No. 1 chromosome was also found to differ in size between the homologs. On the basis of the heteromorphic character of No. 3 chromosome, or an X-autosome complex, it was possible to confirm autoradiographically that X-inactivation had occurred at random.

Molecular characterization of the secondary constriction region (qh) of human chromosome 9 with pericentric inversion

1992 ◽  
Vol 103 (4) ◽  
pp. 919-923
Author(s):  
S. Luke ◽  
R.S. Verma ◽  
R.A. Conte ◽  
T. Mathews
Keyword(s):  
Human Chromosome ◽  
Dna Sequences ◽  
Pericentric Inversion ◽  
Secondary Constriction ◽  
Hierarchical Organization ◽  
Chromosome 9 ◽  
Direct Function ◽  
Alphoid Dna ◽  
Pericentric Inversions ◽  
Constriction Region

Pericentric inversion of the secondary constriction region (qh) of human chromosome 9 is a frequent occurrence. This structural alteration is regarded as a normal familial variant, termed heteromorphism, and is inherited in a Mendelian fashion without any apparent phenotypic consequences. We characterized the qh region of chromosome 9 from five individuals using a series of molecular cytogenetic techniques. Four out of the five individuals have an additional area composed of alphoid DNA sequences on the inverted chromosome 9 while one case was found to have an apparently intact alphoid DNA sequence. Although the direct function(s) of alphoid DNA sequences remain unclear, the centromeric breakage involving these sequences in inverted chromosome 9 raises a series of questions pertaining to the monocentric, dicentric and pseudodicentric nature of pericentric inversions. Nevertheless, these findings have prompted us to suggest that the structural organization of alphoid DNA sequences of the centromeric region of chromosome 9 are apparently “breakage prone” and may be associated with a higher incidence of pericentric inversions. Furthermore, the hierarchical organization of various satellite DNA families (alpha-satellite, beta-satellite and satellite III) within the primary and secondary constriction regions of chromosomes 9 are elucidated here.

Mechanisms of the origin of a G-positive band within the secondary constriction region of human chromosome 9

1995 ◽  
Vol 69 (3-4) ◽  
pp. 235-239 ◽  
Author(s):  
M.J. Macera ◽  
R.S. Verma ◽  
R.A. Conte ◽  
M.G. Bialer ◽  
V.R. Klein
Keyword(s):  
Human Chromosome ◽  
Secondary Constriction ◽  
Chromosome 9 ◽  
Positive Band ◽  
Constriction Region

Small Molecule Permeation Across Membrane Channels: Chemical Modification to Quantify Transport Across OmpF

2018 ◽  
Author(s):  
Jiajun Wang ◽  
Jayesh Arun Bafna ◽  
Satya Prathyusha Bhamidimarri ◽  
Mathias Winterhalter
Keyword(s):  
Dwell Time ◽  
Covalent Binding ◽  
Channel Structure ◽  
Ion Current ◽  
E Coli ◽  
Current Fluctuation ◽  
Wide Range ◽  
Outer Membrane Channel ◽  
Biological Channels ◽  
Constriction Region

Biological channels facilitate the exchange of small molecules across membranes, but surprisingly there is a lack of general tools for the identification and quantification of transport (i.e., translocation and binding). Analyzing the ion current fluctuation of a typical channel with its constriction region in the middle does not allow a direct conclusion on successful transport. For this, we created an additional barrier acting as a molecular counter at the exit of the channel. To identify permeation, we mainly read the molecule residence time in the channel lumen as the indicator whether the molecule reached the exit of the channel. As an example, here we use the well-studied porin, OmpF, an outer membrane channel from <i>E. coli</i>. Inspection of the channel structure suggests that aspartic acid at position 181 is located below the constriction region (CR) and we subsequently mutated this residue to cysteine, where else cysteine free and functionalized it by covalent binding with 2-sulfonatoethyl methanethiosulfonate (MTSES) or the larger glutathione (GLT) blockers. Using the dwell time as the signal for transport, we found that both mono-arginine and tri-arginine permeation process is prolonged by 20% and 50% respectively through OmpF<sub>E181C</sub>MTSES, while the larger sized blocker modification OmpF<sub>E181C</sub>GLT drastically decreased the permeation of mono-arginine by 9-fold and even blocked the pathway of the tri-arginine. In case of the hepta-arginine as substrate, both chemical modifications led to an identical ‘blocked’ pattern observed by the dwell time of ion current fluctuation of the OmpF<sub>wt</sub>. As an instance for antibiotic permeation, we analyzed norfloxacin, a fluoroquinolone antimicrobial agent. The modulation of the interaction dwell time suggests possible successful permeation of norfloxacin across OmpF<sub>wt</sub>. This approach may discriminate blockages from translocation events for a wide range of substrates. A potential application could be screening for scaffolds to improve the permeability of antibiotics.

scholarly journals Omp35, a New Enterobacter aerogenes Porin Involved in Selective Susceptibility to Cephalosporins

2004 ◽  
Vol 48 (6) ◽  
pp. 2153-2158 ◽  
Author(s):  
Charléric Bornet ◽  
Nathalie Saint ◽  
Lilia Fetnaci ◽  
Myrielle Dupont ◽  
Anne Davin-Régli ◽  
...  
Keyword(s):  
Membrane Permeability ◽  
Outer Membrane ◽  
Antibiotic Susceptibility ◽  
Enterobacter Aerogenes ◽  
Artificial Membranes ◽  
Specific Location ◽  
Outer Membrane Permeability ◽  
Constriction Region ◽  
High Conductance

ABSTRACT In Enterobacter aerogenes, β-lactam resistance often involves a decrease in outer membrane permeability induced by modifications of porin synthesis. In ATCC 15038 strain, we observed a different pattern of porin production associated with a variable antibiotic susceptibility. We purified Omp35, which is expressed under conditions of low osmolality and analyzed its pore-forming properties in artificial membranes. This porin was found to be an OmpF-like protein with high conductance values. It showed a noticeably higher conductance compared to Omp36 and a specific location of WNYT residues in the L3 loop. The importance of the constriction region in the porin function suggests that this organization is involved in the level of susceptibility to negative large cephalosporins such as ceftriaxone by bacteria producing the Omp35 porin subfamily.

When rDNA transcription is arrested during mitosis, UBF is still associated with non-condensed rDNA

1997 ◽  
Vol 110 (19) ◽  
pp. 2429-2440 ◽  
Author(s):  
J. Gebrane-Younes ◽  
N. Fomproix ◽  
D. Hernandez-Verdun
Keyword(s):  
Secondary Constriction ◽  
Three Dimensional ◽  
Ribosomal Gene ◽  
Rdna Transcription ◽  
Transcription Machinery ◽  
Late Anaphase ◽  
Early Anaphase ◽  
Dimensional Distribution ◽  
Open Question ◽  
Kinetics Of

The mechanisms that control inactivation of ribosomal gene (rDNA) transcription during mitosis is still an open question. To investigate this fundamental question, the precise timing of mitotic arrest was established. In PtK1 cells, rDNA transcription was still active in prophase, stopped in prometaphase until early anaphase, and activated in late anaphase. Because rDNA transcription can still occur in prophase and late anaphase chromosomes, the kinetics of rDNA condensation during mitosis was questioned. The conformation of the rDNA was analyzed by electron microscopy from the G2/M transition to late anaphase in the secondary constriction, the chromosome regions where the rDNAs are clustered. Whether at transcribing or non-transcribing stages, non-condensed rDNA was observed in addition to axial condensed rDNA. Thus, the persistence of this non-condensed rDNA during inactive transcription argues in favor of the fact that mitotic inactivation is not the consequence of rDNA condensation. Analysis of the three-dimensional distribution of the rDNA transcription factor, UBF, revealed that it was similar at each stage of mitosis in the secondary constriction. In addition, the colocalization of UBF with non-condensed rDNA was demonstrated. This is the first visual evidence of the association of UBF with non-condensed rDNA. As we previously reported that the rDNA transcription machinery remained assembled during mitosis, the colocalization of rDNA fibers with UBF argues in favor of the association of the transcription machinery with certain rDNA copies even in the absence of transcription. If this hypothesis is correct, it can be assumed that condensation of rDNA as well as dissociation of the transcription machinery from rDNA cannot explain the arrest of rDNA transcription during mitosis. It is proposed that modifications of the transcription machinery occurring in prometaphase could explain the arrest of transcription, while reverse modifications in late anaphase could explain activation.

scholarly journals Chromosomal analyses in Megalonema platanum (Siluriformes: Pimelodidae), an endangered species from South American rivers

2011 ◽  
Vol 9 (1) ◽  
pp. 177-182 ◽  
Author(s):  
Rafael Augusto de Carvalho ◽  
Sebástian Sanchez ◽  
Ana Claudia Swarça ◽  
Alberto Sergio Fenocchio ◽  
Isabel C. Martins-Santos ◽  
...  
Keyword(s):  
Diploid Number ◽  
Secondary Constriction ◽  
Centromeric Heterochromatin ◽  
Large Chromosome ◽  
South American ◽  
Terminal Position ◽  
Chromosomal Data ◽  
First Time ◽  
Secondary Constrictions ◽  
Submetacentric Pair

This study presents chromosomal data of Megalonema platanum from rio Tibagi, Paraná, Brazil and from rio Paraná, Argentina. The diploid number was equal 54 with karyotype composition of 24m+16sm+2st+12a in both populations. The AgNOR sites were detected in the terminal position of a submetacentric pair of the two analyzed populations, coinciding with secondary constrictions on the short arm of pair 15. CMA3 and FISH with 18S rDNA probe displayed fluorescent signals that correspond to the AgNOR sites and secondary constriction. The presence of a small acrocentric supernumerary chromosome can be observed in M. platanum from rio Tibagi, with centromeric heterochromatin. Others heterochromatic blocks were evidenced in the terminal position of some chromosome and one metacentric large chromosome pair, probably the first pair, showed an interstitial heterochromatin. In the population of the rio Paraná were still observed heterochromatic blocks in both ends in some chromosomes. This work brings for the first time cytogenetic date of M. platanum, which is a very rare species in the rio Paraná basin and may be endangered.

scholarly journals A Karyological Study in Some Species of Coffea L. and in the Closest Relative Psilanthus travancorensis (Wight & Arn.) J.-F. Leroy

2012 ◽  
Vol 40 (2) ◽  
pp. 39 ◽  
Author(s):  
Neiva Izabel PIEROZZI ◽  
Thalita C. BORGHI ◽  
Maria Bernadete SILVAROLLA
Keyword(s):  
Chromosome Pair ◽  
Secondary Constriction ◽  
Karyological Study ◽  
Karyotype Asymmetry ◽  
Centromeric Position ◽  
Karyotype Formula ◽  
Orcein Staining ◽  
Nor Band ◽  
Chromosome Characterization

Chromosome characterization were carried out in Coffea kapakata A. Chev (Bridson), C. racemosa Lour., C. salvatrix Swynn. & Philipson and in Psilanthus travancorensis (Wight & Arn.) J.-F. Leroy (2n=22) by employing the conventional acetic orcein technique as well as by C- and NOR-banding aiming further comparative studies. Although C. canephora and C. dewevrei have already been studied and depict a C-band karyotype, they have also been included for further comparisons, since NOR-banding and some other morphometric data have not been obtained yet. However, there were observed some differences among the species regarding chromosomal morphometry. The karyotype formula obtained was 3m+6sm+2sms for C. salvatrix and P. travancorensis, 1M +2m + 6sm + 2sms for C. kapakata and 2M +1m + 6sm + 2sms for C. racemosa. All species displayed a moderate karyotype asymmetry and according to Stebbins system, C. canephora, C. dewevrei, C. kapakata and C. racemosa were classified as 3B while C. salvatrix and P. travancorensis were classified as 2A. Among the four indices used to assess karyotype asymmetry, Paszko AI index along with Stebbins were best suited to individualize the species. C-bands were preferentially situated at a pericentromeric/centromeric position. Two pairs of chromosomes, with secondary constriction and satellite segments, were observed in all the species following acetic orcein staining. C. racemosa and C. salvatrix showed NOR-band in both pairs, while only one chromosome pair carrying NOR-band was seen in C. canephora, C. dewevrei, C. kapakata and P. travancorensis. Data on chromosome morphometry, asymmetry indices and NOR-banding were suitable for the characterization of the species.

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