Energy transfer and binding competition between dyes used to enhance staining differentiation in metaphase chromosomes

DNA-Interactive and Damage Study with meso-Tetra(2-thienyl)porphyrins Coordinated with Polypyridyl Pd(II) and Pt(II) Complexes

We report the DNA-binding properties of three porphyrins with peripheral thienyl substituents (TThPor, PdTThPor and PtTThPor). The binding capacity of each porphyrin with DNA was determined by UV-Vis and steady-state fluorescence emission spectroscopy combined with molecular docking calculations. The results suggest that the interaction of these compounds probably occurs via secondary interactions via external grooves (minor grooves) around the DNA macromolecule. Moreover, porphyrins containing peripheral Pd(II) or Pt(II) complexes (PdTThPor and PtTThPor) were able to promote photo-damage in the DNA.

Exploring the cytotoxicity on human lung cancer cells and DNA binding stratagem of camptothecin functionalised silver nanoparticles through multi-spectroscopic, and calorimetric approach

The influence of nanoparticles inside the human body and their interactions with biological macromolecules need to be explored/studied prior to specific applications. The objective of this study is to find the potential of camptothecin functionalised silver nanoparticles (CMT-AgNPs) in biomedical applications. This article primarily investigates the binding stratagem of CMT-AgNPs with calf thymus DNA (ctDNA) through a series of spectroscopic and calorimetric methods and then analyses the anticancer activity and cytotoxicity of CMT-AgNPs. The nanoparticles were synthesized using a simple one pot method and characterized using UV-Visible, fourier transform infrared (FTIR) spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). The average size of CMT-AgNPs is 10 ± 2 nm. A group of experimental techniques such as UV-Visible spectrophotometry, fluorescence dye displacement assay, circular dichroism (CD) and viscosity analysis unravelled the typical groove binding mode of CMT-AgNPs with ctDNA. The CD measurement evidenced the minor conformational alterations of double helical structure of ctDNA in the presence of CMT-AgNPs. The information deduced from the isothermal titration calorimetry (ITC) experiment is that the binding was exothermic and spontaneous in nature. Moreover, all the thermodynamic binding parameters were extracted from the ITC data. The binding constants obtained from UV absorption experiments, fluorescence dye displacement studies and ITC were consistently in the order of 10⁴ Mol^-1. All these results validated the formation of CMT-AgNPs-ctDNA complex and the results unambiguously confirm the typical groove binding mode of CMT-AgNPs. An exhaustive in vitro MTT assay by CMT-AgNPs and CMT against A549, HT29, HeLa and L929 cell lines revealed the capability of CMT-AgNPs as a potential anticancer agent.

A Vanadium(V) complexes derived from pyridoxal/salicylaldehyde. Interaction with CT-DNA/HSA, and molecular docking assessments

With the increasing development of metallopharmaceuticals, coordination compounds become viable alternatives for therapeutic uses. Despite the importance of platinum derivatives in this area, first-row transition metals complexes are welcome due to their characteristics. Vanadium is a promising metal in this context, as it has a range of compounds with different biological applications, including anticancer therapeutic effects. In this effort, the study of interactions between coordination compounds with deoxyribonucleic acid and with human serum albumin is fundamental. In this way, ten iminic ligands were synthesized by condensing p-substituted aromatic benzohydrazides (OH, CH₃, H, NO₂, and NH₂) with salicylaldehyde (L1As-L5As) or pyridoxal hydrochloride (L1P-L5P). These ligands have characteristics that allow the tridentate coordination of vanadium cations, leading to the formation of ten vanadium(V) complexes (C1As-C5As and C1P-C5P) with different structural features, all characterized by single-crystal X-ray diffraction, UV-Vis and infrared spectroscopies, and cyclic voltammetry. In addition, the complexes were tested for their interactions with calf thymus deoxyribonucleic acid and human serum albumin by spectroscopic assays and molecular docking calculations. These new results can contribute to further research and provide different ways to design new vanadium complexes with biological applications.

Chromosome Diversity and Evolution in Helicoide a (Gastropoda: Stylommatophora): A Synthesis from Original and Literature Data

Simple Summary

The superfamily Helicoidea is a large and diverse group of Eupulmonata. The superfamily has been the subject of several molecular and phylogenetic studies which greatly improved our knowledge on the evolutionary relationships and historical biogeography of many families. In contrast, the available karyological information on Helicoidea still results in an obscure general picture, lacking a homogeneous methodological approach and a consistent taxonomic record. Nevertheless, the available karyological information highlights the occurrence of a significant chromosomal diversity in the superfamily in terms of chromosome number (varying from 2n = 40 to 2n = 62), chromosome morphology and the distribution of different karyological features among different taxonomic groups. Here we performed a molecular and a comparative cytogenetic analysis on of 15 Helicoidea species of three different families. Furthermore, to provide an updated assessment of the chromosomal diversity of the superfamily we reviewed all the available chromosome data. Finally, superimposing all the chromosome data gathered from different sources on the available phylogenetic relationships of the studied taxa, we discuss the overall observed chromosome diversity in Helicoidea and advance a hypothesis on its chromosomal evolution.

Abstract

We performed a molecular and a comparative cytogenetic analysis on different Helicoidea species and a review of all the available chromosome data on the superfamily to provide an updated assessment of its karyological diversity. Standard karyotyping, banding techniques, and Fluorescence in situ hybridization of Nucleolus Organizer Region loci (NOR-FISH) were performed on fifteen species of three families: two Geomitridae, four Hygromiidae and nine Helicidae. The karyotypes of the studied species varied from 2n = 44 to 2n = 60, highlighting a high karyological diversity. NORs were on a single chromosome pair in Cernuella virgata and on multiple pairs in four Helicidae, representing ancestral and derived conditions, respectively. Heterochromatic C-bands were found on pericentromeric regions of few chromosomes, being Q- and 4′,6-diamidino-2-phenylindole (DAPI) negative. NOR-associated heterochromatin was C-banding and chromomycin A₃ (CMA₃) positive. Considering the available karyological evidence on Helicoidea and superimposing the chromosome data gathered from different sources on available phylogenetic inferences, we describe a karyotype of 2n = 60 with all biarmed elements as the ancestral state in the superfamily. From this condition, an accumulation of chromosome translocations led to karyotypes with a lower chromosome number (2n = 50–44). This process occurred independently in different lineages, while an augment of the chromosome number was detectable in Polygyridae. Chromosome inversions were also relevant chromosome rearrangements in Helicoidea, leading to the formation of telocentric elements in karyotypes with a relatively low chromosome count.

Karyological Diversification in the Genus Lyciasalamandra (Urodela: Salamandridae)

Simple Summary

The Lycian salamanders of the genus Lyciasalamandra are characterized by a debated taxonomy and phylogenetic relationships. They have been the subject of various molecular and phylogenetic analyses, but their chromosomal diversity is completely unknown. We here present a comparative cytogenetic analysis on five out of the seven described species and seven subspecies of Lyciasalamandra, providing the first karyological assessment on the genus and comparing them to closely related representatives of the genus Salamandra. We analyzed the occurrence and distribution of different conserved (chromosome number and morphology) and highly variable karyological features. We found an impressive diversity in the configuration of nucleolus organizing regions (NORs), which alternatively occur either as heteromorphic or homomorphic loci on distinct regions of different chromosome pairs. We highlight that the observed peculiar taxon-specific pattern of chromosome markers supports the taxonomic validity of the different studied evolutionary lineages and is consistent with a scenario of synchronous evolution in the Lycian salamanders.

Abstract

We performed the first cytogenetic analysis on five out of the seven species of the genus Lyciasalamandra, including seven subspecies, and representatives of its sister genus Salamandra. All the studied species have a similar karyotype of 2n = 24, mostly composed of biarmed elements. C-bands were observed on all chromosomes, at centromeric, telomeric and interstitial position. We found a peculiar taxon-specific NOR configuration, including either heteromorphic and homomorphic NORs on distinct regions of different chromosomes. Lyciasalamandra a.antalyana and L. helverseni showed two homomorphic NORs (pairs 8 and 2, respectively), while heteromorphic NORs were found in L. billae (pairs 6, 12), L. flavimembris (pairs 2, 12), L. l. luschani (pairs 2, 12), L. l. basoglui (pairs 6, 12), L. l. finikensis (pairs 2, 6) and S. lanzai (pairs 8, 10). Homomorphic NORs with an additional supernumerary site were shown by S. s. salamandra (pairs 2, 8) and S. s. gigliolii (pairs 2, 10). This unexpected highly variable NOR configuration is probably derived from multiple independent NOR translocations and paracentric inversions and correlated to lineage divergence in Lyciasalamandra. These results support the taxonomic validity of the studied taxa and are consistent with a hypothesized scenario of synchronous evolution in the genus.

Fluorescent pyrene moiety in fluorinated C6F5-corroles increases the interaction with HSA and CT-DNA

Two fluorinated meso-C6F5-corroles (5,15-bis(pentafluorophenyl)-10-(phenyl)corrole and 5,15-bis(pentafluorophenyl)-10-(1-pyrenyl)corrole) were biologically evaluated in terms of binding affinity to human serum albumin (HSA) and calf-thymus DNA (CT-DNA) via multiple spectroscopic techniques under physiological conditions combined with molecular docking calculations. The HSA:corrole interaction is spontaneous and moderate via static binding, disturbing both secondary and tertiary albumin structures at high fluorinated corrole concentrations. The competitive binding studies indicated positive cooperativity or allosteric activation, while molecular docking calculations suggested that both fluorinated corroles bind preferentially inside subdomains IIA and IB (sites I and III, respectively). The experimental CT-DNA binding assays indicated that fluorinated corroles interact spontaneously by non-classical modes in the minor groove of the CT-DNA strands via static fluorescence quenching mechanism. Molecular docking results also showed the minor groove as the main binding site for CT-DNA. Overall, the pyrene moiety increased the interaction with HSA and CT-DNA, which is probably due to the planarity and volume that favors the pyrene unit to be buried inside the biomacromolecule pockets.

Blind Resolution of Lifetime Components in Individual Pixels of Fluorescence Lifetime Images Using the Phasor Approach

The phasor approach is used in fluorescence lifetime imaging microscopy for several purposes, notably to calculate the metabolic index of single cells and tissues. An important feature of the phasor approach is that it is a fit-free method allowing immediate and easy to interpret analysis of images. In a recent paper, we showed that three or four intensity fractions of exponential components can be resolved in each pixel of an image by the phasor approach using simple algebra, provided the component phasors are known. This method only makes use of the rule of linear combination of phasors rather than fits. Without prior knowledge of the components and their single exponential decay times, resolution of components and fractions is much more challenging. Blind decomposition has been carried out only for cuvette experiments wherein the statistics in terms of the number of photons collected is very good. In this paper, we show that using the phasor approach and measurements of the decay at phasor harmonics 2 and 3, available using modern electronics, we could resolve the decay in each pixel of an image in live cells or mice liver tissues with two or more exponential components without prior knowledge of the values of the components. In this paper, blind decomposition is achieved using a graphical method for two components and a minimization method for three components. This specific use of the phasor approach to resolve multicomponents in a pixel enables applications where multiplexing species with different lifetimes and potentially different spectra can provide a different type of super-resolved image content.

Cytological evidence for population-specific sex chromosome heteromorphism in Palaearctic green toads (Amphibia, Anura)

A chromosome study was carried out on a number of European and Central Asiatic diploid green toad populations by means of standard and various other chromosome banding and staining methods (Ag-NOR-, Q-, CMA3-, late replicating [LR] banding pattern, C-and sequential C-banding + CMA3 + DAPI). This study revealed the remarkable karyological uniformity of specimens from all populations, with the only exception being specimens from a Moldavian population, where one chromosome pair was heteromorphic. Though similar in shape, size and with an identical heterochromatin distribution,the difference in the heteromorphic pair was due to a large inverted segment on its long arms. This heteromorphism was restricted to females, suggesting a female heterogametic sex chromosome system of ZZ/ZW type at a very early step of differentiation.

Karyology of the Antarctic scallop Adamussium colbecki, with some comments on the karyological evolution of pectinids

Karyotype, location of the nucleolar organiser region (NOR) and heterochromatin presence and composition were studied in the Antarctic scallop Adamussium colbecki Smith, 1902. The karyotype exhibits 2n = 38 chromosomes with 11 pairs of metacentrics, 5 of submetacentrics, one subtelocentric and two telocentrics. Ag-NOR, CMA(3), DA/MM and NOR-FISH evidenced paracentromeric NORs on the short arm of 2nd pair chromosomes. Digestion with three restriction endonucleases followed by sequential staining with Giemsa, CMA(3) and DAPI evidenced on all chromosomes centromeric heterochromatin positive for both DAPI and CMA(3). In situ hybridisation analysis showed the presence of an AT-rich satellite DNA in the centromeric heterochromatin of several chromosomes. A mosaicism was detected in the germinal cell lines of one specimen, as in six of the 20 plates examined the set had 37 chromosomes with a missing pair of telocentrics and an unpaired metacentric. Comparison of the chromosome sets of all the pectinids studied to date and comparison with a phyletic tree obtained from molecular mitochondrial genes studies yielded good agreement between karyotype morphology and taxonomic classification.

Meiotic exchange event within the stalk region of an inverted chromosome 22 results in a recombinant chromosome with duplication of the distal long arm

Meiotic recombination occurs between homologous euchromatic regions of human chromosomes in early meiosis. However, such exchanges have been thought not to occur in the stalk regions of acrocentric chromosomes. We describe a child whose chromosome analysis suggests that crossovers do occur in homologous stalk regions. The proband, initially seen as a term female infant, was born to a 28-year-old mother. Dysmorphic features included wide metopic sutures, low anterior hairline, hypertelorism, external ear malformations, and cleft lip and palate. Blood chromosomes of the proband and parents were studied by G-banding, Q-banding, R-banding, and silver staining. The infant karyotype showed a sub-metacentric chromosome 22; that of the mother showed a pericentric inversion of chromosome 22. Chromosomes of the father were normal. In the infant, the abnormal chromosome 22 long arm appeared normal, but with additional long arm material attached to the distal short arm. In the mother, the distal long arm of the abnormal chromosome 22 was translocated to the distal short arm. The abnormal chromosome stalk in the child was intermediate in size to the stalk size of the abnormal and normal chromosomes 22 in the mother. Fluorescent in situ hybridization (FISH) analysis using chromosome 22 paint and ARSA gene probe confirmed that the duplicated material in the proband was of chromosome 22 origin; the karyotype interpretation is: 46,XX,rec(22)dup(22q)inv(22)(p13q13.1)mat. This abnormal karyotype is most likely due to a crossover event within the inversion loop during meiosis. The stalk length discrepancy suggests that the crossover site occurred in the stalk region.

Karyotype characterization of the lake sturgeon, Acipenser fulvescens (Rafinesque 1817) by chromosome banding and fluorescent in situ hybridization

A karyotype analysis using several staining techniques was carried out on the North American lake sturgeon, Acipenser fulvescens. The chromosome number was found to be 2n = 262 ± 6. A representative karyotype of 264 chromosomes was composed of 134 meta- and submetacentrics, 70 telo- and acrocentrics, and 60 microchromosomes. The constitutive heterochromatin, revealed by C banding, was localized in various positions on several chromosomes, including microchromosomes. The signals of fluorescent in situ hybridization (FISH) with a HindIII satellite DNA probe were visible as centromeric heterochromatin blocks on 48 chromosomes. The telomeric repeat (TTAGGG)n detected by FISH was localized at both ends of all chromosomes and two chromosomes were entirely marked. Fluorescent staining with GC-specific chromomycin A3 showed recognizable fluorescent regions, whereas a more uniform base composition was revealed by the AT-specific 4',6-diamidino-2-phenylindole (DAPI). After silver staining, the active nucleolar organizer regions (NORs) were detected on 12 chromosomes. FISH with the 5S probe showed four signals on four small chromosomes. Our data suggest that A. fulvescens is a tetraploid species.Key words: karyotype, C banding, telomeric sequence, fluorochrome staining, satellite DNA, 5S rDNA.

Chromosome banding techniques

Chromosome banding techniques produce a series of consistent landmarks along the length of metaphase chromosomes that allow for both recognition of individual chromosomes within a genome and identification of specific segments of individual chromosomes. These landmarks facilitate assessment of chromosome normalcy, identification of sites of chromosome breaks and alterations, and location of specific genes. This unit covers these basic banding techniques (Q-banding, G-banding, and R-banding), which produce virtually identical patterns of bands along the length of human chromosomes, although the bands and polymorphic regions highlighted may differ with each technique. These techniques highlight reproducible landmarks along the length of the chromosome and specialized staining techniques can be used to highlight particular regions of chromosomes, such as heterochromatic and repeated-sequence segments. These specialized techniques, nucleolar organizer region (NOR) staining, centromeric heterochromatin staining (C-banding), methylated satellite DNA staining (distamycin-DAPI banding), and replication banding are also presented in this unit.

Texture analysis of fluorescence lifetime images of nuclear DNA with effect of fluorescence resonance energy transfer

BACKGROUND

Fluorescence lifetime imaging microscopy (FLIM) is becoming an important tool in cellular imaging. In FLIM, the image contrast is concentration insensitive, whereas it is sensitive to the local environment and interactions of fluorophores such as fluorescence resonance energy transfer (RET).

METHODS

Fluorescence microscopy, lifetime imaging, and texture analysis were used to study the spatial distribution of fluorophores bound to nuclear DNA. 3T3-Swiss albino mice fibroblast nuclei were labeled with Hoechst 33258 (Ho), an AT-specific dye, and 7-aminoactinomycin D (7-AAD), a GC-specific dye. Ho is a RET donor to the 7-AAD acceptor.

RESULTS

Texture analysis of 50 alcohol-fixed nuclei quantitatively showed changes of spatial distribution of apparent donor lifetimes. RET increased the spatial heterogeneity in the phase and modulation lifetime images. In most of the doubly stained cells (about 80%), the phase and modulation lifetime distributions were spatially homogeneous. In about 20% of the cells, we noticed that lower phase and modulation lifetimes caused by RET were correlated with regions of high Ho intensity in the nuclei.

CONCLUSIONS

The spatial lifetime heterogeneity of Ho in presence of 7-AAD seems to be caused by RET between closely spaced strands in the three dimensionally condensed regions of DNA.

Characterization of the heterochromatic chromosome regions in sheep

In order to elucidate the structural chromosome organization of the heterochromatic regions in sheep, we have used C-banding, silver-staining, sequential CDD technique and restriction endonuclease banding. By these banding techniques we obtained four fractions of repetitive DNA, the autosomal fractions A and B, the C fraction in the X chromosome, and the D fraction in the Y chromosome. Silver staining revealed active nucleolus organizer regions (NOR's) on the telomeric GC-rich areas of chromosomes 1, 2, 3, 4, and 25 which were digested with HaeIII restriction endonuclease.

Mapping of the gene encoding human beta-defensin-2 (DEFB2) to chromosome region 8p22-p23.1

We recently reported the isolation of human beta-defensin-2 (hBD-2), a novel epithelia-derived peptide antibiotic belonging to the beta-defensin family. hBD-2 is expressed in skin and epithelia of the airway system, where it is believed to contribute to its antimicrobial defense. By fluorescence in situ hybridization using a hBD-2 genomic DNA probe and subsequent fluorescence R-banding, the hBD-2 gene (HGMW-approved symbol DEFB2) was assigned to human chromosome region 8p22-p23.1. PCR with a set of CEPH YAC clones spanning this chromosomal region revealed CEPH YACs 773G4, 920D12, and 820B4 to contain the hBD-2 gene. Relying on the preexisting physical maps of 8p22-p23.1, the hBD-2 gene was mapped in close proximity to D8S1993 (WI-9956) within the interval flanked by D8S552 and D8S1130 (CHLC.GATA25C10). The fact that all currently described genes encoding defensins map to chromosome 8p21-pter suggests that a gene cluster in this chromosomal region may play a major role in antimicrobial defense.

Combined immunophenotyping and karyotyping in peripheral T cell lymphomas demonstrating different clonal and nonclonal chromosome aberrations in T helper cells

Combined immunophenotyping and karyotyping was performed in seven cases of peripheral T cell lymphoma with complex aberrant clones. Various lymphocytic cell populations entered mitosis, whereas all aberrant cells belonged to the T helper/inducer cell population. Lymphomas with the same recurrent chromosome aberrations, i.e. inversion inv(14)(q11q32.1) and isochromosome i(8)(q10), had a very similar immunophenotype. The aberrant cells in these cases expressed CD3+, CD4+, CD7+, CD45RO+. The immunophenotypic similarity is underlined in one case of T prolymphocytic leukemia, in whom the aberrant cells lost the CD8 antigen originally present, during cultivation with PHA. In one case of Sézary's syndrome, two or possibly even three different clones as well as nonclonal aberrations were identified within the T (helper/inducer) cell population, providing further evidence that chromosomal instability is a characteristic feature of cutaneous T cell lymphoma.

Propidium iodide and the thiol-specific reagent DACM as a dye pair for fluorescence resonance energy transfer analysis: an application to mouse sperm chromatin

The dyes N-(-7-dimethyl-amino-4-methyl-coumarinyl) maleimide and propidium iodide, specific for the thiol group and DNA, respectively, were considered as a donor-acceptor couple suitable for investigating "in situ" the relative spatial distribution of DNA and protamines in mouse spermatozoa chromatin. The two dyes are characterized by favourable spectral properties, so that a simplified analytical procedure, based on the measurement of both donor and acceptor emission in double-stained samples, can be applied to evaluate the relative efficiency of the energy transfer process and its topological distribution. The results obtained indicate that during the maturation process: 1) the basic arrangement of protamine-DNA complex does not undergo structure changes, and 2) the oxidation of sulfhydryl to disulfide groups, resulting in chromatin stabilization, first involves the protamine thiols spatially closer to DNA. Fluorescence energy transfer imaging suggests that chromatin stabilization starts in the midportion of the sperm head, then spreads towards the periphery.

Prenatal identification of small mosaic markers of different chromosomal origins

In situ hybridization using a series of alphoid DNA probes has demonstrated the origin of two small accessory mosaic marker chromosomes ascertained from 1079 amniocenteses. These markers appeared to be de novo, derived from acrocentric chromosomes, and identical by traditional cytogenetic staining (G, Q, C, AgNOR, Hoechst-distamycin). Molecular characterization showed that one marker had originated from chromosome 14, the other from chromosome 22. Clinical outcome in both cases was normal.

Simultaneous assessment of chromatin structure, DNA content, and antigen expression by dual wavelength excitation flow cytometry

7-aminoactinomycin D (7-AMD) efficiently discriminates between cells in the G0 and G1 phases of the cell cycle (Stokke et al., Cancer Res. 48:6708, 1988). The fluorescence and light scatter of cells stained with 7-AMD, Hoechst 33258 (H33258), and fluorescein isothiocyanate (FITC)-labeled antibodies were measured by dual wavelength excitation flow cytometry (488 nm, ultraviolet). The H33258 fluorescence was found to reflect DNA content in the presence of 7-AMD, although energy transfer caused an approximately 50% reduction in H33258 fluorescence intensity. However, energy transfer was more pronounced in dead cells, permitting exclusion of such cells during analysis. The G0, G1, S, and G2 phases of the cell cycle could be identified in the 7-AMD versus H33258 fluorescence histograms, as was demonstrated with mitogen-stimulated B lymphocytes and a mixture of unstimulated B lymphocytes and a proliferating B-cell line. One hour fixation with paraformaldehyde was compatible with prefixation labeling of surface antigens with indirectly FITC-labeled antibodies as well as postfixation labeling of intracellular antigens. Studies of expression of some surface and nuclear activation-associated antigens confirmed that cell cycle-resolved antigen expression and the time course of appearance of such antigens could be assessed accurately. Phycoerythrin could be used to label a second antigen.

Stepwise development of chromosomal abnormalities in angioimmunoblastic lymphadenopathy

Cytogenetic studies of lymphoproliferative diseases, such as angioimmunoblastic lymphadenopathy (AILD), may provide a clue to the understanding of tumor development. Angioimmunoblastic lymphadenopathy may evolve from a nonmalignant lymphoproliferation into a peripheral T-cell lymphoma or even into a high-grade B-cell lymphoma and thus offers the chance to observe cytogenetic changes during lymphoma development. We report the cytogenetic findings in 24 cases of AILD. They are discussed together with 18 previously published cases from the same series. A striking feature was that unrelated chromosome abnormalities, both clonal and nonclonal, were frequently observed. Eighteen of 25 cases with aberrant clones show trisomy 3 (a characteristic chromosome abnormality in peripheral T-cell lymphoma), trisomy 5, or both. This finding provides cytogenetic evidence that these cases are definitely peripheral T-cell lymphomas. From the results of the 42 cases, hypotheses of stepwise evolution of the chromosome abnormalities in AILD are deduced: the first step is the appearance of chromosome abnormalities in different cells because of a genetic instability. At this time, clonal proliferation of T cells was already demonstrated by the rearrangement of T-cell receptor genes. As a second step, chromosomally aberrant clones become established. A cytogenetically detectable monoclonal proliferation represents the third step.

Inv(14) with distal breakpoint in 14q32.1 in three cases of T cell lymphoma

The distal breakpoint of inv(14) in T cell clones, established from patients with ataxia telangiectasia, lies outside the immunoglobulin heavy chain gene locus on 14q32.3, and more proximal to the centromere than the distal breakpoint of inv(14) in the T cell lymphoma cell line SUP-T1. We report 3 cases of T cell lymphoma cytogenetically showing the same type of inv(14) as the AT T cell clones. All 3 cases express a similar immunophenotype, which is that of peripheral T lymphocytes with phenotypic remnants of thymic or postthymic lymphoblasts. This finding provides evidence that this type of inv(14) is involved in the malignant transformation of mature T lymphocytes.

DNA double staining for a fluorescence energy transfer study of chromatin in liver cells

Methodological aspects related to the application of techniques based on fluorescence energy transfer in the study of chromatin structure, were first examined. Fluorochromes specific for DNA with different interaction mechanisms were employed, both in single and double stainings. The following dye pairs were considered as donor/acceptor couples: Hoechst 33342 or DAPI/Mithramycin A or Chromomycin A3, Hoechst 33342 or DAPI/Propidium Iodide, and Mithramycin A or Chromomycin A3/Propidium Iodide. Spectrofluorometric analysis showed that the spectral distribution of the dye pair Ho/PI is more suitable for the evaluation of energy transfer efficiency. This dye pair was used in the study of the chromatin microstructure in rat hepatocytes isolated from livers at two different growth stages. In particular, diploid mono- and binucleated cells from young and adult rats were considered. The results indicated the existence of a more homogeneous situation in young than in adult rats. In the latter case, the statistical analysis indicates the presence of two groups of energy transfer values. The different efficiency values in energy transfer can be considered a consequence of chromatin structure rearrangement and are tentatively interpreted according to the functional role of the diploid cells in the two stages of liver growth.

Evolutionary diversity of reverse (R) fluorescent chromosome bands in vertebrates

Mitotic chromosomes, interphase cell nuclei, and male meiosis of 41 species representing all vertebrate classes were analyzed with distamycin A/mithramycin counterstaining. The purpose of the study was to recognize differences and common characteristics in the reverse (R) fluorescent banding patterns in the chromosomes of vertebrate species at various stages of evolution. In contrast to the warm-blooded mammals and birds, the euchromatic segments in the chromosomes of most reptiles, amphibians, and fishes contain no multiple fluorescent R-bands. This is thought to be due to the absence of the long homogeneous regions (isochores) in the DNA of the cold-blooded vertebrates. Distamycin A/mithramycin banding specifically reveals the GC-rich constitutive heterochromatin in all vertebrates. In most of the vertebrate chromosomes examined, the heterochromatic regions have opposite staining properties with mithramycin and quinacrine. Mithramycin labels the nucleolus organizer regions very brightly in the karyotypes of fishes, amphibians, reptiles and birds, but not of mammals. The lack of mithramycin fluorescence at the nucleolus organizer regions of mammals is attributed to the relatively low level of redundancy of the GC-rich ribosomal DNA in their genomes. Studies on the various meiotic stages of the cold-blooded vertebrates show that the mithramycin labeling of the nucleolus organizers is independent of their state of activity. This can be confirmed by mithramycin fluorescence at the nucleoli of actinomycin-treated cells.

Nucleolus-organizer regions and heterochromatin in three species of bovidae

Ag-NOR staining and a counterstain-enhanced fluorescence technique (chromomycin A3/distamycin A/DAPI staining = CDD-method) have been applied to ibex (Capra ibex L.), chamois (Rupicapra rupicapra L.) and bison (Bison bison L.) chromosomes. Chromomycin A3 visualization led to a well defined R-banding pattern along the chromosome arms and to a clear demonstration of centric heterochromatic bands of variable size. The nucleolus organizer regions (NORs) were found in the telomeric regions of the chromosomes 2, 3, 4, 5 and 28 of the ibex, of the chromosomes 1/3 (short arm), 2, 4, 5 and 28 of the chamois and of the chromosomes 2, 3, 4, 11 and 28 of the bison.

Distinction of leucocyte classes based on chromatin-structure-dependent DNA-binding of 7-aminoactinomycin D

Binding of the DNA-specific dye 7-aminoactinomycin D (7-AMD) in chromatin of human leucocytes was studied by flow cytometry. After formaldehyde fixation and permeabilization, monocytes bound 30-130% more 7-AMD than lymphocytes, while binding in granulocytes was 20-60% higher than in lymphocytes. Monocytes and lymphocytes bound similar amounts of 7-AMD when cells were permeabilized by detergent prior to fixation. Digestion of DNA in formaldehyde-fixed chromatin by DNase 1 was quantitated by measuring Hoechst 33258 (H33258) fluorescence of mononuclear cells. The monocyte/lymphocyte H33258 fluorescence ratio decreased with DNase 1 digestion to an asymptotic value of 0.74, showing that DNA in chromatin of monocytes was more susceptible to DNase 1 digestion. 7-AMD binding increased, reached a maximum and then decreased with extent of DNase 1 digestion in both mononuclear cell types. The monocyte/lymphocyte 7-AMD fluorescence ratio also decreased after DNase 1 digestion. RNA content and RNA synthesis were higher in monocytes than in lymphocytes. The results show that 7-AMD binding in chromatin of mononuclear leucocytes correlates with transcriptional activity as measured by DNase1 susceptibility and RNA synthesis. The staining procedure may be used for differential counting of mature myeloid cells in peripheral blood and bone marrow.

Binding of Hoechst 33258 to the minor groove of B-DNA

An X-ray crystallographic structure analysis has been carried out on the complex between the antibiotic and DNA fluorochrome Hoechst 33258 and a synthetic B-DNA dodecamer of sequence C-G-C-G-A-A-T-T-C-G-C-G. The drug molecule, which can be schematized as: phenol-benzimidazole-benzimidazole-piperazine, sits within the minor groove in the A-T-T-C region of the DNA double helix, displacing the spine of hydration that is found in drug-free DNA. The NH groups of the benzimidazoles make bridging three-center hydrogen bonds between adenine N-3 and thymine O-2 atoms on the edges of base-pairs, in a manner both mimicking the spine of hydration and calling to mind the binding of the auti-tumor drug netropsin. Two conformers of Hoechst are seen in roughly equal populations, related by 180 degrees rotation about the central benzimidazole-benzimidazole bond: one form in which the piperazine ring extends out from the surface of the double helix, and another in which it is buried deep within the minor groove. Steric clash between the drug and DNA dictates that the phenol-benzimidazole-benzimidazole portion of Hoechst 33258 binds only to A.T regions of DNA, whereas the piperazine ring demands the wider groove characteristic of G.C regions. Hence, the piperazine ring suggests a possible G.C-reading element for synthetic DNA sequence-reading drug analogs.

Centromeric index versus DNA content flow karyotypes of human chromosomes measured by means of slit-scan flow cytometry

We have applied slit-scan flow cytometry (SSFCM) to classify human chromosomes according to their centromeric index (CI) and relative DNA content. The resulting bivariate--CI vs. DNA content--distributions shows 14 peaks for normal human chromosomes. Distinct peaks are produced by chromosomes 1, 2, 3, 4 + 5, 6 + 7 + X, 8, 13 + 14 + 15, 16, 17 + 18, 19 + 20, and 21 + 22 + Y. In addition, chromosomes 9 through 12 are resolved into three peaks. The identity of the chromosomes comprising each peak was determined by comparing CI vs. DNA content distributions measured for normal human chromosomes by means of SSFCM with CI and DNA content values measured for human chromosomes with image analysis. The accuracy of CI measurement by SSFCM was verified by measuring CIs for human chromosomes isolated from human/rodent hybrid cell lines containing only a few known human chromosomes. These studies showed CIs measured for human chromosomes 1-19 and 21 to be in close agreement with the CIs calculated by means of image analysis. We further confirmed the chromosome assignments for each peak by showing that the relative volumes of the peaks in the CI vs. DNA content distributions for chromosomes from normal cells are similar to the relative frequencies of chromosomes expected for these peaks based on the peak assignments.

Nucleolus organizer regions and heterochromatin in the zebu (Bos indicus L.)

Ag-NOR staining and a counterstain enhanced fluorescence technique (chromomycin A3/distamycin A/DAPI-staining = CDD-method) and G-banding, respectively, have been applied to the zebu (Bos indicus L.) chromosomes. The nucleolus organizer regions (NORs) were found in the telomeric regions of chromosomes nos. 2, 3, 4, 11, and 28. CDD staining led to a well-defined R-banding pattern along the chromosome arms and to the visualization of centric heterochromatic bands of variable sizes.

Trisomy 14 mosaicism in a liveborn male: clinical report and review of the literature

We present the history and results of chromosome analysis of a liveborn male with mosaic trisomy 14 who was initially evaluated for a congenital heart defect. His chromosome complement was 46,XY/47,XY,+14. The phenotype of the patient is similar in many respects to that of females previously reported with mosaic trisomy 14, whereas the patient's micropenis and cryptorchidism are consistent with findings in males with dup(14q).

Simultaneous production of R-bands and either replication patterns or sister chromatid differentiation

The dye triplet chromomycin/methyl green/DAPI and some related dye combinations were applied to bromodeoxyuridine (BrdU)-substituted and non-substituted chromosomes. In both kinds of chromosome preparations, tri-staining followed by observation at pH 7 resulted in well defined R-bands (excitation wavelength 436 nm) and a mixed DA-DAPI/Q-banding pattern (360 nm). Two approaches have given satisfactory expression both of reverse bands and of the differential BrdU-substitution present in metaphase chromosomes: (1) direct tri-staining at pH 7 and mounting of the preparations at pH 11; or (2) pretreatment of the preparations with Hoechst 33258 plus UV and hot buffer followed by tri-staining and mounting at pH 7. These methods should prove useful for routine chromosome analysis and, in combination with BrdU-labelling, in studies of chromosome structure and replication.

Genome evolution in pocket gophers (genus Thomomys). III. Fluorochrome-revealed heterochromatin heterogeneity

Heterochromatin is a dominant component of the genome in the bottae group of the pocket gopher genus Thomomys, having had a major role in the karyotypic evolution of member species. Heterochromatin characteristics of two subspecies of T. bottae and one of T. umbrinus were examined with fluorochrome dyes identifying presumptive GC- and AT-rich regions. In two karyotype forms of T. b. fulvus and in T. umbrinus, chromatin that fluoresces brightly with chromomycin A3 is also C-band positive, although not all heterochromatin fluoresces. However, in T. b. bottae, only euchromatic regions fluoresce brightly with chromomycin. Fluorescence patterns produced with DAPI are the reverse of the chromomycin banding in all karyotypic forms. Heterochromatin in these taxa is thus highly differentiated, exhibiting heterogeneity in staining characteristics, and presumably in underlying DNA sequences, both across the genome within a given chromosomal complement as well as among the different karyotypic races and species of the bottae group of pocket gophers.

A new technique for retarding fading of fluorescence: DPX-BME

The antioxidant beta-mercaptoethanol (BME) used in conjunction with the permanent mountant DPX (DPX-BME) retarded fluorescent fading of mithramycin, acridine orange and Hoechst 33258 stained chicken erythrocytes, each to a varying degree. The initial fluorescence of all dyes examined was more intense with DPX-BME than with DPX alone. Specimens mounted in DPX-BME showed strong fluorescence and excellent morphology; if kept in the dark, they could be stored indefinitely without deterioration. Retarding fading of fluorescence with DPX-BME faciliated quantitation of DNA using fluorescence cytophotometry.