G-banding and chromosome structure

Romanowsky staining: history, recent advances and future prospects from a chemistry perspective

Romanowsky staining was an important methodological breakthrough in diagnostic hematology and cytopathology during the late 19th and early 20th centuries; it has facilitated for decades the work of biologists, hematologists and pathologists working with blood cells. Despite more than a century of studying Romanowsky staining, no systematic review has been published that explains the chemical processes that produce the "Romanowsky effect" or "Romanowsky-Giemsa effect" (RGE), i.e., a purple coloration arising from the interaction of an azure dye with eosin and not due merely to their simultaneous presence. Our review is an attempt to build a bridge between chemists and biomedical scientists and to summarize the available data on methylene blue (MB) demethylation as well as the related reduction and decomposition of MB to simpler compounds by both light and enzyme systems and microorganisms. To do this, we analyze modern data on the mechanisms of MB demethylation both in the presence of acids and bases and by disproportionation due to the action of light. We also offer an explanation for why the RGE occurs only when azure B, or to a lesser extent, azure A is present by applying experimental and calculated physicochemical parameters including dye-DNA binding constants and electron density distributions in the molecules of these ligands. Finally, we discuss modern techniques for obtaining new varieties of Romanowsky dyes by modifying previously known ones. We hope that our critical literature study will help scientists understand better the chemical and physicochemical processes and mechanisms of cell staining with such dyes.

Development and Assessment of Multiple Illumination Color Fourier Ptychographic Microscopy for High Throughput Sample Digitization

In this study, we proposed a multiplexed color illumination strategy to improve the data acquisition efficiency of Fourier ptychography microscopy (FPM). Instead of sequentially lighting up one single channel LED, our method turns on multiple white light LEDs for each image acquisition via a color camera. Thus, each raw image contains multiplexed spectral information. An FPM prototype was developed, which was equipped with a 4×/0.13 NA objective lens to achieve a spatial resolution equivalent to that of a 20×/0.4 NA objective lens. Both two- and four-LED illumination patterns were designed and applied during the experiments. A USAF 1951 resolution target was first imaged under these illumination conditions, based on which MTF curves were generated to assess the corresponding imaging performance. Next, H&E tissue samples and analyzable metaphase chromosome cells were used to evaluate the clinical utility of our strategy. The results show that the single and multiplexed (two- or four-LED) illumination results achieved comparable imaging performance on all the three channels of the MTF curves. Meanwhile, the reconstructed tissue or cell images successfully retain the definition of cell nuclei and cytoplasm and can better preserve the cell edges as compared to the results from the conventional microscopes. This study initially validates the feasibility of multiplexed color illumination for the future development of high-throughput FPM scanning systems.

Cytogenetic Studies in Primary Amenorrhoea Cases

Background:

Amenorrhoea is considered a kind of menstrual disorder in a woman of reproductive age. It is a symptom with many potential causes such as an abnormality in the hypothalamic–pituitary–ovarian axis, anatomical abnormalities of the genital tract or functional causes.

Aims:

In this study, we aimed to investigate chromosomal abnormalities in patients presenting with primary amenorrhoea.

Study Setting and Design:

This study was conducted in the medical genetic laboratory.

Materials and Methods:

Chromosomal analysis was carried out in 134 cases that were referred to the human genetic laboratory from 2010 to 2017, employing (GTG) Giemsa banding.

Statistical Analysis:

Statistical analyses were carried out by Microsoft Office Excel (2019).

Results:

The karyotype results revealed 77.6% (n = 104) with normal chromosome composition while 22.38% (n = 30) showed chromosomal abnormalities. Among the patients with abnormal chromosome constituents, 53.54% exhibited numerical aberration and 46.66% showed structural abnormalities.

Conclusion:

The present study has emphasised that karyotyping is one of the fundamental investigations in the evaluation of primary amenorrhoea.

Using Fourier ptychography microscopy to achieve high-resolution chromosome imaging: an initial evaluation

SIGNIFICANCE

Searching analyzable metaphase chromosomes is a critical step for the diagnosis and treatment of leukemia patients, and the searching efficiency is limited by the difficulty that the conventional microscopic systems have in simultaneously achieving high resolution and a large field of view (FOV). However, this challenge can be addressed by Fourier ptychography microscopy (FPM) technology.

AIM

The purpose of this study is to investigate the feasibility of utilizing FPM to reconstruct high-resolution chromosome images.

APPROACH

An experimental FPM prototype, which was equipped with 4  ×    /  0.1  NA or 10  ×    /  0.25  NA objective lenses to achieve a theoretical equivalent NA of 0.48 and 0.63, respectively, was developed. Under these configurations, we first generated the system modulation transfer function (MTF) curves to assess the resolving power. Next, a group of analyzable metaphase chromosomes were imaged by the FPM system, which were acquired from the peripheral blood samples of the leukemia patients. The chromosome feature qualities were evaluated and compared with the results accomplished by the corresponding conventional microscopes.

RESULTS

The MTF curve results indicate that the resolving power of the 4  ×    /  0.1  NA FPM system is equivalent and comparable to the 20  ×    /  0.4  NA conventional microscope, whereas the performance of the 10  ×    /  0.25  NA FPM system is close to the 60  ×    /  0.95  NA conventional microscope. When imaging the chromosomes, the feature qualities of the 4  ×    /  0.1  NA FPM system are comparable to the results under the conventional 20  ×    /  0.4  NA lens, whereas the feature qualities of the 10  ×    /  0.25  NA FPM system are better than the conventional 60  ×    /  0.95  NA lens and comparable to the conventional 100  ×    /  1.25  NA lens.

CONCLUSIONS

This study initially verified that it is feasible to utilize FPM to develop a high-resolution and wide-field chromosome sample scanner.

Chromosome Abnormalities and Absolute Telomere Lengths of Leukocytes from Silk Weavers with Emphasis on Potential Genotoxicity and Mutagenicity of Silk Dyes

Objectives:

This study is aimed to assess the possible genotoxicity and mutagenicity of silk dyes on silk weavers.

Methods:

Peripheral blood leukocytes were obtained from 24 silk weavers and 24 age- and sex-matched controls in northeastern Thailand. After mitogen stimulation in culture, chromosome abnormalities were examined using Giemsa banding and the absolute telomere length (aTL) was measured with SYBR green qRT-PCR. To confirm genotoxic and mutagenic effects of silk dyes, leukocytes from one each of healthy male and female volunteers were cultured with various concentrations of 3 dark red silk dyes under the presence of mitogen. Chromosome abnormalities and the telomere length were determined as above.

Results:

The proportion of normal metaphase in the silk weaving workers was significantly lower than that in controls. The frequency of chromosome aberrations was higher in the silk weavers than in control group. Polyploidy was detected only in the silk weavers. The aTL was significantly shorter in the silk weavers than in control group (p < 0.05). When leukocytes from normal volunteers were stimulated with mitogen under the presence of various concentrations of 3 silk dyes, suppressed the mitotic index (MI) and normal metaphase, whereas the proportion of prophase and the incomplete chromosome forming increased significantly. All dyes induced polyploidy. Dye #CA5 induced structural changes in male leukocytes, whereas #30 induced the changes in female leukocytes. The #CA5 increased aTL of normal leukocytes in a dose-dependent manner.

Conclusions:

All dyes, especially #CA5, have high genotoxicity and mutagenicity to induce chromosome aberrations and telomeric instability. Taken all those results together, regular health checking of silk weavers who have been exposed to those dyes is critically necessary to prevent various chemical-induced carcinogenesis.

Karyotyping human chromosomes by optical and X-ray ptychography methods

Sorting and identifying chromosomes, a process known as karyotyping, is widely used to detect changes in chromosome shapes and gene positions. In a karyotype the chromosomes are identified by their size and therefore this process can be performed by measuring macroscopic structural variables. Chromosomes contain a specific number of basepairs that linearly correlate with their size; therefore, it is possible to perform a karyotype on chromosomes using their mass as an identifying factor. Here, we obtain the first images, to our knowledge, of chromosomes using the novel imaging method of ptychography. We can use the images to measure the mass of chromosomes and perform a partial karyotype from the results. We also obtain high spatial resolution using this technique with synchrotron source x-rays.

Atomic force microscope imaging of chromosome structure during G-banding treatments

Surface topography of human chromosomes was examined by atomic force microscopy during treatments for G-banding. Trypsin treatment resulted in a structural modification in the chromatin. Subsequent Giemsa staining caused a general swelling of the chromosomal surface that was greater in the areas of G-band positive regions. By means of a quantitative evaluation method we showed that the G-banding process produces a 10-fold enhancement of a pre-existing pattern of chromatin between G-band positive and G-band negative regions on mitotic chromosomes.

Longitudinal patterns similar to G-banding in untreated human chromosomes: evidence from atomic force microscopy

The structure of human metaphase chromosomes, fixed according to standard procedures for optical microscopy but not treated for banding, was examined by atomic force microscopy (AFM). The images show that chromosomes display a banding pattern very similar to G-banding, detected by the AFM as a variation in the thickness of chromatin. This similarity allows the identification of individual chromosomes.

G-bands without pretreatment of slides, in chemically defined conditions

We investigated the capability of Giemsa dyes to produce G-bands without pretreatment of slides in chemically defined conditions. G-banding was produced between pH 7.0 and pH 11.0. Within this range, we observed that the achievement of G-bands was dependent on the ionic strength and time of staining. From these data and from those of other authors on other chemical variables and on the mechanisms of staining, we propose a working hypothesis of G-band formation, with a step involving shrinkage of the chromatids and rearrangement of the chromosome fiber during the staining process.

New chromosome techniques in the study of human neoplasia

Amethopterin synchronization of bone marrow and lymph node cells makes it possible to obtain well banded and elongated metaphases and prometaphases in the majority of patients with leukemia and lymphoma. Chromosomal analysis of most neoplasias is also possible through the use of mild tumor cell disaggregation methods, short term culture on feeder layers, and special media that help in the preferential proliferation of cancer cells. In the past, only about half of all patients with acute leukemia and lymphoma could be shown to have a chromosomal defect, and only a small proportion of solid tumors could be analyzed. With the new technology, abnormal tissue from the majority of cancer patients can be successfully studied and chromosomal abnormalities detected.

An improved technique of preparing bone-marrow specimens for cytogenetic analysis

Sixty-six bone-marrow specimens, derived from patients with hematological and nonhematological disorders, were processed for cytogenetic analysis. Modifications of various parameters of the standard (direct) culture procedure were investigated and the quality of the preparations determined. As a result of these experiments, an improved culture technique was developed that yielded significantly better quality chromosome preparations. This method is based on a short incubation (25-min) of the bone-marrow specimen, immediately following aspiration, in a solution containing both hypotonic KCl and colcemid and completely omits the use of tissue culture medium.

Human lymphocyte-mouse myeloma somatic cell hybrids: selective hybrid formation

Fusion of unfractionated human lymphocytes with mouse myeloma cells resulted in proliferating hybrid colonies, almost all producting human Ig. We examined whether this high frequency of Ig production was the result of selective formation of human B lymphocyte-mouse myeloma hybrids, rather than induction of Ig genes in T lymphocytes. Unfractionated peripheral lymphocytes and B lymphocytes from patients with the common variable form of agammaglobulinemia formed proliferating somatic cell hybrid colonies. In contrast, peripheral lymphocytes from a patient with agammaglobulinema who lacked B lymphocytes, as well as albumin gradient fractions of peripheral blood which do not contain B lymphocytes, failed to produce somatic cell hybrids with three different myeloma parent cell lines. B, T, and precursor lymphocytes all had Sendai virus receptors, as witnessed by viral agglutination. We conclude that fusion of human lymphocytes with mouse myeloma cells results in selective hybrid formation, rather than activation of Ig genes in disparate cell types. Only B lymphocyte-mouse myeloma heterokaryons form hybrid cells.

Banding and spiralization of human metaphase chromosomes

A new technique is described which produces spiralization of human metaphase chromosomes. The important feature is heat followed by trypsin treatment. By varying conditions, it is possible to produce bands, spirals and intermediate stages. This provides a new approach to the understanding of banding and chromosome structure.

Influence of Q- and G-banding on the Feulgen-stainability of human metaphase chromosomes

In this paper, model experiments on chicken red blood cell nuclei are described concerning the influence of methanol-acetic acid fixation and irradiation at different wavelengths, with and without prior Atebrin staining on subsequent Feulgen-stainability. In addition, data are reported on the influence on Feulgen-stainability of Giemsa-banding procedures, illumination of unstained chromosomes at 220 and 515 nm and exposure of unstained and Atebrin-stained chromosomes to illumination at 440 nm. The ASG and especially the trypsin-Giemsa technique appeared to reduce markedly Feulgen-stainability. The same holds true for Atebrin fluorescence of chromosomes. The data are discussed in relation to their implications for the assumed cause of the Q- and G-banding phenomena. Techniques are described that allow reliable Feulgen DNA measurements of individual chromosomes after application of either G- or Q-banding.

[Differential Giemsa staining of heterochromatic regions in the chromosomes of Vicia faba, Allium cepa and Paeonia tenuifolia]

Hypotheses for the mechanism of differential Giemsa staining of euchromatin and heterochromatin are discussed. The banding-patterns of Vicia faba, Allium cepa and Paeonia tenuifolia are described. Heterochromatic chromosome segments have been identified in metaphase chromosomes to correspond with those to be found in interphase nuclei. The fact that the number of chromocenters is usually smaller than the number of Giemsa bands in the metaphase chromosomes is supposed to be due to fusion of heterochromatic sections during interphase. Within each species non-homologous chromosomes exhibit similar patterns. The significance of this phenomenon, which has been called "aequilocal heterochromacy" by Heitz, is so far unknown.

Configurational changes in chromatids from helical to banded structures

Induction of configurational changes in the helical chromatids of air dried chromosomes was used to explore the mechanism of G-banding. From the water-Giemsa stained metaphase spreads of Chinese hamster cells, chromosomes having clearly helical chromatids were selected and photographed. Then the chromosomes were decolorized, treated with trypsin, and restained with saline-Giemsa (1X SSC). Such procedures were repeatedly carried out upon the same chromosomes. Subsequent examination of the chromosomes showed that configurational changes from a helical structure to a banded structure had occurred. Some chromosomes revealed a variety of transitional changes between these two configurations. During the repeated G-banding treatments, the distances between bands along the same chromatids changed each time. The results obtained seem to indicate that the G-banding results from locally induced compaction of chromosomal materials along the chromatids.

Identification of pachytene bivalents in human male meiosis using G-banding technique

G-banding of human pachytene bivalents is obtained using trypsin digestion. Each of the 22 autosomal bivalents is clearly identified. Such an identification leads to construction of the human pachytene map. Our results show the equivalence between the G-band patterns of mitotic chromosomes and meiotic bivalents. The G-band patterns of mitotic-meiotic chromosomes also correlate closely with the chromomere sequence of pachytene bivalents. Thus, study of chromomeres should constitute an excellent approach to comprehension of G-banding mechanism.

Late replicating bands of human chromosomes demonstrated by fluorochrome and Giemsa staining

The addition of thymidine (TdR) to cells growing in a medium containing 5-bromodeoxyuridine (BUdR) at the end of the first replication cycle results in the incorporation of TdR into the late replicating DNA regions. These sites can be visualized by staining the metaphase chromosomes with the fluorescent dye "33258 Hoechst" or a "33258 Hoechst" Giemsa procedure. A sequence of late replication patterns has been established in metaphase chromosomes of cultured human peripheral lymphocytes. The patterns are in agreement with those obtained by the standard autoradiographic procedures, but are more accurate. As is known from autoradiography, late replicating bands are in the position of G or Q bands. The "33258 Hoechst" Giemsa staining procedure of chromosomes which have replicated in the presence of BUdR first and in TdR for the last 2 hrs of the S phase is preferable to the currently used Giemsa banding techniques: the method yields very well banded metaphases in all preparations examined, as the chromosome structure is not disrupted by the pretreatment. The bands are very distinct, even in the "difficult" chromosomes (e.g. No. 4, 5, 8 and X). In female cells the late replicating X chromosome can be identified by its size and staining pattern. In addition to the replication asynchrony, the sequence of replication within both X chromosomes in female cells is not absolutely identical. The phenomenon of a phase difference in replication between the homologues is not a peculiarity of the X chromosome, but can be found in all autosomes as well as in homologous positions on the chromatids of individual chromosomes.

The G-banded prophase chromosomes of man

Using a simple G-banding technique developed in our laboratory, analysis of late prophases enables the visualization of approximately 1000 bands in the haploid set of human chromosomes. These bands have been classified according to the recommendations of the Paris Conference. The increased resolution offered by this technique is likely to be useful in the study of the structure and molecular organization of chromosomes and in identifying minute chromosome defects in birth defects and neoplasia.