scholarly journals Units of chromosome replication and packing

1983 ◽  
Vol 64 (1) ◽  
pp. 179-193
Author(s):  
A.M. Mullinger ◽  
R.T. Johnson
Keyword(s):  
Spatial Distribution ◽  
Light Microscope ◽  
Individual Cell ◽  
S Phase ◽  
Scanning Electron Micrographs ◽  
Metaphase Chromosomes ◽  
Impregnation Technique ◽  
Osmium Impregnation ◽  
The Relationship ◽  
Scanning Electron

Fusion between mitotic and S-phase cells induces the formation of prematurely condensed chromosomes (PCC) in the interphase partner. Viewed in the light microscope, S-phase PCC derived from the Indian muntjac appear to be fragmented and heterogeneous. In scanning electron micrographs prepared by an osmium impregnation technique, which avoids the need to sputter-coat the specimen, the S-phase fragments derived from an individual cell are resolved into about 1000 fibre aggregates, together with more dispersed fibres. Aggregates are roughly spherical and vary in diameter between about 0.25 and 1.6 micron. The spatial distribution of the aggregates shows some order: chains of single aggregates and, less commonly, duplicated chains occur. Regions of the PCC where the fibres are more dispersed are considered to be likely candidates for sites of replication at the time of fusion. The relationship between the condensed aggregate structure of the S-phase PCC and replication clusters is discussed, and also the assembly of aggregates to form metaphase chromosomes.

The relationship between cell proliferation and the transcription of the nuclear oncogenes c-myc, c-myb and c-ets-1 during feather morphogenesis in the chick embryo

Development ◽  
1991 ◽  
Vol 111 (3) ◽  
pp. 699-713 ◽  
Author(s):  
X. Desbiens ◽  
C. Queva ◽  
T. Jaffredo ◽  
D. Stehelin ◽  
B. Vandenbunder
Keyword(s):  
Cell Proliferation ◽  
Endothelial Cells ◽  
Spatial Distribution ◽  
Chick Embryo ◽  
Expression Patterns ◽  
S Phase ◽  
Skin Morphogenesis ◽  
Dermal Cells ◽  
The Relationship

We have described the expression of three nuclear protooncogenes, c-myc, c-myb and c-ets-1 during feather morphogenesis in the chick embryo. In parallel with the expression patterns obtained by in situ hybridization, we have mapped the spatial distribution of S-phase cells by monitoring the incorporation of 5-bromodeoxyuridine. We do not detect c-myc or c-myb transcripts during the early stages when S-phase cells are scattered in the dermis and in the epidermis. Rather c-ets-1 transcripts are abundant in the dermal cells which divide and accumulate under the uniform epidermis. At the onset of the formation of the feather bud, cells within each rudiment cease DNA replicative activities and c-myc transcripts are detected both in the epidermis and in the underlying dermis. This expression precedes the reentry into the S phase. The transcription of c-myb, which has been previously tightly linked to hemopoietic cells is also detected in the developing skin. This expression is essentially located in proliferating epidermal cells on and after the beginning of feather outgrowth. As feather outgrowth proceeds, the distribution of c-myc and c-myb transcripts is restricted to the highly proliferating epidermis. In contrast c-ets-1 transcripts are never detected in the epidermis. During the later stages of skin morphogenesis, the transcription of c-ets-1 is restricted to the endothelial cells of blood vessels, as previously described. We suggest that the differential expression of these nuclear oncogenes reflects the activation of different mitotic controlling pathways during the development of the skin.

The distribution and fine structure of the integumentary papillae of the cercaria ofHimasthla secunda(Nicoll)

Parasitology ◽  
1970 ◽  
Vol 61 (2) ◽  
pp. 219-227 ◽  
Author(s):  
H. D. Chapman ◽  
R. A. Wilson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Spatial Distribution ◽  
Fine Structure ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Silver Nitrate ◽  
Light Microscope ◽  
Transmission Electron ◽  
Scanning Electron

The distribution of the integumentary papillae of the cercaria ofHimasthla secundahas been studied by a variety of techniques. Structures stained by silver nitrate and visible under the light microscope correspond in their spatial distribution with papillae observed under the scanning electron microscope. The tegumentary papillae described with the light and scanning electron microscope are correlated with the specialized nerve endings in the tegument as seen in transmission electron microscopy. The ultrastructure of these papillae is examined by conventional transmission electron microscopy and the probability that these structures are sensory is discussed.

High-resolution scanning electron microscopy of human metaphase chromosomes

1982 ◽  
Vol 56 (1) ◽  
pp. 409-422 ◽  
Author(s):  
C.J. Harrison ◽  
T.D. Allen ◽  
M. Britch ◽  
R. Harris
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Three Dimensional ◽  
Loop Model ◽  
Giemsa Banding ◽  
Metaphase Chromosomes ◽  
Osmium Impregnation ◽  
Chromosome Integrity ◽  
Scanning Electron

Human metaphase chromosomes, prepared for light microscopy were examined by scanning electron microscopy. Use of an osmium impregnation technique eliminated the need for sputter-coating and allowed high-resolution visualization of uncoated specimens. Chromosomes were of three-dimensional cylindrical profile, with well-defined chromatids and centromeres. Prior to Giemsa-banding a smooth surface morphology was observed. Relaxation of chromosome integrity by Giemsa-banding pretreatment allowed resolution of several orders of chromosome structure not previously demonstrated by scanning electron microscopy. The observed organization of the chromatin fibres allowed parallels to be drawn with the radial loop model of chromosome construction as described by Marsden and Laemmli.

scholarly journals Colouring the Human Landscapes

Nuncius ◽  
2014 ◽  
Vol 29 (2) ◽  
pp. 464-497 ◽  
Author(s):  
Solveig Jülich
Keyword(s):  
Human Body ◽  
Scanning Electron Micrographs ◽  
Advertising Industry ◽  
Scientific Images ◽  
Black And White ◽  
Internal Structures ◽  
History Of ◽  
The Media ◽  
The Relationship ◽  
Scanning Electron

This article explores the relationship between Swedish photographer Lennart Nilsson’s scanning electron micrographs and commercial culture from the late 1960s to the mid-1980s. By retracing how Nilsson’s micrographs of the internal structures of the human body were made, circulated, and received, its aim is to investigate three aspects of this relationship. First, it highlights how the complex and sometimes conflicting interplay between the photographer and various actors in science, industry and the media shaped the pictures and their trajectories. Second, it analyses the processes used to colour Nilsson’s original black-and-white micrographs in relation to tendencies in the media and the advertising industry during this period. Third, it examines what motivated Nilsson and his collaborators in their use of colour and also the critical debates concerning the spectacular and commercial qualities of his pictures. In the concluding section, the implications of this analysis for the history of the objectivity of scientific images is discussed.

scholarly journals Light and scanning electron microscopy of the same human metaphase chromosomes

1985 ◽  
Vol 77 (1) ◽  
pp. 143-153
Author(s):  
C.J. Harrison ◽  
E.M. Jack ◽  
T.D. Allen ◽  
R. Harris
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Banding Pattern ◽  
Light Microscope ◽  
Chromosome Banding ◽  
Metaphase Chromosomes ◽  
Scanning Electron

A technique has been developed to examine the same G-banded human metaphase chromosomes, first in the light microscope and then in the scanning electron microscope (SEM). A structural involvement in chromosome banding was confirmed by a positional correlation between the G-positive bands observed in the light microscope and the circumferential grooves between the quaternary coils of the metaphase chromosomes, observed in the SEM. In further support of this the regions between the grooves showed a positional relationship with the G-negative or reverse (R) bands. The examination of slightly extended metaphase chromosomes in the light microscope demonstrated that the G-banding pattern corresponded to that described by the Paris nomenclature for metaphase chromosomes. The arrangement of the circumferential grooves of the same chromosomes, observed in the SEM, was shown to relate to that described by the Paris nomenclature for prometaphase chromosomes. Therefore, using the SEM it is possible to demonstrate the details of prometaphase banding in metaphase chromosomes.

Pollen morphology of Rhynchosia and Eriosema (Fabaceae)

1973 ◽  
Vol 51 (12) ◽  
pp. 2395-2399 ◽  
Author(s):  
E. K. Ramcharan ◽  
J. H. McAndrews ◽  
J. W. Grear
Keyword(s):  
Electron Micrographs ◽  
Light Microscope ◽  
Pollen Morphology ◽  
Scanning Electron Micrographs ◽  
Opposite Pole ◽  
Pollen Characters ◽  
Single Grain ◽  
Scanning Electron

The closely related genera Rhynchosia and Eriosema have tricolporate pollen. Twenty-two species of Rhynchosia and nine species of Eriosema were examined with the light microscope. Most of the species have isopolar-type grains, but 11 species have the hitherto rarely described heteropolar-type pollen, i.e. on a single grain, the ends of the colpi subtend a greater area at one pole than at the opposite pole. Duplicate examination of 13 species indicates that polarity types are constant within those species. While the genera cannot be separated on the basis of pollen morphology alone, there are some pollen characters which embrace most species in any one genus. Eriosema species are mostly heteropolar (67%) and Rhynchosia are predominantly isopolar (77%). The lumina of the reticulum of Rhynchosia tend to be smaller than those of Eriosema and, with one exception, the muri of Eriosema have acute tops while those of Rhynchosia are obtuse. Scanning electron micrographs illustrate pollen morphology.

Some nivicolous species of Lamproderma and Meriderma from the Himalayan Mountains of northwestern India

Phytotaxa ◽  
2018 ◽  
Vol 373 (3) ◽  
pp. 221
Author(s):  
GABRIEL MORENO ◽  
ANGELA LÓPEZ VILLALBA ◽  
AURELIO CASTILLO ◽  
STEVEN L. STEPHENSON
Keyword(s):  
Electron Micrographs ◽  
Light Microscope ◽  
Morphological Characters ◽  
Scanning Electron Micrographs ◽  
Morphological Examination ◽  
Northwestern India ◽  
Himalayan Mountains ◽  
Scanning Electron

A detailed morphological examination of 12 specimens representing seven species in the genera Lamproderma and Meriderma collected from snowbank habitats in the Himalayan Mountains in northwestern India was carried out. Two of the specimens are described herein as Lamproderma spinisporum, a species new to science. In addition, the material from northwestern India is compared with other similar taxa belonging to the genus Lamproderma. Light microscope photographs and scanning electron micrographs of the most representative morphological characters are provided.

scholarly journals Insights Into the Correspondence Between Land Use Pattern and Spatial Distribution of Rail Transit Services

2021 ◽  
Author(s):  
Zhongqi Wang ◽  
Qi Han ◽  
Bauke de Vries ◽  
Li Dai
Keyword(s):  
Land Use ◽  
Spatial Distribution ◽  
Operations Management ◽  
Latent Variable ◽  
Structural Equation ◽  
Equation Modeling ◽  
Rail Transit ◽  
Land Use Patterns ◽  
Transit Services ◽  
The Relationship

AbstractThe identification of the relationship between land use and transport lays the foundation for integrated land use and transport planning and management. This work aims to investigate how rail transit is linked to land use. The research on the relationship between land use and rail-based transport is dominated by the impacts of rail projects on land use, without an in-depth understanding of the reverse. However, it is important to note that issues of operation management rather than new constructions deserve greater attention for regions with established rail networks. Given that there is a correspondence between land use patterns and spatial distribution of heavy railway transit (HRT) services at such regions, the study area (i.e., the Netherlands) is partitioned by the Voronoi diagram of HRT stations and the causal relationship between land use and HRT services is examined by structural equation modeling (SEM). The case study of Helmond (a Dutch city) shows the potential of the SEM model for discussing the rail station selection problem in a multiple transit station region (MTSR). Furthermore, in this study, the node place model is adapted with the derivatives of the SEM model (i.e., the latent variable scores for rail service levels and land use characteristics), which are assigned as node and place indexes respectively, to analyze and differentiate the integration of land use and HRT services at the regional level. The answer to whether and how land use affects rail transit services from this study strengthens the scientific basis for rail transit operations management. The SEM model and the modified node place model are complementary to be used as analytical and decision-making tools for rail transit-oriented regional development.

scholarly journals Double parton distributions in the pion from lattice QCD

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Gunnar S. Bali ◽  
Luca Castagnini ◽  
Markus Diehl ◽  
Jonathan R. Gaunt ◽  
Benjamin Gläßle ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Lattice Qcd ◽  
Quark Mass ◽  
Matrix Elements ◽  
Parton Distributions ◽  
Almost All ◽  
The Relationship

Abstract We perform a lattice study of double parton distributions in the pion, using the relationship between their Mellin moments and pion matrix elements of two local currents. A good statistical signal is obtained for almost all relevant Wick contractions. We investigate correlations in the spatial distribution of two partons in the pion, as well as correlations involving the parton polarisation. The patterns we observe depend significantly on the quark mass. We investigate the assumption that double parton distributions approximately factorise into a convolution of single parton distributions.

Sign in / Sign up

Export Citation Format

Share Document