Stellaria media embryogenesis: the development and ultrastructure of the suspensor

1974 ◽  
Vol 52 (3) ◽  
pp. 607-614 ◽  
Author(s):  
William Newcomb ◽  
L. C. Fowke
Keyword(s):  
Subsequent Development ◽  
Early Embryogenesis ◽  
The Other ◽  
Structural Level ◽  
Embryonic Cells ◽  
Cell Type ◽  
Stellaria Media ◽  
Side Walls ◽  
Metabolic Activities ◽  
Suspensor Cells

As early as the three-celled stage of embryogenesis, the basal cell of chickweed, Stellaria media, is larger than the other embryonic cells and contains large differentiating plastids, microbodies, and wall ingrowths of the transfer cell type at the micropylar end of the cell. Subsequent development produces a suspensor with unique plastids, microbodies, and extensive profiles of dilated endoplasmic reticulum not found in the embryo proper. The suspensor plastids, which appear to be different from any other plastids previously described on the ultra-structural level, are large and contain two types of tubules and electron-translucent inclusions. Plasmodesmata occur in the end walls but not in the side walls of the suspensor cells. It is suggested that the suspensor of chickweed is involved in important, possibly essential, translocation and metabolic activities during early embryogenesis.

The Other Entrepreneurs - Migrant Economies as Spaces for Social Innovation?

2019 ◽  
Vol 16 (2) ◽  
pp. 265-271
Author(s):  
Claudia Lintner
Keyword(s):  
Social Innovation ◽  
Close Relation ◽  
The Other ◽  
Structural Level ◽  
Structured Interviews ◽  
Economic Activities ◽  
Migrant Entrepreneurship ◽  
False Dichotomy ◽  
Migrant Entrepreneurs ◽  
The One

This article analyses the relationship between migrant entrepreneurship, marginalisation and social innovation. It does so, by looking how their ‘otherness’ is used on the one hand to reproduce their marginalised situation in society and on the other to develop new living and working arrangements promoting social innovation in society. The paper is based on a qualitative study, which was carried out from March 2014- 2016. In this period, twenty semi-structured interviews were conducted with migrant entrepreneurs and experts. As the results show, migrant entrepreneurs are characterised by a false dichotomy of “native weakness” in economic self-organisation against the “classical strength” of majority entrepreneurs. It is shown that new possibilities of acting in the context of migrant entrepreneurship are mostly organised in close relation to the lifeworlds and specific needs deriving from this sphere. Social innovation processes initiated by migrant entrepreneurs through their economic activities thus develop on a micro level and are hence less apparent. Supportive networks are missing on a structural level, so it becomes difficult for single innovative initiatives to be long-lasting.

THE “REVOLUTION” IN FINANCIAL REPORTING THEORY: A KUHNIAN INTERPRETATION

1993 ◽  
Vol 20 (1) ◽  
pp. 33-57 ◽  
Author(s):  
Tom Mouck
Keyword(s):  
Financial Reporting ◽  
Subsequent Development ◽  
The Other ◽  
Other Hand ◽  
Research Problems ◽  
Market Economics ◽  
Economic Income ◽  
The Revolution

A Kuhnian perspective is used to explain the transition in financial reporting theory from an “economic income perspective” to an “informational perspective” (a transition that Beaver refers to as a “revolution”), and to examine the subsequent development of the latter. The demise of the economic income perspective (represented by the normative a priorists) is attributed to the lack of a paradigm which could serve to identify research problems and provide methodological guidance. The success of the informational paradigm, on the other hand, is attributed to the fact that it was, in essence, a sub-paradigm of the broader and well-established market economics paradigm. The study concludes, however, with a discussion of two types of persistent anomalous findings (the first with respect to the EMH and the second with respect to the CAPM) that have the potential to generate a crisis for the informational paradigm.

scholarly journals Antagonising Chromatin Remodelling Activities in the Regulation of Mammalian Ribosomal Transcription

Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 961
Author(s):  
Kanwal Tariq ◽  
Ann-Kristin Östlund Farrants
Keyword(s):  
Stress Responses ◽  
Ribosomal Gene ◽  
Chromatin Remodelling ◽  
Chromatin State ◽  
Rrna Gene ◽  
Open Chromatin ◽  
Histone Chaperones ◽  
Embryonic Cells ◽  
Cell Type ◽  
Chromatin States

Ribosomal transcription constitutes the major energy consuming process in cells and is regulated in response to proliferation, differentiation and metabolic conditions by several signalling pathways. These act on the transcription machinery but also on chromatin factors and ncRNA. The many ribosomal gene repeats are organised in a number of different chromatin states; active, poised, pseudosilent and repressed gene repeats. Some of these chromatin states are unique to the 47rRNA gene repeat and do not occur at other locations in the genome, such as the active state organised with the HMG protein UBF whereas other chromatin state are nucleosomal, harbouring both active and inactive histone marks. The number of repeats in a certain state varies on developmental stage and cell type; embryonic cells have more rRNA gene repeats organised in an open chromatin state, which is replaced by heterochromatin during differentiation, establishing different states depending on cell type. The 47S rRNA gene transcription is regulated in different ways depending on stimulus and chromatin state of individual gene repeats. This review will discuss the present knowledge about factors involved, such as chromatin remodelling factors NuRD, NoRC, CSB, B-WICH, histone modifying enzymes and histone chaperones, in altering gene expression and switching chromatin states in proliferation, differentiation, metabolic changes and stress responses.

scholarly journals Secondary Myelitis in Dermal Sinus Causing Paraplegia in a Child with Previously Normal Neurological Function

2016 ◽  
Vol 2016 ◽  
pp. 1-4 ◽  
Author(s):  
Sakina Rashid ◽  
Grace Kinabo ◽  
Marissa Kellogg ◽  
William P. Howlett ◽  
Marieke C. J. Dekker
Keyword(s):  
Congenital Anomaly ◽  
Spina Bifida ◽  
Neural Tube ◽  
Clinical Course ◽  
Acute Infection ◽  
Early Embryogenesis ◽  
The Other ◽  
Neurological Deficits ◽  
Dermal Sinus ◽  
Neurological Development

Neural tube defects result from failure of neural tube fusion during early embryogenesis, the fourth week after conception. The spectrum of severity is not uniform across the various forms of this congenital anomaly as certain presentations are not compatible with extrauterine life (anencephaly) while, on the other hand, other defects may remain undiagnosed as they are entirely asymptomatic (occult spina bifida). We report a child with previously normal neurological development, a devastating clinical course following superinfection of a subtle spina bifida defect which resulted in a flaccid paralysis below the level of the lesion and permanent neurological deficits following resolution of the acute infection and a back closure surgery.

The effect of pancreatic mesenchyme on the differentiation of endocrine cells from gastric endoderm

Development ◽  
1987 ◽  
Vol 100 (4) ◽  
pp. 661-671 ◽  
Author(s):  
B. Kramer ◽  
A. Andrew ◽  
B.B. Rawdon ◽  
P. Becker
Keyword(s):  
Endocrine Cell ◽  
Endocrine Cells ◽  
Cell Types ◽  
The Other ◽  
Chick Embryos ◽  
Cell Type ◽  
Pancreatic Insulin ◽  
Somatostatin Cells ◽  
Regional Specificity ◽  
Gut Endocrine Cells

To determine whether mesenchyme plays a part in the differentiation of gut endocrine cells, proventricular endoderm from 4- to 5-day chick or quail embryos was associated with mesenchyme from the dorsal pancreatic bud of chick embryos of the same age. The combinations were grown on the chorioallantoic membranes of host chick embryos until they reached a total incubation age of 21 days. Proventricular or pancreatic endoderm of the appropriate age and species reassociated with its own mesenchyme provided the controls. Morphogenesis in the experimental grafts corresponded closely to that in proventricular controls, i.e. the pancreatic mesenchyme supported the development of proventricular glands from proventricular endoderm. Insulin, glucagon and somatostatin cells and cells with pancreatic polypeptide-like immunoreactivity differentiated in the pancreatic controls. The latter three endocrine cell types, together with neurotensin and bombesin/gastrin-releasing polypeptide (GRP) cells, developed in proventricular controls and experimental grafts. The proportions of the major types common to proventriculus and pancreas (somatostatin and glucagon cells) were in general similar when experimental grafts were compared with proventricular controls but different when experimental and pancreatic control grafts were compared. Hence pancreatic mesenchyme did not materially affect the proportions of these three cell types in experimental grafts, induced no specific pancreatic (insulin) cell type and allowed the differentiation of the characteristic proventricular endocrine cell types, neurotensin and bombesin/GRP cells. However, an important finding was a significant reduction in the proportion of bombesin/GRP cells, attributable in part to a decrease in their number and in part to an increase in the numbers of endocrine cells of the other types. This indicates that mesenchyme may well play a part in determining the regional specificity of populations of gut endocrine cells.

The retinotectal projections after uncrossing the optic chiasma in Xenopus with one compound eye

Development ◽  
1971 ◽  
Vol 26 (3) ◽  
pp. 523-542
Author(s):  
K. Straznicky ◽  
R. M. Gaze ◽  
M. J. Keating
Keyword(s):  
Compound Eye ◽  
The Other ◽  
Cell Type ◽  
Cell Type Specificity ◽  
Optic Chiasma ◽  
Normal Side ◽  
Cell Specificity ◽  
Normal Projection ◽  
Retinotectal Projections ◽  
Fixed Cell

The nature of the retinotectal projection from a compound (NN or TT) eye in Xenopus raises certain problems concerning the mode of formation of connexions between the eye and the tectum. Each half of the compound eye appears to spread its connexions across the entire extent of the (apparently normal) contralateral tectum. This could indicate a certain plasticity in the way in which optic fibres can connect with the tectum. Alternatively, it is conceivable that each (similar) half of the compound eye is only able to innervate its corresponding half-tectum; in which case the uninnervated half-tectum could remain undeveloped and the innervated half-tectum could overgrow to resemble a normal tectum. This mechanism would preserve the idea of a rigidly fixed cell-to-cell specificity between retina and tectum. In an attempt to distinguish between these two mechanisms (spreading or overgrown half-tectum) we have given each of a series of Xenopus embryos at stage 32 one compound eye (NN or TT). Then, shortly after metamorphosis, we uncrossed the optic chiasma and 6 months later recorded the retinotectal projections from each eye to the tecta. Thus by connecting up the normal eye to the suspect tectum, and the compound eye to the normal tectum, we used the normal side in each case to provide an indication of the degree of abnormality with which the other side was connected. The results showed that a compound eye (NN or TT), connected to a normal tectum, gave a typical reduplicated map across the entire tectum, whereas the normal eye, when connected to the tectum which was previously innervated by the compound eye, gave an approximately normal projection across the whole of that tectum. These results lead us to conclude that, in the Xenopus visual system, no strict cell-to-cell type specificity exists; rather, what is preserved throughout these experimental manoeuvres is the polarity and extent of the projection.

scholarly journals Mechanisms for pattern formation leading to axis formation and lineage allocation in mammals: a marsupial perspective

Reproduction ◽  
2001 ◽  
pp. 677-683 ◽  
Author(s):  
L Selwood
Keyword(s):  
Cell Division ◽  
Early Embryogenesis ◽  
Boundary Effects ◽  
Axis Formation ◽  
Blastocyst Formation ◽  
Cell Type ◽  
Sperm Entry ◽  
Type Boundary ◽  
Point Gravity ◽  
Anterior Posterior

Developing patterns in early embryogenesis are analysed in conceptuses from several families, including Dasyuridae, Phalangeridae, Macropodidae and Didelphidae, in which cleavage has been examined in some detail. Features common to cleavage and blastocyst formation, and in some cases to hypoblast formation, are used to develop an outline of possible mechanisms leading to axis formation and lineage allocation. Relevant features that have been described only in some species are also included. It is suggested that certain features of marsupial cleavage establish patterns in the developing blastocyst epithelia, pluriblast, trophoblast and hypoblast that contribute to axis formation and lineage allocation. All marsupials examined had a polarized oocyte or conceptus, the polarity of which was related to the conceptus embryonic-abembryonic axis and, eventually, the conceptus dorsal-ventral axis and the formation of the pluriblast (future embryo) and trophoblast. The embryonic dorsal-ventral and anterior-posterior axes were established after the allocation of hypoblast and epiblast. Mechanisms that appear to result in patterning of the developing epithelia leading to axis formation and lineage allocation are discussed, and include sperm entry point, gravity, conceptus polarity, differentials in cell-zona, cell-cell and cell-type (boundary effects) contacts, cell division order during cleavage and signals external to the conceptus. A model of the patterning effects is included. The applicability of these mechanisms to other amniotes, including eutherian mammals, is also examined.

scholarly journals Periaqueductal efferents to dopamine and GABA neurons of the VTA

2017 ◽  
Author(s):  
Niels R. Ntamati ◽  
Meaghan Creed ◽  
Christian Lüscher
Keyword(s):  
Functional Analysis ◽  
Ventral Tegmental Area ◽  
Periaqueductal Gray ◽  
Retrograde Tracing ◽  
The Other ◽  
Projection Neurons ◽  
Cell Type ◽  
Gaba Neurons ◽  
Other Hand ◽  
Cell Type Specific

AbstractNeurons in the periaqueductal gray (PAG) modulate threat responses and nociception. Activity in the ventral tegmental area (VTA) on the other hand can cause reinforcement and aversion. While in many situations these behaviors are related, the anatomical substrate of a crosstalk between the PAG and VTA remains poorly understood. Here we describe the anatomical and electrophysiological organization of the VTA-projecting PAG neurons. Using rabies-based, cell type-specific retrograde tracing, we observed that PAG to VTA projection neurons are evenly distributed along the rostro-caudal axis of the PAG, but concentrated in its posterior and ventrolateral segments. Optogenetic projection targeting demonstrated that the PAG-to-VTA pathway is predominantly excitatory and targets similar proportions of Ih-expressing VTA DA and GABA neurons. Taken together, these results set the framework for functional analysis of the interplay between PAG and VTA in the regulation of reward and aversion.

The Politics of Economic Adjustment: Explaining the Transformation of Industry-State Relationships in Australia

1995 ◽  
Vol 43 (1) ◽  
pp. 22-47 ◽  
Author(s):  
Stephen Bell
Keyword(s):  
Free Trade ◽  
Policy Making ◽  
Manufacturing Industry ◽  
Policy Networks ◽  
Structural Theory ◽  
The State ◽  
The Other ◽  
Structural Level ◽  
Economic Adjustment ◽  
Meso Level

Recent theories of the state (pluralism, statism, Marxism and corporatism) are evaluated in terms of their capacity to explain an historic transformation in industry-state relationships in Australia over the last two decades. The explanatory tasks focus on explaining the shift from high protectionism to free trade for manufacturing industry, coupled with an increase in positive industry assistance measures. The paper argues that a suitably tailored Marxist account avoids most of the limitations of the other theories examined. Yet it is stressed that Marxism's strength lies not in explaining policy details but in providing a broad macro-structural theory of the state in capitalist societies. Marxism's explanatory ‘superstructure’, needs to be filled in at the meso-level by other explanatory elements so that the contours and dynamics of policy making below the macro-structural level can be more fully explained. Concepts such as accumulation strategy, political coalitions and policy networks are suggested for this purpose.

Basaglia in France

2020 ◽  
pp. 275-294
Author(s):  
Nicolas Henckes ◽  
Anne M. Lovell
Keyword(s):  
Subsequent Development ◽  
Second World War ◽  
The Other ◽  
World War ◽  
Community Based ◽  
Institutional Practice ◽  
The One ◽  
Mental Health Policies ◽  
Second World ◽  
French Paradox

This chapter assesses Franco Basaglia’s enduring influence in France by focusing on the circulation of concepts and practices and their effects on French mental health policies and scattered experimentation. Despite similar origins, Basaglia’s early work contrasts with the Second World War movement of French psychiatric reformers to humanize the asylum, including through ‘psychothérapie institutionnelle’ and the subsequent development of a sectorization policy. The chapter then examines the extent to which Basaglia’s ideas took ground in France through the efforts of a small network of psychiatric practitioners and intellectuals, within roughly three periods: 1960–1980, 1980–2000, and 2000 to the present. In conclusion, the chapter asks what might explain the French paradox: the early receptivity to Basaglia’s politically-oriented, community-based, anti-institutional practice, on the one hand; and a tenacious hospital-centric psychiatric system and increased use of constraints and high-security confinement, on the other.

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