The role of the dorsal lip in the induction of heart mesoderm in Xenopus laevis

Development ◽  
1990 ◽  
Vol 108 (3) ◽  
pp. 461-470 ◽  
Author(s):  
A.K. Sater ◽  
A.G. Jacobson
Keyword(s):  
Xenopus Laevis ◽  
Marginal Zone ◽  
Dorsal Midline ◽  
Tissue Interactions ◽  
Secondary Axis ◽  
Heart Formation

We have examined the tissue interactions responsible for the expression of heart-forming potency during gastrulation. By comparing the specification of different regions of the marginal zone, we show that heart-forming potency is expressed only in explants containing both the dorsal lip of the blastopore and deep mesoderm between 30 degrees and 45 degrees lateral to the dorsal midline. Embryos from which both of these 30 degrees-45 degrees dorsolateral regions have been removed undergo heart formation in two thirds of cases, as long as the dorsal lip is left intact. If the dorsal lip is removed along with the 30 degrees-45 degrees regions, heart formation does not occur. These results indicate that the dorsolateral deep mesoderm must interact with the dorsal lip in order to express heart-forming potency. Transplantation of the dorsal lip into the ventral marginal zone of host embryos results in the formation of a secondary axis; in over half of cases, this secondary axis includes a heart derived from the host mesoderm. These findings suggest that the establishment of heart mesoderm is initiated by a dorsalizing signal from the dorsal lip of the blastopore.

The anterior extent of dorsal development of the Xenopus embryonic axis depends on the quantity of organizer in the late blastula

Development ◽  
1990 ◽  
Vol 109 (2) ◽  
pp. 363-372 ◽  
Author(s):  
R.M. Stewart ◽  
J.C. Gerhart
Keyword(s):  
Xenopus Laevis ◽  
Cell Population ◽  
Marginal Zone ◽  
Organizer Region ◽  
Blastula Stage ◽  
Dorsal Midline ◽  
Anterior Dorsal ◽  
Lateral Width ◽  
Anterior Extent ◽  
Anterior Posterior

In amphibian gastrulae, the cell population of the organizer region of the marginal zone (MZ) establishes morphogenesis and patterning within itself and within surrounding regions of the MZ, presumptive neurectoderm, and archenteron roof. We have tested the effects on pattern of reducing the amount of organizer region by recombining halves of Xenopus laevis late blastulae cut at different angles from the bilateral plane. When regions within 30 degrees of the dorsal midline are excluded from recombinants, ventralized embryos develop lacking the entire anterior-posterior sequence of dorsal structures, suggesting that the organizer is only 60 degrees wide (centered on the dorsal midline) at the late blastula stage. As more and more dorsal MZ (organizer) is included in the recombinant, progressively more anterior dorsal structures are formed. In all cases, when any dorsal structures are missing they are deleted serially from the anterior end. Thus, we suggest that the amount (lateral width) of the organizer in the MZ determines the anterior extent of dorsal development.

Competition during innervation of embryonic amphibian head skin

1983 ◽  
Vol 218 (1210) ◽  
pp. 49-59 ◽  
Keyword(s):  
Horseradish Peroxidase ◽  
Xenopus Laevis ◽  
Trigeminal Ganglion ◽  
Nerve Endings ◽  
Movement Detector ◽  
Dorsal Midline ◽  
Intact Side ◽  
Free Nerve Endings ◽  
Peripheral Innervation ◽  
Peripheral Sensory

We have examined the initial innervation of the head skin in Xenopus laevis embryos which is by two classes of trigeminal mechanoreceptor with beaded ‘free’ nerve-endings. By recording receptive areas electrophysiologically and staining peripheral sensory neurites with horseradish peroxidase, we have shown that ‘movement detector’ neurites from one trigeminal ganglion do not normally cross the dorsal midline of the head to innervate areas of skin on the opposite side. However, if one trigeminal ganglion is removed before peripheral innervation starts, movement detector neurites from the intact side will now cross the midline to innervate contralateral skin. These observations suggest a specific competitive interaction between movement detector neurites during their innervation of head skin. The second class of receptor, ‘rapid transient’ detectors, have a different pattern of innervation, crossing the midline in both normal and operated animals.

The origins of primitive blood in Xenopus: implications for axial patterning

Development ◽  
1999 ◽  
Vol 126 (3) ◽  
pp. 423-434 ◽  
Author(s):  
M.C. Lane ◽  
W.C. Smith
Keyword(s):  
Xenopus Laevis ◽  
Marginal Zone ◽  
Cell Stage ◽  
Axial Patterning ◽  
Xenopus Embryos ◽  
Spemann's Organizer ◽  
Dorsal Mesoderm

The marginal zone in Xenopus laevis is proposed to be patterned with dorsal mesoderm situated near the upper blastoporal lip and ventral mesoderm near the lower blastoporal lip. We determined the origins of the ventralmost mesoderm, primitive blood, and show it arises from all vegetal blastomeres at the 32-cell stage, including blastomere C1, a progenitor of Spemann's organizer. This demonstrates that cells located at the upper blastoporal lip become ventral mesoderm, not solely dorsal mesoderm as previously believed. Reassessment of extant fate maps shows dorsal mesoderm and dorsal endoderm descend from the animal region of the marginal zone, whereas ventral mesoderm descends from the vegetal region of the marginal zone, and ventral endoderm descends from cells located vegetal of the bottle cells. Thus, the orientation of the dorsal-ventral axis of the mesoderm and endoderm is rotated 90(degrees) from its current portrayal in fate maps. This reassessment leads us to propose revisions in the nomenclature of the marginal zone and the orientation of the axes in pre-gastrula Xenopus embryos.

scholarly journals INFECTIOUS AETIOLOGY OF MARGINAL ZONE LYMPHOMA AND ROLE OF ANTI-INFECTIVE THERAPY

2016 ◽  
Vol 8 ◽  
pp. 2016006 ◽  
Author(s):  
Salvatore Perrone ◽  
Gianna Maria D'Elia ◽  
Alessandro Pulsoni
Keyword(s):  
Malt Lymphoma ◽  
Marginal Zone ◽  
Case Reports ◽  
Lymphocyte Activation ◽  
Chlamydia Psittaci ◽  
Gastric Malt Lymphoma ◽  
First Line Therapy ◽  
Causative Relationship ◽  
Chronic Hcv

Marginal zone lymphomas have been associated with several infectious agents covering both viral and bacterial pathogens and in some cases a clear aetiological role has been established. Pathogenetic mechanisms are currently not completely understood, however the role of chronic stimulation of the host immune response with persistent lymphocyte activation represents the most convincing explanation for lymphoproliferation. Gastric MALT lymphoma is strictly associated with Helicobacter pylori infection and various eradicating protocols, developed due to increasing antibiotic resistance, represent the first line therapy. The response rate to eradication is good with 80% of response at 1 year; this finding is also noteworthy because recapitulates a cancer cured only by antibacterial approach and it satisfies the Koch postulates of causation, establishing a causative relationship between Hp and gastric MALT lymphoma. Patients with chronic HCV infection have 5 times higher risk to develop MZL, in particular an association with splenic and nodal MZL has been shown in several studies. Moreover, there is evidence of lymphoma regression after antiviral therapy with interferon+ribavirin, thus rising hope that new available drugs, extremely effective against HCV replication, could improve outcome also in HCV-driven lymphomas. The rare cases of MZL localized to orbital fat and eye conjunctivas have been associated with Chlamydia psittaci infection carried by birds. Efficacy of antibacterial therapy against C. psittaci are conflicting and generally poorer thain gastric MALT. Finally some case-reports will cover the relationship between primary cutaneous B-cell Lymphomas and Borrelia Burgdorferi.

2,4-D Butoxyethyl Ester Kinetics in Embryos of Xenopus laevis: The Role of the Embryonic Jelly Coat in Reducing Chemical Absorption

2006 ◽  
Vol 52 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Andrea N. Edginton ◽  
Claude Rouleau ◽  
Gerald R. Stephenson ◽  
Herman J. Boermans
Keyword(s):  
Xenopus Laevis ◽  
Chemical Absorption ◽  
Jelly Coat

scholarly journals Morphometric and Histopathologic Analysis of Lymphoid Depletion in Murine Spleens Following Infection with Brucella abortus strains 2308 or RB51 or an htrA Deletion Mutant

1996 ◽  
Vol 33 (3) ◽  
pp. 282-289 ◽  
Author(s):  
M. V. Palmer ◽  
N. F. Cheville ◽  
F. M. Tatum
Keyword(s):  
Morphometric Analysis ◽  
Brucella Abortus ◽  
Marginal Zone ◽  
White Pulp ◽  
Splenic White Pulp ◽  
Lymphoid Depletion ◽  
Histopathologic Changes ◽  
Histopathologic Analysis ◽  
Marginal Zones

BALB/C mice were inoculated intraperitoneally with suspensions of Brucella abortus strains 2308 or RB51 or an htrA mutant. Spleens were examined on postinoculation day (PID) 2, 4, 7, 10, 15, 21, 30, and 60. Brucellae were cultured in high numbers from the spleens of mice infected with strains 2308 or htrA through PID 60; however, mice infected with strain RB51 cleared the infection between PID 30 and PID 60. Histopathologic changes in spleens from 2308-infected mice were characterized by marked accumulations of macrophages, which expanded marginal zones beginning as early as PID 7 and persisting through PID 60. Morphometric analysis showed a decrease in splenic white pulp in 2308-infected mice at PID 10, which correlated with the peak of bacterial infection. Although this decrease was significant ( P < 0.05) when compared with values at the previous (PID 7) and the following (PID 15) time periods, it was not significantly different from white pulp values noted at PID 2 or PID 4 or the values for control spleens. Spleens from RB51-infected mice showed only mild to moderate accumulations of macrophages in marginal zone areas during the peak of RB51 infection (PID 7-10). Morphometric analysis of RB51-infected spleens showed a decrease in white pulp area, which coincided with peak bacterial numbers. However, this decrease was not significant ( P > 0.05). Spleens from mice infected with the htrA mutant showed moderate to marked accumulations of macrophages in marginal zone areas, which persisted through PID 60. Multifocal necrosis in lymphoid follicles as early as PID 4 was seen in both htrA and 2308 infection. Morphometric analysis of htrA-infected spleens revealed no significant decrease in white pulp and no obvious correlation with bacterial numbers in the spleen. These results suggest that virulent B. abortus does not induce lymphoid depletion significantly below those values seen in noninfected mice; thus, the possible role of lymphoid depletion in the pathogenesis of brucellosis remains questionable.

scholarly journals The specification of noradrenergic locus coeruleus (LC) neurones depends on bone morphogenetic proteins (BMPs)

Development ◽  
2002 ◽  
Vol 129 (4) ◽  
pp. 983-991 ◽  
Author(s):  
Astrid Vogel-Höpker ◽  
Hermann Rohrer
Keyword(s):  
Transcription Factors ◽  
Locus Coeruleus ◽  
Bone Morphogenetic Proteins ◽  
Chick Embryos ◽  
Dorsal Midline ◽  
Neural Crest Development ◽  
Roof Plate ◽  
Rhombic Lip ◽  
The Brain

The role of BMPs in the development of the major noradrenergic centre of the brain, the locus coeruleus (LC), was investigated. LC generation is reflected by initial expression of the transcription factors Phox2a and Phox2b in dorsal rhombomere1 (r1), followed by expression of dopamine-β-hydroxylase and tyrosine hydroxylase. Bmp5 is expressed in the dorsal neuroepithelium in proximity to Phox2-expressing cells. BMP inhibition in stage 10 chick embryos resulted in the lack of LC neurones or in their generation at the dorsal midline, and loss of roof plate and rhombic lip, but it did not affect neural crest development. These results reveal late essential BMP functions in the specification of dorsal neuronal phenotypes in r1, including LC neurones, and in the development of dorsal midline structures.

scholarly journals Origins of the avian neural crest: the role of neural plate-epidermal interactions

Development ◽  
1995 ◽  
Vol 121 (2) ◽  
pp. 525-538 ◽  
Author(s):  
M.A. Selleck ◽  
M. Bronner-Fraser
Keyword(s):  
Neural Crest ◽  
Neural Crest Cell ◽  
Neural Crest Cells ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
Whole Embryo Culture ◽  
Early Stages ◽  
Tissue Interactions ◽  
Neural Ectoderm

We have investigated the lineage and tissue interactions that result in avian neural crest cell formation from the ectoderm. Presumptive neural plate was grafted adjacent to non-neural ectoderm in whole embryo culture to examine the role of tissue interactions in ontogeny of the neural crest. Our results show that juxtaposition of non-neural ectoderm and presumptive neural plate induces the formation of neural crest cells. Quail/chick recombinations demonstrate that both the prospective neural plate and the prospective epidermis can contribute to the neural crest. When similar neural plate/epidermal confrontations are performed in tissue culture to look at the formation of neural crest derivatives, juxtaposition of epidermis with either early (stages 4–5) or later (stages 6–10) neural plate results in the generation of both melanocytes and sympathoadrenal cells. Interestingly, neural plates isolated from early stages form no neural crest cells, whereas those isolated later give rise to melanocytes but not crest-derived sympathoadrenal cells. Single cell lineage analysis was performed to determine the time at which the neural crest lineage diverges from the epidermal lineage and to elucidate the timing of neural plate/epidermis interactions during normal development. Our results from stage 8 to 10+ embryos show that the neural plate/neural crest lineage segregates from the epidermis around the time of neural tube closure, suggesting that neural induction is still underway at open neural plate stages.

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