Disruption of segmentation in a short germ insect embryo

Development ◽  
1986 ◽  
Vol 96 (1) ◽  
pp. 267-294
Author(s):  
Jane E. Mee ◽  
Vernon French
Keyword(s):  
Heat Shock ◽  
Schistocerca Gregaria ◽  
Intercalary Regeneration ◽  
Early Embryos ◽  
Pattern Regulation ◽  
Segment Pattern

A heat shock (of 15min at 48° C) given to early embryos of the locust, Schistocerca gregaria, results in localized abnormalities in the segment pattern subsequently formed. Most defects involve two consecutive segments of the thorax or abdomen, and these are analysed in detail. The abdominal defects fall into three main classes each of which involves the absence of a particular region of the segment pair and, in one class, duplication of the region which remains. The thoracic defects similarly involve absence of parts of the segments and the formation of a single limb base from which one, two, or three limbs develop. Heat shock may result in the absence of parts of segments in two distinct ways. It may interfere with the process of segmentation or it may delete parts of already formed segment primordia. These possibilities are discussed although, at present, neither can be excluded. The duplication observed in some abdominal disruptions and the formation of triple limbs indicates that the absence of parts of embryonic segments is followed by pattern regulation similar to that occurring in regeneration studies on larval segments and appendages of other insects. Two out of the three classes of abnormality can be explained in terms of intercalary regeneration restoring pattern continuity, but it is possible that discontinuities persist in the remaining class.

Disruption of segmentation in a short germ insect embryo

Development ◽  
1986 ◽  
Vol 96 (1) ◽  
pp. 245-266
Author(s):  
Jane E. Mee ◽  
Vernon French
Keyword(s):  
Heat Shock ◽  
Schistocerca Gregaria ◽  
Constant Number ◽  
Segment Pattern ◽  
Different Parts

The effect of heat shock (15 min at 48 °C) on segmentation has been investigated in the short germ embryo of the locust (Schistocerca gregaria). Prior to formation of the germ anlage and at the disc stage heat shock considerably reduced the survival of eggs but appeared to have little effect upon segmentation. At later stages heat shock had no effect on survival but resulted in disruptions of the segmental pattern. The location of abnormal segments depended upon the stage at heat shock and the number affected depended on its severity. A constant number of normal segments developed between the last segment visible at the time of heat shock and the first abnormal segment. These results are similar to the disruptions observed in amphibian somites following heat shock. However, different parts of the segment pattern varied in their response; the head segments were very rarely affected, and disrupted regions rarely started in the middle abdomen (segments A5 and A6). The results are discussed in relation to two models (the clock and wavefront and progress zone models) that have been proposed as an explanation for the specification of the somite pattern in amphibians.

scholarly journals Transient Heat-Shock Disrupts Molecular Signals and Competence of Riverine Bubalus Bubalis Oocytes and Early Embryos in a Stage-Specific Manner

2020 ◽  
Author(s):  
Devender Singh ◽  
Manish Kumar ◽  
Rakesh Kumar ◽  
Tirtha Kumar Datta
Keyword(s):  
Heat Stress ◽  
Thermal Stress ◽  
Heat Shock ◽  
Detrimental Effect ◽  
Bubalus Bubalis ◽  
Early Embryos ◽  
Specific Manner ◽  
Cell Embryo ◽  
Molecular Signals

Abstract Background Thermal stress elicits detrimental effect in reproduction performance of Bubalus bubalis, buffalo. Riverine buffalo oocytes and early embryos possess differential ability to grow and survive under thermal stress condition. It is interesting to know how precisely the short and transient heat stress impacts growth and development of buffalo oocytes and early embryos in a stage specific manner. In this study, we aim to identify the most sensitive and vulnerable stage of oocytes and early embryos against transient heat stress as well as unravel the underlying molecular signals responsible for the stunted embryo development under thermal stress. It was assessed by utilizing six different groups of oocytes and embryos with an incorporation of 4 h transient heat shock at 40ºC during different stage of in-vitro maturation (IVM) and in vitro culture (IVC). Results The stressed oocytes of group (grp) 1, 2 and 3 exhibit comparable paces of attaining metaphase-II (M-II) phase at different time interval of IVM. The most detrimental effect of heat stress was observed in grp 2 with sharp reduction in morula to blastocysts transition rate (p<0.05). Expression of mRNA transcripts of HSP8, MnSOD and Sirt-3 genes were significantly increased from mid-IVM to 4-cell embryo although subsequently, down-regulated in embryos of 8-16 cells, morulae and blastocysts. Expression of maternal to embryo transition (MET) genes viz. PAP, U2Af and eIF4A was significantly down regulated from 2-cell embryo to morula (p<0.05). Maternal recognition of pregnancy (MRP) and morulae to blastocyst transition genes were poorly expressed in grp 2 than of the other stress groups (p<0.05). Conclusions Disruption of molecular signal has implicated in the poor formation of inner cell mass (ICM) and trophectoderm (TE) cells, this results in compromised development prospects of early buffalo embryos in a stage specific manner. Well-coordinated molecular signals associated with heat stress held responsible for reduced development of early embryo. We establish the most vulnerable stage of buffalo oocytes and presumptive zygotes against transient heat shock and observe a narrow window as the most critical stage for regulating the development potential of the prospective embryos under short heat stress environment.

Developmentally regulated nuclear transport of transcription factors in Drosophila embryos enable the heat shock response

Development ◽  
1998 ◽  
Vol 125 (23) ◽  
pp. 4841-4850 ◽  
Author(s):  
Z. Wang ◽  
S. Lindquist
Keyword(s):  
Transcription Factors ◽  
Heat Shock ◽  
Heat Shock Response ◽  
Nuclear Transport ◽  
Binding Activity ◽  
Spatiotemporal Pattern ◽  
Dna Binding Activity ◽  
Early Embryos ◽  
Shock Response ◽  
Drosophila Embryos

Hsp70 is a broadly conserved thermotolerance factor, but inhibits growth at normal temperatures and cannot be induced in early embryos. We report that in Drosophila embryos the temporal and spatial patterns of Hsp70 inducibility were unexpectedly complex, with striking differences between the soma and the germline. In both, regulation occurred at the level of transcription. During the refractory period for Hsp70 induction, HSF (heat-shock transcription factor) exhibited specific DNA-binding activity characteristic of activation in extracts of heated embryos. Remarkably, however, HSF was restricted to the cytoplasm in intact embryos even after heat shock. HSF moved from the cytoplasm to the nucleus in the absence of heat precisely when the capacity to induce Hsp70 was acquired (cycle 12 of the germline, cycle 13 in the soma). During oogenesis, Hsp70 inducibility was lost in nurse cells around stage 10, in a posterior-to-anterior gradient and HSF redistributed from nucleus to cytoplasm in the same spatiotemporal pattern. In a highly inbred derivative of the Samarkind strain, HSF moved into embryonic nuclei earlier than in our standard wild-type strain. Correspondingly, Hsp70 was inducible earlier, confirming that nuclear transport of HSF controls the inducibility of Hsp70 in early embryos. We also report for the first time the nuclear import patterns of two general transcription factors, RNA polymerase subunit Ilc and TATA binding protein (TBP). Both enter nuclei in a highly synchronous manner, independently of each other and of HSF. The import of TBP coincides with the first reported appearance of transcripts in the embryo. We suggest that the potentiation of general and heat shock-specific transcription in Drosophila embryos is controlled by the developmentally programmed relocalization of general and heat shock-specific transcription factors. Restricted nuclear entry of HSF represents a newly described mechanism for regulating the heat-shock response.

scholarly journals Heat shock during in vitro maturation induces chromatin modifications in the bovine embryo

Reproduction ◽  
2019 ◽  
Vol 158 (4) ◽  
pp. 313-322
Author(s):  
Luiz Sergio Almeida Camargo ◽  
Tiphaine Aguirre-Lavin ◽  
Pierre Adenot ◽  
Thamiris Dornelas Araujo ◽  
Vivian Rachel Araujo Mendes ◽  
...  
Keyword(s):  
Heat Shock ◽  
In Vitro Maturation ◽  
Cell Number ◽  
Developmental Competence ◽  
Bovine Embryo ◽  
Cell Stage ◽  
Early Embryos ◽  
Further Development ◽  
Bovine Oocytes

Heat stress compromises bovine oocyte developmental competence, but the effects of high temperature during oocyte maturation on embryo chromatin organization is unknown. In this study bovine oocytes were exposed to heat shock (41°C) for 12 h during in vitro maturation and then submitted to in vitro fertilization. The heat shock did not affect (P > 0.05) the cleavage but reduced (P < 0.01) the blastocyst rate on Day 7 and Day 8. No effect (P > 0.05) on total cell number was found, but the heat shock increased (P < 0.05) the proportion of apoptotic cells in blastocysts at Day 8. Immunofluorescence analysis of H3K9me3 and HP1 was performed in embryos at 52 h post in vitro fertilization. An accumulation of H3K9me3 in the nuclei of embryos derived from heat-shocked oocytes at four-cell and eight-cell stages was found. Also, a non-expected higher proportion (P < 0.05) of four-cell stage embryos displaying nuclei with increased HP1 fluorescence was observed, suggesting an abnormal chromatin compaction in embryos from heat-shocked oocytes. Embryos at eight-cell stage derived from heat-shocked oocytes displayed lower (P < 0.05) relative amount of HSP40 transcripts than control ones. In conclusion, heat shock before fertilization has an effect on embryo chromatin, influencing the accumulation of H3K9me3 and HP1 in early embryos as well as further development.

scholarly journals Heat shock proteins development in different stages of schistocerca gregaria as response to heavy metals intoxication

2011 ◽  
Vol 03 (03) ◽  
pp. 218-226
Author(s):  
Hesham A. Yousef ◽  
Amira Afify ◽  
Afaf Abdel Meguid ◽  
Hany M. Hassan
Keyword(s):  
Heavy Metals ◽  
Heat Shock ◽  
Heat Shock Proteins ◽  
Schistocerca Gregaria ◽  
Shock Proteins

Pattern regulation in isolated halves and blastomeres of early Xenopus laevis

Development ◽  
1983 ◽  
Vol 74 (1) ◽  
pp. 221-234
Author(s):  
H. Kageura ◽  
K. Yamana
Keyword(s):  
Xenopus Laevis ◽  
Calf Serum ◽  
The Other ◽  
Foetal Calf Serum ◽  
Cell Stage ◽  
Macroscopic Appearance ◽  
Xenopus Embryos ◽  
Early Embryos ◽  
Tailbud Stage ◽  
Pattern Regulation

Xenopus embryos at the 2-cell stage were cut into right and left halves, those at the 4-cell stage into dorsal and ventral halves or individual blastomeres, and those at the 8-cell stage into lateral, animal and vegetal halves. Defect embryos, that is, 8-cell embryos from which a particular pair of blastomeres had been removed, were also prepared. These halves, blastomeres and defect embryos were cultured in 50% Leibovitz (L-15) medium supplemented with 10% foetal calf serum and then in 10% Steinberg solution. Their development was determined from their macroscopic appearance when controls reached stage 26 (early tailbud stage) or later. The only halves that could develop into normal larvae or frogs were lateral ones of 2- and 8-cell embryos. An interesting finding was that these halves of 2-cell embryos developed into only half-embryos when cultured in the above Leibovitz medium beyond the beginning of gastrulation. On the other hand, most or all the dorsal and ventral halves at the 4-cell stage and the animal and vegetal quartets at the 8-cell stage did not form normally proportioned embryos. Defect embryos lacking any two blastomeres of the animal half gave rise to nearly normal embryos, whereas those lacking two dorsal or two ventral blastomeres of the vegetal half did not. From the present results and those of studies now in progress, it is concluded that development of blastomeres and halves from these early embryos, except lateral halves from 2- and 8-cell embryos, is not regulative as expected earlier, and that a certain combination of blastomeres is essential for complete pattern regulation.

Cell division during intercalary regeneration in the cockroach leg

Development ◽  
1985 ◽  
Vol 90 (1) ◽  
pp. 57-78
Author(s):  
Hilary Anderson ◽  
Vernon French
Keyword(s):  
Wound Healing ◽  
Cell Division ◽  
Epidermal Cells ◽  
Moult Cycle ◽  
Intercalary Regeneration ◽  
Polar Coordinate ◽  
Coordinate Model ◽  
Local Cell ◽  
Cuticular Structures ◽  
Pattern Regulation

In a series of grafting operations on cockroach legs, epidermal cells from different positions or from the same position on the circumference of the femur were placed together. Where cells from different positions were confronted, new cuticular structures corresponding to the positions which would normally have lain between them were formed during the following moults. At the control junctions, where cells from the same positions were placed together, no new structures were formed. Grafted legs were examined histologically at various times after the operation. The events following grafting fell into four phases: wound healing — when epidermal cells migrated over the wound to re-establish epidermal continuity and cells adjacent to the wound divided to compensate for cell emigration; intercalation — when cell divisions took place at the host-graft borders where there was a positional discrepancy; proliferation — when the general growth of the epidermis occurred by widespread cell division; cuticle secretion — when apolysis occurred, cell division ceased, and cuticle secretion began. The results show that intercalary regeneration is associated with local cell division at the graft-host borders, and that these divisions are not confined to the normal proliferative phase of the moult cycle, but begin much earlier in the cycle, as soon as wound healing is complete. These results support epimorphic models (such as the Polar Coordinate Model) of pattern regulation, where change of positional value is tied to cell division, but they do not discount the possibility of a limited initial morphallactic phase.

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