scholarly journals A clonal analysis of segment development in Oncopeltus (Hemiptera)

Development ◽  
1973 ◽  
Vol 30 (3) ◽  
pp. 681-699 ◽  
Author(s):  
Peter A. Lawrence
Keyword(s):  
Cell Division ◽  
Anterior Margin ◽  
Cleavage Plane ◽  
Clonal Analysis ◽  
Epidermal Cells ◽  
Oncopeltus Fasciatus ◽  
Moult Cycle ◽  
Plane Parallel ◽  
X Irradiation ◽  
Eggs And Larvae

X-irradiation of eggs and larvae of Oncopeltus fasciatus results in the development of clonal patches of epidermal cells of unusual pigmentation. The frequency, size and distribution of these patches is dependent on the dose and timing of irradiation. Analysis of these clones in the abdomen has shown that the presumptive epidermis becomes effectively segmented during blastoderm formation and thereafter the clones are restricted to within a segment quadrant (dorsal or ventral, left or right). There are approximately 10 presumptive epidermal cells per segment quadrant. The shape of the clones and the orientation of mitoses in larvae suggest that both early and late cells of the anterior margin of the segments divide with a preferred orientation (cleavage plane parallel to the antero-posterior axis). Elsewhere in the larval segment the mitoses are randomly oriented, and the segment grows evenly all over. The number of mitoses/cell/moult cycle is not precisely determined, but the amount of cell division is perhaps under a general probabilistic control. It is suggested that the segmental gradient may be involved in this control.

Separation of wound healing from regeneration in the cockroach leg

Development ◽  
1985 ◽  
Vol 85 (1) ◽  
pp. 177-190
Author(s):  
Paul R. Truby
Keyword(s):  
Wound Healing ◽  
Cell Division ◽  
Critical Point ◽  
Electron Micrographs ◽  
Resting State ◽  
Epidermal Cells ◽  
Moult Cycle ◽  
Scanning Electron Micrographs ◽  
Distal Half ◽  
Scanning Electron

It has been shown that after a critical point in the moult cycle of a cockroach, wound healing can occur but regeneration of pattern does not take place until the following intermoult period. Leg removal after the critical point is used to separate the processes of wound healing and leg regeneration. This permits the study of patterns of cell division resulting from wound healing to be distinguished from those involved in leg regeneration. During wound healing, cell division occurs in the epidermal cells of approximately the distal half of the trochanter. The cells then return to the resting state until after the next ecdysis. Regeneration starts with cell division occurring in the distal half of the trochanter, and then spreading to include cells of the proximal trochanter and distal coxa. This spread and the following patterns of growth and redifferentiation appear to be the same as for regeneration following leg removal prior to the critical point, with the more distal structures completing early stages of regeneration first. Scanning electron micrographs of the cuticle of the trochanter after the ecdysis following leg removal support the evidence from the patterns of cell division in suggesting that the distal half of the trochanter is dedifferentiated during wound healing.

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.

The Hormonal Control of the Development of Hairs and Bristles in the Milkweed Bug, ONCOPELTUS FASCIATUS, DALL

1966 ◽  
Vol 44 (3) ◽  
pp. 507-522
Author(s):  
PETER A. LAWRENCE
Keyword(s):  
Juvenile Hormone ◽  
Mode Of Action ◽  
Hormonal Control ◽  
Oncopeltus Fasciatus ◽  
Corpora Allata ◽  
Moult Cycle ◽  
Dense Population ◽  
Milkweed Bug ◽  
Larval Stages ◽  
Hormonal Milieu

1. As in Rhodnius, the larval Oncopeltus has bristles which are supplemented at each moult. However, at metamorphosis a dense population of non-innervated hairs develops. 2. Implantation of corpora allata into 5th-stage larvae showed that the development of these hairs can be inhibited universally or locally by the juvenile hormone (JH). 3. Transplantations of integument between 5th-stage larvae of different stages in the moult cycle gave some information about the power of the host to synchronize the graft to its own moult cycle. 4. Transplantations between different larval stages showed that the grafted in tegument responded to the hormonal milieu of the host. 5. Adult integument was transplanted onto larvae to study the reversal of metamorphosis. It was found that the development of a supernumerary population of hairs depended on the integument passing through a moult cycle in the presence of JH. After two moults in the presence of JH, reversal of metamorphosis was found to vary over the surface of the transplant, being further advanced at the margin. At the edge of the graft properly formed larval bristles developed, while at the centre adult hairs were formed in adult cuticle. Intermediately formed bristles were found in the intervening areas. It is suggested that reactions associated with wounding are the cause of this heterogeneous result. 6. The significance of these results in relation to other work and to theories concerning the mode of action of the juvenile hormone is discussed.

Fine structure of Wolffia arrhiza

1973 ◽  
Vol 51 (9) ◽  
pp. 1619-1622 ◽  
Author(s):  
J. L. Anderson ◽  
W. W. Thomson ◽  
J. A. Swader
Keyword(s):  
Fine Structure ◽  
Cell Division ◽  
Vegetative Reproduction ◽  
Guard Cells ◽  
Epidermal Cells ◽  
Electron Microscopic ◽  
Meristematic Cells ◽  
Wolffia Arrhiza ◽  
Microscopic Studies

Light and electron microscopic studies of Wolffia arrhiza L. frond development during vegetative reproduction showed that the fronds were composed entirely of chlorenchymous cells. Chloroplasts in the epidermal cells other than the guard cells were unique in that they contained no starch. Cell division occurred only at the proximal end of daughter fronds early in their development. Meristematic cells contained chloroplasts with clearly defined grana. Proplastids, commonly observed in meristematic cells of apical regions of other plants, were absent in the cells of these plants.

Divisions cellulaires au niveau de l'épiderme de l'hypocotyle du lin (Linum usitatissimum) cultivé in vitro

1985 ◽  
Vol 63 (10) ◽  
pp. 1691-1695 ◽  
Author(s):  
M. Sqalli ◽  
H. Chlyah
Keyword(s):  
Cell Division ◽  
Culture Cell ◽  
Epidermal Cells ◽  
Isolated Cells ◽  
Initiation And Propagation ◽  
A Cell ◽  
The Mean ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes

A study of the initiation and propagation of cell divisions in the epidermis of flax hypocotyl segments cultured in vitro was made using surface observations (light and scanning electron microscopes) as well as transverse and longitudinal sections. Epidermal cells were of two types: long, narrow cells and short, wide cells. The latter, less numerous, rarely participated in cell division. Nuclear activation and the first mitoses appeared very early (after 4–8 h of culture). Cell division began in isolated cells and spread progressively to surrounding cells arranged transversely. At 24 h, approximately 50 cells in division or newly divided were observed on an epidermal strip of 10 × 2 mm composed of about 8000 original cells. At 48 h, about 110 cells had divided forming 22 division centers; 26 prophase, 10 metaphase, and 7 telophase figures were observed. The mean number of original cells which participated in the formation of a cell division center was three at 12 h, five at 72 h, with no increase thereafter. The percentage of cells in mitosis or already divided remained low (1.9%) in relation to the total number of epidermal cells. For 22 division centers, only 7 would participate in vegetative bud formation.

scholarly journals STUDIES ON THE MECHANISM OF ACTION OF IONIZING RADIATIONS

1952 ◽  
Vol 35 (6) ◽  
pp. 865-871 ◽  
Author(s):  
E. S. Guzman Barron ◽  
S. Louise Seki
Keyword(s):  
Cell Division ◽  
Sperm Cells ◽  
X Rays ◽  
Thiol Compounds ◽  
X Ray ◽  
Arbacia Punctulata ◽  
Inhibiting Effect ◽  
Small Doses ◽  
X Irradiation ◽  
Ionizing Radiations

On x-irradiation of the eggs and sperm of Arbacia punctulata there was inhibition of respiration with relatively large doses, whereas there was an increase with small doses. The dose required to produce an increase of respiration depended on the degree of sensitivity of the cell to the effect of ionizing radiation. Sperm cells were more sensitive; then came fertilized eggs; unfertilized eggs were the least sensitive. The inhibiting effect of x-rays on cell division was observed even on irradiation with x-ray doses which produced an increase of respiration. These results are compared to similar effects produced by thiol reagents and are attributed to oxidation of the thiol compounds in the cell.

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