Use of retinoids to analyze the cellular basis of positional memory in regenerating amphibian limbs

1987 ◽  
Vol 65 (8) ◽  
pp. 750-761 ◽  
Author(s):  
David L. Stocum ◽  
Karen Crawford
Keyword(s):  
Retinoic Acid ◽  
Molecular Basis ◽  
Limb Regeneration ◽  
Molecular Property ◽  
Cell Recognition ◽  
Dorsoventral Axis ◽  
Modifying Agent ◽  
A Cell ◽  
Regeneration Blastema

Cells of the amphibian limb regeneration blastema inherit memories of their level of origin (positional memory) along the limb axes. These memories serve as boundaries of what is to be regenerated, thus preventing regeneration of any but the missing structures. Because of its importance in determining the boundaries of regenerate pattern, it is essential to understand the cellular and molecular basis of positional memory. One approach to this problem is to look for position-related differences in a cell or molecular property along a limb axis and then show, using an agent that modifies regenerate pattern, that the cell or molecular property and the pattern are coordinately modified. We have done this using retinoic acid (RA) as a pattern-modifying agent and an in vivo assay that detects position-related differences in a cell recognition–affinity property along the proximodistal (PD) axis of the regenerating axolotl limb. RA proximalizes positional memory in the PD axis, posteriorizes it in the anteroposterior axis, and ventralizes it in the dorsoventral axis. The level-specific PD cell recognition–affinity property is proximalized by RA, indicating that this property and positional memory are causally related. The effects of RA on positional memory may be mediated through a cellular RA-binding protein (CRABP), since the concentration of unbound (apo) CRABP molecules is highest during early stages of regeneration when the proximalizing effects of RA are greatest.

Symmetrical vascularization patterns in normal and retinoic acid treated limb regenerates of the axolotl, Ambystoma mexicanum

1998 ◽  
Vol 76 (9) ◽  
pp. 1795-1796 ◽  
Author(s):  
Steven R Scadding ◽  
Andrew Burns
Keyword(s):  
Retinoic Acid ◽  
Pattern Formation ◽  
Vascular System ◽  
Limb Regeneration ◽  
Ambystoma Mexicanum ◽  
Limb Pattern ◽  
Regeneration Blastema

The purpose of this investigation was to determine whether there were any asymmetries in the vascularization of the limb-regeneration blastema in the axolotl, Ambystoma mexicanum, that might be related to pattern formation, and to determine if retinoic acid could modify the vascular patterns of the blastema. We used acrylic casts of the vascular system of the limbs to assess the pattern of vascularization. We observed a very regular symmetrical arrangement of capillaries in the limb-regeneration blastema that did not appear to be modified by doses of retinoic acid sufficient to modify the limb pattern.

Retinoic acid coordinately proximalizes regenerate pattern and blastema differential affinity in axolotl limbs

Development ◽  
1988 ◽  
Vol 102 (4) ◽  
pp. 687-698 ◽  
Author(s):  
K. Crawford ◽  
D.L. Stocum
Keyword(s):  
Retinoic Acid ◽  
Dorsal Surface ◽  
Blastema Cell ◽  
Specific Affinity ◽  
Cell Affinity ◽  
Differential Affinity ◽  
Regeneration Blastema

An assay that detects position-related differences in affinity of axolotl regeneration blastema cells in vivo was used to test whether retinoic acid, which proximalizes regenerate pattern, simultaneously proximalizes blastema cell affinity. The assay involved autografting or homografting late bud forelimb blastomas derived from the wrist, elbow or midupper arm levels to the dorsal surface of the blastema-stump junction of an ipsilateral, medium-bud-stage hindlimb regenerating from the midthigh level. The grafted blastemas consistently displaced to their corresponding levels on the proximodistal axis of the host regenerate, indicating the existence of level-specific differences in blastema cell affinity. Retinoic acid proximalized the pattern of donor forelimb regenerates to the level of the girdle and abolished their displacement behaviour on untreated host hindlimbs. Conversely, untreated forelimb donor blastemas displaced distally to their corresponding levels on host ankle regenerates, that had been proximalized to the level of the girdle by retinoic acid. These results indicate that positional memory in regenerating limbs is directly related to blastema cell affinity, and that very similar or identical sets of level-specific affinity properties are shared by forelimb and hindlimb cells.

Gap junctions in the limb regeneration blastema of the axolotl, Ambystoma mexicanum, are not distributed uniformly and are regulated by retinoic acid

1999 ◽  
Vol 77 (6) ◽  
pp. 902-909
Author(s):  
Leigh-Anne D Miller ◽  
Melissa L Farquhar ◽  
John S Greenwood ◽  
Steven R Scadding
Keyword(s):  
Retinoic Acid ◽  
Gap Junctions ◽  
Limb Regeneration ◽  
Ambystoma Mexicanum ◽  
Limb Bud ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Regeneration Blastema

Gap junctions are thought to play a role in pattern formation during limb development and regeneration by controlling the movement of small regulatory molecules between cells. An anteroposterior gradient of gap junctional communication that is higher posteriorly has been reported in the developing chick limb bud. In both the developing chick limb bud and the amphibian regenerating limb, an anteroposterior retinoic acid gradient is present, and this is also higher posteriorly. On the basis of these observations, we decided to examine the role of gap junctional communication in the regenerating amphibian limb. Gap junctions were observed in both the axolotl, Ambystoma mexicanum, limb regeneration blastema and cardiac tissue (as a positive control), using immunohistochemical labelling and laser scanning confocal microscopy. The scrape-loading/dye transfer technique for tracing the movement of a gap junction permeable dye, Lucifer yellow, showed that in blastemal epidermis there were nonuniform distributions of gap junctions in both the dorsoventral and anteroposterior axes of the blastema. Retinoic acid was found to increase gap junctional permeability in blastemal epidermis 48 h after injection and in blastemal mesenchyme 76 h after injection. The potential role of gap junctions during pattern formation in limb regeneration is discussed based on these results.

scholarly journals Cd1b-Mediated T Cell Recognition of a Glycolipid Antigen Generated from Mycobacterial Lipid and Host Carbohydrate during Infection

2000 ◽  
Vol 192 (7) ◽  
pp. 965-976 ◽  
Author(s):  
D. Branch Moody ◽  
Mark R. Guy ◽  
Ethan Grant ◽  
Tan-Yun Cheng ◽  
Michael B. Brenner ◽  
...  
Keyword(s):  
T Cell ◽  
T Cell Receptor ◽  
Molecular Basis ◽  
Cell Receptor ◽  
Cell Recognition ◽  
T Cell Recognition ◽  
Environmental Mycobacteria ◽  
Mammalian Tissues ◽  
In Vivo Transfection

T cells recognize microbial glycolipids presented by CD1 proteins, but there is no information regarding the generation of natural glycolipid antigens within infected tissues. Therefore, we determined the molecular basis of CD1b-restricted T cell recognition of mycobacterial glycosylated mycolates, including those produced during tissue infection in vivo. Transfection of the T cell receptor (TCR) α and β chains from a glucose monomycolate (GMM)-specific T cell line reconstituted GMM recognition in TCR-deficient T lymphoblastoma cells. This TCR-mediated response was highly specific for natural mycobacterial glucose-6-O-(2R, 3R) monomycolate, including the precise structure of the glucose moiety, the stereochemistry of the mycolate lipid, and the linkage between the carbohydrate and the lipid. Mycobacterial production of antigenic GMM absolutely required a nonmycobacterial source of glucose that could be supplied by adding glucose to media at concentrations found in mammalian tissues or by infecting tissue in vivo. These results indicate that mycobacteria synthesized antigenic GMM by coupling mycobacterial mycolates to host-derived glucose. Specific T cell recognition of an epitope formed by interaction of host and pathogen biosynthetic pathways provides a mechanism for immune response to those pathogenic mycobacteria that have productively infected tissues, as distinguished from ubiquitous, but innocuous, environmental mycobacteria.

Ultrastructure of melanocyte-keratinocyte interactions and pigment transfer in vitro

1978 ◽  
Vol 36 (2) ◽  
pp. 650-651
Author(s):  
Raul I. Garcia ◽  
Evelyn A. Flynn ◽  
George Szabo
Keyword(s):  
Direct Injection ◽  
Skin Pigmentation ◽  
Freeze Fracture ◽  
Pigment Granule ◽  
Time Lapse ◽  
Ultrastructural Level ◽  
Lanthanum Tracer ◽  
A Cell

Skin pigmentation in mammals involves the interaction of epidermal melanocytes and keratinocytes in the structural and functional unit known as the Epidermal Melanin Unit. Melanocytes(M) synthesize melanin within specialized membrane-bound organelles, the melanosome or pigment granule. These are subsequently transferred by way of M dendrites to keratinocytes(K) by a mechanism still to be clearly defined. Three different, though not necessarily mutually exclusive, mechanisms of melanosome transfer have been proposed: cytophagocytosis by K of M dendrite tips containing melanosomes, direct injection of melanosomes into the K cytoplasm through a cell-to-cell pore or communicating channel formed by localized fusion of M and K cell membranes, release of melanosomes into the extracellular space(ECS) by exocytosis followed by K uptake using conventional phagocytosis. Variability in methods of transfer has been noted both in vivo and in vitro and there is evidence in support of each transfer mechanism. We Have previously studied M-K interactions in vitro using time-lapse cinemicrography and in vivo at the ultrastructural level using lanthanum tracer and freeze-fracture.

Aflatoxins biosynthesis, toxicity and intervention strategies: A review

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Developing Countries ◽  
Molecular Basis ◽  
Genetic Regulation ◽  
Intervention Strategies ◽  
Historical Background ◽  
Economic Losses ◽  
Factors Affecting ◽  
Biomarkers Of Exposure ◽  
Food Commodities

Aflatoxins (AFTs) are toxic products of fungal metabolism, associated with serious health consequences and substantial economic losses to agriculture, livestock and poultry sectors, particularly in the developing countries. This review outlines the current information on AFTs in terms of historical background, classification, relative occurrence and co-existence with other mycotoxins in various food commodities. The phenomenon of aflatoxin (AFT) biosynthesis has been elucidated with reference to molecular basis, genetic regulation and factors affecting the AFT production. Moreover, the in vivo disposition kinetics, toxicological action and toxico-pathological consequences of AFTs have also been highlighted. Currently employed strategies for the detection and detoxification of AFTs, biomarkers of exposure assessment, potential economic impact and regulatory considerations regarding the AFTs have been emphasized.

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