Biomedical subjects

P J McCaffery

Publications and source records attributed to P J McCaffery.

7 recordsLinked to original sources

PubMed2003

Too much of a good thing: retinoic acid as an endogenous regulator of neural differentiation and exogenous teratogen.

Retinoic acid (RA) is essential for both embryonic and adult growth, activating gene transcription via specific nuclear receptors. It is generated, via a retinaldehyde intermediate, from retinol (vitamin A). RA levels require precise regulation by controlled synthesis and catabolism, and when RA concentrations deviate from normal, in either direction, abnormal growth and development occurs. This review describes: (i) how the pattern of RA metabolic enzymes controls the actions of RA; and (ii) the type of abnormalities that result when this pattern breaks down. Examples are given of RA control of the anterior/posterior axis of the hindbrain, the dorsal/ventral axis of the spinal cord, as well as certain sex-specific segments of the spinal cord, using varied animal models including mouse, quail and mosquitofish. These functions are highly sensitive to abnormal changes in RA concentration. In rodents, the control of neural patterning and differentiation are disrupted when RA concentrations are lowered, whereas inappropriately high concentrations of RA result in abnormal development of cerebellum and hindbrain nuclei. The latter parallels the malformations seen in the human embryo exposed to RA due to treatment of the mother with the acne drug Accutane (13-cis RA) and, in cases where the child survives beyond birth, a particular set of behavioural anomalies can be described. Even the adult brain may be susceptible to an imbalance of RA, particularly the hippocampus. This report shows how the properties of RA as a neural induction agent and organizer of segmentation can explain the consequences of RA depletion and overexpression.

Animals↗

PubMed2000

Retinoids in embryonal development.

The key role of vitamin A in embryonal development is reviewed. Special emphasis is given to the physiological action of retinoids, as evident from the retinoid ligand knockout models. Retinoid metabolism in embryonic tissues and teratogenic consequences of retinoid administration at high doses are presented. Physiological and pharmacological actions of retinoids are outlined and explained on the basis of their interactions as ligands of the nuclear retinoid receptors. Immediate target genes and the retinoid response elements of their promoters are summarized. The fundamental role of homeobox genes in embryonal development and the actions of retinoids on their expression are discussed. The similarity of the effects of retinoid ligand knockouts to effects of compound retinoid receptor knockouts on embryogenesis is presented. Although much remains to be clarified, the emerging landscape offers exciting views for future research.

Abnormalities, Drug-Induced↗

PubMed1997

Sex differences in endogenous retinoid release in the post-embryonic spinal cord of the western mosquitofish, Gambusia affinis affinis.

In this study we have shown sex differences in endogenous retinoic acid synthesis and retinaldehyde dehydrogenase activity in the post-embryonic spinal cords of immature female and male G. a. affinis. The F9 reporter cell assay and the zymography bioassay showed that the endogenous retinoic acid levels correlated with the levels of the endogenous enzyme(s) responsible for retinoic acid synthesis. These data also showed that both the endogenous retinoic acid levels and the enzyme(s) were higher in spinal cord segments 8-16 of immature males than in immature females. We have also shown that exogenous treatment of 17 alpha-methyltestosterone results in the masculinization of the immature female's anal fin and its appendicular support elements as well as the endogenous synthesis of retinoic acid and retinaldehyde dehydrogenase activity. The F9 reporter cell assay showed that the endogenous retinoic acid levels were relatively unchanged in spinal cord segments 8-16 of immature males treated with 17 alpha-methyltestosterone. However, the F9 reporter cell assay showed that the endogenous retinoic acid levels in spinal cord segments 8-16 of immature females treated with 17 alpha-methyltestosterone were markedly higher than levels observed in the immature males. The data also showed that the activity of the enzyme(s) responsible for the synthesis of endogenous retinoic acid was higher in spinal cord segments 8-16 of immature females treated with 17 alpha-methyltestosterone than in immature males treated with 17 alpha-methyltestosterone. Currently under investigation is the question of what role the endogenous enzyme(s) responsible for the synthesis of retinoic acid plays either alone or in concert with androgen in organizing hormone-dependent sexually dimorphic areas in the teleost body plan.

Aging↗

PubMed1989

Subunit structure of the erythropoietin receptor.

Chemical cross-linking of the red blood cell hormone, erythropoietin (Epo), to its receptor on erythroid cells has revealed the presence of two proteins closely associated with Epo, but the relationship between these two proteins is controversial. Using the cross-linking reagents disuccinimidyl suberate and dithiobissuccinimidyl propionate, we show that 125I-Epo can be specifically conjugated in a complex of 224kDa using mouse fetal liver cells, bone marrow cells, and Friend virus-induced splenic erythroblasts as demonstrated by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels under nonreducing conditions. Under reducing conditions, the 224-kDa complex appeared as two Epo conjugates of 136 kDa and 119 kDa, and these bands were also observed to a variable extent in some nonreducing gels. Disulfide linking of the 136-kDa and 119-kDa bands was confirmed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis run under nonreducing followed by reducing conditions. With increasing time of 125I-Epo binding to Friend virus erythroblasts in the presence of sodium azide to inhibit receptor internalization, the 136-kDa and 119-kDa bands seen under reducing conditions increased markedly in intensity, whereas the 224-kDa band seen under nonreducing conditions declined. These results suggest that the 224-kDa Epo conjugate is inefficiently solubilized under nonreducing conditions following prolonged periods of Epo binding. A single class of saturable, high affinity receptors for Epo on each of the cell types tested is demonstrated. It is concluded that the two disulfide-linked Epo-binding proteins which can be independently cross-linked to Epo form a single ligand binding site.

Animals↗

PubMed1989

Monoclonal antibodies that bind to hemopoietic stem cells: characterization and immunohistochemical localization of cells expressing gp50-65.

The cell surface of hemopoietic stem cells has been shown to express several antigens in common with more mature hemopoietic cells. One set of stem cell antigens is defined by a group of three monoclonal antibodies (13C6, 1C10, and 1A9), selected on the basis of binding to subpopulations of spleen colony-forming stem cells (CFU-S). These antibodies are shown to recognize cell surface glycoproteins of 50-65 kd (gp50-65) that occur widely on hemopoietic cells. Each cell type investigated shows a distinctive pattern of expression of these glycoproteins. To further investigate the presence of gp50-65 on stem cells, low-density bone marrow cells were labeled with 1C10 and sorted according to fluorescence intensity. Most (73%) of the stem cells (CFU-S10) were recovered in the two most highly fluorescent fractions containing 2.6% of starting marrow cells. Immunohistochemistry of frozen sections of normal spleen and spleens during repopulation after lethal irradiation and bone marrow transplantation showed that the most strongly 1C10-labeled cells occurred under the splenic capsule and along trabeculae. Although many of these cells were also alpha-naphthylacetate esterase positive and Mac-1 positive, indicating cells of the monocyte-macrophage lineage, a distinctive population of singular cells were stained with 1C10 alone. These cells were negative for surface Ig and closely corresponded with a small population of cells in a similar location that were doubly labeled with 1C10 and anti-Thy-1. These results show that stem cells express high levels of gp50-65 and suggest that stem cells can be identified by immunohistochemical methods using dual labeling procedures.

Animals↗

PubMed1987

Polymorphic glycoprotein-1 on mouse platelets: possible role of Pgp-1 and LFA-1 in antibody-dependent platelet cytotoxicity involving complement.

The presence of the Pgp-1 glycoprotein on mouse platelets is demonstrated by antibody-binding techniques, by immunoprecipitation, and by transblotting using the monoclonal antibody (MoAb) C71/26 against Pgp-1. C71/26 immunoprecipitates as a broad band of mol wt 87,000 to 100,000 as determined by radioiodination of the platelet cell surface and by the 3H-sodium borohydride labeling technique. Immunoblotting showed Pgp-1 expression on platelets to be quantitatively similar to its presence on macrophages and resolved platelet Pgp-1 into two bands of mol wt 87,000 and 97,000 whereas Pgp-1 on parasite-elicited peritoneal macrophages showed 82,000 and 87,000 mol wt species. Platelets and monocyte/macrophage cells from either peripheral blood or from the peritoneal cavity showed homogeneous binding of Pgp-1 antibody to greater than 97% of cells by flow cytometry. In contrast, lymphocytes from peripheral blood or from the spleen showed a heterogeneous binding pattern with 20% to 30% of cells being negative, and the majority weakly positive. In functional studies, MoAbs against CR1 and CR3 substantially inhibited platelet immune adherence, whereas C71/26 showed only marginal inhibitor. In contrast, C71/26 and other MoAbs against Pgp-1 inhibited platelet-dependent cytotoxicity of antibody-coated sheep erythrocytes in the presence of C5-deficient mouse plasma whereas M1/70 against CR3 showed no effect. In this assay, MoAbs against the alpha- and beta-subunits of leukocyte functional molecule LFA-1 also inhibited platelet cytotoxicity. These results show that the platelet cell surface moieties Pgp-1 and LFA-1 are involved in or closely associated with antibody-dependent cellular cytotoxicity by platelets.

Animals↗

PubMed1986

Expression of the leukocyte functional molecule (LFA-1) on mouse platelets.

Platelet involvement in adhesion, hemostasis, and immune adherence is mediated by functionally associated cell surface molecules. Platelets are also involved in cytolytic reactions, but little is known about the mechanisms or biologic significance of these processes. To further investigate cell surface molecules concerned with platelet function, antisera against mouse platelets, thymocytes, and macrophages and monoclonal antibodies against Mac-1 (complement receptor type 3) and leukocyte function-associated glycoprotein type 1 (LFA-1) were used to demonstrate LFA-1--like molecules on mouse platelets. The alpha subunits of platelet and thymocyte LFA-1 showed identical electrophoretic mobility but differed significantly from the alpha subunit of macrophage Mac-1. Peptide mapping demonstrated the identity of the beta subunits of these three molecules but showed that the alpha subunit of Mac-1 was distinct from the alpha subunits of platelet and thymocyte LFA-1. Platelet LFA-1, as demonstrated by surface iodination with lactoperoxidase and by labeling sialic acid residues with sodium borohydride, was not a major component of the platelet membrane. The functional significance of LFA-1 on mouse platelets has yet to be demonstrated, monoclonal antibodies against LFA-1 having little effect on adenosine diphosphate-induced platelet aggregation and immune adherence. In contrast, although Mac-1 could not be demonstrated on mouse platelets in immunoprecipitation studies, its presence was clearly demonstrated by low levels of antibody binding in enzyme-linked immunosorbent assays and by the ability of M1/70 monoclonal antibody to inhibit platelet immune adherence. Human platelets, which are inactive in immune adherence assays, are shown to lack LFA-1 and Mac-1.

Animals↗