Catalases and peroxidases histochemical detection; techniques suitable to discriminate these enzymes

Adipose tissue macrophages develop from bone marrow-independent progenitors in Xenopus laevis and mouse

ATMs have a metabolic impact in mammals as they contribute to metabolically harmful AT inflammation. The control of the ATM number may have therapeutic potential; however, information on ATM ontogeny is scarce. Whereas it is thought that ATMs develop from circulating monocytes, various tissue-resident Mϕs are capable of self-renewal and develop from BM-independent progenitors without a monocyte intermediate. Here, we show that amphibian AT contains self-renewing ATMs that populate the AT before the establishment of BM hematopoiesis. Xenopus ATMs develop from progenitors of aVBI. In the mouse, a significant amount of ATM develops from the yolk sac, the mammalian equivalent of aVBI. In summary, this study provides evidence for a prenatal origin of ATMs and shows that the study of amphibian ATMs can enhance the understanding of the role of the prenatal environment in ATM development.

Metabolism of 1,3-butadiene to butadiene monoxide in mouse and human bone marrow cells

1,3-Butadiene (BD), a gas used in the production of rubber and plastics, induces a high incidence of leukemias and lymphomas in B6C3F1 mice. Because of the potential involvement of the hematopoietic system in response to BD, we have examined metabolism of BD by B6C3F1 mouse and human bone marrow and by purified human myeloperoxidase (MPO), an enzyme rich in bone marrow. BD was metabolized to butadiene monoxide (BMO) by MPO and by mouse and human bone marrow cells. In all of these systems metabolism was stimulated by hydrogen peroxide suggesting a peroxidase-mediated process. In B6C3F1 mouse bone marrow cell lysates, hydrogen peroxide but not NADPH stimulated metabolism suggesting that cytochrome P450 was not involved in BMO formation. Metabolism of BD to BMO in hydrogen peroxide-fortified mouse bone marrow cell lysates was more than two orders of magnitude lower than in either NADPH-fortified rat or mouse hepatic microsomes. Experiments using both mouse and human bone marrow cells showed that cells from both sources could generate BMO from BD. These data show that BD can be converted to BMO in a target organ of BD carcinogenicity.

Critical study of endogenous peroxidase activity: its role in the morphofunctional setting of the thyroid follicle in the rat fetus

Endogenous peroxidase is associated with thyroglobulin iodination. It first appears at 17 day of pregnancy in rat fetal thyroid and seems to be synthesized within the perinuclear cistern and the rough endoplasmic reticulum. Then, the enzyme is transferred by vesicles up to the follicular lumen where thyroglobulin iodination takes place. The different steps of this process can occur within a very short time, since peroxidase activity is already located in the apical plasma membrane of follicles formed as early as 17 days of pregnancy, which is consistent with autoradiographic data showing iodinated thyroglobulin at 17 days. It can be concluded that the follicle is functional as soon as it is formed.