The evolutionary initiation of the appearance in lymphomyeloid tissue of the hemopoietic stem cell in the earliest (most primitive) vertebrate model, i.e. the elasmobranch (chondroichthyan) Torpedo marmorata Risso, has been studied. The three consecutive developmental stages of torpedo embryos were obtained by cesarean section from a total of six pregnant torpedoes. Lymphomyeloid tissue was identified in the Leydig organ and epigonal tissue. The sections were treated with monoclonal anti-CD34 and anti-CD38 antibodies to detect hematopoietic stem cells. At stage I (2-cm-long embryos with external gills) and at stage II (3-4 cm-long embryos with a discoidal shape and internal gills), some lymphoid-like cells that do not demonstrate any immunolabeling for these antibodies are present. Neither CD34+ nor CD38+ cells are identifiable in lymphomyeloid tissue of stage I and stage II embryos, while a CD34+CD38- cell was identified in the external yolk sac of stage II embryo. The stage III (10-11-cm-long embryos), the lymphomyeloid tissue contained four cell populations, respectively CD34+CD38-, CD34+CD38+, CD34-CD38+, and CD34-CD38- cells. The spleen and lymphomyeloid tissue are the principal sites for the development of hematopoietic progenitors in embryonic Torpedo marmorata Risso. The results demonstrated that the CD34 expression on hematopoietic progenitor cells and its extraembryonic origin is conserved throughout the vertebrate evolutionary scale.

中文翻译：

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造血干细胞首次出现于软骨鱼胚胎淋巴骨髓组织中。

最早（最原始）的脊椎动物模型，即软骨鱼类Torpedo marmorata Risso，造血干细胞在淋巴骨髓组织中出现的进化起始已被研究。鱼雷胚胎的三个连续发育阶段是从总共六只怀孕鱼雷中通过剖腹产获得的。在间质器官和外阴组织中发现了淋巴骨髓组织。将切片用单克隆抗CD34和抗CD38抗体处理以检测造血干细胞。在第一阶段（具有外部鳃的 2 厘米长胚胎）和第二阶段（具有盘状形状和内部鳃的 3-4 厘米长胚胎），一些未表现出这些抗体的任何免疫标记的淋巴样细胞是展示。在 I 期和 II 期胚胎的淋巴骨髓组织中均未鉴定出 CD34+ 和 CD38+ 细胞，而在 II 期胚胎的外部卵黄囊中鉴定出 CD34+CD38- 细胞。III期（10-11厘米长的胚胎），淋巴骨髓组织含有四个细胞群，分别为CD34+CD38-、CD34+CD38+、CD34-CD38+和CD34-CD38-细胞。脾脏和淋巴骨髓组织是鱼雷鱼胚胎中造血祖细胞发育的主要部位。结果表明，造血祖细胞上的 CD34 表达及其胚胎外起源在整个脊椎动物进化规模中是保守的。