Tumor necrosis factor-beta is associated with thymic apoptosis during acute rejection.

BACKGROUND: Intrathymic events undergoing allograft rejection remain undefined. The present study investigated the role of tumor necrosis factor-beta on acute thymic involution in rat hepatic allograft recipients during rejection. METHODS: Apoptosis and cellular phenotypic changes in the thymus were studied after hepatic transplantation. RESULTS: Thymocytes in both the medulla and cortex were sparse during acute rejection. Phenotypically, CD4+CD8+ T cells decreased significantly, whereas there were relative increases in CD4-CD8-, CD4+CD8-, and CD4-CD8+ T cells in untreated allograft recipients. Additionally, thymic apoptosis was found by in situ DNA end labeling and electron microscopy. Apoptotic cells were predominantly distributed in the cortex. Biologic lymphotoxin (tumor necrosis factor-beta)/tumor necrosis factor-alpha cytotoxic activity in the serum was significantly increased in untreated hepatic allograft recipients. Tumor necrosis factor-beta mRNA was detected in untreated allograft livers, and intraperitoneal administration of recombinant human tumor necrosis factor-beta induced extensive apoptosis of thymocytes in vivo. In contrast, no significant thymic involution was observed in donor-specific blood transfusion-treated allograft and isograft recipients. Intraperitoneal administration of rabbit anti-human tumor necrosis factor-beta polyclonal antibody or recombinant human interleukin-10 inhibited thymic apoptosis in untreated hepatic allograft recipients. CONCLUSIONS: Allograft rejection, but not donor-specific transfusion-induced immunologic unresponsiveness, is associated with thymic involution, a process that may be mediated by tumor necrosis factor-beta.

Ectopic colonization of primordial germ cells in the chick embryo lacking the gonads.

Chick primordial germ cells (PGCs) first appear in the extraembryonic region in the early embryo, then temporarily circulate via the blood vascular system and finally migrate into the gonadal anlagen. In the present study, we examined the trend of ectopic distribution of PGCs in the chick embryo when its future gonadal region had been removed at an early stage. Embryos at stage 10, from which the caudal third region was excised, were incubated until they reached stages 14 to 20. In embryos at stage 14, about 80% of the total PGCs were found in the capillaries of the yolk sac, whereas others were observed in the head, mainly in the mesenchyme and small vessels close to the neural tube. From stage 18 onward, many PGCs accumulated in the embryo proper; about 90% of them colonized in the head region around the neural tube. These ectopic PGCs in the head were found in the capillaries, sometimes as thrombi or emerging from them into the adjacent mesenchyme. These results show that, when the chick embryo lacked gonads, the PGCs could be concentrated in the head region and migrated from the capillaries into the mesenchyme.

Extragonadal distribution of primordial germ cells in the early chick embryo.

Chick primordial germ cells (PGCs), after separation from the endoderm in early embryonic development, temporarily circulate via the blood vascular system and finally migrate into the gonadal anlagen. It has been noted by some authors that some PGCs are present in extragonadal sites in some vertebrates. In the present study, we examined the distribution and localization of PGCs in extragonadal sites in the chick embryo. PGCs were identified by periodic acid-Schiff staining with light microscopy. In embryos at stages 20-24 (PGCs are in the settlement stage in the gonadal primordium), approximately 20% of the total number of PGCs were observed in extragonadal regions. Approximately 90% of these ectopic PGCs were found in the head, mainly in the mesenchyme surrounding the neural tube. Even at stage 14 when PGCs were usually circulating in the blood vessels, some of the PGCs had emerged from the blood vessels and were detected in the extragonadal site. This pattern of distribution of ectopic PGCs in the head area is probably attributed to the earlier, dominant development of the capillary network, and to the sluggish capillary blood flow in that region, which allows intravascular PGCs to escape into the tissue.

Behavior of chick primordial germ cells moving toward gonadal primordium in vitro: scanning electron microscopic study.

Primordial germ cells (PGCs) from embryonic chick blood were cultured in vitro and the cells being attracted by the gonadal primordium (germinal ridge; GR) were studied by scanning electron microscopy (SEM). Immediately after confirming PGC locomotion by 16-mm time-lapse filming or time-lapse video recorder under the microscope, PGCs in various phases of locomotion were prepared for SEM, and their locomotion was analyzed. With the thin collagen layer as a substrate, the sequence of the PGC locomotion was as follows: 1) The PGC produced a small pseudopodium. 2) This pseudopodium enlarged to the GR, and PGC-substrate contact was consolidated around the periphery of the pseudopodium, while the body of PGC remained detached from the substrate. 3) Finally, the PGC as a whole moved toward the GR, being trailed by the process. The locomotion of the PGC on the thick collagen layer as a three-dimensional substrate was as follows: 1) The PGC protruded a pseudopodium in the direction of the GR. 2) This pseudopodium elongated through the collagen network. 3) The tip of the pseudopodium swelled and the main body of the PGC flowed into the swelling portion, leaving a slender cytoplasmic tail. 4) The tail was finally incorporated into the leading part of the cell. This behavior of the PGC seemed to reflect the features of interstitial PGC in vivo.

[Endocrine profile and electron microscopic study of ovarian androblastoma].

The endocrine profile of a 23-year-old woman with an androblastoma of the right ovary and the results of electron microscopic observation of the tumor are presented. The calculated ratio of testosterone in testosterone intraoperative peripheral vein blood, right ovarian vein blood, and right ovarian tumor fluid was 1:1.4:4.0. The peripheral levels of hormones before right salpingo-oophorectomy were testosterone, 6.26 ng/ml; dehydroepiandrosterone, 17.80 ng/ml; androstenedione, 1.61 ng/ml; and cortisol, 16.5 micrograms/ml, and the corresponding levels at 14 days after surgery were 0.50 ng/ml; 13.80 ng/ml; 1.27 ng/ml; and 15.2 micrograms/ml, respectively. The tumor was responsive to hCG, resulting in a marked increase in the serum concentrations of testosterone, androstenedione, and dehydroepiandrosterone (3.7 times, 5.3 times, and 2.4 times, respectively). Preoperatively, an elevated basal level of luteinizing hormone (LH) and a normal basal level of follicle-stimulating hormone (FSH) (high LH:FSH ratio, 6.6) were found. The electron microscopic findings for the tumor revealed Leydig cells, Sertoli cells, transitional cells with features of both Sertoli cells and Leydig cells, and dark cells. The dark cells had features similar to dark cells of normal ovarian stroma.

[Electron microscopic study on the angioarchitecture of glomeruli in experimental toxemia of pregnant rabbits].

The present paper reports studies on the change in the angioarchitecture of the glomeruli in induced hypertensive pregnancy in rabbits. Experimental toxemia of pregnancy in late pregnancy in rabbits was induced by constriction of the aorta below the renal arteries, followed by estradiol administration. The results are as follows: 1) Constriction of the aorta in the pregnant rabbits on the 21st day of gestation significantly elevated the blood pressure and resulted in intrauterine growth retardation in 88.9% of the living fetuses. 2) When the pregnant rabbits underwent constriction of the aorta and estradiol treatment, all the fetuses were in a state of intra-uterine death. 3) The transmission electron microscopic findings of the glomeruli revealed swelling of endothelial cells with vacuolization and vacuolated mesangial cells. 4) The angioarchitecture of the glomeruli was observed by scanning electron microscopy. The enlargement of the endothelial cells was found to reduce the size of cavities of vessels.

The origin, migration and fine morphology of human primordial germ cells.

Human primordial germ cells (PGCs) were observed ultrastructurally in stages from their endodermal to gonadal locations. Primitive PGCs in the hind-gut epithelium of the 4-week embryo, were recognized as well demarcated cells from the neighboring cells. At the time fo separation, the basal lamina of the epithelium was broken, then, through the gap so opened, the PGCs started to escape into the outer mesenchyme. In embryos at five weeks, PGCs were in the migration stage, and were found in the dorsal mesentery, at the coelomic angle and in the forming germinal ridge. In embryos at six weeks or later, almost all PGCS were accumulated in the gonad. The PGC was characterized by its large size and the large and round nucleus with conspicuous nucleolus, and by the presence of abundant glycogen particles and a considerable number of lipid droplets in the cytoplasm. Alkaline phosphatase activity was demonstrated selectively on the plasma membrane of the PGC. The shape of PGC was irregular, often had pseudopodia in PGCs in the separation and migration stages, suggesting their amoeboid movement in vivo, but was generally round or elliptic in PGCs in the settlement stage. The PGC was usually surrounded by and in close association with adjacent somatic cells.