Although surgical induction of cryptorchidism in the rat is known to cause infertility due to disruption of spermatogenesis, the exact cellular mechanism responsible for the degenerative changes in cryptorchid testes is unclear. Using a sensitive autoradiographic method for the detection of apoptotic DNA fragmentation, we have investigated the effect of experimentally induced cryptorchidism on apoptotic cell death in testes of immature rats. Bilateral or unilateral cryptorchidism decreased the weight of affected testes within 4 days; these decreases (24-27%) became significant (P < 0.05) at 7 days after the operation. Testes of sham-operated animals contained predominantly high molecular weight DNA (> 15 kb), whereas DNA cleavage into low molecular weight ladders characteristic of apoptosis was increased by induction of bilateral cryptorchidism in a time-dependent manner, i.e., 2.0-, 2.8-, and 4.2-fold (p < 0.05) at 2, 4, and 7 days after operation, respectively. In unilaterally cryptorchid animals, sham-operated testes also contained predominantly high molecular weight DNA, whereas induction of cryptorchidism of the contralateral testes increased DNA cleavage into low molecular weight fragments 3.0-, 2.8-, and 3.9-fold (p < 0.05) at 2, 4, and 7 days after the operation, respectively. In situ analysis of DNA fragmentation in testes of unilaterally cryptorchid rats at 7 days after the operation indicated that germ cells, mainly primary spermatocytes were affected and that the percentage of seminiferous tubules containing labeled cells increased in the operated testis as compared to the contralateral control in the same animal.(ABSTRACT TRUNCATED AT 250 WORDS)

To elucidate the role of apoptotic cell death in human corpus luteum (CL) regression, human CL during the menstrual cycle and early pregnancy were isolated and processed for biochemical (radio-labeling) analysis of DNA integrity. Total DNA extracted from human CL of the early luteal phase contained predominantly high mol wt DNA, whereas CL of the midluteal phase exhibited the appearance of DNA cleavage into low mol wt ladders characteristic of apoptosis. Although apoptotic DNA cleavage of human CL significantly increased from the midluteal phase to the late luteal phase (P < 0.05), CL of early pregnancy did not exhibit apoptotic DNA fragmentation by biochemical analysis. In situ analysis of DNA fragmentation revealed that both large and small luteal cells exhibited DNA cleavage in human CL of the midluteal and late luteal phases and in regressive CL. The present findings suggest that 1) human luteal regression may be mediated by apoptosis; and 2) CL of early pregnancy may be rescued from luteolysis through inhibiting the occurrence of apoptotic luteal cell death.

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Pituitary gonadotropin FSH acts exclusively on ovarian granulosa cells by binding to specific plasma membrane receptors. Transforming growth factors alpha and beta (TGF alpha and TGF beta), produced locally within the ovary, have been shown to regulate diverse follicle functions, although their potential role in the regulation of FSH receptors has not been assessed. Our first objective was to demonstrate developmental changes in the expression of FSH receptor gene and protein; we then analyzed the regulation of FSH receptor expression by TGF beta s and TGF alpha in cultured granulosa cells. Analysis of steady-state FSH receptor mRNA and protein levels in neonatal and prepubertal ovaries revealed the existence of two predominant FSH receptor mRNA transcripts, 7.0 and 2.5 kb in size, showing a dramatic increase between Day 15 and Day 18 of age followed by a plateau up to 27 days of age. A close parallelism in the developmental changes in FSH receptor mRNA levels and FSH receptor content was observed. Cultured granulosa cells obtained from estrogen-treated immature rats exhibited FSH receptor transcripts similar in size to those seen in whole ovaries. Treatment of granulosa cells for 48 h with TGF beta 1 increased the levels of FSH receptor mRNA for both the 7.0- and 2.5-kb transcripts in a dose-dependent manner (ED50, 1.5 ng/ml), with a maximal 4.0 +/- 0.8-fold increase over control levels observed in response to 10 ng/ml TGF beta 1. Also, TGF beta 2 was as potent as TGF beta 1 in increasing FSH receptor mRNA levels.(ABSTRACT TRUNCATED AT 250 WORDS)

To investigate apoptotic changes, we studied the cleavage of DNA in the uterine endometrium obtained from regularly cycling women by a quantitative end labeling of DNA gel fractionation and in situ analysis. The ladder pattern characteristic of the apoptotic cleavage of DNA into fragments of low mol wt was identified at three different phases of the cycle, namely the early proliferative, late secretory, and menstrual phases. However, DNA of high mol wt was predominant in the endometrium during the late proliferative, early secretory, and midsecretory phases. Our analysis in situ revealed that cells undergoing apoptosis were scattered in the functional layer of the early proliferative endometrium. However, apoptotic cells were no longer detectable during the late proliferative phase, and none was observed until the midsecretory phase. At the beginning of the late secretory phase, apoptosis reappeared in the stromal cells and spread gradually to almost all components of the functional layer. By contrast, cells in the basal layer showed no evidence of apoptosis throughout the menstrual cycle. The present study demonstrates that apoptosis occurs in specific populations of cells during three phases of the human endometrial cycle. Our results indicate, moreover, that apoptosis might have an important role in the regulation of the menstrual cycle in women.

To elucidate the role of apoptotic cell death in human corpus luteum (CL) regression, human CL during the menstrual cycle and early pregnancy were isolated and processed for biochemical (radio-labeling) analysis of DNA integrity. Total DNA extracted from human CL of the early luteal phase contained predominantly high mol wt DNA, whereas CL of the midluteal phase exhibited the appearance of DNA cleavage into low mol wt ladders characteristic of apoptosis. Although apoptotic DNA cleavage of human CL significantly increased from the midluteal phase to the late luteal phase (P < 0.05), CL of early pregnancy did not exhibit apoptotic DNA fragmentation by biochemical analysis. In situ analysis of DNA fragmentation revealed that both large and small luteal cells exhibited DNA cleavage in human CL of the midluteal and late luteal phases and in regressive CL. The present findings suggest that 1) human luteal regression may be mediated by apoptosis; and 2) CL of early pregnancy may be rescued from luteolysis through inhibiting the occurrence of apoptotic luteal cell death.

The hCG beta-subunit contains a carboxy-terminal extension bearing four serine-linked oligosaccharides [carboxy-terminal peptide (CTP)], which is important for maintaining its longer half-life compared with the other glycoprotein hormones. Previously, we enhanced the in vivo half-life of FSH by fusing the CTP to the carboxy end of FSH beta coding sequence. The alpha-subunit is common to the glycoprotein family. We constructed alpha-subunit CTP chimeras, since such analogs with the appropriate O-linked glycosylation and conformation would increase the in vivo stability of the entire glycoprotein hormone family. Two chimeras were constructed using overlapping polymerase chain reaction mutagenesis: a variant with CTP at the carboxy end and another analog with the CTP at the N-terminal region of the subunit, between amino acids 3 and 4. The latter design was based on models showing that the amino-terminal region of alpha is not involved in assembly with the beta-subunit, nor is it essential for receptor binding and signal transduction. These chimeras were cotransfected with the hCG beta gene into Chinese hamster ovary cells. The chimeras were secreted and combined efficiently with the CG beta-subunit, comparable to the wild type alpha-subunit. CG dimers containing the alpha-subunit chimera with CTP at the carboxy end of the subunit had a much lower binding affinity for the hLH-hCG receptor in vitro, whereas the binding of the dimer containing the CTP at the amino-terminal end of the subunit was similar to wild type hCG. Furthermore, the in vivo activity of this analog was enhanced significantly. Moreover, regardless of the two insertion points in the alpha-subunit, the CTP sequence was O-glycosylated. These data suggest that the entire signal for O-glycosylation is primarily contained within the CTP sequence and is not dependent on the flanking regions of the recipient protein. The transfer of CTP to the alpha-subunit of hCG results in an agonist with prolonged biological action in vivo. These data further support the rationale for using the CTP as a general target to increase the potency of bioactive glycoproteins.

These results suggest that cells in hyperplasia expressing Bcl-2 might have prolonged survival ability. Neoplastic cells in adenocarcinoma might show apoptosis in association with a decreased expression of Bcl-2 and an increased expression of Bax. Therefore, the frequency of apoptosis and the expression of Bcl-2 and Bax might be correlated with carcinogenesis in the uterine endometrium of humans.