Carolyn H. Srivastava

Localization of group IIc low molecular weight phospholipase A2 mRNA to meiotic cells in the mouse

We use in situ hybridization to demonstrate that the testicular expression of a novel, mouse, low molecular weight phospholipase A2 (PLA2 Group IIc) mRNA is specific to cells undergoing meiosis. A complete cDNA (1421 bp) encoding the mouse Pla2g2c gene was generated with reverse transcription‐PCR (RT‐PCR) and 5′ and 3′ RACE (rapid amplification of cDNA ends) RT‐PCR, and its nucleotide sequence was determined. Northern blots of RNA from different tissues revealed a single 1.6 kb transcript only in testis. In situ hybridization indicated that this mouse gene is transcribed mainly in pachytene spermatocytes, secondary spermatocytes, and round spermatids. Expression of the gene is seen in all stages of the seminiferous epithelium, especially in stages VI–VII. J. Cell. Biochem. 64:369–375.

Paracrine control of spermatogenesis

Spermatogenesis is a complex process that is both remarkable and enigmatic. While circulating hormones clearly play an important role in initiating and regulating the process, the Sertoli cell barrier prevents most substances from entering the seminiferous tubule compartment and directly influencing germ cell development. Therefore, the testis cannot rely solely upon the delivery of circulating hormones, nutrients, and growth factors, but must independently produce its own regulatory substances. A rapidly increasing number of testicular factors that appear to modulate spermatogenesis in a paracrine fashion are now being identified. These discoveries are beginning to contribute to our understanding of the intricate network of testicular cell-cell interactions that control male reproduction.

Parvovirus B19 replication in human umbilical cord blood cells

The human parvovirus B19 is now known to be one of the causative agents of nonimmune hydrops fetalis and spontaneous abortions in pregnant women. The presence of the viral proteins and antibodies in fetuses of B19-infected women suggests that the virus can cross the placental barrier. In order to gain an insight into the mechanism of intrauterine fetal infection and the virus-induced hydrops fetalis, we examined whether human umbilical cord blood cells were permissive for B19 replication. Cord blood cells were infected with B19 in vitro, and Southern blot analyses of low M(r) DNA isolated from these cells revealed the presence of the characteristic replicative intermediates of B19 DNA. In addition, B19 genome expression in cord blood cells was detected by Northern blot analysis. Quantitative DNA dot blot analysis of culture supernatants documented complete assembly and release of B19 progeny virions in these cells. The progeny virions were biologically active in secondary infections of normal human bone marrow cells. The human umbilical cord blood cells may be a useful alternative to bone marrow and fetal liver culture systems for further studies on B19 since the need for bone marrow donors is obviated and, unlike fetal tissues, there are no ethical questions associated with the experimental use of cord blood because it is normally discarded. These studies also suggest that the umbilical cord blood may be a site for active replication of parvovirus B19 in vivo and may thus provide a means for transmission of the virus during intrauterine fetal infections.

Identification and localization of secretin and secretin receptor mRNAs in rat testis

Secretin is a well-conserved member of the growth hormone-releasing hormone (GHRH) family of peptides expressed in brain, gut and gonads. To determine whether secretin may also play a physiological role in testis, we examined the level and cellular distribution of secretin and secretin receptor gene expression in rat testis. RNAs from total testis, Sertoli, germ and Leydig cells were amplified by comparative reverse transcription-polymerase chain reaction (RT-PCR). Southern blot analysis of the PCR products indicated secretin and secretin receptor mRNA expression primarily in germ cells. Sequence comparisons of cloned secretin and secretin receptor PCR products showed 100% identity with the previously reported sequences. To localize secretin and secretin receptor mRNAs at the cellular level within testis,in situ hybridization was performed. Specific hybridization to secretin mRNA was observed in low abundance in many germ cell types, but was heaviest over step 19 spermatids in stages VII and VIII tubules. Secretin receptor mRNA was detected in approximately the same cell types as was secretin mRNA, except that labeling was greatest in round spermatids (steps 6–8). Since the patterns of gene expression of secretin and its receptor overlap, these data suggest that there may be an intrinsic secretin system in testis.