Jaydev N. Dholakia

Protein kinase B, P34cdc2 kinase, and p21 ras GTP-binding in kidneys of aging rats.

Renal nephropathy present in male Wistar rats more than 13 months of age was reported as an indication that the rats were in renal failure. In this study, the renal tissue damage at 14 months of age in male Munich Wistar rats was similar to that reported for Wistar rats, indicating that Munich Wistar rats could be another model for study of kidney function in the aging rat. The usual renal response to injury involves increased cell division and/or reparative processes that involve tyrosine kinase activity (TyrK) and/or guanosine triphosphate-binding (G) protein signal transduction pathways. This study reveals the presence of renal tissue damage coinciding with significantly reduced activitiy of Ras, Akt, and p34cdc2 kinase, the signaling proteins that regulate cell division and/or growth, in renal cortical tissues of aging rats compared to young rats (P < 0.005, P < 0.005, and P < 0.001, respectively). These results suggest that proteins involved in signal transduction pathways associated with cell replication are downregulated in the aging kidney cortex at a time when renal cellular damage is also present.

The signal cascade for the activation of protein synthesis during the maturation of starfish oocytes: a role for protein kinase C and homologies with maturation in Xenopus and mammatian oocytes

Summary The goal of a growing oocyte is to prepare the female gamete for the rapid cleavages that follow fertilization. The oocyte stores proteins and mRNAs required for meiosis and mitosis, since little or no transcription of new mRNAs occurs during the early cleavage stages of most animal embryos. Immature oocytes of mammals, amphibians, and starfish are arrested in the prophase of meiosis I. Meiotic maturation of these oocytes is induced by a maturation hormone that reinitiates meiosis, completes the nuclear reduction of meiosis I and meiosis II, prepares the oocytes for activation by the male gametes, and activates stores of proteins and mRNAs needed for the early cleavage stages. Maturation hormones induce at least three distinct and parallel molecular pathways in animal oocytes: the activation of the maturation promotion factor (MPF); the activation and polyadenylation of mRNAs stored during oogenesis; the activation of the protein synthesis machinery of the oocyte, which is required to translate th...