Quiescent cells from adult vertebrate liver and contact-inhibited or serum-deprived tissue cultures are active metabolically but do not carry out nuclear DNA replication and cell division. Replication of intact nuclei isolated from either quiescent Xenopus liver or cultured Xenopus A6 cells in quiescence was barely detectable in interphase extracts of Xenopus laevis eggs, although Xenopus sperm...

Both TGF beta 2 and 5 have been described in the South African clawed frog Xenopus laevis and have been cloned from the tadpole-derived fibroblast cell line, XTC. Because TGF beta has such a profound inhibitory effect on the mammalian immune system, this study was performed to determine whether TGF beta: (a) has any in vitro effects on the growth of Xenopus lymphoblasts, and (b) is produced by ...

DNA binding activity and nuclear transport of B-Myb in Xenopus oocytes are negatively regulated. Two distinct sequence elements in the C-terminal portion of the protein are responsible for these different inhibitory activities. A C-terminal Xenopus B-Myb protein fragment inhibits the DNA binding activity of the N-terminal repeats in trans, indicating that intramolecular folding may result in ma...

Xenopus is an essential vertebrate model system for biomedical research that has contributed to important discoveries in many disciplines, including cell biology, molecular biology, physiology, developmental biology, and neurobiology. However, unlike other model systems no central repository/stock center for Xenopus had been established until recently. Similar to mouse, zebrafish, and fly commu...

Relationships of the pipid frog genus Silurana ( = Xenopus tropicalis group of some authors) are of particular interest to developmental and molecular biologists because of the purported ancestral (i.e., unduplicated) karyotype of S. tropicaks relative to the genus Xenopus. Although most previous studies have assumed that SiZuruna is the sister group of Xenopus, recent morphological work sugges...

Anticonvulsant activity of N-(p-aminobenzoyl)-1,2,3,4- tetrahydro-quinoline (NTQ), a newly synthesized ameltolide analog, was investigated with regards to efficacy and toxicity in mice. Additionally, its effect on NMDA receptors was also performed on NR1a/NR2B expressed in Xenopus oocytes. NTQ, given intraperitoneally, was able to protect the animals in both maximal electroshock seizure and pen...

The enzyme CYP17 primarily regulates androgen production by mediating four reactions: conversion of pregnenolone and progesterone to 17-hydroxypregnenolone and 17-hydroxyprogesterone, respectively (17 -hydroxylase activity), followed by conversion of the 17-hydroxylated steroids to dehydroepiandrosterone and androstenedione, respectively (17,20-lyase activity). Most mammalian CYP17 isoforms hav...

Cell polarity is manifest along the animal/vegetal axis in eggs of the frog, Xenopus laevis. Along this axis, maternal cytoplasmic components are asymmetrically distributed and are thought to underlie specification of distinct cell fates. To ascertain the molecular identities of such cytoplasmic components, we have used a monoclonal antibody that specifically stains the vegetal hemisphere of Xe...