The cDNA sequence of murine Nkx-2.2.

We isolated and sequenced a 2026-bp murine Nkx-2.2 cDNA clone that contains an open reading frame encoding 273 amino acids (aa). The 273-aa protein includes a homeobox, an NK-2 box and a N-terminal decapeptide found in other Nk family members.

Longitudinal organization of the anterior neural plate and neural tube.

Over the last century, several morphological models of forebrain organization have been proposed that hypothesize alternative topological solutions for the relationships of the histogenic primordia. Central to all of these models are their definitions of the longitudinal axis and the longitudinal organization of the neural plate and neural tube. To understand the longitudinal organization of the anterior brain, we have sought to identify molecular properties that are continuous along the entire longitudinal axis of the embryonic CNS. In this essay, we describe studies of the expression of several genes in the mouse between 7.5 (presomite stage) and 10.5 days post coitum (dpc) that provide evidence for the trajectory of the anterior-posterior axis and the longitudinal organization of the anterior CNS. Specifically, we report that the expression of noggin, sonic hedgehog and Nkx-2.2 define longitudinal columns of cells that are present along the entire CNS axis. Within the forebrain, the expression of these genes, as well as that of Nkx-2.1 and BF-1, are in distinct longitudinal regions in the neural plate and tube. We demonstrate that the earliest longitudinal axon pathways of the forebrain are spatially correlated with the longitudinal domain defined by Nkx-2.2. Finally, expression of the former genes, and Otx-1 and Emx-2, suggests that the cephalic neural plate is organized into molecularly distinct domains delimited by longitudinal and transverse borders; these results provide a foundation for defining the mechanisms that pattern the neural plate.

Enhancement of antineoplastic activity of 5-fluorouracil in mice bearing colon 38 tumor by (6R)5,10-dideazatetrahydrofolic acid.

(6R)5,10-Dideazatetrahydrofolic acid (DDATHF, Lometrexol), a potent antitumor drug in vivo and in vitro, is an inhibitor of the two folate-dependent enzymes in the de novo purine biosynthesis pathway: glycinamide ribonucleotide (GAR) and amino imidazole carboxamide (AICAR) transformylases. A single dose of DDATHF (50 mg/kg, i.p.) in C57/BL6 mice caused a prolonged depletion of purine nucleotides (ATP and GTP) in colon 38 tumor and only a temporary effect in liver. GAR transformylase activity was higher in colon 38 tumor than in liver, but a kinetic analysis on the purified enzyme showed no differences in Ki values for DDATHF or Km values for the folate substrate. As a consequence of de novo purine synthesis inhibition, there was a 2- to 3-fold elevation of 5-phosphoribosyl-1-pyrophosphate pools in colon 38 tumor between 4 and 12 hr after DDATHF administration. When DDATHF (50 mg/kg) was administered 4 or 8 hr prior to 5-fluorouracil (5-FU; 85 mg/kg, i.p., weekly), these biochemical effects significantly increased the antitumor activity of 5-FU, with a modest increase in toxicity. Lower doses of DDATHF (25 and 37.5 mg/kg) when combined with 5-FU also resulted in an improved antitumor activity without additional toxicity. The two different schedules of administration for DDATHF, 4 and 8 hr prior to 5-FU, showed no differences in antitumor activity or toxicity.

Induction of immediate early genes by cyclic AMP in primary cultures of neurons from rat cerebral cortex.

In this paper, we tested whether physiological activators of the cAMP second messenger pathway in primary cultures of neurons from rat cerebral cortex directly induce c-fos and other immediate early gene (IEG) transcription factors. We have found that brief (30 s to 2 min) stimulation of neurons with vasoactive intestinal peptide (VIP) and SKF-38393, a D1-dopaminergic receptor agonist, potently increased mRNA levels for the IEGs c-fos, jun-B, and NGFI-A, with weaker increases for c-jun. This action was mimicked by forskolin and dibutyryl cAMP. IEG induction by VIP and dibutyryl cAMP was not blocked by excitatory amino acid receptor antagonists or by blockers of dihydropyridine-sensitive calcium channels. Moreover, calcium-free medium did not modify IEG induction by dibutyryl cAMP, suggesting that cAMP can directly regulate IEG expression in differentiated neurons independently of calcium.