Stimulation of fibroblasts with serum or purified growth factors leads to a dramatic induction of expression of both c-fos mRNA and protein within a few minutes, followed by activation of c-myc. This suggests that c-fos induction is a primary event and the earliest known effect on gene expression by growth factors.

Genes whose expression is growth factor regulated are likely to be important components in the mechanisms controlling cell proliferation and differentiation. With the aim of identifying some of those genes, a A cDNA library was prepared with poly(A)+ RNA from quiescent NIH 3T3 cells stimulated with serum for 4 h in the presence of cycloheximide. Differential screening of approximately 200,000 recombinant phage plaques revealed 2,540 clones that cross hybridized preferentially with [32P]cDNA derived from RNA of stimulated cells rather than with cDNA derived from nonstimulated cells. Cross hybridization of these clones identified 82 independent sequences, including c-fos and c-myc. Seventy-one clones were further studied. Analysis of the changes in transcription and mRNA levels after serum stimulation demonstrated that the kinetics and extent of the induction vary dramatically between the different genes. Cycloheximide in all cases superinduced the mRNA levels by two mechanisms, inhibiting the shutoff of transcription and prolonging the half-lives of the mRNAs. Our results showed that induction of proliferation is accompanied by the onset of a complex genetic program.A detailed knowledge of the biochemical events and the identification of the genes that are involved in the response to growth factors is currently being accumulated. A subset of these genes may play a critical role in cellular transformation. It is well established that the synthesis of new mRNA in quiescent cells is required for the cells to respond to mitogens and progress through Gl and enter the S phase (1). Furthermore, Gl seems to be a critical point of control of proliferation, where normal cells deprived of growth factors halt cycling, while transformed cells do not, suggesting that regulatory genes uncontrolled in the neoplastic phenotype are expressed during this transition. It has been estimated that in mouse fibroblasts, 3% of the mRNA species in logarithmically growing cells are absent in quiescent cells (49); thus, a set of these genes must be under the control of growth factors to allow cell proliferation. Evidence that gene expression could be controlled by the binding of a specific ligand to its receptor initially came from studies done with beta interferon (27,28) which demonstrated the transcriptional activation of two genes in human cells after interferon treatment. These findings were further supported by the interesting observation that the proto-oncogenes c-fos and c-myc present an immediate change in expression after stimulation of fibroblasts with growth factors (4,8,14,23,25,32), emphasizing also that important growth-controlling genes operate during the GO-to-Gl transition. Both genes are induced in the presence of protein synthesis inhibitors, demonstrating that their induction is a direct consequence of the growth factor-receptor interaction. Expression of c-fos is undetectable during the cell cycle (3), suggesting that its expression could be essential during the transition from GO to Gl and not for continuously growing ...

Human African trypanosomiasis (HAT) is transmitted by tsetse flies and, if untreated, is fatal. Treatment depends on infection stage, and early diagnosis is crucial for effective disease management. The systemic host biochemical changes induced by HAT that enable biomarker discovery or relate to therapeutic outcome are largely unknown. We have characterized the multivariate temporal responses of mice to Trypanosoma brucei brucei infection, using 1 H nuclear magnetic resonance (NMR) spectroscopic metabolic phenotyping of urine and plasma. Marked alterations in plasma metabolic profiles were detected already 1 day postinfection. Elevated plasma concentrations of lactate, branched chain amino acids, and acetylglycoprotein fragments were noted. T. brucei brucei-infected mice also had an imbalance of plasma alanine and valine, consistent with differential gluconeogenesis (parasite)-ketogenesis (host) pathway counterflux, involving stimulated host glycolysis, ketogenesis, and enhanced lipid oxidation in the host. Histopathologic evidence of T. brucei brucei-induced extramedullary hepatic hemopoiesis, renal interstitial nephritis, and a provoked inflammatory response was also noted. Metabolic disturbance of gut microbiotal activity was associated with infection, as indicated by changes in the urinary concentrations of the microbial co-metabolites, including hippurate. Concluding, parasite infection results in multiple systemic biochemical effects in the host and disturbance of the symbiotic gut microbial metabolic interactions. Investigation of these transgenomic metabolic alterations may underpin the development of new diagnostic criteria and metrics of therapeutic efficacy. diagnosis ͉ metabonomics ͉ NMR spectroscopy ͉ trypanosomiasis

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