The phosphoinositide (PI)-specific phospholipase C gene (TcPI-PLC) of the protozoan parasite Trypanosoma cruzi was cloned, sequenced, expressed in Escherichia coli, and the protein product (TcPI-PLC) was shown to have enzymatic characteristics similar to those of mammalian ␦-type PI-PLCs. The TcPI-PLC gene is expressed at high levels in the epimastigote and amastigote stages of the parasite, and its expression is induced during the differentiation of trypomastigotes into amastigotes, where TcPI-PLC associates with the plasma membrane and increases its catalytic activity. In contrast to other PI-PLCs described so far, the deduced amino acid sequence of TcPI-PLC revealed some unique features such as an N-myristoylation consensus sequence at its aminoterminal end, lack of an apparent pleckstrin homology domain and a highly charged linker region between the catalytic X and Y domains. Many pathogenic parasites have developed the ability to live in two distinct hosts, one vertebrate and the other invertebrate. Such parasites include Trypanosoma cruzi, the etiologic agent of Chagas' disease or American trypanosomiasis. During its life cycle, T. cruzi has to adapt to environments of different temperature, osmolarity, ionic composition, and pH, and some of these adaptation processes are paralleled by morphological and functional changes. Very litttle is known about the signaling mechanisms involved in these processes.Phosphoinositide-specific phospholipases C (PI-PLCs) 1 catalyze the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP 2 ) to D-myo-inositol-1,4,5-trisphosphate (IP 3 ) and sn-1,2-diacylglycerol (DAG) (1, 2). Both products of this reaction function as second messengers in eukaryotic signal transduction cascades. The soluble IP 3 triggers release of calcium from intracellular stores (1). The membrane-resident DAG controls cellular protein phosphorylation states by activating various protein kinase C isozymes (2). Three classes of mammalian PI-PLCs with 10 different isozymes have been characterized (␤1-␤4, ␥1-␥2, and ␦1-␦4) (3). The activity of ␤-and ␥-isozymes (145-150 kDa) is regulated by G protein-coupled and tyrosine kinase-linked receptors, respectively. These isozymes are related to the much smaller ␦-isozymes (ϳ85 kDa) (3). It seems very likely that PI-PLC-␦ evolved first, because every PI-PLC cloned so far from a non-mammalian species (for example, Dictyostelium, yeast, higher plants, and Chlamydomonas) is clearly a ␦-isoform (3). It is currently not known how ␦-isozymes are regulated in vivo (4). It is possible that they are regulated only by calcium ions (3) although the idea of PI-PLC-␦ being regulated by GTP-binding proteins is one which has increasing support (3, 5). Results from several laboratories (6 -8) have suggested that, at least in yeasts, PI-PLC-␦ is required for a number of nutritional and stress-related responses. It has also been postulated that PI-PLC-␦ could have a role in differentiation of Dictyostelium discoideum (9). Transcription of this PI-PLC-␦ appears to be enhanced dur...

Most viral infections in small mammals are transient and rarely produce clinical signs. When clinical signs do appear, they are often of a multifactorial etiology such as respiratory infection with Sendai virus and the bacteria M. pulmonis in rodents. Diagnosis is generally made based on clinical signs, while therapy involves treatment for concurrent bacterial infections and supportive care. Small mammals may carry zoonotic viruses such as LCMV, but natural infections are uncommon. Viral diseases are rare (or largely unknown) for hedgehogs, chinchillas, and prairie dogs, while no known naturally occurring, clinically relevant viral diseases exist for gerbils and sugar gliders. This article is intended to aid the clinician in identifying viral infections in small mammals and to help determine the significance each virus has during clinical disease.