Cloning and differential expression of manganese superoxide dismutase (Mn-SOD) of Trichinella pseudospiralis.

The complete coding sequence of manganese superoxide dismutase (Mn-SOD) of Trichinella pseudospiralis (Tp) was obtained and characterized for the first time by degenerative reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of complementary DNA ends (RACE) reactions. The open reading frame of Tp Mn-SOD contained 663 nucleotides, encoding 220 amino acid residues. This included the conserved histidine and aspartate residues for metal binding, cysteine residues for disulfide bond formation, and arginine residue for directing the superoxide ion to the protein. The presence of mitochondrial transit peptides and maturation cleavage site suggest that the cloned Tp Mn-SOD gene is a mitochondrial enzyme. It is a single copy gene containing three introns. Northern blotting suggested that the expression level of Mn-SOD is lower than Cu/Zn SOD in infective stage larvae. Semi-quantitative RT-PCR demonstrated that a single dominant transcript of Tp Mn-SOD was highly expressed in the infective-stage larvae but not in adult worms. The information provides a better understanding of the highly compartmentalized superoxide dismutases of adenophorean nematodes.

Trichinella pseudospiralis: X-ray analysis of the infected muscle cells and the muscle larva compartments after exponential growth of the larva in situ.

The distribution of nutrients such as Na, Cl, K, P, S, and Ca was investigated by energy-dispersive X-ray microanalysis (EDXA) on bulk-frozen mouse muscles infected with Trichinella pseudospiralis. In an attempt to gain information as to whether muscle larvae would modify the element status within muscles of their host. Significant increases in phosphorus concentrations within nurse cells and internal cells of the larva, e.g., the somatic muscle cells and the stichocytes, were shown. This could reflect changes in the energy metabolism and/or in the turnover of nucleic acids of the nurse cell. High phosphorus concentrations within the internal larva cells corresponded to high levels of expression of thymidylate synthase shown elsewhere in both T. pseudospiralis and T. spiralis muscle larvae, most likely reflecting more intensive DNA replication. Furthermore, the Na+-concentration gradient between the nurse cell and neighboring host muscle cells indicated the plasma membrane as a diffusion barrier for Na+. Moreover, the cuticle seemed to maintain the Cl--concentration gradient between the nurse cell and the internal cells of the larva. Nevertheless, the mechanisms involved in the transport of both ions, the collagen cuticle appeared, strong permeability that serves the transcuticular transport maintaining the Cl--concentration gradient.

An in vitro screening test for compounds active against the parenteral stages of Trichinella spiralis.

A new in vitro screening test for compounds showing activity against the tissue stages of Trichinella spiralis is described. In this test freshly decapsulated larvae of the parasite are exposed to low concentrations of experimental compound in a medium capable of supporting th partial development of the worms. The screen which does not require elaborate continuous flow equipment nor special gas phase detects the activity of those compounds known to be effective against the parenteral stages of the parasite in mice. It has been shown to be a highly selective test giving rise to very few irrelevant or misleading results.