Heligmosomoides polygyrus
January 27, 2012 § 2 Comments
Preliminary sketch for drawing to measure 1.5m x 1.5m.
Heligmosomoides polygyrus is a common nematode found in the duodenum and small intestine of woodmice and other rodents. It is often used to model human helminth infection in laboratory mice.
These worms are 5–20mm in length and bright red due to the pigmentation of their tissues. They are usually heavily coiled, with the female having 12–15 coils and the male 8–12. The male can be distinguished from the female by a prominent copulatory bursa and two long, thin spicules at the posterior end.
They have a direct life cycle. The eggs pass out with the faeces of the host into the environment. After 2 days they hatch as larvae which are about 300μm in length. The larvae moult 3 days later but retain the shed cuticle for protection. It is at this point they become infective. The larvae shed the outer protective sheath after they are eaten by a suitable host. The larvae then penetrate the submucosa of the duodenum where they undergo 2 further moults. About 7 days later the male and female adult worms emerge into the lumen of the duodenum where they attach to the epithelial layer and begin to feed off the contents of the gut. The adult worms mate and eggs are shed in the faeces. The complete life cycle from egg to egg takes a minimum of 15 days, and the female worms will live inside their host for 8 months.
These worms often form cysts in the wall of the intestine. These cysts often become infected with bacteria, but it is not yet known if these are harmful to the host.
This nematode has been previously called Nematospiroides dubius.
Trypanosoma and Darwin’s Disease
December 1, 2011 § Leave a comment
Preliminary sketch for drawing to measure 1.5m x 1.5m.
Trypanosoma is a genus of kinetoplastids (class Kinetoplastida), a group of unicellular parasitic flagellate protozoa. The name is derived from the Greek trypano (borer) and soma (body) because of their corkscrew-like motion. All trypanosomes are heteroxenous (requiring more than one obligatory host to complete life cycle) and are transmitted via a vector. The majority of species are transmitted by blood-feeding invertebrates, but there are different mechanisms among the varying species. When in the invertebrate host they are generally found in the intestine and, after transmission, they normally occupy the bloodstream or intracellular environment in the mammalian host.
Trypanosomes infect a variety of hosts and cause various diseases, including the fatal human diseases sleeping sickness, caused by Trypanosoma brucei, and Chagas disease, caused by Trypanosoma cruzi.
It has been hypothesized that Charles Darwin might have suffered from Chagas disease as a result of a bite of the so-called great black bug of the Pampas (vinchuca). The episode was reported by Darwin in his diaries of the Voyage of the Beagle as occurring in March 1835 to the east of the Andes near Mendoza. Darwin was young and generally in good health; though six months previously he had been ill for a month near Valparaiso. In 1837, however, and almost a year after he returned to England, he began to suffer intermittently from a strange group of symptoms, becoming incapacitated for much of the rest of his life.
Attempts to test Darwin’s remains at the Westminster Abbey by using modern PCR techniques were met with a refusal by the Abbey’s curator.