Excretory/secretory (ES) products obtained by in vitro culture of infective-stage larvae of Trichinella spiralis and T. pseudospiralis were injected intramuscularly at various intervals into mice. Mini-osmotic pumps containing T. spiralis ES products were also implanted subcutaneously and intraperitoneally into rats. The introduction of ES materials into muscles elicited extensive lesions which included dissolution of myofibres, mobilization of mononuclear and polymorphonuclear leucocytes, angiogenesis, hypertrophy of myonuclei, myotube formation, mitosis, muscle bundles becoming rounded and separated from each other, disappearance of Z, I and A bands of sarcomeres, increase in endoplasmic reticulum and Golgi complexes, decrease in glycogen and relocation of mitochondria. These are considered as degenerative/regenerative changes of muscles to injury. Immunodominant epitopes of specific 45–53 kDa glycoproteins in ES antigens of T. spiralis could not be detected in hypertrophic nuclei of injected muscles by using polyclonal and monoclonal antibodies and immunocytochemical methods. ES products of T. spiralis failed to stimulate unsensitized lymphocytes in the lymphocyte transformation test. Infective-stage larvae of T. spiralis released from muscles were found capable of forming nurse cells after injection subcutaneously into rats. It is postulated that the invasion of muscles by trichinellids elicits two independent events, i.e. a general degenerative/regenerative response of muscles and a specific change in genomic expression of myonuclei. The two events are probably mediated by different effector molecules.

A polytrophic ovariole of the fleshfly, Sarcophaga tibialis Macquart, is composed of two successively maturing egg chambers, each consisting of an oocyte, an interconnected cluster of 15 nurse cells, and an enveloping layer of follicle cells. The oocyte is established at the posterior end of the egg chamber. Nurse cell differentiation is characterized by nucleolar multiplication. At 25°C the first egg generation took approximately 8 days to develop. During this period, the growth rate of the egg chamber increased with time. A dramatic increase occurred during days 4–6, and was associated with the formation of large intercellular spaces between the follicle cells as well as an accumulation of numerous yolk globules. Completion of egg-chamber development was marked by the degeneration of the cluster of nurse cells and that of follicle cells.

—The flesh fly, Sarcophaga ruficornis Fabr., was fed on thiotepa, and it was found that a 1% thiotepa solution produced complete sterility, which was due to the damage to the follicle cells and nurse cells. The passage of the female protein, ‘vitellogenin’, was blocked. Therefore, no trace of yolk granules was visible in the treated oocytes, but the oocytes and cytoplasm of the nurse cell contained vacuoles, and their nuclei were characterized by clumped chromatin contents.