Pathophysiology of abomasal parasitism: is the host or parasite responsible?

Nematode larvae developing within the glands cause local loss of parietal cells and mucous cell hyperplasia whereas reduced acid secretion, increased serum gastrin and pepsinogen concentrations and generalized histological changes are associated with parasites in the abomasal lumen. Parietal cells with dilated canaliculi and/or degenerative changes typical of necrosis are present soon after the transplantation of adult worms, and abomasal secretion is also affected. Anaerobic bacteria survive in greater numbers as the pH rises, with bacterial densities becoming similar to ruminal populations at an abomasal pH of 4 and above. Failure to lyse bacteria may affect adversely the nutrition of the host. The parasites may initiate the pathophysiology through the release of excretory/secretory (ES) products which either act directly on parietal cells or indirectly through enterochromaffin-like (ECL) cells by provoking inflammation or by disrupting the protective mucosal defence system.Parietal cell dysfunction is proposed as a key event which leads to loss of mature chief cells and mucous cell hyperplasia, as well as hypergastrinaemia. Inflammation increases circulating pepsinogen concentrations and may also contribute to increased gastrin secretion. Stimulation of mucosal proliferation and differentiation of parietal cells in the isthmus by the raised serum gastrin levels will be beneficial by generating a new population of active parietal cells and adequate acid secretion.     

Are bacillary bands responsible for expulsion of Trichinella spiralis?

Newborn larvae, muscle larvae, intestinal larvae, and adults of Trichinella spiralis were examined by light, scanning and transmission electron microscopy for the presence of bacillary bands and pores of the gland cells. Vital staining of living adults disclosed that the bacillary bands, approximately 5 microm in width, begin at the cephalic end of the worms, on each side of the worm, as a row of single cells. The bands extend, gradually increasing in width, to the posterior end of the worms; and in the mid-body and posterior end of the worms they measure approximately 17 microm wide and accommodate at least two cells side by side. Each gland cell communicates with the outside of the worms through a 1.5--2 microm pore, containing dense material, in the cuticle. The pores constitute anatomic weak points of Trichinella since they can be can be targeted by the host's humoral immune responses and enzymatic attacks. The appearance of patent pores after the first intestinal molt correlates in time with the early expulsion of Trichinella from the intestine, suggesting that the bands may be the source of secreted metabolic or antigenic irritants that initiate, or contribute, to the expulsion mechanisms. Further studies to elucidate the functions of these organs would greatly increase our understanding of the biology of Trichinella and the mechanisms of expulsion.     

What is leadership?

The demand for more effective leadership is heard throughout the health professions. Modern concepts of leadership differ from the traditional definition of a charismatic individual leader. Historically, leadership has been vested in positions, while today leadership is seen as a role one moves continuously into and out of, depending on the circumstance. Leadership ideas have evolved so that newer characteristics of leaders include being a team builder; possessing creative and strategic thinking skills; demonstrating honesty and integrity; and having the ability to motivate others to action. This article discusses some of the history of leadership, current thoughts on attributes of effective leaders, and the differences and similarities between leaders and managers; identifies selected teachable leadership tools; and describes various styles and purposes of existing leadership programs.