Cutaneous basophil responses and immune resistance of guinea pigs to ticks: passive transfer with peritoneal exudate cells or serum

Resistance to infestation by larval Amblyomma americanum or Rhipicephalus sanguineus ticks was transferred to naive guinea pigs with peritoneal exudate cells (PEC) or serum from donors immunized by prior infestation with homologous tick larvae. In the A. americanum system, PEC transfer induced 87% tick rejection, which was similar to the level of resistance in actively sensitized hosts. In the R. sanguineus system, PEC conferred resistance (39% rejection) that was weaker than in actively sensitized hosts (57% rejection). In both systems, immune serum conferred significant but weaker resistance (20 to 29% rejection). In actively sensitized hosts, resistance to each tick species was specific, but there was considerable cross-reactive resistance. Basophils dominated the 24-hr challenge feeding sites of A. americanum ticks in actively sensitized hosts (69% of the infiltrate) and recipients of sensitized PEC (69%). Mononuclear cells were dominant (69% of the infiltrate) in the challenged tissues of immune serum recipients that had a significant but weaker cutaneous basophil response (24%). Mononuclear cells also dominated (58% of the infiltrate) the 24-hr challenge feeding sites of R. sanguineus ticks in actively sensitized hosts, but there were also 24% basophils. These studies demonstrate that immune resistance to tick is dependent on sensitized lymphoid cells or serum components, and that sensitized cells or serum can transfer a cutaneous basophil response that is associated with immune resistance. Rejection of ticks is usually associated with large basophil infiltrates, but sometimes mononuclear cells are dominant. Thus, immune resistance of guinea pigs to ticks is a heterogeneous response in which immune cells and serum probably act to recruit diverse effector leukocytes to mediate rejection that is specific but significantly cross-reactive.

Response of hypersensitized guinea pigs to the feeding of Amblyomma americanum ticks

Guinea pigs acquired resistance to the feeding of immature Amblyomma americanum ticks after a single infestation. The initial larval and nymphal feedings resulted in cumulative mortalities of 27.2 and 28.9%, respectively. The second and third larval infestations yielded cumulative mortalities of 50.5 and 52.4%, compared to 18.9 and 24.4% cumulative mortality from controls. Second and third nymphal feedings resulted in 75.7 and 73.4%, and ticks from controls exhibited 36.6 and 34.7% cumulative mortality. The development of host resistance adversely affected tick feeding and resulted in abnormally coloured ticks and a protracted moulting period with a marked decrease in moulting ability. Histological examination of tick feeding sites on guinea pigs challenged twice revealed greater cavity and lesion sizes in hosts fed upon by nymphs than larvae. The primary cell type within these feeding sites were basophils at 12 h post-attachment, but by 72 h post-attachment eosinophils were dominant. The upper epidermal layer adjacent to both larval and nymphal feeding ticks had accumulations of basophils with a few eosinophils. Lymphocytes may have been involved in the resistance response because local lymph nodes in resistant hosts were much larger than in uninfested and singly infested hosts. Some of these nodes had secondary germinal centres.

Sensory control of dauer larva formation in Caenorhabditis elegans

As a sensory response to starvation or overcrowding, Caenorhabditis elegans second-stage larvae may molt into a developmentally arrested state called the dauer larva. When environmental conditions become favorable for growth, dauer larvae mold and resume development. Some mutants unable to form dauer larvae are simultaneously affected in a number of sensory functions, including chemotaxis and mating. The behavior and sensory neuroanatomy of three such mutants, representing three distinct genetic loci, have been determined and compared with wild-type strain. Morphological abnormalities in afferent nerve endings were detected in each mutant. Both amphid and outer labial sensilla are affected in the mutant CB1377 (daf-6)X, while another mutant, CB1387 (daf-10)IV, is abnormal in amphidial cells and in the tips of the cephalic neurons. The most pleitropic mutant, CB1379 (che-3)I, exhibits gross abnormalities in the tips of virtually all anterior and posterior sensory neurons. The primary structural defect in CB1377 appears to be in the nonneuronal amphidial sheath cells. The disruption of neural organization in CB1377 is much greater in the adult than in the L2 stage. Of all the anterior sense organs examined, only the amphids are morphologically affected in all three mutants. Thus, one or more of the amphidial neurons may mediate the sensory signals for entry into the dauer larva stage in normal animals. Using temperature-sensitive mutants we determined that the same defects which block entry into the dauer stage also prevent recovery of dauer larvae.

Geometrical optics of tapered gradient-index rods

Starting from the ray equation, analytic solutions for the ray paths are found and used to determine the equivalent focal length and the cardinal points of tapered gradient-index (GRIN) rods.