Light intensity appears to be more important than an endogenous seasonal clock for regulating structural rhythms in the lateral eye of the horseshoe crab.

The lateral compound eye of the American horseshoe crab, Limulus polyphemus, is an established model system for studying visual and circadian processes. Previous studies have shown there is an endogenous rhythm in retinal structure and this rhythm is enhanced by light. The purpose of this study was to determine whether changes in natural lighting influence these rhythms independent of season. To test this concept, horseshoe crabs were maintained in an aquarium tank and exposed to natural lighting only. The angle of the sun and foliage outside the room where the horseshoe crabs were maintained were such that more natural lighting reached the aquarium tank during winter days than summer days despite the fact that sunlight is more intense in the summer. Horseshoe crabs were sacrificed 2 hours, 5 hours, and 8 hours following local sunrise on a winter day (January 11th) and a summer day (June 19th), respectively, and the dimensions of several retinal parameters were quantified. Preliminary data indicate that certain structural rhythms were significantly more pronounced on the winter day when natural lighting was more intense. For example, 8 hours following sunrise, apertures were 4.2 times as long and 3.2 times more narrow on the winter day than on the summer day. These data suggest that the intensity of natural lighting is more important for regulating structural rhythms in the lateral eye than an endogenous seasonal clock.

Apparent inhibition of apoptosis by polyamines and aminothiols in DNA fragmentation assays is artifactual.

We report that, in commonly used DNA fragmentation assays, polyamines and the radioprotective aminothiol WR1065 artifactually depress the degree of spontaneous or induced cellular apoptosis in two distinct ways. Firstly, in assays utilizing Hoechst 33258 dye to measure apoptotic DNA, both amines quench the fluorescence of low affinity dye/DNA binding resulting in preferential underestimation of DNA in the apoptotic DNA fraction and a resultant underestimation of the extent of DNA fragmentation. Secondly, these amines can cause aggregation and condensation of apoptotic DNA, causing anomalous sedimentation under conditions universally employed to separate apoptotic from intact DNA in cell lysates. This anomalous sedimentation of apoptotic DNA leads to underestimation of fragmentation in fluorescence assays as well as in agarose gel assays. We demonstrate that manipulation of the ionic strength of the lysis buffer or lowering the dye concentration ameliorates the effects of dye quenching in the Hoechst assay. Alternatively, this effect is alleviated by substituting DAPI for Hoechst in this assay. Inclusion of a polyanion to the lysis buffer antagonizes the condensation and anomalous sedimentation of apoptotic DNA observed regardless of which dye is used in the assay. These studies call into question the validity of previously reported studies suggesting that polyamines and the radioprotective aminothiol, WR1065, inherently suppress the apoptotic process and underline the need to consider alternative endpoints of apoptosis such as morphology in order to assess effects on cellular apoptosis of exogenously added agents, particularly di- or polycations.

Structure-activity relationships among aromatic analogs of trail-following pheromone of subterranean termites.

A series of 12 substituted (Z)-4-phenyl-3-buten-l-ol (PBO) derivatives were synthesized and evaluated for trail-following activity in five species of subterranean termites in the generaCoptotermes, Prorhinotermes, Reticulitermes, andSchedorhinotermes (Isoptera: Rhinotermitidae). The unsubstituted parent PBO was the most active for all species, and electron-withdrawing and electron-donating groups both reduced potency. Sensitivity to substitution in the ortho position suggests steric inhibition of binding by the 2'-substituted analogs. Different sensitivities to these pheromone analogs were found among the five species, withR.flavipes andS. lamanianus showing the highest level of trail-following activity for the PBO analogs.