The I/LWEQ module superfamily is a class of actin-binding proteins that contains a conserved C-terminal actin-binding element known as the I/LWEQ module. I/LWEQ module proteins include the metazoan talins, the cellular slime mold talin homologues TalA and TalB, fungal Sla2p, and the metazoan Sla2 homologues Hip1 and Hip12 (Hip1R). These proteins possess a similar modular organization that includes an I/LWEQ module at their C-termini and either a FERM domain or an ENTH domain at their N-termini. As a result of this modular organization, I/LWEQ module proteins may serve as linkers between cellular compartments, such as the plasma membrane and the endocytic machinery, and the actin cytoskeleton. Previous studies have shown that I/LWEQ module proteins bind to F-actin. In this report, we have determined the affinity of the I/LWEQ module proteins Talin1, Talin2, huntingtin interacting protein-1 (Hip1), and the Hip1-related protein (Hip1R/Hip12) for F-actin and identified a conserved structural element that interferes with the actin binding capacity of these proteins. Our data support the hypothesis that the actin-binding determinants in native talin and other I/LWEQ module proteins are cryptic and indicate that the actin binding capacities of Talin1, Talin2, Hip1, and Hip12 are regulated by intrasteric occlusion of primary actin-binding determinants within the I/LWEQ module. We have also found that the I/LWEQ module contains a dimerization motif and stabilizes actin filaments against depolymerization. This activity may contribute to the function of talin in cell adhesion and the roles of Hip1, Hip12 (Hip1R), and Sla2p in endocytosis.

The ultrastructure of the sensory receptors located on the labium of the rice brown planthopper is described; possible functions of individual receptors are suggested on morphological grounds. Uniporous chemosensilla which may or may not possess a mechanoreceptive dendrite, domed multiporous chemosensilla, and mechanoreceptive pegs are present on the flattened labial tip. Mechanoreceptive pegs are distributed over the labium. The fine structure of a multilobed sensillum located on either side of the labium is also described.

Culture methods to propagate glial cells from the avascular adult rabbit neural retina are described. To determine the site(s) in the retina from which the cells originated, retina fragments were retrieved from culture at intervals after explanation and processed for light microscopy to localize surviving cells. Tritiated-thymidine radioautography was used to determine the time of onset and the localization of proliferating cells in the isolated retina and in the early culture outgrowth. Although some glial cells located just subjacent to the inner limiting membrane and at the interface between the ganglion cell and inner plexiform layers were activated to DNA synthesis in three to five days after explanation of the retina, the dominant cell type in the cultures derived from the retina appeared to be the Muller cell. Regionally, in isolated retina fragments, Muller cells became hyperplastic and formed tissue masses of proliferating cells surrounding photoreceptor remnants. These proliferating clusters could be retrieved from the culture medium after about 10 days in vitro and replated whereupon they attached to the culture substrate and gave rise to cellular outgrowths. The cells in the early explant outgrowth were heteromorphic, but passaged cultures contained a relatively homogeneous population of cells that exhibited a low maximal growth rate and senesced quickly in vitro.

The stylets of Nilapavarta lugens consist of two maxillae that interlock to form separate food and salivary ducts partially surrounded by two mandibles. The ultrastructure of the sensory innervation of the stylets is described. Each maxilla possesses five neurones which extend to the tip of the stylet. The mandibles also contain five neurones, four of which are paired. The paired neurones comprise a shorter dendrite extending part of the way along the stylet and a longer one extending to the tip. The possible functions of these neurones are discussed. Gustatory receptors are located in the small passageway leading from the food duct to the cibarium. The receptors are in two distinct groups on the epipharyngeal side and one group on the hypopharyngeal side of the food canal. Two to five neurones innervate each receptor which connects to the food canal via a small pore.

Samples of aqueous humor from rabbits and humans were examined for growth effects on subconfluent monolayer fibroblast cultures from ocular and extraocular tissues. At a concentration of 20% aqueous by medium volume, both homologous and heterologous aqueous stimulated DNA synthesis in fibroblasts from both species. The stimulation was independent of medium serum. When fibroblasts were exposed to 0 to 100% aqueous in serum-free medium or 0 to 98% aqueous in 2% serum-supplemented medium, no concentration of aqueous was observed in which DNA synthesis was inhibited. However, higher concentrations of aqueous led to increasing cell loss resulting in an apparent net inhibition of culture growth. Net growth effects of aqueous humor were, therefore, dependent upon aqueous concentration and were apparently due to the combined effects of stimulation of proliferation and reduction in cell survival.