Previous research has demonstrated that distinct, gender-related differences exist in lacrimal glands in a variety of adult species. The objective of the current investigation was to examine whether this influence of gender extends throughout development and aging. Towards that end, morphological parameters of the lacrimal gland, as well as the volume, protein and IgG content of tears, were measured in male and female infant, preweanling, pubertal, adult, mid-life and senescent rats. Our results showed that dramatic, age-related variations occurred in the weight and morphological appearance of the lacrimal gland. Moreover, the magnitude of structural changes was dependent upon gender. Acinar area was significantly greater in lacrimal tissue of males, as compared to females, at all ages except pre-weanling; this sexual dimorphism was most evident in senescent rats. In contrast, acinar density in lacrimal glands of females was higher than, or equal to, that of males throughout development and aging. With regard to tears, pronounced increases were evident in tear volume, protein and IgG content from the pre-weanling stage to adulthood. After this time, these tear indices tended either to plateau or rise slightly until senescence. Gender had little or no impact of the volume of, or protein and IgG level in, tears. Of interest, the IgG/protein ratio in tears was 49- to 105-fold less than that found in lacrimal tissue, indicating that IgG moves down a gradient from the lacrimal gland to tears. Overall, our findings demonstrate that gender has a significant influence on lacrimal gland structure during development and aging. However, this impact is limited with respect to tear volume and protein content.

We report that the competitive translational activity of alfalfa mosaic virus coat protein mRNA (CP RNA), a nonadenylated mRNA, is determined in part by the 3 untranslated region (UTR). Competitive translation was characterized both in vitro, with cotranslation assays, and in vivo, with microinjected Xenopus laevis oocytes. In wheat germ extracts, coat protein synthesis was constant when a fixed amount of full-length CP RNA was cotranslated with increasing concentrations of competitor globin mRNA. However, translation of CP RNA lacking the 3 UTR decreased significantly under competitive conditions. RNA stabilities were equivalent. In X. laevis oocytes, which are translationally saturated and are an inherently competitive translational environment, full-length CP RNA assembled into large polysomes and coat protein synthesis was readily detectable. Alternatively, CP RNA lacking the 3 UTR sedimented as small polysomes, and little coat protein was detected. Again, RNA stabilities were equivalent. Site-directed mutagenesis was used to localize RNA sequences or structures required for competitive translation. Since the CP RNA 3 UTR has an unusually large number of AUG nucleotide triplets, two AUG-containing sites were altered in full-length RNA prior to oocyte injections. Nucleotide substitutions at the sequence GAUG, 20 nucleotides downstream of the coat protein termination codon, specifically reduced full-length CP RNA translation, while similar substitutions at the next AUG triplet had little effect on translation. The competitive influence of the 3 UTR could be explained by RNA-protein interactions that affect translation initiation or by ribosome reinitiation at downstream AUG codons, which would increase the number of ribosomes committed to coat protein synthesis.