Analysis In Vitro of Capacity of Fetal Fat Pad to Support Mammary Gland Embryogenesis

Fourteen-day fetal mammary fat pad precursor tissue (FP) has the capacity to support various fetal epithelia allowing them to accomplish their characteristic development in vivo , without their own mesenchyme (1). This capacity decreases with age of fetal fat pad and is lost postnatally. To analyse the molecular mechanism of such interaction, a method for in vitro duplication of organogenesis is necessary. In the present paper, a co-culture system of fetal epithelium with prospective mammary fat pad is described. The explanted mammary epithelium started budding, then grew out forming branched mammary ducts with end buds. Ultrastructurally, the developing ductal structures exhibited the typical mammary gland morphogenesis.
³H-Thymidine incorportion assessed by autoradiography showed that the mammary gland morphogenesis in vitro was due to the proliferation of epithelial cells, not merely to a change of the shape of the epithelium. This supportive capacity of 14-day FP also decreased with aging; explanted mammary epithelium did not grow into 17-day FP. When insoluble, non-living biomatrix was used in place of living FP the epithelium grew into the matrix but the resulting structures lacked characteristic morphology of epithelium on living fetal FP. The difference of capacity between 14-day and 17-day tissues was also lost.     

PRODUCT TESTING 1: THE DISTINCTION BETWEEN S-R (STIMULUS-RESPONSE) AND R-R (RESPONSE-RESPONSE) MODELS

There are two approaches to modeling key relations among variables when one tests products. S-R or stimulus-response modeling assumes that the researcher controls the antecedent physical variables (such as ingredients or processing), and that these physical variables are the primary cause of product-to-product differences. R-R or response-response modeling assumes that the researcher can measure co-varying physical measures of a food, but may or may not have control (or even knowledge) of the antecedent physical variables that generate product differences. S-R modeling allows for true optimization, in terms of defining the operations needed to maximize an attribute (e.g., acceptance). R-R modeling allows only a guess as to what particular combination of physical measures would correspond to a maximum level of the attribute. Often S-R and R-R modeling and optimization are confused with each other, leading to incorrect conclusions.     

Alternative Mating Behaviors of Young Male Bullfrogs

Yearling male bullfrogs often attempt to intercept and matewith females attracted to older, larger males (male parasitism)instead of defending a territory and attracting their own mates.Mating behaviors like male parasitism are thought to occur onlywhen individuals suffer some strong disadvantage in using thebehaviors that are more typical of their species. In this paper,I consider the relative benefits and costs of territorialityvs male parasitism for yearling males. Yearlings employing maleparasitism are only occasionally successful at mating, and inyears of reduced male-male competition, they produce significantlyfewer young than territorial males of their age. Yearling malesthat vary in the degree to which they employ territorial behaviorsinstead of male parasitism do not differ measurably in growthrate or chances of mortality; however, indirect informationsuggests that territoriality should entail a greater chanceof mortality. A computer simulation based solely on observeddemographic parameters predicts that yearling males should beterritorial whenever they can compete as effectively as two-year-oldmales. This condition appears to provide little restrictionon the breeding tactics of yearling males; however, data onmale-male aggressive encounters show that the size differencesbetween one-year-old and two-year-old males are usually sufficientto preclude yearling males from competing successfully. Thus,the observed behavioral plasticity of yearling males may bebest interpreted as a means of adjusting their behavioral tacticsto levels of male-male competition that can vary within andbetween breeding seasons.     

Radioiodination of Parasite Antigens with 1,3,4,6,-Tetrachloro-3α,6α-diphenylglycoluril (IODOGEN): Studies with Zygotes of Plasmodium gallinaceum

The iodinating reagent 1,3,4,6,-tetrachloro-3α,6α-diphenylglycoluril (IODOGEN³) was used to label antigens on zygotes of Plasmodium gallinaceum with parallel studies using lactoperoxidase-catalyzed radioiodination for comparison. Proteins labeled by the IODOGEN method are most probably on the surface of the zygote, as the pattern of labeled proteins analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was very similar to the pattern of lactoperoxidase-labeled proteins. Furthermore, the labeled proteins represented only a subset of the total Coomassie Blue-stained proteins. The radioiodinated zygote proteins were immuno-reactive after IODOGEN or lactoperoxidase labeling. The IODOGEN method is technically much more simple than the lactoperoxidase method and does not require the addition of extraneous proteins or H₂O₂. The advantages of IODOGEN labeling, together with the essential equivalence of results obtained by these two, methods, make the IODOGEN method attractive for labeling parasite antigens in general.