Notions of heredity in the correspondence of Edwin Grant Conklin.

This article examines five letters from the correspondence of American zoologist Edwin Grant Conklin that highlight his theories of genetic and social inheritance, in order to suggest that Conklin's eugenic beliefs--like those of many American authorities during this time--were complex and sometimes contradictory. The letters reveal the international prestige of American science after the two world wars and illuminate key moments in the emergence of the concepts of heredity and inheritance, within both the science of genetics and the social movement of eugenics.

Animals models for the development of human sexuality: a critical evaluation.

Biological explanations of human homosexuality build upon a theoretical framework developed from the study of animals, especially that of rodents. Researchers have constructed a physiological model to explain the origin and development of "masculine" and "feminine" behavior. According to this model hormones acting at critical stages in early development organize cells in key areas of the brain. After puberty these hormonally organized brain regions are purportedly capable of activation by post-pubertally produced circulating hormones. This model of sexual development, called the organizational-activational (O/A) model, has framed research on sexual behavior in animals and animal-based account of human behavior for more than 30 years. However, evidence from a variety of sources has slowly accumulated, requiring modification after modification of the original premise. Continuing to use the organizational-activational model now interferes with the acquisition of new knowledge. I sketch the outlines of an alternative bio-social program for research on the development of sexual behavior in animals.

In vitro culture of Drosophila imaginal disc cells: aggregation, sorting out, and differentiative abilities.

This paper describes the aggregation in vitro of cells dissociated from imaginal discs and demonstrates the sorting out of undifferentiated cells from different imaginal discs and from differently determined regions of the same imaginal disc, as well as the abilities of such cells to undergo pattern reconstruction when injected into larvae. Dissociated cells begin to aggregate by 1.5 hr of rotation. By 5 hr of rotation, large aggregates of loosely associated cells appear. By 18 hr the aggregates have condensed and taken on a characteristic epithelial structure. To study sorting out in undifferentiated cells, we combined a histochemical stain for acid phosphatase with the use of the acid phosphatase null mutant acphn-11. We performed cell mixing experiments with 0-2 (prospective notum) and 2-8 (prospective wing) fragments, with the A and P (prospective anterior and posterior) fragments of the dorsal mesothoracic disc and with mixtures of cells from ventral prothoracic and dorsal mesothoracic discs. We found that prospective anterior and posterior dorsal mesothoracic cells do not sort out, but that prospective notum and wing and leg and wing cells do. The results from differentiated implants are consistent with those from undifferentiated mixes.

Some determinants of cellular adhesiveness in an embryonic cell line from Drosophila melanogaster.

We have examined, under a number of conditions, the aggregation behavior of Schneider Line 2 cells established originally from embryos of Drosophila melanogaster. The work presented in this paper further establishes appropriate conditions for the study of cellular adhesion in Drosophila cell lines; shows that the adhesive capacity of Drosophila cell line cells, under our experimental conditions, depends upon the presence of CA2+ but not Mg2+; shows that Drosophila cell line cells will not aggregate in the cold; and shows that trypsin treatment inhibits the aggregation of cell line cells, although high concentrations of calcium ions interfere with the action of trypsin.

The behavior during the initial phase of in vitro aggregation of dissociated imaginal disc cells from Drosophila melanogaster.

Aspects of the initial phase of aggregation in vitro of dissociated imaginal disc cells from Drosophila melanogaster are described. Using the methods described certain interdisc differences in the percent decrease in single cell units during the first hour of aggregation can be demonstrated. In addition it is shown that prospective notum cells isolated from the dorsal mesothoracic disc show less of a decrease than do prospective wing cells. This difference shows up in a variety of different wild-type stocks and in several mutant stocks as well. Prospective notum cells from the mutation fu59 show only a limited ability to adhere to one another, while the percentage of single cell units from prospective wing blade cells from r9 larvae grown on pyrimidine-poor medium decrease less compared to cells from the same stock grown on RNA-supplemented medium. There is a significantly greater decrease in the percent single cell units in cultures of prospective eye cells than in cultures of prospective antennal cells. Furthermore, cells from the antennal disc of larvae bearing the homeotic mutation ssa show a significantly lower decrease in single cell units when grown at restrictive temperatures. In contrast, antennal disc cells from the homeotic mutation ophthalmoptera; eyeless Dominant, a mutation which affects the eye disc, are unaffected, while cells from the eye disc are slightly less able to reassociate with one another.

Interactions between FUSED and ENGRAILED, Two Mutations Affecting Pattern Formation in DROSOPHILA MELANOGASTER.

In this paper we demonstrate that the severity of the engrailed phenotype is greatly increased when engrailed is combined with the X-linked mutation fused. The secondary sex combs of fu;en flies contain from two to four times more setae than do those of en siblings. The number of transverse rows of bristles on the metatarsus of the metathoracic leg is reduced by a factor of one and a half to two in fu;en flies when compared to their en siblings, while the frequency of reversed bract polarity, bristle abnormalities and misshapen metatarsi increases greatly. In addition, fu;en flies express the en wing phenotype more completely than their siblings and have a much higher frequency of wing vein abnormalities-some of which we have interpreted as triplications of the third and first longitudinal wing veins. We briefly discuss the significance of the fused-engrailed gene interaction.

Hybrid Dysgenesis in DROSOPHILA MELANOGASTER: Morphological and Cytological Studies of Ovarian Dysgenesis.

A type of intraspecific hybrid sterility, between two strains of Drosophila melanogaster, referred to as GD (gonadal dysgenesis) sterility, is observed when females from a type of strain called M are crossed with males from a second type called P. Absence of egg-laying is characteristic of female GD sterility and its manifestation is conditional on high developmental temperatures. Morphological and cytological studies of GD sterile females are described. These individuals were normal in body size and external appearance. No defects in sperm storage were observed. Both adult and larval ovaries were drastically reduced in size in comparison with control ovaries. This ovarian dysgenesis was sometimes unilateral, but more frequently it was bilateral, particularly in females developing at the highest test temperature. The ovarioles of dysgenic ovaries contained no vitellaria; the germaria lacked any cells resembling the cystocyte clusters of normal ovaries. It is concluded that sterility results from an early blockage in ovarian development, rather than from atrophy of previously developed structures. Possible mechanisms for this developmental arrest are discussed.

Studies on the female sterile mutant rudimentary of Drosophila melanogaster. II. An analysis of aspartate transcarbamylase and dihydroorotase activities in wild-type and rudimentary strains.

The activities of the enzymes aspartate transcarbamylase (ATCase) and dihydroorotase (DHOase) were determined in adult females from a wild-type strain and from eight different alleles of the X-linked mutation rudimentary (r) of Drosophila melanogaster. The alleles chosen span the genetic map of the r locus. The characteristics of the DHOase-catalyzed reaction which converts carbamyl aspartate to dehydroorotate are briefly described. Of all of the r strains tested, only one, r9, has wild-type levels of aspartate transcarbamylase and dihydroorotase activities. The other seven show either intermediate or very low levels of activity for both enzymes. The lowered ATCase and DHOase activities observed in mutants which do not map in the region of the structural gene for these enzymes are interpreted in light of recent evidence that ATCase and DHOase are part of a three-enzyme complex.

Analysis of a newly-isolated temperature sensitive maternal effect mutation of Drosophila melanogaster.

A mutation located near the tip of the X chromosome in Drosophila melanogaster has been isolated, and its developmental effects described. This mutation (1(1)ts-1 is temperature sensitive, and at permissive temperature (18 degrees C) develops normally. However, zygotes from females raised or aged at restrictive temperature (28 degrees C) never hatch, regardless of the embryonic genotype. Midgut formation is abnormal in lethal zygotes and dorsal closure is probably incomplete. Temperature shift experiments have shown that the zygotic lethality is governed by a temperature sensitive period in oocytes of stage seven or older. If viable 1(1)ts-1 embryos are shifted to restrictive temperatures, they develop as far as the pupal stage, but never eclose. The temperature sensitive period for pupal lethality includes the last 2.5 days of pupal development and does not involve a maternal effect.