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The cell patterning (proportion of spores, stalk cells, and basal disk cells) of individual asexual fruiting bodies of haploid and isogenic diploid strains of D. discoideum was examined to test the hypothesis that the patterning mechanism is based on the ‘sensing’ of only a single parameter, e.g., cell volume, in dividing the aggregate into the three cell types. If cell patterning is based on sensing only a single parameter, there is no reason to predict a change in cell patterning with ploidy change, and thus haploid and isogenic diploid strains should not differ in their cell patterning. The cell patterning of each of the three pairs of haploid and isogenic diploid strains examined was different. Therefore we conclude that the cell patterning mechanism must involve at least two components not changing in the same way with change in ploidy. The cell patterning of both the haploid and the diploid strains was qualitatively similar, i.e., relationships between the three cell types were described by equations of the same form in the haploid and diploid strains. However a quantitative change in cell patterning led to an increased percentage of stalk and basal disk cells in each diploid compared to its parent haploid. The ratio of basal disk to stalk cell was also greater in the diploids than in their parent haploids. We conclude that these are general ploidy-related changes because the cell patterning of each of the three parent haploid strains was different; the average percentage of stalk cells was 11.6% for X22 (12.4% for its diploid DU162), 20.5% for NP73 (27.2% for its diploid DP62), and 24.5% for HU127 (29.1% for its diploid DU310). One possible patterning mechanism could involve a diffusible signal (s), which shows gene dosage, interacting with cell-surface molecules which we predict occupy a limited number of sites per unit area of the cell membrane. The observed change in cell patterning leading to an increased percentage of stalk cells in diploid strains is predicted from such a model involving diffusible signal interacting with cell-surface molecules.

Investigations were performed in eight young women to determine if the findings of secondary amenorrhea and high follicle-stimulating hormone levels were due to primary ovarian follicular atresia or to other causes. Karyotypes were determined from both peripheral leukocytes and ovarian tissue; one woman had XXX/XX/XO mosaicism. Another woman had normal ovarian histology and probably had the "gonadotropin-resistant ovary syndrome." No autoimmune antibodies were detected, but one woman with myasthenia gravis also had ovarian histology that demonstrated primary ova and a developing follicle. Only five of eight women had primary ovarian follicular atresia, and two of the other three women had conditions theoretically compatible with subsequent pregnancy.

The numbers of spores, stalk cells, and basal disk cells in fruiting bodies of Dictyostelium discoideum were estimated by direct cell counting. It was found that the ratios of differentiated cells varied with the number of cells in the fruiting body. Hence, this invalidates, in D. discoideum at least, an assumption used in many theories of differentiation that proportions do not vary with size. Simple statistical analysis showed that a semilogarithmic equation could describe the relationship of spore to stalk cell number and spore to basal disk cell number, whereas a double-logarithmic equation described the basal disk and stalk cell number relationship. Studies under different environmental conditions and with different strains suggest that the basic equations describing the relationships are conserved. However, quantitative differences in the proportioning of the cell types have been observed. Previous papers concerning the proportions of D. discoideum are reviewed, and the implications of the results, in regard to theories of differentiation, are analyzed.

Two maternally derived chromosome sets and both maternal histocompatibility antigen haplotypes were identified in the tissues of a malformed triploid acardiac twin that developed within the same chorion as its normal twin. These findings indicate that the twins arose as a result of independent fertilizations, by two different spermatozoa, of a normal haploid ovum and its diploid first-meiotic-division polar body.

Publisher Summary This chapter discusses the quantitative analysis of the proportions of the Dictyostelium discoideum asexual fruiting body. The asexual fruiting body of Dictyostelium discoideum represents one of the simplest multicellular organisms. It is comprised of three cell types, spores, stalk cells, and basal disc cells, which form a linear array. As few as 10 cells and as many as 105 cells make up the fruiting body that looks roughly the same over this huge size range. The chapter also discusses the relationship between spores, stalk, and basal disc cells. Spore numbers are linearly related to total cell numbers in fruiting bodies of different sizes in strain X22, whereas both stalk cell numbers and basal disc cell numbers are exponentially related to total cell numbers. This means that proportions of the different cell types are not size invariant. For example, strain X22 fruited in the light instead of the dark has a greater percentage of both stalk and basal disc cells, but the equation relating these two cells types is unaltered. Strain X22 is a haploid segregant of the diploid DP4. There is a difference in the proportioning of strains M28 and NP14 that is statistically significant. The proportioning in strain X22 is statistically indistinguishable from strain M28. This shows that it will be possible to analyze proportioning mutants genetically.

Cell patterning, the percentage of spores and stalk cells, was measured in branched and unbranched asexual fruiting bodies of Polysphondylium pallidum. Unlike D. discoideum, where small and large fruiting bodies are more stalky than average-sized fruiting bodies, the overall cell patterning was the same in branched and unbranched fruiting bodies of all sizes in P. pallidum. Light greatly increased the numbers of fruiting bodies in P. pallidum per unit area (or decreased aggregation territory size) so that most fruiting bodies formed in the light were small and unbranched. By contrast, light had little effect on the cell patterning of P. pallidum, although there was a slight increase in the percentage of stalk cells in the light compared to the dark. This indicates that the mechanisms governing light sensitivity of aggregation territory size and cell patterning have different components in P. pallidum. The accuracy of cell patterning of individual branches of branched fruiting bodies was so imprecise as to leave doubt that patterning is occurring at the branch level. Individual whorls of branched fruiting bodies had a greater percentage spores (90%) than whole fruiting bodies (78%) and the cell patterning was relatively imprecise. Only in whole fruiting bodies was the spore:stalk ratio highly correlated. These findings are consistent with cell pattern determination operating at the whole aggregate level, rather than at the individual whorl or branch level in P. pallidum.

In the recent past, major achievements have been obtained in the understanding of the molecular defects at the basis of several different diseases. The field of 'Molecular Medicine' has thus become more solid, and several reports have been published linking the basic molecular investigation to the clinical practice. In line with this new approach to medicine a Symposium was organized where the linkage between investigations in basic science could be explored in view of clinical disorders, and vice versa. in Rosario, Argentina, September 9-11, 1999, molecular biologists, molecular pathologists and clinicians discussed the molecular defects possibly at the basis of some common diseases. This report summarizes the presentations and discussions during the symposium.