Distinguished Lecture in Archeology: Breaking and Entering the Ecosystem—Gender, Class, and Faction Steal the Show

This article was presented as the third annual Distinguished Lecture in Archeology at the 90th annual meeting of the American Anthropological Association, November 22, 1991, in Chicago, Illinois.     

Comparisons of tests for aneuploidy

The fundamental problems that face us in the development of suitable assay systems for the detection of potentially aneugenic (aneuploidy-inducing) chemicals include: (a) the diversity of cellular targets and mechanisms where perturbations of structure and function may give rise to changes in chromosome number, and (b) the phylogenetic differences that exist between species in their mechanism and kinetics of cell division and their metabolic profiles. A diverse range of assay systems have been developed, which have been shown to have potential for use in the detection of either changes in chromosome number or of perturbations of the events which may be causal in the induction of aneuploidy.

Chromosome number changes may be detected cytologically by karyotypic analysis, or by the use of specialised strains in which aneuploid progeny may be observed due to phenotypic differences with aneuploid parental cells or whole organisms. Techniques for the detection of cellular target modifications range from in vitro studies of tubulin polymerisation to observations of the behaviour of various cellular organelles and their fidelity of action during the division cycle.

The diversity of mechanisms which may give rise to aneuploidy and the qualitative relevance of events observed in experimental organisms compared to man make it unlikely that the detection and risk assessment of the aneugenic activity of chemicals will be possible using a single assay system. Optimal screening and assessment procedures will thus be dependent upon the selection of an appropriate battery of predictive tests for the measurement of the potentially damaging effects of aneuploidy induction.     

Ultrastructure and histochemistry,of the stomach of Asplanchna sieboldi

Stomach cells of female Asplanchna sieboldi are specialized for absorption and intracellular digestion of nutrients. Evidence is presented to show that electron-opaque colloidal substances, present in the medium and within digestive vacuoles of the prey (Paramecium), are taken up by the stomach cells at the apical cell membrane and sequestered within food vacuoles which contain hydrolases working in both the acid and alkaline pH range. The stomach cells are also implicated in the absorption of molecules below the resolving power of the electron microscope. In rotifers possessing a complete digestive tract, this task is presumed to be handled by the intestine.     

Mitochondrial DNA of the extinct quagga: Relatedness and extent of postmortem change

Sequences are reported for portions of two mitochondrial genes from a domestic horse and a plains zebra and compared to those published for a quagga and a mountain zebra. The extinct quagga and plains zebra sequences are identical at all silent sites, whereas the horse sequence differs from both of them by 11 silent substitutions. Postmortem changes in quagga DNA may account for the two coding substitutions between the quagga and plains zebra sequences. The hypothesis that the closest relative of the quagga is the domestic horse receives no support from these data. From the extent of sequence divergence between horse and zebra mitochondrial DNAs (mtDNAs), as well as from information about the fossil record, we estimate that the mean rate of mtDNA divergence in Equus is similar to that in other mammals, i.e., roughly 2% per million years.     

Comparative biochemical and immunological studies of the glycine betaine synthesis pathway in diverse families of dicotyledons

Members of the Chenopodiaceae can accumulate high levels (>100 mol·(g DW)^-1) of glycine betaine (betaine) in leaves when salinized. Chenopodiaceae synthesize betaine by a two-step oxidation of choline (cholinebetaine aldehyde betaine), with the second step catalyzed by betaine aldehyde dehydrogenase (BADH, EC 1.2.1.8). High betaine levels have also been reported in leaves of species from several distantly-related families of dicotyledons, raising the question of whether the same betaine-synthesis pathway is used in all cases.Fast atom bombardment mass spectrometry showed that betaine levels of >100 mol·(g DW)^-1 are present in Lycium ferocissimum Miers (Solanaceae), Helianthus annuus L. (Asteraceae), Convolvulus arvensis L. (Convolvulaceae), and Amaranthus caudatus L. (Amaranthaceae), that salinization promotes betaine accumulation in these plants, and that they can convert supplied choline to betaine aldehyde and betaine. Nicotiana tabacum L. and Lycopersicon lycopersicum (L.) Karst. ex Farw. (Solanaceae), Lactuca sativa L. (Asteraceae) and Ipomoea purpurea L. (Convolvulaceae) also contained betaine, but at a low level (0.1–0.5 mol·(g DW)^-1. Betaine aldehyde dehydrogenase activity assays, immunotitration and immunoblotting demonstrated that the betaine-accumulating species have a BADH enzyme recognized by antibodies raised against BADH from Spinacia oleracea L. (Chenopodiaceae), and that the M_r of the BADH monomer is in all cases close to 63 000. These data indicate that the cholinebetaine aldehydebetaine pathway may have evolved by vertical descent from an early angiosperm ancestor, and might be widespread (albeit not always strongly expressed) among flowering plants. Consistent with these suggestions, Magnolia x soulangiana was found to have a low level of betaine, and to express a protein of M_r 63 000 which cross-reacted with antibodies to BADH from Spinacia oleracea.Abbreviations BADH Betaine aldehyde dehydrogenase - DCIMS desorption chemical ionization mass spectrometry - FABMS fast atom bombardment mass spectrometry - M_r relative molecular mass - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate - TLC thin-layer chromatography     

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Transneuronal degeneration in the Rolando substance of the primate spinal cord evoked by axotomy-induced transganglionic degenerative atrophy of central primary sensory terminals

Summary Transection of the sciatic nerve in Rhesus monkeys and the consequent transganglionic degenerative atrophy (TDA) of central terminals of primary afferents result in transneuronal degeneration of substantia gelatinosa (SG) cells. Severe degeneration is characterized by an increased electron density of the nucleus and by conspicuous shrinkage of the cytoplasm, mitochondrial swelling, dilation of cisterns of the rough-surfaced endoplasmic reticulum, accumulation of free ribosomes and an electron-dense material in the cytoplasm. In the mild form, dilation of cisternal elements of the endoplasmic reticulum, swollen mitochondria and accumulation of free ribosomes takes place. About 10% of SG cells in segment L₅ undergo the severe form whereas the rest shows signs of the mild form. Cytoplasmic alterations that occur during transneuronal degeneration seem to start at the level of subsurface cisterns. Dendrites and axons of transneuronally degenerating SG cells also show a conspicuous electron density. By analyzing the synaptic relationships of such darkened dendrites, connections in the upper dorsal horn can be deciphered. Modular units of the primary nociceptive analyzer that evaluate noxious and innocuous inputs on the basis of thin versus thick (AC/A) afferent activity and subjecting them to descending control appear to be recruited from structurally dispersed elements of synaptic glomeruli. These are arranged alongside dendritic processes of large antenna cells which relay impulses to projection cells of the spinothalamic tract.     

Influence of cyanobacterial diet on Asplanchna predation risk in Brachionus calyciflorus

Asplanchna sylvestrii does not discriminate between groups of Brachionus calyciflorus fed either the cyanobacterium Anabaena flos-aquae or a control diet of Euglena gracilis. We based our analysis on the observed probabilities of attack, capture and ingestion during encounters between predator and prey. While A. sylvestrii was very sensitive to brachionid size, we found no significant affects of prey diet on predatory behavior. Thus, cyanobacterial diet did not influence the short-term predation risk of B. calyciflorus exposed to an effective predator. On the other hand, matched cohorts of A. sylvestrii fed B. calyciflorus cultured on the cyanobacterium reproduced more slowly than those fed the same prey cultured on the control food. With prolonged sympatry, therefore, the long-term risk of Asplanchna predation may be reduced for Brachionus by the latter's consumption of cyanobacteria.