The Origin of Bodyplans

Paleontologists have documented the progressive originationof metazoan bodyplans beginning about 610 million years ago(Ma) with the major period of innovation occurring from 570Ma to about 525 Ma. The breadth of this event is now well documentedamong soft-bodied, skeletonized and trace fossils. Changes inboth the phytoplankton and in geochemical markers suggest pervasivetransformation of the environment during this interval, implicatingan ecological role in triggering this innovative burst. Theextent to which developmental innovations contributed to thisevolutionary burst requires placement of the protostome-deuterostomeancestor (PDA) in time: a PDA close to the radiation could indicatea greater role for developmental innovation. Molecular evidencepoints to a maximum age of about 670 Ma. Uncertainties overthe extent of functional homologies among the widely conserveddevelopmental control genes, and gene pathways, bracket plausibledates for such an ancestor: the maximally complex ancestor couldnot predate about 545 Ma; the least complex alternative coulddate to 575 Ma or even earlier. The nested hierarchical structureof developmental control genes and bodyplan originations suggestscertain temporal inhomogeneities to the evolutionary process:as certain developmental patterns are established they limitsubsequent evolutionary trajectories.     

Reversible Blocking Effect of Anti-mouse Immunoglobulin Serum on the Induction of Immunity and Tolerance <Emphasis Type="Italic">in vitro</Emphasis>

THE induction of blast transformation by incubating lymphocytes with anti-immunoglobulin¹ and anti-allotype² sera has suggested that these cells have immunoglobulin on their surface. This hypothesis was directly verified by the demonstration of immunoglobulin on living mouse lymphoid cells by Raff et al.³. There is much evidence to indicate that immunocompetent cells have surface receptors for antigen. This idea is based on the finding that lymphocytes can bind radioactively labelled antigen to their surface^4,5 and that specific immune unresponsiveness occurs if lymphoid cells are exposed to either highly radioactive antigen⁶ or haptens capable of forming covalent bonds with proteins^7,8. The immunoglobulin nature of these antigen receptors is suggested by recent work showing that the binding of radioactively labelled antigen can be blocked by anti-immunoglobulin sera^5,9. Reports that the adoptive immune response of mouse spleen cells can be inhibited by anti-mouse immunoglobulin sera (AMS)^9,10 suggest that the interaction of antigen with the immunoglobulin receptor sites is a crucial step in the induction of the antibody response. We report here that the inhibitory action of AMS on the immune response is potentially reversible and that the induction of immune tolerance to polymerized flagellin (POL) in vitro may be blocked in the presence of AMS.     

Naturally occurring variation in high temperature induced floral bud abortion across Arabidopsis thaliana accessions

A system to study the basis of high temperature-induced floral bud abortion using naturally occurring variation for heat-tolerance of floral development among Arabidopsis thaliana (L.) Heynh. wild-collected accessions is described. High temperature-induced floral bud abortion was dependent on both temperature and duration of exposure. Normalizing high temperature exposures to degree-hours (°C-h) above 33 °C indicated that abortion of flower buds increased as exposure increased between 200 and 300 °C-h above 33 °C and exposures > 300 °C-h above 33 °C resulted in abortion of the entire primary inflorescence. Thirteen wild-collected Arabidopsis accessions representing a latitudinal gradient were screened for variation in high temperature-induced floral bud abortion, and Col-0 and No-0 were selected as models for heat-tolerance and -sensitivity for flower development, respectively. No-0 flower buds were heat-sensitive across a wider range of developmental stages (stages 9–12, compared to stage 12 for Col-0 flower buds). Exposing the inflorescence alone to high temperature was sufficient to induce floral bud abortion, and Col-0 and No-0 photosynthetic rates were similar during high temperature exposure and recovery, indicating that high temperature induced floral abortion is not simply due to reductions in carbon assimilation under high temperatures. Determining that exposing floral buds alone to high temperature is sufficient to induce abortion and identifying the stages of floral development sensitive to high temperature-induced abortion will aid in identifying the developmental events subject to disruption under high temperatures.     

Ecteinascidia turbinata Extract Activates Components of Inflammatory Responses Throughout the Phylogenetic Spectrum

The tunicate Ecteinascidia turbinata contains a substance orsubstances capable of exerting a number of biological effects.Extracts of tunicate tissues have been shown to kill tumorcells in vitro and arrest tumor growth in vivo. The extractsalso suppress allograft rejection, graft-US.-host reactionsand lymphocyte proliferative responses as well as humoral responsesto immunization. By modifying the conditions, the extracts couldpotentiate antibody responses. In addition, they augment functionsof monocyte-macrophages as evidenced by in vitro phagocytosis,in vivo clearance, and cytotoxic activity against target cells.After studies in mice, we were able to demonstrate that theextracts could activate the phagocytic systems of shrimp, bluecrab, and fish (the American eel). In fish, the intraperitonealroute was superior to the intravenous route for promotion ofphagocytosis, increase in percent presentation of granulocytesand for enhancement of resistance to bacterial infection. Intrarriuscularand intraperitoneal injection led to local inflammation withaccumulation of granulocytes and macrophages.     

The Induction of a Phospholipid Requirement and Morphological Abnormalities in Tetrahymena pyriformis by Growth at Supraoptimal Temperatures*†

SYNOPSIS. Supplementation of a chemically-defined medium that supported excellent axenic growth of Tetrahymena pyriformis, mating type II, variety 1, at 35 C, with nucleic acid derivatives allowed full growth at 37, and further addition of phospholipids permitted equivalent growth at 39 and 1/3 of that at 40. No other nutrients tested were active at 40. Population growth could be sustained continuously by serial sub-culture every 48 hr at 40 only if the medium contained synthetic phospholipids or phospholipids isolated from natural sources. The requirement was specific for phosphatidyl choline and phosphatidyl ethanolamine. Phospholipids which contained only saturated fatty acids, and ones which contained unsaturated acids were active. Phospholipids and neutral lipids isolated from 35-grown T. pyriformis were also effective. Phospholipid precursors, sterols, neutral lipids and fatty acids were not. A 48–72 hr exposure to 40 in either the unsupplemented medium or the nucleic acid derivatives-phospholipid-supplemented medium caused extreme variation in size and shape, fractured and displaced kineties, and abnormalities of karyokinesis. The frequency and degree of teratology was greater in the unsupplemented medium, but not markedly so. A possible metabolic basis for the temperature-induced phospholipid requirement and the morphological abnormalities is discussed.