Using diffusion distances for flexible molecular shape comparison

Background  

Many molecules are flexible and undergo significant shape deformation as part of their function, and yet most existing molecular shape comparison (MSC) methods treat them as rigid bodies, which may lead to incorrect shape recognition.     

Evaluation of past and potential phosphorus uptake at the Orlando Easterly Wetland

The Orlando Easterly Wetland (OEW), located near Christmas, Florida, USA, is among the longer-lived treatment wetlands in the United States. It was established in the late 1980s to reduce nitrogen and phosphorus concentrations from tertiary treated wastewater bound for the St. Johns River. A goal of 0.07 mg/l total phosphorus concentration has been set by the regulating agency (St. Johns River Water Management District). In order to understand and define the operating conditions for which this target could be met, a systematic study of historic phosphorus uptake was performed using a traditional first-order model. Phosphorus uptake performance is shown to correlate well with hydraulic performance for two parallel upstream cells. The first-order model is enhanced with predictive capabilities that acknowledge the correlation between the phosphorus uptake rate constant and the hydraulic loading rate observed in the system. Inherent limitations with the first-order modeling approach are addressed and uncertainty in model performance is used to bound predictions.     

APOLAR MOVEMENT OF ZEATIN THROUGH COLEUS PETIOLES AND PISUM ROOTS AS ESTIMATED BY BIOASSAY AND RADIOACTIVE LABELLING

The movement and polarity of zeatin, a highly active, endogenous cytokinin, through petioles and roots were tested in the classical experimental arrangement using excised 5-mm sections. Zeatin in the receiver cylinders of agar was measured by soybean callus bioassay and by liquid scintillation counting of ¹⁴C that had been added in the donor cylinders as [8-¹⁴C] zeatin. Both methods agreed in showing movement, but there was no polarity in Coleus #5 petioles. The amounts moved were about one-tenth of the GA-3 movement through petioles of the third pair of leaves of the same clone. Movement of ¹⁴C-zeatin through Pisum roots was similarly statistically significant but non-polar; the amounts moved were similar to those previously observed for polar GA-3 movement through Zea roots.     

The acquisition of conscience and Developmental Systems Theory

Summary Proponents of Developmental Systems Theory (DST) argue that it offers an alternative to current research programs in biology that are built on the historic disjunction between evolutionary and developmental biology. In this paper I illustrate how DST can be used to account for the acquisition of an important component of moral agency, conscience. Susan Oyama, a major proponent of DST, has set moral issues outside the compass of DST. Thus, I examine her reasons for restricting DST to non-moral matters, and argue that they are not decisive. On the positive side, I argue that DST not only is compatible with attempts to describe and explain moral agency but also aids us in understanding it. In particular, I show how DST can provide a fruitful perspective for viewing some significant current findings and theories in moral developmental psychology about the acquisition of conscience. The familiar dichotomies resisted by DST, those between genes and environment, inherited and acquired, innate and learned, and biological and cultural, have also plagued human developmental psychology, including moral development. By bringing a DST perspective to the study of moral development, I illustrate how a DST perspective might offer a promising way to reconceive that phenomenon, and provide some insights into how further work in understanding the development of moral agency might proceed. Thus, I hope to contribute to the current efforts of proponents of DST to integrate developmental and evolutionary considerations.     

Paternal cyclophosphamide treatment causes postimplantation loss via inner cell mass-specific cell death.

Treatment of the father with the anticancer alkylating agent cyclophosphamide has negative effects on embryonic development in the rat. Four-week treatment of male rats with a low dose of cyclophosphamide causes a dramatic, dose-dependent increase in postimplantation death of the progeny. Several recent studies have indicated that the paternal genome is required for the development of the extraembryonic tissues. Thus, the purpose of this study was to determine which tissues of the implanting embryo were affected by paternal exposure to cyclophosphamide. Male Sprague-Dawley rats were given cyclophosphamide (6 mg/kg/day) or saline by gavage and bred to untreated female rats after 4 weeks of treatment. Pregnant female rats were killed on day 7 of gestation, and implantation sites were dissected from the uterus, fixed, embedded in Epon for semithin serial sectioning, and stained for subsequent light microscopy. Strikingly, many of the implantation sites of affected embryos sired by treated males displayed an apparently normal trophectoderm enclosing a region of dying cells, containing dark-stained pyknotic nuclei. Very few or no inner cell mass-derived embryonic cells were present in these implantation sites. Therefore, there is a selective death of inner cell mass-derived cells in day 7 implantation sites obtained from the progeny of cyclophosphamide-treated males. The results of this study suggest that treatment of the male with cyclophosphamide can affect paternal genes specifically required for development of the inner cell mass cells of the embryo, without an apparent effect on those genes required for normal trophectoderm.