During dominant-lethal testing for muta-genic effects, chemicals are usually administered intraperitoneally or orally to male animals as a single dose. These treated animals are subsequently housed for mating with virgin females which are replaced at weekly intervals. For screening purposes, a reduction in total living implants is monitored as an indication of the induction of chromosomal anoma...

Consider a scheduling problem of parallel computations in multiproces-sor systems. Let a parallel program be represented by a task graph, where vertices represent tasks and arcs represent the communications between the tasks. An in-terprocessor communication time incurs when two tasks assigned to two diierent processors have to communicate. Such a scheduling problem has recently been studied in...

There are several methods for approximating the multiple zeros of a nonlinear function when the multiplicity is known. The methods are classified by the order, informational efficiency and efficiency index. Here we consider other criteria, namely the basin of attraction of the method and its dependence on the order. We discuss all known methods of orders two to four and present the basin of att...

Observations have been made upon the nature of early and late post-tetanic potentiation and upon post-tetanic block of presynaptic collaterals with particular reference to behavior in circumstances of varied duration and frequency of conditioning stimulation. Early potentiation is most conspicuous following brief tetani at high frequency, late potentiation following long tetani, much lower freq...

Mini-Monograph series this year, instead publishing more Review articles on topics that might once have been covered by Mini-Monographs. Here, we explain that decision and give some historical perspective on the Mini-Monographs. EHP was begun in 1972 by David P. Rall, then director of the NIEHS. In addition to publishing original research articles, the journal was intended as a means of publish...

Synaptic interactions are essential to neural network models of all levels of complexity. Synaptic interactions in \realistic" network models pose a particular challenge, since the aim is not to only to capture the essence of synaptic mechanisms, but also to do so in a computationally eecient manner to facilitate simulations of large networks. In this paper, we review several types of models wh...

A recent report has provided evidence that there are no significant increases in the neuronal input conductance during the response of cortical cells in cat visual cortex to non-preferred visual stimuli (Douglas et al., 1988). A criticism of experiments of this kind is that changes in the membrane conductance occurring in the dendritic tree may not be visible from electrodes that impale the som...

Vitrification is a method of storing cells in a supercooled state, and is particularly useful for the cryostorage of embryos. With a supply of liquid nitrogen and simple apparatus, vitrification in the field situation is feasible and is potentially simpler and cheaper than the standard freezing processes. However, survival of embryos after vitrification has not yet proved better than after free...

we lost a great human being, a staunch advocate for public health, a thorough and delving scientist, and a humanitarian par excellence. Lorenzo Tomatis, MD, above all, was a learned teacher and creative innovator. His accomplishments are legion, and his far-reaching impact on human health, including the well-being of future generations, will be impossible to replace. Tomatis was clearly a true ...

Our previous experiments on the mechanism of action of estradiol (l-5) had led to the hypothesis that the soluble protein fraction (Ssr,ooo) of homogenates of human plac.enta contains a DPNl-linked isocitric dehydrogenase that is activated by minute amounts of estrogen added in vitro. The same fraction when incubated with TPN instead of DPX showed marked TPN-linked isocitric dehydrogenase activ...