A Context-Sensitive Mechanism in Hippocampal CA1 Networks

This paper presents a possible context-sensitive mechanism in a neural network and at single neuron levels based on the experiments of hippocampal CA1 and their theoretical models. First, the spatiotemporal learning rule (STLR, non-Hebbian) and the Hebbian rule (HEBB) are experimentally shown to coexist in dendrite–soma interactions in single hippocampal pyramidal cells of CA1. Second, the functional differences between STLR and HEBB are theoretically shown in pattern separation and pattern completion. Third, the interaction between STLR and HEBB in neural levels is proposed to play an important role in forming a selective context determined by value information, which is related to expected reward and behavioral estimation.     

Purification and properties of neuraminidase isozymes in Arthrobacter ureafaciens mutant

An Arthrobacter ureafaciens mutant (M1057) capable of producing neuraminidase constitutively was isolated by NTG mutagenesis from A. ureafaciens KMS 3663. Four molecular species (L, M1, M2, and S) of neuraminidase isozymes were homogeneously purified from the mutant and parent strains by means of DEAE-cellulose, affinity chromatography, ammonium sulfate precipitation, chromatofocusing, and Ultrogel AcA44 gel filtration. The molecular weights of L, M1, M2, and S isozymes were shown to be approximately 88,000, 66,000, 66,000, and 52,000, respectively. The optimal pHs and Km values of these isozymes for N-acetylneuraminosyl-alpha,(2-6)-lactose were 4.5-5.5 and 0.6-0.8 mM. Neuraminidase L, M1, M2, and S were able to hydrolyze oligosaccharides, glycoproteins and gangliosides containing alpha,(2-3)-, alpha,(2-6)-, and alpha,(2-8)-linked N-acetylneuraminic acid. Among these isozymes isolated, isozyme S was most active on colominic acid.     

A novel sulfatase from Pseudomonas testosteroni hydrolyzing lithocholic acid sulfate.

Pseudomonas testosteroni ATCC 11996 was found to produce a novel bile acid sulfate sulfatase that hydrolyzes the sulfate ester bond in lithocholic acid sulfate (LCA-S). The enzyme synthesis was induced by several kinds of bile acids including LCA-S. Mn2+ functioned as an essential component for the enzyme synthesis and SO4(2-) suppressed it. This sulfatase hydrolyzes LCA-S to isolithocholic acid and sulfuric acid with inversion of alpha- to beta-configuration of the hydroxyl group at the third position of lithocholic acid.     

Growth of fetal rat gastro-intestinal epithelial cells is region-specifically controlled by growth factors and substrata in primary culture

The mammalian gastro-intestinal tract can be divided into three parts: esophagus and forestomach, glandular stomach, and intestine. We have previously reported primary culture systems for duodenal and glandular stomach epithelial cells in which the cells express tissue-specific marker proteins. However, the effects of growth factors and substrata on cell growth have not been fully investigated. In this study a primary culture system was established for forestomach epithelial cells and the mechanism by which the growth of gastro-intestinal epithelial cells is controlled in primary culture was examined. Forestomach, glandular stomach and duodenal epithelial cells proliferated rapidly in culture, increasing their numbers about 30-, 20-and 10-fold, respectively, in the first 5 days. Scanning electron microscopy showed that these three types of epithelial cells exhibited region-specific morphologies in culture. Results on the effects of growth factors and substrata on the proliferation of the epithelial cells revealed that the culture conditions required to induce maximal epithelial growth differed. Forestomach and glandular stomach epithelial cells required similar combinations of growth factors to proliferate, and these were quite different from those required for duodenal epithelial cells. Glandular stomach and duodenal epithelial cells could proliferate in a serum-free condition while forestomach epithelial cells could not. Thus, glandular stomach epithelial cells exhibited intermediate characteristics between forestomach and duodenal epithelial cells regarding their growth factor requirement. Glandular stomach and duodenal epithelial cells could not proliferate on plastic without collagen substrata while forestomach epithelial cells could. Duodenal epithelial cells proliferated faster on collagen gels than on collagen films, and forestomach epithelial cells faster on collagen films than on collagen gels. Glandular stomach epithelial cells proliferated similarly on both substrata. Thus again, glandular stomach epithelial cells exhibited intermediate characteristics between forestomach and duodenal epithelial cells regarding their substratum dependency. We conclude that the growth of gastro-intestinal epithelial cells is affected by both growth factors and substrata, and that glandular stomach epithelial cells exhibit intermediate characteristics between forestomach and duodenal epithelial cells in responding to these factors. These results suggest that a head-to-tail gradient exists in the gastro-intestinal tract which controls the epithelial response to growth factors and substrata.     

Low Latency High Bandwidth Message Transfer Mechanisms for a Network Interface Plugged into a Memory Slot

The communication architecture of the DIMMnet-1 network interface based on MEMOnet is described. MEMOnet is a class of a network interface plugged into a memory slot. This paper proposes three message transfer mechanisms named atomic on-the-fly sending (AOTF), block on-the-fly sending (BOTF) and OTF receiving with selective address translation. The DIMMnet-1 prototype will have an ASIC named Martini, two banks of PC133 based SO-DIMM slots and an 8 Gbps full duplex optical link. The software overhead incurred to generate a message is only 1 CPU cycle and the estimated hardware delay is 105 ns using AOTF. The estimated hardware delay for receiving to on chip memory using OTF receiver is 90 ns. The estimated achievable sending bandwidth of DIMMnet-1 using BOTF is 984 MB/s which was observed in our experiments. This bandwidth is 7.4 times higher than the maximum bandwidth of PCI. This high performance is available even when simultaneous sending and receiving are executed on a cheap personal computer with DIMM slots. This paper also discribes the effects of BOTF for a PCI-based NIC.