A genetic animal model of human neocortical heterotopia associated with seizures

Malformations of the human neocortex are commonly associated with developmental delays, mental retardation, and epilepsy. This study describes a novel neurologically mutant rat exhibiting a forebrain anomaly resembling the human neuronal migration disorder of double cortex. This mutant displays a telencephalic internal structural heterotopia (tish) that is inherited in an autosomal recessive manner. The bilateral heterotopia is prominent below the frontal and parietal neocortices but is rarely observed in temporal neocortex. Neurons in the heterotopia exhibit neocortical-like morphologies and send typical projections to subcortical sites; however, characteristic lamination and radial orientation are disturbed in the heterotopia. The period of neurogenesis during which cells in the heterotopia are generated is the same as in the normotopic neocortex; however, the cells in the heterotopia exhibit a "rim-to-core" neurogenetic pattern rather than the characteristic "inside-out" pattern observed in normotopic neocortex. Similar to the human syndrome of double cortex, some of the animals with the tish phenotype exhibit spontaneous recurrent electrographic and behavioral seizures. The tish rat is a unique neurological mutant that shares several features with a human cortical malformation associated with epilepsy. On the basis of its regional connectivity, histological composition, and period of neurogenesis, the heterotopic region in the tish rat is neocortical in nature. This neurological mutant represents a novel model system for investigating mechanisms of aberrant neocortical development and is likely to provide insights into the cellular and molecular events contributing to seizure development in dysplastic neocortex.     

Specific heat measurements of intercalation compounds M x TiS2 (M=3d transition metals) using ac calorimetry technique

Specific heats of 3d transition metal intercalates of 1T-CdI₂-type TiS₂, M _x TiS₂ (M=V, Cr, Mn, Fe, Co, and Ni; 0x1), have been measured in the temperature range 1.6–300 K using an ac calorimetry technique. The electronic specific heat coefficient (2–100 mJ/mole K²) and the Debye temperature _D (240–430 K) are found to depend on the guest 3d metals and their concentrations. All the intercalates show anomalous specific heat at low temperatures following an – lnT dependence ( and are constants), as found in dilute alloys.     

Monohexosylceramides of larval and adult forms of the tapeworm,spirometra erinacei

The occurrence of glycosphingolipids with unique carbohydrate structures in different species of cestode, Platyhelminth, which had been shown, previously, prompted us to study the molecular species of the monohexosylceramides (cerebrosides) in the pseudophyllidean cestode,Spirometra erinacei. The purpose of the study was to obtain a basis for future investigations of the physiological role of glycolipids in parasitism. Cerebrosides were isolated froms. erinacei at two growth stages, i.e., from the larval form (plerocercoid) and from the adult tapeworms (intestinal form). The cerebrosides were separated into four subfractions by silica gel column chromatography, and their constituents were analyzed by gasliquid chromatography, gas chromatography/mass spectrometry, and high-performance liquid chromatography/mass spectrometry. The hexoses of the cerebrosides consisted primarily of galactose in both growth stages, while only a small amount of glucose was detected. The ceramides were composed of sphinganine (d18∶0) and phytosphingosine (t18∶0) as sphingoid bases, and of nonhydroxy fatty acids ranging from C₁₆ to C₃₀ and hydroxy stearic acid (18h∶0). The cerebrosides of adult tapeworms contained more 18h∶0 than those of plerocercoids. The combination of hexoses and ceramides in the cerebroside molecules was slightly different in the two growth stages: the glucocerebrosides of plerocercoids contained only d18∶0-nonhydroxy fatty acids in their ceramide moieties, whereas those of adult tapeworms contained varying ceramide moieties. Our data indicate that the molecular species of glycolipids present were essentially homeostatic throughout growth in spite of the entirely different environmental conditions, although there were slight differences in the hexose distribution in the two growth stages.     

Vinyl polymerization: 414. Polymerization of vinyl monomer initiated by poly(N,N,N-trimethyl-N-2-methacryloxyethyl)ammonium chloride

The polymerization of vinyl monomer initiated by an aqueous solution of poly(N,N,N-trimethyl-N-2-methacryloxyethyl)ammonium chloride (poly(Q-DMAEM-CI) has been carried out at 85°C. The effects of the amounts of vinyl monomer, poly(Q-DMAEM-CI) and water on the conversion of vinyl monomer have been studied. The overall activation energy in the polymerization of MMA is estimated as 41.9 kJ mol^?1. The polymerization proceeds through a radical mechanism. The location in which the polymerization occurs is discussed. The selectivity for vinyl monomer is explained by ‘the concept of hard and soft hydrophobic areas and monomers’.     

Vinyl Polymerization. 218. Polymerization of Methyl Methacrylate in the Presence of Nylon-6 Fiber and Water

The polymerization of methyl methacrylate in the presence of nylon-6 fibers and water was carried out. It was found that the conversion in the absence of water was the same as that of thermal polymerization, but in the presence of water the conversion was much higher. When methyl methacrylate and water existed sufficiently in the polymerization system, the rate of polymerization (R_p) was given by the following equation; R_p = k (Nylon)^1,0 (Methyl methacrylate)⁰ (Water)⁰. The over-all activation energy of the polymerization was found to be 13 kcal/mole. The polymerization of styrene, acrylonitrile, vinyl acetate, and methyl acrylate could not be initiated by the system of nylon and water. Apparent grafting efficiency of polymethyl methacrylate onto nylon was calculated from the amount of polymer which was not extracted with acetone. The efficiency was independent on the reaction time and the amount of water, and increased with the amount of nylon, while it decreased with the amount of methyl methacrylate and with reaction temperature. From the fact that a major part of the polymethyl methacrylate could not be extracted, it was concluded that the polymerization of methyl methacrylate in the presence of nylon and water occured predominantly inside the fiber. The degree of the polymerization of polymethyl methacrylate formed inside the nylon fiber was considerably higher than that of homopolymethyl methacrylate formed outside the fiber. It was qualitatively recognized that the major part of the polymethyl methacrylate generated in the fiber was not grafted onto nylon, but existed as homopolymer.     

Synthesis of nanocrystalline nitrogen-rich carbon nitride powders at high pressure

Nitrogen-rich carbon nitride powders with composition close to C₄N_2.8–3.3 were synthesized by using a chemical reaction between sodium azide and hexachlorobenzene under high pressure (7.7 GPa) and a temperature of 500 °C for 30 min. The final black powders were relatively hard materials with high resistance to hot acids and common organic solvents. Analytical electron microscopy and X-ray diffraction studies showed that the powders are predominantly amorphous, containing nanometer-sized crystallites. Carbon and nitrogen K-edge structures obtained by electron energy-loss spectroscopy suggest the existence of chemical bonding between C and N, and that the amorphous carbon nitride matrix is primarily sp²-bonded. Raman and infrared features of the carbon nitride powders closely resemble those in carbon and diamond-like films and also characterize the powders as strongly disordered, sp²-bonded carbon nitride exhibiting graphite-like microdomains with dimensions of approximately 1 nm.     

Influence of electron donors on the initial stage of cyclopolymerization of 1,5‐hexadiene with MgCl2‐supported Ziegler catalysts analyzed by temperature rising elution fractionation

Additive effects of donors on the initial polymerization of 1,5‐hexadiene with the MgCl₂‐supported Ziegler catalysts were investigated by using the stopped‐flow method, temperature rising elution fractionation (TREF) analysis, and kinetic study. The cyclopolymerization of 1,5‐hexadiene proceeded within an extremely short period (≤ 0.2 s) and yielded a unique poly(methylene‐1,3‐cyclopentane). cis ring content and cis–cis unit in meso dyad of the resulting polymer were increased by the addition of electron donors. The influence of internal and external donors was examined by the estimation of kinetic parameters and TREF analysis. Because the addition of the internal donor caused an obvious change in one of the kinetic parameters and the microstructure, an isospecific active site was considered to be formed by the addition of the internal donor. In the case of the external donor, the additive effects on the stereospecificity were weaker than those of the internal donor. It was expected from TREF measurements that the external donor modified an aspecific active site into a lower isospecific active site. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2976–2983, 2002; DOI 10.1002/app.2326     

Cation-Exchange Characteristics of Sintered Hydroxyapatite in the Strongly Acidic Region

The ion-exchange behavior of hydroxyapatite (Ca₁₀(PO₄)₆-OH)₂) (HAp), fired at high temperatures, has been investigated in the strongly acidic region (pH 2 and 3). According to the present study, HAp fired above 1000°C can exchange ions from Ca²⁺ to Pb²⁺, even at pH 2, without dissolution. The molar ratios of Pb²⁺/Ca²⁺ after ion exchange are approximately unity in all cases. Ion exchange occurs in a thin layer near the surface of HAp particles fired at 1300°C. After ion exchange, Pb-Cl-apatite crystals are created in the strongly acidic region (pH 2).