Enantiomerization of 2,2′-diisopropylbiphenyl during chiral inclusion gas chromatography: Determination of the rotational energy barrier by computer simulation of dynamic chromatographic elution profiles

By computer simulation of experimental dynamic gas chromatographic elution profiles, the rotational energy barrier ΔG⁼ of racemic 2,2′-diisopropylbiphenyl has been determined as 114.6–115.0 kJ/mol (75–100°C). These data are in good agreement with a value that was determined previously by measuring the racemization kinetics of an enriched sample. This indicates that there is no measurable catalytic or inhibitory effect of the stationary phase. © 1994 Wiley-Liss, Inc.     

CCK－8和NDAP对大鼠脑和脊髓组织c－fos表达的影响

为探讨八肽胆囊收缩素（ＣＣｋ－８）和阿片肽相互作用的分子机理,利用抗体免疫沉淀技术研究了ＣＣＫ－８与ＮＤＡＰ（ｋ阿片受体激动剂）对大鼠脑（去皮层和小脑）和脊髓背柱组织Ｆｏｓ蛋白的影响。结果表明,０．１μｍｏｌ／ＬＣＣＫ－８可显著刺激脑和脊髓组织中Ｆｏｓ蛋白增加（分别是对照组的３．８倍和３．６倍）。相同浓度的ＮＤＡＰ对Ｆｏｓ蛋白的生成亦有一定的诱导作用,分别是对照组的２．７倍和２．６倍。ＣＣＫ－８和ＮＤＡＰ共同处理组织,Ｆｏｓ蛋白生成水平相似（脑）或高于（脊髓）ＣＣＫ~－８单独诱导的水平。结果表明,ＣＣＫ－８和ＮＤＡＰ均可直接诱导大鼠脑和脊髓组织ｃ－ｆｏｓ的表达,它们对ｃ－ｆｏｓ表达的相互作用在脑和脊髓中呈现不同的模式。     

Rate of 59Fe Uptake into Brain and Cerebrospinal Fluid and the Influence Thereon of Antibodies Against the Transferrin Receptor

Abstract: Uptake of ⁵⁹Fe from blood into brains of anaesthetized rats and mice has been studied by intravenous infusion of [⁵⁹Fe]ferrous ascorbate or of ⁵⁹Fe-transferrin, the results not being significantly different. Uptakes in the rat were linear with time, but increased at longer times in the mouse. Transfer constants, K _in (in ml/g/h × 10³), for cerebral hemispheres were 5.2 in the adult rat and 5.6 in the mouse. These K _in values corresponded to ⁵⁹Fe influxes of 145 and 322 pmol/g/h, respectively. ⁵⁹Fe uptake into the mouse brain occurred in the following order: cerebellum > brainstem > frontal cerebral cortex > parietal cortex > occipital cortex > hippocampus > caudate nucleus. In genetically hypotransferrinaemic mice, ⁵⁹Fe uptake into brain was 80–95 times greater than in To strain mice. Pretreatment of young rats and mice with monoclonal antibodies to transferrin receptors, i.e., the anti-rat immunoglobulin G OX 26 and the anti-mouse immunoglobulin M RI7 208, inhibited ⁵⁹Fe uptake into spleen by 94% and 98%, respectively, indicating saturation of receptors. The antibodies reduced ⁵⁹Fe uptake into rat brain by 35–60% and that into mouse brain by 65–85%. Although a major portion of iron transport across the blood-brain barrier is normally transferrin-mediated, non-transferrin-bound iron readily crosses it at low serum transferrin levels.     

Calcium/Calmodulin-Stimulated Protein Kinase II Is Present in Primary Cultures of Cerebral Endothelial Cells

Abstract: Calcium/calmodulin-stimulated protein kinase II (CaMPK II). a major kinase in brain, has been established to play an important role in neurotransmitter release and organization of postsynaptic receptors, and it is known to be involved in long-term potentiation and memory. Less is known about the function of this enzyme in nonneural cells. Here we report on the production, presence, and phosphorylation of the α-subunit of CaM-PK II in primary cultures of cerebral endothelial cells. These results raise the possibility that α-CaM-PK II can act as one of the key enzymes of calcium-mediated intracellular signaling in the cerebral endothelial cells and suggest that α-CaM-PK II may participate in such basic cellular processes as permeability in physiological and pathological conditions.     

Presynaptic α2 Adrenoceptors Inhibit Glutamate Release from Rat Spinal Cord Synaptosomes

Abstract: The presynaptic regulation of amino acid release from nerve terminals was investigated using synaptosomes prepared from the rat spinal cord. The basal releases of endogenous glutamate (Glu), aspartate (Asp), and γ-amino-butyric acid (GABA) were 34.6, 21.5, and 10.0 pmol/min/mg of protein, respectively. Exposure to a depolarizing concentration of KCl (30 m M ) evoked 2.7-, 1.5-, and 2.9-fold increases in Glu, Asp, and GABA release, respectively. Clonidine reduced the K⁺-evoked overflow of Glu to 56% of the control overflow with a potency (IC₅₀) of 17 n M , but it did not affect K⁺-evoked overflow of Asp, GABA, and their basal releases. Similarly, noradrenaline inhibited the K⁺-evoked overflow of Glu, although phenylephrine and isoproterenol showed no effect. The inhibitory effect of clonidine was counteracted by α₂-adrenoceptor antagonists, rauwolscine, yohimbine, and idazoxan, regardless of the imidazoline structures. Because Glu is considered a neurotransmitter of primary afferents that transmit both nociceptive and nonnociceptive stimuli in the spinal cord, these data suggest that part of Glu release may be regulated by the noradrenergic system through α₂ adrenoceptors localized on the primary afferent terminals.     

Cellular components of the immune barrier in the spinal meninges and dorsal root ganglia of the normal rat: immunohistochemical (MHC class II) and electron-microscopic observations

This report deals with the distribution, morphology and specific topical relationships of bone-marrow-derived cells (free cells) in the spinal meninges and dorsal root ganglia of the normal rat. The morphology of these cells has been studied by transmission and scanning electron microscopy. Cells expressing the major histocompatibility complex (MHC) class II gene product have been recognized by immunofluorescence. At the level of the transmission electron microscope, free cells are found in all layers of the meninges. Many of them display characteristic ultrastructural features of macrophages, whereas others show a highly vacuolated cytoplasm and are endowed with many processes. These elements lack a conspicuous lysosomal system and might represent dendritic cells. Scanning electron microscopy has revealed that free cells contact the cerebrospinal fluid via abundant cytoplasmic processes that cross the cell layers of the pia mater and of the arachnoid. Cells expressing the MHC class II antigen are also found in all layers of the meninges. They are particularly abundant in the layers immediately adjacent to the subarachnoid space, in the neighbourhood of dural vessels, along the spinal roots and in the dural funnels. In addition to the meninges, strong immunoreactivity for MHC class II antigen is observed in the dorsal root ganglia. The ultrastructural and immunohistochemical findings of this study suggest the existence of a well-developed system of immunological surveillance of the subarachnoid space and of the dorsal root ganglia.     

Successful synthesis of a glial-specific blood–brain barrier shuttle peptide following a fragment condensation approach on a solid-phase resin

Successful manual synthesis of the TD2.2 peptide acting as a blood–brain barrier shuttle was achieved. TD2.2 was successfully synthesised by sequential condensation of four protected peptide fragments on solid-phase settings, after several unsuccessful attempts using the stepwise approach. These fragments were chosen to minimise the number of demanding amino acids (in terms of coupling, Fmoc removal) in each fragment that are expected to hamper the overall synthetic process. Thus, the hydrophobic amino acids as well as Arg(Pbf) were strategically spread over multiple fragments rather than having them congested in one fragment. This study shows how a peptide that shows big challenges in the synthesis using the common stepwise elongation methodology can be synthesised with an acceptable purity. It also emphasises that choosing the right fragment with certain amino acid constituents is key for a successful synthesis. It is worth highlighting that lower amounts of reagents were required to synthesise the final peptide with an identical purity to that obtained by the automatic synthesiser.     

Embedding of Neural Tissue in Agarose or Glyoxyl Agarose for Vibratome Sectioning

Agarose was used to embed the brain or spinal cord of lampreys or rats before cutting vibratome sections. Agarose embedding was compatible with immunocytochemistry or the use of horseradish peroxidase as a neuroanatomical tracer. Concentrated agarose with high intrinsic gel strength was optimal for embedding glutaraldehyde fixed neural tissue. A quick procedure was to blot tissue and embed in 5% (w/v] Sigma type I-A or Litex type LSL agarose at 45-55 C dissolved in 50 mM neutral-pH TFUS buffer before cutting 50-100 μm vibratome sections. An alternative procedure that improved retention of tissue sections in the agarose was to rinse the tissue in H₂0, blot and embed in 5% (w/v] Sigma type I-A or Litex type LSL agarose at 45-55 C dissolved in H₂0, then equilibrate the block overnight in buffer. Phosphate buffer prevented complete dissolving of agarose. Tissue could be covalently linked to the embedding matrix using a novel aldehyde-derived agarose (NuFix® FMC BioProducts). Slices of spinal cord from neonatal rats could be cut after embedding in 5% FMC Seaprep® agarose in rat Ringer's at 23-26 C.     

Differences in growth of neurons from normal and regenerated teleost spinal cord in vitro

Summary Explants and dissociated cells from normal adult spinal cord and regenerating cord of the teleostApteronotus albifrons were grown in vitro for periods of 8 to 12 wk. During this time the neurons showed extensive neurite outgrowth. Neurite outgrowth from tissue explants and dissociated cells of regenerated spinal cord starts sooner and is more profuse than that from normal (unregenerated) cord. Neurite outgrowth is maximized by using adhesive substrata and a high density of explants or dissociated cells. Inasmuch asApteronotus does regenerate its spinal cord naturally after injury, whereas mammals do not, this culture system will be useful to study factors that control (permit) regeneration of spinal neurons in this adult vertebrate.     

Glycine: An important potential component of spinal shock

Amino acid neurotransmitters (AANTs) play a major role in maintenance of muscle tone. Abnormal AANT concentrations are associated with hyper- or hypotonic states. Flaccidity from spinal shock commonly occurs after spinal cord injury (SCI) and may be associated with changes in AANT concentrations. Ischemic SCIs created in the lumbar region of rabbits by intraaortic balloon occlusion produced spastic or flaccid injuries. Microdialysis sampling of AANTs from the injured segmental structures was done 3 days after SCI. Evoked potentials were used to monitor spinal cord stability. No significant changes in AANT levels occurred in the spastic or flaccid group after 4 hour sampling. However, flaccid animals had baseline glycine levels 2–3 times higher (p<0.001) than spastic animals or controls. High concentrations of the inhibitory AANT glycine is associated with flaccidity following SCI, or spinal shock, but not spasticity. Glycinergic compounds directed toward suppression of excess muscle tone deserve further study.