Heterogeneity of Soluble Neural Cell Adhesion Molecule

Soluble neural cell adhesion molecule (NCAM) from rat brain neuronal cell culture media consists predominantly of a polypeptide of Mr approximately 115,000. Minor amounts of a polypeptide of Mr approximately 180,000 and two inconsistently appearing components of Mr 160,000 and 145,000 are also observed. The Mr 115,000 component is derived from the neuronal membrane NCAM components NCAM-A of Mr 190,000, NCAM-B of Mr 140,000, or both. Thus, as a part of the catabolism of membrane NCAM-A plus -B, a minor fraction is posttranslationally cleaved and recovered in the media as discernible soluble NCAM polypeptides. The half-life of membrane NCAM-A plus -B is less than 24 h. Astrocyte culture media contains a predominant soluble NCAM component of Mr 120,000 derived from membrane-associated NCAM-C. A close comparison of deglycosylated soluble NCAM from astrocyte and neuronal cultures showed a small but consistent difference in Mr, a result suggesting that different NCAM polypeptides are released from the membrane of neurons and astrocytes. In contrast to the Mr 115,000-120,000 NCAM polypeptides, the Mr 180,000 polypeptide from neuronal culture media does not seem to be derived from membrane-attached NCAM and may therefore represent a secreted NCAM isoform.     

有机物沟埋还田模式与花后灌水量对玉米光合特性和产量的影响

有机物沟埋还田与花后灌水配合对增加玉米田保水供水能力,提高玉米花后光合性能、实现节水增产有重要意义.本试验以郑单958为供试材料,设置有机物沟埋还田和花后灌水量两个因素,有机物沟埋还田包括不还田(M₀)、秸秆单还田(M₁)和牛粪秸秆混合还田(M₂)3个还田类型,花后灌水量包括450 mm(W₁)和325 mm(W₂)2个水平,研究了其对玉米穗位叶光合性能、光系统Ⅱ(PSⅡ)效率和产量等的影响.结果表明:与秸秆单还田比较,牛粪秸秆混合还田有效提高了玉米花后光合能力和各器官的干物质积累量;与节水灌溉相比,正常灌溉加强了有机物还田对玉米光合能力的促进作用.牛粪秸秆混合还田与正常灌溉结合可显著提高玉米花后叶片的光合速率(P_n)、气孔导度(g_s)和蒸腾速率(T_r),降低胞间CO₂浓度(C_i);提高玉米花后叶片PSⅡ的最大光化学效率(φ_po)和捕获的激子将电子传递到电子传递链中Q_A下游的电子受体的概率(Ψ_o);改善花后叶片光能利用率,维持花后叶片较高的光合性能;同时增加花后玉米各器官干物质的量,提高干物质总积累量和转运能力,有利于花后同化物对籽粒的分配,最终获得高产.节水灌溉降低了叶片的光合性能,造成产量的下降;但配合牛粪秸秆混合还田与不还田处理相比,水分利用效率、籽粒增长速率和增产效果均优于正常灌水.这表明牛粪秸秆混合还田与正常灌溉结合可有效提高玉米花后光合性能,增加干物质积累量,促进玉米增产;牛粪秸秆混合还田与节水灌溉结合一定程度上降低了因减少灌溉量造成的减产.     

有机肥氮投入比例对双季稻田根际土壤微生物生物量碳、氮和微生物熵的影响

为探明不同有机肥氮素占总氮投入的百分比对双季稻区早、晚稻各生育时期稻田根际土壤微生物的影响,本研究以大田定位试验为平台,应用氯仿熏蒸-K₂SO₄提取法和化学分析法系统分析了施用化肥N(M₁)、30%有机肥N(M₂)、50%有机肥N(M₃)、100%有机肥N(M₄)和无N对照(M₀)5个不同施肥处理双季稻田根际土壤微生物生物量碳(MBC)、微生物生物量氮(MBN)和微生物熵的差异.结果表明: 在早稻和晚稻各主要生育时期,施肥措施均能提高稻田根际土壤MBC、MBN和微生物熵,各施肥处理根际土壤MBC、MBN和微生物熵均随水稻生育期推进呈先增加后降低的变化趋势,均于齐穗期达到最大值,成熟期为最低值;其中,各处理双季稻田根际土壤MBC、MBN、MBC/MBN值和微生物熵一般均表现为M₄＞M₃＞M₂＞M₁＞M₀,M₂、M₃和M₄处理间均无显著差异,但均显著高于M₀处理.可见,单独施用化肥措施对提高根际土壤微生物生物量碳、氮和微生物熵效果有限,施用有机肥或有机无机肥配施提高根际土壤微生物生物量碳、氮和微生物熵的效果较好.     

Phosphatidylinositol is involved in the membrane attachment of NCAM-120, the smallest component of the neural cell adhesion molecule.

The rodent neural cell adhesion molecule (NCAM) consists of three glycoproteins with Mr of 180,000, 140,000 and 120,000. The Mr 120,000 protein (NCAM-120) has been shown to exist in membrane-bound and soluble forms but the nature of its membrane association and release has remained obscure. We show here that phosphatidylinositol-specific phospholipase C (PI-PLC), but not a phospholipase C of different specificity, releases a substantial proportion of NCAM-120 from brain membranes and solubilizes almost quantitatively NCAM-120 present at the surface of C6 astroglial cells. The PI-PLC effect was highly selective since only one other protein species was detectably released from C6 cells. These results suggest that NCAM-120 is held in the membrane by covalently bound phosphatidylinositol or a closely related lipid in a way similar to several other surface proteins from eukaryotic cells. The presence of NCAM in a form which can be released from the cell surface by a highly selective mechanism raises additional possibilities for modulation and control of cell--cell adhesion.     

GANGLIOSIDE ABNORMALITIES IN MULTIPLE SCLEROSIS

Abstract— Gangliosides were isolated from plaque tissue and normal appearing white matter of multiple sclerosis (MS) brain. All four plaques showed decreased ganglioside concn relative to normal human white matter on a wet wt basis, but significant elevation in terms of dry wt. The wet wt and dry wt concn of MS white matter gangliosides showed smaller but statistically significant decreases below normal. Thin-layer patterns of the plaques showed several departures from normal white matter, including decrease of G₄ and G₅, and complete loss of G₇ (sialosylgalactosylceramide). Most of the plaques had significant elevation of G_2A and G_3A along with increases of the slower-migrating polysialogangliosides. An additional ganglioside was present between G₂ and G_2A which was not seen in normal white matter. The TLC pattern of MS white matter gangliosides was essentially normal. The evidence for a general decrease of acidic lipids within normal appearing white matter is discussed.     

The neuroprotective effect of tacrine on trimethyltin induced memory and muscarinic receptor dysfunction in the rat

In this study chronic (39 days) tacrine (3 mg/kg i.p.) treatment significantly improved trimethyltin (8 mg/kg i.p.) induced deficits in spatial navigation. Tacrine also reduced trimethyltin induced hyperactivity and passive avoidance deficits but these effects did not reach statistical significance. The effect of trimethyltin on muscarinic (M₁ and M₂) receptor sites was determined by means of quantitative autoradiography using [³H]quinuclidinyl benzilate. A selective pattern of M₁ and M₂ receptor loss was observed mainly affecting the hippocampus and other limbic structures while leaving other brain regions intact. Tacrine successfully prevented the M₁ and M₂ receptor loss in the CA₁ and CA₁ hippocampal subfields. The improvement in trimethyltin behavioural toxicity following tacrine treatment may be related to the protective effect of this compound on muscarinic receptor density in the hippocampal formation and lends support to the hypothesis that cholinergic system dysfunction may be primarily responsible for trimethyltin induced deficits in cognitive function.     

Novel oxotremorine-related heterocyclic derivatives: Synthesis and in vitro pharmacology at the muscarinic receptor subtypes

A set of novel heterocyclic ligands (6–27) structurally related to Oxotremorine 2 was designed, synthesized and tested at muscarinic receptor subtypes (mAChRs). In the binding experiments at cloned human receptors (hm1–5), compounds 7 and 15 evidenced a remarkable affinity and selectivity for the hm2 subtype. The in vitro functional assays, performed on a selected group of derivatives at M₁, M₂, and M₃ tissue preparations, singled out the 3-butynyloxy-5-methylisoxazole trimethylammonium salt 7 as a potent unselective muscarinic agonist [pEC₅₀: 7.40 (M₁), 8.18 (M₂), and 8.14 (M₃)], whereas its 5-phenyl analogue 12 behaved as a muscarinic antagonist, slightly selective for the M₁ subtype [pK_B: 6.88 (M₁), 5.95 (M₂), 5.53 (M₃)]. Moreover, the functional data put in evidence that the presence of the piperidine ring may generate a functional selectivity, e.g., an M₁ antagonist/M₂ partial agonist/M₃ full agonist profile (compound 21), at variance with the corresponding quaternary ammonium salt (compound 22) which behaved as a muscarinic agonist at all M_1–3 receptors, with an appreciable selectivity for the cardiac M₂ receptors.     

Individual neural cell types express immunologically distinct N-CAM forms

The neural cell adhesion molecules, or N-CAMs, are a group of structurally and immunologically related glycoproteins found in vertebrate neural tissues. Adult brain N-CAMs have apparent molecular weights of 180,000, 140,000, and 120,000. In this article we identify, using monoclonal antibody (Mab) 3G6.41, an immunologically distinct adult rat N-CAM form and show that this form is selectively expressed by some clonal neural cell lines. Consecutive immunoprecipitation experiments indicate that rabbit anti-N-CAM can remove from solubilized cerebellar neuron primary cultures all 180,000- and 140,000-mol-wt N-CAM molecules that react with Mab 3G6.41. However Mab 3G6.41 cannot remove all N-CAM molecules that react with rabbit anti-N-CAM. Rabbit anti-N-CAM binds to and immunoprecipitates N-CAM forms from the rat neuronal cell lines B35, B65, and B104, the glial lines B12 and C6, and L6 myoblasts. Mab 3G6.41 does not bind to or immunoprecipitate N-CAM from the B12 and B65 lines but does react with the other four lines by both criteria. Many cells in primary cultures of postnatal rat that express glial fibrillary acidic protein also bind Mab 3G6.41. Thus a unique form of rat N-CAM recognized by Mab 3G6.41 is found on some but not all neuronal, glial, and muscle cells.     

Effects of JO 1784, A selective sigma ligand, on the autoradiographic localization of M2 and M2 muscarinic receptor subtypes in trimethyltin treated rats

The distribution patterns of M₁ and M₂ muscarinic receptor subtypes following TMT and JO 1784 administration in the male Sprague-Dawley rat were investigated. In the present study, JO 1784 was injected in doses of 1, 4 and 16 mg/kg i.p. for one week prior to the single injection of TMT (8 mg/kg i.p.) and subsequently for 33 days. The effects of JO 1784 on the density of muscarinic receptor sub-types (M₁ and M₂) in the control and trimethyltin (TMT) treated rats were then evaluated. The topographic distribution and changes in muscarinic (M₁ and M₂) receptor densities were determined by means of autoradiography using [³H]quinuclidinylbenzilate (QNB). Both sub-types of muscarinic receptors contributed to the observed decrease in total muscarinic receptor binding in TMT-treated rats. In control rats, JO 1784 alone decreased M₁ receptor density in the amygdaloid nuclei, basal ganglia, cortex and hippocampus and decreased M₂ receptor density in the amygdaloid nuclei, basal ganglia, cortex, hippocampus, hypothalamus and septal regions. In TMT treated rats, chronic JO 1784 administration has a “neuroprotective effect” on both M₁ and M₂ receptors subtypes. Thus, following chronic administration of JO 1784 to TMT treated rats, both increases and decreases in M₁ receptor density were observed relative to TMT animals. A significant increase in M₁ receptor density was found in the cortex, olfactory regions, septum, thalamus and basal forebrain nuclei. In the hippocampus (CA₂ and CA₃), a significant decrease in M₁ receptor density was observed. In TMT-treated rats, JO 1784 produced a significant increase in M₂ receptor density in several brain regions with the most marked effects occurring in the amygdaloid nuclei, basal ganglia, cortex, hippocampus and hypothalamus. The ability of the selective sigma ligand, JO 1784, to attenuate the loss of muscarinic receptors in TMT treated rats could be of importance in the development of novel neuroprotective drugs.     

Structural and immunological characterization of the amino-terminal domain of mammalian neural cell adhesion molecules

The neural cell adhesion molecules (N-CAMs) are a group of structurally and immunologically related glycoproteins found in vertebrate neural tissues. Adult brain N-CAMs have apparent molecular weights of 180,000 and 140,000 with an additional form at 120,000 in murine brain. In embryonic brain, N-CAMs are represented by a highly sialylated form with an apparent molecular weight greater than 180,000. We have used monoclonal antibodies that cross-react with N-CAMs of various mammalian species to purify N-CAMs from adult murine and bovine brains and from embryonic murine brains. We determined the amino acid sequences of the amino-terminal domains of these molecules: Leu-Gln-Val-Asp-Ile-Val-Pro-Ser-Gln-Gly-Glu-Ile-Ser-Val-Gly-Glu-Ser. This sequence is highly conserved among all three forms of adult murine brain N-CAM as well as embryonic murine brain N-CAM and adult bovine brain N-CAM. Based on this sequence, we synthesized an undecapeptide and used it to raise a site-directed polyclonal antiserum. This antiserum reacted with the intact N-CAM in liquid phase radioimmunoassays, immunoblotting experiments, and immunofluorescent labeling of cells. The antiserum also reacted with N-CAMs in extracts of brain tissues from different species, confirming the highly conserved nature of the amino-terminal domain of mammalian N-CAMs. Immunofluorescence experiments indicated that this domain resides on the outer surfaces of cells that express N-CAMs, in both primary neuronal cell culture and in cell lines.     

Resonance raman spectroscopy of chemically modified and isotopically labelled purple membranes. II. Kinetic studies

Kinetic resonance Raman spectra of native and isotopically labelled purple membranes are compared. Using these data and the assignments of the previous paper in this sequence, we have confirmed that the Schiff base is deprotonated at times that are short in comparison to M₄₁₂ evolution. In addition, by monitoring the kinetic resonance Raman spectra in ²H₂O with 488.0 nm excitation we have been able to characterize in more detail the vibrational features associated with this unprotonated intermediate that precedes M₄₁₂. Furthermore, the kinetic spectra of fully deuterated purple membranes in H₂O have allowed us to assign the 1465 cm⁻¹ band in these spectra to the C=C stretching frequency of BR₅₇₀ and the 1512 cm⁻¹ band to the C=C stretching frequency of M₄₁₂. These spectra have also provided an indication of a Raman spectral feature associated with O₆₄₀ and, finally, our kinetic spectra have provided evidence that there is a significant alteration in the rate constants for the evolution of the various intermediates when the non-exchangeable protons on the membrane are replaced by deuterons.     

Diphenidol-related diamines as novel muscarinic M4 receptor antagonists

A series of hydrochloride derivatives 2a–9a and quaternary ammonium derivatives 3b–9b of diphenidol have been synthesized and characterized in receptor binding and cellular functional assays versus human muscarinic M₁–M₅ receptors expressed in CHO cells. Compound 8b, a methiodide derivative with a bipiperidinyl moiety and a second diphenidol framework, showed a potent and selective M₄ activity as competitive antagonist. Moreover 8b, acting as an allosteric modulator, was able to retard the dissociation rate of [³H]-N-methylscopolamine from CHO-M₄ cell membranes exposed to atropine. Taken together, these data suggest that 8b might open new avenues to the discovery of novel multivalent antagonists for the muscarinic receptors.     

长期不同施肥对玉米根茬生物量及养分累积量的影响

以黄土高原南部两个长期定位试验（分别开始于1990和2003年）为研究对象,探讨了不同肥料处理对玉米根茬生物产量和养分累积的影响.于2011年10月玉米收获后采集0～20 cm土层不同施肥处理玉米根茬.结果表明：与不施肥及偏施N、NK、PK化肥相比,氮磷配施（NP）、氮磷钾平衡施肥（NPK）、有机无机配施（M₁NPK、M₂NPK）及化肥配合秸秆（SNPK）处理均显著提高了玉米根茬干质量.根茬固碳量及氮、磷、钾养分累积量在NP、NPK、M₁NPK、M₂NPK、SNPK处理显著高于不施肥和偏施N、NK、PK化肥处理,其中以有机无机配施处理效果最好.与不施氮肥（N₀）相比,施氮120 kg N·hm^-2（N₁₂₀）和240 kg N·hm^-2（N₂₄₀）处理根茬干质量分别提高38%和45%,高量氮肥对根茬增量效果不显著.施用氮肥也显著提高了根茬碳、氮、磷、钾累积量.根茬可溶性有机碳、可溶性总氮含量在NP、NPK、M₁NPK、M₂NPK、SNPK及N₁₂₀和N240处理中较高.氮磷钾平衡施肥、有机无机配施以及秸秆还田处理降低了根茬的纤维素、木质素含量.根茬C/N、木质素/N在CK、PK、N₀处理间显著高于其他施肥处理.因此,氮磷配施、氮磷钾平衡施肥、有机无机配施及秸秆还田处理能够促进玉米根生长,提高营养成分含量,有利于土壤培肥和固碳.     

Developmental Expression of Neural Cell Adhesion Molecules of Oligodendrocytes In Vivo and in Culture

Abstract: Previously, we have shown that oligodendrocyte adhesion molecules are related to the 120,000–M_r neural cell adhesion molecule (NCAM-120). In this report, we present further evidence that the oligodendrocyte adhesion molecule is NCAM-120. Studies on the expression of NCAM-120 and other molecular forms of NCAM in vivo in rat brain, in vitro in primary mixed cultures, and in cultures enriched for oligodendrocytes are described. Western blot analysis of rat brain using anti-NCAM showed that NCAM-120 first appears at postnatal day 7 and increases in quantity thereafter, coincident with the development of oligodendrocytes in vivo and comparable to the expression of myelin basic protein. Purified oligodendrocytes from 4-week-old rat brains expressed only NCAM-120. Quantitation of various forms of NCAMs in rat brain showed marked age-related differences in the expression of three molecular forms of NCAM. Immunofluorescence analysis showed that oligodendrocytes, at all ages tested, expressed NCAM, but in older oligodendrocytes, the intensity of staining was less. Western blot analysis of oligodendrocyte-enriched cultures showed that from day 1 after isolation (12 days of age) through day 7 after isolation (18 days of age) only NCAM-120 is seen. A possible role for NCAM in myelination and remyelination is discussed.     

6-(4-Phenyl-benzyloxy-methyl) guvacine. Synthesis, GABA uptake inhibitor and muscarinic properties

6-(4-Phenyl-benzyloxy-methyl) guvacine was synthesized. Surprisingly the compound was devoid of the γ-aminobutyric acid (GABA) uptake inhibitory activity of its parent compound guvacine, but instead showed affinities for the muscarinic M₁ and M₂ receptors.     

Modulation of immobilized enzyme activity by altering the hydrophobicity of nylon-grafted membranes: Part 2: Non-isothermal conditions

Lactose hydrolysis by β-galactosidase immobilized on two nylon membranes, differently grafted, has been studied in a bioreactor operating under isothermal and non-isothermal conditions. One membrane (M₁) was obtained by chemical grafting of methylmethacrylate (MAA); the other one (M₂) by a double chemical grafting: styrene (Sty) and MAA. Hexamethylenediamine was used as a spacer between the grafted membranes and the enzyme. Both membranes have been physically characterized studying their permeabilities in presence of pressure or temperature gradients. Under non-isothermal conditions, the increase in activity of membrane M₂ was higher than that of membrane M₁. The and β coefficients, giving the percentage of activity increase when a temperature difference of 1°C is applied across the catalytic membranes, have been calculated. Results have been discussed with reference to the greater hydrophobicity of membrane M₂ with respect to membrane M₁, the hydrophobicity being a prerequisite for the occurrence of the process of thermodialysis.     

小家鼠(Mus musculus)种群动态预测及机制的探讨

我国学者夏武平(1966)用9月铗日捕获率预测东北棕背(鼠平)(Clethrionomys rufocanus)数量以来,严志堂等(1983)应用种群年龄结构的回归方程预测新疆天山北麓农区塔西河地区的小家鼠(Mus musculus)种群密度获初步成功,并根据该文提供的一个改进公式M₁₀=5.60x+5.80(x表示种群年龄的成亚比,M₁₀表示小家鼠10月数量,即年内最高数量),提前11个月预测该地的小家鼠种群最高数量。