Thiamine release from nerve membranes by tetrodotoxin

Tetrodotoxin (3 x 10(-8) molar) promoted the release of thiamine from perfused rat and frog nerve preparations in a manner similar to other neuroactive drugs. When the rats were injected with thiamine labeled with sulfur-35, analyses of brain, spinal cord, and sciatic nerve homogenates revealed labeled thiamine in membrane, synaptosomes, and mitochondrial subfractions. However, on incubation of these fractions with tetrodotoxin, thiamine was released only from the membrane fragments.     

Tritiated norepinephrine: release from brain slices by electrical stimulation

Slices of rat brain and heart that had concentrated H(3)-norepinephrine were superfused and electrically stimulated. Stimulation induced a marked release of H(3)-norepinephrine with a threshold and a maximum repsonse. Release also occurred with increased concentrations of potassium, presumably due to neuronal depolarization. Inhibition of electrically induced release occurred with low calcium and with chlorpromazine and pentobarbital.     

Amitotic neuroblastoma cells used for neural implants in monkeys

The potential utility of cultured neuroblastoma cells as donor tissue for neutral implants into the mammalian brain has been examined. Cells from a human neuroblastoma cell line, IMR-32, were labeled with [3H]thymidine and chemically rendered amitotic. These differentiated IMR-32 cells were grafted into the hippocampi of five adult African Green monkeys, and graft survival was evaluated for up to 270 days after transplantation. Autoradiographically labeled grafted cells were identified in four animals. Processes from grafted cells could be followed for distances of up to 150 micrometers into the host brain. No evidence for neoplastic growth of the transplant was found. Thus, grafted neuroblastoma cells can survive for prolonged periods in the primate brain and may serve as a practical source of donor tissue for neural implants.     

Reexamination of glucose-6-phosphatase activity in the brain in vivo: no evidence for a futile cycle

Glucose-6-phosphatase activity in the rat brain in vivo was estimated by measuring the differential loss of tritium and carbon-14 from the glucose pool labeled by a mixture of [2-3H]glucose and [U-14C]glucose. The results provide no evidence of significant dephosphorylation of glucose-6-phosphate and do not support the hypothesis of a futile cycle involving glucose-6-phosphatase activity in the brain.     

Recognition sites for norepinephrine uptake: regulation by neurotransmitter

Recognition sites for the uptake of norepinephrine on adrenergic neurons in the brain and periphery were labeled with [3H]desipramine. The number of these uptake sites varied with the concentration of transmitter; depletion of norepinephrine with reserpine reduced the number of uptake sites, whereas increasing the concentration of norepinephrine induced by treatment with monoamine oxidase inhibitors raised the number of binding sites. These dynamic alterations in norepinephrine uptake recognition sites may regulate synaptic function homeostatically, providing less inactivation of reuptake when the synaptic concentration of the transmitter is low and increased inactivation when it is high.     

Phosphatidylinositol-glycan anchors of membrane proteins: potential precursors of insulin mediators

BC3H1 myocytes release membrane-bound alkaline phosphatase to the incubation medium upon stimulation with insulin, following a time course that is consistent with the generation of dimyristoylglycerol and the appearance of a putative insulin mediator in the extracellular medium. The use of specific blocking agents shows, however, that alkaline phosphatase release and dimyristoylglycerol production are independent processes and that the blockade of either event inhibits the production of insulin mediator. These experiments suggest a new model of insulin action.     

Ribosome biogenesis: nonrandom addition of structural proteins to 50S subunits

Assemblage of structural proteins into 50S subunits was examined in Escherichia coli recovering fromt chloramphenicol treatment. Cells previously labeled with H3-leucine for three generations were incuibated for 30 minutes with chloramnlphenicol. Proteins synthesized during the initial 5 minuites of recovery from chlorarmphenicol treatmnent were labeled with C(14)-leucine. Marked variation in the ratios of C(14)- to H(3)-leucine in ribosomal protein occurred in cells that had been treated with chloramphenicol; luntreated cells displayed little variation. Thle resuilts sliggest that ribosomal proteins are assenmbled into 50S subunits in a nonrandom manner.     

Lability of host-cell DNA in growing cell cultures due to Mycoplasma

In HeLa-cell cultures chronically infected with Mycoplasma, (PPLO) host-cell DNA is unstable as detected by incorporation of H(3)-or C1 i-thymidine into DNA and subsequent release into the medium as acidsoluble radioactivity. This characteristic can be transmitted to PPLO-free cultures of strain L cells by inoculation with preparations of PPLO from the HeLa cells, although chronically infected cultures of L cells continue to multiply. In addition, virus preparations also may carry PPLO contamination through numerous passages.     

Simian sarcoma virus--transformed cells secrete a mitogen identical to platelet-derived growth factor

Normal rat kidney (NRK) cells transformed by simian sarcoma virus (SSV) release into the culture medium a biologically active mitogen with properties identical to those of human platelet-derived growth factor (PDGF). Like PDGF, the growth factor derived from SSV-NRK cells was shown to be stable to heat and sensitive to reducing agents. It was capable of inhibiting binding of labeled PDGF to the receptor on human fibroblasts. It also stimulated the phosphorylation of the same membrane protein (185 kilodaltons) in isolated plasma membranes from human fibroblasts. Immunoprecipitation of metabolically labeled proteins released by SSV-NRK cells showed that a 34-kilodalton protein was specifically precipitated by antiserum to PDGF. Upon reduction, this protein had a molecular size of 17 kilodaltons. PDGF has been shown to consist of two 14- to 18-kilodalton proteins linked by disulfide bonds.     

The 36-kilodalton substrate of pp60v-src is myristylated in a transformation-sensitive manner

A primary intracellular substrate for pp60v-src kinase in a variety of avian and mammalian cells is a protein of 34 to 39 kilodaltons (kD). After incubation of chicken embryo fibroblasts (CEF) with [3H]myristic acid for 4 hours, the 36-kD protein contained covalently bound myristic acid by several criteria: (i) the radioactively labeled material comigrated with the 36-kD protein on sodium dodecyl sulfate-polyacrylamide gels in one and two dimensions, (ii) the labeled material was insoluble in chloroform-methanol, and (iii) radioactively labeled myristate could be recovered from the purified 36-kD protein. The resistance of the acyl fatty acid moiety to hydrolysis by hydroxylamine suggested that the covalent linkage to the 36-kD protein may be through an amide linkage. The [3H]myristic-acid labeling of the 36-kD protein in Rous sarcoma virus-transformed CEF showed a reduction of up to 45 percent when compared to an identical amount of 36-kD protein derived from normal cells; this reduction was not due to general changes in myristic acid metabolism in transformed cells.     

Identification of geranylgeranyl-modified proteins in HeLa cells

Previous studies have shown that animal cells contain isoprenoid-modified proteins and that one of these proteins, lamin B, contains a thioether-linked farnesyl group that is attached to cysteine. In the present study, a novel isoprenoid-modification was identified by labeling HeLa cells with [3H]mevalonic acid and analyzing proteolytic digests of the total cell protein. Radioactive fragments were purified from these digests and treated with Raney nickel. The released, labeled material was analyzed by gas-liquid chromatography (GC) and mass spectrometry (MS). This approach revealed that an all-trans geranylgeranyl group was a major isoprenoid modification.     

H9亚型AIV型特异性电化学发光免疫检测方法的建立

【目的】H9亚型禽流感是重要的人兽共患性传染病,该亚型病毒为H7N9亚型和H10N8亚型流感病毒提供了6个内部基因（PB2、PB1、PA、NP、M、NS）,并且一直处于动态重组过程中。因此,建立针对H9亚型禽流感的型特异性电化学发光免疫的高通量快速检测方法,加强H9亚型流感的监测,具有重要意义。【方法】用钌联吡啶标记H9亚型AIV的单克隆抗体,用MPI-E型电致化学发光分析系统评价钌标单抗标记效率;用生物素标记H9亚型AIV的多克隆抗体,HABA法检测抗体生物素化的效率;待测抗原与钌标单抗作用1 h后,将此抗原-抗体复合物与通过生物素-链霉亲和素系统固定在磁微球表面的多克隆抗体反应,最后加入反应底物三丙胺后即可在电化学分析系统进行发光检测。优化生物素化多抗和钌标单抗最佳工作浓度,确定临界值和反应谱,对所建立的方法进行敏感性、特异性和重复性试验。攻毒后3 d和5 d,采集攻毒组和空白对照组鸡只的88份咽拭子和肛拭子,分别用电化学发光免疫检测方法和鸡胚病毒分离法进行检测和比较。【结果】钌标抗H9亚型AIV单克隆抗体的标记效率为每个单抗IgG分子上结合21个Ru²⁺,且间接免疫荧光方法证明其仍具有生物活性;生物素化兔抗H9N2亚型AIV多克隆抗体的标记效率为每个IgG分子上结合了6个生物素分子,且Western blotting试验证明其仍保持生物活性;该方法的检测临界值为28.3,可疑区间为23.4-33.2;阴性和阳性变异系数均小于10%;检测限为5×10⁴EID₅₀,能够特异性地检测H9亚型AIV,不与其他亚型流感病毒（H1、H3、H4、H5和H6亚型）和其他类型的禽源病毒（NDV、IBV和IBDV）反应。3 h内即可完成检测,与鸡胚病毒分离法的符合率为86.4%。【结论】所建立的H9亚型AIV型特异性电化学发光免疫检测方法可以用于临床样品检测,对H9亚型禽流感的监测和防控具有重要意义。     

Tricyclic antidepressants: evidence for an intraneuronal site of action

Desipramine, a tricyclic antidepressant drug, almost completely prevents the accumulation of tritiated norepinephrine by sympathetic neurons of the rat heart after the injection of a tracer dose of the labeled amine. However, desipramine does not alter the accumulation of norepinephrine after the injection of a large dose of the neurohormone. Despite the failure of desipramine to block the neuronal uptake of norepinephrine, it still prevents exogenous norepinephrine from displacing the endogenous neurohormone (previously labeled with H(3)-norepinephrine) from intraneuronal storage sites.     

Viking labeled release biology experiment: interim results

This report summarizes all results of the labeled release life detection experiment conducted on Mars prior to conjunction. Tests at both landing sites provide remarkably similar evolution of radioactive gas upon addition of a radioactive nutrient to the Mars sample. The "active" agent in the Mars sample is stable to 18 degrees C, but is substantially inactivated by heat treatment for 3 hours at 50 degrees C and completely inactivated at 160 degrees C, as would be anticipated if the active response were caused by microorganisms. Results from test and heat-sterilized control Mars samples are compared to those obtained from terrestrial soils and from a lunar sample. Possible nonbiological explanations of the Mars data are reviewed along with plans for resolution of the Mars data. Although such explanations of the labeled release data depend on ultraviolet irradiation, the labeled release response does not appear to depend on recent direct ultraviolet activation of surface material. Available facts do not yet permit a conclusion regarding the existence of life on Mars. Plans for conclusion of the experiment are discussed.     

Metabolic dependence of fast axoplasmic transport in nerve

Fast axoplasmic transport, shown in cat sciatic nerves by a crest of labeled activity after injection of the L7 ganglion with [(3)H]-leucine or [ (3)H]-lysine, was stopped within 15 minutes after death of the animals by bleeding. If the sciatic nerves were removed from the animals and placed in a chamber supplied with oxygen at 38 degrees centigrade, fast transport was sustained. Transport was rapidly blocked in similar in vitro preparations when the nerves were kept in a nitrogen environment. Fast axoplasmic transport is closely dependent upon oxibdative metabolism.     

Norepinephrine pools in rat brain: differences in turnover rates and pathways of metabolism

The rate of disappearance of intracisternally administered [(3)H]norepinephrine from rat brain gradually declines as a multiphasic exponential function of time. Conversion to [(3)H]normetanephrine accounts for a larger fraction of the [(3)H]norepinephrine released in the brain shortly after its intracisternal injection than that released at later times. Pools of norepinephrine in the brain thus appear to differ in their turnover rates and pathways of metabolism. The pool of norepinephrine with a rapid rate of turnover and an appreciable conversion to normetanephrine, identified by the techniques reported here, may correspond to a pool of newly synthesized norepinephrine in the brain.     

不同连续提取条件下土壤K素的释放速率

以 1mol· L-1HNO3 (85℃ )、2 mol· L-1HNO3 (2 0℃ )和氢质阳离子交换树脂恒温连续提取法 (2 0℃ ) ,利用 Elovich模型 ,结合生物吸 K试验 ,研究了不同连续提取条件下土壤 K素释放速率的差异及其与K素有效性的关系 .研究结果表明 :1mol· L-1HNO3 提取法的释 K速率 >2 mol· L-1HNO3 提取法的释 K速率 >氢饱和交换树脂提取法的释 K速率 ;氢质交换树脂和 2 mol· L-1HNO3 提取法结合 Elovich模型较理想地描述了土壤 K素的释放特性 ,拟合方程的相关系数均达极显著水平 (r=0 .956 * * - 0 .999* * ) ,土壤特征累积释 K量的计算值与实测值的标准差较小 (s=1.6 1和 3.52 ) ,且通过速率方程计算的土壤特征释 K速率与K素有效性指标 (速效 K、缓效 K、有效 K及黑麦草总吸 K量 )的相关性也较为密切 .因此 ,氢质阳离子交换树脂和 2 mol· L-1HNO3 提取法结合 Elovich模型可较好地描述土壤 K素的释放及其速率     

A corticosteroid receptor in neuronal membranes

Steroids may rapidly alter neuronal function and behavior through poorly characterized, direct actions on neuronal membranes. The membrane-bound receptors mediating these behavioral responses have not been identified. [3H]Corticosterone labels a population of specific, high-affinity recognition sites (dissociation constant = 0.51 nanomolar) in synaptic membranes from an amphibian brain. These binding sites were localized by receptor autoradiography in the neuropil, outside the regions of perikarya. The affinities of corticoids for this [3H]corticosterone binding site were linearly related to their potencies in rapidly suppressing male reproductive behavior. Thus, it appears that brain membranes contain a corticosteroid receptor that could participate in the regulation of behavior.     

Immunohistochemistry of adenosine deaminase: implications for adenosine neurotransmission

Immunohistochemical analysis of adenosine deaminase in rat brain revealed an extensive plexus of adenosine deaminase-containing neurons in the basal hypothalamus. These neurons converged on and were most numerous in three major centers, namely, the tuberal, caudal, and postmammillary caudal magnocellular nuclei. Most other brain regions were devoid of cells containing adenosine deaminase. Some adenosine deaminase-containing neurons were retrogradely labeled with the fluorescent dye fast blue when the dye was injected into the frontal cortex and striatum. Specific populations of neurons having high levels of adenosine deaminase may release adenosine as a neurotransmitter.