Nicotine Enhances the Cyclic AMP-Dependent Protein Kinase-Mediated Phosphorylation of α4 Subunits of Neuronal Nicotinic Receptors

Abstract: Studies determined whether α4β2 or α3β2 neuronal nicotinic receptors expressed in Xenopus oocytes are substrates for cyclic AMP-dependent protein kinase (PKA) and whether nicotine affects receptor phosphorylation. The cRNAs for the subunits were coinjected into oocytes, and cells were incubated for 24 h in the absence or presence of nicotine (50 n M for α4β2 and 500 n M for α3β2 receptors). Nicotine did not interfere with the isolation of the receptors. When receptors isolated from oocytes expressing α4β2 receptors were incubated with [γ-³²P]ATP and the catalytic subunit of PKA, separated by electrophoresis, and visualized by autoradiography, a labeled phosphoprotein with the predicted molecular size of the α4 subunit was present. Phosphorylation of α4 subunits of α4β2 receptors increased within the first 5 min of incubation with nicotine and persisted for 24 h. In contrast, receptors isolated from oocytes expressing α3β2 receptors did not exhibit a labeled phosphoprotein corresponding to the size of the α3 subunit. Results suggest that the PKA-mediated phosphorylation of α4 and not α3 subunits may explain the differential inactivation by nicotine of these receptors subtypes expressed in oocytes.     

Mapping eight new polymorphisms in 11q13 in the vicinity of multiple endocrine neoplasia type 1: identification of a new distal recombinant

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder that predisposes affected individuals to neoplasms of the parathyroid glands, endocrine pancreas, anterior pituitary, and carcinoids. The MEN1 locus has been localized by family studies to 11q13, flanked by markers PGA and D11S97. Eight new polymorphisms located in three separate radiation-reduced somatic cell hybrid segregation groups were developed. The order of the new markers, within the context of previously described loci, was determined by linkage analysis on the Venezuelan reference pedigree. Four independent MEN1 families, consisting of 57 affected individuals, and 70 individuals at-risk for the disease were genotyped. Sixteen people inherited a chromosome that shows recombination between a linked marker and the disease. The nearest proximal and distal markers that show recombination with the disease are D11S822 and GSTP1, respectively, thereby narrowing the candidate region for MEN1 by 50% on the distal side. Using these loci in haplotype analysis, an accurate presymptomatic molecular diagnostic test has been developed. These new markers in 11q13 linked to MEN1 also facilitate the genetic and physical characterization of this very gene-rich region.     

Genetic and functional evidence that Type IV pili are required for social gliding motility in Myxococcus xanthus

The social gliding behaviour of Myxococcus xanthus has previously been associated with the presence of polar pili. A Tn 5 transposon insertion was isolated which introduces a defect in social gliding and is genetically linked to a known sgl locus; this insertion was found also to cause a piliation defect. A 2.7 kb section of DNA was isolated from either side of this transposon and sequenced, revealing three genes which encode amino acid sequences with substantial similarity to components of the Type IV pilus biogenesis pathway in Pseudomonas aeruginosa . The myxococcal pilA gene encodes a putative pilin precursor with a short signal sequence and processing site similar to those of other Type IV pilins. Myxococcal pilS and pilR encode amino acid sequences with similarity to PilS and PilR of P. aeruginosa , as well as to other members of the NtrB/C family of two-component regulators. Mutations within pilR and pilA that have no polar effect were demonstrated to be responsible for pilus and social motility defects. These results indicate that the pili of M. xanthus belong to the Type IV family of pili, and demonstrate that these pili are actually required for social motility.     

Interactions in cytochrome oxidase: Functions and structure

Mitochondrial cytochromec oxidase is an exceedingly complex multistructural and multifunctional membranous enzyme. In this review, we will provide an overview of the many interactions of cytochrome oxidase, stressing developments not covered by the excellent monograph of Wikström, Krab, and Saraste (1981), and continuing into early 1983. First we describe its functions (both in the nominal sense, as a transporter of electrons between cytochromec and oxygen, and in its role in energy transduction). Then we describe its structure, emphasizing the protein (its structure as a whole, the number and stoichiometry of its subunits, their biosynthetic origin, and their interactions with each other, with other components of the enzyme complex, and with the membrane as a whole). Finally, we present a model in which the protein conformation serves as the focus for the dynamic interaction of its two major functions.Abbreviations DCCD N,N-dicyclohexylcarbodiimide - E _m midpoint potential - EPR electron paramagnetic resonance - F₁ soluble portion of the ATP synthetase complex - NMR nuclear magnetic resonance - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate - SUPAGE SDS-urea-PAGE     

丁酸钠和pH值对离体蚕豆花药中小孢子有丝分裂的影响

含单核中后期至后期花粉的蚕豆离体花药,经过2mM丁酸钠24小时预处理后,再漂浮培养于pH5.8或7.0的液体培养基。以不经预处理的作为对照。结果如下: 1.培养后9天内,丁酸钠预处理和培养基pH值并不明显影响花粉退化百分率。2.培养初期,pH7.0显著促进小孢子不等分裂。3.丁酸钠预处理抑制培养初期的小孢子有丝分裂,而后又显著增加小孢子均等分裂百分率。4.丁酸钠预处理导致小孢子有丝分裂类型的趋向改变。本文还对丁酸钠导致有丝分裂类型趋向改变的可能原因,进行了讨论。     

人工补充寄主卵对松林内卵蜂种群消长的影响

在不同生境的松林中,人工补充寄主卵都能提高寄生效果。但林地生境不同,寄生率有明显差异。在松阔混交林中补充寄主,其寄生率比对照提高5.5—16.2倍。植被稀疏的纯松林效果较差,补充的寄生率比对照提高3.0倍。 卵蜂种群消长随季节温度而变化,全年以5月中旬至6月下旬和9月中旬至10月中旬为两个寄生高峰。卵蜂种群与松毛虫种群的消长存在较明显的相依关系,卵蜂种群随着松毛虫种群的消长而消长。施药对卵蜂种群有较大影响,施药区比对照区的寄生率约降低一倍。在混交林中填充寄主卵,能促进卵蜂种群世代延续。在逐步改善林地生境的基础上,利用人工补充寄主,可以代替人工繁蜂放蜂。     

The influence of adenosine 3′,5′-monophosphate upon the activity of the membrane-associated (Ca2++Mg2+)-dependent adenosine triphosphatase of the human erythrocyte

The phosphohydrolase activity of the membrane-associated $\text{(}\text{Ca}{}^{\mathrm{2+}}\text{+Mg}{}^{\mathrm{2+}}\text{)-dependent}$ adenosine triphosphatase (ATPase) of the human erythrocyte can be inhibited by micromolar or nanomolar concentrations of cyclic AMP. Millimolar concentrations of cyclic AMP are less effective. The inhibitory effect of cyclic AMP is potentiated in the presence of the phosphodiesterase inhibitor, theophylline.     

CAENORHABDITIS ELEGANS Fertilization-Defective Mutants with Abnormal Sperm

Seven new fertilization-defective mutants of C. elegans have been isolated and characterized; six are temperature sensitive, one is absolute and all are autosomal recessive. One mutation is in a previously described gene, while the other six define six new fer genes that appear to code for sperm-specific functions necessary for normal fertilization. In all fer mutants, both males and hermaphrodites accumulate sperm in near normal numbers. In hermaphrodites, mutant sperm contact the oocytes, but fail to fertilize them. Instead, the sperm are swept into the uterus by the passing oocytes and are expelled when oocytes are laid. Males of two fer mutants do not transfer sperm during copulation, but the other mutant males transfer sperm that fail to move to the spermatheca. Spermatozoa from fer-1 and fer-4 mutants are motility-defective in vitro as well as in vivo, and their pseudopods have an altered morphology. The period of development during which mutant hermaphrodites are temperature sensitive for fertility overlaps the time of sperm development. Some mutants are temperature sensitive throughout the entire period, and others are temperature sensitive during or just prior to spermiogenesis. In fer-4/+ and fer-7/+ males, the fertility of the mutation-bearing sperm is diminished, reducing the transmission ratio. This implies some post-meiotic expression of these genes.—This set of mutants provides a variety of functional and structural alterations in nematode sperm that should help identify and analyze gene products involved in sperm morphogenesis and motility.     

Sesquiterpene lactones of Vernonia — influence of glaucolide-A on the growth rate and survival of Lepidopterous larvae

Summary Sesquiterpene lactone glaucolide-A from Vernonia, incorporated in the rearing diets of five species of Lepidoptera, significantly reduced the rate of growth of larvae of the southern armyworm, Spodoptera eridania; fall armyworm, S. frugiperda; and yellowstriped armyworm, S. ornithogalli. Quantitative feeding tests demonstrated that decreased feeding levels and reduced growth resulted from ingestion of a sesquiterpene lactone. Ingestion of glaucolide-A increased the number of days to pupation in four of the species. In the southern armyworm, it significantly reduced pupal weight. Glaucolide-A decidedly reduced percentage of survival of southern and fall armyworms. Yellow woollybear, Diacrisia virginica, and cabbage looper, Trichoplusia ni, larvae were essentially uneffected by the ingestion of the sesquiterpene lactone. Sesquiterpene lactones adversely affect growth rate and survival of certain insects that feed upon plants containing them. They apparently function as defensive products, screening out a portion of the potential herbivores.Vernonieae: Compositae     

Heparin-inhibitable lectins: Marked similarities in chicken and rat

Extracts of young rat lung contain a heparin-inhibitable lectin that closely resembles one recently purified from chicken liver. Both lectins interact with heparin and N-acetyl-D-galactosamine, and were purified by gel filtration on Sepharose CL-2B followed by affinity chromatography on heparin-Sepharose. They both behave as high molecular weight aggregates that can be dissociated into two peptides with apparent molecular weights of 13,000 and 16,000 by gel electrophoresis in SDS. Samples of purified lectin contained up to 20% DNA by weight, and the degree of lectin aggregation and hemagglutination activity was greatly reduced by treatment with micrococcal nuclease without inhibiting heparin-binding activity. Association of lectin with DNA is an artifact of homogenization in high salt, since only 2% of the lectin is found associated with a purified nuclear fraction.