Localization of ribosomal genes and nucleolar activity in lymphocytes of swine (Sus scrofa domestica) stimulated by phytohemagglutinins

The Pig chromosomes that contain rDNA sites displayed a polymorphism in the distribution of the genes among the nucleolar organizers located on pairs Nos. 8 and 10. Two, or more often three, active sites were observed in the chromosomes of lymphocytes stimulated with phytohemagglutinin. Only 5% of the metaphases showed a 4th small active site. At the onset of stimulation most cells contained one-two nucleoli; four nucleoli were never observed. After prolonged stimulation, the number of nuclei containing three nucleoli increased. A 4th small nucleolus appeared in a few cells, presumably formed by activation of the smallest rDNA site.     

Morpho-colorimetric characterization by image analysis to identify diaspores of wild plant species

Digital images of ex situ germplasm stored in the Sardinian Germplasm Bank (BG-SAR) were used for the application of image analysis techniques at the Stazione Sperimentale di Granicoltura per la Sicilia. The analysed accessions refer to 148 taxonomic units belonging to 102 genera and 47 families, typical of the Sardinian flora, and of the Mediterranean basin in general.The images of diaspores were acquired by a flatbed scanner and elaborated with a macro specially developed for the morphometric and colorimetric measurements. This method allowed carrying out a database for the characterization of autochthonous germplasm in entry to the bank and the realization of statistic classifiers for the discrimination of genera and species within the following families: Apiaceae, Boraginaceae, Caryophyllaceae, Cistaceae, Fabaceae and Scrophulariaceae. Such classifiers, based on the linear discriminant analysis (LDA) technique and checked by cross-validation, showed a performance included between 74.3% and 96.4%.In addition, for the genus Astragalus, it was possible to elaborate a classifier able to identify very similar taxa of a species complex, obtaining a performance between 83.7% and 100%. Such analysis proved the validity of the methodology also from the taxonomic point of view.Suggestions for subsequent methodological progress, which could offer applications in other research issues, such as ecological analysis, soil seed bank and archaeological botany are proposed.     

JAR human placental choriocarcinoma cells actively synthesize,take up and release polyamines

Uptake of polyamines has been investigated extensively in many cells, but not in placenta, where the polyamine– polyamine oxidase system is supposed to have an immunoregulatory function in pregnancy. Due to the importance of the transfer in this tissue, we have started this study. JAR human placental choriocarcinoma cells in monolayer at confluency were used as a model for measuring the key enzymes of polyamine synthesis and interconversion, rate of uptake and efflux, and the polyamine content. Polyamines were taken up by JAR cells and released by an independent mechanism. Ornithine decarboxylase and spermidine acetyltransferase activities and the rate of transport in and out of the cell were much higher than in other cells, such as L1210 cells. However the systems used for uptake and release appear in many respects to be similar to those observed in L1210 cells, but different from others. The uptake appears to be regulated by an inhibitory protein. Moreover, protein kinase C appears to be involved in the process. The efflux also is regulated as in L1210 cells, through control of H⁺ and Ca²⁺ concentration. In conclusion, this study shows that, in JAR cells, ornithine decarboxylase and spermidine acetyltransferase activities were much higher than in other cells, and so was the rate of transport in and out of the cells. As a result, a much higher polyamine content was observed.     

Effects of phototherapy with blue light on chromosomes from human lymphocytes

The dangerous effects of phototherapy have been matter of discussion in recent years. In order to evaluate its in vitro action on the human DNA, the authors have performed the karyotypic analysis on 20 cultures of lymphocytes. In different times 16 cultures have been exposed to the action of a "blue light" fluorescent lamp, commonly used for the treatment of neonatal jaundice. The authors have not evidenced any morphological or numerical change of the karyotype in any of the cultures.     

S-(N-methylcarbamoyl)glutathione: a reactive S-linked metabolite of methyl isocyanate

S-(N-methylcarbamoyl)glutathione, a chemically-reactive glutathione conjugate, has been isolated from the bile of rats administered methyl isocyanate and characterized, as its N-benzyloxycarbonyl dimethylester derivative, by tandem mass spectrometry. The ability of this glutathione adduct to donate an N-methylcarbamoyl moiety to the free -SH group of cysteine was evaluated in vitro with the aid of a highly specific thermospray LC/MS assay procedure. The glutathione adduct reacted readily with cysteine in buffered aqueous media (pH 7.4, 37 degrees C) and after 2 hr, 42.5% of the substrate existed in the form of S-(N-methylcarbamoyl)cysteine. The reverse reaction, i.e. between the cysteine adduct and free glutathione, also took place readily under these conditions. It is concluded that conjugation of methyl isocyanate with glutathione in vivo affords a reactive S-linked product which displays the potential to carbamoylate nucleophilic amino acids. The various systemic toxicities associated with exposure of animals or humans to methyl isocyanate could therefore be due to release of the isocyanate from its glutathione conjugate, which thus may serve as a vehicle for the transport of methyl isocyanate in vivo.     

Transposition of the kanamycin-resistance transposon Tn903

Summary The insertion of the kanamycin-resistance transposon, Tn903, into the Escherichia coli chromosome was studied. Tn903 is similar in structure to the well known transposons Tn5 and Tn10 in that it has a unique central sequence flanked by inverted repeat sequences extending more than a thousand base pairs. However, the central region of Tn903 has enough single-frame coding capacity only for the drug modifying enzyme, whereas Tn5 and Tn10 carry multigenic unique sequences. In this paper we demonstrate that two different classes of insertion event occur: (1) the first class is a complex event in which all or part of the genome of the bacteriophage lambda vector is co-inserted near the purE locus on the E. coli chromosome (11.7 min); (2) the second class appears to be a simple transposition event in which the transposon alone is inserted at relatively nonspecific sites in the chromosome, as has been described for Tn5 and Tn10. Furthermore both classes show dependency on homology-requiring recombination systems. We suggest that Tn903 transposes infrequently because it must utilize a recA-controlled host function, whereas Tn5 and Tn10 are recA-independent and encode similar but more active functions on the transposon DNA.     

Synthesis of nitrogenase and heterocysts by Anabaena sp. CA in the presence of high levels of ammonia.

Anabaena sp. CA fails to synthesize heterocysts and nitrogenase when grown with KNO3 as the nitrogen source. By contrast, both heterocysts and proheterocysts are synthesized in NH4Cl-containing media to a level nearly commensurate with cells grown in the absence of combined nitrogen. The growth rate of the organism in NH4Cl-containing media was similar to that obtained with KNO3 as the nitrogen source and was independent of the presence of N2 in the atmosphere. Thus, our results indicate that the organism assimilated nitrate and ammonium nitrogen equally well to meet the nitrogen requirements for growth. Moreover, in contrast to previous studies with other cyanobacteria, the repressor singal for heterocyst differentiation in Anabaena sp. CA is not derived from the metabolism of ammonia but appears to be involved with nitrate metabolism. Nitrogenase activity was partially expressed in NH4Cl-grown cultures. Increasing the level of nitrogenase activity to a value representative of a N2-grown culture required both the inhibition of ammonia assimilation and de novo protein synthesis. An increase in the number of mature heterocysts was not required. The fact that high levels of exogenous ammonia only partially repress the synthesis of proteins required for the maximum expression of nitrogenase activity in Anabaena sp. CA has important implications.     

Analysis of transmembrane proteins from eukaryotic cells

The topography and properties of plasma membrane proteins from mouse L-929 cells are studied by comparing their availability for enzymatic labeling on the external and internal surfaces of the membrane. In order to study the internal surface, phagolysosomes are prepared from cells after they ingest latex particles. The plasma membrane surrounding these seems to have an “inside-out” orientation. The sugars of the membrane glycoproteins in intact phagolysosomes are not available for interaction with lectins or available for periodate-borotritide labeling. A comparison of the lectin-binding proteins lableled by lactoperoxidase-catalyzed iodination on the external cell surface with those labeled on the internal cell surface suggests that a variety of plasma membrane glycoproteins span the lipid bilayer. Using two-dimensional gel electrophoresis it has been shown that selected proteins are labeled at both the internal and external faces of the plasma membrane. Analysis of the 2-D gel electrophoregrams reveals that there are two distinct prominent proteins at 60,000 and 100,000 daltons which are enzymatically iodinated from both sides of the membrane. The partial hydrolysis of the 100,000 dalton protein reveals that different peptides are iodinated when the iodination is performed on intact cells or on the phagolysosomes. These proteins are extensively phosphorylated in cells incubated with inorganic ³²P. We conclude that the phagolysosome is probably oriented in an “inside-out” configuration and that this membrane preparation can be used to study the topographic organization of membrane proteins. The use of oriented membranes, selective labeling of proteins, and affinity separation of proteins in combination with gel electrophoresis to define the position and properties of proteins is discussed.     

自然保护区管理中生态与娱乐属性的权衡:一个选择实验的应用

随着自然保护区多样化的发展以及旅游需求的日益增长,保护区管理者面临着保护生态环境与满足娱乐需求的双重压力,这使得保护区管理者需要更多的信息进行决策。以中国东北部的扎龙国家级自然保护区为例,进行了一项选择实验,选取生物多样性、预期游客数量、景区的环境教育设施、门票价格等4个属性,分别采用多项logit模型、随机参数logit模型和潜在分类模型,探究游客在可能存在冲突的管理优先级之间的偏好。目的是揭示游客如何评价保护区不同的管理属性,以及各属性的边际支付意愿和偏好,并根据这些信息制定有效的保护区管理指南。研究结果表明生物多样性是保护区游客最关注的属性,并且游客对于生态属性的关注度高于娱乐属性。因此,保护区管理者应首先维持并改善生物多样性及其生态环境,在不破坏生态环境的基础上开发具有环境教育作用的娱乐服务。此外,研究发现游客可分为生态友好型和价格敏感型两种类别,不同类型的群体对游览保护区存在不同偏好,女性和年轻的受访者对生态更友好,男性和年长的受访者对价格更敏感。本文的贡献是将某一方面属性价值的描述扩展到涵盖多个管理属性的研究,并为保护区管理中生态与娱乐的权衡问题提供了更具体的见解。