Deprenyl Protects Dopamine Neurons from the Neurotoxic Effect of 1-Methyl-4-Phenylpyridinium Ion

1-Methyl-4-phenylpyridinium ion (MPP+) is the product of the metabolic oxidation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by monoamine oxidase (MAO). MPP+ is toxic to 3,4-dihydroxyphenylethylamine (dopamine, DA) neurons in explant cultures of rat embryonic midbrain. Addition of 2.5 microM MPP+ to the feeding medium for 6 days results in significant reduction of the DA levels in the cultures (to 19% of control) as well as in the uptake of [3H]DA (to 32% of control). When the cultures are treated with the MAO inhibitor deprenyl (10 microM) 24 h prior to and during exposure to MPP+, the DA neurons are protected from the toxicity of the drug. In the combined deprenyl plus MPP+ treatment, the levels of DA in the cultures remain at the control range and the [3H]DA uptake is reduced to only 73% of control. These results indicate that MAO is involved in the toxicity of MPP+ on DA neurons.     

Extracellular matrix (ECM) modulates the EGF-induced migration of liver epithelial cells in serum-free,hormone-supplemented medium

Summary The influence of the extracellular matrix (ECM) glycoproteins collagen, IV laminin (LN), and fibronectin (FN) on the in vitro migration of epithelial cells was studied using the ECM migration track method (4) with preparations immunostained for LN and FN. The locomotion of rat liver epithelial cells stimulated to migrate in serum-free medium by epidermal growth factor (EGF) in the presence of the protein per cm². Neither LN nor collagen IV decreased the number of migrating cells, indicating that the inhibition is a specific effect of fibronectin. The data also indicate that the FN-mediated inhibition of migration is an additional and not alternative mechanism to the well-established contact inhibition of locomotion (1) which also occurs in liver epithelial cell cultures. The system is being used for a further analysis of the factors that influence migration of normal and neoplastic epithelial cells and the biochemical mechanisms underlying the migration reaction. Editor’s Statement This paper describes new and heretofore neglected aspects of EGF and fibronectin action on the migratory behavior of cultured cells. Gordon H. Sato     

苯胺嘧啶衍生物X-9通过下调整合素β1表达抑制肝细胞癌迁移侵袭

整合素在许多肿瘤细胞中高表达,并且参与肿瘤细胞的侵袭转移。在肝细胞癌中,整合素β1被报导高表达,并促进肿瘤细胞的侵袭。目前,对于整合素的表达调控癌细胞机制以及干预其表达进而抑制肿瘤细胞转移的研究较少。本研究探讨利用小分子化合物抑制整合素表达来抑制肿瘤细胞迁移和侵袭的可能。首先,对临床肝癌细胞患者癌组织和癌旁组织中的整合素β1的表达进行检测,发现其在癌组织中的表达显著高于癌旁组织（P<0.05）。对TCGA肿瘤数据库的生物信息学分析结果同样显示,整合素β1的高表达与肝癌的分期（P=0.019）和预后（P=0.013）相关。通过筛选发现,苯胺嘧啶衍生物X09可以抑制肝癌细胞中整合素β1的mRNA和蛋白质的表达（P<0.01）。细胞划痕愈合实验和细胞穿孔实验结果显示,苯胺嘧啶衍生物X-9能够抑制肝癌细胞的迁移和侵袭（P<0.01）。进一步的研究证实,在肝癌细胞中外源表达整合素β1可以逆转X-9对肝癌细胞迁移和侵袭的抑制;而在敲低整合素β1的细胞中,X-9对细胞的迁移和侵袭的抑制被消除。因此,鉴定出苯胺嘧啶衍生物X-9可以通过下调整合素β1表达,进而抑制肝癌细胞的迁移和侵袭。     

Transition Metals Potentiate Paraquat Toxicity

The involvement of transition metal ions in paraquat toxicity was studied in bacterial model system. We show that the addition of micromolar, or lower, concentrations of copper dramatically enhanced the rate of bacterial inactivation. In contrast, the addition of chelating agents totally eliminated the killing of E. coli. No inactivation was observed under anaerobic exposure to paraquat, both in the absence and presence of copper. However, in the presence of copper, the anaerobic addition of hydrogen peroxide resulted in complete restoration of inactivation as under aerobiosis.

Paraquat either produces superoxide ions or directly reduces bound copper ions in a catalytic mode. The reduced cuprous complexes react with hydrogen peroxide to locally form hydroxyl radicals (OH) which are probably responsible for the deleterious effects.

This study indicates the involvement of a site-specific metal-mediated Haber-Weiss mechanism in paraquat toxicity. It is in agreement with earlier observations that copper unusually enhance biological damage induced by either superoxide or ascorbate.     

Do Chaoborus larvae migrate in temporary pools?

A diurnal vertical migration of larvae of Chaoborus punctipennis (Say) was observed in shallow temporary woodland pools in East Texas. In the laboratory, in 153 cm tall columns, the larvae underwent a much greater migration than possible in the shallow pools. We hypothesize that the migratory behavior and transparent body of Chaoborus larvae may have originally evolved in such shallow water habitats. These traits enabled Chaoborus to successfully invade the quite different adaptive zone of predation in the plankton of deep lakes.     

Diel migration and vertical distribution of Cladocera in Lake D. Helvecio (Minas Gerais,Brazil)

Six genera of Clad ocera (Diaphanosoma, Daphnia, Ceriodaphnia, Moina, Bosmina, Bosminopsis), each of them usually with only one species were found in Lake D. Helvecio, a natural valley lake located in the eastern part of Brazil. Diurnal migratory movements of the organisms observed in this lake showed a different pattern in different species. Closely related species, which explore the same food source, live in different layers, thus avoiding interspecific competition. The migratory behaviour of the species was studied mainly in relation to temperature and oxygen distribution in the lake. Thus, analyses were made in the summer (January, 1978) when a strong stratification occurs with the establishment of a thermocline and an oxycline. Comparisons were made also with the data obtained in winter (July, 1978), when a complete mixing of water occurs.     

Effect of nonanoic acid and other short chain fatty acids on exchange properties in embryonic axes of Cicer arietinum during germination

Nonanoic acid, which inhibits germination in several seeds, enhanced ion efflux from embryonic axes of Cicer arietinum L., especially at temperatures above 25°C. Other short chain fatty acids had little effect on germination and ion leakage. Nonanoic acid also decreased uptake of ⁸⁶Rb⁺ and ²²Na⁺ and increased efflux of both isotopes from the embryonic axes into the incubation solution. Fusicoccin, which stimulates early germination in C. arietinum , counteracted the effects of nonanoic acid at both 25 and 30°C. These results suggest that nonanoic acid affects the integrity of plasmalemma and other membrane systems. Nonanoic acid thus inhibits cell elongation during early germination by disturbing ion exchange and inhibiting water uptake.     

The effects of various nutritional supplements on the growth,migration and differentiation ofxenopus laevis neural crest cells in vitro

Summary This study investigates the nutritional requirements ofXenopus laevis neural crest cells and melanophores developing in vitro. A comparison is made between the growth and differentiation of cells in serum-containing medium and a chemically defined, serum-free medium that we have designed. Our chemically defined medium is more efficient than serum-supplemented medium in promoting proliferation of these cells. Several supplements are required to enhance culture development. These include insulin, α-melanocyte stimulating hormone, somatotropin, luteotrophic hormone, linoleic acid, uridine, and putrescine. In addition, collagen and fibronectin provide the most conductive environment tested for cell migration and adhesion. This work was supported by establishment and major equipment grants from the Alberta Heritage Foundation for Medical Research to N. C. M. Nadine C. Milos is a Heritage Medical Research Scholar of the Alberta Heritage Foundation for Medical Research.     

Effect of calcium ion on cytoplasmic streaming during turgor regulation in a brackish water charophyte Lamprothamnium

Abstract The brackish water charophyte Lamprothamnium succinctum regulates its turgor pressure against changes in the external osmotic pressure. Upon hypotonic treatment, the rate of cytoplasmic streaming in the internodal cells fell to almost zero, and then recovered to the original value within 20 min. The decrease could be inhibited by lowering the external Ca²⁺ concentration in the hypotonic medium. Also, cytoplasmic streaming in tonoplast-free cells of L. succintum was sensitive to Ca²⁺ like freshwater charophyte. Thus, the concentration of free Ca²⁺ in the cytoplasm seems to increase transiently upon hypotonic treatment.