Increased assembly of cytoskeletal proteins associated with the transformation of human liver cells into fibroblast-like cells.

A topoisomerase II inhibitor, novobiocin, and a deacetylase inhibitor, butyrate, synergistically transformed human liver cells into fibroblast-like cells. This morphological change was associated with an increased production of procollagen type III peptide and a simultaneous assembly of actin, tubulin, vimentin and cytokeratin. Novobiocin and butyrate had no marked effect on the phosphorylation state of cytokeratin proteins, but synergistically enhanced [3H]acetate uptake. From these results, it can be speculated that protein acetylation plays an important role in inducing the assembly of cytoskeletal proteins and the morphological transformation of human liver cells.     

Innate versus learned odour processing in the mouse olfactory bulb

The mammalian olfactory system mediates various responses, including aversive behaviours to spoiled foods and fear responses to predator odours. In the olfactory bulb, each glomerulus represents a single species of odorant receptor. Because a single odorant can interact with several different receptor species, the odour information received in the olfactory epithelium is converted to a topographical map of multiple glomeruli activated in distinct areas in the olfactory bulb. To study how the odour map is interpreted in the brain, we generated mutant mice in which olfactory sensory neurons in a specific area of the olfactory epithelium are ablated by targeted expression of the diphtheria toxin gene. Here we show that, in dorsal-zone-depleted mice, the dorsal domain of the olfactory bulb was devoid of glomerular structures, although second-order neurons were present in the vacant areas. The mutant mice lacked innate responses to aversive odorants, even though they were capable of detecting them and could be conditioned for aversion with the remaining glomeruli. These results indicate that, in mice, aversive information is received in the olfactory bulb by separate sets of glomeruli, those dedicated for innate and those for learned responses.     

Shoot control of root development and nodulation is mediated by a receptor-like kinase

In legumes, root nodule organogenesis is activated in response to morphogenic lipochitin oligosaccharides that are synthesized by bacteria, commonly known as rhizobia. Successful symbiotic interaction results in the formation of highly specialized organs called root nodules, which provide a unique environment for symbiotic nitrogen fixation. In wild-type plants the number of nodules is regulated by a signalling mechanism integrating environmental and developmental cues to arrest most rhizobial infections within the susceptible zone of the root. Furthermore, a feedback mechanism controls the temporal and spatial susceptibility to infection of the root system. This mechanism is referred to as autoregulation of nodulation, as earlier nodulation events inhibit nodulation of younger root tissues. Lotus japonicus plants homozygous for a mutation in the hypernodulation aberrant root (har1) locus escape this regulation and form an excessive number of nodules. Here we report the molecular cloning and expression analysis of the HAR1 gene and the pea orthologue, Pisum sativum, SYM29. HAR1 encodes a putative serine/threonine receptor kinase, which is required for shoot-controlled regulation of root growth, nodule number, and for nitrate sensitivity of symbiotic development.     

Smart Processing in Materials Tectonics: Fabrication of Photonic Crystals for Terahertz Wave Control by Using Micro-Stereolithography

Photonic crystals with three-dimensional dielectric structures were fabricated to control terahertz waves effectively by using micro-stereolithography of a CAD/CAM process. The photonic crystals with a diamond structure composed of acrylic lattice with nanosized alumina particles were fabricated. Dense alumina structures were obtained by successive dewaxing and sintering in an air atmosphere. The electromagnetic wave properties of these samples were measured by using a terahertz spectroscopy device. The micro periodic structures exhibited perfect band gaps in the terahertz range. To control terahertz waves, micrometer sized electromagnetic devices for cavities, filters, and antennas will be necessary.     

Cigarette smoke induces DNA single-strand breaks in human cells

Epidemiological evidence suggests that smoking is a major cause of human lung cancer. However, the mechanism by which cigarette smoke induces the cancer remains obscure, although in tobacco carcinogenesis, promotion and/or co-carcinogenesis may have crucial roles. The epidemiological data show that if an individual stops smoking, the risk of his contracting lung cancer increases no further. Moreover, laboratory experiments show that cigarette smoke condensate (CSC) exhibits co-carcinogenic and promoting activities in tumour production and malignant transformation. Clastogenic action is thought to be intimately involved in tumour promotion, and it is therefore interesting that visible chromosome changes such as chromosome aberrations and sister chromatid exchanges are known to be caused by cigarette smoke. However, there has been no previous direct demonstration that cigarette smoke can cause single-strand breaks (SSB) in DNA. Here we report that cigarette smoke induces considerable numbers of DNA SSB in cultured human cells, and that such strand breaks may be ascribed to active oxygen generated from cigarette smoke.     

Epidermal growth factor stimulates proliferation of rat hepatoma cells producing alpha-fetoprotein.

Epidermal growth factor stimulated both [3H]thymidine uptake and proliferation of rat AH66 hepatoma cells. However, the increase in cell number was not accompanied by a proportional increase in the levels of alpha-fetoprotein of the culture media. The effects of EGF on the cell proliferation were antagonized by N6,O2'-dibutyryl cAMP.     

Stimulation of human chorionic gonadotropin and progesterone secretion by tumor promoters,phorbol ester and teleocidin B,in cultured choriocarcinoma cells

Summary Both 12-O-tetradecanoyl-phorbol-1-acetate and teleocidin B stimulated the secretion of human chorionic gonadotropin by cultured choriocarcinoma cells. These tumor promoters also stimulated production of progesterone in the cells. However, the 2 tumor promoters did not exert a marked effect on the cellular binding of epidermal growth factor that also had a stimulatory effect on production of these hormones.     

Influence of pulsing electromagnetic field on the frequency of sister-chromatid exchanges in cultured mammalian cells

Exposures of Chinese hamster cells to pulsing electromagnetic field (PEMF) with 0.18-2.5 mT did not influence the baseline frequency of sister-chromatid exchanges (SCE). The results suggest that PEMF with the magnetic intensity examined does not interfere with DNA replication nor produce DNA lesions, thereby leading to an increased frequency of SCE.