Expression of HOX homeogenes in human neuroblastoma cell culture lines

Mammalian genes containing a class-I homeobox (HOX genes) are highly expressed in the embryonic nervous system. As a first step towards the molecular analysis of the role these genes play in neural cells, we studied the expression of four human HOX genes in five neuroblastoma (NB) cell lines - SK-N-BE, CHP-134, IMR-32, SK-N-SH and LAN-1 - during the process of differentiation induced by treatment with retinoic acid (RA). The four genes, HOX1D, 2F, 3E and 4B, located at corresponding positions in the four HOX loci, share a high degree of sequence similarity with the Drosophila Deformed homeotic gene and constitute a homology group, group 10. One of these genes, HOX1D, is not expressed in the cells used, whereas the other three are highly expressed in untreated and RA-induced NB cells, even though the expression pattern in the various lines is slightly different for the three genes. Our analysis reveals a complex and specific expression pattern in these lines, paving the way to an identification of different NB-cell populations by means of specific HOX gene expression schemes. On the other hand, in every line studied, morphological maturation toward a neuronal differentiated phenotype appears to be associated with increased HOX gene expression.     

Chemical composition and antimicrobial activity of 2 Peruvian plants]

In this work we determined the hydrocarbon , sterol and triterpenoid composition of two plants used as antibacterial drug in traditional peruvian medicine, Berberis rariflora and Chenopodium multifidum. In both plants the presence of unsaturated hydrocarbons is very low, whereas the presence of odd hydrocarbons is considerable. The delta 7 sterols are more abundant than delta 5 sterols. We found also a great presence of stigmasterol derivatives in both plants, whereas lanosterol derivates are more abundant in B. rariflora. The microbiological tests shows for both plants an evident antibacterial activity against Gram(+) bacteria.     

gltF, a member of the gltBDF operon of Escherichia coli, is involved in nitrogen-regulated gene expression

We report here the construction and analysis of insertional mutations in each of the three genes of the gltBDF operon and the nucleotide sequence of the region downstream from gltD. Two open reading frames were identified, the first of which corresponds to gltF. The gltB and gltD genes code for the large and small subunits, respectively, of the enzyme glutamate synthase (GOGAT). gltF codes for a protein, with a molecular mass of 26,350 Da, which is required for Ntr induction. Histidase synthesis was determined as a measure of Ntr function. First, insertions in gltB, gltD or gltF all prevent Ntr induction. Second, complementation analysis indicates that high-level expression of both the gltD and gltF genes is required for the induction of the Ntr enzymes under nitrogen-limiting conditions, indicating that the phenotype of the gltB insertion probably results from polarity on gltD and gltF. Third, glutamate-dependent repression of the glt operon appears to be mediated by the product of the gltF gene. Thus, the gltBDF operon of Escherichia coli is involved in induction of the so-called Ntr enzymes in response to nitrogen deprivation, as well as in glutamate biosynthesis.     

Competition between laboratory populations of green leafhoppers,Nephotettix spp. (Homoptera: Cicadellidae)

Intra- and interspecific competition between laboratory populations of four green leafhoppers, Nephotettix spp. was studied in the laboratory under three different temperature regimes of 24°C, 27°C and 30°C. For the single-species population of the three tropical species, the equilibrium density increased as the temperature increased. On the other hand, for the temperature species N. cincticeps, the highest equilibrium density was at the intermediate temperature and the lowest at high temperature. Interspecific interactions between two tropical (N. virescens vs. N. nigropictus), a tropical and a temperature (N. virescens vs. N. cincticeps) and a rice-feeding and a grass-inhabiting (N. virescens vs. N. malayanus) Nephotettix species were also studied in the laboratory at the three temperature regimes. Temperature differentially affected the outcome of competition between two Nephotettix species. Between N. virescens and N. nigropictus, the latter was more successful over the former at low and intermediate temperatures, while the former was more successful at high temperature. Between N. virescens and N. cincticeps, the temperate species inhibited the growth of the tropical species at low temperature while the tropical species inhibited the growth of the temperate species at high temperature. At intermediate temperature, the population of N. virescens persisted at a slightly higher density over the population of N. cincticeps. Between the rice-feeding N. virescens and the grass-inhabiting N. malayanus, regardless of temperature the population density of the latter was greatly reduced and later became extinct while the population of the former continued its growth. These consequences of competition between two Nephotettix species conformed fairly well to those predicted by theLotka-Volterra model using demographic parameters specified for each species.     

Neuron-specific enolase (NSE)-like and neurofilament protein (NFP)-like immunoreactivities in the rat dorsal root ganglia and sciatic nerve

The presence of neuron-specific enolase (NSF) and neurofilament proteins (NFP) immunoreactivities (IR) was investigated in dorsal root ganglia (DRG) of adult rats at cervical, thoracic, lumbar and sacral levels. All neurons display NSE-like IR with a variable intensity of immunostain which is not related to the neuronal size. Conversely, the antibody against all three proteic subunits of NFP no labelled the primary sensory neurons, whereas the intraganglionic axons and dorsal root of spinal nerves result positives. In the sciatic nerve the immunoreactivity was similar for NSE- and NFP-like IR. No regional differences were found among the different levels of DRG for NSE-like IR. The present results demonstrate heterogeneity in the neurons of the rat. DRG for NSE-like IR, and differences between sensory neurons and fibers in the distribution of NFP-like IR.     

c-Myc induces cellular susceptibility to the cytotoxic action of TNF-alpha.

Tumor necrosis factor-alpha (TNF) is a multifunctional cytokine which is cytotoxic for some tumor cells and transformed cells. The molecular mechanisms which render transformed and tumor cells sensitive to the cytotoxic action of TNF are unclear. We show here that an increased expression of the c-Myc oncoprotein strongly increases cellular sensitivity to TNF cytotoxicity. In Rat1A fibroblasts, which are resistant to TNF, the addition of TNF with a concomitant activation of a hormone-inducible c-Myc-estrogen receptor chimera (MycER) resulted in apoptotic cell death. Similarly, c-Myc overexpression enhanced the sensitivity of NIH3T3 fibroblasts to TNF-induced death. The c-Myc and TNF-induced apoptosis was inhibited by ectopic expression of the Bcl2 oncoprotein and by the free oxygen radical scavenging enzyme Mn superoxide dismutase. Furthermore, in highly TNF-sensitive fibrosarcoma cells, antisense c-myc oligodeoxynucleotides caused a specific inhibition of TNF cytotoxicity. Our results suggest that the deregulation of c-Myc, which is common in human tumors and tumor cell lines is one reason why these cells are TNF sensitive.     

Two homologous genes, originated by duplication, encode the human hnRNP proteins A2 and A1.

Heterogeneous nuclear ribonucleoprotein (hnRNP) A2 belongs, with A1, B1 and B2, to the basic protein subset of the hnRNP complex in mammalian cells. All these proteins share a modular structure consisting of two conserved RNA binding domains linked to less conserved Gly-rich domains (2xRBD-Gly). In the framework of our studies on the genetic basis of hnRNP proteins structure and diversity we have isolated and sequenced the A2 gene and compared it to the previously described A1 gene. The A2 gene, which exists in a single copy on Ch. 7 band p15, is split in 12 exons including an alternatively spliced 36 nt mini exon specific for the human hnRNP protein B1. In this work we show that the intron/exon organisation of the A2 gene is identical to that of the A1 gene over the entire length, indicating a common origin by gene duplication. Moreover the comparison of corresponding exons evidences significant conservation also in the apparently divergent Gly-rich domains that could define previously unenvisaged structural and/or functional motifs. The A2 gene promoter is also analysed in comparison to that of the A1 gene.     

In Vivo and in Vitro Experimental Analysis of Lens Regeneration in Larval Xenopus laevis

After lentectomy of larval Xenopus laevis , the outer cornea undergoes tissue transformation resulting in formation of a new lens. This lens regeneration is triggered and sustained by neural retina. In the present study, lens-forming transformation of the outer cornea was completed in vitro when the outer cornea was cultured within the lentectomized eye-cup. Well-differentiated lens fiber cells, which showed positive immunofluorescence for total crystallins, were also formed when the outer cornea was cultivated with the retina. No lens tissue was formed when the cornea was cultured alone. Lens-forming transformation, originating from the cornea three and five days after lentectomy, completely regressed when the tissue was isolated in vitro . Fom the present and previous findings, we concluded that, the interaction of corneal cells with the retina plays a decisive role in lens regeneration in situ .