Packing of ribosomes in crystals from the lizard Lacerta sicula

The packing of ribosomes in the large crystalline sheets found in the lizard Lacerta sicula has been investigated by electron microscopy. The ribosomes in each of the two layers composing a sheet are organised as tetramers on a P4 space group lattice. The two layers face in opposite directions and tend to be related to one another crystallographically, generating a family of P422 crystals of different unit cell dimensions. The projected structure of one layer was determined from negatively stained, isolated sheets by separating the contributions from each layer in Fourier transforms computed from electron micrographs. Comparison of the projection map with other, low resolution, analyses of images of isolated eukaryotic ribosomes indicates that the large subunit- small subunit axis lies approximately parallel to the plane of the sheet.     

Acylphosphatase increases the rate of ethanol production from glucose in cell-free extracts of Saccharomyces cerevisiae

Addition of acylphosphatase exerted a stimulating effect on the alcoholic fermentation of glucose by Saccharomyces cerevisiae. The rates of glucose degradation and ethanol production by cell-free extracts of the S-288C strain were measured in the absence and in the presence of various levels of this enzyme. Two acylphosphatase isoenzymes were used; one was purified from horse skeletal muscle and the other from human erythrocytes. Both increased the rate of alcoholic fermentation, but that from erythrocytes proved to be the more efficient. This stimulating action is probably due to an "uncoupling effect" of acylphosphatase on the fermentative process, through hydrolysis of 3-phosphoglyceroyl phosphate. This was demonstrated by the fact that alcoholic fermentation was stimulated considerably by a mixture of ADP and inorganic phosphate and by arsenate as well. The possibility of improving the fermentative capacity of microorganisms may have important biotechnological applications.     

Silicone-stimulated anthraquinone production and release by Morinda citrifolia in a two-liquid-phase system

Summary A 2.5-fold increase in the release of intracellular anthraquinones was obtained by adding 1 ml L^-1 silicone A to suspension cultures of Morinda citrifolia. Cell growth and secondary metabolite production were not affected even at high silicone A concentrations. Performance of the silicone treatment in a two-liquid-phase system (5 ml n-hexadecane/50 ml medium) resulted in a 150% increase of the overall secondary metabolite productivity.     

Effect of propylthiouracil-induced hypothyroidism on cerebral cortex of young and aged rats: Lipid composition of synaptosomes,muscarinic receptor sites,and acetylcholinesterase activity

The effect of hypothyroidism on the lipid composition of synaptosomes, density and affinity of muscarinic receptor sites, and acetylcholinesterase activity in the cerebral cortex of young and aged rats was investigated. The animals were made hypothyroid by adding 0.05% propyl-2-thiouracil to their drinking water for four weeks. This pathological state induced an increase in the relative percentage of sphingomyelin in young rats. In aged rats hypothyroidism induced a decrease of sphingomyelin and glycerophosphocholine and an increase of cholesterol. The effect of hypothyroid state on cerebral cortex resulted in an increase of acethylcholinesterase activity both in young and aged rats and was also reflected in an increase of density of M1-AChRs but only in the former.     

Routine colposcopic survey of patients with squamous atypia. A method for identifying cases with false-negative smears

Routine colposcopy was performed on 376 women with cervical squamous atypia (originally reported as "inflammatory atypia"). Colposcopy showed no abnormalities in 240 cases and a lesion in 136 cases; the latter were sampled by colposcopy-guided biopsy. The biopsy samples showed evidence of human papillomavirus (HPV) infection and/or grade I cervical intraepithelial neoplasia (CIN I) in 42 cases (11.1%), CIN II in 4 cases (1.1%) and CIN III in 5 cases (1.3%); the other 85 biopsied cases were histologically negative. Most cases of HPV/CIN I (35 of 42) and all of the cases of CIN II-III occurred in women under the age of 40. The detection rates were 4.4% for CIN II-III in women under the age of 40, 4.0% for HPV/CIN I in women 40 and older and 17.2% for HPV/CIN I in women under the age of 40 (P less than .001). It thus appears that women under the age of 40 who show cytologic evidence of squamous atypia would benefit from colposcopic examination.     

Nuclear localization of TRK-A in liver cells

The liver represents a site of expression of neurotrophins and their receptors. We have characterized the expression and intracellular localization of the nerve growth factor (NGF) receptor, Trk-A, in liver cells in vivo and in vitro. In both normal and fibrotic liver tissue, Trk-A immunostaining was present in different cell types, including parenchymal cells and cells of the inflammatory infiltrate. In hepatocytes and activated stellate cells (HSC), Trk-A showed a predominant nuclear localization, both in the presence and absence of injury. In cultured HSC, Trk-A was found to be functional, because exposure of the cells to recombinant NGF resulted in stimulation of cell migration and activation of intracellular signaling pathways, including Ras-ERK and PI3K/Akt. Remarkably, in cultured HSC, Trk-A staining was found constitutively in the nucleus. In these cells, Trk-A could be stained only by antibodies directed against the intracellular domain but not by those recognizing the extracellular portion of Trk-A suggesting that the intracellular portion of the receptor is the major determinant of nuclear Trk-A staining. In contrast to HSC, freshly isolated hepatocytes did not show any nuclear localization of the intracellular portion of Trk-A. In pheocromocytoma cells, nuclear staining for Trk-A was not present in conditions of serum deprivation, but could be induced by exposure to NGF or to a mixture of soluble mediators. We conclude that nuclear localization of the intracellular domain of Trk-A is observed constitutively in liver cells such as HSC, while in other cell types it could be induced in response to soluble factors.     

Co-culture of human fibroblasts,smooth muscle and endothelial cells promotes osteopontin induction in hypoxia

Arteriovenous fistulas (AVFs) are the preferred vascular access for haemodialysis of patients suffering from end-stage renal disease, a worldwide public health problem. However, they are prone to a high rate of failure due to neointimal hyperplasia and stenosis. This study aimed to determine if osteopontin (OPN) was induced in hypoxia and if OPN could be responsible for driving AVF failure. Identification of new factors that participate in remodelling of AVFs is a challenge. Three cell lines representing the cells of the three layers of the walls of arteries and veins, fibroblasts, smooth muscle cells and endothelial cells, were tested in mono- and co-culture in vitro for OPN expression and secretion in normoxia compared to hypoxia after silencing the hypoxia-inducible factors (HIF-1α, HIF-2α and HIF-1/2α) with siRNA or after treatment with an inhibitor of NF-kB. None of the cells in mono-culture showed OPN induction in hypoxia, whereas cells in co-culture secreted OPN in hypoxia. The changes in oxygenation that occur during AVF maturation up-regulate secretion of OPN through cell-cell interactions between the different cell layers that form AVF, and in turn, these promote endothelial cell proliferation and could participate in neointimal hyperplasia.     

Effect of copper on callus growth and gene expression of in vitro-cultured pith explants of Nicotiana glauca

Abstract

Copper is a vital component of electron transfer reactions mediated by proteins such as superoxide dismutase, cytochrome c oxidase and plastocyanin, but its concentrations in the cells needs to be maintained at low levels. In fact, the same ability of this essential metal ion to transfer electrons can also make it toxic to cells when present in excess. In vitro cultured explants of Nicotiana have been extensively used as a model to analyse metal-DNA interactions. In this report, we examined the effect of copper (1, 10 and 100 μM CuSO₄) on callus growth and protein synthesis of in vitro-cultured pith explants of Nicotiana glauca. In addition, a N. glauca cDNA library from Cu-treated (100 μM CuSO₄) pith explants cultured in vitro for 24 h was analysed by mRNA differential screening. The copper treatments inhibited callus growth of pith explants. The extent of inhibition was directly correlated to metal concentration. One and 10 μM CuSO₄ induced a notable increase of proteins synthesis relative to control explants. By contrast, 100 μM CuSO₄ inhibited protein synthesis relative to control extracts. The SDS-PAGE fluorography of pith proteins revealed, in Cu-treated extracts qualitative and/or quantitative differences in the synthesis of some polypeptides compared with control explants. Copper-modulated patterns of gene expression were also analysed by mRNA differential screening. The N. glauca genes isolated from Cu-treated pith explants shared common identities with other genes known to be elicited by diverse stresses, including pathogenesis and abiotic stress. In particular, the cDNAs were homologues to genes encoding cell wall proteins (i.e., extensin, and arabinogalactan-protein) and pathogenesis-related proteins (i.e., osmotin, endochitinase and a member of the Systemic Acquired Resistance gene family). In addition, an MD-2-related lipid-recognition (ML) domain protein and the enzyme S-adenosyl-L-homocysteine (AdoHcy) hydrolase appeared involved in the response to copper stress. In animal cells, AdoHcy hydrolase is a copper binding protein in vivo, which suggests that, also in plant tissues, this enzyme may play an important role in regulating the levels and intracellular distribution of copper.