fimA-folD genes linkage in Salmonella identifies a putative junctional site of chromosomal rearrangement in the enterobacterial genome

Abstract Analysis of the Salmonella chromosomal region located upstream of the fimA gene (coding for the major type 1 fimbrial subunit) showed a close linkage of this gene to the folD gene (coding for the enzyme 5,10-methylenetetrahydrofolate dehydrogenase/5, 10-methenyltetrahydrofolate cyclohydrolase), indicating that the fim gene cluster of Salmonella , unlike that of Escherichia coli , has no regulatory genes located upstream of fimA and apparently terminates with this gene. The respective locations of the fim and folD genes in the E. coli and Salmonella genetic maps suggests that the fimA-folD intergenic region of Salmonella encompasses a junctional site of a genetic rearrangement that probably originated from the different chromosomal location of the fim genes in these species.     

Lung tissue mechanics and extracellular matrix composition in a murine model of silicosis.

The dynamic mechanical properties of lung tissue and its contents of collagen and elastic fibers were studied in strips prepared from mice instilled intratracheally with saline (C) or silica [15 (S15) and 30 days (S30) after instillation]. Resistance, elastance, and hysteresivity were studied during oscillations at different frequencies on S15 and S30. Elastance increased from C to silica groups but was similar between S15 and S30. Resistance was augmented from C to S15 and S30 and was greater in S30 than in S15 at higher frequencies. Hysteresivity was higher in S30 than in C and S15. Silica groups presented a greater amount of collagen than did C. Elastic fiber content increased progressively along time. This increment was related to the higher amount of oxytalan fibers at 15 and 30 days, whereas elaunin and fully developed elastic fibers were augmented only at 30 days. Silicosis led not only to pulmonary fibrosis but also to fibroelastosis, thus assigning a major role to the elastic system in the silicotic lung.     

D-aspartate oxidase from beef kidney. Purification and properties

The flavoprotein D-aspartate oxidase (EC 1.4.3.1) has been purified to homogeneity from beef kidney cortex. The protein is a monomer with a molecular weight of 39,000 containing 1 molecule of flavin. The enzyme as isolated is a mixture of a major active form containing FAD and a minor inactive form containing 6-hydroxy-flavin adenine dinucleotide (6-OH-FAD). The absorption and fluorescence spectral properties of the two forms have been studied separately after reconstitution of the apoprotein with FAD or 6-OH-FAD, respectively. FAD-reconstituted D-aspartate oxidase has flavin fluorescence, shows characteristic spectral perturbation upon binding of the competitive inhibitor tartaric acid, is promptly reduced by D-aspartic acid under anaerobiosis, reacts with sulfite to form a reversible covalent adduct, stabilizes the red anionic form of the flavin semiquinone upon photoreduction, and yields the 3,4-dihydro-FAD-form after reduction with borohydride. A Kd of 5 X 10(-8) M was calculated for the binding of FAD to the apoprotein. 6-OH-FAD-reconstituted D-aspartate oxidase has no flavin fluorescence, shows no spectral perturbation in the presence of tartaric acid, is not reduced by D-aspartic acid under anaerobiosis, does not stabilize any semiquinone upon photoreduction, and does not yield the 3,4-dihydro-form of the coenzyme when reduced with borohydride; the enzyme stabilizes the p-quinoid anionic form of 6-OH-FAD and lowers its pKa more than two pH units below the value observed for the free flavin. The general properties of the enzyme thus resemble those of the dehydrogenase/oxidase class of flavoprotein, particularly those of the amino acid oxidases.     

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.     

Hydrolysis and protection from hydrolysis of enkephalins in human plasma

Seven groups of enkephalin-degrading enzymes and three groups of inhibitors active on these enzymes were separated from human plasma. The activity of the enzymes in hydrolyzing enkephalins and of the inhibitors in protecting enkephalins from proteolysis was measured. Results obtained with the endogenous inhibitors were compared to those relative to synthetic inhibitors. Data obtained indicate that all enkephalin-degrading enzymes found in plasma are significantly inhibited by the endogenous substances present in this tissue. The inhibition of the different classes of plasma enzymes by two of the three groups of endogenous substances is quite uniform, while one group of inhibitors appears specific to dipeptidylpeptidases. Results obtained are discussed in terms of the functional role of the inhibitory substances and of the possible pharmacological implication of their presence in human plasma.     

Voltammetric studies on the electrochemical behaviour of membrane-entrapped hemes

Summary The electrochemical behaviour of Fe(III)-protoporphyrin IX entrapped into a cellulose triacetate membrane has been investigated by cyclic voltammetry. The physical entrapment into a solid matrix does not modify the redox properties of the entrapped berries, which also act as efficient promoters in the electrochemistry of cytochromec. Such a system represents a promising example of a simple solid-state promoter, and stimulates further investigations in order to obtain more complex systems that may be of significance for basic and applied bioelectrochemistry.     

Short term increase in risk of breast cancer after full term pregnancy.

To determine whether there is a short term increase in the risk of breast cancer after a full term birth data from two hospital based, case-control studies in Italy were pooled. Analysis was restricted to women aged under 50 with two or more children (573 women with cancer and 570 controls). A relative risk for breast cancer of 2.66 was seen in women who had given birth during the three years preceding the interview compared with women whose last birth had occurred 10 or more years before, after adjustment for age, age at first birth, and parity. The relative risk slowly decreased for women who had last given birth three to 10 years before. Multivariate analyses confirmed the protective effect of an early age at first birth and the age dependent effect of parity on the risk of breast cancer--that is, a direct relation below age 40 and an inverse one in older women. These data provide epidemiological evidence that a full term birth is followed by a transient increase in the risk of breast cancer, which for some time contrasts with and overcomes the long term protection of pregnancy at an early age. They therefore confirm predictions from animal studies and theoretical models that pregnancy prevents the early stages of breast carcinogenesis but promotes the late stages of the process.     

Antibiotic resistance in strains of Listeria spp. from meat products

The susceptibility or resistance to 26 antimicrobial agents was determined for 64 strains of Listeria monocytogenes and 102 strains of L. innocua isolated from Italian meat products. Some strains of L. monocytogenes were found to be resistant to tetracycline, erythromycin, co-trimoxazole and clindamycin. No plasmids were found in any L. monocytogenes strain. Five strains of L. innocua contained a 7.9 kbp plasmid, but these isolates were not resistant to any antibiotic in common and treatment with curing agents could not eliminate resistance to antibiotics. These results suggest that antibiotic resistance was not likely to be plasmid mediated in our strains.     

Characterization of amine oxidases from pisum, lens, Lathyrus and Cicer

Amine oxidases have been purified to homogeneity from Pisum sativum, Lens esculenta, Lathyrus sativus and Cicer arietinum. The enzymes have a M_r. of 150 000 and are composed of two identical subunits of 72 000. The amine oxidases showed an isoelectrophoretic heterogeneity.