Insulin and nitric oxide stimulates glucose transport in human placenta

The present work examines whether insulin and NO can act as regulators of glucose transport in placenta. Glucose uptake (2-deoxy D-[(3)H]glucose) was measured in the absence (control or basal values) and in the presence of insulin (1200 microU/ml) or SNP (20 microM) in isolated perfused cotyledons and tissue slices preparations of human placenta. Both insulin and NO significantly increased glucose uptake by 20 and 27 per cent, respectively. Insulin decreased the Km of glucose transport from 42.5 +/- 2.69 to 35.1 +/- 2.58 mM. The stimulatory effect of SNP was mimicked by 8-CPT-cGMP and was completely blocked by the guanylate cyclase inhibitor, ODQ (10 microM). ODQ and the NOS inhibitor, L-NAME (100 microM), decreased basal glucose uptake but did not affect insulin-stimulated glucose transport. Taken together, these findings indicate that insulin and NO stimulate glucose uptake in human placenta and suggest that both potential regulators of glucose transport use different signaling pathways.     

A fungal tRNA of Aspergillus niger induces IFN-beta synthesis in HEp-2 cells

In this work, we evaluated the capacity of a fungal transfer RNA (F-tRNA) from Aspergillus niger to protect HEp-2 cells against a viral infection, and as an inducer of IFN-beta synthesis. HEp-2 cells previously incubated with F-tRNA, polyI:polyC, or IFN-alpha, at different concentrations for 24 h were infected with 200 pfu of adenovirus type 6 (AdV-6); after 5 days, we determined cellular viability, cytopathic effect of the virus, optimal concentration necessary to inhibit the cytopathic effect, and IFN-beta expression by RT-PCR. Results showed that HEp-2 cells treated with F-tRNA were less susceptible to the cytopathic effect of AdV-6 infection than those incubated with polyI:polyC (p < 0.05). On the other hand, F-tRNA- treated HEp-2 cells expressed IFN-beta mRNA, whereas monolayers incubated with polyI:polyC or IFN-alpha did not. Our results suggest that F-tRNA protected HEp-2 cells against AdV-6 infection, due to its capacity to induce IFN-beta synthesis.     

The Leptospira interrogans lexA gene is not autoregulated

Footprinting and mutagenesis experiments demonstrated that Leptospira interrogans LexA binds the palindrome TTTGN(5)CAAA found in the recA promoter but not in the lexA promoter. In silico analysis revealed that none of the other canonical SOS genes is under direct control of LexA, making the leptospiral lexA gene the first described which is not autoregulated.     

A second outer-core region in Klebsiella pneumoniae lipopolysaccharide

Up to now only one major type of core oligosaccharide has been found in the lipopolysaccharide of all Klebsiella pneumoniae strains analyzed. Applying a different screening approach, we identified a novel Klebsiella pneumoniae core (type 2). Both Klebsiella core types share the same inner core and the outer-core-proximal disaccharide, GlcN-(1,4)-GalA, but they differ in the GlcN substituents. In core type 2, the GlcpN residue is substituted at the O-4 position by the disaccharide beta-Glcp(1-6)-alpha-Glcp(1, while in core type 1 the GlcpN residue is substituted at the O-6 position by either the disaccharide alpha-Hep(1-4)-alpha-Kdo(2 or a Kdo residue (Kdo is 3-deoxy-D-manno-octulosonic acid). This difference correlates with the presence of a three-gene region in the corresponding core biosynthetic clusters. Engineering of both core types by interchanging this specific region allowed studying the effect on virulence. The replacement of Klebsiella core type 1 in a highly type 2 virulent strain (52145) induces lower virulence than core type 2 in a murine infection model.     

Polyamines and proline are affected by cadmium stress in nodules and roots of soybean plants

The effect of moderate (50 M) and high (200 M) doses of Cd were studied in relation to polyamine (Pas) metabolism, proline level and the glutamine synthetase/glutamate synthase system (GS/GOGAT) activity in nodules and roots of soybean plants during 6 days of treatment. The lower Cd concentration increased putrescine (Put) in both nodules and roots, while 200 M Cd increased Spm only in nodules and Put in roots. Spermidine (Spd) decreased in roots under both Cd concentrations. Arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) were both involved in Put biosynthesis in roots. In nodules, Put formation could mainly be attributed to ODC activity. Diamine oxidase (DAO) activity was severely reduced by 50 and 200 M Cd either in nodules or roots. The GS/GOGAT system activity was depressed either with 50 or 200 M Cd, but most significantly with the highest metal concentration. Under 200 M Cd, GS activity decayed to 25% or 60% of the control in nodules and roots, respectively, while GOGAT decreased 85% in nodules and 79% in roots by day 4 of treatment. Ammonium increased greatly in nodules (200% over the controls) and roots (100%) under 200 M Cd. Proline concentration increased significantly in nodules and roots under both Cd treatments, more markedly under 200 M Cd. The relationship between Pas and proline accumulation and nitrogen assimilation is discussed.     

Effects of oral estrone on rat energy balance

Oral doses of estrone from 10 nmol/(kg day) to 10 micromol/(kg day) were given to adult Wistar male rats for 10 days. Body composition, energy balance, total body estrone balance and plasma metabolites and hormones were measured at the end of the treatment. Body weight (as well as food intake, body energy, fat and water accrual) increased at doses in the 10--100 nmol/(kg day) range, but decreased at higher doses. Energy expenditure decreased with increasing doses of estrone. Plasma metabolite changes suggested the maintenance of energy homeostasis, and lipid parameters indicated that lipid mobilization increased with the increasing doses of estrone. Plasma estrone, acyl-estrone and estradiol levels decreased at low doses and increased at high doses of estrone. We conclude that: (a) repeated estrone gavages, even at very high doses, do not result in the accrual of estrone in the body; (b) low doses of estrone promote growth and high doses decrease body mass and fat accretion; (c) administration of estrone at low doses decreases its circulating levels and the levels of estradiol and acyl-estrone, a situation reverted at higher doses and (d) estrone administration induces a dose-dependent shift towards lower energy expenditure.     

Nonhealing infection despite Th1 polarization produced by a strain of Leishmania major in C57BL/6 mice

Experimental Leishmania major infection in mice has been of immense interest because it was among the first models to demonstrate the importance of the Th1/Th2 balance to infection outcome in vivo. However, the Th2 polarization that promotes the development of nonhealing cutaneous lesions in BALB/c mice has failed to adequately explain the mechanisms underlying nonhealing forms of leishmaniasis in humans. We have studied a L. major strain from a patient with nonhealing lesions that also produces nonhealing lesions with ulcerations and high parasite burden in conventionally resistant C57BL/6 mice. Surprisingly, these mice develop a strong, polarized, and sustained Th1 response, as evidenced by high levels of IFN-gamma produced by Leishmania-specific cells in the draining lymph node and in the ear lesion, and an absence of IL-4 or IL-13. The parasites fail to be effectively cleared despite high level induction of inducible NO synthase in the lesion, and despite their sensitivity to killing by IFN-gamma-activated macrophages in vitro. Infection of IL-10(-/-) mice, blockade of the IL-10R, or depletion of CD25(+) cells during the chronic phase promotes parasite killing, indicating that IL-10 and regulatory T cells play a role in rendering the Th1 responses ineffective at controlling infection in the skin. Mice with nonhealing primary lesions are nonetheless resistant to reinfection in the other ear. We suggest that nonhealing infections in animal models that are explained not by aberrant Th2 development, but by overactivation of homeostatic pathways designed to control inflammation, provide better models to understand nonhealing or reactivation forms of leishmaniasis in humans.     

Genome Replication and Postencapsidation Functions Mapping to the Nonstructural Gene Restrict the Host Range of a Murine Parvovirus in Human Cells

The infection outcome of the Parvoviridae largely relies on poorly characterized intracellular factors modulated by proliferation, differentiation, and transformation of host cells. We have studied the interactions displayed by the highly homologous p and i strains of the murine parvovirus minute virus of mice (MVM), with a series of transformed cells of rat (C6) and human (U373, U87, SW1088, SK-N-SH) nervous system origin, seeking for molecular mechanisms governing parvovirus host range. The MVMp infection of C6 and U373 cells was cytotoxic and productive, whereas the other nervous cells behaved essentially as resistant to this virus. In contrast, MVMi did not complete its life cycle in any of the human nervous cells, though it efficiently killed the astrocytic tumor cells by two types of nonproductive infections: (i) normal synthesis of all viral macromolecules with a late defect in infectious virion maturation and release to the medium in U373; and (ii) high levels of accumulation of the full set of viral messenger RNAs and of both nonstructural (NS-1) and structural (VP-1 and VP-2) proteins, under a very low viral DNA amplification, in U87 and SW1088 cells. Further analyses showed that U87 was permissive for nuclear transport of MVMi proteins, leading to efficient assembly of empty viral capsids with a normal phosphorylation and VP1-to-VP2 ratio. The DNA amplification blockade in U87 occurred after conversion of the incoming MVMi genome to the monomeric replicative form, and it operated independently of the delivery pathway used by the viral particle, since it could not be overcome by transfection with cloned infectious viral DNA. Significantly, a chimeric MVMi virus harboring the coding region of the nonstructural (NS) gene replaced with that of MVMp showed a similar pattern of restriction in U87 cells as the parental MVMi virus, and it attained in U373 cultures an infectious titer above 100-fold higher under equal levels of DNA amplification and genome encapsidation. The results suggest that the activity of complexes formed by the NS polypeptides and recruited cellular factors restrict parvovirus DNA amplification in a cell type-dependent manner and that NS functions may in addition determine MVM host range acting at postencapsidation steps of viral maturation. These data are relevant for understanding the increased multiplication of autonomous parvovirus in some transformed cells and the transduction efficacy of nonreplicative parvoviral vectors, as well as a general remark on the mechanisms by which NS genes may regulate viral tropism and pathogenesis.