Trait-independent habitat associations explain low co-occurrence in native and exotic birds on a tropical volcanic island

On oceanic islands, strong human impacts on habitats, combined with introductions of exotic species, modify the composition of terrestrial bird assemblages and threaten their ecological functions. In La Réunion, an oceanic island located in the Madagascan region, a national park was established in 2007 to counter the ecosystem-level effects of three centuries of habitat conversion, native species destruction and exotic species introductions. Here, we investigated how bird assemblages were structured in these human-modified landscapes, 10 years before the national park set out its first conservation measures. We used a combination of multivariate statistics and generalized additive models to describe variations in the taxonomic and functional composition and diversity of 372 local bird assemblages, encompassing 20 species, along gradients of habitat composition and configuration. We found that native species were tied to native habitats while exotic species were associated with urban areas and man-modified landscape mosaics, with some overlap at mid-elevations. Species' trophic preferences were segregated along habitat gradients, but ecological traits had an overall weak role in explaining the composition of species assemblages. Hence, at the time of the survey, native and exotic species in La Réunion formed two spatially distinct species assemblages with contrasting ecological trait suites that benefited from antagonistic habitat compositions and dynamics. We conclude that our results support the analysis of historical data sets to establish reference points to monitor human impacts on insular ecosystems.

The feasibility of masks and face shields designed by 3D printing makers; some considerations of their use against the COVID-19

The use of mask and face shield has been established as one of the main preventive measures for the control of COVID 19 spread. In Mexico, as well as in other regions of the world, 3D printing has been employed for the design and production of masks and face shields as personal protective equipment (PPE). These models have been fabricated mainly by the makers, industries, and university communities; therefore, it is necessary to analyze the feasibility of the 3D printed PPE to understand its advantages and limitations. In this work, some characteristics of masks and face shields fabricated by additive manufacturing were studied to explore their viability as protection against flow fluids similar to human sneeze. In the present paper, the PPE was designed, and 3D printed utilizing three types of polylactic acid (PLA) as base material. The morphology and the surface elemental analyses of sectioned samples were analyzed by scanning electron microscopy (SEM) and energy dispersion x-ray spectroscopy (EDS). Showing spacing between printed layers, porous areas, and dispersed copper particles. On the other hand, a computational fluid dynamics (CFD) simulation was carried out, the results demonstrated the importance of using PPE for protection of a possible exposure to a “contaminated” aerosol and human sneeze. Based on the abovementioned results, it is possible to consider the commercial PLA as suitable material for the manufacturing of PPE due to its capability to be disinfected employing isopropanol, ethanol, or commercial disinfectants.

Forests Without Frugivores and Frugivores Without Forests – An Investigation Into the Causes of a Paradox in One of the Last Archipelagos Colonized by Humans

The Mascarenes are sadly famous worldwide for the massive extinction of their native vertebrates since recent human colonization. However, extinction patterns show astonishing disparities between the two main islands and between lineages of forest vertebrates. On Réunion (2,512 km2, 3,070 m) where about a third of native habitats remains, most large-bodied vertebrates, especially frugivores, collapsed by the first half of the 18th century, while several have survived longer and some still exist on Mauritius (1,865 km2, 828 m) where more than 95% of native habitats have been transformed. Considering lineages of forest vertebrates shared by both islands (23 genera, 53 species), we test the hypothesis that differing patterns of lowland suitable habitat destruction is the main cause behind this paradox. Before that, we assess the potential impact of other major drivers of extinctions since first contact with humans. Firstly, Mauritius shows earlier and more numerous introductions of mammal predators known for their devastating impact (except northern islets which have thus become important sanctuaries for several squamates). Secondly, settlers were inveterate hunters on both islands, but while Réunion was overhunted before Mauritius, the burst of human population in the latter in late 18th century has not led to the rapid extinction of all large native vertebrates. These two factors alone therefore cannot explain the observed paradox. Rather, the early destruction of lowland habitats (<400 m) on Réunion is concomitant with most extinctions of forest vertebrate, notably frugivores that rapidly lost most lowland habitats dominated by large fleshy-fruited plants. Moreover, landform-induced fragmentation has likely decreased the ability of adjacent habitats to act as effective refuges. Conversely, Mauritius retained suitable low-fragmented habitats until the late 19th which probably allowed, at least for a time, several native vertebrates to escape from multiple human-induced disturbances. Despite the almost total destruction of native habitats since then on Mauritius, conservation actions have saved several threatened vertebrate species that play a fundamental role in the functioning of native ecosystems. The fact that there are now more favorable habitats on Réunion than on Mauritius argues for the rewilding of Réunion with these extant large vertebrates.

Changes in Bacterial Diversity, Composition and Interactions During the Development of the Seabird Tick Ornithodoros maritimus (Argasidae)

Characterising within-host microbial interactions is essential to understand the drivers that shape these interactions and their consequences for host ecology and evolution. Here, we examined the bacterial microbiota hosted by the seabird soft tick Ornithodoros maritimus (Argasidae) in order to uncover bacterial interactions within ticks and how these interactions change over tick development. Bacterial communities were characterised through next-generation sequencing of the V3-V4 hypervariable region of the bacterial 16S ribosomal RNA gene. Bacterial co-occurrence and co-exclusion were determined by analysing networks generated from the metagenomic data obtained at each life stage. Overall, the microbiota of O. maritimus was dominated by four bacterial genera, namely Coxiella, Rickettsia, Brevibacterium and Arsenophonus, representing almost 60% of the reads. Bacterial diversity increased over tick development, and adult male ticks showed higher diversity than did adult female ticks. Bacterial networks showed that co-occurrence was more frequent than co-exclusion and highlighted substantial shifts across tick life stages; interaction networks changed from one stage to the next with a steady increase in the number of interactions through development. Although many bacterial interactions appeared unstable across life stages, some were maintained throughout development and were found in both sexes, such as Coxiella and Arsenophonus. Our data support the existence of a few stable interactions in O. maritimus ticks, on top of which bacterial taxa accumulate from hosts and/or the environment during development. We propose that stable associations delineate core microbial interactions, which are likely to be responsible for key biological functions.

Great Genetic Diversity but High Selfing Rates and Short-Distance Gene Flow Characterize Populations of a Tree (Foetidia; Lecythidaceae) in the Fragmented Tropical Dry Forest of the Mascarene Islands

Following the global trend of deforestation and degradation, tropical dry forests in the Mascarenes archipelago on Reunion has undergone harsh reduction and fragmentation within 3 centuries of human occupation. We investigated the genetic diversity, mating system, and gene flow in fragmented populations of the native tree Foetidia mauritiana (Lecythidaceae) on Reunion, using microsatellite genotyping of adults (in- and ex situ) and seed progenies (in situ only). To test genetic isolation between the Mascarene islands, we also genotyped conspecific adults on Mauritius, and trees of Foetidia rodriguesiana on Rodrigues. We found a high genetic diversity among the trees on Reunion, but no population structure (G'ST: 0.039-0.090), and an increase of the fixation index (FIS) from adults to progenies. A subsequent analysis of mating systems from progeny arrays revealed selfing rates >50% in fragmented populations and close to 100% in lone trees. A paternity analysis revealed pollen flow ranging from 15.6 to 296.1 m within fragments. At broader scale, the populations of F. mauritiana on Reunion and Mauritius are genetically differentiated. The morphologically allied taxa F. rodriguesiana and F. mauritiana are clearly isolated. Therefore, this case study shows that genetic diversity may persist after deforestation, especially in long-lived tree species, but the reproductive features may be deeply altered during this process. This would explain the low seed production and the absence of recruitment in F. mauritiana. Restoration programs should take into account these features, as well as the importance that trees ex situ represent in restoring and conserving diversity.

Macroalgae as a tool for assessing the ecological status of coral reefs under the Water Framework Directive: A case study on the reef flats of La Réunion (Indian Ocean)

The monitoring of macroalgae is required by the Water Framework Directive (WFD) to achieve good ecological status for coastal waters and specific questions arise for tropical ecosystems belonging to the outermost European regions. To assess the suitability of macroalgae as a biological quality indicator for La Réunion reef flats (France), we performed multivariate analyses linking the abundance and composition of macroalgae to water physico-chemistry. Three hydrological groups of stations were identified according to dissolved inorganic nitrogen (DIN) concentrations and DIN/PO₄ ratios. Some indicator species were found at the N-enriched stations (Bryopsis pennata, Caulerpa lamourouxii, Chaetomoropha vieillardii, Derbesia sp., Blennothrix lyngbyacea, Sphacelaria tribuloides), and others at the non-impacted stations (Anabaena sp1, Blennothrix glutinosa, Codium arabicum, Neomeris vanbosseae). Another key result was the significant increase in red algal cover at the most N-enriched station. Our findings are discussed in the context of the application of the WFD in the outermost French regions.

Randomised clinical trial: a leucine-metformin-sildenafil combination (NS-0200) vs placebo in patients with non-alcoholic fatty liver disease

BACKGROUND

Sirtuin 1 (Sirt1) is suppressed in non-alcoholic fatty liver disease (NAFLD), while its' stimulation or overexpression results in reduced disease severity in pre-clinical NAFLD models. Leucine allosterically activates Sirt1 and synergise with other Sirt/AMPK/NO pathway activators. We developed a triple combination of leucine, metformin and sildenafil (NS-0200), which was effective in a mouse model of non-alcoholic steatohepatitis (NASH).

AIM

To report the results from a Phase 2, randomised clinical trial of of NS-0200 in 91 subjects with NAFLD (liver fat ≥15% by magnetic resonance imaging-proton-density fat fraction (MRI-PDFF)).

METHODS

Subjects were randomised to placebo, low-dose (1.1 g leucine/0.5 g metformin/0.5 mg sildenafil) or high-dose NS-0200 (1.1 g leucine/0.5 g metformin/1.0 mg sildenafil) b.d. for 16 weeks; change in hepatic fat was assessed via MRI-PDFF, and lipid metabolism was assessed via changes in the lipidomic signature. Seventy subjects completed the trial and met a priori compliance criteria. Analyses were conducted on the full cohort and on those with alanine aminotransferase (ALT) values above median (50 U/L; n = 35).

RESULTS

In the full cohort, active treatments did not separate from placebo. High dose NS-0200 reduced hepatic fat by 15.7% (relative change from baseline) in the high ALT group (P < 0.005) while low dose NS-0200 and placebo did not significantly change hepatic fat. Lipidomic analysis showed dose-responsive treatment effects in both overall and high ALT cohorts, with significant decreases in metabolically active lipids and up-regulation of fatty acid oxidation.

CONCLUSION

These data support further evaluation of high-dose NS-0200 for treating NASH, especially in those with elevated ALT (NCT 02546609).

Kinematics and dynamics of the auto-rotation of a model winged seed

Numerical simulations of the auto-rotation of a model winged seed are presented. The calculations are performed by solving simultaneously the Navier-Stokes equations for the flow surrounding the seed and the rigid-body equations for the motion of the seed. The Reynolds number based on the descent speed and a characteristic chord length is varied in the range 80-240. Within this range, the seed attains an asymptotic state with finite amplitude auto-rotation, while for smaller values of the Reynolds number no auto-rotation is observed. The motion of the seed is characterized by the coning and pitch angles, the angular velocity and the horizontal translation of the seed. The values obtained for these quantities are qualitatively similar to those reported in the literature in experiments with real winged seeds. When increasing the Reynolds number, the seed tends to rotate at higher speeds, with less inclination with respect to the horizontal plane, and with a larger translation velocity. With respect to the aerodynamic forces, it is observed that, with increasing Reynolds number, the horizontal components decrease in magnitude while the vertical component increases. The force distribution along the wing span is characterized using both global and local characteristic speeds and chord lengths for the non-dimensionalisation of the force coefficients. It is found that the vertical component does not depend on the Reynolds number when using local scaling, while the chordwise component of the force does.

An eco-epidemiological study of Morbilli-related paramyxovirus infection in Madagascar bats reveals host-switching as the dominant macro-evolutionary mechanism

An eco-epidemiological investigation was carried out on Madagascar bat communities to better understand the evolutionary mechanisms and environmental factors that affect virus transmission among bat species in closely related members of the genus Morbillivirus, currently referred to as Unclassified Morbilli-related paramyxoviruses (UMRVs). A total of 947 bats were investigated originating from 52 capture sites (22 caves, 18 buildings, and 12 outdoor sites) distributed over different bioclimatic zones of the island. Using RT-PCR targeting the L-polymerase gene of the Paramyxoviridae family, we found that 10.5% of sampled bats were infected, representing six out of seven families and 15 out of 31 species analyzed. Univariate analysis indicates that both abiotic and biotic factors may promote viral infection. Using generalized linear modeling of UMRV infection overlaid on biotic and abiotic variables, we demonstrate that sympatric occurrence of bats is a major factor for virus transmission. Phylogenetic analyses revealed that all paramyxoviruses infecting Malagasy bats are UMRVs and showed little host specificity. Analyses using the maximum parsimony reconciliation tool CoRe-PA, indicate that host-switching, rather than co-speciation, is the dominant macro-evolutionary mechanism of UMRVs among Malagasy bats.

Abstract P5-03-02: The dynamic duo: A breast cancer-targeting nanoparticle loaded with a cytotoxic peptide as a treatment for metastatic disease

Metastatic breast cancer is a uniformly fatal disease with a 5-year survival rate of 15 percent. To date there are no effective approaches for targeted therapy. To develop a treatment for metastatic cancer, our group discovered a novel cytotoxic peptide, CT20p, and developed a nanotechnology-based platform to deliver and concentrate CT20p in breast tumors. CT20p was derived from Bax, a member of the Bcl-2 family. Unlike the parent protein, CT20p does not cause apoptosis and its cytotoxicity is independent of caspases and Bcl-2 overexpression. Rather, the intracellular target of CT20p is a protein called chaperonin-containing T-complex (CCT), which is required for the folding of actin and tubulin into their native forms. Inhibition of CCT activity by CT20p, indicated by decreased F-actin and tubulin, impaired the polymerization of microfilaments and microtubules, causing loss of cell migration and adhesion that promoted breast cancer cell death. In contrast, normal, non-transformed cells were resistant to the cytotoxicity of CT20p. On its own, CT20p is not membrane-permeable. To deliver the peptide to cells, we used nanoparticles formed with a novel aliphatic hyperbranched polyester polymer (HBPE-NPs). The surface of HBPE-NPs retains carboxylic acid groups for labeling of targeting ligands to enable accumulation in tumors. To concentrate on breast cancer, we functionalized the HBPE-NPs with either folate (FOL) or glutamate (GLU), which target the folate receptor (FR) or the metabotropic glutamate receptor (GRM-1) respectively. FR and GRM-2 are essential metabolic components that are highly expressed in solid tumors like breast cancer. In vitro targeting studies using triple negative breast cancer cell (TNBC) lines established that folate FOL or GLU-HBPE-NPs loaded with fluorescent dyes were readily up taken at high efficiency by TNBC cells. HBPE-NPs also contain unique hydrophobic cavities especially suited for encapsulating CT20p. We found that once the CT20p-HBPE-NPs were taken up by cancer cells, the peptide was released inside cells under acidic conditions (e.g. endosomes) and directly interacted with its intracellular target, CCT. Studies using primary cells derived from human breast tumors confirmed the targeted uptake of HBPE-NPs as well as demonstrated the cancer-specific cytotoxicity of CT20p. We treated a murine TNBC xenograft model with nanomolar amounts of FOL-CT20p-HBPE-NPs and achieved 100% regression of established tumors as well as prevented tumor growth. These studies indicated that CT20p is a potent and specific anti-cancer agent due to its inhibition of CCT, an essential molecular complex highly expressed in cancer cells, and that the peptide can be efficiently delivered to tumor sites using HBPE-NPs decorated with ligands to receptors, such FR or GRM-1, found on tumor cells.

Citation Format: Vishnubhotla P, Khaled AR, Khaled AS, Perez JM, Bassiouni R, Flores O, Nierenberg D. The dynamic duo: A breast cancer-targeting nanoparticle loaded with a cytotoxic peptide as a treatment for metastatic disease. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-03-02.

A functional characterisation of a wide range of cover crop species: growth and nitrogen acquisition rates, leaf traits and ecological strategies

Cover crops can produce ecosystem services during the fallow period, as reducing nitrate leaching and producing green manure. Crop growth rate (CGR) and crop nitrogen acquisition rate (CNR) can be used as two indicators of the ability of cover crops to produce these services in agrosystems. We used leaf functional traits to characterise the growth strategies of 36 cover crops as an approach to assess their ability to grow and acquire N rapidly. We measured specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content (LNC) and leaf area (LA) and we evaluated their relevance to characterise CGR and CNR. Cover crop species were positioned along the Leaf Economics Spectrum (LES), the SLA-LDMC plane, and the CSR triangle of plant strategies. LA was positively correlated with CGR and CNR, while LDMC was negatively correlated with CNR. All cover crops could be classified as resource-acquisitive species from their relative position on the LES and the SLA-LDMC plane. Most cover crops were located along the Competition/Ruderality axis in the CSR triangle. In particular, Brassicaceae species were classified as very competitive, which was consistent with their high CGR and CNR. Leaf functional traits, especially LA and LDMC, allowed to differentiate some cover crops strategies related to their ability to grow and acquire N. LDMC was lower and LNC was higher in cover crop than in wild species, pointing to an efficient acquisitive syndrome in the former, corresponding to the high resource availability found in agrosystems. Combining several leaf traits explained approximately half of the CGR and CNR variances, which might be considered insufficient to precisely characterise and rank cover crop species for agronomic purposes. We hypothesised that may be the consequence of domestication process, which has reduced the range of plant strategies and modified the leaf trait syndrome in cultivated species.

Wolbachia-based population control strategy targeting Culex quinquefasciatus mosquitoes proves efficient under semi-field conditions

In mosquitoes, the maternally inherited bacterial Wolbachia induce a form of embryonic lethality called cytoplasmic incompatibility (CI). This property can be used to reduce the density of mosquito field populations through inundative releases of incompatible males in order to sterilize females (Incompatible Insect Technique, or IIT, strategy). We have previously constructed the LR[wPip(Is)] line representing a good candidate for controlling field populations of the Culex quinquefasciatus mosquito in the islands of the south-western Indian Ocean. The main purpose of the present study was to fill the gap between laboratory experiments and field implementation, i.e. assessing mating competitiveness of these incompatible males under semi-field conditions. In a first set of experiments, we analyzed crossing relationships between LR[wPip(Is)] males and La Réunion field females collected as larvae in 19 distinct localities throughout the island. This investigation revealed total embryonic mortality, confirming the strong sterilizing capacity of LR[wPip(Is)] males. Subsequently, mating competitiveness of LR[wPip(Is)] males was assessed under semi-field conditions in the presence of field males and females from La Réunion. Confrontations were carried out in April and December using different ratios of LR[wPip(Is)] to field males. The results indicated that the LR[wPip(Is)] males successfully compete with field males in mating with field females, displaying even higher competitiveness than field males in April. Our results support the implementation of small-scale field tests in order to assess the feasibility of IIT against Cx. quinquefasciatus in the islands of southwestern Indian Ocean where this mosquito species is a proven competent vector for human pathogens.

Processing and characterization of large diameter ceramic SiCN monofilaments from commercial oligosilazanes

Large diameter ceramic SiCN fibers were processed via the precursor route using tailored polysilazanes synthesized from liquid commercially available oligosilazanes. Their strength as well as creep and oxidation behavior were investigated.

Wood production response to climate change will depend critically on forest composition and structure

Established forests currently function as a major carbon sink, sequestering as woody biomass about 26% of global fossil fuel emissions. Whether forests continue to act as a global sink will depend on many factors, including the response of aboveground wood production (AWP; MgC ha(-1 ) yr(-1) ) to climate change. Here, we explore how AWP in New Zealand's natural forests is likely to change. We start by statistically modelling the present-day growth of 97 199 individual trees within 1070 permanently marked inventory plots as a function of tree size, competitive neighbourhood and climate. We then use these growth models to identify the factors that most influence present-day AWP and to predict responses to medium-term climate change under different assumptions. We find that if the composition and structure of New Zealand's forests were to remain unchanged over the next 30 years, then AWP would increase by 6-23%, primarily as a result of physiological responses to warmer temperatures (with no appreciable effect of changing rainfall). However, if warmth-requiring trees were able to migrate into currently cooler areas and if denser canopies were able to form, then a different AWP response is likely: forests growing in the cool mountain environments would show a 30% increase in AWP, while those in the lowland would hardly respond (on average, -3% when mean annual temperature exceeds 8.0 °C). We conclude that response of wood production to anthropogenic climate change is not only dependent on the physiological responses of individual trees, but is highly contingent on whether forests adjust in composition and structure.

Functional traits help predict post-disturbance demography of tropical trees

How tropical tree species respond to disturbance is a central issue of forest ecology, conservation and resource management. We define a hierarchical model to investigate how functional traits measured in control plots relate to the population change rate and to demographic rates for recruitment and mortality after disturbance by logging operations. Population change and demographic rates were quantified on a 12-year period after disturbance and related to seven functional traits measured in control plots. The model was calibrated using a Bayesian Network approach on 53 species surveyed in permanent forest plots (37.5 ha) at Paracou in French Guiana. The network analysis allowed us to highlight both direct and indirect relationships among predictive variables. Overall, 89% of interspecific variability in the population change rate after disturbance were explained by the two demographic rates, the recruitment rate being the most explicative variable. Three direct drivers explained 45% of the variability in recruitment rates, including leaf phosphorus concentration, with a positive effect, and seed size and wood density with negative effects. Mortality rates were explained by interspecific variability in maximum diameter only (25%). Wood density, leaf nitrogen concentration, maximum diameter and seed size were not explained by variables in the analysis and thus appear as independent drivers of post-disturbance demography. Relationships between functional traits and demographic parameters were consistent with results found in undisturbed forests. Functional traits measured in control conditions can thus help predict the fate of tropical tree species after disturbance. Indirect relationships also suggest how different processes interact to mediate species demographic response.

An evolutionary perspective on leaf economics: phylogenetics of leaf mass per area in vascular plants

In plant leaves, resource use follows a trade-off between rapid resource capture and conservative storage. This "worldwide leaf economics spectrum" consists of a suite of intercorrelated leaf traits, among which leaf mass per area, LMA, is one of the most fundamental as it indicates the cost of leaf construction and light-interception borne by plants. We conducted a broad-scale analysis of the evolutionary history of LMA across a large dataset of 5401 vascular plant species. The phylogenetic signal in LMA displayed low but significant conservatism, that is, leaf economics tended to be more similar among close relatives than expected by chance alone. Models of trait evolution indicated that LMA evolved under weak stabilizing selection. Moreover, results suggest that different optimal phenotypes evolved among large clades within which extremes tended to be selected against. Conservatism in LMA was strongly related to growth form, as were selection intensity and phenotypic evolutionary rates: woody plants showed higher conservatism in relation to stronger stabilizing selection and lower evolutionary rates compared to herbaceous taxa. The evolutionary history of LMA thus paints different evolutionary trajectories of vascular plant species across clades, revealing the coordination of leaf trait evolution with growth forms in response to varying selection regimes.

The detection of brain ischaemia in rats by inductive phase shift spectroscopy

Ischaemia in the brain is an important clinical problem that is often monitored and studied with expensive devices such as MRI and PET, which are not readily available in low economical resource parts of the world. We have developed a new less expensive tool for non-invasive monitoring of ischaemia in the brain. This is a first feasibility study describing the concept. The system is based on the hypothesis that electromagnetic properties of the tissue change during ischaemia and that measuring the electromagnetic properties of the bulk of the brain with non-contact means can detect these changes. The apparatus we have built and whose design we describe here consists of two electromagnetic coils placed around the head. The system measures the bulk change in time of the phase difference between the electromagnetic signal on the two coils in a range of frequencies. A mathematical model simulating the device and the measurement is also introduced. Ischaemia was induced in the brain of rats by occlusion of the right cerebral and carotid arteries. Experimental subjects were monitored for 24 h. Inductive phase shift measurements were made at five frequencies in the range of 0.1-50 MHz eight times during the observation period. An ex vivo estimation of the percentage of necrosis in the ischemic subjects at t = 24 h was done. The mathematical model was also applied to the experimental tested situation. The results of both experiments and theory show significant phase shifts increase as a function of frequency and ischaemia time. The theoretical and experimental results suggest that the tested technique has the potential to detect the processes and level of ischaemia in the brain by non-invasive, continuous, bulk volumetric monitoring with a simple and inexpensive apparatus.

Genetic analysis of antibiotic-resistance determinants in multidrug-resistant Shigella strains isolated from Chilean children

A total of 162 clinical isolates of Shigella collected from children in a semi-rural community of Chile were examined for the presence of genetic determinants of resistance to ampicillin, chloramphenicol, tetracycline, and trimethoprim. Ampicillin resistance was most frequently associated with the presence of bla(OXA) in S. flexneri and with bla(TEM) in S. sonnei. The bla(OXA) gene but not bla(TEM) was located in class 1 integrons. The dhfrIa gene encoding for resistance to trimethoprim was associated to class 2 integrons and detected exclusively in S. flexneri, whereas dhfrIIIc was found in all S. sonnei strains and in 10% of the S. flexneri isolates. Cat, coding for choramphenicol resistance, and bla(OXA) genes were located in the chromosome in all cases, whereas tetA gene, coding for tetracycline resistance, and bla(TEM), dhfrIa and dhfrIIIc genes were found either in the chromosome or in conjugative plasmids. Our results show a heterogenous distribution of antibiotic-resistance determinants between S. flexneri and S. sonnei.

Beneficial effect of verapamil added to chronic ACE inhibitor treatment on renal function in hypertensive elderly patients

This study analysed the effect of low doses of verapamil added to chronic treatment with angiotensin-converting enzyme (ACE) inhibitors on blood pressure and serum creatinine levels in eight elderly hypertensive patients who had a steady increase of serum creatinine while on ACE inhibitors. The study was performed in eight elderly hypertensive subjects, five men and three women (mean age 70+/-2 years; systolic blood pressure 173+/-4 mm Hg; diastolic blood pressure 99+/-1 mm Hg) and serum creatinine of 1.60+/-0.27 mg/dl before treatment. During an average of 25 weeks, ACE inhibitors significantly reduced both systolic and diastolic blood pressures, but serum creatinine levels were increased over basal levels (0,68+/-0,20 mg/dl, p < 0.05). During an average of 10 weeks, the addition of verapamil did not decrease blood pressure further, but serum creatinine levels were reduced to baseline. Our study suggests that the addition of verapamil to ACE inhibitors can reverse ACE-induced increase in creatinine levels in elderly hypertensive patients in whom this side effect is observed.

Renal fibrosis in diabetic and aortic-constricted hypertensive rats

To assess if the renal damage observed in rats with diabetes and hypertension is due to hemodynamic or metabolic changes, a progressive aortic constriction between the two renal arteries has been done in streptozotocin-induced diabetic rats (constriction + diabetes group) and in nondiabetic rats (constriction group). This model allows us to study two kidneys subjected to different perfusion pressure (PP) in the same metabolic environment. One-month-old rats (100-120 g body wt) were subjected to the aortic constriction procedure. Three months after constriction, glomerular filtration rate and renal plasma flow were similar in both kidneys of the two groups. PP was greater in the kidney placed over the ligature [constriction high-pressure kidney (CH) or constriction + diabetic high-pressure kidney (DH)] than in the one placed below the ligature [constriction low pressure (CL) or constriction + diabetic low pressure (DL)]. Proteinuria was higher in the CH than in the CL kidneys (512 +/- 61 vs. 361 +/- 38 microg/30 min, respectively) and much higher in the DH kidney (770 +/- 106 microg/30 min). Renal fibrosis was measured in tissue sections stained with Syrius red using a computer-assisted image analysis system. DH and DL kidneys showed higher corpuscular cross-sectional and capillary tuft areas than the CH and CL ones. The DH kidney showed slight mesangial expansion and thickening of the capillary walls, which were more pronounced in the former. Most renal corpuscles from CH and DH groups were nearly normal in morphology appearance, and only in some instances a slight increment in mesangium was observed. Transforming growth factor-beta1 (TGF-beta1) immunostaining revealed that DH kidneys showed the highest glomerular expression. We concluded that 1) diabetic animals develop glomerular but not interstitial fibrosis to a greater extent than nondiabetic animals and that this lesion principally occurs in the hypertensive kidney (DH), and 2) increased TGF-beta expression is associated with diabetic renal damage.

Effect of chronic and progressive aortic constriction on renal function and structure in rats

The purpose of this study was to evaluate the functional and structural renal damage observed in aortic-constricted hypertensive rats and to identify their possible relationship with transforming growth factor beta (TGF-beta) expression. Progressive renovascular hypertension was induced by progressive aortic constriction between the two renal arteries. Three months after constriction, the glomerular filtration rate (GFR), effective renal blood flow (ERBF), perfusion pressure (PP), urinary protein excretion (UPE) and urinary electrolyte excretion (U(Na)V and U(K)V) in the kidney above (right kidney, RK) and below the ligature (left kidney, LK) were measured. The cross-sectional corpuscular, capillary tuft and mesangial matrix area and tubulo-interstitial fibrosis were measured in tissue sections stained with Syrius Red using a computer-assisted image analysis system. TGF-beta was detected by immunohistochemistry. The functional parameters were similar in the two kidneys of aortic-constricted hypertensive rats (GFR-RK, 1.33+/-0.08 vs. LK, 1.18+/-0.08 mL/min; ERBF-RK, 9.23+/-1.32 vs. LK, 8.18+/-0.91 mL/min; RVR-RK, 28.3+/-3.9 vs. LK, 21.7+/-3.2 mmHg x min/mL). The RK was subject to a higher PP than the LK (176+/-7 vs. 128+/-5 mmHg, P < 0.05). UPE, U(Na)V, and U(K)V were greater in the RK than in the LK (UPE-RK, 512+/-61 vs. LK, 361+/-38 microg/30 min, P < 0.05; U(Na)V-RK, 0.056+/-0.012 vs. LK, 0.022+/-0.006 mEq/30 min, P < 0.05; UKV-RK, 0.042+/-0.006 vs. LK, 0.029+/-0.003 mEq/30 min, P < 0.05). Morphometric analysis revealed that the RK capillary tuft area and mesangial matrix area were higher than those in the LK. The LK had a higher degree of interstitial fibrosis than the RK. No significant differences in TGF-beta immunostaining were observed between the RK and the LK. In conclusion, the RK (subjected to hypertension) of aortic-constricted hypertensive animals developed glomerular fibrosis, only in the outer glomeruli whereas the LK developed mild interstitial fibrosis. Neither glomerular nor interstitial fibrosis seem to be responsible for the proteinuria observed in both kidneys.

Effect of chronic and progressive aortic constriction on renal function and structure in rats

The purpose of this study was to evaluate the functional and structural renal damage observed in aortic-constricted hypertensive rats and to identify their possible relationship with transforming growth factor β (TGF-β) expression. Progressive renovascular hypertension was induced by progressive aortic constriction between the two renal arteries. Three months after constriction, the glomerular filtration rate (GFR), effective renal blood flow (ERBF), perfusion pressure (PP), urinary protein excretion (UPE) and urinary electrolyte excretion (UNaV and UKV) in the kidney above (right kidney, RK) and below the ligature (left kidney, LK) were measured. The cross-sectional corpuscular, capillary tuft and mesangial matrix area and tubulo-interstitial fibrosis were measured in tissue sections stained with Syrius Red using a computer-assisted image analysis system. TGF-β was detected by immunohistochemistry. The functional parameters were similar in the two kidneys of aortic-constricted hypertensive rats (GFR-RK, 1.33 ± 0.08 vs. LK, 1.18 ± 0.08 mL/min; ERBF-RK, 9.23 ± 1.32 vs. LK, 8.18 ± 0.91 mL/min; RVR-RK, 28.3 ± 3.9 vs. LK, 21.7 ± 3.2 mmHg·min/mL). The RK was subject to a higher PP than the LK (176 ± 7 vs. 128 ± 5 mmHg, P < 0.05). UPE, UNaV, and UKV were greater in the RK than in the LK (UPE-RK, 512 ± 61 vs. LK, 361 ± 38 µg/30 min, P < 0.05; UNaV-RK, 0.056 ± 0.012 vs. LK, 0.022 ± 0.006 mEq/30 min, P < 0.05; UKV-RK, 0.042 ± 0.006 vs. LK, 0.029 ± 0.003 mEq/30 min, P < 0.05). Morphometric analysis revealed that the RK capillary tuft area and mesangial matrix area were higher than those in the LK. The LK had a higher degree of interstitial fibrosis than the RK. No significant differences in TGF-β immunostaining were observed between the RK and the LK. In conclusion, the RK (subjected to hypertension) of aortic-constricted hypertensive animals developed glomerular fibrosis, only in the outer glomeruli whereas the LK developed mild interstitial fibrosis. Neither glomerular nor interstitial fibrosis seem to be responsible for the proteinuria observed in both kidneys.Key words: renovascular hypertension, renal fibrosis, rats, TGF-β.

Correlation of high levels of hyaluronan and cytokines (IL-1beta, IL-6, and TGF-beta) in ascitic fluid of cirrhotic patients

Our objective was to investigate the relationship between endotoxin and hyaluronan synthesis and release in serum and ascitic fluid from cirrhotic patients. We studied hyaluronan, endotoxin, albumin, and creatinine levels in ascitic fluid and plasma and cytokine levels (IL-1beta, IL-6, TGF-beta) in ascitic fluid. TGF-beta, IL-6, and IL-1beta correlation analyses indicated a strong dependence of the production of these cytokines on endotoxin levels. Correlation analyses for TGF-beta and IL-6 indicated a strong dependence of the production of hyaluronan on cytokine levels and, to a lesser extent, on IL-1beta levels. Hyaluronan analysis indicated that a certain glycosaminoglycan level is required in ascites before its appearance in plasma. Our results disclosed elevated plasma hyaluronan concentrations. The simultaneous increased hyaluronan levels in ascitic fluid do not seem to be derived from the systemic circulation. In conclusion, the high hyaluronan-ascites/hyaluronan-plasma ratio suggests an intrinsic hyaluronan production from peritoneal cells induced by endotoxins.

Role of prostanoids and nitric oxide inhibition in rats with experimental hepatic fibrosis

Nitric oxide (NO) and prostaglandins have been proposed as vasodilator substances involved in peripheral vasodilatation characteristic of the liver cirrhosis. A link between NO and prostanoids has been suggested. The present study investigated the effect of simultaneous blockade of both, NO synthase (NOS) and cyclooxigenase (COX) in sham-operated (SO), or rats with bile-duct ligation (BDL) in the development of liver fibrosis. Animals were distributed in two groups SO (n=15) or BDL (n=15). Treatments (5 days) started three weeks after surgical procedure. Both, SO and BDL animals were treated with indomethacin (INDO) (5 mg/kg/day) alone, with NG-nitro-L-arginine-methyl-ester (NAME) (4 mg/kg/day) alone or with INDO and NAME combination at the same doses. At the end of follow-up body weight, packed cell volume, mean arterial blood pressure (MAP) and heart rate were measured. Liver tissue was processed for histological studies. In this study, BDL animals showed a decreased MAP. Treatment with L-NAME in BDL rats increased MAP. The chronic COX inhibition alone did not play an important role in the haemodynamic changes. The BDL produced a loss of hepatic structure, with ductular metaplasia that occupied the greater part of the hepatic parenchyma. Also, an important degree of fibrosis was observed. Both NO and PG synthesis inhibitors, alone or in combination, induced enhancing collagen fiber deposition in the hepatic parenchyma. These findings support the notion that the interaction between the NOS and COX pathways should be relevant in hepatic cirrhosis in which both NOS and COX are induced.

Increased apoptosis susceptibility in mesangial cells from spontaneously hypertensive rats

We have examined the susceptibility to apoptosis in mesangial cells from spontaneously hypertensive rats (SHR) or from normotensive rats (WKY) and the possible involvement of nitric oxide in this process. Mesangial cells monolayers from either SHR or normal rats were incubated for 12 h in medium with or without fetal calf serum (FCS) and with or without thapsigargin (Tg, 10(-6) M). A series of cultures from rats of both groups was treated with N(G)-nitro-l-arginine methyl ester (l-NAME, 10(-4) M). We assessed apoptosis by propidium iodide staining, by TUNEL nitrite production (Griess reaction), by inducible nitric oxide synthase (iNOS) and Bcl-2 and Bax by Western blot. Incubated with a FCS-free medium, cells from SHR showed a significantly higher apoptotic rate (10.7 +/- 2.0) than with 10% FCS (10% FCS, 4.7 +/- 0.3), while WKY cells did not show this increment (10% FCS, 4.7 +/- 0.3; 0% FCS, 5.9 +/- 0. 3). Apoptosis in cells from WKY increased when incubated with thapsigargin in FCS-free medium (0% FCS+ Tg, 17.7 +/- 2.9%) and increased even more in SHR cells (0% FCS+ Tg, 19.7 +/- 2.9%). Treatment with l-NAME decreased thapsigargin-induced apoptosis in both SHR (8.2 +/- 2.4%) and WKY cells (9.3 +/- 2.4%). An increase in nitrite production and iNOS expression was detected in groups in which the apoptosis rate was elevated. A high rate of apoptosis was also associated with a decrease in the Bcl-2/Bax ratio. Our results indicate that in SHR cells, short-term serum deprivation and the increase in intracellular free calcium concentration with thapsigargin are able to enhance the apoptosis rate in primary cultures and that the expression of iNOS, and hence NO production, is involved in this effect.

Cyclin K functions as a CDK9 regulatory subunit and participates in RNA polymerase II transcription

Important progress in the understanding of elongation control by RNA polymerase II (RNAPII) has come from the recent identification of the positive transcription elongation factor b (P-TEFb) and the demonstration that this factor is a protein kinase that phosphorylates the carboxyl-terminal domain (CTD) of the RNAPII largest subunit. The P-TEFb complex isolated from mammalian cells contains a catalytic subunit (CDK9), a cyclin subunit (cyclin T1 or cyclin T2), and additional, yet unidentified, polypeptides of unknown function. To identify additional factors involved in P-TEFb function we performed a yeast two-hybrid screen using CDK9 as bait and found that cyclin K interacts with CDK9 in vivo. Biochemical analyses indicate that cyclin K functions as a regulatory subunit of CDK9. The CDK9-cyclin K complex phosphorylated the CTD of RNAPII and functionally substituted for P-TEFb comprised of CDK9 and cyclin T in in vitro transcription reactions.

Host-cell positive transcription elongation factor b kinase activity is essential and limiting for HIV type 1 replication

HIV-1 gene expression and viral replication require the viral transactivator protein Tat. The RNA polymerase II transcriptional elongation factor P-TEFb (cyclin-dependent kinase 9/cyclin T) is a cellular protein kinase that has recently been shown to be a key component of the Tat-transactivation process. For this report, we studied the requirement for P-TEFb in HIV-1 infection, and we now show that P-TEFb is both essential and limiting for HIV-1 replication. Attenuation of P-TEFb kinase activity either by expression of a dominant-negative cyclin-dependent kinase 9 transgene or through the use of small-molecule inhibitors suppresses HIV-1 gene expression and HIV-1 replication. Inhibition of HIV-1 replication is affected in a manner consistent with a direct and specific effect on P-TEFb and the known functional role of P-TEFb in Tat-activated transcription. Tat-activated expression of HIV-1 genes seems uniquely dependent on P-TEFb, as inhibition of P-TEFb activity and HIV-1 replication can be achieved without compromising cell viability or RNA polymerase II-dependent cellular gene transcription. Selective inhibition of the P-TEFb kinase may therefore provide a novel approach for developing chemotherapeutic agents against HIV-1.

A protein phosphatase functions to recycle RNA polymerase II

Transcription is regulated by the state of phosphorylation of a heptapeptide repeat known as the carboxy-terminal domain (CTD) present in the largest subunit of RNA polymerase II (RNAPII). RNAPII that associates with transcription initiation complexes contains an unphosphorylated CTD, whereas the elongating polymerase has a phosphorylated CTD. Transcription factor IIH has a kinase activity specific for the CTD that is stimulated by the formation of a transcription initiation complex. Here, we report the isolation of a cDNA clone encoding a 150-kD polypeptide, which, together with RNAPII, reconstitutes a highly specific CTD phosphatase activity. Functional analysis demonstrates that the CTD phosphatase allows recycling of RNAPII. The phosphatase dephosphorylates the CTD allowing efficient incorporation of RNAPII into transcription initiation complexes, which results in increased transcription. The CTD phosphatase was found to be active in ternary elongation complexes. Moreover, the phosphatase stimulates elongation by RNAPII; however, this function is independent of its catalytic activity.

Antihypertensive effect of trandolapril and verapamil in rats with induced hypertension

The antihypertensive effect of long-term treatment (6 months) with placebo (as control), verapamil, trandolapril, and their combination (verapamil plus trandolapril) was investigated in Wistar rats rendered hypertensive by extensive renal mass ablation, as a model lacking genetic hypertensive determinants. Arterial pressure was monitored during treatment and at the end, aortic structure and functionality were investigated. Trandolapril and the combination prevented the increase in pressure observed in the control group after renal handicap, whereas verapamil was much less effective. Trandolapril and the combination were similarly effective, whereas verapamil was ineffective, or even deleterious, at reducing aortic lamina media hypertrophy, the wall-to-lumen ratio, lamina media cross-sectional area, potassium chloride-induced contraction, and at increasing acetylcholine relaxation. The response to noradrenaline decreased in the trandolapril group, increased in the verapamil group, and remained unmodified in the association group. In conclusion, treatment with trandolapril exerts beneficial antihypertensive actions in this model of induced hypertension, showing continuous control of blood pressure and prevention of structural and functional alteration of the aorta. Verapamil exerts weak control of arterial pressure and produces, if any, deleterious effects on the structure and function of the aorta. These negative effects of verapamil are overcome by coadministration of trandolapril.

Effects of chronic nitric oxide activation or inhibition on early hepatic fibrosis in rats with bile duct ligation

Hepatic fibrosis or increased liver collagen contents drive functional abnormalities that, when extensive, may be life threatening. The purpose of this study was to assess the effects of the chronic stimulation or inhibition of nitric oxide synthesis in rats with hepatic fibrosis induced by permanent common bile duct ligation (3 weeks) and the role of expression of the different nitric oxide synthase isoforms. Bile duct ligation led to an important accumulation of collagen in the hepatic parenchyma, as shown both histologically and by the hydroxyproline contents of livers. Bilirubin and serum enzyme activities (measured as markers of cholestasis) increased several-fold after bile duct ligation. The area of fibrotic tissue, liver hydroxyproline content and serum markers of cholestasis were clearly related in obstructed rats. The absence of modifications in haemodynamic parameters excludes circulatory changes from being responsible for the development of liver alterations. In animals treated with NG-nitro-L-arginine methyl ester (L-NAME) the area of fibrosis was similar to that of untreated animals, the signs of cholestasis and cellular injury being more evident. In rats treated with L-arginine the area of fibrosis was almost three times larger than that found in bile duct ligated rats and in L-NAME-treated bile duct ligated rats, although the observed biochemical changes were similar to those seen in rats treated with L-NAME. Our results with inducible nitric oxide synthase, obtained by Western blots and immunohistochemistry, indicate a greater expression of the inducible enzyme in bile duct ligated and L-arginine-treated animals and a lower expression in the L-NAME and control groups. Constitutive nitric oxide synthase expression, obtained by Western blots, was very similar in all groups, except for the L-arginine-treated rats in which it was lower. These results suggest that nitric oxide production may be a key factor in the development of fibrosis in bile duct ligated rats. They also support the hypothesis of a dual role for nitric oxide; one beneficial, mediated by its circulatory effects, and the second negative, through its local toxic effects.

Interaction between prostanoids and nitric oxide in the control of tubular function in rats with chronic bile duct ligation

Recent work indicates that both nitric oxide and cyclooxygenase products play an important role in the renal alterations of liver cirrhosis, although the interactions between them have not been completely established. The purpose of this study was to assess the effect of simultaneous blockade of nitric oxide synthase and cyclooxygenase in rats with chronic bile duct ligation and in control, sham-operated rats. Compared with control rats, chronic bile duct ligation rats, 23-25 days after surgery, showed a decreased mean arterial pressure, natriuresis, and kaliuresis, without differences in glomerular filtration rate, and an increased urinary nitrite excretion. Nitric oxide synthesis inhibition by administration of N(G)-nitro-L-arginine methyl ester induced, in control rats, an increase in mean arterial pressure, without significant changes in natriuresis or glomerular filtration rate. In chronic bile duct ligation rats, N(G)-nitro-L-arginine methyl ester induced an increase in mean arterial pressure, natriuresis, and kaliuresis, together with a reduction in urinary nitrite excretion and an increase in prostaglandin E2 excretion. Cyclooxygenase inhibition with indomethacin induced in both experimental groups a marked inhibition in urinary prostaglandin E2 excretion without significant changes in Na+ or K+ excretion, and a significant increase in urinary nitrite excretion in control rats. N(G)-Nitro-L-arginine methyl ester in addition to indomethacin prevented the indomethacin-induced increase in nitrite excretion and dramatically reduced sodium excretion in both experimental groups. Thus, the present study suggests that both nitric oxide and cyclooxygenase products interact in the control of urinary sodium excretion and that each system is activated in the absence of the other one.

Glomerular cell proliferation and apoptosis in uninephrectomized spontaneously hypertensive rats

We studied renal function, glomerular cell proliferation and apoptosis for three months after uninephrectomy (UNX) in young, male, spontaneously hypertensive rats (SHR). Apoptosis was assessed by in situ dUTP biotin nick-end labeling method (TUNEL) and by propidium iodide staining. Proliferation rate was determined by immunohistochemistry to proliferating cell nuclear antigen (PCNA). Glomerular bcl-2 expression was assessed by Northern blot analysis. Our results indicate a parallel increase in proliferation and in apoptotic rates in glomerular cells from the first to the second month after UNX. In the third month after UNX, PCNA-labeled cell number continues increasing, whereas TUNEL-labeled cells did not increase. Bcl-2 expression was negative in the first and second months and increased in the third month. Glomerular size and proteinuria increased progressively along the three months of follow-up. Our observations demonstrate a different profile of cell proliferation and apoptosis during the genesis of early glomerular damage in UNX-SHR.

Antihypertensive action of trandolapril and verapamil in spontaneously hypertensive rats after unilateral nephrectomy

It is well documented that the kidney plays a fundamental role in long-term arterial pressure regulation, and, as an endocrine organ, in the regulation of cardiovascular structure and functionality. In this study, the antihypertensive effect of long-term treatment (6 months) with placebo, verapamil, trandolapril, and a combination of the latter (verapamil plus trandolapril) was investigated in spontaneously hypertensive rats after half-renal-mass ablation. Arterial pressure was monitored during treatment and at the end, aortic structure and functionality were investigated. Trandolapril and the combination returned pressure to normal, whereas verapamil was less effective. All three treatment groups were similarly effective at reducing aortic medial hypertrophy, the wall-to-lumen ratio, and contraction evoked by potassium chloride and noradrenaline. Verapamil and veratran were more effective than trandolapril at reducing lamina media cross-sectional area. Trandolapril and the combination were more effective than verapamil at improving endothelial dysfunction.

Renal effects of antihypertensive therapy in uninephrectomized diabetic rats

Diabetic nephropathy is a major cause of chronic renal failure. The evidence available indicates that renal hemodynamics are altered in clinical and experimental diabetes mellitus. In these circumstances, an increased glomerular filtration rate (GFR) is associated with albuminuria and eventually with glomerulosclerosis. We studied the renal and hemodynamic effects of long-term treatment (5 months) using an angiotensin-converting enzyme inhibitor (trandolapril, 0.7 mg/g b.w. per day) and a calcium antagonist (verapamil, 20 mg/g b.w. per day), and the combination of the two (veratran) at the same dose, on streptozotocin-diabetic uninephrectomized rats. A moderate degree of hyperglycemia (2-4 g/l) was maintained with daily insulin. Mean arterial pressure (MAP) was measured monthly using the tail-cuff method. Determinations were made of urinary protein excretion, creatinine clearance, urinary electrolyte excretion and, at the end of treatment, renal and cardiac hypertrophy. MAP was similar in control and untreated diabetic rats. Trandolapril and veratran reduced MAP whereas verapamil alone had no effect on these animals. All groups showed a slight proteinuria that increased with verapamil treatment. The GFR of diabetic animals was higher than in the control group (mainly the first 2 months), except for veratran group, in which it was similar to the control value. Urinary electrolyte excretion increased in all diabetic groups with no significant differences among them. Veratran induced a protective effect against cardiac hypertrophy. None of the treatments affected renal hypertrophy. It is concluded that in a murine model of diabetes without hypertension or proteinuria, a combination of verapamil and trandolapril prevents hyperfiltration whereas verapamil alone increases proteinuria.

Effect of chronic NG-nitro-L-arginine methyl ester (L-NAME) on blood pressure and renal function in conscious uninephrectomized spontaneously hypertensive rats

We have studied during 30 days the effect of a low dose of NG-nitro-L-arginine methyl ester (1 mg.kg-1.day-1 in drinking water) in the presence of D- or L-arginine (1 mg.kg-1.day-1 in drinking water) in comparison with D- or L-arginine alone on blood pressure and renal function in conscious uninephrectomized female spontaneously hypertensive rats. At the end of the study, there was a significant increase in systolic blood pressure in the NG-nitro-L-arginine methyl ester + D-arginine group (307 +/- 6 mmHg (1 mmHg = 133.3 Pa), n = 14, p < 0.05) in comparison with NG-nitro-L-arginine methyl ester + L-arginine (281 +/- 6 mmHg, n = 14), L-arginine (262 +/- 5 mmHg, n = 13), and D-arginine (258 +/- 7 mmHg, n = 12) groups. There were no changes in diuresis, proteinuria, or sodium and potassium excretion between differently treated animals during this study. These results suggest that in uninephrectomized female spontaneously hypertensive rats, after 1 month blockade of NO synthesis with a low dose of NG-nitro-L-arginine methyl ester, vasculature is under tonic control by NO and it is not correlated with renal dysfunction.

Beneficial effect of the long-term treatment with the combination of an ACE inhibitor and a calcium channel blocker on renal injury in rats with 5/6 nephrectomy

The effects of the addition of a calcium channel blocker, verapamil (20 mg/kg/day) to an ACE inhibitor, trandolapril (0.7 mg/kg/day) in a 6-month treatment on renal insufficiency development in rats with 5/6th nephrectomy, were studied. Every month we measured heart rate and arterial pressure by the tail-cuff method. Renal function studies were performed in metabolic cages. At the end of the study, renal tissue was prepared for light microscope analysis. Renal lesions were assessed by semiquantitative scores in a blind fashion. Corpuscular section area, intraglomerular and tubulointerstitial fibrosis were determined by digital image analysis with a specific software (Fibrosis HR) on syrium red-stained renal sections. Trandolapril markedly increased the survival ratio that after 6 months reached 87% in comparison with 61% in untreated rats. No mortality was observed in rats treated with the combination of verapamil and trandolapril. Trandolapril treatment prevented the development of hypertension. The combination verapamil-trandolapril did not induce further reduction on blood pressure. The untreated group showed a marked proteinuria, that in the trandolapril group showed an important reduction. The verapamil + trandolapril group showed a proteinuria significantly smaller than that of all the other groups. Light microscopy semiquantitative studies of the renal injury showed that the trandolapril and verapamil + trandolapril groups had a marked reduction in glomerular and tubulointerstitial alterations, compared with untreated animals. Quantitative determinations of glomerular and interstitial fibrosis performed on syrium red-stained renal sections demonstrated that fibrosis was reduced when rats when treated with trandolapril and even more with verapamil + trandolapril when they were compared to untreated animals' values. In conclusion, long-term treatment with verapamil given in addition to trandolapril produces additional protection against progressive renal injury associated to subtotal nephrectomy.

P-TEFb kinase is required for HIV Tat transcriptional activation in vivo and in vitro

To identify novel inhibitors of transcriptional activation by the HIV Tat protein, we used a combination of in vitro and in vivo Tat-dependent transcription assays to screen >100,000 compounds. All compounds identified blocked Tat-dependent stimulation of transcriptional elongation. Analysis of a panel of structurally diverse inhibitors indicated that their target is the human homolog of Drosophila positive transcription elongation factor b (P-TEFb). Loss of Tat transactivation in extracts depleted of the kinase subunit of human P-TEFb, PITALRE, was reversed by addition of partially purified human P-TEFb. Transfection experiments with wild-type or kinase knockout PITALRE demonstrated that P-TEFb is required for Tat function. Our results suggest that P-TEFb represents an attractive target for the development of novel HIV therapeutics.

Binding of SP1 to the immediate-early protein-responsive element of the human cytomegalovirus DNA polymerase promoter

Human cytomegalovirus (HCMV), a member of the herpesvirus family of DNA viruses, encodes two major immediate-early (IE) transcription factors, IE72 and IE86, that are important for regulated expression of the viral genome. The purpose of this study was to identify the host cellular components required for regulation of the HCMV DNA polymerase promoter (UL54) by HCMV IE proteins. Extensive mutagenesis defined a DNA element located between -54 and -43 relative to the transcription start site that was required for both basal transcriptional activity and transactivation by viral IE proteins. A single copy of the UL54 -54/-43 sequence enhanced the responsiveness of a heterologous minimal promoter to HCMV IE proteins. Fractionation of extracts prepared from uninfected cells led to the isolation of two cellular proteins with apparent molecular masses of 95 and 105 kDa that bound specifically to the UL54 -54/-43 element. Biochemical and immunochemical analyses identified this protein as the transcription factor SP1. Although initial inspection of the UL54 -54/-43 sequence did not predict an SP1 binding site, subsequent analyses indicated that it is indeed a nonconsensus GC box. We propose that SP1 is required to direct basal levels of promoter activity and that SP1-regulated transcription complexes allow the entry of HCMV IE proteins into the transcription cycle.

Elevated glomerular and blood mononuclear lymphocyte nitric oxide production in rats with chronic bile duct ligation: role of inducible nitric oxide synthase activation

Recent work indicates that nitric oxide (NO) plays an important role in the systemic and renal alterations of cirrhosis. In the present study, we have evaluated whether the inducible NO synthase (iNOS) isoform participates in the enhanced renal and systemic NO production of a rat model of cirrhosis. In vitro and in vivo experiments were performed in rats subjected to chronic bile duct ligation (BDL) and in sham-operated (SO) animals. Plasma nitrite (3.1 +/- 0.1 micromol/L in SO and 6.6 +/- 0.2 micromol/L in BDL), glomerular nitrite production (6.4 +/- 0.1 vs. 9.8 +/- 0.1 nmol/24h/7,000 glomeruli, respectively), and mononuclear lymphocyte cells nitrite production (0.3 +/- 0.04 vs. 0.6 +/- 0.12 nmol/10(6) cells, respectively) were all significantly higher in BDL than in SO. Moreover, mononuclear lymphocytes and glomeruli from BDL rats showed an increased expression of macrophage-type iNOS, detected by Western blot. Kidneys from BDL animals also showed an increased calcium-independent NO synthase activity, compared with those from SO rats. Constitutive endothelial-type NO synthase expression in glomeruli or the activity of calcium-dependent NO synthase in whole kidney did not show differences between BDL and SO rats. In cultured mesangial cells from normal rats, the addition of plasma from BDL but not of plasma from SO significantly stimulated (35%) nitrite production and increased the expression of macrophage-type iNOS. In addition, administration of aminoguanidine (AG), a preferential iNOS inhibitor, elevated dose-dependently mean arterial pressure in both groups, but this increase was greater in BDL (26.5 +/- 4.4 mm hg) than in SO (13.6 +/- 2.6). In BDL, AG also increased sodium and water excretion and glomerular filtration rate. In contrast, there were only small nonsignificant changes in SO animals. Therefore, these results indicate that the expression, activity and production of NO in kidneys, glomeruli, and mononuclear lymphocyte cells is elevated in BDL rats, and this is partly because of a plasma-derived substance(s), which stimulates iNOS formation. The amelioration of the arterial hypotension and the associated reduced excretory levels of these cirrhotic animals by aminoguanidine further support the involvement of the inducible NO synthase isoform in the renal alterations observed in BDL animals.