Higher-order combinatorial chromatin perturbations by engineered CRISPR-Cas12a for functional genomics

Multiplexed genetic perturbations are critical for testing functional interactions among coding or non-coding genetic elements. Compared to double-stranded DNA cutting, repressive chromatin formation using CRISPR interference (CRISPRi) avoids genotoxicity and is more effective for perturbing non-coding regulatory elements in pooled assays. However, current CRISPRi pooled screening approaches are limited to targeting 1-3 genomic sites per cell. To develop a tool for higher-order ( > 3) combinatorial targeting of genomic sites with CRISPRi in functional genomics screens, we engineered an Acidaminococcus Cas12a variant -- referred to as mul tiplexed transcriptional interference AsCas12a (multiAsCas12a). multiAsCas12a incorporates a key mutation, R1226A, motivated by the hypothesis of nicking-induced stabilization of the ribonucleoprotein:DNA complex for improving CRISPRi activity. multiAsCas12a significantly outperforms prior state-of-the-art Cas12a variants in combinatorial CRISPRi targeting using high-order multiplexed arrays of lentivirally transduced CRISPR RNAs (crRNA), including in high-throughput pooled screens using 6-plex crRNA array libraries. Using multiAsCas12a CRISPRi, we discover new enhancer elements and dissect the combinatorial function of cis-regulatory elements. These results instantiate a group testing framework for efficiently surveying potentially numerous combinations of chromatin perturbations for biological discovery and engineering.

Termites are the main dung removals in a degraded landscape in Brazil

Termites are one of the most relevant groups for recycling nutrients and keeping the flow of energy in ecosystems. Although their role as lignocellulose decomposers is the focus of studies, they also act as dung recyclers, but their importance in this process is poorly understood. Here we performed manipulation experiments to determine dung removal by termites in forest remnants and cattle pastures in a fragmented Atlantic Forest landscape. We used wire bags of different mesh sizes placed along transects in three forest fragments and pastures for 10 days to compare the contribution of termites and other coprophagous macrodetritivores to dung removal. Our results indicated that termites removed more dung in pastures than in the forest fragments. In addition, dung beetle exclusion significantly reduced the percentage of dung removal within forest fragments, but not on pastures, indicating termites are important dung recyclers in pastures.

Body Size and Symmetry Properties of Termite Soldiers Under Two Intraspecific Competition Scenarios

Single-piece nesting termites live and forage in the same piece of wood throughout their life, which limit their colony size. In certain species, more than one colony thrive in a given piece of wood (multicolonial substrate) and intraspecific competition become important in this limited resource, as has been reported in Zootermopsis nevadensis (Hagen, 1858) and Neotermes chilensis (Blattodea: Kalotermitidae) (Blanchard, 1851). The effects of such competition have been described mainly at population and colony levels rather than at the individual level. In eusocial insects such as termites, intraspecific competition constitutes a stress factor imposed to a colony as a whole and should also cause developmental instability in soldiers produced under such conditions. Investment in the production of soldiers involves a trade-off between colony maintenance costs and defense benefits. Hence, we hypothesize that body size and fluctuating asymmetry, two indicators of developmental instability, will increase when two or more colonies of N. chilensis share a piece of wood (high intraspecific competition scenario). Our results showed that soldiers developing in multicolonial substrates were indeed larger and more asymmetric than soldiers developing in unicolonial substrates. The large body size in a soldier could improve its chance to win a physical contest with a non-nestmate opponent; thus, despite the high cost to produce large soldiers in small colonies, larger soldier production could be an adaptative strategy to avoid being outcompeted. However, the effects of deviations from perfect symmetry on soldier performance are not clear.

Cerambycid Beetle Communities in Caatinga Dry Forests Are Structured by Seasonal Species Turnover

Dry forests in the Caatinga biome of Brazil are seasonal ecosystems where diversity is driven by water availability. Understanding how the distribution of communities is driven by temporal climate changes has intrigued researchers for decades. However, temporal diversity patterns should be more evident in dry environments, since seasonality is characterized by being highly limiting to insect activities. Cerambycid beetles are considered good ecological indicators because they respond well to impacts of environmental changes. Thus, we asked two questions: (i) How do climatic changes affect the diversity of these insects across seasons? (ii) Are diversity components correlated with increasing air humidity, rainfall, and temperature? Our results showed a marked seasonality of cerambycid beetles, with higher abundance and richness in the wet season. The mean temperature and relative humidity were predictors of the composition of beetle assemblages. However, the variation of cerambycid assemblages between seasons is related mainly to species turnover. Our study demonstrates that the combined effect of temperature and humidity drives the temporal distribution of the cerambycids in dry forests. Although thermal sensitivity was low, the decrease in air moisture during the dry season was the limiting factor for these insects. Species turnover increased continuously with air moisture and temperature rise, creating temporal segregation among cerambycid species and maintaining the stability of the assemblage. Thus, our results are consistent with mechanisms invoking activity patterns, desiccation resistance, and physiologic constraints that predict a decrease in richness and abundance of the cerambycids from warmer and moister to colder and drier conditions.

Complementary Contribution of Fungi and Bacteria to Lignocellulose Digestion in the Food Stored by a Neotropical Higher Termite

Lignocellulose digestion in termites is achieved through the functional synergy between gut symbionts and host enzymes. However, some species have evolved additional associations with nest microorganisms that collaborate in the decomposition of plant biomass. In a previous study, we determined that plant material packed with feces inside the nests of Cornitermes cumulans (Syntermitinae) harbors a distinct microbial assemblage. These food nodules also showed a high hemicellulolytic activity, possibly acting as an external place for complementary lignocellulose digestion. In this study, we used a combination of ITS sequence analysis, metagenomics, and metatranscriptomics to investigate the presence and differential expression of genes coding for carbohydrate-active enzymes (CAZy) in the food nodules and the gut of workers and soldiers. Our results confirm that food nodules express a distinct set of CAZy genes suggesting that stored plant material is initially decomposed by enzymes that target the lignin and complex polysaccharides from fungi and bacteria before the passage through the gut, where it is further targeted by a complementary set of cellulases, xylanases, and esterases produced by the gut microbiota and the termite host. We also showed that the expression of CAZy transcripts associated to endoglucanases and xylanases was higher in the gut of termites than in the food nodules. An additional finding in this study was the presence of fungi in the termite gut that expressed CAZy genes. This study highlights the importance of externalization of digestion by nest microbes and provides new evidence of complementary digestion in the context of higher termite evolution.

Microbial Communities of the Gut and Nest of the Humus- and Litter-Feeding Termite Procornitermes araujoi (Syntermitinae)

The evolution of the symbiotic association with microbes allowed termites to decompose ingested lignocellulose from plant-derived substrates, including herbivore dung and soil humus. Representatives of the Syntermitinae (Termitidae) range in their feeding habits from wood and litter-feeding to humus-feeding species. However, only limited information is available about their feeding ecology and associated microbial communities. Here we conducted a study of the microbial communities associated to the termite Procornitermes araujoi using Illumina sequencing of the 16S and ITS rRNA genes. This species has been previously included in different feeding guilds. However, most aspects of its feeding ecology are unknown, especially those associated to its symbiotic microbiota. Our results showed that the microbial communities of termite guts and nest substrates of P. araujoi differed significantly for bacteria and fungi. Firmicutes dominated the bacterial gut community of both workers and soldiers, whereas Actinobacteria was found in higher prevalence in the nest walls. Sordariomycetes was the most abundant fungal class in both gut and nest samples and distinguish P. araujoi from the grass/litter feeding Cornitermes cumulans. Our results also showed that diversity of gut bacteria were higher in P. araujoi and Silvestritermes euamignathus than in the grass/litter feeders (C. cumulans and Syntermes dirus), that could indicate an adaptation of the microbial community of polyphagous termites to the higher complexity of their diets.

Food Storage by the Savanna Termite Cornitermes cumulans (Syntermitinae): a Strategy to Improve Hemicellulose Digestibility?

It has been suggested that food storage inside the nest may offer termites with a nutritional provision during low resource availability. Additionally, feces employed as construction material provide an excellent environment for colonization by microorganisms and, together with the storage of plant material inside the nest, could thus provide some advantage to the termites in terms of lignocellulose decomposition. Here, we conducted for the first time a comprehensive study of the microbial communities associated to a termite exhibiting food storage behavior using Illumina sequencing of the 16S and (ITS2) regions of rRNA genes, together with enzymatic assays and data collected in the field. Cornitermes cumulans (Syntermitinae) stored grass litter in nodules made from feces and saliva located in the nest core. The amount of nodules increased with nest size and isolation, and interestingly, the soluble fraction of extracts from nodules showed a higher activity against hemicellulosic substrates compared to termite guts. Actinobacteria and Sordariales dominated microbial communities of food nodules and nest walls, whereas Spirochetes and Pleosporales dominated gut samples of C. cumulans. Within Syntermitinae, however, gut bacterial assemblages were dissimilar. On the other hand, there is a remarkable convergence of the bacterial community structure of Termitidae nests. Our results suggest that the role of nodules could be related to food storage; however, the higher xylanolytic activity in the nodules and their associated microbiota could also provide C. cumulans with an external source of predigested polysaccharides, which might be advantageous in comparison with litter-feeding termites that do not display food storage behavior.

Dietary patterns and semen quality: a systematic review and meta-analysis of observational studies

A number of studies have examined the association between dietary patterns and semen quality, but the findings have been inconclusive. Herein, we conducted a systematic review and meta-analysis of observational studies to assess the association between dietary patterns and semen quality. PubMed, Cochrane library, Science direct, Scopus, Google Scholar, and ISI web of science databases were searched up to August 2016 for observational studies assessing the association between common dietary patterns and sperm quality markers. Data were pooled by the generic inverse variance method with random effects and expressed as mean differences with 95% confidence intervals (CIs). Heterogeneity was assessed (Cochrane Q-statistic) and quantified (I² -statistic). The Newcastle-Ottawa Scale assessed study quality. Six eligible studies, involving 8207 participants, were included in our systematic review and meta-analysis. The pooled mean difference of sperm concentration for the healthy dietary pattern versus unhealthy dietary pattern intake was mean difference: 0.66; 95% CI, 0.305-1.016; p < 0.001. In comparison with those who had the highest adherence to healthy dietary pattern, individuals in the lowest adherence had significantly lower level of sperm concentration. However, no significant association was seen between eating patterns and other semen quality. Healthy dietary pattern seems to be associated with elevated sperm concentration level. Further longitudinal studies are needed to clarify this relationship.

Usefulness of Ki-67, Mitoses, and Tumor Size for Predicting Metastasis in Carcinoid Tumors of the Lung: A Study of 48 Cases at a Tertiary Care Centre in Canada

Background. Evaluation of Ki-67 index in lung carcinoid tumors (LCTs) has been of interest in order to identify high risk subsets. Our objectives are (1) to evaluate the usefulness of Ki-67 index, mitoses, and tumor size in predicting metastasis and (2) to compare the Manual Conventional Method (MCM) and the Computer Assisted Image Analysis Method (CIAM) for Ki-67 calculation. Methods. We studied 48 patients with LCTs from two academic centres in Canada. For Ki-67 calculation, digital images of 5000 cells were counted using an image processing software and 2000 cells by MCM. Mitoses/10 HPF was counted. Results. We had 37 typical carcinoids (TCs) and 11 atypical carcinoids (ACs). 7/48 patients developed metastasis. There was a positive relationship between metastasis and carcinoid type (P = 0.039) and metastasis and mitoses (≥2) (P = 0.017). Although not statistically significant, the mean Ki-67 index for ACs was higher than for TCs (0.95% versus 0.72%, CIAM, P = 0.299). Similarly, although not statistically significant, the mean Ki-67 index for metastatic group (MG) was higher than for nonmetastatic group (NMG) (1.01% versus 0.71% by CIAM, P = 0.281). However when Ki-67 index data was categorized at various levels, there is suggestion of a useful cutoff (≥0.50%) to predict metastasis (P = 0.106, CIAM). A significantly higher proportion of patients with mitosis ≥2 and Ki-67 index ≥0.50% had metastasis (P = 0.033) compared to other patients. Similarly patients with tumor size ≥3 cm and Ki-67 ≥0.50% had a greater percentage of metastases than others (P = 0.039). Although there was a strong correlation between two (MCM versus CIAM) counting methods (r = 0.929, P = 0.001), overall the calculated Ki-67 index was slightly higher by MCM (range 0 to 6.4, mean 1.5) compared to CIAM (range 0 to 2.9, mean 0.75). Conclusion. This study confirms that mitoses ≥2 is a powerful predictor of metastasis in LCTs. Although this is a small sample size, there is suggestion that analysis of Ki-67 index along with mitoses and tumor size may be a useful adjunct for predicting metastasis in LCTs.

Cuticular Hydrocarbons of Heterotermes tenuis (Isoptera: Rhinotermitidae): Analyses and Electrophysiological Studies

Termites have become an important pest of Eucalyptus and Pinus reforestations, sugarcane and other cultures. An alternative for the control of this pest would be the use of attractive traps that take in account the social behavior of these insects. Diverse factors are important for the insects in the localization of the habitat and the choice of the food and specific odors can facilitate this. Studies referring to Heterotermes tenuis (Isoptera: Rhinotermitidae) are scarce. The objective of this work was to analyze the tergal cuticular extract of H. tenuis and determine the selectivity and sensitivity of its antennae to the components of this extract by electroantennography (EAG). The composition of the cuticular extract was determined by GC-MS analysis. The hydrocarbons found were restricted to linear alkanes, being most abundant C24 to C27 that comprises ca. 65% of the total. Olefins were not detected. EAG and behavioral test responses to the cuticular hydrocarbons were greater and significantly different from the control and the high selectivity of the antennae to the extract indicates its potential as chemical messenger. Cuticular hydrocarbons mixture is species-specific and can be used to identify a given taxon without the diagnostic castes, soldiers or imagoes. Difference in the composition appears to relate with the type of habitat of specie.

Methyl jasmonate increases the tropane alkaloid scopolamine and reduces natural herbivory in Brugmansia suaveolens: is scopolamine responsible for plant resistance?

The tropane alkaloid (TA) scopolamine is suggested to protect Brugmansia suaveolens (Solanaceae) against herbivorous insects. To test this prediction in a natural environment, scopolamine was induced by methyl jasmonate (MJ) in potted plants which were left 10 days in the field. MJ-treated plants increased their scopolamine concentration in leaves and herbivory decreased. These findings suggest a cause-effect relationship. However, experiments in laboratory showed that scopolamine affect differently the performance of the specialist larvae of the ithomiine butterfly Placidina euryanassa (C. Felder & R. Felder) and the generalist fall armyworm Spodoptera frugiperda (J. E. Smith): the specialist that sequester this TA from B. suaveolens leaves was not negatively affected, but the generalist was. Therefore, scopolamine probably acts only against insects that are not adapted to TAs. Other compounds that are MJ elicited may also play a role in plant resistance against herbivory by generalist and specialist insects, and deserve future investigations.

Soldiers initiate foraging activities in the subterranean termite, Heterotermes tenuis

Caste polyethism has been recorded in some termite species, however the foraging behavior of subterranean termites remains poorly known. Heterotermes tenuis Hagen (Isoptera: Rhinotermitidae) is a subterranean termite that is native to Brazil and is an agricultural and urban pest. The aim of this study was to investigate which caste acts as scouts when searching for food sources and determinate the percentages of each caste present in the foraging territories of field colonies of H. tenuis. Our results showed no significant differences among the caste proportions present in the foraging territories of the three colonies studied in the field. Laboratory experiments showed that minor soldiers were the most frequent initiators of foraging activities. This result suggests that the exploratory phase of the foraging behavior may be regulated by the number of soldiers present in the foraging territories of each colony.

Differential Attractiveness of Potato Tuber Volatiles to Phthorimaea operculella (Gelechiidae) and the Predator Orius insidiosus (Anthocoridae)

The behavioral responses of the potato tuberworm moth Phthorimaea operculella and the polyphagous predator Orius insidiosus to volatiles emanating from exposed tubers were studied by four-arm olfactometer bioassays. Mated females of P. operculella distinguished volatiles released by intact potato tubers from volatiles damaged mechanically or by conspecific larvae. Volatiles from intact potato tubers were attractive to them. On the other hand, unmated females of P. operculella did not respond to tuber volatiles. Adults of O. insidiosus were attracted to volatiles from tubers damaged by P. operculella larvae, but did not respond to intact or mechanically damaged tubers. Methyl jasmonate (MeJA) was the only compound identified from the headspace of potato tubers (GC-MS of direct headspace sampling). The amount varied with the type of induction, being 0.001 +/- 0.0003 ng g(-1) in tissues of intact fresh tubers, 0.002 +/- 0.0007 ng g(-1) in mechanically damaged tubers, and showing a six- to tenfold increase in P. operculella damaged tubers (0.090 +/- 0.006 ng g(-1)). Behavioral bioassays with synthetic MeJA confirmed that the response of the insects is dependent on MeJA concentration. Mated females of P. operculella showed the highest response at 0.001 ng g(-1) (concentration released by intact tubers), whereas O. insidiosus showed the highest response, between 0.01 and 0.05 ng g(-1), which is close to the concentration released by P. operculella damaged tubers. Based on these results, we postulate that P. operculella and O. insidiosus have adapted their responses to plant volatiles differently, enabling them to locate suitable hosts or prey.

Plant volatiles: new perspectives for research in Brazil

Agroecosystems consist on complex trophic relationships among host plants, herbivores and their natural enemies. This article reviews the research of plant volatiles in Brazil, in order to determine multiple resistance mechanisms of economically important crops and to contribute to the understanding of insect-plant interactions. Most pest management programs, including chemical and biological control, do not consider the impact of these chemicals on herbivores and their natural enemies. Alternative control methods are being developed in order to improve our understanding on the endogenous mechanisms of plant induced defenses against phytophagous arthropods. The use of plant volatiles technology as an additional tool in integrated pest management programs would offer a new and environmentally sound approach to crop protection. This technique involves the development of baits that attract beneficial organisms and the manipulation of biochemical processes that induce and regulate plant defenses, key factors in the improvement of control programs against economically important pests. The elucidation of the mechanisms involved in the indirect defenses of plants will result in useful tools for biological control of crop pests.

Effect of biotic and abiotic factors on the tunneling behavior of Coptotermes gestroi and Heterotermes tenuis (Isoptera: Rhinotermitidae)

Using bidimensional arenas, the construction and spatial dispersion of tunnels constructed by Coptotermes gestroi and Heterotermes tenuis (Rhinotermitidae) was determined under different laboratory conditions. Workers of both species showed an increase of the tunneled area with the rise in temperature. The activity of workers of C. gestroi also increased with the rise in soil moisture. Primary tunnels showed a high degree of dispersion in the arenas for all treatments. The presence of food did not influence the tunneling pattern of C. gestroi; but for H. tenuis there was a significant decrease in the number of tunnels. In addition, the type of substrate affected the tunneling pattern in both species. The understanding of food searching strategies of subterranean termites could contribute in the improvement of pest management programs based on the use of toxic baits.

Neotenic formation in laboratory colonies of the termite Coptotermes gestroi after orphaning

The termite Coptotermes gestroi (Wasmann 1896) (Rhinotermitidae: Coptotermitinae) is an exotic species in Brazil and information concerning its reproductive developmental biology is scarce. We induced the formation of neotenics in laboratory colonies through orphaning experiments. Orphaning experiments were conducted in three-year old colonies of C. gestroi kept under laboratory conditions. After three months, eight nymphoid neotenics were observed in one colony after queen removal. Histological analysis showed that these neotenics were non-functional. The results suggest that these individuals may have arisen from the first nymphal instar (N1) or from an early N1 instar after one or two larval moults. Neotenics also were recorded on two incipient colonies of C. gestroi that lost the queen naturally.

Segmental specializations in the Malpighian tubules of the fire ant Solenopsis saevissima Forel 1904 (Myrmicinae): an electron microscopical study

The Malpighian tubules of workers of the fire ant Solenopsis saevissima (Myrmicinae) were analyzed by scanning and transmission electron microscopy in order to determine their functional organization and association with the hindgut epithelium. The ants showed six Malpighian tubules with three segments morphologically and structurally different. The proximal segment was long and its cells showed abundant smooth endoplasmic reticulum and lipid droplets, which suggest their role in lipid secretion. The mid segment was long and undulated and it was composed by the cells that showed the typical features of ion transporting epithelia. The distal segment, short and flattened, adheres to the rectum wall. The cells of this segment showed the basal lamina fused to that of the rectum, it is probable that this part of the tubule may play a role in ion and water uptake from the feces.

Failure of a novel balloon-expandable gamma-emitting ((103)Pd) stent to prevent edge effects

BACKGROUND

Balloon-expandable beta-particle-emitting ((32)P) stents inhibit within-stent neointimal hyperplasia but induce lumen narrowing beyond the stent margins, ie, the so-called "edge effects."

METHODS AND RESULTS

We prospectively investigated the performance of novel stents impregnated with the gamma-emitting isotope (103)Pd, designed to reduce edge effects, in 24 rabbits. The stents had a length of 18 mm and were mounted on 20-mm-long delivery balloons for deployment. Angiograms were obtained immediately and 1 month after direct implantation of control and 1-, 2-, and 4-mCi (103)Pd stents into the iliac arteries without predilatation or postdilatation. Late lumen loss was measured with quantitative angiography. Neointimal hyperplasia and vascular remodeling were evaluated by histomorphometry. Late lumen loss was inhibited within (103)Pd stents (control 0.18 mm, 1 mCi 0.08 mm, 2 mCi 0.05 mm, and 4 mCi -0.03 mm, P<0.05 all activities versus control). Conversely, late lumen loss occurred at the edges of (103)Pd stents, correlating with areas of high balloon/artery ratios and vessel overstretch injury. Edge effects were primarily due to neointimal hyperplasia but were also caused by negative vessel remodeling at high stent activities.

CONCLUSIONS

Edge effects after implantation of radioisotope stents can occur independently of the isotope chosen for stent impregnation.

Overestimation of stent delivery balloon diameters by manufacturers' compliance tables: a quantitative coronary analysis of Duet and NIR stent implantation

Although manufacturers' compliance tables of stent delivery balloons indicate the diameter of the balloon at a given inflation pressure, it is unclear whether these data correlate with in vivo true intracoronary balloon diameters (TBDs). The TBDs of two new-generation balloon-expandable stent delivery systems (Duet and NIR) were measured by quantitative coronary analysis (QCA) in 100 consecutive patients. The manufacturers' stated balloon diameter (BD) of the stent delivery systems overestimated the TBD in 94% +/- 4% of patients receiving both Duet or NIR stent implantations. In only 6% of the patients, the TBD matched the manufacturers' stated balloon diameter. There was no underestimation of TBDs by both manufacturers' compliance tables. The Duet tables overestimated TBDs by 14% +/- 8% (range, 1%-36%), the NIR tables by 18% +/- 8% (range, 1%-41%), P < 0.05, Duet vs. NIR, respectively. When the manufacturers' data were corrected for the differences in reporting data from in vitro tests, i.e., balloon compliance data with or without the stent, the degree of overestimation of diameters was similar for Duet and NIR stent delivery balloons (14% +/- 8% vs. 13% +/- 7%, Duet vs. NIR; P = NS). Manufacturers' compliance tables of both the Duet and NIR stent delivery balloon systems significantly overestimate the true intracoronary balloon diameter. The manufacturers' of stent delivery balloons should clearly state on the box, if balloon compliance data were derived from in vitro bench testing, which phantoms were used for compliance analysis, and that the tables may overestimate the true intracoronary balloon diameter. The findings of the present study have important clinical implications with respect to performing coronary stent implantation with precision.

Functional ultrastructure of the midgut of the fire ant Solenopsis saevissima Forel 1904 (Formicidae: Myrmicinae)

Solenopsis saevissima has a midgut composed of columnar, regenerative, and goblet cells. The midgut epithelium was covered by a basal lamina. Outside the basal lamina, layers of inner oblique, circular, and outer longitudinal muscles were present. Columnar cells showed a basal plasma membrane containing numerous folds, mitochondria, and the nucleus. Rough endoplasmic reticulum, Golgi bodies, membrane bounded vacuoles, and spherocrystals were found in this region. The apical plasma membrane was constituted by microvilli, which were above a region rich in mitochondria. Regenerative cells were found in groups lying by the basal lamina. Goblet cells were associated with an ion-transporting mechanism between the haemolymph and the midgut epithelium. These cells were lying by the midgut lumen and large microvilli were evident, but the cytoplasmic features were similar to the columnar cells.

Nitric oxide diminishes apoptosis and p53 gene expression after renal ischemia and reperfusion injury

BACKGROUND

The role of nitric oxide in the ischemic injury of the kidney is still controversial. The aim of this study was to reevaluate the beneficial effect of exogenous nitric oxide and define its effects as regulator of gene p53 expression and apoptosis in the ischemic renal injury.

METHODS

Sprague-Dawley rats were subjected to 75 min of renal warm ischemia and contralateral nephrectomy. The animals were divided into six groups (n=6 per group): Two sham groups at 4 and 24 hr, two ischemic control (IC) at same times and two treated groups (Na-NP), studied at same intervals, where sodium nitroprusside (5 mg/kg) was given 15 min before reperfusion. The parameters evaluated included: serum creatinine, blood urea nitrogen, neutrophil infiltration determined by myeloperoxidase, gene p53 expression determined by reverse transcriptase polymerase chain reaction, apoptosis determined by peroxidase in situ technique and light histology.

RESULTS

There were significant improvements in serum creatinine and blood urea nitrogen at 24 hr in the NA-NP group when compared with the IC group (P<0.05). Myeloperoxidase levels were higher in the IC when evaluated against the Na-NP groups. Na-NP exhibited a downregulating effect in the expression of gene p53 when compared to the IC group. Apoptosis was more evident in the IC group and had moderately increased histological damage when compared to the Na-NP group.

CONCLUSIONS

Nitric oxide demonstrated a protective effect in the ischemic injury of the kidney and exerted an antiapoptotic action dowregulating the expression of gene p53.

Occurrence of sibling species of Lutzomyia longipalpis (Diptera: Psychodidae) in Venezuela: first evidence from reproductively isolated sympatric populations

The delimitation of cryptic species within the main vector of the American visceral leishmaniasis, Lutzomyia longipalpis, remains a topic of controversy. An analysis of genetic variability based on 8 enzymatic loci revealed fixed differences in 2 diagnostic loci, adenylate kinase (Ak) and hexokinase (Hk), between sympatric and allopatric populations at 4 localities in Venezuela. The absence of heterozygotes for these 2 loci within 1 locality indicates, for the first time, the presence of 2 sympatric reproductively isolated populations or cryptic species within L. longipalpis. Significant differences were also detected between these cryptic species in the allele frequencies of glucose-6-phosphate isomerase (Gpi) and malate dehydrogenase, decarboxylating (Me). One species showed mean heterozygosities that ranged between 6.6% and 6.7%, with 1.6-1.9 alleles detected per locus, while the other had mean heterozygosities that ranged from 4.3% to 6.3%, with 1.3-1.6 alleles per locus. Comparisons of isozyme profiles with published data suggests that 1 species is similar to the L. longipalpis described in Colombian and Brazilian populations, whereas the other has not been previously reported.

The effect of DNA methylation on gene regulation of human papillomaviruses

Integration of human papillomaviruses (HPVs) into the host genome is considered to be an early and important event in HPV-linked cervical carcinogenesis. Consequently, the viral DNA potentially becomes a target for cellular control mechanisms normally acting on the corresponding integration site. Besides resulting position effects, host-specific DNA methylation may play a functional role in HPV gene regulation. To elucidate the influence of such a kind of epigenetic modification on viral transcription, in vitro methylation studies on HPV-18 upstream regulatory region (URR)-controlled reporter plasmids were carried out. Selective methylation of the viral URR results in a down-regulation of the transcriptional activity, which can be attributed to nonrandom distribution of methyl-acceptor sites clustered within the constitutive enhancer region. In vivo competition experiments show that suppression is not directly mediated by steric hindrance of methyl residues with transcription factors, but rather is due to the association with methyl-CpG DNA-binding proteins. Using a restriction enzyme accessibility assay on both the DNA and chromatin levels, it could be demonstrated that, in vivo, extensively methylated viral DNA is nucleosomally organized, characteristic of transcriptionally inactive chromatin. These data suggest that DNA methylation is an important regulatory pathway in the modulation of HPV expression and as a consequence the proliferation rate of virus-infected cells.

[Effect of a sodium fluoride solution at different temperatures on the solubility of deciduous dental enamel]

An in vitro study about the influence of temperature on the solubility of deciduous powdered enamel protected by sodium fluoride (0.05%) was made to observe the variation of the weight loss when the tissue was exposed to 0.5 N lactate buffer at pH 4.5. The protective capacity of fluoride to decrease the acid solubility in temporary tooth enamel presumably can be attribute to increase the temperature measured by scale centrigrade.