Genome-wide analyses reveal population structure and identify candidate genes associated with tail fatness in local sheep from a semi-arid area.

Under a climate change perspective, the genetic make-up of local livestock breeds showing adaptive traits should be explored and preserved as a priority. We used genotype data from the ovine 50 k Illumina BeadChip for assessing breed autozygosity based on runs of homozygosity (ROH) and fine-scale genetic structure and for detecting genomic regions under selection in 63 Tunisian sheep samples. The average genomic inbreeding coefficients based on ROH were estimated at 0.017, 0.021, and 0.024 for Barbarine (BAR, n = 26), Noire de Thibar (NDT, n = 23), and Queue fine de l'Ouest (QFO, n = 14) breeds, respectively. The genomic relationships among individuals based on identity by state (IBS) distance matrix highlighted a recent introgression of QFO into the BAR and a genetic differentiation of NDT samples, possibly explained by past introgression of European gene pools. Genome-wide scan for ROH across breeds and within the BAR sample set identified an outstanding signal on chromosome 13 (46.58-49.61 Mbp). These results were confirmed using FST index, differentiating fat vs. thin-tailed individuals. Candidate genes under selection pressure (CDS2, PROKR1, and BMP2) were associated to lipid storage and probably preferentially selected in fat-tailed BAR animals. Our findings suggest paying more attention to preserve the genetic integrity and adaptive alleles of local sheep breeds.

Genome-wide assessment of diversity and differentiation between original and modern Brown cattle populations.

Identifying genomic regions involved in the differences between breeds can provide information on genes that are under the influence of both artificial and natural selection. The aim of this study was to assess the genetic diversity and differentiation among four different Brown cattle populations (two original vs. two modern populations) and to characterize the distribution of runs of homozygosity (ROH) islands using the Illumina Bovine SNP50 BeadChip genotyping data. After quality control, 34 735 SNPs and 106 animals were retained for the analyses. Larger heterogeneity was highlighted for the original populations. Patterns of genetic differentiation, multidimensional scaling, and the neighboring joining tree distinguished the modern from the original populations. The FST -outlier identified several genes putatively involved in the genetic differentiation between the two groups, such as stature and growth, behavior, and adaptability to local environments. The ROH islands within both the original and the modern populations overlapped with QTL associated with relevant traits. In modern Brown (Brown Swiss and Italian Brown), ROH islands harbored candidate genes associated with milk production traits, in evident agreement with the artificial selection conducted to improve this trait in these populations. In original Brown (Original Braunvieh and Braunvieh), we identified candidate genes related with fat deposition, confirming that breeding strategies for the original Brown populations aimed to produce dual-purpose animals. Our study highlighted the presence of several genomic regions that vary between Brown populations, in line with their different breeding histories.

The green tea polyphenol epigallocatechin-3-gallate (EGCG) restores CDKL5-dependent synaptic defects in vitro and in vivo.

CDKL5 deficiency disorder (CDD) is a rare X-linked neurodevelopmental disorder that is characterised by early-onset seizures, intellectual disability, gross motor impairment, and autistic-like features. CDD is caused by mutations in the cyclin-dependent kinase-like 5 (CDKL5) gene that encodes a serine/threonine kinase with a predominant expression in the brain. Loss of CDKL5 causes neurodevelopmental alterations in vitro and in vivo, including defective dendritic arborisation and spine maturation, which most likely underlie the cognitive defects and autistic features present in humans and mice. Here, we show that treatment with epigallatocathechin-3-gallate (EGCG), the major polyphenol of green tea, can restore defects in dendritic and synaptic development of primary Cdkl5 knockout (KO) neurons. Furthermore, defective synaptic maturation in the hippocampi and cortices of adult Cdkl5-KO mice can be rescued through the intraperitoneal administration of EGCG, which is however not sufficient to normalise behavioural CDKL5-dependent deficits. EGCG is a pleiotropic compound with numerous cellular targets, including the dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) that is selectively inhibited by EGCG. DYRK1A controls dendritic development and spine formation and its deregulation has been implicated in neurodevelopmental and degenerative diseases. Treatment with another DYRK1A inhibitor, harmine, was capable of correcting neuronal CDKL5-dependent defects; moreover, DYRK1A levels were upregulated in primary Cdkl5-KO neurons in concomitance with increased phosphorylation of Tau, a well-accepted DYRK1A substrate. Altogether, our results indicate that DYRK1A deregulation may contribute, at least in part, to the neurodevelopmental alterations caused by CDKL5 deficiency.

Old World camels in a modern world - a balancing act between conservation and genetic improvement.

Old World camels have served humans in cross-continental caravans, transporting people and goods, connecting different cultures and providing milk, meat, wool and draught since their domestication around 3000-6000 years ago. In a world of modern transport and fast connectivity, these beasts of burden seem to be out-dated. However, a growing demand for sustainable milk and meat production, especially in countries affected by climate change and increasing desertification, brings dromedaries (Camelus dromedarius) and Bactrian camels (Camelus bactrianus) back onstage and into the focus of animal breeders and scientists. In this review on the molecular genetics of these economically important species we give an overview about the evolutionary history, domestication and dispersal of Old World camels, whereas highlighting the need for conservation of wild two-humped camels (Camelus ferus) as an evolutionarily unique and highly endangered species. We provide cutting-edge information on the current molecular resources and on-going sequencing projects. We cannot emphasise enough the importance of balancing the need for improving camel production traits with maintaining the genetic diversity in two domestic species with specific physiological adaptation to a desert environment.

Runs of homozygosity reveal genome-wide autozygosity in Italian sheep breeds.

The availability of dense single nucleotide polymorphism (SNP) assays allows for the determination of autozygous segments based on runs of consecutive homozygous genotypes (ROH). The aim of the present study was to investigate the occurrence and distribution of ROH in 21 Italian sheep breeds using medium-density SNP genotypes in order to characterize autozygosity and identify genomic regions that frequently appeared in ROH within individuals, namely ROH islands. After filtering, the final number of animals and SNPs retained for analyses were 502 and 46 277 respectively. A total of 12 302 ROH were identified. The mean number of ROH per breed ranged from 10.58 (Comisana) to 44.54 (Valle del Belice). The average length of ROH across breeds was 4.55 Mb and ranged from 3.85 Mb (Biellese) to 5.51 Mb (Leccese). Valle del Belice showed the highest value of inbreeding on the basis of ROH (FROH  = 0.099), whereas Comisana showed the lowest (FROH  = 0.016), and high standard deviation values revealed high variability in autozygosity levels within each breed. Differences also existed in the length of ROH. Analysis of the distribution of ROH according to their size showed that, for all breeds, the majority of the detected ROH were <10 Mb in length, with a few long ROH >25 Mb. The levels of ROH that we estimated here reflect the inbreeding history of the investigated sheep breeds. These results also highlight that ancient and recent inbreeding have had an impact on the genome of the Italian sheep breeds and suggest that several animals have experienced recent autozygosity events. Comisana and Bergamasca appeared as the less consanguineous breeds, whereas Barbaresca, Leccese and Valle del Belice showed ROH patterns typically produced by recent inbreeding. Moreover, within the genomic regions most commonly associated with ROH, several candidate genes were detected.

Exposure to cadmium during in vitro maturation at environmental nanomolar levels impairs oocyte fertilization through oxidative damage: A large animal model study.

Cadmium is a highly toxic heavy metal with negative effects on oocyte fertilization. The aim of this study was to analyse whether cadmium-induced impairment of fertilization is caused by mitochondria dysfunction and oxidative stress in the cumulus-oocyte complex (COC). Preliminarily, 19 trace element levels were measured in ovaries from juvenile and adult ewes and age-related cadmium ovarian bioaccumulation at nanomolar concentrations was found. COCs from juvenile and adult ewes, exposed during in vitro maturation to 1nM or 100nM CdCl2, and subjected to in vitro fertilization showed significantly lower fertilization rates in exposed COCs compared with controls. In vitro matured exposed and control COCs underwent confocal microscopy analysis of mitochondria activity and reactive oxygen species (ROS) levels and lipid peroxidation (LPO) assay at cumulus cell and oocyte level. In both age groups, cadmium at nanomolar concentrations induced cumulus-oocyte mitochondria over-activity and oxidative damage which were related to impaired oocyte fertilization.

Genome-wide analysis highlights genetic dilution in Algerian sheep.

Algeria represents a reservoir of genetic diversity with local sheep breeds adapted to a large range of environments and showing specific features necessary to deal with harsh conditions. This remarkable diversity results from the traditional management of dryland by pastoralists over centuries. Most of these breeds are poorly productive, and the economic pressure leads farmers to realize anarchic cross-breeding (that is, not carried out in the framework of selection plans) with the hope to increase animal's conformation. In this study, eight of the nine local Algerian sheep breeds (D'men, Hamra, Ouled-Djellal, Rembi, Sidaoun, Tazegzawt, Berber and Barbarine) were investigated for the first time by genome-wide single-nucleotide polymorphism genotyping. At an international scale, Algerian sheep occupied an original position shaped by relations with African and European (particularly Italian) breeds. The strong genetic proximity with Caribbean and Brazilian breeds confirmed that the genetic make-up of these American breeds was largely influenced by the Atlantic slave trade. At a national scale, an alarming genetic dilution of the Berber (a primitive breed) and the Rembi was observed, as a consequence of uncontrolled mating practices with Ouled-Djellal. A similar, though less pronounced, phenomenon was also detected for the Barbarine, another ancestral breed. Genetic originality appeared to be better preserved in Tazegzawt, Hamra, D'men and Sidaoun. These breeds should be given high priority in the establishment of conservation plans to halt their progressive loss. For Berber and Barbarine that also occur in the bordering neighbor countries, urgent concerted transnational actions are needed.

Signatures of selection identify loci associated with fat tail in sheep.

Identification of genomic regions that have been targets of selection for phenotypic traits is one of the most challenging applications of dense marker panels in animal genetics. In this study, a genomewide scan using approximately 50,000 SNP was performed in an attempt to identify genomic regions associated with fat deposition in sheep, the importance of this not only being limited to livestock facing future climate changes but also for elucidating the physiology of lipid metabolism. The genotyping results obtained with the Ovine SNP50K BeadChip in 2 fat tail breeds were compared with those obtained in 13 thin tail breeds. Direct sequencing of the annotated genes located in proximity to the markers with opposite allele frequency in thin tail vs. fat tail sheep gave additional SNP of interest. To further confirm the results of the genomewide scan, we genotyped the SNP within these genes in the 2 groups of sheep. A missense mutation in the gene, with different allele frequency in the 2 groups, was detected. The results indicated and as the most probable genes involved in the fat tail phenotype.

Genome-wide analysis of Italian sheep diversity reveals a strong geographic pattern and cryptic relationships between breeds.

Italy counts several sheep breeds, arisen over centuries as a consequence of ancient and recent genetic and demographic events. To finely reconstruct genetic structure and relationships between Italian sheep, 496 subjects from 19 breeds were typed at 50K single nucleotide polymorphism loci. A subset of foreign breeds from the Sheep HapMap dataset was also included in the analyses. Genetic distances (as visualized either in a network or in a multidimensional scaling analysis of identical by state distances) closely reflected geographic proximity between breeds, with a clear north-south gradient, likely because of high levels of past gene flow and admixture all along the peninsula. Sardinian breeds diverged more from other breeds, a probable consequence of the combined effect of ancient sporadic introgression of feral mouflon and long-lasting genetic isolation from continental sheep populations. The study allowed the detection of previously undocumented episodes of recent introgression (Delle Langhe into the endangered Altamurana breed) as well as signatures of known, or claimed, historical introgression (Merino into Sopravissana and Gentile di Puglia; Bergamasca into Fabrianese, Appenninica and, to a lesser extent, Leccese). Arguments that would question, from a genomic point of view, the current breed classification of Bergamasca and Biellese into two separate breeds are presented. Finally, a role for traditional transhumance practices in shaping the genetic makeup of Alpine sheep breeds is proposed. The study represents the first exhaustive analysis of Italian sheep diversity in an European context, and it bridges the gap in the previous HapMap panel between Western Mediterranean and Swiss breeds.

Molecular tools and analytical approaches for the characterization of farm animal genetic diversity.

Genetic studies of livestock populations focus on questions of domestication, within- and among-breed diversity, breed history and adaptive variation. In this review, we describe the use of different molecular markers and methods for data analysis used to address these questions. There is a clear trend towards the use of single nucleotide polymorphisms and whole-genome sequence information, the application of Bayesian or Approximate Bayesian analysis and the use of adaptive next to neutral diversity to support decisions on conservation.

Renal resistive index and low-grade inflammation in patients with essential hypertension.

In essential hypertension, increased renal resistive index (RRI) is associated to a reduction of renal function and microalbuminuria, and to renal tubulo-interstitial damage. A tubulo-interstitial inflammatory infiltration was found in experimental models of hypertension, and serum high-sensitive C-reactive protein (hsCRP) levels correlated with urinary markers of tubulo-interstitial damage in humans. We studied the relationship between RRI and serum hsCRP in hypertensives with preserved renal function, without microalbuminuria. We investigated hypertensive patients without diabetes, renal failure, microalbuminuria or major inflammatory disease. Serum levels of hsCRP were assayed. RRI was calculated by intrarenal Doppler ultrasound and considered pathologic when ≥0.70 or >95% of upper confidence limit expected for age decade. The renal volume-to-resistive index ratio (RV/RRI) was also calculated. We evaluated 85 patients (57±14 years, 61 males). Patients with pathologic RRI (n=21) were older and had significantly higher hsCRP levels (4.70±2.30 vs 2.93±2.09 mg l(-1), P<0.01) compared with patients with normal RRI, as well as patients with decreased RV/RRI (n=43). HsCRP was directly related with RRI (r=0.41, P<0.001) and inversely with RV/RRI (r=-0.35, P<0.001). HsCRP proved to be a significant predictor of both pathologic RRI and decreased RV/RRI, even after adjustment. In essential hypertension low-grade inflammation is associated with tubulo-interstitial damage evaluated by Doppler ultrasonography.

Widespread impairment of cell proliferation in the neonate Ts65Dn mouse, a model for Down syndrome.

OBJECTIVES: Among the many pathological aspects of Down syndrome, brain hypoplasia and mental retardation have been recently ascribed to defective proliferation of neural precursors during central nervous system development. By analogy, other features of Down syndrome, such as heart defects, gastrointestinal abnormalities, craniofacial dystrophy and reduced growth rate could be related, at least in theory, to similar proliferation impairment in peripheral tissues. MATERIALS AND METHODS: In order to test this hypothesis, we evaluated cell proliferation in peripheral tissues of the Ts65Dn mouse, one of the animal models most commonly used to investigate Down syndrome. RESULTS: In fibroblast cultures from neonatal Ts65Dn mice, we found that cell proliferation was notably impaired. While length of the cell cycle was similar in fibroblasts from Ts65Dn and control mice, the number of actively proliferating cells was significantly smaller in Ts65Dn mice. Moreover, fibroblasts from Ts65Dn animals exhibited limited population-doubling capacity, decreased proliferative lifespan and premature senescence. Analysis of cell proliferation in the skin of neonates, in vivo, showed that in Ts65Dn mice, cell proliferation was significantly reduced compared to control mice. CONCLUSIONS: Our results suggest that defective proliferation may be a generalized feature of trisomic mice. In view of the genetic and phenotypic similarities between Ts65Dn mice and individuals with Down syndrome, proliferation impairment in various organs may also occur in subjects with Down syndrome. Thus, perturbation of a basic developmental function, cell proliferation, may be a critical determinant that contributes to the many aspects of pathology of this condition.

Genetic variability of the Gentile di Puglia sheep breed based on microsatellite polymorphism.

The aim of the present study was to estimate the genetic variability of the Gentile di Puglia sheep breed by using microsatellite markers, to provide information useful for conservation. The DNA of 82 animals, belonging to 6 different farms, was analyzed at 19 microsatellite loci. The number of alleles, allele frequencies, deviations from Hardy-Weinberg proportions, linkage disequilibrium among loci, genetic similarity, genetic distances, and molecular coancestry-based parameters were calculated. Seventeen out of 19 microsatellites showed heterozygote deficiency in the whole population, although only 4 (OarAE129, ILSTS28, ILSTS5, MAF33) showed significant deviations from Hardy-Weinberg proportions (P<0.01). The genetic similarity (an index of allele sharing among individuals) within the whole population was low (0.318), and the average number of alleles per locus was quite high (9.68). The results obtained highlighted a population presenting both a deficiency of heterozygotes and great genetic variability. These results suggest that stratification of the breed in subpopulations, probably derived from different farm management in each herd, led to a population characterized by great genetic diversity among different herds and by great similarity within each herd. Moreover, in the past, Gentile di Puglia sheep have undergone a strong numeric decline, involving genetic drift effects and considerable consanguinity within the breed.

The genetic resistance to gastro-intestinal strongylids in Appenninica sheep: preliminary results.

Heritability parameters of resistance to gastro-intestinal strongylids, measured as FEC (Faecal Egg Count), were evaluated in the Appenninica sheep breed. FEC heritability coefficient was 0.11 +/- 0.061 while FEC repeatability coefficients were 0.58 +/- 0.085 and 0.76 +/- 0.223 in adult females and lambs respectively. Subjects were classified, based on FEC, into three different levels of resistance to strongylids. Ewes belonging to the 'resistant class' should be conveniently exploited in mating schemes, in order to provide a method, alternative to drug administration, for a long-term parasite control; this would result particularly helpful under those production systems, such as organic farming, where the use of drugs is not allowed or limited.

Sex differences in the hilar mossy cells of the guinea-pig before puberty.

Numerous sex differences have been detected in the morphology of the dentate and hippocampal neurons and hippocampus-dependent memory functions. The aim of the present study was to ascertain whether the mossy cells, an interneuron population forming a recurrent excitatory circuit with the dentate granule cells, are sexually dimorphic. The brains of juvenile (15-16 days old) and peripubescent (45-46 days old) male and female guinea-pigs were Golgi-Cox stained. Mossy cells were sampled from the hilus in the septal third of the dentate gyrus and their dendritic tree and somata were analyzed. The analysis was separately conducted on mossy cells with soma located in the portions of the hilus that face the upper blade (upper hilus) and lower blade (lower hilus), respectively. The mossy cells in the upper hilus were found to be sexually dimorphic in both juvenile and peripubescent animals. At both ages females had a larger dendritic tree than males. This difference was due to a greater mean branch length and, in peripubescent animals, also to a greater number of branches. In juvenile males, the spines on the proximal dendrites (thorny excrescences) had a greater density than in females. No differences in spine density were present in peripubescent animals. Unlike the mossy cells in the upper hilus, the mossy cells in the lower hilus showed very few sex differences in juvenile animals and no differences in peripubescent animals. The few differences favored females, that had more proximal branches and a greater spine density on the distal dendrites than males. The results show that the mossy cells of the guinea-pig are sexually dimorphic prior to puberty. Extending a previous investigation, the present data provide evidence that sex differences are mainly confined to the dentate region corresponding to the upper blade and upper hilus. The observed segregation of the sexual dimorphism in the upper blade/upper hilus suggests that this region might underlie the sexual dimorphism in hippocampus-dependent memory functions.

Effect of early isolation on signal transfer in the entorhinal cortex-dentate-hippocampal system.

Deprivation of socio-sensory interactions during early life impairs brain function in adulthood. In previous investigations we showed that early isolation severely affects neuron development in several structures of the hippocampal region, including the entorhinal cortex. In the present study we investigated the effects of early isolation on signal processing along the entorhinal cortex-dentate-CA3-CA1 system, a major memory circuit of the hippocampal region. Male and female guinea-pigs were assigned at 6-7 days of age to either a social or an isolated environment. At 90-100 days of age the animals were anesthetized and field potentials were recorded from the entorhinal cortex-dentate-CA3-CA1 circuit, driven by dorsal psalterium commissural volleys. Analysis of the input-output function in the different structures showed that in isolated males there was a small reduction in the input-output function of the population excitatory postsynaptic potential and population spike evoked in layer II of the entorhinal cortex. No changes occurred in isolated females. In isolated males and females there was a reduction in the input-output function of the population excitatory postsynaptic potential and population spike evoked in the dentate gyrus, CA3 and CA1, but this effect was larger in males. In isolated males, but not in females, the population spike/population excitatory postsynaptic potential ratio was reduced in all investigated structures, indicating that in males the size of the discharged neuron population was reduced more than due to the decreased input. Results show that isolation reduces the synaptic function in the whole entorhinal cortex-dentate gyrus-CA3-CA1 system. While the entorhinal cortex was moderately impaired, the dentate-hippocampal system was more severely affected. The impairment in the signal transfer along the entorhinal cortex-dentate gyrus-CA3-CA1 system was heavier in males, confirming the larger susceptibility of this sex to early experience. This work provides evidence that malfunctioning of a major hippocampal network may underlie the learning deficits induced by impoverished surroundings during early life.

Statistical analysis of individual assignment tests among four cattle breeds using fifteen STR loci.

Assignment tests based on multilocus genotypes are becoming increasingly important to certify quality and origin of livestock products and assure food safety and authenticity. The purpose of this study was to determine the potential of microsatellites (STR) for determining the breed origin of beef products among cattle breeds present in the market. We typed 19 STR in 269 animals from 4 cattle breeds. Based on Wright's F-statistics, 4 loci were discarded, and the remaining 15 loci (FIT = 0.101, FST = 0.089, and FIS = 0.013) were used to compute the likelihood that each multilocus genotype of the total sample was drawn from its true breed instead of another breed. To avoid occurrence of zero likelihood when one or more alleles were missing from a tested breed, sample allele frequencies were estimated assuming uniform prior distributions. Log-likelihood ratio [log(LR)] distributions of the individual assignments were determined for all possible breed contrasts, and their means and SD were used to infer the true-positive and false-positive rates at several values of the log(LR). The posterior probability that the animals of a presumed breed were actually drawn from that breed instead of any another breed was then calculated. Given an observed value of log(LR) > 0 and assuming equal priors, these probabilities were > 99.5% in 10 of 12 possible breed contrasts. For the 2 most closely related breeds (FST = 0.041), this probability was 96.3%, and the probability of excluding the origin of an animal from an alleged breed when it was actually derived from another breed was similar.

Sex differences in the stereological parameters of the hippocampal dentate gyrus of the guinea-pig before puberty.

Studies in rats and mice have shown several sex-dependent functional and structural differences in the hippocampal region, a brain structure playing a key role in learning and memory. The aim of the present study was to establish whether sex differences exist prior to puberty in the stereological parameters of the dentate gyrus in the guinea-pig, a long-gestation rodent, whose brain is at a more advanced stage of maturation at birth than the rat and mouse. The number of granule cells and volumes of the granule cell layer, molecular layer and hilus were evaluated in Nissl-stained brains of neonatal (15-16 days old) and peripubescent (45-46 days old) guinea-pigs. Based on a pilot study, the optical disector method was preferred to the optical fractionator method to estimate cell number. For volume (Vref) estimation with the Cavalieri principle, contour tracing was preferred to the point counting method, as the latter appeared to underestimate volumes. The results showed that neonatal males had more granule cells than females in both the dorsal and ventral dentate gyrus and a larger volume in all layers. Peripubescent males had a larger volume of the granule cell layer than females in both the dorsal and ventral dentate gyrus, more granule cells in the ventral dentate gyrus, a larger volume of the hilus in both the dorsal and ventral dentate gyrus and a larger volume of the molecular layer in the ventral dentate gyrus. The results show that sex differences are present in the guinea-pig dentate gyrus prior to puberty and go in the same direction at both investigated ages, with males exhibiting more granule cells and larger volumes than females. The widespread distribution of these sex differences suggests that in the guinea-pig, similarly to other rodents, hippocampus-dependent functions may be sexually dimorphic.

Sex differences in the hippocampal dentate gyrus of the guinea-pig before puberty.

The aim of the present research was to ascertain the presence of sex differences in the hippocampal dentate gyrus of the guinea-pig, a long-gestation rodent which gives birth to mature young and whose brain is at a more advanced stage of maturation at birth than that of the rat and mouse. The brains of neonatal (15-16 days old) and prepubescent (45-46 days old) male and female guinea pigs were Golgi-Cox stained. Granule cells were sampled from the upper (suprapyramidal) and lower (infrapyramidal) blade of the septal dentate gyrus and their dendritic tree and soma were measured. The analysis was conducted separately on granule cells with soma in the superficial (superficial granule cells) and deep (deep granule cells) half of the granule cell layer. Numerous sex differences were found in the upper blade of the dentate gyrus. Neonatal males had more dendritic branches than females in the innermost dendritic tree of both superficial and deep granule cells, but females had more branches over the middle/outer dendritic tree and a longer dendritic length. In prepubescent animals, the sex difference in the middle dendritic tree of the superficial granule cells changed direction, with males having more branches than females. In the deep granule cells, the sex differences were similar to those in neonatal animals. In both granule cell types, the dendritic length was similar in the two sexes. While no sex differences were found in dendritic spine density in neonatal animals, in prepubescent animals spine density was greater in females. In the lower blade the granule cells showed very few sex differences in both neonatal and prepubescent animals. This study shows wide dynamically changing sex differences in the granule cells located in the upper blade of the septal dentate gyrus, but almost no differences in the lower blade. These results demonstrate that sex differences are not ubiquitous in the dentate gyrus and suggest that the lower blade, unlike the upper blade, might be involved in non-sexually dimorphic behaviors.

Sustained, long-lasting inhibition of nitric oxide synthase aggravates the neural damage in some models of excitotoxic brain injury.

Brain nitric oxide (NO) can be a mediator of physiological and neuroprotective actions and an effector of neural damage. The effectiveness of acute or chronic inhibition of NO production in in vivo experiments of neurotoxicity/neuroprotection is controversial. We report here on the effects of a chronic, sustained inhibition of nitric oxide synthase (NOS) on the neurodegenerative damage caused by three different excitotoxic lesions. The damage caused by intrastriatal injection of ibotenic or kainic acid was aggravated in rats subjected to chronic NOS inhibition. On the contrary, the drop of cortical cholinergic input consequent to ibotenic acid-mediated degeneration of basal forebrain neurons was not altered by chronic NOS inhibition. The worsening of the damage was not related to any overt differential sensitivity to excitotoxicity of NOS-containing striatal neurons under conditions of NOS inhibition. These results suggest that, contrary to what has been often reported for short-term, mild inhibition of NO production, chronic and sustained NOS inhibition may exacerbate neuropathology. Thus, long-lasting shortage of NO may be detrimental when neuroprotective mechanisms related to the physiological action of this free radical are severely impaired. Although we cannot exclude that inhibition of the endothelial NOS isoform could have contributed to the worsening of neuropathology, differences among the paradigms of neurotoxicity used in the present study suggest a primary involvement of the neuronal NOS isoform. In view of the potential therapeutic use of NOS inhibitors, the effects of a too drastic alteration of the balance between neuroprotective and neurodegenerative actions of NO should be carefully considered.