Germ cell proliferation and apoptosis during testicular regression in a seasonal breeding fish kept in captivity

Cell proliferation and apoptosis regulate germ cells stock and sperm production, eliminate anomalous gametes, and are essential parameters to consider in fish farming. Herein, spermatogenic activity as well as germ cell proliferation and apoptosis were assessed in Leporinus taeniatus, a seasonal breeding species from the São Francisco River basin, Brazil. Testes of 24 adult fishes from a farming station were sampled between December and July and processed for light and transmission electron microscopy and immunohistochemistry for PCNA and TUNEL assay. The gonadosomatic index and seminiferous tubule diameters presented higher values during the breeding season (December/January and February/March), and then significantly reduced during the regression and resting stages (April/May and June/July). Phagocytosis of spermatozoa by Sertoli cells was evident during gonadal regression, but a significant number (up to 30%) remained at the tubular lumen during the resting stage. A higher PCNA/TUNEL ratio occurred in the breeding period, leading to an elevated proportion (%) of spermatogonia (G_A and G_B) in resting. Moreover, a higher TUNEL/PCNA ratio indicates the contribution of apoptosis to the reduction of germ cells during testicular regression. Together, these results indicate a shift in the balance between cell proliferation and apoptosis that contributes to the regulation of the spermatogenic cycle and germ cells pool of L. taeniatus kept in captivity.     

Diversity and distribution of hidden cultivable fungi associated with marine animals of Antarctica

In the present study, we surveyed the distribution and diversity of fungal assemblages associated with 10 species of marine animals from Antarctica. The collections yielded 83 taxa from 27 distinct genera, which were identified using molecular biology methods. The most abundant taxa were Cladosporium sp. 1, Debaryomyces hansenii, Glaciozyma martinii, Metschnikowia australis, Pseudogymnoascus destructans, Thelebolus cf. globosus, Pseudogymnoascus pannorum, Tolypocladium tundrense, Metschnikowia australis, and different Penicillium species. The diversity, richness, and dominance of fungal assemblages ranged among the host; however, in general, the fungal community, which was composed of endemic and cold-adapted cosmopolitan taxa distributed across the different sites of Antarctic Peninsula, displayed high diversity, richness, and dominance indices. Our results contribute to knowledge about fungal diversity in the marine environment across the Antarctic Peninsula and their phylogenetic relationships with species that occur in other cold, temperate, and tropical regions of the World. Additionally, despite their extreme habitats, marine Antarctic animals shelter cryptic and complex fungal assemblages represented by endemic and cosmopolitan cold-adapted taxa, which may represent interesting models to study different symbiotic associations between fungi and their animal hosts in the extreme conditions of Antarctica.     

Detection of immune complexes and evaluation of alcoholic individuals' serological profile in the diagnosis of strongyloidiasis

Strongyloidiasis is a human parasitosis that is considered a public health problem. Early diagnosis of this infection is extremely important in immunocompromised patients (i.e. subjects with alcoholism). This study aimed to evaluate anti-Strongyloides immunoglobulin G (IgG) and immunoglobulin A (IgA), assess levels of circulating immune complexes (IC) and determine IgG avidity in serum samples from alcoholic and nonalcoholic individuals. A total of 140 blood samples were collected from male individuals (70 alcoholic and 70 nonalcoholic subjects). Serum was obtained and analysed by enzyme-linked immunosorbent assay for IgG, IgA, IC detection and avidity determination. Anti-Strongyloides IgG was detected in 55.7% of alcoholic subjects and 32.8% nonalcoholics, while IC levels showed frequencies of 38.6% and 17.1% in these groups, respectively. Anti-Strongyloides IgA was lower among alcoholics (4.3%) than nonalcoholics (34.3%). Spearman's correlation coefficient reported a positive correlation between IgG, IC and IgA in alcoholic individuals and no correlation in nonalcoholics. The median avidity index was higher in alcoholics (83.8%) than nonalcoholic subjects (73.2%). In conclusion, this study shows that alcoholic subjects produced specific antibodies against S. stercoralis regardless of the possible immunosuppression caused by chronic alcoholism. Considering that alcoholics are more susceptible to the severe forms of strongyloidiasis, the implementation of immunological methods as a complementary approach to parasitological diagnostics (i.e. detection of IgG, IC and antibody avidity) appears to be an alternative method for early diagnosis in these individuals.     

Identification and characterization of Paracoccidioides lutzii proteins interacting with macrophages

Paracoccidioidomycosis (PCM), caused by thermodimorphic fungi of the Paracoccidioides genus, is a systemic disorder that involves the lungs and other organs. The adherence of pathogenic microorganisms to host tissues is an essential event in the onset of colonization and spread. The host–pathogen interaction is a complex interplay between the defense mechanisms of the host and the efforts of pathogenic microorganisms to colonize it. Therefore, the identification of fungi proteins interacting with host proteins is an important step understanding the survival strategies of the fungus within the host. In this paper, we used affinity chromatography based on surface proteomics (ACSP) to investigate the interactions of pathogen proteins with host surface molecules. Paracoccidioides lutzii extracts enriched of surface proteins were captured by chromatographic resin, which was immobilized with macrophage cell surface proteins, and identified by mass spectrometry. A total of 215 proteins of P. lutzii were identified interacting with macrophage proteins. In silico analysis classified those proteins according to the presence of sites for N- and O-glycosylation and secretion by classical and non-classical pathways. Serine proteinase (SP) and fructose-1,6-bisphosphate aldolase (FBA) were identified in our proteomics analysis. Immunolocalization assay and flow cytometry both showed an increase in the expression of these two proteins during host–pathogen interaction.     

The influence of pH on Staphylococcus saprophyticus iron metabolism and the production of siderophores

Staphylococcus saprophyticus is a gram-positive coagulase negative bacteria which shows clinical importance due to its capability of causing urinary tract infections (UTI), as well as its ability to persist in this environment. Little is known about how S. saprophyticus adapts to the pH shift that occurs during infection. Thus, in this study we aim to use a proteomic approach to analyze the metabolic adaptations which occur as a response by S. saprophyticus when exposed to acid (5.5) and alkaline (9.0) pH environments. Proteins related to iron storage are overexpressed in acid pH, whilst iron acquisition proteins are overexpressed in alkaline pH. It likely occurs because iron is soluble at acid pH and insoluble at alkaline pH. To evaluate if S. saprophyticus synthesizes siderophores, CAS assays were performed, and the results confirmed their production. The chemical characterization of siderophores demonstrates that S. saprophyticus produces carboxylates derived from citrate. Of special note is the fact that citrate synthase (CS) is down-regulated during incubation at acid pH, corroborating this result. This data was also confirmed by enzymatic assay. Our results demonstrate that iron metabolism regulation is influenced by different pH levels, and show, for the first time, the production of siderophores by S. saprophyticus. Enzymatic assays suggest that citrate from the tricarboxylic acid cycle (TCA) is used as substrate for siderophore production.