Androgens directly stimulate spermatogonial differentiation in juvenile Atlantic salmon (Salmo salar).

We studied the effects of androgens on early stages of spermatogenesis along with androgen receptor binding characteristics and the expression of selected testicular and pituitary genes. To this end, immature Atlantic salmon postsmolts received testosterone (T), adrenosterone (OA, which is converted in vivo into 11-ketotestosterone, 11-KT) or a combination of the two androgens (T+OA). Treatment with OA and T elevated the plasma levels of 11-KT and T, respectively, and co-injection of OA with T lead to high 11-KT levels but prevented plasma T levels to reach the levels observed after injecting T alone. Clear stimulatory effects were recorded as regards pituitary lhb and gnrhr4 transcript levels in fish receiving T, and to a lesser extent in fish receiving OA (but for the lhb transcript only). The two androgen receptors (Ara1 and Ara2) we cloned bound T and 11-KT and responded to these androgens in a similar way. Both androgens down-regulated testicular amh and increased igf3 transcript levels after 1 week of treatment, but effects on growth factor gene expression required sustained androgen stimulation and faded out in the groups with the decreasing T plasma levels. In fish exhibiting a sustained elevation of 11-KT plasma levels (OA and T+OA groups) for 2 weeks, the number of differentiating spermatogonia had increased while the number of undifferentiated spermatogonia decreased. Previous work showed that circulating gonadotropin levels did not increase following androgen treatments of gonad-intact immature male salmonids. Taken together, androgen treatment of immature males modulated testicular growth factor expression that, when sustained for 2 weeks, stimulated differentiation, but not self-renewal, of undifferentiated type A spermatogonia.

Spermatogenesis recovery in protein-restricted rats subjected to a normal protein diet after weaning.

This study investigated the pre- and postnatal effects of protein restriction (8% vs 20% crude protein) on different parameters of spermatogenesis in adult rat offspring. Body and testis weights as well as the seminiferous tubular diameter were reduced in those animals that received the protein-restricted diet after weaning, although these parameters recovered when a 20% protein diet was offered subsequently. The numbers of spermatogonia, spermatocytes, spermatids and Leydig cells were reduced in undernourished animals, whilst the Sertoli cell number did not change. Prenatal programming effect was observed only in the spermatogonial or proliferative phase of spermatogenesis. However, the intake of the normal protein diet after weaning brought many of the testicular parameters evaluated back to normal in 70-day-old rats. A significant reduction of the meiotic index, Sertoli cell supporting capacity and spermatogenic efficiency was observed in animals subjected to protein undernutrition throughout their lives. The data presented show that protein restriction impairs the normal development of the testis in different ways, depending on the period during which the restriction was imposed, and the negative effects on spermatogenesis are more severe when undernutrition occurs from conception to adulthood; however, the return to a normal protein diet after weaning recovers the spermatogenic process.

Salinity and photoperiod modulate pubertal development in Atlantic salmon (Salmo salar).

The Atlantic salmon shows substantial life cycle plasticity, which also applies to the timing of puberty. While it is characterized by the activation of the brain-pituitary-gonad axis, many morphophysiological aspects of puberty and the influence of environmental conditions, such as water salinity, are not well understood in fish. Here, 12-month-old Atlantic salmon coming from an out-of-season smoltification regime in December were exposed to freshwater (FW) or seawater (SW) at 16 °C to stimulate puberty under a 24-h constant light (LL) or 12 h light:12 h darkness (LD) photoperiod. These four treatment groups (FWLL, SWLL, FWLD, and SWLD) were studied from January to March. Next to 11-ketotestosterone (11-KT) plasma levels, the expression of pituitary genes (gnrhr4, fshb, and lhb) and spermatogenesis was quantified. When spermatogonial proliferation started, fshb mRNA levels increased steeply and began to decrease when spermatogonial mitosis approached completion and most germ cells had reached meiotic or post-meiotic stages. Conversely, lhb mRNA levels increased progressively during spermatogenesis. Most males in all treatment groups matured, but exposure to SW resulted in the strongest stimulation of the onset of spermatogenesis and elevation of pituitary gnrhr4 and fshb mRNA levels. Later on, the LD photoperiod accelerated, irrespective of the salinity, the completion of spermatogenesis, associated with higher lhb mRNA and 11-KT plasma levels than in the LL groups. We find that both salinity and photoperiod modulated different aspects of spermatogenesis, and resulted in a differential activation of pituitary and testis functions; SW stimulating the onset and the shorter photoperiod the completion of spermatogenesis.

Analysis of the genetic diversity of vancomycin-resistant Staphylococcus aureus

Staphylococcus aureus resistente à meticilina (MRSA) e Staphylococcus coagulase negativo resistente à meticilina (MRCoNS) são os agentes mais freqüentes em infeccões hospitalares mundialmente, justificando o incremento no uso de vancomicina. Neste estudo avaliamos a presenca de Staphylococcus resistentes aos glicopeptideos em 41 pacientes, em uso de vancomicina, hospitalizados no Hospital de Clínicas da Universidade Federal de Uberlândia em Uberlândia-MG. Todos os isolados foram semeados em agar Mueller-Hinton acrescido do antimicrobiano. A resistência a vancomicina foi confirmada por crescimento após incubacão por 24-48 horas a 35ºC. A heterorresistência foi avaliada por semeadura com inóculo mais denso (108 UFC/mL). Um paciente com nefrite, no programa de hemodiálise teve o fenótipo de Staphylococcus aureus com resistência intermediária à vancomicina (VISA) (CIM= 8 mg/mL) e em oito pacientes as amostras apresentaram heterorresistência (hVISA). Além do uso prévio de vancomicina outros fatores de risco incluindo três ou mais antimicrobianos, cirurgia e três ou mais procedimentos invasivos, foram observados. A análise molecular foi realizada por amplificacão randômica de DNA polimórfico em reacão em cadeia da polimerase (RAPD-PCR) mostrando dois clusters com duas amostras cada um, em pacientes cirúrgicos, com relacão temporal espacial e com perfil de susceptibilidade semelhantes quando frente à vários outros antimicrobianos.