Higher temperatures directly increase germ cell number, promoting feminization of red-eared slider turtles.

In many reptile species, gonadal sex is affected by environmental temperature during a critical period of embryonic development-a process known as temperature-dependent sex determination (TSD).1 The oviparous red-eared slider turtle, Trachemys scripta, has a warm-female/cool-male TSD system and is among the best-studied members of this group.2 When incubated at low temperatures, the somatic cells of the bipotential gonad differentiate into Sertoli cells, the support cells of the testis, whereas at high temperatures, they differentiate into granulosa cells, the support cells of the ovary.3 Here, we report the unexpected finding that temperature independently affects the number of primordial germ cells (GCs) in the embryonic gonad at a time before somatic cell differentiation has initiated. Specifically, embryos incubated at higher, female-inducing temperatures have more GCs than those incubated at the male-inducing temperature. Furthermore, elimination of GCs in embryos incubating at intermediate temperatures results in a strong shift toward male-biased sex ratios. This is the first evidence that temperature affects GC number and the first evidence that GC number influences sex determination in amniotes. This observation has two important implications. First, it supports a new model in which temperature can impact sex determination in incremental ways through multiple cell types. Second, the findings have important implications for a major unresolved question in the fields of ecology and evolutionary biology-the adaptive significance of TSD. We suggest that linking high GC number with female development improves female reproductive potential and provides an adaptive advantage for TSD.

Ocular candidiasis: a review.

AIMS: To review the epidemiology, diagnosis and changing treatment paradigm of ocular candidiasis, and report current prevalence rates and risk factors at one inpatient hospital. DESIGN: Retrospective review; systematic literature review. METHODS: All Wills Eye Institute inpatient ophthalmology consultations from Thomas Jefferson University Hospital were retrospectively reviewed between June 2006 and November 2006. All consultations for candidaemia were included. The outcome variables included chorioretinitis, endophthalmitis, visual symptoms and Candida speciation. The ophthalmic literature was reviewed using PubMed. Keywords included Candida, candidaemia, chorioretinitis, vitritis and endophthalmitis. Bibliographies were manually searched. RESULTS: Three of the 38 consultations for candidaemia (7.9%) had chorioretinitis. There were no cases of vitritis or endophthalmitis. The presence of symptoms, or the inability to articulate symptoms, was significantly associated with risk of ocular candidiasis (p = 0.003). All three cases of chorioretinitis had positive blood cultures for Candida albicans (p = 0.089) and were treated with oral fluconazole. CONCLUSIONS: Various factors have led to the increasing prevalence of inpatient candidaemia. Risk factors for ocular involvement include albicans species and the presence of, or inability to articulate, visual symptoms. For those without abnormal findings on initial examination, a subsequent retinal examination should be performed in 2 weeks, particularly if new symptoms develop or if the patient is unable to relay symptoms. Patients with chorioretinitis should be treated with systemic antifungal agents. For those with vitritis or endophthalmitis, particularly if worsening on systemic therapy alone, intravitreal antifungal medications or early vitrectomy should be considered.