Radiotherapy effect on frequency of Candida spp. and on virulence of C. albicans isolated from the oral cavity of head and neck cancer patients

The aim of this study was to investigate the diversity and prevalence of yeasts, and the virulence of C.albicans found in the oral cavity during the course of ionizing radiation treatment of patients with head and neck tumor (HNTP). Samples from 21 HNTP and 24 healthy controls were isolated and identified. C. albicans isolated from two patients during radiotherapy were analyzed for virulence factors. Radiotherapy induced a higher level of both yeast colonization (81% vs 33%) and non-albicans Candida (NAC) colonization (52.4% vs 4.0%) in HNTP than the control group. Patients were colonized by 5 different NAC species: C. glabrata, C. tropicalis, C. parapsilosis, C. krusei and C. kefir. On the other hand, C. albicans colonization was similar in patients and controls (6/21, 28.6% vs 7/24, 29.2%, respectively). Also, of the 11 patients assessed before and during radiotherapy, 5 (45.5%) were colonized before the start of treatment and another 5 (45.5%) during treatment. All of the latter were colonized by NAC species alone. Moreover, we observed a significant and continuous enhancement of C. albicans virulence as the radiotherapy progressed, in the two patients involved in this test. Thus, it is concluded that radiotherapy is an important predisposing factor for the oral candidiasis, including NAC species. Also, it may facilitate the development of more virulent C. albicans strains.

O objetivo deste estudo foi avaliar a diversidade e a prevalência de Cândida, bem como a virulência de Cândida albicans, isoladas da cavidade bucal no decurso de tratamento por radiações ionizantes de pacientes acometidos por tumores de cabeça e pescoço (PTCP). Amostras de 21 pacientes e 24 controles foram analisadas. C. albicans isoladas de dois pacientes ao longo do tratamento radioterápico foram avaliadas para fatores de virulência. A radioterapia induziu um grande aumento da colonização de Cândida como um todo (81% vs 33%) e Cândida não albicans (CNA) em particular (52.4% vs 4.0%) em PTCP quando comparado com controles não irradiados. Cinco espécies diferentes de CNA foram encontradas nos pacientes: C. glabrata, C. tropicalis, C. parapsilosis, C. krusei and C. kefir. Por outro lado, a colonização por C. albicans nestes pacientes e controles foi similar (6/21, 28.6% vs 7/24, 29.2%, respectivamente). Além disso, dos 11 pacientes que foram avaliados antes e durante o tratamento radioterápico, 5 pacientes (45,5%) foram colonizados antes do início da radioterapia e outros 5 (45,5%) durante o tratamento radioterápico. Destes últimos, todos foram colonizados apenas com espécies CNA. Observou-se, ainda, um aumento contínuo e significante da virulência de C. albicans com o progresso da radioterapia nos dois pacientes estudados. Conclui-se que o tratamento radioterápico é um importante fator de desenvolvimento de candidíase oral, incluindo candidíase por espécies não albicans, em pacientes portadores de tumor de cabeça e pescoço. A radioterapia pode, ainda, facilitar o desenvolvimento de cepas mais virulentas de C.albicans.

Changes in glycemia induced by exercise in rats: contribution of hepatic glycogenolysis and gluconeogenesis.

The participation of hepatic glycogenolysis and gluconeogenesis to the glycemic changes promoted by exercise was investigated. For this purpose, we employed swimming rats (2.5% body weight extra load attached to the tail, at 24 degrees C) using a favorable condition to measure hepatic glycogenolysis (fed rats) and a favorable condition to measure hepatic gluconeogenesis (fasted rats). This experimental approach permits us to compare the contribution of hepatic glycogenolysis and gluconeogenesis to glucose changes for a specific schedule of exercise. The animals were investigated at rest, after 5 minutes of swimming and after swimming to exhaustion. Our results show that hepatic glycogen has a crucial role to determine hyperglycemia during exercise. In contrast, hypoglycemia developed during exercise when glycogen was depleted. However, the ability of the liver to produce glucose from L-lactate, glycerol and L-glutamine was increased during exercise. Taken together, these findings suggest that the hepatic capacity to produce glucose from gluconeogenic substrates (except for L-alanine) was increased when hepatic glycogen stores were depleted. Thus, the increased capacity to produce glucose shown by livers from exercising rats must to be an important metabolic adaptation to protect against severe hypoglycemia.