Sperm competition, but not major histocompatibility divergence, drives differential fertilization success between alternative reproductive tactics in Chinook salmon.

Post-copulatory sexual selection processes, including sperm competition and cryptic female choice (CFC), can operate based on major histocompatibility (MH) genes. We investigated sperm competition between male alternative reproductive tactics [jack (sneaker) and hooknose (guard)] of Chinook salmon (Oncorhynchus tshawytscha). Using a full factorial design, we examined in vitro competitive fertilization success of paired jack and hooknose males at three time points after sperm activation (0, 15 and 60 s) to test for male competition, CFC and time effects on male fertilization success. We also examined egg-mediated CFC at two MH genes by examining both the relationship between competitive fertilization success and MH divergence as well as inheritance patterns of MH alleles in resulting offspring. We found that jacks sired more offspring than hooknose males at 0 s post-activation; however, jack fertilization success declined over time post-activation, suggesting a trade-off between sperm speed and longevity. Enhanced fertilization success of jacks (presumably via higher sperm quality) may serve to increase sneaker tactic competitiveness relative to dominant hooknose males. We also found evidence of egg-mediated CFC (i.e. female × male interaction) influencing competitive fertilization success; however, CFC was not acting on the MH genes as we found no relationship between fertilization success and MH II ß1 or MH I α1 divergence and we found no deviations from Mendelian inheritance of MH alleles in the offspring. Our study provides insight into evolutionary mechanisms influencing variation in male mating success within alternative reproductive tactics, thus underscoring different strategies that males can adopt to attain success.

The first prospective controlled trial comparing wireless capsule endoscopy with push enteroscopy in chronic gastrointestinal bleeding.

BACKGROUND AND STUDY AIMS: In chronic gastrointestinal bleeding (CGB), bleeding sites located in the small bowel are difficult to detect with conventional radiological or scintigraphic techniques. Push enteroscopy (PE) is at present considered to be the most effective diagnostic procedure. The aim of this prospective trial was to compare the efficacy of wireless capsule endoscopy (CE) with PE. PATIENTS AND METHODS: Between April and October 2001, 65 patients with CGB were referred to our unit. Complete conventional diagnostic work-up (including small-bowel enteroclysis, angiography, and scintigraphy), as well as PE and CE, were performed in 32 patients. RESULTS: On average, the patients had been suffering from CGB for 29 +/- 24 months (6 - 126); the lowest hemoglobin level varied between 3.0 and 9.9 g/dl (mean 5.9 +/- 1.4); 17 +/- 18 blood units (0 - 60) were transfused. Each patient underwent 6 +/- 7 (range 1 - 38) hospitalizations, with a mean of 14 +/- 9 diagnostic procedures before CE was used. Conventional diagnostic procedures revealed relevant pathological findings in five of the 32 patients (16 %). Definite bleeding sites diagnosed by PE in nine patients (28 %) included angiodysplasia (seven patients), small-bowel cancer (one patient) and lymphoma (one patient). CE detected the definite source in 21 of the 32 patients (66 %) ( P < 0.001). Definite bleeding sources included angiodysplasia (17 patients), malignant stenoses (two patients) and inflammatory small-bowel disease (two patients). Questionable bleeding sources were seen on PE in three additional patients (9 %), and using CE in a further seven patients (22 %). Both CE and PE were safe and were not associated with any morbidity. CONCLUSIONS: In the present trial in patients with CGB, wireless CE had the highest diagnostic yield and was significantly superior to PE. CE can help reduce the number of diagnostic procedures and could become the initial diagnostic choice in patients with CGB and negative upper and lower gastrointestinal endoscopy.