Morph-dependent fitness and directional change of morph frequencies over time in a Dutch population of Common buzzards Buteo buteo.

How genetic polymorphisms are maintained in a population is a key question in evolutionary ecology. Previous work on a plumage colour polymorphism in the common buzzard Buteo buteo suggested heterozygote advantage as the mechanism maintaining the co-existence of three morphs (light, intermediate and dark). We took advantage of 20 years of life-history data collected in a Dutch population to replicate earlier studies on the relationship between colour morph and fitness in this species.

Inheritance patterns of plumage coloration in common buzzards do not support a one-locus two-allele model.

Balancing selection is a major mechanism to maintain colour polymorphisms over evolutionary time. In common buzzards, variation in plumage colour was reportedly maintained by a heterozygote advantage: heterozygote intermediates had higher fitness than homozygote light and dark morphs. Here, we challenge one of the basic premises of the heterozygote advantage hypothesis, by testing whether plumage colour variation in common buzzards follows a one-locus two-allele inheritance model.

A comparison of in vitro fertilization results after embryo transfer after 2, 3, and 4 days of embryo culture.

Embryo transfer results after a 2 to 4 day period of embryo culture were compared. Two thousand two hundred ninety-seven ETs, performed in 1991 and 1992, were analyzed. Ongoing pregnancy rates after 2, 3, or 4 days of embryo culture were 23.

Doubling the human menopausal gonadotrophin dose in the course of an in-vitro fertilization treatment cycle in low responders: a randomized study.

The effect of doubling the human menopausal gonadotrophin (HMG) dose in the same treatment cycle in which the ovarian response after 5 days of ovarian stimulation with 225 IU/day is 'low', has been evaluated in a prospective randomized study. Forty-six patients met the ultrasound and oestradiol criteria for enrollment in the study, one patient participated twice. In 22 patients treatment was continued with 225 IU HMG/day and in 25 patients the HMG dose was increased to 450 IU/day.

Comparison of results obtained with human serum and a protein solution as a supplement for in vitro fertilization culture medium.

A prospective controlled study was performed to compare the PRs obtained after use of a uniform IVF culture medium containing a pasteurized serum protein solution or patient serum. The ongoing PRs per ET in the serum and the protein solution group were 32% and 28%, respectively (not significant). Culture of supernumerary embryos showed blastocyst formation and even hatching with both supplements.