Populations with diploid and triploid individuals co-occur in various plant and animal species, but detecting their relative frequencies is problematic. Microsatellite markers can be used to detect triploids that have three distinct alleles at a given locus, but cannot identify triploids that are partially or fully homozygous (i.e., possessing two or three copies of the same allele). Detection of partially homozygous triploids is sometimes possible with allozymes if no dosage compensation occurs. However, the inference of triploidy from uneven band intensities is not always reliable, making it difficult to estimate the actual proportion of triploids in a population. We present an iterative mathematical procedure for estimating the overall proportion of triploids from allozyme and microsatellite data. This method also estimates corrected allele frequencies by accounting for potentially hidden cases of homozygosity occurring in triploid individuals with multiple copies of an allele.

Alleles↗

PubMedDate not supplied

Evolutionary theories of aging. 1. The need to understand the process of natural selection.

BACKGROUND: In a Forum article Le Bourg (1998) criticized recent tests of evolutionary theories of aging and suggested alternative explanations for the long lifespan of ant queens and the positive relationship between body size and lifespan in mammals. Moreover, he attempts to criticize evolutionary theories of aging by showing that explanations other than evolutionary theories of aging probably account for the variation in human lifespan across countries. OBJECTIVE: Here we show that the arguments of Le Bourg suffer several problems. First, many of the arguments reveal a misunderstanding of the process of natural selection. Second, some of the arguments reflect a lack of knowledge of evolutionary theories of aging (e.g. pre-reproductive mortality is not predicted to influence lifespan of organisms contrary to what is claimed). Finally, his final example on lifespan in humans simply is a straw-man because serious evolutionary biologists are well aware of the importance of confounding variables and would certainly not make the type of conclusion suggested by Le Bourg. CONCLUSION: Although a critical discussion of evolutionary theories of aging is welcome, we believe that the alternative explanations proposed by Le Bourg are implausible and reflect a misunderstanding of the process of natural selection.

Aging↗

PubMedDate not supplied

[Isolation of Plesiomonas shigelloides from a pediatric patient].

We report the isolation of P. shigelloides in the stools of a child with acute diarrhea living in the surroundings of Buenos Aires who usually drank untreated water. P. shigelloides has been implicated as an etiological agent in many sporadic cases of diarrhea, probably associated with drinking untreated water, eating uncooked seafood or foreign travel.

Argentina↗

PubMedDate not supplied

Absence of antisperm antibodies in anejaculatory men.

Antisperm antibodies were assessed in the serum samples of 73 men unable to ejaculate naturally and on the sperm cells of 13 of these men. None of the serum samples were found to be positive by sperm agglutination or sperm immobilization methods and antibodies were detected by an immunobead assay on the sperm cells of one of the 13 men examined.

Autoantibodies↗