The effect of biased conversion on the mutation load

The mutation load is sensitive to changes in the segregation ratio caused, for example, by biased conversion. If the distortion, measured by the force of conversion, is greater than the loss of fitness in the mutation heterozygotes, then the mutation load will be far away from its normal value. Examples are given where a small positive bias together with realistic fitness parameters increase the mutation load by more than two orders of magnitude. In practical terms this implies that great restrictions should be placed on the use of substances and treatments that may induce mutations associated with a positive conversion bias.     

The effect of ecoestrogens on the development of the mammalian reproductive system

Recently, it has been shown that the environment contains a large variety of chemical substances possessing estrogenic activity (ecoestrogens/environmental estrogens). In this connection, the problem of estrogenic effects exerted by the environment on animal ontogenesis is very important. Here, we review that available data concerning the effects of ecoestrogens on the development of the reproductive system in mammals. We discuss issues of reproductive toxicology related to the effects of these substances during prenatal and postnatal development, with special attention to the effect of ecoestrogens and modern reproductive technologies on preimplantation embryonic development.     

The effect of ecoestrogens on the development of the mammalian reproductive system

Recently, it has been shown that the environment contains a large variety of chemical substances possessing estrogenic activity (ecoestrogens/environmental estrogens). In this connection, the problem of estrogenic effects exerted by the environment on animal ontogenesis is very important. Here, we review the available data concerning the effects of ecoestrogens on the development of the reproductive system in mammals. We discuss issues of reproductive toxicology related to the effects of these substances during prenatal and postnatal development, with special attention to the effect of ecoestrogens and modern reproductive technologies on preimplantation embryonic development.     

The mechanism of the effect of apterous56f mutation on the reproductive function of Drosophila melanogaster

The effects of L-dihydroxyphenylalanine (L-DOPA) and 20-hydroxyecdysone (20E) were studied with respect to the content of dopamine (DA), intensity of the juvenile hormone (JH) degradation, and fecundity of the wildtype flies (Canton S) and JH-deficient apterous56f mutants (in young females, carrying this mutation, the levels of DA and 20E production were strongly increased). Fly feeding with L-DOPA proved to increase the level of DA in a dose-dependent manner and reduce JH degradation in 2-day-old females of both strains. Feeding with 20E produced the same effect. Treating the wild-type flies with 2.5 mg L-DOPA caused a 24-h delay in beginning of oviposition and reduction in fecundity throughout the experiment. An L-DOPA dose of 1 mg caused no such changes. An experimental increase in 20E titer led to reduced fecundity of the wild-type flies, though no delay in oviposition was observed. In mutant flies, an increase in DA and 20E levels accelerated beginning of oviposition and increased fecundity of young females, though the latter parameter was reduced in mature individuals. Thus, an increase in endogenous DA and 20E characteristic of young apterous56f females is assumed to be a compensatory response that leads to a higher JH titer and induction of vitellogenesis.     

The mechanism of the effect of apterous 56f mutation on the reproductive function of Drosophila melanogaster

The effects of L-dihydroxyphenylalanine (L-DOPA) and 20-hydroxyecdysone (20E) were studied with respect to the content of dopamine (DA), intensity of the juvenile hormone (JH) degradation, and fecundity of the wild-type flies (Canton S) and JH-deficient apterous ^56f mutants (in young females, carrying this mutation, the levels of DA and 20E production were strongly increased). Fly feeding with L-DOPA proved to increase the level of DA in a dose-dependent manner and reduce JH degradation in 2-day-old females of both strains. Feeding with 20E produced the same effect. Treating the wild-type flies with 2.5 mg L-DOPA caused a 24-h delay in beginning of oviposition and reduction in fecundity throughout the experiment. An L-DOPA dose of 1 mg caused no such changes. An experimental increase in 20E titer led to reduced fecundity of the wild-type flies, though no delay in oviposition was observed. In mutant flies, an increase in DA and 20E levels accelerated beginning of oviposition and increased fecundity of young females, though the latter parameter was reduced in mature individuals. Thus, an increase in endogenous DA and 20E characteristic of young apterous ^56f females is assumed to be a compensatory response that leads to a higher JH titer in order to induce vitellogenesis.     

Bovine besnoitiosis and its effect on the male reproductive system

Besnoitia besnoiti and several species of the genus have been reported in a variety of domestic and wild animals in many parts of the world (1, 2, 3, 4, 5). Cutaneous besnoitiosis in cattle has been described as a serious skin condition characterized by painful swellings, alopecia and thickening of the skin (6). It is a chronic, debilitating and occasionally fatal disease with both cutaneous and systemic manifestations (6, 7, 8). Besnoitia cysts and lesions have been observed in the testes, epididymes and blood vessels of bulls (9). The possibility of abortion in cows and sterility in bulls with besnoitiosis has been reported (6). Spontaneous clinical besnoitiosis in cattle with accompanying systemic manifestations has not been fully documented, and the effect of scrotal besnoitiosis on spermatogenesis in bulls has not been previously reported in Nigeria. Case report : Outbreaks of babesiosis, heartwater and suspected cutaneous besnoitiosis were observed in a government farm in the Kano State of Nigeria in March, 1979. The cattle population was over 1500, consisting of exotic (Bos taurus ) and indigenous (Bos indicus ) breeds and their crosses. Clinical Examination : All stages of clinical besnoitiosis were initially observed in 14 bulls and 1 cow in a period of 4 months. The farm was visited bi-weekly for 1 year, during which time 58 bulls and 2 cows showed the lesions. Most of the animals affected with this disease were 3-way crosses of Australian Draughtmaster x Rahaji x Niger Azwak (DM x Rh x AZ). Table 1 summarises the distribution of clinicial cases of besnoitiosis.     

The effect of a commercial UV disinfection system on the bacterial load of shell eggs

AIMS: To study the effect of UV irradiation on the bacterial load of shell eggs and of a roller conveyor belt. METHODS AND RESULTS: The natural bacterial load on the eggshell of clean eggs was significantly reduced by a standard UV treatment of 4.7 s; from 4.47 to 3.57 log CFU per eggshell. For very dirty eggs no significant reduction was observed. Eggs inoculated with Escherichia coli and Staphylococcus aureus (4.74 and 4.64 log CFU per eggshell respectively) passed the conveyor belt and were exposed to UV for 4.7 and 18.8 s. The reduction of both inoculated bacteria on the eggshell was comparable and significant for both exposure times (3 and 4 log CFU per eggshell). Escherichia coli was reduced but still detectable on the conveyor rollers. The internal bacterial contamination of eggs filled up with diluent containing E. coli or S. aureus was not influenced by UV irradiation. Conclusions: There is a significant lethal effect of UV irradiation on the bacterial contamination of clean eggshells and recent shell contamination, contamination of rollers can be controlled and the internal contamination of eggs is not reduced. SIGNIFICANCE AND IMPACT OF THE STUDY: The penetration of UV into organic material appears to be poor and UV disinfection can be used as an alternative for egg washing.     

The reproductive system of Gastrotrichs

Summary A structural, ultrastructural and functional analysis is made of genital organs ofMacrodasys, a member of the hermaphroditic marine Gastrotricha. The gonads are paired, hermaphroditic and polarized into male and female regions. Male and female gametes are produced simultaneously. Fertilization is internal. Accessory organs consist of, from anterior to posterior, simple male pores, a seminal receptacle and spermatheca, and, a complex caudal organ. Copulation results in reciprocal cross insemination. Sperm transfer, however, is indirect. Autosperms are transferred externally from the male pores to the caudal organ while the animals are in copula. The caudal organ then functions as a penis conducting the autosperms into the partner's seminal receptacle. This unique mode of sperm transfer is discussed with reference to the lower Bilateria and the Metazoa.Abbreviations ans anus - ant antrum, antrum feminimum, uptake portion of caudal organ - ccl cap cells - cim circular muscles - eev egg envelope - egl epidermal glands - epd epidermal cells - gmo glandulomuscular portion of caudal organ - int intestine, gut - lgm longitudinal muscles - mpr male pores - npl neuropile - nrv nerve cells - ooc oocytes, eggs - phg pharyngeal gland cells - phx pharynx - ppr pharyngeal pores - rsp residual sperm - sdp secretory droplet - sgb Stempelgruben, piston-pits, probable chemosensory organ - spd spermatids - spm sperm - spt spermatheca - srp seminal receptacle, bursa - tub copulatory tube of glandulomuscular organ - vdf vasa deferentia This project was supported by a Postdoctoral Fellowship from the Smithsonian Institution, and National Science Foundation grants GB-42211, OCE 75-23781 AO1 and OCE 75-20227 AO2 to The University of No. Carolina and the Bermuda Biological Station     

Age- and sex-distribution of the mutation load

We investigate the age and sex distribution of genetic fitness under mutation–selection balance by means of simple one-locus two-allele models. We find that the extent of age and sex variation in the mutation load is very dependent on the average effect of new mutations. If the average heterozygote selective effect of new mutations is large, then age and sex differences may constitute a significant fraction of the total load, and be significant as compared to standing genetic variation. Whether the mutation load will increase or decrease with age depends on the age- and sex-specific effects of the new mutations, and on the rate of accumulation of mutations in the germ line as individuals age. We argue that the load will most likely increase with age in animals with continuous germ-cell division throughout life, and that this will occur even when mutations have unconditionally deleterious effects. We show that a male-biased mutation rate is likely to result in both a male-biased mutation load and a load that increases with male age. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pleiotropic effect of the Black crystal mutation on reproductive indicators in the American mink (Mustela vison)]

The parameters of reproduction were studied in American minks that were homo- and heterozygous for the Black crystal mutation (Cr). The given mutation that changes the hair pigmentation was obtained de novo duration selection of American minks for tame behavior. Apart from changed color, the following reproduction disorders were detected in the Black crystal mutants, as compared to standard animals: (1) delayed entry into the reproductive season in females; (2) greater percentage in both homo- and heterozygous animals of females bearing no offspring; (3) greater early postnatal lethality indices. The most marked suppressing effect on the development of offspring was detected in homozygous females (Cr/Cr), whose progeny perished within a few days after birth. An analysis of reproduction in mutants and standard animals is presented. An attempt was made to explain the conceivable mechanisms that form the basis of disorders detected.     

The effect of differential survivorship on the stability of reproductive queueing

Queues, in which individuals inherit resources in a predictable, temporally stable order, are widespread in animal social groups. We develop an analytic model to explore the effect of differential survivorship on the stability of a reproductive queue. We show that unless fighting for dominance is potentially fatal, future direct benefits are not alone sufficient to stabilize a queue of non-relatives under constant (age-independent) mortality rates, regardless of whether a dominant becomes an isolate or remains a dominant on the death of the first subordinate. In the absence of fatal fighting, stabilization of such a queue by future direct benefits alone requires either the dominant or the subordinate to have age-dependent mortality rates. Even when the queue is stabilized by present direct reproduction, however, the shape of the lifespan distribution can make a significant difference to the size of the required incentive. In contrast to non-relatives, queues of relatives can be stable without age-dependent mortality, so long as relatedness exceeds a critical value; however, age-dependent mortality can lower this critical value.     

Lack of effect of butylparaben and methylparaben on the reproductive system in male rats

BACKGROUND: Parabens are widely used preservatives in cosmetics and pharmaceutical products, and approved as food additives. Parabens have been considered safe for these uses for many years. Recently, adverse effects on male reproductive parameters in rats have been reported when parabens were given orally for 8 weeks starting at three weeks of age. Our studies used two representative parabens, methyl‐ and butylparaben, to try to replicate these studies and thereby evaluate potential reproductive effects in male Wistar rats. METHODS: Diets containing 0, 100, 1000 or 10,000 ppm of either butyl‐ or methylparaben were fed to male rats for eight weeks. Rats were 22 days of age at the start of exposure. Parameters evaluated included organ weights, histopathology of reproductive tissues, sperm production, motility, morphology and reproductive hormone levels (butylparaben only). RESULTS: None of the parameters evaluated for either paraben showed compound‐ or dosage‐dependent adverse effects. Metabolism experiments of butylparaben indicate that it is rapidly metabolized by non‐specific esterases to p‐hydroxybenzoic acid and butanol, neither of which is estrogenic. CONCLUSIONS: Exposure to methyl‐ or butylparaben in the diet for eight weeks did not affect any male reproductive organs or parameters at exposures as high as 10,000 ppm, corresponding to a mean daily dose of 1,141.1±58.9 or 1,087.6±67.8 mg/kg/day for methyl‐ and butylparaben, respectively. The rapid metabolism of parabens by esterases probably explains why these weakly estrogenic substances elicit no in vivo effects when administered by relevant exposure routes (i.e., topical and oral). Birth Defects Research (Part B) 2008. 2008 Wiley‐Liss, Inc.     

The effect of egg load on superparasitism by the snowberry fly

In studies conducted with fruits of the host plant, Symphoricarpus albus (L.), we examine the influence of egg load on the oviposition behaviour of Rhagoletis zephyria Snow (Diptera:Tephritidae). By altering the availability of exogenous protein, three classes of females with progressively increasing egg loads were produced, while keeping confounding factors such as age, experience, and mating status constant. Flies from all three classes were randomly presented with either a pheromone marked fruit, or with an unmarked fruit. Results indicate that increased egg load led to a greater propensity to accept, or superparasitize, the pheromone marked fruit. Upon dissection it was revealed that females which superparasitized had a mean egg load of 19.5 eggs (n=22), while females which rejected marked fruit had a mean egg load of 13.5 eggs (n=26). These results are consistent with the theory of adaptive superparasitism.