Sperm collection

Sperm chromatin is the substrate for nuclear assembly and can be readily prepared after sperm collection from the testes of well-fed freshly killed adult male Xenopus. Two animals contain enough sperm for more than 50 experiments. Sperm should be demembranated with lysolecithin exactly as described by Lohka and Masui (1984). After demembranation, sperm heads (chromatin) should be aliquoted at about 2.4 x IdV/itl in a buffer containing 30% (v/v) glycerol, 200 mM sucrose, 2.4 mM MgCl , and 20 mMNa-maleate, pH 6.8. Once aliquoted into small polypropylene tubes, tubes should be immersed in liquid nitrogen and stored at -70°C. Xenopus sperm chromatin prepared in this way can be stored for at least 5 years without apparent deterioration. (For additional details, see the chapter by Lohka, this volume.)... 

A. Sperm Collection and Storage 13. Membrane Permeabilization C. Isolation of Lipophilic Structures... 

Place ventral side up in a moist sponge bed designed to keep the fish wedged upright. The genital opening is located between the pelvic fins and should be wiped dry before sperm collection. 

Sperm collection and storage Depending on the species and context, sperm and spermatophores are collected either by stripping the male, or by shredding dissected testes. Urine (in fish) and water contamination should be avoided as both can induce motility and cell alteration. In the case of molluscs, sperm can also be obtained after induction (i.e. temperature and hormonal treatment) of sperm release in water. 

Gonadotrophins are also used in assisted reproduction procedures. Here the aim is to administer therapeutic doses of FSH that exceed individual follicular FSH threshold requirements, thus stimulating multiple follicular growth. This, in turn, facilitates harvest of multiple eggs, which are then available for in vitro fertilization. This technique is often employed when a woman has a blocked fallopian tube or some other impediment to normal fertilization of the egg by a sperm cell. After treatment, the resultant eggs are collected, incubated in vitro with her partner s sperm, incubated in culture media until the embryonic blastocyst is formed, and then implanted into the mother s uterus. 

The crypsis is further enhanced by there being a responsive element to ovulation. From about day 5 of the menstrual cycle, ovulation seems to be on hold while the woman meets and assesses males, including perhaps collecting sperm (Clark and Zarrow 1971 Jochle 1975 Baker 1996). This phase may last anything from 2-21 days. Depending on events during this phase ovulation may or may not occur. It seems particularly likely to occur a couple of days after the female has a brief opportunity to collect sperm from an attractive male. 

Previous studies of the number of sperm men ejaculate have had medical origins and have almost universally involved samples collected via masturbation. The multiple regression equations that are the basis of the single variable analyses presented in this paper are given in Table 1. The variables of greatest interest to ethologists are discussed in later sec-... 

For the time being, direct testing of the prediction that bisexuals should inseminate women with more sperm than heterosexuals is not possible. Although 39 masturbatory ejaculates have been collected from five bisexual males we have only two copulatory ejaculates (from two different males), and both of those are from anal intercourse with another male. We do not yet have vaginal inseminations from bisexual males. 

The current data set contains 20 ejaculates (from 11 different men with 13 different women) which were collected under circumstances other than within a long-term partnership. There were three main situations (see Material and Methods). All were outside of a partnership (and thus qualify as EPCs) and all were situations in which the man would have had every reason, consciously and/or subconsciously, to assume that the woman already contained sperm from another man. Sperm competition theory, therefore, would predict that the male should inseminate an above average number of sperm (Parker 1990). However, neither actual sperm numbers, numbers controlled for hours since last ejaculation, nor numbers controlled for all of the factors in Table 1, supported the prediction (Table 2). On the contrary, males seemed to inseminate fewer sperm into women who were not their established partner. 

Radioactivity ( H or "C-1,2-dibromoethane) was detected in spermatozoa collected approximately 1 week following the initial oral dose (Amir 1973). These results indicate that 1,2-dibromoethane exerts spermicidal action during the process of spermiogenesis and sperm maturation. This conclusion was supported by the evidence that the percentage of sperm abnormalities was highest when little 1,2-dibromoethane radioactivity could be detected in sperm. In addition, reduction in sperm concentration was more pronounced in adult bulls than in young bulls, and the period of recovery was longer in adult animals (Amir 1975). In another study, bulls were fed 2 mg/kg/day 1,2-dibromoethane for 12 months followed by 4 mg/kg 1,2-dibromoethane every other day until they reached the age of 14-16 months. The semen samples examined revealed low sperm density, structural abnormalities, and low mobility (Amir and Volcani 1965). Sperm production returned to normal as early as 10 days postexposure (Amir and Lavon 1976 Amir et al. 1977). 

Chemists have adopted several models for depicting protein structure. These include depiction of all the heavy atoms of the protein (the hydrogen atoms are deleted to keep the model simple enough to be understandable), emphasis on the backbone formed by the a carbon atoms, and ribbon diagrams that illustrate secondary structnral elements. These three models for sperm whale myoglobin are collected in figure 11.3. 

The hmnan body s entire system of a billion or more cells develops from a single cell—the egg fertilized by the sperm. As this cell divides to form all the different tissues and structures of the growing fetus, the daughter cells become specialized in the kinds of proteins they produce. Think of the entire set of genes as inherited instructions to form more than 100,000 proteins when and where they are needed. Going from the single-cell embryo to the enormous collection of specialized cells that make up our body is an... 

The following sperm motility parameters are evaluated from spermatozoa collected from the epididymis ... 

The number of sperm in an ejaculate is influenced by several variables, including the length of abstinence and the ability to obtain the entire ejaculate. Intra- and interindividual variability are often high, but less variability is observed in ejaculates collected at regular intervals from the same male (Williams et al., 1990). Because sperm contribute to epididymal weight in experimental animals, expression of results as a ratio of sperm counts to epididymal weight may actually mask a decline in sperm number, and absolute sperm counts can improve resolution. 

In one of the first studies of data collected about sperm quality over time, Carlsen and coworkers analyzed 61 sperm-count studies from several countries published between 1938 and 1991 and showed that there was a significant decrease in mean sperm count from X 106/ml in 1940 to 66 X 106/ml in 1990 (p <... 

Cohort Location Years of Data Collection Sperm Counts (106 /ml)... 

Reproductive hazards in the workplaces can be identified through epidemiologic research, outcomes such as spontaneous abortions and malformations require large sample sizes that cannot usually be collected from single workplaces. Several workplaces need to be pooled and a coordinated effort is required in the execution of the studies. However, a systematic follow-up of the rates of spontaneous abortions and malformations by industrial physicians may offer clues to reproductive hazards. On other outcomes, such as birthweight of children and sperm abnormalities in exposed men, smaller sample sizes are required but many types of confounding factors may exist that impede the interpretation of the results. 

While comprehensive research and surveys were delayed, or lacking, no significant effort had been put toward the overview of the existing data of emissions, sources, distribution, exposure, and fate of POPs. Lee and Kim (1999) collected published data on concentrations of EDCs for almost all environmental media and human tissues and performed a meta-analysis to examine the relationship between the sperm quality of South Korean... 

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