Sterility(redirected from hybrids sterility)
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inability to conceive or carry a child to delivery. The term is usually limited to situations where the couple has had intercourse regularly for one year without using birth control.
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the inability of a mature organism to produce offspring.
In humans. It is believed that, on the average, 10 percent of all marriages are sterile. A marriage is considered sterile when pregnancy does not occur after three years of conjugal living without the use of contraceptives. Sterility may be the result of pathologic processes in males (about 30 percent), or in females (about 70 percent).
A man may be incapable of fertilization even when he retains the ability to perform the sex act. Causes of male sterility may be defects in the development of the sex organ (hypospadias, epispadias), aspermatism, azoospermia, tumors of the testes, and chronic poisoning; abuse of alcohol and nicotine have an extremely unfavorable effect on the male sexual apparatus.
In women, sterility is distinguished as primary (when a woman has never had a single pregnancy) and secondary (appearing after previous deliveries or abortions). Sterility may be absolute, when, for various reasons, pregnancy is altogether impossible (absence of a uterus or its significant underdevelopment, absence of ovaries, defects in development of sex organs, and so on) or relative, when, for certain reasons, pregnancy is impossible but may occur after removal of these reasons.
The causes of female sterility are varied. The most frequent form is tubular sterility, caused by closure of the passage in the oviducts, which obstructs the meeting in them of the male sex cell (spermatazoon) and the female cell (ovum), thus obstructing fertilization. Tubular sterility may occur as a result of gonorrhea, septic infection (after abortion), tuberculosis of the sex organs, and so forth.
An indispensable condition for conception is the ripening and discharge of the egg cell from the ovary (ovulation). This process may be disrupted during pathologic changes in the woman’s body: various changes in the central nervous system (hypothalamus) and in the endocrine glands (pituitary body, adrenals, and thyroid). As a result, menstruation may cease or be delayed (amenorrhea), or various disturbances of menstruation may occur. Sometimes sterility is a function of disease of the uterus and the cervix.
In female sterility that occurs as a result of inflammatory processes, physiotherapy and health-resort treatment is called for; in endocrine disturbances, hormone therapy. Surgical methods for removal of tubular sterility are being developed. Male sterility is treated by removal of the causes, general restorative treatment, and abstention from nicotine and alcohol.
V. A. POKROVSKII
In animals. Sterility in animals may be innate or acquired. Innate sterility in females is comparatively rare and is caused by underdevelopment of sex organs (infantilism) or various deviations in their development. Acquired sterility is observed considerably more frequently in animal breeding. It may be temporary or permanent.
The most common cause of sterility is insufficient and incomplete feeding (alimentary sterility), leading to disruption of the activity of the endocrine glands, which regulate sexual processes. The other principal cause of sterility is disturbance in the organization and performance of natural, and especially of artificial, insemination of animals.
Sterility as a result of disease of the sex organs in the female forms no more than 20 percent of cases on farms and is most often observed when the animals are affected with trichomoniasis, vibriosis, brucellosis, and other infectious and parasitic diseases.
Sterility inflicts considerable economic losses on agriculture. For this reason, the struggle against it is one of the main problems in animal breeding and veterinary medicine. The struggle against sterility consists of general veterinary-zootechnical measures, aimed at decreasing morbidity in animals, and the observance of zoohygienic rules of feeding and maintenance.
Conscientious observance of the rules of artificial and natural insemination is of great value in avoiding sterility. The quality of the sperm in male sires is systematically checked.
REFERENCESIvanov, A. A. “Besplodie (etiologiia, diagnostika, terapiia i pro-filaktika).” In Mnogotomnoe rukovodstvo po akusherstvu i ginekologii, vol. 4, book 2. Moscow, 1963.
Maizel’, E. P. Klinika i terapiia besplodiia zhenshchiny. Leningrad, 1965.
Davydov, S. N. Prichiny besplodnogo braka. Moscow, 1967.
Akusherstvo, ginekologiia i iskusstvennoe osemenenie sel’sko-khoziaistvennykh zhivotnykh. Edited by I. A. Bocharov. Leningrad, 1967.
“Besplodie.” In Veterinarnaia entsiklopediia, vol. 1. Moscow, 1968.
the inability of a sexually mature individual to reproduce sexually. In the broad sense, sterility is synonymous with infertility, although the term “sterility” is ordinarily used in botany and horticulture and the term “infertility” is usually applied to man and animals.
Sterility may develop as a result of the impairment of meiosis and the malformation of sexual cells (gametes), the suppression of the reproductive process, the death of fertilized eggs (zygotes), or the abnormal development of reproductive organs. It may be hereditary (genetic), or it may be caused by external factors, or be induced artificially by sterilization.
In plants with cytoplasmatic male sterility the action of certain cytoplasmatic genes produces underdeveloped pollen. These plants are used in special crossings to increase the productivity of the hybrids of such crops as corn. Cases of self-sterility in monoecious angiosperms have been recorded. This phenomenon can be used to prevent self-pollination, which leads to crop degeneration.
Hybrid sterility is characteristic of interspecific and distant hybrids. In these hybrids the zygote may die as a result of the incompatibility of the genomes or of the nucleus and cytoplasm of the parental gametes. Differences in the number and structure of parental chromosomes in viable hybrids cause meiotic disturbances and an altered number of chromosomes in sexual cells, resulting in the nonviability of the zygote. Methods have been devised for overcoming this type of sterility in order to obtain valuable plant and animal hybrids. Hybrid sterility has great evolutionary importance as a form of reproductive isolation.
In medicine and microbiology the term “sterility” refers to the absence of live microorganisms or their spores in a medium, organism, or any other substance.
I. I. TOLSTORUKOV