The relationship between the proportion of sperm with chromosomal abnormalities (numerical, structural and total abnormalities ), the proportion of morphologically abnormal sperm (head, midpiece and tail defects ), and donor age was correlated using multiple regression analysis. Martin and Rademaker first evaluated the potential relationship between the frequency of chromosomally and morphologically abnormal sperm in thirty healthy fertile men of proven fertility, ranging in age from 22 to 55 years. This technique provides detailed information about each individual chromosome, permitting analysis of both numerical and structural abnormalities. Using karyotype analysis of the human sperm pronucleus after hamster egg penetration, the association between the frequency of morphologically and chromosomally abnormal sperm was examined in fertile men, translocation carriers and post-radiotherapy cancer patients. The advent of techniques such as human sperm karyotyping and fluorescence in situ hybridization (FISH) analysis has allowed these relationships to be explored. The potential relationship between sperm morphology and chromosomal constitution has stimulated investigators to study this relationship in fertile men and in men with elevated frequencies of abnormal forms. It has been suggested that an assay for sperm morphology might prove useful as an initial screen in evaluating men at risk for an increased frequency of sperm chromosomal abnormalities. The frequency of numerical chromosome abnormalities in sperm of fertile men is 1–2%, and the frequency of structural chromosome abnormalities in sperm varies from 7–14%. Structural abnormalities include chromosome breaks, gaps, translocations, inversions, insertions, deletions and acentric fragments. Aneuploidies involve an autosome, a sex chromosome or both polyploidies have a duplication of all chromosomes. Numerical abnormalities include aneuploidies and polyploidies, and arise from a missing or extra chromosome(s) due to meiotic non-disjunction. Intuitively, one might expect that a change in chromosome content is reflected by a change in the size of sperm – thus, people expect to see a relationship between sperm morphology and genetic abnormalities.Īberrations in the genetic information of spermatozoa include numerical and structural chromosome abnormalities. Head defects include large, small, tapered, pyriform, round, and amorphous heads, heads with a small acrosomal area (90°) tails, tails of irregular width, coiled tails, as well as any combination of these.Ī sperm is basically a package of streamlined genetic information. Ībnormal sperm morphology is classified as defects in the head, midpiece or tail of the sperm. The tail is slender, uncoiled and should present a regular outline: it is at least 45 μm in length. The midpiece is slender, less than one third of the width of the head, straight and regular in outline it is aligned with the longitudinal axis of the head and is approximately 7 to 8 μm long. The head length is between 3 and 5 μm, and its width ranges between 2 and 3 μm the width is between one half and two thirds of the length.
Normal spermatozoa exhibit an oval-shaped head with a regular outline and an acrosomal cap covering more than one-third of the head surface. Sperm topography is unique among the known cells and 3 major parts can be immediately distinguished: head, midpiece and tail. Thus, there may be an association between sperm morphology and aneuploidy in infertile men with specific abnormalities. However, FISH studies on some infertile men and mouse strains have suggested that certain types of morphologically abnormal spermatozoa, such as macrocephalic multitailed spermatozoa, are associated with a very significantly increased frequency of aneuploidy. Fluorescence in situ hybridization (FISH) analysis has not generally revealed a specific association between morphologically abnormal sperm and sperm chromosome abnormalities, but has indicated that teratozoospermia, like other forms of abnormal semen profiles (aesthenozoospermia, oligozoospermia) is associated with a modest increase in the frequency of sperm chromosome abnormalities. Using human sperm karyotype analysis, no relationship between sperm chromosome abnormalities and morphology was found in fertile men, translocation carriers or post-radiotherapy cancer patients.
With the advent of techniques for obtaining information on the chromosome complements of spermatozoa, this relationship has been studied in fertile men and in men with a high frequency of chromosomal abnormalities. This review explores the relationship between sperm chromosomal constitution and morphology.
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