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Human spermatozoa with large heads and multiple flagella: a quantitative ultrastructural study of 6 cases
Abstract:
Macrocephalic spermatozoa of six men were studied. In all cases, sperm concentration, proportion of live spermatozoa and sperm motility were very low. A range of ultrastructural abnormalities was found, essentially comprising a threefold increase in nuclear volume and acrosomal hyperdevelopment and malformation. There were on average 3.6 flagella for each sperm head found in the semen, some tails were separate from heads. The various defects appeared with great constancy in all of the six cases: this homogeneity indicated the existence of a defined semen profile whose most significant expression was sterility. In four of the cases large incidences of different flagellar abnormalities were also noted; whether these flagellar abnormalities are intrinsic to the above profile is not clear. Although the increase in nuclear volume suggests a disturbance in meiosis, its association with defective nuclear elongation would also indicate the existence of one or more anomalies of spermiogenesis. These results were discussed in relation to abnormalities already reported in other species either spontaneously in cases of mutations, or by experimental inhibition of microtubular structures.
Insights
Macrocephalic spermatozoa, characterized by large heads and multiple tails, were studied in six men. These sperm defects led to extremely low motility and concentration, resulting in male sterility.
Area of Science:
- Human reproductive biology
- Spermatozoa ultrastructure
- Male infertility genetics
Background:
- Macrocephalic spermatozoa are rare, with limited understanding of their ultrastructural defects and impact on male fertility.
- Previous studies have explored various sperm abnormalities, but a consistent profile for macrocephalic spermatozoa remains undefined.
Purpose of the Study:
- To investigate the ultrastructural characteristics of macrocephalic spermatozoa in infertile men.
- To identify a potential semen profile associated with macrocephalic spermatozoa and sterility.
- To explore the underlying causes of these defects, including potential disturbances in meiosis and spermiogenesis.
Main Methods:
- Semen analysis of six men with macrocephalic spermatozoa.
- Ultrastructural examination of sperm morphology, including nuclear volume, acrosome, and flagella.
- Assessment of sperm concentration, viability, and motility.
Main Results:
- All cases exhibited low sperm concentration, viability, and motility.
- Consistent ultrastructural abnormalities included a threefold increase in nuclear volume and acrosomal malformation.
- An average of 3.6 flagella per sperm head was observed, with some detached tails.
- Four cases showed significant flagellar abnormalities, though their direct link to the primary defect is unclear.
Conclusions:
- Macrocephalic spermatozoa present a distinct semen profile characterized by severe ultrastructural defects and male sterility.
- The observed abnormalities suggest potential disturbances in both meiosis and spermiogenesis.
- Further research is needed to elucidate the genetic and molecular mechanisms underlying these defects and their association with flagellar abnormalities.