Mitochondrial Helix Research Articles

Flagellum tapering and midpiece volume in songbird spermatozoa.

In contrast to numerous studies on spermatozoa length, relatively little work focuses on the width of spermatozoa, and particularly the width of the midpiece and flagellum. In flagellated spermatozoa, the flagellum provides forward thrust while energy may be provided via mitochondria in the midpiece and/or through glycolysis along the flagellum itself. Longer flagella may be able to provide greater thrust but may also require stronger structural features and more or larger mitochondria to supply sufficient energy. Here, we use scanning electron microscopy to investigate the ultrastructure of spermatozoa from 55 passerine species in 26 taxonomic families in the Passerides infraorder. Our data confirm the qualitative observation that the flagellum tapers along its length, and we show that longer flagella are wider at the neck. This pattern is similar to mammals, and likely reflects the need for longer cells to be stronger against shearing forces. We further estimate the volume of the mitochondrial helix and show that it correlates well with midpiece length, supporting the use of midpiece length as a proxy for mitochondrial volume, at least in between-species studies where midpiece length is highly variable. These results provide important context for understanding the evolutionary correlations among different sperm cell components and dimensions.

Correction to: A trade-off between thickness and length in the zebra finch sperm mid-piece.

You have accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Mendonca Tania, Birkhead Tim R., Cadby Ashley J., Forstmeier Wolfgang and Hemmings Nicola 2021Correction to: A trade-off between thickness and length in the zebra finch sperm mid-pieceProc. R. Soc. B.2882021169520211695http://doi.org/10.1098/rspb.2021.1695SectionYou have accessCorrectionCorrection to: A trade-off between thickness and length in the zebra finch sperm mid-piece Tania Mendonca Tania Mendonca http://orcid.org/0000-0002-6232-4970 Google Scholar Find this author on PubMed Search for more papers by this author , Tim R. Birkhead Tim R. Birkhead Google Scholar Find this author on PubMed Search for more papers by this author , Ashley J. Cadby Ashley J. Cadby Google Scholar Find this author on PubMed Search for more papers by this author , Wolfgang Forstmeier Wolfgang Forstmeier http://orcid.org/0000-0002-5984-8925 Google Scholar Find this author on PubMed Search for more papers by this author and Nicola Hemmings Nicola Hemmings http://orcid.org/0000-0003-2418-3625 Google Scholar Find this author on PubMed Search for more papers by this author Tania Mendonca Tania Mendonca http://orcid.org/0000-0002-6232-4970 Google Scholar Find this author on PubMed Search for more papers by this author , Tim R. Birkhead Tim R. Birkhead Google Scholar Find this author on PubMed Search for more papers by this author , Ashley J. Cadby Ashley J. Cadby Google Scholar Find this author on PubMed Search for more papers by this author , Wolfgang Forstmeier Wolfgang Forstmeier http://orcid.org/0000-0002-5984-8925 Google Scholar Find this author on PubMed Search for more papers by this author and Nicola Hemmings Nicola Hemmings http://orcid.org/0000-0003-2418-3625 Google Scholar Find this author on PubMed Search for more papers by this author Published:08 September 2021https://doi.org/10.1098/rspb.2021.1695See original article.A trade-off between thickness and length in the zebra finch sperm mid-pieceProc. R. Soc. B285, 20180865. (Published online 25 July 2018) (doi:10.1098/rspb.2018.0865)The original article contains a typographical mistake in the formula notation for the volume of the sperm mitochondrial helix. In the discussion (paragraph 6), we refer to the formula as ‘v = (1/3)π(r2)T’; however, the formula used in our calculations was ‘v = π(r2)T’, where π(r2) is the mitochondrial cross-section area and T is the straightened helix length. The latter formula can be expanded to ‘v = (1/3)π(r12 + r1r2 + r22)T’ to describe a truncated cone, where r1 and r2 are the radii at either end of the truncated cone. We refer to this formula in our electronic supplementary material where we show that the trade-off between thickness and length persists irrespective of the degree of taper in the mitochondrial helix. This error does not impact any of the data, analyses, results or conclusions of our paper. Previous Article FiguresRelatedReferencesDetailsRelated articlesA trade-off between thickness and length in the zebra finch sperm mid-pieceJul 25, 2018, 12:00:00 AMProceedings of the Royal Society B: Biological Sciences This Issue08 September 2021Volume 288Issue 1958 Article InformationDOI:https://doi.org/10.1098/rspb.2021.1695PubMed:34493085Published by:Royal SocietyPrint ISSN:0962-8452Online ISSN:1471-2954History: Published online08/09/2021Published in print08/09/2021 License:© 2021 The Author(s)Published by the Royal Society. All rights reserved. Citations and impact Subjectsbehaviourevolutioncellular biology Large datasets are available through Proceedings B's partnership with Dryad

Mitochondria: their role in spermatozoa and in male infertility.

The best-known role of spermatozoa is to fertilize the oocyte and to transmit the paternal genome to offspring. These highly specialized cells have a unique structure consisting of all the elements absolutely necessary to each stage of fertilization and to embryonic development. Mature spermatozoa are made up of a head with the nucleus, a neck, and a flagellum that allows motility and that contains a midpiece with a mitochondrial helix. Mitochondria are central to cellular energy production but they also have various other functions. Although mitochondria are recognized as essential to spermatozoa, their exact pathophysiological role and their functioning are complex. Available literature relative to mitochondria in spermatozoa is dense and contradictory in some cases. Furthermore, mitochondria are only indirectly involved in cytoplasmic heredity as their DNA, the paternal mitochondrial DNA, is not transmitted to descendants. This review aims to summarize available literature on mitochondria in spermatozoa, and, in particular, that with respect to humans, with the perspective of better understanding the anomalies that could be implicated in male infertility. PubMed was used to search the MEDLINE database for peer-reviewed original articles and reviews pertaining to human spermatozoa and mitochondria. Searches were performed using keywords belonging to three groups: 'mitochondria' or 'mitochondrial DNA', 'spermatozoa' or 'sperm' and 'reactive oxygen species' or 'calcium' or 'apoptosis' or signaling pathways'. These keywords were combined with other relevant search phrases. References from these articles were used to obtain additional articles. Mitochondria are central to the metabolism of spermatozoa and they are implicated in energy production, redox equilibrium and calcium regulation, as well as apoptotic pathways, all of which are necessary for flagellar motility, capacitation, acrosome reaction and gametic fusion. In numerous cases, alterations in one of the aforementioned functions could be linked to a decline in sperm quality and/or infertility. The link between the mitochondrial genome and the quality of spermatozoa appears to be more complex. Although the quantity of mtDNA, and the existence of large-scale deletions therein, are inversely correlated to sperm quality, the effects of mutations seem to be heterogeneous and particularly related to their pathogenicity. The importance of the role of mitochondria in reproduction, and particularly in gamete quality, has recently emerged following numerous publications. Better understanding of male infertility is of great interest in the current context where a significant decline in sperm quality has been observed.

A trade-off between thickness and length in the zebra finch sperm mid-piece.

The sperm mid-piece has traditionally been considered to be the engine that powers sperm. Larger mid-pieces have therefore been assumed to provide greater energetic capacity. However, in the zebra finch Taeniopygia guttata, a recent study showed a surprising negative relationship between mid-piece length and sperm energy content. Using a multi-dimensional approach to study mid-piece structure, we tested whether this unexpected relationship can be explained by a trade-off between mid-piece length and mid-piece thickness and/or cristae density inside the mitochondrial helix. We used selective plane illumination microscopy to study mid-piece structure from three-dimensional images of zebra finch sperm and used high-resolution transmission electron microscopy to quantify mitochondrial density. Contrary to the assumption that longer mid-pieces are larger and therefore produce or contain a greater amount of energy, our results indicate that the amount of mitochondrial material is consistent across mid-pieces of varying lengths, and longer mid-pieces are simply proportionately ‘thinner’.

Ultrastructure of sperm ‘tail stump’ defect in wild boar

Sperm 'tail stump' defect was found in ejaculates of a wild boar maintained in captivity. It was in good physical condition, the testes and genital tract were found to be of normal size and consistency. There was no evidence of macroscopic abnormalities at the clinical analysis and at necropsy. The volume and concentration of the semen samples obtained by electroejaculation were lower than normal. The slides examined contained a high level of abnormal spermatozoa (52.7%). The most frequent morphological finding was a droplet-like form attached to the base of the head or a very short stump. The non-stumped spermatozoa had no normal tail but a shortened one. Analysing the histological structure with light microscopy, no ring of spermatozoa was observed lining the lumen of the seminiferous tubules and the characteristically cellular structure was not conserved. The ultrastructural examination evidenced a disorganisation of the normal tubular structure of the flagellum, with lost of regular pattern of the axial bundle of fibrils and the mitochondrial helix. The origin of this abnormality is unknown.

Dietary selenium deficiency as well as excess supplementation induces multiple defects in mouse epididymal spermatozoa: understanding the role of selenium in male fertility

Selenium (Se) is essential for male fertility. The present study was carried out to observe the defects associated with Se deficiency as well as excess Se supplementation by analyzing the sperm ultrastructure and chromatin organization. Different Se status mice were generated viz. Se deficient (group I), Se adequate (group II) and Se excess (group III) by feeding the respective diets for a period of 4 (group Ia, IIa and IIIa) and 8 weeks (group Ib, IIb and IIIb). Reduction in sperm concentration, motility and percentage fertility was observed in Se deficient and Se excess groups. Electron microscopy revealed mitochondrial swelling and gaps between adjacent mitochondria in mice fed Se-deficient diet for 4 weeks. At 8 weeks, several abnormalities such as loose contact of the mitochondrial helix with the plasma membrane, loss of mitochondria, retention of cytoplasmic droplet, fracturing of outer dense fibres and presence of both the midpiece and the principal piece cross-sections in a common plasma membrane were observed. In Se excess group, the predominant defect was the frequent presence of equidistant, cross-sectioned midpieces of the tail embedded in a common cytoplasm. These defects are indicative of loss of sperm motility. Spermatozoa from Se-deficient mice had incompletely condensed chromatin and indicated an increase in occurrence of DNA strand breaks. The animals fed Se excess diet also indicated increase in DNA breaks but this was significantly less than the deficient diet fed groups. Our study reveals the defects associated with Se deficiency that result in loss of reproductive ability and also reflects its possible harmful effects on spermatozoa after prolonged consumption at supranutritional level.

Multinuclear–Multiflagellar Sperm Defect in a Bull – a New Sterilizing Sperm Defect

The development and use of modern techniques, such as intracytoplasmic sperm injection (ICSI), gene knockout and sperm fluorescence in situ hybridization with chromosome- specific probes, have significantly increased our knowledge about sperm defects. We describe a new oligoasthenoteratozoospermic defect in a bull. Because of its morphological characteristics the defect was named the multinuclear-multiflagellar sperm defect. All spermatozoa in the ejaculate were abnormal. Many of the spermatozoa had multiple nuclei and multiple sperm tails. All spermatozoa lacked an acrosome, and only seldom did spermatozoa have a mitochondrial helix in the midpiece area. Meiosis and spermiogenesis were severely affected in this otherwise phenotypically normal bull. The sperm defects resembled the phenotype of a targeted gene knockout Hrb(-/-) (HIV-1 Rev-binding/interacting protein) mutant mouse strain, which is expressed as sterility in males, while females remain fertile. Since the father of this bull has been extensively used in at least three countries the defective gene has possibly become widespread in the red and white breeds (Ayrshire, Swedish Red and White, Norwegian Red) in the Nordic countries. However, it is not proved that the father of this bull is a carrier of this defect.

Ultrastructure of the spermatozoon of Myrmecocichla formicivora (Vieillot, 1881) and Philetairus socius (Latham, 1790) (Aves; Passeriformes), with a new interpretation of the passeridan acrosome

AbstractPasserine spermatozoa exhibit apomorphies that distinguish them from non‐passerine neognaths and palaeognaths. The acrosome is longer than the nucleus (excepting the suboscines, most Corvida, and a few Passerida). A perforatorium and endonuclear canals are absent. The proximal centriole is absent (except in the suboscines). The distal centriole is secondarily short, contrasting with its elongate condition in palaeognaths and Galloanserae. In the Passerida a single mitochondrial strand winds extensively along the axoneme (restricted to the anterior axoneme in suboscines and Corvida). A fibrous, or amorphous, periaxonemal sheath, seen in palaeognaths and many non‐passerines, respectively, is absent. The acrosome in Myrmecocichla formicivora and Philetairus socius is bipartite: an acrosome core is surmounted by an acrosome crest; the core is ensheathed by a layer which is a posterior extension of the crest. The acrosome helix is a lateral extension of the crest and the crest layer with (Myrmecocichla) or without (Philetairus) protrusion of material of the acrosome core into it. In M. formicivora, as in other muscicapoids, a fibrous helix is intertwined with at least the more proximal region of the mitochondrial helix. The fibrous helix is absent at maturity in Philetairus and other described passeroid spermatozoa with the possible exception of Passer italiae. In Philetairus a granular helix precedes the mitochondrial helix.

Unusual Sperm Morphology in the Eurasian Bullfinch (Pyrrhula Pyrrhula)

Abstract The sperm of the Eurasian Bullfinch (Pyrrhula pyrrhula) differs markedly in gross morphology from that of all other passerines examined to date. In other passerines, the sperm head is pointed and helical, and the midpiece comprises a mitochondrial helix extending along the flagellum; whereas in the Eurasian Bullfinch, the sperm acrosome is rounded, not helical, and the midpiece is extremely short. In a pairwise study, using principal component analysis (PCA), we combined quantitative and qualitative sperm morphology traits and conducted a phylogenetic correlation to compare the sperm morphology of Eurasian Bullfinch and Beavan's Bullfinch (P. erythaca) with nine other pairs of congeneric passerines. The analysis revealed that Eurasian Bullfinch was a dramatic outlier in sperm morphology and that Eurasian and Beavan's bullfinches are more different than any other pair of species. Excluding Eurasian Bullfinch from the analysis showed that most variation in sperm morphology in the other species was attributable to phylogeny. The Eurasian Bullfinch also has extremely small testes for its body size, which indicates that sperm competition is infrequent in this species; we discuss the possibility that relaxed selection, via lack of sperm competition, may have contributed to the species' unusual sperm morphology. Morfología Espermática Inusual en Pyrrhula pyrrhula

Structural and ultrastructural characterization of zebu (Bos indicus) spermatozoa

The ultrastructure of normal, ejaculated spermatozoa of Bos indicus was studied by means of electron microscopy, being evaluated in two principal parts, the head and the tail. The head is flat, oval or paddle-shaped with a square base, which provides a concave recess for the insertion of the tail. The acrosome tightly covers the anterior two thirds of the nucleus. A distinct unilateral acrosomal bulge was observed along the apical edge of the head. The equatorial region demarcates the acrosome from the post-equatorial region that covers the caudal one third of the nucleus. The classical 9+9+2 fiber pattern which composes the axoneme was observed along three segments of the tail, namely middle, principal and terminal pieces. The axoneme is anteriorly bound by the mitochondrial helix (middle piece) and posteriorly by the fibrous helix (principal piece), except at the terminal piece. The border between the middle piece and principal piece was well defined due to the termination of the thick mitochondrial helix and the presence of the annulus. Some of the spermatozoa presented cytoplasmatic droplets, which appeared as stalk-like appendages.

UNUSUAL SPERM MORPHOLOGY IN THE EURASIAN BULLFINCH (PYRRHULA PYRRHULA)

Abstract The sperm of the Eurasian Bullfinch (Pyrrhula pyrrhula) differs markedly in gross morphology from that of all other passerines examined to date. In other passerines, the sperm head is pointed and helical, and the midpiece comprises a mitochondrial helix extending along the flagellum; whereas in the Eurasian Bullfinch, the sperm acrosome is rounded, not helical, and the midpiece is extremely short. In a pairwise study, using principal component analysis (PCA), we combined quantitative and qualitative sperm morphology traits and conducted a phylogenetic correlation to compare the sperm morphology of Eurasian Bullfinch and Beavan's Bullfinch (P. erythaca) with nine other pairs of congeneric passerines. The analysis revealed that Eurasian Bullfinch was a dramatic outlier in sperm morphology and that Eurasian and Beavan's bullfinches are more different than any other pair of species. Excluding Eurasian Bullfinch from the analysis showed that most variation in sperm morphology in the other species was ...

Sperm Mobility: Phenotype in Roosters (Gallus domesticus) Determined by Mitochondrial Function1

Previously, inheritance of sperm mobility entailed a maternal additive genetic effect, and sperm ATP content was correlated (r = 0.80) with phenotype. The present study was conducted to determine if mitochondrial function was critical to phenotypic expression. Whereas phenotype was independent of mitochondrial helix length, phenotype was correlated with sperm oxygen consumption (r = 0.83) using random-bred roosters. Aberrant mitochondria characterized immobile sperm, as evidenced by transmission-electron microscopy. Such mitochondria were swollen and contained disorganized cristae. Additional experiments were performed with roosters from lines selected for low or high sperm mobility. A threefold difference in sperm oxygen consumption was observed between lines. Single nucleotide polymorphisms were observed in mitochondrial DNA by sequencing replicate mitochondrial genomes from each line. An A-to-G substitution in the gene encoding tRNA(Arg) was inherited consistently, as evidenced by restriction fragment length polymorphism analysis using two male and two female progeny per family group and 14 family groups per line. Motile concentration in semen from low-line males was half that observed in semen from high-line males, as evidenced by computer-assisted sperm motion analysis. Likewise, 47% of sperm from low-line males contained aberrant mitochondria, compared to 4% for high-line males. In summary, sperm mobility phenotype was dependent on mitochondrial function, which in turn was altered by genetic selection. Fowl deferent duct fluid contains a high concentration of glutamate. We propose that variation in sperm mobility phenotype stems from the extent to which glutamate induces excessive mitochondrial Ca2+ uptake before ejaculation.

An ultrastructural and immunocytochemical study of a rare genetic sperm tail defect that causes infertility in humans

Objective To characterize and describe the ontogenesis of a rare flagellar defect affecting the whole sperm population of a sterile man. Design Case report. Setting Regional referral center for male infertility in Siena, Italy. Patient(s) A 28-year-old man with severe asthenozoospermia. Intervention(s) Physical and hormonal assays, semen analysis, and testicular biopsy. Main outcome measure(s) Semen samples and testicular biopsies were analyzed by light and transmission electron microscopy; immunocytochemical study with anti-β-tubulin and anti-AKAP 82 antibodies was performed to detect the presence and distribution of proteins. Result(s) Ultrastructural analysis of ejaculated spermatozoa and testicular biopsy revealed absence of the fibrous sheath in the principal-piece region of the tail. Fibrous sheath-like structures were observed in cytoplasmic residues and residual bodies released by spermatids in the seminiferous epithelium. Other anomalies observed were supplementary axonemes and mitochondrial helix elongation. These features were confirmed by immunocytochemical staining. Conclusion(s) This rare sperm tail defect, characterized by absence of the fibrous sheath, presence of supplementary axonemes, and an abnormally elongated midpiece, originates in the seminiferous tubules during spermiogenesis, as detected in testicular biopsy sections. These defects occur in the whole sperm population, and therefore a genetic origin could be suggested.

Ultrastructure of the mature spermatozoon of the musky rat-kangaroo, Hypsiprymnodon moschatus (Potoroidae: Marsupialia)

It is currently accepted that Hypsiprymnodon moschatus is a basal macropod, retaining several primitive features from the ancestral phalangeroid that gave rise both to modern possums and macropods. Sperm ultrastructure is frequently found to provide informative characters for phylogenetic analysis as these features are not strongly selected for and are thus unlikely to be confounded by effects such as convergence. Caudal epididymal biopsies were taken from two male H. moschatus and prepared for transmission and scanning electron microscopy in order to study mature spermatozoan ultrastructure. Within the diprotodont group, several features were found to be unique to H. moschatus. These were an unusual acrosome covering nearly 100% of the dorsal nuclear surface, a midpiece fibre network which is loose, indistinct and extends to the anterior-most aspect of the midpiece, a nucleus that is very streamlined, while the principal piece is comparatively short, and a mitochondrial helix and annulus which are similar to those of dasyurids. Also reported is the presence of a fibrous network in the connecting piece, not previously reported for any marsupial.

Familial sperm polyploidy induced by genetic spermatogenesis failure: Case report

We report a case of oligoasthenoteratozoospermia in a 40 year-old patient with a familial history that revealed multiple cases of infertility and perinatal deaths. The patient's semen sample contained 2x10(6) spermatozoa/ml, with an overall progressively motile population of <5%. Cytological analysis revealed a teratozoospermia with 100% of abnormal macrocephalic sperm heads and an irregular acrosomal cap in 38% of cells. Moreover, 72% of spermatozoa carried multiple flagella (2-5). The midpiece was elongated and/or enlarged with cytoplasmic droplets in 15% of cells. The multiple anomalies index (MAI) was 3.3 (normal value = 1.6), reflecting the high incidence of spermatozoal morphological abnormalities in this patient. Ultrastructural analysis revealed the presence of 2 or 3 vacuolated nuclei per sperm head. The acrosome was abnormal and the chromatin, partially packaged, appeared rough. In some cases, a large amount of cytoplasm containing vacuoles was observed around the nucleus and the acrosome. The mitochondrial helix was disorganized. Chromosome analysis performed on blood cells revealed a normal karyotype. Three-colour fluorescence in-situ hybridization (FISH) analysis of 1148 spermatozoa showed 21.6% to be diploid, 62.4% triploid, 13.3% quadriploid and 2.7% hyperploid (<4n). In conclusion, we suggest that this case could result from a genetically induced spermiation failure, the origin of which is discussed.

Fine structure of the germinating cells during the spermiogenesis ofArion rufus (Mollusca, Pulmonate Gastropoda)

Changes in spermatozoan ultrastructure have been studied during spermiogenesis of the slug Arion rufus (Gastropoda, Pulmonata, Stylommatophora). The ovotestis was investigated during the male stage, definite by the presence of spermatozoa. Some peculiar characteristics are shown by early spermatids: Around the nucleus, the nuclear envelope presents two thick layers located on opposite sides, the apical and basal plates, that will determine the antero-posterior axis of the spermatid. The chromatin, first dispersed throughout the nucleoplasm gives later on thick filaments which become attached over the inner surface of these plates. The chromatin filaments are then arranged parallel to the anteroposterior axis as the nucleus elongates. The position of the plates determines the antero-posterior axis of the spermatid. In the mature spermatozoa, the chromatin is more condensed and the nucleus presents an helical organization. The acrosome and flagellum are respectively attached externally to the center of the apical and basal plates. The acrosome consists of a membrane-bound vesicle and forms a column of homogeneous material. In the middle piece, the mitochondria have been transformed into a mitochondrial derivate by the way of a complicated metamorphosis. The axoneme is surrounded by three mitochondrial helices but only one of them contains glycogene granules.

Fine structure of the germinating cells during the spermiogenesis of Arion rufus (Mollusca, Pulmonate Gastropoda).

Changes in spermatozoan ultrastructure have been studied during spermiogenesis of the slug Arion rufus (Gastropoda, Pulmonata, Stylommatophora). The ovotestis was investigated during the male stage, definite by the presence of spermatozoa. Some peculiar characteristics are shown by early spermatids: Around the nucleus, the nuclear envelope presents two thick layers located on opposite sides, the apical and basal plates, that will determine the antero-posterior axis of the spermatid. The chromatin, first dispersed throughout the nucleoplasm gives later on thick filaments which become attached over the inner surface of these plates. The chromatin filaments are then arranged parallel to the anteroposterior axis as the nucleus elongates. The position of the plates determines the antero-posterior axis of the spermatid. In the mature spermatozoa, the chromatin is more condensed and the nucleus presents an helical organization. The acrosome and flagellum are respectively attached externally to the center of the apical and basal plates. The acrosome consists of a membrane-bound vesicle and forms a column of homogeneous material. In the middle piece, the mitochondria have been transformed into a mitochondrial derivate by the way of a complicated metamorphosis. The axoneme is surrounded by three mitochondrial helices but only one of them contains glycogene granules.

Identification of a cytoskeletal network adherent to the mitochondria of mammalian spermatozoa

In this study we identify a reticular network of electron-dense material in the spermatozoan midpiece which is immediately peripheral to the outer dense fiber-axoneme complex and is adherent to the overlying mitochondria. This network, termed the submitochondrial lattice, extends throughout the midpiece and terminates at the midpiece-principal piece junction where it fuses to the annulus. In cross sections this material appears as an approximately 10–14-nm-thick, discontinuous layer adherent to the outer mitochondrial membrane; longitudinal sections reveal that the network is arranged as longitudinally oriented electron-dense bands which branch and anastomose laterally to form a cylinder-shaped reticulum. The potential role of this complex in organizing the mitochondrial helix and in maintaining mitochondrial distribution is discussed.

The action of gossypol on rat germinal cells

AbstractAdult male Sprague‐Dawley rats were fed daily with 25 mg/kg of gossypol acetic acid for 55 days. The examination of the testis revealed the constant integrity of the blood‐testis barrier. The earliest damage to the germinal cells appeared on the 14th day of treatment in spermatids in stage 18‐19, and consisted of mitochondrial swelling and cristae disorganization, which was manifested in an altered assembly of the mitochondrial helix and possible axonemal alterations. It appeared that the target cell was a 30–37‐day‐old spermatid that showed the first alterations 6–14 days later, when it reached stage 18. The mitochondrial and eventual axonemal damage was conserved after the migration into the epididymis, affecting 6% of the total sperm population on the 14th day of treatment and reaching the maximum (100%) on the 25th day of treatment. On the 5th day of treatment, epididymal spermatozoa revealed, moreover, the presence of other tail alterations: lack of half of the axonemal components (also in sperm with unaffected mitochondria), loss of midpiece plasma membrane, and breaking of the outer accessory fibers. The conclusion is that a direct action of gossypol on epididymal spermatozoa is superimposed on the action earlier exerted on the spermatids.

An ultrastructural analysis of the mature spermatozoon of Anguispira alternata (say) (pulmonata, stylommatophora)

Mature spermatozoa from the hermaphroditic duct of adult snails were examined using various techniques of light microscopy as well as scanning and transmission electron microscopy. The sperm are approximately 557 μm in length including a dextrally spiral head approximately 13 μm long. The head consists of an electron-dense nucleus sculptured into a double-ridged spiral and an acrosome projecting approximately 0.45 μm beyond the apex of the nucleus. The acrosome consists of a membrane-bound vesicle approximately 0.1 μm in diameter and a column of homogeneous material which extends along one side of the terminal spiral of the nucleus. This material is separated from the nucleus by the nuclear envelope. The neck region, though similar to that found in other pulmonates, possesses a unique coiled structure surrounding the central doublet of the axoneme. The midpiece axoneme possesses a 9+9+2 configuration anteriorly grading into a 9+2 pattern for the majority of its length. There are three mitochondrial helices - one primary and two secondary - in the midpiece. Only the primary helix persists throughout the midpiece.