Routine preparation of seminal fluid specimens for transmission electron microscopy

New insights into sperm rheotaxis, agglutination and bundle formation in Sharkasi chickens based on an in vitro study

Fertility in birds is dependent on their ability to store adequate populations of viable sperm for extended durations in sperm storage tubules (SSTs). The exact mechanisms by which sperm enter, reside, and egress from the SSTs are still controversial. Sharkasi chicken sperm showed a high tendency to agglutinate, forming motile thread-like bundles comprising many cells. Since it is difficult to observe sperm motility and behavior inside the opaque oviduct, we employed a microfluidic device with a microchannel cross-section resembling close to that of sperm glands allowing for the study of sperm agglutination and motility behavior. This study discusses how sperm bundles are formed, how they move, and what role they may have in extending sperm residency inside the SSTs. We investigated sperm velocity and rheotaxis behavior when a fluid flow was generated inside a microfluidic channel by hydrostatic pressure (flow velocity = 33 µm/s). Spermatozoa tended to swim against the flow (positive rheotaxis) and sperm bundles had significantly lower velocity compared to lonesome sperm. Sperm bundles were observed to swim in a spiral-like motion and to grow in length and thickness as more lonesome sperm are recruited. Sperm bundles were observed approaching and adhering to the sidewalls of the microfluidic channels to avoid being swept with fluid flow velocity > 33 µm/s. Scanning and transmission electron microscopy revealed that sperm bundles were supported by a copious dense substance. The findings show the distinct motility of Sharkasi chicken sperm, as well as sperm's capacity to agglutinate and form motile bundles, which provides a better understanding of long-term sperm storage in the SSTs.

Growth and killing of a Salmonella enterica serovar Typhimurium sifA mutant strain in the cytosol of different host cell lines

Intracellular pathogens have developed different mechanisms which enable their survival and replication within the host cells. Some survive and replicate within a membrane-bound vacuole modified by the bacteria to support microbial growth (e.g. Salmonella enterica serovar Typhimurium), whereas others escape from the vacuole into the host cell cytosol, where they proliferate (e.g. Listeria monocytogenes). In this study a Salmonella strain carrying a mutation in sifA which is released from the vacuole was used to analyse Salmonella survival and replication within the cytosol of several cell lines. It was found that Salmonella replicates within the cytosol of epithelial cells at a higher rate than that achieved when replicating within the vacuole, but is defective for replication in the cytosol of fibroblasts or macrophages. Using an aroC purD double mutant strain which does not replicate within host cells, it was shown that Salmonella encounters a killing activity within the cytosol of macrophages. Furthermore, in vitro experiments using cytosol extracted from either infected or uninfected macrophages suggested that this activity is activated upon Salmonella infection.

Salmonella maintains the integrity of its intracellular vacuole through the action of SifA

A method based on the Competitive Index was used to identify Salmonella typhimurium virulence gene interactions during systemic infections of mice. Analysis of mixed infections involving single and double mutant strains showed that OmpR, the type III secretion system of Salmonella pathogenicity island 2 (SPI-2) and SifA [required for the formation in epithelial cells of lysosomal glycoprotein (lgp)-containing structures, termed Sifs] are all involved in the same virulence function. sifA gene expression was induced after Salmonella entry into host cells and was dependent on the SPI-2 regulator ssrA. A sifA(-) mutant strain had a replication defect in macrophages, similar to that of SPI-2 and ompR(-) mutant strains. Whereas wild-type and SPI-2 mutant strains reside in vacuoles that progressively acquire lgps and the vacuolar ATPase, the majority of sifA(-) bacteria lost their vacuolar membrane and were released into the host cell cytosol. We propose that the wild-type strain, through the action of SPI-2 effectors (including SpiC), diverts the Salmonella-containing vacuole from the endocytic pathway, and subsequent recruitment and maintenance of vacuolar ATPase/lgp-containing membranes that enclose replicating bacteria is mediated by translocation of SifA.

Fertility in men with primary ciliary dyskinesia presenting with respiratory infection

BACKGROUND

Primary ciliary dyskinesia is characterised by chronic rhinosinusitis, chronic bronchial sepsis (usually with bronchiectasis), dextrocardia in approximately 50% of cases, and male infertility. The latter, described in patients attending infertility clinics, results from immotile but viable spermatozoa. Experience in a respiratory clinic suggests that infertility in men is not invariable.

METHODS

The seminal fluid of 12 men with primary ciliary dyskinesia, six with dextrocardia, who presented consecutively with upper and lower respiratory tract sepsis was examined. Nasal ciliary beating was dyskinetic or absent in all cases, and nasal ciliary ultrastructure was abnormal in those 11 patients examined.

RESULTS

Viable but immotile spermatozoa with abnormal tail ultrastructure were found in the ejaculate of only two patients. Two other patients had apparently fathered children; seminology in both these cases showed a normal spermatozoa count, one with normal spermatozoal motility and normal ultrastructure, the other with moderately reduced spermatozoal motility and abnormal ultrastructure (dynein arm deficiency on the peripheral microtubule doublets). A further two patients had normal spermatozoa counts, normal spermatozoa tail ultrastructure, and normal or only moderately reduced motility of spermatozoa. The spermatozoa of one patient were normally motile but there was severe oligozoospermia, and five patients were azoospermic.

CONCLUSIONS

Not all men with primary ciliary dyskinesia have immotile spermatozoa. Seminal analysis is recommended in men with primary ciliary dyskinesia so that accurate counselling about reproductive capability may be given.

A quantitative study of sperm head ultrastructure in subfertile males with excess sperm precursors

OBJECTIVE

To make an objective comparison between sperm head ultrastructure in fertile subjects and a subfertile cohort with an excess of immature germinal elements in the ejaculate.

DESIGN

A quantitative analysis of ultrastructural features of the sperm head using transmission electron microscopy in the defined groups.

PATIENTS

Ten men of proven fertility as controls and 10 subfertile subjects with a persistent excess of sperm precursors in the ejaculate were investigated.

SETTING

The Infertility Clinic at Queen Charlotte's and Chelsea Hospital, London.

MAIN OUTCOME MEASURES

Each individual in the study achieved a score for a range of previously defined features of sperm head ultrastructure. These scores provided the basis for comparison between fertile and subfertile subjects.

RESULTS

Subfertile individuals were found to have motile sperm with significantly more hypoplastic, detached, and abnormally shaped acrosomes than fertile controls. Sperm nuclei in these subjects also contained significantly more intranuclear vacuoles and immature chromatin and were associated more commonly with cytoplasmic droplets than fertile controls.

CONCLUSION

Men with an excess of sperm precursors in the ejaculate have motile sperm with a range of abnormalities involving the nucleus and acrosome to account for reduced functional competence.

Ultrastructure sperm defects in addicts

Addiction is a major problem confronting the whole world today. Disruption of interpersonal relationships, economic loss, and crimes against property are frequent consequences. Harm to the individual himself extends to all physiological systems. In the present study, we examined semen samples of six addicts by light and electron microscopy. Oligoasthenospermia was demonstrated in five patients, and necrospermia was observed in one patient. Severe degenerative changes of the sperm heads were noted. Granular condensation of the chromatin with nuclear vacuoles was demonstrated. Persistent cytoplasmic droplets were frequently observed. Degenerated tails showing fragmentation of the plasma membranes and numerical aberrations of the 9 + 2 configuration were also present, together with thickened and disorganized fibrous sheaths. These results confirm the deleterious effects of addiction on the entire sperm structure.

A survey of the ultrastructural defects associated with absent or impaired human sperm motility

The sperm tails of 400 patients having absent or impaired sperm motility were examined by electron microscopy. A wide variety of fine-structural defects were observed although all of the patients fell into clearly defined groups. Total or partial dynein arm deficiency was observed in 12 patients (3%). Ninety-one patients (23%) had sperm with a spectrum of fine-structural defects, whereas 90 patients (23%) were necrospermic. Subjects with low motility, but with at least a few tails of normal structure, had a 5% pregnancy rate, whereas those patients with similar overall motility, but in whom no normal sperm were seen, produced no pregnancies. The results confirm the importance of making an electron microscopical examination of the sperm of patients with asthenozoospermia.