The effects of osmotic pressure and diluent composition on the initiation and duration of spermat ozoan motility in the pejerrey Odontesthes bonariensis, a fresh water atherinid fish, were investigated. Spermatozoa were immotile in the seminal fluid (mean osmotic pressure 331 mOsm/kg), but became motile by dilution with fresh water (4 mOsm/kg), urine (64 mOsm/kg), non-electrolyte solutions (sucrose, mannitol, glycerol) up to 388 mOsm/kg, electrolyte solutions (sea-water, KCl, NaCl) up to 551 mOsm/kg, and KC1 solution at 715 mOsm/kg. Increases in the osmotic pressure of the medium caused progressive reduction in the percentage of motile spermatozoa until complete immotility at 878 mOsm/kg. Thus, osmotic pressure appears to be the major factor regulating the motility of pejerrey spermatozoa, but the presence of cations, especially potassium, is equally capable of inducing motility. The presence of potassium also greatly extended the duration of motility. With the exception of NaCl solutions at 388 and 551 mOsm/kg, all hyperosmotic diluents irreversibly damaged the spermatozoa during a 10-min exposure. These results are discussed in relation to present knowledge on the initiation of motility of fish spermatozoa and the development of fertilization media and sperm preservation techniques for the artifical propagation of pejerrey.

This study investigated the ability of various diluents used in the cryopreservation of fish sperm (extenders) to reversibly suppress the motility of pejerrey Odontesthes bonariensis spermatozoa. A modification of Mounib Solution with 100 mM NaHCO3, 125 mM sucrose, and 6.5 mM reduced glutathione was found to be a satisfactory extender for pejerrey sperm, although variants with higher osmotic pressures may be necessary to minimize motility in some cases. In contrast, other extenders either elicited full activation or irreversibly impaired spermatozoan viability. The effectiveness of Modified Mounib Solution as an extender for pejerrey sperm appeared to be primarily due to the attainment of isosmotic conditions to the seminal fluid through the balance of electrolytes and non-electrolytes, the absence of K+, and the presence of Nat The presence of bicarbonate, the low concentration of proteins or phospholipids, and a slightly alkaline pH apparently contributed to the effectiveness of this extender.

Abstract Background: Yolk sac tumor also known as endodermal sinus tumor, is a rare intracranial germ cell tumor. We reported a case of yolk sac tumor in cerebellar hemisphere, and reviewed associated literatures. The majority of tumor locations are near the midline. On review of literature, very few case reports of intracranial yolk sac tumor have been published, and there is only one case report has described a yolk sac tumor arising from the cerebellum. Case presentation: A two years old boy admitted to our hospital due to headache and unsteady gait for six days. CT and MRI demonstrated a tumor in the right cerebellar hemisphere, and the blood and cerebrospinal fluid alpha-fetoprotein were found increased. It was diagnosed as yolk sac tumor after operation comfirmed by histopathological examination. Postoperative chemotherapy was performed, and the patient suffered no tumor recurrence one year and a half after the surgery. Conclusions: The clinical characteristics and imaging diagnosis of intracranial yolk sac tumor are lack of specificity, the comfirmed diagnosis is depending on the combination of elevated alpha-fetoprotein and histopathological examination.