Golden Hamster Oocytes Research Articles

Variation of Water Permeability (Lp) and Its Activation Energy (Ea) among Unfertilized Golden Hamster and ICR Murine Oocytes

Oocytes provide an excellent model cell type for the exploration of the hypothesis that there is a genetic influence to inter-animal variability in plasma membrane water permeability (Lp) and its activation energy (Ea). Although variability among oocytes pooled across animals has been previously published, variability of oocyte Lp and its Ea among individual animals has yet to be determined. Using a microdiffusion chamber, individual oocytes from five Golden hamsters and six ICR mice were exposed to a 900-mOsm NaCl solution at 37, 22, or 3°C. The resulting change in cell volume over time (dv/dt) was analyzed and hydraulic conductivity (Lp) estimated. The Arrhenius plots (lnLp vs (1/K) × 1000) of the oocytes from each animal were determined and the Ea's were found not to be different among individual Golden hamsters (P > 0.05) with a mean of 7.96 ± 0.96 Kcal/mol (mean ± SD). However, the Ea 's of the oocytes among individual ICR mice were shown to be significantly different (P < 0.05), with a mean of 11.38 ± 2.2 Kcal/mol (mean ± SD). Furthermore, an analysis of the within-mouse and among-mouse variability of Lp was undertaken. The results demonstrated that there was significant variability among ICR mouse oocyte Lp values at all temperatures; however, there was no significant variability within animals. In summary, these data support the hypothesis that significant variability exists in the Lp of ova among mice of the outbred ICR strain. In contrast, the data from the inbred Golden hamster oocyte donors do not show significant variability.

Analysis of sperm chromosome complements from a man heterozygous for a pericentric inversion of chromosome 1.

Human sperm chromosomes were studied in a man heterozygous for a pericentric inversion of chromosome (1)(p31q12). Q-banded pronuclear chromosomes were analyzed after in vitro penetration of golden hamster oocytes. A total of 159 sperm were examined: 54% bearing the inverted chromosome 1 and 46% the normal chromosome 1. These frequencies are not significantly different from the theoretical 1:1 ratio. There were no recombinant sperm with duplications or deficiencies, suggesting that a pairing loop failed to form or that crossing-over was suppressed. The frequency of abnormalities unrelated to the inversion was 5% for numerical, 8.8% for structural, 2.5% for numerical and structural, values not significantly different from control donors studied in our lab. The frequencies of X- and Y-bearing sperm were 46% and 54%, respectively, not significantly different from the expected value of 50%. This is the fifth pericentric inversion studied by human sperm chromosome analysis; recombinant chromosomes have been observed in two of the five cases. Some of the factors associated with an increased risk of recombinant sperm appear to be inversion size greater than 30% of the chromosome and chromosome breakpoints in G-light bands.

A Comparison of the Frequency and Type of Chromosomal Abnormalities in Human Sperm after Different Sperm Capacitation Conditions1

Human sperm karyotypes can be prepared after fusion of human sperm with Golden hamster oocytes. Most laboratories use one of two methods of sperm capacitation: incubation of freshly-ejaculated sperm in Biggers, Whitten, and Whittingham (BWW) medium for 5-7 h at 37 degrees C or sperm storage in (N-tris [hydroxymethyl]methyl-2-aminoethanesulfonic acid; 2-([2-hydroxy-1,1-bis(hydroxymethyl)ethyl]amino)ethanesulfonic acid) (TES)-Tris yolk buffer (TYB) for 1-3 days at 4 degrees C. Since there have been conflicting reports as to whether there is a difference in the frequency of structural chromosomal abnormalities between BWW capacitation and storage in TYB for 2 days, we analyzed a larger number of karyotypes (8974) from 136 donors to determine if there was any difference in the frequency or type of chromosomal abnormalities in sperm treated by fresh BWW capacitation, storage in TYB for 1 day (TYB-1), or storage in TYB for 2 days (TYB-2). There was no difference in the frequency of numerical chromosomal abnormalities or sex ratio in any of the three treatment groups. However, there was a significantly increased frequency of structural chromosomal abnormalities after storage in TYB-1 and TYB-2. There was no difference in the frequency or type of structural chromosomal abnormalities after sperm storage in TYB-1 compared to TYB-2.

A Study of Paternal Age and Sex Ratio in Sperm Chromosome Complements

There is conflicting evidence as to whether the secondary sex ratio in humans decreases with paternal age. Such an age effect could be caused by an altered frequency in the production of X-chromosome and Y-chromosome-bearing sperm as a man ages. To study this possibility we analysed 9,225 sperm karyotypes from 143 men aged 21-55 years. Human pronuclear sperm chromosome complements were obtained after fusion with golden hamster oocytes. The percentage of X- and Y-chromosome complements was not significantly related to donor age.

Repetitive calcium transients in hamster oocytes

Golden hamster oocytes show repetitive Ca 2+ transients at fertilization: a propagating Ca 2+ rise from the sperm attachment site in the first 2–3 responses and synchronous Ca 2+ rise in the entire egg in the succeeding responses. Cyclic Ca 2+ rises are produced in unfertilized eggs by an injection of GTPγS or continuous injection of inositol 1,4,5-trisphosphate (InsP 3). Both InsP 3-induced Ca 2+ release (IICR) and Ca 2+-induced Ca 2+ release (CICR) are observed in hamster eggs, associated with a refractory period of 1–2 min after a Ca 2+ release. In addition, external Ca 2+ is a presequisite for maintaining the repeated Ca 2+ transients. The conditions that are expected to alter Ca 2+ influx affect the frequency of Ca 2+ transients with little effect on each response. The fertilizing sperm causes an increase in Ca 2+ permeability of the egg plasma membrane and an increase in Ca 2+ sensitivity of CICR. Feedback inhibition through protein kinase C is observed in G-protein-mediated Ca 2+ transients but this inhibition seems to operate rather tonically. A model of Ca 2+ oscillation is proposed: basically a second messenger-controlled oscillator model. InsP 3 as the rigger of Ca 2+ release is continuously supplied while an elevated basal [Ca 2+] i level due to Ca 2+ influx provides a favourable condition for IICR and CICR as well as for recharging the Ca 2+ pools ready to release Ca 2+ again.

Cytokeratin filaments are present in golden hamster oocytes and early embryos

Abstract Light and electron microscope methods were used to study cytokeratin expression in the recently ovulated oocytes, fertilized eggs and early embryos from the golden hamster. Two cytokeratin polypeptides (Mr 51,000 and 58,000) were detected in oocyte lysates by immunoblotting using a polyclonal antiserum to prekeratin. In the oocyte, cytokeratin occurred as patchy aggregates consisting of short anastomosing 10-nm filaments that formed tight meshworks distributed throughout the cytoplasm. After fertilization the aggregates appeared to merge, becoming larger and concentrated at the cortical region. Prominent immunofluorescent fibrils were seen interconnecting the aggregates. In the 2-, 4- and 8-cell embryos, networks of cytokeratin filaments extended throughout the cortical and perinuclear regions, while aggregates progressively disappeared.

A note on the inhibition of in vitro meiotic maturation of mammalian oocytes by dibutyryl cyclic AMP.

Cytogenetic data are presented which indicate species differences in the response of oocytes maturing in vitro in the presence of dibutyryl cyclic AMP (dbcAMP). Inhibition of ewe oocyte maturation was noted at germinal vesicle, MI, and MII in the presence of 25-750 microgram/ml of dbcAMP. Cow oocytes were primarily affected at MI and MII by similar concentrations, and only 750 microgram/ml delayed golden hamster oocytes at these stages. These findings highlight the variability between the responses of the oocytes of these mammals and the rat, mouse, or pig.