Nuclear Configuration, Spindle Morphology and Cytoskeletal Organization of In Vivo Maturing Horse Oocytes

Horse oocytes (n = 37) were recovered in vivo from pre-ovulatory follicles 30 h after an ovulation-inducing hCG injection and were examined by fluorescent staining and confocal microscopy. Percentages of metaphase-I (MI), metaphase-II (MII) and atypical oocytes were 11%, 78% and 11% respectively. Microtubules were concentrated in the meiotic spindle in both MI and MII oocytes. Chromosomes in the metaphase plate were anchored at the equatorial region of the spindle. Spindle orientation was perpendicular to the oolema in all MI oocytes, whereas in MII oocytes, 66% were parallel and 34% were perpendicular. In MII oocytes, the nuclear material in the polar body had no specific organization and was intertwined with microtubules. Discrete foci of microfilaments at the sub-cortical region of the ooplasm formed an F-actin band, as seen in the inner confocal sections. The percentage area of oocyte image with discrete foci and/or the thickness of F-actin band was used to indicate microfilament content. Microfilament content was greater (p < 0.006) in MII oocytes than in MI oocytes and greater (p < 0.03) in MII oocytes with a perpendicular spindle than with a parallel spindle. The perpendicular spindle orientation in MII oocytes may have represented a later stage of maturation. Atypical oocytes were based on microtubules that were detached from the kinetochores and spread in the ooplasm or by microtubules that accumulated as an amorphous mass near the condensed chromatin. This is the first description of the nuclear configuration, spindle morphology and cytoskeletal organization of in vivo maturing horse oocytes

The ability of two different Vibrio spp. bacteriophages to infect Vibrio harveyi, Vibrio cholerae and Vibrio mimicus

Aims: To determine the host range of the Vibrio harveyi myovirus-like bacteriophage (VHML) and the cholera toxin conversion bacteriophage (CTX Φ) within a range of Vibrio cholerae and V. mimicus and V. harveyi, V. cholerae and V. mimicus isolates respectively.\ud \ud Methods and Results: Three V. harveyi, eight V. cholerae and five V. mimicus isolates were incubated with VHML and CTX Φ. Polymerase chain reaction (PCR) was used to determine the presence of VHML and CTX Φ in infected isolates. We demonstrated that it was possible to infect one isolate of V. cholerae (isolate ACM #2773/ATCC #14035) with VHML. This isolate successfully incorporated VHML into its genome as evident by positive PCR amplification of the sequence coding part of the tail sheath of VHML. Attempts to infect all other V. cholerae and V. mimicus isolates with VHML were unsuccessful. Attempts to infect V. cholerae non-01, V. harveyi andV. mimicus isolates with CTX Φ were unsuccessful.\ud \ud Conclusions: Bacteriophage infection is limited by bacteriophage-exclusion systems operating within bacterial strains and these systems appear to be highly selective. One system may allow the co-existence of one bacteriophage while excluding another. VHML appears to have a narrow host range which may be related to a common receptor protein in such strains. The lack of the vibrio pathogenicity island bacteriophage (VPI Φ) in the isolates used in this study may explain why infections with CTX Φ were unsuccessful.\ud \ud Significance and Impact of the Study: The current study has demonstrated that Vibrio spp. bacteriophages may infect other Vibrio spp.\u