Oocyte Morphology from Primordial to Early Tertiary Follicles of Yak

The objective of this study was to investigate the developmental morphology of yak oocytes from the primordial follicle to the tertiary follicle. Yak oocytes from resting primordial (n = 6), activated primordial (n = 12), primary (n = 9), secondary (n = 7) and early tertiary (n = 5) follicles were processed and analysed by light and transmission electron microscopy. The resting primordial follicular oocyte was characterized by relatively smooth surface on the oolemma, the accumulation of free and organelle‐related smooth (SER) and rough endoplasmic reticulum (RER), round or oval mitochondria, and polyribosomes on the surface of the RER and throughout the ooplasm. The activated primordial follicular oocyte was dominated by numerous coated pits and coated vesicles on the oolemma, and round mitochondria. Up to the secondary follicular stage the oocyte displayed an increase in the number of microvilli, polyribosome, Golgi complexes and mitochondria with distinct cristae. During the secondary follicular stage, formation of the zona pellucida, development of a desmosome‐like connection between the oocyte and the granulosa cells, formation of the cortical granules in the oocyte and elongated mitochondria in nearly all oocytes were seen. In the early tertiary follicular oocyte, the perivitelline space was present and a decrease in free SER and RER in the ooplasm occurred; finally, the nucleus migrated from an eccentric to a peripheral location. In conclusion, the growth of the yak oocyte is associated with the relocation and modulation of a number of cytoplasmic organelles as well as the development of oocyte‐specific structures such as the zona pellucida, desmosome‐like connection and cortical granules.     

Re‐evaluating the effect of wind on recruitment in Gulf of Maine Atlantic Cod (Gadus morhua) using an environmentally‐explicit stock recruitment model

A previous study documented a correlation between Atlantic Cod (Gadus morhua) recruitment in the Gulf of Maine and an annual index of the north component of May winds. This correlation was supported by modeling studies that indicated strong recruitment of Gulf of Maine Atlantic Cod results from high retention of spring‐spawned larvae in years when winds were predominately out of the north, which favor downwelling. We re‐evaluated this relationship using updated recruitment estimates and found that the correlation decreased between recruitment and wind. The original relationship was largely driven by two recruitment estimates, one of which (2005 year‐class) was highly uncertain because it was near the terminal year of the assessment. With additional data, the updated assessment estimated lower recruitment for the 2005 year‐class, which consequently lowered the correlation between recruitment and wind. We then investigated whether an environmentally‐explicit stock recruit function that incorporated an annual wind index was supported by either the original or updated assessment output. Although incorporation of the annual wind index produced a better fitting model, the uncertainty in the estimated parameters and the implied unexploited conditions were not appropriate for providing management advice. These results suggest the need for caution in the development of environmentally‐explicit stock recruitment relationships, in particular when basing relationships and hypotheses on recruitment estimates from the terminal years of stock assessment models. More broadly, this study highlights a number of sources of uncertainty that should be considered when analyzes are performed on the output of stock assessment models.     

Studies on Oral Transmission of Potomac Horse Fever

Eight normal ponies placed in direct contact with ponies experimentally infected with Ehrlichia risticii for 30 to 90 days did not develop signs of Potomac horse fever. They also did not seroconvert, and they remained susceptible to IV infection. One of 8 ponies that were force fed fresh feces from infected ponies while in direct contact with ponies experimentally infected with E. risticii developed Potomac horse fever and seroconverted. The other 7 remained asymptomatic, did not seroconvert, and were susceptible to IV infection. Six of 9 ponies inoculated with E. risticii via nasogastric intubation and oral drench developed Potomac horse fever and serocon verted. The other 3 remained asymptomatic and did not seroconvert. One of these latter ponies and 2 normal ponies that were inoculated via oral drench only developed Potomac horse fever and seroconverted. The high fever, maximum clinical score for decreased feed intake, depressed mental attitude, decreased borborygmal sounds, severity of diarrhea, and the length of illness of the orally infected ponies was not significantly different from those of IV infected control ponies, although the signs occurred significantly later ( P < .05).     

Regional size, age and growth differences of red grouper (Epinephelus morio) along the west coast of Florida

Red grouper (Epinephelus morio) were collected from the west coast of Florida, the central area of fishery harvest in U.S. waters, by fishery-dependent sources during 2000–2005. The west Florida shelf was divided into two regions: north (capture locations ≥28°N latitude) and south (capture locations <28°N latitude). Significant differences were found for age, length, and size-at-age by region and by gear; red grouper from the north were significantly younger and smaller on average than those from the south. Regional differences were also noted with respect to age progression; year class trends were only detected in the north. The 1996 year class dominated the landings in 2000–2001 (ages 4 and 5) and the 1999 year class dominated in 2004–2005 (ages 5 and 6). Regional data were fit to a size-modified von Bertalanffy growth model indicating smaller asymptotic length (L_∞) and faster growth rate (k) in the north (north: L_∞ = 800 mm, k = 0.23 mm year⁻¹, t₀ = 1.12; south: L_∞ = 863 mm, k = 0.15 mm year⁻¹, t₀ = 0.05). Mortality estimates derived from catch curves resulted in higher total and fishing mortality in the north for both gears. Alternative explanations of regional differences likely depend on nursery delineation and correlation to periodic environmental events such as red tides and hurricanes; all possibly important factors based upon anecdotal information. Nevertheless, our finding of regional demographic differences in red grouper from the west coast of Florida suggests a more complex population spatial structure for red grouper.     

MHC class II-restricted, CD4(+) T-cell proliferative responses of peripheral blood mononuclear cells from Mycobacterium bovis-infected white-tailed deer

White-tailed deer are significant wildlife reservoirs of Mycobacterium bovis for cattle, predators, and, potentially, humans. Infection of cattle with M. bovis stimulates an antigen-specific T-cell response, with both CD4(+) and CD8(+) cells implicated in protective immunity. Few studies, however, have examined lymphocyte subset responses to experimental M. bovis infection of white-tailed deer. In this study, a flow cytometric proliferation assay was used to determine the relative contribution of individual peripheral blood mononuclear cell subsets of M. bovis-infected white-tailed deer in the recall response to M. bovis antigen. Naive deer were challenged with M. bovis by cohabitation with infected deer. These M. bovis-challenged deer developed significant in vivo (delayed-type hypersensitivity) and in vitro (proliferative) responses to M. bovis purified protein derivative (PPD). At necropsy, typical tuberculous lesions containing M. bovis were detected within lungs and lung-associated lymph nodes of infected deer. The predominant subset of lymphocytes that proliferated in response to in vitro stimulation with PPD was the CD4(+) subset. Minimal proliferative responses were detected from CD8(+), gamma delta TCR(+), and B-cells. Addition of monoclonal antibodies specific for MHC II antigens, but not MHC I or CD1 antigens, abrogated the proliferative response. Together, these findings indicate that while CD4(+) cells from infected deer proliferate in the recall response to M. bovis antigens, this response is not sufficient to clear M. bovis and immunologic intervention may require stimulation of alternate subsets of lymphocytes.