Browsing by Author "Dr. William Flowers, Committee Member"

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    Assessment of Nycodenz Gradient on Enrichment and Culture of Perinatal Porcine Spermatogonial Stem Cells
    (2006-11-22) Miller, Stephanie Renee; Dr. Paul Mozdziak, Committee Member; Dr. Jim Petitte, Committee Member; Dr. William Flowers, Committee Member; Dr. Robert Petters, Committee Chair
    The objective of this study was to assess the effectiveness of a Nycodenz gradient enrichment method to enrich a dissociated single cell suspension of porcine testicular cells for spermatogonia, and to observe the separated fractions from the gradient over a 14-day culture period for cell viability and number of spermatogonia in culture. Two germ cell specific genes, VASA and DAZL, were utilized for detection of spermatogonia using immunohistochemistry. The control group included cultures generated from the enzymatic digestion of porcine testes prior to the enrichment protocol for each replicate. The NycoDenz gradient consistently separated the isolated cell suspension into three distinct layers and a pellet, all of which were assessed for spermatogonial enrichment. Testis cells were isolated and seeded in culture on day 0. Cell viability and percent of spermatogonia was assessed on day 0, 7, and 14 of culture. Viability was determined using trypan blue exclusion assay and quantified using a hemocytometer. Spermatogonia were morphologically identified as round, plump cells with a large amount of cytoplasm. Visualization of spermatogonia was facilitated by immunostaining with DAZL and VASA polyclonal antibodies and cells exhibiting morphological characteristics in addition to bright, concentrated fluorescence were counted as spermatogonia.
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    Effect of selection for testosterone production on testicular morphology and daily sperm production in pigs.
    (2003-07-08) Walker, Sara Elizabeth; Dr. O.W. Robison, Committee Member; Dr. William Flowers, Committee Member; Dr. Charlotte Farin, Committee Member; Dr. Joseph Cassady, Committee Chair
    The objective of this study was to determine effects of divergent selection for testosterone on testicular morphology and daily sperm production. Duroc boars from lines divergently selected for testosterone production in response to GnRH challenge for 10 generations followed by random selection were used. In generation 21 endogenous testosterone in the high testosterone line (H, n=54) and low testosterone line (L, n=44) averaged 490 ng/ml and 278 ng/ml (P < 0.01), respectively. Plasma FSH concentrations did not differ between lines (P < 0.3). Body weight, testicular weight, and epididymal weight were recorded for boars from H (n=82) and L (n=44) castrated at an average age of 211 d and 97 kg. Testicular tissues were sampled from animals castrated in generation 20 (H, n=46 and L, n=13). Volume densities for Leydig cells, seminiferous tubules, and Sertoli cells were estimated along with sperm production. After adjustment for body weight, average paired testicular weights for H and L were 417 g and 457 g (P < 0.01), respectively. Adjusted epididymal weights also differed between lines (P < 0.02), with H having larger epididymal weights. Line H (n=46) had greater volume densities of Leydig cells than L (n=13) (P < 0.02). Volume density of seminiferous tubules tended to differ between lines (P < 0.07), and Sertoli cell volume densities did not differ (P < 0.27). Sperm production traits, adjusted for age, did not significantly differ between lines. Selection for testosterone production in response to a GnRH challenge was an effective method of changing testosterone levels, testicular size, epididymal weight, and volume density of Leydig cells and seminiferous tubules. However, daily sperm production per gram of testes was unchanged. At this time, selection for testosterone in order to increase sperm production is not recommended.
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    Genetics of gilt estrous behavior
    (2009-12-11) Knauer, Mark; Dr. Joe Cassady, Committee Co-Chair; Dr. Todd See, Committee Co-Chair; Dr. William Flowers, Committee Member; Dr. Doug Newcom, Committee Member; Dr. Genn Almond, Committee Member
    Studies were conducted to develop and analyze gilt estrous behavior traits. Variance components, genetic correlations, and genetic line differences were estimated for gilt estrus, puberty, growth, composition, structural conformation, and first litter sow reproductive measures. Four groups of Landrace-Large White gilts (n=1,225, GIS of NC) from 59 sires and 330 dams were utilized. Heritability (h2) estimates for estrous traits; estrus length, maximum strength of standing reflex with a boar, total strength of standing reflex with a boar, maximum strength of standing reflex without a boar, total strength of standing reflex without a boar, vulva redness, strength of vulva reddening and swelling (VISUAL VULVA), and vulva width were 0.21, 0.13, 0.26, 0.42, 0.42, 0.26, 0.45, and 0.58, respectively. For puberty traits; age at puberty, puberty weight, puberty backfat, and puberty longissimus muscle, h2 estimates were 0.29, 0.39, 0.41, and 0.38, respectfully. The h2 of whether or not a gilt farrowed a litter (STAY1) was 0.14. Age at puberty had favorable genetic associations with estrus length, maximum strength of standing reflex with a boar, vulva redness, STAY1, and age at first farrowing (AFF) (-0.23, -0.32, 0.20, -0.27, and 0.76, respectively). Genetic correlations between estrus length and the standing reflex traits with STAY1 (0.34 to 0.74) and AFF (-0.04 to -0.41) were positive and negative, respectively. Growth rate had unfavorable genetic correlations with estrus length, the standing reflex traits, vulva redness, STAY1, and AFF (0.30, 0.14 to 0.34, -0.19, 0.52, and -0.25, respectfully). Backfat had unfavorable genetic associations with estrus length, age at puberty, and first litter total number born (TNB1) (0.29, -0.26, and 0.47, respectively). Vulva redness and TNB1 had favorable phenotypic and genetic correlations (-0.14 and -0.53, respectively). For estrous traits, crossbred performance was superior to the pure-line average for estrus length, total strength of standing reflex with a boar, vulva redness, VISUAL VULVA, and vulva width. These findings imply the use of F1 females would increase estrus length and improve vulva traits. The unfavorable genetic associations between production and reproduction traits further strengthen the need for a balanced selection objective. Based on these results it was concluded that selection for a younger age at puberty would have correlated responses of improved gilt estrous behavior and sow reproductive lifetime.