Publications by authors named "Derek McLean"

This study determined whether feeding the immunomodulating supplement, OmniGen-AF, to feedlot heifers would alter metabolic profiles to a glucose tolerance test. Heifer calves ( = 32; 217 ± 2 kg) were allocated into two treatment diets: 1) Control, fed a standard receiving ration, and 2) OmniGen, fed the Control diet supplemented with OmniGen at 4.54 g/45 kg BW/d.

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The ability to positively alter immune and stress response with nutritional compounds is of great interest and importance to the beef industry. There is a proprietary product (OmniGen-AF [OG]; Phibro Animal Health, Quincy, IL) reported to have performance-enhancing benefits by altering animal response to stress and immune challenges. The objective of this 2-yr research project was to study the effect of supplementing OG to beef cows and their calves on breeding and growth performance.

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A greater demand for food animal production without antibiotics has created the common practice of feeding food animals dietary immunomodulatory feed additives (IFA) throughout their life cycle. However, little is known about the impact of IFA on cytokine and chemokine signaling in non-stressed, non-pathogen-challenged food animals during the early feeding period. We evaluated the expression of 82 genes related to cytokine and chemokine signaling in the whole blood of growing Angus heifers to determine the effect of IFA supplementation on cytokine and chemokine signaling during the first 28 d of feeding.

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Heat stress during late gestation negatively affects the physiology, health, and productivity of dairy cows as well as the calves developing in utero. Providing cows with active cooling devices, such as fans and soakers, and supplementing cows with an immunomodulating feed additive, OmniGen-AF (OG; Phibro Animal Health Corporation), improves immune function and milk yield of cows. It is unknown if maternal supplementation of OG combined with active cooling during late gestation might benefit the developing calf as well.

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Heat stress in dairy cows during the dry period impairs milk yield in the next lactation. Feeding OmniGen-AF (OG; Phibro Animal Health Corp., Teaneck, NJ) to lactating cows during heat stress may increase dry matter intake (DMI) and lowers respiration rate (RR) and rectal temperature (RT), but the effects in dry cows are not known.

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Feeding a yeast-containing additive (YCA; OmniGen-AF) improves immune responses in ruminant livestock and reduces subsequent production losses. The objective was to identify molecular pathways by which dietary YCA may modify immune responses using a rodent model. Thirty-seven healthy, unchallenged CD rats received a diet containing 0 (control; n = 5, only 28 d), 0.

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There is little research evaluating flavor preferences among wheat varieties. We previously demonstrated that mice exert very strong preferences when given binary mixtures of wheat varieties. We plan to utilize mice to identify wheat genes associated with flavor, and then relate this back to human preferences.

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Recent evidence has linked human phthalate exposure to abnormal reproductive and hormonal effects. Phthalates are plasticizers that confer flexibility and transparency to plastics, but they readily contaminate the body and the environment. In this study, timed pregnant CD1 outbred mice were treated with di-(2-ethylhexyl) phthalate (DEHP) from Embryonic Day 7 (E7) to E14.

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A balance between self-renewal and differentiation of spermatogonial stem cells (SSCs) is required to maintain sperm production throughout male life. The seminiferous epithelium is organized into stages of spermatogenesis based on the complement of germ cell types within a tubular section of the testis. The stages exist in close physical proximity and foster diverse phases of germ cell development despite exposure to a similar endocrine milieu that supports coordinated spermatogenesis.

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Genetically based diseases constitute a major human health burden, and de novo germline mutations represent a source of heritable genetic alterations that can cause such disorders in offspring. The availability of transgenic rodent systems with recoverable, mutation reporter genes has been used to assess the occurrence of spontaneous point mutations in germline cells. Previous studies using the lacI mutation reporter transgenic mouse system showed that the frequency of spontaneous mutations is significantly lower in advanced male germ cells than in somatic cell types from the same individuals.

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Purpose: To conduct a pilot study to demonstrate a novel method of using a proprietary cyanoacrylate (CA) for closure of superficial veins.

Materials And Methods: Right and left superficial epigastric veins from two swine models were utilized due to the vein's similarities with the human great saphenous vein. Under ultrasound guidance, access was gained and a 5-F delivery catheter was advanced to the junction of the superficial epigastric and abdominus rectus veins.

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Ethanol is a known modulator of neural stem cell development, but the consequences of ethanol toxicity on the cell fate decisions of spermatogonial stem cells (SSCs) is poorly understood. Using an in vivo treatment and stem cell transplantation approach, we investigated the effects of acute ethanol exposure on formation of the growing adult SSC population in neonatal and pre-pubertal mice. Treatment with a single dose of ethanol disrupted SSC homeostasis in vivo evidenced by a significant reduction (7-fold) of stem cell colonization efficiency in the testes of recipient mice following transplantation.

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The objective of the present study was to investigate vascular endothelial growth factor A (VEGFA) isoform regulation of cell fate decisions of spermatogonial stem cells (SSC) in vivo. The expression pattern and cell-specific distribution of VEGF isoforms, receptors, and coreceptors during testis development postnatal d 1-180 suggest a nonvascular function for VEGF regulation of early germ cell homeostasis. Populations of undifferentiated spermatogonia present shortly after birth were positive for VEGF receptor activation as demonstrated by immunohistochemical analysis.

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The Illumina BovineSNP50 BeadChip features 54,001 informative single nucleotide polymorphisms (SNPs) that uniformly span the entire bovine genome. Among them, 52,255 SNPs have locations assigned in the current genome assembly (Btau_4.0), including 19,294 (37%) intragenic SNPs (i.

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The water buffalo is vital to the lives of small farmers and to the economy of many countries worldwide. Not only are they draught animals, but they are also a source of meat, horns, skin and particularly the rich and precious milk that may be converted to creams, butter, yogurt and many cheeses. Genome analysis of water buffalo has advanced significantly in recent years.

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Spermatogonial stem cells (SSCs) are a self-renewing population of adult stem cells capable of producing progeny cells for sperm production throughout the life of the male. Regulation of the SSC population includes establishment and maintenance of a niche microenvironment in the seminiferous tubules of the testis. Signaling from somatic cells within the niche determines the fate of SSCs by either supporting self-renewal or initiating differentiation leading to meiotic entry and production of spermatozoa.

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Vascular endothelial growth factor-A (VEGFA) is a hypoxia-inducible peptide essential for angiogenesis and targets nonvascular cells in a variety of tissues and cell types. The objective of the current study was to determine the function of VEGF during testis development in bulls. We used an explant tissue culture and treatment approach to test the hypothesis that VEGFA-164 could regulate the biological activity of bovine germ cells.

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Mammalian spermatogonial stem cells, sometimes called male germline stem cells, are a small population of adult tissue-specific stem cells present in the testis. Formation of the spermatogonial stem cell population early in life and differentiation of spermatogonial stem cells in adults are responsible for continual production of sperm in the testis. Unfortunately, there are no specific biochemical or morphological markers for spermatogonial stem cells, so investigation of this cell type requires specific and consistent approaches to ensure valid data are obtained.

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Elucidation of the retinoid signaling circuitry in the testis is critical to understanding how male germ cells develop to spermatozoa. Retinoic acid receptor A protein (RARA) is an essential mediator of retinoid signaling in the testis, as shown by a sterility phenotype observed for retinoic acid receptor A gene (Rara) knockout male mice. The seminiferous tubules of Rara knockout mice showed varying degrees of germ-cell degeneration.

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The purpose of this study was to identify factors that contribute to bovine testis development and donor age-dependent differences in the abilities of bovine ectopic testis tissue grafts to produce elongated spermatids. We used real-time RT-PCR and microarrays to evaluate and to identify the expression of genes that are involved in Sertoli and germ cell development in bovine testis tissues. Testis tissues were obtained from 2-, 4-, and 8-wk-old bull calves and were grafted immediately.

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Ovarian response to follicle stimulating hormone (FSH) and luteinising hormone (LH) leads to the formation of a mature follicle that is eventually ovulated. FSH and LH are essential for this process because they direct changes in somatic cells associated with folliculogenesis by regulating the expression of multiple genes. We hypothesised that genes induced by FSH in rat Sertoli cells would also show hormonal regulation during rat folliculogenesis.

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How limited is the ability of stem cells to generate gametes or differentiated somatic cells? Recent outcomes of research with stem cells from both embryonic and adult origin will be discussed with particular attention to results that challenge conventional wisdom about the presence of reproductive stem cells in adults and the plasticity of adult stem cell types. The ability of embryonic germ cells, primordial germ cells, oogonia, gonocytes and spermatogonial stem cells to differentiate or dedifferentiate into overlapping cell types is described as well as the implications of generating differentiated somatic cells of multiple lineages from adult reproductive stem cells.

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Bovine testis tissue xenografts contain elongating spermatids 6 mo after grafting. The percentage of seminiferous tubule cross sections with elongating spermatids at the time of graft removal varies depending on donor age and rarely exceeds 10%. These data indicate significant changes are occurring to bovine testicular cells during the first weeks of life.

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Bovine ectopic testis tissue grafting is a technique that can be used to study bovine spermatogenesis and for the production of germ cells for a variety of applications. Approximately 10% of seminiferous tubule cross sections in testis grafts contain spermatids, providing a unique tool to investigate what regulates germ cell differentiation. We hypothesized that manipulation of testis tissue grafts would increase the percentage of seminiferous tubule cross sections undergoing complete germ cell differentiation.

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