Showing papers by "Gregory A. Johnson published in 2010"

Dietary Supplementation with 0.8% l-Arginine between Days 0 and 25 of Gestation Reduces Litter Size in Gilts

Abstract: In this study, we determined the effects of L-arginine supplementation during early pregnancy on embryonic/fetal survival and growth in gilts Gilts were housed individually in pens and fed twice daily 1 kg of a corn- and soybean meal-based diet supplemented with 00, 04, or 08% L-arginine (wt:wt) between d 0 and 25 of gestation (10 gilts/treatment) The diets were made isonitrogenous by addition of appropriate amounts of L-alanine At d 25 of gestation, gilts were fed L-alanine or L-arginine and hysterectomized 30 min later to obtain uteri and conceptuses (embryos and associated fetal membranes and fluids) Dietary supplementation with 04 or 08% L-arginine enhanced (P < 005) its concentrations in maternal plasma (64 and 98%, respectively) as well as the vascularity of chorionic and allantoic membranes, compared with the control group Reproductive performance [numbers of corpora lutea (CL) and fetuses, placental and fetal weights, and embryonic mortality] did not differ between the 04% Arg and control groups However, supplementation with 08% L-arginine decreased (P < 005) uterine weight (-20%), total number of fetuses (-24%), CL number (-17%), total fetal weight (-34%), total volume of allantoic and amniotic fluids (-34 to 42%), concentrations of progesterone in maternal plasma (-33%), as well as total amounts of progesterone (-35%), estrone (-40%), and estrone sulfate (-37%) in allantoic fluid, compared with the control group These results indicate that dietary supplementation with 08% L-arginine between d 0 and 25 of gestation, while increasing placental vascularity, adversely affects the reproductive performance of gilts

Select Nutrients and Their Associated Transporters Are Increased in the Ovine Uterus Following Early Progesterone Administration

Abstract: The intrauterine milieu is a complex mixture of substances originating from serum and endometrium that support blastocyst growth and development. The present study identified alterations in glucose and amino acids in response to an early rise in progesterone (P4), which accelerates blastocyst growth and development. Bred ewes received daily injections of either corn oil (CO) vehicle or P4 from 36 h postmating (Day 0) to either Day 9 or Day 12. Another group of ewes received P4 to Day 8 and the antiprogestin mifepristone (RU486) from Day 8 to Day 12. The total amount of glucose, aspartate (acidic amino acid), arginine and lysine (basic amino acids), and citrulline, asparagine, serine, glutamine, beta-alanine, and alanine (neutral amino acids) was greater in uterine flushings from early P4- than CO-treated ewes on Day 9. On Day 12, only arginine and lysine were higher in uterine flushings from P4-treated ewes, whereas citrulline was reduced. Glucose transporters, SLC2A1 and SLC5A1, were increased in uterine luminal (LE) and superficial glandular (sGE) epithelia of early P4-treated ewes on Days 9 and 12 but were reduced in endometria from ewes treated with both P4 and RU486 (P4+RU). SLC7A2B, a transporter of basic amino acids, increased in LE/sGE of P4- versus CO-treated ewes on Day 12 but was reduced in P4+RU-treated ewes. Thus, select nutrients are increased in the uterine lumen by P4 concomitant with the upregulation of epithelial transporters for glucose and basic amino acids, suggesting that these nutrients stimulate blastocyst growth and development.

Transforming growth factor beta (TGFB) signaling is activated during porcine implantation: proposed role for latency-associated peptide interactions with integrins at the conceptus–maternal interface

Abstract: The process of implantation is mediated by a complex network of signaling and adhesive factors. In the pig, latent and active transforming growth factor beta (TGFB), TGFB receptors (TGFBR), and integrins (ITGs) are present during the peri-implantation period. TGFB signals via TGFBR and activates downstream effector SMAD proteins 2 and 3 (p-SMAD2/3). Latency-associated peptide (LAP), part of the latent TGFB complex, is known to bind to ITG heterodimers and activate TGFB. We hypothesize that active TGFBs and TGFBRs along with LAP and ITGs functionally interact at the conceptus-maternal interface to mediate events essential for conceptus development and attachment in pigs. Uteri and conceptuses from days 10, 12, 16, 20, and 24 pregnant gilts were immunostained for TGFB, LAP, and ITG subunits (ITGAV, ITGB1, ITGB3, ITGB5, ITGB6, and ITGB8). Activation of TGFBRs was evaluated by the presence of phosphorylated downstream effector SMAD2/3. Binding of LAP to ITGs was also evaluated using porcine trophectoderm cells. Abundant active TGFB was detected at the apical surfaces of epithelia at the conceptus-maternal interface, and p-SMAD2/3 was detected at both conceptus attachment and nonattachment sites during implantation. Separate aggregates of LAP, ITGB1, ITGB5, and later ITGB3 were detected at the porcine conceptus-maternal interface, and binding of LAP to ITGs on apical surfaces was demonstrated. Results suggest that functional LAP-ITG adhesion complexes support conceptus attachment and promote TGFB activation leading to TGFB interaction with TGFBR supporting events of porcine implantation.

Modeling of the Endosomolytic Activity of HA2-TAT Peptides with Red Blood Cells and Ghosts

Abstract: HA2-TAT is a peptide-based delivery agent that combines the pH-sensitive HA2 fusion peptide from influenza and the cell-penetrating peptide TAT from HIV. This chimeric peptide is engineered to induce the cellular uptake of macromolecules into endosomes via the TAT moiety and to respond to the acidifying lumen of endosomes to cause membrane leakage and release of macromolecules into cells via the HA2 moiety. The question of how HA2 and TAT affect the properties of one another remains, however, unanswered, and the behavior of the peptide inside endosomes is mostly uncharacterized. To address these issues, the binding and membrane leakage activity of a glutamic acid-enriched analogue E5-TAT was assessed with red blood cells and giant unilamellar vesicles as membrane models for endosomes. Hemolysis and microscopy assays reveal that E5-TAT binds to membranes in a pH-dependent manner and causes membrane leakage by inducing the formation of pores through which macromolecules can escape. The TAT moiety contributes to this activity by causing a shift in the pH response of E5 and by binding to negatively charged phospholipids. On the other hand, TAT binding to glycosaminoglycans reduces the lytic activity of E5-TAT. Addition of TAT to the C-terminus of E5 can therefore either increase or inhibit the activity of E5 depending on the cellular components present at the membrane. Taken together, these results suggest a model for the endosomolytic activity of the peptide and provide the basis for the molecular design of future delivery agents.