Papers by Ximena Valderrama
Journal of NeuroVirology, 2008
The replication of herpes simplex virus (HSV) in epithelial cells, and during reactivation from l... more The replication of herpes simplex virus (HSV) in epithelial cells, and during reactivation from latency in sensory neurons, depends on a ubiquitous cellular protein called host cell factor (HCF). The HSV transactivator, VP16, which initiates the viral replicative cycle, binds HCF as do some other cellular proteins. Of these, the neuronal transcription factor Zhangfei suppresses the ability of VP16 to initiate the replicative cycle. It also suppresses Luman, another cellular transcription factor that binds HCF. Interactions of nerve growth factor (NGF) and its receptor tropomyosin-related kinase (trkA) appear to be critical for maintaining HSV latency. Because the neuronal transcription factor Brn3a, which regulates trkA expression, has a motif for binding HCF, we investigated if Zhangfei had an effect on its activity. We found that Brn3a required HCF for activating the trkA promoter and Zhangfei suppressed its activity in non-neuronal cells. However, in neuron-like NGF-differentiated PC12 cells, both Brn3a and Zhangfei activated the trkA promoter and induced the expression of endogenous trkA. In addition, capsaicin, a stressor, which activates HSV in in vitro models of latency, decreased levels of Zhangfei and trkA transcripts in NGF-differentiated PC12 cells.
Reproduction, Fertility and Development, Dec 5, 2022
Reproductive Biology and Endocrinology, Jul 22, 2019
Animals
The neurotrophin beta-nerve growth factor (NGF), which is present in the semen of different mamma... more The neurotrophin beta-nerve growth factor (NGF), which is present in the semen of different mammals, elicits potent ovulatory and luteotrophic actions in llamas following systemic administration. Here, we determine if purified NGF given intramuscularly (IM) during the preovulatory stage affects the corpus luteum (CL), hormone production, endometrial gene expression, and pregnancy rate of dairy heifers. Holstein-Friesian heifers were estrus-synchronized using estradiol benzoate (EB) plus an intravaginal progesterone (P4) device (DIB). After eight days, the device was removed and cloprostenol was given IM; the next day (day 9), heifers received EB IM plus one of the following: (i) 1 mg of NGF (NGF D9 group), (ii) 1 mg of NGF 32 h after EB (NGF D10 group), or (iii) phosphate buffer saline (control group). To measure pregnancy rates, heifers were treated similarly, then artificially inseminated with sexed semen 48–52 h after DIB removal, then an ultrasound was conducted 30 days after in...
Domestic Animal Endocrinology
Genetic selection for high yield milk production has led to a decline in dairy cattle's repro... more Genetic selection for high yield milk production has led to a decline in dairy cattle's reproductive performance over the last 40 years. Low progesterone (P4) plasma content following ovulation is associated with suboptimal fertility in dairy cattle. Several pieces of evidence indicate that the protein beta-nerve growth factor (β-NGF) that is present in the male seminal plasma exerts potent ovulatory and luteotrophic effects following systemic administration in camelids but also in other species. In this study, we determine whether systemic administration of purified llama β-NGF given at the induced preovulatory luteinizing hormone (LH) peak improves corpus luteum (CL) function in dairy heifers subjected to an estradiol (E2) / P4 estrus-synchronization protocol. To achieve this, we first determined plasma E2 and LH hormone profiles to establish the timing of the estradiol benzoate (EB)-induced LH peak in estrus-synchronized heifers. Then, we tested whether the administration of β-NGF given at the end of this peak affects the CL and its function by analyzing diameter, vascular area, and P4 output. Our results show that, with the estrus-synchronization protocol applied, plasma LH concentrations peaked (P < 0.01) 40-h and 16-h after removal of the bovine intravaginal device (DIB; containing 1.0 g of P4) plus cloprostenol injection and subsequent EB administration, respectively; after peaking, plasma LH concentrations remained stable for the next 8-h to then return to basal levels. Heifers synchronized with this protocol and receiving a dose of 1 mg of β-NGF at the end of the LH peak (ie, 48-h after DIB removal) did not show significant differences in CL diameter, but these exhibited a greater CL vascular area (P = 0.01) than the observed in vehicle-injected heifers. Furthermore, plasma P4 concentration in β-NGF-treated heifers was higher (P = 0.001) than those quantified in vehicle-injected heifers. These results support the use of β-NGF in estrus-synchronization protocols to improve the early luteal function in dairy heifers.
Frontiers in Veterinary Science, 2021
Recent studies have shown promise for the development of cellular therapies with mesenchymal stem... more Recent studies have shown promise for the development of cellular therapies with mesenchymal stem cells (MSCs) in livestock species, specifically bovines, and cryopreservation is highly relevant for the advancement of these applications. The use of permeable and/or non-permeable cryoprotectant solutions is necessary to reduce cell damage during freezing and thawing, but these same compounds can also cause negative effects on MSCs and their therapeutic properties. Another important factor to consider is the tissue source of MSCs, since it is now known that MSCs from different tissues of the same individual do not behave the same way, so optimizing the type and concentration of cryoprotectants for each cell type is essential to achieve a large and healthy population of MSCs after cryopreservation. Furthermore, sources of MSCs that could provide great quantities, non-invasively and without ethical concerns, such as placental tissue, have great potential for the development of regenerat...
Frontiers in Veterinary Science, 2020
Reproductive Biology and Endocrinology, 2019
Reproduction, Fertility and Development, 2017
Small ruminants are an important livestock species on many island nations of the Eastern Caribbea... more Small ruminants are an important livestock species on many island nations of the Eastern Caribbean region and serve as a vital source of food and income. This study was designed to characterise follicular development during the inter-ovulatory interval (interval between 2 consecutive ovulations) under tropical conditions. Non-lactating, 2- to 4-year-old crossbred Barbados-Black Belly × White Virgin Island ewes weighing a mean 30.4 kg with mean body condition score 2.9 (score 1–5) were used during September–November for the study. Ewes were maintained in a paddock of 100 m2 at the research farm in St. Kitts and Nevis (17.3°N, 62.7°W). Animals were fed daily with 100 g of concentrate (17% crude protein) and had free access to elephant grass (Pennisetum purpureum), mineral salt, water, and shade. Ovaries of 19 females were examined daily for 46 days by transrectal B-mode ultrasonography using a 7.5-MHz lineal array transducer (Honda HS-2200UV, MA, USA) to detect ovulations and growth a...
Journal of Dairy Research, 2016
The objective of this study was to compare the prediction efficiency of IgG concentration in bovi... more The objective of this study was to compare the prediction efficiency of IgG concentration in bovine colostrum by NIRS, using liquid and dried (Dry-Extract Spectroscopy for Infrared Reflectance, DESIR) samples by transflectance and reflectance modes, respectively. Colostrum samples (157), obtained from 2 commercial Holstein dairy farms, were collected within the first hour after calving and kept at −20 °C until analysis. After thawing and homogenisation, a subsample of 500 mg of liquid colostrum was placed in an aluminium mirror transflectance cell (0·1 mm path length), in duplicate, to collect the spectrum. A glass fiber filter disc was infused with another subsample of 500 mg of colostrum, in duplicate, and dried in a forced-air oven at 60 °C for 20 min. The samples were placed in cells for dry samples to collect the spectra. The spectra in the VIS-NIR region (400–2500 nm) were obtained with a NIRSystems 6500 monochromator. Mathematical treatments, scatter correction treatments and...
Chilean Journal of Agricultural Research, Dec 1, 2011
Journal of Dairy Science, 2012
Reproductive Biology and Endocrinology, 2011
Background The purpose of the study was to determine if the effect of llama OIF on LH secretion i... more Background The purpose of the study was to determine if the effect of llama OIF on LH secretion is mediated by stimulation of the hypothalamus or pituitary gland. Methods Using a 2-by-2 factorial design to examine the effects of OIF vs GnRH with or without a GnRH antagonist, llamas with a growing ovarian follicle greater than or equal to 8 mm were assigned randomly to four groups (n = 7 per group) and a) pre-treated with 1.5 mg of GnRH antagonist (cetrorelix acetate) followed by 1 mg of purified llama OIF, b) pre-treated with 1.5 mg of cetrorelix followed by 50 micrograms of GnRH, c) pre-treated with a placebo (2 ml of saline) followed by 1 mg of purified llama OIF or d) pre-treated with a placebo (2 ml of saline) followed by 50 micrograms of GnRH. Pre-treatment with cetrorelix or saline was given as a single slow intravenous dose 2 hours before intramuscular administration of either GnRH or OIF. Blood samples for LH measurement were taken every 15 minutes from 1.5 hours before to 8...
Reproduction, Fertility and Development, 2010
Gestation in camelids occurs in the left horn regardless of whether ovulation has taken place in ... more Gestation in camelids occurs in the left horn regardless of whether ovulation has taken place in the left or right ovary, suggesting uterine embryo migration (Fernandez-Baca S et al. 1970 Biol. Reprod. 3, 243-251). On the other hand, we have previously documented (Ratto MH et al. 2003 Theriogenology 60, 1645-1656) that more than 90% of llamas with the presence of a follicle ≥6 to 7 mm in diameter, regardless of their stage of development, did accept the copula and ovulate after mating. However, it is unknown whether these oocytes are competent to achieving acceptable pregnancy rate. This study was designed to determine the effect of location of the preovulatory dominant follicle (right or left ovary) on ovulation and pregnancy rates and to evaluate the effect of stage of ovarian follicle development at mating (growing, maintenance, and regression) on ovulation rate and embryo survival in alpacas. In Experiment 1, nonlactating alpacas (4-6 years of age) weighing 55 to 75 kg were rand...
Proceedings of the National Academy of Sciences, 2012
A component in seminal fluid elicits an ovulatory response and has been discovered in every speci... more A component in seminal fluid elicits an ovulatory response and has been discovered in every species examined thus far. The existence of an ovulation-inducing factor (OIF) in seminal plasma has broad implications and evokes questions about identity, tissue sources, mechanism of action, role among species, and clinical relevance in infertility. Most of these questions remain unanswered. The goal of this study was to determine the identity of OIF in support of the hypothesis that it is a single distinct and widely conserved entity. Seminal plasma from llamas and bulls was used as representative of induced and spontaneous ovulators, respectively. A fraction isolated from llama seminal plasma by column chromatography was identified as OIF by eliciting luteinizing hormone (LH) release and ovulation in llamas. MALDI-TOF revealed a molecular mass of 13,221 Da, and 12–23 aa sequences of OIF had homology with human, porcine, bovine, and murine sequences of β nerve growth factor (β-NGF). X-ray...
Journal of Neurovirology, 2008
The replication of herpes simplex virus (HSV) in epithelial cells, and during reactivation from l... more The replication of herpes simplex virus (HSV) in epithelial cells, and during reactivation from latency in sensory neurons, depends on a ubiquitous cellular protein called host cell factor (HCF). The HSV transactivator, VP16, which initiates the viral replicative cycle, binds HCF as do some other cellular proteins. Of these, the neuronal transcription factor Zhangfei suppresses the ability of VP16 to initiate the replicative cycle. It also suppresses Luman, another cellular transcription factor that binds HCF. Interactions of nerve growth factor (NGF) and its receptor tropomyosin-related kinase (trkA) appear to be critical for maintaining HSV latency. Because the neuronal transcription factor Brn3a, which regulates trkA expression, has a motif for binding HCF, we investigated if Zhangfei had an effect on its activity. We found that Brn3a required HCF for activating the trkA promoter and Zhangfei suppressed its activity in non-neuronal cells. However, in neuron-like NGF-differentiated PC12 cells, both Brn3a and Zhangfei activated the trkA promoter and induced the expression of endogenous trkA. In addition, capsaicin, a stressor, which activates HSV in in vitro models of latency, decreased levels of Zhangfei and trkA transcripts in NGF-differentiated PC12 cells.
Journal of Neuro-Oncology, 2008
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Papers by Ximena Valderrama