bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Endotoxin Administration on the Secretory Dynamics of Oxytocin in Follicular Phase Mares: Relationship to Stress Axis Hormones
Authors: Alexander S. L. , Irvine C. H. G. 
Published: March 2003

AbstractThe primary aim of this study was to define the secretory dynamics of oxytocin and vasopressin in pituitary venous effluent from ambulatory horses during acute endotoxaemia, a stimulus that may release both hormones. Our secondary aim was to investigate the role of oxytocin in regulating adrenocorticotropic hormone (ACTH) secretion by comparing oxytocin, vasopressin, corticotropin‐releasing hormone (CRH) and ACTH secretory profiles during endotoxaemia and by monitoring the ACTH response to oxytocin administration. Pituitary venous blood was collected nonsurgically continuously and divided into 1‐min segments from eight follicular phase mares. Four mares were sampled for 30 min before and 3.5 h after receiving an i.v. infusion of bacterial endotoxin (TOX). Four control mares were sampled for 2.5 h without infusion of TOX. Another three follicular phase mares were given 5 U of oxytocin to replicate the peak response to TOX and pituitary blood collected every 1 min for 10 min before and 15 min after injection. Endotoxin raised the secretion rates of all hormones measured. All hormones were released episodically throughout the experiment, with TOX increasing the amplitude of peaks in each hormone. Peaks in oxytocin and vasopressin were coincident in each treated mare. Similarly, ACTH peaks were coincident with peaks of oxytocin and vasopressin in each treated mare, and with peaks of CRH in three mares. However, oxytocin administration did not affect ACTH secretion. We conclude that during endotoxaemia in horses: (i) oxytocin and vasopressin are secreted synchronously; (ii) oxytocin is unlikely to be acting as an ACTH secretagogue since inducing peak oxytocin concentrations observed during TOX does not raise ACTH; and therefore (iii) the close relationship between oxytocin and ACTH secretion is circumstantial and due to the fact that oxytocin secretion is concurrent with that of vasopressin, a proven ACTH secretagogue in horses.
Fasting Stimulates Tuberoinfundibular Dopaminergic Neuronal Activity and Inhibits Prolactin Secretion in Oestrogen‐Primed Ovariectomized Rats: Involvement of Orexin A and Neuropeptide Y
Authors: Hsueh Y.‐C. , Cheng S.‐M. , Pan J.‐T. 
Published: March 2003

AbstractFasting up‐regulates central orexigenic systems including orexin A and neuropeptide Y (NPY) and it also inhibits the secretion of prolactin. We hypothesized that fasting may act through orexin A and NPY to influence tuberoinfundibular dopaminergic (TIDA) neurones, the major regulator of prolactin secretion. The effects of orexin A and NPY on TIDA neuronal activity and prolactin secretion were determined in oestrogen‐primed ovariectomized rats, and the effects of fasting and the involvement of orexin A and NPY were tested. Orexin A, NPY and its analogs were administered through preimplanted intracerebroventricular (i.c.v.) cannulae. TIDA neuronal activity was determined by measuring concentrations of 3,4‐dihydroxyphenylacetic acid (DOPAC) or 3,4‐dihydroxyphenylalanine in the median eminence. i.c.v. injection of NPY (10 µg) or orexin A (1 µg) concomitantly increased median eminence DOPAC and decreased serum prolactin concentrations. The effect of NPY was mimicked by a Y1 receptor agonist at lower doses (0.1 and 1 µg) and no additive effect was observed when orexin A and the Y1 agaonist were coadministered. Moreover, a Y1 receptor antagonist, BIBP, not only blocked the effect of Y1 agaonist, but also that of orexin A. Treatment with BIBP alone decreased median eminence DOPAC and increased serum prolactin concentrations, indicating that endogenous NPY may play a role. Moreover, fasting for 48 h significantly increased TIDA neuronal activity, both in the morning and afternoon, and the effect was reversed by treatment with either BIBP or an antibody against orexin A. The findings support our hypothesis that fasting stimulates TIDA neuronal activity and inhibits prolactin secretion through up‐regulated central orexin A and NPY systems.
A Novel Mechanism for Endocrine‐Disrupting Effects of Polychlorinated Biphenyls: Direct Effects on Gonadotropin‐Releasing Hormone Neurones
Authors: Gore A. C. , Wu T. J. , Oung T. , Lee J. B. , Woller M. J. 
Published: March 2003

AbstractPolychlorinated biphenyls (PCBs) cause abnormal development and physiology of the reproductive system. We hypothesized that these effects may be mediated, at least in part, by neuroendocrine cells in the hypothalamus that integrate inputs to and outputs from the central nervous system and reproductive systems. The effects of two PCB mixtures, Aroclor 1221 and Aroclor 1254, were tested on the hypothalamic GT1‐7 cells, which synthesize and secrete the key hypothalamic hormone, gonadotropin‐releasing hormone (GnRH). GT1‐7 cells were treated for 24 h in dose–response experiments and GnRH gene expression and release were quantified. Aroclor 1221 was stimulatory to GnRH gene expression, particularly at post‐transcriptional levels (GnRH cytoplasmic mRNA), and increased GnRH peptide levels, suggesting a post‐translational regulation of GnRH biosynthesis. It also caused a qualitative increase in GT1‐7 neurite outgrowth and cell confluency. Aroclor 1254 had very different effects from Aroclor 1221. It inhibited GnRH nuclear mRNA levels at high dosages, and stimulated GnRH mRNA at low doses, suggesting a post‐transcriptional mechanism of regulation. Aroclor 1254 did not alter GnRH peptide levels. Qualitatively, Aroclor 1254 caused a retraction of GT1‐7 cell processes and neurotoxicity at high dosages. In order to gauge the involvement of the oestrogen receptor in these responses, the oestrogen receptor antagonist, ICI 182,780 (ICI) was coadministered in other studies with the PCBs. While effects of Aroclor 1221 on GnRH gene expression were not blocked by ICI, its effects on GnRH peptide levels were blocked by ICI, indicating that some but not all of the effects of Aroclor 1221 are mediated by the classical oestrogen receptor α and/or β. The inhibitory effects of Aroclor 1254 on GnRH gene expression were not prevented by ICI, although ICI itself had stimulatory effects on GnRH gene expression that were blocked by cotreatment with Aroclor 1254. These results demonstrate a novel mechanism for effects of the two PCBs directly on GnRH gene expression, and indicate a hypothalamic level for endocrine disruption by these environmental toxicants.
Demonstration of Postsynaptic Receptor Plasticity in an Amphibian Neuroendocrine Interface
Authors: Jenks B. G. , Ouwens D. T. W. M. , Coolen M. W. , Roubos E. W. , Martens G. J. M. 
Published: March 2003

AbstractPituitary pars intermedia melanotrope cells are often used as a model to study mechanisms of neuroendocrine integration. In the amphibian Xenopus laevis, the synthesis and release of α‐melanophore‐stimulating hormone (α‐MSH) from these cells is a dynamic process dependent upon the colour of background. In animals on a black background, there is a higher level of synthesis and secretion of α‐MSH than in animals on a white background, and, consequently, there is skin darkening in animals on a black background. The melanotropes are innervated by hypothalamic neurones that produce neuropeptide Y (NPY), a peptide that inhibits α‐MSH secretion via the NPY Y1 receptor. The inhibitory neurones have a higher expression of NPY in animals adapted to a white background and both the size and the number of inhibitory synapses on the melanotrope cells are enhanced. The purpose of the present study was to determine if this presynaptic plasticity displayed by the inhibitory neurones is reciprocated by postsynaptic plasticity (i.e. if there is an enhanced expression of the Y1 receptor in melanotropes of animals adapted to a white background). For this purpose quantitative real‐time reverse transcriptase‐polymerase chain reaction was used to determine the level of Y1 receptor mRNA in melanotropes of animals undergoing the process of background adaptation. The results showed that there is a higher Y1 receptor mRNA expression in melanotropes of white‐adapted animals. We conclude that the inhibitory neuroendocrine interface in the Xenopus pars intermedia displays postsynaptic plasticity in response to changes of background colour. To our knowledge, this is the first demonstration of a physiological environmental change leading to changes in postsynaptic receptor expression in a fully identified vertebrate neuroendocrine reflex.
Oxytocin Inhibits Aggression in Female Syrian Hamsters
Authors: Harmon A. C. , Huhman K. L. , Moore T. O. , Albers H. E. 
Published: March 2003

AbstractDominant subordinate relationships are formed as the result of social conflict and are maintained at least in part by communication. At this time, little is known about the neural mechanisms that are responsible for coordinating the social behaviours (e.g. aggression) that occur in association with the formation and maintenance of these relationships. The purpose of the present study was to investigate the role of oxytocin (OXT) within the medial preoptic anterior hypothalamic continuum (MPOA‐AH) in the control of aggression in female hamsters. OXT injected into the MPOA‐AH immediately before testing significantly reduced the duration of aggression in a dose‐dependent manner. Injection of an OXT antagonist 30 min before testing significantly increased the duration of aggression. In contrast, the duration of aggression was not altered when hamsters were tested either 30 min after injection of OXT or immediately following injection of an OXT‐antagonist. These data support the hypothesis that OXT release within the MPOA‐AH regulates social behaviours important in the formation and maintenance of dominant subordinate relationships in female hamsters.
Central Administration of Neuropeptide FF Causes Activation of Oxytocin Paraventricular Hypothalamic Neurones That Project to the Brainstem
Authors: Jhamandas J. H. , MacTavish D. 
Published: March 2003

AbstractNeuropeptide FF (NPFF), a morphine modulatory peptide, is emerging as an important neuromodulator in the context of central autonomic and neuroendocrine regulation. NPFF immunoreactivity and receptors have been identified in discrete autonomic regions within the brain and spinal cord, including the hypothalamic paraventricular nucleus (PVN). In this study, we examined the effects of intracerebroventricular (i.c.v.) administration of NPFF on activation of chemically identified PVN neurones that project to the brainstem nucleus of the solitary tract (NTS). In conscious rats, i.c.v. NPFF at a dose of 10 µg, but not 8 µg, caused an increase in arterial blood pressure. Immunohistochemical analysis revealed a dose‐dependent increase in activated (Fos positive) PVN neurones following i.c.v. NPFF administration compared to controls receiving i.c.v. saline. Activated PVN neurones were located predominantly in the parvocellular compartment of the nucleus with relatively few Fos positive cells in the magnocellular subdivision. Chemical identification of activated neurones revealed significant number of activated cells to be oxytocin positive, whereas only few vasopressin, tyrosine hydroxylase (TH) or corticotrophin‐releasing factor (CRF) neurones were double‐labelled. Injection of the retrograde tracer fluorogold into the NTS resulted in labelling of significant numbers of parvocellular oxytocin, but not vasopressin, TH or CRF, PVN neurones. We conclude that centrally administered NPFF stimulates brainstem‐projecting oxytocin PVN neurones. Oxytocin released from terminals within the NTS oxytocin thus modulate the activity of ascending visceral autonomic pathways that synapse initially within the NTS.
Cardiac autonomic nervous system activity during presleep wakefulness and Stage 2 NREM sleep
Authors: Burgess Helen J. , Trinder John , Kim Young 
Published: March 2003

SummaryPrevious research has found that cardiac parasympathetic nervous system (PNS) activity increases and cardiac sympathetic nervous system (SNS) activity decreases during night‐time sleep. This study aimed to examine in greater detail the time course of these changes in cardiac autonomic nervous system (ANS) activity. In the week prior to the experimental night, nine subjects maintained a constant sleep–wake schedule and experienced an adaptation night. Each subject's experimental night consisted of 2 h of presleep wakefulness, followed by a night of sleep, commencing at each subject's normal sleep onset time. One hundred and twenty beat blocks of presleep wakefulness and stable Stage 2 non‐rapid eye movement (NREM) sleep across the night were selected. SNS activity was assessed using pre‐ejection period, the amplitude of the T‐wave in the ECG and the 0.1 Hz peak from the spectral analysis of the ECG. PNS activity was assessed using respiratory sinus arrhythmia (spectral analysis). Heart rate and respiratory rate were also measured. The results indicated a progressive decrease in SNS activity throughout sleep and a rise in PNS activity during the first half of the normal sleep period. The changes in PNS activity were similar, while the changes in SNS activity were altered, compared with a previous study in which stage of sleep was not controlled. This indicates a likely sleep stage influence on SNS activity, but not on cardiac PNS activity. These results are consistent with the concept of a primarily circadian, but not sleep, influence on PNS activity, and primarily a sleep, but not circadian, influence on SNS activity.
Spectral analysis of all‐night human sleep EEG in narcoleptic patients and normal subjects
Authors: Mukai Junko , Uchida Sunao , Miyazaki Shinichi , Nishihara Kyoko , Honda Yutaka 
Published: March 2003

SUMMARYTo investigate the pathophysiology of narcoleptic patients' sleep in detail, we analysed and compared the whole‐night polysomnograms of narcoleptic patients and normal human subjects. Eight drug‐naive narcoleptic patients and eight age‐matched normal volunteers underwent polysomnography (PSG) on two consecutive nights. In addition to conventional visual scoring of the polysomnograms, rapid eye movement (REM)‐density and electroencephalograph (EEG) power spectra analyses were also performed. Sleep onset REM periods and fragmented nocturnal sleep were observed as expected in our narcoleptic patients. In the narcoleptic patients, REM period duration across the night did not show the significant increasing trend that is usually observed in normal subjects. In all narcoleptic patient REM periods, eye movement densities were significantly increased. The power spectra of narcoleptic REM sleep significantly increased between 0.3 and 0.9 Hz and decreased between 1.0 and 5.4 Hz. Further analysis revealed that non‐rapid eye movement (NREM) period duration and the declining trend of delta power density in the narcoleptic patients were not significantly different from the normal subjects. Compared with normal subjects, the power spectra of narcoleptic NREM sleep increased in the 1.0–1.4 Hz and 11.0–11.9 Hz frequency bands, and decreased in a 24.0–26.9 Hz frequency band. Thus, increased EEG delta and decreased beta power densities were commonly observed in both the NREM and REM sleep of the narcoleptic patients, although the decrease in beta power during REM sleep was not statistically significant. Our visual analysis revealed fragmented nocturnal sleep and increased phasic REM components in the narcoleptic patients, which suggest the disturbance of sleep maintenance mechanism(s) and excessive effects of the mechanism(s) underlying eye movement activities during REM sleep in narcolepsy. Spectral analysis revealed significant increases in delta components and decreases in beta components, which suggest decreased activity in central arousal mechanisms. These characteristics lead us to hypothesize that two countervailing mechanisms underlie narcoleptic sleep pathology.
Lidocaine in the horse: its pharmacological effects and their relationship to analytical findings
Authors: Harkins  , Mundy  , Woods  , Lehner  , Karpiesiuk  , Rees  , Dirikolu  , Bass  , Carter  , Boyles  , Tobin  
Published: March 2003

Lidocaine is a local anaesthetic agent that is widely used in equine medicine. It is also an Association of Racing Commissioners International (ARCI) Class 2 foreign substance that may cause regulators to impose substantial penalties if residues are identified in post race urine samples. Therefore, an analytical/pharmacological database was developed for this drug. Using our abaxial sesamoid local anaesthetic model, the highest no‐effect dose (HNED) for the local anaesthetic effect of lidocaine was determined to be 4 mg. Using enzyme‐linked immunosorbent assay (ELISA) screening, administration of the HNED of lidocaine to eight horses yielded peak serum and urine concentrations of apparent lidocaine of 0.84 ng/mL at 30 min and 72.8 ng/mL at 60 min after injection, respectively. These concentrations of apparent lidocaine are readily detectable by routine ELISA screening tests (LIDOCAINE ELISA, Neogen, Lexington, KY). ELISA screening does not specifically identify lidocaine or its metabolites, which include 3‐hydroxylidocaine, dimethylaniline, 4‐hydroxydimethylaniline, monoethylglycinexylidine, 3‐hydroxymonoethylglycinexylidine, and glycinexylidine. As 3‐hydroxylidocaine is the major metabolite recovered from equine urine, it was synthesized, purified and characterized, and a quantitative mass spectrometric method was developed for 3‐hydroxylidocaine as recovered from horse urine. Following subcutaneous (s.c.) injection of the HNED of lidocaine, the concentration of 3‐hydroxylidocaine recovered from urine reached a peak of about 315 ng/mL at 1 h after administration. The mean pH of the 1 h post dosing urine samples was 7.7, and there was no apparent effect of pH on the amount of 3‐hydroxylidocaine recovered. Within the context of these experiments, the data suggests that recovery of less than 315 ng/mL of 3‐hydroxylidocaine from a post race urine sample is unlikely to be associated with a recent local anaesthetic effect of lidocaine. Therefore these data may be of assistance to industry professionals in evaluating the significance of small concentrations of lidocaine or its metabolites in postrace urine samples. It should be noted that the quantitative data are based on analytical methods developed specifically for this study, and that methods used by other laboratories may yield different recoveries of urine 3‐hydroxylidocaine.
Comparative pharmacokinetics of enrofloxacin and ciprofloxacin in chickens
Authors: García Ovando H. , Gorla N. , Luders C. , Poloni G. , Errecalde C. , Prieto G. , Puelles I. 
Published: March 2003

The pharmacokinetics of enrofloxacin (EFX) and ciprofloxacin (CFX) was investigated in broiler chickens. Each antimicrobial was administered intravenously at a dose of 5 mg/kg body weight. Blood was taken in different preset times: prior and at 0.03, 0.06, 0.13, 0.25, 0.5, 1, 2, 4, 8, 12 and 24 h following drug administration. The concentrations of EFX and CFX in plasma were determined by high pressure liquid chromatography (HPLC). Plasma concentrations vs. time were analysed by a compartmental independent pharmacokinetic model that provided the most important kinetic parameters. Statistically significant differences between the two antimicrobials were found for most of the pharmacokinetic parameters: Area under the curve (AUC), area under first moment curve (AUMC), mean residence time (MRT), total body cleareance (ClB), volume of distribution beta (Vd beta) and volume of distribution at the steady state (Vdss). Both antimicrobials were widely distributed in chickens throughout the body with a mean Vdss of 1.98 ± 0.18 L/kg for EFX, and 4.04 ± 0.69 L/kg for CFX. The ClB for CFX was five times higher than that obtained for EFX. AUC, MRT and the diminished half time for EFX were two–four times higher than those obtained for CFX. These results indicate that CFX remains in the body for less time than the other quinolone. This characteristic of CFX suggests the advantage of a shorter withdrawal time for food producing animals treated with this antimicrobial.
Disposition of oxytetracycline in pigs after i.m. administration of two long‐acting formulations
Authors: El Korchi G. , Prats C. , Arboix M. , Pérez B. 
Published: March 2003

El Korchi, G., Prats, C., Arboix, M., Pérez, B. Disposition of oxytetracycline in pigs after i.m. administration of two long‐acting formulations J. vet. Pharmacol. Therap.24, 247–250.Two commercially available long‐acting oxytetracycline (OTC) formulations were administered by the intramuscular (i.m.) route to six healthy pigs at the recommended dose of 30 mg/kg. After 2 h the mean maximum concentration (Cmax) reached values of 8.1 ± 2.2 and 15.4 ± 11.1 μg/mL, respectively. These concentrations remained higher than 0.5 μg/mL for more than 5 days after drug administration. The area under the concentration time curve (AUC09 days) of each formulation was 255 ± 76.5 and 399.2 ± 123 μg · h/mL, respectively, and the mean residence time (MRT) was around 3 days for both formulations. No significant differences were observed between the pharmacokinetic parameters of the two formulations, showing the bioequivalence of the two formulations studied according to the criteria established by the Food and Drug Administration (FDA) and the Committee for Veterinary Medicinal Products (CVMP).
A preliminary survey for changes in urban Fox (Vulpes vulpes) densities in England and Wales, and implications for rabies control
Authors: Wilkinson D. , Smith G. C. 
Published: March 2003

ABSTRACTA questionnaire was sent to 139 councils and 44 local mammal groups in England and Wales, requesting data on changes in urban Red Fox (Vulpes vulpes) densities between 1987 and 1997. Of 152 responses, 41% believed Fox numbers had increased, 42% believed Fox numbers were unchanged and 7% believed Fox numbers had decreased. Most of the increases were perceived to be due to increased food availability, and decreases due to sarcoptic mange (Sarcoptes scabiei). In the event of a rabies outbreak in Britain, the models used to determine control strategies are dependent on having sufficiently up‐to‐date urban Fox density data. This survey suggests that urban Fox density data for Britain should be updated in the near future.
Distribution, status and conservation problems of the Spanish Ibex, Capra pyrenaica (Mammalia: Artiodactyla)†
Authors: Pérez Jesús M. , Granados José E. , Soriguer RamóN C. , Fandos Paulino , Márquez Francisco J. , Crampe Jean P. 
Published: March 2003

ABSTRACTIn this paper, the distribution and status of the Spanish Ibex, Capra pyrenaica (Mammalia: Artiodactyla), are revised. The whole Iberian population numbers nearly 50 000, distributed in more than 50 nuclei, and has generally increased during the last decades. Nevertheless, within this wider context, different conditions apply to different populations, including recent extinction (the Pyrenean population), recovery from recent severe epizooty of sarcoptic mange (e.g. the Sierras de Cazorla and Segura y Las Villas range population) and populations at high densities (e.g. Gredos mountain range and Sierra de Grazalema Natural Park, among others). The main factors affecting the conservation of this species are also reported and discussed. On the basis of current information we propose the status of ‘vulnerable’ for the Spanish Ibex.