Changes In Cortisol Concentrations Research Articles

Changes in cortisol concentration in response to stress and postoperative pain in client-owned cats and correlation with objective clinical variables

Abstract Objective To identify clinical variables that indicate postoperative pain in cats after ovariohysterectomy in a veterinary hospital setting. Animals 40 cats. Procedure Cats were anesthetized and ovariohysterectomized by senior veterinary students. Butorphanol (0.1 mg/kg [n = 20] or 0.3 mg/kg [20] of body weight) was administered IM after surgery. Blood samples were obtained before, during, and after the anesthestic period for measurements of PCV and blood glucose and cortisol concentrations. Clinical variables measured included heart rate, systolic blood pressure, respiratory rate, and rectal temperature. Data for these variables were compared with changes in cortisol concentrations and with similar data—which was used as historical control data— obtained from 20 cats in another study (10 that had been ovariohysterectomized but had not received butorphanol and 10 that had only been anesthetized). Results Surgical durations were longer in this study, and cats had higher cortisol concentrations, compared with historical control cats. Objective clinical variables did not consistently correlate with changes in cortisol concentration. Conclusions Cortisol concentration increased in response to surgical stress and pain. This response was greater in cats in which duration of surgery was longer. Clinical Relevance The objective clinical variables evaluated in this study were not consistent indicators of pain in an uncontrolled, clinical situation. (Am J Vet Res 1999;60:432-436)

Effects of High Rearing Densities and Loading Rates on the Growth and Stress Responses of Juvenile Rainbow Trout

Abstract Growth and changes in serum concentrations of cortisol, glucose, and chloride in response to acute stress challenge tests were compared in juvenile rainbow trout Oncorhynchus mykiss (143–190 mm TL) reared at density indices of 2.8–9.3 g/(L · cm) and loading rates of 0.5 and 0.75 kg/(L · min). In experiment 1, there were no differences in growth or measures of physiological stress in fish reared for 4 weeks at loading rates of 0.5 or 0.75 kg/(L · min). Fish reared at density indices of 5.6 and 8.4 g/(L · cm) gained significantly less weight than fish at a density index of 2.8 g/(L · cm), and fish reared at 2.8 and 5.6 g/(L · cm) had better food conversion rates (weight of food fed/weight gained) than those at 8.4 g/(L · cm). Changes in the serum concentrations of cortisol, glucose, and chloride, however, suggested that the reduced growth at elevated densities was not due to physiological stress. In experiment 2, cortisol levels were higher in fish 3 d after transfer to net-pens than in fish 10 or ...

Heart Rate and Stress Hormone Responses of Sheep to Road Transport Following Two Different Loading Procedures

AbstractThis study was designed to investigate the physiological responses induced in sheep (n = 18) by two different loading techniques followed by a short road journey. All animals were prepared with venous catheters, to minimize the disturbing effects of blood sampling, and nine sheep were fitted with heart rate monitors. The animals were loaded onto a transport vehicle in groups of three, alternately using a conventional tailgate ramp or a crate raised with a hydraulic lift. When all of the sheep were loaded, they were taken on a journey lasting 195min. Blood samples were collected in the home pen, directly after loading, and at 15min intervals during the journey. Measurements were made of plasma concentrations of Cortisol, prolactin and catecholamines (adrenaline and noradrenaline). The results indicated that heart rate increased during loading, regardless of the method used. No changes in concentrations of Cortisol or the catecholamines were detected, although a small increase in prolactin was noted when animals were loaded using the ramp. During transport, all sheep exhibited increases in plasma Cortisol concentrations which were greatest during the first 2h of the journey. The results suggest that, under the conditions employed in this experiment, the effects of the two loading procedures were similar and that transport appeared to be more stressful than loading.

Endocrine Responses to Weaning and Changes in Post-Weaning Diet in the Young Pig

The effects of weaning and changing post-weaning diet composition on growth patterns and growth-related hormonal profiles were evaluated in neonatal pigs. Forty-eight crossbred piglets were assigned to two groups ( n = 24/group) based on weaning at 2 or 3 wk of age (2W and 3W groups, respectively). At weaning, piglets were removed from the sow and placed on a commercial starter ration for the first 11 d post-weaning (Phase I diet). At Day 12 post-weaning, pigs were placed on a growing ration for the remainder of the study (Phase II diet). Body weights and blood samples were collected twice weekly from birth until 42 d of age. Serum insulin-like growth factor (IGF)-1, IGF-2, and average daily gain (ADG) were reduced (P < 0.05) in both groups as a result of weaning, whereas serum growth hormone (GH) was elevated (P < 0.05). Earlier weaning resulted in a greater reduction in growth rate and serum IGF-2 values (P < 0.05). Mild reductions in ADG occurred after the Phase I to II dietary change in both weaning groups (P < 0.05), but serum IGF-1 decreased only in the 2W group (P < 0.05). Growth hormone concentrations tended to increase after the change in post-weaning diets (P = 0.07 and 0.16 in 2W and 3W, respectively). Serum thyroxine (T 4) and triiodothyronine (T 3) levels were unaltered by weaning but declined in both groups after the change in starter diets (P < 0.05). Changes in cortisol concentrations were not associated with weaning or the change in post-weaning diets. With the exception of serum IGF-1 concentrations, which were elevated in the 2W group, growth and endocrine endpoints were equivalent between experimental groups at the end of the study (42 d of age). These results indicate that earlier weaning and changing solid diets can more severely affect patterns of early growth and related hormone secretion, but effective compensatory mechanisms restore normal physiological and physical development.

INFLUENCE OF WEIGHT TRAINING EXERCISE AND MODIFICATION OF HORMONAL RESPONSE ON SKELETAL MUSCLE GROWTH

1288 Skeletal muscle growth is influenced by a number of physiological factors such as hormonal action, nutrient supply, and level of contractile activity. Previous research has demonstrated that the consumption of a CHO solution during weight lifting exercise can modify the response of several hormones known to regulate protein. The purpose of this study was to determine if the chronic alteration of the acute hormonal response associated with CHO ingestion would positively impact the skeletal muscle hypertrophic adaptation. Two groups of young men (21.3 ± 1.5-y) engaged in 12 weeks of progressive resistance weight training exercise. Training for one group included the ingestion of a non-caloric placebo beverage (Ex+Pl), and the other, a 6% CHO solution (Ex+CHO) - each at a quantity of 8.5-ml·kg body wt. The hormonal response to exercise was monitored during weeks 1, 6, and 12, as determined by RIA, while muscle growth was determined from differences in pre and post training muscle fiber area as calculated from biopsy samples obtained from the vastus lateralis. Throughout the twelve weeks of training, the Ex+CHO treatment group continued to display a non-significant change in cortisol concentration (pre to post to exercise). This is in contrast to significantly elevated levels (post exercise) observed for the Ex+Pl control group. Corresponding with these response patterns were differences in muscle growth. Weight training exercise with CHO ingestion resulted in significantly greater gains in both type I (1201 ± 195μm2 compared to 26 ± 393 μm2) and type II (1251± 277 μm2 compared to -286 ± 432 μm2) muscle fiber area than weight training exercise alone. The differences in cortisol release accounted for 73.5% of the variance (r = 0.8579, P = 0.006) in change of type I muscle fiber area, and 52.3% of the variance (r = 0.7231, P = 0.043) in change of type II muscle fiber area. These findings suggest that the modification of the hormonal response associated with CHO ingestion can positively impact the skeletal muscle hypertrophic adaptation.

Effects of Early and Late Nocturnal Sleep on Declarative and Procedural Memory

Recall of paired-associate lists (declarative memory) and mirror-tracing skills (procedural memory) was assessed after retention intervals defined over early and late nocturnal sleep. In addition, effects of sleep on recall were compared with those of early and late retention intervals filled with wakefulness. Twenty healthy men served as subjects. Saliva cortisol concentrations were determined before and after the retention intervals to determine pituitary-adrenal secretory activity. Sleep was determined somnopolygraphically. Sleep generally enhanced recall when compared with the effects of corresponding retention intervals of wakefulness. The benefit from sleep on recall depended on the phase of sleep and on the type of memory: Recall of paired-associate lists improved more during early sleep, and recall of mirror-tracing skills improved more during late sleep. The effects may reflect different influences of slow wave sleep (SWS) and rapid eye movement (REM) sleep since time in SWS was 5 times longer during the early than late sleep retention interval, and time in REM sleep was twice as long during late than early sleep (p < 0.005). Changes in cortisol concentrations, which independently of sleep and wakefulness were lower during early retention intervals than late ones, cannot account for the effects of sleep on memory. The experiments for the first time dissociate specific effects of early and late sleep on two principal types of memory, declarative and procedural, in humans.

Validation and application of solid-phase chemiluminescent immunoassays for diagnosis of endocrine diseases in animals

Significant progress has been made in the ability of veterinarians to diagnose endocrine diseases since introduction and development of the radioimmunoassay (RIA) in the 1960s. Alternatives to the radioactive label have been commercialised for human diagnostic applications. Because healthy animals have concentrations of several hormones in serum that are lower than in humans, these non-isotopic assays generally lack the sensitivity for measuring hormones in animals. However, the chemiluminescent enzyme immunoassay may provide this needed sensitivity. We validated the DPC-Cirrus Immulite® automated chemiluminescent immunoassay system for measurement of cortisol in dogs, cats and horses. Serial dilutions of serum inhibited binding of alkaline phosphatase-labelled cortisol in a manner that was parallel with inhibition produced by the stored master calibration curve. Six dogs were injected with adrenocorticotropin (ACTH; 2.2 IU/kg i.m.) and five dogs were injected with dexamethasone (0.015 mg/kg i.v.). Changes in cortisol concentrations measured with the Immulite® were as expected based on published results. Similar tests of biological specificity in other species yielded similar results. Accuracy of the Immulite® cortisol assay was evaluated by comparing cortisol concentrations in serum with concentrations obtained by a validated RIA. The regression equations were: y = 14.6 + 0.8χ for dogs (n = 59, r2 = 0.91), y = 13.5 + 0.9χ for horses (n = 23, r2 = 0.90), and y = 29.8 + 1. Oχ for cats (n = 18, r2 = 0.96), where y = Immulite® result (nmol/l) and χ = RIA result (nmol/l). The regression equation for the canine urinary cortisol: creatinine ratio was y = 0.43 + 1.55χ, where y = ratio calculated from Immulite® cortisol concentrations and χ = ratio using RIA concentrations (n = 35, r2 = 0.93). Initially, the lower limit of the reportable range by the Immulite® was 27.6 nmol/l, a value that was unacceptable for veterinary diagnostics. After consultation with DPC-Cirrus, we adjusted the lower limit to 1.4 nmol/l. Coefficients of variation for two canine, one feline, and two equine quality-control serum samples included in 73 consecutive Immulite® assays ranged from 0.29 (mean = 29.0 nmol/l) to 0.09 (mean = 261.6 nmol/l). We are using the Immulite® routinely for the diagnosis of adrenal disease in animals and have found it to provide diagnostically useful cortisol results for dexamethasone-suppression and ACTH-stimulation tests. Its diagnostic accuracy on single baseline samples is probably less than for the RIA, particularly at concentrations of cortisol less than 27.6 nmol/l.

An investigation into the socioendocrinology of infant care and postpartum fertility in Goeldi’s monkey (Callimico goeldii)

We investigated the existence of interaction between the major behavioral and endocrine events that occur in breeding pairs of Callimicoduring the postpartum period: the reduction in maternal care, the onset of maternal aggression, the onset of paternal care, and the resumption of female fertility. While the frequency of nursing remained constant throughout the 6-week observation period, decreasing amount of time spent nursing generally preceded the onset of paternal carriage. Decreasing nursing duration was not associated with the occurrence of postpartum ovulation. Some mothers frequently acted aggressively toward the infant during the period of first mother-to-father transfer of the infant, while other mothers did not. There is no correlation between the interval to the first transfer and the period to postpartum ovulation. We validated urinary cortisol as a measure of stress and defined the duration of its poststress elevation as approximately 3 hr. There is no consistent relationship between female behavior and endocrine state, or male cortisol values and the onset of infant carrying by fathers. During the peritransfer phase, no significant change in cortisol concentration occurred, while the pre-, peri-, and postovulatory phases appeared to be reflected in urinary cortisol output by some males. Based on these results, we propose an explanatory model for the causal dynamics of infant care in pairs of Callimico.The model stresses the importance of a high reproductive rate to male and female reproductive strategies.

Cortisol, progesterone and β-endorphin response to stress in calves

In evaluating stress in farm animals, it would be useful to know whether there were consistent endocrine responses that could be followed. Adrenal cortisol secretion is quite variable, but β-endorphin secretion and adrenal progesterone production may be useful indicators of stress. Changes in plasma concentrations of cortisol, β-endorphin and progesterone were studied in spring-born, castrated male calves (steers) (6 mo of age ± 18 d, 516 ± 26 kg, n = 12) subjected to the stress of routine dehorning. Steers were isolated from their dams for 2 h before headgate restraint (control) or restraint and dehorning. They were bled 60 and 10 min prior to headgate restraint or restraint and dehorning. Blood samples were also collected immediately after headgate restraint or restraint and dehorning (time 0) and 5, 10, 30 and 60 min later. All blood samples were taken from a jugular catheter, and the blood sampling that was done out of the headgate involved minimal manual restraint. Plasma β-endorphin concentrations were similar in control steers and dehorned steers (P &gt; 0.05) and decreased significantly following restraint or restraint and dehorning (P &lt; 0.05). Plasma cortisol concentrations rose significantly 5 min after dehorning and were elevated for 60 min; but with restraint only, plasma cortisol concentrations rose to a peak 5 min after release from chute restraint and then declined (P &lt; 0.05). Plasma cortisol concentrations were greater in dehorned steers than in control steers in the period from 10 min after dehorning or headgate restraint to 60 min after headgate restraint (P &lt; 0.0043). Plasma progesterone concentrations rose to a peak 10 min after dehorning and then declined, but in control steers, a peak was seen at 5 min after release from restraint (P &lt; 0.05). Plasma progesterone concentrations were greater in dehorned steers between 5 and 60 min after dehorning than in control steers (P &lt; 0.05). From these data, we concluded that in prepubertal, castrated male calves, β-endorphin was not released in any significant quantities in response to the stress of dehorning. In steers, adrenal cortisol and progesterone were secreted in response to acute stress, and a ratio of the two may provide a useful assessment of stress; this requires further study. Key words: Cortisol, progesterone, β-endorphin, stress, calves

Transport-induced stress responses in fed and fasted donkeys

Plasma endocrine and metabolic responses to transport for 30 minutes and four hours were investigated in six fed donkeys. In the unstressed animals there was a pulsatile secretion of cortisol at two-hour intervals, from minima of 51·4 ± 17·6 nmol litre −1 to maxima of 1600 ± 11·0 nmol litre −1, but during transport this pulsatility was lost and the animals' stress response was characterised by steady high concentrations of 110 to 220 nmol litre −1. The cortisol concentration decreased after the journey and remained at a minimum until the restoration of pulsatile secretion 8·5 to 10·5 hours later. The transport-induced adrenocortical response did not produce any significant changes in the plasma concentrations of triglycerides, cholesterol, glucose, total protein, albumin, globulin or urea. The donkeys' responses to transport for four hours were also investigated after they had been deprived of food for one or three days. Food deprivation alone increased plasma cortisol and triglyceride concentrations, and decreased glucose and insulin concentrations, and transport consistently, and feeding after the journey sometimes, accentuated their adrenocortical function; the changes in cortisol concentrations as a result of the journey tended to be lower than in the fed animals. Transport had no effect upon the triglyceride response to either period of fasting. Hyperglycaemia was induced by transport in four of the six donkeys fasted for one day and in all of them after three days of fasting.

The effect of breeding facility and sexual stimulation on plasma cortisol in boars.

Nine boars were used to evaluate effects of breeding facility design and sexual activity on plasma cortisol concentrations . In one breeding facility (conventional), boars were housed individually in small pens, and female pigs were mated in those boar pens. In another breeding facility (Detection-Mating Area [DMA] system), boars were housed individually in stalls, and female pigs were mated in a specific mating pen adjacent to the front of stalls where boars were housed. After 51 d of housing treatment, a catheter was surgically implanted in the cephalic vein for collection of blood samples. Daytime profiles (hourly collections from 0900 to 1700) of cortisol did not differ among boars in the two treatment groups. Cortisol was greater (P < .01) in the morning than in the afternoon. Administration of ACTH increased (P < .001) plasma cortisol in boars, but breeding facility did not affect the ACTH-induced changes in cortisol concentrations. There was a treatment x time interaction (P < .02) for cortisol after sexual stimulation, and the magnitude and duration of increase in cortisol were greater (P < .05) in the DMA treatment group. Cortisol was greater (P < .001) after than before mating for both treatment groups. An acute increase in plasma cortisol concentration in boars seems to be a normal biological response to sexual activity. However, magnitude and duration of the increase in cortisol may be influenced by breeding facility design and mating procedure. There is no evidence, based on physiological data, that housing boars in stalls in the DMA system has any adverse effects on their welfare.

Manipulation of substrate utilization with somatostatin in patients with secondary multiple organ dysfunction syndrome

To determine whether glucose utilization and metabolic substrate (glucose and fat) oxidation could be manipulated in patients with secondary multiple organ dysfunction syndrome. Prospective study. Intensive care units (ICU) of two university hospitals. Eight adults free of hepatic disease and hemodynamically stable at the time of study, but with failed respiratory and gastrointestinal systems, who thus required mechanical ventilation and intravenous nutrition. Patients were infused with 20% dextrose through central venous cannulas at rates that increased and maintained (clamped) their plasma glucose concentration at 216 mg/dL (12 mmol/L) for 3 hrs. Somatostatin was infused continuously during the second and third hours of the clamp to reduce plasma concentrations of endogenous insulin and glucagon. Exogenous insulin was administered together with somatostatin during the third hour to restore basal insulin concentrations. Energy expenditure was measured by indirect calorimetry throughout the study and blood samples were withdrawn regularly for determination of metabolite and hormone concentrations. Main statistical comparisons were made between the baseline data (first hour of the study) and data collected during the second and third hours of the clamp. Plasma glucagon concentrations were reduced by nearly 50% (p < .05) toward the end of the study, whereas no significant changes in plasma concentrations of cortisol or growth hormone occurred. Energy expenditure did not change significantly at any time during the clamp procedure. Glucose utilization (6.1 mg/kg/min [34 mumol/kg/min]) during the first hour of the hyperglycemic clamp, decreased by 53% (p < .05) with the infusion of somatostatin during the second hour of the clamp. However, once exogenous insulin was infused during the third hour, glucose utilization increased by 55% (p < .05) when compared with the baseline (hour 1) rate. Glucose oxidation was nearly doubled during the third hour of the study when compared with oxidation rates during the first and second hours. Fat oxidation decreased steadily during the 3-hr clamp. Glucagon has a significant inhibitory effect on glucose utilization during intravenous glucose infusion in the multiple organ dysfunction syndrome patient. Pharmacologic intervention with somatostatin and insulin (physiologic dose) can facilitate glucose utilization and oxidation in these patients. Further investigations are needed to determine whether long-term alteration of glucose and fat metabolism would be beneficial in the patient with secondary multiple organ dysfunction syndrome.

Lipopolysaccharide-induced increases in porcine serum cortisol and progesterone concentrations are not mediated solely by prostaglandin F2?

The increase in steroid hormone blood levels in response to bacterial lipopolysaccharide (LPS) appears to be an important mechanism by which mammalian species regulate inflammation. This study examined changes in serum concentrations of cortisol, progesterone, and 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) in diestrous pigs following the intravenous injection of LPS and determined whether indomethacin would attenuate these changes. Serum cortisol and progesterone concentrations increased (P < 0.05) within 30 min after the administration of LPS, and the increases in steroid hormones were accompanied by a sharp, transient increase (P < 0.05) in PGFM levels. In the presence of indomethacin, serum PGFM levels did not change (P > 0.05); however, LPS enhanced (P < 0.05) cortisol and progesterone concentrations, although the increases were delayed. Serum concentrations of cortisol acutely increased (P < 0.05) immediately following both infusions of indomethacin. In summary, cortisol and progesterone concentrations increased irrespective of serum PGFM concentrations, thereby indicating that prostaglandin F2 alpha was not the sole mediator of LPS-induced changes in cortisol and progesterone concentrations.

Changes in Cortisol Dynamics in Wild and Hatchery-Reared Juvenile Coho Salmon (Oncorhynchus kisutch) During Smoltification

Cortisol dynamics were examined in hatchery and wild juvenile coho salmon (Oncorhynchus kisutch) over the spring of 1991 and 1992 when the fish were smolting. Wild fish were caught in the upper Quinsam River, British Columbia and at the downstream enumeration fence when they started to migrate. Two groups of hatchery fish were from the top and bottom ends of an earthen rearing channel. Plasma cortisol levels increased during the spring in all groups, but were significantly greater in wild than in hatchery smolts. The half-life of plasma cortisol decreased as fish smolted; however, there was no difference among the groups. Corticosteroid receptor (CR) concentration and affinity decreased during the spring. Wild fish consistently possessed the greatest gill concentration of CR. The change in dissociation constant (kD) was similar for hatchery and wild fish during spring 1991. In 1992, hatchery fish showed a similar gradual increase. In contrast, wild fish did not show an increase in kD until May. The changes in cortisol concentration in the plasma and the CR kD occurred synchronously with the increase in Na+K+ATPase activity in wild fish, which showed the greatest increase in kD, plasma cortisol, and Na+K+ATPase activity.

Pharmacodynamic interpretation of adrenocorticotropin stimulation tests.

To report a pharmacodynamic model that describes increases in cortisol concentrations during administration of an adrenocorticotropin (ACTH) infusion, taking into account both steroid secretion and elimination. Previously published data. Using a population estimate of the elimination rate constant for cortisol and equations describing changes in cortisol concentration versus time, a value for the rate of cortisol secretion (Rcort) was derived. The Rcort value more directly represents the capacity for adrenal secretion of cortisol. Pharmacodynamic modeling techniques were used to successfully describe the rate of cortisol secretion during an ACTH infusion. This model can be applied to assess the extent of adrenal suppression after long-term corticosteroid therapy or in the presence of disease states.

Cortisol reactivity and anxiety and depression in pregnant adolescents: A longitudinal perspective

The purpose of this investigation was to examine: (1) the relations among cortisol reactivity (short term changes in cortisol concentration) and anxiety and depression symptoms in adolescent during pregnancy and early postpartum, and (2) cortisol reactivity and psychosocial variables as predictors of anxiety and depression symptoms in pregnancy and early postpartum. Cortisol reactivity, an index of hypothalamic-pituitary-adrenal activity, was hypothesized to be a vulnerability factor for poor physical and mental health outcomes in adolescents. Forty adolescents aged 14 to 19 years ( M = 17.3, SD = 1.3) were enrolled in the study and were seen at <20 weeks gestation (T1), 34–36 weeks gestation (T2), and 2–3 weeks postpartum (T3). Blood was drawn for cortisol at T1 and T3. Psychological assessments of anxiety and depression symptoms, life optimism, and self-worth were administered at T1, T2, and T3. There were significant correlations among cortisol reactivity and anxiety and depression symptoms at T1 and T3, but the correlations were the reverse of the hypothesized direction. Pregnant adolescents with increased cortisol reactivity and anxiety and depression symptoms at T1 and T3, but the correlations were the reverse of the hypothesized direction. Pregnant adolescents with increased cortisol reactivity (cortisol concentrations that increased across a 40-min period) had fewer symptoms of anxiety and depression than other adolescents. Longitudinal analyses showed that anxiety and depression symptoms at T1 were a stronger predictor of postpartum anxiety and depression than was cortisol reactivity, life optimism, self-worth, or age at pregnancy.

Changes in whole body concentrations of cortisol, thyroid hormones, and sex steroids during early development of the chum salmon, Oncorhynchus keta

Significant amounts of cortisol (20 ng/g) and thyroid hormones thyroxine (T 4, 20 ng/g) and triiodothyronine (T 3, 10 ng/g), as well as estradiol (8 ng/g) and testosterone (4 ng/g), are present in fertilized eggs of chum salmon. Changes in the concentrations of these hormones in the developing embryo and larvae were monitored until after the emergence of the fry from the gravel bed. Cortisol concentrations in the developing embryo fell steadily from 20 ng/g at fertilization to 2.5 ng/g after 3 weeks, increased slightly to 10 ng/g by 1 week before hatching, and maintained this level during the early stages of yolk sac absorption. During the later stages of yolk sac absorption, cortisol concentrations increased markedly and remained at about 30 ng/g until emergence, when they declined to 10–15 ng/g. In contrast, both T 4 and T 3 levels were stable during early development, decreased gradually during yolk sac absorption, and increased slightly during emergence. Estradiol and testosterone profiles were similar to that of cortisol during early development. Testosterone levels remained low throughout emergence. Likewise, estradiol levels were low during yolk sac absorption but showed a transient increase at the time of emergence. These hormonal changes are discussed in the context of egg development and subsequent downstream migration.

Effects of repeated handling on the cortisol responses of young lambs castrated and tailed surgically

Changes in the plasma concentrations of cortisol were recorded in 5-6 weeks-old lambs during the first 480 minutes after surgical castration and tailing in order to define the full post-treatment cortisol response and to determine whether or not the handling associated with repeated blood sampling delayed the return of cortisol concentrations to pretreatment values. Four groups of six or seven lambs were studied: One group was bled regularly throughout the 480 minutes of the study, and in the other three post-treatment blood sampling began at 90, 240 or 480 minutes. Plasma cortisol concentrations increased after treatment and returned to or approached pretreatment values by 480 minutes. No significant differences in mean cortisol concentrations were observed between the groups at any stage. It is concluded that the acute distress response of these lambs to surgical castration and tailing lasted about 8 hours and that repeated handling for blood sampling did not contribute significantly to this distress.

Changes in concentrations of cortisol, dehydroepiandrosterone sulphate and progesterone in fetal and maternal serum during pregnancy

In fetuses, adrenal steroids have been implicated in organ maturation and in some species in initiation of labour. The fetal adrenal gland differs from the adult in its complement of steroid metabolizing enzymes. This study sought to examine the changes in peripheral cortisol, progesterone and dehydroepiandrosterone sulphate (DHEAS) in unstressed fetuses during pregnancy. Paired maternal and fetal samples were collected from 47 patients. Fetal blood samples were collected by transabdominal needling. All fetuses were appropriately grown for age which ranged from 18 to 41 weeks. Hormones were measured using specific, validated immunoassays. Fetal progesterone (mean, 822 nmol/l; 95% data intervals 196-1449 nmol/l) varied considerably between individuals but there was no significant change in serum concentration with gestational age, nor was there any difference between male and female fetuses. There was a small, but significant (y = 0.339x2 - 13.5x + 231; r = 0.72, P = 0.0001) rise in cortisol in the fetal circulation from 32 to 41 weeks gestational age, whereas the mean fetal DHEAS concentration decreased linearly with gestational age from 4.1 mumol/l at 18 weeks to 2.6 mumol/l at 41 weeks (r = -0.41; P = 0.007). Mean progesterone concentration in the maternal serum increased linearly from 98 nmol/l at 18 weeks to 783 nmol/l at 41 weeks. In the fetus there was a significant correlation between progesterone and cortisol concentrations. These results are compatible with the proposed role of cortisol in fetal lung maturation, confirm high levels of progesterone in the fetus from an early stage of gestation, and provide further evidence for placental progesterone being the precursor of fetal cortisol.

Central and peripheral doses of cholecystokinin that inhibit feeding in pigs also stimulate vasopressin and cortisol release

The effects on vasopressin and cortisol secretion of centrally and peripherally administered cholecystokinin octapeptide (CCK) were investigated in conscious prepubertal pigs. Injection of 1.3 micrograms CCK into the lateral cerebral ventricle resulted in a sustained increase in plasma vasopressin after a latency of 5 min but no change in cortisol concentrations. Intravenous injection of 0.7 and 1.3 micrograms/kg CCK initiated a rapid surge (within 2 min) in plasma vasopressin and a later increase in cortisol secretion. The time course of the vasopressin response to the central injection of CCK was found to be similar to the period of behavioural inhibition induced when an equivalent dose of the peptide was given by the same route in an earlier feeding experiment. An analogous situation was also observed when CCK was given peripherally and, in this case, the threshold dose at which the behavioural and endocrine responses were induced was found to be the same.