A simple device for serial blood collection in human subjects and animals

Influence of training on plasma adrenaline and noradrenaline kinetics in untrained standardbreds

REASONS FOR PERFORMING STUDY

Catecholamines (CAT) play an important role in modulating the response to exercise. But the kinetics of CAT changes during exercise are difficult to study due to their short biological half-life.

OBJECTIVES

Learning about variations in plasma CAT levels during training could furnish new information regarding sweating, redistribution of blood flow and energy metabolism.

METHODS

Four untrained Standardbreds, adapted to treadmill work, were used to determine the influence of training on plasma adrenaline (A) and noradrenaline (NA) kinetics. Horses underwent a standardised exercise test (SET) on treadmill before (SET1), and 1 (SET2) and 2 months after (SET3) the start of a moderate training period on treadmill. The SET procedure was: warm-up and a single step of 2 min at 200 beats/min heart rate (SS). The automatic blood collection system (that has been carried out during SS) and the preparation of the horses have been described previously. The system was programmed to obtain a blood sample every 15 sec (8 blood samples per SS). Analyses were performed by HPLC. Training progress was monitored by means of anaerobic threshold velocity (V4) and the velocity during SS (V200). Wilcoxon's test was used for statistical analysis.

RESULTS

Decreased levels of A and NA with significant differences between SET1/SET2 and SET1/SET3 for A (P = 0.007) and NA (P = 0.007) were found. There were no differences between SET2 and SET3 for A (P = 0.195) and NA (P = 0.054).

CONCLUSIONS

Training appears to influence the level of plasma CAT and this influence is greater during the first training period in untrained Standardbreds.

POTENTIAL RELEVANCE

It may prove interesting to associate the study of training-induced modifications of the concentration of plasma CAT with thermoregulation, which is under catecholaminergic control and undergoes important adaptations during training.

Membrane initiated steroid signaling (MISS): computational, in vitro and in vivo evidence for a plasma membrane protein initially involved in genomic steroid hormone effects

Steroid hormones are indispensable for control of vital processes, development, reproduction and modulation of behavior. Lack or complete dysfunction of glucocorticoid (GC) signaling, in particular, have lethal consequences. Even a minor change in the level of circulating cortisol can be of physiological and clinical significance. Analysis of the action mechanisms of GC is therefore of major importance, especially since natural and synthetic GC are widely used in the therapy of GC-responsive diseases. According to the classical genomic concept of steroid hormone action, the effects of GC are mediated by specific nuclear receptors (GR). Recent findings provide evidence for the existence of additional, plasma membrane (PM) located steroid receptors, which are thought to be responsible for rapid, non-genomic responses. We present evidence for a PM-residing protein, termed "steroid hormone recognition and effector complex" (SHREC), which plays a pivotal role in the complex network of PM-related non-genomic responses leading to GR-mediated genomic effects. This conclusion was drawn from studies using different in vitro and in vivo models of a GC-target: (1) highly purified fractions of osmotically active PM-vesicles isolated from rat and human hepatocytes, (2) a computational model of SHREC generated by the "automated receptor modeling" (ARM) method, (3) rat liver cell lines transfected with a GC-responsive reporter gene construct and (4) young women orally administered with selected steroids. We conclude that SHREC and the GR participate in the same signaling chain, SHREC<-->steroid interaction is the initial step and an interdependent part of the complete GC signal propagation, thus called "membrane initiated steroid signaling" (MISS).

Insulin secretion in women who have polycystic ovary syndrome and carry the Gly972Arg variant of insulin receptor substrate-1 in response to a high-glycemic or low-glycemic carbohydrate load

OBJECTIVE

We evaluated metabolic parameters in Chilean women with polycystic ovary syndrome (PCOS) who were carriers and non-carriers of the glycine-to-arginine substitution at codon 972 (Gly972Arg) variant of insulin receptor substrate-1 and to assess insulin response after oral high- and low-glycemic loads

METHODS

In 146 women with PCOS and 97 healthy women (HW), Gly972Arg genotypes were obtained by polymerase chain reaction, and an oral glucose tolerance test was performed with glucose and insulin measurements. An insulinogenic index, a homeostasis model assessment for insulin resistance, and whole-body insulin sensitivity index (composite) were calculated. Eight carriers and eight non-carriers (four PCOS and four HW, respectively) underwent a 50-g glucose (high glycemic) or 50-g fructose (low glycemic) load with serum glucose and insulin measurements at 15-min intervals for 3 h.

RESULTS

The frequency of the Gly972Arg variant was higher in PCOS patients than in HW (P < 0.05). The insulinogenic index was lower in HW carriers than in non-carriers (P < 0.05). In PCOS carriers, 2-h insulin was higher than in those without the mutation. In overweight PCOS carriers, the homeostasis model assessment for insulin resistance was higher and the insulin sensitivity index was lower than in PCOS patients without the mutation. In HW carriers, a delay in the maximal response of insulin secretion was observed, with a decrease of 26.7% in insulin concentrations 30 to 60 min after the 50-g glucose load. Glucose concentrations increased by 19.7% between 60 and 120 min. Glucose concentrations between 0 and 120 min were 14.9% higher in PCOS carriers than in non-carriers after the 50-g glucose load.

CONCLUSIONS

In HW, this polymorphism appears to be associated with a decrease in insulin secretion; in PCOS women, this polymorphism interacts with obesity to influence insulin resistance, thus contributing to the pathogenesis of the metabolic component of PCOS.

Application of a constant blood withdrawal method in equine exercise physiology studies

The aim of the present study was to test a constant blood withdrawal method (CBWM) to collect blood samples from horses during treadmill exercise. CBWM was performed in 4 Standardbreds and 5 Haflinger horses. A peristaltic pump was used to control blood aspiration from an i.v. catheter via an extension line. Blood was collected using an automatic fractions collector, with a constant delay time between the drawing of blood and sample collection. Blood withdrawal using CBWM was made during a treadmill standardised exercise test (SET). A blood flow of 12 m/min was used and samples collected every 60 s during the entire period of exercise. The volume of blood collected in each sample tube was 12.1+/-0.2 ml, with a delay time of mean +/- s.d. 25.3+/-0.8 s. Plasma lactate kinetics based on measurement of lactate in each fraction showed an exponential increase during the first 13 min of exercise (10.5 min of SET and 2.5 min recovery). The peak plasma lactate concentration was observed between 2.5 and 5.5 min after the end of SET. CBWM permits the kinetics of lactate and other blood-borne variables to be studied over time. This method could be a valuable aid for use in studying equine exercise physiology.

Glucagon-like peptide 1 increases secretory burst mass of pulsatile insulin secretion in patients with type 2 diabetes and impaired glucose tolerance

The insulinotropic gut hormone glucagon-like peptide (GLP)-1 increases secretory burst mass and the amplitude of pulsatile insulin secretion in healthy volunteers without affecting burst frequency. Effects of GLP-1 on secretory mechanisms in type 2 diabetic patients and subjects with impaired glucose tolerance (IGT) known to have impaired pulsatile release of insulin have not yet been studied. Eight type 2 diabetic patients (64+/-9 years, BMI 28.9+/-7.2 kg/m2, HbA1c 7.7+/-1.3%) and eight subjects with IGT (63+/-10 years, BMI 31.7+/-6.4 kg/m2, HbA1c 5.7+/-0.4) were studied on separate occasions in the fasting state during the continued administration of exogenous GLP-1 (1.2 pmol x kg(-1) x min(-1), started at 10:00 P.M. the evening before) or placebo. For comparison, eight healthy volunteers (62+/-7 years, BMI 27.7+/-4.8 kg/m2, HbA1c 5.4+/-0.5) were studied only with placebo. Blood was sampled continuously over 60 min (roller-pump) in 1-min fractions for the measurement of plasma glucose and insulin. Pulsatile insulin secretion was characterized by deconvolution, autocorrelation, and spectral analysis and by estimating the degree of randomness (approximate entropy). In type 2 diabetic patients, exogenous GLP-1 at approximately 90 pmol/l improved plasma glucose concentrations (6.4+/-2.1 mmol/l vs. placebo 9.8+/-4.1 mmol/l, P = 0.0005) and significantly increased mean insulin burst mass (by 68%, P = 0.007) and amplitude (by 59%, P = 0.006; deconvolution analysis). In IGT subjects, burst mass was increased by 45% (P = 0.019) and amplitude by 38% (P = 0.02). By deconvolution analysis, insulin secretory burst frequency was not affected by GLP-1 in either type 2 diabetic patients (P = 0.15) or IGT subjects (P = 0.76). However, by both autocorrelation and spectral analysis, GLP-1 prolonged the period (lag time) between subsequent maxima of insulin concentrations significantly from approximately 9 to approximately 13 min in both type 2 diabetic patients and IGT subjects. Under placebo conditions, parameters of pulsatile insulin secretion were similar in normal subjects, type 2 diabetic patients, and IGT subjects based on all methodological approaches (P > 0.05). In conclusion, intravenous GLP-1 reduces plasma glucose in type 2 diabetic patients and improves the oscillatory secretion pattern by amplifying insulin secretory burst mass, whereas the oscillatory period determined by autocorrelation and spectral analysis is significantly prolonged. This was not the case for the interpulse interval determined by deconvolution. Together, these results suggest a normalization of the pulsatile pattern of insulin secretion by GLP-1, which supports the future therapeutic use of GLP-1-derived agents.

Episodic leptin release is independent of luteinizing hormone secretion

Several studies suggest that leptin modulates hypothalamic-pituitary-gonadal axis functions. Leptin may stimulate release of gonadotrophin releasing hormone (GnRH) from the hypothalamus and of gonadotrophins from the pituitary. A synchronicity of luteinizing hormone (LH) and leptin pulses has been described in healthy women and in patients with polycystic ovarian syndrome, suggesting that leptin may modulate the episodic secretion of LH. However, it has not been established whether LH regulates the episodic secretion of leptin. To further examine LH-leptin interactions, we studied the episodic fluctuations of circulating LH and leptin in two patients with Kallmann's syndrome (KS) before and on day 7 of pulsatile GnRH administration, and compared these with those observed in the early follicular phase of 10 regularly menstruating women divided into two control groups according to the body mass index of each patient. To assess episodic hormone secretion, blood samples were collected at 10 min intervals for 6 h, before and on day 7 of GnRH administration in KS patients, and during days 3-7 of the follicular phase in normally cycling women. LH and leptin concentrations were measured in all samples. For pulse analysis, the cluster algorithm was used. Before treatment, an apulsatile pattern with no endogenous LH pulsations was observed in both KS patients. However, leptin pulses were assessed in both women. During GnRH administration, pulsatile LH activity was achieved in both patients with pulse characteristics similar to those of the respective control group. Serum leptin concentrations and leptin pulsatile patterns were not modified. These results suggest that circulating leptin is probably not modulated by pulsatile GnRH-LH secretion.

Clinical pathology and sample collection in the laboratory rodent

Common laboratory rodents have always been a favorite choice as a pet. Although diagnostic clinical pathology has not been viewed as practical for the rodent patient, current advances in technology make processing of small samples possible. Cultivation of the technical skills necessary for rodent sample collection has the potential to improve the standard of rodent veterinary care. This article provides an overview of rodent sample collection techniques, hematology, clinical biochemistry, serology, and clinical pathology of other tissues and fluids for laboratory rodents. General principles of clinical pathology can be applied across species. This article emphasizes the subtleties of the different rodent species which may impact diagnostic interpretation.

Are circulating leptin and luteinizing hormone synchronized in patients with polycystic ovary syndrome?

Animal and human studies suggest that leptin modulates hypothalamic-pituitary-gonadal axis functions. Leptin may stimulate gonadotrophin-releasing hormone (GnRH) release from the hypothalamus and luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion from the pituitary. A synchronicity of LH and leptin pulses has been described in healthy women, suggesting that leptin probably also regulates the episodic secretion of LH. In some pathological conditions, such as polycystic ovarian syndrome (PCOS), LH-leptin interactions are not known. The aim of the present investigation was to assess the episodic fluctuations of circulating LH and leptin in PCOS patients compared to regularly menstruating women. Six PCOS patients and six normal cycling (NC) women of similar age and body mass index (BMI) were studied. To assess episodic hormone secretion, blood samples were collected at 10-min intervals for 6 h. LH and leptin concentrations were measured in all samples. For pulse analysis the cluster algorithm was used. To detect an interaction between LH and leptin pulses, an analysis of copulsatility was employed. LH concentrations were significantly higher in the PCOS group in comparison to NC women, however serum leptin concentrations and leptin pulse characteristics for PCOS patients did not differ from NC women. A strong synchronicity between LH and leptin pulses was observed in NC women; 11 coincident leptin pulses were counted with a phase shift of 0 min (P = 0.027), 18 pulses with a phase shift of -1 (P = 0.025) and 24 pulses with a phase shift of -2 (P = 0.028). PCOS patients also exhibited a synchronicity between LH and leptin pulses but weaker (only 20 of 39 pulses) and with a phase shift greater than in normal women, leptin pulses preceding LH pulses by 20 min (P = 0.0163). These results demonstrate that circulating leptin and LH are synchronized in normal women and patients with PCOS. The real significance of the apparent copulsatility between LH and leptin must be elucidated, as well as the mechanisms that account for the ultradian leptin release.

Neuroendocrine mechanism of anovulation in users of contraceptive subdermal implant of nomegestrol acetate (Uniplant)

OBJECTIVE

To evaluate a nomegestrol acetate subdermal contraceptive implant's (Uniplant; Thermex, Monaco) effect on the hypothalamus-pituitary-ovarian axis.

DESIGN

A prospective clinical trial.

SETTING

San Borja-Arriarán Clinical Hospital, University of Chile, School of Medicine.

PATIENT(S)

Normally cycling healthy women.

INTERVENTION(S)

Insertion of Uniplant.

MAIN OUTCOME MEASURE(S)

Luteinizing hormone pulse and endocrine profiles were assessed before, 48 hours after insertion, and after prolonged use of the implant.

RESULT(S)

Anovulation was noted in 100% of users in the first month. Seventy percent of subjects demonstrated follicular development with the absence of ovulation and an endocrine profile similar to the follicular phase: (LH pulse/8 hours 6.85 +/- 0.67, LH amplitude 3.54 +/- 0.65 mIU/mL (conversion factor to SI unit, 1.00), and E2 193 +/- 29.4 pg/mL (conversion factor to SI unit, 3.67), whereas 30% demonstrated no follicular activity with an endocrine profile similar to the luteal phase: (LH pulse/8 hours; 3.66 +/- 0.66, LH amplitude 5.76 +/- 1.73 mIU/mL, and E2 67.5 +/- 4 pg/mL. Clinical characteristics, serum gonadotropin concentration, and LH pulse characteristics failed to predict which subjects would initiate or remain devoid of follicular activity.

CONCLUSION(S)

Uniplant results in anovulation via two mechanisms: hypothalamic suppression in subjects who lack follicular development, and likely suppression of the pituitary LH surge in subjects who initiate follicular activity.