Influence of oxytocin receptor single nucleotide sequence variants on contractility of human myometrium: an in vitro functional study.

BACKGROUND: Oxytocin receptor (OXTR) gene variants have been shown to affect the prevalence of preterm birth, mode of delivery and oxytocin (OXT) requirements for labor induction and augmentation. We hypothesized that this might be associated with different myometrium responses to oxytocin. Our aim was to investigate the influence of a selection of eight OXTR gene single nucleotide variants on oxytocin-induced stimulation of human myometrium contractility in vitro. METHODS: Human myometrium biopsies were collected during elective cesarean sections at term, if patients had given informed consent. Myometrial strips were submerged under tension in an organ bath and allowed to contract; the remaining material was stored at - 80 °C for further determination of relevant genetics and mRNA level. The area under the curve (AUC) of all contractions taking place in the absence of OXT and of those occurring upon OXT addition (for 30 min each) was measured. OXT stimulation, defined as the ratio between AUC measurements after OXT addition and those in the absence of OXT was calculated for each strip. TaqMan™ Assays were used to detect the allele distribution of the eight OXTR variants and to determine the relative amounts of OXTR-mRNA in the samples. For each variant, oxytocin stimulation of contractility was compared between samples homozygous for the reference allele (reference group) and samples with at least one variant allele (variant group) by linear regression. RESULTS: Sixty samples were included in the present study. For rs1042778, rs11706648, rs4686301, rs53576, rs237895, and rs237902, OXT stimulation was similar in the reference and in the variant groups. However, the values of OXT stimulation differed significantly between the reference and the variant groups for rs4686302 (3.1 vs. 4.1 times; p = 0.022) and rs237888 (3.2 vs. 5.5 times; p = 0.001). No significant differences between the levels of OXTR-mRNA in the various reference and corresponding variant groups were detected. CONCLUSIONS: Patients with variant alleles of rs237888 and/or rs4686302 may be more sensitive to oxytocin stimulation, explaining why these sequence variants have been associated with lower cesarean section prevalence and premature birth, respectively.

Outcome and risk factors of cesarean delivery with and without cesarean myomectomy in women with uterine myomatas.

AIM: To evaluate the outcome of a cesarean myomectomy (CM) versus a cesarean delivery (CD) alone in women with uterine myomas and the risk factors for adverse outcomes. METHODS: A retrospective cohort study of all women undergoing CDs with uterine leiomyomatas and singleton pregnancies was performed. Patients with known risk factors for hemorrhage were excluded. Measured adverse outcome parameters included estimated blood loss, drop in hemoglobin levels (pre/postoperatively), operation time, and the use of additional uterotonics. Outcome parameters of women with CM were compared to women with CD alone. Possible risk factors for adverse outcomes were analyzed in a multivariate regression analysis. Evaluated risk factors for CM were according to localization and type of myomatas, the myoma size, BMI ≥30 kg/m2, age ≥40 years, fetal weight ≥4 kg, repeat CD, and unplanned CD in the first stage of labor. The influence of localization and myoma type were further analyzed in a subgroup analysis. RESULTS: Of the 162 women with uterine myomatas during CD, 48 underwent CM and were analyzed. Overall, CM was not associated with adverse outcomes. Independent of a concomitant myomectomy, a large myoma size of ≥5 cm was associated with an increased blood loss of ≥500 ml (adj. OR 2.7 CI 95 % 1.2-6.2, p = 0.02), and women ≥40 years of age had a significant postoperative drop in hemoglobin (adj. OR 2.4 CI 95 % 1.0-5.4, p = 0.04). In the univariate subgroup analysis, CM of multiple myomatas was associated with an increased blood loss and an increased operation time compared to women with multiple myomatas and CD alone. Prolonged operation times were also observed in women with pedunculated and subserosal myomatas with concomitant myomectomy. There were no cases of hysterectomy or blood transfusions. CONCLUSION: CM performed by an experienced obstetrician can be safe in selected patients who are without additional preexisting risk factors. Risk factors that are associated with increased blood loss in women with uterine leiomyomatas include a larger size of the leiomyoma (≥5 cm) and a maternal age of ≥40 years.

Evaluation of fetal anthropometric measures to predict the risk for shoulder dystocia.

OBJECTIVE: To evaluate the quality of anthropometric measures to improve the prediction of shoulder dystocia by combining different sonographic biometric parameters. METHODS: This was a retrospective cohort study of 12,794 vaginal deliveries with complete sonographic biometry data obtained within 7 days before delivery. Receiver-operating characteristics (ROC) curves of various combinations of the biometric parameters, namely, biparietal diameter (BPD), occipitofrontal diameter (OFD), head circumference, abdominal diameter (AD), abdominal circumference (AC) and femur length were analyzed. The influences of independent risk factors were calculated and their combination used in a predictive model. RESULTS: The incidence of shoulder dystocia was 1.14%. Different combinations of sonographic parameters showed comparable ROC curves without advantage for a particular combination. The difference between AD and BPD (AD - BPD) (area under the curve (AUC) = 0.704) revealed a significant increase in risk (odds ratio (OR) 7.6 (95% CI 4.2-13.9), sensitivity 8.2%, specificity 98.8%) at a suggested cut-off ≥ 2.6 cm. However, the positive predictive value (PPV) was low (7.5%). The AC as a single parameter (AUC = 0.732) with a cut-off ≥ 35 cm performed worse (OR 4.6 (95% CI 3.3-6.5), PPV 2.6%). BPD/OFD (a surrogate for fetal cranial shape) was not significantly different between those with and those without shoulder dystocia. The combination of estimated fetal weight, maternal diabetes, gender and AD - BPD provided a reasonable estimate of the individual risk. CONCLUSION: Sonographic fetal anthropometric measures appear not to be a useful tool to screen for the risk of shoulder dystocia due to a low PPV. However, AD - BPD appears to be a relevant risk factor. While risk stratification including different known risk factors may aid in counseling, shoulder dystocia cannot effectively be predicted.

Continuous independent quality control for fetal nuchal translucency measurements provided by the cumulative summation technique.

PURPOSE: The cumulative summation technique (CUSUM) is an innovative method for the quality control of nuchal translucency (NT) measurements. CUSUM allows immediate corrective intervention as soon as an unacceptable tendency is noted. The aim of this study was to implement an objective and dynamic quality control method based on the CUSUM technique for prompt analysis of fetal NT measurement which would be compatible with different standards in routine clinical practice. The findings were compared to the standard NT quality control methods currently in use. MATERIALS AND METHODS: Three sets of fetal NT measurements performed by three experienced examiners (I, II and III) were selected for retrospective evaluation. One additional set of NT measurements performed by examiner IV was prospectively assessed to approve the practicability of the method. NT measurements were conducted according to the recommendations of Fetal Medical Foundation (FMF) Germany and London. NT values were converted to Z-scores. For quality and accuracy evaluation, data were fed into the Digisono CUSUM software to create double CUSUM charts of Z-scores. In addition, histograms were composed from the Z-scores of each set of measurements and plotted against a normal Gaussian distribution. RESULTS: Three different patterns of retrospective performance and one set of NT measurements that was evaluated prospectively are presented. The full alignment of Z-scores using CUSUM curves reflected exact periods of under- and overestimation of NT measurements. The CUSUM chart of the prospective data set reveals that prompt corrective intervention of poor performance resulted in reconstitution of optimal results and provided sufficient control. In contrast, histograms of NT Z-scores only showed a minor positive or negative shift as compared to the expected values on the basis of Gaussian distribution, but could not identify poor performance. CONCLUSION: Use of the CUSUM technique analysing the quality of sonographic NT measurements provides the possibility to prospectively observe the development of the examiner's skills, to maintain competence and to promptly define the time when inaccurate measurements start to occur.

Continuous independent quality control for fetal ultrasound biometry provided by the cumulative summation technique.

OBJECTIVE: To apply the cumulative summation (CUSUM) technique for an evaluation of the learning process of sonographic fetal weight estimation at term in combination with the z-scores of biometry determinants and to assess the time of appearance and sources of errors. METHODS: Learning curve (LC-CUSUM) and double CUSUM charts for systematic error detection based on absolute and signed mean percentage error were generated to retrospectively estimate the longitudinal accuracy of sonographic fetal weight estimation conducted by three trainees and one experienced examiner. For LC-CUSUM analysis an examination was considered to be a failure when there was an absolute error in birth weight estimation >/= 15%. Fetal biometry measurements (head circumference, abdominal circumference (AC) and femur length (FL)) from 227 routine ultrasound scans of one examiner were separately transformed into z-scores and double CUSUM charts were generated to assess the systematic errors for each determinant. RESULTS: The LC-CUSUM charts revealed that different numbers of scans are required for different examiners to achieve competence in estimating birth weight. AC and FL deviated most significantly from expected values (P < 0.05). The double CUSUM charts revealed exact periods of systematic errors in the measurement of biometry determinants, clearly reflecting errors of fetal weight estimation. CONCLUSIONS: The use of CUSUM techniques in the analysis of sonographic data allows observation of the development of an examiner's skill and maintenance of competence. The CUSUM technique not only allows the reasons for impaired fetal weight estimation to be revealed but also allows determination of the exact time when inaccurate measurements start to occur. We suggest that CUSUM charts should be implemented in routine clinical practice as a measure of objective quality evaluation of sonographic fetal biometry.

Intrathecal catheterisation after observed accidental dural puncture in labouring women: update of a meta-analysis and a trial-sequential analysis.

BACKGROUND: Our meta-analysis from 2013 showed that inserting a catheter intrathecally after an observed accidental dural puncture can reduce the need for epidural blood patch in labouring women requesting epidural analgesia. We updated our conventional meta-analysis and added a trial-sequential analysis (TSA). METHODS: A systematic literature search was conducted to identify studies that compared inserting the catheter intrathecally with an epidural catheter re-site or with no intervention. The extracted data were pooled and the risk ratio (RR) and 95% confidence interval (95%CI) for the incidence of post-dural puncture headache (PDPH) was calculated, using the random effects model. A contour-enhanced funnel plot was constructed. A TSA was performed and the cumulative Z score, monitoring and futility boundaries were constructed. RESULTS: Our search identified 13 studies, reporting on 1653 patients, with a low risk of bias. The RR for the incidence of PDPH was 0.82 (95%CI 0.71 to 0.95) and the RR for the need for epidural blood patch was 0.62 (95%CI 0.49 to 0.79); heterogeneity of both analyses was high. The TSA showed that the monitoring or futility boundaries were not crossed, indicating insufficient data to exclude a type I error of statistical analysis. Contour-enhanced funnel plots were symmetric, suggesting no publication bias. CONCLUSIONS: Conventional meta-analyses showed for the first time that intrathecal catheterisation can reduce the incidence of PDPH. However, TSA did not corroborate this finding. Despite increasing use in clinical practice there is no firm evidence on which to base a definite conclusion.

Sonographic prediction of macrosomia cannot be improved by combination with pregnancy-specific characteristics.

OBJECTIVE: To evaluate the predictive value of a combination of sonographic, clinical and demographic data for detecting fetal macrosomia compared to ultrasound fetal weight estimation alone. METHODS: Retrospective cohort data were obtained from 1062 pregnancies in an unselected population. Estimated fetal sonographic weight was obtained within the last week prior to delivery. Two different combination models-published by Mazouni et al. and Nahum and Stanislaw-were employed to predict the presence of macrosomia at birth in these infants. Receiver-operating characteristics (ROC) curves were generated to compare the prediction of macrosomia when using different observation methods and sensitivity, specificity, positive predictive value, negative predictive value (NPV) and accuracy were calculated. RESULTS: Macrosomia (birth weight >or= 4000 g) was present in 135/1062 (12.7%) newborns. ROC curve analysis revealed the prediction of macrosomia using ultrasound alone to be significantly superior to the combined method of Mazouni et al. (area under the curve (AUC) 0.922, 95% CI 0.902-0.943 vs. 0.747, 95% CI 0.700-0.794, respectively; P < 0.0005), whereas the performance of the Nahum and Stanislaw equation was similar but not superior to ultrasound alone (AUC 0.895, 95% CI 0.839-0.950 vs. 0.912, 95% CI 0.867-0.958, respectively; P > 0.05). The accuracy of macrosomia prediction was similar for ultrasound alone and the Nahum and Stanislaw equation (approximately 90%), whereas the nomogram of Mazouni et al. reached only 51.7% accuracy (using a probability cut-off level of 50%). The NPV was found to be over 90% for all methods. CONCLUSIONS: Combination of sonographic estimates with clinical and demographic variables does not improve the prediction of macrosomia at delivery in comparison with a routine ultrasound scan within a week before delivery, at least in unselected populations.

Effect of maternal smoking on stress physiology in healthy neonates.

OBJECTIVE: To assess the impact of maternal smoking during pregnancy (MSDP) on the neonatal hypothalamic-pituitary-adrenal axis. STUDY DESIGN: In a prospective observational study, salivary cortisol and cortisone levels were measured at the fourth day of life during resting conditions and in response to a pain-induced stress event in healthy neonates whose mothers smoked cigarettes during each stage of pregnancy and compared with controls. RESULTS: Neonates in the control group (n=70) exhibited a physiologic stress response with a significant increase in cortisol (1.3 to 2.1 ng ml-1; P<0.05) and cortisone (11.8 to 17.8 ng ml-1; P<0.05) from baseline levels, whereas in neonates from mothers who smoked (n=33), cortisol (0.9 to 0.8 ng ml-1; P=0.77) and cortisone (11.5 to 13.0; P=0.19) stress response was not significantly different from baseline levels. A two-way analysis of variance confirmed these findings in both groups. CONCLUSIONS: Healthy neonates whose mothers smoked during pregnancy show a blunted stress response on the fourth day of life. Thus, MSDP leads to a dysregulation of the HPA axis with continued effects in neonatal life. This might explain long-term consequences of MSDP such as overweight, diabetes mellitus and modification of blood pressure control mechanisms in adult life.

Characterization of the three 125I-iodination isomers of human insulin-like growth factor I (IGF1).

Human insulin-like growth factor I (IGF1) was labeled with 125I and the resulting mixture of iodination isomers was separated by reverse-phase HPLC. Three major radioactive peaks were isolated and identified by sequencing as the expected three monoiodinated species. The ranking of the affinities of the three isomers for the human IGF1 receptor was found to be Tyr24(125I) > Tyr31(125I) >> Tyr60(125I). The Tyr31(125I) isomer was shown to have an affinity similar to that of unlabeled IGF1 and is thus the tracer of choice for IGF1. The tracers were stable upon storage at -20 degrees C for at least 3 months.

Correlations of receptor binding and metabolic and mitogenic potencies of insulin analogs designed for clinical use.

In recent years, analogs of human insulin have been engineered with the aim of improving therapy for people with diabetes. To ensure that the safety profile of the human hormone is not compromised by the molecular modifications, the toxico-pharmacological properties of insulin analogs should be carefully monitored. In this study, we compared the insulin and IGF-I receptor binding properties and metabolic and mitogenic potencies of insulin aspart (B28Asp human insulin), insulin lispro (B28Lys,B29Pro human insulin), insulin glargine (A21Gly,B31Arg,B32Arg human insulin), insulin detemir (NN304) [B29Lys(epsilon-tetradecanoyl), desB30 human insulin], and reference insulin analogs. Receptor affinities were measured using purified human receptors, insulin receptor dissociation rates were determined using Chinese hamster ovary cells overexpressing the human insulin receptor, metabolic potencies were evaluated using primary mouse adipocytes, and mitogenic potencies were determined in human osteosarcoma cells. Metabolic potencies correlated well with insulin receptor affinities. Mitogenic potencies in general correlated better with IGF-I receptor affinities than with insulin receptor off-rates. The 2 rapid-acting insulin analogs aspart and lispro resembled human insulin on all parameters, except for a slightly elevated IGF-I receptor affinity of lispro. In contrast, the 2 long-acting insulin analogs, glargine and detemir, differed significantly from human insulin. The combination of the B31B32diArg and A21Gly substitutions provided insulin glargine with a 6- to 8-fold increased IGF-I receptor affinity and mitogenic potency compared with human insulin. The attachment of a fatty acid chain to LysB29 provided insulin detemir with reduced receptor affinities and metabolic and mitogenic potencies but did not change the balance between mitogenic and metabolic potencies. The safety implications of the increased growth-stimulating potential of insulin glargine are unclear. The reduced in vitro potency of insulin detemir might explain why this analog is not as effective on a molar basis as human insulin in humans.

Metabolism of oral glucose in pancreas transplant recipients with normal and impaired glucose tolerance.

To gain insight into the pathophysiology of impaired glucose tolerance in pancreas transplantation, glucose kinetics and insulin secretion were assessed after an oral glucose load in four combined pancreas-kidney recipients with impaired glucose tolerance (IPx), in five combined pancreas-kidney recipients with normal glucose tolerance, in six nondiabetic kidney transplant recipients, and in eight normal subjects employing a dual isotope technique, beta-Cell function was evaluated by calculating prehepatic insulin secretion rates, which subsequently were correlated to the ambient glucose concentrations to obtain an index of beta-cell responsiveness. Oxidative and nonoxidative glucose metabolism were assessed by indirect calorimetry. Basal insulin secretion rates, the glucose-stimulated early insulin secretion rates, as well as beta-cell responsiveness were markedly reduced in IPx than in the glucose-tolerant transplant subjects. Total systemic glucose appearance was similar in the groups with apparently comparable inhibition of systemic glucose release and increase in exogenous glucose appearance. The hyperglycemic response in IPx was due to a significant reduction in the glucose disappearance rates during the first 2 h after glucose ingestion. Nonoxidative glucose metabolism increased significantly less in IPx than in glucose-tolerant groups. Glucagon secretion was less suppressed in the early part of the study in IPx, which may have contributed to the excessive hyperglycemia. In conclusion, IPx after pancreas transplantation was characterized by 1) impaired early insulin secretion, 2) reduced beta-cell responsiveness, 3) reduced glucose uptake, 4) impaired nonoxidative glucose metabolism, and 5) impaired early inhibition of glucagon secretion.

Permanent slide preparations of T lymphocyte-sheep red blood cell rosettes.

Rosette formation between sheep erythrocytes (SRBC) and human thymus-derived lymphocytes (T cells) is used to monitor T cells in various human diseases. Rosettes are usually counted in a hemacytometer immediately after preparation. This paper reports a technique for permanently fixing and staining rosettes for serial and comparative studies, a procedure which has probably been less well standardized, less reproducibly performed, and less widely used than many investigators appreciate. The technique describedhas the advantages of providing distinct morphological identification of the rosette-forming cell and it produces a permanent mount for further reference.

Acute hypotensive responses to peptide inhibitors of renin in conscious monkeys: an effect on blood pressure independent of plasma renin inhibition.

In order to investigate the hypotensive mechanisms of action of peptide renin inhibitors, blood pressure responses to five renin inhibitors were compared with those to the angiotensin converting enzyme inhibitor, enalaprilat, in conscious African green and rhesus monkeys. (3S-4S)-4-amino-5-cyclohexyl-3-hydroxy pentanoic acid (ACHPA)-containing renin inhibitory peptide (ACRIP) and enalaprilat both decreased blood pressure in euvolemic and volume-depleted African green monkeys. However, while a maximum dose of enalaprilat reduced blood pressure to 80 +/- 4 and 56 +/- 4 mmHg in the euvolemic and volume-depleted monkeys, respectively, ACRIP lowered pressure to life-threatening levels (less than 40 mmHg) under both conditions. The relative potencies of ACRIP and four other renin inhibitors for inhibiting in vitro plasma renin activity (PRA; IC50) were compared with their potencies in reducing blood pressure by 15 mmHg (ED15 mmHg) and lowering blood pressure more than enalaprilat in volume-depleted rhesus monkeys. All renin inhibitors lowered blood pressure significantly beyond the maximal response to enalaprilat. Despite a significant correlation (r = 0.99, P less than 0.05) between the in vitro PRA inhibitory potency and the in vivo ED15 mmHg, doses which lowered blood pressure beyond the maximal responses to enalaprilat were not significantly correlated (r = 0.53, P greater than 0.05) with the in vitro PRA IC50 values. Furthermore, the profound depressor responses to renin inhibitors in rhesus monkeys were accompanied by increases in the heart rate and decreases in pulse pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Anticoagulant efficacy and immunogenicity of the selective factor Xa inhibitor antistasin following subcutaneous administration in the rhesus monkey.

The antithrombotic efficacy and duration of action of a single subcutaneous administration of the selective factor Xa inhibitor recombinant antistasin (rATS) was evaluated in a rhesus monkey model of mild disseminated intravascular coagulation. rATS (1 mg/kg) was shown to be fully effective and comparable to standard heparin (1,000 U/kg) in the suppression of thromboplastin-induced fibrinopeptide A generation for at least 5 h following a single subcutaneous administration. The absorption rate of rATS, as measured by ex vivo activated partial thromboplastin times (aPTT), mirrored that of standard heparin exhibiting peak anticoagulant activity between 1 and 2 h post administration. The anticoagulant effects of a single rATS dose lasted for longer than 30 h maintaining an aPTT value at least 2-fold higher than baseline. Repeated subcutaneous administrations of rATS resulted in the generation of fully neutralizing antibodies. These results suggest that specific factor Xa inhibition may be as effective as standard heparin in the treatment of venous thrombosis. Due to its antigenicity however, rATS is probably not suitable for chronic subcutaneous anticoagulant therapy.

Oxygen-regulated expression of TGF-beta 3, a growth factor involved in trophoblast differentiation.

The transforming growth factor-beta 3 (TGF-beta 3) is involved in oxygen-dependent differentiation processes during placental development and pregnancy disorders. However, the importance of oxygen partial pressure for the regulation of TGF-beta 3 expression is presently unclear. We and others presented preliminary evidence that the hypoxia-inducible factor-1 (HIF-1) confers TGF-beta 3 transcription but it was unknown whether this occurred directly or indirectly. To analyze how HIF-1 regulates TGF-beta 3 gene transcription, we cloned and sequenced the mouse TGF-beta 3 promoter region. Multiple putative HIF-1 binding sites (HBSs) were identified, many of which co-localized with two G+C rich CpG islands 5' to the TGF-beta 3 transcription start site. A 6.8 kb fragment of the TGF-beta 3 promoter induced reporter gene expression under hypoxic conditions or when treated with an iron chelator known to stabilize and activate the HIF-1 alpha subunit. Deletion of a 2.4 kb fragment upstream of the distal CpG island abolished inducibility of reporter gene expression. Two HBSs (HBS1 and HBS6) that bound the HIF-1 protein could be identified within this 2.4 kb fragment. These results suggest that TGF-beta 3 gene expression is directly regulated by HIF-1.

In vitro investigations of the effects of nonfreezing low temperatures on lesioned and uninjured mammalian spinal neurons.

This two-part investigation explored the parameters and mechanisms of: (1) injury to spinal cord (SC) neurons by nonfreezing low temperatures, and (2) hypothermic protection of SC neurons subjected to a defined, physical injury (dendrite transection). Conclusions from the studies of hypothermic injury were: (1) morphologic and ultrastructural signs of stress developed in SC neurons as the temperature was decreased below 17 degrees C; (2) most neurons showing stress during cooling died upon rewarming to 37 degrees C; (3) spontaneous SC network activity was not significantly changed by cooling to 17 degrees C for 2 hours and rewarming, but cooling to 10 degrees C for 1 hour caused a reduction of burst frequency after rewarming, and cooling to 10 degrees C for 2 hours resulted in electrical silence after rewarming; and (4) application of N-methyl-D-aspartate (NMDA) antagonists before cooling prevented neuronal death, ultrastructural damage, and loss of activity upon rewarming, but application after cooling (before rewarming) was not protective. Conclusions from the studies of hypothermic protection were: (1) cooling at 17 degrees C for 2 hours followed by rewarming to 37 degrees C significantly increased lesioned neuron survival, but protection was lost when the period at 17 degrees C was increased to 6 hours; (2) NMDA blockade under normothermic (37 degrees C) or hypothermic (17 degrees C or 10 degrees C for 2 hours) conditions was not more protective of lesioned neurons than cooling to 17 degrees C (no NMDA antagonist); and (3) 200 microM thiopental or 100 microM pentobarbital increased lesioned neuron survival to a degree comparable to cooling for 2 hours at 17 degrees C.

In vivo pharmacology of a novel AT1 selective angiotensin II receptor antagonist, MK-996.

MK-996, N-(4'-(5,7-dimethyl-2-ethyl-3H-imidazo[4,5-b]pyridin-3-yl- methyl)1,1'-biphenyl-2-yl)-sulfonylbenzamide, is a potent, orally active, highly selective, nonpeptide angiotensin II (AII) receptor antagonist. MK-996 prevents the pressor response to intravenous AII in the conscious rat, dog, and rhesus monkey (ED50, mg/kg; oral/intravenous = 0.067/0.014, 0.035/0.017, and 0.1/0.036, respectively). In the anesthetized chimpanzee, MK-996 (1 mg/kg, iv) produces 100% (peak) inhibition of the AII pressor response and is still active (52%) at 24 h. To our knowledge this pharmacologic profile in the rat, dog, rhesus monkey, and chimpanzee presents the least species variability of any AII receptor antagonist yet described. Responses to methoxamine and arginine vasopressin are not affected by MK-996. In aortic coarcted (high renin) rats, MK-996 (3 mg/kg, by mouth) reduces blood pressure to normotensive (< 120 mm Hg) levels without reflex tachycardia. This dose of MK-996 reduces blood pressure to approximately the same level as both losartan (3 mg/kg, by mouth) and enalapril (3 mg/kg, by mouth) in this model. The duration of antihypertensive activity of MK-996 is similar to enalapril and shorter than losartan at the doses tested. Additionally, in the rat MK-996 does not potentiate the vasodepressor response to bradykinin and completely prevents the ability of AII to stimulate an increase in plasma levels of aldosterone. Therefore, MK-996 is a potent, orally active, nonpeptide AII receptor antagonist with a long duration of action, little species variability, and anti-hypertensive activity.

Failure of intravenous pentagastrin challenge to induce panic-like effects in rhesus monkeys.

We examined the ability of intravenous (i.v.) challenge with pentagastrin to induce behavioural and cardiovascular effects consistent with panic attack in conscious rhesus monkeys. For behavioural evaluation, 4 naive male rhesus monkeys familiar with minimal manual restraint necessary for drug administration received a rapid i.v. bolus of pentagastrin (4, 8 or 16 micrograms/kg) or water on four separate occasions according to a randomised cross-over design. Behaviour was rated by a blind observer continuously during, and for the first 5 min immediately following i.v. injections while the monkey sat on the handler's lap, and then for a further 25 min in an individual observation cage. In separate experiments, the ability of pentagastrin to alter cardiovascular parameters which may accompany panic or anxiety (elevated heart rate and blood pressure) was explored. For cardiovascular studies, 8 male or female rhesus monkeys with femoral artery catheters were chair restrained and received a bolus injection of pentagastrin (4, 8 or 16 micrograms/kg) or saline into the saphenous vein at 30 min intervals. Blood pressure and heart rate were monitored continuously using a Statham Gould pressure transducer. Pentagastrin induced no consistent behavioural or cardiovascular changes. Similar pilot studies using CCK4 also failed to reveal such effects. We conclude that CCK-induced panic-like effects may not be demonstrable following challenge with pentagastrin under laboratory conditions in rhesus monkeys.

Triiodothyronine reverses depressed contractile performance after excessive catecholamine stimulation.

BACKGROUND: Conflicting results have been reported regarding the acute effects of triiodothyronine (T3) on myocardial contractile performance. The present study analyzes the role of T3 in reversing the depressant effect of excessive catecholamine stimulation in isolated porcine left ventricular myocardium. METHODS: Thirty-six left ventricular trabeculae (0.4 x 6.0 mm) obtained from 6 pigs were used for measurements of isometric force development, isotonic shortening, and intracellular calcium in three experimental series (measurement conditions: 37 degrees C; optimal length; supramaximal electrical stimulation, 1 Hz; calcium measurement, fura-2 ratio method; frequency, 225 Hz). In series 1, isometric force development was measured before and after a 60-minute incubation with 10(-7) mol/L epinephrine in preparations with (n = 6) and without (n = 6) preceding fura-2 loading for calcium measurements. In series 2, the acute effects of a 30-minute administration of T3 (10(-9) mol/L) on isometric force and intracellular calcium were analyzed (n = 6). In series 3, after simultaneous fura-2 loading and a 6-hour 10(-7) mol/L epinephrine exposure the effects of T3 (10(-9) mol/L, 30 minutes) on force development, shortening, and intracellular calcium transient were analyzed. RESULTS: Long-term and high-dose epinephrine exposure induced a severe contractile depression with a significant reduction of isometric force development (p < 0.05) and increased diastolic (p < 0.001) and systolic calcium (p < 0.001). In normal porcine myocardium T3 had no effect on the extent of isometric force generation but accelerated the time course of force development (p < 0.05) and increased the calcium transient (p < 0.001). After induction of myocardial depression by epinephrine exposure T3 accelerated the intracellular calcium transients and reduced diastolic calcium. Triiodothyronine increased the shortening amplitude and the force amplitude (p < 0.01). CONCLUSIONS: Triiodothyronine reverses depressed contractile performance after preceding high-dose epinephrine exposure in isolated porcine myocardium. Increased force amplitudes and unaltered or even reduced intracellular calcium transients argue in favor of a resensitization of the contractile apparatus for calcium by T3. The study supports a potential role for T3 treatment in depressed myocardium after previous excessive catecholamine exposure (eg, brain death, catecholamine treatment, ischemia).