Leptin does not influence surfactant synthesis in fetal sheep and mice lungs

In the fetus, leptin in the circulation increases at late gestation and likely influences fetal organ development. Increased surfactant by leptin was previously demonstrated in vitro using fetal lung explant. We hypothesized that leptin treatment given to fetal sheep and pregnant mice might increase surfactant synthesis in the fetal lung in vivo. At 122-124 days gestational age (term: 150 days), fetal sheep were injected with 5 mg of leptin or vehicle using ultrasound guidance. Three and a half days after injection, preterm lambs were delivered, and lung function was studied during 30-min ventilation, followed by pulmonary surfactant components analyses. Pregnant A/J mice were given 30 or 300 mg of leptin or vehicle by intraperitoneal injection according to five study protocols with different doses, number of treatments, and gestational ages to treat. Surfactant components were analyzed in fetal lung 24 h after the last maternal treatment. Leptin injection given to fetal sheep increased fetal body weight. Control and leptin-treated groups were similar in lung function (preterm newborn lamb), surfactant components pool sizes (lamb and fetal mice), and expression of genes related to surfactant synthesis in the lung (fetal mice). Likewise, saturated phosphatidylcholine and phospholipid were normal in mice lungs with absence of circulating leptin (ob/ob mice) at all ages. These studies coincided in findings that neither exogenously given leptin nor deficiency of leptin influenced fetal lung maturation or surfactant pool sizes in vivo. Furthermore, the key genes critically required for surfactant synthesis were not affected by leptin treatment.     

Inhibition of DNA synthesis does not influence the H1 histone synthesis in Tetrahymena pyriformis

In the protozoan Tetrahymena pyriformis the DNA synthesis is stopped immediately and completely after addition of one of the two DNA synthesis inhibitors methotrexate + uridine and hydroxyurea to a cell suspension. However, the present experiments show, that the accumulation of labeled H1 histone in the inhibited cells is almost totally unaffected for more than two-thirds of a cell cycle after addition of either inhibitor.     

Prostacyclin does not affect insulin secretion in humans

The effects of Prostacyclin (PGI₂) infusion on insulin secretion and glucose tolerance were investigated in 7 healthy subjects. PGI₂ infusion caused no statistically significant changes of either glucose or insulin concentration, over the range 2.5–20 ng/Kg/min. A constant PGI₂ infusion (10 ng/Kg/min) did not inhibit acute insulin responses to a glucose (20 g i.v.) pulse (response before PGI₂ = 612±307%; during PGI₂ = 515±468%, mean ± SD, mean change 3–5 min insulin, % basal; P=NS). Glucose disappearance rates were similar after the first and second glucose pulse.Thus, in contrast to PGE₂, PGI₂ does not affect insulin secretion nor glucose disposal at doses producing platelet and vascular changes. It is hypothesized that an altered PGI₂/PGE₂ balance in diabetes may represent a link between vascular, platelet and metabolic changes.     

D2-dopaminergic blockade does not influence post-exercise ketosis in non-athletes

Metoclopramide has previously been shown to inhibit the ketosis of starvation in rats and humans. The effect of D2-dopaminergic blockade on post-exercise ketosis was, therefore, studied in 6 carbohydrate-starved non-athletic persons who had just completed a 9-km walk in mountainous terrain. There were nine control subjects who went on the walk, but who did not ingest metoclopramide. Metoclopramide (0.15 mg·kg⁻¹ body mass) caused a highly significant rise in the plasma prolactin concentration, but did not influence blood concentrations of 3-hydroxybutyrate, free fatty acid, glucose, insulin or glucagon. Unlike ketosis in starvation, therefore, neither prolactin, nor the D2-dopaminergic system play a part in the genesis of post-exercise ketosis.     

Circulating and urinary thromboxane B2 metabolites in the rabbit: 11-dehydro-thromboxane B2 as parameter of thromboxane production

The metabolism of thromboxane B2 was studied in the rabbit. The aim of the study was to identify metabolites in blood and urine that might serve as parameters for monitoring thromboxane production in vivo. [5,6,8,9,11,12,14,15-3H8]-Thromboxane B2 was administered by i.v. injection to rabbits, and blood samples and urine were collected with brief intervals. The metabolic profiles were visualized by two-dimensional thin layer chromatography and autoradiography, and the structures of five major metabolites were determined using chromatographic and mass spectrometric methods. In urine the major metabolites were identified as 11-dehydro-TXB2 and 2,3,4,5-tetranor-TXB1, and other prominent products were 11-dehydro-2,3,4,5-tetranor-TXB1, 2,3-dinor-TXB1 and 2,3-dinor-TXB2. In the circulation, TXB2 was found to disappear rapidly. The first major metabolite to appear was 11-dehydro-TXB2, which also remained a prominent product in blood for the remainder of the experiment (90 min). With time, the profile of circulating products became closely similar to that in urine. TXB2 was not converted into 11-dehydro-TXB2 by blood cells or plasma. The dehydrogenase catalyzing its formation was tissue bound and was found to have a widespread occurrence: the highest conversion was found in lung, kidney, stomach and liver. The results of the present study suggest that 11-dehydro-TXB2 may be a suitable parameter for monitoring thromboxane production in vivo in the rabbit in blood as well as urinary samples, and possibly also several tissues. This was also demonstrated in comparative studies using radioimmunoassays for TXB2 and 11-dehydro-TXB2.     

Quercetin supplementation does not alter antioxidant status in humans

Abstract

This study measured the influence of ingesting quercetin on plasma measures for oxidative stress and antioxidant capacity. Male and female subjects (n = 1002) varying in age (18–85 years) and body mass index (BMI) (16.7–52.7 kg/m²) were studied. Subjects were randomized to one of three groups using double-blinded methods: placebo, 500 mg or 1000 mg quercetin/day with 125 mg or 250 mg vitamin C/day, respectively. Pre- and post-study fasting blood samples show that plasma quercetin increased in a dose-responsive manner. The pattern of change in plasma F₂-isoprostanes, oxidized low density lipoprotein, reduced glutathione, ferric reducing ability of plasma (FRAP) and oxygen radical absorbance capacity (ORAC) did not differ between supplementation groups or after adjustment for gender, age, BMI and disease status. In summary, quercetin supplementation over 12 weeks in doses of 500 mg or 1000 mg/day significantly increased plasma quercetin levels, but had no influence on several measures of oxidative stress and antioxidant capacity.     

Inhalation of warm and cold air does not influence brain stem or core temperature in normothermic humans.

The present study tested the hypothesis that inhalation rewarming provides a thermal increment to central neural structures adjacent to the nasopharyngeal region. Auditory-evoked brain stem responses of 14 subjects (7 men and 7 women) were monitored for 25 min while they inspired room air (24 degrees C) followed by hot air (41 degrees C) saturated with water vapor and cold dry air (-1 degrees C). The latencies of peaks I, III, and V and the interpeak latencies (IPLs) I-III, III-V, and I-V were compared among the three conditions with a repeated-measures ANOVA. Changes in IPLs are sensitive markers of changes in brain stem temperature. Tympanic temperature (T(ty)) was measured with an infrared tympanic thermometer. There were no significant differences in T(ty), peak latencies I, III, and V, and IPLs I-III, III-V, and I-V. The results indicate that inhalation of hot and cold air does not influence T(ty), nor does it influence the temperature of the brain stem. We conclude that inhalation rewarming is not capable of warming the vital central neural structures adjacent to the naropharynx.     

Aposematic colouration does not explain fear of snakes in humans

Snakes elicit a higher level of fear than other vertebrate animals, yet specific cues responsible for fear of snakes are equivocal. The bright colouration hypothesis suggests that fear responses to snakes are triggered by aposematic colouration, not by snakes per se. We investigated the role of aposematic colouration in fear of snakes in a sample of 10- to 15-year-old Slovak children. Both aposematically and cryptically coloured snakes presented as both colour and black-and-white pictures received higher perceived fear scores than other vertebrates. This suggests that aposematic colouration does not play a crucial role in eliciting fear of snakes. Our results support the snake detection theory suggesting that the human visual system has been influenced by long coexistence between predatory snakes and mammals. As a result, humans have evolved an attentional bias ultimately focused on the correct and rapid detection of these threats.     

Enzyme immunoassay of thromboxane B2

An immunoassay for thromboxane B2 was developed in which the hapten molecule was labeled with beta-galactosidase. The immunoprecipitate formed after competition between enzyme-labeled and unlabeled thromboxane B2 was subjected to a fluorometric assay of beta-galactosidase. Thromboxane B2 was detectable in the range of 0.1-30 pmol. Both enzyme immunoassay and radioimmunoassay showed essentially the same cross-reactivities with other prostaglandins and their metabolites when the same antibody was used. Known amounts of thromboxane B2 were added to human plasma, and the sample was applied to an octadecyl silica column. The extract was analyzed by enzyme immunoassay to examine the correlation between the added (x) and measured (y) thromboxane B2 (y = 1.09x + 11.07 pmol/ml, r = 0.99). A satisfactory correlation was observed between radioimmunoassay (x) and enzyme immunoassay (y) (y = 0.92x + 4.64 pmol/ml, r = 0.96). The validity of enzyme immunoassay was also confirmed by gas chromatography-mass spectrometry of a dimethylisopropylsilyl ether derivative of thromboxane B2 methyl ester. The method was applicable to the assay of thromboxane B2 produced from endogenous precursor during thrombin-induced aggregation of human platelets.     

Metabolism of thromboxane B2 in the monkey.

[3H8]Thromboxane B2 was biosynthesized and infused into an unanesthetized monkey. Several urinary metabolites were isolated and their structures elucidated using gas chromatography-mass spectrometry. In addition to the major urinary metabolite, dinor-thromboxane B2, a series of metabolites resulting from dehydrogenetion of the alcohol group at C-11 were identified: 11-dehydro-thromboxane B2, 11-dehydro-15-keto-13,14-dihydro-2,3-dinor-thromboxane B2, and 11-dehydro-15-keto-13,14-dihydro-19-carboxyl-2,3,4,5-tetranor-thromboxane B2. 6-(1,3-dihydroxypropyl)-7-hydroxy-10-oxo-3-pentadecaenoic acid was also identified. Three mono-O-ethylated metabolites were formed from thromboxane B2, which in this study was infused in an ethanolic solution. A small quantity of thromboxane B2 was excreted unchanged into the urine.     

Presence of maternal anti-HBs antibodies does not influence hepatitis B vaccine response in Brazilian neonates

Recently, it was suggested that maternal hepatitis B surface antigen antibodies (anti-HBs) acquired transplacentally could play a negative role in newborn infants' immune response to the hepatitis B vaccine. We compared the hepatitis B virus (HBV) vaccine response in infants born to mothers previously vaccinated against HBV (n = 91) to infants born to mothers who were not previously vaccinated (n = 221). All newborn infants received three intramuscular doses (10 μg) of HBV vaccine (Butang?) at 0,1 and six months. The first dose was administered at the maternity hospital within 12 h of birth. The geometric mean titres of anti-HBs were not different among newborn infants born to mothers who were anti-HBs-negative (492.7 mIU/mL) and anti-HBs-positive (578.7 mIU/mL) (p = 0.38). Eight infants did not respond to the HBV vaccine. Of them, six were born to anti-HBs-negative mothers and two were born to mothers with anti-HBs titres less than 50 mlU/mL. Despite the mother's anti-HBs-positive status, our data show a good immunogenicity of the Brazilian HBV recombinant vaccine in neonates.     

Vagal blockade does not prevent adrenocorticotropin, cortisol, and cardiopulmonary responses to thromboxane A2.

Previously, we reported that thromboxane A2 (TxA2) mediates heart rate, adrenocorticotropin (ACTH), cortisol, and blood gas responses, although the specific site of action was not identified. In the present study, we interrupted vagal nervous transmission in chronically instrumented conscious sheep and infused the TxA2 mimetic U46619 or saline into the carotid artery or U46619 into the vena cava to determine whether TxA2 acts at vagal afferent nerves. Heart rate increased in all three groups during vagal blockade, and responses were not different between groups. Carotid artery and intravenous infusions of U46619 resulted in an increase in blood pressure, but responses were not different between groups. PaO2 decreased in response to vagal blockade in all groups, and responses were not different among groups. Arterial pH increased and PaCO2 decreased during vagal blockade in response to carotid artery U46619 infusions but not in response to vagal blockade alone or combined with carotid artery saline or intravenous U46619. ACTH, cortisol, and hematocrit increased significantly in response to carotid artery infusions of U46619 during vagal blockade but not in response to carotid artery saline or intravenous U46619 infusions. In summary, carotid artery infusions of TxA2 mimetic result in ACTH, cortisol, PaCO2, pHa, and hematocrit responses that are not prevented by vagal blockade. We conclude that these responses are mediated at a site perfused by the carotid vasculature and not at a site innervated by the vagal nerves, findings consistent with the hypothesis that TxA2 acts on the brain to mediate cardiopulmonary and pituitary-adrenal responses.     

Plasma thromboxane B2 in haemodialysed patients

Plasma thromboxane B2 (TXB2) concentration was measured in 7 cases of terminal renal failure before and after haemodialysis. The TXB2 levels were higher in the investigated group than in the control group (p less than 0.05). Haemodialysis induced a further increase in the TXB2 concentration. Increased thromboxane production may play a part in the pathogenesis of accelerated atherosclerosis in uraemic patients treated with chronic haemodialysis.     

Catecholamines decrease leukotriene B4 and increase thromboxane B2 synthesis in A23187-stimulated human whole blood.

Catecholamines (adrenaline, dopamine, isoprenaline, noradrenaline) and caffeic acid (catecholic compound without adrenergic receptor activity) decreased leukotriene (LT)B4 synthesis in A23187-stimulated human whole blood. Salbutamol, a non-catecholic beta 2-adrenergic agonist, did not influence LTB4 synthesis. Catecholamines stimulated thromboxane (TX)B2 synthesis with a concomitant inhibition of LTB4 synthesis; caffeic acid and salbutamol did not stimulate TXB2 synthesis. These results, obtained in A23187-stimulated whole blood, which also takes into account the complex interaction between different cell types, are similar to our previous results with polymorphonuclear leukocytes. Catecholamines show an opposite effect on lipoxygenase and cyclooxygenase pathways, which may give rise to a marked change in LT/TX ratio in physiological or pathological conditions where sufficient concentrations of catecholamines are present.     

Plasma thromboxane B2 levels and thromboxane B2 production by platelets are increased in patients during spinal and epidural anesthesia

Concentrations of thromboxane (Tx) B2 in plasma and its production by platelets were measured in 20 spinal and 10 epidural anesthesia patients scheduled for small operations in the lower extremities. The main metabolite of prostacyclin, 6-keto-PGF1 alpha and prostaglandin (PG) E2 in plasma were also determined. Plasma TxB2 and TxB2 production by platelets increased during both spinal and epidural anesthesia. Plasma TxB2 levels also remained elevated 1 h after anesthesia. The plasma concentrations of 6-keto-PGF1 alpha and PGE2 did not change during spinal or epidural anesthesia. In in vitro studies, only low concentrations of lidocaine (0.5-1.0 micrograms/ml) and bupivacaine (0.5-3.0 micrograms/ml) increased platelet TxB2 production. In platelet rich plasma, neither lidocaine nor bupivacaine in concentrations of 0.5-3.0 micrograms/ml caused constant changes in ADP-induced platelet aggregation, but they inhibited it in toxic concentrations (12 micrograms/ml). The results suggest that the increased TxB2 plasma levels and platelet TxB2 production during regional anesthesia are not caused by local anesthetics itself but by other factors, e.g. tissue trauma. In clinically found concentrations, local anesthetics do not cause any constant changes in platelet aggregation.     

Development of radioimmunoassay for thromboxane B2

A simple method for the preparation of rat liver urate oxidase is described. The enzyme was purified from rat liver homogenate by cell fractionation, detergent treatment, alkali treatment, and affinity chromatography on 8-aminoxanthine-bound Sepharose 4B. This enzyme preparation had a specific activity of 9.1 U/mg of protein and was purified about 1000-fold from the liver homogenate. After sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis followed by staining with Coomassie brilliant blue, this preparation yielded one protein band at a position corresponding to a molecular weight of 33,000.     

PPADS does not block contraction-induced prostaglandin E2 synthesis in cat skeletal muscle

Pyridoxal-phosphate-6-azophenyl-2'-4-disulfonate (PPADS), a purinergic 2 (P2) receptor antagonist, has been shown to attenuate the exercise pressor reflex in cats. In vitro, however, PPADS has been shown to block the production of prostaglandins, some of which play a role in evoking the exercise pressor reflex. Thus the possibility exists that PPADS blocks the exercise pressor reflex through a reduction in prostaglandin synthesis rather than through the blockade of P2 receptors. Using microdialysis, we collected interstitial fluid from skeletal muscle to determine prostaglandin E2 (PGE2) concentrations during the intermittent contraction of the triceps surae muscle before and after a popliteal arterial injection of PPADS (10 mg/kg). We found that the PGE2 concentration increased in response to the intermittent contraction before and after the injection of PPADS (both, P < 0.05). PPADS reduced the pressor response to exercise (P < 0.05) but had no effect on the magnitude of PGE2 production during contraction (P = 0.48). These experiments demonstrate that PPADS does not block the exercise pressor reflex through a reduction in PGE2 synthesis. We suggest that PGE2 and P2 receptors play independent roles in stimulating the exercise pressor reflex.