Molecular interaction of Agouti protein and Agouti-related protein with human melanocortin receptors

Agouti protein and the Agouti-related protein (AGRP) are antagonists of the melanocortin-3 receptor and melanocortin-4 receptor. Both proteins contain 10 cysteines in the C-terminal domain arranged in five disulfide bonds. One possible arrangement of the disulfide bonds predicts an octapeptide loop, and the chemical properties of four residues within this loop (residues 111-114 in human AGRP) bear striking resemblance to those of several melanocortin peptides, including alpha-MSH, MT-II, and SHU-9119. We showed that cyclic synthetic octapeptides based on the sequence of this loop from Agouti protein or human AGRP are functional antagonists of the human melanocortin-4 receptor. All peptides had a lower affinity for the melanocortin-3 receptor than for the melanocortin-4 receptor. Substitution of serines for cysteines resulted in linear peptides which had reduced binding affinities for both receptors. Mutational analysis of human AGRP indicated that its C-terminal domain is functionally equivalent to the intact human AGRP. The RFF111-113 triplet appears to be the most critical portion of AGRP in determining the binding affinity for both melanocortin-3 and melanocortin-4 receptors. These data strongly suggest that the loop defined by Cys-110 and Cys-117 is critical in determining the antagonist activity of human AGRP. Our data provide indirect evidence for the suggestion that the Cys-110 to Cys-117 octapeptide loop of human AGRP mimics the conformation of alpha-MSH, MT-II, and SHU-9119.     

Synthesis and characterization of poly{hexakis[(methyl)(4‐hydroxyphenoxy)]cyclotriphosphazene}

The reaction of methylhydroquinone with hexachlorocyclotriphosphazene in the presence of a base, 4‐picoline, in cyclohexane was investigated. Nuclear magnetic resonance spectroscopy, multiangle laser light scattering, and elemental analyses were performed on the product and two other related phosphazene materials produced by analogous synthetic routes: poly[hexakis(4‐hydroxyphenoxy)cyclotriphosphazene] (1) and hexakis[(3‐tert‐butyl)(4‐hydroxyphenoxy)]cyclotriphosphazene (2) . Unlike the data for 2 where the tert‐butyl moiety enforced regiospecific nucleophilic addition, the data for the methylhydroquinone‐substituted cyclotriphosphazene product indicate that the less sterically bulky methyl group provides only limited protection for the adjacent hydroxyl group. The result is the formation of a low molecular weight oligomer, poly{hexakis[(methyl)(4‐hydroxyphenoxy)]cyclotriphosphazene} (3) , instead of a discrete cyclic trimer species. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3439–3446, 2001     

Evaluation of two commercially available carbon dioxide sampling nasal cannulae

Our study compared two commercially available carbon dioxide sampling nasal cannulae for efficacy of oxygenation and relationship of end-tidal carbon dioxide (PETCO2) to arterial carbon dioxide (PaCO2). The two-prong nasal cannula (2PNC) has one prong dedicated to delivering O2 via one naris and the second prong dedicated to sampling exhaled gases via the other naris. The four-prong nasal cannula (4PNC) delivers O2 via a prong in each naris, and samples exhaled gases via another set of prongs in each naris. Forty six patients were divided into three groups, which received either 2 (n = 15), 3 (n = 16), or 4 (n = 15) L/min O2, respectively, and were studied sequentially with standard nasal cannula (SNC), the 2PNC, and then the 4PNC. At each O2 flow rate, PaO2 was equivalent regardless of whether the SNC, 2PNC, or 4PNC was used. Seventy-four percent (34/46) of the 2PNC and 0% (0/46) of the 4PNC PETCO2 values were within +/- 4 torr of the PaCO2 value. The authors conclude that the 2PNC and 4PNC are equally effective compared with an SNC in oxygenating patients, but the PETCO2 measured by the 2PNC provides a superior quantitative estimate of the PaCO2 than that obtained by the 4PNC.     

Levels of urinary beta-core fragment, total oestriol, and the ratio of the two in second-trimester screening for Down syndrome

Levels of beta-core fragment and total oestriol in second-trimester maternal urine samples were measured in 32 Down syndrome pregnancies and 206 control pregnancies. Beta-core fragment and total oestriol values were corrected for the urinary creatinine level and expressed as multiples of the control medians (MOM). In addition, the ratio of the beta-core fragment level to the total oestriol level, without creatinine correction, was calculated, and expressed as MOM values. The median beta-core fragment, total oestriol, and ratio levels in Down syndrome cases were 5.42, 0.64, and 9.32 MOM, respectively. In the Down syndrome pregnancies, 66 per cent of the beta-core fragment levels were above the 95th centile of control levels, while 22 per cent of the total oestriol levels were below the fifth centile of control levels. In combination with maternal age, measurement of beta-core fragment and total oestriol levels in Down syndrome pregnancy resulted in an 80 per cent detection rate at a 5 per cent false-positive rate. Use of the ratio resulted in a univariate detection rate of 72 per cent. In combination with maternal age, the ratio resulted in a detection rate of 81 per cent at a 5 per cent false-positive rate. Based on this unmatched study, the measurement of a ratio of beta-core fragment to total oestriol levels, without the need for creatinine correction, may be useful in screening for fetal Down syndrome in second-trimester urine.     

Neuroendocrine and behavioral responses to intravenous m-chlorophenylpiperazine (mCPP) in depressed patients and healthy comparison subjects

OBJECTIVE: This double-blind study was undertaken to compare central serotonergic function in depressed patients and healthy comparison subjects by examining neuroendocrine and mood responses to intravenous infusion of the serotonin agonist m-chlorophenylpiperazine (mCPP). METHOD: The participants were 20 drug-free patients with DSM-III-R major depression and 18 healty comparison subjects. After an overnight fast, the subjects received an intravenous infusion of mCPP, 0.1 mg/kg, or placebo saline. Blood was obtained for measurement of serum prolactin, growth hormone (GH), and cortisol. Visual analogue scales were used to assess mood. RESULTS: The depressed patients had a blunted GH response and felt less drowsy than the comparison subjects; prolactin, cortisol, and the remaining behavioral ratings showed no differences between the two groups. CONCLUSIONS: In light of findings with other provocative agents, the blunted GH response to mCPP may reflect a defect in GH production in depression and could be a marker of the depressed state. The lack of differences in the other neuroendocrine variables suggests that the functioning of postsynaptic serotonergic receptors responsive to mCPP may be relatively intact in depression.     

Esterase coupled with the H2O2/horseradish peroxidase system triggers chemiluminescence from 2-methyl-1-propenylbenzoate: a potential analytical tool for esterase analysis

Suppression of the fibrinolytic activity plays an important role in the prevention of hemorrhage during pregnancy and labor. A hypofibrinolytic and hypercoagulable state may be established in the placenta during pregnancy. However, little infraction is present in the normal placenta. This evidence shows that placenta maintains the fibrinolytic activity in spite of hypercoagulable state. As there is a high amount of APC in the placenta, APC is thought to be involved in fibrinolysis of placenta. Thus, we studied the role of APC on fibrinolysis in placenta. (1) uPA activity of cell membrane reappears after incubation with uPA/PAI-1 complex and a large amount of APC by flow cytometry, (2) APC was made PAI-1/APC complex after incubation of uPA/PAI-1 complex with APC. Our results suggest that APC is the important substance for fibrinolysis in the placenta by decreasing of PAI activity.     

Fluoroacetate content of some species of the toxic Australian plant genus, Gastrolobium, and its environmental persistence

Gas chromatography confirmed the relatively high concentrations of fluoroacetate found in toxic Gastrolobiums, a genus of indigenous Australian plants. Fluoroacetate concentration in these plants ranged from 0.1 to 3875 micrograms/g (ppm) dry weight, with young leaves and flowers containing the highest concentrations. However, there was considerable intrastand variation between individual plants of at least two species with coefficients of variation ranging from 94% to 129%. Despite the high concentrations of fluoroacetate in many species, only one of nine soil samples collected from beneath these plants contained fluoroacetate. None of the 16 water samples collected from nearby streams and catchment dams contained fluoroacetate. This suggests that fluoroacetate does not persist in this environment. Fluoroacetate was also found in the genus Nemcia, and very low levels of fluoroacetate (ng/g) were detected in the foodstuffs, tea and guar gum. The latter indicates that other plant species may produce biologically insignificant amounts of fluoroacetate.     

Determinants of physical activity in obese children assessed by accelerometer and self-report

Previous research has shown that predictors of activity in adults depend upon the method of measurement. This study is designed to assess the predictors of activity in a sample of 59 obese children. Activity was measured using self-reported and TriTrac accelerometer METs. Self-report and TriTrac accelerometer measures were moderately correlated, r = 0.46, with the self-reported activity (2.3 METs) significantly greater than TriTrac (1.6 METs). Hierarchical regression analysis examined the influence of socioeconomic level, body composition, fitness, hedonics of child and adult activity behaviors, and decisional balance on self-reported and accelerometer-measured activity, controlling for child and parent psychopathology. Child and parent psychological symptoms accounted for 8.3% and 3.4% of the variance in accelerometer and self-reported METs, respectively. The model for accelerometer-measured activity showed socioeconomic level and parent self-report of activity accounted for 14.8% of the incremental variance in child activity. The model for self-report of child activity found that child fitness accounted for 23.5% of the incremental variance in child activity. These results suggest that the predictors of activity level are different based upon the method of measurement, consistent with research in adults.