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D L Hay

Publications and source records attributed to D L Hay.

At least 19 recordsLinked to original sources
PubMed2004

The pharmacology of CGRP-responsive receptors in cultured and transfected cells.

Historically, CGRP receptors have been classified as CGRP(1) or CGRP(2) subtypes, chiefly depending on their affinity for the antagonist CGRP(8-37). It has been shown that the complex between calcitonin receptor-like receptor (CRLR or CL) and receptor activity modifying protein (RAMP) 1 provides a molecular correlate for the CGRP(1) receptor; however, this does not explain the range of affinities seen for CGRP(8-37) in isolated tissues. It is suggested that these may largely be explained by a combination of methodological factors and CGRP-responsive receptors generated by CL and RAMP2 or RAMP3 and complexes of RAMPs with the calcitonin receptor.

Animals↗
PubMed2004

Heterodimers and family-B GPCRs: RAMPs, CGRP and adrenomedullin.

RAMPs (receptor activity-modifying proteins) are single-pass transmembrane proteins that associate with certain family-B GPCRs (G-protein-coupled receptors). Specifically for the CT (calcitonin) receptor-like receptor and the CT receptor, this results in profound changes in ligand binding and receptor pharmacology, allowing the generation of six distinct receptors with preferences for CGRP (CT gene-related peptide), adrenomedullin, amylin and CT. There are three RAMPs: RAMP1-RAMP3. The N-terminus appears to be the main determinant of receptor pharmacology, whereas the transmembrane domain contributes to association of the RAMP with the GPCR. The N-terminus of all members of the RAMP family probably contains two disulphide bonds; a potential third disulphide is found in RAMP1 and RAMP3. The N-terminus appears to be in close proximity to the ligand and plays a key role in its binding, either directly or indirectly. BIBN4096BS, a CGRP antagonist, targets RAMP1 and this gives the compound very high selectivity for the human CGRP(1) receptor.

Adrenomedullin↗
PubMed2004

Amylin receptors: molecular composition and pharmacology.

Several receptors which bind the hormone AMY (amylin) with high affinity have now been identified. The minimum binding unit is composed of the CT (calcitonin) receptor at its core, plus a RAMP (receptor activity modifying protein). The receptors have been named AMY(1(a)), AMY(2(a)) and AMY(3(a)) in accordance with the association of the CT receptor (CT((a))) with RAMP1, RAMP2 and RAMP3 respectively. The challenge is now to determine the localization and pharmacological nature of each of these receptors. Recent attempts to achieve these aims will be briefly discussed.

Animals↗
PubMed2003

CL/RAMP2 and CL/RAMP3 produce pharmacologically distinct adrenomedullin receptors: a comparison of effects of adrenomedullin22-52, CGRP8-37 and BIBN4096BS.

Adrenomedullin (AM) has two known receptors formed by the calcitonin receptor-like receptor (CL) and receptor activity-modifying protein (RAMP) 2 or 3: we report the effects of the antagonist fragments of human AM and CGRP (AM22-52 and CGRP8-37) in inhibiting AM at human (h), rat (r) and mixed species CL/RAMP2 and CL/RAMP3 receptors transiently expressed in Cos 7 cells or endogenously expressed as rCL/rRAMP2 complexes by Rat 2 and L6 cells. AM22-52 (10 microM) antagonised AM at all CL/RAMP2 complexes (apparent pA2 values: 7.34+/-0.14 (hCL/hRAMP2), 7.28+/-0.06 (Rat 2), 7.00+/-0.05 (L6), 6.25+/-0.17 (rCL/hRAMP2)). CGRP8-37 (10 microM) resembled AM22-52 except on the rCL/hRAMP2 complex, where it did not antagonise AM (apparent pA2 values: 7.04+/-0.13 (hCL/hRAMP2), 6.72+/-0.06 (Rat2), 7.03+/-0.12 (L6)). On CL/RAMP3 receptors, 10 microM CGRP8-37 was an effective antagonist at all combinations (apparent pA2 values: 6.96+/-0.08 (hCL/hRAMP3), 6.18+/-0.18 (rCL/rRAMP3), 6.48+/-0.20 (rCL/hRAMP3)). However, 10 microM AM22-52 only antagonised AM at the hCL/hRAMP3 receptor (apparent pA2 6.73+/-0.14). BIBN4096BS (10 microM) did not antagonise AM at any of the receptors. Where investigated (all-rat and rat/human combinations), the agonist potency order on the CL/RAMP3 receptor was AM approximately betaCGRP>alphaCGRP. rRAMP3 showed three apparent polymorphisms, none of which altered its coding sequence. This study shows that on CL/RAMP complexes, AM22-52 has significant selectivity for the CL/RAMP2 combination over the CL/RAMP3 combination. On the mixed species receptor, CGRP8-37 showed the opposite selectivity. Thus, depending on the species, it is possible to discriminate pharmacologically between CL/RAMP2 and CL/RAMP3 AM receptors.

Adrenomedullin↗
PubMed2002

Adrenomedullin: receptor and signal transduction.

Adrenomedullin is a vascular tissue peptide and a member of the calcitonin family of peptides, which includes calcitonin, calcitonin-gene-related peptide (CGRP) and amylin. Its many biological actions are mediated via CGRP type 1 (CGRP(1)) receptors and by specific adrenomedullin receptors. Although the pharmacology of these receptors is distinct, they are both represented in molecular terms by the type II family G-protein-coupled receptor, calcitonin-receptor-like receptor (CRLR). The specificity here is defined by co-expression of receptor-activity-modifying proteins (RAMPs). CGRP(1) receptors are represented by CRLR and RAMP1, and specific adrenomedullin receptors by CRLR and RAMP2 or 3. Here we discuss how CRLR/RAMP2 relates to adrenomedullin binding, pharmacology and pathophysiology, and how chemical cross-linking of receptor-ligand complexes in tissue relates to that in CRLR/RAMP2-expressing cells. CRLR, like other type II family G-protein-coupled receptors, signals via G(s) and adenylate cyclase activation. We demonstrated that adrenomedullin signalling in cell lines expressing specific adrenomedullin receptors followed this expected pattern.

Adrenomedullin↗
PubMed2002

Interaction of calcitonin-gene-related peptide with its receptors.

The receptor for calcitonin-gene-related peptide (CGRP) is a heterodimer formed by calcitonin-receptor-like receptor (CRLR), a type II (family B) G-protein-coupled receptor, and receptor-activity-modifying protein 1 (RAMP1), a single-membrane-pass protein. It is likely that the first seven or so amino acids of CGRP (which form a disulphide-bonded loop) interact with the transmembrane domain of CRLR to cause receptor activation. The rest of the CGRP molecule falls into three domains. Residues 28-37 and 8-18 are normally required for high-affinity binding, while residues 19-27 form a hinge region. The 28-37 region is almost certainly in direct contact with the receptor; 8-18 may make additional receptor contacts or may stabilize an appropriate conformation of 28-37. It is likely that these regions of CGRP interact both with CRLR and with the extracellular domain of RAMP1.

Animals↗
PubMed2002

Effects of melanocortin receptor ligands on thyrotropin-releasing hormone release: evidence for the differential roles of melanocortin 3 and 4 receptors.

The hypothalamic melanocortin system is important in the central regulation of food intake and body weight. We have previously demonstrated that intracerebroventricular administration of alpha-melanocyte stimulating hormone (alpha-MSH), a nonselective MC3 and MC4 receptor agonist, stimulated plasma thyroid-stimulating hormone, and agouti-related protein (AgRP), an MC3 and MC4 receptor antagonist, suppressed it. In this study, we investigated the effects of MC3 and MC4 receptor (MC3-R and MC4-R) selective agonists and antagonists on the release of thyrotropin-releasing hormone (TRH) from hypothalamic explants in vitro. alpha-MSH stimulated TRH release from the rat hypothalamic explants (alpha-MSH 100 nm 230 +/- 22.9% basal, P < 0.005). In contrast, gamma 2-MSH, a selective MC3-R agonist, suppressed TRH release (gamma 2-MSH 10 microns 76.2 +/- 7.4% basal, P < 0.05). AgRP (83-132), a nonselective MC3/4-R antagonist, induced no change in TRH release whilst JKC-363 (cyclic [Mpr11, D-Nal14, Cys18, Asp22-NH2]-beta-MSH 11-22), a selective MC4-R antagonist, suppressed it (JKC-363 10 nm 57.2 +/- 11.5% basal, P < 0.05). Both AgRP (83-132) and JKC-363 blocked alpha-MSH stimulated TRH release but only AgRP (83-132) blocked the inhibitory effect of gamma 2-MSH on TRH release. These data suggest differential roles for the MC3 and MC4 receptors in TRH release; MC3-R agonism inhibiting and MC4-R agonism stimulating TRH release.

Agouti-Related Protein↗
PubMed2001

Adrenomedullin receptors: molecular identity and function.

Since its discovery in 1993 adrenomedullin (AM) has been the subject over 600 published articles. This multifunctional peptide has powerful vasodilator actions and recent evidence from AM gene-deleted mice suggest that AM plays an essential role in vascular development. However the lack of valid AM receptor clones and non-peptide receptor ligands has considerably slowed research progress on this important peptide. In this review we have focused on the proposition that the calcitonin receptor-like receptor (CRLR) is a receptor both for AM and the related vasoactive peptide calcitonin gene-related peptide (CGRP). The receptor activity modifying proteins (RAMPs) that are essential for defining CRLR pharmacology will also be discussed. We will describe how AM receptors have been reported to signal and be regulated and to consider whether further receptors for AM beyond CRLR/RAMP combinations might exist.

Adrenomedullin↗
PubMed2001

Oxyntomodulin inhibits food intake in the rat.

Oxyntomodulin is derived from proglucagon processing in the intestine and the central nervous system. To date, no role in the central nervous system has been demonstrated. We report here that oxyntomodulin inhibits refeeding when injected intracerebroventricularly and into the hypothalamic paraventricular nucleus of 24-h fasted rats [intracerebroventricularly and into the paraventricular nucleus, 1 h, oxyntomodulin (1 nmol), 3.1 +/- 0.5 g; saline, 6.2 +/- 0.4 g; P < 0.005]. In addition, oxyntomodulin inhibits food intake in nonfasted rats injected at the onset of the dark phase (intracerebroventricularly, 1 h: oxyntomodulin, 3 nmol, 1.1 +/- 0.19 g vs. saline, 2.3 +/- 0.2 g; P < 0.05). This effect of oxyntomodulin on feeding is of a similar time course and magnitude as that of an equimolar dose of glucagon-like peptide-1. Other proglucagon-derived products investigated [glucagon, glicentin (intracerebroventricularly, 3 nmol; into the paraventricular nucleus, 1 nmol), and spacer peptide-1 (intracerebroventricularly and into the paraventricular nucleus, 3 nmol)] had no effect on feeding at any time point examined. The anorectic effect of oxyntomodulin (intracerebroventricularly, 3 nmol; into the paraventricular nucleus, 1 nmol) was blocked when it was coadministered with the glucagon-like peptide-1 receptor antagonist, exendin-(9-39) (intracerebroventricularly, 100 nmol; into the paraventricular nucleus, 10 nmol). However, oxyntomodulin has a lower affinity for the glucagon-like peptide-1 receptor compared with glucagon-like peptide-1 (IC(50): oxyntomodulin, 8.2 nM; glucagon-like peptide-1, 0.16 nM). One explanation for this is that there might be an oxyntomodulin receptor to which exendin-(9-39) can also bind and act as an antagonist.

Animals↗
PubMed1991

Human chorionic gonadotropin and free beta subunit secretion in three events of pregnancy.

Serum hCG and free beta hCG subunit were measured in intrauterine pregnancies (n = 21), ectopic pregnancies (n = 20) and spontaneous abortions (n = 19) matched for gestational age. Significantly higher concentrations of both dimer and free beta subunit hCG were detected in normal pregnancies (86,336 IU/L) and 21.02 IU/L respectively) compared to abortions (10,460 IU/L and 3.73 IU/L) and ectopic pregnancies (3,900 IU/L and 3.73 IU/L) (p less than .05). When the ratio of free beta hCG/intact hCG (%) was studied, however, EP had significantly higher ratios (0.09 +/- 0.09) than IUP (p less than .05). Assessment of the relative distributions of these ratios revealed that 100% of IUP and AB and 65% of EP had ratios less than 0.10. Most notably, 35% of EP were uniquely characterized by ratios greater than 0.10. This ratio was sufficiently higher in 35% of EP to define a profile completely unique to EP. These data suggest that an increased free beta to dimer hCG ratio of greater than 0.10 may assist in the differentiation of ectopic from intrauterine pregnancies of spontaneous abortions and provide insight into a possible trophoblastic mechanics in these clinical events.

Abortion, Threatened↗
PubMed1991

Serial monitoring of human chorionic gonadotropin and free beta subunit secretion in ectopic pregnancy.

The diagnosis of ectopic pregnancy (EP) has relied primarily on serial serum sampling for human chorionic gonadotropin (hCG) and timely pelvic ultrasound examinations. We recently described the applicability of free beta hCG, intact hCG ratio (%) to distinguish EP from spontaneous abortion or intrauterine pregnancy and found that 35% of EP were uniquely characterized by ratios greater than 0.10. In the present study, we sought to determine if this altered pattern of free beta subunit and intact hCG secretion when present persisted as the EP progressed and whether this ratio was influenced by estradiol (E2) and progesterone (P4) secretion. Twelve patients with histologically-confirmed EP and ratios greater than 0.10 were studied longitudinally from initial presentation to surgical intervention. Ratios (%) ranged from .10 to .52 and persisted at levels greater than 0.10 throughout the period of monitoring in all patients. Intact hCG, free beta hCG and ratios (%) showed no correlation to E2 or P4 concentrations. These data suggest that ratios greater than 0.10 when present persist throughout gestation in EP and may serve as a marker for early diagnosis of EP. Such patterns of hCG secretion in EP may be secondary to altered placental histology with persistence of histologic patterns characteristic of early gestation.

Biomarkers↗
PubMed1990

Chromic gut pelviscopic loop ligature. Effect of the number of pulls on the tensile strength.

The failure load of a pelviscopic loop ligature (PLL) was determined after tightening the slip knot with one, two or three pulls. The PLL showed a significant decrease in strength when tightened with three or more pulls. In each group some PLLs failed from slippage rather than from fracture of the suture material at the base of the knot. Slippage occurred more frequently with each additional pull. The findings indicate that the surgeon should apply only one pull on the device for the most secure knot. In addition, there was no strength difference between the suture material itself and the junction of the suture and its plastic tail grip. The plastic tail grip of the PLL will not release the tail end of the suture material before either the suture material or the slip knot fails.

Catgut↗
PubMed1989

Amniotic fluid enzymes in pregnancies with trisomy 21.

The activities of a range of microvillous enzymes in amniotic fluid from normal pregnancies (n = 213) and those complicated by trisomy 21 (n = 26) were compared in a prospective study. Using a centrifugal analyser, the activities of leucine aminopeptidase (LAP), gamma glutamyl transferase (GGT), aspartate transferase (AST), and isoenzymes of alkaline phosphate (ALP) were measured in amniotic fluid alongside alpha fetoprotein (AFP) levels. Of the markers studied, LAP was found to be the most reliable indicator of trisomy 21. Using levels below the 5th percentile, LAP showed sensitivity 73 per cent, specificity 94 per cent, and predictive value positive 63 per cent. Although these tests would not replace karyotyping in all cases, the measurement of LAP could be useful as a rapid initial screening test, particularly when amniocentesis is performed for indications other than chromosomal abnormalities.

Alkaline Phosphatase↗
PubMed1989

Hemostasis in blood vessels after ligation.

The length of time required to achieve hemostasis after ligation of blood vessels with a diameter of 1.0 to 3.5 mm was studied. Canine limb vessels were ligated with stainless steel clips. These were removed at 48, 60, 72, 84, or 96 hours after ligation, and the degree of hemostasis was evaluated by observing the effect of varying amounts of trauma applied to the vessels. The vessels were first observed for 1 minute. In the second phase the vessels were stroked for 15 seconds and then observed for 1 minute. In the second phase the vessels were stroked for 15 seconds and then observed for any bleeding. An additional 15 seconds of stroking followed by observation completed the evaluation. All blood vessels achieved hemostasis after 96 hours of secure ligation despite the trauma. All ligating devices must provide secure ligation to achieve hemostasis for at least 96 hours. The presence of disease processes or medications interfering with clotting would necessitate a longer period of secure ligation to achieve hemostasis.

Animals↗
PubMed1989

The surplus human embryo: its potential for growth, blastulation, hatching, and human chorionic gonadotropin production in culture.

Early embryos that were unsuitable for transfer to patients or for cryopreservation were cultured either in a human tubal fluid (HTF) or a minimum essential medium (MEM). A significantly higher proportion of embryos developed to blastocysts in MEM (26.8%) than in HTF (14.5%). Approximately similar proportions of embryos formed blastocysts in MEM in the presence or absence of serum. The rate of embryo growth to blastocysts was similar in all media. Blastocyst hatching occurred in MEM + or - serum, but it failed to occur in HTF with serum. Released human chorionic gonadotropin (hCG) from hatched and intrazonal blastocysts was detected by day 8 after fertilization. The mean amount of hCG produced by day 14 was 19,500 mIU from hatched and 1,550 mIU from intrazonal blastocysts. Serum stimulated the output of hCG.

Blastocyst↗
PubMed1989

The potential of early human embryos to form blastocysts, hatch from their zona and secrete HCG in culture.

Early embryos assessed to be unsuitable for transfer to patients or for cryopreservation were cultured either in minimum essential medium (MEM) or in synthetic human tubal fluid (HFT). A significantly higher percentage of embryos developed to blastocysts in MEM (26.5%) than in HTF (14.5%). Serum was not required for blastocyst formation nor for hatching in MEM. HTF containing 1% human cord serum failed to support blastocyst hatching. Haploid (monopronucleate) and diploid (bipronucleate) embryos formed blastocysts and hatched with a similar frequency but triploid (tripronucleate) embryos developed poorly. Human chorionic gonadotrophin (HCG) released by hatched and intrazonal blastocysts was detected between days 7 and 8 after fertilization. The mean total HCG produced by hatched blastocysts by day 14 was 19,500 mIU, but embryos trapped inside their zonae released a mean level of 1550 mIU. Serum was shown to stimulate the output of HCG from both hatched and intrazonal blastocyst tissues. Free beta- and alpha-subunits of HCG were not released by developing blastocysts, but low levels of beta-HCG were produced by some embryonic tissues between days 12 and 14 when degenerative changes were observed.

Blastocyst↗
PubMed1989

Monitoring early pregnancy with transvaginal ultrasound and choriogonadotrophin levels.

Serum human chorionic gonadotrophin levels were correlated with gestational sac size detected by transvaginal ultrasound in a series of 178 women undergoing in vitro fertilization. The improved resolution of transvaginal ultrasound enables pregnancy to be detected between 17 and 20 days post-ovum retrieval, when HCG levels were greater than an average threshold level of 1,300 IU/L. The lower HCG discriminatory zone enables improved evaluation of ectopic pregnancies. Also, higher HCG titres observed in multiple pregnancies enable estimation of implantation rates when more than one embryo is transferred.

Chorionic Gonadotropin↗