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Biomedical subjects

H Juan

Publications and source records attributed to H Juan.

At least 19 recordsLinked to original sources
PubMed2001

Roles of nodal-lefty regulatory loops in embryonic patterning of vertebrates.

Nodal is a signalling molecule that belongs to the transforming growth factor-beta superfamily of proteins, and Lefty proteins are antagonists of Nodal signalling. The nodal and lefty genes form positive and negative regulatory loops that resemble the reaction-diffusion system. As a pair, these genes control various events of vertebrate embryonic patterning, including left-right specification and mesoderm formation. In this review, we will focus on recent studies that have addressed the roles of nodal and lefty in mouse development.

Animals↗
PubMed2000

Characterization of prostanoid receptors mediating actions of the isoprostanes, 8-iso-PGE(2) and 8-iso-PGF(2alpha), in some isolated smooth muscle preparations.

We investigated the contracting actions of the isoprostanes (isoPs), 8-iso-prostaglandin (PG) F(2alpha) and 8-iso-PGE(2), in comparison to the effects of the thromboxane (TX) A(2)-mimetic U 46619 and the traditional prostaglandin PGE(2) in the isolated rat aorta, isolated rat gastric fundus and the isolated guinea-pig ileum. U 46619 and 8-iso-PGF(2alpha) caused contractions in the rat aorta and rat gastric fundus in a concentration-dependent manner, whereas these agonists showed no effects in the guinea-pig ileum. However, 8-iso-PGE(2) and PGE(2) caused contractions in all isolated organs used. The prostanoid TP-receptor antagonist SQ 29,548 (10 nM) significantly antagonized vasoconstrictions induced by the agonists used in the rat aorta. SQ 29,548 at a final concentration of 3 microM, but not at lower concentrations, significantly inhibited contractions induced by U 46619, 8-iso-PGF(2alpha) and 8-iso-PGE(2) in the rat fundus. Responses to PGE(2) were unchanged. The prostanoid EP(1)-receptor antagonist SC 51089 (3 microM) significantly inhibited contractions induced by 8-iso-PGE(2) and PGE(2) in the rat fundus and in the guinea-pig ileum. SC 51089 had no effect on responses to any of the agonists tested. Our results show that 8-iso-PGE(2), in contrast to 8-iso-PGF(2alpha), can also cause contractions by activation of the EP(1)-receptors in the rat gastric fundus and the guinea-pig ileum. The findings of the present study do not support the existence of a unique isoP-receptor in the tissues used.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2000

Formation of 8-iso-PGF(2alpha) and thromboxane A(2) by stimulation with several activators of phospholipase A(2) in the isolated human umbilical vein.

We investigated the effects of the phospholipase A(2) (PLA(2)) activators calcium ionophore A 23187, hydrogen peroxide (H(2)O(2)), bradykinin (BK), histamine and noradrenaline (NA) on the 8-iso-prostaglandin (PG)F(2alpha) formation in the isolated human umbilical vein and the isolated rabbit ear. For comparison, the influence of these substances on the thromboxane A(2) (TXA(2)) release was also investigated. The release of total (esterified as well as free) 8-iso-PGF(2alpha), free 8-iso-PGF(2alpha) and TXB(2), the stable metabolite of TXA(2), was determined by specific enzyme immunoassays. The results show that bolus injections of 5.4 mmol H(2)O(2), 30 nmol A 23187, 10 nmol BK, 50 nmol histamine and 20 nmol NA caused an increased release of total 8-iso-PGF(2alpha) in the umbilical vein and the rabbit ear. A perfusion with H(2)O(2) at a final concentration of 0.3 mM also increased the release of this isoprostane. Increased formation of free 8-iso-PGF(2alpha) was induced by A 23187 injection and by both modes of H(2)O(2) administration, but not by the other treatments. Bolus injections of A 23187, BK and histamine induced an increased release of TXB(2) in both organs. Both modes of H(2)O(2) administration and NA showed no releasing effects. In conclusion, our results show that the substances used are able to stimulate the formation of 8-iso-PGF(2alpha) concurrently with the release of PGs. This effect might be of pathophysiological relevance in inflammatory and cardiovascular diseases in which an enhanced release of free radicals, BK, histamine or NA play an important role.

Animals↗
PubMed2000

Influence of polyunsaturated fatty acids on vasoconstrictions induced by 8-iso-PGF(2alpha) and 8-iso-PGE(2).

8-iso-PGF(2alpha) and 8-iso-PGE(2), which are released in vivo by free radical catalyzed peroxidation of arachidonic acid, are equipotent vasoconstrictors in vivo and in vitro. It is assumed that they exert this effect via activation of the thromboxane A(2) (TP) receptor or a TP-receptor-like isoprostane receptor. Increased levels of 8-iso-PGF(2alpha) have been detected in human cardiovascular diseases. It has been found that polyunsaturated fatty acids (PUFAs) have many beneficial effects in cardiovascular diseases, including antivasoconstrictor actions. Therefore, we investigated the influence of perfusions with eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and dihomo-gamma-linolenic acid (DGLA) at final concentrations of 3 and 30 micromol/l on vasoconstriction induced by 8-iso-PGF(2alpha), 8-iso-PGE(2) and the thromboxane A(2) mimetic U 46619 in the vasculature of the isolated perfused rabbit ear. Additionally, the effect of indomethacin (final concentration 3 micromol/l) on the effects of the PUFAs was investigated. Our results show that the PUFAs at a concentration of 30 micromol/l caused a significant inhibition of the vasoconstrictions induced by 8-iso-PGF(2alpha), 8-iso-PGE(2) and U 46619. Furthermore, it can be assumed that a part of the inhibitory effect of DGLA is due to the effect of a cyclooxygenase product, probably PGE(1), because indomethacin reduced the inhibitory effect of DGLA.

8,11,14-Eicosatrienoic Acid↗
PubMed1999

Direct cloning of genomic DNA by recombinogenic targeting method using a yeast-bacterial shuttle vector, pClasper.

We have developed a method to clone genomic DNA selectively into a yeast-bacterial shuttle vector, pClasper, by recombinogenic targeting in yeast. A gene-specific pClasper targeting vector was constructed with small recombinogenic ends (500 bp) derived from flanking sequences of the genomic region to be cloned. Linearized, recombinogenic pClasper targeting vector and native genomic DNA were cotransformed into yeast. The gene of interest is selectively cloned by recombination between the recombinogenic ends in the targeting vector and homologous regions in the genomic DNA. Here we demonstrate direct cloning of a stably integrated Hoxc8-LacZ-Ura3 reporter gene construct from a mouse embryo fibroblast cell line and single-copy genes from total human genomic DNA. The frequency of capture of the recombinant insert was 0.05-3% of transformants. In contrast to previous reports, we were able to clone genomic DNA directly with a vector containing yeast autonomous replicating sequences. This approach provides a powerful method with which to clone and modify genes precisely for functional analysis.

Animals↗
PubMed1999

Influence of isoprostanes on vasoconstrictor effects of noradrenaline and angiotensin II.

The isoprostanes, 8-iso-prostaglandin F2alpha and 8-iso-prostaglandin E2, which are released in vivo by free radical-catalyzed peroxidation of arachidonic acid, are potent vasoconstrictors. Increased formation of 8-iso-prostaglandin F2alpha has been detected in human cardiovascular diseases, in which enhanced plasma levels of noradrenaline and angiotensin II have harmful vasoconstrictor effects. Therefore, we investigated the influence of perfusions with the thromboxane A2 mimetic, U 46619, and with the isoprostanes, 8-iso-prostaglandin F2alpha, 8-iso-prostaglandin E2, 8-iso-prostaglandin E1 and 8-iso-prostaglandin F3alpha, on the vasoconstrictor effects of noradrenaline and angiotensin II in the isolated perfused rabbit ear. Our results demonstrate that perfusions with U 46619, 8-iso-prostaglandin E2 and 8-iso-prostaglandin F2alpha, at a subthreshold concentration (30 nM), amplified the vasoconstrictions induced by noradrenaline or angiotensin II significantly. In addition, the results show that U 46619, 8-iso-prostaglandin F2alpha, 8-iso-prostaglandin E2 and 8-iso-prostaglandin E1, which were applied as a bolus, induced much more pronounced vasoconstrictions than prostaglandin F2alpha, prostaglandin E2 and prostaglandin F3alpha. Prostaglandin E1 and 8-iso-prostaglandin F3alpha, showed no effects. In conclusion, it can be assumed that the powerful vasoconstrictions induced by 8-iso-prostaglandin E2 and 8-iso-prostaglandin F2alpha and their potentiating effects on vasoconstrictions induced by noradrenaline or angiotensin II might be of pathophysiological relevance in cardiovascular diseases.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1999

Perioperative catecholamine changes in cardiac risk patients.

BACKGROUND: It has previously been found that in cardiac risk patients undergoing non-cardiac surgery post-operative cardiac complications are correlated with high post-operative serum levels of troponin T (TNT) and troponin I (TNI). We investigated whether perioperative changes in the release of free (fCAs) and conjugated catecholamines (cCAs) correlate with the increased serum level of TN (TN upward arrow). MATERIALS AND METHODS: Plasma levels of CAs were determined in 28 patients at risk for or with definite coronary artery disease. Blood sampling was performed in the morning on the day before surgery, on the day of surgery before induction of anaesthesia and until the fifth post-operative day for measurement of CAs by high-performance liquid chromatography. RESULTS: The plasma concentrations of free and conjugated noradrenaline (fNA and cNA) as well as of free and conjugated adrenaline (fA and cA) were increased significantly in TN upward arrow patients post-operatively. The plasma levels of free as well as of conjugated NA and A in TN upward arrow patients were significantly higher than in TN0 patients over the whole post-operative period. CONCLUSION: This study demonstrates that increased post-operative release of fNA and fA as well as of cNA and cA correlates with high post-operative serum levels of troponins in cardiac risk patients undergoing non-cardiac surgery.

Aged↗
PubMed1999

Vascular effects of isoprostanes after endothelial damage.

The isoprostanes, 8-iso-PGF2alpha and 8-iso-PGE2, are powerful vasoconstrictors in vitro and in vivo. Increased formation of 8-iso-PGF2alpha was detected in atherosclerotic patients. In this disease endothelial injuries appear, followed by a reduced release of nitric oxide (NO). Our results show that the vasoconstrictor effects of 8-iso-PGF2alpha as well as of 8-iso-PGE2 were amplified after endothelial damage of the vasculature of the isolated perfused rabbit ear. Also vasoconstrictions induced by both isoprostanes were amplified by perfusions with the NO-synthase blocker N(G)-nitro-L-arginine methylester (L-NAME) at a final concentration of 100 micromol/l. Therefore, we can assume that the amplification of the vasoconstrictor effects of the isoprostanes used after damage of endothelium might be mainly due to the reduced formation of NO.

Animals↗
PubMed1998

The nonpeptide B2 receptor antagonist FR173657: inhibition of effects of bradykinin related to its role in nociception.

1. The nonpeptide bradykinin B2 receptor antagonist, FR173657 ((E)-3-(6-acetamido-3-pyridyl)-N-[N-(2, 4-dichloro-3-[(2-methyl-8-quinolinyl) oxymethyl] phenyl]-N-methylaminocarbonylmethyl] acrylamide), was tested in models involving bradykinin-induced activation of primary afferent neurones in vitro and in vivo. 2. Bradykinin-induced contractions of the rabbit isolated iris sphincter muscle mediated by tachykinin release from trigeminal afferent neurones were inhibited in a non-competitive manner by FR173657. A pKB value of 7.9 was calculated. Effects of substance P were unaffected by FR173657. 3. Nociceptive behavioural responses following intraplantar injection of bradykinin in unanaesthetized rats were reduced by 0.3 micromol kg(-1) FR173657 s.c. (P < 0.05), and completely abolished by 3 micromol kg(-1) (P < 0.05). Peroral administration of 5 micromol kg(-1) FR173657 abolished the bradykinin effects (P < 0.05); lower doses had no significant effect. 4. Shortening by intraplantar injection of bradykinin of the paw withdrawal latency in response to radiant heat was abolished by 3 micromol kg(-1) FR173657 s.c. (P < 0.05), while 300 nmol kg(-1) had an intermediate effect. Hyperalgesia induced by prostaglandin E2 remained unaffected by FR173657. 5. Blood pressure reflexes following i.p. instillation of bradykinin in anaesthetized rats were inhibited by FR173657 s.c. with an ID50 of 1.1 micromol kg(-1), while the peptidic B2 antagonist icatibant (Hoe-140; D-Arg0-[Hyp3, Thi5, D-Tic7, Oic8]-bradykinin) caused inhibition at significantly lower doses (ID50 8.5 nmol kg(-1) P < 0.001). Responses to hydrochloric acid i.p. remained unaffected by FR173657. 6. FR173657 or similar nonpeptide compounds may be useful for the development of drugs for diseases involving pain induced by the release of endogenous kinins, i.e. especially in acute inflammatory conditions.

Analgesics↗
PubMed1997

Effects of the non-peptide B2 antagonist FR173657 on kinin-induced smooth muscle contraction and relaxation, vasoconstriction and prostaglandin release.

1. The non-peptide bradykinin (BK) antagonist (E)-3-(6-acetamido-3-pyridyl)-N-[N-[2,4-dichloro-3-[(2-methyl-8-quinolin yl) oxymethyl]phenyl]-N-methylaminocarbonylmethyl]acrylamide (FR173657) was tested in intestinal, uterine, tracheal and vascular in vitro preparations. The investigation aimed at determining the antagonistic potency, duration of action, specificity for BK receptors and apparent mode of antagonistic action of FR173657. 2. Contractions of the isolated ileum of the guinea-pig in response to BK were inhibited by FR173657 (10-300 nM) in a concentration-dependent manner. The inhibition lasted for up to 90 min after wash-out of FR173657. Cumulative concentration-response curves to BK were shifted to the right with a concomitant decrease in the maximum effect. A pKB value of 8.7 was determined. FR173657 had no effect on contractions induced by acetylcholine, histamine, 5-hydroxytryptamine, substance P, angiotensin II or caerulein. 3. The concentration-response curves for B2 receptor-mediated relaxations of the rat isolated duodenum induced by BK were shifted to the right together with a concomitant reduction of the maximum BK effect in the presence of FR173657 (10-300 nM). A pKB of 9.0 +/- 0.2 was calculated. FR173657 had no effect on B1 receptor-mediated relaxations in response to des-Arg9-BK. 4. The concentration-response curves for BK-induced contractions of the rat isolated uterus were shifted to the right by FR173657 (3-300 nM) in a concentration-dependent and parallel manner. The Schild plot for the inhibition caused by FR173657 had a slope of -0.98 indicating a competitive mode of antagonism. A pA2 value of 9.1 was determined. 5. Contractions of the circular smooth muscles of the guinea-pig isolated trachea in response to BK were concentration-dependently inhibited by FR173657 (10-100 nM). An affinity estimate of 9.3 was calculated for FR173657. Contractions induced by acetylcholine and relaxations in response to isoprenaline remained completely unaffected by FR173657. 6. In the rabbit isolated perfused ear, BK (0.01-10 nmol) produced a dose-dependent vasoconstriction. In the presence of 30 nM FR173657, the effects of BK were reduced by at least 60%, while FR173657 completely abolished the effects of all BK doses at 300 nM. FR173657 did not affect vasoconstriction induced by noradrenaline or angiotensin II. 7. The arterial injection of BK (10 nmol) into the rabbit isolated perfused ear caused an approximately three fold increase in the release of the prostaglandins E2 and I2 into the venous effluent. The BK-stimulated prostaglandin release was completely abolished in the presence of FR173657 (300 nM) while the basal prostaglandin release was unchanged. 8. In summary, FR173657 was shown to be a highly potent and selective BK antagonist which was active on B2, but not B1, receptors. FR173657 was a competitive antagonist in the rat uterus but showed a deviation from competitive inhibition in the other preparations studied similar to other second generation peptide antagonists. The inhibitory action in vitro was long-lasting, but was fully reversible.

Animals↗
PubMed1994

Determination of traces of pyrethrins and piperonyl butoxide in biological material by high-performance liquid chromatography.

A liquid chromatographic method for the determination of pyrethrins and of the synergist piperonyl butoxide in human plasma after C18 solid-phase extraction is described. UV detection was found to be sensitive enough to determine concentrations far below the limit of toxicity. With respect to future investigations concerning studies in biological materials, a column-switching system for sample preparation was developed and compared with solid-phase extraction. Both methods show comparable limits of detection, but the column-switching technique has the advantage of fully automating the system.

Chromatography, High Pressure Liquid↗
PubMed1991

[Isolation of the antiphlogistic principle from Epilobium angustifolium].

From the leaves of Epilobium angustifolium L. (Onagraceae) an antiphlogistic principle was isolated and identified as myricetin 3-O-beta-D-glucuronide. This novel flavonoid exhibited a very strong anti-inflammatory effect on carrageenan-induced edema in the rat hind paw (more than ten times more effective than indomethacin) and an inhibitory effect on prostaglandin biosynthesis (as effective as indomethacin).

Animals↗
PubMed1989

Fish oil diet rich in eicosapentaenoic acid increases bleeding time in the rat by interaction with sympathetic transmitters.

The influence of a diet supplemented with MaxEPA (a fish oil concentrate, rich in eicosapentaenoic acid = EPA) on bleeding time in small mesenteric arteries of the rat and on formation of thromboxane B2 (TXB2) by ADP-stimulated platelets was investigated. Since EPA has been found to antagonize noradrenaline (NA) - induced vasoconstriction, the influences on bleeding time of the alpha-receptor antagonist phentolamine and of the adrenergic neuron blocking agent guanethidine alone as well as during dietary supplementation with MaxEPA were studied. Bleeding time slowly increased during the MaxEPA diet over a period of 12 weeks resulting in a final prolongation of about 75%. Indomethacin which dose-dependently increased bleeding time in control rats, further increased the already prolonged bleeding time in rats on the MaxEPA diet. Guanethidine prolonged bleeding time strongly in control animals but caused no further increase in those on the MaxEPA diet. Indomethacin also further increased the bleeding time prolonged by guanethidine, just as it did in animals on MaxEPA diet. In contrast to guanethidine, phentolamine prolonged bleeding time only slightly. The ability of platelets from rats on the diet to generate TXB2 was reduced to 59.5% but was more drastically reduced (to 26.7%) from rats pretreated with indomethacin. The results indicate that MaxEPA feeding prolongs bleeding time by a mechanism other than that of indomethacin. We speculate that EPA prolongs bleeding time rather by antagonizing the vasoconstrictor effect of sympathetic transmitters at the site of the injured vessel than by a reduced formation of TXA2.

Animals↗
PubMed1989

Experimental evaluation of radiographic contrast media in perivascular pain receptors in the perfused isolated rabbit ear.

The algesic effects of intravascularly injected solutions of sorbitol and ionic and nonionic contrast media (CM) with high and low osmolality were tested in the perfused isolated rabbit ear connected to the body by the great auricular nerve. The threshold for the pain reflex effect was found to be at an osmolality of between 600 and 700 mosm/kg H2O, that is, at about twice the osmolality of blood. This result is consistent with results obtained to date in investigations in the non-anesthetized rat and in diagnostic examinations with CM in humans. The effects of both sorbitol and the ionic CM at a given osmolality were dose dependent only after low doses and not after a high dose. There were no pain reactions after injection of ionic and nonionic CM with a low osmolality. Release of prostacyclin was observed in preliminary tests after injection of ionic substances with high osmolality, but not after injection of CM with low osmolality.

Angiography↗
PubMed1988

Eicosapentaenoic acid inhibits vasoconstrictor- and noradrenaline-potentiating effects of neuropeptide Y in the isolated rabbit ear.

The vasoconstrictor effect of neuropeptide Y (NPY) was compared with that of noradrenaline (NA) in the isolated perfused rabbit ear. Phentolamine at a concentration which completely abolished the effect of NA, did not diminish the effect of NPY. The combined vasoconstrictor effect of NPY and NA was significantly stronger than the calculated effect of an additive interaction, but not significantly stronger than an independent combination. This can be interpreted as an overadditive effect, and may be an indication for different points of attack with independent actions of these two transmitters in the vessels of the rabbit ear. Eicosapentaenoic acid (EPA) dose-dependently antagonized the effect of NPY to a similar degree as that of NA. In the presence of indomethacin (8.6 mumol/l), neither the effect of NPY nor that of EPA was changed. Moreover, EPA (33 mumol/l) diminished the combined vasoconstrictor effect of NA and NPY. These findings indicate that EPA is a non-selective antagonist of sympathetic transmitters in small peripheral vessels and excludes an interaction at specific receptors.

Animals↗
PubMed1987

Modulation of the contractile activity of the guinea-pig lung parenchymal strip by exogenous 5,8,11,14,17-eicosapentaenoic acid.

Exogenous eicosapentaenoic acid (EPA, 16.5 mumol/l or 33 mumol/l) inhibited dose-dependently the anaphylactic contractile response of guinea-pig lung parenchymal strips suspended in an organ bath. As determined by radioimmunoassay, EPA inhibited in a dose-dependent manner the anaphylactic release of the cyclooxygenase products thromboxane (TX) B2 and 6-keto-prostaglandin (PG) F1 alpha but simultaneously enhanced the release of sulfidopeptide (SP)-leukotrienes (LT). Indomethacin (2.8 mumol/l) abolished the release of cyclooxygenase products but potentiated the release of SP-LT. However, indomethacin treatment did not affect the inhibitory action of EPA on the contractile response of the anaphylactic lung strips. The lipoxygenase inhibitor, esculetin (50 mumol/l), inhibited the release of SP-LT and also that of cyclooxygenase products of polyunsaturated fatty acid metabolism. The combination of esculetin and EPA resulted in enhanced inhibition of the anaphylactic contractile response as compared to EPA alone. By reversed phase high pressure liquid chromatography (HPLC), SP-LT from anaphylactic lung parenchymal strips was shown to consist of LTD4 and LTE4. EPA-pretreated lung strips released upon immunologic challenge additional immunoreactivity comigrating with authentic LTC4, LTC5, LTD5 and LTE5. While anaphylactic control strips also released LTB4, in the bath fluid of EPA-treated strips, an additional immunoreactive compound migrating with the retention time of LTB5 was observed. In non-sensitized guinea-pig lung parenchymal strips EPA inhibited the myotropic activity of exogenous mediators such as histamine (9 mumol/l), LTC4 (16 nmol/l) and the TX mimetic U 46619 (28.4 nmol/l), an effect which was neither affected by indomethacin (2.8 mumol/l) nor by the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA, 10 mumol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗