Biomedical subjects

I O Haefliger

Publications and source records attributed to I O Haefliger.

At least 37 records · Page 2Linked to original sources

PubMed2001

Lacrimal drainage system endoscopic examination and surgery through the lacrimal punctum.

BACKGROUND: To describe an approach to restore the physiological tear passages of an obstructed lacrimal drainage system with instruments introduced through one of the lacrimal punctum. METHOD: In a first step a miniature endoscope (Ø: 0.9, 1.1, 1.3 mm) is introduced in one of the lacrimal punctum to visualize the level, the extent, and the nature of an obstruction along the lacrimal drainage system. In a second step, the miniature endoscope is replaced by a lacrimal trephine (Ø: 0.9, 1.1, 1.3 mm) that holds an optic fiber in its lumen, and the obstruction is removed under endoscopic visual control. The entire procedure is performed under local anesthesia. RESULTS: With this approach it is possible to visualize and remove partial or total fibrous obstructions along the lacrimal drainage system (lacrimal canaliculus, nasolacrimal duct). Lacrimal sac lithiasis can also be fragmented and eliminate in the nose through the nasolacrimal duct. During or after the procedure only minor, and no major, complications can sometime occur, such as hematoma or edema (after lacrimal irrigation) of the surrounding soft tissues. CONCLUSION: The approach described here is straight forward, quick, and can be performed under visual endoscopic control and in local anesthesia. With this approach partial stenosis can easily be diagnosed and cured. This procedure might potentially change our current concepts regarding surgical indications for obstructive epiphora and dacryocystitis. However, the long-term results of this type of surgery need to be challenged.

Dacryocystorhinostomy↗

PubMed2001

[Masquerade of sebaceous gland carcinoma as a rapidly recurring "chalazion", a case report].

PURPOSE: Demonstration of the importance of surgical excision and histological examination in presence of an apparently harmless tumoral alteration of the eyelids. CASE PRESENTATION: We report the case of a 65 year old patient suffering from systemic lupus erythematosus who noted a tumoral lesion on his left lower eyelid. Suspecting a chalazion, his dermatologist simply performed a cauterization. Six weeks later, a recurrence of the tumor appeared at the same location, and again, cauterization was done. A few weeks later, the patient consulted our clinic with a polycyclic tumor of 5 mm in diameter, involving the lid margin of the temporal part of the lower left eyelid. The patient had only moderate signs of blepharitis. There were no palpable preauricular and cervical lymph nodes. Suspecting a malignant tumor, the entire tumoral lesion was removed surgically. HISTOPATHOLOGY: The histopathologic examination showed a highly differentiated sebaceous gland carcinoma, most probably originating from a meibomian gland. The margins of the excision were found to be tumor-free. DISCUSSION: Sebaceous cell carcinoma is a rare entity. Depending on its histological differentiation it can be highly malignant. Infiltrative, and can metastasize. The mortality may reach 30% if low differentiation is present. As illustrated in the present case, the lesion may masquerade a chalazion. Therefore, in case of atypical lesion of the eyelid region complete surgical removal followed by a histopathological examination should be performed.

Adenocarcinoma, Sebaceous↗

PubMed2001

Immunosuppressive therapy in serpiginous choroiditis--case report and brief review of the literature.

BACKGROUND: At present there is no consensus regarding the efficacy of the immunosuppressive therapy in serpiginous choroiditis. PATIENT AND METHODS: We describe the case of a patient with a macular serpiginous choroiditis. Despite corticosteroid therapy the choroiditis was progressive and threatened the central vision. Therefore a triple immunosuppressive therapy with prednisone 1 mg/kg body weight/day (mg/kg/d), azathioprine 1.5 mg/kg/d, and low-dose cyclosporine A 4.5 mg/kg/d was introduced. RESULTS: Under this triple immunosuppressive therapy a prompt stabilisation of the chorioretinal process could be observed in fluorescein angiography. After five months of therapy the examination of the visual field shows an impressive recovery. No significant side effects have been noted. CONCLUSIONS: In the literature, until now only six patients with serpiginous choroiditis treated with a triple agent immunosuppressive therapy have been reported. In all cases this regimen seemed to have a positive influence on the disease. Our present observation corroborates the beneficial effect of a triple agent immunosuppressive therapy on the course of serpiginous choroiditis. However, the beneficial effect of such a therapeutic approach needs to be confirmed by further observations.

Adult↗

PubMed2001

Lipid peroxidation in porcine irises: dependence on pigmentation.

PURPOSE: Pigmentation of the iris is caused by varying amounts of melanin pigment granula in a constant number of melanocytes in the superficial stroma. Melanin has been shown to act as antioxidant. We have now investigated lipid peroxidation in dependence on stromal pigmentation in isolated porcine irises. METHODS: The same number of lightly and heavily pigmented porcine irises (visual selection) were homogenized (1 : 20 w/v) in buffer (50 mmol/l phosphate buffer and 4 mmol/l sodium azide). 500 microl homogenate were incubated at 37 degrees C in duplicate for 5, 10, 20 and 40 min in absence and presence of Fe2+ as inducer of lipid peroxidation. The amount of lipid peroxidation was assayed by the thiobarbituric acid (TBA) test. The results are expressed as nmol of TBA reactive material (TBAR) produced/mg protein. Fe2+ concentration of the supernatant was determined spectrophotometrically with 1,10 orthophenanthroline. Concentrations of D-glucose and D -fructose in iris tissue homogenates were determined spectrophotometrically by enzymatic bioanalysis. RESULTS: 70, 180 and 360 micromol/l Fe2+ induced lipid peroxidation. A plateau region was reached after 20 min. The amount of lipid peroxidation differed in dependence on stromal pigmentation in porcine irises. The effect was most significant at 180 micromol/l Fe2+, which induced 1.373 +/- 0.138 nmol TBAR/mg protein in lightly compared to 0.491 +/- 0.125 nmol TBAR/mg protein in heavily pigmented irises after 10 min incubation (p < 0.0001, n = 4). Similar effects (factor 2-3) were also measured after 20 and 40 min incubation. On the other hand, the content of Fe2+ in the supernatant was the same within error. Sugar concentrations (D-glucose and D-fructose) did not differ significantly for the two differently pigmented iris tissues. CONCLUSIONS: There is a stronger induction of lipid peroxidation in lightly compared to heavily pigmented porcine irises. This effect may be related to the difference in stromal melanin content and its antioxidant activity.

Animals↗

PubMed2000

Nitric oxide production by isolated human and porcine ciliary processes.

BACKGROUND: In the kidney, the trachea, and the colon, nitric oxide (NO) can modulate transepithelial fluid transport. This study investigates whether isolated human and porcine ciliary processes produce NO. METHODS: Porcine ciliary processes and iris were used either fresh or thawed after storage at -70 degrees C. Post-mortem (8-12 h) human ciliary processes were used thawed after storage at -70 degrees C. NO was measured by placing a nafion-coated polymeric porphyrinic microsensor (differential pulse voltammetry) on the surface of the tissue. Measurements were conducted in the absence or in the presence of the NO formation inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME; 0.2 mM, 1 mM) or its biologically inactive D-enantiomer N(G)-nitro-D-arginine methyl ester (D-NAME; 1 mM). RESULTS: NO concentrations in porcine ciliary processes (1.27+/-0.25 microM) were higher (P=0.001) than those in the iris (0.00+/-0.02 microM) and were significantly (P<0.001) decreased by L-NAME (fresh specimen). From thawed porcine ciliary processes, NO concentrations measured (1.85+/-0.47 microM) were not significantly different (P=0.16) from those measured in fresh specimen and were also reduced (P <0.001) by L-NAME, but not by D-NAME. In human ciliary processes, NO concentrations measured (0.08+/-0.11 microM) were somehow lower but were again decreased (P<0.001) by L-NAME (thawed specimen). CONCLUSION: Reflecting the biological activity of a nitric oxide synthase, isolated human and porcine ciliary processes produce NO.

Aged↗

PubMed2000

In glaucoma, should enthusiasm about neuroprotection be tempered by the experience obtained in other neurodegenerative disorders?

Some in vitro and in vivo evidence, as well as rare observations in human eyes with glaucoma, suggests that retinal ganglion cells could be lost by apoptosis during the course of glaucomatous optic neuropathy. There exist also observations indicating that in the vitreous of patients with glaucoma it is possible to measure an increased concentration of glutamate (an excitotoxic amino acid known to induce neuronal apoptosis in animal models). These observations, among others, suggest the possibility of an excitotoxicity mechanism in the pathogenesis of glaucoma and as a consequence the potential for a neuroprotective approach to treating this disorder. Amazingly, not only in glaucoma but also in other neurodegenerative disorders (Parkinson's disease, amyotrophic lateral sclerosis, stroke, etc.) it has been postulated that neurons could be lost through an excitotoxic mechanism. In these non-glaucomatous disorders, quite a large number of clinical trials have already been conducted to determine the potential benefit of different neuroprotective therapies. Unfortunately, with a few rare exceptions, the results of these clinical studies have been very disappointing (in contrast to encouraging results obtained in preclinical trials). The experience acquired in other neurodegenerative disorders should probably be kept in mind when addressing the question of neuroprotection in glaucoma. In particular, the hope raised by preclinical studies showing that drugs could have a beneficial effect on the survival of retinal ganglion cells should certainly be tempered until such an effect is confirmed by clinical trials conducted in patients with glaucoma.

Apoptosis↗

PubMed2000

Vasorelaxing properties of carteolol in isolated porcine ciliary arteries.

INTRODUCTION: Carteolol is a topical beta-blocker used in ophthalmology to decrease the intraocular pressure. This study investigates the vasoactive effect of carteolol in isolated porcine ciliary processes. MATERIAL AND METHODS: With a myograph system isometric force measurements, quiescent vessels or vessels either precontracted with endothelin-1 (0.03 microM) or the thromboxane A2 analog U 46619 (0.3 microM) were exposed, in cumulative manner, to increasing concentrations of carteolol (10 microM-3 mM). Vessels that had a functional endothelium were compared with vessels that had a non functional endothelium (intentionally and mechanically damaged). RESULTS: In quiescent vessels carteolol did not induce contractions. In contrast, in precontracted arteries, carteolol evoked marked relaxations which were endothelium-independent. CONCLUSIONS: In vitro, carteolol has a marked vasorelaxing effect on porcine ciliary arteries, however the clinical relevance of this observation for the care of glaucoma patients requires further evaluation.

Adrenergic beta-Antagonists↗

PubMed2000

[Membrane potential depolarization in the porcine ciliary epithelium evoked by nitric oxide].

BACKGROUND: The present work studies if in porcine ciliary body epithelium the intracellular signal transduction pathway nitric oxide (NO)--guanylate cyclase (GC)--3',5'-cyclic guanosinemonophosphate (cGMP) can change the membrane potential of the epithelium of the ciliary body. MATERIAL AND METHODS: Recordings of membrane potentials were done by means of intracellular microelectrodes in the presence of the NO donor Sodium Nitroprusside (SNP; 100 microM; n = 5) or the membrane permeable cGMP analogue 8-parachlorophenyl-thioguanosine-3',5' cyclic monophosphate (8-pCPT-cGMP; 100 microM; n = 5). To test whether the GC is involved in this process, recordings were repeated in both groups in presence or in absence of the GC inhibitor 1-H-(1,2,4)oxadiazole-(4,3-a)quinoxalin-1-one (ODQ; 10 microM; n = 4). RESULTS: SNP and 8-pCPT-cGMP both induced significant membrane potential depolarizations (7.7 +/- 1.8 mV and 13.1 +/- 1.3 mV, mean +/- SEM). Membrane depolarizations induced by SNP were significantly inhibited by ODQ (p < 0.01), whereas depolarizations induced by 8-pCPT-cGMP were not altered by the presence of ODQ (p > 0.2). CONCLUSIONS: Nitric oxide induces depolarizations of the membrane potential in the isolated porcine ciliary body. This process is transduced by activation of the GC. We conclude that nitric oxide might be involved in the regulation of permeability of the cellular membrane for ions in the ciliary body.

Animals↗

PubMed2000

Altered gene expression in lymphocytes of patients with normal-tension glaucoma.

BACKGROUND: In glaucoma there is a loss of retinal ganglion cells. There is evidence that this loss can occur by apoptosis. The signal transduction leading to retinal ganglion cell apoptosis in glaucoma is not yet clear. The present study compares the gene expression in lymphocytes of normal tension glaucoma patients (NTG-patients) with the one of healthy controls. METHODS: Subtractive hybridization was used to compare mRNA in lymphocytes of six vasospastic NTG-patients with six age and sex matched healthy subjects. RESULTS: Genes coding for p53-protein, NTP (neural thread protein) and 20 S proteasome subunit XAPC7 were overexpressed, whereas those coding for XPGC (Xeroderma pigmentosum gene), the survivin protein as well as one type of ABC transport protein were underexpressed. CONCLUSION: In comparison to healthy controls, patients with vasospastic NTG seem to over- as well as under-express certain genes in their lymphocytes.

ATP-Binding Cassette Transporters↗

PubMed2000

NO/cGMP pathway activation and membrane potential depolarization in pig ciliary epithelium.

PURPOSE: To investigate whether in isolated porcine ciliary processes, stimulation of the nitric oxide (NO)-guanylate cyclase (GC)-3',5'-cyclic guanosine monophosphate (cGMP) pathway modulates ciliary epithelial transmembrane potential. METHODS: Changes in transmembrane potential induced by the two NO donors, sodium nitroprusside (SNP; 100 microM) and S-nitroso-N-acetyl-penicillamine (SNAP; 100 microM), or by the cGMP-analogue 8-para-chlorophenylthioguanosine-3', 5'-cyclic guanosine monophosphate (8-pCPT-cGMP; 100 microM) were measured with microelectrodes in the presence or in the absence of the GC-inhibitor 1-H-(1,2,4)oxadiazole(4,3-alpha)quinoxalin-1-1 (ODQ; 10 microM). The effect of 8-pCPT-cGMP was also assessed in the presence of the anion channel inhibitors niflumic acid (100 microM), diisothiocyanatostilbene-2,2' disulfonic acid (DIDS; 1 mM), anthracene-9-carboxylic acid (9-AC; 1 mM), or the K+ channel blocker tetraethylammonium chloride (TEA; 10 mM). cGMP production was measured by immunoassay. RESULTS: Significant membrane depolarizations (P < 0.05-0.001; n = 5-8) were induced by SNP (6 +/- 1 mV; mean +/- SEM), SNAP (8 +/- 1 mV), or 8-pCPT-cGMP (13 +/- 1 mV). In presence of ODQ, the effect of SNP and SNAP were significantly inhibited (-2 +/- 0 mV and 0 +/- 0 mV, respectively; P < 0.05; n = 5-6), but not depolarizations elicited by 8-pCPT-cGMP. These were prevented (P < 0.05-0.01; n = 5) by niflumic acid (1 +/- 1 mV), DIDS (1 +/- 1 mV), or 9-AC (5 +/- 1 mV), but not by TEA (12 +/- 2 mV). The increase in cGMP production induced by SNP (9.5-fold) was inhibited by ODQ (P < 0.001; n = 6). CONCLUSIONS: Activation of the NO-GC-cGMP pathway modulates epithelial transmembrane potential in isolated porcine ciliary processes.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1999

Modulation of Heidelberg Retinal Flowmeter parameter flow at the papilla of healthy subjects: effect of carbogen, oxygen, high intraocular pressure, and beta-blockers.

The Heidelberg Retina Flowmeter (HRF) is intended to assess ocular blood flow by scanning laser doppler flowmetry. In the retina and possibly in the optic nerve head, carbogen increases blood flow, whereas pure oxygen or high intraocular pressure (IOP) decrease it. This study addresses whether at the papilla of healthy volunteers, the HRF parameter flow, is modulated by breathing 5% carbogen (5% carbon dioxide + 95% oxygen) for 7 minutes, breathing 100% oxygen for 7 minutes, increasing IOP to 50 mm Hg with a suction cup, or decreasing IOP with a single topical ocular instillation of the beta-blockers 0.5% betaxolol (betoptic) or 0.5% timolol (timoptic). At the papilla (20 degrees x 5 degrees, 256 X 64 pixels), values of HRF parameter, flow (50 X 50) pixels, increased after carbogen (N = 5, P < 0.05), but decreased after oxygen (N = 5, P < 0.05) or IOP increase (N = 5, P < 0.01). Although IOP values were significantly reduced by betaxolol (N = 9, P < 0.05) and timolol (N = 9, P < 0.01), HRF values were only significantly decreased (N = 9, P < 0.05) after timolol. In conclusion, at the papilla of healthy volunteers, a positive correlation exists between changes in values of the HRF-parameter, flow, and stimuli considered to modulate retinal and ONH blood flow. Furthermore, although of unkown clinical relevance, it appears that in contrast to betaxolol, values of the HRF parameter, flow, at the papilla of healthy volunteers are significantly decreased after a single instillation of timolol.

Administration, Inhalation↗

PubMed1999

Potential role of nitric oxide and endothelin in the pathogenesis of glaucoma.

Glaucoma is an optic nerve head neuropathy in which retinal ganglion cells are lost. A clear association exists between glaucoma and different risk factors, such as high intraocular pressure (IOP) or blood-flow dysregulation. Nitric oxide (NO) and endothelin, two recently identified cellular mediators, appear to be involved in the regulation of IOP as well as in the modulation of ocular blood flow. To some extent, NO is also involved in apoptosis, a mechanism of cell death that can lead to retinal ganglion cell loss in glaucoma. This article provides a short and simplified overview of the biochemistry of NO and endothelin and highlights the potential role of these two mediators in certain important aspects related to the pathogenesis of glaucoma.

Apoptosis↗

PubMed1999

Localization of nitric oxide synthase isoforms in porcine ocular tissues.

PURPOSE: To determine by immunohistochemistry the distribution of different nitric oxide synthases (NOS) isoforms in the porcine eye. METHODS: By light microscopy (immunofluorescence), porcine ocular tissues were investigated using monoclonal antibodies against neuronal NOS (nNOS; NOS I), endothelial NOS (ecNOS; NOS III), and macrophage NOS (macNOS; NOS II). RESULTS: Specific nNOS immunoreactivity was detected along the apical cytoplasmic portions of the non-pigmented and pigmented ciliary epithelial cells, in the endothelial lining of the corneoscleral meshwork and the uveal cords of the iridocorneal angle tissue, as well as in the photoreceptor layer of the sensory retina. Immunoreactivity for ecNOS was confined to the vascular endothelium of the vessels of the conjunctiva, iris, ciliary body, retina, choroid and optic nerve. A mild immunostaining for macNOS was present in the cytoplasm of some non-pigmented ciliary epithelial cells. CONCLUSIONS: The predominant localization of nNOS in ciliary epithelial and trabecular endothelial cells suggests a possible involvement of nNOS in both the production and outflow of aqueous humor in porcine eyes.

Animals↗

PubMed1999

Effect of Ox-LDL on endothelium-dependent response in pig ciliary artery: prevention by an ET(A) antagonist.

PURPOSE: To investigate whether oxidized low-density lipoprotein (Ox-LDL) affects endothelium-dependent responses in isolated porcine ciliary arteries. METHODS: In a myograph system for isometric force measurements, quiescent vessels were incubated with 50 microg/ml, 100 microg/ml, or 200 microg/ml Ox-LDL; 100 microg/ml native LDL (n-LDL); 1 microM of the ET(A)- endothelin receptor antagonist BQ 123; 100 microg/ml Ox-LDL coadministered with 1 microM BQ 123; or 100 microg/ml Ox-LDL coadministered with 50 microM of the protein synthesis inhibitor cycloheximide. Vessels with nonfunctional endothelium (intentionally and mechanically damaged) were also exposed to 100 microg/ml Ox-LDL. Two hours later, vessels were washed, precontracted with the thromboxane A2 analog U 46619 (approximately 0.1 microM), and exposed to bradykinin (0.1 nM to 3 microM), an endothelium-dependent relaxing agent. RESULTS: In quiescent vessels, Ox-LDL evoked delayed contractions. In contrast, no contractions were observed after exposure to n-LDL, BQ 123, Ox-LDL with BQ 123, or Ox-LDL with cycloheximide. In vessels with nonfunctional endothelium, Ox-LDL did not evoke contraction. Bradykinin-induced relaxations were inhibited in a dose-dependent manner by Ox-LDL, but not by n-LDL, BQ 123 alone, Ox-LDL with BQ 123, or Ox-LDL with cycloheximide. CONCLUSIONS: In porcine ciliary arteries, Ox-LDL affects endothelium-dependent responses through the activation of ET(A)- endothelin receptors. As Ox-LDL can accumulate in atherosclerotic plaques, such a mechanism might be involved in the occlusion of the ophthalmic circulation observed in patients with hypercholesterolemia and atherosclerosis.

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

PubMed1999

Vascular dysregulation: a principal risk factor for glaucomatous damage?

Both intraocular pressure (IOP) and vascular factors appear to play an important role in the pathogenesis of glaucomatous optic neuropathy (GON). Arteriosclerosis and its risk factors are of minor importance, whereas vasospastic syndrome clearly is associated with GON. A vascular endotheliopathy seems to be involved in the diathetic hyperresponsiveness to stimuli, such as coldness or emotional stress. This in turn leads to a compromised autoregulation, and thereby renders the eye more sensitive to IOP or to a decrease in blood pressure. A variation in ocular perfusion may lead to an increase in free oxygen radicals. This may finally lead to apoptosis.

Animals↗

PubMed1999

Isoproterenol, forskolin, and cAMP-induced nitric oxide production in pig ciliary processes.

PURPOSE: To investigate whether isoproterenol and forskolin, two adenylylcyclase activators, or 8-bromo-cAMP, an adenosine 3',5'-cyclic monophosphate (cAMP) analog, increase nitric oxide (NO) production in isolated porcine ciliary processes. METHODS: Nitrite (an NO metabolite) was measured (Griess reaction) before and 2 hours after exposure to 0.1 to 100 microM isoproterenol (a beta-adrenoreceptor agonist), 0.01 to 100 microM forskolin, or 0.1 to 1000 microM 8-bromo-cAMP. Some experiments were conducted in the presence of 0.5 mM N(G)-nitro-L-arginine methyl ester (L-NAME; a nitric oxide synthase [NOS] inhibitor), 10 microM propranolol (a beta-adrenoreceptor antagonist), or 1 microM KT 5720 (a cAMP-dependent protein kinase inhibitor). cAMP production was also measured (by immunoassay). RESULTS: Nitrite production was increased by isoproterenol (maximum, 10 microM: 164%; P < 0.001), forskolin (maximum, 10 microM: 254%; P < 0.001), and 8-bromo-cAMP (maximum, 100 microM: 184%; P < 0.001), an effect prevented by L-NAME (P < 0.05-0.001). Propranolol inhibited only isoproterenol-induced (10 microM) nitrite production (P < 0.05), whereas KT 5720 (P < 0.05) inhibited isoproterenol- (10 microM) and 8-bromo-cAMP-induced (10 microM) nitrite production. Furthermore, cAMP production evoked by isoproterenol (10 microM, P < 0.05) but not by forskolin (10 microM, P < 0.001) was inhibited by propranolol (P < 0.05). CONCLUSIONS: In isolated porcine ciliary processes, drugs activating adenylylcyclase or mimicking cAMP increase the production of NO by a mechanism that appears to involve both a cAMP-dependent protein kinase and NOS.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1998

Modulation of endothelin-1-induced contractions by magnesium/calcium in porcine ciliary arteries.

BACKGROUND: The present study was performed to investigate the influence of extracellular magnesium on changes in contractile tone induced by endothelin-1, and on relaxations to bradykinin in isolated porcine ciliary arteries. METHODS: Vessels were studied in a myograph system for measurement of isometric forces. Concentration-response curves (10(-10)-10(-7) M) to endothelin-1 were constructed in the presence of different concentrations (0, 1.2, 2, 10 mM) of magnesium (MgSO4). Endothelin-1-precontracted vessels (approximately 10(-8) M) were exposed to magnesium (10(-5)-10(-2) M) in the presence or absence of either the inhibitor of nitric oxide formation L-NAME (approximately 10(-4) M), or different concentrations of calcium (2.5, 5, 10 mM). In endothelin-1-precontracted vessels (10(-8) M), relaxations to bradykinin (10(-10)-10(-6) M) were conducted in the presence of different concentrations of magnesium (0, 1.2, 10 mM). RESULTS: Contractions to endothelin-1 were reduced only in the presence of 10 mM magnesium. (1.2 mM vs 10 mM, P = 0.001). In endothelin-1-precontracted vessels, magnesium evoked complete concentration-dependent relaxations (pD2 = 3.1 +/- 0.1), which were shifted to the right by increasing extracellular concentrations of calcium (2.5 vs 5 mM, P < 0.05). L-NAME had no influence on magnesium-induced relaxations. Relaxations to bradykinin remained unaffected by changes in extracellular magnesium concentrations. CONCLUSIONS: In a mechanism which appears to be compatible with a calcium-antagonist effect, magnesium strongly modulates changes in contractile tone evoked by endothelin-1, but has no effect on bradykinin-induced relaxations.

Animals↗

PubMed1998

beta-Adrenergic agonist-induced nitrite production in isolated pig ciliary processes.

BACKGROUND: We performed an experiment to assess whether in ciliary processes adrenergic-receptor agents can modulate the production of nitrite, an oxidized metabolite of nitric oxide (NO). METHODS: The porcine ciliary processes and the iris were dissected and stored at -20 degrees C. Later, tissues were thawed, and nitrite measured by Griess reaction, before and 2 h after exposure to various drugs. RESULTS: In the ciliary processes, but not in the iris, the alpha-, beta-adrenergic receptor agonist, norepinephrine (0.01-10 microM), increased nitrite production (95 +/- 12%, P < 0.01). The norepinephrine-induced (0.1 microM) nitrite production was inhibited by the inhibitor of NO synthase, N omega-nitro-L-arginine methyl ester (0.5 mM; P < 0.05) and by the non-selective beta-adrenergic receptor antagonist, propranolol (10 microM; P < 0.01), but not by the non-selective alpha-adrenergic receptor antagonist, phentolamine (10 microM). CONCLUSION: In isolated porcine ciliary processes, beta-adrenergic receptor stimulation increases NO production.

Adrenergic beta-Agonists↗