Mona Pache

Distribution of Melatonin MT1 Receptor Immunoreactivity in Human Retina

Melatonin is synthesized in the pineal gland and retina during the night. Retinal melatonin is believed to be involved in local cellular modulation and in regulation of light-induced entrainment of circadian rhythms. The present study provides the first immunohistochemical evidence for the localization of melatonin 1a-receptor (MT1) in human retina of aged subjects. Ganglion, amacrine, and photoreceptor cells expressed MT1. In addition, MT1 immunoreactivity was localized to cell processes in the inner plexiform layer and to central vessels of the retina, as well as to retinal vessels but not to ciliary or choroidal vessels. These results support a variety of cellular and vascular effects of melatonin in the human retina. Preliminary evidence from patients with Alzheimers disease (AD) revealed increased MT1 immunoreactivity in ganglion and amacrine cells, as well as in vessels. In AD cases photoreceptor cells were degenerated and showed low MT1 expression.

Thermoregulatory effects of melatonin in relation to sleepiness

Thermoregulatory processes have long been implicated in the initiation of human sleep. In this paper, we review our own studies conducted over the last decade showing a crucial role for melatonin as a mediator between the thermoregulatory and arousal system in humans. Distal heat loss, via increased skin temperature, seems to be intimately coupled with increased sleepiness and sleep induction. Exogenous melatonin administration during the day when melatonin is essentially absent mimics the endogenous thermophysiological processes occurring in the evening and induces sleepiness. Using a cold thermic challenge test, it was shown that melatonin‐induced sleepiness occurs in parallel with reduction in the thermoregulatory set‐point (threshold); thus, melatonin may act as a circadian modulator of the thermoregulatory set‐point. In addition, an orthostatic challenge can partially block the melatonin‐induced effects, suggesting an important role of the sympathetic nervous system as a link between the thermoregulatory and arousal systems. A topographical analysis of finger skin temperature with infrared thermometry revealed that the most distal parts of the fingers, i.e., fingertips, represent the important skin regions for heat loss regulation, most probably via opening the arteriovenous anastomoses, and this is clearly potentiated by melatonin. Taken together, melatonin is involved in the fine‐tuning of vascular tone in selective vascular beds, as circulating melatonin levels rise and fall throughout the night. Besides the role of melatonin as “natures soporific”, it can also serve as natures nocturnal vascular modulator.

Cold feet and prolonged sleep-onset latency in vasospastic syndrome

People with vasospastic syndrome have cold hands and feet and abnormal vasoconstriction after local cold exposure. Normally there is a circadian rhythm of distal vasodilation, with onset in the early evening, which directly influences ability to fall asleep. We gave a sleep questionnaire to 32 patients with primary vasospastic syndrome and 31 healthy controls. People with vasospasticity had significantly prolonged sleep-onset latency both at onset of night-time sleep and after nocturnal disturbance. This prolonged latency could be associated with impaired capacity for distal vasodilation.

Extraocular Blood Flow and Endothelin-1 Plasma Levels in Patients with Multiple Sclerosis

In order to evaluate whether plasma levels of the potent vasoconstrictor endothelin-1 (ET-1) are increased in patients with multiple sclerosis (MS) and whether these patients exhibit an ET-1-mediated vascular dysregulation, ET-1 plasma levels were measured in 30 patients with MS. Blood flow velocities in the ophthalmic artery, central retinal artery, central retinal vein, short lateral posterior ciliary artery, and short medial posterior ciliary artery were assessed in parallel. ET-1 plasma levels were significantly increased in MS patients when compared to sex- and age-matched healthy controls (2.0 ± 0.4 pg/ml, range 1.1–2.8 vs. 1.5 ± 0.2 pg/ml, range 0.9–2.0; p < 0.001). Moreover, the patients exhibited significant alterations of extraocular blood flow. The role of ET-1 in the inflammatory process remains to be clarified.

Melatonin MT-1-receptor immunoreactivity in the human eye

Aim: To examine the distribution of melatonin 1a (MT1) receptors in the human eye. Methods: Seven normal human eyes were examined by immunohistochemical staining of paraffin sections, using an anti-MT1 primary antibody and an ABC detection system. Results: MT1 receptor immunoreactivity (MT1-IR) was detected primarily in the inner segments of rods and cones and in retinal ganglion cells. In addition, MT1-IR was present in the adventitia of retinal arteries and veins, including the papillary region, but absent in ciliary and choroidal vessels. Mild staining of corneal endothelial cells and keratocytes was observed in all but two eyes. Conclusion: MT1-IR is present in various ocular tissues with the highest density in photoreceptor cells and ganglion cells. The physiological function of these receptors deserves further investigation.

Sequence analysis and high-throughput immunhistochemical profiling of KIT (CD 117) expression in uveal melanoma using tissue microarrays

We aimed to immunohistochemically examine the expression of KIT (CD 117) in human posterior uveal melanoma and to analyze KIT-positive tumors for gene mutations. Brought into a tissue microarray (TMA) format were 101 formalin-fixed, paraffin-embedded posterior uveal melanomas. Immunhistochemistry was performed using the polyclonal anti-CD117 antibody from Dako (A4502). In ten selected KIT-positive tumors, exons 2, 8, 9, 11, 13 and 17 were sequenced. Of the 101 cases, 89 (88%) could be evaluated on the TMAs. Immunohistochemistry for CD 117 was weakly positive in 5 cases (6%), moderately positive in 10 cases (12%) and strongly positive in 57 cases (69%). No KIT mutations were detected in the analyzed exons. In conclusion, human posterior uveal melanoma frequently expresses CD117 at high levels. Although KIT mutations could not be found, it appears justified to investigate the utility of imatinib mesylate in the treatment of these patients.

Peripheral vasospasm and nocturnal blood pressure dipping--two distinct risk factors for glaucomatous damage?

Purpose To evaluate the relationship between peripheral vasospasm and circadian blood pressure rhythm in patients with primary open angle glaucoma (POAG). Methods Nail-fold capillaroscopy, combined with a cold provocation test, and 24-hour blood pressure monitoring was carried out in 130 patients with POAG (M:F 58:72; mean age 60 ± 14 years), 99 with high-tension glaucoma (HTG) and 31 with normal-tension glaucoma (NTG). Peripheral blood flow parameters were compared for patients with a nocturnal fall in mean systemic blood pressure (MBP) of less than 10% (non-dippers), patients with a nighttime MBP fall of 10–20% (dippers), and patients with a nighttime MBP fall of more than 20% (over-dippers). Results Patients with POAG showed a significantly lower blood flow velocity both at baseline (p <0.01) and after cold provocation (p <0.02) and a significantly higher percentage of cold-induced blood-flow standstill (p <0.0001) in the nail-fold capillaroscopy than normal controls. The numbers of non-dippers (50), dippers (66) and over-dippers (14) did not differ between the HTG and NTG group. There were no significant differences between non-dippers, dippers, and over-dippers in peripheral blood flow parameters. Conclusions Our findings indicate that vasospasm and low blood pressure may be distinct risk factors for glaucomatous damage. It also appears that screening for vascular dysregulation and systemic hypotension should not be restricted to NTG patients alone.

Sildenafil induces retinal vasodilatation in healthy subjects

Background: The cardiovascular effects of sildenafil (Viagra), a selective inhibitor of phosphodiesterase type 5 (PDE5), have been extensively studied. However, its effect on human retinal arteries and veins has not yet been investigated. The effect of a single dose administration of sildenafil on the retinal vessel diameters of healthy subjects was evaluated. Methods: Sildenafil 50 mg was administered to 10 healthy subjects (male:female = 4:6; mean age 31 (SD 6) years). The diameters of retinal arteries and veins were measured by means of a retinal vessel analyser (RVA) immediately before and at 30, 60, 90, and 120 minutes after sildenafil uptake. Blood pressure, heart rate, and intraocular pressure were monitored in parallel. Results: A significant increase of 5.8% (p<0.001) in both retinal arterial and venous diameters was found 30 minutes after sildenafil uptake. The diameters returned to baseline after 120 minutes. A mild systemic hypotensive response was seen. Changes in heart rate and intraocular pressure were not observed. Conclusion: Sildenafil causes a significant dilatation of retinal arteries and veins in healthy subjects. A possible role for PDE5 in the regulation of retinal blood flow is implicated.

Anatomic site-specific patterns of gene copy number gains in skin, mucosal, and uveal melanomas detected by fluorescence in situ hybridization

To assess the differences between melanomas of different location and different etiology, 372 malignant melanomas were brought in a tissue microarray format. The collection included 23 acral and 118 non-acral skin melanomas, 9 mucosal melanomas, 100 uveal melanomas, and 122 melanoma metastases. Fluorescence in situ hybridization (FISH) was used to assess copy number changes of the cyclin D1 (CCND1), MDM2, c-myc (MYC), and HER2 genes. FISH analysis revealed distinct differences between melanomas from different locations. CCND1 amplifications were detected in skin melanomas from sites with chronic sun exposure (6 of 32 cases), acral melanomas (4 of 17 cases), and mucosal melanomas (one of ten cases) but not in uveal melanomas. High-level MDM2 amplifications were exclusively present in acral melanomas (2 of 19 cases). MYC copy number gains were detected in 32 of 71 uveal melanomas, five of eight mucosal melanomas, and 6 of 67 melanomas from sites with intermittent sun exposure but not in acral melanomas nor melanomas from sites with chronic sun exposure. Alterations of the MYC gene were associated with advanced tumor stage. There were no high-level HER2 amplifications. Site-specific genetic and epigenetic features may impact the response of melanomas to various anti-cancer drugs and should be considered in future studies on the molecular pathogenesis of malignant melanomas.

Increased endothelin-1 plasma levels in giant cell arteritis: a report on four patients

PURPOSE To test the hypothesis that endothelin-1 is increased in giant cell arteritis. METHODS Interventional case series. The medical history of four patients who presented to the University Eye Clinic Basel, Switzerland, with giant cell arteritis is reported. Endothelin-1 plasma levels were measured in all patients. The relevant medical literature was reviewed. RESULTS All patients presented with typical histopathological signs of giant cell arteritis in the temporal artery biopsy. The erythrocyte sedimentation rate was increased in two patients. All patients showed significantly increased endothelin-1 plasma levels, ranging between 3.13 to 4.82 pg/ml (reference value for females: 1.42 pg/ml +/- 0.28 standard deviation, for males: 1.67 pg/ml +/- 0.34 standard deviation). CONCLUSION The data obtained from the patients so far examined indicate that the level of circulating endothelin-1 is increased in giant cell arteritis. The clinical relevance of such an increase needs to be further evaluated.