Highly siderophile elements were stripped from Earth's mantle by iron sulfide segregation.

Highly siderophile elements (HSEs) are strongly depleted in the bulk silicate Earth (BSE) but are present in near-chondritic relative abundances. The conventional explanation is that the HSEs were stripped from the mantle by the segregation of metal during core formation but were added back in near-chondritic proportions by late accretion, after core formation had ceased. Here we show that metal-silicate equilibration and segregation during Earth's core formation actually increased HSE mantle concentrations because HSE partition coefficients are relatively low at the high pressures of core formation within Earth. The pervasive exsolution and segregation of iron sulfide liquid from silicate liquid (the "Hadean matte") stripped magma oceans of HSEs during cooling and crystallization, before late accretion, and resulted in slightly suprachondritic palladium/iridium and ruthenium/iridium ratios.

Bright light therapy in Parkinson's disease: a pilot study.

Several observations suggest a beneficial effect of melatonin antagonism for Parkinson's disease (PD). Although bright light therapy (BLT) suppresses melatonin release and is an established treatment for depression and sleep disturbances, it has not been evaluated in PD. We examined effects of BLT on motor symptoms, depression, and sleep in PD in a randomized placebo-controlled double-blind study in 36 PD patients, using Parkinson's Disease Rating Scale (UPDRS) I-IV, Beck's Depression Inventory, and Epworth Sleepiness Scale. All patients received BLT for 15 days in the morning, 30 min daily. Illuminance was 7.500 lux in the active treatment group and 950 lux in the placebo group. Although group differences were small, BLT led to significant improvement of tremor, UPDRS I, II, and IV, and depression in the active treatment group but not in the placebo group. It was very well tolerated. Follow up studies in more advanced patient populations employing longer treatment durations are warranted.

Histopathologic findings after radial optic neurotomy in central retinal vein occlusion.

PURPOSE: Radial optic neurotomy (RON) in central retinal vein occlusion (CRVO) is a novel strategy that is aimed at relief of mechanical pressure on the central retinal vein. We report on histopathologic findings in a human eye 18 weeks after RON. DESIGN: Interventional case report. METHODS: Eighteen weeks after RON for ischemic CRVO, an eye was enucleated because of neovascular glaucoma and examined histologically. RESULTS: Histopathologic evidence demonstrated displaced fragments of Bruch's membrane surrounded by retinal tissue at the nasal side of the papilla. A discrete scar was noted at this site that reached the cribriform plate without involving the adjacent sclera or the retinal vessels. The optic nerve showed advanced atrophy with a small temporal sector of viable nerve fibers. CONCLUSIONS: Histopathologic findings after RON do not provide evidence for the postulated mechanism of action. It appears prudent to further evaluate this technique before its general implementation in the management of CRVO.

Evaluation of the blood-aqueous barrier by laser flare cell photometry following retinal cryocoagulation.

PURPOSE: To evaluate the influence of peripheral 360 degrees retinal cryocoagulation on the blood-aqueous barrier of patients with retinal vascular disorders. METHODS: The aqueous of 50 eyes of 50 patients with diabetic retinopathy or central vein occlusion was measured by laser flare photometry (FC-2000, Kowa) before peripheral 360 degrees retinal cryocoagulation and 1 day, 1 week, and 1 month thereafter. RESULTS: Mean aqueous flare values before treatment were 15.7 (+/-8.2) photon counts/ms; mean cell count was 9.8 (+/-14.8) cells/0.5 mm(3). One day after retinal cryocoagulation flare values had increased statistically significantly to a mean of 39.2 (+/-85.8) photon counts/ms, while the increase in mean cell number to 15.0 (+/-37.2) cells/0.5 mm(3) did not reach statistical significance. One week following treatment, mean flare values had dropped to 30.9 (+/-49.6) photon counts/ms and were no longer significantly elevated compared with baseline, while the mean cell count of 11.1 (+/-27.0) cells/0.5 mm(3) was now statistically significantly elevated compared with baseline. One month after treatment the flare values had decreased to a mean of 19.7 (+/-12.0) photon counts/ms, and mean cell count had decreased to 8.1 (+/-10.4) cells/0.5 mm(3); at this point neither parameter showed a statistically significant difference from baseline values. CONCLUSION: Peripheral 360 degrees retinocryocoagulation does not lead to permanent disturbance of the blood-aqueous barrier.

[Histopathology of herpetic corneal endotheliitis - a case report]. / Histopathologische Befunde bei herpetischer Endotheliitis corneae - eine Kasuistik.

BACKGROUND: Clinically, corneal endotheliitis is characterized by endothelial cell edema associated with immune precipitates. It is supposed to be triggered by a humoral or cellular immunologic reaction against antigens of the corneal endothelium. As yet, only few histopathologic studies of this disease have been performed. PATIENT: A 42-years-old patient developed a complete corneal nebula with neovascularizations due to relapsing herpetic keratitis. He underwent perforating keratoplasty. The inflammatory infiltrate lining Descemet's membrane and the corneal endothelium consisted mostly of CD 45 R0-positive T-lymphocytes with only few neutrophils, macrophages and CD 20-positive B-lymphocytes. We could not demonstrate any viral particles in the removed corneal tissue by either electron microscopy or using antibodies against Herpes simplex type I or II. CONCLUSIONS: Histologically, herpetic endotheliitis appears to correspond to corneal endotheliitis due to graft rejection. Complete virus particles are not necessarily required in case of long-standing inflammation and corneal neovascularizations.