Purification of an MCM-containing complex as a component of the DNA replication licensing system.

Replication licensing factor (RLF) ensures that eukaryotic chromosomal DNA is replicated exactly once in each cell cycle. On exit from metaphase, RLF is activated and binds to or modifies chromatin. This modification (the 'licence') is required for subsequent DNA replication; the licence is also inactivated in the process of replication. Active RLF is not imported into the nucleus, so further DNA replication cannot occur until the DNA is relicensed by passage throught mitosis. We have developed an assay to purify RLF from Xenopus eggs. Activity resolves into two components, RLF-M and RLF-B, both of which are required for licensing. RLF-M has been purified to apparent homogeneity: it consists of three polypeptides, one of which is a Xenopus homologue of the yeast MCM3 protein. Xenopus Mcm3 associates with chomatin in G1 and is removed during replication, consistent with its being a component of the RLF system.

Spontaneous hematic cysts of the orbit presenting with acute proptosis. A report of three cases.

Three cases of spontaneous hematic cyst of the orbit are described. All cases presented with acute onset of proptosis, conjunctival chemosis, choroidal folds, restricted ocular movement, and optic nerve compression syndrome with very poor vision. A computed tomography scan demonstrated a cystic lesion situated in the upper part of the orbit. Exploration revealed a cyst containing chocolate-colored fluid. Visual recovery was complete in two of three cases. There was no definite history of trauma in all three cases. Chronic hematic cysts have been described recently, but cases with acute onset such as ours have not to our knowledge been described clearly.

Argon laser photocoagulation in diabetic retinopathy: five year review of 697 treated eyes.

Diabetic retinopathy has now become a common cause of blindness in Singapore. Fortunately, laser photocoagulation has prevented blindness in the majority of patients who were treated. An analysis of 872 patients treated with argon laser photocoagulation showed that 424 patients (48.6%) were for diabetic retinopathy. Patients with adequate treatment retained useful vision. Those who lost vision frequently had associated target organ involvement besides inadequate laser treatment. Patients with proliferative diabetic retinopathy were treated with peripheral retinal photocoagulation. Patients with diabetic maculopathy especially those with focal leaks were treated with localised photocoagulation. A common cause of blindness is failure to recognise the condition early. Physicians and general practitioners must, in the management of diabetics, examine their patients periodically with the pupils dilated in a darkened room.