| central canal of the vitreous | A minute canal running through the vitreous from the discus nervi optici to the lens, containing in foetal life a prolongation of the central artery of the retina, the hyaloid artery. See: vitreous, hyaloid artery. Synonym: canalis hyaloideus, central canal of the vitreous, Cloquet's canal, Stilling's canal. (05 Mar 2000) |
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| persistent anterior hyperplastic primary vitreous | A unilateral congenital abnormality occurring in full-term infants; characterised by a retrolental fibrovascular membrane formed by persistent primary vitreous with remnants of the hyaloid artery and tunica vasculosa lentis; associated with leukokoria, microphthalmos, shallow anterior chamber, and elongated ciliary processes. (05 Mar 2000) |
| persistent posterior hyperplastic primary vitreous | A unilateral congenital anomaly in full-term infants; associated with a congenital retinal fold and a vitreous membranous stalk containing remnants of the hyaloid artery. (05 Mar 2000) |
| coloboma of vitreous | A congenital indentation of the vitreous body by mesoderm; associated with severe myopia. (05 Mar 2000) |
| primary vitreous | The vitreous first formed in the embryo between the optic cup and the lens vesicle, and later vascularised by the hyaloid artery and its branches. (05 Mar 2000) |
| secondary vitreous | Avascular vitreous formed around the primary vitreous. (05 Mar 2000) |
| stroma of vitreous | The delicate framework of the vitreous body embedded in or enclosing the vitrous humor. Synonym: stroma vitreum. (05 Mar 2000) |
| tertiary vitreous | Vitreous fibrils derived from the neuroepithelium of the ciliary body and forming the ciliary zonule. (05 Mar 2000) |
| Hermansky-Pudlak syndrome type VI | An autosomal recessive deficiency of pigment in skin, hair, and eyes; in the tyrosinase negative type, there is an absence of tyrosinase; in the tyrosinase positive type, there is normal tyrosinase which cannot enter pigment cells; it is transmitted by an autosomal recessive inheritance. The compound heterozygote is normal so the two forms are not allelic. There are several types: type IA is characterised by absence of tyrosinase with life-long complete absence of melanin, marked photophobia, and nystagmus. Type IB, yellow albinism with low or absent tyrosinase; improves with age. Type II, with normal tyrosinase activity is the most common; hair darkens and nevi and freckles develop. Type III is characterised by absent tyrosinase but pigmentation of the iris in the first decade. Type IV in Africans with normal tyrosinase. Type V with red hair. Type VI, Hermansky-Padlak syndrome, with haemorrhage due to platelet deficiency and low to absent tyrosinase. Synonym: Hermansky-Pudlak syndrome type VI. (05 Mar 2000) |
| acrocephalosyndactyly type 1 | <paediatrics> An inherited disease (autosomal dominant) or a spontaneously occurring disease characterised by a peaked head and unusual facial appearance, due to the premature closure of the cranial sutures. A skull X-ray can confirm the diagnosis and treatment is surgical. Inheritance: autosomal dominant. (27 Sep 1997) |
| Alzheimer type I astrocyte | Enlarged frequently multinucleated astrocytes, seen in progressive multifocal leukoencephalopathy. (05 Mar 2000) |
| Alzheimer type II astrocyte | Enlarged astrocytes with vesicular nuclei and one or more small basophilic nucleoli, seen in hepatocerebral disease and Wilson's disease. (05 Mar 2000) |
| American Type Culture Collection | <cell culture> A key resource for cultured cells, located in Rockville, USA. (12 Dec 1998) |
| Antoni type A neurilemoma | <tumour> Relatively solid or compact arrangement of neoplastic tissue that consists of Schwann cells arranged in twisting bundles and associated with delicate reticulin fibres; the nuclei of the Schwann cells are frequently grouped in parallel rows (so-called palisades), and the nuclei and fibres sometimes form exaggerated tactile corpuscles, called Verocay bodies. (05 Mar 2000) |
| Antoni type B neurilemoma | <tumour> Relatively soft or loose arrangement of neoplastic tissue that consists of Schwann cells in a haphazard or nondescript type of arrangement among reticulin fibres and tiny cystlike foci; fat-laden macrophages may be observed in some of the larger neoplasms. (05 Mar 2000) |