No abstract

17 chromium(III) compounds have been tested for DNA-damaging capabilities using an E. coli differential repair assay and for mutagenicity in strains of Salmonella typhimurium. 4 of these compounds were active in both assays. Another 4 compounds were positive only in the repair assay and 9 were devoid of activity in both assays. Most of the doubly active complexes contain aromatic amine ligands like 2,2'-bipyridine and 1,10-phenanthroline. Closely related complexes of ligands derived from saturated amines are much less active. It appears that chromium(III) in the proper ligand environment can have considerable genetic toxicity and could represent one of the several possible ultimate species in a mechanism for chromium mutagenesis and carcinogenesis.

Fig 1.-Irregular, peripapillary, curvilinear bands (arrows) are characteristic of angioid streaks in a patient with pseudoxanthoma elasticum. Fig 2.-The "gooseflesh" appearance of the neck skin in a patient with pseudo¬ xanthoma elasticum.Angioid streaks are irregular, peripapillary brown to red curvilinear bands that extend in a weblike manner from the optic disc (Fig 1). Often confused with blood vessels, angioid streaks are wider, with tapering ends, lie below the normal retinal vasculature, and are readily discerned by direct ophthalmoscopy. Their importance lies in their association with a host of systemic disorders.Pseudoxanthoma elasticum (PXE), Paget's disease of the bone, and sickle-cell disease account for the majority of diseases linked to angioid streaks. PXE can be demonstrated in more than halfthe patients with angioid streaks1,2; in one large series, 85% of patients with PXE demonstrated angioid streaks.3 Additional associated conditions include acromegaly, abetalipoproteinemia, diabetes mellitus, Ehlers-Danlos syndrome, hemochromatosis, facial hemochromatosis, hemolytic anemia, hypercalcinosis, hyperphosphatemia, neurofibromatosis, senile elastosis, Sturge-Weber syndrome, tuberous sclerosis, lead poisoning, and myopia.1 Additional ocular findings in PXE include a diffuse, yellowish mottling of the retinal pigment epithelium usually seen temporal to the macula and known as "peau d'orange." This finding may precede angioid streaks and is a secondary change of the retinal pigment epithelium overlying a calcified region of Bruch's membrane. Other findings include a reticu¬ lar, nodular pigmentary clumping in the fundus best seen on fluorescein angiography4; punched-out, depigmented, pe¬ ripheral lesions known as "salmon spots'"; and drusen of the optic nerve head.6The histopathology of angioid streaks consists of calcifica¬ tion of Bruch's membrane with degeneration of the surround¬ ing elastic fibers. Disruption of Bruch's membrane may result in fibrovascular ingrowth leading to serous retinal detach-ment, subretinal hemorrhage, and scarring with severe visu¬ al loss. Early symptoms include deteriorating visual acuity and visual distortion. Fundus fluorescein angiography can identify these areas at risk, and laser photocoagulation may be beneficial when fibrovascular membranes do not directly involve the fovea.6Pseudoxanthoma elasticum is a genetically heterogeneous group of disorders affecting the eyes, skin, and cardiovascu¬ lar system. Though most commonly autosomal recessive, at least two autosomal dominant variants are known to exist.7Cutaneous changes described as "gooseflesh" are charac¬ teristic in areas of'Vear and tear" such as the neck, axilla, and inguinal and antecubital regions (Fig 2). The skin may be thickened and leathery. The generalized calcification of elas¬ tic tissue seen in PXE may involve the internal elastic lamel¬ lae ofthe small and medium arteries resulting in cardiovascu¬ lar complications, including decreased extremity pulses, claudication, angina, transient ischémie at...

No abstract

15 cobalt(III) compounds have been tested for DNA-damaging capabilities using an E. coli differential repair assay and for mutagenicity in strains of Salmonella typhimurium. 4 of these compounds were active in both systems. Although the general ligand requirements for genetic activity of cobalt(III) appear to closely parallel those of chromium(III) and rhodium(III), the genetic activity of cobalt compounds seems particularly dependent upon the structure of the ligands coordinated about the metal ion. By a simple methyl substitution on the organic ligands, a compound completely devoid of activity, e.g. trans-[Co(pyr)4Cl2]Cl, could be made slightly mutagenic in Salmonella typhimurium strains e.g. trans-[Co(3-pic)4Cl2]Cl. Substitution at the 4-position rather than the 3-position on the same pyridine ring, e.g. trans-[Co(4-pic)4Cl2]Cl, results in a 50-fold enhancement of activity in both repair and mutagenesis systems. The difference in genetic activity is attributed to the influence of the ligands on the relative lability of the metal complex.