Chromium, like many transition metal elements, is essential to life at low concentrations yet toxic to many systems at higher concentrations. In addition to the overt symptoms of acute chromium tox...

Mechanisms of Chromium Carcinogenicity and Toxicity

Citrulline (Cit, C6H13N3O3), which is a ubiquitous amino acid in mammals, is strongly related to arginine. Citrulline metabolism in mammals is divided into two fields: free citrulline and citrullinated proteins. Free citrulline metabolism involves three key enzymes: NO synthase (NOS) and ornithine carbamoyltransferase (OCT) which produce citrulline, and argininosuccinate synthetase (ASS) that converts it into argininosuccinate. The tissue distribution of these enzymes distinguishes three “orthogonal” metabolic pathways for citrulline. Firstly, in the liver, citrulline is locally synthesized by OCT and metabolized by ASS for urea production. Secondly, in most of the tissues producing NO, citrulline is recycled into arginine via ASS to increase arginine availability for NO production. Thirdly, citrulline is synthesized in the gut from glutamine (with OCT), released into the blood and converted back into arginine in the kidneys (by ASS); in this pathway, circulating citrulline is in fact a masked form of arginine to avoid liver captation. Each of these pathways has related pathologies and, even more interestingly, citrulline could potentially be used to monitor or treat some of these pathologies. Citrulline has long been administered in the treatment of inherited urea cycle disorders, and recent studies suggest that citrulline may be used to control the production of NO. Recently, citrulline was demonstrated as a potentially useful marker of short bowel function in a wide range of pathologies. One of the most promising research directions deals with the administration of citrulline as a more efficient alternative to arginine, especially against underlying splanchnic sequestration of amino acids. Protein citrullination results from post-translational modification of arginine; that occurs mainly in keratinization-related proteins and myelins, and insufficiencies in this citrullination occur in some auto-immune diseases such as rheumatoid arthritis, psoriasis or multiple sclerosis.

Almost all about citrulline in mammals.

The sections in this article are:


1
Manifestations of Skin Permeability

2
Structure of the Skin
2.1
Relevant Structural Features of the Whole Skin




3
The Stratum Corneum
3.1
Regional Variations in Structure




4
Human Versus Other Mammalian Skin

5
Biophysics of Skin Permeability
5.1
Mathematical Analysis of Skin Permeability

5.2
Steady-State Permeability of Skin—Fick's Law

5.3
Appendageal Diffusion

5.4
Concentration Levels in the Skin

5.5
Regional Variations in Permeability




6
Effect of Solvents and Surfactants
6.1
Water

6.2
Aprotic Solvents

6.3
Surfactants

6.4
Organic Solvents

Permeability of the Skin

: Selective review and synthesis of the technical literature on copper and copper salts in the environment and their effects primarily on fishes, birds, mammals, terrestrial and aquatic invertebrates, and other natural resources. The subtopics include copper sources and uses; chemical and biochemical properties; concentrations of copper in field collections of abiotic materials and living organisms; effects of copper deficiency; lethal and sublethal effects on terrestrial plants and invertebrates, aquzatic organisms, birds, and mammals, including effects on survival, growth, reproduction, behavior, metabolism, carcinogenicity, mutagenicity, and teratogenicity; proposed criteria for the protection of human health and sensitive natural resources; and recommendations for additional research.

Copper Hazards to Fish, Wildlife, and Invertebrates : A Synoptic Review

Studies on contact sensitivity to chromium in the guinea pig. The role of valence in the formation of the antigenic determinant.

https://www.jidonline.org/article/S0022-202X(15)46775-2/pdf

A study of the chemical reactions between chromium and skin.

Studies of the diffusion of chromium compounds through skin.

Nickel-epidermal interactions: diffusion and binding.

To the Editor.— Two letters relating to this subject were published recently inThe Journal. 1,2 The following comments are pertinent to this problem. Barranco and Soloman 1 reported a case of eczematous dermatitis from internal exposure to nickel from a stainless steel screw in the patella. (Nickel sensitivity was demonstrated by patch testing: pure nickel, 3% nickel sulfate, and pieces of the stainless steel screw gave positive results; test results were negative with metallic salts such as potassium dichromate, cobalt sulfate, and mercuric chloride.) The stainless steel contained 14% nickel. Following removal of the screws, the dermatitis subsided within 72 hours. This would imply that nickel released from the stainless steel screws (a tenable thesis because Ferguson and co-workers 3 and Mears 4 have reported increased nickel concentrations in parenchymal tissues from implantation of stainless steel rods containing nickel) produced the allergic reaction. Fisher, on the other hand, rejected

Nickel Dermatitis Hazards From Prostheses

The mechanism for the inactivation of hexavalent chromium by ascorbic acid involves reduction to trivalent chromium and subsequent complex formation of the trivalent species. Ascorbic acid and hexavalent chromium react in a ratio of 5:2. This is slightly less than could be expected for oxidation of all the ascorbic acid to dehydroascorbic acid. The chromium-ascorbic acid complex exhibits a strong absorption near 390mμ. The 7:3 ratio may indicate a polymeric species in which the chromium is bound to more than one ascorbic acid molecule.

M.H. Samitz

Papers

A study of the chemical reactions between chromium and skin.

Studies of the diffusion of chromium compounds through skin.

Nickel-epidermal interactions: diffusion and binding.

Nickel Dermatitis Hazards From Prostheses

Ascorbic acid in the prevention of chrome dermatitis. Mechanism of inactivation of chromium.