Serum ferritin isolated from the horse was structurally compared with horse spleen ferritin and was found to differ markedly in molecular weight, iron content, carbohydrate, subunit size and amino acid sequence. The results are summarized and initial results obtained with candidate clones of pieces of two serum ferritin subunits are described.

Prostate specific antigen (PSA, also known as human kallikrein 3) is an important diagnostic indicator of prostatic disease. PSA exhibits low protease activity (>10(4)-fold less than chymotrypsin) under the usual in vitro assay conditions. In addition, PSA does not react readily with prototypical serine protease inactivators. We expressed human PSA (rh-PSA) in Escherichia coli and have demonstrated that rh-PSA has properties similar to those of native PSA isolated from human seminal fluid. Both PSA and rh-PSA are >10(3)-fold more active in the presence of 1.3 M Na(2)SO(4). This activation is anion-dependent, following the Hofmeister series when normality is considered: SO(4)(2)(-) approximately citrate > Ac(-) > Cl(-) > Br(-) > I(-). The nature of the cation has little effect on salt activation. The rate of inactivation of rh-PSA by DFP is 30-fold faster in the presence of 0.9 M Na(2)SO(4), and the rate of inactivation by Suc-Ala-Ala-Pro-Phe-CK is >20-fold faster under these conditions. Azapeptides containing Phe or Tyr at position P(1) also inactivate rh-PSA in the presence of high salt concentrations. These compounds represent the first described inhibitors designed to utilize the substrate binding subsites of PSA. CD spectroscopy demonstrates that the conformation of rh-PSA changes in the presence of high salt concentrations. Analytical ultracentifugation and dynamic light scattering indicate that PSA remains monomeric under high-salt conditions. Interestingly, human prostatic fluid contains as much as 150 micro mol citrate/g wet weight, which suggests that salt concentrations may regulate PSA activity in vivo.

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Malignant catatonia (MC) is a life-threatening manifestation which can occur in the setting of an underlying neuropsychiatric syndrome or general medical illness and shares clinical and pathophysiological features and medical comorbidities with the Neuroleptic Malignant Syndrome (NMS). The subsequent diagnosis and definitive therapy of MC are typically delayed, which increases morbidity and mortality. We present two cases of MC and review recent literature of MC and NMS, illustrating factors which delay diagnosis and management. When clinical features suggest MC or NMS, we propose early critical care consultation and stabilization with collaborative psychiatric management.

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Evidence supports a role for ceruloplasmin (ferroxidase I) in the release of iron to the blood from mammalian cells. However, recent studies with cultured cells have suggested that it has the opposite effect, and that iron deficiency enhances expression of ceruloplasmin. We therefore examined in rats how nutritional iron status would affect expression of ceruloplasmin. Groups of male Sprague-Dawley rats were reared on a low iron, starch-based diet for 6-8 wk; half were supplemented by injection of iron dextran. At killing, hematocrits of deficient rats were half normal. Supplemented rats had normal liver concentrations of ferritin and ferritin iron. No ferritin was detected in the livers of the deficient rats. Northern analysis showed that ferritin L and H mRNAs were present in the deficient livers, but expression was half that of the normal rats. There was also twice as much copper. Levels of circulating ceruloplasmin (measured by rocket immunoelectrophoresis) were not altered by iron deficiency, although p-phenylenediamine oxidase activity and plasma copper were reduced approximately 30%. In repeated studies, no differences in the expression of hepatic ceruloplasmin mRNA were detected. Treatment of rats of both sexes with additional iron (25 mg as iron dextran) 5-14 d before killing increased liver ferritin but did not alter liver ceruloplasmin mRNA expression or levels of circulating ceruloplasmin. We conclude that iron status is not an important factor in the expression of plasma ceruloplasmin made by the liver. However, it does have modest effects on steady-state levels of liver ferritin mRNA.

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