Expression of prostaglandin H synthase (cyclooxygenase) in Hodgkin's mononuclear and Reed-Sternberg cells. Functional resemblance between H-RS cells and histiocytes or interdigitating reticulum cells

The synthesis of prostaglandin, prostacyclin, and thromboxane, which requires the enzyme prostaglandin H (PGH) synthase (cyclooxygenase), is a general property of histiocytes, monocytes, and Langerhans cells. Previously the authors reported the production of prostaglandin E2 in a Hodgkin's cell line, KM-H2, and suggested that these cells therefore have a functional similarity to histiocyte-related cells. The present study confirms that the Hodgkin's neoplastic (Reed-Sternberg, H-RS) cells in tissue are also capable of producing prostaglandins by demonstrating the presence of PGH synthase in these cells in B5-fixed, paraffin-embedded tissue sections. It was found that the H-RS cells from seven of ten patients with Hodgkin's disease were stained variously with anti-PGH synthase antibodies. In normal and reactive lymphoid tissues, anti-PGH synthase staining was restricted to histiocytes, endothelial cells, and interdigitating reticulum cells. Thus, this study provides further evidence for a possible relationship between H-RS cells and histiocytes or interdigitating reticulum cells; this relationship has also been supported by information obtained in extensive immunologic, biochemical, and cell-differentiation studies. The secretion of PGH-synthase products, especially prostaglandin E2, in H-RS cells may play a major role in the regulation of cellular immunity in patients with Hodgkin's disease.

Protein sequence of endothelial glycoprotein IIIa derived from a cDNA clone. Identity with platelet glycoprotein IIIa and similarity to "integrin"

Platelet membrane glycoprotein (GP) IIIa forms a Ca2+-dependent heterodimer complex with GP IIb. The GP IIb-IIIa complex constitutes the fibrinogen and fibronectin receptor on stimulated platelets. A biochemically and immunologically similar membrane glycoprotein complex is present on endothelial cells. A human umbilical vein endothelial cell cDNA library was screened using oligonucleotide probes designed from peptide sequences obtained from platelet GP IIIa. A cDNA clone was sequenced and found to encode a protein of 84.5 kDa. The translated endothelial cDNA contained five sequences that corresponded to peptide sequences in platelet GP IIIa, including the amino-terminal 19 residues. Thus, the endothelial and platelet forms of GP IIIa are apparently identical. Glycoprotein IIIa consists of a long amino-terminal extracellular domain with several potential N-linked glycosylation sites and four cysteine-rich tandem repeats, a 29-residue hydrophobic transmembrane segment, and a short carboxyl-terminal cytoplasmic domain. Glycoprotein IIIa has a 47% amino acid sequence homology to "integrin," a fibronectin receptor from chicken embryo fibroblasts. This homology suggests that GP IIIa is a member of a family of cell-surface adhesion receptors.

Structure-function studies on the bradykinin potentiating peptide from Chinese snake venom (Agkistrodon halys Pallas)

A bradykinin potentiating peptide (BPP) was purified from the Chinese snake venom (Agkistrodon halys Pallas). The amino acid sequence of this BPP was determined to be pyroGlu-Gly-Arg-Pro-Pro-Gly-Pro-Pro-Ile-Pro-Pro. Removal of the N-terminal residue with pyroglutamate aminopeptidase enhanced two-fold the activity of BPP, the resulting despyroGlu-BPP gradually lost its activity on further Edman degradation. However, around 90% of the original activity was still present in the C-terminal tripeptide Ile-Pro-Pro. Some analogs of this tripeptide were synthesized by the conventional method, and investigated by two biological assays, i.e., potentiating response on bradykinin (BK) and inhibitory activity on angiotensin converting enzyme (ACE). It was shown that the two biological activities inherent in the synthetic analogs were not parallel to each other. In addition, the isolated guinea pig ileum strips treated with chelating agent to irreversibly inactivate kininase (the same enzyme ACE) still responded to BPP. Consequently the potentiating effect of BPP on BK in vitro bioassay might be due to its influence on the binding receptor for BK rather than the inhibitory effect on kininase.

The mixed disulfide in the zymogen of streptococcal proteinase. Characterization and implication for its biosynthesis

The identity of the volatile mercaptide and the metabolic pathway by which it becomes combined with the zymogen of streptococcal proteinase in the mixed disulfide were investigated. Mass spectrometric analysis identified the oxidized form of the volatile mercaptan as methanesulfonic acid. The mass spectrum of a peptide isolated from tryptic and subsequent chymotryptic digests of the zymogen was shown to be consistent with the previously reported amino acid sequence for a chymotryptic peptide with the sequence Val-Gly-Gln-Ala-Ala-Thr-Gly-His-Cys(SCH3)-Val. Studies using [35S] cystine, [methyl-35S]methionine and [methyl-14C]methionine in a cell suspension system revealed that the biosynthesis of the mixed disulfide in the zymogen may involve the formation of protein-S-SH followed by transmethylation rather than result from a direct transfer of an intact methanethiol to the cysteinyl residue of the zymogen. It is proposed that the attachment of the CH3-SH group to the protein-SH to form protein-S-S-CH3 is a process that is intimately related to the mechanism of secretion of the proteinase into the culture fluid by streptococci.

Intracellular form of streptococcal proteinase: a clue to a novel mechanism of secretion

The intracellular form of streptococcal proteinase has been isolated and compared with its extracellular form. As shown by double-immunodiffusion studies and radiosequence analysis, the intracellular proteinase was identical to that of the extracellular proteinase. However, the unusual mixed disulfide, protein-S-SR, shown to be present in the extracellular proteinase, was missing in the intracellular proteinase. Protease activity is dependent upon the free sulfhydryl group of the proteinase. Thus, the intracellular proteinase was enzymatically active, while the extracellular proteinase requires activation by exposure to a reducing agent. Because this appears to be the only difference between the intracellular and extracellular protease, it is proposed that the modification of the protein-SH to form protein-S-SR is a process that is intimately related to the mechanism of secretion of the proteinase into the culture fluid by streptococci.

Vitamin E and haemolytic anaemia in premature infants

Studies in 50 premature babies aged 6 to 8 weeks showed that vitamin E plays a significant role in the pathogenesis of the `anaemia of prematurity'. Administration of 10 mg/day vitamin E orally elicited a clear-cut clinical and haematological response. There was a relation between the type of nutrition and the onset of anaemia, anaemia regularly developing within 2 weeks of changing from human milk to a powdered cow's milk formula. Susceptibility to haemolysis was quantitated by measuring the free haemoglobin after exposure of the erythrocytes to hydrogen peroxide. This peroxide haemolysis was increased when the vitamin E level in the blood was below 0·6 mg/100 ml. It became normal a few days after vitamin E administration and the consequent rise in blood concentration. It is concluded that a supplement of vitamin E is advisable from the 10th day onwards in premature infants who are artificially fed.