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Biomedical subjects

S S Lo

Publications and source records attributed to S S Lo.

At least 73 records · Page 4Linked to original sources
PubMed1991

[Malaria in intravenous drug users associated with HIV seropositivity].

Cases of induced malaria have been notified in S. Paulo State, Brazil, in recent years. At the same time the number of cases imported from endemic regions of Brazil has been increasing. One case of induced malaria by Plasmodium vivax was registered in Presidente Prudente, located in the west of the State, in 1988 and a further eleven cases in 1989. This city is considered to be one of the main transit ports for people who come into the State from the Amazonian region. The patients declared that they had not been to any possible transmission area of malaria. All of them had, however, taken cocaine, sharing the same contaminated needle and syringe. Previously, one person with imported malaria was detected, who had transmitted the disease to the first case in 1988 and also to a further group of 3 people in 1989. One of these three latter cases then transmitted the disease to two other people. As the group of people continued to use the drug among themselves, 2 new cases arose. Afterwards, they re-infected themselves again (one of the was re-infected twice). The test for Human Immunodeficiency Virus was positive for 5 individuals, of whom one had a negative result and 2 others did not undergo the test. This information is discussed within the present context.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Stimulation of de novo synthesis of prostaglandin G/H synthase in human endothelial cells by phorbol ester.

The present study was undertaken to determine the mechanism by which phorbol ester stimulates eicosanoid synthesis in endothelial cells. We observed that phorbol 12-myristate 13-acetate (PMA) actively stimulated eicosanoid synthesis over a prolonged period of time, and the stimulatory effect was abolished by cycloheximide and actinomycin D. Western blot was employed to test the hypothesis that PMA elicited sustained eicosanoid synthesis via the stimulation of de novo synthesis of prostaglandin G/H synthase (cyclooxygenase, EC 1.14.99.1). Treatment of cultured human umbilical vein endothelial cells resulted in an enhancement of the 70-kDa immunoreactive prostaglandin G/H synthase band over the control cells treated with medium alone. The enhancement was abolished by cycloheximide. Human umbilical vein endothelial cells were then metabolically labeled with L-[35S]methionine, and the effect of PMA on methionine incorporation was evaluated by immunoblotting. PMA increased the synthetic rate of prostaglandin G/H synthase over the control cells. By pulse-chase experiments, we further showed that prostaglandin G/H synthase has a rapid turnover rate (t1/2 less than 10 min) in control cells, and PMA had no effect on the enzyme turnover. Our data indicate that PMA increases the synthesis of prostaglandin G/H synthase which is required for circumventing the autoinactivation of prostaglandin G/H synthase and hence permit sustained conversion of arachidonic acid into eicosanoids.

Cells, Cultured↗
PubMed1988

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.

Cell Line↗
PubMed1987

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.

Amino Acid Sequence↗
PubMed1985

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.

Amino Acid Sequence↗
PubMed1984

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.

Amino Acid Sequence↗
PubMed1984

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.

Amino Acids↗
PubMed1970

[Stomatocytosis].

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Anemia, Hemolytic↗