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Biomedical subjects

J Beaver

Publications and source records attributed to J Beaver.

13 recordsLinked to original sources
PubMed1999

Increased cell surface exposure of phosphatidylserine on propidium iodide negative thymocytes undergoing death by necrosis.

Phosphatidylserine (PS) exposure on propidium iodide negative cells using FITC labelled annexin-V has been used to quantify apoptosis in vitro and in vivo. Detection of PS within cells undergoing necrosis is also possible if labelled annexin-V specific for PS enters the cell following early membrane damage. Necrotic or late apoptotic cells can be excluded from flow cytometric analysis using propidium iodide which enters and stains cells with compromised membrane integrity. Here we show that thymocytes undergoing death exclusively by necrosis show early exposure of PS prior to loss of membrane integrity. This early exposure of PS occurs in cells treated with agents which both raise intracellular calcium levels and are also capable of interacting with protein thiol groups. We also demonstrate that PS exposure in thymocytes induced to undergo apoptosis by three different agents does not correlate with calcium rises but correlates with and precedes DNA fragmentation.

Animals↗
PubMed1999

Pneumopericardium mimicking acute myocardial ischemia after laparoscopic cholecystectomy.

Pneumopericardium occurred after laparoscopic cholecystectomy in a 57-year-old woman. The patient had chest pain accompanied by T-wave inversion on electrocardiogram, with signs and symptoms suggestive of acute myocardial ischemia. Evaluation for myocardial infarction, however, was negative and clinical findings resolved spontaneously. Although pneumopericardium after laparoscopic procedures has been previously reported, this case illustrates how associated findings may mimic those of acute myocardial ischemia or infarction.

Chest Pain↗
PubMed1996

Cyclosporin A rescues thymocytes from apoptosis induced by very low concentrations of thapsigargin: effects on mitochondrial function.

Raising intracellular calcium levels can induce apoptosis or programmed cell death in many cells. While early rises in intracellular calcium are not universally associated with apoptotic cell death, calcium clearly plays a key role in many of the biochemical events which occur during apoptosis. In this paper we have determined intracellular calcium rises induced by 2, 10, and 100 nM thapsigargin in mouse thymocytes. These concentrations cause increases in cytosolic calcium of 100-250, 400-600, and > 1000 nM, respectively. These rises are sustained for at least 85 min and the ratio between the maximum rise caused by 10 nM compared to 2 nM thapsigargin is 2.1 +/- 0.4 (n = 6). Both 2 and 10 nM thapsigargin cause apoptosis at 24 h as shown by DNA fragmentation and morphology when examined by electron microscopy. Cyclosporin A (CsA) inhibits apoptosis caused by 2 nM thapsigargin but not that caused by 10 nM thapsigargin. Electron microscopy of thymocytes treated with 2 nM thapsigargin at 24 h shows intact mitochondria although with altered morphology. There is no loss of ATP or decrease in the ATP/ADP ratio in these cells over 12 h. Mitochondria in cells treated with 10 nM thapsigargin, however, are swollen by 6 h and many are lost by 24 h. These cells show greatly diminished ATP content by 12 h and a decrease in ATP/ADP ratio. Examination of the effects of PMA, an activator of the plasma membrane calcium ATPase pump, on cells treated with 10 nM thapsigargin suggests that two pools of calcium may be responsible for the differential effects of the two calcium levels in the cells. Probing of the mitochondrial membrane potential (MMP) by rhodamine 123 staining of live cells shows that the collapse of the MMP caused by 10 nM thapsigargin is unaffected by CsA. The MMP is also reduced in cells treated with 2 nM thapsigargin but this is restored by CsA. Cells are also rescued from apoptosis caused by 2 nM thapsigargin by incubation with FK506. This immunosuppressive agent has no effect on the membrane permeability transition induced in isolated mitochondria. These results suggest that very low rises in intracellular calcium in thymocytes cause activation-induced cell death inhibited by CsA and FK506 and are without effect on ATP levels and therefore do not involve irreversible mitochondrial damage. Exceeding these calcium levels by only two-fold results in apoptosis accompanied by reduced ATP levels and mitochondrial damage, although apoptotic cell death in this instance is unaffected by the classic inhibitor of mitochondrial permeability transition, CsA.

Adenosine Diphosphate↗
PubMed1996

Prognostic significance of serum c-erbB-2 protein in breast cancer patients.

The tissue expression of c-erbB-2 protein in breast cancer is a marker of poor prognosis in a number of studies. More recently it has also been suggested that c-erbB-2 expression may predict response to systemic therapy in patients with advanced breast cancer. The measurement of c-erbB-2 protein in the serum of breast cancer patients has now been reported, but the significance of this finding is not clear. In this study an ELISA assay was used to measure c-erbB-2 in the sera of 23 normal controls, 46 benign breast disease patients, and 119 breast cancer patients. Elevated serum c-erbB-2 protein levels were detected in 13% (3/23) of normal controls, 15% (7/46) of benign disease patients, 15% (7/46) of Stage I/II patients, 26% (9/35) of Stage III patients, and 21% (8/38) of Stage IV patients. The tissue expression of the c-erbB-2 protein showed no association with detection of the serum c-erbB-2 protein (p = 0.31). In the 67 Stage III and IV patients who had assessable disease the presence of the c-erbB-2 protein in the serum bore no relationship to response to hormonal therapy (p = 0.71). Serum detection of the c-erbB-2 protein in Stage I/II patients predicted for a worsening of both survival outcome (p = 0.002) and disease free interval (p = 0.002). A worse outcome was also seen for the Stage III patients (p = 0.04) and Stage IV patients, although the latter did not reach statistical significance (p = 0.27). This study found that the presence of c-erbB-2 in the serum of breast cancer patients was of prognostic significance for all stages of disease.

Biomarkers, Tumor↗
PubMed1996

Gliotoxin and related epipolythiodioxopiperazines.

1. Gliotoxin belongs to the epipolythiodioxopiperazine class of secondary metabolites. These compounds show a diverse range of biological activity including antimicrobial, antifungal and antiviral properties. They also display potent in vitro and in vivo immunomodulating activity. 2. Their properties resulted in a number of early studies designed to exploit their possible chemotherapeutic value, although the general toxicity of most members of this class has precluded clinical use. 3. Most recently, their selective immunosuppressive properties have led to the possibility of ex vivo treatment of tissue to selectively remove immune cells responsible for tissue rejection. The mode of action of gliotoxin appears to be via covalent interaction to proteins through mixed disulphide formation and gliotoxin has been shown to inhibit a number of thiol requiring enzymes. 4. Gliotoxin is also a potent inducer of apoptotic cell death in a number of cells. Gliotoxin and other members of this class of toxins may be produced in vivo during the course of fungal infections and contribute to the aetiology of the disease.

Adjuvants, Immunologic↗
PubMed1995

Evidence that gliotoxin enhances lymphocyte activation and induces apoptosis by effects on cyclic AMP levels.

Gliotoxin is a secondary metabolite produced by several pathogenic fungi. It has potential clinical applications as an immunosuppressive agent in preventing allograft rejection. At low doses (< 30 nM) gliotoxin displays co-mitogenic activity, but at higher doses induces apoptosis in cells. Here we demonstrate that gliotoxin, although not mitogenic in its own right, enhances activation in preactivated splenocytes by a calcium-independent mechanism. The enhancement in activation correlates with a decrease in intracellular cyclic AMP levels. This property is inhibited by dibutyryl-cAMP. Increasing the concentration of gliotoxin to levels that caused apoptosis produced a dose-related increase in cAMP levels. Thus, the effects of gliotoxin on cell activation and the induction of apoptosis may both be mediated by changed levels of cAMP.

Animals↗
PubMed1990

Interaction of sulfonamide and sulfone compounds with Toxoplasma gondii dihydropteroate synthase.

Toxoplasma gondii is a common protozoan disease that often causes life-threatening disease, particularly among patients with the acquired immunodeficiency syndrome. This study demonstrates that the dihydropteroate synthase in T. gondii is kinetically distinct from the enzyme characterized from other sources and can be highly purified with a high yield using sequential dye-affinity chromatography. Conditions have been identified that allow for stabilization of the purified enzyme, and its physical characteristics have been elucidated. The molecular weight of the native protein was 125,000 and the protein appeared to contain both dihydropteroate synthase and 6-hydroxymethyl-dihydropterin pyrophosphokinase activities. The sulfonamide class of compounds vary in inhibitory potency by more than three orders of magnitude. Sulfathiazole, sulfamethoxazole, and sulfamethazine, with 50% inhibitory concentrations (IC50's) of 1.7, 2.7, and 5.7 microM, respectively, represent the most potent of this class of inhibitors. Several sulfone analogues, including dapsone, were identified as highly potent inhibitors with IC50's less than 1 microM. The results of these cell-free experiments were corroborated by investigating the metabolic inhibition produced by the various inhibitors in intact organisms. The qualitative and quantitative relations among the inhibitors were preserved in both the cell-free and intact cell assay systems. These studies suggest that the sulfones may be important therapeutic agents for the treatment of toxoplasmosis.

4-Aminobenzoic Acid↗
PubMed1989

Characterization of de novo folate synthesis in Pneumocystis carinii and Toxoplasma gondii: potential for screening therapeutic agents.

Drug therapy studies imply that Pneumocystis carinii and Toxoplasma gondii possess the enzymes necessary for de novo folate synthesis. To verify this, incorporation of [3H]paraaminobenzoic acid [( 3H]PABA) into reduced folates by P. carinii and T. gondii was investigated. Both organisms synthesized tritiated reduced folates. In P. carinii, 10-formyltetrahydrofolate and tetrahydrofolate, and in T. gondii, 5-formyltetrahydrofolate were the major synthesized folates. P. carinii remained metabolically active in vitro for only a few days. Because current systems for screening antipneumocystis agents are cumbersome, the utility of this assay system for screening therapeutic agents was investigated. Sulfonamides and pentamidine efficiently inhibited de novo folate synthesis in P. carinii. Inhibitors of dihydrofolate reductase such as trimethoprim and trimetrexate were poor inhibitors for P. carinii but efficient inhibitors for T. gondii. This study demonstrates the first unambiguous evidence of metabolic activity in P. carinii, and provides a potential assay for efficiently screening antipneumocystis drugs in vitro.

4-Aminobenzoic Acid↗
PubMedDate not supplied

Serum tissue polypeptide specific antigen (TPS) in breast cancer patients: comparison with CA 15.3 and CEA.

Pre-treatment TPS serum levels from patients with Stage IV breast cancer (n = 66) (1386.0 +/- 3504.5) were significantly higher (p < 0.0001), than normal controls (n = 47), (75.5 +/- 111.5 U/L), benign breast disease patients (n = 84) (58.5 +/ 57.1 U/L), and breast cancer patients with Stage I/II (n = 79) (52.7 +I- 49.5U/L) or Stage III disease (n = 57) (166.7 +/- 218.8). Analysis of sequentially obtained samples from Stage IV patients during endocrine treatment showed TPS alone or in combination with CEA and CA 15.3 was less accurate in predicting response than the combination of CEA with CA 15.3. In this study TPS did not usefully add to the established marker combination of CEA and CA 15.3.

Biomarkers, Tumor↗