Peroxyacetyl nitrate and peroxypropionyl nitrate during SCOS 97-NARSTO.

Peroxyacyl nitrates [RC(O)OONO2] play an important role in urban air quality and tropospheric chemistry. They also receive attention as mutagens, phytotoxins, and possible air quality indicators of changes in vehicle fuel composition. Ambient concentrations of PAN (R = CH3) and PPN (R = C2H5) have been measured during summer 1997 at two southern California locations, Azusa (July 14-October 16) and Simi Valley (June 18-October 16). The highest concentrations were 4.8 ppb for PAN and 0.72 ppb for PPN in Azusa and 3.0 ppb for PAN and 0.28 ppb for PPN in Simi Valley. Ambient levels of PAN and PPN during summer 1997 were lower than those measured in the last three studies carried out in southern California in the summers of 1990, 1991, and 1993. Average PPN/PAN concentration ratios were about the same in Azusa (0.142+/-0.025, n = 132) and in Simi Valley (0.135+/-0.028, n = 138). The PPN/PAN ratio measured in Azusa was the same as that measured at that location in 1993 prior to the introduction in 1996 of California Phase 2 reformulated gasoline. Diurnal variations of PAN and PPN generally followed those of ozone with respect to time of day but not with respect to amplitude. The PAN/ozone ratio was lower in Simi Valley than in Azusa, and daytime minima were recorded at both locations. The amount of PAN lost by thermal decomposition accounted for large fractions of the amount of PAN formed (measured + decomposed) during daytime hours at both locations. The amount of PAN lost by thermal decomposition was higher in Azusa and was up to ca. 8.5 ppb, i.e., 4-5 times more than that measured, when afternoon temperatures were ca. 40 degrees C.

Interleukin-10. A role in the development of postoperative immunosuppression.

BACKGROUND: The cause of diminished monocyte major histocompatibility complex class II antigen expression after surgery or trauma is unclear. Interleukin-10 (IL-10) regulates inflammatory cytokine production and major histocompatibility complex class II (HLA-DR) expression in vitro. OBJECTIVES: To quantify in vivo IL-10 messenger RNA (mRNA) and protein and monocyte HLA-DR expression after major surgery and to investigate the effects of IL-10 neutralizing blockade on monocyte HLA-DR expression in vitro. DESIGN: Inception cohort study of 48 surgical patients from preoperative status to postoperative day 7 and 9 healthy volunteers (controls). SETTING: Large teaching hospital, Northern England. PATIENTS: Monocyte HLA-DR and cytokine mRNA expression was determined in 32 of 48 consecutive patients undergoing elective major resectional surgery. Mononuclear cells for in vitro studies and serum samples for IL-10 measurement were obtained from the remaining 16 patients. MAIN OUTCOME MEASURES: Monocyte HLA-DR expression determined by flow cytometry, IL-10, and tumor necrosis factor mRNA in peripheral blood mononuclear cells assayed by multiplex reverse transcriptase polymerase chain reaction, and serum IL-10 determined by enzyme-linked immunosorbent assay. RESULTS: Monocyte HLA-DR expression (in mean channel fluorescence units [MCF]) was significantly reduced 24 hours after surgery (MCF [+/- SEM], 32.6 +/- 2.3 vs 16.3 +/- 1.2; P < .001) and remained low during the first postoperative week. A relative increase in IL-10 to G3PDH mRNA ratio (mean [+/- SEM], 0.95 +/- 0.08 vs 0.59 +/- 0.06; P < .01) and serum IL-10 (mean [+/- SEM], 18.1 +/- 4.1 vs 5.4 +/- 0.8 pg/mL; P < .01) was noted on the first postoperative day. A significant correlation existed between HLA-DR antigen expression and the presence of IL-10 mRNA transcript on the first postoperative day (P < .01). Lipopolysaccharide-induced up-regulation of monocyte HLA-DR expression was significantly impaired on the first postoperative day (mean [+/- SEM], 151% +/- 24.4% vs 60% +/- 10.1%; P < .01), but this was partially reversed by IL-10 neutralizing antibody (mean [+/- SEM], 60% +/- 10.1% vs 115% +/- 11.6%; P < .01). CONCLUSIONS: Interleukin-10 gene expression correlates with the fall in monocyte HLA-DR antigen expression in patients undergoing major abdominal surgery and may account for the immunosuppression associated with surgical injury.

High-affinity binding sites for gastrin-releasing peptide on human colorectal cancer tissue but not uninvolved mucosa.

Human colorectal cancer tissue and matched uninvolved mucosa from 21 patients were examined by radioligand displacement for the presence of binding sites for bombesin-like peptides. Five cancers, but no uninvolved mucosa, expressed high-affinity, low-capacity bombesin binding sites (Kd = 6.53 nM, Bmax = 58.6 fmol mg-1 protein) of the gastrin-releasing peptide (GRP)-preferring subtype (IC50 4.8 nM). Bombesin-like peptides may have a role in the pathogenesis of colorectal cancer, and bombesin receptor antagonists may be of value in the treatment of receptor-positive tumours.

Characterization of a bombesin/gastrin-releasing peptide receptor on a human gastric-cancer cell line.

This study examined the expression of receptors of the bombesin (BBS) family in human gastric-cancer cell lines. Of 5 cell lines screened, only one, St42, demonstrated specific binding sites for 125I-Tyr4-BBS, which have been further characterized. This binding was saturable, and temperature- and time-dependent. Scatchard analysis of displacement data performed at 37 degrees C revealed 2 binding sites: a high-affinity, low-capacity site (KD = 0.13 nM, Bmax = 1500 sites/cell) and a lower-affinity, higher-capacity site (KD = 11 nM, Bmax = 35,000 sites/cell); the latter was lost when internalization of peptide was prevented, suggesting that it may be an artefact. Displacement assays with gastrin-releasing peptide (GRP) and neuromedin B (NMB) revealed that the receptor was of the GRP-preferring sub-type (GRP IC50 = 0.35 nM; NMB IC50 = 112 nM). Co-valent cross-linking of 125I-Tyr4-BBS to the receptor demonstrated the presence of a single band corresponding to a molecular weight of 37 to 44 kDa on SDS-PAGE, similar to that of the cloned GRP receptor protein core. G-protein linkage of this receptor was demonstrated by selective inhibition of 125I-Tyr4-BBS binding by guanosine nucleotides. The binding of BBS to the receptor resulted in a rise in intracellular calcium. Three of four structurally distinct BBS antagonists bound to the receptor with high affinity, but [DPhe12, Leu14]-bombesin did not cause any displacement of 125I-Tyr4-BBS even at 10 mM. The functional significance of GRP receptors on human gastric-cancer cells is as yet unknown, but further studies may determine whether such receptors have importance in the therapy of gastric cancer.

High affinity binding sites for gastrin releasing peptide on human gastric cancer and Ménétrier's mucosa.

The bombesin-like peptides gastrin releasing peptide (GRP) and neuromedin B are found in the submucosal and myenteric plexuses of the human gastrointestinal tract. These peptides are potent mitogens to Swiss 3T3 fibroblasts and are important autocrine growth factors in human small cell lung cancer cells. We have recently described the presence of receptors for the bombesin-like peptide, GRP, on the human gastric cancer cell line St42. In this study, we examined fresh resected gastric cancer and uninvolved mucosa from 23 patients for the presence of binding sites to the bombesin-like peptides. Thirteen of 23 gastric cancers expressed high affinity binding sites for bombesin (mean Kd = 3.42 nM; mean Bmax = 40.5 pmol/mg protein), of which 12 were subsequently characterized and found to be of the GRP-preferring subtype. One of 23 mucosal samples specifically bound bombesin and was the only sample from a patient with Ménétrier's disease, a disorder of mucosal growth known to be premalignant. The early gastric cancer from this patient also possessed high affinity binding sites for GRP. This is the first description of binding sites to bombesin-like peptides on human gastric cancer and Ménétrier's mucosa. The role of bombesin/GRP antagonists in the treatment of gastric cancer warrants investigation.

Somatostatin binding in human gastrointestinal tissues: effect of cations and somatostatin analogues.

This study characterises the somatostatin binding site in human gastrointestinal cancer and mucosa in terms of cationic specificity and relative affinity for three somatostatin analogues. Competitive displacement assays were performed on plasma membranes from human gastric and colonic tissues using radiolabelled somatostatin-14 as ligand. Comparison was made with the somatostatin binding site in rat cerebral cortex. In gastrointestinal tissue, magnesium decreased and sodium increased specific binding. By contrast, in rat cerebral cortex, the converse cationic effect was seen. These changes resulted from alterations in receptor density, with no change in receptor affinity. Displacement studies were then performed with somatostatin-14 and somatostatin analogues RC-160, somatuline, and octreotide. RC-160 and somatuline displaced radiolabel from binding sites in gastric and colonic cancer and mucosa with 10-fold lower affinity than the native peptide. Octreotide did not displace radioligand in gastric or colonic cancer at any concentration tested. By contrast, in rat cortex, although all three analogues displaced with a lower affinity than the native peptide, there was no difference between analogues. These data suggest a distinct somatostatin receptor subtype in gastrointestinal tissues.

Somatostatin binding in normal and malignant human gastrointestinal mucosa.

Somatostatin is a regulatory peptide implicated in the control of cellular proliferation in epithelial tissues and this regulation may occur directly via membrane bound receptor activation. The aim of this study was to investigate somatostatin binding in human gastrointestinal cancer and normal mucosa. Plasma membranes were prepared from specimens of tumour and normal mucosa from 51 patients undergoing surgical resection for malignancy (28 gastric, 23 colorectal). Using a competitive displacement assay, specific 125I-tyrosine-11-somatostatin-14 binding to plasma membranes was assessed and and characterised in terms of receptor affinity (Kd) and maximum binding capacity (Bmax) as determined by Scatchard analysis. Specific low affinity (Kd = 166 nM), high capacity (Bmax = 1.2 pmol mg-1 protein) somatostatin binding was demonstrated in 22 of the gastric cancers and 17 of the colorectal cancers (Kd = 140 nM, Bmax = 1.8 pmol mg-1 protein). Similar affinity and binding capacity was demonstrable in normal mucosal samples. High affinity receptors for somatostatin were expressed by one gastric carcinoma (Kd = 0.9 nM; Bmax = 0.23 pmol mg-1 protein). Thus, low affinity, high capacity binding is a common feature of gastrointestinal tumours and normal mucosa, and high affinity receptors may occasionally be demonstrated. The functional significance of these low affinity binding sites requires elucidation to determine whether long-acting somatostatin analogues may have therapeutic benefit in gastrointestinal malignancy.

Evaluation of an enzyme-linked immunosorbent Raji cell assay (ELISA) in the investigation of gastrointestinal cancer.

The levels of circulating immune complexes (CICs) have been estimated in a group of patients with colorectal cancer and gastric cancer, in addition to which a normal range has been established in a group of patients with benign gastrointestinal disease. A newly developed enzyme-linked immunosorbent Raji cell assay has been used in this study. Overall only 30% of patients with gastrointestinal cancer showed elevation of CIC levels outside the normal range. Elevated levels correlated with tumour differentiation bud did not correlate with site of disease or with the presence of metastases. In an attempt to define the specificity of CIC estimation, soluble tumour extract was added to sera from tumour-bearing patients. Specific IC elevations were produced by addition of allogeneic tumour extract of colon cancer in patients with colorectal cancer; this phenomenon was not seen when the same extract was added to the sera of patients with gastric cancer.

Suppressor cell activity of peripheral mononuclear cells from patients undergoing chronic haemodialysis.

The enhanced in vitro proliferative response of peripheral mononuclear cells (PMNC) when pre-cultured for 24 hours prior to the addition of Concanavalin-A has been used as an indirect parameter of suppressor cell activity in healthy subjects and in patients undergoing chronic haemodialysis. The proliferative response of PMNC from haemodialysis patients is lower than that of control subjects when Con-A is added at the initiation of culture but approximates to that of normal subjects when the addition of Con-A was deferred for 24 hours. The Suppressor Indices of PMNC from haemodialysis patients were at least as great and sometimes greater than those of control subjects but the absolute T-cell counts were lower in haemodialysis patients than in controls. These results suggest that the relative energy of haemodialysis patients is partly attributable to T-cell depletion but this is accompanied by retention, and in some cases augmentation, of suppressor cell activity.