Factors predicting clinical outcomes of continuous ambulatory peritoneal dialysis associated peritonitis - A single centre study.

BACKGROUND: Peritonitis is the common complication among Continuous Ambulatory Peritoneal Dialysis (CAPD) patients. This study is aimed to identify the factors predicting clinical outcomes of peritonitis in patients undergoing CAPD and the demographic, clinical and microbiological features of CAPD patients who were diagnosed with peritonitis. MATERIALS AND METHODS: This is a retrospective observational study conducted to identify factors predicting clinical outcomes of CAPD associated peritonitis over a four-year period in Taiping Hospital, Malaysia. RESULTS: A total of 109 episodes of CAPD associated peritonitis in 54 patients was enrolled with a median age being 56.5 years. In all 43.1% of these were complicated peritonitis. About half (n=54, 49.5%) of the peritonitis was caused by a single gram-positive organism. Coagulase negative Staphylococcus (CoNS) and Escherichia coli was the most often isolated gram-positive and gram-negative microorganism, respectively. We observed that less likelihood of developing complicated peritonitis in presence of abdominal pain (Odd ratio, OR 0.25, 95% confidence interval, 95%CI: 0.10, 0.63). In contrast, presence of more than one previous episode of peritonitis (OR 2.79, 95%CI: 1.11, 7.04) and previous migration and readjustment of Tenkchoff catheter (OR 7.48, 95%CI: 1.39, 40.41), were factors significantly associated with complicated peritonitis. CONCLUSION: Presence of abdominal pain, more than one previous episode of peritonitis, and previous migration and readjustment of Tenkchoff catheter, were found as significant factors in predicting clinical outcomes of CAPD associated peritonitis.

An extracellular proteasome-like structure from C6 astrocytoma cells with serine collagenase IV activity and metallo-dependent activity on alpha-casein and beta-insulin.

An extracellular proteasome-like (EP) structure has been isolated from serum-free media conditioned by C6 astrocytoma cells. EP has a native molecular mass of 1000 kDa and is composed of three subunits, two isoelectric variants at 70 kDa and one at 65 kDa. The extracellular proteasome degraded collagen IV, alpha-casein, beta-insulin, and certain synthetic peptide substrates. A 68-kDa type IV collagenase, identified as the activated form of gelatinase A, was also isolated from this medium. The type IV collagenase activity of the proteasome was sensitive to serine protease inhibitors, while the 68-kDa collagenase IV represented the matrix metalloprotease gelatinase A. The general protease activity of the proteasome was sensitive to metalloprotease inhibitors. Western blot analysis indicates a sequence relationship between the 68-kDa type IV collagenase and either one or both of the 70-kDa isoelectric variants of the proteasome; however, the two enzymes appear to be distinct functionally. Comparison with known proteasomes indicates that EP represents a novel proteasome. The complexity of degradative enzymes in the extracellular microenvironment implies that complete inhibition of tumor growth requires at least a combination of serine and metalloprotease inhibitors.

Degradation of collagen type IV by C6 astrocytoma cells.

The key event associated with the initiation of angiogenesis is the localized degradation of the vascular basement membrane. Because of its complex structure, any remodelling and/or modification of the basement membrane must involve the co-ordinated function of a number of different enzyme systems. Type IV collagen is a major protein component (60-90%) of the basement membrane and its degradation is crucial to the initiation of angiogenesis. This study has focused on the mechanisms by which C6 astrocytoma cells degrade human type IV collagen. C6 astrocytoma cells use components of two major degradative pathways to degrade collagen type IV. The major matrix metalloproteinase identified is the activated form (68-KDa) of gelatinase A (72-KDa matrix metalloproteinase) and a serine sensitive 1000-KDa collagenase type IV degrading activity which appears to have the characteristics of a novel extracellular proteasome.

Serum proteolytic activity during the growth of C6 astrocytoma.

Tumor growth is dependent on the ability of neoplastic cells to induce angiogenesis. Blood-vessel remodeling requires the reconstruction of the nonfibrous proteins and type IV collagen components of the basement membrane. This study has assessed the influence of the growth of C6 astrocytoma cells in the rat spheroid implantation model on serum general protease and type IV collagenase activity. The results demonstrate that general protease activity increased in serum, reaching maximum values on Day 6 and Day 13 following spheroid implantation, and that type IV collagenase activity increased in serum, obtaining maximum values on Day 8 and Day 15. The measurement of serum proteolytic activity may be of value in the detection of recurrent tumors.

The effect of tumor necrosis factor-alpha on human malignant glial cells.

The influence of human recombinant tumor necrosis factor-alpha has been assessed on a cell line (U-251) derived from a human malignant glial tumor. The results of this study demonstrate that tumor necrosis factor-alpha at doses of 50 and 100 ng/ml: 1) did not have cytotoxic or cytostatic effects on the U-251 cell line; 2) significantly increased the intracellular activity of manganese superoxide dismutase but had no effect on copper and zinc superoxide dismutase, catalase, or glutathione peroxidase activity; and 3) did not significantly alter the intracellular or extracellular general protease and collagenase type IV activity of these cells. The resistance of the U-251 cell line to tumor necrosis factor-alpha cytotoxicity may be related in part to the high intrinsic manganese superoxide dismutase activity present in this cell line combined with the ability of this cell line to induce substantial amounts of protective manganese superoxide dismutase activity in response to tumor necrosis factor-alpha.

Proteolytic activity during the growth of C6 astrocytoma in the murine spheroid implantation model.

General protease and collagenase IV activity are involved in the remodelling of the vascular basement membrane that occurs during tumor-induced angiogenesis. This study has assessed the level of these enzymes in tumor, peritumoral or contralateral cerebral cortex tissue during the growth of C6 astrocytoma in the rat spheroid implantation model. General proteolytic activity was increased in tumor tissue beginning on day 8 following spheroid implantation, then increased to a maximum value on day 11 and decreased to control values on day 18. A similar pattern was seen for collagenase IV activity but maximal activity occurred on day 13. The peritumor and tumor patterns of activity were similar. General protease activity was increased in the hemisphere contralateral to the tumor suggesting that the growth of C6 astrocytoma in rat brain was influencing biochemical events distant from the tumor. C6 astrocytoma cells orchestrate a cascade of proteolytic events which may play a crucial role in angiogenesis associated with tumor growth in the model system studied.

General protease and collagenase (IV) activity in C6 astrocytoma cells, C6 spheroids and implanted C6 spheroids.

Tumor growth is dependent on the ability of neoplastic cells to induce angiogenesis. Remodelling of blood vessels requires reconstruction of the collagen (type IV) and non-fibrous protein components of basement membrane. This study assessed the general protease and collagenase (IV) activities of C6 astrocytoma cells in monolayer and spheroid culture and C6 astrocytoma spheroids growing in vivo. Extracellular release of non-specific proteases and collagenase IV was maximal during early exponential cell growth. Increased spheroid size resulted in enhanced extracellular activity of both enzyme groups assessed. The size of the implanted spheroid influenced the activity measured in vivo. General proteolytic activity was significantly greater in tumor tissue at all spheroid sizes while only the implantation of 750 microns spheroids resulted in significantly increased collagenase type IV activity. The growth of C6 astrocytoma cells in monolayer and spheroid culture in vitro and in vivo is associated with distinct alterations in intracellular and extracellular activity of the proteolytic enzymes assessed. Increased extracellular release of these enzymes may play important roles in tumor-associated angiogenesis, tumor invasiveness, tumor induced hemorrhage and tumor-associated edema.

High-molecular-mass proteases (possible proteasomes) in Escherichia coli K12.

Two high-molecular-mass proteases have been detected in E.coli K12 and isolated from the periplasmic fraction released by osmotic shock. The two proteases, designated Protease peri7 and Protease peri8, have similar molecular masses (greater than 2000 kDa) and degrade alpha- and beta-casein, but not insulin B chain. Protease peri7 is a metalloprotease activated 3-6 fold by ATP, dATP and GTP but inhibited by AMP. Nucleotide hydrolysis occurs during protein breakdown. Protease peri8, in contrast, is a serine protease unaffected by nucleotides or metal chelators. The two proteases appear by electron microscopy to be ring-shaped particles of approximately 125 A degrees in diameter. These proteases appear to be very similar to the multi-protease complexes (Proteasomes) detected in a variety of eukaryotic cells.