Birth characteristics and risk of colorectal cancer: a study among Swedish twins

Type-2 diabetes increases the risk of colorectal cancer, and is also associated with low birth weight. However, we found no evidence of associations between birth characteristics and risk of colorectal cancer (m=248) among Swedish twins.

Methylation of the p16INK4A promoter is associated with malignant behavior in abdominal extra-adrenal paragangliomas but not pheochromocytomas

Pheochromocytomas and abdominal extra-adrenal paragangliomas are related to endocrine tumors of the sympathetic nervous system. Studies in animal models have shown that inactivation of the products of the cyclin dependent kinase inhibitor 2A (CDKN2A) gene locus, p16INK4A and p14ARF, promotes the development of pheochromocytoma, especially in malignant form. The present study evaluated the involvement of CDKN2A in human pheochromocytomas and abdominal extra-adrenal paragangliomas from 55 patients. Promoter methylation was assessed using quantitative Pyrosequencing and methylation-specific PCR, and mRNA expression was measured by quantitative real-time PCR. For p16, western blot analysis and sequencing were also performed. succinate dehydrogenase complex subunit B (SDHB) sequencing analysis included extra-adrenal paragangliomas, all tumors classified as malignant, and cases diagnosed at 30 years or younger. The p16INK4A promoter was heavily methylated in a subset of paragangliomas, and this was significantly associated with malignancy (P<0.0043) and SDHB mutation (P<0.002). p16INK4A mRNA expression showed moderate suppression in malignant cases (P<0.05). In contrast, very little p14ARF promoter methylation was seen and there was no significant difference in p14ARF expression between tumors and normal samples. The p16 protein expression was reduced in 16 tumors, and sequence variations were observed in four tumors including the missense mutation A57V and the single nucleotide polymorphism (SNP) A148T. The results suggest that p16INK4A, and not p14ARF, is a subject of frequent involvement in these tumors. Importantly, hypermethylation of the p16INK4A promoter was significantly associated with malignancy and metastasis, and SDHB gene mutations. This finding suggests an etiological link and could provide a clinical utility for diagnostic purposes.

Binding of vitronectin and clusterin by coagulase-negative staphylococci interfering with complement function

Coagulase-negative staphylococci (CoNS) are commonly associated with infections of prosthetic devices mediated by adsorbed host factors on biomaterial surfaces. Complement activation is known to occur and induce unspecific inflammation around the biomaterials. Human vitronectin (Vn) and clusterin (Clu), two potent inhibitors of complement, can be bound by CoNS. With a hypothesis whether binding of Vn or Clu influences complement activation, two measurements were determined. For Vn, complement activation was measured with a mouse anti-activated human C9 antibody. In the presence of Vn-binding strain, Staphylococcus hemolyticus SM13I, complement activation on a surface pre-coated with Vn occurred as it did in the absence of Vn pre-coating. For S. epidermidis 3380, which does not express binding of Vn, complement activation on a Vn-presented surface was significantly decreased. For Clu, erythrocytes lysis was measured to reflect the end product of complement activation (membrane attack complex). The complement-induced hemolysis increased when human serum was pre-incubated with Clu-binding strains, S. epidermidis J9P. The enhancement of hemolysis by J9P decreased when serum was supplemented by exogenous Clu. The data imply that interaction between CoNS and Vn or Clu interferes with one of their physiological functions, complement inhibition.

Characterization of vitronectin-binding proteins of Staphylococcus epidermidis

Staphylococcus epidermidis is the most common microorganism that is isolated from the cerebrospinal fluid (CSF) shunt infection patients. Vitronectin adsorbed on the surface of implants may mediate bacterial adhesion and colonization. To characterize vitronectin-binding properties, we analyzed S. epidermidis BD5703 isolated from a CSF shunt infection. Expression of vitronectin-binding protein(s) depended on culture media. Two proteins (60 and 52 kDa) were purified from vitronectin affinity chromatography. Two other vitronectin-binding proteins (21 and 16 kDa) were purified from an ion-exchange column. All purified proteins blocked bacterial binding of immobilized vitronectin significantly except the 16-kDa protein. The N-terminal sequences of the 21- and 16-kDa proteins did not show any appreciable amino acid sequence homology. The 52-kDa protein was sequenced by mass spectrometry and identified as an autolysin. This report demonstrates that interaction of vitronectin with multiple recognition sites on BD5703 surface may contribute to bacterial colonization.

External ventricular drainage catheters: effect of surface heparinization on bacterial colonization and infection

Surface heparinization of central venous catheters has earlier been shown to reduce the frequency of bacterial colonization and septicaemia. The present study was undertaken to investigate the benefit of surface heparinization of external ventricular drainage (EVD) catheters in relation to bacterial colonization, as measured by bacterial growth and examination by a 16S-rRNA PCR assay, of catheters and of samples of cerebrospinal fluid (CSF). Ninety-eight heparinized and one hundred unheparinized EVD catheters from the same batch of catheters were used. Twenty point five percent of the heparinized and 22.8% (p = 0.63) of the unheparinized EVD catheters were colonized with bacteria. Culture of CSF, which is the definition of clinical infection in this study, yielded growth in 10.3% of patients with heparinized and in 6.3% (p = 0.18) of those with unheparinized catheters. PCR examination yielded positive signal in 31.3% of patients with heparinized catheters and in 37.7% (p = 0.061) of patients without (CSF and catheters). In the subgroup of patients with subarachnoid haemorrhages, there was a tendency, though not statistically significant, towards a lowered frequency of colonization with 23.1% for heparinized and 33.3% (p = 0.31) for unheparinized catheters. PCR examination did not contribute any further to the diagnostic procedure in the patients concerned. The EVD catheters are skin-penetrating devices and contamination from the skin flora is common. Skin cultures, obtained after skin disinfection and insertion of catheters, showed growth of bacteria in 62% of the patients.

Adhesion of staphylococci to polymers with and without immobilized heparin in cerebrospinal fluid

Infections of cerebrospinal fluid (CSF) shunts constitute a serious clinical problem. The role of adhesion by coagulase negative staphylococci, the most common etiological agent, was examined in vitro to polyvinyl chloride (PVC), silicone, and to PVC and silicone with end-point attached (EPA) heparin. These are flexible materials commonly used in neurosurgical implants. Bacterial adhesion was quantitated by bioluminescence. The bacterial adhesion to biomaterial surfaces increased with increasing concentrations of bacterial cells. Scatchard plot analysis showed continuous negative (concave) slopes, indicating multiple interactions between biomaterial and bacteria. The thermodynamic studies showed a positive value of the standard entropy change at 37 degrees C, which indicates that hydrophobic interactions are important in bacterial adhesion to polymers. Incubation with CSF for 1 h decreased bacterial adhesion in 75% of the samples compared to incubation in buffer. Thus, the contribution of CSF proteins, like fibronectin, for the initial bacterial adhesion might be small. Heparinization of silicone and PVC decreased the numbers of adhered bacteria by 23 to 54% and 0 to 43% compared to unheparinized surfaces. Among putative inhibitors tested, suramin, chondroitin sulfate, and fucoidan inhibited adhesion to 81 +/- 19, 78 +/- 22, and 64 +/- 7%, respectively. These findings indicate that hydrophobic interactions play an important role, and heparinization rendering the biomaterial surface hydrophilic is therefore effective to reduce bacterial adhesion. Heparinized polymers incubated with putative inhibitors may be the optimal way to prevent shunt infections.

Exposure of plasma proteins on Dacron and ePTFE vascular graft material in a perfusion model

OBJECTIVES

to compare the exposure of plasma proteins adsorbed onto three vascular graft materials (polytetrafluoroethylene ePTFE and two modifications of polyethyleneterephthalate Dacron).

METHODS

surface exposure of fibronectin, vitronectin, thrombospondin, antithrombin III, IgG, high molecular-weight kininogen, fibrinogen, albumin and plasminogen was studied by incubation with radiolabelled antibodies in a perfusion model. Perfusion times with human plasma were 1, 4, 24 and 48 hours.

RESULTS

all proteins could be detected at 1, 4, 24 and 48 hours after the start of perfusion. Overall, the least amount of proteins adsorbed onto ePTFE.

CONCLUSIONS

the low adsorption of proteins onto ePTFE may be one of the reasons for the lower incidence of infections reported with this material.

Presence of vitronectin and activated complement factor C9 on ventriculoperitoneal shunts and temporary ventricular drainage catheters

OBJECT

The pathogenesis of cerebrospinal fluid (CSF) shunt infection is characterized by staphylococcal adhesion to the polymeric surface of the shunt catheter. Proteins from the CSF--fibronectin, vitronectin, and fibrinogen--are adsorbed to the surface of the catheter immediately after insertion. These proteins can interfere with the biological systems of the host and mediate staphylococcal adhesion to the surface of the catheter. In the present study, the presence of fibronectin, vitronectin, and fibrinogen on CSF shunts and temporary ventricular drainage catheters is shown. The presence of fragments of fibrinogen is also examined.

METHODS

The authors used the following methods: binding radiolabeled antibodies to the catheter surface, immunoblotting of catheter eluates, and scanning force microscopy of immunogold bound to the catheter surface. The immunoblot showed that vitronectin was adsorbed in its native form and that fibronectin was degraded into small fragments. Furthermore, the study demonstrated that the level of vitronectin in CSF increased in patients with an impaired CSF-blood barrier. To study complement activation, an antibody that recognizes the neoepitope of activated complement factor C9 was used. The presence of activated complement factor C9 was shown on both temporary catheters and shunts.

CONCLUSIONS

Activation of complement close to the surface of an inserted catheter could contribute to the pathogenesis of CSF shunt infection.

A new model to assess staphylococcal adhesion to intraocular lenses under in vitro flow conditions

Adhesion of staphylococcal cells to intraocular lenses coated with heparin was studied under in vitro flow conditions (280 microl min(-1)) at 37 degrees C. The intraocular lenses were incubated with human cerebrospinal fluid for 1 h or with cerebrospinal fluid including 0.50% plasma for 12 h, prior to bacterial challenge. Two strains of Staphylococcus epidermidis selected for this study, were isolated from biomaterial-associated infections. Bacterial adhesion was quantitated by bioluminescence and visualized by fluorescence microscopy of acridine orange stained bacteria. Surface coating with heparin significantly decreased bacterial adhesion of both strains after incubation with cerebrospinal fluid including 0.50% plasma for 12 h (p = 0.0209). However, no difference in bacterial adhesion was obtained between intraocular lenses with and without heparin, after incubation with cerebrospinal fluid for 1 h (p = 0.327). Microscopy showed that more bacteria were present on intraocular lenses without heparin than on intraocular lenses with heparin. The results show that preincubation with a proteinaceous fluid influences subsequent bacterial adhesion to the polymer surface. The results suggest that IOLs with heparin coating may be less prone to bacterial adhesion under perfusion conditions after surface conditioning in human CSF with 0.50% plasma and a preincubation period of 12 h. Heparin coating might be a valuable tool to decrease implant-associated bacterial endophthalmitis.

Doxorubicin reversibly decreases the antithrombogenicity of heparin immobilized on central venous catheters

This is an in vitro study of the effects of doxorubicin on heparin immobilized on polyvinyl chloride (PVC) tubing. Doxorubicin contains an amino group that binds up to 16 heparin molecules, forming insoluble complexes if they are added to the same infusion. Three systems were tested: doxorubicin in perfusing blood, cerebrospinal fluid, and 0.9% sodium chloride (NaCl). The antithrombogenicity of immobilized heparin is impaired on exposure to doxorubicin. However, the reaction is reversible provided the PVC tubing system is thoroughly washed. Heparinized tubing perfused for 12 hours in blood with doxorubicin (0.027 mg/mL) decreased the activity of the immobilized heparin to 6.0% compared with 43% of that exposed to blood only. Exposure to doxorubicin (0.27 mg/mL) for 15 minutes in NaCl decreased the activity to 3% compared with that of NaCl only. Continuous washing for 10 minutes (8 mL/min) resulted in regained activity. This indicated a reversible reaction between immobilized heparin and doxorubicin. Cyclophosphamide, netilmicin, and gentamicin did not affect the antithrombogenicity of heparin in any solution.

Quantitation of bacterial adhesion to polymer surfaces by bioluminescence

Quantitation of microbes adhering to a surface is commonly used in studies of microbial adhesion to different surfaces. We have quantified different staphylococcal strains adhering to polymer surfaces by measuring bacterial ATP (adenosine triphosphate) by bioluminescence. The method is sensitive, having a detection limit of 10(4) bacterial cells. Viable counting of bacterial cells may yield falsely low results due to the presence of "dormant" and adherent bacteria. By using bioluminescence, this can be avoided. Cells of different bacterial species and cells of strains of the same species were shown to differ significantly in their basal ATP content (8.7 x 10(-13) - 5.2 x 10(-22) MATP). The size of adherent and planktonic bacteria decreased with time (0.7 micron-->0.3 micron, 20 days). During incubation in nutrient-poor buffer ("starvation"), the ATP content of adherent bacteria decreased after 24-96 h whereas that of planktonic bacteria was stable over 20 days. The presence of human serum or plasma did not interfere significantly with the test results. Since the ATP concentration of bacterial strains of different species varies and is also influenced by the growth conditions of bacteria (solid or liquid culture medium), a species-specific standard curve has to be established for bacteria grown under the same culture conditions. We conclude that the method is a sensitive tool to quantify adherent bacteria during experiments lasting for less than 6 h and constitutes a valuable method to be used in conjunction with different microscopical techniques.

Protein depositions on one hydrocephalus shunt and on fifteen temporary ventricular catheters

Biomaterials are commonly used in modern medicine. Proteins are adsorbed to the surface of the biomaterial immediately after insertion. This report demonstrates the presence of adsorbed proteins in one infected cerebrospinal shunt from a child with hydrocephalus and on fifteen temporary ventricular catheters from adult patients with spontaneous or traumatic brain injuries. Depositions of vitronectin, fibrinogen and thrombospondin-fibronectin to some extent--on the shunt surface was imaged by field-emission scanning electron microscopy. Vitronectin, fibronectin, fibrinogen, and thrombospondin on the ventricular catheters were shown with radio-actively labelled antibodies. Furthermore, protein adsorption from human cerebrospinal fluid to heparinized and unheparinized polymers was studied under flowing conditions in vitro. On heparinized polymer, significantly reduced levels of vitronectin, fibronectin, and thrombospondin were exposed, as measured after 4 hours in vitro perfusion. After 24 hours perfusion, the differences in protein exposition between heparinized and unheparinized polymers were substantially reduced.

Vitronectin may mediate staphylococcal adhesion to polymer surfaces in perfusing human cerebrospinal fluid

Prosthetic devices are frequently used for temporary or permanent drainage of cerebrospinal fluid (CSF), i.e., ventricular catheters with or without external monitoring devices and shunts. Infections constitute a serious complication in the use of biomaterials in contact with CSF; coagulase-negative staphylococci (CNS) are the most common aetiological agents. In the present study, polyvinylchloride (PVC) and PVC with endpoint-attached heparin were exposed to human CSF under perfusion to mimic conditions in vivo. Adhesion of strains of CNS isolated from patients with or without biomaterial-associated infection was determined: (i) after pre-incubation with fibronectin (Fn) or vitronectin (Vn) to block bacterial surface binding structures; and (ii) after preincubation of biomaterials with antibodies to Fn or Vn to block exposure of bacteria-binding domains on these host proteins. Pre-incubation of bacterial cells with Vn significantly reduced subsequent adhesion to polystyrene precoated with Vn 0.5 microg/well. When PVC pre-exposed to CSF was incubated with antibodies to Vn, subsequent bacterial adhesion of a Vn-binding strain, S. epidermidis 5703, was significantly reduced. The study shows that Vn may mediate adhesion of CNS in the presence of CSF. However, strains retrieved from biomaterials did not express binding of Vn or Fn to a higher extent than non-biomaterial-associated strains. Expression of heparin binding under static conditions did not correlate with staphylococcal adhesion to heparinised polymers under perfusion with CSF. The extent of adhesion of staphylococci to heparinised PVC was either reduced or the same as to unheparinised PVC.

Vitronectin-binding staphylococci enhance surface-associated complement activation

Coagulase-negative staphylococci are well recognized in medical device-associated infections. Complement activation is known to occur at the biomaterial surface, resulting in unspecific inflammation around the biomaterial. The human serum protein vitronectin (Vn), a potent inhibitor of complement activation by formation of an inactive terminal complement complex, adsorbs to biomaterial surfaces in contact with blood. In this report, we discuss the possibility that surface-immobilized Vn inhibits complement activation and the effect of Vn-binding staphylococci on complement activation on surfaces precoated with Vn. The extent of complement activation was measured with a rabbit anti-human C3c antibody and a mouse anti-human C9 antibody, raised against the neoepitope of C9. Our data show that Vn immobilized on a biomaterial surface retains its ability to inhibit complement activation. The additive complement activation-inhibitory effect of Vn on a heparinized surface is very small. In the presence of Vn-binding strain, Staphylococcus hemolyticus SM131, complement activation on a surface precoated with Vn occurred as it did in the absence of Vn precoating. For S. epidermidis 3380, which does not express binding of Vn, complement activation on a Vn-precoated surface was significantly decreased. The results could be repeated on heparinized surfaces. These data suggest that Vn adsorbed to a biomaterial surface may serve to protect against surface-associated complement activation. Furthermore, Vn-binding staphylococcal cells may enhance surface-associated complement activation by blocking the inhibitory effect of preadsorbed Vn.