Hypoxia inducible factor-1-alpha (HIF-1alpha) is related to both angiogenesis and inflammation in rheumatoid arthritis

OBJECTIVES

Despite the important role of the transcription factor HIF-1alpha in angiogenesis and inflammation, only a few studies on HIF-1alpha expression have been performed in RA patients. The aim of the present study was to identify the layer in synovial tissue of RA patients where HIF1a is expressed and to find out whether HIF-1alpha expression is related to both angiogenesis and inflammation in synovium from RA patients.

METHODS

A reproducible staining method for HIF-1alpha was developed. HIF-1alpha -positive cells were quantified in synovial tissue from patients with RA. As control we used synovial tissue from patients with osteoarthritis (OA). The number of HIF-1alpha-positive cells was compared with the number of blood vessels present and was correlated with the amount of inflammation. The amount of inflammation was determined by counting inflammatory cells, by estimating the proliferation marker Ki67 in inflamed tissue, and by using a recently published synovitis score which gives an accurate estimate of the amount of inflammation present.

RESULTS

HIF-1alpha was expressed weakly in the lining layer and strongly in the sublining layer in RA synovial tissue. In contrast, HIF-1alpha was only weakly expressed in OA synovial tissue. The number of HIF-1alpha -positive cells correlated strongly with the number of blood vessels in RA synovial tissue and with inflammatory endothelial cell infiltration (blood vessels), cell proliferation (Ki67) and the synovitis score.

CONCLUSIONS

HIF-1alpha expression is strongest in the sub-lining layer of RA synovium and is related to both angiogenesis and inflammation in synovium from RA patients. These results thus suggest that HIF-1alpha could serve as an important new therapeutic target in RA, targeting both angiogenesis and inflammation.

Likelihood-based hypothesis tests for brain activation detection from MRI data disturbed by colored noise: a simulation study

Functional magnetic resonance imaging (fMRI) data that are corrupted by temporally colored noise are generally preprocessed (i.e., prewhitened or precolored) prior to functional activation detection. In this paper, we propose likelihood-based hypothesis tests that account for colored noise directly within the framework of functional activation detection. Three likelihood-based tests are proposed: the generalized likelihood ratio (GLR) test, the Wald test, and the Rao test. The fMRI time series is modeled as a linear regression model, where one regressor describes the task-related hemodynamic response, one regressor accounts for a constant baseline and one regressor describes potential drift. The temporal correlation structure of the noise is modeled as an autoregressive (AR) model. The order of the AR model is determined from practical null data sets using Akaike's information criterion (with penalty factor 3) as order selection criterion. The tests proposed are based on exact expressions for the likelihood function of the data. Using Monte Carlo simulation experiments, the performance of the proposed tests is evaluated in terms of detection rate and false alarm rate properties and compared to the current general linear model (GLM) test, which estimates the coloring of the noise in a separate step. Results show that theoretical asymptotic distributions of the GLM, GLR, and Wald test statistics cannot be reliably used for computing thresholds for activation detection from finite length time series. Furthermore, it is shown that, for a fixed false alarm rate, the detection rate of the proposed GLR test statistic is slightly, but (statistically) significantly improved compared to that of the common GLM-based tests. Finally, simulations results reveal that all tests considered show seriously inferior performance if the order of the AR model is not chosen sufficiently high to give an adequate description of the correlation structure of the noise, whereas the effects of (slightly) overmodeling are observed to be less harmful.

Exploiting the potential of vector control for disease prevention

Although vector control has proven highly effective in preventing disease transmission, it is not being used to its full potential, thereby depriving disadvantaged populations of the benefits of well tried and tested methods. Following the discovery of synthetic residual insecticides in the 1940s, large-scale programmes succeeded in bringing many of the important vector-borne diseases under control. By the late 1960s, most vector-borne diseases--with the exception of malaria in Africa--were no longer considered to be of primary public health importance. The result was that control programmes lapsed, resources dwindled, and specialists in vector control disappeared from public health units. Within two decades, many important vector-borne diseases had re-emerged or spread to new areas. The time has come to restore vector control to its key role in the prevention of disease transmission, albeit with an increased emphasis on multiple measures, whether pesticide-based or involving environmental modification, and with a strengthened managerial and operational capacity. Integrated vector management provides a sound conceptual framework for deployment of cost-effective and sustainable methods of vector control. This approach allows for full consideration of the complex determinants of disease transmission, including local disease ecology, the role of human activity in increasing risks of disease transmission, and the socioeconomic conditions of affected communities.

Hypoxia-inducible factor-1alpha is associated with angiogenesis, and expression of bFGF, PDGF-BB, and EGFR in invasive breast cancer

AIMS

Hypoxia-inducible factor-1 (HIF-1) is the key transcription factor regulating the cellular response to hypoxia, including angiogenesis. Growth factors play an important role in tumour growth and angiogenesis and some have been shown to be induced by HIF-1 in vitro. This study investigated if angiogenesis or growth factors or their receptors are associated with HIF-1alpha in invasive breast cancer.

METHODS AND RESULTS

High levels of HIF-1alpha, detected by immunohistochemistry in 45 breast cancers, were positively associated with increased microvessel density (as a measure of angiogenesis) (P = 0.023). Furthermore, high levels of HIF-1alpha were associated with epithelial expression (> or = 10%) of epidermal growth factor receptor (EGFR) (P = 0.011), platelet-derived growth factor (PDGF)-BB (P < 0.001), and basic fibroblast growth factor (bFGF) (P = 0.045). A positive, yet insignificant, trend for HIF-1alpha to be associated with epithelial expression of transforming growth factor (TGF)-alpha (P = 0.081) and vascular endothelial growth factor (VEGF) (P = 0.109) was noticed as well as an inverse association with stromal expression of TGF-beta-R1 (P = 0.070).

CONCLUSIONS

In invasive breast cancer, HIF-1alpha is associated with angiogenesis, and expression of growth factors bFGF and PDGF-BB, and the receptor EGFR. Thus, agents targeting HIF-1 may combine different pathways of inhibiting breast cancer growth, including angiogenesis and growth factors.

Lack of lymphangiogenesis during breast carcinogenesis

BACKGROUND

Recent evidence suggests that functional intratumorous lymph vessels may be absent from some human cancers. This could result from either the failure of tumours to induce lymphangiogenesis, or the collapse of lymph vessels, caused by high interstitial tumour pressure.

METHODS

To differentiate between these two hypotheses, paraffin wax embedded clinical specimens from normal breast (n = 13), usual ductal hyperplasia (n = 11), ductal carcinoma in situ (n = 21), and invasive breast cancer (n = 40) were compared for lymphatic and blood vessel density by immunohistochemistry with antibodies to the lymphatic endothelial hyaluronan receptor (LYVE-1) and CD31, respectively.

RESULTS

Lymph vessel density was lower than blood vessel density in normal breast tissue. Within breast lobuli, lymph vessels were absent. In premalignant lesions blood microvessel density increased, whereas no increase in lymph vessels could be seen intralesionally. In invasive cancers, lymph vessels were absent in all but a few cases, where probably some pre-existing lymph vessels remained, although blood microvessel density was once again increased.

CONCLUSION

Unlike angiogenesis, lymphangiogenesis is absent during breast carcinogenesis. This, and not rising interstitial pressure caused by an increase in the size of lesions, explains the absence of intratumorous lymph vessels in invasive breast cancer.

Modelling and optimization of inactivation of Lactobacillus plantarum by pulsed electric field treatment

AIMS

The effect of critical pulsed electric field (PEF) process parameters, such as electric field strength, pulse length and number of pulses, on inactivation of Lactobacillus plantarum was investigated.

METHODS AND RESULTS

Experiments were performed in a pH 4.5 sodium phosphate buffer having a conductivity of 0.1 S m-1, using a laboratory-scale continuous PEF apparatus with a co-linear treatment chamber. An inactivation model was developed as a function of field strength, pulse length and number of pulses. Based on this inactivation model, the conditions for a PEF treatment were optimized with respect to the minimum energy required to obtain a certain level of inactivation. It was shown that the least efficient process parameter in the range investigated was the number of pulses. The most efficient way to optimize inactivation of Lact. plantarum was to increase the field strength up to 25.7 kV cm-1, at the shortest pulse length investigated, 0.85 micros, and using a minimum number of pulses. The highest inactivation of Lact. plantarum at the lowest energy costs is obtained by using the equation: E=26.7tau0.23, in which E is the field strength and tau the pulse length. An optimum is reached by substituting tau with 5.1.

CONCLUSIONS

This study demonstrates that the correct choice of parameters, as predicted by the model described here, can considerably improve the PEF process.

SIGNIFICANCE AND IMPACT OF THE STUDY

The knowledge gained in this study improves the understanding of the limitations and opportunities of the PEF process. Consequently, the advantage of the PEF process as a new option for non-thermal decontamination can be better utilized.

Demonstration of spontaneous and stretch induced urinary bladder EMG in the living rabbit

Spontaneous bladder EMG was recorded in the living rabbit from an isovolumetric bladder without chemical or electrical stimulation. Mechanical intervention, either by lifting the bladder out of the abdomen or by rapid filling, resulted in stretch induced bladder EMG. A self made epoxy resin electrode device that embedded 32 EMG recording electrodes in a matrix like pattern, each electrode Ag/AgCl, d = 0.6 mm with an interdistance of 2.3 mm, was used for registration. The recorder used a common average reference technique and a sample frequency of 400 Hz. A signal bandwidth of 0.05 to 108 Hz was available for analysis. Spontaneous EMG consisted of single spikes and bursts (2-20 spikes), but not of continuous activity. The shape of spikes was triphasic. Single spikes appeared with and without burst activity. Small (2-5 spikes) and large bursts (6-20 spikes) were discerned; small bursts not necessarily propagated across electrodes, large bursts did and were able to organize, suggesting that they were under short neuron system control. Spontaneous EMG was probably related to both contraction and relaxation. Stretch induced EMG was characterised by continuous activity on all electrodes, spikes that followed each other immediately, slowly fading away. The spikes had an elongated third phase when compared to the shape of spontaneous activity. Highest activity and amplitudes were found after lifting the bladder out of the abdomen and placing it on the electrode device. A concept is put forward in which the continuous activity is not unequivocally related to muscle shortening, but where the current stress and strain situation of the bladder tissue can cause a muscle fibre elongation upon the appearance of electrical activity. The EMG activity found was in many aspects similar to results of a previous study using mortalized rabbits. Artifact sources like the heart, respiration, or local movement between electrode and bladder could easily be identified due to the new experimental methodology used.

A fast and simple GC MS method for lignan profiling in Anthriscus sylvestris and biosynthetically related Plant species

A new GC-MS method for monitoring lignans was developed to study the variation in plants and elucidate the biosynthetic steps. A simple and fast extraction procedure for lyophilised plant material was developed, giving a lignan-rich extract. A GC-MS method was set up using an apolar WCOT fused silica column using a high temperature programme (150 degrees C to 320 degrees C at 15 degrees C min(-1)). This new GC-MS method gave a clear lignan profile of plant material. It was possible to show the large variation in the concentrations of deoxypodophyllotoxin (DOP), yatein and anhydropodorhizol (AHP) in Anthriscus sylvestris (L.) Hoffm. plants growing on different locations using cinchonidin as an internal standard. In contrast with existing GC methods for lignan analysis no derivatisation is needed. It is also possible to use this method for the detection of different classes of lignans in biosynthetically related plant species.

Co-adhesion and removal of adhering bacteria from salivary pellicles by three different modes of brushing

This study compares removal of pairs of co-adhering and non-co-adhering oral actinomyces and streptococci by hand, electric and sonic brushing from salivary pellicles. In addition, re-deposition of a co-adhering and non-co-adhering streptococcal strain to brushed pellicles was studied. First, actinomyces were allowed to adhere to a pellicle in a flow chamber, after which streptococci suspended in saliva were perfused through the chamber at 33 C. Pellicles with adhering bacterial pairs were brushed and the number of bacteria remaining determined. Whereas sonic brushing removed nearly all adhering bacteria, greater numbers of larger aggregates of the co-adhering pair, involving Streptococcus oralis J22, were left behind after hand and electric brushing than of the non-co-adhering pair with Streptococcus sanguis PK1889. Re-deposition of streptococci to electrically and sonically brushed pellicles, however, was two-fold higher for the co-adhering pair than for the non-co-adhering pair. This demonstrates a role for co-adhesion in de novo plaque formation. Removal by the three different modes of brushing was not affected by the presence of fluoride, indicating that fluoride is not able to disrupt calcium bridges between co-adhering pairs. In contrast, in the presence of lactose only small aggregates of co-adhering pair were left behind.

Adhesive interactions between voice prosthetic yeast and bacteria on silicone rubber in the absence and presence of saliva

Biofilms on silicone rubber voice prostheses are the major cause for frequent failure and replacement of these devices. The presence of both bacterial strains and yeast has been suggested to be crucial for the development of voice prosthetic biofilms. Adhesive interactions between Candida albicans, Candida krusei, and Candida tropicalis with 14 bacterial strains, all isolated from explanted voice prostheses were investigated in a parallel plate flow chamber. Bacteria were first allowed to adhere to silicone rubber, after which the flow chamber was perfused with yeast, suspended either in saliva or buffer. Generally, when yeast were adhering from buffer and saliva, the presence of adhering bacteria suppressed adhesion of yeast. In saliva, Rothia dentocariosa and Staphylococcus aureus enhanced adhesion of yeast, especially of C. albicans. This study shows that bacterial adhesion mostly reduces subsequent adhesion of yeast, while only a few bacterial strains stimulate adhesion of yeast, provided salivary adhesion mediators are present. Interestingly, different clinical studies have identified R. dentocariosa and S. aureus in biofilms on explanted prostheses of patients needing most frequent replacement, while C. albicans is one of the yeast generally held responsible for silicone rubber deterioration.

Charge transfer during staphylococcal adhesion to TiNOX coatings with different specific resistivity

Adhesion of the bacterial strain Staphylococcus epidermidis 3399 to titanium-oxy-nitride (TiNOX) substrata with different specific resistivities was studied in a parallel plate flow chamber, while simultaneously measuring the electric potential of the substrata. During adhesion, bacteria either donated or accepted electrons to the substrata depending on the specific resistivity of the substratum and bacteria that had donated electrons to the substratum adhered more strongly than bacteria that had accepted electrons from the substratum. These results demonstrate that electron transfer plays a role in bacterial adhesion to conducting surfaces, which has hitherto been neglected.

Improvement of patient education and information: development of a patient's information dossier

The demand for patient information in modern medical care is increasing and sound information for patients is becoming a necessity. For haemophilia patients, information about their disease and its complications is already widely available. In order to increase the organization of this information, a 'Patient Information Dossier' (PID) and communication check lists were developed at the Dutch National Hemophilia Center, the Van Creveldkliniek, in cooperation with the Department of Patient Education of the University Medical Center Utrecht. The PID has an unique double function: (1) it contains patient tailored information about the practical facts of hospital care; and (2) it provides a communication checklist used by various members of the comprehensive care team, in order to supply patients with more uniform information. In order to gain a better insight of the gaps in information supply, according to patients and healthcare workers, the Department of Patient Education formulated a questionnaire. The PID itself was written by a study group consisting of members of the comprehensive care team. The entire process was developed, edited and coordinated by an advisor of the Department of Patient Education. The above-mentioned study group developed a specific PID on haemophilia care. Its 10 chapters provide information and guidelines, and advise patients where to find more information about this subject. Each chapter includes a checklist for patients, enabling them to prepare subjects for discussion during clinical visits. The team also developed a communication checklist to be used by various team members during a patient's visit to the clinic, as well as specific checklists covering the possible problem subjects of the PID. The PID is the lifelong property of the patient, and can be used during each visit to the clinic. The PID was implemented in February 2000, and within 4 months, was distributed among 200 patients visiting the Van Creveldkliniek. Evaluation by use of a questionnaire showed that most patients found the information in the PID sufficient and in accordance with that which they had received previously.

Paralogous gene analysis reveals a highly enantioselective 1,2-O-isopropylideneglycerol caprylate esterase of Bacillus subtilis

Carboxylesterase NP of Bacillus subtilis Thai I-8, characterized in 1992 as a very enantioselective (S)-naproxen esterase, was found to show no enantiopreference towards (S)-1,2-O-isopropylideneglycerol (IPG) esters. The ybfK gene was identified by the B. subtilis genome project as an unknown gene with homology to carboxylesterase NP. The purpose of the present study was to characterize the ybfK gene product in order to determine whether this paralogue of carboxylesterase NP had an altered or enhanced stereospecificity. The ybfK gene was cloned and expressed in B. subtilis using a combination of two strong promoters in a multicopy vector. The enzyme was purified from the cytoplasm of B. subtilis by means of anion exchange and hydrophobic interaction chromatography. The purified YbfK is an enzyme of 296 amino acids and shows an apparent molecular mass of 32 kDa (SDS/PAGE). Comparison of the activities of YbfK and carboxylesterase NP towards caprylate esters of IPG revealed that YbfK produces (S)-IPG with 99.9% enantioselectivity. Therefore, we conclude that we have isolated a paralogue of carboxylesterase NP that can be used for the enantioselective production of (S)-IPG.

Levels of hypoxia-inducible factor-1 alpha during breast carcinogenesis

BACKGROUND

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that regulates gene expression in critical pathways involved in tumor growth and metastases. In this report, we investigated whether the level of HIF-1 alpha is increased during carcinogenesis in breast tissue and is associated with other tumor biomarkers.

METHODS

Paraffin-embedded clinical specimens from five pathologic stages of breast tumorigenesis and from normal breast tissue were used. HIF-1 alpha protein and the biomarkers vascular endothelial growth factor (VEGF), HER-2/neu, p53, Ki-67, and estrogen receptor (ER) were identified immunohistochemically, and microvessel density (a measure of angiogenesis) was determined. Associations among levels of HIF-1 alpha and these biomarkers were tested statistically. All statistical tests are two-sided.

RESULTS

The frequency of HIF-1 alpha-positive cells in a specimen increased with the specimen's pathologic stage (P<.001, chi(2) test for trend) as follows: normal breast tissue (0 specimens with > or = 1% HIF-1 alpha-positive cells in 10 specimens tested), ductal hyperplastic lesions (0 in 10), well-differentiated ductal carcinomas in situ (DCIS) (11 in 20), well-differentiated invasive breast cancers (12 in 20), poorly differentiated DCIS (17 in 20), and poorly differentiated invasive carcinomas (20 in 20). Increased levels of HIF-1 alpha were statistically significantly associated with high proliferation and increased expression of VEGF and ER proteins. In DCIS lesions, increased levels of HIF-1 alpha were statistically significantly associated with increased microvessel density. HIF-1alpha showed a borderline association with HER-2/neu but no association with p53.

CONCLUSIONS

The level of HIF-1 alpha increases as the pathologic stage increases and is higher in poorly differentiated lesions than in the corresponding type of well-differentiated lesions. Increased levels of HIF-1 alpha are associated with increased proliferation and increased expression of ER and VEGF. Thus, increased levels of HIF-1 alpha are potentially associated with more aggressive tumors.

Retention of bacteria on a substratum surface with micro-patterned hydrophobicity

Bacteria adhere to almost any surface, despite continuing arguments about the importance of physico-chemical properties of substratum surfaces, such as hydrophobicity and charge in biofilm formation. Nevertheless, in vivo biofilm formation on teeth and also on voice prostheses in laryngectomized patients is less on hydrophobic than on hydrophilic surfaces. With the aid of micro-patterned surfaces consisting of 10-microm wide hydrophobic lines separated by 20-microm wide hydrophilic spacings, we demonstrate here, for the first time in one and the same experiment, that bacteria do not have a strong preference for adhesion to hydrophobic or hydrophilic surfaces. Upon challenging the adhering bacteria, after deposition in a parallel plate flow chamber, with a high detachment force, however, bacteria were easily wiped-off hydrophobic lines, most notably when these lines were oriented parallel to the direction of flow. Adhering bacteria detached slightly less from the hydrophilic spacings in between, but preferentially accumulated adhering on the hydrophilic regions close to the interface between the hydrophilic spacings and hydrophobic lines. It is concluded that substratum hydrophobicity is a major determinant of bacterial retention while it hardly influences bacterial adhesion.

Elastase mediated fibrinolysis in acute promyelocytic leukemia

The bleeding syndrome of acute promyelocytic leukemia (APL) is complex and consists of disseminated intravascular coagulation (DIC) and hyperfibrinolysis. Elastase, derived from malignant promyelocytes, is believed to mediate the fibrinogeno- and fibrinolysis by aspecific proteolysis. In this study we measured the role of elastase in fifteen patients with APL by using an assay for elastase degraded fibrin(ogen) and the results were compared with those obtained in patients with sepsis induced DIC. High levels of elastase were observed in sepsis and APL. The levels of fibrinogen and fibrin degradation products were significantly higher in APL patients compared to patients with sepsis induced DIC. Nevertheless, the level of elastase degraded fibrin(ogen) was higher in the sepsis group (635.3 ng/ml, compared to 144.3 ng/ml in APL; p <0.0001). So, the enormous increase in fibrin and fibrinogen degradation products in APL cannot be explained by elastase activity. This study suggests a minor role for elastase mediated proteolysis in the hemorrhagic diathesis in APL patients.

Direct probing by atomic force microscopy of the cell surface softness of a fibrillated and nonfibrillated oral streptococcal strain

In this paper, direct measurement by atomic force microscopy (AFM) of the cell surface softness of a fibrillated oral streptococcal strain Streptococcus salivarius HB and of a nonfibrillated strain S. salivarius HBC12 is presented, and the data interpretation is validated by comparison with results from independent techniques. Upon approach of the fibrillated strain in water, the AFM tip experienced a long-range repulsion force, starting at approximately 100 nm, attributed to the compression of the soft layer of fibrils present at the cell surface. In 0.1 M KCl, repulsion was only experienced when the tip was closer than approximately 10 nm, reflecting a stiffer cell surface due to collapse of the fibrillar mass. Force-distance curves indicated that the nonfibrillated strain, probed both in water and in 0.1 M KCl, was much stiffer than the fibrillated strain in water, and a repulsion force was experienced by the tip at close approach only (20 nm in water and 10 nm in 0.1 M KCl). Differences in cell surface softness were further supported by differences in cell surface morphology, the fibrillated strain imaged in water being the only specimen that showed characteristic topographical features attributable to fibrils. These results are in excellent agreement with previous indirect measurements of cell surface softness by dynamic light scattering and particulate microelectrophoresis and demonstrate the potential of AFM to directly probe the softness of microbial cell surfaces.

Factor V antigen levels and venous thrombosis: risk profile, interaction with factor V leiden, and relation with factor VIII antigen levels

Clotting factor V has a dual function in coagulation: after activation, procoagulant factor V stimulates the formation of thrombin, whereas anticoagulant factor V acts as a cofactor for activated protein C (APC) in the degradation of factor VIII/VIIIa, thereby reducing thrombin formation. In the present study, we evaluated whether plasma factor V levels, either decreased or increased, are associated with venous thrombosis. High procoagulant factor V levels may enhance prothrombinase activity and increase the thrombosis risk. Low anticoagulant factor V levels could reduce APC-cofactor activity in the factor VIII inactivation (APC-resistant phenotype), which might also promote thrombosis. Low factor V levels in combination with factor V Leiden could lead to a more severe APC-resistant phenotype (pseudohomozygous APC resistance). To address these issues, we have measured factor V antigen (factor V:Ag) levels in 474 patients with thrombosis and 474 control subjects that were part of the Leiden Thrombophilia Study (LETS). Factor V:Ag levels increased by 7.6 U/dL for every successive 10 years of age. Mean factor V:Ag levels were 134 (range 41 to 305) U/dL in patients and 132 (range 47 to 302) U/dL in controls. Neither high nor low factor V:Ag levels were associated with venous thrombosis. We found that factor V:Ag and factor VIII antigen levels in plasma were correlated, but factor V did not modify the thrombotic risk of high factor VIII levels. The normalized APC ratio was not influenced by the factor V:Ag level in subjects with or without factor V Leiden. We conclude that neither low nor high factor V:Ag levels are associated with venous thrombosis and that factor V:Ag levels do not mediate the thrombotic risk associated with high factor VIII levels.

Dot assay for determining adhesive interactions between yeasts and bacteria under controlled hydrodynamic conditions

Candida belongs to the normal human microflora and are found adhering to a number of human body tissues as well as to a variety of biomaterials implants. Often, yeasts adhere in association with bacteria, but to date there is no definitive assay to investigate adhesive interactions between yeasts and bacteria adhering on surfaces. Although we recently described the use of a parallel plate flow chamber to this purpose [Millsap, K.W., Bos, R., Van der Mei, H. C., Busscher, H.J., 1998. Adhesive interactions between medically important yeasts and bacteria. FEMS Microbiol. Rev. 21, 321-336], the method was slow and evaluation of a large number of strains showed major biological variation between experiments. Here, we describe a new assay for the simultaneous determination of the adhesive interactions between yeasts and different bacterial strains on a surface under controlled hydrodynamic conditions. On an acrylic surface, the presence of adhering bacteria suppressed adhesion of Candida albicans ATCC 10261 to various degrees, depending on the bacterial strain involved. Suppression of C. albicans ATCC 10261 adhesion was strongest by Actinomyces naeslundii T14V-J1, while adhering Streptococcus gordonii NCTC 7869 caused the weakest suppression of yeast adhesion. When adhering yeasts and bacteria were challenged with the high detachment force of a passing liquid-air interface, the majority of the yeasts detached, while C. albicans adhering on the control, bare polymethylmethacrylate surface formed aggregates. Summarizing, this study presents a new method to determine suggested adhesive interactions between yeasts and adhering bacteria under controlled hydrodynamic conditions. However, the results seem to indicate that these adhesive interactions may well not exist, but that instead different bacterial strains have varying abilities to discourage yeast adhesion.

Reduced activity of TAFI (thrombin-activatable fibrinolysis inhibitor) in acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APL) is a disease that is distinguished from other leukaemias by the high potential for early haemorrhagic death. Several processes are involved, such as disseminated intravascular coagulation and hyperfibrinolysis. Recently, TAFI (thrombin-activatable fibrinolysis inhibitor) was identified as a link between coagulation and fibrinolysis. TAFI can be activated by thrombin, and in its activated form potently attenuates fibrinolysis by removing C-terminal lysine and arginine residues that are important for the binding and activation of plasminogen. Activation of TAFI by the coagulation system results in a down-regulation of fibrinolytic activity and, thereby, prevents a rapid dissolution of the fibrin clot. To establish whether TAFI was involved in the severity of the bleeding complications in APL, the TAFI antigen and activity levels were determined in a group of 15 patients. The TAFI antigen concentration was normal, but the activity of TAFI was severely reduced in APL by approximately 60%. The reduction of TAFI activity was most probably caused by the action of plasmin on TAFI because in vitro experiments revealed that plasmin slightly reduced antigen levels but severely reduced TAFI activity. The acquired functional TAFI deficiency in APL may contribute to the severity of the haemorrhagic diathesis because of the impaired capacity of the coagulation system to protect the fibrin clot from fibrinolysis.

Controlled electrophoretic deposition of bacteria to surfaces for the design of biofilms

In this report, the formation of ordered clusters of both spherical and rod-shaped bacteria on an electrode during electrophoretic deposition is described. Inside clusters, adhering bacteria are regularly spaced with an interbacterial distance that can be controlled by adjusting the ionic strength of the suspending solution and the DC density used. Formed clusters can be immobilized on the surface by applying a sufficiently high current density. This method enables the design of bacterial biofilms for biotechnological and biomedical applications. When AC fields were used, rod-shaped bacteria adhering on the electrode were seen to align parallel to the applied field.