Comparison of machine learning algorithms for clinical event prediction (risk of coronary heart disease)

AIM

The aim of this study is to compare the utility of several supervised machine learning (ML) algorithms for predicting clinical events in terms of their internal validity and accuracy. The results, which were obtained using two statistical software platforms, were also compared.

MATERIALS AND METHODS

The data used in this research come from the open database of the Framingham Heart Study, which originated in 1948 in Framingham, Massachusetts as a prospective study of risk factors for cardiovascular disease. Through data mining processes, three data models were elaborated and a comparative methodological study between the different ML algorithms - decision tree, random forest, support vector machines, neural networks, and logistic regression - was carried out. The global selection criterium for choosing the right set of hyperparameters and the type of data manipulation was the area under a curve (AUC). The software tools used to analyze the data were R-Studio® and RapidMiner®.

RESULTS

The Framingham study open database contains 4240 observations. The algorithm that yielded the greatest AUC when analyzing the data in R-Studio was neural network applied to a model that excluded all observations in which there was at least one missing value (AUC = 0.71); when analyzing the data in RapidMiner and applying the same model, the best algorithm was support vector machines (AUC = 0.75).

CONCLUSIONS

ML algorithms can reinforce the diagnostic and prognostic capacity of traditional regression techniques. Differences between the applicability of those algorithms and the results obtained with them were a function of the software platforms used in the data analysis.

Determination of biofilm production by Candida tropicalis isolated from hospitalized patients and its relation to cellular surface hydrophobicity, plastic adherence and filamentation ability

Candida tropicalis is an emerging virulent species. The aim of this study is to determine the biofilm-forming ability of 29 strains of C. tropicalis isolated from inpatients, and to examine its relation with other virulence factors such as cellular surface hydrophobicity (CSH), immediate (15 min, IA) and late (24 h, LA) plastic adherence and filamentation ability. The study was performed in parallel using two incubation temperatures - 37 and 22 °C - to determine the effect of growth temperature variations on these pathogenic attributes of C. tropicalis. Biofilm formation (BF) was measured by optical density (OD) and by XTT reduction (XTT); Slime index (SI), which includes growth as a correction factor in BF, was calculated in both methods. All strains were hydrophobic and adherent - at 15 min and 24 h - at both temperatures, with higher values for 22 °C; the adhered basal yeast layer appears to be necessary to achieve subsequent development of biofilm. Filamentation ability varied from 76.2% of strains at 37 °C to 26.6% at 22 °C. All C. tropicalis strains were biofilm producers, with similar results obtained using OD determination and XTT measurement to evaluation methods; SI is useful when good growth is not presented. BF at 37 °C was similar at 24 h and 96 h incubation; conversely, at 22 °C, the highest number of biofilm-producing strains was detected at 96 h. CSH is an important pathogenic factor which is involved in adherence, is influenced by the filamentation of yeast, and plays a critical role in BF.

Encephalitozoon microsporidia modulates p53-mediated apoptosis in infected cells

Microsporidia are intracellular obligate parasites which have recently been found to be related to fungi. They have a unique extrusion apparatus that is able to inject the sporoplasm directly into the target cell without using receptors. Encephalitozoon microsporidia are a source of morbidity and mortality in humans. It has been suggested that microsporidia may modulate the host cell cycle and apoptosis. We report here that caspase-3 cleavage is inhibited at different times of Vero cell infection by Encephalitozoon microsporidia and that the phosphorylation and translocation of p53 to the nucleus, previous steps for the activation of this protein, do not occur after infection of Vero cells. Consequently, the transcriptional function of p53 is impaired during the infection cycle as demonstrated by luciferase reporter assays. Thus, to our knowledge, for the first time it is shown that an intracellular parasite may be able to multiply in the host cell without activating the p53 apoptotic pathway of that cell. However, changes in the expression of Bcl-2 or Bax levels were not observed.

Modification of adherence to plastic and to human buccal cells of Candida albicans and Candida dubliniensis by a subinhibitory concentration of itraconazole

Exposure to subinhibitory concentrations of antifungal agents can influence the adherence of Candida spp. to the host cell. In this study the adherence of Candida albicans ATCC 10231 and Candida dubliniensis CECT 11455 to plastic and to human buccal epithelial cells was evaluated following pre-exposure to 0.5 x minimum inhibitory capacity (MIC) of itraconazole and compared with the corresponding cellular surface hydrophobicity. The yeasts were grown in Sabouraud broth or RPMI-1640 with itraconazole (0.5 x MIC) for 24-26 h at 37 degrees C and the drug was then removed. The adhesion capacity to plastic was studied by turbidimetry in a polystyrene microtiter plate. The adhesion of the yeast to buccal epithelial cells was determined using microscopy techniques. The cellular surface hydrophobicity levels were determined by the microbial adhesion hydrocarbons test. Pre-exposure to itraconazole decreased plastic adherence and cellular surface hydrophobicity in both species when grown in RPMI. When C. albicans was grown in Sabouraud broth, it was nonhydrophobic and did not adhere and therefore no change was detected with the antibiotic. Itraconazole increased adherence to buccal epithelial cells in both species and media studied, as compared to controls without antifungal agents. To study the effects of these antifungal agents on pathogenicity mechanisms, it will be necessary to standardize the methodology for evaluation to determine their in vivo therapeutic efficacy.

Exposure to therapeutic concentrations of ritonavir, but not saquinavir, reduces secreted aspartyl proteinase of Candida parapsilosis

The effect of ritonavir and saquinavir, HIV proteinase inhibitors, on the secreted aspartyl proteinase (Sap) activity of Candida parapsilosis was studied. In a proteinase-inducing medium (yeast carbon base-bovine serum albumin), Sap activity in all clinical isolates of C. parapsilosis (n = 20) was observed at 37 degrees C but not at 22 degrees C. The presence of ritonavir at a concentration of 8 microg/ml produced an inhibition close to 50% albumin consumption and also delayed yeast growth; however, saquinavir did not have any effect on growth or on Sap activity. In Sabouraud broth, which does not induce Sap production, no effect was shown on yeast growth by either of the two HIV proteinase inhibitors studied.

[Chronic hepatitis C and celiac sprue: an infrequent association]

Celiac sprue (CS) has been described in association with hepatitis C virus (HCV) as another immunologic manifestation of this infectious disease. We report 2 patients, a 42-year-old woman and a 59-year-old man, with chronic HCV hepatitis. Upper digestive endoscopy and duodenal biopsy were performed to investigate diverse symptoms. The results of histological analysis and serological study were compatible with CS. The association between both diseases, including immunological aspects and the implications of anti-HCV treatment, is discussed.

Moxifloxacin and biofilm production by coagulase-negative staphylococci

The in vitro activity of moxifloxacin against 41 strains of coagulase-negative staphylococci was determined. A relationship between the activity of moxifloxacin and biofilm formation was detected. Biofilm-producing strains were more resistant to moxifloxacin than biofilm-negative strains. Our global results obtained with six strains of Staphylococcus epidermidis showed that subinhibitory concentrations of moxifloxacin did not significantly modify biofilm formation. On the other hand, moxifloxacin concentrations of 2, 10, 50 and 100 x MIC produced a log decrease in viable count (included in a biofilm) of 0.20, 0.37, 1.10 and 1.69, respectively.

Effect of ritonavir and saquinavir on Candida albicans growth rate and in vitro activity of aspartyl proteinases

An in vitro study to evaluate the antifungal effect and activity of aspartyl proteinases of the HIV-proteinase inhibitors ritonavir and saquinavir was conducted. Ritonavir diminished the growth rate of Candida albicans as well as the activity of its secreted aspartyl proteinases (Saps) in a nitrogen-limited medium, yeast carbon base and bovine serum albumin (YCB-BSA). This inhibition occurred in a dose-dependent fashion; with 8 mg l(-1) of ritonavir a partial growth inhibition (44%) was produced. The growth rate of C. albicans in medium with saquinavir was similar to that seen in the control, and Sap activity was inhibited only at high concentrations. In conventional medium (RPMI-1640), which does not induce the production of yeast proteases, no inhibitory effect was detected with either HIV-protease inhibitor.

Resistance to vancomycin, LY333328, ciprofloxacin and trovafloxacin of community-acquired and nosocomial strains of Enterococcus faecalis isolated in Badajoz (Spain) with and without high-level resistance to streptomycin and gentamicin

In vitro resistance of community-acquired and nosocomial strains of Enterococcus faecalis isolated in Badajoz (Spain) were determined by a microdilution method. The isolates were identified with conventional MicroScan Pos Combo 4 I dehydrated panels. No resistance to glycopeptides was found, but LY333328 was 2-4 times more active than vancomycin. In the nosocomial strains, high-level resistance to streptomycin (HLRS) was 54.7%, and high-level resistance to gentamicin (HLRG) was 38.1%. Resistance to ciprofloxacin and trovafloxacin was 45.3 and 38.9%, respectively. In the community-acquired isolates, HLRS, HLRG, resistance to ciprofloxacin and resistance to trovafloxacin were 44.2, 17.3, 15.4 and 13.5%, respectively. Trovafloxacin was 2-4 times more active than ciprofloxacin against both groups of strains. An association between high-level resistance to aminoglycosides and resistance to fluoroquinolones was noted. The resistance to aminoglycosides did not influence the activity of vancomycin and LY333328.

Sodium-hydrogen exchange inhibition: pre-versus post-ischemic treatment

Sodium-hydrogen exchange is involved in ischemia-reperfusion injury. Despite the strong research support for the use of sodium-hydrogen exchange blockers to protect the myocardium during ischemia-reperfusion, there is still controversy regarding the most effective time for drug delivery. Studies that initiate drug treatment immediately before or at reperfusion have given conflicting results. The conflict in results may be due to differences in the experimental design. Post-ischemic cardioprotection may be less than optimal due to the vascular permeability barrier or a limited collateral circulation. Increasing the drug dose or allowing more time for the drug to cross the vessel wall may overcome this limitation. Determining the correct dose and delivery protocol, therefore, will be critical for the generation of positive results in future clinical trials and will optimize the beneficial effects of sodium-hydrogen exchange inhibition in the treatment of reperfusion injury.

ERK 1,2 and p38 pathways are involved in the proliferative stimuli mediated by urokinase in osteoblastic SaOS-2 cell line

Bone metastases from prostate origin generate an osteoblastic reaction that is expressed in vitro by increased osteoblast proliferation. The urokinase-like plasminogen activator (u-PA) present in the media conditioned by tumoral prostatic cells acting as a ligand of the cellular membrane receptor (u-PAR), has been identified as the specific factor that modulates this proliferative reaction. The present study represents an effort to unravel the intracellular pathway by which u-PA activates osteoblastic proliferation and to evaluate the role of cellular receptor u-PAR in this proliferative phenomenon. Our results show that in vitro u-PA stimulates proliferation of SaOS-2 osteoblastic cells by activating the MAP kinase route of ERK 1 and 2 and the p38 pathway. These results are in accordance with the inhibition of intermediate activation and cell proliferation by PD 098059 and SB 203580, specific inhibitors of MEK and p38, respectively. We also show that SaOS-2 cells increase their proliferative response when cells are plated onto vitronectin, the second natural ligand of u-PAR, and that culturing SaOS-2 cells in the presence of u-PA represents a stimuli for u-PAR expression. On the basis of these results we propose that osteoblastic cells respond to the prostate-derived u-PA stimuli in a very efficient manner that includes the utilization of two different signaling routes and the stimulation of the expression of the u-PA receptor.

Long-Term treatment with cisapride and antibiotics in liver cirrhosis: effect on small intestinal motility, bacterial overgrowth, and liver function

OBJECTIVES

Altered small-bowel motility, lengthening of the orocecal transit time, and small-intestinal bacterial overgrowth have been described in patients with liver cirrhosis. These changes might be related to the progressive course and poor prognosis of the disease. We investigated the effect of a long-term treatment with cisapride and an antibiotic regimen on small-intestinal motor activity, orocecal transit time, bacterial overgrowth, and some parameters of liver function.

METHODS

Thirty-four patients with liver cirrhosis of different etiology entered in the study. They were randomly allocated to receive cisapride (12), an alternating regimen of norfloxacin and neomycin (12), or placebo (10) during a period of 6 months. At entry and at 3 and 6 months, a stationary small-intestinal manometry was performed, and orocecal transit time and small-intestinal bacterial overgrowth were also investigated using the H2 breath test. Liver function was estimated with clinical and laboratory measurements (Child-Pugh score).

RESULTS

After 6 months, both cisapride and antibiotics significantly improved fasting cyclic activity, reduced the duration of orocecal transit time, and decreased small-intestinal bacterial overgrowth. Cisapride administration was followed also by an increase in the amplitude of contractions. No statistically significant variations in these parameters were observed with placebo. An improvement of liver function was observed at 3 and 6 months with both cisapride and antibiotics.

CONCLUSIONS

Long-term treatment with cisapride or antibiotics reversed altered small-intestinal motility and bacterial overgrowth in patients with liver cirrhosis. These findings suggest a possible role for prokinetics and antibiotics as a modality of treatment in selected cases of decompensated cirrhosis.

Influence of methylene blue photoinactivation treatment on coagulation factors from fresh frozen plasma, cryoprecipitates and cryosupernatants

OBJECTIVE

To study the influence of virus photoinactivation with methylene blue (MB) on the coagulation factors of fresh frozen plasma (FFP) and the corresponding cryoprecipitates and cryosupernatants derived from it.

MATERIALS AND METHODS

The photoinactivation procedure of the German Red Cross (Springe) was applied using Biomat (Grifols, Spain). Twenty isogroup pools of three plasma units were made from 60 U of FFP. The pools were split into three bags. One of them was photoinactivated, and pre- and postinactivation samples (MB-plasma) were obtained. The second bag was treated in the same way, followed by the preparation of MB-cryoprecipitate and MB-cryosupernatant. The third bag was not photoinactivated, and was processed in the same way to obtain control cryoprecipitate and cryosupernatant. The prothrombin time and activated partial thromboplastin time were analysed, as well as fibrinogen, factors (F) II, V, VII, VIII, IX, XI and XIII, antithrombin III, von Willebrand (vW) F:RCo, vWF:Ag and the multimeric structure of vWF.

RESULTS

In plasma, the proteins most sensitive to photoinactivation were fibrinogen, FV, FVIII, FIX and FXI (24, 32, 28, 23 and 27% loss, respectively). In the MB-cryoprecipitate, the losses were higher for FVIII (23%), moderate for fibrinogen, FXIII and vWF:RCo (18, 14 and 13%, respectively) and minimal (only 3%) for vWF:Ag. In MB-cryosupernatants, the losses were higher for FV (26%) and moderate for fibrinogen (16%), FIX (18%) and FXI (19%), as well as for FII and FXIII (15%). The multimeric structure of vWF was not modified in MB-plasma or in MB-cryoprecipitates. The supernatants (both MB treated as well as controls) showed an absence of multimers of very high and high molecular weight.

CONCLUSIONS

The quantitative and qualitative conservation of coagulation factors achieved in MB-plasma-derived products suggest that they are useful for the global replacement of coagulation factors and for deficiencies in FV and FXI. In countries lacking the economic resources to obtain virally inactivated concentrates, MB-cryoprecipitates could be useful in von Willebrand's disease and fibrinogen and FXIII deficiencies. MB-cryosupernatants could be employed in thrombotic thrombocytopenic purpura, in the correction of total or partial deficiencies of prothrombin complex factors and in specific deficiencies of FV and FXI.

Increase in nuclear calcium in smooth muscle cells exposed to oxidized low density lipoprotein

Vascular smooth muscle cells respond with an increase in intracellular Ca2+ within seconds after exposure to oxidized low density lipoprotein (oxLDL). This has been suggested to represent a signaling response that may have implications for gene expression. If so, oxLDL may induce increases in nuclear Ca2+ in smooth muscle cells in response to oxLDL. Aortic smooth muscle cells were exposed to 100 microg/ml oxLDL. Large, rapid increases in [Ca2+]i were observed using fluo-3 as an indicator dye to detect intracellular Ca2+ on the stage of a confocal microscope. This was also confirmed using ratiometric imaging of indo signals. These elevations appeared to be localized to the nuclear region of the cell. DNA staining of the cells confirmed its localization to the nuclear/perinuclear region of the cell. Our data demonstrate that oxLDL induces a nuclear localized elevation in Ca2+i that may have important implications for nuclear function.

Inhibition of Na(+)/H(+) exchange at the beginning of reperfusion is cardioprotective in isolated, beating adult cardiomyocytes

Stimulation of Na(+)/H(+)exchange during ischemia-reperfusion results in cardiac damage. However, it is unclear whether the Na(+)/H(+)exchanger is active during the ischemic period or during reperfusion. Adult beating cardiomyocytes were exposed to an ischemia mimetic solution for 90 min and then reperfused with a normal solution for 30 min. 5-(N,N-dimethyl)-amiloride (DMA), a blocker of the Na(+)/H(+)exchanger, was administered during ischemia and the first 3 min of reperfusion or only during the first 3 min of reperfusion. Administration of DMA only upon reperfusion resulted in increased cell survival (81+/-1%, P<0.05) compared to using the drug during ischemia and reperfusion (63+/-3%) and in the absence of drug (60+/-1%). During ischemia, pH(i)was lower when DMA was present in the ischemic solution. The inhibition of the Na(+)/H(+)exchanger retarded the recovery of pH during reperfusion. The highest recovery of active cell shortening was observed when DMA was used at the beginning of reperfusion. The use of DMA also reduced the level of passive cell shortening during reperfusion, and when used at the beginning of reperfusion significantly increased the recovery of Ca(2+)transients. Our results demonstrate that the exchanger is primarily active during reperfusion and that inhibition of the exchanger solely at this time has a strong cardioprotective effect.

In vitro proliferation, differentiation and immuno-magnetic bead purification of human myoblasts

OBJECTIVES

In vitro culture of myoblasts and subsequent grafting into injured myocardium represents a new therapeutic approach for the treatment of myocardial infarct. A major limitation to developing enough myoblasts to engrafting purpose is the isolation and purification. In the present work we purified myoblast from primary culture using an immunomagnetic bead technique.

METHODS

Primary culture was obtained by trypsin-EDTA digestion of human muscle biopsies. Cells were cultured in DMEM growth medium containing 10% FBS, 2 mM L-glutamine and antibiotics. Immunotechniques using both monoclonal anti-myosin heavy chain (skeletal fast) and 5.1.H11 antibody combining with flow cytometry did identification of myoblasts. Positive selection was on myoblasts bound to 5.1.H11 incubating with human antimouse IgG coated magnetic beads (Dynabead) and subsequent isolation by magnet, releasing cells from beads with DNAse.

RESULTS

More than 59% of primary cell culture are positive to 5.1.H11 and decreasing with passage. The coating of culture dish surface increased specific growth rate of myoblast clones twice. Positive selection allows to increasing concentration of myoblasts from 8.4% in mixed culture to more than 90% without affecting neither viability nor platting efficiency.

CONCLUSION

Purification procedure reported here is easy, efficient and requires small amount of sample, which will facilitate the purpose of autologous implant.

Quality analysis of blood components obtained by automated buffy-coat layer removal with a top & bottom system (Optipress (R)II)

BACKGROUND AND OBJECTIVE

There are Council of Europe recommendations for the quality of blood components. We analyzed the quality of blood components processed by a top & bottom system (Optipress((R)) II), the routine method used in our blood bank, to test whether the components reached the recommended quality.

DESIGN AND METHODS

Blood was collected in triple CPD-SAGM bags (Optipac((R)) Baxter). Whole blood (WB) was centrifuged at 4,158 g for 14 min before separation by an automated top & bottom system (Optipress((R) )II). Platelet concentrate (PC) was prepared by pooling four isogroup buffy-coat (BC) units before low-speed centrifugation, and transferring the supernatant (4 BC-PC) to a 5-day storage bag (PL732, Baxter). An alternative approach involved PC preparation from a single BC unit by adding approximately 70 mL of plasma before centrifugation, followed by transfer of the platelet concentrate (1BC-PC) to a 300 mL Teruflex((R)) transfer bag. Both 4 BC-PC and 1 BC-PC were stored in a flat agitator at 22 degrees C for up to 5 days after collection. Cell counts were determined, along with hemoglobin and hematocrit in a Sysmex K-800 cell counter. The pH was determined on day 5 at 22 degrees C. Weights were measured and volumes were calculated based on specific gravity. Statistical analyses were carried out using the Kolmogorov-Smirnov test as a normality distribution test, the t-test for parametric values and Wilcoxon's test as a non-parametric test. Statistical significance between samples was considered to have been reached when p<0.05.

RESULTS

The best parameters for configuring the system were: strength 25; BC volume 33-55; level of BC 5.5. Red blood cell (n = 1,434) volume was 279+/-20 mL, with 54.92+/-7.16 g of hemoglobin. More than 96% of units had fewer than 1.2x10(9) white blood cells. Fresh plasma volume (n = 803) averaged 279+/-19 mL, with a white blood cell contamination of fewer than 0.1x10(9)/L in all samples examined (n = 23). Platelet recovery in BC was 92+/-9% of platelets present in WB; the percentage of removed leukocytes was 74+/-10%, and between 13 and 15% of RBCs were lost in the BC (95% confidence interval). The BC volume (n = 1,037) fitted the target volume of 60 mL, except for some devices, when Optipress II((R)) lost the configuration for this parameter. Of 4 BC-PCs 80.3% yielded more than 0.6x10(11) platelets per unit, whereas this criterion was only met by 59.7% of 1 BC-PCs, and a greater proportion of 1 BC-PCs (58.8%) showed pH values within the range of 6.5-7.4 after 5 days of storage in comparison with 4 BC-PCs (44.25%).

INTERPRETATION AND CONCLUSIONS

Optipress II((R)) provides standardized, leukocyte-poor blood components. Council of Europe requirements were met in a large percentage of red-cell concentrates, with less than 92 and 74% of the original platelets and leukocytes, respectively, and a small hemoglobin loss per unit. The system gave an optimal yield in terms of plasma volume. The top & bottom technique allowed us to reduce the number of blood units per platelet concentrate from 6 to 4 units, with similar platelet yields compared with traditional procedures. Nevertheless, the storage conditions must be improved to satisfy all Council of Europe requirements for platelet concentrates.

Oxidized low-density lipoprotein induces cytoskeletal disorganization in smooth muscle cells

Vascular smooth muscle cells in atherosclerotic vessels proliferate and change from a contractile to a synthetic phenotype. To determine whether oxidized low-density lipoprotein (oxLDL) is involved in this transformation, we chronically incubated cultured smooth muscle cells with native and oxidized LDL. Western blot analysis detected a decrease in actin and myosin content in treated cells. This was dependent on the time and concentration of oxLDL employed. Confocal microscopic images of cells immunostained for smooth muscle-specific alpha-actin and myosin showed a normal, elongated alignment of myofilaments in cells after incubation with native LDL. Surprisingly, when the cells were treated with oxLDL, actin and myosin filaments underwent a striking process of disorganization and accumulation into ball-shaped aggregates. These changes were dependent on the duration and concentration of oxLDL employed. Our results demonstrate that oxLDL has the capacity to decrease the content of myofilaments in smooth muscle cells. The loss in myosin and actin protein may be associated with an unusual formation of large cellular aggregates that appear to be in the process of being expelled from the cell.

[Analysis of the quality of hemoderivatives obtained using a buffy-coat extraction system with a top-and-bottom technique (Optipress II)]

PURPOSE

The aim of the present study is to know the results of the quality analysis of blood components processed with a Top & Bottom system (Optipress II) as a routine method in our blood bank, and compare it with the CE recommendations for quality of blood components.

MATERIAL AND METHODS

Blood was collected in triple CPD-SAGM bags (Optipac, Baxter) and whole blood (WB) were centrifuged at 4,158 g, 14 min. Blood separation was performed by an automated Top & Bottom system (Optipress II), in which parameters were individually configured in preliminary trials. The buffy-coat (BC) layer was maintained within the configured levels during the separation process and remained into the original bag, whereas red cells (RBC) were collected into the bottom satellite bag (with 100 mL of SAGM) and fresh plasma (FP) was sent to the top satellite bag. Platelet concentrate (PC) was prepared by two different ways: 4 isogroup buffy-coats units were pooled by means of a sterile connector device (TSCD-201, Terumo) before a low centrifugation (1,040 g, 9 min) and the supernatant (4BC-PC) was transferred into a PL732 bag (Fenwal, Baxter); the other PC was prepared from one unit of BC by additioning approximately 70 mL of FP before centrifugation (321 g, 6 min) and following transference of the platelet concentrate (1BC-CP) into a 300 mL (Teruflex, Terumo) transfer bag. Both, 4BC-PC and 1BC-PC, were stored in a flat agitator at 22 degrees C to up five days after collection. We determined cell counts, haemoglobin, and hematocrit in a Sysmex K-800 cell counter in WB and blood components. Nageotte chamber was used when low white blood cells (WBC) counts were obtained. We also determined pH values on day five at 22 degrees C in a Crison 2000. Weights were measured and volumes were calculated using specificity gravity. Statistical analysis were carried out by Kolmogorov-Smirnov test as a normality distribution test, t-test for parametrical values and Wilcoxon-test as a no parametrical test (p < 0.05 was considered as Wilcoxon a significant value between different samples).

RESULTS

The best parameters to configure the system were: strength: 25; BC volume: 33-35; level of BC: 5.5. RBCs (n: 1434) volume was 279 +/- 20 mL with 54.92 +/- 7.16 g of haemoglobin. More than 96% units had less than 1.2 x 10(9) WBC. FP volume (n: 803) averaged 279 +/- 19 mL with a WBC contamination less than 0.1 x 10(9)/L in all examined samples (n: 23). Platelet recovery in BC 92 +/- 9 percent of platelets present in WB, the percentage of removed leukocytes was 74 +/- 10 and between 13 and 15% of RBCs were lost in the BC (CI 95%). The BC volume (n: 1037) fitted the target volume of 60 mL (59-61 mL, CI 95%) except in some devices, where Optipress II lost the configuration for this parameter. 4BC-CPs (n: 325) showed a platelet yield per unit greater than 1BC-CPs (226). In addition, 80.3% of 4BC-CPs yielded more than 0.6 x 10(11) platelets per unit, whereas this criteria was only met in 59.7% of 1BC-CPs (p < 0.001). The ratio volume oper 10(9) platelets in 1 BC-CPs was significantly higher (1.57 mL) than 4BC-CPs (1.31 mL), and a greater level of 1BC-CPs (58.8%) showed pH values within 6.5-7.4 after 5 days of storage in comparison with 4BC-CPs (44.25%) (p < 0.001).

CONCLUSIONS

Optipress II provides standardized and poor leukocytes blood components. CE requirements were met in a great percentage of red-cell concentrates with less than 92 and 74 percent of original platelets and leukocytes, respectively and a low loss of haemoglobin per unit. Plasma volume obtained with this system represents an optimal yield. Top and Bottom technique allowed us to reduce the number of blood units per platelet concentrate, from six to four units with similar platelet yield compared to traditional procedures. Nevertheless, we must improve the storage conditions, in orter to satisfy all the CE requirements for platelet concentrates.

A model of low-flow ischemia and reperfusion in single, beating adult cardiomyocytes

The present study was undertaken to comprehensively characterize low-flow ischemia and reperfusion in single adult cardiomyocytes and to determine whether it is important to control contractile activity. The ischemia-mimetic solution was hypoxic, acidic (pH 6.0), and deficient in glucose but contained elevated KCl. Cardiomyocytes were stimulated to contract throughout ischemia and during reperfusion with control perfusate. After the ischemia-reperfusion insult, cells exhibited poor recovery of active cell shortening, a decrease in passive cell length, increased frequency of necrosis, lower ATP content, and evidence of the generation of oxygen-derived free radicals within the cells. Intracellular lactate concentration increased, pH decreased, and Ca(2+) transients were depressed during the ischemic insult, but the latter two parameters recovered partially on reperfusion. Basal intracellular Ca(2+) concentration was elevated during ischemia and early into reperfusion. Recovery was attenuated in cells that were electrically stimulated to contract throughout ischemia. The duration of ischemia, stimulation frequency, and composition of the ischemia-mimetic solution were important variables. The inclusion of 10 mM lactate in the ischemia-mimetic solution significantly aggravated all the parameters examined above. Our data demonstrate that 1) an ischemia-mimetic solution administered to single, isolated adult cardiomyocytes can reproduce many of the responses observed in whole hearts, 2) caution should be used in adding lactate to an ischemic solution, and 3) it is important to stimulate contractile activity throughout ischemia to reproduce the effects of ischemia in whole hearts.

Laparoscopic repair of pleural laceration produced during truncal vagotomy: case report

A partial pneumothorax developed in a patient undergoing laparoscopic truncal vagotomy when a small pleural laceration was accidentally produced. Changes in oxygen saturation and PETCO2 were immediately detected by the anesthesiologist and measures were taken to maintain the patient's ventilatory stability. The pleural laceration was repaired laparoscopically, and the pneumothorax was corrected by ventilatory manipulation, avoiding the placement of a chest tube. The procedure was completed uneventfully. Literature about the causes of pneumothorax during laparoscopic procedures as well as preventive and therapy viewed.

[Prevalence and genotypes of hepatitis C virus in blood donors and in patients with chronic liver disease and hepatocarcinoma in a Chilean population]

BACKGROUND

The impact of hepatitis C virus infection in Chile has not been well established.

AIM

To assess hepatitis C virus infection in normal Chileans and in patients with liver disease.

SUBJECTS AND METHODS

Antibodies against hepatitis C virus were investigated in 21,000 blood donors, 133 patients with non alcoholic chronic liver disease and in 50 patients with hepatocarcinoma. Viral RNA was studied by polymerase chain reaction in all positive blood donors, in 51 patients with chronic liver disease and in all patients with hepatocarcinoma. Hepatitis C virus genotype was established using restriction fragment length polymorphism in 118 RNA positive samples.

RESULTS

In blood donors, a 0.3% prevalence of positive antibodies was found. The figure for chronic liver disease was 53% and for hepatocarcinoma, 48%. Viral RNA was detected in 100% of patients with chronic liver disease and hepatocarcinoma and in 68% of blood donors with positive antibodies. Genotype 1b was identified in all infected patients with hepatocarcinoma, in 86% of patients with chronic liver disease and in 46% of blood donors.

CONCLUSIONS

Hepatitis C virus infection is an important etiologic agent for chronic liver disease in Chile. The predominance of genotype 1b among patients with the most severe form of liver disease is in agreement with observations made abroad.

Phagocytosis and killing of slime-producing Staphylococcus epidermidis bypolymorphonuclear leukocytes. Effects of sparfloxacin

The interaction of slime-producing Staphylococcus epidermidis (S+ strain) with human polymorphonuclear leukocytes (PMNs) was analyzed. The phagocytosis index (PI) and the killing index (KI) were evaluated, and the effect of subinhibitory concentrations (sub-MICs) of sparfloxacin in this interaction was determined. The study was carried out in parallel with a non-slime-producing strain (S- strain). The MIC values of sparfloxacin against both strains was 0. 06 mg/ml. In the S- strain the mean values of PI and KI were 82% and 31%, respectively, whereas in the S+ strain these values diminished to 49% and 8%, respectively (p <0.05) when the inocula were prepared in aerobiosis. In a constant flow atmosphere of 5% CO2, the results were similar to the previous ones in the S- strain (PI = 79% and KI = 27%), whereas in the S+ strain a increase in the PI (59%) and a similar value to the KI (9%) were observed. Significant increases (p <0.05) in the PI were noted when PMNs were preincubated with 1/4 and 1/16 MIC of sparfloxacin, and S. epidermidis S+ grown in aerobiosis were used. In the other assays the variations in PI and KI were not statistically significant (p >0.05). Our results confirm that slime protects against phagocytosis and killing by PMNs, although they also suggest that the S+ strains possess additional properties which make them resistant to the action of the PMNs.

[The study of patient survival in cerebral hemorrhagic and ischemic accident]

The aim of this study was to study stroke survival in Chile in a historic cohort from a random sample of 333 inpatients. All alive selected patients were visited and examined. All the death certificates were reviewed. The diagnosis was done by a neurologist, 35% had a CT scan. Survival was measured in days using lifetest procedure to generate survival curves, Cox's proportional hazards models in Stata 3.1 statistic package and logistic regression analysis. The mean age was 70.5 for the group of died and 62.3 years old for alive patients (p = 0.01). Infectious disease (p = 0.05), localization of stroke (p = 0.01) and rehabilitation (p = 0.005) were significant at univariate analysis. The cumulative probability of survival was 38 days, after one year and after five years, 48.1, 39.0 and 19.8%, respectively. The probability of survival by age, localization, heart disease and rehabilitation was statistically significant. Analysis of survival by sex, and previous stroke risk factors was not significant. Using Cox's proportional hazards regression we found that survival after 5 years depends on age (p = 0.03), rehabilitation (p = 0.008), infection (p = 0.05) and heart disease (p = 0.04). Stroke survival function is close to a decreasing exponential curve with high death probability at one month after the stroke. Survival is conditioned by stroke localization, age, heart disease and rehabilitation.

Influence of N-acetylcysteine on the formation of biofilm by Staphylococcus epidermidis

The influence of various concentrations (0.003-8 mg/mL) of N-acetylcysteine on the formation of biofilms by 15 strains of Staphylococcus epidermidis has been studied. A dose-related decrease in biofilm formation was observed, except with the lowest concentrations. The 'slime' index relative to the control was 63%, 55%, 46%, 34%, 26% and 26% in the presence of 0.25, 0.5, 1, 2, 4, and 8 mg/mL of N-acetylcysteine, respectively. These data are statistically significant. The inhibitory effect of 2 mg/mL of N-acetylcysteine on slime formation was also verified by electron microscopy.

Incubation temperatures affect adherence to plastic of Candida albicans by changing the cellular surface hydrophobicity

The influence of cellular surface hydrophobicity on the adherence capacity to plastic of Candida albicans was investigated at two culture temperatures (37 and 22 degrees C). The majority of the 42 strains studied were hydrophobic at 22 degrees C and hydrophilic at 36 degrees C. The hydrophobic cells showed a consistent adherence capacity which was absent from the hydrophilic strains. The culture temperatures affect adherence to plastic of C. albicans by changing the cellular surface hydrophobicity.

[Hepatitis E virus infection in Chile: preliminary report]

BACKGROUND

Hepatitis E virus is an enterally transmitted virus that produces an acute self limited infection.

AIM

To study serum antibodies against hepatitis E virus in different patients.

PATIENTS AND METHODS

Using and ELISA technique, IgG antibodies against hepatitis E virus were measured in 40 alcoholics, 40 hemophiliacs, 174 blood donors, 36 subjects with acute non A-non B-non C hepatitis and 66 subjects with acute hepatitis A.

RESULTS

Antibodies were detected in one alcoholic (2.5%), 3 hemophiliacs (7.5%), 7 blood donors (4%), 3 patients with non A-non B-non C hepatitis (8.3%) and 3 patients with acute hepatitis A (4.5%).

CONCLUSIONS

A low frequency of hepatitis E infection was detected in the studied subjects.

Man-biting activity of Anopheles (Nyssorhynchus) albimanus and An. (Kerteszia) neivai (Diptera: Culicidae) in the Pacific lowlands of Colombia

The daily man-biting activity of Anopheles (Nyssorhynchus) albimanus and An. (Kerteszia) neivai was determined in four ecologically distinct settlements of the Naya River, Department of Valle, Colombia. Differences were found among the settlements with respect to the mosquito species present, intradomiciliary and extradomiciliary biting activity and population densities.

[Pre S1 antigen in different forms of hepatitis B virus infection]

Pre S1 antigen was measured using an ELISA technique in patients with different forms of hepatitis B virus infection. It was detected in 10 of 19 patients with acute hepatitis B (53%), 12 of 15 chronic hepatitis B virus carriers (80%), 9 of 11 patients with chronic hepatitis B (82%) and 3 of 4 patients with hepatoma and positive markers of hepatitis B virus infection. Pre S1 remained positive beyond 150 days in two patients with acute hepatitis that evolved to chronicity. Among subjects with chronic hepatitis B that received interferon, pre S1 antigen negativized only in the patient that had a complete response. Pre S1 detection is an index of hepatitis B virus replication and its persistence determines chronicity. Its negativization after antiviral therapy should have a predictive value.

Influence of the incubation atmosphere on the production of slime by Staphylococcus epidermidis

The influence of various incubation atmospheres on the growth and slime production of 23 Staphylococcus epidermidis strains was studied. The atmospheres evaluated were aerobiosis (control), anaerobiosis, candle jar, 5% CO2 and 10% CO2. As compared to the aerobic control, growth was 55.7 +/- 19% (p < 0.01) in anaerobic incubation, 113.7 +/- 12% (p < 0.01) in 5% CO2, 112.8 +/- 13% (p < 0.01) in 10% CO2 and 106.4 +/- 7% (p > 0.1) in the candle jar. The slime production in relation to the aerobic control was 20.3 +/- 19% in anaerobiosis (p < 0.01), 22.3 +/- 27% (p < 0.01) in 5% CO2, 29.4 +/- 39% (p < 0.01) in 10% CO2 and 68.3 +/- 26% (p > 0.1) in the candle jar. The results of this study may explain the discrepancies which have been noted on occasion between slime formation data and pathogenicity.

[Primary HIV infection. Clinical and serologic characteristics]

An acute clinical picture of variable intensity may occur during the initial primary phase of HIV infection, it may however pass unnoticed. We report 12 seronegative subjects (11 male homosexuals, 1 female heterosexual, aged 18 to 44 years old), that presented an acute clinical picture preceding seroconversion. All had a sudden beginning, resembling an acute mononucleosis in 10 and with an aseptic meningitis in two. Intensity and duration were variable, lasting a mean of 14 (range 5-44) days an remaining asymptomatic thereafter. Most patients presented a discrete leukopenia with lymphopenia at the expense of CD4 lymphocytes, followed by an absolute lymphocytosis in some, with an increase in CD8 lymphocytes. All became positive for HIV; circulating HIV antigen was identified in three and IgM anti-HIV antibodies were detected during the symptomatic period by third generation ELISA in other three. It is concluded that the clinical picture of primary HIV infection has identifiable clinical serological and immunological features and its recognition has diagnostic and preventive implications.

[Hepatitis B and C virus infections in children with congenital coagulation disorders]

The prevalence of hepatitis B and C virus infections, transmitted by blood transfusions, was studied in 79 children with congenital coagulation disorders. Twenty nine percent had evidences of hepatitis B virus infection and 52% evidences of hepatitis C virus infection. Older children and those with the higher number of transfusions had the highest rates of infections. It is concluded that children with congenital coagulation disorders constitute a high risk group for hepatitis B and C virus infections.

Effects of cefpirome in comparison with cefuroxime against human polymorphonuclear leucocytes in vitro

The interaction of cefpirome and cefuroxime, with human polymorphonuclear leucocytes (PMNs) was examined. The effects of therapeutic concentration (1, 10, and 50 mg/L) of both antimicrobial agents on the adherence, spontaneous mobility, chemotaxis, chemokinesis, phagocytosis and candidacidal capacity were studied in vitro. No statistically significant variations, in relation to the control, were observed in the ability of PMNs to adhere to nylon fibre at the concentrations of cefuroxime and cefpirome used. With both antimicrobial agents, PMN mobility increased as the antibiotic concentration was increased. A statistically significant increase (P < 0.05) in spontaneous mobility, chemotaxis and chemokinesis was observed with cefpirome at only 10 mg/L. However, only spontaneous mobility was increased significantly with cefuroxime at 10 mg/L. The strongest effects were observed with cefpirome at 50 mg/L with variations of about 70% (P < 0.01), in chemotaxis and chemokinesis. In general, cefpirome had a positive effect on phagocytosis and candidacidal power, which was significant at a concentration of 50 mg/L (P < 0.01). Cefuroxime, in general, produced no modifications in either phagocytosis or candidacidal power.

[Correlation between serum globulin levels and hepatitis C virus antibody]

BACKGROUND

some studies have suggested that the elevation of serum globulins in patients with chronic autoimmune hepatitis, paraproteinemias and rheumatoid arthritis could affect the determination of false positive hepatitis C virus antibodies (anti-HCV).

AIM

to study the relationship between positive anti-HCV and serum levels of globulins in patients with liver disease.

PATIENTS AND METHODS

one hundred thirty one patients with liver disease, 49 alcoholic, 38 cryptogenetic, 17 autoimmune and 27 with other causes, were studies prospectively measuring simultaneously anti-HCV and serum levels of total, gamma and immuno-globulins (IgA, IgG and IgM). These levels were compared between anti-HCV positive and negative groups and correlated with the ratio between serum optical density/cutoff optical density of the anti HCV assay.

RESULTS

Twenty eight patients (21.3%) were anti-HCV positive, no differences in serum globulins between these patients and anti-HCV negative patients and no correlations between serum globulins and anti-HCV optical densities were observed.

CONCLUSIONS

the hypergamma-globulinemia observed in these patients with liver diseases would not be responsible for positive hepatitis C virus antibodies.