Time Series of Counts under Censoring: A Bayesian Approach

Censored data are frequently found in diverse fields including environmental monitoring, medicine, economics and social sciences. Censoring occurs when observations are available only for a restricted range, e.g., due to a detection limit. Ignoring censoring produces biased estimates and unreliable statistical inference. The aim of this work is to contribute to the modelling of time series of counts under censoring using convolution closed infinitely divisible (CCID) models. The emphasis is on estimation and inference problems, using Bayesian approaches with Approximate Bayesian Computation (ABC) and Gibbs sampler with Data Augmentation (GDA) algorithms.

Multiscale partial information decomposition of dynamic processes with short and long-range correlations: theory and application to cardiovascular control

OBJECTIVE

In this work, an analytical framework for the multiscale analysis of multivariate Gaussian processes is presented, whereby the computation of Partial Information Decomposition measures is achieved accounting for the simultaneous presence of short-term dynamics and long-range correlations.

APPROACH

We consider physiological time series mapping the activity of the cardiac, vascular and respiratory systems in the field of Network Physiology. In this context, the multiscale representation of transfer entropy within the network of interactions among Systolic arterial pressure (S), respiration (R) and heart period (H), as well as the decomposition into unique, redundant and synergistic contributions, is obtained using a Vector AutoRegressive Fractionally Integrated (VARFI) framework for Gaussian processes. This novel approach allows to quantify the directed information flow accounting for the simultaneous presence of short-term dynamics and long-range correlations among the analyzed processes. Additionally, it provides analytical expressions for the computation of the information measures, by exploiting the theory of state space models. The approach is first illustrated in simulated VARFI processes and then applied to H, S and R time series measured in healthy subjects monitored at rest and during mental and postural stress.

MAIN RESULTS

We demonstrate the ability of the VARFI modeling approach to account for the coexistence of short-term and long-range correlations in the study of multivariate processes. Physiologically, we show that postural stress induces larger redundant and synergistic effects from S and R to H at short time scales, while mental stress induces larger information transfer from S to H at longer time scales, thus evidencing the different nature of the two stressors.

SIGNIFICANCE

The proposed methodology allows to extract useful information about the dependence of the information transfer on the balance between short-term and long-range correlations in coupled dynamical systems, which cannot be observed using standard methods that do not consider long-range correlations.

Novel features for time series analysis: a complex networks approach

Being able to capture the characteristics of a time series with a feature vector is a very important task with a multitude of applications, such as classification, clustering or forecasting. Usually, the features are obtained from linear and nonlinear time series measures, that may present several data related drawbacks. In this work we introduce NetF as an alternative set of features, incorporating several representative topological measures of different complex networks mappings of the time series. Our approach does not require data preprocessing and is applicable regardless of any data characteristics. Exploring our novel feature vector, we are able to connect mapped network features to properties inherent in diversified time series models, showing that NetF can be useful to characterize time data. Furthermore, we also demonstrate the applicability of our methodology in clustering synthetic and benchmark time series sets, comparing its performance with more conventional features, showcasing how NetF can achieve high-accuracy clusters. Our results are very promising, with network features from different mapping methods capturing different properties of the time series, adding a different and rich feature set to the literature.

Assessing Transfer Entropy in cardiovascular and respiratory time series under long-range correlations

Heart Period (H) results from the activity of several coexisting control mechanisms, involving Systolic Arterial Pressure (S) and Respiration (R), which operate across multiple time scales encompassing not only short-term dynamics but also long-range correlations. In this work, multiscale representation of Transfer Entropy (TE) and of its decomposition in the network of these three interacting processes is obtained by extending the multivariate approach based on linear parametric VAR models to the Vector AutoRegressive Fractionally Integrated (VARFI) framework for Gaussian processes. This approach allows to dissect the different contributions to cardiac dynamics accounting for the simultaneous presence of short and long term dynamics. The proposed method is first tested on simulations of a benchmark VARFI model and then applied to experimental data consisting of H, S and R time series measured in healthy subjects monitored at rest and during mental and postural stress. The results reveal that the proposed method can highlight the dependence of the information transfer on the balance between short-term and long-range correlations in coupled dynamical systems.

Multivariate and Multiscale Complexity of Long-Range Correlated Cardiovascular and Respiratory Variability Series

Assessing the dynamical complexity of biological time series represents an important topic with potential applications ranging from the characterization of physiological states and pathological conditions to the calculation of diagnostic parameters. In particular, cardiovascular time series exhibit a variability produced by different physiological control mechanisms coupled with each other, which take into account several variables and operate across multiple time scales that result in the coexistence of short term dynamics and long-range correlations. The most widely employed technique to evaluate the dynamical complexity of a time series at different time scales, the so-called multiscale entropy (MSE), has been proven to be unsuitable in the presence of short multivariate time series to be analyzed at long time scales. This work aims at overcoming these issues via the introduction of a new method for the assessment of the multiscale complexity of multivariate time series. The method first exploits vector autoregressive fractionally integrated (VARFI) models to yield a linear parametric representation of vector stochastic processes characterized by short- and long-range correlations. Then, it provides an analytical formulation, within the theory of state-space models, of how the VARFI parameters change when the processes are observed across multiple time scales, which is finally exploited to derive MSE measures relevant to the overall multivariate process or to one constituent scalar process. The proposed approach is applied on cardiovascular and respiratory time series to assess the complexity of the heart period, systolic arterial pressure and respiration variability measured in a group of healthy subjects during conditions of postural and mental stress. Our results document that the proposed methodology can detect physiologically meaningful multiscale patterns of complexity documented previously, but can also capture significant variations in complexity which cannot be observed using standard methods that do not take into account long-range correlations.

Multiscale information storage of linear long-range correlated stochastic processes

Information storage, reflecting the capability of a dynamical system to keep predictable information during its evolution over time, is a key element of intrinsic distributed computation, useful for the description of the dynamical complexity of several physical and biological processes. Here we introduce a parametric approach which allows one to compute information storage across multiple timescales in stochastic processes displaying both short-term dynamics and long-range correlations (LRC). Our analysis is performed in the popular framework of multiscale entropy, whereby a time series is first "coarse grained" at the chosen timescale through low-pass filtering and downsampling, and then its complexity is evaluated in terms of conditional entropy. Within this framework, our approach makes use of linear fractionally integrated autoregressive (ARFI) models to derive analytical expressions for the information storage computed at multiple timescales. Specifically, we exploit state space models to provide the representation of lowpass filtered and downsampled ARFI processes, from which information storage is computed at any given timescale relating the process variance to the prediction error variance. This enhances the practical usability of multiscale information storage, as it enables a computationally reliable quantification of a complexity measure which incorporates the effects of LRC together with that of short-term dynamics. The proposed measure is first assessed in simulated ARFI processes reproducing different types of autoregressive dynamics and different degrees of LRC, studying both the theoretical values and the finite sample performance. We find that LRC alter substantially the complexity of ARFI processes even at short timescales, and that reliable estimation of complexity can be achieved at longer timescales only when LRC are properly modeled. Then, we assess multiscale information storage in physiological time series measured in humans during resting state and postural stress, revealing unprecedented responses to stress of the complexity of heart period and systolic arterial pressure variability, which are related to the different role played by LRC in the two conditions.

Model-Based Classification of Heart Rate Variability

Several Heart Rate Variability (HRV) based novel methodologies for describing heart rate dynamics have been proposed in the literature with the aim of risk assessment. One such methodology is ARFIMA-EGARCH modeling which allows the quantification of long range dependence and time-varying volatility with the aim of describing non-linear and complex characteristics of HRV. This study applies the ARFIMA-EGARCH modeling of HRV recordings from 30 patients of the Noltisalis database to investigate the discrimination power of a set of features comprising currently used linear HRV features (low and high frequency components) and new measures obtained from the modeling such as, long memory in the mean, and persistence and asymmetry in volatility. A subset of the multidimensional HRV features is selected in a two-step procedure using Principal Components Analysis (PCA). Additionally, supervised classification by quadratic discriminant analysis achieves 93.3% of discrimination accuracy between the groups using the new feature set created by PCA.

In situ Multispecies Colonization of An Acrylic Resin: Comparison to Oral Microbiome and Potential for Inflammatory Response

Background:

Conventional acrylic resin is prone to microbial colonization and may cause inflammatory and allergic response.

Aims:

This study aims to research the initial microbial adhesion in situ and tissue response to an acrylic resin used in prosthodontics.

Materials and Methods:

Disks of a commercial acrylic resin were prepared and included on the surface of individual intraoral splints fabricated for 50 participants. The splints were used for 4 h, under clinical conditions. Beforehand, each participant was swabbed to provide a control for microbiological comparison. A cytological control sample was also taken from the palate. After the time elapsed, each splint was removed and growth of anaerobes, aerobes, Pseudomonas, oral streptococci, staphylococci, yeasts, and Streptococcus mutans was determined by plate counts and compared to the oral microbiome. A cytological sample was taken from the contact zone, stained using the Papanicolaou technique, analyzed in light microscopy, and classified accordingly. Means and standard deviations were calculated, and a nonparametric Wilcoxon test was employed to compare experimental groups. The significance level was set at 0.05 (95% confidence interval, and statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) version 20.0.

Results:

Nuclear-cytoplasm ratio increase was found in 84% of the smears retrieved from the contact zone. Over 60% showed nuclear alterations. With exception to yeasts and Pseudomonas, all microbial groups colonized the resin. No statistically significant differences were found between the oral microbiome and the acrylic resin's colonization except regarding yeasts (P > 0.05).

Conclusions:

Cellular alterations were found but a diagnosis of inflammation is inconclusive. Microbial adhesion to the acrylic resin was substantial, with multiple species adhering.

Modeling volatility in heat rate variability

Modeling Heart Rate Variability (HRV) data has become important for clinical applications and as a research tool. These data exhibit long memory and time-varying conditional variance (volatility). In HRV, volatility is traditionally estimated by recursive least squares combined with short memory AutoRegressive (AR) models. This work considers a parametric approach based on long memory Fractionally Integrated AutoRegressive Moving Average (ARFIMA) models with heteroscedastic errors. To model the heteroscedasticity nonlinear Generalized Autoregressive Conditionally Heteroscedastic (GARCH) and Exponential Generalized Autoregressive Conditionally Heteroscedastic (EGARCH) models are considered. The latter are necessary to model empirical characteristics of conditional volatility such as clustering and asymmetry in the response, usually called leverage in time series literature. The ARFIMA-EGARCH models are used to capture and remove long memory and characterize conditional volatility in 24 hour HRV recordings from the Noltisalis database.

Starch characterization in seven raw, boiled and roasted chestnuts (Castanea sativa Mill.) cultivars from Portugal

Changes occurring in seven chestnut (Castanea sativa sp.) cultivars, caused by boiling and roasting, on starch content, cell and starch granules dimension were evaluated, and morphological changes were characterized by scanning electron microscopy. Three clear patterns of variation were detected after processing, namely: i) decrease of starch content with processing; ii) starch increase with the applied treatments; iii) increase of starch with boiling and decrease with roasting. Starch granules of raw chestnuts presented round, oval or elliptical form, external smooth surface and eccentric hilum, with rather ellipsoid-shaped growth rings. Processing resulted in modifications of the granules, with fusion of individual granules, and gelatinization taking place with the formation of elongated clusters. The present results indicate that boiling and roasting, besides changing the starch content of chestnut, causes important modifications in the starch granules, which can affect the sensory, rheological and chemical characteristics of chestnuts.

Time-course effects of aerobic exercise training on cardiovascular and renal parameters in 2K1C renovascular hypertensive rats

Exercise training (Ex) has been recommended for its beneficial effects in hypertensive states. The present study evaluated the time-course effects of Ex without workload on mean arterial pressure (MAP), reflex bradycardia, cardiac and renal histology, and oxidative stress in two-kidney, one-clip (2K1C) hypertensive rats. Male Fischer rats (10 weeks old; 150–180 g) underwent surgery (2K1C or SHAM) and were subsequently divided into a sedentary (SED) group and Ex group (swimming 1 h/day, 5 days/week for 2, 4, 6, 8, or 10 weeks). Until week 4, Ex decreased MAP, increased reflex bradycardia, prevented concentric hypertrophy, reduced collagen deposition in the myocardium and kidneys, decreased the level of thiobarbituric acid-reactive substances (TBARS) in the left ventricle, and increased the catalase (CAT) activity in the left ventricle and both kidneys. From week 6 to week 10, however, MAP and reflex bradycardia in 2K1C Ex rats became similar to those in 2K1C SED rats. Ex effectively reduced heart rate and prevented collagen deposition in the heart and both kidneys up to week 10, and restored the level of TBARS in the left ventricle and clipped kidney and the CAT activity in both kidneys until week 8. Ex without workload for 10 weeks in 2K1C rats provided distinct beneficial effects. The early effects of Ex on cardiovascular function included reversing MAP and reflex bradycardia. The later effects of Ex included preventing structural alterations in the heart and kidney by decreasing oxidative stress and reducing injuries in these organs during hypertension.

Individualizing propofol dosage: a multivariate linear model approach

In the last decades propofol became established as an intravenous agent for the induction and maintenance of both sedation and general anesthesia procedures. In order to achieve the desired clinical effects appropriate infusion rate strategies must be designed. Moreover, it is important to avoid or minimize associated side effects namely adverse cardiorespiratory effects and delayed recovery. Nowadays, to attain these purposes the continuous propofol delivery is usually performed through target-controlled infusion (TCI) systems whose algorithms rely on pharmacokinetic and pharmacodynamic models. This work presents statistical models to estimate both the infusion rate and the bolus administration. The modeling strategy relies on multivariate linear models, based on patient characteristics such as age, height, weight and gender along with the desired target concentration. A clinical database collected with a RugLoopII device on 84 patients undergoing ultrasonographic endoscopy under sedation-analgesia with propofol and remifentanil is used to estimate the models (training set with 74 cases) and assess their performance (test set with 10 cases). The results obtained in the test set comprising a broad range of characteristics are satisfactory since the models are able to predict bolus, infusion rates and the effect-site concentrations comparable to those of TCI. Furthermore, comparisons of the effect-site concentrations for dosages predicted by the proposed Linear model and the Marsh model for the same target concentration is achieved using Schnider model and a factorial design on the factors (patients characteristics). The results indicate that the Linear model predicts a dosage profile that is faster in leading to an effect-site concentration closer to the desired target concentration.

A Low Protein Diet Causes an Increase in the Basal Levels and Variability of Mean Arterial Pressure and Heart Rate in Fisher Rats

The correlation between nutrition and cardiovascular related disorders is a well-established fact. Previous work from our Laboratory has suggested a significant compromise of cardiovascular reflexes in conscious rats submitted to a low-protein (LP) diet. Our working hypothesis is that the basal level of mean arterial pressure (MAP), variability of the mean arterial pressure (VMAP), heart rate (HR) and variability of heart rate (VHR) are altered in rats submitted to a protein restricted diet. Two experimental groups were used: control group (normal protein 15%, NP) and malnourished group (low-protein 6%, LP). In order to verify the efficiency of the dietary restriction we measured body weight, total blood protein, plasma albumin, urea and glucose. Our experiments demonstrated that the malnourished rats presented augment levels of basal MAP (LP 122+/-2 mmHg vs. NP 113+/-1 mmHg) and of VMAP (LP 12.8+/-1.5mmHg vs. NP 9+/-1mmHg) when compared to the control group. We observed similar increased levels, in the malnourished group, for both HR (LP 429+/-8 bpm vs. NP 381+/-7bpm) and VHR (LP 67.6+/-8.3bpm vs. NP 44.4+/-4.9bpm). Our results suggest a correlation between the LP diet in Fisher rats and the increased basal levels of mean arterial pressure, HR and their respective variability.

Beyond long memory in heart rate variability: an approach based on fractionally integrated autoregressive moving average time series models with conditional heteroscedasticity

Heart Rate Variability (HRV) series exhibit long memory and time-varying conditional variance. This work considers the Fractionally Integrated AutoRegressive Moving Average (ARFIMA) models with Generalized AutoRegressive Conditional Heteroscedastic (GARCH) errors. ARFIMA-GARCH models may be used to capture and remove long memory and estimate the conditional volatility in 24 h HRV recordings. The ARFIMA-GARCH approach is applied to fifteen long term HRV series available at Physionet, leading to the discrimination among normal individuals, heart failure patients, and patients with atrial fibrillation.

Protein restriction does not impair adaptations induced in cardiomyocytes by exercise in rats

The effect of a treadmill running program on physical performance and morphofunctional adaptations was investigated in control and malnourished rats. Male 4-week old Wistar rats were randomized in groups of 12 animals: control trained (CT), control sedentary (CS), malnourished trained (MT) and malnourished sedentary (MS). Control and malnourished animals received chow with 12% protein or 6% protein, respectively. Trained groups were subjected to a treadmill running program for 8 weeks. Physical performance, biochemical parameters, cardiomyocytes morphology and biomechanics were determined. Malnourished animals presented reduction in body mass, serum levels of total protein, albumin and hemoglobin compared to the control groups. At 1 and 3 Hz cardiomyocytes from CT and MT showed higher cell shortening, speed of contraction and relaxation compared to the other groups. At 3 Hz cardiomyocytes from MS showed reduction in cell shortening and speed of contraction compared to CS. Protein restriction does not prevent the improvement in physical performance or cardiomyocytes biomechanical efficiency and growth in response to exercise. These findings could represent a modulatory effect of exercise to maintain cardiomyocyte growth at the expense of reducing the rate of body growth in order to ensure proper cellular function in conditions of cardiovascular overload imposed by exercise.

GnRH dose reduction decreases pituitary LH release and ovulatory response but does not affect corpus luteum (CL) development and function in llamas

Gonadotrophin releasing hormone (GnRH) is commonly used in llamas to induce ovulation; however, the consequence of reduced doses of GnRH on luteinizing hormone (LH) release, ovulatory response, and subsequent corpus luteum (CL) development and function have apparently not been investigated. Hence, we examined the effect of gradual reduction of gonadorelin acetate (GnRH) dosage on pituitary LH release, ovulatory response, CL development, and plasma progesterone concentrations in llamas. Non-pregnant, non-lactating adult llamas were examined once daily by transrectal ultrasonography, and those with a follicle ≥8 mm in diameter that had grown for three consecutive days were randomly assigned to receive 50 (GnRH50, n = 23), 25 (GnRH25, n = 29), 12.5 (GnRH12.5, n = 29), or 6.25 μg (GnRH6.25, n = 29) of GnRH, or 0.5 mL of PBS (Control group, n = 16) im. In a subset (7 or 8 animals/group), intense blood sampling was done to measure LH concentrations. All females were examined by ultrasonography every 12 h from treatment (Day 0) to Day 2 to determinate ovulation, and thereafter on alternate days until Day 16 to evaluate CL development (9-13 animals/group). Also, blood samples for progesterone determination were taken (9 or 10 animals/group) on alternate days from Days 0-16. Ovulatory response (%) was highest (P < 0.05) in the GnRH50 (82.6), intermediate in the GnRH25 (72.3) and GnRH12.5 (75.9) groups, and lowest in the GnRH6.25 group (48.3). No ovulations were detected in the Control group. Mean peak LH concentrations (ng/mL) were highest (P < 0.05) for GnRH50 (6.2), intermediate for GnRH25 (4.4) and GnRH12.5 (2.9), and lowest for GnRH6.25 (2.2) groups. In addition, based on regression analysis, llamas with an LH peak <4 ng/mL were less likely to ovulate. Llamas given 50 μg of GnRH released more (P < 0.05) pituitary LH and had an LH surge of longer duration than those given 25, 12.5, or 6.25 μg. However, in those that ovulated, neither GnRH treatment nor treatment by time interaction affected (P > 0.05) CL diameter or plasma progesterone concentrations. In summary, reducing the dose of GnRH gradually decreased the magnitude of the preovulatory LH surge and ovulatory response; however, subsequent CL development and plasma progesterone concentrations were not affected.

STAT6 links IL-4/IL-13 stimulation with pendrin expression in asthma and chronic obstructive pulmonary disease

Signaling through the interleukin-4/interleukin-13 (IL-4/IL-13) receptor complex is a crucial mechanism in the development of bronchial asthma and chronic obstructive pulmonary disease (COPD). In bronchial epithelial cells, this signaling pathway leads to changes in the expression levels of several genes that are possibly involved in protection against and/or pathogenesis of these diseases. The expression of pendrin (SLC26A4), a candidate for the latter category, is upregulated by IL-4/IL-13 and leads to overproduction of mucus and increased viscosity of the airway surface liquid (ASL). Therefore, elucidating the transcriptional regulation of pendrin could aid in the development of new pharmacological leads for asthma and/or COPD therapy. Here we show that IL-4/IL-13 significantly increased human pendrin promoter activity in HEK-Blue cells but not in STAT6-deficient HEK293 Phoenix cells; that mutation of the STAT6 binding site (N(4) GAS motif) rendered the promoter insensitive to IL-4/IL-13; and that addition of the N(4) GAS motif to an IL-4/IL-13-unresponsive sequence of the human pendrin promoter conferred sensitivity to both ILs.

STAT6 links IL-4/IL-13 stimulation with pendrin expression in asthma and chronic obstructive pulmonary disease

Signaling through the interleukin-4/interleukin-13 (IL-4/IL-13) receptor complex is a crucial mechanism in the development of bronchial asthma and chronic obstructive pulmonary disease (COPD). In bronchial epithelial cells, this signaling pathway leads to changes in the expression levels of several genes that are possibly involved in protection against and/or pathogenesis of these diseases. The expression of pendrin (SLC26A4), a candidate for the latter category, is upregulated by IL-4/IL-13 and leads to overproduction of mucus and increased viscosity of the airway surface liquid (ASL). Therefore, elucidating the transcriptional regulation of pendrin could aid in the development of new pharmacological leads for asthma and/or COPD therapy. Here we show that IL-4/IL-13 significantly increased human pendrin promoter activity in HEK-Blue cells but not in STAT6-deficient HEK293 Phoenix cells; that mutation of the STAT6 binding site (N(4) GAS motif) rendered the promoter insensitive to IL-4/IL-13; and that addition of the N(4) GAS motif to an IL-4/IL-13-unresponsive sequence of the human pendrin promoter conferred sensitivity to both ILs.

Evidence for a role of AT(2) receptors at the CVLM in the cardiovascular changes induced by low-intensity physical activity in renovascular hypertensive rats

In the present study, we evaluated the involvement of the rennin-angiotensin system (RAS) in the control of the blood pressure (BP), baroreceptor-mediated bradycardia and the reactivity of caudal ventrolateral medulla (CVLM) neurons to Ang II and to AT(2) receptor antagonist in sedentary or trained renovascular hypertensive rats. Physical activity did not significantly change the baseline mean arterial pressure (MAP), heart rate (HR) or the sensitivity of the baroreflex bradycardia in normotensive Sham rats. However, in 2K1C hypertensive rats, physical activity induced a significant fall in baseline MAP and HR and produced an improvement of the baroreflex function (bradycardic component). The microinjections of Ang II into the CVLM produced similar decreases in MAP in all groups, Sham and 2K1C, sedentary and trained rats. The hypotensive effect of Ang II at the CVLM was blocked by previous microinjection of the AT(2) receptors antagonist, PD123319, in all groups of rats. Unexpectedly, microinjection of PD123319 at the CVLM produced a depressor effect in 2K1C sedentary that was attenuated in 2K1C trained rats. No significant changes in MAP were observed after PD123319 in Sham rats, sedentary or trained. These data showed that low-intensity physical activity is effective in lowering blood pressure and restoring the sensitivity of the baroreflex bradycardia, however these cardiovascular effects are not accompanied by changes in the responsiveness to Ang II at CVLM in normotensive or hypertensive, 2K1C rats. In addition, the blood pressure changes observed after AT(2) blockade in 2K1C rats suggest that hypertension may trigger an imbalance of AT(1)/AT(2) receptors at the CVLM that may be restored, at least in part, by low-intensity physical activity.

Entamoeba histolytica: ADP-ribosylation of secreted glyceraldehyde-3-phosphate dehydrogenase

In addition to its classic glycolytic role, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been implicated in many activities unrelated to glycolysis, such as membrane fusion, binding to host proteins and signal transduction. GAPDH can be the target of several modifications that allow incorporation to membranes and possible regulation of its activity; among these modifications is mono-ADP-ribosylation. This post-translational modification is important for the regulation of many cellular processes and is the mechanism of action of several bacterial toxins. In a previous study, we observed the extracellular ADP-ribosylation of a 37-kDa ameba protein. We report here that GAPDH and cysteine synthase A are the main ADP-ribosylated proteins in Entamoeba histolytica extracellular medium, GAPDH is secreted from ameba at 37 degrees C in a time-dependent manner, and its enzymatic activity is not inhibited by ADP-ribosylation. Extracellular GAPDH from ameba may play an important role in the survival of this human pathogen or in interaction with host molecules, as occurs in other organisms.

Baroreflex function in conscious rats submitted to iron overload

Our hypothesis is that iron accumulated in tissue, rather than in serum, may compromise cardiovascular control. Male Fischer 344 rats weighing 180 to 220 g were divided into 2 groups. In the serum iron overload group (SIO, N = 12), 20 mg elemental iron was injected ip daily for 7 days. In the tissue iron overload group (TIO, N = 19), a smaller amount of elemental iron was injected (10 mg, daily) for 5 days followed by a resting period of 7 days. Reflex heart rate responses were elicited by iv injections of either phenylephrine (0.5 to 5.0 microg/kg) or sodium nitroprusside (1.0 to 10.0 microg/kg). Baroreflex curves were determined and fitted to sigmoidal equations and the baroreflex gain coefficient was evaluated. To evaluate the role of other than a direct effect of iron on tissue, acute treatment with the iron chelator deferoxamine (20 mg/kg, iv) was performed on the TIO group and the baroreflex was re-evaluated. At the end of the experiments, evaluation of iron levels in serum confirmed a pronounced overload for the SIO group (30-fold), in contrast to the TIO group (2-fold). Tissue levels of iron, however, were higher in the TIO group. The SIO protocol did not produce significant alterations in the baroreflex curve response, while the TIO protocol produced a nearly 2-fold increase in baroreflex gain (-4.34 +/- 0.74 and -7.93 +/- 1.08 bpm/mmHg, respectively). The TIO protocol animals treated with deferoxamine returned to sham levels of baroreflex gain (-3.7 +/- 0.3 sham vs -3.6 +/- 0.2 bpm/mmHg) 30 min after the injection. Our results indicate an effect of tissue iron overload on the enhancement of baroreflex sensitivity.

Effects of low-protein diet on the baroreflex and Bezold-Jarisch reflex in conscious rats

The present study evaluated the effects of a low-protein diet (LP, 6% protein) on cardiovascular reflexes of Male Fisher rats. Three experimental groups, and their respective controls (15% protein), were used: (1) Baroreceptor reflex (BAR); (2) Bezold-Jarisch reflex (BJR); and (3) Prazosin treated. Dietary restriction began after weaning (three weeks) and lasted for a period of five weeks, after which animals were subjected to the experimental protocols. The BAR group was evaluated through injections of phenylephrine (0.5-5.0 microgram/Kg, i.v.) and sodium nitroprusside (0.7-7.0 microgram/Kg, i.v.) while the BJR was evaluated through injections of serotonin (2.5-10 microgram/Kg, i.v.). Our results showed an increased baroreflex gain bradycardia for the LP group (-0.96+/-0.34 vs. -2.12+/-1.06 bpm/mmHg) and a larger bradycardia for the BJR the LP group (160+/-18% greater than controls). Basal cardiovascular parameters were not different between LP and control rats, however LP animals treated with prazosin resulted in a larger fall of blood pressure (-19+/-3 vs. -28+/-5 mmHg). In conclusion, LP rats present an increased responsiveness of BAR and BJR, which could contribute to their normal levels of cardiovascular parameters, in spite of the possible increase in the sympathetic vasomotor tonus observed with the prazosin protocol.

Family-based association of HLA class II alleles and haplotypes with type I diabetes in Brazilians reveals some characteristics of a highly diversified population

The association of HLA class II haplotypes with type I diabetes was analyzed in 56 Southeastern Brazilian families using affected family-based controls (AFBAC) method. DRB1-DQA1-DQB1 alleles were determined by polymerase chain reaction/sequence-specific primer genotyping. This study first revealed the great haplotype diversity of Brazilians (65 different haplotypes even with incomplete DRB1 subtyping), probably due to the admixture of Africans genes with European and Amerindian genes in this population. The results revealed increased frequencies of the DRB1*03-DQA1*0501-DQB1*02 and DRB1*0401-DQA1*03-DQB1*0302 haplotypes in the patient group The highest risk for type I diabetes was associated with the heterozygote DRB1*03/*04 genotype as largely reported, and DRB1*03/X and DRB1*04/Y genotypes conferred a significant, but much lower disease risk. Protection from type I diabetes revealed some peculiarities in Southeastern Brazilians: a lack of significant protecting effect of the DRB1*1501-DQA1*0102-DQB1*0602 haplotype, and an apparent protection conferred by the DRB1*13-DQB1*0301, DRB1*11-DQB1*0301, and DRB1*01-DQB1*0501 two-locus haplotypes. The risk to type I diabetes in the highly diversified Southeastern Brazilians evidenced specific information to the prediction of the disease in this region of the country.

Mycotic aneurysm of the thoracic aorta due to Aspergillus terreus: case report and review

Mycotic aneurysms of the aorta caused by fungi are uncommon. We describe an unusual case of aortic aneurysm infection caused by Aspergillus terreus, which most likely spread from an adjacent pulmonary focus. Successful treatment included partial pneumonectomy, resection of the aneurysm with graft repair, and prolonged sequential administration of amphotericin B and itraconazole. A review of the published experience with aortic aneurysms caused by Aspergillus species is also presented. When invasive aspergillosis is suspected in proximity to areas with major vascular structures in immunocompromised patients, further investigation to rule out vascular invasion may be warranted. If the diagnosis is confirmed, aggressive and prompt treatment with antifungal agents combined with surgical debridement is essential to improve outcome.

[Does heart sarcoma mimick lupus erythematosus and vasculitis? Report of 2 cases]

Primary heart tumors are rare. The most common one is myxoma. It may synthetize IL-6 and frequently shown systemic clinical manifestations that confuse the diagnosis. Primary heart sarcomas are even more rare, as far as we know they have been not associated with systemic illnesses. We observed two cases with a presumptive diagnosis of systemic lupus erythematosus who were identified as primary sarcomatous heart neoplasms after surgical excision.

Overnight lowering of free fatty acids with Acipimox improves insulin resistance and glucose tolerance in obese diabetic and nondiabetic subjects

Obesity is commonly associated with elevated plasma free fatty acid (FFA) levels, as well as with insulin resistance and hyperinsulinemia, two important cardiovascular risk factors. What causes insulin resistance and hyperinsulinemia in obesity remains uncertain. Here, we have tested the hypothesis that FFAs are the link between obesity and insulin resistance/hyperinsulinemia and that, therefore, lowering of chronically elevated plasma FFA levels would improve insulin resistance/hyperinsulinemia and glucose tolerance in obese nondiabetic and diabetic subjects. Acipimox (250 mg), a long-acting antilipolytic drug, or placebo was given overnight (at 7:00 P.M., 1:00 A.M., 7:00 A.M.) to 9 lean control subjects, 13 obese nondiabetic subjects, 10 obese subjects with impaired glucose tolerance, and 11 patients with type 2 diabetes. Euglycemic-hyperinsulinemic clamps and oral glucose tolerance tests (75 g) were performed on separate mornings after overnight Acipimox or placebo treatment. In the three obese study groups, Acipimox lowered fasting levels of plasma FFAs (by 60-70%) and plasma insulin (by approximately 50%). Insulin-stimulated glucose uptake during euglycemic-hyperinsulinemic clamping was more than twofold higher after Acipimox than after placebo. Areas under the glucose and insulin curves during oral glucose tolerance testing were both approximately 30% lower after Acipimox administration than after placebo. We conclude that lowering of elevated plasma FFA levels can reduce insulin resistance/hyperinsulinemia and improve oral glucose tolerance in lean and obese nondiabetic subjects and in obese patients with type 2 diabetes.

Influence of dietary protein content on Trypanosoma cruzi infection in germfree and conventional mice

Germfree (GF) and conventional (CV) mice were fed on diets containing 4.4, 13.2 or 26.4% of protein (weight/weight). CV mice fed on low protein diet did not gain weight during four weeks, whereas the protein deficient diet did not affect the growth of GF mice. After four weeks on these diets, the mice were inoculated with 5 x 10(3) trypomastigotes of Trypanosoma cruzi. The protein deficiency affected less the GF than the CV mice, according to the following parameters: weight gain, hemoglobin, plasma protein and albumin levels and water and protein contents of the carcass. Infection with T. cruzi produced a significant decrease in hemoglobin levels, red blood cell count, and water and protein contents in the carcass. This decrease was more pronounced in the GF mice. Histopathologically, there was no difference between the treatments in animals with the same microbiological status (GF or CV). However, the disease was more severe in the GF than in the CV mice.

Mechanism of the diabetogenic action of cyclosporin A

To investigate the mechanism of diabetogenic action of cyclosporin A (CsA), 7 male Wistar albino rats received 10 mg/kg/day of the drug for 4 weeks (CsA). The results were compared with controls (C); blood CsA levels measured weekly remained stable throughout the experiment (mean +/- SEM) (X = 2657.9+/-155.1 ng/ml). Intravenous glucose load (0.75 g/kg) performed after 2 weeks of CsA therapy showed glucose intolerance in treated animals as evaluated by the glucose area under the curve (CsA = 409.2+/-17.8 vs. C = 313.3+/-12.6 umol x ml(-1) x min(-1)) (p < 0.05) with insulin levels being similar in the two groups (CsA = 8603.9+/-1645.5 vs. C = 9571.9+/-828.5 pmol x ml(-1) x min(-1)). After 4 weeks of CsA administration, glucose intolerance was maintained (CsA = 398.6+/-35.6 vs. C = 301.7+/-23.0 umol x ml(-1) x min(-1)) (p < 0.05) associated with a significant decrease in insulin secretion (CsA = 4404.9+/-2392.0 vs. C = 10075.9+/-2861.0 pmol x ml(-1) x min(-1) (p < 0.05). These results suggest that CsA induced a state of insulin resistance preceding the failure of insulin secretion. After 4 weeks, the pancreatic insulin content was also decreased (CsA = 0.7+/-0.1 vs. C = 1.4+/-0.5 mU/mg) (p < 0.05). Maximal insulin binding to isolated adipocytes was not affected by CsA (CsA = 7.4+/-2.6 vs. C = 6.4+/-2.0%), although glucose transport and oxidation decreased after CsA treatment (p < 0.05). In conclusion, glucose intolerance induced by CsA in Wistar albino rats is due to decreased insulin production and impaired insulin action by a post-binding mechanism.

[Protein hydrolysate as a dietetic resource]

OBJECTIVE: The central goal of this paper was to study the application of beef meat and poultry (turkey and chicken) hydrolysates to the preparations used in our Brazilian current feeding practices. METHODS: The various kinds of meat were hydrolyzed with fresh pineapple under similar conditions to those daily used at home. The selection of three types of preparation was dependent on whether their contents included starch or gelatin and liquid, like soup, mousse and fruit-shake. Hydrolysate were added to the preparations as part of the liquid content of their recipes. The acceptability of the preparations was checked out by employing the hedonic-scale affective test with untrained tasters. Variance analysis and the Tukeýs test were performed with a 5% level of significance for the results.RESULTS: The selected recipes were the following: bitterroot soup, fruit and vegetable-shakes and grape mousse, all of them containing starch or gelatin as an element to camouflage the bitter taste of the aminoacids. The preparations were well accepted: approximately 76% of the tasters reported having liked the soup at least somewhat; as to the shakes, more than 50% gave positive answers, and as to the mousse, approximately 88% reported having liked it. There were no statistically significant differences (p< 0.05) concerning the application of the three hydrolysates in all the preparations tested. CONCLUSIONS: The use of hydrolysed meat to replace liquid content of recipes is highly practicable, requiring only an adequate selection of recipes and their ingredients, that should include starch and gelatin in order to get fully satisfactory products. These preparations might serve as a basis for other ones, adapted to each diet.

Oral glucose ingestion increases endurance capacity in normal and diabetic (type I) humans

The effects of an oral glucose administration (1 g/kg) 30 min before exercise on endurance capacity and metabolic responses were studied in 21 type I diabetic patients [insulin-dependent diabetes mellitus (IDDM)] and 23 normal controls (Con). Cycle ergometer exercise (55-60% of maximal O2 uptake) was performed until exhaustion. Glucose administration significantly increased endurance capacity in Con (112 +/- 7 vs. 125 +/- 6 min, P < 0.05) but only in IDDM patients whose blood glucose decreased during exercise (70.8 +/- 8.2 vs. 82.8 +/- 9.4 min, P < 0.05). Hyperglycemia was normalized at 15 min of exercise in Con (7.4 +/- 0.2 vs. 4.8 +/- 0.2 mM) but not in IDDM patients (12.4 +/- 0.7 vs. 15.6 +/- 0.9 mM). In Con, insulin and C-peptide levels were normalized during exercise. Glucose administration decreased growth hormone levels in both groups. In conclusion, oral glucose ingestion 30 min before exercise increases endurance capacity in Con and in some IDDM patients. In IDDM patients, in contrast with Con, exercise to exhaustion attenuates hyperglycemia but does not bring blood glucose levels to preglucose levels.

Human insulin allergy-immediate and late type III reactions in a long-standing IDDM patient

Human insulin allergy-immediate or late type III reaction-is a rare event. We report the case of a 33-year-old female patient with insulin-dependent diabetes mellitus for 25 years who presented, in the last 8 years, mild but generalized urticaria partially controlled with oral antihistamines. There was no improvement after changing from mixed beef-pork to human insulin. In the last 3 years another allergic manifestation began: small, localized, subdermal and painful non-erythematous nodules with central hematomas at injection sites, occurring 6-8 h after the insulin injection and lasting for 48 h. The following maneuvers had no benefit: (1) Human insulin (NPH or Lente) administered with dexametasone or xylocain locally, (2) Short acting human insulin with or without previous boiling, (3) Anti-histamine cetirizine dihydrochloride-10 mg/day. The allergic symptoms disappeared only after treatment with short acting human insulin (up to 100 U/day) associated to prednisone-40 mg/day and cetirizine dihydrochloride for 4 months. However, after stopping prednisone the urticaria reappeared and it was relieved with insulin desensitization. The pain at the site of injections persisted.

CONCLUSION

This long-standing IDDM patient presented two types of reactions to human insulin: the immediate type (systemic urticaria), treated with antihistamines and desensitization, and the Arthus' type III reaction (nodules and hematomas occurring 6-8 h after the insulin injection) that required glucocorticoid therapy for more than 4 months.

Factors favoring houseplant container infestation with Aedes aegypti larvae in Marília, São Paulo, Brazil

Since reinvasion of São Paulo State by the Aedes aegypti (L.) mosquito in 1985, flower pots and vases have been important larval habitats despite educational messages focusing on their control. The objectives of this study were to characterize flower pots and vases as larval habitats with respect to the quantities present and infested, the types of plants involved, and the specific locations of the mosquito larvae; to explore local names for houseplants; and to examine factors affecting acceptance of control measures. The results showed an average of more than four potential plant-related larval habitats per premises, of which only 0.4% were occupied by the vector. Plant-related containers represented 31% of all the containers with Aedes aegypti larvae. Although a sample of 126 respondents was able to list 105 different houseplant names, 49% of the positive plants were of two types: ferns and the ornamental plant Dieffenbachia avoena. The public's apparent unwillingness to accept recommended anti-aegypti control measures involving houseplants seems related to the relative rarity of aegypti larvae in the very common houseplant containers, the control program's poor credibility as a source of information about plants, and a perception that the recommended control measures are harmful to plants. An intervention currently being planned for dengue control will use educational material that refers specifically to those plants whose containers are most commonly found to harbor aegypti larvae; it will also utilize information sources such as botanists with greater credibility regarding plants; and it will set out alternative plant care recommendations that are more likely to appeal as beneficial to the plants and that will stand a better chance of being accepted.

Insulin resistance in limb and trunk partial lipodystrophy (type 2 Köbberling-Dunnigan syndrome)

We studied insulin action in two patients with limb and trunk partial lipodystrophy with hirsutism and acanthosis nigricans. Glucose was normal in one of the patients and slightly above normal in the other during an oral glucose tolerance test (OGTT). An intravenous glucose tolerance test (IVGTT) was normal in both patients. Basal and glucose-stimulated insulin levels were elevated in both the OGTT and IVGTT in both patients. The response of plasma glucose to exogenously administered insulin was decreased. A euglycemic-hyperinsulinemic clamp performed in patient no. 2 indicated insulin resistance, which was not corrected by reducing the increased basal level of serum free fatty acids (FFAs). Binding of insulin to neck adipocytes was normal in both subjects, but glucose transport and oxidation in these cells was impaired. Insulin binding to abdominal adipocytes was increased in one patient whose adipocytes displayed higher glucose transport at low insulin concentrations. Glucose oxidation was decreased in abdominal adipocytes of both patients. We conclude that insulin resistance in Köbberling-Dunnigan type 2 partial lipodystrophy is not related to an alteration of the insulin molecule or to changes in insulin binding, but is more likely associated with a postreceptor defect, since glucose oxidation was impaired in adipocytes of the neck and abdomen.

Disposable containers as larval habitats for Aedes aegypti in a city with regular refuse collection: a study in Marília, São Paulo State, Brazil

In Marília, Brazil, refuse is collected at least every other day, yet non-useful, non-returnable containers such as cans, plastic bottles and tires account for almost half of the container habitats found positive for the Aedes aegypti mosquito. A study was therefore conducted to investigate why these containers exist despite regular refuse collection and a high level of awareness of dengue prevention, and how the control program could most effectively respond. Differing community perceptions as to what constitutes refuse were found to lead people to store a variety of containers in their yard. Other dimensions of the problem include the presence of informal refuse collectors in search of saleable materials, and dumping of refuse in vacant lots and along roads. An intervention based on these data will involve the informal refuse collectors in implementation of a community-based recycling project.

Protective effect of Saccharomyces boulardii against the cholera toxin in rats

The effect of orogastric administration of Saccharomyces boulardii on the anatomopathological aspect of the jejunal villi was studied in male Fischer rats (weighing about 40 g) orogastrically infected with a culture of Vibrio cholerae. Experimental and control groups received lyophilized S. boulardii (25 mg suspended in 0.5 ml saline) or 0.5 ml saline, respectively, three times a day for 10 days by gastric intubation. On day 5 of treatment, 0.5 ml of a culture of V. cholerae containing 10(8) viable cells was inoculated by gastric intubation into both groups. Histopathological examination of the jejunal mucosa showed extensive lesions of the superficial epithelium of the villi from the control group whereas few lesions of this superficial epithelium were observed in the experimental group. These data show that the inhibition of the action of the cholera toxin on enterocytes by S. boulardii suggested by recent results in vitro can be demonstrated in vivo.

Endocrine and psychological evaluation of women with recent weight gain

A group of 13 consecutive regularly menstruating women who gained at least 5 kg the previous year (Group I) was compared to a control group of similar age, parity, and social class (Group II). The two groups were similar in estimated and observed food intakes; pre- and postprandial gastrin levels; hourly 24-h profiles of cortisol and insulin; urinary cortisol and 17-hydroxycorticosteroids. Group I had higher serum prolactin concentrations at all times than Group II (mean values 14.60 micrograms/l vs. 8.84 micrograms/l; p = .0121). Galactorrhea was observed in 5 women from Group I and in none of the women from Group II (p < .05). Group I also differed from Group II in a higher incidence of meaningful life-events the year preceding the study, higher prevalence of sexual dysfunction (9/13 vs. 4/13; p < .01) and higher indexes (p < .05) of several parameters in the MMPI and SCL 90. Median serum cortisol and prolactin concentrations were negatively correlated, both in Group I (R = -.669; p = .012) and in the whole sample (R = -.453; p = .0298). It is suggested that the rapid weight gain is part of a neuroendocrine response to environmental stimuli also characterized by hyperprolactinemia. The significant negative correlation between serum prolactin and cortisol indicates that this response differs from, and is possibly an alternative to, the sympathoadrenal "stress" response.

The effect of iron nutritional status on Trypanosoma cruzi infection in germfree and conventional mice

1. Conventional (CV) and gnotobiotic (GN) female CFW mice were infected with the Y strain of Trypanosoma cruzi. 2. After infection, both CV and GN groups received injections of iron-dextran or desferrioxamine. Non-injected mice served as controls. 3. The parasitemia was more intense in iron-dextran-treated mice. 4. The iron levels in serum, liver, and spleen were: (a) not decreased by desferrioxamine and (b) increased by iron-dextran treatments. 5. An increase in leukocyte numbers was observed in all GN and CV groups after infection. 6. There was no difference in total iron binding capacity (TIBC) and iron saturation transferrin (IST) between GN and CV mice before infection. 7. In CV groups, after infection, TIBC was decreased whereas the levels of IST were increased; in GN the opposite occurred. 8. Trypanosome-specific IgG and IgM antibody levels were raised in the GN group but not in the CV group.

The effect of chronic ingestion of ethanol on modulation of granulomatous inflammation in experimental schistosomiasis in mice

We studied the role of ethanol on the modulation of liver granulomata around Schistosoma mansoni eggs in mice. Albino mice, receiving 7% ethanol as the sole drinking liquid, at 60 and 90 days post-infection, presented smaller granulomata than controls did, when sacrificed at 120 days post-infection. No differences in diameters could be observed, when ethanol was given 4 months before up to 120 days after infection. The results suggested that modulation of schistosome granulomata by ethanol ingestion varies with time and duration of drug consumption.