Experimental investigation of the chaotification of a Duffing-like electronic oscillator under two-frequency excitation.

Two-frequency excitation has recently emerged as an efficient method to generate strong chaotification of Duffing and Duffing-like dynamical systems with both single- and double-well potentials. For the systems with a double-well potential, large continuous regions with robust chaos (chaotic attractor insensitive to changes in the system parameters) have been predicted to exist when the method is applied. Motivated by these theoretical results, in this work, we investigate experimentally the chaotification under two-frequency excitation of a simple electronic circuit analogous to the double-well Duffing oscillator. The experimental results confirm the theoretical expectations, and a strong chaotification is observed. Evidences are also presented that the chaotic attractor is robust. Therefore, the work establishes experimentally the two-frequency excitation as a simple and reliable method of chaotification. Furthermore, because of its ease of fabrication, the experimental results turn the particular circuit considered in this work into an interesting practical alternative as a reliable source of continuous-time chaotic signals.

Opinion inertia and coarsening in the persistent voter model.

We consider the persistent voter model (PVM), a variant of the voter model (VM) that includes transient, dynamically induced zealots. Due to peer reinforcement, the internal confidence η_{i} of a normal voter increases in steps of size Δη. Once it surpasses a given threshold, it becomes a zealot. Its opinion remains frozen until enough interactions with the opposing opinion occur, resetting its confidence. No longer a zealot, the regular voter may change opinion once again. This mechanism of opinion inertia, though simplified, is responsible for an effective surface tension, and the PVM exhibits a crossover from a fluctuation-driven dynamics, as in the VM, to a curvature-driven one, akin to the Ising model at low temperature. The average time τ to attain consensus is nonmonotonic with respect to Δη and reaches a minimum at Δη_{min}. In this paper we elucidate the mechanisms that accelerate the system towards consensus close to Δη_{min}. Near the crossover at Δη_{min}, the intermediate region around the domains where the regular voters accumulate (the active region, AR) is large. The surface tension, albeit small, is sufficient to maintain the shape and reduce the domain fragmentation. The large size of the AR in the region of Δη_{min} has two important effects that accelerate the dynamics. First, it dislodges the zealots within the bulk of the domains. Secondly, it maximally suppresses the formation of slowly evolving stripes typical in Ising-like models. This suggests the importance of understanding the role of the AR, where opinion changes are facilitated, and the interplay between regular voters and zealots in disrupting polarized states.

Ketogenic propensity is differentially related to lipid-induced hepatic and peripheral insulin resistance.

AIM: Determine the ketogenic response (ß-hydroxybutyrate, a surrogate of hepatic ketogenesis) to a controlled lipid overload in humans. METHODS: In total, nineteen young, healthy adults (age: 28.4 ± 1.7 years; BMI: 22.7 ± 0.3 kg/m2 ) received either a 12 h overnight lipid infusion or saline in a randomized, crossover design. Plasma ketones and inflammatory markers were quantified by colorimetric and multiplex assays. Hepatic and peripheral insulin sensitivity was assessed by the hyperinsulinemic-euglycemic clamp. Skeletal muscle biopsies were obtained to quantify gene expression related to ketone body metabolism and inflammation. RESULTS: By design, the lipid overload-induced hepatic (50%, p < 0.001) and peripheral insulin resistance (73%, p < 0.01) in healthy adults. Ketones increased with hyperlipidemia and were subsequently reduced with hyperinsulinemia during the clamp procedure (Saline: Basal = 0.22 mM, Insulin = 0.07 mM; Lipid: Basal = 0.78 mM, Insulin = 0.51 mM; 2-way ANOVA: Lipid p < 0.001, Insulin p < 0.001, Interaction p = 0.07). In the saline control condition, ketones did not correlate with hepatic or peripheral insulin sensitivity. Conversely, in the lipid condition, ketones were positively correlated with hepatic insulin sensitivity (r = 0.59, p < 0.01), but inversely related to peripheral insulin sensitivity (r = -0.64, p < 0.01). Hyperlipidemia increased plasma inflammatory markers, but did not impact skeletal muscle inflammatory gene expression. Gene expression related to ketone and fatty acid metabolism in skeletal muscle increased in response to hyperlipidemia. CONCLUSION: This work provides important insight into the role of ketones in human health and suggests that ketone body metabolism is altered at the onset of lipid-induced insulin resistance.

Entropy of rigid k-mers on a square lattice.

Using the transfer matrix technique, we estimate the entropy for a gas of rods of sizes equal to k (named k-mers), which cover completely a square lattice. Our calculations were made considering three different constructions, using periodical and helical boundary conditions. One of those constructions, which we call profile method, was based on the calculations performed by Dhar and Rajesh to obtain a lower limit to the entropy of very large chains placed on the square lattice. This method, so far as we know, was never used before to define the transfer matrix, but turned out to be very useful, since it produces matrices with smaller dimensions than those obtained using the usual approach. Our results were obtained for chain sizes ranging from k=2 to k=10 and they are compared with results already available in the literature. In the case of dimers (k=2) our results are compatible with the exact result. For trimers (k=3), recently investigated by Ghosh et al., also our results were compatible, with the same happening for the simulational estimates obtained by Pasinetti et al. in the whole range of rod sizes. Our results are also consistent with the asymptotic expression for the behavior of the entropy as a function of the size k, proposed by Dhar and Rajesh for very large rods (k≫1).

Does the presence of third molars during sagittal split mandibular ramus osteotomy favour complications? Systematic review and meta-analysis.

The aim of this systematic review and meta-analysis was to assess whether the presence of inferior third molars during sagittal split mandibular ramus osteotomy increases the risk of intraoperative and postoperative complications. The PRISMA protocol was followed in this study, and the review was registered in the PROSPERO database (CRD42020147642). A search was conducted in the MEDLINE (PubMed), Web of Science, Cochrane Central, and Scopus databases on November 1, 2021. Nineteen articles were included, and the variables analysed were unfavourable fractures, infection, neurosensory disturbance, removal of osteosynthesis material, and duration of surgery. Meta-analyses were performed for the variables unfavourable fractures (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.58-1.57, P = 0.84), infection (RR 0.75, 95% CI 0.48-1.18, P = 0.21), and neurosensory disturbance (RR 1.55, 95% CI 0.61-3.91, P = 0.35); no statistically significant difference in the risk of these variables was found between the groups with and without third molars. The third molars did not increase the need to remove fixation material, but increased the surgery time. The presence of the third molar during sagittal split mandibular ramus osteotomy appears not to increase the risk of intraoperative and postoperative complications. The results presented here must be interpreted with caution due to the heterogeneity presented by the observational studies included.

Curvature-driven growth and interfacial noise in the voter model with self-induced zealots.

We introduce a variant of the voter model in which agents may have different degrees of confidence in their opinions. Those with low confidence are normal voters whose state can change upon a single contact with a different neighboring opinion. However, confidence increases with opinion reinforcement, and above a certain threshold, these agents become zealots, irreducible agents who do not change their opinion. We show that both strategies, normal voters and zealots, may coexist (in the thermodynamical limit), leading to competition between two different kinetic mechanisms: curvature-driven growth and interfacial noise. The kinetically constrained zealots are formed well inside the clusters, away from the different opinions at the surfaces that help limit their confidence. Normal voters concentrate in a region around the interfaces, and their number, which is related to the distance between the surface and the zealotry bulk, depends on the rate at which the confidence changes. Despite this interface being rough and fragmented, typical of the voter model, the presence of zealots in the bulk of these domains induces a curvature-driven dynamics, similar to the low temperature coarsening behavior of the nonconserved Ising model after a temperature quench.

Skepticism and rumor spreading: The role of spatial correlations.

Critical thinking and skepticism are fundamental mechanisms that one may use to prevent the spreading of rumors, fake news, and misinformation. We consider a simple model in which agents without previous contact with the rumor, being skeptically oriented, may convince spreaders to stop their activity or, once exposed to the rumor, decide not to propagate it as a consequence, for example, of fact checking. We extend a previous, mean-field analysis of the combined effect of these two mechanisms, active and passive skepticism, to include spatial correlations. This can be done either analytically, through the pair approximation, or simulating an agent-based version on diverse networks. Our results show that while in mean field there is no coexistence between spreaders and susceptibles (although, depending on the parameters, there may be bistability depending on the initial conditions), when spatial correlations are included, because of the protective effect of the isolation provided by removed agents, coexistence is possible.

Using nanoresonators with robust chaos as hardware random number generators.

In this paper, we investigate theoretically the potential of a nanoelectromechanical suspended beam resonator excited by two-external frequencies as a hardware random number generator. This system exhibits robust chaos, which is usually required for practical applications of chaos. Taking advantage of the robust chaotic oscillations, we consider the beam position as a possible random variable and perform tests to check its randomness. The beam position collected at fixed time intervals is used to create a set of values that is a candidate for a random sequence of numbers. To determine how close to a random sequence this set is, we perform several known statistical tests of randomness. The performance of the random sequence in the simulation of two relevant physical problems, the random walk and the Ising model, is also investigated. An excellent overall performance of the system as a random number generator is obtained.

DNA methylation pattern changes following a short-term hypocaloric diet in women with obesity.

BACKGROUND/OBJECTIVES: We aimed to investigate the effects of short-term hypocaloric diet-induced weight loss on DNA methylation profile in leukocytes from women with severe obesity. METHODS: Eleven women with morbid obesity (age: 36.9 ± 10.3 years; BMI: 58.5 ± 10.5 kg/m2) were assessed before and after 6 weeks of a hypocaloric dietary intervention. The participants were compared with women of average weight and the same age (age: 36.9 ± 11.8 years; BMI: 22.5 ± 1.6 kg/m2). Genome-wide DNA methylation analysis was performed in DNA extracted from peripheral blood leukocytes using the Infinium Human Methylation 450 BeadChip assay. Changes (Δß) in the methylation level of each CpGs were calculated. A threshold with a minimum value of 10%, p < 0.001, for the significant CpG sites based on Δß and a false discovery rate of <0.05 was set. RESULTS: Dietary intervention changed the methylation levels at 16,064 CpG sites. These CpGs sites were related to cancer, cell cycle-related, MAPK, Rap1, and Ras signaling pathways. However, regardless of hypocaloric intervention, a group of 878 CpGs (related to 649 genes) remained significantly altered in obese women when compared with normal-weight women. Pathway enrichment analysis identified genes related to the cadherin and Wnt pathway, angiogenesis signaling, and p53 pathways by glucose deprivation. CONCLUSION: A short-term hypocaloric intervention in patients with severe obesity partially restored the obesity-related DNA methylation pattern. Thus, the full change of obesity-related DNA methylation patterns could be proportional to the weight-loss rate in these patients after dietary interventions.

Maintenance enteral electrolyte solutions for neonatal calves: sodium acetate and osmolarity effects / Soluções eletrolíticas enterais de manutenção para bezerros neonatos: efeitos do acetato de sódio e da osmolaridade

The use of hypotonic electrolytic solutions in enteral fluid therapy is still understudied in calves. The objective of the present study was to evaluate the effects of maintenance enteral electrolytic solutions with different concentrations of sodium acetate and different osmolarities in calves. For this, 18 Holstein calves, six male and 12 female, 20 days old and weighing around 52kg, were used. The animals were randomly divided into three groups and each group received one of the treatments. The three electrolytic solutions contained the same components in different concentrations, resulting in a hyposmotic, an isosmotic and a hyperosmotic solution. Each animal was maintained in enteral fluid therapy for 12 hours with infusion rate of 15mL kg-1 h-1. Abdominal circumference, body weight, feces consistency, glucose and plasma lactate, pH, pCO2, HCO- 3 and BE were measured at the following times: T0h, T6h, T12h and T24h. The hyposmotic solution did not generate the onset of diarrhea, while the isosmotic and the hyperosmotic did. Regardless of the dose used, acetate did not cause metabolic alkalosis in the evaluated animals. The results suggest that the use of hyposmotic solution in diarrheic calves, dehydrated and without metabolic acidosis, may be clinically important.(AU)

O uso de soluções eletrolíticas hipotônicas na hidratação enteral ainda é pouco estudado em bezerros. O objetivo do presente estudo foi avaliar os efeitos de soluções eletrolíticas enterais de manutenção com diferentes concentrações de acetato de sódio e diferentes osmolaridades em bezerros. Para isso, foram utilizados 18 bezerros, seis machos e 12 fêmeas, holandeses, com 20 dias de nascidos e pesando por volta dos 52kg. Os animais foram divididos aleatoriamente em três grupos e cada grupo recebeu um dos tratamentos. As três soluções eletrolíticas continham os mesmos componentes, mas em diferentes concentrações, resultando em uma solução hiposmótica, uma isosmótica e uma hiperosmótica. Cada animal foi mantido em hidratação enteral durante 12 horas com taxa de infusão de 15mL kg-1h-1. Foram aferidos perímetro abdominal, peso corporal, consistência das fezes, glicose e lactato plasmático, pH, pCO2, HCO- 3 e excesso de base nos seguintes tempos: T0h, T6h, T12h e T24h. A solução hiposmótica não gerou aparecimento de diarreia, enquanto a isosmótica e a hiperosmótica geraram. Independentemente da dose utilizada, o acetato não causou alcalose metabólica nos animais avaliados. Os resultados sugerem que o uso da solução hiposmótica em bezerros diarreicos, desidratados e sem acidose metabólica, pode ser clinicamente importante.(AU)

Hematological and biochemical profiles of Mangalarga Marchador mares in the transition period bred on pasture / Perfis hematológico e bioquímico de éguas da raça Mangalarga Marchador no período de transição mantidas a pasto

The present study aimed to evaluate the effects of the transition period on hematological and biochemical constituents in Mangalarga Marchador mares. Forty-eight mares were used to form a maintenance group (MG) and transition group (TG), formed by pregnant mares and, after delivery, infants. Blood samples were collected at the following times: T-60 (60 d pre-delivery), T-30 (30 d pre-delivery), T-15 (15 d pre-delivery), T0 (first 6h post-delivery), T15 (15 d post-delivery), T30 (30 d post-delivery), and T60 (60 d post-delivery). The TG had lower values (P< 0.05) of red blood cells, hematocrit and hemoglobin at T0, T15, T30 and T60 times than MG. The mean corpuscular volume was lower in MG (P< 0.05) than in TG (T0, T15, T30 and T60) and mean corpuscular hemoglobin concentration was higher (P< 0.05) in MG than in TG (T15, T30 and T60). On the other hand, the diameter distribution of red blood cells presented a lower value (P< 0.05) in MG than in TG (T15 and T30). Mares in transition period presented regenerative anemia. The results demonstrate physiological metabolic variations of different intensities during pregnancy, delivery and early lactation.(AU)

O presente estudo teve como objetivo avaliar os efeitos do período de transição em constituintes hematológicos e bioquímicos em éguas Mangalarga Marchador. Foram utilizadas 48 éguas para formar um grupo de manutenção (GM) e um grupo de transição (GT), composto por éguas gestantes e, após o parto, lactentes. Amostras de sangue foram coletadas nos seguintes tempos: T-60 (60 dias pré-parto), T-30 (30 dias pré-parto), T-15 (15 dias pré-parto), T0 (seis primeiras horas pós-parto), T15 (15 dias pós-parto), T30 (30 dias pós-parto) e T60 (60 dias pós-parto). O GT apresentou valores menores (P<0,05) de hemácias, hematócrito e hemoglobina, nos tempos T0, T15, T30 e T60, do que o GM. O volume corpuscular médio foi menor no GM (P<0,05) do que no GT (T0, T15, T30, T60) e a concentração corpórea de hemoglobina corpórea foi maior (P<0,05) no GM do que no GT (T15, T30, T60). Por outro lado, a distribuição do diâmetro dos eritrócitos apresentou um valor menor (P<0,05) no GM do que no GT (T15 e T30). Éguas em período de transição apresentam anemia regenerativa. Os resultados demonstram variações metabólicas de diferentes intensidades durante a gestação, o parto e o início de lactação.(AU)

Prediction of robust chaos in micro and nanoresonators under two-frequency excitation.

Robust chaos in a dynamical system is characterized by the persistence of the chaotic attractor with changes in the system parameters and is generally required in practical applications based upon physical sources of chaos. However, for applications that rely upon continuous time chaotic signals, there are now very few alternatives of dynamical systems with robust chaos that could be used. In this context, it is important to find a new dynamical system and, particularly, new physical systems that present robust chaos. In this work, we show through simulations that a relevant physical system, suspended beam micro and nanoelectromechanical resonators, can present robust chaos when excited by two distinct frequencies. To demonstrate the existence of robust chaos in the system, we perform an extensive numerical analysis, showing that the attractor is unique and changes smoothly in a large region of the relevant physical parameter space. We find that the robustness of the chaotic dynamics depends crucially on the dissipation, which must be sufficiently small. When the dissipation is small, we find a large range of frequencies, frequency ratios, and applied voltages where robust chaos is observed. These findings turn these systems into viable and strong candidates for practical applications since the chaotic dynamics becomes quite insensitive to fabrication tolerances, changes in the physical parameters induced by the environment, and aging.

Hypotonic enteral electrolyte solutions administered by nasoesophageal tube in continuous flow in dogs dehydrated by water restriction: Part 1 / Soluções eletrolíticas enterais hipotônicas administradas por sonda nasoesofágica em fluxo contínuo em cães desidratados por restrição hídrica: Parte 1

The present study assessed and compared the effects of hypotonic enteral electrolyte solutions administered by nasoesophageal tube in continuous flow in dogs submitted to water restriction on packed cell volume; total serum protein and serum osmolarity concentrations; blood volume; plasma glucose and lactate levels; blood gas analysis, anion gap, and strong ion difference. Six adult dogs were used (four males and two females). All animals were submitted to both proposed treatments in a crossover design 6×2. The treatments were as follows: ESmalt consisting of 5g sodium chloride, 1g potassium chloride, 1g calcium acetate, 0.2g magnesium pidolate, and 9.6g maltodextrin that were diluted in 1.000mL water (measured osmotic concentration of 215mOsm L−1) and ESdext consisting of 5g sodium chloride, 1g potassium chloride, 1g calcium acetate, 0.2g magnesium pidolate, and 9.6g dextrose that were diluted in 1.000mL water (measured osmotic concentration of 243mOsm L−1). All solutions were administered at 15ml kg−1 h−1 for 4 hours. Both solutions increased the plasma volume in dehydrated dogs without causing adverse effects. However, ESmalt was more effective in promoting the increase in blood volume.(AU)

O presente estudo avaliou e comparou os efeitos de soluções eletrolíticas enterais hipotônicas, administradas por sonda nasoesofágica em fluxo contínuo em cães submetidos a restrição hídrica, sobre o hematócrito, proteínas totais séricas, osmolaridade sérica, volemia, glicose e lactato plasmáticos, hemogasometria, ânion gap e DIF. Foram utilizados seis cães adultos (quatro machos e duas fêmeas). Todos os animais foram submetidos aos dois tratamentos propostos, em um delineamento crossover 6×2. Os tratamentos foram os seguintes: SEmalt - 5g de cloreto de sódio, 1g de cloreto de potássio, 1g de acetato de cálcio, 0,2g de pidolato de magnésio e 9,6g de maltodextrina, diluídos em 1.000mL de água (osmolaridade mensurada: 215mOsm L -1 ); SEdext - 5g de cloreto de sódio, 1g de cloreto de potássio, 1g de acetato de cálcio, 0,2g de pidolato de magnésio e 9,6g de dextrose, diluídos em 1.000mL de água (osmolaridade mensurada: 243mOsm L -1 ). Todas as soluções foram administradas no volume de 15mL kg -1 hora -1 , durante quatro horas, em fluxo contínuo. Ambas as soluções aumentaram o volume plasmático em cães desidratados, sem gerar o aparecimento de efeitos adversos. Porém, a SEmalt foi mais eficaz em promover a expansão da volemia.

A Comparative Study of Hummingbirds and Chickens Provides Mechanistic Insight on the Histidine Containing Dipeptide Role in Skeletal Muscle Metabolism.

Histidine containing dipeptides (HCDs) have numerous ergogenic and therapeutic properties, but their primary role in skeletal muscle remains unclear. Potential functions include pH regulation, protection against reactive oxygen/nitrogen species, or Ca2+ regulation. In recognition of the challenge of isolating physiological processes in-vivo, we employed a comparative physiology approach to investigate the primary mechanism of HCD action in skeletal muscle. We selected two avian species (i.e., hummingbirds and chickens), who represented the extremes of the physiological processes in which HCDs are likely to function. Our findings indicate that HCDs are non-essential to the development of highly oxidative and contractile muscle, given their very low content in hummingbird skeletal tissue. In contrast, their abundance in the glycolytic chicken muscle, indicate that they are important in anaerobic bioenergetics as pH regulators. This evidence provides new insights on the HCD role in skeletal muscle, which could inform widespread interventions, from health to elite performance.

Discriminating between virilizing ovary tumors and ovary hyperthecosis in postmenopausal women: clinical data, hormonal profiles and image studies.

BACKGROUND: The presence of virilizing signs associated with high serum androgen levels in postmenopausal women is rare. Virilizing ovarian tumors (VOTs) and ovarian stromal hyperthecosis (OH) are the most common etiologies in virilized postmenopausal women. The differential diagnosis between these two conditions is often difficult. OBJECTIVE: To evaluate the contribution of clinical features, hormonal profiles and radiological studies to the differential diagnosis of VOT and OH. DESIGN: A retrospective study. SETTING: A tertiary center. MAIN OUTCOME MEASURES: Clinical data, hormonal status (T, E2, LH and FSH), pelvic images (transvaginal sonography and MRI) and anatomopathology were reviewed. PATIENTS: Thirty-four postmenopausal women with a diagnosis of VOT (13 women) and OH (21 women) were evaluated retrospectively. RESULTS: Clinical signs of hyperandrogenism were more prevalent in the VOT group than the OH group. Although the VOT group showed higher T and E2 levels and lower gonadotropin levels than the OH group, a great overlap occurred among the hormone levels. A pelvic MRI provided an accurate differentiation of these two conditions. CONCLUSION: In this group of patients, the main features contributing to the differential diagnosis of VOT and OH were serum levels of testosterone and gonadotropins and the presence of an ovarian nodule identified on the MRI. Although the association of clinical, hormonal and radiological features contributes to the differential diagnosis of these two conditions, histopathological analysis remains the gold standard for the diagnosis of ovarian hyperandrogenism in postmenopausal women.

Grand-canonical solution of semiflexible self-avoiding trails on the Bethe lattice.

We consider a model of semiflexible interacting self-avoiding trails (sISATs) on a lattice, where the walks are constrained to visit each lattice edge at most once. Such models have been studied as an alternative to the self-attracting self-avoiding walks (SASAWs) to investigate the collapse transition of polymers, with the attractive interactions being on site as opposed to nearest-neighbor interactions in SASAWs. The grand-canonical version of the sISAT model is solved on a four-coordinated Bethe lattice, and four phases appear: non-polymerized (NP), regular polymerized (P), dense polymerized (DP), and anisotropic nematic (AN), the last one present in the phase diagram only for sufficiently stiff chains. The last two phases are dense, in the sense that all lattice sites are visited once in the AN phase and twice in the DP phase. In general, critical NP-P and DP-P transition surfaces meet with a NP-DP coexistence surface at a line of bicritical points. The region in which the AN phase is stable is limited by a discontinuous critical transition to the P phase, and we study this somewhat unusual transition in some detail. In the limit of rods, where the chains are totally rigid, the P phase is absent and the three coexistence lines (NP-AN, AN-DP, and NP-DP) meet at a triple point, which is the endpoint of the bicritical line.

Exercise training, creatine supplementation, and bone health in ovariectomized rats.

UNLABELLED: Evidence suggests that creatine may have some beneficial effects on bone. The study aimed to investigate the effects of exercise alone or combined with creatine on bone health in ovariectomized rats. Findings show that exercise, but not creatine, has an important role in improving bone health. INTRODUCTION: The aim of this study was to investigate the effects of exercise training alone or combined with creatine supplementation on bone health parameters in ovariectomized rats. METHODS: Wistar rats were randomly allocated into one of five groups: (i) sham-operated, (ii) ovariectomized non-trained placebo-supplemented, (iii) ovariectomized non-trained creatine-supplemented, (iv) ovariectomized exercise-trained placebo-supplemented, and (v) ovariectomized exercise-trained creatine-supplemented. Downhill running training and/or creatine supplementation (300 mg/kg body weight) were administered for 12 weeks. Bone mineral content (BMC), bone mineral density (BMD), and biomechanical and histomorphometric parameters were assessed. RESULTS: No interaction effects were observed for BMC and BMD at whole body, femur, and lumbar spine (p > 0.05). Importantly, a main effect of training was detected for whole body BMC and BMD (p = 0.003 and p < 0.001, respectively), femoral BMC and BMD (p = 0.005 and p < 0.001, respectively), and lumbar spine BMC and BMD (p < 0.001 and p < 0.001, respectively), suggesting that the trained animals had higher bone mass, irrespective of creatine supplementation. Main effects of training were also observed for maximal load (p < 0.001), stiffness (p < 0.001), and toughness (p = 0.046), indicating beneficial effects of exercise training on bone strength. Neither a main effect of supplementation nor an interaction effect was detected for biomechanical parameters (p > 0.05). No main or interaction effects were observed for any of the histomorphometric parameters evaluated (p > 0.05). CONCLUSIONS: Exercise training, but not creatine supplementation, attenuated ovariectomy-induced bone loss in this rat model.

Asymptotic behavior of the entropy of chains placed on cylinders.

By using the transfer matrix approach, we investigate the asymptotic behavior of the entropy of flexible chains with M monomers each placed on strips with periodic boundary conditions (cylinders). In the limit of high density of monomers, we study the behavior of the entropy as a function of the density of monomers and the width of the strip, inspired by recent analytical studies of this problem for the particular case of dimers (M=2). We obtain the entropy in the asymptotic regime of high densities for chains with M=2,...,9 monomers, as well as for the special case of polymers, where M-->infinity, and find that the results show a regular behavior similar to the one found analytically for dimers. We also verify that in the low-density limit the mean-field expression for the entropy is followed by the results from our transfer matrix calculations.

Long-term follow-up of co-infected HIV and Trypanosoma cruzi Brazilian patients.

Three cases of Trypanosoma cruzi-HIV co-infected haemophiliacs are described. Parasitological (xenodiagnosis, haemoculture, PCR) and immunological (CD4+ and CD8+ T cell counts, in vitro lymphoproliferative responses) studies were performed. Hybridization of isolated parasites with a specific probe confirmed the T. cruzi aetiology. We observed that despite the high parasitaemia, no clinical or parasitological evidence of T. cruzi reactivation was detected. CD4+ T cells decreased with time in two patients and the lymphocyte proliferative response to T. cruzi was very low in all patients. These data suggest that T. cruzi infection may have a long silent course in immunosuppressed HIV patients. Therefore, this parasitic infection should be investigated in any AIDS patient coming from areas endemic for Chagas' disease.

[Hereditary hemochromatosis]. / Hemocromatose Hereditária.

Hereditary hemochromatosis is an inherited autosomal recessive disease, associated to a mutation in the recently described HFE gene, which is located on the short arm of chromosome 6. The product of this gene combines with the beta-2-microglobulin and the ferritin receptor, and regulates the iron absorption in the small intestine crypt cells. It is possible that the mutation may cause the increased iron uptake by the intestinal cells. The disease is very much common in men after the forties, and its expression is influenced by concomitant alcoholism, iron rich diet, oral and parenteral iron administration, menstrual blood loss or abnormal hemorrhages, blood donations, pregnancy, lactation, and iron malabsorption clinical conditions, like celiac disease. Many patients are asymptomatic, and the diagnosis may be suspected by hepatomegaly of unknown cause, abnormal iron metabolism tests, increased serum aminotransferase levels, diabetes mellitus, and anonymous arthropathy. Less commonly hereditary hemochromatosis presented by symptoms and signs of chronic liver disease, or by the classic triad described by Trousseau skin pigmentation, hepatomegaly and diabetes mellitus. The diagnosis is confirmed by the increased serum ferritin levels and transferrin saturation, and the stainable iron in hepatocytes, measured by scale devised by Scheuer et al, or the measurement of the hepatic iron. The C282Y mutation was found in 64 to 100% of patients; eventually, subjects with hepatic iron overload identical to hereditary hemochromatosis has no mutation, and homozygous for the C282Y mutation do not express iron overload. Iron is best and quickly removed by weekly or twice-weekly phlebotomy of 500 ml, containing approximately 250 mg iron. One to 3 years of weekly phlebotomy may be required to reduce stores to normal. As a guide to long-term maintenance therapy, is recommended phlebotomy every 3 months and the serum ferritin level should be maintained by less than 50 ng/ml.