Pivotal role of inosine triphosphate pyrophosphatase in maintaining genome stability and the prevention of apoptosis in human cells

Pure nucleotide precursor pools are a prerequisite for high-fidelity DNA replication and the suppression of mutagenesis and carcinogenesis. ITPases are nucleoside triphosphate pyrophosphatases that clean the precursor pools of the non-canonical triphosphates of inosine and xanthine. The precise role of the human ITPase, encoded by the ITPA gene, is not clearly defined. ITPA is clinically important because a widespread polymorphism, 94C>A, leads to null ITPase activity in erythrocytes and is associated with an adverse reaction to thiopurine drugs. We studied the cellular function of ITPA in HeLa cells using the purine analog 6-N hydroxylaminopurine (HAP), whose triphosphate is also a substrate for ITPA. In this study, we demonstrate that ITPA knockdown sensitizes HeLa cells to HAP-induced DNA breaks and apoptosis. The HAP-induced DNA damage and cytotoxicity observed in ITPA knockdown cells are rescued by an overexpression of the yeast ITPase encoded by the HAM1 gene. We further show that ITPA knockdown results in elevated mutagenesis in response to HAP treatment. Our studies reveal the significance of ITPA in preventing base analog-induced apoptosis, DNA damage and mutagenesis in human cells. This implies that individuals with defective ITPase are predisposed to genome damage by impurities in nucleotide pools, which is drastically augmented by therapy with purine analogs. They are also at an elevated risk for degenerative diseases and cancer.     

Neural networks learning with sliding mode control: the sliding mode backpropagation algorithm

Based on the classical backpropagation weight update equations, sliding mode control theory is introduced as a technique to adapt weights of a multi-layer perceptron. As will be demonstrated, the introduction of sliding mode has resulted in a much faster version of the standard backpropagation. The results show also that the proposed algorithm presents some important features of sliding mode control, which are robustness and high speed of learning. In addition to that, this paper shows also how control theory can be applied to train neural networks.     

In vitro chloroquine resistance modulation study on fresh isolates of Brazilian Plasmodium falciparum: intrinsic antimalarial activity of phenothiazine drugs

Phenothiazine drugs - fluphenazine, chlorpromazine, methotrimeprazine and trifluoperazine - were evaluated as modulating agents against Brazilian chloroquine-resistant fresh isolates of Plasmodium falciparum. Aiming to simulate therapeutic schedules, chloroquine was employed at the concentration used for sensitive falciparum malaria treatment and anti-psychotic therapeutic concentrations of the phenothiazine drugs were adopted in two-fold serial dilutions. The in vitro microtechnique for drug susceptibility was employed. Unlike earlier reported data, the phenothiazine modulating effect was not observed. However, all the drugs demonstrated intrinsic antiplasmodial activity in concentrations lower than those described in the literature. In addition, IC50 estimates have been shown to be inferior to the usual anti-psychotic therapeutic concentrations. Statistical analysis also suggested an increase in the parasitaemia rate or, even, a predominant antiparasitic effect of phenothiazine over chloroquine when used in combination.     

Elevated serum transforming growth factor beta1 levels in Epstein-Barr virus-associated diseases and their correlation with virus-specific immunoglobulin A (IgA) and IgM

Transforming growth factor beta (TGF-beta) is an immunosuppressive cytokine which can induce immunoglobulin A (IgA) switch and Epstein-Barr virus (EBV) replication in latently infected cells. Here we report elevated serum levels of TGF-beta in various EBV-associated diseases correlating positively with EBV-specific IgA titers and negatively with IgM titers, suggesting a role for this cytokine in the pathogenesis of these diseases.     

Circadian Rhythmicity of Grooming Behavior During Pregnancy in a Marmoset (Callithrix jacchus) Family Group in Captivity

One family group of common marmoset ( Callithrix jacchus ) was observed in captivity under natural environmental conditions to describe the circadian pattern of grooming behavior during the pregnancy of the reproductive female. The animals were observed by focal sampling, from the beginning to the end of animal's active phase, during two non-consecutive days per week, from August to November 1996. The duration of self-grooming and social grooming behavior of each animal were totalled each hour. The time series obtained were analyzed by Cluster Analysis and by Sin gle Cosinor Analysis. The daily patterns of grooming behavior during pregnancy were divided by Cluster Analysis into two stages, one corresponding to the second half of the third month of pregnancy, and the other from the last half of the third month to the last week before parturition. The confidence intervals of acrophases overlapped in all stages. The acrophases values of the first stage occurred between 10:09 h and 11:00 h, and on the second stage between 8:51 h and 11:13 h. The daily pattern of grooming behavior of adult male and female showed a trend to increase in the first hours of the active phase. This trend to advance grooming behavior during the second stage of pregnancy may be due to an effect of the coming parturition itself or to seasonal influences.     

Association between cervical lesion grade and micronucleus frequency in the Papanicolaou test

The aim of this study was to evaluate the association between the frequency of micronuclei (MN) and the cellular changes detected in the conventional Papanicolaou test. One hundred and seventy-four Papanicolaou test smears with cellular changes were examined. MN screening was done in cytopathological smears by counting 1,000 cervical cells in a light microscope. MN frequencies were significantly higher in the group with cellular changes compared to the control group (p < 0.001). The mean MN frequencies were 0.95 ± 1.12 (mean ± SD) in the control group (n = 223), 2.98 ± 1.20 in individuals with atypical squamous cells of undetermined significance (ASC-US) (n = 50), 4.04 ± 1.45 in cervical intraepithelial neoplasia (CIN) I (n = 52), 5.97 ± 1.83 in CIN II (n = 30), 7.29 ± 1.55 in CIN III (n = 17) and 8.64 ± 1.55 in invasive cancer (n = 25). These findings suggest that MN monitoring should be included as an additional criterion for the early detection of cytogenetic damage in routine examinations. This monitoring should be done in the same smear as used for cytopathological examination. More specific and systematic studies are necessary to confirm this proposal.     

Patau syndrome with a long survival. A case report

Trisomy 13 is a clinically severe entity; 85% of the patients do not survive beyond one year, and most children die before completing six months of age. We report a female child, 28 months old, white, the fourth child of a non-consanguineous couple, who presented trisomy 13. The child was born at term, from a vaginal delivery, weighing 2600 g. At birth, she was cyanotic, icteric, spastic, and cried weakly. The initial clinical examination detected polydactyly in the left hand, congenital clubfoot and convex soles, ocular hypertelorism, a low nasal bridge, numerous hemangiomas distributed throughout the body, cardiomegaly, and perimembranous inter-ventricular communication. There was no cleft lip or palate. On physical examination at 18 months old, the child weighed 6,900 g, had a cephalic perimeter of 41 cm, a thoracic perimeter of 43 cm and was 76 cm tall. At 28 months, she weighed 10,760 g and was 88.5 cm tall. Neuropsychomotor development retardation was evident from birth and, according to the psychologist and the social assistant of APAE (Handicapped Parents and Friends Association) in Cangu?u, Rio Grande do Sul, there was a noticeable improvement after physiotherapy and recreational sessions.