Showing papers by "University of São Paulo published in 1993"

On sparse spanners of weighted graphs

Abstract: Given a graphG, a subgraphG' is at-spanner ofG if, for everyu,v ?V, the distance fromu tov inG' is at mostt times longer than the distance inG. In this paper we give a simple algorithm for constructing sparse spanners for arbitrary weighted graphs. We then apply this algorithm to obtain specific results for planar graphs and Euclidean graphs. We discuss the optimality of our results and present several nearly matching lower bounds.

Implantation and decidualization in rodents.

Abstract: This article reviews the main events of embryo-implantation and decidualization in rodents. In common laboratory rodents the embryo attaches to the uterine epithelial lining, usually on days 4 to 6 of pregnancy. A progressive degree of proximity between trophoblast and epithelium occurs until the epithelial cells undergo apoptosis and detach from the basement membrane. During the attachment stage, the spindle-shaped connective tissue cells that underlie the epithelium next to the embryos transform into polyhedral and closely packed decidual cells. Following the epithelial detachment and the breaching of the basement membrane the embryo is thus in direct contact with decidual cells. These cells accumulate organelles associated with synthesis of macro-molecules, intermediate filaments, and eventually lipid droplets and glycogen. Another remarkable feature of decidual cells is the establishment of gap and adherens intercellular junctions. Differentiation of fibroblasts into decidual cells advances antimesometrially and mesometrially, creating in the endometrium several regions of cells with different morphology. The whole phenomenon of decidualization which is normally triggered by the embryo can be artificially induced in pseudo-pregnant or hormonally-prepared animals with the use of diverse stimuli. The uterine epithelium is probably responsible for the transduction of the initial stimulus. Prostaglandins have been shown to be important in the induction of decidualization. More recently other substances such as leukotrienes, platelet-activating factor (PAF), and transforming growth factor (TGF) have been thought to play a role in induction. Much evidence points to prostaglandin production by the decidual cells. New proteins such as a luteotropic factor, desmin, and other molecules were shown to be produced after rat stromal cells undergo decidual transformation. The extracellular matrix of the mouse decidua contains very thick collagen fibrils. Mouse decidual cells are also very active in phagocytosing the thick fibrils, contributing to the remodeling and involution of the decidua that accompanies embryonic growth. Radioautographic data indicates that mouse decidual cells produce and secrete collagen and sulfated proteoglycans.

Bradykinin initiates cytokine‐mediated inflammatory hyperalgesia

Abstract: 1. The hyperalgesic activities in rats of bradykinin, carrageenin and lipopolysaccharide (LPS) were investigated in a model of mechanical hyperalgesia. 2. Bradykinin and carrageenin evoked dose-dependent hyperalgesia with maximum responses of similar magnitude to responses to LPS (1 and 5 micrograms). 3. Hoe 140, an antagonist of BK2 receptors, inhibited in a dose-dependent manner hyperalgesic responses to bradykinin, carrageenin and LPS (1 microgram) but not responses to LPS (5 micrograms), prostaglandin E2, dopamine, tumour necrosis factor alpha (TNF alpha), IL-1, IL-6 and IL-8. 4. Responses to bradykinin and LPS (1 and 5 micrograms) were inhibited by the cyclo-oxygenase inhibitor, indomethacin and by the beta-adrenoceptor antagonist, atenolol. The effects of indomethacin and atenolol were additive: their combination abolished responses to bradykinin and LPS (1 microgram) and markedly attenuated the response to LPS (5 micrograms). 5. Antiserum neutralizing endogenous TNF alpha abolished the response to bradykinin whereas antisera neutralizing endogenous IL-1 beta, IL-6 and IL-8 each partially inhibited the response. The combination of antisera neutralizing endogenous IL-1 beta+IL-8 or IL-6+IL-8 abolished the response to bradykinin. 6. Antisera neutralizing endogenous TNF alpha, IL-1 beta, IL-6 and IL-8 each partially inhibited responses to LPS (1 and 5 micrograms). Increasing the dose of antiserum to TNF alpha or giving a combination of antisera to IL-1 beta+IL-8 or IL-6+IL-8 further inhibited responses to LPS (1 and 5 micrograms). 7. These data show that bradykinin can initiate the cascade of cytokine release that mediates hyperalgesic responses to carrageenin and endotoxin (1 microgram). The lack of effect of Hoe 140 on hyperalgesic responses to LPS (5 microgram) suggests that the release of hyperalgesic cytokines can be initiated independently of bradykinin BK2 receptors.

The relation between biological activity of the rain forest and mineral composition of soils.

Abstract: In most soils of the humid tropics, kaolinitic topsoil horizons overlie more gibbsitic horizons This arrangement cannot be produced simply by leaching Quantitative measurement of the turnover of chemical elements in the litterfall in an Amazonian ecosystem indicates that the forest cycles a significant amount of elements, particularly silicon As a result, fluids that percolate through topsoil horizons already contain dissolved silicon This effect keeps silicon from being leached down and may account for the stability of kaolinite in the soil upper horizons The soil mineral composition is thus maintained by biological activity

Metallothionein protects DNA from oxidative damage.

Abstract: Metallothionein (MT) is a potent hydroxyl radical scavenger but its antioxidant properties in vivo have not been defined. Most of the recent results indicate that it does not afford protection to cells against the lethal action of oxidative stress. However, the possibility that MT confers protection against oxidative damage to a specific cellular target, such as DNA, had not been considered. We compared V79 Chinese hamster cells enriched in and depleted of MT in terms of DNA-strand scission. Zinc induces an increase in MT content of V79 Chinese hamster cells, without concomitant increase in the GSH level. These induced cells are more resistant to the production of DNA-strand scission by H2O2 than the parental cells. Conversely, cells rendered partially deprived of MT, by transfection with a plasmid vector in which the MT-I cDNA is antisense oriented in relation to a simian virus 40 promoter, became more susceptible to the DNA-damaging action of H2O2. The transfected cells did not exhibit alterations of GSH, superoxide dismutase- and H2O2-destroying enzymes. Indirect immunofluorescence indicated that most of the MT was concentrated in the cell nucleus. Neither overexpression nor lower expression of MT resulted in differential resistance to the killing action of H2O2. However, the combined high nuclear concentration of MT and its excellent hydroxyl scavenger properties confer protection to DNA from hydroxyl radical attack.

Induction of immediate spatiotemporal changes in thalamic networks by peripheral block of ascending cutaneous information.

Abstract: PERIPHERAL sensory deprivation induces reorganization within the somatosensory cortex of adult animals1-6. Although most studies have focused on the somatosensory cortex1–6, changes at subcortical levels (for example the thalamus) could also play a fundamental role in sensory plasticity7–11. To investigate this, we made chronic simultaneous recordings of large numbers of single neurons across the ventral posterior medial thalamus (VPM) in adult rats. This allowed a continuous and quantitative evaluation of the receptive fields of the same sample of single VPM neurons per animal, before and after sensory deprivation. Local anaesthesia in the face induced an immediate and reversible reorganization of a large portion of the VPM map. This differentially affected the short latency (4–6 ms) responses (SLRs) and long latency (15–25 ms) responses (LLRs) of single VPM neurons. The SLRs and LLRs normally define spatiotemporally complex receptive fields in the VPM12. Here we report that 73% of single neurons whose original receptive fields included the anaesthetized zone showed immediate unmasking of SLRs in response to stimulation of adjacent cutaneous regions, and/or loss of SLRs with preservation or enhancement of LLRs in response to stimulation of regions just surrounding the anaesthetized zone. This thalamic reorganization demonstrates that peripheral sensory deprivation may induce immediate plastic changes at multiple levels of the somatosensory system. Further, its spatiotemporally complex character suggests a disruption of the normal dynamic equilibrium between multiple ascending and descending influences on the VPM.

A method for chromosome preparations from large fish specimens using in vitro short-term treatment with colchicine

Abstract: This paper describes a new technique for preparing mitotic fish chromosomes using short-term in vitro treatment with colchicine. The results show that a large number of good quality metaphases (many suitable for chromosome banding) can be obtained by this technique, which requires an average of 1 h and 30 min for all steps. The procedure considerably reduces the time normally required for chromosome preparations in fish.

Trial 2 in the elevated plus-maze: a different form of fear?

Abstract: A factor analysis of the scores from rats given two trials in the elevated plus-maze showed that four independent factors emerged. Measures of anxiolytic activity on trial 1 (number of open arm entries and time spent on open arms) loaded on factor 1, measures of anxiolytic activity on trial 2 loaded on factor 2, the measure of general activity (number of closed arm entries) on both trials loaded on factor 3, and a measure of decision time (time spent in central square) for both trials loaded on factor 4. The independence of trials 1 and 2 anxiety measures raises the possibility that the state of anxiety/fear on the second trial in the plus-maze is qualitatively different from that on trial 1. This difference is reflected in the loss of anxiolytic action of diazepam (2 mg/kg) on trial 2. However, this occurs only when the trials are short (5 min); when they are longer (10 min) diazepam retains anxiolytic efficacy. It is concluded that during a brief (5 min) trial in the plus-maze rats acquire a specific phobic anxiety, which is relatively resistant to benzodiazepines. With a longer exposure to the plus-maze this form of fear extinguishes.

Limb deficiency with or without Möbius sequence in seven Brazilian children associated with misoprostol use in the first trimester of pregnancy.

Abstract: Misoprostol, a synthetic analog of prostaglandin, has been widely used in Brazil as an abortifacient. Abortion is illegal in Brazil. An uncertain number of these abortion attempts are unsuccessful and the pregnancy continues. We report on 7 patients whose mothers attempted to abort using this drug in the first trimester of gestation without success. The 7 patients presented with limb defects and in 4 of them a diagnosis of Mobius sequence was made. © 1993 Wiley-Liss, Inc.

Lyapunov function for the Kuramoto model of nonlinearly coupled oscillators

Abstract: A Lyapunov function for the phase-locked state of the Kuramoto model of non-linearly coupled oscillators is presented. It is also valid for finite-range interactions and allows the introduction of thermodynamic formalism such as ground states and universality classes. For the Kuramoto model, a minimum of the Lyapunov function corresponds to a ground state of a system with frustration: the interaction between the oscillators,XY spins, is ferromagnetic, whereas the random frequencies induce random fields which try to break the ferromagnetic order, i.e., global phase locking. The ensuing arguments imply asymptotic stability of the phase-locked state (up to degeneracy) and hold for any probability distribution of the frequencies. Special attention is given to discrete distribution functions. We argue that in this case a perfect locking on each of the sublattices which correspond to the frequencies results, but that a partial locking of some but not all sublattices is not to be expected. The order parameter of the phase-locked state is shown to have a strictly positive lower bound (r ⩾ 1/2), so that a continuous transition to a nonlocked state with vanishing order parameter is to be excluded.

Algebraic model for the evolution of the genetic code

Abstract: A search for symmetries based on the compact simple Lie algebras is performed to verify to what extent the genetic code is a manifestation of some underlying symmetry. An exact continuous symmetry group cannot be found to reproduce the present genetic code. However, a unique approximate symmetry group is compatible with codon assignment for the fundamental amino acids and the termination codon. In order to obtain the actual genetic code, the symmetry must be slightly broken.

Characterization of preimaginal developmental stages in Africanized honey bee workers (Apis mellifera L)

Abstract: Le developpement preimaginal d'Apis mellifera a deja ete decrit par plusieurs chercheurs et l'existence de 5 stades larvaires consacres a l'alimentation et a la croissance est bien etablie. Le dernier stade larvaire peut etre subdivise en diverses periodes, qui impliquent une serie de modifications morphologiques et physiologiques en liaison avec la metamorphose. Plusieurs stades ont egalement ete observes pendant la phase nymphale. Diverses etudes ont montre que la duree des stades des phases larvaire et nymphale varie d'une race d'abeilles a l'autre. Nous avons etudie en detail ces 2 phases du developpement preimaginal chez des abeilles africanisees recoltees a Ribeirao Preto, SP, Bresil, et caracterise les divers stades ainsi que leur duree

The desmopressin stimulation test in the differential diagnosis of Cushing's syndrome

Abstract: Summary objective We assessed the ability of desmopressin to stimulate the pituitary-adrenal axis in patients with Cushing's syndrome. DESIGN AND SUBJECTS The Cortisol response to 5 or 10 fig of intravenous desmopressin was evaluated in 31 patients with Cushing's syndrome of several aetiologies and in 15 normal subjects. RESULTS Cortisol responses were observed in 15 out of 16 patients with pituitary dependence and in two patients with adrenal nodular hyperplasia, the increase above baseline ranging from 61 to 379% in the responders. Eight patients with adrenal tumours and one with the ectopic ACTH syndrome did not respond to desmopressin, having shown changes In their Cortisol levels from -5 to 42% above baseline. Responses occurred in two out of the 15 normal Individuals, whose Cortisol increased 58 and 69% above baseline, respectively. Stimulation tests with standard agents as lysine vasopressin or ovine corticotrophin-releasing hormone were performed in the same patients and there was a high degree of concordance. No serious adverse reactions were observed in the tests with desmopressin. CONCLUSIONS Desmopressin was able to stimulate the pituitary-adrenal axis in patients with Cushing's disease and, like corticotrophin releasing hormone, it may prove useful in the differential diagnosis of Cushing's syndrome.

Trans-sialidase: a unique enzyme activity discovered in the protozoan Trypanosoma cruzi.

Abstract: Trypanosoma cruzi, the agent of Chagas' disease, an ailment characterized by a progressive chronic fibrotic myocarditis and degeneration of tissues that are innervated by the autonomic nervous system, is a voracious sialic acid eater from glycoconjugates of the surrounding medium This is accomplished through an active trans-sialidase residing on the surface membrane of the trypomastigote stage, which is the parasite form that invades vertebrate cells The existence of the enzyme was proposed and established only 7 years ago and yet a flood of information on the subject is already available Trans-sialidase is able to reversibly transfer sialic acid alpha(2-->3)-linked to an external Gal beta from the host cell surface sialoglycoconjugates to a terminal Gal beta of an appropriate acceptor on the parasite surface In the absence of an acceptor, the enzyme acts as a hydrolase transferring sialic acid to water Trans-sialidase belongs to a highly heterogeneous gene family of surface molecules sharing with each other and with bacterial neuraminidases variable degrees of nucleotide sequence homology and common motifs It has been proposed that sialylation of the parasite surface catalyzed by trans-sialidase is necessary for successful invasion of the host cell, but the evidence available is still indirect Another function could be a protection from lysis by the alternative pathway of complement while the parasite is circulating in the acute phase of the disease

Cardiovascular responses of conscious rats to carotid body chemoreceptor stimulation by intravenous KCN

Abstract: In the present study we analyzed the cardiovascular, respiratory and behavioral responses evoked in rats by KCN. Hypertension, hyperpnea and alerting behavior were characteristic responses in unanesthetized animals. Selective denervation of aortic and carotid bifurcation areas confirmed the carotid body chemoreceptor (CBC) origin of these responses. Sino-aortic denervation, as well as selective carotid sinus denervation abolished the responses, while, after selective aortic denervation, the responses were not different from those of the control rats. The administration of prazosin abolished the hypertensive response but did not change the bradycardic response, whereas the administration of atropine eliminated the bradycardic response and potentiated the hypertensive response to KCN. Increasing doses of KCN (10–80 μg/rat) produced proportionally larger bradycardia, hypertension and hyperventilation. Slight attenuation of bradycardic responses to KCN were observed in rats under chloralose anesthesia, while marked depression of bradycardic responses were observed under pentobarbitone anesthesia. Both anesthetics changed the hypertensive responses to hypotensive responses. In conclusion, the cardiovascular, respiratory and behavioral responses to intravenous KCN are a good functional test to CBC stimulation in unanesthetized rats, producing simultaneously intense bradycardia with hyperventilation and behaviour responses.

Bothropstoxin-I: amino acid sequence and function.

Abstract: The complete amino acid sequence of bothropstoxin-I (BthTX-I), a myotoxin isolated from Bothrops jararacussu snake venom, is reported. The results show that BthTX-I is a Lys49 phospholipase A2 (PLA2)-like protein composed of a single polypeptide chain of 121 amino acid residues (M(r) = 13,720), containing one methionine and 14 half-cystines. Although deprived of any detectable PLA2 activity, BthTX-I reveals a high degree of sequence homology with Asp49-PLA2s and with other Lys49-myotoxins. Critical mutations--such as Leu5 for Phe5; Gln11 for X11; Asn28 for Tyr28; Leu32 for Gly32; Lys49 for Asp49; and Asp71 for Asn71--which are apparently involved with the decreasing or elimination of PLA2 activity, have been detected. The same mutations occurred in myotoxin II from Bothrops asper venom, but five extra changes--namely, Pro90 for Ser90; Gly111 for Asn111; His120 for Tyr120; Phe124 for Leu124; and Pro132 for Ala132--have been found relative to myotoxin II.

Metabolic behavior in rats of a nonprotein microemulsion resembling low‐density lipoprotein

Abstract: A protein-free microemulsion (LDE) with a lipid composition resembling that of low-density lipoprotein (LDL) was used in metabolic studies in rats to compare LDE with the native lipoprotein. LDE labeled with radioactive lipids was injected into the bloodstream of male Wistar rats, and plasma kinetics of the labeled lipids were followed on plasma samples collected at regular intervals for 12 h after injection. The 24-h LDE uptake by different tissues was also measured in tissue samples excised after the animals had been sacrificed. We found that LDE plasma kinetics were similar to those described for native LDL [fractional clearance rate (FCR) of cholesteryl ester, 0.42 +/- 0.11 h-1]. The major site for LDE uptake was the liver, and the tissue distribution of the LDE injected radioactivity was as one would expect for LDL. To test whether LDE was taken up by the specific LDL receptors, the LDE emulsion was injected into rats treated with 17 alpha-ethinylestradiol, which is known to increase the activity of these receptors; as expected, removal of LDE from the bloodstream increased (FCR = 0.90 +/- 0.35 h-1). On the other hand, saturation of the receptors that remove remnants by prior infusion of massive amounts of lymph chylomicrons did not change LDE plasma kinetics. These results indicate that LDE is cleared from plasma by B,E receptors and not by the E receptors that remove remnants. Incorporation of free cholesterol into LDE increased LDE plasma clearance. Incubation studies also showed that LDE incorporates a variety of apolipoproteins, including apo E, a ligand for recognition of lipoproteins by specific receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

State-of-the-art of reservoir limnology and water quality management

Abstract: The chapter presents state-of-the-art of reservoir limnology and water quality modelling and their use in reservoir water quality management. Reservoirs are classified into dam reservoirs and impoundments. The features of dam reservoirs and lakes are confronted, both qualitative (absolute) and quantitative (relative) differences being specified. Different consequences of reservoir construction for the river are outlined. Methodological problems concerning sampling and mathematical modelling are dealt with. Theoretical aspects of reservoir limnology cover the position of reservoirs in the river continuum concept, retention time as a key factor of reservoir limnology and reservoir aging (short term trophic upsurge) and long term reservoir ecosystem evolution. Pulse effects are treated as a theoretical problem with considerable consequences for reservoir management. Specific attention is devoted to multiple reservoir systems. Reservoir water quality management approaches and options as well as their use for specific reservoir uses are analyzed. The perspective for future reservoir investigations is treated.

The role of interleukins and nitric oxide in the mediation of inflammatory pain and its control by peripheral analgesics.

Abstract: Tissue injury or the presence of foreign material initiates a series of pathophysiological events that may manifest as inflammatory pain. The physicochemical characteristics of the initiating factor trigger the release of a unique range of pain mediators that control the threshold and activation of nociceptors. It has been suggested that many nociceptors associated with inflammatory pain are dormant, and are activated by cyclo-oxygenase metabolites and sympathomimetic amines into a state of hyperalgesia. In this state, pain receptors may be activated by previously ineffective stimuli. The relative contribution of the mediators to the activation process varies with the experimental model or the pathophysiological process involved. The mechanisms that control the activity of the pain receptor are unfolding. Indeed, research has shown a central role for bradykinin (released from plasma) and cytokines (released from tissues and resident cells) in this process. The release of tumour necrosis factor-alpha (TNF-alpha) initiates the release of interleukin-1 and interleukin-8, which in turn liberate cyclo-oxygenase metabolites and sympathomimetic amines, respectively. In some models of inflammatory pain, bradykinin causes hyperalgesia via release of TNF-alpha. Drugs blocking cyclo-oxygenase (aspirin-like drugs), or those antagonising the effects of sympathomimetic amines (beta-blockers), prevent sensitisation of the pain receptors. However, during hyperalgesia only specific types of analgesics are capable of nociceptor downregulation. It is assumed that sensitisation of nociceptors is due to increased concentrations of cAMP/Ca++ in the sensory neurons. The effect of increased cAMP concentrations may be counteracted by stimulation of the arginine/nitric oxide/cGMP pathway. Peripherally acting opiates and dipyrone are examples of analgesics that act via this mechanism. The analgesic effects of glucocorticoids and nimesulide appear to be attributable to inhibition of cytokine release.

Who are the Whites?: Imposed census categories and the racial demography of Brazil.

Abstract: Censuses and other surveys ask respondents to identify their race and/or to which ethnic group they belong. Individuals of mixed race/color however may not find the category to which they feel they truly belong listed on the survey. For example many people in Brazil are not simply white or black but somewhere in between. The authors therefore test the consequences of ignoring or overriding the distinctive features of the cognitive system by which Brazilians express their "race-color" identities. They substituted the more used vernacular term morena for the seldom-used term parda which the Brazilian census offers as self-identification for a person who has both black and white color-race features. When morena is offered in a split census the proportion of respondents we self-identify as being of mixed color-race increases substantially while the proportion identifying as white or black substantially declines. These findings support a much-needed reevaluation of the imposition of rigid dichotomous or trichotomous categories used to establish racial identity in the US.

Avaliação do sistema de informação sobre nascidos vivos e o uso de seus dados em epidemiologia e estatísticas de saúde

Abstract: O Ministerio da Saude, considerando a existencia de falhas do ponto de vista quantitativo (cobertura) no registro de nascidos vivos, no Brasil, e a impossibilidade de conhecer a distribuicao dos nascidos vivos segundo algumas variaveis importantes sob a optica clinico/epidemiologica (peso ao nascer, Indice de Apgar, duracao da gestacao, tipo de parto, paridade, idade e instrucao da mae), implantou em 1990, no Brasil, o Sistema de Informacoes sobre Nascidos Vivos - SINASC- tendo como documento-base a Declaracao de Nascido Vivo - DN - com a finalidade de suprir essas lacunas. Com o objetivo de avaliar a cobertura e a fidedignidade das informacoes geradas pelo SINASC, foi analisada a distribuicao dos nascidos vivos hospitalares segundo caracteristicas epidcmiologicas relativas ao produto de concepcao, a gravidez, ao parto e a mae. A populacao de estudo compreendeu 15.142 nascidos vivos hospitalares ocorridos em cinco municipios do Estado de Sao Paulo, Brasil, no periodo de janeiro a julho de 1992. Os resultados permitiram reconhecer excelente cobertura do SINASC (emissao de DN acima de 99,5%) e otima fidedignidade do preenchimento das DNs, para a maioria das variaveis, quando comparadas aos documentos hospitalares. Para algumas caracteristicas foi observada maior fragilidade (Indice de Apgar, duracao da gestacao, instrucao da mae, numero total de filhos tidos e nome do pai). Sao apresentadas sugestoes para o aperfeicoamento do SINASC e recomendados treinamentos/reciclagens do pessoal envolvido no preenchimento das DNs. O estudo confirma o fato de os dados permitirem analise valida para o conhecimento de aspectos ligados a saude materno-infantil. Do ponto de vista epidemiologico, o estudo permitiu detectar proporcoes elevadas de parto operatorio (48,4%), maes adolescentes (17,5%) e o valor estimado para o baixo peso ao nascer foi de 8,5%.