Controlling the transport of active matter in disordered lattices of asymmetrical obstacles.

We investigate the transport of active matter in the presence of a disordered square lattice of asymmetric obstacles, which is built by removing a fraction of them from the initial full lattice. We obtain a spontaneous inversion of the net particle current, compared to the usual sense of such a current as a function of the fraction of removed obstacles and particle density. We observed that the negative current regime is the consequence of trapping of particles among the obstacles which favors that more particles move in the negative current direction. The same reasoning applies to the positive current regime as well. We show a calculation that partially reproduces our numerical results, based on the argument that the mean current is given by the product of the mean speed and the mean number of travelers in each direction; the breakdown of this assumption is responsible for the failure of our calculation to reproduce the initial negative current regime.

Mutagenesis by hydrogen peroxide treatment of mammalian cells: a molecular analysis.

Hydrogen peroxide is an oxidizing agent which can be generated intracellularly either during normal metabolism or by treatment with external agents including solar UV radiation. Simian cells (CV-1) transfected with the SV40-based shuttle vector plasmid pZ189 have been treated with H2O2 and then incubated to allow repair and replication of the plasmid. The frequency of mutations at the supF locus of the recovered plasmid increases by a factor of up to four over the spontaneous value. The nucleotide changes associated with 100 spontaneous and 100 H2O2-induced mutants have been determined directly by sequencing a 150 bp fragment that includes the entire supF tRNA coding region. Deletions were observed in approximately 45% of both the spontaneous and induced mutants, whereas single or multiple base changes arose in 68 and 57% of the induced and spontaneous mutants respectively. The spectrum of induced mutations is characterized by (i) the occurrence of deletions associated with base changes (16% of all mutants analysed) and (ii) small deletions of 3 bp and less (51% of all deletion mutants sequenced). Sixty-five per cent (15 out of 23) of all small deletions (spontaneous and induced) are associated with runs of between two and five identical bases and eight of them arise at a mutational 'hotspot' region of five cytosines between bp 172 and 176. The majority (19 out of 30) of completely sequenced deletions observed in the spontaneous spectrum contain either (i) small (2-10 bp) direct repeat sequences that lie immediately outside one deletion terminus and immediately inside the second deletion terminus or (ii) small (2-3 bp) inverted repeat sequences lying immediately inside the two deletion termini. Most deletions that we have observed are therefore likely to arise as a consequence of specific aspects of DNA structure.

The spectrum of mutations generated by passage of a hydrogen peroxide damaged shuttle vector plasmid through a mammalian host.

Treatment of a plasmid shuttle vector (pZ189) with a combination of hydrogen peroxide and a ferric iron/EDTA complex prior to transfection and passage in simian (CV-1) cells increases the frequency of mutations at the supF locus by up to 60-fold over the spontaneous background. This increase in mutation frequency is abolished when the inhibitors desferrioxamine, superoxide dismutase, catalase or dimethyl sulfoxide are included in the initial reaction or when the iron/EDTA complex is omitted, a strong indication that the premutagenic damage arises as a result of direct attack by hydroxyl radical generated in a superoxide driven Fenton reaction. DNA sequence analysis of the mutated plasmids shows that 1) Deletions occuring in combination with base-substitutions arise in 22.5 percent of the induced mutants compared with only 3 percent of spontaneous mutants 2) Sixty percent of all induced deletion mutations involve the loss of a single base and 77 percent of these (20 out of 26) occur at two adenine-containing sites 3) The base-change spectrum of mutants arising in the treated plasmid population is marked by the predominance of mutants containing a single base-change and by an increase in changes at AT base pairs. These results provide direct information concerning the nature of mutations arising in mammalian cells as a result of hydroxyl radical mediated DNA damage.

Homovanillic acid (HVA) and manganese in urine of workers exposed in a ferromanganese alloy plant.

Forty workers occupationally exposed to manganese in a ferromanganese alloy plant and twenty-five controls were investigated in order to assess the validity of urinary homovanillic acid (HVA) as a potential indicator of early effects of manganese intoxication. None of the exposed workers showed signs and symptoms of typical manganese intoxication, but most of them reported subjective symptoms which may be related to a prodromic phase of manganism. Urinary HVA levels were not significantly different among the groups under study. On the other hand, mean urinary manganese levels were higher in the exposed group (compared with the controls). A negative correlation between urinary HVA and duration of exposure to manganese was found.

[Ectopic meningioma of the calvarium: report of a case]. / Meningeoma ectópico do calvário: registro de um caso.

A case of calvarial meningeoma in a 42 year old female is reported. Arising from the inner table of the skull, it projected a extracranial mass without neurological simptomatology. The surgical procedure give good results. Some aspects of the literature and radiologics finds are commented. The infrequency of this pathology is resulted.

Porfirias. Consideracoes a respeito de 26 casos. / Porphyria. Considerations apropos of 26 cases

Foram estudados 26 pacientes com porfirias, internados no Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo, no periodo de 1965 a 1978. Foram salientados os aspectos clinico e laboratorial, especialmente a sintomatologia, os metodos bioquimicos de diagnostico e o tratamento. Tres pacientes com porfiria aguda intermitente foram tratados com hematina durante o ataque agudo da molestia

Mutagenic interactions between near-ultraviolet (365 nm) radiation and alkylating agents in Escherichia coli.

The mutagenic interaction between near-ultraviolet (365 nm) radiation and the alkylating agents ethyl methanesulphonate (EMS) and methyl methanesulphonate (MMS) was studied in a repair-competent and an excision-deficient strain of Escherichia coli. Near-UV radiation modified the metabolic response of exposure to these chemicals and either reduced or increased their mutagenic efficiency. Based on these results, an experimental model was formulated to explain the mutagenic interactions that occur between near-UV and various agents that induce prototrophic revertants via error-prone repair of DNA. According to this model, low doses of near-UV provoke conditions for mutation frequency decline (MFD) and lead to a mutagenic antagonism. With increasing near-UV doses, damage to constitutive error-free repair systems increases, favouring the error-prone system and inhibiting the MFD. Under these conditions there will be a progressive decrease in antagonism until at high doses an enhancement of mutation frequency (positive interaction) will occur.

Indices biologicos de exposicao a agentes quimicos. / Biological indices of exposition to chemical agents

Face a dificuldade do estabelecimento, na pratica, dos valores dos "chamados" limites de tolerancia (LT), sao introduzidos os valores limites de tolerancia biologica (LTB). Os primeiros dizem respeito a concentracao dos xenobioticos no ar (exposicao) e os ultimos, a concentracao dos mesmos no organismo (absorcao), tendo pois, mais significado quanto as condicoes de salubridade do ambiente de trabalho e quanto ao grau de deterioracao da saude. Sao, tambem, apresentadas, sob forma esquematica, figuras que visam ilustrar as consideracoes relativas aos indices biologicos de exposicao a luz das fases da intoxicacao

Exposicao ocupacional ao sulfeto de carbono. / Occupational exposure to carbon sulphide

Reponsavel por mais de um tipo de acao toxica e com largo emprego industrial, o sulfeto de carbono constitui, segundo o presente trabalho, um exemplo tipico de substancia quimica, que se enquadra na categoria de compostos,cujo binomio causa-efeito nem sempre pode ser considerado. Medidas tecnicas de protecao,como ventilacao, exaustao, cortinas protetoras, sao aplicadas para reduzir as possibilidades de risco de exposicao a esse solvente. Contudo,estas se apresentam "quase sempre ineficientes para uma reducao tao drastica de sua concentracao no ambiente. O autor preconiza a introducao dos Limites de Tolerancia Biologicos (LTB)como medida suplementar para a determinacao da absorcao total do xenobiotico, "que devera estar aquem dos limites maximos toleraveis". A determinacao biologica do grau de exposicao ao sulfeto de carbono e comumente obtida atraves do teste cinetico da iodoazida. Relata, tambem, o mecanismo de acao toxica do CS considerando a velocidade e extensao da absorcao, a velocidade de eliminacao, a biotransformacao, os possiveis sitios de acao e, ainda, observa que a teoria do efeito quelante dos produtos de biotransformacao, os possiveis sitios de acao, e, ainda observa que a teoria do efeito quelante dos produtos de biotransformacao do CS2 e a mais promissora para elucidar o seu mecanismo de acao, sugerindo que estudos nesse sentido sejam intensos

Identificacao e determinacao quantitativa de barbituricos em amostras de sangue e de urina. / Identification and quantitative determination of barbiturates in blood and urine

Amostras de sangue (heparinizado) provenientes de 15 pacientes em coma barbiturico e de 15 em tratamento de epilepsia, foram analisadas pela espectrofotometria do ultravioleta.Os extratos alcalinos em pH 13 (NaOH 0,45N) e em pH 10,5 (apos adicao de NH4Cl 16%) foram lidos, um contra o outro, e verificada a absorvancia diferencial dos dois extratos, em 260nm. A cromatografia em camada delgada foi utilizada para a identificacao dos barbituricos paralelamente a quantificacao

Cromatografia em papel circular na analise toxicologica. / Circular chromatography in the toxicological analysis

Descrevem-se a preparacao e o emprego de 15 agentes cromogenicos com vistas a identificacao de farmacos. O resultado obtido pela revelacao de 52 farmacos, apos desenvolvimento com o sistema solvente Ba 30, permitiu selecionar os 10 agentes mais adequados para a aplicacao da cromatografia em papel circular na analise toxicologica, em funcao da sensibilidade e especificidade apresentadas

Identificacao cromatografica de farmacos em urina para controle antidopagem. / Chromatographic identification of drugs in urine for doping control

E proposto um esquema de analise para a identificacao de alguns farmacos de interesse para o controle da dopagem no esporte. A tecnica cromatografica em camada delgada foi usada para a triagem e a gas-liquido para confirmacao. E recomendado o uso do indice de Kovats.O esquema foi aplicado para analise de amostras de urina de individuos nao medicados,medicados e em competicao esportiva, apos extracao com solvente organico

Determinacao de lidocaina, prilocaina e etidocaina em amostras de sangue por cromatografia em fase gasosa. / Determination of lidocaine, prilocaine and etidocaine in blood by gas chromatography

E descrito um metodo de determinacao de lidocaina, prilocaina e etidocaina em amostras de sangue. Esses farmacos sao extraidos do material biologico, em meio alcalino, com diclorometano e a seguir determinados quantitativamente por cromatografia em fase gasosa. Este metodo permite a determinacao destes anestesicos locais, individualmente ou em associacao, quando presentes no sangue de pacientes que se submetem a uma anestesia regional

Determinacao de residuo de aflatoxina M1 em leite por fluordensitometria. / Determination of aflatoxin M1 residues in milk by fluordensitometry

O trabalho apresenta um esquema analitico para determinacao de aflatoxina M1 no leite com sensibilidade superior a estabelecida por stubblefield e col. (1973) para este tipo de analise. A tecnica cromatografica em camada delgada bidimensional foi utilizada para purificacao do extrato obtido, permitindo melhor utilizacao da fluordensitometria. A analise de amostras de leite enriquecidas com aflatoxina M1(0,1 ug/L) mostrou rendimento medio de 89,1%. Foram feitas analises de amostras de leite comercializado com vistas a verificacao da aplicabilidade do metodo

[Hematin treatment of acute intermittent porphyria. A case report (author's transl)]. / Tratamento da porfiria aguda intermitente com hematina. Registro de caso.

A young woman with acute intermittent porphyria in profound relapse and severe nervous and respiratory involvement was treated by intravenous infusions of hematin, followed by improvement of symptoms. The diet with high carbohydrate and protein content and a B-adrenergic blocking agent, not showed any beneficial effect on acute attack. The infusion of hematin was followed by a lowering effect on urine porphybilinogen and delta-aminolevulinic acid and clinical improvement. The return to normal of porphyrin precursors in the urine was accompanied by almost complete clinical remission. The relationship of remission and repression of delta-aminolevulinic acid, decrease of urinary levels of porphyrin precursors, pulmonaries tests and electromyograms, were discussed.