Theophylline antagonizes the effect of diazepam on ventricular automaticity

The effect of diazepam on ventricular automaticity induced by a local injury was investigated in the isolated right ventricle of the rat in the presence of the diazepam central antagonist, RO 15-1788, and of the adenosine antagonist, theophylline. Theophylline but not RO 15-1788 antagonized the inhibitory effect induced by diazepam on ventricular automaticity. The inhibitory effect of adenosine but not that of 2-chloroadenosine was potentiated in the presence of diazepam. The results suggest that the inhibitory effect of diazepam on ventricular automaticity results from the inhibition of adenosine uptake.

Air pollution impact on phagocytic capacity of peripheral blood macrophages and antioxidant activity of plasma among school children

Peripheral blood macrophages of school children from downtown Santiago, Chile--a highly polluted city--exhibited a lower phagocytic index with higher percentage of killing than those of the rural village of María Pinto. These findings were observed concomitantly with a lower antioxidant activity of plasma in Santiago students. No differences were observed in serum immunoglobulins (IgA, IgG, and IgM), secretory IgA in saliva, and complement component C3. White blood cell count was higher in María Pinto residents than in Santiago students, including those cells with phagocytic capacity. It is suggested that particulate air pollution may enhance macrophage activity with impairment of the antioxidant capacity of plasma.

The effects of propranolol stereoisomers on nomotopic and ectopic cardiac automaticity in the rat

The effect of the two isomers of propranolol was tested on nomotopic and ectopic cardiac automaticity in the rat. The spontaneously beating isolated right atria of the rat was used as a model for studying the effect of these drugs on nomotopic automaticity. Ectopic automaticity was induced by local injury of the isolated right ventricle. Both dextro and levopropranolol reduce nomotopic and abolish ectopic automaticity (ID50 was 0.17 microM for d-propranolol and 0.96 microM for 1-propranolol) in the rat heart. We conclude that the membrane stabilizing activity, which is present functionally in both stereoisomers, plays a significant role in the effect of these drugs on cardiac automaticity. On the other hand, the property of competitive blocking of beta-adrenergic receptors, which mainly resides in the levoisomer of propranolol does not seem to be essential for this effect.

A mutation affecting basal body duplication and cell shape in Paramecium

The thermosensitive mutant sm19 of Paramecium tetraurelia undergoes a progressive reduction in cell length and basal body number over successive divisions at the nonpermissive temperature of 35 degrees C. In spite of these defects, sm19 cells retain the same generation time as wild-type cells at 35 degrees C. Cytological observations at both electron and light microscopy levels reveal no other perturbation than the rarefaction of basal bodies and the rare (3%) absence of one or two microtubules in basal bodies or ciliary axonemes. The temperature-sensitive period, during the last 30 min of the cell cycle, corresponds to the phase of basal body duplication. Upon transfer back to the permissive temperature, all basal bodies are normally duplicated. The mutational defect is transiently restored by microinjection of wild-type cytoplasm or of a soluble proteic fraction from wild-type cell homogenates. Altogether, the cytological and physiological data support the conclusion that the sm19+ gene codes for a diffusible product required for the initiation of basal body duplication and would thus be the first identified gene involved in this process. Our data also indicate that in Paramecium basal body number is not coupled with control of the cell cycle, but helps determine the shape of the cell via the organization of the cytoskeleton.

Delayed gametogenesis and spawning of sea bass (Dicentrarchus labrax L.) kept under different photoperiod and temperature regimes

The present work investigates the importance of day length and temperature in the control of reproduction of sea bass, as well as the effectiveness of LHRHa and HCG in inducing spawning out of season in this species. A controlled regime was produced and seasonal cycles with high components of temperature and photoperiod were extended from the summer solstice for at least 6 months, followed by a short photoperiod regime for 3 months before a new increase in these components. Natural spawning in the control fish occurred more frequently in mid February, although it was also observed in January and early March. Temperature manipulation delayed the spawning one month with respect to the controls, although some of the animals entered into gonadal regression. Photoperiodic manipulation delayed maturation for three months with respect to controls but it was necessary to perform hormonal induction of spawning. Although LHRHa and HCG were both applied, only intraperitoneal injections of LHRHa were effective in inducing spawning of sea bass out of season when the temperatures were 17°C. Dephasing between the annual changes in photoperiod in relation to the coordination of the different events of the sexual cycle of sea bass is considered.

Genetic interactions in the control of mitochondrial functions in Paramecium. I. Interactions between nuclear genes

The genetic and physiological properties of two nuclear mutants of Paramecium tetraurelia affecting mitochondrial properties, and first screened as resistant to tetrazolium (TTC) are described. The mutant TTC64-1R is strongly deficient in cytochrome c and the mutant TTC66pR is partially deficient in cytochrome aa3; both mutants display cyanide insensitive respiration in exponential growth phase. In the double mutant TTC64-1R -- TTC66pR/TTC64-1R -- TTC66pR the deficiency in cytochrome aa3 due to the TTC66pR mutation is suppressed. The mutation TTC64-1R does not suppress cytochrome aa3 deficiencies due to mitochondrial mutations, but does interact with another nuclear mutation, cl1, (compatible only with mitochondria deficient in cytochrome oxidase) in such a way that the double mutant TTC64-1R -- cl1/TTC64-1R -- cl1 displays a normal amount of cytochrome aa3. The possible mechanisms and physiological significance of these suppressive effects are discussed.

Genetic interactions in the control of mitochondrial function in Paramecium. II. Interactions between nuclear and mitochondrial genomes

In an attempt to understand the genetic interactions between nuclear and mitochondrial genomes leading to mitochondrial biogenesis, different combinations of known nuclear and mitochondrial mutations have been constructed by microinjection. Eleven different tetrazolium resistant mutant strains, many clearly affecting mitochondrial function, were injected with mitochondria from four different erythromycin resistant mitochondrial mutants. Cases were found in which mutant mitochondria were unable to replicate in tetrazolium resistant mutants. The successful mitochondrial transfers were characterized for growth rate, temperature and cold sensitivity. Several selected combinations were characterised also for cytochrome spectra and cyanide resistance. Many different phenotypes were produced by the interaction of the different nuclear and mitochondrial mutations. These ranged from a positive interaction in which mutant mitochondria were selected by a nuclear mutant in preference to wild-type, through apparent absence of interaction, to negative interaction in which the mitochondrial-nuclear combination was temperature sensitive even though both 'parents' were thermoresistant. The possible molecular basis of these interactions is discussed.

Age at diagnosis and seasonal variation in the onset of insulin-dependent diabetes in Chile (Southern hemisphere)

The age at diagnosis, sex, and the date of both the diagnosis (month--year) and the onset of symptoms of 525 insulin-depdendent diabetic patients, under 30 years of age at the time of diagnosis, were collected retrospectively from hospital records. The patients came from Chilean cities located in the Central Zone: Santiago (87%) and Temuco--Concepcion (13%). The age at diagnosis showed a bimodal distribution up to 19 years of age, with the main peak at 12 years and another at 6 years. The female peak preceded the male peak by 1 to 2 years. The onset of symptoms showed a seasonal variation, with the highest frequency in winter and the lowest in spring (P less than 0.01). There was also a significant variation in the time of diagnosis, especially in the 0--19 age group: most cases were diagnosed in winter (June, July) with the lowest number in summer (December).

[Electrolytic and electrocardiographical correlations under 7% oxygen in nitrogen in dogs (author's transl)]

Electrolytic concentrations in plasma and electrocardiographic parameters in dogs have been studied by means of lineal and canonical correlations, after the animals have been submitted to 7% oxygen in nitrogen for three hours. At the end of hypoxia there appeared hypokalemia, increased T wave potential, low R wave and enlargement of ST segment and PQ interval. The coefficients of lineal correlation between Mg++ levels in plasma and R wave potential and those of Na+ and QRS interval were reversed at the final stages of hypoxia.

Selection and characterization of nuclear mutations affecting mitochondria in Paramecium

A screening method, based upon resistance to a tetrazolium salt (TTC), is described which permitted the isolation in Paramecium of 28 mutants resistant to TTC. These mutants displayed various defects in mitochondrial functions (cytochromic content cyanide insensitive respiration). Some mutations seemed to affect directly the respiration chain while others seemed to cause indirect modifications, possibly altering mitochondrial protein synthesis. Genetic analysis of four mutants showed in all that the resistance to TTC was of nuclear origin.