The spike activity of neuromodulatory dorsal unpaired median (DUM) neurons was analyzed during a pilocarpine-induced motor pattern in the locust. Paired intracellular recordings were made from these ...octopaminergic neurons during rhythmic activity in hindleg motor neurons evoked by applying pilocarpine to an isolated metathoracic ganglion. This motor pattern is characterized by two alternating phases: a levator phase, during which levator, flexor, and common inhibitor motor neurons spike, and a depressor phase, during which depressor and extensor motor neurons spike. Three different subpopulations of efferent DUM neurons could be distinguished during this rhythmical motor pattern according to their characteristic spike output. DUM 1 neurons, which in the intact animal do not innervate muscles involved in leg movements, showed no change apart from a general increase in spike frequency. DUM 3 and DUM 3,4 neurons produced the most variable activity but received frequent and sometimes pronounced hyperpolarizations that were often common to both recorded neurons. DUM 5 and DUM 3,4,5 neurons innervate muscles of the hindleg and showed rhythmical excitation leading to bursts of spikes during rhythmic activity of the motor neurons, which innervate these same muscles. Sometimes the motor output was coordinated across both sides of the ganglion so that there was alternating activity between levators of both sides. In these cases, the spikes of DUM 5 and DUM 3,4,5 neurons and the hyperpolarization of DUM 3 and DUM 3,4 neurons occurred at particular phases in the motor pattern. Our data demonstrate a central coupling of specific types of DUM neurons to a rhythmical motor pattern. Changes in the spike output of these particular efferent DUM neurons parallel changes in the motor output. The spike activity of DUM neurons thus may be controlled by the same circuits that determine the action of the motor neurons. Functional implications for real walking are discussed.
The significant impact of dust deposition on heterotrophic bacterial dynamics in the surface oligotrophic ocean has recently been evidenced. Considering the central role of bacteria in the microbial ...loop, it is likely that dust deposition also affects the structure and the functioning of the whole microbial food web. In the frame of the DUNE project, aiming to estimate the impact of dust deposition on the oligotrophic Mediterranean Sea through mesocosm experiments, the main goal of the present paper was to assess how two successive dust deposition events affect the dynamics of the microbial food web. The first dust seeding delivered new P and N to the amended mesocosms and resulted in a pronounced stimulation of bacterial respiration. It also induced pronounced, but transient, changes in the bacterial community composition. No significant effects were observed on the abundances of viruses and heterotrophic nanoflagellates. The second dust seeding also delivered new P and N to the amended mesocosms, but the effect on the microbial food web was very different. Bacterial respiration remained constant and bacterial abundance decreased. Compositional changes following the second seeding were minor compared to the first one. The decrease in bacterial abundance coincided with an increase in virus abundance, resulting in higher virus : bacteria ratios throughout the second seeding period. Our study shows that dust deposition to the surface oligotrophic ocean may involve important modifications of the trophic links among the components of the microbial food web with presumed consequences on C and nutrient cycling.
Since Plasmodium falciparum malaria is a frequent cause of anemia among African children, and blood transfusions, unscreened for human immunodeficiency virus (HIV) antibody, are used frequently in ...the treatment of children with severe malaria, the relationships between malaria, transfusions, and HIV seropositivity were investigated in a pediatric population in Kinshasa, Zaire. In a cross-sectional survey of 167 hospitalized children, 112 (67%) had malaria, 78 (47%) had received transfusions during the current hospitalization, and 21 (13%) were HIV seropositive. Ten of the 11 seropositive malaria patients had received transfusions during the current hospitalization; pretransfusion specimens were available for four of these children and were seronegative. Of all blood transfusions, 87% were administered to malaria patients, and there was a strong dose-response association between transfusions and HIV seropositivity. A review of 1000 emergency ward records demonstrated that 69% of transfusions were administered to malaria patients, and 97% of children who received transfusions had pretransfusion hematocrits of 0.25 or less (less than or equal to 25%). The treatment of malaria with blood transfusions is an important factor in the exposure of Kinshasa children to HIV infection.
Titanium alloys are well known as candidates for aeronautical applications in turbine engines because they remain efficient at moderately elevated temperatures. The permanent need to increase the ...operating temperature requires intensive tseting on the fatigue crack propagation behavior of new generation alloys. These alloys are still at an early stage of development and are intended to push the maximum application temperature up to 500 deg C. As they will be exposed in turbine engines to long term elevated temperatures, oxidation effects must also be taken into account. The upper-use temperature for the usual Ti alloys is approx300 deg C. Increasing the operating temperature of the material leads to increased environmental influence. Cycling in air can result in significant rapid degradation of the material due to embrittlement at the crack tip as a result of reaction with active species. The present paper deals with a study on fatigue crack propagation (FCP) in a Ti alloy tested in ambiant air at temperatures ranging from 300-500 deg C.
A serological survey was carried out in the suburban forest zone of Abidjan from July to September 2004 to estimate the prevalence of brucellosis in dairy cattle. Three hundred and eighty one (381) ...serums were collected from a total of 927 animals, of which 506 originated from the dairy farms supervised by the South Dairy Project (demonstration farm and private farms), and 421 from neighboring traditional herds. Four serological tests were performed: the rose bengal test, indirect ELISA, the complement fixation test, and the slow agglutination test of Wright with EDTA (micromethod). On the basis of serological and bayesian analyses, seroprevalence rates of about 3.6 and 4.3% were found in the dairy farms and traditional herds, respectively. No significant difference was found between the farms and traditional herds (p < 0.05).
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