The antennal benzoic acid receptor cell of the female silk moth <Emphasis Type="Italic">Bombyx mori</Emphasis> L.: structure–activity relationship studies with halogen substitutes

Studies on structure–activity relationships were carried out to characterize the response specificity of the benzoic acid cell of the female of the moth Bombyx mori by means of single sensillum electrophysiological recordings. We demonstrated that this cell type responds best to a natural key substance (benzoic acid) and has similar response profiles for less effective compounds, including various halogen substitutes of benzoic acid, benzaldehyde and other derivates of the key compound. Using different halogen substitutes (F, Cl, Br, I), we showed that the cellular response decreases with increasing atomic size of the substitute and that halogen substitutes were most effective in the meta-position. Thus, m-fluor benzoic acid was even more effective than benzoic acid. These results indicate that a critical feature of the stimulus molecule is the inductive effect generated by the halogen substitutes. Increasing the atomic size of the halogen substitute impairs the recognition of the molecule by the receptor cell, possibly due to steric effects. Decreasing the electron density in the aromatic ring improves the receptor response. The benzoic acid receptor cell can be considered as specialist despite not being involved in pheromone detection as it responds maximally to a key substance and has similar response profiles for less effective compounds.     

Pushing forces drive the comet-like motility of microtubule arrays in Dictyostelium

Overexpression of dynein fragments in Dictyostelium induces the movement of the entire interphase microtubule array. Centrosomes in these cells circulate through the cytoplasm at rates between 0.4 and 2.5 microm/s and are trailed by a comet-tail like arrangement of the microtubule array. Previous work suggested that these cells use a dynein-mediated pulling mechanism to generate this dramatic movement and that similar forces are at work to maintain the interphase MTOC position in wild-type cells. In the present study, we address the nature of the forces used to produce microtubule movement. We have used a laser microbeam to sever the connection between the motile centrosomes and trailing microtubules, demonstrating that the major force for such motility results from a pushing on the microtubules. We eliminate the possibility that microtubule assembly/disassembly reactions are significant contributors to this motility and suggest that the cell cortex figures prominently in locating force-producing molecules. Our findings indicate that interphase microtubules in Dictyostelium are subject to both dynein- and kinesin-like forces and that these act in concert to maintain centrosome position in the cell and to support the radial character of the microtubule network.     

Adaptation to a high protein, carbohydrate-free diet induces a marked reduction of fatty acid synthesis and lipogenic enzymes in rat adipose tissue that is rapidly reverted by a balanced diet

We have previously shown that in vivo lipogenesis is markedly reduced in liver, carcass, and in 4 different depots of adipose tissue of rats adapted to a high protein, carbohydrate-free (HP) diet. In the present work, we investigate the activity of enzymes involved in lipogenesis in the epididymal adipose tissue (EPI) of rats adapted to an HP diet before and 12 h after a balanced diet was introduced. Rats fed an HP diet for 15 days showed a 60% reduction of EPI fatty acid synthesis in vivo that was accompanied by 45%-55% decreases in the activities of pyruvate dehydrogenase complex, ATP-citrate lyase, acetyl-CoA carboxylase, glucose-6-phosphate dehydrogenase, and malic enzyme. Reversion to a balanced diet for 12 h resulted in a normalization of in vivo EPI lipogenesis, and in a restoration of acetyl-CoA carboxylase activity to levels that did not differ significantly from control values. The activities of ATP-citrate lyase and pyruvate dehydrogenase complex increased to about 75%-86% of control values, but the activities of glucose-6-phosphate dehydrogenase and malic enzyme remained unchanged 12 h after diet reversion. The data indicate that in rats, the adjustment of adipose tissue lipogenic activity is an important component of the metabolic adaptation to different nutritional conditions.     

Yeast population dynamics of industrial fuel-ethanol fermentation process assessed by PCR-fingerprinting

Yeast population used in industrial production of fuel-ethanol may vary according to the plant process condition and to the environmental stresses imposed to yeast cells. Therefore, yeast strains isolated from a particular industrial process may be adapted to such conditions and should be used as starter strain instead of less adapted commercial strains. This work reports the use of PCR-fingerprinting method based on microsatellite primer (GTG)₅ to characterize the yeast population dynamics along the fermentation period in six distilleries. The results show that indigenous fermenting strains present in the crude substrate can be more adapted to the industrial process than commercial strains. We also identified new strains that dominate the yeast population and were more present either in molasses or sugar cane fermenting distilleries. Those strains were proposed to be used as starters in those industrial processes. This is the first report on the use of molecular markers to discriminate Saccharomyces cerevisiae strains from fuel-ethanol producing process.     

Bismuth citrate in the quantification of inorganic phosphate and its utility in the determination of membrane-bound phosphatases

This paper describes a rapid and sensitive method to determine inorganic phosphate, even in the presence of labile organic phosphate compounds and large quantities of proteins. The method eliminates the use of sodium arsenite, a highly toxic compound, substituting bismuth citrate for it to stabilize the phosphomolybdic acid complex formed during the interaction of inorganic phosphate and molybdate reduced by ascorbic acid. This method has also been adapted to microplates and has been used to determine the activities of Na/K ATPase and alkaline phosphatase of intestinal basolateral and luminal plasma membranes.     

Gas chromatography/mass spectrometry characterization of urinary metabolites of danazol after oral administration in human

Danazol (17alpha-pregna-2,4-dien-20-yno [2,3-d]-isoxazol-17beta-ol), is a synthetic derivative of ethisterone, structurally related to stanozolol. For this reason its use as doping agent has been investigated. Danazol (Runch) (200 mg) were orally administered to two healthy male volunteers. Urine samples were collected up to 1-week post-dose. Four new metabolites have been identified in addition to the five previously reported. We propose the monitorization of 6beta-hydroxy-2-hydroxymethyl-1,2-dehydroethisterone and 6beta,16epsilon-dihydroxy-2epsilon-hydroxymethyl-ethisterone by free fraction analysis. In a same way, we proposed to detect the principal isomer of a mono-hydroxylated metabolite of 6beta-hydroxy-2epsilon-hydroxymethylethisterone in the conjugated fraction. We conclude that new metabolites can be included for the detection of danazol abuse since the main metabolite ethisterone is excreted relatively fast in urine.     

Regulation of ventilation in the caiman (Caiman latirostris): effects of inspired CO2 on pulmonary and upper airway chemoreceptors

In order to study the relative roles of receptors in the upper airways, lungs and systemic circulation in modulating the ventilatory response of caiman (Caiman latirostris) to inhaled CO₂, gas mixtures of varying concentrations of CO₂ were administered to animals breathing through an intact respiratory system, via a tracheal cannula by-passing the upper airways (before and after vagotomy), or via a cannula delivering gas to the upper airways alone. While increasing levels of hypercarbia led to a progressive increase in tidal volume in animals with intact respiratory systems (Series I), breathing frequency did not change until the CO₂ level reached 7%, at which time it decreased. Despite this, at the higher levels of hypercarbia, the net effect was a large and progressive increase in total ventilation. There were no associated changes in heart rate or arterial blood pressure. On return to air, there was an immediate change in breathing pattern; breathing frequency increased above air-breathing values, roughly to the same maximum level regardless of the level of CO₂ the animal had been previously breathing, and tidal volume returned rapidly toward resting (baseline) values. Total ventilation slowly returned to air breathing values. Administration of CO₂ via different routes indicated that inhaled CO₂ acted at both upper airway and pulmonary CO₂-sensitive receptors to modify breathing pattern without inhibiting breathing overall. Our data suggest that in caiman, high levels of inspired CO₂ promote slow, deep breathing. This will decrease dead-space ventilation and may reduce stratification in the saccular portions of the lung.     

Inhibition of Nitric Oxide Production by Macrophages in Chromoblastomycosis: A Role for Fonsecaea pedrosoi Melanin

Chromoblastomycosis is a chronic and progressive deep mycosis that is usually found in tropical and subtropical areas. Fonsecaea pedrosoi is considered its most frequent etiologic agent and causes a typical granulomatous inflammatory response, whose degree reflects the immune status of the host. Since macrophages play a fundamental role in the control of the infection, this study aimed at investigating the production of oxygen reactive specimens, the phagocytic capacity and the production of nitric oxide (NO) by macrophages employing in vitro assays and an in vivo model of chromoblastomycosis. Our results demonstrated that, during the infection, peritoneal macrophages show an increased phagocytic capacity and H₂O₂ production, but also a reduced ability to produce NO. Moreover, F. pedrosoi stimulated H₂O₂ production in vitro but not the synthesis of NO. The incubation of IFNγ and LPS-stimulated macrophages with melanin, obtained from the fungus, inhibited NO production. Examination of the liver and spleen of infected animals, at day 30 or 60 following inoculation, showed a progressive increase in the number and size of granulomas, indicating that macrophages are properly mobilized and activated. Our data suggest that the inability of the host to clear F. pedrosoi, leading to a chronic disease, is due, at least in part, to the inhibition of NO synthesis by macrophages by fungus-produced melanin.