A wavelet multiscale based method to separate the high and low frequency components of mechanomyographic signals.

The study of mechanomyographic (MMG) signals during dynamic contraction requires a criterion to select the cut-off frequency of the filter utilized to separate the low frequency (L.F) component (basically due to gross movement of the muscle or of the body) and the high frequency (HF) component (related with the vibration of the muscle fibers during contraction). To date, there is not an established criterion to carry out this selection. In this study, we propose a wavelet multiscale based method to aid to select a suitable cut-off frequency to separate correctly the LF and HF components. This method has been tested in an animal model, with the signal acquired during spontaneous ventilations with a capacitive accelerometer applied on the costal wall. This signal, as the MMG signals during dynamic contractions, has a LF component that is related with the movement of the thoracic cage, and a HF component that could be related with the vibration of diaphragm muscle fibers during contraction. The results obtained in the two respiratory tests analyzed indicate that cut-off frequencies around 10 and 3 Hz, respectively, must be employed to eliminate the LF component. The proposed wavelet multiscale method appears to be suitable to carry out a preliminary study of the MMG frequency content in dynamic contraction protocols.

Assessment of respiratory muscle effort studying diaphragm movement registered with surface sensors. Animal model (dogs).

The diaphragm movement (DM) signal during spontaneous ventilations is analyzed in this work. The DM signal is acquired by means two surface sensors (a piezoelectric contact sensor -PCS- and a piezoelectric accelerometer -ACP) applied on the costal wall. The main objective is to develop a new non invasive technique to assess respiratory muscle effort. Experiments were performed in an animal model: four pentobarbital-anesthetized and two awake mongrel dogs, carrying out spontaneous ventilations against an inspiratory load. DM signal has been decomposed in two components: a low frequency component (lower than 5 Hz) due to the overall lateral movement of the muscle (MOV component), and a high frequency component (higher than 5 Hz) due to the lateral vibration of active muscle fibers (VIB component). It has been seen that the PCS acquires only MOV components of MD signal, while ACP acquires both components. Positive high correlation coefficients have been found between amplitude parameters of VIB components of DM signal, acquired by means the ACP, and the respiratory muscle effort during ventilation, measured with inspiratory pressures.

Inhibitory action of extracellular adenosine 5'-triphosphate on parietal cells isolated from rabbit gastric mucosa.

The effects of the purine nucleotides, adenosine 5'-triphosphate (ATP) and their analogs 2-methylthio ATP and beta, gamma-methylene ATP, as well as those of the pyrimidine nucleotide, uridine 5'-triphosphate (UTP), on acid production in isolated rabbit gastric parietal cells prepared by enzymatic dispersion and enriched by counterflow elutriation were studied. The (14C)-aminopyrine (AP) accumulation method was used as an index of acid production by the parietal cells. In histamine-stimulated parietal cells, ATP and 2-methylthio ATP, but not beta, gamma-methylene ATP or UTP, produced significant and concentration-related inhibition of the histamine-stimulated AP uptake. The rank order of potency of these nucleotides in inhibiting histamine-stimulated AP accumulation was 2-methylthio ATP > ATP > > beta, gamma-methylene ATP, UTP. In contrast to these results, the AP accumulation responses to secretagogues other than histamine such as carbachol and dibutyryl-cAMP, were not significantly modified by ATP and analogs. Pretreatment of parietal cells with indomethacin, a prostaglandin synthesis inhibitor, led to a significant reduction of the inhibitory responses elicited by ATP on histamine-stimulated AP uptake. These data suggest that ATP selectively inhibits the histamine-stimulated gastric acid secretion in rabbits by acting directly on parietal cells; that a component of this action seems to be related with a stimulation of prostaglandin production; and that the antisecretory effect of ATP on isolated rabbit parietal cells may be mediated via P2Y-purinoceptors.

[Current use, methodology and evaluation of nonspecific bronchial provocation tests in our country]. / Implantación, metodología y valoración de las pruebas de provocación bronquial inespecíficas en nuestro país.

With the aim of determining the current use of non-specific bronchial inhalation challenge (BIC) testing in Spain, 147 questionnaires were sent to hospitals with pneumology departments or units. The questionnaire covered general, technical and methodological aspects of this diagnostic procedure, as well as its assessment and interpretation. Of the 42 informants who returned questionnaires, mainly from large urban hospitals, 34 reported using BIC. The most widespread criterion applied in deciding to use BIC was the presence of atypical asthma symptoms (33/34). The stimulus most often used was methacholine inhalation (33/34). We found that technical preparation of the drug was highly standardized, but that administration and follow-up protocols differed greatly. There was also great variety in the PC20/PD20 value assigned to indicate bronchial hyperresponsiveness. This study contributes to our better understanding of the current use of BIC in Spain and highlights the need to work toward greater standardization for this diagnostic procedure, to enable us to assess and interpret the results more consistently.

Effect of adenosine 5'-triphosphate on secretagogue-stimulated (14C)-aminopyrine accumulation by rabbit isolated gastric glands.

The effect of adenosine 5'-triphosphate (ATP) on gastric acid secretion stimulated by histamine, carbachol and dibutyryl-cAMP (db-cAMP) was studied using glands isolated from rabbit gastric mucosa. The (14C)-aminopyrine (AP) accumulation method was used as an index of acid production by the gastric glands. Histamine-stimulated AP accumulation was significantly inhibited by ATP (10 mumol/l-1 mmol/l). The inhibitory action of ATP appeared to be specific, inasmuch as this nucleotide had no significant effect on basal secretion or secretion stimulated by carbachol or db-cAMP. The antisecretory effect of ATP on histamine-stimulated glands was not affected by the P1-purinoceptor antagonist, theophylline. Pretreatment of glands with indomethacin, a well known prostaglandin synthesis inhibitor, led to a significant reduction of the inhibitory responses to ATP. These results show that ATP inhibits the histamine-stimulated AP accumulation by rabbit isolated gastric glands and suggest that this effect is not due to an ectoenzymatic conversion of ATP into adenosine but to a direct effect of ATP which may be mediated via a P2-purinoceptor subtype linked to prostaglandin production.

[Specific inhibition by ATP of histamine-stimulated acid secretion in the gastric glands of the rabbit]. / Inhibición específica por ATP de la secreción ácida estimulada por histamina en glándulas gástricas de conejo.

The influence of adenosine 5'-triphosphate on gastric acid secretion stimulated by histamine, carbachol, dibutyryl-cAMP and the phosphodiesterase inhibitors 8-phenyl-theophylline and rolipram in isolated rabbit gastric glands was studied. Changes oi gastric acid secretion were measured by the aminopyrine accumulation method. Histamine-stimulated acid secretion was significantly inhibited by ATP 1 mM, whereas the secretory responses elicited by carbachol, dibutyryl-cAMP, 8-phenyl-theophylline or rolipram were not. Assays with indomethacin, a well known prostaglandin synthesis inhibitor, showed that this agent significantly reduced the inhibitory effect of ATP on histamine responses. The results indicate that the antisecretory effect of ATP was specific for histamine and that it was mediated, at least in part, via stimulation of endogenous prostaglandin production.

Characterization of the effects of adenosine, adenosine 5'-triphosphate and related purines on acid secretion in isolated rabbit gastric glands.

The influence of adenosine, AMP, ADP, ATP, the adenosine analogue L-PIA and the ATP analogue beta,gamma-methylene ATP, on gastric acid secretion, as measured by the aminopyrine accumulation method, in resting and histamine-stimulated glands isolated from rabbit gastric mucosa was studied. In resting glands, adenosine and its analogue L-PIA (10 microM-1 mM) caused significant concentration-related increases of the basal H+ secretion, whereas no changes were obtained in response to the other purines tested. In histamine-stimulated glands, adenosine, L-PIA and AMP (10 microM-1 mM) induced concentration-related increases of the H+ secretory rate, whereas ATP, beta,gamma-methylene ATP and ADP (10 microM-1 mM) produced concentration-related decreases of the H+ raised rate. The rank order of potency of the purine compounds in increasing the stimulated H+ secretion was: adenosine greater than L-PIA much greater than AMP, and in decreasing it was: ATP much greater than ADP greater than beta,gamma-methylene ATP. The stimulatory responses to adenosine were inhibited by theophylline (10 microM-100 microM) and caffeine (10 microM-1 mM); whereas, the inhibitory responses to ATP were significantly reduced by the well known prostaglandin synthesis inhibitor indomethacin (1 microM-100 microM). From the results it is concluded that in isolated rabbit gastric glands, purine compounds are effective modulators of the gastric H+ secretory process. The pattern of purine activity obtained suggests that the stimulatory responses, inhibited by methylxanthines, may be mediated via P1-purinoceptors, while the inhibitory responses, reduced by indomethacin, may be mediated via P2-purinoceptors.

Activities and some properties of 5'nucleotidase in isolated hamster fat cells.

Kinetic parameters and the possible cellular location of 5'nucleotidase were studied in isolated hamster fat cells. Measurements of the enzyme were performed using 5'IMP instead of 5'AMP as substrate. The apparent Vmax and Km values obtained support the view that two forms of 5'nucleotidase, having different affinities, are present in hamster fat cells. The major form was located in the outer surface of plasma membrane and the other one inside the cell. The effects of ADP, adenosine and inosine on the enzyme were studied. ADP and adenosine were competitive inhibitors. The enzyme was not modified by inosine.

Effects of thyroid hormone deficiency on lipolysis in chicken fat cells.

Effect of lack of thyroid hormones on lipolysis in chicken fat cells was studied. Isolated fat cells from hypothyroid chickens in contrast to normal animals, have an impaired ability to give lipolytic response to glucagon. However activation of triglyceride lipolysis was induced to the same level by theophylline in hypothyroid and normal chickens.