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Biomedical subjects

J Gallego

Publications and source records attributed to J Gallego.

At least 55 records · Page 3Linked to original sources
PubMed1997

Influence of thoracoabdominal pattern of breathing on respiratory resistance.

The purpose of this study was to test the hypothesis that voluntary changes in thoracoabdominal pattern of breathing may increase total respiratory resistance. Thirty-one normal subjects were asked to control their thoracoabdominal pattern of breathing by using a visual feedback. Thoracic and abdominal volume changes were measured by inductance plethysmography. Respiratory resistance and elastance were measured by forced oscillometry. The mean (+/-SD) percent thoracic contributions to tidal volume during thoracic or abdominal breathing were 75 (+/-11) and 25% (+/-9), respectively. These changes induced small but significant increases in resistance (P < 0.005) and elastance (P < 0.002). The increased resistance was observed in 22 subjects for thoracic breathing (P < 0.016) and in 21 subjects for abdominal breathing (P < 0.043). The mean value (+/-SD) of individual increases in resistance during thoracic or abdominal breathing, compared with normal breathing, were 9.2 +/- 17.5 and 9.4 +/- 19.9%, respectively. The fact that departing from spontaneous pattern increases respiratory resistance is consistent with the notion that breathing pattern is optimally adjusted on the basis of mechanical criteria.

Abdomen↗
PubMed1997

Structure-affinity relationships for the binding of actinomycin D to DNA.

Molecular models of the complexes between actinomycin D and 14 different DNA hexamers were built based on the X-ray crystal structure of the actinomycin-d(GAAGCTTC)2 complex. The DNA sequences included the canonical GpC binding step flanked by different base pairs, nonclassical binding sites such as GpG and GpT, and sites containing 2,6-diamino-purine. A good correlation was found between the intermolecular interaction energies calculated for the refined complexes and the relative preferences of actinomycin binding to standard and modified DNA. A detailed energy decomposition into van der Waals and electrostatic components for the interactions between the DNA base pairs and either the chromophore or the peptidic part of the antibiotic was performed for each complex. The resulting energy matrix was then subjected to principal component analysis, which showed that actinomycin D discriminates among different DNA sequences by an interplay of hydrogen bonding and stacking interactions. The structure-affinity relationships for this important antitumor drug are thus rationalized and may be used to advantage in design of novel sequence-specific DNA-binding agents.

Anti-Bacterial Agents↗
PubMed1997

Hypermethylation of a 5' CpG island of p16 is a frequent event in non-Hodgkin's lymphoma.

Hypermethylation of a 5' CpG island of p16 gene has been recently described as a possible way of inactivation of this tumor suppressor gene, alternative to deletions and mutations. We have investigated if hypermethylation of a 5' CpG island of p16 occurs in non-Hodgkin's lymphoma (NHL) and normal lymphoid tissue. A total of 82 NHLs were examined for p16 methylation by Southern blot and PCR analysis. Hypermethylation was detected in approximately 20% of B cell lymphomas of both low and high grade and in 15% of T cell NHL. The highest rate of p16 gene methylation in tumors was found among MALT (mucosa-associated lymphoid tissue) lymphomas in which the percentage of cases with p16 gene methylation reached 67%. However, normal lymphoid tissue was always unmethylated at p16 locus. These results indicate that p16 gene methylation is a frequent event in NHLs, mainly in MALT lymphomas, and suggest that it could be an important mechanism of inactivation of this gene.

Binding Sites↗
PubMed1997

Classic conditioning of the ventilatory responses in rats.

Recent authors have stressed the role of conditioning in the control of breathing, but experimental evidence of this role is still sparse and contradictory. To establish that classic conditioning of the ventilatory responses can occur in rats, we performed a controlled experiment in which a 1-min tone [conditioned stimulus (CS)] was paired with a hypercapnic stimulus [8.5% CO2, unconditioned stimulus (US)]. The experimental group (n = 9) received five paired CS-US presentations, followed by one CS alone to test conditioning. This sequence was repeated six times. The control group (n = 7) received the same number of CS and US, but each US was delivered 3 min after the CS. We observed that after the CS alone, breath duration was significantly longer in the experimental than in the control group and mean ventilation was significantly lower, thus showing inhibitory conditioning. This conditioning may have resulted from the association between the CS and the inhibitory and aversive effects of CO2. The present results confirmed the high sensitivity of the respiratory controller to conditioning processes.

Acoustic Stimulation↗
PubMed1996

Molecular dynamics simulations of the bis-intercalated complexes of ditercalinium and Flexi-Di with the hexanucleotide d(GCGCGC)2: theoretical analysis of the interaction and rationale for the sequence binding specificity.

The X-ray crystal structures of the complexes of ditercalinium and Flexi-Di with d(CGCG)2 have been studied by computational chemistry methods in an attempt to rationalize their distinct structural features. In addition, the complexes of these two bisintercalating drugs with d(GCGCGC)2 have been modeled and subjected to 0.5 ns of molecular dynamics simulations in explicit solvent with the aim of evaluating the relative importance of hydrogen bonding and stacking interactions in the sequence binding specificity of these compounds. According to our calculations, the electrostatic term is attractive for the stacking interactions between the pyridocarbazole chromophores of these drugs and the base pairs that make up the sandwiched GpC step. On the contrary, this energy term is repulsive for the base pairs that make up the boundaries of the bisintercalation site. This differential electrostatic binding energy component, which is shown to have a strong orientational dependence, could lie at the origin of the observed binding preferences of these drugs. In addition, both the Lennard-Jones and the electrostatic energy terms contribute to stabilizing the underwound central GpC step. The attractive electrostatic interactions between the linkers and the major groove are in concert with the stacking specificities for the sandwiched GpC step, which is thus very effectively stapled by the drugs. The hydrogen-bonding potential of the linkers, however, appears to be reduced in an aqueous medium due to competing interactions with water. Binding of either ditercalinium or Flexi-Di to d(GCGCGC)2 appears to favor the A-type conformation that this DNA molecule most likely adopts in the free state. The possible relevance of these findings to the process of bis-intercalation and to the pharmacological action of these compounds is discussed.

Carbazoles↗
PubMed1996

The effects of breathing pattern training on ventilatory function in patients with COPD.

The purpose of this study was to assess the effects of a particular breathing pattern training (BPT) on forced expiratory volume during the first second (FEV1) and forced vital capacity (FVC) in patients with chronic obstructive pulmonary disease (COPD). The subjects adjusted each breath to a target breath displayed on a video screen, by using visual feedback. This target was chosen in an individual sample recorded at rest. We used a randomized, controlled group design. Twenty patients with stable COPD, FEV1 less than 1.5 liters, undergoing a traditional rehabilitation program were randomly assigned to the BPT group or to the control group. Each BPT subject underwent 30-35 training sessions spread out over four weeks, in addition to the traditional program. FEV1 and FVC were performed before and after this program. ANOVAs showed that FEV1 and FVC significantly improved in BPT subjects, with a mean percent increase of 22% and 19%, respectively. Corresponding changes in controls were not significant. This study showed short-term increases in FEV1 and FVC in COPD patients practicing BPT in addition to respiratory rehabilitation, in comparison with controls. Further studies should incorporate outcome data to clarify the mechanisms and the duration of this effect.

Aged↗
PubMed1996

Incidence of homogeneously staining regions in non-Hodgkin lymphomas.

We report a series of 86 non-Hodgkin's lymphomas (NHL) studied cytogenetically in which two cases with a homogeneously staining region (HSR) located on chromosome 19 and on chromosome 1, respectively, were observed. The low incidence detected (2.3%) suggests that HSR are rare events in NHL. An oncogenetic amplification study was performed with probes for genes that are currently known to undergo amplification and with probes for two genes located on chromosome 19q (AKT2 and BCL-3). We detected no amplification except for AKT2 putative oncogene in the lymphoma in which the HSR was located on chromosome 19. Because amplification of AKT2 putative oncogene has been detected in ovarian carcinomas bearing HSR and in this case NHL, we believe that this gene may be implicated in the pathogenesis of other neoplasias in cooperation with other genes. Further investigation is needed to confirm the low incidence of HSR in NHL and the origin of the amplified material.

Adult↗
PubMed1996

Bionomics of Lutzomyia evansi (Diptera: Psychodidae) vector of visceral leishmaniasis in northern Columbia.

The feeding behavior, seasonality, and natural infection rate of Lutzomyia evansi (Nuñez-Tovar) with Leishmania chagasi (Cuna & Chagas) was studied during a 12-mo period at 2 hamlets, El Contento and Vidales. Sand fly abundance in extra-, peri-, and intradomestic habitats was evaluated with sticky traps and CDC light traps, whereas human bait and Shannon trap collections were made only in peridomestic habitats. All trapping methods showed a clear predominance of L. evansi throughout the year. Sand flies were present during most of the year, with the exception of the driest months (February and March). Although the total number of sand flies was higher in El Contento than in Vidales, a larger proportion of L. evansi was found in intradomestic habitat than in the peri- and extradomestic habitats at Vidales. Also, sand flies from Vidales had a higher infection rate with L. chagasi than did those from El Contento. Although 2 of 9 promastigote infections detected in L. evansi were identified as L. chagasi, the difficulty of isolating and propagating leishmania strains from this visceral leishmaniasis focus precluded characterization of most parasite samples. Parous and infected sand flies were most abundant toward the end of the rainy season (October-December). For this reason, control strategies based on reducing sand fly populations or avoiding human-vector contact should be concentrated during the October-December period.

Animals↗
PubMed1996

Ventilatory responses to imagined exercise.

We studied whether the ventilatory responses to imagined exercise are influenced by automatic processes. Twentynine athletes produced mental images of a sport event with successive focus on the environment, the preparation, and the exercise. Mean breathing frequency increased from 15 to 22 breaths/min. Five participants reported having voluntarily controlled breathing, two of them during preparation. Twenty participants reported that their breathing pattern changed during the experiment: 11 participants were unable to correctly report on the direction of changes in frequency, and 13 incorrectly reported changes in amplitude. This finding suggests that these changes were not voluntary in most participants and may therefore reveal automatic forebrain influences on exercise hyperpnea. However, these changes may also reflect nonspecific processes (e.g., arousal) different from those occurring during actual exercise.

Adult↗
PubMed1996

Voluntary decrease in breathing frequency in exercising asthmatic subjects.

Exercise rehabilitation programmes are increasingly recommended in young asthmatics, but it is unclear whether or not training should incorporate instructions on breathing pattern. In this study, we examined the effects of voluntarily decreasing breathing frequency on their ventilatory equivalents for oxygen and carbon dioxide (minute ventilation (V'E)/oxygen consumption (V'O2) and V'E/CO2 production (V'CO2), respectively), noninvasively determined physiological dead space/tidal volume (VD/VT) and dyspnoea. Fifteen young asthmatic subjects were assigned to two groups: low frequency breathing (LFB) and controls. They first underwent an exercise test at a cardiac frequency of 150 beats x min(-1). They were trained at this level for nine sessions. LFB subjects were instructed to decrease respiratory frequency by 40% during exercise. Control subjects received no instructions. A second test was then performed in the same conditions. LFB subjects decreased V'E/V'O2, V'E/V'CO2 and VD/VT by 22, 19 and 12%, respectively. Arterial oxygen saturation (Sa,O2) fell to 89+/-4% and end-tidal carbon dioxide tension (PET,CO2) rose to 6.5+/-0.7 kPa (49+/-5 mmHg). In controls, these variables were identical in the two tests. Dyspnoea was lower in the second test in all subjects. In conclusion, breathing pattern may be profoundly altered during exercise without concomitant increase in dyspnoea. However, directing breathing patterns for exercise rehabilitation requires an individual assessment of the desired pattern in order to prevent hypercapnia or hypoxia.

Adaptation, Physiological↗
PubMed1996

Thoracoabdominal pattern of breathing in neuromuscular disorders.

STUDY OBJECTIVE: To assess abnormalities in thoracoabdominal pattern of breathing (TAPB) in neuromuscular disorders during spontaneous breathing, intermittent positive pressure ventilation (IPPV) with and without abdominal (AB) binder, and immediately after IPPV. DESIGN: Repeated measures design: Pre-IPPV spontaneous breathing, IPPV, IPPV with AB binder, and post-IPPV spontaneous breathing. In protocol 1, ventilator pressure was held constant at the individual value habitually adopted in sessions of IPPV. In protocol 2, it was increased stepwise from 5 to 30 cm H2O. SETTING: University hospital, Department of Pediatrics, Intensive Care, and Neuro-Ventilatory Rehabilitation. PATIENTS: Thirty-one patients with spinal muscular atrophy (SMA) and 19 patients with myopathy, mean age (+/- SD) 9.7 +/- 3 years. MEASUREMENTS: Tidal volume (VT), percent thoracic contribution to VT (%RC), the phase angle between the thoracic and the AB volume changes and the labored breathing index, which is an index of asynchrony taking into account both the phase relationships and relative volumes of rib cage and AB compartments. RESULTS: We observed marked abnormalities in TAPB during spontaneous breathing, especially in the SMA group. %RC, labored breathing index, and phase angle displayed nearly normal values during IPPV. IPPV pressures of 25 to 30 cm H2O were necessary to increase %RC above 80%. AB binding decreased VT, but led to larger thoracic volumes, especially in patients with SMA. Thoracic contribution to VT and thoracic volume after IPPV were higher than baseline levels. CONCLUSIONS: The quantitative assessment of TAPB enhances the ability to estimate pulmonary function in neuromuscular disorders, and the efficiency of mechanical ventilation.

Abdomen↗
PubMed1996

Voluntary control of breathing pattern in asthmatic children.

15 asthmatic children and 15 healthy children were trained to adjust their breathing pattern to a target pattern displayed on a video screen by using visual feedback. The error scores in the two groups were not significantly different. These data did not support the hypothesis that voluntary control of respiratory muscles is impaired in asthmatics.

Asthma↗
PubMed1995

Percutaneous venography and embolization of the internal spermatic vein by spring coil for treatment of the left varicocele in children.

The treatment of varicocele is controversial in boys and it is a contributing factor to male infertility. Recently it has been proposed that early therapy of a varicocele during childhood or adolescence may improve the prognosis of fertility. The authors review their experience with the diagnosis and management of left varicocele in 20 pediatric patients 6 to 15 years old. All were managed under local anesthesia by spermatic venography and percutaneous transcatheter embolization of the internal spermatic vein with spring coils. All achieved satisfactory occlusion, and during the follow-up, from 13 years to 9 months, there was only one recurrence, noted in a patient 6 months after the procedure. Complications were phlebitis of the pampiniform plexus, leading to swelling and erythema of the left scrotum, and mild flank pain; these symptoms resolved without sequelae. This is a safe and effective nonsurgical method of obliterating varicoceles in children, with a low morbidity rate and a short hospital stay.

Child↗