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Biomedical subjects

R Montoya

Publications and source records attributed to R Montoya.

At least 19 recordsLinked to original sources
PubMed2005

[Is electrical stimulation with voluntary muscle contraction of physiologic interest in aging women?].

OBJECTIVE: To analyze the physiological effects of electrical stimulation with voluntary muscle contraction exercise in postmenopausal women. MATERIALS AND METHODS: Thirty-two females aged 62 to 75 years were randomly assigned to three groups to perform four activity sessions for six weeks: group ME (N =11) climbed up and down stairs, group ES (N =11) practised electrostimulation, and group ME + ES (N = 10) undertook both activities. Physiological adaptations of body composition (lean and fat masses and bone mineral density), muscular strength (isometric and dynamic), vertical jump and posturokinetic activities (balance and gait) were analysed. RESULTS: For the three groups, the isometric strength at angle 100 degrees (average increase right and left legs, ME: 19 N.m; ES: 4.5 N.m; ME + ES: 11.5 N.m), the dynamic strength at speed 60 degrees.s(-1) (average increase right and left leg, ME: 15 N.m; ES: 14 N.m; ME+ES: 18.5 N.m) and the vertical jump (ME: 23 mm; ES: 16 mm; ME + ES: 34 mm) increased contrary in the body composition and posturokinetic activities. Nevertheless, the group ME + ES adapted differently on some parameters of bone mineral density (P < 0.05) and dynamic strength (P < 0.01) in relation to the groups ES and ME. CONCLUSION: Electrostimulation with voluntary muscle contraction exercise could induce different physiologic adaptations compared with electrostimulation or voluntary muscle contraction exercise alone.

Adaptation, Physiological↗
PubMed2004

Neuromuscular effects of three training methods in ageing women.

AIM: The present study aimed to compare the effects of 3 strength development methods on muscular mass and muscular strength in healthy ageing women. METHODS: Thirty-two healthy women, 62 to 75 years old were randomised into 3 groups. The 3 groups performed 4 sessions a week of strength development for 6 weeks. The 1(st) group (SC) climbed up and down 300 stairs per session. The 2(nd) group (ES) followed an electrostimulation programme on the quadriceps muscles. The 3(rd) group (SC+ES) combined stair climbing with electrostimulation. Before and after the 3 programmes, the muscular mass of the leg was assessed using a biphotonic absorptiometry machine. Isometric (angle 20 degrees and 100 degrees ) and isokinetic (60 degrees /s and 240 degrees /s) knee extension torque was measured using an isokinetic dynamometer. RESULTS: None of the programmes changed the muscular mass. All 3 groups increased isometric (angle 20 degrees, p<0.001; angle 100 degrees, p<0.003) and isokinetic (60 degrees /s, p<0.0001; 240 degrees /s, p<0.0001) knee extension torque. None of the programmes appeared more efficient than the others for muscular mass or muscular strength. CONCLUSION: Six weeks of activity (SC, ES or SC+ES) improved the isometric and dynamic muscular strength in ageing healthy women. However, this period was too short to change the muscular mass. None of the activities presented a real advantage over the others in ageing women.

Age Factors↗
PubMed2001

Analysis of lung tumor initiation and progression using conditional expression of oncogenic K-ras.

Adenocarcinoma of the lung is the most common form of lung cancer, but the cell of origin and the stages of progression of this tumor type are not well understood. We have developed a new model of lung adenocarcinoma in mice harboring a conditionally activatable allele of oncogenic K-ras. Here we show that the use of a recombinant adenovirus expressing Cre recombinase (AdenoCre) to induce K-ras G12D expression in the lungs of mice allows control of the timing and multiplicity of tumor initiation. Through the ability to synchronize tumor initiation in these mice, we have been able to characterize the stages of tumor progression. Of particular significance, this system has led to the identification of a new cell type contributing to the development of pulmonary adenocarcinoma.

Adenocarcinoma↗
PubMed2001

[Helicobacter pylori: cagA analysis and vacA genotyping in Chile. Detection of a s2/m1 strain].

BACKGROUND: The genes cagA and vacA encode H pylori virulence factors. AIM: To genotype these genes in H pylori strains isolated from patients with upper gastrointestinal symptoms. MATERIAL AND METHODS: We studied 50 patients who underwent an upper gastrointestinal endoscopy, with positive culture for H pylori. Detection of cagA and vacA genotyping was done using polymerase chain reactions. RESULTS: The gene cagA was detected in 19 samples (38%). Signal sequences s1 and s2 of vacA gene were detected in 16 samples each (32%). There was simultaneous amplification of s1 and s2 in 6 samples and they were not detected in 9 samples. The middle region of vacA was m1 in 9 samples, m2 in 29 samples and there was simultaneous amplification of m1 and m2 in 12 samples. In 16 samples (32%), more than one type of signal sequence or medial region was detected. Of those patients in whom vacA was the only genotype detected, 15 were s2/m2, 7 were s1/m1, 4 were s1/m2 and 1 was s2/m1. CONCLUSIONS: In these patients, the infection with cagA- H pylori strains, predominates, the prevalence of infection with s1 or s2 strains is similar and the predominant medial region is m2.

Antigens, Bacterial↗
PubMed1999

Specificity of the monocular crescents of the visual field in postural control.

Postural reactions elicited by monocular visual stimulation in the temporal crescent of the visual field were studied in adult subjects in dynamic balance on a rocking platform. Circular translation of a visual scene was induced in the temporal crescent by the rotation of membrane prisms placed laterally to the stimulated eye. In anteroposterior balance, postural reactions are identical whichever eyes is stimulated: ventral extension of the body when the visual scene moves upwards and dorsal extension when it moves downwards. In lateral balance, postural reactions vary with the stimulated eye: extension of the right side of the body when the right eye is stimulated by an upward displacement of the visual scene, extension of the left side when the left eye is stimulated. This difference, which contrasts with the similarity of reactions elicited by the stimulation of either para-foveal fields, suggests that the most peripheral part of the nasal retina has a specific role in head and body stabilisation.

Adult↗
PubMed1996

Differentiation of Acinetobacter baumannii biotypes by amplification of 16S-23S rRNA intergenic spacer sequences.

Isolates of Acinetobacter baumannii (32 strains) from blood samples obtained from patients in five Chilean hospitals were identified and biotyped according to their phenotypic properties. They were also submitted to random amplified polymorphic DNA (RAPD) using eight randomly designed 10-mers and the core sequence of M13 phage (15-mers) as well as amplification of the spacer regions between 16S and 23S genes in the prokaryotic rRNA genetic loci. With some primers, RAPD discriminated between biotypes, whereas with others each isolate showed a particular profile. When amplification of spacer regions was performed, a clear correlation between patterns and biotypes was found. This last technique allowed correct biotyping of clinical isolates. Both genetic methods might be used for the identification of A. baumannii biotypes.

Acinetobacter↗
PubMed1994

Step-length biofeedback device for walk rehabilitation.

A biofeedback gait training system for step length is proposed, adapted to the correction of spatial walking asymmetries by means of a simple, quick and reliable method for daily clinical use. The system is composed of a walkway and a gait analysis device (locometer) measuring the main temporal and distance factors of gait. The step length is imposed on the subject by lighted targets appearing on the walkway, alternately on the right and left side; the subject is asked to place a swinging foot on the lighted target. Feedback to the subject is supplied by direct visual information (the subject looking at the movement and the position of the foot with respect to the lighted target) and an acoustic signal delivered in real time when the length step error is greater than an allowed value. The method is validated on a population of hemiparetic patients who have suffered from a stroke and who have been reeducated with traditional rehabilitation methods. The patients were divided into two groups; one group following a gait training with biofeedback (BFB group) and one group following a gait training without biofeedback (reference group). Preliminary results are presented, showing a significant beneficial effect of the biofeedback method in increasing the step length of paretic limbs and in correcting step-length asymmetry.

Aged↗
PubMed1993

Characterization of a plasmid codifying the synthesis of a beta-lactamase produced by Shigella flexneri.

The resistance to beta-lactam antibiotics shown by a strain of Shigella flexneri was plasmid-coded. This plasmid, pMAM-1, when transferred to Escherichia coli K-12 by conjugation, presented the same molecular weight (100 kbp) and conferred the same high level of resistance to ampicillin in the transconjugant as in the wild type strains (MIC, 2048-4096). Restriction analysis of the plasmid in transconjugants revealed various restrictive sites to some endonucleases (i.e. Bam HI, Eco RI, Pst I, Nco I, Cla I, Sf I and Sau 3AI, Nhe and Hin dIII), and no restrictive sites at all for other endonucleases (such as Xho I, Dra I, Kpn I, and Sal I). Some restricted DNA fragments were appropriate for cloning and isolation of the beta-lactamase gene present in Shigella flexneri UCSF 129. This work provides the first step in this direction.

Ampicillin Resistance↗
PubMed1992

Balance and gait analysis after 30 days -6 degrees bed rest: influence of lower-body negative-pressure sessions.

Five volunteers took part in -6 degrees head-down bed-rest experiments for 30 d. In the first experiment, three subjects underwent several sessions of lower-body negative-pressure (LBNP) per day, with two others serving as controls. In the second, the LBNP group of the first experiment became the control and vice versa. Two experimental protocols analyzed the bed-rest-induced modifications of balance and gait and the efficiency of LBNP in counteracting these modifications. A kymographic method allowed the measurement of walking parameters. Anteroposterior and lateral sways were successively studied with both a force platform (static condition) and a rocking platform (dynamic condition). The tests were performed 2 d before the bed-rest period, and over the 1st, 3rd and 4th days of the recovery period. When the subjects were controls, bed rest decreased step length, walking velocity, and balance stability. LBNP completely counteracted the bed-rest-induced modifications of gait and static balance and of dynamic balance for the lateral sway. As LBNP was ineffective in counteracting the modifications of the anteroposterior sway, dynamic balance deficiency was independent of the beneficial effect of LBNP on the decreased orthostatic tolerance induced by -6 degrees head-down bed rest. The results indicate that head-down bed rest, like spaceflight, induces certain sensorimotor changes involved in the decrease of gait and balance performance.

Adult↗
PubMed1992

Susceptibility to antimicrobial agents and plasmid carrying in Aeromonas hydrophila isolated from two estuarine systems.

Susceptibility to various antimicrobial agents and the presence of plasmids was investigated in eleven strains of Aeromonas hydrophila isolated from samples of sea water and these strains isolated from Aulacomya ater. Transference of resistance to Escherichia coli was attempted by conjugation and transformation experiments. The strains showed multiple resistance toward beta-lactam antibiotics and susceptibility to other antimicrobial agents. Five strains harboured plasmids with molecular weights below 5.7 MD. It was not possible to relate the resistance of the strains with the presence of their plasmids.

Aeromonas hydrophila↗
PubMed1992

Effect of inclusion of beans in a mixed diet for the treatment of Peruvian children with acute watery diarrhea.

A double-masked clinical trial was conducted to assess the effects of inclusion of beans in a mixed diet for young Peruvian children with acute diarrhea. Dietary treatment consisted of either rice, beans, and vegetable oil (group RB, n = 25) or rice, soy-protein isolate, corn syrup solids, and vegetable oil (group RS, n = 21), each given in amounts up to 150 kcal/kg body weight per day immediately following rehydration therapy. The groups were generally similar at the time of admission, and there were no differences in the rates of treatment failure (8% in group RB, 14% in group RS; P = .65). Mean stool outputs were 83 +/- 46 (SD) g/kg body weight in group RB and 71 +/- 43 g/kg body weight in group RS on day 1, and these outputs consistently ranged from 25% to 40% greater in group RB than in group RS (P = .058). By contrast, the median duration of liquid stool excretion was substantially less in group RB than in group RS (60 vs 121 hours, P = .01). The fractional absorption of carbohydrate, fat, and total energy was significantly greater by children in group RS, but there were no differences in net apparent absorption of these nutrients because the children in group RB consumed significantly more of their assigned diet. Children in group RS gained significantly more weight during the whole period of observation (194 g vs 1 g, P = .047), but these differences could be entirely explained by the weight (and presumably fluid) changes on day 1. There were no consistent differences by dietary group in any of the other anthropometric indicators.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1991

Clinical trial of home available, mixed diets versus a lactose-free, soy-protein formula for the dietary management of acute childhood diarrhea.

A randomized clinical trial was completed to study the severity, duration, and nutritional outcome of acute diarrhea in 85 Peruvian children between 5 and 24 months of age who received a soy-protein-isolate, lactose-free formula (group SF) or one of two mixtures of home-available foods, all in amounts up to 110 kcal/kg of body weight/day. The mixed diets contained either wheat flour, pea flour, carrot flour, sucrose, and vegetable oil (group WP) or potato flour, dried whole milk, carrot flour, sucrose, and oil (group PM). The characteristics of the children in each group were generally similar initially. There were no differences in treatment failure rate by diet group. Fecal outputs were similar in all groups during the first day of treatment, averaging 60 to 65 g/kg/day. However, stool outputs were greater for the PM group than for other groups on days 3 and 4, and were less for the SF group than the other groups on days 5 and 6. The estimated median durations of diarrhea in the WP group (52 h) and PM group (53 h) were significantly less than in the SF group (154 h, p = 0.005). Energy intakes, energy absorption, and nitrogen retention (% of intake) were generally similar in all dietary groups, although there were minor differences in the absorption of specific macronutrients. Children in all groups gained weight during hospitalization, and there were no significant differences by diet group in the change in anthropometric status during treatment. We conclude that these locally available, low-cost staple food mixtures offer a safe and nutritionally adequate alternative to a commercially produced lactose-free formula for the dietary management of young children with acute diarrhea in this setting.

Acute Disease↗
PubMed1991

[Effect of ultrafiltered peritoneal fluid from patients with pelvic endometriosis on the in vitro motility of their spouse's sperm].

Recently, there has been information about the ultrafiltrated peritoneal fluid in patients with endometriosis, containing macromollecules that diminish tubal fimbria action, and the in vitro ovular captation in experimental animals. In order to investigate the presence of these substances in the peritoneal fluid, and to know the possible effect that could have on spermatic motivility in vitro, of their mates; 11 sterile women with diagnosis of pelvic endometriosis, and 11 normal fertile women, were studied. On the other side, the same day of study, the mate of each of these women, produced semen obtained by masturbation, where amount and motility of sperm, in basal conditions, and after, it was capacitated with Ham-F10, were determined. The final results was evaluated as to percentage of spermatozoon with excellent and progressive motility, and percentage of motionless spermatozoo as well as based on average values (mean +/- EE), of each one of them. The statistic analysis of differences was done by t Student that in coupled samples. The results confirm that peritoneal fluid of patient with endometriosis contains macromollecules, and it shows that these substances affect the motility in vitro of mate's spermatozoon, which could explain, partially at least, the origin of sterility in this disease.

Adult↗
PubMed1990

Evidence of the co-activation of alpha-motoneurones and static gamma-motoneurones of the sartorius medialis muscle during locomotion in the thalamic cat.

The activity in alpha and gamma efferent axon populations and in group I and group II afferent fibre populations innervating a flexor muscle, the sartorius medialis, was observed during spontaneous locomotor movements in the thalamic cat. Multi-unit discharges of each kind of fibre were obtained by electronic sorting of the action potentials from the overall activity of a thin, intact branch of the sartorius medialis nerve. The following results were obtained: (1) The gamma-motoneurones have a phasic behaviour characterized by a single discharge period during the hip flexion (swing phase of the step-cycle). (2) The gamma-motoneurones are co-activated with the homonymous alpha-motoneurones. (3) Between rhythmic alpha and gamma discharges, i.e. during the hip extension (stance phase of the step cycle), both alpha- and gamma-motoneurones were normally silent. However, in 5 out of 17 experiments, a few units of the gamma population fired at very low frequency. (4) Two observations indicate that the gamma-motoneurones that are co-activated with the alpha-motoneurones by central locomotor commands are predominantly of the static type. In actual locomotion, the rhythmic fusimotor discharges over-compensate the depressor effect on the firing rate of the group II afferents of the unloading of muscle spindles by the active shortening of the parent muscle. In fictive locomotion, when the transmission of the excitation is blocked by selective curarization in alpha skeleto-motor junctions alone, the rhythmic fusimotor discharges elicit in-phase modulations not only of the group I but also of the group II fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Intestinal malacoplakia in pediatrics: report of a case and review of the literature].

We are presenting the case of a 13 year-old male child who was hospitalized at INSN, with generalized edema, chronic diarrhea and hematoquezia. Biopsy studies of the intestine established the diagnosis of Malacoplakia. Despite of the treatment the clinical evolution didn't improve. A review of medical literature is discussed principally relate a Pediatrics.

Adolescent↗
PubMed1989

Discharge patterns of gamma motoneurone populations of extensor and flexor hindlimb muscles during walking in the thalamic cat.

Two monopolar recordings of the whole activity in a fine nerve branch innervating the gastrocnemius lateralis (GL) or the sartorius medialis (SM) muscle were obtained during spontaneous walking in thalamic cats. Using a special electronic device, the potentials of several groups of efferent (alpha and gamma) and afferent (I and II) fibres constituting the whole nerve activity were separated. In the present paper we compare the data obtained for an ankle extensor (GL) and a hip-knee flexor (SM) during the step cycle. In both muscles the gamma motoneurone population is activated in parallel with the alpha motoneurone population. Usually, between the cyclic locomotor discharges, the GL gamma neurones are tonically active whereas the SM gamma neurones are silent. During muscle contraction, the group I and II afferent discharges are both length and gamma dependent, but the prevailing factor is the muscle shortening for the GL afferents and the cyclic gamma drive for the SM afferents. Both dynamic and static fusimotor efferents appear to be activated during muscle contraction, but on indirect evidence it is suggested that dynamic action prevails in GL spindles whereas static action dominates in SM spindles.

Animals↗
PubMed1987

The distribution of services to the underserved. A comparison of minority and majority medical graduates in California.

We assessed the belief that minority physicians are more likely to serve traditionally underserved minority populations by examining the medical practice profiles of minority and majority physicians who graduated from seven California medical schools in 1974 and 1975. The results indicate that minority graduates are more likely to locate their practices in areas with health care personnel shortages (53%) than are majority graduates (26%). Minority physicians had a higher proportion of Medicaid or Medi-Cal patients, and they saw a greater percentage of minority patients (60%) than did majority physicians (21%). We conclude that minority graduates of US medical schools, at least those from California, serve traditionally underserved populations to a greater degree than do their majority graduate colleagues. These findings lend strong support to the contention that aggressive affirmative action programs by medical school admission committees serve the important utility function of improving the distribution of medical services.

California↗