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Biomedical subjects

F Peña

Publications and source records attributed to F Peña.

At least 19 recordsLinked to original sources
PubMed1998

Study on the possible involvement of protein kinases in the modulation of brain presynaptic sodium channels; comparison with calcium channels.

A possible modulatory role of kinases on voltage sensitive Na+ channels of presynaptic brain nerve endings was investigated by testing the effect of several kinase activators and inhibitors on the elevation of [Nai] induced by veratridine in mouse brain synaptosomes loaded with a selective Na+ indicator dye. Veratridine (20 microM) increases the basal [Nai] level (20 mM) more than twofold. This increase is independent of external Ca2+, but abolished by tetrodotoxin (1 microM). Activation of cAMP dependent protein kinase with forskolin or cAMP analogs, or of protein kinase C with diacylglycerol did not affect the veratridine-induced elevation in [Nai]. Drugs reported to inhibit calmodulin-dependent events, as well as the regulatory domain of protein kinase C, were potent and effective inhibitors of the increase in [Nai] induced by veratridine, as well as other veratridine induced responses, namely elevation of [Cai] (monitored with the Ca2+ indicator dye fura-2) and neurotransmitter (GABA) release. Drugs that inhibit kinases by binding to the catalytic site were ineffective, however, as was the phosphatase inhibitor, okadaic acid. A selective inhibitor of Ca2+ and calmodulin dependent protein kinase II also did not affect the elevation of [Nai] induced by veratridine, but markedly diminished the elevation of [Cai] induced by depolarization either with veratridine or with high K+ (15 and 30 mM). On the basis of these results it is concluded that, the dramatic inhibition exerted by some of the drugs tested on the elevation of [Nai] induced by veratridine is not due to their effects on kinases, but to a possible interaction of these compounds with an intracellular site of the Na+ channel. On the other hand, while Ca2+ and calmodulin dependent protein kinase II is unable to modulate brain presynaptic voltage sensitive Na+ channels, it facilitates the activation of brain presynaptic voltage sensitive Ca2+ channels.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

Fixation strength of interference screw fixation in bovine, young human, and elderly human cadaver knees: influence of insertion torque, tunnel-bone block gap, and interference.

A failure analysis of interference screw fixation was performed to test the hypothesis that bovine and/or elderly human cadavers are appropriate models for bone-patellar tendon-bone anterior cruciate ligament (ACL) reconstruction fixation studies. Failure mode is an important criterion for validating experimental models. The bovine, young human, and elderly human failure loads were 799 +/- 261 N, 655 +/- 186 N, and 382 +/- 118 N, respectively, and the failure modes were 75%, 69%, and 30% tissue failures, respectively. The similarities between the bovine and young human models in failure loads and failure modes indicate that bovine models are appropriate for ACL reconstruction fixation studies. The statistically significant differences between the young human and elderly human models in failure loads and failure modes indicate that elderly human cadavers are not an appropriate model for ACL reconstruction fixation studies. The differences in failure modes are consistent with previous studies using elderly human cadavers in which the predominant failure mode was bone block pullout. The tissue failures observed in the bovine and young human models contradict previous studies suggesting fixation strength is the weakest link in bone-patellar tendon-bone ACL reconstruction. Results of linear regression modeling showed statistically significant correlations between insertion torque and failure load (R2 = 0.44, P < 0.0001) and interference (defined as the screw outer thread diameter minus the tunnel-bone block gap) and insertion torque (R2 = 0.18, P = 0.003) when data from all models was combined. Results for the bovine model multiple regression showed a statistically significant regression of insertion torque (linear) and interference (quadritic) versus failure load (R2 = 0.56, P = 0.02). Regression slopes for screw diameter (P = 0.52) and gap size (P = 1.00) were not statistically significant. These results indicate that insertion torque and interference are independent predictors of failure load and should be included in future interference screw studies in addition to bone block dimensions, tunnel size, gap size, and screw diameter. Clinicians may consider using insertion torque and interference as indicators of postoperative graft fixation regarding rehabilitation decisions.

Adult↗
PubMed1995

Hering-Breüer reflexes in high-altitude infants.

1. Pulmonary ventilation was found to be similar in high-altitude and low-altitude newborn infants, but the breathing pattern was deeper and slower at high altitude (Mortola, J.P., Frappell, P.B., Frappell, D.E., Villena-Cabrera, N., Villena-Cabrera, M., Peña, F., Am Rev Respir Dis 1992, 46: 1206-9). We questioned the contribution of vagal reflexes to these differences in breathing pattern. 2. Measurements were performed on high-altitude (La Paz, Bolivia, 3600-4050 m, inspired O2 pressure approximately 92 mmHg, n = 34) and low-altitude infants (Santa Cruz, Bolivia, 400 m, PIO2 approximately 141 mmHg, n = 26). The strength of the Hering-Breüer inspiratory inhibitory reflex was estimated from the inspiratory time during a respiratory effort against airways closed at end-expiration (Tloccl). The strength of the Hering-Breüer expiratory facilitatory reflex was estimated from the expiratory duration when airways were occluded during expiration (TEoccl). 3. Tloccl was significantly longer than the open-airways TI at both low and high altitude, but significantly more so (approximately 14%) at high altitude. TEoccl was longer than open-airways TE in both groups of infants, but significantly less so at high altitude, whether TEoccl was compared between occlusions of similar tidal volume (on average, TEoccl at high altitude was 79% of that at low altitude) or similar airway pressure (87%). 4. The results suggest that at high altitude the contribution of the phasic volume-dependent vagal input to the inspiratory off-switch threshold is higher, and that the tonic vagal expiratory facilitation is lower, than at low altitude, presumably because of hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Altitude↗
PubMed1992

Ventilation and gaseous metabolism in infants born at high altitude, and their responses to hyperoxia.

Hyperventilation and decreased metabolic rate are commonly observed in newborns during acute hypoxia; whether these responses are also present during sustained hypoxia is not known. We asked whether infants at high altitude had higher ventilation and lower metabolism than lowlanders. Ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) were measured in newborn (< 1 day old) full-term infants in La Paz (altitude 3,800 m; inspired oxygen pressure [PIO2], 92 mm Hg) and in Santa Cruz (altitude, 400 m; PIO2, 141 mm Hg), Bolivia. Each group consisted of 30 infants selected to have similar body weight. The mothers, Amerindians and mestizos, were born in the corresponding cities or at equivalent altitudes. Despite the lower inspired oxygen concentration in La Paz (0.107 ml STPD O2/ml BTPS air) than in Santa Cruz (0.164), neither VE nor VO2 or VCO2 differed between the two groups. The breathing pattern was deeper and slower at high altitude. From the values of VE and VO2 it was calculated that high-altitude infants extracted more O2 (+62%) from the inspired air than did the lowlanders. When given pure O2 to breathe, both groups of infants similarly increased VE and gaseous metabolism; even during hyperoxia, however, the ventilatory O2 extraction was higher (+50%) in the highlanders. We conclude that, contrary to what is observed in acute hypoxia, infants at high altitude maintain metabolic rate with no major alterations in VE. The ability to use a greater fraction of the inspired O2 at high altitude probably results from functional and structural alterations stimulated by fetal hypoxia.

Altitude↗
PubMed1991

Tracheobronchomegaly associated with interstitial pulmonary fibrosis.

Tracheobronchomegaly (TBM) is the syndrome of enlarged trachea and main bronchi associated with recurrent and chronic respiratory tract infections. A 42-year-old man with TBM and diffuse interstitial pulmonary fibrosis is described. The possible relationship between the two entities is discussed and the etiology, pathogenesis, clinical manifestations, prognosis and treatment of TBM are reviewed.

Adult↗
PubMed1990

Compliance of the respiratory system in infants born at high altitude.

Populations living at high altitude are known to have a number of distinctive physiologic traits, including an increase in lung volume and compliance. We asked whether the factors that result in the increased compliance of high altitude natives were sufficiently expressed in utero that an increase in respiratory system compliance (Crs) could be detected at birth. Measurements were performed at about 1 day after birth on 34 infants born in La Paz, Bolivia (3,600 m, Pb about 495 mm Hg) and 36 born in Santa Cruz (400 m, Pb about 735 mm Hg). All infants were full-term and healthy, with body weights of at least 2,700 g. We measured Crs from expirations within the tidal volume range by the multiple occlusion method. Breathing pattern was measured from the spirometric record, and an index of chest wall distortion was obtained from the ratio of volume and abdominal displacement during spontaneous breathing and relaxations against closed airways. Rib cage and abdomen dimensions did not differ between the two groups. Crs values in Santa Cruz were similar to those previously obtained in Montreal and in other Caucasian infant populations at low altitudes. Crs was 33% and Crs/kg 37% greater (p less than 0.001) in the high altitude group, which included equal numbers of Amerindians and Mestizos of European ancestry. Dynamic elevation of the end-expiratory level was similar in both groups. Ventilation/kg and the distortion ratio were slightly yet significantly higher in the high altitude infants, suggesting an increased ventilatory drive.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1979

Effects of captivity on glucose tolerance in dogs.

Captivity decreased tolerance to glucose and increased blood serotonin levels in 6 normal dogs investigated. Return to freedom brought normalization in the glucose tolerance test and reverted blood serotonin to control levels.

Animals↗
PubMed1979

Radiologic aspects of hepatic echinococcosis. Value of the intravenous viscerogram and computed tomography.

Over five years, 105 patients with hepatic echinococcosis were studied. Plain radiographs of the hepatic area yielded the correct diagnosis in 35% of patients. Intravenous viscerograms were diagnostic in all but 14 of the patients (an accuracy of 83%). Computed tomography was performed in 19 cases and proved the most efficient of the techniques--it was diagnostic in all 19 cases. The radiological signs of this entity are discussed.

Calcinosis↗
PubMed1978

Adrenergic influences on the gallbladder emptying.

Dihydroergotamine (dhe) (or phentolamine), an alpha-adrenergic blocking agent, induced important changes on the CCK-stimulated gallbladder emptying of 70 volunteer subjects. Two cholecystograms were performed with 10-day intervals in each subject. The first cholecystogram showed gallbladder emptying provoked by a test meal (35 subjects or by 0.5 U. CCK Kg. injected intravenously (35 subjects). During the second cholecystogram 1 mg. of DHE was injected intramuscularly 45 minutes befor the cholecystokinetic stimulus. The drug counteracted the gallbladder emptying induced by both endogenous and exogenous CCK. The effect was more pronounced when DHE was administered prior to the test meal stimulus than before CCK administration. This difference could be explained by a delayed gastric emptying induced by the alpha-adrenergic blockade. Our results suggest that the lack of gallbladder emptying could be due to the relaxation of this organ, in addition to a duodenal spasticity induced by DHE (or phentolamine).

Adolescent↗
PubMed1977

The "spastic colon" syndrome: therapeutic and pathophysiologic considerations.

Low doses of d-amphetamine plus propranolol rapidly improved the abdominal pain in 165 "spastic colon" patients. Concomitantly, these drugs reduced the sigmoidal hypertonicity and the rectal inhibition found in the manometric studies performed in some of those patients. The sigmoidal tone and phasic activity were also decreased by anticholinergic drugs. These results suggest that a cholinergic-serotonergic hyperactivity of the myenteric plexus may be responsible for the "spastic colon" syndrome.

Adolescent↗
PubMed1976

Effect of fasting and insulin on the glucagon-induced orthophosphate incorporation to the isolated perfused rat liver.

Isolated perfused fed rat livers spontaneously liberated glucose and orthophosphate to the medium; 24-hr fasted rat livers did not exhibit these phenomena. In perfused fed rat livers, glucagon (2 mug) increased glucose output and promoted orthophosphate incorporation. In perfused fed rat livers, insulin (250 or 500 mU) inhibited the spontaneous liberation of glucose and orthophosphate. Comparable doses of insulin significantly reduced the glucagon (2 mug)-induced increase in glucose output from perfused fed rat liver, but did not affect orthophosphate uptake by the organ.

Animals↗