Conditioned and discriminatory responses in wakeful and in sleeping cats.
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Animals↗
Biomedical subjects
G Sierra
Publications and source records attributed to G Sierra.
Spontaneous changes in ventricular tachycardia cycle length and their relation to earliest sites of epicardial activation in a canine model.
BACKGROUND: The purpose of this study was to examine the spontaneous changes in cycle length during episodes of sustained monomorphic (MVT) and polymorphic (PVT) ventricular tachycardias and to relate these changes with the earliest epicardial activation site of the beat. METHODS: Isochronal activation maps were obtained from 127 unipolar electrograms recorded from the surface of both ventricles with a sock electrode array in 24 open chest anesthetized dogs. After atrioventricular block, the left anterior descending coronary artery was occluded for 60 min under ventricular pacing (140/min), followed by reperfusion. In 7 dogs the left stellate ganglion was stimulated 5 min after reperfusion. RESULTS: In 7 MVTs (reperfusion) and 4 PVTs (sympathetic stimulation), cycle length changes showed an initial acceleration, reaching a minimum cycle length and then decelerating before termination. Isochronal maps showed radial spread from earliest activation, without conduction block. Cycle length (481 +/- 80 msec) in MVT had beat to beat variations of 15 +/- 17 msec corresponding to small shifts in sites of the earliest activation, clustered along the border of the ischemic myocardium. In PVTs the cycle length (352 +/- 90 msec, p < 0.01) had a variability of 62 +/- 23 msec, corresponding to wide changes in the sites of earliest activation in right and left ventricles. Linear regression analysis showed a strong and significant correlation between cycle length variability and the number of electrodes with the earliest activation (r = 0.77, p < 0.0001). CONCLUSION: In these models of monomorphic and polymorphic ventricular tachycardias, cycle length variability showed a significant correlation with the number of electrodes with the earliest activation. MVTs showed concentrated origins with regular cycle length, whereas PVTs showed dispersed origins with irregular cycle length. These results suggest that the earliest epicardial activation site of the beat could be a factor in determining the dynamics in the cycle length.
Animals↗
[Microbiology of chronic otitis media in children and comparison of 2 technics for obtaining otic secretions].
Samples of otic secretion for culture were taken to 50 children with suppurative chronic otitis media; two techniques were followed: with a cotton swab from the external meatus or with a sterile metal aspirator, through the tympanic perforation under microscopic control. To 20 of them with unilateral chronic otitis media, a swab with product from the external meatus of the healthy ear was also taken; in 65% of the latter, the same germs were found in both ears, but when the sample was taken with the aspirator, only in 15% were the germs the same (p less than 0.01). Two or more germs were isolated in 54% of the ears following the technique of the swab and in 32% with the aspiration. The predominant microorganisms with the swab technique were gram-positive cocci (S. epidermidis 48% S. aureus 16%); while the aspiration technique reported gram-negative germs in 96% of cultures (Proteus sp. 42%, Pseudomonas sp. 30% and S. aureus only in 14%). We believe that the sample obtained with a swab has a high degree of contamination with the normal flora of the external meatus; therefore, it should be relinquished.
Adolescent↗
[Utilization of different microbiological markers in the study of Haemophilus influenzae].
The present study includes 178 Haemophilus influenzae strains isolated in different pediatric hospitals from Havana, Cuba, during 1991-1994, associated to divers infections (meningitis, respiratory sepsis, primary bacteremia). A combination of various typing and subtyping methods was used as epidemiological markers: serotyping (slide agglutination with diagnostical serum a-f and latex agglutination), biotyping according to Killian's procedures (by determination of indole production, urease and ornithine decarboxylase activity), subtyping by fermentative profiles according to Roberts' methods (glucose, maltose, xylose and fructose) and outer membrane protein profile subtyping (vesicles extraction by a modified Barenkamp's method, analysis by lineal and gradient SDS-PAGE and assessment according to our own classification system). Serotype b was identified in 89.3%, biotype I was the most frequent (79.1%), other biotypes (II, III, IV and V) were also identified. Fermentative profile D (glucose, maltose, xylose and fructose positive) was the most frequent (52.8%) while profile G (glucose, maltose, xylose positive and fructose negative) represented 20.2%. Other known profiles were present. PA2 (33.7%) was the most frequent OMP subtype. Even though 11 different protein subtypes were found, the 77.5% of the strains were located in only three OMP electrophoretic subtypes (PA2, PC1, LA2).
Agglutination Tests↗