RESUMEN
Variability of regional myocardial blood flow (RMBF) during reflow after 20 minutes of left anterior descending (LAD) coronary occlusion was measured by the radioactive microsphere technique in nine open-chest dogs. Preocclusion RMBF in the LAD territory was 0.89 +/- 0.27 ml/min/gm. Twenty minutes of LAD occlusion resulted in uniform and severe ischemia (RMBF < or = 0.25 ml/min/gm). After 1 minute of reperfusion, RMBF in the LAD territory rose to 3.48 +/- 1.88 ml/min/gm, and declined to 1.06 +/- 0.29 ml/min/gm after 20 minutes of reperfusion. RMBF variance increased significantly from 0.046 preocclusion to 0.2857 after 1 minute of reperfusion (p < 0.01) and declining to 0.086 after 20 minutes of reperfusion. By contrast, RMBF variance analysis of myocardial segments from the nonischemic left circumflex territory exhibited no significant change throughout the experiment. In any given dog this heterogeneous reperfusion of previously ischemic tissue resulted in a disorganized topography of blood flow rates. Myocardium with relatively high regional flow was intermingled with islands of tissue with relatively low blood flow. In conclusion, despite a relatively uniform and severe myocardial ischemic insult, the subsequent initial hyperemic response during reperfusion exhibits marked spatial heterogeneity. The juxtaposition of myocardial regions exposed to vastly differing rates of oxygen delivery and washout of toxic metabolites may set the stage for nonuniform recovery of myocardial function.
Asunto(s)
Circulación Coronaria , Modelos Animales de Enfermedad , Isquemia Miocárdica/fisiopatología , Reperfusión Miocárdica , Análisis de Varianza , Animales , Perros , Hemodinámica , Microesferas , Isquemia Miocárdica/epidemiología , Isquemia Miocárdica/terapia , Reperfusión Miocárdica/estadística & datos numéricos , Radioisótopos , Factores de TiempoRESUMEN
Miracidia of Megalodiscus temperatus from newly hatched until 10 hr old were tested for their ability to react to Helisoma trivolvis snail-conditioned water (SCW) by contact with return (CR) to agar blocks and by percentage of miracidia reacting to a point inoculation of SCW as determined by a photographic time exposure method. CR to agar blocks containing 1:50 SCW was greatest during the first 6 hr after hatching but declined thereafter. The reaction during the first hour to a point inoculation was lower than during the 2nd and 3rd hr. Results were variable from 4 to 10 hr after hatching with the lowest response recorded from 9 to 10 hr. Miracidial responses to dilutions of SCW were assessed by the same two methods. CR to agar blocks containing decreasing concentrations of SCW declined until at a dilution of 1:500 CR was only slightly above the controls. On the other hand, miracidial reactions to point inoculations of SCW as determined by the photographic method were still apparent at a dilution of 1:25,000, when 12% of the miracidia tested reacted. Thus, the photographic time exposure method gives a sensitive means for detecting altered miracidial behavior to various intrinsic and extrinsic factors.
Asunto(s)
Caracoles/parasitología , Trematodos/fisiología , Microbiología del Agua , Animales , Larva , Schistosoma/parasitología , Trematodos/crecimiento & desarrolloRESUMEN
Analysis of snail-conditioned water (SCW) from Helisoma trivolvis revealed 17 free amino acids. Those in great concentration were glycine, serine, and alanine. The concentration of sialic acid was found to be twice that of the most abundant amino acid. The behavior of miracidia of Megalodiscus temperatus, measured by the contact with return method, to agar cylinders containing single amino acids and sialic acid indicated greater responses to polar molecules charged either positively or negatively at neutral pH. The molecules elicting the greatest response were aspartic, glutamic, and sialic acid. No correlation was found between concentration of amino acids in H. trivolvis SCW and response of M. temperatus miracidia.