Biochemical correlates of cardiac hypertrophy. I. Experimental model; changes in heart weight, RNA content, and nuclear RNA polymerase activity

Cardiac hypertrophy occurred in mature rats after producing supravalvular aortic stenosis with a specially designed silver clip. For 2 weeks following this procedure, heart weight, body weight, and RNA content of the myocardium were serially determined. Heart weight and RNA content increased within 24 hours of aortic banding, reaching a maximal level in 2 days and remaining elevated during the 2 weeks of observation. Nuclei were isolated and purified from heart muscle homogenates, and changes in RNA polymerase activity following aortic banding were determined. The nearest neighbor frequency of the bases of the RNA synthesized by the polymerase from nuclear preparations was identical in both the banded animals and the sham-operated controls. Both groups could thus be compared on the basis of the enzyme assay. RNA polymerase activity in nuclei from the hearts of banded rats rose rapidly when compared with the activity in sham-operated rats; peak values were reached on the second day, the earliest detectable change being around 12 hours. The increase in RNA polymerase activity represents one of the earliest biochemical events that take place in the myocardium following aortic banding

Pubertal administration of antiserum against nerve growth factor regresses renal vascular remodeling in spontaneously hypertensive rats

To investigate the role of nerve growth factor (NGF) in the development of hypertensive renal vascular remodeling, anti-serum against NGF (anti-NGF) or vehicle was injected at 3 weeks of age in spontaneously hypertensive rats (SHR) and Wistar–Kyoto (WKY) rats (n = 9 for each treatment in each strain). Flow-pressure (F-P) and pressure-glomerular filtra-tion rate (P-GFR) relationships at vasodilated perfused kid-neys were determined at 10 weeks of age. In the vehicle rats, blood pressure, renal noradrenaline content, the gradient of F-P (minimal vascular resistance at pre- and post-glomerular vasculature) and the X-intercept of P-GFR (preglomeru-lar : postglomerular vascular resistance ratio) were greater in SHR than in WKY rats, although the gradient of P-GFR (glo-merular filtration capacity) did not differ significantly between the strains. Blood pressure and renal noradrenaline content were lower in SHR receiving anti-NGF than in SHR receiving vehicle, although such difference was not observed in WKY rats. The gradient of F-P was less but the gradient of P-GFR was greater in SHR receiving anti-NGF compared with SHR receiving vehicle, although the similar differences did not occur in WKY rats. Blood pressure and renal nor-adrenaline content remained greater in SHR treated with anti-NGF compared with WKY rats treated with vehicle; however, the gradient of F-P did not differ significantly between them. Contrary, anti-NGF did not affect the X-inter-cept of P-GFR in either strain. In conclusion, NGF could con-tribute to the genesis of renal vascular remodeling, at least in part, through modification of renal sympathetic activity and blood pressure in SHR

Can Two 1/2- and 3 1/2 -year-old Children Learn Verbs Even when IrrelevantEvents are Present?

Children learning verbs benefit from seeing multiple events. Study 1 asks whether children can learn verbs when irrelevantevents are present, as is common in everyday contexts. Two- and 3-year-olds saw events in one of three experimentalconditions or one of two control conditions. They successfully extended the verbs only in the experimental conditions.Three-year-olds were more successful than were 2-year-olds, though the younger children could extend verbs. In Study 2,children saw similar events while an eye tracker tracked visual attention to events. Over trials, children looked longer atrelevant than irrelevant events, and maintained their looking to relevant events while increasing their looking to distractorevents. Two-year-olds performed at chance, but 3-year-olds extended the verbs. Together, these results show children canignore irrelevant events and extend new verbs by 3 years. Results reveal mechanisms for learning in everyday contextswhen verbs are heard in varied situations over time

Does Children’s Visual Attention to Objects Influence their Verb Learning?

Children benefit from comparing events when learning verbs, but it is unclear whether variability across events is helpfulor harmful. Additionally, no prior study has tested childrens visual attention to specific objects under different variabilityconditions. A Tobii x30-120 tracked 21/2-year-olds(n=36) and 31/2-year-olds(n=34) visual attention as they watchedevents that showed no change (control), events with varied tools (Tool condition) or events with varied affected objects(Affected Object condition) when learning a verb. Children pointed to one of two new events at test; repeated for two moreverbs. Results showed children could extend the verbs, but were more successful with age. Analyses of looking patternsin the learning phase show childrens attention to specific objects varied by condition, and that reduced looking to the toolwas linked to less success at test. Results are important to better understand processes that underlie verb learning, andlanguage development as a whole