Experimental evaluation of birds as disseminators of the cosmopolitan tick Rhipicephalus sanguineus (Acari: Ixodidae).

Rhipicephalus sanguineus is believed to be the most widespread tick species of the world and its dissemination seems to rely on the diffusion of its main host, the dog. Empirical observations indicate that several bird species in urban areas regularly steal dog food. Such circumstances create a chance for R. sanguineus ticks to climb on birds and carry ticks to another site. In this work we evaluated experimentally the likelihood of birds (chicks) to either feed and/or carry R. sanguineus ticks from an infested site to another and to infest a host (rabbit) in the new location. Chicks were not suitable hosts for R. sanguineus ticks. Not a single adult tick engorged on chicks, yield as well as weight of engorged larvae and nymphs were very low and feeding period of these ticks was very long. However, a few larvae and, chiefly, nymphs were delivered to a new location either mechanically or after attachment and engorging total or partially on chicks. A few of these ticks fed successfully on rabbits. Further evidence on the capacity of birds to introduce R. sanguineus into non-infested dog settings should be provided by systematic examination of birds from urban areas, close to tick infested households.

Funçäo ventricular de animais submetidos a ablaçäo da massa renal: efeito do controle da pressäo arterial / Ventricular function in animals subjected to renal mass ablation: effect of blood pressure control

A determinaçäo da hipertrofia ventricular na insuficiência renal crônica é multifatorial. Foram estudadas a pressäo arterial da cauda, peso cardíaco, máxima pressäo desenvolvida e as relaçöes pressäo-volume de animais com ablaçäo de5/6 de massa renal, cuja pressäo arterial se mantinha elevada (IRC; n=16) ou que recebiam furosemida na dose de 16mg/Kg para controlar a pressäo (IRC-F; n=17). Animais submetidos a cirurgia fictícia serviram como controles (SHAM; n=15). Os animais que sofreram ablaçäo da massa renal apresentavan níveis de creatinina sérica maiores do que os näo-operados )IRC = 1,81 ñ 0,05; IRC - F = 1,75 ñ 0,08; SHAM = 0,72 ñ 0,09; p 0,001). A massa cardíaca estava aumentada nos grupos IRC hipertenso (0,99 ñ 0,02g) e normotenso (1,01 ñ 0,02g) comparativamente ao SHAM (0,84 ñ 0,01) [p < 0,01]. A máxima pressäo desenvolvida durante a oclusäo transitória da aorta foi semelhante nos três grupos (IRC = 221,2 ñ 7,04; IRC-F = 255,7 ñ 10,01; SHAM = 239,9 ñ 5,5 mmHg, n.s.). Entretanto, o volume diastólico final operacional dos grupos IRC-H e IRC-N (91,4 ñ 9,44; 70,9 ñ 6,22µl, respectivamente) eram significativamente maiores do que o observado no grupo SHAM (28,75 ñ 3,12µL, p < 0,001). Portanto, a HVE induzida pela uremia näo é dependente da hipertensäo arterial que acompanha esta condiçäo. Ainda, o rendimento sistólico dos animais com hipertrofia é semelhante ao dos animais normais, mas, aparentemente, depende de uma maior utilizaçäo do mecanismo de Frank-Starling para seu funcionamento normal

[Ventricular function in animals undergoing renal mass ablation. Effect of blood pressure control]. / Função ventricular de animais submetidos a ablação da massa renal. Efeito do controle da pressão arterial.

The causes of left ventricular hypertrophy (LVH) in chronic renal failure are multifactorial. The tail arterial pressure, heart weight, maximum developed pressure and pressure-volume relationship in animals with 5/6 nephrectomy (CRF, n = 16) and CRF animals who received furosemide by oral gavage (CRF-F, n = 17) were studied. All CRF animals increased their blood pressure (Basal: 117.2 +/- 0.8; 6th week: 184.8 +/- 2.9, p < 0.001) but in those treated with furosemide the blood pressure stayed within normal levels (Basal: 118.23 +/- 1.3; 6th week = 118.8 +/- 1.6, p = 0.5734). SHAM animals served as control (SHAM, n = 15). All CRF and CRF-F animals increased their levels of serum creatinine (CRF = 1.81 +/- 0.05; CRF-F = 1.75 +/- 0.05; SHAM = 0.72 +/- 0.09 mg/dL p < 0.001). Cardiac weight was elevated in CRF and CRF-F when compared with SHAM rats. The operational maximum developed pressure was similar in the three groups (CRF = 221.2 +/- 7.04; CRF-F = 255.7 +/- 10.1; SHAM = 239.9 +/- 5.5 mmHg, n.s.). However, the end-diastolic volume was significantly increased in both CRF and CRF-F when compared with SHAM rats (CRF = 91.4 +/- 9.44; CRF-F = 70.9 +/- 6.22; SHAM = 28.75 +/- 3.12 microL. p < 0.001). These data demonstrate that LVH in chronic renal failure is not dependent of the arterial hypertension, that accompanies this condition. Moreover, the systolic work of LVH animals is similar to that of normal animals, but a greater utilization of Frank-Starling mechanism to maintain normal ventricular function is needed.

Pump performance after regression of cardiac hypertrophy following treatment of hypertension with isradipine.

In view of the possibility that cardiac hypertrophy may be reversed by isradipine, we studied the effect of two different doses of isradipine (1.0 and 7.0 mg/kg per day) on relative cardiac weight in the rat. These doses have proved equipotent in lowering the blood pressure of the two-kidney, one clip model of hypertension. Untreated hypertensive rats had significantly greater cardiac weights than the untreated controls (3.16 +/- 0.06 versus 2.31 +/- 0.05 mg/g, P less than 0.001). Hypertrophy was still present in the group treated with isradipine at 1.0 mg/kg per day (3.17 +/- 0.07 versus 2.30 +/- 0.03 mg/g; P less than 0.001) but not with 7.0 mg/kg per day (2.55 +/- 0.17 versus 2.37 +/- 0.11 mg/g; NS). Functional studies revealed that reversal of cardiac hypertrophy did not affect cardiac performance compared with the ventricles with increased mass. These results suggest that reversal of left ventricular hypertrophy with isradipine is dependent on complex mechanisms, possibly unrelated to the unloading of the heart.

Consequences of reversal of hypertensive cardiac hypertrophy by captopril on left ventricular pumping ability and performance.

Left ventricular hypertrophy can be reversed by treatment of hypertension with captopril but the consequences of this regression are not yet fully described. We studied the maximal capacity of the hypertrophied and hypertrophy-reversed ventricle to generate pressure during transient total occlusion of the aorta, and also the left ventricular end-diastolic pressure required to meet this maximal effort. Two-kidney, one clip Goldblatt (renal hypertensive rats; RHR) hypertension was induced in 17 Wistar rats, eight of which were treated with captopril (RHR-C: 50 mg/kg given orally) from the fourth to the eighth week. Sham-operated controls (SC) remained untreated, or were treated with similar doses of captopril (SC-C). Significantly lower heart weights were found in RHR-C than in RHR (2.88 +/- 0.15 versus 2.38 +/- 0.04; P less than 0.001). During transient total occlusion of the aorta, the maximal intraventricular pressure developed in RHR-C was not significantly different from that in RHR, but left ventricular end-diastolic pressure was significantly less in RHR-C than in RHR (21.4 +/- 2.2 versus 34.3 +/- 3.8; P less than 0.01). The analysis of pressure-volume characteristics of the hypertrophied left ventricles and those in which hypertrophy was reversed revealed similar compliances between these two groups. Our data suggest that there was a mechanical improvement in the heart function after reversal of left ventricular hypertrophy.