RESUMO
We study the population size time series of a Neotropical small mammal with the intent of detecting and modelling population regulation processes generated by density-dependent factors and their possible delayed effects. The application of analysis tools based on principles of statistical generality are nowadays a common practice for describing these phenomena, but, in general, they are more capable of generating clear diagnosis rather than granting valuable modelling. For this reason, in our approach, we detect the principal temporal structures on the bases of different correlation measures, and from these results we build an ad-hoc minimalist autoregressive model that incorporates the main drivers of the dynamics. Surprisingly our model is capable of reproducing very well the time patterns of the empirical series and, for the first time, clearly outlines the importance of the time of attaining sexual maturity as a central temporal scale for the dynamics of this species. In fact, an important advantage of this analysis scheme is that all the model parameters are directly biologically interpretable and potentially measurable, allowing a consistency check between model outputs and independent measurements.
Assuntos
Didelphis/fisiologia , Modelos Estatísticos , Reprodução/fisiologia , Maturidade Sexual/fisiologia , Animais , Brasil , Feminino , Masculino , Densidade Demográfica , Dinâmica Populacional/estatística & dados numéricosRESUMO
This study aimed to evaluate urea excretion, nitrogen balance and microbial protein synthesis in lactating goats fed with diets containing different protein sources in the concentrate (soybean meal, cottonseed meal, aerial part of cassava hay and leucaena hay). Four Alpine goats whose mean body weight was 42.6±6.1 kg at the beginning of the experiment, a mean lactation period of 94.0±9.0 days and a production of 1.7±0.4 kg of milk were distributed in a 4×4 Latin square with four periods of 15 days. Diets were formulated to be isonitrogenous, containing 103.0 g/kg of CP, 400 g/kg of Tifton 85 hay and 600 g/kg of concentrate. Diet containing cottonseed meal provided (p<0.05) increased excretion of urea and urea nitrogen in the urine (g/d and mg/kg of BW) when compared with leucaena hay. The diets affected the concentrations of urea nitrogen in plasma (p<0.05) and excretion of urea nitrogen in milk, being that soybean meal and cottonseed meal showed (p<0.05) higher than the average aerial part of the cassava hay. The use of diets with cottonseed meal as protein source in the concentrate in feeding of lactating goats provides greater nitrogen excretion in urine and negative nitrogen balance, while the concentrate with leucaena hay as a source of protein, provides greater ruminal microbial protein synthesis.
RESUMO
Norepinephrine-induced responses in isolated perfused mesenteric vascular bed from normotensive and renovascular hypertensive rats were examined in the presence of adenosine diphosphate (ADP, 2 x 10(-6) M). Responses to norepinephrine were significantly greater in vessels from hypertensive rats. Norepinephrine-induced contractions increased after the removal of endothelium. N omega-Nitro-L-arginine (L-NOARG), a potent inhibitor of nitric oxide formation, similarly increased contractions. The greatest responses were obtained, however, after treatment of the vascular segments with methylene blue. The presence of ADP caused significant endothelium-dependent decreases in contractions. Although decreases caused by ADP in vessels with endothelium after treatment with L-NOARG were not statistically significant, a tendency to decreased responses seems to suggest that L-NOARG diminishes but does not completely prevent the effect of ADP in mesenteric vessels. Methylene blue partially reduced the endothelium-dependent ADP-induced relaxant effects in sham-operated nephrectomized rats. A tendency to increased contractions to norepinephrine was observed in the presence of ADP after removal of endothelium. Thus, in the mesenteric resistance arteries of the rat under stimulation by ADP, it appears that nitric oxide released from L-arginine and the activity of soluble guanylate cyclase account only in part for the endothelium-dependent decreased responses to norepinephrine. When nitric oxide formation or soluble guanylate cyclase activity are depressed simultaneously with endothelium damage, ADP released from platelets or red blood cells may be an important factor that acts synergically with vasoconstrictor stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Difosfato de Adenosina/farmacologia , Endotélio Vascular/efeitos dos fármacos , Hipertensão Renovascular/fisiopatologia , Animais , Pressão Sanguínea , Frequência Cardíaca , Masculino , Artérias Mesentéricas/efeitos dos fármacos , Veias Mesentéricas/efeitos dos fármacos , Norepinefrina/farmacologia , Ratos , Ratos EndogâmicosAssuntos
Ácidos Araquidônicos/metabolismo , Colágeno/metabolismo , Homeostase , Adesividade Plaquetária/efeitos dos fármacos , Agregação Plaquetária/efeitos dos fármacos , Trombina/metabolismo , Difosfato de Adenosina/metabolismo , Animais , Sítios de Ligação , Humanos , Fator de Ativação de Plaquetas/metabolismo , Fator de von Willebrand/metabolismoRESUMO
Os autores apresentam o caso de uma portadora de carcinoma broncogenico que comprometia a arteria pulmonar esquerda, na qual foi realizada, por motivos funcionais, uma lobectomia superior esquerda com resseccao em manguito da arteria pulmonar, associada a uma broncoplastia em cunha. A paciente teve uma boa recuperacao, e uma arteriografia pulmonar constatou boa perfusao no lobo residual. Os autores reviram a literatura medica e verificaram que apenas 16 casos foram descritos a partir de 1952, epoca da primeira resseccao em manguito da arteria pulmonar, o que demonstra ser uma tatica de indicacao muito precisa e raramente utilizada