State estimators for some epidemiological systems.

We consider a class of epidemiological models that includes most well-known dynamics for directly transmitted diseases, and some reduced models for indirectly transmitted diseases. We then propose a simple observer that can be applied to models in this class. The error analysis of this observer leads to a non-autonomous error equation, and a new bound for fundamental matrices is also presented. We analyse and implement this observer in two examples: the classical SIR model, and a reduced Bailey-Dietz model for vector-borne diseases. In both cases we obtain arbitrary exponential convergence of the observer. For the latter model, we also applied the observer to recover the number of susceptible using dengue infection data from a district in the city of Rio de Janeiro.

A derivation of Holling's type I, II and III functional responses in predator-prey systems.

Predator-prey dynamics is most simply and commonly described by Lotka-Volterra-type ordinary differential equations (ODEs) for continuous population density variables in the limit of large population sizes. One popular extension of these ODEs is the so-called Rosenzweig-MacArthur model in which various interaction rates between the populations have a nonlinear dependence on the prey concentration. Nonlinear 'functional responses' of this type were originally proposed by Holling on the basis of a general argument concerning the allocation of a predator's time between two activities: 'prey searching' and 'prey handling'. Although these functional responses are constructed in terms of the behaviour of an individual predator, they are routinely incorporated at the population level in models that include reproduction and death. In this paper we derive a novel three variable model for the simplest possible mathematical formulation of predator-prey dynamics that allows the interplay between these various processes to take place, on their different characteristic timescales. We study its properties in detail and show how it reduces to Holling's functional responses in special limits. As a result we are able to establish direct links between individual-level and population-level behaviour in the context of these well-known functional responses.

Atrial natriuretic peptide modulates the effect of angiotensin II on the concentration of free calcium in the cytosol of Mandin-Darby canine kidney cells.

The effect of angiotensin II (ANG II) and atrial natriuretic peptide (ANP) on intracellular free calcium concentration [Ca2+]i was investigated in Mandin-Darby canine kidney (MDCK) cells in culture. Changes in [Ca2+]i were monitored fluorometrically with the Ca(2+)-sensitive probe fura-2/AM at 37 degrees C using a Perkin-Elmer LS-5 spectrofluorimeter (excitation 340/380 nm, slit 3 nm; emission 520 nm, slit 10 nm). MDCK cells exhibited a mean baseline [Ca2+]i of 98 +/- 10 nM. The addition of increasing concentrations of ANG II (1 pM to 1 microM) to the cell suspension led to a progressive increase in [Ca2+]i to 2-3 times basal levels. In contrast, addition of 1 microM ANP to the cell suspension led to a very rapid 60% decrease in [Ca2+]i. The addition of 1 pM to 1 microM ANG II immediately after 1 microM ANP caused an increase in [Ca2+]i which never exceeded the basal level in the absence of ANP. The data indicate that ANG II increases cell [Ca2+]i, as expected, and provide the new observation that ANP reduces [Ca2+]i in these cells. Furthermore, ANP reduces the increase in [Ca2+]i elicited by ANG II, thus modulating the effect of ANG II on [Ca2+]i.

Mechanisms and regulation of H+ transport in distal tubule epithelial cells.

The mechanism of acidification in the cortical distal tubule of mammalian kidney was analysed by "in vivo" microperfusion and using MDCK cells in culture, by electrophysiological and by cell pH microfluorescence techniques. An electrogenic effect of the vacuolar H(+)-ATPase, which has been localized to the intercalated cells of the cortical distal tubule (connecting segment and initial collecting duct) was only observed after blocking Cl- channels by NPPB. In MDCK cells, the recovery of cell pH after an acid pulse in Na(+)-free medium was also depressed by NPPB, indicating that Cl- ions have an important role in the function of H+ ATPase. The regulation by hormonal agents of distal H+ transport due to Na+/H+ exchange and to vacuolar H+ ATPase, was also studied by microperfusion and cell pH techniques. Angiotensin and vasopressin at picomolar concentrations stimulated both transport mechanisms in late distal tubule, and only Na+/H+ exchange in the early segment. In MDCK cells, cell pH recovery in the presence of Na+ was stimulated by picomolar concentrations of angiotensin and vasopressin, and inhibited by micromolar levels, both effects being reverted by micromolar ANP. Studies with specific antagonists suggest that the luminal effect of angiotensin is mediated by AT1 receptors, and of vasopressin by V1 receptors. There is evidence that cell Ca2+ may have an important regulatory role in the action of these hormones.

Exercise training and detraining modify the morphological and mechanical properties of single cardiac myocytes obtained from spontaneously hypertensive rats.

We determined the effects of exercise training and detraining on the morphological and mechanical properties of left ventricular myocytes in 4-month-old spontaneously hypertensive rats (SHR) randomly divided into the following groups: sedentary for 8 weeks (SED-8), sedentary for 12 weeks (SED-12), treadmill-running trained for 8 weeks (TRA, 16 m/min, 60 min/day, 5 days/week), and treadmill-running trained for 8 weeks followed by 4 weeks of detraining (DET). At sacrifice, left ventricular myocytes were isolated enzymatically, and resting cell length, width, and cell shortening after stimulation at a frequency of 1 Hz (~25°C) were measured. Cell length was greater in TRA than in SED-8 (161.30 ± 1.01 vs 156.10 ± 1.02 µm, P < 0.05, 667 vs 618 cells, respectively) and remained larger after detraining. Cell width and volume were unaffected by either exercise training or detraining. Cell length to width ratio was higher in TRA than in SED-8 (8.50 ± 0.08 vs 8.22 ± 0.10, P < 0.05) and was maintained after detraining. Exercise training did not affect cell shortening, which was unchanged with detraining. TRA cells exhibited higher maximum velocity of shortening than SED-8 (102.01 ± 4.50 vs 82.01 ± 5.30 µm/s, P < 0.05, 70 cells per group), with almost complete regression after detraining. The maximum velocity of relengthening was higher in TRA cells than in SED-8 (88.20 ± 4.01 vs70.01 ± 4.80 µm/s, P < 0.05), returning to sedentary values with detraining. Therefore, exercise training affected left ventricle remodeling in SHR towards eccentric hypertrophy, which remained after detraining. It also improved single left ventricular myocyte contractile function, which was reversed by detraining.

Exercise training and detraining modify the morphological and mechanical properties of single cardiac myocytes obtained from spontaneously hypertensive rats

We determined the effects of exercise training and detraining on the morphological and mechanical properties of left ventricular myocytes in 4-month-old spontaneously hypertensive rats (SHR) randomly divided into the following groups: sedentary for 8 weeks (SED-8), sedentary for 12 weeks (SED-12), treadmill-running trained for 8 weeks (TRA, 16 m/min, 60 min/day, 5 days/week), and treadmill-running trained for 8 weeks followed by 4 weeks of detraining (DET). At sacrifice, left ventricular myocytes were isolated enzymatically, and resting cell length, width, and cell shortening after stimulation at a frequency of 1 Hz (~25°C) were measured. Cell length was greater in TRA than in SED-8 (161.30 ± 1.01 vs 156.10 ± 1.02 μm, P < 0.05, 667 vs 618 cells, respectively) and remained larger after detraining. Cell width and volume were unaffected by either exercise training or detraining. Cell length to width ratio was higher in TRA than in SED-8 (8.50 ± 0.08 vs 8.22 ± 0.10, P < 0.05) and was maintained after detraining. Exercise training did not affect cell shortening, which was unchanged with detraining. TRA cells exhibited higher maximum velocity of shortening than SED-8 (102.01 ± 4.50 vs 82.01 ± 5.30 μm/s, P < 0.05, 70 cells per group), with almost complete regression after detraining. The maximum velocity of relengthening was higher in TRA cells than in SED-8 (88.20 ± 4.01 vs70.01 ± 4.80 μm/s, P < 0.05), returning to sedentary values with detraining. Therefore, exercise training affected left ventricle remodeling in SHR towards eccentric hypertrophy, which remained after detraining. It also improved single left ventricular myocyte contractile function, which was reversed by detraining.

Hemoglobinas anormais: frequencia em individuos que apresentam reduçao do conteudo hemoglobinico / Hemoglobinopathies: a reduction of hemoglobinic's content

Um estudo sobre hemoglobinopatias, na grande Belo Horizonte, vem revelando dados bastante significativos em relaçao a sua frequencia. Ja foram observados 27 (vinte e sete) casos de pacientes com hemoglobinopatias em um numero total de 165 (cento e sesenta e cinco) individuos com hemoglobina abaixo do valor referencia e/ou quadro hematologico sugestivo de hemoglobinopatia. Em paralelo, tem-se observado, minuciosamente, as alteraçoes hematologicas presentes no esfregaço sanguineo dos individuos portadores de hemoglobina anormal. Dos 27 casos, foram registradas as seguintes hemoglobinas anormais: S/S (08); A/S (06); A/Beta tal menor (05); A/C (03); S/C (03); C/C (01); A/Migraçao rapida (01). Quanto a frequencia, os dados acima perfazem um total de 16,4 por cento . Em virtude da grande importancia das hemoglobinopatias, em nosso meio, as autoras sugerem aos profissionais que atuam na area, um estudo mais profundo nos pacientes que apresentarem reduçao no conteudo hemoglobinico buscando melhor elucidaçao do diagnostico, com a finalidade de se evitar tratamentos erroneos e propiciar, a cada caso, a orientaçao adequada

Atrial natriuretic peptide modulates the effect of angiotensin II on the concentration of free calcium in the cytosol of Mandin-Darby canine kidney cells

The effect of angiotensin II (ANG II) and atrial natriuretic peptide (ANP) on intracellular free calcium concentration [ Ca²+]i was investigated in Mandin-Darby canine kidney (MDCK) cells in culture. Changes in [Ca²+]i were monitored fluorometrically with the Ca²+ -sensitive probel fura -2/AM at 37ºC using Perkin-Elmer LS-5 spectrofluorimeter (excitation 340/380 nm,slite 3 nm; emission 520 nm, slit 10 nm). MDCK cells exhibited a mean baseline [Ca²+]i of 98 ñ 10 nM. the addition of increasing concentrations of SNG II (1 pM to 1 µM) to the cell suspension led to a progressive increase in [Ca²+]i to 2-3 times basal levels. In contrast, addition of 1 µM ANP to the cell suspension led to a very rapid 60 percent decrease in [Ca²+]i. The addition of 1 pM to 1 µM ANG II immediately after 1 µM ANP caused an increase in [Ca²+]i which never exceded the basal level in the absence of ANP. The data indicate that ANG II increases cell [Ca²+]i as expected, and provide the new observation that ANP reduces [Ca²+]i in these cells. Further more, ANP reduces the increase in [Ca²+]i elicited by ANG II, thus modulating the effect of ANG II on [Ca²+]i

Hemoglobinas anormais: perfil estatístico em doadores de sangue do Centro de Hematologia e Hemoterapia de Minas Gerais / Haemoglobinophaties in capable and uncapable blood samples donors from the Centro de Hematologia e Hemoterapia de Minas Gerais

As autoras apresentam um estudo sobre a frequência de hemoglobinopatias em amostras de sangue de doadores aptos e inaptos do Centro de Hematologia e Hemoterapia de Minas Gerais. Foram observados percentuais de 4,7 porcento e 6,7 para doadores aptos e inaptos em relaçäo à frequência de hemoglobinopatias. Devido aos possíveis prejuízos causados por transfusäo de sangue com hemoglobinopatias e levando em consideraçäo a significativa frequência desta alteraçäo, as autoras sugerem a intruduçäo dos principais métodos de diagnóstico nos serviços de Hemoterapia

Perfil hematologico e bioquimico de pacientes com tuberculose / Hematological and biochemical profile of patients carrying lung tuberculosis

Foram colhidas amostras de sangue de 30 pacientes com tuberculose pulmonar comprovada atraves do encontro do B.A.A.R. em esfregaços de escarro corados pelo Ziehl-Neelsen.. As amostras de sangue foram empregadas, atraves de metodologia adequada, para a determinaçao do perfil hematologico e bioquimico dos tuberculosos em busca de alteraçoes que pudessem ser distribuidas a infeccao. Os resultados observados revelaram uma tendencia a leucocitose (23//dos casos com global acima de 10.000/mm3) e um elevado aumento da velocidade de hemossedimentaçao (86//apresentaram elevaçao com media de 72 a 44 mm para mulheres ehomens, respectivamente). A monocitose, referida por varios autores na tuberculose ativa, nao foi observada. Quanto ao perfil bioquimico, os resultados da determinaçao de fosfatase alcalina e valores obtidos de globulinas se mostraram elevados em 46//dos casos. Esses resultados representaram dados preliminares obtidos atraves das avaliaçoes hematologicas e bioquimicas de pacientes com tuberculose,realizadas antes do emprego da terapeutica recomendada. Estes pacientes representam uma amostragem adequadamente selecionada para a primeira etapa do projeto depesquisa sobre a avaliaçao da conduta farmacoterapeutica no setor publico, com aparticipaçao integrada dos Departamentos de Farmacia Social, Produtos Farmaceuticos e Analises Clinicas e Toxicologicas da Faculdade de Farmacia da UFMG.