The dynamics of acute malaria infections. I. Effect of the parasite's red blood cell preference

What determines the dynamics of parasite and anaemia during acute primary malaria infections? Why do some strains of malaria reach higher densities and cause greater anaemia than others? The conventional view is that the fastest replicating parasites reach the highest densities and cause the greatest loss of red blood cells (RBCs). Other current hypotheses suggest that the maximum parasite density is achieved by strains that either elicit the weakest immune responses or infect the youngest RBCs (reticulocytes). Yet another hypothesis is a simple resource limitation model where the peak parasite density and the maximum anaemia (percentage loss of RBCs) during the acute phase of infection equal the fraction of RBCs that the malaria parasite can infect. We discriminate between these hypotheses by developing a mathematical model of acute malaria infections and confronting it with experimental data from the rodent malaria parasite Plasmodium chabaudi. We show that the resource limitation model can explain the initial dynamics of infection of mice with different strains of this parasite. We further test the model by showing that without modification it closely reproduces the dynamics of competing strains in mixed infections of mice with these strains of P. chabaudi. Our results suggest that a simple resource limitation is capable of capturing the basic features of the dynamics of both parasite and RBC loss during acute malaria infections of mice with P. chabaudi, suggesting that it might be worth exploring if similar results might hold for other acute malaria infections, including those of humans

Estimulação elétrica neuromuscular de média freqüência (russa) em cães com atrofia muscular induzida Medium frequency neuromuscular electrical stimulation (russian) in dogs with induced muscle atrophy

A estimulação elétrica neuromuscular (EENM) de média freqüência (Russa) ou de Kotz pode ser empregada para a recuperação de massa muscular em animais apresentando atrofia muscular por desuso. Assim, o objetivo deste trabalho foi empregar a EENM de média freqüência no quadríceps femoral de cães com atrofia muscular induzida, avaliando-se a ocorrência de ganho de massa. Foram utilizados oito cães em dois grupos denominados de GI ou controle e de GII ou tratado. Para a indução da atrofia muscular, a articulação fêmoro-tíbio-patelar esquerda foi imobilizada por 30 dias. Após 48 horas da remoção, foi realizada a EENM nos cães do grupo II, três vezes por semana, com intervalo de 48 horas cada sessão, pelo período de 60 dias. Foram avaliadas a mensuração da perimetria da coxa, da goniometria do joelho, as enzimas creatina-quinase (CK) e morfometria das fibras musculares em cortes transversais do músculo vasto lateral, colhido mediante a biópsia muscular. A EENM foi empregada no músculo quadríceps femoral numa freqüência de 2.500Hz, largura de pulso de 50% e relação de tempo on/off de 1:2. Não houve diferença significativa quanto aos valores de perimetria da coxa e a atividade da enzima CK entre os grupos I e II. Na goniometria, houve diminuição significativa (P<0,05) da amplitude articular após a remoção do aparelho de fixação externa somente nos animais do grupo II, em comparação a com tempo zero. Quanto à morfometria das fibras do músculo vasto lateral, foram notados valores maiores de área das fibras no grupo Tratado, em relação ao Controle (P<0,05), no dia 90, e, no grupo Tratado, entre os dias zero e 90. A EENM de média freqüência ocasiona hipertrofia do músculo vasto lateral em cães após a atrofia muscular induzida.<br>The medium frequency neuromuscular electrical stimulation (NMES) (Russa) or Kotz is designed for recuperation of muscle mass in dogs with muscular atrophy in disuse. This study aims to utilize medium frequency NMES on the femoral quadriceps of dogs with induced muscular atrophy and evaluate the occurrence of gain in mass. Eight dogs in two groups denominated GI, or control, and GII, or treated were used. For the induction of muscular atrophy, the left femoral-tibial-patellar joint was immobilized for 30 days. NMES treatment began 48 hours after the removal of the immobilization device on dogs from group II and was carried out three times per week, with an interval of 48 hours between each session, during 60 days. The following parameters were measured: thigh perimeter, goniometry of the knee, creatine kinase (CK) enzymes and morphometry of the muscular fibers in transversal cuts of the vastus lateralis muscle, collected through a muscular biopsy. EENM was utilized on the femoral quadriceps at a frequency of 2500 Hz, with pulse duration of 50%, and the time on/off was at a proportion of 1:2. There was no significant difference between the thigh perimeter and the activity of enzyme CK between groups I and II. As for the goniometry a significant increase (P<0,05) was observed among 0 and 30 days after the immobilization in group II. As for the morphometry of the fibers of the vastus lateralis, a significant increase (P<0,05) was observed in the transversal area of the treated group on the 90th day when compared with that observed at the time of immobilization and among the groups, group II presented a greater transversal area (P<0.05) on the 90th day. The medium frequency NMES brings about a hypertrophy of the vastus lateralis muscle in dogs after induced muscular atrophy

Estimulação elétrica neuromuscular em cães com atrofia muscular induzida Neuromuscular electric stimulation in dogs with induced muscle atrophy

Empregou-se a estimulação elétrica neuromuscular (EENM) de baixa freqüência no músculo quadríceps femoral de cães com atrofia induzida e avaliou-se a ocorrência de ganho de massa nessa musculatura. Foram utilizados oito cães com pesos entre 15 e 30kg, distribuídos aleatoriamente em dois grupos denominados de I ou controle e II ou tratado. A articulação femorotibiopatelar esquerda foi imobilizada por 30 dias pelo método de transfixação percutânea tipo II, com retirada de aparelho de imobilização após esse período. Decorridas 48 horas da remoção, foi realizada a EENM nos cães do grupo II, cinco vezes por semana, com intervalo de 24 horas cada sessão, pelo período de 60 dias. Foram avaliadas a circunferência da coxa, a goniometria do joelho, a análise clínica da marcha, as enzimas creatina-quinase (CK) e aspartato-amino-transferase (AST) e a morfometria das fibras musculares em cortes transversais do músculo vasto lateral colhido mediante biópsia muscular. A EENM foi empregada no músculo quadríceps femoral na freqüência de 50Hz, duração de pulso de 300 milisegundos e relação de tempo on/off de 1:2. Quanto à morfometria das fibras do músculo vasto lateral, no grupo tratado houve aumento significativo (P<0,05) da área transversal aos 90 dias em relação ao dia zero. A EENM de baixa freqüência ocasiona hipertrofia do músculo vasto lateral em cães após a imobilização rígida temporária da articulação do joelho.<br>Low frequency neuromuscular electrical stimulation (NMES) was used on the femoral quadriceps of dogs with induced muscular atrophy and the occurrence of gain in mass in these muscles was evaluated. Eight dogs from 15 to 30kg were randomly distributed in two groups named I, or control; and II, or treated. For the induction of muscular atrophy, the left femoral-tibial-patellar joint was immobilized for 30 days by percutaneous transfixation type II. After 30 days, the immobilization device was removed. The NMES treatment began 48 hours after the removal of the immobilization device of the dogs of group II, and it was carried out five times per week with an interval of 24 hours between each session, for 60 days. The following parameters were measured: thigh circumference, goniometry of the knee, clinical gait analysis, creatine kinase (CK) and aspartate aminotransferase (AST) enzymes, and morphometry of the muscular fibers in transversal cuts of the vastus lateralis muscle collected through muscular biopsy. The NMES was applied on the femoral quadriceps at a frequency of 50 Hz, with pulse duration of 300 milliseconds, and the on/off time was at a proportion of 1:2. Regarding the morphometry of the vastus lateralis fibers, a significant increase (P<0.05) in the transversal area of the treated group at 90 days was observed when compared with that identified at the time of immobilization. Thus, it can be concluded that low frequency NMES brings about hypertrophy of the vastus lateralis muscle in dogs after temporary rigid immobilization of the knee joint

Wild justice and fair play: cooperation, forgiveness, and morality in animals

Abstract. In this paper I argue that we can learn much about ‘wild justice ’ and the evolutionary origins of social morality – behaving fairly – by studying social play behavior in group-living animals, and that interdisciplinary cooperation will help immensely. In our efforts to learn more about the evolution of morality we need to broaden our comparative research to include animals other than non-human primates. If one is a good Darwinian, it is premature to claim that only humans can be empathic and moral beings. By asking the question ‘What is it like to be another animal? ’ we can discover rules of engagement that guide animals in their social encounters. When I study dogs, for example, I try to be a ‘dogocentrist ’ and practice ‘dogomorphism. ’ My major arguments center on the following ‘big ’ questions: Can animals be moral beings or do they merely act as if they are? What are the evolutionary roots of cooperation, fairness, trust, forgiveness, and morality? What do animals do when they engage in social play? How do animals negotiate agreements to cooperate, to forgive, to behave fairly, to develop trust? Can animals forgive? Why cooperate and play fairly? Why did play evolve as it has? Does ‘being fair ’ mean being more fit – do individual variations in play influence an individual’s reproductive fitness, are more virtuous individuals more fit than less virtuous individuals? What is the taxonomic distribution of cognitiv