Neonatal erythropoiesis and subsequent anemia in HIV-positive and HIV-negative Zimbabwean babies during the first year of life: a longitudinal study

BACKGROUND: Anemia is common in HIV infection and independently associated with disease progression and mortality. The pathophysiology of HIV-related anemia is not well understood especially in infancy. METHODS: We conducted a longitudinal cohort study nested within the Zimbabwe Vitamin A for Mothers and Babies Project. We measured hemoglobin, erythropoietin (EPO), serum transferrin receptor (TfR) and serum ferritin at 6 weeks, 3 and 6 months of age and hemoglobin at 9 and 12 months in 3 groups of randomly selected infants: 136 born to HIV-negative mothers, and 99 born to HIV-positive mothers and who were infected themselves by 6 weeks of age, and 324 born to HIV-positive mothers but who did not become infected in the 6 months following birth. RESULTS: At one year of age, HIV-positive infants were 5.26 (adjusted odds ratio, P < 0.001) times more likely to be anemic compared to HIV-negative infants. Among, HIV-negative infants, EPO was or tended to be inversely associated with hemoglobin and was significantly positively associated with TfR throughout the first 6 months of life; TfR was significantly inversely associated with ferritin at 6 months; and EPO explained more of the variability in TfR than did ferritin. Among infected infants, the inverse association of EPO to hemoglobin was attenuated during early infancy, but significant at 6 months. Similar to HIV-negative infants, EPO was significantly positively associated with TfR throughout the first 6 months of life. However, the inverse association between TfR and ferritin observed among HIV-negative infants at 6 months was not observed among infected infants. Between birth and 6 months, mean serum ferritin concentration declined sharply (by ~90%) in all three groups of babies, but was significantly higher among HIV-positive compared to HIV-negative babies at all time points. CONCLUSION: HIV strongly increases anemia risk and confounds interpretation of hematologic indicators in infants. Among HIV-infected infants, the EPO response to anemia is attenuated near the time of infection in the first weeks of life, but normalizes by 6 months

Differences in Membrane Properties in Simulated Cases of Demyelinating Neuropathies: Internodal Focal Demyelinations with Conduction Block

The aim of this study is to investigate the membrane properties (potentials and axonal excitability indices) in the case of myelin wrap reduction (96%) in one, two and three consecutive internodes along the length of human motor nerve fibre. The internodally focally demyelinated cases (termed as IFD1, IFD2 and IFD3, respectively, with one, two and three demyelinated internodes are simulated using our previous double cable model of the fibre. The progressively greater increase of focal loss of myelin lamellae blocks the invasion of the intracellular potentials into the demyelinated zones. For all investigated cases, the radial decline of the extracellular potential amplitudes increases with the increase of the radial distance and demyelination, whereas the electrotonic potentials show a decrease in the slow part of the depolarizing and hyperpolarizing responses. The time constants are shorter and the rheobases higher for the IFD2 and IFD3 cases than for the normal case. In the recovery cycles, the same cases have less refractoriness, greater supernormality and less late subnormality than the normal case. The simulated membrane abnormalities can be observed in vivo in patients with demyelinating forms of Guillain-Barré syndrome. The study provides new information about the pathophysiology of acquired demyelinating neuropathies