Hepatitis B screening in hematology patients receiving intravenous immunoglobulin.

BACKGROUND: Transient positivity for hepatitis B core antibody (Anti-HBc) following intravenous immunoglobulin (IVIG) and subcutaneous immunoglobulin exposure is a well-described phenomenon. The aim of this study was to retrospectively review Hepatitis B viral screening practices in IVIG recipients in a hematology specific cohort at a single center. METHODS: Electronic databases were analyzed to identify all hematology patients who received IVIG from September 2022 to March 2022 at a single Irish center (n = 43). The proportion of patients that had a baseline anti-HBc tested prior to IVIG receipt was assessed as well as the proportion of patients that developed a transiently positive anti-HBc following IVIG exposure. Data were also collected relating to signal cut-off ratios in patients with detectable anti-HBc post-IVIG. RESULTS: 58.1% of patients had at least one serological hepatitis B viral test sent prior to IVIG exposure. Anti-HBc was the least common serological investigation performed prior to IVIG exposure (21% of recipients). A positive or equivocal "low level antibody" was identified in 15% of recipients and this was proven to be transient in all cases. CONCLUSION: The minority of hematology patients had a baseline anti-HBc assessed prior to IVIG exposure. All patients in this study had the potential to require further immunosuppressive therapies, which could be limited by a misleading anti-HBc result. We therefore advocate for baseline anti-HBc testing to be performed prior to IVIG exposure in hematology patients and for cautious interpretation of anti-HBc results taking into account signal cut-off ratios post-IVIG exposure.

Significance of pacemaker vs. non-pacemaker neurons in an excitatory rhythmic network.

This modeling study investigates the functional role of pacemaker neurons in generating stable rhythms in the pre-Botzinger complex, a subcircuit of the respiratory pattern-generating circuitry in mammals. While the presence of pacemakers within the network is without doubt, the percentage and significance of such pacemakers is still unresolved. Here we revisited earlier network simulations by varying the fraction of pacemaker and non-pacemaker neurons within the network, and quantifying the robustness of the input parameter space and range of frequencies output by the network. Stable network rhythms were possible even with no pacemakers. However, we found that a network of at least 50% pacemakers produced the greatest range of output frequencies and had the more robust input space.

Ionic current model of a hypoglossal motoneuron.

We have developed a single-compartment, electrophysiological, hypoglossal motoneuron (HM) model based primarily on experimental data from neonatal rat HMs. The model is able to reproduce the fine features of the HM action potential: the fast afterhyperpolarization, the afterdepolarization, and the medium-duration afterhyperpolarization (mAHP). The model also reproduces the repetitive firing properties seen in neonatal HMs and replicates the neuron's response to pharmacological experiments. The model was used to study the role of specific ionic currents in HM firing and how variations in the densities of these currents may account for age-dependent changes in excitability seen in HMs. By varying the density of a fast inactivating calcium current, the model alternates between accelerating and adapting firing patterns. Modeling the age-dependent increase in H current density accounts for the decrease in mAHP duration observed experimentally, but does not fully account for the decrease in input resistance. An increase in the density of the voltage-dependent potassium currents and the H current is required to account for the decrease in input resistance. These changes also account for the age-dependent decrease in action potential duration.