Analytical Solution of a New SEIR Model Based on Latent Period-Infectious Period Chronological Order

The Susceptible-Infectious-Recovered (SIR) and SIR derived epidemic models have been commonly used to analyze the spread of infectious diseases. The underlying assumption in these models, such as Susceptible-Exposed-Infectious-Recovered (SEIR) model, is that the change in variables E, I or R at time t is dependent on a fraction of E and I at time t. This means that after exposed on a day, this individual may become contagious or even recover on the same day. However, the real situation is different: an exposed individual will become infectious after a latent period (l) and then recover after an infectious period (i). In this study, we proposed a new SEIR model based on the latent period-infectious period chronological order (Liu X., Results Phys. 2021; 20:103712). An analytical solution to equations of this new SEIR model was derived. From this new SEIR model, we obtained a propagated curve of infectious cases under conditions l>i. Similar propagated epidemic curves were reported in literature. However, the conventional SEIR model failed to simulate the propagated epidemic curves under the same conditions. For l<i, the new SEIR models generated bell-shaped curves for infectious cases, and the curve is near symmetrical to the vertical line passing the curve peak. This characteristic can be found in many epidemic curves of daily COVID-19 cases reported from different countries. However, the curve generated from the conventional SEIR model is a right-skewed bell-shaped curve. An example for applying the analytical solution of the new SEIR model equations to simulate the reported daily COVID-19 cases was also given in this paper.

COVID-19 Infection: Impact on Hair

With a practice dedicated to hair restoration and hair loss management, the authors have seen a large number of patients presenting with increased hair fall in the last 18 months. Hair fall after a stressfull event such as infections with febrile episodes is known. However, the latent period between the infective episode and hair fall has been shorter after COVID-19 infection than before. This review attempts to look at various pathways responsible for hair fall and if this differs from the conventional hair fall seen after any infection. It also tries to understand if the infection with the SARS-CoV-2 virus has a direct impact on the hair follicle leading to hair fall.

Mitophagy Eliminates the Accumulation of SARM1 on the Mitochondria, Alleviating Axon Degeneration in Acrylamide Neuropathy

Background: Sterile-α and toll/interleukin 1 receptor motif containing protein 1 (SARM1) is the central executioner of axon degeneration. Although it has been confirmed to have a mitochondrial targeting sequence and can bind to and stabilize PINK1 on depolarized mitochondria, the biological significance for mitochondrial localization of SARM1 is still unclear. Chronic acrylamide (ACR) intoxication can cause typical pathology of axonal injury, owning the potential to explore the interaction between mitochondria and SARM1 during the latent period of axon destruction.Methods: The expression and the mitochondria distribution of SARM1 were evaluated in in vivo and in vitro ACR neuropathy models. Transmission electron microscopy, immunoblotting, and immunofluorescence were performed to evaluate mitochondrial dynamics and PINK1-dependent mitophagy. LC3 turnover experiment and live cell imaging were conducted to further assess the state of mitophagy flux. In order to verify the effect of mitophagy in SARM1-mediated axon degeneration, low-dose and low-frequency rapamycin was administered in ACR-exposed rats to increase basal autophagy.Results: In a time- and dose-dependent manner, ACR induced peripheral nerve injury in rats and truncated axons of differentiated N2a cell. Moreover, the severity of this axon damage was consistent with the up-regulation of SARM1. SARM1 prominently accumulated on mitochondria, and at the same time mitophagy was activated. Importantly, rapamycin (RAPA) administration eliminated mitochondrial accumulated SARM1 and alleviated SARM1 dependent axonal degeneration.Conclusions: Complementing to the coordinated activity of NMNAT2 and SARM1, mitochondrial localization of SARM1 may be part of the self-limiting molecular mechanisms of Wallerian axon destruction. In the early latent period of axon damage, the mitochondrial localization of SARM1 will help it to be isolated by the mitochondrial network and to be degraded through PINK1-dependent mitophagy to maintain local axon homeostasis. When the mitochondrial quality control mechanisms are broken down, SARM1 will cause irreversible damage for axon degeneration. Moderate autophagy activation can be invoked as potential strategies to alleviate axon degeneration in ACR neuropathy and even other axon degeneration diseases.

TPPU Pre-Treatment Rescues Dendritic Spine Loss and Alleviates Depressive Behaviours during the Latent Period in the Lithium Chloride-Pilocarpine-Induced Status Epilepticus Rat Model

Epileptogenesis may be responsible for both of recurrent seizures and comorbid depression in epilepsy. Disease-modifying treatments targeting the latent period before spontaneous recurrent seizures may contribute to the remission of seizures and comorbid depression. We hypothesized that pre-treatment with 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), a soluble epoxide hydrolase (sEH) inhibitor, which has anti-inflammatory and neuroprotective effects might rescue status epilepticus (SE)-induced dendritic spine loss and alleviate depressive behaviours. Rats were either pre-treated with TPPU (0.1 mg/kg/d) intragastrically or with vehicle (40% polyethylene glycol 400) from 7 days before to 7 days after SE that was induced with lithium chloride and pilocarpine intraperitoneally. Rats in the Control group were given saline instead. The forced swim test (FST) was performed on the 8th day after SE to evaluate the depression-like behaviours in rats. The results showed that seizures severity during SE was significantly decreased, and the immobility time during FST was significantly increased through TPPU pre-treatment. Moreover, pre-treatment with TPPU attenuated inflammations including microglial gliosis and the level of proinflammatory cytokine IL-1β in the hippocampus; in addition, neuronal and dendritic spine loss in the subfields of hippocampus was selectively rescued, and the expression of NR1 subunit of N-methyl-D-aspartate (NMDA) receptor, ERK1/2, CREB, and their phosphorylated forms involved in the dendritic spine development were all significantly increased. We concluded that pre-treatment with TPPU attenuated seizures severity during SE and depressive behaviours during the period of epileptogenesis probably by rescuing dendritic spine loss in the hippocampus.

Antiparkinsonian activity of new N-methyl-D-aspartate receptor ligands in the arecoline hyperkinesis test

Introduction. Parkinson’s disease (PD) is one of the most common neurodegenerative diseases in the population of older patients. Even though long-term combination therapy helps to cope with the main manifestations of PD. It inevitably leads to the appearance of such side effects as drowsiness, hallucinations, dyskinesia, and many others. [12]. Therefore, the search for effective antiparkinsonian drugs devoid of the above-mentioned adverse reactions remains an urgent task of modern neuropharmacology.The explored substances are derivatives of imidazole-4,5-dicarboxylic acid. These compounds belong to a fundamentally new class of N-methyl-D-aspartate ligands (NMDA) that are not channel blockers. Their pharmacological effect is realized due to interaction with the NMDA receptor recognition site, which, along with high efficiency, allows us to assume their higher safety, compared to previously existing channel blockers from the NMDA ligand group.Objective. Studing of the antiparkinsonian activity of new ligands of the glutamate NMDA-receptor complex-1,2-substituted imidazole-4,5-dicarboxylic acids on an experimental model of arecoline hyperkinesis.Materials and methods. Imidazole-dicarboxylic acid derivatives (IEM2258, IEM2248, IEM2247, and IEM1574) were injected into the lateral ventricles of the mouse brain 10 minutes before arecoline in a volume of 5 µl at doses of 0.1-0.5 µmol, then the latent period, intensity, and duration of tremor were recorded. Amantadine was used as a comparison drug.Results. Preliminary administration of the studied examined substances led to a significant decrease in the intensity and duration of arecoline tremor. The highest inhibitory activity with respect to the intensity and duration of the experimental tremor was demonstrated with the introduction of the compound IEM-2247 (at a dose of 0.1-0.5 mmol, the duration of the latent period of the tremor was 1.7-2.3 times longer than the control one, respectively, the duration of the tremor decreased by 1.5 - 2.5 times).Conclusions. The dose-dependent antiparkinsonian activity of imidazole-dicarboxylic acid derivatives is shown, indicating the prospects for the development of these substances and the further search for effective and safe antiparkinsonian agents among the compounds of this class.

Estimating the latent period of coronavirus disease 2019 (COVID-19)

Using detailed exposure information on COVID-19 cases, we estimated the mean latent period to be 5.5 days (95% confidence interval: 5.1-5.9 days), shorter than the mean incubation period (6.9 days). Laboratory testing may allow shorter quarantines since 95% of COVID-19 cases shed virus within 10.6 days (95%CI: 9.6-11.6) of infection.