Latent and incubation periods of Delta, BA.1, and BA.2 variant cases and associated factors: a cross-sectional study in China.

BACKGROUND: The latent and incubation periods characterize the transmission of infectious viruses and are the basis for the development of outbreak prevention and control strategies. However, systematic studies on the latent period and associated factors with the incubation period for SAS-CoV-2 variants are still lacking. We inferred the two durations of Delta, BA.1, and BA.2 cases and analyzed the associated factors. METHODS: The Delta, BA.1, and BA.2 (and its lineages BA.2.2 and BA.2.76) cases with clear transmission chains and infectors from 10 local SAS-CoV-2 epidemics in China were enrolled. The latent and incubation periods were fitted by the Gamma distribution, and associated factors were analyzed using the accelerated failure time model. RESULTS: The mean latent period for 672 Delta, 208 BA.1, and 677 BA.2 cases was 4.40 (95%CI: 4.24 ~ 4.63), 2.50 (95%CI: 2.27 ~ 2.76), and 2.58 (95%CI: 2.48 ~ 2.69) days, respectively, with 85.65% (95%CI: 83.40 ~ 87.77%), 97.80% (95%CI: 96.35 ~ 98.89%), and 98.87% (95%CI: 98.40 ~ 99.27%) of them starting to shed viruses within 7 days after exposure. In 405 Delta, 75 BA.1, and 345 BA.2 symptomatic cases, the mean latent period was 0.76, 1.07, and 0.79 days shorter than the mean incubation period [5.04 (95%CI: 4.83 ~ 5.33), 3.42 (95%CI: 3.00 ~ 3.89), and 3.39 (95%CI: 3.24 ~ 3.55) days], respectively. No significant difference was observed in the two durations between BA.1 and BA.2 cases. After controlling for the sex, clinical severity, vaccination history, number of infectors, the length of exposure window and shedding window, the latent period [Delta: exp(ß) = 0.81, 95%CI: 0.66 ~ 0.98, p = 0.034; Omicron: exp(ß) = 0.82, 95%CI: 0.71 ~ 0.94, p = 0.004] and incubation period [Delta: exp(ß) = 0.69, 95%CI: 0.55 ~ 0.86, p < 0.001; Omicron: exp(ß) = 0.83, 95%CI: 0.72 ~ 0.96, p = 0.013] were significantly shorter in 18 ~ 49 years but did not change significantly in ≥ 50 years compared with 0 ~ 17 years. CONCLUSION: Pre-symptomatic transmission can occur in Delta, BA.1, and BA.2 cases. The latent and incubation periods between BA.1 and BA.2 were similar but shorter compared with Delta. Age may be associated with the latent and incubation periods of SARS-CoV-2.

Characterization of Quantitative Trait Loci for Leaf Rust Resistance from CI 13227 in Three Winter Wheat Populations.

Leaf rust is a widespread foliar wheat disease causing substantial yield losses worldwide. Slow rusting is "adult plant" resistance that significantly slows epidemic development and thereby reduces yield loss. Wheat accession CI 13227 was previously characterized as having slow-rusting resistance. To validate the quantitative trait loci (QTLs) and develop diagnostic markers for slow rusting resistance in CI 13227, a new population of recombinant inbred lines of CI 13227 × Everest was evaluated for latent period, final severity, area under the disease progress curve, and infection type in greenhouses and genotyped using genotyping-by-sequencing. Four QTLs were identified on chromosome arms 2BL, 2DS, 3BS, and 7BL, explaining 6.82 to 28.45% of the phenotypic variance for these traits. Seven kompetitive allele-specific polymorphism markers previously reported to be linked to the QTLs in two other CI 13227 populations were validated. In addition, the previously reported QLr.hwwg-7AL was remapped to 2BL (renamed QLr.hwwg-2BL) after adding new markers in this study. Phenotypic data showed that the recombinant inbred lines harboring two or three of the QTLs had a significantly longer latent period. QLr.hwwg-2DS on 2DS showed a major effect on all rust resistance traits and was finely mapped to a 2.7-Mb interval by two newly developed flanking markers from exome capture. Three disease-resistance genes and two transporter genes were identified as the putative candidates for QLr.hwwg-2DS. The validated QTLs can be used as slow-rusting resistance resources, and the markers developed in this study will be useful for marker-assisted selection.

Projection of the prevalence of tracheal, bronchus, and lung cancer incidence using cigarette smoking prevalence in Iran from 1990 to 2018: a comparison of latent period-based models with standard forecasting models.

BACKGROUND: Smoking is the major risk factor for tracheal, bronchus, and lung (TBL) cancers. We investigated the feasibility of projecting TBL cancer incidence using smoking incidence rates by incorporating a range of latent periods from the main risk factor exposure to TBL cancer diagnosis. METHODS: In this ecological study, we extracted data on TBL cancer incidence rates in Iran from 1990 to 2018 from the Global Burden of Disease (GBD) database. We also collected data on Iranian cigarette smoking patterns over the past 40 years through a literature review. The weighted average smoking incidence was calculated using a fixed-effects model with Comprehensive Meta-Analysis (CMA) software. Using these data, the five-year TBL cancer incidence in Iran was projected through time series modeling with IT Service Management (ITSM) 2000 software. A second model was developed based on cigarette smoking incidence using linear regression with SPSS (version 22), incorporating different latent periods. The results of these two models were compared to determine the best latent periods. RESULTS: An increasing trend in TBL cancer incidence was observed from 2019 to 2023 (first model: 10.30 [95% CI: 9.62, 10.99] to 11.42 [95% CI: 10.85, 11.99] per 100,000 people). In the second model, the most accurate prediction was obtained with latent periods of 17 to 20 years, with the best prediction using a 17-year latent period (10.13 to 11.40 per 100,000 people) and the smallest mean difference of 0.08 (0.84%) per 100,000 people using the standard forecasting model (the ARIMA model). CONCLUSION: Projecting an increase in TBL cancer incidence rates in the future, an optimal latent period of 17 to 20 years between exposure to cigarette smoke and TBL cancer incidence has implications for macrolevel preventive health policymaking to help reduce the burden of TBL cancer in upcoming years.

Reactivation of varicella zoster virus following trigeminal schwannoma resection.

Varicella zoster is found exclusively in humans. Infected people with this virus result in chickenpox followed by dormant virus within neural ganglia. This dormant virus, once activated, may affect any ganglia or nerves of the body but most commonly involves the thoracic, cervical and trigeminal nerves in decreasing order of frequency. We review three such cases in which manipulation of the trigeminal ganglion resulted in reactivation of varicella at homologous operative sites. Each patient underwent surgeries in which the trigeminal ganglion was manipulated for the resection of trigeminal schwannoma under a microscope through various approaches. All three patients developed reactivation of varicella at homologous operative sites. A thorough history of chickenpox infection should be taken in patients who are undergoing surgeries for trigeminal pathology. Early diagnosis should be made once any vesicular lesions are seen with prompt treatment. Reassurance and counselling are necessary in these patients. If possible, prophylaxis may be started in all such patients. Further studies are warranted to determine the exact cause of reactivation.

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 (95% CI: 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 (95% CI: 9.6-11.6) days of infection.

Citrus limon L. (lemon) seed extract shows neuro-modulatory activity in an in vivo thiopental-sodium sleep model by reducing the sleep onset and enhancing the sleep duration.

Citrus limon L. is an ingenious alternative medication and has a broad scope in managing several health conditions as part of natural remedies. Recently, medicinal plants have witnessed incredible consideration worldwide in the field of neuroscience for remedial intervention. The present work has investigated the phytochemical compounds and neuropharmacological potential of the seed extract of Citrus limon as a step to partially validate its formulations as nutraceuticals using an in vivo model. Diverse phytochemical groups such as alkaloids, glycosides, flavonoids, tannins, gums, saponins, steroids were qualitatively identified through colorimetric methods utilizing standard compounds. The neuropharmacological properties were studied in Swiss albino mice with the sleep time induced by thiopental sodium taken as an end-point, in standard hole cross, hole board, and open-field experiments at varying doses of 50 and 100 mg/kg body weight. Phytochemical screening showed that alkaloids, flavonoids, saponins, tannins, steroids, and glycosides are present in the aqueous extract of the seed. The extracts demonstrated a significant reduction in sleep onset and enhanced the sleep duration in a dose-dependent manner in thiopental sodium-induced sleeping time, along with a marked decrease in unconstrained locomotors and explorative properties in both hole cross and open field tests. Moreover, in the hole board study, the extracts minimized the count of head dips observed in the treated mice. The results shown in this study demonstrate that Citrus limon extracts have neuropharmacological properties that can be further examined for their potential role as an adjuvant with conventional medications or nutraceuticals.

Defining the latent period of epileptogenesis and epileptogenic zone in a focal cortical dysplasia type II (FCDII) rat model.

OBJECTIVES: Focal cortical dysplasia type II (FCDII) is one of the most common underlying pathologies in patients with drug-resistant epilepsy. However, mechanistic understanding of FCDII fails to keep pace with genetic discoveries, primarily due to the significant challenge in developing a clinically relevant animal model. Conceptually and clinically important questions, such as the unknown latent period of epileptogenesis and the controversial epileptogenic zone, remain unknown in all experimental FCDII animal models, making it even more challenging to investigate the underlying epileptogenic mechanisms. METHODS: In this study, we used continuous video-electroencephalography (EEG) monitoring to detect the earliest interictal and ictal events in a clustered regularly interspaced short palindromic repeats (CRISPR)-in utero electroporation (IUE) FCDII rat model that shares genetic, pathological, and electroclinical signatures with those observed in humans. We then took advantage of in vivo local field potential (LFP) recordings to localize the epileptogenic zone in these animals. RESULTS: To the best of our knowledge, we showed for the first time that epileptiform discharges emerged during the third postnatal week, and that the first seizure occurred as early as during the fourth postnatal week. We also showed that both interictal and ictal discharges are localized within the dysplastic cortex, concordant with human clinical data. SIGNIFICANCE: Together, our work identified the temporal and spatial frame of epileptogenesis in a highly clinically relevant FCDII animal model, paving the way for mechanistic studies at molecular, cellular, and circuitry levels.

Comparison of the maternal serum endocan levels in preterm premature rupture of membrane and normal pregnancy.

OBJECTIVE: Endocan is a novel marker of endothelial inflammation. In this study, we aimed to show whether there was a significant difference between the endocan levels of pregnant women with and without preterm premature rupture of membranes (PPROM and non-PPROM). Also, we aimed to find a relation between endocan levels and the latent period. MATERIAL AND METHODS: Pregnant women with PPROM between 28 and 34 weeks of gestation and those without PPROM with similar gestational weeks were included in the study. A total of 88 pregnant women, 44 with PROM and 44 healthy pregnancies, were evaluated. Demographic and obstetric features, leukocyte, and endocan levels of the study and control groups were compared. RESULTS: The demographic features and obstetric history of both groups were similar. The mean leukocyte and endocan levels of the study group were higher than in the control group (p < 0.001 and 0.029, respectively). The leukocyte level was the only independent factor predicting PPROM after multivariate logistic regression analysis. CONCLUSION: Although the endocan levels were higher in patients with PPROM, multivariate analysis showed that the only independent predictive factor was the leukocyte level.

A time-delayed SVEIR model for imperfect vaccine with a generalized nonmonotone incidence and application to measles.

In this paper, we investigate the effects of the latent period on the dynamics of infectious disease with an imperfect vaccine. We assume a general incidence rate function with a non-monotonicity property to interpret the psychological effect in the susceptible population when the number of infectious individuals increases. After we propose the model, we provide the well-posedness property by verifying the non-negativity and boundedness of the models solutions. Then, we calculate the effective reproduction number R E . The threshold dynamics of the system is obtained with respect to R E . We discuss the global stability of the disease-free equilibrium when R E < 1 and explore the system persistence when R E > 1 . Moreover, we prove the coexistence of an endemic equilibrium when the system persists. Then, we discuss the critical vaccination coverage rate that is required to eliminate the disease. Numerical simulations are provided to: (i) implement a case study regarding the measles disease transmission in the United States from 1963 to 2016; (ii) study the local and global sensitivity of R E with respect to the model parameters; (iii) discuss the stability of endemic equilibrium; and (iv) explore the sensitivity of the proposed model solutions with respect to the main parameters.

A face-to-face comparison of the intra-amygdala and intrahippocampal kainate mouse models of mesial temporal lobe epilepsy and their utility for testing novel therapies.

OBJECTIVE: Intracranial (intrahippocampal or intra-amygdala) administration of kainate in rodents leads to spatially restricted brain injury and development of focal epilepsy with characteristics that resemble mesial temporal lobe epilepsy. Such rodent models are used both in the search for more effective antiseizure drugs (ASDs) and in the development of antiepileptogenic strategies. However, it is not clear which of the models is best suited for testing different types of epilepsy therapies. METHODS: In the present study, we performed a face-to-face comparison of the intra-amygdala kainate (IAK) and intrahippocampal kainate (IHK) mouse models using the same mouse inbred strain (C57BL/6). For comparison, some experiments were performed in mouse outbred strains. RESULTS: Intra-amygdala kainate injection led to more severe status epilepticus and higher mortality than intrahippocampal injection. In male C57BL/6 mice, the latent period to spontaneous recurrent seizures (SRSs) was short or absent in both models, whereas a significantly longer latent period was determined in NMRI and CD-1 outbred mice. When SRSs were recorded from the ipsilateral hippocampus, relatively frequent electroclinical seizures were determined in the IAK model, whereas only infrequent electroclinical seizures but extremely frequent focal electrographic seizures were determined in the IHK model. As a consequence of the differences in SRS frequency, prolonged video-electroencephalographic monitoring and drug administration were needed for testing efficacy of the benchmark ASD carbamazepine in the IAK model, whereas acute drug testing was possible in the IHK model. In both models, carbamazepine was only effective at high doses, indicating ASD resistance to this benchmark drug. SIGNIFICANCE: We found a variety of significant differences between the IAK and IHK models, which are important when deciding which of these models is best suited for studies on novel epilepsy therapies. The IAK model appears particularly interesting for studies on disease-modifying treatments, whereas the IHK model is well suited for studying the antiseizure activity of novel ASDs against difficult-to-treated focal seizures.

Does the Latent Period of Leaf Fungal Pathogens Reflect Their Trophic Type? A Meta-Analysis of Biotrophs, Hemibiotrophs, and Necrotrophs.

We performed a meta-analysis to search for a relation between the trophic type and latent period of fungal pathogens. The pathogen incubation period and the level of resistance of the hosts were also investigated. This ecological knowledge would help us to more efficiently regulate crop epidemics for different types of pathogens. We gathered latent period data from 103 studies dealing with 51 fungal pathogens of the three major trophic types (25 biotrophs, 15 hemibiotrophs, and 11 necrotrophs), representing 2,542 mean latent periods. We show that these three trophic types display significantly different latent periods. Necrotrophs exhibited the shortest latent periods (<100 degree-days [DD]), biotrophs had intermediate ones (between 100 and 200 DD), and hemibiotrophs had the longest latent periods (>200 DD). We argue that this relation between trophic type and latent period points to two opposing host exploitation strategies: necrotrophs mount a rapid destructive attack on the host tissue, whereas biotrophs and hemibiotrophs avoid or delay the damaging phase. We query the definition of hemibiotrophic pathogens and discuss whether the length of the latent period is determined by the physiological limits inherent to each trophic type or by the adaptation of pathogens of different trophic types to the contrasting conditions experienced in their interaction with the host.

Quantification of In Planta Zymoseptoria tritici Progression Through Different Infection Phases and Related Association with Components of Aggressiveness.

In planta growth of Zymoseptoria tritici, causal agent of Septoria tritici blotch of wheat, during the infection process has remained an understudied topic due to the long symptomless latent period before the emergence of fruiting bodies. In this study, we attempted to understand the relationship between in planta growth of Z. tritici relative to the primary components of aggressiveness, i.e., latent period and pycnidia coverage in regard to contrasting host resistance. We tested isolates collected from Ireland against the susceptible cultivar Gallant and cultivar Stigg, which has strong partial resistance. A clear isolate-host interaction effect (F = 3.018; P = 0.005, and F = 6.008; P < 0.001) for latent period and pycnidia coverage, respectively, was identified. Furthermore, during the early infection phase of latency from 5 to 11 days postinoculation (dpi), in planta growth rate of fungal biomass was significantly (F = 30.06; P < 0.001) more affected by host resistance than isolate specificity (F = 1.27; P = 0.27), indicating the importance of host resistance in the early infection phase. In planta Z. tritici growth rates in cultivar Gallant spiked between 11 and 16 dpi followed by a continuous fall onward, whereas in cultivar Stigg it was slowly progressive in nature. From correlation and regression analysis, we found that the in planta growth rate preceding the average latent period of cultivar Gallant has more influence on latency duration and pycnidia production. Likewise, correlation between component of aggressiveness and in planta growth rate of pathogen supports our understanding of aggressiveness to be driven by the pathogen's multiplication capacity within host tissue.

Dynamic analysis of a mathematical model with health care capacity for COVID-19 pandemic.

The fact that no there exists yet an absolute treatment or vaccine for COVID-19, which was declared as a pandemic by the World Health Organization (WHO) in 2020, makes very important spread out over time of the epidemic in order to burden less on hospitals and prevent collapsing of the health care system. This case is a consequence of limited resources and is valid for all countries in the world facing with this serious threat. Slowing the speed of spread will probably make that the outbreak last longer, but it will cause lower total death count. In this study, a new SEIR epidemic model formed by taking into account the impact of health care capacity has been examined and local and global stability of the model has been analyzed. In addition, the model has been also supported by some numerical simulations.

Molecular Profile of Phage Infection: A Novel Approach for the Characterization of Erwinia Phages through qPCR.

Due to the emergence of antibiotic resistance, phage-mediated biocontrol has become an attractive alternative for pathogen management in agriculture. While the infection characteristics of many phages can be adequately described using plaque assays and optical density, the results from phages of the apple pathogen Erwinia amylovora have low reproducibility with these techniques. Using quantitative real-time PCR (qPCR), the stage of the lytic cycle was determined through a combination of chloroform-based sampling, centrifugation, and DNase treatment. Monitoring the transition of phage genomes through the lytic cycle generates a molecular profile from which phage infection characteristics such as adsorption rate and burst size can be determined. To our knowledge, this is the first report of qPCR being used to determine these infection parameters. The characteristics of four different genera of Erwinia phages were determined. The phage ΦEa461A1 was able to adsorb at a rate up to 6.6 times faster than ΦEa35-70 and ΦEa9-2. The low enrichment titer of ΦEa92 was shown to be due to the absence of lysis. The ΦEa461A1 and ΦEa214 phages had the highest productivity, with burst sizes of 57 virions in 38 min and 185 virions in 98 min, respectively, suggesting these genera would make stronger candidates for the phage-mediated biocontrol of E. amylovora.

A new SAIR model on complex networks for analysing the 2019 novel coronavirus (COVID-19).

Nowadays, the novel coronavirus (COVID-19) is spreading around the world and has attracted extremely wide public attention. From the beginning of the outbreak to now, there have been many mathematical models proposed to describe the spread of the pandemic, and most of them are established with the assumption that people contact with each other in a homogeneous pattern. However, owing to the difference of individuals in reality, social contact is usually heterogeneous, and the models on homogeneous networks cannot accurately describe the outbreak. Thus, we propose a susceptible-asymptomatic-infected-removed (SAIR) model on social networks to describe the spread of COVID-19 and analyse the outbreak based on the epidemic data of Wuhan from January 24 to March 2. Then, according to the results of the simulations, we discover that the measures that can curb the spread of COVID-19 include increasing the recovery rate and the removed rate, cutting off connections between symptomatically infected individuals and their neighbours, and cutting off connections between hub nodes and their neighbours. The feasible measures proposed in the paper are in fair agreement with the measures that the government took to suppress the outbreak. Furthermore, effective measures should be carried out immediately, otherwise the pandemic would spread more rapidly and last longer. In addition, we use the epidemic data of Wuhan from January 24 to March 2 to analyse the outbreak in the city and explain why the number of the infected rose in the early stage of the outbreak though a total lockdown was implemented. Moreover, besides the above measures, a feasible way to curb the spread of COVID-19 is to reduce the density of social networks, such as restricting mobility and decreasing in-person social contacts. This work provides a series of effective measures, which can facilitate the selection of appropriate approaches for controlling the spread of the COVID-19 pandemic to mitigate its adverse impact on people's livelihood, societies and economies.

Threshold dynamics of a time-delayed epidemic model for continuous imperfect-vaccine with a generalized nonmonotone incidence rate.

In this paper, we study the dynamics of an infectious disease in the presence of a continuous-imperfect vaccine and latent period. We consider a general incidence rate function with a non-monotonicity property to interpret the psychological effect in the susceptible population. After we propose the model, we provide the well-posedness property and calculate the effective reproduction number R E . Then, we obtain the threshold dynamics of the system with respect to R E by studying the global stability of the disease-free equilibrium when R E < 1 and the system persistence when R E > 1 . For the endemic equilibrium, we use the semi-discretization method to analyze its linear stability. Then, we discuss the critical vaccination coverage rate that is required to eliminate the disease. Numerical simulations are provided to implement a case study regarding data of influenza patients, study the local and global sensitivity of R E < 1 , construct approximate stability charts for the endemic equilibrium over different parameter spaces and explore the sensitivity of the proposed model solutions.

Isolation and characterization of a moderately halophilic Marinobacter phage-host system from the Arabian Sea.

Marinobacter is an ecologically important genus of Gammaproteobacteria found in diverse marine habitats, many species of which are capable of degrading hydrocarbons. In this study, we isolated a Marinobacter phage-host system from the surface waters of the Arabian Sea using enrichment culture methods, studied their growth characteristics and investigated the effect of salinity and nitrate concentrations on phage-host interactions. The bacterial isolate had maximum identity to Marinobacter salsuginis based on 16S rRNA similarities and was termed as Marinobacter sp., strain D1S9. It could tolerate up to 14% of NaCl with maximum growth at 11% NaCl. The host grew optimally between 35 and 40 °C and at pH 8. It had a generation time of 3.7 h with a mean growth rate of 0.27 h-1. The phage infected the host forming clear, round plaques of 1-2 mm diameter. It had a narrow host range restricted to the strain Marinobacter D1S9. The latent period and burst size of the phage were estimated to be 30 min and 106 phages per infected cell, respectively. The phage had an adsorption rate of 3.4 × 10-8 ml min-1 and retained 40.4% of its adsorption efficiency at 16% NaCl with a maximum at 4% NaCl (76.1%). Inorganic nitrate was found to have a direct role in controlling host growth and phage burst size.

[Analysis of transmission characteristics of COVID-19 in Shaanxi Province].

A total of 245 cases of COVID-19 in Shaanxi Province reported in the China information system for disease control and prevention as of February 24, 2020 were selected as the research objects, the cases are divided into imported cases (116 cases, 47.3%) and local cases (129 cases, 52.7%), their basic characteristics, time distribution, transmission mode, intergenerational interval and latent period transmission are analyzed. The age of local cases [(51.74±15.67) years old], female patients (69 cases, 53.5%), housework and retired staff (40 cases, 31.0%), and patients isolated at the time of onset (50 cases, 38.8%) were higher than imported cases, respectively[(40.66±15.41) years old, (45 cases, 38.8%), (21 cases, 18.1%), (17 cases, 14.6%)] (P values were < 0.05); The infection rate was 0.8% (31/3 666) in close contacts with local cases, which was lower than imported cases 2.0% (69/3 435) (P<0.001); The main source of infection in local cases was relatives (70 cases, 54.3%), and the main way of infection was living together and party (90 cases, 69.8%); the proportion of latent period transmission in our province was 15.5% (20 cases), and the interval between the second-generation case and the source of infection was about 4 days, and the interval between generations was about 6 days. In summary, the main way of infection of local cases in Shaanxi Province was living together and party, there were a certain proportion of latent period transmission cases at present, it's suggested that the investigation of close contacts should be started 4 days or earlier before the onset of the case.

A periodic SEIRS epidemic model with a time-dependent latent period.

Many infectious diseases have seasonal trends and exhibit variable periods of peak seasonality. Understanding the population dynamics due to seasonal changes becomes very important for predicting and controlling disease transmission risks. In order to investigate the impact of time-dependent delays on disease control, we propose an SEIRS epidemic model with a periodic latent period. We introduce the basic reproduction ratio [Formula: see text] for this model and establish a threshold type result on its global dynamics in terms of [Formula: see text]. More precisely, we show that the disease-free periodic solution is globally attractive if [Formula: see text]; while the system admits a positive periodic solution and the disease is uniformly persistent if [Formula: see text]. Numerical simulations are also carried out to illustrate the analytic results. In addition, we find that the use of the temporal average of the periodic delay may underestimate or overestimate the real value of [Formula: see text].

Infradian Rhythms of Resistance to a Dissociative Anesthetic in Wistar Male Rats under Normal Conditions and After Surgical Removal of the Adrenal Glands and Testes.

Daily dynamics of changes in the latency of a response to dissociative anesthetic tiletamine (time from injection to ataxia) was studied in mature Wistar rats. Both intramuscular and intravenous administration of the anesthetic was associated with 4-day oscillations of the latent period synchronous with the dynamics of changes in the concentration of glucocorticoid hormones. The period and phases of the infradian rhythm of resistance to the anesthetic remained unchanged after removal of both adrenal glands and testes and administration of corticosterone synthesis blocker trilostane diminishing the 4-day cycle of changes in corticosterone level. Therefore, hormones of the adrenal glands and testes do not play the key role in the mechanisms of formation of the 4-day infradian rhythm.