Exact Distribution of the Quantal Content in Synaptic Transmission.

During electrochemical signal transmission through synapses, triggered by an action potential (AP), a stochastic number of synaptic vesicles (SVs), called the "quantal content," release neurotransmitters in the synaptic cleft. It is widely accepted that the quantal content probability distribution is a binomial based on the number of ready-release SVs in the presynaptic terminal. But the latter number itself fluctuates due to its stochastic replenishment, hence the actual distribution of quantal content is unknown. We show that exact distribution of quantal content can be derived for general stochastic AP inputs in the steady state. For fixed interval AP train, we prove that the distribution is a binomial, and corroborate our predictions by comparison with electrophysiological recordings from MNTB-LSO synapses of juvenile mice. For a Poisson train, we show that the distribution is nonbinomial. Moreover, we find exact moments of the quantal content in the Poisson and other general cases, which may be used to obtain the model parameters from experiments.

First passage in the presence of stochastic resetting and a potential barrier.

Diffusion and first passage in the presence of stochastic resetting and potential bias have been of recent interest. We study a few models, systematically progressing in their complexity, to understand the usefulness of resetting. In the parameter space of the models, there are multiple continuous and discontinuous transitions where the advantage of resetting vanishes. We show these results analytically exactly for a tent potential, and numerically accurately for a quartic potential relevant to a magnetic system at low temperatures. We find that the spatial asymmetry of the potential across the barrier, and the number of absorbing boundaries, play a crucial role in determining the type of transition.

Exact Distribution of Threshold Crossing Times for Protein Concentrations: Implication for Biological Timekeeping.

Stochastic protein accumulation up to some concentration threshold sets the timing of many cellular physiological processes. Here we obtain the exact distribution of first threshold crossing times of protein concentration, in either Laplace or time domain, and its associated cumulants: mean, variance, and skewness. The distribution is asymmetric, and its skewness nonmonotonically varies with the threshold. We study lysis times of E. coli cells for holin gene mutants of bacteriophage-λ and find a good match with theory. Mutants requiring higher holin thresholds show more skewed lysis time distributions as predicted. The theory also predicts a linear relationship between infection delay time and host doubling time for lytic viruses, that has recently been experimentally observed.

Surgical Procedure among Patients with Foreign Body Obstruction in Food Passage in a Tertiary Care Hospital: A Descriptive Cross-sectional Study.

INTRODUCTION: Foreign body is any object in a region it is not meant to be, where it can cause harm if immediate medical attention is not sought. Its removal by surgical procedure is one of the commonest surgeries done. The objective is to find out prevalence of the patients who underwent operation for foreign bodies obstruction in food passage in the Department of Otorhinolaryngology-Head and Neck Surgery in a tertiary care centre. METHODS: A descriptive cross-sectional study conducted among patients operated in the Department of Otorhinolaryngology and Head and Neck Surgery of a tertiary care center from August 2014 to May 2017. Ethical approval was received from the Institutional Review Committee of the Institute. Convenience sampling method was used. Statistical Package for the Social Sciences was used for analysis. Point estimate at 95% Confidence Interval was calculated along with frequency and proportion for binary data. RESULTS: Out of total 700 patients having operation in department, 115 (16.42%) (95% Confidence Interval = 13.67-19.16) had operation for foreign body obstruction in the food passage. Among 115 patients, 62 (53.90%) were males and 53 (46.10%) were females. Most common foreign bodies ingested in children was coin 17 (14.78%) and bone chips 40 (34.78%) in adults. Cricopharynx 90 (78.26%) is the commonest site for foreign body lodgement. CONCLUSIONS: Prevalence of the patients who underwent operation for foreign bodies obstruction in food passage in a tertiary care hospital is high. Their removal by rigid oesophagoscopy is one of the commonest surgical procedures done in tertiary care center.

Protein hourglass: Exact first passage time distributions for protein thresholds.

Protein thresholds have been shown to act as an ancient timekeeping device, such as in the time to lysis of Escherichia coli infected with bacteriophage λ. The time taken for protein levels to reach a particular threshold for the first time is defined as the first passage time (FPT) of the protein synthesis system, which is a stochastic quantity. The first few moments of the distribution of first passage times were known earlier, but an analytical expression for the full distribution was not available. In this work, we derive an analytical expression for the first passage times for a long-lived protein. This expression allows us to calculate the full distribution not only for cases of no self-regulation, but also for both positive and negative self-regulation of the threshold protein. We show that the shape of the distribution matches previous experimental data on λ-phage lysis time distributions. We also provide analytical expressions for the FPT distribution with non-zero degradation in Laplace space. Furthermore, we study the noise in the precision of the first passage times described by coefficient of variation (CV) of the distribution as a function of the protein threshold value. We show that under conditions of positive self-regulation, the CV declines monotonically with increasing protein threshold, while under conditions of linear negative self-regulation, there is an optimal protein threshold that minimizes the noise in the first passage times.

Primary invasive laryngeal mycosis in an immunocompetent patient: a case report and clinico-epidemiological update.

BACKGROUND: Laryngeal aspergillosis is uncommon and is usually secondary to pulmonary involvement in immunocompromised patients. Primary laryngeal aspergillosis in immunocompetent individuals is extremely rare, with a few cases documented over the last five decades. CASE PRESENTATION: We report a case of primary localised laryngeal aspergillosis in a 21-year-old apparently immunocompetent student. Septate hyphae were observed on histopathology of the laryngeal lesion, which was further confirmed as Aspergillus fumigatus after extraction of fungal DNA from formalin fixed paraffin embedded tissue (FFPET) and sequencing. The patient responded well to oral itraconazole therapy over a month. CONCLUSIONS: Since last few decades, cases of primary laryngeal aspergillosis in immunocompetent individuals are on the rise, globally. This is the first case of invasive laryngeal aspergillosis reported in Nepal. The extraction of DNA from tissue and sequencing helps to identify the etiological agent, when culture fails to isolate the fungus.