Impact of extracellular current flow on action potential propagation in myelinated axons

Myelinated axons conduct action potentials, or spikes, in a saltatory manner. Inward current caused by a spike occurring at one node of Ranvier spreads axially to the next node, which regenerates the spike when depolarized enough for voltage-gated sodium channels to activate, and so on. The rate at which this process progresses dictates the velocity at which the spike is conducted, and depends on several factors including axial resistivity and axon diameter that directly affect axial current. Here we show through computational simulations in modified double-cable axon models that conduction velocity also depends on extracellular factors whose effects can be explained by their indirect influence on axial current. Specifically, we show that a conventional double-cable model, with its outside layer connected to ground, transmits less axial current than a model whose outside layer is less absorptive. A more resistive barrier exists when an axon is packed tightly between other myelinated fibers, for example. We show that realistically resistive boundary conditions can significantly increase the velocity and energy efficiency of spike propagation, while also protecting against propagation failure. Certain factors like myelin thickness may be less important than typically thought if extracellular conditions are more resistive than normally considered. We also show how realistically resistive boundary conditions affect ephaptic interactions. Overall, these results highlight the unappreciated importance of extracellular conditions for axon function.Significance Statement Axons transmit spikes over long distances. Transmission is sped up and made more efficient by myelination, which allows spikes to jump between nodes of Ranvier without activating the intervening (internodal) membrane. Conduction velocity depends on the current transmitted axially from one node to the next. Axial current is known to depend on a variety of features intrinsic to myelinated fibers (e.g. axon diameter, myelin thickness) but we show here, through detailed biophysical simulations, how extracellular conditions (e.g. axon packing density) are also important. The effects ultimately boil down to the variety of paths current can follow, and the amount of current taking alternative paths rather than flowing directly from one node to the next.

Association between adherence to a dietary approach to stop hypertension and the Mediterranean diets and risk of colorectal cancer: A matched case-control study

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers and is currently the third leading cause of cancer-related deaths worldwide. This study aimed to evaluate whether the dietary approach to stop hypertension (DASH) and Mediterranean (MED) diets are associated with CRC in Iranian adults.

METHODS

This hospital-based case-control study was conducted on 71 cases and 142 controls (40-75 years old) in three general hospitals in Tehran, Iran. The dietary intakes of individuals were collected through face-to-face interviews using a semi-quantitative food frequency questionnaire (FFQ) that included 125 food items. The DASH and MED diet scores were calculated according to food items based on guidelines. Two logistic regression models were applied to evaluate the association between DASH and MED score adherence.

RESULTS

After adjusting for confounding factors, a negative association between DASH diet adherence and CRC risk was observed in the second and last tertile compared to the first tertile (T) (T2: odds ratio (OR) = 0.33; 95% confidence interval (CI): 0.14-0.77 - T3: OR = 0.09; 95% CI: 0.03-0.27). There was no significant association between the MED diet and the risk of CRC.

CONCLUSIONS

In conclusion, the current study's findings presented that adherence to a DASH diet could reduce the odds of CRC.

Absence of paresthesia during high-rate spinal cord stimulation reveals importance of synchrony for sensations evoked by electrical stimulation

Electrically activating mechanoreceptive afferents inhibits pain. However, paresthesia evoked by spinal cord stimulation (SCS) at 40-60 Hz becomes uncomfortable at high pulse amplitudes, limiting SCS "dosage." Kilohertz-frequency SCS produces analgesia without paresthesia and is thought, therefore, not to activate afferent axons. We show that paresthesia is absent not because axons do not spike but because they spike asynchronously. In a pain patient, selectively increasing SCS frequency abolished paresthesia and epidurally recorded evoked compound action potentials (ECAPs). Dependence of ECAP amplitude on SCS frequency was reproduced in pigs, rats, and computer simulations and is explained by overdrive desynchronization: spikes desychronize when axons are stimulated faster than their refractory period. Unlike synchronous spikes, asynchronous spikes fail to produce paresthesia because their transmission to somatosensory cortex is blocked by feedforward inhibition. Our results demonstrate how stimulation frequency impacts synchrony based on axon properties and how synchrony impacts sensation based on circuit properties.

The Effect of Quercetin on Stress Oxidative Markers: A Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials

Background: Quercetin is one of the main flavonoids, overall distributed in plants. The antioxidant capacity of quercetin is several times vitamin E and glutathione. This systematic review and meta‐analysis of randomized controlled trials were performed to determine the effect of quercetin on oxidative stress (OS) markers. Methods: A literature search was conducted in PubMed, ISI Web of Science, Scopus, and Google Scholar to February of 2021. Meta-analysis was conducted on 8 eligible RCTs containing a total of 668 participants. The weighted mean difference (WMD) with 95% confidence intervals (CIs) was calculated for a pool effect size of Malondialdehyde (MDA), Total Antioxidant Capacity (TAC), and Ferric Reducing Ability of Plasma (FRAP). Subgroup analyses were performed based on intervention duration and dosage. The heterogeneity of studies was examined by Cochran's Q test and I-squared (I2) statistic. Results: Effect sizes from 668 participants based on the random effect model showed that quercetin supplementation had no significant effect on TAC and MDA compared to the control group. The analysis illustrated that quercetin supplementation significantly increased FRAP in adults (WMD = -0.159 mmol/l, 95% confidence interval (CI):-0.178, -0.141, P ≤ 0.001). Conclusions: The finding of the current study showed that quercetin supplementation had no significant effect on TAC levels, although it significantly increased FRAP levels in adults. Also, MDA level did not markedly change. It has needed to conduct clinical trials with more quality and bigger sample sizes to verify the positive impact of quercetin on stress oxidative marker.

The Effect of Nigella Sativa on Cardio-Metabolic Parameters: A Protocol for A Systematic Review and Meta-Analysis

Background: Among non-communicable diseases, cardiovascular diseases (CVDs) account for 44% of all deaths. Among natural alternatives, Nigella sativa (NS) exert beneficial effects on cardio-metabolic factors. This is the first systematic review and meta-analysis protocol aimed to identify all the findings relevant to the effects of NS on cardio-metabolic factors among adults. Methods: This study was prepared according to PRISMA-P checklist based on Cochrane Handbook for Systematic Reviews of Interventions. An initial literature search was conducted in various databases using MeSH terms and related synonyms. Trials examining the effects of NS versus control group were included. Main outcomes consisted of blood pressure, lipid and glycemic factors, and atherogenic indices. Seven reviewers independently evaluated titles and abstracts, reviewed full texts, extracted information, and assessed the risk of bias. Methodological quality of each randomized controlled trial was assessed using the Cochrane Handbook and the GRADE system, while Newcastle-Ottawa Quality Assessment Scale was used for non-randomized studies. Continuous data of homogeneous studies were meta-analyzed via STATA. Mean differences were calculated as the effect size with 95% CIs. Heterogeneity assessment, sensitivity analysis, and publication bias were performed. Conclusion: The quality of both randomized and non-randomized studies was assessed. The evidence from this study can provide information for future clinical trials.

The Relationship between Plant-Based Diet Index and Semen Parameters of Men with Infertility: A Cross-Sectional Study

BACKGROUND

Infertility is a major clinical problem that affects people psychologically and medically. For the past 40 years, studies have linked nearly 50% of childlessness to male infertility. It is worth noting that unlike other factors contributing to infertility, diet is a tunable factor and can be applied in counseling infertile men. The goal of this study was to determine the relationship between plant diet index (PDI) and semen parameters in Iranian infertile men.

MATERIALS AND METHODS

In this cross-sectional study, dietary intake was determined by a valid 168-item questionnaire (FFQ). In this study, four dependent semen parameters, including total sperm motility (TSM), sperm concentration (SC), normal sperm morphology (NSM), and semen volume (SV) were measured.

RESULTS

Results of this study stated that greater adherence to the healthful plant-based diet index (hPDI), can significantly increase sperm density and motility in men, as well as greater adherence to the PDI dietary pattern is related to a lower risk of sperm volume deficiency, and ultimately more adherence to the unhealthful plant-based diet index (uPDI), can reduce the risk of sperm motility.

CONCLUSION

In this study, for the first time, the relationship between PDI, hPDI, uPDI and male infertility was evaluated. Altogether, this study demonstrated that nutrition has an impact on semen quality and fertility of men.

Frequency and co-colonization of vancomycin-resistant Enterococci and Candida in ICU-hospitalized children

In the time span between January 2018 and September 2020, 205 patients were enrolled in a prospective cohort study at Mofid Children's Hospital. Demographic information and clinical data on all the participating children were collected and rectal swabs were performed for the sampling method. All samples were analysed so as to identify the presence of Enterococcus and Candida colonization by the use of conventional biochemical tests. Resistance to vancomycin in Enterococcus isolates was phenotypically identified using an E-test kit and MIC value, interpreted according to the CLSI criteria. The presence of vanA and vanB genes, which encode the resistance to vancomycin, was screened by PCR assay. Candida species were detected in 21.5% of rectal swab samples. Candida glabrata (56.8%) and Candida albicans (43.2%) were the only Candida species detected. Enterococcus species were detected in 29.3% of rectal swab samples. Out of 60 Enterococcus isolates, 33 (55%) were resistant to vancomycin. Moreover, vanA was detected in 84.8% and vanB was detected in 3% of the 33 vancomycin-resistant Enterococcus isolates. Enterococcus and Candida species were frequently detected in the <1 year and 1–3 years age groups, respectively. Central venous access catheter and brain tumour were the main reasons for hospital admissions, 32.2% and 20.1% of total admissions, respectively. Furthermore, it must be noted that the most frequent underlying medical conditions in participating patients were esophageal atresia and hydrocephalus. The results of the present study demonstrated the necessity of determining the susceptibility of Enterococcus isolates to vancomycin before prescribing antibiotics.

The effect of Nigella sativa on appetite, anthropometric and body composition indices among overweight and obese women: A crossover, double-blind, placebo-controlled, randomized clinical trial

OBJECTIVES

Obesity is a global concern which is associated with several complications and disease.

DESIGN

Present study is the first crossover, double-blind, placebo-controlled, randomized clinical trial aimed to evaluate the effect of Nigella Sativa (N. sativa) intervention on anthropometric and body composition parameters as well as dietary intake and appetite in a crossover design.

METHOD

Forty-five healthy women with obesity or overweight were randomized into two groups of intervention and placebo, and the study conducted in two 8-week periods of intervention separated by a 4-week washout period. Anthropometric and body composition indices and dietary intake were measured. Also, appetite sensation was evaluated via a standard visual analog scale (VAS) questionnaire. Pkcross procedure was performed for statistical analysis using STATA. Cohen's d effect size was estimated for all outcomes to determine the magnitude of the effects.

RESULTS

Supplementation with 2000 mg of N. sativa oil found to have a considerable increment in the measures of body mass index (P < 0.001, Cohen's d = 0.5), body weight (P < 0.001, Cohen's d = 0.6) and waist circumference (P = 0.020, Cohen's d = 0.4) with a medium effect size measure, and a significant decrease in body fat mass (P = 0.019, Cohen's d = 0.2), body fat percent (P < 0.001, Cohen's d = 0.2) and visceral fat area (P = 0.011, Cohen's d = 0.2) with a small effect size measure.

CONCLUSION

The overall improvements in anthropometric and body composition parameters and a significant decrease in appetite represents the beneficial effects of N. sativa supplements in the treatment of obesity. More studies with different dosages, a larger number of participants, and longer intervention duration are recommended to illustrate the exact effects of N. sativa as a complementary therapy for obesity.

Effects of oral Nigella sativa oil on the expression levels and serum concentrations of adiponectin, PPAR-γ, and TNF-α in overweight and obese women: a study protocol for a crossover-designed, double-blind, placebo-controlled randomized clinical trial

BACKGROUND

Obesity is a major public health problem in recent decades. The accumulation of excessive fat promotes inflammatory status. Meanwhile, herbal products are marketed for their weight-loss properties, such as Nigella sativa (N. Sativa) which has been used for centuries to treat rheumatoid arthritis, diabetes, and asthma; recently, the anti-obesity characteristics of N. sativa have also been indicated. However, the exact mechanisms and cellular-related pathways are still unclear. Thus, we will aim to assess the effects of oral N. sativa on the gene expression of inflammatory and adipogenesis-related factors, including TNF-α, PPAR-γ, and adiponectin as well as assessing their serum concentrations among obese and overweight individuals.

METHODS

Obese and overweight women aged 25-55 years with a body mass index (BMI) of 25-35 kg/m² will be recruited from the Obesity Clinic in Shahid Sadoughi University of Medical Sciences and will be assessed for eligibility against inclusion criteria. They will be randomly assigned into two groups to receive either two capsules of N. sativa or two capsules of placebo per day for eight weeks (each capsule contains 1000 mg of N. sativa or placebo). There will be a four-week wash-out period and then participants will receive the reverse supplements for another eight weeks. Biochemical assessments and gene expressions (using real-time polymerase chain reaction) will be conducted at the beginning and at the end of every intervention period.

DISCUSSION

The present study will investigate the probable cellular pathways for the anti-obesity effects of N. sativa in overweight/obese women.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials, IRCT20180528039884N1 . Registered on 2nd of July, 2018.