Thermal annealing gradient tailoring on ammonium nitrate-capped CdS nanospheres synthesized via green precipitation.

This study explores the impact of thermal annealing gradients on the physical properties and structural evolution of cadmium sulphide (CdS) nanospheres capped with ammonium nitrate as a modifier, which were fabricated through precipitation and subsequent annealing within 160-480 °C temperature range. The properties were characterized using X-ray diffraction (XRD), ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques The XRD results show that the present CdS exhibits superior crystallinity compared to pure CdS without capping, transitions from a cubic to a hexagonal phase structure, and increases in crystallite size and crystallinity with increasing temperature. The FTIR spectra postulate that a vibrational band presence evidences ammonium nitrate capping on CdS, with another distinct band that represents CdS in the lower wavenumber region, both intensifying at elevated temperatures. The UV-Vis analysis reveals that CdS exhibits strong ultraviolet (UV) absorption suitable for effective photoreaction under UV light and has a broader band gap compared to bulk CdS. SEM images show an extensive distribution of homogeneous nanospheres over the surface, with increased growth in size when capped with ammonium nitrate and at higher temperatures. As validated by TGA and DSC results, CdS with a smaller crystallite size improves thermal stability and energy transfer, as evidenced by reduced weight loss and a lower endothermic temperature, respectively. Varying the annealing temperature with ammonium nitrate capping can improve the structural and physical properties of CdS, which are beneficial for varied applications such as optoelectronics, energy storage, and photocatalysts.

Experimental and computational investigation of the effect of Hsc70 structural variants on inhibiting amylin aggregation.

The misfolding and aggregation of human islet amyloid polypeptide (hIAPP), also known as amylin, have been implicated in the pathogenesis of type 2 diabetes (T2D). Heat shock proteins, specifically, heat shock cognate 70 (Hsc70), are molecular chaperones that protect against hIAPP misfolding and inhibits its aggregation. Nevertheless, there is an incomplete understanding of the mechanistic interactions between Hsc70 domains and hIAPP, thus limiting their potential therapeutic role in diabetes. This study investigates the inhibitory capacities of different Hsc70 variants, aiming to identify the structural determinants that strike a balance between efficacy and cytotoxicity. Our experimental findings demonstrate that the ATPase activity of Hsc70 is not a pivotal factor for inhibiting hIAPP misfolding. We underscore the significance of the C-terminal substrate-binding domain of Hsc70 in inhibiting hIAPP aggregation, emphasizing that the removal of the lid subdomain diminishes the inhibitory effect of Hsc70. Additionally, we employed atomistic discrete molecular dynamics simulations to gain deeper insights into the interaction between Hsc70 variants and hIAPP. Integrating both experimental and computational findings, we propose a mechanism by which Hsc70's interaction with hIAPP monomers disrupts protein-protein connections, primarily by shielding the ß-sheet edges of the Hsc70-ß-sandwich. The distinctive conformational dynamics of the alpha helices of Hsc70 potentially enhance hIAPP binding by obstructing the exposed edges of the ß-sandwich, particularly at the ß5-ß8 region along the alpha helix interface. This, in turn, inhibits fibril growth, and similar results were observed following hIAPP dimerization. Overall, this study elucidates the structural intricacies of Hsc70 crucial for impeding hIAPP aggregation, improving our understanding of the potential anti-aggregative properties of molecular chaperones in diabetes treatment.

The Epidemiology of Prehospital Ambulance Crashes: A National Experience Across Saudi Red Crescent Authority.

Introduction Road traffic injuries (RTIs) have a significant impact on the healthcare system as well as the global economy. RTIs involving ambulance crashes not only cause delays in patient transfers but also endanger ambulance occupants and other road users. Due to the rising numbers of RTIs in the Kingdom of Saudi Arabia (KSA), the country's primary provider of prehospital services the Saudi Red Crescent Authority (SRCA) has established a new Trauma Epidemiology Center (TEC) following the KSA 2030 vision. Objective This current study was conducted to determine the causes and management-related aspects of RTIs involving ambulance crashes in KSA. We aim to highlight the current status and guide further efforts to fill gaps in knowledge and on-ground changes to prevent ambulance crashes, enhance patient care, and reduce morbidity and mortality. Method This is a descriptive, retrospective cross-sectional observational study of ambulance crashes in Saudi Arabia between January 2020 and July 2022. The data was extracted from the SRCA electronic database platform. Results One hundred and sixty accidents were recorded between 2020 and 2022 with the highest proportion of accidents recorded in Riyadh 44.29%; followed by the Eastern Province and Makkah, 15% and 12%, respectively. Ninety percent of ambulance crashes were due to direct collisions and caused by other parties in 58% of cases. It is worth mentioning that ambulance drivers fastened their seat belts in 99% of crashes. Conclusion This study highlights the epidemiology and distribution of prehospital ambulance crashes in the KSA. Most crashes occurred in urban areas with a reasonable contribution of the public in such crashes. Understanding contributing factors related to the vector, driver behaviors, and the surrounding environment is crucial to guide national preventive measures and help decision-makers to implement proper corrective actions.

Deep Brain Stimulation beyond the Clinic: Navigating the Future of Parkinson's and Alzheimer's Disease Therapy.

Deep brain stimulation (DBS) is a surgical procedure that uses electrical neuromodulation to target specific regions of the brain, showing potential in the treatment of neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer's disease (AD). Despite similarities in disease pathology, DBS is currently only approved for use in PD patients, with limited literature on its effectiveness in AD. While DBS has shown promise in ameliorating brain circuits in PD, further research is needed to determine the optimal parameters for DBS and address any potential side effects. This review emphasizes the need for foundational and clinical research on DBS in different brain regions to treat AD and recommends the development of a classification system for adverse effects. Furthermore, this review suggests the use of either a low-frequency system (LFS) or high-frequency system (HFS) depending on the specific symptoms of the patient for both PD and AD.

pH-induced wurtzite-zinc blende heterogeneous phase formation, optical properties tuning and thermal stability improvement of green synthesized CdS nanoparticles.

This is the first paper to report on the pH response to heterogeneous wurtzite/zinc blende phase transformation, optical tunability and thermal stability advancement of the CdS nanoparticles synthesized via co-precipitation, followed by subsequent thermal treatment at a desired annealing temperature of 320 °C, while the solution pH was varied during CdS synthesis by adjusting the ammonium salt concentration. The surface morphology, crystalline structure, functional groups, optical properties and thermal stability of CdS were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier-transform infrared spectroscopy (FTIR), UV-visible spectrophotometer, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. The results show that a dominant sharp band occurs in the FTIR spectra, which authenticates the presence of Cd-S bonds. XRD results reveal that as the pH declines, CdS in the initial cubic phase has gradually transformed into a heterogeneous phase with the coexistence of cubic and hexagonal structures. As observed from the SEM images, the CdS nanoparticles display a homogeneous, smooth and spherically shaped morphology. Optical absorption characterized by UV-visible spectrophotometry denotes that the band gap decreases proportionally with pH, which could be attributed to the formation of larger grain sizes from the aggregation of many small nanocrystallites. TGA and DSC analyses demonstrate an improvement in the thermal stability of CdS with increasing pH values. Consequently, the present findings dictate that pH tunability could be a valuable approach to procuring the desired properties for the respective applications of CdS in diverse fields.

Does Gender, Academic Status, Years of Teaching Experience, and Discipline Affiliation Affect Strategies Used to Promote Creativity in Medical Education at King Abdulaziz University?

Background This study aimed to explore the effect of gender, academic status, years of teaching experience, and discipline affiliation on strategies used to promote creativity in medical education. Methodology This study was conducted in the Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia. Faculty teaching in both the basic sciences and clinical disciplines was included. A 15-item electronic survey was created. The frequencies were obtained for the demographic and academic characteristics of the participants. For each question (Q5-Q15), the mean and SD of participant responses were obtained. The chi-square test was used to compare all categorical variables. This included the comparison of the participants' demographic characteristics with their academic characteristics. The chi-square test was also used for the comparison of participant characteristics among the categorical questions (Q5-Q15). Results A statistically significant association was determined between academic status, years of teaching experience, faculty's perception of the curriculum, tasks used in teaching, and the suitability of the used assessment strategies in promoting creativity. Teaching in clinical disciplines was statistically associated with using real-life problems, challenging students, and deliberately creating chaos or disorder in the classroom. Conclusions Academic status, years of teaching experience, and discipline affiliation are more likely to affect how faculty members promote creativity in medical education.

Emergency Medical Service Response Time for Road Traffic Accidents in the Kingdom of Saudi Arabia: Analysis of National Data (2016-2020).

Despite preventive measures and initiatives, road traffic accidents are on the rise in the Kingdom of Saudi Arabia. This study aimed to investigate the emergency medical service unit's response to RTA by socio-demographic and accident-related variables in the Kingdom of Saudi Arabia. This retrospective survey included Saudi Red Crescent Authority data on road traffic accidents between 2016 and 2020. As part of the study, information on sociodemographic characteristics (e.g., age, sex, and nationality), accident-related data (type and place of the accident), and response time to road traffic accidents were extracted. Our study included 95,372 cases of road traffic accidents recorded by the Saudi Red Crescent Authority in the Kingdom of Saudi Arabia between 2016 and 2020. Descriptive analyses were performed to explore the emergency medical service unit's response time to road traffic accidents, and linear regression analyses were performed to investigate the predictors of response time. Most of the road traffic accident cases were among males (59.1%), and the age group of 25-34 years accounted for about a quarter (24.3%), while the mean age of the road traffic accident cases was 30.13 (±12.86) years. Among the regions, the capital city of Riyadh experienced the highest proportion of road traffic accidents (25.3%). In most road traffic accidents, the mission acceptance time was excellent (0-60 s; 93.7%), movement duration was excellent (<120 s; 91.1%), reaching site duration was excellent (<12 min; 57.9%), treatment start time was excellent (<120 s; 76.4%), duration at the scene was poor (>15 min; 40.8%), reaching hospital duration was good (30-60 min; 52.7%), and in-hospital duration was poor (>15 min; 44.1%). Regions, places and types of accidents, age, gender, and nationality of victims were significantly associated with different parameters of response time. Excellent response time was observed in most of the parameters except the duration at the scene, reaching hospital duration, and in-hospital duration. Apart from the initiatives to prevent road traffic accidents, policymakers should focus on strategies to improve accident response time to save lives.

Omental infarction mimicking acute appendicitis with negative radiological findings.

A male in his 30s presented to the emergency department with a 1-day history of supra-umbilical pain migrating to the right iliac fossa. On examination, his abdomen was soft but tender with localised guarding in the right iliac fossa and a positive Rovsing's sign. The patient was admitted under a presumptive diagnosis of acute appendicitis. A CT scan and ultrasound scan of the abdomen and pelvis showed no acute intra-abdominal pathology. He stayed in hospital for 2 days for observation without improvement of symptoms. A diagnostic laparoscopy was therefore performed that revealed an infarcted omentum adherent to the abdominal wall and ascending colon causing congestion of the appendix. The infarcted omentum was resected, and the appendix was removed. The CT images were reviewed by multiple consultant radiologists, but no positive findings were appreciated. This case report demonstrates the potential difficulty in diagnosing omental infarction clinically and radiologically.

A suggested scientific research environment measure SREM in medical faculties.

Background: Creating a supportive environment for scientific research is vital to improve the quality of research and its impact on development of society. This study outlines the development of a new scale that can measure the scientific research environment of postgraduate medical students. This tool aimed to allow medical institutions to measure their scientific research environment from the researchers' point of view. This may ensure an appropriate scientific research environment for researchers by identifying and overcoming obstacles. Methods: Based on literature, an initial list with 58 items was formulated. After discussing with postgraduate students and academic staff members from Damascus University and the Syrian Virtual University, A 38-item scale remained from the initial list of 58 items. To test the scale, postgraduate medical students (n = 30) were asked to fill the scale and answer 38 questions-with a 5-point Likert scale-twice in two separate occasions. The Pearson's correlation coefficient was performed to study the internal correlation. The internal consistency test was performed with Cronbach's Alpha, and the Test-Retest Reliability was conducted to study the reliability of the scale. Moreover, factor analysis was used to determine the sampling adequacy. Results: Thirty postgraduate medical students at Damascus University completed the 38-item scale. Scale scores in the sample displayed good reliability in relation to published results. Findings, showed an internal correlation among its sub-scales. The results showed an acceptable reliability values such as internal consistency (α = 0.863) and test-retest reliability (ICC = 0.093). KMO had a value bigger than 0.7 (KMO = 0.849) which indicate sampling adequacy, also, Bartlett's test of the sphericity was (1142.76, Df = 91, P-value = 0.000) which prove meaningful of the factor analysis. The results of varimax rotation found that five main factors were retained. Conclusions: The Scientific Research Environment Measure (SREM), can be suggested as an effective evaluation instrument which can be applied easily to assess the scientific research environment of postgraduate medical students. This would help the decision makers to support teaching, learning, and research environment through implementing new strategies that inspire postgraduate medical students and increase their engagement.

Rhus coriaria extracts inhibit quorum sensing-related virulence and biofilm production in drug-resistant Pseudomonas aeruginosa recovered from burn wounds.

Objectives: Numerous studies have confirmed sumac's ability to inhibit pathogens and even eradicate chronic drug-resistant infections. Current research was conducted to demonstrate the action of various sumac extracts at sub-inhibitory concentrations in modulating pathogen-related characteristics instead of killing them. Materials and Methods: The influence of sumac extracts on the quorum sensing dependent virulence of multidrug-resistant isolates of Pseudomonas aeruginosa recovered from burn wounds was considered by detecting the effect on biofilm development, various virulence factors, and expression of bacterial exotoxin A and quorum sensing related genes. Results: Experiments to characterize and measure sumac extract's impact on the P. aeruginosa growth, biofilm, exoproteases, pyocyanin, motility, and the quorum sensing networks revealed that all studied characteristics were reduced by concentrations below inhibition without affecting bacterial growth. Furthermore, the expression of exotoxin A, rhl, and las glucons was declined or even inhibited by lower levels of sumac fruit fractions. Conclusion: The findings revealed that sumac fights infections either by its inhibitory effect on the bacterial cells or by reducing bacterial signaling and virulence by disruption of the bacterial signal system.

Curcumin and Derivatives in Nanoformulations with Therapeutic Potential on Colorectal Cancer.

There is growing concern in the rise of colorectal cancer (CRC) cases globally, and with this rise is the presentation of drug resistance. Like other cancers, current treatment options are either invasive or manifest severe side effects. Thus, there is a move towards implementing safer treatment options. Curcumin (CUR), extracted from Curcuma longa, has received significant attention by scientists as possible alternative to chemotherapeutic agents. It is safe and effective against CRC and nontoxic in moderate concentrations. Crucially, it specifically modulates apoptotic effects on CRC. However, the use of CUR is limited by its low solubility and poor bioavailability in aqueous media. These limitations are surmountable through novel approaches, such as nanoencapsulation of CUR, which masks the physicochemical properties of CUR, thus potentiating its anti-CRC effects. Furthermore, chemical derivatization of CUR is another approach that can be used to address the above constraints. This review spans published work in the last two decades, with key findings employing either of the two approaches, in addition to a combined approach in managing CRC. The combined approach affords the possibility of better treatment outcomes but not widely investigated nor yet clinically implemented.

A combined model for COVID-19 pandemic control: The application of Haddon's matrix and community risk reduction tools combined.

INTRODUCTION: To mitigate morbidity, mortality, and impacts of COVID-19 on health, it was essential to implement a comprehensive framework for COVID-19 control and prevention. A well-recognized tool from the field of injury prevention known as the Haddon matrix was utilized. The matrix states that any accident is affected by the host, agent, and environment. Another well-recognized tool used by the national fire protection association known as the Community risk reduction tool (CRR). The (CRR) tool utilizes the Five E's of Community Risk Reduction. AIM OF THE STUDY: To describe the risk factors that increase the susceptibility and the severity of COVID-19 infection based on the Haddon matrix and the proposed prevention strategies by the CRR tool by using the combined model. METHODOLOGY: We reviewed the literature to assess known factors contributing to COVID-19 susceptibility, infection, and severity of infection. We then used the Haddon matrix to structure, separating human factors from technical and environmental details and timing. We then used the community risk reduction (CRR) model to set all responses and control measures for each element obtained from the Haddon matrix tool. Subsequently, we incorporated both tools to develop the combined model. CONCLUSION: we proposed and implemented a combined model that utilizes the CRR model as the systematic strategy for the more theoretical framework of Haddon's matrix. Combining both models was practical and helpful in planning the preparedness and control of the COVID-19 pandemic in Saudi Arabia that can be generalized to national and international levels.

Late-Term Complications of COVID-19: Retropharyngeal Infection and Myocarditis in a 26-Year-Old Patient.

Deep neck space infection and viral myocarditis related to coronavirus disease 2019 (COVID-19) have both been described in the medical literature. However, there are only three reported cases of retropharyngeal infection as a presenting pathology in the setting of COVID-19. A 26-year-old woman presented to the emergency room with fever and neck swelling and pain 1 month after COVID-19 infection. A computed tomography scan of the neck demonstrated tonsillitis with retropharyngeal infection. She was also found to have heart failure with an ejection fraction (EF) of <20% due to acute myocarditis. Her infection resolved and the EF improved to 40% prior to discharge. Our case is the first to describe retropharyngeal infection as a late complication in an adult with a history of COVID-19 several weeks previously. It also presented a clinical challenge in terms of tailoring goal-directed medical therapy to manage severe left ventricular dysfunction caused by myocarditis. LEARNING POINTS: Deep neck space infections may be a long-term complication of SARS-CoV-2 infection.Fever, neck swelling and pain should arouse suspicion of deep neck space infection even in adults.Acute viral myocarditis in the setting of SARS-CoV-2 can present many weeks after the initial infection.

Potential Cross-Reactive Immunity to COVID-19 Infection in Individuals With Laboratory-Confirmed MERS-CoV Infection: A National Retrospective Cohort Study From Saudi Arabia.

BACKGROUND: A growing number of experiments have suggested potential cross-reactive immunity between severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and previous human coronaviruses. We conducted the present retrospective cohort study to investigate the relationship between previous Middle East respiratory syndrome-coronavirus (MERS-CoV) infection and the risk of SARS-CoV-2 infection as well as the relationship between previous MERS-CoV and COVID-19-related hospitalization and mortality. METHODS: Starting in March 2020, we prospectively followed two groups of individuals who tested negative for COVID-19 infection. The first group had a previously confirmed MERS-CoV infection, which was compared to a control group of MERS-negative individuals. The studied cohort was then followed until November 2020 to track evidence of contracting COVID-19 infection. FINDINGS: A total of 82 (24%) MERS-positive and 260 (31%) MERS-negative individuals had COVID-19 infection. Patients in the MERS-positive group had a lower risk of COVID-19 infection than those in the MERS-negative group (Risk ratio [RR] 0.696, 95% confidence interval [CI] 0.522-0.929; p =0.014). The risk of COVID-19-related hospitalization in the MERS-positive group was significantly higher (RR 4.036, 95% CI 1.705-9.555; p =0.002). The case fatality rate (CFR) from COVID-19 was 4.9% in the MERS-positive group and 1.2% in the MERS-negative group (p =0.038). The MERS-positive group had a higher risk of death than the MERS-negative group (RR 6.222, 95% CI 1.342-28.839; p =0.019). However, the risk of mortality was similar between the two groups when death was adjusted for age (p =0.068) and age and sex (p =0.057). After controlling for all the independent variables, only healthcare worker occupation and >1 comorbidity were independent predictors of SARS-CoV-2 infection. INTERPRETATION: Individuals with previous MERS-CoV infection can exhibit a cross-reactive immune response to SARS-CoV-2 infection. Our study demonstrated that patients with MERS-CoV infection had higher risks of COVID-19-related hospitalization and death than MERS-negative individuals.

Virtual Reality Therapy for Depression and Mood in Long-Term Care Facilities.

Virtual reality (VR) describes a family of technologies which immerse users in sensorily-stimulating virtual environments. Such technologies have increasingly found applications in the treatment of neurological and mental health disorders. Depression, anxiety, and other mood abnormalities are of concern in the growing older population-especially those who reside in long-term care facilities (LTCFs). The transition from the familiar home environment to the foreign LTCF introduces a number of stressors that can precipitate depression. However, recent studies reveal that VR therapy (VRT) can promote positive emotionality and improve cognitive abilities in older people, both at home and in LTCFs. VR thus holds potential in allowing older individuals to gradually adapt to their new environments-thereby mitigating the detrimental effects of place attachment and social exclusion. Nevertheless, while the current psychological literature is promising, the implementation of VR in LTCFs faces many challenges. LTCF residents must gain trust in VR technologies, care providers require training to maximize the positive effects of VRT, and decision makers must evaluate both the opportunities and obstacles in adopting VR. In this review article, we concisely discuss the implications of depression related to place attachment in LTCFs, and explore the potential therapeutic applications of VR.

Proximal Migration of Pancreatic Duct Stent in Pancreas Divisum: Challenges in Retrieval and Review of the Literature.

Pancreas divisum is the most common congenital malformation of the pancreas. Sometimes it is considered an etiology when patients present with recurrent episodes of pancreatitis. Endoscopic retrograde pancreatography (ERP) with selective cannulation of the minor papilla with sphincterotomy and stent placement are performed in these patients. Proximal migration of pancreatic stents in pancreas divisum is rare and challenging to manage. We describe a case of proximal migration of a pancreatic stent in a patient with pancreas divisum and perform a review of literature.

COVID-19 and Plasmodium vivax malaria co-infection.

The ongoing outbreak of COVID-19 poses an unprecedented global health challenge. With its variety of clinical manifestations including, but not limited to, fever, cough, diarrhea, vomiting, headache, myalgia and fatigue, it may be challenging to distinguish COVID-19 from a spectrum of diseases with similar presentations, such as malaria, especially in endemic areas. Risk of concomitant infections also remains a concern owing to overburdening of healthcare services and possible scarcity of resources. We present the first reported case of confirmed COVID and malaria co-infection. In this case, we emphasize the need for vigilance from frontline clinicians for timely diagnosis and appropriate clinical management of potential co-infections in the COVID era.

Therapeutic approaches in hypertriglyceridemia-induced acute pancreatitis: A literature review of available therapies and case series.

Hypertriglyceridemia-induced acute pancreatitis (HGAP) is the third most common etiology of acute pancreatitis. HGAP can be attributed to genetic disturbances in triglyceride metabolism or multiple secondary causes. Here, we presented three cases for HGAP and explored different therapeutic approaches for treating HGAP. A case series of three patients who presented with HGAP and underwent different therapeutic approaches was conducted. The first patient was a 37-year-old male who presented with nonsevere HGAP; he was treated with conservative therapy with insulin and heparin infusion, which resulted in clinical and laboratory improvement. The second patient was a 64-year-old male with human immunodeficiency virus on multiple highly active antiretroviral therapy. He presented with severe HGAP and multiorgan failure. After initiation of therapeutic plasma exchange, his HGAP resolved. The third patient was a 28-year-old male who presented with recurrent episodes of HGAP; his conservative therapy failed and was eventually escalated to therapeutic plasma exchange (TPE). HGAP can be attributed to genetic disturbances of lipid or secondary etiologies. A nonsevere form of HGAP can be managed with conventional therapy including insulin and heparin; however, severe HGAP may require TPE.

Molecular dynamics simulations of an engineered T4 lysozyme exclude helix to sheet transition, and provide insights into long distance, intra-protein switchable motion.

An engineered variant of T4 lysozyme serves as a model for studying induced remote conformational changes in a full protein context. The design involves a duplicated surface helix, flanked by two loops, that switches between two different conformations spanning about 20 Å. Molecular dynamics simulations of the engineered protein, up to 1 µs, rule out α-helix to ß-sheet transitions within the duplicated helix as suggested by others. These simulations highlight how the use of different force fields can lead to radical differences in the structure of the protein. In addition, Markov state modeling and transition path theory were employed to map a 6.6 µs simulation for possible early intermediate states and to provide insights into the onset of the switching motion. The putative intermediates involve the folding of one helical turn in the C-terminal loop through energy driven, sequential rearrangement of nearby salt bridges around the key residue Arg63. These results provide a first step towards understanding the energetics and dynamics of a rather complicated intra-protein motion.

Study of the hydromineral regulation of Typhlonectes compressicauda according to the seasonal variation.

INTRODUCTION: Typhlonectes compressicauda is a viviparous gymnophionan amphibian living in tropical areas of South America. This lengthened amphibian is submitted to seasonal variations characterized by the rainy season (from January to June) and the dry season (from July to December). The mineral homeostasis in amphibians is partly ensured by the neurohormones arginine-vasotocin (AVT), and mesotocin (MST). These two hormones were localized in the hypothalamus, and their receptors, mesotocin receptors (MTR) and vasotocin receptors (VTR2) in the kidney. The aim of the study was to better understand the physiology of the hydromineral regulation of the studied species. MATERIAL AND METHODS: The specimens of T. compressicauda male and female adult were divided into 6 groups: males in the rainy season, males in the dry season, females pregnant in the rainy season, females pregnant in the dry season, females not pregnant in the rainy season, females not pregnant in the dry season. We studied the expression of hormones (AVT, MST) and their receptors (MTR, VTR2) in the hypothalamus and the kidney, respectively, by immunohistochemical and histological techniques. We also studied the expression of aquaporin-2 (AQP2), a water-channel protein in the kidney. RESULTS: We found that the MST (diuretic hormone) and its receptor were more intensively expressed during the rainy season, whereas the period of maximal AVT (anti-diuretic hormone) and VTR2 expression was the dry season. A quantitative analysis showed significant differences in the number of labeled cells in the hypothalamus depending on the seasonal variation. The expression of AQP2 was observed in renal tubules during both seasons with an increased intensity during the dry season. CONCLUSION: The expression of the MST/AVT in brain, their receptors MTRs/VTR2, and AQP2 in kidney changed in T. compressicauda according to the seasonal variations. A direct relationship between the seasonal cycle and reproduction cycle was demonstrated in this species.