Numerical model for electrogenic transport by the ATP-dependent potassium pump KdpFABC.

In vitro assays of ion transport are an essential tool for understanding molecular mechanisms associated with ATP-dependent pumps. Because ion transport is generally electrogenic, principles of electrophysiology are applicable, but conventional tools like patch-clamp are ineffective due to relatively low turnover rates of the pumps. Instead, assays have been developed to measure either voltage or current generated by transport activity of a population of molecules either in cell-derived membrane fragments or after reconstituting purified protein into proteoliposomes. In order to understand the nuances of these assays and to characterize effects of various operational parameters, we have developed a numerical model to simulate data produced by two relevant assays: fluorescence from voltage-sensitive dyes and current recorded by capacitive coupling on solid supported membranes. Parameters of the model, which has been implemented in Python, are described along with underlying principles of the computational algorithm. Experimental data from KdpFABC, a K+ pump associated with P-type ATPases, are presented, and model parameters have been adjusted to mimic these data. In addition, effects of key parameters such as nonselective leak conductance and turnover rate are demonstrated. Finally, simulated data are used to illustrate the effects of capacitive coupling on measured current and to compare alternative methods for quantification of raw data.

Energy coupling and stoichiometry of Zn2+/H+ antiport by the prokaryotic cation diffusion facilitator YiiP.

YiiP from Shewanella oneidensis is a prokaryotic Zn2+/H+ antiporter that serves as a model for the Cation Diffusion Facilitator (CDF) superfamily, members of which are generally responsible for homeostasis of transition metal ions. Previous studies of YiiP as well as related CDF transporters have established a homodimeric architecture and the presence of three distinct Zn2+ binding sites named A, B, and C. In this study, we use cryo-EM, microscale thermophoresis and molecular dynamics simulations to address the structural and functional roles of individual sites as well as the interplay between Zn2+ binding and protonation. Structural studies indicate that site C in the cytoplasmic domain is primarily responsible for stabilizing the dimer and that site B at the cytoplasmic membrane surface controls the structural transition from an inward facing conformation to an occluded conformation. Binding data show that intramembrane site A, which is directly responsible for transport, has a dramatic pH dependence consistent with coupling to the proton motive force. A comprehensive thermodynamic model encompassing Zn2+ binding and protonation states of individual residues indicates a transport stoichiometry of 1 Zn2+ to 2-3 H+ depending on the external pH. This stoichiometry would be favorable in a physiological context, allowing the cell to use the proton gradient as well as the membrane potential to drive the export of Zn2+.

Energy Coupling and Stoichiometry of Zn2+/H+ Antiport by the Cation Diffusion Facilitator YiiP.

YiiP is a prokaryotic Zn2+/H+ antiporter that serves as a model for the Cation Diffusion Facilitator (CDF) superfamily, members of which are generally responsible for homeostasis of transition metal ions. Previous studies of YiiP as well as related CDF transporters have established a homodimeric architecture and the presence of three distinct Zn2+ binding sites named A, B, and C. In this study, we use cryo-EM, microscale thermophoresis and molecular dynamics simulations to address the structural and functional roles of individual sites as well as the interplay between Zn2+ binding and protonation. Structural studies indicate that site C in the cytoplasmic domain is primarily responsible for stabilizing the dimer and that site B at the cytoplasmic membrane surface controls the structural transition from an inward facing conformation to an occluded conformation. Binding data show that intramembrane site A, which is directly responsible for transport, has a dramatic pH dependence consistent with coupling to the proton motive force. A comprehensive thermodynamic model encompassing Zn2+ binding and protonation states of individual residues indicates a transport stoichiometry of 1 Zn2+ to 2-3 H+ depending on the external pH. This stoichiometry would be favorable in a physiological context, allowing the cell to use the proton gradient as well as the membrane potential to drive the export of Zn2+.

Burnout among ICU Healthcare Workers at Two Tertiary Care Hospitals in Makkah during the Hajj Season.

Background: The Hajj season results in increased workload and longer shift hours for healthcare workers at the intensive care units (ICUs), which may result in burnout. Objective: To determine the point prevalence of professional burnout and its predictors among healthcare workers at the ICUs of two tertiary care hospitals in Makkah during the Hajj season. Methods: This cross-sectional descriptive study included all healthcare professionals working at the ICU departments of two of the largest tertiary care hospitals in the Makkah region during the 1439/2018 Hajj season. The original Maslach Burnout Inventory (MBI) questionnaire was used to measure burnout. Logistic regression models were fitted to estimate the effect size of the associated risk factors. Results: A total of 354 participants completed the questionnaire. Moderate to severe burnout was found in each of the three subscales: emotional exhaustion, 56%; depersonalization, 82%, and impaired personal achievement, 72%. Nurses were significantly more likely to experience burnout compared with physicians (P = 0.017). Independent predictors of moderate or severe burnout were being aged ≤40 years (odds ratio [OR]: 2.1, 95% CI: 0.395-4.002; P = 0.045), female gender (OR: 2.2, 95% CI: 0.242-4.346; P = 0.037); work having a negative impact on family (OR: 3, 95% CI: 0.164-5.504; P = 0.019); unsatisfaction with salary (OR: 2.8, 95% CI: 0.28-5.056; P = 0.025); and working at the cardiac critical care unit (OR: 2.6, 95% CI: 0.440-4.467; P = 0.035). Conclusion: This study revealed that the point prevalence of burnout is common among ICU healthcare workers during the Hajj season. These findings can be used by policymakers to devise strategies to mitigate the risks of burnout during the Hajj season.

Discovery of peptide ligands through docking and virtual screening at nicotinic acetylcholine receptor homology models.

Venom peptide toxins such as conotoxins play a critical role in the characterization of nicotinic acetylcholine receptor (nAChR) structure and function and have potential as nervous system therapeutics as well. However, the lack of solved structures of conotoxins bound to nAChRs and the large size of these peptides are barriers to their computational docking and design. We addressed these challenges in the context of the α4ß2 nAChR, a widespread ligand-gated ion channel in the brain and a target for nicotine addiction therapy, and the 19-residue conotoxin α-GID that antagonizes it. We developed a docking algorithm, ToxDock, which used ensemble-docking and extensive conformational sampling to dock α-GID and its analogs to an α4ß2 nAChR homology model. Experimental testing demonstrated that a virtual screen with ToxDock correctly identified three bioactive α-GID mutants (α-GID[A10V], α-GID[V13I], and α-GID[V13Y]) and one inactive variant (α-GID[A10Q]). Two mutants, α-GID[A10V] and α-GID[V13Y], had substantially reduced potency at the human α7 nAChR relative to α-GID, a desirable feature for α-GID analogs. The general usefulness of the docking algorithm was highlighted by redocking of peptide toxins to two ion channels and a binding protein in which the peptide toxins successfully reverted back to near-native crystallographic poses after being perturbed. Our results demonstrate that ToxDock can overcome two fundamental challenges of docking large toxin peptides to ion channel homology models, as exemplified by the α-GID:α4ß2 nAChR complex, and is extendable to other toxin peptides and ion channels. ToxDock is freely available at rosie.rosettacommons.org/tox_dock.

Assessment of the Heavy Metals in Al Asfar Lake, Al-Hassa, Saudi Arabia.

Al Asfar Lake is a shallow wetland and habitat for wildlife and birds in a desert environment. The water of this lake is originated from the drainage water collected by earthen drainage network and discharged into the lake. The purpose of this study was to assess physico- chemical characteristics and some of heavy metals in Al Asfar lake water. The studied parameters are iron, manganese, copper, zinc, cadmium, chromium, lead, pH, electrical conductivity, and nitrate. Forty-five surface water samples were collected in March 2013. The results revealed that the pH ranged from 7.33 to 8.67, electrical conductivity ranged from 8.28 to 11.34 dS/m, and NO(3)(-) ranged from 0.84 to 2.29 mg/L. In addition, heavy metals concentrations in water were found in the following order: Fe > Mn > Cu > Zn > Cd > Cr = Pb. The mean concentrations of heavy metals in surface water of Al Asfar lake ranged from 0.027 to 0.159 ppm, 0.007 to 0.142 ppm, 0.005 to 0.017 ppm, 0.005 to 0.066 ppm, 0.001 to 0.033 ppm, 0 ppm, and 0 ppm for iron, manganese, copper, zinc, cadmium, chromium, and lead, respectively. Moreover, pH, NO(3)(-), Fe, Mn, and Zn concentrations in the surface water of Al Asfar Lake were found to be within the international permissible limits. On the other hand, Cu and Cd concentrations exceeded the international permissible limits. The high level of some parameters of the measured heavy metals could be attributed to the contamination of Al Asfar Lake with discharge water enriched with chemical fertilizers in addition to domestic and industrial effluents.

Effect of sodium selenite and vitamin E on the renal cortex in rats: an ultrastructure study.

This study examined the use of vitamin E to alleviate toxic effects of sodium selenite. Adult male albino rats (n=50) was divided into five groups. Group 1 was control, Groups 2 and 4 were treated with sodium selenite (2 mg/kg) for 2 and 4 weeks, respectively, Groups 3 and 5 were treated with sodium selenite (2 mg/kg) and vitamin E (100 mg/kg) for 2 and 4 weeks, respectively. Renal tissues were studied using anti-BCL2 and examined ultrastructurally. Positive Bax immunoreactivity was detected after 2 and more positive after 4 weeks and nearly all groups improved with co-administration of vitamin E. Ultrastructural study revealed lesions in Bowman's capsule and proximal convoluted tubules. The submicroscopic study revealed damage and necrosis of cortical structures after 2 and 4 weeks, respectively. After 4 weeks, cellular changes were seen, such as vacuolation and moderate degeneration of cells, widening of the urinary space scattered through the cortex with loss of cellular details, formation of apical buds, degeneration, and cellular rupture. Present findings disclosed an ameliorative effect of adding vitamin E to sodium selenite-induced changes in cortical tissues. Clinically, it is advised to add vitamin E to avoid selenium overdose hazards.

Origin of profunda femoris artery and its circumflex femoral branches: anatomical variations and clinical significance.

BACKGROUND: Knowledge of the anatomical variations of the profunda femoris artery and its circumflex branches is important during angiographic diagnostic procedures as well as during performing surgery in the femoral region. The aim of this study was to examine the original sites, distances and variations of the profunda femoris artery and its circumflex branches. MATERIALS AND METHODS: The study was conducted in the Department of Anatomy, Faculty of Medicine, King Abdulaziz University from October, 2011 to May, 2013 after the approval of the medical ethical committee. Dissections of 90 femoral triangles of 25 male and 20 female adult human cadavers were performed to demonstrate the origin and distribution of the profunda femoris artery and its circumflex branches. RESULTS: The profunda femoris artery mostly originated from the posterolateral aspect of the femoral artery in 42% of male limbs and in 42.5% of female limbs, from the posterior side in 24% of male and 27.5% of female limbs, from the lateral side in 20% of males and female limbs and from the posteromedial aspect in 14% of male limbs and in 7.5% of female limbs. The mean distance of origin of profunda femoris artery from the midpoint of inguinal ligament was 51.5 ± 1.9 mm in right male, 49.7 ± 1.9 mm in left male, 48.5 ± 2.2 mm in right female and 48.9 ± 2.2 mm in left female limbs. The medial and lateral circumflex arteries originated mostly from the profunda femoris artery (60% in males; 57.7% in females) at a mean distance of 18.6 ± 2.1 mm and 20.2 ± 2.2 mm in right male, 19.6 ± 1.9 mm and 22.5 ± 2.3 mm in left male, 18.8 ± 2.7 mm and 21 ± 2.6 mm in right female and 19.1 ± 2.1 mm and 21.7 ± 2.6 mm in left female limbs, respectively. The original incidence of the medial and lateral circumflex femoral arteries from the femoral artery including the common trunk was 40% in male and 42.3% in female limbs. CONCLUSIONS: Awareness of the original sites and distances of the profunda femoris artery and its circumflex femoral branches will allow the surgeon to define the vascular pattern before performing any invasive procedure and to avoid unexpected iatrogenic injuries.

The effects of diethylstilbestrol administration on rat kidney. Ultrastructural study.

OBJECTIVE: To assess the histological and ultrastructural changes that can be induced by diethylstilbestrol (DES) on renal tissues using histological, immunohistochemical, and ultrastructural methods. METHODS: Thirty adult male Wistar rats were divided into 3 groups (10 rats each): Group 1 - control; Group 2 - received DES at a dose of 60 ug/kg/day, dissolved in 0.1 ml corn oil for 20 days; and Group 3 - received the same dose of DES for 50 days by oral gavage. The renal tissues were studied histologically, immunohistochemically (using an anti-BCL2-associated X protein [BAX protein] antibody), and ultrastructurally. This study was carried out at the Anatomy Department, Faculty of Medicine, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia between December 2011 and December 2012. RESULTS: The DES administration for 50 days caused noticeable degeneration, and alteration of the morphology of the renal tissues in the form of damaged renal tubules with loss of the brush border of the proximal convoluted tubules and increased cellularity of the glomeruli. In addition, there was a significant increase in BAX protein expression based on immunoreactivity, and in renal tubules, as well as glomerular cells. These changes were less obvious after 20 days of treatment. CONCLUSION: Non-steroidal, synthetic estrogens showed harmful effects on the renal tissues and altered their morphology with an increased number of apoptotic cells, and these changes were duration dependent.

Morphology and clinical implication of the extra-head of biceps brachii muscle.

The biceps brachii muscle is present in the anterior aspect of the arm. Its morphological variations have great clinical significance for surgeons, orthopaedic surgeons, anaesthetists, neurologists and anatomists. This study aimed to describe the incidence and morphology of the extra-heads of the biceps brachii muscle. Hundred upper limbs of 50 adult human cadavers (30 men and 20 women) were used in this study after the approval of the medical ethical committee. These cadavers were obtained from the Anatomy Department, Faculty of Medicine, King Abdul-Aziz University. The incidence of anatomical variations of biceps muscle was equal in both male and female cadavers (10%) with predominance of the left side (7%). The 3-headed biceps brachii muscle was noticed in 7% (4% male and 3% female), while the 4-headed biceps was seen in 2 (2%) left limbs, 1 male and 1 female. The third head of the biceps muscle arose from the anteromedial aspect of humerus, between the coracobrachialis insertion and the brachialis origin, in 6% and from middle of the medial border of humerus in 3%. While the fourth head originated from the articular capsule of shoulder joint in 1 (1%) limb and from the coracoid process of scapula in the other limb. The biceps common tendon of insertion received the supernumerary heads in 7% of the limbs. However, the extra-head fused with the long head in 2 (2%) limbs and united with the short head in 1 (1%) limb. The mean of the third head length was 118.8±10.9 in all limbs, where it was 121.8±12.3 in male and 113.5±8.1 in female cadavers. The third head length/arm length ratio was 38.4±2.6 in all, 38.3±3.4 in male and 38.8±1.8 in female cadavers. The length of the extra-head was extremely significant with those of the corresponding limb in all, male and female cadavers (p<0.0001). Knowledge of the morphological variations of biceps muscle provides better pre-operative evaluation, safe surgical intervention within the arm and better postoperative outcomes.

Effects of a low level laser on the acceleration of wound healing in rabbits.

BACKGROUND: Tissue healing is a complex process that involves local and systemic responses. The use of low level laser therapy for wound healing has been shown to be effective in modulating both local and systemic response. AIM: The aim of this study was to accelerate and facilitate wound healing and reduce scar formation and wound contraction of an open wound by a low level laser. MATERIALS #ENTITYSTARTX00026; METHODS: Twenty adult male rabbits, lepus cuniculus demostica, were brought from a Basrah local market and raised under proper management conditions in Basrah Veterinary Medicine College. The age of these rabbits ranged between 8-10 months and their body weight was 1.5-2 Kg. The rabbits were divided into two groups, group I (Control) and group II (Treated). General anesthesia was provided by a mixture of Xylazine and Ketamine at a ratio of 1:0.5m intramuscularly. Selected sites were shaved, cleaned and disinfected. A wound of 4-cm length and 3-cm depth was made on the gluteal region; six hours later, the wound was treated with gallium aluminum and an arsenide diode laser with a power output of 10m at a wavelength of 890nm in pulsed nods, with a frequency of 20 KLTZ. The wound exposure to the laser was once a day at 890 nm wavelength for 5 minutes over a 7-day period. Histopathological study was obtained regarding the wound depth and edge of the skin on the 3(rd), 7(th) and 14(th) days. RESULTS: The histopathological finding of group I at three days postoperative showed hemorrhage with inflammatory cell infiltration, mainly neutrophils as well as congested blood vessels in the gap. At seven days, the gap contained necrotized neutrophils together with hemolysis and granulation tissue under the dermis tissue. Hemolysis was seen between the muscle fibers. At 14 days, there was irregular fibrous connective tissue proliferation with congested blood vessels seen in the gap with mononuclear cell infiltration. In group II at three days postoperative, severe inflammatory cell infiltration was observed, mainly neutrophils with proliferation of fibroblasts from a few fibrous connective tissues. On the 7(th) day, the main lesion was characterized by severe granulation tissue that consisted of proliferation of fibrous connective tissue and congested blood vessels in the gap of the incision with mononuclear cell infiltration. CONCLUSIONS: The study found that low level laser therapy (II) was effective in open wounds, which showed better regeneration and faster restoration of structural and functional integrity as compared to the control group.

Impact of progressive sinotubular junction dilatation on valve competence of the 3F Aortic and Sorin Solo stentless bioprosthetic heart valves.

OBJECTIVE: The use of stentless bioprostheses for aortic valve replacement provides excellent haemodynamics; however, these valves bear the potential risk of progressive regurgitation over time. To overcome this disadvantage, a new generation of pericardial stentless prostheses has been developed. This study aims to assess the tolerance of such bioprotheses against progressive sinotubular junction dilatation. METHODS: Five specimens of both the 3F Aortic and Sorin Solo stentless bioprotheses (diameter 25 mm) were investigated in a pulsatile flow simulator incorporating a device for gradual expansion of the sinotubular junction diameter. Closing characteristics were obtained by high-speed video imaging and the corresponding regurgitations were determined by ultrasonic flow measurements. The diameters D(R), at which primary distinct regurgitation occurs, were correlated to the original diameters D(A) and expressed as percentage values. RESULTS: The highest tolerance against sinotubular junction dilatation was found for the 3F Aortic (156+/-5%) compared to the Sorin Solo (145+/-6%, p=0.0127) bioprothesis. Visualisation of the valves revealed strong leaflet folding at labelled diameter, similar in both valve types. CONCLUSIONS: New-generation pericardial stentless bioprotheses provide favourable adaptability to sinotubular junction dilatation, more pronounced for the 3F prosthesis. Whether undue leaflet folding caused by the redundant tissue influences long-term function remains to be established.