Spontaneous maturation of starfish oocytes: Role of follicle cells and calcium ions

Starfish oocytes released from the ovary into sea water during the breeding season underwent spontaneous meiotic maturation. In the absence of calcium ions, follicle cells surrounding the oocyte were dispersed and oocyte maturation did not occur. Immature oocytes in the absence of follicle cells did not mature even when calcium was available. Calcium ions stimulated the release of a meiosis-inducing substance from follicle cells which had been isolated in calcium-free sea water. Increasing numbers of follicle cells produced a parallel increase in the amount of meiosis inducing substance released. Spontaneous oocyte maturation appeared to be initiated and mediated in part by calcium sensitive processes in the follicle cells rather than the oocyte.     

Associations between Stroke Mortality and Weekend Working by Stroke Specialist Physicians and Registered Nurses: Prospective Multicentre Cohort Study

Background

Observational studies have reported higher mortality for patients admitted on weekends. It is not known whether this “weekend effect” is modified by clinical staffing levels on weekends. We aimed to test the hypotheses that rounds by stroke specialist physicians 7 d per week and the ratio of registered nurses to beds on weekends are associated with mortality after stroke.

Methods and Findings

We conducted a prospective cohort study of 103 stroke units (SUs) in England. Data of 56,666 patients with stroke admitted between 1 June 2011 and 1 December 2012 were extracted from a national register of stroke care in England. SU characteristics and staffing levels were derived from cross-sectional survey. Cox proportional hazards models were used to estimate hazard ratios (HRs) of 30-d post-admission mortality, adjusting for case mix, organisational, staffing, and care quality variables. After adjusting for confounders, there was no significant difference in mortality risk for patients admitted to a stroke service with stroke specialist physician rounds fewer than 7 d per week (adjusted HR [aHR] 1.04, 95% CI 0.91–1.18) compared to patients admitted to a service with rounds 7 d per week. There was a dose–response relationship between weekend nurse/bed ratios and mortality risk, with the highest risk of death observed in stroke services with the lowest nurse/bed ratios. In multivariable analysis, patients admitted on a weekend to a SU with 1.5 nurses/ten beds had an estimated adjusted 30-d mortality risk of 15.2% (aHR 1.18, 95% CI 1.07–1.29) compared to 11.2% for patients admitted to a unit with 3.0 nurses/ten beds (aHR 0.85, 95% CI 0.77–0.93), equivalent to one excess death per 25 admissions. The main limitation is the risk of confounding from unmeasured characteristics of stroke services.

Conclusions

Mortality outcomes after stroke are associated with the intensity of weekend staffing by registered nurses but not 7-d/wk ward rounds by stroke specialist physicians. The findings have implications for quality improvement and resource allocation in stroke care. Please see later in the article for the Editors'' Summary     

Homology modeling, simulation and molecular docking studies of catechol-2, 3-Dioxygenase from Burkholderia cepacia: Involved in degradation of Petroleum hydrocarbons

Catechol 2, 3-dioxygenase is present in several types of bacteria and undergoes degradation of environmental pollutants through an important key biochemical pathways. Specifically, this enzyme cleaves aromatic rings of several environmental pollutants such as toluene, xylene, naphthalene and biphenyl derivatives. Hence, the importance of Catechol 2, 3-dioxygenase and its role in the degradation of environmental pollutants made us to predict the three-dimensional structure of Catechol 2, 3-dioxygenase from Burkholderia cepacia. The 10ns molecular dynamics simulation was carried out to check the stability of the modeled Catechol 2, 3- dioxygenase. The results show that the model was energetically stable, and it attains their equilibrium within 2000 ps of production MD run. The docking of various petroleum hydrocarbons into the Catechol 2,3-dioxygenase reveals that the benzene, O-xylene, Toluene, Fluorene, Naphthalene, Carbazol, Pyrene, Dibenzothiophene, Anthracene, Phenanthrene, Biphenyl makes strong hydrogen bond and Van der waals interaction with the active site residues of H150, L152, W198, H206, H220, H252, I254, T255, Y261, E271, L276 and F309. Free energy of binding and estimated inhibition constant of these compounds demonstrates that they are energetically stable in their binding cavity. Chrysene shows positive energy of binding in the active site atom of Fe. Except Pyrene all the substrates made close contact with Fe atom by the distance ranges from 1.67 to 2.43 Å. In addition to that, the above mentioned substrate except pyrene all other made π-π stacking interaction with H252 by the distance ranges from 3.40 to 3.90 Å. All these docking results reveal that, except Chrysene all other substrate has good free energy of binding to hold enough in the active site and makes strong VdW interaction with Catechol-2,3-dioxygenase. These results suggest that, the enzyme is capable of catalyzing the above-mentioned substrate.     

Does CO2 enhance short-term storage success of Chinook salmon (Oncorhynchus tshawytscha) milt?

Successful short-term storage of salmonid milt depends on numerous factors, including temperature, fluid volume, and gaseous environment, with storage at low temperatures under an atmosphere of 100% O2 being the most common method. Salmonid sperm maintained in a storage environment with elevated carbon dioxide (CO2) levels, such as the approximately 4% CO2 in exhaled air, are not motile when activated. While these modest levels of CO2 inhibit sperm motility, the effect is reversible within hours after exposure to a CO2-free oxygenated environment. Therefore, the effect of CO2 (as a component gas in the storage environment) on chinook salmon (Oncorhynchus tshawytscha) sperm motility and viability was examined. The hypothesis of the current investigation was that CO2-exposure with subsequent CO2 removal would be beneficial during short-term chinook salmon milt storage. Milt samples were collected from mature (adult) and precocious (jack) male chinook salmon and stored under various CO2 and O2 levels at 3 to 4 degrees C for up to 14 days. Milt samples were then removed from the incubation environments and maintained under CO2-free humidified air with continuous mixing for 4 h at 10 degrees C before analysis of motility. The resultant motility of samples incubated under 3.5% or less CO2 was not different than controls during the 14 d incubation period; motility of samples stored under higher CO2 tensions were significantly lower. The motility of samples incubated under 3.5% CO2 reached the maximum recovered motility after 2 h exposure to CO2-free humidified air, while the motility of sperm incubated under 13.4% CO2 levels recovered no motility even after 6 h exposure to CO2-free humidified air. The motility of samples incubated under normoxia was significantly greater than that of samples incubated under hyperoxia (approximately 90% O2) at both 7 and 14 d, regardless of the CO2 level. Sperm viability was relatively unaltered by any of the incubation conditions examined. The results of this investigation suggest that there is no apparent advantage to storage of chinook salmon sperm in the presence of CO2 and that storage under hyperoxia negatively affects sperm function compared to storage under normoxia.