Nursing Practice Competency of Accelerated Bachelor of Science in Nursing Program Students

The purposes of this study were to quantify the perception of nursing practice competency by students in an accelerated bachelor of science in nursing program at the beginning and the end of the program of study and to compare the student's perception of their competency at the end of the program of study with the unit-based nurses expert's perception of the students nursing practice competency. A quantitative pre–post intervention design was used to measure the perception of students at the beginning (T-1) and the end (T-2) of their program of study in nursing. Using Benner's domains of nursing practice, there was a significant difference in self-perception at the beginning and the end of the program. At the end of the program, the unit-based nurse expert rated the student's nursing practice higher on all domains, as compared to the student self-rating. The nursing practice competency of these students was quantified. It is interesting to note that self-rating at the end of the program of study were just below the midpoint of the scale. However, the scoring on a global item of how competent are you to begin practicing as a professional nurse was scored higher than any of the individual domains of practice.     

Bacteria in an intense competition for iron: Key component of the Campylobacter jejuni iron uptake system scavenges enterobactin hydrolysis product

To acquire essential Fe(III), bacteria produce and secrete siderophores with high affinity and selectivity for Fe(III) to mediate its uptake into the cell. Here, we show that the periplasmic binding protein CeuE of Campylobacter jejuni, which was previously thought to bind the Fe(III) complex of the hexadentate siderophore enterobactin (K_d ∼ 0.4 ± 0.1 µM), preferentially binds the Fe(III) complex of the tetradentate enterobactin hydrolysis product bis(2,3-dihydroxybenzoyl-l-Ser) (H₅-bisDHBS) (K_d = 10.1 ± 3.8 nM). The protein selects Λ-configured [Fe(bisDHBS)]²⁻ from a pool of diastereomeric Fe(III)-bisDHBS species that includes complexes with metal-to-ligand ratios of 1:1 and 2:3. Cocrystal structures show that, in addition to electrostatic interactions and hydrogen bonding, [Fe(bisDHBS)]²⁻ binds through coordination of His227 and Tyr288 to the iron center. Similar binding is observed for the Fe(III) complex of the bidentate hydrolysis product 2,3-dihydroxybenzoyl-l-Ser, [Fe(monoDHBS)₂]³⁻. The mutation of His227 and Tyr288 to noncoordinating residues (H227L/Y288F) resulted in a substantial loss of affinity for [Fe(bisDHBS)]²⁻ (K_d ∼ 0.5 ± 0.2 µM). These results suggest a previously unidentified role for CeuE within the Fe(III) uptake system of C. jejuni, provide a molecular-level understanding of the underlying binding pocket adaptations, and rationalize reports on the use of enterobactin hydrolysis products by C. jejuni, Vibrio cholerae, and other bacteria with homologous periplasmic binding proteins.With the rapid rise in bacterial resistance to antibiotics, a better understanding of cooperative behavior in microbial communities is urgently needed for the development of novel approaches to controlling infections caused by resistant bacteria (1, 2). As an essential nutrient, iron is often a growth-limiting factor for beneficial, commensal, and pathogenic bacteria alike, not only due to its low solubility in water under aerobic conditions at and around neutral pH, but also because the host organism and competing microbes actively limit its availability (3, 4). Microorganisms evolved efficient Fe(III) uptake mechanisms to overcome this challenge, a common strategy being the production of siderophores, small Fe(III)-chelating molecules with high affinity and selectivity for Fe(III), with over 500 examples known to date (5). The sharing of siderophores is a recognized example for positive cooperativity that has been linked to bacterial virulence (6). The best-characterized siderophores are hexadentate ligands that form coordinatively saturated, octahedral 1:1 complexes with Fe(III) (3, 5, 7), the most studied being the triscatecholate enterobactin (H₆-ENT) produced by many enteric bacteria (8).In Escherichia coli, enterobactin is synthesized within the cell and secreted through the cell membranes to capture Fe(III) from the environment. The resulting Fe(III)-enterobactin complex [Fe(ENT)]³⁻ is recognized by the outer membrane receptor FepA and actively transported into the periplasm. In the periplasm, [Fe(ENT)]³⁻ is sequestered by the periplasmic binding protein (PBP) FepB, which transfers it to an inner membrane transporter for further transport into the cytoplasm (9). Once there, [Fe(ENT)]³⁻ is hydrolyzed by an intracellular esterase to release Fe(III) for use in the cell (8).Along with the development of structurally diverse siderophores, microorganisms adapted their associated receptor and transport proteins for the uptake of the appropriate Fe(III) complexes (9). To gain a competitive advantage, many bacteria have evolved to poach siderophores produced by other bacteria. Campylobacter jejuni, for example, does not itself produce siderophores yet possesses an uptake system that is able to use siderophores from competing species (10). Initially, it was proposed that in C. jejuni [Fe(ENT)]³⁻ is transported across the outer membrane by the receptors CfrA and CfrB (11). Once in the periplasm, [Fe(ENT)]³⁻ was proposed to bind to the PBP CeuE, the resulting complex enabling the transport of the ferric siderophore into the cytoplasm (12, 13).In addition, increasing numbers of lower-denticity siderophores are being isolated from bacterial cultures and found to coordinate Fe(III) and mediate its uptake (14–18). For example, the trilactone backbone of enterobactin makes it prone to hydrolysis, and although this lability is necessary to allow the intracellular release of Fe(III) from the siderophore, it in addition leads to its slow degradation in aqueous media (7, 19–21). Three hydrolysis products are formed: tris(2,3-dihydroxybenzoyl-l-Ser) (H₇-trisDHBS), bis(2,3-dihydroxybenzoyl-l-Ser) (H₅-bisDHBS), and 2,3-dihydroxybenzoyl-l-Ser (H₃-monoDHBS), with all three found in the growth medium of E. coli (Fig. 1). Although enterobactin, once secreted, is also available to other cells (producers or nonproducers), it can only be used once because Fe(III) release requires its hydrolysis. The enterobactin hydrolysis products, however, could be used again as secondary, lower-denticity siderophores.Open in a separate windowFig. 1.Molecular structure of enterobactin, its hydrolysis products, the siderophore mimic H₆-MECAM, and a selection of tetradentate siderophores.It has been demonstrated that the human pathogens C. jejuni (10, 22, 23) and Vibrio cholerae (24), the causes of food poisoning and cholera, respectively, can use enterobactin hydrolysis products for the uptake of Fe(III) from their environment. Both are known not to produce enterobactin.An alternative Campylobacter Fe(III) acquisition model that relies on these linear hydrolysis products was recently proposed based on the finding that Cee, the sole trilactone esterase of C. jejuni and Campylobacter coli, is located in the periplasm, i.e., these bacteria are unable to degrade enterobactin within the cytoplasm (25). The model suggests that, once the Fe(III) complex of enterobactin enters the periplasm, its ester backbone is cleaved by Cee, which is highly efficient in hydrolyzing both the Fe(III) complex and apo-enterobactin. The resulting hydrolysis products, mainly the tetradentate ligand bisDHBS⁵⁻ and the bidentate ligand monoDHBS³⁻, are then used to mediate the subsequent transport of Fe(III) into the cytoplasm.The identification of the esterase Cee and in particular the observation that bisDHBS⁵⁻ can be used independently of enterobactin (25) raise important questions about the siderophore preference of the PBP CeuE and its role in the iron uptake in C. jejuni. By using siderophore mimics, we previously demonstrated that CeuE can bind the Fe(III) complexes of both hexadentate and tetradentate catecholate ligands (26, 27). Our cocrystal structures revealed that CeuE interacts with the coordinatively saturated Fe(III) complex of the hexadentate mimic MECAM⁶⁻ through electrostatic interactions and hydrogen bonding, whereas it binds the coordinatively unsaturated complex of the tetradentate mimic 4-LICAM⁴⁻ by recruiting the side chains of two amino acid residues (His227 and Tyr288) to complete the coordination sphere of the Fe(III) center. We established that His227 and Tyr288 are conserved among a subset of related PBPs, including VctP from V. cholerae, and suggested that this subset of PBPs undergo similar structural changes to adapt to the binding of lower-denticity sidero-phores (27). The recent report that V. cholerae most efficiently uses trisDHBS⁷⁻ and bisDHBS⁵⁻ for the acquisition of Fe(III) provided a partial confirmation of this prediction (24).Here, we report that CeuE binds [Fe(bisDHBS)]²⁻ with much higher affinity than the Fe(III) complex of enterobactin, reveal the structural basis for this difference in binding strength, and examine key aspects of the relevant Fe(III) coordination chemistry in solution.     

Multimeric analysis of von Willebrand factor by molecular sieving electrophoresis in sodium dodecyl sulphate agarose gel

We report the development and optimisation of an agarose gel electrophoretic method for the separation and detection of von Willebrand Factor (vWF) multimers. The method has been specifically developed for use in the clinical evaluation and classification of patients with von Willebrand's Disease (vWD) and clearly shows structural multimer abnormalities associated with the bleeding diathesis of this inherited bleeding disorder.     

Fundus changes in mesangiocapillary glomerulonephritis type II: vitreous fluorophotometry.

We have described a complex abnormality of retinal pigment epithelium, Bruch's membrane, and choriocapillaris in mesangiocapillary glomerulonephritis (MCGN) type II. Patients with MCGN type II were examined by vitreous fluorophotometry which reveals that there is a breakdown of the blood retinal barrier (BRB) in those patients with the typical fundus lesions. The function of this barrier was calculated as a penetration ratio and was statistically greater in these patients when compared with a group of (a) normal persons, (b) patients with drusen, and (c) patients with other forms of glomerulonephritis.     

Halothane Interactions with Nicotinic Acetylcholine Receptor Membranes: Steady-state and Kinetic Studies of Intrinsic Fluorescence Quenching

Background: Although it has been suggested that anesthetics alter protein conformational states by binding to nonpolar sites within the interior regions of proteins, the rate and extent to which anesthetics penetrate membrane proteins has not been characterized. The authors report the use of steady-state and stopped-flow spectroscopy to characterize the interactions of halothane with receptor membranes.

Methods: Steady-state and stopped-flow fluorescence spectroscopy was used to characterize halothane quenching of nicotinic acetylcholine receptor (nAcChoR)-rich membrane intrinsic fluorescence and the rate of isoflurane-induced nAcChoR desensitization.

Results: At equilibrium, halothane quenched only 54 +/- 1.4% of all tryptophan fluorescence. Diethyl ether failed to reduce fluorescence quenching by halothane, suggesting that it does not bind to the same protein sites as halothane. Stopped-flow fluorescence traces defined two kinetic components of quenching: a fast component that occurred in less than 1 ms followed by a slower biphasic fluorescence decay. Protein unfolding with sodium dodecyl sulfate reduced halothane's Stern-Volmer quenching constant, eliminated the biphasic decay, and rendered fluorescence accessible to quenching by halothane within 1 ms. Functional studies indicate that anesthetic-induced desensitization of nAcChoR occurs in less than 2 ms.     

The mitogen-activated protein kinase pathway can mediate growth inhibition and proliferation in smooth muscle cells. Dependence on the availability of downstream targets.

Activation of the classical mitogen-activated protein kinase (MAPK) pathway leads to proliferation of many cell types. Accordingly, an inhibitor of MAPK kinase, PD 098059, inhibits PDGF-induced proliferation of human arterial smooth muscle cells (SMCs) that do not secrete growth-inhibitory PGs such as PGE2. In striking contrast, in SMCs that express the inducible form of cyclooxygenase (COX-2), activation of MAPK serves as a negative regulator of proliferation. In these cells, PDGF-induced MAPK activation leads to cytosolic phospholipase A2 activation, PGE2 release, and subsequent activation of the cAMP-dependent protein kinase (PKA), which acts as a strong inhibitor of SMC proliferation. Inhibition of either MAPK kinase signaling or of COX-2 in these cells releases them from the influence of the growth-inhibitory PGs and results in the subsequent cell cycle traverse and proliferation. Thus, the MAPK pathway mediates either proliferation or growth inhibition in human arterial SMCs depending on the availability of specific downstream enzyme targets.