Biological synthesis and characterisation of silver nanoparticles using Pseudomonas geniculata H10 for pharmaceutical activity

In the present study, silver nanoparticles (SNPs) were synthesised for the first time using Pseudomonas geniculata H10 as reducing and stabilising agents. The synthesis of SNPs was the maximum when the culture supernatant was treated with 2.5 mM AgNO3 at pH 7 and 40°C for 10 h. The SNPs were characterised by field emission scanning electron microscopy-energy-dispersive spectroscopy, transmission electron microscopy, dynamic light scattering, X-ray diffraction and UV-vis spectroscopy. Fourier transform infrared spectroscopy indicated the presence of proteins, suggesting they may have been responsible for the reduction and acted as capping agents. The SNPs displayed 1,1-diphenyl-2-picrylhydrazyl (IC50 = 28.301 μg/ml) and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonate (IC50 = 27.076 μg/ml) radical scavenging activities. The SNPs exhibited a broad antimicrobial spectrum against several human pathogenic Gram-positive and Gram-negative bacteria and Candida albicans. The antimicrobial action of SNPs was due to cell deformation resulting in cytoplasmic leakage and subsequent lysis. The authors' results indicate P. geniculata H10 could be used to produce antimicrobial SNPs in a facile, non-toxic, cost-effective manner, and that these SNPs can be used as effective growth inhibitors in various microorganisms, making them applicable to various biomedical and environmental systems. As far as the authors are aware, this study is the first to describe the potential biomedical applications of SNPs synthesised using P. geniculata.

Hydro-nanofibrous mesh deep cell penetration: a strategy based on peeling of electrospun coaxial nanofibers

A two-step strategy for coaxial electrospinning and postelectrospinning is an effective method for fabricating superfine nanofibers composed of highly swellable hydrogels. Alginate and poly(ε-caprolactone) [PCL] were coelectrospun via fibrous meshes with a coaxial nozzle; alginate at the core was subsequently cross-linked in calcium chloride solution. The PCL sheath was removed from the meshes by repeated organic-phase washing. The peeling process was monitored by scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry, and the complete removal of the PCL outer layers was confirmed by the thinning of the fiber volume. The obtained alginate hydronanofiber showed extreme water-swellability and mass erosion depending on the degree of cross-linking. We also measured the nanoscale and macroscale mechanical properties of a single nanofiber and of the whole mesh by atomic force microscopy and rheometry. Quantitative analysis of nanomechanical properties indicated that the hydronanofiber with higher cross-linking density had higher stiffness and Derjaguin-Müller-Toporov modulus. Cells laid on the mesh and the vertical infiltration distance were visualized and quantified by confocal laser scanning microscopy. Cells on the mesh with higher cross-linking density infiltrated deeply to the bottom of the mesh. Thus, hydrogel-like nanofibrous meshes are versatile matrices allowing for deep infiltration of cells throughout the mesh via manipulation of the mechanical properties of the nanofiber.

Coil protection using small helical coils for wide-neck intracranial aneurysms: a novel approach

BACKGROUND AND PURPOSE

A number of remodeling or protective techniques available to treat wide-neck intracranial aneurysms are increasingly being used, provided that the shape/type of aneurysm, vessel diameter, and inherent course of the vessel are conducive to their use. The purpose of this study was to describe a novel method using coil protection for treatment of wide-neck aneurysms.

MATERIALS AND METHODS

This technique involves sequential maneuvers to the aneurysm and affected branch artery. A microcatheter is first introduced into the aneurysmal sac, and another microcatheter is introduced into the entrance of the branch artery, followed by partial deployment of a small helical coil into the branch artery. A framing coil is then placed within the aneurysmal sac, under the protection of the helical coil. After completion of the first coil insertion, the helical coil should be retrieved to confirm the stability of the framing coil. The helical coil can also serve as a filler.

RESULTS

This technique was successfully applied to 12 intracranial saccular aneurysms of the MCA bifurcation (5 patients); anterior communicating artery (3 patients); and A1 and M1 segments, distal ACA, and basilar tip (1 patient each). Selective endovascular treatment was successfully performed and resulted in excellent outcomes in all patients. There were no complications directly related to coil protection.

CONCLUSIONS

Our small study suggests that coil protection can be a safe alternative to traditional remodeling or protective techniques when those techniques have failed or are not possible due to vascular geometry. It is particularly suited for the treatment of wide-neck aneurysms arising from small and acutely angulated branching vessels.

Intra-arterial nimodipine infusion for cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage

This study evaluated the efficacy of intra-arterial nimodipine infusion for symptomatic vasospasm in patients with aneurysmal subarachnoid hemorrhage (aSAH). Clinical data collected from 42 consecutive patients with symptomatic vasospasm after aSAH were retrospectively reviewed. Forty-two patients underwent 101 sessions of intra-arterial nimodipine infusion. Angiographic response, immediate clinical response, and clinical outcome were evaluated at discharge and six months later. Angiographic improvement was achieved in 82.2% of patients. The immediate clinical improvement rate was 68.3%, while the deterioration rate was 5.0%. A favorable clinical outcome was achieved in 76.2% at discharge and 84.6% six months. Vasospasm-related infarction occurred in 21.4%. There was no drug-related complication. The nimodipine group showed satisfactory outcomes. Nimodipine can be recommended as an effective and safe intra-arterial agent for the treatment of symptomatic vasospasm after aSAH.

Video-based self-assessment: implementation and evaluation in an undergraduate nursing course

This research was performed to investigate the effects of video-based self-assessment on the ability of nursing students to accurately measure vital signs, their communication skills, and their satisfaction. This research was conducted between March 2007 and June 2007 as a quasi-experimental control-group, pretest-posttest design. The study population was composed of 40 second-year student nurses who enrolled in a fundamentals of nursing course of a college of nursing, Ajou University in Korea. Results of the research indicate that there was a statistically significant difference in exam scores for assessing long-term memory video-review group demonstrating higher scores. Student satisfaction was also significantly higher in the video-review group than in the control group. These results may suggest video-based self-assessment is a beneficial and effective instructional method of training undergraduate nursing students to develop awareness of their strengths and weaknesses, and to improve their clinical and communication skills.

Characterization of inwardly rectifying K(+) conductance across the basolateral membrane of rat tracheal epithelia

The rat primary cultured-airway monolayer has been an excellent model for deciphering the ion channel after nystatin permeabilization of its basolateral or apical membrane. Inwardly rectifying K(+) currents were characterized across the basolateral membrane in symmetrical HCO(-)(3)-free high K(+) Ringer's solution (125 mM) in this study. The potency of K(+) channel inhibitors against K(+) conductance was Ba(2+) (IC(50) = 5 microM) > Cs(+) (IC(50) = 2 mM) >> glybenclamide (IC(50) > 5 mM) >> TEA (IC(50) >> 100 mM). The application of basolateral Cs(+) changed K(+) conductance into an oscillating current, and its frequency (holding voltage = -100 mV) increased with increase in concentration of basolateral Cs(+) (0.05-5 mM) and in degree of hyperpolarization. Addition of basolateral Cs(+) blocked inward current strongly at -100 mV and hardly at all at -60 mV, giving a sharp curvature to the I-V relation of the IRK current. RT-PCR, Western blotting, and immunohistochemical analyses showed that Kir2.1 might be present in basolateral membrane of tracheal epithelia and plasma membrane of pulmonary alveolar cells.

Nerve terminals form but fail to mature when postsynaptic differentiation is blocked: in vivo analysis using mammalian nerve-muscle chimeras

To better understand the role of the postsynaptic cell in the differentiation of presynaptic terminals, we transplanted muscles that lacked postsynaptic differentiation from mutant mice into normal adult immunocompatible hosts and attached the host nerve to the grafts. Host motor axons innervated wild-type grafted muscle fibers and established normal appearing chimeric neuromuscular junctions. By repeated in vivo imaging, we found that these synapses were stably maintained. Results were different when nerves entered transplanted muscles derived from mice lacking muscle-specific receptor tyrosine kinase (MuSK) or rapsyn, muscle-specific components required for postsynaptic differentiation. Initial steps in presynaptic differentiation (e.g., formation of rudimentary arbors and vesicle clustering at terminals) occurred when wild-type neurites contacted MuSK- or rapsyn deficient muscle fibers, either in vivo or in vitro. However, wild-type terminals contacting MuSK or rapsyn mutant muscle fibers were unable to mature, even when the chimeras were maintained for up to 7 months. Moreover, in contrast to the stability of wild-type synapses, wild-type nerve terminals in mutant muscles underwent continuous remodeling. These results suggest that postsynaptic cells supply two types of signals to motor axons: ones that initiate presynaptic differentiation and others that stabilize the immature contacts so that they can mature. Normal postsynaptic differentiation appears to be dispensable for initial stages of presynaptic differentiation but required for presynaptic maturation.

The presynaptic calcium channel is part of a transmembrane complex linking a synaptic laminin (alpha4beta2gamma1) with non-erythroid spectrin

Nerve regeneration studies at the neuromuscular junction (NMJ) suggest that synaptic basal lamina components tell the returning axon where to locate neurotransmitter release machinery, including synaptic vesicle clusters and active zones. Good candidates for these components are the synaptic laminins (LNs) containing alpha4, alpha5, or beta2 chains. Results from a beta2 laminin knockout mouse have suggested a linkage of this extracellular laminin to cytosolic synaptic vesicle clusters. Here we report such a transmembrane link at the electric organ synapse, which is homologous to the NMJ. We immunopurified electric organ synaptosomes and found on their surface two laminins of 740 and 900 kDa. The 740 kDa laminin has a composition of alpha4beta2gamma1 (laminin-9). Immunostaining reveals that as in the NMJ, alpha4 and beta2 chains are concentrated at the electric organ synapse. Using detergent-solubilized synaptosomes, we immunoprecipitated a complex containing alpha4beta2gamma1 laminin, the voltage-gated calcium channel, and the cytoskeletal protein spectrin. Other presynaptic proteins such as 900 kDa laminin are not found in this complex. We hypothesize that alpha4beta2gamma1 laminin in the synaptic basal lamina attaches to calcium channel, which in turn is attached to cytosolic spectrin. Spectrin could then organize synaptic vesicle clusters by binding vesicle-associated proteins.

The synaptic vesicle protein SV2 is complexed with an alpha5-containing laminin on the nerve terminal surface

Interactions between growing axons and synaptic basal lamina components direct the formation of neuromuscular junctions during nerve regeneration. Isoforms of laminin containing alpha5 or beta2 chains are potential basal lamina ligands for these interactions. The nerve terminal receptors are unknown. Here we show that SV2, a synaptic vesicle transmembrane proteoglycan, is complexed with a 900-kDa laminin on synaptosomes from the electric organ synapse that is similar to the neuromuscular junctions. Although two laminins are present on synaptosomes, only the 900-kDa laminin is associated with SV2. Other nerve terminal components are absent from this complex. The 900-kDa laminin contains an alpha5, a beta1, and a novel gamma chain. To test whether SV2 directly binds the 900-kDa laminin, we looked for interaction between purified SV2 and laminin-1, a laminin isoform with a similar structure. We find SV2 binds with high affinity to purified laminin-1. Our results suggest that a synaptic vesicle component may act as a laminin receptor on the presynaptic plasma membrane; they also suggest a mechanism for activity-dependent adhesion at the synapse.

Comparison of localizing values of various diagnostic tests in non-lesional medial temporal lobe epilepsy

Though the surgical treatment for medial temporal lobe epilepsy yields a high success rate, more studies are needed in order to determine the most efficacious pre-operative algorithm. The authors studied the relationship between surgical outcome and the localization results of various pre-operative diagnostic tests to assess the predictive value. Seventy-one consecutive patients who had undergone anterior temporal lobectomy with amygdalohippocampectomy with the diagnosis of non-lesional medial temporal lobe epilepsy, who had been followed up more than 24 months, were analyzed retrospectively. Electroencephalogy (EEG), magnetic resonance imaging (MRI), proton emission tomography (PET), single photon emission computed tomography (SPECT), the Wada test, and neuropsychological testing were analyzed. There was no diagnostic test that was found to have a statistically significant relationship between Engel Class I outcome and localization results (P & 0.05). SPECT, neuropsychological testing, and the Wada test all had less predictive values (P < 0.01). EEG and PET had comparable predictive values for Engel Class I with MRI (P & 0.05). No single diagnostic test alone is sufficient to make a diagnosis of non-lesional medial temporal lobe epilepsy. MRI, EEG and PET had comparable predictive values for Engel Class I. SPECT, neuropsychological testing, and the Wada test had less predictive values.

Induction of presynaptic differentiation in cultured neurons by extracellular matrix components

Motoneurons reinnervating skeletal muscles form nerve terminals at sites of contact with a specialized basal lamina. To analyse the molecules and mechanisms that underly these responses, we introduce two systems in which basal lamina-derived components induce presynaptic differentiation of cultured neurons from chick ciliary ganglia in the absence of a postsynaptic cell. In one, ciliary neurites that contact substrates coated with a recombinant laminin beta2 fragment form varicosities that are rich in synaptic vesicle proteins, depleted of neurofilaments, and capable of depolarization-dependent exocytosis and endocytosis. Thus, a single molecule can trigger a complex, coordinated program of presynaptic differentiation. In a second system, neurites growing on cryostat sections of adult kidney form vesicle-rich, neurofilament-poor arbors on glomeruli. Glomerular basal lamina, like synaptic basal lamina, is rich in laminin beta2 and collagen (alpha3-5) IV. However, glomeruli from mutant mice lacking these proteins were capable of inducing differentiation, suggesting the glomerulus as a source of novel presynaptic organizing molecules.

Mice lacking alpha-calcitonin gene-related peptide exhibit normal cardiovascular regulation and neuromuscular development

alpha-Calcitonin gene-related peptide (alphaCGRP) is a pleiotropic peptide neuromodulator that is widely expressed throughout the Central and peripheral nervous systems. CGRP has been implicated in a variety of physiological processes including peripheral vasodilation, cardiac acceleration nicotinic acetylcholine receptor (AChR) synthesis and function, testicular descent, nociception, carbohydrate metabolism, gastrointestinal motility, neurogenic inflammation, and gastric acid secretion. To provide a better understanding of the physiological role(s) mediated by this peptide neurotransmitter, we have generated alphaCGRP-null mice by targeted modification in embryonic stem cells. Mice lacking alpha CGRP expression demonstrate no obvious phenotypic differences from their wild-type littermates. Detailed analysis of systemic cardiovascular function revealed no differences between control and mutant mice regarding heart rate and blood pressure under basal or exercise-induced conditions and subsequent to pharmacological manipulation. Characterization of neuromuscular junction in morphology including nicotinic receptor localization, terminal sprouting in response to denervation, developmental regulation of AChR subunit expression, and synapse elimination also revealed no differences in alphaCGRP-deficient animals. These results suggest that alphaCGRP is not required for the systemic regulation of cardiovascular hemodynamics or development of the neuromuscular junction.

Alternatively spliced isoforms of nerve- and muscle-derived agrin: their roles at the neuromuscular junction

Agrin induces synaptic differentiation at the skeletal neuromuscular junction (NMJ); both pre- and postsynaptic differentiation are drastically impaired in its absence. Multiple alternatively spliced forms of agrin that differ in binding characteristics and bioactivity are synthesized by nerve and muscle cells. We used surgical chimeras, isoform-specific mutant mice, and nerve-muscle cocultures to determine the origins and nature of the agrin required for synaptogenesis. We show that agrin containing Z exons (Z+) is a critical nerve-derived inducer of postsynaptic differentiation, whereas neural isoforms containing a heparin binding site (Y+) and all muscle-derived isoforms are dispensable for major steps in synaptogenesis. Our results also suggest that the requirement of agrin for presynaptic differentiation is mediated indirectly by its ability to promote postsynaptic production or localization of appropriate retrograde signals.

Development of the neuromuscular junction: genetic analysis in mice

Formation of the skeletal neuromuscular junction is a multi-step process that requires communication between the nerve and muscle. Studies in many laboratories have led to identification of factors that seem likely to mediate these interactions. 'Knock-out' mice have now been generated with mutations in several genes that encode candidate transsynaptic messengers and components of their effector mechanisms. Using these mice, it is possible to test hypotheses about the control of synaptogenesis. Here, we review our studies on neuromuscular development in mutant mice lacking agrin alpha CGRP, rapsyn, MuSK, dystrophin, dystrobrevin, utrophin, laminin alpha 5, laminin beta 2, collagen alpha 3 (IV), the acetylcholine receptor epsilon subunit, the collagenous tail of acetylcholinesterase, fibroblast growth factor-5, the neural cell adhesion molecule, and tenascin-C.

Release properties of isolated neuromuscular boutons of the garter snake

1. Motor nerve terminals innervating fibres in the transversus abdominis muscle of the garter snake comprise discrete boutons. Using a combination of enzymatic digestion and mechanical manipulation, individual boutons were removed from living terminals for study in isolation. 2. Boutons freed from terminals were usually allowed to remain in their original location on the endplate ('attached' one-bouton synapse). Alternatively, they were removed from the endplate, and then placed on the same or another vacant endplate site to form a 'reconstructed' one-bouton synapse. When removed from the endplate, boutons were 2-4 microns in diameter and nearly spherical in shape, in contrast to the variety of complex shapes seen among boutons still in contact with muscle fibre endplates. 3. Transmitter release was assessed by intracellular recording from the postsynaptic fibre. Boutons produced spontaneous miniature endplate potentials (MEPPs) of nearly normal amplitude; extracellular stimulation elicited endplate potentials (EPPs) which resembled MEPPs. Typical EPP amplitudes fluctuated between zero and five quanta per stimulus. For low-frequency stimulation under normal physiological conditions, mean quantal content, m, averaged 1.4; the binomial number of release sites, n, averaged 2.4; and the binomial probability of release, p, averaged 0.57. Statistics of the quantal fluctuations recorded from single boutons agreed only approximately with predictions of simple binomial theory, the discrepancy being that the apparent number of quanta released exceeded n in 5% of the events. 4. In separate experiments, activity-dependent probes were used to locate rare naturally occurring nerve terminals comprising a single bouton. Activation of these small synapses evoked quantal responses similar to those of attached and reconstructed one-bouton synapses described above.

Schwann cells induce and guide sprouting and reinnervation of neuromuscular junctions

The "terminal' Schwann cells that sit atop the neuromuscular junction sense neuromuscular transmission and respond to perturbations of this transmission by extending long processes. These processes have the ability to induce nerve growth and serve as substrates to guide this growth. These processes thus play major roles in muscle reinnervation and in sprouting. An absence of nerve sprouting is correlated with the apoptotic death of terminal Schwann cells at denervated endplates in neonatal muscles. Thus, Schwann cells appear to participate actively in the maintenance and repair of neuromuscular synapses.

Schwann cell processes guide regeneration of peripheral axons

Terminal Schwann cells overlying the neuromuscular junction sprout elaborate processes upon muscle denervation. We show here that motor axons use these processes as guides/substrates during regeneration; in so doing, they escape the confines of endplates and grow between endplates to generate polyneuronal innervation. We also show that Schwann cells in the nerve provide similar guidance. Axons extend from the cut end of a nerve in association with Schwann cell processes and appear to navigate along them. The processes extend from axotomized nerves at the same rate and in the same manner as they do from axon-containing nerves. The rate of process extension limits the rate at which axons regenerate. Thus, Schwann cell processes lead and guide peripheral regeneration.

Nerve sprouting in muscle is induced and guided by processes extended by Schwann cells

Partial denervation or paralysis with botulinum toxin, manipulations that induce sprouting of nerve terminals in muscle, also induced terminal Schwann cells to extend processes. These processes were associated with every nerve sprout and in some cases were longer than the sprouts that appeared to be growing along them. Following partial denervation, more than 70% of the nerve sprouts that grew to innervate nearby denervated endplates were associated with Schwann cell processes that had extended from the denervated endplates, i.e., in the direction opposite to nerve growth. Implantation of Schwann cells into an innervated muscle induced sprouting upon contact of an axon or nerve terminal by Schwann cell processes. These observations show that Schwann cells induce and guide axonal sprouting in muscle.

Differential neural regulation of a neuromuscular junction-associated antigen in muscle fibers and Schwann cells

Monoclonal antibodies 3G2 and 4E2 recognize a postsynaptic component of rat neuromuscular junctions. In contrast to many other postsynaptic junctional antigens, expression of this antigen is nerve-dependent: immunoreactivity disappears from junctions following denervation and returns upon reinnervation (Astrow et al., 1992 J. Neurosci. 12:1602-1615). Here we show that the epitope is also expressed by Schwann cells and that this expression is also neurally regulated. Weak mAb 3G2/4E2 immunoreactivity was found in myelinating Schwann cells but was not detected in either nonmyelinating Schwann cells or in terminal Schwann cells at the neuromuscular junction. Following axotomy, immunoreactivity increased in myelinating Schwann cells, and nonmyelinating and terminal Schwann cells became immunopositive. Moreover, the immunoreactivity in terminal Schwann cells revealed their extensive sprouting in response to denervation (Reynolds and Woolf, 1992, J. Neurocytol. 21: 50-66). After nerve regeneration, mAb 3G2/4E2 immunoreactivity in all Schwann cells returned towards normal: it disappeared from terminal Schwann cells, returned to low levels in myelinating Schwann cells, and decreased in nonmyelinating Schwann cells. Immunoblots of axotomized nerve and cultured muscle fibers revealed the same set of immunoreactive bands. Therefore, Schwann cells and muscle fibers share the expression of an epitope that is under neural control, but is regulated differently at each site. In Schwann cells, the presence of the nerve suppresses expression of the epitope, whereas in muscle fibers, the nerve terminal promotes this expression. The differential regulation of mAb 3G2/4E2 immunoreactivity in terminal Schwann cells and muscle fibers suggests that the epitope may be involved in interactions between nerve terminals and these cells.