Membrane interactions of Ocellatins. Where do antimicrobial gaps stem from?

The antimicrobial peptides Ocellatin-LB1, -LB2 and -F1, isolated from frogs, are identical from residue 1 to 22, which correspond to the -LB1 sequence, whereas -LB2 carries an extra N and -F1 additional NKL residues at their C-termini. Despite the similar sequences, previous investigations showed different spectra of activities and biophysical investigations indicated a direct correlation between both membrane-disruptive properties and activities, i.e., ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. This study presents experimental evidence as well as results from theoretical studies that contribute to a deeper understanding on how these peptides exert their antimicrobial activities and how small differences in the amino acid composition and their secondary structure can be correlated to these activity gaps. Solid-state NMR experiments allied to the simulation of anisotropic NMR parameters allowed the determination of the membrane topologies of these ocellatins. Interestingly, the extra Asn residue at the Ocellatin-LB2 C-terminus results in increased topological flexibility, which is mainly related to wobbling of the helix main axis as noticed by molecular dynamics simulations. Binding kinetics and thermodynamics of the interactions have also been assessed by Surface Plasmon Resonance and Isothermal Titration Calorimetry. Therefore, these investigations allowed to understand in atomic detail the relationships between peptide structure and membrane topology, which are in tune within the series -F1 > > -LB1 ≥ -LB2, as well as how peptide dynamics can affect membrane topology, insertion and binding.

Cytoskeletal architecture and cell motility remain unperturbed in mouse embryonic fibroblasts from Plk3 knockout mice.

Polo-like kinase 3 (Plk3) is best known for its involvement in cell cycle checkpoint regulation following exposure to cytotoxicants or induction of DNA damage. Yet, Plk3 has also been implicated in roles beyond those of cellular responses to DNA damage. Here, we have investigated the proposition, suggested by the Plk literature, that Plk3 regulates cytoskeletal architecture and cell functions mediated by the cytoskeleton. To this end, we have assayed mouse embryonic fibroblasts (MEFs) generated from both Plk3 knockout and wild-type mice. In particular, we asked whether Plk3 is involved in actin fiber and microtubule integrity, cell migration, cell attachment, and/or cell invasion. Our results demonstrate that functional Plk3 is not critical for the regulation of cytoskeletal integrity, cell morphology, cell adhesion, or motility in MEFs.

Mechanical insertion properties of calcium-phosphate implant coatings.

OBJECTIVES: To investigate the influence of protein incorporation on the resistance of biomimetic calcium-phosphate coatings to the shear forces that are generated during implant insertion. MATERIALS AND METHODS: Thirty-eight standard (5 × 13 mm) Osseotite® implants were coated biomimetically with a layer of calcium phosphate, which either lacked or bore a co-precipitated (incorporated) depot of the model protein bovine serum albumin (BSA). The coated implants were inserted into either artificial bone (n=18) or the explanted mandibles of adult pigs (n=12). The former set-up was established for the measurement of torque and of coating losses during the insertion process. The latter set-up was established for the histological and histomorphometric analysis of the fate of the coatings after implantation. RESULTS: BSA-bearing coatings had higher mean torque values than did those that bore no protein depot. During the insertion process, less material was lost from the former than from the latter type of coating. The histological and histomorphometric analysis revealed fragments of material to be sheared off from both types of coating at vulnerable points, namely, at the tips of the threads. The sheared-off fragments were retained within the peri-implant space. CONCLUSION: The incorporation of a protein into a biomimetically prepared calcium-phosphate coating increases its resistance to the shear forces that are generated during implant insertion. In a clinical setting, the incorporated protein would be an osteogenic agent, whose osteoinductive potential would not be compromised by the shearing off of coating material, and the osteoconductivity of an exposed implant surface would not be less than that of a coated one.

High seroprevalence of herpes simplex virus type 2 infection in French human immunodeficiency virus type 1-infected outpatients.

Using commercially available herpes simplex virus (HSV) type-specific serological diagnostic tests, HSV type 2 (HSV-2) antibody prevalence was assessed in two parallel prospective studies including 534 human immunodeficiency virus type 1 (HIV-1)-infected outpatients living in two areas of northern France. In the first cohort of 434 subjects, 223 (51%) individuals demonstrated a positive HSV-2 serological status while 66 (66%) of 100 subjects in the second cohort were seropositive for HSV-2 (51 versus 66%; P = 0.08). Among the 223 HSV-2-seropositive subjects identified in the first study cohort, only 22 (10%) had suffered from recurrent anogenital lesions during the past 12 months while 154 (69%) had no clinical history of herpesvirus infection. Our findings demonstrate high proportions of subclinical and undiagnosed HSV-2 infection in HIV-1-infected individuals and suggest that HSV type-specific serological testing in the French HIV-1-infected subpopulation could be an efficient strategy to diagnose clinically asymptomatic HSV-2 infections.

Automatic cardiac event recorders reveal paroxysmal atrial fibrillation after unexplained strokes or transient ischemic attacks.

BACKGROUND: The etiology of stroke or transitory ischemic attack (TIA) remains frequently unknown. While paroxysmal atrial fibrillation (PAF) is often suspected, its presence remains difficult to establish. Therefore, we investigated the occurrence of PAF episodes in such a population using a long-term automatic cardiac event recorder. METHODS: We prospectively investigated 60 consecutive subjects admitted in our university hospital for stroke (n=44) or TIA (n=16), adding long-term automatic cardiac event recorders, with a target duration of 4 days, to standard investigations, which included 12-lead ECGs and 24-hour Holter recordings. RESULTS: In 28 patients no etiology was found for their stroke or TIA. However, one or more than one PAF episode was found in 4 of them (14.3%) using the long-term automatic event recorder. In the 32 remaining patients, 8 presented with PAF, and this was considered as the cause of their stroke. In both groups, AF was paroxysmal. The PAF episodes' duration went from 1 to 96 hours (mean +/- standard deviation, 18 hours and 30 minutes+/-30 hours). CONCLUSIONS: Patients suffering PAF episodes after ischemic stroke or TIA were statistically less often recognized using the 24-hour Holter ECG recording alone than the R-Test Evolution alone.

Objective tinnitus associated with essential laryngeal myoclonus: report of two cases.

We report on two patients with an objective tinnitus. In the first one, the objective tinnitus was unique as it was due to bilateral rhythmic contractions of the vocal cords. In the second, the objective tinnitus arose from Eustachian tube contractions and was associated with up and down movements of the larynx. In both patients, the abnormal laryngeal movement shared most of the characteristics of palatal or palatolaryngeal myoclonus and was thought to be laryngeal myoclonus. Its origin remained essential as all the investigations were negative.

Paraneoplastic peripheral neuropathy associated with anti-Hu antibodies. A clinical and electrophysiological study of 20 patients.

Although paraneoplastic subacute sensory neuronopathy is the most frequent presentation of peripheral neuropathy in patients with anti-Hu antibodies, other neuropathies have been reported. In order to investigate the clinical and electrophysiological manifestations of neuropathies associated with anti-Hu antibodies, we conducted a retrospective study of 20 patients. For the electrophysiological study, each nerve was classified as normal, demyelinating, axonal/neuronal or axonal/demyelinating. Peripheral neuropathy was the presenting symptom in 95% of patients. CNS and autonomic neuropathy were present in 40% and 30% of patients, respectively. The course of the neuropathy was acute, mimicking Guillain-Barré syndrome in one patient (5%), and subacute (55%) or progressive (40%) in the others. Clinically, the neuropathy was sensory (70%), sensorimotor (25%) or motor (5%). At onset, symptoms were symmetrical (65%), asymmetrical (25%) or multifocal (10%). Pain was a predominant manifestation (80%). Amyotrophia and fasciculations were rare. The median Rankin's score was 2, three patients having an indolent form. Electrophysiology showed the axonal/neuronal pattern to be the most frequent (46.9% of studied nerves); an axonal/demyelinating or demyelinating pattern being seen in 18.3% and 4.9% of nerves, respectively. The axonal/neuronal pattern was more frequent in sensory nerves and the mixed axonal/demyelinating pattern more frequent in motor nerves (P < 0.01). A higher proportion of abnormal nerves correlated with a progressive course (P < 0.05) or a Rankin's score between 3 and 5 (P < 0.01). In patients with sensory neuropathy, 88.5% of sensory nerves were abnormal, mostly with an axonal/neuronal pattern. In addition, 47% of motor nerves were abnormal so that only four out of 14 patients with a clinically pure sensory neuropathy (28.6%) had an electrophysiological pattern typical of sensory neuronopathy. In patients with a sensorimotor neuropathy, 96.6% of sensory and 71% of motor nerves were abnormal. The only statistical difference between sensory and sensorimotor neuropathies was that patients with sensorimotor neuropathy had more frequent motor nerve involvement (P < 0.05) without differences concerning the distribution of the abnormal patterns. Needle neuromyography showed only limited evidence of motor neurone degeneration in both sensory and sensorimotor neuropathy. The present work shows that the typical clinical and electrophysiological pattern of subacute sensory neuronopathy is rarely encountered in patients with anti-Hu antibody and that motor nerve involvement is frequently seen, even in the absence of a motor deficit. In addition to their potential pathophysiological involvement in the mechanism of the paraneoplastic neuropathy, these findings have practical consequences for the diagnosis of the disorder.