Neuroprotective effects of extracellular glutamate are absent in hippocampal organotypic cultures treated with the amyloid peptide Aβ25–35

Hippocampal cells are particularly vulnerable in Alzheimer’s disease but the cause of cell death is unknown. Amyloid toxicity has been implicated in hippocampal cell death, but its specific mechanisms are poorly understood. We used confocal microscopy to examine the effects of the amyloid peptide fragment 25–35 (Aβ_25–35) on cell death in organotypic hippocampal slice cultures. Addition of glutamate to the culture medium significantly improved nerve cell survival in cultures subjected to consecutive medium exchanges. This effect was lost if cultures were treated with the amyloid peptide fragment Aβ_25–35 but not the inactive peptide 35–25. These data suggest that one of the mechanisms responsible for amyloid toxicity may be inhibition of the survival promoting effects of extracellular glutamate.     

CX3CR1-dependent renal macrophage survival promotes Candida control and host survival

Systemic Candida albicans infection causes high morbidity and mortality and is associated with neutropenia; however, the roles of other innate immune cells in pathogenesis are poorly defined. Here, using a mouse model of systemic candidiasis, we found that resident macrophages accumulated in the kidney, the main target organ of infection, and formed direct contacts with the fungus in vivo mainly within the first few hours after infection. Macrophage accumulation and contact with Candida were both markedly reduced in mice lacking chemokine receptor CX₃CR1, which was found almost exclusively on resident macrophages in uninfected kidneys. Infected Cx3cr1^–/– mice uniformly succumbed to Candida-induced renal failure, but exhibited clearance of the fungus in all other organs tested. Renal macrophage deficiency in infected Cx3cr1^–/– mice was due to reduced macrophage survival, not impaired proliferation, trafficking, or differentiation. In humans, the dysfunctional CX₃CR1 allele CX₃CR1-M280 was associated with increased risk of systemic candidiasis. Together, these data indicate that CX₃CR1-mediated renal resident macrophage survival is a critical innate mechanism of early fungal control that influences host survival in systemic candidiasis.     

Effects of different kinds of meshes on postoperative adhesion formation in the New Zealand White rabbit

The aim of this study was to compare the effect of different kinds of surgical meshes on postoperative adhesion formation. Forty-two New Zealand White rabbits were studied. The rabbits were grouped into six groups, according to the type of surgical meshes (Prolene, Mersilene, Vypro, polytetraflouroethylene (PTFE), Proceed and control group) implanted into the peritoneum cavity. Thirty days after the operation, the relaparotomies were carried out, and any adhesions observed between the implanted mesh and tissues were evaluated and graded. The mean adhesion degree was 9.2 in the Mersilene mesh group, 9.5 in the Prolene mesh group, 9.7 and in the Vypro mesh group (P > 0.05). The mean adhesion degree was 1 in the control group, 2.75 in the Proceed mesh group and 2.25 in the PTFE mesh group. There was a significant difference in adhesion degree between the control, Proceed and PTFE groups and the Prolene, Mersilene and Vypro mesh groups. The adhesion degree was significantly lower in the Proceed and PTFE mesh groups when comparing them with the Prolene, Mersilene and Vypro meshes.     

Single vs. multiple fraction regimens for palliative radiotherapy treatment of multiple myeloma

Purpose

To compare the impact of a single fraction (8?Gy × 1?fraction) and multifraction (3?Gy × 10?fractions) radiotherapy regimens on pain relief, recalcification and the quality of life (QoL) in patients with bone destructions due to multiple myeloma (MM).

Patients and methods

In all, 101 patients were included in a randomised prospective clinical trial: 58 patients were included in the control arm (3?Gy × 10?fractions) and 43 patients into the experimental arm (8?Gy × 1?fraction). The response rate was defined according to the International Consensus on Palliative Radiotherapy criteria. Recalcification was evaluated with radiographs. QoL questionnaires were completed before and 4 weeks after treatment.

Results

Pain relief was obtained in 81/101 patients (80.2%): complete response in 56 (69%) and partial in 25 patients (30.9%). No significant differences were observed in analgesic response between the groups. Significant factors for pain relief were female gender, age under 65, IgG MM type, presence of recalcification at the irradiated site. Recalcification was found in 32/101 patients (33.7%): complete in 17 (53.2%) and partial in 15 (46.2%). No significant differences were observed in recalcification between the groups. Significant factors for recalcification were Karnofsky index ≥ 60%, haemoglobin level ≤ 80?g/dl, MM stage II and analgesic response at the irradiated site. The QoL after radiotherapy was improved in the control group.

Conclusion

The same analgesic and recalcification response was observed using two different radiotherapy regimens. Higher doses should be used to achieve a better QoL.

     

A potential role for PDGF-C in experimental and clinical proliferative vitreoretinopathy

PURPOSE: Proliferative vitreoretinopathy (PVR) is a disorder characterized by the formation of cellular membranes on both surfaces of the retina and within the vitreous cavity. It occurs in 5% to 10% of patients who undergo retinal reattachment surgery. In the rabbit model of the disease, the platelet-derived growth factor alpha receptor (PDGFRalpha) is dramatically more capable of promoting PVR than is closely related PDGFRbeta. To test the ligand hypothesis (i.e., that this phenomenon can be explained by a predominance of PDGFRalpha-specific ligands) this study was conducted to determine the profile of PDGF ligands expressed by cells that induce PVR and in the vitreous of rabbits that have PVR. In addition, we examined which PDGF isoforms were present in the vitreous of patients with PVR, to assess the relevance of the rabbit model to the clinical setting. METHODS: PDGF isoforms were detected and quantified by Western blot analysis and ELISA. An assay was performed of conditioned medium from mouse embryo fibroblasts expressing the PDGFRalpha (Falpha) and rabbit conjunctival fibroblasts (RCFs), both of which cause PVR in the experimental model, and from human retinal pigment epithelial cells (ARPE-19). Because PDGF-C is secreted in a latent form and must be proteolytically processed to become biologically active, a PDGF-C processing assay was established, and conditioned medium was tested from these cells lines, for processing activity. Vitreous specimens, from control and PVR rabbits and from patients undergoing vitrectomy surgery, either to repair retinal detachment or for other reasons, were also tested for PDGF isoforms and for PDGF-C processing activity. RESULTS: PDGF isoforms that activate PDGFRbeta (PDGF-B and -D) were either undetectable or were present at very low levels in all the samples tested. Relatively low levels of PDGF-A and -AB were detected, whereas PDGF-C was the predominant isoform. Falpha, RCFs, and ARPE-19 cells accumulated PDGF-C in the conditioned medium at an average rate of 2.0 +/- 0.2, 2.9 +/- 0.3, and 71.3 +/- 6.0 ng/mL per day, respectively. Although there was no detectable PDGF-C in the vitreous of control rabbits (n = 8), there was an average of 1784 +/- 1150 ng/mL latent PDGF-C in the vitreous from rabbits with PVR (n= 14). Of the patients with PVR, eight of nine contained PDGF-C (range, 50-1000 ng/mL). In contrast, PDGF-C was detected in only 1 of 16 of the patients without PVR. In both conditioned medium and vitreous samples, the latent (instead of the active) form of PDGF-C was detected, even though processing activity was present in all the samples tested. CONCLUSIONS: The predominance of PDGF isoforms that activate PDGFRalpha support the ligand hypothesis as an explanation of why PDGFRalpha is more capable of inducing PVR than is PDGFRbeta. Furthermore, the profile of PDGF isoforms observed in the rabbit model accurately reflected the clinical specimens from patients with PVR. Finally, these findings implicate one of the new PDGF family members as an important contributor to experimental and clinical PVR.     

Anesthetic complications of awake craniotomies for epilepsy surgery

Awake craniotomies are often performed for resection of epileptogenic foci close to vital areas of the brain. For awake craniotomies at our institution, propofol is infused during local anesthetic injection and craniotomy, spontaneous ventilation is preserved, and no endotracheal tube or laryngeal mask airway is used. Propofol is discontinued for language, motor, and/or sensory mapping and for electrocorticography. Patients are re-sedated with propofol for resection and closure. We performed a retrospective chart review of 332 propofol-based "asleep-awake-asleep" (AAA) techniques with unsecured airways and 129 general anesthesia with endotracheal intubation craniotomies for epilepsy surgery. We compared the incidence of intraoperative respiratory and hemodynamic complications and incidence of seizures, nausea, brain swelling, patient movement, bleeding, aspiration, air embolism, and death. Airway compromise was uncommon in AAA cases and although incidences of hypertension, hypotension, and tachycardia were statistically increased in AAA versus general anesthesia craniotomy, these were treated appropriately. In only one patient the use of our AAA technique may have contributed to a poor clinical outcome.     

Neuroprotection against NMDA excitotoxicity by group I metabotropic glutamate receptors is associated with reduction of NMDA stimulated currents

The neurotransmitter glutamate can have both excitotoxic and protective effects on neurons. The excitotoxic effects have been intensively studied, whereas the protective effects, including the involvement of metabotropic glutamate receptors (mGluRs), remain unclear. In the present study, we tested the protective effects of the group-I-mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) on organotypic hippocampal slice cultures exposed to excitotoxic concentrations of N-methyl-D-aspartate (NMDA). Effects of DHPG on electrophysiological responses induced by NMDA receptor activation were also recorded. Experiments were performed on organotypic hippocampal slice cultures derived from 7-day-old rats, with cellular uptake of propidium iodide as a marker for neuronal cell death. Slice cultures pretreated with DHPG (10 or 100 microM) for 2 h prior to exposure to 50 microM NMDA for 30 min displayed reduced propidium iodide uptake, compared to cultures exposed to NMDA only. The neuroprotective effect was confirmed by Hoechst 33342 staining, where the appearance of pycnotic nuclei after NMDA treatment was prevented by the DHPG pretreatment. Using caspase-3 activity to monitor the presence of apoptosis, failed to demonstrate this type of cell death in CA1 after NMDA application. The protective effect of DHPG was abolished by the mGluR1 selective antagonist (S)-(+)-alpha-amino-4-carboxy-2-methylbenzeneacetic acid (LY367385; 5 or 10 microM), whereas the mGluR5-selective antagonist 2-methyl-6-phenylethynylpyridine (MPEP; 1 microM) had no effect. Voltage-clamping of CA1 pyramidal cells in cultures treated with 10 microM DHPG for 2 h showed a significant depression of NMDA-induced inward currents compared to untreated controls. We conclude that neuroprotection induced by activation of group-I-mGluRs involve mGluR1 and is associated with decreased NMDA-stimulated currents.