Benoit Schaller

Effects of cerebral perfusion pressure and increased fraction of inspired oxygen on brain tissue oxygen, lactate and glucose in patients with severe head injury

Summary¶Objective. The purpose of the study was to measure the effects of increased inspired oxygen on patients suffering severe head injury and consequent influences on the correlations between CPP and brain tissue oxygen (PtiO2) and the effects on brain microdialysate glucose and lactate. Methods. In a prospective, observational study 20 patients suffering severe head injury (GCS≤8) were studied between January 2000 and December 2001. Each patient received an intraparenchymal ICP device and an oxygen sensor and, in 17 patients brain microdialysis was performed at the cortical-subcortical junction. A 6 h 100% oxygen challenge (FIO2 1.0) (Period A) was performed as early as possible in the first 24 hours after injury and compared with a similar 6 hour period following the challenge (Period B). Statistics were performed using the linear correlation analysis, one sample t-test, as well as the Lorentzian peak correlation analysis. Results. FIO2 was positively correlated with PtiO2 (p<0.0001) over the whole study period. PtiO2 was significantly higher (p<0.001) during Period A compared to Period B. CPP was positively correlated with PtiO2 (p<0.001) during the whole study. PtiO2 peaked at a CPP value of 78 mmHg performing a Lorentzian peak correlation analysis of all patients over the whole study. During Period A the brain microdialysate lactate was significantly lower (p=0.015) compared with Period B. However the brain microdialysate glucose remained unchanged. Conclusion. PtiO2 is significantly positively correlated with FIO2, meaning that PtiO2 can be improved by the simple manipulation of increasing FIO2 and ABGAO2. PtiO2 is positively correlated with CPP, peaking at a CPP value of 78 mmHg. Brain microdialysate lactate can be lowered by increasing PtiO2 values, as observed during the oxygen challenge, whereas microdialysate glucose is unchanged during this procedure. Extension of the oxygen challenge time and measurement of the intermediate energy metabolite pyruvate may clarify the metabolic effects of the intervention. Prospective comparative studies, including analysis of outcome on a larger multicenter basis, are necessary to assess the long term clinical benefits of this procedure.

The GDNF family members neurturin, artemin and persephin promote the morphological differentiation of cultured ventral mesencephalic dopaminergic neurons.

Neurturin (NRTN), artemin (ARTN), persephin (PSPN) and glial cell line-derived neurotrophic factor (GDNF) form a group of neurotrophic factors, also known as the GDNF family ligands (GFLs). They signal through a receptor complex composed of a high-affinity ligand binding subunit, postulated ligand specific, and a common membrane-bound tyrosine kinase RET. Recently, also NCAM has been identified as an alternative signaling receptor. GFLs have been reported to promote survival of cultured dopaminergic neurons. In addition, GDNF treatments have been shown to increase morphological differentiation of tyrosine hydroxylase immunoreactive (TH-ir) neurons. The present comparative study investigated the dose-dependent effects of GFLs on survival and morphological differentiation of TH-ir neurons in primary cultures of E14 rat ventral mesencephalon. Both NRTN and ARTN chronically administered for 5 days significantly increased survival and morphological differentiation of TH-ir cells at all doses investigated [0.1-100 ng/ml], whereas PSPN was found to be slightly less potent with effects on TH-ir cell numbers and morphology at 1.6-100 ng/ml and 6.3-100 ng/ml, respectively. In conclusion, our findings identify NRTN, ARTN and PSPN as potent neurotrophic factors that may play an important role in the structural development and plasticity of ventral mesencephalic dopaminergic neurons.

GDNF family ligands display distinct action profiles on cultured GABAergic and serotonergic neurons of rat ventral mesencephalon.

Glial-cell-line-derived neurotrophic factor (GDNF), neurturin (NRTN), artemin (ARTN) and persephin (PSPN), known as the GDNF family ligands (GFLs), influence the development, survival and differentiation of cultured dopaminergic neurons from ventral mesencephalon (VM). Detailed knowledge about the effects of GFLs on other neuronal populations in the VM is essential for their potential application as therapeutic molecules for Parkinsons disease. Hence, in a comparative study, we investigated the effects of GFLs on cell densities and morphological differentiation of gamma-aminobutyric acid-immunoreactive (GABA-ir) and serotonin-ir (5-HT-ir) neurons in primary cultures of E14 rat VM. We observed that all GFLs [10 ng/ml] significantly increased GABA-ir cell densities (1.6-fold) as well as neurite length/neuron. However, only GDNF significantly increased the number of primary neurites/neuron, and none of the GFLs affected soma size of GABA-ir neurons. In contrast, only NRTN treatment significantly increased 5-HT-ir cells densities at 10 ng/ml (1.3-fold), while an augmentation was seen for GDNF and PSPN at 100 ng/ml (2.4-fold and 1.7-fold, respectively). ARTN had no effect on 5-HT-ir cell densities. Morphological analysis of 5-HT-ir neurons revealed a significant increase of soma size, number of primary neurites/neuron and neurite length/neuron after GDNF exposure, while PSPN only affected soma size, and NRTN and ARTN failed to exert any effect. In conclusion, we identified GFLs as effective neurotrophic factors for VM GABAergic and serotonergic neurons, demonstrating characteristic individual action profiles emphasizing their important and distinct roles during brain development.

Glial Cell Line-Derived Neurotrophic Factor Stimulates the Morphological Differentiation of Cultured Ventral Mesencephalic Calbindin- and Calretinin-Expressing Neurons

Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor for mesencephalic dopaminergic neurons. Subpopulations of these neurons express the calcium-binding proteins calbindin (CB) and calretinin (CR). Understanding the specific effects of GDNF on these neurons is important for the development of an optimal cell replacement therapy for Parkinsons disease. To investigate the effects of GDNF on the morphological complexity of mesencephalic tyrosine hydroxylase (TH)-immunoreactive (-ir), CB-ir, and CR-ir neurons, dissociated cultures of embryonic (E14) rat ventral mesencephalon were prepared. Chronic administration of GDNF (10 ng/ml) for 7 days promoted the survival of TH-ir and CB-ir neurons but did not alter the density of CR-ir neurons. Total fiber length/neuron and number of branching points/neuron of CB-ir and CR-ir cells were significantly increased after GDNF treatment (2x for CB-ir cells and 1.4x and 1.7x, respectively, for CR-ir cells), which resulted in a significantly larger size of neurite field/neuron (2.9x and 1.5x for CB-ir and CR-ir neurons, respectively). The number of primary neurites/neuron of CB-ir neurons was found to be 1.5x larger, while no difference could be detected for CR-ir cells. Assessment of the effects of GDNF on TH-ir neurons unveiled a similar outcome with an increased total fiber length/neuron (1.5x), an increased number of primary neurites/neuron (1.6x), and a twofold larger size of neurite field/neuron. In conclusion, our findings recognize GDNF as a neurotrophic factor that stimulates the morphological differentiation of ventral mesencephalic CB-ir and CR-ir neurons.

Effect of GDNF on differentiation of cultured ventral mesencephalic dopaminergic and non-dopaminergic calretinin-expressing neurons

Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for ventral mesencephalic (VM) dopaminergic neurons. Subpopulations of dopaminergic and non-dopaminergic VM neurons express the calcium-binding proteins calbindin (CB) and calretinin (CR). Characterization of the actions of GDNF on distinct subpopulations of VM cells is of great importance for its potential use as a therapeutic molecule and for understanding its role in neuronal development. The present study investigated the effects of GDNF on the survival and morphological differentiation of dopaminergic and non-dopaminergic neurons in primary cultures of embryonic day (E) 18 rat VM. As expected from our results obtained using E14 VM cells, GDNF significantly increased the morphological complexity of E18 CB-immunoreractive (CB-ir), tyrosine hydroxylase (TH)-ir, and CR-ir neurons and also the densities of CB-ir and TH-ir neurons. Interestingly, densities of E18 CR-ir neurons, contrarily to our previous observations on E14 CR-ir neurons, were significantly higher after GDNF treatment (by 1.5-fold). Colocalization analyses demonstrated that GDNF increased the densitiy of dopaminergic neurons expressing CR (TH+/CR+/CB-), while no significant effects were observed for TH-/CR+/CB- cell densities. In contrast, we found that GDNF significantly increased the total fiber length (2-fold), number of primary neurites (1.4-fold), number of branching points (2.5-fold), and the size of neurite field per neuron (1.8-fold) of the non-dopaminergic CR-expressing neurons (TH-/CR+/CB-). These cells were identified as GABA-expressing neurons. In conclusion, our findings recognize GDNF as a potent differentiation factor for the development of VM dopaminergic and non-dopaminergic CR-expressing neurons.

The role of postoperative prophylactic antibiotics in the treatment of facial fractures: a randomised, double-blind, placebo-controlled pilot clinical study. Part 1: orbital fractures in 62 patients

The aim of this study was to evaluate the difference between the effects of a 5-day and a 1-day course of antibiotics on the incidence of postoperative infection after displaced fractures of the orbit. A total of 62 patients with orbital blow-out fractures were randomly assigned to two groups, both of which were given amoxicillin/clavulanic acid 1.2g intravenously every 8h from the time of admission to 24h postoperatively. The 5-day group were then given amoxicillin/clavulanic acid 625 mg orally every 8h for 4 further days. The 1-day group were given placebo orally at the same time intervals. Follow up appointments were 1, 2, 4, 6, and 12 weeks, and 6 months, postoperatively. An infection in the orbital region was the primary end point. Sixty of the 62 patients completed the study. Two of the 29 patients in the 5-day group (6.8%) and 1/31 patients in the 1-day group (3.2%) developed local infections. In the 5-day group 1 patient developed diarrhoea. In the 1-day group 1 patient developed a rash on the trunk. There were no significant differences in the incidence of infection or side effects between the groups. We conclude that in displaced orbital fractures a postoperative 1-day course of antibiotics is as effective in preventing infective complications as a 5-day regimen.

Effect of a plasmaelectrolytic coating on the strength retention of in vivo and in vitro degraded magnesium implants

The strength decrease in magnesium implants was studied in vitro and in vivo, with and without a protective plasmaelectrolytic coating. In vivo, degradation was examined by implanting rectangular plates on top of the nasal bone of miniature pigs. The presence of gas pockets in the soft tissue surrounding the implants was evaluated with intermediate X-rays and computed X-ray tomography scans before euthanasia. After 12 and 24 weeks of in vivo degradation, the large rectangular plates were removed and mechanically tested in three-point bending. In vitro, identical plates were immersed in simulated body fluid for 4, 8 and 12 weeks. In vitro and in vivo results showed that onset of gas release can be delayed by the plasmaelectrolytic coating. Mass loss and strength retention during in vivo degradation is about four times slower than during in vitro degradation for the chosen test conditions. Despite the slow degradation of the investigated WE43 alloy, the occurrence of gas pockets could not be completely avoided. Nevertheless, uniformity of degradation and reliable strength retention make this alloy a prime candidate for the use of magnesium in cranio-maxillofacial surgery.

Repair of orbital floor fractures using bioresorbable poly-L/DL-lactide plates.

OBJECTIVE To assess the long-term clinical and radiologic findings after insertion of a bioresorbable polylactide plates P(L/DL)LA 70/30 implant (PolyMax) in the repair of orbital floor and wall defects, with special focus on stability and clinical signs of foreign-body reaction. METHODS Forty-six patients who had orbital blowout fractures with at least 1.5-cm(2) bone defects in 1 or 2 walls were included in this retrospective study. Each defect was reconstructed within 2 weeks of injury using a triangle form plate of polylactide. Computed tomography (CT) was performed before the operation and 1 year postoperatively. In 17 patients, additional CT was performed within 2 to 3 years postoperatively. Clinical assessments were performed preoperatively and at 3-, 6-, and 12-month intervals postoperatively. RESULTS None of the patients showed clinical foreign-body reactions. There was no evidence of infection. Diplopia was seen in 6 patients 3 months postoperatively but normalized in 5 patients at 6 months. Mild enophthalmos was seen in 2 patients postoperatively at 1 year. No sagging of the reconstructed area was found on CT. CONCLUSIONS The P(L/DL)LA 70/30 implant is a well-tolerated, reliable material in orbital repair of relatively large defects. The bioresorbable plate leaves a stable bridge of healed bone or soft tissue after complete degradation.

Bone-Conditioned Medium Inhibits Osteogenic and Adipogenic Differentiation of Mesenchymal Cells In Vitro

BACKGROUND AND PURPOSE Autografts are used for bone reconstruction in regenerative medicine including oral and maxillofacial surgery. Bone grafts release paracrine signals that can reach mesenchymal cells at defect sites. The impact of the paracrine signals on osteogenic, adipogenic, and chondrogenic differentiation of mesenchymal cells has remained unclear. MATERIAL AND METHODS Osteogenesis, adipogenesis, and chondrogenesis were studied with murine ST2 osteoblast progenitors, 3T3-L1 preadipocytes, and ATDC5 prechondrogenic cells, respectively. Primary periodontal fibroblasts from the gingiva, from the periodontal ligament, and from bone were also included in the analysis. Cells were exposed to bone-conditioned medium (BCM) that was prepared from porcine cortical bone chips. RESULTS BCM inhibited osteogenic and adipogenic differentiation of ST2 and 3T3-L1 cells, respectively, as shown by histological staining and gene expression. No substantial changes in the expression of chondrogenic genes were observed in ATDC5 cells. Primary periodontal fibroblasts also showed a robust decrease in alkaline phosphatase and peroxisome proliferator-activated receptor gamma (PPARγ) expression when exposed to BCM. BCM also increased collagen type 10 expression. Pharmacologic blocking of transforming growth factor (TGF)-β receptor type I kinase with SB431542 and the smad-3 inhibitor SIS3 at least partially reversed the effect of BCM on PPARγ and collagen type 10 expression. In support of BCM having TGF-β activity, the respective target genes were increasingly expressed in periodontal fibroblasts. CONCLUSIONS The present work is a pioneer study on the paracrine activity of bone grafts. The findings suggest that cortical bone chips release soluble signals that can modulate differentiation of mesenchymal cells in vitro at least partially involving TGF-β signaling.

The role of postoperative prophylactic antibiotics in the treatment of facial fractures: a randomised, double-blind, placebo-controlled pilot clinical study. Part 3: Le Fort and zygomatic fractures in 94 patients

The aim of this study was to evaluate the difference between the effect of a 5-day and a 1-day postoperative course of antibiotics on the incidence of infection after midfacial fractures. A total of 98 patients with displaced Le Fort or zygomatic fractures that required operation were randomly assigned into 2 groups, both of which were given amoxicillin/clavulanic acid 1.2g intravenously every 8h from the time of admission until 24h postoperatively. The 5-day group was then given amoxicillin/clavulanic acid 625 mg orally 8-hourly for another 4 days. The 1-day group was given placebo orally at the same time points. Patients were followed up 1, 2, 4, 6, and 12 weeks, and 6 months, postoperatively. The development of an infection of the wound was the primary end point. Ninety-four of the 98 patients completed the study. Two of the 45 patients in the 5-day group (4%) and 2/49 in the 1-day group (4%) developed postoperative wound infections. One in each group had a purulent infection, while the others had only wound breakdown. Two patients of the 5-day group and one in the 1-day group developed rashes on the trunk. There were no significant differences in the incidence of infection or side effects between the groups. In midfacial fractures a 1-day course of antibiotics postoperatively is as effective in preventing infective complications as a 5-day regimen.