Finite-Size Effects on Traveling Wave Solutions to Neural Field Equations.

Neural field equations are used to describe the spatio-temporal evolution of the activity in a network of synaptically coupled populations of neurons in the continuum limit. Their heuristic derivation involves two approximation steps. Under the assumption that each population in the network is large, the activity is described in terms of a population average. The discrete network is then approximated by a continuum. In this article we make the two approximation steps explicit. Extending a model by Bressloff and Newby, we describe the evolution of the activity in a discrete network of finite populations by a Markov chain. In order to determine finite-size effects-deviations from the mean-field limit due to the finite size of the populations in the network-we analyze the fluctuations of this Markov chain and set up an approximating system of diffusion processes. We show that a well-posed stochastic neural field equation with a noise term accounting for finite-size effects on traveling wave solutions is obtained as the strong continuum limit.

Comparison of Schwann cells and olfactory ensheathing cells for peripheral nerve gap bridging.

INTRODUCTION: Previously, we introduced the biogenic conduit (BC) as a novel autologous nerve conduit for bridging peripheral nerve defects and tested its regenerative capacity in a short- and long-term setting. The aim of the present study was to clarify whether intraluminal application of regeneration-promoting glial cells, including Schwann cells (SC) and olfactory ensheathing cells (OEC), displayed differential effects after sciatic nerve gap bridging. MATERIAL AND METHODS: BCs were generated as previously described. The conduits filled with fibrin/SC (n = 8) and fibrin/OEC (n = 8) were compared to autologous nerve transplants (NT; n = 8) in the 15-mm sciatic nerve gap lesion model of the rat. The sciatic functional index was evaluated every 4 weeks. After 16 weeks, histological evaluation followed regarding nerve area, axon number, myelination index and N ratio. RESULTS: Common to all groups was a continual improvement in motor function during the observation period. Recovery was significantly better after SC transplantation compared to OEC (p < 0.01). Both cell transplantation groups showed significantly worse function than the NT group (p < 0.01). Whereas nerve area and axon number were correlated to function, being significantly lowest in the OEC group (p < 0.001), both cell groups showed lowered myelination (p < 0.001) and lower N ratio compared to the NT group. DISCUSSION: SC-filled BCs led to improved regeneration compared to OEC-filled BCs in a 15-mm-long nerve gap model of the rat.

The long-term functional recovery of repair of sciatic nerve transection with biogenic conduits.

INTRODUCTION: The aim of this study was to evaluate long-term regenerative capacity over a 15-mm nerve gap of an autologous nerve conduit, the biogenic conduit (BC), 16 weeks after sciatic nerve transection in the rat. METHODS: A 19-mm long polyvinyl chloride (PVC) tube was implanted parallely to the sciatic nerve. After implantation, a connective tissue cover developed around the PVC-tube, the so-called BC. After removal of the PVC-tube the BCs filled with fibrin (n = 8) were compared to autologous nerve grafts (n = 8). Sciatic functional index (SFI) was evaluated every 4 weeks, histological evaluation was performed at 16 weeks postimplantation. Regenerating axons were visualized by retrograde labelling. RESULTS: SFI revealed no significant differences. Nerve area and axon number in the BC group were significantly lower than in the autologous nerve group (P < 0.05; P < 0.01). Analysis of myelin formation showed no significant difference in both groups. Analysis of N-ratio revealed lower values in the BC group (P < 0.001). CONCLUSION: This study reveals the suitability of BC for nerve gap bridging over a period of 16 weeks with functional recovery to comparable extent as the autologous nerve graft despite impaired histomorphometric parameters.

An in vivo engineered nerve conduit--fabrication and experimental study in rats.

BACKGROUND: Several types of nerve conduits have been used for peripheral nerve gap bridging. This study investigated the in vivo engineering of a biological nerve conduit and its suitability for nerve gap bridging. MATERIAL AND METHODS: A 19-mm long polyvinyl chloride (PVC) tube was implanted parallely to the sciatic nerve. After implantation, a connective tissue cover developed around the PVC-tube, the so-called biogenic conduit. Histological cross-sections were performed after 1, 2, 3, and 4 weeks. Wall thicknesses were measured and all vessels per cross-section were counted. The biogenic conduit filled with fibrin was used to bridge a 15-mm long nerve gap in the sciatic lesion model of the rat (n = 8). The results of nerve repair with the conduit were compared to the autologous nerve graft (n = 8). Sciatic functional index (SFI), nerve area, axon count, myelination index, and ratio of total myelinated fiber area/nerve area (N-ratio) were analyzed after 4 weeks. RESULTS: The wall thickness of biogenic conduits increased over the 4 weeks implantation time. Biogenic conduits revealed highest number of vessels per cross-section after 4 weeks. The results of SFI analysis did not show significant difference between the repairs with biogenic conduit and autologous nerve graft. Nerve area and axon count in the biogenic conduit group were significantly lower than in the autologous nerve group (P < 0.001). The biogenic conduit group showed significant higher myelination values, but lower N-ratio when compared to the nerve graft group (P < 0.001). CONCLUSIONS: The in vivo engineered conduits allow nerve gap bridging of 15 mm. However, quality of regeneration after 4 weeks observation time is not comparable to autologous nerve grafts. Whether biogenic conduits might be a suitable alternative to artificial and biological conduits for gap bridging will have to be evaluated in further studies.

Effective treatment of vaginal atrophy with an ultra-low-dose estradiol vaginal tablet.

OBJECTIVE: To evaluate the efficacy of ultra-low-dose 10-microgram 17beta-estradiol (E2) vaginal tablets for treatment of vaginal atrophy. METHODS: Postmenopausal women (N=309) were randomly assigned to 10-microgram E2 or placebo vaginal tablets for 52 weeks in a multicenter, double-blind study. Primary efficacy endpoints included change from baseline to week 12 in vaginal cytology, vaginal pH, and most bothersome urogenital symptoms score. Grading of vaginal health was a secondary efficacy assessment. Safety assessments included endometrial biopsy, physical and gynecologic examinations, and recording adverse events. RESULTS: At week 12, the change from baseline for 10 micrograms E2 compared with placebo demonstrated significant improvement in vaginal Maturation Index (proportion of parabasal cells: -37% compared with -9%; superficial cells: 13% compared with 4%; intermediate cells: 24% compared with 5%; P<.001 for each), Maturation Value (25.0 compared with 6.5, P<.001), grading of vaginal health (-0.91 compared with -0.51, P<.001), vaginal pH grade (-1.3 compared with -0.4, P<.001), and most bothersome symptoms score (-1.23 compared with -0.87, P=.003). For each component of vaginal Maturation Index, vaginal Maturation Value, grading of vaginal health, and vaginal pH, treatment effects were statistically different from placebo after 2 weeks of treatment. For most bothersome symptoms, treatment effect became apparent after 4 weeks and reached statistical significance at week 8 of therapy. All treatment effects were statistically significant at week 52. There were no major safety findings regarding physical, gynecologic, or laboratory assessments. CONCLUSION: After 12 weeks of treatment, an ultra-low-dose 10-microgram E2 vaginal tablet, compared with placebo, demonstrated significant improvement for the primary endpoints: vaginal cytology and pH and most bothersome urogenital symptoms score. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, http://clinicaltrials.gov, NCT00108849 LEVEL OF EVIDENCE: I.

Rho kinase inhibitors Y27632 and H1152 augment neurite extension in the presence of cultured Schwann cells.

BACKGROUND: RhoA and Rho kinase inhibitors overcome the inhibition of axonal regeneration posed by central nervous system (CNS) substrates. METHODS: To investigate if inhibition of the Rho pathway augments the neurite extension that naturally occurs in the peripheral nervous system (PNS) following nerve damage, dorsal root ganglion neurons and Schwann cell co-cultures were incubated with culture medium, C3 fusion toxin, and the Rho kinase (ROCK) inhibitors Y27632 and H1152. The longest neurite per neuron were measured and compared. Incubation with Y27632 and H1152 resulted in significantly longer neurites than controls when the neurons were in contact with Schwann cells. When separated by a porous P.E.T. membrane, only the group incubated with H1152 developed significantly longer neurites. This work demonstrates that Rho kinase inhibition augments neurite elongation in the presence of contact with a PNS-like substrate.

Single-dose application of CNTF and BDNF improves remyelination of regenerating nerve fibers after C7 ventral root avulsion and replantation.

Although axonal regeneration has been observed after replantation of avulsed ventral roots (VR) into the spinal cord, the functional outcome of this treatment in terms of motor reinnervation is unsatisfactory. In the present study, effects of single-dose ciliary and/or brain-derived neurotrophic factor (CNTF, BDNF) application on axon regeneration after C7 VR avulsion and replantation in adult rabbits were morphologically assessed by analysis of numbers, calibers, and myelination of axons in replanted VRs. Electromyography (EMG) was carried out to document the time course of de- and reinnervation in individual animals. After 3 weeks, replanted C7 VRs were almost devoid of myelinated axons. At week 8, active EMG-denervation was confirmed in affected muscles, but was less pronounced in neurotrophic factor (NF)-treated animals than in controls. Reinnervation potentials were identified in paraspinal muscles in more NF-treated animals than in controls. After 6 months, the number of myelinated axons in replanted VRs was approximately 45% of that in unlesioned roots in all groups, with small-sized axons constituting the majority of axons. At this time, more NF-treated animals than controls featured reinnervation. Moreover, myelination deficits of regenerated axons in controls were less pronounced in NF-treated animals. Especially in CNTF + BDNF-treated animals, myelination of regenerated axons of specific sizes was significantly increased compared to regenerated controls. In summary, NFs stimulated reinnervation early after the lesion and, for the first time, our morphological data quantitatively indicate positive effects of CNTF + BDNF on remyelination.

Oral hormone therapy with 17beta-estradiol and 17beta-estradiol in combination with norethindrone acetate in the prevention of bone loss in early postmenopausal women: dose-dependent effects.

OBJECTIVE: A 2-year multicenter, double-blind, randomized, placebo-controlled study examined the efficacy and safety of different doses of 17beta-estradiol (E(2)) alone and continuous-combined oral formulations of E(2) and norethindrone acetate (NETA) versus placebo in the prevention of bone loss in newly menopausal women. DESIGN: Patients were randomized to one of seven groups: placebo, E(2) 0.25 mg, E2 0.5 mg, E(2) 1 mg, E(2) 1 mg/NETA 0.25 mg, E(2) 1 mg/NETA 0.5 mg, or E(2) 2 mg/NETA 1 mg. Treatment was a once-daily tablet taken for 26 months. The primary efficacy endpoint was the change in bone mineral density (BMD) at the lumbar spine, measured by dual-energy x-ray absorptiometry, at screening and at 13, 19, and 26 months. BMD changes at the femoral neck and trochanter were also assessed. Biochemical markers of bone metabolism were measured at baseline, and at 3, 6, 13, 19, and 26 months. Histological diagnoses of endometrial samples were tabulated for each treatment group. RESULTS: A total of 327 women were randomized and 189 women completed the 2-year trial. BMD at the lumbar spine decreased 2.3% in the placebo group. The lowest dose of unopposed E(2) prevented bone loss at the spine and hip. Significant increases in spine BMD compared with placebo occurred in all groups of treatment with E(2) and were more pronounced in the combination groups. Compared with placebo, women receiving active treatment experienced greater reductions in bone resorption markers. The effects were evident by 6 months and generally remained stable thereafter. Adverse events, primarily associated with the endometrium, were the most common reasons for discontinuation. CONCLUSIONS: There is a dose-dependent effect of E(2) on BMD. The addition of NETA seems to enhance the response in BMD observed with E(2). Low doses of E(2) (1 mg and lower) can be considered for the prevention of osteoporosis, while titrating the hormone dose to individual patient's needs.

Biobrane in the treatment of burn and scald injuries in children.

Eighty-four children with a burn (n = 7) or scald injury (n = 77), treated with Biobrane, were investigated in a retrospective and clinical study. In most patients (n = 71), the Biobrane was adherent and without any reactions or infections. An infection was seen in 10.7% (9 from 84 patients). Twenty-one of 49 patients of the follow-up had limited scar areas. In scarless healed areas, 54.3% had normopigmentation and 39.1% were hypopigmented. The skin quality of the scars was mostly hypopigmented with a softness between minimal and middle resistance, under 2-mm high, and of normal to pink skin color. Compared with other dressings, Biobrane is no more expensive than others. We conclude that when used on properly selected wounds, Biobrane is an effective and, for the children, less traumatic therapy for superficial partial-thickness burns without increasing the cost of outpatient burn care.

Motoneuron survival after C7 nerve root avulsion and replantation in the adult rabbit: effects of local ciliary neurotrophic factor and brain-derived neurotrophic factor application.

BACKGROUND: The authors investigated the extent and time course of motoneuron cell death after C7 ventral nerve root avulsion under conditions resembling the trauma mechanism in clinical situations. In addition, they evaluated the effect on motoneuron survival of locally applied ciliary neurotrophic factor and brain-derived neurotrophic factor, with the aim of improving preconditions for successful regeneration of peripheral motor innervation. METHODS: Forty-four New Zealand White rabbits were operated on using a dorsal approach. The dorsal spinal nerve roots of segment C7 were cut, and the ventral roots were completely pulled out from the spinal cord. In seven experimental groups, ciliary neurotrophic factor, brain-derived neurotrophic factor, or both were applied to the lesion site using different application methods and compared with two control groups. One or 3 weeks after the operation, the animals were euthanized and segments C6 to C8 were studied histologically. In group 9, the avulsed rootlets were replanted into the ventrolateral spinal cord and the effect of replantation on motoneuron survival was assessed at 3 weeks postoperatively. RESULTS: The results indicated that within a period of 7 days, 54.4 +/- 12.1 percent of the motoneurons in segments C6 to C8 died without any therapy. Local application of ciliary neurotrophic factor or brain-derived neurotrophic factor lowered motoneuron loss significantly to 16.9 +/- 14.3 percent and 28.0 +/- 11.4 percent, respectively (p < 0.05). The reduction in motoneuron loss persisted after 3 weeks' survival time (23.1 +/- 4.3 percent in ciliary neurotrophic factor-treated animals, and 22.3 +/- 8.4 percent in brain-derived neurotrophic factor-treated animals, p < 0.05). Survival rates were not significantly higher after treatment with a combination of both factors (motoneuron loss, 33.5 +/- 7.1 percent). CONCLUSION: The authors conclude that the early application of neurotrophic factors appears to be a promising technique to improve motoneuron survival after nerve root avulsion.

Influence of different HRT regimens on mammographic density.

OBJECTIVES: A prospective, randomized, open-label study was conducted to evaluate effects on mammographic density in postmenopausal and late perimenopausal women receiving continuous combined or sequential combined hormone replacement therapy (HRT). METHODS: The subjects were randomized to treatment with low-dose continuous combined HRT containing 1 mg 17beta-estradiol plus 0.5 mg norethisterone acetate (Activelle) or a sequential combined HRT regimen consisting of 0.625 mg conjugated equine estrogens for 28 days plus 5 mg medrogestone for 14 days (Presomen). Mammograms were obtained at baseline and after 9 cycles (each 28 days) of treatment. RESULTS: The majority of women (approximately two-thirds in each treatment group) had no changes in mammographic breast density between baseline and the final study visit. There were no marked differences between treatment groups. Approximately 20% of women in both groups had a slight increase in mammographic density. Only 10-14% of women in both groups had a pronounced increase in mammographic density. The analyses of the degree of change showed no remarkable differences between treatments. CONCLUSION: These results indicate that the increase in mammographic density with a low-dose continuous combined HRT regimen is no greater than that with a sequential combined HRT regimen. The type of progestogen does not have an impact on the extent of mammographic density changes.

Surgical treatment of lumbosacral plexus injuries.

OBJECT: The purpose of this study was to analyze therapeutic possibilities and clinical outcomes in patients with lumbosacral plexus injuries to develop surgical concepts of treatment. METHODS: In a retrospective investigation 10 patients with injuries to the lumbosacral plexus were evaluated after surgery. The patients were assessed clinically, electrophysiologically, and based on the results of magnetic resonance imaging and computerized tomography myelography. In most patients a traction injury had occurred due to severe trauma that also caused pelvic fractures. In most cases the roots of the cauda equina of the lumbosacral plexus had ruptured. In cases of spinal root ruptures repair with nerve grafts were performed. In cases in which proximal stumps of the plexus could not be retrieved palliative nerve transfers by using lower intercostals nerves or fascicles from the femoral nerve were performed. CONCLUSIONS: Lesions of the proximal spinal nerves and cauda equina occur in the most serious lumbosacral plexus injuries. Patients with such injuries subjected to reconstruction of spinal nerves, repair of ventral roots in the cauda equina, and nerve transfers recovered basic lower-extremity functions such as unsupported standing and walking.

Chorioallantoic membrane angiogenesis model for tissue engineering: a new twist on a classic model.

Tissue-engineering (TE) applications include the isolation, culture, and seeding of cells into a suitable matrix or scaffold before in vivo transplantation. After transplantation, vascularization of the scaffold is a principal limiting factor for cell viability for the first 6-8 days posttransplantation. A model for systematic analysis of this process has been developed. Fertilized White Leghorn eggs were incubated (at 37.8 degrees C in 60% relative humidity) and opened on day 3 of incubation. Preadipocyte-seeded fibrin constructs were implanted in a specially designed plastic cylinder and placed through the opening on the surface of the chorioallantoic membrane (CAM) on day 8 of incubation. Vascularization of the constructs by chorioallantoic blood vessels was assessed for up to 8 days posttransplantation. The survival rate for embryos receiving transplanted constructs was about 90%. Histology confirmed transplant cell viability at day 4 posttransplantation and vascularization of the constructs by avian endothelial cells began at this time. A new in vivo model to study the effect of angiogenesis in TE constructs, including assessments of viability, proliferation, and differentiation of transplanted cells and biomaterial properties, is presented. Advantages include easy access to the vascular network of the CAM, lack of immunocompetence, low costs, and avoidance of animal experiments.

Bleeding patterns in peri and postmenopausal women taking a continuous combined regimen of estradiol with norethisterone acetate or a conventional sequential regimen of conjugated equine estrogens with medrogestone.

OBJECTIVES: The aim of this study was to compare the incidence of women presenting irregular bleeding episodes following 9 months of treatment with a low dose continuous combined hormone replacement therapy consisting of estradiol (E(2)) and norethisterone acetate (NETA) versus a sequential hormone replacement therapy consisting of conjugated equine estrogens (CEE) and medrogestone (MG). Secondary aims were to establish the relationship between menopausal age and the occurrence of irregular bleeding for both therapies and to assess the efficacy of both therapies in alleviating menopausal symptoms. METHODS: This was a stratified and randomised, open label study conducted with late peri and postmenopausal women at 35 sites in Austria and Germany. A total of 446 women were randomly allocated into two cohorts based on time since last bleeding and then stratified to either a low dose continuous combined therapy consisting of 1 mg E(2) and 0.5 mg NETA for 28 days or a sequential therapy consisting of 0.625 mg CEE for 28 days and 5 mg MG for the final 14 days. Bleeding and menopausal complaints were continuously assessed. Treatments were administered for 9 lunar months. RESULTS: The incidence rate of women presenting irregular bleeding episodes including spotting during cycle 9 was 12.2% with 1mgE(2)/0.5mgNETA and 25.8% with 0.625mgCEE/5mgMG (P = 0.0014). In the group of postmenopausal women (time since last bleeding > or = 12 months) the incidence of irregular bleeding during cycle 9 was 11.0% for 1mgE(2)/0.5mgNETA and 25.0% for 0.625mgCEE/5mgMG). In the group of late perimenopausal women (time since last bleeding 6-11 months) the incidence of irregular bleeding was similar for both treatments at cycle 3, but markedly less in patients with 1mgE(2)/0.5mgNETA at cycle 6 and 9, being significantly different compared to patients with 0.625mgCEE/5mgMG at cycle 6 (P < 0.05). The cumulative rate of amenorrhea (no bleeding or spotting) achieved with 1mgE(2)/0.5mgNETA was 89% for the postmenopausal women and 83.7% for the late perimenopausal women. Both treatments relieved menopausal complaints equally effective. CONCLUSIONS: Regarding the occurrence of irregular bleeding, the low dose continuous combined therapy was superior to the sequential therapy (0.625mgCEE/5mgMG). The low dose continuous combined E(2)/NETA regimen is also suitable for late perimenopausal women since more than 80% of the women had no bleeding or spotting after 9 months of treatment.