Catecholaminergic innervation of the human dura mater involved in headache

The effects of pulsed Nd:YAG laser irradiation with different laser initiators on the permeability and ultrastructure of the root canal wall dentin were investigated in vitro. Forty extracted human single-rooted teeth were randomly assigned to four groups. Group 1 teeth were not lased as a control. Group 2 specimens received four 10-s duration laser exposures for a total exposure of 40 s/canal. In group 3 specimens, the root canals were painted with black ink and then lased by the same method as group 2 teeth. In group 4 specimens, root canals were treated with 38% Ag(NH3)2F and then lased by the same method as group 2 teeth. Laser parameters were set at 2 W, 20 pps. After being placed in 0.6% rhodamine B solution for 48 h, the teeth were sectioned for study by stereoscope and scanning electron microscopy. Statistical analysis showed there were significant differences (p < 0.05) in dentin permeability in the apical areas between groups 3 and 1, 4 and 1, and 4 and 2. Scanning electron microscopic examination showed that laser treatment alone had no obvious effects on the root canal wall. The root canal surfaces prepared for by laser irradiation with black ink or 38% Ag(NH3)2F revealed melting, smear layer evaporation, and open dentinal tubules. Black ink was more effective than 38% Ag(NH3)2F as a Nd:YAG laser initiator.     

Development of a dural substitute for preventing prion diseases induced by grafting of freeze-dried human dura mater

To provide a substitute for the dura mater a new bioabsorbable composite sheet was developed. This composite was composed of two L-lactic acid-epsilon-caprolactone (50:50) copolymer films and a poly (glycolic acid) nonwoven fabric. They displayed good mechanical properties and were completely absorbed 24 weeks after implantation in the back of rats. Histological evaluation of the composite sheet was undertaken by implanting it in 31 rabbits with dural defects and examining the sites of implantation 2 weeks to 26 months later. Any infection, cerebrospinal fluid leakage, evidence of convulsive disorders, significant adhesion to underlying cortex, and calcification was not noticed in any cases. In addition, the regenerated duralike tissue had a high pressure-resistant strength 2 weeks after implantation.     

Electron microscopy of the lesions produced in the human dura mater by Quincke beveled and Whitacre needles

INTRODUCTION: Comparisons of Quincke needles and non traumatic "pencil point" needles in recent years have reported lower rates of post dural puncture headache using the later type. Our new understanding of the morphology of the human dura mater motivated us to study dural lesions caused by the Whitacre 25 G and Quincke 26 G needles, using scanning electron microscopy with the aim of determining whether there is an anatomic basis for the different outcomes. METHOD: The dura mater from three fresh cadavers of individuals aged 65, 70 and 72 years were punctured 40 times at an angle of 90 degrees each time. The Whitacre 25 G needle was used for 20 punctures and the Quincke 26 G needle was used for the other 20. Half the punctures were performed with the bevel in the parallel alignment and the other half with the bevel perpendicular to the spinal column. Fifteen min after causing the punctures, specimens were fixed in solutions of glutaraldehyde phosphate buffer and dehydrated in acetone. After critical point removal of the acetone, after the specimens were treated with carbon and metallized with gold. The lesions were examined externally and internally and expressed as the ratio of area of lesion to diameter of the needle that had caused them. RESULTS: Whitacre needle: each lesion consisted in the superimposition of multiple damaged layers that started to close individually. After 15 min the outermost layers were 90% closed and the innermost ones had closed entirely. Layers in the arachnoid surface of the dura mater had closed from 86 to 88%, while deeper layers in the thick part had closed 97 to 98%. Quincke needle: lesions were V-shaped or half-moon shaped, much like the opening formed by a can opener, on both the external and internal surfaces. Alignment of the bevel of the needle parallel to the spinal column did not lead to a different shape of puncture. After 15 min the lesions had closed 94 to 95% on the epidural surface and 95 to 96% on the arachnoid side, a difference attributable to the retraction of the arachnoid layers over the spinal column. CONCLUSION: Non traumatic beveled dural needles, termed "pencil point needles", only partially separate dural fibers, and lesions caused by these needles develop in a more complex way. The Quincke 26G needle produced a puncture that is morphologically different from that caused by the Whitacre 25G needle, although lesions produced by both types close more than 94% after 15 min. We believe the size of the lesion caused by these needles does not explain the difference in post dural puncture headache due to loss of spinal fluid.     

Vicryl-mesh wrap for the implantation of hydroxyapatite orbital implants: an animal model

OBJECTIVE: To evaluate host fibrovascularization of hydroxyapatite orbital implants wrapped in sclera or in Vicryl (polyglactin 910) mesh in a rabbit model. NUMBERS: Eight adult New Zealand white rabbits that received hydroxyapatite orbital implants wrapped in homologous donor sclera (four animals) or Vicryl mesh (four animals). INTERVENTIONS: The rabbits had one eye enucleated and then received a 12-mm hydroxyapatite implant wrapped in sclera or Vicryl mesh. Magnetic resonance imaging (MRI) and bone scintigraphy were done to assess host fibrovascularization of the implant 4, 8, 12 and 20 weeks after implantation. Two animals (one in each group) were killed at each of these times, and the implant was removed for histopathological examination. MAIN OUTCOME MEASURES: Enhancement on MRI, uptake on bone scintigraphy, fibrovascularization seen on histopathological examination. RESULTS: The degree of fibrovascularization was substantial in all the specimens but appeared greater in the Vicryl-mesh-wrapped implants in the first 12 weeks after implantation on both histopathological and MRI studies. At 20 weeks these findings were similar in the two groups. A granulomatous foreign-body giant-cell reaction to both the Vicryl mesh and the implant itself was present up to 8 weeks after implantation. Bone scans showed only grade 1+ activity in all the implants. CONCLUSIONS: Host fibrovascularization in the rabbit appears to occur to a greater degree in Vicryl-mesh-wrapped hydroxyapatite implants than in those wrapped in donor sclera during the first 12 weeks after implantation. Vicryl mesh appears to be an acceptable alternative wrap for the hydroxyapatite implant, eliminating the need for donor sclera and its potential risks of transmissible diseases.     

Release of immunoreactive substance P in the trigeminal brain stem nuclear complex evoked by chemical stimulation of the nasal mucosa and the dura mater encephali--a study with antibody microprobes

In order to study a possible involvement of substance P in the processing of chemonociceptive input from the nasal mucosa and the dura mater encephali in the spinal trigeminal, the release of immunoreactive substance P was measured in the trigeminal brain stem nuclear complex in anaesthetized rats. Microprobes coated with antibody to substance P were inserted into the lateral area of the brain stem up to 1 mm posterior to the obex corresponding to the trigeminal subnucleus caudalis. When the nasal mucosa was stimulated by topical administration of mustard oil (1% and 5%) into the nostrils, immunoreactive substance P was mainly detected in the dorsal region of the trigeminal brain stem nuclear complex with a maximum in the superficial gray matter. When the dura mater encephali was stimulated by topical administration of Tyrode's solution (pH 6.2), immunoreactive substance P was mainly released in the ventral region of the trigeminal brain stem nuclear complex; with pH 5.5 the release was more diffuse extending from the ventral to the dorsal part of the spinal trigeminal nucleus. Release was maximal rather after than during the administration of the stimuli, and it considerably outlasted the stimulation periods. These data suggest that substance P plays an important role in the processing of chemonociceptive inputs from the nasal mucosa and the dura mater encephali in the trigeminal brain stem nuclear complex. Substance P may be important, therefore, in the generation of those headaches that are caused by affections of the nasal mucosa and the dura mater encephali. Since enhanced levels of immunoreactive substance P were present for considerable time periods beyond the administration of the stimuli, substance P and neurokinin-1 receptors may be involved in long-lasting neuronal events following noxious stimulation.     

Detailed evaluation of 2959 allogeneic and xenogeneic dense connective tissue grafts (fascia lata, pericardium, and dura mater) used in the course of 20 years for duraplasty in neurosurgery

Surgical experience with 2959 allogeneic and xenogeneic dense connective tissue grafts (1767 of fascia lata, 909 of pericardium, and 283 of dura mater), used in 2665 neurosurgical operations performed in the course of 20 years (1976 to 1995) is reported. Duraplasty using either allogeneic or xenogeneic grafts has had a similar, and favourable clinical outcome. Nevertheless, the pliable deep frozen fascia lata grafts, which could be used in any location, have been reserved for sella turcica plugging, anterior cranial base plasty, aneurysmal wrapping, and surgery of lipomyelomeningocele. Pericardium and dura mater grafts were in the majority of cases used over the brain convexity and posterior cranial fossa. Ovine pericardium proved to be superior to bovine and allogeneic pericardia because of its workability, flexibility, reduced thickness, and better transparency. Postsurgical complications occurred in 7.3%, and they were: 1) cerebrospinal fluid fistulas in 2.8%; 2) meningites in 2.3% (aseptic 1.4%, bacterial 0.8%, and tumoural 0.1% meningites); 3) pseudomeningoceles in 2.2%; 4) wound infections in 0.6%; 5) malresorptive hydrocephalus in 0.5%; and 6) adhesions to nerve tissue in 0.5%. The majority of complications healed without surgery. Forty-eight grafts (1.6%) failed to fulfil the requirements of the surgeon, and 46 of them were re-operated upon. Though another thirty-nine grafts healed successfully, 39 shunts (1.5%) had to be performed for malresorptive hydrocephalus (0.9%), and/or for a big pseudomeningocele (0.6%). So, the pure complication rate in 2665 duraplasties was 3.1%. The complex evaluation of the allogeneic and xenogeneic grafts (fascia, pericardium, and dura mater), used for duraplasty in neurosurgery during the last 20 years proved them, as remarkably good, with a success rates of 96.9%.     

Stump-socket interface pressure as an aid to socket design in prostheses for trans-femoral amputees--a preliminary study

We describe the effects on cell function of treating porous bioactive glass (BG) such that its surface is a composite of carbonated hydroxyapatite and serum protein. The effects on bone cell function of porous hydroxyapatite (HA) ceramic and porous glass treated to become amorphous calcium phosphate only also were studied subsequent to their having adsorbed a serum protein layer. Substrates treated for different durations were seeded with MC3T3-E1 cells and cultured for 3-17 days. Whereas cells seeded on any substrates, BG and HA produced collagen types I and III, bone sialoprotein, and osteopontin, there were significant differences between HA and BG, and among the various surface conditions created on BG. Covering the glass surface with hydroxyapatite and serum protein enhanced expression of high alkaline phosphatase activity, high rates of cell proliferation, and production of mineralized extracellular matrix. The enhancement may be due to the adsorption of a high quantity of fibronectin from the serum onto the reacted bioactive glass surface.     

Titanium as a biomaterial for ossicular replacement: results after implantation in the middle ear of the rabbit

The middle ear poses unique challenges when finding suitable materials for ossicular reconstruction, primarily because of its link to the external environment via the eustachian tube and, hence, its greater exposure to infectious agents. In this study, the biocompatability of titanium was examined in the middle ear of rabbits by using light and scanning electron microscopy. Implants were placed as middle ear prostheses or as free implants. These were inspected at 28 days, 84 days, 168 days, 336 days and 504 days following implantation for mucosal coverage, percent epithelization and any sign of foreign-body reaction. After 28 days, the prostheses were covered by regular mucosa. Although a majority of the free implants took up to 336 days for complete epithelialization, some of the free implants were not epithelialized even at day 504. There were no inflammatory cells observed on the surface of the material, nor were unusual amounts of fibrous tissue seen. In addition, the titanium material exhibited an affinity toward bone. The results of this animal experiment indicate that titanium is a favorable material for ossicular replacement prostheses.     

Ni-based superalloy as a potential tool material for thixoforming of steels

Abstract

Semisolid processing, already a well established manufacturing route for the production of intricate, thin walled aluminium and magnesium parts with mechanical properties as good as forged grades, faces a major challenge in the case of steels. The tool materials must withstand complex load profiles and relatively higher forming temperatures for thousands of forming cycles for this near-net shape process to be attractive for steels on an industrial scale. The potential of a Ni-based superalloy, Inconel 617, reported to exhibit superior thermal fatigue resistance in demanding tooling applications, was investigated. The response to thermal cycling of this alloy at high temperatures was compared with that of X38CrMoV5 hot work tool steel widely used in the manufacture of conventional forging dies. The favourable thermophysical properties of the latter were completely negated by its limited temper resistance, while the Inconel 617 alloy responded to thermal cycling by the usual heat cracking mechanism.     

Cognitive load as a factor in the structuring of technical material.

Several cognitive concepts can provide hypotheses concerning appropriate structures for instructional material in mathematics, science, and technology: (a) Schema acquisition is the primary component of skilled problem-solving performance; (b) learning through schema acquisition is interfered with if instructional material misdirects attention and imposes a heavy cognitive load; (c) for these reasons, conventional problem solving can sometimes interfere with learning; and (d) instructional material that requires learners to mentally integrate disparate sources of mutually referring information (e.g., text and diagrams) also interferes with learning by misdirecting attention and imposing a heavy cognitive load. Using mathematics and engineering materials, we found evidence for both the relevant cognitive concepts and the efficacy of alternative instructional materials generated by the concepts. Radical recasting of current instructional formats in most technical areas is called for. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human vestibular schwannoma growth in the nude mouse: evaluation of a modified subcutaneous implantation model

HYPOTHESIS: Based on the hypothesis that vestibular schwannomas can be successfully implanted and grown in the nude mouse model, an in vivo experiment was designed for subcutaneous implantation of solid vestibular schwannoma tissue. BACKGROUND: Vestibular schwannomas are benign tumors arising from Schwann cells of cranial nerve VIII. Little in vivo research has been carried out with these tumors, due in part to the difficulty to grow cells in culture or maintain tumor in an animal model. Recently, vestibular schwannomas have been implanted in nude mice with moderate success. The current study evaluates a modification of prior techniques in an effort to establish a dependable research model. METHODS: Thirty-six nude mice were implanted with variable-sized vestibular schwannoma tissue from three human subjects. Volumes implanted ranged from 14-170 mm3. Mice were observed for 28 days and individual volumes recalculated. Eleven of the mice were observed for a total of 56 days with volumes re-evaluated, and tumors subsequently were removed for assessment of viability and vascularity. RESULTS: At 28 days, 36 tumors (100%) showed take with 34 tumors (94%) showing macroscopic growth. The 11 tumors observed for 56 days showed a trend of stable or decreased size at 56 days compared with that of the 28-day measurement. Overall growth from time of implantation to measurements at 56 days was noted in 8 (73%) of 11 tumors when measured at the skin and in 10 (91%) of 11 tumors when direct tumor volume was measured. One hundred percent of tumors evaluated microscopically at 56 days was viable. All tumors at the time of removal had significant vascularity with a mean of 70.68% (SD = 23.42) of surface covered with vessels. There were no significant differences in take and growth for the larger tumor specimens compared with those of smaller sizes. CONCLUSION: Human vestibular schwannomas successfully can be implanted and maintained in the subcutaneous pocket of the nude mouse. This in vivo tumor model provides a reliable, accessible base for further research with vestibular schwannomas.     

Application of thermosensitive polymers as a new embolic material for intravascular neurosurgery

Application of thermosensitive polymers as an embolic material for intravascular neurosurgery was investigated. We intended to use thermosensitive polymers to occlude vessels by precipitation in response to body temperature. Copolymers of N-isopropylacrylamide (NIPAM) and N-n-propylacrylamide (NPAM) were selected as thermosensitive polymers. To determine the optimal lower critical soluble temperature (LCST) for the embolic material, we developed an in vitro flow model. In this study the copolymers with an LCST of 24-26 degrees C showed appropriate precipitation. To prove the occlusion of vessels in vivo, we injected the copolymers into a rabbit kidney through a microcatheter. The extent of embolization was judged by angiography and histological examination. An acute toxicity test of the copolymer of NIPAM and NPAM was performed in comparison with that of the NIPAM monomer. The copolymer used in this paper showed no acute toxicity in mice. Water solubility, non-adhesiveness, and non-toxicity are the advantages of the use of thermosensitive polymers as an embolic material. By changing the LCST, various embolic materials can be designed. Based on our results, we believe that the application of thermosensitive polymers as a new embolic material is very promising.     

Preliminary studies of the use of nail as a material for reconstructive or cosmetic surgery

The purpose of this study was to assess the biocompatibility and stability of implanted nail as a preliminary step in the assessment of its potential as a material for small scale reconstructive or cosmetic surgery. Rat nails were placed subcutaneously in the back of 12 Lewis rats, which were then sacrificed in groups of 4 at 4, 8, and 12 months for macroscopic and microscopic examination of the implants. A layer of strongly adherent connective tissue, containing inflammatory cells, had formed around the nails at 4 months, but by 8 to 12 months this reaction had subsided, leaving the nails imbedded in connective tissue adhering to the dermal wall, with no evidence of implant rejection, granuloma formation, or degradation. The results suggest that nail merits further study as a surgical implant material, because of its staying power and lack of immunogenicity.     

The use of human dura in urology, except as a substitute of urinary bladder (author''s transl)]

The human dura cannot only be used to replace the urinary bladder wall, but also to replace the capsula fibrosa of the kidney for transposition of aberrant vessels in hydronephrosis, for interposition in vesicovaginal fistula, for suspension of the urethra in stress incontinence and to replace the tunica albuginea of the corpus cavernosum penis after resection of plaque in Peyronie's disease.     

Ti-6Al-4V-2Ni as a matrix material for a SiC-reinforced composite

Ti-6Al-4V-2Ni is being considered as a composite matrix material because of its potential for a lower consolidation temperature and reduced reaction product formation compared with conventional Ti-6A1-4V. Stress/strain-rate measurements of Ti-6Al-4V-2Ni in sheet form provided data for calculation of diffusion bonding parameters required for efficient consolidation. These data were used as consolidation parameters for fabrication of SiC (SCS-6) reinforced Ti-6Al-4V-2Ni. The composite with 10.5 vol pct SiC exhibits room temperature tensile strength approximately 80 pct of that observed for conventional Ti-6Al-4V/SiC having 35 to 40 vol pct SiC. Scanning and transmission electron microscopy revealed that the fiber-matrix reaction zone is roughly one-half the thickness of that found in SiC-reinforced Ti -6A1-4V, and that it consists of TiC and Ti₅Si₃. Nickel does not enter into the reaction zone products, but rather promotes the formation of Ti₂Ni in the matrix.