Thermo-debonding mechanisms in dentin bonding systems using finite element analysis

The finite element method (FEM) has been extensively used in evaluating the interfacial status of biomaterials. We used FEM to explore the microscopic debonding mechanism of the dentin/hybrid layer/resin adhesive interface. The stress status of the local material was used as an index to judge whether the adhesive interface would develop a debonding mechanism. To generate the local stress concentration, the thermal boundary condition was applied to the model which has the phenomenon of the coefficient of thermal expansion (CTE) mismatch. The thermal boundary condition was used to emulute a previous study conducted with a laser thermoacoustic technique (LTAT). The materials, Scotchbond MP, Optibond, and Tenure bonding systems, used in the previous experiment were also tested in this study. The results show that interfacial debonding in the finite element model occurred through the hybrid layer for both the Scotchbond MP and Tenure systems, as well as within the adhesive layer itself for the Optibond system. These findings are compatible with observations by SEM obtained by LTAT. Another transformed model was created to test the "elastic cavity wall" concept. The result also confirms the importance of the elastic cavity wall concept. These compatible results between FEM and LTAT indicate that FEM can be a very useful supplement to thermoacoustic testing.

Effect of temperature and flux concentration on soldering of base metal

The present study used the acoustic emission (AE) technique to evaluate interactions among soldering temperature, flux treatment, and the resultant ultimate tensile strength (UTS). Scanning electron microscopy (SEM) was used to examine fracture surfaces of the solder joints. Specimens were cast from removable partial denture alloy and then placed in a jig with a gap distance of 1.0 mm. A high-frequency soldering machine with an optical pyrometer was used for soldering at 1150 degrees C and 1200 degrees C, respectively. The flux concentrations were 67% and 75%. The soldered specimens were subjected to tensile test at a crosshead speed of 0.05 mm/min. During testing, acoustic emissions in the frequency range of 100--1200 kHz were collected, filtered, recorded, and processed by a sensing device. The results were analysed by ANOVA and Tukey LSD test. UTS at different temperatures showed no significant difference according to either mechanical or acoustic results. But in the 1200 degrees C group, the UTSs and AE counts showed significant differences (P<0.05) at both flux concentrations. SEM showed that the 1200C group had better dendritic crystal structure than did the 1150 degrees C group. In the 1200 degrees C group specimens with 67% flux had fewer flux inclusion bodies and dendritic crystals than did specimens with 75% flux. The 75% flux subgroup produced high-amplitude (60--70 dB) acoustic signals within the elastic deformation zone, while the 67% flux subgroup produced similar signals within the plastic deformation zone, either beyond the 0.2% yield point or before fracture.

Influence of silanization and filler fraction on aged dental composites

The effect of silanization and filler fraction on the mechanical properties of aged dental composites was investigated. Experimental composites (75/25 Bis-GMA/TEGDMA resin reinforced with 0, 12.6, 30.0, and 56.5 vol% 8 microm silanized/unsilanized BaSiO6) were fabricated into 4.7 mm diameter x 2.2 mm thick discs and 3.5 mm diameter x 7.3 mm thick discs for diametral tensile and compressive tests, respectively. The effect of immersion in 75% ethanol at 37 degrees C for 0-30 days on the diametral tensile strength (DTS) and compressive strength (CS) of the samples was evaluated and analysed by ANOVA and Tukey LSD test. The fracture interface between filler and resin matrix was then examined by scanning electron microscope. Results and subsequent statistical evidence from DTS (18.6+/-7.6 MPa, silanized versus 11.7+/-2.6 MPa, unsilanized) and CS (85.1+/-29.7 MPa, silanized versus 56.0+/-11.3 MPa, unsilanized) strongly implies that silanization may greatly enhance the mechanical properties of the resin composites. Furthermore, it also shows that both DTS and CS increased proportionally as the filler fraction of the composites increased. However, in the unsilanized groups, DTS decreased (up to 40%) as the filler fraction increased, and CS showed no relevance to the filler fraction at all. As for the influence of aging, it was found that both DTS and CS showed a significant decrease after immersion in 75% ethanol, and silanization heavily correlated with the filler fraction of aged-resin composites. Microscopic examination of the fractured samples showed that failure primarily occurred within the resin matrix per se for silanized composites and adjacent to the filler particles for unsilanized composites. All the evidence points to the conclusion that mechanical properties of aged-resin composites can be greatly influenced by silanization and the filler fraction.

Acoustic emissions generated in aged dental composites using a laser thermoacoustic technique

The heating up of dental composites by laser will produce acoustic emissions (AEs) that may be related to fracture mechanisms in the composites. It has been proved that the mechanical properties of dental composites are affected by storage in food simulating liquids, i.e. 75% ethanol, which has a solubility parameter approximating to that of bisphenol glycidyl dimethacrylate (BisGMA) resin. A new method was innovated to evaluate the laser-induced AEs in dental composites aged by 75% ethanol solution. Model systems (50/50 BisGMA/TEGDMA resin filled with 0% and 75 wt.% 5-10 microm silanized BaSiO6) as well as three commercial composites (Marathon One, Z100 and Herculite XRV) were used in this study. Nine samples acting as the control group were tested to establish the correlation of AEs to laser power. The effect of ageing by immersion in 75% ethanol on AEs and diametral tensile strength (DTS) was then evaluated. A quasi-continuous wave CO2 laser was used to heat up the composites. AEs of frequency 100-200 kHz were collected, filtered, recorded and processed using a 4610 Smart Acoustic Monitor. Burst patterns, which formally were assumed to be correlated to fracture mechanisms, were also identified from the data obtained at laser power > or = 5 W for commercial composites and > or = 4 W for model systems. Higher laser powers cause the AE to increase for all composites except unfilled model resin. AEs as a function of power for all aged systems were flat (< 100 events) below 4 W. Emissions then rose sharply to > 1000 events at 7.1 W. Statistically significant differences were found between the AEs obtained at 5 W (commercial composites) and those at 4.3 W (model systems) for material systems and storage times. Marathon One was less affected by the laser and an abrupt change in AE was found between days 0 and 7 of storage for all commercial composites. The AE value from the unfilled model resin was found to be significantly different from that of the model composites. However, they showed an increase in AEs with length of storage time, which was inversely associated with the decreased tendency of their immersed DTS values. Laser-induced AEs may be a valuable adjunct to conventional mechanical testing.

Fluoride ion diffusion from a glass-ionomer cement

The aims of this study were to observe the release of fluoride ions (F-) from GC-Fuji Lining-LC(R) glass-ionomer cement, to assess the diffusion process, and to measure fluoride diffusivity (D) in the set cement. Specimens of various dimensions and shapes, ranging from discs to cylindrical rods, were fabricated for both open and embedded modes of testing. In the open mode studies, specimens with different surface to volume ratios were selected and immersed in 37 degrees C distilled water. In the embedded mode studies, only one diametral surface of the rod-shaped specimens of different lengths and diameters was exposed. F- concentration was measured using a fluoride electrode. The storage solution was analysed at predetermined intervals hourly, daily, and weekly (up to 10 weeks). Immediately after each sampling, the old storage solution was discarded and replaced with new distilled water. F- release from the set cements was detectable (0.4-3.8 ppm, varied with sample geometry), even after a 10-week sampling interval. F- release was greater in ground set cements (0.37 ppm/mg powder) than in control samples of unmixed powder (0.01 ppm/mg powder) immersed for 1 h. Two mechanisms for F- release were proposed. One was short-term and involved rapid dissolution from the cement surface. The other was more gradual and resulted in the sustained diffusion of ions through the bulk cement, which can be modelled by applying a mathematical technique known as separation of variables to Fick's Second Law of Diffusion. The mean D of F- in embedded set cements of glass-ionomer was (1.4+/-0.5)x10-11 cm2/s, with higher apparent D observed in open mode samples [(7.6+/-1.4)x10-11 cm2/s].

Laser-induced acoustic emissions in experimental dental composites

A laser thermoacoustic technique was innovated to evaluate laser-induced acoustic emissions (AEs) in experimental dental composites aged with 75% ethanol solution. Experimental composite systems of 75/25 BisGMA/TEGDMA resin filled with 0, 12.6, 30.0, and 56.5 vol% of 8-microm silanized and unsilanized BaSiO6 were analyzed. The sample size was 4.65 mm (diameter) x 0.5 mm (thick). Aging effects of immersing in 75% ethanol for up to 14 h on AEs were then evaluated. A continuous-wave CO2 laser was used to heat the samples. Acoustic emissions were collected as a function of filler fraction, laser power, silanization, and immersion time. Onset of burst-pattern acoustic signals characteristic of fracturing occurred at different laser powers for different tested groups. Acoustic emissions generally increased with laser power, in which lower laser powers produced low-amplitude (45-50 dB) signals; the amplitude distribution (50-85 dB) became more extensive as laser powers increased. After immersion, the lower laser powers could produce the same phenomenon. The higher the filler fraction, the fewer AEs generated. A large percentage AE reduction due to silanization was noted as a function of filler fraction. Unsilanized specimens showed more thermal damages than did silanized ones.

PD 158771, a potential antipsychotic agent with D(2)/D(3) partial agonist and 5-HT(1A) agonist actions. I. Neurochemical effects

The neurochemical effects of a novel dopamine (DA) D(2)-like and serotonin (5-HT) 5-HT(1A) agonist, PD 158771, are described. PD 158771 exhibited affinities for human D(2L), D(3) and D(4.2) receptors expressed in Chinese hamster ovary (CHO)-K1 cells with K(i) (nM) values of 5.2, 13.7 and 34.8 respectively. PD 158771 showed high affinity for cloned human 5-HT(1A) (K(i) = 2.6 nM) and rat hippocampal 5-HT(1A) receptors (K(i) = 3.5 nM). Weaker affinities were observed at alpha 1-adrenergic (K(i) = 43 nM), histamine H(1) (IC(50) = 30 nM), 5-HT(2A) (K(i) = 24.5 nM) and sigma (sigma) -1 binding sites (K(i) = 24.5 nM). In measures of in vitro functional activity, PD 158771 stimulated [(3)H]thymidine uptake in CHO p-5 cells transfected with hD(3) receptors with a maximal effect of 23% relative to quinpirole. In hD(2)L, the corresponding value was 60% with an EC(50) of 29 nM, again indicating partial DA agonist action of PD 158771. In vivo, PD 158771 produced a dose-related decrease in DA synthesis in the striatum and mesolimbic regions of rat brain treated with gamma-butyrolactone (GBL), indicating a DA autoreceptor agonist action. In animals not treated with GBL, PD 158771 produced a dose-related decrease in DA synthesis and extracellular DA. A decrease in 5-HT synthesis in several brain areas was observed consistent with an agonist response. Further support for DA autoreceptor agonist action is that PD 158771 produced a partial inhibition of the firing of substantia nigra zona compacta DA neurons, an effect reversed by haloperidol. In conclusion, PD 158771 exhibited affinities for DA and 5-HT receptors, appears to possess DA and 5-HT agonist actions; and it could provide improved antipsychotic profile with minimal side effects.

In vivo and in vitro natural frequency analysis of periodontal conditions: an innovative method

BACKGROUND

When measuring periodontal disease, various types of equipment for making objective measurements of tooth mobility have been proposed. However, these devices and methodology are insufficient in terms of reliability. An innovative method using vibrational theories to assess the periodontal attachment level of natural teeth is presented in this study.

METHODS

Modal testing technique, a non-destructive and time-saving method, was used for non-invasive and quantitative measurement of the natural frequencies of the upper central incisor in vivo and in vitro. A finite element model was established, and modal testing experiments were simulated to assess the relationship between bone level and teeth.

RESULTS

The first dominant natural frequency of healthy human upper central incisors ranges from 710 Hz to 3,360 Hz, with an average of 1,701+/-679 Hz. Both in vitro experiment and finite element simulation showed that lowering of the attachment level causes a significant decrease in the natural frequencies, and a strong relationship (r = -0.99, P <0.01) was observed between the frequency and the bone level height.

CONCLUSIONS

Our results suggested that natural frequency is an important parameter for assessing the periodontal condition and that the modal testing technique is a useful supplemental method for assessing the attachment conditions of the periodontium.

Degradation of repaired denture base materials in simulated oral fluid

This in vitro study evaluates the degradation of repaired denture bases upon immersion in a simulated oral fluid. Denture base materials (Luciton 199), after being repaired by Repair Material and Triad, using three different joint surface designs (butt, round and 45 degrees bevel), were immersed onto 99.5 vol.% ethanol/water solution (with similar solubility parameter) for various amounts of time (0-72 h). The flexural loads of the six combination of groups were measured by the three-point bending tests using a universal testing machine. Acoustic emission (AE) during sample fracturing were processed using the MISTRA 2001 system. The fracture pattern and surface details of the interface were examined with a scanning electronic microscope (SEM). Data were analysed using three-way ANOVA and Tukey LSD tests. SEM micrographs of the fracture interface were used to differentiate the fracture mode. The flexural loads (2.72 +/- 0.51 Kgf) of the round joint specimens were significantly higher (P< 0.05) than those (butt: 1.66 +/- 0.38 Kgf, 45 degrees bevel: 1.93 +/- 0.41 Kgf) of the other two designs. This corresponds to the microscopic examination in which more cohesive failure mode was found for the round joint group after storage. The flexural loads (2.54 +/- 0.39 Kgf) of the specimens repaired with Triad were significantly higher (P < 0.05) than those (1.59 +/- 0.40 Kgf) of specimens repaired with Repair Material. Significant progressive reduction of the flexural load and/or AE signals of the specimens was noted in proportion to the length of time of the immersion in the simulated oral fluid. Mechanical strength of a denture base repaired with a round joint design and light-cured material is significantly higher after immersion in simulated oral fluid.

A series of 6- and 7-piperazinyl- and -piperidinylmethylbenzoxazinones with dopamine D4 antagonist activity: discovery of a potential atypical antipsychotic agent

As part of a program to develop dopamine D4 antagonists for the treatment of schizophrenia, we discovered a series of 6- and 7-(phenylpiperazinyl)- and -(phenylpiperidinyl)methylbenzoxazinones through mass screening of our compound library. A structure-activity relationship SAR study was carried out involving substituents on the phenyl ring, and several selective D4 antagonists were identified. The 7-substituted benzoxazinones showed more activity in neurochemical and behavioral tests than the 6-substituted series. One of the most potent and selective compounds (26) was found to have potent activity in animal tests predictive of antipsychotic activity in humans after oral administration. This paper describes the SAR of the benzoxazinone series and the preclinical characterization of 26.

Ictal vomiting in partial seizures of temporal lobe origin

We report 3 cases presenting ictal vomiting during partial seizures of temporal lobe origin. Two patients had complex partial seizures accompanying vomiting characteristics. Ictal vomiting occurred early in the course of the seizure when rhythmic discharges involved predominantly the left hemisphere, the language dominance hemisphere. The other patient had ictal vomiting in simple partial seizures which originated from the right temporal lobe or the language nondominant side. All 3 patients underwent anterior temporal lobectomy with promising outcomes. Pathologic diagnosis included hippocampal sclerosis in 2 patients and astrocytoma in 1 patient. In our patients, ictal vomiting does not lateralize temporal lobe epilepsy and is not specific to pathology.

Leached components from dental composites in oral simulating fluids and the resultant composite strengths

The aim of this study was to analyse the leached moieties of dental composites after storage in ethanol and organic acids of plaque and further evaluate the resultant effect on the diametral tensile strength (DTS) of the composites. Three commercial composites were used: Bis-GMA-based Z100, Bis-GMA/UDMA-based Heliomolar, and Bis-MPEPP-based Marathon One. The solutions used were: 99.9% acetic acid, 99% propionic acid and 75% ethanol. Specimens (4 mm diam. x 2 mm thick) were stored at 37 degrees C in 3 mL of solution for up to 30 days. Gas chromatography/mass spectrometry was used to characterize the leached moieties and DTS of the specimens after immersion was evaluated. Data were analysed using ANOVA and Tukey LSD test. The eluted substances were not all the same in different solutions and composites but mostly increased with immersion time, and included diluents (TEGDMA and decamethacrylate) and some additives, such as an ultra-violet stabilizer (TINUVINP), plasticizers (dicyclohexyl phthalate and bis(2-ethylhexyl) phthalate), initiator (triphenyl stibine), coupling agent (gamma-methacryloxypropyl trimethoxysilane), and phenyl benzoate. The chief polymerizing monomers were not found. More kinds of components were found in the acetic acid and ethanol groups studied. The fewest kinds and quantities of leached moieties were found for Bis-GMA specimens and then Bis-GMA/UDMA ones, most of which are diluent agents. Bis-MPEPP specimens leached the most substances, which were composed mostly of a short phenyl group chain structure. The BisGMA composite showed the highest DTS (54.8 +/- 5.7 MPa), which was not greatly affected by the length of storage. Bis-GMA/UDMA (36.2 +/- 6.8 MPa) and Bis-MPEPP (26.1 +/- 4.5 MPa) composites were significantly reduced (P < 0.05) after 30 days storage in the ethanol (35-50%), in the propionic acid (25-30%), and in the acetic acid (40-60%). Irreversible processes such as the leaching of components occur in fluids simulating an oral environment, which may contribute to irreversible material degradation, especially for non-Bis-GMA-based composites.

Measuring absolute infrared spectral radiance with correlated visible photons: technique verification and measurement uncertainty

An experimental system in which correlated photons for radiometric measurements were used has been set up at the National Institute of Standards and Technology. We use visible-IR pairs of correlated photons produced by means of optical parametric downconversion to measure the radiance of a high-temperature IR source at 3.415 and 4.772 mum in an intrinsically absolute manner (i.e., without requiring any externally calibrated radiometric standard). To our knowledge, this is the only radiometric method with which one measures radiance directly, instead of using radiant power and aperture geometry measurements to deduce radiance indirectly. This technique has an additional unusual characteristic: It allows absolute radiometric measurements of IR radiation to be made with high-quality visible detectors. We compare measurements made with this technique with radiance measurements made with conventional means tied to existing radiometric standards. These comparisons show an average agreement to within ~3% between the two methods. The results demonstrate an accuracy consistent with the estimated uncertainty of the currentmeasurements. This is the first time to our knowledge that this method has been used to provide absolute radiance measurements of a source that has been calibrated conventionally, revealing unexpected systematic effects and allowing estimates of the ultimate accuracy of this method. In addition, these measurements are further into the IR than any previous measurements of this process and have produced the highest thermally stimulated downconversion signal yet seen.

Cloning of porcine neuron growth inhibitory factor (metallothionein III) cDNA and expression of the gene in Saccharomyces cerevisiae

Growth inhibitory factor (GIF), a member of the metallothionein (MT) family, is also known as MTIII. This protein distinguishes itself from other MT isoforms by exerting an inhibitory effect on cortical neuron growth instead of metal ion buffering. In this work, we cloned MTIII genes from a porcine brain cDNA library. Two species of clones were isolated that vary with respect to one nt in the coding sequence. This discrepancy results in the translation of two MTIII primary structures having a different amino acid at residue 46. Herein, both MTIII cDNAs were constructed into an expression vector and transformed into yeast cells, respectively. The yeast carrying either MTIII gene displayed a similar metal tolerance when cultured in a medium containing metal. The resistance to metal toxicity was attributed to the expression of MTIII gene which was confirmed by RNA and protein analyses. The characteristics of the protein stability, metal binding affinity and ultraviolet absorption spectrum of the yeast produced MTIII are also compared with those of MTII. The comparison reveals that both MTs have similar physical characteristics. Moreover, circular dichroism spectrum of Cd saturated MTIII was analyzed as well. Typical Cys-Cd bands for MTII appear in the spectrum, indicating similar metal-thiol interactions for MTIII to those for other MT isoforms.

Optical and nonlinear optical study of KTa(0.52) Nb(0.48) O(3) epitaxial film

The second-order nonlinear optical coefficients d(33) , d(31) , and d(15) of KTa(0.52) Nb(0.48) O(3) epitaxial thin films grown upon MgO were studied by the standard Maker fringe method of an anisotropic medium. The measured d(33)=-84pm/V is 2.8 times the d(33) of LiNbO(3). The refractive indices n(e) and n(o) at several wavelengths were determined by TE and TM waveguide mode measurements. The data presented here point out the excellent qualities of KTa(1-x) Nb(x)O (3) films for use in integrated optics applications.

Effects of the dopamine D3 antagonist PD 58491 and its interaction with the dopamine D3 agonist PD 128907 on brain dopamine synthesis in rat

The dopamine (DA) D3 receptor antagonist PD 58491 [3-[4-[1-[4-[2-[4-(3-diethylaminopropoxy)phenyl]benzoimidazol++ +-1-yl-butyl]-1H-benzoimidazol-2-yl]phenoxy]propyl]diethylamine] bound with high affinity and selectivity to recombinant human DA D3 versus D2L and D4.2 receptors transfected into Chinese hamster ovary cells: Ki values of 19.5 nM versus 2,362 and >3,000 nM, respectively. In contrast, the putative DA D3 receptor antagonist (+)-AJ76 displayed low affinity and selectivity for D3 versus D2L and D4.2 receptors (91 nM vs. 253 and 193 nM, respectively). In vitro, PD 58491 (1 nM-1 microM) exhibited D3 receptor antagonist activity, reversing the quinpirole (10 nM)-induced stimulation of [3H]thymidine uptake in D3 CHOpro-5 cells, but did not have any significant intrinsic activity by itself in this assay. PD 58491 did not decrease the gamma-butyrolactone-induced increase in DA synthesis (L-3,4-dihydroxyphenylalanine accumulation) in rat striatum, indicating that the compound possessed no in vivo DA D2/D3 receptor agonist action at DA autoreceptors. PD 58491 (3-30 mg/kg, i.p.) generally did not alter DA or serotonin synthesis in either the striatum or mesolimbic region of rat brain. The D3-preferring agonist PD 128907 decreased DA synthesis in striatum and mesolimbic regions, and this effect was attenuated by pretreatment with PD 58491. These findings support the hypothesis that DA D3 autoreceptors may in part modulate the synthesis and release of DA in striatum and mesolimbic regions.

A nationwide epidemiological study of spinal cord injuries in Taiwan from July 1992 to June 1996

This prospective epidemiological survey of spinal cord injury (SCI) in Taiwan was carried out by recruiting patients attended by physicians from various medical centers and general hospitals all over Taiwan from July 1992 to June 1996. A total of 6,410 cases of traumatic spinal fracture were registered among which were 1,586 new cases of SCI. The results represented 70% of the scope of SCI in Taiwan. The observed average annual incidence of SCI in Taiwan was 18.8 per million population. The mean age was 46.1 years-old with a plateau distribution for over 20 years and older. Geriatric victims are a major group of SCI in Taiwan. The male to female ratio was 3 to 1. The leading causes of SCI were traffic accidents and accidental falls. Motorcycle collisions accounted for 62% of the traffic accidents, and as most of the motorcycle riders were not helmet users, head injury became the major associated injury of SCI in Taiwan. The effectiveness of the comprehensive care system for SCI patients in Taiwan is relatively good, as reflected by the low rates of complications of SCI, the low mortality rate (6.6%) and the high percentage (67.4%) of SCI patients achieving self-care ultimately at home after rehabilitation. The analysis of person days healthy life loss and quality adjusted survival time revealed that SCI patients in Taiwan required 4 years to cope with the morbidity, and on average, could return to the main stream of life for another 30 years.

A nationwide epidemiological study of spinal cord injury in geriatric patients in Taiwan

This prospective epidemiological survey of spinal cord injury (SCI) in Taiwan was carried out among patients attended by physicians from various medical centers and general hospitals all over Taiwan from July 1992 to June 1996. In all, 1,586 new cases of SCI were registered, representing about 70% of all possible SCI cases in Taiwan. The observed average annual incidence of SCI in Taiwan was 18.8 per million people, whereas it was 47.5 for the geriatric section. The mean age was 46.1 years with a plateau distribution after 20 years and older. Geriatric victims (297 cases, 18.7%, group II) formed a major section of SCI cases in Taiwan. Another group of younger SCI patients (15-64 years old, 1,232 cases, group I) was selected for comparison. The results showed that the male-to-female ratio, pattern of neurological deficits, and causes of injury and death of geriatric SCI patients differed significantly from those of the younger SCI group. Elderly women were exposed to a higher risk of SCI than younger women (M/F ratio 1.7:1). Falls were the leading cause of geriatric SCI, and two thirds of them occurred on level ground. Traffic accidents accounted for a third of SCI cases, half of which involved motorcycle accidents, a fifth of them pedestrians. Quadriplegia and quadriparesis occurred more frequently among elderly cases of SCI than in the younger group and a higher proportion of them died of SCI complications. Two thirds of elderly SCI patients recovered well enough after comprehensive treatment to be able to take care of themselves at home. The government should initiate programs of prevention to reduce the prevalence of geriatric SCI in Taiwan.

Role of foramen ovale electrodes in presurgical evaluation of intractable complex partial seizures

BACKGROUND

The value of intracranial electrodes such as depth electrodes and subdural grids for intracranial electroencephalographic (EEG) recording in patients with intractable epilepsies has been well recognized. A new technique, foramen ovale electrode (FOE) implantation, was first introduced by Wieser in 1984 for the lateralization of bilateral mesiotemporal lobe (MTL) onset of seizures.

METHODS

Since October 1993, a multipolar, three-contact FOE has been used in 12 intractable epileptic patients for presurgical evaluation. The reasons for FOE implantation included bilateral MTL onset of seizures recorded by extracranial EEGs in nine patients, and extracranial EEG abnormalities inconsistent with the results of magnetic resonance imaging (MRI), positron emission tomogram (PET) or Wada test in three patients. Under general anesthesia, the FOEs were implanted according to the technique introduced by Kirschner, using Barters landmarks.

RESULTS

After long-term telemetry recording with FOE, seven patients revealed clear onset of seizures originating from one side of the MTL and underwent anterior temporal lobectomy (ATL). Two patients had seizures of bilateral MTL onset. However, they received ATL due to predominantly unilateral interictal epileptiform discharges (EDs) and/or MRI and PET abnormalities. Seven (78%) of the nine operated patients became seizure-free after ATL. Three patients were considered not operable because two had multifocal onset of seizures and one had seizures with independent bilateral MTL onset. No serious complication resulted from implantation of FOE in this series.

CONCLUSIONS

The semi-invasive technique of FOE is reliable for lateralization of bilateral MTL onset of seizures which are often not clearly recorded by extracranial EEGs. This procedure is safe and can be an alternative to invasive implantation of depth electrodes and subdural grids.

Relationship between mesial temporal seizure focus and elevated serum prolactin in temporal lobe epilepsy

We evaluated the relationship between mesial temporal seizure focus and serum prolactin (PRL) in patients before and after they underwent anterior temporal lobectomy (ATL) for medically intractable temporal lobe epilepsy (TLE). These patients had a confirmed unilateral epileptogenic focus in mesial temporal structures, a postictal rise in serum PRL 15 to 20 minutes after onset of complex partial seizures, and were refractory for more than 2 years to antiepileptic drugs. Presurgical interictal serum PRL levels were significantly elevated (16.47 +/- 0.85 ng/mL, n = 62) and declined after ATL to normal values (patients, 9.63 +/- 0.55 ng/mL, n = 54; normal subjects, 8.99 +/- 0.57 ng/mL, n = 52). Serial evaluations indicated that normalization was seen 3 months after surgery (9.42 +/- 1.22 ng/mL, n = 9). The postsurgical reduction in serum PRL was similar in men and women, in patients with epileptogenic focus on either side of mesial temporal structures, and was unaffected by antiepileptic medication. We conclude that PRL is elevated following seizures and that a seizure focus in mesial temporal structures may exert a sustained excitatory influence on PRL release in patients with medically intractable TLE.

Cloning, expression and CNS distribution of Kv4.3, an A-type K+ channel alpha subunit

A full-length K+ channel cDNA of Kv4.3, with an open reading frame of 611 amino acids, was isolated from rat hippocampus. Functional expression of Kv4.3 cDNA in Xenopus oocytes revealed an A-type K+ channel. In the central nervous system, Kv4.3 is most prominently expressed in the retrosplenial cortex, medial habenula, anterior thalamus, hippocampus, cerebellum, as well as lateral geniculate and superior colliculus, which are important for vision. The abundant expression of Kv4.3 in many CNS neurons supports its important role as a major component of subthreshold A currents in the control of action potentials and thus neuronal excitability.

Cloning, expression and characterization of a human dopamine D4.2 receptor (CHO K1 cells) and various D4.2/D2L chimeras (COS-7 cells)

1. Using the gene splicing technique a synthetic human dopamine (DA) D4.2 gene was constructed and subsequently stably expressed in CHO K1 cells. 2. Binding of [3H]spiperone to membranes prepared from human DA D4.2 CHO K1 cells was saturable with a Kd of 93 +/- 0.51 pM and a Bmax of 768 +/- 22 fmol per mg protein. 3. Clozapine, apomorphine, and S(+)-NPA were more selective for D4.2 than for D2L receptors, with D2L/D4.2 ratios of 5.7, 7.1, and 19.6, respectively. 4. Functional studies indicated that DA D4.2 receptors expressed in CHO K1 cells inhibited forskolin stimulated cAMP levels showing coupling to G-proteins. 5. Two reciprocal human D2L and D4.2 chimeric receptors (D2L/D4.2 and D4.2/D2L) were constructed by exchanging the amino-terminal end to the third transmembrane (TM) of one receptor with the counter part of the other receptor and expressing them transiently into COS-7 cells. The chimeric D2L/D4.2 receptor displayed non-detectable specific binding of [3H] spiperone and other ligands. The chimeric D4.2/D2L receptor binding affinities of DA agonists were more affected than that of antagonists, suggesting that binding affinities of agonists are more sensitive to changes in receptor conformation than that of antagonists. 6. This study characterized the pharmacology of a novel synthesized DA D4.2 receptor that provides a useful model for screening of potential D4.2 receptor agonist and antagonist.

Waveguide study and refractive indices of GaN:Mg epitaxial film

Waveguide TE and TM modes in a GaN:Mg epitaxial crystalline film were studied in a wide spectral range (457.9-1053 nm). The refractive indices n(e) and n(o) were accurately determined by TM and TE mode measurements at six different wavelengths (457.9, 514.5, 632.8, 724.3, 855.1, and 1053 nm). Dispersive curves of n(e) versus lambda and no versus lambda were obtained. It was found that bireferingence slightly increases (n(e) - n(o) = 0.033-0.038) from 1053 to 457.9 nm.