BIOMECHANICAL ANALYSIS OF THE APPLICATION OF ZYGOMA IMPLANTS FOR PROSTHESIS IN UNILATERAL MAXILLARY DEFECT

The objective of this research is to evaluate the biomechanical effect of zygomatic implant-supported obturator prostheses in unilateral maxillary defect. Based on CT data, four 3D numerical models were built. One model was a normal craniofacial complex (model 1) and other three models were structures with unilateral maxilla defect reconstructed using clasp-retained obturator prosthesis (model 2), one zygomatic implant-supported and clasp-retained prosthesis (model 3), two zygomatic implant-supported and clasp-retained prosthesis (model 4). Bilateral vertical loads of 300[Formula: see text]N were imposed and the stress and displacement distribution were calculated, analyzed and compared. The bilateral occlusal forces dispersed along the three-mechanical-pillar of the maxillofacial region and the displacement distributed symmetrically in model 1. Because of mechanical pillars break on the affected side, all occlusal forces were transferred by clasps and abutment teeth in model 2, which induced the increase in stress and displacement level. The zygomatic implant restored mechanical pillars and greatly reduced the stress and displacements levels in models 3 and 4. The stress and displacement distributions on clasps, bones, teeth and periodontal ligaments were more reasonable with the support of zygomatic implants. Therefore, the zygomatic implant-supported and clasp-retained prostheses were found to be more effective for unilateral maxillary defect reestablishment.

Online breath analysis of propofol during anesthesia: clinical application of membrane inlet-ion mobility spectrometry

BACKGROUND

Breath analysis of propofol is a potential noninvasive method for approximating the plasma propofol concentration. There have been various reported techniques for measuring the exhaled propofol concentration at steady state; however, the propofol concentration undergoes marked changes during clinical anesthesia. Therefore, this study investigated the use of membrane inlet-ion mobility spectrometry (MI-IMS) to monitor exhaled propofol discontinuously and continuously during propofol anesthesia.

METHODS

The study included 19 patients of American Society of Anesthesiologists physical status I or II. In experiment I (discontinuous study), breath and blood samples were collected discontinuously, with stable target propofol concentrations of 2.8 μg/ml, 3.2 μg/ml, 3.5 μg/ml, and 3.8 μg/ml. In experiment II (continuous study), propofol concentration was maintained at 3.5 μg/ml after induction, and exhaled breath was collected continuously every 3 min during propofol infusion. Relationships of the exhaled propofol concentration with the plasma propofol concentration, measured by high-performance liquid chromatography and the continuously measured bispectral (BIS) index were investigated.

RESULTS

Comparison of the exhaled and plasma propofol concentrations revealed a bias ± precision of 2.1% ± 14.6% (95% limits of agreement: - 26.5-30.7%) in experiment I and - 10.4% ± 13.2 (- 36.3-15.4%) in experiment II. In both experiments, exhaled propofol concentrations measured by MI-IMS were consistent with, the propofol effect represented by the BIS index.

CONCLUSIONS

MI-IMS may be a suitable method to predict plasma propofol concentration online during propofol anesthesia. Monitoring exhaled propofol may improve the safety of propofol anesthesia.

BIOSYNTHESIS OF NUCLEOTIDES IN WHEAT: II. PYRIMIDINES FROM C14-LABELLED COMPOUNDS

Aspartate-U-C14 and uracil-2-C14 were fed to wheat leaves and embryos respectively. The alcohol-soluble and perchloric acid soluble fractions were treated with Norit A, and the Norit eluates were subjected to paper chromatography to identify the pyrimidines and derivatives synthesized from the labelled compounds. Both compounds were found to be precursors of pyrimidine nucleotides. The results are discussed in relation to recent views on the pathway of pyrimidine nucleotide synthesis in plants.

BIOSYNTHESIS OF NUCLEOTIDES IN WHEAT: III. PURINE AND PYRIMIDINE NUCLEOTIDES FROM P32-LABELLED PHOSPHATE

Phosphate labelled with P32 was fed to viable wheat embryos with and without 5-amino-4-imidazole carboxamide (AICA). The cold perchloric acid fraction was treated with Norit A; the adsorbed nucleotides were eluted by pyridine–alcohol and subjected to chromatographic analysis for identification. Approximately 30% of the label in the soluble fraction was incorporated into identifiable purine and pyrimidine nucleotides. AICA had no effect on the amount of incorporation. This study shows the existence of a pool of free nucleotides in wheat embryos.

BIOSYNTHESIS OF NUCLEOTIDES IN WHEAT: I. PURINES FROM C14-LABELLED COMPOUNDS

Glycine-2-C14and 5-amino-4-imidazole carboxamide-2-C14(AICA) were fed to wheat leaves and embryos respectively. The soluble fractions were treated with Norit A, and the Norit eluates were subjected to paper chromatographic analysis to identify the purines and derivatives synthesized from the labelled compounds. Glycine and AICA were shown to be precursors of purine nucleotides, and both compounds gained access to nucleic acids (AICA being more efficient). The results are discussed in relation to recent investigations on purine nucleotide synthesis in the wheat plant.