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At least 829 records · Page 46Linked to original sources
PubMed2000

[The degradation of glycoproteins with lithium borohydride. Isolation and analysis of O-glycopeptides with reduced C-terminal amino acid residue].

By the example of fetuin and a blood-group-specific mucin from porcine stomach, we showed that, under conditions of reductive degradation of glycoproteins with LiBH4-LiOH in 70% aqueous tert-butyl alcohol, the reduction and cleavage of amide bonds occur much faster than the simultaneous beta-elimination of carbohydrate chains O-linked with Ser and Thr residues of the peptide chain. The major degradation products containing the O-linked glycans are the O-glycosylated derivatives of 2-aminopropane-1,3-diol and 2-aminobutane-1,3-diol (the products of reduction of glycosylated Ser and Thr) and the glycopeptides containing 2-4 amino acid residues with reduced C-terminal amino acid. Seventeen homogeneous O-glycopeptides were isolated from the fetuin degradation products by ion-exchange and reversed-phase HPLC. Their structures were determined by MALDI-TOF mass spectrometry and by analyses for amino acids, amino alcohols, and carbohydrates. The application of the reaction for characterization of O-glycans and localization of O-glycosylation sites in O- and N,O-glycoproteins is discussed.

Animals↗
PubMed2000

Suicidal behavior and prophylactic lithium treatment of major mood disorders: a review of reviews.

This paper briefly summarizes and discusses at length two recent reviews. Their main findings were the following: (1) During prophylactic lithium treatment the overall mortality of patients with major mood disorders was much lower than in such patients in general. (2) The frequency of suicidal acts was many times lower in patients on lithium than in patients not on lithium. The limitations of the studies reviewed and the difficulty of interpreting their findings are discussed. It is concluded that prophylactic lithium treatment is indicated in patients with major mood disorders who are at high risk of committing suicide, that is, those with severe depressions or depressions with persistent suicidal thoughts or with suicide attempts in the past.

Antidepressive Agents↗
PubMedDate not supplied

Strength and microstructure of IPS Empress 2 glass-ceramic after different treatments.

PURPOSE: This investigation was designed to determine whether heat pressing and/or simulated heat treatments affect the flexure strength and microstructure of the lithium disilicate glass-ceramic of the IPS Empress 2 system. MATERIALS AND METHODS: Four groups of the lithium disilicate glass-ceramic were prepared as follows: group 1 = as-received material; group 2 = heat-pressed material; group 3 = heat-pressed and stimulated initial heat-treated material; and group 4 = heat-pressed and simulated heat-treated material with full firings for a final restoration. Three-point bending tests and scanning electron microscopy (SEM) analysis were conducted. RESULTS: The flexure strength of group 2 was significantly higher than that of group 1. However, there were no significant differences in strength among groups 2, 3, and 4, or between groups 1 and 4. The SEM micrographs of the lithium disilicate glass-ceramic showed a closely packed, multidirectionally interlocking microstructure of numerous lithium disilicate crystals protruding from the glass matrix. The crystals in the glass matrix of the heat-pressed materials (groups 2, 3, and 4) were a little more homogeneous and about 2 times bigger than those of the as-received material (group 1). These changes of the microstructure were greatest between groups 1 and 2. However, there were no marked differences among groups 2, 3, and 4. CONCLUSION: Although there were significant increases in the strength and some changes of the microstructure after the heat-pressing operation, the combination of heat pressing and simulated subsequent heat treatments did not produce an increase of strength of IPS Empress 2 glass-ceramic.

Crystallization↗
PubMed2001

[Lithium intoxication due to simultaneous use of trimethoprim].

A 40-year-old woman with a schizoaffective disorder was, inter alia, receiving lithium carbonate. During a simultaneous treatment with trimethoprim, she experienced symptoms of nausea, a feeling of malaise, concentration problems, trembling, an uncertain gait, diarrhoea and muscle spasms, without fever. The lithium level appeared to be elevated. The only cause of the intoxication indicated was the simultaneous use of trimethoprim. Following clinical rehydration, the patient made a good recovery. Trimethoprim has the same effect on the kidney as amiloride, a potassium-sparing diuretic, for which it is known that its combined use with lithium can result in an elevated lithium level.

Adult↗
PubMed2000

In vitro repair of all-ceramic and fibre-reinforced composite crowns.

Shear bond strength between fibre reinforced composite and all-ceramic frameworks and veneering/repair composites was investigated after different surface treatments for evaluating the possibility of a repair. Then, 24 crowns were adhesively luted on human teeth and artificially aged. Repair quality was characterized by a loading to fracture test, where undamaged crowns were compared to repaired crowns. To simulate repeated damage, aging and repair, the procedure was performed three times for each crown. A combined silicate-silane treatment of the fibre-reinforced composite frameworks and the hydrofluoric acid etching of the ceramic showed good repair qualities and a sufficient fracture strength for clinical application.

Analysis of Variance↗
PubMed2001

Long-term clinical effectiveness of lithium maintenance treatment in types I and II bipolar disorders.

BACKGROUND: The effectiveness of lithium is being questioned increasingly and requires clarification. AIMS: To assess the effectiveness of lithium treatment in depression and mania, syndromal types I and II, with predominantly mixed or psychotic episodes or rapid cycling, during treatment resumed following discontinuation, and across three decades. METHOD: The longitudinal course of 360 patients with bipolar disorder compliant with lithium treatment for at least 1 year and without comorbidity for substance use disorder was reviewed. RESULTS: Risk of single-episode recurrences, a common index of treatment failure, was similar to that in other reports. Both episode frequency and 'time ill' improved more in type II than type I cases. Reduced morbidity during treatment was similar in patients with mixed or psychotic episodes, or rapid cycling, and in less complex cases. Retreatment yielded minor decrements in response, and there was no tendency for lesser responses in more recent years. CONCLUSIONS: Based on overall affective morbidity, long-term lithium treatment in compliant patients without comorbid substance use disorder, though imperfect, remains effective, even in subgroups of supposedly poor prognosis.

Adult↗
PubMedDate not supplied

Fracture resistance of lithium disilicate-, alumina-, and zirconia-based three-unit fixed partial dentures: a laboratory study.

PURPOSE: The purpose of this study was to determine the fracture resistance of three-unit fixed partial dentures (FPD) made of new core ceramics. MATERIALS AND METHODS: A base metal three-unit master FPD model with a maxillary premolar and molar abutment was made. Tooth preparation showed 0.8-mm circumferential and 1.5-mm occlusal reduction and a chamfer margin design. FPDs were constructed with a uniform 0.8-mm-thick core ceramic and a porcelain veneer layer. In-Ceram Alumina, In-Ceram Zirconia, and DC-Zirkon core ceramics were machined by a computer-aided design/manufacturing system, whereas IPS Empress 2 core ceramic was indirectly built up using the fabrication technology of waxing and heat pressing. FPDs of IPS Empress were heat pressed as complete restorations without core material. To ensure standardized dimensions, the FPDs were controlled at different points. All FPDs were cemented with ZnPO4 on the master model and loaded on a universal testing machine until failure. The failure load and mode of failure were recorded. RESULTS: The highest failure loads, exceeding 2,000 N, were associated with FPDs of DC-Zirkon. FPDs of IPS Empress and In-Ceram Alumina showed the lowest failure loads, below 1,000 N, whereas intermediate values were observed for FPDs of IPS Empress 2 and In-Ceram Zirconia. Differences in mean values were statistically significant. CONCLUSION: The high fracture resistance evaluated for FPDs made of DC-Zirkon underscores the remarkable mechanical properties of high-performance ceramic, which could be useful for highly loaded all-ceramic restorations, especially in the molar region.

Aluminum Oxide↗
PubMed2000

[Measurements of proton response of two lithium fluoride detectors with different thicknesses].

OBJECTIVE: To study the response characteristics of LiF detectors to proton fluence rate and energy, and to observe the thickness effect of the detector. METHOD: Protons were generated by an accelerator. Proton energy was changed in two ways, i.e. changing the accelerator energy directly, or using detector stacks to absorb the proton energy. The incident proton energy on each chip of detector stacks was calculated according to proton range in LiF. RESULT: The response of the detector to proton fluence rate was almost constant; when proton energy was above 9 MeV, the response of the detector to proton energy was constant (less than 10% errors). When proton energy was below 9 MeV, the response reduced gradually with the decrease of proton energy. Thickness effect for LiF thicknesses of 0.4mm and 0.8mm was not obvious. CONCLUSION: The homemade LiF detector is suitable for measurement of space radiation dose. When proton component (below 9 MeV) was abundant in radiation field, the decrease of the relative thermoluminescence efficiency should be taken into consideration.

Cosmic Radiation↗
PubMed1999

Three-unit bridge construction in anterior single-pontic areas using a metal-free restorative.

A new glass-ceramic material, IPS Empress 2, is revolutionizing esthetic restorative dentistry by allowing metal-free, three-unit bridge construction in anterior and premolar single-pontic areas. The case discussed in this article illustrates the material's application in the dual-arch restoration of a young woman with congenitally missing teeth. The material was used as an alternative to single-tooth implant restorations to place two maxillary three-unit bridges, one mandibular three-unit bridge, and two mandibular porcelain veneers. IPS Empress 2 provides an esthetic alternative to porcelain-fused-to-metal restorations by facilitating attractive, functional tooth restoration.

Adult↗
PubMed2001

[Response of lithium fluoride detector to charged particle LET].

Response of LiF thermoluminescence (TL) detector to charged particle is dependent on particles' LET. High LET can cause reduction of detector response and underestimation of radiation dose. This paper summarized the response of LiF detector to charged particles' LET, and suggested a new approach to solve the dose contribution of high LET charged particles.

Extraterrestrial Environment↗
PubMed2001

Does the lead apron and collar always reduce radiation dose?

The possibility that personal lead shielding devices can increase absorption of radiation has not been entertained. The purpose of the present investigation specifically was to determine whether pituitary dose might be increased when a leaded apron and thyroid collar are used. Thermoluminescent dosimeters (TLDs) were used to measure absorbed dose. They were calibrated at the kVp used in the clinical situation and a calibration curve relating light output to dose was generated. Lithium fluoride TLD discs were placed in the pituitary gland region of a Rando-Alderson female human phantom. The equivalent of 100 transpharyngeal exposures were delivered. The resultant light output from recovered dosimeters was converted to a uGy value using the calibration curve. The experiment was repeated using a 0.25 mm lead equivalent collar and apron fitted to the phantom in the customary manner. The entire process was repeated in order to have 30 dosimeters for the unshielded and 30 dosimeters for the shielded conditions. A further 30 dosimeters were sham irradiated and served as controls. A statistical comparison between unshielded and shielded conditions was performed. When the leaded apron and thyroid collar were used the absorbed dose to the pituitary gland was increased significantly (P < 0.05). Following this a second group, using a different dosimetry system and a male phantom repeated the experiment. In both cases, the shielded phantom received significantly higher dose to the pituitary region than the unshielded.

Absorption↗
PubMed1976

Irradiation of bio-objects aboard the Cosmos 690 biosatellite.

Animals on the Cosmos 690 were exposed to Cs 137 gamma-radiation of 320 curies. The on board emitter was a spherical container made of tungsten alloy with a gamma source placed in the centre. A special dose filter provided a uniform +/-10% distribution of the dose field. Animal containers were equipped with thermoluminescent dosimeters. Radiation was monitored by an on-board dosimeter and displayed. The emitter was controlled by commands from the ground. On the tenth flight day the emitter was turned on and bio-objects were exposed for 24 hours. The dose received by bio-objects located in different areas of the biosatellite varied from 200 to 1000 rad. The flight experiment confirmed entirely the reliability of the radiation system.

Animals↗
PubMed2002

Fracture strength of all-ceramic lithium disilicate and porcelain-fused-to-metal bridges for molar replacement after dynamic loading.

The replacement of missing posterior teeth using all-ceramic bridges remains a challenge. This study compares the fracture resistance of all-ceramic 3-unit bridges for the replacement of first molars to conventional porcelain-fused-to-metal bridges. Human premolars and molars were used to create two test groups and one control group of 16 specimens each. To simulate clinical parameters, the specimens were exposed to cyclic fatigue loading in an artificial mouth with simultaneous thermocycling. All samples were thereafter exposed to fracture strength testing. Porcelain-fused-to-metal bridges showed significantly higher fracture strengths than all-ceramic bridges. However, the fracture strength of the all-ceramic bridges was higher than peak physiological chewing forces.

Aluminum Silicates↗
PubMedDate not supplied

Clinical considerations in case selection for all-ceramic fixed partial dentures.

All-ceramic systems have been utilized for fixed partial dentures (FPDs) to replace a missing tooth since the early 1990s. Clinical studies that assess the long-term outcome of both anterior and posterior three-unit all-ceramic FPDs are required to determine whether they can serve as a viable treatment option for functional and aesthetic tooth replacement. This article discusses the evolution and development of all-ceramic systems for FPDs as well as the clinical and laboratory considerations for treating patients using these restorations.

Adult↗
PubMed2002

[Progressive renal failure caused by lithium nephropathy].

OBJECTIVES: Study the renal consequences of lithium therapy and find out whether lithium-induced chronic renal toxicity can provoke a progressive nephropathy, leading to advanced renal failure, requiring periodical dialysis. METHODS: Fifty-three patients treated with long-term lithium salts were included in the study. They had developed chronic renal failure (creatinine clearance inferior to 80 ml/min) not due to any other cause. RESULTS: These patients had received lithium salts for a mean period of 17.7 years. The mean reduction in creatinine clearance was of 2.23 ml/min/year. Final clearance correlated negatively with the duration of lithium administration. In 7 patients treated a mean of 22 years, progression towards terminal kidney failure required periodical dialysis. Around 30% of patients exhibited mild hypercalcemia. CONCLUSION: Lithium nephropathy inducing progressive renal failure is a reality. Its prevalence in patients treated long-term with lithium should be assessed.

Adult↗
PubMed2000

[An analysis on thickness effect of lithium fluoride detector in proton measurement].

OBJECTIVE: To theoretically analyze the thickness effect of a LiF detector for proton measurement. METHOD: Thickness effect of the detector was calculated by using the definition of the detector dose under ideal and reasonable hypothesis. RESULT: The thickness effect of the detector was not obvious when protons could penetrate the detector: when proton energy was above 12 MeV, the thickness effect was obvious only on condition that the detector thickness approaches proton range, when proton energy was less than 12 MeV, the thickness effect was not obvious. The thickness effect of the detector was obvious, when protons could not penetrate the detector. CONCLUSION: Thin detectors should be used in low energy proton measurements to avoid thickness effect of the detector.

Fluorides↗