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Reaction of a lithiated dithiinyl reagent with a O-perbenzylated D-glycono-delta-lactone readily generates the corresponding masked C-vinyl galactosides in high yields and full beta-selectivity. Removal of the sulfur mask renders the free vinyl aglycone with the vinyl group in either the Z or E configuration, depending on the desulfurization conditions chosen.
Cannabinoids from three samples of cannabis obtained from the Pitt-Rivers Museum, Oxford, and dating from the turn of the century were examined by gas chromatography and mass spectometry for the presence of cannabinoids. Although the samples were from different geographical locations, the profiles of constituent cannabinoids were similar. In common with other aged material, most of the cannabinoid content was present as cannabinol (CBN), the main chemical degradation product of the major psychoactive constituent, delta-9-tetrahydrocannabinol (delta-9-THC). However, a substantial concentration of CBN acid-A was also present; this compound is unstable to heat and readily undergoes decarboxylation to CBN. Methyl and propyl homologues of CBN, together with delta-9-THC and its naturally occurring acid-A were also found at low concentrations in all samples. Intermediates in the formation of CBN from delta-9-THC, previously identified in aged solutions of the drug, were absent or present in only trace concentrations. However, oxidation products involving hydroxylation at the benzylic positions, C-11 and C-1', not seen in solution, were identified in substantial abundance. The results suggest that decomposition of cannabis samples may proceed more slowly than originally thought.
OBJECTIVES: The aims of the study were to explore the nucleation and crystallization kinetics of an aluminosilicate glass in K2O-Al2O3-SiO2 system and to characterize it. OBJECTIVES: A starting glass composition of wt%; 64.2% SiO2, 16.1% Al2O3, 10.9% K2O, 4.3% Na2O, 1.7% CaO, 0.5% LiO and 0.4% TiO2 was heated in an electric furnace and later quenched to produce glasses. The glass powders were heat treated using differing heat treatment schedules and quenched. Dta, Xrd, Eds and Sem analyses were used to characterize and explore the crystallization kinetics of the glasses. RESULTS: Phase separation of the glasses was identified and characterized in the glasses. Tetragonal leucite, cubic leucite and sanadine glass-ceramics were produced. Fine leucite crystals (1 microm2) were crystallized with minimal matrix microcracking. SIGNIFICANCE: Amorphous phase separation appeared to be an important precursor to nucleation and crystal growth in the alkali aluminosilicate glasses explored. It was possible to control the crystallization of tetragonal leucite and sanidine phases by selected heat treatment of glass powders and monoliths, resulting in the production of fine grained tetragonal leucite glass-ceramics.
The analysis of low-molecular-mass anionic compounds using capillary zone electrophoresis (CZE) with simultaneous direct conductivity and indirect UV detection is described. A number of carrier electrolyte compositions has been investigated with respect to the crucial parameters for their compatibility with both detection principles discussed in this paper (UV absorptivity and electrophoretic mobility of the buffer coion). Additionally, parameters including pH and buffer concentration affecting both peak symmetry and signal-to-noise ratio obtained for the analytes of interest had to be optimized. Best results could be achieved with a carrier electrolyte consisting of 4-aminobenzoic acid, bis(2-hydroxyethyl)imino-tris(hydroxymethyl)aminomethane (BIS-Tris) and a pH of 7.0 adjusted with LiOH. This running buffer was used for the analysis of low-molecular-mass anionic compounds in a sample of white wine.
PURPOSE: This study evaluated the wear area of human enamel opposing 2 conventional and 2 low-fusing dental porcelains, as well as abrasive wear, attrition, surface hardness, and fracture toughness for the 4 porcelain substrates. MATERIALS AND METHODS: Two low-fusing and 2 conventional metal-ceramic porcelains were used to form 15-mm-diameter disks (n = 10), which were fired according to manufacturer's recommendations. Enamel cusps (n = 40) were formed from extracted third molars. All ceramic and enamel specimens were finished to a 1000-grit silicon carbide surface. The Oregon Health Sciences University (Portland, OR) oral wear simulator was used to deliver a 20-N load from the cusps to the ceramic substrates through a food-like slurry. The sliding action of the cusps over an 8-mm linear path produced abrasive wear. A static 70-N load was applied at the end of the path to create attrition. This sequence was repeated at 1.0 Hz for 50,000 cycles. Ceramic wear was measured with a profilometer (+/-2 micrometers), and enamel wear was evaluated using optical scanning methods. After wear testing, the hardness and fracture toughness of the ceramic surfaces were determined, and scanning electron photomicrographs were made using representative ceramic and enamel specimens from each group. Enamel wear areas, abrasion and attrition depths, hardness, and fracture toughness values were subjected to analysis of variance and Tukey-Kramer post hoc tests to determine significant differences. RESULTS: Enamel wear was not significantly different for low-fusing and conventional porcelains (p =.29). The wear of conventional and low-fusing ceramic substrates was also not significantly different (p =.79). However, depth of porcelain wear caused by attrition was in general significantly greater than abrasive wear (p =.0004). Although no significant differences were found in the measured porcelain hardness values (p =.08), 1 conventional porcelain exhibited fracture toughness significantly greater than 1 low-fusing porcelain (p <.01). CONCLUSIONS: No differences in wear patterns were noted among low-fusing compared with conventional metal-ceramic porcelains, but static loading resulted in significantly greater attrition compared with the observed sliding abrasive wear. J Prosthodont 2001;10:8-15.
OBJECTIVES: The present study aims to evaluate the core-veneer bond strength and the cohesive strength of the components of three commercial layered all-ceramic systems. Two surface treatments for the core surface finish and different veneering ceramics with different thermal expansion coefficients (TEC) were applied. The selected systems were two CAD-CAM ceramics; Cercon and Vita Mark II and one pressable system; (IPS)Empress 2 for layering technique. METHODS: Standardized core specimens were fabricated according to the manufacturer's instructions, or polished with 1200 siliconcarbide polishing paper. The core specimens were veneered with either its manufacturer's veneer or an experimental veneer with higher TEC. The obtained micro-bars were subjected to the microtensile bond strength test. The obtained data were analyzed using one and two-way ANOVA. A finite element analysis (FEA) model of the test setup was analyzed. Scanning Electron Microscopy (SEM) was carried out at the fracture surface. RESULTS: The core materials were significantly stronger than the veneering materials and the layered core-veneer specimens of which the results were statistically comparable. Polishing the core surfaces did not have an effect on the core-veneer bond strength. Experimental veneer with higher TEC resulted in massive fractures in both the core and veneering material. SEM and FEA demonstrated fracture pattern and mechanism of failure. SIGNIFICANCE: The core-veneer bond strength is one of the weakest links of layered all-ceramic restorations and has a significant role in their success. To exploit fully the high strength of zirconium oxide cores, further research work is needed to improve its bond with its corresponding veneering material.
Frog sartorius muscles were made Na-rich by immersion in K-free sulfate Ringer's solution in the cold. The muscles were then loaded with Na(24) and the extracellular space cleared of radioactivity. When such Na-rich muscles were transferred to lithium sulfate Ringer's solution at 20 degrees C, Na efflux was observed to increase with time, to reach a maximum about 15 minutes after the transfer of the muscles to Li(2)SO(4), and then to decline. The decline in efflux from these muscles was proportional to ([Na](i))(8) over a considerable range of [Na](i). The membrane potential of Na-rich muscles was about -48 mv in K-free sulfate Ringer's at 4 degrees C but changed to -76 mv in the same solution at 20 degrees C and to -98 mv in Li(2)SO(4) Ringer's at 20 degrees C. By contrast, muscles with a normal [Na](i) showed a fall in membrane potential when transferred from K-free sulfate Ringer's to Li(2)SO(4) Ringer's solution. The general conclusions from this study are (a) that Na extrusion is capable of generating an electrical potential, and (b) that increases in [Na](i) lead to reversible increases in P(Na) of muscle fibers.
Solvent-free [LiCH2SMe]infinity forms a layer structure consisting of four- (Li2C2), five- (Li2CS2), and six-membered (Li2C2S2) rings in the solid state; the compound violently explodes upon heating to T=160+/-5 degrees C under an argon atmosphere.
The test results of lithium carbonate tablets made by direct compression were presented. The content of lithium carbonate, tablets weight variation, hardness, friability, disintegration, as well as the lithium carbonate dissolution rate were determined. The best properties were observed in tablets made with microcrystalline cellulose (Avicel PH 101), spray dried lactose and corn starch.
This article reviews critically the present status of lithium in the treatment and prophylaxis of manic-depressive illness compared to the two anticonvulsant drugs, carbamazepine and valproic acid. Lithium is used successfully in the prophylaxis and treatment of manic-depression. The mechanism by which it exerts its effects is still not very clear. There is much evidence to indicate that lithium may exert its therapeutic action by interfering with the metabolism of phosphoinositides which play an important role in synaptic transmission. Because of lithium's narrow therapeutic/toxic ratio, blood concentration monitoring is crucial. Published data suggest that, compared to lithium, carbamazepine is similar in its relative specificity in treating mania. It is often faster in achieving its antimanic effects and best established as an alternative for patients not responding or intolerant to lithium. Carbamazepine is a good substitute for lithium when severe renal problems exclude the use of lithium. The therapeutic profile of valproic acid in manic-depression, although less extensively studied, appears to be similar to that of carbamazepine. As carbamazepine, it seems to be best indicated in patients with rapid cycles. Whereas lithium inhibits myo-inositol monophosphatase, carbamazepine shows a stimulating effect and valproic acid has no effect on this biochemical target. The implication of the inositol pathway in the pathogenesis of adverse effects, such as neurotoxicity and dermatological irritation, is discussed. A further understanding of this pathway is important for the future development of new lithium-like compounds in order to maximize the therapeutic benefits without the adverse effects.
A new class of potent antifungal agents, namely, 3-aryl-4-[alpha-(1H-imidazol-1-yl)arylmethyl]-pyrroles, is described. These compounds are related to bifonazole and pyrrolnitrin, two compounds belonging to the class of antimycotic drugs. The synthesis of the title pyrroles has been performed starting from 1,3-diaryl-2-propen-1-ones, which were reacted with tosylmethyl isocyanide to give 3-aroyl-4-arylpyrroles. Reduction of the resulting compounds by lithium aluminum hydride furnished the related alcohols, which were treated with 1,1'-carbonyldimidazole to afford the required imidazole derivatives. Forty-four new pyrroles which incorporate an (arylmethyl)imidazole moiety in the 3-arylpyrrole structure were prepared by the above procedure and tested in vitro against Candida albicans and Candida spp. Among test compounds, 10 were found to be highly active against C. albicans. The most active derivative (27) was twice as potent (MIC90) as bifonazole, and its activity was 4 times greater than those of miconazole and ketoconazole. The other nine compounds showed antifungal activity of the same order of that of bifonazole and were ca. 2 times as active as miconazole and ketoconazole. Derivatives 21 and 27 tested in vivo against C. albicans A170 were shown to be highly effective in rabbit skin candidosis. Pharmacological studies on compounds 27 and other related pyrroles (19, 35, 36, 38, 39, and 49) are in progress to select one of them as a potential candidate for clinical experiments.
A series of new (silylamino)phosphines that contain sterically bulky silyl groups on nitrogen were prepared by deprotonation/substitution reactions of the hindered disilylamines t-BuR(2)Si(Me(3)Si)NH (1, R = Me; 2, R = Ph) and (Et(3)Si)(2)NH (3). Sequential treatment of the N-lithio derivatives of 1-3 with PCl(3) or PhPCl(2) and MeLi gave the corresponding (silylamino)phosphines t-BuR(2)Si(Me(3)Si)NP(R')Me (5, R = Me, R' = Ph; 6, R = Ph, R' = Me) and (Et(3)Si)(2)NP(R)Me (11, R = Me; 12, R = Ph) in high yields. Two of the P-chloro intermediates t-BuR(2)Si(Me(3)Si)NP(Ph)Cl (7, R = Ph; 9, R = Me) were also isolated and fully characterized. Hydrolysis of 7 afforded the crystalline PH-substituted aminophosphine oxide t-BuPh(2)SiN(H)P(Ph)(=O)H (10). Thermal decomposition of 7 occurred with elimination of Me(3)SiCl and formation of a novel P(2)N(2) four-membered ring system (36) that contains both P(III) and P(V) centers. Reactions of the N-lithio derivatives of amines 1 and 2 with phosphorus trihalides afforded the thermally stable -PF(2) derivatives t-BuR(2)Si(Me(3)Si)NPF(2) (13, R = Me; 14, R = Ph) and the unstable -PCl(2) analogue 17 (R = Ph). Reduction (using LiAlH(4)) of the SiPh-substituted dihalophosphines 14 and 17 gave the unstable parent phosphine t-BuPh(2)Si(Me(3)Si)NPH(2) (15). The P-organo-substituted (silylamino)phosphines underwent oxidative bromination to afford high yields of the corresponding N-silyl-P-bromophosphoranimines t-BuR(2)SiN=P(R')(Me)Br (18, R = R' = Me; 19, R = Me, R' = Ph; 20, R = Ph, R' = Me) and Et(3)SiN=P(R)(Me)Br (23, R = Me; 24, R = Ph). Subsequent treatment of these reactive PBr compounds with lithium trifluoroethoxide or phenoxide produced the corresponding PO derivatives t-BuR(2)SiN=P(R')(Me)OR' ' (25 and 26, R' ' = CH(2)CF(3); 28-30, R' ' = Ph) and Et(3)SiN=P(R)(Me)OR' (31 and 33, R' = CH(2)CF(3); 32 and 34, R = Ph), respectively. Many of the new compounds containing the bulky tert-butyldiphenylsilyl group, t-BuPh(2)Si, were solids that gave crystals suitable for X-ray diffraction studies. Consequently, the crystal structures of three (silylamino)phosphines (6, 7, and 14), one (silylamino)phosphine oxide (10), one N-silylphosphoranimine (30), and the cyclic compound 36 were determined. Among the (silylamino)phosphines, the P-N bond distances [6, N-PMe(2), 1.725(3) A; 7, N-P(Ph)Cl, 1.68(1) A, 14, N-PF(2), 1.652(4) A] decreased significantly as the electron-withdrawing nature of the phosphorus substituents increased. The N-silylphosphoranimine t-BuPh(2)SiN=PMe(2)OPh (30), which is a model system for poly(phosphazene) precursors, had a much shorter P=N distance of 1.512(6) A and a wide Si-N-P bond angle of 166.4(3) degrees. A similar P=N bond distance [1.514(7) A] and Si-N-P angle [169.9(6) degrees ] were observed for the exocyclic P=N-Si linkage in the ring compound 36, while the phosphine oxide 10 had P-N and P=O distances of 1.637(4) and 1.496(3) A, respectively, and a Si-N-P angle of 134.3(2) degrees.
Lithium salt compounds are used to limit the degree and duration of neutropenia in patients receiving chemotherapy for cancer. Interleukin-15 (IL-15) is a cytokine which possesses promoting activities on hematopoiesis and is also involved in antitumor response, activating NK, CTL and LAK cells. In this study we analyzed IL-15 production by monocyte cultures treated with lithium chloride (LiCl). Monocytes were obtained from patients affected by non-metastatic and metastatic breast cancer. LiCl treatment induced IL-15 production by monocytes mainly from non-metastatic patients. Combined lipopolysaccharide/LiCl treatment of monocyte cultures up-regulated IL-15 release compared to those treated with LPS alone (p<0.0001). The modulation of LiCl-induced IL-15 could counteract the immunosuppression state of cancer patients, which should be taken into account when developing new immunotherapeutic strategies.
The test results of lithium carbonate tablets, made of various binding substances (maize starch, gelatin, sodium carboxymethylcellulose 7pp, kollidon 30) were presented. The content of lithium carbonate, tablets weight variation, hardness, friability, disintegration, as well as the lithium carbonate dissolution rate were determined. The best properties were observed in tablets made with maize starch paste with the addition of starch in the internal phase.
[reaction: see text] 1alpha,25-Dihydroxyvitamin D(3) was synthesized by the Suzuki-Miyaura coupling of the A-ring intermediate 1, which was efficiently prepared from readily available 1,7-enyne 2, with the corresponding boronate compound of the C,D-ring portion. The method was applied to prepare des-C,D analogues of 1alpha,25-dihydroxyvitamin D(3).
Prolonged administration of either lithium (7 mg/kg body wt.) or ethanol (30% of daily caloric intake) for 10 days to pregnant rats results in several anatomical abnormalities in the fetus. Intragastric administration of lithium carbonate to pregnant rats immediately after confirmation of pregnancy resulted in high incidence of cleft palate, growth retardation, brain liquification and pulpy brain, hepatomegaly and digital abnormalities, when compared to the saline-treated controls. Furthermore, lithium administration during gestation also resulted in other less frequently observed abnormalities in the fetus, e.g., cardiomegaly, hydronephrosis, ankle-joint defects, syndactyly, defected ribs and sternum ossification defects. Chronic ethanol consumption by pregnant rats during early gestation also resulted in several anatomical abnormalities of prenatal growth retardation, resorption and still births, cleft palate, hydrocephaly and hydronephrosis. The severity and frequency of several of the fetal abnormalities were compounded when lithium and ethanol were administered simultaneously. The possible mechanisms of lithium and ethanol teratogenicity and their synergistic effects have been explained on a biochemical basis.
Various lithium (Li(+)) compounds have been proven to be effective in the therapy of bipolar affective disorder, but their mechanism of pharmacological action is not clearly defined. In our present in vivo electrophysiological study we tested the action of microiontophoretically applied Li(+) and NE on the maintained firing activity of prefrontal cortical neurons of the rat. Target cells were located in the prelimbic cortical projection region (PrL) of the ascending norepinephrinergic pathway. Our data, collected from single unit activity of 59 PrL neurons, demonstrate that lithium can (1) suppress maintained discharge activity, or (2) antagonize both the inhibitory and excitatory modulation of firing activity elicited by NE. These effects of Li(+) were not replicable with GABA-initiated inhibition or glutamate analogue-initiated excitation of discharge activity. Our findings suggest that the action of Li(+) mainly targets the NE-coupled receptor mechanisms and, therefore, it may play an important role in stabilizing the modulation of discharge activity in the PFC caused by different extracellular levels of NE.
The use of lithium-containing compounds has increased dramatically since their introduction into the pharmacopoeia in 1968. However, there is no evidence of more than transitory decreases in admissions to hospital with mania. Such admissions, particularly for female readmissions, have increased. Reasons for this are suggested.