SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
It has been shown that bromodimethylsulfonium bromide, generated in situ by treating dimethyl sulfoxide with aqueous hydrobromic acid, is a milder and more selective reagent for electrophilic aromatic bromination than elemental bromine.
[reaction: see text] Vanadium pentoxide very effectively promotes the bromination of organic substrates, including selective bromination of some aromatics, by tetrabutylammonium bromide in the presence of hydrogen peroxide; mild conditions, high selectivity, yield, and reaction rate, and redundancy of bromine and hydrobromic acid are some of the major advantages of the synthetic protocol.
1. Treatment of 3-dehydroretinyl acetate with aqueous hydrobromic acid resulted in the formation of retro-3-dehydroretinyl acetate, which, on alkaline hydrolysis, gave the corresponding alcohol. 2. retro-3-Dehydroretinyl acetate was isomerized to 3-dehydrovitamin A when fed to vitamin A-deficient rats. 3. When retro-3-dehydroretinyl acetate was administered orally, it was hydrolysed to retro-3-dehydroretinol in the rat intestine, isomerized to 3-dehydroretinol and esterified before being transported to the liver for storage. 4. When administered intraperitoneally, both 3-dehydrovitamin A and retro-3-dehydrovitamin A were accumulated in liver and other tissues, whereas after enterectomy 3-dehydrovitamin A was not detected anywhere in the body. 5. The small intestine was shown to be the major site of conversion of retro-3-dehydrovitamin A into 3-dehydrovitamin A. 6. The extent of conversion of retro-3-dehydroretinyl acetate into 3-dehydrovitamin A was much smaller than that of the conversion of retro-retinyl acetate into vitamin A. 7. The biological potency of retro-3-dehydroretinyl acetate, determined by the rat-growth assay, was 2.6% of that all-trans-retinyl acetate, when given orally.
The innervation of the skin of hairless mice has been studied following induction of epidermal hyperplasia by physical and chemical methods. Physical stimuli comprised ultraviolet irradiation, heat, wounding, and friction. Effective chemicals included benzene, carbon tetrachloride, chloroform, creosote, formaldehyde, hexadecane, hydrobromic acid, sodium lauryl sulfate, and turpentine. Epidermal hyperplasia, however produced, was associated with growth of sensory nerve fibers into the outer part of the epidermis. Following a single 10-min exposure to an ultraviolet sunalmp at 40 cm, the nerves extended into the epidermis within 24 hr and disappeared during the second week as the epidermis reverted to its normal thickness. Repeated irradiation (until tumors appeared) was accompanied by persistent hyperplasia and neural invasion. Of 32 papillomas examined, intraepithelial nerves were found in 28. The presence and location of nerves in the tumor epithelium were related to the incorporation of tactile hair disc epithelium. The hyperplastic regenerative epithelium at the margins of skin ulcers were also invaded by nerves which sometimes followed the migrating epithelium across the ulcer floor. Since the regenerative epithelium was not directly treated, it was concluded that the proliferation of nervous tissue in response to skin injury was the result of the hyperplasia per se, regardless of the method used to produce it.
The tetrahydrogeraniol (THG) derivative, ethyl-(3,7-dimethyl octyl thio) acetate (EDOTA) was prepared by reacting tetrahydrogeranyl bromide (obtained by reaction of 40% hydrobromic acid and concentrated sulfuric acid) with ethyl 2-mercaptoacetate, while 3,7-dimethyl octyl propionate (DOP) was synthesized by a common esterification reaction by reacting THG with propionic acid in the presence of cyclohexane and concentrated sulfuric acid. The penetration-enhancing effect of the new enhancers were compared with THG and Azone in vitro using excised rat skin in modified Franz-type diffusion cells. 5-Fluorouracil (5-FU), a hydrophilic drug with poor skin permeability was used as a model permeant. Skin samples were pretreated with pure liquid enhancers for 12 h. 5-FU flux through the control and enhancer-treated skin increased linearly with its concentration in the receptor compartment. EDOTA and DOP interacted with the skin rapidly (< 2h), and the duration of action is at least 24 h. Significant differences were found in the flux values of 5-FU; EDOTA and DOP enhanced the permeability of the drug about 6-fold and 11-fold respectively. Increased partition coefficient and diffusion coefficient values were obtained by these enhancers. The results suggested that the amount of EDOTA and DOP in the skin, especially in the stratum corneum, may be related to their penetration-enhancing effect.
Dibutyltin compounds (DBTC) in polyvinyl chloride resin (PVC) were examined by capillary gas chromatography using a flame photometric detector (FPD). DBTC was extracted with a carbon tetrachloride-methanol (2:1) mixture under reflux. The extract was mixed with a hydrobromic acid solution. Dibutyltin dibromide was converted to dibutyldipentyltin (DBDPeT) by the Grignard reaction with pentylmagnessium bromide and then subjected to gas chromatography. A linear correlation between the amount of tin and peak height was observed in the range of 7.8 to 250 pg of tin on log-log paper. Recoveries of DBTC added to PVC were 92.6-108.1%. The results show that this procedure is more useful and sensitive (the detection limit is 3-4 pg, as tin) than previous methods reported.
Determination of tributyltin and its metabolites, dibutyltin and monobutyltin, in biological materials was made by capillary gas chromatography (C-GC) using a flame photometric detector (FPD). Butyltin compounds (BuTC) were extracted (as bromides) from tissue homogenates with hydrobromic acid and ethyl acetate. These compounds were converted to pentyl derivatives with pentyl Grignard reagent and then analysed by C-GC. The recoveries of each BuTC added to tissues were 96-99% for monobutyltin, 87-93% for dibutyltin and 90-93% for tributyltin. The detection limit of BuTC was 4-5 pg as tin. This method was applied to the analysis of BuTC in the liver and kidney of rats orally administered tributyltin chloride. Time course of three BuTC showed that the maximum value appeared 24 h after administration of the tin compound, which was followed by a rapid decrease. The order of the concentration of BuTC in both organs was dibutyltin greater than tributyltin greater than monobutyltin. The rate of dealkylation was more rapid in liver than in kidney.
The reaction of 2-(beta-hydroxyethyl)-pyrrolidine with isothiocyanates gave rise to the formation of thiourea derivatives which cyclised on refluxing in hydrobromic acid to yield N-(3,4,4a,5,6,7-hexahydro-1H-pyrrolo[1,2-c][1,3]thiazin-1-ylidene)-aryl(alkyl)amines. The results of preliminary pharmacological screening are presented.
Dehydration of 2-hydroxy(ethoxy)-2-aryl-N.N-penta(tetra) methylenemorpholinium bromide was achieved either by heating (175 degrees C) the compound with catalytic amounts of hydrobromic acid, or by refluxing the compound in a glacial acetic acid-hydrogen bromide mixture or by treating it with phosphorus tribromide at room temperature. In the acetic acid-hydrogenbromide method, the product was accompanied by N-bromoethyl(carbethoxy)-N-phenacylmorpholinium bromide, while strong heating (210 degrees C) of the title compounds or reflux in xylene yielded N-2-bromoethylpiperidine hydrobromide. Under the latter conditions, N-methyl-N-phenacylpiperidinium bromide gave similarly N-methylpiperidine hydrobromide. A preliminary biologic activity study in the synthesized compounds has also been conducted.
A sensitive method is described to determine trace quantities of ethylene oxide (EO) in EO-sterilized intraocular lenses (IOLs). An IOL is dipped in ethanol containing 0.25 ppm propylene oxide (PO) in a 4 mL vial, 2 drops of freshly distilled hydrobromic acid is added through a septum, and the mixture is warmed at 50 degrees C for 24 h. It is then neutralized by vigorous shaking with sodium bicarbonate, dehydrated with anhydrous sodium sulfate, and filtered. The filtrate is injected into a gas chromatograph with electron-capture detection, and the peak height ratio of ethylene bromohydrin/propylene bromohydrin is measured. EO residue is calculated from the calibration curve obtained through a similar procedure with the standard EO/PO solutions. The limit of determination is 0.04 microgram/lens (ca 2.0 ppm). When EO residue levels were determined for IOLs sampled at 3 different aeration periods after sterilization, we found that 9 days of aeration was necessary to meet the U.S. Food and Drug Administration proposed limit for EO residue in IOLs.
Within the relationship of the structure and effect of new beta-adrenolytic agents derivatived from p-hydroxyacetophenone and p-hydroxypropiophenone with a propoxymethyl group in the lipophilic part of the molecule and with a propanamine, a butanamine and a pyrrolidine in the side-chain were studied. In order to prepare these substances, a procedure was selected from several tested ones, in which 4-hydroxy-3propoxymethylphenylketone were treated with chloromethyloxirane and subsequent reaction a hydrobromic acid were prepared 4-(3-brom-2-hydroxypropoxy)-3-propoxymethylalkylketone. Final substances were prepared reaction with amine. The structure of prepared compounds was confirmed on the basic interpretation of the IR, UV and 1H NMR spectra. The results of pharmacological evaluation of selected compounds showed a significant beta 1-blocking activity lower than acebutolol. Their local anesthetic activity is low according with their partition coefficients. The characteristic of the prepared compounds was supplemented by the determination of their partition coefficients, surface tension, dissociation constants and acute toxicity.
A series of 3-(aminoalkyl)-2,7-dihydro-6-nitropyrimido [4,5,6-kl] acridin-2-ones 3, strictly related to the pyrazoloacridines 1, have been synthesized. Thus, the reaction of the suitable 1-(aminoalkyl)amino-9, 10-dihydro-9-imino-4-nitroacridine 2 with ethyl chloroformate afforded the pyrimidoacridines 3a-f. By hydrolysis in hydrobromic acid of the 10-methoxy derivatives 3d-f, the 10-hydroxy derivatives 3g-i were obtained. The pyrimidoacridines 3a-i were tested in vitro for their cytotoxic activity against L1210 murine leukemia and HT29 human colon adenocarcinoma cell lines, showing significant potency of growth inhibition. Different DNA-binding assays as well as attempts to correlate cytotoxicity and DNA affinity have been carried out.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Hydrogen fluoride (HF), hydrogen bromide (HBr), and hydrogen chloride (HCl) gases can be generated during the pyrolysis of a variety of materials and they may be encountered in numerous industrial settings. Although injury to the respiratory tract has been characterized following the inhalation of halide gases via the nasal route, essentially no experimental information is currently available about their injurious effects when they are inhaled during mouth breathing. In this study, we simulated mouth breathing by using a pseudo-mouth-breathing (MB) rat model in order to: (1) characterize the profiles and magnitudes of respiratory tract injury that result from the acute inhalation of relatively high mass concentrations of the above halides when the upper airway is bypassed, and (2) assess the relative toxicities of HF, HBr, and HCl when inhaled by way of either the nasal or the oral pathways. Tracheal tubes connected to mouthpieces were inserted into temporarily anesthetized rats, i.e., mouth breathers. Awake rats were placed into whole body flow plethysmographs for pulmonary ventilation studies while they were exposed either to air or to 1300 ppm of HF, HBr, or HCl for 30 min. Similarly pretreated rats were also exposed but without the mouthpiece, i.e., nose breathers (NB). The animals were euthanized 24 hr after exposure for histopathologic analyses of their upper and lower respiratory tracts and for lung gravimetric measurements. Tissue injury following NB exposure to the halides was confined to the nasal region, e.g., epithelial and submucosal necrosis, accumulations of inflammatory cells, exudates, and the extravasation of erythrocytes. MB exposure caused higher mortality rates and major tissue disruption in the trachea, including epithelial, submucosal, glandular, and cartilage necrosis, and accumulations of inflammatory cells and exudates. More peripheral lung damage was manifested by lung gravimetric increases and histopathologic changes primarily in the larger conducting airways. The results of this study demonstrate that the injurious response profiles to HF, HBr, and HCl markedly differ as a function of the route by which they are inhaled. Furthermore, examinations of the magnitudes of injury caused by exposure to the halides during nose or mouth breathing in conjunction with animal ventilatory data obtained during exposure to the halides suggest that HF, HBr, and HCl are quantitatively similar in their toxic effects in the respiratory tract.
A general and efficient method for the synthesis of unsymmetrical 1,3,4,6-tetrasubstituted 2,5-diketo- piperazines (DKPs) is described. Cyclization of N-amide alkylated dipeptide methyl esters, followed by alkylation, furnished the corresponding tetrasubstituted DKPs in good overall yields. The influence of steric hindrance in the alkylation reactions appeared to be of lesser importance as long as reactive alkylating agents were used. Furthermore, we have demonstrated the use of tetrasubstituted DKPs as a scaffold for further chemical manipulations to produce novel DKPs with desired properties.