Urethane

The prolonged and localized delivery of nitric oxide (NO), a potent antithrombotic and antimicrobial agent, has many potential biomedical applications. In this work, the origin of the long-term storage stability and sustained NO release mechanism of S-nitroso-N-acetyl-D-penicillamine (SNAP)-doped CarboSil 20 80A polymer, a biomedical thermoplastic silicone-polycarbonate-urethane, is explored. Long-term (22 d) localized NO release is achieved by utilizing a cross-linked silicone rubber as topcoats, which can greatly reduce the amount of SNAP, NAP, and NAP disulfide leaching from the SNAP-doped CarboSil films, as measured by LC-MS. Raman spectroscopy and powder X-ray diffraction (PXRD) characterization of SNAP-doped CarboSil films demonstrate that a polymer-crystal composite is formed during the solvent evaporation process when SNAP exceeds its solubility in CarboSil (ca. 3.4-4.0 wt%). Further, when exceeding this solubility threshold, SNAP exists in an orthorhombic crystal form withi...

The purpose of this study was to evaluate and compare the retention strength of five cement types commonly used in implant-retained fixed partial dentures, before and after compressive cyclic loading. In five solid abutments screwed to 5 implant analogs, 50 metal Cr-Ni alloy copings were cemented with five luting agents: resin-modified glass ionomer (RmGI), resin composite (RC), glass ionomer (GI), resin urethane-based (RUB), and compomer cement (CC). Two tensile tests were conducted with a universal testing machine, one after the first luting of the copings and the other after 100,000 cycles of 100 N loading at 0.72 Hz. The one way ANOVA test was applied for the statistical analysis using the post hoc Tukey test when required. Before and after applying the compressive load, RmGI and RC cement types showed the greatest retention strength. After compressive loading, RUB cement showed the highest percentage loss of retention (64.45%). GI cement recorded the lowest retention strength (...

To assess the sealing properties of four luting materials used for cementation of full cast crowns. 40 human premolars were prepared with a chamfer finish line. Stone dies were fabricated and copings were waxed, invested and cast in gold. Ten samples (n = 10) were randomly assigned to four groups. In two groups, resin modified glass-ionomer cements were used, ACTIVA BioACTIVE-CEMENT/BASE/LINER and FujiCem2; the third group received the self-adhesive resin cement Embrace WetBond, while the fourth group served as control with a zinc phosphate cement. After cementation, excess cement was removed followed by bench-set for 10 minutes. All samples were stored in water at 37 degrees C and subjected to thermal cycling (x2000 between 5 and 55 degrees C). Subsequently the occlusal surface was reduced exposing the dentin. After sterilization the specimens were subjected to bacterial microleakage with E. faecalis in a dual chamber apparatus for a period of 60 days. Bacterial leakage was checked...

To study the interactions between chemical carcinogens and oncogenic retroviruses, BALB/Mo mice which carry the Moloney murine leukemia virus (M-MuLV) as an endogenous virus, and conventional (M-MuLV-free) BALB/c mice, as well as their Bc1 (M-MuLV+ or M-MuLV−) hybrids were injected neonatally with a single dose of urethane. BALB/Mo and V+ Bc1 mice showed accelerated lymphoma development; similar results were obtained in BALB/Mo mice receiving one or two doses of urethane transplacentally. Lung adenomas developed with shorter latency and higher incidence in BALB/Mo mice given urethane at birth; however, significant differences in the incidence of lung adenomas in BALB/Mo mice were found only in two experiments. Additional short-term experiments were carried out to investigate the mechanism of the higher susceptibility to sister chromatid exchange induction observed in BALB/Mo lymphocytes. It was found that BALB/Mo spleen lymphocytes incubated with cordycepin, an antiviral antibiotic,...

An innovative procedure to separate the 3 isomeric sn-monoacylglycerols (MAG) classes (sn-1-, sn-2-, sn-3-MAG) is described. MAGs, obtained by chemical deacylation of triacylglycerols (TAGs), have been derivatized with (S)-(+)-1-(1-naphtyl)ethyl-isocyanate, and the resulting urethane derivatives have been separated by normal-phase high-performance liquid chromatography. This procedure allows resolution as diasteroisomers of the 2 enantiomeric classes (sn-1-MAG and sn-3-MAG), without the need of a chiral column, and to separate also the isomeric sn-2-MAG class; moreover, by introducing a chromophoric moiety, this reagent makes possible the ultraviolet detection of the analyte molecules. This procedure has been used to obtain the stereospecific analysis of the TAG fraction of extra virgin olive oil samples. The use of a nondestructive detector permitted the collection of the individual urethane classes; the fatty acid composition of each was determined by high-resolution gas chromatog...

To determine if hemizygous transgenic mice carrying the human c-Ha-ras gene (CB6F1-Tg Hras2 mice (Hras2 mice)) are susceptible to the carcinogenic potential of known murine carcinogens, male and female Hras2 mice and their non-transgenic CB6F1 littermates (non-Tg mice) were each given a single intraperitoneal injection of 60 mg of vinyl carbamate (VC)/kg body weight or saline (vehicle control) and monitored for 16 wk without further treatment. At necropsy, grossly visible tumors were fixed for histopathologic diagnosis and, when of sufficient size, portions were frozen for subsequent molecular analysis. Nine of 31 male and nine of 29 female Hras2 mice treated with VC died within 16 wk as a result of lung tumor burden. At the termination of the study, lung tumors (alveolar-bronchiolar epithelial neoplasms and hemangiosarcomas) and focal alveolar-bronchiolar hyperplasias were present in both sexes of Hras2 and non-Tg mice treated with VC; there were significantly more proliferative lung lesions in Hras2 than non-Tg mice. Splenic hemangiosarcomas and squamous cell tumors of the forestomach were induced in male and female VC-treated Hras2 mice but not in VC-treated non-Tg mice. Polymerase chain reaction-single-strand conformation polymorphism analysis and DNA sequencing of the induced lung tumors revealed point mutations at codon 61 of the transgene in two of 29 lung tumors (one of 16 in males and one of 13 in females) from VC-treated Hras2 mice; no mutations in murine Ki-ras were found in these tumors. Point mutations at codons 12 and 61 of the murine Ki-ras gene were observed, however, in one of 10 and six of 10 lung tumors respectively, from VC-treated non-Tg mice. These findings indicate that Hras2 mice are highly sensitive to pulmonary neoplasms and splenic and lung hemangiosarcomas after treatment with VC. The molecular analyses suggest that point mutations of the transgene and the murine Ki-ras gene do not play a major role in VC induction of pulmonary neoplasms in these transgenic mice.

Concentration of polyunsaturated fatty acids ethyl esters (FAEE) by urea complexation from Echium oil was studied. Different variables involved in the process were investigated: amount and particle size of urea, solvent volume and ratio (hexane/ethanol), load of FAEE and reaction time. Hence, the main goal was to optimize SDA concentration (%) and yield (%) of stearidonic acid (SDA, 18:4 ω-3) and other bioactive FAEE. Similar behaviors were observed in fractionation between α-linolenic (ALA)-linoleic (LA), and γ-linolenic (GLA)-stearidonic (SDA) acids, attributed to similarities on their chemical structures, due to the position of the double bonds. At laboratory scale, the optimal conditions were 3 g urea (powder), 3.6 mL of hexane, 0.54 mL of ethanol and 800 mg of FAEE, during 20 h at 25°C. A scaling-up at pilot plant was carried out twice, obtaining more than 100 g of a final product, with ~29% SDA concentration and ~78% yield. Besides, after two washings with water, ethyl carbama...

The transcription factor CCAAT/enhancer-binding protein α (C/EBPα) is a basic leucine zipper transcription factor and is expressed in alveolar type II cells, alveolar macrophages and Clara cells in the lung. Although decrease or absence of C/EBPα expression in human non-small cell lung cancer suggests a possible role of C/EBPα as a lung tumor suppressor, there is no direct proof for this hypothesis. In this study, we investigated, for the first time, the role of C/EBPα in lung tumors in vivo using transgenic mice with lung epithelial specific conditional deletion of Cebpa (Cebpα(Δ/Δ) mice) and a urethane-induced lung tumor model. C/EBPα expression in the lung was dispensable, and its deletion was not oncogenic under unstressed conditions. However, at 28 wk after urethane injection, the number and size of tumors and the tumor burden were significantly higher in Cebpα(Δ/Δ) mice than in littermate control mice. Urethane-injected Cebpα(Δ/Δ) mice showed highly proliferative adenomas and ...

Clones of epithelial-like cells were established from urethan-induced mouse lung adenoma. Electron microscopy of one clone showed that the cells contained lamellar inclusion bodies similar in appearance to those seen in the adenoma precursor, the type II alveolar pneumocyte. The clones exhibited characteristics associated with both "transformed" and "normal" cells in culture; i.e., although aneuploid, the cells grew at a slower rate than most transformed cells, did not form colonies in soft agar and, after prolonged subculture, were not tumorigenic when transplanted s.c. into appropriate hosts. Hydrocortisone treatment of the cloned cells led to growth stimulation and the eventual acquisition of neoplastic potential. Epithelial tumors were produced more readily in athymic, nude mice than in antilymphocyte serum-treated A/He mice. The cells are producing a C-type RNA virus into the culture medium.

The cyclic adenosine 3':5'-monophosphate (cAMP)-dependent protein kinases in lung adenomas are functionally different from those of normal lung. The relevance of this change to neoplastic conversion was examined by comparing tumor kinases with those obtained from the normal cell of origin and by studying the kinases at different stages of tumor growth. Lung tumors were collected from A strain mice at different times after a single injection of urethan. These tumors are predominantly of alveolar type two cell origin, and cAMP-binding proteins in extracts from isolated type two cells and from lung adenomas at various stages of tumor progression were compared. Both the incorporation of the cAMP photoaffinity analogue, cyclic 8-azidoadenosine 3':5'-[32P]monophosphate (8-N3-[32P]cAMP), into the regulatory subunits of the type I (RI) and type II (RII) cAMP-dependent protein kinases and the autophosphorylation of RII were similar in extracts from whole normal lung and from ...

Concentration of polyunsaturated fatty acids ethyl esters (FAEE) by urea complexation from Echium oil was studied. Different variables involved in the process were investigated: amount and particle size of urea, solvent volume and ratio (hexane/ethanol), load of FAEE and reaction time. Hence, the main goal was to optimize SDA concentration (%) and yield (%) of stearidonic acid (SDA, 18:4 ω-3) and other bioactive FAEE. Similar behaviors were observed in fractionation between α-linolenic (ALA)-linoleic (LA), and γ-linolenic (GLA)-stearidonic (SDA) acids, attributed to similarities on their chemical structures, due to the position of the double bonds. At laboratory scale, the optimal conditions were 3 g urea (powder), 3.6 mL of hexane, 0.54 mL of ethanol and 800 mg of FAEE, during 20 h at 25°C. A scaling-up at pilot plant was carried out twice, obtaining more than 100 g of a final product, with ~29% SDA concentration and ~78% yield. Besides, after two washings with water, ethyl carbama...

A urethane-based analogue containing an azo aromatic linkage in the backbone was synthesized for use in colon-specific delivery systems by reacting toluene-2,6-diisocyanate with a mixture of an aromatic azo diol, (bis-4-hydroxyphenyl)-4,4′-diazobiphenyl, poly(ethylene glycol) (Mn = 4000; number-average molecular weight) and 1,2-propanediol (propylene glycol). The resultant compounds (UR-1 and UR-2) were characterized by IR spectroscopy, 1H NMR spectroscopy, DSC studies, X-ray diffraction studies and molecular weight determination by gel permeation chromatography. The compounds exhibited low molecular weight, lacked film-forming properties and crystallinity in the structure. An in-vitro bacterial degradation test to demonstrate the susceptibility of azo bond to bacterial enzymes was performed using media inoculated with lactobacillus culture. The results indicated degradation of films by azoreductase. In-vitro permeation of 5-aminosalicylic acid was studied in control and lactobacill...

Experiments have shown that the lateral profile of a point target measured with a clinical ultrasound scanner is wider when the target is embedded in a urethane phantom than when it is in a traditional gel phantom. The behavior has been attributed to the low speed of sound in the urethane material, with the possibility that some of the broadening is caused by increased attenuation in this material. In this paper we apply a computer simulation model to study this behavior. Lateral beam profiles modeled for targets within a medium having a speed of sound and an attenuation matching that of urethane are compared with profiles for targets in a water-based gel. Simulations yield results that agree qualitatively with published experimental results. The lateral profile broadening in urethane is caused by the 6 % mismatch between speed of sound in this material and the speed of sound assumed in the receive focusing and beam forming. Attenuation plays a lesser role than the mismatch of the s...

Modulation of receptive field properties of thalamic somatosensory neurons by the depth of anesthesia. The dominant frequency of electrocorticographic (ECoG) recordings was used to determine the depth of halothane or urethan anesthesia while recording extracellular single-unit responses from thalamic ventral posterior medial (VPM) neurons. A piezoelectric stimulator was used to deflect individual whiskers to assess the peak onset latency, magnitude, probability of response, and receptive field (RF) size. There was a predictable increase in the dominant ECoG frequency from deep stage IV to light stage III-1 anesthetic levels. There was no detectable frequency at stage IV, a 1- to 2-Hz dominant frequency at stage III-4, 3-4 Hz at stage III-3, 5-7 Hz at stage III-2, and a dual 6- and 10- to 13-Hz pattern at stage III-1. Reflexes and other physical signs showed a correlation with depth of anesthesia but exhibited too much overlap between stages to be used as a criterion for any single s...

In quiescent states such as anesthesia and slow wave sleep, cortical networks show slow rhythmic synchronized activity. In sensory cortices this rhythmic activity shows a stereotypical pattern that is recapitulated by stimulation of the appropriate sensory modality. The amygdala receives sensory input from a variety of sources, and in anesthetized animals, neurons in the basolateral amygdala (BLA) show slow rhythmic synchronized activity. Extracellular field potential recordings show that these oscillations are synchronized with sensory cortex and the thalamus, with both the thalamus and cortex leading the BLA. Using whole-cell recording in vivo we show that the membrane potential of principal neurons spontaneously oscillates between up- and down-states. Footshock and auditory stimulation delivered during down-states evokes an up-state that fully recapitulates those occurring spontaneously. These results suggest that neurons in the BLA receive convergent input from networks of corti...

Urethane is widely used in neurophysiological experiments to anesthetize animals, yet little is known about its actions at the cellular and synaptic levels. This limits our ability to model systems-level cortical function using results from urethane-anesthetized preparations. The present study found that action potential discharge of cortical neurons in vitro, in response to depolarizing current, was strongly depressed by urethane and this was accompanied by a significant decrease in membrane resistance. Voltage-clamp experiments suggest that the mechanism of this depression involves selective activation of a Ba2+-sensitive K+ leak conductance. Urethane did not alter excitatory glutamate-mediated or inhibitory (GABAA- or GABAB-mediated) synaptic transmission. Neither the amplitude nor decay time constant of GABAA- or GABAB-mediated monosynaptic inhibitory postsynaptic currents (IPSCs) were altered by urethane, nor was the frequency of spontaneous IPSCs. These results are consistent ...

Corticotropin-releasing factor (CRF) injected peripherally or released in response to stressful challenges to the organism reduces gastric tone and contractility, in part by vagal pathways. However, information on the changes in gastric vagal impulse activity evoked by peripheral CRF administration is entirely lacking. Using a novel “dual recording” method in urethane-anesthetized rats, vagal efferent (VE) and afferent (VA) impulse activities were recorded simultaneously from separate, fine bundles dissected from the ventral gastric vagus nerve branch innervating the glandular stomach. Activity records for 38 VA single units (SUs) and 33 VE SUs were sorted from multiunit records obtained from 13 preparations. Intravenous (iv) administration of saline had no effect on multiunit VE activity, whereas CRF (1 μg/kg, iv) immediately inhibited VE activity, reaching a nadir of 54 ± 8.0% of preinjection levels at 3.0 min postinjection. CRF (1 μg/kg, iv) inhibited 25/33 (75.8%) VE SUs and exc...

A good process understanding is the foundation for process optimization, process monitoring, end-point detection, and estimation of the end-product quality. Performing good process measurements and the construction of process models will contribute to a better process understanding. To improve the process knowledge it is common to build process models. These models are often based on first principles such as kinetic rates or mass balances. These types of models are also known as hard or white models. White models are characterized by being generally applicable but often having only a reasonable fit to real process data. Other commonly used types of models are empirical or black-box models such as regression and neural nets. Black-box models are characterized by having a good data fit but they lack a chemically meaningful model interpretation. Alternative models are grey models, which are combinations of white models and black models. The aim of a grey model is to combine the advanta...