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PubMed1984

The effect of urethane on spontaneous and stimulated contractions of isolated rabbit urinary bladder.

The effects of urethane on the spontaneous and stimulated contractility of isolated strips from rabbit urinary bladder has been investigated to assess if, and at which concentrations, this anaesthetic interferes with the contractility of the bladder smooth muscle. Urethane produces a generalized depression of both spontaneous and stimulated bladder muscle contractility but is expected that, in concentrations similar to those found in plasma during anaesthesia, its effect does not exceed the 10-20% inhibition. Urethane depression of bladder muscle contractility appears attributable, at least in part, to an inhibition of calcium ions mobilization from an intracellular store.

Animals↗
PubMed1982

Relationship between urethan dose rate and adenoma latency: relevance of tumor growth rate and target cell number.

Outbred Swiss Cox mice of both sexes were chronically exposed to urethan added to their drinking water at levels of 0.02--0.10% by weight. The number and sizes of lung adenomas that developed as a result were monitored as functions of time and dose rate (DR). The relationship between dose per unit time, or DR, and time (t1) needed for the development of a mean of one observable tumor per mouse was: DR x tn1 = k, where K and n are constants. The value of n was 2.75. This value could be largely accounted for by the DR-independent tumor growth time, although an increase in the number of target cells at higher urethan dose rates may also be a factor in the relationship between DR and t1. Examination of the relationships between cumulative incidence and DR and between cumulative incidence and adenoma induction time suggests that urethan acts at one stage of a two-stage mechanism in the induction of mouse lung adenomas.

Adenoma↗
PubMedDate not supplied

[The carcinogen urethane induces high-amplitudes circaseptan variations in target tissues and disrupts the rhythm of cell count in lymphoid organs].

The presence of tumor is accompanied by biological rhythms disturbance both in damaged (target) organ, and in nondamaged systems. As discoordination of biorhythms is sometimes one of the causes of pathologic states, we have investigated, which changes in system of about 7-day duration (circaseptan) biorhythms preceded the tumor appearance. The model of lung carcinogenesis, induced by single dose (0.25 mg/g of body weight) of carcinogen urethan in A mice, was used. Characteristics of both target organ, and other organs was studied at the stage, preceding the tumor appearance. The data obtained were compared with the analogous characteristics of the control group, once injected with noncarcinogenic analog of urethan, methylcarbamate. The presence of about 7-day rhythms in several organs, nonsensitive to carcinogenic action of urethan, was demonstrated in the control group. The periods of oscillations were: in bone marrow (the number of nuclear cells)--5.2 days; in thymus (mass; the number of nuclear cells)--7.8, 8.2 days; in liver (mass)--6.2 days; in kidney) mass)--8.9 days; in blood (the number of leukocytes)--10.6 and 4.0 days, ect. In the control lungs low-amplitude rhythm of tissue mechanical characteristics (T = 3.5 days), was revealed (these characteristics indicate the extent to which cells are integrated into tissue). Single carcinogen injection resulted in statistically significant decrease (1.4-1.8 fold) of the periods of the main garmonic in the resistant organs. In lungs (target organ) powerful high-amplitude circaseptan oscillations, not inherent to the lungs of control mice, arise in this tissue after the carcinogen injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMedDate not supplied

[Smoking. Changes produced by urethane on macrophage receptors and the complement system].

The present of communication result of the analysis action urethane, that is yield of burning tobacco, provoked alterations on macrophages, complement system and red blood cells. Our data show that urethane high concentration kill macrophages and red blood cells and severely inhibits complement activity. These findings suggest that urethane high concentrations injury to macrophage's receptors, complement system and red blood cells and these are associated with pathologic process related with passively and actively smoking individuals.

Animals↗
PubMed1997

The effect of hard segment size on the hydrolytic stability of polyether-urea-urethanes when exposed to cholesterol esterase.

Previous studies have shown that both polyester and polyether-based polyurea-urethanes are susceptible to cleavage by hydrolytic enzymes. Furthermore, it has been hypothesized that the degree of hard segment micro-domain formation in polyurethane materials, as well as its structure, influences the ability of enzymes to degrade the polymers. The current study has investigated a series of segmented polyether-urea-urethanes synthesized with the same reagents but having different hard segment content. Using these materials, the relationship between the formation of hard segment domains and the hydrolysis of urea/urethane groups was specifically addressed. Both differential scanning calorimetry and X-ray photo-electron spectroscopy data indicated that the three materials differed significantly in the extent of hard segment domain formation and the nature of the chemical groups located in the top 10 nm of the surface. Biodegradation studies showed a strong dependence on hard segment domain formation and indicated that the polymer containing the highest number of hydrolytically labile urea and urethane bonds exhibited the least degradation. The ability of a polyurethane material to form hard segment micro-domains may contribute to the formation of a protective structure for the hydrolysable hard segment linkages located within the micro-domains.

Biocompatible Materials↗
PubMed1998

Differential synthesis of cholesterol esterase by monocyte-derived macrophages cultured on poly(ether or ester)-based poly(urethane)s.

Monocytes adherent to implanted biomaterials differentiate into macrophages while synthesizing large amounts of degradative enzymes, including cholesterol esterase (CE), which previously has been shown to degrade poly(urethane)s. Human peripheral blood monocytes were cultured on tissue culture grade polystyrene (PS), and two model poly(urethane)s were synthesized from (1) polycaprolactone (PCL) and (2) polytetramethylene oxide (PTMO), both with 2,4-toluene diisocyanate (TDI) and ethylene diamine (ED). The increase in CE and total protein per cell were measured on days 8 and 28 in culture and normalized to the DNA content per cell. At day 8 there consistently were fewer cells remaining on the PTMO-based polymer than on the PCL-based polymer or the PS (p < 0.05). When comparing day 28 to day 8, there was more CE activity and protein per cell on all materials. However, there was a disproportionate synthesis of CE per mg of total protein on PS and TDI/PCL/ED whereas on PTMO there was not. Significantly, there was more protein and CE per cell on PTMO than on PS or TDI/PCL/ED (p < 0.05). This in vitro model system of the chronic phase of inflammation has shown that it is possible to culture monocytes for a month and assess the material surface itself as a potent activator of the differentiation into macrophages without secondary stimulation. Since CE has been shown to degrade poly(ether and ester)-based poly(urethane)s, the differential production of this enzyme relative to the total protein on different surfaces may impact on the potential long-term biostability of an implanted material.

Biocompatible Materials↗
PubMed2005

The in vitro hydrolysis of poly(ester urethane)s consisting of poly[(R)-3-hydroxybutyrate] and poly(ethylene glycol).

This paper reports the study of the complete degradation process for a series of newly synthesized multi-block poly(ester urethane)s consisting of poly[(R)-3-hydroxybutyrate] (PHB) as hard and hydrophobic block and poly(ethylene glycol) (PEG) as soft and hydrophilic segment. The initial stages of degradation of the poly(PHB/PEG urethane)s were monitored by carrying out the degradation experiments at pH 7.4 and 37 degrees C. The weight loss of the copolymer films was traced, and the degraded copolymer films were characterized by GPC, (1)H NMR, TGA, and SEM. The induction phase of the polymer degradation was characterized by a random chain scission of the ester backbone bonds of the PHB segments and an insignificant decline in the weight of the polymer films. An accelerated degradation process was carried out at pH 11.5 and 37 degrees C to investigate the long-term degradation behaviour. The characterization of the degraded polymer films was similar to that for the experiment at pH 7.4. In addition, the water-soluble degradation products were characterized by GPC, (1)H NMR, and FTIR. The main components of the water-soluble degradation products were found to be PEG blocks (monomeric up to quadmeric), 3-hydroxybutyric acid, and crotonic acid. It was found that the copolymer incorporating the highest amount of PEG degraded at the highest rate of all the copolymers studied. The complete degradation of the poly(PHB/PEG urethane)s was monitored using a combination of the physiological and accelerated hydrolytic degradation.

Biocompatible Materials↗
PubMed2004

Synthesis and characterization of polyurethane and poly(ether urethane) nanocapsules using a new technique of interfacial polycondensation combined to spontaneous emulsification.

Polyurethane polymers and poly(ether urethane) copolymers were chosen as drug carriers for alpha-tocopherol. This active ingredient is widely used as a strong antioxidant in many medical and cosmetic applications, but is rapidly degraded, because of its light, heat and oxygen sensitivity. Polyurethane and poly(ether urethane)-based nanocapsules were synthesized by interfacial reaction between two monomers. Interfacial polycondensation combined with spontaneous emulsification is a new technique for nanoparticles formation. Nanocapsules were characterized by studying particle size (150-500 nm), pH, yield of encapsulation and morphologies. Polyurethanes (PUR) were obtained from the condensation of diisocyanate (isophorone diisocyanate: IPDI) and polyol: 1,2-ethanediol (EG), 1,4-butanediol (BD), 1,6-hexanediol (HD). Poly(ether urethane) copolymers were obtained by replacing diols by polyethylene glycol oligomers (PEG) M(w) 200, 300, 400 and 600. Molecular weights of di- and polyols have a considerable influence on nanocapsules characteristics cited above. The increase of molecular weight of polyols tends to increase the mean size of nanocapsules from (232+/-3)nm using EG to (615+/-39)nm using PEG 600, and led to the apparition of a population of agglomerate particles. We also noted that the yield of encapsulation increases with the increase of polyol length (from 85.6 to 92.2% w/w). Microscopic observations confirmed particle size analysis, but cannot predict the membrane structure owing the small size of the particles.

Administration, Topical↗
PubMed2000

A new peptide-based urethane polymer: synthesis, biodegradation, and potential to support cell growth in vitro.

A novel non-toxic biodegradable lysine-di-isocyanate (LDI)-based urethane polymer was developed for use in tissue engineering applications. This matrix was synthesized with highly purified LDI made from the lysine diethylester. The ethyl ester of LDI was polymerized with glycerol to form a prepolymer. LDI-glycerol prepolymer when reacted with water foamed with the liberation of CO2 to provide a pliable spongy urethane polymer. The LDI-glycerol matrix degraded in aqueous solutions at 100, 37, 22, and 4 degrees C at a rate of 27.7, 1.8, 0.8, and 0.1 mM per 10 days, respectively. Its thermal stability in water allowed its sterilization by autoclaving. The degradation of the LDI-glycerol polymer yielded lysine, ethanol, and glycerol as breakdown products. The degradation products of LDI-glycerol polymer did not significantly affect the pH of the solution. The glass transition temperature (Tg) of this polymer was found to be 103.4 degrees C. The physical properties of the polymer network were found to be adequate to support the cell growth in vitro, as evidenced by the fact that rabbit bone marrow stromal cells (BMSC) attached to the polymer matrix and remained viable on its surface. Culture of BMSC on LDI-glycerol matrix for long durations resulted in the formation of multilayered confluent cultures, a characteristic typical of bone cells. Furthermore, cells grown on LDI-glycerol matrix did not differ phenotypically from the cells grown on the tissue culture polystyrene plates as assessed by the cell growth, and expression of mRNA for collagen type I, and transforming growth factor-beta1 (TGF-beta1). The observations suggest that biodegradable peptide-based urethane polymers can be synthesized which may pave their way for possible use in tissue engineering applications.

Absorbable Implants↗
PubMed2002

Thermo-mechanical analysis of a compliant poly(carbonate-urea)urethane after exposure to hydrolytic, oxidative, peroxidative and biological solutions.

AIMS: To date, there is still a great need for a fully viable small diameter (< 6 mm) polymeric vascular graft. Currently in such low flow locations, non-elastic expanded polytetrafluoroethylene (ePTFE) is the best available but it is quite inferior to autologous saphenous vein since it fails due to intimal hyperplasia caused by compliance mismatch between the graft and elastic host artery. Recently, a novel compliant poly(carbonate-urea)urethane vascular graft whose trade name is MyoLink has been developed. In this article, we report the findings of a thermo-mechanical analysis of the polymers chemistry postexposure to in vitro solutions comprised of hydrolytic, oxidative, peroxidative and biological media. METHODS AND MATERIALS: The following degradative solutions were used in vitro: plasma fractions I-IV; phospholipase A2 (PLA); cholesterol esterase (CE) and solutions of H2O2/CoCl2, t-butyl peroxide/CoCl2 (t-but/CoCl2) and glutathione/t-butyl peroxide/ CoCl2 (glut/t-but/CoCl2). The MyoLink graft was compared against a conventional poly(ether)urethane (Pulse-Tec). All the graft specimens were 100 mm in length (5.0 mm ID) and were incubated in the latter solutions at 37 degrees C for 70 days in total. The following thermo-mechanical methods were used to analyse both graft types: thermo-mechanical analysis (TMA) and dynamic mechanical thermal analysis (DMTA). RESULTS: Incubation of Pulse-Tec in plasma fractions I-IV, PLA and CE reveals only one observable modification: an increase in the size of the low temperature, melting phase. But incubation in H2O2/CoCl2, and t-but/CoCl2 leads to an increase in the polymeric phase separation coupled with an enlargement in the size of the low temperature melting crystalline phase in Pulse-Tec. The glut/t-but/CoCl2 solution leads to a phase separation between the hard and soft segment domains, coupled with an increase of the internal order within the hard segment domains in Pulse-Tec. The only system in which MyoLink degraded was glut/t-but/CoCl2. In this system, an increase of the phase separation coupled with a simultaneous increase of the crystal size of the low-temperature melting crystalline phase occurred. CONCLUSION: This study shows dramatic changes in the chemistry of the soft and hard segments occurred in the case of the conventional poly(ether)urethane Pulse-Tec graft material. Such changes were not manifested in the majority of solutions in the case of MyoLink but a hydrolytic-led degradation of the carbonate soft segment was evidenced only in the glut/t-but/CoCl2 system.

Blood Vessel Prosthesis↗
PubMed2003

The influence of protein adsorption and surface modifying macromolecules on the hydrolytic degradation of a poly(ether-urethane) by cholesterol esterase.

Previous investigations have demonstrated that the inflammatory cell derived enzyme, cholesterol esterase (CE) could degrade polyurethanes (PUs) by hydrolyzing ester and urethane bonds. Studies that have investigated the development of protective coatings for PUs have reported that the polymer degradation of polyester-urethanes (PESUs) can be reduced with the use of fluorine containing surface modifying macromolecules (SMMs). Since these latter studies were carried out in the presence of relatively pure enzyme, it has not been shown if SMMs would still provide an enhanced inhibitory effect if surfaces were pre-exposed to plasma proteins. This would be more representative of the in vivo scenario since protein adsorption would occur before the appearance of monocyte-derived macrophages which would be a primary source of esterase activities. The current investigation has focused on studying the influence of fibrinogen (Fg) as a simple model of protein adsorption in order to assess the effect of CE in combination with protein on polyether-urethane (PEU) surfaces. The materials were prepared with and without SMMs, and were pre-coated with Fg prior to carrying out biodegradation studies. The pre-adsorption of Fg onto the modified and non-modified surfaces provided a significant delay in the hydrolytic action of CE onto the PEU substrates. However, the effect was gone by 70 days and by the 126th day of incubation, both Fg coated and non-Fg coated groups had the same level of degradation. The difference between Fg coated and non-coated substrates was much smaller for materials containing SMMs. In addition, the pre-adsorption of Fg did not alter the SMMs' ability to provide a more biostable surface over the 4 month incubation period.

Adsorption↗
PubMed2003

Pressure-dependent Fourier transform infrared spectroscopy of a poly (ester urethane).

The effects of hydrostatic pressure upon (1) a segmented poly (ester urethane), (2) a hydrolytically degraded sample of the same polymer, and (3) models for the polyurethane and polyester segments in this polymer have been studied by Fourier transform infrared spectroscopy using high-pressure diamond anvil cells (DACs). The pressure responses of the vibrational frequencies of specific functional groups of the poly (ester urethane) in the 0-100-kbar range are compared with data for individual segment models and the partially degraded sample. The results indicated that the polymer is highly stable in this pressure regime, with no measurable degradation or phase changes. Differences in the pressure dependency of specific infrared bands between the poly (ester urethane) sample and the partially degraded sample are slight and consistent with changes in hydrogen-bonding interactions and shorter chain lengths in the degraded sample.

Diamond↗
PubMed1970

A cytological study of the relation of the cortical reaction to subsequent events of fertilization in urethane-treated eggs of the sea urchin, Arbacia punctulata.

Eggs of the sea urchin, Arbacia punctulata, treated with 3% urethane for 30 sec followed by 0.3% urethane and inseminated are polyspermic and fail to undergo a typical cortical reaction. Upon insemination the vitelline layer of urethane-treated eggs either does not separate or is raised only a short distance from the oolemma. 1-6 min after insemination, almost all of the cortical granules remain intact and are dislodged from the plasmalemma. Later (6 min to the two-cell stage) some cortical granules are released randomly along the surface of the zygote. Not all zygotes show the same degree of cortical granule dehiscence; most of them experience little if any granule release whereas others demonstrate considerably more. The thickness of the hyaline layer appears to be directly related to the number of cortical granules released. Subsequent to pronuclear migration, several male pronuclei become associated with the female pronucleus. Later the male and female pronuclear envelopes contact and the outer and the inner laminae fuse, thereby forming the zygote nucleus. The male pronuclei remaining in the cytoplasm increase in size and progressively migrate to, and fuse with, the zygote nucleus. By 60 min some zygotes appear to contain only one large zygote nucleus which subsequently enters mitosis. Other zygotes possess a number of male pronuclei which remain unfused, and later these pronuclei along with the zygote nucleus undergo mitosis. There does not appear to be a direct relation between the number of cortical granules a zygote possesses and the above mentioned dichotomy.

Animals↗
PubMed2003

Gap junctional intercellular communication in cells isolated from urethane-induced tumors in A/J mice.

Studies using normal or neoplastically transformed established mouse lung epithelial cell lines revealed a reduction in gap junctional, intercellular communication (GJIC) with transformation. To determine the stage in tumor development at which GJIC is interrupted, we used the well-established model of lung tumors induced in strain A/J mice by urethane. In this system, tumor development follows a well-characterized pattern; hyperplasias, adenomas, and carcinomas are manifested at approximately 8, 16, and 40 weeks after urethane treatment, respectively. GJIC levels were examined using a novel technique where cells are grown on a glass slide, half of which is coated with electrically conductive, optically transparent, indium-tin oxide. An electric pulse that opens transient pores on the plasma membrane is applied in the presence of the fluorescent dye, Lucifer yellow, causing dye penetration into cells growing on the conductive part of the slide. Migration of the dye through gap junctions to nonelectroporated cells growing on the nonconductive area is then microscopically observed under fluorescence illumination. Unexpectedly, primary cells cultured from urethane-induced tumors, even late stage carcinomas, possessed extensive GJIC immediately upon isolation. Upon passage for several months however, these cells lost GJIC. These results suggest that the molecular changes that lead to the formation of the tumor in vivo are not sufficient to interrupt gap junctions. Propagation of tumor cells in culture induces additional alterations that can lead to gap junction closure.

Animals↗
PubMed1983

Allergic contact dermatitis due to urethane acrylate in ultraviolet cured inks.

Seven workers exposed to ultraviolet printing inks developed contact dermatitis. Six cases were allergic and one irritant. A urethane acrylate resin accounted for five cases of sensitisation, one of which was also sensitive to pentaerythritol triacrylate and another also to an epoxy acrylate resin. One instance of allergy to trimethylpropane triacrylate accounted for the sixth case of contact dermatitis in this group of workers. An irritant reaction is presumed to account for the dermatitis in the individual not proved to have cutaneous allergy by patch tests. In this instance trimethylpropane triacrylate was thought to be the most likely irritating agent. Laboratory investigation proved urethane acrylate to be an allergen. The results of investigations of the sensitisation potentials of urethane acrylate, methylmethacrylate, epoxy acrylate resins, toluene-2,4-diisocyanate, and other multifunctional acrylic monomers in the albino guinea pig are presented. The interpretation of such predictive tests is discussed.

Acrylates↗
PubMed1983

Antiparasitic activity of natural and semisynthetic monensin urethanes.

A total of 17 monensin urethanes, including two naturally produced phenethylurethanes (Streptomyces sp.), were evaluated for antiparasitic activity. All of the compounds had the characteristic properties of the polyether antibiotics including their ability to transport cations across membranes. Several of the semisynthetic derivatives demonstrated in vitro and in vivo anticoccidial activity in chickens. In vitro activity was shown utilizing chick kidney cell culture experimental procedures in which several of the semisynthetic antibiotics were active at 1 ppm or less. Derivatives having anticoccidial efficacy exhibited activity in vitro against Treponema hyodysenteriae, the causative agent of swine dysentery. Mice previously treated with specific semisynthetic urethanes survived a severe Plasmodium berghei challenge indicative of antimalarial properties as well. Specific biological activity could be correlated with structural relationships of the semisynthetic urethanes.

Animals↗
PubMed1999

The biodegradation of poly(urethane)s by the esterolytic activity of serine proteases and oxidative enzyme systems.

Biodegradation of poly(urethane)s (PU)s using single enzymes in vitro was assessed by measuring radiolabel release from model poly(ester-urea-urethane) (PESU) and poly(ether-urea-urethane) (PETU) materials synthesized with 14C-labelled monomers. Cholesterol esterase (CE), an enzyme found in monocyte-derived macrophages (MDM), has been reported to cause a significant level of radiolabel release from both of these PUs. Previous work has shown that CE activity could be inhibited by the serine protease/esterase inhibitor, phenylmethylsulfonyl fluoride. Since many serine proteases are present in circulating blood and can be released by cells other than MDM, this study investigated the ability of serine proteases relative to that of CE to cause the degradation of PUs. In addition, the possible role of several oxidative enzymes in the breakdown of PUs was investigated. Proteinase K, chymotrypsin and thrombin, when incubated with PESU, coated on glass slips, caused significant radiolabel release, with proteinase K giving the highest values. However, the highest radiolabel release which proteinase K could elicit was ten times less than CE. Thrombin and then chymotrypsin were progressively worse in their biodegradative activity. Only CE, and not the serine proteases, could elicit a detectable radiolabel release from PETU. Although the release of reactive oxygen species and molecular oxygen occur around an implanted biomaterial, several oxidative systems (peroxidase, xanthine oxidase, catalase), known to produce one or more of these molecular species, were unable to induce radiolabel release from these PUs. The process of biodegradation as assessed by radiolabel release appears to be a specific hydrolytic process, while the role of oxidative enzymes remains less clear.

Biodegradation, Environmental↗
PubMed2000

In vitro stability of polyether and polycarbonate urethanes.

The in vitro structural stability of poly-ether-urethanes (PEUs) and poly-carbonate-urethanes (PCUs) was examined under strong acidic (HNO3) or alkaline (NaClO) oxidative conditions and in presence of a constant strain state. Polyurethane (PU) samples were represented by sheets solvent-cast from commercial pellets or by tubular specimens cut from commercial catheters. The specimens were strained at 100% uniaxial elongation over appropriate extension devices and completely immersed into the oxidative solutions at 50 degrees C for 7-14 days. The changes induced by the oxidative treatments were then evaluated by molecular weight analysis, tensile mechanical tests, and scanning electron microscopy. In the experiments with solvent-cast samples, the PEU Pellethane was degraded more in the alkaline oxidative conditions and mainly in the absence of an applied uniaxial stress. All the tested PCUs were, on the contrary, more affected by the acidic oxidative agent. All the PCUs proved to have overall better stability than the PEU. The susceptibility to oxidation was also dependent on the shape and bulk/surface organisation acquired by the same polymer during its processing. When the oxidative test was applied to catheters made of a PEU and a PCU, the results confirmed the better stability of poly-carbonate-urethanes.

Biocompatible Materials↗