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PubMed2004

Prevalence of liver tumours in HIV-1 tat-transgenic mice treated with urethane.

The human immunodeficiency virus type 1 (HIV-1) Tat protein stimulates cell proliferation, inhibits apoptosis, displays angiogenic functions and is believed to be involved in the pathogenesis of Kaposi's sarcoma (KS) and other tumours arising in AIDS patients. Tat-transgenic (TT) mice, which constitutively express Tat in all tissues and organs, may therefore be predisposed to tumorigenesis. To test this hypothesis, we treated TT mice with urethane, a general carcinogen inducing tumours of various organs. The results indicate that, after injection of urethane, the incidence of lung tumours and lymphomas is not significantly different in the TT and control (CC) mice, whereas liver preneoplastic lesions and tumours show a significantly greater incidence in TT than in CC mice. This remarkable carcinogenic effect of urethane for the liver may be due to a tat-induced predisposition, manifested as a liver cell dysplasia (LCD), spontaneously affecting most of the TT mice. LCD may exert a promoting effect by stimulating proliferation of cell clones initiated by the mutagenic effect of urethane. In addition, LCD, which is associated with aneuploidy and chromosome instability, may enhance the progression to malignancy of the preneoplastic lesions induced by urethane. Interestingly, a significantly greater incidence of vascular ectasias and haemangiomas was detected in the liver of urethane-treated TT mice, most likely due to the marked angiogenic properties of Tat. This study suggests a role for Tat in the promotion and progression of tumours initiated by exogenous and endogenous carcinogens in HIV-1-infected patients, thereby contributing to the tumorigenesis in the course of AIDS.

Animals↗
PubMed2004

Respiratory chemoreflexes and effects of cortical activation state in urethane anesthetized rats.

Urethane anesthetized (< 1 .3 g/kg), Sprague-Dawley (SD) rats spontaneously cycled between a cortically desynchronized state (State I) and a cortically synchronized state (State III), which were very similar to awake and slow wave sleep (SWS) states in unanesthetized animals, based on EEG criteria. These low levels of urethane anaesthesia did not cause significant respiratory depression or reductions in sensitivity to hypoxia (10% O2 in nitrogen) or hypercapnia (5% CO2 in air) in rats in either State I or State III. Thus, breathing frequency (fR), tidal volume (VT) and total ventilation (VTOT) all increased on cortical activation in urethane-anaesthetized rats whether breathing air, the hypoxic or the hypercapnic gas mixture, in a manner that was very similar to that observed in unanaesthetized animals. The relative sensitivity to hypoxia was greater in State III than State I, the relative sensitivity to CO2, overall, was equal in both states, State III occurred less often during hypoxia and hypercapnia, and hypoxic, urethane-anaesthetized rats sighed frequently, particularly in State I. This is also similar to the situation seen in unanesthetized rats. Given the similarities seen between urethane anesthetized rats in the present study and literature values for unanesthetized rats, the data suggest that urethane-anaesthetized rats provide a good model system for studying respiratory patterns and chemoreflexes as a function of cortical activation state.

Analysis of Variance↗
PubMed2003

Synthesis, characterization and evaluation of urethane derivatives of Bis-GMA.

OBJECTIVES: The aims of the study were to synthesize derivatives of Bis-GMA having pendant n-alkyl urethane substituents and to characterize and evaluate their physicochemical properties. METHODS: Stoichiometric amounts of Bis-GMA and n-alkyl isocyanates were reacted in dichloromethane with dibutyltin dilaurate as a catalyst. Volumetric shrinkage, water uptake, degree of vinyl conversion, refractive index and viscosity of resulting urethane monomers and those of Bis-GMA were measured. The flexural strengths of their corresponding homopolymers and that of Bis-GMA were also measured. RESULTS: These types of urethane derivatives of Bis-GMA exhibited lower viscosities and were more hydrophobic than Bis-GMA. Generally, the viscosity of these experimental monomers decreased with increasing chain length of the alkyl urethane substituent. Photopolymerization of the new monomers gave high degrees of vinyl conversion compared to Bis-GMA. The experimental monomers also yielded polymers with lower polymerization shrinkages at equivalent degrees of vinyl conversion, than Bis-GMA. The refractive indices of these urethane derivatives were similar to Bis-GMA, but the flexural strengths of their polymers were lower than that of the Bis-GMA homopolymer, decreasing with increasing chain length of the alkyl urethane substituent. SIGNIFICANCE: Because of their excellent overall properties, these new derivatives of Bis-GMA have potential as dental monomers that can improve many properties of resin based dental materials that utilize methacrylate monomer systems.

Bisphenol A-Glycidyl Methacrylate↗
PubMedDate not supplied

Poly(ester urethane)s consisting of poly[(R)-3-hydroxybutyrate] and poly(ethylene glycol) as candidate biomaterials: characterization and mechanical property study.

Poly(ester urethane)s with poly[(R)-3-hydroxybutyrate] (PHB) as the hard and hydrophobic segment and poly(ethylene glycol) (PEG) as the soft and hydrophilic segment were synthesized from telechelic hydroxylated PHB (PHB-diol) and PEG using 1,6-hexamethylene diisocyanate as a nontoxic coupling reagent. Their chemical structures and molecular characteristics were studied by gel permeation chromatography, 1H NMR, and Fourier transform infrared spectroscopy. Results of differential scanning calorimetry and X-ray diffraction indicated that the PHB segment and PEG segment in the poly(ester urethane)s formed separate crystalline phases with lower crystallinity and a lower melting point than those of their corresponding precursors, except no PHB crystalline phase was observed in those with a relatively low PHB fraction. Thermogravimetric analysis showed that the poly(ester urethane)s had better thermal stability than their precursors. The segment compositions were calculated from the two-step thermal decomposition profiles, which were in good agreement with those obtained from 1H NMR. Water contact angle measurement and water swelling analysis revealed that both surface hydrophilicity and bulk hydrophilicity of the poly(ester urethane)s were enhanced by incorporating the PEG segment into PHB polymer chains. The mechanical properties of the poly(ester urethane)s were also assessed by tensile strength measurement. It was found that the poly(ester urethane)s were ductile, while natural source PHB is brittle. Young's modulus and the stress at break increased with increasing PHB segment length or PEG segment length, whereas the strain at break increased with increasing PEG segment length or decreasing PHB segment length.

Biocompatible Materials↗
PubMed1968

Some aspects of the metabolism of urethane and N-hydroxyurethane in rodents.

1. Urethane and N-hydroxyurethane are interconvertible in C(-) and C57 mice. 2. In newborn C57/DBA hybrid mice, prior treatment with 3-methylcholanthrene or urethane stimulated the N-hydroxylation of urethane; SKF 525A inhibited the N-hydroxylation at 24hr. but stimulated it at 48hr. after administration. 3. Liver homogenates of CBA and C3H mice, and of Chester Beatty and hooded rats, but not whole-body homogenates of 1-day-old C57/DBA mice or lung homogenate of 3-week-old Chester Beatty rats, metabolized urethane into N-hydroxyurethane in small but definite amounts. 4. Nitrite was detected in the bodies of newborn C57/DBA hybrid mice treated with lethal doses of urethane or N-hydroxyurethane; nitrite formation from N-hydroxyurethane was stimulated by pretreatment of the animals with 3-methylcholanthrene. 5. The rate of catabolism of N-hydroxyurethane by C57/DBA mice was faster in 8-day-old than in 1-day-old animals of the same sex, and faster in females than in males of the same age. 6. Liver slices of several species of rats and mice catabolized N-hydroxyurethane at rates that varied with the age and sex of animals of the same species; liver homogenates or microsomes were less effective than slices from the same liver. 7. The enzyme activity was destroyed by boiling or freezing the liver; it was inhibited by increasing substrate concentration and by urethane, n-butyl carbamate, cyanide, p-benzoquinone or 2,4-dinitrophenol, but not by p-chloromercuribenzoate or menadione. 8. The catabolism of N-hydroxyurethane by liver slices from adult H-strain rats was not oxygen-dependent. 9. Lung homogenates of 4-week-old female Chester Beatty rats catabolized N-hydroxyurethane at 40% of the rate of liver slices from the same source. 10. O-Acetyl- and O-ethoxycarbonyl-N-hydroxyurethane were rapidly deacylated by liver homogenates from adult hooded rats and adult C57 mice, and by human erythrocytes. 11. N-Hydroxyurethane reacted rapidly with pyridoxal phosphate at pH7.4 and 37 degrees . 12. The rate of decomposition of N-hydroxyurethane in 0.1 n-sodium hydroxide was increased by Ni(2+), Cu(2+), Mn(2+) and [Fe(CN)(6)](3-) and decreased by Cr(2+), Zn(2+), Co(2+), Mg(2+) and Fe(2+). 13. Attempts to synthesize sulphonates of N-hydroxyurethane gave ethyl hydrogen sulphate, probably via rearrangement of the unstable O-sulphonate.

Aging↗
PubMed2001

Involvement of a urethane-sensitive system in timing the onset of gastrulation in Xenopus laevis embryos.

This paper describes success in delaying the onset of gastrulation in Xenopus laevis embryos without damage to their subsequent development by temporarily arresting cleavage with urethane. Exposure of X. laevis embryos to 150 mM urethane before gastrulation resulted in cleavage arrest and its removal led to cleavage resumption. During cleavage arrest, cyclic activities including nuclear replication and the M-phase-promoting factor cycle continued, although their duration was lengthened to nearly 1.8-fold that of the controls. Because of a 30-min time lag from removal of urethane to resumption of cleavage, as well as the retardation of cyclic activities during cleavage arrest, the development of embryos after a 60-min exposure to urethane lagged two cell cycles behind that of control embryos. Here, the two cell cycle delay is equivalent to 50 min at 22-23 degrees C. The start of gastrulation in exposed embryos was accordingly delayed about 50 min, although the delay in mid-blastula transition was as little as 20-25 min. Consistent results were obtained in embryos exposed to urethane for 90 or 120 min and those exposed to procaine or NH4Cl for 60 min. Although these results imply that delay in the start of gastrulation in exposed embryos is ascribed simply to delay in their development raised by cleavage arrest, at the same time they suggest that the onset of gastrulation is timed by systems sensitive to urethane, procaine and NH4Cl in X. laevis embryos.

Ammonium Chloride↗
PubMed1985

Genetic influence on type 2 or Clara cell origin of pulmonary adenomas in urethan-treated mice.

Urethan-induced lung adenomas arising from alveolar type 2 cells and from bronchiolar Clara cells have distinct histologic patterns; and examination of all lung adenomas found in A/J, SWR/J, BALB/cByJ, 129/J, and RIIIS/J inbred mice, 14-16 weeks after a single urethan injection, demonstrated that both tumor types were present in all five strains. The relative numbers of each tumor type varied significantly among the different strains. No correlation was observed between the type of tumor formed and tumor multiplicity. Augmentation of tumor multiplicity by chronic butylated hydroxytoluene (BHT) treatment following urethan injection did not change the proportion of the 2 tumors from that observed with urethan alone. This finding demonstrated that BHT stimulated the development of both tumor types equally. The tumors found 14 weeks after a single urethan injection into neonatal BALB mice were larger than those found 14 weeks after urethan injection into adult BALB mice, but the proportion of alveolar and papillary tumors was the same for both groups. Lymphocytic infiltration into tumors was mainly associated with Clara cell-derived tumors. The proportion of type 2 cell- and Clara cell-derived lung adenomas appeared to be controlled primarily by the genetic background.

Adenoma↗
PubMed1975

The effects of urethane, sodium monohydrogen arsenate and selenocystine on crossing-over in Drosophila melanogaster.

The effects of 0 - 25 mM urethane, 0 - 50 muM selenocystine and 0 - 100 muM sodium monohydrogen arsenate on marker-exchange frequencies have been studied along a region of the X chromosome of Drosophila melanogaster marked by y, cv, v and f. Clear and consistent effects seen in concentration curves were usually but not always found significant in analyses of variance. Urethane concentration curves rose to a higher level at 0.5 to 3 mM and dropped to control levels between 10 and 25 mM. It is proposed that this reversibility was due to a competition between two categories of lesions mimicking natural recombination sites, those on unpaired regions of the chromosome competing with those on already paired regions for recombination-repair enzymes. Selenocystine affected exchange frequencies mainly toward the ends of the unmarked region, especially y - cv, negatively from 2 to 10 muM and positively above 10 muM. These effects are interpreted as being mediated by selenocystine control over restriction of synaptic pairing to terminal regions, especially y - cv. Interaction between urethane and selenocystine in two-chemical treatments satisfactorily support the above explantations for both the urethane and selenocystine effects. Sodium monohydrogen arsenate effects, tentatively attributed to the arsenate ion, differed markedly from those of the other chemicals: "arsenate" concentration curves for single-exchange classes tended to be broadly convex and those for double-exchange classes concave, while interactions with urethane tended to be synergistic or neutral except in one exchange class (that for single exchange in y - cv). No satisfactory explanation of the arsenate effects has yet been found. At 25 mM only, urethane caused male-specific, 95% pupal mortality.

Animals↗
PubMed1998

Intraretinal oxygen distribution in urethan-induced retinopathy in rats.

This study was performed to explore the interaction between chronic neural degeneration and the subsequent vascular remodeling. Weekly urethan administration in rats from birth produces a retinopathy model characterized by photoreceptor degeneration, retinal vascular regression, and retinal pigment epithelium (RPE) neovascularization. We investigated the hypothesis that altered oxygen distribution across the retina and choroid could be involved in the vascular changes seen in this retinopathy. We compared measurements of vitreal, intraretinal, and choroidal oxygen tension (PO2) distribution in anesthetized and ventilated control and urethan-treated rats at 8 and 16 wk of age with the use of oxygen-sensitive microelectrodes. Striking differences were observed in both choroidal and intraretinal PO2 distribution in urethan-treated rats compared with controls. At both ages, intrachoroidal PO2 was much lower in the urethan-treated rats. In addition, the intraretinal PO2 distribution across the inner retinal layers was more uniform than normal. A small elevation in PO2 was present at 8 wk in the inner nuclear layer where subsequent vascular regression occurred, and a small reduction in PO2 was present at the RPE, which recovered to normal values by 16 wk in regions where RPE vessel networks were first evident. Although the retinal arteries were considerably thinner at both ages in the urethan-treated rats, the vitreal PO2 profiles and superficial retinal PO2 remained normal. The unexpected and large reduction in the oxygen delivery from the choroid found in the urethan-treated rats may account for the lack of major hyperoxia within the pathological retina and the lower oxygen tension in the RPE before the vascular proliferation in this region. We propose that tissue PO2 is an important determinant of the vascular remodeling, which is seen in this model of neural degeneration and that the PO2 distribution changes described in this study help provide a new view of the pathogenesis of this model.

Animals↗
PubMed2006

Urethane inhibits the GABAergic neurotransmission in the nucleus of the solitary tract of rat brain stem slices.

Because urethane is a widely used anesthetic in animal experimentation, in the present study, we evaluated its effects on neurons of the nucleus of the solitary tract (NTS) in brain stem slices from young rats (25-30 days old). Using the whole cell configuration of the patch-clamp technique, spontaneous postsynaptic currents (sPSCs) and evoked excitatory postsynaptic currents (eEPSCs) were recorded. Urethane (20 mM) decreased by approximately 60% the frequency of GABAergic sPSCs (1.0 +/- 0.2 vs. 0.4 +/- 0.1 Hz) but did not change the frequency, amplitude, or half-width of glutamatergic events or TTX-resistant inhibitory sPSCs [miniature inhibitory postsynaptic currents (IPSCs)]. Miniature IPSCs were measured in the presence of urethane plus 1 mM diazepam (1 mM), and no changes were seen in their amplitude. This suggests that the GABA concentration in the NTS synapses is set at saturating level. We also evaluated the effect of urethane on eEPSCs, and no significant change was observed in the amplitude of N-methyl-d-aspartate [NMDA; 44.2 +/- 11.5 vs. 37.6 +/- 10.6 pA (holding potential = 40 mV)] and non-NMDA currents [204.4 +/- 35.5 vs. 196.6 +/- 31.2 pA (holding potential = -70 mV)]. Current-clamp experiments showed that urethane did not alter the action potential characteristics and passive membrane properties. These data suggest that urethane has an inhibitory effect on GABAergic neurons in the NTS but does not change the spontaneous or evoked excitatory responses.

Anesthetics, Intravenous↗
PubMed2002

Evaluation of myopathy risk for HMG-CoA reductase inhibitors by urethane infusion method.

Purpose of the present study was to evaluate the myopathy risk using a urethane infusion method following oral administration of five kinds of commercial HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase inhibitors (HCRIs), (pravastatin (PV), simvastatin (SV), cerivastatin (CeV), atorvastatin (AV), and fluvastatin (FV)) alone or with coadministration of bezafibrate (BF). The solubility of HCRIs in various solvents was determined as a criterion of the physicochemical property. The plasma creatine phosphokinase (CPK) level as a marker of myopathy in normal rats was screened under urethane infusion after oral administration of HCRI alone or with BF coadministration. Also, renal tissue specimens were prepared and the myoglobin remaining in the tissue was visualized by the labeled avidin-biotin technique. The plasma CPK level in normal rats under urethane infusion following oral administration of five kinds of HCRI increased as the dose of HCRI increased, and coadministration of BF further increased the CPK level for each drug. The risk of myopathy evaluated from the CPK level was ranked as follows: CeV>FV>AV>SV>PV. Myoglobin deposition was observed in the cast of proximal tubules, cytoplasm of distal tubules and collecting ducts of rat kidney extracted from rats treated with HCRIs under urethane infusion. Histopathological findings showed that the extent of myoglobin deposition increased on coadministration of BF with each drug. The correlation was found for myopathy risk evaluated by CPK level using the urethane infusion method and drug lipophilicity, ie., the water/n-octanol partition coefficient except for the case of SV. Histopathological findings for the kidney following HCRI treatment also reflected the CPK level in rats under urethane infusion.

Administration, Oral↗
PubMed1991

Suppression of the prolactin surges in the pseudopregnant rat by urethane anesthesia.

In pseudopregnancy of the rat prolactin (PRL) is released in the form of twice daily surges (nocturnal and diurnal surges). An attempt was made to examine the effects of urethane anesthesia on PRL surges during pseudopregnancy of the rat. In a preliminary study, using the continuous blood sampling method, the nocturnal PRL surge was completely blocked when urethane (1.0g/kg BW) was administered at 0:00 hr. Urethane (1.0g/kg BW) was injected at 0:00 or 12:00 hr, and serum and pituitary PRL concentrations were measured at 6:00 or 18:00 hr, respectively, to study the effects of urethane on nocturnal or diurnal PRL surges. There were no serum PRL surges during either the nocturnal or diurnal periods following urethane injection. The experiment examining pituitary PRL concentration at 6:00 or 18:00 hr confirmed that urethane (1.0g/kg) anesthesia suppressed the release of PRL surge from the pituitary.

Anesthesia↗
PubMed1984

Organ-specific susceptibility to clastogenic effect of urethane, a trial of application of whole embryo culture to testing system for clastogen.

Urethane has been known for its transplacental carcinogenic effect in mice. Whether or not the treatment of urethane affects embryonic growth and development and induces chromosome aberrations in the embryonic cells in vitro was investigated using the mouse whole embryo culture method. Reports on experiments in vivo showed that lungs and liver were target organs of carcinogenic effects of urethane. In the present experiment, organ (lung and liver)-specific susceptibility to clastogenic effect of urethane was observed in cultured embryonic cells. Further, it is stressed that urethane induced chromosome breaks at concentrations lower than the threshold value for the retardation on embryonic growth and development. Comparing with clastogenic effect of 4NQO on cultured embryonic cells, the clastogenic action of urethane was examined to point out its characteristic feature as a clastogen with special reference to the carcinogenic effects obtained by in vivo experiment.

Animals↗
PubMedDate not supplied

Clomipramine actions on firing rate in septal nuclei of the rat are not related to anaesthesia (urethane).

An increased firing rate in lateral septal nuclei (LSN) appears in urethane-anesthetized rats after several acute drug and non-drug human antidepressant treatments. A still more pronounced increase in firing rate is produced in LSN after clomipramine (CMI) long-term treatment. In spite of urethane is a widely used anesthetic for single unit extracellular recordings, it modifies evoked potentials wave-form. Therefore, present study discards urethane interaction with CMI in LSN single unit extracellular recordings. CMI was acutely injected (1.25 mg/kg: IP) either to urethane-anesthetized, or non-anesthetized encephale-isolé rats. The CMI treated groups showed higher rates of firing in LSN regardless of the use of general anesthesia during recordings. Another group of urethane-anesthetized rats received intracerebroventricular (ICV) microinjections of CMI (100 micrograms/10 microliters/1 min). An amount of 42.8% of LSN-recorded neurons responded with a long-lasting increased firing rate. Results discard urethane and CMI interactions. Additionally, systemic actions of CMI on firing rate of LSN are reproduced by ICV/route microinjections.

Action Potentials↗
PubMed1996

[Effect of radiation emitted from personal computer terminal on urethan-induced lung tumors in mice].

Female SHR mice were injected intraperitoneally 0.2 ml of 1% solution of urethan on days 1, 8, 54 and 61 of the experiment. Beginning from day 1, they were exposed to radiation emitted from the video terminal of the EGA/PC/AT-286 (personal computer), for 1 hr, 5 times a week. The exposure was conducted with or without the Ergostar G-14 protective filter. The distance between the PC screen and the cage bottom was 38 cm. It was found during the 12 months of the experiment that the lifespan of urethan-injected animals was somewhat shorter as a result of the exposure. A significantly higher frequency of all or only malignant tumors of the lung and uterine polyps was recorded in urethan- and irradiation-treated mice than in non-irradiated controls. However, irradiation of urethan-treated animals from a filter-protected screen was followed by a significant decrease in frequency of incidence of all neoplasms and multiple tumors of the lung, as compared with those exposed to unfiltered radiation. It is suggested that long-term exposure to PC-emitted irradiation may cause slight stimulation of urethan-induced carcinogenesis of the lung. The Ergostare filter was found to make no contribution to carcinogenesis. It is also thought that the urethan dose was too large and the entire model--too rigid to adequately assess the PC influence on neoplastic formation.

Animals↗
PubMed2002

In vitro stability of a novel compliant poly(carbonate-urea)urethane to oxidative and hydrolytic stress.

Poly(ester)urethane and poly(ether)urethane vascular grafts fail in vivo because of hydrolytic and oxidative degradative mechanisms. Studies have shown that poly(carbonate)urethanes have enhanced resistance. There is still a need for a viable, nonrigid, small-diameter, synthetic vascular graft. In this study, we sought to confirm this by exposing a novel formulation of compliant poly(carbonate-urea)urethane (CPU) manufactured by an innovative process, resulting in a stress-free. Small-diameter prosthesis, and a conventional poly(ether)urethane Pulse-Tec graft known to readily undergo oxidation in a variety of degradative solutions, and we assessed them for the development of oxidative and hydrolytic degradation, changes in elastic properties, and chemical stability. To simulate the in vivo environment, we used buffered solutions of phospholipase A(2) and cholesterol esterase; solutions of H(2)O(2)/CoCl(2), t-butyl peroxide/CoCl(2) (t-but/CoCl(2)), and glutathione/t-butyl peroxide/CoCl(2) (Glut/t-but/CoCl(2)); and plasma fractions I-IV, which were derived from fresh human plasma centrifuged in poly(ethylene glycol). To act as a negative control, both graft types were incubated in distilled water. Samples of both graft types (100 mm with a 5.0-mm inner diameter) were incubated in these solutions at 37 degrees C for 70 days before environmental scanning electron microscopy, radial tensile strength and quality control, gel permeation chromatography, and in vitro compliance assessments were performed. Oxidative degradation was ascertained from significant changes in molecular weight with respect to a control on all Pulse-Tec grafts treated with t-but/CoCl(2), Glut/t-but/CoCl(2), and plasma fractions I-III. Pulse-Tec grafts exposed to the H(2)O(2)/CoCl(2) mixture had significantly greater compliance than controls incubated in distilled water (p < 0.001 at 50 mmHg). No changes in molecular weight with respect to the control were observed for the CPU samples; only those immersed in t-but/CoCl(2) and Glut/t-but/CoCl(2) showed an 11% increase in molecular weight to 108,000. Only CPU grafts treated with the Glut/t-but/CoCl(2) mixture exhibited significantly greater compliance (p < 0.05 at 50 mmHg). Overall, results from this study indicate that CPU presents a far greater chemical stability than poly(ether)-urethane grafts do.

Biocompatible Materials↗
PubMed2005

Synthesis and chemical recycling of novel poly(ester-urethane)s using an enzyme.

A series of enzymatically recyclable poly(ester-urethane)s consisting of a biodegradable diurethane moiety as a hard segment and an ester moiety as an enzymatically cleavable linkage was chemo-enzymatically prepared by two routes. The poly(ester-urethane) was prepared by a) the ring-opening polymerization of a cyclic ester-urethane monomer synthesized via the transesterification reaction of biodegradable diurethanediol and dicarboxylate ester using lipase and b) the direct polycondensation of a diurethanediol and a dicarboxylate ester. A significantly higher molecular-weight poly(ester-urethane) having the highest molecular weight (Mw) of 101,000 was produced by the ring-opening polymerization of the cyclic ester-urethane monomer when compared with that produced by the polycondensation of the dicarboxylate ester with diurethanediol. The poly(ester-urethane) was readily degraded by lipase into the corresponding cyclic oligomers; the oligomers were readily repolymerized by the ring-opening polymerization using lipase for chemical recycling.

Biodegradation, Environmental↗
PubMed1965

THE MATABOLISM OF URETHANE AND RELATED COMPOUNDS.

1. Urethane is metabolized in the rat, rabbit and man by a process of N-hydroxylation. This occurs to a smaller extent when methyl, n-propyl and n-butyl carbamates are administered to the rat and rabbit. 2. Other metabolites which have been detected in urine of animals dosed with urethane and N-hydroxyurethane are ethylmercapturic acid, ethylmercapturic acid sulphoxide and N-acetyl-S-carbethoxycysteine. 3. Substances which appear to be S-ethylglutathione and S-ethylglutathione sulphoxide have been detected in the bile of rats dosed with urethane or N-hydroxyurethane. 4. Methyl, ethyl, n-propyl and n-butyl N-hydroxycarbamates are excreted unchanged in the urine of rats dosed with these compounds to extents depending on the dose administered. 5. Animals dosed with methyl, ethyl, n-propyl or n-butyl carbamate or the corresponding N-hydroxycarbamate excrete the corresponding carbamate and N-hydroxycarbamate in the urine. 6. Methyl, n-propyl and n-butyl carbamates and N-hydroxycarbamates are excreted more slowly than are urethane and N-hydroxyurethane. 7. The probable role of N-hydroxyurethane and the processes of alkylation and carbethoxylation, and of hydroxylamine, nitroxyl and hyponitrous acid in carcinogenesis and chemotherapy with urethane, have been discussed.

Animals↗