Synthesis of CdS Nanoparticles Dispersed Within Poly(urethane acrylate‐co‐styrene) Films Using an Amphiphilic Urethane Acrylate Nonionomer

Summary: CdS nanoparticles dispersed within poly(urethane acrylate‐co‐styrene) ( PUCS ) films were prepared using amphiphilic urethane acrylate nonionomer (UAN) precursor chains, which had a poly(propylene oxide)‐based hydrophobic segment and a hydrophilic poly(ethylene oxide) segment. CdS nanoparticles were first prepared and dispersed in UAN/styrene mixtures, and then these nano‐colloid solutions could be directly converted to CdS/ PUCS nanocomposite films via radical bulk polymerization process. Formation of CdS nanoparticles was confirmed by UV absorption spectra, PL emission spectra and TEM images. The size of the CdS nanoparticles was varied from 10.2 to 14.5 nm, in correlation with the increase of amount of cadmium salt in the preparation composition, which was also confirmed by a red shift in the UV and PL emission spectra. In the course of the formation of the CdS nanoparticles within the UAN/styrene mixtures, the PEO segments of UAN are microphase‐separated from the hydrophobic segments of UAN and styrene to make a complex with the cadmium cations and stabilize the CdS nanoparticles. This was also confirmed by TEM images and DMA measurements.

TEM micrograph of the polyurethane acrylate films containing CdS nanoparticles, prepared using a weight fraction of cadmium acetate of 0.125 wt.‐%.     

Comparison of urethane/chloralose and pentobarbitone anaesthesia for examining effects of bacterial lipopolysaccharide in mice

Although anaesthetics are widely used to alleviate stress in endotoxaemic animals, these drugs themselves may interfere with the effects of lipopolysaccharide (LPS). The effects of LPS on serum glucose, biochemical markers of hepatic, renal and pancreatic exocrine function, and lung myeloperoxidase (MPO) activity were compared using anaesthesia with either urethane/chloralose or pentobarbitone. Groups of 10-13 of C57B1/6 mice (22.3 +/- 0.18 g) were treated with 40 mg/kg LPS or the same volume of saline (10 mL/kg, i.p.) at time 0, Animals were anaesthetized either with urethane (1000 mg/kg) and chloralose (50 mg/kg) or with pentobarbitone (90 mg/kg, i.p.) after 2 h and blood and lung samples obtained after 6 h. In pentobarbitone-anaesthetized mice, LPS caused hypoglycaemia and increased serum levels of alanine aminotransferase (ALT), lipase and creatinine suggesting damage/dysfunction of liver, exocrine pancreas and kidney respectively. Lung tissue MPO activity, an indicator of neutrophil infiltration, was also increased. Urethane/chloralose-treated mice demonstrated hypoglycaemia and enhanced serum levels of ALT and creatinine in response to LPS, but failed to show LPS-induced increases in serum lipase and lung MPO activity. It is concluded that while pentobarbitone may be successfully used in experimental models of endotoxaemia in mice, anaesthesia with urethane and chloralose may protect mice against LPS-mediated damage/dysfunction in the exocrine pancreas and in the lung, and therefore, is not recommended in studies on endotoxaemic mice.     

Genotoxicity studies of organically grown broccoli (Brassica oleracea var. italica) and its interactions with urethane,methyl methanesulfonate and 4-nitroquinoline-1-oxide genotoxicity in the wing spot test of Drosophila melanogaster

Broccoli (Brassica oleracea var. italica) has been defined as a cancer preventive food. Nevertheless, broccoli contains potentially genotoxic compounds as well. We performed the wing spot test of Drosophila melanogaster in treatments with organically grown broccoli (OGB) and co-treatments with the promutagen urethane (URE), the direct alkylating agent methyl methanesulfonate (MMS) and the carcinogen 4-nitroquinoline-1-oxide (4-NQO) in the standard (ST) and high bioactivation (HB) crosses with inducible and high levels of cytochrome P450s (CYPs), respectively. Larvae of both crosses were chronically fed with OGB or fresh market broccoli (FMB) as a non-organically grown control, added with solvents or mutagens solutions. In both crosses, the OGB added with Tween–ethanol yielded the expected reduction in the genotoxicity spontaneous rate. OGB co-treatments did not affect the URE effect, MMS showed synergy and 4-NQO damage was modulated in both crosses. In contrast, FMB controls produced damage increase; co-treatments modulated URE genotoxicity, diminished MMS damage, and did not change the 4-NQO damage. The high dietary consumption of both types of broccoli and its protective effects in D. melanogaster are discussed.     

Stereocomplexes from Biosourced Lactide/Butylene Succinate‐Based Copolymers and Their Role as Crystallization Accelerating Agent

Biosourced co(polyester urethane)s containing different ratios of enantiomeric oligo(L ‐ or D ‐ lactide) (OLLA/ODLA) sequences and oligo(butylene succinate) (OBS) blocks (P(OD(L)LA‐b‐OBS)) are synthesized. Their stereocomplexation is confirmed by differential scanning calorimetry and X‐ray diffraction. The process is efficient independently on the OLA/OBS ratio and for OLLA/ODLA ratios from 2:3 to 3:2. The preformed stereocomplexes show remarkable crystallization accelerating efficiency when melt‐blended with a commercial PLLA in amounts from 2.5 to 10 wt%. Spectacular increase in the polyester matrix crystallinity (from 2 up to 42%) and crystallization rate (half‐time of ca. 3 min compared to ca. 30 min for the neat PLLA) is observed.     

Sulfur‐Containing Polyesters, 9. The Synthesis and Characterization of New Diphenylmethane‐Derivative Thiopolyester Diols and Their Use for the Preparation of Thermoplastic Polyurethanes

The new linear thiopolyester diols (PEs) containing sulfur in the main chain were prepared by melt polymerization of newly obtained diphenylmethane‐4,4′‐bis(methylthiopropionic acid) with excess of 1,4‐butanediol, 1,5‐pentanediol, and 1,6‐hexanediol. All these PEs (M̄_n of ≈2 000) were converted to thiopoly(ester‐urethane)s (PEUs) by addition reaction with hexamethylene diisocyanate (HDI) or 4,4′‐diphenylmethane diisocyanate (MDI) which was carried out in melt at a ratio of NCO/OH = 1 or 1.05. The resulting thermoplastic PEUs were elastomeric products, completely amorphous from MDI, with glass transition temperatures ranging from –22 to –8°C. Segmented PEUs (hard segment content ≈53–60 wt.‐%) prepared by using PEs, HDI or MDI, and bis[4‐(6′‐hydroxyhexylthio)phenyl] ether as chain extender were elastomeric materials, particularly those from MDI, with tensile strength of 9.4–12.7 MPa. All the polymers were thermally stable up to 200–270°C. The structures of the polymers were determined by Fourier transform infrared, ¹H NMR, and X‐ray analysis.     

Field potential recordings in dentate gyrus of anesthetized rats: Stability of baseline

Urethane is a standard anesthetic utilized for in vivo recordings in the hippocampus. In studies of long‐term potentiation (LTP), the measure of interest is the response amplitude minutes to hours following train delivery. In the absence of experimental treatment, we have consistently observed upward drift in the amplitude of the population spike (PS) and EPSP slope of the dentate gyrus (DG) evoked field response in acute surgical preparations performed in the urethanized rat. The present study systematically monitored PS amplitude and EPSP slope in the DG every 30 minutes for 6 hours following optimal positioning of Teflon‐coated bipolar stainless steel electrodes under urethane anesthesia. At maximal stimulus intensities, large time‐dependent increases in PS amplitude (70–80%) were observed over the first 2–4 hours, an effect that was exaggerated at lower stimulus intensities. Increases in the EPSP slope were smaller in magnitude (20–30%) and stabilized within a shorter period of time (1–2 hours). Animals were warmed on a heating pad and body and brain temperature remained constant over the recording session. Reducing stimulating electrode size and recording with glass micropipettes did not alleviate the upward drift in response amplitude. Similar increases were also seen under pentobarbital anesthesia. To dissociate anesthetic from surgical effects, recordings were obtained from animals previously prepared with indwelling electrodes and injected with urethane. Although slight declines (10–15%) in EPSP slope occurred over time, no significant alterations in PS amplitude were seen in the chronic preparation at high stimulus intensities. Low stimulus intensities yielded a more variable response pattern and, in direct contrast to the acute preparation, time‐dependent declines, not increases, were noted in both parameters. These data suggest that generalized surgical trauma contributes to the upward drift in response amplitude and indicate that long stabilization periods are required in acute surgical preparations for accurate field potential recordings. Hippocampus 1999;9:277–287. Published 1999 Wiley‐Liss, Inc.     

Instability of Dentate Gyrus Field Potentials in Awake and Anesthetized Rats

Adult male Long‐Evans rats were prepared with stimulating and recording electrodes in the perforant path and dentate gyrus, respectively. Urethane‐anesthetized acute (ACU) preparations and chronically‐implanted freely‐moving (CHR) animals received moderate‐intensity (50–75% of maximum) stimulation pulses every 15–20 s for 4–5 hr in order to assess the stability of evoked field potentials. Significant increases in both population spike amplitude (+6.3%/hr) and EPSP slope (+2.5%/hr) were seen over the course of testing in the ACU group as a whole, while the CHR group showed significant decreases in EPSP slope (−3.3%/hr) but not spike (−1.2%/hr). Thus, both preparations were unstable, though the group mean drift differed in direction. Field potential drift was also affected by body temperature and stimulation intensity; drift was significantly greater when temperature was not controlled, and responses to moderate‐intensity stimulation tended to be less stable than responses to high‐intensity pulses. Our results indicate that a drift of 4–6% per hour in individual subjects is common; in unheated acute preparations, drift can equal or exceed 20% per hour (3/7 cases). These findings show that response instability can pose significant problems for electrophysiological investigations of neural plasticity. Hippocampus 1999; 9:333–339. © 1999 Wiley‐Liss, Inc.     

乌拉坦对大鼠肾脏滤过功能的影响

以９９ｍＴｃ－ＤＴＰＡ颈静脉“弹丸”式注入，用ＳＰＥＣＴ技术研究乌拉坦麻醉大鼠的肾脏滤过功能。结果表明乌拉坦麻醉大鼠肾脏滤过功能明显降低（Ｐ＜０．０５），与给药途径无关。     

Excitation of striatal neurons by dexamphetamine is not abolished by either chloral hydrate or urethane anaesthesia

In order to understand differences between studies maintaining that dopamine actions are siqnificantly reduced as a result of chloral hydrate anaesthesia or not affected to any appreciable extent, striatal neuronal responses to the indirect dopamine aqonist, dexamphetamine, were examined in rats anaesthetized with either chloral hydrate (400 mg/kg) or urethane (1.5 q/kg). Striatal neuronal activity was markedly depressed by chloral hydrate and urethane. However, striatal neurons still responded to 2.5 mg/kg dexamphetamine with marked excitation. These results indirectly support earlier iontophoretic studies on the excitatory action of dopamine on striatal neurons in chloral hydrate-anaesthetized animals. Furthermore, the ability of dexamphetamine, primarily an indirect dopamine agonist, to excite striatal neurons in these anaesthetized animals suggests that stimulation of both D₁ and D₂ receptors is not abolished by anaesthesia.     

Interactions between N-acetylcysteine and sodium selenite in modulating the clastogenicity of urethane and 2-acetylaminofluorene in mice

Combined treatment with different agents represents a promising approach in cancer chemoprevention. Therefore, it is useful to assess in preclinical models the efficacy of combinations that are selected by taking into account mechanistic considerations. We designed 2 studies evaluating the interaction between N-acetylcysteine (NAC) and sodium selenite (Se), both given with the drinking water to Balb/c mice, in modulating clastogenic effects in bone marrow polychromatic erythrocytes. In a first study, a single i.p. injection of urethane considerably enhanced the frequency of micronucleated cells. While NAC produced a significant inhibition, Se further enhanced urethane clastogenicity. When given in combination at the same doses, NAC prevented the adverse effect of Se. In a second study, a single i.p. injection of 2-acetylaminofluorene enhanced the frequency of micronucleated cells. Se did not reduce this effect to a significant extent, while NAC produced a dose-dependent inhibition. When tested at the lower dose in combination with Se, the protective effect of NAC was unchanged. Especially in association with Se, NAC also prevented the toxicity of 2-acetylaminofluorene by normalizing the ratio of polychromatic to normochromatic erythrocytes. In conclusion, NAC attenuated the clastogenicity of both urethane and 2-acetylaminofluorene and the toxicity of this aromatic amine. In addition, NAC prevented the clastogenic and toxic effects resulting from the interaction of Se with urethane. Together with the findings of previous studies, it appears that, besides its intrinsic protective properties in carcinogenesis, NAC is capable of attenuating the adverse effects of several cytotoxic drugs and chemopreventive agents.