Improved interfacial surface generator for the co‐extrusion of micro‐ and nanolayered polymers

Two dies for polymer co‐extrusion layer multiplication are evaluated experimentally and computationally in terms of pressure drop and layer uniformity. The first design is that of the original die, is compact, and has successfully been used to co‐extrude low elasticity polymers with closely matched rheological properties. The second die design, the one that is being modified, achieves a more balanced flow path with constant cross‐sectional area. Flow visualization experiments and computational simulations show matched performance between the dies when layering similar viscosity materials and better layering performance of rheologically dissimilar materials with the improved dies compared to the original die design. Furthermore, the improved die has a much lower pressure drop. This facilitates decreased energy consumption or the allowance of additional multiplier dies to be added resulting in an increased total number of layers. POLYM. ENG. SCI., 54:636–645, 2014. © 2013 Society of Plastics Engineers     

The management of unsalvageable free flaps

The loss of vascular flow in the early postoperative period will generally lead to free flap failure. When attempts at flap salvage are unsuccessful, conservative management with delayed flap debridement may be indicated. Seven unsalvageable free flaps were managed with observation and flap debridement 4 to 14 days following loss of vascular signals. At the time of debridement, six of the seven wounds had viable granulation tissue and were successfully closed with skin grafts. The seventh patient had loss of vascular flow to the free flap within 12 hr of surgery and, at the time of delayed debridement, had no evidence of granulation ingrowth. Local revascularization of flaps is known to occur and offers an explanation for these findings. Delayed debridement of unsalvageable free flaps is indicated for noncritical wounds, and may obviate the need for a second free-tissue transfer to obtain wound closure.     

Toward a simplified measure of asthma severity for applied research

The synthesis and preliminary evaluation of new benzo[f]quinoline and pyridine derivatives, obtained by application of the Reissert method and its modifications, as HIV-1 RT inhibitors and anti-infectives are presented. The most active products against HIV-1 RT wild type are the ethyl 2-cyano-1,2-dihydrobenzo[f]quinoline-1-carboxylate 2b, propyl 2-cyano-1,2-dihydrobenzo[f]quinoline-1-carboxylate 2c, and 2-cyano-1-(2'-furoyl)-1,2-dihydrobenzo[f]quinoline 2n, which maintain their activity against the mutant type P236L, resulting inactive against the Y181C type. Using the data previously obtained by our research team for analogous series derived from quinoline as reference, the compounds which have now been obtained present an increase in the cytotoxic character attributable to the introduction of a benzene ring fused with the quinoline base nucleus, as well as a decrease of the activity as HIV-1 RT inhibitors when the quinoline benzenic ring is eliminated.     

Direct injection of 5-HT2A receptor agonists into the medial prefrontal cortex produces a head-twitch response in rats

The serotonin (5-HT)(2A/2c) agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), the 5-HT2C agonist 6-chloro-2-[1-piperazinyl]-pyrazine and the 5-HT2A partial agonist m-chloro-phenylpiperazine (mCPP) were injected bilaterally into the medial prefrontal cortex of male rats. DOI and mCPP, but not 6-chloro-2-[1-piperazinly]-pyrazine, elicited a dose-dependent head-twitch response (HTR). DOI-induced HTR had an ED50 of 12.8 nmoles/0.5 microl/side and was inhibited by the 5-HT2A antagonists ketanserin and MDL 100,907 but was not blocked by pretreatment with the selective 5-HT(2C/2B) antagonist SDZ SER 082. The HTR to mCPP demonstrated a bell-shaped dose-response curve with an ED50 of 1.5 nmoles/0.5 microl/side and a peak effect after 3 nmoles/side. The response to mCPP was greatly diminished by both ketanserin and MDL 100,907 and was partially reversed by SDZ SER 082. These findings suggest that the HTR produced by the direct injection of serotonergic agonists into the medial prefrontal cortex is, in part, mediated by the activation of 5-HT2A receptors. Pretreatment of rats with the 5-HT1A agonist (+/-)-8-hydroxy-dipropylaminotetralin hydrobromide inhibited the HTR to DOI. This is consistent with other evidence that suggests a functional antagonism between 5-HT1A and 5-HT2A receptor activation. The HTR to DOI was potentiated by the novel 5-HT1A selective antagonist WAY 100,635, which suggests that 5-HT1A receptors tonically regulate this behavioral response to stimulation of cortical 5-HT2A receptors.     

The influence of thermo‐mechanical history on structure development of elastomeric and amorphous glass thermoplastic polyurethanes

In this work, the effect of processing and subsequent thermal treatment on the rheological behavior and microstructure aggregation of two different types of thermoplastic polyurethanes (TPUs) are investigated. Elastomeric TPUs, which are segmented block copolymers composed of alternating soft and hard segments, and amorphous glassy TPU, predominantly composed of hard segments, were subjected to heating/cooling cycles after extrusion. All materials show rheological hystereses after the first thermal cycle; in amorphous glassy TPUs, there is an increase in dynamic moduli but the loss tangent remains unchanged, whereas in the elastomeric TPUs, there are both decreases in dynamic moduli and hystereses in the loss tangent. The changes in molecular weight during the thermal cycle were tracked by gel permeation chromatography and shown not to be responsible for the rheological hystereses. For both elastomeric and amorphous glassy TPUs, fourier transform infrared spectroscopy results indicate that an increase in dynamic moduli, especially G′, is associated with a higher degree of hydrogen bonding. These results combined with X‐ray data indicate that upon extrusion the elastomeric TPUs form a network in which hydrogen bonding plays an important role. This structure can be disrupted upon subsequent heating and cooling. POLYM. ENG. SCI., 54:1383–1393, 2014. © 2013 Society of Plastics Engineers     

GM2 gangliosidosis B1 variant: biochemical and molecular characterization of hexosaminidase A

This paper, based on functional radiological knowledge of normal cervical spine kinematics, develops the hypothesis that compressive vertebral injury can be produced by abrupt reversal of curve between hyperflexed and hyperextended parts of the cervical spine. Reversal of curve occurs when the main vector of a compressive force passes between two centers of flexion-extension motion. The hypothesis more clearly explains reverse dislocation of fractured vertebrae than the current concept of Whitley and Forsyth of motion of the head through an arc. The mechanism of injuries with characteristics of hyperflexion of one segment and hyperextension of an adjacent segment, e.g., in certain types of hangman's fractures, is better understood. The hypothesis is expected to be helpful in guiding experimental cervical spine injury, as it relates direction of force to level and type of the resulting vertebral injury.     

Parafilariosis in African buffaloes (Syncerus caffer)

BACKGROUND: (99m)Tc-labeled (bis(N-ethoxy, N-ethyl dithiocarbamato) nitrido technetium(V)) ([99m]TcN-NOET) is a new lipophilic, neutral-charge cardiac perfusion imaging agent that demonstrates apparent redistribution in animal models and humans. The purpose of this study was to determine whether the kinetics of (99m)TcN-NOET are suitable for the detection of resting ischemia. METHODS AND RESULTS: Microspheres were injected at baseline and simultaneously with (99m)TcN-NOET after a 90% reduction in resting flow in the left circumflex coronary artery in six open-chest canine experiments. The relationship of flow and activity early after injection was determined in one experiment by termination at 10 minutes. The flow ratio (left circumflex/left anterior descending coronary artery) after stenosis fell significantly (0.87 +/- 0.04 vs 0.46 +/- 0.04; p < 0.05). The end-tissue (99m)Tc ratio (0.78 +/- 0.05) was significantly higher than the flow ratio at injection (0.46 +/- 0.04; p < 0.05), indicating substantial redistribution. In vivo imaging was conducted during 2 hours in five experiments, followed by ex vivo imaging. Myocardial clearance from 10 minutes onward was biphasic in left anterior descending and monophasic in left circumflex coronary arteries. Myocardial clearance from 10 to 60 minutes was delayed in left circumflex (35.5% +/- 8.1%) versus left anterior descending coronary arteries (49.2% +/- 8.6%; p < 0.05). No significant difference was observed from 60- to 120-minute clearance. Five of five experiments demonstrated initial defects and complete fill-in at 90 to 120 minutes by qualitative assessment. Quantitation of ex vivo images confirmed significant redistribution. CONCLUSIONS: Resting ischemia caused by moderate to severe stenosis can be detected on scans with (99m)TcN-NOET. Redistribution was near complete in this model by 90 to 120 minutes. (99m)TcN-NOET is a promising new agent for the detection of coronary artery disease in viable myocardium and warrants further investigation.     

Role of membrane lipids in the immunological killing of tumor cells: II. Effector cell lipids

Peritoneal macrophages (MØ) from mice become cytotoxic after incubation in lymphokine (LK)-rich supernatants of antigen-stimulated spleen cell cultures. Tumoricidal activity is evident with MØ treated with LK for 4 hr, becomes maximal after 8–12 hr incubation and decreases to control levels by 24–36 hr. To gain insight into LK-induced functional changes, the lipid composition of MØ cultured with LK for 0–36 hr was analyzed by high pressure liquid chromatography. LK induced marked changes in MØ lipid composition: cellular content of cholesterol (CHOL) and polyunsaturated fatty acids increased 2- to 3-fold after 8 hr when the cells showed maximal tumoricidal activity. Cellular lipid and fatty acid content returned to control levels by 24 hr when the MØ had lost tumoricidal activity. These changes were not observed with equal numbers of MØ cultured in control supernatants. To analyze further the role of CHOL and unsaturated fatty acids in MØ tumor cytotoxicity, MØ were enriched in CHOL or linolenic acid (18∶3) and tested for their ability to kill 1023 tumor cells. Within 1 hr of culture, MØ showed a 3- to 4-fold increase in CHOL or 18∶3 content. 18∶3-enriched cells were markedly tumoricidal, whereas controls cultured in delipidized medium alone or enriched with saturated fatty acid were not cytotoxic. CHOL-enriched MØ were not tumoricidal; indeed, these cells were inhibited in their killing after treatment with LK compared to MØ cultured in delipidized medium with LK alone. These results suggest that UFA aids, whereas CHOL negates, expression of MØ tumor cytotoxicity.