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Selected AbstractsGrafting itaconic anhydride onto polyethylene using extrusionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010C. J. R. Verbeek Abstract Reactive extrusion was employed to graft itaconic anhydride (IA) onto polyethylene, using thermally induced peroxide decomposition. It was found that an increase in IA concentration lead to an increase in the degree of grafting (DOG), but only up to 6 wt % IA. Using di-cumyl peroxide (DCP) as the initiator resulted in a higher DOG compared to di- tert -butyl peroxide (DTBP) and required less reaction time to achieve the same DOG. However, raising the IA concentration also resulted in an increase in cross-linking. Increasing the initiator concentration from 0.2 to 2 wt % resulted in a higher DOG. However, 5 wt % initiator showed similar results compared to using 0.2 wt % due to termination by disproportionation, which has been shown to be more prevalent at high initiator concentrations. Degradation was clearly observed by the inability to form a continuous extrudate during extrusion as well as discolouration. A residence time of more than 50 seconds, using DCP and 120 s for DTBP didn't offer any further increase in the DOG and also resulted in more pronounced degradation. Optimizing grafting is therefore a trade-off between maximal DOG and minimizing side reactions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Dimensional Stability of the Free Fascia Grafts: An Animal Experiment,THE LARYNGOSCOPE, Issue 4 2002Shabbir Indorewala MS (ENT) Abstract Objectives/Hypothesis It appears that autologous free fascia grafts (fascia lata and temporal fascia) change their dimensions during the vital first 5 days of healing. Poor dimensional stability of these grafts can be an important reason for failure of complete closure of tympanic membrane perforations in tympanoplasty operations. There has been no study regarding this dimensional instability. Study Design Prospectively dimensional instability of the free fascia grafts was studied in 14 mongrel dogs. Methods Fourteen healthy Mongrel dogs were operated on twice. During the first surgery, fascia lata and temporal fascia grafts of measured dimensions (length, breadth, and thickness) were implanted in the subcutaneous pockets on the thoracoabdominal wall of the same dog (autograft). Five dogs were operated on again after 2 days, and 7 dogs were operated on again after 5 days to harvest the implanted grafts. The dimensions of the harvested grafts were noted. Changes with respect to their implant dimensions after 2 days and after 5 days were calculated. Results It was found that free fascia lata exhibits significantly superior dimensional stability when compared with free temporal fascia during the early healing phase, before graft integration has occurred. Shrinking and thickening of temporal fascia are greaterand are also most unpredictable. Conclusions Poor dimensional stability of temporal fascia may compromise a well-sealed perforation at the time of surgery, and it may reopen by the 5th day. This must be one of the causes of failure of tympanoplasty, which needs to be studied further. [source] ACUTE CORONARY LIGATION IN THE DOG INDUCES TIME-DEPENDENT TRANSITIONAL CHANGES IN MITOCHONDRIAL CRISTA IN THE NON-ISCHAEMIC VENTRICULAR MYOCARDIUMCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2007Craig Steven McLachlan SUMMARY 1The aim of the present study was to examine, in the dog myocardium, the incidence of zig-zag mitochondrial cristae over time in the non-ischaemic posterior wall, following an acute anterior wall infarct. 2Changes within the myocardial mitochondrial crista membrane in dogs were investigated following acute left anterior descending coronary artery ligation. Transmyocardial biopsy samples were taken serially from the posterior non-ischaemic wall in the same dog. Changes in heart mitochondrial cristae were examined by transmission electron microscopy prior to coronary ligation (control) and 40 min and 2, 4, 6 and 24 h postinfarction. 3In control hearts, 90% of mitochondrial cristae had a lamelliform appearance. Following infarction, there were twotransitional states with respect to mitochondrial cristae, the first characterized by undulating lamelliform cristae that are also found in 10% of control samples and a second transitional state that was zig-zag and reached a maximum between 6 and 24 h after infarction. 4In conclusion, an undulating lamelliform crista pattern is present in the non-ischaemic wall of the acute infarcted dog and we hypothesize that this may be an intermediate from, between ,normal' lamelliform and ,abnormal' zig-zag cristae. [source] The relationship between peripheral glucose utilisation and insulin sensitivity in the regulation of hepatic glucose production: studies in normal and alloxan-diabetic dogsDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 2 2006M. J. Christopher Abstract Background Hepatic glucose overproduction (HGP) of diabetes could be primary or could occur in response to the metabolic needs of peripheral (skeletal muscle (SkM)) tissues. This question was tested in normal and diabetic dogs. Methods HGP, SkM glucose uptake (Rdtissue), metabolic clearance of glucose (MCRg) and glycolytic flux (GFexog), and SkM biopsies were measured in the same dogs before and after alloxan-induced diabetes. Normal dogs were exposed to (1) an extended 20-h fast, (2) low- and high-dose glucose infusions (GINF) at basal insulinaemia, and chronic diabetic dogs were exposed to (3) hyperglycaemia, (4) phlorizin-induced normoglycaemia, and (5) poor and good diabetic control. Results (1) Prolonged fast: HGP, Rdtissue, and GFexog fell in parallel (p < 0.05). (2) Low-dose GINF: plasma glucose, insulin, Rdtissue, MCRg, and GFexog were unchanged, but HGP fell by ,40%, paralleling the supplemental GINF. (3) High-dose GINF at basal insulin: plasma glucose doubled and synchronous changes in HGP, Rdtissue, MCRg, and GFexog occurred; ICglucose, G6P, and glycogen were unchanged. (4) Hyperglycaemic diabetes: HGP was raised (p < 0.05), matching urinary glucose loss (UGL) and decreased MCRg, and maintaining normal basal Rdtissue and GFexog. SkM ICglucose was increased and glycogen decreased (both p < 0.05). (5) Phlorizin-induced normoglycaemia in diabetic dogs: HGP rose, matching the increased UGL, while maintaining normal Rdtissue and GFexog. Intramuscular substrates normalised. (6) Whole body and SkM metabolism normalised with correction of the insulin resistance and good diabetic control. Conclusion HGP reflects whether SkM is in a state of relative glucose ,excess' or absolute/relative glucose ,deprivation'. Copyright © 2005 John Wiley & Sons, Ltd. [source] Comparative bioavailability study in dogs of a self-emulsifying formulation of progesterone presented in a pellet and liquid form compared with an aqueous suspension of progesteroneJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2004Catherine Tuleu Abstract A pellet formulation of progesterone in a self-emulsifying system (SES) was prepared by the process of extrusion/spheronization to provide a good in vitro drug release (100% within 30 min, T50% at 13 min). A three-way randomized crossover study was performed in six fasted male beagle dogs with these pellets and the same SES liquid formulation, both contained in a hard shell capsule, and an aqueous suspension. The same dose of progesterone (16 mg) in pellets and in the SES liquid formulation resulted in similar AUC, Cmax and Tmax values, estimated from progesterone plasma levels by 125I radioimmunoassay. Although the maximum absorption was slightly retarded (0.5 to 1 h) by SES (pellets and liquid), AUC and Cmax were approximately seven and nine times greater then those obtained when an aqueous suspension formulation of the same dose of progesterone was administered to the same dogs. These results showed that it was possible to improve the bioavailability of the poorly soluble, poorly permeable progesterone when administered in SES. Moreover, presenting the progesterone in the form of a pellet did not prevent the release of the drug in vivo. These data demonstrate the utility of extrusion/spheronization in delivering a nonaqueous system in a novel solid dosage form. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1495,1502, 2004 [source] Formulation and food effects on the oral absorption of a poorly water soluble, highly permeable antiretroviral agentJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2002Bruce J. Aungst Abstract DPC 961 is a low-solubility, high-permeability, second-generation non-nucleoside reverse transcriptase inhibitor. The purpose of these studies was to evaluate the effects of drug substance and formulation variables on DPC 961 oral absorption, and to compare fed and fasted state oral absorption. To accomplish this, groups of four to six dogs were dosed with various formulations of DPC 961 under fasted or fed conditions, and DPC 961 pharmacokinetics were examined. Absolute oral bioavailability, based on i.v. AUC in the same dogs, was 24% after a suspension dose in fasted dogs and was 51% in fed dogs. Bioavailability with an unoptimized tablet formulation was 30% in fasted dogs and 86% in fed dogs. DPC 961 oral absorption was shown to be dependent on drug substance particle size in fasted dogs, after dosing with a tablet formulation where only the drug substance particle size was varied, but there was no difference in fed dogs. AUC and Cmax increased in proportion with increases in tablet strength from 100 to 400 mg, using tablets manufactured from a common granulation. Tablets made with 50 and 66% drug loadings showed similar relative oral bioavailabilities. Tablets prepared with two different polymorphic forms of DPC 961 were also compared, and these were found to be equivalent. These studies provided a useful component of the formulation development process, to help identify and control the variables affecting oral absorption of this potential new therapeutic agent. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:1390,1395, 2002 [source] | ||||||||||