The stability of methacrylate biomaterials when enzyme challenged: kinetic and systematic evaluations.

This study addressed whether methacrylate monomers and polymers used in dentistry might degrade from enzymolysis by acetylcholinesterase (ACHE), cholesterol esterase (CHE), porcine liver esterase (PRLE), and a pancreatic lipase (PNL). Short (hour) and long-term (day) exposures were performed. Product ratios were used to determine surface hydrolysis of the polymeric materials. Enzyme kinetics were studied for the monomers when challenged by ACHE, CHE, and PRLE. In the case of PRLE, the V(max) for the dimethacrylate substrates varied slightly, but amounted to as much as 10% of that of p-nitrophenylacetate. The K(m) for triethylene glycol dimethacrylate (TEGDMA) was 197 microM for ACHE and 1107 microM for CHE. The V(max) was 2.7 nmol/min for ACHE and 3.5 nmol/min for CHE. TEGDMA was converted by CHE at 2% the rate of cholesteryl oleate. Long-term incubations of monomers with CHE and ACHE produced degrees of hydrolysis that evidenced structure dependency in the ability of the enzymes to effect hydrolysis. Particularly resistant were aromativ derivatives and those with branching in methacrylate linkages. Overall, the study confirms the ability of physiologically important esterases to catalyze the hydrolysis of biomaterial methacrylates.

Bisphenol A and its biomaterial monomer derivatives alteration of in vitro cytochrome P450 metabolism in rat, minipig, and human.

Bisphenol A (BPA) is a common structural component in a wide variety of biomaterial monomers. The effects of BPA and the following derivatives: bisphenol A glycidyl methacrylate (BisGMA), bisphenol A glycidyl diacrylate (BAGDA), bisphenol A ethoxylate dimethacrylate (BAEDM), bisphenol A dimethacrylate (BADM), and bisphenol A diglycidyl ether (BADGE) on mixed function oxidases (MFOs) are reported in this study. The rate of formation of metabolites from isoform-specific substrates for the MFOs (or cytochromes) CYP 1A, 2A, 2C, 2E, 3A, and 4A in the absence (control) and presence of BPA and derivatives was used to assess inhibition or stimulation of human, rat (male and female) liver, and minipig liver microsomal MFO activity. For human preparations the strongest inhibition by BPA was observed for CYP 2C. The inhibition was most prominent when a lower dose of BPA was used on the complete post-mitochondrial fraction. BPA inhibited rat microsomal CYP 1A isoform-specific metabolite production to 29 +/- 3% of control levels (100%). Biomaterial monomers exhibited mixed effects. For example, BPA stimulated CYP 4A in pooled human S9 to 129 +/- 1% of control. Also, BADM and BAGDA stimulated CYP 4A to 141% and 142% of control values, respectively.

Hospital and parish (county) utilization of master's-prepared nurses in Louisiana.

Recent regulation in Louisiana involving advanced practice nursing, combined with new educational standards at the Master's level established by the Louisiana State Board of Nursing, prompted a statewide survey of hospitals and parish health units. The purpose of the survey was to determine whether and to what extent Master's-prepared nurses were being used in Louisiana and to identify the importance placed on role functions and activities generally associated with the advanced practice nurse (APN). The survey included open-ended questions concerning expectations about future hirings and perceptions of future roles and duties of the Master's-prepared nurse as well as suggestions to educators on what is needed to better prepare nursing students at the Master's level. Results from this exploratory survey provide information on APN utilization with implications for nursing educators and administrators as well as APNs.

Schistosomiasis in Saudi Arabia, Egypt, and Iraq.

The incidence of schistosomiasis, a parasitic infestation caused by trematodes, or flukes, has decreased significantly in Egypt and other Middle Eastern countries. The education of people in the countryside is a primary reason. The water supply in these countries is now good, and, in most areas, women no longer use the stagnant river tributaries for washing clothes. Medications, which can be used to prevent the infection or kill the parasite include praziquante and metrifonate.

Comparison of the Cytobrush plus plastic spatula with the Cervex Brush for obtaining endocervical cells.

OBJECTIVE: To compare the effectiveness of the Cytobrush plus plastic spatula with that of the Cervex Brush for obtaining acceptable yields of endocervical cells in Papanicolaou smears. METHODS: We collected 309 smears over a 6-month period, 132 with the Cytobrush plus spatula and 177 with the Cervex Brush. About one-third of the patients in each group were pregnant. Numbers of endocervical cells in the smears were described as none, few, moderate, or many. RESULTS: Moderate or large numbers of endocervical cells were collected from 60.5% of the women in the Cervex Brush group and 65.2% of those in the Cytobrush-spatula group. The percentages were not statistically different. CONCLUSION: The Cytobrush plus spatula and the Cervex Brush sampling methods were equally effective in obtaining endocervical cells in routine Papanicolaou smears.

Effects of intracoronary dipyridamole infusion on regional myocardial blood flow and intrinsic thallium-201 washout in dogs with a critical coronary stenosis.

Intravenous dipyridamole (DP) infusion produces a significant endocardial-to-epicardial flow gradient distal to a critical coronary stenosis, resulting in diminished regional thallium-201 (Tl-201) uptake and washout. Intravenous DP can also produce a significant decrease in arterial blood pressure and therefore in coronary perfusion pressure. We determined to further clarify the mechanism of this transmural coronary "steal" employing intracoronary DP administration, thereby avoiding systemic hypotension. In five of eight dogs with a critical left anterior descending (LAD) stenosis, intracoronary DP caused no significant fall in systemic arterial pressure, a rise in epicardial flow from 1.15 +/- 0.2 to 1.75 +/- 0.2 ml/min/gm, and a slight fall in subendocardial flow from 1.15 +/- 0.2 to 1.03 +/- 0.5 ml/min/gm. Intracoronary DP caused no prolongation of the intrinsic Tl-201 washout rate. In three dogs that developed systemic hypotension after intracoronary DP, endocardial flow fell from 1.14 to 0.63 ml/min/gm, the epicardial/endocardial flow ratio fell to 0.35, and Tl-201 washout became more prolonged. Thus intracoronary DP in the setting of a critical LAD stenosis caused minimal endocardial-to-epicardial steal and had no effect on the intrinsic Tl-201 washout rate unless it was accompanied by a fall in systemic arterial pressure. The magnitude of the transmural steal was substantially less than reported in our previous experiments utilizing intravenous DP infusion. This study provides a further insight into the mechanism of DP-induced subendocardial ischemia and suggests that systemic hemodynamic alterations play an important role in the effects of the vasodilator on myocardial blood flow and Tl-201 kinetics.

Effects of dipyridamole and aminophylline on hemodynamics, regional myocardial blood flow and thallium-201 washout in the setting of a critical coronary stenosis.

Experiments were performed to characterize the interaction of intravenous dipyridamole and aminophylline on thallium-201 transport kinetics, regional myocardial blood flow and systemic hemodynamics in the presence of a critical coronary artery stenosis. In 12 dogs with a critical left anterior descending coronary artery stenosis, arterial pressure decreased from a mean value (+/- SEM) of 107 +/- 6 to 94 +/- 3 mm Hg (p less than 0.05) and distal left anterior descending artery pressure decreased from 70 +/- 7 to 55 +/- 4 mm Hg (p less than 0.05) after intravenous administration of dipyridamole (0.25 mg/kg body weight). In the left anterior descending perfusion zone, the endocardial/epicardial flow ratio decreased from 0.70 to 0.36 and the intrinsic thallium washout rate was significantly prolonged. Intravenous aminophylline (5 mg/kg) reversed the dipyridamole-induced systemic hypotension and transmural coronary steal and restored the thallium washout rate to baseline values. In six other dogs, aminophylline alone resulted in no alterations in systemic and coronary hemodynamics or regional myocardial blood flow. As expected, dipyridamole-induced vasodilation and coronary steal were prevented by aminophylline pretreatment. These data show that in a canine model of partial coronary stenosis, systemic hypotension, adverse regional flow effects (coronary steal) and prolonged thallium-201 washout consequent to intravenously administered dipyridamole are promptly reversed by intravenous aminophylline administration. Aminophylline alone had no significant hemodynamic and coronary flow effects. This study provides further insight into the altered thallium kinetics occurring as a consequence of dipyridamole-induced vasodilation and suggests that the prompt reversal of symptoms and signs of ischemia with aminophylline in patients receiving intravenous dipyridamole for clinical imaging studies probably reflects the reversal of transmural coronary steal.

Effect of ischemia and postischemic dysfunction on myocardial uptake of technetium-99m-labeled methoxyisobutyl isonitrile and thallium-201.

The myocardial uptake of a new technetium-99m-labeled myocardial perfusion agent, methoxyisobutyl isonitrile (Tc-99m MIBI), and thallium-201 was correlated with microsphere flow in an open chest canine model of low coronary flow and postischemic dysfunction. Eighteen dogs were given an injection of thallium-201 (0.5 mCi) and Tc-99m MIBI (5 mCi) either after 40 min of partial left anterior descending artery occlusion (Group I, 10 dogs) or during reperfusion after 15 min of left anterior descending artery occlusion (Group II, 8 dogs). Regional dysfunction was documented during injection in both groups by quantitative two-dimensional echocardiography. Regional blood flow was assessed by radiolabeled microspheres. The heart was excised 15 min after radionuclide injection and the left ventricle divided into 96 segments for gamma well counting. Among Group I dogs, central ischemic thallium-201 and Tc-99m MIBI activity (expressed as a percent of the activity in the corresponding nonischemic zone) was comparable, respectively, for endocardial (54 +/- 17% and 52 +/- 17%), mid-wall (71 +/- 20% and 69 +/- 17%) and epicardial (89 +/- 13% and 94 +/- 9%) segments and increased proportionally with flow. There was a good linear correlation among these endocardial segments between flow and both thallium-201 (r = 0.78) and Tc-99m MIBI (r = 0.85) activity. Among Group II dogs, central ischemic endocardial flow (59 +/- 14%) was comparable to thallium-201 (70 +/- 18%) and Tc-99m MIBI (74 +/- 12%) activity. Similarly, relative endocardial flow in the intermediate ischemic region (71 +/- 11%) was comparable to thallium-201 (77 +/- 11%) and Tc-99m MIBI (81 +/- 10%) activity. Thus, myocardial uptake of Tc-99m MIBI and thallium-201 is comparable under conditions of low coronary flow and postischemic dysfunction and closely parallels flow alterations.

Identification of components in iodinated glycerol.

Iodinated glycerol (CAS no. 5634-39-9), therapeutically used as an expectorant and source of organically bound iodine, was analyzed to determine the purity and composition of the chemical samples used in carcinogenicity and toxicity studies. The manufactured product is described by the patent and chemical literature as a mixture of two isomeric iodopropylideneglycerols (structures 1 and 2). The results of our studies, however, indicate that the two principal components of the product were 3-iodo-1,2-propanediol (IPD) and glycerol (GLY). Analyses from GC-MS (full scan electron impact) and carbon-13 nuclear magnetic resonance spectrometry provided conclusive identification of these components. The quantification of IPD and GLY in one of two samples of commercial product using GC-flame ionization detection indicated concentrations of 33 and 17%, respectively (Sample A). Similar concentrations were determined for a second sample from the same source (Sample B), which was a gratis sample procured approximately nine years after Sample A. Numerous minor components were also observed in these two samples. These components were tentatively identified as condensation products of glycerol and iodine-containing analogues. The iodopropylideneglycerol compounds, described in the patent, were not observed in either of the two samples.