Mechanical properties of a light-polymerizing provisional restorative material with and without reinforcement fibers

Interim restorations are vulnerable to inadvertent fracture during mastication. Autopolymerizing acrylic resins have traditionally been selected for fabrication of provisional restorations. Triad light-polymerizing tooth-colored acrylic resin was recently introduced as an alternative material for this procedure. This material does not contain methyl methacrylate monomer and permits an increased working time. Heavy occlusal forces may initiate cracks within these restorations, and propagation of these cracks may ultimately lead to failure. Various forms of reinforcement fibers are available and are marketed for strengthening dental resins used for provisional restorations. Investigators have demonstrated that the mechanical properties of acrylic resins may be improved with the incorporation of reinforcing fibers, but a published evaluation of fiber-reinforced light-polymerizing provisional restorative materials is lacking. This investigation recorded and compared two mechanical properties of one light-polymerizing provisional restorative material with and without incorporation of vertically and horizontally oriented woven, matted, polyethylene fibers. No significant difference in modulus of rupture was recorded between groups with and without fibers. The mean flexural elastic modulus of the group with the horizontally oriented fibers was significantly greater than the mean flexural elastic modulus of the specimens without incorporated fibers.     

Storage, surgery outcome, and complications of corneal and conjunctival grafts

Recent articles related to corneal storage, surgery outcome, and complications of corneal and conjunctival grafts are reviewed. It appears that the addition of insulin and human epidermal growth factor may benefit storage solutions. Several multivariant analyses of risks for graft rejections are included, and include corneal vascularization, failed previous grafts, and preoperative endothelial damage. Transverse keratotomy as a method of controlling astigmatism after grafting may be effective. The incidence of acute hydrops in patients with keratoconus is about 2.8%. Free conjunctival grafts are reported to be useful in repairing failed filtering blebs and persistent bleb leaks.     

Polymeric Microspheres Prepared by Spraying into Compressed Carbon Dioxide

Purpose. The objective was to prepare polymeric microparticles by atomizing organic polymer solutions into a spray chamber containing compressed CO₂ (PCA-process) and to study the influence of various process parameters on their morphological characteristics. Methods. The swelling of various pharmaceutically acceptable polymers [ethyl cellulose, poly(methyl methacrylate), poly(-caprolactone), poly(dl-lactide), poly(l-lactide) and poly(dl-lactide-glycolide) copolymers] in CO₂ was investigated in order to find polymers which did not agglomerate during the spraying process. Poly(l-lactide) (L-PLA) microparticles were prepared by spraying the organic polymer solution into CO₂ in a specially designed spraying apparatus. The effect of various process (pressure and temperature of the CO₂ phase, flow rate) and formulation (polymer concentration) variables on the morphology and particle size of L-PLA-microparticles was investigated. Results. Polymers with low glass transition temperatures agglomerated even at low temperatures. The formation of microparticles was favored at moderate temperatures, low polymer concentrations, high pressures and high flow rates of CO₂. High polymer concentrations and low flow rates resulted in the formation of polymeric fibers. Colloidal L-PLA particles could also be prepared with this technique in a surfactant-free environment. Initial studies on the microencapsulation of drugs resulted in low encapsulation efficiencies. Conclusions. The PCA method is a promising technique for the preparation of drug-containing microparticles. Potential advantages of this method include the flexibility of preparing microparticles of different size and morphology, the elimination of surfactants, the minimization of residual organic solvents, low to moderate processing temperatures and the potential for scale-up.     

Accuracy of intraoperative frozen-section analysis of axillary nodes. Edinburgh Breast Unit team

BACKGROUND: Intraoperative assessment of axillary lymph node involvement would allow selection of patients who would benefit from axillary lymph node dissection. METHODS: Eighty-eight patients undergoing mastectomy or wide excision had four nodes sampled and sent for frozen-section examination. RESULTS: Frozen-section analysis of the nodes was correct in 81 of the 88 patients but missed seven of the 26 patients who had involved nodes on paraffin section (sensitivity 73 per cent). CONCLUSION: Frozen-section analysis of axillary lymph nodes as currently practised cannot be recommended for routine use although it may have a role in specific groups of patients.     

One-year study of spatial memory performance, brain morphology, and cholinergic markers after moderate controlled cortical impact in rats

Persistent cognitive deficits are one of the most important sequelae of head injury in humans. In an effort to model some of the structural and neuropharmacological changes that occur in chronic postinjury brains, we examined the longitudinal effects of moderate vertical controlled cortical impact (CCI) on place learning and memory using the Morris water maze (MWM) test, morphology, and vesicular acetylcholine (ACh) transporter (VAChT) and muscarinic receptor subtype 2 (M2) immunohistochemistry. Vertical CCI (left parietal cortex, 4 m/sec, 2.5 mm; n = 10) or craniotomy (sham) was produced in male Sprague-Dawley rats (n = 10). Place learning was tested at 2 weeks, 4 weeks, 3 months, 6 months, and 12 months postinjury with the escape platform in a different maze quadrant for each time point. At each interval, rats received 5 days of water maze acquisition (latency to find hidden platform), a probe trial to measure place memory, and 2 days of visible platform trials to control for nonspecific deficits. At 3 weeks, half the animals were sacrificed for histology. At these injury parameters, CCI produced no significant differences in place learning between injured and sham rats at 2 weeks, 4 weeks, or 6 months after injury. However, at 3 and 12 months, the injured rats took significantly longer to find the hidden platform than the sham rats. Probe trial performance differed only at 12 months postinjury between injured (25.73+/-2.1%, standard error of the mean) and sham rats (44.09+/-7.0%, p < 0.05). The maze deficits at 1 year were not due to a worsening of performance, but may have resulted from a reduced ability of injured rats to benefit from previous water maze experience. Hemispheric loss of 30.4+/-5.5 mm3 was seen at 3 weeks after injury (versus respective sham). However, hemispheric loss almost doubled by 1 year after injury (51.5+/-8.5 mm3, p < 0.05 versus all other groups). Progressive tissue loss was also reflected by a three- to fourfold increase in ipsilateral ventricular volume between 3 weeks and 1 year after injury. At 1 year after injury, immunostaining for VAChT was dramatically increased in all sectors of the hippocampus and cortex after injury. Muscarinic receptor subtype 2 (M2) immunoreactivity was dramatically decreased in the ipsilateral hippocampus. This suggests a compensatory response of cholinergic neurons to increase the efficiency of ACh neurotransmission. Moderate CCI in rats produces subtle MWM performance deficits accompanied by persistent alteration in M2 and VAChT immunohistochemistry and progressive tissue atrophy. The inability of injured rats to benefit from repeated exposures to the MWM may represent a deficit in procedural memory that is independent of changes in hippocampal cholinergic systems.     

Lysophosphatidic acid-induced proliferation in opossum kidney proximal tubular cells: role of PI 3-kinase and ERK

Lysophosphatidic acid-induced proliferation in opossum kidney proximal tubular cells: Role of PI 3-kinase and ERK. BACKGROUND: Lysophosphatidic acid (LPA) is a mitogenic lipid bound to albumin in the circulation and implicated in the induction of proximal tubular cell (PTC) injury in proteinuric states. In this study, we investigated the effect of LPA on proliferation of opossum kidney (OK) cells and the roles of the p85/p110 phosphatidylinositol 3-kinase (PI 3-kinase) and extracellular signal-regulated kinases (ERKs) ERK-1 and ERK-2 in LPA-induced proliferation. METHODS: [3H]-thymidine incorporation was used as an index of OK cell proliferation. PI 3-kinase and ERK activities were measured by in vitro kinase assays of immunoprecipitates from both wild-type OK cells and OK cells expressing a dominant negative p85 (Deltap85) subunit of PI 3-kinase in an inducible vector. RESULTS: LPA stimulated a marked increase in [3H]-thymidine uptake in wild-type and Deltap85 OK cells. OK cell PI 3-kinase activity was stimulated by LPA and was inhibited by expression of Deltap85. LPA-induced proliferation was inhibited by wortmannin and the induction of Deltap85 expression. These data suggest that LPA stimulates PI 3-kinase activity, which is essential for signaling the induction of proliferation. LPA also stimulated ERK activity (peak at 5 min, return to baseline by 60 min) maximally at a dose of 100 microM LPA. This increase was approximately 600% above basal and was similar to the effects of 10% fetal calf serum. The proliferative effect of LPA was decreased by the ERK-kinase (MEK) inhibitor PD98059 (5 microM), therefore suggesting that ERK as well as PI 3-kinase activation is important for proliferation. ERK activation by LPA was not affected by pretreatment with wortmannin or by the expression of Deltap85. PI 3-kinase activation by LPA was not affected by pretreatment with PD98059. CONCLUSIONS: We conclude that activation of PI 3-kinase is essential for the LPA-induced proliferation of OK cells and that ERK activation is also important. Therefore, they are both vital elements in separate signaling pathways leading to cell proliferation. LPA filtered into the proximal tubule in proteinuric states is likely to have profound effects on PTC growth.     

Measuring health-related quality of life in patients with venous leg ulcers

Introduction: The effect on quality of life by healing leg ulcers is not known and no validated disease-specific tool is available for measuring health-related quality of life (HRQoL) for people with venous leg ulcers. The objective of this paper was to compare four generic instruments [MOS 36-Item Short-Form Health Survey (SF-36); EuroQol (EQ); McGill Short Form Pain Questionnaire (SF-MPQ) and the Frenchay Activities Index (FAI)] used for measuring HRQoL in people with venous leg ulcers, and to offer guidance on the most appropriate tool for researchers. Methods: Two hundred and thirty-three patients with venous leg ulcers were recruited as part of a randomised controlled trial of the cost-effectiveness of community leg ulcer clinics. Subjects completed questionnaires containing the four instruments on three occasions (initial assessment, 3 and 12 months). The discriminative and evaluative properties of the four instruments were compared. Results: All four instruments were acceptable to patients, taking a mean of 19.3 (SD 6.3) min to complete. At initial assessment, the SF-MPQ had poorer discriminative properties than the other three instruments and was not able to distinguish between the different patient groups in relation to age and ulcer duration. The FAI was good at discriminating between the different patient groups (at initial assessment) in relation to age, mobility and ulcer size. At the three-month follow-up, the SF-MPQ was more responsive than the other measures and detected changes in HRQoL, whereas the EQ and SF-36 did not. At 12 months, the SF-MPQ still identified differences and the SF-36 and EQ also did at this stage. Conclusion: In the absence of a validated condition-specific tool for measuring changes in general health status for patients with venous leg ulcers, we make the following recommendations. For evaluating the outcome of interventions with a short-term follow-up (three months) in a clinical study we recommend the SF-MPQ and for 12-month follow-up in a clinical study the SF-36, with or without the SF-MPQ.     

Cardiac allograft vasculopathy: the green lane hospital experience 1987-1998

AIMS: To determine the prevalence of cardiac allograft vasculopathy in heart transplant recipients at Green Lane Hospital and to examine potential risk factors for vasculopathy. METHODS: We retrospectively reviewed the coronary angiograms of all cardiac transplant recipients. Angiography was usually performed one, two and five years after operation. The diagnosis of allograft vasculopathy was made if there was any evidence of coronary artery disease. Patients' medical records were reviewed for potential risk factors. RESULTS: Ninety-one patients underwent cardiac transplantation between December 1987 and March 1998. One year survival was 87%. Angiographic evidence of coronary disease was present in 30 patients and in three patients coronary lesions were first identified at post mortem. Vasculopathy was present in 25%, 35% and 61% of patients at one two and five years following transplant. Donor-acquired lesions could not be excluded as few patients had immediate postoperative angiograms for comparison. Five late deaths have been due to vasculopathy. Recipient age, race, donor age and ischaemic time were similar for those with and without vasculopathy. Frequency or severity of acute rejection episodes, cytomegalovirus infection, lipid profiles, diabetes and hypertension were not significantly different in patients with vasculopathy. CONCLUSION: Cardiac allograft vasculopathy is a common finding after heart transplantation. No definite risk factors were identified in this patient group.