Experimental wax mixtures for dental use

summary Improvements in the properties of dental waxes were sought by alterations in their composition. Twenty-six blends of paraffin wax, beeswax and inorganic filler were subjected to the following tests: plastic deformation (flow), linear thermal expansion, elastic modulus and flexural strength. Flow tests were conducted in accordance with the corresponding ISO specification, Thermal expansion coefficients were estimated using thermomechanical analysis. Mechanical properties were tested using a universal testing machine. Pure paraffin and beeswax were used as controls. The results were subjected to analysis using correlation and regression. Regression coefficients in the range of 0.90–0.99 were obtained in most cases, flow tests exhibiting the highest coefficients and flexural strength the lowest. The incorporated filler particles reduced the flow of the natural waxes, especially of the ester-containing beeswax, and improved the elastic modulus and strength. Good correlation was found between the ingredient proportions and measured properties, suggesting a relationship between them, although this is quite complicated in the case of tertiary wax mixtures. The experimental blends exhibited properties that are potentially useful for a range of clinical applications.     

Prospective study of antigenemia,plasma viremia and lymphocytic viremia in HIV-infected hemophiliacs

A total of 186 blood samples from 24 HIV-1 seropositive hemophiliac patients, monitored every four months for 29 months, were investigated for the presence of viral antigen in plasma. In addition, peripheral blood mononuclear cells (PBMC) were cultured for HIV-1, using normal PBMC as a target for replication. Antigenemia was detected in 51 % of the patients and from PBMC in 87.5 % of the patients. The incidence of HIV isolation in asymptomatic patients (42.8 %) was similar to that found in symptomatic patients (51.4 %). Patients with opportunistic infections had a higher incidence of lymphocytic viremia (p<0.05). Plasma viremia was closely associated (p<0.05) with low CD4+ counts and infection progression. The persistence of antigenemia was also a marker of a poor clinical course. In treated patients, plasma viremia was the marker that better correlated with the clinical course, and it did not appear during the first nine months of therapy. Zidovudine doses of >500 mg/day significantly lowered the appearance of antigenemia and lymphocytic viremia (p<0.05).     

In vivo efficacy of azithromycin in treatment of systemic infection and septic arthritis induced by type IV group B Streptococcus strains in mice: comparative study with erythromycin and penicillin G.

We compared the activities of azithromycin, erythromycin, and penicillin G in a mouse model of systemic infection and septic arthritis induced by type IV group B streptococci (GBS). The in vitro and in vivo efficacy data for these drugs were analyzed relative to the pharmacokinetics of the drugs in sera, joints, and kidneys. Adult CD-1 mice were infected intravenously with 10(7) CFU of type IV GBS. Intraperitoneal drug administration was initiated with different dose regimens at different times after infection. A single dose of azithromycin (100 mg/kg) strongly reduced the incidence of articular lesions with respect to that with erythromycin or penicillin G. Treatment with azithromycin (three intraperitoneal administrations of 50 mg/kg at 12-h intervals) resulted in the complete prevention of arthritis. In contrast, erythromycin was poorly effective and penicillin G was effective only if inoculated 30 min after infection and at high doses (400,000 or 600,000 IU/kg). Furthermore, azithromycin was able to cure about 70% of the mice when administered 7, 8, and 9 days after GBS infection. Azithromycin was much more active than erythromycin and penicillin G with respect to bacterial killing in the joints and kidneys. In fact, cultures from these tissues were always negative no matter what treatment schedule was employed. The pharmacokinetics of azithromycin account for its superior in vivo efficacy against type IV GBS. A longer half-life and higher levels of this drug in serum and tissues with respect to those for erythromycin or penicillin G were achieved. The high affinity of azithromycin for the joints strongly supports its potential value for therapy of septic arthritis, which is a severe and frequent clinical manifestation of GBS infection.     

Chemical traumatization of adult mouse olfactory epithelium in situ stimulates growth and differentiation of olfactory neurons in vitro

This study demonstrates that ZnSO₄ induced chemical trauma results in an in situ regeneration of the olfactory epithelium which, when maintained in vitro, provides an enriched population of olfactory neurons. Therefore, the ability of the olfactory epithelium to respond to chemical trauma with increased mitotic activity can be used to increase growth of neurons in culture. Tissue obtained from normal or vehicle-treated adult mice produced few olfactory neurons, when maintained in culture, compared to cultures established from tissue following an in situ ZnSO₄ trauma. Maximal neuronal yields were obtained in cultures established from tissue that was removed 4–6 days following chemical trauma. The morphological appearance and the presence of cell specific intermediate filament proteins were used to classify the cell types in these olfactory epithelial cultures. Single cells and aggregates of cells which were immunopositive for keratin, but immunonegative for neurofilament protein and GFAP, were identified as epithelioid. Flattened polygonal cells immunopositive for GFAP were identified as glia. A small population of flattened cells was immunonegative for all of the antibodies used in this study. Cells that had processes were immunonegative for GFAP and keratin. Some were immunopositive for 200 kDa and 160 kDa neurofilament proteins but immunonegative for the 68 kDa neurofilament protein. A few of these cells showed positive immunoreactivity with the olfactory marker protein (OMP) antibody and most likely represented the most mature olfactory neurons in the cultures. This trauma-induced culture model using olfactory tissue from adult mice can serve as a source of CNS neurons for comparison with cultured embryonic neurons.     

Self-expanding nitinol stents in canine vertebral arteries: hemodynamics and tissue response.

PURPOSETo evaluate the hemodynamics and tissue response associated with stent placement in low-flow-velocity arteries.METHODSSix self-expanding nitinol stents (5.5 mm caliber) were implanted transfemorally within the proximal segments of vertebral arteries (2.5 mm diameter) in six adult dogs during anticoagulative protection.RESULTSControl angiograms demonstrated patency and 20% dilatation of all stented arteries. One artery was partially thrombosed 1 week later and subsequently showed a 50% stenosis. Throughout the observation period (4 to 9 months after stenting), the other five arteries remained patent without significant narrowing (< or = 15%). Small cervical muscle branches originating from the vertebral arteries within the stented segments remained patent. No major branch occlusions of the vertebrobasilar system were detected. Stent migration or kinking did not occur. MR studies of the brain 4 months after implantation revealed no infarcted areas. These findings were confirmed with brain sections. Stented artery specimens showed delayed stent dilatation. A comparison of the total mean thickness of intima covering the five 30- to 40-mm stents removed at 4, 6, and 9 months showed no significant difference (338, 332, and 389 microns, respectively). Histologic findings verified the macroscopic impression of a thicker intima at the inner curve of the stented artery segments and at the junctions of the stent filaments. The shortest (10 mm) stent had the thinnest neointimal growth (155 microns). Stented vessels showed compression of the media with atrophy, but without necrosis or perforation. Scanning electron photomicrographs revealed intact endothelial cell linings with typical elongated cells.CONCLUSIONSNo significant risk of thromboembolic events exists after implanting these nitinol stents in nonatherosclerotic vertebral arteries in dogs. Thicker neointimal growth after stenting may result from either low wall shear stress with possible flow separation or from changes in the shape and size of the stent, or both.