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Biomedical subjects

R L Sherwood

Publications and source records attributed to R L Sherwood.

18 recordsLinked to original sources
PubMed2001

Long-term performance of Osseotite implants: a 6-year clinical follow-up.

In this prospective, multicenter study, 147 Osseotite implants were placed in 75 patients (32 men and 43 women with a mean age of 54 years) using a conventional two-stage surgical protocol with 3 months of healing time in the mandible and 6 months in the maxilla. Of the 147 implants, 69% were inserted in posterior sites and 64% were short implants of 10 mm or less. From the time of implant insertion to second-stage surgery, 5.1 months (+/- 2.4 months) elapsed. Restorative treatments included 25 single-tooth replacements (28.4%), 58 short span fixed bridges (65.9%), 1 full-arch reconstruction (1.1%), and 4 overdentures (4.5%). The mean time from implant placement to final recall was 74.1 months (+/- 8.9 months). At second-stage surgery and at 6-month and annual follow-up examinations, implants were evaluated for mobility, peri-implant radiolucency, gingival health, signs and symptoms of infection, neuropathies, paresthesia, and crestal bone levels. A 3-year interim report identified 5 implant failures, 4 of which occurred as a clustering phenomenon in a single, medically compromised patient. Using the life table analysis method, the cumulative implant success rate was calculated at 96.6%. The 3-year interim report indicates that the implants developed an extended, functional osseous state that remained stable for more than 6 years.

Adult↗
PubMed1997

Preliminary results of a multicenter study evaluating a chemically enhanced surface for machined commercially pure titanium implants.

PURPOSE: This report presents the preliminary results of a prospective multicenter study to evaluate the efficacy of a chemically etched pure titanium surface on screw-type dental implants. MATERIAL AND METHODS: The results of 147 implants placed in 75 patients were evaluated and followed for up to 3 years, using clinical and radiographic examinations. The implants were inserted to support single crowns, overdentures, and fixed prostheses, as dictated by the individual patient's need. RESULTS: Of the 147 implants placed, 5 were lost and the remaining implants were followed throughout, to the end of the study period. Crestal bone levels adjacent to each implant were monitored and the amount of total bone loss was calculated. Clinically healthy peri-implant gingival tissues were observed on 95% of the implants, whereas 88.3% demonstrated no bleeding on probing and no recession during the follow-up period. According to the criteria used in this study, the total success rate was calculated to be 96.6%.

Acid Etching, Dental↗
PubMed1995

Local versus systemic immunotoxicity of isobutyl nitrite following subchronic inhalation exposure of female B6C3F1 mice.

Female B6C3F1 mice were exposed to isobutyl nitrite (IBN) by inhalation at 0, 37.5, 75, or 150 ppm for 6 hr per day, 5 days per week for 15 weeks. The potential of this compound to induce immunotoxicity was assessed during the 3rd, 13th, 14th, and 15th week of exposure and after 2 weeks of recovery following the 15 weeks of exposure. Both systemic and lung immune functions were examined, including body and lymphoid organs weights, pulmonary macrophage function and host defense, expression of splenic lymphocyte cell-surface markers, natural killer cell function, mixed lymphocyte reaction, and induction of specific antibody to a T-cell-dependent antigen. There was a dose-related suppression of T-cell-dependent antibody-forming cell responses in the spleen following IBN exposure; however, other measures of T-cell and nonspecific immunity were not significantly affected. A dose-related increase of H202 production by alveolar macrophages was present after 12 but not after 68 exposures to IBN. In contrast, pulmonary host defense mechanisms against Klebsiella pneumoniae were unaffected. These results suggest that in the absence of changes in host resistance, IBN may have selective and partially reversible effects on the immune system.

Administration, Inhalation↗
PubMed1995

Influence of steric stabilization of liposome-encapsulated hemoglobin on Listeria monocytogenes host defense.

Liposome-encapsulated hemoglobin (LEH) products are being investigated as potential blood substitutes. To determine if changes in LEH composition can modify the immune response, red blood cell substitutes based on conventional lipids containing phosphatidylinositol (LEH1) and sterically stabilized lipid vesicles containing polyethylene glycol phosphatidylethanolamine (LEH2) were tested for effects on host resistance. On Day 0, groups of 18 to 20 female CD-1 mice were given an intravenous (i.v.) infectious challenge with a 20% lethal dose of Listeria monocytogenes. Mice received a single i.v. dose of LEH1, LEH2, or albumin vehicle on Day +1 or Day -3 relative to infectious challenge. Mice dosed with LEH1 and LEH2 on Day +1 died rapidly from Listeria infection; but mice dosed with LEH2 lived significantly longer than did mice receiving LEH1. By contrast, when administered on Day -3, LEH1 had no significant effect on host immunity, while LEH2 increased susceptibility to Listeria infection. In addition, LEH1 and LEH2 both caused significant reduction of phagocytic activity as measured by rat alveolar macrophage (AM) ingestion of latex microspheres. AM incubated 4 hr with either LEH1 or LEH2 prior to addition of microspheres ingested fewer beads in a dose-dependent manner. No difference in in vitro phagocytic activity was observed between LEH1 or LEH2. The inability to differentiate LEH formulations based on in vitro phagocytic activity suggests that the in vivo Listeria infection model may be more relevant in discerning the immunotoxicity of the LEH formulations tested.

Animals↗
PubMed1991

Distribution, clearance, and mortality of environmental pseudomonads in mice upon intranasal exposure.

When introduced intranasally, P. cepacia AC1100 (approximately 10(8) CFU/animal) and P. aeruginosa AC869 (approximately 10(3) CFU/animal) were readily cleared from the mouse. However, a approximately 10(7)-CFU dose of AC869 persisted for 14 days. Strain AC869 had a 50% lethal dose of 2.7 x 10(7) CFU. Slight morbidity occurred in animals treated with approximately 10(7) CFU of AC869 or approximately 10(8) CFU of AC1100.

Administration, Intranasal↗
PubMed1989

Prosthetic management of unparallel titanium plasma-sprayed screw implants.

Iatrogenic problems may occur in the treatment of implant patients. Hopefully implant screws can be placed parallel to each other, but there are situations where they are not, because of operator error or the configuration of the alveolar ridge. The technique presented will assist in the prosthetic management of unparallel screw implants.

Aged↗
PubMed1989

Effects of inhaled hexachlorobenzene aerosols on rat pulmonary host defenses.

Pulmonary bactericidal activity, macrophage phagocytic activity, alveolar macrophage (AM) enzyme activity, and T- and B-cell mitogenesis of lymphocytes from lung associated lymph nodes (LALN) or mesenteric lymph nodes (MESLN) were assessed in Sprague-Dawley rats exposed 4 hr/d, 4 days/wk for 1, 4, or 16 days to hexachlorobenzene (HCB) aerosols. Pulmonary bactericidal activity was depressed after 1 or 4 but not 16 exposures to 35 mg/m3 of HCB. AM phagocytosis of 51Cr-RBC in vitro was increased after 4 but not 1 or 16 exposures to HCB, and no effect was observed in peritoneal macrophages. HCB significantly enhanced mitogenesis in MESLN to the B-cell mitogen Salmonella typhimurium lipopolysaccharide (STM) after 4 exposures; LALN STM mitogenesis and LALN and MESLN mitogenesis to phytohemagglutinin (PHA) were not affected. After 16 exposures, however, the PHA responses in LALN and MESLN were significantly increased and decreased, respectively.

Administration, Intranasal↗
PubMed1988

Comparison of Streptococcus zooepidemicus and influenza virus pathogenicity in mice by three pulmonary exposure routes.

Pulmonary infections may be induced in experimental animals by using several exposure routes. Inhalation of microbial aerosols is often viewed as the most relevant exposure route, although the comparability of either intranasal (i.n.) or intratracheal (i.t.) inoculation to aerosol inhalation is unclear. In these studies, the infection of mice with either Streptococcus zooepidemicus or influenza virus was compared following i.n., i.t., or aerosol challenge. The 50% lethal dose was determined by each exposure route for both microbes, and the organ clearance of a 50% lethal dose was determined. Mice were as or more sensitive to bacterial or viral infection following i.n. or i.t. instillation as compared with aerosol challenge. Organ clearance patterns of virus or bacteria varied slightly with exposure route.

Aerosols↗
PubMed1987

Effects of inhalation of ethylene dichloride on pulmonary defenses of mice and rats.

The effects of single or multiple inhalation exposures to ethylene dichloride (DCE) on the pulmonary defense systems of mice and rats were evaluated. Single exposures of mice to the threshold limit value of DCE (10 ppm) resulted in decreased pulmonary bactericidal activity to inhaled Klebsiella pneumoniae and increased mortality from Streptococcus zooepidemicus respiratory infection. A single exposure to 5 ppm DCE caused increased mortality from streptococcal pneumonia although bactericidal activity was not affected. Neither of these two parameters changed following single or five consecutive daily exposures to 2.5 ppm DCE. Single exposures to 10 or 100 ppm DCE did not affect mouse alveolar macrophage (AM) inhibition of the proliferation of a tumor target cell in vitro or AM in vitro phagocytosis of red blood cells. In rats, no effects were observed on pulmonary bactericidal activity. AM in vitro phagocytosis, AM cytostasis and cytolysis of tumor target cells, AM ectoenzymes, or blastogenesis of mitogen-stimulated rat T- and B-lymphocytes from lung-associated, mesenteric, and popliteal lymph nodes following single exposure to 100 or 200 ppm DCE or after twelve 5-hr exposures to 10, 20, 50, or 100 ppm DCE.

Administration, Inhalation↗
PubMed1986

Effect of 0.64 ppm ozone on alveolar macrophage lysozyme levels in rats with chronic pulmonary bacterial infection.

A rat model of chronic pulmonary infection (CPI) initiated by Pseudomonas aeruginosa embedded in agar beads was used to test the effect of ozone on lysosomal enzyme levels in alveolar macrophages (AM). CPI was induced by intratracheal instillation of a 0.1-ml suspension of infected beads into the left lung. Ten days after infection half the rats were exposed to atmospheres of air and half to 0.64 ppm ozone for 4 weeks. Enzyme levels were measured using a scanning cytospectrophotometer linked to PDP/11 computer. Measurement of lysozyme in individual rat AM in situ showed a significant decrease in cell size and enzyme content in ozone-exposed uninfected animals. Cell size and enzyme content of ozone-exposed animals with CPI were further reduced, suggesting a synergistic effect between ozone exposure and chronic infection.

Animals↗
PubMed1985

Effects of toluene inhalation on pulmonary host defenses of mice.

The potential hazards of exposure to vapor-phase toluene on pulmonary host defenses were evaluated. Mice exposed to concentrations ranging from 2.5-500 ppm, including the threshold limit value level of 100 ppm, exhibited increased susceptibility to respiratory infection with Streptococcus zooepidemicus. The no-measurable-effect level for single, as well as for 5 exposures was 1 ppm. Significantly decreased pulmonary bactericidal activity was observed after single exposures to 500, 250, 100 and 2.5 ppm toluene, and after 5 daily 3-h exposures to 1.0 ppm of toluene. A 20-exposure study with toluene at 1 ppm produced no changes in either of the 2 assays.

Animals↗
PubMed1984

Effect of 0.64 ppm ozone on rats with chronic pulmonary bacterial infection.

Rats were chronically infected with Pseudomonas aeruginosa by entrapping viable bacteria in agar beads and intratracheally inoculating the beads into the left lung. The infection was allowed to stabilize over a 10-d period and the animals were then placed in environmental chambers and exposed to either filtered air or 0.64 ppm ozone (23 h/d) for 14 or 28 d. Rats exposed to ozone had reduced body weight and increased lung sizes and lung weights when compared with animals breathing filtered air. Rats inoculated with beads containing live P. aeruginosa had increased lung weights when compared with rats inoculated with beads containing heat-killed P. aeruginosa or controls. Quantitation of total viable bacteria in rats exposed to ozone or to filtered air revealed no significant differences in bacterial numbers. Thus, in this model, chronic exposure to ozone produces increases in lung volume and weight but does not enhance a smoldering Pseudomonas infection.

Animals↗
PubMed1983

Glucan alteration of pulmonary antibacterial defense.

Particulate yeast glucan, prepared by the methods of Northcote and Horne and Peat et al, was studied in rats and mice to determine its protective capacity in respiratory infection. Glucan was administered intravenously to rodents prior to infection with aerosols of bacteria. Glucan-treated rats had significantly increased rates of phagocytosis and killing of Staphylococcus aureus immediately after infection and minimal increases at 4 h. In contrast, pulmonary killing of Klebsiella pneumoniae in rats was markedly enhanced by glucan at 4 h. Glucan treatment of mice provided only transient protection against pulmonary infection with group C streptococci. Histological studies demonstrated greatly increased numbers of macrophages in the lungs of glucan-treated rats; the lungs of glucan-treated mice appeared normal. These results show that glucan can enhance intrapulmonary bacterial killing. In rats, this is due to the ability of glucan to increase the number of lung macrophages resulting in increased bacterial ingestion. Glucan-induced protection in mice is less clear.

Animals↗
PubMedDate not supplied

Effects of acrolein on macrophage functions in rats.

Male Sprague-Dawley rats were exposed to 0.1, 1.0 or 3.0 ppm acrolein or filtered air 6 h/day, 5 days/week for 3 weeks. Rats were tested one day following the last exposure and exhibited no change in pulmonary clearance of inhaled 35S-labeled Klebsiella pneumoniae at any acrolein concentration. Decreased numbers of peritoneal cells were obtained from exposed rats while the number of cells lavaged from the lungs was unchanged. Macrophages of acrolein-exposed rats had altered phagocytic and enzymatic patterns as compared to macrophages from animals breathing filtered air. However, these changes had no apparent effect on macrophage killing of inhaled bacteria and were therefore probably not indicative of extreme chemical toxicity.

5'-Nucleotidase↗
PubMedDate not supplied

Effect of ferrous sulfate aerosols and nitrogen dioxide on murine pulmonary defense.

A murine infectivity model was used to test the effect of exposure to atmospheres containing 290 +/- 50 microgram/m3 of respirable sized ferrous sulfate (FeSO4) particles (0.4 micron mass median aerodynamic diameter) and 1.0 ppm nitrogen dioxide (NO2) prior to infection with aerosols of Staphylococcus aureus or group C streptococci. Exposure to these combined pollutants for 24 or 48 hr did not impair pulmonary inactivation of S. aureus. Exposure to FeSO4 or NO2 for 48 hr, or to both pollutants for 24 or 48 hr, resulted in significant decreases in inactivation of inhaled group C streptococci. Mortality studies following pollutant exposure demonstrated earlier, but not an increased number of deaths. These studies demonstrate the importance of the test organism in assessing air quality standards with the infectivity model and enhanced toxicity and prolongation of exposure to relatively low levels of submicron-size particles of FeSO4 and NO2.

Aerosols↗
PubMedDate not supplied

The reverse-torque test: a clinical report.

Reverse torque to failure on implants has been studied in animals. Three implants were reverse torqued to failure in a human volunteer, with failure rates between 45 and 58 Ncm. Clinical data are presented on 404 implants examined after reverse-torque testing and loading, with no increase in failure rates. Reverse-torque testing at 20 Ncm appears to be a safe, reliable method for verifying osseointegration with pure titanium screw-shaped implants.

Animals↗