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At least 1,711 records · Page 95Linked to original sources
PubMed1993

Comparison of vasovasostomy techniques in rats utilizing conventional microsurgical suture, carbon dioxide laser, and fibrin tissue adhesives.

An evaluation of vas reanastomoses in rats comparing suture only, carbon dioxide (CO2) laser-assisted, and fibrin-based tissue adhesive was performed in our laboratory. A cohort of 60 known fertile male Sprague Dawley rats initially underwent lower midline abdominal exploration and transection of their vas deferens bilaterally, followed by immediate microsurgical vasovasostomy by one of the three experimental methods. All groups initially had the severed vasa ends coapted by two or three transmural (mucosa through serosa) sutures of 10-0 nylon under an operating microscope. The conventionally sutured group had an additional four to six nylon 10-0 sutures placed externally in the serosa only to complete the anastomosis. The CO2 laser-assisted group underwent laser welding with denaturation of the serosa to seal the anastomosis. A fibrin-based tissue adhesive, produced by combining human cryoprecipitate and thrombin, was placed topically over the coapted vas ends to seal the anastomosis in the third group. Postoperative evaluation revealed similarities among the three surgical groups with the fibrin-based tissue adhesive group resulting in the highest patency rate (89%) and pregnancy rate (85%) as well as the lowest granulation rate (18%) and shortest operative time (27 minutes). The laser-assisted group resulted in the lowest pregnancy rate (68%), while the sewn anastomosis group had the lowest patency rate (76%). Both laser-assisted and conventionally sewn vasectomy reversals required significantly longer operative time (39 and 46 minutes, respectively) compared with the fibrin-based tissue adhesive-assisted procedures (p < 0.01). This study provides evidence that alternative microsurgical techniques may be utilized to perform uncomplicated, expeditious, and successful vasectomy reversals.

Animals↗
PubMed1980

Mutagenicity of airborne particles.

The physical and chemical properties of airborne particles are important for the interpretation of their potential biologic significance as genotoxic hazards. For polydisperse particle size distributions, the smallest, most respirable particles are generally the most mutagenic. Particulate collection for testing purposes should be designed to reduce artifact formation and allow condensation of mutagenic compounds. Other critical factors such as UV irradiation, wind direction, chemical reactivity, humidity, sample storage, and temperature of combustion are important. Application of chemical extraction methods and subsequent class fractionation techniques influence the observed mutagenic activity. Particles from urban air, coal fly ash, automobile and diesel exhaust, agricultural burning and welding fumes contain primarily direct-acting mutagens. Cigarette smoke condensate, smoke from charred meat and protein pyrolysates, kerosene soot and cigarette smoke condensates contain primarily mutagens which require metabolic activation. Fractionation coupled with mutagenicity testing indicates that the most potent mutagens are found in the acidic fractions of urban air, coal fly ash, and automobile diesel exhaust, whereas mutagens in rice straw smoke and cigarette smoke condensate are found primarily in the basic fractions. The interaction of the many chemical compounds in complex mixtures from airborne particles is likely to be important in determining mutagenic or comutagenic potentials. Because the mode of exposure is generally frequent and prolonged, the presence of tumor-promoting agents in complex mixtures may be a major factor in evaluation of the carcinogenic potential of airborne particles.

Air Pollutants↗
PubMed1992

Biosphere 2 Test Module: a ground-based sunlight-driven prototype of a closed ecological life support system.

Constructed in 1986, the Biosphere 2 Test Module has been used since the end of that year for closed ecological systems experiments. It is the largest closed ecological facility ever built, with a sealed variable volume of some 480 cubic meters. It is built with a skin of steel spaceframes with double-laminated glass panels admitting about 65 percent Photosynthetically Active Radiation (PAR). The floor is of welded steel and there is an underground atmospheric connection via an air duct to a variable volume chamber ("lung") permitting expansion and contraction of the Test Module's air volume caused by changes in temperature and barometric pressure, which causes a slight positive pressure from inside the closed system to the outside thereby insuring that the very small leakage rate is outward. Several series of closed ecological system investigations have been carried out in this facility. One series of experiments investigated the dynamics of higher plants and associated soils with the atmosphere under varying light and temperature conditions. Another series of experiments included one human in the closed system for three, five and twenty-one days. During these experiments the Test Module had subsystems which completely recycled its water and atmosphere; all the human dietary needs were produced within the facility, and all wastes were recycled using a marsh plant/microbe system. Other experiments have examined the capability of individual component systems used, such as the soil bed reactors, to eliminate experimentally introduced trace gases. Analytic systems developed for these experiments include continuous monitors of eleven atmospheric gases in addition to the complete gas chromatography mass spectrometry (GCMS) examinations of potable, waste system and irrigation water quality.

Air Conditioning↗
PubMed1990

Acute leukaemia in workers exposed to electromagnetic fields.

Results from a French case-control study of acute leukaemia and occupational exposure for the risk associated with exposure to electromagnetic fields (EMF) are reported. There were 185 cases and 513 controls. A significantly increased risk of acute leukaemia was observed for exposure to EMF other than that from arc welding (odds ratio = 4.04, 95% CI 1.26-12.88) which persisted after adjustment for possible confounding exposures. This study supports the hypothesis that workers exposed to some EMF have an increased risk of leukaemia.

Acute Disease↗
PubMed1996

Possible health risks from low level exposure to beryllium.

The first case of chronic beryllium disease (CBD) at the Rocky Flats Environmental Technology Site (Rocky Flats) was diagnosed in a machinist in 1984. Rocky Flats, located 16 miles northwest of Denver, Colorado, is part of the United States Department of Energy (DOE) nuclear weapons complex. Research and development operations using beryllium began at Rocky Flats in 1953, and beryllium production operations began in 1957. Exposures could have occurred during foundry operations, casting, shearing, rolling, cutting, welding, machining, sanding, polishing, assembly, and chemical analysis operations. The Beryllium Health Surveillance Program (BHSP) was established in June 1991 at Rocky Flats to provide health surveillance for beryllium exposed employees using the Lymphocyte Proliferation Test (LPT) to identify sensitized individuals. Of the 29 cases of CBD and 76 cases of beryllium sensitization identified since 1991, several cases appear to have had only minimal opportunistic exposures to beryllium, since they were employed in administrative functions rather than primary beryllium operations. In conjunction with other health surveillance programs, a questionnaire and interview are administered to obtain detailed work and health histories. These histories, along with other data, are utilized to estimate the extent of an individual's exposure. Additional surveillance is in progress to attempt to characterize the possible risks from intermittent or brief exposures to beryllium in the workplace.

Berylliosis↗
PubMed1994

Microwave balloon angioplasty effectively seals arterial dissections in an atherosclerotic rabbit model.

OBJECTIVES: The purpose of this study was to determine the effectiveness of microwave balloon angioplasty in sealing arterial dissections and to characterize the histologic features associated with this intervention. BACKGROUND: Coronary dissection accompanying balloon dilation is frequently associated with abrupt closure and acute ischemic complications. Effective management of this complication remains an active area of investigation. Because thermal energy is effective in welding separated atherosclerotic plaques, a microwave-based catheter system that provides controlled local heating was utilized in vessels with angioplasty-induced dissections. METHODS: Iliac artery dissections were induced in ahypercholesterolemic rabbit model. Vessels were randomly assigned to treatment with standard balloon angioplasty (control vessels) or microwave balloon angioplasty using an average temperature of 80 degrees C. The response of the artery was assessed angiographically and histologically. RESULTS: Angiographic success, defined as a reduction of dissection length by > 50% or the resolution of lumen haziness, was achieved in 63% of microwave-treated vessels and in 16% of control vessels (p < 0.005). Dissection length (mean +/- SD) was reduced 8.0 +/- 4.8 mm in microwave-treated vessels compared with 0.1 +/- 7.9 mm in vessels receiving standard balloon inflations (p < 0.005). Cellular necrosis was more commonly observed in microwave-treated vessels than in control vessels (73% vs. 17%, p < 0.05), but less intraluminal thrombus was seen in vessels exposed to microwave energy (p < 0.05). CONCLUSIONS: Microwave balloon angioplasty is more effective than routine balloon inflations in sealing arterial dissections in this model and appears to be less thrombogenic in these markedly disrupted vessels.

Angiography↗
PubMed1985

Metal fume fever--a review.

Metal fume fever (MFF) is an acute industrial disease caused by the inhalation of a variety of heavy metal oxides. MFF occurs most commonly during welding operations, particularly those involving zinc oxide. The illness is of short duration and produces symptoms of cough, fever, chills, malaise, and myalgias. Its etiology is uncertain, and its diagnosis is difficult because symptoms resemble a number of pulmonary illnesses. Supportive treatment, with bed rest, analgesics, and fever control is used for symptomatic relief. Emergency medicine physicians must differentiate the clinical picture from other common respiratory illnesses. The mainstay of therapy for MFF consists of recognizing the disease and preventing subsequent exposure to harmful metals.

Diagnosis, Differential↗
PubMed1994

Radiographic assessment of cementless femoral components. Correlation with intraoperative mechanical stability.

The correlation between preoperative radiographic findings and intraoperative testing for stability was evaluated for 75 cementless femoral components. Fourteen of 45 porous-coated prostheses were unstable. The following radiographic signs were correlated with instability in order of significance: radiolucent lines at the bone-prosthesis interface covering greater than 50% of the porous interface, a distal pedestal, calcar hypertrophy, poor implant-cortical contact, and varus component alignment. Signs consistent with implant stability were good implant-cortical contact, spot welds, and calcar atrophy. Preoperative radiographs have predictive value in assessing the mechanical stability of the cementless femoral component at the time of surgery.

Hip↗
PubMed1994

Taperloc femoral component. A 2-6-year study of the first 100 consecutive cases.

The first 100 consecutive patients who underwent insertion of the Taperloc (Biomet, Warsaw, IN) femoral stem were prospectively studied with a mean follow-up period of 3.8 years (range, 2-6 years). Two of the original 100 patients were lost, giving a 98% follow-up rate. The diagnoses included osteoarthritis (76 patients), avascular necrosis (19), rheumatoid arthritis (3), chrondrolysis (1), and post-traumatic arthritis (1). The mean age at surgery was 56 years (range, 25-79 years), mean weight was 78 kg (range, 45-127 kg), and the female to male ratio was 29:71. Charnley pain and function scores were 3.0 and 2.8 before surgery and 5.5 and 5.4 after surgery. Thigh pain was present in 2% of the patients at the final follow-up evaluation. There were no revisions. Radiographic signs of bone-ingrowth fixation (calcar atrophy, spot welds) were seen in 92 of 94 components (98%). No component had complete demarcation of the porous-coated zones. Fifty-two of 94 patients were able to be matched for age, sex, weight, diagnosis, and length of follow-up period with a series of patients who received a contemporary cemented total hip. In this matched subset, the Charnley pain and function scores were 5.6 and 5.5 for the cementless Taperloc stem and 5.7 and 5.5 for the cemented control group; this is not a significant difference. These data indicate a clinical performance equivalent to a matched group of contemporary cemented total hip arthroplasties.

Adult↗
PubMed1993

Polar zippers.

BACKGROUND: Certain proteins are known to form leucine zippers - alpha-helical coiled-coils in which the non-polar side chains of two leucine-rich helices intermesh. We recently presented the first evidence for a polar zipper, formed by the carboxy-terminal peptides of the eight subunits of Ascaris haemoglobin. The evidence was based on the presence of pairs of acidic residues alternating with pairs of basic residues ( + + - - ) in an amino-acid sequence that has since been shown to be incomplete. The complete sequence, derived from the haemoglobin's cDNA, now shows a self-complementary polar sequence extending along the entire length of its 24-residue carboxy-terminal peptide. RESULTS: From the complete sequence, it is clear that the eight identical subunits of the haemoglobin could be held together by an eight-stranded antiparallel beta barrel made up of the carboxy-terminal 24 residues of each of the subunits, such that each strand forms 10 salt bridges with each of its neighbours. A computer search of the protein database revealed similar, but shorter, + + - - repeats in several other proteins. It also revealed long repeats of alternating arginine and aspartate residues, and long stretches of only glutamines, or only serines, suggestive of several other kinds of polar zippers. CONCLUSION: Several proteins have amino-acid sequences that suggest the formation of polar zippers made of beta strands. These could form antiparallel pleated sheets linked together by hydrogen bonds between polar side chains both above and below the plane of the sheets. Polar zippers may be important in welding together oligomeric proteins which have subunits lacking the extensive complementary surfaces necessary for stability, or in promoting the association of functionally complementary proteins.

Journal Article↗
PubMed1996

Biologically weighted personal UV dosimetry.

People are exposed to natural or artificial UV radiation in different ways; unintentionally or intentionally, at their workplace on their spare time. To quantify the amount of individual UV exposure, a personal dosimetry is necessary. In research, polysulphone film (PSF) dosimeters are the most frequently used personal UV dosimeters. We use calculated weighting factors in the measurement processing of polysulphone film dosimeters. The special weighting factor transforms the dosimeter reading from an equivalent UV dose to the biologically effective UV dose. The factor depends on the investigated problem (action spectrum of the photobiological effect and spectral distribution of the incident UV source), the calibration of PSF was carried out once by a monochromatic radiation (gamma = 295 nm). The equivalent dose readings are available from this calibration curve for any investigated question. A presented result of this method is the seasonal measurement of erythemally effective UV exposure by ambient solar radiation, and the individual exposure level in a "normal" person concerning UV exposure and also in groups with the risk of a lack of sunshine. Further applications are occupational measurements of the risk of health damage by UV radiation (with respect to the limit of the maximum permissible 8 h-exposure according to IRPA/INIRC-guidelines). We controlled the extent of UV exposure in workers in the area of arc welding workplaces. The biological weighting of PSF readings simplifies a routine use of PSF in personal UV monitoring to investigators without the expending special measurement technology (e.g. spectroradiometer).

Film Dosimetry↗
PubMed1991

Zones of membrane adhesion in the cryofixed envelope of Escherichia coli.

The envelopes of Escherichia coli B and E. coli K29 were examined using cryofixation and freeze substitution. Emphasis was directed toward the question whether membrane adhesion zones (which connect inner membrane (IM) and outer membrane (OM) after plasmolysis in 10-20% sucrose) can be visualized with the use of cryotechniques. Plasmolysis in 10-20% sucrose was observed to have no effect on cell viability. We found that simple plunge-freezing methods preserve adhesion sites, whereas these sites were not observed after impact-freezing. Also, plasmolysis "bays," visible in light microscopic preparations of living cells, were seen to be maintained intact after plunge-freezing. Employment of photocrosslinking with UV-flashes before or after plasmolysis showed a significant increase in the number of adhesion areas compared to noncrosslinked specimens. To control the contact speed of the specimen during immersion into the cryogen, a hollow rotor was constructed in which the cryogenic liquid is moving at desired high speeds. Adhesion sites presented themselves in the plasmolyzed cell as sites of close contact of the outer and inner membrane, an arrangement that would leave very limited space for peptidoglycan layers at the contact site of the two membranes. Adhesion sites may occur either as single, isolated sites or within stretches of IM/OM apposition where they appear to function as "spot welds" between the two membranes. Exposure of cells to sucrose concentrations of 35% caused rupture of adhesions with cytoplasmic fragments remaining attached to the envelope. The cryofixation procedures described here do not presently yield the number of membrane adhesions obtainable with conventional aldehyde fixation. However, since the combination of millisecond photocrosslinking and cryofixation of plasmolyzed cells resulted in a higher membrane stabilization and in an increase of the number of adhesion sites, this combination appears to be a useful tool for the analysis of sensitive membrane structures.

Bacterial Adhesion↗
PubMed1992

Measurement of cardiac left ventricular pressure in conscious rats using a fluid-filled catheter.

A fluid-filled catheter consisting of 100 cm of PE50 polyethylene tubing welded to 7 cm of PE10 polyethylene tubing (PE50/PE10) was constructed for the purpose of measuring the rate of left ventricular pressure development (+dP/dt) in conscious, freely moving rats. Prior to in vivo experiments, four PE50/PE10 catheters were randomly selected, and their natural frequencies and damping ratios were determined using a square wave impact. The mean (n = 4), natural frequency of these catheters was shown to be 35.0 +/- 5.5 Hz, and the mean damping ratio was 0.83 +/- 0.10. Natural frequency plotted against increasing PE50 tubing length was shown to have a slope of -0.44 Hz/cm with a correlation coefficient of 0.99. The effect of the 7-cm PE10 tubing segment on the catheter damping ratio was also demonstrated. One of the four PE50/PE10 type catheters exhibited a damping ratio of 0.74 +/- 0.09. When the 7-cm PE10 tube was removed, the damping ratio was reduced to 0.31 +/- 0.04. Left ventricular +dP/dt obtained in conscious rats with a PE50/PE10 catheter (n = 7; 6300 +/- 300 mmHg/sec) was significantly less than the +dP/dt obtained using a 100-cm PE50 catheter (n = 6; 9400 +/- 400 mmHg/sec). The results of this study make it clear that the PE50/PE10 catheter is suitable for the measurement of left ventricular +dP/dt in the conscious rat, and that catheter design has a profound influence on both the catheter natural frequency and damping ratio.

Animals↗
PubMed2004

Bond strength of various bracket base designs.

To determine the influence of various bracket base designs on bond strength and debond interface, 6 types of metal interlock brackets of different sizes and with different base designs were evaluated. The bracket base types and mesh sizes tested were as follows: retention groove base (Dynalock, Unitek, Monrovia, Calif), circular concave base (Accuarch appliance Formula-R, Tomy, Tokyo, Japan), double mesh with 5.1 x 10(-2) mm2 mesh size (Ultratrimm, Dentaurum, Ispringen, Germany), double mesh, 3.1 x 10(-2) mm2 (Minidiagonali Roth, Leone, Florence, Italy), double mesh, 3.1 x 10(-2) mm2 (Tip-edge Rx-I, TP Orthodontics, LaPorte Ind), and double mesh, 2.9 x 10(-2) mm2 (Mini Diamond, Ormco, Glendora, Calif). The Unitek bracket is cast in 1 piece; the other brackets are welded together. Brackets were bonded to human teeth and then debonded on a testing machine. The debond interface was recorded and analyzed with scanning electron microscopy and energy-dispersive x-ray spectrometry, and the distribution of interfaces was determined. The ranking of bond strength of individual bases (kg/base) from highest to lowest was Tomy, Dentaurum, Unitek, Leone, TP Orthodontics, and Ormco. The ranking of bonding strength per area squared MPa from highest to lowest was Tomy, Dentaurum, Leone, Unitek, TP Orthodontics, and Ormco. Debond in interfaces occurred between the bracket and resin, within the resin, or between the resin and enamel. The most debonded interfaces were between the bracket and resin and between the resin and enamel. The Tomy bracket, with its circular concave base, produced greater bond strength than did the mesh-based brackets; among the mesh-based brackets, Dentaurum, with the larger mesh size, produced greater bond strength than the brackets with smaller mesh sizes. The Unitek bracket, with its 1-piece cast base with retention grooves, ranked in the midrange of bond strength.

Analysis of Variance↗
PubMed2006

Forces released during alignment with a preadjusted appliance with different types of elastomeric ligatures.

INTRODUCTION: The purpose of this in-vitro study was to compare the forces generated by new nonconventional elastomeric ligatures (NCEL) and conventional elastomeric ligatures (CEL) during leveling and aligning phases. METHODS: The testing model consisted of 5 stainless steel 0.022-in preadjusted brackets for second premolar, first premolar, canine, lateral incisor, and central incisor. The canine bracket was welded to a sliding bar that allowed for different vertical positions. The forces generated by 3 sizes of wires (0.012-, 0.014-, and 0.016-in superelastic nickel-titanium) with the 2 types of elastomeric ligatures at different amounts of upward canine misalignment (1.5, 3, 4.5, and 6 mm) were recorded. RESULTS AND CONCLUSIONS: Significant differences between CEL and NCEL were found for all tested variables (P <.01) with the exception of the 0.014- and 0.016-in wires at canine misalignment of 1.5 mm. A noticeable amount of force was generated with the NCEL at all 4 canine positions with all 3 wire sizes (from about 50 to about 150 g). With 4.5 mm of canine misalignment or more, the average amount of released force with the CEL was approximately zero.

Dental Alloys↗
PubMed2005

Rheumatoid arthritis among women in the Agricultural Health Study: risk associated with farming activities and exposures.

PURPOSE: Farming has been associated with increased risk of rheumatoid arthritis (RA) in some studies, but specific causes have not been identified. We studied risk factors for RA in the Agricultural Health Study, a cohort of over 57,000 licensed pesticide applicators and their spouses. METHODS: We used a nested case-control design, limited to female participants. Physician-confirmed cases (n = 135) were matched to five controls each (n = 675) by birth date. We used logistic regression, adjusting for birth date and state to examine associations, as estimated by odds ratios (OR) and 95% confidence intervals (CI). RESULTS: Risk of RA was not associated with mixing or applying pesticides overall or with any pesticide class, nor did it vary by number of days or years of use. Certain pesticides were associated with small nonsignificantly increased risks, including lindane (OR = 1.8, 95% CI: 0.6-5.0). RA risk was associated with welding (OR = 2.1, 95% CI: 0.8-5.4), albeit imprecisely, but not with solvents or sunlight. CONCLUSIONS: We did not identify any strong risk factors for RA. Because of the severe disability associated with this relatively common disease, further investigation into causes is warranted both in the Agricultural Health Study and elsewhere.

Adult↗
PubMed2005

Studies on the production and quality assurance of miniature (125)I radioactive sources suitable for treatment of ocular and prostate cancers.

(125)I sources were prepared by adsorption of (125)I on palladium-coated silver wires. The effect of reducing agent on percentage adsorption of (125)I was studied and the amount of adsorbed activity on source core was studied by repeated adsorption cycles. The activity per source in the sources produced from the same batch varied with coefficient of variation (i.e. the ratio of standard deviation to mean multiplied by 100) less than 10%. The unencapsulated source exhibited low leachability (< 0.01%). The laser parameters were optimized to obtain quality welds with negligible leak rate. The sources were laser-encapsulated in titanium capsules of 0.8 mm (OD) x 4.5mm (l). The release of radioactivity from encapsulated sources in an immersion test at 50 degrees C for 5 h was <5 nCi (185 Bq). The surface contamination on the sealed capsules was found to be<0.05 nCi or 1.85 Bq per source. The sources were used in the treatment of a child having retinoblastoma.

Adsorption↗