Search PubMed⌕ Search

Biomedical subjects

L G Smith

Publications and source records attributed to L G Smith.

At least 91 records · Page 5Linked to original sources
PubMed1989

Effects of sulfur dioxide or ammonium sulfate exposure, alone or combined, for 4 or 8 months on normal and elastase-impaired rats.

Normal and lung-impaired rats were compared after exposure to SO2 and/or (NH4)2SO4 for 4 or 8 months, or for 8 months plus 3 months recovery. Young adult male Sprague-Dawley rats were pretreated intratracheally with either physiologic saline (normal lungs) or porcine pancreatic elastase (impaired lungs). Rats from each pretreatment group were exposed to filtered air (control), to SO2 (1 ppm) or (NH4)2SO4 (0.5 mg/m3), or to combined SO2 + (NH4)2SO4 for 5 hr/day, 5 days/week. Morphologic, physiologic, and immunologic criteria were evaluated. At 4 months cellular immunologic responsiveness was not impaired, but physiologic changes were detected. Morphologic changes were apparent in all time periods. Elastase-induced changes included greater lung volumes, emphysema, and alveolar interstitial fibrosis. Pollutant effects included bronchiolar epithelial hyperplasia and changes in alveolar mean chord length (MCL). Relative to controls, bronchiolar epithelial hyperplasia and MCL increased in saline/pollutant groups, but decreased in elastase/pollutant rats at 4 months. The pretreatment/pollutant interaction was not observed at 8 months. Elastase effects persisted throughout the recovery period. Pollutant effects were more transitory, although alveolar septal fibrosis was greater in saline/(NH4)2SO4 rats at 8 months. Pulmonary function changes associated with elastase included increases in residual volume, functional residual capacity, and the residual volume/total lung capacity ratios. The alveolar plateau of single-breath washout (N2 slope) was significantly steeper in elastase-treated rats but less steep in animals exposed to SO2 or to (NH4)2SO4 than in those exposed to air only.

Air Pollutants↗
PubMed1989

Preparation of microgram quantities of BaP-DNA adducts using isolated rat hepatocytes in vitro.

The analysis of carcinogen-DNA adducts generally requires the preparation (by chemical or biological means) of DNA adduct standards, in amounts sufficient for chemical characterization. We have established conditions for the in vitro biological preparation of microgram quantities of DNA adducts derived from benzo[a]pyrene (BaP), fluoranthene and 7,12-dimethylbenzanthracene, using isolated rat hepatocytes. The metabolic activation of 180 microM BaP by isolated rat hepatocytes in a calf-thymus-DNA (CT-DNA)-supplemented medium resulted in the formation of 2.9 micrograms of BaP adducted to 56.7 mg of DNA. The average level of binding in this experiment was 148 +/- 8 pmol BaP bound/1 mg DNA, which compares favorably to the 10-30 pmol BAP/1 mg DNA which is typical of mouse skin adducts in vivo. In another experiment, BaP-DNA adduct formation in calf-thymus DNA added to hepatocyte incubations was further increased to 327 +/- 27 pmol/mg DNA, by physical shearing of the DNA prior to the incubation. The HPLC profile of the BaP adducts produced using hepatocytes plus CT-DNA is virtually indistinguishable from that produced by tumor-initiating doses of BaP applied to mouse skin in vivo, and the major DNA adduct formed by the hepatocytes co-elutes with the (+)-anti-diol-epoxide adduct of deoxyguanosine. Similar experiments using fluoranthene and 7,12-dimethylbenzanthracene also resulted in substantial DNA adduct formation; however, incubations using dibenz[a,h]anthracene did not. These results indicate that isolated rat hepatocytes in vitro can be useful for the preparation of DNA adducts of a number of polycyclic aromatic hydrocarbons, in quantities sufficient for chemical characterization.

Animals↗
PubMed1989

Evaluation of blunt abdominal trauma occurring during pregnancy.

Evaluation of abdominal trauma in pregnant patients presents a number of dilemmas. Few series compare the various modalities available in this situation. The present review characterizes various techniques and their results. The charts of all patients with a secondary diagnosis of pregnancy admitted to a Level I trauma center over a 7 1/2-year period were reviewed. Forty were considered to have sustained possible blunt abdominal trauma: 30 were occupants in motor vehicle collisions, five were pedestrians, four sustained falls, and one was riding a motorcycle. Immediate laparotomy for emergency caesarean section or other indications was performed in three cases (7%). In 13 cases (32%) evaluation was accomplished by diagnostic peritoneal lavage (DPL). Three patients (7%) underwent computerized tomography of the abdomen. The remaining 22 patients (55%) were observed with serial physical exams, and hematocrits. The group that was observed had a mean ISS of 5.9. The mean Glasgow Coma Score (GCS) was 14.9. No patients had to undergo exploratory laparotomy for abdominal injury during hospitalization. In the 13 patients undergoing DPL, the mean ISS was 34.6, and the mean GCS was 10.6. Overall accuracy was 92% with no major complications. Pregnant patients sustaining minor injuries and blunt abdominal trauma may be safely observed. Those with major injuries, shock, altered mental status, or neurologic deficit require further studies to rule out intra-abdominal injury. Diagnostic peritoneal lavage proved to be safe and accurate in these patients. Diagnostic peritoneal lavage proved to be safe and accurate in these patients. CT scan and ultrasonography are other modalities which merit further assessment as a primary diagnostic technique in abdominal trauma occurring during pregnancy.

Abdominal Injuries↗
PubMed1989

New frontiers in the management of the multiple injured patient.

This article describes current theories and technological advances in trauma management. The technologies are constantly changing, with new therapeutic modalities on the horizon. As approaches to trauma patient care become more complex, it remains a challenge and a requirement to remain abreast of current theories and practices in the field of traumatology.

Analgesia↗
PubMed1988

Viral hepatitis. The alphabet game.

Differential diagnosis of viral hepatitis begins with a check for darkened urine and bile in the urine. These hallmarks of conjugated hyperbilirubinemia immediately rule out prehepatic liver disease. Next, studies are done for the elevated transaminase levels that are characteristic of hepatitis infection, and a thorough history is taken to rule out drug- and toxin-induced hepatitis that may mimic acute viral hepatitis. Elevated alkaline phosphatase is a good marker of cholestasis. Ultrasonography can clarify this diagnosis. The classic presenting symptoms of viral hepatitis are jaundice, nausea, vomiting, malaise, anorexia, and dull right upper quadrant pain. However, serologic studies are needed to detect the presence of specific viral agents.

Acute Disease↗
PubMed1988

Computed tomography of the abdomen in the diagnosis of splenic emboli.

Abdominal computed tomographic scans were performed in 25 consecutive patients with bacterial endocarditis. Six patients had splenic infarcts, only two of whom had symptoms. Three of the six patients had no evidence of emboli to other organs. In patients with endocarditis who have had clinically apparent emboli or who are, for other reasons, being considered for valvular surgery, a computed tomographic scan of the abdomen may help in decision making.

Adult↗
PubMed1987

The pregnant hepatitis B carrier: evidence favoring comprehensive antepartum screening.

The prevalence of hepatitis B surface antigen among 15,399 gravidas screened in the prenatal clinic at Charity Hospital of Louisiana in New Orleans was 0.88%. The race-specific prevalence was 0.56% for whites, 0.62% for blacks, and 8.8% for Orientals. Identifiable risk factors could not be found for approximately half of the hepatitis B surface antigen-positive women. Comprehensive antepartum hepatitis B screening is recommended, based upon the significant risk of perinatal transmission to the neonate and upon the failure of selective screening to identify the majority of maternal hepatitis B surface antigen carriers in our population. The cost-effectiveness of general antepartum screening compares favorably with current blood bank hepatitis screening costs.

Carrier State↗
PubMed1986

Epidermal carcinogenesis studies of synthetic fossil fuel materials in mice.

Skin tumor response in mice to solvent fractions of heavy distillate (HD) from a solvent-refined coal (SRC-II) process indicated that the basic tar and neutral tar were the most carcinogenically potent fractions. Assays of another SRC-II coal liquid that had been fractionally distilled indicated that the carcinogenicity of this material for mouse skin is due to that portion boiling above 371 degrees C (700 degrees F), and that the carcinogenic potency of the material increased with boiling point. Samples of the 399-427 degrees C (750-800 degrees F) distillate were nitrosated to destroy primary aromatic amines and were chemically fractionated to assess the carcinogenicity of chemical class fractions of these complex mixtures. Data from these assays indicated that neutral polycyclic aromatic hydrocarbons (PAH) and nitrogen-containing polycyclic aromatic compounds (NPAC) both contribute to the carcinogenicity of this distillate.

Animals↗
PubMed1986

Effects of ammonium nitrate aerosol exposure on lung structure of normal and elastase-impaired rats and guinea pigs.

Groups of rats and guinea pigs with normal lungs and others with elastase-induced emphysema were exposed to NH4NO3 aerosols of 0.60 mass median aerodynamic diameter at 1 mg/m3 for 6 hr/day, 5 days/week, for 4 weeks. Morphologic and morphometric studies were performed on lungs perfused with cacodylate-buffered 2% glutaraldehyde under 20 cm H2O pressure at necropsy. The tissues were studied for pathologic change by light and electron microscopy; emphysema was evaluated by subgross and microscopic methods, including changes in mean alveolar chord length using scanning electron microscopy techniques. Elastase produced emphysema to a degree quantifiable by all criteria studied; however, it apparently obscured the effects of nitrate inhalation. The NH4NO3 exposure (compared to air alone) tended to increase values for pulmonary parameters in normal animals of both species and to decrease them in elastase-treated animals. The NH4NO3 exposure increased values for lung volume in rats, percentage area affected in elastase-treated rats, and chord length beta in normal animals of both species. The responses to NH4NO3 were slight (P less than 0.10) and were not accompanied by any detectable changes in alveolar structure. Therefore, the effects of NH4NO3 at this exposure level and duration, are regarded as biologically insignificant for rats and guinea pigs.

Aerosols↗
PubMed1986

Future Fit: a cardiovascular health education and fitness project in an after-school setting.

Future Fit was developed to provide a low cost, heart health education and fitness program that could be incorporated readily into existing after-school programs with minimal teacher training and nominal expenditures for equipment and supplies. Participants in the 12-week demonstration project were 55 third and fourth grade students enrolled in after-school programs at four sites, randomly assigned to experimental and control conditions. Results indicated significant knowledge gains and changes in knowledge, attitude, and behavior at home. These outcomes suggest health and fitness programming in the after-school setting can be an effective complement to the education provided within the school setting.

Attitude to Health↗
PubMed1985

Ventilatory responses when altering stride frequency at a constant oxygen uptake.

Ten women completed a slow walk (SW), fast walk (FW) and a slow run (R) on a motor driven treadmill to evaluate the effect of varying stride frequency on ventilatory responses. The treadmill grade was adjusted during the walks such that the oxygen uptake was the same as during running at 0% grade. Stride frequencies averaged 59, 69 and 80 strides/min for the SW, FW and R, respectively. Oxygen uptake was similar for all three trials (1.78 L/min); as were heart frequencies (154.6 beats/min). Mean blood pressure was unaffected by changing stride frequency. Minute ventilation was similar for all three trials (ca. 47.3 L/min). Significant differences in respiratory frequency were observed (SW = 33.2, FW = 35.4, R = 37.2 breaths/min). Tidal volumes were significantly greater during the slow walk (1417 ml) than either the fast walk (1331 ml) or the run (1301 ml). CO2 output was significantly greater during the run compared to either of the walking trials. End-tidal CO2 was 38.6 mm Hg during the slow walk and was significantly reduced during the fast walk (36.3) and run (36.0). The results suggest the existence of a mild hypocapnia during the fast walk and running exercise. These results further suggest that variations in ventilatory patterns exist during walking and running that are not totally accountable by blood pressure or CO2 and may be related to extra-metabolic stimuli.

Blood Pressure↗