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Biomedical subjects

C C Edwards

Publications and source records attributed to C C Edwards.

At least 19 recordsLinked to original sources
PubMed1992

Predictors of participation in a school-based anti-tobacco activism program.

This study investigated the predictors of participation in a school-based, anti-tobacco activism program. Subjects in this study consisted of 7th grade students participating in the intervention component of Project S.H.O.U.T., a tobacco use prevention program in San Diego County, California. In the activism component, a newsletter containing an activism contest was distributed to each student. Small prizes were awarded to contest winners at each school. "Activism" included letter and petition writing, anti-tobacco poster contests, merchant education, peer surveys and magazine subscription cards. A total of 170 students participated in the activities, with 81.1 percent participating two or more times. Of those who participated, 59 percent were female and 60 percent were White, non-Hispanic. Two sets of logistic analyses were conducted. Variables such as SES, gender, ethnicity, friends' tobacco use and parental tobacco use were used to predict participation in activism activities. The choice of variables was intended to provide information regarding activism participation in reference to known tobacco risk factors. Results of the first analysis indicated that students with a higher SES, and in an urban vs. rural location were more likely to participate in the activism activities. The second analysis used the same set of characteristics to predict "ever-use" of tobacco. Results of this analysis indicated that male gender, low grades, White, non-Hispanic ethnicity, friends' and parents' tobacco use were positively associated with tobacco experimentation.

Adolescent↗
PubMed1992

Chronic donor site pain complicating bone graft harvesting from the posterior iliac crest for spinal fusion.

To explore the relationship between surgical approach and chronic posterior iliac crest donor site pain, 151 bone graft harvests with follow-up periods longer than 1 year were evaluated using a detailed questionnaire and follow-up clinical visits. There was no difference in the incidence of chronic donor site pain between harvests performed through the primary midline incision versus a separate lateral oblique incision (28 vs 31%). Twice as many donor sites harvested for reconstructive spinal procedures were reported as having chronic pain as compared with those harvested for spinal trauma, regardless of approach used (39 vs 18%). The association of chronic donor site pain with residual back pain was also greater in the spinal reconstructive group. Thus, it appears that incidence of chronic donor site pain is more dependent on diagnosis than on surgical approach.

Bone Transplantation↗
PubMed1991

Anatomic consideration for sacral screw placement.

Instrumentation of the lumbosacral spine increasingly involves screw fixation to the sacrum. Recommended locations and techniques for screw placement vary, particularly when bicortical purchase of the sacrum is performed. The purpose of this study was to describe the critical anatomy and potential injuries to neurovascular and visceral structures anterior to the sacrum. Lack of awareness can lead to life-threatening complications. The study included 22 fresh human cadavers with no prior spinal surgery. Specimens were placed in a prone position, and the lumbosacral spine was exposed. Two 6.5-mm screws were inserted using one of two techniques, respectively: Starting just inferior to the S1 facet one screw was angled 25 degrees caudally and 30 degrees laterally; in the second technique, lateral inclination was increased to 45 degrees. In addition, all specimens had screws placed in the S2 pedicles. An anterior dissection was performed to allow evaluation of the neurovascular and visceral structures at risk for injury by, or adjacent to, the screw tips. All significant neurovascular structures in the area of concern were constant in position. The internal iliac vein and the lumbosacral nerve trunk were most at risk for injury by the 30 and 45 degrees laterally directed screws. The sigmoid colon, though close to the S2 screw, was protected by its mesentery. Screws placed in the S1 pedicle were least likely to injure the neurovascular bundle. A lateral and a midline safe zone were identified.

Aged↗
PubMed1991

Fractures of the atlas.

Thirty-four patients who had fractures of the atlas (the first cervical vertebra) were reviewed at an average follow-up of 4.5 years. Seventeen patients had bilateral fracture of the posterior arch of the first cervical vertebra. Eight were treated with immobilization in a cervical orthosis, with no long-term problems secondary to the injury. Nine of these patients had additional fractures in the first and second cervical vertebral complex, complicating the management of the fractures of the posterior arch. Two of the nine patients died, and the treatment of the other seven was dependent on the additional fractures. A second group of six patients had a fracture in the area of the lateral mass, with one fracture just anterior to or within the anterior portion of the lateral mass of the first cervical vertebra and a second fracture posterior to the lateral mass of the first cervical vertebra on the same side; resultant asymmetrical displacement of the lateral masses was seen on the open-mouth roentgenogram that was made for each patient. A third group of eleven patients sustained a Jefferson, or burst, fracture of the first cervical vertebra. These patients had either four fractures (two in the anterior arch and two in the posterior arch) or three fractures (one in the anterior arch and two in the posterior arch). Spreading of the lateral masses was relatively symmetrical on the open-mouth roentgenogram. Patients who had fractures with displacement of two to seven millimeters were treated with immobilization in a halo vest. Patients who had fractures with severe spreading of the lateral masses (more than seven millimeters) were treated with reduction of the lateral masses by axial traction until healing of the arch had occurred. No atlanto-axial instability was evident in any patient at follow-up.

Adolescent↗
PubMed1979

Relationship between packed cell volume, platelets, and platelet survival in red blood cell-hypertransfused mice.

In this study we have measured platelet and megakaryocyte concentration, blood volume, and platelet survival of mice after RBC hypertransfusion to PCVs of 62% to 90%. The platelet concentration of mice with PCVs up to 75% was decreased by up to one half. At higher PCVs a more severe thrombocytopenia developed, with platelet concentrations decreased to less than 10% of baseline in approximately one half of the mice. Blood volumes of the hypertransfused mice were increased up to twofold. Megakaryocyte concentrations were normal or increased. Platelet survival in mice with PCVs less than 75% was normal but was sharply decreased for mice with higher PCVs. The decrease in platelet concentration at moderately elevated PCVs may be explained by hemodilution in the larger blood volume. However, hemodilution alone cannot explain the severe thrombocytopenia at higher PCVs. The presence of decreased platelet survival with normal or increased megakaryocyte concentrations in this latter group suggests that the severe thrombocytopenia is the result of more rapid platelet destruction. In summary, elevation of the PCV by RBC hypertransfusion produces thrombocytopenia. The severity of the thrombocytopenia and the mechanisms involved in producing it change abruptly when the PCV exceeds 75%. These findings should be considered in interpretations of the influence of RBC hypertransfusion on hematopoiesis and in clinical and experimental studies of thrombopoiesis in polycythemic subjects.

Animals↗
PubMed1977

Biphasic thrombopoietic response to severe hypobaric hypoxia.

Thrombopoiesis has been studied during and after an 11 d exposure to discontinuous hypobaric hypoxia. Exposure of rats to 0.4 atmospheres for 16--17 h daily initially caused an increase in platelet count which reached a peak of 1.5 times baseline on days 4 and 5. This thrombocytosis was followed by a decrease in platelets to a nadir of 50--60% of baseline on days 12 and 13. That thrombocytosis results from increased platelet production is supported by increased [35S]sulphate incorporation into platelets and increased megakaryocyte size and turnover. The thrombocytopenia with continued hypoxia seems to result from decreased platelet production since 51Cr-platelet survival was normal while megakaryocyte concentration was decreased to one-half that of untreated controls. These observations suggest that differentiation of precursors into megakaryocytes was decreased during the thrombocytopenic period, although the fewer remaining megakaryocytes appeared stimulated because of their larger size and increased [3H]thymidine labelling. Thus, hypobaric hypoxia had a biphasic effect on thrombopoiesis with increased platelet production in the first few days of exposure followed by subnormal production.

Animals↗
PubMed1977

Evidence that stimulation of megakaryocytopoiesis by low dose vincristine results from an effect on platelets.

Appropriate low dosages of vincristine stimulate megakaryocytopoiesis and produce thrombocytosis. In this study of the thrombocytotic action of vincristine, administration of a single dose of 0.1 mg/kg to rats produced an increase in megakaryocyte concentration, diameter and 24 h [3H]thymidine labelling index. Transfusion of one body equivalent of platelets from normal donors prevented stimulation of megakaryocytopoiesis by vincristine whereas platelets from vincristine-treated donors did not. These results suggest that vincristine stimulates megakaryocytopoiesis by altering the functional role of circulating platelets in the regulation of thrombopoiesis.

Animals↗
PubMed1977

In vitro inhibition of platelet function and coagulation by pentamidine isethionate.

Pentamidine isethionate is a trypanocidal drug used for the treatment of Pneumocystis carinii pneumonitis. Hematological complications have occasionally been reported and include anemia, leukopenia, and thrombocytopenia. We report here several qualitative abnormalities of in vitro platelet function and coagulation that have not been described previously. Platelets were exposed in vitro to concentrations of pentamidine isethionate ranging from 0.5 to 100 mug/ml of platelet-rich plasma. Clot retraction, platelet adhesiveness to glass beads, and platelet aggregation (adenosine 5'-diphosphate [ADP], thrombin, epinephrine, collagen, and ristocetin) were inhibited in a dose-dependent fashion. The addition of pentamidine isethionate after aggregation had been initiated with ADP reversed both primary and, to a lesser degree, secondary aggregation. Platelet factor 3 availability and serotonin uptake and release (using collagen as the releasing agent) were not inhibited. Serotonin release with 10(-4) M ADP was slightly inhibited. Pentamidine isethionate prolonged the thrombin time of plasma at concentrations of 5 mug/ml and greater. The prothrombin time was prolonged at concentrations greater than 10 mug/ml of plasma. The inhibition of aggregation was reversed by washing and resuspension in plasma or by the addition of calcium or magnesium ions.

Amidines↗
PubMed1976

Platelet production capacity at intervals after acute thrombocytopenia.

Platelet producing capacity was examined at intervals after acute platelet depletion by reinduction of acute thrombocytopenia and assessment of the subsequent platelet recovery rates of 35S-sulfate incorporation into platelets. Platelet producing capacity was increased on days 1 and 2, somewhat decreased on days 3 and 4 and had returned to baseline by day 5. These studies suggest that there is an initial increase followed by a decrease on days 3 and 4 in cells which can respond to thrombopoietic stimulating factor after induction of acute thrombocytopenia.

Acute Disease↗