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Biomedical subjects

G Scott

Publications and source records attributed to G Scott.

At least 235 records · Page 13Linked to original sources
PubMed1988

Potential toxicological problems associated with antioxidants in plastics and rubber consumables.

Antioxidants and stabilisers are of critical importance in the manufacture and use of polymer artifacts. Most conventional additives are readily leached from plastics or rubbers by foodstuffs or body fluids with consequent danger associated with the potential toxicity in the body. Strategy for the development of biologically "safe" stabilisation systems for polymers are discussed and it is concluded that the attachment of the appropriate reactive functional group to the polymer backbone by "reactive processing" provides the best means of immobilising the functional group to leaching fluids without sacrificing its protective action.

Antioxidants↗
PubMed1988

Bilirubin and the induction of intracranial arterial spasm.

Although a number of substances which participate in the physiological control of vascular caliber have been proposed to play a causative role in cerebral vasospasm, none of these has been shown to induce the profound, sustained degree of constriction or the vasculopathy that characterize this disorder. The present study was undertaken to determine whether bilirubin, a hemoglobin breakdown product with detergent-like activity, accrued in incubated blood or in intracranial hematoma and whether topical application of bilirubin altered the caliber or morphology of cerebral arteries. As a model of blood residing in the subarachnoid space, sterile vials of cat blood and of human blood were incubated in vitro at 37 degrees C. The concentration of bilirubin in the supernatant of cat blood increased from a value of 0.27 +/- 0.3 mg% (mean +/- standard error of the mean) on Day 0 to a value of 9.57 +/- 2.4 mg% on Day 10; the respective values for human blood were 0.53 +/- 0.02 mg% and 13.4 +/- 5.4 mg%. Samples of intracranial hematoma that had been surgically removed from three patients between 4 and 11 days after hemorrhage yielded bilirubin levels from 2.1 to 15.2 mg%. Application of a bilirubin suspension of 5, 10, or 20 mg% in buffered Ringer's solution to cat basilar artery in vivo led to progressive and sustained constriction; at 4 hours the mean decrease in the width of the blood column was 34% +/- 2.1%. Ultrastructural analysis of these vessels showed widespread pathological changes similar to those associated with cerebral vasospasm. Application of a 10-mg% bilirubin suspension to the basilar artery of two baboons produced similar alterations. Minimal changes in diameter or morphology were observed in cat arteries bathed in buffer solution alone. These findings in animal models indicate that bilirubin may play a central role in the development of cerebral vasospasm.

Animals↗
PubMed1988

Molecular lesions involved in the progression of a human breast cancer.

Specific genetic alterations are observed in human breast cancer, but little is known about when these occur in the evolution of the disease. Three breast cancer effusions that occurred sequentially in a single patient were examined. Common cytogenic abnormalities were found in all effusion samples suggesting a single progenitor metastatic cell. Only the last effusion, however, exhibited a mutation of the c-K-ras gene and a loss of heterozygosity at the c-H-ras locus. These specific genetic abnormalities detected in the last effusion was correlated with improved in vitro growth of the primary cells, and with the ability to establish breast cancer cell lines. Thus a mutant ras gene and the loss of heterozygosity at the c-H-ras locus were associated with a more aggressive tumor phenotype occurring late in the course of this patient's disease and not with the initiation of the primary breast cancer, or in the establishment of metastases.

Adult↗
PubMed1987

The intra-aortic balloon pump as an adjunctive therapy for severe myocardial contusion.

The management of patients with post-traumatic myocardial contusion requires close electrocardiographic and hemodynamic monitoring. When complications such as cardiogenic shock occur, aggressive treatment using Swan-Ganz catheterization for monitoring of intravascular volume and cardiac inotropic support are necessary. Failure to restore hemodynamic stability using these measures is an indication for the use of intra-aortic balloon pump counterpulsation. A case of successful management of a patient with post-traumatic myocardial contusion complicated by refractory cardiogenic shock using intra-aortic balloon pump counterpulsation is presented. Use of the intra-aortic balloon pump improved cardiac output, eventually resulting in hemodynamic stabilization.

Adult↗
PubMed1987

Naturally occurring antibodies to phosphocholine as a potential index of antibody responsiveness to polysaccharides.

Naturally occurring antibodies reactive with the phosphocholine (PC) determinant of pneumococcal teichoic acids may be useful for evaluating the potential of patients to make antibodies to polysaccharides. Antibodies to PC are present in most adults under the age of 60 years, are absent in very young children, and are present at low levels in Wiscott-Aldrich patients and in IgG2-deficient adults. These last three groups respond very poorly to polysaccharide antigens. Antibodies to PC are also found at low levels in the elderly, a group that has previously been shown to have low levels of antibody to blood groups A and B carbohydrates. The levels of antibody to PC over time were constant in most individuals and, in adults, seemed to show slightly less variation than did titers of antibody to blood group B. Our findings suggest that titers of antibody to PC may be superior to titers of antibody to blood group A or B for monitoring responsiveness to carbohydrate antigens.

ABO Blood-Group System↗
PubMed1986

Analysis of a surface protein of Streptococcus pneumoniae recognised by protective monoclonal antibodies.

Using two monoclonal antibodies which protect mice from a fatal challenge with S. pneumoniae, we have identified a surface protein antigen on the pneumococcus. These antibodies recognised components of 84 and 76 kD in a cell wall extract of the nonencapsulated strain, R36A, against which they were made. Absorption experiments indicated that both of the antibodies recognised the same two proteins. The proteins detected by the antibodies in the encapsulated type 2 strain D39 and type 3 strain WU2, exhibited different molecular weights than those proteins detected from R36A. Using a colony blot procedure and a quantitative ELISA, we have shown that these antibodies react with 6 of the 21 pneumococcal strains tested. There was no association between reactivity with these anti-protein antibodies and the capsular serotype of the pneumococcal isolates tested.

Animals↗
PubMed1986

Ultrastructural evidence of arterial denervation following experimental subarachnoid hemorrhage.

Loss of catecholamine histofluorescence, increased sensitivity to norepinephrine, and changes in alpha1 receptor binding have led to the proposal that denervation hypersensitivity may play a role in cerebrovascular spasm. Because the significance of these alterations has remained unclear, the present study was undertaken to determine whether there was direct ultrastructural evidence of arterial denervation following experimental subarachnoid hemorrhage. Under general anesthesia, adult cats were subjected to pre-pontine injection of blood or serum (5 to 7 ml) via a transclival approach. The animals were sacrificed 4, 7, or 10 days later and basilar artery segments were prepared for electron microscopy. Control vessels appeared normal, whereas those bathed in blood revealed unequivocal changes in neural and supporting elements, including: 1) disintegration of both clear- and dense-core vesicles; 2) fragmentation of varicosities; 3) loss of Schwann cell cytoplasm; and 4) axonal degeneration. These changes were most pronounced 7 days after instillation of blood, and correlated in time with maximal injury of the media and endothelium. Although the development of smooth-muscle hypersensitivity remains unsettled, this study indicates that prolonged exposure to blood can cause extensive denervation of cerebral arteries.

Animals↗
PubMed1985

Improvements in the diagnosis and management of aortoenteric fistula.

To assess the impact of an aggressive approach (early operation, graft removal, and extraanatomic bypass) adopted by us 5 years ago in patients with aortic synthetic grafts and gastrointestinal bleeding, we reviewed our 15 year experience with aortoenteric fistula in 13 patients. The courses of six patients from the recent series (1979 through 1984) were contrasted with those of seven patients from our earlier series (1968 through 1978). Twelve of 13 patients presented with gastrointestinal bleeding (usually low volume), and no patient presented in shock. Six of seven patients in Series I (earlier series) had positive blood cultures, whereas only two of six in Series II (recent series) had this finding. Of the 13 patients, 10 underwent preoperative endoscopy. It was only with consistent visualization of third and fourth portions of the duodenum that a diagnosis of aortoenteric fistula was established (three of four patients 75 percent). Although the upper gastrointestinal series was abnormal more frequently (five of seven patients, 71 percent) than arteriograms (three of nine patients, 33 percent), the latter was more specific for a predisposing lesion. At surgery, nine (70 percent) patients had an anastomotic fistula and four (30 percent), a false aneurysm. Although only one of seven patients in Series I survived (14 percent), four of six patients in Series II were alive at last follow-up in September 1984 (67 percent). Early diagnosis followed by prompt operation with removal of the synthetic graft and extraanatomic bypass is associated with an improved survival for patients with aortoenteric fistula, but the degree of preoperative sepsis as indicated by positive blood cultures appears to be an important prognostic sign.

Aged↗
PubMed1985

Pulmonary function of London firemen.

In a longitudinal study of a sample of firemen in London 1006 firemen were interviewed and examined in 1976 and 895 were seen a second time 12 months later. On each occasion a Medical Research Council respiratory questionnaire was administered and forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were measured. The average levels of FEV1, FVC, and FEV1/FVC in both years compared favourably with conventional predicted values. Separate multiple regression analysis for the two years indicated that the FEV1 and FVC fell more rapidly in those aged over 40, and that cigarette smoking had a strong harmful effect on these measures of function. Only among men with over 20 years' service was there possibly any evidence (not statistically significant) of an effect from duration of employment. The comparatively large fall in FEV1 and FVC from 1976 to 1977 was due mainly to instrumental variation. The prevalence of respiratory symptoms was higher in smokers than non-smokers and increased with the number of cigarettes smoked.

Adolescent↗