Search PubMed⌕ Search

Biomedical subjects

S Fredericks

Publications and source records attributed to S Fredericks.

At least 19 recordsLinked to original sources
PubMed2000

Release of platelet activation markers during coronary angioplasty.

BACKGROUND: Authors of several studies have reported that activation of platelets occurs during coronary angioplasty, but consistent results have not been obtained. Levels of serotonin in coronary circulation have been found to be elevated during percutaneous transluminal coronary angioplasty but greater than normal concentrations of beta-thromboglobulin and platelet factor 4 have not been detected. OBJECTIVE: To perform a serial analysis of platelet-activation markers with simultaneous measurements of levels of serotonin, beta-thromboglobulin and platelet factor 4 in blood samples from the coronary artery and coronary sinus of patients undergoing coronary angioplasty. METHODS: Twenty patients undergoing elective coronary angioplasty were studied. Measurements of levels of beta-thromboglobulin, platelet factor 4, and serotonin in samples from the ostium of the coronary artery and the coronary sinus were performed immediately before angioplasty and after the first balloon deflation. RESULTS: Concentrations of beta-thromboglobulin and platelet factor 4 in coronary artery and coronary sinus were elevated in all patients before dilatation, whereas concentrations of serotonin were elevated in 85% of the patients. Concentrations of all markers in coronary sinus decreased after the first inflation. The coronary-sinus: coronary-artery concentration ratios before dilatation for beta-thromboglobulin, platelet factor 4, and serotonin were > 1 for the majority of patients, particularly for those with complex culprit lesions, indicating that coronary activation of platelets was occurring. Ratios remained unchanged or decreased after the first inflation, depending on initial values. CONCLUSIONS: Both systemic and coronary activation occur in patients subjected to percutaneous transluminal coronary angioplasty before the onset of intervention. After balloon deflation the greater than normal baseline coronary-sinus:coronary-artery concentration ratios of all markers (beta-thromboglobulin, platelet factor 4 and serotonin) tend to decline or remain unchanged, depending on the level of activation.

Adult↗
PubMed1998

Differential plasma endothelin levels in subgroups of patients with angina and angiographically normal coronary arteries. Coronary Artery Disease Research Group.

BACKGROUND: Raised plasma endothelin concentrations have previously been reported in patients with cardiac syndrome X, but it is not known whether these levels vary between clinically distinct subgroups in this heterogeneous condition. METHODS AND RESULTS: We compared plasma immunoreactive endothelin levels in 54 patients with angina pectoris and normal coronary angiograms and 21 healthy control subjects. The patient group was divided into 4 clinically distinct subgroups: 7 with left bundle branch block (group A); 7 with previous myocardial infarction (group B); 24 with positive exercise electrocardiography (group C); and 16 with negative exercise electrocardiography (group D). The plasma endothelin concentration was significantly higher in patients compared with control subjects (3.7 [2.9 to 4.3] vs 2.96 [2.4 to 3.4] pg/mL, respectively, median [interquartile range]; P=0.002). Endothelin concentrations were most significantly elevated in group A and group B (4.5 [3.6 to 5.2] pg/mL; P=0.005 and 4.1 [3.9 to 4.5] pg/mL; P=0.001, respectively). Plasma endothelin concentrations were also significantly elevated in group C (3.7 [2.8 to 4.1] pg/mL; P=0.02) but not in group D (3.0 [2.5 to 3.8] pg/mL; P=0.3). CONCLUSIONS: Plasma endothelin concentration is elevated in patients with angina pectoris and angiographically normal coronary arteries, particularly those with left bundle branch block or previous myocardial infarction.

Aged↗
PubMed1998

Raised endothelin 1 levels in patients with colorectal liver metastases.

BACKGROUND: Endothelin 1 (ET-1), a vasoconstrictor peptide, has been implicated as a tumour growth stimulator and an angiogenesis factor. METHODS: To assess the involvement of ET-1 in colorectal cancer, immunoelectron microscopy for ET-1 was performed in colorectal liver metastases and normal liver (n = 6). ET-1 plasma levels were measured by radioimmunoassay in patients with colorectal cancer, with (n = 18) and without (n = 12) liver metastases, and in controls (n = 22). RESULTS: In normal liver, ET-1 was present in endothelial cells; in tumour, it was observed in endothelial cells, tumour cells and myofibroblasts. Mean(s.d.) plasma ET-1 levels were 2.75 (1.37) pg/ml in controls, 4.53(1.61) pg/ml in patients with colorectal liver metastases (P = 0.001) and 3.92(1.32) pg/ml in patients without metastases (P = 0.02). CONCLUSION: ET-1 was present in various cell types within colorectal liver metastases and raised levels were found in the plasma of patients with colorectal cancer. ET-1 may not only modulate tumour vascular tone but also act on tumour growth and angiogenesis, both locally and systemically.

Aged↗
PubMed1993

Safety conscious.

Explore the source record for details and available documents.

Accidents, Occupational↗
PubMed1982

Amitriptyline-related peripheral neuropathy relieved during pyridoxine hydrochloride administration.

Tricyclic antidepressants rarely cause peripheral neuropathy. In fact, this class of drugs has been used to control the symptoms of pain and paresthesia that accompany peripheral neuropathy. We report peripheral paresthesias that occurred in a 39-year-old female during five years of amitriptyline administration. The patient's symptoms were relieved by oral pyridoxine hydrochloride, associated with elevated plasma pyridoxal phosphate.

Adult↗
PubMed1975

A 10-year experience with subcutaneous mastectomy.

Subcutaneous mastectomy appears to remain a procedure of promise. This 10-year experience indicated that it is feasible in at least 80 per cent of selected patients to successfully remove the breast parenchyma and subsequently reconstruct the breast without serious complications. It is resonable to assume that as surgical technique and experience improve, the complication rate will diminish. Furthermore, it is essential that better breast implants be devised and developed in the future. This would clearly enhance all forms of cosmetic breast surgery. The use of subcutaneous mastectomy as a prophylactic cancer procedure will parellel the improvement of implant breast reconstruction. Whether subcutaneous mastectomy will measurably reduce the mortality rate of carcinoma of the breast will, of course, take a generation to determine. However, I have no doubts that is it as justifiable and valuable surgical tool in the treatment of breast disease. The concept of almost total breast biopsy has great merit in the discovery of occult carcinoma. Clearly, caution should be exercised in the selection of cases for this modality, and further study must be devoted to develop diagnostic guidelines of ever-increasing precision to determine which breasts are potentially malignant and should be afforded the procedure.

Adult↗