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Biomedical subjects

G Hamilton

Publications and source records attributed to G Hamilton.

At least 37 records · Page 2Linked to original sources
PubMed1991

Comparison of prostanoid synthesis in cultured human vascular endothelial cells derived from omentum and umbilical vein.

Endothelial seeding of vascular grafts may reduce thrombogenicity and significantly improve graft patency. For clinical studies endothelial cells derived from human omentum may be the ideal source of cells as they are obtainable in large numbers. This study was designed to assess their ability to produce the antithrombogenic substance prostacyclin (PGI2). Human omental microvascular endothelial cells (HOTMECs) were grown and their ability to produce prostacyclin (PGI2), PGE2, PGF2 alpha and thromboxane A2 (TXA2) in response to a range of agonists was measured by radioimmunoassay. Control experiments were performed using human umbilical vein endothelial cells (HUVECs). Both HUVECs and HOTMECs synthesised similar quantities of PGI2 basally and both increased production after adding A23187 (calcium ionophore), arachidonic acid, sodium fluoride and phorbol ester. In contrast, both thrombin and histamine were potent stimulators of PGI2 release in HUVECs but were without effect on HOTMECs. In both cell types serotonin, carbachol and noradrenaline were without effect. The pattern of release of PGE2, PGF2 alpha and TXA2 were identical to those of PGI2 in both cell types but the quantities released were lower. These results show that HOTMECs can produce the antithrombogenic agent PGI2 in significant quantities and that they do so by mechanisms similar to those of large vessel endothelium. This supports the proposal that they would be a suitable cell source for vascular graft seeding.

Cells, Cultured↗
PubMed1991

Cryptosporidiosis in the Isle of Thanet; an outbreak associated with local drinking water.

An outbreak of cryptosporidiosis occurred in the Isle of Thanet during December 1990 and January 1991. A total of 47 cases ranging in age from 2 months to 85 years were identified in residents from the Margate, Broadstairs and Ramsgate areas, with dates of onset of illness from 3 December to 14 January. A case-control study demonstrated a strong statistical association between illness and the consumption of unboiled tap water from a particular source, with evidence of a dose-response relationship. Although no cryptosporidial oocysts were identified in samples of untreated or treated water taken during the investigation, the results were consistent with the view that the source of infection was treated river water which was used to supplement borehole water.

Adolescent↗
PubMed1991

The use of captopril-DTPA scanning in the diagnosis of atherosclerotic renal artery stenosis in patients with impaired renal function.

We have analyzed our use of captopril-diethylene-triaminepentaacetic acid (DTPA) scanning in patients presenting to the Royal Free Hospital predominantly with renal impairment. The sensitivity was found to be as good in patients with bilateral disease or disease of a single kidney as in patients with unilateral disease. On a number of occasions, though, the scan suggested unilateral disease when bilateral disease existed. There were, however, a large number of patients for whom captopril-DTPA scanning was not performed because of severe renal impairment or the possibility of renal artery stenosis in a single functioning kidney.

Aged↗
PubMed1991

Intraoperative estimation of endotoxin, TNF alpha, and IL-6 in orthotopic liver transplantation and their relation to rejection and postoperative infection.

The course of endotoxemia, TNF alpha, and IL-6 during orthotopic liver transplantation was studied in 28 transplantations performed in 27 patients to evaluate their impact on early postoperative rejection and infection. The preoperative levels of endotoxin, TNF alpha, and IL-6 were not different in patients who did or did not develop postoperative rejection and/or infection within the first 10 postoperative days. At the end of surgery, TNF alpha levels increased in patients who developed rejection (median 100 pg/ml vs. 11.5 pg/ml, P = 0.004). A TNF alpha level of greater than 100 pg/ml at the end of transplantation predicted rejection in 82% of the patients. During surgery, IL-6 levels increased significantly in patients with subsequent postoperative infection, reaching significance after revascularization of the graft (median 975 pg/ml vs. 185 pg/ml, P = 0.006). An IL-6 cutoff level of 800 pg/ml predicted postoperative infection in 75% of the patients. Endotoxins were elevated intraoperatively in patients with postoperative infection, but the difference did not reach significance. There was no prognostic relevance with respect to the intraoperative values of TNF alpha and infection or IL-6 values and rejection. An intraoperative elevation of TNF alpha seems to precede early postoperative rejection, and highly increased IL-6 may be a predictor of subsequent infection in human liver transplantation.

Adult↗
PubMed1991

The monoclonal HBA-71 antibody modulates proliferation of thymocytes and Ewing's sarcoma cells by interfering with the action of insulin-like growth factor I.

The monoclonal HBA-71 antibody recognizes a Ewing's sarcoma associated antigen, which is also highly expressed on the cell surface of human cortical thymocytes and islets of Langerhans among normal tissues. The antibody was found to inhibit partially the growth of ES tumor cell lines and to trigger proliferation in thymocyte cultures. The influence of growth factors and the effect of the HBA-71 antibody was further investigated in the present study. The growth of ES tumor cells was demonstrated to be dependent on the presence of insulin-like growth factor I or insulin. The HBA-71 antibody (25 micrograms/ml) enhanced the growth stimulatory effect of IGF-I under serum-free conditions. The expression of the HBA-71 epitope is modulated positively by IGF-I and insulin and negatively by dexamethasone and human growth hormone in ES/PNET tumor cells and thymocytes. IGF-I either alone or in combination with HBA-71 stimulated the proliferation of thymocytes under serum-free conditions whereas in complete medium, IGF-I stimulated thymidine incorporation and the HBA-71 antibody either alone or in the presence of IGF-I showed inhibitory activity most likely due to down-regulation of the receptor. These data demonstrate the important role of IGF-I in the growth of ES/PNET tumor cells as well in the proliferative activity of HBA-71 positive normal thymocytes. The biological activity of IGF-I in malignant thymocytes, pancreas tumors, fetal muscle, brain, granulosa and Sertoli cells has been documented in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[A comparison of the effects of verapamil and nifedipine on the quality of life].

Aspects of quality of life (symptoms, psychological well-being and activity) were evaluated by self-administered questionnaires in a 4 months randomized double-blind trial of titrated doses of verapamil slow release (n = 41) compared with nifedipine retard (n = 40). An untreated diastolic blood pressure of 95 to 115 mm Hg was required for inclusion in the trial. The mean age in both groups was 55 years. A significant difference between the two drugs was found in the average reporting of symptoms with an increase on nifedipine (p less than 0.01). The reporting of swollen ankles and flushing (p less than 0.05) increased on nifedipine, and nocturia (p less than 0.05) increased on verapamil. Measures of psychiatric morbidity tended to improve on verapamil and deteriorate on nifedipine. Only the change in cognitive function was significant between the drugs, being worse on nifedipine (p = 0.05). There was no difference between the two groups in the fall in diastolic blood pressure (average 18 mm Hg on nifedipine and 17 mm Hg on verapamil). There was a significantly greater fall in systolic blood pressure on nifedipine (23 mm Hg) compared with verapamil (13 mm Hg) (p less than 0.01). The two drugs differed in their effects on measures of quality of life. The improvements in symptomatic complaints and psychological well-being on verapamil may have been due to inclusion in a trial, although we cannot exclude the possibility of a drug effect. Conversely the increase in symptoms and self-assessed cognitive impairment on nifedipine were considered to be side-effects of the drug.

Adult↗
PubMed1991

A simple method of producing diagnostic copies from overexposed radiographs.

Overexposed radiographs that have density measurements greater than three can yield diagnostic copies. An unexposed standard radiographic film is sandwiched between a completely black film and the film to be copied in a cassette with standard-speed rare earth intensifying screens. The fluorescence of the unblocked intensifying screen, induced by a measured x-ray dose from an x-ray machine, is the light source that exposes the film, yielding a negative copy. The negative can also be copied to produce a positive-phase radiographic image. The high degree of contrast achieved by this copy method regains the contrast scale that is lost on overexposure. It is capable of enhancing faint calcification and other low-contrast features of soft tissues.

Copying Processes↗