PubMed Health⌕ Search

Biomedical subjects

G Hamilton

Publications and source records attributed to G Hamilton.

At least 163 records · Page 9Linked to original sources
PubMed1994

Comparison of laser Doppler perfusion imaging, laser Doppler flowmetry, and thermographic imaging for assessment of blood flow in human skin.

In this study we compared three non-invasive methods of measuring skin perfusion, thermographic imaging (TI), laser Doppler flowmetry (LDF) and the new technique of laser Doppler imaging (LDI). Seven normal volunteers were studied in a temperature-controlled room with an ambient temperature of 22 +/- 1 degree C. Images of the left hand were recorded using LDI followed by TI. LDF was then used on two standard locations on the fingers and back of the hand. The measurements were then repeated for a hot (37 degrees C) and then a cold (10 degrees C) challenge. A significant linear correlation (r = 0.960, p < 0.01, with 95% confidence limit of 0.35-0.77, n = 38) was found between LDF and LDI. However, LDF and LDI did not correlate well with TI (r = 0.577, p < 0.01, with 95% confidence limit of 0.32-0.76, n = 38). The LDI method was found to be highly reproducible (mean +/- 1 SD; 625 +/- 30, with coefficient of variation 5%). The blood flow and temperature distribution of skin of the hand was then recorded using TI and LDI in 10 patients (mean age +/- SD, 41.7 +/- 9.9) with scleroderma and eight normal volunteers (mean age +/- SD, 30.6 +/- 6.5). The overall mean blood flow and temperature in the hands of patients with scleroderma (mean +/- SD 444 +/- 265 flux, 29.3 +/- 3.3 degrees C) was significantly (p < 0.0001) lower compared with the normal volunteers (mean +/- SD, 912 +/- 390 flux, 34.0 +/- 3.2 degrees).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Outbreak of measles in a teenage school population: the need to immunize susceptible adolescents.

An outbreak of measles occurred in a community school and the surrounding area in Crowborough, East Sussex, UK, from December 1992 to February 1993. There were 96 suspected cases reported: 66 cases among 1673 students at one school and 30 community cases. The majority of suspected cases were in those aged 11-17 (78%), 2 cases occurred in infants < 1 year old and 8 cases in adults aged 18 years or over. Data collected on 60 (91%) of the 66 suspect school cases showed 56 (93%) had an illness which met a case definition of measles. Eighteen had confirmatory IgM measles antibody. Two cases were hospitalized. The local percentage uptake for measles immunization for the school age years affected varied between 64% and 84%. A survey of parents showed that approximately 74% of the students attending the school had a history of measles immunization. The immunization rates reported by parents for children who developed measles was 21%, (29% based on GP records) compared with 77% for those who remained well. Vaccine efficacy was estimated to be 92%. This outbreak, along with others recently reported in older unimmunized children in the UK, reinforces the need for catch-up immunization programmes to reach this susceptible group of adolescents.

Adolescent↗
PubMed1994

Intermittent claudication due to spinal stenosis in a vascular surgical practice.

Intermittent claudication can be due to spinal canal stenosis. In order to define the frequency with which this condition presents to a vascular surgeon a review of 271 patients referred with claudication was carried out. Twenty-one (8%) were ultimately diagnosed as having spinal stenosis. There were no significant differences with regard to age or sex between these patients and those with true vascular claudication. There was, however, a significantly lower number of smokers in the spinal stenosis group. When the presenting features of the spinal stenosis group were analysed 62% (13/21) reported sensory symptoms such as numbness or parasthesiae, 38% (8/21) back pain and 67% (14/21) true pain in the legs on walking. In 71% (15/21), symptoms were reported as being bilateral and 29% (6/21) had reduced Doppler pressures. It is stressed that vascular surgeons need to maintain a high index of suspicion for spinal stenosis especially as the condition may coexist with vascular disease, making diagnosis difficult.

Adult↗
PubMed1994

Diminished platelet yield and enhanced platelet aggregability in platelet-rich plasma of peripheral vascular disease patients.

Centrifugation of citrated whole blood (cit-WB) for platelet rich plasma (PRP) preparation resulted in a significantly diminished platelet yield compared to when blood was collected in citrate + aspirin (acetylsalicylic acid; ASA) or EDTA anticoagulants in both apparently healthy young subjects and peripheral vascular disease (PVD) patients. The loss in platelets was significantly greater in PVD patients than in young apparently healthy subjects when using cit-WB. Median platelet volume (MePV) of PRP preparations was not different between PVD patients and apparently healthy subjects. The MePV of EDTA-PRP preparations was significantly bigger than cit-PRP and cit + ASA-PRP in both PVD patients and apparently healthy subjects. Citrate and citrate + ASA-PRP of patients was significantly more aggregable to adrenaline. In EDTA-PRP, adrenaline-induced aggregation did not occur. These findings indicate that platelet hyperactivity occurs in PVD even in the presence of ASA. Furthermore, studies involving the use of PRP may not be representative in PVD due to the significant loss of platelets during centrifugation. The methodology described here can be used by those who do not have facilities designed specifically for platelet research.

Aged↗
PubMed1994

Ischaemia of the small intestine in patients with systemic sclerosis: Raynaud's phenomenon or chronic vasculopathy?

We investigated duodenal and gastric mucosal blood flow by endoscopic laser Doppler flowmetry (LDF) in ten patients with systemic sclerosis (SSc) and in ten healthy volunteers. In addition, we tested for the presence of small bowel bacterial overgrowth by jejunal aspiration. Jejunal aspiration and LDF were done consecutively, via a gastroscope, using a flexible catheter and laser Doppler probe. Following these procedures, two duodenal biopsies were obtained for light and electron microscopy. Mean duodenal and gastric blood flow were significantly lower in patients with SSc than in normal subjects (516 flux units vs. 240, 521 vs. 202, both p < 0.001). There was no correlation between age and blood flow in patients or volunteers. Four of the ten patients had evidence of significant bacterial overgrowth on jejunal aspiration (> 10(5) colony-forming units/ml). These findings support the hypothesis that within the small intestine of patients with SSc, factors independent of bacterial overgrowth may be responsible for malabsorption. The observed reduction in small-intestine mucosal blood flow may play an important contributory role. Further studies are required to determine whether this represents reversible or chronic progressive ischaemia, and its effect on nutrient absorption.

Adult↗
PubMed1994

Indexing guidelines: applications in use of pulmonary artery catheters and pressure ulcer prevention.

In a busy clinical environment, access to knowledge must be rapid and specific to the clinical query at hand. This requires indices which support easy navigation within a knowledge source. We have developed a computer-based tool for trouble-shooting pulmonary artery waveforms using a graphical index. Preliminary results of domain knowledge tests for a group of clinicians exposed to the system (N = 33) show a mean improvement on a 30-point test of 5.33 (p < 0.001) compared to a control group (N = 19) improvement of 0.47 (p = 0.61). Survey of the experimental group (N = 25) showed 84% (p = 0.001) found the system easy to use. We discuss lessons learned in indexing this domain area to computer-based indexing of guidelines for pressure ulcer prevention.

Abstracting and Indexing↗
PubMed1993

Acute limb deterioration during intra-arterial thrombolysis.

Approximately 12 per cent of limbs undergoing intra-arterial thrombolysis (IAT) develop distal embolism or extension of thrombus during the procedure. These are usually of little clinical consequence and can be treated by increasing the rate of administration of the lytic agent. However, in some patients the clinical condition of the limb deteriorates rapidly. In an attempt to define the incidence of acute limb deterioration during IAT, information was collected from five centres in the UK with experience of the technique. A total of 866 treatments were recorded, with 20 limbs (2.3 per cent) undergoing acute deterioration. This complication was more common during the treatment of thrombosed popliteal aneurysm than during that of emboli or thrombosed atheromatous arteries or grafts (P < 0.001). The amputation rate associated with the complication was high, and operative intervention provided better results than continuation of lysis.

Aneurysm↗
PubMed1993

Insulin-like growth factor-I-dependent growth and in vitro chemosensitivity of Ewing's sarcoma and peripheral primitive neuroectodermal tumour cell lines.

Serum-free growth of Ewing's sarcoma (ES) and primitive peripheral neuroectodermal tumour (pPNET) cell lines was achieved by supplementing a basal medium with insulin-like growth factor-I (IGF-I). These cultures were used to investigate the sensitivity of 3 ES (EW-2, RD-ES, SK-ES-1) and 3 pPNET (SIM-1, KAL, SAL) cell lines to a panel of anti-tumour agents in short-term (48-h) proliferation assays. Of the four cytostatic drugs included in the currently used multi-drug regimens, cyclophosphamide, doxorubicin and actinomycin-D inhibit the proliferation of the cell lines with high efficacy, whereas the vinca alkaloids were less effective. Cisplatin, etoposide, mitomycin-C and mitoxanthrone were also found to have a high inhibitory activity in this in vitro ES/pPNET system. The most remarkable effect was observed for cytosine arabinoside (ARA-C), which gave a half-maximal inhibition at drug concentrations approximately 5000 times below the clinical peak plasma concentrations (250 micrograms/ml). The ARA-C sensitivity of ES and pPNET cell lines is comparable with the established ARA-C sensitivities of leukaemia-derived cells. The different ES and pPNET cell lines showed a rather uniform response to the different cytostatic drugs with decreased sensitivity of individual pPNET cell lines to vinblastin, ARA-C and mitoxanthrone. Modulation of the IGF-I/IGF-I receptor/IGF-I binding protein system, which seems to constitute an important stimulator of cell growth in neuroectoderm-derived or -related tumours, can be used to enhance the drug sensitivity of the tumour cells in vivo or in vitro therapeutic procedures. According to our results, serum-free conditions for autologous bone marrow purification are expected to result in significantly increased chemosensitivity of ES and pPNET cells in response to anthracyclines and cisplatin.

Antineoplastic Agents↗
PubMed1993

Role of the MDR-1-encoded multiple drug resistance phenotype in prostate cancer cell lines.

The treatment of advanced metastatic prostate cancer by hormone manipulation or orchiectomy is frequently followed by the appearance of hormone-insensitive and highly chemoresistant tumor cells. In this study we have investigated the contribution of the P-glycoprotein-mediated drug efflux (multidrug-resistance; MDR) to the cellular resistance of prostate carcinoma-derived cell lines to diverse cytotoxic drugs by detection of P-glycoprotein (P-gp) measurement of P-gp-mediated drug transport and reversal of MDR by chemosensitizers. The in vitro chemosensitivity of three prostate cancer cell lines (PC-3, DU-145 and LNCaP) to doxorubicin was measured in a thymidine incorporation proliferation assay. Growth of the partially hormone-sensitive cell line LNCaP is inhibited by low doses of doxorubicin (IC50:27 ng./ml.), but PC-3 and DU-145 are highly resistant to the drug, with IC50 values of 10 micrograms./ml. and 7.5 micrograms./ml., respectively. The chemosensitivity of the PC-3 and DU-145 cells is increased in response to 1 microM. verapamil, 1 micrograms./ml. cyclosporine A and 2 microM. tamoxifen, which are known to partially reverse the MDR phenotype in other resistant tumors. A verapamil-sensitive drug efflux has been demonstrated for the PC-3 and Du-145, but not for the LNCaP, cell lines, using flow cytometric measurements of the P-gp substrate rhodamine 123 efflux from preloaded cells. In agreement with the functional measurements, the expression of the P-glycoprotein was detected in the PC-3 and Du-145 cell lines in Western blots using the monoclonal C 219 antibody. In conclusion, the chemoresistant and hormone-insensitive PC-3 and Du-145 cell lines express P-gp and exhibit verapamil-sensitive drug efflux, indicative of MDR. However, the low MDR-reversal rates observed in these cell lines in response to chemosensitizers in clinically achievable concentrations (approximately 2- to 3-fold reversal), point to non-MDR-associated cellular mechanisms as dominant factors of chemoresistance in prostate cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Compliance of vascular anastomoses with polybutester and polypropylene sutures.

PURPOSE: Polybutester suture is more easily stretched than other vascular sutures and may produce more compliant anastomoses. The effects of using polybutester and polypropylene sutures were compared acutely in arterial autografts and in chronic implants of cephalic vein grafts into the femoral arteries of dogs. METHODS: Paraanastomotic profiles of diameter and compliance were measured with echo-tracked ultrasonography, and profiles of intimal thickening were generated from histologic sections of the vessels harvested after 3 months. RESULTS: Polybutester produced more compliant anastomoses, compared with polypropylene, in arterial autografts (in vitro: 5.9% +/- 2.0% vs 3.3% +/- 0.6% diameter change/100 mm Hg, p < 0.01; in vivo: 3.1% +/- 1.1% vs 1.6% +/- 0.5%, p < 0.05), but this difference was not observed with vein as the graft material, either initially (1.1% +/- 1.2% vs 1.7% +/- 0.5%) or after 3 months (2.1% +/- 1.2% vs 2.4% +/- 0.8%). This dichotomy may reflect a governing influence of the stiffer veingrafts, compared with host artery (2.6% +/- 1.0% vs 5.4% +/- 1.2%), or the use of suboptimal tension on the polybutester suture when creating the anastomosis. CONCLUSIONS: Both sutures produced similar compliance and thickness profiles. Polybutester initially produces a more compliant anastomosis when both artery and graft are compliant, reducing anastomotic compliance mismatch. However, this benefit may not apply when the anastomosis includes a vessel of low compliance.

Anastomosis, Surgical↗