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Biomedical subjects

R Dick

Publications and source records attributed to R Dick.

At least 19 recordsLinked to original sources
PubMed1992

Peptide-induced conformational changes in class I heavy chains alter major histocompatibility complex recognition.

Small peptides, derived from endogenous proteins bind within the antigen binding groove created by the beta-pleated sheets and alpha helices of the alpha 1 and alpha 2 domains of the class I molecule of the major histocompatibility complex (MHC). However, the precise role of peptide in class I MHC conformation remains unclear. Here, we have shown that, in at least some instances, changes induced in the MHC molecule by the binding of distinct peptides can be identified as specific alterations in serological epitopes expressed on the class I protein. The nature of specific peptides expressed by class I-bearing cells may, therefore, have a dramatic influence on T cell development, self-tolerance, and alloreactivity.

Amino Acid Sequence↗
PubMed1992

Treatment of small hepatocellular carcinomas.

There is growing interest in screening to detect symptomless hepatocellular carcinoma (HCC), which should be easier to treat than symptomatic tumours. Combined alpha-fetoprotein and ultrasound monitoring can detect HCCs of 1 cm, and Lipiodol retention can be detected in tumours smaller than 1 cm. A number of treatment options are available. Surgical resection may be curative in selected patients with a single small tumour, but the cirrhotic patient is left with a diseased liver and the risk of tumour recurrence or death from underlying liver dysfunction. Orthotopic liver transplantation is a rational treatment for patients with decompensating cirrhosis and a small HCC, but it is expensive and necessitates immunosuppression. A variety of targeted or local therapies, either individually or in combination, can be used to treat HCC. These include percutaneous alcohol injection into an HCC, which may be an alternative to surgical resection. Tumour necrosis can be seen after targeted Lipiodol chemotherapy or radiotherapy. Transcatheter arterial embolisation selectively embolises the feeding artery, and can be combined with Lipiodol chemotherapy. Small tumours are thus amenable to treatment, even in patients who cannot have surgery. Screening and treatment for symptomless HCC seems justified, unless controlled trials teach us differently.

Antineoplastic Agents↗
PubMed1992

P300 and traffic scenes: the effect of temazepam.

The present research investigated the effects of a minor tranquillizer (temazepam) on P300 in a paradigm that may be relevant for traffic behaviour. Because accident scenes have not been used previously in P300 research, Experiment 1 (n = 8) examined whether the P300 elicited by safe traffic scenes and scenes of imminent road accidents were sensitive to the probability of occurrence. Event-related potentials were recorded from C3, Cz, C4, P3, Pz and P4 within an oddball paradigm. The type of stimulus to which subjects responded (pictures of imminent accidents or safe road scenes) was crossed with the probability (0.1 or 0.5) of the relevant (to which a response was required) event. The results indicated that P300 amplitude increased with decreasing probability of the relevant stimulus and that P300 was most pronounced at Pz. Experiment 2 (n = 12) employed a drug treatment (10 mg temazepam) and a placebo treatment (100 mg Vitamin E). An oddball paradigm with a probability of the relevant stimulus of 0.1 was used and P300 was recorded from Cz, C3, C4, Pz, P3 and P4. Generally, the ingestion of temazepam decreased P300 amplitude and increased P300 latency at all sites. Reaction time, on the other hand, was not influenced by drug administration. The data demonstrate the clear effect of minor tranquillizers on the psychological processes associated with P300.

Accidents, Traffic↗
PubMed1992

Value of exfoliative cytology for investigating bile duct strictures.

The cause of a biliary tract stricture may be difficult to determine radiologically. Exfoliative biliary cytology was evaluated in 62 patients (median age 65 years, range 30-94) with biliary tract strictures presenting to the Hepatobiliary Unit between January 1984 and December 1989. Bile samples were taken during endoscopic retrograde cholangiopancreatography (ERCP) in 42 patients, percutaneous cholangiography in 14, and both in six. The site of stricturing was upper third of the bile duct in 43% (n = 27), middle third in 10% (n = six), and lower third in 47% (n = 29). Of the 47 patients with radiological appearances of a malignant stricture, 22 (47%) had histological confirmation by biopsy either under computed tomography guidance, at endoscopy, at operation, or at necropsy. Fourteen of the 47 patients had positive cytology (30%). In seven patients cytology alone established the presence of malignancy (15%) and in the other seven positive cytology was confirmed by histology. The addition of cytology to tissue biopsy therefore allowed malignancy to be confirmed in 29 of the 47 patients (62%). None of the 15 patients subsequently shown to have benign disease had positive cytology. Sensitivity of the technique was 30% and specificity 100%. Samples for exfoliative cytology are simple to obtain, the results are highly specific and should be a routine part of the investigation of biliary strictures.

Adult↗
PubMed1992

A prospective controlled study comparing brush and bile exfoliative cytology for diagnosing bile duct strictures.

Imaging of biliary strictures may suggest malignancy but cytology can provide a tissue diagnosis. The aim of this study is to compare the diagnostic value of brush cytology and bile cytology. Thirty two patients (20 males, 12 females, median age 66 years, range 31-84) with biliary strictures at endoscopic retrograde cholangio pancreatography (24) or percutaneous transhepatic cholangiography (8) had bile cytology and brush cytology. Brushings were taken using a modified Geenan cytology brush (6 Fr gauge, Wilson Cook) passed alongside a guide wire placed through the stricture. Bile was aspirated after insertion of an internal/external catheter or an endoprosthesis. Bile and brushings were examined by one experienced cytologist (AD) and was reported as positive or negative for malignant cells. Twenty nine patients had malignant strictures. Sixteen were confirmed by histology and 13 had malignancy suggested by clinical follow up. Three patients had resection of histologically benign strictures. The overall sensitivity of brush cytology (17 of 29 positive, 59%) was significantly greater than bile cytology (seven of 29 positive, 24%) (p < 0.01) as was the diagnostic accuracy (63 v 31%, p < 0.01). None of the patients had positive bile cytology with negative brush cytology. There were no procedure related complications and the average sampling time once the guide wire had been inserted was less than five minutes. It is concluded that brush cytology is more sensitive than bile cytology and with the technique described is safe and rapid.

Adult↗
PubMed1992

[Treatment of Buruli's ulcers by excision-graft].

Buruli's ulcer is a real disease of public health. In Ivory Coast, 50 patients were treated from February 1987 to August 1991. It realizes a real destruction of skin and subcutaneous tissues. The germ is Mycobacterium ulcerans. The preferential localisation is the limbs in children of 14 years old. Large ulcer with polycyclic margin are treated by extended excision and thin skin grafts. But deformities persist after the surgical treatment. Hospitalisation is long and drugs are expensive.

Adolescent↗
PubMed1992

Octreotide inhibits the meal-induced increases in the portal venous pressure of cirrhotic patients with portal hypertension: a double-blind, placebo-controlled study.

The aim of this study was to determine the effects of the long-acting somatostatin analog, octreotide, on portal venous pressure and collateral blood flow in cirrhotic patients with portal hypertension during fasting and postprandial states. In a double-blind, placebo-controlled study, we investigated the effects of octreotide on the hepatic venous pressures and azygos blood flow of 21 patients before and after a standard liquid meal containing 40 gm of protein in 250 ml. Octreotide significantly reduced azygos blood flow from a mean of 499 +/- 65 ml/min to a mean of 355 +/- 47 ml/min (p < 0.01), but it had no effect on the hepatic venous pressure gradient. The hepatic venous pressure gradient of patients in the placebo group increased significantly, from a fasting mean of 16.4 +/- 1.6 mm Hg to a mean of 20.0 +/- 1.7 mm Hg 30 min after the meal (p < 0.01). In a second protocol hepatic venous pressures were measured in 20 patients at 30-min intervals for 2 hr after ingestion of the mixed meal. Again the placebo group showed a significant increase in the hepatic venous pressure gradient 30 min after the meal (20.4 +/- 1.5 mm Hg vs. 18.2 +/- 1.2 mm Hg; p < 0.05), but the group receiving octreotide showed no significant changes during the 2 hr of observation. We conclude that octreotide significantly reduces azygos blood flow, with little effect on portal venous pressure, and that it appears to inhibit postprandial increases in portal pressure in cirrhotic patients with portal hypertension.

Blood Flow Velocity↗
PubMed1991

Dietary intake and risk assessment of phototoxic furocoumarins in humans.

The question of whether the furocoumarin content of vegetables is sufficient to induce phototoxic skin reactions after ultraviolet irradiation was examined in two experiments with four human volunteers. In a first experiment, 300 g of celery roots (total phototoxic furocoumarin content 28.2 micrograms/g) was ingested. No skin reactions were observed after UVA exposure (1.5-9 J/cm2), and the blood levels of the furocoumarins--psoralen, 8-methoxypsoralen (8-MOP) and 5-methoxypsoralen (5-MOP)--were below the analytical detection limit of 2 ng/ml. To investigate the phototoxic effects of a mixture of the two most important furocoumarins in vegetables, after gastro-intestinal uptake, 8-MOP and 5-MOP (15 mg each) were ingested separately in a 50% alcoholic solution. A strong and persistent erythema was induced in three out of the four subjects (UVA dose: 3-25 J/cm2). The blood levels immediately before UVA irradiation varied between 14 and 114 ng/ml (8-MOP), and 17 and 70 ng/ml (5-MOP). In the subject who did not show phototoxicity, the blood levels remained at trace levels (3 ng/ml). Two subjects were also tested with a mixture of 10 mg 8-MOP plus 10 mg 5-MOP; in one subject the mixture induced pigmentation only, while in the other a mild-to-medium erythema was induced. The blood levels of the furocoumarins in the two subjects were similar (12-15 ng/ml for 8-MOP and 5-MOP). It is concluded that in humans the phototoxic threshold dose of furocoumarin mixtures is of the order of 10 mg 8-MOP plus 10 mg 5-MOP, which is equivalent to about 15 mg 8-MOP per person (blood levels of 8-MOP and 5-MOP at 30 min after ingestion of about 10-15 ng/ml each). This phototoxic threshold dose was not reached by the consumption of celery roots and other conventional vegetables under normal dietary habits (experimental intake of 2-8 mg per subject of the potentially phototoxic furocoumarin mixture). However, the safety factor between the possible actual intake of furocoumarins and the phototoxic threshold dose is about 2-10, which is relatively small.

5-Methoxypsoralen↗
PubMed1991

Selective regional chemotherapy of unresectable hepatic tumours using lipiodol.

Over a 30 month period from 1987 to 1990, selective hepatic cannulation under fluoroscopic control was performed in 57 consecutive patients with primary and secondary malignancies of the liver. Fifty-three patients were subsequently treated using intra-arterial Lipiodol emulsified with epirubicin. The tumours treated were hepatocellular carcinoma (n = 35), metastatic adenocarcinoma (n = 14), intrahepatic cholangiocarcinoma (n = 3) and leiomyosarcoma (n = 1). For hepatocellular carcinoma the cumulative survival was 38% at one year; the median survival was 12.2 months for Stage I, 6.3 months for Stage II and 0.9 months for Stage III tumours. In metastatic disease the cumulative survival was 63% at one year. These data suggest that targeted intra-arterial chemotherapy with Lipiodol-epirubicin is a useful palliative therapy for patients with Stage I and II HCC, and that a controlled trial of this treatment should be undertaken.

Adenocarcinoma↗
PubMed1991

[Femoral anteversion in upper femoral epiphysiolysis in adolescents. Apropos of 25 cases].

CT-scan examinations have been performed in 25 children with slipped capital femoral epiphysis (SCFE) and in 127 children in an out-patients orthopaedic consultation. A low femoral anteversion (FA) was present in SCFE. This morphological abnormality, in association with other factors, could explain the production of SCFE at the moment of the most important fragility of the upper femoral growth plate, which is puberty. A statistical analysis showed that the risk of SCFE was distinctly greater, even for the contralateral hip when FA was low.

Adolescent↗
PubMed1990

Use of Gianturco self-expandable stents in the tracheobronchial tree.

Gianturco self-expandable stents were used successfully in the management of 5 patients with tracheobronchial pathology. Placement was performed under endoscopic and fluoroscopic guidance. None of the patients has experienced complications secondary to the stent placement, and in all of them the clinical problems resolved satisfactorily. Longer follow-up is required to determine the place of tracheobronchial stenting in patients with respiratory compromise.

Aged↗