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At least 1,009 records · Page 56Linked to original sources
PubMed1996

Studies on radio-opaque polymeric biomaterials with potential applications to endovascular prostheses.

A new polymeric biomaterial, which uniquely combines radio-opacity (X-ray visibility) and low thrombogenicity, is described. First, preparation, purification, and identification of the essential monomeric building block, 2-[2'-iodobenzoyl]-ethyl methacrylate (3), are outlined. Second, [Figure: See text] the synthesis of the biomaterial, a terpolymer with composition MMA: HEMA: 3 = 65:15:20 (mole/mole/mole) is described. Third, the physico-chemical characteristics of the polymer (e.g. NMR spectroscopy, thermal behaviour) are given. Fourth, the in vitro thrombogenicity of the material was characterized by means of recent test assay. The combined results reveal that the terpolymer is very suitable for prosthetic applications in the cardiovascular system. A new prototype of an endovascular stent, made from the terpolymer, is presented. Stents find clinical use in interventional cardiology, in conjunction with percutaneous transluminal coronary angioplasty (PTCA). It is put forward that the stent prototype presented herein has, at least in principle, some advantages over existing (metallic) stents; these advantages are primarily owing to the unique combination of X-ray visibility and haemocompatibility which is presently achieved.

Biocompatible Materials↗
PubMed1986

Simultaneous determination of radio-immunoassayable methionine-enkephalin and radioreceptor-active opiate peptides in CSF of chronic pain suffering and non suffering patients.

Radio-immunoassayable methionine-enkephalin (ME) and radioreceptor-active opiate peptide levels (OP) were determined in CSF from patients, both with and without chronic pain, under investigation for vertebral disk disease. This study showed: that there was no direct correlation between ME and OP levels in CSF; OP levels were negatively correlated with the ME/OP ratio; migraine patients had higher levels of ME; ME concentrations were reduced in patients receiving anti-inflammatory drugs (nonsteroidal): patients with chronic pain (non migraine, no anti-inflammatory drug therapy) had lower ME levels than patients without pain. The data are discussed in relation to animal models of chronic pain.

Adolescent↗
PubMed1984

The effect of endotoxin and radio-detoxified endotoxin on the serum T4 level of rats and response of their thyroid gland to exogenous TSH.

We have demonstrated that, while the shock-inducing dose of parent (toxic) endotoxin significantly decreases the serum T4 level of rats and inhibits the T4 response given to exogenous thyroid stimulating hormone (TSH), the radio-detoxified (60Co-gamma, 150 kGy) endotoxin preparation does not inhibit the response to exogenous TSH and decreases serum T4 level to a lesser extent than untreated endotoxin.

Animals↗
PubMed1984

Prevention of cardiac damage induced by formyl-leurosine, a potent cytostatic agent, by radio-detoxified endotoxin (Tolerin) in dogs.

Radio-detoxified endotoxin (Tolerin), produced by 60Co-gamma irradiation of Escherichia coli 089 endotoxin, can protect dogs against the acute cardiotoxic side-effects of formyl-leurosine, a semi-synthetic Vinca derivative with promising antineoplastic potency. Formyl-leurosine induces a rapid decrease in arterial blood pressure and diminishes the contractile force of the myocardium in the anaesthetized dog. These responses indicate a direct pharmacologic relaxant effect of the drug on the heart and vasculature smooth muscle. The early cardiovascular depression is of short duration and is unaffected by Tolerin. Tolerin can prevent, however, the secondary, more dangerous phase of circulatory depression that is associated with the severe cardiotoxic manifestations of the drug, as demonstrated by hemodynamic and morphologic (light and electronmicroscopic) patterns.

Animals↗
PubMed1993

Mapping of [3H]vasopressin binding sites in the brain of jerboa (Jaculus orientalis) by an high resolution beta-radio imager.

The distribution of vasopressin receptors in the brain of the jerboa (Jaculus orientalis) was studied using tritiated arginin vasopressin ([3H]vasopressin). beta-Particles emitted from tritiated ligand bound to brain sections were detected by a newly developed beta-radio imager to generate a light spot which was read by a charge coupled device camera. The number and coordinate of the center of gravity of the light spot were recorded. After summation in pixels of the counts collected during 2-20 h, an image was produced representing the distribution of [3H]vasopressin bound to brain sections. Specific vasopressin binding was detected in various brain regions such as the cerebral cortex, islands of Calleja, pallidum, amygdala and the hippocampus as well as in the pituitary gland. The intensity of the binding was quantified directly from the images obtained and expressed in decays/min/surface unit. The linearity of this method of detection allowed a relevant measurement of non-specific binding, therefore its subtraction from images representing the total binding. Three-dimensional reconstructions of labeled structures were also performed. The presence of numerous vasopressin receptors in the jerboa hippocampus suggests a major role for this neuropeptide in this part of the brain.

Animals↗
PubMed1991

Intercalated radio-chemotherapy in small cell lung cancer: toxicity and implications for future regimens.

Thirty-six patients with small cell lung cancer have been treated using chemotherapy comprising carboplatin, ifosphamide and etoposide. A total of six cycles of chemotherapy were given. In 15 patients with limited disease intercalated radio-chemotherapy was used in which two 5-day courses of hyperfractionated radiotherapy were given to the thorax after the first and second cycles of chemotherapy. Each course of thoracic radiotherapy delivered 15 Gy in 15 fractions over 5 days. Oesophagitis occurred in 7 patients (40%), in 5 of whom this was severe (WHO grade 3). Radiological pneumonitis developed in 6 patients (40%) with subsequent fibrosis in 2 patients. These effects are greater than would be expected with this dose of radiation alone and reflect marked enhancement of normal tissue toxicity.

Adult↗
PubMed1993

Insulin autoantibodies and immune response to human insulin therapy in 24 type 1 (insulin-dependent) diabetic children: superiority of radio binding assay over solid phase assay.

To evaluate the immunization pattern against human insulin, 24 newly diagnosed diabetic children (12 females, 12 males; mean age: 7 +/- 4 years) were treated from diagnosis onwards with semisynthetic human insulin (NOVO). Informed consent was obtained from all parents. Blood samples were taken before, 1, 2, 3, 4, 6 and 8 weeks after the start of therapy and, thereafter, at monthly intervals for 2 years. Insulin (auto) antibodies (I(A)A) were measured by radio binding assay (RBA) and by enzyme-linked immunosorbent assay (ELISA). IAA, determined by RBA, were detected in eight children. Using ELISA, IgM IA were not detected after onset of therapy. By contrast, IgG IA were found in 8 children after 2 weeks of treatment and in 12 after 1 month. Using RBA, all children had IA after 2 months of therapy, whereas with ELISA, IA remained undetectable during the study period in 8 out of 24 patients. These results confirm previous observations suggesting that the 2 methods are not interchangeable and yield different estimations of the insulin immune reaction, not only before but also after the start of insulin therapy. In addition, the detection of IA by RBA in all treated patients unambiguously demonstrates that human insulin is immunogenic in man.

Adolescent↗
PubMed1986

Plasma prostaglandins: 6-keto-PGF1 alpha, TXB2 and PGE2 in juvenile-onset diabetes determined by high-pressure liquid chromatography and radio-immunoassay.

Some studies have recently reported increased production of platelet thromboxane and decreased vascular prostacyclin in patients with diabetes mellitus. The impact of these changes on platelet and vascular functions in vivo is still speculative. Using radio-immunoassay and high pressure liquid chromatography we have studied the plasma levels of 6-keto-PGF1 alpha, TXB2 and PGE2 in 23 juvenile-onset diabetics. There was no significant difference in these plasma prostaglandins between the diabetics and a control group. The prostaglandins were neither correlated to blood-glucose nor the degree of glycosylation (HbA1c). Our results can not support the hypothesis that decreased vascular prostacyclin and increased platelet production of TXB2 are important factors in diabetic patients.

6-Ketoprostaglandin F1 alpha↗
PubMed1994

Cystic radio-lucency of carpal bones in haemodialysis patients. An early indicator of the onset of carpal tunnel syndrome.

Patients receiving haemodialysis for more than 10 years were selected for this study in order to clarify an apparent sequential association of cystic lesions of carpal bones and carpal tunnel syndrome. X-rays and computed tomographs of 138 hands of 69 patients revealed cystic radiolucency of carpal bones in 35% of the hands. Radiographs were classified into three groups: Group A--cyst growing, Group B--cyst not growing, and Group C--cyst absent. The prevalence of carpal tunnel syndrome was 100% (27/27) in Group A, 5.6% (1/18) in Group B, and 6.5% (6/93) in Group C. Growth of the cyst precedes the development of carpal tunnel syndrome by about 2 or 3 years. Growth of the bone cyst indicates that inflammation had already extended to the tenosynovium and median nerve. Cystic radio-lucency of the carpal bones appears to be a useful indicator of the onset of carpal tunnel syndrome.

Adult↗
PubMed1990

Corrosion protection of metal implants by hard biocompatible ceramic coatings deposited by radio-frequency sputtering.

Most metals used for orthopaedic and stomatology implants and prostheses belong to the families of titanium or nickel-based and cobalt-based superalloys designed for advanced technology industries (e.g. space, aeronautic and nuclear industries). Ideal materials should be as insoluble and biologically compatible as possible. In the present paper the corrosion behaviour of Ni-Cr and Co-Cr alloys in biological media is evaluated through potentiodynamic polarization tests. It is shown that these metals exhibit some minor release of the component elements and degradation products, which may induce cytotoxic and allergic effects. The corrosion resistance of these alloys can be strongly enhanced by hard ceramic coatings deposited by radio-frequency sputtering. The biocompatibility of coated and uncoated metals is compared from differentiated human cell cultures.

Chromium Alloys↗
PubMed1993

Volumetric arterial flow quantification using echo contrast. An in vitro comparison of three ultrasonic intensity methods: radio frequency, video and Doppler.

The two hypotheses presented in this paper are: (1) absolute and relative volumetric flow rates in vessels can be measured by echo contrast time-intensity curves; and (2) echo contrast time-intensity curves generated by different ultrasound backscatter intensity techniques have equivalent capability for flow measurements. A nonpulsatile flow system was built for quantitative ultrasound backscatter measurements from bolus echo contrast injections using two different volumes of mixing. A total of 49 echo contrast bolus injections were made at various flow rates (0.44-2.59 L/min). Ultrasound backscatter time-intensity curves were generated by ultrasound radio frequency, video and Doppler techniques. The rate of backscattered ultrasound intensity washout for each technique (WASHOUT RATE), and relative change in WASHOUT RATE (delta WASHOUT RATE) were compared to the volumetric flow rate (FLOW) and changes in flow rate (delta FLOW), respectively. The relationship between WASHOUT RATE, FLOW and the volume of contrast mixing was studied. A linear relationship was demonstrated between WASHOUT RATE and delta WASHOUT RATE and the corresponding FLOW and delta FLOW by all three methods (r > 0.90 for all comparisons). The WASHOUT RATE was found to depend on the FLOW and the volume of contrast mixing, but the delta WASHOUT RATE was equal to the delta FLOW and independent of the volume of mixing. Time-intensity curves can be generated from different ultrasound backscatter intensity techniques and the WASHOUT RATE correlates well with FLOW. delta FLOW can be determined directly from the corresponding delta WASHOUT RATE. Doppler ultrasound, because of its natural association with the assessment of flow in chambers and vessels, is uniquely suited to assessment of arterial volumetric blood flow in vitro.

Arteries↗
PubMed1994

Acquisition and processing of the radio-frequency signal in echocardiography: a new global approach.

Recently there has been an increasing interest in the use of the "raw" radio-frequency (RF) signal generated in echocardiography for use in tissue-characterization to distinguish between normal and pathological myocardium, for automatic delineation of the endocardial border without being limited by the weak contrast of the traditional video images, and for use in contrast echography, where it could offer the possibility to visualize perfusion using intravenous contrast injections. One of the main problems in this kind of research is the acquisition of the signal having a high frequency and large bandwidth. We have developed a new global method for the acquisition of this RF signal. To digitize the data, a video sequencer is used. In this way it becomes possible to sample all available data generated by the echographic equipment during at least 1 s. This means that all data of the complete sector scan during a complete heart-cycle can be digitized without using any data reduction technique or triggering on the electrocardiogram. The advantage of this approach is that all characteristics of the signal can be studied, without being limited by data reduction techniques used during acquisition. This method enables us to calculate parameters such as "integrated backscatter," or to investigate the signal more extensively, e.g., by using spectrum analysis. We can compare different regions of the myocardium and examine them during the heart-cycle, all within the same beat. We have also written a software package for the processing of the large amount of data resulting from the acquisition.

Animals↗
PubMed1991

Electrochemically induced adsorption of radio-labeled DNA on gold and HOPG substrates for STM investigations.

In a scanning tunneling microscope (STM) electrochemical cell we have studied the effects of electrode potential on both the surface topography and the adsorption of deoxyribonucleic acid (DNA) to graphite and gold surfaces. Images of the surface of highly oriented pyrolytic graphite (HOPG), of the same area, in response to a positive increase in surface potential show degradation of the step edges with little change in the crystal plane. Images of the same area of a gold surface demonstrate the formation of and the progressive increase in nodular structures on the crystal planes, in response to increased potential, with little effect on the step edges. Using radio-labeled DNA we monitored electrochemical absorption onto HOPG and gold surfaces. Although at no applied potential and at negative surface potentials some DNA was bound, at positive potentials 3 to 5 times more DNA was incorporated onto both surfaces. DNA adsorbed to a surface at a positive potential was not removed by reversing the potential.

Adsorption↗
PubMed1992

Phase I/II study of external radio frequency phased array hyperthermia and external beam radiotherapy in the treatment of prostate cancer: technique and results of intraprostatic temperature measurements.

As part of an ongoing Phase I/II study at Duke University Medical Center investigating the toxicity and efficacy of external beam radiotherapy plus hyperthermia for deep-seated, locally advanced or recurrent solid tumors, 12 patients with prostate malignancies (adenocarcinoma--11, leiomyosarcoma--1) were treated with radiotherapy plus hyperthermia. Hyperthermia was given after radiotherapy using a Radio Frequency Phase/Amplitude Control Sigma 60 annular phased array device. All patients had simultaneous temperature measurements made in the rectal lumen and within the prostate during at least one hyperthermia session. Intraprostate thermometers were placed via a unique method described herein using both computerized tomography scan and a rigid sigmoidoscope for guidance. We were able to achieve the desired tumor temperature of > or = 42.5 degrees C in only 1/28 (3.5%) of hyperthermia treatments. Subjective symptoms of pain and/or pressure limited power deposition in 79% of hyperthermia treatments. Higher temperatures were achieved in the distal rectum than in the prostate in all treatments, although the differences were not statistically significant. This temperature differential could not be compensated by using phase and amplitude steering. Rectal temperatures adjacent to the prostate were predictive of prostate temperatures. We conclude that using this regional heating technique we were unable to demonstrate an ability to get an advantageous temperature differential between the prostate and normal tissue. This technique is not useful as an adjuvant to radiation therapy for prostate cancer. The usefulness of other regional heating techniques and devices should be explored.

Adenocarcinoma↗
PubMedDate not supplied

Radio-opaque liposomes for the improved visualisation of focal liver disease by computerized tomography.

Liposomes laden with radio-opaque agents (ROA) were prepared by the reverse phase evaporation method. The liposome solutions--containing 1.7-2.5 mg iodine per mg lipid--were injected into Wistar rats. 60 min post injection the rats were scanned in a Siemens CT scanner. Following the injection of 260 mg encapsulated iodine per kg bodyweight--less than half the iodine of the normal ROA bolus injection--there was a long lasting arise in liver enhancement of 40 Hounsfield units (HU). In animals with liver tumours induced by nitrosamine lesions of 2-3 mm in diameter could be detected.

Animals↗