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Biomedical subjects

A Constantinescu

Publications and source records attributed to A Constantinescu.

120 records · Page 7Linked to original sources
PubMedDate not supplied

Methodological aspects concerning radio-immunoassay of blood thyroxine applicable to population screening.

A research methodology concerning introduction of thyroxine radioimmunoassay applicable to screening programs is reported. The reagents necessary for T4 assay were prepared and tested and the technical parameters, the stages and technical characteristics of RIA-T4 in the laboratory were established. The RIA method for T4 was compared with the CPBA method and with the commercially available kits, both on samples taken from experimental animals and on hypo-, hyper- and normo-thyroid subjects. The range of T4 normal values could thus be established for the geographic area of Romania: 7.5-10.5 microgram dl-1, with a mean of 9.1 +/- 2 SD. The reagents were applied by extension to thyroxine assay on dry blood spots. The results are comparable with those of direct serum assay. The value of these assays in screening thyroid function in newborns and in the population with remnant thyreopathic endemic dystrophy is discussed.

Animals↗
PubMedDate not supplied

Thyroid hormones homeostasis and TSH in autonomic thyroid nodule.

Thirty patients with autonomic thyroid nodules were studied. Thyroid scintigram, iodine uptake at 2 and 24 hrs, PBI, total thyroxine, serum T3(RIA), basal TSH and 30 minutes after TRH administration were performed. A lack of concordance was found between the clinical signs and the laboratory data. According to the data obtained the patients were grouped into 3 categories: having 1) autonomic thyroid nodules with normal PBI, T4t, T3 values and absent or diminished TSH response to TRH; 2) autonomic thyroid nodules with increased T3 secretion and no response to TRH despite a normal T4 and iodine uptake, 3) hyperfunctional autonomic nodules in which PBI, T4t, T3 and iodine uptake are increased. TSH response to TRH is the most sensitive test for hyperthyroidism, more sensitive than the circulating thyroid hormones assay, and best fitted for adequate therapeutic management. Serum triiodothyronine was found to be increased in 95% of the patients. Thus, there is a T3 thyreotoxicosis in most of the autonomic nodules. TRH test and serum T3 assay being essential elements in starting the treatment, they have to be included among the tests used in autonomic thyroid nodules investigation.

Adenoma↗
PubMedDate not supplied

Noninvasive quantification of platelet accumulation and release on indwelling venous catheters.

An important element in the evaluation of biomaterials is quantification of the relationships and the sequence of events between blood elements, blood flow, and the foreign surface. We adapted a qualitative two-dimensional 111In-labeled platelet imaging method to a quantitative noninvasive analysis of platelet uptake/release kinetics for infusion catheters in a canine model. Bilateral femoral vein 6 Fr. Groshong catheters (one treated with a hydroxylated siloxane to improve albumin affinity) were monitored at femoral vein sites with a GE 400T gamma camera, interfaced with a Technicare 560 image acquisition computer. The field of view was sufficiently large that all events below the diaphragm were recorded without having to move the camera. Image acquisition time was 2.5 min; images were obtained every 5-15 min for 3 hrs. Continuous recordings were obtained from bilateral ultrasonic velocity probes, attached distal to the catheter implant sites. A 5 ml blood sample was placed in the field to permit calibration of gamma emissions per pixel in terms of labeled platelet density. Signal compensation for near field capillary perfusion was performed. The two-dimensional platelet distribution was computed and displayed. Local, time dependent platelet accumulation on the catheters and adjacent vessel walls was observed. Platelet accumulation proceeded in irregular steps during the implant period. Loss of local platelet deposits was observed. Downstream reattachment of platelet emboli was inferred from simultaneous reductions and increases in local platelet densities at two catheter positions. Platelet attachment was inversely related to vein blood velocity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Analysis of albumin deposits on hydroxylated siloxane films. Implications for surface treatment of medical devices.

The authors have developed methods to enhance albumin binding to modified silicone rubber (SR) films. An intermediate bifunctional coupling agent, polyvinylmethyl siloxane-comethyl-1-ethanol siloxane (PVMS-CO-MES), is prepared from a cyclic tetramer, vinyl-methyl siloxane, by an oxymercuration-demercuration reaction, and cross-linked to silicone rubber under mild peroxide catalytic conditions. Free mercury on the surface was obtained under many reaction conditions and is shown to materially enhance 125I-labeled albumin binding. The mechanism most likely occurs via disulfide bond breakage, protein denaturation, and aggregation. The possible role of iodine-mercury bonds, an artefactual source, is ruled out with the aid of total internal reflectance-fluorescence measurements of the albumin adsorption rate constant. Although in situ albumin aggregation via disulfide bond breakage is a potentially attractive method for biocompatible protein gel formation, the toxicity of mercury makes the current method unfit for clinical practice.

Adsorption↗
PubMedDate not supplied

Calcium 45 autoradiography and dual-isotope single-photon emission CT in a canine model of cerebral ischemia and middle cerebral artery occlusion.

PURPOSE: To determine whether transient ischemia can be separated from permanent ischemia via calcium 45 autoradiography and to assess the applicability of dual isotope single-photon emission CT (SPECT) in the evaluation of cerebral blood flow. METHODS: We examined calcium influx in 12 dogs (group A) by using whole-brain calcium 45 autoradiography: Animals received 250 microCi/kg 24 hours after 30-minute (n = 6) or permanent (n = 6) middle cerebral artery (MCA) occlusion. Forty-eight hours after MCA occlusion, 5-mm coronal brain sections were fixed for either autoradiography or pathologic examination. In a separate study, 9 mongrel dogs (group B) were given 250 microCi/kg calcium 45 and a mean dose of 700 microCi/kg technetium Tc 99m hexamethylpropyleneamine oxime intravenously. A silicone plug was then injected into the internal carotid artery and angiography was performed to verify MCA occlusion. A 10th (control) animal did not undergo occlusion. In an 11th animal, placement of the plug could not be achieved and a slurry of microfibrillar collagen was injected into the carotid artery. No angiography was performed in animals 10 and 11. After occlusion, each animal was injected with a mean dose of 126 microCi/kg simultaneous acquisition for technetium 99m and 123I-iodoamphetamine. RESULTS: In group A, all animals who had permanent MCA occlusion showed infarction and increased calcium 45 uptake in infarcted territories. None of the animals who had 30-minute occlusion had either increased calcium 45 uptake or infarction at 48 hours. In group B, 7 or 10 dogs had SPECT findings that were consistent with the calcium autoradiographic marker for ischemia. One animal died during the procedure and 1 dog served as a control. CONCLUSION: Calcium 45 autoradiography allowed distinction between areas of temporary and permanent occlusion. Iodoamphetamine imaging was not consistently sensitive to that level of ischemia. Timing of calcium influx may lead to insight that could impact timing of pharmacologic or endovascular intervention.

Amphetamines↗
PubMedDate not supplied

Paraneoplastic ophthalmological syndromes.

The different pathogenic and clinical aspects of the paraneoplastic ophthalmological syndromes are discussed by the author. Opsoclonus-myoclonus, retinal degeneration are largely reviewed. It is possible that new modern immunological methods to elucidate the role of antibodies in the genesis of paraneoplastic syndrome and the role of these antigens in the functioning of nervous system. Recognising a ophthalmological syndrome as paraneoplastic will prompt a search for an early detection of a cancer and a more prompt treatment.

Autoimmune Diseases↗
PubMedDate not supplied

Design of an oxygenator with enhanced gas transfer efficiency.

Membrane oxygenator designs were examined with particular attention to the influence of radial and axial flow around windings of microporous polypropylene hollow fibers. Oxygen transfer performance was calculated, employing the Mockros-Leonard modified heat transfer analysis and Curtis-Eberhart normalization methods. Flow through an Avecor Affinity oxygenator was imaged by gamma scintigraphy using a bolus injection of 99mTc-DTPA. Experimental mass transfer correlations were developed for this oxygenator using saline. The oxygen exchange of the Avecor Affinity was slightly less than that for the Medtronic Maxima or COBE Optima models, which are based on similar designs.

Biomedical Engineering↗
PubMedDate not supplied

Influence of cardiopulmonary bypass on platelet and neutrophil accumulations in internal organs.

The authors employed gamma scintigraphy to quantify the post bypass accumulations of platelets and neutrophils in the lung, liver, and heart of adult pigs subjected to a standard 90 min regimen of normothermic cardiopulmonary bypass (CPB). Coated and uncoated microporous polypropylene oxygenator circuits were studied for Cobe Duo (Arvada, CO) oxygenators (amphophilic silicone-caprolactone oligomer [SMA] coating, n = 8 each) and Medtronic Maxima (Irvine, CA) oxygenators (Carmeda heparin coating, n = 5 each). Images of cells in the organs (deposited + blood pool) were corrected for tissue absorption and other factors and compared for a 2 hr period post CPB, using repeat measures ANOVA and rank tests. Platelet accumulations in internal organs correlated positively with whole blood platelet counts and negatively with platelet deposits in oxygenators during CPB. In general, uncoated CPB circuits significantly reduced platelet and neutrophil accumulations in lung, liver, and heart versus preCPB controls for the post CPB interval, for both systems. The SMA treatment significantly increased platelet accumulations versus uncoated controls in lung, liver, and heart for the 2 hr period, including the majority of the post CPB sampling intervals; platelet densities did not reach preCPB levels. Neutrophil accumulations were unaffected by the SMA coating. Carmeda heparin treatment significantly increased platelet accumulations in the liver, but not lung or heart. Despite preservation of circulating neutrophils observed with the Carmeda heparin treatment, neutrophil accumulations in internal organs were not elevated post CPB.

Animals↗
PubMedDate not supplied

[Diagnostic difficulties in hemiplegic stroke--a neurological or neurosurgical case?].

Parting from the personal experiences and the actual information existing in the bibliography, the authors present, briefly, a general view on the complexity of the cerebral vascular pathology, insisting on the hemiplegic ictus. The aetiopathology of this syndrome is diversified so that it is difficult to make a strong correlation between age, way of beginning and clinical aspect. By way of example, the authors present 4 personal observations of hemiplegic ictus at different ages. In order to take a therapeutic decision, either neurologic or neurosurgical, the diagnosis in emergency can be determined correctly only with CT and RMN.

Adult↗