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Biomedical subjects

H J Smith

Publications and source records attributed to H J Smith.

At least 109 records · Page 6Linked to original sources
PubMed1990

[Magnetic tomography in congenital heart defects].

Magnetic resonance imaging (MR) has been shown to be valuable in defining cardiac anatomy in a variety of cardiac abnormalities. The article describes the technique and results of MR in 32 children with congenital heart disease. MR clearly depicts the anatomy of the great vessels, and may be used for the evaluation of palliative systemic-pulmonary artery shunts. In postoperative controls, MR may replace or postpone angio-cardiography. MR is also a promising technique for the evaluation of myocardial and valvular function. Especially in small children, the non-invasive nature of MR is of great importance.

Child, Preschool↗
PubMed1990

[Magnetic tomography at Rikshospitalet].

During the first 18 months of operation of the magnetic resonance unit at Rikshospitalet, 1,453 MR examinations have been performed on 1,431 patients. 64% of the time has been devoted to examinations of the central nervous system and spine in children and adults, nine % of the time has been used on non-neuroradiology pediatric patients, while the rest of the time has been spent equally on ear, nose and throat, thoracic (including cardiac) and abdominal examinations in adult patients. The indications for doing MRI at Rikshospitalet are listed and discussed, and it is concluded that MRI has proved to be useful at several conditions in most organ systems. However, the capacity of our single MR unit is much smaller than the need for examinations. The author discusses reasons.

Denmark↗
PubMed1990

Intravascular lead extraction using locking stylets, sheaths, and other techniques.

UNLABELLED: Septicemia necessitates extraction of chronic pacemaker leads. Using locking stylets and sheaths to extract leads via the implantation vein (subclavian, cephalic, or jugular) and maneuvering devices, sheaths, and retrieval baskets via the femoral approach, extraction of 228 leads implanted 5 days to 240 months (mean 55 months) was attempted in 136 patients (mean 62 years) at 34 institutions. In addition to septicemia (9%) and infection (39%), total 48%, indications included prophylaxis/replacement (40%), and other (12%). Seventy-seven leads were atrial, 151 ventricular; 147 were unipolar, 81 bipolar; 96 had silicone insulation, 127 polyurethane, 1 poly/silicone, and 2 undetermined. Fixation included tines or fins (160), screw (40), flange (12), and other (16). One hundred and ninety-four leads were completely extracted, 19 partly extracted, and 15 not extracted. Procedural complications were: torn atrium requiring open heart repair (1), hemothorax requiring a chest tube and blood transfusions (1), subacute hemothorax requiring drainage 18 days after discharge (1), thrombosis treated by drugs (1), and myocardial avulsion without sequela (1). Important observations included the significant training required due to the large number of possible clinical variables, and the need to be prepared for life-threatening cardiovascular complications. With training, procedures done at higher volume and lower volume institutions met with similar success. CONCLUSION: Intravascular lead extraction is a viable technique whose benefits outweigh the risks, given the proper intensive training and open heart surgical backup, and may obviate the need for open heart surgery for lead extraction.

Adult↗
PubMed1990

Intravascular lead extraction using locking stylets and sheaths.

Chronic lead extraction using intravascular countertraction techniques was studied in patients with over 65 different lead models including passive and active fixation devices. Indications for removal of 115 leads implanted 5 days to 264 months (mean 58 months) in 62 patients (mean 65 years) included septicemia, subcutaneous tissue infection, preerosion, free-floating lead, lead trapped in valve, too many leads, pain, and vein thrombosis. The superior vena cava (SVC) approach was attempted in 101 leads and was successful in 82 attempts (71% of total leads). The inferior vena cava (IVC) approach via the femoral vein was required to extract 14 (12%) leads inaccessible to the SVC approach and the 19 leads that failed the SVC approach (29% of total leads). The SVC procedure includes a sized stylet locked at the tip and telescoping sheaths advanced over the lead to the heart. An IVC procedure includes placement of a 16 F sheath workstation via a femoral vein into the right atrium. A deflection catheter and Dotter snare in an 11 F sheath were advanced through the workstation into the right atrium. The lead was maneuvered into position, snared, and pulled into the workstation. For both the SVC and IVC approaches, the leads were removed by applying traction on the lead and countertraction with the sheaths. In experienced hands, these techniques have proven safe and effective for removing chronic transvenous leads.

Adult↗
PubMed1990

Rheumatic disease of the temporomandibular joint: MR imaging and tomographic manifestations.

Thirty-six temporomandibular joints (TMJs) in 28 symptomatic patients (aged 14-40 years) with rheumatic disease (mostly rheumatoid arthritis) were studied with magnetic resonance (MR) imaging and hypocycloidal tomography. MR images of four TMJs were normal. Another four TMJs showed internal derangement. Of the 28 TMJs presumed to show rheumatic disease involvement (26 with condylar destruction or deformation), 23 showed abnormal disk structure--five showing severe disk destruction and 18 showing less severe abnormalities (inhomogeneous structure, fragmentation, poor delineation, and severe flattening). MR images showed bone abnormalities in 27 of the 36 TMJs, and tomography showed abnormalities in 25 of the 36 TMJs. Good agreement between the two imaging modalities regarding surface irregularities was found. However, MR imaging demonstrated more extensive bone abnormalities than did tomography in 11 TMJs. The potential of MR imaging for depicting bone and soft-tissue abnormalities associated with rheumatic TMJ involvement was clearly demonstrated.

Adolescent↗
PubMed1990

Assessment of an enzyme-linked immunosorbent assay using a Taenia hydatigena fraction antigen in the diagnosis of cysticercosis in cattle.

Enzyme linked immunosorbent assay (ELISA) using a fraction of larval Taenia hydatigena cyst fluid antigen was carried out on 469 bovine sera collected at slaughter from feedlot cattle for the presence of anticysticercosis antibodies. Cysticerci, in low numbers, were found in the heart, tongue and/or masseter muscles of 84 of the 469 cattle at postmortem inspection. Only nine sera gave positive ELISA reactions and in only one of these nine animals were cysticerci found. Within the limitations of this study, the high rate of false negative and false positive reactions suggests that the ELISA with the antigen used is not a satisfactory procedure to diagnose cysticercosis in cattle, at least in animals with light infections.

Animals↗
PubMed1990

Pathogenesis and serodiagnosis of experimental Trichinella spiralis spiralis and Trichinella spiralis nativa infections in cattle.

Trichinella spiralis spiralis infections were established in cattle by gavage and by feeding infected musculature in the ration. Trichinae were present in greatest numbers in masseter, tongue and diaphragm. Trichinella spiralis nativa had a low infectivity to cattle although a light infection was established in one cow by a heavy challenge. Cattle had an aversion to eating musculature unless it was camouflaged with molasses. Clinical signs of reluctance to eat and masticate were observed between 10 and 30 days postinfection. Eosinophil counts started to increase at seven days and peaked at about 30 days postinfection. By day 60 eosinophil counts returned to near preinfection levels but in animals examined greater than 90 days postinfection, the counts were variable. Focal lesions of eosinophilic myositis were observed up to about 90 days postinfection. Little cellular reaction was observed surrounding trichinae after muscle invasion and cyst development was completed except for cysts undergoing disintegration. Seroconversion occurred in all cattle examined between 7 and 14 days postinfection. Seroconversion was associated with IgG1 and IgG2 immunoglobulins. Peak levels of antibody occurred between 30 and 60 days. Cattle examined at 182 and 369 days postinfection showed a gradual decrease in antibody levels over time.

Animals↗
PubMed1989

[Magnetic tomography in lung cancer].

Reasonable long-term survival in bronchogenic carcinoma can be expected only if complete resection is performed. Accurate preoperative staging is essential, and computed tomography is not always sufficient as staging investigation. We discuss the indications for magnetic resonance imaging in these patients, and describe the use of this method in three patients. Magnetic resonance imaging should be used as a supplement to computed tomography in selected patients.

Aged↗
PubMed1989

[Magnetic tomography of intracranial hemorrhage. A study of paramagnetic effects].

The signal intensity of a hematoma at MRI is largely determined by the presence of paramagnetic substances derived from hemoglobin. Depending upon their structure and molecular mobility, paramagnetic substances may shorten the T1 and T2 of surrounding water protons and thus alter the MRI signal intensity and contrast. The article describes the evolution of intracranial hematomas and explains the relationship between the paramagnetic substance present and the resultant signal intensity at 1.5 T.

Adolescent↗
PubMed1989

Expression of a C3 plant Rubisco SSU gene in regenerated C4 Flaveria plants.

We report the successful transformation, via Agrobacterium tumefaciens infection, and regeneration of two species of the genus Flaveria: F. brownii and F. palmeri. We document the expression of a C3 plant gene, an abundantly expressed ribulose 1,5-bisphosphate carboxylase/oxygenase small subunit gene isolated from petunia, in these C4 plants. The organ-specific expression of this petunia gene in Flaveria brownii is qualitatively identical to its endogenous pattern of expression.

DNA↗
PubMed1989

Evaluation of the temperature response to exercise testing in patients with single chamber, rate adaptive pacemakers: a multicenter study.

UNLABELLED: Temperature responsive pacemakers were implanted in 45 patients (ages 44 to 90); 31 patients were evaluated by randomized, paired treadmill exercise tests 1 month postimplant. Of 28 males and 17 females, 19 had coronary artery disease; 8 had congestive heart failure. Pacing indications included sinus node disease (26), atrial fibrillation (15), AV block (10), and brady/tachy syndrome (10); some had multiple indications. Blood temperature (every 10 seconds, resolution = 0.004 degrees C) and pacing rate (every minute) were telemetered from the pacemaker. Average heart rate, exercise duration (5.7 min VVI; 6.7 min VVIR), VVIR response time (22 sec), initial temperature drop (0.23 degrees C) and maximum rate of drop (0.65 degrees C/min), temperature rise (0.31 degrees C VVI; 0.38 degrees C VVIR) and rate of rise (0.27 degrees C/min) were studied in a subset of patients. In pacer-dependent patients, average paired increases in exercise duration and heart rate was 56% and 34%, respectively. Including all (31) patients, some with intermittent sinus rhythm, increases were 28% and 9%, respectively. Because exercise duration increased, temperature rise was higher with rate adaptation. Rate adaptation was obtainable in all patients and patients averaged 99 +/- 48 increases above basic pacing rate per day at nominal temperature sensitivity. CONCLUSION: Beneficial rate adaptation is achievable using blood temperature to modify rate in a sensor based system.

Aged↗
PubMed1989

Case studies on the effect of exercise and hot water submersion on intracardiac temperature and the performance of a pacemaker which varies pacing rate based on temperature.

The effectiveness of using blood temperature change as an indicator to automatically vary heart rate physiologically was evaluated in 3 patients implanted with Model Sensor Kelvin 500 (Cook Pacemaker Corporation, Leechburg, PA, USA) pacemakers. Each patient performed two block-randomized treadmill exercise tests: one while programmed for temperature-based, rate-modulated pacing and the other while programmed without rate modulation. In 1 pacemaker patient and 4 volunteers, heart rates were recorded during exposure to a hot water bath. Blood temperature measured at 10 sec intervals and pacing rate measured at 1 min intervals were telemetered to a diagnostic programmer and data collector for storage and transfer to a computer. Observation comments and ECG-derived heart rates were manually recorded. The temperature-based pacemaker was shown to respond promptly not only to physical exertion but also to emotionally caused stress and submersion in a hot bath. These events cause increased heart rate in the normal heart. Using a suitable algorithm to process the measurement of blood temperature, it was possible to produce appropriate pacing rates in paced patients.

Aged↗
PubMed1989

Novel inhibitors of enkephalin-degrading enzymes. I: Inhibitors of enkephalinase by penicillins.

Several penicillins have been found to have pro-antinociceptive properties and also to be enkephalinase (neutral endopeptidase-24.11) inhibitors, carfecillin being the most potent. Carfecillin i.c.v. (but not i.p.) had significant antinociceptive activity in the mouse tail immersion test and completely suppressed abdominal constrictions (acetic acid) in mice (IC50 = 23 micrograms/animal). In combination with (D-Ala2-D-leu5)-enkephalin (DADL) i.c.v. in the abdominal constriction test the complete protection observed was reversed by the opioid receptor antagonist naltrexone. Carfecillin was a competitive inhibitor of enkephalinase from mouse brain striata (IC50 = 207 + 57 nM, cf thiorphan 10.6 +/- 1.9 nM) but did not inhibit other known enkephalin- degrading enzymes. Carfecillin provides a new lead structure for the development of more potent enkephalinase inhibitors.

Analgesics↗