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Biomedical subjects

B Dunn

Publications and source records attributed to B Dunn.

At least 55 records · Page 3Linked to original sources
PubMed1992

Balloon valvotomy for pregnant patients with severe pliable mitral stenosis using the Inoue technique with total abdominal and pelvic shielding.

Balloon valvotomy by means of the Inoue technique was attempted in seven pregnant (5 to 9 months) patients with severe mitral stenosis; the mean age of the patients was 32 +/- 8 years, and all had a two-dimensional echocardiographic mitral valve score of < 8. Indications for Inoue balloon valvotomy included severe symptomatic mitral stenosis with a Doppler mitral valve area < or = 1 cm2 and heart failure refractory to medical therapy, or absolute contraindications for the use of beta-blockade; Inoue valvotomy was also indicated for patients who lived a long distance from the hospital. Inoue balloon valvotomy was performed with no angiography and total pelvic and abdominal shielding; the balloon catheter was introduced into the right atrium without the aid of fluoroscopy, which was used for the transseptal puncture. Stepwise two-dimensional echocardiographic Doppler mitral valve dilatation was done. After Inoue balloon valvotomy the mean Doppler mitral valve area increased from 0.8 +/- 0.1 to 2.0 +/- 0.3 cm2 (p < 0.01) and by two-dimensional echocardiography from 0.8 +/- 0.2 to 1.9 +/- 0.3 cm2 (p < 0.01), with no significant Doppler residual stenosis (defined as mitral valve area < or = 1.5 cm2). The mean total fluoroscopy time was 16 +/- 7 minutes. The degree of mitral regurgitation increased in two patients from grade 1+/4+ to grade 2+/4+ and from grade 0+/4+ to grade 2+/4+, respectively. There was no mortality or significant morbidity. Pregnancy was uneventful in all patients, and all were delivered of normal babies without complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1992

Percutaneous mitral valvotomy with the Inoue balloon catheter in children and adults: immediate results and early follow-up.

Percutaneous mitral balloon valvotomy (PMV) using the Inoue balloon catheter was attempted in 60 consecutive patients with severe symptomatic mitral stenosis. There were 10 children (mean age 13 years) and 50 adults (mean age 31 years). Forty patients were females and 20 were males; 53 were in sinus rhythm. The procedure was technically successfully performed in 57 (95%) patients. There were no deaths or thromboembolic complications. Balloon valvotomy was done using a 22 to 30 mm diameter catheter with the echo/Doppler guided stepwise mitral dilatation technique. After PMV the mean left atrial pressure decreased from 23.0 +/- 5.0 to 14.0 +/- 4.0 mm Hg (p less than 0.001). The mean mitral valve gradient (MVG) decreased from 15.0 +/- 4.0 to 6.0 +/- 2.0 mm Hg (p less than 0.001). The mitral valve area (Gorlin formula) increased from 0.7 +/- 0.2 to 1.6 +/- 0.4 cm2 (p less than 0.001). The mitral valve area as determined by echocardiography increased from 0.8 +/- 0.1 to 1.9 +/- 0.3 cm2 (p less than 0.001). Mild mitral regurgitation (MR) developed in six patients (11%) and increased by one grade in another five patients (9%). No patient developed severe mitral regurgitation. Mitral valve area at mean follow-up of 4.8 months remained unchanged at 1.9 +/- 0.3 cm2. We conclude that PMV, using the Inoue balloon catheter, is safe and effective in the treatment of severe mitral stenosis in children and adults, without inducing significant mitral regurgitation.

Adolescent↗
PubMed1992

Balloon coarctation angioplasty in adolescents and adults: early and intermediate results.

Twenty-three adolescent and adult patients with native coarctation of the aorta underwent balloon dilatation. Dissection of the aorta developed in one patient. Data were collected on the remaining 22 patients. They ranged in age from 15 to 55 years (mean 23 +/- 9.2 years). Invasive measurement of the peak systolic gradient (PSG) and biplane angiography were performed before and immediately after angioplasty and at follow-up 4 to 48 months (mean 15 months) later. PSG before dilatation was 37 to 100 mm Hg (mean 66.9 +/- 19.9 mm Hg) and decreased to 0 to 30 mm Hg (mean 9.1 +/- 11 mm Hg) immediately after dilatation (p less than 0.001). Restenosis occurred in two patients 6 months after dilatation, and one patient had an incomplete dilatation. These three patients underwent successful redilatation and remained improved 12 to 19 months later. There was no significant change in gradient at repeat catheterization in the remaining 20 patients. PSG was 0 to 20 mm Hg (mean 5.8 +/- 7.2 mm Hg). Angiography showed that a small aneurysm developed in one patient immediately after dilatation and in another 6 months later. Eleven patients were restudied more than once, and no change in gradient or size of the aneurysm was noted at mean follow-up 25 months after dilatation. This study demonstrated that balloon angioplasty is an effective method of treating adolescent and adult patient with native coarctation of the aorta. However, because of the uncertain natural history of aneurysm after dilatation, this procedure should be considered investigational until much longer follow-up times are available.

Adolescent↗
PubMed1992

Protection by beta-carotene and related compounds against oxygen-mediated cytotoxicity and genotoxicity: implications for carcinogenesis and anticarcinogenesis.

beta-Carotene protects against photooxidative dermatitis in porphyric humans and mice by quenching of photoactivated species. Other actions of beta-carotene in vivo are explained on the basis of its ability to scavenge free radicals in vitro. For example, in guinea pigs treated with CCl4, beta-carotene decreases pentane and ethane production. Epidemiological studies link low serum beta-carotene levels to elevated risk of lung and other cancers, and in intervention trials, beta-carotene diminishes preneoplastic lesions. However, the dose/response relationships are not well established, and antineoplastic mechanisms await clarification. Given a radical quenching mechanism, beta-carotene should block tumor promotion, but more typically the site of action is progression and an even later role in invasion has not been ruled out. Some antineoplastic actions of carotenoids (such as increased rejection of fibrosarcomas in mice) are attributed to immunoenhancement; others may reflect conversion to retinoids and subsequent gene regulation. Carotenoids other than beta-carotene may act at an earlier stage of carcinogenesis or be more effective as anticarcinogens at certain target sites. As scavengers of hydroxyl radicals, canthaxanthin and astaxanthin are more effective than beta-carotene. Canthaxanthin is sometimes more effective than beta-carotene in chemoprevention, but it is sometimes completely ineffective. Lycopene quenches singlet oxygen more than twice as effectively as beta-carotene. However, the antineoplastic actions of lycopene or astaxanthin remain untested. Explorations of the interactions of carotenoids with other nutrients are just beginning. Dietary fat increases absorption of carotene but decreases antineoplastic effectiveness. Research is hampered by technical problems, including the unavailability of rigorous controls, the instability of carotenoids, and the heterogeneous phase structure induced by hydrophobic compounds in aqueous media. Areas of current controversy and promising approaches for future research are identified.

Animals↗
PubMed1992

PET imaging of opiate receptor binding in human epilepsy using [18F]cyclofoxy.

We used [18F]cyclofoxy (CF), a potent opiate antagonist with affinity for mu and kappa receptors, and the Scanditronix PC1024-7B PET scanner to study 14 patients with complex partial seizures (CPS), and 14 normal controls. Epileptic foci were localized by prolonged EEG-video monitoring. EEG was recorded continuously during each scan. Immediately before CF administration, [15O]labeled water was used to measure cerebral blood flow, and showed hypoperfusion ipsilateral to the EEG focus. Blood samples (corrected for radiolabeled metabolites) and tissue time-activity data were acquired over 90 min following bolus CF injection. Anatomic regions were outlined directly on the PET images. A kinetic model was used to derive the total volume of distribution (Vt) in each brain region. Specific binding (Vs) was determined by substracting non-specific binding (Vt) measured in a receptor-poor brain region (occipital cortex). Regions with high Vs included mesial temporal lobes, thalamus, basal ganglia, and frontal cortex. Individual patients appeared to have higher binding in temporal lobe ipsilateral to the EEG focus, but there was no asymmetry for the patients as a group in mean Vt or Vs in anterior mesial, posterior mesial, anterior lateral, posterior lateral temporal cortex, thalamus, basal ganglia, or, for Vt, in regions of low specific binding: occipital lobe, parietal lobe, cerebellum.

Adolescent↗
PubMed1991

Regional brain measurement of Bmax and KD with the opiate antagonist cyclofoxy: equilibrium studies in the conscious rat.

Brain distribution of the opiate receptor antagonist, cyclofoxy (CF), was evaluated at equilibrium in rats. A combination of i.v. injection and constant i.v. infusion was used to administer CF over a wide dose range (2.4-450 nmol/rat). Kinetic simulations and experimental results showed that this administration schedule accomplishes "true" tissue-blood equilibrium of CF within 60 min. To estimate the receptor-ligand binding parameters, we assumed that the CF concentration at the receptor site is identical to that in plasma water at equilibrium, and can be calculated from measured blood data after corrections for radiolabeled metabolites and plasma protein binding. This assumption was supported by CSF and plasma water measurements at equilibrium. Regional KD, Bmax, and a nonspecific tissue binding equilibrium constant (Keq) were estimated by fitting the tissue and plasma water concentrations to a single receptor model; the estimated values were 1.4-2.9 nM, 15-74 pmol/g of tissue, and 5.2-8.0, respectively. They are in good agreement with previous in vitro measurements (Rothman and McLean, 1988) as well as in vivo estimates from i.v. injection experiments (Sawada et al., 1990c). The conventional method to estimate the receptor-ligand binding parameters using data from cerebellum to approximate nonspecific tissue binding was found to be unacceptable. Although cerebellum is a brain region with no opiate receptors in rats, small differences in nonspecific tissue binding in different brain regions resulted in significant overestimations of KD and Bmax with this method. Receptor-active and -inactive enantiomers [[18F](-)-CF and [3H](+)-CF)] were simultaneously administered to the same animal and the receptor-bound CF concentration could be accurately measured; this method was used to estimate Bmax from a single study in a single animal and has potential for direct application in human studies using positron emission tomography.

Animals↗
PubMed1991

Coronary artery disease and apolipoprotein A-I/C-III gene polymorphism: a study of Saudi Arabians.

The infrequent band of 3.2-kb of the apolipoprotein A-I/C-III polymorphic region has previously been found to be associated with coronary artery disease and with hypertriglyceridaemia in Caucasians. We studied the apolipoprotein A-I/C-III gene cluster polymorphism in 97 Saudi Arabians in relation to coronary artery disease. Patients were categorized as being with or without coronary artery disease on the basis of coronary angiography. Genomic blotting of Sac I-digested chromosomal DNA with the use of an apolipoprotein A-I gene probe revealed 4.2-kb and 3.2-kb hybridization bands. The genotype frequency of patients with and without coronary artery disease was not different. The frequency of the 3.2-kb allele occurred in 16% of patients with coronary artery disease and in 21% of patients with normal coronary arteries (non-significant). In conclusion, we have not been able to confirm in Saudi Arabians associations previously reported in Caucasians of the 3.2-kb band and coronary artery disease.

Apolipoprotein A-I↗
PubMed1991

Mitral balloon valvotomy using the Inoue balloon technique for selected patients with severe pliable rheumatic mitral valve stenosis: immediate and short-term results.

We selected 40 patients with severe symptomatic rheumatic mitral stenosis for balloon valvotomy using the Inoue balloon technique. The patients' mean age was 31 +/- 14 years and there were 24 females and 16 males. The patients were selected according to the following echo/Doppler criteria; 1. Severe mitral stenosis, i. e. mitral valve area (MVA) less than 1.1 cm2; 2. pliable anterior mitral valve leaflet; 3. absence of calcification of the mitral commissures and 4. absence of significant subvalvular mitral valve disease (Block echo score less than 8). We failed to cross the mitral valve in three cases and repeat attempts in two patients with higher transeptal puncture was successful. Thirty-nine procedures were technically successful (98%). There were no complications. We used an Inoue balloon size 24-30 mm using echo/Doppler guided stepwise mitral dilatation. After mitral balloon valvotomy, the MVA increased from 0.8 +/- 0.2 to 1.7 +/- 0.5 cm2 (p less than 0.001). Five patients developed mild mitral regurgitation and in one patient the degree of mitral regurgitation increased from mild to moderate. The mean mitral valve area 48 hours after the procedure measured 1.9 +/- 0.4 cm2 (echo/Doppler); one patient (2.5%) had residual mitral stenosis (MVA less than 1.5 cm2). At six weeks follow-up study the mean mitral valve area was 1.9 +/- 0.5 cm2 (Echo/Doppler), with no restenosis. We conclude that in selected cases of severe pliable mitral stenosis, the Inoue balloon technique achieves a greater than 100% increase of the MVA, without inducing significant iatrogenic mitral regurgitation or residual stenosis.

Catheterization↗
PubMed1990

Regression of infundibular pulmonary stenosis after successful balloon pulmonary valvuloplasty in adults.

Between July 1985 and March 1988, 22 adult patients with congenital pulmonary stenosis underwent balloon pulmonary valvuloplasty. There were 10 males and 12 females aged 16-45 (average 25 +/- 9.9) years. All patients had additional mild to severe infundibular stenosis; 16 were restudied 6-36 (mean 12.6) months later by repeat catheterization. Student's t-test was used for comparison of data. Right ventricular (RV) systolic pressure before dilatation was 84-196 (mean 129 +/- 32.3) mm Hg, and the peak pulmonary gradient (PPG) was 60-176 (mean 111 +/- 33.2) mm Hg immediately after dilatation. The RV systolic pressure dropped to 32-140 (mean 59.2 +/- 27) (P less than 0.001); and PPG dropped to 10-113 (mean 37.8 +/- 26.4) (P less than 0.001), and the infundibular gradient ranged from 8 to 113 (mean 35.1 +/- 25.8) mm Hg. The infundibular diameter, before dilatation, ranged from 2 to 15 (mean 9.5 +/- 4) mm Hg. At repeat catheterization, the RV systolic pressure dropped further to 33-66 (mean 42.8 +/- 9.7) mm Hg and the PPG was reduced to 0-48 (mean 18.4 +/- 10.9) mm Hg (P less than 0.001). The infundibular gradient regressed to 0-34 (mean 15 +/- 8.8) mm Hg (P less than 0.001). The infundibular diameter increased to 8-25 (mean 15.8 +/- 5.4) (P less than 0.001). It is concluded that moderate to severe infundibular stenosis, in adults, can regress after successful pulmonary valvuloplasty.

Adult↗
PubMed1990

Percutaneous balloon pulmonary valvuloplasty in sickle cell anemia: a case report.

Percutaneous balloon pulmonary valvuloplasty was performed on a 19-year-old female who had moderate pulmonary valve stenosis with sickle cell anemia. The patient developed sickle cell crisis resulting in occipital infarction, but she made a good recovery. We describe this case and the methods of reducing the risk of sickle cell crisis.

Adult↗
PubMed1990

Lectin-resistant CHO cells: selection of seven new mutants resistant to ricin.

In attempts to isolate new CHO glycosylation mutants, selection protocols using plant lectins that bind galactose residues of cell surface carbohydrates were applied to mutagenized CHO populations. The lectins were used alone or in combination to obtain seven ricin-resistant phenotypes. Each mutant had distinctive properties compared with previously described ricin-resistant CHO cells. One of the new phenotypes was dominant in somatic cell hybrids, and the others were recessive. Complementation analyses between related lectin-resistant (LecR) phenotypes indicated that each new isolate represented a novel genotype. Five of the mutants had properties typical of new CHO glycosylation mutants. The remaining two mutants were not readily categorized. Although they did not appear to be ricin-internalization or protein-synthesis mutants, they also did not display the marked alterations in sensitivity to several lectins of different sugar specificity expected for glycosylation mutants. The seven new LecR mutants described in these studies brings the total number of different LecR CHO mutants isolated by this and other laboratories to about 40. Criteria for identifying new LecR mutations in CHO cells are discussed.

Animals↗
PubMed1990

Kinetic analysis of the opiate antagonist cyclofoxy in rat brain: simultaneous infusion of active and inactive enantiomers.

The opiate antagonist (-)-cyclofoxy [(-)-CF] and the receptor inert enantiomer (+)-CF were radiolabeled with 18F or 3H and administered to conscious Sprague-Dawley rats; an isotope effect was not observed. Constant i.v. infusion of both 18F-(-)-CF and 3H-(+)-CF in tracer amounts showed a marked difference in the tissue level of 18F-(-)-CF among various brain structures, whereas the values for 3H-(+)-CF were lower and much less variable. Co-infusion of unlabeled (-)-CF (1 mg/rat) did not change the tissue binding of 3H-(+)-CF in any brain structure, but reduced that of 18F-(-)-CF to the same level as 3H-(+)-CF. These results demonstrate an identical nonspecific tissue binding for (+)- and (-)-CF in vivo, and suggest that (+)-CF can be used to measure the "nonspecific" component of (-)-CF binding in brain. A nonlinear analysis of the 3H-(+)-CF data indicated the presence of both "instantaneous" and time-dependent components in nonspecific tissue binding and that nonspecific binding varied 1.5-fold in different brain structures. The combined 3H-(+)-CF and 18F-(-)-CF data were fitted to a four-compartment model, which includes parameters for capillary transport, "instantaneous" and time-dependent nonspecific tissue binding, as well as receptor association and dissociation. The receptor-association rate constant varied considerably in various structures of cerebrum (2.0-8.7 min-1), whereas receptor dissociation was estimated within a narrow range (0.12-0.17 min-1). The receptor binding potential (receptor association/dissociation) ranged between 12.7 and 56.2 and was in good agreement with previous estimates in vitro.

Animals↗
PubMed1990

[Short- and long-term problems in dilatation of untreated aortic isthmus stenosis in children].

We examined problems and complications during and after balloon dilation of native coarctation of the aorta in 31 children with a mean age at first dilation of 5.77 +/- 5.4 years (0.08-16 years), who had a total of 37 balloon dilations. Twenty-six patients were restudied 3 to 24 months after the first procedure. In six patients, because of recoarctation, further dilations were performed. In two patients the second procedure was not successful and they required surgery. In 14/37 (37.8%) dilations the routine sedation was insufficient. The retrograde catheter could be introduced percutaneously in all but one patient. Because of small femoral arteries the introduction of the balloon catheter was not possible in three cases (8.1%). In three more patients (8.1%) the adequate catheters were not in stock. Complications included: transfusion because of blood loss in six patients (16.2%), chest pain in three (8.1%), rupture of balloon in three (8.1%), thrombectomy in three (8.1%), and partial reopening of ductus arteriosus in one patient. Duration of hospital stay was a mean of 1.81 days +/- 1.65 (range 1-9 days). Ninety percent of the patients were discharged within 2 days. On follow-up (range: 3-50 months), eight patients (21.6%) had a weak femoral pulse, of whom only one had an absent pulse, eight patients (21.6%) had paradoxical hypertension despite good dilation and no significant gradients, and only one patient showed a small aneurysm. We conclude that balloon angioplasty of native coarctation is a successful and relatively safe method of treatment of native coarctation. The most serious complication is arterial occlusion of the affected leg.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Doppler echocardiography in the evaluation of tricuspid stenosis.

Seventeen patients (12 with native and five with prosthetic tricuspid valves) with tricuspid stenosis were studied by Doppler echocardiography followed by cardiac catheterization within 24 h. The mean tricuspid diastolic pressure gradient was calculated using the modified Bernoulli equation. Tricuspid valve area (TVA) was calculated by the pressure half-time method (TVA = 190 divided by pressure half-time). Data from Doppler echocardiography and cardiac catheterization were compared. The Doppler-derived tricuspid mean diastolic gradient was 1.9-9.9 mmHg (average 5.3 +/- 2.5 mmHg), which correlated moderately well with the catheterization-determined mean diastolic gradient of 2-17 mmHg (average 7.3 +/- 4.0 mmHg), R = 0.74, standard error of the estimate (SEE) 1.70 mmHg, Y = 0.45 x + 2.00, P less than 0.001. The Doppler-derived TVA was 0.56-1.58 cm2 (average 1.06 +/- 0.32 cm2), which correlated well with the catheterization-determined TVA of 0.4-2.2 cm2 (average 1.06 +/- 0.46 cm2), R = 0.81, SEE = 0.20 cm2, Y = 0.56 x + 0.46, P less than 0.001. Of 12 patients undergoing right ventricular angiography, the angiographic and Doppler grades of tricuspid regurgitation matched exactly in six and differed by one grade in the remaining six. This study demonstrated that Doppler echocardiography compares very well to cardiac catheterization in the quantification of tricuspid stenosis and in the assessment of concomitant tricuspid regurgitation.

Adult↗
PubMed1989

Coronary artery disease, HDL cholesterol, and insulin-gene flanking sequences.

The relationship between coronary artery disease, HDL cholesterol, and the hypervariable region flanking the human insulin gene was studied in Saudi Arabian non-diabetic subjects (n = 68) and in patients with Type 2 diabetes (n = 35). A locus of insulin-gene-linked DNA polymorphism with three average size classes of alleles was found: a small class 1, a rare medium size class 2, and a large class 3 allele. In the total group of subjects (n = 103), those with the class 3 allele had a lower plasma HDL cholesterol concentration than those without the class 3 allele (0.93 +/- 0.26 vs 1.12 +/- 0.30 mmol l-1, 2p less than 0.003). No difference in genotype and allelic frequency was found between patients with and without coronary artery disease in the combined group of subjects, with and without diabetes. Similarly the genotype distribution was not different between non-diabetic subjects and patients with Type 2 diabetes in the combined group of subjects, both with and without coronary artery disease. In conclusion, the study did not confirm a previous study showing an association between the class 3 allele and atherosclerosis in a Caucasian population. However, the class 3 allele was associated with a low plasma HDL cholesterol concentration.

Alleles↗