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Biomedical subjects

S E Mitchell

Publications and source records attributed to S E Mitchell.

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

Digital subtraction spinal cord angiography in patients undergoing thoracic aneurysm surgery.

Thoraco-abdominal aortic replacement can be associated with a high incidence of paraplegia. Because the major source of blood supply to the thoraco-abdominal spinal cord is through the anterior spinal artery of Adamkiewicz, reimplantation of intercostal and lumbar arteries could reduce the risk of this operation. We used intraarterial digital subtraction angiography (DSA) for preoperative localization of the anterior spinal artery in 12 patients. This vessel was successfully located in 9 patients, with DSA providing good quality images in all patients. Preoperative knowledge of the origin of this vessel was helpful in the planning of the operation in all patients, but its efficacy as a routine procedure was not established.

Adult↗
PubMedDate not supplied

Percutaneous embolotherapy of adolescent varicocele: results and long-term follow-up.

PURPOSE: The authors evaluated the technical success and immediate and long-term results of percutaneous varicocele embolotherapy in the adolescent population. PATIENTS AND METHODS: Fifty-nine adolescent patients were referred for outpatient spermatic venography and possible varicocele embolotherapy. Embolization was attempted with use of detachable balloons, coils, "sandwiched" dextrose, or a combination of these techniques. Data regarding follow-up were obtained through telephone interviews or mailed questionnaires. RESULTS: The technical success rate for spermatic vein occlusion was 90%. Follow-up, obtained in 79% of the patients, ranged from 6 months to 8.75 years (mean, 4 years). Thirty-nine of 42 patients (93%) reported disappearance (n = 31) or only a slight, asymptomatic residual varicocele (n = 8). Three patients reported a recurrence of their varicocele. Complications occurred in three of 59 cases (5%), none had any long-term sequelae. In six cases, embolization was not feasible because of multiple collateral vessels or venous spasm. CONCLUSIONS: Given the convenience of performing the procedure on an outpatient basis, the rapid recovery time, and long-term success and complication rates comparable to those with surgical ligation, we believe spermatic venography and percutaneous embolization is the treatment modality of choice for adolescent varicocele.

Adolescent↗
PubMedDate not supplied

Percutaneous varicocele occlusion: long-term follow-up.

PURPOSE: The authors summarize their 11-year experience with percutaneous varicocele occlusion at the Johns Hopkins Hospital. PATIENTS AND METHODS: Data were obtained from the patients' medical records and from a mailed questionnaire. Most of the data analysis is based on the 182 patients who responded to the questionnaire. RESULTS: Most of the occlusions were performed for infertility. The mean length of time couples had been attempting to conceive was approximately 44 months. Occlusion was technically successful in 95.7% of cases. Patients were followed up for a mean period of 59 months. Success is difficult to define because many patients and/or their wives received additional infertility treatment. Fifty-seven percent of all couples and 60% of a subgroup of couples who received no other treatment eventually conceived. CONCLUSION: Percutaneous occlusion is a well-established treatment for varicoceles. Pregnancy rates and recurrence rates are comparable to those following surgical varicocelectomy. It is unlikely that resultant pregnancies occur from random chance alone.

Adult↗
PubMedDate not supplied

Repeat dilation of Palmaz stents in pulmonary arteries: study of safety and effectiveness in a growing animal model.

PURPOSE: This study assessed the technical feasibility and safety of repeat dilation of Palmaz stents in growing pulmonary arteries. MATERIALS AND METHODS: Palmaz stents (1.2 cm long) were placed percutaneously into the pulmonary arteries of 20 newborn lambs. After 4 months, pulmonary arteriography was performed. Where vessel growth in excess of stent diameter had created a stenosis (> 15%), stents were dilated again percutaneously. Six months later, pulmonary arteriography was performed, before the animal was killed and histologic examination performed. RESULTS: Twenty-four pulmonary artery stent placements were attempted; 23 were successful. One stent placement was unsuccessful owing to stent displacement from the balloon. Acute complications included branch pulmonary artery occlusion (n = 3) and stent displacement from the delivery balloon (n = 2). At 4 months, the desired degree of stenosis (> 15%) was achieved in 11 animals. The average stenosis was 35% (standard deviation, 16%; range, 17%-66%). The mean predilation stent diameter was 6 mm +/- 1.1 (range, 4-8 mm), and the final diameter of 8 mm +/- 1.4 (range, 6-10 mm), represented a 35% mean increase (P < .001). Complications included stent (n = 1) and branch vessel (n = 1) thrombosis. At 6-month follow-up, all stents were patent. Areas of previously noted branch thrombosis were fully recanalized in all cases. At histologic inspection, only a thin layer of neointima was found on the stents. CONCLUSION: Repeat dilation of Palmaz stents may be safely performed in growing pulmonary arteries in an animal model. Neointimal hyperplasia is minimal in pulmonary artery stents.

Animals↗
PubMedDate not supplied

Visual and quantitative computerized assessment of disease severity on peripheral angiograms.

PURPOSE: This study was designed to determine and compare the intra- and interobserver variability of visual and computerized assessment of peripheral arterial disease (PAD) severity from lower extremity angiograms, and to correlate quantitative angiographic measures with clinical predictors of PAD. PATIENTS AND METHODS: Peripheral angiograms of 13 segments from the ilio-femoral-popliteal system were evaluated on two separate occasions by nine radiologists and with a quantitative computerized method. In a separate study, images from 18 patients undergoing diagnostic lower extremity angiography were analyzed with use of quantitative angiography and the results were compared with clinical and lipid risk factors. RESULTS: The data demonstrate that computerized assessment of peripheral angiograms is associated with lower intra- and interobserver variability than visual assessment of the same films. Despite this, there was excellent intraobserver and good interobserver agreement on the presence or absence of a severe lesion with visual assessment. Quantitative computerized measures of disease severity correlate with several known predictors of large vessel PAD. CONCLUSION: Computerized assessment of peripheral angiograms may be a useful tool in the clinical and investigational evaluation of PAD.

Aged↗
PubMedDate not supplied

Biliary manometry versus clinical trial: value as predictors of success after treatment of biliary tract strictures.

PURPOSE: To evaluate the biliary manometric-perfusion test (BMPT) and clinical trial as predictors of long-term success after percutaneous and surgical treatment of biliary tract strictures. PATIENTS AND METHODS: After percutaneous intervention or surgical repair of extrahepatic bile duct strictures, 43 patients underwent long-term biliary intubation (mean, 13 months) with 61 internal-external stents. Before removal of the stents, all 43 patients underwent a BMPT (n = 65) and 24 underwent a 2-3-week clinical trial (n = 27) with stents positioned above the treated region. Patients were followed up 1-46 months (mean, 16 months) after stent removal, with clinical outcome determined by means of physical examination, biochemical evaluation, chart review, and telephone interview. RESULTS: With logistic regression analysis, the BMPT and clinical trial were shown to have equal predictive value in determining treatment success or failure. Eighty-four percent of the clinical outcomes were correctly predicted with BMPT, versus 88% for the clinical trial. Kaplan-Meier survival curve analysis demonstrated the probability of remaining stricture free at 1 year after passing a BMPT and after passing a clinical trial to be 90% and 86% (P = .55), respectively. CONCLUSION: BMPT and clinical trial have similar capabilities in the prediction of long-term patency after treatment of benign biliary tract strictures, but the BMPT is less costly and time consuming for the patient.

Anastomosis, Roux-en-Y↗
PubMedDate not supplied

The biliary manometric perfusion test and clinical trial--long-term predictive value of success after treatment of bile duct strictures: ten-year experience.

PURPOSE: To evaluate the long-term predictive value of the biliary manometric perfusion test and clinical trial for determining patency after treatment of bile duct strictures. MATERIALS AND METHODS: One hundred four patients with benign biliary disease were treated with surgical (n = 59) or percutaneous (n = 45) techniques followed by intubation with large-caliber silicone stents. Prior to removal of the biliary stents, patients underwent a biliary manometric perfusion test (n = 168) and/or a clinical trial (n = 105) to objectively and subjectively evaluate the treated site for potential long-term patency. The patients were followed up for 1-87 months, and clinical outcomes were determined. Kaplan-Meier survival curves were generated for three patient groups, including those who (i) passed either test, (ii) failed either test, and (iii) failed either test, were re-treated, and passed either test. RESULTS: Final successful treatment outcomes were documented in 47 (92%) surgically and 31 (86%) percutaneously treated patients, respectively (P = .001). The Kaplan-Meier survival curves determined the probability of patency at 0, 2, 4, and 6 years after treatment to be 1.0, .96, .78, and .59, respectively, after passing a biliary manometric perfusion test; and 1.0, .91, .78, and .78, respectively, after passing a clinical trial (P > .10). The probability of patency at 4 years after treatment was .45 after failing a biliary manometric perfusion test, and at 6 months was zero after failing a clinical trial (P = .001 and .001, respectively, vs the same test in the passing group). Seventy-nine percent of patients who failed either test required an additional period of repeated stent placement or reoperation. After repeated treatment, the probability of patency at 0-4 years was .80 and .88, respectively, for the biliary manometric perfusion test and clinical trial (P > .05 and P > .10, respectively, vs same test in the group that passed). CONCLUSION: Patients who initially pass either the biliary manometric perfusion test or clinical trial have a significantly increased probability of patency versus those who fail; however, patients who fail either test and who then receive definitive additional treatment have a similar probability of patency as those who initially pass. Although the log rank test demonstrated the Kaplan-Meier survival curves from the biliary manometric perfusion test and clinical trial not to be significantly different in any of the three groups (ie, passing, failing, re-treated), the biliary manometric perfusion test is recommended over the clinical trial because of its simplicity, immediate results, and predicted cost savings.

Adult↗
PubMedDate not supplied

RAPD analysis reveals genetic variability among sexual and Apomictic Paspalum dilatatum poiret biotypes.

Paspalum dilatatum is a valuable forage grass in the subtropics. This species consists of several sexual (tetraploid) and apomict (penta- and hexaploid) biotypes. It has been proposed that the presence of a genome of unknown origin, the X genome, is responsible for apomixis in penta- and hexaploid biotypes. Here we evaluated the utility of random amplified polymorphic DNA (RAPD) markers for discriminating sexual and apomictic P. dilatatum biotypes. DNA samples from nine accessions, including P. intermedium, P. juergensii, and P. dilatatum (ssp. flavescens, and the common and Uruguayan biotypes) were analyzed with 86 RAPD primers. Three hundred sixty-two fragments were scored and genetic similarity estimates revealed that the penta- and hexaploid biotypes were highly similar (S(D) > or = 0.913). Forty RAPDs were unique to the penta- and hexaploid biotypes. Overall RAPD markers were useful for assessing genetic variation among closely related P. dilatatum genotypes as well as generating putative X genome markers.

DNA Primers↗
PubMedDate not supplied

Mitochondrial DNA variation within and between two species of neotropical anopheline mosquitoes (Diptera:Culicidae).

We analyzed variation in mitochondrial DNA (mtDNA) of two neotropical mosquitoes, Anopheles rangeli (n = 181) and A. trinkae (n = 45), with very different distribution patterns in Latin America, to assess species boundaries for these putative sister taxa and to examine population genetic structure. Phylogenetic analyses revealed (1) support for the monophyletic origin of each species; (2) diagnostic restriction site differences between the species; (3) geographic partitioning of haplotypes by country in A. rangeli from Bolivia, Ecuador, and Venezuela compared with considerable overlap in haplotypes of A. trinkae from Bolivia and Ecuador; and (4) similar levels of mean haplotype and nucleotide diversity in both species, but lower levels of mean nucleotide divergence in A. trinkae compared with A. rangeli. We hypothesize that higher maternal gene flow and lower divergence in A. trinkae are most likely due either to a distinctive matrilineal history or to a smaller effective population size, which may have been influenced by a smaller, essentially linear geographic range along the eastern flank of the Andes. In the cladistic analysis of A. rangell, the Bolivian haplotypes appear to be more derived than those from Ecuador or Venezuela, yet there is no evidence to support the hypothesis of a recent range expansion from Ecuador into Bolivia.

Animals↗
PubMedDate not supplied

Chromosome-linkage group correlation in Anopheles quadrimaculatus (Say).

Brown body (bw) is a recessive, autosomal mutant in Anopheles quadrimaculatus (Say). Independent linkage was noted between stripe (st+) and bw, and an epistatic interaction was noted for the altered expression of st+ in bw homozygotes. Reciprocal autosomal translocations and a Y-autosome translocation were used to assign bw to the left arm of chromosome 2 and st+ to the right arm of chromosome 3.

Animals↗
PubMedDate not supplied

A red stripe mutant and its relationship in an allelic series in Anopheles quadrimaculatus.

A red stripe phenotype from a natural population of Anopheles quadrimaculatus (Say) was introduced into a laboratory colony by induced copulation. Genetic crosses made with the red stripe (strd) mutant showed it to be a member of an allelic series with stripe (st+) and nonstripe (st). The strd character is condominant with st+, and st is recessive to both strd and st+.

Alleles↗
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EMS-induced mutations in Anopheles quadrimaculatus (Say), species A.

Three new mutants were induced in a laboratory strain of Anopheles quadrimaculatus (Say), species A, by feeding adult males ethyl methanesulfonate (EMS). Rose eye (ro) is a recessive X-linked trait. Short antenna (Sa) and melanotic (Mel) are dominant autosomal traits that are lethal in the homozygous condition. Linkage crosses and X-autosome translocations were used to assign short antenna to the right arm of chromosome 3 about 45 map units proximal to stripe (st+), and melanotic was located on chromosome 2 near the centromere.

Animals↗
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Assignment of two enzyme loci to the X chromosome of Anopheles quadrimaculatus species A.

Analysis of isozyme variability in four natural populations of Anopheles quadrimaculatus Species A indicated that the loci for Malic enzyme (Me) and Mannose phosphate isomerase-1 (Mpi-1) are on the X chromosome. There were female heterozygotes, but no male heterozygotes were observed. Strains fixed for fast- and slow-migrating allozymes were devised and crossed. Progeny phenotypes conformed to expectations for sex linkage; female progeny were heterozygous, and male progeny were hemizygous for the maternal allele. The three-point cross, using the Me and Mpi-1 loci with the sex-linked mutant rose eye (ro), established the gene sequence Mpi-1-11.1-Me-40.8-ro.

Animals↗
PubMedDate not supplied

Population differentiation of the malaria vector Anopheles aquasalis using mitochondrial DNA.

Populations of the malaria vector Anopheles aquasalis from Venezuela, Trinidad, and Brazil were analyzed using restriction enzyme digestion of mitochondrial DNA (mtDNA). The five enzymes surveyed yielded 12 mtDNA haplotypes. Three restriction endonuclease profiles (Bcl I, Eco RI, and Hind III) differentiated the Venezuelan and Trinidadian A. aquasalis from two Brazilian populations. Estimates of mtDNA sequence divergence between the Venezuelan/Trinidadian populations and each Brazilian population (0.023-0.032), as well as divergence between the two Brazilian populations (0.030), were within the range of interspecific distances calculated for members of anopheline species complexes. Ribosomal DNA (rDNA) restriction profiles of the A. aquasalis populations examined were identical.

Animals↗
PubMedDate not supplied

Clinical implementation of electrical impedance tomography with hyperthermia.

We describe the use of electrical impedance tomography (EIT) for non-invasive thermal imaging in conjunction with a clinical treatment of a superficial scalp lesion utilizing a spiral microstrip antenna. This is our first reported use of EIT with a clinical hyperthermia treatment and perhaps the first world-wide. The thermal measurements recorded during treatment compare favourably with the images reconstructed from impedance data gathered during heating. A linear relation, measured in phantom material, between the change in temperature with the change in reconstructed impedance was assumed. The average discrepancy between the measured temperature changes with the temperatures reconstructed from the impedance changes was 1.4 degrees C, with the maximum being 8.9 degrees C. These preliminary data suggest that impedance changes can be measured during hyperthermia delivery and temperature estimates based on these observed changes are possible in the clinical setting. These findings also point to the complex, yet critical nature of the impedance versus temperature relationship for tissue in vivo. The reconstructed thermal images may provide complementary information about the overall thermal damage imposed during heating. Based on this initial clinical experience we feel that EIT has great potential as a viable clinical aid in imaging the temperature changes imposed during hyperthermia.

Electric Impedance↗