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Biomedical subjects

A Dwyer

Publications and source records attributed to A Dwyer.

At least 19 recordsLinked to original sources
PubMed2000

Spectroscopic imaging of radiation-induced effects in the white matter of glioma patients.

External radiation therapy of brain tumors may cause adverse effects on normal brain tissue, resulting in severe neuropsychological and cognitive impairment. We investigated the late delayed radiation effects in the white matter (WM) using (1)H magnetic resonance spectroscopic imaging ((1)HMRSI). Nine glioma patients with local radiation-induced signal abnormalities in the T(2)-weighted MR images were studied with nine age- and sex-matched controls. The metabolite ratios in the radiation-induced hyper intensity area (RIHA) and in the normal appearing white matter (NAWM) of the patients were compared with respective WM areas of the controls. In RIHA, choline/creatine (Cho/Cr) was 17% decreased (1.22 +/- 0.13 vs 1.47 +/- 0.16, p = 0.0027, significant (s), unpaired Student's t test with Bonferroni correction) in the patients compared to the controls, while there was no difference in N-acetyl aspartate/Cr (NAA/Cr) (2.49 +/- 0.57 vs 2.98 +/- 0.32, p = 0.039) or NAA/Cho (2. 03 +/- 0.40 vs 2.04 +/- 0.17, p = 0.95). In NAWM, Cho/Cr was 24% decreased (1.21 +/- 0.15 vs 1.59 +/- 0.13, p < 0.0001, s) and NAA/Cho was 20% increased (2.49 +/- 0.49 vs 1.98 +/- 0.15, p = 0. 0082, s) in the patients compared to the controls, while there was no difference in NAA/Cr (2.99 +/- 0.46 vs 3.16 +/- 0.32, p = 0.38). NAA(RIHA)/NAA(NAWM) was 25% decreased (0.75 +/- 0.20 vs 1.00 +/- 0. 12, p = 0.0043, s) and Cr(RIHA)/Cr(NAWM) was 16% decreased (0.89 +/- 0.15 vs 1.06 +/- 0.10, p = 0.013, s) in the patients compared to the controls, while there was no difference in Cho(RIHA)/Cho(NAWM) (0.92 +/- 0.23 vs 0.98 +/- 0.10, p = 0.47). (1)HMRSI reveals widespread chemical changes in the WM after radiation therapy. In RIHA, there is loss of NAA, Cho, and Cr implying axonal and membrane damage and in NAWM, there is loss of Cho, reflecting membrane damage.

Adult↗
PubMed1998

Disease induction by virus derived from molecular clones of equine infectious anemia virus.

Equine infectious anemia virus (EIAV), a macrophage-tropic lentivirus, causes persistent infections of horses. A number of biologic features, including the rapid development of acute disease, the episodic nature of chronic disease, the propensity for viral genetic variation, and the ability for many infected animals to eventually control virus replication, render EIAV a potentially useful model system for the testing of antiretroviral therapies and vaccine strategies. The utility of the EIAV system has been hampered by the lack of proviral clones that encode promptly pathogenic viral stocks. In this report, we describe the generation and characterization of two infectious molecular clones capable of causing acute clinical syndromes similar to those seen in natural infections. Virus derived from clone p19/wenv17 caused severe debilitating disease at 5 to 7 days postinfection; initial febrile episodes were fatal in two of three infected animals. Virus derived from a second clone, p19/wenv16, caused somewhat milder primary febrile episodes by 10 to 12 days postinfection in two of two infected animals. Virus derived from both clones caused persistent infections such that some animals exhibited chronic equine infectious anemia, characterized by multiple disease episodes. The two virulent clones differ in envelope and rev sequences.

Acute Disease↗
PubMed1994

Reversible urinary retention secondary to excessive morphine delivered by an intrathecal morphine pump.

Reversible complication of intrathecal morphine delivered by an implanted pump is described in one patient. The patient was evaluated initially using a contrast CT of the thoracic spine as well as urodynamics studies. After decreasing the intrathecally administered morphine from 2 mg/24 hr to .5 mg/24 hr, the patient's neurogenic bladder reversed within 4 days. Implanted pumps to deliver intrathecal narcotic medications are being used currently to treat intractable pain. This is a case report of reversible urinary retention secondary to the intrathecal narcotic.

Aged↗
PubMed1991

Reconstruction of failed lumbar surgery with narrow AO DCP plates for spinal arthrodesis.

Forty-five patients underwent surgical reconstruction with transpedicular fixation of the lumbar spine with narrow AO DCP plates. Preoperatively, all patients underwent spinal imaging with either magnetic resonance imaging, computed tomography, or myelogram as well as provocative discography to determine the location and the number of symptomatic segments. The minimum follow-up in this series was 2 years. The determination of solid posterior fusion in the presence of plate instrumentation was difficult. The patients in the series were classified as having 1) solid fusion; 2) radiographic flaws within the posterolateral fusion without implant failure; or 3) frank pseudarthrosis with implant failure. Thirty-six (80%) of the patients had a solid fusion, 9 of whom required an additional anterior interbody fusion to obtain symptom control. Twenty percent of the patients in the series had radiographic evidence of reabsorption without implant failure. Four patients in the series (8.8%) had screw breakage, three of which required anterior interbody fusions. The highest rate of reabsorption and pseudarthrosis implant failure was in the 12 patients who had three-level instrumentation; 33% of these patients required anterior interbody fusion to obtain a solid arthrodesis. The average preoperative pain scale was 8.9, and the average postoperative pain scale was a 3.3. Twenty-two patients in the series were cigarette smokers and had a slightly lower fusion rate than non-smokers. They did, however, have a higher use of narcotics after surgery. Forty percent of the patients in this series continued to have radiculopathy after their reconstruction. This study demonstrates the utility of transpedicular fixation in salvage lumbar surgery in obtaining a solid arthrodesis with a beneficial clinical result. Anterior interbody fusions are highly successful in the management of pseudarthrosis and implant failure after transpedicular instrumentation.

Adult↗
PubMed1990

Gastric dysrhythmias and nausea of pregnancy.

Gastric dysrhythmias have been recorded from patients with a variety of nausea syndromes. The aim of this study was to measure gastric myoelectric activity in women with and without nausea during the first trimester of pregnancy. In 32 pregnant women gastric myoeletric activity was recorded for 30-45 min with cutaneous electrodes that yielded electrogastrograms (EGGs). Frequencies of the EGG waves were analyzed visually and by computer. Subjects rated their nausea at the time of EGG recording on a visual analog scale with 0 representing no nausea and 300 mm severe nausea. Gastric dysrhythmias were found in 26 pregnant subject: Seventeen had tachygastrias (EGG frequencies of 4-9 cpm), five had 1- to 2-cpm EGG waves, and four had flat-line patterns Mean nausea scores of the subjects with tachygastrias, 1- to 2-cpm, and flat-line patterns were 64.8 +/- 13, 93.4 +/- 23, and 77.2 +/- 36, respectively. Six pregnant subjects had normal 3-cpm EGG patterns, and their nausea scores averaged 2.8 +/- 1.1 (P less than 0.05 compared with nausea scores in subjects with tachygastrias, 1- to 2-cpm, and flat-line rhythms). Six subjects with gastric dysrhythmias during pregnancy were restudied after delivery; each of these subjects had normal 3-cpm EGG patterns and none had nausea. Thus, gastric dysrhythmias are objective pathophysiologic events associated with symptoms of nausea reported during the first trimester of pregnancy.

Adult↗
PubMed1990

Cervical zygapophyseal joint pain patterns. I: A study in normal volunteers.

The pain patterns evoked by stimulation of normal cervical zygapophyseal joints were determined in five volunteers. Under fluoroscopic control, joints at segments C2-3 to C6-7 were stimulated by distending the joint capsule with injections of contrast medium. Each joint produced a clinically distinguishable, characteristic pattern of pain, which enabled the construction of pain charts that putatively could be of value in determining the segmental location of symptomatic joints in patients presenting with cervical zygapophyseal pain.

Cervical Vertebrae↗
PubMed1990

Cervical zygapophyseal joint pain patterns. II: A clinical evaluation.

To test the predictive value of segmental pain charts, ten patients with suspected cervical zygapophyseal pain were studied. Their pain distribution was recorded on a body diagram, and using pain charts derived from studies on normal volunteers, predictions were made by two observers of the segmental location of the symptomatic joint. Correct predictions were made in all nine patients who were shown to have symptomatic joints on the basis of diagnostic joint blocks. The results vindicate the accuracy of pain charts for predicting the segmental location of symptomatic joints in patients with cervical joint pain.

Cervical Vertebrae↗
PubMed1988

Computerized tomographic prediction of extraluminal spread and prognostic implications of lesion width in esophageal carcinoma.

The use of preoperative computed tomographic (CT) scans of the chest in carcinoma of the esophagus to associate preoperative staging with postoperative survival is controversial. Thirty-two patients who underwent esophagectomy and reconstruction were examined with respect to a variety of variables available on preoperative evaluation, including lesion width on CT scan, lesion length on CT scan, and barium esophagogram. Each variable was evaluated for its ability to predict the presence of extraesophageal spread of tumor, as determined pathologically by logistic regression analysis. Lesions greater than 3.0 cm in width by CT scan were associated with a significantly higher incidence of extraesophageal spread. Tumor location, gender, histologic grade, presence of in situ lesions, vascular invasion, eosinophilia, nodal metastases, and preoperative chemotherapy had no predictive value for survival. Duration of survival was affected by the presence of esophageal spread of disease and lesion width. These results indicate that preoperative CT scanning can predict extraesophageal spread of tumor, and this is associated with overall survival.

Actuarial Analysis↗
PubMed1988

Effects of acetylsalicylic acid on electromechanical activity of in vivo rabbit ileum.

Aspirin has antisecretory and ulcerogenic properties in the gastrointestinal tract. The aim of this study was to determine the effects of acetylsalicylic acid (ASA) on the electrical and mechanical activity of the ileum in anesthetized New Zealand White rabbits. Ileal electromechanical activity was recorded from serosal electrodes and a miniature intraluminal balloon. Thirty minutes after injection of ASA (30, 60 and 100 mg/kg intravenous) significant and dose-dependent increases in the percentage of slow waves with action potentials were observed when compared with saline-infected animals. The onset of action potentials correlated with phasic increases in intraluminal pressure, indicating the onset of circular muscle contractions. Injection of 15 mg/kg ASA, sodium salicylate (100 mg/kg intravenous) or saline had no effect on baseline action potential activity. Prostaglandin E2 (PGE2) (5 and 10 micrograms/kg intravenous) significantly increased slow-wave frequency and decreased ASA-induced action potential activity. This study demonstrates that (1) ASA, but not sodium salicylate, stimulates phasic ileal action potential and contractile activity and (2) in ASA-treated animals, PGE2 produces differential effects on in vivo slow-wave frequency and action potential activity.

Action Potentials↗
PubMed1987

A simplified plan for follow-up of patients with colon and rectal cancer supported by prospective studies of laboratory and radiologic test results.

Reports of prolonged survival in patients with recurrent colon or rectal cancer following a reoperative surgery suggest that early diagnosis of locally persistent or limited metastatic disease may save some patients. To determine which laboratory and radiologic tests were useful, a prospective comparison of all currently available modalities was begun in 1978. Sixty-six patients at high risk for recurrent large-bowel cancer were studied. At present, mean follow-up is at 4 1/2 years. Protocol studies included monthly carcinoembryonic antigen (CEA) assays for 3 years and then at 3-month intervals for 2 more years. A review of symptoms and a physical examination were performed every 4 months for 3 years and then every 6 months for 2 more years. Computerized tomograms of the abdomen, full lung tomograms, and liver/spleen scintigrams were obtained every 4 months for 3 years and then annually for 2 more years. Intravenous pyelography, barium enema, and bone scintigraphy were performed yearly for 5 years. Thirty-three recurrences were observed in 31 patients. A progressive rise in serial CEA values was the first indication of recurrence in 22 of 33 patients (67%), review of symptoms and physical examination in seven of 33 (21%), CT scan in two of 33, and bone scintigraphy and full lung tomography each in one of 33 patients. Serial CEA assays and routine visits to a physician's office were the most useful tests in this study population. Use of a simplified follow-up plan will result in the earliest detection of recurrent colon cancer.

Adult↗
PubMed1986

Treatment of precocious puberty in the McCune-Albright syndrome with the aromatase inhibitor testolactone.

The McCune-Albright syndrome is characterized by café au lait spots, fibrous dysplasia of bones, and sexual precocity. Girls with precocious puberty due to this syndrome have episodic increases in serum estrogen levels together with the formation of large ovarian cysts. The serum gonadotropin levels are typically suppressed, and the precocious puberty has not responded to treatment with long-acting analogues of luteinizing hormone-releasing hormone (LHRH). Encouraged by our initial success in a pilot study of one patient, we have now treated five girls with the McCune-Albright syndrome with the aromatase inhibitor testolactone, which blocks the synthesis of estrogens. Testolactone decreased the levels of circulating estradiol (P less than 0.05) and the ovarian volume (P less than 0.05), and there was a return to pretreatment levels after testolactone was stopped. During treatment, the peak responses of luteinizing hormone and follicle-stimulating hormone to stimulation by LHRH rose above suppressed pretreatment levels--significantly above pretreatment levels for follicle-stimulating hormone (P less than 0.02)--and then returned to pretreatment levels after testolactone was discontinued. Growth rates fell in three patients during treatment but could not be assessed in the other two because of bone deformities. The mean rate of bone maturation decreased and menses stopped in three of the four girls who were menstruating regularly. We conclude that testolactone is an effective treatment of precocious puberty in the McCune-Albright syndrome.

Aromatase Inhibitors↗
PubMed1986

Luteinizing hormone releasing hormone analogue therapy for central precocious puberty. Long-term effect on somatic growth, bone maturation, and predicted height.

The long-acting analogue of luteinizing hormone releasing hormone, D-Trp6-Pro9-NEt-LHRH (LHRHa), is effective in the short-term treatment of central precocious puberty. We report the results of two to four years of LHRHa therapy in 27 children with this disorder. Secondary sex characteristics regressed in most patients. Sex steroid levels and basal and LHRH-stimulated gonadotropin levels remained suppressed compared with pretreatment values. Linear growth rates decreased from 11.0 +/- 0.8 (SEM) cm/yr before treatment to 5.7 +/- 0.4 cm/yr at two years of treatment and 3.7 +/- 0.7 cm/yr at four years of treatment. Predicted heights by the Bayley-Pinneau method increased from 156.4 +/- 2.0 cm before treatment to 162.3 +/- 2.3 cm at two years and 163.4 +/- 2.4 cm at three years. Five patients treated for four years had a mean increase in predicted height of 5.5 cm. To date no adverse effects have been observed. However, the ultimate safety of this analogue is not known. We conclude that LHRHa appears to be an effective long-term therapy for central precocious puberty.

Body Height↗
PubMed1986

Dose-response effects of indomethacin and PGE2 on electromechanical activity of in vivo rabbit ileum.

We determined dose-response characteristics of indomethacin and prostaglandin E2 on the myoelectric activity in ileum of anesthetized New Zealand White rabbits. Monopolar electrodes and an intraluminal saline-filled catheter were used to simultaneously record electrical and mechanical activity. Thirty minutes after injection of 3.0, 5.0, and 10.0 mg/kg indomethacin, the percentage of slow waves with action potentials increased significantly from 10% to over 80%; at 60 min action potential activity decreased but remained dose dependent and significantly greater than controls. Action potential activity correlated with phasic increases in intraluminal pressure. Low-dose indomethacin (1.5 mg/kg) did not significantly alter action potential activity. Action potential activity induced by indomethacin (5 mg/kg) decreased dose dependently after infusion of prostaglandin E2 (PGE2, 1-28 micrograms/kg). In summary, dose-dependent action potential activity was induced by indomethacin and reversed by PGE2. Endogenous inhibitory prostaglandins (PGE2 or others) appear to modulate activity of specific excitatory neuromuscular circuits in in vivo ileum.

Action Potentials↗
PubMed1985

Plasma vitamin C and uterine cervical dysplasia.

Plasma concentrations of vitamin C were determined in a case-control study of women (n = 80) who had sought a Papanicolaou test in the Bronx Municipal Hospital Center. Controls (n = 34) were women having negative cytologic tests, negative colposcopic findings, and no known gynecologic dysfunction. Cases (n = 46) were defined as women who had either one positive or two consecutive suspicious Papanicolaou smears in a 12-month period. The mean concentration of vitamin C in the plasma was significantly lower in the cases than in the controls (0.36 versus 0.75 mg/dl, p less than 0.0001). Cases were further stratified according to the histopathologic diagnosis. The data direct attention to a possible etiologic association of vitamin C in human cervical epithelial abnormalities. A clinical trial with vitamin C intervention is suggested.

Adult↗
PubMed1985

Chemoprevention of cervix cancer: Phase I-II: A feasibility study involving the topical vaginal administration of retinyl acetate gel.

A Phase I-II clinical trial has been conducted with a retinyl acetate (RA) gel applied cervicovaginally in women having a histopathologic lesion diagnosed as mild or moderate dysplasia. With informed consent, volunteer subjects were observed and followed with Pap smears and colposcopy in a standardized protocol involving a self-administered 7-day treatment course for three successive menstrual cycles. Varying dosages of RA including placebo, 3, 6, 9, and 18 mg per 6 g of an inert vehicle were employed. A total of 50 subjects were monitored for local and systemic side effects. No intolerable side effects or disturbing toxicity was reported or detected at any of these doses. With the 18-mg dosage, significant discomfort was reported by all women. Despite associated side effects and a considerable patient effort involved in carrying out the self-administration of the gel, a high level of compliance was achieved in this trial. It has been established that women will voluntarily participate in an intervention clinical trial to determine whether retinyl acetate is an alternative method of therapy of presumed precancerous lesions of the cervix. The analysis of the side effects of the gel at the various dosage concentrations favors the selection of the 9-mg dosage for a multicenter Phase III clinical trial to determine efficacy.

Colposcopy↗
PubMed1985

Evaluation of noninvasive tests for the preoperative staging of carcinoma of the esophagus: a prospective study.

A prospective study was undertaken to define the usefulness of conventional full-lung linear tomography, radionuclide liver plus spleen and bone scans, and thoracic and abdominal computed tomography for the preoperative staging of carcinoma of the esophagus. Thirty-three patients with carcinoma of the esophagus were studied. The computed tomographic (CT) scan of the thorax and upper abdomen was the single most accurate noninvasive study. With computed tomography, the relationship of the tumor to the tracheobronchial tree was the feature most useful in predicting local resectability. In all patients with the finding of tracheobronchial compression by the tumor, the tumor could not be resected completely. The predictive value of this CT finding in patients with locally unresectable tumor was high (0.83), indicating its usefulness in assessing unresectability. The CT finding of visible separation between tumor mass and tracheobronchial tree was present in 10 of 14 patients with locally resectable tumor (predictive value, 0.63). However, tumor abutting the tracheobronchial tree without compression was a poor predictor of unresectability (predictive value, 0.36). The radionuclide bone scan was the only other noninvasive study to demonstrate a metastasis not evident by CT scan. The combination of chest and abdominal CT scan, bone scan, and bronchoscopy before operation will accurately stage the majority of patients with esophageal cancer but no noninvasive test is of sufficient reliability to exclude patients from operative resection if otherwise indicated.

Adenocarcinoma↗