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R C Duncan

Publications and source records attributed to R C Duncan.

At least 55 records · Page 3Linked to original sources
PubMed1993

Prochlorperazine as a doxorubicin-efflux blocker: phase I clinical and pharmacokinetics studies.

Doxorubicin (DOX) efflux in drug-resistant cells is blocked by phenothiazines such as trifluoperazine (TFP) and prochlorperazine (PCZ) in vitro. The present phase I study was conducted in 13 patients with advanced, incurable, nonhematologic tumors to determine whether PCZ plasma levels high enough to block DOX efflux could be achieved in vivo. The treatment schedule consisted of prehydration and i.v. administration of 15, 30, 50, and 75 mg/m2 PCZ followed by a standard dose of 60 mg/m2 DOX. The hematologic toxicities attributable to DOX were as expected and independent of the PCZ dose used. Toxicities attributable to PCZ were sedation, dryness of the mouth, cramps, chills, and restlessness. The maximal tolerated dose (MTD) of PCZ in this schedule was 75 mg/m2. Pharmacokinetic analysis indicated a large interpatient variation in peak plasma PCZ levels that ranged from 95 to 1100 ng/ml. The three plasma half-lives of PCZ were: t1/2 alpha (+/- SE), 20.9 +/- 5.3 min; t1/2 beta, 1.8 +/- 0.3 h; and t1/2 gamma, 21.9 +/- 5.3 h. The volume of distribution (Vd), total clearance (ClT), and area under the curve (AUC) for PCZ were 2254 +/- 886 l/m2, 60.2 +/- 13.5 l m-2 h-1, and 1624 +/- 686 ng ml-1 h, respectively. DOX retention in tumor cells retrieved from patients during the course of therapy indicated the appearance of cells with enhanced DOX retention. The combination of DOX and high-dose i.v. PCZ appeared to be safe, well tolerated, and active in non-small-cell lung carcinoma.

Aged↗
PubMed1993

Decision-making orientation and AIDS-related knowledge, attitudes, and behaviors of Hispanic, African-American, and white adolescents.

How adolescents' personal sense of directedness (i.e., peer, parent, or self-directed orientation) affects the decision-making processes of adolescent students regarding AIDS-related knowledge, attitudes, beliefs, behaviors, and skills (KABBS) is examined. The sample consisted of 10th-grade students in 8 public high schools (N = 2,515) in Dade County (greater Miami), Florida. The findings showed that decision-making orientation and directedness was a significant predictor of AIDS-related KABBS of adolescents. Overall, the level of AIDS-related KABBS that were associated with low risk was found significantly more often among self-directed students and least often among peer-directed students. The findings of this study suggest that future preadult health-risk research should incorporate the concept of differences of information processing across adolescents.

Acquired Immunodeficiency Syndrome↗
PubMed1993

The accuracy of the histological classification of lung carcinoma and its reproducibility: a study of 75 archival cases of adenosquamous carcinoma.

The classification of lung carcinoma into a small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC), is highly reproducible. There are few studies on the reproducibility of subtyping NSCLC, with anecdotal reports on the subtype of adenosquamous carcinoma. We undertook a study of 75 cases archived as adenosquamous carcinoma. All cases were accepted as NSCLC on independent review by three pathologists utilizing the 1982 World Health Organization (WHO) classification criteria. The acceptance rate of adenosquamous carcinoma by the three pathologists was 65%, 28%, and 65%. Cases not accepted as adenosquamous fell into the different subtypes of NSCLC, with a concordance rate between each pair of pathologists of 49%, 61% and 43%, indicating poor agreement between pathologists. The study confirms the high reproducibility of the classification into SCLC and NSCLC; it shows poor concordance for all subtypes of NSCLC with poor reproducibility of diagnosis of adenosquamous carcinoma as specified by the 1982 WHO classification. Physicians dealing with lung carcinoma should be aware of this limitation of classification.

Carcinoma, Adenosquamous↗
PubMed1992

Electromyographic activity of the jaw-closing muscles in patients with osseointegrated implant fixed partial dentures.

The control of postural and synergistic jaw reflexes involves interrelated sensory input from receptors in the jaw muscles, temporomandibular joint, periodontal ligament, and mucosa. This investigation was done to determine whether a decrease in intraoral sensory afferent discharge significantly altered the onset of the jaw-unloading reflex. The subject population consisted of three groups with 10 subjects in each group. Group 1 had maxillary and mandibular natural teeth and group 2 consisted of edentulous subjects with complete dentures. Group 3 consisted of edentulous subjects with maxillary complete dentures and mandibular complete implant-supported prostheses. The unloading reflex was initiated with a muscle-unloading device and recorded with a storage oscilloscope. A one-way analysis of variance found no significant differences in the unloading-reflex latency for the masseter or temporal muscles among the three experimental groups (p less than 0.05).

Dental Implantation, Endosseous↗
PubMed1992

The significance of brain temperature in focal cerebral ischemia: histopathological consequences of middle cerebral artery occlusion in the rat.

The purpose of this study was to determine the effect of selective modulation of brain temperature in the experimental settings of permanent and reversible middle cerebral artery (MCA) occlusion in Sprague-Dawley rats. Three models of proximal MCA occlusion were used, in which the effect of brain-temperature modulations could be studied. These included (a) permanent MCA occlusion with an initial 30-min period of hypotension (30 or 36 degrees C x 4 h), (b) permanent MCA occlusion alone (30, 36, or 39 degrees C x 2 h), and (c) 2 h of reversible MCA occlusion (30, 36, or 39 degrees C x 2 h). In the transient MCA occlusion series, intra- and postischemic cortical blood flow was assessed using a laser-Doppler flowmeter placed over the dorsolateral cortex. After a 3-day survival, all rats were perfusion fixed for histopathological analysis and the determination of infarct volume. In animals with permanent MCA occlusion plus hypotension, no significant difference in infarct volume was demonstrated between the 30 and 36 degrees C groups. In rats with permanent MCA occlusion without hypotension, significant differences in infarct volume were again not demonstrable, but an interaction between infarct area and temperature class was shown by repeated-measures analysis, indicating that hypothermia altered the topographic pattern of the cortical infarct. With 2 h of reversible MCA occlusion, there was a statistically significant reduction in infarct volume in the 30 degrees C group compared to 39 degrees C rats. Although intra- and postischemic CBF were not significantly different among the three temperature groups, the cortical infarct volume was positively correlated with postischemic CBF. The postischemic CBF, in turn, was positively correlated to the intraischemic brain temperature and was negatively correlated to CBF during the ischemic period. These findings demonstrate that moderate manipulations of brain temperature have a greater influence on the resulting cortical infarction in the setting of transient focal ischemia than in the context of permanent vascular occlusion.

Animals↗
PubMed1992

The increasing recognition of adenosquamous lung carcinoma (1977-1986).

A retrospective analysis of the data in the tumor registry on all 103 patients with adenosquamous lung carcinoma diagnosed and treated at our center between 1977 and 1986 was performed. The history of tobacco use was available for 100 patients (72 men and 28 women). Ninety-four percent of the patients (100% of men and 79% of women) were smokers, suggesting that adenosquamous carcinoma may be a Kreyberg I type of lung carcinoma. The gender, race, and age distributions in adenosquamous carcinoma were similar to other histologic subtypes of lung carcinoma. Patients less than 45 years old constituted 10%; 45-54 years old, 24%; 55-64 years old, 34%; 65-74 years old, 25%; and greater than 75 years, 7%. In the 95 patients whose stage at the time of diagnosis was known, 11% had local stage; 28%, regional; and 61%, distant stage. The 1-, 2- and 5-year survival of the 103 patients were 27%, 18%, and 8%, respectively. Survival was related to stage. Local stage had the best survival, and greater than 50% of patients were alive at 4 years. Regional stage had an intermediate median survival of 10 months but no survivors at 5 years. Distant stage had the worst median survival (5 months), and one patient (2%) was alive at 3 years. There was a significant increase (two- to three-fold) in the frequency of adenosquamous carcinoma over the 10-year study period, 1977-1986.

Adenocarcinoma↗
PubMed1992

Transcranial Doppler assessment of cerebral flow velocity during cognitive tasks.

BACKGROUND AND PURPOSE: The purpose of this study was to assess the ability of transcranial Doppler ultrasonography to detect selective circulatory changes during cognitive activity. METHODS: We measured cerebral artery flow velocity in 21 normal volunteers by transcranial Doppler ultrasonography during rest followed by cerebral activation. Mean and peak systolic flow velocities of the anterior, middle, and posterior cerebral arteries were measured during the performance of a commercial video game. We also measured flow velocity of the anterior cerebral arteries in 18 subjects during a mental arithmetic task. Serial measurements of the right and left sides were made with a headband with two probes. RESULTS: We observed a global increase in the flow velocity above baseline measurements during task performance. During the video game, both middle cerebral arteries (t = 2.6, p = 0.02 for the left; t = 3.3, p = 0.004 for the right) and the left posterior cerebral artery (t = 2.2, p = 0.004) had selective increase in mean flow velocity compared with the ipsilateral anterior cerebral artery. This selective activation was most prominent in the right middle cerebral artery, which had a greater degree of activation than the right posterior cerebral artery (t = 2.8, p = 0.013). We did not observe a statistically significant difference between the right and left middle cerebral arteries, but there was a trend toward a greater activation on the right for both the mean velocity (t = 1.7, p = 0.098) and the peak velocity (t = 1.9, p = 0.079). CONCLUSIONS: Our preliminary investigation suggests that this noninvasive technique has the potential to correlate selective cerebral artery flow dynamics with cognitive activity.

Adolescent↗
PubMed1992

Neurolinguistic programming training, trait anxiety, and locus of control.

Training in the neurolinguistic programming techniques of shifting perceptual position, visual-kinesthetic dissociation, timelines, and change-history, all based on experiential cognitive processing of remembered events, leads to an increased awareness of behavioral contingencies and a more sensitive recognition of environmental cues which could serve to lower trait anxiety and increase the sense of internal control. This study reports on within-person and between-group changes in trait anxiety and locus of control as measured on the Spielberger State-Trait Anxiety Inventory and Wallston, Wallston, and DeVallis' Multiple Health Locus of Control immediately following a 21-day residential training in neurolinguistic programming. Significant with-in-person decreases in trait-anxiety scores and increases in internal locus of control scores were observed as predicted. Chance and powerful other locus of control scores were unchanged. Significant differences were noted on trait anxiety and locus of control scores between European and U.S. participants, although change scores were similar for the two groups. These findings are consistent with the hypothesis that this training may lower trait-anxiety scores and increase internal locus of control scores. A matched control group was not available, and follow-up was unfortunately not possible.

Adult↗
PubMed1992

Estimation of completeness and adjustment of age-specific and age-standardized incidence rates.

This note discusses the use of capture-mark-recapture methods and log-linear, linear, product models for incomplete tables (Espeland, 1986, Communications in Statistics--Simulation and Computing 15, 405-424) to estimate completeness of reporting in a disease registry and to estimate incompleteness-adjusted incidence rates. The method had several desirable features, including the ability to handle complex experimental designs, to incorporate auxiliary data (that may be related to the likelihood of reporting), to test the contribution of model terms, and to generate point estimates and associated standard errors.

Adolescent↗
PubMed1992

Descriptive analysis of the tumor registry experience for malignant melanoma from 1977 to 1986 at the University of Miami School of Medicine/Jackson Memorial Hospital.

A descriptive analysis was performed of malignant melanoma data ascertained by the University of Miami School of Medicine/Jackson Memorial Hospital (UM/JMH) Tumor Registry. A total of 376 melanoma cases were collected and reviewed. Most of the melanoma lesions occurred on the trunk, especially in the 40- to 49- and 50- to 54-year-old age groups. Local-stage cases had the best 5-year survival--77%. The difference in survival between local-stage case and regional- and distant-stage cases was statistically significant (p = 0.0000). In males with local-stage disease, lesions on the trunk were associated with better survival than lesions at other sites (p = 0.04). In females with local-stage disease, survival was 68% for 5 years for trunk sites vs. 87% for other sites (p = 0.05). In local-stage disease, the overall 5-year survival was 85%.

Adult↗
PubMed1991

Lung carcinoma in 1,336 patients.

Characteristics of 1336 successive lung cancer patients diagnosed between 1977 and 1986 according to the Tumor Registry of the University of Miami and Jackson Memorial Hospitals were 92% smokers, 69% men, and 68% white. The histologic subtypes were 32% squamous cell carcinoma, 26% adenocarcinoma, 19% small-cell carcinoma, 12% large-cell carcinoma, 8% adenosquamous carcinoma, and 3% bronchioalveolar carcinoma. Age distribution was as follows: younger than 45, 8%; 45-54, 21%; 55-64, 36%; 65-74, 25%; and 75 years or older, 10%. Local stage constituted 15%; regional, 26%; and distant 60%. Women had a higher number of nonsmokers and adenocarcinoma. Black patients presented with lung carcinoma at a younger age than white patients. Younger patients and black patients presented with more advanced stages than older patients and white patients. The significant factors predictive of better survival were local stage and white race. Patients with bronchioloalveolar carcinoma had a better survival rate (p less than 0.02) than the other histologic subtypes, probably because of a higher incidence of local stage. There were no differences in survival between the other histologic subtypes. There were significant increases in adenocarcinoma (p less than 0.01) and adenosquamous histologies (p less than 0.025) and in distant stage (p less than 0.0001); but there were no significant changes in the age and sex distribution, smoking history, and survival rate at our center over the 10-year study period.

Adult↗
PubMed1991

Impact of a humanmade disaster on the utilization pattern of a psychiatric emergency service.

In May 1980, Liberty City Miami, a black area, suffered a humanmade disaster: a riot. The effects of the riot on the utilization pattern of the only psychiatric emergency service (PES) for the Liberty City catchment area were studied in two ways: autocorrelation and cross-correlation analyses were used to determine whether PES presentations demonstrated a 7-day cycle and whether this cycle was disturbed by the riot; and analyses of variance (ANOVAs) were used to compare numerically the riot week to the preceding week, the riot week to the following 12 weeks, and the 12 pre-riot weeks to the 12 post-riot weeks. Black PES presentations did not demonstrate a statistically discernable cycle, and none of the ANOVAs were statistically significant. It was concluded that the riot did not have a significant psychiatric morbidity effect as measured by PES presentation data. These results are discussed in reference to previous disaster studies.

Analysis of Variance↗
PubMed1991

Postischemic (S)-emopamil therapy ameliorates focal ischemic brain injury in rats.

(S)-Emopamil is a calcium channel blocker of the phenylalkylamine class, having potent serotonin S2 antagonistic properties and high blood-brain barrier penetrability. Previous studies have documented cerebroprotective effect in animal models of both focal and global ischemia. The present study was undertaken to define the postischemic "window" of therapeutic efficacy for this agent. Sprague-Dawley rats were subjected to permanent proximal middle cerebral artery occlusion, combined with an initial 30-minute period of halothane-induced hypotension (50 mm Hg). (S)-Emopamil (20 mg/kg) was administered intraperitoneally either 20-30 minutes prior to middle cerebral artery occlusion or 1 hour, 2 hours, or 3 hours following occlusion. Treated groups received a second similar dose 2.5 hours later and twice daily for 2 days thereafter. Brains were perfusion-fixed on the third day. Planimetric analysis of hemotoxylin and eosin-stained coronal brain sections documented a cortical infarct averaging 72.9 +/- 33.3 mm3 (mean +/- SD) in untreated rats. Cortical infarct volume was reduced by 48% (to 37.6 +/- 27.6 mm3) when therapy was initiated 1 hour postischemia (p less than 0.05). When treatment was deferred to 2 hours postichemia, mean cortical infarct volume was reduced by 34%, but this difference did not attain statistical significance. Infarct volume in rats with treatment initiated at 3 hours postischemia was indistinguishable from that in controls. Striatal infarct volume was similar in all groups. These results document a postischemic therapeutic window of cerebroprotection for (S)-emopamil lying between 1 and 2 hours after middle cerebral artery occlusion.

Animals↗
PubMed1990

A phase I study of 4'-0-tetrahydropyranyladriamycin. Clinical pharmacology and pharmacokinetics.

A Phase I study of intravenous (IV) bolus 4'-0-tetrahydropyranyladriamycin (Pirarubicin) was done in 55 patients in good performance status with refractory tumors. Twenty-six had minimal prior therapy (good risk), 23 had extensive prior therapy (poor risk), and six had renal and/or hepatic dysfunction. A total of 167 courses at doses of 15 to 70 mg/m2 were evaluable. Maximum tolerated dose in good-risk patients was 70 mg/m2, and in poor-risk patients, 60 mg/m2. The dose-limiting toxic effect was transient noncumulative granulocytopenia. Granulocyte nadir was on day 14 (range, 4-22). Less frequent toxic effects included thrombocytopenia, anemia, nausea, mild alopecia, phlebitis, and mucositis. Myelosuppression was more in patients with hepatic dysfunction. Pharmacokinetic analyses in 21 patients revealed Pirarubicin plasma T 1/2 alpha (+/- SE) of 2.5 +/- 0.85 minutes, T beta 1/2 of 25.6 +/- 6.5 minutes, and T 1/2 gamma of 23.6 +/- 7.6 hours. The area under the curve was 537 +/- 149 ng/ml x hours, volume of distribution (Vd) 3504 +/- 644 l/m2, and total clearance (ClT) was 204 + 39.3 l/hour/m2. Adriamycinol, doxorubicin, adriamycinone, and tetrahydropyranyladriamycinol were the metabolites detected in plasma and the amount of doxorubicin was less than or equal to 10% of the total metabolites. Urinary excretion of Pirarubicin in the first 24 hours was less than or equal to 10%. Activity was noted in mesothelioma, leiomyosarcoma, and basal cell carcinoma. The recommended starting dose for Phase II trials is 60 mg/m2 IV bolus every 3 weeks.

Adult↗
PubMed1990

Acute nonlymphocytic leukemia in a dog.

Acute nonlymphocytic leukemia was diagnosed in a 1-year-old Rhodesian Ridgeback. Clinical signs of disease included weight loss, anorexia, lethargy, lymphadenopathy, splenomegaly, and hepatomegaly. Doxorubicin was administered IV on day 4 at a dosage of 30 mg/m2 of body surface, followed 2 days later by oral administration of cyclophosphamide at a dosage of 100 mg/m2. The cyclophosphamide was given for 4 consecutive days (days 8, 9, 10, and 11), but the WBC count did not respond. The dog was administered 500 ml of blood; but on day 12, it died. Necropsy was not performed, but the presumptive cause of death was related to leukostasis.

Animals↗
PubMed1990

Regional beta-adrenergic receptors and adenylate cyclase activity after healing of myocardial infarction in cats.

Augmented sensitivity to sympathetic mediators occurs in non-infarcted tissues after healing of myocardial infarction. We studied regional beta-adrenergic receptor numbers and adenylate cyclase activity in cat ventricles with healed myocardial infarctions and in the same regions from control hearts. Tissues were obtained from regions remote from and adjacent to the infarct and from the infarct zone itself. Beta-adrenergic receptor numbers were significantly reduced in adjacent and infarcted regions of the healed infarction model. Basal adenylate cyclase activity was increased in tissues remote from and adjacent to the infarct. In remote tissues, total adenylate cyclase activity during maximum isoproterenol stimulation was increased, but the isoproterenol stimulated increment was normal after subtraction of basal activity. In adjacent tissues, total adenylate cyclase activity during isoproterenol stimulation was normal, but the stimulated increment was reduced after subtraction of basal activity. This reduction in activity was reversed when GTP was replaced with Gpp(NH)p. No changes in adenylate cyclase activity, relative to control, were observed in tissues from the infarcted area. These results indicate that chronic changes in the beta-adrenergic receptor/adenylate cyclase system persist after healing of myocardial infarction, and that the nature of the changes are regional depending on proximity to the healed scar.

Adenylyl Cyclases↗
PubMed1990

A field test of the TIME patient simulation model.

The Technological Innovations in Medical Education (TIME) Project has created an interactive videodisc patient-simulation model that provides faculty with a new method for patient-centered teaching in the medical school classroom. The TIME model is designed to be controlled by a professor in the classroom setting, and incorporates voice recognition technology and video dramatization to create a believable patient encounter. Under the auspices of the Lister Hill National Center for Biomedical Communications, National Library of Medicine, where the Project originated in 1983, three medical schools participated in a field test of this "high-tech" model. Six faculty members made ten classroom presentations of two TIME simulations to 306 second-year medical students. The principal finding was that, in a group setting, a large majority of the students at all three schools became individually committed to the care and management of the simulated patient. They acted as if the patient's problems were real and left the session feeling as though they had interacted with an actual person. Therefore, in terms of simulating a real patient, the TIME patient-simulation model was validated, providing the basis for the development of new patient-centered methods to teach and test medical students in the classroom setting. The Project has been at the Georgetown University School of Medicine, where the model is being introduced into the existing curriculum, since 1988. It is currently being used as a part of the final examination for second-year students and in discussion-group settings for fourth-year students in the internal medicine clerkship. A field test is also under way using the TIME model to assess the clinical performance of third-year students.

Clinical Competence↗