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Biomedical subjects

D R Allen

Publications and source records attributed to D R Allen.

36 records · Page 2Linked to original sources
PubMed1983

Comparison of results following modified Widman flap surgery with and without surgical dressing.

The clinical effects of a periodontal dressing after modified Widman flap surgery were studied. A total of thirty surgical sites in 13 patients were included in the study. Half of the sites were not covered by a periodontal dressing while the other half were. To effect a blind evaluation, the dressings were placed and removed by someone other than the examiner. Gingival crevicular fluid flow and gingival inflammation were measured prior to surgery, 2 weeks, 1 month and 2 months after surgery. Clinical attachment level and pocket depth were measured prior to surgery, 1 month and 2 months after surgery. All patients were instructed in oral hygiene procedures and received rubber cup prophylaxes and flossing at 1 week, 2 weeks, 1 month and 2 months postoperatively. At the conclusion of the study, a questionnaire was administered to each patient. No significant differences were found between dressed and undressed segments regarding changes in clinical attachment levels, pocket depth, or gingival inflammation. The omission of a dressing did not result in a greater incidence of discomfort. More patients stated preference for no dressing.

Adult↗
PubMed1980

Pulmonary arteriovenous shunts during halothane anesthesia in dogs.

The fraction of cardiac output flowing through pulmonary arteriovenous anastomoses (Qav/Qt) was measured in dogs during halothane anesthesia and compared with results obtained in normal awake dogs. Flow through arteriovenous anastomoses was measured using 99mTc-labelled polystyrene microspheres (50 microns diameter). The fraction of cardiac output perfusing pulmonary arteriovenous anastomoses during halothane anaesthesia was 4.1% (+/- SD 1.75) compared with 4.6% (+/- SD 0.73) in air-breathing awake control dogs. In spite of variations in arteriovenous shunt fraction, no significant relationship between the Qav/Qt and Qs/Qt was detected. These results suggest that pulmonary arteriovenous anastomases do not contribute significantly to the physiological shunt observed during halothane anaesthesia.

Anesthesia, Inhalation↗
PubMed1980

Common pathway for tumor cell uptake of gallium-67 and iron-59 via a transferrin receptor.

We studied the tumor uptake of [67Ga]citrate, [59Fe]citrate, and 125I-labeled transferrin (TF) by the in vitro growth form of EMT-6, a sarcoma-like mammary tumor of BALB/c mice. In analyzing the binding experiments, we developed a new mathematical model based on a formulation originally used to express the interaction of hormones with specific tissue receptors. The uptake of both carrier-free 67Ga and 59Fe by tumor cells was mediated by kinetically identical TF receptors. We also studied teric acid extracts of the stroma of EMT-6 tumors grown both in vivo and in vitro. Chromatography of these extracts on Sephacryl S-200 SF demonstrated that the cellular stroma contained specific TF-binding macromolecules. On the basis of these findings, we proposed the "transferrin receptor hypothesis" for the mechanism of 67Ga uptake by tumors. According to this view, a tumor-associated TF receptor is the functional unit responsible for the affinity of gallium for certain neoplasms. This receptor was also active in the uptake of iron by tumors.

Animals↗
PubMed1979

Pharmacologic enhancement of gallium-67 tumor-to-blood ratios for EMT-6 sarcoma (BALB/c mice).

At various intervals after intravenous injection of carrier-free 67Ga-citrate, iron dextrane or deferoxamine mesylate was injected into EMT-6 tumor-bearing BALB/c mice. After treatment, rapid clearance of 67Ga from soft tissues was observed. Tumor uptake was not greatly affected, and so increased tumor-to-blood ratios were observed. The authors conclude that these drugs can enhance target-to-nontarget uptake ratios for tumors.

Animals↗
PubMed1979

Technetium-99m-labeled methylene diphosphonate and hydroxyethylidine diphosphonate--biologic and clinical comparison: concise communication.

The biologic and imaging characteristics of Tc-99m MDP and Tc-99m HEDP were compared in ten patients: Tc-99m MDP exhibited lower blood activity, lower 4-hr urinary excretion, and higher normal bone-to-background ratio. Assessment of overall image quality also favored Tc-99m MDP, indicating that the normal skeleton is better visualized with this agent. The total number of lesions seen (18) was not large enough to allow critical comparison of relative lesion-detecting efficacy. However, discrepancies between the two agents were observed, suggesting additional evaluation of the relative lesion-detecting efficacy of these two bone agents.

Adult↗
PubMed1979

A transferrin-mediated uptake of gallium-67 by EMT-6 sarcoma. I. Studies in tissue culture.

We have studied the in vitro uptake of gallium-67 by exponentially growing EMT-6 sarcoma cells in long-term tissue culture. In this system, the addition of transferrin to the medium was required before an appreciable cellular uptake of Ga-67 occurred. The transferrin effect was complex, with an initial stimulation to a peak cell-to-medium ratio of 8--10:1 at low concentrations of transferrin (0.2 mg/ml), followed by a gradual decline in uptake as transferrin in the medium was increased further. EMT-6 tumor-cell uptake of Ga-67 was probably mediated by a specific cellular receptor for transferrin. Scatchard analysis of the EMT-6 cellular binding of human transferrin labeled with iodine-125 indicated a cellular receptor with affinity for transferrin of 5 X 10(6) l/mole and abundance of 500,000 receptors per cell. Over the experimental range of transferrin concentration in the medium, the observed uptake of Ga-67 was closely correlated with the degree of formation of Ga-67-labeled transferrin and the fraction of transferrin bound to the cellular receptor (N = 69, r = 0.86, p less than 0.0001).

Animals↗
PubMed1979

A transferrin-mediated uptake of gallium-67 by EMT-6 sarcoma. II. Studies in vivo (BALB/c mice): concise communication.

The EMT-6 sarcoma-like tumor of BALB/c mice can be grown as a solid subcutaneous transplantable tumor in vivo or as a monolayer culture in vitro. We have studied the uptake of gallium-67 by this tumor growing subcutaneously on the backs of 6-week-old BALB/c mice. After i.v. administration of Ga-67 citrate, tumor uptakes were as high as any others reported for mouse tumors. Also, for unknown reasons, there was appreciable reduction in tumor uptake with increasing amounts of Ga-67 citrate, even in the microcurie range. Furthermore, when mouse serum is prelabeled with Ga-67 and then injected, the EMT-6 uptake is greater than with Ga-67 administered as citrate (p less than 0.02). We believe that the finding of avid Ga-67 uptake in vivo helps to establish this unique in vivo/in vitro tumor system as a valid experimental model for studies regarding the mechanism of Ga-67 accumulation by neoplastic tissue.

Animals↗
PubMed1977

Tc-99m methylene diphosphonate versus Tc-99m pyrophosphate: biologic and clinical comparison.

The biologic and imaging characteristics of Tc-99m MDP and Tc-99m PPi were compared in animals and patients using freeze-dried bone-imaging kits. Biodistribution data in rabbits showed Tc-99m MDP had slightly higher bone uptake, significantly lower blood levels, and faster urinary excretion compared with Tc-99m PPi. Duplicate studies performed on ten patients showed the following: (a) blood clearance of Tc-99m MDP was more prompt and complete, resulting in significantly lower blood levels at 4 hr; (b) urinary excretion was greater with Tc-99m MDP than with Tc-99m PPi; and (c) Tc-99m PPi showed significant red-cell labeling, whereas Tc-99m MDP did not. Image quality was generally better with Tc-99m MDP than with Tc-99 m PPi, although there was no obvious difference in diagnostic sensitivity between the two agents.

Animals↗
PubMedDate not supplied

Hoarseness as the initial clinical presentation of anomalous left coronary artery from the pulmonary artery.

Anomalous origin of the left coronary artery from the pulmonary artery is a rare congenital anomaly that, if left untreated, will most often result in severe myocardial ischemia and significant morbidity and mortality. We report an unusual presentation of this defect in a 2-month-old infant who had an initial complaint of a "hoarse cry." We theorize that impingement of the recurrent laryngeal nerve due to dilatation of the pulmonary artery was the most likely etiology of the patient's symptoms. This case serves as an important reminder that serious congenital heart disease may present with any number of complaints and unusual findings.

Blood Vessel Prosthesis Implantation↗