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Biomedical subjects

L Allen

Publications and source records attributed to L Allen.

At least 73 records · Page 4Linked to original sources
PubMed1994

Wound complications in patients receiving adjuvant chemotherapy after mastectomy and immediate breast reconstruction for breast cancer.

A retrospective study was done to evaluate the frequency and severity of wound complications in 112 patients with breast cancer who received adjuvant chemotherapy following mastectomy with immediate breast reconstruction. Data on wound complications were available for 120 mastectomies. The rate of complications in 36 mastectomies treated with chemotherapy after mastectomy and immediate reconstruction was compared to that in 84 mastectomies not receiving adjuvant therapy. There were 25 wound complications (20.8%) in the entire group. The rate of wound complications was 27.8% (10 of 36 mastectomies) in the group treated with adjuvant chemotherapy and 17.9% (15 of 84 mastectomies) in the group that did not receive adjuvant therapy (P = 0.13). No patient had a delay in the initiation of adjuvant therapy because of wound complications secondary to immediate reconstruction. Logistic regression analysis found no correlation between age, type of operation, tumor pathology, stage, number of lymph nodes harvested, type of prosthesis or chemotherapy, and wound complications in patients undergoing immediate breast reconstruction after mastectomy. The frequency of wound complications was not increased in patients receiving adjuvant chemotherapy after mastectomy and immediate breast reconstruction. The administration of adjuvant chemotherapy does not need to be delayed in patients who have had immediate breast reconstruction following mastectomy for breast cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

Psychophysical foundations of a model of amplified night vision in target detection tasks.

In this article we examine some of the basic psychophysics relevant to amplified night vision devices. These devices produce images that are substantially different from ordinary visual scenes. Distortions in contrast and luminance and the introduction of visual interference and geometrical artifacts contribute to unusual viewing conditions. We carried out experiments to determine the effect of these parameters of the image on a highly controlled visual target detection task simulated on a computer graphics system that closely models a night vision device. Our results indicate that display luminance and geometrical artifacts degrade detection performance only slightly, whereas contrast and visual interference have a substantial degrading effect.

Adult↗
PubMed1994

Decompression for dysthyroid ophthalmopathy via the orbital rim approach. Technical note.

A technique is described wherein the approach to the orbital cavity, with resection of its roof and lateral wall, is facilitated by a single burr hole and local en bloc removal of the lateral and supraorbital margins. A satisfactory decompression with reduction of proptosis of the orbital contents and a good cosmetic result is achieved without the need for a large dural exposure. The approach may be combined with removal of the anterior wall of the frontal sinus in cases where the lateral aspect extends appreciably laterally. Access to the orbital roof and lateral wall is straightforward and can be coupled with further removal of the floor lateral to the infraorbital nerve and medial wall. Advancement of the orbital rim upon bone replacement adds to orbital volume, creating better mechanical advantage for eyelid closure.

Adolescent↗
PubMed1994

The impact of school transitions in early adolescence on the self-system and perceived social context of poor urban youth.

This study examined the effects of the normative school transition (n = 580) during early adolescence on the self-system and perceived school and peer social contexts of poor, black (n = 161), white (n = 146), and Latino (n = 273) youth in the public school systems of 3 eastern urban cities. The results revealed negative effects of the school transition on the affective and behavioral domains of the self-system. These declines in self-esteem, class preparation, and grade-point average (GPA) were common across race/ethnicity and gender. Concurrently, the school transition was perceived to be associated with changes in the school and peer contexts. Daily hassles with the school increased, while social support and extracurricular involvement decreased over the transition. Daily hassles with peers decreased, and peer values were perceived as more antisocial. These changes in the school and peer microsystems were also common across race/ethnicity and gender. In addition, transition-associated school and peer changes and, in particular, changes in daily hassles with the school were associated with changes in the academic dimensions of the self-system, that is, academic efficacy expectations, class preparation, and GPA. The results are discussed within a developmental mismatch framework.

Adolescent↗
PubMed1993

Quantification and kinetics of 25-hydroxyvitamin D3 by isotope dilution liquid chromatography/thermospray mass spectrometry.

A liquid chromatography/thermospray mass spectrometry method has been developed and used to measure the plasma levels and half-life of 25-hydroxyvitamin D3 in adults. The mean plasma levels of 25-hydroxyvitamin D3 averaged 40 ng ml-1 (n = 4) in summer and 30 ng ml-1 (n = 6) in winter. The method was also used to determine the half-life of serum 25-hydroxyvitamin D3 in subjects maintained on either high or low-fiber diets who had been given an intravenous infusion of (6,19,19-2H3)25-hydroxyvitamin D3 sufficient to label 5% of their estimated body pools. The half-life was determined to be 10.4 days (n = 4), which is approximately 50% of the currently accepted value of 19 days, determined using radiolabeled methods. This difference may be due to kinetic isotope effects arising as a result of the tritiated compounds being labeled at sites that undergo Cyt-P450-catalyzed oxidations.

Adult↗
PubMed1992

Preliminary assessment of a scientific curriculum in a surgical residency program.

A structured, basic science curriculum was instituted for surgical residents of the University of Connecticut (Farmington) Integrated Residency Program during the 1990-1991 academic year in concordance with American Board of Surgery guidelines. The impact of the new program was measured by comparing performance on monthly basic science examinations, the in-training examination, and "mock" oral examinations for the 1990-1991 academic year with that of the preceding academic year. While monthly examination scores improved for the entire group of residents (67.7 vs 64.6), in-training and oral examination scores did not change significantly. Categorical residents generally demonstrated superior performance and greater improvement than did preliminary residents. Data analysis suggested that the new curriculum was an effective educational device and that university-designed monthly examinations were valid testing instruments, but there was an apparent incongruity between the goals of the curriculum and the American Board of Surgery In-Training Examination.

Attitude↗
PubMed1992

Effects of surfactant apolipoproteins on liposome structure: implications for tubular myelin formation.

Tubular myelin is one of several forms of lung surfactant and may play an important role in its surface activity. To determine possible mechanisms of tubular myelin formation, we studied the effects of purified surfactant proteins (SP-A, SP-B, and SP-C) on large unilamellar dipalmitoylphosphatidylcholine-egg phosphatidylglycerol (7/3; wt/wt) liposomes. We studied different types of membrane interaction induced by the apolipoproteins and correlated these with the observed changes in ultrastructure. Aggregation was assessed by measurement of light absorbance, lysis, and fusion by measurement of the fluorescence emitted by water-soluble and lipid-soluble probes, respectively. Mixtures of the apolipoproteins and liposomes were examined in ultrastructural studies by negative staining and by thin sectioning. We found that each protein had a pronounced and distinct effect on liposome structure. SP-A caused aggregation, whereas SP-B and SP-C also caused extensive leakage of liposome contents (lysis) and some degree of lipid mixing (fusion). The disruptive effects of SP-B and to a lesser extent those of SP-C were correlated by negative staining with the appearance of bilayer disks, which tended to aggregate into large sheets. There was a marked synergy between SP-A and SP-B in the process of membrane fusion in the presence of calcium, which correlated with an early (10 min) and extensive rearrangement of the structures seen by electron microscopy followed by a delayed (24 h) appearance of small amounts of tubular myelin.

Animals↗
PubMed1992

Phase I trial of the chimeric anti-GD2 monoclonal antibody ch14.18 in patients with malignant melanoma.

The chimeric monoclonal anti-GD2 antibody ch14.18 is made up of the variable region of the murine anti-GD2 antibody 14.18 (or its IgG2a switch variant 14G2a) and the constant region of human IgG1k. Ch14.18 mediates antibody dependent cytotoxicity and complement dependent lysis in vitro. In a phase I trial, 13 patients with metastatic melanoma received ch14.18 as a single dose of 5-100 mg. Therapy was associated with an infusion-related abdominal/pelvic pain syndrome, which required intravenous morphine for control. The pharmacokinetics of ch14.18 best fit a two-compartment model with a T1/2 alpha of 24 +/- 1 hr and a T1/2 beta of 181 +/- 73 hr. Eight of 13 patients developed a weak-modest antibody response directed at the variable region of ch14.18. Clinical antitumor responses were not observed at the doses employed in this study. However, patients receiving greater than 45 mg of ch14.18 had antibody detectable on tumor cells analyzed by fluorescent activated cell sorter. Further modification of the therapeutic regime employing larger doses and frequent administration of ch14.18 are planned.

Adult↗
PubMed1991

Multiple human D5 dopamine receptor genes: a functional receptor and two pseudogenes.

Three genes closely related to the D1 dopamine receptor were identified in the human genome. One of the genes lacks introns and encodes a functional human dopamine receptor, D5, whose deduced amino acid sequence is 49% identical to that of the human D1 receptor. Compared with the human D1 dopamine receptor, the D5 receptor displayed a higher affinity for dopamine and was able to stimulate a biphasic rather than a monophasic intracellular accumulation of cAMP. Neither of the other two genes was able to direct the synthesis of a receptor. Nucleotide sequence analysis revealed that these two genes are 98% identical to each other and 95% identical to the D5 sequence. Relative to the D5 sequence, both contain insertions and deletions that result in several in-frame termination codons. Premature termination of translation is the most likely explanation for the failure of these genes to produce receptors in COS-7 and 293 cells even though their messages are transcribed. We conclude that the two are pseudogenes. Blot hybridization experiments performed on rat genomic DNA suggest that there is one D5 gene in this species and that the pseudogenes may be the result of a relatively recent evolutionary event.

Amino Acid Sequence↗
PubMed1991

Pharmacokinetics and immune response of 131I-chimeric mouse/human B72.3 (human gamma 4) monoclonal antibody in humans.

Chimeric B72.3, composed of the V-regions of murine B72.3 and the constant regions of human immunoglobulin G4 heavy and kappa light chain, was administered as a 131I-labeled conjugate to 12 patients with metastatic colon cancer. Seven of these patients had an antibody response after initial infusion, and the immune response was primarily directed to the murine V-region, although a small proportion of the antibody response was directed to topographical epitopes requiring the presence of both murine V-region and human CH-1 and kappa constant regions (neo-epitopes). The pharmacokinetics included a plasma disappearance curve best fit by a two-compartmental model with an alpha t 1/2 of 18 +/- 7 h and a beta t 1/2 of 224 +/- 66 h. A second infusion of the same dose of 131I-chimeric B72.3 was administered to four of these patients 8 wk after the first infusion. Two patients who had a high antibody response to initial infusion had an anamnestic antibody response, and the infused ch-B72.3 rapidly disappeared from the circulation with associated immune complexes and free 131I in the plasma. One patient with no initial antibody response had no antibody response and identical pharmacokinetics on second infusion. One patient with a modest transient antibody response to initial infusion had no antibody response on second infusion and a modest shortening of plasma circulation. Thus, the human immunoglobulin G4 isotype chimeric B72.3 monoclonal antibody has a plasma half-life 6 to 8 times as long as murine B72.3 and retains considerable immunogenicity in some patients which can adversely affect repetitive infusions.

Animals↗