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Biomedical subjects

K Papadopoulos

Publications and source records attributed to K Papadopoulos.

9 recordsLinked to original sources
PubMed1998

Respiratory complications after coronary artery bypass surgery with unilateral or bilateral internal mammary artery grafting.

BACKGROUND AND STUDY OBJECTIVE: Use of bilateral internal mammary artery (IMA) grafts during coronary artery revascularization procedures carries the potential for increased incidence of postoperative respiratory complications compared with use of unilateral IMA grafts. The purpose of this study was to compare the incidence of respiratory complications such as hypoxemia, atelectasis, pleural effusion, and diaphragmatic dysfunction in patients who received one or both IMAs as conduit grafts. DESIGN: Prospective, comparative study. SETTING: Surgical ICU at a tertiary teaching hospital. PATIENTS: Seventy-five patients with bilateral and 75 patients with unilateral IMA grafts. MEASUREMENTS: Serial postoperative PaO2/fraction of inspired oxygen measurements, radiographic scores of atelectasis and pleural effusion, duration of mechanical ventilation, length of ICU and hospital stay, and incidence of pneumothorax, pneumonia, and wound infection. RESULTS: There was a higher incidence (51% vs 25%; p=0.002) and severity (0.48+/-0.09 vs 0.15+/-0.05 on the first postoperative day, 0.39+/-0.07 vs 0.27+/-0.07 on the fourth postoperative day, mean+/-SEM; p=0.004) of postoperative right lower lobe atelectasis in the group who received bilateral IMA grafts than in those who received left IMA grafts. This finding probably reflects the effects of additional surgical intervention on the right side of the chest. Incidence and severity of pleural effusion, gas exchange impairment, duration of mechanical ventilation, ICU and hospital stay, and incidence of pneumothorax, pneumonia, and wound infection were not influenced by use of bilateral IMA grafts (p>0.05). CONCLUSION: We conclude that use of bilateral IMA grafts during coronary artery revascularization does not increase the incidence of postoperative respiratory complications compared with unilateral IMA grafting.

Case-Control Studies↗
PubMed1998

Phase I trial of sequential high-dose chemotherapy with escalating dose paclitaxel, melphalan, and cyclophosphamide, thiotepa, and carboplatin with peripheral blood progenitor support in women with responding metastatic breast cancer.

A single high-dose cycle of chemotherapy with stem cell support can produce disease-free survival of 15-20% for at least 3 years in women with responding stage IV breast cancer. North American Autologous Bone Marrow Transplant Registry data suggest that a complete response (CR) is the single most important prognostic factor associated with prolonged disease-free survival. Therefore, if sequential high-dose chemotherapy can increase the CR rate, then perhaps an increased proportion of patients will remain disease free. Women with at least a partial response (PR) to induction chemotherapy received three separate high-dose cycles of chemotherapy with peripheral blood progenitor support and granulocyte colony-stimulating factor. The first intensification was a dose escalation of paclitaxel (400-825 mg/ m2), the second intensification was melphalan (180 mg/m2), and the third intensification consisted of 6000 mg/m2 cyclophosphamide (1500 mg/m2/day), 500 mg/m2 thiotepa (125 mg/m2/day), and 800 mg/m2 carboplatin (200 mg/m2/day; CTCb). Thirty-six women were enrolled and 31 completed all three cycles. After the paclitaxel infusion most patients developed reversible predominantly sensory neuropathy. Of the 19 patients with measurable disease, 6 converted to CR, 7 converted to a PR* (the complete resolution of all soft tissue or visceral disease with sclerosis of prior lytic bone lesions), and 2 had a further PR for an overall response rate of 79%. Two patients had no further response and disease in two patients progressed, and thus they were taken off the study before CTCb. Seventy-eight percent are progression-free at a median follow-up of 14 months (range, 3-24+). Three sequential cycles of high-dose chemotherapy are feasible and were administered in this study with no mortality. Single agent paclitaxel at doses up to 825 mg/m2 were well tolerated with moderate reversible toxicity.

Adult↗
PubMed1997

MHC class I antigen processing pathways.

The multistep process that culminates in major histocompatibility complex (MHC) class I presentation of foreign of self-peptides begins in the last phases of protein catabolism. Although the individual roles of many key molecules-such as proteasomes, the transporter associated with antigen processing, and various endoplasmic reticulum chaperones-have recently been elucidated, there still remain many questions regarding processing of proteins into MHC class I bound peptides. This review summarizes the recent developments in antigen processing for MHC class I molecules, with a focus on how proteins are believed to be sampled and selected for degradation.

Antigen Presentation↗
PubMed1997

Temporal variation in chlorinated hydrocarbons in healthy women.

Chlorinated hydrocarbons may increase breast cancer risk. Most epidemiological studies addressing this possibility have used one biological sample to measure a subject's cumulative exposure to these compounds. Little is known about short-term temporal variation in organochlorines, particularly in individuals with low levels. Thus, the reliability of using one sample to assess blood levels of chlorinated hydrocarbons in an epidemiological study is unknown. To better understand the temporal changes in blood measures among women with nonoccupational exposures to these compounds, we collected two 5-ml blood samples, an average of 2 months apart, from each of 31 nonfasting healthy women, ages 45-81 years. Samples were assayed for 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), polychlorinated biphenyls (PCBs), and trans-nonachlor in blinded, matched pairs. Results were adjusted for estimated total plasma lipids. The correlations between the two blood samples were high for DDE and PCBs (lipid-adjusted, r = 0.96 and r = 0.89, respectively). For trans-nonachlor, the correlation was relatively poor (lipid-adjusted r = 0.57); however, with the removal of one outlier, the correlation improved substantially (lipid-adjusted, r = 0.90). The mean difference between the two blood samples in unadjusted [-0.36 ng/ml, 95% confidence interval (CI), -0.97, 0.24 ng/ml, P = 0.23] and lipid-adjusted (-0.035 microgram/g lipid; 95% CI, -0.124, 0.055; P = 0.44) DDE levels was small. Similarly, there was little change in the mean difference for unadjusted (-0.14 ng/ml; 95% CI, -0.53, 0.25 ng/ml; P = 0.47) and lipid-adjusted (0.006 microgram/g lipid; 95% CI, -0.050, 0.062; P = 0.82) PCB levels. The mean differences in trans-nonachlor levels between the two blood draws were also small: unadjusted (-0.03 ng/ml; 95% CI, -0.07, 0.02 ng/ml; P = 0.20) and lipid-adjusted (-0.003 microgram/g lipid; 95% CI, -0.010, 0.004; P = 0.33). These data suggest that temporal changes in organochlorine levels within a 1 to 3-month period are minimal for noncancer patients and that a single measure for estimating exposure is highly reliable for DDE and PCB. For trans-nonachlor, however, where the correlation between blood draws was lower, three samples would be needed for estimating exposure; if an outlier is removed from our data, however, then we can conclude that only a single measure is sufficient. These data, therefore, offer no clear conclusion for the use of a single measurement for trans-nonachlor.

Aged↗
PubMed1992

Interactions between digitoxin and some antiarrhythmic drugs.

In the present study the pharmacokinetic interactions between digitoxin and the antiarrhythmic drugs amiodarone, mexiletine and propafenone have been examined. Experiments were performed on rabbits in which serum digitoxin concentration was used as indicator to detect drug interactions. The radioimmunoassay "Coat-A-Count" procedure of DPC was used for the quantitative measurement of digitoxin. It was determined that in order to achieve a considerable level of serum digitoxin, it was necessary to administer a multiple dose rather than the one tolerated by humans. It was also observed that serum contained digitalis like immunoreactive factor(s) (DLIF) measured as digitoxin. The mean (+/- SE) digitoxin equivalent value of the DLIF, measured by the "Coat-A-Count" radioimmunoassay in the serum of rabbits (n = 34) was 4.15 +/- 0.059 ng/ml. Each of the three antiarrhythmic drugs increased serum digitoxin levels; its values were almost double in relation to the control group where only digitoxin was administered. This increased digitoxin value was detected one hour after administration of the first dose of the antiarrhythmic drug and remained at a higher level than that of the control group for 6-8 hours. Rabbits given a single high dose of digitoxin and some of the antiarrhythmic drugs and those given a small dose of digitoxin for only four days, presented a retrogressive increase of digitoxin level in serum 5-6 days later. This mechanism needs to be further investigated.

Amiodarone↗
PubMed1990

The influence of methionine-5-enkephalin on calcium uptake by the bovine aortic media.

The influence of methionine-5-enkephalin (M-5-E), an endogenous opioid receptor agonist, on calcium uptake by bovine aortic media was investigated in vitro. 45Ca was used and radioactivity was counted in a beta scintillation counter. M-5-E increases Ca2+ uptake by the preparation. This action is inhibited by naloxone and that is proof that an opioid receptor is stimulated. A comparative study showed that phenylephrine, an alpha-adrenoceptor agonist, exhibits the same action as M-5-E, whereas morphine's action is negligible. Phenylephrine contracts the deendotheliazed ring of the bovine aorta, whereas M-5-E fails to do so. It is concluded that an opioid receptor was identified at the bovine aortic smooth muscle. This receptor is stimulated by M-5-E resulting in an increase of the extracellular Ca2+ entrance. Although no relationship was observed between the receptor and the contraction mechanism, a possible role of M-5-E in the maintenance of the vascular tone cannot be excluded.

Animals↗
PubMed1989

Precursor T-cell lymphoma associated with human immunodeficiency virus type 1 (HIV-1) infection. First reported case.

The majority of lymphomas that develop in human immunodeficiency virus type 1 (HIV-1) positive patients have a B-cell phenotype, with few reported cases of T-cell lymphoma. Within the latter group, those that have been comprehensively phenotyped had a mature helper T-cell phenotype (CD4+). We report, for the first time, an HIV-1 positive patient with a precursor T-cell lymphoma (CD7+,CD1-,CD3-,CD4-, and CD8-). T-cell receptor beta and gamma genes were in the germline configuration and integration of HIV-1 DNA could not be detected in the lymphoma cell genome.

Acquired Immunodeficiency Syndrome↗