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Biomedical subjects

C A Meyer

Publications and source records attributed to C A Meyer.

At least 19 recordsLinked to original sources
PubMed2002

Measurement of spin-transfer observables in p p-->Lambda Lambda at 1.637 GeV/c.

Spin-transfer observables for p p-->Lambda Lambda have been measured using a transversely polarized frozen-spin target and a beam momentum of 1.637 GeV/c. Current models of the reaction near threshold are in good agreement with existing measurements performed with unpolarized particles in the initial state but produce conflicting predictions for the spin-transfer observables Dnn and Knn (the normal-to-normal depolarization and polarization transfer), which are measurable only with polarized target or beam. Measurements of Dnn and Knn presented here are found to be in disagreement with predictions from these models.

Journal Article↗
PubMed2001

Regulation of the embryonic cell proliferation by Drosophila cyclin D and cyclin E complexes.

Cell proliferation during Drosophila development occurs in a well known spatial and temporal pattern which can readily be studied in vivo. The cells which form the larval epidermis exit from the cell division cycle during embryogenesis after the 16th round of mitosis when they enter for the first time into a G1/0 phase. We are interested in the mechanistic basis of this cell proliferation arrest. We have shown that the arrest requires the down-regulation of cyclin E/Cdk2 activity by inhibition of cyclin E expression and parallel activation of Dacapo/p27 expression. In addition, up-regulation of Fizzy-related is observed and is required for inhibition of Cdk1 activity. Do these processes result from the down-regulation of D-type cyclin/Cdk complexes? Extensive evidence from mammalian cells, and in particular from tumour cells has suggested that these complexes act as master regulators of cell proliferation upstream of cyclin E. Our genetic analyses indicate that Drosophila cyclin D/Cdk4, which interacts with the Drosophila Rb family member as expected, does not play an essential role in the regulation of cell proliferation.

Animals↗
PubMed2001

Intrathoracic splenosis: superiority of technetium Tc 99m heat-damaged RBC imaging.

Intrathoracic splenosis is a rare diagnosis that is usually made following an invasive procedure. Although radiographic and CT findings are nonspecific, these findings combined with a history of splenic injury should suggest the possibility of this diagnosis. We present a patient with intrathoracic splenosis diagnosed on the basis of a technetium Tc 99m heat-damaged RBC scan following false-negative technetium Tc 99m sulfur colloid scan results.

Diaphragm↗
PubMed2000

Drosophila Cdk4 is required for normal growth and is dispensable for cell cycle progression.

Complexes of D-type cyclins and cdk4 or 6 are thought to govern progression through the G(1) phase of the cell cycle. In Drosophila, single genes for Cyclin D and Cdk4 have been identified, simplifying genetic analysis. Here, we show that Drosophila Cdk4 interacts with Cyclin D and the Rb homolog RBF as expected, but is not absolutely essential. Flies homozygous for null mutations develop to the adult stage and are fertile, although only to a very limited degree. Overexpression of inactive mutant Cdk4, which is able to bind Cyclin D, does not enhance the Cdk4 mutant phenotype, confirming the absence of additional Cyclin D-dependent cdks. Our results indicate, therefore, that progression into and through the cell cycle can occur in the absence of Cdk4. However, the growth of cells and of the organism is reduced in Cdk4 mutants, indicating a role of D-type cyclin-dependent protein kinases in the modulation of growth rates.

Animals↗
PubMed2000

CT fluoroscopy for thoracic interventional procedures.

In the past several years, CT fluoroscopy has proved a valuable new technique in guiding the performance of intrathoracic procedures. Several approaches to using CT fluoroscopy are discussed. We have found an interrupted, real-time technique optimal to facilitate biopsy of percutaneous lung nodules, particularly small lesions. The technique is also valuable in assisting thoracic drainage procedures. This article also discusses the use of CT fluoroscopy to guide transbronchial needle aspiration, which is another potentially important application.

Biopsy, Needle↗
PubMed1999

Missed lung cancer on chest radiography and computed tomography: imaging and medicolegal issues.

Missed lung cancer is an important medicolegal issue and is the second leading cause for malpractice actions against radiologists. Contributing factors to overlooked lung cancer can be ascribed to observer performance, lesion characteristics, and technical considerations. Of these, errors related to observer performance are probably the most important. Missed lung cancer does not necessarily constitute malpractice, but lesions of high conspicuity are more likely to be associated with an adverse legal outcome. Multiple strategies have been advocated to reduce the frequency of missed lung cancer. Several studies have emphasized the importance of careful comparison of the current radiograph with one or more prior examinations.

Clinical Competence↗
PubMed1999

Portable CT: assessing thoracic disease in the intensive care unit.

OBJECTIVE: The objective of this study was to assess the usefulness of a portable CT scanner to evaluate and treat thoracic disease in patients in the intensive care unit. MATERIALS AND METHODS: Fourteen patients who were being treated in the intensive care unit underwent 20 portable CT scans. Twice a CT scan was obtained to guide an interventional chest procedure. The remaining 18 scans were assessed for findings not evident on portable chest radiography and for findings that altered treatment. Image quality was judged in comparison with fixed CT scans. RESULTS: Unsuspected abnormalities, most relating to the pleura or chest wall, were found in 13 of the 17 available portable CT scans. Treatment was affected in four (25%) of the 16 cases in which medical records were available for review. Two interventional procedures were performed successfully using portable CT guidance. Scan quality was judged to be comparable with that of fixed CT for mediastinal windows and somewhat inferior for lung windows. CONCLUSION: Portable CT gives images of diagnostic quality and allows confident guidance during interventional procedures in critically ill patients who therefore need not leave the intensive care unit environment.

Adult↗
PubMed1998

Constrictive (obliterative) bronchiolitis: diagnosis, etiology, and a critical review of the literature.

Constrictive bronchiolitis (CB) (or obliterative bronchiolitis) designates inflammation and fibrosis occurring predominantly in the walls and contiguous tissues of membranous and respiratory bronchioles, with resultant narrowing of their lumens. It differs from bronchiolitis obliterans-organizing pneumonia in its histopathology and clinical course. Most cases of CB occur in the setting of organ transplants, particularly lung and heart-lung transplants, but also in bone marrow transplants. Other bona fide cases are rare: infection, particularly viral infection, appears to be a well-documented precursor to CB in children, but not in immunocompetent adults. Constrictive bronchiolitis also has been reported in the course of rheumatoid arthritis, in certain other autoimmune diseases such as pemphigus vulgaris, after inhalation of toxic gases such as nitrogen oxide, after ingestion of certain drugs or medicinal agents such as Sauropus androgynous, and as a cryptogenic illness. Recent reports suggest that CB, as defined by clinical criteria (that is, bronchiolitis obliterans syndrome), is very common in lung allograft recipients who survive more than 5 years and, although it is associated with significant mortality, it also can be clinically stable. Furthermore, with the current practice of close monitoring of these patients, it appears that CB may now be diagnosed at an earlier stage, at which resolution, or at least stabilization of progression, is possible. A histopathologic diagnosis of CB in lung transplant and other patients may be difficult to make due to the patchy distribution of lesions, the technical difficulty in obtaining tissue in late lesions with extensive fibrosis, and the failure to recognize lesions. With regard to the last of these, in early stages of disease, CB may be subtle and easily missed in routine hematoxylin-eosin-stained specimens, while in advanced stages the disease may be equally difficult to diagnose if the patchy scarring in the lung is interpreted as nonspecific. The relative loss of bronchioles and the relationship of the scars to contiguous arteries should signal the need for elastic stains to look for the residual elastica of the bronchioles amidst the foci of fibrosis. Increasingly, clinical grounds, including pulmonary functions studies and high-resolution computed tomography findings, are proving to be relatively sensitive methods of detecting CB. Finally, the progressive airway destruction in chronic transplantation rejection appears to be a T-cell-mediated process. The "active" form of constrictive bronchiolitis, with attendant lymphocytic inflammation of the airways, likely precedes the "inactive" or scarred form of constrictive bronchiolitis.

Adult↗
PubMed1998

Real-time CT fluoroscopy: usefulness in thoracic drainage.

OBJECTIVE: The purpose of our study was to review the application of real-time CT fluoroscopy in the drainage of localized pleural and mediastinal collections. SUBJECTS AND METHODS: Between July 1996 and August 1997, 20 patients with 10 loculated pleural effusions, two mediastinal fluid collections, and 12 focal pneumothoraces were treated using CT fluoroscopy. The patient population was 25-77 years old and included 14 men and six women. Methods of drainage included using a modified Seldinger technique with a guidewire and serial dilators in 10 patients and a single-stick trocar technique in the remaining 14. Total room time, procedure time, and CT fluoroscopy time were recorded. RESULTS: All 24 collections were successfully evacuated using either real-time or interrupted real-time CT fluoroscopy. The real-time capability of CT fluoroscopy proved particularly useful for rapid placement of drainage tubes in patients who were unable to cooperate with breathing instructions and in patients who had a narrow window of access. Average total room time was 65 min. Average procedure time was 32 min, and average CT fluoroscopy time was 143 sec. CONCLUSION: CT fluoroscopy permits rapid drainage of intrathoracic collections. CT fluoroscopy is a particularly useful treatment for patients who are unable to perform breath-holding or in whom access to the drainage site is difficult.

Drainage↗
PubMed1996

Sulfasalazine pulmonary toxicity in ulcerative colitis mimicking clinical features of Wegener's granulomatosis.

The centrally accentuated antineutrophil cytoplasmic antibody test (c-ANCA) is widely regarded as a sensitive and specific marker for Wegener's granulomatosis (WG). There are increasing reports, however, of false-positive c-ANCAs, usually in the setting of other vasculidities. We report a case of a 27-year-old man with ulcerative colitis who developed pulmonary symptoms, peripheral nodular lung infiltrates, and an elevated c-ANCA suggesting WG. Chest CT and open lung biopsy specimens were consistent with WG. The symptoms and pulmonary infiltrates resolved after discontinuation of sulfasalazine therapy. The c-ANCA remained elevated due to the occurrence of false-positive values in ulcerative colitis. We conclude sulfasalazine toxicity can mimic clinical aspects of WG and that c-ANCA testing should be interpreted with caution in patients with ulcerative colitis.

Adult↗
PubMed1996

Inflammatory diseases of the lung causing false-positive 131iodine whole body scans in the evaluation of papillary thyroid carcinoma. Two case reports.

The 131I whole body scan is commonly used to establish the presence of metastatic disease in papillary thyroid carcinoma. False-positive scans are rare, but have been reported. We present two cases of aberrant uptake of radioiodine after thyroidectomy and 131I ablation due to inflammatory conditions of the lung, aspergilloma, and respiratory bronchiolitis.

Adult↗
PubMed1994

Structure of the novel heme adduct formed during the reaction of human hemoglobin with BrCCl3 in red cell lysates.

It was previously shown that the reductive debromination of BrCCl3 to trichloromethyl radical by human hemoglobin leads to formation of dissociable altered heme products, two of which are identical to those formed from myoglobin and one which is novel. In this study, we have elucidated the structure of this novel adduct with the use of mass spectrometry, as well as 1H and 13C NMR as a substitution product of a -C(Cl) = CCl2 moiety for a beta-hydrogen atom on the prosthetic heme's ring I vinyl group. From studies with the use of 13C-enriched BrCCl3, it was determined that the added carbon atoms were derived from 2 eq of BrCCl3. A mechanism that involves multiple reductive events and a radical cation heme intermediate is proposed. Consistent with this mechanism, cellular reductants were found to selectively enhance the amount of this novel dissociable heme adduct. These studies reveal fine differences between myoglobin and hemoglobin in the accessibility of reactive intermediates to the ring I vinyl group, as well as the potential importance of cellular reductants on the course of heme alteration.

Ascorbic Acid↗
PubMed1993

Differential susceptibilities of the prosthetic heme of hemoglobin-based red cell substitutes. Implications in the design of safer agents.

One approach to the development of an effective red cell substitute has been chemical modification of human hemoglobin to optimize oxygen transport and plasma half-life. Human hemoglobin A0 and two of these modified hemoglobins, one prepared from the cross-linking of the alpha-chains at lysine residue 99 by bis(3,5-dibromosalicyl)fumarate (Hb-DBBF) and the other by acylation of lysine residue 82 of the beta-chain by mono-(3,5-dibromosalicyl)fumarate (Hb-FMDA), were tested by HPLC for their susceptibility to oxidative damage caused by H2O2. Such oxidative insult may occur during ischemia and reperfusion of tissues after transfusion of red cell substitutes to patients with hypovolemic shock and trauma. Hb-DBBF was extremely susceptible to damage of its heme and protein moieties with stoichiometric amounts of H2O2, whereas Hb-FMDA was highly resistant, even at 10-fold molar excess and at an acidic pH of 4.7. Hemoglobin A0 was of intermediate susceptibility, exhibiting alteration of heme and protein moieties at acidic but not neutral pH. Since the degradation of heme can release the potentially toxic agent iron, Hb-FMDA may be a more promising candidate than Hb-DBBF for development as a red cell substitute. A similar approach may be used to assess the susceptibility of other hemoglobin-based red cell substitutes to oxidative damage in order to determine the molecular basis of heme and protein alteration.

Aspirin↗