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Biomedical subjects

M Marcus

Publications and source records attributed to M Marcus.

At least 91 records · Page 5Linked to original sources
PubMed1991

Relative accuracy of three scintigraphic methods for determination of right ventricular ejection fraction: a correlative study with ultrafast computed tomography.

The accuracy of three scintigraphic methods for determination of right ventricular ejection fraction (RVEF) was tested in 29 patients using ultrafast computed tomography (UFCT) as the gold standard. RVEF measurements by the ECG-gated first-pass approach showed excellent correlation with the UFCT results (r = 0.96, y = 0.06 + 0.91x), while both the standard gated acquisition blood-pool imaging (r = 0.71, y = 0.14 + 0.59x) and the nongated first-pass curve approach (r = 0.63, y = 0.18 + 0.37x) significantly underestimated RVEF. The error can be ascribed to partial inclusion of the atrial activity in the region assigned to the right ventricle. The tricuspid valve plane was found to move by a distance equal to 9%-33% (mean = 20%) of the right ventricular long-axis between systole and diastole. This translational motion was more pronounced with higher EFs.

Adult↗
PubMed1990

A proposed new system for valuing dental procedures. The relative time-cost unit.

The relative time cost unit (RTCU) is a proposed new system for valuing dental procedures that provides an alternative to traditional relative value units in fee-setting and reimbursement allowances. It incorporates personnel costs, task mixes, and task times into relative weights for dental procedures. The frequently performed procedure, "2-surface amalgam restoration," is used to illustrate how the RTCU values are derived from hospital task analysis data. The RTCU, as a data-based construct, holds appeal for restructuring fee schedules and has been used for almost a decade by insurance companies to value dental services, construct fee schedules, and evaluate reimbursement to providers.

California↗
PubMed1990

Comparison of two-dimensional echocardiography and ultrafast cardiac computed tomography for evaluating intracardiac thrombi in cerebral ischemia.

Two-dimensional echocardiography has a high specificity for the detection of intracardiac thrombi, but technically difficult studies are often encountered. Ultrafast cardiac computed tomography may be useful in such cases. Using transthoracic two-dimensional echocardiography and ultrafast cardiac computed tomography, we studied 36 patients with cerebral ischemia; one patient had the studies performed on two occasions, making a total of 37 sets of studies. Technical difficulties occurred in 12 echocardiographic (32%) and two ultrafast cardiac computed tomographic (5%) studies. The two techniques agreed in 29 sets of studies (78%). Among the eight discrepant sets of studies, two-dimensional echocardiography was positive for a left ventricular thrombus while ultrafast cardiac computed tomography was negative in three and equivocal in one and echocardiography was equivocal while ultrafast cardiac computed tomography was negative in two and positive in one. In the latter case, a left ventricular thrombus was confirmed at autopsy. In the other discrepant set of studies echocardiography was negative while ultrafast cardiac computed tomography revealed a left atrial and appendage thrombus. Because of its ease of performance and safety, two-dimensional echocardiography is the appropriate initial screening test for left ventricular thrombus. Ultrafast cardiac computed tomography can provide additional information in patients with technically difficult or equivocal two-dimensional echocardiographic studies or patients with cardiac disorders predisposing to atrial thrombi formation.

Adult↗
PubMed1990

Detection of adducts of deoxyribonucleic acid in white blood cells of roofers by 32P-postlabeling. Relationship of adduct levels to measures of exposure to polycyclic aromatic hydrocarbons.

To assess the utility of adducts of deoxyribonucleic acid (DNA) as biomarkers of exposure to carcinogens in an industrial population, a pilot study of roofers occupationally exposed to polycyclic aromatic hydrocarbons was conducted. DNA isolated from white blood cells of roofers and nonoccupationally exposed comparison subjects matched for age, sex, and smoking status was analyzed for DNA adducts with the use of 32P-postlabeling methods. Occupational exposures to polycyclic aromatic hydrocarbons were assessed by personal air sampling and skin wipes. Ten of the 12 roofers, but only 2 of the 12 comparison subjects, had detectable levels of aromatic DNA adducts in the 32P-postlabeling assay. Among the roofers, the post-shift levels of polycyclic aromatic hydrocarbons in the skin wipes were correlated with the DNA adduct levels. These results suggest that 32P-postlabeling assay may be useful for monitoring internal exposures to complex mixtures of aromatic hydrocarbons in industrial populations.

Adult↗
PubMed1990

A pilot study of detection of DNA adducts in white blood cells of roofers by 32P-postlabelling.

To assess the utility of DNA adducts as biomarkers of exposure to carcinogens in an industrial population, a pilot study of roofers occupationally exposed to a mixture of polycyclic aromatic hydrocarbons was conducted. DNA was isolated from peripheral white blood cells of roofers and non-occupationally exposed subjects matched for age, sex and smoking status. Occupational exposures to anthracene, fluoranthene, pyrene, benzanthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[g,h,i]perylene and benzo[k]fluoranthene were assessed by personal breathing zone air sampling and skin wipes. Exposures to benzo[a]pyrene in air of exposed subjects ranged from 0.60 microgram/m3 to 1.39 micrograms/m3, and exposures to total polycyclic aromatic hydrocarbon (the sum of eight hydrocarbons) ranged from 6.0 micrograms/m3 to 13.8 micrograms/m3 on the day before blood collection. In the biomarker studies 10 of 12 roofers, but only 2 of 12 comparison subjects, had detectable levels of aromatic DNA adducts by 32P-postlabelling assay (p less than 0.01). The two non-roofers with detectable adducts had levels at or near the detection limit of 2 adducts per 10(9) nucleotides. In two roofer samples which were studied in a mixing experiment, the major adduct spots did not co-migrate with the guanosine N2 adduct of benzo[a]pyrene diol epoxide. These results suggest that the 32P-postlabelling assay may be useful for monitoring exposures to complex mixtures of aromatic hydrocarbons in industrial populations.

Adult↗
PubMed1990

Trends in quality assurance in the dental profession.

I have dealt with three questions concerning trends in quality assurance. In summary, we must ask ourselves whether the profession can develop methods for dealing effectively with dentists whose performance is found to be continually unsatisfactory. This may be achieved by making available effective tools for others to use in developing quality assurance systems. These tools will involve criteria and standards for services, appropriateness of treatment, measuring outcomes of care, and methods for assessing dental practices. This may involve working closely with consumer representatives to assist in gaining the consumer's point of view and incorporating it into the technology of quality assurance. Berwick, in a recent article in the New England Journal of Medicine, called for the application of a "Theory of Continuous Improvement" rather than the "Theory of Bad Apples." His view is that we should examine the process itself and try to improve it rather than look for outliers or bad apples. His point of view is consistent with the concept of quality assurance I have been talking about. Quality assurance systems should assure quality by proper assessment, identifying strengths and weaknesses in the provision of care. The strengths should be reinforced and the weaknesses should be rectified. This necessitates positive communication between those who perform quality assurance and those who are being evaluated. It also assumes that the technology is appropriate, recommendations are reasonable and that, when changes are made, quality will improve. In order to make the theory of continuous improvement work, it should be consistent with financial incentives and professional values.(ABSTRACT TRUNCATED AT 250 WORDS)

Dentistry↗
PubMed1989

A temperature-sensitive mutation in asparaginyl-tRNA synthetase causes cell-cycle arrest in early S phase.

The Chinese hamster temperature-sensitive cell-cycle mutant ts24 was analyzed biochemically in order to determine the nature of this lesion. The inability of these cells to proceed through S phase at the restrictive temperature could be complemented by the addition of asparagine to the growth medium, and enzymological analysis showed that this line contains a temperature-sensitive asparaginyl-tRNA synthetase. Normal asparaginyl-tRNA synthetase activity was restored in cells transfected with cloned genomic DNA that overcomes the mutational defect. In corroboration with these results it was shown that a different temperature-sensitive asparaginyl-tRNA synthetase mutant isolated in another laboratory was blocked in S phase in a manner similar to that of ts24. While the mechanism by which asparaginyl-tRNA synthetase affects cell-cycle progression has not been elucidated, it can be shown that it is not mediated through alteration in overall levels of protein synthesis.

Amino Acyl-tRNA Synthetases↗
PubMed1989

Assessment of probability of survival in penetrating injuries using the TRISS methodology.

By the TRISS methodology, probability of survival in injury can be estimated. It is based on a statistical analysis of outcome which is influenced by the severity of the injuries as expressed in the Injury Severity Score (ISS), the physiological function as expressed in the Trauma Score (TS) and the patient's age. We have used the TRISS formula in 206 patients with penetrating injury. Of these patients, 149 sustained stab wounds, 32 gunshot wounds and 25 others. ISS ranged from 2 to 38, the mean ISS being 9. The function was good (TS greater than 14) in 85 per cent. Estimated probability of survival ranged from 1.00 to 0.42. Three patients (1.5 per cent) died. The probability of their survival was 0.92, 0.96 and 0.98, respectively. All the fatal cases had serious predisposing conditions: chronic pulmonary disease, alcoholism, and psychiatric illness. In penetrating injury, the patient's functional status at the start of treatment is of greater importance for the outcome than the anatomical severity. The concept of the methodology of TRISS for assessment of probability of survival seems useful for review and comparison in injury care.

Abbreviated Injury Scale↗
PubMed1989

Developing population profiles from dental claims data for conceptualizing effectiveness of care.

The purpose of this study was to explore longitudinal observational analysis of insurance claims data with goal of graphically demonstrating that effective dental care leads to the diminished use of services in subsequent time intervals. Using the Rand HIE claims data, definitions of the best patients for whom claims data would be profiled and the best parameters to use in rate calculations for the time series graphs were empirically derived. Profiles using these definitions were found to be very similar to a conceptual model of such profiles.

Adult↗
PubMed1989

Ontogeny of the antibody response to cow milk proteins.

Twenty-nine infants were followed prospectively for the development of immunoglobulin G (IgG) and IgE antibodies to the cow milk proteins (CMPs) alpha-lactalbumin, alpha-casein, and beta-lactoglobulin. Thirteen infants were fed formula, eight were exclusively breast fed, and eight were breast fed with formula supplementation. By 4 months of life, infants fed formula or breast milk with formula supplementation had elevated IgE and IgG antibody levels to CMPs, when compared with values before 1 month of age. Further, breast-fed infants demonstrated significantly lower levels of IgE and IgG antibodies to CMPs than infants who received formula or breast milk with formula supplementation. Clinical symptoms of cow milk allergy were more common in infants fed formula or breast fed with supplementation, but were not significantly related to the presence of specific antibody. Our data suggest that the formation of CMP antibodies may reflect a normal humoral response following exposure to CMP antigens in this age group.

Animals↗
PubMed1988

A Chinese hamster cell cycle mutant arrested at G2 phase has a temperature-sensitive ubiquitin-activating enzyme, E1.

The effect of restrictive temperature on ubiquitin conjugation activity has been studied in cells of ts20, a temperature-sensitive cell cycle mutant of the Chinese hamster cell line E36. Ts20 is arrested in early G2 phase at nonpermissive temperature. Immunoblotting with antibodies to ubiquitin conjugates shows that conjugates disappear rapidly at restrictive temperatures in ts20 mutant but not in wild type E36 cells. The incorporation of 125I-ubiquitin into permeabilized ts20 cells is temperature-sensitive. Addition of extracts of another G2 phase mutant, FM3A ts85, with a temperature-sensitive ubiquitin activation enzyme (E1), to permeabilized ts20 cells at restrictive temperatures fails to complement their ubiquitin ligation activity. This indicates that the lesions in the two mutants are similar. Purified E1 from reticulocytes restores the conjugation activity of heat-inactivated permeabilized ts20 cells. Ubiquitin conjugation activity of cell-free extracts of ts20 cells was temperature-sensitive and could be restored by adding purified reticulocyte E1. Purified reticulocyte E2 or E3, on the other hand, did not restore the ubiquitin conjugation activity of heat-treated ts20 extracts. These results are consistent with the conclusion that ts20 has temperature-sensitive ubiquitin-activating enzyme (E1). The fact that two E1 mutants (ts20 and ts85) derived from different cell lines are arrested at the S/G2 boundary at restrictive temperatures strongly indicates that ubiquitin ligation is necessary for passage through this part of the cell cycle. The temperature thresholds of heat shock protein synthesis of ts20 and wild type E36 cells were identical. The implications of these findings with respect to a suggested role of ubiquitin in coupling between protein denaturation and the heat shock response are discussed.

Animals↗
PubMed1988

The phylogenetic history of immunodeficiency viruses.

Knowledge of the phylogenetic history of the human immunodeficiency viruses (HIV-1 and HIV-2) is important for our understanding of the epidemiology of AIDS, the disease caused by these viruses. Reconstruction of the evolutionary tree is hampered, however, by two problems. One is the high variation in nucleotide sequence between the known HIV isolates which can create formidable difficulties in identifying homologous genomic sites that may be used in a molecular phylogenetic reconstruction. Another impediment has been the lack of unequivocal time calibration points: there is only a sparse 'fossil record' for HIV and limited historical epidemiological data. We have largely overcome these difficulties by: (1) a thorough optimal-sequence alignment analysis; (2) the inclusion of sequences of an early (1976) HIV-1 isolate, a recent (1986) HIV-2 isolate and two simian immunodeficiency viruses (SIV) along with five other HIV-1 isolates; and (3) the reconstruction of a minimum-length evolutionary tree based on the envelope-gene variable positions. We conclude that HIV-1 may have evolved from its common ancestor with HIV-2 as recently as 40 years ago.

Animals↗
PubMed1988

Regulation of mouse satellite DNA replication time.

The satellite DNA sequences located near the centromeric regions of mouse chromosomes replicate very late in S in both fibroblast and lymphocyte cells and are heavily methylated at CpG residues. F9 teratocarcinoma cells, on the other hand, contain satellite sequences which are undermethylated and replicate much earlier in S. DNA methylation probably plays some role in the control of satellite replication time since 5-azacytidine treatment of RAG fibroblasts causes a dramatic temporal shift of replication to mid S. In contrast to similar changes accompanying the inactivation of the X-chromosome, early replication of satellite DNA is not associated with an increase in local chromosomal DNase I sensitivity. Fusion of F9 with mouse lymphocytes caused a dramatic early shift in the timing of the normally late replicating lymphocyte satellite heterochromatin, suggesting that trans-activating factors may be responsible for the regulation of replication timing.

Animals↗
PubMed1988

DNase I sensitivity of Microtus agrestis active, inactive and reactivated X chromosomes in mouse-Microtus cell hybrids.

We isolated Microtus agrestis-mouse somatic cell hybrid clones which had retained either the active or the inactive M. agrestis X chromosome. In both hybrid clones the X chromosomes retained their original chromatin conformation as studied by the in situ nick translation technique--the active X chromosome retained its high sensitivity to DNase I while the inactive one remained insensitive. A clone in which the hypoxanthine guanine phosphoribosyltransferase (HPRT) gene had been spontaneously reactivated was isolated from the hybrid containing the inactive X chromosome. The in situ nick translation technique was used to study possible DNA conformation changes in the euchromatin of the inactive X chromosome with special reference to the reactivated HPRT locus. We found that the euchromatin in this X chromosome exhibited the same low sensitivity to DNase I as is characteristic of the inactive X chromosome.

Animals↗
PubMed1988

Evaluation of coronary bypass graft patency by ultrafast computed tomography.

A noninvasive technique for determining bypass graft patency is greatly needed. To determine if bypass graft patency could be accurately assessed with ultrafast computed tomography (CT) following an intravenous contrast injection, ten patients with 21 coronary bypass grafts were studied. All patients had cardiac catheterization and ultrafast computed tomographic studies within one month of each other. The sensitivity of detecting angiographically open grafts with ultrafast CT was 94.1% (16/17), specificity of detecting angiographically closed grafts was 100% (4/4), and accuracy was 95.2% (20/21). These preliminary results in a small clinical series indicate that ultrafast CT may be a useful, minimally invasive technique for evaluating coronary bypass graft patency.

Contrast Media↗