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Biomedical subjects

M Marcus

Publications and source records attributed to M Marcus.

At least 127 records · Page 7Linked to original sources
PubMed1985

A children's oral health status index based on dentists' judgment.

The children's oral health status index was developed as an integrated measure for the direct appraisal of pediatric patient populations in private practices, dental clinics, or school programs. The index is derived from a paired preference experiment with five pedodontists and five general dentists acting as judges of oral health in 200 case comparisons. Four easily measured variables are united numerically by the index: decayed teeth, occlusion, tooth position, and missing teeth (which have not been exfoliated). Clinical applications of the index in three geographic areas have all had good results.

Adolescent↗
PubMed1985

Quality assurance and prepaid programs.

This article presents the concepts of quality assurance and the various mechanisms that are employed in quality assurance systems. The implications for quality assurance are discussed in relation to the major types of prepaid programs. Capitation dental plans have certain opportunities to engage in quality assurance, whereas indemnity plans face a more complex set of constraints. Each type of plan faces different problems and requirements, and each needs to design quality assurance systems that address their concerns.

Dental Care↗
PubMed1984

Analysis of a Chinese hamster temperature-sensitive cell cycle mutant arrested in early S phase.

E36 ts24 is a temperature-sensitive cell cycle mutant which has been derived from the Chinese hamster lung cell line E36. This mutant is arrested in phase S when incubated at the restrictive temperature (40.3 degrees C) for growth. At this temperature, proliferation of the mutant cells ceases after 10 h. About 2 h earlier, DNA synthesis is arrested. These kinetic studies indicate that the execution point of the mutant cells is in early S phase well beyond the G1/S boundary. The pattern of replication bands in E36 ts24 cell grown for 9 h at 40.3 degrees C strengthen the kinetic studies and map the execution point to early S phase. The exact point of arrest of the mutant cells in phase S was mapped in early S phase near the execution point. At the point of arrest the cells continue to synthesize DNA at at a high rate but practically all of the newly synthesized DNA is degraded. This high rate of DNA degradation is limited to nascent DNA at the point of arrest. In the presence of 5-bromodeoxyuridine (5-BudR), the last E36 ts24 cells which reach mitosis at the restrictive temperature for growth show asymmetric replication bands which illustrate DNA degradation and resynthesis occurring in these cells at 40.3 degrees C.

Animals↗
PubMed1984

Mapping of DNAase I sensitive regions on mitotic chromosomes.

We have shown that in fixed mitotic chromosomes from female G. gerbillus cells the inactive X chromosome is distinctly less sensitive to DNAase I than the active X chromosome, as demonstrated by in situ nick translation. These results indicated that the specific chromatin conformation that renders potentially active genes sensitive to DNAase I is maintained in fixed mitotic chromosomes. We increased the sensitivity and accuracy of in situ nick translation using biotinylated dUTP and a specific detection and staining procedure instead of radioactive label and autoradiography and now show that in both human and CHO chromosomes, the DNAase I sensitive and insensitive chromosomal regions form a specific dark and light banding pattern. The DNAase I sensitive dark D-bands usually correspond to the light G-bands, but not all light G-bands are DNAase I sensitive. Identifiable regions of inactive constitutive heterochromatin are in a DNAase I insensitive conformation. Our methodology provides a new and important tool for studying the structural and functional organization of chromosomes.

Animals↗
PubMed1984

Regional brain activity in dyslexic and control children during reading tasks: visual probe event-related potentials.

Event-related potentials (ERPs) elicited by task-irrelevant visual stimuli were recorded from 34 control and 32 dyslexic 10- to 12-year-old boys while they performed silent and oral reading at two levels of difficulty. All subjects were extensively screened for neurological problems, IQ, and sensory acuity. Specific features of the ERPs were affected in amplitude and latency by the experimental variables: group membership, oral vs. silent reading, difficulty level, and recording site (within and between hemispheres). A specific effect of difficulty on the central and parietal ERP was seen in the dyslexics but not the controls. Different patterns of asymmetry were found for the two groups in silent vs. oral reading at midtemporal placements. A marked asymmetry (R greater than L) was found at the midtemporal region for both groups.

Attention↗
PubMed1984

Partial purification and characterization of the mRNA complementing a temperature-sensitive S-phase cell cycle mutation.

E36ts24 is a temperature-sensitive (ts) cell cycle mutant derived from the Chinese hamster lung cell line E36. At the restrictive temperature for growth (40.3 degrees C), the mutant cells are arrested at early S phase. We have microinjected poly(A)+ RNA isolated from the wild-type E36 cells into the cytoplasm of E36ts24 cells arrested at early S phase after 24 hr of incubation at 40.3 degrees C. The ts mutation was transiently complemented in a significant fraction of the microinjected cells as evidenced by the incorporation of [3H]thymidine assayed by autoradiography. Microinjection of mRNA fractionated by methylmercuric hydroxide/agarose gel showed that the mRNA capable of transiently complementing the mutation in E36ts24 contains about 940 nucleotides. Hence, it can code at most for a protein containing about 230 amino acids. We estimate that the partial purification by fractionation of the mRNA active in the transient complementation is on the order of 100- to 200-fold.

Animals↗
PubMed1984

The relationship of activity level ratings and cognitive impulsivity to task performance and academic achievement.

The relationship of activity level ratings and cognitive impulsivity were analyzed in relation to performance of second-graders on several cognitive tasks and standardized achievement tests. Vocabulary was a strong and significant covariate on most dependent measures. In general, impulsivity-reflectivity had a far stronger effect on task performance and academic achievement than did activity level ratings, even when comparisons were made for groups with extremes of activity level ratings. The authors urge further research on the task approaches and compensatory strategies of children who are behaviorally hyperactive but cognitively reflective and academically successful.

Achievement↗
PubMed1984

Patterns of heterochromatin replication and condensation correlate in rat kangaroo PtK2 cells.

Chromosome replication in mammalian cells in an ordered phenomenon. This is true also for the condensation in G2 of the heterochromatic chromosomal regions in mouse cells. The generality of this phenomenon and its mechanism are not known, nor is it known whether the order of condensation of the heterochromatic chromosomal segments in G2 reflects the order of replication or is independent of it. We determined the order of replication during the S phase and of condensation in G2 of the short heterochromatic chromosomal regions in the rat kangaroo cell line PtK2. The kinetics of condensation of these regions in G2 was studied in cells treated with Hoechst 33258. Their order of replication was established with the use of a sensitive technique based on the treatment of living cells with 5-bromodeoxyuridine and Hoechst 33258. Our results show that these regions exhibit a similar pattern of replication in S and condensation in G2.

Animals↗
PubMed1983

Dyslexic children have normal vestibular responses to rotation.

We examined the rotational vestibular responses of carefully screened dyslexic and control populations (34 dyslexics and 33 controls). The subject groups had equivalent performance IQs but differed significantly on verbal IQ and on silent and oral reading. Children with significant neurologic, visual, or hearing deficits were excluded. We measured eye movements provoked by sinusoidal rotation of the subjects (in total darkness) at low frequencies (0.01 to 0.16 Hz). Gain, phase, and preponderance (asymmetry) of the responses were calculated from the eye velocity and stimulus velocity waveforms. There were no differences between the groups in any of these measures. We conclude that there are no clinically measurable differences in this aspect of vestibular function in our carefully selected populations of dyslexic and control children.

Child↗
PubMed1983

Predictive eye movements do not discriminate between dyslexic and control children.

Pavlidis has suggested that predictive saccadic tracking eye movements distinguish between reading disabled and normal children. We have examined saccadic eye movement tracking in 34 dyslexic and 33 control subjects, between 10 and 12 yr old. The subjects were equivalent in performance IQ (WISC-R), with differences between verbal and performance IQ of less than 30 points. Children with neurological, visual or auditory deficits or histories of emotional problems and hyperactivity were excluded. There were no differences between the groups on the eye movement tracking task when scored objectively by computerized analysis of the eye movement records, or by ranking of the records by an experienced observer. Our results (and those of other recent studies) fail to support Pavlidis' contention that eye movements hold the key to dyslexia.

Child↗
PubMed1983

Mutations in alpha- and beta-tubulin affect spindle formation in Chinese hamster ovary cells.

Two Chinese hamster ovary cell lines with mutated beta-tubulins (Grs-2 and Cmd-4) and one that has a mutation in alpha-tubulin (Tax-1) are temperature sensitive for growth at 40.5 degrees C. To determine the functional defect in these mutant cells at the nonpermissive temperature, they were characterized with respect to cell cycle parameters and microtubule organization and function after relatively short periods at 40.5 degrees C. At the nonpermissive temperature all the mutants had normal appearing cytoplasmic microtubules. Premature chromosome condensation analysis failed to show any discrete step in the interphase cell cycle in which these mutants are arrested. These cells, however, show several defects at the nonpermissive temperature that appear related to the function of microtubules during mitosis. Time-lapse studies showed that mitosis was lengthened in the three mutant lines at 40.5 degrees C as compared with the wild-type cells at this temperature, resulting in a higher proportion of cells in mitosis after temperature shift. There was also a large increase in multinucleated cells in mutant populations after incubation at the nonpermissive temperature. Immunofluorescent studies using a monoclonal anti--alpha-tubulin antibody showed that the mutant cells had a high proportion of abnormal spindles at the nonpermissive temperature. The two altered beta-tubulins and the altered alpha-tubulin all were found to cause a similar phenotype at the high temperature that results in mitotic delay, defective cytokinesis, multinucleation, and ultimately, cell death. We conclude that spindle formation is the limiting microtubule function in these mutant cell lines at the nonpermissive temperature and that these cell lines will be of value for the study of the precise role of tubulin in mammalian spindle formation.

Animals↗
PubMed1983

Tracking eye movements are normal in dyslexic children.

We measured saccadic and smooth eye tracking movements in 34 dyslexic and 35 control subjects and were unable to show differences in any of the tasks or parameters measured. Subjects were carefully screened for neurological, optometric, audiological, and behavioral problems before admission to the study. We suggest that differences between our results and those of previous investigators are based on sampling differences. We conclude that while there may be children with reading disorders secondary to visual or oculomotor deficits, dyslexia can and does exist independent of such deficits. Because, in this and other studies, we have ruled out peripheral involvement, we feel that dyslexia is primarily a deficit of central information processing of written or spoken material.

Child↗