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Biomedical subjects

D Hershey

Publications and source records attributed to D Hershey.

11 recordsLinked to original sources
PubMed2004

Late first-trimester invasive prenatal diagnosis: results of an international randomized trial.

OBJECTIVE: To assess, in a randomized trial, the safety and accuracy of amniocentesis and transabdominal chorionic villus sampling (CVS) performed at 11-14 weeks of gestation, given that this time frame is increasingly relevant to early trisomy screening. METHODS: We compared amniocentesis with CVS from 77 to 104 days of gestation in a randomized trial in a predominantly advanced maternal age population. Before randomization, the feasibility of both procedures was confirmed by ultrasonography, and experienced operators performed sampling under ultrasound guidance; conventional cytogenetic analysis was employed. The primary outcome measure was a composite of fetal loss plus preterm delivery before 28 weeks of gestation in cytogenetically normal pregnancies. RESULTS: We randomized 3,775 women into 2 groups (1,914 to CVS; 1,861 to amniocentesis), which were comparable at baseline. More than 99.6% had the assigned procedure, and 99.9% were followed through delivery. In contrast to previous thinking, in the cytogenetically normal cohort (n = 3,698), no difference in primary study outcome was observed: 2.1% (95% confidence interval 1.5, 2.8) for CVS and 2.3% (95% confidence interval, 1.7, 3.1) for amniocentesis. However, spontaneous losses before 20 weeks and procedure-related, indicated terminations combined were increased in the amniocentesis group (P =.07, relative risk 1.74). We found a 4-fold increase in the rate of talipes equinovarus after amniocentesis (P =.02) overall and in week 13 (P =.03, relative risk = 4.65), but data were insufficient to determine this risk in week 14. CONCLUSION: Amniocentesis at 13 weeks carries a significantly increased risk of talipes equinovarus compared with CVS and also suggests an increase in early, unintended pregnancy loss. LEVEL OF EVIDENCE: I

Abortion, Induced↗
PubMed2000

Common trisomy mosaicism diagnosed in amniocytes involving chromosomes 13, 18, 20 and 21: karyotype-phenotype correlations.

Karyotype-phenotype correlations of common trisomy mosaicism prenatally diagnosed via amniocentesis was reviewed in 305 new cases from a collaboration of North American cytogenetic laboratories. Abnormal outcome was noted in 10/25 (40%) cases of 47,+13/46, 17/31 (54%) cases of 47,+18/46, 10/152 (6.5%) cases of 47,+20/46, and in 49/97 (50%) cases of 47,+21/46 mosaicism. Risk of abnormal outcome in pregnancies with less than 50% trisomic cells and greater than 50% trisomic cells were: 26% (4/15) versus 60% (6/10) for 47,+13/46, 52% (11/21) versus 75% (6/8) for 47,+18/46, 4.5% (6/132) versus 20% (4/20) 47,+20/46, and 45% (27/60) versus 59% (22/37) for 47,+21/46. Phenotypically normal liveborns were observed with mean trisomic cell lines of 9.3% for 47,+13/46, 8.6% for 47,+18/46, 27% for 47, +20/46, and 17% for 47,+21/46. Cytogenetic confirmation rates were 46% (6/13 cases) for 47,+13/46 mosaicism, 66% (8/12 cases) for 47, +18/46, 10% (10/97 cases) for 47,+20/46, and 44% (24/54 cases) for 47,+21/46. There were higher confirmation rates in pregnancies with abnormal versus normal outcome: 50% versus 44% for 47,+13/46 mosaicism, 100% versus 33% for 47,+18/46, 66% versus 7% for 47, +20/46, and 55% versus 40% for 47,+21/46. Repeat amniocentesis is not helpful in predicting clinical outcome. It may be considered when there is insufficient number of cells or cultures to establish a diagnosis. Fetal blood sampling may have a role in mosaic trisomy 13, 18, and 21 as the risk for abnormal outcome increases with positive confirmation: 1/5 (20%) normal cases versus 5/8 (62%) abnormal cases. High resolution ultrasound examination(s) is recommended for clinical correlation and to facilitate genetic counselling.

Abnormalities, Multiple↗
PubMed1996

Analysis of structure and discriminative power of the Mattis Dementia Rating Scale.

The study examines the factor structure and provides test of the discriminative properties of the 38-item Mattis Dementia Rating Scale (MDRS). The MDRS was designed a priori to measure five broad domains of cognitive abilities: attention, initiation/perseveration, conceptualization, construction, and memory. Complete item level data were collected at the USC Alzheimer Disease Research Center from 19 probable Alzheimer's Disease (AD) patients, 17 cases with dementia of various etiologies (e.g., multiple infarct), and 49 contrast subjects. Factor analyses, with rotation to equamax criterion, were performed on education partialled data. Five and six factor solutions accounted for most of the reliable variance and permitted simple structure theoretical description for separate subscales. These factors, similar to Mattis' design, can be characterized as Memory (Recall)/Verbal Fluency, Construction, Memory (short-term), Initiation/Perseveration, and Simple Commands. Cross-validated discriminant analyses performed on five unit-weighted composite variables derived from factor analysis provided better classification (72% vs 62%) than the 38 Mattis items alone.

Adult↗
PubMed1992

Quantitative analysis of DNA-sequencing electrophoresis.

At the heart of the DNA-sequencing process is a remarkably selective electrophoretic separation of up to 1000 oligonucleotide fragments, each differing in size by only a single nucleotide unit. A quantitative analysis of this separation is performed in terms of both selectivity and efficiency. It is shown that both the Ogston sieving and reptation migration mechanisms are operative. It is demonstrated that, under the conditions used in traditional sequencing electrophoresis, Joule heating does not significantly contribute to band broadening, and that diffusion is the primary contributor to plate height. An analytic expression is derived relating the peak width for each fragment to its molecular size. Calculations are presented showing that, when longer sequences are required, the maximum electrical field strength will be limited by the influence of biased reptation on the separation selectivity. Finally, it is shown that, when short sequences are required, the electrical field strength is limited by the ability to dissipate Joule heat, and that in these cases a tube format will be approximately 50% faster than a slab having a thickness equivalent to the tube diameter.

DNA↗
PubMed1985

The utilization of BMR measurements as a routine diagnostic procedure in normal health maintenance.

The hypothesis that BMR measurements should become part of the routine diagnostics utilized by physicians in long term health maintenance programs is developed. The hypothesis is supported from two viewpoints. First, a number of conditions are known to cause increases in BMR. The conditions include endocrine disorders, cardiovascular abnormalities, and cancer. Thus an observed substantial rise in BMR could indicate the onset of a medical problem if the higher level is maintained over an extended period of time. Second, available data from a longitudinal aging study suggests that sustained periods of increased BMR indicate "killing" stresses which can be detrimental or even fatal to individual subjects. The recent improvements in BMR measurements techniques reported here now make it possible to set up an inexpensive, reliable, and easy-to-use apparatus. Thus it would not be difficult to incorporate BMR measurement techniques as one of the routinely utilized diagnostic procedures.

Aging↗