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Biomedical subjects

D Cohen

Publications and source records attributed to D Cohen.

At least 739 records · Page 41Linked to original sources
PubMed1976

Part I: abnormal patterns and physiological variations in magnetocardiograms.

Magnetocardiograms (MCGs) of six subjects with representative cardiac abnormalities and of one well-studied normal subject are compared with the 12-lead ECGs and VCGs of these subjects. The MCGs are recordings of the component of the magnetic vector which is normal to the skin, measured across the chest on a 5 cm X 5 am grid; an example is also presented of a sequence of instantaneous MCG maps. The heart abnormalities include myocardial infarction, angina pectoris, intraventricular conduction disturbances, and ventricular hypertrophy. The various MCG maps of the normal subject show MCG changes as a result of changes in body morphology (loss of weight), changes in the subject's position during recording, and changes as a result of exercise. They are presented as a basis for understanding some of the variability of MCG maps.

Angina Pectoris↗
PubMed1976

Part II: magnetic field produced by a current dipole.

To understand the MCG, electrical models of the heart must be used in which the basic building-block is usually the current dipole. The dipole's magnetic field is generally made up of two parts: 1. the contribution by the dipole element itself, which is mathematically simple; 2. the contribution by the current generated in the volume conductor by the dipole, which is complicated and depends on the boundaries; for special boundaries this contribution is zero to Bz, the component of magnetic field which is normal to the boundary. This applies to the boundaries of the semi-infinite volume conductor, the infinite slab, and the sphere. This property allows great simplification in solving the magnetic forward and inverse problems. Because of its importance, it is proven with electrolytic tank experiments. Based on this property, a method is presented for estimating the presence of those dipole combinations which produce a suppressed surface potential; it consists of a visual examination of an "arrow" display of Bz.

Electromagnetic Fields↗
PubMed1976

Part III: the effect of the torso boundaries on the magnetocardiogram.

The magnetic field produced by a current dipole is made up of two parts: the field from the dipole element, and from the current generated by the dipole in the volume conductor. It was previously shown for the semi-infinite volume conductor, infinite slab, and the sphere that the volume-current contribution is zero to the component of magnetic field which is normal to the boundary. The volume conductor in the form of the human torso is here investigated by computer simulation. Three different heart-torso models are used. The contribution to the normal field component (Bn) by the volume current (via the boundaries) and by the heart dipoles are computed. For comparison, the boundary contribution to the surface potential (V) is also computed. For Bn the three models yield a ratio of boundary to dipole contribution in the same range, with 0.28 as the average. Simple subtractions can make this ratio negligible. For V the equivalent ratio is somewhat greater. The arrow map, developed previously to display Bn over special surfaces, is shown to be valid for the human torso, for visually estimating the heart dipoles.

Electromagnetic Phenomena↗
PubMed1976

Part IV: visual determination of generators of the magnetocardiogram.

Previously it was shown that Bn, the component of the heart's magnetic field which is normal to the chest, is in large part produced directly by the generators in the heart; the volume-current (or boundary) contribution to Bn is relatively small. It was also shown that the distribution of Bn across the chest could be displayed as an arrow map which visually reveals the underlying dipole sources, in particular those dipole combinations which produce suppresed surface potentials but undiminished Bn. Arrow maps of two normal and one abnormal heart subject are here presented. The purpose is to demonstrate that the generators of the MCG can be coarsely estimated by visual inspection of these maps. The generators of the normal hearts are visually determined by comparing their arrow maps with those computed from the Cuffin-Selvester model. The generators of the abnormal heart are visually determined by trial-and-error, with the aid of a simple computing program. These examples are the first determinations, however approximate, of multi-dipole generators of the actual MCGs. Some possible new information is indicated.

Electromagnetic Phenomena↗
PubMed1976

A behavioral-chromosome relationship in the elderly: a critical review of a biobehavioral hypothesis.

The evidence for the hypothesis that an increased frequency of hypodiploid cells is related to mental status in older persons, as well as the underlying assumptions crucial to the hypothesis, are reviewed. Results of chromosome examinations reported by several independent laboratories favor an increasing proportion of hypodiploid cells in older age groups as well as sex differences in the level and distribution of missing chromosomes. However, the presence, extent, and development course of chromosome loss associated with major modifying variables and their interactions, e.g., age, morbidity, sex, environmental conditions, remain to be empirically documented. Furthermore, the meaning of chromosome loss, including its relationship to mental status, is not clear.

Adult↗
PubMed1976

Immunoglobulin levels and intellectual functioning in the aged.

Significant positive correlations between vocabulary test scores and serum levels of immunoglobulins, IgG and IgM, were obtained for 14 subjects ranging in age from 83-100 years (mean 89.0 years). This positive association with vocabulary scores is a result contrary to data reported by other investigators. The interrelationship between measures of behavior, central nervous system and immunologic function deserve further attention.

Aged↗
PubMed1976

Effects of Water Stress on the Ultrastructure of Leaf Cells of Sorghum bicolor.

The subcellular changes which occurred in sorghum leaves during increasing water stress and subsequent rewatering are described. Stomata were closed, abscisic acid levels were elevated, and the amounts of starch in the bundle sheath chloroplasts were much reduced by - 14 bars leaf water potential. Swelling of the outer chloroplast membrane, and reorganization of the tonoplast to form small vesicles from the large central vacuole, occurred by a leaf water potential of - 37 bars. Complete structural disruption of the tonoplast, as previously described for maize was not found. On rewatering, large amounts of starch reappeared within three hours. These findings strengthen the hypothesis that maintenance of tonoplast integrity is an important factor in the ability of plants to withstand drought.

Journal Article↗
PubMed1976

Chemoimmunotherapy of syngeneic mouse mammary carcinomas employing methanol extraction residue.

Isografts of two mammary carcinomas, one spontaneously arising in a BALB/cfC3H female infected with MTV and one free of MTV (tumor D7T4S), were removed surgically from Balb/c (MTV free) female hosts, and fragments of each tumor were immediately reimplanted in situ (simulated local recurrence challenge). The animals were then subjected to treatment with the MER fraction of tubercle bacilli, with one of three chemotherapeutic drugs (5-FU, cyclophosphamide, and methotrexate), or with both MER and one of the chemotherapeutic agents (chemoimmunotherapy). The incidence of progressively developing recurrence tumors and the longevity of the animals were determined. The therapeutic effects of treatment with MER alone were ascertained by comparing groups of mice that received the fraction by various schedules with saline-injected control groups; the efficacy of chemoimmunotherapy was assassed by comparing groups that received MER plus one of the drugs with groups subjected to drug intervention by itself. MER administered alone did not reduce the incidence of recurrent tumors but was consistently efficacious in prolonging the lives of animals challenged with the MTV (+) carcinoma, although considerably less so in animals tested with the weakly immunogenic tumor D7T4S. A negative effect by MER on tumor frequency did not occur and was seen only once with regard to host life duration. Combined intervention with MER and 5-FU proved to be significantly and consistently superior to similar treatment with only 5-FU in animals challenged with the MTV(+) carcinoma. No such additive action by MER plus 5-FU was seen in mice challenged with D7T4S, however, nor did the other two chemoimmunotherapeutic regimens differ significantly in therapeutic efficacy from the corresponding chemotherapy alone in most of the trials with both tumors.

Adenocarcinoma↗
PubMed1976

Usefulness of the group-comparison method to demonstrate sex differences in spatial orientation and spatial visualization in older men and women.

This paper reports an analysis of sex differences in cognitive test scores covering the dimensions of spatial orientation and spatial visualization in groups of 6 older men and 6 women matched for speed of performance on a maze test and level of performance on a spatial relations task. Older men were more proficient solving spatial problems using the body as a referent, whereas there was no significant difference between the sexes in imagining spatial displacement. Matched comparisons appear a useful adjunct to population research to understand the type(s) of cognitive processes where differential performance by the sexes is observed.

Age Factors↗
PubMed1976

Teratomas in childhood.

Of 109 teratomas in children 86 were benign and 23 malignant. Sacro-coccygeal and pelvic teratomas predominated 52 cases, and these fell into three groups, post-sacral, dumb bell and pre-sacral. The 34 purely posterior tumours were always congenital and benign whilst the incidence of malignancy in dum bell and pre-sacral teratomas increased as the tumour became more internal. Other sites affected in order of frequency were: the gonads, head and neck, retroperitoneal anterior mediastinum and the central nervous system. Malignant teratomas were carcinomas usually containing glandular, capillary and clear cell areas, and metastases were similar. Immature tissues in benign teratomas were usually neural or connective tissue. They did not give rise to neuroblastomas or sarcomas and did not indicate a worse prognosis. Only two originally benign teratomas later developed malignancy.

Child, Preschool↗
PubMed1976

Tracheomalacia in association with congenital tracheoesophageal fistula.

Tracheomalacia is an important cause of morbidity and death following correction of congenital tracheoesophageal fistula and is a well defined syndrome which requires recognition and appropriate treatment. The symptoms and signs allow division into mild, moderate, and severe groups. When the clinical features suggest the presence of tracheomalacia, endoscopy should be carried out in order to confirm the diagnosis and document the severity. Mild and moderate cases can be managed conservatively; efficient and regular physiotherapy is the mainstay of treatment. Severe cases warrant consideration for the operation of tracheopexy which may be lifesaving and will certainly reduce the period of hospitalization and will simplify management.

Age Factors↗