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Biomedical subjects

J Abbott

Publications and source records attributed to J Abbott.

At least 91 records · Page 5Linked to original sources
PubMed1987

Augmented preexcitation assessed by scintigraphic phase analysis during atrial pacing.

We sought to characterize the effect of augmented preexcitation on the phase image pattern associated with scintigraphic acquisition during conduction via accessory arteriovenous connections. For this reason we assessed phase image scintigraphy, acquired in sinus rhythm and during rapid atrial pacing in 12 patients with documented right (five patients) or left (seven patients) lateral accessory pathways. Augmented preexcitation during atrial pacing was documented at electrophysiologic study in all patients during atrial pacing at similar rates. Phase analysis was abnormal in only 8 patients during sinus rhythm but in all 12 patients during atrial pacing. Atrial pacing brought a significant delay in both mean left and right ventricular phase angles, LV phi and RV phi, respectively. With atrial pacing, the site of earliest phase angle, interpreted to indicate the site of earliest excitation, shifted to the site of the accessory pathway. There was increased relative "prematurity" of the mean phase angle of the ipsilateral ventricle and an absolute increase in the difference between mean and earliest left and right ventricular phase angles, delta phi (LV-RV) and delta phi 0 (LV-RV), respectively. In patients with right-sided pathways, delta phi (LV-RV) increased from 9.5 +/- 12.6 degrees to 47.9 +/- 22.8 degrees, whereas delta phi 0 (LV-RV) increased from 28.1 +/- 18.0 degrees to 67.6 +/- 25.0 degrees (both p less than 0.05). Patients with left-sided pathways demonstrated similar changes in which delta phi (LV-RV) decreased from 2.9 +/- 10.8 degrees to -26.5 +/- 9.0 degrees and delta phi 0 (LV-RV) decreased from 3.4 +/- 14.2 degrees to -27.4 +/- 17.9 degrees (both p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Induction of immunoglobulin isotype switching in cultured I.29 B lymphoma cells. Characterization of the accompanying rearrangements of heavy chain genes.

The murine B cell lymphoma I.29 contains cells expressing surface IgM or IgA with identical heavy chain variable regions (9, 25, and D. Klein and J. Stavnezer, unpublished data). Purified IgM+ cells from the lymphoma have been adapted to culture and induced to switch to IgA, IgE, or IgG2 by treatment with lipopolysaccharide (LPS) or by treatment with a monoclonal anti-I.29 antiidiotype plus LPS. Clones of IgM+ cells have been obtained and induced to switch. Under optimal conditions, 30% of the cells in the culture expressed IgA 8 d after the inducers were added, and by 15 d 90% of the cells were IgA+. In actively switching cultures, up to 50% of the cells whose cytoplasm stained positively with anti-IgA stained simultaneously with anti-IgM, which indicates that the appearance of IgA+ cells in the cultures was due to isotype switching and not to clonal outgrowth. Examination by Southern blotting experiments of the Ig heavy chain genes in I.29 cells before and after switching revealed that isotype switching was accompanied by DNA recombinations that occurred within or immediately 5' to the tandemly repeated switch sequences. Within 3 d after the addition of inducers of switching, the nonexpressed chromosome underwent a variety of deletions or expansions within the S mu region, and a portion of the S alpha regions had undergone a 0.9-kb deletion. In cultures that contained at least 12% IgA+ cells, rearranged, expressed alpha genes, produced by recombination between the S mu region within the expressed mu gene and the S alpha region, were detected.

Animals↗
PubMed1983

Knowledge of Social Security: survivor families with young children.

This article addresses how well informed survivor family heads are regarding Social Security program provisions that are specifically relevant to them and to their families. Based on responses to 10 questions on benefit provisions, the evaluation finds that among three groups of beneficiaries--widowers, current widows, and remarried widows--widowers were least well informed. Overall, about 23 percent of all widows (compared with only 6 percent of the widowers) were able to correctly respond to 8 or more of the 10 questions. The strongest of the three subject areas of program knowledge--child's benefits, spouse's benefits, and work and earnings provisions--was the child's benefits area. The relative differences between widows and widowers in their knowledge in this area were not as large as in the other two areas. The article concludes that the heads of most survivor beneficiary units were aware of the program provisions they need to know to participate effectively in the program, indicating that this population is well served by the agency information system.

Adolescent↗
PubMed1982

Specific IgA and IgE in childhood asthma, eczema and food allergy.

Allergen-specific IgA and IgE antibodies were compared in 250 children with asthma (Dermatophagoides pteronyssinus, rye grass pollen), in eighty-six children with eczema (whole egg, cow's milk) and in two groups of children with egg and cow's milk allergy. In each of the conditions investigated, food allergy, asthma and eczema increasing atopy was associated with increasing specific IgE levels to relevant allergens. There was no association of high IgE antibody levels with low IgA antibody levels in any of the conditions or allergens studied. There was, however, a tendency for subjects with more severe asthma to have high IgA levels with high IgE levels. IgA deficiency does not appear to be associated with atopic conditions of childhood.

Antibodies, Anti-Idiotypic↗
PubMed1981

Sequential expression of B lymphocyte surface antigens in vitro.

Serological techniques were used to examine the process of sequential surface antigen expression on differentiating B cells in vitro. A 4-day culture system is described in which bone marrow lymphocytes from neonatal mice acquire in sequence the ability to express Lyb-2, IgM, Ia and IgD in response to a 3-h induction with E. coli lipopoly-saccharide (LPS). Lyb-2 can be induced on day 1, IgM can be induced after 24 h, Ia after 48 h and IgD only after 96 h in culture. This sequence mimics the order of appearance of B cell surface antigens during ontogeny. When DNA synthesis is blocked from 0.24 h with hydroxyurea (HU), all surface antigens can be induced simultaneously by LPS. Immunoselection of one antigen-bearing population results in the loss of cells bearing other B cell antigens indicating that the surface antigens are induced on the same cells. When both HU and LPS were added to the cultures from the start, IgM appears after 11-14 h, Ia afer 14-15 h and IgD only after 19 h. Induction of antigen was demonstrated by he cytotoxicity assay, quantitative absorption and the protein A sheep red blood cell rosetting assaying. The results obtained show that there is a population of surface IgM-negative precursor B cells in young bone marrow which, when grown in vitro, become sequentially inducible for expression of B surface antigens. Inhibition of DNA synthesis promotes acquisition of the inducible state, and the sequence of antigen expression is correlated with specific time intervals after DNA synthesis has stopped.

Animals↗
PubMed1981

House dust mite counts in different types of mattresses, sheepskins and carpets, and a comparison of brushing and vacuuming collection methods.

Mite counts were compared in dust from three types of mattresses. Foam rubber mattresses appear preferable for mite sensitive atopic subjects; the surface of kapok mattresses averaged twice, and innerspring mattresses three times, the number of mites per square metre found on foam rubber mattresses (P less than 0.01). Sheepskins used for infant bedding were also found to be heavily infested, harbouring as many mites per square metre as bedroom carpet. Mite collections are best made with vacuum sampling methods in preference to a brush and results are best expressed in mites/m2.

Animals↗
PubMed1980

Work experience and earnings of middle-aged black and white men, 1965-71.

This article compares the work experience and earnings of a group of middle-aged black and white men over a period 1965-71. Differences in the likelihood of holding full-time/full-year jobs, in receiving comparable earnings, and in reducing labor-market activity were examined in relation to health, education, and occupation. Much similarity between the races was found in the frequency with which health affected work, but black men were clearly disadvantaged with respect to education and occupation. Even when these characteristic were similar, black men were less likely than white men to hold full-time, full-year jobs; when they did, they tended to have lower earnings. Racial differences in the proportion of full-time, full-year workers were smaller in 1971 than in 1965, but this shift resulted from a sharper decrease in full-time, full-year work among whites than blacks as they became older rather than from an increase in such employment among blacks. Even though the percentage increase in the median earnings of blacks was greater than that for whites, their 1970 median earnings did not reach the level of the 1965 median earnings of white men. The implications of these findings are that older black men share little, if at all, in the reported labor market and economic gains realized by young black workers. As a result, overall differences in retirement benefits between blacks and whites are likely to continue into the foreseeable future.

Adult↗
PubMed1979

The ontogeny of B lymphocytes. V. Lipopolysaccharide-induced changes of IgD expression on murine B lymphocytes.

Murine splenocytes contain two minor subpopulations of B cells, one inducible by lipopolysaccharide to convert within 2 h from IgD- to IgD+ and the other to change from IgD+ TO IgD-. These two subpopulations can be separated by density centrifugation. Their relative proportions show a marked age dependency: IgD- leads to IgD+ cells are more frequent in suckling mice, while IgD+ leads to IgD- inducible cells become predominant in mice older than 3 weeks. The age dependency observed in the relative proportions between the two cell types suggest that they are ontogenetically related as progenitor-successor. This hypothesis is corroborated by phenotype analysis of the two subsets, revealing IgD- leads to IgD+ cells as IgM+, Ia+, complement receptor- (CR-) and IgD+ leads to IgD- cells as IgM+, Ia+, CR+. Our data show that IgD and CR are expressed concomitantly during B cell differentiation. On further differentiation, induced by lipopolysaccharide, both markers are lost from the cell surface at different rates: IgD decreases significantly in a very short period (less than 2.5 h) while induction of a decline in CR requires longer culture periods (greater than 8 h). Th: loss of IgD may thus herald an early differentiation event toward antibody-producing cells.

Aging↗
PubMed1979

Simple and choice reaction time methods in the study of motor programming.

In an extensive series of experiments Sternberg, Monsell, Knoll, and Wright (1978) reported that simple RT increased as a linear function of the number of items to be pronounced or typed. The present experiments replicate a portion of these results, but show that the effect is less general than may have been supposed. Since the effect does not occur in every case in which a response programming interpretation would predict it, this interpretation must be rejected. This conclusion is consistent with the viewpoint that response programming should be investigated in a choice- rather than simple-RT paradigm. In this view, motivated subjects can program responses in advance of the simple-RT interval because the particular response to be made has been precued. Effects of response parameters which are observed for motivated subjects in the simple-RT paradigm, such as those reported by Sternberg et al. (1978), should be attributed to processes other than programming motor responses.

Journal Article↗
PubMed1979

Action of complement in the lysis of mouse sarcoma cells sensitized with H-2 alloantibody.

A modified cytotoxicity assay was adapted from classical erythrocytolytic assays, in which complement components were added in sequence to antibody-sensitized cells. This assay was applied to a model system in which mouse sarcoma cells were sensitized with H-2 alloantibody. The stepwise presentation of complement components combined with the stabilization of C2 by iodine treatment considerably augmented the lytic efficiency of human complement. More generally, the techniques adopted for this study provide a new model for obtaining basic information about selective reaction steps concerned in lysis of nucleated cells by alloantibody and complement. Comparisons of the lysis of sheep erythrocytes by xenoantibody with the lysis of mouse sarcoma cells by H-2 alloantibody, in our assay system with oxidized or untreated human complement, disclosed a difference in the kinetics of C142 formation, manifest in a lag phase and a protracted tmax for the sarcoma cells. These data may suggest that multiple complement-mediated functional lesions are necessary for immune lysis of nucleated cells.

Animals↗
PubMed1977

Role of cardiac catheterization in infective endocarditis.

The benefits and hazards of catheterization and angiography were evaluated in 19 patients with acute aortic and/or mitral endocarditis and heart failure. In 14 patients (74%), the bedside diagnosis of valvular insufficiency and heart failure was proved correct. In three patients with both aortic and mitral valve disease, angiography (without hemodynamic measurements) was necessary to clarify the diagnosis. Angiography detected four aortic aneurysmal erosions that were unsuspected clinically, but missed three others. After angiography, heart failure worsened in two patients with severe progressive aortic insufficiency and one died. Thus, catheterization-angiography was of greatest value if more than one left-sided valve lesion was present, if extravalvular diseases mimicked heart failure, or if extravalvular infection was present. Patients with isolated, clear-cut mitral insufficiency usually do not need these diagnostic procedures, and they are probably contraindicated in patients with severe aortic regurgitation with rapidly progressing heart failure.

Adult↗