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J Abbott

Publications and source records attributed to J Abbott.

At least 109 records · Page 6Linked to original sources
PubMed1977

Socioeconomic characteristics of the elderly: some black-white differences.

This article compares several characteristics of the black and white population aged 60 and older in March 1972. To distinguish race from economic-status effects the population is divided into quintiles of elderly units ranked by size of money income, and comparisons of selected demographic and economic characteristics are made within and across quintiles. Differences between social security beneficiaries and nonbeneficiaries are also analyzed to ascertain the effects of social security benefits. The educational and occupational disadvantages of blacks were evident even at the highest income level--a status more likely to be achieved by married black couples with both spouses working. Black elderly units were less likely than whites to have social security benefits, other government or private pensions, or income from assets. They were generally more likely to have earned income or to receive public assistance payments.

Black or African American↗
PubMed1976

Control of mating preferences in mice by genes in the major histocompatibility complex.

When a male mouse is presented with two H-2 congenic two female in estrus, his choice of a mate is influenced by their H-2 types. The term "strain preference" is used to describe the general tendency of the male population of one inbred strain to prefer two female of one H-2 type rather than another. The term "consistency of choice" is used to describe the added tendency of particular two males of one inbred strain, in sequential mating trials, to prefer two females of the H-2 type they chose in previous trials. Statistical analysis showed trends in the data that support the following conclusions: (a) The choice is made by the male, not the female. (b) The strain preference of two males may favor two females of dissimilar H-2 type (four of six comparisons), or of similar H-2 type (one of six comparisons). (c) Consistency of choice does not always correspond with strain preference. In one of six comparisons of H-2 genotypes there was no strain preference but pronounced consistency of choice by individual two male. This suggests memory, but fortuitous bias is not excluded. (d) Strain preference of the same male population may favor two male of the same or a different H-2 type, depending on which different H-2 type is offered as the choice alternative to self. These findings conform to a provisional model in which olfactory mating preference is governed by two linked genes in the region of H-2, one for the female signal and one for the male receptor. These mating preferences could in natural populations serve the purpose of increasing the representation of particular H-2 haplotypes or of maintaining heterozygosity of genes in the region of H-2.

Animals↗
PubMed1976

Ontogeny of murine B lymphocytes: sequence of B-cell differentiation from surface-immunoglobulin-negative precursors to plasma cells.

Among bone-marrow-derived (B) lymphocytes exist subpopulations of cells that can be induced to express the markers: surface immunoglobulin (Ig), the antigen associated with the immune response gene (Ia), and the receptor for the third complement component (CR). Inducible cells for the first two markers are found in bone marrow, and inducible cells for all three are in spleen. Experiments were designed to determine whether induction involves a single precursor cell population that on triggering with lipopolysaccharide expresses all three surface markers, or three separate precursor cell populations each of which expresses a single marker. Specific B cell subpopulations were eliminated by treatment with anti-Ig or anti-Ia and complement, or by rosette formation with erythrocytes-antibody-complement followed by differential centrifugation, and surviving cells were subsequently tested for inducibility of the three B cell markers. After anti-Ig cytolysis only Ig, but not Ia and CR, could be induced, implying that the Ia- and the CR-inducible cells are Ig+. Similarly, after anti-Ia cytolysis Ig and Ia but not CR could be induced. Thus, CR-inducible cells must have the Ig+Ia+ phenotype. Elimination of CR+ cells did not affect the induction of Ig, Ia, or CR from their precursors. None of the three elimination experiments affected the conversion of prothymocytes (Thy-1-) to thymocytes (Thy-1+). From these results we propose the hypothesis that the differentiation of B lymphocytes proceeds through at least four distinct stages characterized by the following phenotypes: Ig-Ia-CR- leads to Ig+Ia-CR- leads to Ig+Ia+CR- leads to Ig+Ia+CR+.

Animals↗
PubMed1975

The ontogeny of murine B lymphocytes. I. Induction of phenotypic conversion of Ia-to Ia+ lymphocytes.

When bone marrow and spleen cells of 4 week-old mice are fractionated on a discontinuous BSA gradient, a small fraction of Ia- cells is obtained which can be induced in vitro to express the Ia alloantigen within 2 hr. This is in precise parallel to the prothymocyte induction system of Komuro and Boyse. Ia specificity is ascertained by the use of two reciprocal antisera, A.TH anti-A.TL (anti-Iak) and A.TL anti-A.TH (anti-Ias), which yield the expected reaction pattern on induced bone marrow cells of (B6 X A)F1 (Iak) and SJL/J (Ias) mice. Induction can be effected by a number of agents, such as catecholamines, prostaglandin PGE1, cAMP, bacterial endotoxin, lipid A, ubiquitin, and thymopoietin. The last requires a 100-fold higher concentration for Ia+ induction as compared to prothymocyte induction, thus implying a lower affinity for the B cell receptor than for the thymocyte receptor. Ia- to Ia+ conversion involves cells different from prothymocytes, as indicated by: 1) the specific cytolytic effect of our anti-Ia sera which were shown to be free of activity against thymocytes; 2) an additive cytolytic effect of anti-Ia and anti-Thy-1 sera; and 3) the fact that the Ia inducible cells are sensitive to pretreatment with anti-immunoglobulin and C. This finding that Ia- precursor cells are already Ig+ is of interest for the B cell ontogeny, as it implies that Ig expression precedes Ia expression.

Animals↗
PubMed1974

The phenotypic complexity of myogenic clones.

A single cell isolated from cultured 8-day leg muscle may, when subcultured, yield a myogenic clone. A myogenic clone consists of myotubes and mononucleated cells. When such a myogenic clone is subcultured, large numbers of mononucleated cells are recovered. These mononucleated cells histologically and biochemically are indistinguishable from authentic fibroblasts cultured under the same conditions: they synthesize (alpha1)(2)alpha2 chains of collagen, large amounts of hyaluronic acid, and modest amounts of chondroitin sulfate. These mononucleated cells, however, will not chondrify when grown under culture conditions known to permit presumptive chondroblasts to differentiate terminally. These findings demonstrate that there is a population of single cells in 8-day muscle that is neither a myoblast nor a fibroblast, but is the common progenitor for cells in the myogenic and fibrogenic lineages: this progenitor, however, is beyond the point of readily yielding chondrogenic cells. These findings are discussed in terms of the limited number of phenotypic options open to differentiating cells in each of the successive compartments of their respective lineages.

Animals↗
PubMed1972

Chromosome studies in a neonatal population.

The results of chromosome studies on 6809 consecutive newborn infants are presented. One hundred and one (1.48%) were heterozygous for a marker chromosome, the significance of which is not at present clear. Twenty-two infants (0.32%) had a major chromosome abnormality. Only six of these infants (0.09%) had a clinically recognizable abnormal phenotype (Down's syndrome). The occult chromosome abnormalities included five sex chromosome abnormalities (one 47,XYY; two 47,XXY; two 47,XXX) and 11 balanced translocations. Seven of these were t(DqDq) and four were reciprocal translocations. The results of the present survey are combined with four other similar neonatal surveys in which a total of 23,328 newborns have been screened. Of these, 117 (0.5%; range 0.65-0.32%) had major chromosome abnormalities. The majority of these (72.7%) would not have been detected at birth without chromosome studies, an important fact in the context of prenatal diagnosis of chromosome disease and the early ascertainment of high-risk families.

Cells, Cultured↗
PubMed1969

The loss of phenotypic traits by differentiated cells. VI. Behavior of the progeny of a single chondrocyte.

A single, functional, mitotically quiescent chondrocyte may be induced to reenter the mitotic cyde, and produce a progeny of over 10(11) cells. Sessile, adherent, polygonal cells deposit matrix, whereas amoeboid, dispersed, flattened fibroblastic cells do not. The prior synthetic history of a cell is of greater importance in determining whether the characteristic chondrogenic phenotype will be expressed, rather than growth in "permissive" or "nonpermissive" medium. Clonal conditions select for stem-like cells, some of whose progeny may become polygonal chondrocytes. The retention of the characteristic chondrogenic phenotype in vitro is favored by pruning the dedifferentiated chondrocytes which arise in these cultures. Dedifferentiated chondrocytes interfere with the deposition and synthesis of chondroitin sulfate by neighboring functional chondrocytes. Possible mechanisms are proposed to explain this type of cell-cell or cell exudate interference. If the progeny of a single, genetically programmed chondrocyte may or may not synthesize chondroitin sulfate, then extragenic sites in the cytoplasm or cell surface must influence the decision as to which cluster of "luxur" molecules the cell will synthesize.

Animals↗