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Biomedical subjects

P L Jackson

Publications and source records attributed to P L Jackson.

At least 19 recordsLinked to original sources
PubMed1995

A hybrid-hybrid matrix method for 3D NOE-NOE data analysis.

A hybrid-hybrid matrix method is described that quantitatively analyzes 3D NOE-NOE NMR data. Experimental 3D data are merged with simulated 3D data to create a hybrid 3D NOE-NOE spectrum. This is then deconvoluted into a 2D hybrid NOESY spectrum. The deconvoluted, 2D hybrid NOESY spectrum can then be merged with other 2D NOESY experimental data along with additional simulated 2D data as necessary to create a hybrid-hybrid 2D NOE volume matrix. This hybrid-hybrid volume matrix is then used with the complete relaxation program, MORASS, to calculate a rate matrix, and the resulting distances taken from the off-diagonal cross-relaxation rates can then be utilized in a distance geometry or restrained molecular-dynamics refinement of the structure. This process is repeated until a satisfactory agreement between the calculated and observed 3D volumes is obtained. This hybrid-hybrid matrix method retains computational efficiency and utilizes the resolution of the 3D data set while retaining any information content of the available 2D data. The initial tests of the deconvolution algorithm give high correlation results even with the introduction of random error into the 3D data set. Our results suggest that the hybrid-hybrid matrix method for analysis of 3D NOE-NOE spectra may provide a viable tool in the refinement of large molecules.

Algorithms↗
PubMed1990

Perceived self-esteem among children diagnosed with precocious puberty.

Self-esteem is known to be altered in children with chronic illness. Do accelerated normal changes, such as those that occur in children with precocious puberty, also alter the child's self-esteem? Twenty-eight children with precocious puberty participated in a nonrandomized descriptive pilot study using a structured interview, the Piers-Harris Children's Self-Concept Scale, and self-portrait drawings. Results indicate that the overall self-esteem of the majority of children was within normal limits as measured by the Piers-Harris Children's Self-Concept Scale, but closer analysis found that many of the children had difficulty with peer relationships and increased levels of anxiety. These findings were supported by the results of the structured interview and the children's self-portraits. Nursing implications from this pilot study are discussed.

Adolescent↗
PubMed1989

Precocious puberty: identifying early sexual development.

Primary care providers should have the ability to identify normal and abnormal variations of sexual development in children. The incidence of precocious puberty is approximately one child in every 10,000 children in the United States. While etiologies vary, precise differential diagnosis is essential because it will determine the course of treatment required. New forms of therapy using long-acting luteinizing releasing factor agonists are currently being investigated. Developmentally appropriate explanations for affected children regarding the diagnosis and treatment plan are a crucial component of care. Ongoing educational and emotional support for the child and family are essential as they learn to cope with early sexual development.

Adolescent↗
PubMed1983

Physical characteristics of the lips underlying vowel lipreading performance.

To evaluate the relationship between physical characteristics of the lips during vowel production and vowel lipreading confusions, four female talkers were videotaped producing 15 American English vowels and diphthongs in an /h/-V-/g/ context. Ten normal-hearing adults identified the stimuli through lipreading. Three analyses were performed. First, using confusion matrices for individual and pooled talkers, the stimuli were located in a two-dimensional space using multidimensional scaling. The ten monophthongs revealed a clear lip spreading/rounding dimension and a tongue height dimension, and while diphthongs also showed influence of lip rounding, more variability on the tongue height dimension was apparent. Second, tracings were made of the talkers' lips on a single videotape field representing the maximum opening or constriction for each of the 40 monophthong tokens (ten vowels X four talkers), and six physical measurements of the tokens were derived as descriptors of the vowel nuclei. Third, difference scores and other measures of physical pairwise similarity were used as predictors of two ways of representing the vowel lipreading confusions in a multiple regression paradigm. Results indicated that the physical measures were moderately successful as predictors of vowel perception (accounting for approximately 50% of the variance in the perceptual distance measure), although considerable differences in the strength of the prediction occurred among talkers.

Lip↗
PubMed1981

Control of the simian fetal hemoglobin switch at the progenitor cell level.

This investigation was designed to define the cellular level at which the gamma to beta globin switch is established in the developing simian fetus in order to determine whether the switch is controlled by environmental influences within differentiating erythroid precursors or predetermined by the genetic program of erythroid progenitors. Samples of marrow and liver were obtained from rhesus fetuses throughout the switch period, and marrow was obtained from adult rhesus monkeys. Globin chain synthesis was then measured in differentiated erythroblasts and in erythroid progenitor-derived colonies grown in semisolid media. The relative rates of synthesis of gamma and beta chains were determined by the uptake of [(3)H]leucine into the respective chains separated by Triton gel electrophoresis and in some cases by urea carboxymethyl cellulose chromatography. Four periods of the switch were defined during fetal development. In the preswitch period both erythroblasts and progenitor-derived colonies produced <5% beta globin. In the early switch erythroblasts produced 5-15% beta globin, while progenitor-derived colonies produced 10-35% beta globin. In mid-switch erythroblasts synthesized 50% beta globin, whereas progenitor-derived colonies produced only 15-35% beta. At the completion of the switch erythroblasts produced 100% beta globin, while progenitor-derived colonies produced as little as 40% beta chains. We conclude that the program of globin synthesis that characterizes the fetal switch is established at the level of erythroid progenitors. Fetal erythroid burst-forming units (BFU-E) dominate the marrow prior to the switch. The early switch period is heralded by the appearances of adult erythroid burst-forming units programmed to express increasing beta chain synthesis in colonies. By mid-switch a second class of adult erythroid progenitors capable of giving rise to fetal and adult hemoglobin synthesis in in vitro colonies becomes apparent. These shifting populations of erythroid progenitors with unique globin synthesis programs give rise to the erythroblasts that create the sigmoid pattern of the fetal to adult hemoglobin switch in the developing simian fetus.

Age Factors↗
PubMed1980

Mature bone marrow erythroid burst-forming units do not require T cells for induction of erythropoietin-dependent differentiation.

Cell-cell interactions between mature T cells and peripheral blood null cells induce erythropoietin-stimulated differentiation of peripheral blood-derived erythroid progenitors. By the use of complement-fixing cytolytic murine hybridoma and antibody uniquely reactive with mature T lymphocytes, this dependence of immature peripheral blood erythroid burst-forming unit (BFU-E) differentiation upon mature T cells or a T cell conditioned medium is confirmed. By using the same antibody, it is demonstrated that the differentiation of mature bone marrow BFU-E does not require either mature T cells or lymphocyte mitogenic factor. These findings do not preclude the presence in the bone marrow of other cells, perhaps even immature T cells, that influence erythropoietin-dependent erythroid differentiation of mature marrow BFU-E.

Bone Marrow Cells↗
PubMed1980

Monocytes do not inhibit peripheral blood erythroid burst forming unit colony formation.

To determine a possible role of peripheral blood monocytes in erythroid differentiation, various fractions of peripheral blood mononuclear cells were prepared from normal volunteers. The fractions contained 3-95% monocytes. These freshly prepared monocytes did not inhibit erythroid burst forming unit expression in plasma clot erythroid colony culture. Null cell preparations contaminated by up to 84% monocytes expressed erythroid burst forming unit colony formation when either T lymphocytes or T-cell conditioned medium was added. These results indicate that certain peripheral blood null cells engage the program of erythroid differentiation in the presence of T cells and erythropoietin. Monocytes do not inhibit this engagement.

Adult↗
PubMed1980

Virus and cell requirements for Friend virus granulocytic leukemogenesis in long-term bone marrow cultures of NIH swiss [N:NIH(S)] mice.

The effect of hematopoietic stem cell age on leukemogenesis in vitro was tested in nonrecharged, corticosterold-supplemented NIH Swiss [N:NIH(S)] mouse long-term bone marrow cultures infected with Friend murine leukemia virus of anemia-inducing strain (F-MuLV-A) or spleen focus-forming virus (SFFV) [Rauscher murine leukemia virus (R-MuLV)], a pseudotype virus derived by rescue of the SFFV genome from SFFV-Balb/3T3 clone A31 nonproducer cells with clonal helper R-MuLV. Cultures at 33 degrees C derived from 10-day-old or adult mouse marrow generated colony-forming unit culture granulocytic macrophage (CFUc) progenitor cells for over 20 weeks and colony-forming unit spleen cells for 14 weeks and generated permanent granulocytic leukemia cell lines after infection with F-MuLV-A at week 1, 2, or 4 but not at week 8. Leukemia lines were of granulocyte phenotype whether induced by F-MuLV-A or SFFV (R-MuLV) and synthesized myeloperoxidase and lysozyme but were restricted in ability to generate superoxide in response to phorbol myristate acetate stimulation. Cultures (31 degrees C) infected with temperature-sensitive (ts) helper virus mutant pseudotypes of SFFV as well as SFFV (R-MuLV) generated granulocytic leukemia lines, whereas only SFFV (R-MuLV) pseudotype virus-infected cultures became leukemic at 37 degrees C. R-MuLV wild type or ts mutant helper virus infection alone increased cell proliferation and numbers of CFUc but did not generate leukemia. These data indicated that gene(s) specific to F-MuLV-A or a virus rescued from SFFV-Balb/3T3 clone A31 nonproducer cells are required for transformation in vitro of a hematopoietic stem cell present in early but absent in late bone marrow cultures.

Animals↗
PubMed1979

Visual vowel and diphthong perception from two horizontal viewing angles.

This study investigated vowel and diphthong lipreading performance from 0 degree and 90 degree angles of observation. Sixteen English vowels and diphthongs were placed in an /h-g/ context to form the stimulus items. Each item was presented by a speaker ten times in random order for a total of 160 items. The speaker was simultaneously videotaped from 0 degree and 90 degree angles under optimal lighting conditions. Ten normal hearing adults subjects phonetically recorded the vowel or diphtong they perceived as each item was visually presented. The diphthong stimuli were significantly easier to identify than the vowel stimuli at both angles of observation. In addition, no significant differences were found between the 0 degree and 90 degree angles in terms of percentage of correct identifications of all phonemes examined. Orderly, predictable confusions also were observed. Those confusions occurring in visual diphthong recognition tended to shift toward the stressed vowel element of the diphthong or to a vowel produced in a manner similar to the stressed element.

Adult↗
PubMed1978

Actin--membrane interactions: association of G-actin with the red cell membrane.

Chemically tritiated actin from rabbit skeletal muscle was used to investigate the association of G-actin with the red cell membrane. The tritiated actin was shown to be identical to unmodified actin in its ability to polymerize and to activate heavy meromyosin ATPase. Using sealed and unsealed red cell ghosts we have shown that G-actin binds to the cytoplasmic but not the extracellular membrane surface of ghosts. Inside-out vesicles which have been stripped of endogenous actin and spectrin by low-ionic-strength incubation bind little G-actin. However, when a crude spectrin extract containing primarily spectrin, actin, and band 4.1 is added back to stripped vesicles, subsequent binding of G-actin can be increased up to 40-fold. Further, this crude spectrin extract can compete for and abolish G-actin binding to unsealed ghosts. Actin binding to ghosts increases linearly with added G-actin and requires the presence of magnesium. In addition, actin binding is inhibited by cytochalasin B and DNAase I. Negative staining reveals an abundance of actin filaments formed when G-actin is added to reconstituted inside-out vesicles but none when it is added to unreconstituted vesicles. These observations indicate that added G-actin binds to the red cell membrane via filament formation nucleated by some membrane component at the cytoplasmic surface.

Actins↗