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Biomedical subjects

K Gallagher

Publications and source records attributed to K Gallagher.

At least 19 recordsLinked to original sources
PubMed2000

Roles for polarity and nuclear determinants in specifying daughter cell fates after an asymmetric cell division in the maize leaf.

Asymmetric cell divisions occur repeatedly during plant development, but the mechanisms by which daughter cells are directed to adopt different fates are not well understood [1,2]. Previous studies have demonstrated roles for positional information in specification of daughter cell fates following asymmetric divisions in the embryo [3] and root [4]. Unequally inherited cytoplasmic determinants have also been proposed to specify daughter cell fates after some asymmetric cell divisions in plants [1,2,5], but direct evidence is lacking. Here we investigate the requirements for specification of stomatal subsidiary cell fate in the maize leaf by analyzing four mutants disrupting the asymmetric divisions of subsidiary mother cells (SMCs). We show that subsidiary cell fate does not depend on proper localization of the new cell wall during the SMC division, and is not specified by positional information acting on daughter cells after completion of the division. Instead, our data suggest that specification of subsidiary cell fate depends on polarization of SMCs and on inheritance of the appropriate daughter nucleus. We thus provide evidence of a role for unequal inheritance of an intracellular determinant in specification of cell fate after an asymmetric plant cell division.

Cell Division↗
PubMed2000

Patient compliance and blood pressure control on a nuclear-powered aircraft carrier: impact of a pharmacy officer.

The impact of a pharmacy officer on patient compliance and blood pressure control on a deployed nuclear-powered aircraft carrier for a 2-week at-sea period was evaluated. Before any counseling by a pharmacy officer, 43 crewmembers on chronic medications anonymously completed a compliance questionnaire. The pharmacy officer then counseled these crewmembers. A follow-up compliance questionnaire was completed 2 weeks later. After counseling, compliance had increased 58% (p < 0.0001) from compliance measured before counseling. The pharmacy officer also initiated therapeutic interventions. Among 26 crewmembers diagnosed as hypertensive, preintervention blood pressure (BP) measurements were obtained. Ten to 14 days after the initial BP measurement, BP was remeasured. After intervention, 31% (p < 0.02) more crewmembers were at BP goal compared with before intervention. A pharmacy officer, working closely with a medical officer, improved patient compliance and blood pressure control. One problem identified was that these warships require computer software that can prospectively identify drug-drug interactions.

Blood Pressure↗
PubMed1999

discordia mutations specifically misorient asymmetric cell divisions during development of the maize leaf epidermis.

In plant cells, cytokinesis depends on a cytoskeletal structure called a phragmoplast, which directs the formation of a new cell wall between daughter nuclei after mitosis. The orientation of cell division depends on guidance of the phragmoplast during cytokinesis to a cortical site marked throughout prophase by another cytoskeletal structure called a preprophase band. Asymmetrically dividing cells become polarized and form asymmetric preprophase bands prior to mitosis; phragmoplasts are subsequently guided to these asymmetric cortical sites to form daughter cells of different shapes and/or sizes. Here we describe two new recessive mutations, discordia1 (dcd1) and discordia2 (dcd2), which disrupt the spatial regulation of cytokinesis during asymmetric cell divisions. Both mutations disrupt four classes of asymmetric cell divisions during the development of the maize leaf epidermis, without affecting the symmetric divisions through which most epidermal cells arise. The effects of dcd mutations on asymmetric cell division can be mimicked by cytochalasin D treatment, and divisions affected by dcd1 are hypersensitive to the effects of cytochalasin D. Analysis of actin and microtubule organization in these mutants showed no effect of either mutation on cell polarity, or on formation and localization of preprophase bands and spindles. In mutant cells, phragmoplasts in asymmetrically dividing cells are structurally normal and are initiated in the correct location, but often fail to move to the position formerly occupied by the preprophase band. We propose that dcd mutations disrupt an actin-dependent process necessary for the guidance of phragmoplasts during cytokinesis in asymmetrically dividing cells.

Actins↗
PubMed1998

Electrostatic contributions to heat capacity changes of DNA-ligand binding.

Significant heat capacity changes (DeltaCp) often accompany protein unfolding, protein binding, and specific DNA-ligand binding reactions. Such changes are widely used to analyze contributions arising from hydrophobic and polar hydration. Current models relate the magnitude of DeltaCp to the solvent accessible surface area (ASA) of the molecule. However, for many binding systems-particularly those involving non-peptide ligands-these models predict a DeltaCp that is significantly different from the experimentally measured value. Electrostatic interactions provide a potential source of heat capacity changes and do not scale with ASA. Using finite-difference Poisson-Boltzmann methods (FDPB), we have determined the contribution of electrostatics to the DeltaCp associated with binding for DNA binding reactions involving the ligands DAPI, netropsin, lexitropsin, and the lambda repressor binding domain.

Antineoplastic Agents↗
PubMed1998

Induction of mortality and malformation in Xenopus laevis embryos by water sources associated with field frog deformities.

Water samples from several ponds in Minnesota were evaluated for their capacity to induce malformations in embryos of Xenopus laevis. The FETAX assay was used to assess the occurrence of malformations following a 96-hr period of exposure to water samples. These studies were conducted following reports of high incidences of malformation in natural populations of frogs in Minnesota wetlands. The purpose of these studies was to determine if a biologically active agent(s) was present in the waters and could be detected using the FETAX assay. Water samples from ponds with high incidences of frog malformations (affected sites), along with water samples from ponds with unaffected frog populations (reference sites), were studied. Initial experiments clearly showed that water from affected sites induced mortality and malformation in Xenopus embryos, while water from reference sites had little or no effect. Induction of malformation was dose dependent and highly reproducible, both with stored samples and with samples taken at different times throughout the summer. The biological activity of the samples was reduced or eliminated when samples were passed through activated carbon. Limited evidence from these samples indicates that the causal factor(s) is not an infectious organism nor are ion concentrations or metals responsible for the effects observed. Results do indicate that the water matrix has a significant effect on the severity of toxicity. Based on the FETAX results and the occurrence of frog malformations observed in the field, these studies suggest that water in the affected sites contains one or more unknown agents that induce developmental abnormalities in Xenopus. These same factors may contribute to the increased incidence of malformation in native species.

Animals↗
PubMed1997

Investigation into the concanavalin A reactivity, fucosylation and oligosaccharide microheterogeneity of alpha 1-acid glycoprotein expressed in the sera of patients with rheumatoid arthritis.

alpha 1-Acid glycoprotein (AGP) exists as an heterogeneous population of glycosylated variants (glycoforms) in plasma. The concentration of AGP increases some 2-5 fold in certain pathophysiological states exemplified by the chronic inflammatory disease, rheumatoid arthritis (RA). Moreover, the expressed glycosylation pattern alters in such conditions, indicating functional significance that is likely to be related to the oligosaccharide heterogeneity. We have investigated the heterogeneity of AGP glycosylation using the technique of high pH anion-exchange chromatography (HPAEC). AGP was isolated from the blood of RA sufferers, partially separated by Concanavalin A (Con A) affinity chromatography into bound and non-bound fractions and was enzymatically deglycosylated. Chromatography on the pellicular HPAE resin at pH 13 separated the released oligosaccharides and allowed a comparison of profiles in terms of branching and fucosylation. Results demonstrate an abnormal RA AGP glycosylation, with a tendency towards tri- and tetra-antennary oligosaccharides and enhanced fucosylation, in addition to the possible existence of penta-sialylated RA AGP glycoforms.

Arthritis, Rheumatoid↗
PubMed1997

The Michigan equine monitoring system. I. Design, implementation and population estimates.

The Michigan equine monitoring system (MEMS) was designed and implemented in the State of Michigan, starting in 1991. The program was designed systematically to track the State's equine population, its health, and its economic implications to the equine industry. The MEMS was designed as a two-phase program. Phase I (the population and economic survey; the subject of this paper) was designed to provide new and statistically valid information describing the size, composition, location and economic characteristics of the Michigan equine industry. A standardized questionnaire was used to collect data via mail, telephone and personal interviews. Of the 3000 randomly selected list-frame samples, 2800 (93%) participated. However, 650 of these had no equids. There were 129,932 equids reported compared with 160,000 in 1984. The American Quarter Horse, Standardbred and Arabian breeds were the most numerous. Detailed results, including the size of equine operations/herds, uses, geographical distribution and the financial structure of the industry, are presented. A detailed account of the strategies used in designing and implementing the system is provided.

Animal Husbandry↗
PubMed1997

Risk factors for colic in the Michigan (USA) equine population.

A population-based prospective epidemiological study was conducted to assess risk factors for equine colic. A stratified sample of 3925 equids in 138 randomly selected equine farms in the state of Michigan was monitored in two 12-month rounds of data collection. Incidence densities were used to describe the rate of development of colic in the study population. Mortality rates, case fatality rates and survival rates were used to describe the severity of colic on the study population. Multivariable logistic regressions with random effects (grouped according to farm) were used to identify risk factors associated with occurrence of colic. A total of 3175 equids from 132 farms from the starting population of 3925 equids in 138 farms was used in the multivariable analysis. There were 77 cases of colic reported during the study period in 62 animals. Of these animals, 54 (87%) had one case, 5 (8%) had two cases, 2 (3%) had three cases, and 1 (2%) had seven cases. Of the cases reported, 49 (64%) were non-specific diagnoses, 13 (17%) impaction/acute intestinal obstruction colics, 7 (9%) spasmodic colics, 4 (5%) sand colics, 2 (3%) gas colics, 1 (1%) verminous mesenteric arteritis, and 1 (1%) enteritis due to ingestion of moldy grain. The annual incidence density of colic in the study was 3.5 cases per 100 equid-years. The surgical treatment risk was 17% (13/77). The overall mortality risk due to colic was 0.5 deaths per 100 equids, and the case fatality risk was 13% (10/77). The case fatality risk for cases treated surgically was 31% (4/13), while the case fatality risk for non-surgical colics was 10% (7/69). Risk factors associated with significantly increased likelihood of developing colic were foaling during the study, deworming during the study, increased age, and participation in showing activities. Geldings and equids provided group drinking water from sources other than tanks, buckets and automatic waterers were significantly associated with reduced risk of colic.

Animals↗
PubMed1997

Asymmetric cell division and cell fate in plants.

A variety of approaches has recently been employed to investigate how sister cells adopt distinct fates following asymmetric divisions during plant development. Surgical and drug studies have been used to analyze asymmetric divisions during both early embryogenesis in brown algae and pollen development in tobacco. Genetic screens have been used to identify genes in Arabidopsis thaliana that are required for specific asymmetric cell divisions during pollen and root development. These studies indicate that cell polarity and division orientation are closely tied to the process of cell fate specification, and suggest that differential inheritance of determinants and positional information may both be involved in the specification of cell fates following asymmetric cell division.

Cell Division↗
PubMed1997

Timing of lymphocyte activation in neonates infected with human immunodeficiency virus.

Human immunodeficiency virus (HIV) infection in children is associated with qualitative and quantitative changes in the peripheral lymphocyte surface phenotype beyond the normal maturational changes. Neonates, however, have been reported to have a delayed immune response to HIV compared to HIV-infected adults. We prospectively performed immunophenotyping of T lymphocytes by three-color immunofluorescent labeling and laser flow cytometry to determine the timing of phenotypic alterations in 112 neonates born to HIV-infected mothers. Serial testing was performed at birth (cord blood) and at 2, 6, and 12 weeks of age. Data were divided retrospectively for analysis into those for HIV-infected (n = 14) infants and those for exposed, uninfected infants. Our results show that both infected and uninfected infants had a decline in the percentages and numbers of CD4 cells beginning at 2 weeks of age but that the decline was greater in the HIV-infected group. The activation and differentiation of CD8 T cells in HIV+ infants were shown by a significant increase in CD45RA- CD45RO+ CD8+ cells by 6 weeks of age and by increases in CD8+ S6F1+ CD3+ cells and HLA-DR+ CD38+ CD8+ cells by 2 weeks of age. These results indicate that HIV-infected neonates show alterations in T-cell phenotype reflecting those reported for older HIV-infected children. Most importantly, neonatal T cells are able to respond to HIV within the first weeks of life.

Antigens, CD↗
PubMed1996

Maternal occupation and pregnancy outcome.

Few studies have addressed the effect of maternal employment on late pregnancy outcomes. The National Maternal and Infant Health Survey, a probability sample of U.S. livebirths, stillbirths, and infant deaths in 1988, provided an opportunity to evaluate mothers' jobs in relation to preterm delivery, very low birthweight ( < 1,500 gm), moderately low birthweight (1,500-2,499 gm), small-for-gestational-age (SGA) birth, stillbirth, and infant death. We aggregated mothers' jobs, which were ascertained by mailed questionnaire or telephone interview, into categories for analysis. We considered jobs held at any time during pregnancy and jobs held during the fifth month of pregnancy. Relative to the referent group of clerks, textile workers had adjusted odds ratios of 1.5 or greater for all outcomes, with elevated risks also found sporadically for food service workers (preterm delivery, SGA birth, stillbirth) and electrical equipment operators (all outcomes except for still-birth and infant death). Janitors had elevated adjusted odds ratios of 2.0 or greater for preterm delivery and stillbirth. Relative to clerks, teachers and librarians tended to have reduced risks for adverse outcomes.

Adolescent↗
PubMed1996

Report of the American Diabetes Association's Task Force on standardization of the insulin assay.

Recent large-scale epidemiological studies demonstrate that blood concentrations of immunoreactive insulin predict the development of NIDDM and IDDM and are associated with the risk of several degenerative diseases, such as coronary and peripheral vessel atherosclerosis, hypertension, and dyslipidemia. The reliability of these measurements is dependent on a biological assay that has not been well standardized between laboratories. Recognizing this, the American Diabetes Association organized a task force to assess comparability of blood insulin measurements between laboratories and to suggest techniques to improve comparability. The task force found that identical serum and plasma samples measured in different laboratories produced widely disparate values that were unacceptable for population comparisons. Use of a single reference standard did little to improve comparability. Assay characteristics such as linearity, recovery, accuracy, and cross-reactivity to proinsulin and its primary conversion intermediates varied among the laboratories, and they did not readily explain differences in the measurements made from assay to assay. Use of the same assay kit in different laboratories did not always ensure comparable measurements. Linear regression of assay results from one laboratory to an arbitrarily chosen reference assay greatly improved comparability and demonstrated the potential value in comparing each assay to a reference method. The task force report defines acceptable assay characteristics and proposes a three-step process of insulin assay proficiency and comparability. A central reference assay and ongoing sample exchange will be needed to allow reliable comparisons of insulin measurements made in different laboratories. Rigorous quality control and continuous quality improvement are needed to maintain reliability of the insulin measurement.

Diabetes Mellitus↗