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Biomedical subjects

M A McDowell

Publications and source records attributed to M A McDowell.

At least 19 recordsLinked to original sources
PubMed2000

IL-12p70 production by Leishmania major-harboring human dendritic cells is a CD40/CD40 ligand-dependent process.

Leishmaniasis, a vector-borne parasitic disease, is transmitted during a sandfly blood meal as the parasite is delivered into the dermis. The parasite displays a unique immune evasion mechanism: prevention of IL-12 production within its host cell, the macrophage (i.e., where it differentiates and multiplies). Given the close proximity of skin dendritic cells (DC) to the site of parasite delivery, their critical role in initiating immune responses and the self-healing nature of Leishmania major (Lm) infection, we examined the interaction between myeloid-derived human DC and Lm metacyclic promastigotes (infectious-stage parasites) to model the early "natural" events of infection. We found that DC can take up Lm and, after this internalization, undergo changes in surface phenotype suggesting "maturation". Despite the intracellular location of the parasite and resultant up-regulation of costimulatory and class II molecules, there was no detectable cytokine release by these Lm-harboring DC. However, using intracellular staining and flow cytometry to analyze cytokine production at the single-cell level, we found that Lm-harboring DC, but not monocytes, produce large amounts of IL-12p70 in a CD40 ligand (CD40L)-dependent manner. Finally, DC generated from mononuclear cells from patients with cutaneous leishmaniasis (Lm), once loaded with live metacyclic promastigotes, were found to reactivate autologous primed T lymphocytes and induce a CD40L-dependent IFN-gamma response. Our results link the required CD40/CD40L interactions for healing with DC-derived IL-12p70 production and provide a mechanism to explain the genesis of a protective T cell-mediated response in the face of local immune evasion within the macrophage at the site of Leishmania delivery.

Animals↗
PubMed2000

Zinc intake of the U.S. population: findings from the third National Health and Nutrition Examination Survey, 1988-1994.

National survey data for 29,103 examinees in the third National Health and Nutrition Examination Survey were used to estimate mean and percentile distributions of dietary and total zinc intakes based on 24-h dietary recalls and vitamin/supplement use. Mean daily total intakes ranged from 5.5 mg in non-breast-feeding infants to 13 mg in adults and were higher in adolescent and adult males than in females (P <0.01). Mean total zinc intakes (22 mg) were approximately 10 mg higher in pregnant and lactating females than in nonpregnant, nonlactating females of the same age. Mean total zinc intakes were 0. 7 mg higher in adolescents (11.1 mg) and 2.5-3.5 mg higher in adults (13 mg) compared with mean dietary intakes, indicating the average contribution of supplements to total zinc intake. Mean total zinc intakes were significantly higher in non-Hispanic whites than in non-Hispanic blacks (P<0.01) and Mexican Americans (P<0.01) for men and women aged 51-70 y and > or =71 y due to higher zinc supplement use. The prevalence of zinc-containing supplements use ranged from 0. 1% in infants to 20.5% in adults. "Adequate" zinc intake in this survey population was 55.6% based on total intakes of >77% of the 1989 recommended dietary allowance. Young children aged 1-3 y, adolescent females aged 12-19 y and persons aged > or =71 y were at the greatest risk of inadequate zinc intakes.

Adolescent↗
PubMed1999

Inhibition of host cell signal transduction by Leishmania: observations relevant to the selective impairment of IL-12 responses.

Leishmania parasites are able to delay the onset of cell-mediated immunity by selectively impairing the ability of infected macrophages to produce interleukin (IL)-12. Leishmania infection arrests the JAK/STAT-mediated signal transduction involved in activation of the IL-12 p40 promoter; the phosphorylation defects may be initiated by ligation of the phagocyte receptors used by these organisms to gain entry into the host cell.

Animals↗
PubMed1998

Glycosylphosphatidylinositol-dependent secretory transport in Trypanosoma brucei.

We have investigated the role of glycosylphosphatidylinositol (GPI) anchors in forward secretory trafficking using African trypanosomes as a model system. Soluble GPI-minus forms of variant surface glycoprotein (VSG), in which the C-terminal GPI-addition peptide signal is deleted, are secreted from transformed procyclic trypanosomes with 5-fold reduced kinetics, relative to matched GPI-anchored constructs. Cell fractionation and immunofluorescence localization studies indicate that the GPI-minus VSG reporters accumulate in the endoplasmic reticulum (ER). This transport defect is specific, since overexpression of GPI-minus VSG has no effect on the rate of transport of a second soluble secretory reporter (BiPN) when co-expressed in the same cells. Two results suggest that delayed forward transport cannot be accounted for by failure to fold/assemble in the absence of a GPI anchor, thereby leading to prolonged association with ER quality-control machinery. First, no evidence was found for elevated association of GPI-minus VSG with the ER molecular chaperone, BiP. Secondly, newly synthesized GPI-minus VSG is dimerized efficiently, as judged by velocity-sedimentation analysis. GPI-dependent transport is not confined to the VSG reporters, because a similar dependence is found with another trypanosomal GPI-anchored protein, trans-sialidase. These findings suggest that GPI structures act in a positive manner to mediate efficient forward transport of some, and perhaps all, GPI-anchored proteins in the early secretory pathway of trypanosomes. Possible mechanisms for GPI-dependent transport are discussed with respect to current models of vesicular trafficking.

Animals↗
PubMed1998

Identification of an additional isoform of STAT5 expressed in immature macrophages.

We are interested in understanding the molecular basis of macrophage (Mphi) differentiation and activation by cytokines. Recent reports have suggested that the transcription factor STAT5 may play a role in Mphi differentiation. In the experiments described here, we assessed the expression of STAT5-related molecules in three Mphi cell lines, RAW 264.7, WEHI-3, and WEHI-3D+, which represent different stages of Mphi maturation, and also in primary peritoneal and bone marrow Mphi from BALB/c mice. The studies revealed that the previously characterized STAT5a and STAT5b isoforms are detectable at both the mRNA and protein levels in these Mphi populations. Additional STAT5-related proteins were detected by immunoblot analysis and were preferentially expressed in both the immature WEHI-3 cell population and the adherent bone marrow population containing immature Mphi. These results identify new isoforms of STAT5 and demonstrate that distinct patterns of expression of STAT5-related proteins are observed in Mphi at different stages of maturation.

Animals↗
PubMed1998

Analysis of the IFN-gamma-signaling pathway in macrophages at different stages of maturation.

We previously demonstrated that the macrophage cell lines RAW 264.7 and WEHI-3 exhibit distinct patterns of gene expression in response to IFN-gamma. This difference is controlled at the transcriptional level and results from a specific inability of the less mature WEHI-3 cells to utilize either the IFN-stimulated response element or the gamma-activated sequence DNA regulatory element in response to stimulation with IFN-gamma, while other aspects of IFN-gamma gene induction remain intact. In the work described here, we examined the components of the IFN-gamma signal transduction pathway in RAW 264.7 and WEHI-3 cells to determine whether differences in pathway components or activity exist in WEHI-3 cells that could give rise to this difference in transcriptional response. Reverse transcriptase-PCR (RT-PCR) and flow cytometric analyses indicated that the levels of IFN-gamma receptor mRNA accumulation and protein expression are comparable for RAW 264.7 and WEHI-3 cells. RT-PCR and immunoblot analyses revealed that the principal components of this signaling pathway, including JAK1, JAK2, and STAT1, are present in both RAW 264.7 and WEHI-3 cells. However, analysis of STAT1 DNA-binding activity by electrophoretic mobility shift assay and of STAT1 phosphorylation by immunoblot revealed that this DNA-binding factor is active in RAW 264.7, but not in WEHI-3, cells after IFN-gamma stimulation. These results demonstrate that the components of the IFN-gamma signal transduction pathway are intact in WEHI-3 cells, but stimulation of these cells by IFN-gamma does not result in STAT1 activation.

Cell Differentiation↗
PubMed1997

Expression of bloodstream variant surface glycoproteins in procyclic stage Trypanosoma brucei: role of GPI anchors in secretion.

Using transformed procyclic trypanosomes, the synthesis, intracellular transport and secretion of wild-type and mutant variant surface glycoprotein (VSG) is characterized. We find no impediment to the expression of this bloodstream stage protein in insect stage cells. VSG receives a procyclic-type phosphatidylinositol-specific phospholipase C-resistant glycosyl phosphatidylinositol (GPI) anchor, dimerizes and is N-glycosylated. It is transported to the plasma membrane with rapid kinetics (t(1/2) approximately 1 h) and then released by a cell surface zinc-dependent metalloendoprotease activity, a possible homolog of leishmanial gp63. Deletion of the C-terminal GPI addition signal generates a soluble form of VSG that is exported with greatly reduced kinetics (t(1/2) approximately 5 h). Fusion of the procyclic acidic repetitive protein (PARP) GPI anchor signal to the C-terminus of the truncated VSG reporter restores both GPI addition and transport competence, suggesting that GPI anchors play a critical role in the folding and/or forward transport of newly synthesized VSG. The VSG-PARP fusion is also processed near the C-terminus by events that do not involve N-linked oligosaccharides and which are consistent with GPI side chain modification. This unexpected result suggests that GPI processing may be influenced by adjacent peptide sequence or conformation.

Amino Acid Sequence↗
PubMed1997

Dietary methods research in the third National Health and Nutrition Examination Survey: underreporting of energy intake.

Assessment of diet is a critical component of the third National Health and Nutrition Examination Survey (NHANES III), which was designed to describe the health and nutritional status of the US population. We analyzed data collected with the primary dietary assessment instrument used in NHANES III, the 24-h recall, for 7769 nonpregnant adults aged > or = 20 y to investigate underreporting of total energy intake. Underreporting was addressed by computing a ratio of energy intake (EI) to estimated basal metabolic rate (BMRest). EI:BMRest was 1.47 for men and 1.26 for nonpregnant women; a population level of 1.55 is expected for a sedentary population. About 18% of the men and 28% of the women were classified as underreporters. Underreporting of energy intake was highest in women and persons who were older, overweight, or trying to lose weight. Underreporting varied according to smoking status, level of education, physical activity, and the day of the week the 24-h recall covered. Additionally, underreporting was associated with diets lower in fat (P < 0.01) and alcohol (P < 0.01 in women) when expressed as a percentage of total energy intake.

Adult↗
PubMed1995

Differential utilization of IFN-gamma-responsive elements in two maturationally distinct macrophage cell lines.

We have characterized the transcriptional response to IFN-gamma in two maturationally distinct macrophage populations: the mature RAW 264.7 cell line, phenotypically identical to thioglycollate-elicited peritoneal macrophages, and the less mature WEHI-3 cell line. We first investigated the use of two IFN-gamma-responsive regulatory elements, the interferon-stimulated response element (ISRE) and the gamma-activated sequence (GAS), in these cells. Transient transfection assays revealed that synthetic promoter constructs containing either the ISRE or GAS regulatory motif fused to a luciferase reporter gene were transcriptionally inactive in the WEHI-3 cell line. We then analyzed the expression in the two cell lines of a panel of known IFN-gamma-responsive genes that are transcriptionally controlled by different regulatory elements. RT-PCR analysis revealed that both cell lines responded to IFN-gamma treatment by up-regulating genes that are transcriptionally controlled by kappa B or W box DNA binding motifs. However, genes regulated by ISRE or GAS elements were induced by IFN-gamma only in the RAW 264.7 cell line. Kinetic analysis of the transcriptional activity of synthetic promoter constructs in the RAW 264.7 cell line showed rapid IFN-gamma induction through both the ISRE and GAS motifs, indicating that both elements are utilized early after IFN-gamma stimulation in mature macrophages. These results suggest that cis-acting DNA response element utilization, and the subsequent profiles of IFN-gamma-induced gene expression, differ in macrophages at different stages of maturation.

Base Sequence↗
PubMed1995

Total energy intake of the US population: the third National Health and Nutrition Examination Survey, 1988-1991.

The third National Health and Nutrition Examination Survey (NHANES III) was conducted to assess the health and nutritional status of the US population. As part of the nutritional status assessment, reliable 24-h dietary recalls were collected for 14,801 examined persons. Mean (+/- SEM) energy intakes are reported for persons aged > or = 2 mo by age, sex, and race-ethnicity. Males had higher mean energy intakes than did females. Energy intakes peaked during late adolescence and young adulthood and declined thereafter. Energy intake patterns were similar among non-Hispanic whites, non-Hispanic blacks, and Mexican Americans. Underreporting was addressed by computing a ratio of energy intake (EI) to estimated basal metabolic rate (BMRest). This ratio (EI:BMRest) was 1.47 for adult males and 1.26 for nonpregnant adult females. Overweight adults had a lower mean EI:BMRest (1.09 in females and 1.28 in males). Underreporting in food consumption surveys remains problematic among females and overweight persons.

Adolescent↗
PubMed1995

Macronutrient intakes among adult Hispanics: a comparison of Mexican Americans, Cuban Americans, and mainland Puerto Ricans.

OBJECTIVES: The purpose of this study was to compare energy and macronutrient intakes between adult Mexican Americans, Cuban Americans, mainland Puerto Ricans, and non-Hispanics. METHODS: Age-specific mean intakes were estimated based on 24-hour recalls from the Hispanic Health and Nutrition Examination Survey (HHANES) (1982 to 1984) and the Second National Health and Nutrition Examination Survey (NHANES II) (1976 to 1980) and were compared with the use of t tests. RESULTS: Mexican Americans had higher total fat, saturated fat, and monounsaturated fat intakes than did Puerto Ricans and older Cuban Americans. Cuban Americans and Puerto Ricans had similar intakes, except for younger Cuban Americans, who had higher total and saturated fat and lower carbohydrate intakes. Cholesterol intakes among Mexican American men and 60- to 74-year-old women were higher than those among other Hispanic groups. Carbohydrate and protein intakes were higher among Hispanic groups compared with those among non-Hispanics while total fat intakes were generally lower. CONCLUSIONS: Since macronutrient intakes differ between Hispanic groups, dietary research, recommendations, and interventions should be targeted to each group individually. Older Puerto Rican and Cuban American adults met population guidelines for reducing chronic disease risk for more macronutrients than any other group.

Adult↗
PubMed1994

Dietary intake of vitamins, minerals, and fiber of persons ages 2 months and over in the United States: Third National Health and Nutrition Examination Survey, Phase 1, 1988-91.

Intervention strategies aimed at reducing the prevalence of nutrition-related diseases, including designing nutrition policies and nutrition education and assistance programs, require effective monitoring of what Americans are eating. Nutrient reference data from the third National Health and Nutrition Examination Survey provide essential information to achieve these goals. Mean and median iron intakes were adequate in males of all race-ethnic groups but were generally low in females and young children. Mean and median calcium intakes were also higher in males than in females and were lower than recommendations in adolescents and in women of all ages. Mean sodium intakes for all age, sex, and race-ethnic groups exceeded the minimum requirements of healthy persons and were higher in non-Hispanic black children and adolescents than in non-Hispanic white and Mexican American children and adolescents. Mean fiber intakes also did not meet recommendations in most subgroups and were higher in Mexican American adults followed by non-Hispanic white adults and non-Hispanic black adults. Further research is planned to compare the food sources of energy and nutrients consumed by different population groups in NHANES III to similar results from earlier nation surveys. NHANES III, Phase 2 (1991-94) recalls were collected using the same dietary method as those collected in Phase 1 (1988-91), and other analyses will compare findings from both phases of NHANES III.

Adolescent↗
PubMed1994

The NHANES III Supplemental Nutrition Survey of older Americans.

The number of Americans aged > or = 65 y will reach 70 million by the mid-21st century. Health and nutritional-status data for older populations are urgently needed to identify future health resource and program needs. The Third National Health and Nutrition Examination Survey (NHANES III), a 6-y survey of the civilian, noninstitutionalized US population > or = 2 mo old began in 1988; approximately 7000 of the 30,000 examinees are aged > or = 50 y. The NHANES III dietary assessment component includes 24-h dietary recall and food-frequency interviews; information on dietary practices, vitamin and mineral supplement use, food sufficiency, and functional status is obtained. The National Institute on Aging funded a special dietary study to collect two independent replicate 24-h recalls by telephone from NHANES III-Cycle I examinees aged > or = 50 y. The expanded dietary data set for older people will be analyzed to examine characteristics of in-house and telephone dietary interviews and to examine factors previously shown to affect energy and nutrient intake estimates for older people.

Adolescent↗
PubMed1993

Calcium intakes of Mexican Americans, Cubans, Puerto Ricans, non-Hispanic whites, and non-Hispanic blacks in the United States.

OBJECTIVE: To compare dietary calcium intakes from food in Mexican Americans, Cubans, Puerto Ricans, non-Hispanic whites, and non-Hispanic blacks aged 11 through 74 years. DESIGN: Population survey data from the Hispanic Health and Nutrition Examination Survey and the second National Health and Nutrition Examination Survey were used to calculate calcium intake from a single 24-hour recall. These data were compared by age and sex between the five population groups. Food sources of calcium in the three Hispanic groups were also examined using 24-hour recall data. SUBJECTS: The sample consisted of 11,773 non-Hispanic whites, 1,728 non-Hispanic blacks, 4,739 Mexican Americans, 1,076 Cubans, and 1,835 Puerto Ricans. MAIN OUTCOME MEASURES: Mean calcium intake, percentage intake of Recommended Dietary Allowance, and, for Hispanics, food sources of calcium. STATISTICAL ANALYSES: Means were compared within age and sex groups between the five population groups using a t test. RESULTS: Calcium intakes from food in the three Hispanic groups were similar to intakes of non-Hispanic whites and higher than intakes of non-Hispanic blacks. Although dairy foods were the main sources of calcium for Hispanics, corn tortillas were important calcium sources among Mexican Americans. Women consumed less calcium than the Recommended Dietary Allowance in all age and racial or ethnic groups. APPLICATIONS: When assessing calcium intakes of the three Hispanic groups, ethnic differences in food sources of calcium need to be considered. Efforts to increase calcium intake in Hispanics also need to account for ethnic differences.

Adolescent↗
PubMed1993

Patterns of morphological variation of Salsuginus yutanensis (Monogenea: Ancyrocephalidae) over space and time.

Salsuginus yutanensis occurs on the gills of the plains topminnow Fundulus sciadicus Cope. The fish of this species have been found to vary morphologically and biochemically among disjunct populations. Morphological characteristics of the sclerotized parts of S. yutanensis were examined from 3 localities in Nebraska, over a 2-yr collecting period. Analysis of variance was used to assess morphological variation with respect to site and date. Worms from 2 localities, Keith and Saunders counties, differed significantly for most characters considered. A third site, also in Keith County, contained worms for which measurement means tended to be intermediate between those in the other 2 sites. This site-related difference was maintained over a pattern of broad seasonal variation and suggests that the site-related differences are of evolutionary origin. If this interpretation is true, then the parasite populations likely are isolated in a manner analogous to those of the host. However, differences due to effects of temperature on worm development were not ruled out as possible explanations for the observations although consistent temperature differences between the sites are unlikely, given the nature of the habitats studied.

Analysis of Variance↗