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P Archer

Publications and source records attributed to P Archer.

At least 19 recordsLinked to original sources
PubMed2005

Quantitative experimental determination of the Landau-potential of chiral enantiomer doped ferroelectric liquid crystals.

The full Landau potential was determined for a ferroelectric liquid crystal doped with varying concentrations of the chiral dopant R1011 and its enantiomer S1011. A multi-curve fitting procedure using temperature and electric field dependent tilt angle and polarization data was employed to the generalized Landau model of ferroelectric liquid crystals. From this analysis the three Landau coefficients as well as the polarization-tilt coupling parameters were obtained as a function of dopant concentration and configuration. It is shown that the two most varied parameters are those of the first Landau coefficient alpha and the (chiral) linear polarization-tilt coupling constant C. The effect on the first Landau term is equivalent for the two dopants of opposite handedness indicating its achiral nature, while the effect on the (chiral) bilinear coupling term differs for the R1011 and S1011 dopant, increasing and decreasing the coupling between tilt and polarization respectively. This difference in the bilinear coupling term quantifiably evidences that the R1011 dopant increases and S1011 dopant reduces the inherent chirality in this system.

Journal Article↗
PubMed2005

Experimental determination of the full Landau potential of bent-core doped ferroelectric liquid crystals.

The full Landau potential of a ferroelectric liquid crystal, doped with two different bent-core molecules at varying concentration, was determined experimentally. Using a multicurve fitting procedure, temperature and electric field dependent tilt angle and polarization measurements were analyzed according to the generalized Landau model of ferroelectric liquid crystals. From this analysis the three Landau coefficients as well as the polarization-tilt coupling parameters were obtained as a function of dopant concentration. It is shown that the two most varied parameters are those of the first Landau coefficient and the (chiral) linear polarization-tilt coupling constant. The results quantitatively verify the chiral induction capability of nonchiral bent-core shaped dopants and an observed increase in the electroclinic effect with increasing dopant concentration.

Journal Article↗
PubMed1999

Depletion of CD34+ CD4+ cells in bone marrow from HIV-1-infected individuals.

Pancytopenia as a consequence of bone marrow abnormalities is commonly seen in HIV-infected individuals. To examine the effect that HIV-1 has on hematopoietic cells, we compared hematopoietic properties of bone marrow samples from HTV+ patients at various stages of disease with bone marrow samples from uninfected donors. While the absolute number of recovered CD34+ cells and the cloning efficiency of these cells did not differ significantly in HIV+ donors, the percentage of CD34+ CD4+ cells was significantly depleted in late-stage HIV+ patients. We observed a direct correlation between the numbers of CD34+ CD4+ cells in the bone marrow and the peripheral CD4 count. Further characterization of the CD34+ CD4+ subpopulation demonstrated that these cells expressed lower levels of HLA-DR on their surface compared with CD34+ CD4- cells, suggesting an immature phenotype. We also found evidence for expression of HIV-1 coreceptors CXCR-4 and CKR-5 message and protein in CD34+ bone marrow cells. While this finding suggested that hematopoietic cells might be susceptible to HIV infection at an early stage of maturation, thus affecting different cell lineages as they matured, we did not find any evidence for infection of HIV in these cells. These data suggest that HIV affects early hematopoietic progenitor cells either directly or indirectly, and in particular CD34+ CD4+ cells. This finding has important implications for disease pathogenesis and for application of gene therapy approaches that use CD34+ hematopoietic cells.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Melanocortin antagonists define two distinct pathways of cardiovascular control by alpha- and gamma-melanocyte-stimulating hormones.

Melanocortin peptides and at least two subtypes of melanocortin receptors (MC3-R and MC4-R) are present in brain regions involved in cardiovascular regulation. In urethane-anesthetized rats, unilateral microinjection of alpha-melanocyte-stimulating hormone (MSH) into the medullary dorsal-vagal complex (DVC) causes dose-dependent (125-250 pmol) hypotension and bradycardia, whereas gamma-MSH is less effective. The effects of alpha-MSH are inhibited by microinjection to the same site of the novel MG4-R/MC3-R antagonist SHU9119 (2-100 pmol) but not naloxone (270 pmol), whereas the similar effects of intra-DVC injection of beta-endorphin (1 pmol) are inhibited by naloxone and not by SHU9119. Hypotensive and bradycardic responses to electrical stimulation of the arcuate nucleus also are inhibited by ipsilateral intra-DVC microinjection of SHU9119. gamma-MSH and ACTH(4-10), but not alpha-MSH, elicit dose-dependent (0.1-12.5 nmol) pressor and tachycardic effects, which are much more pronounced after intracarotid than after intravenous administration. The effects of gamma-MSH (1.25 nmol) are not inhibited by the intracarotid injection of SHU9119 (1.25-12.5 nmol) or the novel MC3-R antagonist SHU9005 (1.25-12.5 nmol). We conclude that the hypotension and bradycardia elicited by the release of alpha-MSH from arcuate neurons is mediated by neural melanocortin receptors (MC4-R/MC3-R) located in the DVC, whereas the similar effects of beta-endorphin, a peptide derived from the same precursor, are mediated by opiate receptors at the same site. In contrast, neither MC3-R nor MC4-R is involved in the centrally mediated pressor and tachycardic actions of gamma-MSH, which, likely, are mediated by an as yet unidentified receptor.

Animals↗
PubMed1996

Immunocytochemical detection of breast cancer cells in marrow and peripheral blood of patients undergoing high dose chemotherapy with autologous stem cell support.

Detection of small numbers of breast cancer cells is important in staging the disease and can be helpful in assessing the efficacy of purging regimens prior to autologous stem cell infusion. Immunohistochemical methods are potentially useful and broadly applicable for this purpose since they are simple to perform, sensitive, and may be quite specific. We have used a combination of four monoclonal antibodies [260F9, 520C9, 317G5 (Baxter Corp); BrE-3 (Dr. R. Ceriani)] against tumor cell surface glycoproteins in a sensitive immunocytochemical assay to identify breast tumor cells in bone marrow and peripheral blood. Immunostained cytospin preparations were fixed prior to staining to preserve cytological details of immunopositive cells. After immunostaining, slides were counterstained with hematoxylin to confirm the identify of labeled cells. In cytocentrifuge experiments in which small numbers of CAMA human breast tumor cells were added to bone marrow mononuclear cells, a linear relationship between the number of tumor cells added and the number of tumor cells detected was obtained over a broad range of tumor cell concentrations. The probability of detecting tumor cells was dependent on the number of cytocentrifuge slides examined. When ten slides (5 million cells) were examined, the probability of detecting tumor at a concentration of 4 tumor cells per million bone marrow mononuclear cells was 98%. In clinical specimens, tumor cells were detected in marrow aspirates from 73 of 240 (30%) patients undergoing autologous transplantation, including 70 (37%) of 190 patients with clinical stage IV disease, 0 of 7 patients with clinical stage III disease, and 3 of 43 (7%) patients with clinical stage II disease. Seventy-three of 657 peripheral blood specimens from 26 of 155 patients (17%) contained breast cancer cells with counts ranging from 1 to 97 tumor cells per million leukocytes. Tumor cells were most frequently found in the blood of patients with stage IV disease [21 of 107 (20%)] but were also found in a substantial number [5 of 44 (11%)] of patients with stage II disease. Positive selection of CD34-positive hematopoietic progenitor cells as well as negative purging methods such as incubation with 4-hydroxyperoxy-cyclophosphamide (4-HC) were evaluated with respect to tumor cell depletion. Selection of CD34-positive progenitor cells from bone marrow or peripheral blood resulted in log reduction of 1 to > 4 tumor cells reinfused at autologous transplantation. A lesser log reduction (up to 1) was demonstrated following 4-HC purging. We conclude that properly performed and controlled immunocytochemical staining of bone marrow and peripheral blood cytospins is a sensitive and simple way to detect and quantitate breast cancer cells in hematopoietic specimens harvested for autotransplantation and that CD34-positive progenitor cell selection results in significant reduction in the number of breast cancer cells reinfused with marrow or peripheral blood stem cells.

Antibodies, Monoclonal↗
PubMed1994

Indications, Integration, and Technical Aspects of Local-Regional Irradiation in the Management of Advanced Breast Cancer.

This article reviews the indications for radiotherapy in advanced stage disease and discusses the recent prospective trials demonstrating a survival benefit by the addition of radiotherapy. Various treatment plans are reviewed with and without internal mammary node coverage. Although it is not clear whether internal mammary node irradiation can have a favorable impact on survival, it is clear that inadequate treatment planning of the parasternal region can result in excess cardiac morbidity and mortality. Careful planning using computed tomographic systems is required to optimize chest wall planning. With individualized treatment planning, it is hoped that the next generation of trials will show improved survival from further reduction in breast cancer deaths and significantly decreased cardiac toxicity.

Journal Article↗
PubMed1993

Estimation of body composition changes during weight cycling by bioelectrical impedance analysis in rats.

The effects of body weight cycling (WC) in rats on body composition (BC) and feeding efficiency were studied. The usefulness of estimating BC by bioelectrical impedance analysis (BIA) was also examined. Female Sprague-Dawley rats were divided into high-fat ad libitum feeding, either noncycling or cycling, or restricted feeding (75% of control feed) cycling groups. Control rats were fed a regular laboratory ad libitum diet and did not cycle. All rats were killed at the end of week 61. A BIA unit was used at each stage of WC to obtain resistance and reactance readings. Final BC was determined by chemical analysis. On the basis of the final chemical analysis and BIA measurements, an equation was established and applied to estimate BC at each stage of WC: fat-free mass (g) = 0.38 x body wt (g) + 13.8 x [length (cm)2/resistance] + 70.9 (r = 0.95, P < 0.001). High-fat ad libitum feeding induced rapid body weight and fat gains as well as an elevated feeding efficiency and an internal fat-to-subcutaneous fat ratio, regardless of whether the rats cycled. This change in fat mass was clearly detected by the BIA. Although rats fed restricted diets had similar body weights as did control rats, they had a significantly higher internal fat-to-subcutaneous fat ratio. Thus, not only the amount of food but also the composition of the diet is important for proper weight management. The BIA method is capable of detecting the body fat mass change during WC.

Adipose Tissue↗
PubMed1992

Long-term exercise training and retirement in genetically obese rats: effects on food intake, feeding efficiency and carcass composition.

Short-term physical exercise (EX) can reduce body weight and fat gain in obese humans and animals. However, the beneficial effects of physical exercise are not long-lasting. In this study, the effects of long-term physical exercise and retirement from exercise (R) on body weight, body composition and fat distribution were examined in genetically obese (OB) and lean (LE) female rats. Fifty OB and 45 LE rats, four weeks old, were divided into EX (swimming, 2h/day, 5 days/week) or sedentary (SD) groups. At the end of the 28th week of treatment, EX groups were further divided into continued EX or R groups for another 11-12 weeks. It was found that at the end of the 28th week EX had reduced the rate of weight gain in OB and LE rats. Percentage body fat was only reduced in OBEX rats and this was achieved by a significant reduction of subcutaneous fat mass. At the end of the 40th week, EX had further reduced the weight gain, fat mass and body fat percentage in OBEX rats while only body fat percentage was reduced in the LEEX group. Retirement from exercise reversed these phenomena. Thus there were no differences between OBSD and OBEX-R rats in body weight, fat mass and percentage body fat. However, the OBEX-R group had a significantly higher amount of internal fat than the other two OB groups. Therefore, exercise, even long-term to cover the entire fat cell proliferation period, still only exerted temporary beneficial effects in OB rats. After retirement, the beneficial effects all disappeared rapidly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1992

The Denver II: a major revision and restandardization of the Denver Developmental Screening Test.

Since the Denver Developmental Screening Test was first published 23 years ago, it has been utilized worldwide and restandardized in more than a dozen countries. Concerns raised through the years by test users about specific items and features of the Denver Developmental Screening Test, coupled with a need for more current norms, have prompted a major revision and restandardization of the test. For the revision, 336 potential items were administered to more than 2000 children. The average number of times each item was administered was 540. Using regression analysis, composite norms for the total sample and norms for subgroups (based on gender, ethnicity, maternal education, and place of residence), were used to determine new age norms. The final selection of the 125 Denver II items was based on the following criteria: ease of administration and scoring, item appeal to child and examiner, item test-retest and inter-rater reliability, minimal "refusal" scores, minimal "no opportunity" scores, minimal subgroup differences, and a smooth step-like progression of ages at which 90% of children could perform the tasks. The major differences between the Denver II and the Denver Developmental Screening Test are: 1) an 86% increase in language items; 2) two articulation items; 3) a new age scale; 4) a new category of item interpretation to identify milder delays; 6) a behavior rating scale; and 7) new training materials.

Child↗
PubMed1991

Studies in human lactation: milk composition and daily secretion rates of macronutrients in the first year of lactation.

Time-dependent changes in milk composition and secretion from pregnancy through greater than or equal to 6 mo of exclusive breast-feeding were studied in 13 multiparous women. Concentrations and secretion rates of lipid, lactose, protein, sodium, chloride, potassium, total calcium, ionized calcium, magnesium, glucose, citrate, inorganic phosphate, creatinine, and urea and pH were analyzed longitudinally from day 6 until weaning commenced. The composition of the antepartum secretion was related to the permeability of the junctional complexes between mammary cells. Significant increases in lactose, glucose, pH, and ionized calcium and significant decreases in protein, sodium, potassium, chloride, and calcium concentrations were observed between 1 and 6 mo. Significant differences among individuals, which persisted through lactation, were observed for the concentrations of sodium, potassium, chloride, and inorganic phosphate. The amount of lactose, ionized calcium, and magnesium transferred to the infant was also characteristic of each mother-infant pair. Our data imply that lactation performance is determined in the first month postpartum.

Breast Feeding↗
PubMed1990

The use of the Markov process in describing the natural course of diabetic retinopathy.

The natural course of early diabetic retinopathy in young subjects with insulin-dependent diabetes mellitus was evaluated during 693 patient visits for 259 subjects during a mean of 2.4 years. Diabetic retinopathy is considered a progressive disease among people with insulin-dependent diabetes mellitus (type I). Improvement of early retinopathy has not been recognized as a part of the natural course. In our experience, 25% of observations in subjects with early diabetic retinopathy (grades 2 and 3) showed improvement. Thus, 28 of 174 observations of diabetic retinopathy improved from grade 2 to grade 1, and 34 of 79 observations improved from grade 3 to grades 2 or 1. Markov chains indicate that 25% of observations of diabetic retinopathy will change from grade 1 to grade 5 or 6 in 17.0 years and 25% will change from grade 2 to grade 5 or 6 in 16.0 years. Future studies of diabetic retinopathy should consider a matrix of estimated transition probabilities, depending on the population, to judge probabilities of transition between states of retinopathy.

Adolescent↗
PubMed1990

Growth of Listeria monocytogenes at refrigeration temperatures.

The growth of three strains of Listeria monocytogenes at refrigeration temperatures (-0.5 to 9.3 degrees C) in chicken broth and/or UHT milk was determined using a rocking temperature gradient incubator. Minimum growth temperatures ranged from -0.1 to -0.4 degree C for the three strains. Lag times of 1-3 d and 3 to greater than 34 d were observed with incubation at 5 and 0 degrees C respectively. Corresponding generation times ranged from 13-24 h at 5 degrees C and 62-131 h at 0 degree C. The type of culture medium had an influence on both the rate and extent of growth. Incubation of cultures at 4 degrees C before inoculation caused a marked reduction in the lag time when compared with cultures which had been previously incubated at 30 degrees C.

Animals↗
PubMed1988

Studies in human lactation: milk volumes in lactating women during the onset of lactation and full lactation.

After validation of test-weighing procedures milk volumes produced by 13 multiparous Caucasian women were followed longitudinally through the first year of lactation. All practiced exclusive breast-feeding for at least 5 mo. Milk transfer to the infant was low on days 1 and 2 and increased rapidly to 498 +/- 129 g/d (means +/- SD) on day 5 and then more slowly to 753 +/- 89 g/d during months 3-5. There was a characteristic milk volume for each mother-infant pair that was significantly related neither to milk yield on days 4-6 nor to birth weight. It was, however, strongly related to infant weight at 1 mo, suggesting that infant and/or maternal factors coming into play during the first month of life are strong determinants of subsequent milk transfer to the infant.

Adult↗
PubMed1986

Statistical analyses for in vitro cytogenetic assays using Chinese hamster ovary cells.

It is a widely held view that objective statistical criteria are needed for the evaluation of genetic toxicity assays. This paper presents statistical methods for the analysis of data from in vitro sister chromatid exchange (SCE) and chromosome aberration tests that use Chinese hamster ovary cells. For SCEs, an extensive study of solvent control results demonstrated that there is a substantial interday component of variability in the data, and that a Poisson sampling model is applicable to data generated via the protocol of Galloway et al [1985]. Consequently, a trend test for evidence of a dose response is proposed for such SCE data. As an illustration of this statistical method, analysis of data previously considered to be negative [Gulati et al, 1985] indicates that di(2-ethyl-hexyl) phthalate induces a weak, but reproducible, SCE dose response in CHO cells. Monte Carlo methods are used to show that the trend test is more sensitive than four other statistical procedures considered for the analysis of Poisson-distributed SCEs. A similar trend test for dose response in proportions is proposed for chromosome aberration data, where the percent of cells with chromosome aberrations is the response of interest. Sensitivity (or power) studies indicate that three doses and a control with 50 cells/dose point is a reasonable design for an in vitro SCE study that uses the Galloway et al protocol. For in vitro chromosome aberrations, however, three doses and a control with 100 cells/dose point appears to produce too insensitive an assay; an increase to 200 cells/dose point in the Galloway et al protocol seems worthy of serious consideration.

Animals↗