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Biomedical subjects

A Richters

Publications and source records attributed to A Richters.

At least 19 recordsLinked to original sources
PubMed2000

CD34 splice variant: an attractive marker for selection of gene-modified cells.

This study presents a promising selection system for gene-modified cells other than human hematopoietic progenitor and endothelial cells based on transgenic expression of human CD34. Three retrovirally transduced variants of CD34 were compared, differing in the length of their cytoplasmic domains. These were the full-length transmembrane protein (flCD34), a truncated form (tCD34) that is found as a naturally occurring splice variant and has a partial deletion of the cytoplasmic domain for signal transduction, and an engineered variant which is completely deprived of its cytoplasmic tail (dCD34). All three variants allowed selection of gene-modified cells using commercially available immunoaffinity technology. However, examination by flow cytometry as well as by Southern, Northern, and Western blot revealed that dCD34, as opposed to tCD34, is not stably anchored in the membrane and thus is expressed at low levels on the surface of transduced cells. Therefore, tCD34 was chosen as the more promising candidate for a clinically applicable cell surface marker. We show that gene-modified human primary T lymphocytes expressing tCD34 can be enriched to high purity (>95%) using clinically approved immunoaffinity columns. In addition, we demonstrate the utility of tCD34 for surface marking of murine hematopoietic cells in vivo, including primary T lymphocytes detected 9 weeks after bone marrow transplantation.

Animals↗
PubMed2000

Centriacinar region inflammatory disease in young individuals: a comparative study of Miami and Los Angeles residents.

Semiquantitative measurements of chronic inflammation of the centriacinar region (proximal acinus of lung) were compared between 20 Miami and 18 Los Angeles residents (ages 11-30 years) for whom smoking histories were available. Mean extent and severity scores of four lung sites were higher for Los Angeles than Miami residents, with effect of city statistically significant for extent (P=0.02). Also, maximum scores for extent and severity by city were significantly greater for Los Angeles residents (P=0.02, each), but not by smoking history. Smokers did have higher scores for mean extent and severity (by lung site and smoking history), but neither this nor inclusion of smoking and city in the model reached significance. With respect to maximum extent and maximum severity scores, a stratified comparison of cities by smoking history showed a trend (not significant) toward higher scores for Los Angeles residents. Mean extent and severity scores for the lower lobe were higher for basilar sections than for apical sections (each P<0.001). Cumulative data indicate that expanded pathologic studies are essential for efforts to complete a convergence of epidemiological and experimental data implicating exceedences of the Federal ozone standard as a contributor to human lung injury.

Adolescent↗
PubMed2000

Socio-cultural plurality in obstetrics and gynaecology in The Netherlands: research note.

This article reports on an ongoing exploratory study of the quality of obstetrical and gynaecological care for an ethnic pluriform patient population in two non-academic city hospitals in the Netherlands. A bird's eye view is given of the study's background, goals and methodology, followed by a few preliminary results and by some concluding remarks about the need to pay more attention to cultural diversity in health care.

Cultural Diversity↗
PubMed1999

Cholesterol oxidation products induce vascular foam cell lesion formation in hypercholesterolemic New Zealand white rabbits.

Circulating cholesterol oxidation products (ChOx) have long been implicated in the etiology of early atherosclerosis; however, direct in vivo evidence elucidating their role in atherogenesis is only recently becoming available. This study investigated ChOx effects on vascular lesion formation in New Zealand White rabbits under controlled hypercholesterolemic conditions. By closely monitoring plasma cholesterol levels and adjusting dietary cholesterol intake during a 78-day period, total plasma cholesterol exposures (cumulative plasma cholesterol levels over time) were controlled between 27 000 and 34 000 mg/dLxday (final plasma cholesterol concentration, 467+/-77 mg/mL), representing a threshold range for sudanophilic lesion formation in the aorta. Twenty injections of a ChOx mixture (70 mg per injection) were made bearing an oxysterol composition similar to that found in circulating oxidatively modified low density lipoprotein. At sacrifice, the ChOx-injected rabbits (n=5) had (1) significantly higher plasma ChOx levels, (2) significantly increased cholesterol content in the aortas, mainly as esterified cholesterol, and (3) significantly greater sudanophilic lesion size and frequency in the aortas compared with vehicle-injected control rabbits (n=5). The aortic cholesterol content and extent of sudanophilic lesion area were correlated significantly with total plasma ChOx exposure (P<0.003 and P<0.0001, respectively) but not with total cholesterol exposure. The results indicate that for moderate experimental hypercholesterolemia, a situation more relevant to physiological hypercholesterolemia in humans, circulating ChOx may play an important role in inducing formation of early atherosclerotic lesions. Because ChOx are often present in cholesterol-containing diets, foam cell lesion formation induced by ChOx rather than cholesterol cannot be overlooked.

Animals↗
PubMed1999

Androgen influence on lacrimal gland apoptosis, necrosis, and lymphocytic infiltration.

PURPOSE: Previous studies have shown that ovariectomy and hypophysectomy cause regression of the lacrimal gland and have implicated androgens as trophic hormones that support the gland. The purposes of this study were to test the hypothesis that glandular regression after ovariectomy is due to apoptosis, to identify the cell type or types that undergo apoptosis, to survey the time course of the apoptosis, and to determine whether ovariectomy-induced apoptosis could be prevented by dihydrotestosterone (DHT) treatment. METHODS: Groups of sexually mature female New Zealand White rabbits were ovariectomized and killed at various time periods up to 9 days. Additional groups of ovariectomized rabbits were treated with 4 mg/kg DHT per day. At each time period, sham-operated rabbits were used as controls. Lacrimal glands were removed and processed for analysis of apoptosis as assessed by DNA fragmentation and for morphologic examination. DNA fragmentation was determined using the TdT-dUTP terminal nick-end labeling assay and by agarose gel electrophoresis. Labeled nuclei were quantified by automated densitometry. Sections were also stained for RTLA (rabbit thymic lymphocyte antigen), rabbit CD18, and La antigen. Morphology was evaluated by both light and electron microscopy. RESULTS: The time course of apoptosis exhibited two phases, a rapid and transient phase and a second prolonged phase. A transient phase peaked at approximately 4 to 6 hours after ovariectomy. The values for degraded DNA as a percentage of total nuclear area were 4.29%+/-0.79% and 4.26%+/-0.54%, respectively. The values for sham-operated controls examined at the same time periods were 1.77%+/-0.08% and 0.82%+/-0.21%, respectively. The percentage of degraded DNA at 24 hours after ovariectomy was not different from controls examined at the same interval after sham operation. The percentage of degraded DNA 6 days after ovariectomy was significantly increased (8.5%+/-2.4%), compared with sham-operated animals at the same time period (0.68%+/-0.03%). DNA laddering was more pronounced after ovariectomy. Dihydrotestosterone treatment in ovariectomized rabbits suppressed the increase in DNA degradation. Morphologic examination of lacrimal gland sections indicated that ovariectomy caused apoptosis of interstitial cells rather than acinar or ductal epithelial cells. Tissue taken 4 hours and 6 days after ovariectomy showed nuclear chromatin condensation principally in plasma cells. Increased numbers of macrophages were also evident. Significant levels of cell degeneration and cell debris, characteristic of necrosis, were observed in acinar regions 6 days after ovariectomy. Dihydrotestosterone prevented this necrosis. Increased numbers of RTLA+, CD18+, and La+ interstitial cells were also evident 6 days after ovariectomy. In addition, ovariectomy increased La expression in ductal cells. Dihydrotestosterone treatment prevented the increase in numbers of lymphoid cells and La expression. Dihydrotestosterone also promoted the appearance of mitotic figures in acinar cells and increased the sizes of acini by 43% (P < 0.05). CONCLUSIONS: Glandular atrophy observed after ovariectomy is likely to proceed by necrosis of acinar cells rather than apoptosis. This process begins with an apparent time lag after a rapid phase of interstitial cell apoptosis. These processes are accompanied by increased lymphocytic infiltration. These results suggest that a critical level of androgen is necessary to maintain lacrimal gland structure and function and that a decrease in available androgen below this level could trigger lacrimal gland apoptosis and necrosis, and an autoimmune response. Because apoptotic and necrotic cell fragments may be sources of autoantigens that can be processed and presented to initiate an autoimmune reaction, we surmise that cell death triggered by androgen withdrawal may trigger an autoimmune response such as that encountered in Sjögren's syndrome. (ABSTRACT TRUNCATED)

Animals↗
PubMed1999

Retroviral vector-mediated gene expression in hematopoietic cells.

Gene transfer vectors based on simple retroviruses and more complex lentiviruses are currently the most reliable tools for stable establishment of transgenes in hematopoietic cells. While important hurdles in basic gene transfer technologies have been overcome in recent years, there is still some uncertainty in the choice of the cis-regulatory elements of the vector. These elements dictate the overall level, clonal variability, response to differentiation and persistence of transgene expression in vivo and thus have a significant influence on the outcome of therapeutic applications of somatic gene transfer. The rationale underlying the further improvement of such cis-elements is reviewed here.

Animals↗
PubMed1998

Chronic glandular bronchitis in young individuals residing in a metropolitan area.

A study of 161 Los Angeles County residents aged 12-28 years old who had died sudden violent deaths showed frequent and severe chronic glandular bronchitis (CGB), that is to say grade > or =5 (0-10) chronic inflammation involving at least one, half or more, and all submucosal glands in 53.4%, 21%, and 4.4% of the main stem bronchi, respectively. The mean plasma cell/gland/bronchus was high (> or =5) for 22 subjects (13.7%), while only 2 bronchi (1.2%) had a correspondingly high lymphocyte mean (P<0.001). Of the bronchi, 75.2% were affected by glandular atrophy (> or =5 in 8.1%), 10.6% had neutrophil infiltration of glands, and 3.1% had acute sialadenitis. Of the total of 1040 glands, CGB was found in 83.8% (> or =5 in 26.5%). Of 25 non-smokers identified, 14 (56%) had some degree of CGB in > or =50% of the glands, severe in 7 (26%). Severe CGB in many young individuals raises concern that a subpopulation of living cohorts may have an increased susceptibility to disease and a rising incidence of chronic lung disease. Demographic analysis is pending, but respiratory infection, smoking, adverse socioeconomic factors, and air pollution are all potential causative factors. Since pollution in Los Angeles frequently exceeds air quality standards, an ongoing multicity study is attempting to distinguish between the suspected effects of air pollution and confounding variables.

Adolescent↗
PubMed1998

cis-Active elements of Friend spleen focus-forming virus: from disease induction to disease prevention.

The polycythemic strain of the Friend spleen focus-forming virus (SFFVp) is a replication-defective, acutely transforming retrovirus inducing a bistage erythroleukemia in susceptible mice. The first stage of the disease is an acute polyclonal erythroblastosis induced by the proliferation-promoting effect of gp55. gp55 is expressed from a spliced subgenomic message of SFFVp and stimulates the cellular receptor for erythropoietin. Using a selectable SFFVp that otherwise mimics the specificity of the disease, we demonstrate that the kinetics of the polyclonal expansion depends on the transcriptional strength of the retroviral cis-active elements. By exchanging gp55 for apathogenic genes, we show that SFFVp enhancer and splice signals can be successfully utilized for the development of retroviral vectors mediating very efficient transgene expression in hematopoietic cells. Apathogenic selectable SFFVp-based vectors carrying distinct enhancer alterations are a valuable tool to analyze transcriptional control of leukemia viruses in the absence of oncogenic proteins. Moreover they might have therapeutic potential.

Animals↗
PubMed1996

Mutational analysis and molecular modeling of the nonapeptide hormone binding domains of the [Arg8]vasotocin receptor.

To identify determinants that form nonapeptide hormone binding domains of the white sucker Catostomus commersoni [Arg8]vasotocin receptor, chimeric constructs encoding parts of the vasotocin receptor and parts of the isotocin receptor have been analyzed by [(3,5-3H)Tyr2, Arg8]vasotocin binding to membranes of human embryonic kidney cells previously transfected with the different cDNA constructs and by functional expression studies in Xenopus laevis oocytes injected with mutant cRNAs. The results indicate that the N terminus and a region spanning the second extracellular loop and its flanking transmembrane segments, which contains a number of amino acid residues that are conserved throughout the nonapeptide receptor family, contribute to the affinity of the receptor for its ligand. Nonapeptide selectivity, however, is mainly defined by transmembrane region VI and the third extracellular loop. These results are complemented by a molecular model of the vasotocin receptor obtained by aligning its sequence with those of other G-protein coupled receptors as well as that of bacteriorhodopsin. The model indicates that amino acid residues of transmembrane regions II-VII that are located close to the extracellular surface also contribute to the binding of vasotocin.

Amino Acid Sequence↗
PubMed1993

Depression of stimulated arachidonate metabolism and superoxide production in rat alveolar macrophages following in vivo exposure to 0.5 ppm NO2.

Alveolar macrophages (AM) have been found to suffer significant functional deficits in response to nitrogen dioxide (NO2) exposure. The present investigation examined changes in the activation of AM arachidonate metabolism and superoxide production in response to an environmentally relevant level of NO2. Rats were exposed to 0.5 ppm NO2 for periods of 0.5-10 d and AM were obtained by bronchoalveolar lavage (BAL). NO2 exposure produced complex effects upon both unstimulated and stimulated AM arachidonate metabolism. Unstimulated AM synthesis of leukotriene B4 (LTB4) was depressed rapidly within 1 d of exposure, and depressed again at 5 d. Alveolar macrophage production of thromboxane B2 (TxB2), LTB4, and 5-hydroxyeicosatetraenoate (5-HETE) in response to stimulation with the calcium ionophore, A23187, were acutely depressed within 1 d of exposure; however, generation of these compounds recovered to air-control levels with longer exposure, while 5-HETE was increased at 10 d. In contrast, AM production of LTB4 in response to another stimulus, zymosan-activated rat serum (ZAS), was not depressed until following 5 d of exposure and remained slightly lower than air-control levels at 10 d. Levels of TxB2, LTB4, prostaglandin E2 (PGE2), and prostaglandin F2 alpha (PGF2 alpha) measured in BAL fluid (BALF) were found to be depressed within 4 h of exposure, suggesting an acute decrease in the in vivo pulmonary arachidonate metabolism; however, production of these compounds generally recovered to air-control levels with longer exposure. The AM superoxide production stimulated by phorbol myristate acetate (PMA) was decreased rapidly and continuously throughout the study. Thus, exposure to a low concentration of NO2 acutely depresses activation of AM arachidonate metabolism and superoxide production in response to external stimuli, and may impede defense against pulmonary infection.

Animals↗
PubMed1989

Reduction in T lymphocyte subpopulations following acute exposure to 4 ppm nitrogen dioxide.

The effect of acute exposure to nitrogen dioxide (NO2) on splenic T lymphocyte subpopulations was studied in C57BL/6cum mice. The mice were exposed to 4 ppm NO2 for 8 hr. Monoclonal antibodies to T lymphocyte differentiation antigens and fluorescence-activated cell sorter (FACS) analysis were used to detect changes in T lymphocyte subpopulations. Percentages of total T lymphocytes (Thy-1.2-positive), T-helper/inducer lymphocytes (L3T4-positive), and T-cytotoxic/suppressor lymphocytes (Lyt-2-positive) were significantly lower in NO2-exposed animals than in filtered-air-breathing controls. Large T-cytotoxic/suppressor cells were found to be the most susceptible subpopulation. Spleen and body weights of the mice were also determined. There were no differences between body weights of control and exposed animals; however, exposed mice had significantly lower spleen weights. This is the first report providing evidence linking alterations in T lymphocyte subpopulations to acute NO2 exposure at occupational levels. T lymphocytes play a central role in regulatory and effector immunological functions such as mediating delayed hypersensitivity, regulating immunoglobulin production, and lysing virus-infected and neoplastic cells. The biological significance of these findings remains to be established, but it is very likely that functional impairment occurs since an optimal immune response depends upon a proper balance of the T lymphocyte subpopulations. Detection of alterations in T lymphocyte subpopulations using monoclonal antibodies and FACS analysis may provide an extremely sensitive means of demonstrating NO2-induced changes in the immune system.

Animals↗
PubMed1989

Spleen cellularity shifts from the inhalation of 0.25-0.35 PPM nitrogen dioxide.

The effects of ambient level (0.25-0.35 ppm)NO2 on percent spleen cell counts, relative percentages of spleen lymphocyte subpopulations, spleen lymphoid nodule size, and differential peripheral blood cell counts were investigated in 170 young adult male mice following various NO2 exposure periods. The total spleen cell counts, surface IgM-positive lymphocytes and spleen mean lymphoid nodule area were all significantly decreased in the groups exposed to NO2 following extended time periods. The relative percentages of peripheral blood lymphocytes were also significantly decreased in the groups exposed to NO2 for 8 weeks. The mechanism for these observed spleen changes following ambient level NO2 exposure remains unclear, but the results warrant further investigation and concern, especially since such changes may reflect altered immune responsiveness.

Animals↗
PubMed1989

Nitrogen dioxide (NO2) inhalation, formation of microthrombi in lungs and cancer metastasis.

It is recognized that cancer cells may be introduced into circulation during surgical removal of a malignant neoplasm. The fate of these cells depends upon many factors. In this paper we present findings from an animal model which indicate that inhalation of nitrogen dioxide facilitates blood-borne cancer cell metastasis to lungs by injuring lung capillary endothelium and formation of microthrombi. Lung capillaries were evaluated by light and electron microscopy. The main lesions observed were microthrombi and injury to capillary endothelial cells, following 6 weeks of 0.35 +/- 0.05 ppm NO2 exposure. The blood-borne cancer cell metastasis was studied utilizing B16 melanoma cells in C57Bl/6J mice. A correlation was observed between increased incidence of microthrombi, endothelial cell injury and lung metastasis in exposed animals. Other adverse NO2 effects such as impairment of immune system may also participate. Inhalation of nitrogen dioxide and other air pollutants may play a significant role in enhancement of metastasis and blood vessel associated disorders.

Administration, Inhalation↗
PubMed1988

Changes in T-lymphocyte subpopulations and natural killer cells following exposure to ambient levels of nitrogen dioxide.

The effects of ambient levels of NO2 on murine splenic T-lymphocyte subpopulations and natural killer cells were investigated. AKR/cum and C57BL/6J mice were exposed, in inhalation chambers, to 0.25 ppm NO2 for 7 wk and 0.35 ppm NO2 for 12 wk, respectively. Monoclonal antibody technology was used in conjunction with fluorescence-activated cell sorter (FACS) analysis to detect quantitative changes in total T-lymphocytes (Thy-1.2-positive), mature T-lymphocytes (Lyt-1-positive), T-helper/inducer lymphocytes (L3T4-positive), T-cytotoxic/suppressor lymphocytes (Lyt-2-positive), and natural killer cells (asialo GM1-positive). Percentages of all T-lymphocyte subpopulations tested and natural killer cells were lower in spleens of mice exposed to NO2 compared to filtered-air controls. This is the first report providing evidence linking alterations in T-lymphocyte subpopulations and natural killer cells to NO2 exposure at ambient levels. Changes in T-lymphocyte subpopulations detected by FACS and correlated to impaired immune function may provide an extremely sensitive means of demonstrating NO2-induced changes in the immune system.

Animals↗
PubMed1988

Effects of nitrogen dioxide and ozone on blood-borne cancer cell colonization of the lungs.

In this article we report inhalation effects of nitrogen dioxide (NO2) and ozone (O3) mixture as well as O3 alone on blood-borne cancer cell colonization of lungs. The findings are discussed in light of our earlier studies with NO2 exposure alone. In all of these studies the mouse B16 melanoma model was used. Animals were exposed to ambient concentrations of pollutants before melanoma-cell infusion. The results have indicated that inhalation of NO2 played a significant role in facilitation of blood-borne cancer cell spread, while O3 inhalation did not. With respect to mechanisms involved, the role of natural immunity was investigated and its was postulated that nitrogen dioxide may affect cells of the immune system and may in part account for the results. These findings may have direct bearing on dissemination of human cancer cells, since many cancer patients have circulating cancer cells and are exposed daily to noxious air pollutants. Most importantly, this effect may be preventable by reducing air pollution in urban areas.

Air Pollutants↗
PubMed1985

The mortality rate from lung metastases in animals inhaling nitrogen dioxide (NO2).

A study was carried out to determine the interrelationship between the inhalation of nitrogen dioxide (0.4 +/- 0.50 ppm), lung metastases development from circulating cancer cells, and death rate from such metastases. C57 BL/6J mice were used in these experiments. Animals were divided into control and NO2-exposed groups, and were exposed to filtered air and 0.4 ppm of NO2, respectively. Following 12 weeks of exposure, all animals were infused intravenously with syngeneic, viable B16 melanoma cells. The results indicate that a subpopulation of NO2-exposed animals showed a significant increase in mortality rate during the early part of the experiment. The interpretation is that animals especially sensitive to the NO2 insult developed extensive metastases at an early stage. The question raised is whether or not the progression of human cancer is influenced by the inhalation of noxious pollutants in the ambient atmosphere.

Air Pollutants↗
PubMed1985

Altered characteristics of B16 melanoma cells induced by chemically crosslinking fibronectin to cell surfaces.

The loss of fibronectin from tumor cell surfaces has been correlated with an increased incidence of metastases. To determine directly whether cell surface fibronectin influences the metastatic potential of solid tumors, we chemically crosslinked fibronectin to B16 murine melanoma cells using a photosensitive heterobifunctional crosslinking reagent, N-succinimidyl-4-azidophenyl-1,3 dithiopropionate (SADP). Cell attachment to plastic surfaces was increased in cells to which fibronectin was attached; cell growth over a 24-hr period was not significantly affected by the addition of fibronectin. When C57BL/6 mice were injected with fibronectin-crosslinked B16 cells, there was a 63% reduction in the number of pulmonary nodules compared to untreated controls. These results are consistent with the hypothesis that fibronectin enhances the recognition and removal of tumor cells from the circulation, possibly by cells of the reticuloendothelial system.

Animals↗