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L Gardner

Publications and source records attributed to L Gardner.

At least 19 recordsLinked to original sources
PubMed1997

Design factors in epidemiologic cohort studies of work-related low back injury or pain.

The connection between work-related exposures and the onset of back injury or pain is complex and not clearly understood. This paper raises design issues related to the planning and conduct of cohort studies of industrial low back pain (or injury)(LBP), with care given to definition and measurement of exposure and outcome events. These issues include sample size, outcome definition, study biases, and practical considerations when seeking and maintaining company collaboration with a research effort. Without resolving these issues, the authors conclude: (1) cohort studies of worksite-based LBP are needed to elucidate the causal associations between work tasks and LBP onset, (2) both acute and cumulative exposures should be assessed as risk factors for low back injury or pain, and (3) attention should be paid to the planning of such studies and minimization of potential biases that can limit the validity of the results. These design issues will benefit researchers and companies engaged in the planning and conduct of cohort studies of industrial LBP.

Accidents, Occupational↗
PubMed1997

Evaluation of trophoblast HLA-G antigen with a specific monoclonal antibody.

A monoclonal antibody to HLA-G has been generated by immunizing HLA-A2.1/human beta 2-microglobulin (beta 2 m) double transgenic mice with murine L cells transfected with both human beta 2 m and HLA-G. This monoclonal antibody, designated as G233, has been found not to cross-react with other HLA class I antigens when tested on numerous cell lines by flow cytometry. With immunohistology, all populations of extravillous trophoblast (cell columns, interstitial trophoblast, endovascular trophoblast, placental bed giant cells) were stained. An extensive range of adult and fetal tissues was also tested but none reacted with monoclonal antibody G233, including those previously reported to express HLA-G mRNA, indicating that the protein has a highly restricted distribution. Failure to detect HLA-G in the fetal thymus raises the question as to how T-cell tolerance to this antigen is induced. Immunoprecipitation of trophoblast surface proteins with monoclonal antibody G233 revealed a heavy chain of 39 kDa and a light chain of 12 kDa, indicating that HLA-G expressed on the surface of trophoblast is complexed with beta 2 m. However, sequential immunoprecipitation with monoclonal antibody W6/32 followed by monoclonal antibody G233 continued to detect a residual band of 39 kDa, suggesting that trophoblast surface HLA-G may also occur as free heavy chains not associated with beta 2 m. Immunoprecipitation followed by two dimensional gel electrophoresis showed that monoclonal antibody G233 recognizes several isoforms of HLA-G from trophoblast similar to the characteristic spot array previously described for HLA-G. This monoclonal antibody G233 will be highly useful in future experiments to elucidate the function of HLA-G.

Adult↗
PubMed1997

Uterine NK cells and trophoblast HLA class I molecules.

PROBLEM: To investigate the proposal that NK cells in decidua may control trophoblast migration during implantation of the human placenta. METHOD: Use Mab specific for HLA-G and for HLA-C in association with flow cytometry and immunoprecipitation to determine the expression of these HLA molecules by trophoblast. Expression of Killer inhibitory/activatory receptors (KIR/KAR) and the CD94 receptor by decidual NK cells was also studied. RESULTS: Extravillous trophoblast expressed HLA-G and HLA-C in both beta2m-associated form and as free heavy chains. KIR and KAR are expressed by decidual NK cells. The repertoire of receptors varied between different women and also between blood and decidual NK cells from the same women. The expression of CD94 was also different between blood and decidual NK cells. CONCLUSION: The recognition of HLA-G/HLA-C by KIR/KAR and CD94 could provide a mechanism by which decidual NK cells control trophoblast migration.

Antibodies, Monoclonal↗
PubMed1996

Evidence for the expression of HLAA-C class I mRNA and protein by human first trimester trophoblast.

In this study, evidence is provided that normal human first trimester extravillous trophoblast expresses class I HLA-C molecules in addition to HLA-G. cDNA from highly purified trophoblast cells obtained by flow cytometric sorting was amplified by reverse-transcriptase PCR using HLA locus-specific primers. The identity of the product was confirmed by Southern blotting and hybridization by a second HLA-C-specific oligonucleotide. HLA-C mRNA was clearly demonstrated in all trophoblast samples as well as in JEG-3 and BeWo choriocarcinoma cells. JAR choriocarcinoma cells did not express HLA-C. The presence of HLA-C protein in extravillous trophoblast was investigated using a panel of Abs: L31 is specific for heavy chains of all HLA-C alleles; Q1/28 reacts with all HLA class I products except HLA-G; HC-10 has preferential reactivity with HLA-B and HLA-C heavy chains. We performed 35S metabolic and 125I surface labeling of normal first trimester trophoblast and found abundant HLA-C intracellularly together with low levels of expression of both the beta 2m-associated forms and free heavy chains on the surface. Flow cytometric analysis of normal trophoblast confirmed the expression of a class I HLA molecule distinct from HLA-G by positive reactivity with Q1/28. Immunohistologic studies of first trimester placenta and the implantation site clearly showed expression of HLA-C in all extravillous trophoblast populations. Our results demonstrate the presence of two HLA class I molecules, HLA-G and HLA-C, on the surface of extravillous trophoblast. These results have implications in understanding how maternal uterine lymphocytes, notably the abundant NK-like cells, might recognize the implanting placenta.

Base Sequence↗
PubMed1996

Human decidual leukocytes do not proliferate in response to either extravillous trophoblast or allogeneic peripheral blood lymphocytes.

The maternal leukocytes present in human decidua during the early weeks of pregnancy are composed of CD56+ NK cells (approximately 80%), CD3+ T cells (approximately 10%), and CD14+ macrophages (approximately 10%). These leukocytes are present in large numbers at the implantation site where trophoblast invades. The migrating extravillous trophoblast (EVT) cells express HLA class I antigens HLA-G and HLA-C. To examine whether EVT or other allogeneic cells are capable of inducing a local proliferative response in maternal decidual leukocytes, we have assayed [3H]thymidine incorporation by decidual leukocytes co-cultured with irradiated trophoblast or peripheral blood lymphocytes (PBL). No proliferative response was seen in decidual leukocytes either to trophoblast or to PBL as stimulators. In addition trophoblast did not stimulate a proliferative response in PBL. These findings indicate that extravillous trophoblast is not capable of initiating a classical immune response at the implantation site.

Cell Division↗
PubMed1996

Is delayed surgery really better for congenital diaphragmatic hernia?: a prospective randomized clinical trial.

Delayed surgery has become widely accepted in the management of congenital diaphragmatic hernia after comparing outcomes only with historical retrospective controls. It was the aim of this study to compare early and delayed hernia repair in a randomized prospective clinical trial. Fifty-four infants were randomized to receive either early repair (within 4 hours of admission) or delayed repair (more than 24 hours after birth). The survival rate was higher for the delayed group (57% v 46%), but the difference was not significant (difference: -11; 95% confidence limits: -37.5, 15.5). There were no significant differences between the two groups with respect to length of hospital stay, ventilator dependency, or survival time. Recorded preoperative risk factors were similar for the two groups. Eight infants in the delayed repair group died without having undergone surgery. The optimum time for surgery still needs clarification.

Blood Gas Analysis↗
PubMed1996

Evaluation of oestrogen and progesterone receptor expression in uterine mucosal lymphocytes.

Expression of the oestrogen and progesterone receptors on uterine mucosal leukocytes has been examined by dual immunohistology. Neither the oestrogen receptor nor the progesterone receptor was expressed by lymphocytes, macrophages or the distinctive population of uterine natural killer (NK) cells. Although the accumulation and survival of these NK cells appears to be hormonally dependent, the effects must therefore be indirect.

Decidua↗
PubMed1996

Functions of human decidual NK cells.

The main population of lymphocytes found in the human decidua during early pregnancy are NK-like cells with a distinctive phenotype, CD56bright CD16- CD3-. These cells are in close association with invading trophoblast that may be their in vivo target. We have examined three aspects of decidual NK function in vitro: cytotoxicity, proliferation, and cytokine production. The functional assays indicate uterine lymphocytes differ fundamentally from both PBL and even from classical circulating NK cells. Their role in the establishment of normal pregnancy remains unknown.

Cytotoxicity, Immunologic↗
PubMed1994

Generation of an antibody to HLA-G in transgenic mice and demonstration of the tissue reactivity of this antibody.

A method was devised to generate antibodies against the non-classical class I HLA-G antigen. This consisted of immunising HLA-A2/beta 2m double transgenic mice with HLA-G transfected into mouse Ltk- cells. A polyclonal antibody was obtained which appears to be specific for HLA-G. The staining pattern of this antibody was restricted solely to all populations of extravillous trophoblast. No fetal tissues reacted with this antibody, including those where HLA-G mRNA has been demonstrated, such as fetal eye, thymus and liver. This study confirms that HLA-G is a trophoblast-specific protein, although it remains a possibility that the technique of immunohistology is not sufficiently sensitive to detect low level HLA-G antigen expression in non-trophoblast tissues.

Animals↗
PubMed1994

Predicting the risk of abrupt vessel closure after angioplasty in an individual patient.

OBJECTIVES: We proposed to examine the relation between angiographic morphologic characteristics and abrupt closure after coronary angioplasty and to develop an empirically based risk stratification system. BACKGROUND: Certain lesion morphologic characteristics are associated with higher rates of abrupt closure after coronary angioplasty. Previous approaches have been limited by relatively small sample sizes and an inability to combine multiple characteristics to predict risk in an individual patient. METHODS: Lesion morphology was determined for 779 lesions in 658 patients undergoing an elective first angioplasty. Abrupt closure occurred in 63 lesions (8.1%). Variables associated with abrupt closure were identified by univariate and stepwise multiple logistic regression analysis, and internal validity was assessed by use of bootstrapping. An empirically based scoring system was developed by assigning different weights to each predictive characteristic and was then validated. RESULTS: Almost all lesion characteristics previously labeled "adverse" were associated with an increased risk of abrupt closure, but only total occlusion, location at a branch point, increasing lesion length, evidence for thrombus and right coronary artery location were statistically significant independent predictors. Despite the large sample size, the study was underpowered to detect even a 50% increase in risk with many characteristics. Using a scoring system, we assigned each lesion a specific risk of abrupt closure. The distribution of risk was broad, with 20% of patients having < or = 2.5% risk and 25% having > 10% risk. Internal validation techniques revealed that when 10% of patients were randomly eliminated from the sample in multiple iterations, the risk estimates varied, again pointing to the need for a larger sample. CONCLUSIONS: Empirically based weighting of lesion characteristics could quantify the risk of abrupt closure for individual patients, but a very large sample will be required to understand the interplay of complex lesion characteristics in altering expected outcomes.

Aged↗
PubMed1993

Expression of perforin, granzyme A and TIA-1 by human uterine CD56+ NK cells implies they are activated and capable of effector functions.

At the time the human placenta is established, the uterine mucosal lining (decidua) is infiltrated by abundant CD3- CD56bright natural killer (NK) cells. NK cells circulating in blood are known to contain perforin and granzyme A in their cytoplasmic granules. TIA-1, an RNA-binding protein capable of inducing DNA fragmentation, has also been found in the granules of cytolytic cells. In this paper, we demonstrate the presence of perforin, granzyme A and TIA-1 in the granules of uterine NK cells. Sixteen sections of non-pregnant endometrium throughout the menstrual cycle and six sections of early decidua, together with cytospins of four preparations of isolated decidual leukocytes were stained by both immunohistology and immuno-electron microscopy to localize perforin, granzyme A and TIA-1 to the cytoplasmic granules of CD56+ cells. The presence in vivo of these cytolytic molecules in a normal physiological situation implies that these uterine NK cells may have effector functions in the control of normal placentation.

Antigens, CD↗
PubMed1993

Expression of the colony stimulating factor-1 receptor (c-fms product) by cells at the human uteroplacental interface.

BACKGROUND: The hematopoietic growth factor colony-stimulating factor-1 (CSF-1) and its receptor (encoded by the proto-oncogene c-fms) are implicated in the regulation of human placental development. EXPERIMENTAL DESIGN: In this study, we have performed a detailed immunohistochemical localization of the CSF-1 receptor (CSF-1R) on cells of the uteroplacental interface in human first trimester pregnancy, supplemented by Northern blot, in situ hybridization, and flow cytometric analysis. CSF-1R expression by JEG-3 and JAR choriocarcinoma cells was also investigated. RESULTS: c-fms mRNA was detected in primary cultures of first trimester trophoblast and was localized to the extravillous cytotrophoblast columns streaming off the anchoring villi. CSF-1R was expressed by fetal Hofbauer cells in the mesenchyme of the chorionic villi, and this expression increased considerably from first trimester to term. No expression was seen on first trimester and term villous cytotrophoblast. CSF-1R expression on villous syncytiotrophoblast was absent at 6 weeks, strongest at 8-10 weeks, and faded by 12 weeks. First trimester extravillous cytotrophoblast columns were strongly and consistently positive for CSF-1R expression, as was the superficial shell of extravillous trophoblast over the maternal decidua. However, with deeper invasion and terminal differentiation into placental bed giant cells, this expression became weak or absent. Endovascular trophoblast was also only weakly positive for CSF-1R. At the implantation site itself, large numbers of decidual macrophages and CD3-, CD56bright large granular lymphocytes were seen. The macrophages expressed CSF-1R strongly, but large granular lymphocytes, decidual stromal cells, glandular epithelium, and endothelial cells were found to be negative for CSF-1R expression. No CSF-1R expression was detected in JAR choriocarcinoma cells, but CSF-1R was present in first trimester cultured trophoblast and JEG-3 choriocarcinoma cells, although this was shown to be intracellular. CONCLUSIONS: These results suggest that CSF-1 may regulate invasion and differentiation of human placental trophoblast, depending upon the spatial and temporal distribution of its receptor. CSF-1 may also influence placental development and function by acting via decidual and fetal macrophages, which are the other cell populations expressing the receptor.

Blotting, Northern↗
PubMed1992

Evidence for the expression of granulocyte-macrophage colony-stimulating factor receptors by human first trimester extravillous trophoblast and its response to this cytokine.

The present study has demonstrated that human extravillous trophoblast cells isolated from first trimester placentae can bind granulocyte-macrophage colony-stimulating factor (GM-CSF). We have used a technique which incorporates a phycoerythrin (PE)-conjugated GM-CSF in association with a monoclonal antibody against trophoblast (BC-1) in single and double flow cytometric analysis. Trophoblast cells are also observed to show increased DNA synthesis in response to GM-CSF as assayed by [3H]thymidine incorporation and proliferative activity as demonstrated by double immunocytochemical staining of cells with a trophoblast cytokeratin marker (PKK1) and for the nuclear proliferation antigen (Ki-67). These findings provide evidence that human extravillous trophoblast expresses receptors for GM-CSF and responds to this cytokine.

Antibodies, Monoclonal↗
PubMed1990

Cryopreservation of Drosophila melanogaster embryos.

There is an urgent need to preserve the ever-increasing number (greater than 30,000) of different genetic strains of D. melanogaster that are maintained in national and international stock centres and in the laboratories of individual investigators. In all cases, the stocks are maintained as adult populations and require transfer to fresh medium every two to four weeks. This is not only costly in terms of materials, labour and space, but unique strains are vulnerable to accidental loss, contamination, and changes in genotype that can occur during continuous culture through mutation, genetic drift or selection. Although cryopreservation of Drosophila germ-plasm would be an enormous advantage, many attempts using conventional procedures have been unsuccessful. D. melanogaster embryos are refractory to conventional cryopreservation procedures because of the contravening conditions required to minimize mortality resulting from both intracellular ice formation and chilling injury at subzero temperatures. To overcome these obstacles, we have developed a vitrification procedure that precludes intracellular ice formation so that the embryos can be cooled and warmed at ultra-rapid rates to minimize chilling injury, and have recovered viable embryos following storage in liquid nitrogen. In a series of 53 experiments, a total of 3,711 larvae emerged from 17,280 eggs that were cooled in liquid nitrogen (18.4 +/- 8.8%). Further, using a subset from this population, approximately 3% of the surviving larvae (24/800) developed into adults. These adults were fertile and produced an F1 generation.

Animals↗
PubMed1989

The Escherichia coli melR gene encodes a DNA-binding protein with affinity for specific sequences located in the melibiose-operon regulatory region.

Crude extracts, made from Escherichia coli cells carrying a plasmid in which the melR gene was expressed from the galP2 promoter, were used as a source of MelR protein. Using DNase I footprinting and gel retardation assays, we show that MelR binds to two sites located from nucleotides (nt) -49 to -75 and -85 to -113, upstream from the melAB transcription start point. The two sites contain identical 18-bp sequences. Specific binding is unaltered by deletions that remove 1 or 6 amino acids (aa) from the C terminus of MelR, but is abolished by deletion of 16, 24 or more aa residues. Sequence homologies between MelR and other DNA-binding proteins are discussed.

Amino Acid Sequence↗
PubMed1989

Psychosocial determinants of compliance in adolescents with iron deficiency.

The relationship between selected psychosocial variables and compliance was studied in 71 adolescents prescribed medication for iron deficiency. The mean compliance rate in the study group was 67%. Home pill counts were highly correlated with the other methods of measuring compliance, ie, change in serum ferritin level and urinary assay for tracer riboflavin. Statistically significant predictors of compliance included adverse side effects, initial estimate by the adolescent as to his probable level of compliance, and frequency of family reminders to take the medication. There was no significant correlation between self-esteem, locus of control, or most variables of the Health Belief Model and the level of patient compliance. Our findings suggest that home pill counts are an accurate method of assessing compliance and that instituting family reminders may be helpful in those adolescents who are potentially non-compliant.

Adolescent↗