Biomedical subjects

Mark R Johnson

Publications and source records attributed to Mark R Johnson.

10 recordsLinked to original sources

PubMed2007

The effect of mechanical stretch on cyclooxygenase type 2 expression and activator protein-1 and nuclear factor-kappaB activity in human amnion cells.

Stretch of the uterus plays a role in parturition. Uterine stretch also leads to stretch of the fetal membranes, including the amnion, an important source of prostaglandin E2 (PGE2). We tested the hypothesis that stretch of the amnion leads to increased cyclooxygenase (COX)-2 expression and PGE2 synthesis and investigated the mechanisms involved. We obtained amnion from women undergoing term elective cesarean section and isolated amnion epithelial cells. These cells were subjected to 11% static stretch. Stretch increased COX-2 expression and PGE2 production. EMSA studies showed that stretch increased both activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) DNA binding at 1 and 6 h. In contrast, IL-1beta increased both AP-1 and NF-kappaB DNA binding at 1 h only. Chromatin immunoprecipitation studies confirmed that stretch increased binding of NF-kappaB to the COX-2 promoter in vivo. Stretch had no effect on inhibitory-kappaBalpha (IkappaBalpha) levels at the early time points but caused a decrease at 4 h. IL-1beta stimulation decreased IkappaBalpha levels after 30 min. MG132, a proteasome inhibitor, inhibited only the second stretch-induced increase in NF-kappaB binding. This suggests that stretch initially activates NF-kappaB via a nonclassical pathway, which does not involve the inhibitory-kappa kinase-induced degradation of IkappaBalpha. The second peak of NF-kappaB activation may be mediated by the classical mechanism. Stretch of the amnion may contribute to increased expression of COX-2- and other AP-1- and NF-kappaB-regulated genes with the onset of labor in the human.

Amnion↗

PubMed2006

Regional expression of prostaglandin E2 and F2alpha receptors in human myometrium, amnion, and choriodecidua with advancing gestation and labor.

The change from uterine quiescence to enhanced contractile activity may be due to the differential expression of prostaglandin receptors within the myometrium and fetal membranes, in a temporal and topographically distinct manner. To address this question, we determined the localization and expression of the PGE2 receptor subtypes (PTGER1-4) and the PGF2alpha receptor (PTGFR) in paired upper and lower segment myometrium, amnion, and choriodecidual samples throughout human pregnancy, with and without labor. All receptor subtypes were found throughout the muscle layers in both the upper and lower uterine segments, colocalizing with alpha smooth muscle actin. A change in intracellular localization was observed at term labor, where PTGER1 and PTGER4 were predominately associated with the nucleus. Minimal changes in the expression of the PGE2 and PGF2alpha receptor subtypes were observed with gestational age, labor, or between the upper and lower myometrial segments. Receptor expression in maternal and fetal tissues differed between the receptor subtypes; PTGER1 and PTGER4 were predominately expressed in the fetal membranes, PTGER2 was greatest in the myometrium, whereas PTGER3 and PTGFR were similarly expressed in the myometrium and fetal membranes. Myometrial activation through the prostaglandin receptors is perhaps more subtle and may be mediated by a balance between one or several of the prostaglandin receptor subtypes together with other known contraction associated proteins. Lack of coordination in receptor expression between the myometrium and fetal membranes may indicate different regulatory mechanisms between these tissues, or it may suggest a function for these receptors in the amnion and choriodecidua that is independent of that seen in the myometrium.

Amnion↗

PubMed2006

Localization and expression of prostaglandin E2 receptors in human placenta and corresponding fetal membranes with labor.

OBJECTIVE: The effects of prostaglandin E2 (PGE2) are mediated through G-protein coupled receptors, acting via different second messengers. The aim of this study was to characterize the temporal and tissue specific localization and expression of the PGE2 receptor subtypes (EP1-4) in uteroplacental tissues during human pregnancy. STUDY DESIGN: Placenta and fetal membranes were collected after delivery at preterm or term, each with or without labor. The localization and expression of the PGE2 receptor subtypes were determined by immunohistochemistry and Western blot. RESULTS: All 4 receptors were expressed in the placenta and fetal membranes; only EP3 was present in the syncytiotrophoblast layer. EP1 to EP4 were consistently expressed across gestation in the fetal membranes; however, a different cellular localization with labor was observed in the amnion for EP1, EP2, and EP4. CONCLUSION: The presence of these receptors in the placenta and fetal membranes may indicate autocrine roles for PGE2 in the signaling pathways associated with placental function and parturition.

Adult↗

PubMed2006

How phonons govern the behavior of short, strong hydrogen bonds in urea-phosphoric acid.

Recent neutron diffraction data have shown that the hydrogen atom involved in the short, strong hydrogen bond in urea-phosphoric acid migrates toward the midpoint of the hydrogen bond as the temperature increases. With the help of solid state ab initio calculations and inelastic neutron scattering, we have investigated the temperature dependence of the structural and vibrational properties of the system. The potential energy surface of the proton in the short, strong hydrogen bond and the thermal population of the energy levels therein cannot account for the observed proton migration. Ab initio molecular dynamics simulations clearly reveal the migration of the proton. This molecular dynamics result was reported recently by other authors, but they only offered a tentative explanation in terms of a resonance between high-frequency vibrations, which is not supported by the calculations presented here. We explain the proton migration in terms of phonon-driven structural fluctuations and their impact on the temperature-dependent evolution of the potential energy surface of the short hydrogen-bond proton.

Hydrogen Bonding↗

PubMed2006

The team approach to pregnancy and congenital heart disease.

The successful pediatric management of congenital heart disease has resulted in increasing numbers of these patients in the reproductive age group and increasing clinical challenges for their physicians. These challenges can be met successfully, with improved results for mother and child, through a concerted comprehensive team approach that relies on a thorough understanding of the patient's underlying cardiac pathology and its anticipated interaction with the pregnancy, and ongoing close evaluation and communication with a team of trained and experienced specialist, including (but not limited to) cardiologist, obstetricians, anesthetists, pediatricians, clinical nurse specialists, and clinical geneticists. Such teams are not always available locally and it will be necessary to refer medium- and high-risk patients to a specialized tertiary care center.

Adult↗

PubMed2005

Energy cost of activity and exercise in children and adolescents with cystic fibrosis.

UNLABELLED: In cystic fibrosis (CF), perturbations of total daily energy expenditure (TDEE) may be a major determinant of altered nutrition and growth. Measurement of TDEE is problematic, though the flex-heart rate method (FHRM) provides a close estimation of TDEE, as compared to the cost-prohibitive, gold standard, the double-labeled water method, and permits estimates of the energy cost of daily activities (ECA) above resting energy expenditure (REE). We hypothesize that alterations in ECA affects TDEE in CF. PURPOSE: To measure components of TDEE in adolescents with CF and normal lung function compared with controls, and to determine whether ECA can be improved by diet and exercise. METHODS: Clinically stable CF subjects (aged 9-13, n=12) and age- and gender-matched controls (n=13) had repeated measurements of TDEE by FHRM, REE, and maximal cardiopulmonary exercise testing (CPET) during a 6-week exercise and diet program. RESULTS: While the mean REE was similar in both groups, ECA was significantly lower in CF adolescents as compared to controls (p=0.02). During CPET, maximal exercise in CF was characterized by hyperventilation, which was unrelated to ventilation-perfusion mismatching. There were no changes in REE after dietary intervention. CONCLUSION: ECA in CF adolescents with normal lung function is lower when compared to healthy controls. These findings support the hypothesis that clinically stable patients with CF have inefficient energy metabolism or alternatively conserve energy during activities of daily living.

Activities of Daily Living↗

PubMed2004

Mechanical stretch up-regulates the human oxytocin receptor in primary human uterine myocytes.

Oxytocin receptor (OTR) expression is increased before the onset of labor in all models of parturition. However, the mechanisms responsible for the increase in OTR expression are uncertain. Animal data suggest that uterine stretch increases OTR mRNA expression. In primary cultures of human uterine smooth muscle cells obtained from nonpregnant (NP) women and pregnant women before (NL) and after (L) the onset of labor, we investigated the effect of stretch on the expression of OTR mRNA and DNA binding of activator protein-1 (AP-1), CCAAT/enhancer binding protein (C/EBP)beta, and nuclear factor-kappaB transcription factors. OTR expression was least in NL, intermediate in NP, and greatest in L cells. Stretch of NL cells resulted in up-regulation of OTR mRNA expression associated with increased OTR gene promoter activity. Stretch of NP and L cells did not affect OTR mRNA expression. The increased promoter activity was associated with increased DNA binding of C/EBP and AP-1 but not nuclear factor-kappaB transcription factors. Overexpression of C/EBP, but not AP-1, increased OTR promoter activity. We conclude that stretch of NL cells results in increased OTR mRNA expression probably through increased C/EBPbeta DNA binding. These data suggest that stretch contributes to the massive increase in OTR expression before the onset of human labor.

Adult↗

PubMed2004

Garlic supplementation increases peripheral blood flow: a role for interleukin-6?

There is considerable epidemiological and clinical evidence that regular garlic supplementation reduces cardiovascular risk. In this study, we have investigated the hypothesis that dietary garlic supplementation increases tissue blood flow and this is mediated by the vasodilatory actions of interleukin-6 (IL-6). Venous occlusion plethysmography was used to measure resting calf blood flow before and after oral administration of 600 mg of garlic tablets once daily for 7 days in 13 young healthy female volunteers (treatment group) and 13 female controls matched for age and body mass index (BMI). Blood samples were obtained at the time of plethysmography to measure plasma levels of IL-6, nitrate, nitrite and c-GMP. In the treatment group, calf blood flow increased significantly from 3.01 (2.56 to 3.3) ml min(-1) 100 mL(-1) of tissue before garlic to 3.46 (3.0 to 4.03) ml min(-1) 100 mL(-1) of tissue after 7 days of garlic (P = 0.001). Plasma IL-6 concentrations increased significantly from 54.6 (32.3 to 151.6) mcg/mL before to 151 (135.75 to 422.3) mcg/mL after 7 days of garlic (P = 0.02). However, there was no significant change in the plasma levels of nitrate, nitrite and c-GMP after the garlic (P = 0.4, 0.9 and 0.65 respectively). In the control group, resting calf blood flow and plasma levels of IL-6, nitrite, nitrate and c-GMP remained unchanged after 7 days (P = 0.62, 0.92, 0.28 and 0.35 respectively). Calf blood flow showed a non-linear correlation with plasma IL-6 levels after garlic supplementation (r = 0.86, p = <0.001) but not before. There was no significant relationship between blood flow and plasma nitrate, nitrite and c-GMP in either groups and between blood flow and IL-6 in the control group. These data suggest that garlic supplementation increases resting tissue blood flow and this may be mediated by IL-6.

Adult↗

PubMed2004

EAnnot: a genome annotation tool using experimental evidence.

The sequence of any genome becomes most useful for biological experimentation when a complete and accurate gene set is available. Gene prediction programs offer an efficient way to generate an automated gene set. Manual annotation, when performed by experienced annotators, is more accurate and complete than automated annotation. However, it is a laborious and expensive process, and by its nature, introduces a degree of variability not found with automated annotation. EAnnot (Electronic Annotation) is a program originally developed for manually annotating the human genome. It combines the latest bioinformatics tools to extract and analyze a wide range of publicly available data in order to achieve fast and reliable automatic gene prediction and annotation. EAnnot builds gene models based on mRNA, EST, and protein alignments to genomic sequence, attaches supporting evidence to the corresponding genes, identifies pseudogenes, and locates poly(A) sites and signals. Here, we compare manual annotation of human chromosome 6 with annotation performed by EAnnot in order to assess the latter's accuracy. EAnnot can readily be applied to manual annotation of other eukaryotic genomes and can be used to rapidly obtain an automated gene set.

Algorithms↗

PubMed2003

Microvascular permeability is related to circulating levels of tumour necrosis factor-alpha in pre-eclampsia.

INTRODUCTION: The mechanism for the increased microvascular permeability which, underline many of the complications of pre-eclampsia, remain unexplained. It has been suggested that a factor present in the maternal circulation in pregnancies complicated by the disease may be responsible for increased microvascular permeability. In this study, we have investigated the relationship between filtration capacity (K(f)), an index of microvascular permeability, and maternal levels of VEGF, leptin and TNF-alpha, all of which are known permeability factors whose plasma levels are increased in pre-eclampsia. METHODS: We used a small cumulative pressure step venous congestion plethysmography protocol to compare K(f), an index of microvascular permeability, during the third trimester of 20 women with pre-eclampsia, 18 normal pregnant women and 18 non-pregnant female matched controls. Blood samples were obtained to measure plasma levels of VEGF, leptin, TNF-alpha plasma protein concentrations and full blood count. RESULTS: Microvascular filtration capacity (K(f)) was significantly increased in pre-eclampsia compared to the other groups (P<<0.0001, ANOVA). K(f) was also increased in the normal pregnant group when compared to the non-pregnant controls (P=0.02). Plasma levels of VEGF, leptin and TNF-alpha were significantly greater in pre-eclampsia compared to normal pregnancy and non-pregnant controls (P<0.0001, ANOVA, for all three analyses). Total plasma protein and albumin concentrations were significantly lower in the normal pregnant and pre-eclamptic groups, compared to the non-pregnant controls (P<0.0001, ANOVA). K(f) was significantly related to TNF-alpha in pre-eclampsia (r=0.53, P=0.018), and with VEGF in the non-pregnant controls (r=0.6, P=0.02). No significant relationship was observed between K(f) and VEGF, leptin and TNF-alpha during normal pregnancy. There was a significant inverse correlation between plasma albumin concentration and filtration capacity in the normal pregnant (r=-0.94, P<0.0001) and non-pregnant (r=-0.87, P<0.0001) groups but not in the women with pre-eclampsia (r=-0.18, P=0.8). CONCLUSIONS: These data show that that microvascular filtration capacity is significantly increased in pre-eclampsia, and correlates with circulating levels of TNF-alpha but not leptin or VEGF.

Adult↗