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The Journal of Biological Chemistry Aug 1984Neutrophilic granulocytes contain an oxidase system in their plasma membrane that can be activated to generate superoxide radicals and hydrogen peroxide. Cytochrome b,...
Neutrophilic granulocytes contain an oxidase system in their plasma membrane that can be activated to generate superoxide radicals and hydrogen peroxide. Cytochrome b, flavoprotein, and ubiquinone-50 have been proposed as components of this oxidase system. These components have been quantitated, but the results are obscured by different isolation procedures for plasma membranes from resting and activated neutrophils. This problem has now been avoided by the use of enucleated neutrophils (polymorphonuclear leukocyte cytoplasts), which are almost completely devoid of intracellular structures but contain an intact, activatable oxidase system (Roos, D., Voetman, A.A., and Meerhof, L.J. (1983) J. Cell Biol. 97, 368-377). Membranes of resting and phorbol myristate acetate-stimulated cytoplasts contain equal amounts of cytochrome b (4 pmol/milliunit of alkaline phosphatase) and also equal amounts of noncovalently bound FAD (2 pmol/milliunit of alkaline phosphatase). These findings refute the hypothesis that incorporation of cytochrome b and/or a flavoprotein into the plasma membrane constitutes the mechanism of activation of the oxidase system. Ubiquinone-50 is present neither in intact neutrophils nor in cytoplasts, excluding a role for this compound in the generation of bactericidal oxygen species by neutrophils.
Topics: Cell Fractionation; Coenzymes; Cytochrome b Group; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Flavins; Humans; Hydrogen Peroxide; Neutrophils; Ubiquinone
PubMed: 6746662
DOI: No ID Found -
American Journal of Obstetrics and... Jun 2024The principal fetal energy source is glucose provided by the placental transfer of maternal glucose. However, the placenta's glucose consumption exhibits considerable...
BACKGROUND
The principal fetal energy source is glucose provided by the placental transfer of maternal glucose. However, the placenta's glucose consumption exhibits considerable variation. Hexokinase is the first and one of the rate-limiting enzymes of glycolysis that phosphorylates glucose to glucose-6-phosphate. The role of placental hexokinase activity in human placental glucose metabolism is unknown.
OBJECTIVE
This study aimed to test the hypothesis that placental hexokinase activity is related to maternal body mass index, placental glucose uptake and consumption, and birthweight.
STUDY DESIGN
Overall, 67 healthy pregnant participants at term were included in this study at Oslo University Hospital, Oslo, Norway. Placental hexokinase activity was measured by using a colorimetric assay. The mass of glucose taken up by the uteroplacental unit and the fetus was obtained by measuring arteriovenous glucose differences combined with Doppler assessment of uterine and umbilical blood flow. Blood samples were obtained from the maternal radial artery, uterine vein, and umbilical artery and vein. The uteroplacental glucose consumption constituted the difference between uteroplacental and fetal glucose uptakes. The Spearman rank correlation was performed for statistical analyses to study the correlation of placental hexokinase activity (milliunit per milligram of protein) with prepregnancy body mass index, maternal glucose and insulin, birthweight, uteroplacental glucose uptake and consumption, and fetal glucose uptake (micromole per minute). Partial rank correlation analysis was performed when controlling for hours of fasting or placental weight.
RESULTS
Hexokinase activity was detectable in all placental tissue samples. The mean activity was 19.6 (standard deviation, 4.64) mU/mg protein. Placental hexokinase activity correlated positively with prepregnancy body mass index (Spearman rho=0.33; P=.006). On controlling for hours of fasting, hexokinase activity showed positive correlations with both maternal glucose (r=0.30; P=.01) and insulin (r=0.28; P=.02). Hexokinase activity was positively correlated with uteroplacental glucose uptake (Spearman rho=0.31; P=.01) and consumption (Spearman rho=0.28; P=.02). Hexokinase activity did not correlate with fetal glucose uptake. On controlling for placental weight, hexokinase activity showed a positive correlation with birthweight (r=0.31; P=.01).
CONCLUSION
Our findings suggest that placental hexokinase, being crucial for uteroplacental retention of glucose for disposition, is related to both maternal body mass index and birthweight independent of placental weight. Placental hexokinase may play a central role in the relationship between maternal glucose dysregulation and fetal growth. Thus, the current study supports the need to develop clinically useful tools to assess the metabolic properties of the placenta.
Topics: Humans; Female; Hexokinase; Pregnancy; Placenta; Body Mass Index; Birth Weight; Adult; Glucose; Blood Glucose; Infant, Newborn
PubMed: 37925123
DOI: 10.1016/j.ajog.2023.10.043 -
ACS Chemical Biology Feb 2020The enzymatic transamination of ketones into ()-amines represents an important route for accessing a range of pharmaceuticals or building blocks. Although many...
The enzymatic transamination of ketones into ()-amines represents an important route for accessing a range of pharmaceuticals or building blocks. Although many publications have dealt with enzyme discovery, protein engineering, and the application of ()-selective amine transaminases [()-ATA] in biocatalysis, little is known about the actual role and how these enzymes have evolved from the ubiquitous α-amino acid transaminases (α-AATs). Here, we show the successful introduction of an ()-transaminase activity in an α-amino acid aminotransferase with one to six amino acid substitutions in the enzyme's active site. Bioinformatic analysis combined with computational redesign of the d-amino acid aminotransferase (DATA) led to the identification of a sextuple variant having a specific activity of 326 milliunits mg in the conversion of ()-phenylethylamine and pyruvate to acetophenone and d-alanine. This value is similar to those of natural ()-ATAs, which typically are in the range of 250 milliunits mg. These results demonstrate that ()-ATAs can evolve from α-AAT as shown here for the DATA scaffold.
Topics: Bacillus subtilis; Escherichia coli; Escherichia coli Proteins; Mutagenesis, Site-Directed; Mutation; Phenethylamines; Protein Binding; Stereoisomerism; Substrate Specificity; Transaminases
PubMed: 31990173
DOI: 10.1021/acschembio.9b00888 -
Obstetrics and Gynecology Aug 2011To examine the effects and safety of high-dose (compared with low-dose) oxytocin regimen for labor augmentation on perinatal outcomes.
OBJECTIVE
To examine the effects and safety of high-dose (compared with low-dose) oxytocin regimen for labor augmentation on perinatal outcomes.
METHODS
Data from the Consortium on Safe Labor were used. A total of 15,054 women from six hospitals were eligible for the analysis. Women were grouped based on their oxytocin starting dose and incremental dosing of 1, 2, and 4 milliunits/min. Duration of labor and a number of maternal and neonatal outcomes were compared among these three groups stratified by parity. Multivariable logistic regression and generalized linear mixed model were used to adjust for potential confounders.
RESULTS
Oxytocin regimen did not affect the rate of cesarean delivery or other perinatal outcomes. Compared with 1 milliunit/min, the regimens starting with 2 milliunits/min and 4 milliunits/min reduced the duration of first stage by 0.8 hours (95% confidence interval 0.5-1.1) and 1.3 hours (1.0-1.7), respectively, in nulliparous women. No effect was observed on the second stage of labor. Similar patterns were observed in multiparous women. High-dose regimen was associated with a reduced risk of meconium stain, chorioamnionitis, and newborn fever in multiparous women.
CONCLUSION
High-dose oxytocin regimen (starting dose at 4 milliunits/min and increment of 4 millliunits/min) is associated with a shorter duration of first-stage of labor for all parities without increasing the cesarean delivery rate or adversely affecting perinatal outcomes.
LEVEL OF EVIDENCE
II.
Topics: Adult; Female; Humans; Infant, Newborn; Infant, Newborn, Diseases; Labor Onset; Labor, Induced; Obstetric Labor Complications; Oxytocics; Oxytocin; Parity; Pregnancy; Pregnancy Outcome; Young Adult
PubMed: 21775839
DOI: 10.1097/AOG.0b013e3182220192 -
The Journal of Biological Chemistry Jun 1979It is well documented that adipose tissue glycogen content decreases during fasting and increases above control during refeeding. We now present evidence that these... (Comparative Study)
Comparative Study
It is well documented that adipose tissue glycogen content decreases during fasting and increases above control during refeeding. We now present evidence that these fluctuations result from adaptations intrinsic to adipose tissue glycogen metabolism that persist in vitro: in response to insulin (1 milliunit/ml), [3H]glucose incorporation into rat fat pad glycogen was reduced to 10% of control after a 3-day fast; incorporation increased 6-fold over fed control on the 4th day of refeeding following a 3-day fast. We have characterized this adaptation with regard to alterations in glycogen synthase and phosphorylase activity. In addition, we found that incubation of fat pads from fasted rats with insulin (1 milliunit/ml) increased glucose-6-P content, indicating that glucose transport was not the rate-limiting step for glucose incorporation into glycogen in the presence of insulin. In contrast, feeding a fat-free diet resulted in dramatic increases in glycogen content of fat pads without a concomitant increase in glucose incorporation into glycogen in response to insulin (1 milliunit/ml). Thus, fasting and refeeding appeared to alter insulin action on adipose tissue glycogen metabolism more than this dietary manipulation.
Topics: Adipose Tissue; Animals; Eating; Fasting; Glucose; Glucosephosphates; Glycogen; Glycogen Synthase; Insulin; Kinetics; Male; Phosphorylases; Rats
PubMed: 108280
DOI: No ID Found -
Journal of Bacteriology Jan 1994Methanococcus maripaludis, a facultatively autotrophic archaebacterium that grows with H2 or formate as the electron donor, does not assimilate sugars and other complex...
Methanococcus maripaludis, a facultatively autotrophic archaebacterium that grows with H2 or formate as the electron donor, does not assimilate sugars and other complex organic substrates. However, glycogen is biosynthesized intracellularly and commonly reaches values of 0.34% of the cellular dry weight in the early stationary phase. To determine the pathway of glycogen catabolism, specific enzymes of sugar metabolism were assayed in cell extracts. The following enzymes were found (specific activity in milliunits per milligram of protein): glycogen phosphorylase, 4.4; phosphoglucomutase, 10; glucose-6-phosphate isomerase, 9; 6-phosphofructokinase, 5.6, fructose-1,6-bisphosphatase, 10; fructose-1,6-bisphosphate aldolase, 4.2; triosephosphate isomerase, 44; glyceraldehyde-3-phosphate dehydrogenase, 26; phosphoglycerate kinase, 20; phosphoglycerate mutase, 78; enolase, 107; and pyruvate kinase, 4.0. Glyceraldehyde-3-phosphate dehydrogenase was NADP+ dependent, and the pyruvate kinase required MnCl2. The 6-phosphofructokinase had an unusually low pH optimum of 6.0. Four nonoxidative pentose-biosynthetic enzymes were found (specific activity in milliunits per milligram of protein): transketolase, 12; transaldolase, 24; ribulose-5-phosphate-3-epimerase, 55; and ribulose-5-phosphate isomerase, 100. However, the key enzymes of the oxidative pentose phosphate pathway, the reductive pentose phosphate pathway, and the classical and modified Entner-Duodoroff pathways were not detected. Thus, glycogen appears to be catabolized by the Embden-Meyerhoff-Parnas pathway. This result is in striking contrast to the nonmethanogenic archaebacteria that have been examined, among which the Entner-Doudoroff pathway is common. A dithiothreitol-specific NADP(+)-reducing activity was also found (8.5 mU/mg of protein). Other thiol compounds, such as cysteine hydrochloride, reduced glutathione, and 2-mercaptoethanesulfonic acid, did not replace dithiothreitol for this activity. The physiological significance of this activity is not known.
Topics: Dithiothreitol; Gluconeogenesis; Glycogen; Glycolysis; Methanococcus; NADP; Oxidation-Reduction; Pentoses; Phosphofructokinase-1
PubMed: 8288525
DOI: 10.1128/jb.176.2.325-332.1994 -
Cureus Oct 2023Primary hypothyroidism is a commonly encountered endocrine disorder and can be associated with pericardial effusion and cardiac tamponade in severe cases. Early...
Primary hypothyroidism is a commonly encountered endocrine disorder and can be associated with pericardial effusion and cardiac tamponade in severe cases. Early detection of hypothyroidism is key since it is a potentially treatable and reversible cause of pericardial effusions. A 53-year-old female was admitted following a fall. The clinical history was remarkable, with symptoms of persistent tiredness and fatigue for six months. She had no known medical conditions and was not taking any regular medications. Vital signs were stable. Physical examination revealed bilateral pitting pedal oedema and a tense abdomen with shifting dullness. Cardiovascular and respiratory examinations were normal. Notably, the patient exhibited delayed relaxation of deep-tendon reflexes bilaterally at the patellar and ankle sites. Pertinent laboratory findings showed an elevated thyroid-stimulating hormone (TSH) level of 151.69 milliunits/L, a low free thyroxine (fT4) level of <5.4 pmol/L, a haemoglobin level of 85 g/L, and a markedly high anti-thyroid peroxidase antibody level of 957.35 IU/mL. An electrocardiogram revealed a normal sinus rhythm with a low-voltage QRS complex. Chest X-ray findings indicated cardiomegaly suggestive of left heart failure. An emergent transthoracic echocardiography (TTE) demonstrated a large pericardial effusion measuring 5.4 cm posterior to the left ventricle. The most likely aetiology in this case was severe primary hypothyroidism. She initially received intravenous liothyronine 10 micrograms every four hours, followed by oral liothyronine 5 micrograms twice a day in conjunction with levothyroxine 100 micrograms once a day. The adrenal reserve assessment was satisfactory. An urgent pericardiocentesis was performed, draining a total of 900 mL of serosanguinous fluid. Serial echocardiograms demonstrated the absence of residual effusion. Hypothyroidism is a relatively uncommon cause of pericardial effusion. By ensuring early detection and appropriate treatment, we can optimise patient outcomes and prevent potential complications associated with untreated hypothyroidism.
PubMed: 38021716
DOI: 10.7759/cureus.46947 -
The Journal of Clinical Endocrinology... Jul 2010The relationship between thyroid function and bone mineral density (BMD) is controversial. Existing studies are conflicting and confounded by differences in study...
Thyroid function within the upper normal range is associated with reduced bone mineral density and an increased risk of nonvertebral fractures in healthy euthyroid postmenopausal women.
CONTEXT
The relationship between thyroid function and bone mineral density (BMD) is controversial. Existing studies are conflicting and confounded by differences in study design, small patient numbers, and sparse prospective data.
OBJECTIVE
We hypothesized that variation across the normal range of thyroid status in healthy postmenopausal women is associated with differences in BMD and fracture susceptibility.
DESIGN
The Osteoporosis and Ultrasound Study (OPUS) is a 6-yr prospective study of fracture-related factors.
SETTING
We studied a population-based cohort from five European cities.
PARTICIPANTS
A total of 2374 postmenopausal women participated. Subjects with thyroid disease and nonthyroidal illness and those receiving drugs affecting thyroid status or bone metabolism were excluded, leaving a study population of 1278 healthy euthyroid postmenopausal women.
INTERVENTIONS
There were no interventions.
MAIN OUTCOME MEASURES
We measured free T(4) (fT4) (picomoles/liter), free T(3) (fT3) (picomoles/liter), TSH (milliunits/liter), bone turnover markers, BMD, and vertebral, hip, and nonvertebral fractures.
RESULTS
Higher fT4 (beta = -0.091; P = 0.004) and fT3 (beta = -0.087; P = 0.005) were associated with lower BMD at the hip, and higher fT4 was associated with increasing bone loss at the hip (beta = -0.09; P = 0.015). After adjustment for age, body mass index, and BMD, the risk of nonvertebral fracture was increased by 20% (P = 0.002) and 33% (P = 0.006) in women with higher fT4 or fT3, respectively, whereas higher TSH was protective and the risk was reduced by 35% (P = 0.028). There were independent associations between fT3 and pulse rate (beta = 0.080; P = 0.006), increased grip strength (beta = 0.171; P<0.001), and better balance (beta = 0.099; P < 0.001), indicating that the relationship between thyroid status and fracture risk is complex.
CONCLUSIONS
Physiological variation in normal thyroid status is related to BMD and nonvertebral fracture.
Topics: Absorptiometry, Photon; Aged; Aged, 80 and over; Analysis of Variance; Bone Density; Female; Fractures, Bone; Humans; Middle Aged; Osteoporosis, Postmenopausal; Postmenopause; Prospective Studies; Reference Values; Regression Analysis; Risk Factors; Thyroid Function Tests; Thyroxine; Triiodothyronine; Women's Health
PubMed: 20410228
DOI: 10.1210/jc.2009-2630 -
The Journal of Clinical Investigation Mar 1985Hypertension and glucose intolerance, determined in a random population sample (n = 2,475), showed a highly significant (P less than 0.001) association from the mildest...
Hypertension and glucose intolerance, determined in a random population sample (n = 2,475), showed a highly significant (P less than 0.001) association from the mildest levels of both conditions, independent of the confounding effects of age, sex, obesity, and antihypertensive medications. Summary rate ratios for hypertension were 1.48 (1.18-1.87) in abnormal tolerance and 2.26 (1.69-2.84) in diabetes compared with normal tolerance. Altogether, 83.4% of the hypertensives were either glucose-intolerant or obese--both established insulin-resistant conditions. Fasting and post-load insulin levels in a representative subgroup (n = 1,241) were significantly elevated in hypertension independent of obesity, glucose intolerance, age, and antihypertensive medications. The mean increment in summed 1- and 2-h insulin levels (milliunits per liter) compared with nonobese normotensives with normal tolerance was 12 for hypertension alone, 47 for obesity alone, 52 for abnormal tolerance alone, and 124 when all three conditions were present. The prevalence of concentrations (milliequivalents per liter) of erythrocyte Na+ greater than or equal to 7.0, K+ less than 92.5, and plasma K+ greater than or equal to 4.5 in a subsample of 59 individuals with all combinations of abnormal tolerance obesity and hypertension was compared with those in 30 individuals free of these conditions. Altogether, 88.1% of the former vs. 40.0% of the latter group presented at least one of these three markers of internal cation imbalance (P less than 0.001). We conclude that insulin resistance and/or hyperinsulinemia (a) are present in the majority of hypertensives, (b) constitute a common pathophysiologic feature of obesity, glucose intolerance, and hypertension, possibly explaining their ubiquitous association, and (c) may be linked to the increased peripheral vascular resistance of hypertension, which is putatively related to elevated intracellular sodium concentration.
Topics: Adult; Age Factors; Aged; Body Surface Area; Diabetes Mellitus; Diabetes Mellitus, Type 2; Erythrocytes; Glucose Tolerance Test; Humans; Hypertension; Insulin; Middle Aged; Obesity; Potassium; Sodium
PubMed: 3884667
DOI: 10.1172/JCI111776 -
The Journal of Clinical Endocrinology... Nov 2012Selenium status may have direct effects on bone and indirect effects through changes in thyroid hormone sensitivity.
CONTEXT
Selenium status may have direct effects on bone and indirect effects through changes in thyroid hormone sensitivity.
OBJECTIVE
We hypothesized that variation in selenium status in healthy euthyroid postmenopausal women is associated with differences in bone turnover, bone mineral density (BMD) and fracture susceptibility.
DESIGN
The Osteoporosis and Ultrasound Study (OPUS) is a 6-yr prospective study of fracture-related factors.
SETTING
The study was comprised of a population-based cohort from five European cities.
PARTICIPANTS
A total of 2374 postmenopausal women participated. Subjects with thyroid disease and nonthyroidal illness and those receiving drugs affecting thyroid status or bone metabolism were excluded, leaving a study population of 1144.
INTERVENTIONS
There were no interventions.
MAIN OUTCOME MEASURES
We measured selenium (micrograms per liter); selenoprotein P (milligrams per liter); free T(4) (picomoles per liter); free T(3) (picomoles per liter); TSH (milliunits per liter); bone turnover markers; BMD; and vertebral, hip, and nonvertebral fractures.
RESULTS
Higher selenium levels were associated with higher hip BMD at study entry (β = 0.072, P = 0.004) and lower levels of bone formation (osteocalcin: β = -0.101, P < 0.001; procollagen type 1 N-terminal propeptide: β = -0.074, P = 0.013) and resorption markers (C-telopeptide of type 1 collagen: β = -0.058, P = 0.050; N-telopeptide of type 1 collagen: β = -0.095, P = 0.002). Higher selenoprotein P was associated with higher hip (β = 0.113, P < 0.001) and lumbar spine BMD (β = 0.088, P = 0.003) at study entry, higher hip BMD after the 6-yr follow-up (β = 0.106, P = 0.001) and lower osteocalcin (β = -0.077, P = 0.009), C-telopeptide of type 1 collagen (β = -0.075, P = 0.012), and N-telopeptide of type 1 collagen (β = -0.110, P < 0.001).
CONCLUSION
Selenium status is inversely related to bone turnover and positively correlated with BMD in healthy euthyroid postmenopausal women independent of thyroid status.
Topics: Aged; Aged, 80 and over; Bone Density; Female; Fractures, Bone; Humans; Middle Aged; Postmenopause; Prospective Studies; Selenium; Selenoprotein P; Thyroid Hormones; Women's Health
PubMed: 22904175
DOI: 10.1210/jc.2012-2121