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1.
Ultrasound Obstet Gynecol ; 61(2): 181-190, 2023 02.
Article in English | MEDLINE | ID: mdl-36370447

ABSTRACT

OBJECTIVE: To analyze the ability to predict perinatal survival and severe neonatal morbidity of cases with early-onset fetal growth restriction (eoFGR) using maternal variables, ultrasound parameters and angiogenic markers at the time of diagnosis. METHODS: This was a prospective observational study in a cohort of singleton pregnancies with a diagnosis of eoFGR (< 32 weeks of gestation). At diagnosis of eoFGR, complete assessment was performed, including ultrasound examination (anatomy, biometry and Doppler assessment) and maternal serum measurement of the angiogenic biomarkers, soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF). Logistic regression models for the prediction of perinatal survival (in cases diagnosed at < 28 weeks) and severe neonatal morbidity (in all liveborn cases) were calculated. RESULTS: In total, 210 eoFGR cases were included, of which 185 (88.1%) survived perinatally. The median gestational age at diagnosis was 27 + 0 weeks. All cases diagnosed at ≥ 28 weeks survived. In cases diagnosed < 28 weeks, survivors (vs non-survivors) had a higher gestational age (26.1 vs 24.4 weeks), estimated fetal weight (EFW; 626 vs 384 g), cerebroplacental ratio (1.1 vs 0.9), PlGF (41 vs 18 pg/mL) and PlGF multiples of the median (MoM; 0.10 vs 0.06) and lower sFlt-1/PlGF ratio (129 vs 479) at the time of diagnosis (all P < 0.001). The best combination of two variables for predicting perinatal survival was provided by EFW and PlGF MoM (area under the receiver-operating-characteristics curve (AUC), 0.84 (95% CI, 0.75-0.92)). These were also the best variables for predicting severe neonatal morbidity (AUC, 0.73 (95% CI, 0.66-0.80)). CONCLUSIONS: A model combining EFW and maternal serum PlGF predicts accurately perinatal survival in eoFGR cases diagnosed before 28 weeks of gestation. Prenatal prediction of severe neonatal morbidity in eoFGR cases is modest regardless of the model used. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.


Subject(s)
Fetal Growth Retardation , Infant, Small for Gestational Age , Pregnancy , Infant, Newborn , Female , Humans , Infant , Placenta Growth Factor , Fetal Growth Retardation/diagnostic imaging , Predictive Value of Tests , Prenatal Care , Biomarkers , Vascular Endothelial Growth Factor Receptor-1 , Ultrasonography, Prenatal
2.
Ultrasound Obstet Gynecol ; 56(4): 549-556, 2020 10.
Article in English | MEDLINE | ID: mdl-31840879

ABSTRACT

OBJECTIVE: To analyze the value of the soluble fms-like tyrosine kinase-1/placental growth factor (sFlt-1/PlGF) ratio in predicting the time to delivery in early-onset fetal growth restriction (FGR) with preserved antegrade umbilical artery (UA) flow at diagnosis. METHODS: This was a prospective observational single-center cohort study of pregnancies with early-onset (< 32 + 0 weeks) FGR and antegrade UA flow, in which maternal serum sFlt-1/PlGF ratio was determined at diagnosis. FGR was defined as estimated fetal weight < 3rd centile or < 10th centile with UA pulsatility index > 95th centile, fetal middle cerebral artery pulsatility index < 5th centile or cerebroplacental ratio < 5th centile. The previously described sFlt-1/PlGF ratio cut-off value of 85 for facilitating the diagnosis of pre-eclampsia was assessed in the prediction of the need to deliver in < 1 week and ≥ 4 weeks. RESULTS: In total, 120 cases were included. There were 116 (96.7%) liveborn neonates and 108 (90.0%) perinatal survivors. Median (interquartile range (IQR)) gestational age at diagnosis of early-onset FGR was 27.1 (25.7-29.4) weeks. Median (IQR) sFlt-1/PlGF ratio at diagnosis was 196 (84-474). Ninety (75.0%) cases had a sFlt-1/PlGF ratio ≥ 85. Among pregnancies with a liveborn neonate, median (IQR) interval to delivery in the groups with sFlt-1/PlGF ratio < 85 and ≥ 85 was 41 (22-54) days and 11 (4-20) days, respectively (P < 0.01). The probability of having to deliver within 1 week after diagnosis was 0% and 35.6% in those with sFlt-1/PlGF ratio < 85 and ≥ 85, respectively (P = 0.03), and the probability of delaying delivery for ≥ 4 weeks was 72.4% and 19.5%, respectively (P < 0.01). CONCLUSION: sFlt-1/PlGF ratio < 85 at diagnosis of early-onset FGR with antegrade UA flow identifies a group of pregnancies in which the need to deliver within 1 week is very low and the interval to delivery is expected to be prolonged for ≥ 4 weeks in > 70% of cases. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.


Subject(s)
Delivery, Obstetric/statistics & numerical data , Fetal Growth Retardation/diagnosis , Placenta Growth Factor/blood , Umbilical Arteries/embryology , Vascular Endothelial Growth Factor Receptor-1/blood , Adult , Biomarkers/blood , Female , Fetal Growth Retardation/physiopathology , Fetal Weight , Gestational Age , Humans , Live Birth , Middle Cerebral Artery/embryology , Middle Cerebral Artery/physiopathology , Predictive Value of Tests , Pregnancy , Prospective Studies , Pulsatile Flow , Time Factors , Umbilical Arteries/physiopathology
3.
Pregnancy Hypertens ; 13: 279-285, 2018 Jul.
Article in English | MEDLINE | ID: mdl-30177066

ABSTRACT

OBJECTIVE: To analyze the usefulness of a clinical protocol for early detection of preeclampsia and/or fetal growth restriction (PE/FGR) using, in previously selected pregnancies, the measurement of the sFlt-1/PlGF ratio at 24-28 weeks of gestation. STUDY DESIGN: Prospective observational cohort study carried out in a single tertiary hospital in Spain. 5601 consecutive singleton pregnancies with complete follow-up were included. High-risk women for PE/FGR were selected by combining data from maternal history and second trimester uterine artery Doppler. Subsequently these patients underwent intensive monitoring, including the measurement of the sFlt-1/PlGF ratio at 24-28 weeks to predict PE/FGR. MAIN OUTCOME MEASURES: Early, intermediate and late PE/FGR (delivery <32 + 0, 32 + 0 - <36 + 0 and ≥36 + 0 weeks, respectively). RESULTS: Overall incidence of early, intermediate and late PE/FGR was 0.3%, 0.7% and 3.2%, respectively, being higher in the 4.3% of women selected for intensive monitoring: 5.8%, 8.7% and 15.4%, respectively (all p < 0.001). The area under the curve (AUC) with 95%CI of the sFlt-1/PlGF ratio for detecting early PE/FGR was 0.98 (0.97-1.00), and the sFlt-1/PlGF ratio >95th centile showed a sensitivity (%) of 100 (95%CI, 78.5-100) and specificity (%) of 80.6 (95%CI, 75.0-85.2). The AUC of the sFlt-1/PlGF ratio for detecting intermediate and late PE/FGR was of 0.87 (95%CI, 0.77-0.97) and 0.68 (95%CI, 0.58-0.79), respectively. CONCLUSION: A contingent strategy of measuring the sFlt-1/PlGF ratio at 24-28 weeks in women previously selected by clinical factors and uterine artery Doppler enables an accurate prediction of PE/FGR. This performance is optimal to predict PE/FGR requiring delivery before 32 weeks.


Subject(s)
Fetal Growth Retardation/blood , Placenta Growth Factor/blood , Pre-Eclampsia/blood , Vascular Endothelial Growth Factor Receptor-1/blood , Adult , Biomarkers/blood , Blood Pressure , Early Diagnosis , Female , Fetal Growth Retardation/diagnosis , Fetal Growth Retardation/physiopathology , Fetal Weight , Humans , Pre-Eclampsia/diagnosis , Pre-Eclampsia/physiopathology , Predictive Value of Tests , Pregnancy , Pregnancy Outcome , Prognosis , Prospective Studies , Risk Factors , Spain , Ultrasonography, Doppler , Ultrasonography, Prenatal/methods , Uterine Artery/diagnostic imaging , Uterine Artery/physiopathology
4.
Pregnancy Hypertens ; 11: 99-104, 2018 Jan.
Article in English | MEDLINE | ID: mdl-29523283

ABSTRACT

OBJECTIVE: To evaluate the usefulness of the uterine artery mean pulsatility index (mPI-UtA) and the sFlt-1/PlGF ratio in women with systemic lupus erythematosus (SLE) or antiphospholipid syndrome (APS) for the prediction of placental dysfunction-related adverse outcomes (AO), namely pre-eclampsia (PE) and intrauterine growth restriction (IUGR), and for differential diagnosis between PE and SLE flares. STUDY DESIGN: Observational prospective cohort study of 57 pregnant women with SLE or APS. MAIN OUTCOME MEASURES: mPI-UtA and sFlt-1/PlGF ratio in maternal serum were obtained at four gestational age periods (11-14, 19-22, 24-29 and 32-34 weeks). Comparisons among pregnancies with normal outcome, SLE flare and AO were performed. RESULTS: Overall, we had 44 ongoing pregnancies (36 with SLE and 8 with APS) of which most (n = 35, 80%) were uncomplicated. The overall rate of AO was 9% (n = 4), that was diagnosed at a mean (SD) gestational age of 34.1 (7.5) weeks. Five SLE patients (14%) suffered a SLE flare. No differences for these markers were found between normal pregnancies and those affected by SLE flare. mUtA-PI values were significantly higher in the AO group when compared with normal and SLE flare groups, at 19-22 weeks (1.52, 0.95 and 0.76) and 32-34 weeks (1.13, 0.68 and 0.65), respectively. The sFlt-1/PlGF ratio was significantly higher in the AO group at 24-29 weeks (191.1, 3.1 and 9.2), respectively. CONCLUSION: Our preliminary results indicate that mPI-UtA and sFlt1/PlGF ratio may be useful to predict AO in women with SLE, and to make the differential diagnosis with a lupus flare.


Subject(s)
Antiphospholipid Syndrome , Fetal Growth Retardation , Lupus Erythematosus, Systemic , Placenta Growth Factor/blood , Pre-Eclampsia , Ultrasonography, Doppler , Uterine Artery/diagnostic imaging , Vascular Endothelial Growth Factor Receptor-1/blood , Antiphospholipid Syndrome/blood , Antiphospholipid Syndrome/diagnostic imaging , Antiphospholipid Syndrome/physiopathology , Biomarkers/blood , Diagnosis, Differential , Disease Progression , Female , Fetal Growth Retardation/blood , Fetal Growth Retardation/diagnostic imaging , Fetal Growth Retardation/physiopathology , Gestational Age , Humans , Lupus Erythematosus, Systemic/blood , Lupus Erythematosus, Systemic/diagnostic imaging , Lupus Erythematosus, Systemic/physiopathology , Pre-Eclampsia/blood , Pre-Eclampsia/diagnostic imaging , Pre-Eclampsia/physiopathology , Predictive Value of Tests , Pregnancy , Prospective Studies , Pulsatile Flow , Regional Blood Flow , Risk Factors , Uterine Artery/physiopathology
5.
Science ; 350(6256): 64-7, 2015 Oct 02.
Article in English | MEDLINE | ID: mdl-26272904

ABSTRACT

Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric compositions and luminosities, which are influenced by their formation mechanisms. Using the Gemini Planet Imager, we discovered a planet orbiting the ~20-million-year-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water-vapor absorption. Modeling of the spectra and photometry yields a luminosity (normalized by the luminosity of the Sun) of 1.6 to 4.0 × 10(-6) and an effective temperature of 600 to 750 kelvin. For this age and luminosity, "hot-start" formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the "cold-start" core-accretion process that may have formed Jupiter.

6.
Health Educ Res ; 29(6): 1058-76, 2014 Dec.
Article in English | MEDLINE | ID: mdl-25348207

ABSTRACT

This study developed three types of educational preoperative materials and examined their efficacy in preparing children for surgery by analysing children's preoperative worries and parental anxiety. The sample was recruited from three hospitals in Lisbon and consisted of 125 children, aged 8-12 years, scheduled to undergo outpatient surgery. The participants were randomly assigned to one of the seven independent conditions that were combined into the following three main groups: an experimental group, which received educational materials with information about surgery and hospitalization (a board game, a video or a booklet); a comparison group, which received entertaining material with the same format type; and a control group, which did not receive any material. Children's preoperative worries and parental anxiety were evaluated after the experimental manipulation. Children who received educational materials were significantly less worried about surgery and hospital procedures than children in the comparison and the control groups, although no statistically differences were found between the type of materials within the experimental group, and no significant effect occurred on parental state anxiety. These results do however support the hypothesis that providing preoperative materials with educational information reduce children's preoperative worries.


Subject(s)
Ambulatory Surgical Procedures/psychology , Anxiety/prevention & control , Patient Education as Topic , Teaching Materials , Child , Female , Humans , Male , Portugal
7.
Ultrasound Obstet Gynecol ; 43(5): 525-32, 2014 May.
Article in English | MEDLINE | ID: mdl-24185845

ABSTRACT

OBJECTIVE: To evaluate the performance of the mean uterine artery pulsatility index (UtA-PI) and the automated measurement of the soluble fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PlGF) ratio for the prognostic assessment of both maternal and perinatal outcomes, and the time-to-delivery interval in early-onset (≤ 34 + 0 weeks) pre-eclampsia (PE) cases with attempted expectant management. METHODS: Fifty-one singleton pregnancies with early-onset PE were enrolled in the study. Mean UtA-PI and sFlt/PlGF ratio were measured at diagnosis. The association of each marker and their combinations with adverse maternal and perinatal outcomes was assessed by univariable comparisons and multivariable logistic regression analysis and time-to-delivery interval by survival analysis. RESULTS: Twenty-six (51%) had adverse maternal outcome and 14 (27%) had adverse perinatal outcome. At the time of onset of PE, only gestational age was significantly related to maternal complications. Gestational age at onset, mean UtA-PI and sFlt-1/PlGF ratio were significantly associated with perinatal complications, their combination reaching a sensitivity of 64% with 95% specificity, and an area under the receiver-operating characteristics curve of 0.89 (95% CI, 0.79-0.99). Regarding the time until delivery, 92% (12/13) of cases with sFlt-1/PlGF ratio > 655 and 39% (15/38) of cases with a ratio ≤ 655 delivered within the first 48 h, 8% (1/13) and 19% (7/38), respectively, delivered between 48 h and 7 days and 0% (0/13) and 42% (16/38), respectively, delivered after 7 days. CONCLUSION: Mean UtA-PI and sFlt-1/PlGF ratio in combination with gestational age are useful for the prognostic assessment of perinatal complications at the time of diagnosis of early-onset PE, but this combination has limited value for the prediction of maternal complications. Moreover, sFlt-1/PlGF ratio > 655 is closely related to the need to deliver within 48 h. [[ArtCopyrightmsg]].


Subject(s)
Pre-Eclampsia/blood , Pre-Eclampsia/diagnostic imaging , Pregnancy Proteins/blood , Ultrasonography, Doppler, Pulsed , Uterine Artery/diagnostic imaging , Vascular Endothelial Growth Factor Receptor-1/blood , Biomarkers/blood , Female , Humans , Male , Placenta Growth Factor , Predictive Value of Tests , Pregnancy , Pregnancy Trimesters , Prognosis , Pulsatile Flow , ROC Curve , Reproducibility of Results , Time Factors
8.
Ultrasound Obstet Gynecol ; 41(5): 530-7, 2013 May.
Article in English | MEDLINE | ID: mdl-23303638

ABSTRACT

OBJECTIVE: To evaluate the usefulness of the mean pulsatility index of the uterine arteries (mPI-UtA) and automated measurement of the soluble fms-like tyrosine kinase 1 (sFlt-1)/placental growth factor (PlGF) ratio on suspicion or at diagnosis of pre-eclampsia (PE). METHODS: Patients with singleton pregnancies with PE (n = 60) diagnosed according to current recommendations, or with suspected PE (n = 32) defined by (1) blood pressure (BP) ≥ 160/100 mmHg, (2) BP ≥ 140/90 mmHg or proteinuria, together with suggestive clinical symptoms or (3) intrauterine growth restriction (IUGR) at < 34 + 0 weeks, were enrolled and mPI-UtA and the sFlt-1/PlGF ratio were measured. Values > 95(th) centile were considered abnormal. All cases were classified according to occurrence of PE and/or IUGR and subclassified, depending on gestational age at delivery, as early (< 34 + 0 weeks) or late (≥ 34 + 0 weeks). RESULTS: PE was confirmed in 72 cases, in which 32 early deliveries occurred. Isolated IUGR was diagnosed in nine early cases and one late case, while the remaining 10 cases were late deliveries without PE or IUGR. In pregnancies in which PE and IUGR were excluded, mPI-UtA was abnormal in 40% but the sFlt-1/PlGF ratio was normal in 100%. In early PE, mPI-UtA at diagnosis was abnormal in 100% of cases with IUGR and in 91% without IUGR, while sFlt-1/PlGF was abnormal in 100% and 96%, respectively. In late PE, mPI-UtA was abnormal in 50% and 37% of cases with and without IUGR while the sFlt-1/PlGF ratio was abnormal in 50% and 26%, respectively. CONCLUSION: Abnormal mPI-UtA and sFlt-1/PlGF ratio are common in early PE. In late PE, mPI-UtA is normal in most cases and thus not diagnostically useful. The sFlt-1/PlGF ratio shows high specificity but low sensitivity to confirm PE when suspected.


Subject(s)
Pre-Eclampsia/diagnosis , Pregnancy Proteins/metabolism , Uterine Artery/physiology , Vascular Endothelial Growth Factor Receptor-1/metabolism , Adult , Female , Fetal Growth Retardation/etiology , Humans , Placenta Growth Factor , Pregnancy , Pregnancy Outcome , Pulsatile Flow/physiology , Ultrasonography, Doppler, Pulsed
9.
Ultrasound Obstet Gynecol ; 40(1): 68-74, 2012 Jul.
Article in English | MEDLINE | ID: mdl-22102516

ABSTRACT

OBJECTIVE: To evaluate the performance of models described previously for the prediction of pre-eclampsia (PE), based on the sequential evaluation of uterine artery resistance at 11-13 weeks and 19-22 weeks, in a high-risk population. METHODS: This was a prospective study in 135 women with singleton pregnancies and at least one of the following high-risk conditions: PE and/or intrauterine growth restriction in a previous pregnancy, chronic hypertension, pregestational diabetes, renal disease, body mass index > 30 kg/m(2) , autoimmune disease (systemic lupus erythematosus, antiphospholipid syndrome or rheumatoid arthritis) and thrombophilia. Mean uterine artery pulsatility index (mUtA-PI) at 11-13 and at 19-22 weeks' gestation was measured and analyzed according to quantitative and semi-quantitative models, to predict late PE (resulting in delivery ≥ 34 weeks) and early PE (delivery < 34 weeks). RESULTS: Late PE developed in 21 (15.6%) pregnancies and early PE in six (4.4%). Using mUtA-PI, the detection rates of late and early PE for a false-positive rate of 10% were 14.3% and 33.3%, respectively, at 11-13 weeks, and 19.0% and 66.7%, respectively, at 19-22 weeks. Using a semi-quantitative approach, the group of pregnant women with mUtA-PI ≥ 90(th) percentile at both 11-13 and 19-22 weeks had a greater risk for early PE (odds ratio, 21.4 (95% CI, 2.5-184.7)) compared with the group with mUtA-PI < 90(th) percentile at both periods. Using a quantitative approach, there was relative worsening in the mUtA-PI (multiples of the median) from the first to the second trimester in all cases of early PE. CONCLUSION: The application of semi-quantitative and especially quantitative models to evaluate sequential changes in uterine artery Doppler findings between the first and second trimesters could be of additional value in assessing high-risk women regarding their true risk of developing early PE.


Subject(s)
Pre-Eclampsia/diagnostic imaging , Pregnancy, High-Risk , Ultrasonography, Doppler, Color , Uterine Artery/diagnostic imaging , Uterus/diagnostic imaging , Adult , Female , Humans , Infant, Newborn , Models, Statistical , Pre-Eclampsia/physiopathology , Pre-Eclampsia/prevention & control , Predictive Value of Tests , Pregnancy , Prospective Studies , Pulsatile Flow , Ultrasonography, Prenatal , Uterine Artery/embryology , Uterine Artery/physiopathology , Uterus/blood supply , Uterus/physiopathology , Vascular Resistance
10.
MAPFRE med ; 18(4): 292-304, oct.-dic. 2007. ilus, tab
Article in Es | IBECS | ID: ibc-67869

ABSTRACT

Objetivo: Comprobar que polimorfismos implicados en genes del metabolismo de carcinógenos pueden contribuir a la susceptibilidad individual a desarrollar cáncer de pulmón. Hemos estudiado la relación entre dos polimorfismos en estos genes (CYP1A1 MspI y GSTP1 Ile105Val) y el riesgo de desarrollar cáncer de pulmón.Diseño: Estudio caso control de base hospitalaria que incluye 406 casos incidentes de cáncer de pulmón y 436 controles apareados por edad, género y área geográfica. Los genotipos fueron determinados por PCR-RFLP y los resultados fueron analizados usando un método de regresión logística.Resultados: Encontramos asociación entre el polimorfismoCYP1A1MspI y el riesgo de desarrollar cáncer de pulmón mientras que no encontramos asociación al estudiar el polimorfismo GSTP1 Ile105Val. El valor de la OR ajustada obtenida en el caso del CYP1A1MspI es de 1,47; 95% CI = 0,35-6,14, lo cual indica que aumenta el riesgo a desarrollar cáncer de pulmón aunque nuestros datos no son estadísticamente significativos. Por otra parte, parece que el genotipo heterocigoto para el polimorfismoGSTP1 Ile105Val tiene un papel protector frente aldesarrollo del cáncer de pulmón en mujeres (OR ajustada=0,22; CI = 0,09-0,56).Conclusión: Nuestros resultados apoyan la hipótesis de que polimorfismos en genes implicados en el metabolismo de carcinógenos y sus combinaciones pueden influir en la etiología del cáncer de pulmón


Purpose: Polymorphisms in genes involved in carcinogens metabolism might contribute to the individual susceptibility to develop different types of cancer. We have investigated the relationship between polymorphisms in two of these genes, CYP1A1 (MspI) and GSTP (Ile105Val) and the risk of developing lung cancer.Experimental Design: A hospital-based case-control studywas designed including 406 lung cancer patients and 436control subjects matched on age, gender, and geographicalarea. Genotypes were determined by PCR-RFLP and the results were analyzed using unconditional logistic regression, adjusting for relevant confounding variables.Results: A slight association was found for CYP1A1 MspI polymorphism, while no association was observed for GSTP1Ile105Val polymorphism. In this regard, the CYP1A1MspI genotype was associated with an increased risk of lung cancer(adjusted OR=1,47; 95% CI = 0,35-6,14) but there was no statistical significance. It seems that heterozygous GSTP1 variant protects to develop lung cancer in women (adjusted OR= 0,22; CI = 0,09-0,56). Furthermore, an interaction between CYP1A1 MspI and GSTP1 Ile105Val was observed, resulting in a further increase in the risk of developing lung cancer.Conclusions: These results support the hypothesis that polymorphisms and their combined effects in metabolic genes might play a role in lung cancer etiology (AU)


Subject(s)
Humans , Male , Female , Adult , Middle Aged , Aged , Polymorphism, Genetic/genetics , Lung Neoplasms/genetics , Carcinogens/metabolism , Lung Neoplasms/etiology , Tobacco Use Disorder , Cytochrome P-450 CYP1A1/genetics , Case-Control Studies , Glutathione Transferase/genetics
11.
Biochemistry ; 31(28): 6603-7, 1992 Jul 21.
Article in English | MEDLINE | ID: mdl-1633173

ABSTRACT

The irreversible thermal unfolding of the class A beta-lactamase I from Bacillus cereus has been investigated at pH 7.0, using differential scanning calorimetry (DSC) and inactivation kinetic techniques. DSC transitions showed a single peak with a denaturation enthalpy of 646 kJ.mol-1 and were moderately scan rate dependent, suggesting that the process was partially kinetically controlled. The inactivation kinetics at constant temperature showed that the irreversible denaturation of the enzyme occurs as the sum of two exponential terms whose amplitudes are strongly temperature dependent within the transition range so that, at the lowest temperatures within this interval, irreversible inactivation would proceed mainly through the slow phase. The fraction of irreversibly denatured enzyme (D) as a function of temperature for a given scanning rate was calculated by numerical integration of the kinetic equation with temperature, using previously determined kinetic parameters. This D form was the most populated of the unfolded states only at temperatures well above the maximum in the calorimetric transition. Combination of the results of kinetic and DSC experiments has allowed us to separate the contribution of the final D state to the excess enthalpy change from the contribution arising from the reversibly denatured forms of the enzyme (I(i), i = 1,..., n), with the resulting conclusion that the scan rate dependence of the calorimetric traces was the result of two different dynamic effects, viz., the irreversible step and a slow relaxation process during formation of the reversibly denatured intermediate states. Finally, the problems of using results obtained at a single scan rate to validate the two-state kinetic model are commented on.


Subject(s)
Protein Denaturation , beta-Lactamases/chemistry , Bacillus cereus/enzymology , Calorimetry, Differential Scanning , Hot Temperature , Thermodynamics
12.
Biochem J ; 279 ( Pt 1): 111-4, 1991 Oct 01.
Article in English | MEDLINE | ID: mdl-1930129

ABSTRACT

The influence of C-6 alpha- or C-7 alpha-methoxylation of the beta-lactam ring in the catalytic action of class A and B beta-lactamases has been investigated. For this purpose the kinetic behaviour of beta-lactamases I (class A) and II (class B) from Bacillus cereus was analysed by using several cephamycins, moxalactam, temocillin and related antibiotics. These compounds behaved as poor substrates for beta-lactamase II, with high Km values and very low catalytic efficiencies. In the case of beta-lactamase I, the substitution of a methoxy group for a H atom at C-7 alpha or C-6 alpha decreased the affinity of the substrates for the enzyme. Furthermore, the acylation of cephamycins was completely blocked, whereas that of penicillins was slowed down by a factor of 10(4)-10(5), acylation being the rate-determining step of the process.


Subject(s)
Bacillus cereus/enzymology , Cephamycins/metabolism , beta-Lactamases/metabolism , Acylation , Anti-Bacterial Agents/metabolism , Catalysis , Kinetics , beta-Lactamase Inhibitors
13.
Biochem J ; 265(1): 69-77, 1990 Jan 01.
Article in English | MEDLINE | ID: mdl-2137332

ABSTRACT

The thermodynamics of the interaction of the glycopeptidic antibiotic teicoplanin and its peptidic moiety with analogues of bacterial cell-wall peptides were studied by means of calorimetric and spectrophotometric techniques. The analysis of the thermodynamic data has allowed us to evaluate the contributions of the different peptide groups to the binding process. The nature of the primary binding forces is also discussed for each interacting group, on the basis of their enthalpic and entropic contribution and in connection with the detailed structural information available for these antibiotics from n.m.r. data. Similar analyses for the case of vancomycin and ristocetin are also reported.


Subject(s)
Anti-Bacterial Agents/metabolism , Peptides/metabolism , Amino Acid Sequence , Calorimetry , Cell Membrane/metabolism , Glycopeptides/metabolism , Membrane Proteins/metabolism , Molecular Sequence Data , Ristocetin/metabolism , Spectrophotometry, Ultraviolet , Teicoplanin , Thermodynamics , Vancomycin/metabolism
14.
J Antibiot (Tokyo) ; 39(7): 914-21, 1986 Jul.
Article in English | MEDLINE | ID: mdl-3531129

ABSTRACT

We have studied the modification of Escherichia coli peptidoglycan induced by bicyclomycin. For this purpose liquid chromatography for peptidoglycan analysis has been used. The main alteration found was an increase of diaminopimelyl-diaminopimelyl bridge containing subunits. Our results show that bicyclomycin impairs the normal breakage of that interpeptidic bond, whose cleavage is needed for the normal remodeling of peptidoglycan and cell growth. Based on the analysis of the possible structure of diaminopimelyl-diaminopimelyl bond and bicyclomycin, we propose a hypothesis on the mechanism of action of bicyclomycin.


Subject(s)
Anti-Bacterial Agents/pharmacology , Escherichia coli/drug effects , Peptidoglycan/analysis , Bridged Bicyclo Compounds/pharmacology , Bridged Bicyclo Compounds, Heterocyclic , Diaminopimelic Acid , Escherichia coli/analysis , Escherichia coli/growth & development , Lipoproteins/analysis
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