Inter-Specialty Controversies on the Treatment of Cardiovascular Diseases during Pregnancy: A Questionnaire Study.

Background and Objectives: Management of cardiovascular disease (CVD) during pregnancy is challenging and usually requires eminence-based decisions due to limited strong-evidence data in this field. The purpose of our study was to compare the attitudes of anaesthesiologists, cardiologists, and gynaecologists towards the diagnosis and treatment of potentially life-threatening CVDs during pregnancy. Materials and Methods: A cross-sectional, questionnaire-based study was performed among 111 doctors (55 anaesthesiologists, 36 cardiologists, 20 gynaecologists). Personal opinions on the recommendations (n = 19) regarding rare, potentially life-threatening CVDs during pregnancy were recorded using a five-item Likert scale. Results: Opinions regarding eight statements (42%) varied substantially between specialties (p < 0.05). The most distinctive differences between physicians concerned the following recommendations: "thrombolysis should only be used in pulmonary embolism with cardiogenic shock" (agree: 52.7% of anaesthesiologists, 80.4% of cardiologists, 25.0% of gynaecologists; p < 0.001); "women with the antiphospholipid syndrome should restart treatment with vitamin K antagonists from the second trimester of pregnancy" (agree: 12.7% of anaesthesiologists, 69.4% of cardiologists, 20.0% of gynaecologists; p < 0.001); "women with symptomatic pulmonary hypertension should have a Swan-Ganz catheter inserted for labour" (agree: 20.0% of anaesthesiologists, 11.1% of cardiologists, 55.0% of gynaecologists; p = 0.001). Conclusions: Physicians' opinions regarding diagnostics and treatment of CVDs in pregnancy remain controversial. A multidisciplinary approach is recommended to ensure the safety and effectiveness of management in these unique medical conditions.

Association of single nucleotide polymorphism rs7579169 with hypertension disorders during pregnancy and perinatal outcome.

BACKGROUND: Hypertension during pregnancy is a heterogeneous group of disorders with elevated blood pressure with or without proteinuria. The multiple researches are held on the subject of a genetic conditioning of preeclampsia and pregnancy induced hypertension. OBJECTIVES: The study was designed to evaluate the impact of the single nucleotide polymorphism (SNP) rs7579169 on hypertension disorders in pregnancy, especially on PE and PIH as well as on the perinatal outcome. METHODS: It is a case-control study. The study included 104 women with uncomplicated pregnancies in the control group and 75 pregnant women with hypertension disorders in the study group, hospitalized in the Perinatology and Obstetrics Department of the University Hospital in Cracow. Genomic DNA was extracted from peripheral blood leukocytes and SNP rs7579169 was genotyped from all patients. We analyzed the genotypes distribution and allele frequencies of polymorphism rs7579169 and its association with perinatal outcome in all groups. A p-value<0.05 was considered as significant. RESULTS: Clinical evaluation included standard anthropometric measures like weight and height for the calculation of the body mass index in the beginning and in the end of the pregnancy, blood pressure, time and a method of delivery, birth weight, Apgar score. The heterozygote CT was associated with a 4.5-fold increased risk of preeclampsia in pregnant patients. The presence of TT genotype significantly increased the risk of intrauterine growth restriction (<10 percentile). CONCLUSIONS: The study show probable impact of SNP rs7579169 on pregnancy, but further studies on larger groups are needed.

[Selected polymorphisms of Renin-Angiotensin System in the pathology of hypertensive disorders of pregnancy]. / Wybrane polimorfizmy genów ukladu renina-angiotensyna w patogenezie nadcisnienia w przebiegu ciazy.

Pregnancy induced hypertension and pre-eclampsia, defined as hypertension and proteinuria after 20 weeks of pregnancy with no history of such symptoms, are a great challenge in the field of perinatology They are a serious threat to the mother and the child. Regardless of numerous studies on the subject, the pathogenesis of pregnancy-induced hypertension and pre-eclampsia is still unknown, although a crucial role of genetic factors combined with environmental factors has been confirmed. New theory based on genetic analysis of Renin-Angiotensin System and its impact on blood pressure in pregnant women, has been subject to much debate recently Numerous genes have been studied but angiotensinogen remains to be the best known. Little is known about angiotensin receptor type 1 and 2. This paper presents the knowledge about selected genes of RAS and their impact on pregnancy

Modeling and Machine Learning of Vibration Amplitude and Surface Roughness after Waterjet Cutting.

This study focused on analyzing vibrations during waterjet cutting with variable technological parameters (speed, vfi; and pressure, pi), using a three-axis accelerometer from SEQUOIA for three different materials: aluminum alloy, titanium alloy, and steel. Difficult-to-machine materials often require specialized tools and machinery for machining; however, waterjet cutting offers an alternative. Vibrations during this process can affect the quality of cutting edges and surfaces. Surface roughness was measured by contact methods after waterjet cutting. A machine learning (ML) model was developed using the obtained maximum acceleration values and surface roughness parameters (Ra, Rz, and RSm). In this study, five different models were adopted. Due to the characteristics of the data, five regression methods were selected: Random Forest Regressor, Linear Regression, Gradient Boosting Regressor, LGBM Regressor, and XGBRF Regressor. The maximum vibration amplitude reached the lowest acceleration value for aluminum alloy (not exceeding 5 m/s2), indicating its susceptibility to cutting while maintaining a high surface quality. However, significantly higher acceleration amplitudes (up to 60 m/s2) were registered for steel and titanium alloy in all process zones. The predicted roughness parameters were determined from the developed models using second-degree regression equations. The prediction of vibration parameters and surface quality estimators after waterjet cutting can be a useful tool that for allows for the selection of the optimal abrasive waterjet machining (AWJM) technological parameters.

Analysis of Vibration, Deflection Angle and Surface Roughness in Water-Jet Cutting of AZ91D Magnesium Alloy and Simulation of Selected Surface Roughness Parameters Using ANN.

The use of magnesium alloys in various industries and commerce is increasing due to their properties such as high strength and casting properties, high vibration damping capability, good shielding of electromagnetic radiation and high machinability. Conventional machining methods can, however, pose a risk of ignition. AWJM is a safe alternative to conventional machining, but the deflection and vibration of the water jet can affect surface quality. Therefore, the aim of this study was to investigate the effects of selected AWJM parameters on the surface quality and vibration of machined magnesium alloys. Jet deflection angle, surface roughness parameters and vibration during AWJM were investigated. The findings showed that higher skewness occurred at a lower abrasive flow rate, while higher average values of the Sku roughness parameter were obtained at ma = 8 g/s in the range of 60-140 mm/min. It was also observed that higher vibration values occurred at ma = 8 g/s. The input parameters for creating an artificial neural network (ANN) model used in this study were the cutting speed vf and the mass flow rate ma. The results of this study provided valuable insights into ways of ensuring a safe and efficient machining environment for magnesium alloys. The use of ANN modeling for predicting the vibration and surface roughness of AZ91D magnesium alloy after water-jet cutting could be an effective tool for optimizing AWJM parameters.

Machine Learning Models in Drilling of Different Types of Glass-Fiber-Reinforced Polymer Composites.

The aim of the research presented in this paper was to simulate the relationship between selected technological drilling parameters (cutting speed, vc, and feed per tooth, fz) and cutting forces and the delamination in machining of a new glass-fiber-reinforced polymer (GFRP) composite. Four different types of new materials were manufactured with the use of a specially designed pressing device and differed in the fiber type (plain and twill woven materials) and weight fraction (wf) ratio, but they had the same number of layers and the same stacking sequence. A vertical machining center Avia VMC800HS was used for drilling holes with a two-edge carbide diamond coated drill. Measurements of the cutting force Fz in the drilling process conducted with variable technological parameters were carried out on a special test stand, 9257B, from Kistler. The new ink penetration method, involving covering the drilled hole surface with a colored liquid that spreads over the inner surface of the hole showing damage, was used to determine the delamination area. The cause-and-effect relationship between the drilling parameters was simulated with the use of five machine learning (ML) regression models (Linear Regression; Decision Tree Regressor; Decision Tree Regressor with Ada Boost; XGBRF Regressor; Gradient Boosting Regressor). Gradient Boosting Regressor results showed that the feed per tooth had the greatest impact on delamination-the higher the feed was, the greater the delamination became. Push-out delamination factors had higher values for materials that were made of plain woven fibers. The lowest amplitude of the cutting force component Fz was obtained for the lowest tested feed per tooth of 0.04 mm for all tested materials, with the lowest values obtained for the materials with twill fibers.

Leptin and interferon-gamma as possible predictors of cesarean section among women with hypertensive disorders of pregnancy.

BACKGROUND: This study was designed to evaluate maternal levels of leptin and interferon-gamma (IFN-gamma) in pregnancy complicated with hypertension and to assess the role of cytokines in predicting the risk of cesarean section. MATERIAL/METHODS: This was a cohort study with a prospective follow-up. After proportional sampling procedure, the study included the follow-up of 40 women with hypertensive disorders of pregnancy (pregnancy-induced hypertension [PIH] or preeclampsia [PE]) and 40 uncomplicated pregnancies. Women were followed from the time of admission to the delivery. Levels of leptin and interferon-gamma were measured in serum samples from all women. A p-value <0.05 was considered as significant. RESULTS: Significant increase in IFN-gamma and leptin concentration in women with pre-eclampsia was observed. We found a significant 1.4-fold increase in the risk of birth by cesarean section associated with the increase of the IFN-gamma concentration by 0.1 pg/ml and almost 3-fold increase in the risk associated with the increase of the leptin concentration. CONCLUSIONS: IFN-γ and leptin might be risk markers of cesarean section in hypertension disorders of pregnancy, but further studies supporting this evidence are needed.

Experimental Study and Artificial Neural Network Simulation of Cutting Forces and Delamination Analysis in GFRP Drilling.

This paper reports the results of measurements of cutting forces and delamination in drilling of Glass-Fiber-Reinforced Polymer (GFRP) composites. Four different types of GFRP composites were tested, made by a different manufacturing method and had a different fiber type, weight fraction (wf) ratio, number of layers, but the same stacking sequence. GFRP samples were made using two technologies: a novel method based on the use of a specially designed pressing device and hand lay-up and vacuum bag technology process. The study was conducted with variable technological parameters: cutting speed vc and feed per tooth fz. The two-edge carbide diamond-coated drill produced by Seco Company was used in the experiments. Cutting-force components and delamination factor were measured in the experiments, and photos of the holes were taken to determine the delamination. In addition, modeling of cause-and-effect relationships between the technological drilling parameters vc and fz was simulated with the use of artificial neural network modeling. For all tested GFRP materials, an increase in fz led to an increase in the amplitude of cutting-force component Fz. The lowest values of the amplitude of cutting-force component Fz were obtained with the lowest tested feed per tooth value of 0.04 mm/tooth for all tested materials. It was observed that materials produced with the use of the specially designed pressing device were characterized by lower values of the cutting-force component Fz. It was also found that the delamination factor increased with an increase in fz for all tested GFRP materials. A comparison of the lowest and the highest values of fz revealed that the lowest delamination factor increase was archived by the B1 material and amounted to about 12.5%. The error margin of the obtained numerical modeling results does not exceed 15%, so it can be concluded that artificial neural networks are a suitable tool for modeling cutting force amplitudes as a function of vc and fz. The study has shown that the use of the special pressing device during the manufacturing of composite materials has a positive effect on delamination.

Pregnancy-related comorbidities and labor induction - the effectiveness and safety of dinoprostone compared to misoprostol.

OBJECTIVES: The aim of the study was to evaluate whether the presence of the disease in pregnancy influences the effectiveness and safety of delivery preinduction with prostaglandins: misoprostol vaginal insert and dinoprostone vaginal gel. MATERIAL AND METHODS: This is aretrospective cohort study conducted of 560 pregnant women. The concomitant diseases mainly recorded were diabetes mellitus, hypertensive diseases, intrahepatic cholestasis of pregnancy, asthma, thrombocytopenia, and hypothyroidism. The primary study outcome was a successful vaginal delivery. The study above others evaluates the time from treatment implementation to the beginning of a labor and to a final delivery, the rate of Cesarean sections, and the presence of delivery complications. RESULTS: Among women with a concomitant disease, Caesarean section was observed more frequently in the misoprostol group. In the dinoprostone group, mothers with the concomitant disease as compared to healthy mothers required more time to the delivery and to achieve the beginning of labor. There were no differences in postpartum complications regardless of the prostaglandins, comorbidities or mothers' age. Neonates of mothers ≥ 35 years old with concomitant disease had lower average Apgar scores. CONCLUSIONS: Our study showed that comorbidities seem to increase the caesarean section risk in the misoprostol preinduction group but in the dinoprostone group they prolong the time needed to achieve an active labour phase and a delivery.

Comparison of Misoprostol versus Dinoprostone for delivery induction among pregnant women without concomitant disease.

OBJECTIVES: Induction of labour is a part of an active prenatal care nowadays and the ideal method of that procedure still remains to be identified. The purpose of this study was to evaluate effectiveness of misoprostol vaginal insert as compared to dinoprostone gel for delivery induction in pregnant women without any comorbidities. MATERIAL AND METHODS: It was a retrospective cohort study of 240 pregnant women. The primary study outcome was successful delivery. Other analysed parameters included time to delivery of a baby, time to the beginning of the first stage of labour, time to vaginal delivery, and duration of all delivery stages. We compared both methods regarding maternal complications during and after delivery. We also reviewed neonatal outcomes such as birth weight, birth length and 1-minute Apgar scores. RESULTS: The patients' basic characteristics were similar regarding their age, gravidity, parity, height, weight and Bishop score. Time to any delivery and to the onset of a labour in the misoprostol group versus in the dinoprostone group was 14.5 vs 35.6 h (p < 0.001) and 9.9 h vs 25.3 h (p < 0.001) respectively. The chance of the beginning of labour and the baby's delivery over time has been observed to be approximately two times higher for misoprostol as compared to dinoprostone. CONCLUSIONS: Our study showed that using misoprostol vaginal insert in comparison to dinoprostone seems to shorten the time to beginning of the first stage of labour as well as the time to the delivery itself. Some lower Apgar scores observed in the misoprostol group requires further investigation.

Evaluation of certain constituents of antioxidant defense in youth treated in the past for steroid-sensitive idiopathic nephrotic syndrome.

Disorders of lipid metabolism and antioxidant defense capacity reported during idiopathic nephrotic syndrome (INS) exacerbations are known. The aim of this study was to evaluate constituents of antioxidant defense [total antioxidant potential: ferric-reducing antioxidant power (FRAP), paraoxonase-1 (PON-1), tocopherols, ascorbic acid] in patients formerly treated for INS. The studied group consisted of 30 patients (20 males and 10 females) treated 4-15 years ago for INS. The control group consisted of 30 healthy teenagers. There were no statistically significant differences in PON-1 activity (156.4 +/- 97.1 vs 137.7 +/- 80.2 U/l), alpha-tocopherol levels (23.9 +/- 7.3 vs 22.4 +/- 3.2 micromol/l) and sum of beta- and gamma-tocopherols (2.1 +/- 1.0 vs 2.3 +/- 0.6 micromol/l), and in FRAP (484.9 +/- 87.2 vs 452.8 +/- 76.9 micromol/l) between groups. In the study group, a significantly lower concentration of ascorbic acid (53.0 +/- 20.8 vs 69.4 +/- 16 micromol/l; p < 0.002), decreased values of alpha-tocopherol/cholesterol (4.9 +/- 0.7 vs 5.5 +/- 1.2; p = 0.03), and total tocopherol/cholesterol (5.3 +/- 0.8 vs 6.1 +/- 1.4; p = 0.016) ratios were observed. A positive correlation between tocopherol/total cholesterol (TCh) (r = 0.41; p < 0.05) and alpha-tocopherol/TCh (r = 0.50; p < 0.001) ratios and INS relapse frequency was reported. The relationship between the study parameters and group of variables (relapse frequency, duration of the last remission, age, gender) was tested using the multiple linear regression analysis. The results of this study suggest that the nonenzymatic antioxidant defense in young persons formerly treated for INS is weaker than in their healthy counterparts.

[Structure and biogenesis of cytochrome b6f complex]. / Budowa i biogeneza kompleksu cytochromów b6f.

Both photosynthetic cytochrome b6f complex, and respiratory cytochrome bc1 belong to the family of cytochrome bc complexes. Both protein supercomplexes participate in the transport of electrons, proton translocation through the biological membrane, and they catalyze chinon oxidation as well. The function, composition, spatial organization and biosynthesis of cytochrome b6f complex has been being the subject of research for years. The obtained crystal structures revealed the presence of the third haem in the cytochrome b6, whereas mutagenic experiments indicated the participation of the additional protein factor (TCA) engaged in the regulation of b6f cytochrome complex synthesis through the interaction between TCA and 5'UTR of the PETA transcript. The following compendium is the collection of the current data and knowledge with reference to the structure and biogenesis of the above mentioned protein complex.

[Assessment of association of birth weight and existence of hypertension in children and adolescents normostenic, obese or with metabolic syndrome]. / Masa urodzeniowa ciala a wystepowanie nadcisnienia tetniczego w grupie dzieci i mlodziezy normostenicznej, z otyloscia lub z cechami zespolu metabolicznego.

UNLABELLED: It has been proved that Low Birth Weight (LBW) is a predisposing factor of elevated blood pressure in children. The aim of our study was to analyze birth weight of patients with diagnosed hypertension (HT). There has been 114 children, 6 to 17 years old, included into our study. We decided to divide them into 3 following groups: Group I--normal body mass and HT (51 children); Group II--metabolic syndrome (MS) with HT (32 children); Group III--overweight and obese children with HT (31 children). At 85% of all patients HT was diagnosed after performing ABPM. Statistically significant difference of birth weight was observed between patients with normal body mass (I) and those with overweight or obesity (III) (p<0,01). The most number of children with LBW (<2500 g) was observed in Group I (15.7%) and Group II (12.5%). It was observed that obese children with HT had had normal or high birth weigh (96.8%). CONCLUSION: 1. The frequency of low birth weight is similar in normostenic children with hipertension and children with metabolic syndrome. 2. The birth weight higher than 4000 g is more frequent in obesy hipertensive children and children with metabolic syndrome than in normo-stenic patients with hipertension.

[Characteristics of metabolic syndrome in children and adolescents with arterial hypertension]. / Cechy zespolu metabolicznego u dzieci i mlodziezy z nadcisnieniem tetniczym.

UNLABELLED: Among the components of metabolic syndrome (MS) obesity, arterial hypertension, insulin resistance, abnormal plasma lipoproteins balance: decreased HDL concentration and increased level of triglycerides are mentioned. In diagnosis of MS the coexistence of three of these criteria is obligatory. MS is frequently diagnosed in adult patients. The aim of the study was the evaluation of MS components in the group of 118 children with arterial hypertension (HT) who were hospitalized in Pediatric Department of Silesian Medical University in Bytom. The criterium of qualification to HT group was: blood pressure higher than 97 percentile in at least 20% of ABPM measurements. BMI, glucose blood concentration, HDL levels, triglycerides (TG) levels, uric acid concentration were also analyzed. Thirty children (25%) presented at least three of MS components: 16 (53%) - three of them, 12 (40%) - four of them and 2 (6,7%) all of them. Mean age of children with MS was 13,5 years, the youngest was 6 years old. BMI of 83% children with metabolic syndrome was considerably above 97 percentile. 53% had low HDL levels and 80% high TG levels. TG levels highly increased above normal values for sex and age. Mean TG concentration was 2,26 mmol/l. 83% of our patients with MS had primary (idiopathic) arterial hypertension, at 13,3% arterial hypertension of renal cause. CONCLUSIONS: The study revealed that all children with arterial hypertension especially those with primary HT should be evaluated for MS in order to start the early prevention of cardiovascular disease.

Concentrations of tumour necrosis factor-α and its soluble receptors in the serum of teenagers with atherosclerosis risk factors: obesity or obesity combined with hypertension.

INTRODUCTION: Obesity and hypertension are recognised risk factors for the development of atherosclerosis. It has not been proven whether their co-existence increases the synthesis of pro-inflammatory TNF-α and what the levels of soluble receptors of this cytokine (sTNF-R) are. This study is aimed to investigate whether there exists a relationship between TNF-α and sTNF-R concentrations in blood serum with the occurrence of obesity or obesity combined with primary hypertension in teenagers. MATERIAL AND METHOD: 68 persons, aged 9-17, including 32 persons with primary obesity (Group I) and 36 with primary obesity combined with primary hypertension (Group II). TNF-α (pg/mL) and sTNF-R (ng/mL) concentrations were determined in serum samples using the ELISA method with sets of reagents manufactured by Bender Med Systems GmbH. RESULTS: No significant differences in TNF-α, sTNF-R, glucose or insulin concentrations were found between Group I and Group II. These concentrations were not correlated with the age and the nutritional status of the patients or with each other in either of the groups. CONCLUSION: Both obese teenagers and teenagers exhibiting obesity combined with hypertension (as two atherosclerosis risk factors) are characterised by comparable concentrations of TNF-α and its soluble receptors.

Influence of selenium and/or magnesium on alleviation alcohol induced oxidative stress in rats, normalization function of liver and changes in serum lipid parameters.

The aim of this study was to evaluate the attenuating effect of given selenium and/or magnesium on ethanol-induced oxidative stress, disturbances of liver function and cholesterol metabolism. Forty male rats were divided into five groups: C - control, Et - intoxicated with alcohol (15% solution in drinking water), Et + Mg, Et + Se, Et + Mg + Se - intoxicated with alcohol and supplemented with selenium (0.4 mg Se/l water), magnesium (100 mg Mg/l water) and combination of Se and Mg, respectively. The experiment was carried out over the 3 months. The results show that the chronic ingestion of alcohol induces lipid peroxidation and histopathological changes in liver. Supplementation with magnesium only partially alleviates oxidative stress and damages in this tissue. The both selenium alone and combination of magnesium and selenium significantly elevated total antioxidant status (TAS) in serum, activity of glutathione peroxidase and ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) in liver and retarded oxidative stress and histopathological changes in this tissue. Chronic administration of ethanol (alone and with magnesium) resulted in significant decrease in the serum total cholesterol and retardation in the body weight gain in comparison with the control group. In the groups supplemented with selenium and selenium and magnesium simultaneously, concentration of total cholesterol in serum and body gains was similar to the control group. Supplementation of Se or selenium and magnesium simultaneously significantly enhances antioxidant defence and is more effective against alcohol-induced oxidative stress, disturbance of liver function and cholesterol metabolism than the separate use of magnesium.

Atherosclerosis risk factors in young patients formerly treated for idiopathic nephrotic syndrome.

UNLABELLED: A total of 30 patients (ten female/20 male), 9 years to 22 years old (mean age 17.3 years) and 30 healthy teenage controls (mean age 16.4 years) were included in our study. The patients had steroid-sensitive idiopathic nephrotic syndrome (INS) and had completed steroid therapy 4 years to 15 years ago. Height and weight, body mass index (BMI), body composition, and intima-media thickness (IMT) were determined, as were levels of total cholesterol (TCh), low-density lipoprotein cholesterol (LDL-Ch), high-density lipoprotein cholesterol (HDL-Ch), triacylglycerols (TAGs), homocysteine (HCY), and high-sensitivity C-reactive protein (hsCRP). We did not observe any differences between the study and control groups in IMT (0.47 +/- 0.1 vs 0.46 +/- 0.1 mm) and body composition (fat tissue and water content). Differences in HDL-Ch and hsCRP levels between groups were not significant. In the study group we found significantly higher TCh levels (187.6 +/- 57.2 mg/dl vs 158.8 +/- 25.7 mg/dl; P = 0.012), LDL-Ch (115.9 +/- 63.7 mg/dl vs 79.4 +/- 25.4 mg/dl; P = 0.005), HCY (12.3 +/- 7.7 micromol/l vs 7.6 +/- 1.6 micromol/dl; P < 0.001), apolipoprotein B (ApoB) (113.6 +/- 30.0 mg/dl vs 78.7 +/- 13.6 mg/dl; P < 0.001) and ApoA1 (203.5 +/- 50.8 mg/dl vs 156.5 +/- 12.4 mg/dl; P < 0.001) levels. Multi-factor analysis of the influence of independent factors (number of recurrences, duration of remission, age, gender, and BMI) on the parameters under investigation indicated a positive correlation between IMT and the number of recurrences. CONCLUSIONS: 1. Patients treated for idiopathic nephrotic syndrome in the past should undergo regular laboratory tests of atherosclerosis risk factors, including not only cholesterol and its fractions, but also ApoA1, ApoB and HCY. 2. It is necessary to continue systematic check-ups of the intima-media thickness of the carotid arteries among young patients with anamnesis of INS, especially among patients who suffered from numerous relapses of this disease.

Integration of the thylakoid membrane protein cytochrome b6 in the cytoplasmic membrane of Escherichia coli.

An overexpression system for spinach apocytochrome b(6) as a fusion protein to a maltose-binding protein in Escherichia coli was established using the expression vector pMalp2. The fusion of the cytochrome b(6) to the periplasmic maltose-binding protein directs the cytochrome on the Sec-dependent pathway. The cytochrome b(6) has a native structure in the bacterial cytoplasmic membrane with both NH(2) and COOH termini on the same, periplasmic side of the membrane but has the opposite orientation compared to that in thylakoid. Our data also show that in the E. coli cytoplasmic membrane, apocytochrome b(6) and exogenic hemes added into a culture media spontaneously form a complex with similar spectroscopic properties to native cytochrome b(6). Reconstituted membrane-bound cytochrome b(6) contain two b hemes (alpha band, 563 nm; average E(m,7) = -61 +/- 0.84 and -171 +/- 1.27 mV).