Birthweight trends and their explanatory factors in Hungary between 1999 and 2018: an analysis of the Hungarian Tauffer registry.

BACKGROUND: The increasing birthweight trend stopped and even reversed in several high income countries in the last 20 years, however the reason for these changes is not well characterized. We aimed to describe birthweight trends of term deliveries in Hungary between 1999 and 2018 and to investigate potential maternal and foetal variables that could drive these changes. METHODS: We analysed data from the Hungarian Tauffer registry, a compulsory anonymized data collection of each delivery. We included all singleton term deliveries in 1999-2018 (n = 1,591,932). We modelled birthweight trends separately in 1999-2008 and 2008-2018 in hierarchical multiple linear regression models adjusted for calendar year, newborn sex, maternal age, gestational age at delivery, and other important determinants. RESULTS: Median birthweights increased from 3250/3400 g (girl/boy) to 3300/3440 g from 1999 to 2008 and decreased to 3260/3400 g in 2018. When we adjusted for gestational age at delivery the increase in the first period became more pronounced (5.4 g/year). During the second period, similar adjustment substantially decreased the rate of decline from 2.5 to 1.4 g/year. Further adjustment for maternal age halved the rate of increase to 2.4 g/year in the first period. During the second period, adjustment for maternal age had little effect on the estimate. CONCLUSIONS: Our findings of an increasing birthweight trend (mostly related to the aging of the mothers) in 1999-2008 may forecast an increased risk of cardiometabolic diseases in offsprings born in this period. In contrast, the decreasing birthweight trends after 2008 may reflect some beneficial effects on perinatal morbidity. However, the long-term effect cannot be predicted, as the trend is mostly explained by the shorter pregnancies.

Birthweights showed an increase followed by a decrease in several high income countries in the last 20 years, however the reasons for these changes is not well described. Thus, we aimed to investigate birthweight trends and their potential explanatory factors in Hungary between 1999 and 2018. We used registry data of all deliveries from Hungary in 1999­2018 (n = 1 591 932). Birthweights increased from 3250/3400 g (girl/boy) to 3300/3440 g from 1999 to 2008 and decreased to 3260/3400 g until 2018. Maternal age explained approximately half of increase in the first period, while a substantial part of the decrease in the second period was explained by the presence of shorter pregnancies. The increasing birthweights in 1999­2008 may forecast an increased risk of cardiometabolic diseases in offsprings born in this period. In contrast, the decreasing birthweight trends after 2008 may reflect some beneficial effects on perinatal morbidity. However, its long-term consequences cannot be predicted, as the trend is mostly explained by the shorter pregnancies.

Pregnancy outcomes of women with untreated 'mild' gestational diabetes (gestational diabetes by the WHO 2013 but not by the WHO-1999 diagnostic criteria) - A population-based cohort study.

AIMS: We compared pregnancy outcomes of untreated 'mild' GDM (GDM by WHO 2013 but not by WHO-1999) to normal glucose tolerant women (NGT). METHODS: In a universal screening program 4333 pregnant women had a 3-point 75 g OGTT in Hungary in 2009-2013. By WHO-2013 untreated NGT was diagnosed in n = 3303, 'mild' GDM in n = 336 cases. RESULTS: 'Mild' GDM women were older (mean difference, SE: 1.4, 0.3 yrs), had higher fasting (1.0, 0.02), 60-minute (1.0, 0.09), and 120-minute (0.4, 0.06 mmol/l) blood glucose, and blood pressure (2.6, 0.5/2.0, 0.5 mmHg). Weight gain was similar in both groups (-0.3, 0.3 kg). GDM newborns were heavier (142, 50 g) and were more frequently macrosomic (>4000 g, OR 1.85, 95 %CI 1.35-2.54). Hypertension during pregnancy was more prevalent in the GDM group (OR 1.55, 95 %CI 1.05-2.28), as well as induced (OR 1.38, 95 %CI 1.10-1.74) and instrumental delivery (OR 1.34, 95 %CI 1.07-1.68), and acute caesarean section (OR 1.32, 95 %CI 1.04-1.64). Most of these differences substantially attenuated or became non-significant after adjustment for pre-pregnancy BMI. CONCLUSIONS: Pregnancy outcomes of 'mild' GDM were worse compared to normal glucose tolerant women however these differences were explained by the pre-pregnancy BMI difference between groups.

Comparison of Efficacy and Safety of Commercially Available Fixed-Ratio Combinations of Insulin Degludec/Liraglutide and Insulin Glargine/Lixisenatide: A Network Meta-analysis.

OBJECTIVES: Our aim in this study was to compare the efficacy and safety of commercially available fixed-ratio combinations (FRCs) of glucagon-like peptide-1 receptor agonists (GLP-1RAs) and basal insulins by a network meta-analysis of randomized controlled trials (RCTs) of people with type 2 diabetes. METHODS: We present a systematic review and network meta-analyses of RCTs of individuals with type 2 diabetes randomized to FRCs or to their components for ≥24 weeks. All reports were obtained from PubMed or ClinicalTrials.gov up to February 28, 2022. The primary outcome was glycated hemoglobin (A1C) level attained. Secondary outcomes included fasting plasma glucose, change in body weight, and incident hypoglycemia. Treatment effects were estimated as mean difference (MD) and standard error (SE), or as odds ratio (OR) with 95% confidence interval (CI) using the fixed combination of insulin glargine 100 IU/mL and lixisenatide (iGlarLixi) as reference. RESULTS: We included 29 RCTs from among the 1,404 articles identified. No direct comparisons between FRCs were found. After excluding some insulin-capped trials to reach model consistency, both FRCs were more efficacious regarding A1C than their components, but no difference between FRCs was found (MD, -0.10%; SE, 0.10%). The effect of the fixed combination of insulin degludec and liraglutide (IDegLira) (MD, -0.47 mmol/L; SE, 0.24 mmol/L) and basal insulins was similar to that of iGlarLixi (reference) on fasting glucose, whereas GLP-1RAs had lower efficacy than iGlarLixi. Weight gain was lower with GLP-1RAs and IDegLira (MD, -0.72 kg; SE, 0.32 kg) than with iGlarLixi (reference) and higher with basal insulins. Incident hypoglycemia (based on different definitions) was least frequent with GLP-1RAs, followed by IDegLira (OR, 0.78; 95% CI, 0.39 to 1.57), iGlarLixi (reference), and basal insulins. CONCLUSIONS: For A1C, both FRCs were more efficacious over their individual components, with similar efficacies of the 2 FRCs.

Evaluation of critical design parameters for RT-qPCR-based analysis of multiple dUTPase isoform genes in mice.

The coupling of nucleotide biosynthesis and genome integrity plays an important role in ensuring faithful maintenance and transmission of genetic information. The enzyme dUTPase is a prime example of such coupling, as it generates dUMP for thymidylate biosynthesis and removes dUTP for synthesis of uracil-free DNA. Despite its significant role, the expression patterns of dUTPase isoforms in animals have not yet been described. Here, we developed a detailed optimization procedure for RT-qPCR-based isoform-specific analysis of dUTPase expression levels in various organs of adult mice. Primer design, optimal annealing temperature, and primer concentrations were specified for both nuclear and mitochondrial dUTPase isoforms, as well as two commonly used reference genes, GAPDH and PPIA. The linear range of the RNA concentration for the reverse transcription reaction was determined. The PCR efficiencies were calculated using serial dilutions of cDNA. Our data indicate that organs involved in lymphocyte production, as well as reproductive organs, are characterized by high levels of expression of the nuclear dUTPase isoform. On the other hand, we observed that expression of the mitochondrial dUTPase isoform is considerably increased in heart, kidney, and ovary. Despite the differences in expression levels among the various organs, we also found that the mitochondrial dUTPase isoform shows a much more uniform expression pattern as compared to the reference genes GAPDH and PPIA.

Carbon nanotubes exert basic excitatory enhancement in rat brain slices.

Carbon nanotubes are promising new tools in biomedicine but they may have yet some unknown influences on the organism. In the present study, the acute effect of solubilized, multi-walled carbon nanotubes (MWCNTs) on basic neuronal functions was examined. Rat brain slices were treated in vitro with nanotube-containing colloid solutions at concentrations of 100-800 µg/ml and evoked field potentials were recorded from the somatosensory cortex and hippocampus. Basic excitability of the treated slices was characterized by the amplitude of field excitatory postsynaptic potentials (fEPSPs) and population spikes. Experimental results indicated significantly higher excitability of treated samples than that of controls. Multiple components in evoked potentials were observed, which is in accordance with the increased excitability of investigated brain areas. Tests of short- and long-term plasticity were also performed, which revealed no difference between control and treated slices. Experimental results suggest an interaction between nanotubes and brain tissue. MWCNTs seem to act on the basic membrane potential of neurons by changing membrane properties or via a mechanism linked to voltage-gated ion channels, rather than influencing specific synaptic transmission. Further investigation is needed to clarify the nature of interactions between nanotubes and brain tissue.

[Long term persistence of yellow fever neutralising antibodies in elderly persons]. / Persistance à long terme des anticorps neutralisants de la fièvre jaune chez les personnes âgées de 60 ans et plus.

The activity of the yellow fever virus is reemerging in areas without recent transmission history, such as northern Argentina and Paraguay, and persists in an epidemic mode in other countries in Africa and Latin America. Thus more and more travelers are at risk of being exposed to this disease. The population is becoming older, sometimes suffering from multiple pathologies. Moreover, the risk of serious adverse events associated with live-attenuated YF17D vaccine, such as multiple organ failure (YEL-AVD), reaches 1/50,000 vaccines in people over 65 versus 1/200,000 in the general population. We analyzed, in a retrospective study, the results of neutralizing antibody titers against yellow fever in people aged 60 and older, who had been previously vaccinated against yellow fever and had visited the International Vaccination Centre of the Institut Pasteur between January 2005 and February 2009. In this population of 84 persons (median age 69 years), the date of the last vaccination was always more than 10 years: it was precisely known in 68 subjects and alleged in 16 subjects. The median time since the previous vaccination was 14 years, with a maximum of 60 years. The indications of serology were: immunosuppressive therapy (19% of cases), cancer (32%), hemopathy (10.7%), HIV infection (3.6%), chronic hepatitis/chronic renal failure/dialysis (2.4%), autoimmune diseases (2.4%), and in 29.8% of cases, age alone was the indication of serology. The antibody titer was at a protective level in 95.2% of cases. The four individuals with negative serology had no formal documented proof of a previous vaccination against yellow fever. This serological study was able to show a persistent protective antibody titer, after a previous vaccination, even going back 60 years, allowing patients to travel in a yellow-fever endemic area despite a contraindication, and without requiring any vaccine booster.

Regulation of cerebral endothelial cell morphology by extracellular calcium.

Cerebral endothelial cells interconnected by tight and adherens junctions constitute the structural basis of the blood-brain barrier. Extracellular calcium ions have been reported to play an important role in the formation and maintenance of the junctional complex. However, little is known about the action of calcium depletion on the structural characteristics of cerebral endothelial cells. Using atomic force microscopy we analyzed the effect of calcium depletion and readdition on the shape and size of living brain endothelial cells. It was found that the removal of extracellular calcium from confluent cell cultures induced the dissociation of the cells from each other accompanied by an increase in their height. After readdition of calcium a gradual recovery was observed until total confluency was regained. We have also demonstrated that Rho-kinase plays an important role in the calcium-depletion-induced disassembly of endothelial tight and adherens junctions. The Rho-kinase inhibitor Y27632 could prevent the morphological changes induced by a lack of calcium as well. Our results suggest that calcium depletion induces Rho-kinase-dependent cytoskeletal changes that may be partly responsible for the disassembly of the junctional complex.

Modification of multi-walled carbon nanotubes by Diels-Alder and Sandmeyer reactions.

Random (L) and aligned (A) multi-walled carbon nanotubes (MWNTs) were modified by Diels-Alder (DA) [4+2] cycloaddition, Sandmeyer (SM) reaction and by catalytic oxidation (OX). The properties of modified carbon nanotubes were studied by dispersability tests, elemental analysis, thermogravimetry/mass spectrometry, X-ray photoelectron spectroscopy, and NMR spectroscopy. The cycloaddition reaction could only be successfully performed with the L-MWNTs in molten and in solution state by using an aluminum chloride homogeneous catalyst. The efficiency and thermal stability of the solution phase cycloaddition were much higher than in the case of modification in the molten phase. The functionalization of both types of MWNTs by Sandmeyer reaction was carried out by copper(I) and iron(ll) ions that helped in the radical decomposition of diazonium salts. Successful functionalization of nanotubes is achieved by a long decomposition time of the thermally activated diazonium salts. To the contrary, in the case of radical decomposition of diazonium salts, the time is not a decisive parameter. The dispersability tests have proved the changes in the physical features of modified carbon nanotubes depending on the hydrophobic and hydrophilic character of the solvents. The presence of the modifying groups and their fragments from the functionalized MWNTs has been demonstrated by thermogravimetry/mass spectrometry (TG/MS). Relatively high concentration of sulfur atoms was detected by X-ray photoelectron spectroscopy in nanotubes modified by sulfur substituent groups. In the case of catalytic oxidation, the X-ray photoelectron spectroscopic signal of oxygen bound to nanotubes showed considerable change as compared to pristine nanotubes. Due to the high thermal stability of modified multi-walled carbon nanotubes, the functionalized derivatives are applicable in several industrial fields.

Direct observation of protein motion during the photochemical reaction cycle of bacteriorhodopsin.

Platinum-coated, conductive atomic force microscope cantilevers were used to deposit electrophoretically purple membranes from Halobacterium salinarum on the bottom part of the cantilevers. By illuminating the bacteriorhodopsin-containing purple membranes, the protein goes through its photochemical reaction cycle, during which a conformational change happens in the protein, changing its shape and size. The size change of the protein acts upon the cantilever by causing its deflection, which can be monitored by the detection system of the atomic force microscope. The shape of the signal, the action spectrum of the deflection amplitude, and the blue light inhibition of the deflection all prove that the origin of the signal is the conformational change arising in the bacteriorhodopsin during the photocycle. From the size of the signal, the magnitude of the protein motion could be estimated. Using polarized light, the orientation of the motion was determined, relative to the transition moment of the retinal.

HPLC analysis of K-48 concentration in plasma.

K-48 is a new oxime-type compound to be used as an enzyme reactivator in the treatment of exposure to organophosphorous compounds. Plasma concentration of K-48 can be determined using reversed-phase HPLC. Analysis using octyl silica stationary phase and ultraviolet-absorbance detection is fast and simple. K-48 displays a relatively high dose-normalized area under the curve as compared to pralidoxime, which might be beneficial for an antidote. After i.m. administration of 50 mumol K-48, the time course of the concentration can be approximated by a straight line between 15 and 120 min meaning the elimination follows zero-order kinetics.

Evaluation of CD detection in an HPLC system for analysis of DHEA and related steroids.

The biological importance of dehydroepiandrosterone (DHEA) is reflected by the fact that DHEA is a crucial precursor of the biosynthesis of the steroidal sex hormones. Simultaneous separation of DHEA, dehydroepiandrosterone sulfate (DHEA-S), pregnenolone, androstenedione and testosterone has been accomplished by reversed-phase ion-pair high-performance liquid chromatography (RP-IP-HPLC) based on isocratic elution applying circular dichroism (CD) detection at 295 nm. Addition of tetrabutylammonium hydrogensulfate to the mobile phase increases the retention of DHEA-S on the C8-silica column by an apparent ion-pairing mechanism without affecting the retention of the other (non-ionic) steroids. CD spectroscopy provides highly selective detection of compounds possessing optically active absorption bands and the separation is even more selective in the higher wavelength range applied. The linearity of the steroid concentration (c, mg mL(-1)) versus peak area was tested in the concentration range of 0.5-2 mg mL(-1) (injected quantities were 10-40 microg). The relative standard deviation (RSD) values for DHEA and DHEA-S indicated a good intra-assay and inter-assay precision of the method.

6-oxo-morphinane oximes: pharmacology, chemistry and analytical application.

The permanent therapeutic importance of morphine derivatives in pain treatment has inspired continual synthetic efforts to modify the rigid pentacyclic systems in search for new selective analgesic agents. As a result, several morphinane oximes have been synthesized recently, which have the additional advantage of possessing an oxime group that can provide a method for selective determination of opiate alkaloids in biological matrices. The oximes of hydrocodone and oxycodone have stronger analgesic effect than the parent ketones and they also proved to be effective in preventing the respiratory depressant and hypotensive actions of fentanyl. In this work a review is given on the present status of oxime pharmacology, chemistry and analysis and also the oxime and O-methyl oxime formation of 6-oxo-morphinanes with therapeutic interest (codeinone, oxycodone, hydrocodone and 14-OH-codeinone). The oxime formation was monitored by reversed-phase HPLC and the chromatographic properties of oxime isomers have been characterized. The assignation of the individual isomers isolated by preparative HPLC was performed by (1)H NMR spectroscopy based on the chemical shift differences of the 5-H signals. In this way the isomeric ratio in the oxime products could also be determined. It was found that in the case of Delta(7)-6-oxo-morphinanes, depending on the substituents, the formation of the Z-isomer highly dominates (73-96%) over that of the E-isomer. However, for the saturated 7,8-(dihydro) derivatives the E-isomer is definitely preferred (>98%). In conclusion of a survey on the theoretical background of oxime isomerism, the conformational differences between the saturated and unsaturated morphinane systems were found responsible for the different E/Z ratios. On the basis of the isomeric ratio and the on-line CD and UV spectra of the pure isomers, the molar ellipticities and absorbancies of the isomers were calculated by a parameter estimation method.

[Use of erythropoietin in the treatment of anemia induced by ribavirin/interferon in patients with hepatitis C]. / Traitement de l'anémie des patients atteints d'une hépatite C chronique sous interféron/ribavirine par l'érythropoïétine.

We are presenting 20 patients with hepatitis C, who developed anemia on interferon alpha-2b/ribavirin treatment and were treated with recombinant human c alpha. Median age was 43 years (range 25-72). Four patients received previous treatment. Interferon-alpha-2b was given at six million units three times a week to 10 patients and at three million units three times a week to five patients. PEG-interferon-alpha-2b (80-120 mug/week) was given to five patients. The dose of ribavirin was 800-1200 mg/day (19 patients) and 200 mg/day (one patient with renal failure). Duration of an interferon/ribavirin treatment was 6-12 months. Baseline median hemoglobin was 13.3 g/dl (range 12.2-15.8); median hemoglobin nadir: 9.8 g/dl (range 8.4-11.2). On erythropoietin, the hemoglobin increased to median 11.7 g/dl (range 9.6-12.8). The ribavirin dose had been decreased to 800 mg in four patients, to 600 mg in four patients, to 400 mg in one patient. Thirteen patients responded to interferon/ribavirin treatment, six patients (all genotype 1) did not. Of the 13 initial responders 11 had sustained response, one still under treatment and two patients relapsed. In conclusion, in our patients with chronic hepatitis C treated with interferon/ribavirin combination therapy, erythropoietin was beneficial in the treatment of ribavirin-induced anemia.

CD spectrometric methods for the simultaneous determination of ethisterone and its delta5-isomer.

Quick and accurate direct and indirect circular dichroism (CD) spectrometric methods were developed for the simultaneous determination of ethisterone (17alpha-ethinyl-17-hydroxy-4-androstene-3-one) and its delta(5)-isomer (delta(5)-ethisterone). The direct method is based on the selective negative Cotton effect of the delta(4)-3-oxo group in ethisterone (negative maximum at 348 nm in dioxan) and measurement of the ellipticity at 296 nm (positive maximum of delta(5)-ethisterone), where the measured ellipticity is the sum of those of the two isomers. In the indirect procedure delta(5)-ethisterone is transformed to ethisterone by base-catalysed isomerization and the ellipticities are measured at 339 nm in ethanol before and after isomerization. Preliminary experiments show the usefulness of CD detector in the HPLC determination of the mixture of the isomers. A major advantage of the direct CD spectrometric and the HPLC/CD methods is that the delta(5)-isomer with extremely low UV activity can also be directly measured with high sensitivity.

Determination of 6-oxo-morphinans, as the oximes, by difference circular dichroism spectroscopy.

A negative Cotton effect is observed in the circular dichroism (CD) spectra of 6-oxo-morphinans in the wavelength range of n-pi* electron transitions. 6-oxo-Morphinans can be transformed into oxime derivatives with hydroxylamine and after oxime formation the CD spectra are significantly different. Oxime formation was monitored by CD and by HPLC. It was established that under the experimental conditions used oxime formation was complete within 90 min. The method suggested for the determination of 6-oxo-morphinans is based on the considerable differences between the ellipticities before and after the oxime formation. The ellipticity difference varies linearly with concentration in the range 2 x 10(-5)-5 x 10(-4) mol L(-1) for the three 6-oxo-morphinans examined (oxycodone, hydrocodone, and 14-hydroxycodeinone). For hydrocodone the dependence is also linear in a lower concentration range (5 x 10(-6)-10(-4) mol L(-1)). The new difference CD spectroscopic method can be applied to the selective determination of 6-oxo-morphinans in bulk and dosage forms.

Determination of circular dichroism and ultraviolet spectral parameters of norgestimate- and other Delta(4)-3-ketosteroid oxime isomers via normal phase HPLC method.

The oxime formation reaction of therapeutical progestogen (levonorgestrel, levonorgestrel acetate, norethisterone), androgen (methyltestosterone, testosterone phenylpropionate) and anabolic (nortestosterone phenylpropionate) Delta(4)-3-ketosteroids has been investigated. The ketosteroid-hydroxylamine reaction was monitored by reversed phase HPLC system. It was established, that under the experimental conditions applied the oxime formation was complete within 2 h. The reaction leads to the formation of Z and E oxime isomers. The isomers of norgestimate (levonorgestrel 17-acetate oxime) and other Delta(4)-3-ketosteroid oximes have been separated by a new normal phase HPLC method. The identification (elution order assignation) and determination of the formation ratio of the isomers have been performed by 1H NMR spectroscopy on the basis of the chemical shift differences of 4-H signals. The on-line CD and UV spectra of the pure oxime isomers were recorded and then molar ellipticities and absorbances of the isomers were calculated in the wavelength range of 200-300 nm via parameter estimation method.

Stereochemical study of tolperisone, a muscle relaxant agent, by circular dichroism and ultraviolet spectroscopy.

The stereochemistry of tolperisone, a chiral aryl-alkyl basic ketone was investigated by means of circular dichroism (CD) and ultraviolet (UV) spectroscopy. The unusually high optical activity of tolperisone hydrochloride in the n-->pi* region is interpreted by the presence of a chiral conformer in solution. For stereochemical reasons, the C = O group and the aromatic moiety lack coplanarity by forming an inherently dissymetric chromophore, of M helicity. Similar helicity prevails in the crystal phase, according to the solid-state CD spectrum of (-)-tolperisone HCl salt. The chirality rule proposed by Snatzke for nonplanar benzoyl chromophores predicts the absolute configuration of (-)-tolperisone hydrochloride to be R, in agreement with other alpha-methyl-beta-amino-ketones.

Deconvolution of composite chromatographic peaks by simultaneous dual detections.

Composite chromatographic peaks are deconvoluted by a method that uses ratio formation from signals of simultaneous double detection. The method is generally suitable if two detector signals can simultaneously be acquired and their uses do not need any a priori assumption or mathematical shape analysis. A simple deduction makes the compound- and detector-specific intensive parameters explicit, which allows for the digital construction of directly invisible component peaks. The simultaneous double detection is shown to be superior to coupled detectors, sequentially fixed chromatograms, and subsequently synchronized peaks. The combination of circular dichroism and ultraviolet (UV) detection is shown to be especially advantageous in the analysis of enantiomers for which the other ratio-forming peak-deconvolution techniques have inherently been insensitive. The double chiroptical UV detection can be of further use to decompose overlapping peaks of nonenantiomeric compounds that are highly similar. The capacity of the method is exemplified by the analysis of morphine alkaloids, steroid oximes, and synthetic heterocycles.

Optical resolution of a series of potential cholecystokinin antagonist 4(3H)-quinazolone derivatives by chiral liquid chromatography on alpha1-acid glycoprotein stationary phase.

Optical resolution of the enantiomers of new 4(3H)-quinazolone derivatives is investigated using the alpha1-acid glycoprotein chiral stationary phase (Chiral-AGP). Stereoselective separation of the model compounds can be controlled by varying the pH and adding uncharged organic modifiers (acetonitrile and 2-propanol) to the mobile phase. For the majority of quinazolone derivatives, Chiral-AGP is proved to be an excellent enantioselector, because optimized chromatographic conditions allow for the baseline separation of the enantiomers. Separation factors between 1.19 and 1.85 are obtained. The effects of acetonitrile and 2-propanol on the chromatographic behavior of the model compounds are quite different because of their different hydrophobic- and hydrogen-bonding properties. The eluent pH and organic modifier concentration also contributes to the chiral recognition by altering the protein environment. The analysis of the experimental results leads to new information about the chromatographic mechanism on a Chiral-AGP surface.

Determination of delta4-3-ketosteroids based on oxime formation by difference circular dichroism spectroscopy.

delta4-3-Ketosteroids exhibit an intensive negative Cotton effect on the circular dichroism (CD) spectra in the wavelength range for the n-pi* electronic transition (270-350 nm). With hydroxylamine hydrochloride, delta4-3-ketosteroid compounds can be transformed into oxime derivatives. Following oxime formation, positive ellipticity with low intensity can be registered in this wavelength range. The quantitative determination of delta4-3-ketosteroids is based on the considerable difference between the ellipticities before and after oxime formation. The difference ellipticity for the six ketosteroids examined (norethisterone, levonorgestrel, levonorgestrel acetate, methyltestosterone, testosterone phenylpropionate, nortestosterone phenylpropionate) varies linearly with the concentration in the interval 6 x 10(-6)-3 x 10(-3) mol/L. The method can be well applied to determination of delta4-3-ketosteroid contamination of norgestimate [(+)-13-ethyl-17-hydroxy-18,19-dinor-17alpha-pregn4-en-20-yn-3-one oxime acetate]; 0.02-10% impurity can be measured.