Morphological and secretory dysfunction of left atrium in Marfan syndrome

Introduction

Marfan syndrome (MFS) is characterized by a mutation in the FBN1-gene which leads to a structural deficiency of the extracellular matrix component fibrillin-1 and a dysregulation of TGFβ. In recent years, cardiac remodeling with systolic and/or diastolic left ventricular dysfunction was shown in some MFS patients (Marfan Cardiomyopathy). Interestingly, in animal studies it has been shown that fibrillin-1 is abundantly present in atria and that TGFβ overexpression leads to atrial but not ventricular fibrosis (1, 2). However, the role of MFS for atrial remodeling and secretion (NT-proBNP) is unclear.

Purpose

To assess morphological and secretory function of the left atrium (LA) in patients with MFS and its relationship to left ventricular function.

Methods

We retrospectively analyzed echocardiographic and laboratory data in 307 Patients with MFS and in 147 healthy controls who had presented at our Marfan clinic between 23 February 2016 and 15 June 2020. At every visit, echocardiography had been carried out and NT-proBNP levels had been taken. A two-level mixed effects model was now performed to compare left atrial size between patients with MFS and controls.

Results

Left atrial size was significantly increased in patients with Marfan syndrome with and without aortic operation in medical history compared with controls (adjusted means: 18.4cm2 and 17.6cm2 vs. 15.5cm2 p<0.05). Body surface area (6.12, 95% CI: 4.26, 7.98 p<0.001), age (0.06, 95% CI: 0.02, 0.1 p<0.01), E/e' (0.3, 95% CI: 0.14, 0.46 p<0.001) and EF (−0.05, 95% CI: −0.10, −0.01 p=0.011) were significantly correlated with LA size.

NT-proBNP was also increased, after logarithmic transformation, mean difference between unoperated patients with MFS and controls was 0.34 (95% CI: 0.11,0.57 p=0.004).

Interestingly, NT-proBNP and LA size both were increased also in patients with normal left ventricular filling pressures, assessed by E/e' (see Figure 1). For increased LV filling pressures (E/e'>8), regression analyses revealed a more extensive dilatation of LA size in patients with MFS for further increase of E/e' compared to controls, although not significant for the latter.

Haploinsufficiency mutations were associated with significant higher levels of NT-proBNP than dominant-negative (p=0.043) (see Figure 2), although this could not be shown for LA size. Atrial fibrillation (AF) tended to be more common in Marfan group (17/307 to 4/147, χ2 (1) = 1.79, p=0.181) but most patients with AF also had prior aortic operation.

Conclusions

Our data show that Marfan syndrome is associated with left atrial dilatation, accompanied by increased levels of NT-proBNP which seem to be independent of elevated left ventricular filling pressure. This supports the idea of a primary impairment of cardiac function. If this leads to an impaired clinical outcome, e.g. characterized by increased prevalence of AF and stroke, needs be investigated by further research.

Funding Acknowledgement

Type of funding sources: None.

Volumetry of Mesiotemporal Structures Reflects Serostatus in Patients with Limbic Encephalitis

BACKGROUND AND PURPOSE

Limbic encephalitis is an autoimmune disease. A variety of autoantibodies have been associated with different subtypes of limbic encephalitis, whereas its MR imaging signature is uniformly characterized by mesiotemporal abnormalities across subtypes. Here, we hypothesized that patients with limbic encephalitis would show subtype-specific mesiotemporal structural correlates, which could be classified by supervised machine learning on an individual level.

MATERIALS AND METHODS

T1WI MPRAGE scans from 46 patients with antibodies against glutamic acid decarboxylase and 34 patients with antibodies against the voltage-gated potassium channel complex (including 10 patients with leucine-rich glioma-inactivated 1 autoantibodies) and 48 healthy controls were retrospectively ascertained. Parcellation of the amygdala, hippocampus, and hippocampal subfields was performed using FreeSurfer. Volumes were extracted and compared between groups using unpaired, 2-tailed t tests. The volumes of hippocampal subfields were analyzed using a multivariate linear model and a binary decision tree classifier.

RESULTS

Temporomesial volume alterations were most pronounced in an early stage and in the affected hemispheric side of patients. Statistical analysis revealed antibody-specific hippocampal fingerprints with a higher volume of CA1 in patients with glutamic acid decarboxylase-associated limbic encephalitis (P = .02), compared with controls, whereas CA1 did not differ from that in controls in patients with voltage-gated potassium channel complex autoantibodies. The classifier could successfully distinguish between patients with autoantibodies against leucine-rich glioma-inactivated 1 and glutamic acid decarboxylase with a specificity of 87% and a sensitivity of 80%.

CONCLUSIONS

Our results suggest stage-, side- and antibody-specific structural correlates of limbic encephalitis; thus, they create a perspective toward an MR imaging-based diagnosis.

The pathogenic LRRK2 R1441C mutation induces specific deficits modeling the prodromal phase of Parkinson's disease in the mouse

The aim of the present study was to further explore the in vivo function of the Leucine-rich repeat kinase 2 (LRRK2)-gene, which is mutated in certain familial forms of Parkinson's disease (PD). We generated a mouse model harboring the disease-associated point mutation R1441C in the GTPase domain of the endogenous murine LRRK2 gene (LRRK2 R1441C line) and performed a comprehensive analysis of these animals throughout lifespan in comparison with an existing knockdown line of LRRK2 (LRRK2 knockdown line). Animals of both lines do not exhibit severe motor dysfunction or pathological signs of neurodegeneration neither at young nor old age. However, at old age the homozygous LRRK2 R1441C animals exhibit clear phenotypes related to the prodromal phase of PD such as impairments in fine motor tasks, gait, and olfaction. These phenotypes are only marginally observable in the LRRK2 knockdown animals, possibly due to activation of compensatory mechanisms as suggested by in vitro studies of synaptic transmission. Thus, at the organismal level the LRRK2 R1441C mutation does not emerge as a loss of function of the protein, but induces mutation specific deficits. Furthermore, judged by the phenotypes presented, the LRRK2-R1441C knock-in line is a valid preclinical model for the prodromal phase of PD.

Sila-Pharmaka, 24. Mitt. [1]. Sila-Analoga von Nifedipin-ähnlichen 4-Aryl-2.6-dimethyl-1.4-dihydropyridin- 3.5-dicarbonsäure-dialkylestern, II. / Sila-Drugs, 24th Communication [1]. Sila-Analogues of Nifedipine-Like Dialkyl 4-Aryl-2,6-dimethyl-1,4-dihydropyridine- 3,5-dicarboxylates, II

In the course of systematic studies on sila-substituted drugs the nifedipine-like 1.4-dihydropyridine derivatives 4a, 4b and 4c were prepared and investigated with respect to sila-substitution effects. By X-ray diffraction analyses 4a, 4b and 4c were found to be isostructural. The C/Si-analogues exhibit similar spasmolytic activities (in vitro, guinea pig ileum), comparable with that of nifedipine. However, the compounds differ substantially in their in vivo activity, as measured by the antihypertensive effect on the renal-hypertensive rat. The experimental results are discussed with respect to the carbon/silicon exchange.

Ferric Chloride Induced Dehydrodimerization of Tetrahydrocarbazole

Ferric chloride induced dehydrodimerization of 1,2,3,4 -tetrahydro -9 H-carbazole (1) gives product 6 , the structure of which was established on the basis of its spectroscopic properties. The 1H and 13C chemical shifts of the aromatic part of 1, as well as of 4a-methyl-2,3,4,4a-tetrahydro-1 H-carbazole (7a) and 4a-phenyl-2,3,4,4a-tetrahydro-1H-carbazole (7b) have also been securely assigned.

Association between placental mineral deposition, villous architecture and fetal aneuploidy

We retrospectively evaluated the relationship between fetal aneuploidy and placental mineral deposits and villous architecture in 2nd trimester placentas of mid-trimester pregnancy terminations for fetal anomaly. Study cases were aneuploid and matched with euploid controls. Six slides per case were histologically evaluated. Our findings showed significantly increased subtrophoblastic mineral depositions in aneuploidy placentas; also, villous architecture changes between study and control cases were significant for multifocal/extensive villous scalloping and syncytial budding. Our conclusion was that placental histological findings of extensive subtrophoblastic mineral deposition, multifocal/extensive villous scalloping and syncytial budding may suggest aneuploidy.

Acquired and Partially De Novo Synthesized Pyrrolizidine Alkaloids in Two Polyphagous Arctiids and the Alkaloid Profiles of Their Larval Food-Plants

The profiles of pyrrolizidine alkaloids (PAs) in the two highly polyphagous arctiids Estigmene acrea and Grammia geneura and their potential PA sources in southeastern Arizona were compiled. One of four species of Boraginaceae, Plagiobothrys arizonicus, contained PAs; this is the first PA record for this plant species. The principle PA sources are Senecio longilobus (Asteraceae) and Crotalaria pumila (Fabaceae). The known PA pattern of S. longilobus was extended; the species was found to contain six closely related PAs of the senecionine type. Three novel PAs of the monocrotaline type, named pumilines A-C, were isolated and characterized from C. pumila, a species not studied before. The pumilines are the major PAs in the seeds, while in the vegetative organs they are accompanied by the simple necine derivatives supinidine and as the dominant compound subulacine (1beta,2beta-epoxytrachelanthamidine). In both plant species, the PAs are stored as N-oxides, except C. pumila seeds, which accumulate the free bases. Great variation in PA composition was observed between local populations of C. pumila. The PA profiles were established for larvae and adults of E. acrea that as larvae had fed on an artificial diet supplemented with crotalaria-powder and of G. geneura fed with S. longilobus. In both experiments, the larvae had a free choice between the respective PA source and diet or food plants free of PAs. The profiles compiled for the two species reflect the alkaloid profiles of their PA sources with one exception, subulacine could never be detected in E. acrea. Besides acquired PAs, insect PAs synthesized from acquired necine bases and necic acids of insect origin were detected in the two arctiid species. These insect PAs that do not occur in the larval food sources accounted for some 40-70% (E. acrea) and 17-37% (G. geneura) of total PAs extracted from the insects. A number of novel insect PAs were identified. Plant-acquired and insect PAs were found to accumulate as N-oxides. The results are discussed in relation to specific biochemical, electrophysiological, and behavioral mechanisms involved in PA sequestration by arctiids.

Sensitive and specific quantification of sirolimus (rapamycin) and its metabolites in blood of kidney graft recipients by HPLC/electrospray-mass spectrometry

Sirolimus (rapamycin) has a macrolide structure and is under clinical investigation as an immunosuppressant after organ transplantation. An HPLC/mass spectrometry assay to quantify sirolimus in blood was developed. 28-O-Acetyl sirolimus was used as internal standard. Blood samples were extracted with C18 columns. The extracts were injected into an HPLC system and isocratically eluted with methanol/1% formic acid (90/10 by vol) from a 150 X 4 mm C18 analytical column. The HPLC system was connected to a triple-stage quadrupole mass spectrometer with an electrospray interface and positive ions were detected. The limit of quantification in 1 mL of blood was 0.25 microgram/L and the calibration curve in blood was linear up to 250 microgram/L. The recovery from blood was 88 +/- 26% and interassay variation at 1 microgram/L was 19% and at 15 microgram/L 9.3%. Hydroxy, dihydroxy, demethyl, and didemethyl sirolimus as well as sirolimus were detected in blood of kidney graft patients.

Sensitive and specific quantification of sirolimus (rapamycin) and its metabolites in blood of kidney graft recipients by HPLC/electrospray-mass spectrometry

Sirolimus (rapamycin) has a macrolide structure and is under clinical investigation as an immunosuppressant after organ transplantation. An HPLC/mass spectrometry assay to quantify sirolimus in blood was developed. 28-O-Acetyl sirolimus was used as internal standard. Blood samples were extracted with C18 columns. The extracts were injected into an HPLC system and isocratically eluted with methanol/1% formic acid (90/10 by vol) from a 150 X 4 mm C18 analytical column. The HPLC system was connected to a triple-stage quadrupole mass spectrometer with an electrospray interface and positive ions were detected. The limit of quantification in 1 mL of blood was 0.25 microgram/L and the calibration curve in blood was linear up to 250 microgram/L. The recovery from blood was 88 +/- 26% and interassay variation at 1 microgram/L was 19% and at 15 microgram/L 9.3%. Hydroxy, dihydroxy, demethyl, and didemethyl sirolimus as well as sirolimus were detected in blood of kidney graft patients.

Retinopathy screening in type 2 diabetes: reliability of wide angle fundus photography

The purpose of the study was to assess the reliability of mydriatic 60 degrees fundus photography in a retinopathy screening programme for Type 2 diabetic patients in a primary health care setting. In 323 eligible consecutive Type 2 diabetic patients above 40 years of age, attending a regional shared care diabetes project, mydriatic wide angle fundus photography was compared with standardized fundoscopy in dilated pupils as the recommended test for the detection of diabetic retinopathy. Fundus photography included two black and white transparencies per eye visualizing the central and nasal retinal field. Fundoscopy findings and pictures were scored according to modified Wisconsin criteria. Fundoscopy revealed in 95/646 eyes (14.7%) some degree of diabetic retinopathy. Sensitivity and specificity of fundus photography (omitting ungradable transparencies) were 97% for the diagnosis of any diabetic retinopathy (DRP). All patients with moderate and severe DRP (Wisconsin grade 3 and worse) according to fundoscopy were detected by fundus photography. In conclusion, mydriatic wide angle 60 degrees fundus photography, making two pictures per eye, can be applied effectively and reliably in the detection of diabetic retinopathy in patients with Type 2 diabetes.

Placental basal plate myometrial fibers: clinical correlations of abnormally deep trophoblast invasion

OBJECTIVE

To assess the incidence of placental basal plate myometrial fibers in preterm and term gestations and correlate this finding with clinical observations and placental histopathology.

METHODS

Placentas from 457 singleton births before 32 weeks' gestation and 108 uncomplicated singleton births after 37 weeks' gestation were examined histopathologically. Pregnancies complicated by maternal chronic hypertension, diabetes mellitus, coagulopathy, placenta previa, stillbirth, multiple fetuses, and fetal congenital anomalies were excluded from both groups. In the preterm group, 158 patients had preterm labor with intact membranes, 192 had preterm premature rupture of membranes (PROM), 31 had placental abruption without hypertension, and 76 had preeclampsia. Histopathology detected the presence of placental basal plate myometrial fibers, placental vascular lesions, and villous damage related to vascular insufficiency.

RESULTS

Forty-four of 457 (9.6%) of preterm placentas had basal plate myometrial fibers, compared with one of 108 (0.9%) term controls (P < .001). Uteroplacental vessels with abnormal physiologic changes were more frequent and placental weights were lower in cases with basal plate myometrial fibers (P < .003 and P < .03, respectively). No other uteroplacental vascular lesions were related to basal plate myometrial fibers. The frequency of placental basal plate myometrial fibers was nine of 76 (12%) in cases complicated by preeclampsia, 21 of 192 (11%) cases of PROM, nine of 158 (5.7%) cases of preterm labor, and four of 31 (13%) cases of placental abruption without hypertension; these frequencies were not significantly different, and there was no significant relationship to gravidity, parity, mode of delivery, or birth weight.

CONCLUSION

Placental basal plate myometrial fibers occur in ten times as many preterm births as term births. This finding is associated with both abnormal uteroplacental physiologic changes and decreased placental weight, and may explain the increased incidence of abnormalities of the third stage of labor associated with preterm delivery.

Low-dose aspirin therapy and placental pathology in women with poor prior pregnancy outcomes

PROBLEM

To determine if low dose aspirin therapy improves placental histology in women with a prior complicated pregnancy demonstrating uterine vascular pathology.

METHOD

A retrospective chart review identified patients with a prior complicated pregnancy with placental changes showing uterine vascular pathology (control pregnancy, CP). In the treated pregnancy (TP), 81 mg/day of ASA was started prior to 10 weeks. Placental reports from the CP and TP were reviewed. Pregnancy outcomes and placental histology from the CP were compared to the TP for each patient.

RESULTS

Thirteen patients were enrolled. The majority of patients (8/13, 61.5%) exhibited recurrent, histologic evidence of uterine vascular pathology in the TP. The TP was more likely to be uncomplicated (P < 0.05), delivered after 36 weeks (P < 0.05), and result in the delivery of a viable infant (P < 0.05) compared to the CP.

CONCLUSIONS

Despite an improvement in outcomes in the aspirin treated pregnancy, histologic evidence of uterine vascular pathology persisted in the majority of women with a prior complicated pregnancy demonstrating similar placental lesions. Abnormal placental histology may be useful in identifying a group of women with poor obstetrical histories who could benefit from low-dose aspirin therapy.

Treatment of cyclic vomiting in childhood with erythromycin

Cyclic vomiting syndrome (CVS) is an unusual cause of episodic emesis in children. It manifests as intermittent episodes of severe vomiting, similar in time of onset and duration, with no symptoms during the intervening period. Dehydration necessitating intravenous fluid therapy may occur. Most therapeutic maneuvers have proven unsuccessful. We report the use of erythromycin as a prokinetic agent in the treatment of cyclic vomiting in 24 children (10 boys, 14 girls). Many patients had mild associated abdominal pain with their vomiting. Fourteen patients had previously been given metoclopramide but none responded. Two patients were mildly developmentally delayed. Twenty-four patients were given oral erythromycin ethylsuccinate, approximately 20 mg/kg/day, in two to four divided doses for 7 days. This dose was repeated as needed when symptoms reappeared. Eighteen of 24 patients reported total resolution of symptoms when re-evaluated at 2 and 6 months. All males responded, eight of 18 responders were female, and all six with partial or no response to therapy were female. This uncontrolled trial suggests that erythromycin may be a useful prokinetic agent in the treatment of CVS in childhood. Because the study was uncontrolled, placebo effect cannot be excluded. Case-controlled, double-blinded prospective trials should be considered to evaluate the effectiveness of erythromycin in CVS.

Treatment of cyclic vomiting in childhood with erythromycin

Cyclic vomiting syndrome is an unusual cause of episodic emesis in children. It manifests as intermittent episodes of severe vomiting, similar in time of onset and duration, with no symptoms during the intervening period. Dehydration necessitating intravenous fluid therapy may occur. Most therapeutic maneuvers have proven unsuccessful. We report the use of erythromycin as a prokinetic agent in the treatment of cyclic vomiting in 20 children (9 boys, 11 girls). Many patients had mild associated abdominal pain with their vomiting. Thirteen patients had previously been given metoclopramide, but none responded. Two patients were mildly developmentally delayed. Twenty patients were given oral erythromycin ethylsuccinate, approximately 20 mg/kg/day, in 2-4 divided doses for 7 days. This dosage was repeated as needed when symptoms reappeared. Thirteen of 20 patients reported total resolution of symptoms when reevaluated at 2 and 6 months. All males responded, 4 of 13 responders were female, and all seven with partial or no response to therapy were female. This uncontrolled trial suggests that erythromycin may be a useful prokinetic agent in the treatment of cyclic vomiting syndrome in childhood. As the study was uncontrolled, placebo effect cannot be excluded. Case-controlled, double-blinded prospective trials should be considered to evaluate the effectiveness of erythromycin in cyclic vomiting syndrome.

Specific and sensitive measurement of FK506 and its metabolites in blood and urine of liver-graft recipients

A specific and sensitive assay for quantifying the immunosuppressant FK506 and its metabolites in blood and urine was developed. 32-O-Acetyl FK506 was synthesized and used as internal standard. FK506 and its metabolites were purified from the samples by solid-liquid extraction and were injected into a high-performance liquid chromatographic (HPLC) system linked to a mass spectrometer (MS) by particle-beam interface. The FK506 derivatives were separated from interfering material by use of a 100 x 4 mm C8 analytical column and water/acetonitrile or water/methanol gradient elution; they were detected by negative chemical ionization with methane as reagent gas. The limit of detection was 25 pg in a standard solution, and the limit of quantification in blood was 250 pg (extracted from 1 mL of blood). The CV was 11.3% at 5 ng, and no interferences with other drugs were found.

Specific and Sensitive Measurement of FK506 and Its Metabolites in Blood and Urine of Liver-Graft Recipients

A specific and sensitive assay for quantifying the immunosuppressant FK506 and its metabolites in blood and urine was developed. 32-O-Acetyl FK506 was synthesized and used as internal standard. FK506 and its metabolites were purified from the samples by solid-liquid extraction and were injected into a high-performance liquid chromatographic (HPLC) system linked to a mass spectrometer (MS) by particle-beam interface. The FK506 derivatives were separated from interfering material by use of a 100 x 4 mm C8 analytical column and water/acetonitrile or water/methanol gradient elution; they were detected by negative chemical ionization with methane as reagent gas. The limit of detection was 25 pg in a standard solution, and the limit of quantification in blood was 250 pg (extracted from 1 mL of blood). The CV was 11.3% at 5 ng, and no interferences with other drugs were found.

Sensitive detection of RNAs in single cells by flow cytometry

A rapid and sensitive fluorescent in situ hybridization method has been developed to probe RNA contents of individual cells by flow cytometry. Fixed cells in suspension were hybridized with 5' end-fluorophore-labeled oligodeoxynucleotides complementary to defined regions of the RNA of interest and analyzed by flow cytometry. With this method, we monitored combinations of histone H4 mRNA, 18S rRNA and 28S rRNA levels in synchronized HeLa S3 cells by multicolor analysis. A fluorescence signal equivalent to 1800 copies of histone H4 mRNA per cell was detected with signal-to-background ratio of 5.4. If non-specific binding of the fluorophore-labeled probe can be reduced, as few as 100 copies of mRNA of the size of H4 could be detected in individual cells by flow cytometry.

A unique immune response control locus mapping with the H-2D class I region

The immune response to the polysaccharide antigen Trinitrophenyl (TNP)-ficoll is controlled by two complementing loci in the murine major histocompatibility complex. One locus of control is present in the I-A subregion and the second is located between the S and D regions. A monoclonal antibody 48-21.7 was selected for its ability to significantly block the in vitro primary response to TNP-ficoll. This antibody bound to antigen-presenting cells does not interfere with the presentation of other antigens. Experiments are presented to demonstrate that the monoclonal antibody 48-21.7 precipitates a unique protein of approximately 40,000 daltons. Sequential immunoprecipitation with monoclonal antibodies to the class I Db antigen and to relevant Ia antigens demonstrated no cross-reactivity. Amino acid sequencing has found unique amino acids to be present at three class I N-terminal invariant positions. These observations indicate the presence of a unique class I-like molecule coded for by genes mapping between S and D and involved in the response to the polysaccharide ficoll.

Extracellular metal-free corrinoids from Rhodopseudomonas spheroides

Rhodopseudomonas spheroides when grown on a medium deficient of cobalt excretes significant amounts of descobaltocorrinoids into the culture broth. If grown in the presence of 4 microM CoCl2 only intracellular cobalt-containing corrinoids are detected. The extracellular corrinoids have been identified as hydrogenobyrinic acid c-amide and hydrogenobyrinic acid a,c-diamide which are accompanied by varying amounts of the corresponding 13-epicorrinoids. The latter, which could not be separated in the metal-free form, are artifacts arising from the excreted descobaltocorrinoids under the alkaline conditions of the culture broth. The red metal-free corrinoids have been converted into the corresponding cobalt-containing corrinoids and were characterized by their CD, UV, 1H NMR, and 13C NMR spectra. Insertion of cobalt into the fraction of hydrogenobyrinic acid c-amide has yielded small amounts of a cobalt-containing corrinoid, for which the structure of 18,19-didehydrocobyrinic acid c-amide is suggested. A 14C-labeled specimen of hydrogenobyrinic acid a,c-diamide was obtained by feeding [14C]acetate to growing cultures of R. spheroides. Experiments with broken cell systems of Propionibacterium shermanii and R. spheroides have indicated that metal-free corrinoids are not precursors of the cobamides. The results are discussed with respect to the final steps of the biosynthesis of vitamin B12.

The Conformational Equilibrium of 1,2,3-Tribromopropane in Solution

The p.m.r. spectra of dilute solutions of 1,2,3-tribromopropane in carbon tetrachloride, acetonitrile, and dimethylsulfoxide as well as of the neat compound are examined. From the three- and four-bond spin–spin coupling constants and from a comparison between observed and calculated dipole moments it is concluded that in nonpolar solvents the title compound exists preferably in the enantiomeric conformations a and i. In polar solvents other rotamers contribute to the equilibrium but still seem to play only a minor role. Semiempirical calculations of conformational energies rule out contributions to the conformational equilibrium from rotamers having (1:3) bromine–bromine interactions, but otherwise are only in moderate agreement with experiment.

Long-range Spin–Spin Coupling Constants from Amino Protons and 15N to Ring Protons in Aniline-15N and Some Derivatives. INDO Molecular Orbital Calculations

A complete analysis (8-spins) is given of the p.m.r. spectrum of aniline-15N, of the spectra of some haloanilines-15N and of 2-aminoacetophenone-15N. Intermolecular exchange of the amino protons is slow enough for observation of their spin–spin coupling to the ring protons. The magnitudes of the coupling constants between amino protons and 15N or ring protons are a measure of the geometry of the amino group. This is not true of the couplings between 15N and the ring protons. Long-range couplings computed in the CNDO/2 and INDO approximations of molecular orbital theory show points of agreement with experiment. For example, their signs and magnitudes are consistent with a nonplanar but not with a planar conformation of aniline. Couplings from 15N to ring protons are also computed for nitrobenzene.

Proton Magnetic Resonance Spectrum of 1-Penten-3-yne. INDO and CNDO/2 Molecular Orbital Calculations on Long-Range Spin–Spin Coupling Constants in Enynes

The high resolution p.m.r. spectra of 1-penten-3-yne in carbon disulfide and in benzene solution are analyzed. Long-range spin–spin coupling constants are discussed in terms of σ and π electron contributions. Comparisons are made with the isomeric 2-methyl-1-buten-3-yne and the parent compound, vinylacetylene. The results of INDO and CNDO/2 molecular orbital calculations are compared to the experimental coupling constants. It is concluded that the π electron contribution to 5J in enyne systems is +0.6 to 0.7 Hz and that σ electron contributions are rather small, the transoid ("pseudo-zig–zag") being larger than the cisoid one. Observed allylic coupling constants in the propene derivative are compared with the calculated values, including those for propene and 2-cyanopropene, available in the literature.