Interruption of the enterohepatic circulation of digitoxin by cholestyramine. II. Effect on metabolic disposition of tritium-labeled digitoxin and cardiac systolic intervals in man.

Previous studies of digitalis glycoside metabolism and excretion have indicated that these compounds undergo a significant enterohepatic cycle in some species. It has been suggested that the existence of such a cycle in man contributes to the prolonged action of certain cardiac glycosides. Previous studies have demonstrated that cholestyramine binds digitoxin and digoxin in vitro and accelerates the metabolic disposition of digitoxin in rats and guinea pigs, presumably by interrupting the enterohepatic circulation. In order to assess the role of the enterohepatic circulation in the metabolism of digitalis glycosides in humans, maintenance doses of cholestyramine were administered to 7 of 15 normal human subjects beginning 8 hr after digitalization with 1.2 mg of digitoxin-(3)H. All subjects had frequent measurements of serum radioactivity, left ventricular ejection time (LVET), and electromechanical systole (QS(2)), the latter recorded as the interval from onset of Q wave to first major component of second heart sound. Measurement of the LVET and QS(2) intervals affords a sensitive index of the cardiac response to digitalis. In addition, chloroform extraction of serum was performed to separate unchanged digitoxin and active metabolites from cardioinactive metabolites of digitoxin. Cholestyramine treatment resulted in reduction in half-life to total serum radioactivity from 11.5 to 6.6 days, and in chloroform-extractable radioactivity from 6.0 to 4.5 days, as compared to controls. In addition, cholestyramine treatment was accompanied by more rapid return to base line values of digitoxin-induced changes in the LVET and QS(2) intervals. A significant positive correlation was found between QS(2) values and chloroform-extractable radioactivity, the latter reflecting unchanged digitoxin-H(3) (r=0.64; P=<0.01). The results indicate that administration of cholestyramine to digitalized human subjects accelerates the metabolic disposition of digitoxin and abbreviates the physiologic response to the glycoside. This effect is presumably mediated by interruption of the enterohepatic circulation of digitoxin by cholestyramine.

The capsule polysaccharide structure and biogenesis for non-O1 Vibrio cholerae NRT36S: genes are embedded in the LPS region.

BACKGROUND: In V. cholerae, the biogenesis of capsule polysaccharide is poorly understood. The elucidation of capsule structure and biogenesis is critical to understanding the evolution of surface polysaccharide and the internal relationship between the capsule and LPS in this species. V. cholerae serogroup O31 NRT36S, a human pathogen that produces a heat-stable enterotoxin (NAG-ST), is encapsulated. Here, we report the covalent structure and studies of the biogenesis of the capsule in V. cholerae NRT36S. RESULTS: The structure of the capsular (CPS) polysaccharide was determined by high resolution NMR spectroscopy and shown to be a complex structure with four residues in the repeating subunit. The gene cluster of capsule biogenesis was identified by transposon mutagenesis combined with whole genome sequencing data (GenBank accession DQ915177). The capsule gene cluster shared the same genetic locus as that of the O-antigen of lipopolysaccharide (LPS) biogenesis gene cluster. Other than V. cholerae O139, this is the first V. cholerae CPS for which a structure has been fully elucidated and the genetic locus responsible for biosynthesis identified. CONCLUSION: The co-location of CPS and LPS biosynthesis genes was unexpected, and would provide a mechanism for simultaneous emergence of new O and K antigens in a single strain. This, in turn, may be a key element for V. cholerae to evolve new strains that can escape immunologic detection by host populations.

Isolation of a novel O-linked, sulfated polysaccharide of high molecular weight from an ovarian cyst glycoprotein having blood group "A" activity.

Treatment of a blood group A-active ovarian cyst mucin glycoprotein with alkaline borohydride under conditions expected to cleave O-glycosidic linkages between carbohydrate and peptide releases a sulfated polysaccharide of average molecular weight 20,000. Its peptide and mannose content is less than 1%, and carbohydrate analysis gives Fuc/GalNAc/Gal/GlcNAc in the ratio of 1:1:2.2:2.2. Galactosaminitol is recovered at the level of one residue per 112-residue average polysaccharide chain. The 13C- and 1H-NMR spectra show that the polysaccharide has side chains whose non-reducing terminals have the blood group A structure on a type 1 chain: (Formula: see text). Methylation analysis confirms the presence of these blood group A type 1 sidechains as well as 4-substituted GlcNAc, 3-substituted galactose and 3,6-substituted galactose branch points. Periodate oxidation removes all the fucose and GalNAc from the non-reducing terminal but leaves intact the backbone composed of beta-linked Gal and GlcNAc, as would be expected for a polylactosamine. Although the native polysaccharide is resistant to endo-beta-galactosidase digestion, the product of periodate degradation is partially digested, giving a 30% yield of a trisaccharide shown by 1H-NMR spectroscopy to be: Gal(beta 1----3)GlcNAc(beta 1----3)Gal We conclude that this is a high molecular weight sulfated polysaccharide which is related to the asparagine-linked polylactosamine chains of cell surface glycoproteins which have been implicated in cell differentiation. However, the blood group A polysaccharide from the ovarian cyst mucin is unique in several respects. It is linked to the protein by an O-glycosidic bond rather than the N-asparagine linkage of the previously known polylactosamines which have a trimannosyl core, and its blood group A side chains are on a type 1 core rather than type 2 which is found on other polylactosamines.

The combination of normal-phase and reverse-phase high-pressure liquid chromatography with NMR for the isolation and characterization of oligosaccharide alditols from ovarian cyst mucins.

Normal-phase high-pressure liquid chromatography (HPLC) on amino-bonded silica with elution by aqueous acetonitrile is shown to be an especially suitable complement to reverse-phase HPLC on octadecyl silica for the fractionation of oligosaccharide alditols produced by alkaline borohydride degradation of mucin glycoproteins. The former technique separates well on the basis of molecular size, while the latter method shows selectivity for stereoisomers. Stereoisomeric pairs of tetra-, penta- and hexasaccharide alditols show relative retention times ranging from 3 to 12, resulting in excellent preparative separations in reverse-phase chromatography. From a single ovarian cyst glycoprotein, H and Lewis b active, 13 oligosaccharides, representing essentially the entire carbohydrate content, have been isolated. The structures of 12 of the oligosaccharides have been determined by 1H-NMR spectroscopy. For those oligosaccharides which have been isolated from other sources and whose NMR spectra have been previously reported, unambiguous structural identification follows directly. Structures of oligosaccharides differing by only one or two residues from those whose NMR spectra are known may be deduced by a simple algorithm utilizing chemical shift analogies.

In vivo validation of the origin of the esophageal electrocardiogram.

Esophageal electrocardiography is a clinical and investigational technique that is useful for determining atrial conduction intervals, analyzing atrial rhythms and mapping conduction pathways. Although the left atrial origin of the esophageal electrocardiogram has long been implied, recently that origin has been questioned. In the present study, the origin of the esophageal deflection is defined by direct right and left atrial mapping studies performed with simultaneous esophageal electrograms obtained from three positions (high, mid and low). Seven patients with normal left atrial dimensions (group I) and five patients with left atrial enlargement (group II) underwent transseptal catheterization during the course of electrophysiologic study. In group I (normal left atrial dimensions), conduction time from the high right atrium to each of the three esophageal positions corresponded to conduction times to left atrial sites ranging from 1 to 3 cm lateral to the left interatrial septum. The mid- and low esophageal conduction times were all significantly longer than conduction time to the left side of the septum (p less than 0.05). In group II (enlarged left atrium), conduction times to each of the esophageal sites corresponded to conduction times to left atrial sites lying between the mid-left atrium and a point 1 cm lateral to the left side of the septum. A significant trend toward longer conduction time to the mid-esophageal position than to the left septum was noted (p less than 0.1). In both groups, conduction times measured with the esophageal catheter were significantly longer than conduction time to the right interatrial septum (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic distensibility abnormalities in coronary artery disease.

Vasodilatory capacity of nonstenotic arteries in experimental animals with atherosclerosis is decreased. It was postulated that aortic distensibility may be abnormal in patients with coronary artery disease (CAD). Aortic distensibility was determined in 24 normotensive patients with CAD and an angiographically normal aorta and values were compared with those in 18 age-matched normal subjects. Aortic diameters were measured at 3 levels--2, 4 and 6 cm above the aortic valve--by angiographic techniques. The area of the first 6 cm of the aorta above the aortic valve was planimetered and mean aortic diameters were calculated. Distensibility was calculated using the formula: [2 X (changes of the aortic diameter)/(diastolic aortic diameter) X (changes of the aortic pressure)]. CAD patients had similar aortic pressures but markedly lower distensibility than normal subjects: 0.7 +/- 0.2 vs 1.7 +/- 0.3 (p less than 0.02); 1.5 +/- 0.3 vs 4.0 +/- 0.6 (p less than 0.02); and 1.2 +/- 0.2 vs 5.3 +/- 0.6 (p less than 0.001) at 2, 4 and 6 cm above the aortic valve, respectively. Distensibility was also calculated from the mean aortic diameters and was greater in normal subjects than in CAD patients (3.4 +/- 0.4 vs 1.6 +/- 0.1, p less than 0.001). Decreased aortic distensibility in CAD may be related to the common atherosclerotic process or to reduced ascending aorta vasa vasorum flow from coronary arteries.

Prolonged electrical systole and QT greater than QS2 secondary to coronary artery disease.

Dyssynchronous depolarization-repolarization in the left ventricular (LV) myocardium may produce QT greater than QS2 or long QT. In 41 patients with coronary artery disease (CAD) and LV aneurysm, 46 patients with CAD and a history of acute myocardial infarction (AMI) but no LV aneurysm, and 52 patients with CAD without previous AMI, QT and QS2 were measured simultaneously at a speed of 100 mm/s within 48 hours of cardiac catheterization. Patients receiving class I antiarrhythmic drugs were excluded. The incidence of QT greater than QS2 was significantly greater in patients with LV aneurysm (71%) than in those with previous AMI (22%) and those with CAD but no previous AMI (20%) (p less than 0.001). Likewise, the incidence of long QT corrected for heart rate was significantly greater in patients with LV aneurysm (54%) than in those with previous AMI (7%) and those with CAD and no previous AMI (6%) (p less than 0.0001). The incidence of QT greater than QS2 in another 19 patients with previous AMI who were receiving digitalis therapy was significantly greater (65%) than in those with previous AMI but not receiving digitalis therapy (22%) (p less than 0.001). The incidence of long QT corrected for heart rate and QT greater than QS2 was not statistically different between patients with previous AMI and those with CAD but no previous AMI. The QT greater than QS2 or long QT in patients with aneurysm is probably a result of dyssynchronous depolarization or repolarization within or in the border zone of the LV aneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitral valve prolapse syndrome: analysis of 62 patients aged 60 years and older.

Sixty-two patients diagnosed as having mitral valve prolapse, 60 to 81 years old, presented with disabling chest pain (20), symptoms of arrhythmias including palpitations and syncope (16), or mitral regurgitation (MR) with symptoms of congestive heart failure (26). The diagnosis of MVP was made on the basis of a combination of classic auscultatory, echocardiographic and angiographic findings. Thirteen of the 20 patients with chest pain had normal coronary angiograms and 7 had significant coronary artery disease (CAD). Patients with CAD could not be differentiated by clinical presentation alone. Furthermore, the incidence and types of arrhythmias, the presence of a positive stress test, and hemodynamic findings were similar in all patients in this group whether or not CAD was present. The 16 patients with palpitations had a broad spectrum of rhythm disorders, including both supraventricular and ventricular arrhythmias. Two patients had prehospital "sudden death" and 2 others had systemic emboli. Twenty-one of the 26 patients with MR had valve surgery. Intraoperatively the valves were described as enlarged, floppy and with redundant leaflets. Histologic examination showed extensive "myxomatous" changes throughout the valve leaflets. Thus, mitral valve prolapse is a cause of symptomatic heart disease in the elderly. It has a predictable pattern of clinical presentation and should be considered in the differential diagnosis of older patients with disabling chest pain and arrhythmias and as the cause of progressive or severe MR.

Evidence for progression from mild to severe mitral regurgitation in mitral valve prolapse.

Little information is available concerning the progression of mild to severe mitral regurgitation (MR) in patients with mitral valve prolapse (MVP). This study reports 86 patients, average age 60 years, who presented with cardiac symptoms, precordial systolic murmur, severe MR and a high incidence of MVP on echocardiography (57 of 75 [75%] ) and left ventriculography (61 of 84 [73%] ). Seventy-five surgically excised mitral valves appeared grossly enlarged and floppy. Histologic studies showed extensive myxomatous changes throughout the leaflets and chordae. Eighty patients had had precordial murmurs first described at average age 34 years, but the average age at which symptoms of cardiac dysfunction appeared was 59. However, once symptoms developed, mitral valve surgery was required within 1 year in 67 of 76 patients who had undergone surgery. Atrial fibrillation, present in 48 of 86 patients (56%), or ruptured chordae tendineae, present in 39 of 76 patients (51%), may have contributed to this rapid progression and deterioration. Additionally, 13 patients had a remote history of documented infective endocarditis. Twenty-eight patients had at least 1 type of serial clinical evaluation that indicated progressive MR in all 28 patients on the basis of changing auscultatory findings (24 of 26), progressive radiographic cardiomegaly (24 of 25), echocardiographic left atrial enlargement (4.3 to 5 cm in 11 patients) and angiographically worsening MR (14 of 15). Twenty-four of these patients had evidence of MVP on at least 1 of their initial studies. Thus, mild MR due to MVP and myxomatous mitral valves is a progressive disease in some patients with MVP.

Systolic time intervals in atrial fibrillation.

Forty patients with atrial fibrillation and 20 patients with congestive heart failure and sinus rhythm were studied. Patients were divided into two groups. Group A consisted of 20 patients with atrial fibrillation in whom systolic time intervals were measured. Twenty to 50 beats were analyzed. Five of the patients had high-fidelity measurements of left ventricular pressure simultaneous with determination of systolic time intervals. Analysis of the systolic time intervals for the entire group showed that the preejection period lengthened at faster heart rates and that the left ventricular ejection time was relatively constant at slower heart rates. This resulted in a progressive increase in the ratio of preejection period over left ventricular ejection time (PEP/LVET) as the heart rate increased. The rate of increase in PEP/LVET was minimal below a heart rate of 75 beats per minute. The increase in preejection period at faster heart rates is due to greater isovolumic developed pressure without a corresponding increase in left ventricular dp/dt. Group B consisted of 40 additional patients (20 with atrial fibrillation and 20 with sinus rhythm). In group B, the total electromechanical systole corrected for heart rate (QS2I) and the levels of digoxin in the blood were compared. The QS2I was significantly shorter in atrial fibrillation (497 +/- 5 msec vs 528 +/- 4 msec; P less than 0.01), while the levels of digoxin in the blood were identical (0.9 +/- 0.1 vs 1.0 +/- 0.1 ng/ml). The results of this study must be considered when systolic time intervals are to be employed in patients with atrial fibrillation.

Extensive myocardial blood flow distribution through individual coronary artery bypass grafts.

The regional myocardial perfusion distribution of coronary artery bypass grafts were studied in 61 patients who received 162 grafts. Selective intragraft instillations of radioactive-labeled macroaggregated albumin particles were used to study perfusion. The extent of individual graft perfusion was assessed in 100 patent grafts. Regional myocardial blood flow distribution was similar to the blood flow distribution of the native vessel receiving the graft in 64 of 100 grafts and less than that expected of the native vessel in 12 grafts. However, 24 grafts demonstrated a blood flow distribution pattern which extended beyond the normal distribution expected of the native vessel receiving the graft. This extensive perfusion could be attributed to collateral vessels or retrograde flow. A high incidence of both graft and native vessel occlusion was found in areas receiving blood from these distant grafts with extensive distributions (16/24), and left ventricular wall motion was preserved or significantly improved postoperatively in 28/31 segments in such areas. When comparing angiographic and scintigraphic methods of evaluating myocardial perfusion, the angiogram underestimated the full extent of graft blood flow distribution in 13 of 24 instances (54 percent).

Antibodies that react with the capsular polysaccharide of Vibrio vulnificus are detectable in infected patients, and in persons without known exposure to the organism.

In serious infections with Vibrio vulnificus, IgG antibodies to the capsular polysaccharide of the infecting strain were demonstrable in patient serum. It was not possible to show that persons with probable increased exposure to V. vulnificus (shellfish industry workers) had increased levels of antibodies to any one of three capsular types tested when compared with persons who would be expected to have had minimal exposure to the organism (Seventh Day Adventists). Antibodies that reacted with the capsular polysaccharides were demonstrable in persons without a history of V. vulnificus infection, suggesting that cross-reacting antibodies are present in the general population.

Assessment of ventricular function by combined noninvasive measures: factors accounting for methodologic disparities.

We studied the predictive accuracy and disparities among cineventriculographic ejection fraction, pre-ejection period over left ventricular ejection time (PEP/LVET) obtained from the systolic time intervals and the percent shortening of the internal echocardiographic diameter (% delta D) in assessing left ventricular performance in 453 consecutive patients without valvular heart disease. In 308 patients all three tests were normal, and in 78 patients all three tests were abnormal. Overall agreement (predictive accuracy) among ejection fraction (normal greater than or equal to 57), % delta D (normal greater than or equal to 28%) and PEP/LVET (normal less than or equal to 0.42) was 85%. In 67 patients disparities among the tests as measures of global left ventricular performance were found. The major mechanisms accounting for such disparities were: (a) large segmental contraction abnormalities which selectively distort the % delta D and ejection fraction and (b) diminished isovolumic pressure (less than 45 mmHg) which distorts PEP/LVET. When patients with segmental contraction abnormalities and low isovolumic pressure were excluded the agreement between PEP/LVET and ejection fraction was 97%, ejection fraction and % delta D 98% and PEP/LVET and % delta D 97%. The combined uses of systolic time intervals and echocardiogram minimizes error due to segmental contraction abnormalities and isovolumic pressure. If both PEP/LVET and % delta D are concordant the agreement with ejection fraction is 94% for normal and 99% for abnormal left ventricular function.

Gas chromatography and mass spectrometry of disaccharides from glycoproteins.

Partial acid hydrolysis and methanolysis released disaccharides and disaccharide methylglycosides from the glycoproteins, ovomucoid and porcine gastric mucin in amounts of 0.5--7 microgram disaccharide per mg of glycoprotein. These disaccharides were fractionated by gas chromatography as the trimethylsilyl (Me3Si) derivatives. The composition of recovered disaccharides has been determined by hydrolysis and rechromatography of the Me3Si monosaccharides. The intersaccharide linkages of the disaccharides have been determined by electron impact mass spectrometry. This simple and rapid method can give structural information on small glycoprotein samples.

Case report. Congestive heart failure complicating the hungry bone syndrome.

A patient with the hungry bone syndrome following parathyroidectomy for hyperparathyroidism developed congestive heart failure, probably due to the myocardial depressant effects of hypocalcemia and hypomagnesmia. Calcium and magnesium alone were instrumental in relieving his symptoms, decreasing his heart size, and clearing the pulmonary congestion. A mechanism for the pathogenesis of hypocalcemia and hypomagnesemia induced heart failure is proposed.

The use of NMR residual dipolar couplings in aqueous dilute liquid crystalline medium for conformational studies of complex oligosaccharides.

C-H dipolar coupling values were measured for a natural-abundance sample of the pentasaccharide beta-D-Galp-(1-->3)-[alpha-L-Fucp-(1-->4)]-beta-D-GlcNAcp-(1 -->3)-beta-D- Galp-(1-->4)-beta-D-Glcp ('lacto-N-fucopentaose 2') (LNF-2), in a 7.5% solution of dimyristoyl phosphatidylcholine-dihexanoyl phosphatidylcholine bicelle liquid crystals oriented in the NMR magnetic field. Interpretation of the dipolar coupling data and NOE confirms the conformational model for the Lewis(a) trisaccharide epitope based on NOE, molecular dynamics simulations, and scalar coupling data and provided new structural information for the remaining residues of the pentasaccharide. Since residual dipolar coupling provides information on long-range order, it is a valuable complement to other types of NMR data such as NOE and scalar coupling for exploring conformations of complex oligosaccharides.

The determination of the structure of blood group oligosaccharides from fully assigned 1H-n.m.r. spectra for solutions in non-aqueous solvents.

The fully assigned 1H-n.m.r. spectra of a blood group A tetrasaccharide and of a blood group H hexasaccharide in dimethyl sulfoxide and in pyridine by use of two-dimensional COSY and homonuclear Hartmann-Hann coherence transfer methods are reported. The 1H-n.m.r. spectra of both of these compounds in deuterium oxide had been previously assigned. Since the relative proton chemical shifts in the three solvents are quite different, resonances which overlap or are strongly coupled for one solvent may be well resolved for another, thus providing an extension of the method of complete proton assignments for determination of the structure of complex oligosaccharides. Although the rotational correlation times (tau c) of these oligosaccharides are similar to the reciprocal of the spectrometer frequency, either negative or positive n.O.e. values were measurable for both oligosaccharides in all three solvents in one-dimensional difference spectroscopy by taking advantage of the dependence of tau c on the solvent viscosity and, thus, on sample temperature. Whereas n.O.e. depend strongly on temperature and solvent viscosity, the ratios of the effects between protons on the same pyranoside ring and those on different rings were observed to be similar, suggesting that the oligosaccharide conformations are not strongly dependent on solvent or temperature.

Measurement of long-range carbon-carbon coupling constants in a uniformly enriched complex polysaccharide.

A quantitative coherence transfer scheme for 1H-detected measurement of long-range carbon-carbon coupling constants in NMR spectra of complex carbohydrates is described. It is applied to a uniformly highly 13C-enriched monosaccharide and to a complex cell wall polysaccharide from Streptococcus mitis J22 having seven distinct sugars in the repeating subunit. Coupling values within the ring were compared to published values for monosaccharides to demonstrate the validity of the method. An attempt was made to relate coupling constants between carbon atoms across the glycosidic linkage to the dihedral angles of a recently published flexible model for the polysaccharide which is based on 3JCH data. The experimental coupling constants do not agree with any single conformation demonstrating that the repeating subunit of the polysaccharide must be flexible. This conclusion is in accord with results of molecular modeling nuclear Overhauser effect and 3JCH data.

Determination of the linkages of disaccharides containing a 2-acetamido-2-deoxy sugar unit by solvent effects in circular dichroism.

The circular dichroism spectra of 2-acetamido-2-deoxy sugars in 1,1,1,3,3,3-hexafluoro-2-propanol (F6Pr-2-ol) solutions show a positive band in the n-pi region (209 nm) in contrast to a negative c.d. band in water solution. This difference is interpreted as an indication of a change in the average orientation of the hydroxyl groups adjacent to the amide group. C.d. spectra of 2-acetamido-2-deoxy sugars having a methyl group at O-1 and O-3 confirm this interpretation and suggest that the c.d. spectrum of a disaccharide in F6Pr-2-ol reflects strongly the disaccharide linkage. Large differences in the c.d. spectra of (1 leads to 4) and (1 leads to 6)-linked disaccharides in this solvent lead to rules for distinguishing the linkages of the disaccharides.

The complete structure of the capsular polysaccharide from Streptococcus sanguis 34.

A complete structure for the capsular polysaccharide of Streptococcus sanguis 34, which is responsible for coaggregation of this bacterium with Actinomyces viscosus T14V, an important step in the formation of dental plaque, is proposed, based partly on the 1H-n.m.r. spectrum, which was assigned by 2-dimensional COSY, homonuclear Hartmann-Hahn spectroscopy, and nuclear Overhauser effects. A phosphoric diester linkage was identified from the 31P-n.m.r. spectrum, and the linkage was determined from long range 1H-31P correlation spectroscopy. The proposed structure is supported both by methylation analysis before and after dephosphorylation and by g.l.c.-m.s. of the phosphorylated monosaccharides as their trimethylsilyl derivatives, isolated by partial hydrolysis of the polysaccharide. The structure is composed of repeating linear hexasaccharide units joined by a phosphoric diester linkage, i.e., [----PO4(-)----6)-alpha-D-GalpNAc-(1----3)-beta-L-Rhap-(1----4)-be ta -D-Glcp- (1----6)-beta-D-Galf-(1----6)-beta-D-GalpNAc-(1----3)-alpha-D-Galp -(1----]n.