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Biomedical subjects

T Hofmann

Publications and source records attributed to T Hofmann.

At least 127 records · Page 7Linked to original sources
PubMed1989

Nucleotide and deduced amino acid sequence of the hydrophobic surfactant protein SP-C from rat: expression in alveolar type II cells and homology with SP-C from other species.

Pulmonary surfactant lowers surface tension in the lung. Its deficiency leads to the severe physiologic abnormalities seen in the respiratory distress syndrome. The hydrophobic surfactant proteins, SP-B and SP-C, appear to be especially important in the surface-spreading characteristics of pulmonary surfactant. We report the nucleotide sequence of cDNA clones for rat SP-C and compare the deduced amino acid sequence for SP-C from several species. A highly conserved domain exists within the confines of mature human SP-C. An Eisenberg plot of this region predicts a membrane-associated helix. We also demonstrate by Northern analysis the tissue-specific expression of SP-C. A comparison of signal strength between total lung RNA and RNA derived from isolated type II cells supports the idea that most SP-C messenger RNA in total lung can be accounted for by that present in alveolar type II cells.

Amino Acid Sequence↗
PubMed1989

Tryptophanyl-tRNA synthetase from Bacillus subtilis. Characterization and role of hydrophobicity in substrate recognition.

The tryptophanyl-tRNA synthetase from Bacillus subtilis was purified to homogeneity and characterized. It has an alpha 2 subunit structure and a molecular weight of 77,000. Tryptophanyl-tRNA synthetase does not catalyze any significant proofreading. It activates tryptophan as well as the three fluorinated analogues, DL-4-fluoro-, DL-5-fluoro-, or DL-6-fluorotryptophan (4F-, 5F-, and 6F-Trp), in the ATP-pyrophosphate exchange reaction. In the aminoacylation reaction, the fluorotryptophans act as competitive inhibitors of Trp. Their relative activities follow the same order in both reactions: Trp greater than 4F-Trp greater than 6F-Trp greater than 5F-Trp. This order is the inverse of the order of relative hydrophobicities of these compounds, pointing to the importance of hydrophobic interactions in the selective recognition by tryptophanyl-tRNA synthetase among this group of substrates. To define the physical basis of the relative hydrophobicities, the crystallographic structure of 4F-Trp was determined and compared to that of trptophan. Charge distributions calculated for tryptophan and its different fluoroanalogues on the basis of molecular structures were supported by their carbon-13 NMR spectra. Correlations between charge distributions and relative hydrophobicities suggest that the polarity of the C-F bond represents an underlying factor determining the hydrophobicities of 4F-, 5F-, and 6F-Trp, thus relating tryptophanyl-tRNA synthetase selectivity toward tryptophan and its fluoroanalogues directly to their electronic configurations.

Adenosine Monophosphate↗
PubMed1989

Influence of enoximone on myocardial energetics in patients with idiopathic dilated cardiomyopathy: comparison with nitroprusside.

Enoximone may influence myocardial energetics by vasodilation, which may reduce and by inotropism which may increase myocardial energy demand. To separate both pharmacological properties, the influence of enoximone on myocardial oxygen consumption and its hemodynamic determinants was analyzed and compared to the effects of the pure vasodilator nitroprusside. The relationship between myocardial oxygen consumption and left ventricular hemodynamics was evaluated in 22 patients with idiopathic dilated cardiomyopathy (NYHA stages II-III). During control, myocardial oxygen consumption per beat [MVO2 (beat)] correlated closely with left ventricular systolic stress-time integral (STI) (r = 0.74; p less than 0.001). The ratio of MVO2 (beat) and STI was used as an inverse measure of the economy of myocardial contraction. Following nitroprusside (10 patients) the STI decreased by 35% (p less than 0.005) and MVO2 (beat) by 30% (p less than 0.005). MVO2 (beat)/STI did not significantly change. Following enoximone (12 patients), STI decreased by 60% (p less than 0.001), MVO2 (beat) by 19% (p less than 0.001), and MVO2 (beat)/STI increased from 1.31 +/- 0.16 to 2.72 +/- 0.78 nl.cm2/100 g.dyn.s (p less than 0.001). In summary, vasodilation by nitroprusside decreased MVO2 (beat) in proportion to its major determinant, STI; the economy of myocardial contraction remained unchanged. Compared to nitroprusside, enoximone reduced the economy of contraction. Thus, with enoximone, the energy-saving effect of vasodilation is counteracted by increased energy demand due to the inotropic stimulation of the myocardium. Global myocardial oxygen consumption depends on the balance of both pharmacological properties.

Cardiomyopathy, Dilated↗
PubMed1989

[Echocardiography detection of reversible regional disorders of contraction in patients with unstable angina pectoris and Prinzmetal angina during an attack].

We studied seven patients with Prinzmetal's angina and three patients with unstable angina pectoris type III (according to the criteria of Conti) during and after a spontaneous attack of angina pectoris by two-dimensional echocardiography. All patients underwent coronary angiography. The echocardiographic studies were performed during the attack (phase I), immediately after the attack (phase II), and 24 h after the attack (control). Left ventricular ejection fraction was significantly decreased during the attack (38.1 +/- 11% vs 59.8 +/- 7%), while left ventricular end-diastolic volume was increased (71.9 +/- 28 ml/m2 vs 50.3 +/- 13 ml/m2). The double product of heart rate and systolic blood pressure was equal at the 3 different examination times. In all patients transient regional disturbances of left ventricular contraction could be observed. In six patients the wall motion disturbances had already disappeared at phase II, while in four patients hypokinetic regions could still be found. At control, nine patients showed a normal left ventricular contraction pattern, while one patient with previous anterior myocardial infarction showed a small region of anterior akinesia. In all patients coronary artery obstructions were found in the same region of the left ventricle, where transient wall motion abnormalities occurred. Thus, two-dimensional echocardiography performed during an attack of angina pectoris in patients with Prinzmetal's angina and unstable angina pectoris type III can evaluate the localization, as well as the extent of transient myocardial wall motion abnormalities.

Angina Pectoris↗
PubMed1989

[Echocardiography in the diagnosis of lung embolism].

In the Federal Republic of Germany, approximately 10,000 to 20,000 persons die of pulmonary embolism (PE) each year. The mortality of treated PE is about 8% as compared with 18 to 35% in nondiagnosed PE. Massive PE is detected in only about 15 to 30% of the patients while, on the other hand, in 30 to 80% of those in whom PE is suspected the pulmonary angiogram may be normal. On use of pulmonary ventilation-perfusion scintigraphy, in 30 to 40% of the cases, both false negative as well as false positive findings have been described. ROLE OF ECHOCARDIOGRAPHY IN PATIENTS WITH ACUTE PULMONARY EMBOLISM. With echocardiographic imaging, the right heart as well as the central vessels in the proximity of the heart, in particular the pulmonary arteries, can be visualized. In addition to direct detection of right-sided-intraluminal thrombi, echocardiographic diagnosis is based predominantly on indirect signs, such as evidence of an acute cor pulmonale with dilatation of the right atrium and ventricle, the central pulmonary vessels and the inferior vena cava which, however, are relatively unspecific and may also be found in the presence of other diseases. Echocardiographic changes in acute pulmonary embolism can only be expected in the presence of increased pressure in the pulmonary circulation, that is, when at least a 30%-reduction in the cross-sectional area of the pulmonary vascular bed can be found. This can be documented in 60 to 70% of patients with acute PE. According to the literature and our own studies, of a total of 284 patients 84% had dilatation of the right ventricle, 70% paradoxic or hypokinetic motion of the interventricular septum in 102/141 patients there was dilatation of the right pulmonary artery. These changes regressed rapidly after therapeutic intervention. In about 30% of the patients a reduction in the left ventricular dimensions can be seen. Paradoxic septum motion and a decrease in the closing amplitude (EF-slope) of the anterior mitral leaflet can be seen. The extent of dilatation of the right ventricle and the right pulmonary artery correlate with the extent of the angiographic severity of acute PE provided that there is no marked preexisting left ventricular function impairment. NONINVASIVE ESTIMATION OF THE PRESSURE INCREASE IN THE PULMONARY CIRCULATION. On use of Doppler echocardiography, most patients with acute cor pulmonale have tricuspid regurgitation. This enables through determination of the systolic RV-RA pressure gradient an estimation of the systolic right ventricular pressure and, accordingly, the pulmonary artery pressure. In our experience, a systolic acceleration time in the pulmonary artery of less than 90 to 95 ms is

Echocardiography↗
PubMed1988

Effect of amino acid substitutions and deletions on the thermal stability, the pH stability and unfolding by urea of bovine calbindin D9k.

The influence of amino acid substitutions and deletions on the stability of bovine calbindin D9k, the smallest protein known with a pair of EF-hand calcium-binding sites, has been studied using circular dichroism and ultraviolet absorption spectroscopy. The five modifications are confined to one of the two Ca2+ -binding sites. The Ca2+-loaded forms of the wild-type and mutant calbindins are too stable to be significantly denatured by heating at 90 degrees C or by adding 8 M urea. For the Ca2+-free (apo) forms thermal unfolding appears to be only half complete at 90 degrees C, while denaturation is complete in 7-8 M urea. Four of the mutant proteins show reduced resistance towards unfolding by urea, but one of the modified proteins (Glu-17----Gln) shows an increased stability, presumably because of a reduced electrostatic repulsion in the native state. According to X-ray crystallographic data the OH group of the single tyrosine of calbindin (Tyr-13) is hydrogen-bonded to the carboxyl group of Glu-35, thus linking the two alpha helices flanking the N-terminal Ca2+ site. The pK of ionization of the Tyr-13 hydroxyl group was over 13 for calcium forms of the wild-type protein, between 12.3 and 12.8 for the calcium form of three mutants and between 11.5 and 11.7 for the apoproteins. Significant differences in pH stability between wild type and mutants were observed in the calcium forms, but were not apparent in the apo forms.

Amino Acids↗
PubMed1988

Characterization of porcine osteonectin extracted from foetal calvariae.

Osteonectin, extracted from foetal porcine calvariae with 0.5 M-EDTA, was purified to homogeneity by using gel filtration and polyanion anion-exchange fast protein liquid chromatography under dissociative conditions without the need of reducing agents. The purified protein migrated with an Mr of 40,300 on SDS/polyacrylamide gels and was similar to bovine osteonectin in both amino acid composition and in its ability to bind to hydroxyapatite in the presence of 4 M-guanidinium hydrochloride (GdmCl). However, unlike the bovine protein, porcine osteonectin did not bind selectively to hydroxyapatite when EDTA tissue extracts were used. In addition, purified porcine osteonectin did not show any apparent affinity for either native or denatured type I collagen, but did bind to serum albumin. Primary sequence analysis revealed an N-terminal alanine residue, with approximately one-half of the subsequent 35 residues identified as small hydrophobic amino acids and one-quarter as acidic amino acids. The only significant difference between the N-terminal sequences of the bovine and porcine proteins was the deletion of the tripeptide Val-Ala-Glu in porcine osteonectin. In contrast with bovine osteonectin, far-u.v.c.d. of porcine osteonectin revealed considerable secondary structure, of which 27% was alpha-helix and 39% was beta-sheet. Cleavage of the molecule with CNBr under non-reducing conditions generated five fragments, of which two major fragments (Mr 27,900 and 12,400) stained blue with Stains All, a reagent that stains sialic-acid-rich proteins/phosphate-containing proteins and/or Ca2+-binding proteins blue while staining other proteins pink. The 12,400-Mr fragment bound 45Ca2+ selectively, indicating a Ca2+-binding site in this part of the molecule. The 27,900-Mr fragment did not bind Ca2+, and since biosynthetic studies with 32PO4(3-) did not show phosphorylation of porcine osteonectin, this fragment is likely to be highly acidic. The incomplete cleavage of the molecule with CNBr and the ability of the molecule to regain its secondary structure after exposure to 7 M-urea are features consistent with the molecule having a compact structure that is stabilized by numerous disulphide bridges. The chemical and binding properties of porcine osteonectin are closely similar to the recently described 'culture shock', SPARC and BM-40 proteins, indicating that these are homologous proteins.

Amino Acid Sequence↗
PubMed1988

Transpeptidation reactions of porcine pepsin. Formation of tetrapeptides from dipeptide substrates.

Pepsin-catalyzed transpeptidation was studied by high resolution 75 MHz 13C nuclear magnetic resonance spectroscopy. Enrichment with 13C at the carbonyl carbons of the substrates Leu-Tyr-NH2 and Leu-Leu-NH2 facilitated detection and identification of the transpeptidation and hydrolysis products of enzymic action. Porcine pepsin was found in each case to synthesize and release the tetrapeptide Leu-Leu-Leu-Leu as the primary product of transpeptidation, the longest oligomeric product of transpeptidation observed to date. Productive binding of the dipeptide substrates into the active site groove of pepsin required an induction period of several minutes. Quenching experiments suggested the presence of strongly bound intermediate forms of Leu and Leu-Leu prior to observation of any enzyme-free products. The finding of the tetrapeptide as a primary product is discussed as an instance where transpeptidation of the tripeptide competes successfully with the action of pepsin subsite S3 as a trigger for product release.

Animals↗
PubMed1988

Site-site interactions in EF-hand calcium-binding proteins. Laser-excited europium luminescence studies of 9-kDa calbindin, the pig intestinal calcium-binding protein.

Europium(III) binding to 9-kDa calbindin from pig intestines was studied by direct excitation of the 7Fo----5Do transition of the ion and by near-ultraviolet circular dichroic spectroscopy. Europium(III) binding is clearly biphasic. As with other lanthanides the C-terminal metal-binding site (site II) is filled first. The europium ion in this site gives an excitation spectrum with a single peak at 579.1 nm (peak 2). The occupation of the N-terminal site (site I) by europium gives excitation spectra that are pH-dependent and show a peak at 579.4 nm (peak 1a) at pH 5 which shifts to 578.7 nm (peak 1b) over the pH range 5-7. At pH 8.07 the fluorescence from europium in site I largely disappears because of weak binding, whereas that from site II is quenched by about 75% in spite of full occupancy of the site as shown by circular dichroic titration. There is a strong interaction between the two sites in spite of the very different affinities. The fluorescence from site II increases stoichiometrically with the addition not only of the first equivalent of europium, but also concomitantly with the fluorescence from site I upon addition of the second equivalent. Furthermore, when Eu1-calbindin is titrated with calcium the fluorescence at 579.1 nm is quenched by about 30% during the addition of one equivalent of calcium which fills site I. Subsequent titration with large excesses of calcium displaces europium from site II. The affinity of site II for europium is about 100 times that of calcium under these conditions.

Animals↗
PubMed1988

Effect of secondary substrate binding in penicillopepsin: contributions of subsites S3 and S2' to kcat.

The kinetic parameters kcat, KM, and kcat/KM were determined at 25 degrees C and pH 4.5, 5.5, and 6.0 for the series of penicillopepsin substrates Ac-Alam-Lys-(NO2)Phe-Alan-amide, where (NO2)Phe is p-nitrophenylalanine and m and n equal 0-3. KM values at pH 6.0 were the same for all 12 peptides and averaged 0.088 +/- 0.02 mM but increased to different degrees at lower pH. In contrast, kcat values increased with increasing chain length. At pH 6 and at the pH optimum of kcat, the largest increases (about 37-fold on average) were obtained when alanine residues were added in positions P2' and P3. Only 1-2-fold increases were observed for positions P2, P3', P4, and P4'. These results show that occupation of subsites S2' and S3 is largely responsible for the rate enhancements caused by secondary substrate interactions with this series of peptides. Additional support for an important role of subsite S3 comes from the observation that the two peptides where m = 1 and n = 1 or 2, respectively, are cleaved not only between lysine and p-nitrophenylalanine but also between the latter and alanine, suggesting that occupation of subsite S3 by the N-terminal alanine overcomes the unfavorable interaction of alanine in subsite P1'. Subsite S3 is also important in the binding of pepstatin analogues and in transpeptidation reactions. It is proposed that the roles of subsites S3 and S2' are to facilitate the conversion of the first enzyme-substrate complex into a productive complex and to assist in the distortion of the scissile bond.(ABSTRACT TRUNCATED AT 250 WORDS)

Aspartic Acid Endopeptidases↗
PubMed1988

Extraction of an intracardial catheter embolus using combined radiography and transesophageal echocardiography.

Embolism of a fragment of a central venous catheter is a serious clinical complication, especially when the fragment cannot be made visible by radiological methods. We report a case where such a fragment could only be localized by transesophageal echocardiography (TEE). With combined use of x-rays and TEE, the catheter embolus was successfully extracted using a conventional Dormia catheter. For similar situations the described procedure is recommended.

Adult↗
PubMed1988

The coding sequence for the human 18,000-dalton hydrophobic pulmonary surfactant protein is located on chromosome 2 and identifies a restriction fragment length polymorphism.

The 18-kd hydrophobic pulmonary surfactant protein (PSP-B) is a developmentally regulated protein which is important for normal lung function. A complementary DNA probe for 221 NH2 terminal amino acids of PSP-B was used to determine the chromosomal location of this gene and identify a restriction fragment length polymorphism (RFLP). Southern blot hybridization to genomic DNA isolated from a panel of human-CHO somatic cell hybrids unambiguously maps this gene to chromosome 2. Human DNA cut with BamHI yields a RFLP with variable bands at 2.8 and 2.6 kb. Since there is a relative lack of polymorphic markers for chromosome 2, this sequence may be useful in linkage analysis.

Animals↗
PubMed1988

Mode of death in idiopathic dilated cardiomyopathy: a multivariate analysis of prognostic determinants.

A total of 110 patients with idiopathic dilated cardiomyopathy were followed prospectively for 53 +/- 8 (range 41 to 69) months to determine prognostic factors identifying patients at risk for sudden death or death from congestive heart failure. During the follow-up period 39 patients died, 14 of congestive heart failure and 25 suddenly. The incidence of cardiac death after 1 year was 18%, after 2 years 35%, and after 4 years 39%. Multivariate logistic regression analysis identified four independent prognostic factors: left ventricular ejection fraction, cardiac index, number of ventricular pairs/24 hours, and atrial rhythm (sinus rhythm or atrial fibrillation). With the final model of logistic regression 77 of 88 patients (88%) could be classified correctly as being at risk for death from chronic heart failure or sudden cardiac death. Patients who were likely to die of congestive heart failure were characterized by a markedly impaired left ventricular function (measured in terms of left ventricular ejection fraction, cardiac index, or both) and a low number of pairs/24 hours. The association between frequent complex ventricular arrhythmias and depressed left ventricular function identifies patients who are at risk for sudden death. The presence of atrial fibrillation significantly increases the risk of sudden death and death from congestive heart failure.

Adult↗
PubMed1988

The gene encoding the hydrophobic surfactant protein SP-C is located on 8p and identifies an EcoRI RFLP.

Pulmonary surfactant is composed primarily of phospholipids but also contains three known surfactant-specific proteins. These proteins are important in determining the physical properties of pulmonary surfactant--including its ability to adsorb to an air-liquid interface and its structure--but also appear to influence surfactant metabolism. We have previously assigned two surfactant proteins, SP-A (a 28-36-kDa glycoprotein) and SP-B (an 18-kDa hydrophobic protein), to the short arm of chromosome 10 and to chromosome 2, respectively. We now report that the gene encoding the 5-8 kDa hydrophobic surfactant protein SP-C is located on the short arm of chromosome 8. A cDNA clone encoding the entire protein recognizes a useful EcoRI restriction-site-length polymorphism. Evaluation of congenital syndromes manifesting autosomal abnormalities does not further elucidate the functional role of this protein in promoting normal respiratory physiology.

Animals↗
PubMed1987

Evaluation of long-term oral levodopa therapy in chronic congestive heart failure.

To evaluate the long-term effects of orally administered levodopa, 11 patients with chronic congestive heart failure (NYHA III-IV) were studied during maintenance therapy (30 +/- 1 days) and after withdrawal from levodopa. The daily levodopa dose was 4 g in six patients; because of side effects the levodopa dose was reduced to 2-3 g in the remaining patients. After withdrawal of levodopa, mean pulmonary capillary wedge pressure and mean right atrial pressure increased significantly (from 19 +/- 2 to 24 +/- 3 and from 7 +/- 2 to 9 +/- 2 mmHg, respectively). Effective renal plasma flow was 329 +/- 57 during levodopa therapy and decreased significantly to 252 +/- 27 ml/min after withdrawal of levodopa. The number of ventricular premature contractions and couplets increased during levodopa therapy and decreased again significantly after withdrawal of levodopa. No significant differences between on and off levodopa were observed in resting heart rate, arterial blood pressure, cardiac index, stroke work index, systemic vascular resistance, sodium and water excretion, or creatinine clearance. Seven patients improved on levodopa therapy by one NYHA class; four of these seven patients deteriorated again by one NYHA class after withdrawal of levodopa. Regarding both clinical and hemodynamic changes after withdrawal of levodopa, three patients were classified as responders to long-term levodopa therapy. All three responders received 4 g levodopa per day. Average dopamine plasma level was 5.3 +/- 0.8 ng/ml in the responder group and 2.0 +/- 0.5 ng/ml in the nonresponder group. Long-term administration of oral levodopa is associated with beneficial clinical and hemodynamic response in only a minority of patients with chronic congestive heart failure.

Administration, Oral↗
PubMed1987

Tyrosine and tyrosinate fluorescence of pig intestinal Ca2+-binding protein.

The single tyrosine residue in both pig and cow intestinal Ca2+-binding proteins fluoresces at 303 nm although the crystal structure of the cow protein shows a hydrogen bond between the hydroxy group of the tyrosine and glutamate-38 [Szebenyi & Moffat (1986) J. Biol. Chem. 261, 8761-8777]. The latter interaction suggests that tyrosinate fluorescence should dominate the emission spectra of these proteins. A fluorescence difference spectrum, produced by subtracting the spectrum of free tyrosine from the spectrum of the protein, gives a peak at 334 nm due to ionized tyrosine. That this component of the emission spectrum is not due to a tryptophan-containing contaminant is shown by its elimination when the protein is denatured by guanidine and when glutamate-38 is protonated. We conclude that, in solution, the tyrosine residue in this protein interacts occasionally with glutamate-38 but that a permanent hydrogen bond is not formed.

Animals↗
PubMed1987

Determination of aortic valve orifice area in aortic valve stenosis by two-dimensional transesophageal echocardiography.

Two-dimensional transesophageal echocardiography was used to measure aortic valve orifice area in 24 patients with aortic valve stenosis (AS) and 15 patients without aortic valve disease. Using transesophageal echocardiography, orifice area could be measured in 20 of 24 patients with AS. With transthoracic echocardiography, orifice area could be determined in only 2 of 24 patients. In patients with AS, orifice area determined by transesophageal echocardiography was 0.75 +/- 0.34 cm2 and that calculated with Gorlin's formula was 0.75 +/- 0.32 cm2. In normal aortic valves, orifice area was 3.9 +/- 1.2 cm2 by transesophageal echocardiography. A good correlation was demonstrated between aortic valve orifice area determined using transesophageal echocardiography and calculated orifice area using Gorlin's formula in patients with AS: r = 0.92, standard error of estimate = 0.14 cm2. The absolute difference between orifice area measured with both methods ranged from 0.0 to 0.4 cm2 (mean 0.09 +/- 0.1). In 4 patients orifice area could not be determined with transesophageal echocardiography. The orifice could not be identified in 2 patients because an appropriate cross-sectional view of the aortic valve could not be achieved and in 2 patients with pinhole stenosis (aortic valve orifice area 0.3 cm2). These data show that aortic valve orifice area can be measured reliably using 2-dimensional transesophageal echocardiography.

Aged↗