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Biomedical subjects

B Schneider

Publications and source records attributed to B Schneider.

At least 19 recordsLinked to original sources
PubMed1992

Crystal and molecular structure of a DNA fragment containing a 2-aminoadenine modification: the relationship between conformation, packing, and hydration in Z-DNA hexamers.

The crystal and molecular structure of d(CGUA'CG)2 (where A' is 2-aminoadenine) has been determined and refined to an R factor of 13.8% for data 8.0-1.3 A. The structure is very similar to the original Z-DNA structures with the sequence d(CGCGCG)2 [Gessner, R. V., Frederick, C. A., Quigley, G. J., Rich, A., & Wang, A. H.-J. (1989) J. Biol. Chem. 264, 7921] and shows that the substitution of 2-aminoadenine-uracil base pairs in the two central steps is consistent with Z-DNA formation. In addition, we show how waters mediating intermolecular interactions may help to explain the ZI-ZII conformational pattern found in many Z-DNA structures.

2-Aminopurine↗
PubMed1992

Derived amino acid sequences of the nosZ gene (respiratory N2O reductase) from Alcaligenes eutrophus, Pseudomonas aeruginosa and Pseudomonas stutzeri reveal potential copper-binding residues. Implications for the CuA site of N2O reductase and cytochrome-c oxidase.

The nosZ genes encoding the multicopper enzyme nitrous oxide reductase of Alcaligenes eutrophus H16 and the type strain of Pseudomonas aeruginosa were cloned and sequenced for structural comparison of their gene products with the homologous product of the nosZ gene from Pseudomonas stutzeri [Viebrock, A. & Zumft, W. G. (1988) J. Bacteriol. 170, 4658-4668] and the subunit II of cytochrome-c oxidase (COII). Both types of enzymes possess the CuA binding site. The nosZ genes were identified in cosmid libraries by hybridization with an internal 1.22-kb PstI fragment (NS220) of nosZ from P. stutzeri. The derived amino acid sequences indicate unprocessed gene products of 70084 Da (A. eutrophus) and 70695 Da (P. aeruginosa). The N-terminal sequences of the NosZ proteins have the characteristics of signal peptides for transport. A homologous domain, extending over at least 50 residues, is shared among the three derived NosZ sequences and the CuA binding region of 32 COII sequences. Only three out of nine cysteine residues of the NosZ protein (P. stutzeri) are invariant. Cys618 and Cys622 are assigned to a binuclear center, A, which is thought to represent the CuA site of NosZ and is located close to the C terminus. Two conserved histidines, one methionine, one aspartate, one valine and two aromatic residues are also part of the CuA consensus sequence, which is the domain homologous between the two enzymes. The CuA consensus sequence, however, lacks four strictly conserved residues present in all COII sequences. Cys165 is likely to be a ligand of a second binuclear center, Z, for which we assume mainly histidine coordination. Of 23 histidine residues in NosZ (P. stutzeri), 14 are invariant, 7 of which are in regions with a degree of conservation well above the 50% positional identity between the Alcaligenes and Pseudomonas sequences. Conserved tryptophan residues are located close to several potential copper ligands. Trp615 may contribute to the observed quenching of fluorescence when the CuA site is occupied.

Alcaligenes↗
PubMed1992

Polar secretion of endothelin-1 by cultured endothelial cells.

The aim of this study was to determine the permeability of endothelial monolayers for endothelin-1 and a possible directionality of the endothelin-1 secretion process. Human umbilical vein endothelial cells were cultured on acellular amniotic membranes, dividing the tissue culture wells into an apical (luminal) and a basolateral (abluminal) compartment. Whereas in the absence of endothelial monolayers 44.9 +/- 2.3 and 43.5 +/- 2.0% of the unilaterally added endothelin-1 permeated from the apical to the basolateral side and from the basolateral to the apical side, respectively, only 6.5 +/- 0.6 and 6.6 +/- 0.4% diffused in the presence of endothelial cells. Analyzing endothelin-1 secretion, approximately 80% of the total amount of synthesized endothelin-1 was found in the basolateral compartment; thrombin (10 units/ml) stimulated the production of endothelin-1 approximately 2-fold, but did not change the relative distribution of endothelin-1 between the apical and basolateral compartments. In the presence of dexamethasone (10(-7) M), a decrease in the level of endothelin-1 was found in the apical compartment, whereas the total amount of endothelin-1 produced was not affected. Dexamethasone did not influence the permeability of human umbilical vein endothelial cell monolayers for endothelin-1. These results strongly support the hypothesis that endothelin-1 is a local paracrine regulator of vasotone.

Amnion↗
PubMed1992

Prognostic impact of karyotype and immunologic phenotype in 125 adult patients with de novo AML.

One hundred-twenty-five adult patients with de novo acute myeloid leukemia (AML) were treated according to a standard 7 + 3 induction regimen. Karyotype and immunological phenotype of blasts examined prior to treatment were correlated with each other, with response to treatment and duration of survival. The following monoclonal antibodies (mAbs) were used for immunological phenotyping: VIM-D5 (CD15), MY7 (CD13), MY9 (CD33), VIM-2 (CDw65), VIM-13 (CD14), 63D3 (CD14), VID-1 (anti HLA-DR), WT1 (CD7), CLB-Ery3 (antiblood group H antigen), C17-27 (CD61), and an antiserum against TdT. Despite a considerable overlap between the individual groups, patients with specific aberrations as defined by the MIC classification (n = 39) showed distinct, characteristic, myeloid or myelomonocytic immunophenotypes. In M2/t(8;21) there was a significant association with negativity to CD13, in M3/t(15;17) with negativity to CD15 and HLA-DR, whereas in M4/inv(16) expression of blood group H antigen was unexpectedly found. The response to therapy, as well as rate of complete remission as duration of survival, was better in patients with M2/t(8;21), M3/t(15;17), and M4Eo/inv(16) as compared to all other patients and significantly worse in patients with M5a/t/del(11)(q23). In 35 patients with normal karyotype and 16 patients with cytogenetic anomalies not presently associated with FAB subtypes the expected correlations of rather immature myeloid immunologic phenotypes with M1 and M2 morphology and CD14 expression in monoblastic leukemias was found. Remission rate and survival were significantly worse in 19 patients with complex nonrandom aberrations, where blast cell expression of blood group H antigen and of TdT were significantly increased.

Adolescent↗
PubMed1992

[Therapy of respiratory tract diseases with N-acetylcysteine. An open therapeutic observation study of 2,512 patients].

STUDY DESIGN: Open therapeutic observational study. PATIENTS: 2,510 patients with acute and chronic bronchitis, bronchial asthma, and emphysema. TREATMENT: 4-week treatment with N-acetylcystein administered three times a day 200 mg dissolved (n = 1734) or undissolved (n = 608) or at some other, usually lower, dosage (n = 173). During the f-week treatment phase, any other drugs being taken were neither discontinued nor changed. TARGET PARAMETERS: In addition to 1-sec capacity (FEV1), various, mainly subjective, parameters were noted, in particular coughing, amount and nature of expectorate. RESULTS: for the evaluation, the patients were assigned either to the acute bronchitis or the chronic bronchitis group; the latter group also contained patients with other diseases, such as asthma and emphysema, since such conditions often presented simultaneously. All selected parameters clearly improved under treatment, equally in the acute and chronic bronchitis groups. As expected, the mucolytic effect was very pronounced, the 1-sec capacity increased significantly. No major difference was to be found in the results observed in patients on and those not on other additional medication.

Acetylcysteine↗
PubMed1992

Pharmacokinetics and bioavailability of spiramycin in pigs.

The pharmacokinetics of spiramycin in pigs were investigated after intravenous and oral administration. The potential therapeutically effective blood level was established after a single administration and examined in a subsidiary five day study. The rapid intravenous injection of 25 mg spiramycin/kg bodyweight produced marked salivation in all the test animals. The elimination half-life (2.3 +/- 1.2 hours) was relatively short, in accordance with the total body clearance rate (27.3 +/- 10.1 ml/minute/kg). The high volume of distribution (5.2 +/- 2.2 litres/kg) was due to the accumulation of the drug in the body tissues. The maximum plasma concentration (4.1 +/- 1.7 micrograms/ml) after oral administration of 85 to 100 mg spiramycin/kg bodyweight was reached after 3.7 +/- 0.8 hours and the half-life of the elimination phase was 6.0 +/- 2.4 hours. The oral bioavailability was 45.4 +/- 23.4 per cent. Ad libitum feeding of a diet containing 2550 mg spiramycin/kg produced a steady state concentration of 0.96 +/- 0.27 micrograms/ml. This plasma concentration would provide a potentially therapeutically effective blood concentration against Mycoplasma species, Streptococcus species and Staphylococcus species.

Administration, Oral↗
PubMed1992

[Sympathetic reflex dystrophy. Effectiveness of physical therapy treatment of Sudeck's syndrome].

To investigate the impairment of patients with reflex sympathetic dystrophy syndrome (RSDS) and to establish the effectiveness of two physiotherapeutic regimens in the treatment of this entity, 54 RSDS patients were examined clinically, radiologically and scintigraphically an average of 112 days after the triggering event. The patients were assigned to either of two treatment groups in accordance with the results of preliminary scintigraphic examinations. After physiotherapy comprising exercises and cryotherapy either with or without galvanic stimulation, a significant therapeutic effect on clinical and scintigraphic parameters was found in both treatment groups. Scanning, in combination with clinical diagnostic measures proved a valuable tool in the diagnostic evaluation, selection of treatment and follow-up in patients with RSDS.

Combined Modality Therapy↗
PubMed1992

Cholinergic baroreflex vasodilatation: defect in heart transplant recipients due to denervation of the ventricular baroreceptor.

Afferent denervation of the ventricular baroreceptor may impair reflex vasodilatation after heart transplantation. This may alter the regulation of blood pressure and contribute to arterial hypertension. A baroreceptor-loading procedure was performed in 23 heart transplant recipients with cyclosporine A immunosuppression and 11 control subjects using a continuous infusion of increasing doses of angiotensin II (15 and 30 ng/kg.min). After m-cholinoceptor blockade the procedure was repeated in order to study the contribution of cholinergic effects on vasodilatation in humans. Instantaneous vascular resistance was calculated as the ratio of mean blood pressure to stroke volume as evaluated by echocardiography. When heart transplant recipients were compared with control subjects, infusion of 30 ng/kg.min of angiotensin II resulted in an increase in mean blood pressure of 43 +/- 20 vs 31 +/- 13 mm Hg (p less than 0.05) and an increase in instantaneous resistance of 1.21 +/- 0.61 vs 0.65 +/- 0.38 mm Hg/ml (p less than 0.01), respectively. M-cholinoceptor blockade with atropine (0.015 mg/kg) did not produce any change in blood pressure or resistance response to angiotensin II in heart transplant recipients. However, m-cholinoceptor blockade resulted in a significantly increased blood pressure and resistance response to angiotensin II in control subjects, which was similar to the response in heart transplant recipients to angiotensin II alone: The increase in mean blood pressure during administration of 30 ng/kg.min angiotensin II amounted to 47 +/- 11 mm Hg, and the increase in instantaneous resistance to 1.13 +/- 0.48 mm Hg/ml (for both, p less than 0.001 vs control subjects without atropine; p = not significant vs heart transplant recipients).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Cardiac involvement in systemic sclerosis.

OBJECTIVE: To assess the incidence and extent of cardiac involvement in systemic sclerosis (SSc) patients with no apparent cardiac symptoms. METHODS: Surface electrocardiography, ambulatory electrocardiography, radionuclide ventriculography, myocardial scintigraphy, and echocardiography were performed in 18 patients. RESULTS: These studies demonstrated ventricular tachycardia in 1 patient, nonsustained ventricular tachycardia in 5, supraventricular tachycardia in 6, decreased left ventricular ejection fraction in 2, decreased right ventricular ejection fraction in 8, and stress-induced reversible myocardial perfusion abnormalities in 6. CONCLUSION: These observations demonstrate a high rate of cardiac abnormalities in SSc patients without cardiac symptoms.

Aged↗
PubMed1992

Hydration of DNA bases: analysis of crystallographic data.

We present a systematic analysis of water structure around nucleic acid bases. We have examined 28 crystal structures of oligonucleotides, and have studied the patterns of water around the four bases, guanine, cytosine, adenine, and thymine. The geometries of water positions were calculated up to 4.00 A from base atoms. We have found conformation-dependent differences in both the geometry and extent of hydration of the bases.

Adenine↗
PubMed1992

Erb:YAG and Hol:YAG laser ablation of meniscus and intervertebral discs.

Erb:YAG and Hol:YAG laser ablation rates of fibrocartilage and nucleus pulposus were measured in vitro simulating clinical conditions. After ablation macroscopic and microscopic appearance of the ablation site was investigated. Hol:YAG and Erb:YAG laser mean ablation rates increased almost linearly with rising energies, showing higher total ablation rates for the Hol:YAG laser due to its higher achievable energy density. At comparable energy densities the Erb:YAG laser appears to be more effective with respect to the corresponding ablation rates. Consequently, the ablational threshold proved to be lower for the Erb:YAG laser. Whereas during Hol:YAG laser ablation, some smoke formation and considerable tissue shrinking occurred, these effects could not be observed during Erb:YAG laser ablation. Consequently macroscopic and microscopic inspection showed some thermal damage after Hol:YAG and only minimal alterations after Erb:YAG laser ablation. Adjacent thermal damage was determined and proved to be lower for the Erb:YAG laser. In our opinion the characteristics of each laser system provide certain advantages for special clinical indications.

Aluminum Silicates↗
PubMed1992

Studies on the effect of two angiotensin-converting enzyme inhibitors, captopril and cilazapril, on platelet and vascular prostaglandin metabolism in vivo.

We have studied in 12 healthy volunteers the effects of two angiotensin-converting enzyme (ACE) inhibitors, captopril and cilazapril, on vascular and platelet prostaglandin metabolism, in a double-blind, placebo-controlled, randomized cross-over study. Formation of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TxB2) was measured locally at the site of a microvascular injury. Similar amounts of TxB2 and 6-keto-PGF1 alpha were generated following administration of either ACE inhibitor as compared to placebo. It is concluded that neither captopril nor cilazapril significantly influence vascular and platelet prostaglandin metabolism.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

Urodilatin: a new peptide with beneficial effects in the postoperative therapy of cardiac transplant recipients.

Renal failure after heart transplantation (HTx) still remains a serious problem, especially when cyclosporin A is used for immunosuppression in the early postoperative therapy. To preserve good renal function without reducing immunosuppressive cyclosporin A treatment, we administered urodilatin (CDD/ANP-95-126) in a long-term, low-dose infusion in addition to the usual medication after heart transplantation. From November 1990 to June 1991, 51 patients (46 male and 5 female; mean age 48 years) were treated with a 6-20 ng/kg bw.min infusion for 96 h after HTx. The renal function and hemodynamic parameters of these urodilatin-treated patients were compared in this sequential study with 40 patients (33 male and 7 female; mean age 49 years) who had undergone HTx previously from May to November, 1990, as controls. In this phase IIa study, both groups did not differ significantly with respect to age, sex, indication for HTx, and preoperative renal function. In comparison with controls patients treated with urodilatin had a significantly better renal function: a reduction in the peak plasma creatinine (PC values day 4: 1.5 +/- 0.11 vs. 2.19 +/- 0.19 mg/dl; P = 0.002), a lower peak serum urea (SU values day 4: 109 +/- 8 vs. 154.7 +/- 8.94 mg/dl; P = 0.0036), and a lower incidence of hemodialysis (6% vs. 10%) were observed. Adequate diuresis was maintained in spite of the reduction of furosemide by more than 60% (P = 0.005) on each day of urodilatin infusion in comparison with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1992

Diagnostic value of transesophageal echocardiography in atrial septal aneurysm.

Transthoracic and transesophageal echocardiography was performed in 40 consecutive adult patients with an atrial septal aneurysm. In 11 (27%) of 40 patients transthoracic echocardiography failed to demonstrate the lesion and the diagnosis was established by the transesophageal approach only. Interatrial shunting, assessed by echocardiographic contrast study and/or color flow mapping, was detected in 13 (54%) of 24 patients on transthoracic imaging and in 29 (76%) of 38 patients during transesophageal echocardiography. Identification of multiple fenestrations (n = 9) and thrombi within the aneurysm (n = 2) could be achieved only by transesophageal ultrasound. A cerebrovascular event of suspected embolic origin occurred in 20 (50%) of 40 patients; 11 (55%) of the 20 patients had repeated cerebral events. Except for mitral valve prolapse in 2 patients and spontaneous left atrial contrast phenomenon in 1 patient no other potential cardiac source of embolism could be identified by transesophageal echocardiography. A marked thickening of the aneurysm was present in 14 (70%) of 20 patients with a cerebrovascular event versus only 4 (20%) of 20 patients without a cerebrovascular event (p less than 0.01). The mechanism of embolization may be both primary thrombus formation within the aneurysm and paradoxical embolization through an interatrial communication as suggested by the findings on transesophageal ultrasound in 2 patients. Although the patients of this study represent a highly selected group it may be concluded that atrial septal aneurysm is a cardiac abnormality with embolic potential. Transesophageal echocardiography has to be regarded the imaging method of choice for evaluation of this lesion.

Adult↗
PubMed1992

[Space closure with T loops (Burstone)--a clinical study].

The theoretically favourable aspects of orthodontic space closure with segmented arch technique and the T-loop type A are clinically reproducible. In our study of eleven patients we found for the isolated canine retraction, as well as for the en masse retraction, controlled types of movement for the active units and maximum anchorage situations for the passive units produced by the torquing force. Because of these good anchorage conditions space closure could be done without headgear. The level of the anchorage segments was negligibly influenced but in the anterior segments a marked tilting was found in several cases. Besides other factors the intrusive force of the T-loops type A must be considered. As a rule the positioning of the T-loop between central and lateral incisor is to be recommended.

Activator Appliances↗
PubMed1992

On binocular unmasking of signals in noise: further tests of the summation hypothesis.

Observers detected the presence of Gabor signals in fields of two-dimensional broadband Gaussian noise encased by a frame of uniform noise. These images, displayed for 1 sec on a t.v. monitor, were seen through a simple-lens stereoscope. While the left and right eye were presented with the same view of the noise frame, the right-eye Gaussian noise field was right-shifted relative to the left-eye's by 20.3 min arc along the horizontal axis. Useful interocular cues concerning signal presence were not available in one set of trials (control condition), the right-eye signal being displaced by the same amount and direction as that of the noise. In another set of trials (experimental condition), such cues were made available by presenting the Gabor signals in exactly corresponding locations in the centres of the two frames. We tested the predictions of a model in terms of which the usefulness of binocular cues for the "unmasking" of the signal rests upon the characteristics of the summed monocular inputs, specifically the signal-to-noise ratio in the summed pattern. The two-dimensional power spectrum for the summed Gaussian noises shows "notches" at specific horizontal- and vertical-frequency intersections where the power density is at or close to zero. If the spectral power in the summed Gabor signal is concentrated at these locations in the experimental condition, the signal should be unmasked. Accordingly, the spatial frequencies and orientation of three Gabor patterns were chosen in such a way that the power density of the summed signals would fit in notches of the power spectrum of the summed noise, while it would overlap with a noise peak for a fourth Gabor signal. The findings were consistent with the summation hypothesis: binocular masking level differences of up to 18 dB were observed, but only for the three signals "falling" in the two-dimensional noise notches.

Adult↗
PubMed1992

Low temperature structures of dCpG-proflavine. Conformational and hydration effects.

The structure of the complex of dCpG with proflavine was determined using x-ray data taken at -130 degrees C (low temperature) and at -2 degrees C (cold temperature) and compared with the structure of the complex determined previously at room temperature (Shieh, H. S., H. M. Berman, M. Dabrow, and S. Neidle. 1980. Nucleic Acids Res. 8:85-97). Low temperature was refined with 5,125 reflections between 8.0 and 0.93 A, Anisotropically modeled temperature factors were used for DNA/drug atoms and isotropic ones for water oxygens to R factor of 12.2% in P2(1)2(1)2; a = 32.853, b = 21.760, c = 13.296 A. Cold temperature was refined isotropically with 2,846 reflections 8.0-0.89 A to R = 15.1% in P2(1)2(1)2; a = 32.867, b = 22.356, c = 13.461 A. Both structures are very similar to the room temperature one, though some important differences were observed: one guanine sugar moiety is disordered and additional water molecules have been located that give rise to infinite polyhedral hydration networks.

Biophysical Phenomena↗