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Biomedical subjects

A Geiger

Publications and source records attributed to A Geiger.

At least 37 records · Page 2Linked to original sources
PubMed1998

Coronary artery bypass grafting in a patient with type II heparin associated thrombopenia.

Two types of heparin-associated thrombopenia can be distinguished. Patients with the type II condition present a particularly difficult management problem when they require full anticoagulation. There is no consensus about the proper anticoagulation management for type II patients who have to undergo cardiopulmonary bypass. The case is reported of a type II heparin-associated thrombopenia patient who underwent successful aortocoronary saphenous vein grafting. Sodium-danaparoid was used for anticoagulation. The anti-factor Xa level was kept below the value reported in the literature for patients undergoing cardiopulmonary bypass. No fibrin formation was observed during the time of cardiopulmonary bypass, nor was any severe postoperative haemorrhage seen, as is frequently described in the literature.

Aged↗
PubMed1997

The neuronal NOS inhibitor L-MIN, but not 7-NINA, reduces neurotoxic effects of chronic intrastriatal administration of quinolinic acid.

Rat striata were exposed to 15 mM quinolinic acid (QUIN), or QUIN plus the nitric oxide synthase inhibitors S-methyl-L-thiocitrulline dihydrochloride (L-MIN) or 7-nitroindazole monosodium salt (7-NINA) for 21 days. Co-administration of 100 microM or 1 mM L-MIN with QUIN significantly reduced lesion volume compared to QUIN alone. Co-administration of 1 microM or 10 microM L-MIN with QUIN had no significant effect. There was no significant effect of 7-NINA co-administered with QUIN compared to QUIN alone. L-MIN reduction of lesion volume supports the contention that neuronal nitric oxide synthase is a mediator of excitotoxic injury.

Animals↗
PubMed1996

RNA aptamers that bind L-arginine with sub-micromolar dissociation constants and high enantioselectivity.

A completely randomized RNA pool as well as a degenerate pool comprised of an RNA sequence which binds citrulline with a dissociation constant of 0 muM were used to select for tight binding arginine specific RNA aptamers. A modified in vitro selection scheme, based on affinity chromatography was applied to allow the enrichment of high affinity solution binders. The selection scheme included a negative selection with the non-cognate ligand citrulline, and a heat denaturation step prior to affinity elution with an excess of the cognate ligand arginine. After 20 cycles the majority of the pools bound specifically to the arginine matrix even after denaturation/renaturation in the presence of 20 mM of a non-cognate amino acid. When denatured and eluted in the presence of 20 mM arginine, the selected RNAs quantitatively washed off the column. These RNA aptamers were cloned and sequenced. Equilibrium dialysis performed with the most abundant clone among the selected sequence revealed Kd values of 330 nM for the RNA/arginine affinity, which is nearly a 200-fold improvement over the tightest binding arginine binding RNAs known to date. Arginine recognition by this RNA is highly enantioselectice: L- arginine is bound 12 000-fold better than D-arginine. Chemical modification analysis revealed that the secondary structure of the aptamer might contain a pseudoknot motif. Our tight binding arginine aptamers join a number of natural and in vitro selected RNAs which recognize arginine. The RNAs described here compare in their binding affinity with the tightest binding RNA aptamers for low molecular weight molecules isolated in other in vitro selection experiments.

Animals↗
PubMed1996

Quality control of bioprosthetic heart valves by means of holographic interferometry.

BACKGROUND AND AIMS OF THE STUDY: Limited durability of porcine bioprostheses is mainly caused by the progressive development of calcification. We tested the hypothesis that hidden tissue anomalies or unfavorable stress concentrations of commercially available bioprostheses may lead to later calcification and dysfunction. Application of holographic interferometry for non-destructive testing of biological heart valves enables a full-field analysis of heart valves and reveals deformation irregularities of valve tissue. MATERIAL AND METHODS: We developed an accelerated calcification protocol for bioprosthetic heart valves including an accelerated pulsatile valve tester for simultaneous testing of 10 heart valves under identical conditions and a rapid synthetic calcification fluid containing a final Ca x P of 130 (mg/dl)2 in barbital buffer solution. Ten porcine bioprostheses (St. Jude Medical, Bioimplant) were assessed by holographic interferometry and subjected to the pulsatile accelerated calcification process. Distribution and amount of calcification was evaluated by microradiography after 12 x 10(6) and 19 x 10(6) cycles, respectively. Areas of irregular fringe patterns detected by holography as well as areas of calcification were calculated and compared using a personal computer. RESULTS: All tested bioprostheses had localized or extended areas with holographic irregularities and the accelerated valve testing protocol resulted in even macroscopically visible calcifications at various sites. Comparative analysis of the obtained microradiographs revealed that 74.2% +/- 6.0% of calcified leaflet areas lay within the previously detected holographic anomalies. CONCLUSIONS: Our first results show a strong correlation between holographic anomalies and calcification of porcine bioprostheses. We conclude that suitable methods for evaluation and quality control of bioprosthetic heart valves are available and seem to be predictive with regard to valve calcification.

Aortic Valve↗
PubMed1994

Formamidopyrimidine DNA glycosylase in the yeast Saccharomyces cerevisiae.

A DNA glycosylase that excises, 2,6-diamino-4-hydroxy-5N-methylformamidopyrimidine (Fapy) from double stranded DNA has been purified 28,570-fold from the yeast Saccharomyces cerevisiae. Gel filtration chromatography shows that yeast Fapy DNA glycosylase has a molecular weight of about 40 kDa. The Fapy DNA glycosylase is active in the presence of EDTA, but is completely inhibited by 0.2 M KCl. Yeast Fapy DNA glycosylase does not excise N7-methylguanine, N3-methyladenine or uracil. A repair enzyme for 7,8-dihydro-8-oxoguanine (8-OxoG) co-purifies with the Fapy DNA glycosylase. This repair activity causes strand cleavage at the site of 8-OxoG in DNA duplexes. The highest rate of incision of the 8-OxoG-containing strand was observed for duplexes where 8-OxoG was opposite guanine. The mode of incision at 8-OxoG was not established yet. The results however suggest that the Fapy- and 8-OxoG-repair activities are associated with a single protein.

Base Sequence↗
PubMed1994

A simple technique for thoracoscopic resection of lung tumors.

Mainly incited by the bushfirelike spread of endoscopic operative techniques in general surgery, thoracoscopy has become the object of new interest in the field of thoracic surgery. Location and resection of lung tumors are problematic for several reasons and so far not standardized. The main problems are pointed out. A new technique together with the instruments and their advantages is demonstrated. Future aspects are discussed.

Humans↗
PubMed1994

Single-incision implantation of cardioverter defibrillators using nonthoracotomy lead systems.

This study describes the placement of a newly designed implantable cardioverter defibrillator in a subpectoral device pocket using the incision for venous access in 16 patients undergoing implantation of an implantable cardioverter defibrillator with a nonthoracotomy lead system. The endocardial lead system consisted of a right atrial/superior vena cava defibrillation spring electrode and a right ventricular bipolar sensing/defibrillation electrode, inserted by cephalic venotomy or by puncturing of the subclavian vein. As a result of intraoperative testing using biphasic shocks the defibrillation threshold (DFT) had to be less than 24 J, otherwise an additional subcutaneous patch electrode was placed in the lateral chest wall near the cardiac apex through another incision. All patients received a nonthoracotomy lead system in combination with a subpectoral device placement. In 11 of 16 patients the endocardial leads alone were sufficient (DFT, 13.4 +/- 7.0 J), 5 of 16 patients (31%) required an additional subcutaneous patch electrode to achieve proper device function (DFT, 14.6 +/- 9.0 J). The operation lasted 93 +/- 20 minutes. This was a significant (p < 0.05) lower time consumption than standard nonthoracotomy approach combined with abdominal device placement (120 +/- 50 minutes). There were no postoperative complications. During follow-up period (average, 4 months), none of the patients reported major local symptoms, especially no device migration occurred. This approach, in contrast to an abdominal device placement, avoids another incision and subcutaneous tunneling of leads. In 11 of 16 patients defibrillator implantation by a single incision in the deltoideopectoral groove was possible.

Aged↗
PubMed1993

Cleavage and binding of a DNA fragment containing a single 8-oxoguanine by wild type and mutant FPG proteins.

A 34-mer oligonucleotide containing a single 7,8-dihydro-8-oxoguanine (8-OxoG) residue was used to study the enzymatic and DNA binding properties of the Fpg protein from E. coli. The highest rates of incision of the 8-OxoG containing strand by the Fpg protein were observed for duplexes where 8-OxoG was opposite C (*G/C) or T (*G/T). In contrast, the rates of incision of duplexes containing 8-OxoG opposite G (*G/G) and A (*G/A) were 5-fold and 200-fold slower. Gel retardation studies showed that the Fpg protein had a strong affinity for duplexes where the 8-OxoG was opposite pyrimidines and less affinity for duplexes where the 8-OxoG was opposite purines. KDapp values were 0.6 nM (*G/C), 1.0 nM (*G/T), 6.0 nM (*G/G) and 16.0 nM (*G/A). The Fpg protein also binds to unmodified (G/C) duplex and a KDapp of 90 nM was measured. The cleavage and binding of the (*G/C) duplex were also studied using bacterial crude lysates. Wild type E. coli crude extract incised the 8-OxoG containing strand and formed a specific retardation complex with the (*G/C) duplex. These two reactions were mediated by the Fpg protein, since they were not observed with a crude extract from a bacterial strain whose fpg gene was inactivated. Furthermore, we have studied the properties of 6 mutant Fpg proteins with Cys-->Gly mutations. The results showed that the 2 Fpg proteins with Cys-->Gly mutations outside the zinc finger sequence cleaved the 8-OxoG containing strand, formed complexes with the (*G/C) duplex and suppressed the mutator phenotype of the fpg-1 mutant. In contrast, the 4 Fpg proteins with Cys-->Gly mutations within the zinc finger motif neither cleave nor bind the (*G/C) duplex, nor do these proteins suppress the fpg-1 mutator phenotype.

Amino Acid Sequence↗
PubMed1993

Surgical experience with defibrillator implantation using nonthoracotomy leads.

Between October 10, 1989, and June 17, 1991, 109 patients with life-threatening ventricular arrhythmias received an implantable cardioverter-defibrillator at our institution. In 50 patients, nonthoracotomy lead systems consisting of a subcutaneous chest wall patch electrode near the cardiac apex and one (Cardiac Pacemakers, Inc: Endotak C) or two (Medtronic: Transvene) transvenous electrodes were tested. The mean ejection fraction was 0.44 +/- 0.15 with a range from 0.19 to 0.81. Twenty-four patients had a history of open heart operation. In 43 patients the nonthoracotomy lead system was implanted, whereas in 7 patients epicardial patch lead systems were required due to elevated defibrillation thresholds during nonthoracotomy lead testing. There was one perioperative death unrelated to the operative procedure (hydrocephalus internus). Hemorrhage from the subcutaneous patch pocket or the device pocket that required reintervention occurred in 4 patients. During a mean follow-up of 13 +/- 5 months (range, 4 to 26 months) no dislocation of an endocardial lead, insulation defect, or lead fracture has been observed. In 1 patient, the lead system had to be removed due to infection of the subcutaneous patch pocket. The cardiovascular survival rate was 98% at 12 and 18 months, and freedom from sudden cardiac death was 100% at 6 and 12 months. In conclusion, defibrillator implantation using nonthoracotomy lead systems is feasible with a success rate of 86%, and during short-term follow-up no problems related to the lead system such as dislocation, fracture, or insulation defect have occurred.

Adolescent↗
PubMed1991

Quantitative assessment of the effects of 'inodilators' on the myocardium in patients without primary cardiac insufficiency after coronary surgery: Part I--Amrinone.

The positive inotropic and peripheral vasodilating effect of amrinone has been measured in 20 patients without manifest cardiac insufficiency during the early (8-18 h postoperative) and late (18-48 h postoperative) recovery phase after coronary surgery. On conclusion of the surgical intervention first the aortocoronary bypass flow was compared during dobutamine and amrinone administration. It increased by 88% with amrinone and by 19% with dobutamine. Then a needle force probe was implanted in the myocardium. Directly measured local myocardial force increased not significantly by 3.5% after the first and by 5.1% after the second bolus injection of 2 mg/kg amrinone. The rate of myocardial contraction increased by 18.7% and 12%. The rate of relaxation decreased by 5.3% after the first and increased by 15% after the second injection. Mean pulmonary arterial pressure fell from 18.5 to 15.5 mmHg and from 19.7 to 17 mmHg. Cardiac output increased by 23% after the first and by 20% after the second injection. Heart rate rose from 88 to 99 bpm and from 86 to 94 bpm. Total peripheral resistance fell from 1,035 to 706 dyn*s*cm-5 and from 1,036 to 819 dyn*s*cm-5. The systolic arterial pressure fell from 132 to 116 mmHg after the first injection and did not change after the second injection. Amrinone was found to be a powerful peripheral vasodilator with a mild positive inotropic action. The variations in the effects between the early and late recovery phases mainly reflect a progressive haemodynamic stabilization with a decreasing tendency toward hypotensive disregulation. Careful consideration has to be paid to a properly balanced filling of the vascular system before administering amrinone.

Adult↗
PubMed1991

Quantitative assessment of the effects of 'inodilators' on the myocardium in patients without primary cardiac insufficiency after coronary surgery: Part II--Enoximone.

Twelve patients undergoing routine coronary artery surgery received a bolus injection of 1.5 mg/kg enoximone between 8 and 18 hours and again between 18 and 48 hours after operation. No patient showed clinically manifest myocardial heart failure. The haemodynamic and cardiodynamic response to enoximone was quantified over a 30 minutes period following injection. Local myocardial developed force increased by 24 +/- 7% after the first and by 12 +/- 6% after the second injection. The rate of myocardial contraction increased by 50 +/- 14% and 15 +/- 10%, respectively, and relaxation increased by 35 +/- 14% and 22 +/- 19%. There was a decrease in total peripheral resistance of 38.8 and 42.9%, and an increase in heart rate of 11 and 15%. The mean arterial pressure showed small reductions from 73 (+/- 3.7) to 67 (+/- 2.6) mmHg for the first dose and from 83 (+/- 3.1) to 78.4 (+/- 2.8) mmHg for the second. Central venous and pulmonary artery pressures were essentially unaltered. The substantial positive inotropic effect of enoximone has been shown to match its peripheral vasodilatory activity, so that in the normovolaemic patient there is a clinically insignificant small fall in mean arterial pressure.

Aged↗
PubMed1990

High frequency of fibromyalgia in patients with chronic fatigue seen in a primary care practice.

We administered a standardized history questionnaire and performed a tender point examination on 27 patients with debilitating fatigue of at least 6 months duration, seen in a primary care practice, as well as on 20 patients with fibromyalgia. Sixteen of the 27 patients with chronic fatigue met the full criteria for the working case definition of chronic fatigue syndrome (CFS). Eight patients with chronic fatigue denied having any current persistent, diffuse musculoskeletal pain, and their tender point scores were similar to those in 10 normal control subjects. In contrast, 19 patients with chronic fatigue (70%) had persistent, diffuse musculoskeletal pain. The results of their tender point examinations were similar to those of the patients with fibromyalgia. Thus, the majority of these patients with debilitating chronic fatigue, including those who met criteria for CFS, met the historical and tender point diagnostic criteria for fibromyalgia. The presence of current musculoskeletal pain will identify those CFS patients who have fibromyalgia.

Adult↗
PubMed1988

Metabolites of microorganisms. 247. Phenazines from Streptomyces antibioticus, strain Tü 2706.

From a strain of Streptomyces antibioticus seven yellow phenazines were isolated. The antibacterially most active antibiotic was identified as (-)-saphenamycin, a second one with compound DC-86-Y (saphenic acid). Three compounds were new: Saphenic acid methyl ether, 6-acetylphenazine-1-carboxylic acid and an inseparable mixture of fatty acid esters of saphenic acid. Two simple phenazines were phenazine-1-carboxylic acid (tubermycin B) and unsubstituted phenazine, which was isolated for the first time from a microorganism.

Microbial Sensitivity Tests↗
PubMed1987

[Importance of emission computed tomography in chronic disorders of the knee joint].

Twenty-eight patients with chronic abnormalities of the knee were examined by 3-phase scintigraphy and ECT. The unobscured images produced by ECT provide additional information for evaluating the localisation, extent and activity of the lesions. The diagnosis of meniscus abnormalities in particular revealed pathognomonic patterns. The indications and value of ECT was compared with other diagnostic measures and particularly with invasive techniques (arthroscopy and arthrotomy).

Humans↗
PubMed1987

The effect of a protein on the radiolysis of DNA studied by gel filtration.

Double stranded DNA from calf thymus was irradiated in the presence of bovine serum albumin with a ratio of 1:10 in weight under aerobic and anaerobic conditions. The irradiated biomolecules were separated by gel filtration on Sepharose Cl-2B with and without sodium dodecylsulphate. By scavenging OH-radicals the protein protects DNA, but in contrast to radiolysis of DNA in phosphate buffer, in the presence of serum albumin oxygen enhances the degradation of DNA. Radiolysis under N2 leads to crosslinking of serum albumin to DNA with higher yields at pH 5 than at pH 7. Oxygen largely prevents crosslinking.

Chemical Phenomena↗