Biomedical subjects

A Moritz

Publications and source records attributed to A Moritz.

At least 109 records · Page 6Linked to original sources

PubMed1997

[Platelet count in the cat].

The technique of collecting blood samples is primarily responsible for the appearance of platelet-agglomeration in cats. Blood obtained by the conventional way ("one syringe technology", drips of blood) caused in 52% of the cases an activation of the large and therefore active thrombocytes however. Rejection of the first 2-5 ml blood for the platelet count ("two syringe technology") reduced the rate of platelet-agglomeration significantly. No big differences in platelet-agglomeration were found with regard to the place used for collecting blood (V. cephalica antebrachii/V. jugularis). Platelet-agglutination was observed with Li-Heparin, K-EDTA, Na-Citrat or ACD anticoagulated blood samples. Citrat (Na-Citrat, ACD) seemed to have a stabilizing effect on feline thrombocytes as has been described for human thrombocytes. The platelet count in cats should be performed within 30 minutes.

Animals↗

PubMed1996

Complete repair of PA-VSD with diminutive or discontinuous pulmonary arteries by transverse thoracosternotomy.

BACKGROUND: Optimal treatment and the optimal sequence of surgical and interventional steps to correct pulmonary atresia with ventricular septal defect and hypoplastic or discontinuous intrapericardial pulmonary arteries is still under discussion. Collateral arteries may be hardly accessible through median sternotomy at total correction. Bilateral transsternal thoracotomy gives wide access to the heart, both pleural spaces and hilar structures. METHODS: We used this incision for total correction of pulmonary atresia with ventricular septal defect in 6 patients. Three had Blalock-Taussig shunts placed previously, and intrapericardial pulmonary arteries were absent in all patients but 1, in whom they were hypoplastic. Central pulmonary arteries were enlarged with pericardial patches or replaced with tube grafts; the number of unifocalized collateral arteries varied between two and eight. RESULTS: One patient died of respiratory failure and sepsis (16.7%). Oxygen saturation increased from 76% (range, 65% to 88%) preoperatively to 96% (range 91% to 99%) postoperatively. Mean postoperative pulmonary artery pressure was 30 mm Hg (range, 28 to 34 mm Hg). One patient had to be reoperated on through the same incision due to scarring and shrinkage of the peripheral anastomoses. Six months after operation 2 patients are in New York Heart Association functional class I and 2 are in class II. CONCLUSIONS: Transverse thoracosternotomy gives excellent access to the anatomical structures necessary to correct complex cases of pulmonary atresia with ventricular septal defect and may reduce the number of surgical procedures.

Abnormalities, Multiple↗

PubMed1996

[Retinal hemodynamics in diabetic retinopathy before and after laser coagulation].

PATIENTS AND METHODS: By means of video-fluoresce in angiography arm-retina-time (ART) and retinal arteriovenous passage time (AVP) were measured in order to determine the effect of panretinal laser-coagulation on retinal circulation in patients with diabetic retinopathy. 55 patients with either preproliferative (n = 29) or proliferative (n = 26) retinopathy we reexamined before, 3-9 weeks after panretinal laser-coagulation (mean: 848 burns, 0.5 mm diameter), and 0.5-3 years later. RESULTS: The ART of the diabetic patients was in the normal range and showed no differences among the three measuring times. The retinal AVP was significantly prolonged in the three measuring times (nasal and temporal) when compared to normals. Laser-coagulation showed no significant effect on AVP in the temporal branches, whereas in the nasal branches AVP decreased from 2.38 +/- 0.69 s (before laser-coagulation) to 2.11 +/- 0.68 s (3-9 weeks after treatment) and 2.06 +/- 0.67 s (0.5-3 years after treatment) (p < 0.01). In branches with neovascularisation (n = 24) a pronounced decrease of AVP from 2.60 +/- 0.70 s to 1.96 +/- 0.61 s and 2.09 +/- 0.64 s (p < 0.01) was detected. CONCLUSIONS: Thus, laser-coagulation leads to a faster circulation in areas with laser burns within 3-9 weeks post-treatment.

Adult↗

PubMed1996

Alternatives in enamel conditioning: a comparison of conventional and innovative methods.

When composite restorative materials are used, conditioning of the enamel surface is necessary to achieve adequate retention of the composite material. Aside from conventional acid etching, laser treatment and pretreatment with kinetic cavity preparation technique are available. In our study, we compared the different methods using scanning electron microscopy and measurements of tensile strength. The results obtained using both laser treatments of Nd:YAG and Er:YAG lasers and kinetic cavity preparation were comparable to those obtained with the acid etching technique.

Acid Etching, Dental↗

PubMed1996

The advantage of CO2-treated dental necks, in comparison with a standard method: results of an in vivo study.

Various methods are used for treatment of hypersensitive dental necks. They all aim to seal exposed dentinal tubules, which are open toward the oral cavity and transmit stimuli to the sensitive nerve endings of the tooth pulp. The main sealing materials are fluoride preparations, strontium chloride, and hydroxyapatite. However, these materials must be applied periodically to achieve permanent freedom from pain. Since the introduction of laser technology into dentistry, efforts have been made to treat dentine hypersensitivity with the laser. An in vitro study revealed that CO2 laser irradiation results in almost complete closure of the dentinal tubules in the dental neck region. In the present in vivo study, the efficacy of laser treatment was examined in 72 patients with dentine hypersensitivity and 72 control patients over a period of 12 weeks. When success was defined as complete freedom from pain, the success rate in the laser group was 94.5%; when marked pain relief was included in the definition of treatment success, 98.6% of the patients were treated successfully. Treatment of the control group with conventional dental neck fluoridation resulted in no marked improvement. Laser Doppler measurements of pulpal blood flow immediately before and after treatment revealed no effects of laser irradiation on pulpal blood flow. Dentine samples were obtained from the dental necks 6 weeks after laser treatment and examined with atomic absorption spectroscopy (AAS). Tin was present in the samples, which suggests that the combined laser treatment and fluoridation result in permanent integration of fluoride in the dentine surface.

Adult↗

PubMed1996

Bactericidal effect of the Nd:YAG laser in in vitro root canals.

The current study investigates the bactericidal effect of a pulsed Nd:YAG laser on 40, classically prepared, in vitro root canals under standardized conditions. The output of the device including quartz fiber was measured before and after every treatment to exclude any technical faults. A 300-micron fiber was used for the anterior teeth and a 200-micron fiber for the posterior teeth. The Enterococcus faecalis bacteria, as gram-positive cocci, display a heat tolerance in the upper range of the bacilli that can be found in the endodontology and the concentration also reflects the in vivo conditions. The results are quoted in "log kills" in accordance with the work of Rooney et al. On average, 99.91% of the Enterococcus faecalis bacteria injected into the root canals prepared in vitro could be eliminated (97.12% minimum, 99.9997% maximum). This setup suggests that the bactericidal effect of laser therapy in the framework presented here can also be achieved in vivo in clinical cases.

Colony Count, Microbial↗

PubMed1996

Selectively enhanced cellular signaling by Gi proteins in essential hypertension. G alpha i2, G alpha i3, G beta 1, and G beta 2 are not mutated.

Recent studies have shown an enhanced signaling capacity of receptors coupled to pertussis toxin (PTX)-sensitive guanine nucleotide-binding proteins (G proteins) in immortalized B lymphoblasts from patients with essential hypertension. In the present study, we analyzed (1) whether such alterations would also be expressed in nontransformed cells of these individuals and (2) whether other G protein-mediated signaling pathways were also altered. Therefore, we established primary cultures of skin fibroblasts from previously characterized normotensive and hypertensive individuals (NT and HT cells, respectively). [Ca2+]i rises induced by lyso-phosphatidic acid (LPA), thrombin, and sphingosine-1-phosphate as well as the formation of inositol 1,4,5-trisphosphate and [3H]thymidine incorporation evoked by LPA were PTX sensitive and enhanced twofold in HT fibroblasts. In contrast, cellular responses induced by bradykinin, endothelin-1, and angiotensin II (all PTX insensitive) were similar in NT and HT cells. Formation of cAMP induced by stimulation of Gs with isoproterenol was identical in NT and HT cells. Western blot analysis yielded no evidence for an overexpression of G alpha i2, G alpha i3, G beta 2, and G beta 4. Furthermore, sequencing of cDNAs encoding for the ubiquitously expressed PTX-sensitive G protein subunits G alpha i2, G alpha i3, G beta 1, and G beta 2 from NT and HT cell lines yielded no evidence for mutations in these genes. Although the molecular mechanisms remain to be defined, these data support the concept of a selective enhancement of signal transduction via PTX-sensitive G proteins in essential hypertension.

Base Sequence↗

PubMed1996

Impact of glutaraldehyde on calcification of pericardial bioprosthetic heart valve material.

BACKGROUND: This study was conducted to investigate the impact of the preservation method of bioprosthetic heart valve materials on calcification rates and biocompatibility of the biologic tissue. METHODS: In subcutaneous rat implants, conventionally preserved bioprosthetic heart valve material was compared with bovine pericardium that was treated with L-glutamic acid to reduce residual glutaraldehyde released from the fixed tissue. Both these methods were compared with bovine pericardium that was stabilized by a dye-mediated photooxidation reaction without glutaraldehyde. Biocompatibility of these biomaterials was tested in vitro using human endothelial cell cultures. RESULTS: Conventionally preserved bovine pericardium with a high amount of glutaraldehyde incorporated into the tissue resulted in severe calcification 63 days after subcutaneous implantation in rats (165.4 +/- 20 mg Ca2+/g dry weight). Postfixation treatment with L-glutamic acid, which reduces free, unbound aldehyde groups, showed a significant decrease in calcification (89.6 +/- 14 mg Ca2+/g dry weight). Glutaraldehyde-free preservation by dye-mediated photooxidation showed no calcification after 63 days of subcutaneous implantation (1.0 +/- 0.4 mg Ca2+/g dry weight). Regular endothelial cell proliferation was observed on photooxidized and L-glutamic acid-treated tissue, whereas conventionally treated tissue caused endothelial cell death. CONCLUSIONS: This study underlines the detrimental role of glutaraldehyde in the calcification process of bioprosthetic heart valve materials and emphasizes alternative preservation methods that reduce or avoid the use of glutaraldehyde.

Animals↗

PubMed1995

Echocardiographic results after repair of incompetent bicuspid aortic valves.

INTRODUCTION: Valve-related complications and the necessity of anticoagulation after aortic valve replacement have led to new operative techniques for correction of aortic insufficiency (AI). Fourteen patients with bicuspid aortic valves and significant AI underwent valve repair. METHODS: Transthoracic echocardiography was performed preoperatively and 1 week postoperatively and in 10 patients who have come to follow-up so far. Operative procedures were triangular resection of one leaflet in all patients. Five patients had pericardial patch plasty in addition. RESULTS: Mean AI decreased significantly from grade 3.5 +/- 0.1 preoperatively to 0.5 +/- 0.1 postoperatively (p < 0.001). Postoperatively, 10 patients had no or trivial AI (0 to 0.5), and 2 patients had mild AI (1 to 1.5). Within the first week, 2 patients were reoperated on after echocardiography established significant AI. Ventricular dimensions decreased from preoperative to postoperative and were normal after 1 year. At follow-up, 7 patients show no change of AI; in 3 patients AI increased to moderate because of dilatation of the sinus of Valsalva or the sinotubular junction. CONCLUSIONS: Reconstruction of bicuspid aortic valves is feasible with good early results. Echocardiography shows that asymmetric sinuses may lead to early perioperative failures and postoperative dilatation of the proximal aorta to increasing AI. Operative techniques may have to consider the pathology of the proximal aorta.

Adolescent↗

PubMed1995

Compliance mismatch and formation of distal anastomotic intimal hyperplasia in externally stiffened and lumen-adapted venous grafts.

OBJECTIVE: Compliance and formation of distal anastomotic intimal hyperplasia (DAIH) were investigated in externally stiffened venous grafts of varying calibers. METHODS: 36 femoropopliteal reconstructions were performed in 18 sheep. The autologous venous grafts were inserted into tubes made of Dacron mesh to achieve compliance-mismatch and lumen adaptation. Compliance was measured by echotracked ultrasonography and profiles of DAIH were generated from histologic sections harvested after 8.3 months. MAIN RESULTS: The external mesh tube significantly lowered the local compliance of graft and host artery. DAIH appeared extensively in those groups where mesh tube constricted venous grafts met untreated host arteries (p = 0.002). No differences in compliance and DAIH formation were observed when grafts with large and adapted diameters were compared. CONCLUSIONS: For prevention of DAIH the distal venous graft diameter is not important, while the local compliance of an autologous vein is a predictive factor for DAIH formation and thus long-term patency.

Anastomosis, Surgical↗

PubMed1995

The CarboMedics "top hat" supraannular prosthesis in the small aortic root.

Twenty-three patients, 11 men and 12 women, with a mean age of 64 (range, 34 to 78) underwent aortic valve replacement (AVR) with a CarboMedics "Top Hat" supraannular prosthesis between March 1993 and August 1994. The top hat supraannular prosthesis, a standard bileaflet valve with the cuff transferred to the valve inflow level, allowed implantation of 21-mm, 23-mm, and 25-mm valves, where a standard 19-mm or 21-mm valve would have usually been placed. One patient who had been in preoperative cardiogenic shock died in the perioperative period. Another had an intraoperative cerebral embolism with permanent impairment. Follow-up on 22 of 23 patients over a mean period of 9 months revealed mean Doppler gradients of 18 +/- 6 mmHg, 15 +/- 2.8 mmHg, and 11 mmHg, for the 21-mm, 23-mm, and 25-mm valves, respectively. Functional improvement was noted, with 17 patients in New York Heart Association (NYHA) Class I and 6 in NYHA Class II, postoperatively, compared with 0 in Class I, 9 in Class II, 10 in Class III, and 4 in Class IV, preoperatively. One patient showed reduced postoperative ventricular function with fractional shortening below 25%. Pandiastolic regurgitation intrinsic to the valve graded as slight was noted in all patients. Other postoperative complications included one patient with anticoagulant-related gastrointestinal bleeding and one other with prosthetic valve endocarditis successfully treated with antibiotics. The CarboMedics top hat valve allows a gain in prosthesis size of 2 mm to 4 mm in the aortic position over standard prostheses, resulting in favorable postoperative hemodynamics.

Adult↗

PubMed1995

Enhanced G protein activation in immortalized lymphoblasts from patients with essential hypertension.

Epstein-Barr virus-immortalized B lymphoblasts obtained from hypertensive patients with enhanced Na+/H+ exchanger activity (HT cells) proliferate distinctly faster upon serum stimulation than those from normotensive controls with low exchanger activity (NT cells) (Rosskopf, D., E. Frömter, and W. Siffert. 1993. J. Clin. Invest. 92:2553-2559). Stimulation with platelet-activating factor (PAF) as well caused an enhanced proliferation of HT cells. In analyzing possible differences in signal transduction between the immortalized NT and HT lymphoblasts, we observed that cell stimulation with PAF and somatostatin caused a twofold higher increase in [Ca2+]i in HT than in NT cell lines. This difference was completely abrogated by pertussis toxin (PTX) treatment. Furthermore, PAF-stimulated formation of inositol 1,4,5-trisphosphate (IP3) was twofold enhanced in HT cell lines. On the other hand, PAF receptor density and affinity, total cellular phospholipase C activity, expression of PTX-sensitive G proteins, and control binding of the stable GTP analogue, guanosine 5'-[gamma-thio]triphosphate (GTP gamma S), to membrane G proteins were not different in NT and HT cell lines. However, PAF- and mastoparan-stimulated binding of GTP gamma S to G proteins, which was fully PTX-sensitive, was 2.5-fold higher in HT than NT cell lines. These data suggest an enhanced receptor-mediated activation of PTX-sensitive G proteins despite unchanged receptor and G protein expression. Thus, this study not only suggests that enhanced signal transduction and cell proliferation are abnormalities in a certain group of patients with essential hypertension but also explains these findings as a result of an enhanced G protein activation in this common disorder.

Animals↗

PubMed1995

[Chronic thromboembolic pulmonary hypertension and its treatment with pulmonary thrombendarterectomy].

Chronic recurrent pulmonary embolism can lead to extensive pulmonary hypertension by obstruction of the pulmonary vessels. Pulmonary thrombendarteriectomy is a new approach to normalizing the elevated pulmonary vascular resistance by removal of the adsorbed thrombi. Between 1992 and 1994 we have operated on 8 patients aged between 34 and 62 years. The first patient died due to extensive reperfusion edema, all others showed significant improvement in hemodynamic parameters (mean pulmonary artery pressure preop. 63 +/- 5 mmHg; postop. 30 +/- 9 mmHg; Cardiac Index preop. 2.0 +/- 0.2 l/min; postop. 3.5 +/- 0.5 l/min; pulmonary vascular resistance preop. 1169 +/- 75 dyn; postop. 228 +/- 55 dyn) and exercise performance (NYHA classification preop. III-IV, postop. I-II). Pulmonary thrombendarteriectomy represents an efficient method to normalize elevated pulmonary pressure and exercise performance of patients with far-advanced chronic thromboembolic pulmonary hypertension.

Adult↗

PubMed1995

[Results of valve-sparing correction of aortic valve insufficiency].

The risk of valve-related complications and the necessity of anticoagulation in patients with prosthetic valves, has led to new operative techniques in the correction of severe aortic insufficiency. In the last 2 years, 35 patients (mean age 41.3 years, range 10-80 years) with aortic insufficiency underwent reconstructive valves surgery. Eighteen patients had a commissuroplasty with or without triangular resection. In 5 patients with perforation, the valves could be reconstructed with a pericardial patch. In 12 patients with insufficiency due to aortic aneurysm, the valves were resuspended within the aortic prosthesis. In 2 patients the aortic valves were replaced intraoperatively because of unsatisfactory results. The perioperative mortality was 5.7%. The echocardiographic degree of aortic insufficiency decreased from 3.3 +/- 0.5 preoperatively to 0.45 +/- 0.53 postoperatively. Two patients were reoperated within the first week. Five of 23 patients at 1-year follow-up have mild to moderate aortic insufficiency. Mean ventricular dimensions and function at discharge and after 1-year follow-up are normal. With the new operative techniques described recently, valve-sparing corrections of aortic insufficiency are possible in an increasing number of patients, and autologous valve tissue can be saved. With more refinement of surgical technique, early postoperative results will further improve.

Adolescent↗

PubMed1994

Mesh tube-calibrated varicose veins for coronary artery bypass grafting.

Complex arterial bypass grafting may be contraindicated for patients with multivessel disease and inadequate saphenous veins. In such cases varicose veins may be used as bypass conduits after calibration by insertion into mesh tubes. After in vitro and experimental testing, as well as gratifying results in infrainguinal arterial reconstructions, wrapped varicose vein grafts in addition to arterial bypass grafts were used in 6 patients undergoing coronary artery bypass grafting.

Calibration↗

PubMed1994

Distribution of muscle degeneration in Welander distal myopathy--a magnetic resonance imaging and muscle biopsy study.

Seven patients with Welander distal myopathy were subjected to magnetic resonance imaging (MRI) of the lower extremity, and muscle biopsies of the tibialis anterior, soleus and vastus lateralis muscles. MRI revealed abnormalities in both the anterior and posterior compartments of the lower leg in three of the patients, and in only the posterior compartment in the rest of the patients. No MRI abnormalities were found in either the proximal muscles of the leg or in the peroneal or posterior tibial muscle groups. Affected muscles had T1- and T2-values indicating a replacement of muscle fibres with fat tissue. Muscle biopsies showed pathological changes varying from slight to severe in tibialis anterior and soleus muscles in all patients. No muscle fibre abnormalities were seen in the vastus lateralis muscle in any of the patients. In accordance with earlier reports from patients with Welander distal myopathy, there was muscle degeneration of tibialis anterior muscles corresponding to the weakness of dorsal extension of the feet, but also degeneration in the muscles of the posterior compartment. The patients did not, however, show any clinical signs of weakness related to posterior muscle groups. There is no evidence of involvement of proximal muscles of the leg clinically, with MRI or in muscle biopsies.

Adult↗

PubMed1994

Failure mode of a new pericardial valve prosthesis (Sorin Pericarbon). A morphological study.

Between February 1986 and February 1992, 144 patients (mean age 69 years) received 149 bovine pericardial valve bioprostheses (Sorin Pericarbon). Out of this group 10 patients required reoperation because of valvular dysfunction. Defect bioprostheses (7 aortic valves, 3 mitral valves), removed 34 to 81 months after implantation, were studied by X-ray analysis as well as light and electron microscopy. Seven out of ten valves were explanted because of valvular stenosis, two valves had to be replaced because of valvular regurgitation and one because of paravalvular leakage. X-ray analysis revealed severe clacification of the cusps in all cases. Mineralization occurred predominantly next to commissural attachment zones. Cuspal tearing, associated with calcific degeneration of the tissue, was observed in two cases. Beside the commissures, accelerated tissue degeneration could be detected near the basal suture line: disintegration of collagen bundles by invading macrophages and mineral deposits was prominent in these regions. Scanning electron microscopy revealed the presence of circumscribed areas of endothelial-like cell lining on both surfaces of the cusps of five explants. Valvular stenosis, caused by severe calcification of commissural as well as basal regions of the leaflets, is the principal failure mode of the Sorin Pericarbon heart valve prostheses. As an additional aspect, the basal suture line must be assumed to be a critical determinant in accelerating tissue degeneration. Long-term clinical studies will be required to evaluate the clinical performance of this valve, focusing on thromboembolic complications, hemodynamic function and long-term durability.

Aged↗

PubMed1994

Changes following in vitro endothelial cell lining of ePTFE prostheses: late morphologic evaluation of six failed grafts.

This paper describes the morphologic appearance during long term follow-up of in vitro endothelialised ePTFE grafts (IVECL) implanted in patients with crural reocclusions. Between June 1989 and December 1990, 13 femorocrural IVECL bypasses were implanted. Follow-up angiograms demonstrated stenoses in the middle of the graft in six patients. Two of these patients developed symptoms, and the grafts were biopsied approximately 1.5 years after implantation during a patchplasty procedure. The remaining four patients with asymptomatic stenoses refused elective reoperation and suffered a graft occlusion 53 to 619 days after implantation, all leading to amputation. Biopsy specimens and explanted grafts were examined with standard and electron microscopy. Both biopsies demonstrated multiple layers of degenerating myofibroblasts (MFB). The four explanted grafts also showed altered MFB in addition to necrosis of the graft surface. No endothelial cells were seen on any of the preparations. Long term follow up of IVECL protheses in the crural position has demonstrated that it is possible to lastingly bind cells on an artificial surface. Whether the MFB found are a substitute of lost endothelial cells, or are an end product of metaplastic and/or degenerative alterations, can only be clarified through further biopsy studies.

Arterial Occlusive Diseases↗