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Biomedical subjects

M Dahm

Publications and source records attributed to M Dahm.

At least 55 records · Page 3Linked to original sources
PubMed1996

[Effect of single UVA and UVB irradiation on the surface composition and viscoelastic properties of skin in vivo].

The present study was designed to evaluate the effects of single irradiation either with UVA (dosage: 50 J/ cm2) or UVB (dosage: 1 MED) on surface structure and viscoelastic properties of human skin. Biophysical measurements by means of profilometry and cutometry were carried out on normally sunprotected skin areas directly before and 24 hours after irradiation. UVA induced neither measurable changes in skin surface structure (expressed by the profilometrically calculated parameters of roughness Ra and RzDIN and the parameter Wt reflecting depths of furrows) nor in its viscoelastic properties (expressed by the cutometrically calculated ratio Uv/Ue reflecting viscosity and the ratio Ur/Uf reflecting biological elasticity). However, a single erythemogenic dose of UVB radiation was followed by significant increase in the depths of furrows, increase in viscosity and decrease in biological elasticity.

Adolescent↗
PubMed1996

Mid-term results of pulmonary thromboendarterectomy for chronic thromboembolic pulmonary hypertension.

BACKGROUND: In patients with chronic thromboembolic pulmonary hypertension, acute and striking decreases of pulmonary artery pressures and vascular resistance can be achieved by pulmonary thromboendarterectomy. In this study, the long-term effects of pulmonary thromboendarterectomy on hemodynamic indices and right ventricular function were investigated. METHODS: Sixty-five patients (31 women and 34 men; mean age, 47 +/- 17 years; range, 19 to 69 years; New York Heart Association [NYHA] functional class II, n = 3; class III, n = 38; class IV, n = 24) were reassessed 13 to 48 months (mean, 27 months) after pulmonary thromboendarterectomy. Measurements are reported as mean +/- standard deviation. RESULTS: All patients reported a significant improvement of symptoms: 46 patients were in NYHA functional class I, 16 patients in class II, and 3 patients in class III. Mean pulmonary vascular resistance was significantly reduced compared with preoperative and postoperative values (preoperative: 1,015 +/- 454 dynes.s.cm-5; postoperative: 322 +/- 154 dynes.s.cm-5; follow-up: 198 +/- 72 dynes.s.cm-5; p < 0.001 versus preoperative; p < 0.025 versus postoperative). Concomitantly, cardiac index was significantly increased compared with preoperative values (preoperative: 2.0 +/- 0.7 L.min-1.m-2; follow-up: 2.9 +/- 0.5 L.min-1.m-2; p < 0.001). Significant reductions of right ventricular dimensions and recovery of right ventricular function could be demonstrated radiologically and echocardiographically. In 3 patients (preoperative NYHA class IV, NYHA class III at follow-up) with proven coagulation abnormalities, pulmonary vascular resistance was moderately increased at follow-up compared with postoperative measurements. CONCLUSIONS: In patients with chronic thromboembolic pulmonary hypertension, a persistent decrease of pulmonary vascular resistance and improvement of right ventricular function and NYHA functional status can be achieved by pulmonary thromboendarterectomy.

Adult↗
PubMed1996

The extended transseptal approach in complex mitral valve surgery--evaluation of risks and benefits.

The extended transseptal approach to the mitral valve was used in 32 patients undergoing isolated or combined mitral valve surgery. In all cases exposure of the entire mitral valvular apparatus was excellent. Two patients died of low output within 30 days of surgery. No cause of death was related to the extended transseptal approach. In one early patient reexploration revealed arterial bleeding from the right atrial suture line which was caused by damage to the sinus nodal artery. In 7 patients temporary atrial conduction disturbances occurred which completely resolved within 10 days after responding well to dual-chamber pacing. Temporary ventricular pacing was necessary in two patients with preoperative bradyarrhythmia. In two patients undergoing mitral re-do surgery a permanent ventricular pacer was implanted. The extended transseptal approach offers an excellent exposure of the entire mitral valve both in primary isolated or combined mitral surgery particularly in re-do surgery where the primary standard vertical left atriotomy is impeded or the conventional transseptal approach gives only limited access. Temporary atrial dysrhythmia is not crucial and is easily controlled by short-term dual-chamber pacing.

Arrhythmias, Cardiac↗
PubMed1996

Effects of surface seeding with vital cells on the calcium uptake of biological materials for heart valve replacement.

BACKGROUND AND AIMS OF THE STUDY: Up to 35% of bioprosthetic heart valves need to be replaced during the first decade after implantation because of tissue degeneration or calcification. The aim of the studies was to evaluate the influence of surface seeding with viable cells on the calcium uptake of biomaterials. MATERIALS AND METHODS: Samples of glutaraldehyde tanned bovine pericardium (GBP, n = 52) or porcine valves (GPV, n = 50), or glycerol treated bovine pericardium (GlyBP, n = 35), which had either been rinsed with saline (GBP, n = 30; GPV, n = 26; GlyBP, n = 18) or seeded with rat fibrocytes (GBP, n = 22; GPV, n = 24; GlyBP, n = 17) were incubated with cell culture medium containing physiologic levels of calcium. Similarly treated material was implanted into the abdominal muscles of 88 rats (seeded: GBP, n = 16; GPV, n = 16; GlyBP, n = 14; non-seeded: GBP, n = 6; GPV, n = 8; GlyBP, n = 7). The specimens were analyzed two and four weeks later for their calcium content. RESULTS: Over time untreated GBP and GlyBP calcified in vitro and in vivo while GPV retained low calcium levels in vivo. Surface seeding with rat fibrocytes significantly reduced the calcium accumulation in GBP and GlyBP in vitro and in vivo (p < 0.05). CONCLUSIONS: Seeding with viable cells might be a promising method of reducing calcium accumulation in bovine pericardial implants.

Animals↗
PubMed1995

Relevance of immunologic reactions for tissue failure of bioprosthetic heart valves.

The use of biologic heart valve prostheses is decreasing because of the high incidence of failure of these bioprostheses resulting from tissue degeneration or tearing. Immunologic reactions might play a decisive role in this process. The present experimental and clinical studies were conducted to investigate the relevance of immunologic reactions to the tissue failure of glutaraldehydetanned bovine pericardial and porcine valves. Specimens of the two different types of valve material were implanted in the abdominal muscles of rats. Enzyme-linked immunosorbent assays and tritiated thymidine incorporation tests were performed to detect specific antibodies and activated T cells. All specimens were studied histologically. Identical enzyme-linked immunosorbent assays and tritiated thymidine incorporation tests were performed in 29 patients with bioimplants and in 48 controls. Twenty explanted bioprostheses were investigated using histologic and immune histologic methods. The results of the enzyme-linked immunosorbent assays and lymphocyte proliferation tests showed that glutaraldehyde-tanned bovine pericardial valves can provoke cellular and humoral immunologic reactions in rats and human beings. In explanted bovine valves, macrophages were found invading and degrading implant collagen, starting from surface lesions. The combination of the formation of mechanical lesions, the development of cellular infiltrates, and collagen disruption strongly indicates that initial surface lesions initiate the immunologic reactions in bovine pericardial valves as the result of the exposure of incompletely tanned collagen. These immune responses might accelerate tissue degeneration. Porcine valves do not provoke immunologic reactions.

Animals↗
PubMed1993

Troponin T--a reliable marker of perioperative myocardial infarction?

Following cardiac surgery, electrocardiography and creatine kinase isoenzyme MB (CK-MB) activities are of limited value in diagnosing a non-transmural infarction. With the recent availability of an assay to detect serial levels of the specific cardiocyte contractile protein troponin T the possibility has been increased of closing a diagnostic gap among cardiosurgical patients. Ninety patients with severe diffuse three-vessel disease undergoing myocardial revascularization were grouped by their postoperative electrocardiographic (ECG) findings (group I--unchanged ECG; group II--new Q-waves representing perioperative myocardial infarction (PMI)). Serial levels of troponin T and the activity of CK-MB were measured 6, 12, 24 and 48 h after aortic unclamping. The course of CK-MB activity was compared to a profile and values derived from patients with unchanged (n = 1312) or new Q-wave ECGS (n = 89). In 72 patients (80.0%) with unchanged postoperative ECG (group I) serial troponin T levels remained constantly low and reached a median peak value of 0.37 microgram/l (quartile 0.13-0.50 microgram/l) after 24 h. Serial CK-MB activities demonstrated the typical non-ischemic course with a monoexponential decline from an initial median peak value of 15.5 U/l (quartile 12.0-21.0 U/l) to 7.0 U/l (quartile 6.0-9.0 U/l). In seven patients (7.8%) with new Q-waves and a pathologic CK-MB profile (group II) troponin T reached median levels of 10.47 micrograms/l (quartile 6.34-12.50 micrograms/l) (P < 0.001 I vs II). Four of five patients with a new right bundle branch block demonstrated low troponin T levels below 1 microgram/l and a normal CK-MB profile. Among six patients with unchanged QRS-configuration and elevated troponin T levels between 0.84 and 4.99 micrograms/l CK-MB activity showed a characteristic PMI pattern in two patients. Troponin T is characterized by a very narrow margin of normal values represented by a maximum third quartile of 0.50 microgram/l. A singular value of troponin after 6 h or 24 h may be sufficient evidence to confirm the diagnosis of a PMI.

Aged↗
PubMed1993

[Results of angiographic follow-up of percutaneous stent implantation in the pelvic arteries with a comparison between Wall and Palmaz stents].

51 occlusions of iliac arteries and 67 stenoses have been treated, including 22 patients with bilateral lesions. Indications for stent implantations were: vascular occlusions (51), restenosis following previous PTA (22) and immediate unsatisfactory results or extensive dissection after PTA (45). Successful placement of a stent was achieved in 116 out of 118 attempts. Period of observation averaged 16 months (3-36 months). Stent occlusion was observed in 8 cases. There was mild intima hyperplasia in 25 patients and in a further 14 intima hyperplasia exceeded 75%. Patency rate after 36 months was 67%; 74 wall stents and 39 Palmaz stents were patent, a patency rate of 73 and 65% respectively after 24 months.

Adult↗
PubMed1993

Element concentrations (selenium, copper, zinc, iron, magnesium, potassium, phosphorous) in heart tissue of patients with coronary heart disease correlated with physiological parameters of the heart.

The element concentrations (Cu, Zn, Se, Fe, K, Mg, P) of heart tissue taken from patients with coronary heart disease during bypass surgery were measured and related to physiological parameters of the heart. There was no relationship between the element concentrations and the number of vessels stenosed, the occurrence of myocardial infarction or classification according to the NYHA. When the element concentrations of the heart were related with parameters characterizing cardiac output, such as ejection fraction and cardiac index, positive statistically significant correlations were found for selenium, iron, copper, zinc and phosphorus.

Adult↗
PubMed1993

Mesoglycan treatment restores defective fibrinolytic potential in cutaneous necrotizing venulitis.

BACKGROUND: Cutaneous necrotizing venulitis (CNV) is a clinical disorder associated with segmental inflammation and fibrinoid necrosis of the dermal venules. It usually presents clinically as palpable purpura, even sometimes as nodules, bullae, ulcers, and urticarial lesions. This form, when showing as leukocytoclastic vasculitis is apparently characterized by the tissue deposition of circulating immune complexes and by reduced cutaneous (CFA) and plasma (PFA) fibrinolytic activity due to reduced release of plasminogen activator (PA) from the venular endotheliocytes. Reduced CFA and PFA cause large amounts of fibrin deposits in both intra- and perivascular areas, which are able to magnify and self perpetuate the inflammatory processes following immune complex deposition. METHODS: We have studied both the PFA and CFA potential (the maximum amount of PA released in the skin after certain stimuli) and the deposits of immunoglobulins, C3, and fibrin related antigen, before and after intradermal injection of histamine (a substance able to provoke endothelial release of PA), in three subjects affected by CNV before and 20 days after 10 mg/kg/day I.M. treatment with the fibrinolytic agent mesoglycan. RESULTS: Cutaneous fibrinolytic activity and CFA potential, reduced prior to treatment, was normal after treatment, while the deposits of immunoglobulins (IgA, IgG and IgM), C3, and fibrin related antigen, detected with direct immune fluorescence (DIF) showed similar findings before and after treatment. CONCLUSIONS: These data suggest that reduced CFA may play a major role in the pathogenesis of the immunologically mediated injury in CNV. The intraperivascular deposition of fibrin is favored. The fibrinolytic agent mesoglycan seems effective in restoring defective fibrinolysis in patients affected by cutaneous necrotizing venulitis, suggesting that in cases with reduced cutaneous fibrinolytic activity (or potential) the use of a fibrinolytic agent should be considered.

Adult↗
PubMed1993

[Cushing syndrome in ACTH-producing neuroendocrine tumor of the hepatic duct].

We present a patient with an ACTH producing neuroendocrine tumor of the hepatic bile duct which was detected by chance during abdominal surgery for Cushing's syndrome. Diagnostic strategy and surgical therapy in patients with neuroendocrine tumors are discussed. The diagnostic problems caused by combination with an endocrine function disorder like Cushing's syndrome are pointed out.

ACTH Syndrome, Ectopic↗
PubMed1992

[Distribution of the incidence of sonographically detected focal liver changes in patients with colorectal cancer].

Aim of the following study was to investigate how often liver metastases are detected in oncologic patients as compared to other focal liver lesions. Preoperative sonographic examinations of 209 patients with proven colonic or rectal cancer were studied. In 19 liver metastases were detected, which in only one patient were homogeneous echogenic. Liver cysts were found in 17, hemangiomas in 15 patients, all of whom where solitary lesions and between 6 and 25 mm in diameter. Focal fatty infiltration was diagnosed in 14 patients. In conclusion, a sonographically detected liver lesion, which is homogeneous echogenic and less than 20 mm in size, is most likely to be a hemangioma and should be further investigated, if therapeutically relevant.

Colorectal Neoplasms↗
PubMed1991

[A new photographic method for measuring squint angles in infants and small children].

A new photographic method for measuring squint angles in children and infants is presented. A photographic picture is taken from the subject, using a camera with the three flashes bulle. One flashbulle is placed vertically over the lens, two other flashbulles are placed symmetrically in an angle of 10 degrees beside the middle flash. Six reflections can be seen on the photographic picture in each pupil. (1. and 4. Purkinje Sanson Images of each light source.) The horizontal distance of two reflections is determined by the distance of the flashguns. If the reflection lines in both eyes are symmetrical, there is no squint. If there is a shift, it can be measured on the slide and by using a simple formula the squint angle can be calculated. The accuracy of the method is between 2 and 3 degrees.

Child, Preschool↗
PubMed1990

Relationship between diastolic shape (eccentricity) and passive elastic properties in canine left ventricle.

This study was designed to investigate the relationship between left ventricular (LV) eccentricity, volume, and passive elastic properties. Eight open-chest fentanyl-anesthetized dogs were instrumented with an LV micromanometer, a remote-controlled mitral valve occluder, and two pairs of ultrasonic crystals to measure anterior-posterior and base-apex dimensions. We identified the presence of elastic recoil forces with negative LV diastolic pressure in nonfilling diastoles (end-systolic volume clamp). Using linear regression analysis we related midwall eccentricity to volume in nonfilling diastoles at the time of LVPmin and at end diastole, and in normal beats at end systole at LVPmin and at end-diastole. Intersection of the end-systolic and end-diastolic lines (transitional volume, Vt = 38.0 + 6.4 ml) divides cycles with and without the presence of elastic recoil forces. Vt is analogous to the equilibrium volume (V0), determined as the volume intercept of the logarithmic passive pressure-volume (P-V) relationship using LV volume estimated from LV weights (V0 nl = 37.6 + 4.4 ml), or the volume intercept of the linearized P-V relationship calculated from a prolate spheroidal model using measured minor and major diameters (V0 l = 44.5 + 3.5 ml). Linear regression analysis was also used to relate the square of peak mitral flow (MF2) with the corresponding atrioventricular pressure gradient (delta P); the slope represents a dissipative constant for the cycles without, P = 0.00058(MF)2 + 0.35 (n = 48, r = 0.73), and with elastic recoil P = 0.00035(MF)2 + 0.21 (n = 24, r = 0.81).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Diastolic viscous properties of the intact canine left ventricle.

The viscoelastic model of the ventricle predicts that the rate of change of volume (strain rate) is a determinant of the instantaneous pressure in the ventricle during diastole. Because relaxation is not complete before the onset of filling, one cannot distinguish the individual effects of relaxation and viscosity unless the passive and active components that determine the ventricular pressure are separated. To overcome this problem, we used the method of ventricular volume clamping to compare the pressures in the fully relaxed ventricle at a given volume at zero strain rate (static pressure) and high strain rate (dynamic pressure). Six open-chest, fentanyl-anesthetized dogs were instrumented with micromanometers and an electronically controlled mitral valve occluder in series with the electromagnetic flow probe. We reasoned as follows: If there were significant viscosity, then the dynamic pressure would be higher than the static pressure. The static pressure was measured when the ventricle was completely relaxed following a mitral valve occlusion after an arbitrary filling volume had been achieved. The dynamic pressure was determined by delaying the onset of filling until relaxation was complete and then measuring the pressure at the same volume that was achieved when the static pressure was measured. In 19 different hemodynamic situations, the dynamic and static pressures were identical (mean difference, 0.1 +/- 0.8 mm Hg), indicating that in the passive ventricle viscoelastic effects are insignificant and do not contribute to the left ventricular diastolic pressure under normal filling rates.

Animals↗