Biomedical subjects
Publications and source records attributed to J Lindner.
The temperature dependence of the interlayer exchange coupling in ferromagnetic films coupled across nonmagnetic spacers is determined via in situ ferromagnetic resonance experiments for various systems. Clear evidence for a T(3/2) law is found over a wide temperature regime.
OBJECTIVE: To give an overview of the preventive and therapeutic measures in thromboembolic disease in association with pregnancy and delivery. SUBJECT: Case report. SETTING: Department of Obstetrics and Gynaecology, First Faculty of Medicine, Charles University and General Faculty Hospital, Prague. SUBJECT AND METHOD: The surgical treatment of massive pulmonary embolism in a patient after delivery by caesarean section. CONCLUSION: Surgical embolectomy still has its place in the treatment of pulmonary embolism in the early phase of critical cases, when thrombolysis is contraindicated, and mechanical disintegration with the catheter is unsuccessful. In such cases it is the only one possibility of saving the patient. However, prevention of thromboembolic disease remains of primary importance.
OBJECTIVES: To evaluate mid-term results and one-year graft patency of less invasive coronary artery bypass grafting through a median sternotomy. METHODS: From January 1, 1998, to December 31, 1999, 250 patients had coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB) through a median sternotomy. The patient base of 188 men and 62 women averaged 61.7 years, mean ejection fraction (EF) was 55.1%. An average of 2.7 (range 1 to 5) distal anastomoses per patient was achieved. Results are compared with a CPB subgroup of patients operated on through a median sternotomy in the same time (N = 1126). In a random subgroup of 100 patients (50 per group) an angiographic control of graft patency was done. RESULTS: A non-CPB group showed lesser occurrence of postoperative acute myocardial infarction (p = 0.038), atrial fibrillation (p = 0.029) and lower incidence of renal (p = 0.033) complications. We observed lower operative mortality (p = 0.019), as well as the occurrence of low cardiac output syndrome (p < 0.001) in the off pump group. The follow-up is 36 +/- 12 months and the number of patients with recurrent angina (5.4%), late AMI (0%) and late death (0.4%) is acceptable. We did not find an inordinate number of vein grafts occlusions (2.2%) and stenoses (7.8%) at anastomotic sites. None of the arterial grafts in both groups were occluded. CONCLUSIONS: We detected lower incidence of postoperative complications and decreased operative mortality in a non-CPB group. Angiographic assessment displayed an excellent run-off in both groups of patients. Off-pump coronary bypass grafting is associated with sufficient short-term graft patency and mid-term clinical outcomes.
A clinical study of 47 patients with reconstruction of the large saphenous vein by the in situ technique indicates a statistically insignificant difference in the patency for venous grafts from 3 to 4 mm as compared with those above 4 mm. This confirms that the in situ technique extends the possibilities of venous reconstructions. In the author's group it extended the possibility to use a venous graft by 12.8%. The study confirms also the fundamental importance of patency of the pedal arch for long-term patency. Secondary patency of reconstructions in situ and reverse reconstructions in our department is comparable during the five-year period: 82 and 84%.
The authors submit a retrospective group of 245 patients operated in the course of 6 years at the Second Surgical Clinic of Cardiovascular Surgery of the General Faculty Hospital and First Medical Faculty Charles University on account of mitral valve disease. The early results of mitral valve prostheses are comparable or in some combined operations better than reported in world statistics. In the etiology the authors found a relative decrease of rheumatic defects and higher incidence of ischaemic affections. The general mortality in mitral valve prostheses was 7.1%, combined operations incl. acute ones being predominant. In mitral plastic operations the authors lost 4 patients, i.e. 19%. In all instances acute combined operations were involved and the result is consistent with the predicted mortality according to the Merged Cardiac Registry. The mean hospitalization period was 7.52 days. A postoperative QIM was recorded in one patient, i.e. in 0.46%, revision after mediastinitis also in one patient (0.41%) and revision after haemorrhage in 14 patients, i.e. in 5.7%. Neurological complications were recorded in 10 patients i.e. 4%. The work emphasizes the trend of improving results in this important area of cardiosurgery and indicates further possibilities and ways of development in the treatment of mitral valve diseases.
Effects of an external electric field on the propagation of excitable cyclic adenosin monophosphate (cAMP) pulses in aggregating cells of Dictyostelium discoideum have been studied by means of numerical simulations. The mathematical model includes a three-variable version of the Martiel-Goldbeter kinetic model of cAMP production by cells, and diffusion and electromigration of cAMP through intercellular space. Electric field effects on the planar pulses propagating in a spatially one-dimensional system and on circular and spiral pulses propagating in a spatially two-dimensional system include changes in the propagation velocities of pulses initiated in the field-free system, the annihilation of pulses propagating towards the cathode by electric fields of high intensities, and the formation of region(s) of spontaneous excitation permanently generating trains of cAMP pulses. The spiral patterns were found to drift in the electric fields of low intensities, fields of high intensities were found to decompose the spiral arms on the side facing the negative electrode.
The stationary behavior of ionic reaction-transport systems contained in hydrogel located between two reservoirs of electrolytes is investigated. The effects of the applied voltage, the composition of the electrolytes in the reservoirs and the distribution of fixed charge in the hydrogel on the spatial patterns of charge, electric potential, temperature and concentrations of the individual components are studied systematically by mathematical modelling. Such systems, containing only several ions (for example, Cl-, K+, OH- and H+) can function as electrolyte diodes and transistors and can exhibit oscillations and hysteresis. The mathematical description of the studied systems is based on balances of species, enthalpy and charge, on Poisson's equation and on the finite rate description of the water dissociation/recombination reaction, without assuming local electroneutrality. The modeling results are compared with experiments, including the system with hydrogel connecting reservoirs of strong base and acid studied by Noszticzius and co-workers. [L.H. Hegedus, N. Kirschner, M. Wittmann and Z. Noszticzius, J. Phys. Chem. A, 1998, 102, 6491 (ref. 1); L. H. Hegedus, N. Kirschner, M. Wittmann, P. Simon and Z. Noszticzius, Chaos, 1999, 9, 283 (ref. 2).]
Despite intensive study, the relation between insulin's action on blood flow and glucose metabolism remains unclear. Insulin-induced changes in microvascular perfusion, independent from effects on total blood flow, could be an important variable contributing to insulin's metabolic action. We hypothesized that modest, physiologic increments in plasma insulin concentration alter microvascular perfusion in human skeletal muscle and that these changes can be assessed using contrast-enhanced ultrasound (CEU), a validated method for quantifying flow by measurement of microvascular blood volume (MBV) and microvascular flow velocity (MFV). In the first protocol, 10 healthy, fasting adults received insulin (0.05 mU. kg(-1). min(-1)) via a brachial artery for 4 h under euglycemic conditions. At baseline and after insulin infusion, MBV and MFV were measured by CEU during continuous intravenous infusion of albumin microbubbles with intermittent harmonic ultrasound imaging of the forearm deep flexor muscles. In the second protocol, 17 healthy, fasting adults received a 4-h infusion of either insulin (0.1 mU. kg(-1). min(-1), n = 9) or saline (n = 8) via a brachial artery. Microvascular volume was assessed in these subjects by an alternate CEU technique using an intra-arterial bolus injection of albumin microbubbles at baseline and after the 4-h infusion. With both protocols, muscle glucose uptake, plasma insulin concentration, and total blood flow to the forearm were measured at each stage. In protocol 2 subjects, tissue extraction of 1-methylxanthine (1-MX) was measured as an index of perfused capillary volume. Caffeine, which produces 1-MX as a metabolite, was administered to these subjects before the study to raise plasma 1-MX levels. In protocol 1 subjects, insulin increased muscle glucose uptake (180%, P < 0.05) and MBV (54%, P < 0.01) and decreased MFV (-42%, P = 0.07) in the absence of significant changes in total forearm blood flow. In protocol 2 subjects, insulin increased glucose uptake (220%, P < 0.01) and microvascular volume (45%, P < 0.05) with an associated moderate increase in total forearm blood flow (P < 0.05). Using forearm 1-MX extraction, we observed a trend, though not significant, toward increasing capillary volume in the insulin-treated subjects. In conclusion, modest physiologic increments in plasma insulin concentration increased microvascular blood volume, indicating altered microvascular perfusion consistent with a mechanism of capillary recruitment. The increases in microvascular (capillary) volume (despite unchanged total blood flow) indicate that the relation between insulin's vascular and metabolic actions cannot be fully understood using measurements of bulk blood flow alone.
The experimental study took interest in measurement of the flow through great saphenous vein graft. This study compared the flow through reversed vein graft and nonreversed vein graft with cutting vein valvules in the similar conditions. The flow in nonreversed graft lenght of 65 cm was Q = 697 +/- 26 ml/min, in reversed graft lenght of 65 cm Q = 836 +/- 8.61 ml/min. The flow in nonreversed graft lenght of 55 cm was Q = 1002.5 +/- 12.9 ml/min in reversed graft 55 cm Q = 1059 +/- 7.36 ml/min. The results of measurements show higher flow the shorter the graft as well as higher flow through the reversed graft. The statistically significant difference in values of the flow was also confirmed by Wilcoxon-Mann-Whitney test. The conclusion of our study can be applied on usage of allogenous vein grafts and autogenous vein grafts that could be transferred on the other leg. In these indications we can recommend the usage of reversed technique, because the measured flow through the reversed graft is statistically higher than through the nonreversed graft.
The objective of the first part of this study was to use an animal model to investigate the relationship between temperature in the cerebrovenous compartment and cerebral perfusion pressure. In the second part of the study, the objective was to examine the influence of hyperventilation and hypothermia on jugular bulb temperature and body temperature in patients undergoing elective neurosurgery. Intracranial pressure was increased artificially by inflating an infratentorial supracerebellar placed balloon catheter in nine pigs under general anesthesia. Temperature was monitored by thermocouples inserted in the sagittal sinus, white matter of the left lobe and abdominal aorta during the ensuing decrease in cerebral profusion pressure (CPP). Cerebrovenous blood temperature (jugular bulb) and body temperature (urinary bladder) were simultaneously monitored in 24 patients undergoing craniotomy. Moderate hyperventilation was performed in all patients. Cerebrovenous blood and core body temperature were recorded and differences between these two temperatures calculated at the beginning and the end of hyperventilation. At the beginning of the intracranial pressure (ICP), increase mean temperatures of cerebrovenous blood and cerebral tissue (left lobe) were lower than core body temperature. During CPP reduction the difference between core body temperature and cerebrovenous blood temperature increased significantly from 0.86+/-0.44 degrees C prior to ICP rise to 1.19+/-0.58 degrees C at maximum ICP. Before hyperventilation, cerebrovenous blood temperature was higher in 19 patients (+/- difference: 0.34 degrees C +/- 0.27) and equal or lower in five patients (difference: -0.08 degrees C +/- 0.11), than core body temperature. At the end of hyperventilation, the difference between cerebrovenous blood temperature and core body temperature increased (+0.42 degrees C +/- 0.24) in those 19 patients who had started with a higher cerebrovenous blood temperature and decreased (-0.10 degrees C +/- 0. 18) in the other five patients. Both studies demonstrated that the temperature of cerebrovenous blood is influenced by maneuvers which are supposed to decrease cerebral blood flow.
Glucokinase (GK) gene mutations cause diabetes mellitus in both humans and mouse models, but the pathophysiological basis is only partially defined. We have used cre-loxP technology in combination with gene targeting to perform global, beta cell-, and hepatocyte-specific gene knock-outs of this enzyme in mice. Gene targeting was used to create a triple-loxed gk allele, which was converted by partial or total Cre-mediated recombination to a conditional allele lacking neomycin resistance, or to a null allele, respectively. beta cell- and hepatocyte-specific expression of Cre was achieved using transgenes that contain either insulin or albumin promoter/enhancer sequences. By intercrossing the transgenic mice that express Cre in a cell-specific manner with mice containing a conditional gk allele, we obtained animals with either a beta cell or hepatocyte-specific knock-out of GK. Animals either globally deficient in GK, or lacking GK just in beta cells, die within a few days of birth from severe diabetes. Mice that are heterozygous null for GK, either globally or just in the beta cell, survive but are moderately hyperglycemic. Mice that lack GK only in the liver are only mildly hyperglycemic but display pronounced defects in both glycogen synthesis and glucose turnover rates during a hyperglycemic clamp. Interestingly, hepatic GK knock-out mice also have impaired insulin secretion in response to glucose. These studies indicate that deficiencies in both beta cell and hepatic GK contribute to the hyperglycemia of MODY-2.
Transgenic mice containing an upstream glucokinase (betaGK) promoter- simian virus 40 T antigen (Tag) fusion gene develop neuroendocrine tumors primarily in the pancreas, gut, and pituitary. Pancreatic tumors from a line with delayed tumorigenesis were of two different types: insulinomas and noninsulinomas. The noninsulinomas are often periductal in location, express none of the four major islet peptide hormones, Glut-2, Pdx1, tyrosine hydroxylase, Pax4, Pax6, or Nkx6.1, but do express glucokinase, Sur1, Isl1, Hnf3beta, Hnf6, Beta2/NeuroD, and Nkx2.2. Cells from two different noninsulinoma tumors, when adapted to culture, began to express either insulin, glucagon, or somatostatin. Given the partial gene expression repertoire of the noninsulinoma tumors, their apparent periductal origin, and the ability of these cells to partially cytodifferentiate in culture, we suggest that these tumors are derived from islet progenitor cells. Thus, betaGK-Tag transgenic mice provide a new model system for studying the events that occur during both islet cell neogenesis and normal embryonic development.
OBJECTIVES: The aim of this study was to compare the sensitivity of a newly applied transoesophageal ultrasonic Doppler sensor for detection of air with the traditional precordial ultrasonic Doppler sensor in clinical use. METHODS: We studied 16 patients undergoing neurosurgical procedures in a sitting position. Two ultrasonic Doppler devices were compared as to their ability to detect venous air embolisms (VAE): transoesophageal (ODM II, co. Abbott) versus a precordial ultrasonic Doppler sensor (Parks Medical Electronics Inc.). After establishing general anaesthesia and endotracheal intubation, we applied an ultrasonic Doppler sensor to the right sternal border of the patient's chest and inserted an ultrasonic Doppler probe into the oesophagus. With the patient in the sitting position, microparticularly d-galactose was injected to verify the efficacy of both ultrasonic Doppler devices. RESULTS: Using ODM II by positioning the probe toward the azygos vein, a dosage of 1 ml microparticularly d-galactose was detected in every patient. When adjusting the ODM II-probe on the right myocardial wall or using the precordial ultrasonic Doppler sensor, the administration of microparticularly d-galactose was detected by the devices in only 11 patients. CONCLUSIONS: This study demonstrates that a transoesophageal ultrasonic Doppler sensor (ODM II) is more efficient than the precordial ultrasonic Doppler sensor for monitoring patients who are at risk of VAE by sonification of the azygos vein.
AIMS: To determine among a cohort of patients newly dispensed a prescription for a proton pump inhibitor (PPI) the extent of prior use of other less expensive agents such as antacids and H2-receptor antagonists as evidence of a 'stepped care' approach to peptic ulcer and oesophageal disease. METHODS: A retrospective drug utilization study was conducted within the Pharmaceutical Benefits Scheme (PBS) claims database in Australia. A cohort of social security recipients, who received approval for PPI supply in the month of October 1996, had no prior PPI approval in the previous 18 months and went on to have the drug dispensed, was assembled. This group of 'new PPI starters' was then examined for supply of less expensive prescription medicines to treat peptic ulcer and oesophageal disease in the 12 months prior to obtaining their PPI approval. RESULTS: In a cohort of 4554 defined new PPI users, 1205 (26.5%) showed no use of H2-receptor antagonists, antacids, cisapride, cytoprotectants or antiregurgitants in the 12 month period prior to commencing the PPI. The major reason for use given by prescribers for PBS supply was 'severe refractory ulcerating oesophagitis'. CONCLUSIONS: Subsidized supply is currently restricted on cost-effectiveness grounds to refractory peptic ulcer disease or severe oesophageal disease. Despite this, utilization and epidemiological data suggest that there is widespread leakage of use outside these indications particularly to less severe forms of oesophageal disease. This patient tracking study has shown within the PBS database that around a quarter of the patients are treated directly with a PPI without being prescribed less expensive agents at least in the preceding 12 months.
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The author presents an account on a less frequently used vascular approach suitable in particular in patients with repeated a-v shunts. The group comprises 10 patients operated in 1994-1995. The patency up to one year was 80%, after two years 7 shunts are patent, one female patient died one year after establishment of the shunt with the shunt in a functional state. One shunt closed after six months and the second one 11 months after operation. Complications were recorded in three patients, in none of them abolition of the shunt was necessary. Based on the author's experience and data in the literature the authors assume that this approach is a useful alternative to secondary vascular approaches with better results than those of vascular prostheses.
OBJECTIVE: To determine the pattern of use of non-steroidal anti-inflammatory drugs (NSAIDs) in the Australian community, 1990-1994. DESIGN: Data from the national drug utilisation database were expressed in defined daily doses per 1000 population per day (DDDs/1000 population per day). Temporal trends were assessed and comparisons were made with NSAID use in other countries. Epidemiological data were used to estimate the likely impact of changing NSAID use on peptic ulcer hospitalisation rates. SETTING: Australian community (excluding hospitals). MAIN OUTCOME MEASURES: Estimated consumption of prescription NSAIDs, expressed in DDDs/1000 population per day. RESULTS: NSAID use in the Australian community fell from 50.1 DDDs/1000 population per day in 1990 to 34.6 DDDs/1000 population per day in 1994 (down 31%). From this reduced exposure we estimated that the number of admissions for NSAID-related upper gastrointestinal complications will have fallen by about 400 per year. Market research data for this period show a lower percentage use of NSAIDs for osteoarthritis and a decrease in the proportion of use in age groups over 50 years. CONCLUSIONS: The level of use of non-steroidal anti-inflammatory drugs in Australia has been high in comparison with other countries, but in recent years has fallen markedly. This fall occurred in conjunction with regulatory interventions, educational campaigns and increased concern in the medical and lay press regarding the risks associated with the use of NSAIDs.