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Biomedical subjects

O Franzen

Publications and source records attributed to O Franzen.

15 recordsLinked to original sources
PubMed2005

Coronary artery anomalies Part II: recent insights from clinical investigations.

Congenital anomalies of the coronary arteries occur in 0.2-1.2% of the general population; they cause 12% of sports-related sudden cardiac deaths and 1.2% of non-sports-related deaths. We review some of the substantial advances that have been made both, in the understanding of the embryonic development of the coronary arteries and in the clinical diagnosis and management of their anomalies. In this second part of our review we elucidate recent approaches to defining coronary anomalies and provide information on their incidence and prognosis. In addition, we discuss the options for screening large populations for potentially lethal coronary malformations and elucidate the role of invasive diagnostic modalities such as intravascular ultrasound, flow wire and pressure wire. The clinical relevance of coronary anomalies is discussed particularly for the ill-defined group of anomalies that only occasionally cause severe clinical events comprising anomalous origination of a coronary artery from the opposite sinus (ACAOS), coronary artery fistulae and myocardial bridging. Finally, we provide an update on current diagnostic and therapeutic recommendations.

Arrhythmias, Cardiac↗
PubMed2005

[Improved analysis of left ventricular function using three-dimensional echocardiography].

Left ventricular geometry and function are important pathophysiologic and prognostic parameters. However, especially in patients with cardiac pathologies left ventricular geometry can be complex. Quantification of left ventricular volumes using conventional two-dimensional echocardiography is only possible when simplifying assumptions of left ventricular geometry are made. In contrast three-dimensional echocardiography allows direct quantification of left ventricular volumes even in complex distortions of left ventricular shape. The availability of real-time three-dimensional echocardiography has brought this technique into clinical practice. Three-dimensional echocardiography is a technique that may be used as a routine echocardiographic method in the near future.

Cardiac Volume↗
PubMed2004

Coronary artery anomalies. Part I: Recent insights from molecular embryology.

Congenital anomalies of the coronary arteries occur in 0.2-1.2% of the general population and may cause substantial cardiovascular morbidity and mortality. We review some of the advances that have been made both, in the understanding of the embryonic development of the coronary arteries (part I) and in the clinical diagnosis and management of their anomalies (part II). In this first part of our review we elucidate basic mechanisms of coronary vasculogenesis, angiogenesis and embryonic arteriogenesis. Moreover, we review the role of cellular progenitors such as epicardium-derived cells, cardiac neural crest cells and cells of the peripheral conduction system. Then we discuss the role of growths factors (such as FGV, HIF 1, PDGF B, TGFbeta1, VEGF, and VEGFR-2) and genes (such as FOG-2, VCAM-1, Bves, and RALDH2) at different states of coronary development. and we discuss the role of the cardiac neural crest in the concurrence of coronary anomalies with aortic root malformations. This part of the article is designed to review major determinants of coronary vascular development to provide a better understanding of the multiplicity of options and mechanisms that may give rise to coronary anomaly. To this end, we highlight results from experiments that provide insight in mechanisms of coronary malformation.

Animals↗
PubMed2003

Possible role of intramembrane receptor-receptor interactions in memory and learning via formation of long-lived heteromeric complexes: focus on motor learning in the basal ganglia.

Learning in neuronal networks occurs by instructions to the neurons to change their synaptic weights (i.e., efficacies). According to the present model a molecular mechanism that can contribute to change synaptic weights may be represented by multiple interactions between membrane receptors forming aggregates (receptor mosaics) via oligomerization at both pre- and post-synaptic level. These assemblies of receptors together with inter alia single receptors, adapter proteins, G-proteins and ion channels form the membrane bound part of a complex three-dimensional (3D) molecular circuit, the cytoplasmic part of which consists especially of protein kinases, protein phosphatases and phosphoproteins. It is suggested that this molecular circuit has the capability to learn and store information. Thus, engram formation will depend on the resetting of 3D molecular circuits via the formation of new receptor mosaics capable of addressing the transduction of the chemical messages impinging on the cell membrane to certain sets of G-proteins. Short-term memory occurs by a transient stabilization of the receptor mosaics producing the appropriate change in the synaptic weight. Engram consolidation (long-term memory) may involve intracellular signals that translocate to the nucleus to cause the activation of immediate early genes and subsequent formation of postulated adapter proteins which stabilize the receptor mosaics with the formation of long-lived heteromeric receptor complexes. The receptor mosaic hypothesis of the engram formation has been formulated in agreement with the Hebbian rule and gives a novel molecular basis for it by postulating that the pre-synaptic activity change in transmitter and modulator release reorganizes the receptor mosaics at post-synaptic level and subsequently at pre-synaptic level with the formation of novel 3D molecular circuits leading to a different integration of chemical signals impinging on pre- and post-synaptic membranes hence leading to a new value of the synaptic weight. Engram retrieval is brought about by the scanning of the target networks by the highly divergent arousal systems. Hence, a continuous reverberating process occurs both at the level of the neural networks as well as at the level of the 3D molecular circuits within each neuron of the network until the appropriate tuning of the synaptic weights is obtained and, subsequently, the reappearance of the engram occurs. Learning and memory in the basal ganglia is discussed in the frame of the present hypothesis. It is proposed that formation of long-term memories (consolidated receptor mosaics) in the plasma membranes of the striosomal GABA neurons may play a major role in the motivational learning of motor skills of relevance for survival. In conclusion, long-lived heteromeric receptor complexes of high order may be crucial for learning, memory and retrieval processes, where extensive reciprocal feedback loops give rise to coherent synchronized neural activity (binding) essential for a sophisticated information handling by the central nervous system.

Animals↗
PubMed2002

[Diagnosis and therapy of infectious endocarditis. What measures are required?].

Infectious endocarditis remains a potentially life-threatening disease, the outcome of which can be substantially influenced by rapid diagnosis and initiation of suitable treatment. Leading clinical features are fever, a new sound suggestive of valvular insufficiency and, when the course is subacute, anemia. The main diagnostic procedures are transthoracic and transesophageal echocardiography that reliably identify vegetation, valvular insufficiency and abscess. Of decisive importance for treatment and prognosis is the rapid identification of the pathogen by means of blood culture and, if necessary, serologic and molecular-biologic measures. Antimicrobial treatment is applied in accordance with the recommendations of the American Heart Association. Surgical treatment is indicated in the event of refractory infection, severe valvular insufficiency with heart failure, valve avulsion, recurrent emboli or large floating vegetation with an elevated risk of embolism.

Anti-Bacterial Agents↗
PubMed1998

Percutaneous closure of secundum atrial septal defect with a new self centering device ("angel wings").

OBJECTIVE: To investigate the safety, efficacy, and clinical application of a new self centering device ("angel wings") for closure of secundum atrial septal defects (ASD II) and persistent foramen ovale in all age groups. DESIGN: Multicentre, prospective, nonrandomised study. PATIENTS INCLUSION CRITERIA: defects with an occlusive diameter of < or = 20 mm and a surrounding rim of > 4 mm; body weight > 10 kg; and an indication for surgical closure of secundum atrial septal defect. Additionally, there were compassionate indications for closure in patients with persistent foramen ovale. INTERVENTIONS: Defects were closed by a transcatheter device consisting of two square frames made of superelastic nitinol wire. The frames are covered by elastic polyester fabric, which is sewn together at a central circle. All procedures, except for three interventions that were carried out under sedation, were performed under general anaesthesia using transoesophageal echocardiography and fluoroscopy to monitor intervention. RESULTS: Closure was attempted in 75 (71%) of 105 patients. An ASD II was present in 35 children and 15 adults. A persistent foramen ovale was present in 25 adults with suspected paradoxical embolism. Transcatheter closure was unsuccessful in three children and crossover to surgery was required. Residual shunts were found in 20 patients (27%) immediately after the procedure. A transient atrioventricular third degree block occurred in three patients (4%) and the right atrial disk was not fully deployed in three. A minor shunt (< 3 mm) was present in only three (4%) of 72 patients during follow up of 1-17 months. Blood clots on the right atrial disks in two patients (one required lysis) were seen during follow up transoesophageal echocardiography. Serious complications demanding surgical removal of the device occurred in three patients. One patient had haemopericardial tamponade because of an aortic lesion. Left atrial thrombus formation due to an unfolded right atrial disk was found in a second patient and dislodgement of the left atrial disk resulted in a large residual shunt in a third. CONCLUSIONS: Percutaneous closure of a central ASD with a diameter < or = 20 mm in paediatric and adult patients is feasible and effective with this new device. It is a promising alternative to surgical closure. Modifications of the design, however, seem to be mandatory as 4% of patients developed serious complications.

Adolescent↗
PubMed1992

Characterization of the percepts evoked by discontinuous motion over the perioral skin.

The capacity of human subjects to process information about discontinuous and continuous movement was evaluated. Constant-velocity brushing stimuli were delivered through aperture plates that rested lightly upon the mandibular skin. Each plate consisted of either two spatially separated, slit-like openings or a single continuous, longer opening. It was discovered that percepts of smooth apparent motion were achieved with the split apertures (i.e., from discontinuous movement) for only limited ranges of stimulus velocity. Moreover, the optimal velocity supporting smooth apparent motion increased with the separation between the slit-like openings. In a second series of experiments, subjects' ability to discriminate opposing directions of discontinuous and continuous movement was evaluated. It was found that subjects could derive directional information from percepts elicited by discontinuous movement. However, the capacity to discriminate opposing directions of continuous movement cannot be explained solely in terms of the ability to process information about the change in position of a stimulus from its onset to its offset.

Discrimination Learning↗
PubMed1988

Discrimination and scaling of velocity of stimulus motion across the skin.

The capacity of human subjects to discriminate and to scale the velocity of tactile brushing stimuli was assessed. Signal detection and classical psychophysical techniques were employed to estimate the Weber fraction over a wide range of velocities (from 1.5 to 140 cm/sec). In addition, free magnitude estimates of (1) the velocity and (2) the duration of moving tactile stimuli were obtained. It was found that human capacity to discriminate stimuli delivered to a 4 to 6-cm chord of skin on the dorsal forearm and differing in velocity remains grossly constant over the range of velocities tested and is relatively poor (i.e., the Weber fraction = 0.2-0.25). A simple power function (exponent = 0.6) satisfactorily describes the psychophysical relation (1) between the perceived and actual velocity and (2) between the perceived and actual duration of these stimuli. Since a direct proportionality between the reciprocal of a subject's estimate of duration and his or her estimate of velocity was observed, it is suggested that these two sensory attributes may reflect the operation of a neural mechanism sensitive to the duration of stimulation. Moreover, the data are inconsistent with the hypothesis that the subjects computed estimates of mean velocity from the ratio of perceived distance to perceived duration.

Acceleration↗
PubMed1986

Dependence of subjective traverse length on velocity of moving tactile stimuli.

Two series of experiments were performed to assess the effects of stimulus velocity on human subjects' perception of the distance traversed by a moving tactile stimulus. In all experiments, constant-velocity stimuli were applied to the dorsal surface of the left forearm; velocities ranging between 1.0 and 256 cm/sec were used. In some experiments the stimuli moved from distal to proximal over the skin, and in others they moved from proximal to distal. The length of skin contacted by the moving stimulus was defined by a plate having an aperture of 4.0 X 0.5 cm. In the first series of experiments, subjects were required to compare the distance traversed by a test stimulus delivered 2 sec after a standard stimulus, and also to report the on-locus and the off-locus of the brushing stimulus. In the second series of experiments, the subjects rated the perceived distance on the skin using a free-magnitude-estimation procedure. The data from both series of experiments defined the same relationship between stimulus velocity and perceived stimulus distance. More specifically, although the length of skin contacted by the stimulus was the same at all velocities, subjects' estimates of stimulus distance decreased with increasing stimulus velocity. In addition, the function relating estimates of stimulus distance to velocity was flat for velocities between 5 and 20 cm/sec, but possessed an appreciable negative slope at lower and higher velocities. It is interesting that the plateau of the relationship between perceived stimulus distance and velocity occurred within the range of velocities that human subjects employ to scan textured surfaces; it also corresponded precisely with the range of stimulus velocities at which the directional sensitivity of somatosensory cortical neurons and human subjects is optimal.

Adult↗
PubMed1983

Lumbar spinal cord responses to limb vein distention.

The purpose of this study was to determine if central neural responses were elicited by distention of limb veins, and to compare the pattern of these response to those produced in previous studies using electrical stimulation to excite limb venous afferent fibers. Spinal evoked potentials were measured in response to stretch of the wall of a segment of the femoral-saphenous vein by perfusion-distention or by mechanical stretch. These studies revealed that spinal cord evoked potentials were elicited by these procedures, and that the activated venous afferent fibers coursed through the saphenous nerve and entered the sixth lumber spinal cord segment. The minimum stretches which were required to elicit spinal evoked potentials were produced by perfusion pressures starting at 2-3 mm Hg, or by mechanical stretch of the wall of 5 micron/mm. A vein wall proprioceptor hypothesis is proposed and discussed in the light of these findings. In addition to the cord dorsum evoked potentials, distention or stretch of the vein wall elicited ventral root potentials (excitatory postsynaptic population potentials) which are known to be produced by excitatory inputs to motoneurons. A venous afferent mediated muscle-tonus venopressor mechanism hypothesis is proposed and discussed in the light of these and previous findings.

Afferent Pathways↗