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Biomedical subjects

A Heinze

Publications and source records attributed to A Heinze.

At least 37 records · Page 2Linked to original sources
PubMed1999

Generative character of perception: a neural architecture for sensorimotor anticipation.

The basic idea of our anticipatory approach to perception is to avoid the common separation of perception and generation of behavior and to fuse both aspects into a consistent neural process. Our approach tries to explain the phenomenon of perception, in particular, of perception at the level of sensorimotor intelligence, from a behavior-oriented point of view. Perception is assumed to be a generative process of anticipating the course of events resulting from alternative sequences of hypothetically executed actions. By means of this sensorimotor anticipation, it is possible to characterize a visual scenery immediately in categories of behavior, i.e. by a set of actions which describe possible methods of interaction with the objects in the environment. Thus, the competence to perceive a complex situation can be understood as the capability to anticipate the course of events caused by different action sequences. Starting from an abstract description of anticipatory perception and the essential biological evidence for internal simulation, we present two biologically motivated computational models that are able to anticipate and evaluate hypothetically sensorimotor sequences. Both models consider functional aspects of those cortical and subcortical systems that are assumed to be involved in the process of sensory prediction and sensorimotor control. Our first approach, the Model for Anticipation based on Sensory IMagination (MASIM), realizes a sequential search in sensorimotor space using a simple model of lateral cerebellum as sensory predictor. We demonstrate the efficiency of this model approach in the light of visually guided local navigation behaviors of a mobile system. The second approach, the Model for Anticipation based on Cortical Representations (MACOR), is actually still at a conceptual level of realization. We postulate that this model allows a completely parallel search at the neocortical level using assemblies of spiking neurons for grouping, separation, and selection of sensorimotor sequences. Both models are intended as general schemes for anticipation based perception at the level of sensorimotor intelligence.

Journal Article↗
PubMed1999

Endothelial cell DNA transfer and expression using petri dish electroporation and the nonreplicating vaccinia virus/T7 RNA polymerase hybrid system.

The nonreplicating vaccinia virus MVA/T7 RNA polymerase hybrid system was tested with Petri dish electroporation for ectopic gene expression in human umbilical vein endothelial cells (HUVECs). A range of voltages (150-450 V), pulse times (10-40 ms), DNA concentrations (0-20 microg/ml) and infection levels (0-15 multiplicities of infection) were tested for effects on T7 promoter-directed chloramphenicol acetyltransferase (CAT) activity after MVA/T7RP infection. MVA/T7RP-directed expression was transient and at least 10 000-fold in excess of nonviral, cytomegalovirus enhancer-directed expression. Use of a Petri dish electrode with the MVA/T7RP system showed increased viability compared with a cuvette electrode. Overexpression of interleukin-2 alpha subunit (IL2Ralpha) pro- tein followed by anti-IL2Ralpha-directed magnetic immunoaffinity cell sorting allowed isolation of the transfected population. The high fidelity of cellular sorting was shown by segregation of CAT activity in the IL2Ralpha-sorted population after transfection of T7 promoter-directed bicistronic IL2Ralpha/CAT DNA. Expression of a panel of proteins including the fluorophore green fluorescent protein as detected by fluorescence microscopy and p21cip1, p27kip1, pp60c-src, FGF-1, pRb, p107 and pRb2/p130 proteins was also achieved. Thus, use of the nonreplicating vaccinia virus/T7 RNA polymerase expression system with Petri dish electroporation is feasible for certain applications for the manipulation of HUVECs by gene transfer.

Bacteriophage T7↗
PubMed1999

Open-labeled long-term study of the efficacy, safety, and tolerability of subcutaneous sumatriptan in acute migraine treatment.

In a multicenter study, a long-term analysis was made of the efficacy, safety, and tolerability of subcutaneous (s.c.) sumatriptan in the acute treatment of migraine attacks over a period of up to 18 months. A total of 2263 patients took part in the study, all able to perform their own acute treatment of migraine attacks at home by s.c. administration of 6 mg of sumatriptan. A headache diary was used by each patient to record the various migraine parameters before the injection and 1 h and 2 h after it. A total of 43,691 attacks were treated and analyzed during the study period from October 1991 to June 1993. Therapy was successful in 89.5% of attacks. Freedom from headache was achieved in 71.0% of cases. In 22.7% of the attacks a second injection was administered on recurrence of the headache; 82.9% of the patients achieved an intraindividual therapy success rate ranging from over 80% to 100%. In the course of treatment there was no change in either the therapy success rate or in the frequency of attacks. Some 4.9% of the patients withdrew from the study because of insufficient efficacy or adverse events. A total of 44.5% of patients reported adverse events, and these were rated serious in the case of 1.7%. S.c. administration of sumatriptan for acute migraine therapy is an effective treatment method, with reliable action, that can be used with good tolerability provided the contraindications are taken into account.

Adolescent↗
PubMed1998

Laser catheter coagulation of normal and scarred ventricular myocardium in dogs.

BACKGROUND AND OBJECTIVE: Larger lesions would increase success rates of catheter ablation of ventricular arrhythmias. Therefore, improved radio frequency current application techniques, but also alternative energy sources, are being investigated. The purpose of this study was to determine morphology and dimensions of ventricular lesions induced by transcatheter application of laser energy. MATERIAL AND METHODS: A total of 244 lesions were produced by Nd:YAG laser pulses, 1,064 nm, 10-30 W, 15-60 s, percutaneously (endocardial approach, n = 124) and under visual control (epicardial approach, n = 120) in the left ventricular walls of 24 anesthetized dogs. RESULTS: Dimensions of lesions increased with the amount of energy applied. Maximal values were obtained at 20 W, 60 s: depth = 12.6 +/- 1.1 mm (transmural); width = 15.0 +/- 2.8 mm; volume = 1,582 +/- 777 mm3. Volumes of lesions did not change significantly when induced through previously scarred myocardium. Histologically, lesions were clear-cut, without crater or thrombus formation. Procedures and follow-up periods of up to 22 months were without complications. CONCLUSION: Nd:YAG laser pulses at 10-20 W and 15-60 s produce homogeneous myocardial lesions of coagulation necrosis of reproducible sizes, in a controllable manner, without unwanted effects on the ventricular walls, in normal and through scarred myocardium of dogs. The laser method is a promising alternative for ablation of ventricular arrhythmias including candidates with ischemic heart disease.

Animals↗
PubMed1998

[Acute therapy of episodic and chronic cluster headache with sumatriptan s.c. Results of a one-year long-term study].

The aim of the open prospective study was to investigate the efficacy, safety and tolerability of subcutaneous sumatriptan in the acute treatment of cluster headache. Self-treatment with 6 mg sumatriptan subcutaneously was monitored over a period up to 1 year. Headache parameters were documented by the patients with a headache diary. A total of 2031 attacks in 52 patients were investigated. Treatment with sumatriptan was effective in 88% of the attacks and 57% of the patients were pain-free within 15 min after injection; 42% of the patients became painfree within 15 min after at least 90% of their attacks. During long-time treatment the efficacy remained unchanged. Of the patients 10% withdrew from the study due to lack of efficacy or adverse events. In total, 62% of the patients reported adverse events, which were serious in 3.8% of the cases. Subcutaneous self-treatment of cluster headache is both highly effective and well tolerated.

Acute Disease↗
PubMed1998

Effect of operationalized computer diagnosis on the therapeutic results of sumatriptan in general practice.

A multicenter test was conducted to investigate the effectiveness of the selective serotonin agonist sumatriptan in patients with the computerized headache diagnosis of migraine. A computer program was used for diagnostic evaluation of patients attending a general practice because of headache. The results of the analysis were taken as a direct decision on therapy. If the patients satisfied the criteria for migraine, they were given subcutaneous sumatriptan for treating three migraine attacks. The patients were able to use the study medication under outpatient conditions. The therapeutic efficacy of the medicine was recorded in a headache diary. A total of 91 patients were included in the study at 22 practices in Germany. An average of four patients per practice were recruited. In the first migraine attack treated, headache improvement was experienced by 77.7% of the patients treated. In the second and third attacks an improvement was experienced by 93.5% and 89.8%, respectively. The results show that by optimizing diagnostic reliability with the aid of the computer program a high response rate can be achieved under practice conditions using the selective serotonin agonist sumatriptan. Since the computer program described permits a specific diagnosis, it improves the prospects of effective headache therapy in the individual patient. Thus treatment based on this approach can reduce inputs of time and money in migraine therapy.

Adolescent↗
PubMed1998

Transcatheter endomyocardial laser revascularization: a feasibility test.

By means of a special catheter system, a total of 76 endomyocardial laser channels were percutaneously produced in a controllable manner at selected sites in 6 beating canine hearts. Acute patency of channels (length = 4-11 mm, diameter = 0.5-1.2 mm) was documented angioscopically and histologically. This minimally invasive method might be useful for revascularising certain patients with ischemic heart disease without resorting to open-chest surgery.

Angioscopy↗
PubMed1998

The class II membrane glycoprotein G of bovine respiratory syncytial virus, expressed from a synthetic open reading frame, is incorporated into virions of recombinant bovine herpesvirus 1.

The bovine herpesvirus 1 (BHV-1) recombinants BHV-1/eG(ori) and BHV-1/eG(syn) were isolated after insertion of expression cassettes which contained either a genomic RNA-derived cDNA fragment (BHV-1/eG(ori)) or a modified, chemically synthesized open reading frame (ORF) (BHV-1/eG(syn)), which both encode the attachment glycoprotein G of bovine respiratory syncytial virus (BRSV), a class II membrane glycoprotein. Northern blot analyses and nuclear runoff transcription experiments indicated that transcripts encompassing the authentic BRSV G ORF were unstable in the nucleus of BHV-1/eG(ori)-infected cells. In contrast, high levels of BRSV G RNA were detected in BHV-1/eG(syn)-infected cells. Immunoblots showed that the BHV-1/eG(syn)-expressed BRSV G glycoprotein contains N- and O-linked carbohydrates and that it is incorporated into the membrane of infected cells and into the envelope of BHV-1/eG(syn) virions. The latter was also demonstrated by neutralization of BHV-1/eG(syn) infectivity by monoclonal antibodies or polyclonal anti-BRSV G antisera and complement. Our results show that expression of the BRSV G glycoprotein by BHV-1 was dependent on the modification of the BRSV G ORF and indicate that incorporation of class II membrane glycoproteins into BHV-1 virions does not necessarily require BHV-1-specific signals. This raises the possibility of targeting heterologous polypeptides to the viral envelope, which might enable the construction of BHV-1 recombinants with new biological properties and the development of improved BHV-1-based live and inactivated vector vaccines.

Amino Acid Sequence↗
PubMed1998

Acute therapy for cluster headache with sumatriptan: findings of a one-year long-term study.

The efficacy, safety, and tolerability of subcutaneous sumatriptan in the acute treatment of cluster headache were investigated in a multicenter study over a period of up to 1 year. A total of 2,031 attacks were evaluated in 52 patients. Therapy was successful in 88% of all attacks. Freedom from pain within 15 minutes in more than 90% of all attacks treated was reported by 42% of the patients, and no decline in efficacy occurred during the course of the study. Adverse events were reported by 62% of the patients.

Adult↗
PubMed1998

[Emphysematous pyelonephritis].

Emphysematous pyelonephritisis a relatively rare, gas-producing, destructive and usually unilateral renal infection. Often the patients are female diabetics and mostly the left kidney is affected. The pathological gas formation is either limited to the kidney or extends to the perirenal space. Two cases are reported, which-in clinical presentation, extension of pathological gas, and treatment-present two possible ends of the spectrum of this disease.

Adult↗
PubMed1997

Imaging and staging of avascular osteonecroses at the wrist and hand.

Avascular ostenecroses (AVN) are unspecific focal sceletal lesions of vascular origin. At the wrist, AVNs are mainly seen in the lunate (Kienbock's disease) and the proximal scaphoid fragment in the presence of a nonunion disease (pseudarthrosis). Other types of osteonecroses are rare. The natural process of devitalization proceeds in steps: initially, there is a bone marrow oedema, followed by trabecula sclerosis, cystic transformation of the spongiosa, and bone fragmentation. End stages include carpal collapse (SLAC wrist) and osteoarthritis. For imaging of the sceletal morphology in AVN computed tomography is most useful, whereas initial stages and perfusion damages are better detected with contrast enhanced magnetic resonance imaging (MRI). In this paper a staging classification for Kienböck's disease and the scaphoid nonunion, considering the diagnostic and therapeutic consequences, is presented.

Diagnosis, Differential↗
PubMed1997

Laser catheter coagulation of atrial myocardium for ablation of atrioventricular nodal reentrant tachycardia. First clinical experience.

A new technique for ablation of atrioventricular nodal reentrant tachycardia, using catheter-directed continuous wave Nd-YAG laser light, 1064 nm, via a novel pin-electrode laser catheter, was applied in 10 patients aged 15-63 years (mean 43 years). A total of 22 laser pulses, 1-5 per patient, at 20 or 30 W, of 10-45 s (mean 27 s) were aimed at the postero-inferior aspect of the tricuspid annulus. In all patients the tachycardia was rendered non-inducible at baseline as well as during orciprenaline administration. The amplitudes of the local atrial potentials diminished from 2.0 +/- 0.5 before to 0.4 +/- 0.4 mV after ablation, atrio-His intervals increased from 73 +/- 7 to 157 +/- 36 ms. Anterograde atrioventricular nodal refractory periods (212 +/- 31 vs 238 +/- 31 ms) and Wenckebach rate (174 +/- 8 vs 167 +/- 8 beats.min-1) did not change significantly (P > 0.05). There were no complications or recurrent arrhythmias in a follow-up of 12-35 (mean 27) months. Anatomically guided laser catheter coagulation of the postero-inferior aspect of the tricuspid valve ring is a safe and effective method for the cure of patients with common atrioventricular reentrant tachycardia.

Adult↗
PubMed1996

[Exteroceptive suppression of activity of the temporal muscle in analysis of pain mechanisms].

Stimulating afferent fibers of the trigeminal nerve usually causes two successive suppressions (ES1 and ES2) of the voluntary muscle activity of chewing muscles. The first phase of decreased voluntary activity is called the early exteroceptive suppression period (ES1); the second phase is called the late exteroceptive suppression period (ES2). Between these two suppression periods is a phase of increased muscle activity, the so-called facilitation period (FP). Usually, in healthy subjects this normal pattern of exteroceptive suppression can be elicited regularly. The reflex answer may occur at low non-painful stimulus intensities; however, typically it appears to be most pronounced with high-intensity stimuli. Because of the obvious relationship between stimulus intensity, pain perception and reflex answer, the reflex is regarded as an antinociceptive reaction. Chronic pain syndromes like chronic tension-type headache and migraine without aura cause changes within the normal ES recording pattern. Furthermore, some substances used in pain therapy such as serotoninagonists or antagonists, acetylsalicylic acid or naloxon may also alter the general appearance of the ES. In this review different parameters that influence the ES reflex answer are summarized. Above, the diagnostic value of the changes of the ES for pathophysiological procedures regarding pain perception and pain processing in certain pain diseases is discussed.

English Abstract↗
PubMed1996

[Electrophysiological studies on headache: the contingent negative variation].

The contingent negative variation (CNV) is a slow cortical potential recorded from the scalp. This method allows the pathophysiology of chronic headaches to be elucidated. When assessed during the pain-free interval patients suffering from migraine without aura show significantly more negative amplitudes than healthy controls. This negativity reflects the activity of cerebral noradrenergic systems. Some studies using repeated recordings of the CNV show a periodicity in amplitude change. When migraine patients are assessed a few days before a migraine attack occurs, they show pronounced negativity, which normalized during the attack. Despite these interesting findings that are based on group comparisons, evaluating the CNV on an individual basis does not allow specific conclusions. Thus, assessment of the CNV is an important tool to examine pathophysiological aspects of chronic headaches, but is not suitable as a diagnostic procedure.

English Abstract↗
PubMed1996

[Effectiveness of Oleum menthae piperitae and paracetamol in therapy of headache of the tension type].

The effect of a locally applied peppermint oil preparation on tension-type headache was examined in the design of a randomized, placebo-controlled double-blind crossover study for the first time. The preparation was tested against both the reference substance acetaminophen and to the corresponding placebo. The liquid test preparation contained 10 g of peppermint oil and ethanol (90%) ad 100 (test preparation LI 170, Lichtwer Pharma, Berlin); the placebo was a 90% ethanol solution to which traces of peppermint oil were added for blinding purposes. The reference preparation contained 500 mg acetaminophen; the placebo tablet was identical to the verum in size and appearance. The study included the analysis of 164 headache attacks of 41 patients of both sexes ranging between 18 and 65 years of age, suffering from tension-type headache in accordance with the IHS classification. Four headache episodes per patient were treated in a double-blind, randomized crossover design. Each headache attack was treated by the application of 2 capsules of the oral medication (1,000 mg of acetaminophen or placebo) and the cutaneous application of the oil preparation (peppermint oil or placebo solution). The oil was spread largely across forehead and temples which was repeated after 15 and 30 minutes. Using a headache diary, the headache parameters were assessed after 15, 30, 45 and 60 minutes. Compared to the application of placebo, a 10% peppermint oil in ethanol solution significantly reduced the clinical headache intensity already after 15 minutes (p < 0.01). This significant clinical reduction of the pain intensity continued over the one hour observation period. Acetaminophen, too, proved to be efficient compared to placebo (p < 0.01). There was no significant difference between the efficacy of 1,000 mg of acetaminophen and 10% peppermint oil in ethanol solution. Simultaneous application of 1,000 mg of acetaminophen and 10% peppermint oil in ethanol solution leads to an additive effect which remains below the significance threshold, however. The patients reported no adverse events. This controlled study showed for the first time that a 10% peppermint oil in ethanol solution efficiently alleviates tension-type headache. Peppermint oil thus proves to be a well-tolerated and cost-effective alternative to usual therapies.

Acetaminophen↗
PubMed1996

Mapping guided laser catheter ablation of the atrioventricular conduction in dogs.

Safety and efficacy of mapping guided laser catheter ablation of the AV junction was tested in a canine model. A total of 43 laser pulses (continuous wave, Nd:YAG, 1,064 nm, 30 W, irradiated spot diameter 2.0-2.5 mm) were delivered in 15 dogs (2-5 per dog) via a novel laser catheter system. Pulses were selectively aimed at: (1) the AV node; (2) the His bundle; and (3) the bundle branches. Laser pulses of 9.7 +/- 1.1 seconds (n = 31) produced reversible conduction disturbances in the targeted segment of the AV conduction system, while pulses of 28.6 +/- 7.9 seconds (n = 9) resulted in chronic block. The dogs survived the procedure without complications. Follow-up was 6.5-10.5 months. Histopathologically, lesions showed clear-cut oval-shaped areas of fibrosis of 0.5-18.0 mm in diameter and 0.5-3.5 mm (transmural) in depth, depending on the irradiation time. Pervenous mapping guided laser catheter irradiation of the AV junction can produce AV block consistently and selectively in the targeted segment of the right ventricular conduction system in dogs. The method is safe and can be performed in a controllable manner by using the catheter system presented.

Animals↗