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Biomedical subjects

H Heinrich

Publications and source records attributed to H Heinrich.

At least 37 records · Page 2Linked to original sources
PubMed1997

EP parametrization and classification using wavelet networks--theoretical concept and medical application.

The purpose of this paper is to outline the fundamental concept of wavelet networks (WNs) and to demonstrate its specific advantages in a clinical discrimination task. A group of 25 boys with attention deficit hyperactivity disorder (ADHD) should be separated from a control group of 25 healthy boys by auditory evoked potentials. Because of the high variability of the recorded EP signals quantification of the averaged sweeps by peak latencies and amplitudes failed. However, with wavelet networks a maximum classification rate of 80% was achieved by crossvalidation. A WN is basically described as a multilayer perceptron which consists of two parts for feature extraction/parametrization and classification. These essential steps of a pattern recognition task are not separated in different tasks but linked together by the clamp of the learning algorithm. Because no user interaction is necessary we call this procedure a self-learning method.

Arousal↗
PubMed1993

Influence of high thoracic epidural anesthesia on left ventricular contractility assessed using the end-systolic pressure-length relationship.

The effect of high thoracic epidural anesthesia (TEA on left ventricular contractility was studied in a prospective clinical trial. Forty-eight patients with ASA physical status 1 and 2 and without cardiovascular disease were included in the study. Thirty-six patients scheduled for elective upper abdominal surgery were randomly assigned to Group 1 (TEA, bupivacaine 0.25%, n = 12), Group 2 (TEA, bupivacaine 0.5%, n = 12) or to Group 3 (control without TEA, n = 12). TEA induced a sensory block which extended over all cardiac segments. In order to assess the effect of systemically absorbed bupivacaine, we studied a separate group of patients who received lumbar epidural anesthesia without involvement of the cardiac segments: Group 4 (LEA, bupivacaine 0.5%, n = 10). Left ventricular contractility was assessed using the end-systolic pressure-length relationship. Left ventricular dimensions were measured by transesophageal echocardiography. All hemodynamic measurements were performed under general anesthesia. There was no significant difference in systolic or diastolic arterial pressure, heart rate, left ventricular end-systolic and end-diastolic cross-sectional areas and left ventricular wall stress between the four groups. Left ventricular maximum elastance as a measure of left ventricular contractility was significantly (P < 0.001) reduced in Groups 1 and 2 [8.1 (+/- 3.5) and 9.6 (+/- 4.4) kPa.cm-1, respectively] as compared to Groups 3 and 4 [18.4 (+/- 8.8) and 17.7 (+/- 7.7) kPa.cm-1, respectively]. No significant difference could be demonstrated between Groups 1 and 2 or between Groups 3 and 4. It is concluded that high TEA severely alters left ventricular contractility even in subjects without pre-existing cardiac disease.

Abdomen↗
PubMed1993

Effect of phenylephrine bolus administration on left ventricular function during high thoracic and lumbar epidural anesthesia combined with general anesthesia.

The effect of phenylephrine (PHE) boluses on left ventricular (LV) function was examined in patients without cardiovascular disease who developed arterial hypotension during high thoracic epidural anesthesia (TEA) combined with general anesthesia (GA) (group 1) or lumbar epidural anesthesia (LEA) combined with GA (group 2). LV function was assessed by transesophageal echocardiography (TEE) before and after central venous injection of 1 microgram/kg PHE. Fractional diameter shortening (FDS), end-systolic wall stress (ESWS), and rate-corrected velocity of circumferential fiber shortening (mVcfc) were determined. PHE effectively restored arterial blood pressure in both groups with a peak effect between 30 and 45 s after injection. FDS was reduced from 38% to 25% (mean, P < 0.01) in group 1 and remained unchanged in group 2. ESWS increased from 70 to 143 x 10(3) dyne.cm-2 (P < 0.01) and from 57 to 86 x 10(3) dyne.cm-2 (P < 0.05), in groups 1 and 2, respectively. mVcfc was significantly reduced from 1.11 to 0.80 circ/s (P < 0.05) in group 1 and was not altered in group 2. The authors conclude that PHE given as an intravenous bolus to patients under high TEA plus general anesthesia causes a transient impairment of LV function.

Abdomen↗
PubMed1992

Identification of the ubiquinone-binding site of NADH:ubiquinone oxidoreductase (complex I) from Neurospora crassa.

In order to localize the ubiquinone-binding site of complex I (NADH:ubiquinone oxidoreductase), a novel photoreactive ubiquinone analogue (Q0C7ArN3) has been synthesized. It is shown that the direct chemical precursor of this analogue (Q0C7ArNO2) and the analogue itself are accepted as substrates in an enzyme assay utilizing ubiquinone-depleted mitochondrial membranes of Neurospora crassa. The activity of the enzyme applying these derivatives is inhibited by 50% at a concentration of 9 and 20 microM rotenone. Photoaffinity labeling experiments were performed with both isolated complex I and whole mitochondrial membranes of N. crassa under various conditions. In each of these experiments a protein subunit with an apparent molecular mass of about 9.5 kDa was labeled with high specificity. Radioactive labeling was totally prevented by the addition of ubiquinone-2 at concentrations higher than 500 microM but was not affected by comparable concentrations of rotenone or other hydrophobic substances. In the labeling experiments using whole membranes, the labeling signal was dramatically increased in the presence of 1.5 mM NADH. These results strongly suggest that the ubiquinone analogue interacts specifically with the enzyme.

Affinity Labels↗
PubMed1992

Characterization of the 9.5-kDa ubiquinone-binding protein of NADH:ubiquinone oxidoreductase (complex I) from Neurospora crassa.

A small polypeptide subunit of the NADH:ubiquinone reductase (complex I) from Neurospora crassa has been identified by photoaffinity labeling to participate in the binding of ubiquinone [Heinrich, H., & Werner, S. (1992) Biochemistry (preceding paper in this issue)]. This polypeptide is further characterized by its primary structure and by an assessment of its localization within complex I. A lambda gt11 cDNA expression library was screened using a specific antibody directed against this individual subunit of complex I. Two groups of clones, coding for polypeptide subunits of the appropriate apparent molecular weight, were isolated. One group was shown to contain the relevant recombinants. The derived amino acid sequence for the 9.5-kDa ubiquinone-binding polypeptide shows a similarity with a putative ubiquinol-binding subunit (also a 9.5-kDa polypeptide) from complex III of bovine heart [Usui, S., Yu, L., & Tu, C.-A. (1990) Biochemistry 29, 4618-4626]. The polypeptide has a hydrophobic stretch of a sufficient length to span the membrane. It resists against extraction with NaBr or Na2CO3, and therefore probably is buried in the so-called hydrophobic membrane portion of complex I. This nuclearly-encoded subunit lacks a typical cleavable presequence and is imported into isolated mitochondria by a membrane potential-dependent process.

Amino Acid Sequence↗
PubMed1992

Primary structure and mitochondrial import in vitro of the 20.9 kDa subunit of complex I from Neurospora crassa.

The 20.9 kDa subunit of NADH:ubiquinone oxidoreductase (complex I) from Neurospora crassa is a nuclear-coded component of the hydrophobic arm of the enzyme. We have determined the primary structure of this subunit by sequencing a full-length cDNA and a cleavage product of the isolated polypeptide. The deduced protein sequence is 189 amino acid residues long and contains a putative membrane-spanning domain. Striking similarity over a 60 amino-acid-residue domain with the M (matrix) protein of para-influenza virus was found. No other relationship with already known sequences could be detected, leaving the function of this subunit in complex I still undefined. The biogenetic pathway of this polypeptide was studied using a mitochondrial import system in vitro. The 20.9 kDa subunit synthesized in vitro is efficiently imported into isolated mitochondria, where it obtains distinct features of the endogenous subunit. Our results suggest that the 20.9 kDa polypeptide is made on cytosolic ribosomes lacking a cleavable targeting sequence, interacts with the mitochondrial outer membrane (in a process that does not require an energized inner membrane), and is imported into mitochondria at contact sites. The 20.9 kDa subunit is then inserted into the inner membrane acquiring a topology similar to that of the already assembled subunit.

Amino Acid Sequence↗
PubMed1992

Differential effects of mild hypoglycemia on proximal and distal retinal structures in man as revealed by electroretinography.

We investigated the effect of blood glucose concentration on the human visual system. Blood sugar levels were modified by intravenous infusion with insulin or glucose. Luminance electroretinograms (L-ERG) were elicited with colored flashes, and pattern ERGs (P-ERG) evoked by checkerboard reversal stimuli were obtained simultaneously with cortical visually evoked potential (VEP). With glucose levels above or below the baseline values the b-wave of the L-ERG was significantly larger than with normal glucose levels, whereas the P-ERG displayed maximal amplitudes at normal glucose levels and a significant amplitude decrease with glucose levels below or above normal. Since L-ERG and P-ERG activity is generated by different retinal structures, this indicates that distal and proximal layers of the human retina are affected differently by changing glucose levels probably due to regional differences in retinal circulation.

Adult↗
PubMed1992

Attention, cognition, and motor perseveration in adolescents at genetic risk for schizophrenia and control subjects.

Twenty-three offspring of schizophrenic parents (mean age = 12.1 years, SD = 3.2) and 61 adolescent control subjects (mean age = 12.3 years, SD = 3.3) were compared in their performance of the following psychometric tests: simple reaction times (RTs), warned RTs in a monomodal and cross-modal design, d2 concentration test, a motor perseveration test, and a cognitive performance measure (Wechsler Intelligence Scale). The results were validated in a second analysis in which a subgroup of the control subjects were matched to the high-risk subjects for the following characteristics: age, gender, education, and environmental background. Significant deficits were found in the high-risk group in tests that required sustained attention and information processing under high perceptual load (RT measures and d2 concentration test). Deficits were particularly prominent for the processing of visual stimuli; sensory incongruence might also have been a contributor to this deficit. The attentional dysfunction of high-risk subjects might explain their tendency to show less structured behavior and distractibility as reflected by their higher entropy scores in a motor perseveration test. Cognitive evaluation showed a significant deficit in the high-risk group, primarily as reflected in the verbal IQ score.

Adolescent↗
PubMed1992

Baroreflex control of heart rate during high thoracic epidural anaesthesia. A randomised clinical trial on anaesthetised humans.

Baroreflex control of heart rate after cardiac sympathectomy induced by thoracic epidural anaesthesia was evaluated in 30 patients who were randomly assigned to group 1 (bupivacaine 0.25%), group 2 (bupivacaine 0.5%) or group 3 (control). Plasma volume expanders were given to equalize preload conditions, as assessed using transoesophageal echocardiography. All measurements were made under general anaesthesia. Baroreflex sensitivity was determined from the heart rate response to phenylephrine and nitroglycerin. There was no difference in cardiac slowing in response to phenylephrine between the three groups. Baroreflex sensitivity, measured as cardiac acceleration in response to nitroglycerin, was significantly lower (p < 0.01) in groups 1 and 2 (1.8 and 1.5 ms.mmHg-1 respectively) compared with group 3 (3.5 ms.mmHg-1) with no differences between the two bupivacaine concentrations. The results suggest that baroreflex-mediated response to decreases in arterial pressure is dependent on the integrity of the sympathetic nervous system.

Adult↗
PubMed1992

[A noncardiac pulmonary edema following aortocoronary bypass surgery. Diagnosis and therapy based on a case report].

Noncardiac pulmonary edema can occur not only after cardiac surgery with cardiopulmonary bypass but also after noncardiac operations. This so-called transfusion-related acute lung injury (TRALI) has been attributed to the transfusion of homologous blood and plasma. In the presence of normal left ventricular function an acute increase in pulmonary capillary permeability leads to massive protein-rich pulmonary edema, reduced pulmonary function, and intravascular hypovolemia. This may be caused by leukocyte antibodies. Signs and diagnostic and therapeutic procedures are discussed with reference to a case report.

Coronary Artery Bypass↗
PubMed1991

[The results of resuscitations in an emergency service].

In a prospective study 166 consecutive cases of prehospital resuscitation by emergency doctors were analysed to ascertain those factors which affect the ultimate outcome. Cardiac causes were most frequent (69%): primary ventricular fibrillation was the most common ECG diagnosis (47%). Average time from definite cardiorespiratory arrest until onset of resuscitation procedures by an emergency doctor was 8.2 minutes, to first measures by other resuscitation personnel it was 6.6 minutes. In all cases in which resuscitation procedures were undertaken (in 33 within 10 minutes) this was done by medical personnel who were nearby by chance. 47 patients (28.3%) could be resuscitated and taken to hospital; 16 of them (9.6%) were discharged after "finally successful resuscitation", 13 without any neurological deficit. Favourable factors were: primary ventricular fibrillation and start of resuscitation manoeuvres within 10 minutes. These results highlight the need for training first-aid personnel so that the number of successful resuscitations can be increased.

Electrocardiography↗
PubMed1991

[Safe intra-clinic transport of intensive-care patients. A concept that avoids monitoring and treatment gaps].

We describe a transport concept ensuring unlimited continuation of cardiocirculatory monitoring, drug therapy and artificial ventilation during transfer of critically ill patients within the hospital. The basis of this concept is a mobile transport unit which can be hooked to the patient's bed, containing a power pack for the monitor, respirator or other devices dependent on power supply. The concept probably improves safety of patients not only during postoperative transfer of the ICU but enables also the safe transfer of critically ill patients from the ICU to diagnostic or therapeutic procedures.

Critical Care↗
PubMed1991

Echocardiographic assessment of the haemodynamic effects of propofol: a comparison with etomidate and thiopentone.

The haemodynamic effects of propofol (2 mg/kg), etomidate (0.2 mg/kg) and thiopentone (4 mg/kg) were studied in 30 ASA 1 and 2 patients in whom anaesthesia had been induced with midazolam 0.1 mg/kg, fentanyl 5 micrograms/kg, vecuronium 0.1 mg/kg and atropine 10 micrograms/kg, and maintained with nitrous oxide in oxygen. Arterial pressure was measured directly and left ventricular diameters were determined by transoesophageal echocardiography. Systolic blood pressure after propofol and thiopentone and the end-systolic quotient (systolic pressure/end-systolic diameter), a measure of inotropy, decreased. Fractional shortening (end-diastolic-end-systolic diameter/end-diastolic diameter) decreased only in the thiopentone group. Diastolic blood pressure and end-diastolic diameter (a measure of preload) did not change in any of the groups, and the etomidate group showed no changes in the haemodynamic variables measured. Propofol shows simultaneous negative inotropy and afterload reduction, while thiopentone is exclusively negatively inotropic.

Adult↗
PubMed1991

Hemodynamic effects of different ventilatory patterns. A prospective clinical trial.

We compared the hemodynamic effects of three different ventilatory patterns including two variations of the I:E ratio (2:1 and 3:1) and a PEEP-pattern with the MAWP being equal in all three patterns. The study was performed on 15 patients without lung or cardiovascular disease who were ventilated after elective abdominal surgery. Each of the patients was subjected to the three different pressure wave curves. The IPPV served as control. Hemodynamic measurements included TEE registration of the LV cross-sectional areas, diameters and wall thickness as well as arterial blood pressure and heart rate. As a result, we found no significant differences in the hemodynamic effects of all three patterns. Compared with IPPV, they showed a reduction of systolic and diastolic blood pressure, LV dimensions and systolic wall stress. Assessed with the end systolic quotient, LV contractility remained constant.

Abdomen↗
PubMed1991

[Therapeutic use of fresh plasma and "virus-safe" plasma].

The use of plasma and factor concentrates for the treatment of coagulation disorders is well established, but many questions remain. The indications for fresh frozen plasma are still not clearly established and excessive use is rampant. The safety of all blood products has not yet been firmly established. Peer review of transfusion practice in a hospital can be achieved by a Hospital Transfusion Committee. The review and analysis of the statistical reports of the transfusion service and strategies for enhancing quality of patient care will be presented.

Algorithms↗
PubMed1990

[Changes in redox potentials in serum samples as affected by adenosine triphosphate].

Irradiated serum samples show characteristic alterations of their redoxpotential. This reaction is in close correlation to metabolic alterations, that for instance occur with tumor growth or severe inflammatory diseases. The role of ATP as universal biochemical energy transmitter led us to study the influence of ATP on redoxpotential in serum. In result the sole addition of ATP to serum in vitro gave a clear alteration of the redoxpotentials. In healthy persons a shifting of redoxpotentials was seen to high positive values. On the other hand ATP has slight influence on sera of tumor patients.

Adenosine Triphosphate↗
PubMed1989

[The effect of iodized mineral substance mixtures for cattle and swine on iodine requirements and struma prevention].

In the southern districts of the GDR the calculated iodine uptake of adults was 80 micrograms/day before the iodine supplementation of the mixtures of mineral substances and the packet kitchen salt. The iodine supplementation of the mixtures of mineral substances for cattle and pig tripled the iodine content of the milk or increased it fivefold in the county of Erfurt and doubled the proportion of iodine of the meat, the inner parts and the sausage produced from them. In a daily consumption of 0.31 of milk and 250 g of meat and sausage a surplus supply of 35 micrograms of iodine for adults was calculated in the southern counties of the GDR. The 35 micrograms of iodine for the future necessary for covering the demand of iodine are certainly delivered by the iodized kitchen salt.

Animal Feed↗