Biomedical subjects

B Walter

Publications and source records attributed to B Walter.

At least 55 records · Page 3Linked to original sources

PubMed1999

Regional distribution of cerebral blood volume and cerebral blood flow in newborn piglets--effect of hypoxia/hypercapnia.

The relationship between regional parenchymal cerebral blood volume (CBV), regional cerebral blood flow (CBF) and the calculated mean transit time (MTT) was investigated in 14 newborn piglets. The effects of combined hypoxic hypoxia (PaO2 = 32 +/- 5 mm Hg) and hypercapnia (paCO2 = 68 +/- 5 mm Hg) were measured in seven animals. Remaining animals served as the control group. During baseline conditions the highest CBF and CVB values were found in the lower brainstem and cerebellum, whereas white matter exhibited the lowest values (p < 0.05). MTT was prolonged within the cerebral cortex (2.34 +/- 0.42 s-1) compared with the thalamic MTT (1.53 +/- 0.38 s-1) (p < 0.05). Under moderate hypoxia/hypercapnia, a CBF increase to the forebrain (p < 0.05) resulted in an elevated brain oxygen delivery (p < 0.05) and so CMRO2 remained unchanged. Moreover, a moderate increase of CBV and a marked shortening of MTT occurred (p < 0.05). The CBV increase was higher in structures with lowest baseline values, i.e., thalamus (66% increase) and white matter (62% increase) (p < 0.05). MTT was between 22% of baseline in the lower brainstem and 49% in white matter (p < 0.05). We conclude that under normoxic and normocapnic conditions the newborn piglets exhibit a comparatively enlarged intraparenchymal CBV. Moderate hypoxia and hypercapnia induced a marked increase in cerebral blood flow which appears to be caused by an increased perfusion velocity, expressed by a strongly reduced mean transit time and by a concomitant CBV increase.

Animals↗

PubMed1999

Upregulation of the aromatic amino acid decarboxylase under neonatal asphyxia.

Perinatal hypoxic-ischemic cerebral injury is a major determinant of neurologic morbidity and mortality in the neonatal period and later in childhood. There is evidence that the dopaminergic system is sensitive to asphyxia. However, the respective enzyme activities have not yet been measured in the living neonatal brain. In this study, we have used 18F-labeled 6-fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) together with positron-emission tomography (PET) to estimate the activity of the aromatic amino acid decarboxylase (AADC), the ultimate enzyme in the synthesis of dopamine (DA), in the brain of newborn piglets. Simultaneously, the cerebral blood flow (CBF) was measured with colored microspheres. Asphyxia elicited an up to threefold increase of the CBF. Despite this, the blood-brain transfer of FDOPA as well as the clearance rate constants from brain were unchanged. However, the synthesis rate of FDA from FDOPA was significantly increased in frontal cortex, striatum, and midbrain. This increase of the AADC activity and the decrease of monoamine oxidase activity may contribute to the increase of extracellular DA during asphyxia which is expected to be involved in severe disturbances of neuronal metabolism, e.g., by generating free radicals.

Algorithms↗

PubMed1999

Biomechanical behaviour in vitro of the spine and lumbosacral junction.

Six fresh human specimens extending from the 9th thoracic vertebra (T9) to the pelvis were used to study the biomechanical behaviour of the long lumbopelvic segments, including mobility of the sacrum. The loads were applied at T9 using pure couples up to 5 Nm. The displacements were measured by an optoelectronic method (VICON 140). Stress-displacement curves were obtained for the three angular components of the vertebra studied according to the plane of the principal stresses and of the two other planes corresponding to the coupled mobilities. Mobility decreased from T9 to the sacrum. There was mobility of the sacrum in relation to the pelvis in flexion, with a mean of 1.28 degrees (0.5 to 2.8 degrees); 3 sacrums showed a mobility of the order of one degree for torsional stresses. There was no sacral mobility during stresses in lateral flexion. The use of this experimental protocol with low mechanical stresses should allow the evaluation of long osteosyntheses extending to the sacrum.

Biomechanical Phenomena↗

PubMed1999

Evaluation of micro tip pressure transducers for the measurement of intracerebral pressure transients induced by fluid percussion.

We describe the application of MIKRO TIP miniature pressure transducers (MPT) for the in vivo measurement of intracerebral stresses induced by traumatic brain injury (TBI). In order to test the linearity of these transducers pressure pulses of different amplitudes (duration approximately 10ms) were generated in a closed calibration chamber. A piezoelectric pressure transducer (PPT) served as the reference measure. A linear correlation was found within the pressure range between 0.57 and 5.09 bar (R2 = 0.998). The frequency transmission characteristics of the MPTs are comparable to the PPT. In three juvenile swines (6 weeks of age) pressures within the brain tissue were induced by fluid percussion (FP) and were measured in the anterior, middle, and posterior cranial cavity as well as in the extracranial part of the medulla oblongata. The data obtained in our experiments agree with the basic biomechanics of FP known from studies in cats and rabbits. Due to their small size, MPTs can be applied in living animals. Stereotaxic positioning of these catheters at any site of the brain and spinal cord requires only minimal surgery. Therefore, MPTs are useful in evaluating animal models of brain injury and in generating input data for computational models of head injury as well as to validate the mathematical results of such models with experimental data.

Animals↗

PubMed1999

Ontogenetic aspects of traumatic brain edema--facts and suggestions.

Diffuse brain swelling (DBS) after severe traumatic brain injury (TBI) occurs more commonly in children than adults. Most of the recent clinical studies suggest that young children are more negatively affected by DBS. Until now studies in young animals in which the pathophysiology of DBS was evaluated remained seldom. However, pathogenetic mechanisms of edema formation after TBI in the immature brain appeared to be different in comparison to adult brains. There are evidences that vasogenic as well as cytotoxic edema components may be responsible for the development of DBS. Besides mechanical disturbance, the blood-brain barrier seems to be strongly endangered by oxidative stress after TBI because regional antioxidative capacity is obviously diminished. In addition, cytotoxic components of DBS may be caused by at least two different mechanisms. First, it was shown that a sustained posttraumatic cerebral hypoperfusion occurs in the immature brain. Moreover, a transient increase of NMDA receptor expression at this period of life may be responsible for an increased threat of intracellular sodium ion accumulation in brain cells. Obviously, brain swelling can be detrimental because it can elevate intracranial pressure, impair CBF, and may represent ongoing secondary brain injury.

Animals↗

PubMed1999

Hypothermia related changes in electrocortical activity at stepwise increase of intracranial pressure in piglets.

Recent experimental studies have demonstrated that mild hypothermia can be effective in the control of intracranial hypertension. However, investigations to analyze the effects of hypothermia on changes in brain oxygen metabolism and electrocortical activity caused by increased intracranial pressure (ICP) are lacking. We examined the effects of mild hypothermia on electrocorticogram (ECoG) in combination with measurement of regional cerebral blood flow (CBF) and estimation of brain oxygen metabolism during stepwise increase of ICP. For this purpose thirteen female piglets (14 days old, 4-5 kg b.w.) were anaesthetized and mechanically ventilated. An epidural balloon was gradually inflated in order to increase ICP to 25 mmHg, 35 mmHg and 45 mmHg every 30 minutes at adjusted mean arterial blood pressures (MAP). This procedure resulted in gradual cerebral perfusion pressure (CPP) reduction of about 70%, 50%, and 30% of baseline [baseline CPP: normothermia (NT) 80+/-3 mmHg; hypothermia (HT) 84+/-3 mmHg]. Control animals were maintained in a normothermic state (38.6+/-0.2 degrees C). HT animals were surface cooled and maintained at 31.9+/-0.1 degrees C. ECoG, regional CBF, cerebral oxygen delivery (cDO2) and the cerebral metabolic rate of oxygen (CMRO2) were estimated during the normothermic period, after hypothermic stabilization, and after the gradual CPP reductions. The baseline ECoG showed the typical delta-dominated frequency pattern for isoflurane anaesthesia. At the hypothermic level, a frequency shift was seen from delta activity towards the higher frequencies (theta- and alpha activity) and the total spectral power was significantly reduced (56+/-17% from baseline, p < 0.05). the cortical CBF decreased markedly to 67+/-10% (p < 0.05), whereas the medulla oblongata blood flow increased slightly. During controlled increase of ICP by regional mass expansion from epidural balloon inflation, we found at mild and moderate stages of ICP increase (25 and 35 mmHg) only minimal changes in the ECoG in hypothermic animals compared to the hypothermic baseline, whereas the ECoG in normothermic animals showed a marked decrease in frequency, amplitude and total spectral power. We conclude that mild hypothermia produces an arousal-like ECoG activity with marked frequency shift to alpha activity and a change from high to low voltage activity. Furthermore, the hypothermic brain showed a preserved neuronal function at moderate stages of ICP. Obviously, hypothermia improves the functional tolerance of the brain to impaired oxygen supply.

Animals↗

PubMed1999

Pitfall: a pseudo tumor within the left liver lobe presenting with abdominal pain, jaundice and severe weight loss.

A 51 year old male patient with a history of chronic alcohol consumption and recurrent pancreatitis was referred to our hospital with jaundice, epigastric pain, severe diarrhoea and weight loss of 28 kg within the last 12 months. A CT scan of the abdomen 4 months before admission had shown a pancreatitis with free fluid around the corpus and tail of the pancreas as well as dilated intrahepatic bile ducts and a cavernous transformation of the portal vein. Moreover, a tumor (3.5 x 3.0 x 3.6 cm) with irregular contrast enhancement was seen within the left liver lobe. The patient was referred to us for further evaluation and treatment. The initial B-Mode sonogram revealed a bull's eye like well defined lesion (8.1 x 7.5 x 7.0 cm) within the left liver lobe, consistent with a tumour or abscess. Prior to a diagnostic needle biopsy a PTCD was performed in this case presenting with dilated intrahepatic bile ducts and having a history of Billroth II operation. An additional colour coded Duplex Doppler ultrasonography demonstrated a visceral artery aneurysm and prevented us from performing the diagnostic puncture. The aneurysm was assumed to originate from a variant or a branch of the left hepatic artery. Angiography revealed a pseudoaneurysm of the pancreaticoduodenal artery and coil embolization was performed because of the increasing size and the risk of a bleeding complication. Postinterventional colour duplex ultrasound measurement showed no blood flow within the aneurysm. Retrospectively, the pseudoaneurysm must have led to a compression of the common bile duct, since the patient did not develop cholestasis after embolization and removal of the PTCD. Thus, a pseudoaneurysm of the pancreaticoduodenal artery must be included in the differential diagnosis of liver tumours in patients with chronic pancreatitis, despite its unusual localization near the liver. Therefore, we suggest that colour coded ultrasonography should be applied to any unclear, bull's eye like lesion, even though this method alone cannot exactly determine the origin of the pseudoaneurysm. Interventional angiography remains the gold standard for the diagnosis and therapy of visceral artery aneurysm.

Alcohol-Related Disorders↗

PubMed1999

The nine C-terminal residues of the grapevine fanleaf nepovirus movement protein are critical for systemic virus spread.

The grapevine fanleaf virus (GFLV) RNA2-encoded polyprotein P2 is proteolytically cleaved by the RNA1-encoded proteinase to yield protein 2A, 2B(MP) movement protein and 2C(CP) coat protein. To further investigate the role of the 2B(MP) and 2C(CP) proteins in virus movement, RNA2 was engineered by alternatively replacing the GFLV 2B(MP) and 2C(CP) genes with their counterparts from the closely related Arabis mosaic virus (ArMV). Transcripts of all chimeric RNA2s were able to replicate in Chenopodium quinoa protoplasts and form tubules in tobacco BY-2 protoplasts in the presence of the infectious transcript of GFLV RNA1. Virus particles were produced when the GFLV 2C(CP) gene was replaced with its ArMV counterpart, but systemic virus spread did not occur in C. quinoa plants. In addition, chimeric RNA2 containing the complete ArMV 2B(MP) gene was neither encapsidated nor infectious on plants, probably because polyprotein P2 was incompletely processed. However, chimeric RNA2 encoding ArMV 2B(MP), in which the nine C-terminal residues were those of GFLV 2B(MP), formed virus particles and were infectious in the presence of GFLV but not ArMV 2C(CP). These results suggest that the nine C-terminal residues of 2B(MP) must be of the same virus origin as the proteinase for efficient proteolytic processing of polyprotein P2 and from the same virus origin as the 2C(CP) for systemic virus spread.

Amino Acid Sequence↗

PubMed1999

A piglet model for evaluation of cerebral blood flow and brain oxidative metabolism during gradual cerebral perfusion pressure decrease.

A piglet model was developed to study the effect of epidural volume expansion on cerebral perfusion pressure (CPP) by stepwise elevating intracranial pressure (ICP). Mean arterial blood pressure (ABP) was strictly maintained using an extracorporeal ABP controller. Two-week-old piglets (n = 10) were studied by surgically placing an epidural balloon over the right parietal region and gradually increasing the inflation to increase ICP to 25, 35 and 45 mm Hg, maintaining each pressure level for 30 min. Regional cerebral blood flow was measured using the colored microsphere technique, and cerebral oxygen delivery and cerebral metabolic rate of oxygen were calculated at baseline conditions and after reaching ICP levels of 25, 35 and 45 mm Hg. The results showed that this model of epidural volume expansion reproducibly reduces CPP to 70, 50 and 33% of baseline CPP values with elevation of ICP, and that the physiological variables remained stable throughout each increase in ICP. We conclude that the model simulates the effects of an acute intracranial focal mass expansion and is well suited for the evaluation of different therapeutical strategies for increased ICP in newborns and infants.

Animals↗

PubMed1999

Diagnosis of Chilaiditi's syndrome with abdominal ultrasound.

Chilaiditi's sign is a radiographic term used when the hepatic flexure of the colon is seen interposed between the liver and right hemidiaphragm. When symptomatic, this is Chilaiditi's syndrome. We report a case of a 70-year-old man who presented with abdominal pain, vomiting, singultus and constipation. Ultrasound was initially performed which showed an intestinal loop between the anterior surface of the right liver lobe and the diaphragm. The chest X-ray revealed colon gas under the right diaphragma and the abdominal CT-scan confirmed the hepatodiaphragmatic interposition of the colon. Colonic elongation and laxity of colonic and hepatic suspensory ligaments are the principal predisposing factors. The advantages of the abdominal ultrasound in the diagnosis and follow-up as well as possible complications and forms of therapy with this syndrome are discussed.

Abdominal Pain↗

PubMed1998

Affective distress in fibromyalgia syndrome is associated with pain severity.

OBJECTIVE: Comparison of low back pain (LBP) patients with and without fibromyalgia syndrome (FMS) with regard to affective distress. METHODS: Patients with LBP who had been admitted to various clinics in Germany were examined upon admission. Comparisons were done by dividing the patients into groups with and without signs of FMS. Additionally, both groups were compared after being matched according to sex, age, and pain severity. RESULTS: 15 out of 135 LBP patients met the American College of Rheumatology criteria for fibromyalgia. Patients with FMS showed remarkably higher levels of pain severity and affective distress. After controlling for different levels of pain severity, these pronounced differences disappeared. CONCLUSION: Affective distress is not a unique feature of FMS, but seem to be caused entirely by higher levels of pain severity.

Adult↗

PubMed1998

Simultaneous measurement of [18F]FDOPA metabolism and cerebral blood flow in newborn piglets.

Available information on the dopamine (DA) metabolism of the immature brain is rare. In order to establish a useful animal model we have performed PET experiments in anesthetized neonatal pigs using 6-[18F]-fluoro-L-DOPA (FDOPA) as tracer. In this study, we have simultaneously determined the cerebral blood flow and the rate constant of FDOPA conversion by the aromatic amino acid decarboxylase, the ultimate enzyme in the synthesis of dopamine. The estimated values of FDOPA decarboxylation in the basal ganglia were similar to values calculated in adult animals and humans. However, in contrast to those studies a significant decarboxylation was also found in the frontal cortex and the cerebellum. HPLC analysis of brain samples also revealed extensive and rapid metabolism of FDOPA in the five investigated brain regions. At 8 min after tracer injection about 80% of FDOPA was already converted to FDA and its metabolites. Surprisingly, a rather high fraction (16-21%) of [18F]-fluoro-3-methoxytyramine was found which may indicate a low storage capacity of vesicular DA at this perinatal stage. It is suggested that the findings are related to the ontogenetic development of the dopaminergic system. The knowledge of the regulation of the DA metabolism in the immature brain may have implications for the understanding of neurodevelopmental effects of perinatal oxygen deprivation.

Animals↗

PubMed1998

Cardiovascular function and brain metabolites in normal weight and intrauterine growth restricted newborn piglets--effect of mild hypoxia.

In order to clarify the influence of intrauterine growth restriction on systemic hemodynamics, catecholamine response, and regional distribution of brain energy metabolites per se and during mild hypoxic episodes a study was performed in thirty newborns with a well-characterized state of intrauterine and intra-natal development. Thirty animals were divided into fifteen normal weight piglets (NW) and fifteen intrauterine growth restricted (IUGR) piglets according to their birth weight. Category "NW" covered animals with a birth weight of > 40th percentile; IUGR category covered animals with a birth weight of > 5th and < 10th percentiles. Animals were anesthetized with halothane in 70% nitrous oxide and 30% oxygen and after immobilization artificially ventilated. The acid-base balance and blood gas values at baseline conditions were similar within the different groups investigated and consistent with other data obtained from anesthetized and artificially ventilated newborn piglets. Mild hypoxic hypoxia which was induced by lowering the FiO2 from 0.35 to 0.15 resulted in reduced arterial pO2 (NW: from 115 +/- 37 mmHg to 39 +/- 7 mmHg; IUGR: from 117 +/- 23 mmHg to 39 +/- 3 mmHg; p < 0.05), but arterial pH and pCO2 remained unchanged. Under baseline conditions arterial blood pressure, cardiac output, and myocardial contractility, expressed as dp/dt(max) and plasma catecholamine values were similar in all groups studied. Heart rate was slightly increased in IUGR (p < 0.05). Mild hypoxia led to a strong increase of myocardial contractility in NW as well as IUGR piglets to 2.4 and 2.7 fold and remained increased during recovery (p < 0.05). Moreover, total peripheral resistance was enhanced at the end of recovery period in IUGR animals (p < 0.05). There was a significant increase of epinephrine (E) in NW animals in comparison to sham-operated animals (p < 0.05). Interestingly, during reoxygenation the further increase in E and norepinephrine (NE) levels were enhanced in the animals which suffered from mild hypoxia (p < 0.05). Regional distribution of brain tissue metabolites was partly affected by intrauterine growth restriction. In particular, brain tissue glucose content was strongly reduced by 65 to 72 per cent in all brain regions investigated. Mild hypoxia led to an increase of about 30 percent in NW animals (p < 0.05). In IUGR piglets the percentage increase of brain glucose content was on an average more pronounced but with considerably higher variance. Also, a strong increase of brain lactate content appeared here (p < 0.05). In contrast, brain tissue ATP was quite similar in all groups studied, but brain creatine phosphate was significantly reduced in some forebrain structures of IUGR piglets after mild hypoxia (figure 2, p < 0.05). In summary, this investigation provides information on cardiovascular functions and brain metabolites of normal weight and naturally occurring growth restricted newborn piglets. Mild hypoxemia was well-tolerated from both animal groups. It is suggested that lactate may play a significant role as a source for brain energy production in the newborn IUGR piglets.

Animals↗

PubMed1998

Influence of hypoxia and hypoxia/hypercapnia upon brain and blood peroxidative and glutathione status in normal weight and growth-restricted newborn piglets.

Glutathione (reduced (GSH) and oxidized (GSSG)), lipid peroxidation products (TBAR) and in vitro production of reactive oxygen species (ROS, by means of stimulated lipid peroxidation, H2O2 formation and amplified chemiluminescence (CL) in 9000 xg brain supernatants) were studied in the cerebellum (C) and temporoparietal area (TP) of the brain of normal weight (NW) and spontaneously intra-uterine growth-restricted newborn piglets (IUGR) after 1 hour hypoxia (fractional inspired oxygen concentration (FiO2) 8%), and in combination with 10% CO2, followed by 3 hours recovery (FiO2 30%). The strong GSH depletion accompanied by an increased concentration of GSSG and TBAR, more distinct in IUGR, is the most important result in the brain after hypoxia and reoxygenation. Hypercapnia-related acidosis seems to protect the brain of IUGR from hypoxia/reoxygenation induced injury by reducing GSH depletion as well as GSSG and TBAR increases. But stimulated lipid peroxidation and H2O2 formation in 9000 xg supernatants of C and TP were found to be higher in acidosis and hypercapnia. Decreased or unchanged amplified CL, demonstrating lower in vitro production of ROS, cannot explain the GSH depletion after hypoxia and reoxygenation. The scarce changes in erythrocyte GSH and GSSG as well as plasma TBAR concentrations did not reflect the findings in the brain. Nevertheless, the changes in the brain support the hypothesis that oxidative stress plays a role in neuronal damage after hypoxic stress, but the brain of IUGR did not reveal a special response to moderate hypoxia.

Acid-Base Equilibrium↗

PubMed1998

Influence of hypoxia and hyperthermia upon peroxidative and glutathione status in growth-restricted newborn piglets.

Normal weight (NW) and spontaneously intra-uterine growth-restricted newborn piglets (IUGR) were submitted to 1 hour hypoxia and hyperthermia followed by 3 hours reoxygenation. Glutathione (GSH, GSSG), lipid peroxidation products (TBAR) and cytochrome P450 dependent production of reactive oxygen species were studied by determination of H2O2 production and amplified chemiluminescence (CL) in brain and peripheral organs of NW and IUGR. A severe decrease of GSH was accompanied by enhanced H2O2 formation and lipid peroxidation in the brain of both NW and IUGR after hypoxia/hyperthermia and reoxygenation. In the other organs studied, only muscles showed enhanced lucigenine amplified CL and TBAR production. Nearly the same results in NW and IUGR reveal no higher risk of IUGR.

Animals↗

PubMed1998

Body weight distribution and organ size in newborn swine (sus scrofa domestica) -- a study describing an animal model for asymmetrical intrauterine growth retardation.

Normal growth is the expression of the genetic potential to growth which is neither abnormally constrained nor promoted by internal or external factors. Restricted fetal growth is common in human pregnancy and is associated with increased perinatal morbidity and mortality. Because of ethical restrictions, pathogenetical studies are necessarily dependent on appropriate animal models. In the studies presented, evidence will be provided that the naturally occurring distribution of body weight in newborn piglets, obtained from n = 512 newborn piglets (about 12 hours old) in 50 consecutive deliveries in the breed cohort of the mixed German domestic breed - "Deutsches Land-/Edelschwein" gives an appropriate sampling for providing a statistically reliable basis with which to determine different degrees of fetal growth for further pathophysiological studies intended. A strong inverse correlation (r = -0.66, p < 0.05) was found between the mean weight of the litter and the number of piglets per litter, and an inverse correlation (r = -0.64, p < 0.05) was found between the lowest weight of the littermate and the number of piglets per litter. Moreover, gravimetric investigations were made into an additional 53 one-day-old newborn piglets reflecting the naturally occurring birth weight distribution determined. A marked linear correlation between body weights and various organ weights was found (values of the correlation coefficient amounted to between 0.45 and 0.98; p < 0.05). The lowest variation of organ weights was found in the CNS structures (0.68-1.33). Skeleton and heart exhibited similar ranges of weight variation (0.35-1.81 and 0.38-2.00 of the means) to body weight (0.38-1.77 of the means). This was also expressed in the regression analysis, because the slope values were 0.99 and 0.97 respectively. The hormonal glands investigated, the kidneys, and the abdominal parenchymal organs exhibited the largest ranges of weight variation. Moreover, regression analysis gives evidence that the weight restriction was more pronounced than expected concerning respective body weight. This is indicated by slope values > 1 in almost all of those organs. Plasma concentration of IGF-1 showed an inverse correlation with body weight (r = -0.42; p < 0.05, fig 4). IGF-1 concentration of intrauterine growth retarded (IUGR) newborn piglets was in the mean nearly double that of normal weight animals (p < 0.05) and the brain weight to liver weight ratio was increased more than 2.5 times in IUGR newborn (fig 5 A, p < 0.05). This investigation provides information on the naturally occurring body weight distribution of one-day-old piglets, which was obviously a result of epigenetic factors. Gravimetrical estimation showed clearly that body weight variety is most probably caused by alterations of placental functioning. Severe alterations resulted in asymmetrical growth retardation, which was proved by a significantly increased brain to liver ratio in animals with a body weight < 10th centile. Thus, evidence is provided that naturally occurring asymmetrical intrauterine growth restricted newborn piglets can be identified simply by body weight measurement, so that convenient conditions are given for pathogenetically motivated studies on intrauterine compromised newborns.

Animals↗

PubMed1998

Estimation of nonlinear couplings on the basis of complexity and predictability--a new method applied to cardiorespiratory coordination.

Nonlinear coordination is an essential property of the complex functioning of the autonomic nervous system. Therefore, the coupled behavior of heart rate fluctuations (HRF) and respiratory movements (RM) was analyzed on the basis of their joint reconstruction in the phase space. Independence measures of complexity and predictability were approximated from the correlation integrals which enabled the strength of cardiorespiratory couplings to be quantified. These measures were validated in a simulation study of two coupled nonlinear oscillators in dependence on their coupling strength and respective synchronization effects. The cardiorespiratory coordination during quiet sleep and active sleep of newborn piglets was quantified by means of the proposed independence measures of complexity and predictability. The difference of those measures between the sleep states investigated was more significant than the difference of the respective linear coherence peaks.

Animals↗

PubMed1997

CDRH3 length is the target of selection of disease-associated IgM autoantibodies.

The experiments outlined here provide evidence for positive selection of B-1 lymphocytes secreting IgM autoantibodies in the autoimmune mev mice as a result of the reduced threshold of responsiveness to autoantigens because of PTP1C deficiency, which is targeted at the CDR3 length of the variable region of the heavy chain. In addition, characteristic differences in the size, hydrophobicity pattern, and relative local charge of the CDR3 of the heavy chain of disease-associated IgM autoantibodies from moth-eaten mice help distinguish them from physiological natural autoantibodies present in normal mice.

Animals↗