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Biomedical subjects

W Rautenberg

Publications and source records attributed to W Rautenberg.

At least 55 records · Page 3Linked to original sources
PubMed1986

Improvement of dialyzer compatibility by reduction of membrane surface area.

The present study was devised to investigate, whether reduction of membrane surface area would contribute to enhanced dialyzer membrane compatibility. Therefore, 10 hemodialysis patients were dialyzed with three different cuprophan dialyzers, displaying membrane surface areas of 0.9 m2, 1.2 m2, and 1.8 m2. As an index of biocompatibility release of granulocyte elastase and secretion of granulocyte lactoferrin were determined by enzyme-linked immunoassays. With the three cuprophan membranes, marked leukopenia occurred 15 min after the start of hemodialysis, without significant distinction between the different membranes. On the other hand, the release of leukocyte elastase was strictly dependent on the membrane surface area. Thus, at the end of dialysis, plasma levels of elastase were as follows: 0.9 m2: 255 +/- 51; 1.2 m2: 356 +/- 65; 1.8 m2: 471 +/- 56 ng/ml. The magnitude of secretion of leukocytic lactoferrin was also dependent on membrane surface area. Therefore, the increment during dialysis was 300% with the 1.2 m2 membrane compared to 650% using a 1.8 m2 dialyzer. Based upon these data, we concluded that, using measurements of granulocyte degranulation as an index of biocompatibility, reduction of membrane area resulted in a marked improvement of membrane compatibility.

Adult↗
PubMed1985

Spontaneous progression and regression of small carotid atheroma.

A specially designed high-resolution (10 MHz) ultrasound duplex-system was used to study prospectively the appearance of 43 extracranial non-stenotic carotid plaques (less than 30% lumen narrowing) in 31 patients over 18 months. 13 presented with ipsilateral and 9 with contralateral cerebrovascular events; 9 were asymptomatic. Most carotid atheromas remained unchanged (51%) or progressed (30%), but spontaneous regression was seen in 19% at regular 3 monthly re-examination. Regression was restricted to volume reduction of soft plaques and healing of ulcerative lesions; fibrous and hard plaques remained unchanged or progressed. Intraplaque haemorrhage was only observed in 3 instances and was always associated with later progressive encroachment. Comparison of bilateral plaques in the same individual suggested a uniform advance with duration of the atherosclerotic process. None of the patients had cerebrovascular events during follow-up.

Adult↗
PubMed1985

Dynamics and topography of human temperature regulation in response to thermal and work load.

Climatic chamber experiments were carried out with male subjects who were submitted to various rapid temperature changes. All experiments were performed first with the subjects at rest and later at work on a bicycle ergometer. The aims of the study were to obtain quantitative data enabling to determine effects of abrupt thermal load, abrupt work load, and combined load on the topography and the dynamics of temperatures and effectors, and to answer the question whether the effects of combined load may be computed by a linear superposition of pure thermal plus pure work load. Skin temperatures generally respond more directly to abrupt changes of thermal than of work load. This is in contrast to the dynamic behaviour of central temperatures which moreover exhibit the interesting effect of a transient paradoxical response both to the onset of work and of thermal load. Time constants of the dynamics of metabolic heat production are high in response to changes of thermal load as compared to the time constants at the onset and end of work. Generally the time constants of skin temperatures are shorter at rest than at work. Temperature topography changes only to a small extent in exercising subjects. The central temperature increase to combined thermal and work load is not significantly different from the added amount of temperature increases due to pure thermal and to pure work load. This suggests a quasi-linear superposition of both thermal effects and confirms, in accordance with further evidence of this and former studies, the hypothesis that work load does not interfere non-linearly with the regulatory processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

[Development of nonstenotic extracranial carotid plaques--a prospective study of its course with the Duplex system].

The natural history of a prospectively investigated group of patients with small non-stenotic extracranial carotid lesions (less than 30% lumen narrowing) was studied during 18 months. Using a specially designed high resolution (10 MHz) ultrasound Duplex system, 43 lesions were followed in 31 patients. Whereas the majority of the carotid atheromas remained unchanged (51%) or deteriorated (30%), spontaneous regression could be observed in 19%. Regression was limited to volume reduction of "soft plaques" and healing of "ulcerative" lesions, while "fibrous" and "hard plaques" remained unchanged or deteriorated. None of the patients developed cerebrovascular events during follow-up.

Adult↗
PubMed1985

Respiratory and cardiovascular responses of the exercising chicken to spinal cord cooling at different ambient temperatures. I. Cardiovascular responses and blood gases.

We measured oxygen consumption (VO2), heart rate (HR), stroke volume (SV), cardiac output (CO) and mean arterial blood pressure (MBPa) of chickens during 15 min treadmill exercise at 0.5 ms-1 and 0.8 ms-1 at thermoneutral (23 degrees C), low (9 degrees C) and high (34 degrees C) ambient temperature (Ta); the vertebral canal was cooled to 34 degrees C during the middle 5 min of each exercise period. PO2, PCO2, pH and oxygen content (CO2) of the arterial and mixed venous blood were also measured. VO2 during exercise was not significantly affected by Ta. Spinal cord cooling produced definite increases in VO2, CO and SV during 0.5 ms-1 exercise at 9 degrees C; otherwise, effects of spinal cord cooling were not significant. HR, SV and CO were all linearly related to VO2; these relationships were unaffected by spinal cord cooling or Ta. Blood pressure did not increase during exercise. PaCO2 and P-vCO2 did not increase significantly during exercise. The arterial-venous CO2 difference was increased by exercise only at 34 degrees C. The chickens generally hyperventilated at 34 degrees C Ta compared to the other Ta values. No consistent effect on blood gases or on pH and CO2 of the blood could be attributed to spinal cord cooling.

Animals↗
PubMed1985

Respiratory and cardiovascular responses of the exercising chicken to spinal cord cooling at different ambient temperatures. II. Respiratory responses.

We measured oxygen consumption (VO2), carbon dioxide production (VCO2), minute volume (VE), respiratory frequency (f) and tidal volume (VT) of chickens during 15 min treadmill exercise at 0.5 ms-1 and 0.8 ms-1 at thermoneutral (23 degrees C), low (9 degrees C) and high (34 degrees C) ambient temperature (Ta); the vertebral canal was cooled to 34 degrees C during the middle 5 min of each exercise period. Temperatures of the vertebral canal (TVC) and rectum (Tre) were also measured. Exercise at 0.5 ms-1 caused increases in O2 consumption, CO2 production, minute volume and tidal volume compared to resting controls at each Ta. Minute volume and respiratory frequency were higher and tidal volume was lower in birds exercising at 34 degrees C than at 23 or 9 degrees C. Spinal cord cooling during exercise (0.5 ms-1) at 9 degrees C caused further increases in O2 consumption, tidal volume and respiratory frequency almost equivalent to those produced by an increase in the running speed to 0.8 ms-1. Spinal cord cooling during exercise (0.5 ms-1) at 23 degrees C did not significantly affect O2 consumption, CO2 production, minute volume, tidal volume or respiratory frequency. Spinal cord cooling during exercise (0.5 ms-1) at 34 degrees C did not affect O2 consumption or CO2 production, but caused decreases in minute volume and respiratory frequency and an increase in tidal volume. We conclude that the domestic fowl exhibits spinal thermosensitivity during exercise, although these responses appear to be smaller than those previously reported for the resting bird. Decreased external temperature potentiates the effects of spinal cord cooling during exercise.

Animals↗
PubMed1984

[Spontaneous clinical course of asymptomatic vascular processes of the extracranial cerebral arteries. Further results of a long-term prospective study].

The natural history of a prospectively selected group of neurologically asymptomatic patients with extracranial arterial disease (EAD) was studied. 35 of 184 patients died over a period of follow-up of four years (mean = 21 months). Only four of them had a stroke, while coronary artery disease was the far more common cause of death (n = 19). Among those patients still alive 12 reported transient ischaemic attacks, two a stroke, and 116 remained asymptomatic--only two patients could not be followed. Thus by life-table analysis, the cumulative stroke rate was only 6%, irrespective of death or survival, about the same as the average risk of death in a normal population (5%). However, the probability of EAD progression was 88% as revealed by subsequent continuous-wave Doppler analysis of both the carotid and vertebral arteries in the neck. Neither the degree of initial EAD nor its progression during follow-up were found to represent significant indicators of the patient's cerebrovascular risk. Since the majority of symptomatic patients did not proceed to frank strokes but presented with TIAs, prophylactic surgical treatment may reasonably be delayed.

Aged↗
PubMed1984

Cardiovascular and blood gas responses to shivering produced by external and central cooling in the pigeon.

Cardiovascular and blood gas responses of pigeons to spinal cord cooling (35-36 degrees C) were measured at thermoneutral (28 degrees C) and low (5 degrees C) ambient temperatures. Spinal cord cooling at thermoneutral temperatures caused immediate shivering and increases in heat production (223%), heart rate (152%) and cardiac output (169%), but blood pressure and stroke volume did not change. PaCO2 and PvCO2 increased slightly during the cooling; PaO2 and CaO2 decreased slightly while PvO2 and CvO2 decreased considerably (10 Torr and 1.7 mmol . l-1, respectively), resulting in a greater a-v difference in O2 content. Ambient cooling produced responses comparable to spinal cord cooling. Simultaneous spinal cord and ambient cooling produced similar responses that were generally greater in magnitude than either kind of cooling alone. Consequently, heart rate, cardiac output and O2 extraction from the blood were all significantly, linearly related to heat production over the wide range studied. Comparisons are made between cardiovascular responses of birds to shivering and exercise in regards to the relative importance of increases in heart rate, stroke volume and blood pressure. It is suggested that exercise and shivering may effect cardiovascular responses through similar receptor mechanisms.

Animals↗
PubMed1984

Respiratory responses to shivering produced by external and central cooling in the pigeon.

Respiratory responses of pigeons to spinal cord cooling (5-6 degrees C) in neutral environment (Ta = 28 degrees C), to ambient cooling (Ta = 5 degrees C), and to simultaneous spinal cord and ambient cooling were measured. Spinal cord cooling produced shivering and a 242% increased in heat production (M); expiratory flow rate (VE) increased 216%, a result of increases in both respiratory frequency (160%) and tidal volume (140%). Increases produced by ambient cooling compared to thermoneutral controls were slightly, but not significantly, less than those during spinal cord cooling: M = 203%, VE = 199%, respiratory frequency (fR) = 146%, tidal volume (VT) = 138%. Spinal cord cooling at low ambient temperature produced greater increases in shivering, heat production and respiration compared to thermoneutral controls than either type of cooling alone: M = 337%, VE = 326%, fR = 198%, VT = 178%. The oxygen extraction from the ventilatory gas remained relatively constant among the different groups. fR, VT and VE were all significantly linearly related to M over the wide range studied. These relationships were independent of whether cooling was central or external. Respiratory changes induced by the onset and end of spinal cord cooling were immediate and closely correlated with the magnitude of shivering. It is unlikely that changes in arterial and venous blood gases during shivering effected the major portion of the respiratory response. Thus, it is suggested that a control mechanism of the respiratory center via afferents from the shivering muscles is important in increasing respiration during central or external cooling.

Animals↗
PubMed1984

Cardiovascular and blood gas changes during panting responses induced by ambient or spinal cord heating in the pigeon.

We measured respiratory frequency (fR), oxygen consumption (VO2), cardiovascular responses and arterial and mixed venous PCO2, PO2, pH and CO2 in six pigeons during hyperthermia caused by ambient heating (increase in body temperature = 1 degrees C) and during heating of the spinal cord alone (increase in vertebral canal temperature = 3 degrees C). Spinal cord heating caused an increase in fR to 546 min-1 (+/- 13 min-1 SE) and increases in VO2, heart frequency (fH) and cardiac output (CO); PaCO2 and PVCO2 decreased 3.4 and 4.6 torr, respectively, while PaCO2 increased 6.8 torr. fR during ambient heating was 489 +/- 36 min-1; cardiovascular and blood gas changes were, generally, in the same direction as those during spinal cord heating but of lesser magnitude. In six other pigeons, we characterized fR, VO2, cardiovascular and blood gas changes during a 4 degrees C rise in body temperature caused by increased ambient temperature. Those data showed that with increasing hyperthermia fR increased rapidly, though not stepwise, to a maximum while VO2, fH, CO, PaO2, pHa and the arterial-venous CO2 difference all gradually increased; PaCO2 and PVCO2 gradually decreased. We conclude that, generally, whole body heating by increased ambient temperature and heating of the spinal cord alone produce the same responses and that these responses are dependent on the magnitude of the heat stimulation.

Animals↗
PubMed1984

Aminopeptidases from human leucocytes.

Six aminopeptidases differing in enzymic specificity against various L-amino acid-4-nitroanilides were detected and isolated from the cytosol of leucocytes collected from the buffy coat of human blood. The different enzymes were separated by one step of chromatography on DEAE-Sephacel and were further purified by gel filtration on Sephacryl S-300. The main aminopeptidases of the cytosol were designated aminopeptidases 1, 2, 4 and 5 (AP 1, AP 2, AP 4, AP 5) on the basis of their elution sequence from the first ion-exchange chromatography column on DEAE-Sephacel. Aminopeptidase 1 appeared to be a strongly sulfhydryl-dependent leucine aminopeptidase, activatable by thiol reagents. The enzyme was inhibited by p-chloromercuribenzoate. Its molecular mass was estimated to be 150 kDa. Aminopeptidase 2 showed high specificity for proline-4-nitroanilide. This enzyme was inhibited by p-chloro-mercuribenzoate and bestatin. It exhibited a molecular mass of 70 kDa. Aminopeptidase 4 designated the activities of two different enzymes of apparent molecular masses of 220 and 70 kDa which could be further separated by gel filtration. Aminopeptidase 5 exhibited the properties alike aminopeptidase B with high specific hydrolytic activity against the 4-nitroanilides of lysine and arginine. The molecular mass was estimated to be 90 kDa. Aminopeptidase 3 was a minor component in the cytosol and could be identified as an extracellular leucocyte plasma membrane constituent. The enzyme exhibited properties of a metallo proteinase and could be inhibited by EDTA. The molecular mass was estimated to be 250 kDa.

Aminopeptidases↗
PubMed1983

Circadian and arousal state influences on thermoregulation in the pigeon.

We report here the characteristics of spinal thermosensitivity in pigeons as a function of arousal state and time of day. At any time in the light-dark (LD) cycle, the thresholds for shivering and panting were lower during non-rapid-eye-movement (NREM) sleep than during wakefulness. These thresholds in both awake and sleeping animals were lower during D than during L. The gain of the metabolic response to spinal cooling was nearly the same in wakefulness and NREM sleep. Shivering and panting responses to spinal thermal stimulations were impaired during REM sleep compared with wakefulness and NREM sleep. The results support the idea that central nervous system mechanisms controlling arousal states and circadian rhythmicity have separate and additive influences on temperature regulation in the pigeon.

Animals↗
PubMed1982

Stroke risk from symptomless extracranial arterial disease.

The natural history of a prospectively selected group of neurologically symptomless patients with extracranial arterial disease (EAD) was studied. 23 of 122 patients died over a period of follow-up of from eleven to thirty-six months (mean = seventeen), but only 3 from stroke and 10 from cardiac failure. Among those patients still alive 8 reported transient ischaemic attacks, 1 a stroke, and 90 remain symptomless. Thus, by life-table analysis, the cumulative stroke rate was only 7%, irrespective of death or survival, the same as the average risk of death in a normal population. However, by subsequent continuous-wave Doppler examination of carotid and vertebral arteries, the probability of EAD progression was 85%. Involvement of initially unaffected arteries occurred either alone (25) or in combination with a deterioration of the original stenosis (14)--the latter alone was seen in 9 patients. A combined carotid and vertebral lesion was found to be the only significant indicator of cerebrovascular risk, which was six times greater than that for unilateral or bilateral carotid lesions.

Arterial Occlusive Diseases↗
PubMed1982

Separation of the human leucocyte enzymes alanine aminopeptidase, cathepsin G, collagenase, elastase and myeloperoxidase.

A simple and rapid procedure is described for the separation of the human leucocyte enzymes alanine aminopeptidase, cathepsin G, collagenase, elastase and myeloperoxidase. The enzymes are prepared from leucocytes, obtained from buffy coat, by repeated extraction with buffer A(1 M salt concentration). The pooled extracts are successively subjected to batch adsorption on concanavalin A-Sepharose, gel filtration on Sephacryl S-300, affinity chromatography on collagen-Sepharose 4-B, batch adsorption on CM-Sephadex C-50 and adsorption chromatography on hydroxyapatite. The yields of the isolated enzymes of a typical preparation are 47% alanine aminopeptidase, 9% cathepsin G, 90% latent and active collagenase, 23% elastase and approximately 100% myeloperoxidase with respect to the pooled extracts. The cathepsin G, collagenase and elastase preparations are essentially free from other proteolytic enzymes and may be used without further purifications.

Aminopeptidases↗
PubMed1980

Effect of spinal cord temperature on carotid blood flow in the Pekin duck.

Spinal cord heating in white Pekin ducks increases breathing rate and carotid blood flow. During naturally induced panting, the reverse effect was achieved by spinal cooling. An increased beak and expired air temperature during spinal heating suggest an importance of the increased carotid blood flow in maximizing heat dissipation during polypnoea. The results indicate that both the polypneic response and the increase in carotid blood flow are dependent on the same sensory input, namely the temperature of the spinal cord.

Animals↗
PubMed1975

Effect of spinal deafferentation on temperature regulation and spinal thermosensitivity in pigeons.

1. To study the effect of spinal deafferentation on temperature regulation and spinal thermosensitivity in acute experiments, the spinal cord of pigeons was transected at Th4 and the dorsal roots cut carefully on both sides from Th4 to C6 or C4 (13 or 15 segments); only afferent signals from the upper neck and the head could reach the CNS. Selective changes of the spinal cord temperature in the deafferented region were performed by a thermode in the vertebral canal. 2. At thermoneutral ambient conditions (Ta 23-30 degrees C) the deafferented pigeons were able to maintain a normal body temperature (about 41 degrees C). During ambient cooling (Ta 1-10 degrees C) the core temperature was regulated at a lower level of about 38 degrees C, strong shivering occurred, and heat production was increased. 3. If the decreased spinal cord temperature at low Ta was adjusted experimentally to normal values (about 41 degrees C) then shivering stopped and oxygen consumption decreased. This decrease in heat production was followed by a continuous fall in rectal temperature to values as low as 33-34 degrees C without any initiation of shivering or extra heat production. This means that shivering in the deafferented pigeons must be elicited by cold sensors in the spinal cord alone and that there are no important cold sensors in the non-deafferented region including the brain. 4. Selective spinal cooling of the deafferented region at thermoneutral Ta was followed by an immediate onset of shivering and an increase in heat production. Spinal heating resulted in an increase in wing temperature which served as an indication of vasodilatation, i.e., an activation of a heat loss mechanism. This is a confirmation of the assumption that the spinal temperature sensors are indeed located in the spinal cord and that the responses to experimental changes of spinal canal temperature are not mediated by extraspinal thermoreceptors. The results show clearly that the regulation of body temperature in pigeons at moderate thermal loads can be mediated by these spinal sensors alone. 5. Continued spinal cooling resulted in an increase in body temperature by about 2 degrees C and a subsequent regulation at this high level. This means that there must exist warm sensors in the non-deafferented cranial region.

Animals↗