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Biomedical subjects

A Just

Publications and source records attributed to A Just.

At least 55 records · Page 3Linked to original sources
PubMed1995

On the origin of low-frequency blood pressure variability in the conscious dog.

1. Baroreceptor denervation increases blood pressure variability below 0.1 Hz. This study was undertaken to determine to what extent these fluctuations originate from the central nervous system or from cardiovascular sources. 2. Blood pressure was recorded at a rate of 10 Hz for approximately 3.5 h in conscious, resting dogs. Power density spectra were calculated from all 2(17) points of each recording session and integrated between 0.0002 and 0.1 Hz. 3. Blockade of the afferent limb of the baroreceptor reflex by surgical denervation of sinoaortic and cardiopulmonary afferents (Den; n = 6) significantly increased integrated power more than sixfold compared with a control group (n = 11). 4. Impairment of the efferent limb in non-deafferented dogs by either alpha 1-adrenergic blockade with prazosin (Praz; n = 7) or ganglionic blockade with hexamethonium (Hex; n = 6) failed to raise variability. 5. Both prazosin (n = 6) and hexamethonium (n = 3) reduced the increased variability in denervated dogs. 6. In non-deafferented dogs receiving hexamethonium, elevation of mean blood pressure to the hypertensive level of the Den group, by a continuous infusion of noradrenaline (n = 4), did not change the variability. 7. It is concluded that in the absence of changes in posture, most of the increased blood pressure variability after baroreceptor denervation is derived from the central nervous system. 8. Direct comparison of power spectra of the Den (total variability) and Hex groups (variability derived from the cardiovascular system only) suggests that the central nervous system is also the prevalent source of low-frequency blood pressure variability in intact animals.

Animals↗
PubMed1995

Modulation of erythropoietin formation by changes in blood volume in conscious dogs.

1. A possible influence of the filling of the circulatory system on the plasma concentration of erythropoietin, which is the major regulator of erythrocyte formation, was investigated in conscious dogs. 2. Over an experimental period of 5 h, the animals were subjected to either haemorrhage (hypovolaemia), blood volume expansion (hypervolaemia), or exchange transfusion of blood with dextran (isovolaemic anaemia). 3. A reduction of blood volume by 20% induced by haemorrhage increased plasma erythropoietin levels approximately 1.5-fold in the absence of significant changes in haematocrit. 4. An expansion of blood volume by 12% induced by an intravenous infusion of dextran did not change plasma erythropoietin levels, although the haematocrit decreased by 0.04. 5. A reduction of the haematocrit by 0.12 in the absence of changes in blood volume induced by an isovolaemic exchange transfusion (dextran vs. blood) increased plasma erythropoietin levels approximately 3-fold. 6. Total renal oxygen supply did not change in any of the three experimental protocols. 7. These data indicate that in dogs the erythropoietin production rate is modulated by changes in blood volume, and suggest a possible role of erythropoietin in the regulation of blood volume.

Anemia↗
PubMed1994

The blood pressure buffering capacity of nitric oxide by comparison to the baroreceptor reflex.

To compare the contribution of nitric oxide (NO) to the buffering of short-term and circadian fluctuations of arterial blood pressure with that of the baroreceptor reflex, conscious foxhounds were subjected to continuous 24-h blood pressure recordings. A pressure transducer was placed into the lumen of the abdominal aorta. Telemetry recordings were done under control conditions, following blockade of NO formation by intravenous bolus injection of NG-nitro-L-arginine (L-NNA; 16.5 +/- 2 mg/kg body wt) and after total sinoaortic and cardiopulmonary denervation in five dogs each. L-NNA produced a sustained elevation of mean arterial pressure (MAP; 137.2 +/- 6.4 mmHg vs. control, 112.9 +/- 3.7 mmHg). After denervation, no significant increase of MAP was found (113.5 +/- 4.1 mmHg), but the standard deviation of the MAP histogram was significantly greater (22.5 +/- 3.1 vs. 10.6 +/- 0.9 mmHg, P < 0.05). Sequential spectral analysis showed that total power between 0 and 0.5 Hz was elevated more than twofold after L-NNA (P < 0.05). This was due primarily to increased power in the range above 0.1 Hz. After denervation, total power increased about three-fold (P < 0.05), almost exclusively occurring below 0.04 Hz. Power in the range above 0.2 Hz was diminished, although not significantly. It is concluded that in the conscious dog, NO, as well as the baroreceptor reflex, is an effective blood pressure buffer. NO is most effective above 0.1 Hz, whereas the baroreceptors primarily buffer fluctuations slower than 0.04 Hz.

Animals↗
PubMed1993

Autoregulation and non-homeostatic behaviour of renal blood flow in conscious dogs.

1. Spontaneously occurring haemodynamic variations within 4 h affecting renal blood flow (RBF) were compared with externally induced short changes of renal artery pressure (RAP) in conscious resting dogs. 2. In all animals in which RAP was servo-controlled (n = 6), perfect autoregulation of RBF was observed. 3. In all 4 h recordings of spontaneous renal blood flow (n = 9), certain combinations of blood pressure and blood flow occurred remarkably frequently as indicated by three-dimensional frequency distributions. 4. Cluster analysis demonstrated significant differences between these areas of accumulation (P < 0.001). The average number of 'set points' per 4 h session was 3.1 +/- 0.3. 5. The shift from one set point to another is probably mediated by multiple control systems impinging on renal haemodynamics as suggested by 1/f fluctuations. 6. In seven dogs, an additional renal venous catheter allowed measurements of the arterial-venous (A-V) oxygen partial pressure (PO2) difference as an indicator of the renal metabolic demand. An inverse relationship between A-V PO2 difference and RBF (Y = X(-0.034) + 40.9, r = -0.9, P < 0.001) was found, indicating that the metabolic demands vary little (if at all) between the different set points. 7. The presented data suggest a modified view of renal homeostasis. There exist distinct combinations between RBF and RAP, which are very stable. Autoregulation merely buffers the fluctuations around these set points.

Animals↗
PubMed1992

Physiological concentrations of ANP exert a dual regulatory influence on renin release in conscious dogs.

The influence of physiological increments in circulating atrial natriuretic peptide (ANP) on renin release was determined in conscious dogs. Renin stimulus-response curves (RSRCs) were obtained by controlled reductions of renal perfusion pressure (RPP) under control conditions and during intrarenal or intravenous ANP infusions. Under all experimental conditions, the RSRCs were characterized by a plateau, a threshold pressure (Pth), and a steep slope below Pth. Intrarenal ANP infusion (0.9 ng.kg-1.min-1), which induced a calculated threefold elevation of renal arterial ANP concentration (but did not change systemic arterial ANP levels), increased the slope of the RSRC by 81% (P less than 0.05) with no effect on Pth. A quantitatively similar effect on the slope of the RSRC (+90%; P less than 0.05) was observed when systemic ANP levels were raised (from 37 +/- 2 to 71 +/- 9 pg/ml; P less than 0.05) by intravenous infusions (3.6 ng.kg-1.min-1). In addition, however, intravenously infused ANP reduced Pth from 91 to 85 mmHg (P less than 0.05), which caused a complete suppression of the renin response to a reduction of RPP down to 85 mmHg. These findings indicate that ANP can inhibit renin release at physiological plasma concentrations by shifting the RSRC to a lower pressure level; this shift is mediated by a modulation of extrarenal renin control mechanisms. The direct effect of ANP on renin release is one of stimulation.

Animals↗
PubMed1992

[Hemangioma of the left ventricle].

The authors describe the case of a histologically proven hemangioma in the left coronary artery of the left ventricle of a 24-year-old woman. The results of the different medical imaging methods applied are described and the treatment of cardiac angiomas is discussed.

Adult↗
PubMed1991

[Deformities and trauma sequelae of the ankle joint in children and adolescents].

Knowledge of the normal development of the ankle joint is mandatory to understand the mechanism of injuries in children and adolescents. Some fractures (juvenile Tillaux's or two-fragment triplane fracture) occur only within a particular period of growth, which is determined by the degree of epiphyseal fusion. Tarsal coalitions are the deformities seen most frequently. Special radiographic techniques must be applied for the diagnosis. Ball and socket joint, tibiotalar slant and Trevor's disease are rare deformities, each of which is associated with a pathognomonic radiographic pattern. Some typical joint deformities may be seen in patients with neuromuscular disease. This has to be considered when nothing else is found in the clinical history.

Adolescent↗
PubMed1989

[SPECT of the brain using 99mTc-HMPAO in patients with cerebrovascular disease: a comparison with CT. A report of 100 cases].

In a retrospective study the sensitivity of SPECT and CT in detecting changes in cerebrovascular disease is compared, based on a group of one hundred patients. The higher sensitivity of SPECT with regard to right-positive results, especially in TIA and PRIND and the markedly lower number of false-negative results are underlined and discussed. The fact that both methods reveal only a slight sensitivity regarding the detection of changes in the basal regions of the brain is also pointed out, with SPECT proving to be the more sensitive of the two methods.

Adult↗
PubMed1988

Interactive effects of live weight, basal diet and fat supply on essential fatty acid status and blood concentrations of glucose, insulin and thyroxine measured postprandially in pigs.

1. The composition of the basal diet (purified vs complete feed ingredients provided as a cassava and a barley based diet, respectively), type of dietary fat [saturated fatty acids (18:0) supplied as fully hydrogenated soya bean oil vs unsaturated fatty acids (18:2) supplied in the form of soya bean oil] and the live wt of the animals (40 vs 80 kg) highly influenced the EFA status of the body and postprandial blood concentrations of glucose, insulin and thyroxine. 2. Interactive effects of live wt, type of basal diet and fat supply on EFA status and postprandial blood levels are discussed.

Animals↗
PubMed1988

[An unusual thickening of the gallbladder wall in cholecystitis].

This is a report on a massive thickening of the gallbladder wall accompanying an acute cholecystitis with cholelithiasis. The sonographic criteria for the diagnosis of cholecystitis are discussed. It is pointed out that a thickening of the gallbladder wall is not a specific sign for cholecystitis.

Cholecystitis↗
PubMed1988

[EEG changes in rats after subchronic exposure to ethanol].

EEG-investigations in rats were carried out 2 weeks after finishing a 3-month exposure scheme to ethanol (113 mmol/kg b.w., p.o., 5 times per week). We found pronounced disturbances of the sleep-wake behaviour as a reflection of a serious damage of the alertness-regulating system. The previously exposed animals did show disturbed vigilance and changes in the course and character of sleep, a reduction of power density in the alpha-, and an increase within the beta- and delta frequency bands of the EEG. The essential conclusions drawn from the experiment are comparable with EEG-changes in abstinent alcoholics, as reported in the literature.

Animals↗