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Biomedical subjects

W Ruf

Publications and source records attributed to W Ruf.

At least 109 records · Page 6Linked to original sources
PubMed1983

An electrocardiographic model of myocardial ischemic injury.

Previous electrocardiographic models of myocardial ischemic injury have assumed that transmembrane potential changes are uniform throughout a region of ischemia such that injury currents arise exclusively at the boundary between normal and ischemic myocardium. In such models, the distribution and amplitude of ST segment deflections are considered to arise from a polarized surface interfacing normal and ischemic myocardium. This concept in modeling ischemic injury was derived from the application of principles of electric field theory which had been successfully applied previously to ventricular activation in which QRS potentials are considered to arise from polarized surfaces representing the relatively narrow interfaces between depolarized and nondepolarized myocardium. The present paper outlines the limitations of modeling ischemic injury as a polarized surface in terms of the failure of the predictions of such a model to be supported by the experimentally observed: 1) distribution and relative amplitude of epicardial ST segment elevation overlying a region of ischemia; 2) directional changes in epicardial ST segment elevation that occur with changes in the size of an ischemic region; and 3) nonuniform distribution of transmembrane potential changes which occur within a region of ischemia. A new electrocardiographic model of ischemic injury is formulated which accounts for the nonuniform distribution of transmembrane potential changes which occur throughout a region of ischemia. The model accurately describes experimental observations regarding ST segment deflections which had remained inconsistent with previous models.

Coronary Disease↗
PubMed1981

Effect of left ventricular--to--aortic bypass on infarct size and infarct microcirculation in baboons.

A major diagonal branch of the left anterior descending coronary artery (LAD) was acutely occluded in 17 baboons. Complete left ventricular (LV) decompression was achieved with a left heart bypass (LHB) system in six baboons while 11 baboons served as untreated controls. In the treated group, LHB was initiated after 30 minutes of coronary occlusion. For a period of 6 hours after occlusion, aortic pressure, LV pressure, left atrial pressure, and cardiac output were monitored. During the same monitoring period, electrograms were recorded from a high resolution matrix of fixed epicardial electrodes. Regional myocardial blood flow was determined prior to and at intervals following the initiation of LHB with radioactive microspheres. Infarct size was assessed histologically from serial cross sections of the left ventricle. The degree of salvage achieved by LHB was assessed by comparing the epicardial area of infarction 6 hours after occlusion (AI) to the area of epicardial St-segment elevation (STE) 30 minutes after occlusion (maxAST). In the LHB-treated group, 40.0% +/- 8.1% (SEM) of maxAST showed subsequent infarction; in the control group, 79.8% +/- 2.7% of maxAST showed eventual infarction (p less than 0.01). STE overlying the region of ischemia in the LHB-treated group did not undergo the spontaneous decline observed in the control group, which is normally associated with the progression of necrosis. Regional myocardial blood flow did not change significantly in the ischemic region during the period of occlusion following LHB. LHB. The results suggest that LHB is capable of substantial salvage of acutely ischemic myocardium by reducing myocardial work and thus reducing myocardial oxygen requirements.

Animals↗
PubMed1980

Injuries of the distal radial epiphysis.

From 1964 to 1971 76 children with injuries of the wrist near the radial epiphysis were treated. On this occasion secondary injuries of the ulnar epiphysis, the styloid process ulnae, as well as concommitant bend-fractures of the distal ulna were found. Thirty-one of the patients were able to undergo a clinical and X-ray follow-up program. Restricted movements were not found; however radiologically deviations especially dorsally up to 15 degrees were found. In 5 concommitant strain fractures of the styloid process ulnae 4 pseudarthrotic healings of these strain fractures could be seen. During the follow-up these patients complained of pain after extended periods of utilisation or work involving the wrist. In 2 more patients, also complaining of pain after longer usage of the wrist joint, no objective cause could be found. The possibility of a posttraumatic structural disturbance in the distal radio-ulnar joint is discussed.

Athletic Injuries↗
PubMed1980

Quantitative effect of a single large dose of methylprednisolone on infarct size in baboons.

Despite numerous studies directed at determining the ability of glucocorticoids to minimise myocardial ischaemic damage following acute coronary occlusion, there remains no clear consensus concerning their usefulness. Within an ischaemic region, glucocorticoids produce membrane stabilising effects which decrease the autolytic effects of marked cellular swelling and lysosomal membrane rupture. Their use has also been associated with a decreased cellular lysis due to infiltrating inflammatory cells and with an increase in collateral blood flow. The use of glucocorticoids has remained clinically attractive due to experimental observations regarding these local actions; however, the potential of these actions to enhance long-term viability of ischaemic myocardium has remained uncertain. A major problem in the comparison of the extent of infarction between treated and untreated animals has been the variability in infarct size that results from coronary artery ligation at any given anatomical site. In the experimental baboon model which we have employed, we have previously shown that the ultimate epicardial area of infarction, as well as the volume of infarction as assessed histologically at 7 days post occlusion, shows a good linear relationship to the area of ischaemic injury at 1-hour post occlusion, as assessed by high resolution epicardial ST segment mapping. In this way animals may serve as their own controls and as long as an intervention is initiated at 1 h or later post occlusion, then the epicardial area or transmural volume of histologically assessed infarction at 7 days can be compared with the predicted epicardial area or transmural volume of infarction and hence determine the effect of that intervention in altering infarct size. This experimental model does not rely on a comparison of the absolute magnitude of infarcts between treated and untreated animals and, therefore, avoids the error introduced by the inherent variability in infarct size between animals after coronary occlusion.

Animals↗
PubMed1980

Intestinal blood flow at various intraluminal pressures in the piglet with closed abdomen.

The influence of intraluminal pressure on intestinal blood flow was studied in two segments of the small intestine and two of large intestine ligated after insertion of intraluminal catheters in ten piglets. Intestinal segments were inflated in stepwise increments in intraluminal pressures of 15, 30, 45 and 60 mmHg and blood flow was measured with radioactive microspheres using four isotopes (Ce, Cr, Sr, Sc). Other segments were inflated to a pressure of 60 mmHg and then pressure decreased in a stepwise fashion to 30, then 0 mmHg for the last two injections. Small and large intestinal blood flow fell progressively with increasing intraluminal pressure. At 60 mmHg a forward flow of 25% of normal was still present. Furthermore, not only was there an absolute decrease in blood flow with increasing intraluminal pressure but this decrease was disproportionately large in the intestinal mucosa. A hyperemic response lasting approximately 15 minutes was observed after complete decompression. The intestinal blood flow distal to the ligated segments was always moderately increased as compared to intestinal blood flow proximal to the segments. The results reported herein are at some variance from other reported studies performed with the abdomen open and on isolated segment preparations. The reasons for these variations are discussed.

Abdomen↗
PubMed1980

Dihydroergotamine--stimulation of intestinal peristalsis. An experimental and clinical study.

In an experimental study in 15 beagle hounds using strain gauges a significantly increased motility in the small and large intestine after dihydroergotamine was observed. Since this assessment did not provide any information about mucus transport, gastro-intestinal passage time in patient and control groups was determined using radioopaque catheter material. While transit time in the patient group was significantly reduced by 2 x 0.5 mg DHE s.c./day, this effect was not observed in controls. We related the significantly reduced passage time after DHE in the patient group to a normalisation of a functional disturbance of regulation. The action of the drug is seen in the blocking of the stress induced increased sympathetic tone, without the side effects often seen after pure alpha-antagonists of the phentolamine type or the adrenergic guanethidine type neuronal blocking agents. The specific efficacy of DHE as a partial alpha-antagonist is pointed out. For the clinician, postoperative gastro-intestinal atony might be an indication for its use.

Animals↗
PubMed1980

Small intestinal blood flow after 48 hours ileus, prostigmin and manual decompression.

In eight piglets small intestinal blood flow (IBF) and motility has been measured after 48 hrs mechanical obstruction, prostigmin application and manual decompression using the microspheres method. Intraenteric basic pressure is in a normal range; the number of tonic contraction waves (type 3 waves) is slightly increased. IBF after 48 hrs ileus is markedly increased compared to normal (218%). Prostigmin does not influence IBF significantly. After manual decompression, IBF decreases to 56% of normal and does not recover within 30 minutes. Whereas IBF in the segment proximal to the obstruction is increased, IBF in the distal part is significantly reduced (48%) after 48 hrs of ileus. It is concluded that 48 hrs of ileus have no harmful effect on intestinal blood flow and function. Prostigmin does not increase IBF, whereas motility is stimulated strongly. Mechanical decompression results in a 50% reduction of IBF, which might be in accordance with clinical observation of retarded recovery and reduced motility after this maneuvre.

Animals↗
PubMed1979

Surgical technic for treatment of splenic rupture.

In nine baboons and one dog, a technic for suturing the injured spleen and also providing immediate control of hemorrhage is described. By placing Silastic strips along the wound edges of the transverse incision into the spleen and along the surface and bottom edges of the wound after resection, it was possible to control bleeding with deep U sutures passing through the Silastic bolsters and the spleen tissue. The procedure appears to provide a reliable method of salvaging splenic tissue and thus avoiding the hazard of postsplenectomy sepsis.

Animals↗
PubMed1979

Epicardial mapping and electrocardiographic models of myocardial ischemic injury.

The amplitude and distribution of epicardial ST-segment elevation (ST) were examined for an 8-hour period after coronary occlusion in eight baboons and five pigs. ST was determined from unipolar epicardial electrograms obtained from a high-resolution matrix of fixed electrodes overlying a transmural region of ischemia. A relatively uniform degree of ST was observed overlying the ischemic region for 20 minutes after coronary occlusion. A gradient in ST from the periphery to the center of the ischemic region was documented after 20 minutes of ischemia. In 10 other pigs, change in the degree of ST was examined contingent on either an increase (five pigs) or decrease (five pigs) in the size of the ischemic region after 1 hour of preexisting ischemia. An abrupt increase in the number of electrodes that showed ST (NST) from 7.8 +/- 1.24 (SEM) to 14.8 +/- 1.35 (90%) was associated with an increase in mean ST of 58% from 4.28 +/- 0.61 mV to 6.78 +/- 0.84 (p less than 0.05). An abrupt decrease in NST from 25.2 +/- 2.63 to 14.6 +/- 2.22 (42%) was associated with a decrease in mean ST of 24%, from 8.2 +/- 0.36 mV to 6.3 +/- 0.30 mV (p less than 0.01). The results during early ischemia (less than 20 minutes of ischemia) are accurately represented by a model of ischemia in which injury current arises only at the ischemic boundary. The results during later ischemia (after 20 minutes of ischemia) may be represented by a model in which ST is considered dependent on injury currents generated throughout the ischemic region.

Animals↗
PubMed1977

[The effect of antacids on stress-induced lesions of the gastric mucosa in the piglet (author's transl)].

After administration of antacids, gastric stress lesions due to hemorrhagic shock appear in the pig stomach quicker and more markedly than in animals which have been similarly treated with an indifferent substance or not at all. However, once treated, the administration of antacids seems to favor the healing of mucosal lesions after the end of the stress. At the same time it was observed that after administration of antacids in hemorrhagic shock, the serum gastrin level rises and does not remain constant, as in the control group. An attempt is made to explain the favorable effect of antacids on the genesis of hemorrhagic stress lesions in the pig's stomach through this observation.

Animals↗
PubMed1977

[A pneumatic colostomy closure].

An atraumatic, pneumatic occlusive colostomy appliance has been described which in animal experiments was well tolerated and was effective in preventing leakage. It is hoped that this may improve the unsatisfactory aspects of management in patients using conventional colostomy appliances.

Aftercare↗
PubMed1976

(Na+K+)-activated ATPase in human cornea. Distribution within the cornea and properties of the enzyme from epithelial cells.

Distribution and principal characteristics of (Na+K+)-activated ATPase in human cornea were investigated. (Na+K+)-ATPase was present in both epithelium and endothelium, whereas the corneal stroma did not exhibit significant enzyme activity. In homogenates specific activity of the (Na+K+)-ATPase was 2.3-fold higher in endothelium than in epithelium. Calculation of total enzyme activity revealed a 6.1-fold higher content of (Na+K+)-ATPase in the epithelium. In the epithelium a 7-fold enrichment of (Na+K+)-ATPase compared to the homogenate was obtained in the 150-1500 X gav fraction. Maximum enrichment in the endothelium was 3.5-fold and was achieved in the 1500-2500 X gav fraction. Both fractions showed, however, the same specific activity. The pH-optimum of (Na+K+)-ATPase in the 150-1500 X gav fraction ranged from 8.0-8.2 in both epithelium and endothelium. In the epithelial 150-1500 X gav fraction the apparent Km-values were 4.0 mM for Na+, 2.8 mM for K+ and 0.12 mM for Mg2+ - ATP in equimolar concentrations. The inhibition constant of epithelial (Na+K+)-ATPase for ouabain was determined as Ki = 3.3 X 10(-7) M. The present data support the view that control of corneal hydration in man is a function of both endothelium and epithelium.

Adenosine Triphosphatases↗