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Biomedical subjects

J Holtz

Publications and source records attributed to J Holtz.

At least 127 records · Page 7Linked to original sources
PubMed1982

Norepinephrine constricts the canine coronary bed via postsynaptic alpha 2-adrenoceptors.

The effect of alpha 2-blockade (0.3 mg/kg i.v. rauwolscine) and alpha 1-blockade (1.2 mg/kg i.v. prazosin) on coronary constrictions induced by intracoronary injections of azepexole (B-HT 933, alpha 2-agonist, 0.1-10 microgram/kg), phenylephrine (0.3-3 microgram/kg) and norepinephrine (0.001-0.1 microgram/kg) were studied in dog hearts perfused in situ under beta-blockade. Constrictions by azepexole (antagonized by rauwolscine, yet resistant to prazosin and methysergide) demonstrated coronary alpha 2-adrenoceptors. Norepinephrine-induced constrictions were more attenuated (22-fold) by alpha 2-blockade than by alpha 1-blockade (2.6-fold) and thus were mediated mainly by activation of postsynaptic alpha 2-receptors.

Animals↗
PubMed1982

Observations of arterial and venous vasomotion with the absolute induction angiometer.

This paper provides biological illustrations of the applicability and mode of use of intravascular and perivascular absolute induction angiometers. Artifacts and limitations of the method as well as experimental precautions and calibration procedures are discussed. Tracing are presented to illustrate the capabilities of the method in recording pulsatile diameter changes in veins and arteries and to demonstrate its applicability to moving blood vessels as exemplified by the coronary arteries. Both intravascular and perivascular angiometry can detect diameter changes of a few micra in a vessel 1 cm in diameter. The intravascular angiometer is a resilient loop of fine bifilar wire which can be introduced into the blood vessel percutaneously via an angiographic catheter. A perivascular angiometer is an easily deformable loop made of a soft fine wire pair which is draped around a blood vessel and can thus be chronically implanted.

Animals↗
PubMed1982

[Complications after continence resection and anus praeternaturalis re-anastomosis].

A retrospective analysis was performed of 155 patients treated by anterior resection of a mostly carcinomatous colon (or rectum). During resection of the colon (or rectum), the anastomosis was temporarily protected by a colostomy. Postoperative mortality was 4.5% and the total complication rate was 25.7%. There was a significant reduction in the rate was 25.7%. There was a significant reduction in the rate of infection of those administered with neomycine and erythromycine and metronidazole collectively. There was no mortality in the cases of intraperitoneal closure of transverse colostomy after 3 months. There were complications in 19.2% of these patients.

Aged↗
PubMed1981

Treatment of acute left heart failure using dobutamine and intraaortic counterpulsation. Animal experiments and first clinical experiences.

Ten anesthetized mongrel dogs had a left anterolateral thoracotomy; the left anterior descending coronary artery was then ligated. After 60 min five animals each were treated either with dobutamine (4 microgram/min/kg; for 10 min), or with dobutamine and intraaortic counterpulsation. Combined treatment of cardiogenic shock proved superior. Those five dogs had significantly lower heart rates and dp/dt/p-values. Due to IABP the non-ischemic parts of the left ventricle were better perfused; there was no difference in treatment with regard to ischemic parts. The combined treatment was successfully inaugurated in two patients with cardiogenic shock.

Adult↗
PubMed1981

Huntington disease and Tourette syndrome. II. Uptake of glutamic acid and other amino acids by fibroblasts.

Injection of kainic acid, a rigid analog of the excitatory neurotransmitter glutamic acid (glu), into the neostriatum of rats produces a condition that mimics Huntington disease (HD) in at least 12 different morphological and biochemical parameters. These results suggested that one of the possible basic mechanisms in HD is a defect in the presynaptic of glial uptake of glu, resulting in chronic hyperstimulation and death of a specific set of neurons. To test this hypothesis, the uptake of glu was studied in 12 carefully matched sets of control-HD pairs and two lines of Tourette syndrome fibroblasts. Although the first six sets suggested a glutamate transport defect in HD cells, examination of 12 sets indicated that there were no significant differences between control and HD cells. The fibroblasts showed both a high and low affinity uptake of glutamic acid. Sodium dependent uptake of L-glutamate (L-glu) minus D-glutamate (D-glu) at 100, 1,000, and 10,000 Micrometers glutamate was normal in HD and Tourette syndrome cells.

Adolescent↗
PubMed1978

Phasic registration of venous diameter changes in-situ with the induction angiometer.

The method of induction angiometry has been used for observation of active and passive venous vasomotion, without surgical exposure of the blood vessel. The diameter sensor is a resilient loop introduced into the vasculature through a fine No. 5 French (1 mm i.d.) angiographic catheter or a needle of comparable internal diameter. An extracorporeal a. c. magnet induces an electromotive force (e.m.f.) in the loop which acts as the secondary of a transformer, the electromagnet being the primary. Pulsations in the blood vessel diameter vary the loop area and with it the induced e.m.f. thus providing a linear measure of relative changes in vascular diameter. Changes in the order of 2 micra in a venous diameter of 5 mm can be resolved in-situ. Examples are given of registration of phasic venous diameter changes at the frequencies of the heart beat, respiration and Mayer waves. Pharmacological tests illustrate the ability to detect venous vasomotion in response to a dose below 0.1 microgram/kg of nitroglycerin in dogs.

Animals↗
PubMed1978

[Assisted circulation with the heart-lung machine after cardiosurgical interventions: one year's experience with intra-aortal counter-pulsation with the heart-lung machine after cardiosurgical operations is reported (author's transl)].

In the period from September 1976 to 1977, aortic or mitral valve replacement was performed in 84 and 34 patients respectively. Cardiogenic shock occurred during or immediately after the operation in 3 and 2 patients respectively (= 8.8% and 2.4%). In spite of the use of intra-aortal counter-pulsation, none of the patients survived the acute event. During the same period, 8 (= 5%) out of 113 patients who had undergone coronary surgery needed intra-aortal counter-pulsation. 4 of them survived the acute left heart failure and at the present time are clinically healthy (N.Y. Heart Association Class II).

Acute Disease↗
PubMed1978

tRNA isopentenyltransferase from Zea mays L. Characterization of the isopentenylation reaction of tRNA, oligo (A) and other nucleic acids.

The extraction and purification of the tRNA isopentenyltransferase from maize root tips and kernels are reported. The relative amounts of this enzyme in different organs of maize have been determined. Root tips have the highest enzyme activities, followed by kernels and young leaves. Old leaves exhibit very low activity. The molecular mass of the monomeric enzyme was determined to be 57000 - 63000 dalton. pH and Mg2 optima are in full agreement with the data reported for the enzymes from yeast and Escherichia coli. Spermine enhances the isopentenylation of tRNA from kernels. The "Km" values of KMnO4-treated or untreated bulk tRNA from yeast and maize root tips and kernels were in the range of 10 to 34 micrometer while the Km values of of single species like tRNASer4 from rat liver and tRNATyrKMnO4 from E. coli were 1.1 and 6.6 micrometer, respectively. The tRNA isopentenyltransferase from maize root tips and kernels catalyzes the incorporation of 2-isopentenyl groups into (Ap)3-7A, endogenous bulk oligonucleotos from maize root tips and kernels, and into poly(A), RNA from MS-2 phages and, to a very low extent, into adenosine. The Km values of (Ap)3-7 A varied in the range of 250 to 750micrometer. Although oligonucleotides have less affinity to the enzyme, the formation of i6A within oligonucleotides may occur in vivo, due to their higher concentrations in cells.

Adenosine↗
PubMed1977

Exercise induced augmentation of myocardial oxygen extraction in spite of normal coronary dilatory capacity in dogs.

Myocardial O2-extraction rate was studied during exercise induced augmentation of cardiac work in dogs. The O2-extraction rate at rest was 75% of arterial content. Progressive levels of exercise increased the animals' O2-consumption from 7 ml/min-kg up to 91 ml/min-kg. Cardiac output rose from 108 ml/min-kg at rest to 484 ml/min-kg at the highest exercise level. The increase in myocardial O2-consumption from 9 ml/min-100 g at rest up to 57 ml/min-100g at the highest exercise level was met by an increase in coronary flow from 59 to 256 ml/min-100 g and a rise of myocardial AVDO2 from 15 to 22 Vol%. Thus the latter contributed 40% to the augmented myocardial O2-requirements. Coronary venous O2-saturation decreased to 9% saturation during highest levels of exercise. This low value was not the result of a limited coronary dilatory capacity, of inadequate state of exercise training, or of a relative underperfusion of the inner layers of the left ventricle. Thus, augmentation of myocardial O2-extraction rate seems to be a mechanism of physiological relevance during exercise induced elevation of myocardial O2-requirements in dogs and may be explained by capillary recruitment in the myocardium.

Animals↗
PubMed1975

Viscous and inertial fractions of total perfusion energy dissipation in the coronary circulation of the in situ perfused dog heart.

The effects of changes in viscosity on pressure flow relations in the in situ perfused left circumflex coronary artery were studied in open chest dogs. Vascular reactivity was abolished by maximal pharmacological coronary dilatation. Blood and suspensions of red cells (hematocrit 8-14%) in dextran solutions were used as perfusates. Total perfusion energy dissipation, represented by perfusion pressure drop across the perfused vascular bed, can be separated into a viscous and an inertial fraction: P = Pvisc + Pinert. Perfusing the heart with approximately Newtonian fluids of different viscosities enabled us to compute the amount of the inertial fraction of total perfusion pressure dissipation. At constant viscosity, the inertial fraction increased with flow rate. However, the rise of the inertial fraction due to reduced viscosity at a constant perfusion pressure was much more pronounced. Variations of perfusion pressure and viscosity of the perfusates between 70 to 130 mm Hg and 1.2-3.2 cP, respectively, resulted in inertial perfusion pressure dissipation between 16 and 54%. This inertial pressure drop may become a noteworthy factor under conditions of low whole blood viscosity (e.g. anemia or therapeutical hemodilution.

Animals↗
PubMed1975

Effect of increased blood fluidity through hemodilution on coronary circulation at rest and during exercise in dogs.

Coronary flow and myocardial oxygen consumption were measured in conscious dogs at rest and during two levels of submaximal treadmill exercise (3 and 7 km/h at 15% grade, respectively) during adaptation to progressive hemodilution with dextran 60. At rest coronary flow increased to more than seven-fold with diminishing hematocrit to 12.5% in order to cover myocardial oxygen consumption which increased from 6.5 +/- 0.3 ml/min with 100 g at hematocrit 47.5% to 13.5 +/- 0.8 ml/min with 100 g at hematocrit 12.5%. The dilatory capacity of the coronary vessels, estimated from the reactive hyperemia after a 12 sec occlusion of the left circumflex coronary artery, dropped from 602% at control to 45% at lowest hematocrit levels. During the superimposed stress of exercise coronary flow and myocardial oxygen consumption increased further, so that the dilatory capacity of the coronaries was exhausted at hematocrit levels between 16 and 22%. Myocardial oxygen consumption per unit of oxygen delivered to peripheral tissues increased substantially with progressive hemodilution. In the presence of the reduced arterial oxygen content the augmented myocardial oxygen demand limits the overall adaptability to hemodilution by an exhaustion of the coronary dilatory capacity.

Animals↗