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Biomedical subjects

R Busse

Publications and source records attributed to R Busse.

At least 289 records · Page 16Linked to original sources
PubMed1975

[Endoscopic biopsy using the electrocautery snare (macro particle biopsy)].

The biopsy snare has greatly improved the diagnostic and therapeutic possibilities in gastro-intestinal endoscopy. Experience with endoscopic polypectomy in the digestive tract has stimulated the use of the biopsy snare for the excision of larger particles. Thus, besides that larger particles can be obtained, also deeper excisions are possible. Usually muscularis mucosae and parts of the submucosal layers are included. Mucosal hyperplasia and submucosal processes can be recognized and analysed preoperatively. Even the resection of inoperable stenosing neoplasms is now possible. The results of 93 gastro-intestinal big particle biopsies are reported. The risk of big particle biopsy proved to be minimal; once bleeding occurred and was managed conservatively.

Biopsy↗
PubMed1975

The resolution of arterial pulses into forward and backward waves as an approach to the determination of the characteristic impedance.

Pressure and flow recordings from a given site in an artery can be used for the resolution of the pulse wave into its forward and backward components if the characteristic impedance (Z) is known. The principle of this method was reported by von Kries in 1892. In the present work, the procedure is first applied to a theoretical, non-uniform tube model. The characteristic impedance of the model are assumed to be real magnitudes. From the results it is seen that the calculated backward wave provides a criterion which indicates whether the true value of Z actually has been used for the resolving procedure. If, as in the case of natural pulses, Z is not known, its value can be obtained by repeatedly performing the resolving procedure using various values of Z, and choosing the value of Z employed to calculate the backward wave which best fits the criterion. The method is demonstrated on pulses of the abdominal aorta and carotid artery of the dog. The results are compared with the average values of the input impedance in the higher frequency range.

Analog-Digital Conversion↗
PubMedDate not supplied

The Philippines' National Health Insurance Act: a German perspective.

Through the recent National Health Insurance Act (NHIA), the Philippines have committed themselves to introducing a social health insurance with universal coverage within 15 years. Germany was the first country to introduce a social health insurance system more than 100 years ago. Its system is based on the principles of corporatism, federalism and a mandate for equity. Based on a long-term German experience with equity, quality, cost and efficiency issues, the Philippines' NHIA is analysed concerning the entitlement to benefits and the benefit package, the organization of the health insurance programme, health insurance financing, and provider payment mechanisms. It is suggested that the Philippines could profit from including preventive and promotive services as well as pharmaceuticals in the benefits package. The organization of the health insurance system could be decentralized using the 13 regions as its principal units. To achieve financial equity between regions and health funds, a contribution compensation scheme is proposed. To prevent over-utilization in over-served areas and to promote utilization in under-served areas, a relative value scale for fee-for-service payments seem advisable.

Fee-for-Service Plans↗
PubMedDate not supplied

NG-nitro-L-arginine (N5-[imino(nitroamino)methyl]-L-ornithine) impairs endothelium-dependent dilations by inhibiting cytosolic nitric oxide synthesis from L-arginine.

We studied the effects of the L-arginine analogue NG-nitro-arginine (L-NNA), in comparison with its D-isomer [D-NNA), on endothelium-dependent dilations of rabbit femoral arteries (RFA) and on the release of endothelium-derived relaxant factor (EDRF) from native and cultured endothelial cells. In addition, we examined the effects of L- and D-NNA on the L-arginine- and NADPH-dependent synthesis of nitric oxide (NO) in the cytosol of porcine aortic endothelial cells. L-NNA enhanced the noradrenaline-induced contraction of endothelium-intact, but not of endothelium-denuded segments of RFA, indicating an inhibition of basal EDRF release. L-NNA also inhibited significantly the endothelium-dependent dilations to acetylcholine (ACh). Both effects of L-NNA were attenuated by L-arginine. L-NNA rapidly inhibited the release of EDRF from cultured and native endothelial cells stimulated with thimerosal or ACh. L-NNA concentration-dependently and reversibly antagonized the L-arginine- and NADPH-dependent activation of a purified soluble guanylate cyclase (GC) by cytosol from freshly harvested porcine aortic endothelial cells, suggesting a direct competition between L-NNA and L-arginine at the level of endothelial NO-synthesis. D-NNA was ineffective in all instances. These results prove L-NNA to be a stereospecific inhibitor of the cytosolic NO formation from L-arginine in endothelial cells. Therefore, L-NNA will be a useful tool to elucidate the molecular mechanism of mammalian NO synthesis.

Acetylcholine↗
PubMedDate not supplied

Paracrine functions of the coronary vascular endothelium.

Coronary vascular endothelial cells control vascular tone by modulating the local concentration of circulating vasoactive substances (e.g. adenine nucleotides, biogenic amines and bradykinin) and by synthesising and releasing the vasoactive autacoids nitric oxide (NO) and prostacyclin (PGI2). The fluid shear stress exerted by the streaming blood is the physiologically most important stimulus for a continuous endothelial NO production, which counteracts neuro- and myogenic constriction. This shear stress-dependent NO release represents a highly effective local system for maintaining adequate blood flow to the myocardial tissue. At the transcriptional level endothelium-derived NO modulates the regulation of a number of genes (e.g. monocyte chemoattractant protein-1, P-selectin and vascular cell adhesion molecule-1) most probably by direct and/or indirect interaction with transcription factors. In addition to NO and PGI2, the coronary vascular endothelium is also able to release a factor which causes hyperpolarisation of the underlying smooth muscle. This so-called endothelium-derived hyperpolarising factor (EDHF) displays the characteristics of a cytochrome P450-derived arachidonic acid metabolite. However, since NO is able to attenuate production of this factor, EDHF may contribute to the regulation of vascular tone essentially in situations associated with an apparent dysfunction of the endothelium.

Acetylcholine↗
PubMedDate not supplied

Determination of arterial input impedance spectra from non-invasively recorded pulses.

The frequency spectra of modulus and phase of the input impedance (Zin) of large human arteries (abdominal aorta, femoral and subclavian arteries) were computed from transcutaneously recorded, uncalibrated pressure and flow pulses picked up as sphygmograms and Doppler flow velocity pulses, respectively. Since these pulses cannot be calibrated, the modulus (Zin) of the input impedance is calculated in relative units; its spectrum, however, is not influenced by this fact. A modification of the computing procedure makes it possible to determine approximately quasi-continuous frequency spectra of Zin from natural pressure and flow pulses which may be regarded as periodic functions. This is the prerequisite for a detailed analysis of the wave transmission properties of the arterial bed which manifest themselves of the input impedance. For this purpose the peripheral reflection site was moved in a proximal direction by bilateral occlusion of limb arteries. This was done by inflating cuffs placed symmetrically on both sides around the upper or lower parts of the respective limbs. When the occluding cuffs were placed around both lower legs or both thighs, the shortening of the arterial wave transmission line resulted in a marked shift of the first maximum of Zin to higher frequencies in the spectrum of Zin of the abdominal aorta and femoral artery. Bilateral occlusion of the arteries of the forearms or upper arms, however, did not have any measurable influence on Zin of the subclavian artery. Theoretical considerations show that this difference in behaviour of the several parts of the arterial system may be attributed to the varying extent of their inhomogeneity.

Adult↗
PubMedDate not supplied

[Principles of the genesis of pressure and flow pulse contours of the human carotid artery (author's transl)].

In order to clarify the genesis of the characteristic pressure and flow pulse contours of the common carotid artery of man, at first transcutaneous pulse recordings were carried out on healthy resting subjects during breathing of room air and of a mixture of 95% O2 and 5% CO2 (Carbogen). The latter was used to cause vasodilation of the cerebral resistance vessels and thus reducing the peripheral reflection coefficient. Secondly pulse constructions were performed by means of a theoretical inhomogeneous tube model using a digital computer. A side branch of this model represented the carotid artery. The pressure pulse of the aortic arch of the model was used as generating pulse for the carotid system. A satisfactory simulation of the carotid pressure and flow pulse contours under normal conditions and during peripheral vasodilation requires an intermediate reflection (positive for antegrade waves) at a site near the middle of the total transmission time of the carotid model system. The adequacy of the model is demonstrated by comparison of the recorded and constructed pulses.

Adult↗
PubMedDate not supplied

The mechanical properties of exposed human common carotid arteries in vivo.

In exposed common carotid arteries of 15 patients (36-74 years) undergoing neck surgery, the intra-arterial pressure (P) was recorded by means of a catheter-tip manometer and, at the same site, the external diameter (D) by means of a contact-free photoelectric device. On the average, the pulsatile diameter changes were 5.6% of the end-diastolic diameter at pulse pressures of about 50 mm Hg. Due to viscoelasticity, the P-D diagrams exhibited hysteresis loops. Using the criterion of loop elimination, an iterative procedure was applied which permitted, by the use of an appropriate computer program, the separation of the purely elastic and the purely viscous components of the P-D relationships. In all cases, the purely elastic P-D curves markedly deviated from linearity. The tangential elastic modulus (Et) and the pulse wave velocity (c) calculated from these curves were normalized by dividing these quantities by the respective end-diastolic values and plotted against the normalized external diameters. During each pulse cycle, Et increased, with increasing diameter, by a factor between 1.2 and 3.5, while c increased by a factor between 1.1 and 1.9 with reference to the respective end-diastolic values.

Adult↗
PubMedDate not supplied

The role of endothelium in the control of vascular tone.

In the last few years, experimental evidence has accumulated which suggests a substantial role for the endothelium in the control of vascular tone. Endothelium-dependent dilatations have been demonstrated in various arteries of numerous mammalian species including man. Among the stimuli which elicit endothelium-dependent dilatation are such varying stimuli as increases in blood flow and hypoxia, as well as endogenous (acetylcholine, ATP, ADP, bradykinin, substance P) and pharmacological agents (calcium ionophore A 23187, ergometrine, hydralazine, melittin). The functional importance of endothelium-dependent dilatation is emphasized by the fact that the direct vasoconstrictor effects of some of these substances (acetylcholine, histamine, norepinephrine, serotonin) on vascular smooth muscle is attenuated or even reversed by their simultaneous stimulatory effect on endothelial cells, resulting in the release of a vasodilator signal. Bioassay experiments have shown that a humoral vasodilator agent with a biological half-life in the range of seconds is released from the endothelium (native or cultured) during stimulation with acetylcholine, ATP and calcium ionophore. Experimental data are presented, which suggest that EDRF may act by direct stimulation of guanylate cyclase, resulting in smooth muscle relaxation due to increased smooth muscle cyclic GMP levels. The chemical nature of this nonprostaglandin endothelium-derived relaxant factor (EDRF) is still not known. The possible physiological and pathophysiological significance of endothelium-dependent dilatation in situ is discussed. Special attention is paid in this context to the potential role of EDRF activity in coronary vasomotor control.

Acetylcholine↗
PubMedDate not supplied

Nitric oxide, nitric oxide synthase, and hypertensive vascular disease.

In normotension the endothelium produces mainly nitric oxide (NO) and prostacyclin, and the vasodilator and growth inhibitory influence predominates. Hypertension, however, is associated with a shift towards enhanced constriction and vascular hypertrophy. These effects are associated with an apparent decrease in the production of bioactive NO and concomitant increase in the generation of oxygen-derived free radicals, such as superoxide anions (O(2)-). While the enzymatic source of endothelial O(2)- has been debated intensely over the past few years, it may well turn out that the endothelial NO synthase is itself an important producer of O(2)-. Because the redox state of endothelial cells and, for example, the activation of redox-sensitive transcription factors is regulated by the balance between NO and O(2)- production, endothelial NO synthase may well be the most crucial enzyme determining the anti- or prohypertensive and eventually proatherogenic state of the vascular wall.

Animals↗