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Biomedical subjects

M Moser

Publications and source records attributed to M Moser.

At least 469 records · Page 26Linked to original sources
PubMedDate not supplied

Initial treatment of adult patients with essential hypertension: I. Why conventional stepped-care therapy of hypertension is still indicated.

The stepped-care approach to the treatment of hypertension suggests the use of a diuretic or, in some cases, a beta blocker as initial monotherapy. If either of these agents proves to be ineffective, the other can be tried as monotherapy. Stepped-care suggests the use of different classes of drugs that affect different mechanisms related to hypertension at various stages of treatment. Although empiric, the concept makes good physiologic sense. Results of its use in major clinical trials, as well as an extensive private practice experience, suggest that in a large majority of patients, hypertensive can be controlled with relatively little expense, few titration problems and a high rate of adherence. Advocates of individualization of care, or sequential monotherapy, base their suggestion on theory, but widespread use of this approach would make management more complex and more expensive, and would probably decrease adherence to long-term treatment. Stepped-care treatment allows for adequate individualization and a wide choice of drugs, and should continue to be employed unless data are obtained that demonstrate a better outcome with sequential monotherapy or other more complex approaches.

Adolescent↗
PubMedDate not supplied

Blood flow and blood volume determinations in aorta and in coronary circulation by density dilution.

Continuous blood mass-density measurements were performed in anesthetized dogs and injections of 0.7-1.4 ml/kg isotonic saline solution were applied. The resulting density dilution curves were used to compute blood volume, total flow in the aorta and local flow in the coronary circulation. Blood volume calculations were compared with blood volume determined by Evans blue injections and a close agreement was found. Blood flow determined by density dilution was independent from the investigated sites of injection or sampling. We conclude from these results that small volume injections of isotonic saline solution can be used to determine blood volume and flow by density dilution. In addition to these findings, a marked retention of the injected fluid was observed. Possible mechanisms to explain this retention include albumin deposition in the endothelial pores and/or variations of blood viscosity and capillary pressure.

Animals↗
PubMedDate not supplied

Influence of tonicity on the viscoelastic properties of blood during isovolemic dilution.

The influence of isotonic or hypotonic dilution on viscoelastic properties of blood is examined. The viscous, as well as the elastic, properties of blood samples diluted with isotonic saline or pure water, respectively, and of undiluted whole blood samples are compared by means of a dynamic capillary viscosimeter (OCR-D, A. Paar K.G., Austria). The dilution (approximately 17% of the total blood volume) was performed isovolemically and retained the same rbc count. The rbc swelling observed as a consequence of changes in plasma osmolarity was tracked by the high resolution density measurement, according to the mechanical oscillator technique. Since no significant rbc swelling was found in the dilution with isotonic saline, viscoelastic resistance of blood was efficiently reduced in the observed range of shear rates (2 s-1-100 s-1). This decrease is due to reduced plasma protein concentration, which also lowers plasma viscosity by approximately 18%. Although plasma viscosity is significantly decreased in hypotonic dilutions (-12%), flow properties of the rbc suspensions are, in general, significantly impaired. This is due to the osmotic rbc swelling (hematocrit = +8%), which increases viscous resistance within the suspending fluid, as well as elastic resistance of the rbc due to a loss in rbc deformability. It can be concluded that isotonic dilution leads to a decrease in the viscosity of blood, whereas hypotonic dilution--in an order of magnitude which may occur during resorption of water--leads to increased viscous and elastic resistance of the blood.

Blood Viscosity↗
PubMedDate not supplied

Determination of cardiac output and of transcapillary fluid exchange by continuous recording of blood density.

We have tested the application of the continuous measurement of the density of the arterial blood for the calculation of the cardiac output and for the determination of the transcapillary fluid exchange. The density of arterial blood was continuously recorded in anesthetized dogs with a mechanical oscillator device (DMA 602 MW built by A. Paar KG, Graz). The time resolution of this device is less than 1 sec, the accuracy is 10(-6) g/ml. Simultaneously the arterial blood temperature was recorded with a thermistor probe. The intravenous injection of isotonic solutions yields temperature and density transients which are of a similar shape and proportional to the injected volume in amplitude. There is a good agreement between the cardiac output calculated from thermodilution transients and from density dilution transients. The injection of hypertonic solutions, e.g. 5% NaCl, 20% mannit or 14.4% urea, into a vein yields arterial density dilution transients which show marked differences and very characteristic features. They can be explained by the assumption of osmotic fluid shifts in the microcirculation of the lung. During the transient of a bolus of hypertonic NaCl or mannit, a transcapillary influx of about 0.170 X 10(-3) ml/sec per mosmols/l and per g wet tissue weight is generated. The effect of hypertonic urea is less by a factor of about 1/2, which is in agreement with the fact that urea diffuses rapidly into the erythrocytes. We conclude that the method of density dilution allows to record and quantify cardiac output and osmotic fluid shifts through the microcirculation of the lung of intact dogs.

Animals↗
PubMedDate not supplied

Hypertension update.

Hypertension affects approximately fifty million Americans. About 80% of hypertensive patients are aware that their blood pressure is elevated. While more than 50% are on medication, only about 20% of all hypertensive adults are controlled at normotensive levels. Ophthalmologists should be aware of the seriousness of hypertension because it affects many of their patients and is a risk factor for myocardial infarction, stroke, congestive heart failure, end-stage renal disease and peripheral vascular disease. As medically trained eye specialists, ophthalmologists should be knowledgeable about and take an interest in their patients' medical problems, thus playing an integral role on the health care team. As a primary health care provider, ophthalmologists should perform in-office blood pressure monitoring.

Adult↗
PubMedDate not supplied

Autonomic regulation of circulation and cardiac contractility during a 14-month space flight.

The space flight of physician cosmonaut V.V. Polyakov, the longest to date (438 days), has yielded new data about human adaptation to long-term weightlessness. Autonomic regulation of circulation and cardiac contractility were evaluated in three experiments entitled Pulstrans, Night, and Holter. In the Pulstrans experiment electrocardiographic (ECG), ballistocardiographic (BCG), seismocardiographic (SCG), and some other parameters were recorded. In the Night experiment, only the ballistocardiogram was recorded, but a special feature of this experiment is that the BCG records were obtained with a contactless method. This method has several advantages, the most important of which are the possibility of studying slow-wave variations in physiologic parameters (ultradian rhythms) on the basis of recordings made under standard conditions over a prolonged period. The Holter experiment (24-hour electrocardiographic monitoring) used a portable cardiorecorder (Spacelab, USA). The obtained electrocardiographic data were used to analyze heart rate variability. In the first 6 months of the 14-month flight, the dynamics of cardiovascular parameters in V.V. Polyakov was virtually the same as in the other cosmonauts. The data obtained after the first 6 months of Polyakov's sojourn in space are unique and mention should be made of at least three important aspects: (1) activation of a new, additional adaptive mechanism in the 8th-9th months of flight, as is evidenced by alterations in the periodicity and power of superslow wave oscillations (ultradian rhythms) reflecting the activity of the subcortical cardiovascular centers and of the higher levels of autonomic regulation; (2) growth of cardiac contractility accompanied by a decrease in heart rate during the last few months of flight; (3) a considerable increase in the daily average values of absolute power of heart rate's variability MF component, which reflects the activity of the vasomotor center. Specific mechanisms of adaptation to weightless conditions appear to be associated with activation of higher autonomic centers. The hypothesis that central levels of circulation regulation are activated in a long-term space flight was investigated by analyzing of ultradian rhythms in nighttime. The data, received during the flight of V. V. Polyakov, show, that the process of human adaptation to long influence of weightlessness consists of a number of consecutive stages, during which the activation of more and more high levels of control system of physiological functions occurs.

Adaptation, Physiological↗
PubMedDate not supplied

Induction of endothelin-1 expression by oxidative stress in vascular smooth muscle cells.

Atherosclerosis is based on endothelial dysfunction leading to impaired vasomotor function. This is partially due to nitric oxide (NO) depletion caused by oxidative stress. Since the vasoconstrictor endothelin-1 (ET-1) might also be involved in endothelial dysfunction, we investigated whether oxidative stress regulates ET-1 expression in vascular smooth muscle cells (VSMC). Human aortic VSMC were treated with H(2)O(2) (200 microM) for up to 8 h. mRNA expression of preproendothelin (prepro-ET) was analyzed by RT-PCR. ET-1 protein and the marker for oxidative stress, 8-isoprostane, were determined by ELISA. Activity of cytosolic phospholipase A2 (cPLA(2)) as an indicator of ET-1 autocrine activity was measured photometrically. Stimulation of VSMC with H(2)O(2) resulted in increased expression of prepro-ET mRNA after 1 h with a maximum after 6 h (fourfold), similar to treatment with angiotensin II. ET-1 protein was significantly increased by H(2)O(2) treatment with a maximum after 8 h (P<.05). This effect was inhibited by the antioxidants resveratrol (100 microM) and quercetin (50 microM). In quiesced VSMC, incubation with H(2)O(2)-conditioned medium resulted in increased cPLA(2) activity compared to the controls (P<.05). This activity was partially inhibited by the ET(A)-receptor antagonist, PD 142893 (10 microM), indicating functional ET-1 in the conditioned medium. The presence of oxidative stress in H(2)O(2)-treated VSMC was associated by significantly increased formation of 8-isoprostane (P<.05). The data indicate for the first time that oxidative stress increases ET-1 generation and autocrine ET-1 activity in VSMC, a mechanism that might contribute to endothelial dysfunction in atherosclerosis.

Antioxidants↗
PubMedDate not supplied

Selection based on morphological assessment of oocytes and embryos at different stages of preimplantation development: a review.

In contrast to IVF, in ICSI the surrounding cumulus and corona cells must be removed completely, as only denuded oocytes can be successfully manipulated by the holding pipette. This ancillary effect of ICSI allows us to focus on the morphology of preimplantation development from the earliest stages. Early prognosis regarding the developmental fate of oocytes would help to limit a negative impact of culture conditions. However, little evidence is available that non-invasive selection at the oocyte stage (first polar body, granular cytoplasm) may be of prognostic value. Recently, certain patterns of pronuclei (number and the distribution of nucleoli) at the zygote stage were found to correlate with treatment outcome in IVF and ICSI cycles, offering an additional prognostic tool prior to cleavage. As there is evidence that embryo selection on day 2 or 3 based on morphological criteria (fragmentation, number of blastomeres, multinucleation, uneven cleavage) may be imprecise, patients might benefit from extended embryo culture to day 5. However, not all major chromosomal aberrations are incompatible with blastocyst formation, and prolonged culture in vitro does not exclusively select embryos with a normal chromosomal complement. Consequently, special care should be taken to minimize the presence of aneuploid concepti in culture. In addition, multiple selection at different stages of development will be required to filter out the correct 'candidate' embryo which will result in a healthy newborn.

Blastocyst↗