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Biomedical subjects

J Zipfel

Publications and source records attributed to J Zipfel.

At least 19 recordsLinked to original sources
PubMed2004

Chemistry of rocks and soils at Meridiani Planum from the Alpha Particle X-ray Spectrometer.

The Alpha Particle X-ray Spectrometer on the Opportunity rover determined major and minor elements of soils and rocks in Meridiani Planum. Chemical compositions differentiate between basaltic rocks, evaporite-rich rocks, basaltic soils, and hematite-rich soils. Although soils are compositionally similar to those at previous landing sites, differences in iron and some minor element concentrations signify the addition of local components. Rocky outcrops are rich in sulfur and variably enriched in bromine relative to chlorine. The interaction with water in the past is indicated by the chemical features in rocks and soils at this site.

Alpha Particles↗
PubMed2004

Soils of Eagle crater and Meridiani Planum at the Opportunity Rover landing site.

The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.

Extraterrestrial Environment↗
PubMed2004

Basaltic rocks analyzed by the Spirit Rover in Gusev Crater.

The Spirit landing site in Gusev Crater on Mars contains dark, fine-grained, vesicular rocks interpreted as lavas. Pancam and Mini-Thermal Emission Spectrometer (Mini-TES) spectra suggest that all of these rocks are similar but have variable coatings and dust mantles. Magnified images of brushed and abraded rock surfaces show alteration rinds and veins. Rock interiors contain </=25% megacrysts. Chemical analyses of rocks by the Alpha Particle X-ray Spectrometer are consistent with picritic basalts, containing normative olivine, pyroxenes, plagioclase, and accessory FeTi oxides. Mössbauer, Pancam, and Mini-TES spectra confirm the presence of olivine, magnetite, and probably pyroxene. These basalts extend the known range of rock compositions composing the martian crust.

Extraterrestrial Environment↗
PubMed2004

Chemistry of rocks and soils in Gusev Crater from the alpha particle x-ray spectrometer.

The alpha particle x-ray spectrometer on the Spirit rover determined major and minor elements of soils and rocks in Gusev crater in order to unravel the crustal evolution of planet Mars. The composition of soils is similar to those at previous landing sites, as a result of global mixing and distribution by dust storms. Rocks (fresh surfaces exposed by the rock abrasion tool) resemble volcanic rocks of primitive basaltic composition with low intrinsic potassium contents. High abundance of bromine (up to 170 parts per million) in rocks may indicate the alteration of surfaces formed during a past period of aqueous activity in Gusev crater.

Alpha Particles↗
PubMed2001

[Aortic valve structures as landmarks for determining coronary artery ostia in transthoracic echocardiography].

BACKGROUND: Occasionally, coronary arteries are recorded in transthoracal echocardiography. The question was if this modality could be used as non-invasive screening method of the coronaries. A prerequisite for this is an exact and reproducible measurement of the origin of the coronary arteries. MATERIAL AND METHOD: The topography of the coronary ostia in relation to the aortic valve was examined morphometrically in the aortae of 20 embalmed cadavers and 50 patients of a cardiologist's practice who underwent transthoracal echocardiography. RESULTS: In all cases, the coronary arterial orifices were located eccentrically in the coronary sinus, shifted to the non-coronary aortic sinus. The distance between left coronary orifice to the commissure of the left and the right semilunar valvula was 13.3 mm on average in the anatomical measurements, whereas in the echocardiography this distance was 14.3 mm. The distance between the left ostium and the attachment of the left and the posterior semilunar valvula 9.4 mm, corresponding to 11.6 mm in echocardiography. The distance between right coronary orifice and the attachment of the right and the left semilunar valvula was 18.0 and 17.3 mm respectively, and the distance between right coronary orifice and the commissure of the right and the posterior semilunar valvula accounted for 8.5 and 9.7 mm respectively. On the average, the ostia were located 3.9 mm below the level of the sinotubular junction. Multiple ostia occurred in 65%, 92% of these were in the right coronary aortic sinus, shifted from the main orifice to the attachment of the right and the left semilunar valvula. CONCLUSION: In the cardiologist's routine, the attachments of the aortic leaflets proved to be very useful as landmarks. The coronary arterial orifices have been educible in nearly all cases. These results show that transthoracal echocardiography may be used in the screening for coronary artery disease.

Aged↗
PubMed2000

Supernova Sources and the 92Nb-92Zr p-Process Chronometer.

We report new Zr isotope evidence for live (92)Nb (mean life: tau&d1;92Nb=52 Myr) within the early solar system resulting in &parl0;92Nb&solm0;93Nb&parr0;initial approximately 10-3. The meteoritic minerals rutile and zircon have, respectively, very high and very low Nb/Zr ratios and are ideal for exploring the (92)Nb-(92)Zr chronometer. Rutiles exhibit high positive straightepsilon92Zr ( approximately 14-36) while a zircon has a negative straightepsilon92Zr ( approximately -4), as would be expected if (92)Nb was live in the early solar system. The meteoritic rutiles appear to be young, with apparent times of formation of approximately 80-220 Myr subsequent to the origin of the solar system. The initial (92)Nb/(92)Mo for the solar system is broadly compatible with a model of uniform production if the (92)Nb/(92)Mo production ratio for Type II supernova (SNII) sources with neutrino-driven winds is used. Data for all the now extinct p-process nuclides ((92)Nb, (97)Tc, and (146)Sm) are consistent with these isotopes being derived by uniform production from SNII sources and a free decay interval of approximately 10 Myr. Consideration of a range of models indicates that the average p-process production ratio of (92)Nb/(92)Mo needs to be at least in the range of 0.06-0.25.

Journal Article↗
PubMed1988

Comparison of the effects of right atrial, right ventricular apex and atrioventricular sequential pacing on myocardial oxygen consumption and cardiac efficiency: a laboratory investigation.

As the impact of cardiac pacing on myocardial energetics has not yet been established, this laboratory investigation was undertaken to evaluate the effects of right atrial (AP), right ventricular apex (VP) and atrioventricular sequential pacing (AVP) on cardiac energetics in a closed-chest model. Ninety-two pacing interventions were performed in ten anesthetized mongrel dogs with normal loading conditions and contractile states. The energetic effects of pacing were assessed in terms of myocardial oxygen consumption (MVO2), its hemodynamic determinants and cardiac efficiency. Efficiency was calculated as the ratio of O2-equivalent of external cardiac work to MVO2, using standard definitions. In the first series of experiments 36 intra-individual comparisons were made between AP and VP at identical rates (95-210 beats/min). In the second series AVP was compared to VP in 10 intra-individual comparisons at identical rates (109-190 beats/min). MVO2 was lower (p less than 0.001) during AP (8.30 +/- 2.14 ml O2/min.100 g) compared to VP (10.16 +/- 3.15 ml O2/min.100 g) at the same rate (158 +/- 32 beats/min). Efficiency (p less than 0.001) was considerably higher during AP (21.6 +/- 5.7%) compared to VP (12.8 +/- 5.9%). During AVP, MVO2 (10.85 +/- 1.76 ml O2/min.100 g) was not significantly different from VP (10.57 +/- 1.34 ml O2/min.100 g) at the same rate (146 +/- 25 beats/min). Hemodynamics were superior with AVP compared to VP. Efficiency was significantly higher (p less than 0.01) with sequential (15.4 +/- 3.9%) as compared to ventricular pacing (12.0 +/- 3.2%). In conclusion, this study indicated that VP exerts disadvantageous effects on MVO2 and cardiac efficiency. AP has beneficial effects on cardiac energetics because it improves the relationship between mechanical performance of the heart and its energy requirements. AVP results in a higher efficiency than VP due to superior hemodynamics, despite MVO2 levels comparable to those of VP. The mechanism of energy waste with right ventricular apex pacing is probably related to an asynchronous contraction in the ventricular myocardium due to a nonphysiological spread of excitation.

Animals↗
PubMed1982

[Coronary angiography in chronic and acute coronary artery disease. Advantages of a low osmolality contrast medium].

The advantages of a new low osmolality contrast medium (sodium meglumine ioxaglate) in clinical coronary angiography are demonstrated at two groups of patients in comparison to sodium meglumine diatrizoate. One group included patients undergoing diagnostic angiography in chronic state of CHD, the other during diagnosis and therapy (intracoronary lysis) in state of acute myocardial infarction. Injection of the low osmolality contrast material was followed in both groups by significant reduction of pressure drop and cardiac slowing. In both groups there was also a reduction of changes in ECG compared to side effects of the conventional contrast material.

Aged↗
PubMed1981

Influence of arteriographic contrast media on the Na+/Ca++-ratio in blood.

To investigate the basis of cardiodepressive side effects in coronary arteriography, the isolated effects of different contrast media on electrolyte levels in blood (and blood fractions) were quantified in vitro. Due to their sodium content and calcium chelation, ionic media cause an imbalance in the extracellar Na+/Ca++-ratio that determines myocardial contractility. Ca++-chelation exceeded that due to stabilizing additives indicating a binding by the contrast agents themselves. The amount of calcium bound varied with different media and was greatest with Renografin. It is suggested that the degree of Na+/Ca++-imbalance in blood explains the extent of acute cardiodepression.

Angiography↗
PubMed1981

Basic physiological studies on cardiac pacing with special reference to the optimal mode and rate after cardiac surgery.

Temporary cardiac pacing (CP) is frequently applied postoperatively in the management of low cardiac output (CO) and rhythm instability. However, uncertainty exists about the "optimal" pacing rate, range and mode due to incomplete information on myocardial oxygen consumption (MVO2), related to its hemodynamic determinants, and on myocardial pumping efficiency (eta) at CP. In 10 intact dogs atrial pacing (AP) (90 to 210 beats/min) and ventricular pacing (VP) (70 to 330 beats/min) were investigated in normal and failing hearts. AP and VP were compared at identical rates. MVO2 (4 to 20 ml/min . 100 gr) was measured directly according to the Fick principle. Cardiac efficiency was calculated as the ratio of oxygen equivalent of external cardiac work to MVO2. Rates with maximum CO and a maximal eta occurred only in heart failure. However, maximal CO and eta were obtained at different heart rates (HR). MVO2 was significantly higher (p less than 0.001) under VP as compared to AP at identical rates with a mean increase of 26.5% +/- 6% over AP, although hemodynamics were significantly lower under VP (p less than 0.001). Myocardial pumping efficiency was markedly better under AP with a mean increase of 63% +/- 4.5% over VP even in normal heart. Adjustment of HR at maximal response in CO may become dangerous, particularly under VP, in heart failure. AP, if applicable, may be regarded as the optimal pacing technique due to an optimal relation of improved hemodynamics to MVO2. It may be helpful in correcting an imbalance between oxygen supply and demand in cases of low output syndrome. The pathophysiologic mechanisms and further clinical implications are discussed.

Animals↗
PubMed1981

Effects of AR-L 115 BS on hemodynamics, myocardial oxygen consumption and cardiac pumping efficiency.

The effects of 2-[(2-methoxy-4-methylsulfinyl)phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) on hemodynamics, myocardial oxygen consumption and cardiac pumping efficiency were tested on closed-chest dogs in cardiac catheterization technique. Doses in the range of 0.1 up to 4.0 mg/kg b. w. were injected i.v. A therapeutical dose is to be expected in the range of 1.0 mg/kg b. w., showing a distinct positive inotropic effect and reducing endsystolic volume without increase of heart rate and myocardial oxygen consumption.

Animals↗
PubMed1980

[Reduced cardiotoxicity of contrast media in angiocardiography. Comparative clinical study using diatrizoate with added calcium or metrizamide (author's transl)].

Cardiodepressive side effects of angiocardiography can be reduced by using non-ionic metrizamide (Amipaque) or adding calcium to diatrizoate (Urografin 76%). In 15 patients with coronary artery disease undergoing heart catheterization, we compared cardiac side effects of coronary angiography and left ventricular angiography using metrizamide and diatrizoate with and without additional calcium (11.3 mmol/l) as contrast media under randomized conditions. In selective intracoronary injection with diatrizoate alone, peak left ventricular pressure and contractility (dP/dtmax) showed a fall of 30 +/- 11% and 31 +/- 15% (n = 33 injections). Using diatrizoate with added calcium (11.3 mmol/l), the fall was only 23 +/- 12% and 20 +/- 10% respectively (n = 31 injections). With metrizamide (n = 32 injections) cardiac side effects are even less and the decrease in pressure and contractility only 13 +/- 10% and 7 +/- 7% respectively, which its highly significant (p less than 0.0001) compared with the effect of diatrizoate. The heartrate slowing, not essentially altered by calcium addition, was minimal using non-ionic metrizamide. In left ventricular angiography, the pressure fall in the late phase after injection of diatrizoate, caused by decrease peripheral vascular resistance (vasodilation), was lacking when injecting metrizamide (p less than 0.001). Metrizamide has even less cardiodepressive side effects than diatrizoate with additional calcium when used in angiocardiography and seems to be suitable particularly for the evaluation of high risk patients.

Adult↗
PubMed1980

Decrease in cardiotoxicity of contrast media in coronary angiography by addition of calcium ions: a combined experimental and clinical study.

The cardiotoxicity of commonly used contrast media such as sodium methylglucamine diatrizoate is related to nonphysiologic concentrations of ions and high osmolality. Following injection there is an excessive decrease in ambient calcium which disturbs the extracellular Na+/Ca2+ ratio and results in myocardial depression. In animal studies (anesthetized, intact mongrel dogs) this cardiodepressive effect could be fully compensated by adding 22.5 mEq/1 of ionic calcium to the contrast medium. In 16 patients studied for coronary artery disease (CAD) 72 injections of sodium methylglucamine diatrizoate, mainly in the left coronary artery, were thoroughly investigated. There was marked depression of left ventricular pressure (-22%) and (dP/dt)max (-27%), and marked heart rate slowing (-29%). Added calcium in the concentration cited reduced significantly (p < 0.001) the myocardial depression to -15% and -13%, respectively, but did not completely compensate it. The heart rate slowing was not altered significantly. It was concluded that the addition of calcium may be helpful when studying high-risk patients and using high injection volumes.

Angiography↗
PubMed1980

DPTI/STTI--an index of the myocardial oxygen supply/demand ratio?

The DPTI/STTI (diastolic pressure-time index/tension-time index) ratio is applied as an indicator of myocardial ischemia particularly in cardiovascular and anesthesiologic care units. The validity of the DPTI/STTI ratio was examined in intact dogs with large variations of oxygen supply and demand. The correlation of DPTI/STTI to the directly measured oxygen supply/demand ratio was poor even under maximal coronary vasodilation. Many data points were far below the critical DPTI/STTI values (reported previously) without occurrence of myocardial ischemia, failure, or edema. Therefore caution is necessary if the DPTI/STTI ratio is to applied to humans.

Animals↗
PubMed1980

[Reduction in cardiotoxicity of ionic contrast media used in coronary angiography by added calcium--Clinical study (author's transl)].

In 16 patients with CAD, hemodynamic and electrophysiologic side effects were examined following selective coronary artery injections with Urografin 76%, a commonly used ionic contrast medium. A Millar transducer tipped catheter was placed in the left ventricle for continuous pressure recording also during injections. The unmodified contrast medium decreases peak left ventricular pressure (-22 +/- 8%) and dp/dt max (-27 +/- 13%) markedly at injection. With added calcium (22.5 mEq/l) this cardiodepressive reaction becomes diminished to -15 +/- 7% and -13 +/- 8% respectively with high significance (p < 0.001). This positive effect is even more marked using higher volumes of contrast material for injection. In contrast to animal experiments, calcium did not completely compensate the negative inotropic reaction even in higher concentration (33.75 mEq/l). The marked sinus slowing (-29 +/- 14%)--observed in patients and not influenced by the calcium addition--has an additional effect in the sense of a "negative frequency-inotropism" and is responsible for the residual cardiodepressive reaction. An influence on electrophysiologic side reactions can also be observed with added calcium but only in injections with higher volumes of contrast medium. QT-elongation, T-wave changes are reduced significantly. We did not see any unfavorable reactions caused by added calcium. The cardiodepressive side effects on the contractile force by commonly used ionic contrast media can be reduced by adding calcium in the above-mentioned concentration. This may be helpful when studying high risk patients and using high injection volumes.

Adult↗