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Biomedical subjects

H Hinghofer-Szalkay

Publications and source records attributed to H Hinghofer-Szalkay.

At least 19 recordsLinked to original sources
PubMed2006

Oxytocin levels in the posterior pituitary and in the heart are modified by voluntary wheel running.

We hypothesized that voluntary wheel running results in increased secretion of oxytocin, a peptide involved in the stress response. An additional hypothesis was that prolonged exercise affects oxytocin levels in the heart, which is in line with the potential role of oxytocin in cardiovascular functions. Voluntary wheel running lasted 3 weeks and daily running distances increased progressively reaching maximum levels about 8 km (Sprague-Dawley rats) and 4 km (Lewis strain). The exercise resulted in significant reduction of epididymal fat, slight increase in glucose transporter GLUT4 mRNA levels and significant enhancement of plasma density. Voluntary exercise failed to influence plasma oxytocin levels either in Lewis or Sprague-Dawley rats, but it resulted in a significant decrease of oxytocin concentrations in the posterior pituitary. Plasma oxytocin concentrations were not modified even if the measurements were made in the dark phase of the day. In voluntary wheel running Sprague-Dawley rats, the content of oxytocin in the right heart atrium was lower than in controls. Thus, the present findings demonstrate that prolonged voluntary wheel running results in a decrease in pituitary oxytocin content without evident changes in hormone concentrations in peripheral blood. However, prolonged exercise used has a significant impact on oxytocin levels in the heart.

Animals↗
PubMed2002

'Neutral point titration': cardiovascular regulation during combined (LBNP/HDT vs. LBPP/HUT) stimulation.

This study was undertaken to identify combinations ('neutral points', NP) of orthostatic (tilt: head-down = HDT, head-up = HUT) and pseudo-orthostatic (lower body pressure: positive = LBPP, negative = LBNP) stimuli able to compensate one another in their effect on hemodynamic variables, electrical thoracic impedance (TI), hematocrit and plasma mass density (PD), and blood hormone concentrations. We asked if NP's exist for tested variables (hypothesis 1), if NP's differ with variables (hypothesis 2), and if NP's change as a function of time (hypothesis 3). For the blood volume sensitive variables (PD, plasma total protein concentration, and hematocrit) we found a NP at > or = 30 degrees HDT at LBNP-35 and -15 degrees HUT with LBPP+35. There was no clear PD / total plasma protein concentration effect with various degrees of LBNP-15 / HDT. NP's could be derived for some hemodynamic variables: With LBNP-35, a NP for heart rate was derived at -25 degrees HDT and for MAP at -30 degrees HDT. Heart rate intersected at > or = 30 degrees HDT with LBNP-15 (extrapolated), stroke volume index (SVI) at -20 degrees HDT. With LBPP+35, SVI had its NP at 11 degrees HUT. The hormonal responses displayed a pattern where plasma renin activity (PRA) NP's were logically scattered with LBNP intensity, whereas aldosterone displayed similar NP's with both LBNP intensities.

Comparative Study↗
PubMed2002

Fluid volume changes and LBNP response after simulated weightlessness with varied oral sodium supply.

There is evidence on body fluid volume effects of head-down tilt bed rest and altered oral sodium supply, but the combined impact of both has not been investigated in detail. We therefore studied circulatory adaptation to 8 days -6 degrees head down bed rest (HDBR) with different levels (-140 to -430 mM/d) of oral sodium load (SL). We expected decreased extracellular volume and increased aldosterone and PRA levels with low sodium load, and hypothesized that these effects get exaggerated with additional HDBR, also influencing lower body suction (LBNP) responses. Variations in sodium status seem to influence plasma but not interstitial volume, confirming recent results of another group who used different experimental conditions.

Journal Article↗
PubMed2001

Assessing abdominal fatness with local bioimpedance analysis: basics and experimental findings.

OBJECTIVE: Abdominal fat is of major importance in terms of body fat distribution but is poorly reflected in conventional body impedance measurements. We developed a new technique for assessing the abdominal subcutaneous fat layer thickness (SFL) with single-frequency determination of the electrical impedance across the waist (SAI). SUBJECTS AND MEASUREMENTS: The method uses a tetrapolar arrangement of surface electrodes which are placed symmetrically to the umbilicus in a plane perpendicular to the body axis. Twenty-four test subjects (12 male, 12 female) underwent SAI and abdominal magnetic resonance imaging (MRI). The SFL below the sensing electrodes was determined from MRI and correlated with the SAI data at four different frequencies (5, 20, 50 and 204 kHz). RESULTS: A highly significant linear correlation (r2=0.99) between SFL and SAI over a wide range of the abdominal SFL was found. Separate regression models for female and male subjects did not differ significantly, except at 50 kHz. CONCLUSION: SAI represents a good predictor of the SFL and provides an excellent tool for the assessment of central obesity.

Abdomen↗
PubMed2001

The influence of medical information on the perioperative course of stress in cardiac surgery patients.

UNLABELLED: Cardiac surgery correlates with increased perioperative stress and anxiety. We tested whether preoperative extensive oral information in combination with more personal attention by the surgeon is associated with any effect on patients' perioperative stress, anxiety, and well-being. Sixty patients awaiting open heart surgery were divided into two groups. Group I consisted of 30 patients who received routine medical information through an informative pamphlet. In Group II (n = 30 patients), additional, extensive oral medical information and more personal attention by the surgeon was provided before surgery. Salivary cortisol, plasma cortisol, state anxiety, and patients' well-being were measured perioperatively. Extensive preoperative oral information in combination with more personal attention by the physician did not have any significant influence on the perioperative psychoendocrinologic course of stress. During transport to the operating room, salivary cortisol increased significantly (P < 0.001) in both groups (ranges are 95% confidence intervals) (Group I, 23.2 nmol/L [17.1-31.5]; Group II, 14.6 nmol/L [9.9-21.3]) versus the first day in the hospital (Group I, 8.4 nmol/L [6.2-11.4]; Group II, 6.7 nmol/L [5.3-8.6]). After the induction of anesthesia, plasma cortisol decreased significantly (P < 0.001) in both groups (Group I, 170.1 nmol/L [143.6-201.4]; Group II, 172.0 nmol/L [142.2-208.1]) versus preoperative levels. After surgery, well-being decreased (P = 0.003) in all patients, and patients' state anxiety was reduced (P = 0.001) after surgery. Our data demonstrate a lack of effect of extensive oral medical information that was presented as part of clinical routine on the perioperative psychoendocrinologic course of stress. High levels of stress during transport to the operating room were detected. IMPLICATIONS: The quantity of stress during transport to the operating room and the perioperative psychoendocrinologic course of stress in combination with two different methods of preoperative medical information are described in 60 consecutive patients awaiting cardiac surgery.

Aged↗
PubMed2001

Plasma sodium-osmotic dissociation and hormonal interaction with drinking-induced hypervolemia at 2800 m altitude.

PURPOSE: To study hormonal factors that may account for the dissociation between beverage-induced plasma sodium p[Na+] and osmotic p[Osm] concentrations that appear to refute the high theoretical correlation between p[Na+] and p[Osm]. METHODS: Ten men (24 +/- SD 3 yr of age) sat reclining (head up) for 12 h in a chamber (21-23 degrees C dry bulb, 25-33% relative humidity) at 2800 m (9184 ft, 539 mm Hg) altitude (ALT), and at 321 m (1053 ft, 732 mm Hg) on the ground (GND). During 1000-1030 hours they consumed 3 fluids (12 ml x kg(-1),X = 948 ml x d(-1)) with large differences in sodium and osmotic contents: AstroAde (AA) with 185 mEq x L(-1) Na+ and 283 mOsm x kg(-1), Performance 1 (Shaklee) (P1) with 22 mEq x L(-1) Na+ and 365 mOsm kg(-1), or H2O at ALT; and only H2O on the GND. RESULTS: After drinking: plasma volume (PV) increased at 1200 hours by 8.3% (p < 0.05) with AA but was not significantly (NS) changed in the other sessions (Xdelta = +0.9%, range -0.9 to 2.8%); p[Na+] and p[Osm] were unchanged. Urinary rates and free-water clearances were attenuated with AA and P1 vs. those with H2O. Correlations between and among p[Na+] and p[Osm] suggest that the pNa+ ion is more tightly controlled than pOsm; and that there was no clear hormonal response that could account for this dissociation from theoretical considerations. CONCLUSIONS: There is significant dissociation between plasma sodium and osmotic concentrations after fluid intake. Induction and maintenance of hypervolemia requires increased (near isotonic) drink Na+ osmols rather than increased non-ionic osmols.

Adult↗
PubMed2000

Exercise exacerbates acute mountain sickness at simulated high altitude.

We hypothesized that exercise would cause greater severity and incidence of acute mountain sickness (AMS) in the early hours of exposure to altitude. After passive ascent to simulated high altitude in a decompression chamber [barometric pressure = 429 Torr, approximately 4,800 m (J. B. West, J. Appl. Physiol. 81: 1850-1854, 1996)], seven men exercised (Ex) at 50% of their altitude-specific maximal workload four times for 30 min in the first 6 h of a 10-h exposure. On another day they completed the same protocol but were sedentary (Sed). Measurements included an AMS symptom score, resting minute ventilation (VE), pulmonary function, arterial oxygen saturation (Sa(O(2))), fluid input, and urine volume. Symptoms of AMS were worse in Ex than Sed, with peak AMS scores of 4.4 +/- 1.0 and 1.3 +/- 0.4 in Ex and Sed, respectively (P < 0.01); but resting VE and Sa(O(2)) were not different between trials. However, Sa(O(2)) during the exercise bouts in Ex was at 76.3 +/- 1.7%, lower than during either Sed or at rest in Ex (81.4 +/- 1.8 and 82.2 +/- 2.6%, respectively, P < 0.01). Fluid intake-urine volume shifted to slightly positive values in Ex at 3-6 h (P = 0.06). The mechanism(s) responsible for the rise in severity and incidence of AMS in Ex may be sought in the observed exercise-induced exaggeration of arterial hypoxemia, in the minor fluid shift, or in a combination of these factors.

Acute Disease↗
PubMed1999

LBNP-induced changes in plasma cGMP with and without head down tilt bed rest.

This investigation was conducted to test the following hypotheses: 1) If simulated orthostasis (LBNP) reduces plasma cGMP; 2) if simulated microgravity alters any such LBNP-induced effect; and 3) if simulated microgravity reduces resting plasma cGMP levels. In addition, we studied the time-course of thoracic impedance during, LBNP and asked if there is heart rate/blood pressure reduction after LBNP. During real and simulated spaceflight, blood is re-distributed throughout the vasculature along the body axis, vascular mechanoreceptor loads are altered, "excess" fluid is lost from the organism, and reflexly connected endocrine systems adapt with accompanying changes of hormone output. Altered steady-state plasma concentrations of volume sensitive hormones have been observed inflight as well as postflight. Hormones play a salient role in volume regulation but have barely been studied during microgravitational conditions in conjunction with lower body suction (LBNP). We used LBNP as an analogue to orthostatic stress since this model is useful to investigate, on quantitative grounds, hormone concentration changes as a function of cardiovascular stress in simulated weightless conditions. Earlier we reported consistently reduced plasma ANP and cGMP levels in a case study (14 mo spaceflight); transient hormonal changes after LBNP (as % of pre-LBNP values) were not different (p>0.05) from ground-control findings, and other hormone levels did not consistently deviate from ground control values. This is important since transmural central venous pressure which influences ANP output from the heart, and is elevated despite decreased CVP in parabolic flight, might be downregulated on a long-term basis. TCVP has not yet been measured inflight.

Bed Rest↗
PubMed1998

A model of artefacts produced by stray capacitance during whole body or segmental bioimpedance spectroscopy.

We have developed a novel model for the simulation of artefacts which are produced by stray capacitance during bioimpedance spectroscopy. We focused on whole body and segmental measurements in the frequency range 5-1000 kHz. The current source was assumed to by asymmetric with respect to ground as is the case for many commercial devices. We considered the following stray pathways: 1, cable capacitance; 2, capacitance between neighbouring electrode leads; 3. capacitance between different body segments and earth; 4, capacitance between signal ground of the device and earth. According to our results the pathways 3 and 4 cause a significant spurious dispersion in the measured impedance spectra at frequencies > 500 kHz. During segmental measurements the spectra have been found to be sensitive to an interchange of the electrode cable pairs. The sensitivity was also observed in vivo and is due to asymmetry of the potential distribution along the segment with respect to earth. In contrast to previously published approaches, our model renders possible the simulation of this effect. However, it is unable to fully explain the deviations of in vivo measured impedance spectra from a single Cole circle. We postulate that the remaining deviations are due to a physiologically caused superposition of two dispersions from two different tissues.

Artifacts↗
PubMed1998

Plasma volume expansion with oral fluids in hypohydrated men at rest and during exercise.

BACKGROUND: The purpose for this study was to evaluate various carbohydrate (CHO)-electrolyte fluid formulations for consumption by astronauts to maintain or restore their plasma volume (PV) and total body water (TBW) during and after extravehicular activity (exercise experiment, EE) and for a few hours before reentry and immediately after landing (rest experiment RE). HYPOTHESIS: That fluid formulation electrolyte content would be more important than osmotic (Osm) content for increasing or maintaining PV during the RE and EE. METHODS: In the RE, 5 healthy men (23-44 yr), previously dehydrated for 24 h, drank 6 fluid formulations (Water, 19.6 Na, 157 Na, 19.6 Na + glucose, and the prepared drinks Performances and Power)--one each at weekly intervals, and then sat for 70 min. In the EE, four healthy 24-h dehydrated men (30-46 yr) exercised for 70 min supine on a cycle ergometer (load = 71 +/- 1% peak VO2). RESULTS: Rest: Subjects who consumed formulations with total Osm concentrations nearer the normal range (157 Na - 270 mOsm x kg(-1), Performance with 19.6 mEq x L(-1) Na - 380 mOsm, and to some extent Power with 23.5 mEq x L(-1) Na - 390 mOsm) had the greater increases in PV; intake of drink 157 Na, with the largest Na content, induced the greatest hypervolemia of 7.6% (p < 0.05). The various additional ions, in addition to 19.6 Na, probably contributed to the 4.6% (p < 0.05) hypervolemia with Performance. Water was not effective. Exercise: Stabilization of PV between 15-70 min was not related to drink total CHO, Na or Osm content. Performance and 157 Na were no more effective than 19.6 Na or 19.6 Na + glu for PV stabilization. Water was the least effective. Regulatory mechanisms controlling PV during exercise appear to be independent of oral fluid formulation Osm-electrolyte content. CONCLUSIONS: Drink cation (sodium) content is more important that its total osmotic content for increasing plasma volume at rest. Fluid formulations with greater hypervolemic action in resting subjects may not be as effective during exercise; therefore different formulations for use during exercise appear to be necessary.

Adult↗
PubMed1998

Sodium chloride-citrate beverages attenuate hypovolemia in men resting 12 h at 2800 m altitude.

BACKGROUND: The mechanism for reduction and restoration of total body water and plasma volume (PV) during initial exposure to acute altitude (ALT) is not clear but may involve involuntary dehydration; i.e., delayed voluntary fluid intake. METHOD: Ten men (24 +/- SD 3 yr, 180.8 +/- 8.1 cm height, 78.8 +/- 12.8 kg weight, 1.99 +/- 0.19 m2 surface area, and 12.2 +/- 4.0% body fat) were in a semi-reclining position for 12 h in a chamber at 2800 m (539 mmHg) ALT or at 321 m (732 mmHg; ground). They ate a controlled breakfast (450 kcal + 3 ml x kg(-1) H2O) on the ground, and lunch and dinner at ALT (or on the ground) for a total daily intake of 2850 kcal (14% PRO, 67% CHO, 16% fat, 2.6g NaCl). At hour 10 they consumed fluid-electrolyte beverages or water (12 ml x kg(-1), 948 ml x d(-1)) in 4 sessions at weekly intervals. Beverage compositions were: a) 185 mEq x L(-1) Na+, 283 mOsm x kg(-1); b) 21.6 mEq x L(-1) Na+, 365 mOsm x kg(-1); c) water at ALT; and d) water on the ground. RESULTS: After 10 h at ALT % deltaPV (Hb-Hct) decreased (p < 0.05) by: a) 9.0 +/- SE 1.5%; b) 6.2 +/- 1.7%; c) 7.4 +/- 2.2%; and d) by 9.0 +/- 2.4%, respectively. After drinking from 1000-1030 h, PV at 1200 h changed by: a) +8.3 +/- SE 2.0% (p < 0.05); b) +2.8 +/- 2.7% (NS); c) -0.9 +/- 1.5% (NS); and d) by +0.8 +/- 3.5% (NS), respectively. The similar ground-induced hypovolemia suggests a response to confinement rather than an ALT effect and involuntary dehydration does not appear to be implicated. CONCLUSION: The significant increase in PV after consuming the (a) NaCl-NaCitrate beverage indicates that drink ionic composition appears to be more important than its osmolality for restoring PV in these conditions. Practical considerations: Because this hypovolemia was probably due to the confinement rather that reduced ambient pressure, appropriate countermeasures could be consumption of isotonic beverages, elastic stockings, leg exercise, and leg elevation.

Adult↗
PubMed1997

Ventilation during simulated altitude, normobaric hypoxia and normoxic hypobaria.

To investigate the possible effect of hypobaria on ventilation (VE) at high altitude, we exposed nine men to three conditions for 10 h in a chamber on separate occasions at least 1 week apart. These three conditions were: altitude (PB = 432, FIO2 = 0.207), normobaric hypoxia (PB = 614, FIO2 = 0.142) and normoxic hypobaria (PB = 434, FIO2 = 0.296). In addition, post-test measurements were made 2 h after returning to ambient conditions at normobaric normoxia (PB = 636, FIO2 = 0.204). In the first hour of exposure VE was increased similarly by altitude and normobaric hypoxia. The was 38% above post-test values and end-tidal CO2 (PET(CO2) was lower by 4 mmHg. After 3, 6 and 9 h, the average VE in normobaric hypoxia was 26% higher than at altitude (p < 0.01), resulting primarily from a decline in VE at altitude. The difference between altitude and normobaric hypoxia was greatest at 3 h (+ 39%). In spite of the higher VE during normobaric hypoxia, the PET(CO2) was higher than at altitude. Changes in VE and PET(CO2) in normoxic hypobaria were minimal relative to normobaric normoxia post-test measurements. One possible explanation for the lower VE at altitude is that CO2 elimination is relatively less at altitude because of a reduction in inspired gas density compared to normobaric hypoxia; this may reduce the work of breathing or alveolar deadspace. The greater VE during the first hour at altitude, relative to subsequent measurements, may be related to the appearance of microbubbles in the pulmonary circulation acting to transiently worsen matching. Results indicate that hypobaria per se effects ventilation under altitude conditions.

Adult↗
PubMed1997

Effect of postural changes on the reliability of volume estimations from bioimpedance spectroscopy data.

Bioimpedance spectroscopy (BIS) has been suggested for the assessment of fluid shifts between intracellular (ICV) and extracellular volume (ECV) during dialysis. The electrical tissue parameters are estimated by fitting a Cole-Cole model to the impedance data. Those parameters are used for the calculation of ICV and ECV with a fluid distribution model (FDM). We investigated whether postural changes cause artifacts in the volume data measured with a commercial BIS system. This is of importance at the beginning of dialysis, when the patient lies down for treatment. Volume estimations were performed during tilt table experiments with 11 healthy volunteers. Impedance spectra (5 to 500 kHz) were recorded for the total body as well as for body segments (leg and arm) during three phases: (1) 30 minutes resting in a supine position after standing; (2) 30 minutes 70 degrees head up tilt; and (3) a 30-minute resting period in a supine position. ECV and ICV were estimated with a commercially utilized FDM which is based on Hanai's mixture theory. A monoexponential function was fitted to the data for extracting the time constants and the extrapolated steady state values of the volume changes. The ECV and ICV data changed significantly during all three periods, that is, a steady state could not be reached within 30 minutes. During phase 1 the ECV decreased by 1.8 +/- 0.7%, in the tilt phase it increased by 3.8 +/- 1.1%, and in phase 3 it decreased again by 2.9 +/- 1%. The ICV increased by 3.6 +/- 2.4% during phase 1 and decreased by 6.8 +/- 5.1% during tilting; in phase 3 it increased by 4.6 +/- 1.7%. The time constants were 36.4 +/- 12.7 minutes (ECV) and 10.8 +/- 5.4 minutes (ICV) during phase 3. Segmental measurements revealed that the legs contribute significantly to the measured volume changes. The absolute volume changes in ICV and ECV differed significantly in all phases, and the same was found for the time constants during phases 1 and 3. From this discrepancy it is concluded that the measured volume changes are artifacts that are caused by extracellular fluid redistribution. Furthermore, it appears unlikely that the measured fluid shifts actually occur between ECV and ICV in the absence of osmotic changes in the body fluids. The validity of the method for a reliable assessment of volume changes during dialysis appears questionable, as dialysis-induced volume changes lie in the same range as the orthostatically-induced spurious volume changes.

Adult↗
PubMed1997

Diminished plasma cGMP during weightlessness.

We performed an experiment within the project "RLF" (Russian long-term flight) on a cosmonaut onboard the space station MIR. For creating an analogue to orthostatic stress, we used lower body negative pressure (LBNP) as stimulus. Decrease in central and peripheral baroreceptor load by LBNP can be used as a cardiovascular countermeasure in cosmonauts or for inducing endocrine responses. Altered steady-state plasma concentration values of volume sensitive hormones have been observed inflight as well as postflight. Within this project we measured plasma ANP and cGMP as second messenger. Changes in plasma cGMP concentration are generally considered to be a good indicator of those in ANP activity. However, in our experiments depression of cGMP during space flight was more impressive than ANP decline. We are not aware of previous measurements of plasma cGMP under these conditions, and believe to be the first to report complete suppression of plasma cGMP during long-term stay in space.

Atrial Natriuretic Factor↗
PubMed1995

Detection of 4-hydroxynonenal (HNE) as a physiological component in human plasma.

4-Hydroxynonenal (HNE) is a major aldehydic product formed by peroxidation of omega 6-unsaturated fatty acids and is regarded as a specific marker of lipid peroxidation. In this paper we demonstrate that there is a physiological steady-state concentration of HNE in human venous blood plasma. For the quantitative determination of HNE a modified version of an existing, but tedious and time-consuming HPLC method was developed. The extraction of aldehydic hydrazones from plasma was performed using an Extrelut column and the separation step by thin-layer chromatography was replaced by column chromatography on silica gel. The concentration of HNE in human blood plasma was in the same range as the concentration that was found to inhibit the proliferation of cells of the peripheral tissues, i.e., endothelial cells and fibroblasts in vitro. In an experiment with reduced peripheral blood flow a temporary significant increase of HNE was observed during reperfusion. It was concluded that lipid peroxidation occurs in peripheral tissues of humans following temporary congestion of venous blood flow.

Adult↗
PubMed1993

Transient blood/plasma density and hematocrit effects after passive (sitting) thermoneutral water immersion in men.

At the beginning and with ceasing of suction which is exerted upon the lower parts of the body, we have recently discovered transient hemodilution/hemoconcentration effects by use of the high-precision so-called mechanical oscillator technique. Since transient effects are useful for biological systems analysis, we addressed the question if such transients in blood and plasma mass density also occur with and immediately after water immersion in humans. Water immersion (WI) has been used as an analog of microgravity conditions. The effects on blood volume depend on the test conditions, particularly body position before immersion, and the time of measurement. Consequently, hemodilution has been found as an early effect of WI in many but not all studies. If test persons are immersed after sitting or standing on air, WI counteracts postural hemoconcentration and consistently produces a decrease in hematocrit, hemoglobin, and plasma protein concentration and, hence, plasma and blood mass density. In this paper we present evidence that, like with termination of lower body suction, there might be transient hemoconcentration in the first minutes of thermoneutral WI in a sitting position in men, but no evidence could be obtained for any counterdirected transient hemodilution when test subjects are passively brought out (in sitting position) from the water, as was found with starting lower body suction (in supine position).

Blood Viscosity↗