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PubMedDate not supplied

[Biophysical models of the heart electrical activity].

Based on the fundamental knowledge of the space-temporal organization of extracellular electrical fields of the myocardium, a system for 3-D computer modeling of the cardiac electrical activity at different structural levels of the object is being developed at the Institute of Theoretical and Experimental Biophysics. The system is based on the earlier proposed and modified biophysical model of the electrocardiosignal genesis represented by a double electrical layer along the surface of the electrically active myocardium. The system combines the model for activation and repolarization of the heart ventricles; the advanced model for the evaluation of parameters of the cardiac electric field, which makes it possible to derive model electrocardiosignals both in the direct regime of calculation of the potentials and in the regime of calculation of electrocardiosignals from preliminarily determined components of the multipole equivalent electrical heart generator; a database for the model parameters and their combinations in the form of cards of simulated "patients", and a database of modeled electrocardiosignals. In the present paper (first from three within the framework of the problem), simulation methods in electrocardiology are briefly described and a biophysical model of the heart electrical activity is presented, which has made up the basis of the system for computer modeling of forward and inverse problems of the cardiac electric field. The parameters of the model are electrophysiological, anatomical, and biophysical characteristics of the heart.

Biophysical Phenomena↗
PubMedDate not supplied

[Successes in medical biophysics (on the 40th anniversary of the Medico-biological faculty of the Russian State Medical University)].

On the occasion of the 40-year anniversary of the Medicobiological Faculty of the Russian State Medical University, the research activity of the biophysics department was summed up. The main result is the creation of medical biophysics as part of the medicobiological science. Scientific investigations of the biophysics department are reviewed. They are presented as follows: chemiluminescence of biological systems; effect of visible light on human and animal molecules and cells; application of luminescence methods in laboratory and clinical investigations; free radicals and their role in cell biology and pathology; medical aspects of molecular biophysics; and biological membranes and cell pathology.

Animals↗
PubMed1999

Agriculture sector resource and environmental policy analysis: an economic and biophysical approach.

Agricultural pollution of the environment is jointly determined by economic decisions driving land use, production practices, and stochastic biophysical processes associated with agricultural production, land and climate characteristics. It follows that environmental and economic statistics, traditionally collected independently of each other, offer little insight into non-point pollutant loadings. We argue that effective policy development would be facilitated by integrating environmental and economic data gathering, combined with simulation modelling linking economic and biophysical components. Integrated data collection links economics, land use, production methods and environmental loadings. An integrated economic/biophysical modelling framework facilitates policy analysis because monetary incentives to reduce pollution can be evaluated in the context of market costs and returns that influence land use and production activity. This allows prediction of environmental and economic outcomes from alternative policies to solve environmental problems. We highlight steps taken to merge economic and biophysical modelling for policy analysis within the Economic Research Service of the United States Department of Agriculture. An example analysis of a policy to reduce agricultural nitrogen pollution is presented, with the economic and environmental results illustrating the value of linked economic and biophysical analysis.

Agriculture↗
PubMed2005

Using fetal acoustic stimulation to shorten the biophysical profile.

PURPOSE: To determine whether fetal acoustic stimulation can decrease the time required to achieve a reassuring biophysical profile. METHODS: Patients scheduled for a biophysical profile were prospectively assigned to study and control groups. The study group received 3 seconds of acoustic stimulation if fetal breathing, tone, or movement were not present during the first 5 minutes of the study. The biophysical profile was completed in the standard fashion, for both groups. RESULTS: A total of 870 patients were enrolled (458 control, 412 with stimulation). The fetal acoustic stimulation group had decreased testing time (3 minutes) and fewer non-reassuring tests (5%). The fetal acoustic stimulation group had fewer studies without breathing, potentially reducing the need for further testing or intervention. CONCLUSIONS: Fetal acoustic stimulation can be used to decrease the biophysical profile testing time and to reduce the number of non-reassuring tests.

Acoustic Stimulation↗
PubMed2006

Effects of N- and C-terminal addition of oligolysines or native loop residues on the biophysical properties of transmembrane domain peptides from a G-protein coupled receptor.

Transmembrane domains (TMDs) of G-protein coupled receptors (GPCRs) have very low water solubility and often aggregate during purification and biophysical investigations. To circumvent this problem many laboratories add oligolysines to the N- and C-termini of peptides that correspond to a TMD. To systematically evaluate the effect of the oligolysines on the biophysical properties of a TMD we synthesized 21 peptides corresponding to either the second (TPIFIINQVSLFLIILHSALYFKY) or sixth (SFHILLIMSSQSLLVPSIIFILAYSLK) TMD of Ste2p, a GPCR from Saccharomyces cerevisiae. Added to the termini of these peptides were either Lys(n) (n = 1,2,3) or the corresponding native loop residues. The biophysical properties of the peptides were investigated by circular dichroism (CD) spectroscopy in trifluoroethanol-water mixtures, sodium dodecyl sulfate (SDS) micelles and dimyristoylphosphocholine (DMPC)-dimyristoylphosphoglycerol (DMPG) vesicles, and by attenuated total reflection Fourier transform infrared (ATR-FTIR) in DMPC/DMPG multilayers. The results show that the conformation assumed depends on the number of lysine residues and the sequence of the TMD. Identical peptides with native or an equal number of lysine residues exhibited different biophysical properties and structural tendencies.

Amino Acid Sequence↗
PubMed1989

The effect of magnesium sulfate tocolysis on the fetal biophysical profile.

The biophysical profile has proved to be a valuable tool for the assessment of fetal well-being, independent of gestational age. Magnesium sulfate is commonly used as a tocolytic agent, yet relatively little is known about its effects on the biophysical activities of the fetus. To investigate the effects of magnesium sulfate on the biophysical profile, we performed serial studies on patients who received tocolytic therapy with this agent because of preterm labor. A total of 16 women with 22 fetuses at 26 to 34 weeks' gestation in spontaneous preterm labor were studied. An initial biophysical profile was performed at the time of admission, and a second examination was performed when maternal serum magnesium levels reached 6 to 8 mg/dl. On admission all fetuses had reactive nonstress test results and 21 of 22 (95%) demonstrated sustained fetal breathing movements. With magnesium sulfate tocolysis, 50% of fetuses had nonreactive nonstress test results, and only 4 of 22 (18%) demonstrated sustained fetal breathing movements. Fetal tone, gross body movements, and amniotic fluid volume were found to be unaffected by magnesium sulfate tocolysis.

Adult↗
PubMed1991

Relationship between fetal biophysical activities and umbilical cord blood gas values.

In a prospective study of 62 patients undergoing cesarean section before the onset of labor a fetal biophysical profile assessment was performed within 3 hours before the cesarean section. The presence or absence of the individual fetal biophysical activities (fetal heart rate reactivity, fetal breathing movements, fetal body movements, and fetal tone) were correlated with umbilical cord blood gas and acid-base measurements (artery and vein). Fetuses with nonreactive nonstress test results or the absence of breathing had significantly lower cord artery pH, PO2 bicarbonate, and base excess measurements but not a significantly different PCO2 level as compared with fetuses that had these activities present. Fetuses with the absence of movements or tone had lower pH, PO2 bicarbonate, and base excess levels and higher PCO2 levels as compared with fetuses with the presence of movements or tone, respectively. These blood gas and acid-base differences were observed in both umbilical cord artery and vein. Subsequent analysis of the blood gas and acid-base measurements of the fetuses with compromised biophysical activities revealed that there are different levels of acidemia, hypoxemia, and hypercapnia at which the individual biophysical activities are compromised. These data suggest that the first manifestations of fetal hypoxemia and acidemia are nonreactive nonstress test results and loss of fetal breathing; in advanced acidemia, hypoxemia, and hypercapnia fetal movements and fetal tone are compromised.

Carbon Dioxide↗
PubMed1987

Biophysical activity of synthetic phospholipids combined with purified lung surfactant 6000 dalton apoprotein.

This research studies the biophysical surface activity of synthetic phospholipids combined in vitro with purified lung surfactant apoprotein, having an Mr of 6000. Hydrophobic surfactant-associated protein (SAP-6) was delipidated and purified from both bovine and canine lung lavage, and was combined in vitro with a synthetic phospholipid mixture (SM) of similar composition to natural lung surfactant phospholipids. SM phospholipids were also combined and studied biophysically with another purified surfactant-associated protein, SAP-35. The biophysical activity of synthetic phospholipid-apoprotein combinants was assessed by measurements of adsorption facility and dynamic surface tension lowering ability at 37 degrees C. The SM-SAP-6 combinants had adsorption facility equivalent to natural lung surfactant, and to the surfactant extract preparations CLSE and surfactant-TA used in exogenous surfactant replacement therapy for the neonatal Respiratory Distress Syndrome (RDS). The synthetic phospholipid-SAP-6 combinants also lowered surface tension to less than 1 dyne/cm under dynamic compression in an oscillating bubble apparatus at concentrations as low as 0.5 mg phospholipid/ml. A striking finding was that this excellent dynamic surface activity was preserved as SAP-6 composition was reduced to values as low as 5 micrograms/5 mg SM phospholipid (0.1% SAP-6 protein), an order of magnitude less than the 1% protein content of CLSE and surfactant-TA. Mixtures of SM phospholipids plus SAP-35, the major surfactant glycoprotein, had significantly lower biophysical activity, which did not approach that of a functional lung surfactant. These results suggest that synthetic exogenous surfactants of potential utility for replacement therapy in RDS can be formulated by combining synthetic phospholipids in vitro with specifically purified, hydrophobic surfactant-associated protein, SAP-6.

Animals↗
PubMed1986

Fetal assessment by biophysical profile scoring: 1985 update.

In extrauterine medicine, physicians have come to rely upon sampling of multiple biophysical variables as a means of differentiating states of well-being and compromise. This basic tenet of medicine is expressed by obtaining an Apgar score or some variant in the newborn and as a measure of vital signs in later life. Few, if any, decisions regarding well-being are ever based on a single-variable assessment and, conversely, definition of compromise is rarely based upon a single variable. Through the use of dynamic ultrasound imaging it now becomes possible to visualize the fetus and its biophysical responses in health and disease. Through such visualization it becomes possible to bring to bear some of the basic principles that sustain extrauterine medicine on the intrauterine patient, the fetus. Fetal biophysical profile scoring describes a method that encompasses this concept. The results obtained by application of this method are promising. We would argue that consideration of multiple fetal biophysical variables will, in most instances, yield superior results to single-variable monitoring alone. Hence we have abandoned antepartum fetal heart rate testing as the sole method of fetal risk assessment and used the tool only in conjunction with others of the many variables that may be monitored by dynamic ultrasound methods. This concept of multiple-variable analysis as the superior method for fetal assessment seems clear and well-justified. It is our opinion, however, that the concept of fetal bioprofile scoring may be more important than the method itself in its original description.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniotic Fluid↗
PubMed2005

Principles of bone formation driven by biophysical forces in craniofacial surgery.

Biophysical forces, particularly mechanical loading and electromagnetic signals, are important regulators of bone formation. Indeed, the regenerative capacity of bony tissue is largely the result of the bone's capacity to recognise the functional environment required for the emergence and maintenance of a structurally intact bone. Biophysical methods of stimulation have therefore been introduced and have proved successful in clinical practice with craniofacial bones. Distraction osteogenesis, application of ultrasound, calculated transfer of stresses, and exposure to an electromagnetic field are some examples of biophysically driven approaches to influencing bone formation. The purpose of this review is to provide an insight into cellular and tissue models that are used to study the effects of biophysical stimuli on bone.

Bone Remodeling↗
PubMed2006

Vibroacoustic stimulation in abnormal biophysical profile: verification of facilitation of fetal well-being.

OBJECTIVES: To verify the effect of vibroacoustic stimulation on biophysical profile score, with a prospective randomised study. STUDY DESIGN: All women with singleton pregnancy, gestational age >or=30 weeks, intact membranes and biophysical profile score <or=8/10 entered the study, after giving written consent, and were randomised to two groups. In group A, a 3-s stimulus with an artificial larynx was applied; if biophysical profile remained abnormal for 30 min, a second stimulus was applied and it was assessed again. In group B, the observation time was extended for 60 min to match the time periods of group A. Pregnancies were managed by final test score and patients delivering more than 24 h apart from last examination were disregarded from the study. Outcome criteria were intrauterine deaths, caesarean sections for fetal distress, Apgar score <7 at 5 min postpartum, meconium-stained amniotic fluid and neonatal intensive care unit admissions. Our null hypothesis was that application of vibroacoustic stimulation does not alter test's statistical parameters. RESULTS: 1349 patients were randomised in group A and 1484 in group B (2833 in total). When comparing group A to B, application of vibroacoustic stimulation significantly decreased the number of positive tests (4.74% vs. 6.67%, p<0.05) and increased the prevalence of outcome criteria in this subgroup (positive likelihood ratio: 24.1 95% CI: 11.12-52.46 vs. 7.52 95% CI: 4.93-11.46), without altering perinatal outcome. Furthermore, specificity, positive predictive value and test accuracy were significantly improved, as well as negative predictive value for intrauterine death. CONCLUSION: Vibroacoustic stimulation improves the efficiency of biophysical profile score by decreasing false positive tests and improving test accuracy and should be considered as a means of a more thorough fetal evaluation when fetal compromise is suspected.

Acoustic Stimulation↗
PubMed1994

Fetal biophysical activities in third-trimester pregnancies complicated by diabetes mellitus.

OBJECTIVE: Our purpose was to compare third-trimester fetal biophysical activities in normal and well-controlled insulin-dependent diabetic pregnancies. STUDY DESIGN: We performed serial bimonthly fetal biophysical studies from 30 to 38 weeks in 18 normal and 18 well-controlled insulin-dependent diabetic pregnancies (White classes B through D). Each study contained 60 minutes of simultaneous ultrasonographic recordings of fetal breathing movements and rates, baseline heart rate, and body movements. Mean daily blood glucose levels of diabetic patients were determined from home monitors; HbA1c was determined every 6 weeks and ultrasonographic fetal growth rates every 3 weeks. Data were compared with t tests, analysis of variance with repeated measures, and chi 2 tests. RESULTS: Women in the diabetic group maintained good glycemic control and were delivered of normal infants of weights similar to those of nondiabetic gravidas. Their fetuses had higher mean incidences of fetal breathing movement, fetal heart rates, and fetal breathing rates but lower fetal movements and fetal heart rate acceleration counts than did controls throughout the study. Neither short- nor long-term maternal glycemic levels correlated well with fetal biophysical performance. CONCLUSIONS: In spite of good maternal glycemic control fetuses of diabetic women behaved differently from those of nondiabetic women. Modulation of their biophysical activities may be affected by maternal glycemic status before the last trimester. Different standards might need to be applied to interpret their tests.

Adult↗
PubMed2003

The effect of maternal fasting on the fetal biophysical profile.

OBJECTIVES: To determine fetal biophysical profile changes in women observing Ramadan with uncomplicated singleton pregnancy. METHODS: In this cross-sectional observational study healthy women who were observing Ramadan at 30 weeks or more of gestation were recruited as well as a non-fasting control group matched for age, parity, and gestational age. Ultrasound examination included assessment of amniotic fluid volume, fetal bladder volume, fetal biophysical profile, and umbilical artery Doppler flow. RESULTS: A total of 162 pregnant women were observed. Mean umbilical artery pulsatility index, vertical amniotic pool depth, and fetal bladder volume were similar in the study and control groups. However, there was a significant difference in biophysical scores between the two groups. In the fasting group, 30 of 81 fetuses (37%) had a score of 6/8 compared with 11 of 81 fetuses (13.6%) in the control group (P=0.001). All fetuses in both groups with a biophysical score of 6/8 showed no breathing movements. CONCLUSIONS: Fetal breathing movements are reduced during maternal fasting.

Adult↗
PubMed1997

Transient alteration in fetal biophysical profile immediately following fetomaternal hemorrhage sustained during motor vehicle accident.

Transient altered fetal behavior manifested by decreased fetal biophysical score at 37 weeks' gestation following maternal injuries sustained in a motor vehicle accident, represented an immediate fetal response to fetomaternal hemorrhage occurring during the accident. Although cesarean delivery had initially been considered due to fetal distress (fetal biophysical score of 4 of 10), the fetal biophysical score improved within 2 hr, permitting spontaneous vaginal delivery of a nonasphyxiated fetus, 24 hr after the traumatic event. To our knowledge this is the first report of a transient abnormal fetal biophysical profile in association with a large fetomaternal hemorrhage.

Accidents, Traffic↗
PubMed1995

Evaluation of the nonreactive positive contraction stress test prior to 32 weeks: the role of the biophysical profile.

A nonreactive positive contraction stress test in a pregnancy near term is an indication for delivery. Such nonreassuring antepartum testing combined with severe prematurity presents a management dilemma. Ideally, prolongation of selected pregnancies would allow time for corticosteroid therapy and fetal maturation. Prior to 32 weeks' gestation, we utilized the biophysical profile to select patients for continued intrauterine management as an alternative to immediate delivery. Continued surveillance was undertaken if the fetus had a reassuring biophysical profile score; immediate delivery by cesarean section was undertaken if the biophysical profile score was nonreassuring. This approach allowed a mean gain of 13 days in utero for the continued surveillance group. There was no evidence of further fetal compromise in this group based on umbilical cord pH or 5-minute Apgar scores. These data suggest that the biophysical profile can be safely used to prolong selected preterm pregnancies with nonreactive positive contraction stress tests without adversely affecting the initial neonatal metabolic status.

Adult↗
PubMed1996

An electrical network model of intracranial arteriovenous malformations: analysis of variations in hemodynamic and biophysical parameters.

The propensity of intracranial arteriovenous malformations (AVMs) to hemorrhage is correlated significantly with their hemodynamic features. Biomathematical models offer a theoretical approach to analyse complex AVM hemodynamics, which otherwise are difficult to quantify, particularly within or in close proximity to the nidus. Our purpose was to investigate a newly developed biomathematical AVM model based on electrical network analysis in which morphological, biophysical, and hemodynamic characteristics of intracranial AVMs were replicated accurately. Several factors implemented into the model were altered systematically to study the effects of a possible wide range of normal variations in AVM hemodynamic and biophysical parameters on the behavior of this model and its fidelity to physiological reality. The model represented a complex, noncompartmentalized AVM with four arterial feeders, two draining veins, and a nidus consisting of 28 interconnected plexiform and fistulous components. Various clinically-determined experimentally-observed, or hypothetically-assumed values for the nidus vessel radii (plexiform: 0.01 cm-0.1 cm; fistulous: 0.1 cm-0.2 cm), mean systemic arterial pressure (71 mm Hg-125 mm Hg), mean arterial feeder pressures (21 mm Hg-80 mm Hg), mean draining vein pressures (5 mm Hg-23 mm Hg), wall thickness of nidus vessels (20 microns-70 microns), and elastic modulus of nidus vessels (1 x 10(4) dyn/cm2 to 1 x 10(5) dyn/cm2) were used as normal or realistic ranges of parameters implemented in the model. Using an electrical analogy of Ohm's law, flow was determined based on Poiseuille's law given the aforementioned pressures and resistance of each nidus vessel. Circuit analysis of the AVM vasculature based on the conservation of flow and voltage revealed the flow rate through each vessel in the AVM network. An expression for the risk of AVM nidus rupture was derived based on the functional distribution of the critical radii of component vessels. The two characteristics which were used to judge the fidelity of the theoretical performance of the AVM model against the physiological one of human AVMs were total volumetric flow through the AVM (< or = 900 ml/min), and its risk of rupture (< 100%). Applying these criteria, a series of 216 (out of 260) AVM models using different combinations of these hemodynamic and biophysical parameters resulted in a physiologically-realistic conduct of the model (yielding a total flow through the AVM model varying from 449.9 ml/min to 888.6 ml/min, and a maximum risk of rupture varying from 26.4 to 99.9%). The described novel biomathematical model characterizes the transnidal and intranidal hemodynamics of an intracranial AVM more accurately than previously possible. A wide range of hemodynamic and biophysical parameters can be implemented in this AVM model to result in simulation of human AVMs with differing characteristics (e.g. low-flow and high-flow AVMs). This experimental model should serve as a useful research tool for further theoretical investigations of a variety of intracranial AVMs and their hemodynamic sequelae.

Analysis of Variance↗
PubMed1988

Biophysical profile scoring in the management of the diabetic pregnancy.

Biophysical profile scoring was the principal technique of antepartum fetal surveillance in 238 well-controlled diabetic pregnancies. Fifty insulin-dependent diabetics had twice-weekly testing, and 188 gestational diabetics had weekly testing. Intervention was not pursued unless there were maternal or fetal complications. There were no stillbirths and three neonatal deaths, all resulting from congenital anomalies, giving a corrected perinatal mortality rate of 0. The incidence of abnormal biophysical profile scores, eight of 238 (3.3%) overall, was low, with no significant difference between types of diabetics. In those with an abnormal score, intervention was mandated; the cesarean section rate was 50% and the rate of intensive care nursery admissions was high. Of the 230 fetuses with a normal biophysical profile score, 200 (87%) were delivered at term with minimal maternal or neonatal morbidity. Amniocentesis for phospholipid profile was performed in only 33 cases (13.9%). Hyaline membrane disease was confined to five premature neonates (incidence 2.1%). We conclude that antepartum fetal surveillance using the biophysical profile score permits safe expectant management in the diabetic pregnancy, yielding significant clinical advantages to both mother and fetus.

Amniotic Fluid↗
PubMed2006

Comparison of biophysical properties of skin measured by using non-invasive techniques in the KM mice following 595 nm pulsed dye, 1064 nm Q-Switched Nd:YAG and 1320 nm Nd:YAG laser non-ablative rejuvenation.

BACKGROUNDS/AIMS: The aim of the study was to compare the changes of the biophysical properties and to objectify the effects of 595 nm pulsed dye, 1064 nm Q-switched Nd:YAG and 1320 nm Nd:YAG lasers non-ablative rejuvenation by non-invasive techniques. METHODS: KM mice were used for the study. The 595 nm pulsed dye, 1064 nm Q-switched Nd:YAG and 1320 nm Nd:YAG laser treatments were evaluated with biophysical parameter measurements including skin elasticity, skin color, skin trans-epidermal water loss (TEWL) and skin hydration. RESULTS: All three lasers improved the biophysical properties in the skin of KM mice. In skin elasticity measurements, the 1064 nm laser treatment showed the lowest ratio (0.61+/-0.09) while the 1320 nm laser showed the highest one (0.76+/-0.07) on day 60. For erythema values, a significant increase was observed immediately after the 1064 nm laser treatment (196.67+/-19.17), but the lowest values occurred with the 1320 nm laser treatment (189.83+/-16.54). None of the three lasers resulted in obvious changes of skin melanin. TEWL increased immediately after laser irradiation, then began to recover and decreased 60 days after the 595 and 1064 nm laser treatments. With the 1320 nm laser treatment the TEWL began to decrease from day 7 and obtained the lowest mean values (5.23+/-1.13). The water-holding capacity increased initially for the 595 and 1320 nm laser irradiation, while decreased for the 1064 nm laser. At day 60 of the experiment, skin hydration values in all animals were superior to those of the controls. The 1320 nm laser treatment caused the highest ratio (1.29+/-0.26). Both the values of TEWL and skin hydration for the 1320 nm laser treated areas differed significantly from the other two lasers. CONCLUSIONS: Our data showed the 1064 nm Q-switched Nd:YAG laser treatment was most effective in improving the skins' mechanical properties, while the 1320 nm Nd:YAG laser can enhance greatly the skin barrier function and the water-holding capacity. Moreover, we demonstrated the biophysical properties differed considerably between different areas.

Animals↗