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At least 379 records · Page 21Linked to original sources
PubMed1998

Ocular explosion during cataract surgery: a clinical, histopathological, experimental, and biophysical study.

INTRODUCTION: An increasing number of cases are being recognized in which a peribulbar anesthetic for cataract surgery has been inadvertently injected directly into the globe under high pressure until the globe ruptures or explodes. We reviewed the records of 6 such cases (one of which was reported previously by us), and one additional case has been reported in the literature. Surprisingly, 2 of these 7 cases went unrecognized at the time, and the surgeons proceeded with the cataract operation; all of the patients ultimately developed severe visual loss and/or loss of the eye. OBJECTIVES: To reproduce this eye explosion in a live anesthetized rabbit model and to perform a clinical, histopathological, experimental, biophysical, and mathematical analysis of this injury. METHODS: Eyes of live anesthetized rabbits were ruptured by means of the injection of saline directly into the globe under high pressure. The clinical and pathological findings of the ruptured human and animal eyes were documented photographically and/or histopathologically. An experimental, biophysical, and mathematical analysis of the pressures and forces required to rupture the globe via direct injection using human cadavers, human eye-bank eyes, and classic physics and ophthalmic formulas was performed. The laws of Bernoulli, LaPlace, Friedenwald, and Pascal were applied to the theoretical and experimental models of this phenomenon. RESULTS: The clinical and pathological findings of scleral rupture, retinal detachment, vitreous hemorrhage, and lens extrusion were observed. In the exploded human and rabbit eyes, the scleral ruptures appeared at the equator, the limbal area, or the posterior pole. In 2 of the 7 human eyes, the anterior segments appeared entirely normal despite the rupture, and cataract surgery was completed; surgery was canceled in the other 4 cases. In 4 of the 5 injected and ruptured rabbit eyes, the anterior segments appeared essentially normal. The experiments with human eye-bank eyes and the theoretical analyses of this entity show that the pressure required to produce such an injury is much more easily obtained with a 3- or 5-mL syringe than with a syringe 10 mL or larger. CONCLUSIONS: Explosion of an eyeball during the injection of anesthesia for ocular surgery is a devastating injury that may go unrecognized. The probability of an ocular explosion can be minimized by careful use of a syringe 10 mL or larger with a blunt needle, by discontinuing the injection if resistance is met, and by inspecting the globe prior to ocular massage or placement of a Honan balloon. When ocular explosion occurs, immediate referral to and intervention by a vitreoretinal surgeon is optimal. Practicing ophthalmologists should be aware of this blinding but preventable complication of ocular surgery.

Aged↗
PubMed2000

[Determination of biological age--a group of biophysical tests].

BACKGROUND: Biological age is defined as real state of organism with respect to the processes of aging. From the gerontological point of view, the methodology of determination of biological age is a tool for verification of theories. The role of biological age determination in medicine is wide. It consists, among others in the assessment of the efficiency of anti-aging interventions or in detection of premature aging. Many different batteries of methods for the measurement of biological age were developed till now. The currently applied methods are not standardized and they are, as a rule, significantly time-consuming. METHODS AND RESULTS: The goal of the work was to develop a routine method for biological age determination. Simplicity and reproducibility of measurements was stressed. The result of our work is a set of 7 biophysical methods. Some of the methods are newly developed (measurement of rheological properties of the skin), others are modified classical methods (measurement of accommodation of eye, perception of high frequencies of sound, reaction times). CONCLUSIONS: The battery of biophysical test for the routine biological age assessment was developed in our laboratory. The information is processed by computer, using multiple linear regression analysis for obtaining the best assessment of personal biological age. The duration of measurement is roughly 120 min.

Accommodation, Ocular↗
PubMedDate not supplied

[Cell molecular computer. VII. Cell biophysics and realistic or information physics (1)].

Living organisms measure many parameters in order to have orientation in the outer medium. That is why biophysics cannot use the ordinary laws of physics and must take into account the influence on the phenomena to be studied not only of a measurement but also of a calculation process in the real physical and biophysical device predicting the future. Science taking into account the effects of the calculating process-realistical or informative (RI) physics-has different (laws) for different times, distances and numbers of measuring and predicting parameters. RI-physics deals with unreproducible events and considers only such time intervals and distances for which the prediction can be made on the basis of earlier measurements and calculations according to the laws with optimal difficulty. It is suggested that the living cell uses the laws which are close to these optimal (limiting) laws of RI-physics. Physics and quantum mechanics can be considered as a limiting case of RI-physics. In this case values of distances and times are large enough and the number of simultaneously measured independent parameters is such that the heat effect of the calculating device would become negligible. Molecular cell computer (MCC) [I] cannot calculate the interaction of a great quantity of different molecules, using the equations of quantum mechanics because the expense of the (price of action) would be very large and both MCC and the surrounding world could change.

Cell Physiological Phenomena↗
PubMed2001

[A simulating study of biophysical features along meridians on a gel model].

A physical model was used to study the mechanism of specific biophysical features along the classic acupuncture meridian lines. A sol channel within a gel bed was made by a resistance string heating during electrification. A saline channel was produced by withdrawing some fibers in the gel bed and injecting saline into the gaps. A hydraulic resistance instrument composed by two pressure transducers was used to measure the hydraulic resistance across the two kinds of channels. The impedance on both channels was measured by a four-electrode impedance instrument with 5 KHz constant current. A vibration generator was put on one set of the channel to produce about 50 Hz sound waves. The signal was detected by a crystal pickup on the other set of the channel to examine the transmission of the wave along the two kinds of channels. The results showed that the low hydraulic resistance appeared on saline channel while no such feature on sol channel. Both channels showed low impedance while saline channel had more marked low impedance than control area. There was a better transmission of sound wave along saline channel while a bad transmission along the sol channel. The results suggest that the specific biophysical feature along meridians may be caused by a continuous rich distribution of interstitial fluid which mainly contains salt, water and protein.

Electric Impedance↗
PubMedDate not supplied

[Usefulness and limits of a fetal biophysical profile in the management of pregnancy at risk].

Usefulness and limits of fetal biophysical profile (BPP) were determined in 132 high-risk pregnancies, evaluating the relationship between the last biophysical profile result and perinatal outcome. The presence of a low incidence of perinatal complications when BPP is normal permits the conservative management of these pregnancies. When the score is abnormal instead, there is also high false positive rate that may determine an unnecessary intervention with associated perinatal morbidity. On the other hand, BPP seems to become abnormal relatively late in the chronic asphyxial process, when it may be impossible to prevent mortality or a serious perinatal morbidity: its association with other tests is therefore necessary for a better evaluation of fetal risk.

Female↗
PubMed2004

Selecting an external light source for fetal biophysical testing.

OBJECTIVE: To select the most intense light source that penetrates tissues and is safe for fetal biophysical testing STUDY DESIGN: A 3-step series of experiments was undertaken using a digital light meter (Extech Light Probe Meter, Extech Instruments, Waltham, Massachusetts). First, the density of light through a light filter was compared between the sun and 4 commercially available light sources. Second, penetration of light through the abdominal subcutaneous tissue (3-4 cm thick) of 6 pigs was compared between these light sources. Last, the skin reaction to the preferred light source and the distance in penetrating the uterine cavity were assessed in 50 pregnant women. RESULTS: Light emitted from a halogen bulb was significantly more intense than from a photographic flash, krypton bulb or penlight. Maximal intensity was gained with the light source placed against the skin. The halogen bulb penetrated a pig's abdominal wall more than the photographic flash or krypton bulb. The thickness of a pig's abdominal wall is similar to the distance in pregnant humans near term from the skin to the uterine cavity. No thermal injury or discomfort to the skin was observed for exposures <10 seconds. CONCLUSION: The halogen bulb was safe, penetrated tissues most effectively and was the best light source for fetal biophysical testing.

Abdomen↗
PubMedDate not supplied

Fetal biophysical profile scoring.

Assessment of real-time ultrasound fetal biophysical variables has a limited role in the management of selected high-risk pregnancies. Composite biophysical scores remain inadequately studied and are of unproven value as a first-line test.

Female↗
PubMed2004

Market research on garment-based "wearables" and biophysical monitoring and a new monitoring method.

Technology advancements are foremost on the minds of scientists and developers who are working to overcome the many hurdles associated with bringing consumers the enhanced benefits associated with next generation wearable health systems. Often the technology work takes a front seat to the basic requirements of traditional consumer apparel. The choices of what consumers elect to place and carry on their body can be practical, logical, emotional and sometimes seemingly random. By providing insights and data to support the claims, developers of wearable health systems of the future will be able improve their chance of consumer adoption and continued use by gaining a clearer picture of the people that will be wearing the systems. Results from 5 different consumer research studies are presented, examining consumer buying patterns, gender differences, regional differences, their receptivity to health benefits delivered via clothing and what they want from technology enhanced clothing. Market research related to biophysical monitoring utilizing smart fabrics or interactive textiles show a critical level of commercial activity. Medical applications focused on the aged, infant and critical patient care are taking the lead. This paper presents a look at the biophysical monitoring market and discusses new materials useful in garment systems and the challenges remaining for their development and integration with textiles. A new method of non-invasive monitoring of periodic activity is discussed.

Biosensing Techniques↗
PubMed2004

An introduction to the biophysics of the electrically evoked compound action potential.

A computational model of the electrically evoked compound action potential (ECAP) has been developed. In addition to being a useful research tool, it serves as an excellent introduction to the basic biophysics of ECAP recording techniques. ECAPs are modeled as a sum of single-fiber action potentials (SFAPs) in response to an electrical stimulus. Each SFAP is calculated from the potential induced at the recording site by the membrane currents arising on an axon as a spike propagates along it. The factors that alter SFAP and ECAP morphology and latency are discussed, as are the mechanisms of stimulus artefact and the advantages and limitations of different artefact-suppression techniques. The assumptions of the model are presented, as are potential ways of improving the physiologic data available from clinical recordings. Potential applications of this technology in the investigation of the biophysical mechanisms of the implanted cochlea are suggested.

Action Potentials↗
PubMed2004

[Value of selected biophysical surveillance methods in prediction and prophylaxis of complications associated with adverse pregnancy outcome in intrauterine growth restriction].

Intrauterine growth restriction is associated with higher rate of complications occurring during pregnancy and in labour, increased morbidity and mortality rate in neonatal period, impaired psychosomatic development in childhood and increased susceptibility for particular diseases in adulthood. For improvement of perinatal outcome it is essential to establish objective criteria based on biophysical surveillance methods for prediction and prophylaxis of adverse outcome in IUGR pregnancies. The aim of the study was to compare selected biophysical surveillance methods in prediction and prophylaxis of complications associated with adverse pregnancy outcome in intrauterine growth restriction. There were statistically significant differences in CTG, BPS, AFI, and pulsatile index values in umbilical artery and MCA between IUGR and normal fetuses. The best predictor of adverse pregnancy outcome in IUGR fetuses was PI value in umbilical artery.

Adolescent↗
PubMed2005

Interaction and biophysical properties of human lens Q155* betaB2-crystallin mutant.

PURPOSE: Missense mutations in crystallin genes have been identified in autosomal dominant congenital cataracts. A truncation in the CRYBB2 gene (Q155*) has been associated with cerulean cataract, however its effects on biophysical properties have not been reported. We sought to determine the changes in conformation and protein-protein interactions brought about by this mutation. METHODS: Site specific mutations were performed to obtain the Q155* betaB2-crystallin mutant. Protein-protein interactions were screened by a mammalian two-hybrid system assay. Conformational changes were studied with spectroscopy (circular dichroism and fluorescence) and FPLC chromatography. RESULTS: We detected a decrease in protein-protein interactions for the Q155* betaB2-crystallin mutant. The Q155* mutant shows decreased ordered structure and stability but the partially unfolded protein retains some dimer structure. CONCLUSIONS: The Q155* mutation in betaB2-crystallin causes changes in biophysical properties that might contribute to cataract formation.

Amino Acid Sequence↗
PubMed1992

[Biophysical activity of the fetus during labor in EPH-gestosis].

Fetal respiratory and motor activities were studied in 105 parturients with EPH gestosis of varying severity and in 25 reference ones. The results evidence that, in contrast to the antenatal period, normal fetal condition in labor is associated with biophysical inertness, this fact confirming the known viewpoint on the intranatal fetal hibernation. Active management of labor in parturients with doubtful and abnormal biophysical parameters on the eve of delivery impairs the natural mechanisms of fetal defense in labor. Respiratory or motor activity of the fetus should be regarded as a prognostically unfavorable sign in respect of hypoxic involvement of the CNS and the newborn aspiration syndrome.

Delivery, Obstetric↗
PubMed2006

[Biophysical mechanisms of electromagnetic fields interaction and health effects].

The issue of the biological effect of electromagnetic fields (EMF) has been the subject of interest over one hundred years. Experts in this field agree that exposure to EMF at high levels induce adverse health effects, but their opinions vary on the point whether EMF at levels usually present in the municipal environment and at workposts are also harmful. The expressed doubts apply not only to possible health effects, but also to biophysical mechanisms by which those effects occur. The paper presents these controversies. In general opinion there is as yet no conclusive evidence to consider EMF as a factor harmful to health (may be except the relationship between power frequence magnetic field and some neoplastic diseases, especially leukemia in children). It is also unknown which of biophysical mechanisms may be the underlying reason for possible health effects. All these mean that studies in this area should be continued. A large number of single observations sometimes encourage researchers to intensify their investigations.

Adult↗
PubMed1991

[Alteration of erythrocyte biophysical properties in patients with ischemic cerebrovascular disorders].

Several erythrocyte biophysical properties (erythrocyte deformability, erythrocyte aggregation and erythrocyte electrophoretic mobility) were investigated in patients with cerebral infarction and in individuals with risk factors of stroke (RFS population; RFSP). Blood viscosity, plasma viscosity, hematocrit, plasma fibrinogen level and yield shear stress (YSS) were also tested. In comparison with the results in a control group, erythrocyte deformability (erythrocyte length under a certain constant shear stress and erythrocyte filterability) was less in both the patient group and the group of RFSP and there is an accompanying increase of erythrocyte aggregation. Blood viscosity and fibrinogen level were higher in the patient groups. There was no correlation between erythrocyte deformability and other hemorheological parameters. Our results suggest that significant alteration of erythrocyte biophysical properties may be implicated in the pathogenesis of ischemic stroke. These abnormalities are associated with some of the risk factors of stroke such as hypertension, atherosclerosis and cardiovascular disorders.

Aged↗
PubMed1991

Biophysical profile and its relation to fetal blood gas level obtained by cordocentesis.

Biophysical profile (BPP) score was assessed immediately before fetal blood sampling by cordocentesis in 150 fetuses referred to our hospital, 95 after and 55 before 30 weeks of gestation. In 95 fetuses after 30 weeks of gestation, 39 fetuses were evaluated with BPP scores of 12, 35 were from 8 to 11 and 21 were less than 7. In 55 fetuses before 30 weeks of gestation, 8 fetuses were evaluated with BPP scores of 12, 27 were from 8 to 11 and 20 were less than 7. pO2, pH and pCO2 in fetuses with a score less than 7, either before or after 30 weeks of gestation, (with a score less than 7) did not significantly differ, in comparison to the other two groups. No variables in the biophysical profile precisely reflect fetal hypoxemia, acidemia or hypercarbia. Since even the fetus with a BPP score of greater than 8 may not always be assured of well-being and not all fetuses with a score of less than 7 are necessarily in a deteriorated condition, it is necessary to evaluate fetal condition on the basis of fetal blood gas data obtained by cordocentesis, especially when the fetus is additionally handicapped by prematurity or morbidities such as growth-retardation.

Blood Specimen Collection↗
PubMed1991

Hepatocellular phenotype in vitro is influenced by biophysical features of the collagenous substratum.

Hepatocytes maintained on different substrata in vitro possess strikingly different morphological and biochemical features. Rounded, multicellular aggregates of hepatocytes are seen if the cells are plated onto Matrigel, a reconstituted basement membrane, whereas a flattened, monolayer of hepatocytes is observed with Vitrogen. Hepatocellular protein synthesis is much greater on the Matrigel, although collagen biosynthesis appears selectively enhanced on Vitrogen-grown hepatocytes. We determined that denatured type I collagen could be substituted for Matrigel as the substratum, with the hepatocytes remaining the same both morphologically and biochemically. This suggested that the cells respond to the biophysical state of the extracellular matrix not only to protein sequences that determine a binding site. Measurement of steady-state messenger RNA levels within cells cultured onto different matrices indicated that the fluid substrate of either Matrigel or denatured type I collagen were facilitative for induction of cytochrome P-450b/e, which was not seen with the rigid type I collagen substrata. In contrast the messenger RNA level for the cytoskeletal protein actin was decreased on the fluid matrices, suggesting that the rounded cells had a lower requirement for this protein. These findings indicate that hepatocytes are responsive to the biophysical state of the extracellular matrix, which can lead to significant changes in gene expression by the cells.

Actins↗
PubMed1990

Biochemical and biophysical indices of follicular development in spontaneous and stimulated ovulatory cycles.

This study was designed to evaluate the correlation between the follicular biophysical and biochemical indicators in spontaneous (N = 11) and stimulated (N = 110) ovulatory cycles. Ovulation was induced with clomiphene citrate in 14 cycles, gonadotropin-releasing hormone (GnRH) in 12 cycles, and human menopausal gonadotropins in 84 cycles. Patients were studied daily, starting on day 10, until sonographic verification of ovulation. Each woman had serum estradiol (E2) and LH measured daily and progesterone measured only 7 days after ovulation. In addition, the ovaries were imaged transvaginally daily and the two largest follicular diameters, volumes, cross-sectional areas, and circumferences were measured in all follicles 10 mm or larger in diameter. Ultrasonographic measurements of follicles from clomiphene-stimulated cycles were significantly larger than those from spontaneous, GnRH-, and human menopausal gonadotropins-stimulated cycles (P less than .05). Serum E2 and progesterone secretion in human menopausal gonadotropins- and clomiphene-stimulated cycles were significantly higher than in spontaneous and GnRH-stimulated cycles (P less than .01). Women treated with human menopausal gonadotropins developed significantly more follicles than with any other treatment (P less than .05). Correlation analysis indicated that biophysical variables alone (follicular diameter, volume, cross-sectional area, or circumference) were good indicators of normal follicular development and predicted the mid-cycle LH surge in spontaneous (r = 0.81, P less than .001), GnRH- (r = 0.78, P less than .001), and clomiphene citrate-stimulated cycles (r = 0.83, P less than .001). However, in human menopausal gonadotropins-stimulated cycles, both serum E2 levels and ultrasonographic evaluation were necessary to decide the best time for hCG administration (r = 0.55, P less than .001).

Clomiphene↗
PubMed1990

[Fetal biophysical profile in EPH gestosis].

Fetal biophysical profiles (FBP) have been obtained in 111 women with toxemia of pregnancy at 34-42 weeks. Six biophysical parameters were tested: nonstress test, fetal respirations, motility and tone, amniotic fluid volume and placental maturity. The test findings were compared with pregnancy outcomes, controlling for intrapartum fetal distress. Apgar scores, intrauterine growth retardation, postdate gestation and symptoms of early neonatal adaptation, fetal or neonatal death. The values of FBP were lower with higher severity of gestational toxemia, with the greatest incidence of poor perinatal outcomes in the presence of complicated delivery.

Adult↗