Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Biophysics”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed1989

Sinusoidal heart rate pattern and an normal biophysical profile in a severely compromised fetus.

A case is described in which a woman complained of weakened fetal movements, and a persistent sinusoidal heart rate pattern was demonstrated in the presence of normal fetal breathing movements, normal fetal tone, and normal amount of amniotic fluid. In view of the subjective complaints and disregarding the normal biophysical profile, termination of pregnancy was performed. A compromised, severely anemic fetus was delivered by cesarean section. The role of sinusoidal heart rate pattern and the limitations of biophysical scores as a single determinant of fetal well being are discussed.

Adult↗
PubMed1989

Observations of biophysical activities in the normal fetus.

Biophysical activities such as FBM, GBM, and accelerations in the healthy human fetus near term occur episodically in keeping with the development of behavioral states in utero. It is therefore important to allow for the normal rest-activity cycles of healthy fetuses when designing clinical strategies for the surveillance of fetal health during the antepartum period. Diurnal rhythms are present in the incidence of FBM and GBM, as well as in mean FHR. These appear to be related to intact maternal or fetal adrenal gland function. The incidence and amplitude of FBM are strongly influenced by maternal meals, and therefore by plasma glucose concentrations, whereas maternal meals have no effect on GBM or FHR accelerations. The association of FHR accelerations with GBM becomes stronger with advancing gestational age such that near term close to 90 per cent of accelerations occur with movement. Younger fetuses move overall approximately the same amount of time as term fetuses, although the movements are more frequent and of a shorter duration. Maternal smoking, and alcohol and drug ingestion all affect FBM, GBM, and FHR to various extents, underlining the importance of documenting the prior maternal use of these substances when using biophysical activities to assess fetal health in the antepartum period.

Female↗
PubMed1989

[Stability and flexibility of the lipid layer of the tear film and their pathologic changes in a biophysical experiment].

In vitro experiments with meibomian gland secretion from healthy subjects, patients with keratoconjunctivitis sicca and meibomianitis were performed. In addition, patients of different age groups of both sexes were also tested. The biophysical experiments included continuous measurement of surface pressure and surface potential under compression and decompression conditions. Surface pressure was determined by a Wilhelmy type film balance; surface potential was determined using the vibrating plate method. In the age group up to 60 years, the surface potential of females, males and patients with keratoconjunctivitis sicca showed a characteristic peak of 200 mV under compression, which was fully reversible under decompression. Females, males and patients with keratoconjunctivitis sicca over 60 years of age showed changes in the surface potential under decompression which indicated that the secretion was unstable and inhomogeneons. Patients with meibomianitis presented characteristic changes of surface potential. Qualitative alteration of the secretion may be the corresponding interpretation. The above biophysical methods have been used for the first time under clinical aspects.

Eyelids↗
PubMed1989

[Evaluation of fetal status in risk pregnancy using the biophysical profile].

Experiences with using the biophysical profile according to Manning et al. in diagnosing the danger to the fetus in at risk pregnancy are presented. Examinations were carried out in 143 pregnant women. In 33 of them the following parameters were evaluated with respect to the values of the biophysical profile: placental maturity, urinary estriol, term and mode of termination of pregnancy, body weight, body length, and Apgar score of newborns. The authors recommend to extend this diagnostic method so that in interpreting the results it yields not only the overall clinical state of the pregnant woman should be considered but also biological rhythms of physiologic functions of the fetus as well the administration of drugs to the woman in pregnancy.

Female↗
PubMed1989

Biophysical profile in fetal triploidy. A case report.

A 31-week fetus died 24 hours after a reassuring biophysical profile assessment was obtained. Fetal growth retardation had been evident since early gestation, but genetic amniocentesis was not done until one week prior to death. There were no acute events (abruptio placentae, labor or a change in the maternal condition) believed responsible for the death one day after testing. After delivery by induction, the fetus was found to have features compatible with triploidy. The amniotic fluid obtained earlier ultimately yielded no cell growth, but triploidy was later confirmed by direct fetal tissue analysis. Sudden events, which cannot be predicted by any testing modality, are not the only causes of fetal death after a reassuring test. Chromosome analysis should be sought aggressively, particularly if the first attempt, as in this case, is unsuccessful. This is the first reported case of normal biophysical testing preceding the sudden death of a triploid fetus.

Adult↗
PubMed1984

[Validity of a biophysical model for predicting heart rate values during activities operating under a risk of thermal stress].

After measuring the heart rate values of workers unfolding a standardized job made under unfavourable microclimatic conditions, the Authors calculate them by application of a proposed biophysical model starting from ambient climatic conditions, energetic expenditure and thermal resistance of the clothing. The results, compared by means of statistical methods, do not show any significant difference between the two methods. Therefore is also possible the proposal of the use of the biophysical model for the prevision of heart rate under standardized working conditions.

Heart Rate↗
PubMed1980

Characterizing blood cells by biophysical measurements in flow.

One effect of automation in the hematology laboratory has been to introduce new characterizations of blood cells. Resistive pulse sensing (Coulter) and light scatter measurements in flow provide rapid and reproducible cell counts. They also provide information about red cell size, shape, and deformability. Thus, they have provided new characterization of these cells in terms of their biophysical properties. Leukocytes have been classified by optical scatter and absorption measurements in flow after being stained cytochemically. This provides rapid and precise WBC differential counts. However, here again, additional information about relative cell-enzyme content or activity is also accessible to provide a new characterization of the leukocytes. The ultimate range of utility of this expanding technology in the automated hematology laboratory of the future will, of course, depend upon establishing relations between the biophysical parameters and the functions of the cells. This, in turn, must depend upon the use of the technology by researchers and clinicians in studying cell function and the aberrations of these functions which define disease.

Autoanalysis↗
PubMed1982

Cellular and biophysical mechanisms contributing to regulation of reflex excitability of inking behavior in Aplysia.

Inking behavior in Aplysia offers a simple test system whereby it is possible to examine the cellular and biophysical determinants of a simple behavior and its ability to undergo a short-term behavioral modification. The features of the behavior and its underlying neural circuit, as well as the intrinsic biophysical properties of the effector motor neurons, have been analyzed. Inking behavior shows a selective sensitivity to long-duration stimuli, which appears due to presence of a voltage-dependent fast K+ current and a slow buildup of synaptic input in the ink gland motor neurons. The ability of the behavior to undergo a short-term modification of reflex-excitability appears due to the activation of a prolonged synaptic current in the ink motor neurons.

Animals↗
PubMed1982

Antepartum determination of fetal health: composite biophysical profile scoring.

Antepartum detection, classification, determination of severity, and ultimately treatment of the fetus at risk for death and damage in utero form the very basis of modern perinatal medicine. The availability of accurate methods for assessing the fetus in utero are now becoming available. In extrauterine medicine, assessment of risk is based in part on the patient's activities and response to intrinsic and extrinsic stimuli. In extrauterine medicine, differentiation of normal sleep from coma is made by assessment of multiple biophysical variables and responses. It is most likely that the same principles hold true for differentiating the normal sleeping fetus from the asphyxiated fetus. Biophysical profile scoring offers one method for differentiation. It is likely that incorporation of this principle will improve the quality of perinatal care.

False Negative Reactions↗
PubMed1994

Biophysical and enzymatic properties of the catalytic domain of HIV-1 integrase.

A deletion derivative of the integrase protein from human immunodeficiency virus type-1 (HIV-1) consisting of the central core domain (amino acids 50-212) has been characterized biophysically and biochemically. This deletion mutant is of particular interest for structural studies as it can carry out the disintegration reaction suggesting the presence of an active site and, under certain conditions, is more soluble than full-length integrase. The circular dichroism and fluorescence of the deletion mutant and the 288-residue full-length integrase were similar, indicating that the core residues maintain similar overall conformations in both proteins. The deletion mutant is approximately 10% more alpha-helical than the full-length protein. Analytical centrifugation demonstrated that both proteins undergo monomer-dimer association although the truncated protein showed slightly less tendency to dimerize; the dissociation constants were 2.5 x 10(-5) M for the full-length protein and 8.0 x 10(-5) M for the truncated protein. The disintegration activity of both proteins was also compared. Although a higher concentration of the truncation mutant was required for optimal activity, the mutant did not have altered pH or Mn2+ requirements relative to the full-length protein. The combined biophysical and enzymatic studies suggest that this truncated form of HIV-1 integrase is likely to be useful for structural studies.

Amino Acid Sequence↗
PubMed1995

Prognostic value of biophysical profile score in post-date pregnancy.

OBJECTIVES: This study was undertaken to assess the ability of each individual biophysical profile score variable and combination of variables, to predict fetal distress or imminent labor in the post data pregnancy. MATERIALS AND METHODS: From June 1992 to August 1993, Biophysical Profile Scoring (BPS) was performed on 182 pregnant women. Thirty one patients delivered between 42 and 43 weeks of gestation, while the other 151 pregnant women delivered between 38 and 41+6 days. Monitoring procedures were based on the evaluation of fetal heart rates by Non Stress Test and four ultrasound parameters: Fetal Tone; Gross Body Movements; Fetal breathing movements; Evaluation of amniotic fluid volume. RESULTS: In this analysis the BPS showed a high specificity (82.7%) with a negative predictive value of 100%. The mean value of the last BPS among the 151 term patients was significantly higher if compared with the 31 post term pregnant women (6.73 and 6.12 respectively with p < 0.05). The predictive value of Fetal Breathing Movements (FBM) for the onset of imminent labor was confirmed. CONCLUSION: BPS, as measured in this study, has proved to be a very accurate method of determination of fetal well-being. Although these results will be further verified by other studies, BPS should come into general use to help reach the correct diagnosis and treatment of post date pregnancy.

Amniotic Fluid↗
PubMed1996

Chiropractic biophysics technique: a linear algebra approach to posture in chiropractic.

OBJECTIVE: This paper discusses linear algebra as applied to human posture in chiropractic, specifically chiropractic biophysics technique (CBP). MATHEMATICAL ANALYSIS: Rotations, reflections and translations are geometric functions studied in vector spaces in linear algebra. These mathematical functions are termed rigid body transformations and are applied to segmental spinal movement in the literature. Review of the literature indicates that these linear algebra concepts have been used to describe vertebral motion. However, these rigid body movers are presented here as applying to the global postural movements of the head, thoracic cage and pelvis. CONCLUSION: The unique inverse functions of rotations, reflections and translations provide a theoretical basis for making postural corrections in neutral static resting posture. Chiropractic biophysics technique (CBP) uses these concepts in examination procedures, manual spinal manipulation, instrument assisted spinal manipulation, postural exercises, extension traction and clinical outcome measures.

Biomechanical Phenomena↗
PubMed1996

Biophysical aspects of blood flow in the microvasculature.

The main function of the microvasculature is transport of materials. Water and solutes are carried by blood through the microvessels and exchanged, through vessel walls, with the surrounding tissues. This transport function is highly dependent on the architecture of the microvasculature and on the biophysical behavior of blood flowing through it. For example, the hydrodynamic resistance of a microvascular network, which determines the overall blood flow for a given perfusion pressure, depends on the number, size and arrangement of microvessels, the passive and active mechanisms governing their diameters, and on the apparent viscosity of blood flowing in them. Suspended elements in blood, especially red blood cells, strongly influence the apparent viscosity, which varies with several factors, including vessel diameter, hematocrit and blood flow velocity. The distribution of blood flows and red cell fluxes within a network, which influences the spatial pattern of mass transport, is determined by the mechanics of red cell motion in individual diverging bifurcations. Here, our current understanding of the biophysical processes governing blood flow in the microvasculature is reviewed, and some directions for future research are indicated.

Animals↗
PubMedDate not supplied

Characterization of the biophysical properties of human erythroblasts as a preliminary step to the isolation of fetal erythroblasts from maternal peripheral blood for non invasive prenatal genetic investigation.

BACKGROUND AND OBJECTIVE: Fetal erythroblasts in maternal circulation represent a valuable source of fetal cell material which can be obtained with non-invasive procedures that do not endanger the fetus. Physical separation techniques have been invaluable in the isolation and characterization of different cells. There are basically two principles that have been used most successfully: separation according to density and separation according to size. In order to determine whether physical separation procedures are capable of purifying human erythroblasts, the biophysical characteristics of these cells were determined. METHODS: Bone marrow particles were obtained from formal adults and peripheral blood buffy coats from blood banks. A single cell suspension was initially fractionated by buoyant density gradient centrifugation. Fractions enriched in erythroblasts were pooled and further processed by velocity sedimentation in order to take advantage of the differences in size of erythroblasts and other cells. RESULTS: Density distribution curves were drawn after density gradient centrifugation for the different cell types present in the starting cell samples. Separation of the erythroblast-enriched density fractions by velocity sedimentation was successful and a highly purified population of erythroblasts was obtained. Cell size distribution of the different cell types was determined. INTERPRETATION AND CONCLUSIONS: This initial study defines the biophysical properties (size and density) of human erythroblasts in bone marrow and peripheral blood and is a necessary preliminary step in setting up the optimal procedure for the isolation of fetal erythroblasts from maternal peripheral blood in sufficient amounts and purity for prenatal non-invasive genetic investigation.

Adult↗
PubMed2005

The uterine biophysical profile scoring validity.

OBJECTIVE: To determine the applicability of uterine biophysical profile (UBP) scoring with chances of pregnancy in a spontaneous cycle in a cohort of females with unexplained infertility. DESIGN: Observational study. PLACE AND DURATION OF STUDY: A secondary level private hospital, from June 2003 to June 2004. PATIENTS AND METHODS: The study subjects included 26 infertile females in the third decade of life primarily referred for follicle maturation monitoring by ultrasound with patent tubes and normal utero-ovarian morphology. Male factor infertility was also excluded. The UBP was determined by applying the uterine scoring system for reproduction (USSR). A score of 17 or above, out of a perfect score of 20, was hypothesized to be favorable for pregnancy. Frequency of pregnancy was correlated with the cumulative score as well as individual variable. Significance of correlation was taken at p<0.05. RESULTS: None of the patients showed a perfect score of 20. A score of 17 was noted in 06 patients out of whom 04 conceived (pregnancy rate=66.6%). A score of 15 or less was observed in 20 patients, none of whom conceived (p=0.001). No significant correlation was found with any of the individual variables including the endometrium and myometrium characteristics, as well as the uterine artery flow. Myometrium contraction was the most technically difficult parameter to be observed. CONCLUSION: In this small cohort of patients, an ultrasonographically assessed uterine score of 17 or above was significantly associated with chances of pregnancy in the similar spontaneous cycle.

Adult↗
PubMedDate not supplied

Radiofrequency cartilage reshaping: efficacy, biophysical measurements, and tissue viability.

OBJECTIVES: To assess the feasibility of reshaping cartilage using radiofrequency (RF) heating, and to examine the effects of this process on tissue biophysical properties (optical and thermal) and cellular viability. METHODS: Mechanically deformed porcine septal cartilage was reshaped using 2 RF-generating devices. We performed dynamic measurements of tissue thermal and optical properties while heating cartilage with one of these devices. Cellular viability was assessed immediately and 7 days after treatment. RESULTS: A characteristic change in the diffuse transmittance of light through the cartilage occurred during heating. Change in transmittance has been shown to accompany the onset of stress relaxation in cartilage. Peak radiometric surface temperature during heating was 88.6 degrees C. Specimens retained their user-specified curved shape for the observed period of 14 days. Chondrocyte viability in RF-heated tissue was 19% and 14% of that in untreated control specimens at days 0 and 7 after treatment, respectively. CONCLUSIONS: Radiofrequency heating has been shown to effectively reshape cartilage while maintaining cellular viability, illustrating a novel application for a widely used technology.

Animals↗
PubMed1984

Solar retinopathy. A biophysical analysis.

Funduscopic examination of two young adults complaining of blurred vision revealed small symmetrical macular lesions suggestive of solar retinopathy. Although both patients had recently looked at the sun for less than one minute, it is common to look at the sun for longer periods (ie, sunsets) without incurring visual symptoms of retinal lesions. Our biophysical analysis revealed the important parameters of solar retinopathy and the minimum exposure to the sun that would produce such lesions. Under ideal optical conditions, solar retinopathy can occur following extremely short observations of the sun.

Adult↗
PubMed1996

Collagen-based structures containing the peptoid residue N-isobutylglycine (Nleu): synthesis and biophysical studies of Gly-Pro-Nleu sequences by circular dichroism, ultraviolet absorbance, and optical rotation.

A peptoid residue N-isobutylglycine (Nleu) was introduced as a proline surrogate in collagen-like triple helical structures. A series of single chain and template-assembled collagen-based peptide-peptoid structures composed of Gly-Pro-Nleu sequences were prepared by solid-phase segment condensation methods. Both a synthetic route in solution and a solid phase method were employed to couple the KTA (cis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid, also known as the Kemp triacid) based template, KTA-(Gly-OH)3, to peptide-peptoid chains. Biophysical studies using CD, uv absorbance, and optical rotation measurements demonstrated that these compounds form triple-helical structures when the chains are longer than critical lengths. Results from melting curve measurements indicated that the Gly-Pro-Nleu sequence is comparable to the Gly-Pro-Pro sequence in stabilizing a triple-helical conformation. The KTA-based template stabilized triple-helical structures as can be seen by the increased melting temperatures as compared to equivalent single chain molecules. In addition, the template reduced the minimum chain length necessary to form a triple helix from six to only three trimer repeats.

Biophysical Phenomena↗