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Biomedical subjects

S Weiner

Publications and source records attributed to S Weiner.

At least 73 records · Page 4Linked to original sources
PubMed1997

Rotated plywood structure of primary lamellar bone in the rat: orientations of the collagen fibril arrays.

A basic structural motif of lamellar bone is the arrays of parallel collagen fibrils, with successive arrays having different orientations to form a plywood-like structure. Measurements of the angles between adjacent arrays from cryomicrotomed and vitrified thin sections of demineralized rat bone, cut approximately parallel to the lamellar boundary plane, show that most angles are around 30 degrees, although a subset are around 70 degrees. A structural model for collagen organization based on these measurements is proposed in which an individual lamellar unit (thick and thin lamellae together with transition zones) is composed of five arrays of parallel collagen fibrils, each offset by 30 degrees.

Animals↗
PubMed1997

Cervical funneling: sonographic criteria predictive of preterm delivery.

Our objective was to establish sonographic criteria that are predictive of preterm delivery in patients with internal os dilatation (funneling). The study population consisted of patients with cervical funneling identified on translabial or transvaginal ultrasound examination. Funnel length, functional length, percentage funneling and funnel width were evaluated for their predictive values for preterm delivery. In the 43 patients who met the study criteria, funneling was detected at a mean gestational age of 21.4 weeks (range 16-28). Twenty-three of 31 patients (74%), manually examined immediately following the ultrasound examination, had a closed cervix. Preterm delivery occurred in 42% of patients. Funnel length of > or = 16 mm, functional length of < or = 20 mm, funneling of > or = 40% and funnel width of > or = 14 mm correlated significantly with preterm delivery. Patients with funneling of < 25%, 25-50% and > 50% had preterm delivery rates of 17%, 29% and 79%, respectively.

Adult↗
PubMed1997

Human fetal right ventricular ejection force under abnormal loading conditions during the second half of pregnancy.

Our objective was to determine whether abnormal loading conditions can modify human fetal right ventricular ejection force during the second half of pregnancy. By Doppler echocardiography, we studied 73 normal fetuses between 19 and 41 weeks of gestation, 27 fetuses with hypoplastic left heart syndrome (chronic volume overload) between 18 and 38 weeks of gestation, 14 fetuses with mild to moderate constriction of the ductus arteriosus (pulsatility index (PI) between 1.0 and 1.9) and seven fetuses with severe constriction (PI < 1.0) or occlusion of the ductus arteriosus (relatively acute pressure overload) between 28 and 34 weeks of gestation. In the normal and ductal constriction/occlusion groups, blood velocity waveforms were recorded at the level of the aortic and pulmonary valves, and in the group with hypoplastic left heart syndrome at the level of the pulmonary valve. The ventricular ejection forces were calculated. In the normal group, right (RVEF; r = 0.91, p < 0.0001) and left (LVEF; r = 0.86, p < 0.0001) ventricular ejection forces increased and were equal during the second half of gestation. In the group with hypoplastic left heart syndrome the RVEF increased (r = 0.76, p < 0.0001) with advancing gestation. The RVEF (p < 0.0005) and its average weekly increase (p < 0.0001) were greater in the hypoplastic left heart syndrome group than in the normal group. In the group with mild to moderate ductal constriction, both ventricular ejection forces were similar to those of the normal group. The RVEF (p < 0.003) and its average weekly increase (p < 0.03) were lower in the group with severe ductal constriction or occlusion than in the normal group. The LVEF did not differ from that of the normal group We conclude that chronic volume overload increases and relatively acute pressure overload decreases human fetal RVEF. The right ventricular performance is modified by abnormal loading conditions.

Blood Flow Velocity↗
PubMed1997

The actor-director and patient-therapist relationships: a process comparison.

The relationship between the actor and director, like that between the patient and psychotherapist, relies on intense emotional involvement. Both demand sensitivity, reciprocity, and a deep understanding of human behavior. Because dramatic action is created through continuous conflict between characters, actors must explore not only their actions, but also the reactions of those with whom they are in relationship. The process of therapy is equally interdependent. Through the relationship, therapists provide a context in which their patients can work through their conflicts. As in the rehearsal process, actions are explored in a supportive environment. This paper has presented a process comparison of the actor-director and patient-therapist relationships by proposing that both are art forms that rely on the skill of a trusted facilitator. Some of the techniques explored include: empathic attunement, emotional recall, transference, overcoming performance obstacles, improvisation, risk-taking, the pleasure principle, and creating a sense of family through new object relations. Like therapists, directors never forget that their work cannot be performed alone; it depends on interaction with the most delicate of phenomena: the human soul.

Communication↗
PubMed1997

Isolation of Helicobacter pullorum from patients with enteritis.

Helicobacter pullorum, recently described as sp. nov., is commonly isolated from asymptomatic poultry. Two cases of human enteritis associated with H. pullorum, one of them in an immunocompromised patient, are reported. Problems in the correct species identification by means of phenotypic and genotypic methods are discussed and for the first time a fatty acid pattern of Helicobacter pullorum is presented.

Adult↗
PubMed1996

Role of the pulmonary circulation in the distribution of human fetal cardiac output during the second half of pregnancy.

BACKGROUND: By using Doppler echocardiography, we determined the normal distribution of human fetal combined cardiac output (CCO) from the left and right ventricles. We also established weight-indexed pulmonary and systemic vascular resistances (Rpi and Rsi, respectively) and changes during the second half of pregnancy. METHODS AND RESULTS: Blood flows at the aortic and pulmonary valve annuli (LVCO and RVCO, respectively), right and left pulmonary arteries (QP), and ductus arteriosus (QDA) were calculated in 63 normal fetuses. Foramen ovale blood flow (QFO = LVCO-QP) was estimated. From 20 to 30 weeks of gestation, the proportion of QP of the CCO increased (from 13% to 25%, P < .001), while the proportion of QFO decreased (from 34% to 18%, P < .001). After 30 weeks, the proportions of QP and QFO were unchanged. At 38 weeks, the proportion of RVCO (60%) was higher (P < .05) than that of LVCO (40%). The proportion of QDA did not change significantly. The correlation between RVCO calculated from blood flow through the pulmonary valve and from QDA and QP was good (r = .97, P < .0001). RPi (P < .001) decreased from 20 to 30 weeks of gestation. From 30 to 38 weeks, RPi increased (P < .0001). Rsi increased (P < .001) from 20 to 38 weeks. The ratio of RPi to RSi decreased (P < .01) from 20 to 30 weeks and later remained unchanged. CONCLUSIONS: The human fetal pulmonary circulation has an important role in the distribution of cardiac output.

Blood Pressure↗
PubMed1996

Transitional structures in lamellar bone.

Scanning electron micrographs of fractured surfaces of mineralized bone show a lamellar structure with alternating smooth and rough regions. These have been interpreted as corresponding to two distinct collagen fibril and mineral crystal orientations in a rotated plywood structure. However, in various bones, there are clear indications of transition zones between lamellae in which the fibrils, as well as the plate-like crystals, have intermediate orientations. Strong evidence for intermediate collagen fibril orientations comes from vitrified cryo-sections of demineralized bone. These show zones of fibril segments graded in length between more homogenous regions of fibrils roughly parallel to the specimen section. Evidence for intermediate crystal orientations comes from transmission electron micrographs and electron diffraction patterns of crushed bone fragments. A tentative scheme is presented for an interlamellar transition zone, involving rotation about the collagen fibril axis as well as tilting of this axis parallel to the plane of the interlamellar boundary. Although it may be convenient to think of the structure of lamellar bone as being composed of alternating thick and thin lamellae, it is probably more correct and biologically more relevant to consider one pair of lamellae as the product of a single depositional cycle of varyingly oriented collagen fibrils that subsequently mineralize.

Animals↗
PubMed1996

Microstructure-microhardness relations in parallel-fibered and lamellar bone.

Understanding the mechanical function of bone material in relation to its structure is a fascinating but very complicated problem to resolve. Part of the complexity arises from the hierarchical structural organization of bone. Microhardness measurements, initially on relatively simply structured parallel-fibered bone, show a marked anisotropy in three orthogonal directions. This may, in part, be due to the highly anisotropic structure of the basic building block of bone, the mineralized collagen fibril. Microhardness measurements made face-on to the layers of crystals and collagen triple helical molecules, show much lower values than those made edge-on to these layers. Microhardness measurements of the much more complex "rotated-plywood" structure of lamellar bone, reveal the well-known general tendency toward anisotropy in relation to the long axis of the bone. A detailed examination of microhardness-microstructure relations of lamellar bone, however, shows that only in certain orientations can microhardness values be related directly to a specific attribute of the lamellar structure. Clearly, the gradual tilting and rotating of the mineralized collagen fibrils that form this structure produce a material that tends toward having isotropic microhardness properties, even though its basic building block is highly anisotropic. This may be an important structural attribute that allows lamellar bone to withstand a variety of mechanical challenges.

Animals↗
PubMed1996

Fetal branch pulmonary arterial vascular impedance during the second half of pregnancy.

OBJECTIVE: Our purpose was to establish normal physiologic parameters in the fetal proximal and distal branch pulmonary arterial vascular impedance during the second half of pregnancy and to analyze relationships between proximal and distal pulmonary arterial blood velocity waveforms. STUDY DESIGN: In this cross-sectional study 100 uncomplicated singleton pregnancies were studied by pulsed color Doppler techniques between 18 and 41 weeks of gestation (median 30 weeks). Both right and left proximal (immediately after the bifurcation of the main pulmonary artery) and distal (beyond the first bifurcation of the branch pulmonary artery) pulmonary artery blood velocity waveforms were recorded and pulsatility index values were calculated. Peak systolic velocities and time-to-peak-velocity intervals were measured. Time-to-peak-velocity intervals were also analyzed at the level of aortic and pulmonary valves and at the ductus arteriosus. Right and left pulmonary artery diameters and right lung length were measured. RESULTS: In both right and left proximal and distal pulmonary arteries pulsatility index values decreased (p < 0.0001) and the peak systolic velocities (p < 0.003) and time-to-peak-velocity intervals (p < 0.0001) increased during the second half of pregnancy. In the proximal pulmonary arteries the pulsatility index values decreased linearly until 34 to 35 weeks of gestation and in the distal pulmonary arteries until 31 weeks of gestation. Thereafter they remained unchanged. In pulmonary arteries time-to-peak-velocity intervals were shorter (p < 0.01) than at the pulmonary valve level. There were no significant differences between the right or left pulmonary arteries in the pulsatility index values, peak systolic velocities, time-to-peak-velocity intervals, or pulmonary artery diameters. In the proximal pulmonary arteries the pulsatility index values (p < 0.02) and peak systolic velocities (p < 0.0001) were higher and time-to-peak-velocity intervals (p < 0.0001) were longer than in the distal pulmonary arteries. There was a 2.5-fold increase in pulmonary artery diameters and right lung length. CONCLUSIONS: Fetal branch pulmonary arterial vascular impedance decreases significantly during the second half of pregnancy. The linear decrease in vascular impedance during the second trimester and in the beginning of the third trimester may be related to the growth of the lung and the increase in the number of resistance vessels. During the latter part of the third trimester pulmonary vascular impedance does not decrease further.

Adolescent↗
PubMed1996

Intracrystalline macromolecules are involved in the morphogenesis of calcitic sponge spicules.

Control over the shapes of biologically formed crystals is generally not well understood. We have studied the morphogenesis of the different-shaped calcareous sponge spicules using high-resolution synchrotron X-ray diffraction. We show that a remarkable correlation exists between the distribution of defects within spicule crystals at the nanometer level and their macroscopic morphologies at the millimeter level. These defects are produced by controlled intercalation of specialized macromolecules into the crystals. We also show that such intracrystalline macromolecules are involved in the regulation of the shapes of synthetic crystals grown de novo from solution, and epitaxially overgrown on the spicule surfaces. We conclude that intracrystalline macromolecules play an important role in modulation of the morphologies of the forming biogenic crystals. Possible mechanisms that may account for the observed growth patterns are supported by fluorescence labeling experiments in vivo.

Animals↗
PubMed1996

Regulation of calcite crystal morphology by intracrystalline acidic proteins and glycoproteins.

Many biologically formed calcite crystals contain intracrystalline macromolecules. The ways in which they interact with growing calcite crystals were evaluated by monitoring changes in the morphology of calcite crystals grown in vitro in their presence. Macromolecules were extracted from within isolated prisms from the prismatic layer of the shell of the mollusk Atrina rigida and from spines of the sea urchin Paracentrotus lividus. Two modes of interaction were identified; the interaction of highly acidic proteins with calcite planes perpendicular to the c crystallographic axis and the interaction of glycoproteins with planes roughly parallel to the c axis. By different preparative procedures we demonstrated that the polysaccharide moieties of the sea urchin spine glycoproteins are directly involved in the latter mode of interactions. We suggest that organisms utilize the abilities of these macromolecules to interact in different ways with calcite crystals, and in so doing fine-tune aspects of the control of crystal growth in vivo.

Animals↗
PubMed1995

Effects of relining on long-term marginal stability of provisional crowns.

Provisional resins crowns are commonly placed to protect prepared teeth, but the marginal adaptation of interim crowns has always been a problem. These experiments examined the effects of thermocycling and occlusal loading on relined and unrelined polymethyl methacrylate resin transitional crowns. Three groups of interim crowns were made on a cast metal die tooth preparation; unrelined, relined correction, and paint-on correction. After thermocycling and occlusal loading of the specimens, the change in mean marginal gap was significantly greater for the unrelined group. Axial changes were greatest for relined group and least for the unrelined group. These results suggested that relining of polymethyl methacrylate interim crowns can be useful to prevent increases in marginal gap width during extended intraoral periods.

Analysis of Variance↗
PubMed1995

Morphogenesis of calcitic sponge spicules: a role for specialized proteins interacting with growing crystals.

Crystals formed in biological tissues often adopt remarkable morphologies that are thought to be determined mainly by the shapes of the confined spaces in which they grow. Another possible way of controlling crystal shape, demonstrated only in vitro, is by means of specialized proteins preferentially interacting with certain crystal faces. In so doing, they reduce the rate of growth in these directions and consequently change the overall crystal shape. In an X-ray diffraction study of the distribution of defects within the lattice of calcite crystals produced by certain sponges, we show that a remarkable correlation exists between the defect patterns or crystal texture and the macroscopic morphology of the spicules. This was observed in two cases in which proteins are present within the spicule crystal, but not in a third case where such intracrystalline proteins are absent. Furthermore, one of the spicules exhibited marked differences in texture even within families of structurally identical crystal planes, demonstrating that the organisms exert exquisite control over the microenvironment in which crystals grow. We conclude that highly controlled intercalation of specialized proteins inside the crystals is an additional means by which organisms control spicule growth.

Animals↗
PubMed1995

Inter and intraobserver variability of total skin thickness score (modified Rodnan TSS) in systemic sclerosis.

OBJECTIVE: Assessment of the inter and intraobserver variability of the modified Rodnan (m-Rodnan) total skin thickness score by clinical palpation [a commonly used outcome measure in trials of systemic sclerosis (SSc)]. METHODS: Skin thickness was assessed by clinical palpation of 17 body areas on 0 to 3 scale (normal, mild, moderate, severe). The m-Rodnan total skin thickness score was derived by summation of the scores from all 17 body areas. Using the m-Rodnan, 6-7 investigators assessed skin thickness in 5-6 patients with SSc (22 patients and 23 examiners total) at each of 4 sessions for the determination of interobserver variability (accuracy). In addition 21 of the investigators then assessed m-Rodnan in 2-3 patients each (60 patients total) 3 times over a 2-8 week period to quantitate intraobserver variability (reliability). RESULTS: Interobserver and intraobserver mean +/- within patient standard deviations (SD) for the m-Rodnan were found to be 17.7 +/- 4.6 and 20.7 +/- 2.45, respectively. CONCLUSION: The m-Rodnan total skin thickness score is at least as reliable for measuring skin thickness in SSc as are the ARA and Ritchie joint tenderness counts for assessing joint disease in rheumatoid arthritis. These data are useful for the determination of sample size and for the definitions of clinically meaningful response. Assessment of skin score is sufficiently reproducible to include as a measure of disease outcome, especially if patients are serially evaluated by the same investigator.

Humans↗
PubMed1995

Biomechanics of occlusion and the articulator.

The evaluation of the occlusion is important in prosthodontics and restorative dentistry because the occlusal surfaces of the teeth to be restored must be functional units of the patient's stomatognathic system. Specifically, the morphology of the cusps, fossae, grooves, and marginal ridges should support the mandible in the intercuspal position and where appropriate, during eccentric jaw movements and in functional activities such as mastication. Restored teeth should not interfere with mandibular function in mastication, speech, and swallowing nor should they transmit excessive force to the attachment apparatus or the temporomandibular joint either in the intercuspal or eccentric jaw positions or during movement.

Biomechanical Phenomena↗
PubMed1994

Doppler in non-immune hydrops fetalis.

Fetal ultrasound studies were performed on 24 fetuses with non-immune hydrops to evaluate echocardiographic and cardiovascular Doppler parameters that may be useful in assessing hemodynamics and in predicting outcome. Of all cardiovascular parameters analyzed, only the presence of abnormal pulsations in the umbilical vein (p < 0.001) was found to be significantly different between the 11 survivors and 13 non-survivors. In a smaller subset of 12 fetuses, in whom inferior vena caval waveforms were recorded, survivors (n = 6) had a significantly lower percentage of retrograde flow in the inferior vena cava (p < 0.001) and higher inferior vena caval E/V velocity ratio (p < 0.001) than non-survivors (n = 6). Sixteen of the 24 cases examined had abnormal umbilical venous pulsations; 12 of the 16 (75%) died including all fetuses with hydrops due to twin-to-twin transfusion or congenital heart disease. When fetuses with pulsatile flow in the umbilical vein were compared with fetuses with normal umbilical venous flow, the following significant differences were found: lower right and left ventricular output velocities, larger inferior vena caval diameter, decreased shortening fractions of the right and left ventricles, and lower peak velocities at the aortic and pulmonary valves and in the ductus arteriosus.

Journal Article↗
PubMed1994

Small-angle x-ray scattering study of dispersed crystals from bone and tendon.

A small-angle x-ray scattering study of dispersed crystals from rat bone and mineralized turkey tendon shows that the particles in both preparations have the same scattering behavior. The data are very similar to those reported by Fratzl et al. for intact turkey tendon and are consistent with the crystals being plate shaped. These observations have important implications for understanding both the structure and mineralization processes of these tissues.

Animals↗