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Biomedical subjects

S Weiner

Publications and source records attributed to S Weiner.

At least 91 records · Page 5Linked to original sources
PubMed1994

Pattern recognition and interpretation of electromyogram data from cat jaw muscle.

This study investigates the effect of emotional behavior on the masseteric muscle EMG response patterns. Two experimental protocols are utilized: (1) does not elicit emotional behavior (stick chewing) and (2) elicits emotional behavior (hypothalamic stimulation). The Karhunen-Loève transform is used to compute features which exactly represent the correlated patterns of mean-zero observations, with data compression and noise immunity. Using nonparametric tests, it is found that the populations of biting and hissing features are significantly different (p < 0.05), with increased statistical significance as the size of the training set is increased. No statistically significant difference is seen in a test of the two biting populations.

Animals↗
PubMed1994

Ultrastructural studies of bones from patients with osteogenesis imperfecta.

Bone samples from patients suffering from osteogenesis imperfecta (OI) types I, II, III and IV, as well as normal controls, were studied by scanning (SEM) and transmission electron microscopy (TEM). SEM views of normal bone at low magnification show coherent structure, with regular striations due to a lamellar plywood-like arrangement of the mineralized collagen fibrils. Compact lamellar bone was also found in various OI specimens, but in limited disconnected regions separated by open spaces. Furthermore, some OI, but not normal, bones have regions of loose unconnected fibers and others of apparently abnormally dense mineral deposition. High resolution TEM studies of OI bone fragments have served to elucidate the structures of these different textures. There appears to be a substantial, though reduced, proportion of normal lamellar bone even in quite severe OI. However, the regions of loose fibers are largely unmineralized and probably contain abnormal collagen. Other regions are overmineralized, with generally small unorganized apatite crystals deposited onto fibril surfaces or in separate clusters. These structural abnormalities, together with the paucity of normal bone, may explain the fragility of OI bones.

Adolescent↗
PubMed1994

Pregnancy outcome following Mustard procedure for transposition of the great arteries: a report of five cases and review of the literature.

OBJECTIVE: To review outcomes and complications of pregnancies in women with transposition of the great arteries who had undergone the Mustard procedure. METHODS: Four women with transposition of the great arteries who had undergone Mustard procedures in childhood received their obstetric care for five pregnancies at three institutions in the greater Philadelphia area between 1990-1992. Pregnancy complications and outcomes were reviewed. RESULTS: The most common maternal complication in pregnancy following performance of the Mustard procedure was cardiac arrhythmia, which required treatment in two of four patients. Late-onset fetal growth restriction requiring induction occurred in two of five pregnancies. Third-trimester oligohydramnios requiring induction occurred in one patient, and her second pregnancy was complicated by preterm labor and premature rupture of the membranes (PROM) at 33 weeks. One patient with a twin pregnancy developed mild preeclampsia, preterm labor, and PROM at 30 weeks. There were no neonatal or perinatal deaths or significant morbidity. CONCLUSION: If a patient with transposition of the great arteries who underwent the Mustard procedure is hemodynamically stable before pregnancy, good maternal and fetal outcome can be expected.

Adolescent↗
PubMed1994

Interactions of matrix proteins from mineralized tissues with octacalcium phosphate.

Acidic matrix macromolecules, present in many mineralized tissues, including those of vertebrates, are thought to be involved in controlling crystal formation. Little, however, is known about their in vivo functions, particularly in relation to calcium-phosphate-containing crystals. The manner in which a variety of synthetic and natural acidic macromolecules interact in vitro with crystals of octacalcium phosphate (OCP) has been studied. Interactions were assessed by examining changes in morphology of the crystals resulting from preferential interaction of the additive with some crystal faces and not others. Macromolecules rich in acidic amino acids, with or without polysaccharides, such as polyaspartate and mollusk shell proteins respectively, were shown to interact preferentially with rows of Ca ions exposed on the hydrated plate surface of OCP crystals. In contrast, the phosphorylated proteins, phosphophoryn and phosvitin, interacted specifically with the apatite-like motifs on the OCP side faces. BSP did not interact specifically with OCP, under the experimental conditions used. The observation that these classes of acidic macromolecules recognize different crystal faces should be taken into account when evaluating functions of acidic matrix macromolecules in mineralized tissues.

Animals↗
PubMed1994

Bone crystal sizes: a comparison of transmission electron microscopic and X-ray diffraction line width broadening techniques.

Bone crystals are particularly small and hence estimating their sizes have proved to be difficult and values obtained inconsistent. Here we use rat bone crystals of different ages, as well as different synthetic carbonate apatite crystals, to compare two methods commonly used for determining bone crystal sizes. One method involves direct measurement of crystal lengths and widths, but not thicknesses, from transmission electron microscope (TEM) photographs of dispersed crystals. The second method utilizes X-ray diffraction line width broadening to estimate the average length of crystals. We conclude that line width broadening values tend to reflect crystal coherence lengths rather than the physical dimensions of the whole crystal. TEM measurements provide reliable estimates of average crystal lengths and widths and their ranges. Sample preparation procedures, however, cause breakage of the fragile crystals, which probably results in underestimates of in vivo crystal sizes.

Animals↗
PubMed1994

Prospective multicenter study of second-trimester nuchal skinfold thickness in unaffected and Down syndrome pregnancies.

OBJECTIVE: To determine the distribution of nuchal skinfold thickness in normal and Down syndrome pregnancies and to evaluate the use of this sonographic measurement as a screening test for fetal Down syndrome. METHODS: A prospective, multicenter, population-based study was performed by experienced obstetric sonographers on 1382 women with sonographically normal fetuses undergoing second-trimester amniocentesis for the indication of advanced maternal age. A standard, well-defined sonographic image was obtained at all collaborating centers. The distributions of nuchal skinfold thickness were compared between euploid and Down syndrome fetuses. RESULTS: There were 1346 chromosomally normal pregnancies, 13 fetuses with Down syndrome (1:106), and 23 other chromosome abnormalities. Seventeen fetuses had measurements of 6 mm or greater, and one of these had Down syndrome. The median nuchal skinfold thickness in Down syndrome was 3.2 mm and in euploid fetuses was 3.1 mm. By the Mann-Whitney rank-sum test, there was no statistically significant difference in nuchal skinfold between the euploid and Down syndrome fetuses (P = .5). Overall, using a nuchal skinfold thickness of 6 mm or greater as a screening test, the detection rate for Down syndrome was one of 13 (8%), the false-positive rate was 16 of 1382 (1.2%), the positive predictive value was one of 17 (6%), and the probability of detecting Down syndrome was 6.5%. CONCLUSION: In this investigation, excess nuchal skinfold thickness was a poor and unreliable screening test for Down syndrome.

Adult↗
PubMed1993

Chorionic villus sampling followed by amniocentesis in the same pregnancy.

In our consecutive series of 2,574 chorionic villus sampling (CVS) patients, 146 women (5.7%) underwent a subsequent amniocentesis in the same pregnancy for the indications of absent or insufficient villi (3.3%), elevated maternal serum alpha-fetoprotein (0.93%), CVS mosaicism (0.89%), culture failure (0.23%), specimen contamination (0.15%), and CVS aneuploidy (0.12%). Patients presenting for a CVS should be informed of the possible need for a subsequent amniocentesis in the same pregnancy. There is a need for individual prenatal diagnosis programs to analyze their own data and provide genetic counseling information which pertains specifically to their institution.

Amniocentesis↗
PubMed1993

Acute hemodynamic effects induced by chorionic villus sampling: a preliminary investigation.

OBJECTIVE: Our purpose was to evaluate the effects of chorionic villus sampling on the fetal heart rate, the fetal umbilical artery pulsatility index, and the maternal arcuate artery resistance index. STUDY DESIGN: M-mode fetal heart rate, pulsed Doppler fetal umbilical artery pulsatility index, and maternal arcuate artery resistance index measurements were obtained before and immediately after chorionic villus sampling in 50 patients and were compared with 50 procedure-free, gestational age--matched controls. Comparisons within groups were performed with paired T tests and mean changes between groups with two-sample T tests, and variance comparisons between groups were performed with F tests. RESULTS: The mean changes (SD) in fetal heart rate, umbilical artery pulsatility index, and arcuate artery resistance index in patients undergoing chorionic villus sampling and in controls were not statistically different from zero or from each other. However, the variance around the mean fetal heart rate change was 17.1 times larger in the chorionic villus sampling group than the control group (F 17.1, degrees of freedom 49,49, p < 0.0001), and the variance around the mean pulsatility index change was 2.7 times larger in the chorionic villus sampling group than in the control group (F 2.7, degrees of freedom 49,49, p = 0.0007). There was no significant difference in mean resistance index change or variance around the mean resistance index change between groups. CONCLUSION: Chorionic villus sampling induces significant but unpredictable fluctuations in fetal heart rate and umbilical artery pulsatility index but does not affect maternal arcuate artery resistance index.

Analysis of Variance↗
PubMed1993

Tissue-specific mosaicism among fetuses with prenatally diagnosed diaphragmatic hernia.

OBJECTIVE: Our purpose was to determine if cytogenetic discrepancies between fetal blood and amniotic fluid are present in fetuses with prenatally diagnosed diaphragmatic hernia. STUDY DESIGN: Chromosome analysis was performed on 15 fetuses with prenatally diagnosed diaphragmatic hernia. Fourteen had both amniotic fluid and fetal blood studies. One fetus had an amniocentesis followed by postnatal skin and peripheral lymphocyte chromosome analysis. RESULTS: In one fetus with a normal karyotype on fetal blood, amniotic fluid mosaicism for a supernumerary isochromosome 12p was identified. Another fetus had normal amniotic fluid chromosome analysis but was diagnosed with mosaic isochromosome 12p on skin biopsy after birth. Concordant aneuploidy in both fetal blood and amniocytes was found in five pregnancies (three with trisomy 18, one with an unbalanced translocation, and one with mosaic supernumerary isochromosome 12p). Eight fetuses had normal karyotypes. CONCLUSION: Because diaphragmatic hernia is a common component of mosaic isochromosome 12p syndrome and this chromosome abnormality is predominantly found in fibroblasts but not lymphocytes, an amniocentesis may be more accurate than fetal blood sampling in defining the true fetal chromosome status when diaphragmatic hernia is detected prenatally.

Adult↗
PubMed1993

Effects of thermocycling and occlusal force on the margins of provisional acrylic resin crowns.

Transitional acrylic crowns were examined for changes in axial contour and increases in marginal gap width after simultaneous thermocycling and occlusal loading. Two groups of 10 crowns--one with a shoulder finish line and another with a chamfer finish line--were treated with 3400 thermocycles and 50,000 load cycles simultaneously within an artificial oral environment chamber in an MTS Dental Materials Testing System. The marginal gaps were increased for both groups after treatment. However, the group of crowns with the shoulder finish lines demonstrated a smaller gap width (x = 90 microns) after treatment than the crowns with chamfer finish lines (x = 210 microns). A statistical comparison identified a significant difference in gap width between groups (p < 0.01). Changes in the axial profile of the groups were similar, but one crown with a chamfer finish line exhibited a cracked margin.

Acrylic Resins↗
PubMed1993

Fluoridated carbonatoapatite in the intermediate layer between glass ionomer and dentin.

The intermediate layer between a glass ionomer restoration and dentin was examined morphologically by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). SEM showed strong bonding between the dentin and glass ionomer and formation of an intermediate layer between them. FTIR spectra of successive scrapings through the ionomer/dentin interface zone showed that the intermediate layer is composed primarily of mineral fluoridated carbonatoapatite. The presence of this sparingly soluble mineral at the interface between the tooth and the restoration may provide high resistance to secondary caries and may, thus, be of great clinical importance.

Apatites↗
PubMed1993

Increased risk of aneuploidy in women having unsuccessful chorionic villus sampling procedures.

OBJECTIVE: To determine the incidence of fetal aneuploidy in women who had unsuccessful chorionic villus sampling (CVS) procedures. DESIGN: Retrospective study. SETTING: Pennsylvania Hospital, Philadelphia, Pennsylvania, USA. SUBJECTS: Two thousand six hundred and sixty-eight women who underwent chorionic villus sampling, in 78 (2.9%) of whom villi could not be obtained. INTERVENTIONS: Sixty-nine of 78 (88%) women who had an unsuccessful CVS procedure underwent a subsequent amniocentesis later in the same pregnancy. MAIN OUTCOME MEASURES: The incidence of aneuploidy identified from amniotic fluid chromosome analysis in the 69 women who had an unsuccessful CVS procedure compared to the frequency of aneuploidy in women having a successful CVS procedure. RESULTS: Of the 69 women who underwent a post-CVS amniocentesis because of failure to obtain chorionic villi, six aneuploid pregnancies were identified (8.7%). The frequency of aneuploidy in the 2590 successfully sampled CVS patients was 2.5%. This difference was statistically significant (P = 0.009) by Fisher's exact test (two-tailed). CONCLUSIONS: Women having an unsuccessful CVS procedure should be informed that they may be at increased risk for carrying an aneuploid fetus.

Amniocentesis↗
PubMed1993

Electromyographic activity in the masseter muscle resulting from stimulation of hypothalamic behavioral sites in the cat.

This study examined the relationship between hypothalamically elicited emotional behaviors and electromyographic activity in the masseter muscle of the cat. Electromyographic amplitudes resulting from stimulation at hypothalamic sites at which affective defense and quiet biting attack behaviors were elicited were compared with those recorded during stick biting that simulated mastication. The electromyographic activity elicited by hypothalamic stimulation was greater than that found from stick biting for all behavioral sites. At control sites, from which no behavior could be elicited, the electromyographic activity associated with stick biting exceeded that observed from the hypothalamic sites. These findings suggest a relationship between hypothalamically elicited behaviors and increased levels of jaw muscle activity.

Animals↗
PubMed1993

Has percutaneous umbilical blood sampling improved the outcome of high-risk pregnancies?

PUBS offers distinct advantages to the perinatologist in the management of the high-risk pregnancy. Improvement in outcome has clearly been attained in the severely anemic fetus, for example, whereas fetal blood sampling has also led to great advances in both diagnosis and treatment of many other perinatal abnormalities. The exact role for PUBS in the management of problems such as intrauterine growth retardation and the fetus at risk for thrombocytopenia in ITP remains controversial. It is quite evident, however, that overall PUBS offers tremendous aid to the perinatologist in management of the high-risk pregnancy, with future promise for even greater application.

Blood Transfusion, Intrauterine↗
PubMed1993

Cordocentesis.

Access to the fetal circulation via cordocentesis has resulted in many advances in both prenatal diagnosis and fetal therapy over the past decade. In this review, current research in the assessment and treatment of erythrocyte isoimmunization and fetal infection by fetal blood sampling, as well as the role of cordocentesis in the evaluation of fetal platelet abnormalities, intrauterine growth retardation, fetal thyroid function, and genetic investigation, are discussed. Finally, a brief review of complications and loss rates relating to this procedure is given.

Chromosome Aberrations↗
PubMed1992

Phosphatic shell plate of the barnacle Ibla (Cirripedia): a bone-like structure.

The carbonate apatite crystals and the segmented structure of the shell plates of the barnacles in the genus Ibla distinguish them from the shell plates of all other barnacles, which are coherent calcitic structures. A detailed study of the hierarchical organization of one of the two shell plate types, the tergum, reveals a remarkably complex structure. Cylinders composed of a chitin-protein complex and nodes of plate-shaped crystals constitute the basic building blocks. The crystals are organized into layered stacks in which the c crystallographic axes are all aligned perpendicular to a 25-nm banded structure. The cylinders are, in turn, ordered in arrays such that parts of each cylinder are aligned in a plane, and parts form arcuate out-of-plane structures. The overall result is a lamellar structure, with a plywood-like motif, that is present throughout an individual segment. A series of segments forms an interlocking mineralized core, which is enclosed within a thick organic envelope. The flexible and complex skeletal structure of the tergum shows some marked similarities to the structure of lamellar bone. Although this is undoubtably a product of convergent evolution, the iblid tergum provides a unique perspective on bone structure, which was heretofore unavailable.

Amino Acids↗
PubMed1992

Bone structure: from angstroms to microns.

Bone has a complex hierarchical structure, which despite much investigation, is still not well understood. Here we bring together pieces of this complicated puzzle, albeit from different sources, to present a tentative overview of bone structure. The basic building blocks are the extremely small plate-shaped crystals of carbonate apatite, just hundreds of angstroms long and wide and some 20-30 A thick. They are arranged in parallel layers within the collagenous framework. At the next hierarchical level these mineral-filled collagen fibrils are ordered into arrays in which the fibril axes and the crystal layers are all organized into a 3-dimensional structure that makes up a single layer or lamella of bone a few microns thick. The orientations of the collagen fibrils and the crystal layers in alternating lamellae of rat bone differ such that in the thinner lamellae, the fibrils and the crystal layers are parallel to the lamellar boundaries. In the thicker lamellae the fibrils are parallel to the boundary, but the crystal layers are rotated out of the plane of the boundary. In many bones these alternating lamellae are organized into even larger ordered structures to produce what is truly a remarkably ordered material, all the way from the molecular scale to the macroscopic product.

Animals↗