Biomedical subjects

E Fried

Publications and source records attributed to E Fried.

10 recordsLinked to original sources

PubMed2001

Prediction of disclinations in nematic elastomers.

We present a theory for uniaxial nematic elastomers with variable asphericity. As an application of the theory, we consider the time-independent, isochoric extension of a right circular cylinder. Numerical solutions to the resulting differential equation are obtained for a range of extensions. For sufficiently large extensions, there exists an isotropic core of material surrounding the cylinder axis where the asphericity vanishes and in which the polymeric molecules are shaped as spherical coils. This region, corresponding to a disclination of strength +1 manifesting itself along the axis, is bounded by a narrow transition layer across which the asphericity drops rapidly and attains a nontrivial negative value. Away from the disclination, the material is anisotropic, and the polymeric molecules are shaped as ellipsoidal coils of revolution oblate about the radial direction. Along with the area of steeply changing asphericity between isotropic and anisotropic regimes, a marked drop in the free-energy density is observed. The boundary of the disclination core is associated with the location of this energy drop. For realistic choices of material parameters, this criterion yields a core on the order of 10(-2) microm, which coincides with observations in conventional liquid crystal melts. Finally, we find that the total energy definitively shows a preference for disclinated states.

Journal Article↗

PubMed2000

Diversity of alpha-globin mutations and clinical presentation of alpha-thalassemia in Israel.

Alpha-thalassemia is among the world's most common single gene disorders, caused primarily by gene deletions. In Israel, where alpha(o)-trait thalassemia is uncommon, it is of particular importance because of its phenotypic interactions with beta-thalassemia in hetero- and homozygotes. In a study of 232 individuals referred for molecular evaluation of anemia, 303 chromosomes carried alpha-globin gene abnormalities; 6 gene rearrangements and 11 point mutations were identified. This unexpected heterogeneity is in part due to the many ethnic subgroups represented by these patients. Our findings include nine unique Israeli alleles, 3 of which are described here for the first time. An equal number of point mutations was found in the alpha2-globin gene as compared to alpha1. A threonine deletion in codon 39 of the alpha1-globin gene, found frequently in Arabs, is unique to Israel and probably represents one of several indigenous alleles. Among Arabs, point mutations were more frequent than large deletions. Surprisingly, in Ashkenazi Jews, who resided for many centuries in a nonmalarial environment, a single alpha-globin gene deletion -alpha(3.7) was found in many cases. The clinical presentation of individuals carrying two or more alpha-globin lesions was highly variable. In general, the severity correlated inversely with the number of functional alpha-globin genes. In some cases, impairment of two alpha-globin genes by point mutations led to a thalassemia-intermedia-like picture which could be misdiagnosed as beta-thalassemia. We conclude that alpha-thalassemia is phenotypically and genotypically more heterogeneous than previously recognized. DNA analysis is invaluable as it provides a specific diagnosis and enables reliable genetic counseling.

Ethnicity↗

PubMed1995

The importance of sodium for anoxic transmission damage in rat hippocampal slices: mechanisms of protection by lidocaine.

1. The effect of sodium influx on anoxic damage was investigated in rat hippocampal slices. Previous experiments demonstrated that a concentration of tetrodotoxin which blocks neuronal transmission protects against anoxic damage. In this study we examined low concentrations of lidocaine (lignocaine; which do not block neuronal transmission), for their effect on recovery of the evoked population spike recorded from the CA1 pyramidal cell layer. 2. Recovery of the population spike, measured 60 min after a 5 min anoxic period, was 4 +/- 2% of its preanoxic, predrug level. Lidocaine concentrations of 10, 50, and 100 microM significantly improved recovery to 56 +/- 12, 80 +/- 7 and 70 +/- 14%, respectively. 3. Lidocaine (10 microM) did not alter the size of the evoked response before anoxia and had no significant effect on potassium levels or calcium influx during anoxia. It did, however, reduce cellular sodium levels (146 +/- 7 vs. 202 +/- 12 nmol mg-1) and preserve ATP levels (2.17 +/- 0.07 vs. 1.78 +/- 0.07 nmol mg-1) during anoxia. All values were measured at the end of 5 min of anoxia except those for Ca2+ influx which were measured during 10 min of anoxia. 4. High concentrations of lidocaine (100 microM) did not improve recovery significantly over that observed with 10 microM. They also had no significantly greater effects on sodium levels than 10 microM lidocaine (137 +/- 12 vs. 146 +/- 7 nmol mg-1); however, 100 microM lidocaine significantly improved potassium (202 +/- 18 vs. 145 +/- 6 nmol mg-1) and ATP (2.57 +/- 0.06 vs. 2.17 +/- 0.07 nmol mg-1) levels, while reducing calcium influx (7.76 +/- 0.12 vs. 9.24 +/- 0.39 nmol mg-1 (10 min)-1) when compared with 10 microM lidocaine. 5. We conclude that sodium influx and ATP depletion are of major importance in anoxic damage since 10 microM lidocaine reduced these changes during anoxia and improved recovery of the population spike. In addition, our results indicate that the properties of the sodium channel are altered during anoxia, since sodium influx is blocked by a concentration of lidocaine that does not affect the population spike in the preanoxic period.

Adenosine Triphosphate↗

PubMed1989

The prevalence and management of pain in patients with AIDS: a review of 134 cases.

In light of the lack of any prior systematic evaluations of the prevalence and types of pain syndromes and treatments found in patients with AIDS, a chart review study was undertaken to evaluate this issue. Fifty-two of 96 charts reviewed (54%) had at least one note on nonprocedural pain or analgesic prescription. Although chest pain was the most prevalent pain location (22%), presumably because of the high incidence of Pneumocystis carinii pneumonia, other possible AIDS-related entities, such as peripheral neuropathy and thrombophlebitis, were also found. No specific AIDS syndromes could be identified that were related to a higher incidence of pain. Nearly one-third of patients with pain received codeine (31%), others received acetaminophen (27%), and 17% of patients received acetaminophen and oxycodone HCl. Specific pain management interventions must be evaluated and applied to control the nontrivial occurrence of pain in patients who have AIDS symptoms that may be overlooked by the physician given the overwhelming disease process.

Acquired Immunodeficiency Syndrome↗

PubMed1982