Punch shear testing of extracted vital and endodontically treated teeth

Plano-parallel specimens of human dentin cut from vital and endodontically treated teeth were tested by the punch shear test. Shear strength values were found to positively correlate with approximate toughness values. Statistically significant differences were found between shear strength and toughness values for vital and endodontically treated teeth, the latter showing lower values. The clinical impression that endodontically treated teeth are weaker and more brittle than vital teeth has therefore been quantitated. Anatomically different teeth or the methods used to store and cut teeth could not be consistently correlated with punch shear and toughness values. When dentin slices were constrained during punching so that bending was prevented, the precision of the results was improved and higher values were recorded.     

A Tipula paludosa population with a high incidence of two pathogens

The incidence of lethal parasites in the larvae of a Tipula paludosa population was monitored for two seasons. The proportions of larvae infected with Tipula iridescent virus (TIV) and a tachinid insect were similar to those in previously studied populations, whereas the proportions of larvae infected with Tipula nuclear polyhedrosis virus (NPV) and a spore-forming bacterium (SFB) were higher. Conservative estimates of mortality due to these four agents were 10.7% in 1977–1978 and 7.7% in 1978–1979. The mean population density and the proportion of SFB-infected larvae were lower in 1978–1979 than in 1977–1978, while the proportion of NPV-infected larvae was higher. In 1979 the proportion of NPV-infected larvae was positively correlated with population density, which was highest in the wettest part of the study area. In both seasons the proportion of SFB-infected larvae was negatively correlated with population density. Larvae infected with the NPV or the SFB became pallid at an advanced stage of infection, but, although infected larvae were found throughout the larval period, pallid larvae were only found in the later part. It is suggested that larvae become infected in an early instar, then the infections slowly develop throughout the remainder of the larval period. Five larvae were found with mixed infections; four were infected with the SFB and NPV, while the fifth was infected with the SFB and TIV.     

Evaluation of bone cement failure criteria with applications to the acetabular region

A Strain energy density (SED) criterion based on a fracture mechanics approach was used to assess the possible failure of acetabular bone cement after total hip replacement. Stress distributions in the cement at the bone-cement interface were calculated using two-dimensional finite element analyses. The results indicate that increasing the thickness of bone cement reduces the risk of cement fracture. The addition of a metal backing to the polyethylene cup and retention of the subchondral bone further reduces the risk of failure. The SED criterion was found to predict the same critical regions as zones of possible cement failure as the von Mises' criterion. Although either criterion can be used for predicting failure in this acetabular analysis both criteria are excessively conservative in predicting failure in regions where high principal compressive stresses are present. Further development of cement failure criteria are indicated.     

Sexual differentiation of rat liver carbonic anhydrase III

Using radioimmunoassay, the concentration of carbonic anhydrase III in the livers of adult male rats was found to be approx. 30-times greater than that observed in mature females. Castration of male rats led to a marked reduction in liver carbonic anhydrase III concentrations which could be partially restored to control levels by testosterone replacement. Administration of testosterone to ovariectomised female rats induced about a 5-fold increase in liver carbonic anhydrase III concentration. Immunoprecipitation analysis of the products of liver mRNA translation in vitro with antiserum specific for carbonic anhydrase III showed that hormonal control of the levels of carbonic anhydrase III in liver is mediated by changes in the amount of translatable carbonic anhydrase III mRNA. Marked changes in liver carbonic anhydrase III concentrations were also observed in developing and ageing male rats.     

The partial purification and characterization of cytosol alcohol dehydrogenase from Astasia

1. The cytosol alcohol dehydrogenase (alcohol-NAD oxidoreductase, EC 1.1.1.1) of Astasia longa was partially purified and characterized from cells grown in the presence of air+CO(2) (95:5) or of O(2)+CO(2) (95:5). 2. Under both these growth conditions, the cells contained a fraction, ADHII, which was characterized by its electrophoretic properties, by a high degree of resistance to heat inactivation, by a sharp pH optimum at 8.2 and by its kinetic properties. The estimated molecular weight of this fraction was approx. 150000, which is similar to that of yeast alcohol dehydrogenase. 3. Cells grown in air+CO(2) (95:5) contain another fraction, ADHI, which can be further separated into two subfractions by polyacrylamide-gel electrophoresis and by DEAE-cellulose chromatography. This was termed fraction ;ADHI-air'. 4. In addition to fraction ADHII, cells grown in the presence of O(2) have a twofold increase in fraction ADHI-air activity as well as two new fractions that could not be demonstrated in air-grown cells. These new fractions which we have called fraction ;ADHI-O(2)', account for about 10% of the total activity. 5. The ADHI fractions (air) and (O(2)) have similar broad pH-activity curves and similar kinetic properties, both having a lower K(m) for ethanol and NAD than fraction ADHII. However, they differ from each other with respect to their activity with various substrates. The estimated molecular weight of these two ADHI fractions and their chromatographic behaviour on hydroxyapatite and on DEAE-cellulose also distinguish them.     

Sphingolipids in bean leaves (Phaseolus vulgaris)

Phytoglycolipid has been isolated for the first time from plant leaves (Phaseolus vulgaris). The purified product (almost identical with the phytoglycolipid isolated from flax seed) was a ceramide attached through phosphate diester linkage to an oligosaccharide, which consisted of the usual trisaccharide unit (inositol, hexuronic acid, hexosamine) to which were attached mannose, galactose, and arabinose. The major fatty acids were the saturated 2-hydroxy C(22), C(24), and C(26) acids; the major long-chain bases were dehydrophytosphingosine (d-ribo-1,3,4-trihydroxy-2-amino-8-trans-octadecene) (53%) and phytosphingosine (d-ribo-1,3,4-trihydroxy-2-amino-octadecane) (32%). A ceramide and a cerebroside were also isolated. In the ceramide the major fatty acids and the major long-chain bases were the same as in the phytoglycolipid. In the cerebroside, the fatty acid composition was similar to that in the ceramide and phytoglycolipid, but the long-chain bases consisted of dehydrophytosphingosine and phytosphingosine (7:1) with a substantial amount of unidentified long-chain base. The sugar component was glucose.