Fixation effects on membranous and endochondral onlay bone-graft resorption

Difficulties arise in the prediction of maintenance of graft volume over time when bone grafts are used for facial contour reconstruction. We hypothesize that graft fixation will decrease movement and lead to decreased resorption. Fixed and nonfixed endochondral (rib) and membranous (skull) onlay bone grafts measuring 30 X 10 X 4 mm were grafted to the mandible bilaterally in 10 adult sheep. Fixation was achieved using the lag-screw technique. Volume measurements using caliper technique were made 20 weeks postoperatively. The volume of graft present at 20 weeks was significantly greater for the fixed bone grafts (p less than 0.001): fixed membranous, 85.9 percent; fixed endochondral, 76.2 percent; nonfixed membranous, 55 percent; and nonfixed endochondral, 16.6 percent. The results are explained using biomechanical theories related to the effects of strain. At present, it is suggested by this study that when onlay bone grafts are stabilized, improved results with respect to graft resorption can be expected.     

Length, breadth, and elongation of avian eggs from the tables of Sch?nwetter

Summary UsingSchönwetter's data base regression equations are derived expressing egg length and egg breadth as a function of egg mass for Passerines (n=3929) and non-Passerines (n=3217). For both groups these show a variation around the mean which is twice as large for length as for breadth. The average elongation (length/breadth) ist presented for 27 orders ranging from 1.61 in Apterygiformes and Gaviiformes to 1.21 in Strigiformes as well as examples of a few families where elongation increases or decreases as egg mass becomes larger. Egg mass can be estimated from the relationship where egg mass=k(LB²). Mean values, SD, and range of k for both groups are given, but for any particular species are best derived from the dimensions of L, B, and egg mass inSchönwetter's tables.

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Länge, Breite und Form der Vogeleier auf der Grundlage der Tabellen vonSchönwetter

Zusammenfassung Regressionsgleichungen für Eilänge und Eibreite als Funktion der Eimasse ergeben für Passeres (3929 Arten) und Non-Passeres (3217 Arten) eine Streuung um den Mittelwert, die für Länge doppelt so hoch wie für die Breite ist. Das Verhältnis Länge: Breite reicht bei 27 Ordnungen von 1.61 bei Apterygiformes und Gaviiformes bis 1.21 bei den Strigiformes. In Beispielen für einzelne Familien steigt oder fällt der Wert mit zunehmender Eimasse. Letztere kann bestimmt werden gemäß k · (L · B²), wobei k eine Konstante darstellt. Mittelwerte, Standardabweichung und Konstante werden für Passeriformes und Non-Passeriformes angegeben, doch für einzelne Arten hält man sich am besten an die Werte beiSchönwetter.

     

Chromosome pairing in female and male diploid and polyploid anurans (Amphibia) from South America

Chromosome pairing in females and males of diploid (2n = 22) and tetraploid (2n = 44) Odontophrynus americanus and diploid Ceratophrys cranwelli (2n = 26) and tetraploid C. ornata (2n = 104) showed that diploid females formed more chiasmata per paired arm than diploid males and polyploids of both sexes. There was a reduction in the level of recombination in female polyploids by forming multivalents with terminal chiasmata. The reduction reflected a change in the genetic control of pairing in females after polyploidization.     

Adducts formed between deoxyguanosine and cis-Dichlorodiammineplatinum(II): Separation by means of cation-exchange chromatography

The interaction between deoxyguanosine (dG) and cis-dichlorodiammineplatinum(II) (cis-Pt) leads to the 2:1 and the 1:1 dG-Pt adducts. These adducts were separated on an Aminex A6 cationexchange column by use ot 0.01 M K₂CO₃ (pH 11) as an eluent. The stoichiometry of the adducts was determined from the ^195mPt radioactivity and from the absorbance of the guanine chromophore at 280 nm. Time-course studies show that dG reacts initially with cis-Pt to form the 1:1 adduct, which then interacts with a second molecule of dG to form the 2:1 adduct. Acid hydrolysis (100°C in 88% formic acid for 5–15 min) of the 1:1 and 2:1 adducts results in their conversion to two new products, which elute differently from the column but which still contain Pt bound in the same stoichiometric ratio to dG as in the nonhydrolyzed adducts. The hydrolyzed adducts show a negative diphenylamine reaction indicative ot cleavage of the glycosidic bond. It is concluded that mild acid hydrolysis converts the 1:1 and 2:1 dG-Pt adducts into the corresponding guanine-Pt adducts, which are chromatographically distinguishable. This acid hydrolysis-high pressure liquid chromatography (HPLC) procedure has application to the identification of the Pt adducts formed in DNA.     

Ultraviolet Inactivation and Photoproducts of Transforming DNA Irradiated at Low Temperatures

Solutions of Haemophilus influenzae transforming DNA were irradiated at temperatures ranging from 25°C to - 196°C. Temperature dependence of the formation of thymine-containing dimers was closely correlated with inactivation of transforming activity; in general, both dimerization and inactivation decreased with decreasing temperature. The fraction of nonphotoreactivable damage increased with increasing dose at low temperatures. The nonphotoreactivable spore-type photoproduct was formed at low temperatures with a maximum at - 100°C, a temperature at which the nonphotoreactivable biological inactivation was also a maximum. Intrastrand cross-linking, like dimer formation, decreased with decreasing irradiation temperature.     

Comparison of Vero cell assay and PCR as indicators of the presence of verocytotoxigenic Escherichia coli in bovine and human fecal samples.

Comparisons were made between Vero cell assay (VCA) and PCR as indicators for the detection of verocytotoxigenic Escherichia coli (VTEC; also known as Shiga-like toxin-producing E. coli) and as predictors of VTEC isolation from bovine and human fecal samples. Fecal samples were collected as part of a survey on the prevalence of VTEC on dairy farms in southern Ontario (J. B. Wilson et al., J. Infect. Dis., 174:1021-1027, 1996). A total of 2,655 samples were examined by VCA and PCR, 2,153 originating from cattle and 502 originating from humans. Overall, 36.2% of the samples were positive in the VCA and 38.7% were positive by PCR. Of the VCA-positive samples screened, 41.6% yielded a VTEC isolate. For both human and bovine samples, a significant positive association between PCR result and VCA titer (P = 0.0001) was found. In addition, there was a significant positive association between the PCR result and VTEC isolation from VCA-positive samples for cattle (odds ratio = 9.1, P < 0.0001). For bovine samples positive in the VCA, VCA titer was significantly associated with the probability of obtaining a VTEC isolate. Agreement between VCA and PCR was good for both bovine and human samples (kappa = 0.69 and 0.64, respectively). The sensitivity and specificity of the PCR with respect to the VCA for bovine samples were 82.0 and 86.5%, respectively, and those for human samples were 59.3 and 98.1%, respectively. Although correlation between VCA and PCR results was not absolute, when used in conjunction, these tests complemented one another as predictors of VTEC isolation.     

Microjet impingement followed by scanning electron microscopy as a qualitative technique to compare cellular adhesion to various biomaterials

Adhesion of cells to biomaterial surfaces is one of the major factors which mediates their biocompatibility. Quantitative or qualitative cell adhesion measurements would be useful for screening new implant materials. Microjet impingement has been evaluated by scanning electron microscopy, to determine to what extent it measures cell adhesion. The shear forces of the impingement, on the materials tested here, are seen to be greater than the cohesive strength of the cells in the impinged area, causing their rupture. The cell bodies are removed during impingement, leaving the sites of adhesion and other cellular material behind. Thus the method is shown not to provide quantification of cell adhesion forces for the metals and culture plastic tested. It is suggested that with highly adherent biomaterials, the distribution and patterns of these adhesion sites could be used for qualitative comparisons for screening of implant surfaces.     

Essential role of phosphatidylinositol 3-kinase in insulin-induced activation and phosphorylation of the cGMP-inhibited cAMP phosphodiesterase in rat adipocytes studies using the selective inhibitor wortmannin

Incubation of rat adipocytes with wortmannin, a potent and selective phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, completely blocked the antilipolytic action of insulin (IC₅₀≈ 100 nM), the insulin-induced activation and phosphorylation of cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) as well as the activation of the insulin-stimulated cGI-PDE kinase (IC₅₀≈ 10–30 nM). No direct effects of the inhibitor on the insulin-stimulated cGI-PDE kinase, the cGI-PDE and the hormone-sensitive lipase were observed. These data suggest that activation of PI 3-kinase upstream of the insulin-stimulated cGI-PDE kinase in the antilipolytic insulin signalchain has an essential role for insulin-induced cGI-PDE activation/ phosphorylation and anti-lipolysis.