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.     

Decline in measles mortality: nutrition,age at infection,or exposure?

The mortality from measles was studied in an urban area of Guinea-Bissau one year before and five years after the introduction of a vaccination programme. The years after the introduction of immunisation saw a decline in mortality among unvaccinated children with measles. This decline occurred despite a lower age at infection and an increasing prevalence of malnourished children. State of nutrition (weight for age) did not affect the outcome of measles infection. The incidence of isolated cases, however, increased in the period after the introduction of measles vaccination. As mortality was lower among these cases, diminished clustering explained some of the reduction in mortality. Comparison between the urban district and a rural area inhabited by the same ethnic group showed a lower age at infection, less clustering of cases, and lower case fatality ratios in the urban area.Endemic transmission of measles in urban districts leads to less clustering of cases, which may help explain the usually lower case fatality ratios in these areas. As measles vaccination increases herd immunity and diminishes clustering of cases, it may reduce mortality even among unvaccinated children who contract the disease.     

Floral scent in dioeciousSalix (Salicaceae)—a cue determining the pollination system?

Floral scents of male and female inflorescences of three dioeciousSalix species were collected by head-space adsorption, and analysed by GC-MS. InSalix caprea andS. cinerea 1,4-dimethoxy benzene was the main compound, and male and female scents showed a high degree of resemblance. No dominant compound was found inS. repens and malefemale scent similarity was low. Floral scent inSalix is likely a strong orientation cue, guiding pollinators between male and female plants ensuring pollen transfer and pollination. We suggest that a high degree of male-female floral scent resemblance is coupled to a high degree of insect pollination. Floral scent does not promote reproductive isolation betweenS. caprea andS. cinerea.     

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.

     

Iodoazomycin riboside (1-(5'-iodo-5'-deoxyribofuranosyl)-2-nitroimidazole), a hypoxic cell marker. I. Synthesis and in vitro characterization

Misonidazole (MISO), a selective radiosensitizer of hypoxic cells, forms adducts with cellular biomolecules with rates which are 30-50 X higher under hypoxic as compared to aerobic conditions of incubation. This technique of sensitizer adduct formation was proposed as a possible means of measuring the hypoxic fraction of solid tumors by noninvasive procedures. Iodoazomycin riboside (5'-IAZR) and 5'-[125I]AZR were synthesized and chemically characterized. Measurements of in vitro cytotoxicity and radiosensitizing ability with EMT-6 tumor cells in vitro indicated that 5'-IAZR is approximately 3 X more toxic and effective than is azomycin riboside (AZR) and approximately 10 X more toxic and effective than is MISO. 5'-[125I]AZR was shown to selectively bind to hypoxic EMT-6 cells at rates which were 2.5-3 X faster than those of MISO. The absolute rates of binding of 5'-IAZR to hypoxic cells at concentrations of 10-100 microM are the highest observed in this laboratory for any hypoxic cell radiosensitizer tested to date. These data suggest that 5'-IAZR, when labeled with an appropriate radioisotope (e.g., 131I), might be a useful marker for hypoxic cells in solid tumors amenable to noninvasive detection. Additional studies with animal tumor models appear to be warranted.     

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.