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D F Weber

Publications and source records attributed to D F Weber.

34 records · Page 2Linked to original sources
PubMed1978

Genetically marked Rhizobium identifiable as inoculum strain in nodules of soybean plants grown in fields populated with Rhizobium japonicum.

The fate of an inoculum strain of Rhizobium japonicum was studied using a genetically marked strain I-11O subline carrying resistance markers for azide, rifampin, and streptomycin (I-110 ARS). At the time of planting into a field populated with R. japonicum, seeds of soybean cultivars Kent and Peking were inoculated with varying cell densities of strain I-110 ARS. At various times during the growing season, surface-sterilized root nodules were examined for the presence of the inoculum strain by plating onto selective media. The recovery of the inoculum strain was unambiguous, varying, in the case of Kent cultivar, from about 5% with plants (sampled at 51 days) that had been inoculated with 3 X 10(8) cells per cm of row to about 20% with plants (sampled at 90 days) that had been inoculated with 3 X 10(9) cells per cm. The symbiotically incompatible interaction of Peking and strain 110 in Rhizobium-populated field soil was confirmed by the finding that at 60 days after planting, only one nodule in 360 sampled contained strain I-110 ARS. The use of genetically marked Rhizobium bacteria was found to provide for precise identification of the inoculum strain in nodules of field-grown soybeans.

Azides↗
PubMed1977

Microscopy of the junctional region between human coronal primary and secondary dentine.

The juction between human primary dentine and regular and irregular secondary dentine was examined with a number of different light and electron microscopic techniques. In decalcified material, a narrow band along the innermost surface of the primary dentine stained intensely. The walls of the tubules within the band stained intensely, whereas the tubular walls within the bulk of the primary dentine were not stained. Generally, the walls of the tubules in both types of secondary dentine were also preferentially stained. Although not readily apparent in ground sections, observations of thin sections revealed a dramatic reduction in the number of tubules in regular secondary dentine. Generally, the radiodensity of the intertubular matrix was the same in primary and secondary dentine and the intensely stained band was not seen radiographically. The pulpal ends of the tubules in primary dentine were often occluded with a material having the same radiodensity as peritubular matrix. Both patent and occluded tubules were seen in irregular secondary dentine. Scanning electron microscopy of acid-etched specimens of secondary dentine revealed that some tubules had irregular walls of highly mineralized matrix which was less acid-soluble then the peritubular matrix of primary dentine.

Cuspid↗
PubMed1975

Correlative microscopy of enamel prism orientation.

Both mature and developing human enamel were studied by correlative light and electron microscopic techniques. Ordinary light microscopic observations of routinely prepared ground sections produced a totally inaccurate impression of enamel prism direction. In contrast, ground sections which were acid-etched and viewed with phase contrast optics, as well as thin (0.5 mum) sections, were in concert with further electron microscopic preparations. The appearance of longitudinally sectioned prisms as demonstrated on thick ground sections is often the result of structural interrelation between groups of obliquely sectioned prisms. The arrangement between enamel prism heads and tails is often such as to produce the light microscopic appearance of classical enamel cross striations. The production of such optical artifacts may be related to conflicting interpretations concerning enamel cross striations as well as light microscopic descriptions of the histopathology of enamel caries.

Amelogenesis↗
PubMed1971

Immunodiffusion analysis of isolates of Xanthomonas cyamopsidis.

Immunodiffusion analysis of intact, sonically treated, and sonically treated and heat-treated cell antigen preparations of isolates of races 0 and 1 of Xanthomonas cyamopsidis of guar, Cyamopsis tetragonoloba, indicated that these races differ from one another antigenically. The differentiating precipitin reactions are believed to have been brought about by specific heat-stable surface antigens, possibly similar to lipopolysaccaride somatic antigens of other slime-producing xanthomonads. Because differences in host reaction to inoculation with the two isolates of race 1 were known to be minor, these isolates are considered to represent serotypes of the race rather than distinct separate races. This conclusion is supported by the antigenic behavior of isolates 14 and 19 to antiserum 19. The applicability of immunodiffusion analysis for the study of pathogenic variability in X. cyamopsidis is demonstrated.

Agglutination Tests↗
PubMedDate not supplied

Analysis of total free and glucose-conjugated pyrethroid acid metabolites in tea infusions as hexafluoroisopropyl esters by gas chromatography with electron capture detection.

A gas chromatographic method with electron capture detection (GC-ECD) has been developed to quantitate the sum of free acids of pyrethroid metabolites, their glucosides, and their other base-cleavable conjugates that are extracted from tea leaves when a tea infusion is prepared. Four representative glucoside conjugates were synthesized; hydrolytic conditions were established; and extraction, derivatization and GC conditions were developed for analysis of these pyrethroid acid metabolites at > or = 0.01 ppm on dry tea. GC/mass spectrometry was used to confirm assignment of residues found in some tea samples.

Chromatography, Gas↗