Polyacrylamide Slab Gel Electrophoresis of Soluble Proteins for Studies of Bacterial Floras

A polyacrylamide slab gel electrophoresis procedure was used to compare cellular proteins from bacterial isolates of gingival crevice floras. Isolates with identical protein patterns consistently were shown to be members of the same species. When used to screen isolates, the procedure reduced total analytical time and expense without sacrificing accuracy, and it provided additional verification of the identity of strains characterized by conventional phenotypic tests.     

Variations in the Growth Response of Four Different Vitamin B12 Assay Microorganisms to the Same Tissue and Standard Preparations

Four microbiological assay procedures (Escherichia coli, Lactobacillus leichmanni, Euglena gracilis, and Ochromonas malhamensis) for the vitamin B(12) content of rat liver and kidney tissue were compared. Significant differences in the growth response for portions of the same sample based on the same standard preparations were noted. The liver values with E. coli were strikingly higher than those obtained with the other microorganisms, about which there was rather general agreement. With kidney tissue, E. coli again gave higher values, but not as significantly high as those obtained with L. leichmannii and E. gracilis. O. malhamensis values were significantly lower. These differences were greater than were expected and could not be explained by the differences of specificity and sensitivity of the assay organisms. Several methods of sample preparation, the possible presence of an alkali-heat-stable factor, different methods of sterilization of the sample plus medium, and different chromatographic procedures were explored in an attempt to find explanations for the variations in growth response, with the thought that these various methods would clarify in what form or forms the free and bound vitamin B(12) might exist in the samples. No clear-cut explanation was found.     

THE ROLE OF ALLELOPATHIC SUBSTANCES IN THE “SMOTHER CROP” BARLEY

The high degree of success of barley as a “smother crop” generally has been attributed to physical competition for nutrients and water. However, it was found that even in the absence of such competition, barley still inhibits germination and growth. This occurred both in mixed cultures receiving adequate nutrients and water and in germination tests. Aqueous leachates of seeds and roots of barley caused similar inhibition of germination and growth, thereby indicating an inhibitory allelopathic substance. A specificity of reaction was found, with the greatest inhibition occurring with Stellaria media (L.) Cyr., less with Capsella bursa-pastoris (L.) Medic. and tobacco (Nicotiana tabacum L.), and no significant effect with wheat (Triticum aestivum L.). A concentration effect and possible periodic production of the inhibitor were indicated. Living plants and aqueous leachates of living roots were more inhibitory than dead ones, thereby supporting the hypothesis of an active metabolic secretion of the allelopathic substance. Preliminary attempts to identify the active inhibitory components demonstrated the presence of alkaloids, with a much greater concentration of substance in the living than in the dead root leachates. The alkaloid, gramine, known to occur in barley, was found to have an inhibitory effect on the growth of Stellaria media and it is suspected as an active component of the root leachates. These results suggest that factors other than the previously assumed physical competition are involved in the mechanism of the “smother crop” barley.     

In-vivo and in-vitro measurements of lead and cadmium

Tibia lead is measured in vivo using X-ray fluorescence. A¹⁰⁹Cd source is used to excite Pb K X-rays, and this signals is normalized to that from Rayleigh scattering to remove geometrical variations. The lower limit of detection is 10 μg/g for a mean absorbed dose, to the exposed section of the leg, of 100 μGy. Tibia lead correlated positively with age in normal volunteers (r=0.615,p=0.004) and with duration of exposure in occupationally exposed subjects (r=0.847,p=0.0001). When the X-ray fluorescence technique was applied to autopsy specimens previously analyzed by atomic absorption spectrometry there was excellent agreement between measurement techniques. Cadmium is measured in vivo by neutron activation analysis. The detection limit in liver is 6.5 μg/g for a local skin dose equivalent of 0.5 mSv and in kidney is 6.4 mg for a dose equivalent of 0.9 mSv to the skin. Detailed analysis of the γ-ray spectrum will produce only slight improvements in detection limit. Uncertainties in organ position during measurement, even after ultrasonic localization, are likely to produce uncertainties of 20–25% in cadmium measurement. Autopsy samples were measured, using a fast neutron activation method, from people previously measured in vivo. The results are broadly consistent, but show differences greater than those accounted for by counting statistics.     

Characterization of binding and receptors for epidermal growth factor in smooth muscle

Summary The mitogenic and differentiation-inducing activities of epidermal growth factor (EGF) in epithelial tissues have been well described. Since non-mitogenic effects of EGF, especially in mesenchymal tissues such as smooth muscle are not well-known (Nanney et al. 1984), we have examined EGF-binding and receptors in smooth muscle from many sites. Specific EGF binding sites were detected by incubating small pieces of tissue with ¹²⁵I-EGF; immunoreactive EGF receptors were detected by immunohistochemistry. In-situ localization of ¹²⁵I-EGF binding sites and immunoreactive EGF receptors of smooth muscle cells in intact mammalian tissues were identical using either ¹²⁵I-EGF autoradiography or anti-EGF receptor antibody in an immunoperoxidase method. Cultured rat aortic smooth muscle also contained specific EGF receptors as detected by their biological response to EGF-binding and internalization of ¹²⁵I-EGF, as well as EGF-stimulated phosphorylation of a 170K protein. The presence of EGF receptors in a well-differentiated smooth muscle cell indicates that EGF may play a physiological, but non-mitogenic role in mammalian tissues in vivo.     

X long-arm deletions. A review of non-mosaic cases studied with banding techniques

Summary A woman with secondary amenorrhoea and an X long-arm deletion (pterq21:) is described and compared with 30 adult non-mosaic, banded cases. Approximately 50% of the patients had gonadal dysgenesis associated with a higher frequency of short stature and Turner stigmata than in women with indication of ovarian activity. It is suggested that preservation of bands Xq2628 may be decisive for normal ovarian function.Supported by grants to E.N. from the P. Carl Petersen's Foundation (B995) and the Danish Medical Research Council (512-4276).     

Ultrastructural and cytochemical studies on the cytodifferentiation of duodenal endocrine cells

Summary The development and cytodifferentiation of endocrine cells that produce the gastrointestinal hormones gastrin, cholecystokinin and secretin have been studied by a combined fluorescence-cytochemical, immunocytochemical and ultrastructural approach. The results show that, during development, several ultrastructurally distinct cell types exhibit COOH-terminal gastrin and cholecystokinin immunoreactivity. Furthermore, some cells simultaneously contain both gastrin- and cholecystokinin-specific antigenic determinants. Studies on the time course of development of gastrin and cholecystokinin cells, together with the above-mentioned data, suggest that gastrin cells may be converted into cholecystokinin cells in development. During this period, gastrin, cholecystokinin and secretin cells store the biogenic monoamine, 5-hydroxytryptamine a feature not displayed by the adult counter-parts of these cells. In the adult duodenum, characteristic enterochromaffin (EC) cells store 5-hydroxytryptamin for which, evidence for a possible hormonal role has been presented. Taken together, our data indicate that the differentiation of duodenal endocrine cells occurs in distinct steps, each involving a restriction in the biosynthetic repertoire of the cell.