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21.
Summary Culture conditions have been optimised to enable resting cell cultures ofAcinetobacter calcoaceticus NCIMB 9871 to selectively undertake either oxidative or reductive biotransformations of various bicyclic ketones. 相似文献
22.
Adaptations of Goldner's Masson Trichrome Stain for the Study of Undecalcified Plastic Embedded Bone 总被引:2,自引:0,他引:2
Helen E. Gruber 《Biotechnic & histochemistry》1992,67(1):30-34
Specialized adaptations for application of Goldner's Masson trichrome stain to plastic embedded undecalcified bone specimens are presented. This stain can be used successfully on methyl-glycol methacrylate, glycol methacrylate and Spurr embedded bones. The stain affords the advantage of good cellular staining due to the hematoxylin component with concomitant sharp discrimination of mature bone matrix which stains green, immature new bone matrix which stains red, and calcified cartilage which stains very pale green. Use of red filters during photomicrography aids in bone-osteoid discrimination in black and white photographs. 相似文献
23.
Aleurone tissue from undried immature developing wheat grains (Triticum aestivum L. cv. Sappo), normally insensitive to gibberellic acid, can be made to respond to the hormone by a series of temperature treatments. Incubation of the de-embryoed grains at temperatures above 27° C for at least 8 h causes the tissue to become sensitive. Prolonged incubation at temperatures below 27° C does not effect a change in sensitivity. In addition to the requirement for exposure to an elevated temperature for a period of several hours the tissue must also subsequently be subjected to a period at a lower temperature for just a few seconds for the response to be observed. Once sensitized, the tissue remains responsive to gibberellic acid for substantial periods of time. Exposure of the tissue to temperatures which induce sensitivity to gibberellic acid also results in an increased leakage of amino acids. It is suggested that the increase in sensitivity to gibberellin requires two separate processes to take place. One could be a homeoviscous adaptation of the cell membranes in response to elevated temperature, the other a subsequent, permanent change in conformation of membrane components. 相似文献
24.
Serum albumin is known to bind several divalent metal ions at the amino terminus of the protein. Two peptide analogues for the amino terminus of human albumin, L-aspartyl-L-alanyl-L-histidine-N-Methyl amide (AAHNMA) and glycylglycyl-L-histidine-N-methyl amide (GGHNMA) have been synthesized, and their interactions with Zn(II) and Co(II) ions have been studied using analytical potentiometry. The stability constants of the species and their distribution as a function of pH were determined in 0.16-M KNO3 at 25°. Comparison of the modes of interaction of the Zn(II) and Co(II) with each of the above peptides indicate that, although Co(II) is a valuable tool for the study of Zn(II) interaction with metalloenzymes, it is considerably less useful as a Zn(II) model with small peptide molecules. The potentiometric properties of the two peptide-Zn(II) systems have been compared to the potentiostatic properties of the albumin-Zn(II) system. The results indicate that AAHNMA is a better analogue for the Zn(II)-HSA interaction than is GGHNMA. The findings suggest that the Zn(II)-HSA binding site is best described as a compound site containing both a histidyl and a neighboring carboxyl group. 相似文献
25.
In situ hybridization of Drosophila melanogaster somatic chromosomes has been used to demonstrate the near exact correspondence between the location of highly repetitious DNA and classically defined constitutive heterochromatin. The Y chromosome, in particular, is heavily labeled even by cRNA transcribed from female (XX) DNA templates (i.e., DNA from female Drosophila with 2 Xs and 2 sets of autosomes). This observation confirms earlier reports that the Y chromosome contains repeated DNA sequences that are shared by other chromosomes. In grain counting experiments the Y chromosome shows significantly heavier label than any other chromosome when hybridized with cRNA from XY DNA templates (i.e., DNA from male Drosophila with 1 X and 1 Y plus 2 sets of autosomes). However, the preferential labeling of the Y is abolished if the cRNA is derived from XX DNA. We interpret these results as indicating the presence of a class of Y chromosome specific repeated DNA in D. melanogaster. The relative inefficiency of the X chromosome in binding cRNA from XY and XYY DNA templates, coupled with its ability to bind XX derived cRNA, may also indicate the presence of an X chromosome specific repeated DNA. 相似文献
26.
Jacob S. Hanker Dwight K. Romanovicz Helen A. Padykula 《Histochemistry and cell biology》1976,49(4):263-291
Summary Several compounds of osmiumVIII, including potassium osmiamate and coordination complexes of OsO4 with ammonia and various heterocyclic nitrogen compounds, have been synthesized and characterized. They have also been evaluated as substitutes for OsO4 in postfixation of biological specimens and in light and electron microscopic cytochemical methods resulting in osmium black formation.The most useful of these osmic compounds, a molecular addition complex of hexamethylenetetramine (methenamine) with OsO4, has a negligible vapor pressure of OsO4. It has the molecular formula C6H12N4.2OsO4 and has been designated osmeth. Although it has only limited solubility, aqueous solutions of the compound (or of OsO4) can be rapidly prepared by dissolution in a minimal amount of dimethylformamide and subsequent dilution with distilled water or buffer. Although stable in the solid state, the complex in solution undergoes partial dissociation releasing OsO4, and the odor of OsO4 becomes apparent.Such solutions of osmeth are (0.25%) considerably less concentrated with respect to OsO4 than solutions (1–2%) ordinarily employed for ultrastructural preservation or in cytochemical studies. Osmeth has limited value for postosmication after glutaraldehyde fixation because the generation (release) of OsO4 appears to be slow. Adequate osmication of tissue blocks exists only at the surface, but effective osmication can be achieved throughout tissue sections. In cytochemical reactions resulting in the formation of osmium blacks, the osmeth solutions are as effective as OsO4 solutions of equivalent concentrations. Our findings indicate that OsO4 solutions of less than 1% may be satisfactorily utilized in many cytochemical studies.Osmeth is safer and more convenient to handle than OsO4 because small amounts may be solubilized as needed. It should be considered as a substitute for OsO4 in ultrastructural cytochemistry.This investigation was supported by NIH research grant number DE 02668 from the National Institute of Dental Research and by NIH grant number RR 05333 from the Division of Research Facilities and ResourcesVisiting Professor, Dental Research Center, University of North Carolina at Chapel Hill, Jan.-May, 1975. Supported in part by USPHS Grant HD 09209 相似文献
27.
In the dynamics of the survival of chromosomal polymorphism selection may be operating at the genic level, at the chromosomal level or at the supergene level. Tests designed to distinguish between these levels were run on Drosophila pseudoobscura. There was no evidence for heterosis, a necessary requirement for gene-determined chromosomal polymorphism. A strong chromosmal selection was observed. No evidence was found for the presence within one locality of more than a single superallele for each supergene (= gene order). These results are compared to those found by others. 相似文献
28.
29.
Helen Mahoney West Carly E. Milliren Jennifer Manne-Goehler Jillian Davis Jaime Gallegos Juan Huanuco Perez Julia R. Khler 《PLoS neglected tropical diseases》2022,16(6)
BackgroundChagas disease is a potentially life-threatening neglected disease of poverty that is endemic in continental Latin America. Caused by Trypanosoma cruzi (T. cruzi), it is one of six parasitic diseases in the United States targeted by the Centers for Disease Control as a public health problem in need of action. An estimated 300,000 people are infected with T. cruzi in the United States (US). Although its morbidity, mortality and economic burden are high, awareness of Chagas disease is lacking among many healthcare providers in the US. The purpose of this analysis is to determine if the number of diagnostic tests performed at a community health center serving an at-risk population for Chagas disease increased after information sessions. A secondary aim was to determine if there was a difference by provider type, i.e., nurse practitioner vs. physician, or by specialty in the number of patients screened.Methodology/Principal findingsWe conducted a retrospective data analysis of the number of Chagas serology tests performed at a community health center before and after information sessions for clinicians. A time series analysis was conducted focusing on the Adult and Family Medicine Departments at East Boston Neighborhood Health Center (EBNHC). Across all departments there were 1,957 T. cruzi tests performed before the sessions vs. 2,623 after the sessions. Interrupted time series analysis across departments indicated that testing volume was stable over time prior to the sessions (pre-period slope = +4.1 per month; p = 0.12), followed by an immediate shift after the session (+51.6; p = 0.03), while testing volume remained stable over time after the session (post-period slope = -6.0 per month; p = 0.11).Conclusion/SignificanceIn this study, Chagas testing increased after information sessions. Clinicians who began testing their patients for Chagas disease after learning of the importance of this intervention added an extra, potentially time-consuming task to their already busy workdays without external incentives or recognition. 相似文献
30.
Myotonia congenita (Thomsen's disease) excluded from the region of the myotonic dystrophy locus on chromosome 19 总被引:1,自引:0,他引:1
Manuela Koch Helen Harley M. Sarfarazi K. Bender T. Wienker Barbara Zoll P. S. Harper 《Human genetics》1989,82(2):163-166
Summary Linkage analysis has been carried out in six German families with autosomal dominantly inherited myotonia congenita (Thomsen's disease) using five chromosome 19 markers known to be linked to the gene for myotonic dystrophy (DM). Two of the markers, APOC1 and APOC2, are tightly linked to DM. Close linkage between these markers and myotonia congenita (MC) has been excluded to a distance of 9cM (z=-2.158). These data support the clinical suggestion that MC and DM are non-allelic disorders. 相似文献