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Methods for the Morphological Study of Tracheal and Bronchial Glands
Published in Joan Gil, Models of Lung Disease, 2020
Serous tubules in the human respiratory tract stain moderately for complex carbohydrate at the light microscopic level. With the AB-PAS method, some serous cells in human submucosal gland evidence red staining indicative of neutral mucosubstance and others blue-purple coloration demonstrative of acidic glycoconjugate. The acidic groups are identifiable as sulfate esters from their gray to black staining with the HID-AB sequence. The latter method rarely reveals blue staining demonstrative of neuraminic acid (sialic acid) in serous cells, in contrast with the abundant sialic acid demonstrable histochemically in mucous cells. Meanwhile, serous tubules in mouse trachea have been found to lack affinity for cationic reagents, including AB and iron diamine, and to stain red with the AB-PAS method; they are, therefore, uniformly judged to produce a neutral complex carbohydrate. The peanut lectin-horseradish peroxidase (Stoward et al., 1980) and galactose oxidase-Schiff methods concur in demonstrating terminal galactose in glycoprotein devoid of neuraninic acid (Spicer et al., 1983). Beyond an inconstant degree of affinity for HID, demonstrative of a variable content of sulfate esters in secretory mucosubstance, serous cells differ little from one another at the light microscopic level.
Galactosemia
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
Characterization of the reducing substance found in a urine sample can be done in a number of ways. It is usually done by paper chromatography. Testing with paper infiltrated with galactose oxidase provides for an effective screening procedure [70]. Of course, sugar in urine of an infant who tests positive for reducing substance and negative for glucose oxidase is galactose, until proved otherwise, and indicates direct assay of the enzyme. In patients with normal activity of the uridyl transferase, assays are performed for galactokinase and epimerase.
Sexual Differentiation: Immunological Aspects
Published in Gérard Chaouat, The Immunology of the Fetus, 2020
Joyce A. Shelton, Erwin Goldberg
Biochemical isolation and characterization of H-Y would clarify much of the controversy surrounding this antigen; however, progress in this area has been slow. One of the factors responsible is H-Y antigen’s lack of reactivity, which does not favor its isolation by im-munoprecipitative methods. Nevertheless, a number of attempts have been made to isolate H-Y. Hall and colleagues50 reacted antiserum from male-sensitized female C57BL/6 mice with supernatants from Daudi tumor cells, purported to secrete H-Y antigen. Using protein A binding, they isolated an 18,000 mol wt molecule, which they suggest is the H-Y antigen. The report by Bradley and Heslop51 concurs in part with these results. These investigators raised H-Y antisera in rats. These antisera were mixed and used to immunoprecipitate Daudi cell protein that had been pre-reacted with protein A. They identified three protein species that would bind rat anti-H-Y antibodies. One of these proteins was in excess of 200,000 mol wt, the second was in the 50,000 mol wt range, and a third was 20,000 mol wt. They suggest that the smaller protein may be a subunit of the larger or may be the result of different degrees of glycosylation of the same protein. This latter explanation is consistent with reports that H-Y antigen is a glycoprotein.52,53 In these experiments H-Y antigen’s serological reactivity was sensitive to β-galactosidase and galactose oxidase treatments.
Advances in biocatalytic and chemoenzymatic synthesis of nucleoside analogues
Published in Expert Opinion on Drug Discovery, 2022
Sebastian C. Cosgrove, Gavin J. Miller
Relatedly, researchers from Merck described in 2019 the evolution campaigns for five separate enzymes to realize a fully biocatalytic synthesis of experimental antiviral drug islatravir 7, starting from 2-ethynylglycerol 6 (Scheme 3C) [17]. Enzyme engineering was performed on a galactose oxidase (GOase) to enable a stereoselective desymmetrization of 6, which proceeded in 80% ee, but overoxidation to the acid and subsequent removal of this undesired carboxylate enantiomer delivered an enantiopure aldehyde product in 99% ee. Additional engineering was conducted on a pantothenate kinase (PanK), an aldolase (DERA), and PPM/PNP. This remarkable feat of synthesis was performed in a single vessel, with sequential addition and removal of the enzymes and substrates and delivered 7 in 51% overall yield on half a gram scale. A key technology used here was enzyme immobilization. The GOase was immobilized, and the PanK and AK were co-immobilized. By converting these enzymes to heterogenous catalysts, filtration simplified the downstream processing by enabling removal of them prior to subsequent steps. The final product crystallized out of solution and could be recovered through filtration, obviating the need to immobilize the other enzymes. The use of sucrose phosphorylase was necessary in the final step to deliver 7, preventing the reverse reaction occurring by removing phosphate in situ. The authors did not disclose whether any traces of a 2’,3’-dideoxydidehydro by-product were formed.
Natural inhibitors for acetylcholinesterase and autophagy modulators as effective antagonists for tau and β-amyloid in Alzheimer’s rat model
Published in Biomarkers, 2023
Mervat Hassan, Hisham Ismail, Olfat Hammam, Abdullrahman Elsayed, Othman Othman, Sohair Aly Hassan
D-galactose (D-gal) is a physiological nutrient and the body’s typical reducing sugar. Through the action of galactose oxidase, elevated D-gal undergoes oxidation processes, ultimately leading to the generation of aldose and hyperoxide radicals. When D-gal is oxidised, superoxide anions and other oxygen-derived free radicals are created. Because these radicals can’t be further metabolised, they may build up inside the cells and produce reactive oxygen species (ROS) (Wu et al. 2008). Because D-gal mimics the ageing process and Al provokes neurodegeneration by acting as a neurotoxin, their co-administration may aggravate pathological changes related to AD (Liaquat et al. 2017).