Distribution of the intermediate filament proteins vimentin,keratin, and desmin in the bovine ovary

The distribution of the intermediate filament (IF) proteins desmin, keratin, and vimentin was studied immunohistochemically in bovine ovaries. Special attention was paid to granulosa cells to examine possible marked changes of IF distribution in relation to folliculogenesis during ovarian development. Therefore, ovaries were used from fetuses from 3 months of gestation onward, calves, heifers, and cows. In all ovaries, desmin immunoreactivity was restricted to smooth muscle cells in blood vessel walls. Keratin appeared a characteristic of the ovarian surface epithelium. Co-localization of keratin and vimentin was observed in the epithelium of rete ovarii tubules in fetuses and calves, and in cortical cord epithelium and pregranulosa cells of primordial follicles in fetuses at 3–7 months of gestation. Vimentin was demonstrated in endothelium and in fibroblasts. In addition, vimentin immunoreactivity was present in granulosa cells of primary, secondary, and antral follicles. In antral follicles, these granulosa cells mainly had an elongated appearance and either contained an oblong or a round nucleus. Those with an oblong nucleus were characteristic for atretic antral follicles. In nonatretic follicles, numerous vimentin immunore-active, elongated granulosa cells with a round nucleus were observed, especially in the peripheral granulosa layer and in small (<3 mm in diameter) antral follicles. Additionally, in antral follicles, protrusions of vimentin-positive corona radiata cells were observed, that penetrated the zona pellucida to contact the oocyte. The data show that the distribution of vimentin containing IFs is associated with various aspects of granulosa cell activity, as mitosis, atresia, and intercellular transport. © 1995 Wiley-Liss, Inc.     

Database on the structure of small ribosomal subunit RNA.

The database on small ribosomal subunit RNA structure contains (June 1994) 2824 nucleotide sequences. All these sequences are stored in the form of an alignment based on the adopted secondary structure model, which in turn is corroborated by the observation of compensating substitutions in the alignment. The complete database is made available to the scientific community through anonymous ftp on our server in Antwerp. A special effort was made to improve electronic retrieval and a program is supplied that allows to create different file formats. The database can also be obtained from the EMBL nucleotide sequence library.     

Identification and characterization of a UDP-GalNAc:GlcNAc{eta}-R {eta}->4-N-acetylgalactosaminyltransferase from cercariae of the schistosome Trichobilharzia ocellata. Catalysis of a key step in the synthesis of N,N'-diacetyllactosediamino (lacdiNAc)-type glycans

Three different stages of the avian schistosome Trichobilharziaocellata appeared to contain a novel N-acetylgalac-tosaminyltransferaseactivity. To investigate its function in the biosynthesis ofschistosome glycoconjugates, the enzyme was partially purifiedfrom cercariae, a free-living stage of the parasite, by affinitychromatography on UDP-Sepharose. Acceptor specificity studiesshowed that the enzyme catalyses the transfer of N-acetylgalactosamine(GalNAc) from UDP-GalNAc to oligosaccharides, glyco-peptidesand glycoproteins carrying a terminally     

Introduction of oxygen into the alkyl chain of N-decyl-dNM decreases lipophilicity and results in increased retention of glucose residues on N-linked oligosaccharides

N-Alkylation of the -glucosidase inhibitor 1-deoxynojirimycin(dNM) dramatically increases its inhibitory potency (Tan etal., J. Biol. Chem., 266, 14504–14510, 1991). However,the possibility of extending the alkyl chain to N-decyl-dNMis limited by an increase of detergent-like (amphiphilic) propertiesof long-chain alkylated dNM derivatives. Substitution of methylenegroups in the N-decyl chain by oxygen reduced the amphiphilicityof N-decyl-dNM derivatives, while retaining their superior inhibitoryproperties. In intact HepG2 cells, the compound N-7-oxadecyl-dNMwas found to result in the most pronounced retention of glucoseresidues on N-linked glycans. Permeabilization of the plasmamembrane with the bacterial toxin Streptolysin O improves theinhibitory properties of the derivatives N-3,6,9-trioxadecyl-,N-7,10,13-trioxatetradecyl-, N-3-oxadecyl- and N-7-oxadecyl-dNM,but not those of dNM. These observations suggest differencesin the mode of entry of the oxygen-substituted dNM derivativesin comparison with dNM. We observed that the dNM derivativeN-3,6,9-trioxadecyl-dNM, devoid of inhibitory activity in intactcells, was inhibitory in Streptolysh O-permeabilized cells.Thus, the permeability barriers posed by plasma membrane andendoplasmic reticulum membrane are not equivalent. The use ofa permeabilized cell system thus allows the elaboration of inhibitoryprinciples for novel bioactive compounds where study of theisolated enzymes may not be possible, and where intact cellsare not a suitable target due to permeability barriers. -glucosidase inhibition N-linked glycosylation oxygen-substituted N-decyl-dNM derivatives permeabilized cells     

Reduction in blood pressure with a low sodium,high potassium,high magnesium salt in older subjects with mild to moderate hypertension.

OBJECTIVE--To examine the effect of a reduced sodium and increased potassium and magnesium intake on blood pressure. DESIGN--Randomised double blind placebo controlled trial. SETTING--General population of a suburb of Rotterdam. SUBJECTS--100 men and women between 55 and 75 years of age with untreated mild to moderate hypertension. INTERVENTIONS--During 24 weeks the intervention group received a mineral salt (sodium: potassium: magnesium 8:6:1) and foods prepared with the mineral salt. Controls received common salt and foods. MAIN OUTCOME MEASURE--Change in blood pressure. RESULTS--Complete follow up was achieved for 97 of the 100 randomised subjects. Systolic blood pressure (mean of measurements at weeks 8, 16, and 24) fell by 7.6 mm Hg (95% confidence interval 4.0 to 11.2) and diastolic blood pressure by 3.3 mm Hg (0.8 to 5.8) in the mineral salt group compared with the controls, with a 28% decrease in urinary sodium excretion and a 22% increase in urinary potassium excretion. Twenty five weeks after the study the difference in blood pressure between the groups was no longer detectable. CONCLUSION--Replacing common sodium salt by a low sodium, high potassium, high magnesium mineral salt could offer a valuable non-pharmacological approach to lowering blood pressure in older people with mild to moderate hypertension.     

Crystal structure of cholera toxin B-pentamer bound to receptor GM1 pentasaccharide.

Cholera toxin (CT) is an AB5 hexameric protein responsible for the symptoms produced by Vibrio cholerae infection. In the first step of cell intoxication, the B-pentamer of the toxin binds specifically to the branched pentasaccharide moiety of ganglioside GM1 on the surface of target human intestinal epithelial cells. We present here the crystal structure of the cholera toxin B-pentamer complexed with the GM1 pentasaccharide. Each receptor binding site on the toxin is found to lie primarily within a single B-subunit, with a single solvent-mediated hydrogen bond from residue Gly 33 of an adjacent subunit. The large majority of interactions between the receptor and the toxin involve the 2 terminal sugars of GM1, galactose and sialic acid, with a smaller contribution from the N-acetyl galactosamine residue. The binding of GM1 to cholera toxin thus resembles a 2-fingered grip: the Gal(beta 1-3)GalNAc moiety representing the "forefinger" and the sialic acid representing the "thumb." The residues forming the binding site are conserved between cholera toxin and the homologous heat-labile enterotoxin from Escherichia coli, with the sole exception of His 13. Some reported differences in the binding affinity of the 2 toxins for gangliosides other than GM1 may be rationalized by sequence differences at this residue. The CTB5:GM1 pentasaccharide complex described here provides a detailed view of a protein:ganglioside specific binding interaction, and as such is of interest not only for understanding cholera pathogenesis and for the design of drugs and development of vaccines but also for modeling other protein:ganglioside interactions such as those involved in GM1-mediated signal transduction.     

The barbs (Barbus spp.) of Lake Tana: a forgotten species flock?

Synopsis All living species occupy an ecological niche, and are positioned within a trophic hierarchy. Extinct organisms presumably held similar behavioral and coevolutionary characteristics in the past, and were susceptible to the same kinds of natural ecological pressures operating today. Paleoecological investigations are limited by the incompleteness of the fossil record, and particularly by a lack of behavioral data that are so fundamental to ecological studies of living communities and habitats. Opportunities to examine the coevolutionary structure of ancient communities from empirical data are extremely rare. One such opportunity is provided by the Lower Cretaceous Santana Formation of north-eastern Brazil, a series of richly fossiliferous strata approximately 110 million years old. Many fossil fishes from the Santana Formation contain identifiable prey, including decapod crustaceans and fishes. A trophic hierarchy of these organisms is reconstructed here, and their ecological relationships are discussed. Comparison is made with a similar fish fauna from the Upper Jurassic Solnhofen Limestone of Germany. Low-level, intermediate and high-level predators are identified in each fauna. Predator-prey relationships in the Santana fauna are strongly hierarchical, and are more focussed at the intermediate predator level than in Solnhofen. Comparison with a model of predator-prey relationships between fishes and benthic fauna of the Baltic Sea (which like the Araripe Basin represents a semi-enclosed environment) suggests that heavy predation on teleosts such asRhacolepis, occupying an intermediate trophic level, may have permitted benthic decapods to proliferate and exclude other benthic organisms. Less intense predation on fishes at the intermediate trophic level would allow their numbers to increase, thereby increasing the intensity of predation on the benthos at the base of the trophic hierarchy.