A morphometric and ultrastructural study of lithium-induced changes in the medullary collecting ducts of the rat kidney

Summary Rats were given a lithium-containing diet (40 mmol/kg) to Study the effect of lithium on the structure of collecting ducts from the inner stripe of the outer medulla. The results show that there is a significant increase in the volume density of collecting ducts already after one week on this diet. The volume density of both intercalated and principal cells increases, whereas the volume density of mitochondria in the cytoplasm increases in the intercalated cells only. The increased volume of both principal and intercalated cells seems to be part of a general hyperplasia and hyperactivity of the collecting duct, which may in some way be related to the effects of lithium on vasopressinmediated water transport. The specific changes in the intercalated cells may be a consequence of the effects of lithium on distal nephron potassium and hydrogen ion transport in the distal nephron.     

Cell wall mannoproteins during the population growth phases in Saccharomyces cerevisiae

Mannoproteins from cell walls of Saccharomyces cerevisiae synthesized at successive stages of the population growth cycle have been solubilized with Zymolyase and subsequently analyzed. The major change along the population cycle concerned a large size mannoprotein material; the size of the newly-synthesized molecules varied from 120,000–500,000 (mean of about 200,000) at early exponential phase to 250,000–350,000 (mean of about 300,000) at late exponential phase. These differences are due to modifications in the amount of N-glycosidically linked mannose residues, since the size of the peptide moiety was 90,000–100,000 at all growth stages and the level of O-glycosylation changed only slightly. After, incubation of the purified walls with concanavalin A-ferritin and subsequent analysis by electron microscopy, labelling was localized at the external and internal faces of the walls. The middle space of these was labelled after digestion of the glucan network with Zymolyase, which demonstrate the presence of mannoproteins in close contact with the structural glucan molecules throughout the wall.Abbreviations BSA bovine serum albumin - Con A concanavalin A - SDS sodium dodecyl sulphate     

Chemical structures of a galactose-rich glycoprotein of Leishmania tarentolae

1. Aqueous phenol treatment of water extracted disrupted cells of Leishmania tarentolae (LV-414) provided a glycoprotein mixture which was purified by gel filtration chromatography, and Concanavalin A-Sepharose column. 2. The bound fraction on Concanavalin A-Sepharose column (protein 74%, and carbohydrate, 26%) had [alpha]D + 9 degrees and contained mannose (18%), galactose (60%), and glucose (22%), and some of the galactose residues were resistant to periodate oxidation. 3. Treatment of the phenol extract with hot aqueous NaBH4 containing NaOH gave a preparation having mannose (12%), galactose (82%), and glucose (6%). 4. Methylation analysis showed the presence of a mainly linear structure with non-reducing end-units of mannopyranose (6%), 3-O-substituted galactopyranosyl (64%), 2-O- (11%), and 6-O- (5%) substituted mannopyranosyl, and 4-O- (9%), and 4,6-di-O- (3%) substituted glycopyranosyl units. 5. The specific rotation of the preparation, +20 degrees, indicated beta-linked galactopyranosyl units.     

Base pair opening dynamics of a 2-aminopurine substituted Eco RI restriction sequence and its unsubstituted counterpart in oligonucleotides.

Studies of 1H NMR selective saturation recovery were performed to determine the imino proton exchange with solvent water of the base pairs in the Eco RI endonuclease recognition sequence GAATTC, placed at the center of self-complementary decamer and dodecamer oligonucleotides. In one oligonucleotide the innermost adenine was replaced by the fluorescent base analogue 2-aminopurine (2AP). From the measurements at different concentrations of TRIS buffer acting as proton exchange catalyst, base pair lifetimes were evaluated. The results at 25 degrees show that the AT base pairs have lifetimes of the order of a few ms, whereas the surrounding GC base pairs in a dodecamer have lifetimes of about 100 ms. The (2AP)T base pair has a shorter lifetime than the corresponding AT base pair. The temperature dependent optical absorption, and for the 2AP containing oligonucleotide fluorescence, were used to study the single strand-duplex equilibrium of the decamers. The results indicate that NMR and the optical techniques, although applied at very different concentrations, monitor the same conformational transition of the oligonucleotide.     

Leptomonas samueli glycoconjugates. Comparison with Herpetomonas samuelpessoai

Xylose and mannose are the main manosaccharide components of Herpetomonas samuelpessoai and Leptomonas samueli promastigotes. Variations in the xylose/mannose ratios are related to the age of cultures. Phenol-aqueous extraction disclosed in both species the presence of carbohydrate-containing fractions which were both soluble and insoluble in chloroform/methanol/water (10:10.3). The xylose enriched, uronic acid-containing glycoconjugates of L. samueli were mainly composed of (1----4)-linked xylose units (Methylation-mass spectrometry and 13C NMR), similar to the glucuronoxylan of H. samuelpessoai (Mendon?a-Previato et al., 1979 Biochem 18 149-154). SDS-PAGE and sugar composition analysis disclosed similarities between glycoconjugates of H. samuelpessoai and L. samueli, two species dwelling in the same host, therefore an example of convergent adaptation.