The histone H1°/H5 variant and terminal differentiation of cells during development of Xenopus laevis

The maintenance of the differentiated condition is supposed to be associated with the presence of a histone of the H1(0)/H5 subclass. If the H1(0)/H5 variant has an important role in differentiation distinct from that of H1, it should display differential expression in time and position during development. Here we report that this prediction is verified during Xenopus laevis development, in which tadpoles exhibit a very characteristic, developmentally regulated pattern of histone H1(0)/H5 expression that is different for the derivatives of each embryonic germ layer. However, the pattern of appearance of this variant during development does not reflect a simple correlation between its presence and the state of differentiation. Therefore, these results are pertinent to current ideas on differentiation and the involvement of lysine-rich histones in the repression of eukaryotic genes.     

Neuroanatomy of morphine-modulating peptides

Antisera against two mammalian peptides related to the molluscan cardioexcitatory peptide Phe-Met-Arg-Phe-NH2 were used to locate immunoreactive neurons in the rat brain, nerve fibres and terminals in the spinal cord, sympathetic ganglion cells and adrenal chromaffin cells. Immunoreactivity for the newly characterised octa- and octadecapeptide was detected in nerve cell bodies in the hypothalamic area, including parts of the dorsomedial, periventricular and paraventricular nuclei, and in the nucleus tractus solitarii. Nerve terminals in the superficial laminae of the spinal cord were also immunoreactive for these peptides, while the sensory ganglia were nonreactive. Some principal ganglion cells in the superior cervical ganglia exhibited bright immunofluorescence for the peptides, and a few adrenal medullary cells were immunoreactive. The presence of these peptides in the substantia gelatinosa of the spinal cord suggests that they may be involved in sensory neurotransmission, especially in the mechanisms mediating pain. In the hypothalamo-hypophysial system these peptides may be involved in the regulation of hormonal systems. They may also act as co-transmitters in the sympathetic nervous system.     

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.     

Adenine nucleotide contents and energy charge of Azotobacter vinelandii grown at low phosphate concentration

The effect of a low phosphate concentration on intracellular adenine nucleotide content, oxygen consumption and poly--hydroxybutyrate deposition was investigated with N-free and NH ₄ ⁺ batch cultures of Azotobacter vinelandii. When the microorganisms were cultured under low-phosphate concentrations the cells contained much larger amounts of poly--hydroxybutyrate, but displayed lower oxygen consumption activities and energy charge values than did control cells. Also, the ratio ATP to ADP was much higher in control cells and the intracellular levels of ATP were lower in low-phosphate cells.     

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.