Adenosine mediates transforming growth factor-beta 1 release in kidney glomeruli of diabetic rats

Up regulation of the transforming growth factor-beta 1 (TGF-β1) axis has been recognized as a pathogenic event for progression of glomerulosclerosis in diabetic nephropathy. We demonstrate that glomeruli isolated from diabetic rats accumulate up to sixfold more extracellular adenosine than normal rats. Both decreased nucleoside uptake activity by the equilibrative nucleoside transporter 1 and increased AMP hydrolysis contribute to raise extracellular adenosine. Ex vivo assays indicate that activation of the low affinity adenosine A_2B receptor subtype (A_2BAR) mediates TGF-β1 release from glomeruli of diabetic rats, a pathogenic event that could support progression of glomerulopathy when the bioavailability of adenosine is increased.     

Salinity and germination of annual Melilotus from the Guadalquivir delta (SW Spain)

The germination response to NaCl treatments has been studied in Melilotus seed populations collected from saline and non-saline soils in the Guadalquivir delta. The rank orders for salt tolerance and seed weight were the same in the threeMelilotus species living in this area:Melilotus messanensis>M. segetalis>M. indica. Within the species, differences in germination response to salinity were found inM. indica (6 populations) andM. segetalis (8 populations). The relationship between salt tolerance during germination and salinity of maternal habitat is discussed.     

A descriptive study of some Antarctic notaspidean opisthobranchs (Gastropoda), with description of a new genus and species

During the expedition “ANTARTIDA 9101”, organized by the Spanish Oceanographic Institute to the South Orkney Islands, four specimens of notaspidean gastropods were collected. Three of them have been identified as Bathyberthella antarctica Willan and Bertsch, 1987. However, one specimen, although externally similar to B. antarctica, had an internal anatomy exhibiting features that have enabled us to consider it to be a new genus and species. This new taxon is characterized by the presence of jaws without mandibular elements, and a vaginal gland that partially surrounds the distal region of the vaginal duct. In this paper the new genus and species is described. Additional anatomical data of the specimens of B. antarctica collected during the expedition are also included.     

Coastal intrusion of copepods: mechanisms and consequences on the population biology of Rhincalanus nasutus

In contrast to its usual habitat as a copepod that may occurin shelf or slope waters with low oxygen content between depthsfrom the surface to >2000 m, Rhincalanus nasutus was foundin a shallow (<60 m) embayment, the Arauco Gulf in Chile.Here, we document the complex life history of this copepod wheredid and ontogenetic vertical migratory behavior was co-ordinatedwith the circulation pattern which helped to retain a summerresident population in the vicinity of the gulf. With the onsetof the upwelling season in the southern summer, the mid-depthEquatorial Sub Surface Waters intrude into the gulf, leadingto the formation of a strong thermocline at 10–20 m andthe development of a two-layer circulation pattern. CopepoditesI, C.II and C.III (first stage to exhibit migratory behavior)were found within the gulf in the layer where the net transportwas at a minimum while chlorophyll-a concentrations were ata maximum. Older stages (C.IV-C.VI females and males) migratefrom their daytime depth in the bottom, shoreward-moving, low-oxygenlayer, to their night-time depth in the shallow seaward-movinglayer. The population of copepods retained in the area thuslyreproduce, as reflected in the sequential pulses of differentdevelopmental stages. Because coastal intrusions such as thisof R.nasutus have been documented for several other speciesduring the seasons of maximum phytoplankton production (upwelling),they may form part of a more widespread reproductive strategyof the larger zooplankton of coastal upwelling systems thanpreviously suspected.     

The lepidopteran mitochondrial control region: structure and evolution

For several species of lepidoptera, most of the approximately 350-bp mitochondrial control-region sequences were determined. Six of these species are in one genus, Jalmenus; are closely related; and are believed to have undergone recent rapid speciation. Recent speciation was supported by the observation of low interspecific sequence divergence. Thus, no useful phylogeny could be constructed for the genus. Despite a surprising conservation of control-region length, there was little conservation of primary sequences either among the three lepidopteran genera or between lepidoptera and Drosophila. Analysis of secondary structure indicated only one possible feature in common--inferred stem loops with higher-than-random folding energies-- although the positions of the structures in different species were unrelated to regions of primary sequence similarity. We suggest that the conserved, short length of control regions is related to the observed lack of heteroplasmy in lepidopteran mitochondrial genomes. In addition, determination of flanking sequences for one Jalmenus species indicated (i) only weak support for the available model of insect 12S rRNA structure and (ii) that tRNA translocation is a frequent event in the evolution of insect mitochondrial genomes.      

Glutamine repeats and inherited neurodegenerative diseases: molecular aspects

Several dominantly inherited, late onset, neurodegenerative diseases are due to expansion of CAG repeats, leading to expansion of glutamine repeats in the affected proteins. These proteins are of very different sizes and, with one exception, show no sequence homology to known proteins or to each other; their functions are unknown. In some, the glutamine repeat starts near the N-terminus, in another near the middle and in another near the C-terminus, but regardless of these differences, no disease has been observed in individuals with fewer than 37 repeats, and absence of disease has never been found in those with more than 41 repeats. Protein constructs with more than 41 repeats are toxic to E. coli and to CHO cells in culture, and they elicit ataxia in transgenic mice. These observations argue in favour of a distinct change of structure associated with elongation beyond 37–41 glutamine repeats. The review describes experiments designed to find out what these structures might be and how they could influence the properties of the proteins of which they form part. Poly- -glutamines form pleated sheets of β-strands held together by hydrogen bonds between their amides. Incorporation of glutamine repeats into a small protein of known structure made it associate irreversibly into oligomers. That association took place during the folding of the protein molecules and led to their becoming firmly interlocked by either strand- or domain-swapping. Thermodynamic considerations suggest that elongation of glutamine repeats beyond a certain length may lead to a phase change from random coils to hydrogen-bonded hairpins. Possible mechanisms of expansion of CAG repeats are discussed in the light of looped DNA model structures.     

Modulation of the affinity of the vasopressin receptor by magnesium ions.

The binding of [3H]vasopressin (AVP) and the 125I-labelled vasopressin antagonist (VP-AT) d(CH2)5[Tyr2(Me),Tyr9(NH2)]AVP to rat liver membranes was examined with or without the addition of milimolar concentrations of divalent cations. The binding of vasopressin was enhanced by Mg2+ and Co2+ and markedly decreased by EGTA. The addition of EGTA and Mg2+ together restored the binding to a value similar to that of Mg2+ alone. On the contrary, the addition of Mg2+, Co2+, EGTA, and the combination of EGTA and Mg2+ decreased the binding of VP-AT to rat liver membranes. Kinetic analyses showed that Mg2+ increased the Kd twofold for VP-AT; that is from 0.13 nM to 0.28 nM. Moreover, it showed that the receptor with or without the addition of Mg2+ consists of a single population of binding sites, indicating that the receptor is switched from a high affinity to a low affinity state for VP-AT in the presence of 10 mM Mg2+. GTP gamma S was unable to block the effect of Mg2+ on the binding of VP-AT. These results suggest that this divalent cation interacts with receptor itself producing a conformational changes which thus modulates the affinity of the receptor.     

Development of cell surface saccharides on embryonic pancreatic cells

Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life.