Chromatin Organization and Remodeling of Interstitial Telomeric Sites During Meiosis in the Mongolian Gerbil (Meriones unguiculatus)

Telomeric DNA repeats are key features of chromosomes that allow the maintenance of integrity and stability in the telomeres. However, interstitial telomere sites (ITSs) can also be found along the chromosomes, especially near the centromere, where they may appear following chromosomal rearrangements like Robertsonian translocations. There is no defined role for ITSs, but they are linked to DNA damage-prone sites. We were interested in studying the structural organization of ITSs during meiosis, a kind of cell division in which programmed DNA damage events and noticeable chromatin reorganizations occur. Here we describe the presence of highly amplified ITSs in the pericentromeric region of Mongolian gerbil (Meriones unguiculatus) chromosomes. During meiosis, ITSs show a different chromatin conformation than DNA repeats at telomeres, appearing more extended and accumulating heterochromatin markers. Interestingly, ITSs also recruit the telomeric proteins RAP1 and TRF1, but in a stage-dependent manner, appearing mainly at late prophase I stages. We did not find a specific accumulation of DNA repair factors to the ITSs, such as γH2AX or RAD51 at these stages, but we could detect the presence of MLH1, a marker for reciprocal recombination. However, contrary to previous reports, we did not find a specific accumulation of crossovers at ITSs. Intriguingly, some centromeric regions of metacentric chromosomes may bind the nuclear envelope through the association to SUN1 protein, a feature usually performed by telomeres. Therefore, ITSs present a particular and dynamic chromatin configuration in meiosis, which could be involved in maintaining their genetic stability, but they additionally retain some features of distal telomeres, provided by their capability to associate to telomere-binding proteins.     

Modelling the acidifying activity profile of Lactobacillus bulgaricus cultures

A model that fully describes the typical pH(t) profile representing the lactic acid production kinetics of Lactobacillus bulgaricus cultures is reported. The model, a four-parameter function [pH = (A–D)/(1 + (t/C)^B) + D], is able to fit any change on the experimental pH-time curves, due to variations on the inoculum cell concentration of the culture. The four fitting parameters(A, B, C and D) of this model are closely related to the lactic acid fermentation and they have a physical meaning. Parameters A and D represent the initial and final pH of the culture, respectively. Parameter B is related to the slope of the linear decreasing region from the pH-time curve and C represents the time at which half of the total decrement of pH is achieved. The proposed model can be used not only for evaluating and comparing the acidifying capacity of homolactic cultures but also for predictions of final fermentation times.     

Characteristics and in vitro fertilizing ability of giant panda (Ailuropoda melanoleuca) frozen‐thawed epididymal spermatozoa obtained 4 hours postmortem: A case report

When Chu‐Lin, a male giant panda (studbook #249), died at Madrid Zoo, his reproductive tract was removed 4 hr postmortem and the epididymal spermatozoa were collected. Extended sperm were kept at 5°C for 4 hr, loaded into straws, and frozen for 7 min in liquid nitrogen vapor before the straws were plunged into liquid nitrogen. Two straws were thawed and evaluated. Sperm motility was assessed in fresh, refrigerated, and thawed spermatozoa (75%, 60%, 35%, respectively). Sperm viability and acrosome status were estimated using a triple‐stain technique (TST). The results showed 33% live sperm with intact acrosomes after thawing. A hypoosmotic swelling (HOS) test demonstrated the retention of membrane integrity in 72% of thawed sperm. To evaluate the in vitro fertilizing ability of thawed sperm, a sperm penetration assay (SPA) was performed. The values obtained for the percentage of penetration and the penetration index were 62% and 1.78 sperm/oocyte, respectively. The results obtained demonstrate that epididymal sperm recovered from a giant panda postmortem can be successfully cryopreserved. The sperm fertilizing ability demonstrated in vitro after thawing may provide a final opportunity for this male to contribute to the currently small germplasm reserves of this endangered species, and to reproduce in the future through assisted reproductive technology. Zoo Biol 23:279–285, 2004. © 2004 Wiley‐Liss, Inc.     

Localization of Nickel in Tissues of Streptanthus polygaloides Gray (Cruciferae) and Endemic Nickel Hyperaccumulators from California

The genus Streptanthus Nutt. is one of the most important indicators of ultramafic floras in western North America. This genus contains taxa that are endemic or tolerant of ultramafic soils. Streptanthus polygaloides is an annual nickel hyperaccumulator strictly confined to ultramafic soils throughout the Californian Sierra Nevada foothills. Nickel concentration in S. polygaloides populations was evaluated by elemental microanalysis using inductively coupled plasma mass spectrometry (ICP-MS). Representative samples of S. polygaloides roots, stems, leaves, flowers, and fruits were studied by scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray probe (SEM-EDX). Results show Ni accumulation values between 0.09 and 1.18 %, and a distribution pattern similar to that observed in other Ni hyperaccumulator taxa, with the leaf epidermis accumulating the largest concentrations.     

Synthesis and anti-inflammatory activity of three nitro chalcones

The aim of this study was to synthesize three nitro substituted chalcones and to evaluate their anti-inflammatory activity in the model of carrageenan induced edema in rats. The nitro chalcone were prepared by aldol condensation using of mechanical agitation and environmentally friendly solvents with 72–73% yields in approximately 2 h. The three structures were evaluated on biological activity at dose of 200 mg/kg and they showed anti-inflammatory protective effect by both oral and intraperitoneal administration, this effect was time dependent.     

Effect of semicarbazide on the surfactant phospholipid percentages during fetal and postnatal lung development in rat

1. The effect of 100 mg/kg of semicarbazide on phosphatidylcholine, phosphatidylethanolamine, sphingomyeline, phosphatidylserine and lysophosphatidylcholine of the pulmonary surfactant was studied in offspring of treated rats on the 10th day of gestation. 2. The relative percentages of phosphatidylcholine were smaller in the offspring of treated rats than in controls, but the opposite was observed with the other phospholipids. 3. Significant statistical differences at almost all ages studied were observed in phosphatidylcholine and phosphatidylethanolamine. 4. The ratio of phosphatidylcholine to sphingomyeline, an index of lung maturity, was smaller in the offspring of treated rats, with statistically significant differences just before birth and on the first day of life.     

De novo phosphatidylcholine synthesis is required for autophagosome membrane formation and maintenance during autophagy

ABSTRACT

Macroautophagy/autophagy can enable cancer cells to withstand cellular stress and maintain bioenergetic homeostasis by sequestering cellular components into newly formed double-membrane vesicles destined for lysosomal degradation, potentially affecting the efficacy of anti-cancer treatments. Using ¹³C-labeled choline and ¹³C-magnetic resonance spectroscopy and western blotting, we show increased de novo choline phospholipid (ChoPL) production and activation of PCYT1A (phosphate cytidylyltransferase 1, choline, alpha), the rate-limiting enzyme of phosphatidylcholine (PtdCho) synthesis, during autophagy. We also discovered that the loss of PCYT1A activity results in compromised autophagosome formation and maintenance in autophagic cells. Direct tracing of ChoPLs with fluorescence and immunogold labeling imaging revealed the incorporation of newly synthesized ChoPLs into autophagosomal membranes, endoplasmic reticulum (ER) and mitochondria during anticancer drug-induced autophagy. Significant increase in the colocalization of fluorescence signals from the newly synthesized ChoPLs and mCherry-MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3) was also found on autophagosomes accumulating in cells treated with autophagy-modulating compounds. Interestingly, cells undergoing active autophagy had an altered ChoPL profile, with longer and more unsaturated fatty acid/alcohol chains detected. Our data suggest that de novo synthesis may be required to increase autophagosomal ChoPL content and alter its composition, together with replacing phospholipids consumed from other organelles during autophagosome formation and turnover. This addiction to de novo ChoPL synthesis and the critical role of PCYT1A may lead to development of agents targeting autophagy-induced drug resistance. In addition, fluorescence imaging of choline phospholipids could provide a useful way to visualize autophagosomes in cells and tissues.