Lachemilla jaramilloi and L. talamanquensis spp. nov. (Rosaceae) from Ecuador and Costa Rica

Two new species of Lachemilla (Rosaceae) are described and illustrated. Lachemilla jaramilloi Romoleroux &Morales‐Briones from Ecuador is characterized by its decumbent habit, villous‐hirsute pubescence, long basal petiole, and deeply tri‐parted leaf blades. The flowers are sessile to subsessile and subtended by episepals, and the hypanthia elongated and glabrescent. Lachemilla talamanquensis Romoleroux & Morales‐Briones from Costa Rica is distinguished by its sericeous‐villous, ascending branches, sub‐sessile distal leaves, tri‐lobed leaf blades, forming whorls with the stipule. The flowers are solitary or arranged in few‐flowered inflorescences, with big, dark, villous hypanthia, containing several achenes.     

Roads to polyploidy: the megakaryocyte example.

Polyploidy, recognized by multiple copies of the haploid chromosome number, has been described in plants, insects, and in mammalian cells such as, the platelet precursors, the megakaryocytes. Several of these cell types reach high ploidy via a different cell cycle. Megakaryocytes undergo an endomitotic cell cycle, which consists of an S phase interrupted by a gap, during which the cells enter mitosis but skip anaphase B and cytokinesis. Here, we review the mechanisms that lead to this cell cycle and to polyploidy in megakaryocytes, while also comparing them to those described for other systems in which high ploidy is achieved. Overall, polyploidy is associated with an orchestrated change in expression of several genes, of which, some may be a result of high ploidy and hence a determinant of a new cell physiology, while others are inducers of polyploidization. Future studies will aim to further explore these two groups of genes.     

Expression of apurinic/apyrimidinic endonuclease-1 (APE-1) in H. pylori-associated gastritis, gastric adenoma, and gastric cancer

Background and Aim: Apurinic/apyrimidinic endonuclease‐1 (APE‐1) is a key enzyme in DNA base excision repair (BER), linked to cancer chemosensitivity. However, little is known about the localization of APE‐1 in Helicobacter pylori‐infected gastric mucosa or its role in the development of gastric cancer. To investigate the role of APE‐1 in the development of gastric cancer, we examined APE‐1 expression and localization in cultured cells and gastric biopsies from patients with H. pylori‐infected gastritis or gastric adenoma, and from surgically resected gastric cancer. Methods: APE‐1 mRNA and protein expression were determined in H. pylori (CagA+) water‐extract protein (HPWEP)‐stimulated MKN‐28 cells, gastric adenocarcinoma cell‐line (AGS) cells, and human peripheral macrophages by real‐time polymerase chain reaction and Western blot analysis. APE‐1 expression and 8‐OHdG as a measure of oxidative DNA damage were evaluated by immunostaining. Localization of APE‐1 and IκBα phosphorylation in gastric adenoma and gastric cancer tissues were evaluated by single‐ and double‐label immunohistochemistry. Results: In studies in vitro, HPWEP‐stimulation significantly increased APE‐1 mRNA expression levels in both MKN‐28 cells and human peripheral macrophages. Hypo/reoxygenation treatment significantly increased APE‐1 protein expression in HPWEP‐stimulated MKN‐28 cells. HPWEP stimulation significantly increased both APE‐1 expression and IκBα phosphorylation levels in MKN‐28 and AGS cells. In human tissues, APE‐1 expression in H. pylori‐infected gastritis without goblet cell metaplasia was significantly increased as compared to that in tissues from uninfected subjects. Eradication therapy significantly reduced both APE‐1 and 8‐OHdG expression levels in the gastric mucosa. APE‐1 expression was mainly localized in epithelial cells within gastric adenoma and in mesenchymal cells of gastric cancer tissues. APE‐1 expression in gastric cancer tissues was significantly reduced compared to that in H. pylori‐infected gastric adenoma, while 8‐OHdG index and IκBα phosphorylation levels did not differ between these two neoplastic tissue types. Co‐localization of APE‐1 and IκBα phosphorylation was observed not in gastric cancer cells but in gastric adenoma cells. Conclusion: H. pylori infection is associated with increased APE‐1 expression in human cell lines and in gastric tissues from subjects with gastritis and gastric adenomas. The observed distinct expression patterns of APE‐1 and 8‐OHdG in gastric adenoma and gastric cancer tissues may provide insight into the progression of these conditions and warrants further investigation.     

The reno-vascular A2B adenosine receptor protects the kidney from ischemia

Background

Acute renal failure from ischemia significantly contributes to morbidity and mortality in clinical settings, and strategies to improve renal resistance to ischemia are urgently needed. Here, we identified a novel pathway of renal protection from ischemia using ischemic preconditioning (IP).

Methods and Findings

For this purpose, we utilized a recently developed model of renal ischemia and IP via a hanging weight system that allows repeated and atraumatic occlusion of the renal artery in mice, followed by measurements of specific parameters or renal functions. Studies in gene-targeted mice for each individual adenosine receptor (AR) confirmed renal protection by IP in A1^−/−, A2A^−/−, or A3AR^−/− mice. In contrast, protection from ischemia was abolished in A2BAR^−/− mice. This protection was associated with corresponding changes in tissue inflammation and nitric oxide production. In accordance, the A2BAR-antagonist PSB1115 blocked renal protection by IP, while treatment with the selective A2BAR-agonist BAY 60–6583 dramatically improved renal function and histology following ischemia alone. Using an A2BAR-reporter model, we found exclusive expression of A2BARs within the reno-vasculature. Studies using A2BAR bone-marrow chimera conferred kidney protection selectively to renal A2BARs.

Conclusions

These results identify the A2BAR as a novel therapeutic target for providing potent protection from renal ischemia.     

Deletion of Cavin/PTRF causes global loss of caveolae, dyslipidemia, and glucose intolerance

Caveolae are specialized invaginations of the plasma membrane found in numerous cell types. They have been implicated as playing a role in a variety of physiological processes and are typically characterized by their association with the caveolin family of proteins. We show here by means of targeted gene disruption in mice that a distinct caveolae-associated protein, Cavin/PTRF, is an essential component of caveolae. Animals lacking Cavin have no morphologically detectable caveolae in any cell type examined and have markedly diminished protein expression of all three caveolin isoforms while retaining normal or above normal caveolin mRNA expression. Cavin-knockout mice are viable and of normal weight but have higher circulating triglyceride levels, significantly reduced adipose tissue mass, glucose intolerance, and hyperinsulinemia--characteristics that constitute a lipodystrophic phenotype. Our results underscore the multiorgan role of caveolae in metabolic regulation and the obligate presence of Cavin for caveolae formation.     

Low temperature enhances photosynthetic down-regulation in French bean (Phaseolus vulgaris L.) plants

The mechanisms of photosynthetic adaptation to different combinations of temperature and irradiance during growth, and especially the consequences of exposure to high light (2000 micro mol m(-2) s(-1) PPFD) for 5 min, simulating natural sunflecks, was studied in bean plants (Phaseolus vulgaris L.). A protocol using only short (3 min) dark pre-treatment was introduced to maximize the amount of replication possible in studies of chlorophyll fluorescence. High light at low temperature (10 degrees C) significantly down-regulated photosynthetic electron transport capacity [as measured by the efficiency of photosystem II (PSII)], with the protective acclimation allowing the simulated sunflecks to be used more effectively for photosynthesis by plants grown in low light. The greater energy dissipation by thermal processes (lower F(v)'/F(m)' ratio) at low temperature was related to increased xanthophyll de-epoxidation and to the fact that photosynthetic carbon fixation was more limiting at low than at high temperatures. A key objective was to investigate the role of photorespiration in acclimation to irradiance and temperature by comparing the effect of normal (21 kPa) and low (1.5 kPa) O(2) concentrations. Low [O(2)] decreased F(v)/F(m) and the efficiency of PSII (Phi(PSII)), related to greater PSII down-regulation in cold pre-treated plants, but minimized further inhibition by the mild 'sunfleck' treatment used. Results support the hypothesis that photorespiration provides a 'safety-valve' for excess energy.     

Structural definition of the neuromuscular system in the swimming-paddle opener muscle of blue crabs

Blue crabs are excellent swimmers, using their highly modified last pereiopods as sculling paddles. Hence, the hypertrophied paddle opener muscle was examined for adaptations of its motor innervation by an excitor and a specific inhibitor axon. The muscle has a uniform composition of slow fibers with long (6-12 microm) sarcomere lengths. Individual fibers are richly innervated with approximately two-thirds excitatory and one-third inhibitory innervation. The profuse excitatory innervation reflects the high activity levels of this motoneuron in swimming. Adaptation to sustained activity associated with swimming is also reflected in the motor nerve terminals by a high concentration of energy source, which is equally divided between glycogen granules and mitochondria, the former providing a more rapid source of energy. The excitor axon makes predominantly neuromuscular synapses, but also a few synapses onto the inhibitor axon. The location of these excitatory axoaxonal synapses suggests regional modulation of the inhibitor axon. The specific inhibitor axon makes less than two-thirds of its synapses with the muscle fiber, regulating contraction via postsynaptic inhibition. The remaining inhibitory synapses are onto the excitor axon, signaling very strong presynaptic inhibition. Such presynaptic inhibition will effectively decouple the opener muscle from the stretcher muscle even though both are innervated by a single excitor axon.     

Heparin-binding epidermal growth factor and its receptor ErbB4 mediate implantation of the human blastocyst

The mechanisms that mediate implantation of the human embryo remain poorly understood and represent a fundamental problem in reproductive biology. Candidate molecules that mediate and facilitate implantation have been identified in animal studies, and include heparin binding epidermal growth factor. Here we demonstrate a potential function for the transmembrane form of heparin-binding epidermal growth factor in mediating blastocyst attachment to the endometrium, in two different novel in vitro models for human implantation. Furthermore, we demonstrate specific localisation of the heparin-binding epidermal growth factor receptor ErbB4, on the surface of the trophectoderm in peri-implantation human blastocysts. Our data lead the way for further dissection of the molecular mechanisms of implantation of the human embryo, and have implications for infertility, in vitro fertilization and contraception.