Evolutionary stability of sex chromosomes in snakes

Amniote vertebrates possess various mechanisms of sex determination, but their variability is not equally distributed. The large evolutionary stability of sex chromosomes in viviparous mammals and birds was believed to be connected with their endothermy. However, some ectotherm lineages seem to be comparably conserved in sex determination, but previously there was a lack of molecular evidence to confirm this. Here, we document a stability of sex chromosomes in advanced snakes based on the testing of Z-specificity of genes using quantitative PCR (qPCR) across 37 snake species (our qPCR technique is suitable for molecular sexing in potentially all advanced snakes). We discovered that at least part of sex chromosomes is homologous across all families of caenophidian snakes (Acrochordidae, Xenodermatidae, Pareatidae, Viperidae, Homalopsidae, Colubridae, Elapidae and Lamprophiidae). The emergence of differentiated sex chromosomes can be dated back to about 60 Ma and preceded the extensive diversification of advanced snakes, the group with more than 3000 species. The Z-specific genes of caenophidian snakes are (pseudo)autosomal in the members of the snake families Pythonidae, Xenopeltidae, Boidae, Erycidae and Sanziniidae, as well as in outgroups with differentiated sex chromosomes such as monitor lizards, iguanas and chameleons. Along with iguanas, advanced snakes are therefore another example of ectothermic amniotes with a long-term stability of sex chromosomes comparable with endotherms.     

Genetic variability in sodium-glucose cotransporter 2 influences glycemic control and risk for diabetic retinopathy in type 2 diabetes patients

BackgroundGluconeogenesis and renal glucose excretion in kidneys both play an important role in glucose homeostasis. Sodium-glucose cotransporter (SGLT2), coded by the SLC5A2 gene is responsible for reabsorption up to 99% of the filtered glucose in proximal tubules. SLC5A2 genetic polymorphisms were suggested to influence glucose homeostasis. We investigated if common SLC5A2 rs9934336 polymorphism influences glycemic control and risk for macro or microvascular complications in Slovenian type 2 diabetes (T2D) patients.MethodsAll 181 clinically well characterized T2D patients were genotyped for SLC5A2 rs9934336 G>A polymorphism. Associations with glycemic control and T2D complications were assessed with nonparametric tests and logistic regression.ResultsSLC5A2 rs9934336 was significantly associated with increased fasting blood glucose levels (P<0.001) and HbA1c levels under the dominant genetic model (P=0.030). After adjustment for T2D duration, significantly higher risk for diabetic retinopathy was present in carriers of at least one polymorphic SLC5A2 rs9934336 A allele compared to non-carriers (OR=7.62; 95%CI=1.65-35.28; P=0.009).ConclusionsOur pilot study suggests an important role of SLC5A2 polymorphisms in the physiologic process of glucose reabsorption in kidneys in T2D patients. This is also the first report on the association between SLC5A2 polymorphism and diabetic retinopathy.     

The effect of dietary selenium supplementation on cadmium absorption and retention in suckling rats

Selenium (Se) reduces cadmium (Cd) toxicity in adult animals, but its effects in newborn animals are still unknown. This study investigated Cd (as CdCl₂) absorption, distribution, and retention in suckling rats receiving oral Se supplementation (as Na₂SeO₃) in equimolar doses (8 μmol Cd and/or Se per kg b.w./day). Selenium was given either before and during Cd exposure (Se_pre + Cd group; pre-treatment group) or only during Cd exposure (Se + Cd group). Rats were treated from postnatal day (PND) 6–14 as follows: controls (H₂O, PND 6–14), Se (PND 10–14), Cd (PND 10–14), Se_pre + Cd (Se PND 6–14 + Cd PND 10–14) and Se + Cd (Se + Cd PND 10–14). Selenium supplementation, especially pre-treatment, decreased Cd levels in the blood, brain, liver and kidney of suckling rats. Selenium levels in plasma, brain, and kidney also decreased. These findings suggest that higher Se intake could efficiently reduce Cd retention during the suckling period.     

Stimulation of prolactin synthesis and of adenosine 3':5'-cyclic phosphate formation by prostaglandins and thyroliberin in cultured rat pituitary cells.

1. The effects of prostaglandins E2 and F2alpha on prolactin synthesis were examined in a clonal strain of rat pituitary tumour cells, and compared with those of thyroliberin. 2. The prostaglandins and thyroliberin gave a dose-related and time-dependent stimulation of prolactin synthesis. The maximal effects (about twofold increases) were observed after 54h of treatment with 25nM-prostaglandin E2 and 2.5nM-prostaglandin F2alpha. A similar stimulation of prolactin synthesis was observed after 250nM-thyroliberin. The combined treatment with prostaglandins and thyroliberin did not increase prolactin synthesis over and above that obtained with each compound alone. 3. After removal of prostaglandins E2 and F2alpha there was a complete reversal of prolactin synthesis to pre-stimulation values 18h later (t1/2less than or equal to 9h). The rapid reversible effect of prostaglandins was in contrast with that of thyroliberin, where prolactin synthesis returned to control values with a t1/2 of about 42 h. 4. Prostaglandin E2 (5mum) and thyroliberin (5mum) increased cellular concentrations of cyclic AMP eight- and four-fold respectively. Maximal effects were observed after 2-5min of incubation. The increases in cyclic AMP were biphasic; normal values were obtained 60 min after the start of incubation with prostaglandin E2 or thyroliberin. 5. The dose/response curve showed that prostaglandin E2 caused maximal increase of cyclic AMP at 50nM. Concentrations of prostagland in E2 that caused half-maximal stimulation of cyclic AMP accumulation and of prolactin synthesis were 4 and 5nM respectively. 6. Combined treatment with prostaglandin E2 and thyroliberin in concentrations that separately caused maximal cyclic AMP increases did not result in a further increase in this cyclic nucleotide. 7. These results are consistent with a role of cyclic AMP in mediating the effects or prostaglandins and thyroliberin on prolactin synthesis. However, if cyclic AMP is involved as a common intracellular mediator of prolactin synthesis, it cannot alone explain all the effects of prostaglandins and thyroliberin in this cell system.     

Hydroponic systems: exploring the balance between co-cultivation of Chlorella vulgaris and Swiss chard (Beta vulgaris L. subsp. cicla)

Journal of Applied Phycology - Co-cultivation of plants and microalgae represents an optimized production method which is less resource intense and it is ecologically correct and clean....     

CTCF binding site sequence differences are associated with unique regulatory and functional trends during embryonic stem cell differentiation

CTCF (CCCTC-binding factor) is a highly conserved multifunctional DNA-binding protein with thousands of binding sites genome-wide. Our previous work suggested that differences in CTCF’s binding site sequence may affect the regulation of CTCF recruitment and its function. To investigate this possibility, we characterized changes in genome-wide CTCF binding and gene expression during differentiation of mouse embryonic stem cells. After separating CTCF sites into three classes (LowOc, MedOc and HighOc) based on similarity to the consensus motif, we found that developmentally regulated CTCF binding occurs preferentially at LowOc sites, which have lower similarity to the consensus. By measuring the affinity of CTCF for selected sites, we show that sites lost during differentiation are enriched in motifs associated with weaker CTCF binding in vitro. Specifically, enrichment for T at the 18^th position of the CTCF binding site is associated with regulated binding in the LowOc class and can predictably reduce CTCF affinity for binding sites. Finally, by comparing changes in CTCF binding with changes in gene expression during differentiation, we show that LowOc and HighOc sites are associated with distinct regulatory functions. Our results suggest that the regulatory control of CTCF is dependent in part on specific motifs within its binding site.     

Molecular Characterization of Recombinant Mus a 5 Allergen from Banana Fruit

Allergy to banana fruit appears to have become an important cause of fruit allergy in Europe. Among five allergens that have been found, beta-1,3-glucanase denoted as Mus a 5 was identified as a candidate allergen for the component-resolved allergy diagnosis of banana allergy. Because of the variations in protein levels in banana fruit, in this study Mus a 5 was produced as a fusion protein with glutathione-S-transferase in Escherichia coli. The recombinant Mus a 5 was purified under native conditions by a combination of affinity, ion-exchange, and reversed phase chromatography. N-terminal sequence was confirmed by Edman degradation and 55 % of the primary structure was identified by mass fingerprint, while the secondary structure was assessed by circular dichroism spectroscopy. IgG reactivity of recombinant protein was shown in 2-D immunoblot with anti-Mus a 5 antibodies, while IgG and IgE binding to natural Mus a 5 was inhibited with the recombinant Mus a 5 in immunoblot inhibition test. IgE reactivity of recombinant Mus a 5 was shown in ELISA within a group of ten persons sensitized to banana fruit. Recombinant Mus a 5 is a novel reagent suitable for the component-resolved allergy diagnosis of banana allergy.     

Ultrastructure of the kidney of a South American caecilian,Typhlonectes compressicaudus (Amphibia,Gymnophiona)

Summary The ultrastructure of the distal nephron, the collecting duct and the Wolffian duct was studied in a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona) by transmission and scanning electron microscopy (TEM, SEM). The distal tubule (DT) is made up of one type of cell that has a well-developed membrane labyrinth established both by interdigitating processes and by interlocking ramifications. The processes contain large mitochondria, the ramifications do not. The tight junction is shallow and elongated by a meandering course. The connecting tubule (CNT) is composed of CNT cells proper and intercalated cells, both of which are cuboidal in shape. The CNT cells are characterized by many lateral interlocking folds. The intercalated cells have a dark cytoplasm densely filled with mitochondria. Their apical cell membrane is typically amplified by microplicae beneath which a layer of globular particles (studs) is found. The collecting duct (CD) is composed of principal cells and intercalated cells, again both cuboidal in shape. The CD epithelium is characterized by dilated intercellular spaces, which are often filled with lateral microfolds projecting from adjacent principal cells. The apical membrane is covered by a prominent glycocalyx. The intercalated cells in the CD are similar to those in the CNT. The Wolffian duct (WD) has a tall pseudostratified epithelium established by WD cells proper, intercalated cells and basal cells. The WD cells contain irregular-shaped dense granules located beneath the apical cell membrane. The intercalated cells of the WD have a dark cytoplasm with many mitochondria; their nuclei display a dense chromatin pattern.Research fellow of the Alexander von Humboldt Foundation