Multimodal Optical Microscopy Methods Reveal Polyp Tissue Morphology and Structure in Caribbean Reef Building Corals

An integrated suite of imaging techniques has been applied to determine the three-dimensional (3D) morphology and cellular structure of polyp tissues comprising the Caribbean reef building corals Montastraeaannularis and M. faveolata. These approaches include fluorescence microscopy (FM), serial block face imaging (SBFI), and two-photon confocal laser scanning microscopy (TPLSM). SBFI provides deep tissue imaging after physical sectioning; it details the tissue surface texture and 3D visualization to tissue depths of more than 2 mm. Complementary FM and TPLSM yield ultra-high resolution images of tissue cellular structure. Results have: (1) identified previously unreported lobate tissue morphologies on the outer wall of individual coral polyps and (2) created the first surface maps of the 3D distribution and tissue density of chromatophores and algae-like dinoflagellate zooxanthellae endosymbionts. Spectral absorption peaks of 500 nm and 675 nm, respectively, suggest that M. annularis and M. faveolata contain similar types of chlorophyll and chromatophores. However, M. annularis and M. faveolata exhibit significant differences in the tissue density and 3D distribution of these key cellular components. This study focusing on imaging methods indicates that SBFI is extremely useful for analysis of large mm-scale samples of decalcified coral tissues. Complimentary FM and TPLSM reveal subtle submillimeter scale changes in cellular distribution and density in nondecalcified coral tissue samples. The TPLSM technique affords: (1) minimally invasive sample preparation, (2) superior optical sectioning ability, and (3) minimal light absorption and scattering, while still permitting deep tissue imaging.     

Chromosomal translocations in the evolution of Amorphophallus bonaccordensis from A. hohenackeri

In present study we have made an attempt to trace possible lines in the evolution of A. bonaccordensis separating from A. hohenackeri, where translocations at the chromosomal level could have resulted in a shift of the habitat during evolution of A. bonaccordensis. This species is occurring as an endemic taxon at a higher altitude than it may have been the case with its ancestor that occupied lower altitudes and possibly a broader ecological niche. Morphological and physiological differences between the recent two closely related taxa, in spadix and appendix characters, corm flesh colour, pollen morphology and oxalate content, may be attributed also to the translocation at the cytological level. Detailed karyotype studies have been done in these Amorphophallus species from Southern Western Ghats, where they are critically endangered in their habitats, indicating that the chromosome number in both species is 2n = 26. In both of them there is a considerable variation in the karyotype symmetry. Accordingly, A. hohenackeri is placed under 2B whereas A. bonaccordensis fits well to 3B category of Stebbins’ classification. The highly endemic species Amorphophallus bonaccordensis, known only from the type locality, is supposed to have originated from A. hohenackeri via many cycles of translocations resulting in heteromorphic, nearly telocentric chromosomes, peculiar satellites, and many mitotic abnormalities like bridges, laggards, micronuclei and heteromorpic bivalents, terminalised chiasmata, supernumerary chromosomes and multinucleate cells at meiosis. ISSR analysis with 17 ISSR primers revealed a higher number of unique bands in A. bonaccordensis. Also the ISSR data, when correlated with the karyotype data, indicate that A. bonaccordensis has probably originated from A. hohenackeri due to chromosomal rearrangements and high mutation of the SSR loci.     

Efficiency of open channel blockers of neuronal nicotinic acetylcholine receptors as estimated from the structure/activity relationship

The participation of definite molecular fragments of bis-cationic ammonium compounds in their blocking effect upon neuronal nicotinic acetylcholine receptors (nAChRs) was deduced from the relationship between the blocking efficacy and three-dimensional molecular models of such compounds that have different fragments. The data on the structure and activity of 15 channel blockers were used for this purpose; predicted blocking effects of the substances were calculated. The correlation coefficients between the blocking activity of the compounds and their predicted efficacy were statistically significant (P > 0.95). The results suggest that HCNCCCCCNCH and HCCNCCCCCNCH fragments (atom chains) with the dimensions of 1.42 and 1.36 nm, respectively, provide the most positive contribution, while a HCNCCCCCNCH fragment with the dimension of 1.36 nm corresponds to highly negative contribution to the blocking activity of compounds. Using the data obtained, we identified the optimum compound structures. The mechanism of the blocking effect upon nAChRs is discussed. Neirofiziologiya/Neurophysiology, Vol. 39, Nos. 4/5, pp. 364–370, July–October, 2007.     

Spontaneous Documentation of Bidirectional Block During Pulmonary Vein Isolation - Keep an Eye on the Electrograms!

In the present case, we describe the abrupt transformation of intra-pulmonary vein activity from rapid firing to dissociated ectopic activity during sinus rhythm, as an easily identifiable, though rare to encounter, sign which documents the achievement of bidirectional block.     

Flexible species distribution modelling methods perform well on spatially separated testing data

Aim

To assess whether flexible species distribution models that perform well at nearby testing locations still perform strongly when evaluated on spatially separated testing data.

Location

Australian Wet Tropics (AWT), Ontario, Canada (CAN), north-east New South Wales, Australia (NSW), New Zealand (NZ), five countries of South America (SA), and Switzerland (SWI).

Time period

Most species data were collected between 1950 and 2000.

Major taxa studied

Birds, mammals, plants and reptiles.

Methods

We compared 10 species distribution modelling methods with varying flexibility in terms of the allowed complexity of their fitted functions [boosted regression trees (BRT), generalized additive model (GAM), multivariate adaptive regression splines (MARS), maximum entropy (MaxEnt), support vector machine (SVM), variants of generalized linear model (GLM) and random forest (RF), and an Ensemble model]. We used established practices for model selection to avoid overfitting, including parameter tuning in learning methods. Models were trained on presence–background data for 171 species and tested on presence–absence data. Training and testing data were separated using both random and spatial partitioning, the latter based on 75-km blocks. We calculated the average performance and mean rank of the methods (focussing on the area under the receiver operating characteristic and precision-recall gain curves, and correlation) and assessed the statistical significance of the differences between them.

Results

The ranking of methods did not change when evaluated on spatially separated testing data. Methods with the strongest predictive performance were nonparametric methods known to be flexible. An ensemble formed by averaging predictions of five pre-selected modelling methods was the best model in both random and spatial partitioning, followed by MaxEnt and a variant of random forest.

Main conclusions

Whilst some modellers expect methods limited to simple smooth functions to predict better spatially separated data, we found no evidence of that using blocks of 75 km. We conclude that flexible models that are tuned well enough to avoid overfitting are effective at predicting to spatially distinct areas.     

Cytogenetic effects of sildenafil citrate (Viagra) on SWR/J mouse bone marrow cells

The present study was conducted to investigate the cytogenetic effects of sildenafil citrate in SWR/J mouse bone marrow cells. Thirty-six males and 36 females were used and divided into four groups. Each group contained 18 animals (9 males and 9 females), weighing 30–35 g. These animals were orally administered with a single dose of 13, 26 or 40 mg/kg sildenafil citrate solution. A control group received normal saline in an identical condition. The animals were sacrificed at 12, 24 or 48 h, after the treatment. Chromosome aberrations were investigated in 50 metaphases per animal.No significant differences in the percentages of mitotic indices or in the frequencies of chromosome aberrations were observed between treated male and female mice at any doses or at any time intervals used, therefore, data from the two sexes were pooled when analyzed statistically.No significant (p < 0.05) differences in the percentages of mitotic indices or in the frequencies of chromosome aberrations were observed between sildenafil citrate-treated groups and the control group at any doses or at any time intervals used. However, the percentages of centromeric adhesions increased significantly (p < 0.01) in treated groups as compared with the control group at all doses and at all time intervals used.In conclusion, the results of the present study suggest that sildenafil citrate does not have cytogenetic effects on mouse bone marrow cells, but the centromeric adhesions induced by this drug need further studies to confirm them and to investigate the possible mechanism(s) responsible for such effect.     

Uncoupling of growth and cytological development in egg follicles ofHeteropeza pygmaea (Dipt., Cecidomyiidae)

Summary Oogenesis of egg follicles in paedogenetic reproduction of the gall midgeHeteropeza pygmaea is accompanied by a relatively slight growth of the oocyte. Egg growth takes place mainly during embryonic development. The nurse chamber in the egg follicle degenerates only at the beginning of embryogenesis. When ovaries of the female larvae are cultured in vitro under male-determining conditions, the ovaries produce mostly male-determined egg follicles. These follicles show nurse chamber degeneration and they grow to about the size of an egg in late cleavage division or blastoderm stage developing in situ, but cytological development invariably stops at the first or second meiotic division. Thus, growth and cytological development in such follicles are uncoupled. The presence of a meiotic block in paedogenetically developing follicles ofH. pygmaea gives a clue to the mode of evolution of paedogenetic reproduction.Dedicated to Professor Dr. Hans Bauer on the occasion of his 75th birthday     

Backward chromosome movement in anaphase, after irradiation of kinetochores or kinetochore fibres

Summary We used an ultraviolet microbeam to irradiate kinetochores, or to irradiate kinetochore fibres just in front of kinetochores, in anaphase crane-fly spermatocytes. Forward movements were blocked after most irradiations, but in 7 cells the associated anaphase half-bivalents moved backward, toward their partner half-bivalents, with speeds faster than poleward movements. The occurrence of backward movement suggests that there may be mechanical connections between separating half-bivalents. We have been unable to find conditions to obtain these results reproducibly.