The Spectral Diversity of Resting-State Fluctuations in the Human Brain

In order to assess whole-brain resting-state fluctuations at a wide range of frequencies, resting-state fMRI data of 20 healthy subjects were acquired using a multiband EPI sequence with a low TR (354 ms) and compared to 20 resting-state datasets from standard, high-TR (1800 ms) EPI scans. The spatial distribution of fluctuations in various frequency ranges are analyzed along with the spectra of the time-series in voxels from different regions of interest. Functional connectivity specific to different frequency ranges (<0.1 Hz; 0.1–0.25 Hz; 0.25–0.75 Hz; 0.75–1.4 Hz) was computed for both the low-TR and (for the two lower-frequency ranges) the high-TR datasets using bandpass filters. In the low-TR data, cortical regions exhibited highest contribution of low-frequency fluctuations and the most marked low-frequency peak in the spectrum, while the time courses in subcortical grey matter regions as well as the insula were strongly contaminated by high-frequency signals. White matter and CSF regions had highest contribution of high-frequency fluctuations and a mostly flat power spectrum. In the high-TR data, the basic patterns of the low-TR data can be recognized, but the high-frequency proportions of the signal fluctuations are folded into the low frequency range, thus obfuscating the low-frequency dynamics. Regions with higher proportion of high-frequency oscillations in the low-TR data showed flatter power spectra in the high-TR data due to aliasing of the high-frequency signal components, leading to loss of specificity in the signal from these regions in high-TR data. Functional connectivity analyses showed that there are correlations between resting-state signal fluctuations of distant brain regions even at high frequencies, which can be measured using low-TR fMRI. On the other hand, in the high-TR data, loss of specificity of measured fluctuations leads to lower sensitivity in detecting functional connectivity. This underlines the advantages of low-TR EPI sequences for resting-state and potentially also task-related fMRI experiments.     

Towards a more transparent use of the potential natural vegetation concept – an answer to Chiarucci et al.

In this paper, the concerns of Chiarucci et al. ( 2010 ) regarding use of the potential natural vegetation (PNV) concept are addressed, as voiced in the forum section of the Journal of Vegetation Science. First, we rectify some unfounded expectations concerning PNV, including a relationship with prehuman vegetation and phytosociology. Second, we point out issues that pose considerable challenges in PNV and require common agreement. Here, we address the issue of time and disturbance. We propose to use the static PNV concept as a baseline, a null model for landscape assessment and in comparisons. Instead of changing the PNV concept itself, we introduce a new term, potential future natural vegetation (PFV) to cover estimations of potential successional outcomes. Finally, we offer a new view of PNV with which we intend to make the use of PNV estimates more transparent. We formalize the PNV theory into a partial cause‐effect model of vegetation that clearly states which effects on vegetation are factored out during its estimation. Further, we also propose to assess PNV in a probabilistic setting, rather than providing a single estimate for one location. This multiple PNV would reflect our uncertainty about the vegetation entity that could persist at the locality concerned. Such uncertainty arises from the overlap of environmental preferences of different mature vegetation types. Thus reformulated, we argue that the PNV concept has much to offer as a null model, especially in landscape ecology and in site comparisons in space and time.     

In vitro pollination in poplar of section Populus

Two methods of in vitro pollination of aspen were tested and compared, first with moist pollen by transferring swollen pollen grains from a wet agar surface to the stigma and, second, using dry pollen grains. In vitro pollination with dry pollen grains appeared to be more efficient and this method was applied in three subsequent years. Additionally, pollination was performed with selected pollen grains in order to obtain triploid plants. Diploid pollen was induced by heat-treatment of pollen mother cells, but the enrichment of unreduced pollen from natural pollen mixtures was also successful. The selection of diploid pollen, which is larger in diameter than haploid pollen, was performed by sieving using micro sieves. Five triploid plants from different poplar combinations were obtained from 1,227 zygotic embryos cultured after in vitro pollination of 2,676 ovaries with dry pollen over 3?years. Embryo rescue was used to facilitate the development of immature zygotic embryos. The results of this study demonstrate the possibility to effect pollination using selected single pollen grains with the help of in vitro techniques.     

Purification and characterization of Go alpha and three types of Gi alpha after expression in Escherichia coli

Complementary DNAs for the G protein alpha subunits Gi alpha 1, Gi alpha 2, Gi alpha 3, and Go alpha were expressed in Escherichia coli, and the four proteins were purified to homogeneity. The recombinant proteins exchange and hydrolyze guanine nucleotide, are ADP-ribosylated by pertussis toxin, and interact with beta gamma subunits. The rates of dissociation of GDP from Gi alpha 1 and Gi alpha 3 (0.03 min-1) are an order of magnitude slower than that from rGo alpha; release of GDP from Gi alpha 2 is also relatively slow (0.07 min-1). However, the values of kcat for the hydrolysis of GTP by rGo alpha and the three rGi alpha proteins are approximately the same, about 2 min-1 at 20 degrees C. The recombinant proteins restore inhibition of Ca2+ currents in pertussis toxin-treated dorsal root ganglion neurons in response to neuropeptide Y and bradykinin, indicating that the proteins can interact functionally with all necessary components of at least one signal transduction system. The two different receptors function with different arrays of G proteins to mediate their responses, since all four G proteins restored responses to bradykinin, while Gi alpha 2 was inactive with neuropeptide Y. Despite these results, high concentrations of activated Gi alpha proteins are without effect on adenylyl cyclase activity, either in the presence or absence of forskolin or Gs alpha, the G protein that activates adenylyl cyclase. These results are consistent with the hypothesis that G protein beta gamma subunits are primarily responsible for inhibition of adenylyl cyclase activity.     

Metabolism of 15-hydroxy-5,8,11,13-eicosatetraenoic acid by MOLT-4 cells and blood T-lymphocytes

MOLT-4 lymphocytes metabolize 15-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE) via beta-oxidation with retention of the hydroxyl group at the omega 6-carbon atom. 15-HETE oxidation is accompanied by the time-dependent accumulation of both beta-hydroxy acids and metabolites produced by repetitive cycles of the beta-oxidation spiral. Detection of 7-hydroxy-5-dodecenoic acid shows that these cells continue to beta-oxidize the substrate when the conjugated diene is allylic to a hydroxyl group. When 15-HETE was the substrate, it was also possible to detect 12-hydroxy-5,8,10-heptadecatrien-1-al and 3,15-dihydroxy-8,11,13-eicosatrienoic acid. The former product may be produced by alpha-oxidation of 13-hydroxy-6,9,11-octadecatrienoic acid followed by its decarboxylation. Detection of a 20-carbon metabolite, lacking a double bond at position 5, suggests that an intermediate of beta-oxidation was used as a substrate for chain elongation. When 13-hydroxy-6,9,11-octadecatrienoic acid was used as a substrate, it was indeed possible to detect 3,15-dihydroxy-8,11,13-eicosatrienoic acid as well as 15-hydroxy-8,11,13-eicosatrienoic acid. In addition, 13-hydroxy-6,9,11-octadecatrienoic acid was a precursor for the biosynthesis of both 14-hydroxy-7,10,12-nonadecatrien-1-al and 1,14-dihydroxy-7,10,12-nonadecatriene. These studies with MOLT-4 cells as well as with T-lymphocytes isolated from blood show that products of the 15-lipoxygenase pathway are metabolized with the accumulation of a variety of compounds. Since 15-HETE has been implicated as a modulator of T-cell function, these findings raise the possibility that the newly described metabolites may be involved in regulating lymphocyte function.     

Use of the point-score system for breeding soundness examination in yearling Dorset, Hampshire and Suffolk rams

Performance tests were conducted on 583 purebred Dorset, Hampshire and Suffolk yearling rams at the Virginia Ram Test Station from 1986 to 1989. Birth dates at entry and weights (lbs) at entry and end-of-test were recorded for each ram. Entry and exit scrotal circumference (SC; cm) data were recorded for each year of the study. Breeding soundness examination (BSE) data at entry were obtained for only the last two years (1988-1989). The BSE followed the basic format recommended by the Society for Theriogenology. The number of seminal white blood cells per (100x) microscope field (WBC/LPF) were also recorded for each ram's ejaculate. Classification of rams into breeding groups (satisfactory, questionable and unsatisfactory) were made using a point-scale system based upon values obtained from SC, sperm motility and morphology assessments. Between-breed differences were noted for age at entry to the test station, weight per day of age, final weight at the end of the test period and average daily gain. Suffolk rams were younger in age (P0.05). Overall the percentage of rams classified as unsatisfactory, questionable and satisfactory was 11.8, 16.5 and 71.7, respectively. Rams with more than 10 WBC/LPF had significantly smaller SC at entry (P<0.01) than rams with less than 10 WBC/LPF. Most of the differences (75%) in BSE scores in this study were contributed by differences in semen quality (spermatozoal motility and morphology) not by differences in SC.     

Metabolism of polyunsaturated (n-3) fatty acids by monkey seminal vesicles: isolation and biosynthesis of omega-3 epoxides.

Monooxygenases of monkey seminal vesicles can metabolize arachidonic acid (20:4(n-6)) by w3-hydroxylation to 18(R)-hydroxyeicosatetraenoic acid (18(R)-HETE) and eicosapentaenoic acid (20:5(n-3)) to 17,18-dihydroxyeicosatetraenoic acid (Oliw, E.H. (1989) J. Biol. Chem. 264, 17845-17853). The present study aimed to further characterize the oxygenation of (n-3) polyunsaturated fatty acids. 14C-Labelled 22:6(n-3), 20:5(n-3), 20:4-(n-3) and 18:3(n-3) were incubated with microsomes of seminal vesicles of the cynomolgus monkey, NADPH and a cyclooxygenase inhibitor, diclofenac, and the main metabolites were identified by capillary gas chromatography-mass spectrometry. 22:6(n-3) was slowly metabolized to 19,20-dihydroxy-4,7,10,13,16-docosapentaenoic acid, while 20:5(n-3), 20:4(n-3) and 18:3(n-3) were metabolized more efficiently to the corresponding w4,w3-diols. The w3 epoxides, which were obtained from 20:5(n-3) and 18:3(n-3), were isolated in the presence of an epoxide hydrolase inhibitor, 1(2)epoxy-3,3,3-trichloropropane, and the geometry of the epoxides was determined to be 17S, 18R and 15S, 16R, respectively. While 20:5(n-3) was metabolized almost exclusively to the epoxide and diol pair of metabolites, 18:3(n-3) was metabolized not only to the w3 epoxide and the corresponding diol, but also to the w2 alcohol, 17(R)-hydroxy-9,12,15-octadecatrienoic acid. 22:6(n-3) and 5,8,11,14-eicosatetraynoic acid inhibited the biosynthesis of 18(R)-HETE from arachidonic acid (IC50 0.16 and 0.14 mM, respectively). In comparison with 20:4 or 18:3(n-3), 18:1(n-9) and 22:5(n-6) appeared to be slowly metabolized by seminal monooxygenases, while 18:2(n-6) was converted to the w3 alcohol and to smaller amounts of the w2 alcohol (4:1). Together, the results indicate that the w3-hydroxylase and w3-epoxygenase enzyme(s) metabolize 20:4(n-6) and 20:5(n-3) almost exclusively to the w3(R) alcohol and the w3(R, S) epoxide, respectively, while longer and shorter fatty acids either are poor substrates or metabolized with a lesser degree of position specificity.     

Differences in bull spermiograms using eosin-nigrosin stain, feulgen stain, and phase contrast microscopy methods

The Society for Theriogenology recently adopted a minimum standard of 70% normal spermatozoa for the bull breeding soundness examination (BSE). We conducted this study to determine if spermiograms derived by brightfield microscopy of eosin-nigrosin stained semen smears (Society method) overestimated the proportion of normal spermatozoa. Comparison of the above method was made with that of phase contrast microscopy (Phase method). We then evaluated our ability to discern head abnormalities by comparing brightfield microscopy of Feulgen-stained sperm DNA (Feulgen method) with those of the Society and Phase methods. Spermiograms were determined for each of the 181 beef bulls using all 3 methods. Only bulls that were being routinely tested prior to the 1993 breeding season were included. The mean percentage of normal spermatozoa surpassed the minimum standard with the Society (72.8%) but not the Phase (52.5%) method, which identified more distal cytoplasmic droplets that adhered to cells without distal midpiece reflexes. The Phase method also identified more total primary and fewer primary head abnormalities. We conclude that the Phase method is not a suitable substitute for the Society method when applying the minimum standard during a routine BSE. The Feulgen method identified more head abnormalities, especially in the pattern of DNA, than the other methods, however, when compared to the minimum standard that improvement was not clinically important. Both the Phase and Feulgen methods are better than the Society method for monitoring changes in abnormal spermiograms over time.     

Review of Colombian Conchostraca (Crustacea) — ecological aspects and life cycles — family Cyclestheriidae

This study gives an overview and describes special aspects of the biology, ecology and the life cycle ofCyclestheria hislopi (Baird, 1859). This species is most commonly found in parthenogenically reproducing populations which produce large, directly developing nondiapause eggs. But periodically and under certain environmental conditions, sexually reproducing generations appear and produce diapause eggs. the sexual generations include males and particularly constituted females, which undergo a complete transformation into a special type of ephippium.Cyclestheria is the only known conchostracan species which does not occur in the initial phases of temporary water bodies, but develops in older temporary pools and even in permanent waters. It survives in the presence of effective depredators like fish by hiding within a special self-made mucus capsule.