Lack of geographic variation in anonymous nuclear polymorphisms in the American oyster, Crassostrea virginica

Comparing geographic variation of noncoding nuclear DNA polymorphisms, which presumably are neutral to natural selection, with geographic variation of allozymes is potentially a good way to detect the effects of selection on allozyme polymorphisms. A previous study of four anonymous nuclear markers in the American oyster, Crassostrea virginica, found dramatic differences in allele frequency between the Gulf of Mexico and the Atlantic Ocean. In contrast, 14 allozyme polymorphisms were fairly uniform in frequency between the two areas. This led to the conclusion that all of the allozyme polymorphisms were kept uniform in frequency by balancing selection. To test the robustness of this pattern, six additional anonymous nuclear DNA polymorphisms were surveyed in oysters from Panacea, Fla, and Charleston, S.C. on the Gulf and Atlantic coasts, respectively. Unlike the previously studied DNA markers, the six DNA polymorphisms examined here show geographic variation that is not significantly greater than that of allozymes. The reason for the discrepancy between the two sets of DNA polymorphisms is unclear.      

Analysis of aspartate and glutamate in human cerebrospinal fluid by high-performance liquid chromatography with automated precolumn derivatization

A method is described for the analysis of the neuroexcitatory amino acids, aspartate and glutamate, in human cerebrospinal fluid (CSF) by reverse-phase, high-performance liquid chromatography. Fluorescent isoindole derivatives of the amino acids were prepared by reacting the amino acids with ortho-phthalaldehyde in an automated, precolumn procedure. Chromatographic conditions were developed that resolve the isoindole derivatives of aspartate and glutamate from those of at least 10 unidentified components of CSF. Amino acids were reliably quantified in 5-microliter samples of CSF, and deproteinization of the specimens was not required. Furthermore, it was found that deproteinization by precipitation with strong acid can lead to artifactually high measurements of glutamate. The concentrations of free aspartate and glutamate in lumbar CSF from 15 neurologically normal children were 0.30 +/- 0.11 and 0.48 +/- 0.26 microM (mean +/- SD), respectively. The value for glutamate is considerably lower than has been reported in any previous study of human CSF.     

Relaxin-3 and RXFP3 expression, and steroidogenic actions in the ovary of teleost fish

Relaxins are peptides similar in secondary structure to insulins. In teleost genomes, five or six relaxin genes have been identified. Two relaxins group closely with mammalian relaxin-3 on phylogenetic analysis and are named relaxin-3a and b. We refer to the remainder as relaxins c to f. Ovarian expression of relaxin-3a, d and f genes, and the relaxin-3 receptor gene Rxfp3, was studied in Danio rerio using RT-PCR. Immunohistochemistry was used to determine the distribution of relaxin-3 peptides and RXFP3 in the ovary of Fundulus heteroclitus (killifish). Thirdly, enzyme immunoassays and ovarian follicular culture were used to determine the effect of treatment with human recombinant relaxin-3 on the production of 17beta-estradiol and 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one in killifish ovarian follicles. Relaxin-3a, d, f, and Rxfp3 genes were expressed regardless of sex or reproductive condition. Relaxin-3 immunostaining was present in mid to late follicular stages within cortical alveoli of the oocyte cytopasm, whereas receptor staining was localized to follicular cells. Treatment with relaxin-3 enhanced 17beta-estradiol production in early and late maturing follicles, but did not have an effect in vitellogenic follicles. Relaxin-3 appeared to suppress the release of MIS production. This suggests that relaxin peptides may be involved with estradiol-dependant events in follicular development.     

Interocular yoking in human saccades examined by mutual information analysis

Background

Saccadic eye movements align the two eyes precisely to foveate a target. Trial-by-trial variance of eye movement is always observed within an identical experimental condition. This has often been treated as experimental error without addressing its significance. The present study examined statistical linkages between the two eyes’ movements, namely interocular yoking, for the variance of eye position and velocity.

Methods

Horizontal saccadic movements were recorded from twelve right-eye-dominant subjects while they decided on saccade direction in Go-Only sessions and on both saccade execution and direction in Go/NoGo sessions. We used infrared corneal reflection to record simultaneously and independently the movement of each eye. Quantitative measures of yoking were provided by mutual information analysis of eye position or velocity, which is sensitive to both linear and non-linear relationships between the eyes’ movements. Our mutual information analysis relied on the variance of the eyes movements in each experimental condition. The range of movements for each eye varies for different conditions so yoking was further studied by comparing GO-Only vs. Go/NoGo sessions, leftward vs. rightward saccades.

Results

Mutual information analysis showed that velocity yoking preceded positional yoking. Cognitive load increased trial variances of velocity with no increase in velocity yoking, suggesting that cognitive load may alter neural processes in areas to which oculomotor control is not tightly linked. The comparison between experimental conditions showed that interocular linkage in velocity variance of the right eye lagged that of the left eye during saccades.

Conclusions

We conclude quantitative measure of interocular yoking based on trial-to-trial variance within a condition, as well as variance between conditions, provides a powerful tool for studying the binocular movement mechanism.

     

A step towards non-invasive characterization of the human frontal eye fields of individual subjects

Background

Identifying eye movement related areas in the frontal lobe has a long history, with microstimulation in monkeys producing the most clear-cut results. For humans, however, there is still no consensus about the location and the extent of the frontal eye field (FEF). There is also no simple non-invasive method for unambiguously defining the FEF in individual subjects, a prerequisite for clinical applications. Here we explore the use of magnetoencephalography (MEG) for the non-invasive identification and characterization of FEF activity in an individual subject.

Methods

We mapped human brain activity before, during and after saccades by applying tomographic analysis to MEG data. Statistical parametric maps and circular statistics produced plausible FEF loci, but no unambiguous definition for individual subjects. Here we first computed the spectral decomposition and correlation with electrooculogram (EOG) of the tomographic brain activations. For each of these two measures statistical comparisons were made between different saccades.

Results

In this paper, we first review the frontal cortex activations identified in earlier animal and human studies and place the putative human FEFs in a well-defined anatomical framework. This framework is then used as reference for describing the results of new Fourier analysis of the tomographic solutions comparing active saccade tasks and their controls. The most consistent change in the dorsal frontal cortex was at the putative left FEF, for both saccades to the left and right. The asymmetric result is consistent with the 1-way callosal traffic theory. We also showed that the new correlation analysis had its most consistent change in the contralateral putative FEF. This result was obtained for EOG latencies before saccade onset with delays of a few hundreds of milliseconds (FEF activity leading the EOG) and only for visual cues signaling the execution of a saccade in a previously defined saccade direction.

Conclusions

The FEF definition derived from microstimulation describes only one of the areas in the dorsal lateral frontal lobe that act together to plan, prepare and execute a saccade. The definition and characterization of these areas in an individual subject can be obtained from non-invasive MEG measurements.

     

pH stability of the stromelysin-1 catalytic domain and its mechanism of interaction with a glyoxal inhibitor

The stromelysin-1 catalytic domain(83-247) (SCD) is stable for at least 16 h at pHs 6.0-8.4. At pHs 5.0 and 9.0 there is exponential irreversible denaturation with half lives of 38 and 68 min respectively. At pHs 4.5 and 10.0 irreversible denaturation is biphasic. At 25°C, C-terminal truncation of stromelysin-1 decreases the stability of the stromelysin-1 catalytic domain at pH values >8.4 and <6.0. We describe the conversion of the carboxylate group of (βR)-β-[[[(1S)-1-[[[(1S)-2-Methoxy-1-phenylethyl]amino]carbonyl]-2,2-dimethylpropyl]amino]carbonyl]-2-methyl-[1,1'-biphenyl]-4-hexanoic acid (UK-370106-COOH) a potent inhibitor of the metalloprotease stromelysin-1 to a glyoxal group (UK-370106-CO(13)CHO). At pH 5.5-6.5 the glyoxal inhibitor is a potent inhibitor of stromelysin-1 (K(i)=~1μM). The aldehyde carbon of the glyoxal inhibitor was enriched with carbon-13 and using carbon-13 NMR we show that the glyoxal aldehyde carbon is fully hydrated when it is in aqueous solutions (90.4ppm) and also when it is bound to SCD (~92.0ppm). We conclude that the hemiacetal hydroxyl groups of the glyoxal inhibitor are not ionised when the glyoxal inhibitor is bound to SCD. The free enzyme pK(a) values associated with inhibitor binding were 5.9 and 6.2. The formation and breakdown of the signal at ~92ppm due to the bound UK-370106-CO(13)CHO inhibitor depends on pK(a) values of 5.8 and 7.8 respectively. No strong hydrogen bonds are present in free SCD or in SCD-inhibitor complexes. We conclude that the inhibitor glyoxal group is not directly coordinated to the catalytic zinc atom of SCD.