On the periodicity in the fine structure of histograms during nuclear decay

A possible explanation for the occurrence of periodicity in the fine structure of histograms during nuclear decay is proposed. The hypothesis states that, even in the absence of polarization, when the spin distribution of decaying nuclei over directions is, on the average, isotropic, the fine structure of histograms should depend, due to fluctuations, on the angles at which the sample is observed. There fore, when the Earth after some period would make a full furn, the distribution of fluctuations would return to the initial one, and, correspondingly, the fine structure of the histograms would repeat.     

Correlation of fine structures of distributions of amplitudes of a photomultiplier dark current fluctuations with the Earth rotations about its axis

The fine structures of distributions of photomultiplier dark current fluctuations measured in two laboratories 2000 km distant from other: in the international Institute of Biophysics (Neuss, Germany) and in the Moscow State University (Moscow, Russia) were compared. It is shown that similar forms of appropriate histograms are apparently more often realized at both locations at the same local time. This confirms the previous conclusion that the fine structure of distributions correlates with rotation of the Earth about its axis.     

A new horizon of DNP technology: application to in-vivo 13C magnetic resonance spectroscopy and imaging

Dynamic nuclear polarization (DNP) is an emerging technique for increasing the sensitivity (>10,000-fold) of magnetic resonance spectroscopy and imaging (MRSI), in particularly for low-γ nuclei. DNP methodology is based on polarizing nuclear spins in an amorphous solid state at low temperature (ca. 1 K) through coupling of the nuclear spins with unpaired electron spins that are added to the sample via an organic free radical. In an amorphous solid state, the high electron spin polarization can be transferred to the nuclear spins by microwave irradiation. While this technique has been utilized in solid-state research for many years, it is only recently that dissolution methods and the required hardware have been developed to produce the high nuclear polarization provided by DNP to produce injectable hyperpolarized solutions suitable for in vivo studies. It has been applied to a number of ¹³C-labeled cell metabolites in biological systems and their real-time metabolic conversion has been imaged. This review focuses briefly on the DNP methodology and the significant molecules investigated to date in preclinical cancer models, in terms of their downstream metabolism in vivo or the biological processes that they can probe. In particular, conversion between hyperpolarized ¹³C-labeled pyruvate and lactate, catalyzed by lactate dehydrogenase, has been shown to have a number of potential applications such as diagnosis, staging tumor grade, and monitoring therapy response. Strategies for making this technique more viable to use in clinical settings have been discussed.     

Frozen spin targets in ribosomal structure research.

Polarized neutron scattering strongly depends on nuclear spin polarisation, particularly on proton spin polarisation. A single proton in a deuterated environment then is as efficient as 10 electrons in X-ray anomalous diffraction. Neutron scattering from the nuclear spin label is controlled by the polarisation of neutron spins and nuclear spins. Pure deuteron spin labels and proton spin labels are created by NMR saturation. We report on results obtained from the large subunit of E. coli ribosomes which have been obtained at the research reactor of GKSS using the polarized target facility developed by CERN. The nuclear spins were oriented with respect to an external field by dynamic nuclear polarisation. Proton spin polarisations of more than 80% were obtained in ribosomes at temperatures below 0.5 K. At T = 130 mK the relaxation time of the polarized target is one month (frozen spin target). Polarized small-angle neutron scattering of the in situ structure of rRNA and the total ribosomal protein (TP) has been determined from the frozen spin targets of the large ribosomal subunit, which has been deuterated in the TP and rRNA respectively. The results agree with those from neutron scattering in H2O/D2O mixtures obtained at room temperature. This is a necessary prerequisite for the planned determination of the in situ structure of individual ribosomal proteins and especially of that of ribosome bound mRNA and tRNAs.     

Two new nuclear isolation buffers for plant DNA flow cytometry: a test with 37 species

Background and Aims: After the initial boom in the application of flow cytometryin plant sciences in the late 1980s and early 1990s, which wasaccompanied by development of many nuclear isolation buffers,only a few efforts were made to develop new buffer formulas.In this work, recent data on the performance of nuclear isolationbuffers are utilized in order to develop new buffers, generalpurpose buffer (GPB) and woody plant buffer (WPB), for plantDNA flow cytometry. Methods: GPB and WPB were used to prepare samples for flow cytometricanalysis of nuclear DNA content in a set of 37 plant speciesthat included herbaceous and woody taxa with leaf tissues differingin structure and chemical composition. The following parametersof isolated nuclei were assessed: forward and side light scatter,propidium iodide fluorescence, coefficient of variation of DNApeaks, quantity of debris background, and the number of particlesreleased from sample tissue. The nuclear genome size of 30 selectedspecies was also estimated using the buffer that performed betterfor a given species. Key Results: In unproblematic species, the use of both buffers resulted inhigh quality samples. The analysis of samples obtained withGPB usually resulted in histograms of DNA content with higheror similar resolution than those prepared with the WPB. In morerecalcitrant tissues, such as those from woody plants, WPB performedbetter and GPB failed to provide acceptable results in somecases. Improved resolution of DNA content histograms in comparisonwith previously published buffers was achieved in most of thespecies analysed. Conclusions: WPB is a reliable buffer which is also suitable for the analysisof problematic tissues/species. Although GPB failed with someplant species, it provided high-quality DNA histograms in speciesfrom which nuclear suspensions are easy to prepare. The resultsindicate that even with a broad range of species, either GPBor WPB is suitable for preparation of high-quality suspensionsof intact nuclei suitable for DNA flow cytometry.     

Comparison of microscopic imaging strategies for evaluating immunocytochemical (PAP) steroid receptor heterogeneity

Receptogram analysis was compared with three other imaging strategies for immunocytochemical assay of estrogen receptors. These included nuclear-specific methods for analysis of nuclear integrated optical density (IOD) or mean optical density (MOD) histograms, and field-specific methods, where the pixel optical density (POD) histogram was evaluated for the composite nuclear phase. Measurements in culture and in breast cancer cryosections were treated separately to isolate geometric considerations. In culture receptograms the modality of IOD and MOD histograms and their bivariate contour maps revealed one, two, or more subpopulations with discrete receptor content and concentration. However, when the field of nuclei was imaged as a whole, regardless of the number of subpopulations, POD histograms showed two minima, defining three intranuclear phases. This was due to mottling and variegation of intranuclear chromatin and nucleolar immunostaining and not to differences between nuclei. These limitations were also revealed in breast cancer sections. In POD histograms, % unstained pixels did not provide a reliable estimate of % receptor negative nuclei, as determined by their enumeration. In sections, correction of IOD for nuclear volume variability was essential to suppress artifactual peaks not representing differences in receptor content. This was achieved by multiplying nuclear IOD by the spherical nuclear radius (S) of individual slab sections. Peaks of IOD(S) then reflected receptor content on a true ratio scale. Only receptogram analysis, which incorporates these strategies, permitted objective evaluation of receptor heterogeneity at the level of tumor subpopulations.     

Regular oscillatory behavior of aqueous solutions of CuII salts related to effects on equilibrium dynamics of ortho/para hydrogen spin isomers of water

Cell surface and growth-related NADH oxidases with protein disulfide-thiol interchange activity, ECTO-NOX, exhibit copper-dependent, clock-related, temperature-independent and entrainable patterns of regular oscillations in the rate of oxidation of NAD(P)H as do aqueous solutions of copper salts. Because of time scale similarities, a basis for the oscillatory patterns in nuclear spin orientations of the hydrogen atoms of the copper-associated water was sought. Extended X-ray absorption fine structure (EXAFS) measurements at 9302 eV on pure water were periodic with a ca. 3.5 min peak to peak separation. Decomposition fits revealed 5 unequally spaced maxima similar to those observed previously for Cu(II)Cl(2) to generate a period length of about 18 min. With D(2)O, the period length was proportionately increased by 30% to 24 min. The redox potential of water and of D(2)O also oscillated with 18 and 24 min period lengths, respectively. Measurements in the middle infrared spectral region above a water sample surface revealed apparent oscillations in the two alternative orientations of the nuclear spins (ortho and para) of the hydrogen atoms of the water or D(2)O with 5 unequally spaced maxima and respective period lengths of 18 and 24 min. Thus, the time keeping oscillations of ECTO-NOX proteins appear to reflect the equilibrium dynamics of ortho-para hydrogen atom spin ratios of water where the presence of metal cations such as Cu(II) in solution determine period length.     

Dependence of "macroscopic fluctuations" from cosmophysical factors. Spatial anisotropy

It was shown in experiments with collimators that the changes with time in the shape of histograms constructed from the measurements of the alpha-activity of 239Pu microsamples depend on the direction of the flow alpha-particles. If the flow of alpha-particles was directed to the Polar Star, the dependence of the probability of the realization of histograms of similar shape on time disappeared. The measurements of alpha-particle flows directed to the East and West revealed a high probability of the repeated realization of histograms of similar shape in 1436 min, i.e., in a sederal day. A comparison of "west" and "east" histograms showed a high probability of the realization of similar "west" histograms 718 min (half a sideral day) later than "east" histograms. The results suggest that the shape of histograms depends on the pattern of the starry sky and the space-time inhomogeneity corresponding to this pattern.     

Relationship between the fine structure and statistic fluctuations in measurement result distributions

The "near zone effect" described first in the macroscopic fluctuations researches was studied by numerical modeling. Possible mechanisms of its formation were proposed, and the lengths of portions of experimental data that retain the fine structure of histograms necessary for studying the "near zone effect" and provide the minimum level of statistical noise.     

Biomechanical capabilities influence postural control strategies in the cat hindlimb

During postural responses to perturbations, horizontal plane forces generated by the cat hindlimb are stereotypically directed either towards or away from the animal's center of mass, independent of perturbation direction. We used a static, three-dimensional musculoskeletal model of the hindlimb to investigate possible biomechanical determinants of this "force constraint strategy." We hypothesized that directions in which the hindlimb can produce large forces are preferentially used in postural control. We computed feasible force sets (FFSs) based on hindlimb configurations of three cats during postural equilibrium tasks and compared them to horizontal plane postural force directions. The grand mean FFS was bimodal, with maxima near the posterior-anterior axis (-86+/-8 degrees and 71+/-4 degrees ), and minima near the medial-lateral axis (177+/-8 degrees and 8+/-8 degrees ). Experimental postural force directions clustered near both maxima; there were no medial postural forces near the absolute minimum. However, the medians of the anterior and posterior postural force direction histograms in the right hindlimb were rotated counter-clockwise from the FFS maxima (p<0.05; Wilcoxon signed-rank test). Because the posterior-anterior alignment of the FFS is consistent with a hindlimb structure optimized for locomotion, we conclude that the biomechanical capabilities of the hindlimb strongly influence, but do not uniquely determine the force directions observed in the force constraint strategy. Forces used in postural control may reflect a balance between a neural preference for using forces in the directions of large feasible forces and other criteria, such as the stabilization of the center of mass, and muscular coordination strategies.     

Studies on changes in the nuclear helices of Amoeba proteus during the cell cycle.

The fine structure of the nuclei of synchronously growing cell population of Amoeba proteus was studied at I-h intervals during the interphase. This study showed that the nuclear helices undergo increases in their number at certain stages during interphase. These changes were found to correlate with ultrastructural changes occurring in the nucleoli.     

Spatial association of homologous pericentric regions in human lymphocyte nuclei during repair

Spatial positioning of pericentric chromosome regions in human lymphocyte cell nuclei was investigated during repair after H(2)O(2)/L-histidine treatment. Fifteen to three-hundred minutes after treatment, these regions of chromosomes 1, 15, and X were labeled by fluorescence in situ hybridization. The relative locus distances (LL-distances), the relative distances to the nuclear center (LC-distances), and the locus-nuclear center-locus angles (LCL-angles) were measured in approximately 5000 nuclei after two-dimensional microscopy. Experimental frequency histograms were compared to control data from untreated stimulated and quiescent (G(0)) nuclei and to a theoretical two-dimensional projection from random points. Based on the frequency distributions of the LL-distances and the LCL-angles, an increase of closely associated labeled regions was found shortly after repair activation. For longer repair times this effect decreased. After 300 min the frequency distribution of the LL-distances was found to be compatible with the random distance distribution again. The LL-distance frequency histograms for quiescent nuclei did not significantly differ from the theoretical random distribution, although this was the case for the stimulated control of chromosomes 15 and X. It may be inferred that, concerning the distances, homologous pericentric regions appear not to be randomly distributed during S-phase, and are subjected to dynamic processes during replication and repair.     

On the directional sensitivity of motion detectors

The output of a motion detector depends on the direction of pattern motion, relative to the axis defined by its two input elements. Usually a cosine shaped directional sensitivity characteristics is assumed: The response is strongest for pattern motion along the detector axis, reversing its sign for motion in opposite direction; for motion perpendicular to the detector axis it is expected to be zero, with intermediate values for oblique motion directions. However, geometric considerations show that this expectation is by no means trivial. When a periodic pattern moves along a direction a relative to the detector axis, the spatiotemporal intensity distribution along the detector axis can be described by its apparent spatial wavelength and its apparent velocity, which both vary with 1/cos. In consequence, a motion detector depending exclusively on the apparent velocity of the stimulus would respond strongest to gratings moving perpendicular to the detector axis, whereas motion along the detector axis would yield the smallest response in such a detector. The response of a motion detector of the correlation type, on the other hand, is determined by the ratio between velocity and wavelength, the temporal frequency, which is not influenced by the direction of pattern motion, and by the ratio between sampling base and the wavelength. The latter feature leads to a cosine-shaped directional characteristics for large pattern wavelengths. However, for smaller wavelengths specific deviations from a simple harmonic are expected. These expectations were confirmed by the simulation of an elementary motion detector model and extended for a slightly more elaborated model. Representing a biological motion detecting unit of the correlation type, the directional characteristics of the H1 interneuron in the fly's brain was investigated electrophysiologically, and compared to the simulations.     

Topology and dynamics of the 10 kDa C-terminal domain of DnaK in solution

Hsp70 molecular chaperones contain three distinct structural domains, a 44 kDa N-terminal ATPase domain, a 17 kDa peptide-binding domain, and a 10 kDa C-terminal domain. The ATPase and peptide binding domains are conserved in sequence and are functionally well characterized. The function of the 10 kDa variable C-terminal domain is less well understood. We have characterized the secondary structure and dynamics of the C-terminal domain from the Escherichia coli Hsp70, DnaK, in solution by high-resolution NMR. The domain was shown to be comprised of a rigid structure consisting of four helices and a flexible C-terminal subdomain of approximately 33 amino acids. The mobility of the flexible region is maintained in the context of the full-length protein and does not appear to be modulated by the nucleotide state. The flexibility of this region appears to be a conserved feature of Hsp70 architecture and may have important functional implications. We also developed a method to analyze 15N nuclear spin relaxation data, which allows us to extract amide bond vector directions relative to a unique diffusion axis. The extracted angles and rotational correlation times indicate that the helices form an elongated, bundle-like structure in solution.     

Nuclear transplantation in bovine embryo: fine structural and autoradiographic studies

Nucleolar fine structure, "blebbing" activity of nuclear envelope, and activation of heterogeneous nuclear RNA (hnRNA) synthesis were studied in bovine reconstructed embryos obtained by electrofusion of a single eight-cell blastomere with an enucleated oocyte. Developmental progress of nucleolar fine structure and hnRNA synthesis are arrested during three cell cycles following fusion. The activation of both appears during the eight-cell stage of the reconstructed embryo, after the same number of cell cycles after fusion as in nonmanipulated bovine embryos after fertilization. "Blebbing" activity of nuclear envelope, which is already absent in original blastomeres, reappears after fusion and continues for the next two cell cycles. From the present results, it can be concluded that the donor nuclei are arrested after fusion in morphology and function. Their reactivation corresponds to the developmental pattern typical for normal bovine embryos.     

Asymmetric division in fucoid zygotes is positioned by telophase nuclei

The relative contributions of cell polarity and nuclear position in specifying the plane of asymmetric division in fucoid zygotes were investigated. In zygotes developing normally, telophase nuclei were positioned parallel to the polar growth axis, and the division plane bisected both axes. To assess division plane specification, the colinearity of the nuclear and growth axes was uncoupled by treatment with pharmacological agents. Spatial correlations between the growth axis, telophase nuclei, and the division plane were analyzed in the treated zygotes. In all cases, cytokinesis was oriented transverse to the telophase mitotic array and was less well aligned with the growth axis. Telophase nuclei also played a predominant role in positioning the division plane in polyspermic zygotes. Microtubules from the telophase nuclei interdigitated throughout the plane of subsequent cytokinesis, and we speculate that they specify the division plane. Morphological markers of the division plane were not observed before telophase; the earliest division marker detected was a plate of actin that assembled in the zone of microtubule overlap late in telophase. These findings are consistent with division plane specification at cytoplast boundaries.     

A differential amplifier circuit for reducing noise in axial light loss measurements

Simplified electronics have been developed for reducing laser excitation source light intensity fluctuations in flow cytometric axial light loss (extinction) measurements. By continuously monitoring the laser output with a photodiode detector and combining it with the axial light loss signal from a second detector using a high-speed differential amplifier, background interference is reduced 10 to 40 dB. Oscilloscope waveforms and frequency distribution histograms recorded from uniform-size polystyrene latex spheres and human mononuclear blood cells are used to illustrate the noise reduction capabilities.     

Suppression of spin diffusion in selected frequency bands of nuclear Overhauser spectra

Summary A variant of two-dimensional nuclear Overhauser effect spectroscopy (NOESY) is described that yields information about cross-relaxation rates between pairs of spins, while the migration of magnetization through several consecutive steps (spin diffusion via neighboring spins) is largely suppressed. This can be achieved by inserting a doubly-selective inversion pulse in a conventional NOESY sequence.     

The hind limb step cycle of Iguana and primitive reptiles

The hind limb step cycle of Iguana is described and compared with other lizards. In generalized lizards with well developed limbs, the femur retracts through a large arc and rotates as it retracts, flexion of the crus on the metatarsus occurs during the initial part of the propulsive phase and extension of the knee and ankle during the final part, the crus rotates to face laterally, the metatarsus is laterally directed at the time of pedal plantarflexion, and pedal plantarflexion involves an initial rotation of the metatarsus around its long axis followed by an extension of the ankle joint. The evolutionary significance of the differences in the hind limb step cycle of lizards and salamanders is considered and it is shown that in many, but not all, features, primitive reptiles would have been like salamanders. The primitive step cycle differs from the mammalian pattern in the large amount of rotation of the limb segments, the large amount of femoral retraction, and the reduced amount of lateral movement of the hip relative to the knee that occurs during femoral retraction.