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PubMed2000

Real-time high-resolution optical sectioning suggests biphasic cytokinetic mechanism in Dictyostelium discoideum.

Despite its biological significance, much of the mechanism of cytokinesis is not yet resolved. The problems include: (1) signaling mechanism determining the position of the cleavage furrow, (2) molecular and mechanistic nature of the contractile ring, and (3) the origin of forces responsible for cleavage. Using high-resolution imaging technique, the present study analyzes morphometric changes of cytokinesis in wild type (NC4) Dictyostelium discoideum amoeba. A sample was prepared by the agar-overlay method, creating 3-mm-thick, nearly two-dimensional cells; and high-resolution image was acquired at 16.7 milliseconds' temporal, 234 nm x, y-, and 100 nm z-axis resolutions. Under this condition, the formation of cleavage furrow initiates at mitotic telophase, and daughter cells separate 18-22 minutes after the furrow initiation. We found that the compression of cells and the room temperature need to be carefully controlled for cytokinesis to proceed in an orderly manner. The results demonstrate that the pole-to-pole distance increases by 83% during the initial 5 minutes of cytokinesis, while the distance of equator only decreases by 56%. In contrast, during the subsequent 5 minutes, the pole-to-pole distance only increases by 17%, while the equator distance decreases as much as by 44%. This study indicates that cytokinesis consists of at least two different phases, each of which results from a different mechanism.

Actins↗

PubMed1999

The role of high resolution pulsed and color Doppler ultrasound in the differential diagnosis of benign and malignant lymphadenopathy: results of multivariate analysis.

BACKGROUND: The role of high resolution pulsed and color Doppler ultrasound in the differential diagnosis of benign and malignant lymphadenopathy is still unclear. METHODS: High resolution pulsed and color Doppler ultrasound was used prospectively to investigate superficial lymph node enlargement in 71 patients undergoing surgical biopsy at the onset of lymphadenopathy. The aim of this study was to define, in multivariate analysis, the ultrasonographic parameters useful in the differential diagnosis of benign and malignant lymphadenopathy. RESULTS: Volume, vascularization score, pulsatility index, and resistive index were significantly higher in the 53 malignant lymph nodes studied than in the 18 benign lymph nodes studied. The long-to-short axis ratio was significantly lower in neoplastic lymph nodes than in reactive lymph nodes. Stepwise logistic regression selected only the long-to-short axis ratio and the vascularization score as parameters that independently and significantly contributed to the differentiation of neoplastic from reactive lymph nodes. The diagnostic efficiency of the combined criteria evaluated by the area under the receiver operating characteristic curve was 0.8339. CONCLUSIONS: High resolution pulsed and color Doppler ultrasound may provide information that is useful in making correct differential diagnoses of malignant or benign lymphadenopathy.

Adolescent↗

PubMed1999

Heat pretreatment increases resolution in DNA flow cytometry of paraffin-embedded tumor tissue.

BACKGROUND: Flow cytometry of single-cell suspensions prepared by enzymatic digestion from formalin-fixed, paraffin-embedded tissue suffers from several major drawbacks. The most important factors that influence the results are the high and unpredictable coefficients of variation (CVs) of the G0/G1 peak in the DNA histogram and reduction of propidium iodide (PI) intercalation with DNA, resulting from protein cross-linking by formalin. METHODS: In this study we introduce a heating step (2 h incubation in citrate solution at 80 degrees C) prior to a brief pepsin digestion of tissue sections in the protocol for DNA content analysis of formalin-fixed and paraffin-embedded tissue. This new method is compared with established methods for the preparation of cell suspensions from frozen and paraffin-embedded tissues with respect to cell yield, DNA histogram resolution, DNA dye saturation kinetics, cell cycle parameters, and antigen retrieval in various epithelial and nonepithelial tissues. RESULTS: The recovery of single cells from the paraffin sections was doubled by the heat treatment step, while the limited time of proteolysis resulted in decreased cell debris. Furthermore, an increased fraction of cells became cytokeratin-positive, while these immunocytochemically stained cells also exhibited a higher mean fluorescence intensity. The DNA histograms prepared from cell suspensions obtained according to this new protocol showed a significantly improved resolution, leading to a better identification of peridiploid cell populations. Heat pretreatment of paraffin-embedded archival tissue sections showed PI saturation kinetics similar to, or even better than, those of fresh unfixed tissues, independent of duration of fixation. CONCLUSIONS: This new method, making use of routinely available antigen retrieval principles, thus allows high-resolution DNA analysis of routinely fixed and paraffin-embedded tissue samples. Using external reference cells, inter- and intralaboratory standardization of DNA histograms can be achieved.

Breast Neoplasms↗

PubMed1996

High spatial resolution MRI and proton MRS of human frontal cortex.

High-resolution MR imaging (312 microns in plane resolution) and MR spectroscopy (0.36 cm3 nominal voxel) have been performed on human frontal cortex using a 3 in surface coil. Localized proton spectra have been obtained from contiguous 6 x 6 x 10 mm voxels using one-dimensional phase encoding, TR 2000 ms and TE 31 ms. Seven healthy subjects were studied using this approach. The spectra from frontal gray matter showed a reproducible pattern characterized by a choline to creatine and N-acetylaspartate to creatine ratio significantly lower than those from cortical white matter. These metabolite ratio differences reflect the lower choline and higher creatine content in gray matter. These preliminary results show the potential of this high spatial-resolution approach for studying brain cortex.

Adult↗

PubMed1999

High-resolution pulmonary arterio- and venography using multiple-bolus multiphase 3D-Gd-mRA.

The purpose of this study was to demonstrate selective visualization of pulmonary arteries and veins with high spatial resolution for improved detection of vascular pathologies. Time-resolved pulmonary three-dimensional gadolinium-enhanced magnetic resonance angiograms (3D-Gd-MRA) were acquired with an ultrashort 3D fast low-angle shot (FLASH) sequence (TR/TE 2.3/0.9 msec) using asymmetric k-space sampling in readout, phase-encoding, and partition directions. In a single breath-hold four consecutive acquisitions were performed with a scan time of 6.28 seconds for each phase. A spatial resolution of 1.9 x 1.4 x 2 mm(3) could be achieved for a 12 cm thick 3D volume. To exploit the intrinsic enhancement kinetics of the pulmonary vascular system, the infusion of two gadolinium chelate boli was synchronized with the acquisition of the first and third data sets. This infusion strategy created two predominantly pulmonary arterial and venous data sets with the arterial and venous signal being maximally anti-correlated in time. A further separation of arterial and venous signal could be achieved by means of a correlation analysis. Eight patients with suspected thrombi in the pulmonary veins were studied. The calculated correlation angiographies provided high-quality pulmonary arterio- and venograms. Background signal was completely eliminated, allowing maximum intensity projection analysis of the full data set. In 7/8 patients no venous contamination of the arterial phase and vice versa was found. Patency of the pulmonary arteries and veins could be reliably assessed to the level of the segmental vessels. The combination of ultrafast multiphase 3D-Gd-MRA and dual-bolus injection with a correlation analysis of vascular signal provides high-resolution pulmonary arterio- and venograms. This imaging strategy initiates a new competitor to X-ray angiography.

Adult↗

PubMed2000

Free-breathing 3D coronary MRA: the impact of "isotropic" image resolution.

During conventional x-ray coronary angiography, multiple projections of the coronary arteries are acquired to define coronary anatomy precisely. Due to time constraints, coronary magnetic resonance angiography (MRA) usually provides only one or two views of the major coronary vessels. A coronary MRA approach that allowed for reconstruction of arbitrary isotropic orientations might therefore be desirable. The purpose of the study was to develop a three-dimensional (3D) coronary MRA technique with isotropic image resolution in a relatively short scanning time that allows for reconstruction of arbitrary views of the coronary arteries without constraints given by anisotropic voxel size. Eight healthy adult subjects were examined using a real-time navigator-gated and corrected free-breathing interleaved echoplanar (TFE-EPI) 3D-MRA sequence. Two 3D datasets were acquired for the left and right coronary systems in each subject, one with anisotropic (1.0 x 1.5 x 3.0 mm, 10 slices) and one with "near" isotropic (1.0 x 1.5 x 1.0 mm, 30 slices) image resolution. All other imaging parameters were maintained. In all cases, the entire left main (LM) and extensive portions of the left anterior descending (LAD) and the right coronary artery (RCA) were visualized. Objective assessment of coronary vessel sharpness was similar (41% +/- 5% vs. 42% +/- 5%; P = NS) between in-plane and through-plane views with "isotropic" voxel size but differed (32% +/- 7% vs. 23% +/- 4%; P < 0.001) with nonisotropic voxel size. In reconstructed views oriented in the through-plane direction, the vessel border was 86% more defined (P < 0.01) for isotropic compared with anisotropic images. A smaller (30%; P < 0.001) improvement was seen for in-plane reconstructions. Vessel diameter measurements were view independent (2.81 +/- 0.45 mm vs. 2.66 +/- 0.52 mm; P = NS) for isotropic, but differed (2.71 +/- 0.51 mm vs. 3.30 +/- 0.38 mm; P < 0.001) between anisotropic views. Average scanning time was 2:31 +/- 0:57 minutes for anisotropic and 7:11 +/- 3:02 minutes for isotropic image resolution (P < 0.001). We present a new approach for "near" isotropic 3D coronary artery imaging, which allows for reconstruction of arbitrary views of the coronary arteries. The good delineation of the coronary arteries in all views suggests that isotropic 3D coronary MRA might be a preferred technique for the assessment of coronary disease, although at the expense of prolonged scan times. Comparative studies with conventional x-ray angiography are needed to investigate the clinical utility of the isotropic strategy.

Adult↗

PubMed1999

Theoretical limits of spatial resolution in elliptical-centric contrast-enhanced 3D-MRA.

The point spread function (PSF) for contrast-enhanced three-dimensional (3D) MR angiography using the elliptical centric view order is derived. This view order has been shown previously to provide high venous suppression thereby enabling long acquisition times capable of high spatial resolution. The dependence of the PSF on TR, field of view (FOV), scan time, and trigger time are shown explicitly. Theoretical predictions are corroborated with experimental results in phantoms and in vivo. The PSF width decreases as the square root of the product of TR and the two phase encoding FOV's for fixed nominal voxel size. The PSF peak amplitude increases as the reciprocal of this product. Theory and experiment demonstrate that acquisition times over 40 sec provide superior resolution compared to shorter acquisitions, despite falling levels of contrast agent concentration. The analysis predicts that an isotropic spatial resolution of 1 mm before zero filling is possible in a FOV large enough to encompass the carotid and vertebral arteries bilaterally. Magn Reson Med 42:1106-1116, 1999.

Carotid Arteries↗

PubMed2000

Size-dependent retardation and resolution by electrophoresis of rigid, submicron-sized particles, using buffered solutions in presence of polymers: a review of recent work from the authors' laboratory.

Capillary zone electrophoresis (CZE) was conducted in buffered solutions of polyacrylamide (PA) and polyethylene glycol (PEG) to find the degree and the manner in which separation and resolution of submicron-sized rigid spherical polystyrene sulfate and carboxylate particles were affected by the presence of those polymers. In resolving pairs of representative particles, maximal resolution was observed at or near the entanglement threshold concentration, c*, of the polymer. The value of that maximum represents a several-fold increase in resolution. Since c* can be calculated from intrinsic viscosity, and the latter from the molecular weight of the polymer (and some constants available in the literature), optimally resolving polymer conditions become predictable. The maximum can also be experimentally determined by measuring intrinsic viscosity and calculating c*, or by either systematically varying the concentration of a polymer of constant molecular weight or by varying the molecular weight of a polymer at constant concentration. An optimally resolving field strength is superimposed on the maximally resolving condition of polymer concentration and weight.

Animals↗

PubMed2000

High-resolution LC/MS for analysis of minor components in complex mixtures: negative ion ESI for identification of impurities and degradation products of a novel oligosaccharide antibiotic.

High-resolution mass spectrometry has been routinely used for structural confirmation and identification; however, it has mostly been applied to relatively pure samples. Exact mass measurement of minor components such as impurities, degradation products or metabolites in complex mixtures has been difficult without prior separation and isolation. Here we report the utilization of on-line liquid chromatography in combination with high-resolution mass spectrometry for the identification of impurities and base degradation products of Sch 27899, a member of the everninomicin class of antibiotics. Nine Sch 27899-related impurities and degradation products were detected by negative ion electrospray ionization using a magnetic sector mass spectrometer. Exact mass measurements were obtained at a resolution of 5000 using polyethylene glycol (PEG) sulfates as internal standards. Corresponding elemental compositions were determined within a 2 ppm error tolerance and structures were proposed for all components.

Aminoglycosides↗

PubMed2001

High resolution, fluorescence deconvolution microscopy and tagging with the autofluorescent tracers CFP, GFP, and YFP to study the structural composition of gap junctions in living cells.

High-resolution, fluorescence deconvolution (DV) microscopy was implemented to obtain a detailed view of the organization and structural composition of gap junctions assembled from one or two different connexin isotypes in live and fixed cells. To visualize gap junctions, the structural protein components of gap junction channels, the connexin polypeptides alpha1(Cx43), beta1(Cx32), and beta2(Cx26), were tagged on their C-termini with the autofluorescent tracers green fluorescent protein (GFP), and its cyan (CFP), and yellow (YFP) color variants. Tagged connexins were expressed in transiently transfected HeLa cells. Comprehensive analysis including dye-transfer analysis demonstrated that the tagged connexins trafficked, assembled, and packed normally into functional gap junction channel plaques. Such gap junction plaques were examined by single, dual, and triple-color DV microscopy. High-resolution images and three-dimensional volume reconstructions of gap junction plaques were obtained by this technique, which revealed several new aspects of gap junction structure. Specifically, the studies demonstrated that the mode of channel distribution strictly depends on the connexin isotypes. Here we present such images, and volume reconstructions in context with images obtained by other light, and electron microscopic techniques, such as laser scanning confocal, conventional wide-field fluorescence, thin section, and freeze-fracture electron microscopy. In addition, we give a simple description of the principal mechanisms of DV microscopy, name advantages and disadvantages, and discuss issues such as dual-color imaging using CFP and YFP, spatial resolution, colocalization, and avoiding imaging artifacts.

Connexin 26↗

PubMed2000

Accurate reconstruction of all-atom protein representations from side-chain-based low-resolution models.

A procedure for the reconstruction of all-atom protein structures from side-chain center-based low-resolution models is introduced and applied to a set of test proteins with high-resolution X-ray structures. The accuracy of the rebuilt all-atom models is measured by root mean square deviations to the corresponding X-ray structures and percentages of correct chi(1) and chi(2) side-chain dihedrals. The benefit of including C(alpha) positions in the low-resolution model is examined, and the effect of lattice-based models on the reconstruction accuracy is discussed. Programs and scripts implementing the reconstruction procedure are made available through the NIH research resource for Multiscale Modeling Tools in Structural Biology (http://mmtsb.scripps.edu).

Models, Molecular↗

PubMedDate not supplied

Crystal structure of a collagen-like polypeptide with repeating sequence Pro-Hyp-Gly at 1.4 A resolution: implications for collagen hydration.

The use of polypeptide models has proved to be a valuable tool to obtain accurate information on the collagen triple helix. Here we report the high resolution crystal structure of a collagen-like polypeptide with repeating sequence Pro-Hyp-Gly. The structure has been refined to an R(factor) of 0.137 and an R(free) of 0.163 using synchrotron diffraction data extending up to 1.4 A resolution. The polypeptide triple-helical structure binds a large number of water molecules, in contrast with a previous structure determination at lower resolution. The highly hydrated nature of this polypeptide confirms a number of previous studies conducted both in solution and in the crystal state. In addition, neighboring polypeptide triple helices are directly bound in the crystal through Hyp-Hyp hydrogen-bonding interactions. This finding supports the idea that Hyp residues may be important for the assembly of the triple helices in the collagen fibrils and may stabilize the fibrils by mediating direct contacts between neighboring molecules.

Amino Acid Sequence↗

PubMed2001

A high resolution (1)H magic angle spinning NMR study of a high-M(r) subunit of wheat glutenin.

This work describes the application of (1)H magic angle spinning (MAS) nmr to the study of hydrated 1Dx5 wheat high-M(r) subunit. 1Dx5 is a water-insoluble 88 kDa protein, associated with good baking performance, and whose structure in the solid and low-hydration states is not known. High-resolution MAS (HR-MAS) results in a threefold resolution improvement of the (1)H spectra of the hydrated wheat protein, compared to standard MAS. The spectral resolution achieved enables, for the first time, two-dimensional nmr methods to be employed for the study of hydrated 1Dx5 and the assignment of the spectrum to be carried out on the basis of total correlated spectroscopy and (13)C/(1)H correlation experiments. Considerable shifts are observed for some resonances, relative to the chemical shifts of amino acids in solution, indicating that specific interactions occur in the hydrated protein network. Two main environments are identified for glutamine residues, Q(1) and Q(2), and these were characterized in terms of possible conformation and relative dynamics, with the basis of comparison between the single 90 degrees spectrum and the Carr-Purcel-Heiboom-Gill (CPMG) spectrum. The Q(1) residues are proposed to be situated in protein segments that adopt the beta-sheet conformation and that remain relatively hindered, possibly by hydrogen bonds involving the glutamine amide groups. On the other hand, Q(2) residues are proposed to be situated in a more mobile environment, adopting a looser conformation, possibly a beta-turn conformation. Based on the proximity of the Q(2) residues with glycine residues, as viewed by the nuclear Overhauser effect spectroscopy experiment, it is proposed that the protein segments that form the more mobile (or loop) sections of the network are rich in both glutamine and glycine residues.

Glutens↗

PubMed2001

Effect of mass transfer limitations on the enzymatic kinetic resolution of epoxides in a two-liquid-phase system.

Optically active epoxides can be obtained by kinetic resolution of racemic mixtures using enantioselective epoxide hydrolases. To increase the productivity of the conversion of sparingly aqueous soluble epoxides, we investigated the use of a two-phase aqueous/organic system. A kinetic model which takes into account interphase mass transfer, enzymatic reaction, and enzyme inactivation was developed to describe epoxide conversion in the system by the epoxide hydrolase from Agrobacterium radiobacter. A Lewis cell was used to determine model parameters and results from resolutions carried out in the Lewis cell were compared to model predictions to validate the model. It was found that n-octane is a biocompatible immiscible solvent suitable for use as the organic phase. Good agreement between the model predictions and experimental data was found when the enzyme inactivation rate was fitted. Simulations showed that mass transfer limitations have to be avoided in order to maximize the yield of enantiomerically pure epoxide. Resolution of a 39 g/L solution of racemic styrene oxide in octane was successfully carried out in an emulsion batch reactor to obtain (S)-styrene oxide in high enantiomeric excess (>95% e.e.) with a yield of 30%.

Bioreactors↗

PubMed2001

New concepts to improve resolution and sensitivity of molecular cytogenetic diagnostics by multicolor fluorescence in situ hybridization.

BACKGROUND: Routine application of multicolor fluorescence in situ hybridization (M-FISH) technology for molecular cytogenetic diagnostics has been hampered by several technical limitations. First, when using chromosome-specific painting probes, there is a limit in cytogenetic resolution of approximately 2-3 Mb, which can mask hidden structural abnormalities that have a significant clinical effect. Second, using whole chromosome painting probes, intrachromosomal rearrangements cannot be detected and the exact localization of breakpoints is often not possible. METHODS: We suggest the use of multiplex-labeled region or locus- specific probes in combination with an optimal probe design to improve the sensitivity and resolution of the M-FISH technology. To allow the application of this assay in routine diagnostics, we developed a multipurpose image analysis system. RESULTS: goldFISH was applied to the study of cryptic translocations in mental retardation patients and to the study of high-resolution breakpoint mapping in non-small cell lung cancer patients. For an individual with mental retardation, who had an apparently normal karyotype by G-banding, we detected an unbalanced translocation involving chromosomes 2 and 7. CONCLUSIONS: In combination with optimally designed probe kits, goldFISH overcomes most of the present limitations of the M-FISH technology and results in virtually 100% reliability for detecting interchromosomal and intrachromosomal rearrangements.

Automation↗

PubMed2000

Corticosteroids for the resolution of malignant bowel obstruction in advanced gynaecological and gastrointestinal cancer.

BACKGROUND: Gastrointestinal and ovarian cancers are common cancers. The incidence of associated malignant bowel obstruction in patients with advanced cancers of these types is not known, and the best management of these patients is controversial. Inappropriate management may result in uncontrolled (faeculant) vomiting, pain and distress. Management of the symptoms can include palliative surgery, nasogastric tube suction together with intravenous fluids, or pharmacological means, such as corticosteroids. There is uncertainty regarding both the efficacy and possible harmful effects of corticosteroids, and also the most effective type, dose/dosing regime, route and period of administration. OBJECTIVES: To locate, appraise and summarise evidence from scientific studies on intestinal obstruction due to advanced gynaecological and gastrointestinal cancer, in order to assess the efficacy of corticosteroids. SEARCH STRATEGY: A comprehensive list of all studies was provided by an extensive search of the electronic databases, relevant journals, reference lists, the grey literature, contact with investigators and other search strategies outlined in the methods. SELECTION CRITERIA: As the review concentrates on the 'best evidence' available of the role of corticosteroids in malignant bowel obstruction due to advanced gynaecological and gastrointestinal cancer the inclusion criteria were kept fairly broad so as to include all studies relevant to the question DATA COLLECTION AND ANALYSIS: Data extraction forms were used to collect data from the studies included in the review. The data was checked by a secondary searcher to reduce error. A qualitative analysis was performed of the dichotomous data of resolution of obstruction and death at one month, obtained from the randomised controlled trials of corticosteroids versus placebo. Both fixed and random effect models were used. Number needed to treat (NNT) was derived from the odds ratio. Kaplan-Meier survival curves from individual patient data were also analysed. Studies of lower methodological quality were assessed in a qualitative manner. MAIN RESULTS: Three unpublished, randomised, placebo, double blind controlled trials and seven published (prospective and retrospective) trials were considered eligible. Using only the randomised trials, there is a trend, which is not statistically significant, for the resolution of bowel obstruction using corticosteroids. There is no statistically significant difference in mortality at one month, nor in the Kaplan-Meier curves, which describe the survival of patients on corticosteroids or placebo. Number needed to treat is 6 (3, infinity) ie six patients need to be treated with corticosteroids to resolve one episode of bowel obstruction. The results are robust to fixed and random effects models and to 'best' and 'worst case' scenarios on the missing data from patients. The morbidity associated with corticosteroids appears to be very low, though the quality of the data limits this conclusion. No other outcomes were available from the published data or from the authors. REVIEWER'S CONCLUSIONS: There is a trend for evidence that corticosteroids of dose range 6-16 mg dexamethasone given intravenously may bring about the resolution of bowel obstruction. Equally, the incidence of side effects in all the included studies is extremely low. Corticosteroids do not seem to affect the length of survival of these patients.

Female↗

PubMed2001

Direct chiral resolution of malic acid in apple juice by ligand-exchange capillary electrophoresis using copper(II)-L-tartaric acid as a chiral selector.

Chiral resolution of native DL-malic acid was achieved by ligand-exchange capillary electrophoresis using copper(II)-L-tartrate as a chiral selector. Factors affecting chiral resolution, migration time, and peak area of malic acid were studied. The running conditions for optimum separation of malic acid were found to be 1 mM copper(II) sulfate-1 mM L-tartrate (pH 5.1) with an effective voltage of -20 kV at 30 degrees C, using direct detection at 280 nm, and resolution (Rs) of racemic malic acid was approximately 4. With this system, D- and L-malic acids in apple juice were analyzed successfully.

Beverages↗

PubMed2002

Stepwise gradient of linear polymer matrices in microchip electrophoresis for high-resolution separation of DNA.

The stepwise gradient of linear polymer matrices in microchannel electrophoresis is proposed as a means of achieving high-resolution separation of DNA samples containing a wide range of fragment sizes. In this method, multiple discrete steps in terms of polymer type or concentration are created in the microchannel by injecting appropriate solutions in order. The mixing of the various steps is found to be negligible compared to the effective length of separation channel, confirming that a stepwise gradient of matrices is formed. This technique is successfully applied to the analysis of restriction digest fragments and DNA ladders, and is demonstrated to provide higher resolution than the isocratic method, for both small and large fragments simultaneously. Even though the stepwise gradient is created manually, the reproducibility of the migration times of fragments in DNA samples is found to be quite good. Taken the separation of 100 bp DNA ladder in three steps gradient pattern as an example, the relative standard deviations of migration times are respectively less than 0.53% and 3.1% in six consecutive injections in one channel and in different channels. The migration of DNA fragments in gradient mode is shown to be similar to that for the isocratic scheme, allowing the design of each step to be made in reference to existing knowledge. These promising results indicate the great potential of this stepwise gradient method for the analysis of DNA by microchip electrophoresis, offering both high resolution and good reproducibility.

DNA↗