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Biomedical subjects

J Völker

Publications and source records attributed to J Völker.

17 recordsLinked to original sources
PubMed2002

Conformational energetics of stable and metastable states formed by DNA triplet repeat oligonucleotides: implications for triplet expansion diseases.

We have embedded the hexameric triplet repeats (CAG)(6) and (CTG)(6) between two (GC)(3) domains to produce two 30-mer hairpins with the sequences d[(GC)(3)(CAG)(6)(GC)(3)] and d[(GC)(3)(CTG)(6)(GC)(3)]. This construct reduces the conformational space available to these repetitive DNA sequences. We find that the (CAG)(6) and (CTG)(6) repeats form stable, ordered, single-stranded structures. These structures are stabilized at 62 degrees C by an average enthalpy per base of 1.38 kcal.mol(-1) for the CAG triplet and 2.87 kcal.mol(-1) for the CTG triplet, while being entropically destabilized by 3.50 cal.K(-1).mol(-1) for the CAG triplet and 7.6 cal.K(-1).mol(-1) for the CTG triplet. Remarkably, these values correspond, respectively, to 1/3 (for CAG) and 2/3 (for CTG) of the enthalpy and entropy per base values associated with Watson-Crick base pairs. We show that the presence of the loop structure kinetically inhibits duplex formation from the two complementary 30-mer hairpins, even though the duplex is the thermodynamically more stable state. Duplex formation, however, does occur at elevated temperatures. We propose that this thermally induced formation of a more stable duplex results from thermal disruption of the single-stranded order, thereby allowing the complementary domains to associate (perhaps via "kissing hairpins"). Our melting profiles show that, once duplex formation has occurred, the hairpin intermediate state cannot be reformed, consistent with our interpretation of kinetically trapped hairpin structures. The duplex formed by the two complementary oligonucleotides does not have any unusual optical or thermodynamic properties. By contrast, the very stable structures formed by the individual single-stranded triplet repeat sequences are thermally and thermodynamically unusual. We discuss this stable, triplet repeat, single-stranded structure and its interconversion with duplex in terms of triplet expansion diseases.

Base Sequence↗
PubMed2001

Counterion association with native and denatured nucleic acids: an experimental approach.

The melting temperature of the poly(dA) . poly(dT) double helix is exquisitely sensitive to salt concentration, and the helix-to-coil transition is sharp. Modern calorimetric instrumentation allows this transition to be detected and characterized with high precision at extremely low duplex concentrations. We have taken advantage of these properties to show that this duplex can be used as a sensitive probe to detect and to characterize the influence of other solutes on solution properties. We demonstrate how the temperature associated with poly(dA) . poly(dT) melting can be used to define the change in bulk solution cation concentration imparted by the presence of other duplex and triplex solutes, in both their native and denatured states. We use this information to critically evaluate features of counterion condensation theory, as well as to illustrate "crosstalk" between different, non-contacting solute molecules. Specifically, we probe the melting of a synthetic homopolymer, poly(dA) . poly(dT), in the presence of excess genomic salmon sperm DNA, or in the presence of one of two synthetic RNA polymers (the poly(rA) . poly(rU) duplex or the poly(rU) . poly(rA) . poly(rU) triplex). We find that these additions cause a shift in the melting temperature of poly(dA) . poly(dT), which is proportional to the concentration of the added polymer and dependent on its conformational state (B versus A, native versus denatured, and triplex versus duplex). To a first approximation, the magnitude of the observed tm shift does not depend significantly on whether the added polymer is RNA or DNA, but it does depend on the number of strands making up the helix of the added polymer. We ascribe the observed changes in melting temperature of poly(dA) . poly(dT) to the increase in ionic strength of the bulk solution brought about by the presence of the added nucleic acid and its associated counterions. We refer to this communication between non-contacting biopolymers in solution as solvent-mediated crosstalk. By comparison with a known standard curve of tm versus log[Na+] for poly(dA) . poly(dT), we estimate the magnitude of the apparent change in ionic strength resulting from the presence of the bulk nucleic acid, and we compare these results with predictions from theory. We find that current theoretical considerations correctly predict the direction of the t(m) shift (the melting temperature increases), while overestimating its magnitude. Specifically, we observe an apparent increase in ionic strength equal to 5% of the concentration of the added duplex DNA or RNA (in mol phosphate), and an additional apparent increase of about 9.5 % of the nucleic acid concentration (mol phosphate) upon denaturation of the added DNA or RNA, yielding a total apparent increase of 14.5 %. For the poly(rU) . poly(rA) . poly(rU) triplex, the total apparent increase in ionic strength corresponds to about 13.6% of the amount of added triplex (moles phosphate). The effect we observe is due to coupled equilibria between the solute molecules mediated by modulations in cation concentration induced by the presence and/or the transition of one of the solute molecules. We note that our results are general, so one can use a different solute probe sensitive to proton binding to characterize subtle changes in solution pH induced by the presence of another solute in solution. We discuss some of the broader implications of these measurements/results in terms of nucleic acid melting in multicomponent systems, in terms of probing counterion environments, and in terms of potential regulatory mechanisms.

Animals↗
PubMed2001

Communication between noncontacting macromolecules.

We present a quantitative experimental demonstration of solvent-mediated communication between noncontacting biopolymers. We show that changes in the activity of a solvent component brought about by a conformational change in one biopolymer can result in changes in the physical properties of a second noncontacting biopolymer present in solution. Specifically, we show that the release of protons on denaturation of a donor polymer (in this case, a four-stranded DNA tetraplex, iDNA) modulates the melting temperature of a noncontacting, acceptor polymer [in this case poly(A)]. In addition to such proton-mediated cross talk, we also demonstrate counterion-mediated cross talk between noncontacting biopolymers. Specifically, we show that counterion association/release on denaturation of native salmon sperm DNA (the donor polymer) can modulate the melting temperature of poly(dA) x poly(dT) (the acceptor polymer). Taken together, these two examples demonstrate how poly(A) and poly(dA) x poly(dT) can serve as molecular probes that report the pH and free salt concentrations in solution, respectively. Further, we demonstrate how such through-solvent dialogue between biopolymers that do not directly interact can be used to evaluate (in a model-free manner) association/dissociation reactions of solvent components (e.g., protons, sodium cations) with one of the two biopolymers. We propose that such through-solution dialogue is a general property of all biopolymers. As a result, such solvent-mediated cross talk should be considered when assessing reactions of multicomponent systems such as those that exist in essentially all biological processes.

Animals↗
PubMed2001

Acid- and base-induced conformational transitions of equinatoxin II.

We have investigated the acid- and base-induced conformational transitions of equinatoxin II (EqTxII), a pore-forming protein, by a combination of CD-spectroscopy, ultrasonic velocimetry, high precision densimetry, viscometry, gel electrophoresis, and hemolytic activity assays. Between pH 7 and 2, EqTxII does not exhibit any significant structural changes. Below pH 2, EqTxII undergoes a native-to-partially unfolded transition with a concomitant loss of its rigid tertiary structure and the formation of a non-native secondary structure containing additional alpha-helix. The acid-induced denatured state of EqTxII exhibits a higher intrinsic viscosity and a lower adiabatic compressibility than the native state. Above 50 degrees C, the acid-induced denatured state of EqTxII reversibly denatures to a more unfolded state as judged by the far UV CD spectrum of the protein. At alkaline pH, EqTxII undergoes two base-induced conformational transitions. The first transition occurs between pH 7 and 10 and results in a partial disruption of tertiary structure, while the secondary structure remains largely preserved. The second transition occurs between pH II and 13 and results in the complete loss of tertiary structure and the formation of a non-native, more alpha-helical secondary structure. The acid- and base-induced partially unfolded states of EqTxII form water-soluble oligomers at low salt, while at high salt (> 350 mM NaCl), the acid-induced denatured state precipitates. The hemolytic activity assay shows that the acid- and base-induced denatured states of EqTxII exhibit significantly reduced activity compared to the native state.

Animals↗
PubMed1999

The hydration of nucleic acid duplexes as assessed by a combination of volumetric and structural techniques.

Using high precision densimetric and ultrasonic measurements, we have determined, at 25 degrees C, the apparent molar volumes PhiV and the apparent molar compressibilities PhiK(S) of four nucleic acid duplexes-namely, the DNA duplex, poly(dIdC)poly(dIdC); the RNA duplex, poly(rA)poly(rU); and the two DNA/RNA hybrid duplexes, poly(rA)poly(dT) and poly(dA)poly(rU). Using available fiber diffraction data on these duplexes, we have calculated the molecular volumes as well as the solvent-accessible surface areas of the constituent charged, polar, and nonpolar atomic groups. We found that the hydration properties of these nucleic acid duplexes do not correlate with the extent and the chemical nature of the solvent-exposed surfaces, thereby suggesting a more specific set of duplex-water interactions beyond general solvation effects. A comparative analysis of our volumetric data on the four duplexes, in conjunction with available structural information, suggests the following features of duplex hydration: (a) The four duplexes exhibit different degrees of hydration, in the order poly(dIdC)poly(dIdC) > poly(dGdC)poly(dGdC) > poly(dAdT)poly(dAdT) approximately poly(dA)poly(dT). (b) Repetitive AT and IC sequences within a duplex are solvated beyond general effects by a spine of hydration in the minor groove, with this sequence-specific water network involving about 8 additional water molecules from the second and, perhaps, even the third hydration layers. (c) Repetitive GC and IC sequences within a duplex are solvated beyond general effects by a "patch of hydration" in the major groove, with this water network involving about 13 additional water molecules from the second and, perhaps, even the third hydration layers. (d) Random sequence, polymeric DNA duplexes, which statistically lack extended regions of repetitive AT, GC, or IC sequences, do not experience such specific enhancements of hydration. Consequently, consistent with our previous observations (T. V. Chalikian, A. P. Sarvazyan, G. E. Plum, and K. J. Breslauer, Biochemistry, 1994, Vol. 33, pp. 2394-2401), duplexes with approximately 50% AT content exhibit the weakest hydration, while an increase or decrease from this AT content causes enhancement of hydration, either due to stronger hydration of the minor groove (an increase in AT content) or due to stronger hydration of the major groove (an increase in GC content). (e) In dilute aqueous solutions, a B-DNA duplex is more hydrated than an A-DNA duplex, a volumetric-based conclusion that is in agreement with previous results obtained on crystals, fibers, and DNA solutions in organic solvent-water mixtures. (f) the A-like, RNA duplex poly(rA)poly(rU) and the structurally similar A-like, hybrid duplex poly(rA)poly(dT), exhibit similar hydration properties, while the structurally distinct A-like, hybrid duplex poly(rA)poly(dT) and non-A-like, hybrid duplex poly(dA)poly(rU) exhibit differential hydration properties, consistent with structural features dictating hydration characteristics. We discuss how volumetric characterizations, in conjunction with structural studies, can be used to describe, define, and resolve the general and sequence/conformation-specific hydration properties of nucleic acid duplexes.

Absorptiometry, Photon↗
PubMed1999

A more unified picture for the thermodynamics of nucleic acid duplex melting: a characterization by calorimetric and volumetric techniques.

We use a combination of calorimetric and volumetric techniques to detect and to characterize the thermodynamic changes that accompany helix-to-coil transitions for five polymeric nucleic acid duplexes. Our calorimetric measurements reveal that melting of the duplexes is accompanied by positive changes in heat capacity (DeltaCP) of similar magnitude, with an average DeltaCP value of 64.6 +/- 21.4 cal deg-1 mol-1. When this heat capacity value is used to compare significantly different transition enthalpies (DeltaHo) at a common reference temperature, Tref, we find DeltaHTref for duplex melting to be far less dependent on duplex type, base composition, or base sequence than previously believed on the basis of the conventional assumption of a near-zero value for DeltaCP. Similarly, our densimetric and acoustic measurements reveal that, at a given temperature, all the AT- and AU-containing duplexes studied here melt with nearly the same volume and compressibility changes. In the aggregate, our results, in conjunction with literature data, suggest a more unified picture for the thermodynamics of nucleic acid duplex melting. Specifically, when compared at a common temperature, the apparent large differences present in the literature for the transition enthalpies of different duplexes become much more compressed, and the melting of all-AT- and all-AU-containing duplexes exhibits similar volume and compressibility changes despite differences in sequence and conformation. Thus, insofar as thermodynamic properties are concerned, when comparing duplexes, the temperature under consideration is as important as, if not more important than, the duplex type, the base composition, or the base sequence. This general behavior has significant implications for our basic understanding of the forces that stabilize nucleic acid duplexes. This behavior also is of practical significance in connection with the use of thermodynamic databases for designing probes and for assessing the affinity and specificity associated with hybridization-based protocols used in a wide range of sequencing, diagnostic, and therapeutic applications.

Calorimetry, Differential Scanning↗
PubMed1999

High-resolution calorimetric and optical melting profiles of DNA plasmids: resolving contributions from intrinsic melting domains and specifically designed inserts.

We demonstrate that differential scanning calorimetry (DSC) can be used to yield high-resolution melting profiles for DNA plasmids that agree in all major features with the corresponding plasmid melting profiles derived using more traditional optical techniques. We further demonstrate that by combining information derived from both calorimetric and optical melting profiles one can glean insights that are unavailable from either melting curve alone. By using both optical and calorimetric observables, we show how one can resolve, identify, and measure the thermodynamic properties of particular sequences/domains of interest within a plasmid. We also show that complementary DSC and optical melting studies on plasmids with and without specifically designed inserts can provide fundamental advantages over the corresponding melting studies on other model system constructs for thermodynamically characterizing nucleic acid sequences/structures.

Calorimetry, Differential Scanning↗
PubMed1997

The native and the heat-induced denatured states of alpha-chymotrypsinogen A: thermodynamic and spectroscopic studies.

We report the first protein phase-diagram characterized by a combination of volumetric, calorimetric, and spectroscopic techniques. More specifically, we use ultrasonic velocimetry, densimetry, and differential scanning calorimetry, in conjunction with UV absorbance and CD spectroscopy to detect and to characterize the conformational transitions of alpha-chymotrypsinogen A as a function of both pH and temperature. As judged by the CD spectra, we find that, at room temperature, the protein remains in the native state over the entire pH range investigated (pH 1 to 10). The melting profiles of the native state reveal three distinct pH domains in which protein denaturation produces different final states. Below pH 3.1, we find the heat-induced denatured state of the protein to be molten globule (MG), lacking the native-like tertiary structure, while exhibiting significant secondary structural elements. At neutral and alkaline pH, we find the heat-induced denatured state to be unfolded (U), lacking both tertiary and secondary structures, while being structurally similar to the urea-unfolded state. At intermediate pH values (between pH 3.1 and 7), we find the heat-induced denatured state to exhibit properties characteristic of both the MG and U states. Although at room temperature the protein remains native within the whole pH range studied (pH 1 to 10), our volumetric data reveal that the native state slightly "softens" at low pH, probably, due to pH-induced alterations in electrostatic forces causing the packing of the protein interior at low pH and room temperature to become less "tight". This softening of the protein at low pH is reflected in an 8% increase in the intrinsic compressibility, kM, of the protein "native" state. Our volumetric data also allow us to conclude that the heat-induced MG state retains a liquid-like, water-inaccessible core, with a volume that corresponds to about 40% of the solvent-inaccessible core of the native state. By contrast, our volumetric data are consistent with the U state of the protein being essentially unfolded, with the majority of its constituent atomic groups being solvent exposed and, therefore, strongly hydrated.

Calorimetry, Differential Scanning↗
PubMed1997

Thermodynamic properties of a conformationally constrained intramolecular DNA triple helix.

We describe the thermodynamic properties of an intramolecular triple helix with two all-thymine linker loops in which the Hoogsteen strand is covalently crosslinked to the underlying Watson-Crick hairpin duplex by means of a disulfide bridge. We compare these properties to those of the corresponding intramolecular triplex without the disulfide crosslink. Optical and calorimetric measurements reveal that the uncrosslinked parent triplex melts in a biphasic manner above pH 6, with the initial triplex to duplex transition (Hoogsteen strand release) occurring at lower temperatures than subsequent melting of the hairpin helix. By contrast, crosslinking increases the thermal stability of the Hoogsteen transition such that the triplex and underlying hairpin duplex melt as a single transition under all conditions studied. Model independent thermodynamic data obtained by differential scanning calorimetry reveals the crosslink-induced increase in triplex thermal stability corresponds to a free energy stabilization of about 3 kcal/mol, with this stabilization being entirely entropic in origin. In other words, the crosslink is enthalpically neutral, but nevertheless, induces a triplex stabilization of 3 kcal/mol due to a reduction in the entropy change associated with triplex melting. In an effort to define the origin(s) of this entropic impact, we measured the pH and ionic strength dependence of the melting transitions. From a comparison of the melting transitions at different pH values and ionic strengths, we estimate that 0.4 more protons are associated with the crosslinked triplex state than with the uncrosslinked triplex, and 1.3 fewer counterions are released on melting the crosslinked triplex. We discuss how such crosslink-induced changes in proton binding and counterion release, in conjunction with potential changes in hydration and conformational freedom, could combine to give rise to the observed changes in entropy.

Base Sequence↗
PubMed1996

Triple helical structures involving inosine: there is a penalty for promiscuity.

Inosine has the ability to act as a "wild-card" binding nonspecifically to both A.T and G.C base pairs. This has obvious implications for the design of oligonucleotide site-directed probes. In this paper we present a series of oligonucleotides with a 5'pur9-pyr9-pyr9 motif which are designed to fold up sequentially into intramolecular triple helices. One or more inosines are incorporated into the Hoogsteen strands in place of T's and/or C's. Once folded into the triplex, the inosine-containing third strand is incorporated in parallel orientation to the purine strand of the duplex. The influence of inosine on the triplex-duplex equilibrium, characterized by the melting temperature (Tm) and on the phase boundaries, as a function of pH and/or ionic strength, has been assessed by means of UV and CD spectroscopy. There are two distinguishable influences of third-strand inosines which affect binding, namely, backbone distortion due to bulkiness (I for T and I for C+) and/or loss of intramolecular ion pairs between protonated cytosines and the backbone phosphates (I for C+). A single thymine replacement drops the Tm by 25.0 (+/- 2.1) degrees C, and replacing a single protonated cytosine drops the Tm by 32.1 (+/- 1.0) degrees C at pH 6.0. On introducing two inosines in place of thymines, the Tm at pH 6.0 of the triple helix to hairpin transition is lowered by 35.5 (+/- 1.4) degrees C; on introducing two inosines in place of cytosines, the Tm drops by 44.5 (+/- 1.0) degree C, and on replacing a cytosine and a neighboring thymine with inosines, the Tm of the same transition is lowered by 29.2 (+/- 1.6) degrees C. Replacing more than two thymines or cytosines, respectively, eliminates the binding of the Hoogsteen strand at room temperature altogether. Under no circumstances does inosine replacement stabilize the triplex helix: it is a poor substitute and its role as a wild-card is limited.

Base Composition↗
PubMed1994

Electrostatic effects in DNA triple helices.

Electrostatic effects dominate many aspects of nucleic acid behavior in a sequence independent manner. Sequence dependent electrostatic effects are introduced when a polypyrimidine, which contains one or more protonated cytosines, binds in the major groove (Hoogsteen side) of a complementary Watson-Crick double helix. Depending on the number of cytosines in the third strand (global effect) and on their relative position (local effect), the cytosines either enhance or decrease the binding affinity of the third strand, because adjacent protonated cytosines destabilize the third strand binding compared to cytosines separated by intervening thymines. This local effect (crowding) can reverse the effect of global composition. To investigate the extent of the local and global electrostatic effects further, two families of oligonucleotides have been synthesized. They share as a common design feature that they all fold sequentially into isosterical intramolecular triple helices by way of hairpin intermediates. This is confirmed by P1 nuclease probing, CD spectroscopy, and UV spectroscopy. The thermal stability of these conformations depends on the sequences, pH, and the ionic strength and can be summarized as follows: The energy of third strand binding depends on the protonated cytosine content in the Hoogsteen strand. It increases with increasing cytosine content (global composition) below pH 7.1 (150 mM Na+), decreases above pH 7.1, and is independent of the cytosine content at pH 7.1. At pH 6.75 the energy of binding increases with increasing cytosine content below 400 mM Na+, decreases above 400 mM Na+, and is independent of the global composition at 400 mM Na+.

Animals↗
PubMed1994

Glycosylation of glycoprotein 55 encoded by the anaemia-inducing strain of Friend spleen focus-forming virus.

Normal rat kidney cells, non-productively infected with the anaemia-inducing variant of Friend spleen focus-forming virus (F-SFFVA), were metabolically labelled with [2-3H]mannose. The primary translation product of the viral envelope gene (env), representing a glycoprotein with an apparent molecular M(r) of 55,000 (gp55), was isolated from cell lysates by immunoaffinity chromatography and purified by preparative SDS/PAGE. Radiolabelled oligosaccharides, released from tryptic glycopeptides by treatment with endo-beta-N-acetylglucosaminidase H, were characterized chromatographically, by enzymic digestion and by acetolysis. The results revealed that F-SFFVA gp55 obtained from this source carried predominantly oligomannose type sugar chains with five to nine mannoses. As a characteristic feature, glycans with seven to nine mannoses contained, in part, an additional glucose residue. Although the amount of glucosylated species found was higher in F-SFFVA gp55 (about 25% of total endo-H-sensitive oligosaccharides) than in gp55 of the corresponding polycythaemia-inducing variant (F-SFFVP, 16.3%), the overall glycosylation pattern of the F-SFFVA env product closely resembled that of F-SFFVP gp55 [Strube et al. (1988) J Biol Chem 263:3762-71]. Hence, our results demonstrate that the different intracellular processing and transport of the primary F-SFFVA env product cannot be attributed to aberrant trimming of its oligomannose type glycans.

Animals↗
PubMed1994

Meningeal carcinomatosis: CSF cytology, immunocytochemistry and biochemical tumor markers.

CSF cytology, immunocytochemistry and biochemical tumor markers were compared in 12 patients with a meningeal carcinomatosis regarding diagnostic significance and therapy control; 50 samples were investigated. Cytology was tumor-positive in 39 samples and immunocytochemistry in 45 samples. Intrathecally produced tumor markers were found in 47 samples. On initial examination only immunocytochemical testing correctly classified all cases. Cytology and biochemical tumor markers revealed positive results in 10 respectively 11 of 12 patients, combined use of these two methods would increase the sensitivity to 100%. On follow-up examination tumor markers correlated best with symptoms and were early indicators for clinical relapse. These results could be achieved only if several monoclonal antibodies and biochemical tumor marker tests were combined. It is concluded that immunocytochemistry and biochemical tumor markers are of major help regarding the problems of false-negative cytology and reliable therapy control in meningeal carcinomatosis.

Adult↗
PubMed1993

Energetics of a stable intramolecular DNA triple helix formation.

We have designed and synthesized by conventional chemical techniques a 38mer oligonucleotide consisting of a 5'd(Pu)10d(C)4d(Py)10d(T)4d(Py)10(3') sequence. This oligonucleotide assumes a randomly coiled conformation at pH 12. At pH 8.0 a hairpin helix forms between its 5' purine decamer sequence and the consecutive pyrimidine decamer leaving the second pyrimidine decamer as a dangling disordered 3' extension. On reducing the pH to 4.5 this second pyrimidine decamer folds back onto the major groove of the hairpin helix resulting in an intramolecular triple-stranded stem-loop structure. We have used a variety of biochemical (gel mobility, P1 nuclease digestion) and biophysical (ultraviolet light and circular dichroism spectroscopy, fluorimetry, microcalorimetry) techniques to characterize the different conformers, their stability and the folding pathway into an intramolecular triple helix. The thermodynamic properties of this intramolecular triple strand in 100 mM-Na+ are: tm, 71 degrees C; delta HvH, 119.4(+/- 11.9) kcal mol-1; delta Hcal, 121.9 (+/- 6.1) kcal mol-1 at pH 4.5; those of the hairpin are: tm, 63 degrees C; delta HvH, 71.7(+/- 4.0) kcal mol-1; delta Hcal, 69.9(+/- 3.5) kcal mol-1 at pH 8.0. At intermediate pH values, the triplex to coil transition breaks up into its component triplex to hairpin and hairpin to coil transitions with thermodynamic properties: tm, 41 degrees C; delta HvH, 58.7(+/- 4.2) kcal mol-1; delta Hcal, 39.8(+/- 2.0) kcal mol-1; and tm, 63 degrees C; delta HvH, 71.7(+/- 4.0) kcal mol-1; delta Hcal, 69.6(+/- 3.5) kcal mol-1 at pH 6.7.

Base Sequence↗
PubMed1976

[Results and consequences of clinical-radiological follow-up studies of root canal treated teeth. 2. Dependence of the results on age, degree of root canal obturation and devitalizing drugs. Conclusions for the dental practice].

The authors report of the follow-up examination of root-canal treatments performed at the Policlinic of Conservative Stomatology of the Karl Marx University of Leipzig in 1967, in which 499 teeth were assessed using severe criteria. The results obtained from the various diagnostic groups depended on the age and the degree of root-filling. Of the root-canal treatment techniques employed, devitalization by means of arsenic showed the highest failure rate. Conclusions relevant to stomatological practice are drawn from the results presented in the two parts of this study.

Age Factors↗