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PubMed2000

Proposition of group molar constants for sodium to calculate the partial solubility parameters of sodium salts using the van Krevelen group contribution method.

The aim of this study is to propose, for the first time, a set of group molar constants for sodium to calculate the partial solubility parameters of sodium salts. The values were estimated using the few experimental partial solubility parameters of acid/sodium salt series available either from the literature (benzoic acid/Na, ibuprofen acid/Na, diclofenac Na) or determined in this work (salicylic acid/Na, p-aminobenzoic acid/Na, diclofenac), the group contribution method of van Krevelen to calculate the partial parameters of the acids, and three reasonable hypothesis. The experimental method used is a modification of the extended Hansen approach based on a regression analysis of the solubility mole fraction of the drug lnX(2) against models including three- or four-partial solubility parameters of a series of pure solvents ranging from non-polar (heptane) to highly polar (water). The modified method combined with the four-parameter model provided the best results for both acids and sodium derivatives. The replacement of the acidic proton by sodium increased the dipolar and basic partial solubility parameters, whereas the dispersion parameter remained unaltered, thus increasing the overall total solubility parameter of the salt. The proposed group molar constants of sodium are consistent with the experimental results as sodium has a relatively low London dispersion molar constant (identical to that of -OH), a very high Keesom dipolar molar constant (identical to that of -NO(2), two times larger than that of -OH), and a very high hydrogen bonding molar constant (identical to that of -OH). The proposed values are: F((Na)d)=270 (J cm(3))(1/2) mol(-1); F((Na)p)=1030 (J cm(3))(1/2) mol(-1); U((Na)h)=17000 J mol(-1). Like the constants for the other groups, the group molar constants proposed for sodium are certainly not the exact values. However, they are believed to be a fair approximation of the impact of sodium on the partial solubility parameters and, therefore, can be used as such in the group contribution method of van Krevelen.

Algorithms↗
PubMed2001

Molar mass profiling of synthetic polymers by free-solution capillary electrophoresis of DNA-polymer conjugates.

The molar mass distribution of a polymer sample is a critical determinant of its material properties and is generally analyzed by gel permeation chromatography or more recently, by MALDI-TOF mass spectrometry. We describe here a novel method for the determination of the degree of polymerization of polydisperse, uncharged, water-soluble polymers (e.g., poly(ethylene glycol) (PEG)), based upon single-monomer resolution of DNA-polymer conjugates by free-solution capillary electrophoresis. This is accomplished by end-on covalent conjugation of a polydisperse, uncharged polymer sample (PEG) to a monodisperse, fluorescently labeled DNA oligomer, followed by electrophoretic analysis. The monodisperse, charged DNA "engine" confers to each conjugate an equal amount of electromotive force, while the varying contour lengths of the uncharged, polydisperse polymers engender different amounts of hydrodynamic drag. The balance of electromotive and hydrodynamic forces enables rapid, high-resolution separation of the DNA-polymer conjugates as a function of the size of the uncharged PEG tail. This provides a profile of the molar mass distribution of the original polymer sample that can be detected by laser-induced fluorescence through excitation of the dye-labeled DNA. We call this method free solution conjugate electrophoresis (FSCE). Theory-based analysis of the resulting electrophoresis data allows precise calculation of the degree of polymerization of the PEG portion of each conjugate molecule. Knowledge of the molecular mass of the uncharged polymer's repeat unit allows for direct calculation of the molar mass averages as well as sample polydispersity index. The results of these analyses are strikingly reminiscent of MALDI-TOF spectra taken of the same PEG samples. PEG samples of 3.4-, 5-, and 20-kDa nominal average molar mass were analyzed by FSCE and MALDI-TOF; the values of the molar mass averages, Mw and Mn, typically agree to within 5%. Measurements and molar mass calculations are performed without any internal standards or calibration. Moreover, when DNA-polymer conjugate analysis is performed in a chip-based electrophoresis system, separation is complete in less than 13 min. FSCE offers an alternative to MALDI-TOF for the characterization of uncharged, water-soluble polymers that can be uniquely conjugated to DNA.

DNA↗
PubMed1982

Partial molar volumes of some 1-alkanols in erythrocyte ghosts and lipid bilayers.

The partial molar volumes of 1-heptanol and 1-octanol in red cell ghosts, in egg phosphatidylcholine bilayers, and in water and phosphate buffer have been measured to a precision of better than 4% by using a density meter. In every case, the partial molar volume was independent of concentration in the range studied. In both membranes, the partial molar volume of each alcohol was close to its molar volume whereas in aqueous solution it was considerably less. Comparison of the two membranes suggests that the major contribution to the partial molar volume arises from alcohol-lipid interactions of each case. Further comparison with partial molar volumes in bulk solvents suggests that on average the alcohols retain a hydrogen bond in the lipid bilayer. The magnitude of the volume change in ghosts is some 5 times less than the corresponding area changes previously reported by others [Roth, S. H., & Seeman, P. (1972) Biochim. Biophys. Acta 255, 190-198]. These two observations can only be resolved by assuming either that the bilayer expands anisotropically, experiencing a decrease in thickness with increasing volume, or that conformational changes in membrane-associated proteins can occur at constant volume to increase membrane area. Finally, these data are used to test the critical volume hypothesis of general anesthetic action. A volume change of 0.15% in red cell ghost membranes is found to be associated with anesthesia, which compares with a value of 0.2% predicted previously from pressure reversal of anesthesia studies. In egg phosphatidylcholine bilayers, a volume change of 0.36% is associated with anesthesia. The larger change in the lipid bilayer compared to the biomembrane originates solely in their different membrane/buffer partition coefficients.

Alcohols↗
PubMedDate not supplied

Evaluation of radius of gyration and intrinsic viscosity molar mass dependence and stiffness of hyaluronan.

Nine hyaluronan (HA) samples were fractionated by size-exclusion chromatography, and molar mass (M), radius of gyration (Rg), and intrinsic viscosity ([eta]) were measured in 0.15 M NaCl at 37 degrees C by on-line multiangle light scattering and viscometer detectors. Using such method, we investigated the Rg and [eta] molar mass dependence for HA over a very wide range of molar masses: M ranging from 4 x 10(4) to 5.5 x 10(6) g/mol. The Rg and the [eta] molar mass dependence found for HA showed a meaningful difference. The Rg = f(M) power law was substantially linear in the whole range of molar masses explored with a constant slope of 0.6. In contrast, the [eta] = f(M) power law (Mark-Houwink-Sakurada plot) showed a marked curve shape, and a linear regression over the whole range of molar masses does not make sense. Also the persistence length (stiffness) for HA was estimated. The persistence length derived by using both the Odijk's model (7.5 nm from Rg vs M data) and the Bohdanecky's plot (6.8 nm from [eta] vs M data) were quite similar. These persistence length values are congruent with a semistiff conformation of HA macromolecules.

Chromatography, Gel↗
PubMed1980

Effect of dietary phytate/zinc molar ratio on growth and bone zinc response of rats fed semipurified diets.

In rats fed semipurified diets, bioavailability of dietary zinc was tested at different phytate/zinc molar ratios; growth and zinc in femurs were the criteria of adequacy. On diets with 10--12 ppm zinc, the growth of rats was not affected by phytate/zinc molar ratios of 12 or less if the level of dietary calcium was 0.75% but was depressed at ratios greater than 6 if the level of calcium was 1.75%. Phytate/zinc molar ratios greater than these did not depress growth if the dietary zinc concentration was at least 2.5 and 5 times the minimal requirement for growth at dietary calcium levels of 0.75 and 1.75%, respectively. At the maximum phytate/zinc molar ratio that did not depress growth, accumulation of zinc in femurs was depressed. Small increases in dietary calcium (from 0.75 to 0.87%) depressed growth of rats fed diets with 12 ppm zinc and a phytate/zinc molar ratio of 25. Preformed Zn3 and Zn6 phytate preparations were equivalent to ZnSO4.7H2O as dietary zinc sources. The data indicated that high dietary calcium per se reduced zinc bioavailability. The maximum phytate/zinc molar ratio that did not depress growth of young rats was greatly influenced by dietary calcium level and somewhat influenced by total dietary zinc concentration.

Animals↗
PubMed2000

Left-molar approach improves the laryngeal view in patients with difficult laryngoscopy.

BACKGROUND: The molar approach of laryngoscopy is reported to improve glottic view in sporadic cases of difficult laryngoscopy. The authors studied the effect of molar approaches and optimal external laryngeal manipulation (OELM) using the Macintosh blade. METHODS: A series of 1,015 adult patients who underwent general anesthesia and tracheal intubation was studied. Laryngoscopy was carried out using a Macintosh no. 3 or 4 standard blade. Three consecutive trials of direct laryngoscopy using the midline and left- and right-molar approaches were carried out under full muscle relaxation with optimal head and neck positioning. The best glottic views were recorded for each approach with and without OELM. RESULTS: Difficult laryngoscopy with a midline approach accounted for 6.5% (66 cases) before OELM and 1.97% (20 cases) after OELM. A left-molar approach with OELM further reduced difficult laryngoscopy to seven cases (P < 0.001 vs. midline approach with OELM); a right-molar approach with OELM reduced difficult laryngoscopy to 18 cases (P = 0.48). CONCLUSIONS: The left-molar approach with OELM improves the laryngeal view in patients with difficult laryngoscopy.

Adolescent↗
PubMed2000

Elucidation of vascular structure of molar villi in complete hydatidiform mole by CD-34 antibody.

Vasculature was examined immunohistochemically in the villous stroma in 22 cases of complete hydatidiform mole (CHM). Only antibody CD-34 was able to detect the vasculature. Serial thin and thick sections and squashed preparations of molar villi were stained by CD-34, and sequential photographs of the vasculature were taken and projected on paper, and the vasculature was described and reconstructed. In the stroma of almost all molar villi examined, vessels were found, but their density and structure varied greatly in each molar villus even in the same CHM, and the vessels were irregular in diameter. In fully distended molar villi the vessels often became narrow, continuing like a broken line but eventually vanishing. Generally the density of the vessels was inversely proportional to the grade of the swelling of villi. The vessels sometimes passed through two adjacent molar vesicles. No significant differences in vasculature were found in molar villi at different gestational ages.

Adult↗
PubMed2005

Postevacuation hCG levels and risk of gestational trophoblastic neoplasia in women with complete molar pregnancy.

OBJECTIVES: Women diagnosed with complete hydatidiform molar pregnancy are at 15% to 28% risk of developing persistent gestational trophoblastic neoplasia (GTN) requiring further management with chemotherapy. Our objective was to develop human chorionic gonadotropin (hCG) criteria that establish a patient's risk of developing persistent GTN or achieving remission from their baseline risk within a few weeks of molar evacuation. METHODS: We used a database from the New England Trophoblastic Disease Center to analyze hCG levels from 1,029 women with complete molar pregnancies. We conducted a retrospective cohort study using data from 1973 to 2001. RESULTS: Women whose hCG level declined below 50 mIU/mL during their follow-up were found to be at no more than 1.1% risk for developing persistent GTN, irrespective of when this level was reached. Women whose hCG levels was below 200 mIU/mL in the fourth week after evacuation (59.8% of all women), or below 100 mIU/mL in the sixth week after evacuation (65.8% of all women), had a risk of persistence below 9%. hCG levels above 2,000 mIU/mL in the fourth week after evacuation (13.3% of women) were associated with a 63.8% risk of developing persistent disease. CONCLUSION: These data may allow clinicians to evaluate the risk of persistence that their patients with complete molar pregnancy have based on early hCG results after molar evacuation. In the fourth week after molar evacuation, 59.8% of women may be counseled that their risk of developing persistent GTN is substantially reduced from their baseline, whereas 13.3% of women may be warned that their risk of developing persistent GTN is greater than 50%. LEVEL OF EVIDENCE: II-2.

Adult↗
PubMed2001

Molar fracture resistance after adhesive restoration with ceramic inlays or resin-based composites.

PURPOSE: To determine the fracture resistance of teeth, following treatment with various types of adhesive restorations. MATERIALS AND METHODS: 5 0 caries-free, extracted human molars were randomly divided into five groups consisting of 10 molars each. MOD cavities were prepared in 40 molars with a width in the facio-lingual direction of 50% of the intercuspal distances. The cavities were filled with the following materials: Cerec or IPS Empress ceramic inlays, Arabesk or Charisma F resin-based composite (RBC) restorations. The control group consisted of 10 sound, non-restored molars. All 50 teeth were loaded occlusally until fracture using a tensile testing machine. The statistical analysis included ANOVA, Kolmogorov-Smimov-test, Scheffé test, and boxplots. RESULTS: There was no significant difference (P > 0.05) between the mean values of the sound teeth (2,102 N) and the teeth with the Cerec ceramic inlays (2,139 N). However, both groups demonstrated a significant difference (P < 0.05) when compared with the teeth with IPS Empress ceramic inlays (1,459 N) and Arabesk RBC restorations (1459 N). No significant differences were found between the last two groups. Molars restored with Charisma F composite restorations (1,562 N) revealed no significant difference when compared with all other groups including controls (P > 0.05). A stabilization of molars is possible by means of an adhesive restoration in the form of an "internal splinting" regardless of the restorative material used.

Acrylates↗
PubMed2003

[Unsuspected molar pregnancy in first trimester miscarriages].

OBJECTIVE: To assess the prevalence of unsuspected molar pregnancy in patients with first trimester spontaneous abortions. METHODS: An observational, cross-section study was carried out in 396 consecutive patients with diagnosis of first trimester spontaneous abortions, without clinical or ultrasonographic findings suggesting hydatidiform mole, a histological diagnosis was made from the curettage specimens, the cases with diagnosis of any trophoblastic disease prior of curettage were not included in the study. RESULTS: Diagnosis of molar pregnancy was made in 48 out of 396 patients (12.1%). There was not statistical difference in the sociodemographic variables and risk factors analyzed: patient age, familial incomes, years in scholar courses, prior pregnancies, deliveries, spontaneous abortions, number of sons, and prior hormone contraceptive use between the patients with diagnosed molar pregnancy and those patients without the diagnosis of molar pregnancy. CONCLUSION: The prevalence of unsuspected molar pregnancy found in our study (12.1%) was high and the suspicion in these cases according the risk factors of the disease could be difficult, therefore to rule out systematically molar pregnancy in each case of spontaneous abortions is recommended in order to avoid the complications associated with hydatidiform mole.

Abortion, Spontaneous↗
PubMed1975

Progesterone concentration in placenta, molar tissue, and ovarian theca lutein cyst.

Progesterone concentrations in 2 full-term normal placentas, molar tissue from 3 cases of hydatidiform mole were measured by competitive protein binding. Sephadex LH-20 column chromatographic separation of extracts from these tissues showed that, in placental and molar tissue, 85 to 95% of the extracts were progesterone and very small amounts of 20 alpha-dihydroprogesterone and 17 alpha-hydroxyprogesterone. The concentration of progesterone in the placenta were 368.8 and 317.2 ng/g tissue, respectively, while in molar tissue the concentration were 2474.5, 1974.6, and 4146.0 ng/g tissue, respectively. Progesterone concentration in ovarian tissue was between 1121;2 and 1440.9 ng/g tissue. It is suggested that the high concentration of progesterone in molar tissue reflects functional capacity of the abnormal trophoblast in progesterone synthesis and accumulation of progesterone due to absence of a fetus. The lower concentration of progesterone in the ovary in molar pregnancy would appear to suggest that the ovary is a secondary source of progesterone in molar pregnancy.

Chorionic Gonadotropin↗
PubMed1990

Effect of PAI-1 levels on the molar concentrations of active tissue plasminogen activator (t-PA) and t-PA/PAI-1 complex in plasma.

We determined the in vivo molar concentrations of active tissue plasminogen activator (t-PA), active plasminogen activator inhibitor type 1 (PAI-1), and t-PA/PAI-1 complex. t-PA activity was measured in plasma stabilized by immediate acidification. PAI-1 activity and t-PA/PAI-1 complex antigen were measured in citrated plasma; these measurements were corrected for the loss in PAI-1 activity and increase in complex that occurs in unacidified plasma samples due to the continued reaction between t-PA and PAI-1 after the sample was drawn. To convert t-PA and PAI-1 activity measurements into molar concentrations we determined the specific molar activity of t-PA and PAI-1 in vivo: 4.48 x 10(13) IU/mol. Of 72 subjects studied, 13 had less than 150 pmol/L active PAI-1; in these individuals 33% +/- 21% of their t-PA was active and the molar ratio of active t-PA to active PAI-1 was 0.20 +/- 0.13. In the 11 subjects with greater than 500 pmol/L active PAI-1, 1.5% = 1.1% of the t-PA was active and the molar ratio of active t-PA to active PAI-1 was 0.0043 +/- 0.0036. Overall, the fraction of active t-PA declined exponentially as a function of the active PAI-1 concentration. During the day, the percentage of total t-PA that was active increased from 12% at 8:00 AM to 31% at 8:00 PM, while the molar ratio of active t-PA to active PAI-1 increased from 0.05 to 0.22 from morning to evening (n = 12).

Antithrombins↗
PubMed1987

[Studies on HLA specificities in molar conceptions].

Complete mole is a form of natural allograft since it carries paternal genetic traits alone which differ antigenetically from those of the mother. Successful growth of mole is likely to be immunologically protected. Because the immune system is genetically controlled, the effect of HLA system on the development of androgenetic ova into moles is a subject of interest. In this study, HLA-A and -B specificities in the mole and its parent were compared with the ones of general population in Japan. Fifty-six molar tissues were used for absorption of HLA specificities determined by HLA typing of each patient and her husband. Results obtained were as follows. 1) HLA antigens were expressed on all molar tissues examined, and those antigen were derived selectively from paternal specificities, but not maternal one. 2) Fifty molar tissues had received the paternal haplotype and remaining six molar tissues had showed heterozygosity which were consistent with the paternal diplotype. Those suggested the fertilization of an empty egg by two spermatozoa. 3) A significant association was found with decreased frequency of HLA-Aw19 and HLA-Bw22 in the molar tissues (3.6% and 2.7%) compared with general population (16.4% and 11.5%). 4) The compatibility of HLA-A and -B types among moles with sequelae and the parents was higher(81%) than the estimated value(68%) in the control families. As a result, HLA analysis was useful for distinction of zygosity of molar tissues. Decreased frequencies of HLA-Aw19 and -Bw22 in the mole were assumed to be resulted from the wastage of androgenetic ova.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1994

Variation in enamel thickness and cusp area within human maxillary molars and its bearing on scaling techniques used for studies of enamel thickness between species.

Thirty-nine unworn maxillary molars (M1 = 18, M2 = 12, M3 = 9), representing 37 individuals of a Slavic population, were sectioned through the mesial cusps in a plane perpendicular to the cervical margin of the crown. Whether the range of variation in enamel cross-sectional area between individuals corresponds to the range of variation found between teeth within a species was investigated. Total tooth crown area, as determined by planimetry, was used as a scaling factor on the basis that a biologically meaningful scaling procedure should take into account both enamel thickness and total tooth crown area, rather than the size of the dentine-enamel junction. Uni- and multivariate statistics revealed that the enamel cross-sectional area of second and third molars is absolutely and relatively larger than it is in first upper molars and that it scales close to isometry with tooth crown area. Conversely, first maxillary molars, with their relatively and absolutely thinner enamel, exhibit positive allometry between enamel and tooth crown area. These patterns were retained even when differences in overall tooth size were adjusted for. Hence, the notion that there exists a 'species-specific' amount of enamel over the tooth crown must be reconsidered, and one should refrain from pooling different tooth types for taxonomic purposes. At least two scaling factors are needed to describe human maxillary molars alone. However, this increase in enamel cross-sectional area from anterior to posterior is not unexpected if one bears in mind that posterior teeth occupy a more advantageous position relative to the chewing muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Austria↗
PubMed2004

A prospective study on transplantation of third molars with complete root formation.

OBJECTIVE: The study objective was to evaluate the prognosis for autotransplantation of third molar teeth with fully developed roots followed by endodontic treatment on the basis of a time-table analysis. STUDY DESIGN: A total of 50 third molars with completely developed roots were autotransplanted to replace a lost first or second molar in the same number of admitted patients. Root canal treatment was started 3 to 4 weeks later. Clinical and radiographic checkup of the transplanted and root-filled third molars was done annually according to a predesigned record form. Descriptive statistics including a life table and statistical analysis were performed. RESULTS: The cumulative survival rate during 4 years' follow-up was 81.4%. In all, 7 transplants were lost during the follow-up time, 4 of them due to marginal periodontal pathosis and the other 3 due to root resorption. None of the root resorptions was observed before the second postoperative year. The radiographic periapical status was considered normal in 96% of the transplants at the latest follow-up visit. CONCLUSIONS: Autotransplantation of mature third molar teeth is a reasonable treatment alternative to conventional prosthetic rehabilitation or implant treatment in cases of partial edentualism from both a therapeutic and an economic point of view.

Adult↗
PubMed1997

A device to predict lower third molar eruption.

This study was designed to create a transparent device to be superimposed on a panoramic tomogram taken of a patient at age 20 years to make predictions of future eruption or impaction of lower third molars. The device was developed from data on 40 lower third molars initially retained at age 20 years; one half of these remained impacted, and the other half of them erupted by age 26 years. Tracings were made from panoramic tomograms taken at age 20 years. The critical point for prediction in the overlay was the intersection of a horizontal reference line and the anterior border of the ascending ramus. To estimate this critical separation line, Bayes' Decision Theory was used. The sum of false negatives and false positives was least at a distance of 14.5 mm from the distal surface of the second molar. Mesial from this point, the probability of impaction was 76%; distal from this point, the probability of eruption was 72%. Tested against 35 initially unerupted lower third molars, the predictions made by the device and the actual clinical findings were in conformity in relation to 97% of the test teeth. It could thus be concluded that the method was simple to use and may prove a good addition for predicting lower third molar development.

Adult↗
PubMed1996

Extraction of maxillary second molars in the treatment of Class II malocclusion.

The results of treatment following the extraction of maxillary second molars for Class II correction were evaluated. Records (cephalograms, orthopantomograms, and models) of 32 patients treated with maxillary second molar extraction were analyzed. Cephalograms taken before and after treatment were traced and 18 variables were compared. Changes in the axial inclination of the erupted third molars relative to the occlusal plane were measured on the orthopantomograms. The form and the position (eruption in occlusion, rotations) of the maxillary third molars were evaluated on the models. The average treatment time was 26 months. The results of this study show significant changes of the angles SNA, SNB, ANB, 1/4:SN, and the distances 1-NPog, and 1-APog, as well as significant effects on the soft tissue profile. In 19 cases examined 4 years postretention, all maxillary third molars had erupted into occlusion with a mesial contact point and acceptable mesiodistal axial inclination.

Adolescent↗
PubMed2003

Marginal flap versus paramarginal flap in impacted third molar surgery: a prospective study.

OBJECTIVE: A clinical prospective study was carried out to compare 2 flap designs-marginal and paramarginal-that are used during impacted third molar surgery. MATERIALS AND METHODS: Twenty-seven healthy patients (ages 17 to 31 years) who underwent surgical removal of 4 impacted third molars, including 54 lower and 54 upper, were included. A marginal flap was used in 1 randomly chosen half of the jaw, and a paramarginal flap was used in the other half. The influence of these flaps on wound healing, periodontal pocket depth of the adjacent second molar, pain, trismus, and swelling was studied. RESULTS: Wound dehiscences developed in 8 paramarginal flap cases, whereas none occurred with the use of a marginal flap. The buccal and distal probing depths of the adjacent second molar were significantly bigger in marginal flaps at 5 and 10 days after surgery. However, the probing depth was similar with the use of both techniques at 3 months. Pain, trismus, and swelling were similar with both techniques. CONCLUSIONS: We found no advantages to the use of a paramarginal flap instead of a traditional marginal flap for removing impacted third molars.

Adolescent↗