Dental materials in the new millennium: research at Baylor College of Dentistry and a look at new trends.
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Aged↗
Biomedical subjects
Z Cai
Publications and source records attributed to Z Cai.
[Comparative histomorphological study on the craniomaxillary development of the trisomy-18 with cleft palate and euploid mice].
OBJECTIVE: The aim of this study is to compare histological morphology of craniomaxillary complex of Trisomy 18 with cleft palate (Ts + CP) and euploid mouse foetuses to understand whether cleft palate is associated with maldevelopment of the craniomaxillary complex or with hypoplasia of the adjacent tissues. METHODS: Thirty pairs of Ts + CP and euploid mouse foetuses with about equal body weight were selected, and sixty craniomaxillary complex were precisely orientated in the coronal plane, then serially sectioned with 7 microns thickness through the primary palate, the whole hard palate and the soft palate. Finally six sections were selected for comparative histomorphological study based on anatomical landmarks. RESULTS: The trisomy with cleft palate mouse foetuses had significantly developmental hypoplasia in the primary palatal shelves. The palatal shelves, vomer, palatal bone and nasal septal cartilage in cleft samples showed significantly developmental hypoplasia with a relatively wider nasal septum, nasal capsule and a bigger nasal airway volume, nasopharyngeal cavity. CONCLUSION: The hard tissues of the craniomaxillary complex in Ts + CP mouse foetuses, including bone and cartilage show serious maldevelopment or developmental hypoplasia, and these may be closely related to the autosomal trisomic condition.
Animals↗
[Studies on the correlation between production of L-malic acid and some cytosolic enzymes in the L-malic acid producing strain Aspergillus sp. N1-14].
The cytosol enzymatic study in the case of high L-malic acid(LMA) production of Aspergillus sp. N1-14' was reported. The activities of 4 kind enzymes that catalyse the CO2 fixation reactions have been detected, which are pyruvate carboxylase(PC), phosphoenolpyruvate carboxlase (PEPC), phosphoenolpyurvate carboxykinase(PCK) and malic enzyme(ME). With the exception of ME, the linear correlation was found between activities of three carboxlases and the production rate of LMA. The activity of malate dehydrogenase(MDH) was at the level of 2-3 exponential higher than that of the other analysed enzymes, while the activity of succinate dehydrogenase(SDH) was much lower, and as a discrepancy, SDH was in a positive correlation to the content of LMA in fermenting slurry(r = 0.9252). It is shown that the accumulated LMA acted as an activator of SDH. Through dynamic study, it is found that, in contrast with the slow and even increase of biomass, the content of cytosol protein(Cp) sharply fluctuated mainly due to the changes of aeration conditions. The data of the linear correlation coefficients(r) of activities of cytosol enzymes to Cp(PC r = 0.9563, PEPC r = 0.7688, PCK r = 0.7300, MDH r = 0.3920, SDH r = -0.2086) exhibited an inner law of protein synthesis. Experiment of increasing the amount of spore inoculum resulted in increase of LMA and decrease of SA. After fermenting 120 h in a 5 L stirred fermentor, with 3-fold of original spore inoculum 105.88 g/L of LMA was achieved, the overall productivity was 0.883 g/(L.h), the converting rate of glucose to LMA was 78.43%. This result supports the exist of a inner law of protein synthesis in the early period of LMA fermentation by Aspergillus sp. N1-14'.
Aspergillus↗
[Photoluminescence characteristics of mixed aggregates in Langmuir-Blodgett multilayers].
Effects of the mixed aggregates of different active molecules and UV illumination on photoluminescence(PL) spectra of Langmuir-Blodgett multilayers were investigated. The strong interaction between hemicyanine and stilbazolium salt molecules in the mixed films caused a blue or red shift of the fluorescence band with respect to that of interleaving hemicyanine or stilbazolium salt/arachidic acid multilayers. UV illumination would dissociate the aggregates even more destroy the molecular structure, leading to a significant reduction of fluorescence intensity.
English Abstract↗
Protection of neonatal rat brain from hypoxic-ischemic injury by LY379268, a Group II metabotropic glutamate receptor agonist.
Neuroprotective effects of a Group II metabotropic glutamate receptor agonist, LY379268, were examined in a neonatal rat model of hypoxia-ischemia (unilateral common carotid artery ligation followed by hypoxic exposure for 1.5h in 7-day-old rat pups). LY379268 administered 5 min after hypoxic exposure (2, 5, or 10 mg/kg, i.p.) significantly reduced brain injury as measured by reductions in the ipsilateral brain weight and in CA1 hippocampal neuron density. The significant neuroprotective effects were also observed when this compound (5 mg/kg) was administered 30 min, but not 60 min, after hypoxic exposure. The neonatal hypoxia-ischemia (HI) procedure significantly increased caspase-3 activity and induced DNA fragmentation in the ipsilateral cortex compared with that in the contralateral cortex 24 and 72h after the insult, respectively. LY379268 did not prevent this increase in caspase-3 activity and DNA fragmentation in the ipsilateral cortex. These results suggest that activation of Group II metabotropic glutamate receptors may provide neuroprotection against HI brain injury. However, blockade of caspase-3 activation and the apoptotic pathway appears not to be involved in the neuroprotective effects of LY379268 observed in the neonatal rat model of HI.
Amino Acids↗
Impaired immunoproteasome assembly and immune responses in PA28-/- mice.
In vitro PA28 binds and activates proteasomes. It is shown here that mice with a disrupted PA28b gene lack PA28a and PA28b polypeptides, demonstrating that PA28 functions as a hetero-oligomer in vivo. Processing of antigenic epitopes derived from exogenous or endogenous antigens is altered in PA28-/- mice. Cytotoxic T lymphocyte responses are impaired, and assembly of immunoproteasomes is greatly inhibited in mice lacking PA28. These results show that PA28 is necessary for immunoproteasome assembly and is required for efficient antigen processing, thus demonstrating the importance of PA28-mediated proteasome function in immune responses.
Animals↗
TCR-Mediated internalization of peptide-MHC complexes acquired by T cells.
Peptide-major histocompatibility complex protein complexes (pMHCs) on antigen-presenting cells (APCs) are central to T cell activation. Within minutes of peptide-specific T cells interacting with APCs, pMHCs on APCs formed clusters at the site of T cell contact. Thereafter, these clusters were acquired by T cells and internalized through T cell receptor-mediated endocytosis. During this process, T cells became sensitive to peptide-specific lysis by neighboring T cells (fratricide). This form of immunoregulation could explain the "exhaustion" of T cell responses that is induced by high viral loads and may serve to down-regulate immune responses.
Animals↗
[New subtype of coltivirus isolated from mosquitoes in the northeast part of China].
OBJECTIVE: The purpose of this study was to isolate new arbovirus from mosquitoes collected from the northeast part of China during the summer of 1996. METHODS: The cell used for isolation were C6/36 and BHK-21 cells. RESULTS: Two strains (NE97-12 and NE97-31) of coltivirus were isolated among 68 mosquito specimens. The viruses caused cytopathogenic effects on C6/36 cell, but not on BHK-21 cells. They were resistant to both 5-IDU and ether, but sensitive to pH3.0 and temperature at 56 degrees C for 30 minutes. IFA of new isolates with mouse ascitic fluid anti-coltivirus TRT2 strain showed positive reaction. Polyacrylamide gel electrophoresis (PAGE) of two isolates showed 12 segments of double-stranded(ds) RNA and PAGE profiles were 6-5-1, which were different from that of coltivirus TRT2 strain(6-6). There was no cross neutralization between new isolates and TRT2 strain by tissue culture cross-neutralization test. CONCLUSION: The results indicated while new isolates were serologically related to TRT2 strain of coltivirus by IFA, the neutralization test suggests that it represents a distinct serotype. These new isolates isolated firstly from the northeast part of China belong to a new subtype of coltivirus.
Animals↗
Adenovirus-mediated transfer of wild-type p53 gene sensitizes TNF resistant MCF7 derivatives to the cytotoxic effect of this cytokine: relationship with c-myc and Rb.
Tumor suppressor p53 is a nuclear transcription factor that blocks cell cycle progression and induces apoptosis. We have previously shown that the MCF7 resistance to the cytotoxic action of TNF correlates with p53 mutations. In the present study, we used a recombinant adenovirus carrying a wild-type p53 gene (Adwtp53) in order to investigate the effect of wt p53 transfer on modulation of cell resistance to the cytotoxic action of TNF. Our data indicate that infection of TNF resistant MCF7 cells (1001 and MCF7/Adr) with Adwtp53 resulted in the restoration of wt p53 expression and function as respectively revealed by the yeast assay and the induction of p53 inducible genes MDM2 and p21. Furthermore, the restoration of p53 function significantly sensitized TNF resistant cells to TNF cytotoxic action. This correlated with a significant down-regulation of c-myc in both TNF-resistant cell lines and a decrease of Retinoblastoma protein (Rb) in 1001 clone. In contrast, the effect of p53 seems to be independent from Bcl-2 and Bax protein level regulation. The present study suggests that the combination of TNF and Adwtp53 may be a potential strategy to sensitize mutant p53 TNF-resistant tumors to the cytotoxic action of this cytokine.
Adenoviridae↗
Prenatal hypoxia-ischemia alters expression and activity of nitric oxide synthase in the young rat brain and causes learning deficits.
Inhibition of nitric oxide synthase (NOS) is known to possibly impair learning and memory. Our previous studies have demonstrated that prenatal hypoxia-ischemia (HI) decreases NOS expression and NOS activity in the neonatal rat brain. To investigate whether effects of prenatal HI on NOS expression continue and whether prenatal HI affects learning and memory in young rats, NOS expression and NOS activity were determined in the hippocampus of rat brains at 28 days of age following a prenatal HI insult on G17. Performances in the passive avoidance test and the Morris water maze test were also studied in these young rats prior to sampling. Rat fetuses were subjected to either a 30-min prenatal HI insult or a sham operation (SH) on gestation day 17 and rat pups were delivered naturally. Increased locomotor activity was observed in the prenatal HI rats as compared to the SH rats on postnatal days 13 and 15, but not on postnatal days 20 and 30. Prenatal HI affected learning ability in these young rats at 28 days of age, as indicated by a delayed acquisition of passive avoidance and by longer escape latency in the Morris water maze test as compared to the SH group. Prenatal HI did not affect retention of passive avoidance and spatial memory. Concomitant with these learning deficits, expression of neuronal NOS and endothelial NOS mRNAs as well as Ca2(+)-dependent NOS activity in the hippocampus of the prenatal HI rat brain were significantly decreased as compared to the SH group. These results suggest that a 30-min prenatal HI insult on gestation day 17 in rats has long-lasting effects on NOS expression and NOS activity in the offspring brain and on learning ability of these young rats. The learning deficit in offspring is possibly associated with the reduction in expression of NOS mRNA and NOS activity in the hippocampus of these animals.
Animals↗
Using zone plates for X-ray microimaging and microspectroscopy in environmental science.
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Journal Article↗
Ab Initio Study of the Electronic Spectrum of the SiO(+) Cation.
The potential energy curves of the SiO(+) cation for the low-lying electronic states, correlating to the first two lowest dissociation channels (Si(+)((2)P(u)) + O((3)P(g)) and Si(+)((2)P(u)) + O((1)D(g))), have been calculated at the internally contracted multireference configuration interaction (CMRCI) level with Dunning's correlation-consistent polarized valence quadruple zeta (cc-pVQZ) basis set. The equilibrium bond lengths (r(e)), harmonic frequencies (omega(e)), first- and second-order anharmonicity constants (omega(e)x(e), omega(e)y(e)), rotational constants (B(e)), vibrational separations (DeltaG(1/2)), dipole moments (µ(e)), excitation (T(e)), and dissociation energies (D(e)) for eight bound doublet states (X(2)Sigma(+), A(2)Pi, B(2)Sigma(+), (2)(2)Delta, (3)(2)Sigma(+), (4)(2)Pi, (3)(2)Sigma(-), and (1)(2)Phi) and four bound quartet states (a(4)Sigma(+), (1)(4)Pi, (1)(4)Delta, and (1)(4)Sigma(-)) have been calculated. The spectroscopic constants for the X(2)Sigma(+), A(2)Pi, and B(2)Sigma(+) states are in good agreement with the available experimental data. The dipole-allowed transition moments between the studied doublet states of SiO(+) have also been calculated at the same theoretical level. Based on both the computed potential energy curves and the electronic transition moments, radiative lifetimes for the bound electronic excited states at the v' = 0, 1, and 2 vibrational levels have been calculated. The lifetimes of the B(2)Sigma(+) ( Kv' = 0, 1, and 2) states are in excellent agreement with recent experimental data. Copyright 1999 Academic Press.
Journal Article↗
In vitro corrosion resistance of high-palladium dental casting alloys.
OBJECTIVE: The objective of this study was to characterize the in vitro corrosion behavior of five high-palladium dental alloys in two media using a potentiodynamic polarization technique. METHODS: Potentiodynamic cyclic polarization between -1000 and +1000 mV (SCE), 12 h open-circuit potential measurement, and linear polarization were performed on cast specimens of three Pd-Cu-Ga alloys and two Pd-Ga alloys in deaerated 0.09% NaCl solution and Fusayama artificial saliva at 37 degrees C. Zero-current potential, corrosion current density, open-circuit potential, and polarization resistance were determined. The Kruskal-Wallis test and the Mann-Whitney U-test were used to analyze the numeric findings. RESULTS: The Pd-Cu-Ga and Pd-Ga alloys in both the as-cast and heat-treated conditions showed spontaneous passive behavior under electrochemical conditions similar to those in the oral environment. The Pd-Cu-Ga alloys Liberty and Spartan Plus exhibited increased activity in the Fusayama artificial saliva after the porcelain-firing heat treatment, which may have arisen from internal oxidation of casting defects. Heat-treated Freedom Plus had an unstable oxide film to form on the surface during anodic polarization and may have a limited tendency for pitting corrosion in the Fusayama artificial saliva. The two heat-treated Pd-Ga alloys remained passive in the test media. As a group, the high-palladium alloys exhibited satisfactory corrosion resistance. SIGNIFICANCE: Corrosion of high-palladium alloys in the oral environment involves a release of ions that is related to their biocompatibility. Knowledge of the in vitro corrosion behavior of these alloys may lead to better understanding of any biologically adverse effects in vivo.
Corrosion↗
In vitro corrosion resistance of titanium made using different fabrication methods.
The corrosion of cast or milled ASTM Grade II CP titanium with different surface conditions was studied by potentiodynamic anodic polarization and immersion testing. Specimens were fabricated using three dental titanium casting systems and from machined titanium. Three surface conditions were tested: (1) sandblasted with surface reaction layers remaining; (2) polished surface without surface reaction layers; and (3) sandblasted surface without surface reaction layers. An acidic saline solution (0.1 M lactic acid/0.1 M NaC1 [pH = 2]) and an artificial saliva were used as the corrosion media. Anodic polarization was performed starting at 50 mV below the rest potential and terminating at +2250 mV vs Ag/AgCl. Two surface conditions (sandblasted with the surface reaction layers and polished without such layers) were examined in the immersion test. Specimens were immersed in the corrosion media at 37 degrees C for six months. The recovered solution was analyzed by an atomic absorption spectrophotometer for titanium dissolution. A distinctive passive region on the polarization diagram, ranging from approximately 0 to approximately +1300 mV, was observed for all specimens in both media. Great similarity was observed for all the sandblasted specimens which had larger primary passive current densities and passive regions compared to the polished ones. A current density peak at approximately +1600 mV seen for all the specimens with sandblasted surfaces was less well defined for the polished specimens. Immersion testing in the acidic saline solution revealed no significant differences among the polished specimens. A significant increase (P < 0.05) in titanium dissolution was found for the sandblasted specimens with surface reaction layers remaining on the surfaces made with phosphate-bonded SiO2/Al2O3 investment compared to the polished ones. Significant differences were also found between sandblasted specimens with the surface reaction layers resulting from different investment materials and different casting methods. Measurable amounts of titanium were not found for all specimens in the artificial saliva after six months. It is evident that the corrosion behavior of cast CP titanium is similar to that of machined titanium. The surface roughness appears to be a more prominent factor than do the surface reaction layers on the polarization behavior of the CP titanium under the present experimental conditions. Surface roughness and the presence of the surface reaction layers both affect the dissolution of titanium.
Biocompatible Materials↗
Capability of serum to convert streptomycin to cytotoxin in patients with aminoglycoside-induced hearing loss.
Individual variations in sensitivity to the ototoxic effects of aminoglycoside antibiotics are well documented. Our research demonstrates that there is an apparent difference in serum from patients who are resistant or susceptible to aminoglycoside ototoxicity. In the first study, the cytotoxicity of sera from patients with and without hearing loss after various time periods following the discontinuation of aminoglycoside treatment was assayed using the isolated outer hair cell toxicity assay. The results indicate that sera from patients with hearing loss were significantly more toxic than sera from patients with normal hearing or minimal hearing loss. This toxicity may persist for up to 1 year after discontinuation of aminoglycoside therapy. In a second study, sera were obtained from patients who had received aminoglycoside therapy several years previously. None of these sera was toxic to isolated outer hair cells in vitro. Streptomycin was then incubated with the sera or a protein fraction isolated from sera, and the incubation mixtures were tested for toxicity. The percentage of damaged outer hair cells was significantly higher when streptomycin had been treated with sera or a serum protein fraction from patients with hearing loss (58+/-10% and 68+/-9%, respectively) than with sera or a serum protein fraction from a control group (10+/-5% and 17+/-4%, respectively). In addition, several incubation mixtures were analyzed using high performance liquid chromatography. A new chromatographic peak was only found in the incubations of streptomycin with serum protein from patients with hearing loss. The results suggest that sera from individuals sensitive to aminoglycoside antibiotics may metabolize these drugs to cytotoxins.
Adolescent↗
Interaction of hydrated electron with dietary flavonoids and phenolic acids: rate constants and transient spectra studied by pulse radiolysis.
The reaction rate constants and transient spectra of 11 flavonoids and 4 phenolic acids reacting with e(aq)- at neutral pH were measured. Absorption bands of the transients of e(aq)- reacting with the above compounds all located at a wavelength shorter than 400 nm. The e(aq)- scavenging abilities were divided into three groups: (+)catechin ((1.2 +/-0.1) x 10(8) M(-1)s(-1)) < 4-chromanol ((4.4 +/- 0.4) x 10(8) M(-1)s(-1)) < genistein ((6.2+/-0.4) x 10(9) M (-1) s(-1) approximately genistin ((8 +/- 1) x 10(9) M(-1)s(-1)) approximately rutin ((7.6 +/- 0.4) x M(-1)s(-1) approximately caffeic acid ((8.3 +/- 0.5) x 10(9)M(-1)s(-1)) < transcinnamic acid((1.1 +/- 0.1) x 10(10) M(-1)s(-1)) approximately p-coumaric acid ((1.1 +/- 0.1) x 10(10) M(-1)s(-1) approximately 2,4,6-trihydroxylbenzoic acid((1.1 +/- 0.1) x 10(10) M(-1)s(-1)) approximately baicalein ((1.1 +/- 0.5) x 10(10) M(-1)s(-1)) approximately baicalin((1.3 + 0.1) X 10(10) M(-1)s(-1)) approximately naringenin ((1.2 +/- 0.1) x 10(10) M(-1)s(-1)) approximately naringin ((1.0 +/- 0.1) x 10(10) M(-1)s(-1)) approximately gossypin((1.2 +/- 0.1) x 10(10) M(-1)s(-1)) approximately quercetin((1.3 +/- 0.5) x 10(10) M(-1)s(-1)). These results suggested that C4 keto group is the active site for e(aq)- to attack on flavonoids and phenolic acids, whereas the o-dihydroxy structure in B ring, the C2,3 double bond, the C3-OH group, and glucosylation, which are key structures that influence the antioxidant activities of flavonoids and phenolic acids, have little effects on the e(aq)- scavenging activities.
Electrons↗
TEM analysis of tweed structure in high-palladium dental alloys.
Transmission electron microscopy and convergent-beam electron diffraction were used to study three high-palladium dental alloys: an as-cast Pd-Ga alloy, a cast Pd-Cu-Ga alloy aged at room temperature for over 5 years, and a cast Pd-Cu-Ga alloy annealed at 1023 K for 2 h and slowly cooled to room temperature. Bands containing a tweed structure in the Pd-Ga alloy were 120degrees twins with (1 1 0 mirror planes. Within these bands the alloy had a face-centered tetragonal structure with a c/a ratio of 1.03. The aged Pd-Cu-Ga alloy contained a larger amount of tweed structure than the original as-cast alloy, along with randomly oriented bands and thin lath-like regions. The annealed Pd-Cu-Ga alloy contained rectangular particles of a secondary phase that may be Pd2Ga, Pd5Ga2 or Pd13Ga5. The microtwinned band structure relieves the strain energy arising from transformation of the f.c.c. palladium solid solution on cooling.
Journal Article↗
Inhibition of heterologously expressed cystic fibrosis transmembrane conductance regulator Cl- channels by non-sulphonylurea hypoglycaemic agents.
1. Hypoglycaemia-inducing sulphonylureas, such as glibenclamide, inhibit cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels. In search of modulators of CFTR, we investigated the effects of the non-sulphonylurea hypoglycaemic agents meglitinide, repaglinide, and mitiglinide (KAD-1229) on CFTR Cl- channels in excised inside-out membrane patches from C127 cells expressing wild-type human CFTR. 2. When added to the intracellular solution, meglitinide and mitiglinide inhibited CFTR Cl- currents with half-maximal concentrations of 164+/-19 microM and 148+/-36 microM, respectively. However, repaglinide only weakly inhibited CFTR Cl- currents. 3. To understand better how non-sulphonylurea hypoglycaemic agents inhibit CFTR, we studied single channels. Channel blockade by both meglitinide and mitiglinide was characterized by flickery closures and a significant decrease in open probability (Po). In contrast, repaglinide was without effect on either channel gating or Po, but caused a small decrease in single-channel current amplitude. 4. Analysis of the dwell time distributions of single channels indicated that both meglitinide and mitiglinide greatly decreased the open time of CFTR. Mitiglinide-induced channel closures were about 3-fold longer than those of meglitinide. 5. Inhibition of CFTR by meglitinide and mitiglinide was voltage-dependent: at positive voltages channel blockade was relieved. 6. The data demonstrate that non-sulphonylurea hypoglycaemic agents inhibit CFTR. This indicates that these agents have a wider specificity of action than previously recognized. Like glibenclamide, non-sulphonylurea hypoglycaemic agents may inhibit CFTR by occluding the channel pore and preventing Cl- permeation.
Adenosine Triphosphate↗