A mechanism of noncontinuous supraosseous tooth eruption

Numerous theories have been propounded to explain the various aspects of tooth eruption, but no general consensus exists about some of the underlying mechanisms that govern these aspects. An important unresolved issue is the source of the motive forces that displace teeth. We proposed that supraosseous eruptive forces are generated by tooth socket distortions caused by functional jaw deformations. Previous studies used basic equations of static equilibrium to demonstrate that the concomitant stretching of the oblique periodontal ligament (PDL) fibers give rise to forces that may cause supraosseous tooth eruption. For a more rigorous and expanded analysis, we applied the finite element method (FEM). Three functional loads were considered, but the FEM calculations strongly suggested that all jaw deformations contribute to tooth extrusion. It was also demonstrated that the PDL fiber disruptions that are likely to occur with increased stretching can provide a mechanism to stabilize the erupted position.

The influence of PDL principal fibers in a 3-dimensional analysis of orthodontic tooth movement

The effects of mechanical loads on the tooth-alveolus complex are of particular concern in orthodontics. The concepts of center of resistance (CRes) and center of rotation (CRot) are used to characterize tooth responses to orthodontic loads. The mechanical environment (stresses and strains) associated with orthodontic tooth movement is a unique model in bone adaptation physiology. Numerous finite element models of varying complexity have been developed to calculate tooth movements and stress distributions within the alveolar bone and the periodontal ligament (PDL). In general, the PDL has been idealized as a homogeneous isotropic material. For this project, a 3-dimensional tooth/PDL/mandible/finite element model was developed in which, for the first time in such an analysis, the PDL's principal-fiber structure was also incorporated. Parametric analyses showed that the fiber orientation and the mechanical properties do not exert much influence on the locations of the CRes and the CRot and on the stress patterns within the bone and the PDL matrix. However, the absence of principal fibers produces not only different stress magnitudes, but also differences in stress patterns. Furthermore, the no-fiber-associated CRes and CRot are considerably separated from the cluster of fiber-influenced centers. It was concluded that it may be more realistic to incorporate "generic" principal fibers into finite element models than not to include them at all, despite the lack of reliable information about fibers.

[The phase II clinical trial of Seratia Marcescens Anticancer Vaccine (S311) for malignant pleural effusions]

BACKGROUND

To evaluate the effect and adverse reactions of Seratia Marcescens Anticancer Vaccine ( S311) in the treatment of malignant pleural effusions.

METHODS

0. 32 mg of S311 was administered into intracavity once a week, for successive three weeks, after draining off the pleural cavity completely by thoracocentesis or chest drainage.

RESULTS

Two hundred and forty-one patients with malignant effusions finished the arrangement of S311 therapy. The overall response rate was 92. 1%. The main adverse reactions were fever and pleuritic pain. Some patients had chill, dyspnea, nausea and vomiting. Liver dysfunction was observed in a few cases.

CONCLUSIONS

S311 is an effective drug for malignant pleural effusions.

Nonequilibrium steady-state circulation and heat dissipation functional

A nonequilibrium steady-state (NESS), different from an equilibrium, is sustained by circular balance rather than detailed balance. The circular fluxes are driven by energy input and heat dissipation, accompanied by a positive entropy production. Based on a Master equation formalism for NESS, we show the circulation is intimately related to the recently studied Gallavotti-Cohen symmetry of heat dissipation functional, which in turn suggests a Boltzmann's formulalike relation between rate constants and energy in NESS. Expanding this unifying view on NESS to diffusion is discussed.

TNFalpha induces and insulin inhibits caspase 3-dependent adipocyte apoptosis

Regulation of fat cell number by apoptosis is proposed to be part of a normal physiological cycle in adipose growth and development. To investigate this process, cultured rat adipocytes were treated with various concentrations of tumor necrosis factor alpha (TNFalpha) and/or insulin to determine the roles of these factors in adipocyte apoptosis. The cells were analyzed by flow cytometry using a TUNEL assay. TNFalpha increased adipocyte apoptosis in a dose-dependent fashion. TNFalpha-mediated apoptosis was detectable within 6 h of treatment and continued to increase with time. Decreasing media insulin concentration from 8.5 to 0.85 nM resulted in increased adipocyte apoptosis, whereas high doses of insulin protected adipocytes from TNFalpha-induced apoptosis. TNFalpha-activated apoptosis was accompanied by an increase in caspase 3 activity and could be inhibited by a caspase 3-specific inhibitor. These data suggest that adipose tissue cell number is regulated, in part, by an apoptotic signaling pathway that involves TNFalpha, insulin, and caspase 3.

Casein kinase II sites in the intracellular C-terminal domain of the thyrotropin-releasing hormone receptor and chimeric gonadotropin-releasing hormone receptors contribute to beta-arrestin-dependent internalization

We have previously shown that the mammalian gonadotropin-releasing hormone receptor (GnRHR), a unique G-protein-coupled receptor (GPCR) lacking an intracellular carboxyl tail (C-tail), does not follow a beta-arrestin-dependent internalization pathway. However, internalization of a chimeric GnRHR with the thyrotropin-releasing hormone receptor (TRHR) C-tail does utilize beta-arrestin. Here, we have investigated the sites within the intracellular C-tail domain that are important for conferring beta-arrestin-dependent internalization. In contrast to the chimeric GnRHR with a TRHR C-tail, a chimeric GnRHR with the catfish GnRHR C-tail is not beta-arrestin-dependent. Sequence comparisons between these chimeric receptors show three consensus phosphorylation sites for casein kinase II (CKII) in the TRHR C-tail but none in the catfish GnRHR C-tail. We thus investigated a role for CKII sites in determining GPCR internalization via beta-arrestin. Sequential introduction of three CKII sites into the chimera with the catfish C-tail (H354D,A366E,G371D) resulted in a change in the pattern of receptor phosphorylation and beta-arrestin-dependence, which only occurred when all three sites were introduced. Conversely, mutation of the putative CKII sites (T365A,T371A,S383A) in the C-tail of a beta-arrestin-sensitive GPCR, the TRHR, resulted in decreased receptor phosphorylation and a loss of beta-arrestin-dependence. Mutation of all three CKII sites was necessary before a loss of beta-arrestin-dependence was observed. Visualization of beta-arrestin/GFP redistribution confirmed a loss or gain of beta-arrestin sensitivity for receptor mutants. Internalization of receptors without C-tail CKII sites was promoted by a phosphorylation-independent beta-arrestin mutant (R169E), suggesting that these receptors do not contain the necessary phosphorylation sites required for beta-arrestin-dependent internalization. Apigenin, a specific CKII inhibitor, blocked the increase in receptor internalization by beta-arrestin, thus providing further support for the involvement of CKII. This study presents evidence of a novel role for C-tail CKII consensus sites in targeting these GPCRs to the beta-arrestin-dependent pathway.

Central norepinephrine pathways are involved in cardiovascular response to intracerebroventricular substance P

AIM

To study the role of norepinephrine system in the cardiovascular response to intracerebroventricular substance P (SP) in rabbit.

METHODS

SP was given intracerebroventricularly in anesthetized rabbits pretreated with the catecholaminergic neurotoxin, 6-hydroxydopamine (6-OHDA). The density and affinity of SP receptors on synaptosomal membranes of the hypothalamus and the ventral medulla of rabbits were determined by [125I]SP receptor assay. Arterial blood pressure and heart rate were recorded.

RESULTS

Intracerebroventricular (icv) pretreatment of rabbits with 6-OHDA, reduced norepinephrine in the hypothalamus (by 86.7 %) and in the ventral medulla (by 77.0 %) respectively. The pressor response and tachycardia of these rabbits to icv SP (3.55 nmol . kg-1) were attenuated. The density and the affinity of SP receptors in the hypothalamus and the ventral medulla of 6-OHDA-lesioned rabbits were decreased. The Bmax (pmol . g-1 protein) of SP receptors in hypothalamus and the ventral medulla are 108 +/- 5, 35.9 +/- 2.2 in control group, and 42 +/- 18, 20 +/- 5 in 6-OHDA-lesioned rabbits, respectively. Kd (nmol . L-1) of SP receptors in the two regions are 0.015 +/- 0.004, 0.014 +/- 0.006 in control group and 0.029 +/- 0.001, 0.015 +/- 0.003 in 6-OHDA group. There is a significant difference of Bmax (P < 0.01) and Kd (P < 0.01, P < 0.05) in both regions between 6-OHDA groups and control groups.

CONCLUSION

The results suggested that central norepinephrine pathways are involved in the cardiovascular response to icv SP.

Relative entropy: free energy associated with equilibrium fluctuations and nonequilibrium deviations

Using a one-dimensional macromolecule in aqueous solution as an illustration, we demonstrate that the relative entropy from information theory, Sigma(k)p(k) ln(p(k)/p(*)(k)), has a natural role in the energetics of equilibrium and nonequilibrium conformational fluctuations of the single molecule. It is identified as the free energy difference associated with a fluctuating density in equilibrium, and is associated with the distribution deviate from the equilibrium in nonequilibrium relaxation. This result can be generalized to any other isothermal macromolecular system using the mathematical theories of large deviations and Markov processes, and at the same time provides the well-known mathematical results with interesting physical interpretations.

Protein and DNA oxidation in spinal injury: neurofilaments--an oxidation target

This study measured the time courses of protein and DNA oxidation following spinal cord injury (SCI) in rats and characterized oxidative degradation of proteins. Protein carbonyl content-a marker of protein oxidation-significantly increased at 3-9 h postinjury and the ratio 8-hydroxy-2-deoxyguanosine/deoxyguanosine-an indicator of DNA oxidation-was significantly higher at 3-6 h postinjury in the injured cords than in the sham controls. This suggests that oxidative modification of proteins and DNA contributes to secondary damage in SCI. Densities of selected bands on coomassie-stained gels indicated that most proteins were degraded. Neurofilament protein (NFP) was particularly evaluated immunohistochemically; its light chain (NFP-68) was gradually degraded in nerve fibers, neuron bodies, and large dendrites following SCI. A mixture of Mn (III) tetrakis (4-benzoic acid) porphyrin (10 mg/kg)-a novel SOD mimetic-and nitro-L-arginine (1 mg/kg)-an inhibitor of nitric oxide synthase-injected intraperitoneally, increased NFP-68 immunoreactivity and the numbers of NFP-positive nerve fibers post-SCI, correlating NFP degradation in SCI to free radical-triggered oxidative damage for the first time. Therefore, blockage of protein and DNA oxidation in the secondary injury stage may improve long-term recovery-important information for development of the SCI therapies.

Responses of small- and large-field bipolar cells to GABA and glycine

Morphologically distinct subtypes of retinal bipolar cells transmit information along parallel pathways to convey different aspects of the visual scene, but the synaptic mechanisms that regulate signal transmission are largely unknown. The all-rod retina of skate provides a comparatively simple system in which to correlate bipolar cell morphology with responses to the inhibitory neurotransmitters GABA and glycine. Two subtypes of bipolar cells can be identified when isolated in culture: large-field bipolar cells with extensive dendritic arbors, and small-field bipolar cells with one or two dendritic branches. Under voltage-clamp, glycine elicited significant current responses from small-field cells, but not from large-field bipolar cells. Although all bipolar cells displayed GABA-activated chloride currents mediated by both GABA(A) and GABA(C) receptors, the small-field bipolar cells showed a significantly greater contribution from GABA(A) receptors. The results of the present study reveal for the first time that the relative expression of the two classes of GABA receptor on each bipolar cell type correlates with cell morphology and the presence of the glycine receptor.

[Studies on the manufacture and immunogenicity of purified rabies vaccines on humans Vero cell]

OBJECTIVE

Using Vero cell as basic cultural material to improve the quality of rabies vaccines and to produce rabies vaccines for humans.

METHODS

CTN-1V10 strain were used for production. Vero cell of 150th generation were used for cultivation. Rotating cultivatal method with rotating bottle was used. Fluids with virus were collected at different time. Puritied rabies vaccine was produced on Vero cell after clarification, condensation, purification and extermination. A batch of vaccines made by this techniques were used for immunological observation. Sixty-three people were injected with this rabies vaccine according to the procedure of time of exposure. Thirty of them were injected with vaccines made in France (Verorab) while the others were injected with vaccines to be tested. Side effect and neutralizing antibody were recorded.

RESULTS

The quality of this newly developed rabies vaccines has met the quality set by WHO. After all dosages of injection, the rates of positive antibody were both 100% in two groups. The neutralizing antibody among testing group was 11.94 IU/ml comparing with control as 11.69 IU/ml.

CONCLUSION

Purified rabies vaccines on Vero cell for humans had reasonable manufacture technique and less little effect with good technological imnunogenicity.

p27-p16 Chimera: a superior antiproliferative for the prevention of neointimal hyperplasia

Cyclin-dependent kinase inhibitors (CDKi's) may be useful to treat hyperproliferative vascular disorders, such as restenosis induced following angioplasty or vein engraftment. We have shown that a novel fusion protein of the CDKi's p27 and p16, named W9, significantly reduces proliferation of human coronary smooth muscle cells in vitro, by blocking cell proliferation without inducing apoptosis. We have now evaluated the efficacy of adenovirus-mediated gene transfer of W9 (AV-W9) in a balloon-injury model, in the carotid arteries of cholesterol-fed rabbits. We observed that intravascular delivery of 2 x 10(11) viral particles of AV-W9 3 days following balloon injury inhibited intimal hyperplasia by 60% compared to a control virus (P > 0.001). PCNA expression in the AV-W9-treated vessels, a marker of injury-induced cell proliferation, was also reduced compared to the control virus-treated vessels. Direct comparison of the efficacy of AV-W9 and AV-p16 and AV-p27 in this model indicated that delivery of either of the parental genes was significantly less effective in inhibiting intimal thickening compared to the AV-W9 treatment. We conclude that combining the activities of multiple cell cycle regulatory proteins greatly increases the potency of cytostatic gene therapy in the treatment of balloon injury-induced intimal hyperplasia and represents a promising potential approach to preventing postangioplasty restenosis.

Dietary boron supplementation enhanced the action of estrogen, but not that of parathyroid hormone, to improve trabecular bone quality in ovariectomized rats

This study investigated whether boron would enhance the ability of 17beta-estradiol (E2) or parathyroid hormone (PTH) to improve bone quality in ovariectomized OVX rats. Adult OVX rats were treated for 5 wk with vehicle, boron (5 ppm as boric acid), E2 (30 microg/kg/d, sc), PTH (60 microg/kg/d, sc), or a combination of boron and E2 or PTH, respectively. The E2 treatment corrected many adverse effects of OVX on bone quality, increased bone Ca, P, and Mg contents, and decreased trabecular plate separation. Dietary boron supplementation had no effects on these bone parameters in OVX rats. When OVX rats were treated with boron and E2 together, trabecular bone volume (Tb.BS/TV) and plate density were increased significantly more than that caused by E2 alone. The boron and E2 combination also increased trabecular bone surface (Tb.BV/TV) and decreased trabecular plate separation in OVX rats. In contrast, whereas daily PTH injection also increased bone Ca, Mg, and P contents, Tb.BV/TV, Tb.BS/TV, trabecular plate density and thickness, and decreased trabecular plate separation in OVX rats, the combination of boron and PTH had no additional improvement in bone quality over that achieved by PTH alone. In summary, this study shows for the first time that boron enhanced the action of E2, but not that of PTH, to improve trabecular bone quality in OVX rats.

[The effect of whole pleural cavity irradiation with combined 60Co and electron beam plus local biological agents on malignant pleural effusion]

BACKGROUND

To study the effect and complications of combined 60Co γ ray and electron beam irradiation to malignant pleural effusion.

METHODS

From January,1996 to December,1998,55 patients with malignant pleural effusion (unilateral; 49 cases of primary lung cancer,4 breast cancer and 2 thymic tumor) received whole pleural cavity irradiation of 60Co γ ray with centrally placed lead blocks to protect the vital organs and normal lung tissue,and the electron beam irradiation at the area which was covered by lead blocks in 60Co γ ray irradiation.The pleural effusion was completely drained before radiotherapy,and dose distribution of middle level was calculated by TPS using EXT 2.4 version software (Multidata Co.USA).The 100% isodose curve was 2Gy,15 fractions were given and another 20Gy/10Fx irradiation was added to the visible tumor.All patients received sequential chemotherapy for 3-6 cycles (cisplatin-based regimens for lung cancer and thymic tumor,cyclophosphamide and adriamycin and fluoracil for breast cancer).Kaplan-Meier curve was used to evaluate the pleural effusion control rate and survival rate of patients.

RESULTS

Complete remission of the malignant pleural effusion was seen in 9 patients and partial in 46 when treatment completed.The 6-,12-,18-month pleural effusion control rate and survival rate of the patients were 76%,53%,44% and 64%,34%,26%,respectively.The median control time of effusion and survival time were 14 months (2-32 months) and 9 months (4-32 months) respectively.We did not find any abnormality in liver function as well as in kidney function before and after treatment.Myelosuppression was the main side effect after combined chemotherapy and radiotherapy.Nineteen patients suffered from acute oesophagitis in grade 1-2,and 3 serious pleural fibrosis.There was no acute irradiation pneumonitis.

CONCLUSIONS

The treatment for malignant pleural effusion with combined 60Co γ ray and electron beam irradiation is tolerable and effective in clinical use.

[Phase I clinical trial of dose escalation on three dimensional conformal radiation therapy for non-small cell lung cancer]

BACKGROUND

To establish the technique of 3-dimensional conformal radiation therapy (3DCRT) for non-small cell lung cancer (NSCLC) in stage II-IIIB,and to assess its acute side-effects and to obtain the maximum tolerance dose (MTD).

METHODS

From June,1999 to June,2000,38 cases of NSCLC in stage II-IIIB were enrolled in this study.MTD was identified by dose escalation study.After 42Gy/21Fx/4.2wks by conventional fractionated irradiation through AP/PA fields,which covered the primary tumor and lymph nodes,the technique of 3DCRT was used as boost.The boost fields encompassed the clinical lesions showed on chest CT.The planning of total dose escalation depended on the percentage,i.e.,<25%,25%-37%,and >37% of normal lung volume irradiated to over 20Gy.The scheduled dose escalation ranged from 69 to 81Gy.The criteria for stopping dose escalation was grade III or more worse radiation pneumonitis (RTOG).The boost doses were delivered with 3Gy/fraction,once a day,5 fractions a week.

RESULTS

Thirty-three cases had completed their treatments and could be evaluated by now.Acute radiation pneumonitis occurred in 26% of patients with grade I-II and 3% with grade III,and acute radiation esophagitis in 61% with grade I-II and 9% with grade III,and the hematopoietic toxicity in 58% with grade I-II and 9% with grade III.The current doses implemented were 78,78,and 75Gy respectively for patients with <25%,25%-37%,and >37% of normal lung volume irradiated.The overall immediate response rate of tumors was 88%(29/33).

CONCLUSIONS

Dose escalation in a volume-dependent organ as the lungs is acceptable and applicable.The immediate response is encouraging.MTD is to be determined.The long-term follow-up is needed to observe late complications and treatment efficacy.

[Chemotherapy combined with chest radiation therapy in the treatment of 95 patients with limited stage small cell lung cancer]

BACKGROUND

To analyse retrospectively the results and prognostic factors of 95 patients with limited stage small cell lung cancer treated with chemotherapy plus chest radiation therapy.

METHODS

Ninety-five patients with limited stage small cell lung cancer were treated with combination chemotherapy plus chest radiation therapy from December,1989 to June,1997.There were 84 males and 11 females with median age of 58 years (32-75 years).The P-TNM stages of the disease were as follows:stage I disease,3 patients; stage II disease,7 patients; stage IIIA disease,49 patients and stage IIIB disease,36 patients.Chemotherapy regimens were CAP (cyclophosphamide,doxorubicin,cisplatin),EP(etoposide,cisplatin),TP(Teniposide,cisplatin),or IEP (ifosphamide,etoposide,cisplatin).Median cycles were 6 (1-10).After one cycle of chemotherapy,patients received chest radiation therapy with median total tumor dose of 59.1Gy(43.8-76.9Gy)/31fx(22-64fx) for 48 days(30-73days).The radiation fields covered tumors with 1.5-2.0cm margins.Supraclavicular region and brain did not receive prophylactic irradiation.

RESULTS

Of the ninety-five patients,55(58%) had a complete response,36(38%) had a partial response,three had a stable disease and one had a disease progression.The median survival time was 28 months.The 1-,2-,3- and 5-year survival rates were 85%,62%,31% and 13%,respectively.The 1-,2-,3-,and 5-year local control rates were 95%,86%,77% and 64%,respectively.The 1-,2-,3- and 5-year distant metastasis rates were 23%,52%,73%,and 83%,respectively.From multivariate regression analyses,KPS≥70 and complete response and partial response could be the favorable predictors.

CONCLUSIONS

Chemotherapy combined with chest irradiation in limited stage small cell lung cancer can get better survival and local control and less distant metastases.KPS≥70 and complete response and partial response might be the favorable predictors.

Integrin-like proteins in the pollen tube: detection, localization and function

The distribution of integrin-like proteins in the pollen tube was examined by immunofluorescent labeling and western blotting techniques using antibodies against human placenta integrin vitronectin receptor (VnR), and alpha(v), beta3 and beta1 integrin subunits. Pseudocolor-coded confocal images showed intense immunostaining within 10 and 5 microm of the tip of the pollen tube in Lilium davidii and Nicotiana tabacum respectively. In both segments the site near the plasma membrane was labeled. Western blotting analyses revealed cross-reaction of anti-beta3, anti-alpha(v) and anti-VnR with the proteins in the plasma membrane preparation of L. davidii and Hemerocallis citrina pollen tube. These studies provide evidence for the first time that the integrin-like protein is present in pollen tubes, and it may be mainly composed of alpha(v) and beta3 subunits in lily pollen tubes. In a functional assay, neither anti-VnR antibody nor the Arg-Gly-Asp-Ser tetrapeptide inhibited pollen tube growth of N. tabacum in vitro, but both of them depressed tube growth on the stigma and in style under quasi in vivo culture conditions. The integrin-like proteins localized in the tip and periphery of the pollen tube appeared to play roles in growth of the pollen tube tip and interaction with the extracellular matrix of the style.

A mathematical analysis for the Brownian dynamics of a DNA tether

In the single-particle tracking experiment, the internal motion of a single DNA or polymer molecule whose one end is attached to a microsphere (optical marker) and the other end is anchored to a substratum is studied (Finzi and Gelles, 1995). The stochastic Brownian dynamics of the sphere reflect the spontaneous fluctuations, thus the physical characteristics, of the DNA or polymer molecule (Qian and Elson, 1999, Qian, 2000). In this paper, two continuous models of polymer molecules, a flexible elastic string and a weakly bendable elastic rod, are analyzed. Both models are cast mathematically in terms of linear stochastic differential equations. Based on Fourier analyses, we calculate the mean square displacement (MSD) of the particle motion, the key observable in the experiment. We obtain for both models the short-time asymptomatics for the MSD, as well as the long-time behavior in terms of the smallest non-zero eigenvalues. It is shown that: (i) the long-time dynamics of continuous elastic string model quantitatively agree with that of the discrete bead-spring model. (ii) The short-time MSD of both models are controlled by the tethered particle, with linear dependence on t. (iii) The two models show characteristic difference for long-time behavior: The longest relaxation time is proportional to L2 for long elastic string and to L for short elastic string, but is proportional to L4 for both long and short weakly bendable rod.

Large-scale processes and the Asian bias in species diversity of temperate plants

An important issue in the study of biodiversity is the extent to which global patterns of species richness reflect large-scale processes and historical contingencies. Ecological interactions in local assemblages may constrain the number of species that can coexist, but differences in diversity in similar habitats within different regions (diversity anomalies) suggest that this limit is not firm. Variation in rate of species production could influence regional and perhaps local diversity independently of the ecological capacity of an area to support coexisting species, thereby creating diversity anomalies. Temperate Zone genera of plants that are disjunct between similar environments in eastern Asia and eastern North America (EAS-ENA) have twice as many species in Asia as in North America. Because lineages of these genera in Asia and North America are mostly sister pairs, they share a common history of adaptation and ecological relationship before disjunction. Thus, the diversity anomaly in EAS-ENA genera is not an artefact of taxon or habitat sampling but reflects differences in the net diversification (speciation-extinction) of the lineages in each of the continents. Here we propose that the most probable cause of the EAS-ENA anomaly in diversity is the extreme physiographical heterogeneity of temperate eastern Asia, especially compared with eastern North America, which in conjunction with climate and sea-level change has provided abundant opportunities for evolutionary radiation through allopatric speciation.

Experimental validation of a finite element model of light-activated polymerization shrinkage

An important consideration in improving the longevity of dental resin composite restorations is how to minimize the stresses that develop between resin composites and the wall of the preparation as the resin shrinks during polymerization. If the stress is too great, failure of the bonded interface occurs and microleakage results, with possible margin failure, staining, and secondary caries. This present project was performed to validate a previously developed FEM approach for investigating polymerization shrinkage. Light-cured resin composite was condensed into a cylindrical cavity preparation, which contained a centrally located wire. A profilometer stylus was positioned on the end of the wire to detect the initial surface displacement as the wire moved with the superficial layer of composite resin. The plots of the experimentally derived data were compared to the data plot from the FEM. The initial segments of the experimental plots matched the calculated plot very closely in shape, thus validating the FEM approach.

Nitric oxide synthase in atherosclerosis and vascular injury: insights from experimental gene therapy

Gene therapy aims to intervene in a disease process by transfer and expression of specific genes in a target tissue or organ. Cardiovascular gene therapy in humans remains in its infancy, but in the last decade, experimental gene transfer has emerged as a powerful biological tool to investigate the function of specific genes in vascular disease pathobiology. Nitric oxide synthases, the enzymes that produce nitric oxide, have received considerable attention as potential candidates for vascular gene therapy because nitric oxide has pleiotropic antiatherogenic actions in the vessel wall, and abnormalities in nitric oxide biology are apparent very early in the atherogenic process. In this article, we review the use of nitric oxide synthases in experimental vascular gene therapy and assess the utility of these approaches for investigating the role of nitric oxide in atherosclerosis and their potential for human gene therapy.

A class of flow bifurcation models with lognormal distribution and fractal dispersion

We report a quantitative analysis of a simple dichotomous branching tree model for blood flow in vascular networks. Using the method of moment-generating function and geometric Brownian motion from stochastic mathematics, our analysis shows that a vascular network with asymmetric branching and random variation at each bifurcating point gives rise to an asymptotic lognormal flow distribution with a positive skewness. The model exhibits a fractal scaling in the dispersion of the regional flow in the branches. Experimentally measurable fractal dimension of the relative dispersion in regional flow is analytically calculated in terms of the asymmetry and the variance at local bifurcation; hence the model suggests a powerful method to obtain the physiological information on local flow bifurcation in terms of flow dispersion analysis. Both the fractal behavior and the lognormal distribution are intimately related to the fact that it is the logarithm of flow, rather than flow itself, which is the natural variable in the tree models. The kinetics of tracer washout is also discussed in terms of the lognormal distribution.

Single-particle tracking: Brownian dynamics of viscoelastic materials

A unifying theoretical framework for analyzing stochastic data from single-particle tracking (SPT) in viscoelastic materials is presented. A generalization of the bead-spring model for linear polymers is developed from a molecular point of view and from the standpoint of phenomenological linear viscoelasticity. The hydrodynamic interaction in the former is identified as the dashpots in the latter. In elementary terms, the intimate correspondence between time-correlation of the fluctuation measurements and transient relaxation kinetics after perturbation is discussed, and the central role of the fluctuation-dissipation relation is emphasized. The work presented here provides a bridge between the microscopic and the macroscopic views of linear viscoelastic biological materials, and is applicable to membrane protein diffusion, linear DNA chain dynamics, and mechanics of intracellular cytoskeletal networks.