Exact constructions of a family of dense periodic packings of tetrahedra

The determination of the densest packings of regular tetrahedra (one of the five Platonic solids) is attracting great attention as evidenced by the rapid pace at which packing records are being broken and the fascinating packing structures that have emerged. Here we provide the most general analytical formulation to date to construct dense periodic packings of tetrahedra with four particles per fundamental cell. This analysis results in six-parameter family of dense tetrahedron packings that includes as special cases recently discovered "dimer" packings of tetrahedra, including the densest known packings with density phi=4000/4671=0.856347... . This study strongly suggests that the latter set of packings are the densest among all packings with a four-particle basis. Whether they are the densest packings of tetrahedra among all packings is an open question, but we offer remarks about this issue. Moreover, we describe a procedure that provides estimates of upper bounds on the maximal density of tetrahedron packings, which could aid in assessing the packing efficiency of candidate dense packings.

Geometrical ambiguity of pair statistics: point configurations

Point configurations have been widely used as model systems in condensed-matter physics, materials science, and biology. Statistical descriptors, such as the n -body distribution function g(n), are usually employed to characterize point configurations, among which the most extensively used is the pair distribution function g(2). An intriguing inverse problem of practical importance that has been receiving considerable attention is the degree to which a point configuration can be reconstructed from the pair distribution function of a target configuration. Although it is known that the pair-distance information contained in g(2) is, in general, insufficient to uniquely determine a point configuration, this concept does not seem to be widely appreciated and general claims of uniqueness of the reconstructions using pair information have been made based on numerical studies. In this paper, we present the idea of the distance space called the D space. The pair distances of a specific point configuration are then represented by a single point in the D space. We derive the conditions on the pair distances that can be associated with a point configuration, which are equivalent to the realizability conditions of the pair distribution function g(2). Moreover, we derive the conditions on the pair distances that can be assembled into distinct configurations, i.e., with structural degeneracy. These conditions define a bounded region in the D space. By explicitly constructing a variety of degenerate point configurations using the D space, we show that pair information is indeed insufficient to uniquely determine the configuration in general. We also discuss several important problems in statistical physics based on the D space, including the reconstruction of atomic structures from experimentally obtained g(2) and a recently proposed "decorrelation" principle. The degenerate configurations have relevance to open questions involving the famous traveling salesman problem.

Mir-128 Regulates the Self-Renewal of Breast Tumor-Initiating Cells through HTERT

Background: hTERT (human telomerase reverse transcriptase), which maintains telomere ends by addittion of the telomere repeat sequence TTAGGG, is increased in cancer cells and embryonic stem cells. However, whether hTERT has a role in regulating breast tumor-initiating cells remains unknown. Therefore, the regulation of hTERT in breast tumor initiating cells (BT-IC) would potentially facilitate our understanding of the etiology of breast cancer.Material and Methods: Enrichment for BT-ICs was performed by mammospheres from suspension cultures. The capacity of self-renewal and differentiation of BT-ICs were determined by mammosphere formation, immunohistochemical analysis of epithelial markers and FACS, respectively. TRAP assay was used to detect telomerase activity. The expression levels of hTERT in BT-ICs, with or without lentivirus-mediated mir-128 transduction, were determined by qRT-PCR and western blot. hTERT siRNA or lentivirus-shTERT were used to silence the expression of hTERT in BT-ICs. Differentially expressed mir-128 in BT-ICs was quantified by qRT-PCR and Northern Blot. The expression of BMI1 was determined by Western Blot.Results: hTERT, as well as telomerase activity, had a higher expression in BT-ICs, compared to the differentiated breast cancer cells. BMI1, the target of mir-128, is increased in BT-ICs. Conversely, the expression level of mir-128 is lower in BT-ICs, compared to the differentiated cells. Mir-128 over-expressing reduced the level of BMI1,as well as hTERT, in BT-ICs. Silencing BMI1 by lentivirus-shRNA transfection in BT-ICs leads to the decrease of hTERT protein level. Furthermore, BT-ICs, with hTERT knockdown, lost its ability to form mammospheres and proliferated poorly under differentiating conditions.Conclutions: mir-128 miRNA is reduced in mammospheric BT-ICs, resulting in up-regulation of BMI1, which further brought on the up-regulation of hTERT. And hTERT promotes self-renewal and blocks epithelial differentiation of BT-ICs. Therefore, mir-128 regulates BT-IC stem-cell like properties by BMI1 and hTERT.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5157.

Human airway smooth muscle is structurally and mechanically similar to that of other species

Airway smooth muscle (ASM) plays a vital role in the exaggerated airway narrowing seen in asthma. However, whether asthmatic ASM is mechanically different from nonasthmatic ASM is unclear. Much of our current understanding about ASM mechanics comes from measurements made in other species. Limited data on human ASM mechanics prevents proper comparisons between healthy and asthmatic tissues, as well as human and animal tissues. In the current study, we sought to define the mechanical properties of healthy human ASM using tissue from intact lungs and compare these properties to measurements in other species. The mechanical properties measured included: maximal stress generation, force-length properties, the ability of the muscle to undergo length adaptation, the ability of the muscle to recover from an oscillatory strain, shortening velocity and maximal shortening. The ultrastructure of the cells was also examined. Healthy human ASM was found to be mechanically and ultrastructurally similar to that of other species. It is capable of undergoing length adaptation and responds to mechanical perturbation like ASM from other species. Force generation, shortening capacity and velocity were all similar to other mammalian ASM. These results suggest that human ASM shares similar contractile mechanisms with other animal species and provides an important dataset for comparisons with animal models of disease and asthmatic ASM.

Dense packings of polyhedra: Platonic and Archimedean solids

Understanding the nature of dense particle packings is a subject of intense research in the physical, mathematical, and biological sciences. The preponderance of previous work has focused on spherical particles and very little is known about dense polyhedral packings. We formulate the problem of generating dense packings of nonoverlapping, nontiling polyhedra within an adaptive fundamental cell subject to periodic boundary conditions as an optimization problem, which we call the adaptive shrinking cell (ASC) scheme. This optimization problem is solved here (using a variety of multiparticle initial configurations) to find the dense packings of each of the Platonic solids in three-dimensional Euclidean space R3 , except for the cube, which is the only Platonic solid that tiles space. We find the densest known packings of tetrahedra, icosahedra, dodecahedra, and octahedra with densities 0.823..., 0.836..., 0.904..., and 0.947..., respectively. It is noteworthy that the densest tetrahedral packing possesses no long-range order. Unlike the densest tetrahedral packing, which must not be a Bravais lattice packing, the densest packings of the other nontiling Platonic solids that we obtain are their previously known optimal (Bravais) lattice packings. We also derive a simple upper bound on the maximal density of packings of congruent nonspherical particles and apply it to Platonic solids, Archimedean solids, superballs, and ellipsoids. Provided that what we term the "asphericity" (ratio of the circumradius to inradius) is sufficiently small, the upper bounds are relatively tight and thus close to the corresponding densities of the optimal lattice packings of the centrally symmetric Platonic and Archimedean solids. Our simulation results, rigorous upper bounds, and other theoretical arguments lead us to the conjecture that the densest packings of Platonic and Archimedean solids with central symmetry are given by their corresponding densest lattice packings. This can be regarded to be the analog of Kepler's sphere conjecture for these solids.The truncated tetrahedron is the only nonchiral Archimedean solid that is not centrally symmetric [corrected], the densest known packing of which is a non-lattice packing with density at least as high as 23/24=0.958 333... . We discuss the validity of our conjecture to packings of superballs, prisms, and antiprisms as well as to high-dimensional analogs of the Platonic solids. In addition, we conjecture that the optimal packing of any convex, congruent polyhedron without central symmetry generally is not a lattice packing. Finally, we discuss the possible applications and generalizations of the ASC scheme in predicting the crystal structures of polyhedral nanoparticles and the study of random packings of hard polyhedra.

Dense packings of the Platonic and Archimedean solids

Dense particle packings have served as useful models of the structures of liquid, glassy and crystalline states of matter, granular media, heterogeneous materials and biological systems. Probing the symmetries and other mathematical properties of the densest packings is a problem of interest in discrete geometry and number theory. Previous work has focused mainly on spherical particles-very little is known about dense polyhedral packings. Here we formulate the generation of dense packings of polyhedra as an optimization problem, using an adaptive fundamental cell subject to periodic boundary conditions (we term this the 'adaptive shrinking cell' scheme). Using a variety of multi-particle initial configurations, we find the densest known packings of the four non-tiling Platonic solids (the tetrahedron, octahedron, dodecahedron and icosahedron) in three-dimensional Euclidean space. The densities are 0.782..., 0.947..., 0.904... and 0.836..., respectively. Unlike the densest tetrahedral packing, which must not be a Bravais lattice packing, the densest packings of the other non-tiling Platonic solids that we obtain are their previously known optimal (Bravais) lattice packings. Combining our simulation results with derived rigorous upper bounds and theoretical arguments leads us to the conjecture that the densest packings of the Platonic and Archimedean solids with central symmetry are given by their corresponding densest lattice packings. This is the analogue of Kepler's sphere conjecture for these solids.

Optimal control policy for probabilistic Boolean networks with hard constraints

It is well known that the control/intervention of some genes in a genetic regulatory network is useful for avoiding undesirable states associated with some diseases like cancer. For this purpose, both optimal finite-horizon control and infinite-horizon control policies have been proposed. Boolean networks (BNs) and its extension probabilistic Boolean networks (PBNs) as useful and effective tools for modelling gene regulatory systems have received much attention in the biophysics community. The control problem for these models has been studied widely. The optimal control problem in a PBN can be formulated as a probabilistic dynamic programming problem. In the previous studies, the optimal control problems did not take into account the hard constraints, i.e. to include an upper bound for the number of controls that can be applied to the captured PBN. This is important as more treatments may bring more side effects and the patients may not bear too many treatments. A formulation for the optimal finite-horizon control problem with hard constraints introduced by the authors. This model is state independent and the objective function is only dependent on the distance between the desirable states and the terminal states. An approximation method is also given to reduce the computational cost in solving the problem. Experimental results are given to demonstrate the efficiency of our proposed formulations and methods.

Optimal packings of superballs

Dense hard-particle packings are intimately related to the structure of low-temperature phases of matter and are useful models of heterogeneous materials and granular media. Most studies of the densest packings in three dimensions have considered spherical shapes, and it is only more recently that nonspherical shapes (e.g., ellipsoids) have been investigated. Superballs (whose shapes are defined by |x1|2p+|x2|2p+|x3|2p<or=1) provide a versatile family of convex particles (p>or=0.5) with both cubic-like and octahedral-like shapes as well as concave particles (0<p<0.5) with octahedral-like shapes. In this paper, we provide analytical constructions for the densest known superball packings for all convex and concave cases. The candidate maximally dense packings are certain families of Bravais lattice packings (in which each particle has 12 contacting neighbors) possessing the global symmetries that are consistent with certain symmetries of a superball. We also provide strong evidence that our packings for convex superballs (p>or=0.5) are most likely the optimal ones. The maximal packing density as a function of p is nonanalytic at the sphere point (p=1) and increases dramatically as p moves away from unity. Two more nontrivial nonanalytic behaviors occur at pc*=1.150 9... and po*=ln 3/ln 4=0.792 4... for "cubic" and "octahedral" superballs, respectively, where different Bravais lattice packings possess the same densities. The packing characteristics determined by the broken rotational symmetry of superballs are similar to but richer than their two-dimensional "superdisk" counterparts [Y. Jiao, Phys. Rev. Lett. 100, 245504 (2008)] and are distinctly different from that of ellipsoid packings. Our candidate optimal superball packings provide a starting point to quantify the equilibrium phase behavior of superball systems, which should deepen our understanding of the statistical thermodynamics of nonspherical-particle systems.

Liposome-mediated transfer can improve the efficacy of islet labeling with superparamagnetic iron oxide

An in vivo method for islet visualization using magnetic resonance imaging (MRI), using superparamagnetic iron oxide (SPIO), has been described. Herein we have developed a protocol that uses cationic liposomes to increase the efficiency of islet cell labeling by SPIO in vitro. Fresh islet cells were incubated in RPMI-1640 medium, to which had been added a range of concentrations of ferucarbotran, a SPIO contrast agent. At each SPIO concentration, duplicate samples were incubated with versus without addition of cationic liposomes. We measured intracellular iron concentration, cell viability, and insulin-release function after labeling. We observed that the amount of iron bound to islet cells increased as the concentration of added SPIO increased. The presence of liposomes increased labeling efficiency at each SPIO concentration. In vitro MRI confirmed the effect of liposomes to improve labeling efficiency of islet cells by SPIO.

Phototrophic Fe(II) oxidation in an atmosphere of H2: implications for Archean banded iron formations

The effect of hydrogen on the rate of phototrophic Fe(II) oxidation by two species of purple bacteria was measured at two different bicarbonate concentrations. Hydrogen slowed Fe(II) oxidation to varying degrees depending on the bicarbonate concentration, but even the slowest rate of Fe(II) oxidation remained on the same order of magnitude as that estimated to have been necessary to deposit the Hamersley banded iron formations. Given the hydrogen and bicarbonate concentrations inferred for the Archean, our data suggest that Fe(II) phototrophy could have been a viable process at this time.

Transformation of nitrogen and distribution of nitrogen-related bacteria in a polluted urban stream

Most researchers focused on either nitrogen species or microbial community for polluted urban stream while ignoring the interaction between them and its effect on nitrogen transformation, which restricted the rational selection of an effective and feasible remediation technology. Taking Buji stream in Shenzhen (China) as target stream, the distribution of nitrogen-related bacteria was investigated by most probable number (MPN) besides analysis of nitrogen species etc. The nitrogen-related bacteria in sediment were 10(2) times richer than those in water. Owing to their faster growth, the MPN of ammonifying bacteria and denitrifying bacteria were 10(5) and 10(2) times higher than those of nitrifying bacteria, respectively. The ammonifying bacteria numbers were significantly related to BOD5 in water, while nitrifying bacteria in sediment correlated well with nitrate in water. Thus, nitrification occurred mainly in sediment surface and was limited by low proportion of nitrifying bacteria. The denitrifying bacteria in sediment had good relationship with BOD5 and nitrite and nitrate in water. Low DO and rich organic compounds were beneficial to denitrification but unfavourable to nitrification. Denitrification was restricted by low nitrite and nitrate concentration. These results could be served as a reference for implementing the remediation scheme of nitrogen polluted urban stream.

Optimal packings of superdisks and the role of symmetry

Almost all studies of the densest particle packings consider convex particles. Here, we provide exact constructions for the densest known two-dimensional packings of superdisks whose shapes are defined by |x{1}|{2p}+|x{2}|{2p}<or=1 and thus contain a large family of both convex (p>or=0.5) and concave (0<p<0.5) particles. Our candidate maximal packing arrangements are achieved by certain families of Bravais lattice packings, and the maximal density is nonanalytic at the "circular-disk" point (p=1) and increases dramatically as p moves away from unity. Moreover, we show that the broken rotational symmetry of superdisks influences the packing characteristics in a nontrivial way.

Modeling heterogeneous materials via two-point correlation functions. II. Algorithmic details and applications

In the first part of this series of two papers, we proposed a theoretical formalism that enables one to model and categorize heterogeneous materials (media) via two-point correlation functions S(2) and introduced an efficient heterogeneous-medium (re)construction algorithm called the "lattice-point" algorithm. Here we discuss the algorithmic details of the lattice-point procedure and an algorithm modification using surface optimization to further speed up the (re)construction process. The importance of the error tolerance, which indicates to what accuracy the media are (re)constructed, is also emphasized and discussed. We apply the algorithm to generate three-dimensional digitized realizations of a Fontainebleau sandstone and a boron-carbide/aluminum composite from the two-dimensional tomographic images of their slices through the materials. To ascertain whether the information contained in S(2) is sufficient to capture the salient structural features, we compute the two-point cluster functions of the media, which are superior signatures of the microstructure because they incorporate topological connectedness information. We also study the reconstruction of a binary laser-speckle pattern in two dimensions, in which the algorithm fails to reproduce the pattern accurately. We conclude that in general reconstructions using S(2) only work well for heterogeneous materials with single-scale structures. However, two-point information via S(2) is not sufficient to accurately model multiscale random media. Moreover, we construct realizations of hypothetical materials with desired structural characteristics obtained by manipulating their two-point correlation functions.

Rare earth doped zinc oxide nanowires

Zinc oxide (ZnO) nanowires were grown via thermal transport and subsequently doped with different concentrations of Tm, Yb, and Eu using ion implantation and post annealing. High ion fluences lead to morphology changes due to sputtering; however, freestanding nanowires become less damaged compared to those attached to substrates. No other phases like rare earth (RE) oxides were detected, no amorphization occurs in any sample, and homogeneous doping with the desired concentrations was achieved. Photoluminescence measurements demonstrate the optical activation of trivalent RE-elements and the emission of the characteristic intra-4f-luminescence of the respective RE atoms, which could be assigned according to the Dieke-diagram. An increasing RE concentration results into decreasing luminescence intensity caused by energy transfer mechanisms to non-radiative remaining implantation defect sites. Furthermore, low thermal quenching was observed due to the considerable wide band gap of ZnO.

Modeling heterogeneous materials via two-point correlation functions: basic principles

Heterogeneous materials abound in nature and man-made situations. Examples include porous media, biological materials, and composite materials. Diverse and interesting properties exhibited by these materials result from their complex microstructures, which also make it difficult to model the materials. Yeong and Torquato [Phys. Rev. E 57, 495 (1998)] introduced a stochastic optimization technique that enables one to generate realizations of heterogeneous materials from a prescribed set of correlation functions. In this first part of a series of two papers, we collect the known necessary conditions on the standard two-point correlation function S2(r) and formulate a conjecture. In particular, we argue that given a complete two-point correlation function space, S2(r) of any statistically homogeneous material can be expressed through a map on a selected set of bases of the function space. We provide examples of realizable two-point correlation functions and suggest a set of analytical basis functions. We also discuss an exact mathematical formulation of the (re)construction problem and prove that S2(r) cannot completely specify a two-phase heterogeneous material alone. Moreover, we devise an efficient and isotropy-preserving construction algorithm, namely, the lattice-point algorithm to generate realizations of materials from their two-point correlation functions based on the Yeong-Torquato technique. Subsequent analysis can be performed on the generated images to obtain desired macroscopic properties. These developments are integrated here into a general scheme that enables one to model and categorize heterogeneous materials via two-point correlation functions. We will mainly focus on basic principles in this paper. The algorithmic details and applications of the general scheme are given in the second part of this series of two papers.

Production of gamma-aminobutyric acid by Streptococcus salivarius subsp. thermophilus Y2 under submerged fermentation

Gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter in the central nervous system, has several well-known physiological functions and has been applied to the production of many drugs and functional foods. The technology of GABA production via submerged fermentation by Streptococcus salivarius subsp. thermophilus Y2 was investigated in this paper. It indicated that the GABA production was related to the biochemical characteristics of glutamate decarboxylase (GAD) of S. salivarius subsp. thermophilus Y2. After 24 h of fermentation at 37 degrees C, which is the suitable culture conditions for GAD-production, then the culture condition were adjusted to the optimal temperature (40 degrees C) and pH (4.5) for the GAD reaction activity in biotransformation of cells and pyridoxal 5'-phosphate (0.02 mmol/l) were added to the broth at the 48 h, the GABA production was increased up to 1.76-fold, reaching 7984.75 +/- 293.33 mg/l. The strain shows great potential use as a starter for GABA-containing yoghurt, cheese and other functional fermented food productions.

Neuropeptide Y regulates recurrent mossy fiber synaptic transmission less effectively in mice than in rats: Correlation with Y2 receptor plasticity

A unique feature of temporal lobe epilepsy is the formation of recurrent excitatory connections among granule cells of the dentate gyrus as a result of mossy fiber sprouting. This novel circuit contributes to a reduced threshold for granule cell synchronization. In the rat, activity of the recurrent mossy fiber pathway is restrained by the neoexpression and spontaneous release of neuropeptide Y (NPY). NPY inhibits glutamate release tonically through activation of presynaptic Y2 receptors. In the present study, the effects of endogenous and applied NPY were investigated in C57Bl/6 mice that had experienced pilocarpine-induced status epilepticus and subsequently developed a robust recurrent mossy fiber pathway. Whole cell patch clamp recordings made from dentate granule cells in hippocampal slices demonstrated that, as in rats, applied NPY inhibits recurrent mossy fiber synaptic transmission, the Y2 receptor antagonist (S)-N2-[[1-[2-[4-[(R,S)-5,11-dihydro-6(6H)-oxodibenz[b,e]azepin-11-yl]-1-piperazinyl]-2-oxoethyl]cyclopentyl]acetyl]-N-[2-[1,2-dihydro-3,5(4H)-dioxo-1,2-diphenyl-3H-1,2,4-triazol-4-yl]ethyl]-argininamide (BIIE0246) blocks its action and BIIE0246 enhances synaptic transmission when applied by itself. Y5 receptor agonists had no significant effect. Thus spontaneous release of NPY tonically inhibits synaptic transmission in mice and its effects are mediated by Y2 receptor activation. However, both NPY and BIIE0246 were much less effective in mice than in rats, despite apparently equivalent expression of NPY in the recurrent mossy fibers. Immunohistochemistry indicated greater expression of Y2 receptors in the mossy fiber pathway of normal mice than of normal rats. Pilocarpine-induced status epilepticus markedly reduced the immunoreactivity of mouse mossy fibers, but increased the immunoreactivity of rat mossy fibers. Mossy fiber growth into the inner portion of the dentate molecular layer was associated with increased Y2 receptor immunoreactivity in rat, but not in mouse. These contrasting receptor changes can explain the quantitatively different effects of endogenously released and applied NPY on recurrent mossy fiber transmission in mice and rats.

Single-cell RT-PCR, in situ hybridization histochemical, and immunohistochemical studies of substance P and enkephalin co-occurrence in striatal projection neurons in rats

Single-cell RT-PCR studies in 3-4-week-old rats have raised the possibility that as many as 20% of striatal projection neurons may be a unique type that contains both substance P (SP) and enkephalin (ENK). We used single-cell RT-PCR, retrograde labeling, in situ hybridization histochemistry, and immunolabeling to characterize the abundance of this cell type, its projection target(s), and any developmental changes in its frequency. We found by RT-PCR that 11% of neurons containing either SP or ENK contained both in 4-week-old rats, while in 4-month-old rats SP/ENK colocalization was only 3%. SP-only neurons tended to co-contain dynorphin and ENK-only neurons neurotensin, while SP/ENK neurons tended to contain dynorphin. Single-cell RT-PCR showed SP/ENK co-occurrence in 4-week-old rats to be no more common among striatal neurons retrogradely labeled from the substantia nigra than among those retrogradely labeled from globus pallidus. Double-label in situ hybridization showed SP/ENK perikarya to be scattered throughout striatum, making up 8% of neurons containing either SP or ENK at 4 weeks, but only 4% at 4 months. Immunolabeling showed that presumptive striatal terminals in globus pallidus externus, globus pallidus internus and substantia nigra pars reticulata that colocalized SP and ENK were scarce. Terminals colocalizing SP and ENK were, however, abundant in the substantia nigra pars compacta. Thus, SP-only and ENK-only neurons make up the vast majority of striatal projection neurons in rats, the frequency of SP/ENK colocalizing striatal neurons is low in adult rats (3-4%), and SP/ENK colocalizing neurons primarily project to SNc but do not appear to be confined to striosomes.

Dynamic interactions of p53 with DNA in solution by time-lapse atomic force microscopy

Dynamic interactions of the tumor suppressor protein p53 with a DNA fragment containing a p53-specific recognition sequence were directly observed by time-lapse tapping mode atomic force microscopy (AFM) in liquid. The divalent cation Mg(2+) was used to loosely attach both DNA and p53 to a mica surface so they could be imaged by the AFM while interacting with each other. Various interactions of p53 with DNA were observed, including dissociation/re-association, sliding and possibly direct binding to the specific sequence. Two modes of target recognition of p53 were detected: (a) direct binding, and (b) initial non-specific binding with subsequent translocation by one-dimensional diffusion of the protein along the DNA to the specific site.

[Culture and cryopreservation of human mandibular condylar cartilage cells]

OBJECTIVE

To establish an effective way in cryopreserving mandibular condylar cartilage cells.

METHODS

Human mandibular condylar cartilage (MCC) cells were harvested and amplified by microcarrier culture technique. MCC cells were preserve in liquid nitrogen. The biological properties of cryopreserved MCC cells were investigated.

RESULTS

Cells from liquid nitrogen preservation kept their phenotypic, proliferative an metabolic characteristics of MCC cells in vivo.

CONCLUSIONS

Cryopreservation of MCC cells can supply adequate qualified cells for repairing the defects of mandibular condyle cartilage and temporomandibular joint disk.

[Interleukin-1 increase nitric oxide synthesis through up-regulation of inducible nitric-oxide synthase by rabbit mandibular condylar cartilage cells in vitro]

OBJECTIVE

To investigate the influence of IL-1 on the biosynthesis of nitric oxide by rabbit mandibular condylar cartilage (MCC) cells.

METHODS

MCC cells of white rabbits were harvested enzymatically and cultured in DMEM supplemented with 0.4% newborn calf serum. In the experiment, a variety of concentrations of IL-1 were added to the medium. NO production was determined as nitrite accumulation in the medium. The effects of IL-1 on the mRNA levels of inducible nitric-oxide synthase (iNOS) were assessed by mRNA in situ hybridization method.

RESULTS

IL-1 can significantly increase nitric oxide synthesis by MCC cells in a concentration-dependent manner. In addition, normal MCC cells had light expression of iNOS expression and IL-1 (10-100 micrograms/L) promoted the expression of iNOS.

CONCLUSIONS

IL-1 can inhibit the chondrocytes proliferation and induce apoptosis that might be through the way of up-regulation of iNOS expression.

[Significance of her2 oncogene expression in primary nasopharyngeal carcinoma]

OBJECTIVE

To investigate the status of her2 oncogene at DNA level and the molecular mechanism of overexpression of her2 oncoprotein in part of patients with nasopharyngeal carcinoma (NPC).

METHODS

Forty-five cases of PNC tissue and fifteen cases of normal epithelial tissue adjacent to tumor tissue were examined for her 2 signal and centromere 17 signal. Interphase fluorescence in situ hybridization (FISH) was used to examine the copy number of her 2 and immunohistochemical (IHC) staining were used to analyze the copy number and protein expression of her2.

RESULTS

There were 1.92% +/- 0.10% her2 signals per nucleus in normal epithelial tissue adjacent to tumor. 75.52 +/- 9.33% of the nuclei contained 2 her2 signals and 2 centromere 17 signals. No alteration in gene copy number was found in cancerous nuclei. However, IHC staining of the 45 tumors with antibody against her2 showed that overexpression of her2 oncoprotein occurred in 33% (15/45) of NPC. However, there was no significant correlation between her2 expression and sex, age, clinical staging, and clinical outcome of patients.

CONCLUSION

The overexpression of her2 in NPC does not relate to her2 gene amplification. Immunohistochemistry may not be a good measure to examine her2 expression. The mechanism of her2 oncoprotein overexpression and its biological significance in the development of NPC remain to be elucidated.

A new glycogen synthase activity ratio in skeletal muscle: effects of exercise and insulin

It was recently reported that MnSO4 stimulates glycogen synthase-dependent glucose transfer from UDPglucose into trichloroacetic acid precipitable endogenous glycoproteins (GSMn(T)) in human muscle extracts. To determine the physiologic significance of this reaction, we compared a new GS activity ratio, GSMn(T)/GSH(E) (where GSH(E) represents the usual glucose transfer to ethanol precipitable exogenous glycogen by GS at 7.2 mM glucose 6-phosphate), with the generally used GSL(E)/GSH(E) ratio (where GSL(E) represents glucose transfer at 0.17 mM glucose 6-P concentration). Biopsies were obtained from the quadriceps femoris muscle of healthy subjects at rest, after 40 min of bicycle exercise at approximately 65% of maximal oxygen uptake and after isometric contraction at 2/3 maximal force to fatigue (approximately 1 min). GSMn(T)/GSH(E) increased from 0.012+/-0.002 at rest to 0.054+/-0.008 (P<0.01) after 40 min of bicycle exercise and the increase in GSMn(T) activity was strongly related to the decrease in endogenous glycogen (i.e.. increase in short-chain endogenous glycoproteins) (r=0.90; P<0.05). On the other hand, GSL(E)/GSH(E) did not change significantly after bicycle exercise (rest = 0.49+/-0.04; exercise = 0.58+/-0.08, P>0.05). GSMn(T)/GSH(E) increased from 0.010+/-0.001 at rest to 0.016+/-0.002 (P<0.05) after isometric exercise, whereas GSL(E)/GSH(E) decreased from 0.27+/-0.04 to 0.20+/-0.02 (P<0.05) under corresponding conditions. Last, insulin, which stimulates glycogen synthesis, also increased GSMn(T)/GSH(E) (1.8-fold, P<0.05), as well as GSL(E)/GSH(E) (1.4-fold, P<0.05), in isolated rat soleus muscle. These data indicate that GSMn(T)/GSH(E) is influenced by endogenous substrate availability and covalent modification. Therefore, GSMn(T)/GSH(E) ratio may prove to be a useful alternative to other GS activity ratios that only reflect changes in the phosphorylation state of GS.

Functional receptor-channel coupling compared in contractile and proliferative human vascular smooth muscle

We have previously identified a human vascular smooth muscle clone that can reversibly convert between proliferative and contractile phenotypes. Here we compared receptor-channel coupling in these cells using fura-2 to monitor [Ca(2+)](i) and patch-clamp to record currents. Histamine elevated [Ca(2+)](i) in all cells and caused contraction of cells exhibiting the contractile phenotype. The rise of [Ca(2+)](i) persisted in Ca(2+)-free solution and was abolished by thapsigargin, indicating involvement of stores. Whole cell electrophysiological recording revealed that histamine evoked transient outward K(+) current, indicating functional receptor-channel coupling. The time-course and amplitude of the histamine-activated current were similar in cells of the proliferative and contractile phenotypes. Moreover, a large conductance K(+) channel was recorded in cell-attached patches and was activated by histamine as well as the Ca(2+) ionophore A-23187, identifying it as the large conductance Ca(2+)-dependent K(+) channel. This K(+) channel showed similar characteristics and activation in both proliferative and contractile phenotypes, indicating that expression was independent of phenotype. In contrast, histamine also elicited an inward Cl(-) current in some contractile cells, suggesting differential regulation of this current depending on phenotype. These studies demonstrate the usefulness of this human vascular cell clone for studying functional plasticity of smooth muscle, while avoiding complications arising from extended times in culture.

[Study on nuclear DNA content and image cytometry in cervical cancer and precursor lesions]

OBJECTIVE

The aim of this research was to study the biological and clinical features of cervical cancer and precursor lesions.

METHODS

Nuclear DNA was analyzed by image cytometry (ICM) in 125 embedded tissue 5 microns sections stained with Feulgen stain. Samples included normal cervical squamous epithelium (n = 11), cervical intraepithelial neoplasia I (CIN I) (n = 22), CINII (n = 17) and CINIII (n = 13), cervical neoplasm (n = 62).

RESULTS

The mean DNA content, nuclear area increased progressively from normal cervical epithelium, CINI, CINII, CINIII to invasive squamous carcinoma. Statistical analysis revealed significant difference (P < 0.05, < 0.01). Histograms of cellular DNA ploidy distribution showed different pattern, where 9 components (9C) cells were observed in cervical cancer and CINIII. No differences in DNA mean ploidy (DMP), DNA index (DI) and nuclear area were observed between cervical neoplasm.

CONCLUSIONS

It is increased progressively from normal cervical epithelium to cancer, in which CINIII is turning point.

Altered glycogen synthase and phosphorylase activities in skeletal muscle of tetraplegic patients

Despite marked differences in both the extent of physical activity and in muscle metabolism and structure between tetraplegic and control subjects, the glycogen content in the skeletal muscle of both groups is similar. We determined whether this similarity could be explained by the activities of key enzymes of glycogen metabolism. Muscle biopsies were analysed for glycogen synthase (GS) and glycogen phosphorylase (GP) activities, as well as for metabolites. Glycogen content did not differ significantly between the two groups. Total glycogen synthase activity was reduced by almost 60 % in tetraplegics (P < 0.01), whereas total phosphorylase activity did not differ between groups. GS fractional activity did not differ between groups, whereas phosphorylase fractional activity (-/+ AMP) was significantly higher in the tetraplegics (0.08 +/- 0.01, control; 0.25 +/- 0.02, tetraplegics; P < 0.001). Neither uridine diphosphate (UDP)-glucose nor glucose 6-phosphate (G-6-P) content in muscle differed significantly between groups. These data demonstrate that, in tetraplegics, muscle glycogen content is preserved despite decreases in GS activity and increases in phosphorylase fractional activity. Muscle paralysis has differential effects on the activities of GS and GP. Experimental Physiology (2001) 86.2, 205-209.

Genetic alterations in DNA diploid, aneuploid and multiploid colorectal carcinomas identified by the crypt isolation technique

Loss of heterozygosity (LOH) and microsatellite instability (MSI) commonly occur in colorectal carcinomas. However, the role of these genetic alterations in determining DNA ploidy status of tumors (diploid, aneuploid and multiploid) remains unclear. In the present study, we attempted to clarify the relationship between genetic alterations and DNA ploidy status. Crypt isolation coupled with DNA cytometric sorting and polymerase chain reaction assay (17 microsatellite markers) were used to study allelic losses and MSI in 59 colorectal carcinomas (diploid, 15; aneuploid, 10 and multiploid, 34). Of the 15 diploid carcinomas, 6 exhibited MSI in which allelic losses were rarely found. The other 9 diploid tumors mostly exhibited allelic losses, but none displayed MSI status. Whereas allelic losses frequently occurred in the aneuploid carcinomas and the aneuploid populations of multiploid carcinomas, they were rarely detected in the diploid populations of multiploid carcinomas. MSI status was not observed in aneuploid carcinomas nor in either population of multiploid carcinomas. Although multiploid carcinomas genetically resemble aneuploid carcinomas in the expression of the severe LOH phenotype, the genetic alterations seen in the diploid populations of multiploid carcinomas may differ from those of diploid carcinomas. Furthermore, all diploid, aneuploid and both the diploid and aneuploid fractions of the multiploid tumors that were non-MSI exhibited a high rate of LOH, suggesting that LOH is independent of the tumor's ploidy status.

Pathway tracing using biotinylated dextran amines

Biotinylated dextran amines (BDA) are highly sensitive tools for anterograde and retrograde pathway tracing studies of the nervous system. BDA can be reliably delivered into the nervous system by iontophoretic or pressure injection and visualized with an avidin-biotinylated HRP (ABC) procedure, followed by a standard or metal-enhanced diaminobenzidine (DAB) reaction. High molecular weight BDA (10 k) yields sensitive and exquisitely detailed labeling of axons and terminals, while low molecular weight BDA (3 k) yields sensitive and detailed retrograde labeling of neuronal cell bodies. The detail of neuronal cell body labeling can be Golgi-like. BDA tolerates EM fixation and processing well and can, therefore, be readily used in ultrastructural studies. Additionally, BDA can be combined with other anterograde or retrograde tracers (e.g. PHA-L or cholera toxin B fragment) and visualized either by multi-color DAB multiple-labeling - if permanent labels are desired, or by using multiple simultaneous immunofluorescence - if fluorescence viewing is desired. In the same manner, BDA pathway tracing and neurotransmitter immunolabeling can be combined. Note that BDA pathway tracing can also be combined with anterograde or retrograde labeling with fluorescent dextran amines, if one wishes to exclusively use tracers with the favorable transport properties and sensitivities of dextran amines. In this case, the BDA can be visualized together with the fluorescent dextran amines using fluorescence labeling for the BDA, or the fluorescent dextran amines can be visualized together with the BDA by multicolor DAB labeling via immunolabeling of the fluorescent dextran amines using anti-fluorophore antisera. BDA is, thus, a flexible and valuable pathway tracing tool that has gained widespread popularity in recent years.

Identification of the anterior nucleus of the ansa lenticularis in birds as the homolog of the mammalian subthalamic nucleus

In mammals, the subthalamic nucleus (STN) is a glutamatergic diencephalic cell group that develops in the caudal hypothalamus and migrates to a position above the cerebral peduncle. By its input from the external pallidal segment and projection to the internal pallidal segment, STN plays a critical role in basal ganglia functions. Although the basal ganglia in birds is well developed, possesses the same major neuron types as in mammals, and plays a role in movement control similar to that in mammals, it has been uncertain whether birds possess an STN. We report here evidence indicating that the so-called anterior nucleus of the ansa lenticularis (ALa) is the avian homolog of mammalian STN. First, the avian ALa too develops within the mammillary hypothalamic area and migrates to a position adjacent to the cerebral peduncle. Second, ALa specifically receives input from dorsal pallidal neurons that receive input from enkephalinergic striatal neurons, as is true of STN. Third, ALa projects back to avian dorsal pallidum, as also the case for STN in mammals. Fourth, the neurons of ALa contain glutamate, and the target neurons of ALa in dorsal pallidum possess AMPA-type glutamate receptor profiles resembling those of mammalian pallidal neurons. Fifth, unilateral lesions of ALa yield behavioral disturbances and movement asymmetries resembling those observed in mammals after STN lesions. These various findings indicate that ALa is the avian STN, and they suggest that the output circuitry of the basal ganglia for motor control is similar in birds and mammals.

Ultrastructural architecture and mechanical properties of attachment pads in Tettigonia viridissima (Orthoptera Tettigoniidae)

Natural releasable attachment systems of insect legs, where attachment-detachment performances are often very fast, seem to be optimized to get a maximum of real contact to the substratum. Tarsi of Tettigonia viridissima bear flexible attachment pads with unusual ultrastructural architecture of the cuticle. The indentation of the attachment pads was measured under different loads using a force-tester. Since the mechanical properties are influenced by material structure, the freeze-substitution experiments were undertaken to investigate the influence of loads on material structure. Both profile changes of the surface and the orientation of cuticle microfibrils were visualized by means of scanning electron microscopy followed by fracturing of the frozen material. The results show that the flexible pad material deforms replicating the substrate profile down to the micrometer roughness. The pad material showed both elastic and viscous behavior under loads. Elastic deformation of the pad occurred under normal force applied for 4-6 s (elastic modulus 27.2 +/- 11.6 kPa). Two viscous relaxation processes were found, of time constants tau1 = 1.88+/-0.616 s and tau2 =41.2 +/- 9.95 s. Low stiffness of material studied here aids in surface replication and increase of area of real contact between the pad and the underlying substrate.

[Effects of various growth factors on human mandibular condylar cartilage cell proliferation]

OBJECTIVE

To investigate the effects of transforming growth factor-beta 1 (TGF-beta 1) insulin-like growth factor I (IGF-I) and basic fibroblast growth factor(bFGF) on human mandibular condylar cartilage (MCC) cell proliferation.

METHODS

Isolated human MCC cells were cultured in DMEM supplemented with 10% newborn calf serum(NCS). The second passages were used in order to avoid chondrocyte dedifferentiation. Cells were seeded at 2 x 10(4)/well on 96-well plate. After synchronization, medium was replaced by DMEM containing 0.4% NCS or 10% NCS with various growth factors, concentrations and combinations. Dose-response and time-course were studied by MTT colorimetric method.

RESULTS

In 0.4% serum containing medium, bFGF stimulated the proliferation moderately, whereas TGF-beta 1 and IGF-I had less effect. In 10% NCS condition, all three growth factors had mitogenic effect and acted dose-dependently. The effects were significant after three days. Among them, bFGF was a potent mitogen(increased by 65%), IGF-I the next(24%). The effect of TGF-beta 1 (13%) might be mediated by some other factors in the serum. The synergetic effects were achieved when they were used in combination.

CONCLUSION

It is suggested that optimal combination of growth factors can promote the proliferation of MCC cells significantly, this might be an ideal way in dealing with cartilage damage during pathogenesis.

Physiological and molecular properties of AMPA/Kainate receptors expressed by striatal medium spiny neurons

The mechanisms by which glutamate shapes the activity of striatal medium spiny neurons are of fundamental importance to our understanding of normative and pathological striatal physiology. Non-N-Methyl-D-aspartate (non-NMDA) glutamate receptor expression and function were studied in medium spiny neurons with a combination of single cell RT-PCR, immunocytochemistry and whole-cell voltage-clamp techniques. Reverse transcription polymerase chain reaction analysis found that GluR2 mRNA appeared to be the most abundant and widely distributed AMPA receptor mRNA. GluR1 was also commonly detected. However, GluR3 mRNA was preferentially expressed by neurons coexpressing substance P and enkephalin and GluR4 mRNA was not detected in identified medium spiny neurons. All neuronal classes appeared to express GluR5 or GluR6 and/or GluR7 mRNA in addition to kainate (KA) subunit mRNA. Immunocytochemical studies confirmed the mRNA distributions and also revealed that GluR1 protein was largely restricted to dendritic spines. Although the mRNA and protein for both alpha-amino-3-hydroxy-5-methyl-ioxyzole-4-proprionic acid (AMPA) and KA class subunits was detected, the physiological response to glutamatergic ligands and the benzothiadizine cyclothiazide was characteristic of AMPA, not KA receptors. The AMPA receptor antagonist GYKI 52466 blocked the response to AMPA and all but a small transient component of the response to KA. The current-voltage relationship of the AMPA-evoked currents was relatively linear but Ca2+ fluorometry revealed that substantial changes in intracellular Ca2+ concentration accompanied exposure to either agonist. These results argue that somatodendritic non-NMDA glutamate receptors in medium spiny neurons are primarily GluR2-containing receptors of the AMPA class but that activation of these receptors as a group nevertheless results in a significant Ca2+ influx.

[A quick way in isolation and amplification of mandibular condylar cartilage cell in vitro]

OBJECTIVE

To establish a quick way in acquiring well differentiated mandibular condylar cartilage (MCC) cells with high viability in large scale.

METHODS

Japan white rabbit MCC cells were harvested by enzymatic method. They were grown in a modified bioreactor culture system, which contained the cytodex-3 micro-carriers in the culture medium. Kinetic growth of MCC cells on DEAE-dextran micro-carrier was observed under phase contrast microscope and environmental scanning microscope respectively.

RESULTS

MCC cells attached rapidly to the surface of micro-carriers, but their spreading was slow. A quick growth of these cells was observed when they fully spread onto the micro-carrier. The number of MCC cells increased 16.2 times compared with that of plating.

CONCLUSIONS

Micro-carrier culture of MCC cells can yield a large quantity of cells within a short period of time that will be of benefit in banking MCC cells for reconstruction of impaired cartilage.

Adhesion measured on the attachment pads of Tettigonia viridissima (Orthoptera, insecta)

The tarsi of the cricket Tettigonia viridissima bear flexible attachment pads that are able to deform, replicating the profile of a surface to which they are apposed. This attachment system is supplemented by a secretion produced by epidermal cells and transported onto the surface of the pad through the pore canals of the pad cuticle. This study shows that the secretion alone is necessary, but not sufficient, for adhesion. To account for the full adhesive force, the deformation of the pad and the resulting changes in contact area were considered. In two series of experiments, the adhesive properties of the secretion and the adhesion of the whole pad were measured using a force tester, the sensitivity of which ranged from micronewtons to centinewtons. The adhesive forces of the secretion measured between a smooth sapphire ball with a diameter of 1.47 mm and a flat silicon surface ranged from 0.1 to 0.6 mN. In a control experiment on the silicon surface without secretion, no adhesive force was measured. There was no dependence of the adhesive force on the applied compressive force. When an intact pad was pulled off a flat silicon surface, the adhesive force increased with increasing applied compressive force, but it did not increase further once the applied force exceeded a certain value. The saturated adhesive force, ranging from 0.7 to 1.2 mN, was obtained at applied forces of 0.7-1.5 mN. The hemispherical surface of the pad had a larger contact area and demonstrated greater adhesion under a larger applied force. Adhesion became saturated when a pad was deformed such that contact area was maximal. The tenacity (the adhesive force per unit area) was 1.7-2.2 mN mm(−)(2).

[Fibronectin in adhesion, spreading and proliferation of mandibular condylar cartilage cells on cytodex-3 microcarrier]

OBJECTIVE

The purpose of this study was to investigate the effects of exogenous fibronectin on the attachment and growth of mandibular condylar cartilage (MCC) cells on DEAE-dextran micro-carrier.

METHODS

MCC cells were harvested from newborn New Zealand white rabbits by sequential digestion with trypsin and collagenase. They were grown on the 20 mg/L fibronectin-coated and uncoated cytodex-3 micro-carrier. Samples were collected after 1, 3, 5, 7, 9, 11 days. The kinetics of adhesion and growth were observed with phase contrast microscope and environmental scanning electronic microscope (ESEM) and quantified by 0.1% crystal violet nuclear extrusion method.

RESULTS

MCC cells could rapidly attach and spread onto the fibronectin-coated cytodex-3, and nearly 60 percent cells attached to the micro-carrier within 2 hours. Spreading cells were flat and lowly refractile observed under phase contrast microscope. While the attachment and spreading of the cells in the untreated group were slow, and only 36 percent cells attached to the uncoated micro-carrier. However, most cells attached to the micro-carrier in both groups after 24 hours. The MCC cells attaching to FN-coated cytodex-3 observed under ESEM were flatter and adhered tightly with more processes (pseudopodia) stretching out from cytoplasm. In contrast, cells on untreated cytodex-3 remained regularly round even 24 hours after being plated. Meanwhile, there was an accelerated growth rate of the MCC cells on the fibronectin treated cytodex-3. The cell density in the FN treated group was higher than that of the untreated group at the end of the culture.

CONCLUSION

Fibronectin, one major glycoprotein of extracellular matrix, plays an important role in cell attachment and spreading. The better understanding of the extracellular matrix will be helpful in selecting the optimal substrate for cell growth in vitro.

[Evaluation of plant protectants against pest insects]

An interference index of population control (IIPC) was constructed for investigating the complex effects of plant protectants, including the effects of repelling insect pests away from the plant, deterring the egg laying of adults and the continuation of feeding, and causing death by toxicity. At the same time, indicated by IIPC, the alcohol extracts of some common plants, such as Eucalytus rubusta, Wedelia chinensis etc. and the neem oil gave very good results to protect the plant against Plutella xylostella. The D-C-Tron NR Petroleum Spray Oil (CALTEX) also gave an excellent effect to protect citrus against red mite. All the experiments show the important role of the repellent effect on the pests.

[The regulation effects of growth factors on the procollagen gene expressions of human mandibular condylar cartilage cells]

OBJECTIVE

At the early stage of osteoarthrosis (OA) and joint damage, the cartilage cells proliferation increases dramatically, but this repair process is finally replaced by the progressive destruction of the cartilage. The reason, in accordance to the latest research, is the abnormal phenotype of the involved cartilage cell. This result suggests that the regulation of cartilage cell phenotype may be an effective way in the treatment of OA and other cartilage destructive diseases. In this study, the effects of transforming growth factor-beta(TGF-beta), insulin-like growth factor-I (IGF-I) and basic fibroblast growth factor (bFGF) on collagen expression of human mandibular condylar cartilage cells was investigated.

METHODS

Chondrocytes were isolated from human fetus by enzymatic method. The second passage of the cells was used in this study. They were cultured in DMEM medium supplemented with 20% newborn calf serum (NCS). After the cells reached confluence, the medium was replaced by DMEM containing 0.4% NCS. Then the cells were exposed to different growth factors including IGF-I (10 ng/ml), TGF-beta (5 ng/ml) and bFGF (50 ng/ml). The steady state mRNA levels of different samples were examined by slot-blot hybridization. The results were analysed by Student t test.

RESULTS

IGF-I had the least effects on the mRNA levels of three kinds of procollagen (type I, type II and type III). On the other hand, bFGF and TGF-beta could inhibit the expression of type II collagen by 0.352 and 0.685 times comparing with the control groups separately. TGF-beta increased type I collagen expression. Besides, bFGF and TGF-beta also increased the value of type I collagen/type II collagen. None of the three kinds of growth factors had obvious effects on the expression of type III collagen.

CONCLUSION

IGF-I can maintain the chondrocyte differentiated phenotype, while TGF-beta and bFGF have inhibitory effects.

A simple and sensitive antigen retrieval method for free-floating and slide-mounted tissue sections

The masking of antigens by aldehyde-containing fixatives or by paraffin embedding procedures is a problem for immunohistochemical studies. Enzymatic digestion, formic acid treatment, microwave heating and autoclave heating have been used to deal with this problem, with microwave heating-based antigen retrieval having become widely used as the method of choice. Microwave heating, however, has the shortcoming that it is difficult to precisely control the heating temperature and it is difficult to apply this method of heating to free-floating sections without damaging the sections. We describe here a simple, reliable and sensitive antigen retrieval method that uses water-bath heating. By this method, the temperature can be precisely controlled to yield effective antigen retrieval with minimal tissue damage in free-floating or paraffin-embedded slide-mounted sections. We found that the best results were obtained with a 30 min incubation in a 10-50 mM sodium citrate solution (pH 8.5-9.0) preheated to and maintained at 80 degrees C in a water-bath, followed by 30 min incubation in 0.3-3% nonfat dry milk to reduce nonspecfic staining. This method is highly effective for both 40 microm free floating sections, slide-mounted cryostat sections and paraffin-embedded slide-mounted sections, and it works well for tissue from diverse species (human, rat, mouse, pigeon, and zebra finch) and for diverse antigens (e.g. enkephalin, substance P, huntingtin, GluR1, GFAP, and ubiquitin). This method was also found to enhance immunolabeling in glutaraldehyde-fixed tissue that had been prepared for ultrastructural examination, without having a deleterious effect on the ultrastructure.

[Effects of growth factors on DNA and collagen synthesis of human mandibular condylar cartilage cells]

OBJECTIVE

To investigate the effects of transforming growth factor-beta 1 (TGF-beta 1), insulin-like growth factor-I (IGF-I) and basic fibroblast growth factor(bFGF) on DNA and collagen synthesis of mandibular condylar cartilage(MCC) of human fetus.

METHODS

Cell culture, 3H-TdR and 3H-Proline incorporation methods were used. MCC cells were harvested from 4 to 5 months old human fetus. Cells were seeded at 2 x 10(4)/well on 96-well Plate. After synchronization, medium was replaced by DMEM containing 0.4% NCS with various growth factors and concentrations.

RESULTS

bFGF stimulated the DNA synthesis significantly, and IGF-I had less effect, while the effect of TGF-beta 1 was insignificant. For collagen synthesis, bFGF caused a dose-dependent increase(60%). A greater effect(98%) was achieved when IGF-1 was added. In contrast, TGF-beta 1 could inhibit collagen synthesis (24%).

CONCLUSION

Growth factors play an important part in the proliferation and matrix synthesis of MCC cells, which might be of potential application in treating cartilage destructive lesions.

[Phenotypic changes of mandibular condylar cartilage cells during subculture]

OBJECTIVE

To demonstrate the phenotypic changes of mandibular condylar cartilage(MCC) cells during subculture in vitro.

METHODS

MCC cells were harvested from human fetus by digestion of collagenase and cultured in DMEM supplemented with 10% newborn calf serum, then they were passaged when reached confluence. Morphological changes were observed under phase-contrast microscope. Type II collagen, proteoglycan synthesis and type I, II and III procollagen mRNA levels were also studied in serial monolayer cultures.

RESULTS

During subculture, type II collagen and proteoglycan synthesis were decreased, being accompanied by a lower type II collagen mRNA level. In contrast, type I and III procollagen mRNA levels were elevated progressively. The morphology of polygonal-shaped chondrocytes was lost to the bipolar fibroblastic cells.

CONCLUSION

Passage and culture can affect the phenotypic property of MCC cells.

Evidence from a novel human cell clone that adult vascular smooth muscle cells can convert reversibly between noncontractile and contractile phenotypes

Smooth muscle cells (SMCs) perform diverse functions that can be categorized as contractile and synthetic. A traditional model holds that these distinct functions are performed by the same cell, by virtue of its capacity for bidirectional modulation of phenotype. However, this model has been challenged, in part because there is no physiological evidence that an adult synthetic SMC can acquire the ability to contract. We sought evidence for this by cloning adult SMCs from human internal thoracic artery. One clone, HITB5, expressed smooth muscle alpha-actin, smooth myosin heavy chains, heavy caldesmon, and calponin and showed robust calcium transients in response to histamine and angiotensin II, which confirmed intact transmembrane signaling cascades. On serum withdrawal, these cells adopted an elongated and spindle-shaped morphology, random migration slowed, extracellular matrix protein production fell, and cell proliferation and [(3)H]thymidine incorporation fell to near 0. Cell viability was not compromised, however; in fact, apoptosis rate fell significantly. In this state, agonist-induced elevation of cytoplasmic calcium was even more pronounced and was accompanied by SMC contraction. Readdition of 10% serum completely returned HITB5 cells to a noncontractile, proliferative phenotype. Contractile protein expression increased after serum withdrawal, although modestly, which suggested that the switch to contractile function involved reorganization or sensitization of existing contractile structures. To our knowledge, the physiological properties of HITB5 SMCs provide the first direct demonstration that cultured human adult SMCs can convert between a synthetic, noncontracting state and a contracting state. HITB5 cells should be valuable for characterizing the basis of this critical transition.

[Influence of flavonoid of Astragalus membranaceus's stem and leaves on the function of cell mediated immunity in mice]

OBJECTIVE

To investigate the immune regulation of flavonoid of Astragalus membranaceus's stem and leaves (FAM).

METHODS

Changes of total T cell count and subsets in mice were determined by monoclonal antibody assay before and after treatment with FAM, and the LAK activity was tested simultaneously by isotope technique.

RESULTS

FAM could promote the proliferation of lymphocytes induced by ConA, raise the T cell count and regulate the T cell subsets disorder, elevate the LAK activity induced by IL-2.

CONCLUSION

FAM possesses the effect of immune stimulation and immune regulation in treating immunosuppressive mice. This study provides the experimental basis for clinical application of FAM.