Biomedical subjects

S Luo

Publications and source records attributed to S Luo.

At least 37 records · Page 2Linked to original sources

PubMed2001

[Muscarinic receptor subtype-3 expression in trabecular meshwork of normal human eye and primary open-angle glaucoma].

OBJECTIVE: To identify the muscarinic receptor subtype-3 (M3-receptor) expression in trabecular meshworks (TM) of normal human eyes and eyes with primary open-angle glaucoma (POAG) and discuss the pathological changes of TM in POAG. METHOD: TM specimens were taken from 5 normal persons and 10 patients with POAG at late stage. Then LSAB immunohistochemical technique was used to identify M3-receptors. The results were observed under microscope and compared with computer-image-analysis system. RESULTS: (1) The trabecular meshwork cells in all the 5 normal persons expressed M3-receptors. The positive cells mainly existed in the uveal part of TM, from Schwalbe's line to scleral spur. (2) In TM from eyes with POAG, the amount of both TM cells and M3-receptor positive cells were reduced obviously, even some specimens had no such positive expression. The positive cells were correspondingly decreased in number and scattered in distribution. CONCLUSION: The TM cells in normal human eyes express M3-receptors. The TM cells and M3-positive cells in eyes with late POAG are reduced in number and their distribution is irregular.

Adolescent↗

PubMed2001

[The influence of transforming growth factor beta 1 (TGF beta 1) on fibroblast proliferation and collagen synthesis].

OBJECTIVE: To investigate the significance and the influence of transforming growth factor beta 1 (TGF beta 1) on fibroblast proliferation and collagen synthesis. METHODS: The fibroblasts derived from healthy human dermis and pathologic scar were harvested and cultured in vitro with TGF beta 1. The effects of TGF beta 1 on the proliferation and collagen synthesis of the fibroblasts were investigated during the early phase (24 h) of cell confluence by means of nonradioactive cellular proliferation detection, 3H thymidine and 3H proline incorporation and DNA quantification analysis. RESULTS: After the co-culture with TGF beta 1, the incorporation of 3H thymidine and 3H proline and the proliferation were enhanced significantly in the fibroblasts from pathologic scar (P < 0.01) but remained at normal level in those from healthy human dermis(P > 0.05). CONCLUSION: The cell proliferation and collagen synthesis of scar-derived fibroblasts could be positively modulated and controlled by TGF beta 1, which might be very important in the scar formation.

Cell Division↗

PubMed2001

[Expression of mRNA of osteocalcin in condylar cartilage of young SD rats after functional protrusion].

OBJECTIVE: To study the temporal and spatial patterns of the expression of mRNA in condylar cartilage of young growing SD rats, in condition of different functional treatment time span. METHODS: SD rats are randomly divided into 3 groups: control, all-day group (wearing functional appliance for 24 hours a day) and 12-hour group (wearing appliance for 12 hours in daytime). After one week, animals are sacrificed and Osteocalcin mRNA expression is studied by in situ hybridization using Oligonucleotide probe, calculated by image processing and macroscopic and microscopic statistics. RESULTS: Osteocalcin mRNA is expressed in condylar cartilage of young growing SD rats and the acrophase is around 6:00 am. After wearing the functional appliance, the intensity in all-day group rises more than that in 12-hourgroup. CONCLUSIONS: Better results can be achieved in all-day group with functional appliance.

Animals↗

PubMed2001

[An immunohistochemical study of distribution of insulin in lateral pterygoid muscle after functional mandibular protrusion in rats].

OBJECTIVE: The aim of this study is to investigate the effects of insulin on the lateral pterygoid muscle of growing rats after the functional mandibular protrusion. METHODS: An immunohistochemical (the ABC method) method was used to detect the location and distribution of insulin in the lateral pterygoid muscle of rats. RESULTS: 1. Insulin located in the cell membrane of the lateral pterygoid muscle. 2. The distribution of insulin in the lateral pterygoid muscle of rats was enhanced after the functional mandibular protrusion. CONCLUSION: Insulin may play an important role in adaptive remodeling of the lateral pterygoid muscle after the treatment of functional mandibular protrusion.

Animals↗

PubMed2001

[Effects of fluid shear stress on PGE2 synthesis of primary osteoblast-like cells in rats].

OBJECTIVE: The purpose of this study is to study the function of PGE2 during the signal transduction in which fluid shear stress regulates the proliferation and differentiation of osteoblast-like cells. METHODS: The isolated rat primary osteoblast-like cells were exposed to fluid shear stress 0.12 mN/cm2 for 5, 10, 15, 30, 60 and 120 minutes respectively in a flow chamber. The release of PGE2 was examined. RESULTS: After exposure to fluid shear stress, the PGE2 synthesis of rat primary osteoblast-like cells increased significantly (P < 0.01) when compared with the control. After 10 minutes, the release of PGE2 began to increase significantly (P < 0.01) and the effect was maximal after 60 minutes (P < 0.01). CONCLUSION: PGE2 pathway may be one of the signal-transduction pathways which can transduce the fluid shear stress into osteoblast-like cells and then stimulate the bone remodeling.

Animals↗

PubMed2001

[Changes of osteocalcin in serum of young SD rats after functional protrusion].

OBJECTIVE: The aim of this study is to investigate temporal and spatial change patterns of osteocalcin in serum of young growing SD rats, in conditions of different functional treatment time spans. METHODS: Totally, 72 SD rats are randomly divided into 3 groups, including the control group, the 24-hour wearing group (wearing functional appliance 24 hours a day), and the 12-hour wearing group (wearing appliance for 12 hours in daylight). One week after the experiment, rats were sacrificed and osteocalcin level in serum was measured by using radioimmunoassay. Date was processed using macroscopic and microscopic analysis. RESULTS: Serum osteocalcin had circadian rhythm and the peak was about 12:00 in a day. After wearing the functional appliance, serum osteocalcin level increased with treatment time, and serum osteocalcin level in the 24-hour wearing group rose more obviously than that in the 12-hour wearing group. CONCLUSION: For the functional appliance, better results can be achieved in the 24-hour wearing group.

Animals↗

PubMed2001

[Research and establishment of the computerized orthodontic and orthopedic prediction system].

OBJECTIVE: The aim of this study was to develop a computerized orthopedics and orthodontics interactive prediction system and verify its reliability. METHODS: 24 cases of Angel II division I patients were selected in the study. All of them had been treated by activator or Frankel functional appliance, and had the satisfied therapy result. Both pre and post-treatment cephalogram of them were used verifying veracity of therapy prediction. RESULTS: All of cephalometric measure items include 11 angle measure items and 14 distance measure items. There were 9 coincidence indicators in angle measure items and 7 in distance measure items. CONCLUSION: The results indicate it is liable and effective to use the computerized orthopedics and orthodontics system for prediction.

Activator Appliances↗

PubMed2001

[Establishment and research of the computerized profile and photo prediction system].

OBJECTIVE: The study aims to develop a lateral oral facial profile and photo prediction system and then to verify its reliability. METHODS: 24 paired lateral cepholagrams in both pre- and post-treatment were selected and analyzed by three soft tissue cephalometric analysis methods in this study. All cases were of the angel II division I malocclusion, and had been successfully treated with the orthopedics therapy by activator or Frankel appliance. Soft tissue profile prediction had been automatically completed, following the hard tissue interactive orthopedics prediction approach in the pretreatment lateral cephalogram, and the predictive results were compared to the same cepholametric analysis in post-treatment cephalogram. RESULTS: There are 19 coincidence indicators in 30 measurements of three soft tissue cephalometric analysis, and 7 in 9 angel measurements, 10 in 18 instance measurements, 2 in 3 instance ratio measurements is consistency, respectively. CONCLUSION: The results indicate that the lateral oral facial profile and photo prediction system is effective in profile prediction.

Activator Appliances↗

PubMed2001

[The effect of fluid shear stress on the proliferation of rat primary osteoblast-like cells in vitro].

OBJECTIVE: To inquire into the cellular mechanism by which mechanical stress regulates bone remodeling and make an attempt at establishing the most suitable physiological stress to stimulate bone formation. METHODS: The isolated rat primary osteoblast-like cells were exposed to fluid shear stress 2, 4, 8, 12, 14, 17 and 19 dyn/cm2 for 60 min respectively in the flow chamber. The ability of proliferation of cells was studied by flow cytometry. RESULTS: After exposed to fluid shear stress, the cells rearranged and the cells' axes were elongated following the flow direction. The proliferation indexes (PI) of the cells went up with the gradual increase of shear stress. When fluid stress reached 12 dyn/cm2, the PI of cells increased significantly (P < 0.05), compared with the control. But the PI of cells began to decrease when the fluid stress continued to increase, and when fluid stress reached 14 dyn/cm2, the PI of cells decreased significantly (P < 0.01), compared with the control. CONCLUSION: The mechanism by which mechanical stress regulates bone remodeling is related to the proliferation of the osteoblast cells stimulated by stress-induced fluid flow. Low shear stress has no marked influence on the proliferation of cells. Medium shear stress (12 dyn/cm2) can stimulate cells significantly. Major shear stress (14 dyn/cm2) can inhibit cells significantly.

Animals↗

PubMed2000

The dimerization of folded monomers of ribulose 1,5-bisphosphate carboxylase/oxygenase.

Spontaneous refolding and reconstitution processes of dimeric ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) from Rhodospirillum rubrum have been investigated using size-exclusion high performance liquid chromatography (HPLC), spectroscopic, and activity measurements. When the unfolded Rubisco in guanidine hydrochloride is diluted at 4 degrees C, a folding intermediate (Rubisco-I) is rapidly formed, which remains in an unstable monomeric state and gradually develops into folded monomer (Rubisco-M) at 4 degrees C but undergoes irreversible aggregation at 25 degrees C. Refolding of Rubisco-I to Rubisco-M is a very slow process, taking about 20 h for 70% conversion at 4 degrees C. Rubisco-M is stable at 4 degrees C and is capable of forming an active dimer spontaneously when incubated at a temperature higher than 10 degrees C. The dynamic dimerization process has been measured in a temperature range of 4-35 degrees C by HPLC, and the results demonstrate that the dimerization is strongly facilitated by the temperature. It is found that dithiothreitol is essential for the spontaneous reconstitution of Rubisco.

Chromatography, High Pressure Liquid↗

PubMed2000

Cloning and functional expression of a gene encoding a vacuolar-type proton-translocating pyrophosphatase from Trypanosoma cruzi.

Acidocalcisomes are acidic Ca(2+)-storage organelles found in trypanosomatids that are similar to organelles known historically as volutin granules. Acidification of these organelles is driven in part by a vacuolar H(+)-pyrophosphatase (V-H(+)-PPase), an enzyme that is also present in plant vacuoles and in some bacteria. Here, we report the cloning and sequencing of a gene encoding the acidocalcisomal V-H(+)-PPase of Trypanosoma cruzi. The protein (T. cruzi pyrophosphatase, TcPPase) predicted from the nucleotide sequence of the gene has 816 amino acids and a molecular mass of 85 kDa. Several sequence motifs found in plant V-H(+)-PPases were present in TcPPase, explaining its sensitivity to N-ethylmaleimide and N,N'-dicyclohexylcarbodi-imide. Heterologous expression of the cDNA encoding TcPPase in the yeast Saccharomyces cerevisiae produced a functional enzyme. Phylogenetic analysis of the available V-H(+)-PPase sequences indicates that TcPPase is nearer to the vascular plant cluster and the branch containing Chara, a precursor to land plants, than to any of the other pyrophosphatase sequences included in the analysis. The apparent lack of such a V-H(+)-PPase in mammalian cells may provide a target for the development of new drugs.

Amino Acid Motifs↗

PubMed2000

Arginine to citrulline replacement in substrates of phosphorylase kinase.

Synthetic peptides based on residues 9 to 18 of glycogen phosphorylase were prepared containing citrulline at position 10 or 16, or at both positions 10 and 16. The peptides were compared as substrates for a recombinant, truncated form of the catalytic subunit of phosphorylase kinase (residues 1-300). The peptide having citrulline at position 10 was phosphorylated the same as the parent peptide. Both the peptides with a single citrulline at position 16 and with two citrullines were phosphorylated less effectively than the parent peptide; k(cat)/K(m) values were approximately 20% the value with the parent peptide. Incorporation of the second citrulline had little change in the effectiveness of the peptide as a substrate although the kinetic parameters with the citrulline peptides did show differences. The change in peptide phosphorylation did not seem to result from a change in peptide structure. Two-dimensional nuclear magnetic resonance studies of di-citrulline peptide are reported and showed no change in the solution structure of the peptide compared to the parent peptide. Thus, the change in kinetic parameters with the modified peptides seemed an effect of arginine replacement and was likely a consequence of the loss of charge inasmuch as the size of arginine and citrulline are similar. Arginine-16 was concluded to be more important for phosphorylase kinase recognition than arginine-10. These findings were consistent with the earlier studies using alanine replacement of arginine in synthetic peptides as substrates for the holoenzyme form of phosphorylase kinase.

Amino Acid Sequence↗

PubMed2000

Acidocalcisomes and a vacuolar H+-pyrophosphatase in malaria parasites.

Plasmodium berghei trophozoites were loaded with the fluorescent calcium indicator, fura-2 acetoxymethyl ester, to measure their intracellular Ca(2+) concentration ([Ca(2+)](i)). [Ca(2+)](i) was increased in the presence of the sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase inhibitor, thapsigargin. Trophozoites also possess a significant amount of Ca(2+) stored in an acidic compartment. This was indicated by: (1) the increase in [Ca(2+)](i) induced by bafilomycin A(1), nigericin, monensin, or the weak base, NH(4)Cl, in the nominal absence of extracellular Ca(2+), and (2) the effect of ionomycin, which cannot take Ca(2+) out of acidic organelles and was more effective after alkalinization of this compartment by addition of bafilomycin A(1), nigericin, monensin, or NH(4)Cl. Inorganic PP(i) promoted the acidification of a subcellular compartment in cell homogenates of trophozoites. The proton gradient driven by PP(i) collapsed by addition of the K(+)/H(+) exchanger, nigericin, and eliminated by the PP(i) analogue, aminomethylenediphosphonate (AMDP). Both PP(i) hydrolysis and proton transport were dependent upon K(+), and Na(+) caused partial inhibition of these activities. PP(i) hydrolysis was sensitive in a dose-dependent manner to AMDP, imidodiphosphate, sodium fluoride, dicyclohexylcarbodi-imide and to the thiol reagent, N-ethylmaleimide. Immunofluorescence microscopy using antibodies raised against conserved peptide sequences of a plant vacuolar pyrophosphatase (V-H(+)-PPase) suggested that the proton pyrophosphatase is located in intracellular vacuoles and the plasma membrane of trophozoites. AMDP caused an increase in [Ca(2+)](i) in the nominal absence of extracellular Ca(2+). Ionomycin was more effective in releasing Ca(2+) from this acidic intracellular compartment after treatment of the cells with AMDP. Taken together, these results suggest the presence in malaria parasites of acidocalcisomes with similar characteristics to those described in trypanosomatids and Toxoplasma gondii, and the colocalization of the V-H(+)-PPase and V-H(+)-ATPase in these organelles.

Ammonium Chloride↗

PubMed2000

Oxidative phosphorylation, Ca(2+) transport, and fatty acid-induced uncoupling in malaria parasites mitochondria.

Respiration, oxidative phosphorylation, calcium uptake, and the mitochondrial membrane potential of trophozoites of the malaria parasite Plasmodium berghei were assayed in situ after permeabilization with digitonin. ADP promoted an oligomycin-sensitive transition from resting to phosphorylating respiration. Respiration was sensitive to antimycin A and cyanide. The capacity of trophozoites to sustain oxidative phosphorylation was additionally supported by the detection of an oligomycin-sensitive decrease in mitochondrial membrane potential induced by ADP. Phosphorylation of ADP could be obtained in permeabilized trophozoites in the presence of succinate, citrate, alpha-ketoglutarate, glutamate, malate, dihydroorotate, alpha-glycerophosphate, and N,N,N',N'-tetramethyl-p-phenylenediamine. Ca(2+) uptake caused membrane depolarization compatible with the existence of an electrogenically mediated Ca(2+) transport system in these mitochondria. An uncoupling effect of fatty acids was partly reversed by bovine serum albumin, ATP, or GTP and not affected by atractyloside, ADP, glutamate, or malonate. Evidence for the presence of a mitochondrial uncoupling protein in P. berghei was also obtained by using antibodies raised against plant uncoupling mitochondrial protein. Together these results provide the first direct biochemical evidence of mitochondrial function in ATP synthesis and Ca(2+) transport in a malaria parasite and suggest the presence of an H(+) conductance in trophozoites similar to that produced by a mitochondrial uncoupling protein.

Animals↗

PubMed2000

Conus peptides: novel probes for nicotinic acetylcholine receptor structure and function.

Conus is a genus of predatory marine snails that uses venom to capture prey. Among the neurotoxins widely utilized by the cone snails are the alpha-conotoxins which are disulfide-rich peptides that target muscle or neuronal subtypes of nicotinic acetylcholine receptors. The small size and receptor subtype specificity of these peptides make them particularly useful for characterizing both native and heterologously expressed nicotinic receptors. In this report, we demonstrate that alpha-conotoxin MII potently blocks beta3-containing neuronal nicotinic receptors. Furthermore, initial evidence suggests that subpopulations of alpha3beta2beta3-containing receptors are differentially sensitive to alpha-conotoxin MII. Thus, alpha-conotoxin MII promises to be a useful tool for studying neuronal nicotinic receptors containing the beta3 subunit.

Animals↗

PubMed2000

In vitro cloning of complex mixtures of DNA on microbeads: physical separation of differentially expressed cDNAs.

We describe a method for cloning nucleic acid molecules onto the surfaces of 5-micrometer microbeads rather than in biological hosts. A unique tag sequence is attached to each molecule, and the tagged library is amplified. Unique tagging of the molecules is achieved by sampling a small fraction (1%) of a very large repertoire of tag sequences. The resulting library is hybridized to microbeads that each carry approximately 10(6) strands complementary to one of the tags. About 10(5) copies of each molecule are collected on each microbead. Because such clones are segregated on microbeads, they can be operated on simultaneously and then assayed separately. To demonstrate the utility of this approach, we show how to label and extract microbeads bearing clones differentially expressed between two libraries by using a fluorescence-activated cell sorter (FACS). Because no prior information about the cloned molecules is required, this process is obviously useful where sequence databases are incomplete or nonexistent. More importantly, the process also permits the isolation of clones that are expressed only in given tissues or that are differentially expressed between normal and diseased states. Such clones then may be spotted on much more cost-effective, tissue- or disease-directed, low-density planar microarrays.

Cloning, Molecular↗

PubMed2000

Hyperinsulinemia increases norepinephrine metabolism in the ventromedial hypothalamus of rats.

Numerous studies have implicated increased ventromedial hypothalamic (VMH) norepinephrine (NE) activity as a contributing factor to the obese, hyperinsulinemic, glucose intolerant condition. However, factors contributing to the increased VMH NE activity remain unknown. This study therefore investigated in normal rats the effect of a hyperinsulinemic-euglycemic clamp on VMH monoamine turnover and utilization via simultaneous VMH microdialysis to establish a role for hyperinsulinemia in the stimulation of VMH NE activity. Within 20 min of initiation of the hyperinsulinemic-euglycemic clamp, VMH extracellular methoxyhydroxy phenylglycol (metabolite of NE) level increased by 54% and remained approximately at this level for the 100 min duration of the clamp relative to control values (p<0.05). Hyperinsulinemia did not affect VMH dopamine or serotonin metabolism. Subsequent establishment of a hyperinsulinemic-hypoglycemic camp did not alter the VMH monoamine metabolism profile relative to the hyperinsulinemic-euglycemic clamp. Infusion of saline (as control) in a separate group of rats over the entire clamp period induced no changes in any monoamine metabolic profile relative to baseline. Hyperinsulinemia can feedback to stimulate VMH NE activity and, as a result, may contribute to the initiation and/or perpetuation of the obese, hyperinsulinemic, glucose-intolerant state.

Animals↗

PubMed2000

Oxidized low-density lipoproteins inhibit endothelial cell proliferation by suppressing basic fibroblast growth factor expression.

BACKGROUND: Hyperlipidemia inhibits proliferation of endothelial cells (ECs) in culture and angiogenesis in vivo and in arterial explants. Elucidation of the mechanisms may suggest novel therapies against atherosclerosis. METHODS AND RESULTS: Basic fibroblast growth factor (bFGF) expression and mitogenic effects were assessed in bovine aortic ECs incubated with oxidized LDL (ox-LDL). Compared with native LDL and lipoprotein-free controls, ox-LDL reduced bFGF mRNA levels in a time- and concentration-dependent manner, 100 microg/mL producing a maximum reduction of 40% to 50% within 24 to 48 hours. There were commensurate reductions in intracellular and extracellular bFGF concentrations, DNA and total RNA syntheses, and cell replication. FGF receptor 1 and beta-actin mRNA levels were unchanged. Ox-LDL accelerated bFGF mRNA degradation in actinomycin D-treated cells. However, inhibition of bFGF expression by ox-LDL was attenuated by cyclohexamide, indicating a requirement for continuous new protein synthesis for posttranscriptional destabilization. Reduced syntheses of DNA and total RNA were completely restored by bFGF but not by vascular endothelial growth factor. Inhibition of total RNA synthesis achieved by exposing cells to a bFGF-neutralizing antibody was similar in magnitude to that induced by ox-LDL. CONCLUSIONS: Cytotoxic effects of ox-LDL on ECs are attributable in part to suppression of bFGF expression.

Animals↗