Hydralazine-demethylating systemic therapy for breast cancer

13131

Background: Cancer results from accumulation of gene deregulations. DNA sequence alterations are of unquestioned importance in this process, but are not exclusive. Alterations in gene function unaccounted for by DNA sequence changes (Epigenetic) are quite common, and seem to contribute to carcinogenesis. Abnormal methylation at the promoter region of Tumor Suppressor Genes results in gene transcriptional silencing, and is wide spread in many cancers, including Breast Cancer (BC). Alterations in cancer DNA methylation (DNAm) is among the best characterized epigenetic anomalies. An attractive feature of DNAm is its predisposition to pharmacologic reversal as a therapeutic intervention. Here, we used the cardiovascular drug hydralazine (H) to confirm its proposed demethylating effects and to examine its safety in clinically recommended doses concurrent with chemotherapy. Methods: Operable BC patients undergoing neoadjuvant therapy were enrolled on this study (n = 13). We examined DNAm levels at 2 time points; untreated tumor (biopsy) and H-treated specimen (resection) from the same patient. Global DNAm levels were estimated by examining the methylation level in Alu repeats. The study design conformed to a phase I, dose escalating scheme. H was administered at 50 mg orally TID for the first cohort in addition to standard chemotherapy. Results: H was well tolerated to a maximal dose of 200 mg QID. 1 patient discontinued the drug for headache. 4 patients completed treatment (approx. 4 months) and underwent surgical resection and assessment of methylation. Global Demethylation (defined as decrease of Alu methylation level by ≥5%) was observed in 2/4 [−8% and −9%, respectively]. The remaining patients have undergone surgery but DNA testing not performed as yet (results will be presented in the meeting). Conclusions: Hydralazine is well tolerated in normotensive individuals, in doses ≤ 200 mg/d concurrently with standard chemotherapy for breast cancer. Further, hydralazine produces decrement in DNAm of clinical cancer specimens. Effect of this demethylation on the expression of biologically important genes such as ER and p16 will be evaluated and presented once available. The biologic effect of such alteration in genomic DNAm would require subsequent investigation to prove its therapeutic impact.

No significant financial relationships to disclose.

Expression profiles can predict both general chemotherapy and gemcitabine-specific responses in breast cancer patients receiving neoadjuvant therapy

10008

Background: The identification of markers predictive of neoadjuvant chemotherapy response would be an important advance. Therefore, we sought to identify gene expression profiles predictive of neoadjuvant response and evaluated their drug specificity. Methods: DNA microarray analysis was performed on pre-treatment core biopsies from two different locally advanced breast cancer patient sets receiving neoadjuvant chemotherapy; the first set (L9819) was treated with 4 cycles of doxorubicin + cyclophosphamide (AC) followed by 4 cycles of paclitaxel (T) or paclitaxel + trastuzumab (TH). The second patient set (S329) received 4 cycles of gemcitabine + doxorubicin followed by 4 cycles of gemcitabine + cisplatin. Clinical response was based on RECIST criteria. Results: We obtained successful microarrays on 44 (L9819) and 46 (S329) of the patients enrolled. Ten-fold cross-validated supervised analyses separately performed on each dataset identified gene expression patterns that accurately predicted (75–85% accuracy) response (clinical complete responders vs. others) evaluated on those patients that completed all 8 cycles of chemotherapy. The predictive expression patterns from the L9819 trial were significantly enriched for apoptosis genes, while the predictive gene set from the S329 trial was enriched for nucleotide metabolism genes. The L9819 predictor was able to accurately predict (75% accuracy) response for the S329 patients, however, the S329 predictor was not able to predict response on the L9819 trial (50% accuracy). We speculate that the L9819 predictor was able to predict response on the S329 dataset (despite the fact that only doxorubicin was common to both trials) because this profile was enriched for apoptosis genes that may reflect a general mechanism of chemotherapy response/resistance, while the S329 predictor was more tuned to gemcitabine’s specific mechanism of action. Conclusions: This study may provide the means to predict response to AC-T(H) and GA-GC neoadjuvant chemotherapy. The ability of one predictor to work on the other dataset, but not vise versa, suggests that both general chemotherapy and drug specific response profiles may have been identified.

[Table: see text]

Identification of an ataxia telangiectasia-mutated protein mediated surveillance system to regulate Bcl-2 overexpression

Bcl-2 can both promote and attenuate tumorigenesis. Although the former function is relatively well characterized, the mechanism of the latter remains elusive. We report here that enforced Bcl-2 expression in MCF7 cells stabilizes p53, induces phosphorylation of p53 serine 15 (p53pSer15) and inhibits MCF7 cell growth. Consistent with p53 Ser15 being a target of ataxia telangiectasia mutated protein(ATM)/ATR (ATM- and rad3-related) in the DNA damage response, Bcl-2 activates ATM by inducing ATM Ser1981 phosphorylation, which is accompanied with the phosphorylaton of two additional ATM substrates, Chk2 Thr68 and H2AX Ser139. Downregulation of ATM using a specific small interference RNA fragment (ATMRNAi) abolished Bcl-2-induced p53pSer15 and Bcl-2-mediated growth inhibition of MCF7 cells. Ectopic expression of a dominant-negative p53 mutant, p53175H, partially rescued this growth inhibition. Taken together, these observations demonstrate the contribution of ATM-p53 function to Bcl-2-mediated inhibition of MCF7 cell growth, indicating an ATM-mediated surveillance system for regulating Bcl-2 overexpression. Consistent with this concept, we found that MCF7 cells express Bcl-2 heterogeneously with 34.5% of cells being Bcl-2 negative. In general, Bcl-2-positive MCF7 cells proliferate slower than those of Bcl-2 negative. Thus, we provide evidence suggesting that activation of ATM suppresses Bcl-2-induced tumorigenesis, and that attenuation of ATM function may be an important event in breast cancer progression.

High iodine intake is a risk factor of post-partum thyroiditis: result of a survey from Shenyang, China

The aim of the present study is to obtain the epidemiological data on post-partum thyroiditis (PPT) firstly in Chinese women, and to tryto evaluate whether excessive intake of iodine in post-partum women imposes any danger of occurring PPT. Sixty hundred and ten pregnant women were involved in the cohort just before delivery. Four hundred and eighty-eight (80%) of them accepted taking part in follow-ups more than 6 months post-partum. A blood sample was taken from participants before delivery and every 3 months post-partum for testing of serum TSH, thyroid autoantibodies. Free T3 (FT3), free T4 (FT4) and TSH receptor antibody (TRAb) were detected if TSH was abnormal. The iodine nutrition was evaluated according to the mean level of the fasting urinary iodine excretions at different times during the studying period, and participants were subgrouped into 3 categories with low, adequate and high iodine intake. For those participants who had thyroid dysfunction within 6 months post-partum, the follow-up persisted for 1 yr. Of 488 pregnant women, PPT developed in 11.9% (58/488). Given overt and subclinical PPT, the prevalence was 7.17% (no.=35) and 4.71% (no.=23), respectively. There was a strong association between the presence of thyroid peroxidase antibody (TPOAb) at delivery and the risk of developing PPT [RR=6.76, 95% (CI) 4.42-10.34]. Overt cases had much higher titers of TPOAb than subclinical patients (all p<0.05). The median urinary iodine (MUI) of patients with PPT was significantly higher than that of healthy women (231.93 vs 199.88 microg/l p=0.00153). Both the prevalence of PPT and positive TPOAb rise with the increment of iodine intakes. Pregnant women with high iodine intake had more risk of developing PPT when compared with those with low iodine intake (RR=2.92, 95%CI 1.31-6.50). We concluded that positive TPOAb was of value for predicting the occurrence and severity of PPT, and a high iodine intake was a risk factor triggering PPT.

ERK activity facilitates activation of the S-phase DNA damage checkpoint by modulating ATR function

Although Erk kinase has been recently reported to function in the DNA damage response, the mechanism governing this process is unknown. We report here that hydroxyurea (HU) activates Erk via MEK1, a process that is sensitized by a constitutively active MEK1 (MEK1Q56P) and attenuated by a dominant-negative MEK1 (MEK1K97M). While ectopic MEK1Q56P sensitized HU-induced S-phase arrest, inhibition of Erk activation via U0126, PD98059, and MEK1K97M attenuated the arrest, and thereby enhanced cells to HU-induced toxicity. Taken together, we demonstrate an important contribution of Erk to the activation of the S-phase DNA damage checkpoint. This can be attributed to Erk's regulatory role in modulating ATR function. Inhibition of Erk activation with U0126/PD98059 and MEK1K97M substantially reduced HU-induced ATR nuclear foci, leading to a dramatic reduction of gammaH2AX and its nuclear foci. Reduction of MEK1 function by a small interference RNA (siRNA) MEK1 and ectopic MEK1K97M significantly decreased HU-induced gammaH2AX. Conversely, ectopic MEK1Q56P enhanced gammaH2AX foci. Furthermore, immunofluorescent and cell fractioning experiments revealed cytosolic and nuclear localization of ATR. HU treatment caused the redistribution of ATR from the cytosol to the nucleus, a process that is inhibited by U0126. Collectively, we show that Erk kinase modulates HU-initiated DNA damage response by regulating ATR function.

Evidence of antisense tumor targeting in mice

Even though increased accumulations of radiolabeled antisense DNAs compared to control DNAs are becoming a routine observation in cultured tumor cells, trustworthy evidence of tumor targeting in vivo by an antisense mechanism remains elusive. The goal of this study was to obtain convincing evidence of antisense tumor targeting in nude mice by using two different tumors and both intratumoral (i.t.) and intravenous (i.v.) administration of radiolabeled antisense and control sense DNAs. Both the MDR++ cell line KB-G2 and its parent MDR+ cell line KB-31 were used in this study. The antisense (AS) DNA was directed against the AUG start codon of the MDR1 mRNA and, along with the sense (S) control DNA, was a uniform phosphorothioate administered naked. In previous cell culture studies from our laboratories, the accumulation of this AS DNA was strikingly high in KB-G2 cells and only average in KB-31 cells, a fact we attribute to the 1000-fold higher expression by RT-PCR of MDR1 mRNA in the former cell line. In this study, both DNAs were radiolabeled with (99m)Tc via MAG3 and administered i.t. or i.v. at 1 microg (100 microCi) per animal 24 h prior to sacrifice and dissection in mice bearing thigh tumors of about 1 g. Following i.t. administration, no statistically significant differences (Student's t test, p < 0.05, N = 4) between the AS and S DNA biodistributions in normal tissues were observed except in the KB-G2 mice in which muscle levels were lower for the S control. In contrast, tumor levels in the KB-G2 animals were significantly higher for the AS DNA vs S DNA (14.7 vs 8.5% ID/g) while this difference (8.6 vs 4.3% ID/g) was insignificant in the KB-31 animals. The whole body images obtained just prior to sacrifice clearly show improved targeting of AS DNA vs S DNA in the KB-G2 but not the KB-31 animals. Calculations based on these results show that about 60 000 AS DNAs accumulated specifically (i.e. AS DNA - S DNA) per KB-G2 tumor cell following i.t. administration. When administered i.v. rather than i.t., higher tumor levels in KB-G2 animals compared to KB-31 were not observed, most likely because of the lower dosage reaching the tumors. When the KB-G2 and KB-31 results are combined, no statistically significant differences between the AS and S DNA biodistributions in normal tissues were observed except in blood in which S DNA levels were higher and in spleen in which they were lower. In contrast, tumor levels were significantly higher for the AS DNA vs S DNA (0.100 vs 0.063% ID/g). Calculations based on these results show that about 400 AS DNAs accumulated specifically per tumor cell following i.v. administration. Therefore evidence for tumor targeting in vivo by an antisense mechanism has been obtained in that statistically higher tumor accumulations of the (99m)Tc-AS DNA were observed compared to the control (99m)Tc-S DNA both following i.t. and i.v. administrations. The successful localization of AS DNA in tumor demonstrates that in vivo AS targeting of tumor is feasible although improvements in tumor delivery and normal tissue clearance are needed for practical antisense imaging.

[Studies on ACE gene insertion/deletion polymorphism, serum ACE activity, and diabetic retinopathy in type II diabetic patients]

To clarify the relationship among angiotensin 1-converting enzyme(ACE) gene insertion/deletion(I/D) polymorphism, serum ACE activity, and diabetic retinopathy in Type II diabetic patients, we examined 36 healthy controls, 40 Type II diabetic patients without diabetic retinopathy, and 68 Type II diabetic patients with diabetic retinopathy. All of patients suffered from Type II diabetes beyond 5 years and matched in age and body mass index. An insertion/deletion polymorphism of ACE gene was identified by polymerase chain reaction(PCR). Serum ACE activity was determined using spectrophotometry. The distribution of DD, ID, and II genotypes of the ACE gene did not differ among the three groups (16.7%, 33.3%, and 50.0% in the healthy controls; 22.5%, 35.0%, and 42.5% in Type II diabetic patients patients without diabetic retinopathy; and 20.6%, 30.9%, and 48.5% in Type II diabetic patients with diabetic retinopathy; respectively). The frequency of ACE I/D genotypes was not significantly different between non-proliferative retinopathy and proliferative retinopathy of Type II diabetic patients with diabetic retinopathy (P > 0.05). Serum ACE activity of three groups was similar (P > 0.05). These results do not support the hypothesis that the DD genotype of the ACE gene would be a clinically useful genetic marker for predicting the development of diabetic retinopathy in Type II diabetic patients. There is no association between ACE gene I/D polymorphism and the prognosis of diabetic retinopathy in Type II diabetic patients. ACE may not involve in forming diabetic retinopathy in Type II diabetic patients.

[Relationship between serum angiotensin I-converting enzyme activity and diabetic nephropathy in patients with type II diabetes]

To clarify the relationship between serum angiotensin I-converting enzyme (ACE) activity and Type II diabetic patients with or without diabetic nephropathy. We examined 36 healthy controls, 58 Type II diabetic patients without diabetic nephropathy, and 50 Type II diabetic with diabetic nephropathy. The diabetic duration of all of Type II diabetic patients was more than 5 years. All patients matched well in age and BMI. An insertion/deletion polymorphism of ACE gene was identified by polymerase chain reaction(PCR). Serum ACE activity was determined using spectrophotometry. Although the distribution of DD, ID, and II genotypes of the ACE gene did not differ among the three groups, serum ACE activity was significantly higher in Type II diabetic patients with diabetic nephropathy than in that without diabetic nephropathy(P < 0.05), especially in the groups with D allele of ACE gene. Serum ACE activity had no difference between healthy controls and Type II diabetic patients without diabetic nephropathy. There is no association between serum ACE activity and Type II diabetic patients without diabetic nephropathy in any genotype of ACE gene. The increasing serum ACE activity plays a role in the initiation of diabetic nephropathy or may serve as a risk marker for later development of overt diabetic nephropathy in Type II diabetic patients.

[Experimental study on carcinogenic activity of the organic extracts from water of the sifangtai section of songhua river]

OBJECTIVES

To study the carcinogenic activity and potential mechanism of the organic extracts from the Songhua River in vitro.

METHODS

The in vitro cell transformation and single cell gel electrophoresis (SCGE) tests were detected with the ether extracts of water. The expression of anticancer genes p53, p16, and p21 measured by immunohistochemical assays and the apoptosis by TUNEL assay were also studied.

RESULTS

The extracts from the water induced malignant transformation of BALB/C mouse embryo fibroblast cells and induce DNA damage. p53, p16 and p21 failed to express in transformed cells induced by the water extracts, and the apoptosis rate of transformed cells decreased.

CONCLUSION

This study demonstrates that the organic extracts from the Songhua River has potential carcinogenicity.

[Effect of SP on intracellular free calcium concentration in cultured osteoblast]

OBJECTIVE

To investigate the effect of SP on intracellular free calcium concentration (Ca2+)i in cultured osteoblast.

METHODS

Effect of SP on intracellular free calcium was measured using cell culturing and laser scanning confocal microscopy with fluo-3/AM as a fluorescence probe.

RESULTS

After treated with SP(10(-4) mol/L), 70% of the cells responded to it; the intracellular (Ca2+)i increased markedly [fluorescence intensity increased by (90 +/- 18)%].

CONCLUSIONS

These results suggested that calcium may have a role as a intracellular secondary messenger in the action of SP in osteoblast.

Inhibitory effects of gynostemma pentaphyllum on the UV induction of bacteriophage lambda in lysogenic Escherichia coli

Effects of gynostemma pentaphyllum (GP) on the bacteriophage lambda induced by ultraviolet (UV) irradiation have been studied. The results showed that GP could inhibit the UV induction of bacteriophage lambda in lysogenic cells. The inhibitory effects were dependent on the concentration and the reaction time of GP, and were efficient at 40 to approximately 125 microg ml(-1) for 10 min. The inhibitory rate was higher than 70% when the GP concentration was 50 microg ml(-1). By electron spin resonance (ESR) and spin-trapping techniques, the signals of free radicals were detected in the suspension of the lambda lysogenic bacteria induced by ultraviolet irradiation, but after the addition of GP the signals were decreased. These results indicate that gynostemma pentaphyllum not only is a scavenger of free radicals, but also possesses the biological function of anti-irradiation, and that there is a close relation between the UV irradiation of the bacteriaphage lambda and free radicals.

[Expression of CCR5 and its ligand in joint fluid and synovium of patients with rheumatoid arthritis]

OBJECTIVE

To investigate the expression and distribution of C-C chemokine recepter 5 (CCR5) and its ligand in peripheral blood, synovium, and synovial fluid so as to study the mechanism of selective accumulation of Th1 cells in rheumatoid joints.

METHODS

Synovial fluid mononuclear cells (SFMC) and peripheral blood mononuclear cells (PBMC) were isolated from 15 patients with active rheumatoid arthritis (RA). The expressions of intracellular cytokines, CCR5 and CXCR3 on cytomembraine of SFMCs and PBMCs, and MIP-1 immunofluorescence labelling, and flow cytometry.

RESULTS

(1) The selective pattern of intracellular cytokines in SFMCs was drifted towards Th1 subset. (2) The expression rate of CCR5 was 52% Y 8%, the expression rate of CXCR3 was 61% Y 12% in synovial fluid, significantly higher than those of PBMCs. (3) In RA tissues, most of the infiltrating T cells (especially CD4+ T cells), monocyres/microphages, and B cells expressed macrophage inflammatory protein, ligand of CCR5.

CONCLUSION

Infiltrating T cells (especially CD4+ T((MIP)-1 cells), monocyres/microphages, and B cells in the synovium of inflammatory, RANTES, and other cytokines which cause the accumulation of CCR5+ Th1 cells.

Chemical constituents from Dendrobium densiflorum

5-[2'-(3"-Hydroxy-5"-methoxyphenyl)-ethyl]-1,3-benzodioxole and 7-hydroxy-2-methoxy-1,4-phenanthrenedione, along with 16 known compounds were identified from the stems of Dendrobium densifiorum Lindl. ex Wall. (Orchidaceae). The structure of a previously reported compound dendroflorin obtained from the plant was revised on the basis of spectroscopic analysis. Among the identified compounds, five were found to exhibit anti-platelet aggregation activity in vitro.

Effect of dimethyl sulfoxide on the electron transfer reactivity of hemoglobin

Hemoglobin, after being treated with dimethyl sulfoxide, exhibits a direct electrochemical response at a pyrolytic graphite electrode. The apparent standard potential (E degrees ') of hemoglobin is -0.119 V (vs. NHE). Meanwhile, since no electrochemical mediator is required for its direct electrochemistry, this work provides a convenient way to perform electrochemical research on this protein.

Electron-transfer reactivity and enzymatic activity of hemoglobin in a SP Sephadex membrane

Hemoglobin can exhibit a direct electron-transfer reaction after being entrapped in a SP Sephadex membrane. A pair of stable and well-defined redox waves are obtained at a hemoglobin-SP sephadex modified pyrolytic graphite electrode. The anodic and cathodic peak potentials are located at -0.244 and -0.336 V (vs SCE), respectively. On the other hand, the peroxidase activity of the protein in the membrane is also greatly enhanced. The apparent Michaelis-Menten constant is calculated to be 1.9 mM, which shows a large catalytic activity of hemoglobin in the SP Sephadex membrane toward hydrogen peroxide (H2O2). According to the direct electron-transfer property and enhanced peroxidase activity of Hb in the membrane, a Hb/SP Sephadex membrane-based H2O2 biosensor is prepared, with a linear range approximately 5.0 x 10(-6) to 1.6 x 10(-4) mol/L.

An unmediated hydrogen peroxide biosensor based on hemoglobin incorporated in a montmorillonite membrane

Hemoglobin was incorporated in a montmorillonite membrane. Electrochemical and spectroscopic studies revealed that the electron transfer reactivity and peroxidase activity of the protein were both enhanced. Nevertheless, its structure was still maintained native-like in the membrane. An unmediated hydrogen peroxide biosensor was accordingly prepared. The calibration plot of this H202 sensor was linear in the range of 1.0 x 10(-6)-6.0 x 10(-4) mol L(-1). The relative standard deviation was 3.1% for six successive determinations at a concentration of 1.0 x 10(-4) mol L(-1). The detection limit was 6.0 x 10(-7) mol L(-1). Possible interferences in real sample analyses are discussed.

An evaluation of the hemostatic effects of hydrophilic, alcohol, and lipophilic extracts of notoginseng

STUDY OBJECTIVE

To compare the hemostatic effects of hydrophilic, alcohol, or lipophilic extract of notoginseng with those of the control and placebo.

DESIGN

Hemorrhagic rat model.

SETTING

Hartford Hospital, Hartford, Connecticut; animals were housed at the Hartford Hospital animal facility.

ANIMALS

Sixty-two male Wistar rats. Intervention. Administration of placebo (wheat flour), and alcohol, hydrophilic (water), and lipophilic (hexane) extracts of notoginseng.

METHODS

Rats were divided into five groups, and their tails were transected 5 mm from the tip. Group 1 received no treatment (control), group 2 received placebo, group 3 received alcohol extract, group 4 received hydrophilic extract, and group 5 received lipophilic extract. Total bleeding time was determined and compared among the groups.

MAIN RESULTS

Bleeding time was shorter for the placebo group than the control group (p=0.035). The alcohol extract group had the shortest bleeding time, which was significantly shorter than that of the control (p<0.0001), placebo (p=0.0124), and lipophilic extract groups (p=0.002). The hydrophilic extract group had a shorter bleeding time than the control group (p=0.0058) and showed a trend toward shorter bleeding time than the lipophilic extract group (p=0.068).

CONCLUSIONS

The alcohol extract of notoginseng results in the shortest bleeding time and provides better hemostatic effects than no treatment, placebo treatment, and treatment with lipophilic extract.

Phylogenetic relationships within Cornus (Cornaceae) based on 26S rDNA sequences

Phylogenetic relationships within the dogwood genus Cornus have been highly controversial due to the great morphological heterogeneity. Earlier phylogenetic analyses of Cornus using chloroplast DNA (cpDNA) data (including rbcL and matK sequences, as well as restriction sites) and morphological characters suggested incongruent relationships within the genus. The present study generated sequence data from the nuclear gene 26S rDNA for Cornus to test the phylogenetic hypotheses based on cpDNA and morphological data. The 26S rDNA sequence data obtained represent 16 species, 13 from Cornus and three from outgroups, having an aligned length of 3380 bp. Both parsimony and maximum likelihood analyses of these sequences were conducted. Trees resulting from these analyses suggest relationships among subgroups of Cornus consistent with those inferred from cpDNA data. That is, the dwarf dogwood (subg. Arctocrania) and the big-bracted dogwood (subg. Cynoxylon and subg. Syncarpea) clades are sisters, which are, in turn, sister to the cornelian cherries (subg. Cornus and subg. Afrocrania). This red-fruited clade is sister to the blue- or white-fruited dogwoods (subg. Mesomora, subg. Kraniopsis, and subg. Yinquania). Within the blue- or white-fruited clade, C. oblonga (subg. Yinquania) is sister to the remainder, and subg. Mesomora is sister to subg. Kraniopsis. These relationships were also suggested by the combined 26S rDNA and cpDNA data, but with higher bootstrap and Bremer support in the combined analysis. The 26S rDNA sequence data of Cornus consist of 12 expansion segments spanning 1034 bp. These expansion segments evolve approximately four times as fast as the conserved core regions. The study provides an example of phylogenetic utility of 26S rDNA sequences below the genus level.

[A comparison between 99mTc-Q3 and 201Tl on clearance and retention properties at varying coronary flow rates in isolated rabbit heart]

OBJECTIVE

This study was intended to investigate and compare technetium-99m-N, N'-ethylenebis(acetylacetoneiminato)bis[tris (3-methoxy-1-propyl) phosphine] (99mTc-Q3) versus 201Tl on clearance and retention properties at varying coronary flow rates in isolated rabbit heart.

METHODS

20 New Zealand White rabbits were anaesthetized and excised through a median sternotomy. The hearts were isolated and arrested in ice-cold saline. The external perfusion models with isolated rabbit hearts were installed and were perfused at flow rates ranging from 0.52 to 3.75 ml/(g wet wt.min) in the absence of tracer recirculation. Furthermore, 99mTc-Q3 experimental relations between uptake, clearance and retention were explored in comparison with 201Tl.

RESULTS

201Tl net uptake was higher and also more affected by flow rates (P < 0.05) as compared with 99mTc-Q3 net uptake. 201Tl clearance was faster than 99mTc-Q3 clearance within 4 to 25 minutes after radiopharmaceuticals injection in high flow rates group, and 201Tl clearance was faster than 99mTc-Q3 clearance within 40 minutes after radiopharmaceuticals injection in low flow rates group. 201Tl earlier rapid clearance observed in the high flow rates group did not appear in the low flow rates group, but 99mTc-Q3 did not display early rapid clearance either in the high flow rates group or in the low flow rates group.

CONCLUSION

Owing to faster clearance, the superiority of 201Tl over 99mTc-Q3 as a myocardial perfusion imaging agent would be lost entirely within 10 minutes after injection of agent, therefore 99mTc-Q3 is still a good myocardial perfusion imaging agent, and further study is worth doing.

[The ultrastructure changes of nerve fibers in pressure side of periodontal ligament during orthodontic tooth movement in rats]

OBJECTIVE

To observe the ultrastructure changes of nerve fibers in pressure side of periodontal ligament during orthodontic tooth movement (OTM) in rats.

METHODS

The left maxillary of fifteen rats molar was moved mesially by an appliance for 2 days, 1 week, 2 weeks and 3 weeks. The ultrastructure changes of nerve fibers in pressure side of the periodontal ligament in rats were observed with electron microscope.

RESULTS

The thick myelinated axon was degenerated after 2 days of OTM and not recovered after 3 weeks of OTM; the number of thin unmyelinated axons was increased after 2 days of OTM. It reached a maximum after 1 week of OTM and recovered after 3 weeks of OTM. Only part of thin unmyelinated was slightly degenerated. At the same time, some of the thin myelinated axons were slightly degenerated and partly demyelinated.

CONCLUSION

The nerve fibers were involved in periodontal tissue remodelling.