[Pathological evaluation of endoscopic submucosal dissection for early gastric cancer and precancerous lesion in 411 cases]

OBJECTIVE

To evaluate the pathological characteristics of endoscopic submucosal dissection (ESD) specimens for early gastric cancer and precancerous lesions, accumulating experience for clinical management and pathological analysis.

METHODS

A total of 411 cases of early gastric cancer or precancerous lesions underwent ESD. According to the Japanese guidelines for ESD treatment of early gastric cancer and classification of gastric carcinoma, the clinicopathological data, pathologic evaluation, concordance rate of pathological diagnosis between preoperative endoscopic forceps biopsies and their ESD specimens (in 400 cases), as well as the risk factors of non-curative resection of early gastric cancer, were analyzed retrospectively.

RESULTS

23.4% (96/411) of the 411 cases were adenoma/low-grade dysplasia and 76.6% (315/411) were early gastric cancer. The latter included 28.0% (115/411) non-invasive carcinoma/high-grade dysplasia and 48.7% (200/411) invasive carcinoma. The concordance rate of pathological diagnosis between endoscopic forceps biopsies and ESD specimens was 66.0% (264/400), correlating with pathological diagnosis and lesion location (P < 0.01). The rate of upgraded diagnosis and downgraded diagnosis after ESD was 29.8% (119/400) and 4.2% (17/400), respectively. Among the 315 cases of early gastric cancer, there were 277 cases (87.9%) of differentiated type and 38 cases (12.1%) of undifferentiated type. In the study, 262 cases (83.2%) met with absolute indication, while 53 cases (16.8%) met relative indication. En bloc and curative resection rates were 98.1% and 82.9%, respectively. Risk factors for non-curative resection included a long diameter >20 mm (OR=3.631, 95%CI: 1.170-11.270, P=0.026), tumor infiltration into submucosa (OR=69.761, 95%CI: 21.033-231.376, P < 0.001)and undifferentiated tumor histology (OR=16.950, 95%CI: 4.585-62.664, P < 0.001).

CONCLUSION

Several subjective and objective factors, such as the limitations of biopsy samples, the characteristics and distribution of the lesions, different pathological understanding, and the endoscopic sampling and observation, can lead to the differences between the preoperative and postoperative pathological diagnosis of ESD. In particular, the pathological upgrade of postoperative diagnosis was more significant and should receive more attention by endoscopists and pathologists. The curative resection rate of early gastric cancer in ESD was high. Non-curative resection was related to the long diameter, the depth of tumor invasion and histological classification. ESD can also be performed in undifferentiated early gastric cancer if meeting the indication criteria. The comprehensive and standardized pathological analysis of ESD specimens is clinically important to evaluate the curative effect of ESD operation and patient outcomes.

P-583 PCOS patients got better IVF/ICSI outcomes with “higher” progesterone level on hCG day: a retrospective study of Ten years data

Study question

We aimed to investigate whether serum Progesterone (P) on the day of hCG trigger can be used as a biomarker to predict the IVF/ICSI outcomes in PCOS patients.

Summary answer

PCOS patients got better IVF/ICSI outcomes with “higher” progesterone level (2.7-5.9mmol/L).

What is known already

There were several studies suggesting serum Progesterone (P) on the day of hCG trigger can be used as a biomarker to predict IVF outcomes, and to decide fresh cycle embryo transfer or frozen all. But there was few study focus on PCOS patients.

Study design, size, duration

This is a single-center retrospective cohort study in PCOS women undergoing the first transfer of an IVF cycle between January 1st 2010 and December 31th 2019. There were 141,539 oocyte retrieval cycles during the study period, and 97,189 cycles were their first IVF cycle. PCOS was diagnosed according to the Rotterdam criteria. Among them, 3,146 cycles full filled the inclusion and exclusion criteria, and all with two embryos transferred on Day 3.

Participants/materials, setting, methods

We compared the live birth rate of fresh embryo transfer, stratified for serum P level. We looked for interaction between serum P level and live birth rate of fresh cycles. The serum P level within normal range (&lt; 6nmol/L) on the day of hCG trigger day was divided into 4 quartiles. The four quartiles were defined as ≤ 1.35 nmol/L (Q1), &gt;1.35-1.93 nmol/L (Q2), &gt;1.93-2.7 nmol/L (Q3), &gt;2.7 nmol/L (Q4).

Main results and the role of chance

The baseline characteristics with no different between groups, except BMI. The patients in Q4 group with lowest BMI, significantly higher number of oocytes retrieved and live birth rate (P &lt; 0.05) . The Logistic regression analysis of the relative factors on live birth rate including BMI, basal LH and number of oocytes retrieved [P = 0.003, 0.030, 0.037 respectively, 95%CI (1.022, 1.111), (1.004, 1.076), (1.002, 1.082)].

Limitations, reasons for caution

Due to the retrospective nature of this study, a well-designed and matched large sample prospective study is needed. The definition of elevated P level and the method of hormonal assessments were different between studies, this limiting the comprehensive analysis of researches and the further verification of existing results.

Wider implications of the findings

PCOS patients who with normal range P level on hCG day, got better IVF/ICSI outcomes with “higher” progesterone level (2.7-5.9mmol/L). Weight control is important for PCOS patients accepting IVF treatment.

Trial registration number

NOT APPLICABLE

[Analysis of the self-conscious health status and influencing factors of greenhouse agricultural workers in Beijing suburb]

Objective: To explore the self-conscious health status and related influencing factors of greenhouse agricultural workers in Beijing suburb, so as to provide scientific basis for developing strategies to improve and promote the occupational health conditions of those workers. Methods: According to the production characteristics and scale of the main agricultural districts or counties in the suburb of Beijing, 182 agricultural production personnel were randomly selected to investigate the general situation, occupational situation and self-conscious health status during June 2018 to December 2019. The relevant factors which may affect the self-conscious health conditions were also analyzed by statistical methods. Results: The detection or reported rate of self-conscious health problems was 51.6% (94/182) , among which 29.1% (53/182) workers reported musculoskeletal disorder diseases and 21.4% (39/182) workers reported nervous system diseases. And the self-conscious health status of greenhouse agricultural workers were statistically different in household registration, gender, marital status, working years, mixing or spraying pesticides, smoking or eating in the greenhouse (P<0.05) . Moreover, gender, mixing or spraying pesticide, eating and smoking behavior in the workplace all had an impact on the risk of self-conscious health status of greenhouse agricultural workers (P< 0.05) . Specifically, male is the protective factor to reduce the occurrence of self-conscious symptoms of greenhouse agricultural workers (OR=0.447, 95%CI: 0.234~0.852) , while mixing or spraying pesticides and smoking or eating behaviors in the workplace are the risk factors (OR=1.055, 2.524; 95%CI: 0.503~2.210, 1.107~5.755) . Conclusion: Reducing pesticide use from the source thus minimize related exposure opportunities, strengthening occupational health education thus foster good hygienic habits and improve individual protection consciousness are of great significance for the health protection of greenhouse agricultural workers in Beijing suburb.

Endothelin-1 induces chondrocyte senescence and cartilage damage via endothelin receptor type B in a post-traumatic osteoarthritis mouse model

OBJECTIVES

This study aimed to investigate the role of endothelin-1 (ET-1), originally known as the potent vasoconstrictor, and its receptors in chondrocyte senescence and osteoarthritis (OA) development.

METHOD

Temporal changes of ET-1 and its receptors with OA development were characterized in a posttraumatic OA (PTOA) mouse model at time zero, 1-month and 4-month after surgical induction via destabilization of medial meniscus (DMM). A transgenic ET-1 overexpression (TET-1) mouse model was deployed to assess the impact of upregulated ET-1 on chondrocyte senescence and cartilage degradation. Effects of endothelin receptor blockade on chondrocyte senescence and OA development were further examined both in vitro and in vivo.

RESULTS

Local expression of ET-1 in subchondral bone and synovium upregulated after DMM with an increase of plasma ET-1 level from 3.18 ± 0.21 pg/ml at time zero to 6.47 ± 0.34 pg/ml at 4-month post-surgery. Meanwhile, endothelin type B receptor (ET_BR) (53.31 ± 2.42% to 83.8 ± 2.65%) and p16^INK4a (10.91 ± 1.07% to 28.2 ± 1.0%) positve chondrocytes accumulated in articular cartilage since 1-month prior to cartilage loss at 4-month post-surgery. Overexpressed ET-1 promoted p16^INK4a-positive senescent chondrocytes accumulation and cartilage degradation in TET-1 mice. Selective blockade of ET_BR, but not ET_AR, lowered the expression of p16^INK4a in ET-1 or H₂O₂-induced chondrocyte senescence model, and mitigated the severity of murine PTOA. Intriguingly, reactive oxygen species (ROS) scavenger, Vitamin C, could rescue ET-1-induced chondrocyte senescence in vitro associated with restoration of mitochondrial dynamics.

CONCLUSION

ET-1 could induce chondrocytes senescence and cartilage damages via ET_BR in PTOA.

[Clinical short-term and long-term efficacy of endoscopic submucosal dissection in the treatment of early low rectal cancer and precancerous lesions]

Objective: To evaluate the short-term and long-term efficacy of endoscopic submucosal dissection (ESD) in the treatment of early low rectal cancer and precancerous lesions. Methods: Inclusion criteria: (1) Distance from the lower margin of tumor to the anal was ≤ 5 cm. (2) Early low rectal cancers were any size rectal epithelial tumors with infiltration depth limited to the mucosa and submucosa, which were diagnosed by postoperative pathology as high-grade intraepithelial neoplasia or adenocarcinoma of the rectum with infiltration depth of intramucosal or submucosal cancer (M or SM stage). (3) Precancerous lesions included adenoma and low-grade intraepithelial neoplasia of the rectum. (4) Patients received ESD treatment. Patients with tumor invasion depth over submucosa by pathology were excluded. From January 2008 to January 2018, 63 patients meeting the above criteria in Peking University First Hospital were enrolled in this descriptive cohort study. The disease characteristics, clinical manifestations, pathological types, treatment time, hospitalization time, en bloc resection rate (resection of the whole lesion), complete resection rate (both the horizontal and vertical incision margins were negative), postoperative complications and follow-up results were analyzed. Cummulative survival rate was calculated by Kaplan-Meier. Results: The diameter of the lesion was (29.0±23.4) mm and the distance from the lesion to the anus was (2.7±1.8) cm. The median operation time was 45.0 (range, 10.0 to 360.0) minutes, the median hospitalization time was 3.0 (range, 2.0 to 12.0) days, en bloc resection rate was 100%, complete resection rate was 96.8% (61/63), and 1 case (1.6%) had postoperative bleeding. The follow-up rate was 87.3% (55/63) and the median follow-up time was 57.9 (range, 15.6 to 121.1) months. No local recurrence was found during the follow-up period and the 5-year survival rate was 100%. Conclusion: Short- and long-term efficacy of ESD are quite good in the treatment of patients with early low rectal cancer and precancerous lesions.

Protease sensitivity and redistribution of CD71 and glycophorin A on K562 cells

Transmembrane proteins are delivered to plasma membrane from the endoplasmic reticulum and Golgi complex by vesicular transport along with the cytoskeletal network. Disruption of this process likely affects transmembrane protein expression. K562 cells were digested with Streptomyces griseus protease for different periods of time, and then re-cultured with different cytoskeletal and glycosylation inhibitors. Cell viability and surface expression of transferrin receptor (CD71) and glycophorin A (GPA) were analyzed before and after re-culture by flow cytometry. We found that digestion with protease almost completely removed extracellular CD71 and GPA but their expression recovered to the initial levels after re-culture for 8 h and 24 h, respectively. The microtubule depolymerizer colchicine promoted cell surface recovery of CD71 but inhibited that of GPA; the microtubule stabilizer paclitaxel inhibited cell surface recovery of CD71 but promoted that of GPA; the microfilament depolymerizer cytochalasin D had no effect on cell surface recovery of CD71 and GPA; the microfilament stabilizer phalloidin inhibited cell surface recovery of GPA. The glycosylation inhibitor tunicamycin inhibited the recovery of both CD71 and GPA, and BADGP inhibited the recovery of GPA. These studies show differential sensitivities of surface proteins on K562 cells to proteases, and suggest molecular mechanisms of transmembrane protein transport and cycling.

Answers to if the Lead Aprons are Really Helpful in Nuclear Medicine from the Perspective of Spectroscopy

Wearing lead X-ray-protective aprons is a routine in nuclear medicine department in parts of China. However, the staff are often perplexed by questions such as if it is imperative to wear aprons when injecting radioactive drugs, how much radiation dosage can be shielded and if the apron will produce secondary radiation instead? To answer these questions, a semiconductor detector was employed to record different gamma and X-ray spectra with and without the lead apron or lead sheet. Then, we could estimate the signal shielding ratio to different photons for the lead apron and compare with the hospitals measured data. In general, the two results coincided well. The spectral results showed that the detrimental secondary X-rays irradiation rises when the energy of gamma rays exceeds the K absorption edge of lead (88 keV). Moreover, the aprons are not so effective for gamma rays of 364 keV emitted from 131I and 511 keV emitted from the positron radioactive nuclides. This work is purely a physical measurement in the laboratory. To the best of our knowledge, this is the first quantitative study on the level of gamma rays protection offered by the medical lead aprons and the importance of the spectroscopic measurements is discussed in this paper.

Sirt 1 activator attenuates the bleomycin-induced lung fibrosis in mice via inhibiting epithelial-to-mesenchymal transition (EMT)

OBJECTIVE

The aim of this study was to investigate the effect of resveratrol on the idiopathic bleomycin (BLM)-induced pulmonary fibrosis, which is increasingly recognized as an epithelial-to-mesenchymal transition (EMT)-associated disease.

MATERIALS AND METHODS

We evaluated the effect of resveratrol on the BLM-induced fibrosis in a mouse model, via monitoring the pathological chance in mice lung, the mice body weight change and the mice death. And we also explored the regulation by BLM on (and) resveratrol on the expression and activity of Sirt 1 and on the expression of epithelial-to-mesenchymal transition (EMT)-associated markers in mice lung.

RESULTS

It was demonstrated that resveratrol ameliorated the BLM-induced fibrosis-like pathological change in mice lung, inhibited BLM-induced mice body weight loss and death. Moreover, resveratrol also inhibited the BLM-induced EMT-associated molecular events, such as reduced E-cadherin and elevated Collagen I and α-SMA. We also confirmed the amelioration by resveratrol on the BLM-mediated inhibition of Sirt 1 in expression and activity in mice lung.

CONCLUSIONS

Our study confirmed the inhibitory role of resveratrol in the BLM-induced pulmonary fibrosis in a mouse model. Resveratrol ameliorated the BLM-induced pathological change of fibrosis, mice body weight loss and death. And such amelioration might be associated with the activation of Sirt 1 in mice lung. The present study implied that resveratrol might be a promising agent for effective control the pulmonary fibrosis.

Characterization and molecular mapping of stripe rust resistance gene Yr61 in winter wheat cultivar Pindong 34

We report a new stripe rust resistance gene on chromosome 7AS in wheat and molecular markers useful for transferring it to other wheat genotypes. Several new races of the stripe rust pathogen have established throughout the wheat growing regions of China in recent years. These new races are virulent to most of the designated seedling resistance genes limiting the resistance sources. It is necessary to identify new genes for diversification and for pyramiding different resistance genes in order to achieve more durable resistance. We report here the identification of a new resistance gene, designated as Yr61, in Chinese wheat cultivar Pindong 34. A mapping population of 208 F2 plants and 128 derived F2:3 lines in a cross between Mingxian 169 and Pindong 34 was evaluated for seedling stripe rust response. A genetic map consisting of eight resistance gene analog polymorphism (RGAP), two sequence-tagged site (STS) and four simple sequence repeat (SSR) markers was constructed. Yr61 was located on the short arm of chromosome 7A and flanked by RGAP markers Xwgp5467 and Xwgp5765 about 1.9 and 3.9 cM in distance, which were successfully converted into STS markers STS5467 and STS5765b, respectively. The flanking STS markers could be used for marker-assisted selection of Yr61 in breeding programs.

Immunotherapy, phase I study of immunotherapy with carcinoembryonic antigen peptide -pulsed, autologous human cultured dendritic cells in patients with advanced non-small cell lung cancer

12517

Background: To study toxicity tolerance and dose-effect relationship of carcinoembryuonic antigen peptide-pulsed dendritic cells in patients with advanced lung cancer. Methods: cells preparations enriched for autologous DCs were generated from the patients plastic adherent peripheral blood mononuclear cells in media supplemented with granulocyte macrophage colony -stimulating factor and interleukin-4. 37C0, 5%CO2 culture for 7–10. The DCs were loaded with carcinoembryonic antigen(CEA) in day 7, Groups of three to six patients received four weekly or biweekly i.v. infusions of the CAP-1-loaded DC in escalating dose levels of 1 × 106, 1 × 107, and 1 × 108 cells/dose. Patients with lung cancer received iv injections DCs. There were no toxicities directly referable to the treatments. Results: Total 22 patients with lung cancer received DCs immunotherapy. DCs infusion were 2.5×106-9.6×107,means 15.03×106. The early clinical trials suggest that vaccination with CEA vaccines is safe, producing few side-effects, and can lead to CEA-specific immunity. Conclusions: We conclude that it is feasible and safe to generate and administer large numbers of DCs loaded with CEA peptide to patients with lung cancer.

No significant financial relationships to disclose.

Protein crystallization by using porous glass substrate

The effects of a commercially available porous glass substrate (Corning Porous Glass No.7930) on the heterogeneous nucleation of proteins [hen egg-white lysozyme (HEWL), thaumatin and apoferritin] have been investigated in order to develop an improved method to facilitate the nucleation of protein crystals. It was found that the porous glass substrate could promote the nucleation at lower supersaturations. The induction time for nucleation decreased, and the crystals obtained from porous glass substrates were larger than those from normal glass substrates. Many pores and channels of 10-100 nm in diameter were observed on the porous glass surface by atomic force microscopy (AFM). It is believed that these pores and channels are crucial for facilitating the nucleation process in this work.

RAGE is a multiligand receptor of the immunoglobulin superfamily: implications for homeostasis and chronic disease

Receptor for AGE (RAGE) is a member of the immunoglobulin superfamily that engages distinct classes of ligands. The biology of RAGE is driven by the settings in which these ligands accumulate, such as diabetes, inflammation, neurodegenerative disorders and tumors. In this review, we discuss the context of each of these classes of ligands, including advance glycation end-products, amyloid beta peptide and the family of beta sheet fibrils, S100/calgranulins and amphoterin. Implications for the role of these ligands interacting with RAGE in homeostasis and disease will be considered.

HIV-1 nucleocapsid protein and the secondary structure of the binary complex formed between tRNA(Lys.3) and viral RNA template play different roles during initiation of (-) strand DNA reverse transcription

In human immunodeficiency virus type 1 (HIV-1), the tRNA(Lys.3) primer and viral RNA template can form a specific complex that is characterized by extensive inter- and intramolecular interactions. Initiation of reverse transcription from this complex has been shown to be distinguished from subsequent elongation by early pausing events, such as at the +1 and +3 nucleotide positions. One major concern regarding the biological relevance of these results is that most kinetic studies of HIV-1 reverse transcription have been performed using tRNA(Lys.3)-viral (v) RNA complexes that were formed by heat annealing. In contrast, tRNA(Lys.3) in viruses is placed onto the primer binding site by nucleocapsid (NC) sequences of the Gag protein. In this study, we have further characterized the initiation features of reverse transcription in the presence of HIV-1 NC protein. In contrast to results obtained with a heat-annealed tRNA(Lys.3).vRNA complex, we found that polymerization reactions catalyzed by HIV-1 reverse transcriptase did not commonly pause at the +1 nucleotide position when a NC-annealed RNA complex was used, and that this was true regardless whether NC was actually still present during reverse transcription. This activity of NC required both zinc finger motifs, as demonstrated by experiments that employed zinc finger-mutated forms of NC protein (H23C NC and ddNC), supporting the involvement of the zinc fingers in the RNA chaperone activity of NC. However, NC was not able to help reverse transcriptase to escape the +3 pausing event. Mutagenesis of a stem structure within the tRNA(Lys.3). vRNA complex led to disappearance of the +3 pausing event as well as to significantly reduced rates of reverse transcription. Thus, this stem structure is essential for optimal reverse transcription, despite its role in promotion of the +3 pausing event.

Hydrophobic amino acids in the human immunodeficiency virus type 1 p2 and nucleocapsid proteins can contribute to the rescue of deleted viral RNA packaging signals

An RNA fragment of 75 nucleotides, which is located between the primer binding site and the 5' major splice donor site in human immunodeficiency virus type 1, has been shown to participate in specific encapsidation of viral RNA. Compensation studies have identified two second-site mutations, namely, MP2 (a T12I substitution in p2) and MNC (a T24I substitution in the nucleocapsid [NC] protein) that were involved in the rescue of various deletions in the aforementioned RNA region (i.e., BH-D1, BH-D2, and BH-LD3). To study whether the MP2 and MNC point mutations exert their compensatory effects in a cis manner, production of Gag proteins was blocked by insertion of stop codons into LD3, LD3-MP2-MNC, and wild-type BH10 such that the constructs generated, i.e., LD3-DG, LD3-MP2-MNC-DG, and BH-DG, only provided RNA transcripts for packaging. The results of cotransfection experiments showed that the LD3-MP2-MNC-DG viral RNA was packaged as inefficiently as LD3-DG; in contrast, BH-DG was efficiently packaged. Therefore, nucleotide substitutions in MP2 and MNC did not act in a cis manner to correct the packaging deficits in LD3. Next, we deliberately changed the T12 in p2 or the T24 in the NC to each of 19 other amino acids. We found that amino acids with long hydrophobic side chains, i.e., V, L, I, and M, were favored at either position 12 in p2 or at position 24 in NC to compensate for the above-mentioned deletions. Further studies showed that only a few amino acids could not be used at these two sites by the wild-type virus due to decreased RNA levels in the virion or abnormal Gag protein processing. In this case, W, D, and E could not substitute for T12 in p2, and S, D, and N could not substitute for T24 in NC, without affecting viral infectivity. Therefore, the long hydrophobic side chains of V, L, I, and M are necessary for these amino acids to rescue the BH-D1, BH-D2, and BH-LD3 mutated viruses.

A novel microphysiometer based on MLAPS for drugs screening

This paper presents a novel microphysiometer for simultaneous measurements of several extracellular ions concentrations in living cells based on MLAPS (multi-light addressable potentiometric sensor). In the microphysiometer, different sensitive membranes are illuminated in parallel with n light sources at different frequencies, the response amplitudes of each frequency component can be measured on-line by parallel processing algorithm. By the experiments, we can analyze the relations of the extracellular environmental H(+), Na(+), K(+), Ca(2+) under the effects of western medicines (dilantin, phenobarbital sodium, penicillin sodium) and Chinese drugs (scutellaria, medlar, hemlock parsley), and estimate the effects of several drugs. As the novel microphysiometer works under regular cell culture conditions, cells can be repeatedly simulated with drugs to complete dose-response curve within a few hours. With the detection of a general parameter (extruded protons and ions), the system can be used to monitor the real-time process of the cells' metabolism, observe the functional responses of different kinds of membrane-bound receptors, evaluate the drugs.

Role of calcium in protein folding and function of Tva, the receptor of subgroup A avian sarcoma and leukosis virus

Tva is the cellular receptor for subgroup A avian sarcoma and leukosis virus (ASLV-A). The viral receptor function of Tva is determined by a 40-residue cysteine-rich motif called the LDL-A module. In this study, we expressed and purified the wild-type (wt) Tva LDL-A module as well as several mutants and examined their in vitro folding properties. We found that, as for other LDL-A modules, correct folding and structure of the Tva LDL-A module is Ca2+ dependent. When calcium was present during in vitro protein folding, the wt module was eluted as a single peak by reverse-phase high-pressure liquid chromatography. Furthermore, two-dimensional nuclear magnetic resonance (NMR) spectroscopy gave well-dispersed spectra in the presence of calcium. In contrast, the same protein folded in vitro in the absence of calcium was eluted as multiple broad peaks and gave a poorly dispersed NMR spectrum in the presence of calcium. The calcium affinity (Kd) of the Tva LDL-A module, determined by isothermal titration calorimetry, is approximately 40 microM. Characterization of several Tva mutants provided further evidence that calcium is important in protein folding and function of Tva. Mutations of the Ca2+-binding residues (D46A and E47A) completely abrogated the Ca2+-binding ability of Tva, and the proteins were not correctly folded. Interestingly, mutations of two non-calcium-binding residues (W48A and L34A) also exerted adverse effect on Ca2+-dependent folding, albeit to a much less extent. Our results provide new insights regarding the structure and function of Tva in ASLV-A entry.

Role for human immunodeficiency virus type 1 Tat protein in suppression of viral reverse transcriptase activity during late stages of viral replication

We have examined the role of the human immunodeficiency virus type 1 (HIV-1) Tat protein in the regulation of reverse transcription. We show that a two-exon but not a one-exon form of Tat markedly suppressed cell-free reverse transcriptase (RT) activity. Conversely, viruses expressing two-exon Tat (pNL43 and pNL101) showed rapid replication kinetics and more efficient endogenous RT activity compared with viruses expressing one-exon Tat (pM1ex). The pM1ex virions, as well as pM1ex-infected cells, also contained higher levels of viral DNA than did either the pNL43 or pNL101 viruses, indicating that reverse transcription might have continued during later stages of viral replication in the absence of the second Tat exon. Moreover, degradation of viral genomic RNA was more apparent in the pM1ex virions. Accordingly, we propose that the two-exon Tat may help augment viral infectivity by suppressing the reverse transcription reaction during late stages of viral synthesis and by preventing the synthesis of potentially deleterious viral DNA products.

Simple quantification of ultrasonic intensity using aqueous solution of phenolphthalein

Aqueous phenolphthalein solution under sonication was investigated for use as a chemical dosimeter. The fading time of aqueous phenolphthalein solution under sonication depended on the concentration of phenolphthalein and the pH values of solutions. The fading time was correlated to the ultrasonic intensity in a reaction vessel that is estimated on the basis of decomposition of porphyrin. The relation between the fading time and the ultrasonic intensity for different frequencies is expressed by a single curve. From these results, it is indicated that aqueous solutions of phenolphthalein is useful for simple quantification of ultrasonic intensity for practical use, and one can regard it as one of the ultrasonic intensity indicators.

Roles of Pr55(gag) and NCp7 in tRNA(3)(Lys) genomic placement and the initiation step of reverse transcription in human immunodeficiency virus type 1

To study in vivo tRNA(3)(Lys) genomic placement and the initiation step of reverse transcription in human immunodeficiency virus type 1, total viral RNA isolated from either wild-type or protease-negative (PR(-)) virus was used as the source of primer tRNA(3)(Lys)/genomic RNA templates in an in vitro reverse transcription assay. At low dCTP concentrations, both the rate and extent of the first nucleotide incorporated into tRNA(3)(Lys), dCTP, were lower with PR(-) than with wild-type total viral RNA. Transient in vitro exposure of either type of primer/template RNA to NCp7 increased PR(-) dCTP incorporation to wild-type levels but did not change the level of wild-type dCTP incorporation. Exposure of either primer/template to Pr55(gag) had no effect on initiation. These results indicate that while Pr55(gag) is sufficient for tRNA(3)(Lys) placement onto the genome, exposure of this complex to mature NCp7 is required for optimum tRNA(3)(Lys) placement and initiation of reverse transcription.

Deletion mutagenesis downstream of the 5' long terminal repeat of human immunodeficiency virus type 1 is compensated for by point mutations in both the U5 region and gag gene

We have studied the role of an RNA region at nucleotides (nt) +200 to +233, just downstream of the 5' long terminal repeat, in encapsidation of human immunodeficiency virus type 1 genomic RNA. Three deletion mutations, namely, BH-D0, BH-D1, and BH-D2, were generated to eliminate sequences at positions nt +200 to +219, +200 to +226, and +200 to +233. The result in each case was decreased levels of packaging of viral RNA into the mutated viruses, with the BH-D2 virus being the most severely affected. Consistently, all three deletions resulted in impaired viral infectiousness and the BH-D2 mutation showed the most dramatic impact in this regard. Further analysis revealed additional defects in Gag precursor processing and in the extension efficiency of the tRNA(3)(Lys) primer in reverse transcription reactions performed with these mutated viruses. To shed further light on the function of these deleted sequences in viral replication, the mutated viruses were cultured in MT-2 cells over prolonged periods to enable them to reacquire wild-type replication kinetics. Sequencing of the reverted viruses revealed point mutations in both the noncoding region and the gag gene. In the case of the BH-D0 revertant, two mutations were observed at positions G112A in the U5 region, termed M1, and T24I in the nucleocapsid protein, termed MNC, respectively. Either of these two mutations was able to confer wild-type replication capacity on BH-D0. In the case of BH-D1, each of the M1 mutations, a mutation termed M2, i.e., C227T, just downstream of the primer binding site, a mutation termed MP2 (T12I) in the p2 protein, and the MNC mutation were observed. A combination of either M1 and M2 or MP2 and MNC was able to rescue BH-D1. In the case of the BH-D2 deletion-containing viruses, three point mutations, i.e., M1, MP2, and MNC, were observed and the presence of all three was required to restore viral replication to wild-type levels.

The effect of mutations in the HIV-1 nucleocapsid protein on strand transfer in cell-free reverse transcription reactions

Interactions between the nucleocapsid protein (NC) and reverse transcriptase of HIV-1 have been shown to promote the initiation of reverse transcription. We assayed the effect of NC on later events, using a strand transfer system with donor and acceptor HIV RNA templates and found that the presence of NC resulted in increased synthesis of full-length strand-transferred (FLST) DNA. This effect also occurred with mutated forms of NC that lacked both zinc fingers, or that contained a point mutation (histidine-->cysteine) at amino acid 23. In contrast, NC-derived proteins containing only the proximal or distal zinc fingers, or lacking the N- and C-termini, were all unable to catalyze the synthesis of FLST DNA. Band-shift assays using both the mutated and wild-type forms of these proteins revealed that all the NC proteins promoted strand association between (-) strong-stop DNA [(-)ssDNA] and acceptor RNA. The zinc finger motifs were dispensable for full-length processive reverse transcription, and the N- and C-termini were required; however, all NC domains were dispensable for association of (-)ssDNA and acceptor RNA. This suggests that annealing is a less stringent reaction than DNA polymerization.

Reverse transcriptase inhibitors can selectively block the synthesis of differently sized viral DNA transcripts in cells acutely infected with human immunodeficiency virus type 1

We have recently reported that the in vitro inhibition of human immunodeficiency virus type 1 (HIV-1) reverse transcription by inhibitors of reverse transcriptase (RT) occurred most efficiently when the expected DNA products of RT reactions were long (Quan et al. , Nucleic Acids Res. 26:5692-5698, 1998). Here, we have used a quantitative PCR to analyze HIV-1 reverse transcription within acutely infected cells treated with RT inhibitors. We found that levels of minus-strand strong-stop DNA [(-)ssDNA] formed in acutely infected MT2 cells were only slightly reduced if cells were infected with viruses that had been generated in the presence of either azidothymidine or nevirapine (5 microM) and maintained in the presence of this drug throughout the viral adsorption period and thereafter. Control experiments in which virus inoculation of cells was performed at 4 degrees C, followed directly by cell extraction, showed that less than 1% of total (-)ssDNA within acutely infected cells was attributable to its presence within adsorbed virions. In contrast, synthesis of intermediate-length reverse-transcribed DNA products decreased gradually as viral DNA strand elongation took place in the presence of either of these inhibitors. This establishes that nucleoside and nonnucleoside RT inhibitors can exert similar temporal impacts in regard to inhibition of viral DNA synthesis. Generation of full-length viral DNA, as expected, was almost completely blocked in the presence of these antiviral drugs. These results provide insight into the fact that high concentrations of drugs are often needed to yield inhibitory effects in cell-free RT assays performed with short templates, whereas relatively low drug concentrations are often strongly inhibitory in cellular systems.

Mutations within four distinct gag proteins are required to restore replication of human immunodeficiency virus type 1 after deletion mutagenesis within the dimerization initiation site

Human immunodeficiency virus type 1 (HIV-1) genomic RNA segments at nucleotide (nt) positions +240 to +274 are thought to form a stem-loop secondary structure, termed SL1, that serves as a dimerization initiation site for viral genomic RNA. We have generated two distinct deletion mutations within this region, termed BH10-LD3 and BH10-LD4, involving nt positions +238 to +253 and +261 to +274, respectively, and have shown that each of these resulted in significant diminutions in levels of viral infectiousness. However, long-term culture of each of these viruses in MT-2 cells resulted in a restoration of infectiousness, due to a series of compensatory point mutations within four distinct proteins that are normally cleaved from the Gag precursor. In the case of BH10-LD3, these four mutations were MA1, CA1, MP2, and MNC, and they involved changes of amino acid Val-35 to Ile within the matrix protein (MA), Ile-91 to Thr within the capsid (CA), Thr-12 to Ile within p2, and Thr-24 to Ile within the nucleocapsid (NC). The order in which these mutations were acquired by the mutated BH10-LD3 was MNC > CA1 > MP2 > MA1. The results of site-directed mutagenesis studies confirmed that each of these four substitutions contributed to the increased viability of the mutated BH10-LD3 viruses and that the MNC substitution, which was acquired first, played the most important role in this regard. Three point mutations, MP2, MNC, and MA2, were also shown to be sequentially acquired by viruses that had emerged in culture from the BH10-LD4 deletion. The first two of these were identical to those described above, while the last involved a change of Val-35 to Leu. All three of these substitutions were necessary to restore the infectiousness of mutated BH10-LD4 viruses to wild-type levels, although the MP2 mutation alone, but neither of the other two substitutions, was able to confer some viability on BH10-LD4 viruses. Studies of viral RNA packaging showed that the BH10-LD4 deletion only marginally impaired encapsidation while the BH10-LD3 deletion caused a severe deficit in this regard.

Deletion mutagenesis within the dimerization initiation site of human immunodeficiency virus type 1 results in delayed processing of the p2 peptide from precursor proteins

Previous work has shown that deletions of genomic segments at nucleotide (nt) positions +238 to +253, i.e., construct BH10-LD3, or nt positions +261 to +274, i.e., construct BH10-LD4, within the human immunodeficiency virus type 1 (HIV-1) dimerization initiation site (DIS) destroyed DIS secondary structure and dramatically reduced viral replication capacity. Surprisingly, two point mutations located within the viral peptide 2 (p2) and nucleocapsid (NC) protein termed MP2 and MNC, respectively, were able to compensate for this defect. Since the MP2 mutation involves an amino acid substitution near the cleavage site between p2 and NC, we investigated the effects of the above-mentioned deletions on the processing of Gag proteins. Immunoprecipitation assays performed with monoclonal antibodies against viral capsid (CA) (p24) protein showed that p2 was cleaved from CA with less efficiency in viruses that contained the LD3 and LD4 deletions than in wild-type viruses. The presence of the two compensatory mutations, MP2 and MNC, increased the efficiency of the cleavage of p2 from CA, but neither mutation alone had this effect or was sufficient to compensate for the observed impairment in infectiousness. A virus that contained both of the above-mentioned deletions within the DIS was also impaired in regard to processing and infectiousness, and it could likewise be compensated by the MP2 and MNC point mutations. These results suggest that the DIS region of HIV-1 RNA plays an important role in the processing of Gag proteins.

Substitutions in the receptor-binding domain of the avian sarcoma and leukosis virus envelope uncouple receptor-triggered structural rearrangements in the surface and transmembrane subunits

The retrovirus avian sarcoma and leukosis virus (ASLV) enters cells via pH-independent membrane fusion. This reaction is catalyzed by the viral glycoprotein Env, composed of a membrane-distal subunit, SU, and a membrane-anchored subunit, TM. Previous mutational analysis of a variable region, central within the SU subunit, indicates that this region constitutes part of the receptor-binding domain for subgroup A envelope (EnvA) and furthermore that basic residues (R210, R213, R223, R224, and K227) within this region are critical determinants of efficient ASLV infection. Substitutions of these basic residues exert effects on both receptor binding and postbinding events in EnvA-mediated entry. In this study, we performed biochemical analysis of the EnvA protein from three of the receptor-binding domain mutants (R213A/K227A, R213A/R223A/R224A, and R213S) to define the role of this domain in early molecular events in the entry pathway. Protease sensitivity assays demonstrated that receptor binding was sufficient to trigger conformational changes in the SU subunit of mutants R213A/K227A and R213S similar to those in the wild-type EnvA, while R213A/R223A/R224A was constitutively sensitive to protease. In contrast, all three receptor-binding domain mutants disrupted receptor-triggered conversion of EnvA to an active, membrane-binding conformation as assessed by liposome flotation assays. Our results demonstrate that mutations in the receptor-binding site can dissociate receptor-triggered conformational changes in the SU subunit from membrane binding. Furthermore, they suggest that communication between the receptor-binding subunit, SU, and the fusogenic subunit, TM, is crucial for efficient activation of the fusogenic state of EnvA. Analysis of these mutants continues earlier observations that binding to the cellular receptor provides the trigger for efficient activation of this pH-independent viral envelope protein.

[Principle and application of scattering power function method in X-ray fluorescence analysis. III. Continuous scattering radiation]

The study in this paper shows that the relationship between mass attenuation coefficient and continuous scattering radiation at wavelength 0.081 nm is not an inverse proportion supposed as the scattering internal standard method but a power function in a wide range of matix composition. Experimental results are in good agreement with that of theoretical prediction. A new method is recommended for matrix absorption correction using the 1.22 power function of continuous scattering radiation at wavelength 0.081 nm and used for microelement Sr determination in geological samples as an application example. The accuracy of the results by this method is nearly 4 times better than that from the traditional scattering internal method in a wide range of matrix composition.

Zinc metabolism and requirement in Chinese preschool children consuming different diets

Zinc metabolism of children differs due to diet and this can affect zinc requirement. We used the balance method to study zinc metabolism in 11 Chinese preschool children (six males and five females, 5.5-6.5 y old with a mean age of 6 y) of normal zinc status as judged by comprehensive criteria before and after they were fed a balanced diet. Zinc intakes and excretions via feces, urine, whole body surface and hair were determined in each subject. After all subjects consumed a balanced diet for 3 wk, losses of zinc in feces and urine increased from 3.77 +/- 0.62 mg/d to 5.28 +/- 0.92 mg/d (P < 0.05) and 0.19 +/- 0.05 mg/d to 0.23 +/- 0.05 mg/d (P < 0.05), respectively, as dietary zinc intakes increased from 5.38 +/- 0.71 mg/d to 7.12 +/- 0.64 mg/d (P < 0.05). Whole body surface zinc loss did not change (0.25 +/- 0.07 mg/d vs 0.27 +/- 0.09 mg/d (P = 0.57). Hair zinc loss was 5.26 +/- 2.49 microgram/d. Post-treatment, zinc excretions via feces, urine and whole body surface positively correlated with dietary zinc intakes (0.68-0.88, P < 0.05). Zinc retention did not change (1.17 +/- 0.78 mg/d vs 1.35 +/- 0.52 mg/d, P = 0.53) with balanced diet treatment. After treatment zinc metabolism in these children was positive and stable. The absorbed zinc, 1.84 +/- 0.47 mg/d, was considered their absolute zinc requirement. Assuming that zinc availability is 20%, the zinc requirement in the daily diet of Chinese preschool children should be 9.23 +/- 2.35 mg/d (6.88-11.58 mg/d).

[X-ray fluorescence analysis of Kaolin concentrate]

An X-ray fluorescence technique was developed for the analysis of Al2O3, SiO2 and impurities in Kaolin concentrate. Two standard series, one for dual series of Al2O3-SiO2 and the other for all of the impurities, were prepared, respectively, from spectral pure agents based on the estimates of analyte content ranges and matrix effects in Kaolin concentrate. Powderd sample after determination of loss of ignition was pressed into disc by means of a little powderd sample preparation method modyfied in this paper. All analyte contents were calculated directly from the calibration curves without any matrix correction. In contrast to fusion technique the method has no the effects of flux impurities and dilute ration on the determination of minor and micro components in Kaolin concentrate. Errors of the results are < 1% for major component Al2O3, SiO2 and total, and < 5% for most and < 10% for few of the impurities.

Characterization of human immunodeficiency virus type-1 (HIV-1) particles that express protease-reverse transcriptase fusion proteins

We have selectively mutagenized specific residues at the junction between the protease (PR) and reverse transcriptase (RT) genes of human immunodeficiency virus type 1 (HIV-1) to study the effects of PR-RT fusion proteins in the context of a full-length, infectious proviral construct. Mutant viruses derived from COS-7 cells transfected with this construct were analyzed in regard to each of viral replication, maturation, and infectivity. Immunoblot analysis revealed that the mutation prevented cleavage between the PR and RT proteins and that both existed as a PR-RT fusion protein in each of cellular and viral lysates. Interestingly, intracellular PR that existed within the PR-RT fusion protein remained functionally active, whereby HIV-1 precursor proteins were processed efficiently. Furthermore, the RT component of the fusion protein also retained its enzymatic activity as shown in RT assays. Electron microscopy revealed that the mutant viruses containing the PR-RT fusion protein possessed wild-type morphology. These viruses also displayed wild-type sensitivities to inhibitors of each of the HIV-1 PR and RT activities. However, viruses containing the PR-RT fusion protein were 20 times less infectious than wild-type viruses. This defect was further pronounced when mutated Gag-Pol proteins were overexpressed as a consequence of an additional mutation that interfered with frameshifting. Thus, unlike cleavage site mutations at the N terminus of PR, a cleavage site mutation between PR and RT did not affect the enzymatic activities of either PR or RT and viruses containing PR-RT fusion proteins were viable.

Roles of the human immunodeficiency virus type 1 nucleocapsid protein in annealing and initiation versus elongation in reverse transcription of viral negative-strand strong-stop DNA

To study the initiation of human immunodeficiency virus type 1 reverse transcription, we have used the viral nucleocapsid protein (NC7) to anneal tRNA3Lys primer onto viral genomic RNA and have then eliminated NC7 from this primer-template complex by digestion with proteinase K and phenol-chloroform extraction of residual protein. Our data show that saturating concentrations of NC7 resulted in the formation of an active tRNA-template complex that yielded enhanced production of full-length negative-strand strong-stop DNA [(-)ssDNA] and that this complex remained active even after the elimination of NC7. While both of the two Zn finger motifs found within NC7 were essential for efficient elongation, NC protein that contained a point mutation in the first Zn finger or that was devoid of both Zn fingers yielded primer-template complexes that could still be initiated in 1-base-extension assays. In contrast, the use of heat annealing to produce primer-template complexes resulted in proportions of full-length (-)ssDNA lower than those seen with NC protein, and the addition of NC protein to such preformed primer-template complexes was able to reverse this defect only to a marginal extent.

Dominance of the E89G substitution in HIV-1 reverse transcriptase in regard to increased polymerase processivity and patterns of pausing

The substitution of a glycine for glutamic acid at position 89 in human immunodeficiency virus-1 (HIV-1) reverse transcriptase (RT) (E89G) confers resistance to several nucleoside and non-nucleoside inhibitors of RT. As residue 89 contacts the template strand, it has been suggested that this mutation may modulate the conformation of the RT.template/primer complex. In addition, certain mutations in RT that confer resistance to nucleoside analogs, such as M184V, are located near the polymerase active site. To characterize further these substitutions, we performed processivity assays alongside an analysis of pausing profiles with wild-type (wt) RT and recombinant RTs containing substitutions at E89G, M184V, or both. We now show that E89G RT has higher processivity than wt enzyme as well as a different pattern of pausing sites. Similar findings were obtained with the doubly mutated RT, although enzyme containing only the M184V mutation had lower processivity than wt. Consistent with these observations, and from a mechanistic standpoint, both E89G-containing as well as doubly mutated RT had decreased dissociation constants from a complex consisting of RT and template-primer, in comparison with either wt RT or M184V-containing RT. No significant differences were observed among the various enzymes in regard to Km values for the heteropolymeric RNA template used in these studies. Viruses containing the E89G mutation synthesized longer strand DNA products than either wt viruses or viruses containing only the M184V mutation in endogenous RT assays. Thus, the E89G substitution is a dominant determinant in regard to each of the koff values from an RT.template/primer complex, RT processivity, and specific patterns of pausing during DNA polymerization.

Mechanistic studies of early pausing events during initiation of HIV-1 reverse transcription

We have investigated the role of sequences that surround the primer binding site (PBS) in the reverse transcriptase-mediated initiation of (-) strand DNA synthesis in human immunodeficiency virus type 1. In comparisons of reverse transcription initiated from either the cognate primer tRNALys.3 or a DNA primer D-Lys.3, bound to PBS sequences, we observed that a +3 pausing site occurred in both circumstances. However, the initiation reaction with tRNALys.3 was also characterized by a pausing event after incorporation of the first nucleotide. Alteration of sequences at the 5'-end instead of the 3'-end of the PBS resulted in elimination of the +3 pausing site, suggesting that this site was template sequence-dependent. In contrast, the pausing event at the +1 nucleotide position was still present in experiments that employed either of these mutated RNA templates. The mutations at the 5'-end of the PBS also caused a severely diminished rate of initiation and the strong arrest of reactions at the +1 stage when tRNALys.3 was used as primer. Therefore, we propose that the +1 pausing event is an initiation-specific event in regard to reactions primed by tRNALys.3 and that sequences at the 5'-end of the PBS may facilitate the release of reverse transcription from initiation to elongation.