Gut Metabolite Trimethylamine-N-Oxide in Atherosclerosis: From Mechanism to Therapy

Atherosclerosis is associated with various pathological manifestations, such as ischemic heart disease, ischemic stroke, and peripheral arterial disease, and remains a leading cause of public health concern. Atherosclerosis is an inflammatory disease characterized by endothelial dysfunction; vascular inflammation; and the deposition of lipids, cholesterol, calcium, and cellular debris within the vessel wall intima. In-depth studies of gut flora in recent years have shown that bacterial translocation and the existence of bacterial active products in blood circulation can affect the inflammatory state of the whole blood vessel. The gut flora is considered to be a large “secretory organ,” which produces trimethylamine-N-oxide (TMAO), short-chain fatty acids and secondary bile acids by breaking down the ingested food. Studies have shown that TMAO is an independent risk factor for the occurrence of malignant adverse cardiovascular events, but whether it is harmful or beneficial to patients with cardiovascular diseases with mild or no clinical manifestations remains controversial. We review the relationship between TMAO and its precursor (L-carnitine) and coronary atherosclerosis and summarize the potential molecular mechanism and therapeutic measures of TMAO on coronary atherosclerosis.

[Advice on the rationalized layout of outpatient clinics in a wound repair department]

According to a document issued by the General Office of National Health Commission, "one person, one diagnosis, and one room" is required in the process of outpatient consultation. However, the patient will need to go to another room for dressing change after the doctor checks the wound if sticking to the conventional layout of current wound repair specialist outpatient clinic in hospitals and following the regulation of "separation of diagnosis and treatment". To allow a patient walking back and forth with the exposed wounds to different clinics or going to another clinic for dressing change with the original dressing reapplied to the wound is against the regulation of nosocomial infection control and the principle of sterility. To ensure that the layout of the outpatient clinic in the wound repair outpatient department not only conforms to the principle of "one person, one diagnosis, and one room", but also meets the characteristics of the diagnosis and treatment process of chronic wounds, this paper proposes the layout of "large space and small partition" in the wound repair clinic.

Effects of Spironolactone on Hypoxia-Inducible Factor-1α in the Patients Receiving Coronary Artery Bypass Grafting

ABSTRACT

We explored the protective effect of spironolactone on cardiac function in the patients undergoing coronary artery bypass grafting (CABG) by determining serum hypoxia-inducible factor-1α (HIF-1α) before and after CABG. We used the propensity score matching method retrospectively to select 174 patients undergoing CABG in our hospital from March 2018 to December 2019. Of the 174 patients, 87 patients taking spironolactone for more than 3 months before CABG were used as a test group and other 87 patients who were not taking spironolactone as a control group. In all patients, serum HIF-1α and troponin I levels were determined before as well as 24 hours and 7 days after CABG, serum N-terminal probrain natriuretic peptide (NT-proBNP) level was determined before as well as 12, 24, and 36 hours after CABG, and electrocardiographic monitoring was performed within 36 hours after CABG. The results indicated that there were no significant differences in the HIF-1α level between the test group and the control group before and 7 days after CABG, but the HIF-1α level was significantly lower in the test group than that in the control group 24 hours after CABG (P < 0.01). The 2 groups were not significantly different in the troponin I level at any time point. There was no significant difference in the serum NT-proBNP level between the test group and the control group before CABG, but NT-proBNP (BNP) levels were all significantly lower in the test group than those in the control group at postoperative 12, 24, and 36 hour time points (all P <0.05). The incidence of postoperative atrial fibrillation was also significantly lower in the test group than that in the control group (P = 0.035). Spironolactone protects cardiac function probably by improving myocardial hypoxia and inhibiting myocardial remodeling.

Virtual touch imaging quantification shear-wave elastography for breast lesions: the diagnostic value of qualitative and quantitative features

AIM

To investigate the value of the qualitative and quantitative features of Virtual Touch imaging quantification (VTIQ) shear-wave elastography in the characterisation of breast lesions.

MATERIALS AND METHODS

Conventional ultrasound (US) and VTIQ were performed in 148 solid breast lesions in 148 women. During qualitative analysis, patterns of VTIQ were categorised into two patterns, 1 and 2. During quantitative analysis, the mean SWV (SWVmean) and the maximum SWV (SWVmax) of each lesion were used. The sensitivity, specificity, and the areas under the receiver operating characteristic (ROC) curve (Az value) were calculated for conventional US, VTIQ, and combined conventional US and VTIQ.

RESULTS

Malignant lesions were more likely to show VTIQ pattern 2 than the benign lesions (p<0.001). There was no significant difference in the Az values between SWVmean (0.907) and SWVmax (0.902; p=0.572). There was no significant difference in the Az values between the VTIQ pattern (0.884) and SWVmax (p=0.572). The combined conventional US and VTIQ pattern carried a similar Az value (0.949) as compared with the combined conventional US and SWVmax, which yielded an Az value of 0.952 (p=0.683).

CONCLUSION

The combination of either VTIQ pattern or SWVmax and conventional US may be helpful in the characterisation of benign and malignant breast lesions.

Interobserver variability between experienced radiologists in evaluating the number of abnormal lymph nodes seen on preoperative axillary ultrasound

AIM

To determine the interobserver variability of experienced radiologists in evaluating the number of suspicious lymph nodes (LNs) seen on axillary ultrasound (AUS) examination, and to evaluate the effects of clinicopathological features on the discordance.

MATERIAL AND METHODS

A prospective non-randomised triple-blind study was conducted from July 2016 to December 2017 at Shanghai Ruijin Hospital. Three experienced radiologists performed AUS on 462 patients (469 axillae) with invasive breast cancer independently and assessed the number of abnormal LNs during the real-time AUS examination. Interobserver agreement was determined according to the kappa statistic.

RESULTS

The mean numbers of metastatic LNs on final histology study were 0.35, 0.98, 3.05 and 4.70 for patients with 0, 1, 2 and >2 abnormal nodes on preoperative AUS. When the cut-off (the number of abnormal LNs seen on AUS was >1) at which the maximal sum of sensitivity and specificity for diagnosis of ≥3 tumour-involved LNs was achieved was applied, the Az values ranged from 0.776 to 0.811. When the number of abnormal LNs was grouped into two-category classification (0-1 versus ≥2 abnormal LNs detected by AUS), good interobserver agreement (kappa: 0.601-0.687) was found, and disagreement between the radiologists was more frequently found in patients with T2-stage tumour and in those with one or two tumour-involved nodes.

CONCLUSION

Abnormal LN count according to two-category classification (0-1 versus ≥2 abnormal LNs detected by AUS) was a feasible method with good accuracy and high repeatability to select patients with heavy nodal disease in the post-Z0011 trial era.

Reconstructing the Perceived Faces from Brain Signals without Large Number of Training Samples. Annu Int Conf IEEE Eng Med Biol Soc 2020;2020:1108-1111. [PMID: 33018180 DOI: 10.1109/embc44109.2020.9176684]

Reconstructing the perceived faces from brain signals has become a promising work recently. However, the reconstruction accuracies rely on a large number of brain signals collected for training a stable reconstruction model, which is really time consuming, and greatly limits its application. In our current study, we develop a new framework that can efficiently perform high-quality face reconstruction with only a small number of brain signals as training samples. The framework consists of three mathematical models: principle component analysis (PCA), linear regression (LR) and conditional generative adversarial network (cGAN). We conducted a functional Magnetic Resonance Imaging (fMRI) experiment in which two subjects' brain signals were collected to test the efficiency of our proposed method. Results show that we can achieve state-of-the-art reconstruction performance from brain signals with a very limited number of fMRI training samples.

[Pay attention to the exposure risk of patients with chronic wounds on the way to hospital during coronavirus disease 2019 epidemic prevention and control]

Statistics show that 76.74% (4 688) of 6 109 patients with chronic wounds are over 50 years of age; the proportion of patients with underlying diseases in all age groups above 50 years ranges from 78.25% to 100.00%. Among the underlying diseases of chronic wound patients, the top four diseases are diabetes mellitus, cardiovascular and cerebrovascular diseases, hypertension, and respiratory diseases. The above underlying diseases and ages of patients are the susceptibility factors of coronavirus disease 2019 released by National Health Commission of China. It is an unavoidable fact that the patients with chronic wounds have to go to the hospital for treatment prescribed by the physician. At the same time, we found that quite a few patients preferred going far afield in choosing hospital for treatment due to various reasons. During the prevention and control of coronavirus epidemic, this " go far afield" style of seeking medical treatment may increase the exposure risk during travelling. Accordingly, we convened 36 wound care clinics in different regions in Shanghai to implement the " Five Measures" encouraging the patients with chronic wounds to seek medical treatment nearby. The principle of this operation is that when seeking medical treatment, patients with chronic wounds should try their best to reduce the travel distance as much as possible to minimize the exposure risk during the epidemic period, which will in turn support the campaign of epidemic prevention and control.

Impact of human activities on subaqueous topographic change in Lingding Bay of the Pearl River estuary, China, during 1955-2013

Estuaries have been sites of intensive human activities during the past century. Tracing the evolution of subaqueous topography in estuaries on a decadal timescale enables us to understand the effects of human activities on estuaries. Bathymetric data from 1955 to 2010 show that land reclamation decreased the subaqueous area of Lingding Bay, in the Pearl River estuary, by ~170 km² and decreased its water volume by 615 × 10⁶ m³, representing a net decrease of 11.2 × 10⁶m³ per year and indicating the deposition of approximately 14.5 Mt/yr of sediment in Lingding Bay during that period. Whereas Lingding Bay was mainly governed by natural processes with slight net deposition before 1980, subsequent dredging and large port engineering projects changed the subaqueous topography of the bay by shallowing its shoals and deepening its troughs. Between 2012 and 2013, continuous dredging and a surge of sand excavation resulted in local changes in water depth of ± 5 m/yr, far exceeding the magnitude of natural topographic evolution in Lingding Bay. Reclamation, dredging, and navigation-channel projects removed 8.4 Mt/yr of sediment from Lingding Bay, representing 29% of the sediment input to the bay, and these activities have increased recently.

[Clinical effect of compound internal fixations in treating extreme distal radial fractures]

Objective: To investigate the clinical character and treating strategy of extreme distal radial fractures. Methods: From June 2012 to May 2014, 12 patients who suffered from extreme distal radial fractures were treated in Department of Orthopedics, Tongji Hospital, Tongji University. According to AO/OTA classification, there were 4 cases of type 23B1, 3 cases of 23B2, 3 cases of 23C1 and 2 cases of 23C3.When classified by morphological features, there were 4 of simple styloid process fracture, 3 of simple extreme distal radial fracture without articular surface involved, 3 of styloid process fracture combined with distal radial articular fracture, and 2 of articular surface splintered or collapse fracture. According to the fracture features that radiographic exams showed, different surgical paths and fixation methods were chosen in order to protect soft tissues to the best advantage. To those patients with simple styloid process fracture, screw alone, Kirschner-wire or styloid plate were used for fixation. To the other types of fracture, open reduction and compound internal fixation with low-notch volar plate, dorsal or volar mini-plate, screw or Kirschner-wire was applied to ensure the stability of fixation, and maximally protect soft tissues like tendons, ligaments and neurovascular bundles, counting on the "stuffing-squeezing" effects after reduction or reconstruction of the articular surface. Situation of the wound and soft tissue were mainly checked in the first 2 weeks, and in the 3rd month post-operatively, fracture reduction and internal fixation were evaluated by radiographic methods like X-ray and CT scan. When 12 months post-operatively, not only radiographic follow-up such as fracture reduction, internal fixation and osteoarthritis were taken, but also some other evaluation, such as pain of wrist, rotation range of forearm, grip strength, and function of wrist according to DASH scores. Results: All of the 12 cases were followed up for at least 1 year. The wound healed well in all cases 2 weeks post-operatively, and no soft tissue infections, necrosis or neurovascular complications occurred. All fractures healed and no loss of reduction occurred 3 months post-operatively. Internal fixations were at good condition except in 2 cases, whose Kirschner-wire had been removed 2.5 and 2.8 months after the operation due to loosening and partly backing out on dorsal side. When followed up at 12 months post-operatively, one from these 2 patients suffered from a mild pain of wrist, and grip strength together with the function of the affected wrist dramatic declined when compared to the unaffected side. With the help of radiograph, local collapse on the articular surface was found, which meant to be traumatic arthritis. There were no pain in the rest 11 cases, and flexion-extension range of the wrist, rotation range of forearm and grip strength of the affected side recovered to over 80% of the unaffected side, with a DASH score was from 7 to 15 points(average 11.9 points)below 15 points. Conclusions: Traditional volar plates can not be used for extreme distal radial fractures. It may be an effective way to treat extreme distal radial fractures with compound internal fixation on the basis of morphological feature of fractures and the situation of soft tissue because of vivid of the fixation, reducing damage of soft tissue and early functional training.

Investigation of single nucleotide polymorphisms in phosphodiesterase 4D gene in Mongol and Han patients with ischemic stroke in Inner Mongolia

We investigated single nucleotide polymorphisms (SNP) at 87 sites of the phosphodiesterase 4D (PDE4D) gene in Mongol and Han patients with ischemic stroke in Inner Mongolia. SNPs in 226 patients with ischemic stroke (case group, 110 Mongol patients, 116 Han patients) and 220 patients without neurological disease (control group, 102 Mongol patients, 118 Han patients) were detected by polymerase chain reaction-restriction fragment length polymorphism and gene sequencing. The genotype and allele frequencies of all groups were compared. There were no statistically significant differences in genotypes in the PDE4D gene at 87 sites between the case and control groups (P > 0.05). The C allele frequency in the case group was significantly higher than that in the control group (P < 0.05). The CC genotype and C allele frequencies in the Mongol case subgroup were higher than those in the Mongol control subgroup (P < 0.05). The CC genotype and C allele frequencies in the Han case subgroup were higher than those in the Han control subgroup (P < 0.05). In the case group, there were no significant differences at 87 sites for genotypes and allele frequencies between the Mongol and Han subgroups. In the control group, there were no significant differences at 87 site genotypes and allele frequencies between the Mongol and Han subgroups. The increase in the C allele frequency at 87 SNP sites in PDE4D may increase ischemic stroke risk. We found no differences in the risk between Mongol and Han populations in Inner Mongolia.

Monocyte/macrophage β2-AR as a target of antisympathetic excitation-induced atherosclerotic progression

The aim of this study was to determine whether monocyte/macrophage β2-AR could act as the therapeutic target of antisympathetic excitation-induced atherosclerotic progression. Cultivated human THP-1 cells were divided into different groups and incubated with isoprenaline, metoprolol, propranolol or β2-AR blocker for 24 h, together with oxidized low-density lipoprotein (ox-LDL). Afterwards, each group was analyzed for C-C chemokine receptor type 2 (CCR2) expression, monocyte chemotactic protein 1 (MCP-1) release into medium and cell migration ability. In the isoprenaline group, CCR2 protein level was increased, as well as the secretion of MCP-1, and cell motility was enhanced, in a concentration-dependent manner. Propranolol and ICI 118,551 significantly reversed the stimulatory effect of isoprenaline on THP-1 cells induced by ox-LDL, but only high concentrations of metoprolol interfered significantly with the action of isoprenaline (P < 0.05). Isoprenaline or a β-AR blocker could mediate through β2-AR, affecting MCP-1 secretion, CCR2 protein expression and cell migration capacity of THP-1 cells. Therefore, monocyte-macrophage β2-AR may act as a target of antisympathetic excitation-induced atherosclerotic progression.

Maximal, minimal, and mean pulsed Doppler parameters: which should be utilized in the diagnosis of thyroid nodules?

AIM

To compare the diagnostic efficacy of the maximal, minimal, and mean pulsatility index (PI) and resistance index (RI) and determine which should be utilized in the evaluation of thyroid nodules.

MATERIALS AND METHODS

A total of 224 consecutive patients with thyroid nodules were included in this prospective study. Doppler signals from three different nodular arteries were obtained and six Doppler parameters were used for final analysis: maximal PI (PImax), minimal PI (PImin), mean PI (PImean), maximal RI (RImax), minimal RI (RImin), and mean RI (RImean).

RESULTS

Eighty-five patients had malignant and 139 cases had benign thyroid nodules. All three sets of PI and RI parameters were significantly higher in malignant than in benign thyroid nodules (p = 0.000 for all). The area under the receiver operating characteristic (ROC) curve (Az) of PImax was significantly higher than that of PImin (p = 0.046) and higher than that of PImean (p = 0.161). The Az value of RImax was higher than that of RImean and RImin; however, the differences were not significant (p = 0.403, and p = 0.058, respectively). The Az values of the three sets of PI parameters (PImax, PImin, and PImean) were significantly higher than those of the corresponding sets of RI parameters (p = 0.005, p = 0.003, and p = 0.003, respectively).

CONCLUSION

Maximal pulsed Doppler parameters should be utilized in the evaluation of thyroid nodules. PI parameters were superior to the RI parameters in determining malignant nodules.

Cd-doped ZnO quantum dots-based immunoassay for the quantitative determination of bisphenol A

Bisphenol A (BPA) is a ubiquitous environmental contaminant in food products and aquatic ecosystems. Its endocrine and developmental toxicity presents a serious concern to human health and an effective high-throughput method for its detection is desirable. In this paper, water-soluble quantum dots (QDs) have been conjugated covalently with BPA antibodies and the conjugate has been utilized in a competitive fluorescence-linked immunoassay (FLISA). Cd-doped ZnO QDs were functionalized with poly(amidoamine) (PAMAM) dendrimers, as evidenced by ultraviolet absorption spectrum and fluorescence emission spectra analyses, and this led to their successful transfer into aqueous solution. Biological mass spectrometry demonstrated that the bisphenol A antibodies were successfully coupled to the water-soluble QDs, and the structures of these conjugates kept intact. The FLISA method allowed for BPA determination in a linear working range of 20.8-330.3 ng mL(-1) with the limit of detection (LOD) of 13.1 ng mL(-1). The recoveries of BPA from water samples were from 85.92% to 109.62%. In conclusion, a rapid and sensitive FLISA was developed by utilizing novel QD coupling method and validated for use in aqueous samples.

A study of photoluminescence properties and performance improvement of Cd-doped ZnO quantum dots prepared by the sol-gel method

In the present work, ZnO quantum dots (QDs) have been prepared by the sol-gel method, and the performance of the QDs has been improved. The effect of Cd concentration on the structural and luminescent properties of the QDs, as well as the effect of the mass ratio of trioctylphosphine oxide (TOPO)/octadecylamine (ODA), has been investigated. The ZnO and Cd-doped ZnO QDs have hexagonal wurtzite structures and are 3 to 6 nm in diameter. When the Cd content was increased, the QD particle size was reduced; this effect was confirmed in the corresponding ultraviolet-visible spectra. The fluorescence intensity was simultaneously enhanced significantly. Both the UV and fluorescence spectra were blue-shifted. The luminous intensity was further enhanced when the QDs were modified with TOPO/ODA. Fourier transform infrared and X-ray diffraction techniques proved that the polymer successfully coated the surfaces of the QDs. A TOPO/ODA mass ratio of 1:2 was determined to result in the best optical performance among the different ratios examined. The results showed that the described synthetic method is appropriate for the preparation of doped QDs with high-fluorescence quantum efficiency.

An integrated lab-on-a-disc for automated cell-based allergen screening bioassays

We have utilized various valving scheme to leverage purely rotation-regulated flow control to enable comprehensive cell-based bioassays (CBBs) on centrifuge-based lab-on-a-disc (LOAD). A LOAD has been developed to examine allergic degranulation from live basophils for allergens screening for the first time, which can also be adjusted to suit a wide range of CBBs. In this system, controlled allergic reaction together with mediator separation from basophils using siphon valving and centrifugal sedimentation are realized inside microstructured network. The entire degranulation analysis process including on-demand release of samples, reaction and degranulation, allergic mediator separation and detection is executed in an automatic sequence within a single run. To validate our cell-based approach, detection of degranulation mediated by known secretagagues, ionomycin or chemotatic peptide formyl-methionine-leucine-pheylalanine (fMLP), is first demonstrated. Further experiments using real allergens house dust mite protein (Der p1) and its corresponding human serum IgE also show positive results. The overall efficiency of the assay is 80.6%, which is comparable to other conventional methods. With 4 identical units on a disc running in a parallel format, the device offers the possibility of single-step, multiplexed allergens screening. The device is capable of reporting a result within 30 min. It has many desirable merits including fast and multiplexed analysis, low cost, single-step operation, minimal sample volume, less discomfort and most importantly increased safety as patients are no longer susceptible to possible anaphylactic shock reactions induced by the common skin-prick-test. The flexibility of the flow control within the device makes it suitable to a wide range of CBBs.

Photonic-assisted microwave frequency measurement with higher resolution and tunable range

A photonic-assisted approach to microwave frequency measurement is proposed based on frequency-to-power mapping with the help of the so-called amplitude comparison function. The key component is a dual-output Mach-Zehnder modulator (MZM) working at chirped modulation. The proposed scheme is characterized as having simplicity, higher resolution, and tunable measurement range. Owing to experimental constraint, an equivalent experiment has been carried out using a common single-output MZM at different bias points to prove the concept.

[Study of DNA examination in trace sample by carrier method]

OBJECTIVE

To solve the problems of DNA testing in trace sample.

METHODS

Applying original carrier method to detect known trace blood DNA and to compare it with the results obtained by high effective DNA extracting method of Chelex-100.

RESULTS

The carrier method not only could obtain the right STR genotype in the trace blood sample, but also was twice as sensitive as the Chelex-100 method.

CONCLUSION

The carrier method could improve the DNA detection in trace sample. It is easy to operate and is much more valuable in the forensic case analysis.

[Surgical exploration of the sentinel lymph nodes in the papillary thyroid carcinoma]

OBJECTIVE

To study the technique of sentinel lymph node mapping in the papillary thyroid carcinoma and its evaluation in the search for cervical metastases.

METHOD

Exploration of the sentinel lymph nodes of the papillary thyroid carcinoma by injection of methylene blue around the tumour among 25 patients during surgery. The nodes which stained blue and the other nodes removed by functional neck dissection were examined histologically after staining with hematoxylin-eosin-saffron (HES). We have evaluated the predictive value of the technique in mapping the cervical metastases in the sentinel lymph node.

RESULTS

Among the 25 patients, 22 patients presented sentinel lymph nodes (blue-stained), that is to say a rate of identification of 88%. At histological examination, 19 of the 22 patients had positive sentinel lymph nodes, of which 13 had also positive nodes not coloured with blue. The histological examination of patients without sentinel lymph node was negative.

CONCLUSION

The technique of the sentinel lymph node has a strong positive predictive value in the search for cervical node metastases in the papillary thyroid carcinoma.

Spectral-resolved backreflection measurement of polarization mode dispersion in optical fibers

An improved backreflection technique is proposed to perform the spectral-resolved measurement of polarization mode dispersion (PMD) in optical fibers. This technique is based on the PMD dynamical equation and realized by measuring the polarization state evolutions of the reflected signal in both frequency and time domains. Two experimental setups, employing the far-end Fresnel reflection, are constructed to verify this technique. The agreement between the results of the proposed backreflection technique and the conventional forward technique is observed.

An evaluation of para toluene-sulfonamide metabolism and effect with regard to CYP isoforms, P-glycoprotein, and drug interactions

Aim of this study was to investigate liver metabolism of with regard to para toluene-sulfonamide (PTS), CYP isoforms, P-glycoprotein (P-gp), and drug interactions. Known substrates, inducers and inhibitors of CYP and inhibitor of P-gp were employed and metabolites were determined with HPLC. Male Wistar rats were pretreated with ip phenobarbital (PB), ketoconazole (Ket), or verapamil (Ver) for 3 days and in situ liver perfusion of PTS was conducted in a recirculation system. Rats were also pretreated with ip PTS (33 mg x kg(-1) x d(-1) or PTS 99 mg x kg(-1) x d(-1)) for 4 days before liver perfusions with dextromethorphan (Dex) and phenacetin (Phe) preparations were conducted. Microsome incubation was used to investigate PTS effect on five CYP isoforms and PTS-drug interactions probability with phyllotoxin and 5-fluorouracil (5-FU) in vitro. PTS at 60 min perfusates had areas of 61.4% and 133.6% of the blank control in PB group and Ket group, respectively. The result that PTS metabolism was enhanced by PB and inhibited by Ket treatments suggested liver CYP was attributed to PTS metabolism. PTS 99 mg x kg(-1) x d(-1) pretreatment slowed down the metabolism of Dex and Phe while in vitro incubations did not show a PTS (0-160 micromol/L) effect on CYP activities. PTS metabolite formation when co-incubated with phyllotoxin was 50.7% of the negative control. The potent inhibitory ability of phyllotoxin to PTS requires further clinical investigation regarding in concomitant administration.

Generalized Mueller matrix method for polarization mode dispersion measurement in a system with polarization-dependent loss or gain

A generalized Mueller matrix method (GMMM) is proposed to measure the polarization mode dispersion (PMD) in an optical fiber system with polarization-dependent loss or gain (PDL/G). This algorithm is based on the polar decomposition of a 4X4 matrix which corresponds to a Lorentz transformation. Compared to the generalized Poincaré sphere method, the GMMM can measure PMD accurately with a relatively larger frequency step, and the obtained PMD data has very low noise level.

Quasi-monochromatic fiber depolarizer and its application to polarization-dependent loss measurement

We theoretically derive the relationship between the degrees of polarization (DOPs) of input and output for an optical component with polarization-dependent loss (PDL) and birefringence. Based on the theoretical result, we propose a novel depolarizer for quasi-monochromatic light that can depolarize a fully polarized light with a 50 MHz linewidth to less than 0.2% in the DOP The depolarized light is then used to measure PDL in a single-mode optical fiber link. To the best of our knowledge, our new PDL measurement method is significantly faster than all known methods. Experimental results show excellent agreement with other methods.

The Saccharomyces Pif1p DNA helicase and the highly related Rrm3p have opposite effects on replication fork progression in ribosomal DNA

Replication of Saccharomyces ribosomal DNA (rDNA) proceeds bidirectionally from origins in a subset of the approximately 150 tandem repeats, but the leftward-moving fork stops when it encounters the replication fork barrier (RFB). The Pif1p helicase and the highly related Rrm3p were rDNA associated in vivo. Both proteins affected rDNA replication but had opposing effects on fork progression. Pif1p helped maintain the RFB. Rrm3p appears to be the replicative helicase for rDNA as it acted catalytically to promote fork progression throughout the rDNA. Loss of Rrm3p increased rDNA breakage and accumulation of rDNA circles, whereas breakage and circles were less common in pif1 cells. These data support a model in which replication fork pausing causes breakage and recombination in the rDNA.

The small subunit is required for functional interaction of DNA polymerase delta with the proliferating cell nuclear antigen

DNA polymerase delta is usually isolated as a heterodimer composed of a 125 kDa catalytic subunit and a 50 kDa small subunit of unknown function. The enzyme is distributive by itself and requires an accessory protein, the proliferating cell nuclear antigen (PCNA), for highly processive DNA synthesis. We have recently demonstrated that the catalytic subunit of human DNA polymerase delta (p125) expressed in baculovirus-infected insect cells, in contrast to the native heterodimeric calf thymus DNA polymerase delta, is not responsive to stimulation by PCNA. To determine whether the lack of response to PCNA of the recombinant catalytic subunit is due to the absence of the small subunit or to differences in post-translational modification in insect cells versus mammalian cells, we have co-expressed the two subunits of human DNA polymerase delta in insect cells. We have demonstrated that co-expression of the catalytic and small subunits of human DNA polymerase delta results in formation of a stable, fully functional heterodimer, that the recombinant heterodimer, similar to native heterodimer, is markedly stimulated (40- to 50-fold) by PCNA and that the increase in activity seen in the presence of PCNA is the result of an increase in processivity. These data establish that the 50 kDa subunit is essential for functional interaction of DNA polymerase delta with PCNA and for highly processive DNA synthesis.

Purification and characterization of the catalytic subunit of human DNA polymerase delta expressed in baculovirus-infected insect cells

The catalytic subunit of human DNA polymerase delta has been overexpressed in insect cells by a recombinant baculovirus. The recombinant protein has a Mr = approximately 125,000 and is recognized by polyclonal antisera against N-terminal and C-terminal peptides of the catalytic subunit of human DNA polymerase delta. The recombinant protein was purified to near homogeneity (approximately 1200-fold) from insect cells by chromatography on DEAE-cellulose, phosphocellulose, heparin-agarose, and single-stranded DNA-cellulose. The purified protein had both DNA polymerase and 3'-5' exonuclease activities. The properties of the recombinant catalytic subunit were compared with those of the native heterodimeric DNA polymerase delta isolated from fetal calf thymus, and the enzymes were found to differ in several respects. Although the native heterodimer is equally active with either Mn2+ or Mg2+ as divalent cation activator, the recombinant catalytic subunit is approximately 5-fold more active in Mn2+ than in Mg2+. The most striking difference between the two proteins is the response to the proliferating cell nuclear antigen (PCNA). The activity and processivity of native DNA polymerase delta are markedly stimulated by PCNA whereas it has no effect on the recombinant catalytic subunit. These results suggest that the small subunit of DNA polymerase delta is essential for functional interaction with PCNA.

Exposure of rat muscle phosphoglycerate kinase to a nonenzymatic MFO system generates the old form of the enzyme

The occurrence of age-related modifications in enzymes is a well-established symptom of aging that has been explained by several possible mechanisms including the oxidation of amino acid residues by mixed-function oxidation (MFO) systems. In the present study native old phosphoglycerate kinase was compared with young enzyme which had been modified by oxidation with ascorbate: FeCl3 followed by reduction. The comparison was done by monitoring the rates of heat denaturation of these enzyme forms, as well as their inactivation by trypsin. A remarkable similarity between the old and treated young enzyme was revealed, while native young phosphoglycerate kinase was inactivated with a different rate. Extensive unfolding followed by refolding converted both old and MFO-treated young phosphoglycerate kinase to species which greatly resemble the native young enzyme in their heat inactivation kinetics. These results demonstrate that the exposure of phosphoglycerate kinase to the mixed-function oxidation system introduces some modifications which are not reversed by subsequent enzyme reduction and which resemble those found in the native old enzyme. This mechanism, therefore, may account for the aging of phosphoglycerate kinase in vivo.

Endurance-training induced changes in skeletal muscle phosphoglycerate kinase of old Wistar rats

Sufficiently intense, long-term, endurance training has been shown in several studies to induce a variety of adaptations in skeletal muscle, including a substantial restoration of the activities of several muscle enzymes which are known to be modified during biological aging. This activity-restoration may reflect either an increase in the amounts of enzyme proteins or an enhancement of the specific activities of these molecules. The present study examined the effect of long-term endurance training on the status of phosphoglycerate kinase in skeletal muscle of old rats, as compared with the enzyme isolated either from non-trained old or young animals. The kinetics of heat inactivation, which differ markedly between young and old forms of phosphoglycerate kinase, were used as a sensitive probe for the status of the enzyme. The results reveal a remarkable similarity between the heat inactivation patterns of phosphoglycerate kinase from the muscle of old, exercise-trained rats and enzyme purified from young animals, while enzyme samples isolated from sedentary old animals are significantly more heat-stable. Adaptation to endurance-training is thus evident at the molecular level, and maintains phosphoglycerate kinase in its young form. The aging of this enzyme has been previously shown to involve only conformational changes, which develop following a reversible partial oxidation of reactive cysteine residues. Whether the adaptation of the enzyme to endurance-training results from enhancement in its turnover rate (i.e., dwell time in the cell becoming too short for modifications to develop) or is due to increased protection against oxidation (being the first step in the enzyme's aging) remains to be studied.

[Effect of expression of exogenous PDGF-A chain on growth and transformation of CHO cells]

CHO cells were transfected with plasmid pSV2-PDGF-A (containing human PDGF-A cDNA) by calcium phosphate method. Twenty transfected cell lines were obtained after G418 selection. The selected 2 cell lines At1 and Aot7), with prominent changes in morphology and growth behaviour, showed transcription of PDGF-A chain mRNA much higher than CHO cells, strong fluorescent PDGF-specific reaction, appearing that PDGF-like proteins were synthesized in cytoplasm of these cells. At1 and Aot7 cells not only had increased growth rate, but also formed large colonies in soft agar and grew into fibrosarcomas in nude mice. These results suggested that the expression of exogenous PDGF-A gene might cause the uncontrolled growth and malignant transformation of CHO cells.

Earthworm muscle preparation for studying several potent compounds--the possible existence of a "Soman receptor."

A new model of earthworm (Eisenia foedida) dorsal muscle preparation was studied. It is a specific preparation for testing GABA and its agonist muscimol. The response of muscle could be recorded through mechanical functional changes instead of potential variations. Thus, it is a direct and simple means for measuring GABA activity. ChE-deactivated preparation was suggested for this purpose. By mild membrane modifications of earthworm muscle preparation, it was possible to remove or inactivate GABA, glutamic acid or Soman combining protein. In conjunction with superfusion of Ach-receptor antagonist (alpha-Bungaratoxin) or GABA antagonist (picrotoxin, isopropylbicyclophosphate), we could differentiate Soman receptor from Ach and GABA receptor. The possible existence of a Soman receptor in the earthworm muscle was therefore proposed.