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Biomedical subjects

Y Y Zhu

Publications and source records attributed to Y Y Zhu.

At least 19 recordsLinked to original sources
PubMed2004

Conical second harmonic generation in a two-dimensional chi(2) photonic crystal: a hexagonally poled LiTaO3 crystal.

A new type of conical second-harmonic generation was discovered in a 2D chi((2)) photonic crystal-a hexagonally poled LiTaO3 crystal. It reveals the presence of another type of nonlinear interaction-a scattering involved optical parametric generation in a nonlinear medium. Such a nonlinear interaction can be significantly enlarged in a modulated chi((2)) structure by a quasi-phase-matching process. The conical beam records the spatial distribution of the scattering signal and discloses the structure information and symmetry of the 2D chi((2)) photonic crystal.

Journal Article↗
PubMed2003

Highly efficient direct third-harmonic generation based on control of the electro-optic effect in quasi-periodic optical superlattices.

We present a method for controlling the efficiency of direct third-harmonic generation in quasi-periodic optical superlattices by means of the electro-optic effect. The calculated results manifest that this method is extremely efficient for achieving high efficiency of direct third-harmonic generation in predesigned quasi-phase-matched coupled parametric processes and is feasible at any given fundamental intensity. In addition, we demonstrate that the electro-optic control approach is significantly better than the temperature-control method.

Journal Article↗
PubMed2001

Reverse transcriptase template switching: a SMART approach for full-length cDNA library construction.

Here, we describe a fast, simple method for constructing full-length cDNA libraries using SMART technology. This novel procedure uses the template-switching activity of Moloney murine leukemia virus (MMLV) reverse transcriptase to synthesize and anchor first-strand cDNA in one step. Following reverse transcription, three cycles of PCR are performed using a modified oligo(dT) primer and an anchor primer to enrich the cDNA population for full-length sequences. Starting with 1 microgram human skeletal muscle poly(A)+ RNA, a cDNA library was constructed that contained 3 x 10(6) independent clones with an average insert size of 2 kb. Sequence analysis of 172 randomly selected clones showed that 77% of cDNA clones corresponding to known genes contained intact open reading frames. The average length of complete open reading frames was 2.4 kb. Furthermore, 86% of the full-length clones retained longer 5' UTR sequences than the longest 5' end deposited in the GenBank database. cDNA libraries generated using this method will be useful for accelerating the collection of mRNA 5' end sequence information, which is currently very limited in GenBank.

Cloning, Molecular↗
PubMed1998

Is there any advantage to the acquisition of 24-hour thallium images, in the presence of persistent perfusion defects at 4 h after reinjection?

We determined the incidence of delayed 24-h reversibility post thallium-201 reinjection and imaging at 4 h, as well as the prognostic and significance of such delayed reversibility. We studied 46 consecutive patients with persistent thallium-201 perfusion or incompletely reversible single-photon emission tomography (SPET) perfusion defects acquired within 10 min after reinjection performed 4 h after stress. In 38 of 46 patients (82%) 24-h images showed no further reversibility beyond the post-reinjection 4-h study (group A). Eight of 46 patients (17%) demonstrated reversibility on 24-h imaging (group B). Of these eight, three patients showed no improvement compared with the post-stress images, with a mean perfusion score of the abnormal segments of 1. 25+/-0.50 on the 4-h images, and of 3.00 on the 24-h images, where normal is 4. Four patients presented with nine mixed regions. Four of these regions showed an improvement in the mean perfusion score of 2.50+/-0.58 on 4- and 24-h images. Two of them, with moderate/severe defects, demonstrated complete reversibility at 4-h post-reinjection imaging. In addition, five other regions presented no improvement at 4-h imaging, but showed an improvement in the mean perfusion score from 0.80+/-0.84 at 4-h to 3.30+/-0.89 at 24-h imaging. Two of these regions in one patient showed a severe perfusion score of 0 at 4 h, and complete reversibility at 24 hours, with a mean score improvement of 4. Another patient had three severe perfusion defects; two of them redistributed partially at 4 h and completely at 24 h. The remaining segment with a perfusion score of 0 at 4 h, presented complete reversibility with a score of 4 at 24 h. Two (4%) patients revealed significant reversibility at 24 h in a region that was severely underperfused after post-reinjection imaging at 4 h. Among group B patients, 75% (6/8) had recent acute ischemic syndrome, compared with only 13% (5/38) in group A (P = 0. 001). Among 11 patients with unstable angina, six (55%) had evidence of delayed 24-h reversibility, compared with 2 of 35 (6%) patients without clinically acute ischemia (P = 0.001). On follow-up, there were seven (17%) cardiac deaths among the 38 group A patients but three (38%) among the eight group B patients (P = 0.3). These findings suggest that although the presence of delayed 24-h 201Tl, post-reinjection reversibility is infrequent, it has potential clinical importance. Thus, delayed 24-h imaging should be considered in the context of unstable angina or other acute coronary syndromes.

Aged↗
PubMed1996

Stimulation of new bone formation by direct transfer of osteogenic plasmid genes.

Degradable matrices containing expression plasmid DNA [gene-activated matrices (GAMs)] were implanted into segmental gaps created in the adult rat femur. Implantation of GAMs containing beta-galactosidase or luciferase plasmids led to DNA uptake and functional enzyme expression by repair cells (granulation tissue) growing into the gap. Implantation of a GAM containing either a bone morphogenetic protein-4 plasmid or a plasmid coding for a fragment of parathyroid hormone (amino acids 1-34) resulted in a biological response of new bone filling the gap. Finally, implantation of a two-plasmid GAM encoding bone morphogenetic protein-4 and the parathyroid hormone fragment, which act synergistically in vitro, caused new bone to form faster than with either factor alone. These studies demonstrate for the first time that repair cells (fibroblasts) in bone can be genetically manipulated in vivo. While serving as a useful tool to study the biology of repair fibroblasts and the wound healing response, the GAM technology may also have wide therapeutic utility.

Animals↗
PubMed1995

Cloning of a Corynebacterium diphtheriae iron-repressible gene that shares sequence homology with the AhpC subunit of alkyl hydroperoxide reductase of Salmonella typhimurium.

To understand how Corynebacterium diphtheriae responds to iron limitation, we compared the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) protein profiles of both wild-type cells and iron uptake mutants grown in either high- or low-iron medium. The removal of iron by ethylene diamine di-(o-hydroxy-phenyl acetic acid) from the growth medium of wild-type cells resulted in induction of at least 14 polypeptides. DirA, a major iron-repressible polypeptide, was purified from wild-type cells by preparative SDS-PAGE, and the dirA structural gene was isolated from a genomic library of nontoxigenic C. diphtheriae. The nucleotide sequence of dirA was determined, and the deduced amino acid sequence of DirA revealed strong homologies with the AhpC subunit of Salmonella typhimurium alkyl hydroperoxide reductase and polypeptides of other microorganisms associated with oxidation reduction activity. Like AhpC, cloned DirA reduced the susceptibility of an Escherichia coli ahp mutant to cumene hydroperoxide, suggesting that DirA has alkyl hydroperoxide reductase activity.

Amino Acid Sequence↗
PubMed1993

Myocardial perfusion scintigraphy in left bundle branch block: a perspective on the issue from image analysis in a clinical context.

Among selected study populations, myocardial perfusion scintigraphy (MPS) in patients with left bundle branch block (LBBB) has been reported to show a low specificity for the diagnosis of coronary disease. However, the stress electrocardiogram (ECG) is nondiagnostic in this setting. To place this method in its appropriate clinical context, we evaluated MPS in all 69 consecutive patients with LBBB studied with scintigraphy for clinical reasons during a 4-year period. Among 32 patients who underwent coronary angiography for clinical indications, per patient sensitivity, 96%; per vessel sensitivity, 84%, 50%, and 100% for left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA) involvement, respectively; and per vessel specificity, 95% and 68% for LCX and RCA disease, respectively, were not significantly different from those previously published for the method in patients without LBBB. Although per patient specificity, 38%, and specificity, 39%, for LAD disease were low, the predictive value of a positive test remained relatively high (83%) owing to the small number of patients selected for angiography, in part based on scintigraphic findings, with normal coronary anatomy. In addition to a possible specific pathophysiologic cause related to LBBB, apparent perfusion abnormalities in the LAD distribution may relate to generic conditions that can make scintigraphic interpretation ambiguous, often in the anterior distribution, regardless of the clinical setting. Additionally, the apparent lack of scintigraphic specificity in the LAD distribution could relate in part to a selection bias toward catheterization of patients with induced scintigraphic abnormalities, especially in the LAD distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Studies on the diterpenoids on Teucrium quadrifarium Buch-Ham].

Six neo-clerodane diterpenoids were isolated from the acetone extract of Teucrium quadrifarium Buch-Ham (I, II, IV, V, VI and VII). Five of them (I, II, IV, V and VII) were identified as known compounds, teucvidin, 12-epi-teucvidin, teuflin, 19-acetyl-teuspinin and teucvidin, respectively. Compound VI was found to be a new neo-clerodane diterpene, named teuquadrin B. Its structure has been determined from the physical and spectral data.

Antineoplastic Agents, Phytogenic↗
PubMed1993

A quantitative assessment of patient motion and its effect on myocardial perfusion SPECT images.

Patient motion during image acquisition is a frequent cause of SPECT perfusion image artifacts. We sought to determine the relationship between patient motion and the resultant image artifact. The effect of patient motion on 201Tl SPECT scintigrams was assessed with computer simulation to create 66 new image sets with artifactual vertical, horizontal and combined patient motion introduced over a broad range in six normal studies. Visual analysis of regional radioactivity in these simulated images, as well as quantitative analysis of the resultant polar coordinate display was performed. The presence and extent of "motion" artifacts varied with the number and location of the projection images affected, as well as the extent of their displacement. Although the extent of the defect varied with the frames affected, they were not necessarily more extensive when related to vertical displacement in the center of the orbit. The location of induced defects varied with direction of displacement and the location of frames affected. Vertical and horizontal motion created additive defects. Defect size grew with incremental vertical displacement but subsequently decreased with yet increasing displacement. Both the irregular, "lumpy" distribution of radioactivity, often with opposing "defects", as well as curvilinear extraventricular radioactivity, were visual clues suggesting SPECT defects related to motion artifact. A clinical case review revealed that approximately 25% of studies demonstrate such motion during acquisition but only 5% contribute to visible image deterioration. While detection is important, postacquisition attempts to correct such artifacts are incomplete and optimally, they must be prevented.

Artifacts↗
PubMed1991

Sensitive enzyme immunoassay for human 28 kDa calbindin-D.

A sandwich-type enzyme immunoassay for human 28 kDa vitamin D-dependent calcium binding protein (calbindin-D) was established with a sensitivity of 1 pg/tube. Antisera were generated in rabbits injected with highly purified human kidney calbindin-D, and specific antibodies to calbindin-D were purified by the use of a column of calbindin-D-coupled Sepharose. The purified antibodies showed a single band at the position corresponding to calbindin-D on an immunoblotting test with a crude extract of human kidney. The assay system consisted of polystyrene balls with immobilized F(ab')2 antibodies and the same antibodies labeled with beta-D-galactosidase from Escherichia coli. The assay was specific to 28 kDa calbindin-D, showing no cross-reactivity with other calcium binding proteins such as S-100a0 (alpha alpha), S-100b (beta beta), parvalbumin and calmodulin. The assay was also reproducible (coefficients of variation between assays were less than 10%). With the present method, immunoreactive calbindin-D could be detected in various human tissues, with major concentrations in kidney and brain. The values for immunoreactive calbindin-D in various body fluids of healthy subjects varied from undetectable in serum and semen to 3.8 +/- 2.0 (SD) micrograms/g creatinine in urine and 2.9 +/- 0.8 (SD) micrograms/l in cerebrospinal fluid. Immunohistochemically, the calbindin-D in human kidney was localized in epithelial cells of distal tubules.

Adult↗
PubMed1991

Dipyridamole perfusion scintigraphy: the experience with its application in one hundred seventy patients with known or suspected unstable angina.

We evaluated the safety, accuracy, and potential clinical utility of intravenous dipyridamole perfusion scintigraphy with thallium-201 in 170 patients, 78 with suspected and 92 with known unstable angina. All had coronary angiography. Noncardiac side effects (26%), induced chest discomfort (44%), and ST segment changes (12%) were similar in the two groups. No significant arrhythmias occurred. Two patients had prolonged chest pain, both with extensive reversible image abnormalities and associated creatinine kinase-MB release. Both had elective bypass surgery. Twenty-eight patients had normal coronary arteries, and 35 had single-vessel disease. Scintigraphic per patient sensitivity and specificity were 91% and 79% with a per vessel sensitivity of 74% and a per vessel specificity of 78% without between-group differences. During a brief follow-up period, 62 patients with image abnormalities had coronary revascularization, and there were seven deaths without intergroup differences. In a similar patient group that did not have angiography, scintigraphic defects were less frequent and less extensive, revascularization was not performed, and subsequent deaths occurred less often. Dipyridamole perfusion scintigraphy is an accurate alternative to exercise testing in the evaluation of patients with unstable angina pectoris. Although not without risk, the method appears relatively safe and should be considered as a guide to diagnosis, and probably to prognosis and management.

Adult↗
PubMed1991

An immunochemical and immunohistochemical study of aldolase isozymes in renal cell carcinoma.

To assess changes in aldolase isozyme patterns (A, B, and C) in renal cell carcinoma (RCC) tissues and to evaluate whether serum aldolase A might be a useful marker for RCC, quantitative analysis by enzyme immunoassay and immunohistochemical localization were performed. Concentrations of aldolase A in RCC (7300 +/- 6300 ng./mg. protein n = 26) were significantly higher than those of normal cortex (720 +/- 410 ng./mg. protein, n = 14, p less than 0.01); concentrations of aldolase C in RCC (48.0 +/- 8.0 ng./mg. protein) were also significantly higher than those of normal cortex (8.7 +/- 4.7 ng./mg. protein, p less than 0.01). On the other hand, concentrations of aldolase B in normal cortex were 18,100 +/- 10,100 ng./mg. protein (n = 14), whereas the values in RCC were only 130 +/- 270 ng./mg. protein, a significant lowering (p less than 0.01). Immunohistochemically, aldolases A and C were found localized in all RCC tissues (n = 10); aldolase B was faintly stained in only a few tumor cells of two cases (20%). Levels of serum aldolase A were elevated (greater than 300 ng./ml.) in 30 (75%) of 40 patients with RCC as compared to three (6.3%) of 48 individuals with urogenital benign diseases and in seven (21%) of 34 cases with non-RCC urogenital malignancies. Since it is generally accepted that RCC are derived from renal proximal tubules, these findings indicate that aldolase B, the predominant isozyme in the normal case, changes into aldolases A and C during carcinogenesis and that serum aldolase A could be a new useful biomarker for RCC.

Carcinoma, Renal Cell↗
PubMed1991

Phorbol esters selectively downregulate contractile protein gene expression in terminally differentiated myotubes through transcriptional repression and message destabilization.

Chronic exposure of differentiated avian skeletal muscle cells in culture to the phorbol ester, 12-O-tetradecanoyl phorbol-13-acetate (PMA), results in the selective disassembly of sarcomeric structures and loss of muscle-specific contractile proteins, leaving cytoskeletal structures and their associated proteins intact. We demonstrate here that these morphological and biochemical changes are accompanied by dramatic and selective decreases in the level of the mRNAs that encode the contractile proteins. We measured the effects of PMA on the transcriptional activity and mRNA stability of four contractile protein genes (alpha-cardiac and alpha-skeletal actin, cardiac troponin C [cTnC], and myosin light chain lf [MLClf]) and two nonmuscle genes (beta-cytoplasmic actin and the glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase [GAPDH]). The transcriptional activity of the alpha-cardiac actin and cTnC genes dramatically decreased by 8 h after the addition of PMA, while other muscle and nonmuscle genes examined showed no change. Pulse-chase experiments of in vivo labeled RNA showed significant reductions in mRNA half-lifes for all the contractile protein mRNAs examined, while the half-lifes of beta-actin and GAPDH mRNA were unchanged. All of the above effects occurred under conditions in which cellular protein kinase C (PKC) levels had been reduced by greater than 90%. The fact that many of the contractile protein genes remained transcriptionally active despite the fact that the cells were unable to accumulate their mRNAs to any significant extent indicated that the treated cells were still committed to skeletal muscle differentiation. The selective changes in the stability of the contractile protein mRNAs suggest that the control of mRNA stability may be part of the normal regulatory program of skeletal muscle differentiation and that this control may be linked to the integrity of the contractile apparatus and mediated by second messenger pathways involving PKC activation.

Animals↗
PubMed1991

[S100a0 protein and creatine kinase isozymes (CK-B & CK-M) in serum and urine might be useful markers for non specific tissue damages by extracorporeal shockwave lithotripsy (ESWL)].

In order to demonstrate that the extracorporeal shockwave lithotripsy (ESWL) for urolithiasis causes a renal damage, we immunoassayed S100a0 protein and creatine kinase isozymes (CK-B & CK-M) in the serum and urine from patients with renal stone (N = 21) and those with ureteral stone (N = 18) before and after ESWL. S100a0 protein and CK-B, which are localized in the proximal renal tubules at relatively high concentrations, were enhanced more or less both in the urine and serum samples after the treatment in both groups of patients. Since CK-M, which is mainly localized in muscle tissue, also increased in both groups of patients, S100a0 protein and CK-B may be derived not only from kidney, but also from muscle tissues.

Adult↗
PubMed1988

The clinical and pathophysiologic implications of pain, ST abnormalities, and scintigraphic changes induced during dipyridamole infusion: their relationships to the peripheral hemodynamic response.

In order to determine their significance during dipyridamole perfusion scintigraphy, symptomatic, ECG, and scintigraphic findings were related to each other, to the hemodynamic response, and to angiographic findings in 73 consecutive patients having coronary angiography within 3 months of scintigraphy. The group having induced "cardiac" pain differed from the group without induced pain only in their higher incidence of induced ischemic ST changes, the "marked" hemodynamic response, and their lower incidence of an "absent" hemodynamic response (all p less than 0.01). Induced ST depression was found only in patients with coronary disease. In this population, dipyridamole-induced pain was a moderately specific marker and induced ST abnormalities a more highly specific marker for coronary disease. However, both were insensitive for coronary disease diagnosis. If induced pain or ST abnormalities in the presence of significant coronary disease were accepted as indicators of ischemia, then scintigraphic abnormalities appeared to be produced by dipyridamole in roughly equal incidence by ischemic and nonischemic mechanisms. Induced ischemia related frequently to an exaggerated hypotensive response with no change in double product, suggesting its cause to be an induced increase in myocardial oxygen demand. Dipyridamole-induced image defects were noted even in the absence of a peripheral hemodynamic response. This indicates that the peripheral response does not always correlate with its central coronary effect and an absent peripheral hemodynamic response does not necessarily invalidate scintigraphic results.

Angina Pectoris↗
PubMed1988

Cellular localization of muscle and nonmuscle actin mRNAs in chicken primary myogenic cultures: the induction of alpha-skeletal actin mRNA is regulated independently of alpha-cardiac actin gene expression.

Specific DNA fragments complementary to the 3' untranslated regions of the beta-, alpha-cardiac, and alpha-skeletal actin mRNAs were used as in situ hybridization probes to examine differential expression and distribution of these mRNAs in primary myogenic cultures. We demonstrated that prefusion bipolar-shaped cells derived from day 3 dissociated embryonic somites were equivalent to myoblasts derived from embryonic day 11-12 pectoral tissue with respect to the expression of the alpha-cardiac actin gene. Fibroblasts present in primary muscle cultures were not labeled by the alpha-cardiac actin gene probe. Since virtually all of the bipolar cells express alpha-cardiac actin mRNA before fusion, we suggest that the bipolar phenotype may distinguish a committed myogenic cell type. In contrast, alpha-skeletal actin mRNA accumulates only in multinucleated myotubes and appears to be regulated independently from the alpha-cardiac actin gene. Accumulation of alpha-skeletal but not alpha-cardiac actin mRNA can be blocked by growth in Ca2+-deficient medium which arrests myoblast fusion. Thus, the sequential appearance of alpha-cardiac and then alpha-skeletal actin mRNA may result from factors that arise during terminal differentiation. Finally, the beta-actin mRNA was located in both fibroblasts and myoblasts but diminished in content during myoblast fusion and was absent from differentiated myotubes. It appears that in primary myogenic cultures, an asynchronous stage-dependent induction of two different alpha-striated actin mRNA species occurs concomitant with the deinduction of the nonmuscle beta-actin gene.

Actins↗
PubMed1988

Gallium lung scintigraphy in amiodarone pulmonary toxicity.

We sought to assess the role of gallium-67 lung scintigrams in the evaluation of amiodarone pulmonary toxicity. Images and laboratory studies were evaluated in 54 patients who had chest radiographs and scintigraphic studies during amiodarone treatment of more than one month's duration among 561 patients receiving the medication for refractory arrhythmias. There were 22 patients with pulmonary symptoms and clinical evidence of amiodarone pulmonary toxicity (group 1); 19 patients had other causes for pulmonary symptoms (group 2); and 21 patients were without symptoms or other clinical evidence of pulmonary toxicity (group 3). There was no difference among groups in treatment duration or total amiodarone dose. Symptomatic presentation could not differentiate between group 1 and group 2 patients. However, radiographic findings of isolated pulmonary congestion or a normal radiograph in the presence of symptoms made amiodarone toxicity unlikely, while the appearance of new, dense radiographic infiltrates--often in a nodular distribution--were more frequent among group 1 patients (p less than 0.01). During symptomatic periods, 18 of 22 group 1 patients had abnormal gallium lung uptake, while four revealed more subtle serial changes but there was only one abnormal scintigram among symptomatic group 2 patients. Nonspecific radiographic abnormalities in patients with pulmonary symptoms on amiodarone therapy were rarely attributed to toxicity in the presence of a normal scintigram. One group 3 patient developed scintigraphic abnormalities early during amiodarone treatment, suggesting toxicity in the presence of a normal chest x-ray examination. Comparison of radiographic and scintigraphic studies performed during symptoms with those performed prior to symptom development best indicated the diagnosis, while comparison with later images assessed the efficacy of treatment. Diffusion capacity testing and transbronchial biopsy were sensitive but not specific for the diagnosis of amiodarone toxicity. Gallium image abnormalities parallel the development of amiodarone pulmonary toxicity and aid this diagnosis, especially when the chest radiograph is abnormal and ambiguous. Serial increments in scintigraphic abnormality appear especially helpful for diagnosis in the population at risk.

Adult↗