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Biomedical subjects

L Gao

Publications and source records attributed to L Gao.

At least 199 records · Page 11Linked to original sources
PubMed1995

Differential expression of TnI and TnT isoforms in rabbit heart during the perinatal period and during cardiovascular stress.

We have investigated developmental transitions of TnI and TnT isoforms in fetal, neonatal, and adult rabbit hearts by western blot analysis. Our results provide the first evidence for the existence of two developmentally regulated isoforms of TnI in rabbit heart. These isoforms comigrate with adult rabbit cardiac TnI (cTnI) and slow skeletal TnI (ssTnI). At 23 days of gestation, ssTnI was the predominant TnI isoform. At 29 days of gestation, there was a significant increase in the relative amount of cTnI, that continued with maturation. The TnI isoform transition was significantly faster in right than left ventricles at gestation 30 and 32 days. Four TnT isoforms were detected in fetal rabbit ventricles. The relative amount of TnT isoforms did not change from 23 to 29 days of gestation. However, the relative amount of the adult TnT isoform increased significantly around the time of birth with the increase being significantly more prominent in left than in right ventricles. Maternal injection of phenylephrine (PHE), an alpha-1 adrenergic agonist, increased fetal cardiac force and arterial blood pressure, facilitated TnT, but not TnI, isoform transition in fetal heart. Our results indicate that the developmental transition of rabbit cardiac TnI and TnT isoforms is not coordinated and might be regulated by different mechanisms. Our results also provide evidence that the TnT isoform population is influenced by adrenergic stimulation and stress on the cardiovascular system during development.

Aging↗
PubMed1995

Sonoelasticity imaging: theory and experimental verification.

Sonoelasticity is a rapidly evolving medical imaging technique for visualizing hard tumors in tissues. In this novel diagnostic technique, a low-frequency vibration is externally applied to excite internal vibrations within the tissue under inspection. A small stiff inhomogeneity in a surrounding tissue appears as a disturbance in the normal vibration eigenmode pattern. By employing a properly designed Doppler detection algorithm, a real-time vibration image can be made. A theory for vibrations, or shear wave propagation in inhomogeneous tissue has been developed. A tumor is modeled as an elastic inhomogeneity inside a lossy homogeneous elastic medium. A vibration source is applied at a boundary. The solutions for the shear wave equation have been found both for the cases with tumor (inhomogeneous case) and without tumor (homogeneous case). The solutions take into account varying parameters such as tumor size, tumor stiffness, shape of vibration source, lossy factor of the material, and vibration frequency. The problem of the lowest detectable change in stiffness is addressed using the theory, answering one of the most critical questions in this diagnostic technique. Some experiments were conducted to check the validity of the theory, and the results showed a good correspondence to the theoretical predictions. These studies provide basic understanding of the phenomena observed in the growing field of clinical Sonoelasticity imaging for tumor detection.

Acoustics↗
PubMed1995

Sonoelasticity imaging of prostate cancer: in vitro results.

PURPOSE: To compare sonoelasticity imaging versus ultrasound (US) in detection of prostate cancer. MATERIALS AND METHODS: Sonoelasticity imaging and US were performed on 10 prostatectomy specimens in which cancer was detected at previous biopsy. Six patients had no palpable lesions at digital rectal examination. Specimens were imaged axially at the apex, middle, and base of the gland to correlate with location of pathologic sections. All images were interpreted blindly and prospectively, and results were compared with pathologic findings. RESULTS: Sensitivity and specificity with sonoelasticity imaging were 85% and 84%, respectively, and 30% and 100% with standard US when compared with pathologic findings. Sixty-four percent of pathologically confirmed tumors detected at sonoelasticity imaging were isoechoic on conventional US images. CONCLUSION: In this limited study, sonoelasticity imaging was more sensitive for tumor detection and more accurate for assessment of tumor location than was conventional US.

Adenocarcinoma↗
PubMed1995

M-creatine kinase gene expression in mechanically overloaded skeletal muscle of transgenic mice.

The molecular pathways and regulatory molecules that underlie changes in gene transcription during mechanical overload of skeletal muscle remain obscure. To better understand this process, we have examined mouse muscle creatine kinase (MCK) gene expression in mechanically overloaded plantaris (OP) muscle of transgenic and nontransgenic mice. Northern blot analysis revealed that endogenous MCK-specific mRNA transcripts were decreased 150% in the OP muscles after 6 wk. To identify the MCK gene regions involved in the response to mechanical overload, three different mouse MCKCAT transgenes were studied by measuring chloramphenicol acetyltransferase (CAT assays) activity in OP and sham-operated (control plantaris) muscles. Mouse lines carrying (+enh206)117MCKCAT and -1256MCKCAT transgenes exhibited 30 and 40% lower CAT levels, whereas two mouse lines carrying -3300MCKCAT transgenes exhibited average decreases of 430%. Nearly identical results, including measurements of exogenous CAT mRNA, were obtained 2 days postoverload. Six weeks or 2 days of mechanical overload led to an average decrease in MM-CK isoprotein of 140%. These data provide evidence that mechanical overload induces changes in MCK gene expression that appear to be regulated by at least two portions of the MCK gene: the 206 base pair 5' enhancer and the -3,300 to -1,257 region.

Animals↗
PubMed1995

Viral, host and environmental risk factors for hepatocellular carcinoma: a prospective study in Haimen City, China.

To identify specific environmental, viral, and genetic risk factors for hepatocellular carcinoma (HCC) and the interaction of such factors, we are conducting a prospective study in a high-incidence area of China. Questionnaires were completed and biosamples collected by 60,984 men ages 30-64 years, at study entry. Within 2.5 years, 183 deaths from HCC had occurred. Each HCC case was matched with 5 controls and compared for items on the questionnaire. In addition to chronic hepatitis B virus (HBV) infection, the significant risk factors were: occupation (peasant), corn consumption (in the 1970s), family history of HCC, and history of an episode of acute hepatitis as an adult. HBV, consumption of aflatoxins, a genetic factor, and possibly a second hepatitis virus infection contribute to the risk of HCC.

Adult↗
PubMed1995

Presensitization by skin grafting from major histocompatibility complex class I or major histocompatibility complex class II deficient mice identifies class I antigens as inducers of allosensitization.

Livers but not hearts are accepted spontaneously without immunosuppression when transplanted from B10 (KbAbEbDb) to C3H (KkAkEkDk) mice. Both organs however, undergo accelerated rejection in C3H recipients presensitized with B10 skin grafts. In this study, we have investigated further the role of functional cell-surface major histocompatibility complex (MHC class I or class II molecules in allosensitization. Skin from transgenic MHC class I (b2mmlUncbcr; AbEb) or class II (C2DTM, KbDb) gene 'knockout' mice was grafted onto naive recipients 2-3 weeks prior to whole organ transplantation. When C3H hosts were presensitized with skin from C2DTM (class II deficient) mice, they promptly rejected (within 4 days) subsequently transplanted B10 liver or heart allografts. In contrast, presensitization with skin from b2m (beta 2-m mutant; class I deficient) mice did not significantly affect the survival of either organ graft. Maximal sensitization was established by day 14 after skin grafting and persisted for at least 12 weeks. Splenocytes obtained from C3H mice sensitized with skin from B10, B6 (KbAbEbDb), or C2DTM but not from b2m mice exhibited an H-2b-specific cytolytic response when tested in cell-mediated lymphocytotoxicity assays. Sera from C3H mice sensitized with B10 or b2m skin contained high titres of cytotoxic activity specifically against H-2b class I. Taken together, these observations suggest that in the strain combination studied, MHC class I rather than class II molecules play an important role in allosensitization. The results indicate the potential importance of avoiding transplantation of organs into recipients of secondary grafts from donors that share human leucocyte antigen (HLA) class I antigens with the first donor.

Animals↗
PubMed1995

[Autonomic nervous activity at episodes of myocardial ischemia in patients with coronary artery disease by heart rate power spectral analysis].

Heart rate power spectral analysis in 44 patients with coronary artery disease was obtained from 24-hour dynamic electrocardiogram. 195 episodes of transient myocardial ischemia that was defined as horizontal or down sloping depression of the ST segment of > or = 0.1 mV and lasted for > or = 2 minutes were studied. The area of low frequency components (LF, 0.02-0.10 Hz) representing predominontly sympathetic tone with some contribution from the parasympathetic tone and that of high frequency components (HF, 0.15-0.40 Hz) representing mainly parasympathetic tone and the value of LF/HF on 4 minute heart rate power spectral graph at the deepest depression of ST segment were compared with that before the episode of myocardial ischemia. The area of HF of fast rate myocardial ischemia occurring in night reduces significantly (P < 0.001), the value of LF/HF increases markedly (P < 0.05) and the area of LF increases slightly. The results suggest that there is a change of autonomic nervous activity during the episode of fast rate myocardial ischemia in night, parasympathetic nervous tone decreases markedly, there may be secondary increase of sympathetic nervous activity.

Adult↗
PubMed1995

Spinach chloroplast RNase P: a putative protein enzyme.

Ribonuclease P (RNase P) is the enzyme responsible for endonucleolytically separating the 5'-leader sequence from precursor tRNA molecules. In bacteria, and in the nuclei and mitochondria of all eukaryotes studied so far, RNase P contains an RNA subunit which is necessary for activity in vitro and in vivo. In contrast, we showed earlier that partially-purified RNase P from spinach chloroplasts had physical properties inconsistent with the presence of any RNA. We now report that the properties of the chloroplast enzyme, after 500 to 1500-fold purification, are consistent with enzymatic activity residing in a approximately 70 kDa polypeptide. Gel filtration chromatography on Sephacryl S-200 and S-300 provides a mass for chloroplast RNase P of approximately 70 +/- 5 kDa. A single polypeptide of approximately 70-80 kDa can be crosslinked to iodoUMP-substituted pre-tRNA. The labeling intensity of this polypeptide corresponds closely to the peak of RNase P activity on Sephacryl S-200 chromatography. Unlike the bacterial ribozyme-type RNase P, chloroplast RNase P is not a metalloenzyme. We showed previously that phosphodiester bond cleavage by the E. coli RNA enzyme absolutely requires Mg2+ or Mn2+ coordinated to the pro-Rp oxygen of the scissile phosphodiester phosphate. In contrast, we now find that chloroplast RNase P has no such requirement, and can accurately and efficiently cleave pre-tRNA containing an Rp-thio-substitution at the scissile bond. These data are entirely consistent with the hypothesis that RNase P in plant chloroplasts is not a ribozyme, but a conventional protein enzyme.

Biological Evolution↗
PubMed1995

[The application of the pattern visual-evoked potential in the diagnosis and treatment of amblyopia].

PURPOSE: To research into the value of the application in the diagnosis and treatment of amblyopia, and to discuss the mechanism of amblyopia. METHODS: The subjects were divided into three groups: 108 amblyopia eyes; 180 normal eyes and 26 amblyopia eyes during the treatment with Madopar. PVEP was observed with black-white checks pattern-reversal stimulation at several spatial frequencies (30', 60', 90'). RESULTS: P1 latency of the amblyopia eyes prolongs at the high frequency (30' angle of view), in which the occurrence rate of abnormal PVEP is 68.5%. Through detecting PVEP during the treatment of amblyopia with Madopar, we found P1 latency shortened and amplitude increased (P < 0.05). CONCLUSION: It is better to use P1 latency to observe the visual function of patients with amslyopia with stimulation at 30' angle of view. PVEP is an important objective index in diagnosis and evaluating the curative effect of amblyopia.

Adolescent↗
PubMed1994

Isolation and characterization of HL-60 cells resistant to nitroprusside-induced differentiation.

Sodium nitroprusside and sodium nitrite, which generate nitric oxide and increase the intracellular cGMP concentration, and 8-bromo-cGMP, a membrane-permeable cGMP analog, induce myelomonocytic differentiation of HL-60 cells (Boss, G. R. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 7174-7178). We have selected HL-60 cells resistant to nitroprusside-induced differentiation as assessed by acquisition of the OKM-1 antigen, reduction of nitro blue tetrazolium, and morphologic maturation. The variant cells were also resistant to differentiation induced by sodium nitrite and two cGMP analogs but still differentiated in response to other inducing agents such as dimethyl sulfoxide and cAMP analogs and showed the same changes in c-myc and c-fos expression in response to the latter drugs as occurred in parental cells. We studied the early steps of the NO/cGMP signal transduction pathway in the variant cells and found that basal and nitroprusside-stimulated guanylate cyclase activity was similar in parental and variant cell extracts and that nitroprusside increased the intracellular cGMP concentration to the same extent in parental and variant cells. As part of these studies we found that HL-60 cells expressed only alpha 2 and beta 2 guanylate cyclase mRNA; the abundance of these two mRNA species was similar in parental and variant cells. Neither nitroprusside nor 8-bromo-cGMP changed the intracellular calcium concentration in parental or variant cells. The data suggest that the defect in the variant cells is after guanylate cyclase activation in the NO/cGMP transduction pathway and that the cGMP and cAMP transduction pathways operate independently in inducing differentiation of HL-60 cells.

Cell Differentiation↗
PubMed1994

Split tolerance induced by orthotopic liver transplantation in mice.

Spontaneous orthotopic liver allograft acceptance associated with microchimerism in mice induces tolerance to subsequent skin or heart transplants from the donor but not third-party animals. Despite in vivo hyporesponsiveness, in vitro MLC and CTL assays showed continuing antidonor reactivity. Cells isolated from recipients' spleens and grafted livers, when tested in MLC and CTL assays, were antidonor reactive out to 3 months to the same degree as splenocytes obtained from either naive or presensitized (with skin or heart) mice. Nevertheless, passive transfer of splenocytes or liver lymphocytes from liver tolerant mice, but not naive or sensitized donor strain mice, were able to prolong skin graft survival significantly in naive irradiated recipients. By using a strain combination in which the donor but not the recipient expressed the stimulatory endogenous super-Ag (Mlsf), it was possible to determine whether super-Ag-reactive T cells bearing V beta 5 and V beta 11 were deleted or anergic. Phenotypic analysis of cells isolated from recipients' spleens and grafted livers (up to 90 days after transplant), when compared with naive animals, showed no significant difference in V beta 5 and V beta 11 TCR expression. Additionally, when these isolated spleen cells were tested for antibody-mediated stimulation, both anti-V beta 5 and V beta 11 TCR mAb led to marked proliferation of cells obtained from naive and liver-transplanted recipients, but as expected, proliferation was very low in cells from naive donors. These results suggest that liver transplantation induces donor-specific tolerance in vivo, which may not be reflected in in vitro proliferative and cytotoxicity assays (split tolerance). Furthermore, this tolerance does not seem to be induced by clonal deletion or anergy of minor-lymphocyte-stimulating-antigen-reactive T cells in the recipients.

Animals↗
PubMed1994

Strategies for studying mouse and human immune responses to human papillomavirus type 16.

Cytotoxic T lymphocytes (CTL) are an important protective mechanism in viral infection and can be effective against tumours. We have investigated the tumour-associated E6 and E7 genes of human papillomavirus type 16 as CTL targets. In H-2b mice we have defined epitopes in E6 and E7 which can readily generate CTL in vivo and we have shown that HLA-A2.1 transgenic mice can generate an HLA-A2.1-restricted response. We have been unable to reveal a primed CTL response in humans. These paradoxical findings imply that human papillomavirus may fail to stimulate a systemic CTL response and/or employ strategies for evading or down-regulating such a response.

Amino Acid Sequence↗
PubMed1994

Experimental study of the effects of "fractional" gating on flow measurements.

Velocity encoded phase imaging is subject to errors from phase and amplitude variations of the k-space data caused by beat-to-beat variations of the flow. Fractional cardiac gating is defined as asynchronous gating with each phase encode step occupying a fixed fraction of the RR interval. The gating fraction is the inverse of the number of phase encode steps taken per RR interval. Studies in normal subjects show that deviations and standard errors of ascending and descending aorta flow measurements are significantly greater with decreased gating fraction. Significant errors occur when gating does not separate systolic and diastolic data. The studies establish a graded trade-off between flow measurement accuracy and precision with imaging time, and show that standard nongated phase contrast measurements of strongly pulsatile flow are unreliable.

Angiography↗
PubMed1994

Immune response to human papillomavirus type 16 E6 gene in a live vaccinia vector.

Immunization of mice with a recombinant vaccinia virus expressing the human papillomavirus type 16 (HPV-16) E6 gene elicits specific antibody, proliferative and cytotoxic T lymphocyte responses. T and B cell epitopes were mapped by using synthetic peptides. This study provides the background to future investigation aimed at developing prophylactic and therapeutic vaccines against HPV-16 infection and cervical cancer.

Amino Acid Sequence↗