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Biomedical subjects

M Zhao

Publications and source records attributed to M Zhao.

At least 217 records · Page 12Linked to original sources
PubMed1997

Isolation and transplantation of multipotential populations of epidermal growth factor-responsive, neural progenitor cells from the canine brain.

Glial cell transplantation into myelin-deficient rodent models has resulted in myelination of axons and restoration of conduction velocity. The shaking (sh) pup canine myelin mutant is a useful model in which to test the ability to repair human myelin diseases, but as in humans, the canine donor supply for allografting is limited. A solution may be provided by self-renewing epidermal growth factor (EGF)-responsive multipotential neural progenitor cell populations ("neurospheres"). Nonadherent spherical clusters, similar in appearance to murine neurospheres, have been obtained from the brain of perinatal wildtype (wt) canine brain and expanded in vitro in the presence of EGF for at least 6 months. Most of the cells in these clusters express a nestin-related protein. Within 1-2 weeks after removal of EGF, cells from the clusters generate neurons, astrocytes, and both oligodendroglial progenitors and oligodendrocytes. Transplantation of lacZ-expressing wt neurospheres into the myelin-deficient (md) rat showed that a proportion of the cells differentiated into oligodendrocytes and produced myelin. In addition, cells from the neurosphere populations survived at least 6 weeks after grafting into a 14-day postnatal sh pup recipient and at least 2 weeks after grafting into an adult sh pup recipient. Thus, neurospheres provide a new source of allogeneic donor cells for transplantation studies in this mutant.

Animals↗
PubMed1997

Characterization of the structure and function of the fourth member of p38 group mitogen-activated protein kinases, p38delta.

We have cloned and characterized a new member of the p38 group of mitogen-activated protein kinases here termed p38delta. Sequence comparisons revealed that p38delta is approximately 60% identical to the other three p38 isoforms but only 40-45% to the other mitogen-activated protein kinase family members. It contains the TGY dual phosphorylation site present in all p38 group members and is activated by a group of extracellular stimuli including cytokines and environmental stresses that also activate the other three known p38 isoforms. However, unlike the other p38 isoforms, the kinase activity of p38delta is not blocked by the pyridinyl imidazole, 4-(4-fluorophenyl)-2-2(4-hydroxyphenyl)-5-(4-pyridyl)-imidazole (identicalto SB202190). p38delta can be activated by MKK3 and MKK6, known activators of the other isoforms. Nonetheless, in-gel kinase assays provide evidence for additional activators. The data presented herein show that p38delta has many properties that are similar to those of other p38 group members. Nonetheless important differences exist among the four members of the p38 group of enzymes, and thus each may have highly specific, individual contributions to biologic events involving activation of the p38 pathways.

Amino Acid Sequence↗
PubMed1997

An RNA enhancer in a phage transcriptional antitermination complex functions as a structural switch.

Antitermination protein N regulates the transcriptional program of phage lambda through recognition of RNA enhancer elements. Binding of an arginine-rich peptide to one face of an RNA hairpin organizes the other, which in turn binds to the host antitermination complex. The induced RNA structure mimics a GNRA hairpin, an organizational element of rRNA and ribozymes. The two faces of the RNA, bridged by a sheared GA base pair, exhibit a specific pattern of base stacking and base flipping. This pattern is extended by stacking of an aromatic amino acid side chain with an unpaired adenine at the N-binding surface. Such extended stacking is coupled to induction of a specific internal RNA architecture and is blocked by RNA mutations associated in vivo with loss of transcriptional antitermination activity. Mimicry of a motif of RNA assembly by an RNA-protein complex permits its engagement within the antitermination machinery.

Amino Acid Sequence↗
PubMed1997

Somatosensory- and motor-evoked potentials in a rabbit model of spinal cord ischemia and reperfusion injury.

STUDY DESIGN: Occlusion of the infrarenal abdominal aorta was applied to adult rabbits, which induced spinal cord ischemia, followed by disocclusion and reperfusion. Cortical somatosensory- and motor-evoked potentials were monitored continuously up to 24 hours and correlated to hind limb motor and sensory status. OBJECTIVES: To investigate cortical somatosensory-, and motor-evoked potentials in the rabbit model of spinal cord ischemia and reperfusion injury, especially their changes during reperfusion and their relationship to hind limb motor and sensory function. SUMMARY OF BACKGROUND DATA: Various evoked potentials have been widely studied in neurologic prognosis of spinal cord ischemia. Little information is available from previous studies to correlate cortical somatosensory- and motor-evoked potentials with secondary paraplegia occurring during the reperfusion phase. METHODS: Acute spinal cord ischemia was induced in eight anesthetized rabbits by occlusion of the infrarenal abdominal aorta just beneath left renal artery for 40 minutes. Cortical somatosensory-evoked potentials, elicited by stimulating the posterior tibial nerve and recorded at the skull surface corresponding to sensory projection area, and motor-evoked potentials, elicited by stimulating the skull surface corresponding to the motor projection area and recorded at L4 lamina of the vertebral arch, were monitored immediately before and at different time points during ischemia and reperfusion up to 24 hours after disocclusion. Hind limb motor and sensory functions were evaluated and correlated with cortical somatosensory- and evoked-potentials. RESULTS: Cortical somatosensory-evoked potentials disappeared gradually after the start of occlusion and reappeared during reperfusion. Motor-evoked potentials did not change significantly during occlusion, but deteriorated after disocclusion; they correlated well with hind limb motor and sensory status. CONCLUSIONS: Reperfusion injuries to the spinal cord might occur in the rabbit model after disocclusion. Cortical somatosensory-evoked potentials seemed to be a very sensitive index for spinal cord ischemia, whereas motor-evoked potentials correlated well with the course of reperfusion injuries after disocclusion and reflected long-term follow-up hind limb motor function better than cortical somatosensory-evoked potentials.

Animals↗
PubMed1997

Distinct costimulatory molecules are required for the induction of effector and memory cytotoxic T lymphocytes.

A successful T cell immune response has two major products: effector T cells which directly or indirectly remove the antigens, and memory T cells, which allow a faster and more efficient recall response when challenged by related antigens. An important issue is whether costimulatory molecules on the antigen-presenting cells are involved in determining whether T cells will differentiate into effector or memory cells after antigenic stimulation. To address this issue, we have produced mice with targeted mutations of either the heat-stable antigen (HSA), or both HSA and CD28. We show that CD28/B7 and HSA provide two alternative costimulatory pathways for induction of immunological memory to influenza virus. Furthermore, our results revealed that B7 is essential for the generation of effector T cells from either naive or memory T cells, while HSA is not necessary for the generation of effector T cells. Our results demonstrate that the induction of memory T cells and effector T cells can utilize distinct costimulatory molecules. These results have important implications on lineage relationship between effector and memory T cells.

Animals↗
PubMed1997

Physiological electrical fields modify cell behaviour.

Steady direct current (dc) electric fields exist in many biological systems over many hours. At these times cells are dividing, differentiating, moving to final locations and extending motile processes. Each of these events may be influenced by physiological electric fields in tissue culture and when electric fields are disrupted in vivo, major developmental abnormalities arise. The likelihood of physiological electric fields playing a role in cell behaviours and some potential mechanisms are outlined.

Animals↗
PubMed1997

Color Doppler monitoring of changes of utero-placental-fetal circulation in normal pregnancy and intrauterine growth retardation.

The utero-placental-fetal circulation (UPFC) of 150 subjects during second and third trimester was examined by using color Doppler. Of them 89 were normal woman and 58 were patients with intrauterine growth retardation IUGR). Our results showed that UPFC was increased gradually during normal pregnant period. In IUGR patients it was revealed that TAV and Q of UmA, UmV and UtA decreased at 20th week of gestation, especially after 30th week. PI, RI and S/D ratio of UmA were increased, but TAV, Q of UmA and UmV were markly reduced, so was UtA. PI were increased, but the changes of RI, S/D ratio in UtA were not significant. Hemodynamical findings of UmA, UmV and UtA were abnormal in 92.53% of IUGR patients. Only 81.03% present abnormal S/D ratio of UmA (P < 0.01) and the difference was statistically significant. Maternal serum E3, HPL level in IUGR were significantly lower than that of the normal. 6KP level was reduced, TXB2/6KP ratio was significantly increased. TXB2/6KP ratio was markedly related with TAV, Q of UmA, UmV and UtA. Our results suggested that using color doppler ultrasound for examination of hemodynamical changes of UmA, UmV and UtA could revealed UPFC function directly. It is one of the best methods for monitoring IUGR and might be used for early diagnosis of IUGR. The main pathophysiological changes of IUGR were UPFC obstruction and placental disfunction.

Adult↗
PubMed1997

TUNEL-positive hepatocytes in alcoholic liver disease. A retrospective biopsy study using DNA nick end-labelling.

Alcohol-induced damage to the liver results in a wide array of typical alterations. Whereas the mechanisms involved in the pathogenesis of fatty change, hepatocyte ballooning, Mallory body formation and fibrosis have been studied in detail, little is known about hepatocyte apoptosis in alcoholic liver disease (ALD). In this retrospective study we analysed parenchymal cell death in ALD systematically by the use of in situ DNA nickend labelling (ISEL/TUNEL). We show that increased hepatocyte TdT labelling occurs in ALD. Labelling is observed more frequently in parenchymal areas exhibiting advanced damage (ballooning degeneration with or without Mallory bodies, cholestasis and perisinusoidal fibrosis). In addition, hepatocyte TdT labelling is higher where there is septal fibrosis and nodular remodelling. Conversely, it is not elevated in ballooning hepatocytes themselves, but rather in the apparently normal hepatocytes in their vicinity.

Adult↗
PubMed1997

Differential expressions of cyclin A and the retinoblastoma gene product in histological subtypes of lung cancer cell lines.

Cell-cycle-dependent phosphorylation of the tumor-suppressor protein product of the retinoblastoma gene (RB) is mediated by a family of cyclin-dependent kinases and cyclins. We examined the expressions of RB protein and cyclin A protein in 13 small-cell lung cancer (SCLC) lines and 14 non-small-cell lung cancer (NSCLC) lines by immunoblotting. RB protein was not present or was of a mutant type in 77% of the SCLC lines (10/13) but was present in all the NSCLC lines. Cyclin A was expressed in 38% of the SCLC lines (5/13) and in 86% of the NSCLC lines (12/14). A positive correlation (P = 0.0034) between expression of cyclin A and wild-type RB protein was found by Fisher's exact probability test. Densitometric analysis of the expression of RB protein in RB(+) lung cancer lines showed that the phosphorylated form was predominant in 2/3 of the SCLC and 8/14 of the NSCLC lines. The positive correlation between the expressions of RB protein and cyclin A suggests that RB protein in most RB(+) lung cancer cell lines is a target of cyclin-A-dependent kinase and that the tumor-suppressor function may be inactivated by phosphorylation.

Adenovirus E1A Proteins↗
PubMed1997

AM-loading of fluorescent Ca2+ indicators into intact single fibers of frog muscle.

The AM loading of a number of different fluorescent Ca2+ indicators was compared in intact single fibers of frog muscle. Among the 13 indicators studied, loading rates (the average increase in the fiber concentration of indicator per first 60 min of loading) varied approximately 100-fold, from approximately 3 microM/h to >300 microM/h (16 degrees C). Loading rates were strongly dependent on the molecular weight of the AM compounds, with the rate increasing steeply as molecular weight decreased below approximately 850. Properties of delta F/F (the Ca2(+)-related fluorescence signal observed with fiber stimulation) were also measured in AM-loaded fibers and compared with those previously reported for fibers microinjected with indicator. In general, the time course of delta F/F was very similar with AM-loading and microinjection; however, the amplitude of delta F/F was usually smaller with AM-loading. There was a strong correlation between the rate of indicator loading and the value of the parameter f (the ratio of the amplitude of delta F/F in AM-loaded versus microinjected fibers). For indicators with small loading rates (<10 microM/h, N = 5), f values were generally small (< or =0.4, N = 4); whereas with large loading rates (>100 microM/h, N = 4), f values were large (> or =0.8, N = 4). This suggests that, with any AM indicator, a small concentration may associate nonspecifically with the fiber (either the indicator is incompletely de-esterified or, if completely de-esterified, not located in the myoplasmic compartment). If the loaded concentration is small, the nonspecific indicator will present a significant source of error in the estimation of [Ca2+]i.

Animals↗
PubMed1997

Immune effector cell (IEC)-mediated protection from HSV-1 retinitis occurs in the brain.

Following uniocular anterior chamber inoculation of the KOS strain of HSV-1 into euthymic BALB/c mice, virus spreads from the injected eye to the brain and from the brain to the optic nerve and retina of the uninjected eye resulting in retinitis. Adoptive transfer of HSV-1-specific immune effector cells (IEC) within 24 h of anterior chamber inoculation of virus prevents retinitis. To determine where protection occurs, mice were injected with HSV-1 via the anterior chamber route, and fluorescently-labeled HSV-1-specific-IEC or ovalbumin-specific-lymph node cells were adoptively transferred intravenously. The eyes and brains of these mice were sectioned and examined for virus-infected cells and for fluorescently-labeled adoptively transferred cells. None of the mice in the group receiving an adoptive transfer of virus-specific IEC had evidence of virus infection of the ipsilateral suprachiasmatic nucleus (SCN), whereas the ipsilateral SCN of all of the mice in the control groups were virus-positive by day 5 P.I. Since virus spreads from the ipsilateral SCN to the contralateral optic nerve and retina to cause retinitis in the uninoculated eye, the results of these studies suggest IEC-mediated protection from HSV-1 retinitis occurs proximal to the ipsilateral SCN. Furthermore, since only HSV-1-specific IEC conferred protection and only these cells were observed in the brain, protection and trafficking of cells after adoptive transfer was virus-specific.

Adoptive Transfer↗
PubMed1997

The apoptosis protector, bcl-2 protein, is downregulated in bile duct epithelial cells of human liver allografts.

BACKGROUND/AIMS: Apoptosis of bile duct cells occurs in hepatic allografts and is correlated with acute rejection. bcl-2 protein counteracts apoptosis and prolongs cell survival. We therefore tested the expression of bcl-2 protein in bile ducts of liver grafts in comparison with those of liver cirrhosis. METHODS: 115 biopsies from 17 liver allografts and 47 biopsies of liver cirrhosis were analyzed and compared with 22 normal controls and with biopsies from patients with primary sclerosing cholangitis or primary biliary cirrhosis. bcl-2 protein and PCNA (proliferating cell nuclear antigen) expression was assessed using immunohistochemistry, and apoptosis was analyzed employing in situ DNA end-labeling. RESULTS: A high apoptotic rate was detected in bile duct cells of allograft biopsies. In contrast to controls, bile duct cells of allografts and liver cirrhosis had high proliferative activity (mean PCNA labeling index: 1.0% vs. 40.7% and 18.6%, respectively). In liver grafts, bcl-2 protein positivity of bile duct and ductular cells was found in 3.6% and 4.4% of sections, respectively, and in cirrhosis in 44% and 79%, respectively (allografts vs. cirrhosis p<0.01). In controls, only one biopsy was bcl-2 positive. CONCLUSIONS: Whereas increased proliferative activity of small bile ducts and ductules in cirrhosis is associated with a high degree of bcl-2 expression, bile duct and ductular cells in liver grafts have a very low bcl-2 protein reactivity, even though their proliferative activity is high. These findings suggest that downregulation of bcl-2 expression in allograft bile duct cells might play a role in the increased apoptosis of these cells in acute rejection.

Acute Disease↗
PubMed1997

Human corneal epithelial cells reorient and migrate cathodally in a small applied electric field.

PURPOSE: To test whether human corneal epithelial cells (HCECs) respond to small applied electric fields (EFs) in a similar manner to bovine corneal epithelial cells (BCECs), the orientation and directed migration in small EFs of both primary cultures and of a human corneal epithelial cell line were quantified. METHODS: Primary cultures of human corneal epithelial cells (PHCECs) and transformed human corneal epithelial cells (THCECs) were exposed to EFs (100 mV/mm-250 mV/mm) in different media. Cell migration was traced using an image analyser. RESULTS: PHCECs and THCECs reoriented and migrated towards the cathode (negative pole) when cultured in small direct current (dc) EFs. Both the reorientation and directional migration were voltage- and serum-dependent, as shown previously for bovine cells. PHCECs and THCECs showed significant perpendicular orientation in EFs at 150 mV/mm in medium with serum, while at the same voltage, no significant orientation was found in serum free medium. PHCECs started to show perpendicular reorientation around 30 min after onset of EF at 150 mV/mm. They showed significant directional migration at 150 mV/mm, with directedness of 0.35 +/- 0.07 and a migration rate of 9.1 +/- 0.7 microns/h (n = 90), both significantly higher than that of cells in serum free medium. Addition of EGF-induced significant reorientation and directional migration of THCECs at 100 mV/mm. Additionally, as for BCECs, which remained viable and responsive to electric fields for at least 75 h at 150 mV/mm, THCECs also remained viable and showed responsiveness during long periods of exposure to EFs (at least 20 h). CONCLUSIONS: Cultured human primary CECs and a human corneal epithelial cell line both responded to small EFs with perpendicular reorientation and cathodally-directed migration. Cell responses were qualitatively similar to those reported previously for bovine CECs. The endogenous EFs generated by wounded cornea may play an important role in promoting cell shape changes and directed migration of CECs during the healing process.

Animals↗
PubMed1997

A modified bottle manikin phantom for in vivo neutron activation analysis.

An artificial skeleton was designed and placed inside a bottle manikin absorber phantom to provide a new reference standard for measurements of total body calcium by in vivo neutron activation analysis at Brookhaven National Laboratory. The composition of the epoxy-based calcium and phosphorus mixture used to construct the skeleton, the dimensions and weight of each bone are given for two phantoms representing an adult male and female. Also, the dimensions, composition, and weights of overlays designed to simulate the influence of obesity on in vivo neutron activation analysis are given for each.

Adult↗
PubMed1997

Synthesis and activity of partial retro-inverso analogs of the antimetastatic laminin-derived peptide, YIGSR-NH2.

This paper describes the synthesis and biological evaluation of six partial retro-inverso peptidomimetic analogs of YIGSR-NH2, a synthetic peptide from the beta 1 chain of laminin, which has antimetastatic activity. The intent was to improve the antimetastatic potency of YIGSR-NH2 by limiting the in vivo enzymatic degradation through the incorporation of fraudulent peptide bonds. We have prepared the following retro-inverso peptides, Tyr-Ile-Gly-Ser-gArg-CHO (1), Tyr-gIle-mGly-Ser-Arg-NH2 (2), Tyr-gIle-mGly-Ser-gArg-CHO (3), gTyr-D-rIle-mGly-Ser-Arg-NH2 (4), Tyr-Ile-Gly-gSer-D-rArg-CHO (5) and Tyr-gIle-rGly-D-rSer-D-rArg-CHO (6). In vitro assays for B16F10 melanoma cell adhesion showed no significant activity for these six peptides. Peptides 1-3, 5 and 6 were further tested, in vivo, for their ability to inhibit tumor metastases to the lung in mice injected in the tail vein with B16F10 melanoma cells. All five of the retro-inverso peptides tested showed statistically significant inhibition of metastasis, but the most active peptides were 5 and 6, which showed 57 and 69% inhibition of metastasis, respectively.

Animals↗
PubMed1997

Apoptosis in human hepatocellular carcinoma and in liver cell dysplasia is correlated with p53 protein immunoreactivity.

AIMS: To investigate the prevalence of apoptosis in human hepatocellular carcinomas (HCC) of different types and grades and in liver cell dysplasia, and to test whether the apoptotic rate is correlated with the p53 protein status. METHODS: 37 HCC and 66 six liver samples with liver cell dysplasia were analysed for apoptosis using in situ DNA end labelling (ISEL), and for p53 protein expression by immunohistochemistry. In HCCs, proliferative activity was quantitatively assessed using proliferating cell nuclear antigen labelling. RESULTS: The apoptotic index in HCC as based on ISEL ranged from 0.1 to 13.5 per 1000 cells analysed and was not related to type or grade. No nuclear staining was observed in multinuclear tumour cells. There was a significant correlation between the apoptotic rate and both the proliferative activity and p53 protein reactivity. In liver samples containing p53 protein positive liver cell dysplasia cells, there was a significantly higher apoptotic rate of these cells. CONCLUSIONS: Apoptosis is detectable in HCC, and is not related to type and grade. There is a highly significant positive correlation between the apoptotic rate in HCC and both the proliferative activity and p53 protein expression. A similar phenomenon occurs for putative cancer precursors. The findings support the role of p53 in regulating apoptosis in preneoplastic and neoplastic liver lesions.

Apoptosis↗
PubMed1997

[Effect of EBV-LMP and EGF autocrine on proliferation of nasopharyngeal carcinoma cell line CNE and their relationship in action].

EBV-LMP gene transfection, radioimmuno-binding assay (RIA) and colorimetric cell viability assay (MTT) were used to investigate the effect and relationship of EBV-LMP and EGF autocrine on the growth and proliferation of well differentiated nasopharyngeal carcinoma cell line (CNE1). Autocrine EGF was detected in the supernant of CNE1 cells and CNE1 cells could grow in serum-free medium, implicating that the cell proliferation-promoting effect of EGF autocrine was present in the CNE1 cell line. Nevertheless the positive signals of LMP gene polymerase chain reaction and LMP Mab immunohistochemical staining in pCMV alpha-LMP DNA transfected cells, confirmed the successful transfection of LMP gene. EGF autocrine amount and the proliferation of CNE1 cells in serum-free medium were more obvious in post-transfected cells than those in untransfected cells. The present study represents the first report on promotion of EGF autocrine in EBV-LMP-transfected cells, thus promoting cell proliferation.

Autocrine Communication↗