Biomedical subjects

L Zhou

Publications and source records attributed to L Zhou.

At least 181 records · Page 10Linked to original sources

PubMed2000

Regulation of intron function: efficient splicing in vivo of a bacterial group II intron requires a functional promoter within the intron.

Conjugative transfer of the Lactococcus lactis plasmid pRS01 requires splicing of a group II intron, Ll.ltrB, for accurate translation of the mRNA for the exon gene ltrB. The protein product of ltrB is a conjugative relaxase, essential for pRS01 transfer. Using a molecular technique for the identification of transcription initiation sites in bacteria, a functional promoter within Ll.ltrB was identified upstream from the gene for the intron-encoded protein (IEP) LtrA. LtrA is required for efficient splicing of Ll.ltrB in vivo. Mutation of the ltrA promoter dramatically reduced the steady-state level of ltrA mRNA, LtrA, intron splicing and conjugation in L. lactis. These effects could be relieved by expression in trans of the ltrA gene cloned under the control of an inducible promoter. These results suggest that the ltrA mRNAs are translated inefficiently. We hypothesize that this bacterial intron, in contrast to previously studied group II introns in eukaryotes, requires a promoter within the intron to regulate ltrA expression and to produce an adequate level of the protein in the cell for efficient splicing.

Amino Acid Sequence↗

PubMed2000

Clinical significance of urokinase-type plasminogen activator activity in hepatocellular carcinoma.

BACKGROUND AND METHODS: The plasminogen activation system plays a crucial role in the process of cancer invasion and metastasis. To evaluate the most effective factor in the invasion, metastasis and prognosis of hepatocellular carcinoma (HCC), we examined urokinase-type plasminogen activator (uPA), plasminogen activator inhibitor (PAI)-1, PAI-2 and uPA activity by enzyme-linked immunosorbent assays (ELISA) in HCC tissues obtained from 46 patients. The results were compared with the patients' clinicopathological features and prognoses. RESULTS: Of the clinicopathological features, only histological portal involvement or intrahepatic metastasis, or both (INV), was significantly correlated to the disease-free survival rates (DFS; P < 0.05). The levels of uPA, PAI-1 and PAI-2 antigens were significantly associated with INV and histological grade. The DFS was not different, however, between cases with uPA, PAI-1 and PAI-2 values above and below the median. The high levels of uPA activity were closely related to INV (P < 0.001), and the activity gradually raised histological grades (P < 0.0001). The DFS was significantly different between patients with uPA activity below and above the median (0.70 ng/mL; P = 0.0092); it was also significantly different between such patients without INV (P < 0.05). CONCLUSIONS: Urokinase-type plasminogen activator activity may be the most sensitive factor affecting HCC invasion in the plasminogen activation system and a strong predictor for the recurrence of HCC. We suggest that cases with uPA activity of more than 0.70 ng/mL should be carefully followed up for possible HCC recurrence.

Adolescent↗

PubMed2000

Expression of urokinase-type plasminogen activator, urokinase-type plasminogen activator receptor, and plasminogen activator inhibitor-1 and -2 in hepatocellular carcinoma.

It has become more and more clear in recent decades that the plasminogen activation system, which includes urokinase-type plasminogen activator (uPA), urokinase-type plasminogen activator receptor (uPAR), plasminogen activator inhibitor (PAI)-1 and PAI-2, plays a very important role in the aggressiveness of cancer. Using immunohistochemistry and enzyme-linked immunosorbent assay (ELISA), the expression of these four components of the uPA system was analyzed in 19 cases of hepatocellular carcinoma (HCC) and 18 cases of the adjacent non-cancer tissues which all had chronic active hepatitis with liver fibrosis or liver cirrhosis. Four cases of normal liver tissues, as controls for immunohistochemical stains, were obtained from the hepatectomized liver of patients with metastatic cancer in the liver. The positive rates of uPA, uPAR, PAI-1 and PAI-2 for immunohistochemical stains in cancer tissues were 78.9, 68.4, 57.9 and 31.6%, respectively. Positive signals were mainly distributed in the cytoplasm of the cancer and in stromal cells. Moreover, the strong stains were chiefly located in the invasive front of the cancer cells. No specific stain was detected in four cases of normal liver tissues. In ELISA, there were significant differences between cancer and non-cancer tissues in concentration of uPA, uPAR and PAI-1 (P < 0.0003, 0.0024 and 0.01, respectively), but there was no significant difference in that of PAI-2 (P = 0.37). These results suggest that uPA, uPAR and PAI-1 are related to invasion of HCC.

Carcinoma, Hepatocellular↗

PubMed2000

Early inflammatory response after elective abdominal aortic aneurysm repair: a comparison between endovascular procedure and conventional surgery.

OBJECTIVE: To determine the nature of and to compare the inflammatory responses induced by (1) endovascular and (2) conventional abdominal aortic aneurysm (AAA) repair. MATERIAL AND METHODS: Twelve consecutive patients undergoing elective infrarenal AAA repair were prospectively studied. Seven patients were selected for endovascular procedures (the EAAA group); five patients underwent open surgery (the OAAA group). Three control patients undergoing carotid thromboendarterectomy were also included. Serial peripheral venous blood samples were collected preoperatively, immediately after declamping or placement of the endograft, and at hours 1, 3, 6, 12, 24, 48, and 72. Acute phase response expression of peripheral T lymphocyte and monocyte activation markers and adhesion molecules (flow cytometry), soluble levels of cell adhesion molecules (enzyme-linked immunosorbent assay), cytokine (tumor necrosis factor alpha, interleukin-6, and interleukin-8) release (enzyme-linked immunosorbent assay), and liberation of complement products (nephelometry) were measured. RESULTS: Regarding acute phase response, the EAAA and OAAA groups showed significant increases in C-reactive protein (P <.001 and P =.001), body temperature (P =.035 and P =.048), and leukocyte count (P <.001 and P <.001). Similar time course patterns were observed with respect to body temperature (P =.372). Statistically significant different patterns were demonstrated for C-reactive protein (P =.032) and leukocyte count (P =.002). Regarding leukocyte activation, a significant upregulation of peripheral T lymphocyte CD38 expression was observed in the OAAA group only (P =.001). Analysis of markers such as CD69, CD40L, CD25, and CD54 revealed no perioperative fluctuations in any group. Regarding circulating cell adhesion molecules, the EAAA and OAAA groups displayed significant increases in soluble intercellular adhesion molecule-1 (P =.003 and P =.001); there was no intergroup difference (P =.193). All groups demonstrated high soluble von Willebrand factor levels (P =.018, P =. 007, and P =.027), there being no differences in the patterns (P =. 772). Otherwise, soluble vascular cell adhesion molecule-1, soluble E-selectin, and soluble P-selectin did not appear to vary in any group. Regarding cytokine release, although a tendency toward high tumor necrosis factor alpha and interleukin-8 levels was noticed in the EAAA group, global time course effects failed to reach statistical significance (P =.543 and P =.080). In contrast, interleukin-6 showed elevations in all groups (P =.058, P <.001, and P =.004). Time course patterns did not differ between the EAAA and OAAA groups (P =.840). Regarding complement activation, the C3d/C3 ratio disclosed significant postoperative elevations in the EAAA and OAAA groups (P =.013 and P =.009). This complement product release was reduced in the EAAA group (P <.001). CONCLUSIONS: The current study indicated that both endovascular and coventional AAA repair induced significant inflammatory responses. Our findings showed that there were no large differences between the procedures with respect to circulating cell adhesion molecule and cytokine release. Moreover, the endoluminal approach produced a limited response in terms of acute phase reaction, T lymphocyte activation, and complement product liberation. This might support the concept that endovascular AAA repair represents an attractive alternative to open surgery. Given the relatively small sample size, further larger studies are required for confirmation of our observations.

Aged↗

PubMed2000

Normal expression levels of cathepsins, protease inhibitors, and Sp1 in conjunctival tissues from patients with keratoconus.

PURPOSE: In keratoconus corneas, it has been shown that levels of degradative enzymes and transcription factor Sp1 are elevated and those of inhibitors are reduced, especially in the epithelial layer. This study is to determine whether the biochemical abnormalities identified in corneas also exist in conjunctival tissues. METHODS: Conjunctival tissues were collected from normal subjects and from patients with keratoconus, senile cataract, and other corneal diseases. Immunohistochemical staining for cathepsins B and G, alpha 1-proteinase inhibitor, alpha 2-macro-globulin and Sp1 was performed. RESULTS: The epithelium of all conjunctival specimens showed immunoreactivity toward the antibodies. The staining for cathepsins B and G, and the inhibitors was mostly cytoplasmic, while that for Sp1 was nuclear. The staining intensity in keratoconus specimens was all within normal range. CONCLUSIONS: These results suggest that the abnormalities in cathepsins B and G, protease inhibitors and Sp1 identified in keratoconus corneas are not manifested in the conjunctiva. Keratoconus appears to be a disease localized to the cornea.

Adolescent↗

PubMed2000

Functional identification of phosphodiesterase activity in human trabecular meshwork cells.

The phosphodiesterases (PDE) activity in human trabecular meshwork cells (HTM-3) was investigated in this study in order to better understand the signal transduction pathways in the conventional outflow tract of the eye. Agonists (isoproterenol or nitroprusside) were used to stimulate adenylyl cyclase and guanylyl cyclase, respectively, in the absence and presence of nonselective IBMX or PDE5 specific inhibitors E4021 (1). The subcellular distribution of cAMP and cGMP PDEs was determined directly by PDE enzyme assays using HTM-3 cells. Levels of cyclic nucleotides were measured in the same cells by radioimmunoassay (RIA). Isoproterenol alone elevated cAMP levels, and this response was enhanced by IBMX. Nitroprusside alone caused no increase in basal cGMP levels but, in the presence of E4021, nitroprusside produced significant, dose-related elevation of cGMP levels. Subcellular distribution experiments indicated that the greatest activity for PDEs resided in the supernatant fraction. In conclusion, HTM-3 cells contain PDEs that degrade both cyclic nucleotides. The PDE activities reside predominantly in the supernatant, but the PDE activity for degrading cGMP is more pronounced. Moreover, results with E4021 suggest that PDE5 activity could play a critical role in modulating cGMP-related activity in the trabecular meshwork.

1-Methyl-3-isobutylxanthine↗

PubMed2000

LINE-1 (L1) lineages in the mouse.

Recently, a rapidly amplifying family of mouse LINE-1 (L1) has been identified and named T(F). The evolutionary context surrounding the derivation of the T(F) family was examined through phylogenetic analysis of sequences in the 3' portion of the repeat. The Mus musculus domesticus T(F) family was found to be the terminal subfamily of the previously identified L1Md4 lineage. The L1Md4 lineage joins the other prototypical mouse LINE-1 lineage (the L1MdA2 lineage) approximately 1 MYA at about the time of the common ancestor of M. m. domesticus, Mus spicilegus, and Mus spretus. However, the T(F) family from M. m. domesticus was found to join to the previously reported M. spretus Ms475 and Ms7024 LINE-1 families at just 0.5 MYA, indicating horizontal transfer. The T(F) family from M. m. domesticus was then found to be even more recently related to LINE-1's from another species, M. spicilegus. A separate spretus A2 lineage was found through a directed search of a PCR library. This lineage, in contrast to the spretus T(F) lineage, does join domesticus at about 1 MYA, as would be expected in the absence of horizontal transfer. A third major family was also found that splits off from the L1Md4 lineage shortly after its departure from the L1MdA2 lineage. The new family, named the Z family, was found to contain the de novo LINE-1 inserts causing the beige and med mutations. Whether the split with the Z family was before or after the recombination that introduced the F-type promoters and defined the inception of T(F) as a lineage is unclear. In enumerating copies of the various LINE-1 families, we found that T(F) 3' ends were not much more numerous than the reported number of 5' ends, suggesting that T(F) may not be subjected to the 90% truncation pattern typical of LINE-1 as a whole.

Animals↗

PubMed2000

Simulation of field-induced structural formation and transition in electromagnetorheological suspensions.

A computer simulation method has been used to study the three-dimensional structural formation and transition of electromagnetorheological (EMR) suspensions under compatible electric and magnetic fields. When the fields are applied simultaneously and perpendicularly to each other, the particles rapidly arrange into single layer structures parallel to both fields. In each layer, there is a two-dimensional hexagonal lattice. The single layers then combine together to form thicker sheetlike structures. With the help of the thermal fluctuations, the thicker structures relax into three-dimensional close-packed structures, which may be face-centered cubic (fcc), hexagonal close-packed (hcp) lattices, or, more probably, the mixture of them, depending on the initial configurations and the thermal fluctuations. On the other hand, if the electric field is applied first to induce the body-centered tetragonal (bct) columns in the system, and then the magnetic field is applied in the perpendicular direction, the bct to fcc structure transition is observed in a very short time. Following that, the structure keeps on evolving due to the demagnetization effect and finally forms close-packed structures with fcc and hcp lattice character. The simulation results are in agreement with the theoretical and experimental results.

Journal Article↗

PubMed2000

Evaluating performance of reconstruction algorithms for 3-D [15O] water PET using subtraction analysis.

Positron emission tomography (PET) [15O] activation studies have benefited significantly from three-dimensional (3-D) data acquisition. However, they have been slow to take advantage of new 3-D reconstruction techniques. Compared with the widely used 3-D reprojection reconstruction (3DRP), the advantage of signal and noise for iterative algorithms has been outweighed by concern about long and complicated reconstruction procedures and inconsistent performance. Most pseudo-3-D algorithms, such as rebinning methods, aim at increasing the speed of reconstruction but lack further resolution improvement or noise control. Although many evaluations have been conducted through simulations and phantom experiments, the spatially varying nature of signal and noise and the complexity of biological effects have complicated the interpretation of real data based on simulation or phantom results. We have taken a different approach and used the analysis of real data directly as a measure with which to compare three reconstruction algorithms: 3DRP, iterative filtered backprojection with median root prior (IFBP-MRP), and Fourier rebinning followed by two-dimensional (2-D) filtered backprojection (FORE-FBP) for [15O] PET. Two subjects, each with 32 scans acquired in four sessions during a finger opposition motor task, are analyzed using subtraction. A fixed volume-of-interest (VOI) measurement in regions related to the task demonstrates that at high resolution, IFBP-MRP has the best signal-to-noise performance followed by 3DRP and FORE-FBP; however, this advantage gradually diminishes as the resolution decreases. For a voxel measurement derived from the image of each reconstruction, all three algorithms are capable of detecting highly activated regions. Although there are some differences in the size, shape, and center location of the activated foci, our preliminary results suggest that IFBP-MRP does offer enhanced signal with some noise control compared with 3DRP for the analysis of high-resolution images. If images are to be analyzed at an intermediate to lower resolution, FORE-FBP provides a significant reduction of reconstruction time compared with 3DRP.

Algorithms↗

PubMed2000

A novel class of antitumor prodrug, 1-(2'-oxopropyl)-5-fluorouracil (OFU001), that releases 5-fluorouracil upon hypoxic irradiation.

We have been developing prodrugs of anticancer agents such as 5-fluorouracil (5-FU) that are activated by irradiation under hypoxic conditions via one-electron reduction. Among them, OFU001 [1-(2'-oxopropyl)-5-fluorouracil] is a prototype radiation-activated prodrug. In this study, we investigated the radiation chemical reactivity and the biological effects of OFU001. This prodrug is presumed to release 5-FU through incorporation of hydrated electrons into the antibonding sigma * orbital of the C(1')-N(1) bond. Hydrated electrons are active species derived from radiolysis of water, but are readily deactivated by O(2) into superoxide anion radicals (O(2).(-)) under conditions of aerobic irradiation. Therefore, 5-FU release occurs highly specifically upon irradiation under hypoxic conditions. OFU001 dissolved in phosphate buffer released 5-FU with a G-value (mol number of molecules that are decomposed or produced by 1 J of absorbed radiation energy) of 1.9 x 10(-7) mol / J following hypoxic irradiation, while the G-value for 5-FU release was 1.0 x 10(-8) mol/J following aerobic irradiation. However, the G-values for decomposition of OFU001 were almost the same, i.e., 3.4 x 10(-7) mol/J following hypoxic irradiation and 2. 5 x 10(-7) mol / J following aerobic irradiation. When hypoxically irradiated (7.5 - 30 Gy) OFU001 was added to murine SCCVII cells for 1 - 24 h, a significant cell-killing effect was observed. The degree of this cytotoxicity was consistent with that of authentic 5-FU at the corresponding concentrations. On the other hand, cytotoxicity was minimal when the cells were treated with aerobically irradiated or unirradiated OFU001. This compound had no radiosensitizing effect against SCCVII cells under either aerobic or hypoxic conditions when the drug was removed immediately after irradiation. Since hypoxia is generally most marked in tumors and irradiation is applied at the tumor site, this concept of prodrug design appears to be potentially useful for selective tumor treatment with minimal adverse effects of anticancer agents.

Animals↗

PubMed2000

Sialylation of the host receptor may modulate entry of demyelinating persistent Theiler's virus.

Theiler's murine encephalomyelitis virus (TMEV) is a picornavirus of the Cardiovirus genus. Certain strains of TMEV may cause a chronic demyelinating disease, which is very similar to multiple sclerosis in humans, associated with a persistent viral infection in the mouse central nervous system (CNS). Other strains of TMEV only cause an acute infection without persistence in the CNS. It has been shown that sialic acid is a receptor moiety only for the persistent TMEV strains and not for the nonpersistent strains. We report the effect of sialylation on cell surface on entry and the complex structure of DA virus, a persistent TMEV, and the receptor moiety mimic, sialyllactose, refined to a resolution of 3.0 A. The ligand binds to a pocket on the viral surface, composed mainly of the amino acid residues from capsid protein VP2 puff B, in the vicinity of the VP1 loop and VP3 C terminus. The interaction of the receptor moiety with the persistent DA strain provides new understanding for the demyelinating persistent infection in the mouse CNS by TMEV.

Animals↗

PubMed2000

Analysis of genetic heterogeneity among five gynogenetic clones of silver crucian carp, Carassius auratus gibelio Bloch, based on detection of RAPD molecular markers.

The gynogenetic silver crucian carp, Carassius auratus gibelio, is a unique model system for studying evolutionary genetics and selective breeding, owing to its specific genetic background and reproductive modes. Five gynogenetic clones were analyzed by the random amplified polymorphic DNA (RAPD) technique, using 30 10-nucleotide-long primers. Twenty-six primers produced well-amplified DNA fragments with reproducible banding patterns, and 24 primers were polymorphic. Nearly identical banding patterns were observed among individuals within each clone, suggesting that each clone might possess a specific pattern owing to its gynogenesis. In contrast, the RAPD patterns of the five clones differed from each other. A phylogenetic tree was constructed using UPGMA cluster analysis based on a total of 3,744 distinguishable fragments (156 per individual). Average genetic distances within and among the five clones clearly indicated their intraclonal homogeneity, interclonal heterogeneity, and phylogenetic relationships. Clones A and P were the most closely related, whereas the most divergence was seen between clone D and clone E or F. A total of 88 polymorphic fragments were scored from 24 primers after excluding bands that were monomorphic for the five clones. Most primers corresponding to the polymorphic fragments amplified reproducible markers specific for one clone or that were shared by two, three, or four clones. Several primers (e.g., Opj-1, Opj-7, and Opp-10) produced abundant banding patterns that could be used to discriminate between the five clones. Markers specific for one or two clones were also identified. The RAPD markers identified in this study will likely benefit evolutionary genetics and selective breeding studies.

Animals↗

PubMed2000

Metabolism of the hamster pancreatic carcinogen methyl-2-oxopropylnitrosamine by hamster liver and pancreas.

BACKGROUND: The mechanism whereby methyl-2-oxopropylnitrosamine (MOP) is activated remains unknown. To begin investigating this mechanism, we followed MOP disappearance during its incubation with liver and pancreatic slices and homogenates from Syrian hamsters and rats. METHODS: After the incubations, disappearance of 100 microM MOP and appearance of a metabolite was followed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. RESULTS: Disappearance rates were 1.2 nmol/mg protein/h for hamster liver slices; zero for hamster pancreatic slices, ducts and acini; zero for rat liver and pancreatic slices; and 11.8, 12.8, 1.3, and 2.3 nmol MOP/mg/h for hamster liver homogenate and cytosol, and hamster pancreas homogenate and microsomes, respectively. The principal MOP metabolite was identified as methyl-2-hydroxypropylnitrosamine (MHP) by its HPLC behavior and its 1H-NMR and mass spectra. MHP yields were generally similar to MOP consumption, but were zero for hamster pancreatic homogenate despite its ability to metabolize MOP. CONCLUSION: MOP is a pancreatic carcinogen in hamsters but not in rats. In metabolic studies, hamster liver slices and homogenate (especially the cytosol) produced MHP from MOP. This is probably an inactivation reaction. Hamster pancreas homogenate (especially the microsome fraction), but not rat pancreas homogenate, metabolized MOP without forming MHP, indicating another route of metabolism, perhaps activation to give the proximal carcinogen.

Animals↗

PubMed2000

Effects of increased response effort on self-injury and object manipulation as competing responses.

UNLABELLED: We evaluated the effects of a response-effort intervention on the occurrence of self-injurious hand mouthing and a competing response (object manipulation) with 4 individuals who had profound developmental disabilities. During Phase 1, results of functional analyses showed that all participants engaged in high levels of hand mouthing in the absence of social contingencies, suggesting that the behavior was maintained by automatic reinforcement. In Phase 2, preferred leisure items were identified for participants during assessments in which duration of leisure item manipulation was used as the index of preference. In Phase 3, participants were observed to engage in high levels of hand mouthing and in varying levels of object manipulation when they had free access to their most preferred leisure items during baseline. The effects of increased response effort on hand mouthing and object manipulation were then evaluated in mixed multiple baseline and reversal designs. The response-effort condition was identical to baseline, except that participants wore soft, flexible sleeves that increased resistance for elbow flexion but still enabled participants to engage in hand mouthing. Results showed consistent decreases in SIB and increases in object manipulation during the response-effort condition for all participants. These results suggested that a less preferred reinforcer (produced by object manipulation) may substitute for a more highly preferred reinforcer (produced by hand mouthing) when response effort for hand mouthing was increased. DESCRIPTORS: self-injurious behavior, automatic reinforcement, reinforcer substitutability, response effort

Adult↗

PubMed2000

[Progress in researches on the function of PML gene].

This paper was aimed to review and expound the progreses in studies on biological fuction of wild-type PML gene and hence to have a gain in knowledge about the carcinogenesis of PML-RARalpha protein. Related reports issued at home and abroad and some research results from this institute were collected and reviewed. According to the data collected PML gene has many biological activites. High expression of PML gene can inhibit the growth of cells and induce apoptosis; PML gene is possibly involved in the regulation of gene expression. Moreover, the function of PML gene is related to its three important domains and its nuclear location; PML gene is associated with carcinogenesis of APL.

Animals↗

PubMed2000

[A study of ventricular repolarization duration variability and dependence of RTm/RR].

As an important electrophysiological parameter that reflects cardiac depolarization and repolarization process, ventricular repolarization duration has been drawing growing attention. It is influenced by several physiological and pathological factors and associated with several cardiac diseases. We studied repolarization duration variability (RDV) and dependence of RTm/RR among normal subjects of different age-groups, as well as between normal subjects and subjects with cardiac diseases. It was found that RDV and dependence of RTm/RR are related to age. There are significant differences in the slope of RTm/RR, coherence, CV ratio and RDV between normal subjects and subjects with cardiac diseases. The RDV and dependence of RTm/RR can be employed in providing a more useful evaluation of cardiac disease and function in clinical care.

Adult↗

PubMed2000

A pyrroline derivative of mexiletine offers marked protection against ischemia/reperfusion-induced myocardial contractile dysfunction.

The efficacy and mechanism of protection of a new 2,2,5, 5-tetramethylpyrroline derivative of mexiletine, MEX-NH, against ischemia/reperfusion-induced cardiac dysfunction are reported. The MEX-NH and its nitroxide metabolite are membrane-permeable antioxidants. Studies were performed in an isolated rat heart model to measure the efficacy of MEX-NH in preventing postischemic injury. Serial measurements of contractile function and coronary flow were performed on hearts subjected to 30 min of global 37 degrees C ischemia followed by 45 min of reperfusion. Hearts were either untreated or treated with 25 microM MEX-NH or MEX for 1 min before ischemia. The hearts treated with MEX-NH showed marked recovery of left ventricular developed pressure (96.3 +/- 2.7% of preischemic value) compared with untreated (13.7 +/- 1.0%) or MEX-treated (19.9 +/- 2.7%) hearts. The cardiac sarcolemmal Na(+),K(+)-ATPase activity showed that the enzyme activity was fully restored in hearts treated with MEX-NH compared with 65 +/- 5.3% inhibition in the untreated hearts. Competitive inhibition of [(3)H]ouabain binding revealed that the MEX-NH binds at the K(+)-binding site of the enzyme. The present study establishes that the compound MEX-NH provides marked protection against ischemia/reperfusion-induced contractile dysfunction in isolated hearts. A combination of reversible inhibition of Na(+)/K(+)-ATPase activity during ischemia and site-targeted antioxidative effect upon reperfusion seems to contribute to this cardioprotection.

Animals↗

PubMed2000

[Application of intermittent-feeding of growth-limiting nutrients in suspension culture of insect cells(Sf21)].

On the basis of the growth and metabolism behavior inherent in suspended Sf21 insect cells, the intermittent feeding of growth-limiting nutrients(glucose and protein hydrolysates) was employed in the regulation of cellular growth during the cultivation by using the residual glucose concentration as a reference point. It was shown that as compared with the batch cultivation, the intermittent-feeding of growth-limiting nutrients effectively prolonged the growth and stationary phase for Sf21 insect cells grown in two representative culture medium(TC-100 and IPL-41). The maximum cell density was increased from 3.0 x 10(6) cells/ml to 6.5 x 10(6) cells/mL in TC-100 medium, and in IPL-41 medium, the maximum cell density was increased from 7.05 x 10(6) cells/mL to 9.0 x 10(6) cells/mL. As the defined nutrient solution was used for feeding in lieu of the complicated and expensive base medium, the technique would find prospects in large scale high-density cultivation of insect cells.

Animals↗