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Biomedical subjects

H Zhu

Publications and source records attributed to H Zhu.

At least 451 records · Page 25Linked to original sources
PubMed1995

Sodium pentobarbital versus alpha-chloralose anesthesia. Experimental production of substantially different slopes in the transmural CP/ATP ratios within the left ventricle of the canine myocardium.

BACKGROUND: Transmural analyses of the creatine phosphate (CP)/ATP ratio in various lamina of the canine myocardium have previously revealed significant variations in the CP/ATP ratio, with the subendocardial layer displaying a decreased ratio relative to the subepicardial layer. Without exception, these results were obtained under sodium pentobarbital anesthesia. These findings have been interpreted to imply that the normal endocardium may be operating in the oxygen-limited domain or that there are transmurally varying set points for the regulation of oxidative phosphorylation. METHODS AND RESULTS: In this work, we examine the effect of the anesthetic regimen on the transmural CP/ATP ratio within the left ventricular wall of the canine myocardium using spatially localized 31P-nuclear magnetic resonance (NMR) and an open-chest model. Two anesthetics were compared, alpha-chloralose and sodium pentobarbital. Under sodium pentobarbital, the CP/ATP ratio ranged from 1.92 +/- 0.06 to 2.51 +/- 0.08 from endocardium to epicardium, resulting in a transmural slope in the CP/ATP ratio of 0.149 +/- 0.047 (n = 22). Under alpha-chloralose, CP/ATP ratios ranged from 2.18 +/- 0.05 to 2.32 +/- 0.06, with a transmural slope of 0.035 +/- 0.018 (n = 38). Thus, the transmural slope in CP/ATP ratio was nearly four times greater with sodium pentobarbital than with alpha-chloralose, and the difference in these slopes was statistically significant (P = .029). No difference was observed in average CP/ATP obtained from the entire wall with either anesthetic. CONCLUSIONS: These results demonstrate that the transmural trend in CP/ATP ratio previously reported in the myocardium is likely to be a direct reflection of the sodium pentobarbital anesthetic regimen, not truly reflecting the trend in the normal unanesthetized animal. Moreover, since the transmural variation in CP/ATP ratio was greatly reduced with alpha-chloralose, it appears unlikely that the endocardium in the normal unanesthetized heart is operating in the oxygen-limited domain. These results also point to the importance of the anesthetic regimen in biochemical analysis, indicate the necessity of increased caution in directly translating results obtained under anesthesia, and demonstrate the unique power of in vivo NMR to extract such subtle biochemical information.

Adenosine Triphosphate↗
PubMed1995

Characterization of benzo[a]pyrene quinone-induced toxicity to primary cultured bone marrow stromal cells from DBA/2 mice: potential role of mitochondrial dysfunction.

Oral exposure of DBA/2 mice to benzo[a]pyrene (BP) has been shown to result in hematotoxicity which is manifested as aplastic anemia and leukemia. Since normal hematopoiesis is regulated by bone marrow stromal cells, in this study we have characterized the bone marrow stromal toxicity induced by BP and BP-derived metabolites, particularly quinones. Incubation of stromal cells with various concentrations of BP-1,6-, 3,6-, 6,12-, or 7,8-quinone for 24 hr resulted in a significant decrease of cell survival in a concentration-dependent manner, while cells treated with BP or BP-7,8-dihydrodiol did not exhibit any significant loss of cell survival. Among the BP quinones examined, BP-1,6-quinone was the most cytotoxic to stromal cells. The cytotoxicity induced by BP-1,6-quinone also exhibited a time-dependent relationship. Pretreatment of stromal cells with 1,2-dithiole-3-thione (D3T) resulted in a significant induction of both cellular reduced glutathione (GSH) content and quinone reductase (QR) activity in a concentration-dependent manner. However, D3T pretreatment did not offer any protection against BP-1,6-quinone-induced toxicity. Furthermore, dicumarol, a potent inhibitor of QR, or buthionine sulfoximine, a specific inhibitor of GSH biosynthesis, did not potentiate BP-1,6-quinone-induced cytotoxicity was not altered. However, incubation of stromal cells with BP-1,6-quinone resulted in a significant depletion of cellular ATP content and mitochondrial morphological changes, which preceded the loss of cell survival. In addition to BP-1,6-quinone, other cytotoxic BP quinones also exhibited a capacity to deplete cellular ATP level in stromal cells, while BP, which was not cytotoxic to stromal cells, did not elicit any significant decrease in cellular ATP level. These observations suggest that mitochondria may be a potential target of BP quinones. Overall, the above results indicate that neither cellular GSH and QR nor reactive oxygen species appear to be involved in BP quinone-induced stromal cell injury and that BP quinones may elicit cytotoxicity to stromal cells through directly disrupting mitochondrial energy metabolism.

Adenosine Triphosphate↗
PubMed1995

Multiple simultaneous synthesis of phenolic libraries.

A series of analogous arrays of small, non-peptidyl, non-oligomeric compounds were synthesized on polystyrene resin. With the aid of a functionally differentiated phenolic scaffold, the batch preparation of unique benzamide and urea resins was accomplished, which were further derivatized in modified 96-well plates. An efficient cleavage reaction of the phenyl benzoate link enabled the isolation of more than 600 phenolic compounds in milligram quantities that were suitable for direct biological screening. The technology described herein represents a facile, economical approach to non-peptidyl chemical diversity.

Chemistry, Organic↗
PubMed1995

Walking cadence effect on plantar pressures.

OBJECTIVE: Prior studies have examined the effect of cadence on ground reaction forces by use of a force plate. Force plate studies generally analyze isolated steps and do not provide insight into ongoing step-to-step variations or in-shoe plantar pressures. The objective of this study was to evaluate the effect of walking cadences on in-shoe plantar pressures over extended periods of continuous walking. DESIGN: Nonrandomized control trial. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Volunteer sample of 8 able-bodied subjects. INTERVENTIONS: In-shoe plantar pressures were studied during four minutes of continuous walking at controlled cadences of 70, 80, 90, 100, 110, and 120steps/min. For each cadence more than 200 steps were analyzed for each of the 8 subjects. MAIN OUTCOME MEASURES: Pressure-time integrals, foot-to-floor contact durations, and peak pressures at all 14 locations were processed for each step. Changes were calculated compared to values at 70steps/min. RESULTS: With increasing cadence, mean pressure-time integrals continuously decreased (45% at 120steps/min); mean foot-to-floor contact durations continuously decreased (64% at 120steps/min); and mean peak pressures increased (119% at 120steps/min). CONCLUSIONS: Our results show that as walking cadence increases, pressure-time integrals and foot-to-floor contact durations decrease, and peak plantar pressures increase. This is clinically relevant to all kinetic gait studies because our results suggest that normal values should be established for each cadence.

Adult↗
PubMed1995

Differences in xenobiotic detoxifying activities between bone marrow stromal cells from mice and rats: implications for benzene-induced hematotoxicity.

Benzene is a human carcinogen; exposure to benzene can result in aplastic anemia and leukemia. Data from animal models are frequently used in the risk assessment for benzene. In rodent studies, mice have been shown to be more sensitive to benzene-induced hematotoxicity than rats. In this regard, we have observed that bone marrow stromal cells from mice were significantly more susceptible to the cytotoxicity induced by the benzene metabolites hydroquinone (HQ) and benzoquinone (BQ) than cells from rats. Since cellular glutathione (GSH) and quinone reductase (QR) are known to play critical roles in modulating HQ-induced cytotoxicity, we have measured the GSH content and the QR and glutathione S-transferase (GST) activity in stromal cells from both species. In rat cells, the GSH content and the QR specific activity were 2 and 28 times as much as those from mice, respectively. GSH and QR in both mouse and rat stromal cells were inducible by 1,2-dithiole-3-thione (D3T). D3T pretreatment of both mouse and rat stromal cells resulted in a marked protection against HQ-induced toxicity. Pretreatment of both mouse and rat stromal cells with GSH ethyl ester also provided a dramatic protection against HQ-induced toxicity. Conversely, dicoumarol, an inhibitor of QR, enhanced the HQ-induced toxicity in stromal cells from both mice and rats, indicating an important role for QR in modulating HQ-induced stromal toxicity in both species. Buthionine sulfoximine (BSO), which depleted GSH significantly in both species, potentiated the HQ-induced toxicity in mouse but not in rat stromal cells. Surprisingly, incubation of stromal cells with BSO resulted in a significant induction of QR, especially in rats. The failure of BSO to potentiate HQ-induced toxicity in rat stromal cells may be due to the concomitant induction of QR by BSO. Overall, this study demonstrates that the differences in stromal cellular GSH content and QR activity between mice and rats contribute to their respective susceptibility to HQ-induced cytotoxicity in vitro, and may be involved in the greater in vivo sensitivity of mice to benzene-induced hematotoxicity.

Animals↗
PubMed1995

Modulation of glycosidase and protease activities by chemostat growth conditions in an endocarditis strain of Streptococcus sanguis.

The effects of growth conditions on the properties of the endocarditis-producing oral bacterium Streptococcus sanguis FSS2 were studied. This strain produces a variety of proteases and glycosidases, including a thrombin-like activity that is a potential virulence factor for endocarditis. Cultures were grown with limiting glucose or galactose in chemostats over a range of dilution rates and pH levels, and the following activities were measured at pH 7.5: thrombin-like, Hageman factor-like, N-acetyl-beta-D-galactosaminidase, beta-D-glucosidase, and beta-D-galactosidase. At growth pH 6.5, specific activities generally decreased as the dilution rate increased from 0.05 to 0.40 h(-1). At a dilution rate of 0.1 h(-1), specific activities generally were highest at growth pH 6.5 and lower and approximately equal at growth pH 5.5 and 7.5. The major exception was the thrombin-like activity, for which the specific activity at growth pH 7.5 was approximately 5-fold higher than at growth pH 5.5. Hageman factor-like activity was apparently glucose catabolite repressible, as its activity was 3-fold higher in galactose cultures. The measured activities changed as functions of growth conditions and thus were modulated by environment. Environmental regulation of thrombin-like activity by pH is consistent with an activity that is less important on tooth surfaces than in tissues.

Adaptation, Physiological↗
PubMed1995

Human cytomegalovirus IE1 and IE2 proteins block apoptosis.

Human cytomegalovirus-infected fibroblasts are resistant to the induction of apoptosis by superinfection with a mutant adenovirus unable to produce the viral E1B 19-kDa protein that normally causes an E1A protein-mediated apoptotic response. Two cytomegalovirus gene products that block apoptosis were identified. The IE1 and IE2 proteins each inhibit the induction of apoptosis by tumor necrosis factor alpha or by the E1B 19-kDa-protein-deficient adenovirus but not by irradiation with UV light. Our results suggest a new physiological role for the IE1 and IE2 proteins in the human cytomegalovirus replication cycle.

Animals↗
PubMed1995

The lutropin/choriogonadotropin receptor is palmitoylated at intracellular cysteine residues.

Most members of the family of G protein-coupled receptors have one or more conserved cysteine residues in their carboxy-terminal cytoplasmic tails which are believed to be consensus sites for palmitoylation. Indeed, a growing number of G protein-coupled receptors (rhodopsin, beta 2-, and alpha 2-adrenergic receptors) have now been shown to have palmitic acid covalently attached to this position. In the case of the beta 2-adrenergic receptor, it was also reported that mutation of the palmitoylated cysteine to glycine greatly diminished the ability of this receptor to interact with and activate Gs. Mutation of this conserved cysteine appears to have little or no effect on the ability of other members of this receptor family (rhodopsin, alpha 2-adrenergic and M2 muscarinic) to activate their cognate G proteins, however. The studies presented here were designed to determine whether another Gs-coupled receptor, the LH/CG receptor, is palmitoylated, and whether this modification is important for receptor function. To facilitate biochemical analysis, we examined these issues using cell lines stably transfected with the wild type LH/CG receptor (LHR-wt) or with a mutant receptor in which the two conserved cysteins were mutated to alanines (designated LHR-C621,622A). Our results show that LHR-wt is palmitoylated but that LHR-C621,622A is not. We also show that LHR-C621,622A is capable of binding human CG (hCG) and transducing the cAMP signal. The main difference that we detected between the wild type and mutant receptor is that the latter is trapped intracellularly and does not appear to mature into the 85 kilodalton protein previously identified as the mature cell surface LH/CG receptor.

Animals↗
PubMed1995

[RP-HPLC determination of berberine in cortex Phellodendri].

A reversed-phase high performance liquid chromatographic mothod was developed for the determination of berberine in Cortex Phellodendri using a bonded phase column (Zorbax C8) with diazepam as the internal standard. The column temperature was 25 C. The mobile phase was a mixture of acetonitrile-water (35:65, containing 30mmol/L H3PO4) with a flow rate of lml/min. Berberine was detected by UV absorption at 346nm. The standard curve was linear in the range of 0.14 to 2.0 micrograms. The recovery was 101.7% and RSD 1.83%.

Berberine↗
PubMed1995

[Detection of pathogenic Entamoeba histolytica DNA in liver abscess aspirates with polymerase chain reaction].

Polymerase chain reaction (PCR) was used to diagnose amebic liver abscess by detecting pathogenic Entamoeba histolytica DNA in liver aspirates from patients with liver abscess. Oligonucleotide primers specific for gene encoding of the 30,000 molecule of pathogenic Entamoeba histolytica were used in the test. Liver aspirates from 23 cases with amebic liver abscess as evidenced by typical clinical findings or very high titres of anti-E. Histolytica antibodies with ELISA were found to be positive with PCR. Fourteen control samples (3 cases of bacterial liver abscess, 1 of liver cancer and 10 of abscess in other sites) were all negative to PCR. The results suggest that PCR is a sensitive and useful method for diagnosing amebic liver abscess.

Animals↗
PubMed1995

[Amino acid neurotransmitter receptors of carp brain expressed in amphibian oocytes].

GABA receptor and inotropic glutamate receptors were expressed in amphibian oocytes and studied with the voltage-clamp technique and pharmacological method after injection of mRNA from carp (Carassius carassius) brains. It was found that about 90% of the response to GABA was mediated by GABAA receptor, but there was also about 10% of the response which was insensitive to bicuculline, a selective antagonist to GABAA receptor, baclofen, a selective agonist to GABAB receptor, had no effect on the injected oocytes. These observations suggest the existence of GABAC receptor. Subtypes of glutamate receptors, including NMDA subtype, KA/AMPA subtype and metabotropic glutamate receptors were also expressed and the dose-response relations were studied. Furthermore, we found that NMDA competitively suppressed the current response to KA, suggesting that NMDA probably was a weak antagonist of the KA/AMPA receptor.

Animals↗
PubMed1995

[Preparation and characterization of monoclonal antibodies against esterase of malathion-resistant Culex quinquefasciatus].

Five clones of monoclonal antibodies (McAbs) were generated from BALB/c mice which were activized with PPD and immunized with esterases extracted from malathion-resistant Culex quinquefasciatus. All 5 clones of McAbs belonged to the IgG1 subtype, additive index (A.I.) of every two McAbs did not exceeded 50%. After a 1 h of incubation, the McAbs at the titer of 1:1,000 completely inhibited the activity of the amplified esterases. Of 8 strains of adult mosquitoes studied by Western-blot assay, all exhibited the 64 kDa esterase band recognized by the McAbs, six (SP, FS, SH, CD, RD, RM) showed more bands of different MW (43-60 kDa), the higher the organophosphorus resistant level, the more and the denser the bands. The above McAbs had little or no effect against the esterases of dimethrin-resistant strain and the larva stage of malathion-resistant Culex quinquefasciatus.

Animals↗
PubMed1995

Changes in expression and distribution of Aplysia cell adhesion molecules can influence synapse formation and elimination in vitro.

5-HT or FMRFamide evoke long-lasting changes in the efficacy of sensorimotor (SN-L7) synapses of Aplysia, structural alterations of the presynaptic sensory cell, and cell-specific downregulation in the distribution of the adhesion molecule apCAM. We examined how the cell-specific changes in apCAM might contribute to the formation of new presynaptic varicosities by 5-HT or the elimination of existing presynaptic varicosities by FMRFamide. We report that the formation of new sensory varicosities is directed by the presence of preexisting zones on the motor axon that are enriched for apCAM. Moreover, there was a further enrichment of apCAM levels at existing sensory varicosities contacting the motor axon beginning at 1 hr and lasting 24 hr after treatment with 5-HT. As was found for synapse formation during the early stages of cell-cell interaction, incubation with anti-apCAM mAb blocked the 5-HT-induced long-term changes in synaptic efficacy and the accompanying changes in sensory neuron structure. Long-term synaptic depression with FMRFamide was accompanied by an overall decline of apCAM levels. Treatment with FMRFamide evoked an even greater decline in apCAM levels at sites of sensory varicosities that preceded the structural changes and persisted especially at sites where sensory varicosities are eliminated. These results suggest that neurotransmitters evoke both cell- and site-specific changes in the levels of adhesion molecules that can influence either the formation or the elimination of presynaptic varicosities that accompany long-term heterosynaptic modulation of a behaviorally relevant synaptic connection.

Animals↗
PubMed1995

[Study of the internal canthus with magnetic resonance imaging].

In oculoplastic surgery, the internal canthus is a particular feature of great importance. An analysis has been carried out with 10 MRI tests of the internal canthi and the authors will outline the major difficulties, before detailing a protocol which would enable further studies of pathological canthi.

Adult↗
PubMed1995

Characteristics of an established retinoblastoma cell line HXO-Rb44.

PURPOSE: To study the retinoblastoma cell culture and to establish a new retinoblastoma cell line. METHODS: 22 retinoblastomas were cultured by using the method of single cell suspension. Characteristics of the cultured cells were studied in the following programs: tumor cell morphology in vitro, electron microscopic, growth curve, cloning in soft agar, immunohistochemistry, karyotype and tumorigenicity. RESULTS: 22 retinoblastomas were cultured successfully in vitro, only a continued cell line HXO-Rb44 was established (more than 3 years). The characteristics of this cell line are that it grew as a suspension of round cell in graps like clusters in vitro, its population doubling time was 44 hours, and it could be cloned in soft agar. Histopathologic and ultrastructured pictures showed the characteristics of Rb. HXO-Rb44 cell was positive to NSE and negative to GFAP in immunohistochemical staining. A subcutaneous injection of HXO-Rb44 cells produced a retinoblastoma in BALB/C athumic nude mice. CONCLUSIONS: HXO-Rb44 has the characteristics of retinoblastoma and is a new retinoblastoma cell line. It is a useful material for study this tumor both in basic and clinical fields.

Animals↗
PubMed1995

Plantar pressures with total contact casting.

Total contact casting has been used to aid in the healing of plantar neurotrophic ulcerations. The efficacy of total contact casts in promoting ulcer healing is presumably due to a reduction in the load over high pressure areas with pressure redistribution over the entire surface of the foot. The purpose of this study was to quantify the effectiveness of total contact casting in reducing plantar pressures. A portable microprocessor-based data-acquisition system was used for recording plantar pressures. Plantar pressures were collected from six nondisabled individuals with and without total contact casting at cast-walking cadence. In our study, there was a decrease in plantar loading under the metatarsal heads (first, fourth, fifth), the great toe, and the heel. The average decrease was 32% under the fifth metatarsal, 63% under the fourth metatarsal, 69% under the first metatarsal, 65% under the great toe, and 45% under the heel. Our study quantitatively showed that total contact casting does reduce vertical plantar pressures in high load areas.

Adolescent↗