Biomedical subjects

H Zhao

Publications and source records attributed to H Zhao.

At least 397 records · Page 22Linked to original sources

PubMed1997

Hydrazide-containing inhibitors of HIV-1 integrase.

Inhibitors of HIV integrase are currently being sought as potential new therapeutics for the treatment of AIDS. A large number of inhibitors discovered to date contain the o-bis-hydroxy catechol structure. In an effort to discover structural leads for the development of new HIV integrase inhibitors which do not rely on this potentially cytotoxic catechol substructure, NSC 310217 was identified using a three-point pharmacophore search based on its assigned structure N-(2-hydroxybenzoyl)-N-(2-hydroxy-3-phenoxypropyl)hydrazine (1). When a sample of NSC 310217 was obtained from the NCI repository, it was shown to exhibit potent inhibition of HIV-1 integrase (3'-processing IC50 = 0.6 microgram/mL). In work reported herein, we demonstrate that NSC 310217, rather than containing 1, which has no inhibitory potency against HIV-1 integrase, is comprised of roughly a 1:1 mixture of N-(2-hydroxybenzoyl)-N'-(2-hydroxy-3-phenoxypropyl)hydrazine (6) and N,N'-bis-salicylhydrazine 7, with all inhibitory potency residing with compound 7(IC50 = 0.7 microM for strand transfer). In subsequent structure-activity studies on 7, it is shown that removing a single amide carbonyl (compound 14, IC50 = 5.2 microM) or replacing one aromatic ring system with a naphthyl ring (compound 19, IC50 = 1.1 microM) can be accomplished with little loss of inhibitory potency. Additionally, replacing a single hydroxyl with a sulfhydryl (compound 23, IC50 = 5.8 microM) results in only moderate loss of potency. All other modifications examined, including the replacement of a single hydroxyl with an amino group (compound 22), resulted in complete loss of potency. Being potent, structurally simple, and non-catechol-containing, compounds such as 7 and 14 may provide useful leads for the development of a new class of HIV integrase inhibitor.

Databases, Factual↗

PubMed1997

Coumarin-based inhibitors of HIV integrase.

The structures of a large number of HIV-1 integrase inhibitors have in common two aryl units separated by a central linker. Frequently at least one of these aryl moieties must contain 1,2-dihydroxy substituents in order to exhibit high inhibitory potency. The ability of o-dihydroxy-containing species to undergo in situ oxidation to reactive quinones presents a potential limitation to the utility of such compounds. The recent report of tetrameric 4-hydroxycoumarin-derived inhibitor 5 provided a lead example of an inhibitor which does not contain the catechol moiety. Compound 5 represents a large, highly complex yet symmetrical molecule. It was the purpose of the present study to determine the critical components of 5 and if possible to simplify its structure while maintaining potency. In the present study, dissection of tetrameric 5 (IC50 = 1.5 microM) into its constituent parts showed that the minimum active pharmacophore consisted of a coumarin dimer containing an aryl substituent on the central linker methylene. However, in the simplest case in which the central linker aryl unit consisted of a phenyl ring (compound 8, IC50 = 43 microM), a significant reduction in potency resulted by removing two of the original four coumarin units. Replacement of this central phenyl ring by more extended aromatic systems having higher lipophilicity improved potency, as did the addition of 7-hydroxy substituents to the coumarin rings. Combining these latter two modifications resulted in compounds such as 3,3'-(2-naphthalenomethylene)bis[4,7-dihydroxycoumarin] (34, IC50 = 4.2 microM) which exhibited nearly the full potency of the parent tetramer 5 yet were structurally much simpler.

Anti-HIV Agents↗

PubMed1997

Expression of matrix metalloproteinase-9 mRNA in osteoporotic bone tissues.

Matrix metalloproteinases (MMPs), a sort of important enzymes involved in extracellular matrix metabolism, play critical roles in the process of tissues remodeling, wound healing and metastasis of tumors. Dot blot and in situ hybridization were used in this study to detect the expression and localization of MMP-9, an important proteolytic enzyme implicated in bone resorption in bone tissues. The results showed that the level of MMP-9 mRNA expression in osteoporotic bone tissues was significantly higher than that in normal control group and the cell types that expressed MMP-9 mRNA included mono- and multi-nuclear osteoclasts and some lining cells on the surface of bone matrix. It was suggested that MMP-9 play a key role in the development of bone loss in osteoporosis.

Animals↗

PubMed1997

Bipolar esophageal electrocardiography by using standard limb leads.

The ear-xiphisternum distance (EXD, the distance from the low edge of the ear to the xiphisternal basis in supine position) was used as a reference value for esophageal catheter insertion. ECGs recorded in the esophagus with bipolar electrocardiography using standard limb lead (ESLL) and conventional unipolar lead (ECUL) were compared. 112 patients with sinus rhythm and 76 patients during paroxysmal supraventricular tachycardia (PSVT) whose P-wave and QRS complex did not overlap were studied. The results suggested that in sinus rhythm the amplitude of the P-wave in ESLL was larger and the T-wave was smaller than in ECUL. During PSVT, the P-wave was much clear and higher in each lead of ESLL than that in ECUL. The ideal range of esophageal ECG recording was situated between the end of EXD and 6.5 cm proximal to it.

Adolescent↗

PubMed1997

The correction of Class II, division 1 malocclusion with bionator headgear combination appliance.

The purpose of this study was to evaluate skeletal and dental effects of bionator headgear combination appliances on patients in development period with Class II, division 1 malocclusion. The comparison of computerized X-ray cephalometric measurements between the 26 treated children and 26 untreated children was made. The results showed that ANB angle was significantly reduced and horizontal mandibular growth development tended to be normal in the treated group. It was suggested that the bionator headgear combination appliance can restrain the maxillary growth early and promote the forward mandibular growth which contribute the functional jaws correction.

Activator Appliances↗

PubMed1997

Regulation of signal transduction through the T cell antigen receptor.

Considerable work from numerous laboratories has provided important insights into the biology of T cell activation. Much has been learned about the most proximal signaling events that occur after engagement of the T cell antigen receptor and other cell-surface receptors on T lymphocytes. However, our understanding of how various signaling pathways are integrated, resulting in cellular proliferation and cytokine production or conversely leading to programmed cell death, is far from complete. We summarize what is now known about some of the proximal signals that result from engagement of the T cell antigen receptor and how some of these signals are linked to cellular responses.

Adaptor Proteins, Signal Transducing↗

PubMed1997

Prognostic signs in the surgical management of plexiform neurofibroma: the Children's Hospital of Philadelphia experience, 1974-1994.

OBJECTIVES: To estimate the rate of progression of plexiform neurofibroma after surgery and to identify prognostic factors that predict progression. STUDY DESIGN: A retrospective review of the inpatient and outpatient records of 121 patients, who had 302 procedures on 168 tumors over a 20-year period at a single large pediatric referral center. Data on age, location, indication for surgery, and extent of resection was analyzed for prognostic significance. RESULTS: The overall freedom from progression was 54%. Children < 10 years old had a shorter interval of tumor control than older children (p = 0.0004). Tumors of the head/neck/face fared worse than tumors of the extremities (p = 0.0003). Less extensive resection predicted shorter interval to progression (p < 0.0001). Indication for surgery was not of prognostic importance. In multivariable analysis older age and location in the extremities were predictors of a better outcome. CONCLUSIONS: Tumor progression is a serious problem for children with plexiform neurofibroma. Younger children, children with tumors of the head/neck/face, and tumors that cannot be nearly completely removed are at particular risk. These data may be useful in helping clinicians decide which patients and which tumors are most likely to benefit from surgical intervention.

Adolescent↗

PubMed1997

Screening for hereditary spherocytosis by use of automated erythrocyte indexes.

OBJECTIVE: To determine whether the mean corpuscular hemoglobin concentration (MCHC) or other erythrocyte indexes, as determined by automated cell counters, remains a useful screening test for identifying patients with hereditary spherocytosis (HS). METHODS: Erythrocyte indexes from 112 children with HS who had not undergone splenectomy were compared with those measured in an equal number of healthy, age-matched children. All indexes were derived from measurements obtained by aperture impedance. RESULTS: Mean corpuscular hemoglobin concentration in the HS group was 35.9 gm/dl, significantly higher than in normal control subjects (34.3 gm/dl; p < 0.001). Mean erythrocyte distribution width also was significantly higher in patients with HS (19.3 vs 12.6; p < 0.001). The MCHC distinguishes individuals with HS, with an area under the receiver operating characteristic curve of 0.86. Although not disease specific, an erythrocyte distribution width > 14 has 85% sensitivity and 97% specificity and an area under the receiver operating characteristic curve of 0.92. An MCHC > 35 gm/dl has a sensitivity of 70% and a specificity of 86%. Combining the MCHC and erythrocyte distribution width increases the area under the receiver operating characteristic curve to 0.97. Specificity is 100% and likelihood ratio is infinite when both the MCHC and erythrocyte distribution width are elevated. CONCLUSIONS: The automated MCHC is an effective screening test to identify children with HS. An elevated erythrocyte distribution width adds additional specificity and is itself a powerful screening tool. The combination of the two tests is an excellent predictor for the diagnosis of HS.

Adolescent↗

PubMed1997

Combinatorial protein design: strategies for screening protein libraries.

Powerful strategies for screening protein libraries further strengthen the arguments for applying 'irrational' approaches to understanding and designing new proteins. Developments during the past year include the application of functional complementation and automation to reduce screening loads, as well as the use of computerized data acquisition to characterize whole protein libraries rather than just selected individuals.

Automation↗

PubMed1997

Teen father participation in child rearing: family perspectives.

OBJECTIVES: To explore adolescent fatherhood from the perspectives of teen fathers, teen mothers, paternal grandmothers (PGMs), and maternal grandmothers (MGMs). To identify perceived barriers to and recommendations for the enhancement of teen father participation in child rearing. METHODS: A total of 61 teen parents participated in the design of a structured interview. A community-based sample of 173 teen fathers, 167 teen mothers, 76 PGMs, and 79 MGMs were interviewed by teenage assistants. Multiple logistic regression analysis using maximum likelihood estimation and the best subset algorithm identified barriers most predictive of paternal uninvolvement in child rearing. RESULTS: Fifty-four percent of teen fathers and 70% of partners of teen mothers' met the definition of involvement in child rearing. Disinterest in child rearing most consistently predicted uninvolvement. Fathers were less likely than mothers to report paternal disinterest as a barrier and more likely to attribute their lack of involvement to resistance from mothers and MGMs (p < 0.05). The best model predicting paternal involvement from the fathers' perspective included paternal disinterest [odds ration (OR) = 0.42, confidence interval (CI) = 0.19-0.92] and age (OR = 0.74, CI = 0.56-0.97). The best model from the mothers' perspective included paternal disinterest (OR = 0.16, CI = 0.07-0.36) and lack of time (OR = 0.31, CI = 0.15-0.91). Of those fathers who cited disinterest, there was an association with lack of money (p = 0.002) and lack of knowledge of child care (p = 0.069. While fathers and mothers disagreed on several interventions, they agreed (82% and 95%, respectively) that availability of jobs would promote paternal involvement. CONCLUSIONS: Most teen fathers in this study were involved and interested in child rearing. A young father's financial insecurity or confusion about child care was most likely to lead to a stated disinterest, and that disinterest predicted uninvolvement.

Adolescent↗

PubMed1997

Specific labeling approaches to guanine and adenine imino and amino proton assignments in the AMP-RNA aptamer complex.

The secondary structure of a recently identified ATP-binding RNA aptamer consists of a purine-rich 11-residue internal loop positioned opposite a single guanine bulge flanked on either side by helical stem segments. The ATP ligand targets the internal loop and bulge domains, inducing a structural transition in this RNA segment on complex formation. Specifically, 10 new slowly exchanging proton resonances in the imino, amino and sugar hydroxyl chemical shift range are observed on AMP-RNA aptamer complex formation. This paper outlines site-specific labeling approaches to identify slowly exchanging imino (guanine) and amino (guanine and adenine) protons in internal loop and bulge segments of compact RNA folds such as found in the AMP-RNA aptamer complex. One approach incorporates 15N-labeled guanine (N1 imino and N2 amino positions) and 15N-labeled adenine (N6 amino position), one residue at a time, in the AMP-binding RNA aptamer, with labeling incorporation through chemical synthesis facilitated by generating the aptamer from two separate strands. The unambiguous assignments deduced from the 15N labeling studies have been verified from an independent labeling strategy where individual guanines in the internal loop have been replaced, one at a time, by inosines and assignments were made on the basis of the large 2 ppm downfield shift of the guanine imino protons on inosine substitution. The strengths and limitations of the inosine-for-guanine substitution approach emerge from our studies on the AMP-RNA aptamer complex. The assignment of the internal loop and bulge imino and amino protons was critical in our efforts to define the solution structure of the AMP-RNA aptamer complex since these slowly exchanging protons exhibit a large number of long-range intramolecular NOEs within the RNA, as well as intermolecular NOEs to the AMP in the complex. The current application of specific 15N and inosine labeling approaches for exchangeable imino and imino proton assignments in the nonhelical segments of an RNA aptamer complex in our laboratory complements selective 2H and 13C approaches to assign nonexchangeable base and sugar protons in RNA and ligand-RNA complexes reported in the literature.

Adenosine Monophosphate↗

PubMed1997

Effects of dopamine on L-type Ca2+ current in single atrial and ventricular myocytes of the rat.

1. The effects of dopamine on the L-type Ca2+ current (ICa,L) of both atrial and ventricular single myocytes and on the force of contraction of atrial trabeculae in rat heart were investigated. 2. Dopamine increased atrial ICa,L at concentrations higher than 1 microM, but had little or no effect on ICa,L at lower concentrations. The increase in ICa,L at high concentrations was reversed by propranolol and acetylcholine, but not by phentolamine. Activation and inactivation kinetics of ICa,L were not altered by dopamine. 3. In rat ventricular myocytes in which the D4 receptor mRNA does not express, dopamine (20-100 microM) also increased the ICa,L amplitude and propranolol reversed this effect. 4. Clozapine, a potent D4 receptor antagonist, blocked the augmenting effect of dopamine on ICa,L. However, this effect could be explained by beta-antagonism, since clozapine also inhibited the isoprenaline effect. 5. In the atrial trabeculae, the increase in contraction by dopamine (1 to 30 microM) was reversed by 1 microM propranolol, but not by 2 microM phentolamine. Low doses of dopamine (0.01 to 0.3 microM) did not affect the contraction in the controls or during a modest stimulation of the beta-adrenoceptor with 0.01 microM isoprenaline. 6. These results indicate that the positive inotropic action of dopamine is mediated through direct stimulation of the beta-adrenoceptor in both atrial and ventricular myocytes. Involvement of D4 receptor appears unlikely in the regulation of the atrial contraction.

Animals↗

PubMed1997

Characterization of a constitutive type III nitric oxide synthase in human U937 monocytic cells: stimulation by soluble CD23.

The soluble cleavage fragment of the low-affinity immunoglobulin E (IgE) receptor/CD23 (sCD23 25000 MW) and antibodies directed against their receptors on monocytes, CD11b and CD11c, stimulate the production of nitric oxide (NO) by these cells and we have suggested that the enzyme involved could be related to the endothelial constitutive type III nitric oxide synthase (ecNOS). In the present work, we have analysed the characteristic properties of this NOS isoform in the model of the human promonocytic cells U937 By reverse-transcription polymerase chain reaction (RT-PCR), the presence of an mRNA coding for type III NOS was found in U937 cells and the corresponding protein was detected by immunofluorescence in permeabilized cells with a specific anti-ecNOS monoclonal antibody (mAb). Membrane extracts displayed a NOS activity dependent on the presence of calcium and calmodulin in the reaction medium and that was abrogated in the presence of EGTA. Recombinant soluble CD23 (25000 MW) was found to trigger an NO-dependent cGMP accumulation in these cells, which was abrogated by calcium chelators and inhibitors of the calcium/calmodulin complex. Moreover, sCD23 elicited a transient augmentation of intracytoplasmic free calcium concentration [Ca2+]i that was dependent on the presence of calcium in the external buffer and was prevented in the presence of EGTA, indicating that it was due to a calcium influx. In conclusion, human promonocytic cells such as U937 exhibit a functional type III NOS that can be stimulated by calcium-raising agents, such as sCD23.

Calcium↗

PubMed1997

In vivo phase variation of MR/P fimbrial gene expression in Proteus mirabilis infecting the urinary tract.

Proteus mirabilis, associated with complicated urinary tract infection, expresses mannose-resistant/Proteus-like (MR/P) fimbriae. Expression of these surface structures, which mediate haemagglutination and have a demonstrated role in virulence, undergoes phase variation. By DNA sequence analysis, a 252 bp invertible element was found in the intergenic region between mrpl, the putative site-specific recombinase gene, and mrpA, the primary structural subunit gene. The invertible segment is flanked by identical 21 bp inverted repeats and the presumptive half-sites for recombinase binding show homology to those recognized by FimB and FimE encoded by the Escherichia coli fim (Type 1 fimbriae) gene cluster. When amplified by the polymerase chain reaction (PCR) from static broth cultures expressing MR/P fimbriae, the switch region was found in both ON and OFF positions. When PCR was used to amplify agar cultures which do not express the fimbriae, the switch region was OFF only. A canonical sigma 70 promoter inside the invertible element drives the transcription of mrpA when in the ON position; in the OFF position it is directed away from mrpA but does not appear to drive expression of mrpI. The mrpI gene was able to confer inversion of the mrp switch region in trans from both ON to OFF and OFF to ON. To examine the position of the switch in vivo, urine, bladder, and kidneys from mice transurethrally infected with P. mirabilis were used to prepare template DNA for PCR amplification. In the absence of urolithiasis (urease-mediated stone formation), the switch was found 100% in the ON position, a condition never observed following in vitro culture. We conclude that MR/P phase variation is regulated at the transcriptional level by the action of MrpI on an invertible element and that there is strong selective pressure for the expression of MR/P fimbriae in vivo.

Amino Acid Sequence↗

PubMed1997

An essential tryptophan residue of green crab (syclla serrata) alkaline phosphatase.

The tryptophan residues in green crab (scylla serrata) alkaline phosphatase (EC 3.1.3.1) have been modified by N-bromosuccinimide (NBS). The modification of five tryptophan residues leads to complete loss of enzymatic activity. With the increase of NBS concentration, both the absorption at 278 nm and the fluorescence emission intensity at 335 nm of the modified enzyme decreased markedly indicating the modification of tryptophan residues. Quantitative treatment of the data (Tsou, Sci. Sinica 1962, 11, 1535-1558) shows that among the tryptophan residues modified, one is essential for its catalytic activity. The presence of the substrate markedly protects the modification of tryptophan residues as well as the inactivation, suggesting that the essential tryptophan residue is situated at the active site of this enzyme.

Alkaline Phosphatase↗

PubMed1997

Identification of p185neu sequences required for monoclonal antibody- or ligand-mediated receptor signal attenuation.

Anti-p185neu antibodies downmodulate constitutively active p185neu receptors from the cell surface, which is associated with a reduction in the transformed phenotype. We have analyzed a group of mutant p185neu forms with carboxyl (C)-terminal truncations and/or an internal deletion of amino acids 1008-1057. Receptor endocytosis and degradation were examined by flow cytometric analysis and pulse-chase assays following anti-p185neu monoclonal antibody (MAb) treatment. Deletion of a sequence within the distal carboxyl terminus, including three known autophosphorylation sites, did not affect MAb-mediated receptor surface downmodulation and degradation of surface receptor. However, kinase-active deletion mutants with elimination of the putative internalization sequence (Tint delta), or Tint delta mutants also containing a large C-terminal truncation, displayed markedly impaired receptor endocytosis in response to MAb treatment. Cells expressing endocytosis-defective mutant proteins became insensitive to anti-p185neu MAb-mediated inhibition of anchorage-independent growth and were more oncogenic in vivo. Cells expressing endocytosis-defective mutant EGFR/neu chimeric proteins were more transforming upon EGF addition when compared to cells expressing wild-type EGFR/neu receptors. Taken together, these data suggest that, in addition to kinase activity, p185neu receptor endocytosis requires a functional modular structure, i.e., an internalization sequence, possibly to serve as target for endocytotic adapter proteins. Unattenuated signaling from oncogenic p185neu forms resulting from prolonged surface localization may result in enhanced cellular transformation and desensitization to MAb-mediated downregulation and phenotypic reversion.

Animals↗

PubMed1997

Anaphylactic bronchoconstriction in immunized guinea pigs provoked by inhalation and intravenous administration of hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride.

We established a guinea-pig model of anaphylactic bronchoconstriction provoked in immunized animals by inhalation and intravenous administration of 4,4-methyltetrahydrophthalic anhydride (MTHPA) and hexahydrophthalic anhydride (HHPA). Guinea pigs were immunized intradermally with either MTHPA (n = 8) or HHPA (n = 8) suspended in olive oil. Control animals (n = 8) were injected with olive oil alone. After 4 weeks, the animals were challenged during mechanical ventilation by inhalation or intravenous administration of MTHPA or HHPA conjugated with guinea-pig serum albumin (GPSA). Airway flow, and airway and esophageal pressures were measured. Resistance (R) and static compliance (Cst) of the respiratory system (rs), lung (1), and chest wall were studied with the flow-interruption technique. After challenge with MTHPA-GPSA or HHPA-GPSA, R,rs and R,1 increased dramatically while Cst,rs and Cst,1 decreased, and severe arterial hypoxia developed. The reaction occurred at a well-defined dose of anhydride and lasted about 30 min. When the same dose was repeated after 30 min, the response was much attenuated. MTHPA and HHPA can induce asthma in guinea pigs. The dose-response curve at antigen challenge is steep. Once a threshold dose is reached, a severe reaction occurs. The reactivity is then exhausted. This model may be suitable for assessing occupational asthma caused by acid anhydrides and possibly by other low-molecular-weight chemicals.

Administration, Inhalation↗

PubMed1997

Diarylsulfones, a novel class of human immunodeficiency virus type 1 integrase inhibitors.

A majority of reported human immunodeficiency virus type 1 integrase (HIV-1 IN) inhibitors are polyhydroxylated aromatic compounds containing two phenyl rings separated by aliphatic or aromatic linkers. Most inhibitors possessing a catechol moiety exhibit considerable toxicity in cellular assays. In an effort to identify nonhydroxylated analogs, a series of aromatic sulfones were tested for their ability to inhibit the 3' processing and strand transfer steps that are necessary for HIV replication. Several aromatic sulfones have previously been shown to have moderate activity against HIV-1 reverse transcriptase in cellular assays; however, their inhibitory potencies against IN have not been explored. In the present study, the inhibitory effect of a series of sulfones and sulfonamides against IN was determined. Among 52 diaryl sulfones tested, 4 were determined to be highly potent (50% inhibitory concentration [IC50], 0.8 to 10 micrograms/ml), 5 had good potencies (IC50, 11 to 50 micrograms/ml), 10 showed moderate potencies (IC50, 51 to 100 micrograms/ml), and 33 were inactive (IC50, > 100 micrograms/ml) against IN. All of the active compounds exhibited similar potencies against HIV-2 IN. Sulfa drugs, used extensively in treating Pneumocystis carinii pneumonia, a leading cause of morbidity and mortality in AIDs patients, were also examined. Among 19 sulfonamides tested, sulfasalazine (IC50, 50 micrograms/ml) was the most potent. We conclude that potent inhibitors of IN can be designed based on the results presented in this study.

Cell Line↗