Biomedical subjects

M Zhang

Publications and source records attributed to M Zhang.

At least 361 records · Page 20Linked to original sources

PubMed2000

Stereoselective glucuronidation of formoterol by human liver microsomes.

AIMS: Formoterol is a beta2-adrenoceptor agonist marketed as a racemic mixture of the active (R; R)- and inactive (S; S)-enantiomers (rac-formoterol). The drug produces prolonged bronchodilation by inhalation but there is significant interpatient variability in duration of effect. Previous work has shown that in humans formoterol is metabolized by conjugation with glucuronic acid but little is known about the stereoselectivity of this reaction. The aim of the present study was to investigate the glucuronidation of formoterol enantiomers in vitro by human liver microsomes. METHODS: The kinetics of formation of formoterol glucuronides during incubation of racemate and of single formoterol enantiomers with human liver microsomes (n=9) was characterized by chiral h.p.l.c. assay. RESULTS: The kinetics of glucuronidation of the two formoterol enantiomers obeyed the Michaelis-Menten equation. Glucuronidation of formoterol was stereoselective and occurred more than two times faster for (S; S)-formoterol than for (R; R)-formoterol. In incubations with single formoterol enantiomers, the median (n=9) Km values for (R; R)-glucuronide and (S; S)-glucuronide were 827.6 and 840.4 microm, respectively, and the median V max values were 2625 and 4304 pmol min-1 mg-1, respectively. Corresponding values determined in incubations with rac-formoterol were 357.2 and 312.1 microm and 1435 and 2086 pmol min-1 mg-1 for (R; R)- and (S; S)-glucuronide, respectively. Interindividual variation was large with the ratio of V max/Km (S; S/R; R) ranging from 0.57 to 6.90 for incubations with rac-formoterol. CONCLUSIONS: Our study demonstrates that glucuronidation of formoterol by human liver microsomes is stereoselective and subject to high interindividual variability. These findings suggest that clearance of formoterol in humans is subject to variable stereoselectivity which could explain the variation in duration of bronchodilation produced by inhaled formoterol in patients with asthma.

Aged↗

PubMed2000

Formation of a native-like beta-hairpin finger structure of a peptide from the extended PDZ domain of neuronal nitric oxide synthase in aqueous solution.

Neuronal nitric oxide synthase (nNOS) is targeted to the cell membrane via interactions of its extended PDZ domain with PDZ domains of membrane-associated proteins including PSD-95 and alpha1-syntrophin. The formation of heterodimers between the nNOS PDZ domain and the PDZ domains of nNOS-binding proteins requires a stretch of continuous amino-acid residues C-terminal to the canonical nNOS PDZ domain. In this work, we show that a 27-residue peptide comprising the C-terminal extension of the extended nNOS PDZ domain is capable of binding to PSD-95. The structure of the 27-residue peptide in aqueous solution was determined using multidimensional NMR-spectroscopic techniques. The free peptide adopts a native-like beta-hairpin finger structure in aqueous solution. The results indicate that the C-terminal extension peptide of the nNOS PDZ domain may represent a relatively independent structural unit in the mediation of the interaction between nNOS and PDZ domain-containing proteins including PSD-95 and alpha1-syntrophin.

Amino Acid Sequence↗

PubMed2000

Inhibition of melanin synthesis by cystamine in human melanoma cells.

In studies to determine whether pigmentation can be regulated physiologically by thiols, human melanoma cells (MM418c5) and melanocytes were found to become depigmented when cultured continuously in 50 microM cystamine. Cystamine was depleted from the culture medium and the treatment was nontoxic and reversible. Cysteamine, dithiothreitol, and phenylthiourea were less effective, and glutathione, cysteine, and cystine were inactive. Tyrosinase (dopa oxidase) activity was not greatly affected except for induction of a lag period. In contrast, tyrosinase activity in an amelanotic melanoma cell line (MM96L) was rapidly inhibited without consumption of cystamine/cysteamine, in association with the generation of free thiol in the culture medium, and could be enhanced by the cystine transport inhibitor, glutamate. Tyrosinase expressed by a recombinant vaccinia virus was inhibited by cystamine treatment of MM96L and HeLa cells. Cystamine treatment lowered the degree of cross-linking of the pigmentation antigen gp75/TRP-1 in MM418c5 cells. Tyrosinase protein and mRNA levels in MM418c5 cells were not affected by cystamine. The results show that cystamine at a concentration close to physiologic levels has multiple effects on the melanogenic pathway. In amelanotic cells, tyrosinase has a short half-life and is readily inhibited by cystamine/cysteamine whereas tyrosinase in the more mature melanosomes of the pigmented cell appears to be less accessible to proteolytic and thiol attack. Inhibition of melanin synthesis in the latter cell type may arise to a significant degree from reduction of cystamine to cysteamine, which sequesters quinones.

Cystamine↗

PubMed2000

Light ethanol consumption enhances liver regeneration after partial hepatectomy in rats.

BACKGROUND & AIMS: The effects of "social drinking" on the liver have yet to be fully documented. The aim of this study was to document the effects of daily light, moderate, and heavy ethanol exposure on hepatic regenerative activity in the rat. METHODS: Adult male Sprague-Dawley rats underwent daily gavages with 1.0 (light), 2. 0 (moderate), or 4.0 (heavy) g/kg of ethanol or tap water (controls) for 30 days before 70% partial hepatectomy (PHx). Hepatic regenerative activity was then documented on days 1, 3, 5, and 7 after PHx. RESULTS: Compared with controls, restitution of liver mass, [(3)H]thymidine incorporation, and proliferating cell nuclear antigen expression were decreased in the heavy (-10%, -60%, and -36%, respectively), unchanged in the moderate (-4%, -8%, and -16%, respectively), and increased in the light (+6%, +38%, and +29%, respectively) ethanol groups. Messenger RNA differential display of resected livers at PHx identified a band present only in the light ethanol group that encodes a unique 47-kilodalton protein with growth-promoting features designated light ethanol-induced stimulatory protein. CONCLUSIONS: The results indicate that light ethanol consumption enhances hepatic regenerative activity after PHx in rats. Further studies are required to determine the mechanism involved and whether social drinking has beneficial or adverse effects on the natural history of acute or chronic liver disease in humans.

Alcohol Drinking↗

PubMed2000

Vasoactive intestinal peptide (VIP) exacerbates endotoxin-induced uveitis (EIU) in mice.

PURPOSE: We have previously shown that inhibition of the proinflammatory cytokine tumor necrosis factor- (TNF)-alpha exacerbates the inflammatory process of EIU. To further examine this paradoxic phenomenon, we investigated here the effect on EIU of VIP, a neuropeptide that inbibits TNF-alpha production. METHODS: VIP was injected concurrently with endotoxin at doses that induce EIU or lethality in mice. Severity of EIU was measured by counting infiltrating cells in eye sections, at 1 or 5 days post endotoxin injection. Survival of mice was monitored periodically, while serum levels of TNF-alpha, interleukin-(IL)-1beta and IL-10 were determined by caputure ELISA. RESULTS: Treatment with VIP exacerbated EIU but provided partial protection from the lethal endotoxin effect. VIP treatment also reduced serum levels of TNF-alpha and IL-1beta, but increased levels of IL-10. CONCLUSION: This study further established the paradoxical observation that EIU is exacerbated by lowering the levels of circulating pro-inflammatory cytokines, in particular TNF-alpha.

Animals↗

PubMed2000

Maspin--a novel protease inhibitor with tumor-suppressing activity in breast cancer.

Maspin (mammary serpin) is a novel serine protease inhibitor related to the serpin family with a tumor-suppressing function in breast cancer. Maspin was originally identified from normal mammary epithelium by subtractive hybridization and might function as a class II tumor-suppressor gene. Maspin's decreased expression with increased level of malignancy and its loss in metastatic cells is regulated at the transcriptional level. Cytosin methylation and heterochromatinization in the promoter region might account for this down-regulation of maspin. Transfection of tumor cells with maspin cDNA inhibits invasion and motility and decreases tumor growth and metastatic ability in nude mice. Maspin interacts with the p53 tumor-suppressor pathway and function as an inhibitor of angiogenesis in vitro and in vivo. The progressive loss of expression of maspin during tumor progression makes this new protein an interesting diagnostic and prognostic marker. The re-expression of maspin by pharmacological intervention potentially offers a promising approach as a therapeutic option in breast cancer therapy.

Animals↗

PubMed2000

Restoration of bone mass in the severely osteopenic senescent rat.

Studies in humans and rats suggest that age impairs the ability to form bone. This impairment may be due to a depletion or deficit in osteoprogenitor stem cells. Such a deficit would be expected to reduce the ability of the skeleton to respond to therapy designed to restore lost bone. This study evaluated whether severely osteopenic senescent rats are capable of responding to a potent anabolic factor in bone, prostaglandin E2 (PGE). Growing female Sprague Dawley rats were ovariectomized at 3 months and aged until the start of treatment at 23 months. Rats were treated daily with PGE (3 mg/kg sc) or vehicle for 56 days. Tibiae were harvested for bone histomorphometry and femora were obtained for mRNA analysis of bone matrix proteins. The cancellous bone area was fivefold greater in PGE-treated rats than in vehicle-treated controls and not different from age-matched ovary-intact rats. PGE approximately doubled the bone-forming surface and the mineral apposition rate and increased the bone formation rate fourfold. The increased cancellous bone area in PGE-treated rats was primarily due to an increase in osteoblasts over osteoclasts. One hundred percent of the endocortical surface and 72 +/- 9% of the periosteal surface of cortical bone was undergoing mineralization in PGE-treated rats, whereas no mineratization was evident in vehicle-treated rats. An architectural analysis of cancellous bone indicates that trabecular number and thickness were increased and separation decreased in the treated rats. Imaging by microcomputed tomography further revealed that with PGE treatment, trabeculae in the medial plane of the proximal tibial metaphysis were more robust and continuous with the endocortical surface. PGE also significantly induced message levels for the prepro-alpha (I) subunit of type I collagen (collagen), osteonectin, and osteocalcin. In summary, bone mass can be restored to severely osteopenic senescent rats, suggesting that aging does not necessarily diminish the capacity of the skeleton to form bone.

Aging↗

PubMed2000

Characterization of a new human B7-related protein: B7RP-1 is the ligand to the co-stimulatory protein ICOS.

Optimal T cell activation requires the interactions of co-stimulatory molecules, such as those in the CD28 and B7 protein families. Recently, we described the co-stimulatory properties of the murine ligand to ICOS, which we designated as B7RP-1. Here, we report the co-stimulation of human T cells through the human B7RP-1 and ICOS interaction. This ligand-receptor pair interacts with a K:(D) approximately 33 nM and an off-rate with a t((1/2)) > 10 min. Interestingly, tumor necrosis factor (TNF)-alpha differentially regulates the expression of human B7RP-1 on B cells, monocytes and dendritic cells (DC). TNF-alpha enhances B7RP-1 expression on B cells and monocytes, while it inhibits it on DC. The human B7RP-1-Fc protein or cells that express membrane-bound B7RP-1 co-stimulate T cell proliferation in vitro. Specific cytokines, such as IFN-gamma and IL-10, are induced by B7RP-1 co-stimulation. Although IL-2 levels are not significantly increased, B7RP-1 co-stimulation is dependent on IL-2. These experiments define the human ortholog to murine B7RP-1 and characterize its interaction with human ICOS.

Amino Acid Sequence↗

PubMed2000

Schistosoma mansoni infection cancels the susceptibility to Plasmodium chabaudi through induction of type 1 immune responses in A/J mice.

Susceptibility to Plasmodium chabaudi depends on the relative dominance of T(h)1/T(h)2 responses in host mice. A T(h)2-dominant response during the early phase of infection in susceptible A/J mice causes a fatal disease course due to severe malaria. Schistosoma mansoni is a potent inducer of a T(h)2-dominant response not only to the parasite antigens, but also to other antigens concurrently existing in the host animals. In spite of S. mansoni infection, these A/J mice escape death from malaria and showed accompanied enhanced production of IFN-gamma to malaria antigens. Treatment with anti-IFN-gamma mAb in S. mansoni-infected A/J mice abolished the resistance to malaria, indicating that IFN-gamma was responsible for the resistance to P. chabaudi in S. mansoni-infected A/J mice. Results in this study show that under certain circumstances, S. mansoni infection can promote type 1 immune responses in A/J mice that normally develop T(h)2 responses.

Animals↗

PubMed2000

CD4(+) v(alpha)14 NKT cells play a crucial role in an early stage of protective immunity against infection with Leishmania major.

The roles of gamma delta T, NK and NKT cells in an early stage of protective immunity against infection with Leishmania major were investigated. Further, the contribution of these innate cells to the expression of 65 kDa heat shock protein (HSP65) in host macrophages was examined, since we found previously that this expression prevents apoptotic death of infected macrophages and is a crucial step in the acquisition of protective immunity against infection with various obligate intracellular protozoa including L. major. C57BL/6 and DBA/2 mice were found to be resistant against the infection on the basis of the parasite burden in their regional lymph nodes, and to strongly express HSP65 in their macrophages, whereas BALB/c mice were susceptible and barely expressed the HSP65. In those resistant mice, CD4(+) NKT cells prominently increased in their regional lymph node and were the main effector cells at least for an early stage of the protective immunity and for the HSP65 expression, whereas this subset did not increase in susceptible BALB/c mice. Further, neither gamma delta T nor NK cells in resistant mice contributed to those protective immune responses. The NKT cell subset bore CD3, CD4, TCR alpha beta, IL-2R beta and NK1.1 but scarcely asialo-GM(1). Moreover, this effector subset was confirmed to be V(alpha)14 NKT cells by using J(alpha)281(-/-) mice.

Animals↗

PubMed2000

Regulation of macrophage activation and inflammation by spermine: a new chapter in an old story.

Spermine, a naturally occurring polyamine, is a ubiquitous structural component of all eukaryotic cells. Regenerating tissues produce higher levels of spermine, and injured or dying cells release spermine into the extracellular milieu, so that tissue levels increase significantly at inflammatory sites of infection or injury. Recent research has focused on delineating the significance of spermine accumulation in the inflammatory process. The discovery that spermine is a negative regulator of macrophage activation provided a mechanism by which spermine influences the biology of inflammation. Mechanistic studies indicate that spermine is incorporated into macrophages and restrains the innate immune response. This anti-inflammatory process is facilitated by the negative acute-phase protein, fetuin.

Humans↗

PubMed2000

Liliequist's membrane is a fold of the arachnoid mater: study using sheet plastination and scanning electron microscopy.

OBJECTIVE: The subarachnoid space consists of a number of distinct subarachnoid cisterns. They are separated from each other by trabecular walls, one of which is Liliequist's membrane. The aim of this study was to investigate the anatomic characteristics of Liliequist's membrane. METHODS: The study used a combined approach, consisting of the modified E12 sheet plastination method for 3 adult cadavers and gross anatomic dissection for 35 cadavers, 2 of which were further examined using scanning electron microscopy. RESULTS: The results from this study indicate that 1) Liliequist's membrane is an avascular fold of the arachnoid mater that lacks openings and spreads out laterally, being in direct continuity with the arachnoid mater covering the tentorium; 2) the carotid-chiasmatic walls, which separate the chiasmatic cistern and carotid cisterns and had been considered to be parts of Liliequist's membrane, are vascular and incomplete trabecular walls and should not be considered parts of Liliequist's membrane; and, 3) as a fold of the arachnoid mater, Liliequist's membrane is not directly attached to the temporal lobes and oculomotor nerves. CONCLUSION: Liliequist's membrane is a double-layer fold of the arachnoid mater and has anatomic characteristics different from those of arachnoid trabecular walls.

Arachnoid↗

PubMed2000

Growth and function of isolated canine pancreatic ductal cells.

These studies investigated the growth characteristics and functional properties of isolated canine pancreatic ductal epithelial cells. Cells were isolated from the accessory pancreatic duct and cultured by using three conditions: on vitrogen-coated petri dishes with fibroblast conditioned medium (nonpolarized); in vitrogen-coated Transwells above a fibroblast feeder layer (polarized); or as organotypic rafts above a fibroblast-embedded collagen layer (polarized). Growth characteristics, transepithelial resistances, and carbonic anhydrase and cyclic adenosine monophosphate (AMP) responses were evaluated. Under polarized conditions, the cells grew as monolayers with columnar epithelial characteristics. The monolayers developed high transepithelial resistance and became impervious to the passage of horseradish peroxidase. Epithelial growth factor (EGF) (2 ng/ml) stimulated ductal cell growth and accelerated the formation of a high-resistance monolayer. Forskolin (10 microM) rapidly decreased transepithelial resistance. Carbonic anhydrase activity, which was lower in nonpolarized compared with polarized conditions, was stimulated by carbachol (175 microM). Secretin, however, did not stimulate carbonic anhydrase activity in these cells. Although secretin stimulated adenylyl cyclase activity in early-passage cells, this response was lost in later-passage cells. Both vasoactive intestinal polypeptide (VIP; 1 microM) and forskolin (10 microM) consistently increased adenylyl cyclase activity. Isolated canine pancreatic ductal epithelial cells proliferate in vitro, develop high-resistance epithelial monolayers, and respond to stimuli that activate adenylyl cyclase. These cells should provide a useful model for regulatory studies of ductal cell functions.

Adenylyl Cyclases↗

PubMed2000

The fine connective tissue architecture of the human ligamentum nuchae.

STUDY DESIGN: An anatomic study of the posterior midline structures of the cervical spine was performed using a new sheet-plastination (E12) technique in conjunction with gross anatomic dissection. OBJECTIVES: To clarify the structural status of the human ligamentum nuchae. SUMMARY OF BACKGROUND DATA: Little is known about the arrangement of connective tissue attachments of the neighboring neck muscles to the ligamentum nuchae. In addition, it is not clear whether the cervical supraspinous ligaments form part of the ligamentum nuchae. METHODS: This study used a combined approach of a detailed gross anatomic study on eight cadavers and a macroscopic and microscopic study of the connective tissue organization of the posterior midline structures on serial horizontal thin (2.5 mm) plastinated slices of the cervical spine (occiput-T1) from an adult female cadaver. RESULTS: The dorsal and ventral portions of the ligamentum nuchae are a single entity formed by the aponeurotic fibers of the trapezius, splenius capitis, rhomboideus minor, and serratus posterior superior muscles. CONCLUSIONS: The regional differences in the connective tissue organization of the ligamentum nuchae and its well-defined attachments to the C6 and C7 vertebrae suggest that it is designed to function in the lower cervical spine.

Aged↗

PubMed2000

The crystal structures of human alpha-thrombin complexed with active site-directed diamino benzo[b]thiophene derivatives: a binding mode for a structurally novel class of inhibitors.

The crystal structures of four active site-directed thrombin inhibitors, 1-4, in a complex with human alpha-thrombin have been determined and refined at up to 2.0 A resolution using X-ray crystallography. These compounds belong to a structurally novel family of inhibitors based on a 2,3-disubstituted benzo[b]thiophene structure. Compared to traditional active-site directed inhibitors, the X-ray crystal structures of these complexes reveal a novel binding mode. Unexpectedly, the lipophilic benzo[b]thiophene nucleus of the inhibitor appears to bind in the S1 specificity pocket. At the same time, the basic amine of the C-3 side chain of the inhibitor interacts with the mostly hydrophobic proximal, S2, and distal, S3, binding sites. The second, basic amine side chain at C-2 was found to point away from the active site, occupying a location between the S1 and S1' sites. Together, the aromatic rings of the C-2 and C-3 side chains sandwich the indole ring of Trp60D contained in the thrombin S2 insertion loop defined by the sequence "Tyr-Pro-Pro-Trp." [The thrombin residue numbering used in this study is equivalent to that reported for chymotrypsinogen (Hartley BS, Shotton DM, 1971, The enzymes, vol. 3. New York: Academic Press. pp 323-373).] In contrast to the binding mode of more classical thrombin inhibitors (D-Phe-Pro-Arg-H, NAPAP, Argatroban), this novel class of benzo[b]thiophene derivatives does not engage in hydrogen bond formation with Gly216 of the thrombin active site. A detailed analysis of the three-dimensional structures not only provides a clearer understanding of the interaction of these agents with thrombin, but forms a foundation for rational structure-based drug design. The use of the data from this study has led to the design of derivatives that are up to 2,900-fold more potent than the screening hit 1.

Binding Sites↗

PubMed2000

Dementia diagnostic guidelines: methodologies, results, and implementation costs.

OBJECTIVE: To facilitate the diagnostic process for dementia. Five guidelines and four consensus statements on specific diagnostic recommendations, specialist referral recommendations, and costs of recommended diagnostic procedures were compared and summarized. DATA SOURCES AND SELECTION: A MEDLINE search from 1984 to 1999 and queries to experts yielded 14 guidelines and consensus statements that addressed the diagnosis of dementia. Only nine documents which had national or international scopes were reviewed. METHODS: Comparisons were made on the specific diagnostic criteria for patient history, clinical examination, functional assessment, laboratory tests, neuroimaging, and other diagnostic tests, as well as specialist referral recommendations and costs for the recommended diagnostic procedures. The first three authors reviewed independently each document and completed a table on specific recommendations in each document. To settle disagreements about specific recommendations, they discussed them until they reached a consensus. To interpret the intent of vague statements, they used their best judgment. RESULTS: The documents differed in content, recommendations, and development methodology. They were based on either expert opinion or scientific evidence, or both. Although the nine documents were nearly unanimous in several recommendations, including assessing the presenting problem, taking a medical history, conducting physical and neurological examinations, and assessing the patient's mental and cognitive status, considerable differences in recommendations were common. Such differences led to large differentials in the estimated costs (range, $190 to $2,001) for recommended diagnostic assessments. CONCLUSIONS: A systematic approach to diagnostic recommendations for dementia may induce greater consistency among guidelines and consensus statements. The current approach leads to considerable variability in recommendations and estimated costs.

Consensus Statements as Topic↗

PubMed2000

A functional NSP4 enterotoxin peptide secreted from rotavirus-infected cells.

Previous studies have shown that the nonstructural glycoprotein NSP4 plays a role in rotavirus pathogenesis by functioning as an enterotoxin. One prediction of the mechanism of action of this enterotoxin was that it is secreted from virus-infected cells. In this study, the media of cultured (i) insect cells infected with a recombinant baculovirus expressing NSP4, (ii) monkey kidney (MA104) cells infected with the simian (SA11) or porcine attenuated (OSU-a) rotavirus, and (iii) human intestinal (HT29) cells infected with SA11 were examined to determine if NSP4 was detectable. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis-Western blotting, immunoprecipitation and N-terminal amino acid sequencing identified, in the early media from virus-infected cells, a secreted, cleavage product of NSP4 with an apparent molecular weight of 7,000 that represented amino acids 112 to 175 (NSP4 aa112-175). The secretion of NSP4 aa112-175 was not affected by treatment of cells with brefeldin A but was abolished by treatment with nocodazole and cytochalasin D, indicating that secretion of this protein occurs via a nonclassical, Golgi apparatus-independent mechanism that utilizes the microtubule and actin microfilament network. A partial gene fragment coding for NSP4 aa112-175 was cloned and expressed using the baculovirus-insect cell system. Purified NSP4 aa112-175 increased intracellular calcium mobilization in intestinal cells when added exogenously, and in insect cells when expressed endogenously, similarly to full-length NSP4. NSP4 aa112-175 caused diarrhea in neonatal mice, as did full-length NSP4. These results indicate that NSP4 aa112-175 is a functional NSP4 enterotoxin peptide secreted from rotavirus-infected cells.

Animals↗

PubMed2000

Higherorder neural network group models for financial simulation.

Real world financial data is often discontinuous and non-smooth. If we attempt to use neural networks to simulate such functions, then accuracy will be a problem. Neural network group models perform this function much better. Both Polynomial Higher Order Neural network Group (PHONG) and Trigonometric polynomial Higher Order Neural network Group (THONG) models are developed. These HONG models are open box, convergent models capable of approximating any kind of piecewise continuous function, to any degree of accuracy. Moreover they are capable of handling higher frequency, higher order non-linear and discontinuous data. Results obtained using a Higher Order Neural network Group financial simulator are presented, which confirm that HONG group models converge without difficulty, and are considerably more accurate than neural network models (more specifically, around twice as good for prediction, and a factor of four improvement in the case of simulation).

Computer Simulation↗