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Biomedical subjects

R G Wang

Publications and source records attributed to R G Wang.

15 recordsLinked to original sources
PubMed2002

X-ray photoelectron spectroscopy study of disordering in Gd2(Ti1-xZrx)2O7 pyrochlores.

The dramatic increases in ionic conductivity in Gd2(Ti1-xZrx)2O7 solid solution are related to disordering on the cation and anion lattices. Disordering in Gd2(Ti1-xZrx)2O7 was characterized using x-ray photoelectron spectroscopy (XPS). As Zr substitutes for Ti in Gd2Ti2O7 to form Gd2(Ti1-xZrx)2O7 (0.25 < x < or =0.75), the corresponding O 1s XPS spectrum merges into a single symmetric peak. This confirms that the cation antisite disorder occurs simultaneously with anion disorder. Furthermore, the O 1s XPS spectrum of Gd2Zr2O7 experimentally suggests the formation of a split vacancy.

Journal Article↗
PubMed1999

Neuroprotective rather than neurorescue or neurorestorative effect of selegiline against MPTP-induced dopaminergic toxicity.

AIM: To study the neuroprotective, neurorescue, neurorestorative effects of selegiline (Sel) on nigrostriatal dopaminergic neuronal system and its inhibition of brain monoamine oxidase B (MAO-B). METHODS: The striatal levels of dopamine and its metabolites were measured using HPLC with electrochemical detection (HPLC-EC). The inhibition of MAO-B was tested by an improved fluorimetric assay. RESULTS: 1-Methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP) (30 mg.kg-1 i.p.) reduced the striatal dopamine level by 73% in mice. Selegiline (Sel, 10 mg.kg-1 i.p.) before, but not after, MPTP treatment protected against MPTP-induced nigrostriatal dopaminergic neurotoxicity. There were no differential effects between Sel and saline treatments on the recovery of striatal dopamine levels, which were partially restored during 2 wk. 1-Methyl-4-phenylpyridinium (MPP+) (5 mg.kg-1 i.p.) produced no dopaminergic neurotoxicity. Furthermore, Sel selectively and irreversibly inhibited mouse brain MAO-B in vitro (IC50 = 17 nmol.L-1, 95% confidence limits = 14-20 nmol.L-1). CONCLUSION: Selegiline has neuroprotective rather than neurorescue or neurorestorative effects on MPTP-induced nigrostriatal dopaminergic neuronal degeneration, which is directly pertinent to its selective and irreversible inhibition of brain MAO-B activity.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1998

Pharmacokinetics of recombinant human granulocyte macrophage colony-stimulating factor in Macaca mulatta.

AIM: To examine the pharmacokinetics of i.v. and s.c. recombinant human granulocyte macrophage colony-stimulating factor (rhGM-CSF) in Macaca mulatta. METHODS: Plasma levels of rhGM-CSF were detected with sandwich enzyme-linked immunosorbent assay. RESULTS: Plasma concentration-time curves after i.v. rhGM-CSF in monkeys were best fitted with 3-compartment model. The 1st, 2nd, and 3rd phase T1/2 were 0.05-0.07, 0.14-0.58, and 1.4-4.1 h. Cl and K10 were similar between different doses, respectively. Cmax was 0.93 +/- 0.16 microgram.L-1, Tmax was 2.65 +/- 0.14 h, and elimination T1/2 was 2.5 +/- 0.3 h after s.c. rhGM-CSF. The bioavailability after s.c. rhGM-CSF was 0.61. CONCLUSION: Pharmacokinetics of rhGM-CSF in Macaca mulatta provided a useful index for clinical trial.

Animals↗
PubMed1997

The embryonic development of the human ethmoid labyrinth from 8-40 weeks.

The embryonic development of the human ethmoid labyrinth was studied in 24 fetal heads aged between 8 and 40 weeks of gestation under light microscopy. The uncinate process was identifiable at 8 weeks of gestation on the laterosuperior portion of the inferior turbinate; however, at this stage of development, the ethmoid bulla was not apparent. The ethmoid bulla developed on the lateral wall of the middle meatus by 12 weeks of gestation. By 14 weeks, the primordial ethmoid infundibulum and primordial maxillary sinus were seen developing between the uncinate process and the ethmoid bulla. It was obvious that the anterior and middle ethmoid cells developed from the ethmoid bulla. By 22 weeks of gestation, the first cell of the anterior ethmoid group was evident in the anterior-inferior portion of the ethmoid bulla. By 23 weeks of gestation, the first cell of the middle ethmoid group was visible in the superior portion of the ethmoid bulla. Pneumatization of the middle turbinate occurred as part of normal development of the ethmoid labyrinth. By 32 weeks of gestation, the ostium for the development of the middle turbinate cell was seen in the superior-interior portion of the middle turbinate. These observations provide new insight into the development of the ethmoid labyrinth and have important implications for the understanding of normal anatomy and developmental variants of the ethmoid labyrinth.

Embryonic and Fetal Development↗
PubMed1995

Toxicity of dopamine to mouse neuroblastoma x rat glioma hybrid (NG108) cells in vitro.

AIM: To study toxicity of dopamine to mouse neuroblastoma x rat glioma hybrid (NG108) cells. METHODS: Cell viability was estimated using 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay. RESULTS: Dopamine at 100 mumol L-1 was toxic when added to cultures 24 h after plating. The cell viability was about 1/4 of control. Toxicity did not seem to be mediated by dopaminergic receptors because the dopaminergic antagonists sulpiride and Sch-23390 did not block the toxic effect of dopamine. Catalase 50 kU L-1, superoxide dismutase 50 kU L-1 and l-ascorbic acid 200 mumol L-1 blocked the dopamine (125 mumol L-1) toxicity and elevated the cell viability from 25.9 +/- 11.0% to 74.8 +/- 4.4%, 72.3 +/- 4.5% and 71.4 +/- 2.3%, respectively. CONCLUSION: Dopamine toxicity to NG108 cells was mainly attributed to the oxidation of dopamine and its toxic by-products, eg, H2O2.

Animals↗
PubMed1994

Histopathological findings in failed human epikeratophakia lenticules.

Six human epikeratophakia lenticules were removed 1 to 23 months after refractive keratoplasty for aphakia (n = 2) and myopia (n = 4). The myopic group included one epi-lenticule treated with ArF-excimer laser for hyperopia. Reasons for removal were epithelial defect (n = 4), edema of host cornea (n = 1), and overcorrection (n = 1). The epi-lenticule stroma showed centrally a regular fibrillar structure with a low keratocyte density. Electron microscopy (n = 1) revealed preserved cytoplasmic organelles and nuclear appearance. Mononuclear cells were absent. Polysaccharide was demonstrated in the stroma. Bowman's layer was normal without breaks. The epithelium had variable thickness. In the peripheral wound region stromal and epithelial irregularities were evident.

Adult↗
PubMed1994

The cartilaginous nasal capsule and embryonic development of human paranasal sinuses.

Embryology is of importance to the surgeon both for the study of human developmental anatomy and for the analysis of congenital conditions resulting from malformed or arrested development. The embryonic development of the nose, and especially of the paranasal sinuses, is not yet fully understood. This histologic study of 23 fetal heads aged from 8 to 40 weeks of gestation demonstrates that all four pairs of paranasal sinuses are developed from the cartilaginous nasal capsule. The outpouching of the nasal mucous membranes is only a secondary phenomenon, rather than the primary force. This observation helps to elucidate the following clinical observations: (1) the association of maxillary sinus hypoplasia with hypoplasia of the uncinate process, (2) the origin of chondrosarcoma of the maxillary bone, and (3) pneumatization of the paranasal sinuses.

Cartilage↗
PubMed1991

The embryonic development of the lateral nasal wall from 8 to 24 weeks.

This histological study of 20 fetal heads aged between 8 and 24 weeks of gestation demonstrates and describes the embryonic development of the lateral wall of the nose. The three turbinates (inferior, middle, and superior) arise as soft-tissue swellings (preturbinates) by 8 weeks' gestation. A cartilage capsule surrounds the nose at 8 weeks and by 9 weeks, medially directed flanges of cartilage have invaded all three preturbinates. The uncinate process arises from the medial surface of the lateral cartilaginous capsule and is first identifiable by 10 weeks. An "air space" progressively develops from 11 to 12 weeks lateral to the cartilaginous uncinate process and from this space, the embryonic channel to the maxillary sinus develops. The embryonic woven bone of the maxilla can be identified from 9 to 10 weeks and enlarges both absolutely and relatively to the nasal cavity, so that by 13 to 14 weeks, this expanding bone forms the lateral wall of the inferior meatus as the cartilaginous nasal capsule regresses.

Embryonic and Fetal Development↗
PubMed1991

Persistence of the foramen of Huschke in the adult: an osteological study.

The foramen of Huschke, which appears during the embryological development of the tympanic bone, usually closes by the age of five years. A review of 377 dried skulls revealed that the foramen of Huschke was present in adult life in 7% of the skulls examined. A patent foramen of Huschke in the adult may, in rare cases, be the cause of temporomandibular joint herniation or fistulization through the anterior wall of the bony external canal.

Adult↗
PubMed1988

Spontaneous temporomandibular joint fistula into the external auditory canal.

The clinical and radiological findings in a patient who developed a spontaneous fistula between the right temporo-mandibular joint and the external auditory canal are presented. A high resolution CT scan revealed that the fistula had developed through a congenital dehiscence in the anterior wall of the tympanic bone.

Ear Canal↗
PubMed1988

The embryonic development of the human paraseptal cartilage.

The paraseptal cartilage was first named by Spurgat in 1896. In the late 19th and early 20th century, the paraseptal cartilage of the lower and higher mammals was studied in great detail; however, very few studies were carried out on the human paraseptal cartilage. Over the past 20 years no articles have been published in the English literature on this topic. Despite all the early interest in this topic, several questions still remain unanswered about the origin of paraseptal cartilages, their ultimate fate (i.e. do they disappear or persist?) and their relationship with the vomer, the nasal capsule, and with Jacobson's organ. Eighteen human fetus heads ranging in age from eight to 32 weeks were studied and the literature reviewed. The development of the paraseptal cartilage and its clinical significance are discussed.

Adult↗
PubMed1987

The epidermoid formation (Michaels' structure) in the developing middle ear.

The presence of an epidermoid-like formation located in the mucosa of the anterosuperior quadrant of the lateral wall of the developing middle ear was first described by Michaels in 1986. In a review of 41 middle ears from 20 serially sectioned fetus heads and one fetus temporal bone from our collection, six epidermoid formations were identified. Our study confirms the existence of this formation which we have decided to name Michaels' structure after Professor Leslie Michaels, the discoverer of this structure. The reasons for the different incidence of its occurrence in our series when compared to Michaels' original report, and the possible significance of Michaels' structure in the pathogenesis of congenital cholesteatoma of the middle ear are discussed.

Cholesteatoma↗
PubMed1987

Bilateral spontaneous temporomandibular joint herniation into the external auditory canal.

The clinical and radiological findings in the first case in the literature of spontaneous, bilateral and asymptomatic herniation of soft tissue from the temporomandibular joint into the anterior wall of the external canal are presented. With the patient's mouth closed, the herniations appeared as a dome-shaped swelling located on the anterior wall of each bony external auditory canal. With the patient's mouth opened, the dome-shaped swellings were retracted anteriorly, producing an invagination of the skin of the external canal at the site of the previous herniation. A high resolution CT scan of the temporal bones revealed that the soft tissue of both temporomandibular joints was protruding through a congenital dehiscence in the anterior wall of the tympanic bones.

Aged↗