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Biomedical subjects

M Hu

Publications and source records attributed to M Hu.

At least 109 records · Page 6Linked to original sources
PubMed1999

Chronic ethanol exposure increases 3H-GABA release in rat hippocampus by presynaptic muscarinic receptor modulation.

BACKGROUND: Chronic ethanol treatment (CET) for 28 weeks significantly increases electrically-stimulated 3H-GABA release from hippocampal slices. This increase in GABA release may be one of the mechanisms by which CET decreases the magnitude of long-term potentiation (LTP) in the hippocampus. The present study examined whether CET increases GABA release via an alteration in heterologous presynaptic cholinergic regulation. METHODS: Animals were treated with ethanol or sucrose diet for 28 weeks followed by either no withdrawal or a 48-hr withdrawal period. The electrically-stimulated 3H-GABA release from preloaded superfused hippocampal slices of naive and CET rats was measured. RESULTS: Carbachol increased 3H-GABA release in a concentration-dependent manner, and atropine modulated 3H-GABA release in a biphasic concentration-dependent manner. Atropine (10 microM) significantly blocked the effects of carbachol. Oxotremorine, a selective muscarinic receptor agonist, also increased 3H-GABA release. Mecamylamine, a selective nicotinic antagonist, did not modulate 3H-GABA release and did not block the effects of carbachol. The effects of these agents were also tested in rats 0 or 48 hrs after withdrawal from CET. The biphasic effects of atropine were decreased, whereas the facilitating effects of carbachol were significantly increased. There were no changes in the effects of these agents on 3H-acetylcholine release from hippocampal slices of CET rats compared to sucrose-treated rats. CONCLUSION: These results suggest that presynaptic muscarinic receptors facilitate GABA release, whereas nicotinic receptors do not play a significant role in modulating GABA release in hippocampus. CET selectively alters presynaptic muscarinic regulation of GABA release in hippocampus and may help us to further understand the mechanism underlying the disruption of LTP by CET.

Animals↗
PubMed1999

Relationship between fossa-condylar position, meniscus position, and morphologic change in patients with Class II and III malocclusion.

OBJECTIVE: To evaluate fossa-condylar-meniscus morphologic changes in patients with skeletal and dental Class III and Class II division 1 and 2 malocclusion to determine which type is related to internal derangement of the temporomandibular joint (TMJ) and whether the variation of TMJ structure is related to a particular type of malocclusion. MATERIALS AND METHODS: Seventy-two pretreatment orthodontic patients, ranging in age from 10 to 27 years, underwent examination of the right and left TMJs with corrected Schöller's position radiographs. Bilateral TMJ relationships of the fossa-condyle were examined through subjective evaluation and linear and area measurements. In addition, in 20 of the 72 patients, meniscus positions and morphologic changes were imaged with a 0.5 T sagittal magnetic resonance imaging system on the right and left TMJ. RESULTS: (1) The variation of condyle-fossa positions for identical types of malocclusion was very large. (2) Skeletal and functional Class III malocclusion patients demonstrated significantly more anteriorly positioned condyles. (3) Class II division 1 patients showed concentrically positioned condyles, but with slightly anterior displacement. (4) Class II division 2 patients demonstrated more posteriorly positioned condyles. (5) When condyles were in anterior or concentric positions, meniscus positions and morphology were normal and in concavoconcave shapes. (6) When condyles were in posterior positions, most meniscus positions were in normal or slightly anterior range and their shapes were also concavoconcave. The rest were significantly more anterior and their shapes were abnormal, as evidenced by thickened anterior bands. CONCLUSION: Class III and Class II division 1 malocclusion demonstrated normal structure and function of the TMJ. Class II division 2 malocclusion was obviously associated with abnormal structure and function of the TMJ.

Adolescent↗
PubMed1999

Human antibody isotype responses to Schistosoma japonicum egg antigen.

Schistosoma japonicum-infected subjects from Hubei province of China were investigated to determine the class and subclass of the antibody response to soluble egg antigen (SEA), using an enzyme-linked immunosorbent assay. The subjects were 50 acute and 55 chronic cases. In acute cases, the mean OD values for IgA, IgE and IgG3 were very high, while the positive ratios of IgA and IgE were only 78% and 74%, respectively. The positive ratios of IgG, IgM, IgG1, IgG3 and IgG4 were all above 90%. In chronic cases, the mean OD values for IgG, IgG3 and IgG4 were very high, and the positivity rates of IgG, IgG1, IgG3 and IgG4 were all above 90%. Comparing the two study groups, the mean OD values of IgM, IgA, IgE were higher in acute cases than those of chronic cases (p < 0.0001), while the mean OD values of IgG, IgG4 were higher in chronic cases than in acute cases (p < 0.05). The mean OD values of IgG3 in both groups were high and those of IgG2 in both groups were low.

Acute Disease↗
PubMed1999

Experimental study of sagittal fracture of the mandibular condyle.

OBJECTIVE: To observe the healing of sagittal fracture of the mandibular condyle (SFMC) and its effect on the temporomandibular joint in immature miniature pigs. METHODS: Twenty-seven immature miniature pigs were randomly chosen and divided into three groups. Twelve immature miniature pigs underwent sagittal fracture of the mandible condyle; 12 underwent transverse fracture, and 3 were maintained as a normal control. Three-phase scintigraphy, computed tomography (CT) imaging, and histological tests were conducted at 3 weeks, 6 weeks, 12 weeks, and 24 weeks. RESULTS: The data showed the value of the time-activity curve of blood-flow image increased and blood-flow arriving time was postponed after condylar fracture. The alpha/beta ratio was the highest at 2 weeks after SFMC. The count of blood-pool image and static image were higher than nonfractured sides. Peaks were seen at 2 weeks postfracture. Disc and condyle adhesion was found in all sagittal fractures of the mandibular condyle and bifid mandibular condyle was formed. Adhesive tissues between condyle and disc were fibro-connective tissues, which connected the disc directly to cartilage or bone tissue. A large number of fibroblasts and sparse chondrocytes were seen in the adhesive tissue. Blood vessels and adipose cells were seen in the disc, whereas there were no distinguishable changes in transverse fracture. CONCLUSION: Bifid mandibular condyle was found in most SFMC in childhood. The mechanism of bifid condyle deformity is related to secondary injuries to the disc, adhesions between the condyle and disc, and displacement of the medial split fragment. The age when SFMC occurs is an important factor in bifid condyle formation.

Animals↗
PubMed1999

[Effects of interferon-alpha on the mRNA expression of procollagen type I and III of hepatic stellate cells and on the deposition of collagen type I and III in fibrotic liver of rats].

OBJECTIVE: To observe the effects of interferon-alpha on the proliferation and mRNA expression of procollagen type I and III and on the deposition of collagen type I and III in fibrotic liver of rats. METHODS: CCl4 was used to induce the liver fibrosis rat model. The stellate cells were isolated from liver and cultured in DMEM medium. The effects of interferon-alpha on the proliferation and collagen synthesis of stellate cells were determined with 3H-TdR, 3H-proline incorporating test. Total RNA of stellate cells was extracted and the cDNA of procollagen type I and III and of interstitial collagenase was labeled using Dig High Primer technique. The level of procollagen type I and III and interstitial collagenase mRNA were measured by Northern blot analysis. Deposition of collagen type I and III in fibrotic liver was evaluated with Dot blot. RESULTS: At the 4th, 24th and 48th hour, interferon-alpha inhibited the intake of 3H-TdR and 3H-proline by stellate cells significantly. The inhibition rates were 16%, 19% and 27%, respectively. The intensity of inhibition was proportional to the concentration of interferon-alpha. The expression level of procollagen type I and III mRNA in the interferon-alpha treated group was significantly lower than that in control group in all stages of fibrosis. At the 2nd and 6th week, the deposition of collagen type I and III in interferon-alpha treated group decreased significantly compared with that in control group. However, no difference was found at the 9th week. The expression of collagenase mRNA between interferon-alpha treated group and control group showed no difference. CONCLUSION: Interferon-alpha can inhibid the proliferation and collagen synthesis of stellate cells, down-regulate the expressions of procollagen type I and III mRNA and reduce the deposition of collagen type I and III in fibrotic liver. It has no effect on collagenase.

Animals↗
PubMed1999

[Effects of various condylar operations on its compressive mechanical property and bone density].

OBJECTIVE: To investigate the changes and relationship of condylar mechanical properties and its material character after various condylar operations. METHODS: Condylar compressive mechanical properties and its bone mineral content were analyzed quantitatively by compressive mechanical property measurement technique and dual energy X-ray absorptiometry in 6 and 6 adult dogs undergone either high shaping or reconstruction of condyles respectively, and compared with 12 normals. RESULTS: Condylar elastic--limit load and displacement, its largest load and displacement were the highest in control, but stiffness and bone mineral content were the highest in high-shaping group, all data were the lowest in the reconstruction ones. There was marked and extremely marked linear positive relativity among condylar elastic--limit load, largest load, stiffness and bone density, in which all relative coefficients exceeded 0.862. CONCLUSION: The changes of condylar shape induced by various operations directly influence its compressive mechanical properties and bone mineral content. There is linear positive relativity between condylar compressive mechanical properties and its bone mineral density.

Animals↗
PubMed1999

[Comparative experimental study between longitudinal fracture and transverse fracture of mandibular condyle].

OBJECTIVE: To evaluate the secondary effect of childhood miniature pig longitudinal fracture and transverse fracture of mandibular condyle to Temporomandibular Joint (TMJ). METHODS: Longitudinal and transverse fractures on condyle of 14 childhood miniature pigs were created respectively. After 3 and 6 months the TMJs were studied macroscopically and microscopically. RESULTS: The transverse fracture of mandibular condyle brought about TMJ adaptive changes. There was no adhesion between disc and condyle. The longitudinal fracture led usually to bifid condyle deformity and adhesion between disc and condyle. Many fibroblasts and chondrocytes were seen in the adhesion between disc and condyle. Blood vessels and fatty degeneration appeared in the articular disc. CONCLUSION: Two different types of childhood condylar fractures are apparently different in the aspects of secondary lesions on TMJ. It suggests that an evident correlation between mandibular condyle longitudinal fracture and TMJ ankylosis.

Animals↗
PubMed1999

[A clinico-pathological study of neuroendocrine tumors in stomach].

OBJECTIVE: To study the pathological classification of gastric neuroendocrine tumors and its clinico-pathological significance. METHODS: Paraffin sections of totally 52 gastric neuroendocrine tumors including 42 carcinoid tumors were studied with immunohistochemical technique, which involved 9 endocrine markers of hormones antibodies and electronic microscopy for investigating the endocrine cells and the contiguous gastric mucosa of the neuroendocrine tumors. RESULTS: The 52 gastric neuroendocrine tumors were divided into three types: Type I, carcinoid, associated with atrophic gastritis, altogether 26 cases. Tumor extension was limited in the mucosa or submucosa, accompanying with hypergastrinemia and G cell hyperplasia. This type is consistently preceded by and associated with generalized proliferation of endocrine cells in the mucosa at fundus. Type II, carcinoid of sporadic type, totally 16 cases, not associating with hypergastrinemia, was more aggressive. Type III, Neuroendocrine carcinomas (10 cases), were highly aggressive tumors. CONCLUSION: A correct identification of different types of gastric endocrine tumors is important and implicit for the treatment and prognosis of neuroendocrine tumors.

Adult↗
PubMed1999

[A clinicopathologic study on eight cases of cystic and solid tumors of pancreas].

OBJECTIVE: To study the clinicopathologic characteristics, differentiation patterns and histogenesis of cystic and solid tumors of the pancreas (CSTP). METHODS: 8 cases of CSTP were studied using histologic (HE and PAS), immunohistochemical (S-P method) and electron microscopic techniques. RESULTS: All the patients were adolescent and young adult females, 14-33 years in age (mean 25.3 years) without recurrence after tumor resection. The mean diameter of tumors was 9.6 cm, all encapsulated. Histological examination showed presence of solid sheets, pseudopapillary, in all of the cases. Hemorrhage, foam cells, and cholesterol crystals were often found. Immunohistochemically, 8 cases were positive for alpha(1)-AT and lysozyme; 6 cases expressed vimentin, 2 cases expressed actin, and CgA-positive cells found in the tumor cell nests in one case. All of the cases showed PR, and 4 cases showed ER positive immunoreactivity in the majority of tumor cells, but negative for CK AE1, CK AE3, EMA, Synaptophysin, ACTH, gastrin, somatostatin, insulin, and glucogan in all the cases. Electron microscopy of 3 cases showed evidences of polymorphism in differentiation of the tumor cells, including the transitional appearance into ducts, acinus, and endocrine cells. Weibel-Palade body found in tumor cells in one out of 8 cases. CONCLUSIONS: (1) CSTP is a distinct clinicopathologic entity in young female patients with a benign clinical course. (2) CSTP develops from primitive pancreatic cells, with the potentiality of developing into ducts, acinus, and endocrine cells.

Actins↗
PubMed1999

[Effect of long-term experimental stress on blood glucose level in mice with diabetes-prone: the age difference and its mechanism].

OBJECTIVE: To compare the effects of long-term experimental stressors on blood glucose level and insulin secretion in the aged and young mice with diabetes-prone and to explore the mechanism. METHODS: Diabetes-prone was induced by streptozotocin (STZ) in 40 1.5-month-old mice and 40 15-month-old mice. The young and the aged STZ mice were divided randomly into the stress group and the control group, respectively. Each group contained 20 mice. Both the aged and the young stress mice were exposed to multiple stressors (restrain, rotation, crowding) for 6 weeks. Fasting blood glucose (FBG), fasting plasma insulin (FINS), pancreas lipid peroxidase (LPO) and the metabolic products of nitric oxide (NO2-, NO3-) levels and superoxide dismutase (SOD) activity were measured. The grade of insulitis in STZ mice was also evaluated. RESULTS: After 6-week stress, FBG level, pancreatic tissue LPO and NO2-, NO3- contents were significantly higher while FINS level and SOD activity lower in the aged stress mice than those in the youngs. The insulitis malignization in the aged stress group was severer than that in the young stress group. There were correlativities among the above variables. CONCLUSION: The effects of long-term stress in promoting hyperglycemia exacerbating insulitis, and inhibiting insulin secretion are more significant in the aged STZ mice than in the young ones. This difference may result from the excessive NO and the peroxide injury to the pancreas.

Aging↗
PubMed1999

[The alternation current conductive property of blood].

The blood electro-frequency properties of normal human body were investigated in the range of 1 Hz-10 MHz. The method of testing and the equipment were examined to meet the need for the measurement of blood property. In the experiment, it was discovered that the electric conductivity of blood increased obviously with the increase of testing frequency in the rage of 100 Hz-10 KHz, but almost no change in phase was noted. This result suggests it is necessary to modify the previous work and build up a reasonable equivalent electric model of blood.

Adult↗
PubMed1999

[Protective effect of poly DL-aspartic acid on ototoxicity of gentamicin].

OBJECTIVE: To observe the protective effect of poly DL-aspartic acid (PAA) on ototoxicity of gentamicin (GM). METHODS: Fifty F-344 rats were divided into four groups, GM only PAA + GM, PAA only and saline control. ABR thresholds at different frequencies were measured at different times and hair cell losses were numerated. Two-dimensional diffusion assays in the culture medium were performed to evaluate the effect of PAA on the antimicrobial activity. RESULTS: Eighteen days after the treatment, ABR thresholds at 10 kHz and 8 kHz as well as hair cell losses in the GM-treated group showed significant differences as compared with other three groups (P < 0.01). CONCLUSION: PAA had the protective effect against the cochlear ototoxicity of GM without decreasing its antimicrobial activity.

Animals↗
PubMed1998

Hydroxyphthalocyanines as potential photodynamic agents for cancer therapy.

A series of benzyl-substituted phthalonitriles, substituted at the 3-, 4-, and 4,5-positions, underwent varied condensations with phthalonitrile to give a series of protected (monohydroxy- and polyhydroxyphthalocyaninato)zinc(II) derivatives which were readily cleaved to give several hydroxyphthalocyanines (ZnPc) (phthalocyanine phenol analogues). Their efficacy as sensitizers for the photodynamic therapy (PDT) of cancer was evaluated on the EMT-6 mammary tumor cell line. In vitro, the 2-hydroxy ZnPc (32) was the most active, followed by the 2,3- and 2,9-dihydroxy ZnPc (39 and 45), with the 2,9,16-trihydroxy ZnPc (33) exhibiting the least activity. In vivo, the monohydroxy derivative 32 and the 2,3-dihydroxy derivative 39 were both efficient in inducing tumor necrosis at 1 micromol kg-1, but complete tumor regression was poor, even at 2 micromol/kg. In contrast, the 2,9-dihydroxy isomer 45, at 2 micromol kg-1, induced tumor necrosis in all animals treated, with 75% complete regression. These results underline the importance of the position of the substituents on the Pc macrocycle to optimize tumor response and confirm the PDT potential of the unsymmetrical Pcs bearing functional groups on adjacent benzene rings.

Animals↗
PubMed1998

Depolarization and cAMP elevation rapidly recruit TrkB to the plasma membrane of CNS neurons.

Here, we describe a novel mechanism for the rapid regulation of surface levels of the neurotrophin receptor TrkB. Unlike nodose ganglion neurons, both retinal ganglion cells (RGCs) and spinal motor neurons (SMNs) in culture display only low levels of surface TrkB, though high levels are present intracellularly. Within minutes of depolarization or cAMP elevation, surface TrkB levels increase by nearly 4-fold, and this increase is not blocked by cycloheximide. These findings suggest that activity and cAMP elevation rapidly recruit TrkB to the plasma membrane by translocation from intracellular stores. We propose that a fundamental difference between peripheral nervous system (PNS) and central nervous system (CNS) neurons is the activity dependence of CNS neurons for responsiveness to their peptide trophic factors and that differences in membrane compartmentalization of the receptors underlie this difference.

Animals↗
PubMed1998

Determination of absorption characteristics of AG337, a novel thymidylate synthase inhibitor, using a perfused rat intestinal model.

The purpose of this study was to determine the intestinal absorption characteristics of AG337, a mechanism-based inhibitor of thymidylate synthase, using a perfused rat intestinal model. Effects of site, pH, temperature, concentration, Na+, and inhibitors on the absorption of AG337 were determined, after the compound was shown to be stable in buffers of various pH, blank perfusate, and intestinal homogenate. The results indicated that absorption of AG337 was temperature-, pH-, Na+-, concentration-, and site-dependent. The best site of absorption is duodenum, where the absorption was 3-10 times (p < 0. 05) higher than absorption at jejunum, ileum, and colon. Among the four pH's studied, the best was at pH 6.5 (p < 0.05). Absorption was 80% lower in the absence of Na+, and 75% lower when the temperature of the perfusate was decreased to 4 degreesC. Permeability of AG337 also decreased about 75% when the concentration was raised to 100 microM. These results suggest that a nutrient carrier may be involved in the transport of AG337. To determine the carrier responsible for the absorption of AG337, its absorption was determined in the presence of various inhibitors at different concentrations. The results indicated that transport of AG337 was inhibited significantly (p < 0.01) by 100 microM of adenine, hypoxanthine, and xanthine. The transport was also inhibited significantly (p < 0.01) by a mixture of 100 microM each of adenine, hypoxanthine, and xanthine, but not by a mixture of 100 microM each of thymine and uracil. A higher concentration of hypoxanthine resulted in increased inhibition. In contrast, prototypical inhibitors of nucleoside transporter, dipyridamole and nitrobenzylthioinosine (NBMPR), did not significantly decrease the transport of AG337. The results also showed that absorption of AG337 had a significant nonsaturable component, with a nonsaturable Pw of 0.8. In conclusion, absorption of AG337 in the rat intestine has been shown to be mainly via a purine base carrier with a significant nonsaturable component.

Animals↗
PubMed1998

The expression of GABA(A) receptors during the development of the rabbit retina.

PURPOSE: Gamma-amino butyric acid (GABA) is a major inhibitory neurotransmitter in the retina, possibly participating in its normal development. The distribution of gamma-aminobutyric acid receptors was therefore examined in mature and developing rabbit retina by GABA(A) receptor alpha1 and beta2/3 subunit immunocytochemistry. RESULTS: Beta2/3 subunits appeared already at the E25 stage (25 days after gestation) although only weakly and irregularly. Alpha1 subunit immunoreactivity was first observed at birth. On the fifth postnatal day, immunostaining was clearly seen in the inner plexiform layer, and weaker, in the outer plexiform layer. There were at this stage no well-delineated sublayers in either the inner or the outer plexiform layer, but three clearly defined sublayers appeared in the inner plexiform layer at PN10. Amacrine cell bodies now also appeared, labelling for both the GABA(A) receptor alpha1 and the beta2/3 chains. A punctuate labelling appeared in the outer plexiform layer. From the 20th postnatal day, the immunoreactivity was similar to that seen in adult rabbits. CONCLUSIONS: Like in the adult, the alpha1 and beta2/3 subunits of the GABA(A) receptor thus colocalize predominantly in certain amacrine cells and in processes of the inner plexiform layer during the development of the retina. The GABA(A) receptors appear later than GABA during the development of the rabbit retina, and functioning GABA neurotransmitter circuits appear to be assembled primarily after the 3rd to 5th postnatal day. Our results support the hypothesis that GABA may have other functions than mediating classic synaptic neurotransmission before the formation of receptors containing the alpha1 and beta2/3 subunits. Like in the brain, the alpha subunits may have more selective functions during the development than the beta subunits.

Animals↗
PubMed1998

Clinical performance of the AMDL DR-70 immunoassay kit for cancer detection.

A clinical study using DR-70 immunoassay for the detection of 13 different cancers have been conducted with 277 healthy subjects and 136 cancer patients. The test results showed that the DR-70 immunoassay kit was capable of detecting cancers with high degree of specificity and sensitivity. At 95% specificity level, the sensitivity of the assay was 87.8%, 92.6%, 65.2% and 66.7%, respectively for lung, stomach, breast and rectum cancers. Furthermore the test kits were shown to be stable and performed reproducibly.

Adolescent↗