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Biomedical subjects

M Hong

Publications and source records attributed to M Hong.

At least 109 records · Page 6Linked to original sources
PubMed1997

How important is the N-3 sugar moiety in the tight-binding interaction of coformycin with adenosine deaminase?

Preliminary findings on the possible important role of the N-3 sugar moiety of coformycin in its tight-binding interaction with adenosine deaminase (ADA) are reported. The compound 3-beta-D-Ribofuranosyl-5,6,7,8-tetrahydro-4H-imidazo[4,5-d][1,3]diaze pin-5-one-8-ol (1), its 3-benzyl analogue (6), and the aglycon (7) served as probes. The first two were both found to be competitive inhibitors of ADA with Ki's in the range of 10(-5) M, while the last one was inactive.

Adenosine Deaminase↗
PubMed1997

Coupling amplification in 2D MAS NMR and its application to torsion angle determination in peptides.

A technique for amplifying the apparent magnitudes of 13C-1H and 15N-1H dipolar interactions in magic-angle spinning experiments is described. By inserting rotor-synchronized 180 degrees pulses in the evolution period of a 2D dipolar-chemical shift experiment, heteronuclear dipolar couplings are doubled or quadrupled relative to the spinning speed. The increased number of dipolar sidebands is desirable for retaining structural information in the indirectly detected dipolar dimension while resolving inequivalent sites in the isotropic chemical shift dimension at relatively high spinning speeds. This coupling amplification method is incorporated into an experiment that determines the peptide torsion angle phi through the relative orientation of the Calpha-Halpha and N-HN bonds. It is shown both experimentally and theoretically that the angular resolution of the measurement is enhanced significantly by the selective doubling of the N-HN coupling.

Chemical Phenomena↗
PubMed1997

Effect of mutations in Shigella flexneri chromosomal and plasmid-encoded lipopolysaccharide genes on invasion and serum resistance.

This study shows that both length and distribution of lipopolysaccharide (LPS) are important for Shigella flexneri invasion and virulence. Mutants were generated in the chromosomal LPS synthesis genes rfa, rfb, and rol, and in a plasmid-encoded O-antigen chain-length regulator, cld(pHS-2). LPS analysis showed that mutations in rfb genes and in a candidate rfaL gene either eliminated the entire O-antigen side chains or produced chains of greatly reduced length. Mutation in a previously unidentified gene, rfaX, affected the LPS core region and resulted in reduced amounts of O-antigen. Mutants defective in cld(pHS-2) or rol had different distributions of O-antigen chain lengths. The results of tissue-culture cell invasion and plaque assays, the Serény test, and serum-sensitivity assay suggested roles for the different LPS synthesis genes in bacterial survival and virulence; rfaL, rfaX and rfb loci are required for serum resistance and intercellular spread, but not for invasion; cld(pHS-2) is required for resistance to serum killing and for full inflammation in the Serény test, but not for invasion or intercellular spread, while rol is required for normal invasiveness and plaque formation, but not for serum resistance. Thus, O-antigen synthesis and chain-length regulation genes encoded on both the chromosome and the small plasmid pHS-2 play important roles in S. flexneri invasion and virulence.

Animals↗
PubMed1997

Expression of aerobactin genes by Shigella flexneri during extracellular and intracellular growth.

The expression of the Shigella flexneri chromosomal aerobactin genes during growth of the bacterium within tissue culture cells was assayed. During intracellular growth, aerobactin promoter activity was repressed relative to the level observed in bacteria grown extracellularly, even when the bacteria had been starved for iron prior to infection. Similarly, the level of one of the proteins encoded by this operon, the aerobactin outer membrane receptor, Iut, was reduced in the intracellular environment. These studies indicate that the aerobactin system is not highly expressed by bacteria within host cells, suggesting that siderophore-independent iron acquisition systems can provide essential iron during intracellular multiplication.

Extracellular Space↗
PubMed1997

[The use of panoramic radiograph to observe abnormal movement of condyle].

The abnormal movement of mandible is one of the three chief symptoms of TMJDS, it is described usually by the degree and type of mouth opening. We use close and open mouth position panoramic radiographs of 144 cases with TMJDS to observe the relationship between the head of condyle and the articular eminence. It can show the different degrees of movement of condyle and the degree of movement of both sides to see they are in balance or not. We classified the movement of the condyle in to six types, and measure the degree of mouth opening on the same film. The rela-tionship between the result of them and the climnical symptoms are then analysed. We concluded that the supermovement of the condyle, which cause the acute and chronic trauma to the structures of TMJ and related muscles and ligaments, is one of the chief etiologic factors of TMJDS. The method and advantages of using panoramic radiography to observe movement of condyle are discussed.

Adolescent↗
PubMed1997

The application of a novel thrombin sensitive site in genetic engineering.

To obtain high efficiency of cleavage of thrombin in fusion protein containing alpha-ANP fused to Ref peptides, the linker sequence designed as VIAGR which was different from GVRGPR formerly used was studied. Plasmid pHL carrying the fusion gene Ref-NT-ANP downstream from PL promoter was derived from expression vector pLY1 by inserting the fragment of NT-ANP into it. The expression of fusion gene was induced at 42 degrees C, and the interested protein Ref-NT-ANP accumulated as inclusion bodies was isolated by gradient centrifuge and then dissolved in 7 mol/L guanidinehydrochloride (Gdn-HCl). After dilution, renaturation and dialyzation, the cleavage of thrombin was examined using samples with 1.1 mol/L Gdn-HC1 and samples free of Gdn-HCl respectively. Digestion result showed that the novel-adopted cleavage sequence was highly sensitive to thrombin when the substrate dissolved in 1.1 mol/L Gdn-HCl. The time needed for 87% cleavage (the ratio of substrate to thrombin was 50 micrograms/u) was less than 24 hours. This sequence described here which was specifically recognized by thrombin might be broadly applied in other fusion systems.

Atrial Natriuretic Factor↗
PubMed1997

Study on stress distribution of the condyle.

OBJECTIVE: To investigate the internal state of stress distribution in healthy human condyles and to offer some references for application of the temporomandibular joint (TMJ) biomechanics. METHODS: Six male volunteers were selected to perform CT examination of the TMJ with 1.5 mm-thick sections at 1.5 mm intervals. Three dimensional image reconstruction of the joint was performed in the SUN workstation and the CT data were converted into the decimal system. The three dimensional finite element model mesh generation resulted from 1188 elements and 264 nodes in each condyle. Stress calculation was performed with SAP-V program, and the results were converted into mechanical density scalar. During the study, the internal state of stress distribution on each side condyle in every subject was analysed on the basis of loading on the anterior articular surface of the condyle. RESULTS: Stress was concentrated in the anterior articular surface of the condyle and was highest at the loading point. The condylar cortical bone was the main load-bearing area. The level of stress distribution in the cancellous bone of the condyle was very low. Near condylar neck stress was well-distributed on the cortical. The internal state of stress was essentially symmetrical on the same cuts of both side condyles. CONCLUSIONS: The results showed that three dimensional finite element analysis may indicate the internal state of stress distribution in the condyle, suggesting that a combination of the three dimensional finite element methods and the three dimensional imaging technique may be a useful means for diagnosis and treatment of TMJ diseases.

Adult↗
PubMed1996

Reconstruction of the nigrostriatal pathway by simultaneous intrastriatal and intranigral dopaminergic transplants.

The main strategy in experimental and clinical neural transplantation in Parkinson's disease has been to place fetal nigral grafts not in their ontogenic site (substantia nigra) but in their target area (striatum). The reason for this ectopic placement is the apparent inability of nigral grafts placed in the ventral mesencephalon (VM) of the adult host to grow axons for long distances that are capable of reaching the ipsilateral striatum and thus restoring the nigrostriatal pathway. The present study demonstrates for the first time that simultaneous dopaminergic transplants (double grafts) placed in the substantia nigra and ipsilateral striatum of rats bearing unilateral 6-hydroxydopamine lesions reconstruct the dopaminergic nigrostriatal pathway in the adult rat brain. Numerous tyrosine hydroxylase-immunoreactive axons were observed arising from the intranigral graft and growing rostrally along the internal capsule and medial forebrain bundle to reinnervate the ipsilateral striatum, which also had received a dopaminergic graft. These double grafts achieved not only greater striatal reinnervation than the standard intrastriatal graft but also a faster and more complete rotational recovery to amphetamine challenge 6 weeks after transplantation. These results suggest strongly that embryonic nigral transplants implanted in the striatum are capable of promoting growth and providing guidance to axons arising from a dopaminergic graft placed homotopically in the VM, resulting in restoration of the dopaminergic nigrostriatal projection. Reconstruction of the nigrostriatal pathway by double grafts may not only achieve substantial striatal reinnervation but may also contribute to the reestablishment of dopaminergic regulation of the nigrostriatal circuitry.

Amphetamine↗
PubMed1996

Conformational constraints on the headgroup and sn-2 chain of bilayer DMPC from NMR dipolar couplings.

This paper presents new NMR constraints on the conformation of the headgroup, glycerol backbone, and sn-2 chain of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) in the liquid-crystalline bilayer. Using two-dimensional 13C-1H chemical shift correlation spectroscopy, we find significant dipolar couplings between the carboxyl carbon CO2 and the headgroup protons. This indicates that a conformation in which the DMPC headgroup and the beginning of the sn-2 chain bend toward each other is significantly populated in the fluid bilayer. The predominance of this headgroup orientation can be further confirmed by 31P-13C dipolar couplings from the literature, which constrain the glycerol G2-G3 torsion angle to be close to trans, excluding a significant presence of one of the two conformations found in the DMPC crystal. Combining and reexamining 20 known NMR couplings for the glycerol backbone and its adjacent segments of L alpha-DMPC, we find that several torsion angles and bond orientations in the core of the DMPC molecule are constrained severely and must differ from those in the crystal structure. We propose a consistent molecular model for phosphocholine lipids in the liquid-crystalline phase, with a rigid backbone in the core of the molecule, a bent-back headgroup, and increasing mobility toward the ends of the acyl chains and the headgroup.

Dimyristoylphosphatidylcholine↗
PubMed1996

[Histopathological study of miniature pig temporomandibular joint after missing teeth of one side].

This study evaluated the histologic response of the temporomandibular joint (TMJ) following one side posterior teeth extraction in miniature pig. Right posterior teeth were removed in 12 miniature pigs. Six of them were killed after 1 month and the other six after 3 monthes. 6 miniature pigs were taken as control. We found that obvious degenerative changes were common in all TMJs of the experimental pigs. Hyaline thrombus found in the condyles of posterior teeth losing side suggested that local microcirculation was disturbed. Missing one side posterior teeth had various influence on two side TMJs. Both TMJs changes were not identical, and the changes were more marked in teeth lost side than in control side. The results comfirm that occlusal disturbance can cause degenerative change of the TMJ.

Animals↗
PubMed1996

[Studies on the scale for quality of life for patients with nasopharyngeal carcinoma].

The assessment of quality of life became more and more important, so the scale for quality of life for patients with nasopharyngeal carcinoma was studied by the authors, with changes in disease pattern, increasing needs for people's health, and changes in their views on health and the mode of medicine. The scale for quality of life for the patients consisted of 20 items, including general and specific ones and covering four aspects in physical, psychological, social functioning status and symptoms and side-effects. It could also be used in measuring and evaluating quality of life for patients with other cancers and chronic diseases, with some modification in its specific items and reservation of the general ones.

Female↗
PubMed1996

[Histopathological effects of overextended opening of the mouth on the temporomandibular joint and masticatory muscles].

The purpose of this study is to explore the effects and the pathogenicity of overextended mouth opening on the temporomandibular joint (TMJ) and the masticatory muscles. In this experiment, the animal model of overextended opening was, established by overly opening the miniature pigs' mouths for certain periods with mouth gag, and then the TMJ and the masticatory muscles were studied histopathologically. The results showed that the histosytes of the TMJ and the masticatory muscles had suffered injury, proliferation, atrophy and degeneration from the overextended opening, and the extents of deterioration became greater with the increase of frequency and duration of overextended opening. Among the injured tissues, the cartilage of the condyle, the posterior and anterior portions of the articular disc, the anterior extenting tissue of the disc, the lateral perygoid muscles and the temporalises underwent the most obvious histopathological changes. The result of this study confirms that overextended mouth opening is one of the pathogenic factors of CMD, and it has great significance for the clinical diagnosis, treatment and prevention for CMD.

Animals↗
PubMed1996

[Study on stress distribution of the condyle].

The stress distribution in the condyle was calculated by means of combining CT examination with computed image operating technique and three-dimensional finite element models. The results suggested that there was a higher stress level in condylar cortical bone than in cancellous bone. Stress on the cortical bone were shown to concentrate in middle and lateral 1/3 part of articular surface of the condyle. The distribution of stress on two condyles was symmetrical. That analysis method of biomechanics was introduced into the clinical and baic study on the temporomandibular joint provided a new means for helping diagnosis and treatment of the temporomandibular joint diseases.

Adult↗
PubMed1995

Study of phospholipid structure by 1H, 13C, and 31P dipolar couplings from two-dimensional NMR.

Various motionally averaged 31P-1H, 13C-1H, 1H-1H, and 31P-13C dipolar couplings were measured for natural-abundance and unoriented phosphocholine in the L alpha phase. The couplings were obtained and assigned by a variety of advanced and partly novel two-dimensional solid-state NMR experiments. Whereas 31P-1H and 31P-13C dipolar couplings provide long-range structural constraints, geminal 1H-1H couplings and the signs of 13C-1H couplings are important new elements in a segmental order-tensor analysis of the lipid headgroup and glycerol backbone. The implications of these measured dipolar couplings for the conformational exchange of the lipid headgroup and the bending of the headgroup from the glycerol backbone are discussed. These dipolar couplings are also analyzed semiquantitatively in terms of the segmental order tensor.

Biophysical Phenomena↗
PubMed1995

Role of neuropeptide Y in the regulation of tyrosine hydroxylase messenger ribonucleic acid levels in the male rat arcuate nucleus as evaluated by in situ hybridization.

Neuroanatomical data have clearly demonstrated the existence of synaptic contacts between neuropeptide Y (NPY) endings and tuberoinfundibular dopaminergic (TIDA) neurons in the rat arcuate nucleus. In order to determine the influence of NPY in the biosynthesis of dopamine, we have studied the effects of NPY and some NPY analogs on tyrosine hydroxylase (TH) gene expression in TIDA neurons in the male rat. The following peptides: NPY, PYY, [Leu31, Pro34]-NPY (a Y1 receptor agonist) and NPY13-36 (a Y2 receptor agonist) were injected into the left lateral ventricle of adult male rats. All the animals were perfused with 4% paraformaldehyde 4 h after injection. Cryostat sections through the arcuate nucleus were processed for quantitative in situ hybridization. The intracerebroventricular injection of NPY, PYY and [Leu31, Pro34]-NPY induced an increased of 43, 33 and 42%, respectively, in the number of grains overlying TH neurons. On the other hand, the Y2 receptor agonist NPY13-36 did not influence mRNA levels. These data then strongly suggest that NPY positively regulates the genetic expression of TH in rat TIDA neurons via the Y1 NPY receptor subtype.

Animals↗